JP2006076323A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the generation of hydroplaning by improving drainage property without lowering wet performance. <P>SOLUTION: In this pneumatic tire, main grooves 11 extending in a tire peripheral direction R and lateral grooves 12 for connecting the main grooves 11 to each other are cut on the surface of a tread, and a block 1 is formed by the main grooves 11 and the lateral grooves 12. In the tire, at least a sipe 2 having both closed ends extending in substantially parallel to the tread surface is cut at side walls 3 and 4 on both sides of the tire peripheral direction R and a side wall 5 at the outside of a tire width direction W of the block 1 at the outermost side of the the tire width direction W. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that achieves both wear resistance and braking performance by achieving uniform contact pressure within a contact surface.

  In a pneumatic tire, main grooves and lateral grooves are carved on the tread surface to enhance drainage. In addition, a block is formed by the engraved grooves to obtain desired braking performance and traction performance.

  In general, since the ground contact pressure at the block edge becomes high, the ground contact pressure at the block becomes non-uniform. As a result, the grounding property of the block is lowered, and various performances of the tire such as braking performance may be deteriorated. Moreover, uneven wear was likely to occur.

In the pneumatic tire disclosed in Patent Document 1, a recess is provided on the side wall of the block to reduce the rigidity of the edge of the block. As a result, the ground pressure in the block is made uniform to solve the above problem.
Japanese Patent Laid-Open No. 11-151912

  Even if the ground pressure in the block is made uniform, the ground pressure is not necessarily uniform in the ground plane. This will be described with reference to a diagram schematically showing the shape of the contact surface of the pneumatic tire provided with a block pattern. For example, when a braking load is applied, the ground contact surface may be substantially rectangular as shown in FIG. 1B, and the contact pressure may be made uniform within the contact surface. In this case, during normal load (refers to normal travel other than during braking load), the contact pressure at the center of the tread increases as shown in FIG. 1A (the portion with a high contact pressure is shown in black). ). As a result, uneven wear may occur in which the center portion of the tread is worn more than the shoulder portion of the tread.

  Conversely, with an emphasis on wear resistance, it may be designed so that the ground contact surface becomes substantially rectangular as shown in FIG. 1 (c) and the contact pressure is made uniform within the contact surface during normal load. . At the time of braking load, as shown in FIG. 1D, the contact surface of the shoulder portion of the tread is deformed in the tire width direction W and the contact pressure becomes high, and the contact pressure in the contact surface becomes uneven. As a result, the ground contact property deteriorates and the braking performance may deteriorate.

  It has been difficult to ideally equalize the ground pressure in both normal load and braking load. Therefore, it has been difficult to improve wear resistance and braking performance at the same time.

  Accordingly, an object of the present invention is to make the ground contact pressure in the ground contact surface uniform and achieve both wear resistance performance and braking performance.

As a result of intensive studies to solve the above problems, the invention according to claim 1 is characterized in that a main groove extending in the tire circumferential direction and a horizontal groove connecting the main grooves are engraved on the tread surface, and the main groove and the horizontal groove are engraved. In the pneumatic tire in which the block is formed by
A pneumatic tire in which at least one sipe closed at both ends was carved on the side wall on both sides in the tire circumferential direction and the side wall on the outer side in the tire width direction of the block at the outermost side in the tire width direction.

  Only the block on the outermost side (shoulder) in the tire width direction is siped, and the rigidity of the edges on both sides in the tire circumferential direction and the outer side in the tire width direction is reduced by the sipe, so the block is deformed and braking load The contact surface at the time spreads outward in the tire width direction. For this reason, the contact pressure of the shoulder portion only increases to the same extent as the other portions, and the contact pressure in the contact surface is made uniform. As a result, a good grounding property is ensured at the time of braking load, so that the braking performance is improved.

  Therefore, even when the ground contact surface shown in FIG. 1C is used at the time of normal load, the ground pressure is uniform even at the time of braking load, and the ideal ground pressure distribution is obtained both at the time of normal load and at the time of braking load. realizable. As a result, wear resistance and braking performance can be improved at the same time.

  The invention according to claim 2 is the pneumatic tire according to claim 1, wherein a distance from an end of the sipe to a side of the block is 1 mm or more.

  By setting the distance from the end of the sipe to the side of the block to be 1 mm or more, chipping of the block and cracking of the sipe are prevented.

  According to a third aspect of the present invention, the sipe has an inclination angle θ with respect to the surface of the block and extends inclined toward the groove bottom side, and the inclination angle θ is 0 to 15 degrees. Alternatively, the pneumatic tire described in 2 was used.

  By tilting the sipe toward the bottom of the groove, damage to the sipe or block is prevented when releasing the mold.

  According to the present invention, at least one sipe with both ends closed is carved on the side wall on both sides in the tire circumferential direction of the block on the outermost side in the tire width direction and on the side wall on the outer side in the tire width direction. In FIG. 1, the block 1 is deformed and the ground contact surface extends outward in the tire width direction W. As a result, the contact pressure in the contact surface is made uniform, and the contact property is ensured even during braking load, so that the braking performance is improved.

  Hereinafter, embodiments of a pneumatic tire according to the present invention will be described with reference to the drawings. FIG. 2A is a schematic view showing a block of a pneumatic tire according to the present invention. In the figure, 1 is a block on the outermost side (shoulder portion) in the tire width direction W, and is formed by a main groove 11 and a lateral groove 12 extending in the tire circumferential direction R.

  Sipes 2 are carved on the side walls 3 and 4 on both sides of the tire circumferential direction R of the block 1 and the side walls 5 on the outer side in the tire width direction W. The sipe 2 extends substantially parallel to the tread. The sipe 2 is a closed sipe with both ends closed.

  At the time of braking load, the contact pressure is higher than that at normal load, and the contact pressure is higher at the shoulder. However, in the present invention, the rigidity of the edges of the tire 1 in the tire circumferential direction R and the outer side in the tire width direction W of the block 1 is reduced by the sipe 2, so that the block 1 is deformed and the ground contact surface at the time of braking load is Spread outward. For this reason, the contact pressure of the shoulder portion only increases to the same extent as the other portions, and the contact pressure in the contact surface is made uniform. As a result, a good grounding property is ensured at the time of braking load, so that the braking performance is improved.

  Therefore, the effect of this invention arises by carving the sipe 2 only in the block in the tire width direction W outermost side. Moreover, since the sipe 2 is not carved in the side wall 6 inside the tire width direction W of the block 1, the contact surface easily spreads outside the tire width direction W. Further, the width of the adjacent main groove 11 is not reduced.

  If the sipe 2 is opened, the block 1 may be lost, so that it is a closed sipe. For the same reason, the distance A from the end of the sipe 2 to the side of the block 1 is preferably 1 mm or more.

  The position of the sipe 2 is preferably in the range from 30% to 80% of the height D of the block 1 from the tread surface. If it is out of this range, the distance between the sipe 2 and the groove bottom or tread surface is shortened, and there is a possibility that the block 1 is chipped or a crack is generated at the groove bottom.

  The width of the sipe 2 is preferably 0.1 mm to 1 mm. The depth d of the sipe 2 is preferably 0.5 mm to 1.5 mm. If it is less than 0.5 mm, the effect of reducing the rigidity of the block 1 is small, and if it exceeds 1.5 mm, the block 1 may be lost.

  As shown in FIG. 2C, the sipe 2 may be inclined and extended toward the groove bottom side with an inclination angle θ with respect to the surface of the block 1. The inclination angle θ is preferably 0 ° to 15 °, more preferably 5 ° to 10 °. By providing the inclination angle θ, the mold can be easily released and damage to the sipe 2 and the block 1 can be prevented.

  As shown in FIG. 2B, a plurality of sipes 2 may be carved on one side wall. Since the rigidity of the edge of the block 1 is further lowered, the ground contact surface is further expanded in the tire width direction W. As a result, the contact pressure is made more uniform and the braking performance is improved. In addition, from the viewpoint of preventing cracks between sipes, the distances d1 and d2 of the sipes 2 are preferably 1 mm or more.

  As examples, pneumatic tires according to the present invention and pneumatic tires according to comparative examples and conventional examples were prototyped and performance evaluations were performed. Examples 1 and 2 each have the blocks shown in FIGS. 2A and 2B, and have the sipe shape shown in Table 1. The comparative example includes a sipe, but is a tire having a shallower sipe depth than the embodiment. The conventional example is a tire that does not have sipes on the side wall of the block. In all cases, the tire size was 185 / 65R15, and the performance evaluation was performed by attaching it to a 2000 ccFF sedan type passenger car.

  In Table 1, the braking performance is the reciprocal of the braking distance from 100 km / h on a dry road surface. The wear performance is a ratio of the wear amount of the center portion to the wear amount of the shoulder portion after traveling 10,000 km. 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 example, the braking performance is improved over the conventional example without impairing the wear performance.

(A)-(d) is a figure which shows the tire contact surface and contact pressure roughly. (A) And (b) is a figure which shows embodiment of the pneumatic tire which concerns on this invention, (c) is a figure which shows the cross section of a sipe.

Explanation of symbols

1 block 2 sipe 11 main groove 12 horizontal groove

Claims (3)

In a pneumatic tire in which a main groove extending in the tire circumferential direction on the tread surface and a lateral groove connecting the main grooves are engraved, and a block is formed by the main groove and the lateral groove.
A pneumatic tire in which at least one sipe closed at both ends is engraved on a side wall on both sides in the tire circumferential direction and a side wall on the outer side in the tire width direction of the block on the outermost side in the tire width direction. The pneumatic tire according to claim 1, wherein a distance from an end of the sipe to a side of the block is 1 mm or more. 3. The pneumatic tire according to claim 1, wherein the sipe has an inclination angle θ with respect to the surface of the block and extends toward the groove bottom side, and the inclination angle θ is 0 degrees to 15 degrees.

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