JP4262650B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire in which a sipe is engraved on a tread surface, and more particularly to a pneumatic tire with improved performance on icy and snowy roads.

  In a pneumatic tire, in addition to main grooves and lateral grooves, a narrower sipe has been cut on the tread surface to improve drainage. In addition, in studless tires intended for running on snowy and snowy roads, more sipe is carved and the edge effect of the sipe is exerted to improve braking / driving performance and turning performance (winter performance) on snowy and snowy roads. It was.

In the pneumatic tire disclosed in Patent Document 1, a linear sipe extending in the tire width direction is engraved in the block, and a narrow groove is further engraved between the sipes. As a result, braking performance on icy and snowy roads is improved.
JP 2001-191741 A

  If a large number of sipes are carved, the rigidity of the block will be lowered, the block will fall too much, and the ground contact area will be reduced. As a result, the edge effect of sipe sometimes deteriorated. In the pneumatic tire according to Patent Document 1, the braking performance is improved by the edge effect by the narrow groove extending in the tire width direction, but the turning performance is insufficient because the lateral edge effect does not occur.

  Therefore, an object of the present invention is to improve winter performance including turning performance without reducing the rigidity of land portions (blocks and ribs).

As a result of intensive studies to solve the above problems, the invention according to claim 1 is a pneumatic tire in which a sipe extending in the tire width direction is engraved on the tread surface.
A narrow groove having a shallower groove depth and wider groove width than the sipe is carved with an angle of 10 to 90 degrees with respect to the tire width direction.
The groove density of the narrow grooves increases from the center region to the shoulder region, and the angle of the narrow grooves with respect to the tire width direction increases.
A pneumatic tire having a groove depth of 1 mm to 2 mm and a groove width of 1.0 mm to 1.5 mm was used .

  The braking performance and driving performance are improved by the edge effect in the front-rear direction due to the sipe extending in the tire width direction. Further, the lateral grooves carved with an angle with respect to the tire width direction (sipe) exert an edge effect not only in the front-rear direction but also in the lateral direction, improving braking performance and turning performance. Moreover, since the groove density of the narrow grooves is higher toward the shoulder region that contributes more at the time of turning, the lateral edge effect is more effectively generated and the turning performance is improved.

  Further, since the narrow groove has a groove width wider than that of the sipe, but the groove depth is shallow, the rigidity of land portions such as blocks and ribs is not excessively lowered.

The closer to the shoulder region, which has a higher contribution during turning, the greater the angle of the narrow groove with respect to the tire width direction. As a result, the lateral edge effect is more effectively exhibited, and the turning performance is improved.
If the groove depth of the narrow groove is less than 1 mm, sufficient edge effect may not occur. On the contrary, if it exceeds 2 mm, the rigidity of a land part will fall and a fall will become large. As a result, the ground contact area may be reduced and sufficient winter performance may not be obtained.
If the angle of the narrow groove with respect to the tire width direction (sipe) is less than 10 degrees, uneven wear tends to occur because the angle intersecting the sipe is small. Also, the lateral edge effect may be insufficient.

According to a second aspect of the invention, groove density of the sipe from the center region to the shoulder region is the pneumatic tire of the mounting serial to claim 1 has declined.

  By reducing the groove density of the sipe from the center region to the shoulder region, the rigidity of the block near the shoulder portion becomes higher. As a result, the turning performance on the dry road surface is improved.

  According to the present invention, in addition to the sipe extending in the width direction, the lateral groove carved with an angle with respect to the tire width direction (sipe) exhibits the edge effect in the lateral direction as well as the front and rear direction, The turning performance is improved.

  Hereinafter, embodiments of a pneumatic tire according to the present invention will be described with reference to the drawings. Hereinafter, an example in which a sipe and a narrow groove are engraved on the block will be described, but the same effect can be obtained even when a sipe and a narrow groove are engraved on the rib. FIG. 1 is a schematic view showing a pattern of a pneumatic tire according to the present invention. 1 is a main groove extending in the tire circumferential direction R, and 2 is a lateral groove connecting the main grooves 1 to each other. The main groove 1 and the lateral groove 2 define a center area block 3c, a medium area block 3m, and a shoulder area block 3s. A sipe 4 extending in the tire width direction W is engraved on the blocks 3c, 3m, and 3s.

  Further, narrow grooves 5 having a groove depth shallower than that of the sipe 4 and a wider groove width are engraved in the blocks 3c, 3m, and 3s. The narrow groove 5 extends at an angle θ with respect to the tire width direction W. The groove density of the fine grooves engraved in each block increases in the order of the block 3c in the center area, the block 3m in the medium area, and the block 3s in the shoulder area. Here, the groove density is defined as the sum of the lengths of the grooves per unit area, but in the present embodiment, the number of narrow grooves 5 increases from the center region to the shoulder region.

  First, the braking performance and driving performance are enhanced by the edge effect in the front-rear direction by the sipe 4. At the same time, the braking performance and driving performance are enhanced by the edge effect of the narrow groove 5. Since the narrow groove 5 extends at an angle with respect to the tire width direction W, a lateral edge effect due to the narrow groove 5 is generated, so that turning performance is improved. Moreover, since the groove density of the block near the shoulder portion, which has a large contribution during turning, is large, the lateral edge effect is more effectively exhibited.

  The narrow groove 5 is wider than the sipe 4 but has a shallower groove depth than the sipe 4, so that the rigidity of the block 3c and the like is not extremely lowered. The groove depth of the narrow groove 5 is preferably 1.0 mm to 2.0 mm. Although the groove width of the narrow groove 5 should just be wider than the groove width of the sipe 4, 1.0 mm-1.5 mm are preferable. Further, the sipe 4 may be a straight sipe in addition to the illustrated waveform sipe. In addition to an open sipe with both ends open, a closed sipe with both ends closed or a single open sipe with only one end opened may be used. Similarly, in addition to a form in which both ends of the narrow groove 5 are open, a form in which both ends are closed or a form in which only one end is opened may be used.

  FIG. 2 is a schematic view showing a pattern according to another embodiment of the present invention. The number of fine grooves 5 increases from the center region to the shoulder region, and the groove density of the fine grooves 5 increases. In addition, the angle of the narrow groove 5 is gradually increased from the center region to the shoulder region in the order of θc, θm, and θs. As a result, in the block closer to the shoulder portion, a larger lateral edge effect is exhibited and the turning performance is improved.

  In the embodiment shown in FIGS. 1 and 2, the groove density of the sipe 4 can be decreased from the center region to the shoulder region. In this case, the rigidity of the block near the shoulder portion is increased due to the decrease in the groove density of the sipe, and the turning performance on the dry road surface is improved. Alternatively, the groove density of the narrow grooves 5 may be made substantially constant, and the angle θ of the narrow grooves 5 may be increased from the center region to the shoulder region.

  The angle θ with respect to the width direction W of the narrow groove 5 is preferably 10 degrees to 90 degrees. If the angle is less than 10 degrees, the angle at which the sipe 4 intersects is small, so that uneven wear tends to occur, and the lateral edge effect becomes insufficient. Further, although it is preferable to cut the narrow groove 5 in the shoulder region having the highest contribution at the time of turning, the narrow groove 5 can be omitted in the center region having the smallest contribution.

  As an example, a pneumatic tire according to the present invention and a pneumatic tire according to a comparative example were prototyped and performance evaluation was performed. Examples 1 and 2 have the patterns shown in FIGS. 1 and 2, respectively, and the tire according to the comparative example has a tread pattern having no narrow grooves shown in FIG. The shape and dimensions of the sipe and the narrow groove are as shown in Table 1. The tire size was 195 / 65R15, and the performance was evaluated by mounting it on a 2000 ccFF sedan type passenger car.

  In Table 1, ice braking is the reciprocal of the ABS braking distance from 40 km / h on the ice road surface. The ice turn is the reciprocal of the lap time when driving on the figure 8 course (ice surface). All are represented by an index with the comparative example being 100, and the larger the number, the better the performance.

  According to Table 1, in the tire according to the embodiment, the edge effect in the front-rear direction and the lateral direction is sufficiently exhibited by the narrow grooves extending at an angle with respect to the tire width direction, and the braking performance and the turning performance are improved. Yes.

It is a pattern schematic diagram showing an embodiment of a pneumatic tire according to the present invention. It is the pattern schematic which shows other embodiment of the pneumatic tire which concerns on this invention. It is the pattern schematic which shows embodiment of the pneumatic tire which concerns on a comparative example.

Explanation of symbols

1 Main groove 2 Horizontal groove 3c, 3m, 3s Block 4 Sipe 5 Narrow groove

Claims (5)

In a pneumatic tire in which a sipe extending in the tire width direction is engraved on the tread surface,
A narrow groove having a shallower groove depth and wider groove width than the sipe is carved with an angle of 10 to 90 degrees with respect to the tire width direction.
The groove density of the narrow grooves increases from the center region to the shoulder region, and the angle of the narrow grooves with respect to the tire width direction increases.
A pneumatic tire having a groove depth of 1 mm to 2 mm and a groove width of 1.0 mm to 1.5 mm . The pneumatic tire according to claim 1, wherein the groove density of the sipe decreases from a center region to a shoulder region . The pneumatic tire according to claim 1 or 2, wherein both ends of the narrow groove are open . The pneumatic tire according to claim 1 or 2, wherein both ends of the narrow groove are closed . The pneumatic tire according to claim 1 or 2, wherein only one end of the narrow groove is open .

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