JP2003211918A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire reducing pattern noise caused by lug grooves of a tread part by generating axle force in a direction opposite to fluctuation of tire axle force generated by the lug grooves. <P>SOLUTION: Rib grooves 12 extending in a tire circumferential direction X and the lug grooves 13 extending in a tire width direction Y with appropriate intervals in a circumferential direction of a rib row B formed by the rib grooves 12 are formed on a tread surface part T of the tread part 11, and a plurality of blocks 14 are formed by the rib grooves 12 and the lug grooves 13. By providing rigidity increased portions 20 canceling out a reduced amount of the tire axle force generated by the lug grooves 13 on surfaces of the blocks 14, exciting force of an axle is reduced, and the pattern noise caused by it is effectively reduced. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire in which a lug groove for generating a variation in tire axle force is formed in the circumferential direction of a rib row formed by the rib groove, and more particularly, due to the lug groove. The present invention relates to a pneumatic tire designed to reduce noise in a vehicle compartment.

[0002]

2. Description of the Related Art In a pneumatic tire such as a radial tire mounted on a vehicle such as an automobile, a tread portion is formed in order to improve grip performance with a road surface. In the tread portion, a plurality of rib grooves (circumferential grooves) extending in the tire circumferential direction are formed on a tread surface portion that comes into contact with the road surface to form a plurality of rib rows, and further, the rib rows extend in the tire width direction. It is configured by forming a large number of lug grooves (lateral grooves) at appropriate intervals, and these rib grooves and lug grooves form a block (land portion).

By the way, in order to improve the pattern noise caused by such a pattern of the tread portion, it is called an impact due to the contact of the pattern of the tread portion, especially the block surrounded by the rib groove and the lug groove with the road surface. From the point of view, techniques such as changing the geometric relationship between the ground contact shape and the groove are often used.

[0004]

However, one of the phenomena that is a problem among the noises caused by the tire pattern is noise that can be heard in the passenger compartment while the vehicle is running (hereinafter referred to as pattern noise). is there.

This pattern noise phenomenon has a component directly emitted from the tire, but its frequency is 1000 Hz.
From the following, it is considered that the influence of the indirect sound generated by the tire vibrating the axle and the vibration of the vehicle body is large.

The cause of the indirect sound in this case can be understood as a change in the tire axle force due to the lug groove which becomes a discontinuous component in terms of rigidity in the circumferential direction of the tire. That is, at the moment when the lug groove comes into contact with the road surface, the space of the lug groove becomes a portion where the rigidity is reduced, and the load is greatly reduced, which causes the tire axle force to largely fluctuate.

Therefore, the present invention has been made in view of the above-mentioned conventional problems, and by generating an axial force in the opposite direction to the variation of the tire axial force generated in the lug groove, the lug groove of the tread portion is generated. An object of the present invention is to provide a pneumatic tire in which pattern noise caused by the above is reduced.

[0008]

In order to achieve such an object, the invention of claim 1 forms at least one rib groove extending in the tire circumferential direction on the tread surface portion of the tread portion, and the rib groove. A lug groove extending in the tire width direction at appropriate intervals in the circumferential direction of the rib row is formed, and in a pneumatic tire in which a plurality of blocks are formed by these rib grooves and lug grooves, the lug groove is formed on the surface of the block. It is characterized in that a rigidity increasing portion is provided to cancel out the decrease in the tire axle force generated in 1.

In this case, when the lug groove formed in the rib row reaches the ground contact line as the tire rotates, the tire axle force is reduced by this lug groove, while the rigidity increasing portion provided on the surface of the block increases the tire axial force. Since the axle force is increased, the decrease in the tire axle force due to the lug groove can be canceled by the increase in the stiffness increasing portion. Therefore, the variation of the tire axle force caused by the lug groove can be suppressed, and the excitation force of the axle can be reduced, and the pattern noise caused by this can be effectively reduced.

Here, the ground contact line is the ground contact edge between the tire and the road surface, and can be measured with the tire mounted on the vehicle, but with the tire alone, it is measured in the following conditions. Is also possible. In this case, the load is the maximum load (maximum load capacity) of the single wheel in the applicable size listed in the following standard, and the internal pressure is the maximum load of the single wheel in the application size described in the following standard (maximum load capacity). The air pressure corresponds to the rim, and the rim is a standard rim (or Approved Rim, Recommended Rim) in the applicable size described in the following standard.

The standard is defined by an industrial standard effective in the region where the tire is produced or used.
For example, in the United States, The Tire and Rim Associ
nation Inc.'s Year Book, The Europ in Europe
Standard of ean Tire and Rim Technical Organization
s Manual, JAT of Japan Automobile Tire Manufacturers Association in Japan
Specified in MA Year Book.

A second aspect of the present invention is the pneumatic tire according to the first aspect, wherein the rigidity increasing portion is a raised portion protruding from the surface of the block.

In this case, when the raised portion reaches the ground contact line, the raised portion is compressed by the road surface, and the rigidity of the compressed portion is increased. By this increased rigidity portion, the tire axle force can be increased. . Therefore, the decrease in the tire axle force due to the lug groove can be canceled by a simple structure in which the tire axial force is simply projected from the block surface.

According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, the lug groove is inclined with respect to the ground line of the tire, and the ground line is formed on the wall surface of the lug groove in the tread portion. It is characterized in that the rigidity increasing portion is present in a region of the block surface surrounded by a position passing through a contact start point which first contacts and a contact end point which finally contacts.

In this case, since the lug groove is inclined with respect to the ground contact line, the contact area between the wall surface of the lug groove and the ground contact line, which is the location where the tire axle force fluctuates, corresponds to the amount of inclination of the lug groove. Since the ground line has a certain width in the circumferential direction, the ground line is an area surrounded by a position passing through the contact start point and the contact end point. Therefore, the presence of the increased rigidity portion on the block surface included in this region
It is possible to efficiently reduce the reduction amount of the tire axle force due to the lug groove.

According to a fourth aspect of the present invention, in the pneumatic tire according to the second or third aspect, the raised portion is set to have an area sufficiently larger than the cross-sectional area of the tire spew formed on the tread portion. Is characterized by.

In this case, the tire spew is a vent hole mark formed for venting air at the time of tire molding, and this tire spew is projected on the surface of the tread portion and is usually formed to be thin with a diameter of about 3 mm or less. Therefore,
By making the area of the raised portion sufficiently larger than the cross-sectional area of the tire spew, it is possible to easily obtain the amount of increase in rigidity corresponding to the reduction of the tire axle force due to the lug groove, and to reduce the pattern noise. Can be increased.

According to a fifth aspect of the present invention, in the pneumatic tire according to any one of the second to fourth aspects, the height of the raised portion is set within the range of 1 to 10% of the rib groove depth. Is characterized by.

In this case, by setting the height of the raised portion to be in the range of 1 to 10% of the depth of the rib groove, the raised portion does not collapse when it comes into contact with the ground, and the portion where the raised portion is formed does not fall. The tire rigidity can be increased stably.

According to a sixth aspect of the present invention, in the pneumatic tire according to any of the first to fifth aspects, the rigidity increasing portion is provided for each predetermined number of blocks arranged in the tire circumferential direction. It has a feature.

In this case, even when the rigidity-increased portions are provided in a predetermined number of blocks, the total number of the rigidity-increased portions formed can be reduced without significantly reducing the effect of reducing the fluctuation of the tire axle force in the entire tire. it can.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

(Basic Structure) In disclosing the present embodiment, first, the basic structure of the pneumatic tire 10 of the present invention will be described with reference to FIGS. 1 to 5.

FIG. 1 is an enlarged view showing a block 14 formed by an inclined lug groove, FIG. 2 is an enlarged view showing a block 14 in which the inclination direction of the lug groove is opposite, and FIG. 3 is a block formed on a shoulder portion. 14 is an enlarged view showing FIG. 14, FIG. 4 is an explanatory view showing various planar shapes of the raised portion 20 by (a) to (c), and FIG. 5 is a cross-sectional shape of the raised portion 20 (a) to (d).
It is explanatory drawing which shows various.

That is, the tread portion 11 of the pneumatic tire 10 of the present invention has at least one (usually a plurality of) ribs extending in the tire circumferential direction X on the tread portion T of the tread portion 11 as shown in FIG. Grooves (circumferential grooves) 12 are formed, and rib rows B are formed by the rib grooves 12, and
In the circumferential direction of the rib row B, a large number of lug grooves (horizontal grooves) 13 that are rigid discontinuous portions with respect to the tire circumferential direction X are formed across the rib row B in the tire width direction Y at appropriate intervals. To be done. Further, CL in the figure indicates the tire equatorial plane of the tire.

Then, the rib groove 12 and the lug groove 13
A large number of blocks (land portions) 14 are formed by the above, and the surfaces of these blocks 14 serve as a contact surface with the road surface (not shown).
Incidentally, in this basic example, the lug groove 13 is formed in the tire circumferential direction X.
On the other hand, it is slightly inclined to the right and inclined (inclination angle θ).

In the pneumatic tire 10, a ground contact line K is formed at the boundary of the tread surface portion T, and the ground contact line K moves upward in the drawing as indicated by an arrow U as the tire rotates during running. I shall.

Here, in the present invention, as shown in FIG. 1, in the areas Z1 and Z2 set in the diagonal portions of the surface of the block 14, the rigidity increasing portions shown in FIGS. Is provided so that the decrease in the tire axle force generated in the lug groove 13 is canceled by the raised portion 20. At this time, the raised portion 20
Is preferably included in the areas Z1 and Z2 in an area of half or more.

The regions Z1 and Z2 are the lug grooves 1 which are inclined.
3, the ground contact line K first comes into contact with the wall surface 13a of the lug groove 13 in the tread surface portion T.
It is set as a region surrounded by the contact end point P2 from 1 to the last contact. At this time, the contact start point P1 and the contact end point P2 are respectively provided on the two sides 14a and 14b of the block 14 that face each other in the tire rotation direction X, and the regions Z1 and Z2 form a pair at diagonal positions of the block 14. Will be arranged and arranged.

In particular, the raised portion 20 has the lug groove 13
It is preferable to exist on the ground line K passing through the contact start point P1 that first contacts the wall surface 13a of the.

By the way, as shown in FIG.
When the inclination direction of 3 is opposite to that of the case of FIG. 1, that is, when the inclination is upward to the left, the diagonal direction of the block 14 in which the regions Z1 and Z2 are arranged is opposite.

Further, as shown in FIG. 3, when the blocks 14 are provided on the shoulder ribs B located on both sides in the tire width direction Y, the contact end point P2 at which the grounding line K finally contacts is the tire width. The ground line Kw in the direction Y is determined at the intersection with the wall surface 13a of the lug groove 13.

The raised portion 20 is formed to have an area sufficiently larger than the cross-sectional area of the tire spew formed on the tread portion 11. That is, as shown by the chain double-dashed line in FIG. 4, this tire spew S is a protrusion formed as a vent hole mark provided in a molding die for venting air at the time of tire molding, and usually has a diameter of about 3 mm or less. It has a diameter.

Further, as shown in FIG. 4, the ridge 20 can be formed as a square (a), a circle (b) or a triangle (c) in plan view, and in particular, these (a) to (c). The shape is not limited to the plane shape of), and any other shape can be used. And, when formed in any shape, the raised portion 20 has the tire spew S
Is formed with a sufficiently large area that is equal to or larger than the cross-sectional area of a circle having a diameter of about 3 mm.

The cross-sectional shape of the ridge 20 in the tire diameter direction may be a shape that can be stably crushed when it is grounded on the road surface and compressed. For example, as shown in FIG. Cross-sectional shape that changes (a), cross-sectional shape that rises like a mountain with an inflection point (b), trapezoidal cross-sectional shape that rises with a flat top surface (c), rectangular cross-sectional shape (d) Can be formed as. Of course, the ridge 20
Can be formed as a cross-sectional shape other than these (a) to (d), but in any case, the height H0 of the raised portion 20 is set in the range of 1 to 10% of the rib groove depth. To be done.

Further, the ridges 20 may be provided not in all the blocks 14 arranged in the tire circumferential direction X of the rib array B but in a predetermined number of the blocks 14.

(Operation) In the pneumatic tire 10 having such a configuration, the rib rows B formed by the rib grooves 12 formed in the tread portion T of the tread portion 11 are appropriately spaced in the tire circumferential direction X of the rib rows B. Since the lug groove 13 is formed with, when the lug groove 13 reaches the ground line K as the tire rotates, the space portion of the lug groove 13,
That is, the tire axle force is reduced due to the reduced rigidity portion, but in the present embodiment, a ridge that cancels out the variation of the tire axle force due to the lug groove 13 on the surface of the block 14 formed by the rib groove 12 and the lug groove 13. A section 20 is provided.

That is, the raised portion 20 is formed on the surface of the block 14.
Since the ridge 20 is compressed when it comes into contact with the road surface, the tire rigidity can be increased at the portion where the ridge 20 is formed, and the tire axle force due to the lug groove 13 can be reduced. The amount can be canceled out by the increase in the rigidity of the raised portion 20.

Therefore, the variation of the tire axle force due to the lug groove 13 is suppressed, and the excitation force of the axle can be reduced, and the pattern noise resulting from this can be effectively reduced. As a result, it is possible to secure quietness in the vehicle interior while traveling and improve riding comfort.

Further, since the decrease in the tire axle force due to the lug groove 13 is canceled by the ridge 20, the ridge 20 can be achieved by a simple structure in which the ridge 20 is projected from the surface of the block 14 to vulcanize the tire. The increased rigidity portion can be easily formed without significantly complicating the structure of the mold.

Further, in the basic structure of the present invention, the lug groove 13
Is inclined with respect to the tire width direction Y (inclination angle θ), so that the lug groove 13 is inclined with respect to the ground line K. Therefore, the contact area between the wall surface 13a of the lug groove 13 and the ground contact line K, which is the location where the tire axle force fluctuates, has a certain width in the tire circumferential direction due to the inclination of the lug groove 13. , An area Z1 surrounded by a position where the ground line K passes through the contact start point P1 and the contact end point P2
Z2 is formed.

Therefore, a contact start point P1 and a contact end point P2 at which the location of the raised portion 20 contacts the wall surface 13a of the lug groove 13 where the ground line K is inclined first and last.
By making the regions Z1 and Z2 surrounded by the position passing through, it is possible to efficiently reduce the decrease in the tire axle force due to the lug groove 13.

In particular, it is preferable that the raised portion 20 exists on the ground line K passing through the contact start point P1 that first comes into contact with the wall surface 13a of the lug groove 13, and in this case, the lug groove 13 and the raised portion 20. However, they simultaneously exist on the ground contact line K, which is the starting point of the variation of the tire axle force due to the lug groove 13. Therefore, at the moment when the lug groove 13 starts to contact the road surface and the tire axle force fluctuates, the raised portion 20
Since it is possible to cancel the fluctuation by means of, the fluctuation of the tire axle force due to the lug groove 13 can be suppressed with high accuracy.

Further, as shown in FIG.
Since the area of is set to be sufficiently larger than the cross-sectional area of the tire spew S normally set to have a diameter of 3 mm or less, it is possible to easily obtain an increase amount of rigidity corresponding to the reduction of the tire axle force by the lug groove 13. Therefore, the effect of reducing pattern noise can be enhanced.

Further, as shown in FIG.
Since the height H0 of each of the ribs is set within a range of 1 to 10% of the depth of the rib groove, the ridge 20 does not collapse when it comes into contact with the ground, and the tire rigidity of the portion where the ridge 20 is formed is stable. Can be increased to

By the way, in the case where the raised portions 20 are provided in a predetermined number of the blocks 14 provided in the tire row direction X of the rib row B, for example, in every other block 14,
It is possible to reduce the total number of the raised portions 20 formed without significantly reducing the effect of reducing the variation of the tire axle force in the entire tire, which simplifies the configuration of the tire, for example, simplifies the structure of the tire forming mold. You can
It is possible to reduce tire costs.

(Embodiment) Based on the basic structure of the pneumatic tire 10 described above, the first embodiment shown in FIGS.
~ Pneumatic tire 10a ~ 10g according to the sixth embodiment.
The specific structure of is disclosed.

(First Embodiment) FIG. 6 is a bottom view showing a tread portion 11 of a pneumatic tire 10a according to a first embodiment of the present invention. The same components as those of the basic structure are designated by the same reference numerals and overlap with each other. The description will be omitted.

The pneumatic tire 10a of the first embodiment
The tread portion 11 is provided with three rib rows B1, B2, B3 at the center in the tire width direction Y, and
Wide rib rows B4 and B5 are provided on the lateral side portions of B3 on the outer side in the width direction (on both sides in the width direction Y).

In this case, three rib rows B1 and B in the central portion
In B2 and B3, B1 is referred to as a center rib, B2 and B3 are referred to as second ribs, and rib rows B4 and B5 in the side portions are referred to as shoulder ribs. Of course, each rib row B
1, B2, B3, B4, B5 are formed by a plurality of rib grooves 12 extending in the tire circumferential direction X, and each rib row B1, B
2, B3, B4, B5 are provided with a large number of lug grooves 13, and these rib grooves 12 and lug grooves 13 form a large number of blocks 14. In this embodiment, 60 blocks are arranged in the tire circumferential direction X. 14 are arranged.

In this embodiment, the lug groove 13 formed in the center rib B1 and the second ribs B2, B3 is inclined in a certain direction (inclination angle θ), but the lug groove formed in the shoulder ribs B4, B5. 13 is formed parallel to the tire width direction Y.

The outer peripheral boundary of the tread surface portion T when the pneumatic tire 10 touches the ground serves as a ground line K, and the ground line K continuously moves upward in the drawing as the tire rotates. The boundaries of the tread portion T in the tire width direction Y are located on the shoulder ribs B4 and B5, and the ground contact width line Kw is set.

Here, in this first embodiment, all the blocks 1 of each of the rib rows B1, B2, B3, B4, B5 are arranged.
4, a circular raised portion 20 is provided, and the raised portion 20 is arranged in regions Z1 and Z2 (see FIGS. 1 and 3) set at diagonal positions of each block 14. . Therefore, in this case, the number of blocks 14 provided with the raised portions 20 in the tire circumferential direction X is 60.

(Second Embodiment) FIG. 7 is a bottom view showing a tread portion 11 of a pneumatic tire 10b according to a second embodiment of the present invention. The same components as those in the first embodiment are designated by the same reference numerals. A duplicate description will be omitted.

The pneumatic tire 10b according to the second embodiment.
The tread portion 11 is formed with rib grooves 12 and lug grooves 13 having the same shape and number as those in the first embodiment, and each rib row B1, B2, B3, B4, B5 has 60 in the tire circumferential direction X. Blocks 14 are provided.

In this second embodiment, each rib row B1,
Circular ridges 20 are provided every other block B2, B3, B4, B5.
The number of blocks 14 provided with the raised portions 20 is 30 in the tire circumferential direction X.

(Third Embodiment) FIG. 8 is a bottom view showing a tread portion 11 of a pneumatic tire 10c according to a third embodiment of the present invention. The same components as those in the first embodiment are designated by the same reference numerals. A duplicate description will be omitted.

The pneumatic tire 10c of the third embodiment
The rib groove 12 and the lug groove 13 having the same shape and number as those of the first embodiment are formed in the tread portion 11 of each of the rib rows B1, B2, B3, B4, B.
5 includes 60 blocks 14 in the tire circumferential direction X.

In the third embodiment, the second rib B2
A circular raised portion 20 is provided only on the block 14 of B3. In this case, the second rib B2, B
The ridges 20 are provided on all the blocks 14 of No. 3, and the blocks 14 provided with the ridges 20 are arranged in the tire circumferential direction X by 6 times.
It becomes 0.

(Fourth Embodiment) FIG. 9 is a bottom view showing a tread portion 11 of a pneumatic tire 10d according to a fourth embodiment of the present invention. The same components as those in the first embodiment are designated by the same reference numerals. A duplicate description will be omitted.

Pneumatic tire 10d of the fourth embodiment
The rib groove 12 and the lug groove 13 having the same shape and number as those of the first embodiment are formed in the tread portion 11 of each of the rib rows B1, B2, B3, B4, B.
5 includes 60 blocks 14 in the tire circumferential direction X.

In the fourth embodiment, the circular raised portion 20 is provided only on the block 14 of the center rib B1. In this case, the raised portions 20 are provided on all the blocks 14 of the center rib B1, and the number of blocks 14 provided with the raised portions 20 is 60 in the tire circumferential direction X.

(Fifth Embodiment) FIG. 10 is a bottom view showing a tread portion 11 of a pneumatic tire 10e according to a fifth embodiment of the present invention. The same components as those in the first embodiment are designated by the same reference numerals. A duplicate description will be omitted.

The pneumatic tire 10e of the fifth embodiment
The rib groove 12 and the lug groove 13 having the same shape and number as those of the first embodiment are formed in the tread portion 11 of each of the rib rows B1, B2, B3, B4, B.
5 includes 60 blocks 14 in the tire circumferential direction X.

The pneumatic tire 10e of the fifth embodiment
The raised portion 20 is provided only on the block 14 of the center rib B1 as in the fourth embodiment, but the raised portion 20 in this case is formed in a triangular shape.

The raised portions 20 are provided on all the blocks 14 of the center rib B1, and the number of blocks 14 provided with the raised portions 20 is 60 in the tire circumferential direction X.

(Sixth Embodiment) FIG. 11 is a bottom view showing a tread portion 11 of a pneumatic tire 10f according to a sixth embodiment of the present invention. The same components as those in the first embodiment are designated by the same reference numerals. A duplicate description will be omitted.

The pneumatic tire 10f according to the sixth embodiment.
The rib groove 12 and the lug groove 13 having the same shape and number as those of the first embodiment are formed in the tread portion 11 of each of the rib rows B1, B2, B3, B4, B.
5 includes 60 blocks 14 in the tire circumferential direction X.

The pneumatic tire 10f according to the fifth embodiment.
Is the center rib B1 as in the fourth and fifth embodiments.
The ridge 20 is provided only on the block 14 of FIG. 1, but the ridge 20 in this case has a rectangular shape extending along the diagonal of the block 14.

The raised portions 20 are provided on all the blocks 14 of the center rib B1, and the number of blocks 14 provided with the raised portions 20 is 60 in the tire circumferential direction X.

(Dimensions of Tread Section and Raised Section of Each Embodiment) By the way, specific dimensions of the tread section 11 and the raised section 20 of the pneumatic tires 10a to 10f shown in the first to sixth embodiments are as follows. The rib groove 12 has a width and a depth of 8 mm, which are common to the respective embodiments.
3 has a width and a depth of 8 mm.

The circular raised portion 20 of the first to fourth embodiments has a diameter of 4 mm and a height of 0.3 mm. In addition, the triangular protrusion 20 and the sixth embodiment of the fifth embodiment.
The rectangular ridge 20 of the embodiment is the circular ridge 2
It is formed to a size corresponding to 0 and has the same height of 0.3 mm.

(Vehicle interior noise evaluation test of each embodiment) Next, in a 2000 cc class passenger car, the pneumatic tires 10a to 10g of the first to sixth embodiments (tire size: 195 / 65R14, internal pressure: 200 kPa) were used. Vehicle interior noise (bandwidth value of 400 to 600 Hz including the primary pitch frequency of the pattern) in comparison with the conventional tire is individually measured by using each of the above. In this case, the vehicle interior noise is measured based on the sound around the driver's ears, and the sensory evaluation of the driver is also described. In addition, the traveling condition of the passenger car is such that two passengers are traveling on a smooth concrete road at a vehicle speed of 50 km / h.

[0074]

[Table 1] Therefore, from the above table, the vehicle interior noise is 3d in the first embodiment.
B, 2 dB in the second to fifth embodiments, 2.5 d in the sixth embodiment
A reduction (improvement) of B was observed, and the sensory evaluation of the driver was improved in all the embodiments.

By the way, the rigidity increasing portion is not limited to the uneven portion such as the raised portion 20 and the recessed portion, but the rigidity can be changed by partially changing the material of the portion.

The pneumatic tire of the present invention is not limited to the above-mentioned respective embodiments, and various embodiments can be adopted without departing from the scope of the present invention.

[0077]

According to the first aspect of the present invention, since the block formed by the rib groove and the lug groove is provided with the rigidity increasing portion for canceling the decrease in the tire axle force generated in the lug groove on the surface of the block. The decrease in tire axle force due to the lug groove can be canceled by the increase in rigidity increasing portion. Therefore, it is possible to suppress the variation of the tire axle force caused by the lug groove and effectively reduce the pattern noise caused by this, so that it is possible to secure quietness in the vehicle interior and improve riding comfort. it can.

According to the invention of claim 2, claim 1
In addition to the effect of the present invention, since the rigidity increasing portion is a protruding portion that protrudes from the surface of the block, it is possible to simply protrude the protruding portion from the block surface by a decrease amount of the tire axle force due to the lug groove. Since it can be canceled by the structure, it is possible to easily form the increased rigidity portion without significantly complicating the structure of the vulcanization form of the tire.

According to the invention of claim 3, in addition to the effects of the inventions of claims 1 and 2, the lug groove is inclined with respect to the ground contact line of the tire, and the ground line extends within the tread portion. Since the rigidity increasing portion is present in the area of the block surface surrounded by the position where the contact start point that first contacts the wall surface of the groove and the contact end point that finally contacts the groove surface,
It is possible to efficiently reduce the reduction amount of the tire axle force due to the lug groove.

According to the invention of claim 4, claim 2
In addition to the effect of the invention, since the raised portion is set to an area sufficiently larger than the cross-sectional area of the tire spew formed in the tread portion, the rigidity corresponding to the reduction of the tire axle force by the lug groove is increased. The amount can be easily obtained, and the effect of reducing pattern noise can be enhanced.

According to a fifth aspect of the present invention, in addition to the effects of the second to fourth aspects, the height of the raised portion is set to be 1 to 1 of the rib groove depth.
Since the range is set to 0%, it is possible to stably increase the tire rigidity of the portion where the ridge is formed without causing the ridge to fall when the ridge contacts the ground.

According to the sixth aspect of the invention, in addition to the effects of the first to fifth aspects, the rigidity increasing portion is provided for each predetermined number of blocks arranged in the tire circumferential direction. It is possible to reduce the total number of rigidity-increased portions and simplify the structure without reducing the effect of reducing the fluctuation of the axle force so much, and thus it is possible to reduce the cost of the tire.

[Brief description of drawings]

FIG. 1 is an enlarged view showing blocks in a basic configuration of the present invention.

FIG. 2 is an enlarged view showing a block in which the inclination directions of the lug grooves are opposite in the basic configuration of the present invention.

FIG. 3 is an enlarged view showing a block formed in a shoulder portion in the basic configuration of the present invention.

4A to 4C are explanatory views showing various planar shapes of a raised portion in the basic configuration of the present invention with FIGS.

5 (a) to 5 (d) are explanatory views showing various sectional shapes of a raised portion in the basic configuration of the present invention.

FIG. 6 is a bottom view showing the tread portion of the pneumatic tire according to the first embodiment of the present invention.

FIG. 7 is a bottom view showing the tread portion of the pneumatic tire of the second embodiment of the present invention.

FIG. 8 is a bottom view showing a tread portion of a pneumatic tire according to a third embodiment of the present invention.

FIG. 9 is a bottom view showing a tread portion of a pneumatic tire according to a fourth embodiment of the present invention.

FIG. 10 is a bottom view showing the tread portion of the pneumatic tire of the fifth embodiment of the present invention.

FIG. 11 is a bottom view showing the tread portion of the pneumatic tire of the sixth embodiment of the present invention.

[Explanation of symbols]

10, 10a, 10b, 10c, 10d, 10e, 10
f Pneumatic tire 11 Tread part 12 Rib groove 13 Lug groove 14 Block 20 Raised part (stiffness increasing part) B Rib row B1 Center rib (rib row) B2, B3 Second rib (rib row) B4, B5 Shoulder rib (rib row) ) T Foot surface K Ground line

Claims (6)

[Claims] 1. At least one rib groove extending in the tire circumferential direction and a lug groove extending in the tire width direction at appropriate intervals in the circumferential direction of a rib row formed by the rib groove are provided on the tread portion of the tread portion. In a pneumatic tire having a plurality of blocks formed by these rib grooves and lug grooves, a rigidity increasing portion that cancels out a decrease in tire axle force generated in the lug grooves is provided on the surface of the block. Pneumatic tire characterized by. 2. The pneumatic tire according to claim 1, wherein the rigidity increasing portion is a raised portion protruding from the surface of the block. 3. The pneumatic tire according to claim 1, wherein the lug groove is inclined with respect to a ground line of the tire, and the ground line first contacts the wall surface of the lug groove in the tread surface portion. A pneumatic tire characterized in that the rigidity increasing portion is present in a region of a block surface surrounded by a position passing through a contact end point where a start point and a final contact point pass. 4. The pneumatic tire according to claim 2, wherein the raised portion has an area sufficiently larger than a cross-sectional area of a tire spew formed in the tread portion. Included tires. 5. The pneumatic tire according to claim 2, wherein the height of the raised portion is set in a range of 1 to 10% of a rib groove depth. Included tires. 6. The pneumatic tire according to claim 1, wherein the rigidity increasing portion is provided for each predetermined number of blocks arranged in the tire circumferential direction. tire.