JP2000280714A - Tire tread - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid stress concentration in a corner part of a projecting element without restricting design of a surface shape of the projecting element such as a block by forming a stress dispersing part formed as the corner gentler than the upper side on the groove bottom side of the corner part of the projecting element. SOLUTION: A tire tread has plural longitudinal grooves 10 extending along the circumference, a shoulder block 13 partitioned by a large number of lateral grooves extending in the almost tire axis direction and a center block. A flat surface recessed inside the upper side block 15 is formed on the groove bottom side 17 of a corner part 16 of the shoulder block 15. Thus, the groove bottom side 17 of the corner part 16 is formed as the corner gentler than the upper side 16a, stress concentration is reduced more than a case of being pointed up to the groove bottom side 17, and the groove bottom side of the corner part 16 becomes a stress dispersing part 17 to thereby avoid stress concentration on the groove bottom side of the corner part of the block as well as to enhance a degree of freedom of design of a block pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire tread which suppresses cracks generated at the bottom of a groove at a corner of a block or the like.

[0002]

2. Description of the Related Art As a tread pattern of a tire, for example, there is one shown in FIG. In the case of this tread pattern, the vertical groove 10 extending in a zigzag direction along the circumferential direction.
And a row of shoulder blocks 15 separated by the vertical grooves 10 and the horizontal grooves 11.

[0003]

When such a tire is mounted on a vehicle and the vehicle runs, when the block 15 comes into contact with the road surface, the block 15 is deformed. When the block 15 is deformed, stress is concentrated on the bottom of the block (the portion where the block rises from the groove), and a crack may occur. In particular, of the corners of the shoulder block 15, the corners 16 located along the vertical grooves 11
Is protruded in a direction crossing the vertical groove 10, so that when the tire is grounded and the block is deformed in the circumferential direction, stress concentrates on the corner 16 and there is a problem that the crack C is easily generated accordingly (FIG. 11).

[0004] When the crack C occurs, there is a problem that the block 15 is chipped or the inner belt layer is exposed and damaged. Such concentration of stress is caused by the pointed portion 16 being sharpened so as to protrude into the vertical groove 10. To solve such a problem, a corner having a notch as shown in FIG. It is conceivable to use a curved portion 29 having a rounded tip as shown in FIG. However, if the shape of the block 16 must be adopted as shown in FIGS. 12 and 13 in order to avoid concentration of stress, the degree of freedom of the design of the tread pattern is limited accordingly (the pattern of FIG. This cannot be adopted), and it becomes impossible to design a pattern in consideration of the driving force and the braking force.

Accordingly, an object of the present invention is to avoid stress concentration at the corners of the projecting element without restricting the design of the surface shape of the projecting element such as a block.

[0006]

The present invention employs the following technical means to achieve the above object. That is, a feature of the present invention is that, in a tire tread having a projection element divided by a groove, a stress dispersion portion that is a gentle corner from the upper side is formed on the groove bottom side of the corner of the projection element. There is in the point. A stress dispersing part with gentle corners is formed at the bottom of the groove at the corner of the protruding element where stress due to deformation of the protruding element is likely to concentrate, so that stress is not concentrated and cracks are prevented from occurring it can.

Further, since the stress dispersing portion is not formed up to the upper side of the corner, that is, not to the surface side of the projecting element, the surface shape of the projecting element can be driven regardless of the shape of the stress distributing portion. It can be designed freely considering power and braking force. Here, the projecting element may be either a block or a rib, and the tread pattern may include both a block and a rib. Further, in the present invention, the stress dispersion portion may be formed in a state in which the groove bottom side of the corner is cut inward.

By forming the groove bottom side of the corner portion inwardly notched, that is, recessed inside the block, the surface area of the projection element is secured large and the concentration of stress on the groove bottom side is effectively performed. Can be avoided. Further, the projecting element includes a block separated by a vertical groove extending along a circumferential direction and a horizontal groove extending substantially in a tire axial direction, and a corner protruding in a direction crossing the vertical groove among corners of the block. It is preferable that the stress dispersing portion is formed.

The concentration of stress is most likely to occur at the corners of such a block, and forming a stress dispersion portion at such a corner is effective in preventing the occurrence of cracks.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. Since the tire tread viewed from the tire surface of the present invention is the same as that shown as a conventional example in FIG. 10, a plurality of vertical grooves 10 and 20 extending along the circumference will be described with reference to FIG. 10. The shoulder block 15 and the center block 25 are defined by a large number of lateral grooves 11 and 21 extending substantially in the tire axial direction.
The longitudinal grooves are located on the tire equator and extend linearly along the circumference of the center linear groove 20A, and side linear grooves 20B which extend linearly on both the left and right sides of the center linear groove 20A. 20B and these side straight grooves 20
B, 20B, five zigzag grooves 10, 10 extending in a zigzag shape along the circumference on the left and right outer sides.

In the lateral groove, the shoulder block 15
The horizontal grooves 11 traversing the row of the center block 25 extend obliquely in the center straight groove 20A. Shoulder block 1
5 has the same pentagonal shape as in the related art in plan view. The shape of the block 15 is not limited to this.
A corner 16 of the shoulder block 15 is located along the zigzag groove 10. FIG. 1 shows a cross section of the corner 16 (a diagram corresponding to FIG. 11 showing the prior art).

The corner portion 16 is positioned so as to project in the horizontal direction with respect to the vertical groove 10. FIG. 2 shows one shoulder block 15, the upper part 1 of the corner 16.
6a (the surface side of the block 15) is formed in a sharp state as before, but the groove bottom side (lower part) 17 of the corner portion 16 is formed.
Are formed in a chamfered state. That is, the groove bottom side 17 of the corner 16 has a flat surface that is recessed inside the upper block 15. For this reason, the groove bottom side 17 of the corner portion 16 is a gentler corner than its upper side 16a, and the concentration of stress is less than in the case where it is sharp to the groove bottom side 17. That is, the groove bottom side of the corner portion 16 is the stress dispersion portion 17.

The shape as described above is the same as the shoulder block 1.
10, the shape of the shoulder block 15 on the bottom side of the groove is shown in FIG. 12, while the surface shown in FIG. 10 is conventional. These advantages can be incorporated while eliminating the disadvantages. That is, even when the block is provided with a corner protruding into the vertical groove, stress concentration on the groove bottom side of the corner of the block can be avoided, so that the degree of freedom in designing the block pattern is high. As a relation T (= a / h) between the height a of the stress dispersion portion 17 from the groove bottom and the height h of the shoulder block from the groove bottom, T is 0.1.
It is preferable to be in the range of 0.7 to 0.7 (see FIG. 1A). When T is smaller than 0.1, the stress dispersing portion 17 becomes smaller, so that the effect of relaxing the concentration of stress is reduced accordingly. On the other hand, when T is larger than 0.7,
Becomes too large, the portion where the block is depressed becomes large, and the rigidity of the block decreases.

The stress dispersing portion 17 is located on the upper portion 1 of the corner portion 16.
The relationship L (= b / d) between the length b recessed from 6a and the length d protruding into the vertical groove 10 of the block 15 is L in the range of 0.1 to 0.5. (See FIG. 1B). When L is smaller than 0.1, the stress dispersing portion 17 also becomes smaller, so that the effect of relaxing stress concentration is reduced accordingly. On the other hand, when L is larger than 0.5, the rigidity of the block, particularly the rigidity of the portion of the block 15 projecting into the vertical groove, is reduced. Also, the angle θ of the corner 16
Is preferably in the range of 90 ° to 160 °. Outside this range, the effect of alleviating stress concentration is small.

In order to prevent the occurrence of cracks in the groove bottom of the corner portion 16, it is conceivable to increase the radius R of the groove bottom 16b as shown in FIG. However, in this case, the groove width is narrowed by the increase in R at the end of wear of the block 15, the appearance of wear is poor, and the drainage is also poor. Therefore, from the viewpoint of securing the groove width, as shown in FIG.
It is not preferable to simply increase R of the groove bottom. On the other hand, as shown in FIG. 1 and the like, by providing a concave portion (stress dispersing portion 17) formed on the groove side wall near the groove bottom of the block 15, the block and the groove can be formed without reducing the width of the groove at the groove bottom. It is possible to increase the bottom radius. This makes it possible to excel in the appearance of wear and drainage at the end of wear, and to suppress cracks.

FIG. 3 shows a modification of the above embodiment. In the case of the embodiment shown in FIGS.
In this modified example, the stress dispersing portion 18 is inclined inward as it goes downward from the upper portion 16a of the corner portion 16 instead of being substantially parallel to the upper portion 16a.
Even with such a shape, as shown in FIG.
At the groove bottom, there is no difference from FIG. 2B, and the stress can be dispersed similarly. FIG. 4 shows another modification. Here, the stress dispersion portion 19 is not a flat surface as shown in FIG. 2 but a convex curved surface. That is, the shape shown in FIG.
6 is adopted on the groove bottom side. Even with such a shape, the stress can be dispersed.

FIG. 5 shows still another modification.
Here, the stress dispersion portion 22 has a concavely curved surface. Even with such a shape, the stress can be dispersed. FIG. 6 shows still another modification. Here, the shape of the stress dispersion portion 23 is close to that shown in FIG. 4, and is a convex curved surface. The difference from FIG. 4 is that the stress dispersion portion 23 is recessed inward with a relatively gentle curved surface from the upper side 16a of the corner portion 16 (in FIG. 4, the stress dispersion portion 19 is recessed with a step. 1).

Further, as shown in FIG.
When the portion in contact with the groove bottom is formed with R, stress can be further dispersed. FIG. 8 shows a modified example of the tread pattern to which the present invention is applied. Instead of the block pattern shown in FIG.
This is a mixed pattern of ribs 30 and blocks having shoulder blocks 15 on both left and right sides thereof. The present invention is naturally applicable to such a pattern. Forming the stress dispersion portion at the corner is not limited to the block, but can be applied to the corner of the rib. Therefore, as the tread pattern of the tire,
The present invention can be applied to a rib pattern as shown in FIG. That is, the corners 46 of the zigzag rib 40 are also
A stress dispersion portion as shown in FIGS. 1 to 6 can be formed.

Note that the present invention is not limited to the above-described embodiment.

[0020]

According to the present invention, the degree of freedom in designing the tread pattern can be ensured while avoiding stress concentration at the corners of the projecting elements.

[Brief description of the drawings]

FIG. 1A shows a corner portion 16 of a shoulder block 15;
FIG. 8 is a cross-sectional view (a view corresponding to FIG. 7) of FIG.
7 shows the height relationship, and (b) shows the degree of depression of the stress dispersion portion 17. ,

2A is a perspective view of a shoulder block 15, and FIG. 2B is a plan view of the shoulder block.

3A and 3B show a shoulder block 15 according to a modified example, where FIG. 3A is a perspective view and FIG. 3B is a plan view.

4A and 4B show a shoulder block 15 according to another modified example, where FIG. 4A is a perspective view and FIG. 4B is a plan view.

5A and 5B show a shoulder block 15 according to another modification, wherein FIG. 5A is a perspective view and FIG. 5B is a plan view.

6A and 6B show a shoulder block 15 according to another modification, wherein FIG. 6A is a perspective view, FIG. 6B is a plan view, and FIG.

FIG. 7 is a sectional view of a shoulder block according to a comparative example.

FIG. 8 is a plan view showing a modification of the tread pattern.

FIG. 9 is a plan view showing another modification of the tread pattern.

FIG. 10 is a plan view showing a conventional tread pattern.

FIG. 11 is a sectional view taken along line AA of FIG. 10;

FIG. 12 is a plan view showing another conventional tread pattern.

FIG. 13 is a plan view showing another conventional tread pattern.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Vertical groove (zigzag groove) 15 Shoulder block (projection element) 16 Corner part 16a Upper side of corner part 17 Stress dispersion part 18 Stress dispersion part 19 Stress dispersion part 22 Stress dispersion part 23 Stress dispersion part

Claims (3)

[Claims] 1. A tire tread having a protruding element (15) separated by grooves (10, 11), wherein a corner (16) of the protruding element (15) has an upper side (16a) on a groove bottom side. A tire tread, wherein a stress dispersing portion (17) having gentler corners is formed. 2. The method according to claim 1, wherein the stress dispersion portion has a corner portion.
The tire tread according to claim 1, wherein the groove bottom side is formed with a groove notched inside. 3. The projection element includes a block (15) separated by a circumferential groove (10) extending in a circumferential direction and a transverse groove (11) extending substantially in a tire axial direction, and a corner of the block (15). The tire tread according to claim 1 or 2, wherein the stress dispersing portion (17) is formed at a corner (16) protruding in a direction crossing the longitudinal groove (10).