JP2006051836A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve traction performance and wet performance while preventing stone biting in a pneumatic tire provided with a block pattern.
In a pneumatic tire in which a block 4 is formed by main grooves 1 and 2 that extend in a zigzag manner in a tire circumferential direction R and lateral grooves 3 that connect the main grooves 1 and 2 to each other.
A pneumatic tire in which the inclination angle of the side wall 5 of the main groove 1 located at least on the outermost side in the tire width direction W changes so as to decrease from the zigzag peak portion 6a to the zigzag valley portion 6b.
[Selection] Figure 1

Description

  The present invention relates to a pneumatic tire having a block pattern, and relates to improvement of traction performance and wet performance and prevention of stone biting.

In a pneumatic tire provided with a rib pattern, the main groove extending in the tire circumferential direction is not linear but zigzag to improve traction performance and braking performance. Furthermore, in the pneumatic tire disclosed in Patent Document 1, the inclination of the side wall of the main groove is changed from the zigzag peak to the zigzag valley. As a result, as wear progresses, the amplitude of the zigzag appearing on the tread surface increases, and the traction performance is improved.
JP 2001-187518 A

  In order to further improve the traction performance and the wet performance, it is necessary to provide a lateral groove for connecting the main grooves to adopt a block pattern. However, there has been a problem that a phenomenon called stone biting is likely to occur at a place where the main groove and the horizontal groove intersect with each other so that the stone is caught and the stone cannot be removed.

  Therefore, an object of the present invention is to improve traction performance and wet performance while preventing stone biting in a pneumatic tire having a block pattern.

As a result of intensive studies to solve the above problems, the invention according to claim 1 is a pneumatic tire in which a block is formed by a main groove extending in a zigzag shape in a tire circumferential direction and a lateral groove connecting the main grooves. In
A pneumatic tire in which at least the inclination angle of the side wall of the main groove on the outermost side in the tire width direction changes from a zigzag peak to a zigzag trough.

  By changing the inclination angle of the side wall of the main groove so as to decrease from the zigzag peak to the zigzag valley, the zigzag amplitude of the main groove appearing on the tread surface increases as wear progresses. As a result, traction performance and wet performance can be improved even after the middle stage of wear.

  The invention according to claim 2 is the pneumatic tire according to claim 1, wherein an inclination angle of the zigzag valley and an inclination angle of the peak of the zigzag are in a range of 0 to 25 degrees.

  If the inclination angle of the side wall is less than 0 degree, stone biting or cracks at the groove bottom may be easily generated. On the other hand, if it exceeds 25 degrees, the wear resistance may deteriorate and the wear may easily progress.

  The invention according to claim 3 is the pneumatic tire according to claim 1 or 2, wherein the number of crests of the zigzag is 3 to 10 in the contact length.

  If the number of zigzag peaks in the contact length is 2 or less, the improvement in traction performance may be insufficient. On the other hand, if it is 11 or more, the zigzag interval becomes narrow and stone biting is likely to occur.

  According to the present invention, by changing the inclination angle of the side wall of the main groove so as to decrease from the zigzag peak to the zigzag valley, the traction performance and the wet performance can be improved even after the middle stage of wear. Further, by setting the inclination angle of the side walls and the number of zigzag peaks to a predetermined range, it is possible to prevent stone biting and cracks at the groove bottom and improve wear resistance.

  Hereinafter, embodiments of a pneumatic tire according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing a pattern of a pneumatic tire according to the present invention. 1 is a main groove on the outermost side in the tire width direction W, 2 is a main groove other than the main groove 1, and 3 is a lateral groove connecting the main grooves 1 and 2. The main grooves 1 and 2 extend in a zigzag shape in the tire circumferential direction R, and a block 4 is defined by the main grooves 1 and 2 and the lateral grooves 3.

  FIG. 2A is a view showing a cross section taken along the line AA of FIG. The inclination angle of the side wall 5 of the zigzag peak 6a is β, and the inclination angle of the side wall 5 of the zigzag valley 6b is α, and α <β. The same applies to FIG. 2C showing the CC cross section of FIG. In the BB cross section corresponding to the intermediate position between them, as shown in FIG. 2B, the inclination angle of the side wall 5 is (α + β) / 2 on both sides.

  That is, although the side wall 5 of the main groove 1 is inclined, the inclination angle of the side wall 5 changes from β to α from the zigzag peak 6a to the zigzag valley 6b. As a result, as wear progresses, the zigzag amplitude of the main groove 1 appearing on the tread surface increases from d1 to d2, and traction performance and wet performance are improved. D2 is preferably 1.1 to 2.5 times d1. If it is less than 1.1 times, the effect is poor, and if it exceeds 2.5 times, drainage may be impaired.

  In addition to the cross-sectional shape of the main groove shown in FIG. 2, various cross-sectional shapes can be used. For example, FIG. 3A shows an example in which the inclination angle of a part of the side wall 5 on the ridge 6a side is reduced from β to β ′ (> α). FIG. 3B is an example in which the inclination angle of a part of the side wall 5 on the valley 6b side is set to 0 degree. FIG. 3C shows an example in which a narrow groove 7 is further carved in the groove bottom of the main groove 1.

  The inclination angles α and β of the side wall 5 are preferably in the range of 0 to 25 degrees. If the angle is smaller than this range, stone biting or cracks at the groove bottom may easily occur. When the angle is larger than this range, the wear resistance performance is deteriorated, and wear may easily progress.

  The number of zigzag peaks 6a within the contact length is preferably 3-10. If it is 2 or less, the improvement of the traction performance may be insufficient. If it is 11 or more, the zigzag interval is narrowed and stone biting is likely to occur. Here, the contact length is the tire circumferential direction length of the contact surface at an internal pressure and 100% load defined by JATMA.

  The inclination of the side wall can be changed also for the main grooves 2 other than the outermost side in the tire width direction W. However, it is preferable that the side wall be inclined only in the main groove 1 on the outermost side in the tire width direction W because stone biting is likely to occur in the center portion of the tread.

  As an example, a pneumatic tire according to the present invention and a pneumatic tire according to a conventional example were prototyped and performance evaluation was performed. The tire according to the example includes the pattern illustrated in FIG. 1, and the tire according to the conventional example includes the pattern illustrated in FIG. 1, and the inclination angle of the main groove sidewall is fixed to 10 degrees. The dimensions of the main groove are as shown in Table 1. The tire size was 11R22.5, the rim size was 22.5 × 8.25, the air pressure was 700 kPa, and 100% load specified by JATMA was applied to the front wheel of an axle type 2-D truck for performance evaluation.

  In Table 1, the traction performance indicates a coefficient of friction when running on a dry road surface when new and at the time of wear. The wet performance indicates a coefficient of friction when running on a wet road surface. Both are expressed as an index with the value of the conventional example at the time of a new product as 100, and the larger the index, the better the performance. According to Table 1, in the example tires, the degree of performance deterioration is low even when wear progresses as compared with the conventional example.

  Next, a tire with a changed inclination angle of the main groove was prototyped and performance evaluation was performed. The evaluation tire has the pattern shown in FIG. 1 and the dimensions of the main groove are the same as those in Table 1. The tire size is 11R22.5, the rim size is 22.5 × 8.25, the air pressure is 700 kPa, and 100% load as specified by JATMA is attached to the front wheel of an axle type 2-D truck. The performance was evaluated by running 50000 km at 80 km.

  In Table 2, the wear resistance performance represents the reciprocal of the wear amount of the entire tread. The uneven wear resistance performance indicates the amount of wear step in the circumferential direction in the same block and the difference in wear amount between the shoulder block and the center block. The stone biting performance indicates the reciprocal of the number of stones sandwiched in the groove. The crack resistance performance indicates the reciprocal of the sum of the length and depth of a crack that has occurred. Both are expressed as an index with the tire value of α = 5 degrees and β = 10 degrees as 100, and the larger the index, the better the performance.

  According to Table 2, if the inclination angle of the side wall is in the range of 0 to 25 degrees, the wear resistance performance, uneven wear resistance performance, stone resistance performance and crack resistance performance are compatible.

  Next, tires with different numbers of zigzag peaks were produced for performance evaluation. The evaluation tire has the pattern shown in FIG. 1 and the dimensions of the main groove are the same as those in Table 1. The tire size was 11R22.5, the rim size was 22.5 × 8.25, and the air pressure was 700 kPa. Using a 50 t compression tester, an iron ball having a diameter of 10 mm was pushed into a position where the main groove and the transverse groove intersected, and then a load necessary for extracting the iron ball was measured.

  As shown in Table 3, when the number of zigzag peaks per contact length is 10 or less, the stones are easily removed, and the occurrence of stone biting is prevented.

It is the schematic which shows the pattern of the pneumatic tire which concerns on this invention. (A) is the AA cross section of FIG. 1, (b) is a BB cross section of FIG. 1, (c) is a figure which shows the CC cross section of FIG. (A)-(c) is a figure which shows the example of main groove cross-sectional shape.

Explanation of symbols

1, 2 Main groove 3 Horizontal groove 4 Block 5 Side wall

Claims (3)

In a pneumatic tire in which a block is formed by a main groove extending in a zigzag shape in the tire circumferential direction and a lateral groove connecting the main grooves,
A pneumatic tire in which at least the inclination angle of the side wall of the main groove on the outermost side in the tire width direction changes so as to decrease from a zigzag peak to a zigzag valley. The pneumatic tire according to claim 1, wherein an inclination angle of the zigzag valley and an inclination angle of the zigzag peak are in the range of 0 to 25 degrees. The pneumatic tire according to claim 1 or 2, wherein the number of crests of the zigzag is 3 to 10 in a contact length.

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