RU2699511C1 - Pneumatic tire - Google Patents

Abstract

FIELD: automotive industry.

SUBSTANCE: invention relates to the automotive industry. Pneumatic tire includes: central main groove made in contacting with soil of central part of tread part; main groove of the shoulder zone made on the side of the central main groove, which is external in tire lateral direction; central contact section formed by forming its boundaries by means of central main groove and main groove of shoulder area; part with chamfers, in which plurality of chamfers are located in direction along tire circumference, at that chamfers are made on the edge of inlet part of central main groove on side of central contact section; curved groove made on central contact section located nearby – in lateral direction of tire – with edge of inlet part of central main groove, including part with chamfers, and bent in accordance with shape of chamfers part with chamfers, and passing along direction along circumference of tire, and auxiliary groove made on central contact section between main groove of shoulder area and curved groove and extending towards bent groove in direction intersecting with tire circumferential direction.

EFFECT: increased resistance to non-uniform wear at guarantee of braking characteristic at movement on wet surfaces of roads.

15 cl, 16 dwg

Description

Technical field

The present invention relates to a pneumatic tire, which can provide increased resistance to uneven wear while guaranteeing braking performance when driving on wet surfaces of roads and preventing appearance defects.

State of the art

In the prior art, the pneumatic tire described in JP 4,905,599 B is, for example, formed in the tread portion with at least four circumferential main grooves extending in the direction along the circumference of the tire and a plurality of rib-shaped contact portions that are formed while being limited through the circumferential main grooves. In addition, the second contact sections, the boundaries of which are defined by the circumferential main grooves located farthest from the center in the lateral direction of the tire, and which are located on the side of the circumferential main grooves, inner in the lateral direction of the tire, have a zigzag shape, extend in the direction along the circumference of the tire and made with zigzag narrow grooves that separate the second contact portions in the lateral direction of the tire. Since, in accordance with the design of the pneumatic tire described in JP 4905599 B, the second contact portions are made with zigzag narrow grooves, there is an advantage in that edge components of the contact surface of the tire are provided and thus braking performance is provided when moving on wet surfaces roads, that is, tire performance when driving on wet roads.

Technical problems

However, since the zigzag narrow grooves have curved portions, there is a risk that the contact areas may be damaged during mold release during tire molding, and this may lead to appearance defects. In addition, since the zigzag narrow grooves have curved portions, there is a risk that there may be a difference in stiffness in the area near the zigzag narrow grooves, and this can lead to uneven wear.

In view of the foregoing, it is an object of the present invention to provide a pneumatic tire capable of increasing resistance to uneven wear while providing braking performance when driving on wet surfaces of roads and preventing appearance defects.

Solution of problems

To solve the above problems and achieve the above objectives, the pneumatic tire of the present invention includes: a first main groove made in contact with the soil, the Central part of the tread portion so that it runs along the direction along the circumference of the tire; a second main groove made on the side of the first main groove that is laterally outward of the tire so that it extends along a direction along the circumference of the tire; a contact portion formed as a result of the formation of its boundaries by the first main groove and the second main groove and continuous in the direction along the tire circumference; a portion with bevels in which a plurality of bevels are arranged along a direction along the circumference of the tire, wherein a plurality of bevels are made on the edge of the inlet portion of the first main groove from the contact portion side and provide a change in position of the edge of the inlet portion in a diagonal direction relative to the direction along the tire circumference; a curved groove made in the contact area, located near the edge of the input part of the first main groove, including the part with bevels, in the lateral direction of the tire and made curved in accordance with the shapes of the bevels of the part with bevels, and passing along the direction along the circumference of the tire, and an auxiliary groove made in the contact area between the second main groove and the curved groove and extending towards the curved groove in a direction intersecting with the direction along the tire circumference, in this case, one end of the auxiliary groove is oriented towards the curved groove and ends inside the contact area.

In this pneumatic tire, the edge components of the contact surface of the tire are provided by means of a curved groove, and therefore, braking performance is provided when driving on wet surfaces of roads, that is, tire performance when driving on wet roads. In addition, when making a curved groove, a part with bevels curved in accordance with the shapes of the bevels, made on the edge of the inlet part of the first main groove, and also when making an auxiliary groove with this one end oriented towards the curved groove and ending inside the contact section, when when the mold is removed from the curved groove during tire molding, the curved groove expands as a result of deformation of the contact portion, which includes the curved groove, in the direction to the side of the part with bevels and to the side of the auxiliary groove. As a result, the ability to release the mold is improved, and this prevents a situation in which the contact portion is damaged during release of the mold, whereby it is possible to prevent an appearance defect. In addition, when making a curved groove, a part with bevels, curved in accordance with the shapes of the bevels, made on the edge of the inlet part of the first main groove, and also when making an auxiliary groove with this one end oriented toward the curved groove and ending inside the contact area, decrease differences in stiffness at the contact area, which includes a curved groove, whereby creating uniform contact pressure on the ground. As a result, resistance to uneven wear can be improved.

In addition, in the pneumatic tire of the present invention, a curved groove is formed with a groove width Wa ranging from 4% to 8% with respect to the size W of the contact portion in the lateral direction of the tire.

When the width Wa of the groove, which is a curved groove, is less than 4% relative to the size W of the contact portion in the lateral direction of the tire, the ability of the curved groove to drain water deteriorates, and its contribution to the braking performance when moving on wet surfaces of roads becomes smaller. On the other hand, when the width Wa of the groove, which is a curved groove, is more than 8% relative to the dimension W of the contact portion in the lateral direction of the tire, the rigidity of the contact portion is reduced, and the positive effect on the uneven wear resistance is reduced. Therefore, in order to provide braking performance when driving on wet surfaces of roads and at the same time increase resistance to uneven wear, a curved groove is formed with a groove width Wa, preferably in the range of 4% to 8%, relative to the size W of the contact portion in the lateral direction of the tire.

In addition, in the pneumatic tire of the present invention, the dimension Wb defined in the tire lateral direction from the axial line of the curved groove to the edge of the portion with bevels in the contact portion is such that it is in a range of 20% to 45% with respect to the size W of the contact portion in the lateral direction of the tire.

When the dimension Wb defined in the lateral direction of the tire from the center line of the curved groove to the edge of the bevel portion in the contact portion is less than 20% with respect to the dimension W of the contact portion in the lateral direction of the tire, the curved groove approaches the bevel portion. As a result, the stiffness of the contact area between the curved groove and the part with bevels decreases, and the positive effect on the resistance to uneven wear decreases. On the other hand, when the dimension Wb defined in the tire lateral direction from the axial line of the curved groove to the edge of the part with bevels in the contact portion is more than 45% with respect to the dimension W of the contact portion in the tire lateral direction, the area for the auxiliary groove is narrowed, and this makes it difficult to ensure the length of the auxiliary groove. As a result, the ability of the auxiliary groove to drain water decreases, and its contribution to the braking characteristic when moving on wet surfaces of roads becomes smaller. Therefore, to ensure braking performance when driving on wet surfaces of roads and at the same time increase resistance to uneven wear, the size Wb, determined in the tire lateral direction from the axial line of the curved groove to the edge of the part with bevels on the contact section, is preferably such that it is in the range from 20% to 45% with respect to the size W of the contact portion in the lateral direction of the tire.

Furthermore, in the pneumatic tire of the present invention, a curved groove is formed with a groove depth On ranging from 30% to 55% with respect to a groove depth H representing the first main groove.

When the depth On the groove, which is a curved groove, is less than 30% relative to the depth H of the groove, which is the first main groove, the ability of the curved groove to drain water decreases, and its contribution to the braking characteristic when moving on wet surfaces of roads becomes less. On the other hand, when the depth of the groove representing the curved groove is more than 55% relative to the depth H of the groove representing the first main groove, the depth of the groove representing the curved groove approaches the depth H of the groove representing the first main groove, and increases the likelihood of damage to the contact area when removing the mold from a curved groove during tire molding. As a result, the positive effect on preventing the appearance defect is reduced. Therefore, in order to provide braking performance when driving on wet surfaces of roads and at the same time prevent appearance defects, a curved groove is formed with a depth of grooves, preferably in the range of 30% to 55%, relative to the depth H of the groove representing the first main groove.

In addition, in the pneumatic tire of the present invention, the bevel portion is formed so that the bevels include long sides and short sides that are inclined with respect to a direction along the circumference of the tire and are formed with triangular shapes at the edge of the inlet portion of the first main groove. The curved groove is formed curved and includes first inclined sections that are long and inclined with respect to the direction along the tire circumference along the long sides of the bevels, and second inclined sections that are short and inclined with respect to the direction along the circumference of the tire along the short sides of the bevels. The angle α of the inclination of the first inclined section relative to the direction along the tire circumference is formed so that it is in the range from 2 ° to 7 °, and the angle β of the inclination of the second inclined section relative to the direction along the tire circumference is formed so that it is in the range from 20 ° to 60 °.

When the inclination angle α of the first inclined section relative to the direction along the tire circumference is less than 2 ° or when the inclination angle β of the second inclined section relative to the direction along the tire circumference is less than 20 °, the direction of the curved groove approaches the direction along the circumference of the tire, and the edge effect from it decreases . As a result, the contribution of the curved groove to the braking characteristic when driving on wet surfaces of roads becomes less. On the other hand, when the inclination angle α of the first inclined section relative to the direction along the tire circumference exceeds 7 ° or when the inclination angle β of the second inclined section relative to the direction along the tire circumference exceeds 60 °, the bending of the curved groove becomes excessive and its angular parts “approach” sharp corners. As a result, the stiffness of the contact section decreases, and the positive effect on the resistance to uneven wear decreases. In addition, when the mold is removed from the curved groove during tire molding, the likelihood of damage to the contact portion increases, as a result of which the positive effect on preventing the appearance defect is reduced. Therefore, in order to increase the resistance to uneven wear and at the same time prevent the appearance defect while providing braking performance when driving on wet roads, it is preferable that the inclination angle α of the first inclined section relative to the direction along the tire circumference be formed so that it is in the range from 2 ° to 7 °, and the angle β of the inclination of the second inclined section relative to the direction along the tire circumference was formed so that it was in the range from 20 ° to 60 °.

In addition, in the pneumatic tire of the present invention, a portion with bevels is formed with a tire size Wc in a tire lateral direction ranging from 4% to 15% with respect to a tire portion W in the tire lateral direction.

When the dimension Wc of the portion with bevels defined in the lateral direction of the tire is less than 4% with respect to the dimension W of the contact portion in the lateral direction of the tire, the water drainage ability of the first main groove decreases and its contribution to the braking performance when driving on wet surfaces of roads becomes smaller . On the other hand, when the dimension Wc of the bevel portion determined in the lateral direction of the tire is more than 15% with respect to the dimension W of the contact portion in the lateral direction of the tire, the bevels are cut at the contact portion to a larger value. As a result, the stiffness of the contact portion decreases, and the positive effect on the resistance to uneven wear decreases. Therefore, to provide braking performance when driving on wet surfaces of roads and at the same time increase resistance to uneven wear, a part with bevels is formed with a size Wc in the lateral direction of the tire, preferably in the range from 4% to 15% relative to the size W of the contact portion in the lateral direction of the tire .

In addition, in the pneumatic tire of the present invention, a portion with bevels is formed with a tire size Hb in the radial direction of the tire, ranging from 30% to 60% with respect to the depth H of the groove representing the first main groove.

When the dimension Hb of the bevel portion, determined in the tire radial direction, is less than 30% with respect to the depth H of the groove representing the first main groove, the ability of the first main groove to drain water decreases, and its contribution to the braking performance when driving on wet surfaces of roads becomes smaller. On the other hand, when the dimension Hb of the bevel portion, determined in the tire radial direction, is more than 60% with respect to the depth H of the groove representing the first main groove, the stiffness of the contact portion decreases and the positive effect on the uneven wear resistance decreases. Therefore, to provide braking performance when driving on wet surfaces of roads and at the same time increase resistance to uneven wear, a part with bevels is formed with a tire size Hb in the radial direction of the tire, preferably in the range from 30% to 60% relative to the depth H of the groove, which is the first major groove.

In addition, in the pneumatic tire of the present invention, in the part in which the bevel portion and the curved groove are opposed to each other in the lateral direction of the tire, the lateral dimension of the bevels Wc in the bevel portion is equal to the lateral range of the tire Wd bending that part of the curved groove, which is located opposite the bevels in the lateral direction of the tire. The dimension La defined in the direction along the tire circumference La of a bevel in a part with bevels is made equal to the size Lb in the direction along the tire circumference, which is the size of one curved unit portion in that part of the curved groove that is opposite one bevel in the lateral direction of the tire.

In a given pneumatic tire, when the tire bevel dimension Wc is equal to the tire lateral direction determined by the tire lateral direction to bend that portion of the curved groove which is opposite the bevel in the tire lateral direction and the La size of one bevel in the circumferential direction of the tire is equal to the direction along the tire circumference to the size Lb of one curved unit portion in that part of the curved groove that is opposite one bevel in the lateral direction of the tire, the shape of the bevel edges s become parallel to the bends of the curved groove, and uniform differences are achieved in the stiffness of the contact portion defined between the bevels and the curved groove defined in the direction along the tire circumference. As a result, a significant positive effect can be achieved on increasing the resistance to uneven wear.

In addition, in the pneumatic tire of the present invention, an auxiliary groove is formed with a tire size We in the tire lateral direction ranging from 40% to 50% with respect to the tire dimension W of the tire lateral direction.

When the size We of the auxiliary groove in the lateral direction of the tire is less than 40% with respect to the size W of the contact portion in the lateral direction of the tire, the ability of the auxiliary groove to drain the water decreases, and its contribution to the braking performance when driving on wet surfaces of roads becomes smaller. On the other hand, when the size We of the auxiliary groove in the lateral direction of the tire is more than 50% relative to the size W of the contact portion in the lateral direction of the tire, the stiffness of the contact portion decreases and the positive effect on the resistance to uneven wear decreases. Therefore, to provide braking performance when driving on wet surfaces of roads and at the same time increase resistance to uneven wear, an auxiliary groove is formed with a size We in the lateral direction of the tire, preferably in the range from 40% to 50% with respect to the size W of the contact portion in the lateral direction of the tire.

In addition, in the pneumatic tire of the present invention, all of the second main grooves are formed on both sides of the first main groove in the lateral direction of the tire, contact portions are formed as a result of their boundaries being formed by the first main groove and each of the second main grooves on both sides of the first main groove in the lateral direction of the tire, and parts with bevels are made on both edges of the input part of the first main groove. Curved grooves are made in each of the contact sections, and auxiliary grooves are made in each of the contact sections. When the pneumatic tire is mounted on a standard rim, inflated to normal internal pressure and loaded with a load of 70% of the normal load, and in a state in which the tread portion is in contact with a flat surface of the ground on the ground, the area of the inlet portion of the groove, which is the first main groove, including parts with bevels, exceeds the area of the inlet part of the groove, which is the first main groove, excluding parts with bevels, by an amount in the range from 15% to 20%.

When the area of the inlet of the groove, which is the first main groove, including parts with bevels, exceeds the area of the inlet of the groove, which is the first main groove, excluding parts with bevels, by less than 15%, the edge effect of the bevels decreases, and their contribution to braking performance when driving on wet surfaces of roads becomes less. On the other hand, when the area of the inlet of the groove, which is the first main groove, including parts with bevels, exceeds the area of the inlet of the groove, which is the first main groove, excluding parts with bevels, by more than 20%, the bevels are cut in the contact areas to larger size. As a result, the stiffness of the contact areas decreases, and the positive effect on the resistance to uneven wear decreases. Therefore, to provide braking performance when driving on wet surfaces of roads and at the same time increase resistance to uneven wear, the area of the inlet part of the groove, which is the first main groove, including parts with bevels, is preferably larger than the area of the inlet part of the groove, which is the first main groove excluding parts with bevels, by a value in the range from 15% to 20%.

In addition, in the pneumatic tire of the present invention, all of the second main grooves are formed on both sides of the first main groove in the lateral direction of the tire, contact portions are formed as a result of their boundaries being formed by the first main groove and each of the second main grooves on both sides of the first main groove in the lateral direction of the tire, and parts with bevels are made on both edges of the input part of the first main groove. Curved grooves are made in each of the contact sections, and auxiliary grooves are made in each of the contact sections. In each of the parts with bevels located on the edges of the inlet part of the first main groove, the bevels are made continuously in the direction along the tire circumference, and the boundary parts in which the bevels are continuous relative to each other are displaced relative to each other in the direction along the tire circumference by each of the edges of the inlet of the first main groove.

When the boundary parts in which the bevels are continuous relative to each other are made aligned with each other in the direction along the tire circumference at each of the edges of the inlet part of the first main groove, the bevels are absent in those parts along the tire circumference in which the borders are aligned relative to each other friend. As a result, the ability to drain water in these parts decreases, and the contribution to the braking performance when driving on wet surfaces of roads becomes smaller, which also causes a decrease in resistance to aquaplaning. Therefore, when performing boundary parts in which the bevels are continuous relative to each other, offset relative to each other in the direction along the tire circumference on each of the edges of the inlet part of the first main groove, the bevels will always be in the direction along the tire circumference. Thus, braking performance can be guaranteed when driving on wet road surfaces.

In addition, in the pneumatic tire of the present invention, the second main grooves are formed on each of the sides of the two first main grooves that are laterally outer of the tire, the contact portions are formed as a result of the formation of their boundaries by the first main grooves and the second main grooves located with those sides of the first main grooves that are laterally outer of the tire, and the parts with bevels are made only at the edges of the input parts on those sides of the first main grooves s are the outer tire in the lateral direction. Curved grooves are made in the contact areas, and auxiliary grooves are made in the contact areas. When the pneumatic tire is mounted on a standard rim, inflated to normal internal pressure and loaded with a load of 70% of the normal load, and in a state in which the tread portion is in contact with a flat surface of the ground on the ground, the area of the entrance parts of the grooves, which are the first main grooves, including parts with bevels, exceeds the area of the input parts of the grooves, which are the first main grooves, excluding parts with bevels, by an amount in the range from 8% to 13%.

When the area of the inlet parts of the grooves, which are the first main grooves, including parts with bevels, exceeds the area of the inlet parts of the grooves, which are the first main grooves, excluding parts with bevels, by less than 8%, the edge effect of the bevels decreases and their contribution to braking performance when driving on wet surfaces of roads becomes less. On the other hand, when the area of the inlet parts of the grooves, which are the first main grooves, including parts with bevels, exceeds the area of the inlet parts of the grooves, which are the first main grooves, excluding parts with bevels, by more than 13%, the bevels are cut at the contact areas to larger size. As a result, the stiffness of the contact areas decreases, and the positive effect on the resistance to uneven wear decreases. Therefore, to provide braking performance when driving on wet surfaces of roads and at the same time increase resistance to uneven wear, the area of the input parts of the grooves, which are the first main grooves, including parts with bevels, preferably exceeds the area of the input parts of the grooves, which are the first main grooves, excluding parts with bevels, by a value in the range from 8% to 13%.

In addition, in the pneumatic tire of the present invention, the hardness of the rubber, which is a rubber material forming the tread surface in the tread portion, is preferably set in the range from 62 to 68 at a temperature of 20 ° C.

When the hardness of the rubber is less than 62, the strength of the rubber decreases, and resistance to uneven wear tends to decrease. On the other hand, when the hardness of the rubber exceeds 68, the flexibility of the rubber decreases, and the braking performance when driving on wet surfaces of roads tends to deteriorate. Thus, the hardness of the rubber, which is a rubber material forming the tread surface, is preferably in the range of 62 to 68.

In addition, in the pneumatic tire of the present invention, tan δ of the rubber material forming the tread surface in the tread portion is preferably set in the range from 0.60 to 0.80 at a temperature of 0 ° C.

When tan δ is less than 0.60, the wet performance, i.e. the braking performance when driving on wet roads, tends to deteriorate. On the other hand, when tan δ exceeds 0.8, the rubber strength decreases, and there is a tendency to increase the likelihood of damage to the contact areas as a result of mold release during tire formation. Thus, the tan δ of the rubber material forming the tread surface is preferably in the range of 0.60 to 0.80 at a temperature of 0 ° C.

In addition, in the pneumatic tire of the present invention in meridional section, the actual profile line on the contact portion, which is formed as a result of the formation of its boundaries by the first main groove and the second main groove, is formed so that it extends further outward in the radial direction of the tire than imagined a profile line that runs through the end of the edge located on the side of the second main groove that is laterally inner of the tire and in contact with the top tread, and each of the ends of the edges, which are located on each side of the first main groove adjacent to the second main groove in the lateral direction of the tire, and are in contact with the tread surface.

In a pneumatic tire of this type, when the actual profile line protrudes further outward in the radial direction of the tire compared to an imaginary profile line in the contact area, the length of the soil contact zone, determined in the direction along the tire circumference, in the soil contact zone can be increased compared with the case which uses an imaginary profile line. In other words, the area of contact with the ground can be increased in the direction along the circumference of the tire. As a result, ground contact is improved, and thus braking performance can be improved when driving on wet road surfaces. In addition, as a result of improved contact with the ground, resistance to uneven wear can be improved.

Preferred Effects of the Invention

The pneumatic tire according to the present invention can provide increased resistance to uneven wear while guaranteeing braking performance when driving on wet surfaces of roads and preventing appearance defects.

Brief Description of the Drawings

1 is a plan view of a tread portion of a pneumatic tire according to a first embodiment of the present invention.

FIGS. 2A and 2B are an enlarged plan view (FIG. 2A) and a sectional view (FIG. 2B) of a portion of a tread portion of a pneumatic tire according to a first embodiment of the present invention.

FIG. 3 is an enlarged plan view of a tread portion of another example of a pneumatic tire according to a first embodiment of the present invention.

FIG. 4 is an enlarged plan view of a tread portion of a pneumatic tire according to a first embodiment of the present invention.

5 is an explanatory diagrammatic view of imaginary profile lines of a tread portion of a pneumatic tire according to a first embodiment of the present invention.

6 is a plan view of a tread portion of a pneumatic tire according to a second embodiment of the present invention.

7A and 7B are an enlarged plan view (FIG. 7A) and a sectional view (FIG. 7B) of a portion of a tread portion of a pneumatic tire according to a second embodiment of the present invention.

FIG. 8 is an enlarged plan view of a tread portion of another example of a pneumatic tire according to a second embodiment of the present invention.

FIG. 9 is an enlarged plan view of a tread portion of a pneumatic tire according to a second embodiment of the present invention.

10 is an explanatory diagrammatic view of imaginary profile lines of a tread portion of a pneumatic tire according to a second embodiment of the present invention.

11 is a table showing test results for determining the performance of pneumatic tires according to the Examples of the present invention.

12 is a table showing test results for determining the performance of pneumatic tires according to Examples of the present invention.

13 is a table showing test results for determining the performance of pneumatic tires according to Examples of the present invention.

14 is a table showing test results for determining the performance of pneumatic tires according to Examples of the present invention.

15 is a table showing test results for determining the performance of pneumatic tires according to Examples of the present invention.

16 is a table showing test results for determining the performance of pneumatic tires according to Examples of the present invention.

Description of Embodiments

Embodiments of the present invention will be described in detail below with reference to the drawings. It should be noted that the present invention is not limited to these embodiments. In addition, components of embodiments include elements that can be replaced and easily made by those skilled in the art, or elements substantially the same as components of embodiments. In addition, the modified examples described in the embodiments may be combined as desired within the scope of obviousness to those skilled in the art.

First Embodiment

Figure 1 is a plan view of the tread portion of a pneumatic tire according to this embodiment. 2A and 2B are an enlarged plan view (FIG. 2A) and a sectional view (FIG. 2B) of a portion of a tread portion of a pneumatic tire according to this embodiment. FIG. 3 is an enlarged plan view of a tread portion of another example of a pneumatic tire according to this embodiment. FIG. 4 is an enlarged plan view of a portion of a tread portion of a pneumatic tire according to this embodiment. 5 is an explanatory diagrammatic view of imaginary profile lines of a tread portion of a pneumatic tire according to this embodiment.

Hereinafter, “tire circumferential direction” refers to the circumferential direction with the rotation axis of the (non-illustrated) pneumatic tire 1 as the central axis. In addition, the "lateral direction of the tire" refers to the direction parallel to the axis of rotation, the "side inner in the lateral direction of the tire" refers to the side closer to the equatorial plane CL of the tire (the equatorial line CL of the tire) in the lateral direction of the tire, and "the side "Outer in the lateral direction of the tire" refers to a side remote from the equatorial plane CL of the tire in the lateral direction of the tire. In addition, the “radial direction of the tire” refers to the direction orthogonal to the axis of rotation, the “side inner in the radial direction of the tire” refers to the side closer to the axis of rotation in the radial direction of width, and the “side outer in the radial direction of the tire” refers to the side remote from the axis of rotation in the radial direction of the tire. An “equatorial plane CL of a tire” is a plane that is orthogonal to the axis of rotation and which passes through the center of the pneumatic tire 1 defined in the tire width direction. An “equatorial tire line” refers to a line that runs along the circumferential direction of the pneumatic tire 1 and lies in the equatorial plane CL of the tire. In this embodiment, the equatorial line of the tire and the equatorial plane of the tire are denoted by the same reference numeral ʺCLʺ.

As illustrated in FIG. 1, the pneumatic tire 1 of this embodiment includes a tread portion 2. The tread portion 2, which is formed of a rubber material, is open from the side farthest from the center in the radial direction of the pneumatic tire 1, and its surface forms the profile of the pneumatic tire 1 as the tread surface 2a.

The tread surface 2a in the tread portion 2 includes a plurality of circumferential main grooves (main grooves) 3 (three in this embodiment) that extend along the tire circumferential direction and are adjacent to each other in the tire lateral direction. In this embodiment, the circumferential main groove 3 located centrally in the lateral direction of the tire is the central main groove (first main groove) 3A, and the circumferential main grooves 3 located on those sides of the central main groove 3A that are laterally outer tires are the main grooves of the 3B shoulder zones (second main grooves). It should be noted that the circumferential groove 3 has a groove width of 5 mm to 20 mm and a groove depth (size from the location of its inlet on the tread surface 2a to the bottom of the groove) of 5 mm to 15 mm.

The Central main groove 3A of the circumferential main grooves 3 is located in contact with the soil, the Central part of the contact zone with the soil. In contact with the soil, the central part is a zone near the equatorial plane CL of the tire. The central main groove 3A, which is the circumferential main groove 3 located in the soil contacting center, in this embodiment, is the circumferential main groove 3 closest to the equatorial plane CL of the tire and is located in the equatorial plane CL of the tire.

It should be noted that the soil contact zone is a zone in which the tread surface 2a in the tread portion 2 of the pneumatic tire 1 comes into contact with a dry and flat road surface when the pneumatic tire 1 is mounted on a standard rim, inflated to normal internal pressure and loaded with a load of 70% of the normal load. In this case, “standard rim” refers to the “standard rim” defined by the Japan Automobile Tire Manufacturers Association (JATMA), the “design rim” defined by the Tire and Rim Association (TRA), or the “measuring wheel” defined by the European Technical Organization for tires and rims (ETRTO). In addition, “normal internal pressure” refers to the “maximum air pressure” defined by JATMA, to the maximum value given in “Tire load limits at various cold inflation pressures” defined by TRA, or “Inflation pressures” defined by ETRTO . In addition, “normal load” refers to the “maximum load capacity” defined by JATMA, the maximum value given in the “Tire load limits at various cold inflation pressures” defined by TRA, and the “Load capacity” defined by ETRTO.

The tread surface 2a in the tread portion 2 includes a plurality of contact portions 4 (four in this embodiment) formed by forming their boundaries by circumferential main grooves 3 in the lateral direction of the tire. Moreover, in this embodiment, two rib-shaped contact sections 4, which are formed as a result of the formation of their boundaries by the Central main groove 3A and each of the main grooves 3B of the shoulder areas located on both sides of the Central main groove 3A, which are external in the lateral direction of the tire are the central contact areas 4A. In addition, all rib-shaped contact sections 4, which are located on the side of each of the main grooves 3B of the shoulder zones, external in the lateral direction of the tire, are contact sections 4B of the shoulder zones.

In such a pneumatic tire 1, the central main groove 3A is made with bevels 5 that are located on the edges of the inlet part of the central main groove 3A at the central contact portions 4A located on the side of the main grooves 3B of the shoulder zones. In the bevelled parts 5, a plurality of bevels 5A, which provide a change in the position of the edges of the inlet part in a diagonal direction with respect to the direction along the tire circumference, are located along the direction along the tire circumference. Since the central main groove 3A of this embodiment is made together with the main grooves 3B of the shoulder regions on its both sides, laterally facing the tire, and also with the central contact sections 4A on its both sides, the lateral direction of the tire, part 5 with bevels made on the edges of the inlet on both sides of the central main groove 3A. As illustrated in FIG. 2B, the bevels 5A are formed by cutting — with a triangular shape — the angular portions of the edges of the inlet portion of the central main groove 3A on the tread surface 2a in the central contact portions 4A, and, as illustrated in FIGS. 2A and 3, 5A are formed as triangular recessed parts in a plan view. In particular, each of the bevels 5A is formed with a triangular shape at the edges of the inlet portion of the central main groove 3A, with each of the bevels including a long side 5a and a short side 5b, which have lengths that are different from each other, and which have a slope relative to directions along the circumference of the tire. It should be noted that despite the fact that this is not illustrated in the drawings, each of the bevels 5A can be formed with a triangular shape at the edges of the inlet part of the central main groove 3A, while each of them will include two sides that have the same length and which are inclined relative to the direction along the circumference of the tire. Therefore, thanks to the bevelled parts 5, the central main groove 3A includes edge parts that are inclined with respect to the direction along the tire circumference. Since in this case each of the parts 5 with bevels, which are made on the edges of the inlet part of the central main groove 3A on its both sides in the lateral direction of the tire, is made with bevels 5A that are “inverted” with respect to each other, the input part of the central main groove 3A it is formed with a zigzag shape in which the “lightning” configurations are formed continuously as a result of “bending” of straight lines many times along the direction along the tire circumference. In addition, as illustrated in FIG. 2A, the bevels 5A can be made continuously in the tire circumferential direction, or, as illustrated in FIG. 3, the bevels 5A can be made at intervals 5B in the tire circumferential direction.

In addition, in the pneumatic tire 1 of this embodiment, curved grooves 6 and auxiliary grooves 7 are formed in the central contact portions 4, which are formed as a result of their boundaries being formed by the central main groove 3A and the main shoulder grooves 3B.

Curved grooves 6 are located side by side - in the lateral direction of the tire - with the edges of the input part of the Central main groove 3A, including parts 5 with bevels, and made so that they extend along the direction along the circumference of the tire. The curved grooves 6 are formed curved by means of slopes corresponding to the shapes of the bevels 5A of the bevelled parts 5. In particular, as illustrated in FIGS. 2A and 3, curved grooves 6 are formed curved so that they include first inclined portions 6a that are long and inclined relative to the tire circumferential direction along the long sides 5a of bevels 5A, and the second inclined portions 6b, which are short and inclined relative to the tire circumferential direction along the short sides 5b of the bevels 5A. Since in this case the curved grooves 6 are made along the direction along the tire circumference in accordance with the triangular shapes of the bevels 5A, each of the curved grooves 6 will be formed with a zigzag shape in which the “lightning” configurations are formed as a result of “bending” the straight lines many times along the direction along the circumference of the tire. It should be noted that since in the pneumatic tire 1 illustrated in FIG. 3, the bevels 5A are spaced at intervals 5B in the direction along the tire circumference at the edges of the inlet portion of the central main groove 3A extending in the direction along the tire circumference, the curved grooves 6 include intermediate sections 6c which are not inclined and which extend in the direction along the tire circumference. The central contact portions 4A are divided by these curved grooves 6 into the first central contact portions 4Aa located on the side of the central main groove 3A and the second central contact portions 4Ab located on the side of the main shoulder grooves 3B. It should be noted that the curved groove 6 has a groove width that is 1.5 mm or more and which is less than the width of the circumferential main groove 3, and a depth of the groove that is less than the depth of the circumferential main groove 3.

Auxiliary grooves 7 are made between the main grooves 3B of the shoulder zones and curved grooves 6 and are formed so that they intersect with the direction along the circumference of the tire. As illustrated in FIGS. 2A and 3, the first ends 7a of the auxiliary grooves 7 extend towards the curved grooves 6 and are made to terminate inside the central contact portions 4A (second central contact portions 4Ab), so that between the first ends 7a and the curved grooves 6 a gap is provided. In particular, the first ends 7a of the auxiliary grooves 7 are made oriented towards the second inclined portions 6b, which are short and strongly curved sections of the curved grooves 6. In addition, the second ends 7b of the auxiliary grooves 7 extend towards the main grooves 3B of the shoulder zones and made communicating with the main grooves 3B of the shoulder zones. It should be noted that although this is not illustrated in the drawings, the second ends 7b of the auxiliary grooves 7 can be made terminating inside the central contact portions 4A (second central contact portions 4Ab), so that between the second ends 7b and the main grooves 3B of the shoulder zones a gap will be provided. It should be noted that the auxiliary groove 7 has a groove width that is 1.5 mm or more and which is less than the width of the circumferential main groove 3, and a groove depth that is less than the depth of the circumferential main groove 3.

Thus, the pneumatic tire 1 according to this embodiment includes: a central main groove (first main groove) 3A, which is made in contact with the soil, the Central part of the tread portion 2 so that it runs along the direction along the circumference of the tire; main shoulder grooves 3B (second main grooves), which are formed on the sides of the central main groove 3A, external in the lateral direction of the tire, so that they extend along the direction along the circumference of the tire; central contact portions 4A that are formed by forming their boundaries by the central main groove 3A and the main shoulder grooves 3B and which are formed continuous along the tire circumference; parts 5 with bevels in which a plurality of bevels 5A are arranged in the direction along the tire circumference, while a plurality of bevels 5A are made on the edges of the inlet part of the central main groove 3A from the side of the central contact sections 4A and provide a diagonal change in the position of the edges of the inlet part relative to tire circumference; curved grooves 6, which are made on the central contact sections 4A, are located next to the tire sideways with the edges of the inlet part of the central main groove 3A, including parts 5 with bevels, and are made curved in accordance with the shapes of bevels 5A of parts 5 with bevels and extend in the direction along the tire circumference, and auxiliary grooves 7, which are made in the central contact portions 4A between the main shoulder grooves 3B and the curved grooves 6, and which extend towards the curved channel vkam 6 in a direction intersecting with the tire circumferential direction, wherein the first ends 7a are oriented toward the curved grooves 6 and terminate within the central land portions 4A.

In this pneumatic tire 1, the edge components of the tire contact surface are provided by means of curved grooves 6, and therefore braking performance is provided when driving on wet surfaces of roads, i.e., tire performance when driving on wet roads. In addition, when making the curved grooves 6 curved in accordance with the shapes of the bevels 5A of the parts 5 with bevels made on the edges of the inlet part of the central main groove 3A, as well as when making the auxiliary grooves 7 with the first ends 7a, which are oriented towards the curved grooves 6 and complete inside the central contact sections 4A, when removing the mold from the curved grooves 6 during tire molding, the curved grooves 6 expand as a result of deformation of the central contact sections 4A (first the central contact portions 4Aa, the second central contact portions 4Ab), which include the curved grooves 6, towards the side of the bevelled parts 5 and to the side of the auxiliary grooves 7. As a result, the mold release ability is improved, and this prevents the situation, in which the central contact portion 4A is damaged during release of the mold, and therefore can prevent the appearance of a defect in appearance. In addition, when making the curved grooves 6 curved in accordance with the shapes of the bevels 5A of the parts 5 with bevels made on the edges of the inlet part of the central main groove 3A, as well as when making the auxiliary grooves 7 with the first ends 7a oriented towards the curved grooves 6 and ending inside the central contact portions 4A, the differences in stiffness at the central contact portions 4A including the curved grooves 6 are reduced, thereby ensuring uniform contact contact of pressure on the ground. As a result, resistance to uneven wear can be improved.

In addition, as illustrated in FIGS. 2A and 3, in the pneumatic tire 1 of this embodiment, the curved groove 6 is formed with a groove width Wa (groove width of the inlet portion Wa), preferably in the range of 4% to 8% with respect to size W of the central contact portion 4A in the lateral direction of the tire.

When the width Wa of the groove, which is the curved groove 6, is less than 4% with respect to the lateral dimension of the tire W of the central contact portion 4A, the ability of the curved groove 6 to drain water is impaired, and its contribution to the braking performance when driving on wet surfaces of roads becomes smaller . On the other hand, when the width Wa of the groove, which is the curved groove 6, is more than 8% relative to the size W of the central contact portion 4A in the lateral direction of the tire, the stiffness of the central contact portions 4A decreases and the positive effect on the uneven wear resistance decreases. Therefore, to provide braking performance when driving on wet surfaces of roads and at the same time increase resistance to uneven wear, the curved groove 6 is formed with a groove width Wa, preferably in the range of 4% to 8%, relative to the size W of the central contact portion 4A in the tire lateral direction. It should be noted that in order to provide a significant positive effect both on guaranteeing the braking performance when driving on wet surfaces of roads, and on increasing the resistance to uneven wear, the width Wa of the groove, which is a curved groove 6, is preferably made so that it is in the range from 5% to 7% with respect to the size W of the central contact portion 4A in the tire lateral direction.

In addition, as illustrated in FIGS. 2A and 3, in the pneumatic tire 1 of this embodiment, the dimension Wb defined in the tire lateral direction from the axial line S of the curved groove 6 to the edge 5c of part 5 with bevels in the central contact portion 4A, preferably configured to be in the range of 20% to 45% with respect to the size W of the central contact portion 4A in the tire lateral direction.

The center line S of the curved groove 6 is a straight line passing through the center of the width Wa of the groove, which is the curved groove 6. The edge 5c of part 5 with bevels in the central contact portion 4A is the edge of the part of the tread surface 2a in the central contact portion 4A, and the bevel 5A of part 5 with bevels is cut to the greatest extent at the edge 5c.

When the dimension Wb defined laterally of the tire from the center line S of the curved groove 6 to the edge 5c of part 5 with bevels in the central contact portion 4A is less than 20% with respect to the dimension W of the central contact portion 4A in the lateral direction of the tire, the curved grooves 6 approach parts 5 with bevels. As a result, the stiffness of the central contact portions 4A between the curved grooves 6 and the bevelled parts 5 is reduced, and the positive effect on the uneven wear resistance is reduced. On the other hand, when the dimension Wb, determined laterally of the tire from the center line S of the curved groove 6 to the edge 5c of part 5 with bevels in the central contact portion 4A, is more than 45% relative to the dimension W of the central contact portion 4A in the lateral direction of the tire, areas for the placement of auxiliary grooves 7, and this makes it difficult to ensure the length of the auxiliary grooves 7. As a result, the ability of the auxiliary grooves 7 to drain water and their contribution to the braking performance when driving on a wet track are reduced ited road becomes smaller. Therefore, to ensure braking performance when driving on wet surfaces of roads and at the same time increase resistance to uneven wear, the dimension Wb defined in the tire lateral direction from the axial line S of the curved groove 6 to the edge 5c of part 5 with bevels on the central contact portion 4A is preferably made so that it is in the range from 20% to 45% relative to the size W of the Central contact portion 4A in the lateral direction of the tire. It should be noted that in order to provide a significant positive effect both on guaranteeing the braking performance when driving on wet surfaces of roads, and on increasing the resistance to uneven wear, the size Wb determined in the lateral direction of the tire from the center line S of the curved groove 6 to the edge 5c of part 5 with bevels on the central contact portion 4A, is preferably configured to be in a range of 25% to 35% with respect to the size W of the central contact portion 4A in the tire lateral direction.

In addition, as illustrated in FIG. 2B, in the pneumatic tire 1 of this embodiment, a curved groove 6 is formed with a groove depth On, preferably in the range of 30% to 55%, relative to the groove depth H, which is the central main groove 3A.

When the depth On the grooves, which is the curved groove 6, is less than 30% relative to the depth H of the grooves, which is the central main groove 3A, the ability of the curved grooves 6 to drain water decreases, and their contribution to the braking characteristic when moving on wet surfaces of roads becomes less . On the other hand, when the depth H of the groove representing the curved groove 6 is more than 55% with respect to the depth H of the groove representing the central main groove 3A, the depth H of the groove representing the curved groove 6 approaches the depth H of the groove representing the central the main groove 3A, and the likelihood of damage to the central contact portions 4A increases when the mold is removed from the curved grooves 6 during tire molding, thereby reducing the effect of preventing I have a defect in appearance. Therefore, to provide braking performance when driving on wet surfaces of roads and at the same time prevent appearance defects, a curved groove 6 is formed with a depth On grooves, preferably in the range of 30% to 55%, relative to the depth H of the groove, which is the central main groove 3A. It should be noted that to ensure a significant positive effect both on guaranteeing braking performance when driving on wet surfaces of roads, and on preventing a defect in appearance, the depth of the groove, which is a curved groove 6, is preferably made so that it is in the range from 35 % to 50% relative to the depth H of the groove, which is the Central main groove 3A.

In addition, as illustrated in FIGS. 2A and 3, in the pneumatic tire 1 of this embodiment, it is preferable that the bevel parts 5 are formed so that the bevels 5A are formed with triangular shapes at the edges of the inlet portion of the central main groove 3A and include long sides 5a and short sides 5b that are inclined with respect to the tire circumferential direction so that the curved grooves 6 are formed curved and include first inclined sections 6a that are long and inclined it is relative to the tire circumferential direction along the long sides 5a of the bevels 5A, and the second inclined sections 6b which are short and inclined with respect to the tire circumferential direction along the short sides 5b of the bevels 5A, so that the inclination angle α of the first inclined portion 6a with respect to the tire circumferential direction was formed so that it was in the range from 2 ° to 7 °, and so that the inclination angle β of the second inclined portion 6b with respect to the direction along the tire circumference was formed so that it was in range from 20 ° to 60 °.

When the inclination angle α of the first inclined portion 6a with respect to the tire circumferential direction is less than 2 ° or when the inclination angle β of the second inclined portion 6b with respect to the tire circumferential direction is less than 20 °, the direction of the curved grooves 6 approaches the direction along the circumference of the tire, and the edge effect from them decreases. As a result, the contribution of the curved groove 6 to the braking characteristic when driving on wet road surfaces becomes less. On the other hand, when the inclination angle α of the first inclined section 6a relative to the tire circumferential direction exceeds 7 ° or when the inclination angle β of the second inclined section 6b relative to the tire circumferential direction exceeds 60 °, the bending of the curved grooves 6 becomes excessive, and their angular parts " approaching ”to sharp corners. As a result, the stiffness of the central contact portions 4A is reduced, and the positive effect on the uneven wear resistance is reduced. In addition, when the mold is removed from the curved grooves 6 during tire molding, the likelihood of damage to the central contact portions 4A increases, as a result of which the positive effect on preventing the appearance defect is reduced. Therefore, in order to increase the resistance to uneven wear and at the same time prevent the appearance defect while providing braking performance when driving on wet surfaces of roads, it is preferable that the inclination angle α of the first inclined section 6a relative to the direction along the tire circumference be formed so that it is in the range from 2 ° to 7 °, and the angle β of the inclination of the second inclined portion 6b relative to the direction along the tire circumference was formed so that it was in the range from 20 ° to 60 °. It should be noted that in order to provide a significant positive effect on increasing the resistance to uneven wear, guaranteeing braking performance when driving on wet surfaces of the roads and preventing a defect in appearance, it is preferable that the inclination angle α of the first inclined section 6a relative to the direction along the tire circumference is formed so that it is in the range from 3 ° to 5 °, and so that the inclination angle β of the second inclined portion 6b with respect to the direction along the tire circumference is formed Kim so that it is in the range from 30 ° to 45 °.

In addition, as illustrated in FIG. 2A and FIG. 3, in the pneumatic tire 1 of this embodiment, the bevel portion 5 is formed with a tire size Wc in the lateral direction of the tire, preferably in the range of 4% to 15% with respect to the size W of the central contact section 4A in the lateral direction of the tire.

When the dimension Wc of the bevel portion 5, determined in the lateral direction of the tire, is less than 4% with respect to the dimension W of the central contact portion 4A in the lateral direction of the tire, the ability of the central main groove 3A to drain water decreases and its contribution to the braking performance when driving on wet road surfaces are getting smaller. On the other hand, when the dimension Wc of the bevel portion 5, determined in the lateral direction of the tire, is more than 15% with respect to the dimension W of the central contact portion 4A in the lateral direction of the tire, the bevels 5A are cut off at the central contact portions 4A to a larger size. As a result, the stiffness of the central contact portions 4A decreases, and the positive effect on the uneven wear resistance decreases. Therefore, to provide braking performance when driving on wet surfaces of roads and at the same time increase resistance to uneven wear, the bevelled part 5 is formed with a tire size Wc in the lateral direction of the tire, preferably in the range from 4% to 15% relative to the size W of the central contact portion 4A in lateral direction of the tire. It should be noted that in order to provide a significant positive effect both on guaranteeing the braking performance when driving on wet surfaces of roads, and on increasing the resistance to uneven wear, the dimension Wc of the portion 5 with bevels, determined in the lateral direction of the tire, is preferably made so that it is in the range of 6% to 8% relative to the size W of the central contact portion 4A in the lateral direction of the tire

In addition, as illustrated in FIG. 2B, in the pneumatic tire 1 of this embodiment, the bevel portion 5 is formed with a dimension Hb in the radial direction of the tire, preferably in the range of 30% to 60% with respect to the depth H of the groove representing the central main groove 3A.

When the dimension Hb of the bevel portion 5, determined in the tire radial direction, is less than 30% with respect to the depth H of the groove representing the central main groove 3A, the ability of the central main groove 3A to drain water decreases and its contribution to the braking performance when driving on wet road surfaces are getting smaller. On the other hand, when the dimension Hb of the bevel portion 5, determined in the tire radial direction, is more than 60% with respect to the groove depth H, which is the central main groove 3A, the stiffness of the central contact portions 4A decreases and the positive effect on the uneven wear resistance decreases . Therefore, to provide braking performance when driving on wet surfaces of roads and at the same time increase resistance to uneven wear, the bevelled part 5 is formed with a tire size Hb in the radial direction of the tire, preferably in the range from 30% to 60% relative to the depth H of the groove, which is the central main groove 3A. It should be noted that in order to provide a significant positive effect both on guaranteeing the braking performance when driving on wet surfaces of roads, and on increasing the resistance to uneven wear, the dimension Hb of the part 5 with bevels, determined in the radial direction of the tire, is preferably made so that it is in the range of 40% to 55% with respect to the depth H of the groove, which is the central main groove 3A.

In addition, as illustrated in FIGS. 2A and 3, in the pneumatic tire 1 of this embodiment, in parts in which the beveled parts 5 and the curved grooves 6 are located opposite each other in the tire lateral direction, it is preferable that it is defined laterally to the tire direction, the dimension Wc of the bevel 5A was equal to the laterally determined tire range Wd of that portion of the curved groove 6 which is opposite the bevel 5A in the lateral direction of the tire, and that the dimension La determined in the direction along the circumference of the tire is one The fifth bevel 5A in the bevel portion 5 was made equal to the size Lb in the direction along the tire circumference, which is the size of one curved unit portion in that part of the curved groove 6 which is opposite one bevel 5A in the lateral direction of the tire.

In this pneumatic tire 1, when the dimension Wc of the bevel 5A in the tire lateral direction is equal to the tire lateral direction Wd determined in the tire lateral direction of the portion of the curved groove 6 that is opposite the bevel 5A in the tire lateral direction, and the dimension La of the bevel 5A in the circumferential direction of the tire equal to the dimension Lb determined in the direction along the tire circumference in one curved unit portion in that part of the curved groove 6, which is opposite the bevel 5A in the lateral direction of the tire, the shape of the edges of the bevels 5A become parallel to the bends of the curved grooves 6, and uniform differences are achieved in the stiffness determined along the tire circumference of the central contact portions 4A located between the bevels 5A and the curved grooves 6. As a result, a significant positive effect can be achieved on increasing the resistance to uneven wear.

In addition, as illustrated in FIGS. 2A and 3, in the pneumatic tire 1 of this embodiment, the auxiliary groove 7 is formed with a tire size We in the tire lateral direction, preferably in a range of 40% to 50% with respect to the size W of the central contact portion 4A in the lateral direction of the tire.

The dimension We of the auxiliary groove 7 in the lateral direction of the tire is the lateral dimension of the tire obtained by projecting the auxiliary groove 7 in the tire circumferential direction.

When the size We of the auxiliary groove 7 in the lateral direction of the tire is less than 40% with respect to the size W of the central contact portion 4A in the lateral direction of the tire, the ability of the auxiliary groove 7 to drain the water decreases, and its contribution to the braking performance when driving on wet surfaces of roads becomes smaller. On the other hand, when the size We of the auxiliary groove 7 in the lateral direction of the tire is more than 50% with respect to the size W of the central contact portion 4A in the lateral direction of the tire, the stiffness of the central contact portions 4A decreases and the positive effect on the uneven wear resistance decreases. Therefore, to provide braking performance when driving on wet surfaces of roads and at the same time increase resistance to uneven wear, the auxiliary groove 7 is formed with a size We in the lateral direction of the tire, preferably in the range from 40% to 50% with respect to the size W of the central contact portion 4A in the lateral tire direction. It should be noted that in order to provide a significant positive effect both on guaranteeing the braking performance when driving on wet surfaces of roads, and on increasing the resistance to uneven wear, the size We of the auxiliary groove 7 in the tire lateral direction is preferably such that it is in the range from 43 % to 46% relative to the size W of the central contact portion 4A in the lateral direction of the tire.

In addition, as illustrated in FIG. 2A and FIG. 3, in the pneumatic tire 1 of this embodiment, the auxiliary groove 7 is preferably formed so that the shortest gap size Wf between the end portion of the auxiliary groove 7, oriented toward the curved groove 6, and the curved groove 6 is made so that it is in the range from 7% to 20% relative to the size W of the Central contact portion 4A in the lateral direction of the tire.

When the shortest gap size Wf between the end portion of the auxiliary groove 7 oriented toward the curved groove 6 and the curved groove 6 is less than 7% with respect to the tire dimension W of the central contact portion 4A in the lateral direction of the tire, the stiffness of the central contact portions 4A decreases and the positive the effect on resistance to uneven wear is reduced. On the other hand, when the shortest gap size Wf between the end portion of the auxiliary groove 7 oriented toward the curved groove 6 and the curved groove 6 is more than 20% with respect to the tire dimension W of the central contact portion 4A in the lateral direction of the tire, the stiffness of the central contact portions 4A increases. As a result, when removing the mold from the curved grooves 6 during tire molding, the likelihood of damage to the central contact portions 4A increases, which reduces the positive effect on preventing appearance defect. Therefore, in order to prevent a defect in appearance and at the same time increase resistance to uneven wear, the shortest gap size Wf between the end portion of the auxiliary groove 7 oriented toward the curved groove 6 and the curved groove 6 is preferably such that it is in the range of 7% up to 20% with respect to the size W of the central contact portion 4A in the lateral direction of the tire. It should be noted that in order to provide a significant positive effect both on preventing the appearance defect and increasing the resistance to uneven wear, the shortest gap size Wf between the end portion of the auxiliary groove 7, oriented towards the curved groove 6, and the curved groove 6 is preferably made so that it is in the range from 10% to 15% relative to the size W of the Central contact section 4A in the lateral direction of the tire. It should be noted that to ensure the same effects, the shortest gap size Wf between the end portion of the auxiliary groove 7, oriented towards the curved groove 6, and the curved groove 6 is preferably such that it is in the range from 2 mm to 5 mm, and more preferably configured to be in the range of 3 mm to 4 mm.

In addition, as illustrated in FIGS. 1-3, in the pneumatic tire 1 of this embodiment, the main grooves 3B of the shoulder regions are formed on each side of the central main groove 3A that are laterally external to the tire, the central contact portions 4A are formed as a result of their formation boundaries through the Central main groove 3A and the main grooves 3B of the shoulder areas on both sides of the Central main groove 3A, external in the lateral direction of the tire, part 5 with bevels are made on both edges of the input part of the central main groove 3A, curved grooves 6 are made on each of the central contact sections 4A, and auxiliary grooves 7 are made on each of the central contact sections 7. When the pneumatic tire 1 is mounted on a standard rim, it is inflated to normal internal pressure and loaded with a load component 70% of the normal load, and in a state in which the tread portion 2 is in contact with a flat surface of the ground on the ground, the area of the inlet portion of the groove, which is the central main 3A avku including part 5 with bevels preferably exceeds the area of the inlet portion of the groove, which is the central main groove 3A, except portion 5 with bevels, by an amount in the range of 15% to 20%.

When the area of the inlet of the groove, which is the central main groove 3A, including parts with bevels 5, exceeds the area of the inlet of the groove, which is the central main groove 3A, excluding parts 5 with bevels, by less than 15%, the edge effect of the bevels 5A decreases , and their contribution to the braking performance when driving on wet surfaces of roads becomes smaller. On the other hand, when the area of the inlet part of the groove representing the central main groove 3A, including parts 5 with bevels, exceeds the area of the inlet part of the groove representing the central main groove 3A, excluding parts 5 with bevels, by more than 20%, the bevels 5A cut off in the central contact areas 4A to a larger value. As a result, the stiffness of the central contact portions 4A decreases, and the positive effect on the uneven wear resistance decreases. Therefore, to ensure braking performance when driving on wet surfaces of roads and at the same time increase resistance to uneven wear, the area of the inlet part of the groove, which is the central main groove 3A, including parts 5 with bevels, is preferably formed larger than the area of the inlet part of the groove, which is the central the main groove 3A, excluding parts 5 with bevels, by a value in the range from 15% to 20%. It should be noted that to ensure a significant positive effect both on guaranteeing braking performance when driving on wet surfaces of roads, and on increasing resistance to uneven wear, the area of the inlet part of the groove, which is the central main groove 3A, including parts 5 with bevels, is preferably formed larger than the area of the inlet part of the groove, which is the Central main groove 3A, excluding parts 5 with bevels, by an amount in the range from 17% to 19%.

In addition, as illustrated in FIG. 2A, in the pneumatic tire 1 of this embodiment, the main grooves 3B of the shoulder regions are formed on each side of the central main groove 3A that are laterally outside the tire, the central contact portions 4A are formed by forming their boundaries by the central main groove 3A and the main grooves 3B of the shoulder areas on both sides of the central main groove 3A, external in the lateral direction of the tire, parts 5 with bevels are made on both edges of the input part of the central main grooves 3A, curved grooves 6 are made in each of the central contact portions 4A, and auxiliary grooves 7 are made in each of the central contact portions 4A. In such a pneumatic tire 1, it is preferable that in each of the parts 5 with bevels made on both edges of the inlet part of the central main groove 3A, the bevels 5A are made continuously in the direction along the tire circumference, and the boundary parts A on which the bevels 5A are continuous relative to each other, were performed with offset relative to each other in the direction along the circumference of the tire at each of the edges of the input part of the Central main groove 3A.

When the boundary parts A, in which the bevels 5A are provided with respect to each other, are made aligned with each other in the tire circumferential direction at each of the edges of the inlet part of the central main groove 3A, the bevels 5A are absent in those parts in the tire circumferential direction in which the boundary parts A are aligned with each other. As a result, the ability to drain water in these parts decreases, and the contribution to the braking performance when driving on wet surfaces of roads becomes smaller, which also causes a decrease in resistance to aquaplaning. Therefore, when performing boundary parts A in which the bevels 5A are continuous relative to each other, offset relative to each other in the direction along the tire circumference at each of the edges of the inlet part of the central main groove 3A, the bevels 5A will always be in the direction along the tire circumference, and therefore, braking performance can be guaranteed when driving on wet roads.

Meanwhile, in this embodiment, a circumferential narrow groove 8 is formed at each of the shoulder region contact sections 4B, which extends in the direction along the tire circumference along each of the main shoulder regions grooves 3B. Each of the shoulder portions 4B of the shoulder zones is divided by this circumferential narrow groove 8 into a first shoulder portion 4Ba located on the side of the main shoulder groove 3B and a second shoulder portion 4Bb located on the side that is most distant from the center in the tire lateral direction . It should be noted that the circumferential narrow groove 8 has a groove width that is 1.5 mm or more and which is less than the width of the circumferential main groove 3, and a groove depth that is less than the depth of the circumferential main groove 3.

In addition, in each of the shoulder region contact portions 4B, auxiliary grooves 9 of the shoulder regions are formed which intersect with the direction along the tire circumference in the second shoulder region 4Bb of the shoulder region. The first ends of the auxiliary grooves 9 of the shoulder regions extend through the circumferential main groove 8 and terminate within the first shoulder portion 4Ba of the shoulder region. The second ends of the auxiliary grooves 9 of the shoulder zones are made extending towards the outer side of the tread surface 2a in the lateral direction of the tire. It should be noted that the auxiliary groove 9 of the shoulder region has a groove width that is 1.5 mm or more and which is less than the width of the circumferential main groove 3, and a groove depth that is less than the depth of the circumferential main groove 3.

In addition, narrow shoulder grooves 10 are formed in each of the shoulder region contact portions 4B, which intersect with the tire circumferential direction in the second shoulder region 4Bb of the shoulder region. The first ends of the narrow grooves 10 of the shoulder zones communicate with the circumferential narrow groove 8, and the second ends of the narrow grooves 10 of the shoulder zones are made extending towards the outer side of the tread surface 2a in the lateral direction of the tire. It should be noted that the narrow groove 10 of the shoulder region is formed like a so-called siped drainage groove with a width in the range from 0.4 mm to 1.2 mm.

Meanwhile, as illustrated in FIGS. 4 and 5, in the pneumatic tire 1 of this embodiment, in the meridional section, the actual profile line LB on each of the central contact portions 4A, which are formed as a result of the formation of their boundaries by the central main groove 3A and the main grooves 3B of the shoulder zones, preferably formed so that it protrudes further outward in the radial direction of the tire than the imaginary line LA of the profile, which passes through the ends 3BA of the edges located on those sides explicit shoulder grooves 3B that are laterally inner of the tire and in contact with the tread surface 2a, and each of the ends 3Aa and 3Aa of the edges located on both sides of the central main groove 3A adjacent to the main shoulder grooves 3B in the lateral the direction of the tire, and being in contact with the tread surface 2a.

As described above, in the meridional section, the imaginary profile line LA is an arc that extends through the ends 3Ba of the edges located on those sides of the main grooves 3B of the shoulder zones that are inner in the lateral direction of the tire and in contact with the tread surface 2a, and each of the ends 3Aa and 3Aa of the edges located on both sides of the central main groove 3A adjacent to the main grooves 3B of the shoulder areas in the lateral direction of the tire and in contact with the tread surface 2a, and which has a radius of curvature, the center of which is located on the inner side of the tread surface 2a in the radial direction of the tire. In addition, the imaginary profile line LA may have a center point in the equatorial plane CL of the tire. In addition, the actual profile line LB is an arc that extends through the ends 3Ba of the edges located on those sides of the main shoulder grooves 3B that are laterally internal to the tire and in contact with the tread surface 2a, and the ends 3Aa of the edges, located on that side of the central main groove 3A adjacent to the main grooves 3B of the shoulder areas, which is facing the main groove 3B of the shoulder area, and in contact with the tread surface 2a, and which has a central point, aspolozhennuyu inner side surface 2a of the tread in the tire radial direction.

In a pneumatic tire 1 of this type, when the actual line LB of the profile protrudes further outward in the radial direction of the tire compared to the imaginary line LA of the profile in the central contact portions 4A, the length of the soil contact zone, determined in the direction along the tire circumference, in the soil contact zone can be enlarged compared to the case in which an imaginary line LA profile is used. In other words, the area of contact with the ground can be increased in the direction along the circumference of the tire. As a result, ground contact is improved, and thus braking performance can be improved when driving on wet road surfaces. In addition, as a result of improved contact with the ground, resistance to uneven wear can be improved. Furthermore, when the actual profile line LB extends further outward in the tire radial direction as compared to the imaginary profile line LA on the central contact portions 4A formed on both sides in the tire side direction with the tire equatorial plane CL located therebetween, the above-described effects may be received to a large extent.

In addition, when the pneumatic tire 1 is mounted on a standard rim, inflated to normal internal pressure and loaded with a load of 70% of the normal load, the maximum protrusion value Ga of the actual profile line LB in the central contact portions 4A, which protrudes further outward in the radial direction tires than an imaginary line LA profile, preferably from 0.1 mm to 0.5 mm.

When the maximum protrusion value Ga in the central contact portions 4A is less than 0.1 mm, the protrusion of the central contact portions 4A is reduced, and improvement in ground contact is difficult. On the other hand, when the maximum protrusion value Ga at the central contact portions 4A exceeds 0.5 mm, the protrusion degree of the central contact portions 4A becomes excessive, and the length of the ground contact zone in the central part of the contact portions is excessively increased. This causes uneven wear of a type in which the central part of the contact areas wears out at an early stage. Thus, both to improve the braking performance when driving on wet surfaces of roads, and to increase the resistance to uneven wear, in the central contact portions 4A, the maximum value of the outward radial outward direction Ga of the tire is preferably from 0.1 mm to 0.5 mm .

It should be noted that, as illustrated in FIG. 5, in the pneumatic tire 1 of this embodiment, in the meridional section of the profile line of the shoulder portions 4B of the shoulder regions formed on those sides of the main grooves 3B of the shoulder regions that are laterally external to the tire, preferably formed on an imaginary profile line LA 'and coincide with an imaginary profile line LA', which passes through the edges T of the ground contact zone and the ends 3BA and 3Bb of the edges located on both sides of the main grooves 3B of the shoulder zones in the lateral direction of the tire and in contact with the tread surface 2a, and which is continuous with an imaginary profile line LA. In other words, the contact portions that protrude further outward in the tire radial direction than the imaginary profile line LA are only the central contact portions 4A that are closer to the equatorial plane CL of the tire than the main shoulder grooves 3B. When making curved grooves 6 extending in a circumferential direction on the central contact portions 4A, which are formed as a result of their boundaries being formed by the central main groove 3A and the main shoulder grooves 3B, there is a tendency to decrease ground contact in the central zone of each central contact areas 4A. In addition, the central contact sections 4A, made closer to the equatorial plane CL of the tire, are characterized by a tendency to have lower contact pressure on the ground compared with the contact sections 4B of the shoulder zones. Accordingly, the contact portions that protrude further outward in the tire radial direction than the imaginary profile line LA are preferably only the central contact portions 4A that are closer to the equatorial plane CL of the tire than the main shoulder grooves 3B.

In this case, “edges T of the ground contact zone” refer to the tire farthest from the lateral center of the tire, both edges of the zone in which the tread surface 2a in the tread portion 2 of the pneumatic tire 1 contacts the road surface when the pneumatic tire 1 is mounted on a standard rim, inflated to normal internal pressure and loaded with normal load. The edges T of the soil contact zone are continuous along the circumference of the tire.

Meanwhile, in this embodiment, the rubber material forming the tread surface 2a in the tread portion 2 preferably has a rubber hardness (JIS-A hardness according to JIS-K6253 at 20 ° C ( JIS - Japanese Industrial Standard )) in the range of 62 to 68. When the hardness of the rubber is less than 62, the strength of the rubber decreases, and the resistance to uneven wear tends to decrease. On the other hand, when the hardness of the rubber exceeds 68, the flexibility of the rubber decreases, and the braking performance when driving on wet surfaces of roads tends to deteriorate. Thus, the hardness of the rubber, which is a rubber material forming the tread surface 2a, is preferably in the range of 62 to 68.

In addition, the rubber material forming the tread surface 2a in the tread portion 2 preferably has a tan δ (loss tangent) in the range of 0.60 to 0.80. When tan δ is less than 0.60, the wet performance, i.e. the braking performance when driving on wet roads, tends to deteriorate. On the other hand, when tan δ exceeds 0.80, the strength of the rubber decreases, and there is a tendency to increase the likelihood of damage to the contact areas as a result of the release of the mold during tire molding. Thus, the tan δ of the rubber material forming the tread surface 2a is preferably in the range of 0.60 to 0.80 at a temperature of 0 ° C.

Second Embodiment

6 is a plan view of the tread portion of a pneumatic tire according to this embodiment. FIGS. 7A and 7B are an enlarged plan view (FIG. 7A) and a sectional view (FIG. 7B) of a portion of a tread portion of a pneumatic tire according to this embodiment. Fig. 8 is an enlarged plan view of a tread portion of another example of a pneumatic tire according to this embodiment. FIG. 9 is an enlarged sectional view of a tread portion of a pneumatic tire according to this embodiment. 10 is an explanatory diagrammatic view of imaginary profile lines of a tread portion of a pneumatic tire according to this embodiment.

Hereinafter, “tire circumferential direction” refers to the circumferential direction with the rotation axis of the (non-illustrated) pneumatic tire 11 as the central axis. In addition, “lateral tire direction” refers to a direction parallel to the axis of rotation. “Side inner side in the tire lateral direction” refers to a side closer to the equatorial plane CL of the tire (equatorial line CL of the tire) in the lateral direction of the tire. "Side outer laterally of the tire" refers to a side remote from the equatorial plane CL of the tire in the lateral direction of the tire. In addition, “radial tire direction” refers to a direction orthogonal to the axis of rotation. “Side inner in the radial direction of the tire” refers to a side closer to the axis of rotation in the radial direction of the width. “Side outer in the radial direction of the tire” refers to a side remote from the axis of rotation in the radial direction of the tire. An “equatorial plane CL of a tire” is a plane that is orthogonal to the axis of rotation and which passes through the center of the pneumatic tire 11 defined in the tire width direction. An “equatorial tire line” refers to a line that runs along the circumferential direction of the pneumatic tire 11 and lies in the equatorial plane CL of the tire. In this embodiment, the equatorial line of the tire and the equatorial plane of the tire are denoted by the same reference numeral ʺCLʺ.

As illustrated in FIG. 6, the pneumatic tire 11 of this embodiment includes a tread portion 2. The tread portion 2, which is formed of a rubber material, is open from the side farthest from the center in the radial direction of the pneumatic tire 11, and its surface forms the profile of the pneumatic tire 11 as the tread surface 2a.

The tread surface 2a in the tread portion 2 includes a plurality of circumferential main grooves (main grooves) 3 (four in this embodiment) that extend along the tire circumferential direction and are adjacent to each other in the tire lateral direction. In addition, in this embodiment, the two circumferential main grooves 3 between which the equatorial plane CL of the tire is located and which are located in the portion central in the lateral direction of the tire are the central main grooves (first main grooves) 3A, and the circumferential main grooves 3, located on those sides of the central main grooves 3A that are laterally outer of the tire, are the main grooves 3B of the shoulder zones (second main grooves). It should be noted that the circumferential main groove 3 has a groove width of 5 mm to 20 mm and a groove depth (size from the location of its inlet on the tread surface 2a to the bottom of the groove) of 5 mm to 15 mm.

Each of the central main grooves 3A of the circumferential main grooves 3 is located in contact with the soil, the Central part of the contact zone with the soil. In contact with the soil, the central part is a zone near the equatorial plane CL of the tire, and the central main grooves 3A, which are the circumferential main grooves 3 located in the soil contacting central part in this embodiment, are the circumferential main grooves 3 located near the equatorial plane of the CL bus.

It should be noted that the soil contact zone is a zone in which the tread surface 2a in the tread portion 2 of the pneumatic tire 11 comes into contact with a dry and flat road surface when the pneumatic tire 11 is mounted on a standard rim, inflated to normal internal pressure and loaded with a load of 70% of the normal load. In this case, “standard rim” refers to the “standard rim” defined by JATMA, the “design rim” defined by TRA, or the “measuring wheel” defined by ETRTO. In addition, “normal internal pressure” refers to the “maximum air pressure” defined by JATMA, to the maximum value given in “Tire load limits at various cold inflation pressures” defined by TRA, or “Inflation pressures” defined by ETRTO . In addition, “normal load” refers to the “maximum load capacity” defined by JATMA, the maximum value given in the “Tire load limits at various cold inflation pressures” defined by TRA, and the “Load capacity” defined by ETRTO.

The tread surface 2a in the tread portion 2 includes a plurality of contact portions 41 (five in this embodiment) that are formed as a result of their boundaries being formed by the circumferential main grooves 3 in the lateral direction of the tire. Moreover, in this embodiment, one of the rib-shaped contact sections 41, which is formed as a result of the formation of its boundaries by the Central main grooves 3A between them, is a Central contact section 41A. In addition, two of the rib-shaped contact sections 41, which are formed as a result of the formation of their boundaries by the Central main grooves 3A and the main grooves 3B of the shoulder areas located on those sides of the Central main grooves 3A, which are external in the lateral direction of the tire, are the middle contact sections 41B. In addition, the rib-shaped contact portions 41, which are located on the side of each of the main grooves 3B of the shoulder zones, the laterally outer tire, are contact sections 41C of the shoulder zones.

In such a pneumatic tire 11, the central main grooves 3A are made with bevels 5 that are located on the edges of the inlet parts of the central main grooves 3A at the middle contact portions 41B located on the side of the main grooves 3B of the shoulder zones. In the bevelled parts 5, a plurality of bevels 5A, which provide a change in the position of the edges of the inlet parts in a diagonal direction with respect to the tire circumferential direction, are arranged along the tire circumferential direction. Since the central main grooves 3A of this embodiment are made together with the main grooves 3B of the shoulder regions on their sides that are laterally outside the tire, as well as with the middle contact portions 41B on their sides that are laterally on the tire, the parts 5 with bevels are only on the edges of the inlet parts on those sides of the central main grooves 3A that are laterally outer of the tire. As illustrated in FIG. 7B, the bevels 5A are formed by cutting — with a triangular shape — the angular portions of the edges of the inlet parts of the central main grooves 3A on the tread surface 2a in the middle contact portions 41B, and, as illustrated in FIGS. 7A and FIG. 8, the bevels 5A are formed as triangular recessed parts in a plan view. In particular, each of the bevels 5A is formed with a triangular shape at the edges of the inlet parts of the central main grooves 3A, each of the bevels including a long side 5a and a short side 5b, which have different lengths and which are inclined with respect to directions along the circumference of the tire. It should be noted that despite the fact that this is not illustrated in the drawings, each of the bevels 5A can be formed with a triangular shape at the edges of the inlet parts of the central main grooves 3A, while each of them will include two sides that have the same length and which are inclined relative to the direction along the circumference of the tire. Therefore, thanks to the bevelled parts 5, the central main grooves 3A include edge parts that are inclined with respect to the direction along the tire circumference. In addition, as illustrated in FIG. 7A, bevels 5A can be continuously made in the tire circumferential direction, or, as illustrated in FIG. 8, bevels 5A can be made at intervals 5B in the tire circumferential direction.

Furthermore, in the pneumatic tire 11 of this embodiment, curved grooves 6 and auxiliary grooves 7 are formed in the middle contact portions 41B, which are formed as a result of their boundaries being formed by the central main grooves 3A and the main shoulder grooves 3B.

Curved grooves 6 are located nearby — in the direction along the circumference of the tire — with the edges of the inlet parts of the central main grooves 3A including the parts 5 with bevels and are made so that they extend along the direction along the circumference of the tire. The curved grooves 6 are formed curved by means of slopes corresponding to the shapes of the bevels 5A of the bevelled parts 5. In particular, as illustrated in FIGS. 7A and 8, curved grooves 6 are formed curved so that they include first inclined portions 6a that are long and inclined relative to the tire circumferential direction along the long bevel sides 5a, and second inclined sections 6b that are short and inclined relative to the tire circumferential direction along the short sides 5b of the bevels 5A. Since in this case the curved grooves 6 are made along the direction along the tire circumference in accordance with the triangular shapes of the bevels 5A, each of the curved grooves 6 will be formed with a zigzag shape in which the “lightning” configurations are formed as a result of “bending” the straight lines many times along the direction along the circumference of the tire. It should be noted that since in the pneumatic tire 1 illustrated in FIG. 8, the bevels 5A are spaced at intervals 5B in the direction along the tire circumference at the edges of the inlet parts of the central main grooves 3A extending in the direction along the tire circumference, the curved grooves 6 include intermediate sections 6c which are not inclined and which extend in the direction along the tire circumference. The middle contact portions 41B are divided by these curved grooves 6 into the first middle contact portions 41BA located on the side of the central main grooves 3A and the second middle contact portions 41Bb located on the side of the main grooves 3B of the shoulder zones. It should be noted that the curved groove 6 has a groove width that is 1.5 mm or more and which is less than the width of the circumferential main groove 3, and a depth of the groove that is less than the depth of the circumferential main groove 3.

Auxiliary grooves 7 are made between the main grooves 3B of the shoulder zones and curved grooves 6 and are formed so that they intersect with the direction along the circumference of the tire. As illustrated in FIGS. 7A and 8, the first ends 7a of the auxiliary grooves 7 extend towards the curved grooves 6 and are made to terminate inside the middle contact portions 41B (second middle contact portions 41Bb), so that between the first ends 7a and the curved grooves 6 a gap is provided. In particular, the first ends 7a of the auxiliary grooves 7 are made oriented towards the second inclined portions 6b, which are short and strongly curved sections of the curved grooves 6. In addition, the second ends 7b of the auxiliary grooves 7 extend towards the main grooves 3B of the shoulder zones and made communicating with the main grooves 3B of the shoulder zones. It should be noted that although this is not illustrated in the drawings, the second ends 7b of the auxiliary grooves 7 can be made terminating inside the middle contact portions 41B (second middle contact portions 41Bb), so that between the second ends 7b and the main grooves 3B of the shoulder zones a gap will be provided. It should be noted that the auxiliary groove 7 has a groove width that is 1.5 mm or more and which is less than the width of the circumferential main groove 3, and a groove depth that is less than the depth of the circumferential main groove 3.

Thus, the pneumatic tire 11 of this embodiment includes: central main grooves (first main grooves) 3A, which are made in contact with the soil, the central part of the tread portion 2 so that they extend along the direction along the tire circumference; main shoulder grooves 3B (second main grooves) that are formed on those sides of the central main grooves 3A that are laterally outer of the tire, so that they extend along the tire circumferential direction; middle contact portions 41B that are formed by forming their boundaries by the central main grooves 3A and the main grooves 3B of the shoulder regions and which are formed continuous along the tire circumference; parts 5 with bevels in which a plurality of bevels 5A are arranged in the direction along the tire circumference, while a plurality of bevels 5A are made on the edges of the inlet parts of the central main grooves 3A from the side of the middle contact sections 41B and provide a change in the position of the edges of the inlet parts in a diagonal direction relative to the direction along tire circumference; curved grooves 6, which are made in the middle contact portions 41B, are located next to the tire sideways with the edges of the inlet parts of the central main grooves 3A including parts 5 with bevels and are made curved in accordance with the shapes of bevels 5A of parts 5 with bevels and extend in the direction along the tire circumference, and auxiliary grooves 7 that are formed in the middle contact portions 41B between the main shoulder grooves 3B and the curved grooves 6 and which extend towards the curved grooves 6 in the direction intersecting with the direction along the circumference of the tire, with the first ends 7a oriented toward the curved grooves 6 and terminate within the middle contact portions 41B.

In this pneumatic tire 11, the edge components of the tire contact surface are provided by means of curved grooves 6, and therefore braking performance is provided when driving on wet surfaces of roads, that is, tire performance when driving on wet roads. In addition, when making curved grooves 6 curved in accordance with the shapes of the bevels 5A of parts 5 with bevels made on the edges of the inlet parts of the central main grooves 3A, as well as when making auxiliary grooves 7 with the first ends 7a, which are oriented towards the curved grooves 6 and terminate within the middle contact portions 41B, when the mold is removed from the curved grooves 6 during tire molding, the curved grooves 6 expand as a result of deformation of the middle contact portions 41B (first middle their contact portions 41Ba, the second middle contact portions 41Bb), which include the curved grooves 6, towards the side of the bevelled parts 5 and towards the side of the auxiliary grooves 7. As a result, the mold release ability is improved, and this prevents the situation, in which the middle contact portions 41B are damaged during release of the mold, and therefore can prevent the appearance of a defect in appearance. In addition, when making curved grooves 6 curved in accordance with the shapes of the bevels 5A of parts 5 with bevels made on the edges of the inlet parts of the central main grooves 3A, as well as when making auxiliary grooves 7 with the first ends 7a oriented towards the curved grooves 6 and ending inside the middle contact portions 41B, the differences in stiffness in the middle contact portions 41B including the curved grooves 6 are reduced, thereby ensuring uniform contact pressure soil on the ground. As a result, resistance to uneven wear can be improved.

In addition, as illustrated in FIGS. 7A and 8, in the pneumatic tire 11 of this embodiment, the curved groove 6 is formed with a groove width Wa (groove width of the inlet portion Wa), preferably in the range of 4% to 8% with respect to size W of the middle contact portion 41B in the lateral direction of the tire.

When the width Wa of the groove, which is a curved groove 6, is less than 4% relative to the size W of the middle contact portion 41B in the lateral direction of the tire, the ability of the curved grooves 6 to drain water is deteriorated, and their contribution to the braking performance when driving on wet surfaces of roads becomes smaller . On the other hand, when the width Wa of the groove representing the curved groove 6 is more than 8% with respect to the size W of the middle contact portion 41B in the tire lateral direction, the stiffness of the middle contact portions 41B decreases and the positive effect on the uneven wear resistance decreases. Therefore, in order to provide braking performance when driving on wet surfaces of roads and at the same time increase resistance to uneven wear, a curved groove 6 is formed with a groove width Wa, preferably in the range of 4% to 8%, relative to the size W of the middle contact portion 41B in the tire lateral direction. It should be noted that in order to provide a significant positive effect both on guaranteeing the braking performance when driving on wet surfaces of roads, and on increasing the resistance to uneven wear, the width Wa of the groove, which is a curved groove 6, is preferably made so that it is in the range from 5% to 7% with respect to the size W of the middle contact portion 41B in the tire lateral direction.

In addition, as illustrated in FIGS. 7A and 8, in the pneumatic tire 11 of this embodiment, the dimension Wb defined in the tire lateral direction from the axial line S of the curved groove 6 to the edge 5c of part 5 with bevels in the middle contact portion 41B, preferably configured to be in the range of 20% to 45% with respect to the size W of the middle contact portion 41B in the tire lateral direction.

The center line S of the curved groove 6 is a straight line passing through the center of the width Wa of the groove, which is the curved groove 6. The edge 5c of part 5 with bevels in the middle contact portion 41B is the edge of part of the tread surface 2a in the middle contact portion 41B, and the bevel 5A of part 5 with bevels is cut to the greatest extent at the edge 5c.

When the dimension Wb defined in the tire lateral direction from the center line S of the curved groove 6 to the edge 5c of the portion 5 with bevels in the middle contact portion 41B is less than 20% with respect to the dimension W of the middle tire portion 41B in the lateral direction of the tire, the curved grooves 6 approach parts 5 with bevels. As a result, the stiffness of the middle contact portions 41B between the curved grooves 6 and the bevelled parts 5 is reduced, and the positive effect on the uneven wear resistance is reduced. On the other hand, when the dimension Wb, determined laterally of the tire from the center line S of the curved groove 6 to the edge 5c of part 5 with bevels in the middle contact portion 41B, is more than 45% relative to the dimension W of the middle contact portion 41B in the lateral direction of the tire, areas for the placement of auxiliary grooves 7, and this makes it difficult to ensure the length of the auxiliary grooves 7. As a result, the ability of the auxiliary grooves 7 to drain water and their contribution to the braking performance when moving on a wet surface are reduced road becomes smaller. Therefore, to ensure braking performance when driving on wet surfaces of roads and at the same time increase resistance to uneven wear, the dimension Wb defined in the tire lateral direction from the axial line S of the curved groove 6 to the edge 5c of part 5 with bevels in the middle contact portion 41B is preferably made so that it is in the range from 20% to 45% relative to the size W of the middle contact portion 41B in the lateral direction of the tire. It should be noted that in order to provide a significant positive effect both on guaranteeing the braking performance when driving on wet surfaces of roads, and on increasing the resistance to uneven wear, the size Wb determined in the lateral direction of the tire from the center line S of the curved groove 6 to the edge 5c of part 5 with bevels in the middle contact portion 41B, is preferably configured to be in the range of 25% to 35% with respect to the size W of the middle contact portion 41B in the tire lateral direction.

In addition, as illustrated in FIG. 7B, in the pneumatic tire 11 of this embodiment, a curved groove 6 is formed with a groove depth On, preferably in the range of 30% to 55%, relative to the groove depth H, which is the central main groove 3A.

When the depth On the grooves, which is the curved groove 6, is less than 30% relative to the depth H of the grooves, which is the central main groove 3A, the ability of the curved grooves 6 to drain water decreases, and their contribution to the braking characteristic when moving on wet surfaces of roads becomes less . On the other hand, when the depth H of the groove representing the curved groove 6 is more than 55% with respect to the depth H of the groove representing the central main groove 3A, the depth H of the groove representing the curved groove 6 approaches the depth H of the groove representing the central the main groove 3A, and the likelihood of damage to the middle contact portions 41B increases when the mold is removed from the curved grooves 6 during tire molding, thereby reducing the effect of preventing de effect of appearance. Therefore, to provide braking performance when driving on wet surfaces of roads and at the same time prevent appearance defects, a curved groove 6 is formed with a depth On grooves, preferably in the range of 30% to 55%, relative to the depth H of the groove, which is the central main groove 3A. It should be noted that to ensure a significant positive effect both on guaranteeing braking performance when driving on wet surfaces of roads, and on preventing a defect in appearance, the depth of the groove, which is a curved groove 6, is preferably made so that it is in the range from 35 % to 50% relative to the depth H of the groove, which is the Central main groove 3A.

In addition, as illustrated in FIG. 7A and FIG. 8, in the pneumatic tire 11 of this embodiment, it is preferable that the bevel pieces 5 are formed so that the bevels 5A are formed with triangular shapes at the edges of the inlet parts of the central main grooves 3A and include long sides 5a and short sides 5b that are inclined with respect to the tire circumferential direction so that the curved grooves 6 are formed curved and include first inclined sections 6a that are long and have a fold relative to the tire circumferential direction along the long sides 5a of the bevels 5A, and second inclined sections 6b that are short and tilted with respect to the tire circumferential direction along the short sides 5b of the bevels 5A, so that the inclination angle α of the first inclined portion 6a with respect to the tire circumferential direction was formed so that it was in the range from 2 ° to 7 °, and so that the angle β of the inclination of the second inclined portion 6b relative to the direction along the circumference of the tire was formed so that it was in apazone from 20 ° to 60 °.

When the inclination angle α of the first inclined portion 6a with respect to the tire circumferential direction is less than 2 ° or when the inclination angle β of the second inclined portion 6b with respect to the tire circumferential direction is less than 20 °, the direction of the curved grooves 6 approaches the direction along the circumference of the tire, and the edge effect from them decreases. As a result, the contribution of the curved grooves 6 to the braking characteristic when driving on wet road surfaces becomes less. On the other hand, when the inclination angle α of the first inclined section 6a relative to the tire circumferential direction exceeds 7 ° or when the inclination angle β of the second inclined section 6b relative to the tire circumferential direction exceeds 60 °, the bending of the curved grooves 6 becomes excessive, and their angular parts " approaching ”to sharp corners. As a result, the stiffness of the middle contact portions 41B is reduced, and the positive effect on the uneven wear resistance is reduced. In addition, when the mold is removed from the curved grooves 6 during tire molding, the likelihood of damage to the central contact portions 4A increases, as a result of which the positive effect on preventing the appearance defect is reduced. Therefore, in order to increase the resistance to uneven wear and at the same time prevent the appearance defect while providing braking performance when driving on wet surfaces of roads, it is preferable that the inclination angle α of the first inclined section 6a relative to the direction along the tire circumference be formed so that it is in the range from 2 ° to 7 °, and the angle β of the inclination of the second inclined portion 6b relative to the direction along the tire circumference was formed so that it was in the range from 20 ° to 60 °. It should be noted that in order to provide a significant positive effect on increasing the resistance to uneven wear, guaranteeing braking performance when driving on wet surfaces of the roads and preventing a defect in appearance, it is preferable that the inclination angle α of the first inclined section 6a relative to the direction along the tire circumference is formed so that it is in the range from 3 ° to 5 °, and so that the inclination angle β of the second inclined portion 6b with respect to the direction along the tire circumference is formed Kim so that it is in the range from 30 ° to 45 °.

In addition, as illustrated in FIG. 7A and FIG. 8, in the pneumatic tire 11 of this embodiment, the bevel portion 5 is formed with a tire size Wc in the tire lateral direction, preferably in the range of 4% to 15% with respect to the size W of the middle contact section 41B in the lateral direction of the tire.

When the dimension Wc of the bevel portion 5, determined in the lateral direction of the tire, is less than 4% with respect to the dimension W of the middle contact portion 41B in the lateral direction of the tire, the ability of the central main grooves 3A to drain water and their contribution to the braking performance when driving on wet are reduced road surfaces are getting smaller. On the other hand, when the dimension Wc of the bevel portion 5, determined in the lateral direction of the tire, is more than 15% with respect to the dimension W of the middle contact portion 41B in the lateral direction of the tire, the bevels 5A are cut off at the middle contact portions 41B to a larger value. As a result, the stiffness of the middle contact portions 41B decreases, and the positive effect on the uneven wear resistance decreases. Therefore, to provide braking performance when driving on wet surfaces of roads and at the same time increase resistance to uneven wear, the bevelled part 5 is formed with a tire size Wc in the lateral direction of the tire, preferably in the range from 4% to 15% relative to the size W of the middle contact portion 41B in lateral direction of the tire. It should be noted that in order to provide a significant positive effect both on guaranteeing the braking performance when driving on wet surfaces of roads, and on increasing the resistance to uneven wear, the dimension Wc of the portion 5 with bevels, determined in the lateral direction of the tire, is preferably made so that it is in the range of 6% to 8% relative to the size W of the middle contact portion 41B in the lateral direction of the tire

In addition, as illustrated in FIG. 7B, in the pneumatic tire 11 of this embodiment, the bevel portion 5 is formed with a dimension Hb in the radial direction of the tire, preferably in a range of 30% to 60% with respect to the groove depth H, which is the central main groove 3A.

When the dimension Hb of the bevel portion 5, determined in the tire radial direction, is less than 30% with respect to the depth H of the groove, which is the central main groove 3A, the ability of the central main grooves 3A to drain water decreases and their contribution to the braking performance when driving on wet road surfaces are getting smaller. On the other hand, when the dimension Hb of the bevel portion 5, determined in the tire radial direction, is more than 60% with respect to the groove depth H, which is the central main groove 3A, the stiffness of the middle contact portions 41B decreases, and the positive effect on the uneven wear resistance decreases . Therefore, to provide braking performance when driving on wet surfaces of roads and at the same time increase resistance to uneven wear, the bevelled part 5 is formed with a tire size Hb in the radial direction of the tire, preferably in the range from 30% to 60% relative to the depth H of the groove, which is the central main groove 3A. It should be noted that in order to provide a significant positive effect both on guaranteeing the braking performance when driving on wet surfaces of roads, and on increasing the resistance to uneven wear, the dimension Hb of the part 5 with bevels, determined in the radial direction of the tire, is preferably made so that it is in the range of 40% to 55% with respect to the depth H of the groove, which is the central main groove 3A.

In addition, as illustrated in FIG. 7A and FIG. 8, in the pneumatic tire 11 of this embodiment, in parts in which the beveled parts 5 and the curved grooves 6 are located opposite each other in the tire lateral direction, it is preferable that it is defined laterally to the tire direction, the dimension Wc of the bevel 5A was equal to the laterally determined tire range Wd of that portion of the curved groove 6 which is opposite the bevel 5A in the lateral direction of the tire, and that the size La determined in the direction along the tire circumference 5A th bevel portion 5 was formed with bevels equal size Lb in the tire circumferential direction, which is the size of one unit of the curved portion in a part of a curved groove 6, which is located opposite one bevel 5A in the lateral direction of the tire.

In this pneumatic tire 11, when the dimension Wc of the bevel 5A in the tire lateral direction is equal to the tire lateral direction Wd determined in the tire lateral direction of that portion of the curved groove 6 which is opposite the bevel 5A in the tire lateral direction, and the dimension La of the bevel 5A in the circumferential direction of the tire equal to the dimension Lb determined in the direction along the tire circumference in one curved unit portion in that part of the curved groove 6, which is opposite the bevel 5A in the lateral direction of the tire, the shape of the edges of the bevel 5A bends become parallel curved grooves 6 and provides uniform differences determined in the circumferential direction of the tire rigidity middle contact portions 41B disposed between the bevels 5A and curved grooves 6. The result may be achieved a significant positive impact on improving the resistance to uneven wear.

In addition, as illustrated in FIG. 7A and FIG. 8, in the pneumatic tire 11 of this embodiment, the auxiliary groove 7 is formed with a tire size We in the lateral direction of the tire, preferably in a range of 40% to 50% with respect to the size W of the middle contact portion 41B in the lateral direction of the tire.

The dimension We of the auxiliary groove 7 in the lateral direction of the tire is the lateral dimension of the tire obtained by projecting the auxiliary groove 7 in the tire circumferential direction.

When the size We of the auxiliary groove 7 in the lateral direction of the tire is less than 40% with respect to the size W of the middle contact portion 41B in the lateral direction of the tire, the ability of the auxiliary groove 7 to drain the water decreases, and its contribution to the braking performance when driving on wet surfaces of roads becomes smaller. On the other hand, when the size We of the auxiliary groove 7 in the lateral direction of the tire is more than 50% with respect to the size W of the middle contact portion 41B in the lateral direction of the tire, the stiffness of the middle contact sections 41B decreases and the positive effect on the uneven wear resistance decreases. Therefore, to provide braking performance when driving on wet surfaces of roads and at the same time increase resistance to uneven wear, the auxiliary groove 7 is formed with a size We in the lateral direction of the tire, preferably in the range from 40% to 50% with respect to the size W of the middle lateral contact portion 41B tire direction. It should be noted that in order to provide a significant positive effect both on guaranteeing the braking performance when driving on wet surfaces of roads, and on increasing the resistance to uneven wear, the size We of the auxiliary groove 7 in the tire lateral direction is preferably such that it is in the range from 43 % to 46% relative to the size W of the middle contact portion 41B in the lateral direction of the tire.

In addition, as illustrated in FIG. 7A and FIG. 8, in the pneumatic tire 11 of this embodiment, it is preferable that the auxiliary groove 7 is preferably formed so that the shortest gap dimension Wf between the end portion of the auxiliary groove 7 is oriented towards curved groove 6, and curved groove 6 was made so that it was in the range from 7% to 20% relative to the size W of the middle contact section 41B in the lateral direction of the tire.

When the shortest gap size Wf between the end portion of the auxiliary groove 7 oriented toward the curved groove 6 and the curved groove 6 is less than 7% with respect to the size W of the middle contact portion 41B in the lateral direction of the tire, the rigidity of the middle contact portions 41B is reduced, and positive the effect on resistance to uneven wear is reduced. On the other hand, when the shortest gap size Wf between the end portion of the auxiliary groove 7 oriented toward the curved groove 6 and the curved groove 6 is more than 20% with respect to the tire dimension W of the middle contact portion 41B in the lateral direction of the tire, the stiffness of the middle contact portions 41B increases. As a result, when the mold is removed from the curved grooves 6 during tire molding, the likelihood of damage to the middle contact portions 41B is increased, which reduces the positive effect on preventing the appearance defect. Therefore, in order to prevent a defect in appearance and at the same time increase resistance to uneven wear, the shortest gap size Wf between the end portion of the auxiliary groove 7 oriented toward the curved groove 6 and the curved groove 6 is preferably such that it is in the range of 7% up to 20% with respect to the size W of the middle contact portion 41B in the lateral direction of the tire. It should be noted that in order to provide a significant positive effect both on preventing the appearance defect and increasing the resistance to uneven wear, the shortest gap size Wf between the end portion of the auxiliary groove 7, oriented towards the curved groove 6, and the curved groove 6 is preferably made so that it is in the range from 10% to 15% relative to the size W of the middle contact portion 41B in the lateral direction of the tire. It should be noted that to ensure the same effects, the shortest gap size Wf between the end portion of the auxiliary groove 7, oriented towards the curved groove 6, and the curved groove 6 is preferably such that it is in the range from 2 mm to 5 mm, and more preferably configured to be in the range of 3 mm to 4 mm.

In addition, as illustrated in FIGS. 6-8, in the pneumatic tire 11 of this embodiment, the main grooves 3B of the shoulder regions are formed on the side of each of the two central main grooves 3A, laterally external to the tire, the middle contact portions 41B are formed as a result of their boundaries by means of the central main grooves 3A and the main grooves 3B of the shoulder zones from the side of each of the central main grooves 3A, external in the lateral direction of the tire, parts 5 with bevels are made only at the edges of the input hours s on the sides of center main grooves 3A, which are in the outer side of the tire, curved grooves 6 formed in each of the middle land portions 41B, and the secondary grooves 7 formed on each of the middle land portions 41B. When the pneumatic tire 11 is mounted on a standard rim, inflated to normal internal pressure and loaded with a load of 70% of the normal load, and in a state in which the tread portion 2a is in contact with a flat surface of the ground on the ground, the area of the inlet portions of the grooves representing the Central main grooves 3A, including parts with bevels, preferably exceeds the area of the input parts of the grooves, which are the Central main grooves 3A, excluding parts with bevels, by in the range from 8% to 13%.

When the area of the inlet parts of the grooves representing the central main grooves 3A, including parts 5 with bevels, exceeds the area of the inlet parts of the grooves representing the central main grooves 3A, excluding parts 5 with bevels, by less than 15%, the edge effect of the bevels 5A decreases , and their contribution to the braking performance when driving on wet surfaces of roads becomes smaller. On the other hand, when the area of the inlet parts of the grooves, which are the central main grooves 3A, including parts 5 with bevels, exceeds the area of the inlet parts of the grooves, which is the central main grooves 3A, excluding parts 5 with bevels, by more than 20%, the bevels 5A cut off in the middle contact areas 41B to a larger value. As a result, the rigidity of the middle contact portions 4A decreases, and the positive effect on the uneven wear resistance decreases. Therefore, to ensure braking performance when driving on wet surfaces of roads and at the same time increase resistance to uneven wear, the area of the input parts of the grooves, which are the central main grooves 3A, including parts 5 with bevels, is preferably formed larger than the area of the input parts of the grooves, which are the central main grooves 3A, excluding parts 5 with bevels, by a value in the range from 8% to 13%. It should be noted that in order to provide a significant positive effect both on guaranteeing braking performance when driving on wet surfaces of roads, and on increasing resistance to uneven wear, the area of the input parts of the grooves, which are the central main grooves 3A, including parts 5 with bevels, is preferably formed larger than the area of the input parts of the grooves, which are the central main grooves 3A, excluding parts 5 with bevels, by a value in the range from 9% to 11%.

Meanwhile, in this embodiment, at each of the shoulder region contact portions 41C, a circumferential narrow groove 8 is formed which extends in the direction along the tire circumference along each of the main shoulder region grooves 3B. Each of the shoulder region contact portions 41C is divided by this circumferential narrow groove 8 into a first shoulder region 41Ca of the shoulder region located on the side of the main shoulder region groove 3B and a second shoulder region 41Cb of the shoulder region located on the side most distant from the tire lateral direction . It should be noted that the circumferential narrow groove 8 has a groove width that is 1.5 mm or more and which is less than the width of the circumferential main groove 3, and a groove depth that is less than the depth of the circumferential main groove 3.

In addition, at each of the shoulder region contact portions 41C, auxiliary grooves 9 of the shoulder regions are formed that intersect with the direction along the tire circumference in the second shoulder region 41Cb of the shoulder region. The first ends of the auxiliary grooves 9 of the shoulder regions extend through the circumferential main groove 8 and terminate within the first shoulder portion 41Ca of the shoulder region. The second ends of the auxiliary grooves 9 of the shoulder zones are made extending towards the outer side of the tread surface 2a in the lateral direction of the tire. It should be noted that the auxiliary groove 9 of the shoulder region has a groove width that is 1.5 mm or more and which is less than the width of the circumferential main groove 3, and a groove depth that is less than the depth of the circumferential main groove 3.

In addition, narrow shoulder grooves 10 are formed at each of the shoulder region contact portions 41C, which intersect with the direction along the tire circumference in the second shoulder region 41Cb of the shoulder region. The first ends of the narrow grooves 10 of the shoulder zones communicate with the circumferential narrow groove 8, and the second ends of the narrow grooves 10 of the shoulder zones are made extending towards the outer side of the tread surface 2a in the lateral direction of the tire. It should be noted that the narrow groove 10 of the shoulder region is formed like a so-called siped drainage groove with a width in the range from 0.4 mm to 1.2 mm.

Meanwhile, as illustrated in FIGS. 9 and 10, in the pneumatic tire 11 of this embodiment, in meridional section, the actual profile line LB in the middle contact portions 41B, which are formed as a result of the formation of their boundaries by the central main grooves 3A and the main grooves 3B of the shoulder zones is preferably formed so that it protrudes further outward in the radial direction of the tire than an imaginary profile line LA, which extends through the ends 3BA of the edges located on the side of the main grooves 3 the shoulder zones, the tire inner lateral direction, and being in contact with the tread surface 2a, and each of the ends 3Aa and 3Aa of the edges that are located on both sides of the central main grooves 3A adjacent to the main grooves 3B of the shoulder regions in the tire lateral direction, and which are in contact with the tread surface 2a.

As described above, in the meridional section, the imaginary profile line LA is an arc that extends through the ends 3Ba of the edges located on the side of the main grooves 3B of the shoulder areas, the tire is laterally internal and in contact with the tread surface 2a, and each of them 3Aa and 3Aa of the edges that are located on both sides of the central main grooves 3A adjacent to the main grooves 3B of the shoulder areas in the lateral direction of the tire, and which are in contact with the tread surface 2a, and which has rad radius of curvature, the center of which is located on the inner side of the tread surface 2a in the radial direction of the tire. In addition, the imaginary profile line LA may have a center point in the equatorial plane CL of the tire. In addition, the actual profile line LB is an arc that extends through the ends 3Ba of the edges located on the side of the main grooves 3B of the shoulder regions, the tire laterally inner and in contact with the tread surface 2a, and the ends 3Aa of the edges that are located with of that side of the central main grooves 3A adjacent to the main grooves 3B of the shoulder areas, which faces the main groove 3B of the shoulder area, and is in contact with the tread surface 2a, and which has a central point located at Cored oil side surface 2a of the tread in the tire radial direction.

In a pneumatic tire 11 of this type, when the actual profile line LB protrudes further outward in the tire radial direction as compared to the imaginary profile line LA in the middle contact portions 41B, the length of the soil contact zone, determined in the direction along the tire circumference, in the soil contact zone can be enlarged compared to the case in which an imaginary line LA profile is used. In other words, the area of contact with the ground can be increased in the direction along the circumference of the tire. As a result, ground contact is improved, and thus braking performance can be improved when driving on wet road surfaces. In addition, as a result of improved contact with the ground, resistance to uneven wear can be improved. Furthermore, when the actual profile line LB extends further outward in the tire radial direction as compared to the imaginary profile line LA in the middle contact portions 41B formed on both sides in the tire lateral direction with the tire equatorial plane CL located therebetween, the above-described effects may be received to a large extent.

In addition, when the pneumatic tire 11 is mounted on a standard rim, inflated to normal internal pressure and loaded with a load of 70% of the normal load, the maximum protrusion value Ga of the actual profile line LB in the middle contact portions 41B, which protrudes further outward in the radial direction tires than an imaginary line LA profile, preferably from 0.1 mm to 0.5 mm.

When the maximum protrusion value Ga in the middle contact portions 41B is less than 0.1 mm, the protrusion degree of the middle contact portions 41B is reduced, and soil contact improvement is difficult. On the other hand, when the maximum protrusion value Ga in the middle contact portions 41B exceeds 0.5 mm, the protrusion of the middle contact portions 41B becomes excessive, and the length of the ground contact zone in the central part of the contact portions is excessively increased. This causes uneven wear of a type in which the central part of the contact areas wears out at an early stage. Thus, both to improve the braking performance when driving on wet surfaces of roads, and to increase the resistance to uneven wear, in the middle contact portions 41B, the maximum outward radial dimension Ga of the tire is preferably from 0.1 mm to 0.5 mm .

In addition, as illustrated in FIGS. 9 and 10, in the pneumatic tire 11 of this embodiment, in meridional section, the actual profile line LD at the central contact portion 41A, which is formed as a result of its boundaries being formed by each of the central main grooves 3A, preferably formed of the tire extending farther outward than the imaginary profile line LA, which extends through each of the ends 3Aa and 3Aa of the edges, which are located on both sides of the central main grooves 3A in the lateral direction of the tire and which are in contact with the tread surface 2a.

In a pneumatic tire 11 of this type, when the actual profile line LD extends outward in the tire radial direction as compared to the imaginary profile line LA in the central contact portion 41A, the length of the soil contact zone, determined in the direction along the tire circumference, in the soil contact zone can be enlarged compared to the case in which an imaginary line LA profile is used. In other words, the area of contact with the ground can be increased in the direction along the circumference of the tire. As a result, ground contact is improved, and thus braking performance can be improved when driving on wet road surfaces. In addition, as a result of improved contact with the ground, resistance to uneven wear can be improved.

In addition, when the pneumatic tire 11 is mounted on a standard rim, inflated to normal internal pressure and loaded with a load of 70% of the normal load, in the central contact portion 41A, the maximum protrusion value Gc of the actual profile line LD, which extends further outward in the radial direction tires than an imaginary line LA profile, preferably from 0.1 mm to 0.5 mm.

When the maximum protrusion amount Gc at the central contact portion 41A is less than 0.1 mm, the protrusion of the central contact portion 41A is reduced, and improvement in ground contact is difficult. On the other hand, when the maximum protrusion amount Gc at the central contact portion 41A exceeds 0.5 mm, the protrusion of the central contact portion 41A becomes excessive, and the length of the ground contact zone in the central portion of the contact portion is excessively increased. This causes uneven wear of the kind in which the central part of the contact area wears out at an early stage. Thus, both to improve the braking performance when driving on wet surfaces of roads, and to increase the resistance to uneven wear, in the central contact portion 41A, the maximum value of the protruding outward in the radial direction of the tire is preferably from 0.1 mm to 0.5 mm .

It should be noted that, as illustrated in FIG. 10, in the pneumatic tire 11 of this embodiment, in the meridional section of the profile line of the shoulder portions 41C of the shoulder regions formed on those sides of the main shoulder grooves 3B that are laterally outer in the tire, preferably formed on an imaginary profile line LA 'and coincide with an imaginary profile line LA', which passes through the edges T of the ground contact zone and the ends 3Ba and 3Bb of the edges located on both sides of the main grooves 3B of the shoulder n in the lateral direction of the tire and are in contact with the tread surface 2a, and which is continuous with the imaginary line LA profile. In other words, the contact portions that protrude further outward in the tire radial direction than the imaginary profile line LA are the middle contact portions 41B made closer to the equatorial plane CL of the tire than the main shoulder grooves 3B, or alternatively further include a central contact portion 41A. When making curved grooves 6 extending in a circumferential direction on the middle contact portions 41B that are formed by forming their boundaries by the central main grooves 3A and the main grooves 3B of the shoulder areas, there is a tendency to decrease ground contact in the area near the center of each from middle contact areas 41B. In addition, the middle contact portions 41B made closer to the equatorial plane CL of the tire tend to have lower contact pressure on the ground than the shoulder portions 41C. Accordingly, the contact portions that protrude further outward in the tire radial direction than the imaginary profile line LA are preferably middle contact portions 41B that are closer to the equatorial plane CL of the tire than the main shoulder grooves 3B, or alternatively further include central contact portion 41A.

In this case, “edges T of the ground contact zone” refer to the tire farthest from the lateral center of the tire, both edges of the zone in which the tread surface 2a in the tread portion 2 of the pneumatic tire 11 is in contact with the road surface when the pneumatic tire 11 is mounted on a standard rim, inflated to normal internal pressure and loaded with normal load. The edges T of the soil contact zone are continuous along the circumference of the tire.

Meanwhile, in this embodiment, the rubber material forming the tread surface 2a in the tread portion 2 preferably has a rubber hardness (hardness JIS-A according to JIS-K6253 at 20 ° C.) in the range of 62 to 68. When the rubber hardness is less than 62, the strength of the rubber decreases, and the resistance to uneven wear tends to decrease. On the other hand, when the hardness of the rubber exceeds 68, the flexibility of the rubber decreases, and the braking performance when driving on wet surfaces of roads tends to deteriorate. Thus, the hardness of the rubber, which is a rubber material forming the tread surface 2a, is preferably in the range of 62 to 68.

In addition, the rubber material forming the tread surface 2a in the tread portion 2 preferably has a tan δ (loss tangent) in the range of 0.60 to 0.80. When tan δ is less than 0.60, the wet performance, i.e. the braking performance when driving on wet roads, tends to deteriorate. On the other hand, when tan δ exceeds 0.8, the rubber strength decreases, and there is a tendency to increase the likelihood of damage to the contact areas as a result of mold release during tire formation. Thus, the tan δ of the rubber material forming the tread surface 2a is preferably in the range of 0.60 to 0.80 at a temperature of 0 ° C.

Examples

In the Examples, performance tests to determine braking performance when driving on wet surfaces of roads, resistance to uneven wear and vulcanization defects (appearance defects) were performed for many types of tested tires with different characteristics (see Figs. 11-16).

In these performance tests, a pneumatic tire of the kind illustrated in FIG. 1 and FIGS. 2A and 2B, corresponding to the first embodiment described above, with tire size 195 / 65R15 was used as test tire 1. This test tire 1 was mounted on a standard rim 15 × 6J, inflated to normal internal pressure (200 kPa) and installed for a test vehicle (a vehicle with an engine displacement of 1,400 cm ³ and front-wheel, front-wheel drive monopoly). In addition, a pneumatic tire of the kind illustrated in FIG. 6 and FIGS. 7A and 7B, corresponding to the second embodiment described above, with a tire size of 215 / 45R17 was used as the test tire 2. This test tire 2 was mounted on a standard rim 17 × 7J, pumped up to normal internal pressure (200 kPa) and installed for a test vehicle (a vehicle with an engine displacement of 1,400 cm ³ and a front-engine, front-wheel drive arrangement).

The braking performance when driving on wet surfaces of roads was evaluated by measuring the braking distance of the test vehicle described above at the start of braking at a speed of 100 km / h on a test track with a wet road surface with a water film thickness of 1 mm. The measurement results are expressed as indicator values and evaluated at the value for Common Examples 1 and 2, taken as the base (100). In this assessment, larger values are preferred.

The resistance to uneven wear was evaluated by visual inspection of the state of wear after running the above-described test vehicle along the test track with a dry road at an average speed of 80 km / h, which was 10,000 km. In this case, the measurement results are expressed in the form of indicator values and evaluated at the value for Common Examples 1 and 2, adopted as the base (100). In this assessment, larger values are preferred.

Vulcanization defects were evaluated by curing 200 pieces of test tires 1 and 2 and performing visual inspection of appearance defects such as damage and cracks in the contact areas. In this case, the measurement results are expressed in the form of indicator values and evaluated at the value for Common Examples 1 and 2, adopted as the base (100). In this assessment, larger values are preferred.

In the Examples illustrated in FIGS. 11-13, test tires 1 were used, which were made on the basis of a pneumatic tire of the kind illustrated in FIGS. 1 and 2A and 2B. In contrast to a pneumatic tire of the type illustrated in FIGS. 1 and 2A and 2B, in a pneumatic tire according to the Normal Example 1, the first main groove was not made with parts with bevels, and the straight grooves extending in the direction along the tire circumference, were made instead of curved grooves. Unlike a pneumatic tire of the kind illustrated in FIGS. 1 and 2A and 2B, in the pneumatic tire of Comparative Example 1, the first main groove was not made with bevelled parts. Meanwhile, the pneumatic tires according to Examples 1-40 were pneumatic tires of the kind illustrated in FIGS. 1 and 2A and 2B, in which the first main groove was made with bevelled parts and curved grooves and auxiliary grooves were made.

As the test results in FIGS. 11-13 show, the pneumatic tires of Examples 1-40 have increased resistance to uneven wear and better characteristics with respect to vulcanization defects (appearance defects) while providing braking performance when driving on wet roads.

In the Examples illustrated in FIGS. 14-16, test tires 2 were used, which were made on the basis of a pneumatic tire of the kind illustrated in FIG. 6 and FIGS. 7A and 7B. In contrast to a pneumatic tire of the kind illustrated in FIGS. 6 and 7A and 7B, in the pneumatic tire according to the Example 2, the first main grooves were not made with bevelled parts, and the straight grooves extending in the direction along the tire circumference, were made instead of curved grooves. Unlike a pneumatic tire of the kind illustrated in FIG. 6 and FIGS. 7A and 7B, in the pneumatic tire of Comparative Example 2, the first main grooves were not made with bevelled parts. Meanwhile, the pneumatic tires of Examples 41-79 were pneumatic tires of the kind illustrated in FIGS. 6 and 7A and 7B, in which the first main grooves were made with bevelled parts and curved grooves and auxiliary grooves were made.

As the test results in FIGS. 14-16 show, the pneumatic tires of Examples 41-79 have increased resistance to uneven wear and better characteristics with respect to vulcanization defects (appearance defects) while providing braking performance when driving on wet roads.

List of Reference Items

1 - pneumatic tire

2 - tread part

2a - tread surface

3A - Central main groove (first main groove)

3B is the main groove of the shoulder region (second main groove)

4A - Central contact area (contact area)

5 - part with bevels

5A - bevel

5a - long side

5b - short side

5c - edge

6 - curved groove

6a - the first inclined section

6b - second inclined section

7 - auxiliary groove

7a - first end

7b - second end

A - border

S - center line

11 - pneumatic tire

41B - middle contact area (contact area)

Claims (46)

1. A pneumatic tire comprising: a first main groove made in the central portion of the tread portion in contact with the ground so that it extends along a direction along the circumference of the tire; a second main groove made on the side of the first main groove that is laterally outward of the tire so that it extends along a direction along the circumference of the tire; a contact portion formed as a result of the formation of its boundaries by means of the first main groove and the second main groove and continuous in the direction along the tire circumference; a portion with bevels in which a plurality of bevels are arranged along a direction along the circumference of the tire, wherein a plurality of bevels are made on the edge of the inlet portion of the first main groove from the side of the contact portion and provide a change in position of the edge of the inlet portion in a diagonal direction relative to the direction along the tire circumference; a curved groove made in the contact area, located next to the edge of the input part of the first main groove, containing the part with bevels, in the lateral direction of the tire and made curved in accordance with the shapes of the bevels of the part with bevels and extending along the direction along the tire circumference; and an auxiliary groove made in the contact area between the second main groove and the curved groove and extending towards the curved groove in a direction intersecting with the direction along the tire circumference, wherein one end of the auxiliary groove is oriented towards the curved groove and ends inside the contact portion. 2. The pneumatic tire according to claim 1, in which the curved groove is formed with a groove width Wa ranging from 4% to 8% with respect to the size W of the contact portion in the lateral direction of the tire. 3. The pneumatic tire according to claim 1 or 2, in which the size Wb, determined in the lateral direction of the tire from the axial line of the curved groove to the edge of the part with bevels in the contact area, is such that it is in the range from 20% to 45% relative to size W of the contact portion in the lateral direction of the tire. 4. The pneumatic tire according to any one of claims 1 to 3, in which a curved groove is formed with a depth On grooves in the range from 30% to 55% relative to the depth H of the groove representing the first main groove. 5. The pneumatic tire according to any one of claims 1 to 4, in which the bevel portion is formed so that the bevels comprise long sides and short sides that are inclined with respect to the direction along the tire circumference, and are formed with triangular shapes at the edge of the inlet portion of the first main groove, the curved groove is formed curved and contains first inclined sections that are long and inclined with respect to the tire circumferential direction along the long sides of the bevels, and second inclined sections that are short and inclined with respect to the tire circumferential direction along the short bevel sides, the angle α of the inclination of the first inclined section relative to the direction along the tire circumference is formed so that it is in the range from 2 ° to 7 °, and the angle β of the inclination of the second inclined section relative to the direction along the tire circumference is formed so that it is in the range from 20 ° to 60 °. 6. A pneumatic tire according to any one of claims 1 to 5, wherein the bevel portion is formed with a tire size Wc in a tire lateral direction ranging from 4% to 15% with respect to a tire portion W in the tire lateral direction. 7. A pneumatic tire according to any one of claims 1 to 6, in which the portion with bevels is formed with a dimension Hb in the radial direction of the tire, in the range from 30% to 60% with respect to the depth H of the groove representing the first main groove. 8. The pneumatic tire according to any one of claims 1 to 7, in which in the part in which the part with bevels and the curved groove are located opposite each other in the lateral direction of the tire, the laterally defined tire dimension Wc of the bevels in the portion with the bevels is equal to the bend lateral direction determined by the tire side of the tire Wd of that portion of the curved groove which is opposite the bevels in the lateral direction of the tire, and the La dimension of the bevel defined in the direction along the tire circumference in the part with the bevels is made equal to the size Lb in the direction along the tire circumference, which is the size of one curved unit portion in that part of the curved groove that is opposite one bevel in the lateral direction of the tire. 9. The pneumatic tire according to any one of claims 1 to 8, in which the auxiliary groove is formed with a size We in the lateral direction of the tire, in the range from 40% to 50% relative to the size W of the contact portion in the lateral direction of the tire. 10. A pneumatic tire according to any one of claims 1 to 9, in which all second main grooves are made on both sides of the first main groove in the lateral direction of the tire, the contact areas are formed as a result of the formation of their boundaries by means of the first main groove and each of the second main grooves on both sides of the first main groove in the lateral direction of the tire, parts with bevels are made on both edges of the input part of the first main groove, curved grooves are made in each of the contact areas, auxiliary grooves are made in each of the contact areas, and, when the pneumatic tire is mounted on a standard rim, inflated to normal internal pressure and loaded with a load of 70% of the normal load, and in a state in which the tread portion is in contact with a flat surface of the ground on the ground, the area of the inlet part of the groove, which is the first main groove, including parts with bevels, exceeds the area of the inlet part of the groove, which is the first main groove, excluding parts with bevels, by an amount in the range from 15% to 20%. 11. The pneumatic tire according to any one of claims 1 to 10, in which all second main grooves are made on both sides of the first main groove in the lateral direction of the tire, the contact areas are formed as a result of the formation of their boundaries by means of the first main groove and each of the second main grooves on both sides of the first main groove in the lateral direction of the tire, parts with bevels are made on both edges of the input part of the first main groove, curved grooves are made in each of the contact areas, auxiliary grooves are made in each of the contact areas, and in each of the parts with bevels located on the edges of the inlet part of the first main groove, the bevels are made continuously in the direction along the tire circumference, and the boundary parts on which the bevels are continuous relative to each other are displaced relative to each other in the direction along the tire circumference by each of the edges of the inlet of the first main groove. 12. The pneumatic tire according to any one of claims 1 to 9, in which the second main grooves are made on each of those sides of the two first main grooves, which are external in the lateral direction of the tire, the contact areas are formed as a result of the formation of their boundaries by means of the first main grooves and second main grooves located on those sides of the first main grooves that are external in the lateral direction of the tire, parts with bevels are made only at the edges of the inlet parts on those sides of the first main grooves that are laterally external to the tire, curved grooves are made on the contact areas, auxiliary grooves are made in the contact areas, and, when the pneumatic tire is mounted on a standard rim, inflated to normal internal pressure and loaded with a load of 70% of the normal load, and in a state in which the tread portion is in contact with a flat surface of the ground on the ground, the area of the inlet portions of the grooves, which are the first main grooves, including parts with bevels, exceeds the area of the input parts of the grooves, which are the first main grooves, excluding parts with bevels, by an amount in the range from 8% to 13%. 13. A pneumatic tire according to any one of claims 1 to 12, in which the hardness of the rubber, which is a rubber material forming the tread surface in the tread portion, is set in the range from 62 to 68 at a temperature of 20 ° C. 14. The pneumatic tire according to any one of claims 1 to 13, in which tan δ of the rubber material forming the tread surface in the tread portion is set in the range from 0.60 to 0.80 at a temperature of 0 ° C. 15. The pneumatic tire according to any one of claims 1 to 14, in which in the meridional section the actual profile line on the contact section, which is formed as a result of the formation of its boundaries by the first main groove and the second main groove, is formed so that it protrudes further outward into the radial direction of the tire than the imaginary profile line that runs through the end of the edge, which is located on the side of the second main groove, which is internal in the lateral direction of the tire, and is in contact with the surface the tread, and each of the ends of the edges that are located on each side of the first main groove adjacent to the second main groove in the lateral direction of the tire, and are in contact with the tread surface.

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