JP2006341816A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the road holding ability by suppressing the deformation of a block owing to the rigidity decrease, and to improve the brake performance and drive performance, etc., not only on the snow and ice road surface but a dry road surface so as to suppress the eccentric wear and loss of a sipe from occurring, in a pneumatic tire having a sipe in the block of a tread. <P>SOLUTION: In the pneumatic tire, the sipe 10 is formed so as to have a perpendicular section 11 perpendicular to a tread 5, a first bend 12 bending in a zigzag tilting in the fore-and-aft direction of the tire circumferential direction toward the perpendicular section 11, a second bend 13, a third bend 14 and a bottom perpendicular section 15 perpendicular to the tread 5 and located near the bottom of the block 4, in this order from the tread 5 toward the bottom of the block 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pneumatic tire in which a sipe is formed on a tread block, and more particularly, to a pneumatic tire that suppresses collapse deformation of the block and improves braking and driving performance on a dry road surface as well as an ice / snow road surface.

  In general, a pneumatic tire is provided with a plurality of belt layers and a tread in order on the crown of the toroidal radial carcass, and the contact surface contacting the road surface of the tread has a coefficient of friction between the tire and the road surface. In order to ensure enhanced braking and driving performance, steering stability performance, and the like, a tread pattern composed of various grooves and cuts is formed.

  In recent years, a block pattern in which a large number of blocks are formed on a tread centering on a tire for a passenger car is frequently used as a tread pattern that exhibits good running performance on an icy and snowy road surface. In this block pattern, a plurality of main grooves (rib grooves) extending in the tire circumferential direction are provided to form a plurality of rib rows, and further, a plurality of sub-grooves (dividing the rib rows and extending across the main grooves) Lug grooves) are formed at appropriate intervals in the tire circumferential direction, and blocks (land portions) defined by these main grooves and sub grooves are formed.

  By making the tread block, it is possible to increase the corner (edge) component by scratching the road surface, and to increase the friction coefficient μ of the tire by the edge effect, thereby improving the gripping force on ice and snow. However, particularly when traveling on ice, even a tire having such a block pattern may slip on the ice without being able to grip the road surface. Therefore, in order to further improve the grip force of the tire and improve braking / driving performance and driving stability performance on ice etc., a fine notch extending perpendicularly to the bottom direction (depth or thickness direction) in the tread pattern block ( Sipes) are provided and the block is subdivided to further increase the edge component to improve the friction coefficient.

  In addition to the edge effect described above, by forming a sipe in the block, a water removal effect that absorbs water from the water film generated between the road surface and the tire causing hydroplaning to eliminate the water film, and the road surface by the edge. The number of sipes tends to increase in recent years because the adhesion effect of reliably bringing the water film into contact with the torn road surface is also improved.

  However, if the number of sipes is increased to increase the sipe density, the edge component increases, but the rigidity of the entire block decreases, and when the load is applied to the tire during braking / driving, it falls into the block Deformation occurs, and on the contrary, the edge effect is reduced, resulting in a problem that the gripping force and the like on an icy and snowy road surface are reduced. In addition, there is a problem that the contact area between the tire and the road surface is reduced due to the falling deformation of the block, and the contact property is deteriorated. Furthermore, due to the deterioration of the ground contact property, there is a problem that the amount of slip on the kicking side of the block increases and heel and toe wear in which the kicking side wears unevenly occurs.

  In order to avoid these problems, a pneumatic tire is known in which the shape of a sipe formed in a block is changed in the depth direction and collapse deformation associated with a decrease in block rigidity is suppressed (see Patent Document 1).

  FIG. 4 is an enlarged cross-sectional view of a section of the pneumatic tire block parallel to the tire circumferential direction. This conventional pneumatic tire has a plurality of blocks 50 in the tread. As shown in the figure, each block 50 is provided with two sipes 51 extending in parallel to each other and perpendicular to the bottom direction in the tire width direction. ing. Further, a convex portion 52 is formed on one wall surface (left side in the drawing) of each sipe 51 facing each other, and a dimple 53 that engages the convex portion 52 is formed on the other wall surface (right side in the drawing). In addition, when a load is input to the block 50, the convex portion 52 and the dimple 53 opposed thereto can be engaged with each other to suppress the collapse of the block 50 and maintain the grounding property.

  However, since this conventional pneumatic tire forms the convex portion 52 only on one wall surface of the sipe 51, the collapse deformation suppression effect differs depending on the collapse direction of the block 50, and depending on the input direction of the load, the collapse deformation suppression effect is exerted. There is a problem of becoming insufficient. That is, when the block 50 is tilted to the protruding side of the convex portion 52, the frictional force due to the contact between the engaging portion of the convex portion 52 and the dimple 53 is increased and the effect of suppressing the collapse is increased, while the tilting in the reverse direction is increased. Sometimes, the frictional force of the engaging part of the convex part 52 and the dimple 53 becomes small, and the fall-down deformation suppressing effect becomes small.

  In addition, when this sipe 51 is formed on the block 50 of the all-season tire, a force greater than that on snow or ice is input to the block 50 on a dry road surface or the like where the coefficient of friction is high. There is a problem that the amount of deformation cannot be suppressed and the amount of deformation becomes large.

  In order to deal with such problems, the shape of the sipe is bent a plurality of times to form a zigzag shape (triangular wave shape) toward the bottom of the block, suppressing the collapse deformation regardless of the collapse direction of the block. There is known a pneumatic tire that maintains the ground contact property (see Patent Document 2).

  FIG. 5 is a perspective view of the pneumatic tire block seen through. This conventional pneumatic tire has a plurality of blocks 60 in the tread, and as shown in the figure, each block 60 is provided with four sipes 61 extending along the tire width direction. Each sipe 61 is formed in a zigzag shape by bending a plurality of times in both the front and rear directions of the tire circumferential direction from the tread surface 62 of the block 60 to the bottom portion of the block 60. The area and frictional force that contact each other can be increased, and the collapse deformation of the block 60 can be suppressed.

  Moreover, since the sipe 61 is bent a plurality of times in both the front and rear directions in the tire circumferential direction, even if the block 60 falls down in any direction in the tire circumferential direction, a sufficient contact area between the sipe 61 wall surfaces can be secured. The collapse deformation of the block 60 can be suppressed. Therefore, even when the sipe 61 is increased, it is possible to maintain the grounding property by suppressing the falling deformation accompanying the rigidity reduction of the block 60.

  However, this conventional pneumatic tire is intended to obtain high braking performance and driving performance on icy and snowy road surfaces, and performance on dry road surfaces with a high friction coefficient is not particularly taken into consideration. Therefore, when a large input is made on a dry road surface or the like, a sharp corner portion (sipe edge) of the sipe 61 in the tire width direction is caught between the tread surface 62 and the road surface, the wall surface of the sipe 61 comes into contact with the road surface, and the sipe edge is lost. There is a problem.

JP-A-5-58118 JP 11-170817 A

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to suppress a block collapse deformation caused by a decrease in rigidity in a pneumatic tire having a tread having a plurality of blocks formed with sipes. To improve the ground contact, improve the braking / driving performance to show high grip on not only snowy and snowy road surfaces, but also suppress uneven wear and sipe edge loss. It is.

The invention of claim 1 is a pneumatic in which a tread is provided with a plurality of blocks defined by a plurality of main grooves extending in the tire circumferential direction and a plurality of sub grooves extending in the tire width direction, and sipes are formed in the blocks. In the cross section perpendicular to the sipe longitudinal direction of the block, the sipe includes a vertical portion extending from the tread surface of the block in a normal direction of the tread surface, and a front and back of a tangent line of the tread surface following the vertical portion. A bent portion extending in the direction of the bottom of the block while being bent in a direction, and a vertical portion of the bottom extending in the normal direction of the tread surface to the vicinity of the bottom of the block following the bent portion.
According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the bent portion extends in a tangential direction of the tread surface with respect to a normal line of the tread surface following the vertical portion. A second bent portion extending in a tangential direction of the tread surface opposite to the inclined direction of the first bent portion with respect to the normal line of the tread surface following the first bent portion; And a third bent portion extending in a tangential direction of the tread surface opposite to the inclination direction of the second bent portion with respect to the normal line of the tread surface following the bent portion.
According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, the longitudinal direction of the sipe is a tire width direction.
According to a fourth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects, the sipe is formed in a shape in which a straight line is bent.
According to a fifth aspect of the present invention, in the pneumatic tire according to any one of the first to fourth aspects, a length in a normal direction of the tread surface of the vertical portion is a length in a normal direction of the tread surface of the sipe. The length is 1/7 or more and 1/3 or less.
The invention according to claim 6 is the pneumatic tire according to any one of claims 2 to 5, wherein the distance between the midpoint of the length in the normal direction of the tread surface of the second bent portion and the tread surface is: The length of the sipe in the normal direction of the tread surface is 1/3 or more and 3/5 or less.
A seventh aspect of the present invention is the pneumatic tire according to any one of the second to sixth aspects, wherein the lengths in the normal direction of the tread surface of the first bent portion and the third bent portion are the same length. It is characterized by being.
According to an eighth aspect of the present invention, in the pneumatic tire according to any one of the second to seventh aspects, an angle formed between the first bent portion and the second bent portion and a tangent to the tread surface is 0 °. It is larger and smaller than 70 °, and an angle formed between the third bent portion and the tangent line of the tread surface is larger than 0 ° and smaller than 90 °.

(Function)
According to the present invention, the sipe in the vicinity of the block tread is made a vertical portion extending in the bottom direction to increase the rigidity of the sipe edge, so that the sipe edge is caught between the block tread and the road when a large input is made on a dry road surface. Suppress. In addition, the sipe is provided with a bent portion to increase the area where the wall surfaces of the sipe are in contact with each other at the time of ground contact, and further, the contact area is ensured regardless of the collapse direction of the block. Therefore, the frictional force due to the contact with the sipe wall surface is increased, and the collapse deformation due to the decrease in the rigidity of the block is suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, in the pneumatic tire which equipped the tread with the several block in which the sipe was formed, the fall deformation accompanying the rigidity reduction of a block can be suppressed, and grounding property can be improved. Therefore, high grip force can be demonstrated not only on snowy and snowy road surfaces but also on dry road surfaces, etc., and the braking and driving performance of pneumatic tires can be improved, and further, the occurrence of uneven wear and sipe edge defects can be suppressed. it can.

Hereinafter, an embodiment of a pneumatic tire of the present invention will be described with reference to the drawings.
First, the shape of the tread pattern formed on the tread of the pneumatic tire will be described. FIG. 1 is a developed plan view of a tread pattern shape of the pneumatic tire 1 of the present embodiment.

  Although not shown, the pneumatic tire 1 has a left and right sidewall and a crown portion having a tread straddling between both sidewalls in a toroidal shape, and passes through the crown portion from one sidewall. A carcass made of at least one organic fiber cord radial ply or one steel cord radial ply over the other sidewall, and a belt layer including a plurality of steel cord layers disposed between the carcass and the tread. It has a known structure with.

  As shown in the figure, the tread pattern shape of the pneumatic tire 1 includes two main grooves (rib grooves) 2 extending in parallel to the tire circumferential direction (arrow S direction) on the left and right sides of the equator line CL. A plurality of sub-grooves (lug grooves) 3 that intersect with each of the main grooves 2 and extend in the tire width direction (arrow L direction), and a plurality of rectangular blocks (land land) partitioned by these grooves 2 and 3 Part) 4 and a plurality of sipes 10 formed in the block 4 and extending in the tire width direction L.

  The sipe 10 is formed across the block 4 from one main groove 2 to the other main groove 2, and one or a plurality (four in FIG. 1) are provided in each block 4 at regular intervals in the tire circumferential direction S. Book) is provided. The sipe 10 is formed toward the bottom of the block 4 while being bent in the front-rear direction of the tire circumferential direction S as described below.

FIG. 2 is an enlarged cross-sectional view of the block 4 in a cross section parallel to the tire circumferential direction S of FIG. 1, and shows an example in which the number of sipes 10 is one.
As shown in the figure, the sipe 10 has a vertical portion 11 perpendicular to the tread surface 5 in order from the tread surface 5 of the block 4 toward the bottom portion, and a first bend inclined in the front-rear direction of the tire circumferential direction with respect to the vertical portion 11. Part 12, second bent part 13, third bent part 14, and bottom vertical part 15 that is perpendicular to the tread surface 5 and located near the bottom of the block 4, so that the block 4 is divided in the tire circumferential direction. It is formed from the tread surface 5 to the vicinity of the bottom of the block 4.

  As described above, the sipe 10 in this embodiment has the zigzag-shaped (triangular wave-shaped) bent portions 12, 13 and 14 as in the conventional sipe 61 shown in FIG. It differs from the conventional sipe 61 in that it has vertical portions 11 and 15 perpendicular to the tread surface 5 on the 5 side and the bottom side.

  FIG. 3 is an enlarged cross-sectional view of the sipe 10 of FIG. In the following description, the tread surface 5 side of the block 4 is the upper side, and the bottom side is the lower side. The length of each part of the sipe 10 (L, L1, L2, L3, L4, L5 in the figure) is a direction perpendicular to the tread surface 5, that is, the normal direction of the tread surface 5 that is the tire radial direction (in the figure Arrow Y) (hereinafter simply referred to as the normal direction Y), and the inclination angles (α, β, γ in the drawings, respectively) of the bent portions 12, 13, 14 in the tire circumferential direction are the lengths of the sipe 10. Of the angles formed by the tangential direction (arrow X in the figure) (hereinafter simply referred to as tangential direction X) of the tread surface 5 orthogonal to the direction (tire width direction), the angle is the acute angle (90 ° or less).

  As shown in FIG. 3, the vertical portion 11 has an upper end that opens into the tread surface 5 of the block 4 and is linearly formed along the normal direction Y from the tread surface 5 toward the bottom portion of the block 4. Following the lower end of the vertical portion 11, the first bent portion 12 is inclined at a predetermined angle α in one of the tangential directions X (rightward in the figure) with respect to the normal direction Y and is obliquely downward (inclined rightward in the figure). (Downward) is formed linearly. The second bent portion 13 has a predetermined angle β in the tangential direction X (leftward in the figure) opposite to the inclination direction of the first bent portion 12 with respect to the normal direction Y following the lower end of the first bent portion 12. And is formed in a linear shape obliquely downward (in the drawing, diagonally left downward). The third bent portion 14 is, following the lower end of the second bent portion 13, a tangential direction opposite to the inclination direction of the second bent portion 13 with respect to the normal direction Y (same as the inclination direction of the first bent portion 12). Inclined at a predetermined angle γ in X (rightward in the figure) and formed in a straight line toward obliquely downward (inclined rightward in the figure). The bottom vertical portion 15 is formed linearly along the normal direction Y toward the bottom of the block 4 following the lower end of the third bent portion 14.

  As described above, the sipe 10 is formed to have a shape in which a straight line is bent, that is, a zigzag shape that is formed by straightly bending a straight line. 12, 13 and 14, convex portions 16 and 18 and concave portions 17 and 19 having a triangular cross section are formed in the tire width direction. That is, the first bent portion 12 and the second bent portion 13 cause the convex portion 16 that protrudes toward one of the wall surfaces of the sipe 10 (left side in the drawing) toward the inclined direction side (right side in the drawing) of the first bent portion 12. However, on the other side (the right side in the figure), a concave part 17 substantially the same shape as the convex part 16 is formed, and one of the wall surfaces of the sipe 10 (the right side in the figure) is formed by the second bent part 13 and the third bent part 14. Is formed with a convex portion 18 projecting toward the inclined direction side (left side in the drawing) of the second bent portion 13 and a concave portion 19 having substantially the same shape as the convex portion 18 is formed on the other side (left side in the drawing). Yes.

  The length L1 of the vertical portion 11 is preferably 1/7 or more and 1/3 or less (more preferably about 1/5) of the length (depth) L of the sipe 10; The distance (L1 + L2 + L3 / 2) between the midpoint of the length L3 of the bent portion 13 and the tread surface 5 (L1 + L2 + L3 / 2) is not less than 1/3 and not more than 3/5 of the length L of the sipe 10 (more desirably not less than 3/7 and not more than 1/2). The length L2 of the first bent portion 12 and the length L4 of the third bent portion 14 are preferably the same length. Therefore, the length L2 of the first bent portion 12 and the length L3 of the second bent portion 13 are determined so that the midpoint of the length L3 of the second bent portion 13 is located within the above range.

  The inclination angle α of the first bent portion 12 is preferably greater than 0 ° and smaller than 70 °, and the inclination angle β of the second bent portion 13 is greater than 0 ° and smaller than 70 ° (more preferably 0 ° The inclination angle γ of the third bent portion 14 is preferably larger than 0 ° and smaller than 90 °.

Next, the operation during traveling of the sipe 10 formed as described above will be described.
First, since the vertical portion 11 extending in the bottom direction is formed at the opening portion of the tread surface 5 of the sipe 10, the angle of the sipe edge is increased as compared with the case where only the bent portion is formed as in the conventional sipe 61 of FIG. The rigidity in the vicinity (W in FIG. 3) can be increased. Therefore, in FIG. 3, when the block 4 receives a shear input in the projecting direction of the convex portion 16 from the road surface (the direction from left to right in FIG. 3), the vicinity of the sipe edge indicated by W in FIG. It is possible to prevent the sipe edge from being caught between the sipe edge and the sipe edge, which has occurred at the time of a large input on the dry road surface.

  In addition, when the length L1 of the vertical part 11 is smaller than 1/7 of the length L of the sipe 10, the rigidity in the vicinity of the sipe edge is insufficient and may be lost due to entanglement deformation. If it is larger than 1/3, the region where the bent portions 12, 13, and 14 of the sipe 10 are formed becomes shorter, and the lengths L2, L3, and L4 of the bent portions 12, 13, and 14 are correspondingly reduced. If the length of the sipe 10 is shortened, the area of the sipe 10 wall surface may be reduced, and the effect of suppressing the collapse of the block 4 described later may be reduced. On the other hand, the length of the inclined direction is secured to maintain the area of the sipe 10 wall surface. For this reason, if the inclination angles α, β, γ of the bent portions 12, 13, 14 are reduced, the vulcanized tire 1 is difficult to be removed from the mold, which is not desirable.

  Since the sipe 10 has zigzag bent portions 12, 13, and 14 following the lower end of the vertical portion 11, the wall surfaces of the sipe 10 facing each other when the block 4 is grounded compared to a straight sipe that is not bent. The contact area and the frictional force due to the contact can be increased. Since the blocks 4 sandwiching the sipe 10 support each other by this frictional force, it is possible to suppress the falling deformation accompanying the decrease in the rigidity of the block 4 and to suppress the deterioration of the ground contact property. Therefore, it is possible to reduce the slip on the kicking side of the block 4 and to suppress the occurrence of uneven wear such as heel and toe wear.

  Further, when the block 4 receives a shearing input in the protruding direction of the convex portion 16 from the road surface (the direction from left to right in FIG. 3), the wall surfaces of the sipe 10 are in strong contact with each other at the second bent portion 13. Since the frictional force supports the block 4 on the shear input side (left side in FIG. 3), the block 4 can be prevented from falling down. On the other hand, when the block 4 receives a shear input in the reverse direction from the road surface (the direction from right to left in FIG. 3), the wall surfaces of the sipe 10 are in strong contact with each other at the first bent portion 12 and the third bent portion 14. In addition, since the block 4 on the shear input side (right side in FIG. 3) is supported by the frictional force, the block 4 can be prevented from being collapsed. Thus, even if the block 4 falls down in any direction, the fall-down deformation can be suppressed, and the grounding property can be improved.

  Here, when the length L2 of the first bent portion 12 and the length L4 of the third bent portion 14 are set to the same length as described above, the effect of suppressing the falling deformation of the block 4 is obtained in the depth direction of the sipe 10. In addition, since it can be more uniformly dispersed, the collapse deformation of the block 4 can be more effectively suppressed.

  Further, as described above, when the distance (L1 + L2 + L3 / 2) between the midpoint of the length L3 of the second bent portion 13 and the tread surface 5 is set to 1/3 or more and 3/5 or less of the length L of the sipe 10, The position of the second bent portion 13 can be near the center of the sipe 10 in the depth direction, and particularly when the shear is input to the block 4 from the left to the right in FIG. It is possible to improve the effect of suppressing the falling deformation of the block 4.

  Further, the length L1 of the vertical portion 11 is set to about 1/5 of the length L of the sipe, and the distance (L1 + L2 + L3 / 2) between the midpoint of the length L3 of the second bent portion 13 and the tread surface 5 is the length of the sipe 10. When the inclination angle β of the second bent portion 13 is larger than 0 ° and smaller than 45 ° when it is set to 3/7 or more and 1/2 or less of L, the contact of the sipe 10 wall surface occurs efficiently regardless of the input direction. Therefore, the effect of suppressing the collapse of the block 4 can be further enhanced.

  In addition, when the inclination angle α of the first bending portion 12 and the inclination angle β of the second bending portion 13 are 70 ° or more, the wall surface of the sipe 10 at that portion stands too much and the wall surfaces of the sipe 10 are in contact with each other. The effect may decrease, which is not desirable. Further, when the inclination angle α of the first bending portion 12 and the inclination angle β of the second bending portion 13 are set to the above-described desired range (greater than 0 ° and smaller than 70 °), the blocks 4 in both directions which are sufficient by them are used. Therefore, the inclination angle γ of the third bent portion 14 inclined in the same direction as the first bent portion 12 may be a larger angle (greater than 0 ° and smaller than 90 °). Further, the vertical portion may be formed by setting the inclination angle γ to 90 °.

  In the present embodiment, as shown in FIG. 1, since the sipe 10 is formed in the tire width direction L, the block 4 can be prevented from falling in the tire circumferential direction S. Driving performance, uneven wear resistance performance, etc. can be improved.

  In addition to the tire width direction L, the sipe 10 may be formed in the block 4 by being inclined at the tire circumferential direction S or an arbitrary angle therebetween, and is formed by combining the sipe 10 extending in each direction. May be. In the case of the sipe 10 extending in the tire circumferential direction S, it is possible to improve cornering performance at the time of turning, and in the case of the sipe 10 extending at an inclination, the performance at the time of straight traveling and the performance at the time of turning are provided. be able to.

  As described above, by forming the sipe 10 provided in the block 4 of the pneumatic tire 1 as in the present embodiment, it is possible to suppress the falling deformation accompanying the rigidity reduction of the block 4 and to improve the grounding property. Can be improved. Therefore, a high grip force can be exhibited not only on a snowy and snowy road surface but also on a dry road surface, and the braking / driving performance of the pneumatic tire 1 can be improved. In addition, it is possible to suppress the occurrence of uneven wear and sipe edge defects. Furthermore, since the sipe 10 of this embodiment is formed in a shape in which a straight line is bent, a blade to be attached to a mold forming the sipe 10 can be easily manufactured.

  In the present embodiment, the main groove 2 and the sub-groove 3 are both linear grooves extending in parallel to the tire circumferential direction and the width direction, respectively, but may be inclined and extend in shape. Other shapes such as a zigzag shape, a crank shape, and a round shape may be used. Therefore, the block 4 partitioned by the grooves 2 and 3 may also be a block 4 having another shape such as a parallelogram, a V shape, and a pentagon in addition to a rectangular shape in plan view.

  Further, the cross-sectional shape of the sipe 10 may be any shape other than the zigzag shape, such as a waveform (sine curve or the like) or a rectangular wave shape, as long as it is bent a plurality of times and extends toward the bottom of the block 4. Alternatively, the number of bent portions may be increased. Both ends of the sipe 10 may not be opened in the main groove 2 as in this embodiment, and both ends may be used in the block 4 or only one side, depending on the tread pattern configuration. The number of sipes 10 formed in one block 4 is not limited.

(Example)
In order to confirm the effect of the pneumatic tire 1 of the present invention, the present embodiment shown in FIGS. 2 and 3 is applied to a tire block 4 having a size of 205 / 55R16 defined by JATMA YEAR BOOK (2004, Japan Automobile Tire Association Standard). The tire of the example in which one sipe 10 is formed (hereinafter referred to as an “executed product”) and the tire of a comparative example in which one straight sipe extending linearly in the bottom direction of the block 4 is formed (hereinafter referred to as a “comparative product”). Models were created, and the coefficient of block friction exhibited by contact between sipe wall surfaces when large shear force was applied under constant load conditions was compared.

  As a result, when the block friction coefficient of the comparative product is set to 100, the block friction coefficient of the implementation product is as high as 109 at the maximum, and it was found that the frictional force due to the contact between the sipe wall surfaces can be increased. Thereby, it has confirmed that the fall deformation | transformation inhibitory effect of the block 4 improved and grounding property could be improved.

It is an expansion | deployment top view which shows the tread pattern of the pneumatic tire in one Embodiment of this invention. It is an expanded sectional view of the block in the cross section parallel to the tire circumferential direction of FIG. It is an expanded sectional view of the sipe of FIG. It is sectional drawing parallel to the tire peripheral direction of the block of the conventional pneumatic tire. It is the perspective view which saw through the block of the conventional pneumatic tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Pneumatic tire, 2 ... Main groove, 3 ... Sub groove, 4 ... Block, 5 ... Tread, 10 ... Sipe, 11 ... Vertical part, 12 ... -1st bending part, 13 ... 2nd bending part, 14 ... 3rd bending part, 15 ... Bottom vertical part, 16 ... Convex part, 17 ... Concave part, 18 ... Convex part Part, 19 ... concave part.

Claims (8)

A pneumatic tire in which a tread is provided with a plurality of blocks defined by a plurality of main grooves extending in the tire circumferential direction and a plurality of sub grooves extending in the tire width direction, and sipes are formed in the blocks,
In the cross section orthogonal to the sipe longitudinal direction of the block, the sipe is bent in the front-rear direction of the tangent line of the tread surface following the vertical portion, the vertical portion extending in the normal direction of the tread surface from the tread surface of the block A pneumatic tire comprising: a bent portion extending in a bottom direction of the block; and a bottom vertical portion extending in a normal direction of the tread surface to the vicinity of the bottom portion of the block following the bent portion. In the pneumatic tire according to claim 1,
The bent portion includes a first bent portion extending in a tangential direction of the tread surface with respect to the normal line of the tread surface following the vertical portion, and a normal line of the tread surface following the first bent portion. A second bent portion extending obliquely in a tangential direction of the tread surface opposite to the inclined direction of the first bent portion, and the second bent portion with respect to the normal line of the tread surface following the second bent portion. A pneumatic tire, comprising: a third bent portion extending incline in a tangential direction of the tread surface opposite to the inclination direction. In the pneumatic tire according to claim 1 or 2,
A pneumatic tire characterized in that a longitudinal direction of the sipe is a tire width direction. In the pneumatic tire according to any one of claims 1 to 3,
The said sipe is formed in the shape where the straight line was bent, The pneumatic tire characterized by the above-mentioned. In the pneumatic tire according to any one of claims 1 to 4,
The length of the vertical portion in the normal direction of the tread surface of the vertical portion is 1/7 or more and 1/3 or less of the length of the sipe in the normal direction of the tread surface. In the pneumatic tire according to any one of claims 2 to 5,
The distance between the midpoint of the length in the normal direction of the tread surface of the second bent portion and the tread surface is not less than 1/3 and not more than 3/5 of the length in the normal direction of the tread surface of the sipe. Pneumatic tire characterized by. In the pneumatic tire according to any one of claims 2 to 6,
The length of the tread surface in the normal direction of the first bent portion and the third bent portion is the same length. In the pneumatic tire according to any one of claims 2 to 7,
The angles formed by the first bent portion and the second bent portion and the tangent to the tread surface are both greater than 0 ° and smaller than 70 °.
A pneumatic tire characterized in that an angle formed between the third bent portion and a tangent line of the tread is greater than 0 ° and smaller than 90 °.

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