JP2001071330A - Pneumatic tire and mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire, in which wet grip performance, brake on ice, driving perofrmance and resistance to uneven abrasion performance are enhanced by controlling deterioration of grounding properties in the case of increasing the number of a sipe. SOLUTION: Sipes 20 formed in a blocklike ground part 18 consists of first straight line parts 20A which are extended substantially and vertically for the treads 18A of the blocklike ground part 18 and in contact with the treads 18A, second straight line parts 20B which are extended substantially and vertically for the treads 18A and separated from the treads 18A and slope parts 20C which bond each end part of the first straight line parts 20A and the second straight line parts 20B and are inclined. Surface roughness of the slope parts 20C is set up to >=30 μmRmax and thereby deviation is difficult to be caused at time of pressure welding. Bending deformation amount of the blocklike ground part 18 at time of grounding is suppressed than heretofore. Wet grip performance, braking on ice, driving performance and resistance to uneven abrasion performance can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire and a mold, and more particularly, to a pneumatic tire having excellent running performance on icy and snowy roads and a mold for molding the pneumatic tire.

[0002]

2. Description of the Related Art In order to improve the running performance on ice and snowy roads, there has been known a tire composed of narrow blocks in which blocks are divided by a sipe. As a result, the amount of deformation is increased, and the performance on ice is reduced due to a decrease in the ground contact area. Therefore, there is a limit in reducing the interval between sipes.

In order to solve this problem, as shown in FIG. 5A, a sipe 102 formed in a block 100 is bent (or curved) in a depth direction, and partially bent during load rolling. By closing the block, the finely divided blocks support each other, and the shear rigidity is increased to reduce the amount of deformation of the entire block and suppress a decrease in the ground contact area (for example, JP-A-11-78432). There is.

[0004]

However, in such a tire according to the prior art, the effect of the sipe which bends or curves in the depth direction having a portion which bends and closes during load rolling can be more effectively used. In order to pull out, it is a necessary condition that the bent / closed portion exerts a frictional force sufficient to support the blocks separated by the sipe.

On the other hand, the sipe of the block is formed by a metal plate called a blade provided on the inner surface of the mold.

[0006] However, the surface roughness of the blade generally used in the prior art was about 6.3 µmRmax, and the surface roughness of the wall of the sipe was almost equal to the surface roughness of the blade, and the surface was smooth.

For this reason, when the load and the rolling power (driving force, braking force) are small, sufficient contact pressure is not generated at the bent / closed portion, and the narrowly divided blocks cannot be supported by each other. There was a case.

On the other hand, when a very large load or rolling force is acting on the other side, a force exceeding the frictional force generated at the bent / closed portion is input. As a result, it becomes impossible for the attached blocks to support each other, and as shown in FIG.
In some cases, the deformation amount A of 00 (the two-dot chain line is the state before deformation) was large.

In view of the above facts, the present invention can suppress the deterioration of the contact property when the number of sipes is increased, and suppress the amount of deformation of the whole block even when the load and the rolling power are small or very large. It is an object of the present invention to provide a pneumatic tire capable of forming a pneumatic tire and a pneumatic tire capable of suppressing the amount of deformation of the entire block to a small level.

[0010]

According to the first aspect of the present invention,
A pneumatic tire in which a plurality of block-shaped land portions partitioned by a plurality of intersecting main grooves are provided on a tread, and a plurality of sipes are formed in the block-shaped land portions, wherein the sipe has a depth direction intermediate portion. A bent portion extending at least partially in a direction intersecting with a normal line of the tread surface, and a surface roughness of a wall surface of the bent portion is 30 μmRmax or more.

Next, the operation of the pneumatic tire according to the first aspect will be described.

In the pneumatic tire according to the first aspect of the present invention, the sipe is provided with a bent portion extending in a direction at least partially intersecting with a normal line of the tread at a middle portion in a depth direction of the sipe. When the land part is compressed by touching the ground, the opposing wall surfaces of the bent part are strongly pressed against each other, and the small blocks separated by the sipe support each other. The bending rigidity of the portion is maintained, and the deformation is suppressed. As a result, the amount of deformation of the block-shaped land portion when the number of sipes is increased can be reduced, and deterioration of the grounding property can be suppressed, so that wet grip performance, braking on ice, driving performance, and uneven wear resistance can be improved. it can.

Moreover, the surface roughness of the wall of the bent portion is 30
Since it is at least μmRmax and is formed coarser than in the prior art and the friction coefficient is increased, it is difficult for displacement to occur during pressure welding, and the amount of bending deformation of the block-shaped land portion at the time of ground contact can be suppressed as compared with the conventional case. For this reason, wet grip performance, braking on ice, drive performance, and uneven wear resistance can be improved as compared with the conventional case.

According to a second aspect of the present invention, there is provided a pneumatic tire having a plurality of block-shaped land portions defined by a plurality of intersecting main grooves in a tread, and a plurality of sipes formed in the block-shaped land portions. The sipe includes a bent portion extending in a direction at least partially intersecting with a normal of the tread at a middle portion in the depth direction, and a surface of a wall surface of the bent portion is rougher than other portions. Features.

Next, the operation of the pneumatic tire according to claim 2 will be described.

In the pneumatic tire according to the second aspect of the present invention, since the sipe is provided with a bent portion extending in a direction at least partially intersecting with a normal line of the tread at a middle portion in a depth direction of the sipe, the block is provided. When the land part is compressed by touching the ground, the opposing wall surfaces of the bent part are strongly pressed against each other, and the small blocks separated by the sipe support each other. The bending rigidity of the portion is maintained, and the deformation is suppressed. As a result, the amount of deformation of the block-shaped land portion when the number of sipes is increased can be reduced, and deterioration of the grounding property can be suppressed, so that wet grip performance, braking on ice, driving performance, and uneven wear resistance performance can be improved. it can.

In addition, since the surface roughness of the wall surface of the bent portion is formed to be rougher than other portions, that is, the surface roughness is increased compared with the conventional art, and the friction coefficient is increased, the displacement is less likely to occur at the time of press-contact, and the block at the time of the ground contact is conventionally provided. The amount of bending deformation of the land part can be suppressed. For this reason, wet grip performance, braking on ice, drive performance, and uneven wear resistance can be improved as compared with the conventional case.

According to a third aspect of the present invention, in the pneumatic tire according to the second aspect, a difference between a surface roughness of a wall surface of the bent portion facing each other and another partial surface roughness is 25 μm.
Rmax or more.

Next, the operation of the pneumatic tire according to the third aspect will be described.

In the pneumatic tire according to the third aspect of the present invention, the difference between the surface roughness of the opposed wall surface of the bent portion and the surface roughness of the other portion is 25 μmRmax or more. The displacement can be suppressed more reliably.

According to a fourth aspect of the present invention, there is provided a mold for molding a pneumatic tire in which a block with a sipe is provided on a tread, wherein a concave portion forming the block, a blade provided in the concave portion, The blade comprises a bent portion extending in a direction at least partially intersecting with a normal line of a mold inner peripheral surface corresponding to a tire tread surface in a portion corresponding to a depth direction intermediate portion of the sipe, The surface roughness of the bent portion is at least 30 μmRmax.

Next, the operation of the mold according to claim 4 will be described.

When the tire is vulcanized and molded by the mold having the concave portion according to the fourth aspect, a pneumatic tire having a block in the tread is obtained.

The blade of the mold has a bent portion at a portion corresponding to the middle portion in the depth direction of the sipe, the bent portion extending in a direction at least partially crossing a normal to the inner peripheral surface of the mold corresponding to the tire tread surface. Therefore, the block is provided with a sipe having a bent portion extending in a direction at least partially intersecting with the normal of the tread surface at a middle portion in the depth direction.

The surface roughness of the bent portion of the blade is set to 30
Since it is at least μmRmax, the surface roughness of the wall surface of the bent portion of the sipe is at least 30 μmRmax.

According to a fifth aspect of the present invention, there is provided a mold for molding a pneumatic tire in which a block with a sipe is provided on a tread, wherein a concave portion forming the block, a blade provided in the concave portion, The blade comprises a bent portion extending in a direction at least partially intersecting with a normal line of a mold inner peripheral surface corresponding to a tire tread surface in a portion corresponding to a depth direction intermediate portion of the sipe, It is characterized in that the surface of the bent portion is rougher than other portions.

Next, the operation of the mold according to claim 5 will be described.

When the tire is vulcanized and molded by the mold having the concave portion according to the fifth aspect, a pneumatic tire having a block in the tread is obtained.

The blade of the mold has a bent portion at a portion corresponding to an intermediate portion in the depth direction of the sipe, the bent portion extending in a direction at least partially intersecting a normal to the inner peripheral surface of the mold corresponding to the tire tread surface. Therefore, the block is provided with a sipe having a bent portion extending in a direction at least partially intersecting with the normal of the tread surface at a middle portion in the depth direction.

Further, since the surface of the bent portion of the blade is formed rougher than other portions of the blade, the wall surface of the bent portion of the sipe is formed rougher than other portions of the sipe.

According to a sixth aspect of the present invention, in the mold according to the fifth aspect, in the blade, a difference between a surface roughness of the bent portion and a surface roughness of another portion is 25 μmR.
It is characterized in that it is not less than max.

Next, the operation of the mold according to claim 6 will be described.

In the mold blade according to the sixth aspect, the difference between the surface roughness of the bent portion and the surface roughness of the other portion is 2
Since it is 5 μm Rmax or more, the difference between the surface roughness of the wall surface of the bent portion of the sipe and the surface roughness of the other portion of the sipe is 25 μm.
mRmax or more.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a pneumatic tire according to the present invention will be described below with reference to FIGS.

As shown in FIG. 2, the tread 12 of the studless tire 10 as a pneumatic tire in the present embodiment has a plurality of main grooves 14 extending in the circumferential direction (the direction of arrow A and the direction of arrow B). A large number of lug grooves 16 extending in the tire axial direction (the direction of the arrow L and the direction of the arrow R) intersecting with the main groove 14 are formed, and a plurality of block-shaped land portions 18 are formed by the main groove 14 and the lug groove 16. It is classified.

Further, a plurality of lateral sipes 20 are formed on each block-shaped land portion 18.

As shown in FIG. 1A, the sipe 20 of the block-shaped land portion 18 is
A first linear portion 20A extending substantially perpendicular to A and contacting the tread surface 18A; a second linear portion 20B extending substantially perpendicular to the tread surface 18A of the block-shaped land portion 18 and spaced from the tread surface 18A; The straight portion 20A is connected to the adjacent ends of the second straight portion 20B, and is composed of an inclined portion 20C inclined with respect to the normal HL of the tread surface 18A.

The depth D1 at the center of the inclined portion 20C of the sipe 20 is 10% to 60% of the depth D of the sipe 20.
It is preferable to set the position.

The inclined portion 20C has the surface roughness of both opposing wall surfaces set to 30 μmRmax or more, and is formed to be coarser than the other portions.

The wall surface of the inclined portion 20C may have, for example, random fine irregularities (for example, satin, grain, etc.).
Irregularities having regularity (for example, those in which a number of minute ribs are formed in parallel, or in which a number of pyramid-like minute protrusions are formed at equal intervals in the vertical and horizontal directions, etc.) may be used.

Next, random minute unevenness is formed on the inclined portion 20C.
An example of a mold for forming the studless tire 10 formed as described above will be described with reference to FIG.

As shown in FIG. 3, the mold 22 is provided with a concave portion 24 for forming the block-shaped land portion 18, and the concave portion 24 is made of a thin metal plate for forming the sipe 20. A blade 26 is provided.

The blade 26 is bent similarly to the sipe 20, and includes a first straight portion 26A forming a first straight portion 20A of the sipe 20, a second straight portion 26B forming a second straight portion 20B, and an inclined portion. 20C, the surface roughness of the inclined portion 26C is set to 2626 or more, and the first linear portion 26A and the second linear portion 26B are provided.
It is formed more coarsely.

The surface of the inclined portion 26C can be roughened by shot blasting, etching or the like.

The inclined portion 20C has regular irregularities,
For example, an example of a mold for forming a studless tire 10 having a number of minute ribs formed in parallel will be described with reference to FIG.

As shown in FIGS. 4A and 4B, a plurality of triangular cross sections extending along the longitudinal direction of the blade 26 (the longitudinal direction of the sipe 20) are provided on the surface of the inclined portion 26C of the blade 26. A rib 28 is formed. Note that such a rib 28 can be processed by a shaper or the like.

Here, in order to set the surface roughness of the wall surface of the inclined portion 20C of the sipe 20 to 30 μmRmax or more, the surface roughness of the inclined portion 26C of the blade 26 is set to 30 μmRmax.
What is necessary is just to set above.

Although not shown, the studless tire of the present invention has a crown portion having a tread 12 extending between the left and right sidewalls and both sidewalls in a toroidal manner. Through the crown and across the other side wall,
A carcass consisting of at least one fiber cord radial ply represented by nylon or polyester (usually two sheets) or one steel cord radial ply, and a plurality of steel cord layers disposed between the carcass and the tread 12 Reinforced by a non-extensible belt layer, including
A known structure can be applied.

In FIG. 2, the main groove 14, the lug groove 1
6 are straight, but the main groove 14 may be a known groove such as a zigzag shape, a crank shape, or the like that extends in the circumferential direction with a predetermined amplitude on the left and right. For example, a concave or convex groove can be used.

The shape of the block-shaped land portion 18 may be a shape other than a rectangle.

The horizontal sipe 20 provided on the block-shaped land portion 18 is provided. In the present embodiment, two horizontal sipe 20 are provided at the center of the block-shaped land portion 18 which is rectangular in plan view. (Operation) When the studless tire 10 rotates on the road surface, and the block-shaped land portion 18 is compressed upon contact with the ground, FIG.
As shown in the figure, the opposing wall surfaces of the inclined portion 20C are strongly pressed against each other, and the small blocks separated by the sipe 20 support each other, and the bending rigidity of the block-shaped land portion 18 is maintained even when the input F is applied. And deformation is suppressed.

Here, the surface roughness of the wall surface of the inclined portion 20C is not less than 30 μmRmax, and the wall surface is formed coarser than in the prior art and the friction coefficient is increased. Block land part 1 when touching down
8 is suppressed (see FIG. 1B and FIG. 5B).

Therefore, even when the number of sipes is increased, the amount of deformation of the block-shaped land portion 18 can be reduced more than in the conventional case, and the deterioration of the ground contact can be suppressed. And uneven wear resistance performance can be improved.

In the above embodiment, the inclined portion 20C corresponding to the bent portion of the present invention has a linear shape when viewed from the side of the block, but the shape of the bent portion is not limited to this. For example, as shown in FIG. 6, the inclined portion 20C has a semicircular shape (a semicircular cross section extending in the longitudinal direction of the sipe) as viewed from the side surface of the block. Combination of a rib having a shape and a groove having a semicircular cross-section. The surface roughness of the rib and the groove is rough as in the above embodiment.) Or, although not shown, a convex hemispherical portion and a concave hemispherical portion are provided. (The surface roughness of the convex hemispherical portion and the concave hemispherical portion is as rough as in the above-described embodiment), and may have other shapes. [Test Examples] In order to confirm the effects of the present invention, tests were performed on the on-ice brake performance and the wet brake performance of the conventional tire and the tire of the example to which the present invention was applied. The tire size used was 195 / 65R15.

The braking performance on ice was measured from the point at which the tire was applied to the point at which it was stopped by mounting the tire on a vehicle (Mark II manufactured by Toyota Motor Co., Ltd .; two passengers) and applying an abrupt brake while driving at 20 km / h on ice. The distance was measured, and the reciprocal thereof was defined as an index on the ice as an on-ice brake performance.

The wet performance was measured with a tire mounted on a vehicle (same as above) and a wet road surface (water depth 1.0 at 50 km / h).
mm) The driver applied a sudden brake while driving, measured the distance from the applied point to the stop point, displayed the index as the wet brake performance as an index (the conventional example was set to 100), and set the index to 100.
It was shown to.

The tire was assembled on a 6J · 15 rim and filled with an internal pressure of 2.1 kgf / cm ² .

The tire of the example is the tire of the above-described embodiment, in which the surface of the inclined portion of the sipe has a grain shape and the surface roughness is set to 50 μm Rmax.

The conventional tire has a sipe having the same shape as that of the embodiment, and has a smooth inclined portion (surface roughness of 5 μm Rmax).

[0060]

[Table 1]

From the results shown in Table 1, the tire of the present invention, ie,
It was revealed that the tire of the example in which the surface roughness of the inclined portion 20C was set to 50 μmRmax was superior to the conventional tire in both the on-ice braking performance and the wet braking performance.

[0062]

As described above, it is possible to suppress the deterioration of the contact property when the number of sipes is increased, and to suppress the amount of deformation of the entire block even when the load and the rolling power are small or very large. And a mold for molding a pneumatic tire capable of suppressing the amount of deformation of the entire block to a small level.

[Brief description of the drawings]

FIG. 1A is a perspective view of an unloaded block-like land portion of a pneumatic tire according to one embodiment of the present invention,
(B) is a perspective view of the block-shaped land portion under load.

FIG. 2 is a plan view showing a part of a tread of the pneumatic tire according to one embodiment of the present invention.

FIG. 3 is a sectional view showing an embodiment of the mold of the present invention.

4A is a sectional view showing another embodiment of the mold of the present invention, and FIG. 4B is an enlarged view of the blade shown in FIG. 4A.

FIG. 5A is a perspective view of a block-shaped land portion of a conventional pneumatic tire in a no-load state, and FIG. 5B is a perspective view of the block-shaped land portion under a load.

FIG. 6 is a perspective view of a no-load block-like land portion of a pneumatic tire according to another embodiment of the present invention.

[Description of Signs] 10 Studless tire (pneumatic tire) 12 Tread 14 Main groove 18 Block-shaped land portion 20 Sipe 20C Inclined portion (bent portion) 22 Mold 26 Blade 26C Inclined portion (bent portion)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29K 105: 24 B29L 30:00

Claims (6)

[Claims] 1. A pneumatic tire including a plurality of block-shaped land portions defined by a plurality of intersecting main grooves in a tread, and a plurality of sipes formed in the block-shaped land portions. A bent portion extending in a direction at least partially intersecting with a normal to the tread surface in a depth direction intermediate portion,
A pneumatic tire, wherein the surface roughness of the wall surface of the bent portion is 30 μmRmax or more. 2. A pneumatic tire having a plurality of block-shaped land portions defined by a plurality of intersecting main grooves on a tread, and a plurality of sipes formed on the block-shaped land portions, A bent portion extending in a direction at least partially intersecting with a normal to the tread surface in a depth direction intermediate portion,
A pneumatic tire, wherein a surface of a wall surface of the bent portion is rougher than other portions. 3. The pneumatic tire according to claim 2, wherein the difference between the surface roughness of the wall surface of the bent portion facing each other and the surface roughness of the other portion is 25 μmRmax or more. 4. A mold for molding a pneumatic tire in which a block with a sipe is provided on a tread, comprising: a recess forming the block; and a blade provided in the recess. A portion corresponding to the middle portion in the depth direction of the sipe is provided with a bent portion extending in a direction at least partially crossing a normal to a mold inner peripheral surface corresponding to the tire tread surface, and the surface roughness of the bent portion is reduced. , 30 μm Rmax or more. 5. A mold for molding a pneumatic tire in which a block with a sipe is provided on a tread, comprising: a recess forming the block; and a blade provided in the recess. A portion corresponding to the middle portion of the sipe in the depth direction is provided with a bent portion extending in a direction at least partially intersecting with a normal line of the inner peripheral surface of the mold corresponding to the tire tread surface, and the surface of the bent portion has another surface. A mold characterized by being coarser than a part. 6. The mold according to claim 5, wherein in the blade, a difference between a surface roughness of the bent portion and a surface roughness of another portion is 25 μmRmax or more.