JP2008184039A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the rolling resistance of a tire, and to maintain traction performance after middle stage of abrasion. <P>SOLUTION: In the pneumatic tire, a plurality of main grooves 1 extending in a tire circumferential direction is provided on a tread, and a sub-groove 2 extending in a tire circumferential direction is provided at an area clamped by the main groove 1 at the outermost side in a tire width direction and a ground-contact end E. A thin rib 3 is formed by the main groove 1 and the sub-groove 2, and a slit 4 for communicating the ground-contact end E with the sub-groove 2 is provided. A row of blocks 5 formed by the ground-contact end E, the sub-groove 2 and the slit 4 is arranged at an outer side in a width direction of the thin rib 3. Depth of the sub-groove 2 is 10-60% of the depth of the main groove 1, and width of the sub-groove 2 is 0.5-3.0 mm. Width of the thin rib 3 is 4-12% of ground-contact end width W, and depth of the slit 4 is 40-80% of the depth of the main groove 1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire in which the rolling resistance of the tire is reduced and the traction performance after the middle stage of wear is maintained.

  In a pneumatic tire having a block row in which blocks are arranged in the tire circumferential direction, the blocks may move excessively, causing uneven wear. In addition, tires generate heat due to excessive movement of the block, which may increase rolling resistance and deteriorate fuel consumption. For this reason, in the pneumatic tire described in Patent Document 1, the groove depth of the central portion of the lateral groove (lug groove) forming the block is made shallow to suppress excessive movement of the block and to suppress uneven wear. The shallow portion is called a bridge, and the depth of the bridge is usually 30% to 60% of the main groove depth.

  In some tires, the lateral groove is extremely shallow (for example, about 10% of the depth of the main groove), and excessive movement of the block is suppressed to solve the above problem.

JP-A-7-172114 (FIGS. 1 and 2)

  In the pneumatic tire described above, when tread wear proceeds, a bridge appears on the tread surface and the lateral grooves are separated. Alternatively, when the lateral groove is extremely shallow, the lateral groove disappears early. As a result, sufficient traction performance cannot be obtained, and it has been difficult to achieve both reduction in rolling resistance of the tire and maintenance of traction performance after the middle period of wear.

  Therefore, an object of the present invention is to reduce the rolling resistance of the tire and maintain the traction performance after the middle stage of wear.

In order to solve the above problems, the pneumatic tire of the present invention has a plurality of main grooves extending in the tire circumferential direction, which are carved into the tread.
In the region sandwiched between the outermost main groove and the ground contact end in the tire width direction, a sub-groove extending in the tire circumferential direction is carved, and a thin rib is formed by the main groove and the sub-groove,
A slit communicating the grounding end and the sub-groove is engraved, and a row of blocks formed by the grounding end, the sub-groove and the slit is arranged on the outer side in the width direction of the thin ribs,
The depth of the sub-groove is 10% to 60% of the depth of the main groove, the width of the sub-groove is 0.5 mm to 3.0 mm, and the width of the thin rib is 4% to the width of the ground end. The depth of the slit is 40% to 80% of the depth of the main groove.

  Compared to the slit, the groove width of the sub-groove is set narrower and the groove depth is shallower. As a result, the rigidity of the connecting portion between the block and the thin rib is increased, and excessive movement of the block is suppressed. As a result, heat generation of the tire is suppressed and rolling resistance is reduced. Further, since it is not necessary to provide a bridge in the slit or to extremely reduce the depth of the slit, the traction performance after the middle stage of wear can be maintained.

  Hereinafter, an embodiment of a pneumatic tire according to the present invention will be described with reference to the drawings. FIG. 1 is a view showing a tread pattern of a pneumatic tire according to the present invention. In the drawing, a plurality of main grooves 1 extending in the tire circumferential direction R are engraved. In a region sandwiched between the outermost main groove 1 and the ground contact end E in the tire width direction, a sub-groove 2 extending in the circumferential direction R is cut, and the main groove 1 and the sub-groove 2 form a thin rib 3. . Furthermore, the slit 4 which connects the grounding end E and the subgroove 2 is carved. Therefore, a block 5 is formed by the ground contact E, the sub-groove 2 and the slit 4, and a block row in which the blocks 5 are arranged in the tire circumferential direction is arranged on the outer side in the width direction of the thin rib 3.

  Compared to the slit 4, the groove width of the sub-groove 2 is set narrow and the groove depth is shallow. As a result, the rigidity of the connecting portion between the block 5 and the thin rib 3 is increased, and excessive movement of the block 5 is suppressed. As a result, heat generation of the tire is suppressed and rolling resistance is reduced. Moreover, since it is not necessary to provide a bridge in the slit 4 or to make the depth of the slit 4 extremely shallow, the traction performance after the middle stage of wear can be maintained.

  The depth of the sub groove 2 is preferably 10% to 60% of the depth of the main groove 1, and the width of the sub groove 2 is preferably 0.5 mm to 3.0 mm. If the depth of the sub-groove 2 exceeds 60% of the depth of the main groove 1 or the width of the sub-groove 2 exceeds 3.0 mm, the block 5 becomes easy to move and the amount of heat generated by the tire increases, and the rolling resistance increases. Will increase. Conversely, if the depth of the secondary groove 2 is less than 10% of the depth of the main groove 1 or the width of the secondary groove 2 is less than 0.5 mm, the traction performance after the middle stage of wear can be maintained. become unable.

  Further, the width W1 of the thin rib 3 is preferably 4% to 12% of the ground end width W of the tread. If it is less than 4%, the block 5 is easy to move, the amount of heat generated by the tire increases, and the rolling resistance increases. On the contrary, if it exceeds 12%, the length of the slit 4 is shortened, so that the traction performance is lowered. In addition, when the width | variety of the thin rib 3 is not constant, W1 is taken as the average value of the whole circumferential direction.

It is not necessary to make the depth of the slit 4 extremely shallow. The depth of the slit 4 is preferably 40% to 80% of the depth of the main groove 1, and the width of the slit 4 is 5.0 mm to 12.0 mm. Is preferred. If the depth of the slit 4 exceeds 80% of the depth of the main groove 1 or the width of the slit 4 exceeds 12.0 mm, the block 5 becomes easy to move and the amount of heat generated by the tire increases, and the rolling resistance increases. Resulting in. Conversely, if the depth of the slit 4 is less than 40% of the depth of the main groove 1 or the width of the slit 4 is less than 5.0 mm, the traction performance after the middle stage of wear cannot be maintained. .

  As an example, a pneumatic tire according to the present invention was prototyped and evaluated. The tread pattern of the example and the comparative example is the pattern shown in FIG. 1, and the depth of the slit 4 was 50% of the depth of the main groove 1 and the width was 6.0 mm. As shown in FIG. 2, the tread pattern of the conventional examples 1 and 2 includes a tread pattern having no thin ribs on the inner side in the width direction of the row of the shoulder blocks 105, and the conventional example 1 has a length of 15.0 mm and a depth of A bridge (not shown) which is 50% of the depth of the main groove 101 is provided in each slit 104 (depth: 50% of the depth of the main groove, width: 6.0 mm), and the depth of the slit 104 of the conventional example 2 is provided. Was 10% of the depth of the main groove 101. The dimensions of the minor groove and the like are as shown in Table 1, and the tire size was 11R22.5 and the internal pressure was 700 kPa, and the rim (size: 22.5 × 7.50) was attached and evaluated.

  The evaluation results are shown in Table 1. The traction performance is expressed as an index (conventional example 1) in which a tire is mounted on all wheels of a small truck (axle arrangement: 2-D) and a braking distance from a speed of 60 km / h on a wet road is applied with a load specified by JATMA. Is 100). Rolling resistance is a value measured with a single-axis drum tester under the condition of 60 km / h and a load of 2500 kg after running for 1 hour at 60 km / h by the force measurement method of the rolling resistance test method for JATMA truck and bus tires. Is represented by an index (conventional example 1 is assumed to be 100). In any evaluation, the larger the number, the better the performance.

  According to Table 1, the traction performance at the time of traveling 30000 km of the example is better than the conventional example 1, so that the traction performance after the middle stage of wear is maintained, the rolling resistance of the example is lower than the conventional example 1, and the tire The rolling resistance was reduced and the traction performance after the middle wear was maintained.

It is a figure which shows the tread pattern of the pneumatic tire which concerns on this invention. It is a figure which shows the tread pattern of the pneumatic tire which concerns on a prior art example.

Explanation of symbols

1 Main groove 2 Sub groove 3 Thin rib 4 Slit 5 Block

Claims (1)

A plurality of main grooves extending in the tire circumferential direction are carved in the tread,
In the region sandwiched between the outermost main groove and the ground contact end in the tire width direction, a sub-groove extending in the tire circumferential direction is carved, and a thin rib is formed by the main groove and the sub-groove,
A slit communicating the grounding end and the sub-groove is engraved, and a row of blocks formed by the grounding end, the sub-groove and the slit is arranged on the outer side in the width direction of the thin ribs,
The depth of the sub-groove is 10% to 60% of the depth of the main groove, the width of the sub-groove is 0.5 mm to 3.0 mm, and the width of the thin rib is 4% to the width of the ground end. The pneumatic tire is 12%, and the depth of the slit is 40% to 80% of the depth of the main groove.

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