JP2009280035A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire which can be improved in on-ice performance while retaining rigidity of a block and a rib. <P>SOLUTION: A large number of blocks 18 are divided on a tread part 12 of the pneumatic tire 10. A plurality of sipes 20 extending in a zig-zag shape in a tire width direction are aligned/provided on ground-contact surfaces 18A of the respective blocks 18 in a tire circumferential direction with an interval in the tire circumferential direction. A bottom part of the sipe 20 has a depth uniform part 22 of uniform depth; and a shallow bottom part 24 connected to an end part of the depth uniform part 22 in which the depth becomes shallow as it approaches to an end part in an extending direction of the sipe 20. On the shallow bottom part 24, a hole 26 having a larger diameter than width of the sipe 20 is formed while directed from an upper portion of the shallow bottom part 24 to a lower side of the shallow bottom part 24. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pneumatic tire having a sipe.

In recent years, studless tires tend to have a large number of sipes arranged on blocks and ribs constituting the land portion of the tread portion in order to improve the performance on ice (Patent Documents 1 and 2).
JP 2006-176055 A JP 2004-25954 A

However, increasing the number of sipes and increasing the sipe density will increase the number of edges, but the rigidity of the blocks and ribs will decrease, and if the sipe falls down, the grounding performance will decrease and the on-ice performance will deteriorate. .
The present inventor has been devised in view of the above circumstances, and an object of the present invention is to provide a pneumatic tire capable of improving the performance on ice while maintaining the rigidity of blocks and ribs.

  In order to achieve the above object, the present invention provides a pneumatic tire in which a sipe is provided on a contact surface of a land portion of a tread portion, and a bottom portion of the sipe has a depth as it approaches an end portion in the extending direction of the sipe. It has a shallow bottom portion that becomes shallow, and a hole having a diameter larger than the width of the sipe is formed in the shallow bottom portion from a position above the shallow bottom portion toward a position below the shallow bottom portion. .

According to the present invention, the bottom portion of the sipe has a shallow bottom portion, which is advantageous in suppressing a decrease in block rigidity due to the sipe.
In addition, since the shallow bottom portion is provided with holes, it is advantageous for maintaining water absorption.
In addition, a mold can be easily created by inserting a cylindrical rod between blades.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory view of a tread portion of a tire, FIG. 2 is an explanatory view of a sipe, (A) is a plan view, (B) is a sectional view, (C) is a CC sectional view of (B), and (D) is (B) DD sectional drawing, (E) is EE sectional drawing of (B), (F) shows FF sectional drawing of (B).
A plurality of main grooves 14 extending in the tire circumferential direction are provided in the tread portion 12 of the pneumatic tire 10. A plurality of lateral grooves 16 extending in the tire width direction are provided between the main grooves 14.
A large number of blocks 18 as land portions are defined by the main grooves 14 and the lateral grooves 16.
The blocks 18 are divided into six block rows by the main groove 14.

A plurality of sipes 20 extending in a zigzag shape in the tire width direction are provided on the ground contact surface 18A of each block 18 and arranged in the tire circumferential direction at intervals in the tire circumferential direction.
As shown in FIG. 2B, the bottom of the sipe 20 is connected to the uniform depth portion 22 having a uniform depth and the end portion of the uniform depth portion 22, and approaches the end portion in the extending direction of the sipe 20. And a shallow bottom portion 24 having a shallow depth.
Note that the shallow bottom portion 24 may be formed as an inclined portion whose depth becomes steplessly (gradually) shallower toward the end portion in the extending direction of the sipe 20 or the end portion in the extending direction of the sipe 20. It may be formed in a staircase shape whose depth gradually decreases as it approaches the portion.
2B, (D), (E), and (F), a hole 26 having a diameter larger than the width of the sipe 20 is formed in the shallow bottom portion 24 from a location above the shallow bottom portion 24. It is formed toward the bottom of the bottom 24. In addition, the sipe 20 extends in a zigzag shape in a straight line while changing the direction through the bent portion. In the present embodiment, the hole 26 is a second bent portion that jumps over one bent portion. It is provided for each.

In the present embodiment, the bottom portion of the sipe 20 has the shallow bottom portion 24, which is advantageous in suppressing a decrease in block rigidity due to the sipe.
Moreover, since the shallow bottom part 24 is equipped with the hole 26, it becomes advantageous when maintaining water absorption.
Further, when the mold is produced, the production is easily performed by sandwiching a cylindrical rod between the blades, and the strength of the rod is excellent by taking a sufficiently large diameter of the cylindrical rod.

The sipe 20 of each block 18 constituting the four rows of blocks located at the center of the tread portion 12 is shown in FIG. 3 (A) as a plan view of the tread portion before wear, and in FIG. 3 (B) after wear. As shown in the plan view of the tread portion, the sipe 20 adjacent to each other in the tire circumferential direction is provided such that the uniform depth portion 22 and the shallow bottom portion 24 of the bottom portions are opposite to each other. As shown in FIG. 3B, when the tread surface is worn, only the hole 26 remains in the shallow bottom portion 24.
Providing the sipes 20 of the respective blocks 18 constituting the four block rows of the center portion in this manner is advantageous in preventing a decrease in rigidity of the block 18 while maintaining the water absorption effect.

The sipes 20 of the respective blocks 18 constituting the two rows of blocks located on the shoulder portion side of the tread portion 12 are shown in FIG. 4 (A) as a plan view of the tread portion before wear, and in FIG. 4 (B). As shown in the plan view of the tread portion after wear, the bottom portion located on the inner side in the tire width direction is the depth uniform portion 22, and the bottom portion located on the outer side in the tire width direction is the shallow bottom portion 24. ing. As shown in FIG. 4B, when the tread surface is worn, only the hole 26 remains in the shallow bottom portion 24.
By providing the sipes 20 of the respective blocks 18 constituting the two block rows on both sides of the shoulder portion in this way, it is advantageous in suppressing a reduction in rigidity of the shoulder portion block 18 and improving steering stability. .

As shown in FIG. 5, the sipe 20 having such a configuration is for forming a sipe comprising a blade 30 having a wave shape and a bottom portion gradually increasing, and a cylindrical pin 32 attached to the lower edge of the blade 30. The member 34 is formed in the mold by placing it in the mold.
5A is a plan view of the sipe forming member 34, FIG. 5B is a front view of the sipe forming member 34, FIG. 5C is a front view of the blade 30, and FIG. 5D is a perspective view of the blade 30 and the pin 32. (E) is a perspective view of the sipe forming member 34.
A slot 3202 is formed at the tip of the pin 32, and the pin 32 is attached to the blade by fitting the slot 3202 to the lower edge of the blade 30.

The depth of the hole 26 provided in the shallow bottom portion 24 is equal to the depth of the uniform depth portion 22 as shown in FIG.
The center of the hole 26 is located on the center of the width of the sipe 20.

The position of the upper end of the hole 26 in the depth direction, that is, the depth X of the hole 26 from the ground contact surface 18A is X ≦ 0 with respect to the depth M of the shallow bottom portion 24 provided with the hole 26. The relationship of 9 × M is satisfied.
If the position of the upper end of the hole 26 is set in this way, it is advantageous in terms of easily producing a mold and in terms of the strength of the mold.

Further, when the total length of the sipe 20 is Y and the total length L of the shallow bottom portion 24, the relationship of 0.5Y ≦ L ≦ Y is satisfied.
If 0.5Y> L, there is a possibility that the rigidity of the block 18 is lowered similarly to the conventional sipe 20, and the effect is reduced by limiting the number of holes 26.

Further, when the width of the sipe 20 is Z, the diameter D of the hole 26 satisfies the relationship of Z <D ≦ 5Z.
In consideration of performance improvement and ease of mold manufacture, the diameter D of the hole 26 is preferably larger than the width Z of the sipe 20.
Further, considering the removal from the mold during vulcanization, the diameter D of the hole 26 is desirably 5 times or less the width Z of the sipe 20.

  The cross-sectional shape of the hole 26 may be various conventionally known shapes such as a circle, a triangle, a quadrangle, and other polygons, and the performance can be improved by the cross-sectional shape and its size.

  Further, the shape of the sipe 20 may be any of various known shapes such as a two-dimensional plate shape, a wave shape, and a three-dimensional shape (3D) bent in the depth direction. Is desirable.

Further, the upper end of the pin 32 constituting the sipe forming member 34 is chamfered, and as shown in FIGS. 2D, 2E, and 2F, the periphery of the upper end of the hole 26 is a ground surface. It is formed by a curved surface 2602 whose inner diameter gradually decreases as it approaches the 18A side. In other words, a chamfer 2602 is provided around the upper end of the hole 26.
Providing such a chamfer 2602 is advantageous in suppressing the generation of cracks in the peripheral portion of the hole 26 when the hole 26 is exposed to the ground contact surface 18A due to wear of the tire.

(Example)
As shown in FIG. 6, studless tires having sipes of Conventional Examples 1 and 2, Comparative Example, and Example were respectively prepared.
6 (A), (C), (E), and (G) are plan views of the sipe, and FIGS. 6 (B), (D), (F), and (H) are front views of the sipe. Show.
The sipe 20 of the conventional example 1 has a bottom portion having a uniform depth, and only the end portion of the sipe 20 has a shallow bottom portion.
The sipe 20 of the conventional example 2 has a bottom portion having a uniform depth, a shallow bottom portion only at the end portion of the sipe 20, and a hole 21 having a diameter smaller than the width of the sipe 20 is formed at the bottom portion of the sipe 20. Is formed.
The sipe 20 of the comparative example includes a depth uniform portion 22 having a uniform depth, and a shallow bottom portion 24 that is connected to the end portion of the uniform depth portion 22 and becomes shallower as it approaches the end portion in the extending direction of the sipe 20. However, the hole 26 is not provided.
The sipe 20 of the embodiment includes a depth uniform portion 22 having a uniform depth, and a shallow bottom portion 24 that is connected to an end portion of the uniform depth portion 22 and decreases in depth as it approaches the end portion in the extending direction of the sipe 20. have. A hole 26 having a diameter larger than the width of the sipe 20 is formed in the shallow bottom portion 24 from a location above the shallow bottom portion 24 toward a location below the shallow bottom portion 24.

And the following evaluation tests were conducted.
A studless tire with a size of 215 / 55R17 was assembled on a 17 × 7J wheel and mounted on a FR drive type vehicle with a displacement of 2400 cc.
FIG. 7 and FIG. 8 show performance obtained by indexing the result of evaluating the braking performance on ice by ABS braking.
Moreover, what indexed the result of sensory evaluation of the steering stability at the time of driving | running | working on snow is shown in FIG. 7, FIG.
7 shows the evaluation result in the early stage of wear, and FIG. 8 shows the evaluation result in the late stage of wear. The larger the index, the better the performance.
From FIG. 7 and FIG. 8, it is clear that the embodiment is excellent in braking performance on ice and steering stability when traveling on snow.

Moreover, the braking performance on ice was evaluated in the case where the shape of the sipe 20 extends linearly, in the case of a wave shape, and in the case of 3D, and the result is shown in FIG.
From FIG. 9, it is clear that the braking performance on ice is the best when the shape of the sipe 20 is 3D.
In addition, the braking performance on ice is obtained in each case where the width of the sipe 20 is 0.4 mm and the diameter of the hole 26 formed in the shallow bottom portion 24 is 0.4 mm, 0.6 mm, 1.0 mm, and 2.0 mm. The results are shown in FIG.
From FIG. 10, it is clear that the braking performance on ice is better when the diameter of the hole 26 is larger than the width of the sipe 20 than when the diameter of the sipe 20 is larger.

It is explanatory drawing of the tread part of a tire. It is explanatory drawing of a sipe, (A) is a top view, (B) is sectional drawing, (C) is CC sectional drawing of (B), (D) is DD sectional drawing of (B), (E) is (B ) Is an EE sectional view, and (F) is an FF sectional view of (B). FIG. 3A is a plan view of the tread portion before wear, and FIG. 3B is a plan view of the tread portion after wear. FIG. 3A is a plan view of the tread portion before wear, and FIG. 3B is a plan view of the tread portion after wear. (A) is a plan view of the sipe forming member 34, (B) is a front view of the sipe forming member 34, (C) is a front view of the blade 30, (D) is a perspective view of the blade 30 and the pin 32, ( E) is a perspective view of the sipe forming member 34. It is explanatory drawing of the sipe of the prior art examples 1 and 2, a comparative example, and an Example. It is a figure which shows the result of the evaluation test in the wear initial stage about the sipe of the prior art examples 1 and 2, a comparative example, and an Example. It is a figure which shows the result of the evaluation test in the abrasion late stage about the sipe of the prior art examples 1 and 2, a comparative example, and an Example. It is a figure which shows the result of having evaluated the braking performance on ice about the case where the shape of the sipe 20 extends linearly, the case of a wave shape, and the case of 3D. The braking performance on ice was evaluated in each case where the width of the sipe 20 was 0.4 mm and the diameter of the hole 26 formed in the shallow bottom portion 24 was 0.4 mm, 0.6 mm, 1.0 mm, and 2.0 mm. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Pneumatic tire, 12 ... Tread part, 18 ... Block, 20 ... Sipe, 22 ... Depth uniform part, 24 ... Shallow bottom part.

Claims (9)

In a pneumatic tire with a sipe provided on the ground contact surface of the land part of the tread part,
The bottom of the sipe has a shallow bottom that becomes shallower as it approaches the end in the extending direction of the sipe,
A hole having a diameter larger than the width of the sipe is formed in the shallow bottom portion from a location above the shallow bottom to a location below the shallow bottom.
A pneumatic tire characterized by that. The bottom part of the sipe has a uniform depth part having a uniform depth,
The shallow bottom portion is connected to an end of the uniform depth portion;
The depth of the hole is equal to the depth of the uniform depth portion,
The pneumatic tire according to claim 1. When the width of the sipe is Z,
The diameter D of the hole satisfies a relationship of Z <D ≦ 5Z.
The pneumatic tire according to claim 1. The depth X of the upper end of the hole from the ground contact surface satisfies the relationship of X ≦ 0.9 × M with respect to the depth M of the shallow bottom portion where the hole is formed.
The pneumatic tire according to claim 1. When the total length of the sipe is Y and the total length L of the shallow bottom portion, the relationship of 0.5Y ≦ L ≦ Y is satisfied.
The pneumatic tire according to claim 1. The center of the hole is located on the center of the width of the sipe,
The pneumatic tire according to claim 1. Chamfered around the upper end of the hole,
The pneumatic tire according to claim 1. The bottom part of the sipe has a uniform depth part having a uniform depth,
The shallow bottom portion is connected to an end of the uniform depth portion;
The sipe of the land part located in the center part of the tread part is provided so that the uniform depth part and the shallow bottom part of those bottom parts are opposite to each other in the sipe adjacent in the tire circumferential direction.
The pneumatic tire according to claim 1. The bottom part of the sipe has a uniform depth part having a uniform depth,
The shallow bottom portion is connected to an end of the uniform depth portion;
The sipe of the land part located in the shoulder part of the tread part is provided so that the bottom part located inside in the tire width direction is a uniform depth part and the bottom part located outside in the tire width direction is a shallow bottom part. Yes,
The pneumatic tire according to claim 1.

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