JP2001063319A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve performance on snow without sacrificing performance on ice therefor. SOLUTION: The pneumatic tire has a plurality of saw-toothed ribs 20 formed in a stepping side block wall surface 18A to increase the coefficient of friction. This causes a column 26 of compact snow in the tread not to slide off the block wall surface 18A but to experience effective shearing force F in the direction of tire rotation, which in turn provides larger traction force on snow and larger braking force on snow as well. The change in the coefficient of friction of the block wall surface 18A without changes in negative ratio can improve performance on snow without lowering performance on ice.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire for use in automobiles running on snowy roads, and more particularly to a pneumatic tire with improved on-snow performance.

[0002]

2. Description of the Related Art Conventionally, in pneumatic tires for winter,
When traveling on a snowy road, the tire sometimes slips on the snow without gripping the snowy road.

In order to improve acceleration (traction on snow) and braking (braking on snow) at the time of starting on a snowy road, the area of a groove portion of a tire tread pattern has been increased. The performance required on ice, which is the required performance, has the drawback that if the area of the groove is increased, the area that comes into contact with ice is reduced, and there is a disadvantage that the performance on snow is improved by the area of the groove from both the snow performance and the ice performance. At present there are limitations.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic tire capable of improving the performance on snow without changing the groove area of the tread pattern, that is, without sacrificing the performance on ice. It is in.

[0005]

The present invention according to claim 1 is a pneumatic tire having a plurality of block-like land portions defined by a plurality of mutually intersecting grooves on a tread, wherein the block-like land is provided. It is characterized in that, among the block side surfaces of the portion, the friction coefficient of the step side wall surface is set to be larger than the friction coefficient of the other block side surfaces.

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

When the pneumatic tire travels on a snowy road, snow enters the circumferential groove and the lateral groove at the time of contact with the ground, and the entered snow is compacted in the lateral groove of the tread pattern portion to form a snow column, and the pneumatic tire rolls. As it moves, the gutter walls shear the compacted snow column, thereby creating traction.

[0008] Traction has another effect (edge effect) of digging snow by the tire surface friction force and the edge portion (of the block or sipe) penetrating the snow.
As long as the negative ratio of the tread does not change, the tire surface friction force does not change. Therefore, in order to effectively improve the traction on snow, it is necessary to increase the shear force acting on the snow column and the edge effect.

[0009] The magnitude of the shearing force acting on the snow column depends on the quality of the snow, but to maximize it, it is necessary to reduce the sliding of the snow column in the lateral groove and to effectively shear the snow column. There is.

[0010] In the pneumatic tire according to the first aspect, since the coefficient of friction of the block side wall surface on the stepping side is made larger than that of the other block side wall surfaces, a snow column in the ground contact surface is formed on the block side wall surface during traction. It is no longer slippery, and a shear force along the tire rotation direction can be effectively generated on the snow column, and a large traction force on snow can be obtained.

[0011] It should be noted that the snow column is less likely to slip even during braking, thereby improving the braking performance.

Further, since the performance on snow can be improved by changing the friction coefficient of the side wall surface of the block without changing the negative ratio, the performance on ice does not decrease.

According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the coefficient of friction of the block side wall surface on the stepping side is set to be larger on the tread side than on the base side.

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

In the pneumatic tire according to the second aspect, the coefficient of friction of the block side wall on the stepping side is set to be larger on the tread side than on the base side, that is, on the base side of the snow column (wide portion on the road surface side). Since the friction coefficient is set to be large, the slip on the side wall surface of the block on the stepping side can be effectively suppressed.

According to a third aspect of the present invention, there is provided a pneumatic tire having a plurality of block-shaped land portions provided on a tread sectioned by a plurality of grooves intersecting each other. In addition, at least one of a concave portion and a convex portion is provided on the block side wall surface on the stepping side.

Next, the operation of the pneumatic tire according to claim 3 will be described.

When the pneumatic tire travels on a snowy road, snow enters the circumferential groove and the lateral groove at the time of contact with the ground, and the entered snow is compacted in the lateral groove of the tread pattern portion to form a snow column, and the pneumatic tire rolls. As it moves, the gutter walls shear the compacted snow column, thereby creating traction.

Traction has another effect (edge effect) of digging snow by the tire surface friction force and the edge portion (of the block or sipe) penetrating the snow.
As long as the negative ratio of the tread does not change, the tire surface friction force does not change. Therefore, in order to effectively improve the traction on snow, it is necessary to increase the shear force acting on the snow column and the edge effect.

The magnitude of the shearing force acting on the snow column depends on the quality of the snow, but in order to maximize it, it is necessary to reduce the slip of the snow column in the lateral groove and to effectively shear the snow column. There is.

In the pneumatic tire according to the third aspect, since the friction coefficient is increased by making the block side wall surface on the stepping side uneven, the snow column in the ground contact surface does not slip on the block side wall surface during traction, and A shear force along the tire rotation direction can be effectively generated on the pillar, and a large snow traction force can be obtained.

It is to be noted that the snow column is less likely to slip even during braking, thereby improving the braking performance.

The concave portion on the side wall surface of the block may be, for example, a substantially hemispherical dimple (other shapes may be used, the shape is not particularly limited), a groove (a cross-sectional shape such as a V-shape, etc.). Other shapes may be used, and the cross-sectional shape is not particularly limited.).

The projection on the side wall surface of the block includes, for example, a trapezoidal pyramid, a triangular pyramid, a prism, and the like (the shape may be any other shape, and the shape is not particularly limited), and a rib (the cross-sectional shape is Other shapes such as a triangle may be used, and the cross-sectional shape is not particularly limited.).

The concave portion and the convex portion may be used alone or in combination.

In order to increase the coefficient of friction, it is preferable to provide a plurality of concave portions and convex portions.

Incidentally, the depth of the concave portion and the height of the convex portion are preferably set to 0.5 mm or more, preferably 1 mm or more in order to increase the coefficient of friction with the snow column. In order to secure the rigidity of the block, it is desirable that the depth of the concave portion is 3 mm or less.

The concave and convex portions are provided to increase the coefficient of friction with the snow column. For example, the size of the concave portion is extremely large, and the size of the convex portion is extremely large. Then, the rigidity of the stepped side of the block-shaped land portion is reduced, which is not preferable.

If the rigidity of the stepped side of the block-shaped land portion is reduced, uneven wear may occur in the block-shaped land portion, and the snow at the edge portion of the stepped side of the block-shaped land portion when it contacts the snowy road. In some cases, the amount of digging in may decrease, and the performance on snow may decrease.

For this reason, the rigidity near the side wall surface of the block on the stepping side (compression rigidity in the direction perpendicular to the tread surface) is reduced to 90% or less of the rigidity near the side wall surface of the block where no concave portion or convex portion is not formed. It is not preferable.

For example, the depth of the concave portion (or the height of the convex portion)
Is preferably set to 3 mm or less.

According to a fourth aspect of the present invention, in the pneumatic tire according to the third aspect, the arrangement density of at least one of the concave portion and the convex portion per unit area is set higher on the tread side than on the base side. It is characterized by doing.

Further, since the performance on snow can be improved by changing the friction coefficient of the side wall surface of the block without changing the negative ratio, the performance on ice does not decrease.

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

In the pneumatic tire according to the fourth aspect, since the arrangement density of at least one of the concave portion and the convex portion per unit area is set higher on the tread side than on the base side, the friction coefficient of the block side wall surface on the tread side is set. Is larger on the tread side than on the base side, that is, the coefficient of friction on the base side of the snow column (wide portion on the road surface side) is increased, so that it is possible to effectively suppress the slip of the block side wall surface on the tread side. it can.

When the block edge becomes obtuse after the block is worn, the edge effect at the block edge portion is reduced. However, irregularities (jagged) on the wall near the tread
Appear as a new sharp edge near the block surface after abrasion, so that it is possible to suppress a decrease in edge effect (during abrasion). For this reason, it is desirable that the unevenness density be dense near the tread surface.

According to a fifth aspect of the present invention, in the pneumatic tire according to the third or fourth aspect, at least one of the height of the convex portion or the depth of the concave portion is set closer to the tread side than the base side. It is characterized by having been set large.

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

In the pneumatic tire according to the fifth aspect, since at least one of the height of the convex portion and the depth of the concave portion is set to be larger on the tread side than on the base side, the coefficient of friction of the block side wall surface on the tread side is set. Is larger on the tread side than on the base side, that is, the coefficient of friction on the base side of the snow column (wide portion on the road surface side) is increased, so that it is possible to effectively suppress the slip of the block side wall surface on the tread side. it can.

According to a sixth aspect of the present invention, there is provided a pneumatic tire having a plurality of block-shaped land portions defined by a plurality of grooves intersecting with each other on a tread, wherein the block-shaped land portion has a block side surface. When the friction coefficient of the side wall surface of the stepping side is set to μ1 and the friction coefficient of the other block side surfaces is set to μ2, μ1 / μ2 is set to 1.2 or more.

In the pneumatic tire according to the first aspect, the coefficient of friction of the block side wall surface on the stepping side is increased by 20% or more as compared with the other block side wall surfaces. No longer slips on the wall,
A shear force along the tire rotation direction can be effectively generated on the snow column, and a large snow traction force can be obtained.

It is to be noted that the snow column hardly slips even during braking, whereby the braking performance can be improved.

In addition, since the performance on snow can be improved by changing the friction coefficient of the side wall surface of the block without changing the negative ratio, the performance on ice does not decrease.

[0044]

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

As shown in FIG. 2, the tread 12 of the pneumatic tire 10 of the present embodiment has a tire circumferential direction (arrow A).
Circumferential grooves 1 extending along the direction (arrow B direction)
4 and a plurality of blocks 1 formed by a plurality of lateral grooves 16 extending along the tire axial direction (the direction of the arrow L and the direction of the arrow R).
8 are sectioned.

The pneumatic tire 10 rotates in the direction of arrow A when the vehicle moves forward.

As shown in FIG. 1 and FIG.
The block side wall surface 18A on the stepping side, the block side wall surface 18B on the kick side, and the block side wall surfaces (not shown) on both sides in the tire axial direction are slightly inclined in the groove width increasing direction.

The block side wall surface 18A on the stepping side of the block 18 has a plurality of triangular ribs 20 each having a triangular cross section and extending along the tire axial direction, from the tire tread side to the groove bottom side.

The triangular rib 20 of this embodiment has a height H (average value) of 1.0 mm, a bottom width W (average value) of 1.5 mm,
The arrangement pitch P (the average value of the center-to-center distances) is 2 mm.

The surface of the other block side wall surface 18B and the like is smooth as before (the surface roughness peak to peak value is 30 μm).
m), the friction coefficient in the groove depth direction of the block side wall surface 18A provided with the plurality of triangular ribs 20 is set to be larger than the other block side wall surfaces 18B and the like.

Next, the operation of the pneumatic tire 10 of the present embodiment will be described.

As shown in FIG. 3, when the pneumatic tire 10 travels on the snowy road 22, snow 24 enters the circumferential groove 14 (not shown in FIG. 3) and the lateral groove 16 at the time of contact with the ground, and the tread pattern portion is formed. In the lateral groove 16, the entered snow 24 is compacted to form a snow column 26, and as the pneumatic tire 10 rolls, the groove wall shears the compacted snow column 26, thereby generating traction.

The traction has an effect (edge effect) of digging the snow by the tire surface frictional force and the edge portion (of the block 18 or the sipe) penetrating the snow 24, but the negative ratio of the tread 12 changes. Otherwise, the tire surface frictional force does not change, so it is necessary to increase the shearing force F acting on the snow column 26 and the edge effect to effectively improve traction on snow.

The magnitude of the shearing force F acting on the snow column 26 depends on the snow quality.
It is necessary to effectively shear the snow column 26 by reducing the sliding of the snow column 26 in the snow.

In the pneumatic tire 10 of this embodiment, a plurality of triangular ribs 20 are provided on the block side wall surface 18A on the stepping side.
To increase the coefficient of friction.
6 no longer slides on the block side wall surface 18A,
A shear force F along the tire rotation direction can be effectively generated, a large snow traction force can be obtained, and a large snow braking force can be obtained.

Further, the pneumatic tire 10 of the present embodiment
Then, without changing the negative ratio, the block side wall surface 18A
The performance on snow can be improved by changing the friction coefficient of
There is no decrease in performance on ice.

Note that a triangular rib 20 may be formed on the kick-out side block side wall surface 18B opposite to the block side wall surface 18A. Thereby, the directionality at the time of mounting the pneumatic tire 10 is lost.

If the height H (average value) of the triangular rib 20 is too high, the rigidity of the kick-out side of the block 18 decreases, so that it is preferable that the height does not exceed 3 mm.

Although no sipe is provided in the block 18 of the pneumatic tire 10 of the present embodiment, it is a matter of course that a conventionally well-known sipe may be provided in order to obtain performance on ice. Second Embodiment A pneumatic tire according to a second embodiment of the present invention will be described with reference to FIG. The same components as those of the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

[0060] The pneumatic tire 10 of the present embodiment is shown in FIG.
As shown in the figure, the arrangement pitch P of the triangular ribs 20 is set to be larger on the tread side than on the base side of the block 20 on the block side wall surface 18A on the stepping side.

Incidentally, the arrangement pitch P of the triangular ribs 20 is
It is set to about 1 mm on the base side and about 2 mm on the tread side. Note that the height H and the width W of the bottom of the triangular rib 20 are the same as in the first embodiment.

If the arrangement pitch P of the triangular ribs 20 is set smaller on the tread side than on the base side as in the present embodiment (in other words, when the density of the triangular ribs 20 is increased).
The coefficient of friction on the base side (the wide part on the road surface side) of the snow column 26 becomes large, and the block side wall surface 18 on the stepping side is effectively made.
A can be suppressed from slipping.

When the density of the triangular rib 20 is increased,
Even when worn, the effect of the unevenness can be expected continuously. Third Embodiment A third embodiment of the pneumatic tire according to the present invention will be described with reference to FIG. The same components as those of the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

The pneumatic tire 10 of the present embodiment is shown in FIG.
As shown in the figure, the arrangement pitch P of the triangular ribs 20 is set to be larger on the base side than on the tread side of the block 20 on the block side wall surface 18A on the stepping side.

Incidentally, the arrangement pitch P of the triangular ribs 20 is
It is set to about 2 mm on the base side and about 0.5 mm on the tread side. The height H and the width W of the bottom of the triangular rib 20 are:
This is equivalent to the first embodiment.

When the block edge becomes obtuse after the block 20 of the pneumatic tire 10 is worn, the edge effect at the block edge portion is reduced.

However, the block side wall surface 18A near the tread surface
Since irregularities (jaggies) due to the triangular ribs 20 appear as new sharp edges after wear near the block tread surface,
Edge effect reduction (during wear) can be suppressed. For this reason, it is desirable that the unevenness density be dense near the tread surface. Fourth Embodiment A pneumatic tire according to a fourth embodiment of the present invention will be described with reference to FIG. The same components as those of the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

FIG. 6 shows a pneumatic tire 10 according to this embodiment.
As shown in FIG. 7, a plurality of dimples 28 are provided on the block side wall surface 18A on the stepping side to increase the friction coefficient.

The dimensions of the dimple 28 in the groove depth direction are substantially equal to the dimensions in the groove longitudinal direction (the direction perpendicular to the plane of the drawing), and have a substantially rectangular cross-sectional shape.

Incidentally, the dimple 28 of the present embodiment has a depth D (average value) of 0.5 mm, a width W (average value) of 1 mm, and an arrangement pitch P (average value of the distance between centers) of 1 mm.

The operation and effect are the same as those of the first embodiment. [Fifth Embodiment] A pneumatic tire according to a fifth embodiment of the present invention will be described with reference to FIG. The same components as those of the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

The pneumatic tire 10 of the present embodiment is shown in FIG.
As shown in FIG. 7, the step side block side wall surface 18A has a wavy shape (note that one wave 30 has a rib shape extending in the longitudinal direction of the lateral groove 16 like the triangular rib 20 of the first embodiment). To increase the friction coefficient.

The wave 30 of the present embodiment has a height H (average value from the wave bottom to the wave crest) of 1 mm, a width W (average value) of 3 mm, and an arrangement pitch P (average value of the center-to-center distance) of 3 mm. It is.

The dashed line in FIG. 7 indicates the average position of the block side wall surface 18A (the position where no wave is formed).

The operation and effect are the same as those of the first embodiment. Sixth Embodiment A fifth embodiment of the pneumatic tire according to the present invention will be described with reference to FIG. The same components as those of the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

FIG. 8 shows a pneumatic tire 10 according to this embodiment.
As shown in FIG. 5, a plurality of trapezoidal ribs 32 having a trapezoidal cross section and extending along the tire axial direction and a plurality of trapezoidal grooves 34 having a trapezoidal cross section and extending along the tire axial direction are formed on the tread side wall surface 18A. It is formed alternately from the side toward the groove bottom side.

The dashed line in FIG. 8 indicates the average position of the block side wall surface 18A (the position where the trapezoidal rib 32 and the trapezoidal groove 34 are not formed).

The height H (average value) of the trapezoidal rib 32 is 0.5
mm, the base width W1 (average value) is 3 mm, the trapezoidal groove 34 has a depth D (average value) of 0.5 mm, and the opening width W2 (average value) is 3 mm.

The operation and effect are the same as those of the first embodiment.

In the above embodiment, the rectangular block 18 is formed on the tread 12 by the plurality of circumferential grooves 14 extending along the tire circumferential direction and the plurality of lateral grooves 16 extending along the tire axial direction. The shape of the block 18 may be a shape other than a rectangle (for example, a conventionally known shape such as a polygon such as a square, a hexagon, or a parallelogram, or a circle).

The block side wall surface on the stepping side is a side wall surface that can be seen when the grounded block (single unit) 18 is viewed from the rear of the vehicle, and may be parallel to the tire axial direction.
It may be inclined.

In the above embodiment, the pitch of the projections or recesses is changed in order to make the friction coefficient on the tread surface side of the block side wall surface 18A different from the friction coefficient on the groove bottom side.
The present invention is not limited to this, and as shown in FIG.
The coefficient of friction may be changed by changing the height of 0 (convex portion) (or the depth of concave portion). Incidentally, in order to increase the coefficient of friction, the height of the convex portion or the depth of the concave portion is increased.

The step side wall surface 18A
Μ1 and the friction coefficient of the other block
In the case of 2, if the value of μ1 / μ2 is set to 1.2 or more, the effect of the present invention is obtained, and the surface shape of the block side wall surface 18A may be any shape other than the above. (Test Example) In order to confirm the effect of the present invention, one kind of conventional tire and six kinds of tires of the embodiment to which the present invention is applied are prepared, and the tire is assembled on a rim of 6J-15 at an internal pressure of 200 kPa, and the tire is mounted on a passenger car. We put on and performed a start test on the snowy road. In the start test, the accelerator is fully opened from the stationary state,
The evaluation was performed based on the time required for traveling 0 m (acceleration time).

In the evaluation, the reciprocal of the acceleration time was calculated, and was expressed by an index with the conventional tire set to 100. The larger the value, the better the traction performance.

[0085]

[Table 1]

As shown in the test results in Table 1 above, it can be seen that the tires of the examples to which the present invention is applied have a better acceleration time and better traction performance on snow than the conventional tires.

[0087]

As described above, since the pneumatic tire of the present invention has the above-described structure, it has an excellent effect that the performance on snow can be improved without sacrificing the performance on ice.

Further, in the pneumatic tire according to the second, fourth and fifth aspects, a shearing force along the tire rotation direction can be effectively generated on the snow column, and a large traction force on snow can be obtained. , Which is an excellent effect.

[Brief description of the drawings]

FIG. 1 is a sectional view of the vicinity of a lateral groove grounded on a snowy road of a pneumatic tire according to a first embodiment of the present invention.

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

FIG. 3 is a cross-sectional view of a tread grounded on a snowy road of the pneumatic tire according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view of the vicinity of a lateral groove grounded on a snowy road of a pneumatic tire according to a second embodiment of the present invention.

FIG. 5 is a sectional view of the vicinity of a lateral groove grounded on a snowy road of a pneumatic tire according to a third embodiment of the present invention.

FIG. 6 is a cross-sectional view of the vicinity of a lateral groove grounded on a snowy road of a pneumatic tire according to a fourth embodiment of the present invention.

FIG. 7 is a cross-sectional view of a pneumatic tire according to a fifth embodiment in the vicinity of a lateral groove grounded on a snowy road.

FIG. 8 is a cross-sectional view of the vicinity of a lateral groove grounded on a snowy road of a pneumatic tire according to a sixth embodiment of the present invention.

FIG. 9 is a cross-sectional view of the vicinity of a lateral groove grounded on a snowy road of a pneumatic tire according to another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Pneumatic tire 12 Tread 16 Side groove (groove) 18 Block (block-shaped land portion) 18A Block side wall surface on the stepping side 20 Triangular rib (convex portion) 28 Dimple (concave portion) 30 Wave (convex portion) 32 Trapezoidal rib (convex portion) )

Claims (6)

[Claims] 1. A pneumatic tire having a plurality of block-shaped land portions defined by a plurality of grooves intersecting with each other on a tread, and among the block side surfaces of the block-shaped land portions, a block side wall surface on a stepping side. Characterized in that the friction coefficient of the pneumatic tire is set larger than the friction coefficient of the other block side wall surface. 2. The pneumatic tire according to claim 1, wherein a coefficient of friction of the block side wall surface on the stepping side is set to be larger on the tread side than on the base side. 3. A pneumatic tire having a tread having a plurality of block-shaped land portions defined by a plurality of grooves intersecting with each other, wherein a block side wall surface on a stepping side among block side surfaces of the block-shaped land portion. A pneumatic tire characterized in that at least one of a concave portion and a convex portion is provided on the tire. 4. The pneumatic tire according to claim 3, wherein the arrangement density of at least one of the concave portion and the convex portion per unit area is set higher on the tread side than on the base side. 5. The pneumatic tire according to claim 3, wherein at least one of the height of the convex portion and the depth of the concave portion is set to be larger on the tread side than on the base side. . 6. A pneumatic tire having a plurality of block-shaped land portions defined by a plurality of grooves intersecting with each other on a tread, wherein a block side wall surface on a stepping side among block side surfaces of the block-shaped land portions. Where μ1 / μ2 is 1.2 and the friction coefficient of the other block side wall is μ2, μ1 / μ2 is 1.2.
A pneumatic tire characterized by the above settings.