JPH10278514A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire having excellent overall performance as a well balanced tire for dart contests. SOLUTION: In a pneumatic tire with a plurality of block patterns, a) pitch length P satisfies an inequality 0.2SL<=P<=0.3SL (SL represents tread peripheral length at a JATMA static load radius value), b) a width W, a length L and an angle α of a cross section direction groove Z satisfy inequality 0.05SL<=W<=0.09SL L>=TW×0.25, 10 deg.<=α<=18 deg. respectively, and c) the total number Sa of the two kinds of blocks in the periphery and the individual number Sb, Sc and Sd of three kinds of blocks in the periphery satisfy 1.5×Sb<=Sa<=2×Sb, 1.5×Sc<=Sa<=2×Sc, and 1.5×Sd<=Sa<=2×Sd, and d) blocks (b), (c) and (d) have an overlap section in the horizontal direction (n) and (m), and e) the rate (G/H) that occupies the width G of blocks a1 and a2 in a range H satisfies an inequality 0.2<=G/H<=0.4, and f) tread groove area rate is from 53 to 46%, and the rate (I/O) of the tread inside and tread outside in this groove area rate satisfies 1<=I/O<=1.05.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly to an improvement in overall performance of a pneumatic tire for dirt competition such as rally.

[0002]

2. Description of the Related Art A tread of a pneumatic tire for dirt competition such as a rally includes a plurality of circumferential grooves extending along a tread circumferential line, and a number of circumferential grooves connecting the circumferential grooves and between the circumferential groove and a tread end. It has a block pattern in which a block is divided by a lateral groove, and this pattern generally has a point symmetry with respect to a center point on a central circumferential line (M) of the tread.

[0003] However, in recent years, asymmetric tread block patterns have been adopted to improve the performance of dirt competition tires. For example, as shown in FIG. 2, when the vehicle is mounted on the vehicle, the ratio of the groove area occupying the inside and outside of the ground with respect to the center circumferential line (M) is changed (Japanese Unexamined Patent Publication No. Hei 6-191).
No. 233), and as shown in FIG. 3, the groove component is changed between the inside and outside of the ground, and the lug component (groove in the cross-section direction) is emphasized on the inside, while the road surface rigidity is emphasized on the outside, and the direction is further improved. As shown in FIG. 4, a pattern in which the block rigidity is changed between the inside and the outside is often known as a characteristic pattern.

[0004]

However, in pneumatic tires having the above-described asymmetric tread block pattern, all the performances are not necessarily improved in a well-balanced and comprehensive manner.

For example, in the tread pattern shown in FIG. 2, since the cross-sectional edge component is larger than the circumferential edge component, it cannot be said that the balance between the traction performance and the sideslip performance is good.

Further, in the tread pattern shown in FIG. 3, the difference in block rigidity between the inside and outside of the ground is small. This means that a wide road performance can be obtained because the matching road surface is determined by the size of the block. It means difficult. That is, on a hard road, a larger block is more excellent in matching with the road surface, while a low friction coefficient μ
On the road surface, the smaller the block, the better the matching.

Further, in the tread pattern shown in FIG. 4, the angle of the groove in the sectional direction of the tread central circumferential line (M) is 20 ° or more with respect to the sectional direction, so that the directional pattern is improved rather than the traction performance. It is used. In addition, there is no overlap amount of the blocks outside the ground, and it is inevitable that the circumferential edge is greatly damaged when traveling on a pavement road or a dirt hard road surface.

Accordingly, an object of the present invention is to solve the above-mentioned problems of a conventional pneumatic tire for dirt competition having an asymmetric tread block pattern, and to provide a pneumatic tire having excellent overall performance balanced for dirt competition. Is to do.

[0009]

In the rally competition, when the wear mode of the tire tread after running is observed, the amount of wear on the outside of the ground located outside the center circumference (M) when the vehicle is mounted is compared with the amount of wear on the inside of the ground. It can be seen that the damage of the circumferential edge is particularly large. This means that the tire on the outer side of the corner during cornering, particularly the severity on the outer side of the tire ground, is higher than the inside of the ground used when traveling straight. Based on such knowledge, the present inventors have earnestly studied how to effectively use the inside of the ground and the outside of the ground independently of each other, and furthermore, it is possible to reduce the reduction in performance due to wear, particularly the reduction in traction performance. As a result, the following findings were further obtained.

[0010] The load during straight traveling is approximately equally distributed to the four wheels. In addition, since the tires of the competition vehicles are generally used for negative camber, the load during straight traveling is received inside the tire contacting. Therefore, it is necessary to improve the traction performance when traveling straight and the generality of the performance by making the block inside the ground smaller.

On the other hand, during cornering, the load concentrates on the tire on the outer side of the turn, so that the load on the outer side of the ground increases when compared between the inner side and the outer side of the tire. This is the reason why the tire wear amount after use is larger on the outside of the contact surface than on the inside of the contact surface, and particularly, the damage of the circumferential edge becomes large. Therefore, it is necessary to make the block rigidity outside the ground contact higher than the block rigidity inside the ground contact.

In addition, the circumferential edge is important for controlling the sideslip at the time of cornering on a dirt road surface, and it is necessary to make the peripheral length of the block outside the ground contact longer than the peripheral length of the block inside the ground contact.

Furthermore, if the circumferential grooves forming the block outside the ground contact are straight, the buckling (bending) in the circumferential grooves becomes large due to a large load during cornering,
While promoting the wear of the circumferential edge of the block,
The contact property deteriorates, and the exercise performance on a hard road surface is reduced. Therefore, it is important that the block on the outer side of the ground is formed of a stepwise circumferential groove, and that the adjacent blocks in the lateral direction overlap to secure tread surface rigidity.

In order to generate good traction, it is effective to have a cross-sectional groove at 90 ° with respect to the circumferential direction. In this case, the cross-sectional groove edge is severely worn, and the traction performance due to the wear is reduced. The decline is fast. Therefore, it is necessary to extend the life of traction generation by suppressing the damage of the block edge by forming an angle in the cross-sectional groove, but it is necessary to limit the cross-sectional groove angle to a range in which the directionality of the exercise performance does not occur. .

The inventors of the present invention have conducted intensive studies based on all the above findings, and as a result, the above-mentioned problems have been solved by forming the tire tread pattern as described below, thereby exhibiting a well-balanced overall performance as a dirt competition tire. The inventors have found that the present invention can be performed, and have completed the present invention.

That is, the pneumatic tire of the present invention is formed on the tread surface by a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of cross-sectional grooves extending in the tire width direction crossing the circumferential grooves. In the pneumatic tire having a plurality of block patterns, a) the circumferential repetition pitch length (P) of the block pattern is represented by the following formula: 0.2SL ≦ P ≦ 0.3SL (SL is the 1997 JATMA YEAR BOO.)
B) tread at intervals of the pitch length (P) and centered on the central circumference (M). Sectional width (TW) × 0.
6, the width (W) of the cross-sectional groove (Z) existing in the center area of the tire in the range (H), the length (L) of the cross-sectional direction linear with respect to the TW, and the angle (α) with respect to the cross-sectional direction are respectively. A) 0.05SL ≦ W ≦ 0.09SL a) L ≧ TW × 0.25 c) 10 ° ≦ α ≦ 18 °, c) in the tire width direction when mounted on the vehicle The two types of blocks (a ₁ , a 2) that are adjacent to each other in the tire circumferential direction on the TW × １ ／ point on the inner side of the ground located inside the center circumference line (M).
the total circumferential upper number of a _{2) (Sa),} each peripheral on the number of the three blocks existing adjacent in the tire width direction in the range (H) in other positions (b, c, d) (Sb, S
c, Sd) satisfy the following expression: 1.5 × Sb ≦ Sa ≦ 2 × Sb 1.5 × Sc ≦ Sa ≦ 2 × Sc 1.5 × Sd ≦ Sa ≦ 2 × Sd , d) the three blocks (b, c and d) are divided by each step-like circumferential groove (X, Y), step-like lateral step blocks adjacent in the horizontal direction (M _1, M ₂ , N ₁ ,
N ₂₎ is overlapped portion in the lateral direction (n, has m), e) the range (H) within the second species blocks _(a 1, _a
2 ) The ratio (G / H) occupied by the width (G) satisfies the relationship represented by the following formula: 0.2 ≦ G / H ≦ 0.4. F) The groove area ratio of the tread is 53 to 46. %, And the ratio (I / O) of the groove area ratio between the inside of the ground and the outside of the ground satisfies a relationship represented by the following formula: 1 ≦ I / O ≦ 1.05 tire.

Here, "1997 JATMA YE
"The static load radius value specified in AR BOOK" means that the tire is mounted on the applicable rim, the air pressure is specified, the tire is placed perpendicular to the flat plate in a stationary state, and from the center of the tire axis when the specified mass is applied. It refers to the shortest distance to the contact surface, and the “length in the contact circumferential direction” refers to the maximum linear length in the tire circumferential direction at the contact surface.

In the pneumatic tire of the present invention, when the tread pattern is used as a directional pattern, the angle of the edge side wall on the stepped side of the cross-sectional groove is made smaller than the angle of the edge side wall on the buttoned side. More effective.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to FIG. In the pneumatic tire of the present invention, the circumferential repetition pitch length (P) of the block pattern is expressed by the following equation: 0.2SL ≦ P ≦ 0.3SL (SL is the circumferential length in the contact circumferential direction at the JATMA static load radius value) It is necessary to satisfy the relationship expressed by (sa).

P is 20% of the ground circumferential length SL.
If it is less than this, it is difficult to dispose a block having a circumferential component edge effective for sideslip during turning, which is not preferable for cornering performance. On the other hand, if it exceeds 30%, the contact property in the circumferential direction is reduced, and the traction performance when traveling straight is deteriorated.

At the interval of the pitch length (P) and with the center circumference (M) as the center, the width (TW) in the cross section direction of the tread ×
The width (W) of the cross-sectional groove (Z) existing in the center region of the tire in the range (H) of 0.6, the linear cross-sectional length (L) along the TW, and the angle (α) with respect to the cross-sectional direction are as follows. It is necessary to satisfy the relationship expressed by the following formulas: a) 0.05SL ≦ W ≦ 0.09SL a) L ≧ TW × 0.25 c) 10 ° ≦ α ≦ 18 °

When the groove width (W) of the cross-sectional groove (Z) is less than 5% with respect to the ground length SL, the edge effect is small and the generation of traction is low, while when it exceeds 9%, the edge effect is large. However, wear of the edge becomes severe.

In order to obtain high traction performance during cornering, a cross-sectional groove extending linearly outward from the center of the tire is effective, and its cross-sectional length (L) is effective.
Requires at least 25% of TW, preferably 6% of TW.
0% or less. When L is less than 25% of the TW, the effect of improving the circumferential contact property is low, and the occurrence of traction is low.

Further, the angle (α) of the cross-sectional groove (Z) with respect to the tire cross-sectional direction must be in the range of 10 ° to 18 °. When this angle is less than 10 °, the traction in a new article is large, but the amount of wear of the block edge is large, and the traction performance is greatly reduced as the wear progresses. On the other hand, when the angle is more than 18 °, the edge is less damaged, and stable traction is obtained although it is slightly lower. However, since the pattern performance has directionality, the mounting position is limited and the versatility is poor. Will be.
When carrying spare tires is necessary as in a rally event, separate spare tires for left and right need to be loaded, which is disadvantageous.

Further, in the pneumatic tire of the present invention, when the vehicle is mounted on the vehicle, two types of blocks (a ₁₎ existing on the TW × １ ／ point on the inner side of the ground located inside the center circumference (M). , A ₂ ), and the respective numbers (Sb, Sc, Sd) of the three types of blocks (b, c, d) existing in the range (H) at other positions. )
Must satisfy the relationship expressed by the following equation: 1.5 × Sb ≦ Sa ≦ 2 × Sb 1.5 × Sc ≦ Sa ≦ 2 × Sc1.5 × Sd ≦ Sa ≦ 2 × Sd

By making the inside-ground blocks (a ₁ , a ₂ ) smaller than the outside-ground blocks (b, c, d) within a range that satisfies the above expression, the traction performance when traveling straight and the road surface condition are improved. It can be made to effectively work to improve the versatility against the change.

The ground outer blocks (b, c,
d) is longer in the circumferential direction than the grounding inner blocks (a ₁ , a ₂ ) and has higher rigidity, thereby ensuring high block rigidity against a large load during cornering and a circumferential edge effective for sideslip. can do.

Said ground outer blocks (b, c and d)
Are divided by stepwise circumferential grooves (X, Y), respectively, and stepwise lateral steps (M ₁ ,
M ₂ , N ₁ , N ₂ ) are overlapped horizontally (n,
m).

If the lateral overlap (n, m) of the outer blocks (b, c, d) in the lateral direction is eliminated, the bending (buckling) of the circumferential groove becomes large under a large load, and the edge is damaged. Also increases. In addition, such a buckling deteriorates the grounding property, and thus has poor cornering performance on a pavement or a hard dirt road.

In the present invention, the range (H)
Wherein the ratio (G / H) occupied by the width (G) of the _two seed blocks (a ₁ , a ₂ ) satisfies the relationship represented by the following equation: 0.2 ≦ G / H ≦ 0.4. I need to do that. If the G / H value is less than 0.2, good traction performance during straight running cannot be obtained, while if it exceeds 0.4, good skid performance during turning cannot be obtained. That is, when the value is 0.2 or more and 0.4 or less, the balance between the traction performance and the skid performance is good.

Furthermore, in the present invention, the ratio of the groove area ratio of the tread is 53 to 46% and the ratio (I / O) of the groove area ratio between the inside of the ground and the outside of the ground is as follows: 1 ≦ I / O It is necessary to satisfy the relationship represented by ≦ 1.05.

If the groove area ratio exceeds 53%, the block rigidity (tread surface rigidity) decreases, and the exercise performance on a hard road decreases. However, the performance on a road surface having a low friction coefficient μ value is high. On the other hand, if it is less than 46%, the performance on a hard road surface is high because the block rigidity (tread surface rigidity) is high, but the performance on a dirt road surface with a low μ value is low. In the present invention,
Since the pattern is designed by changing the block stiffness between the inner side and the outer side of the ground, the ratio (I / O) of the groove area between the inner side and the outer side of the ground is preferably as equal to or more than possible and there is little difference. It is necessary to do.

The structure other than the tread pattern of the pneumatic tire of the present invention may be in accordance with the conventional tire practice. For example, the carcass has at least one (at most three) turn-up ply wound around the bead core from the inside to the outside of the tire, and the ply is formed by attaching a fiber cord represented by rayon, nylon and polyester to the tire equatorial plane. In the belt layer, non-extensible cords such as steel cords and aromatic polyamide fiber cords are arranged at an angle of 10 to 35 ° with respect to the tire equatorial plane. At least one auxiliary belt layer in which a heat-shrinkable cord typified by a nylon cord is disposed substantially parallel to the equatorial plane of the tire over the entire width of a main belt layer in which at least two layers of the belt are arranged so as to cross each other. In the formation, do not spirally wind in a ribbon state where a plurality of cords are arranged along the circumference of the main belt layer. Things each use. Then, on the belt layer, a tread having the above-described tread pattern is arranged.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A pneumatic tire according to an embodiment of the present invention according to the tread pattern shown in FIG. 1 and a pneumatic tire (control) according to a comparative example according to the conventional tread pattern shown in FIG. 2 both have a tire size of 195 / 65R15. Prototype. The specific conditions of the tread pattern of the example tire are as follows.

Pattern design Repeated pitch length (P): circumferential length in the ground contact direction (SL) × 0.26: SL is mounted on a standard rim with a tire of the above tire size, and placed perpendicular to a flat plate in a stationary state. , 1997 JATMA Y
When a load of 88% of the maximum load capacity of the EAR BOOK was applied, the maximum linear distance in the tire circumferential direction of the ground contact surface was determined (the internal pressure was an air pressure corresponding to the above load). -Cross-sectional groove (Z) groove width (W): SL x 0.06-Cross-sectional groove (Z) cross-sectional length (L): Tread cross-sectional direction width (TW) x 0.36-Grounding inner block (A ₁ , b ₂ ) and the number ratio of the outer blocks (b, c, d) on the circumference: Sa: Sb = 2: 1 Sa: Sc = 2: 1 Sa: Sc = 2: 1 ・ Ground outer block (b , C, d) lateral overlap amount (m, n) m = 4 mm n = 3 mm Angle (α) of the cross-sectional groove arranged in the range (H) of TW × 0.6 with respect to the cross-sectional direction: 14 ° Groove area ratio: 49% Groove area inside / outside ratio = 1.03 TW × 0.6 range (H) occupies width (G) of block (a ₁ , b ₂ ) Ratio: H x 0.26 (TW: 167mm, SL: 170mm)

Various performance evaluation tests shown in Table 1 below were performed on the example tires and the comparative example tires under the following running conditions. -Tire pressure: front wheel 2.1 kgf / cm ² , rear wheel 2.3
kgf / cm ²・ Test course: Evaluate by going back and forth on a 2km section of the forest road (setting so that the outbound path goes up and the return path goes down) ・ Road condition: changes from weak wet to dry (gravel and gap, but quite・ Driver / vehicle: 2 persons / 4-wheel drive vehicle The results obtained are shown in Table 1 below.

[0037]

[Table 1] Note) In the table, “actual” refers to the example tire, and “ratio” refers to the comparative tire. The display of the feeling comparison has the following meaning, respectively. "(Good) Actual >>Ratio": Example tire is much better than Comparative Example tire "(Good) Actual>Ratio": Example tire is better than Comparative Example tire "(Good) Actual ≧ ratio ”: Example tire is better or equivalently better than comparative tire“ (Good) Actual = ratio ”: Example tire is as good as comparative tire

[0038]

As described above, in the pneumatic tire of the present invention, the tread pattern is a non-conventional asymmetric tread block pattern. Demonstrates excellent balanced overall performance for dirt competition.

[Brief description of the drawings]

FIG. 1 is a developed view of a tread pattern according to the present invention.

FIG. 2 is a development view of a conventional asymmetric tread pattern.

FIG. 3 is a development view of another conventional asymmetric tread pattern.

FIG. 4 is a development view of another conventional asymmetric tread pattern.

[Explanation of symbols]

Block b present in the P peripheral direction repetitive pitch length SL grounded circumferential length M central circumferential line TW sectional width Z section groove X, Y stepped circumferential groove _{a 1, a 2 TW × 1} /4 -point , C, d and other blocks present in H

Claims (2)

[Claims] 1. An air having, on a tread surface, a plurality of circumferential grooves extending in the tire circumferential direction and a plurality of block patterns formed by a plurality of cross-sectional grooves extending in the tire width direction to intersect with the circumferential grooves. In the tire with a, a) the circumferential repetition pitch length (P) of the block pattern is expressed by the following formula: 0.2SL ≦ P ≦ 0.3SL (SL is the 1997 JATMA YEAR BOO.)
B) tread at intervals of the pitch length (P) and centered on the central circumference (M). Sectional width (TW) × 0.
6, the width (W) of the cross-sectional groove (Z) existing in the center area of the tire in the range (H), the length (L) of the cross-sectional direction linear with respect to the TW, and the angle (α) with respect to the cross-sectional direction are respectively. A) 0.05SL ≦ W ≦ 0.09SL a) L ≧ TW × 0.25 c) 10 ° ≦ α ≦ 18 °, c) in the tire width direction when mounted on the vehicle The two types of blocks (a ₁ , a 2) that are adjacent to each other in the tire circumferential direction on the TW × １ ／ point on the inner side of the ground located inside the center circumference line (M).
the total circumferential upper number of a _{2) (Sa),} each peripheral on the number of the three blocks existing adjacent in the tire width direction in the range (H) in other positions (b, c, d) (Sb, S
c, Sd) satisfy the following expression: 1.5 × Sb ≦ Sa ≦ 2 × Sb 1.5 × Sc ≦ Sa ≦ 2 × Sc 1.5 × Sd ≦ Sa ≦ 2 × Sd , d) the three blocks (b, c and d) are divided by each step-like circumferential groove (X, Y), step-like lateral step blocks adjacent in the horizontal direction (M _1, M ₂ , N ₁ ,
N ₂₎ is overlapped portion in the lateral direction (n, has m), e) the range (H) in the above two blocks _(a 1, _a
2 ) The ratio (G / H) occupied by the width (G) satisfies the relationship represented by the following formula: 0.2 ≦ G / H ≦ 0.4. 53-46%
And the ratio (I /
O) which satisfies the relationship represented by the following formula: 1 ≦ I / O ≦ 1.05. 2. The pneumatic tire according to claim 1, wherein the angle of the edge side wall of the stepped side of the cross-sectional direction groove is smaller than the angle of the edge side wall of the buttoned side.