JPH0880713A - Studless tire - Google Patents

Abstract

PURPOSE: To enhance heel-and-toe wear resistance, maintain the running performance on an ice and snow road by setting a ratio of block length in the circumferential direction of a tire to block height at a prescribed value, by forming the block into a hourglass-shape, in which width-increased parts are provided to both sides of a constricted part, and by providing the block with a sipe, which extends at a specified angle with respect to the axial direction of the tire. CONSTITUTION: A block 5 has shape of an hourglass, in which width-increased part 7, 9 on the firs-come/post-come sides, in which the width of the tire gradually increases toward the first-come/post-come sides, are installed in both sides in the circumferential direction of the tire of a constricted part 6, at which the block width in the axial direction of the tire becomes minimum. The position of first-come edge 11 of the block 5 and the post-come edge 12 are shifted with each other with respect to the first-come edge 11 and the post-come edge 12 of the block 5 in the neighboring block line, which neighbors with the block 5 at both sides in the axial direction of the tire. The ratio of the length A of each block 5 in the circumferential direction on the tread surface to the height H should be 1.6 to 2.8. In addition, each block 5 is provided with a sipe 10 extending at an angle not more than 5 degrees with respect to the axial direction of the tire.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a studless tire having improved uneven wear resistance while maintaining running performance on ice and snow.

[0002]

2. Description of the Related Art Spike tires are known as tires for traveling on ice and snow in winter. However, when running on a dry road surface, the spiked tire may damage the road surface due to the spikes, and may cause environmental deterioration such as generation of noise and dust. For this reason, so-called studless tires that do not use spikes have become popular in recent years as tires that replace spike tires.

Studless tires require a block pattern having a high snow-biting property to ensure sufficient snow road performance and, at the same time, to improve running performance on a frozen road as much as possible. Therefore, a rubber has been developed that retains flexibility even at low temperatures in the atmosphere, and while adopting that rubber in the tread part, it aims to improve grip performance on both snowy and icy road surfaces by increasing the actual contact area of the tire. The development of tires has been promoted.

[0004]

However, in such a conventional studless tire, since the tread rubber is flexible, the running performance on snow and ice roads is improved, but so-called heel and toe wear is encountered when running on a dry road surface. There is a problem that the uneven wear resistance is inferior such as (hereinafter referred to as H / T wear). H / T wear is a phenomenon in which a large amount of slippage occurs with the road surface at the start of stepping on the road surface of the block and at the start of kicking, and the first-arriving side and the second-arriving side of the block are worn early. In particular, it is known that a large number of tires are generated on non-driving wheels (idle wheels) of a vehicle, and that the trailing side of the block is more easily worn than the leading side.
Therefore, the present inventors have further studied the mechanism of occurrence of this H / T wear.

As a result, as shown in FIG. 11, when an external force F, such as braking / driving, acts on the tire on the idle wheel side, the block B falls in the direction of the external force. Especially, like a studless tire, the block rigidity is too low. Alternatively, when the external force F is too large, the first-arrival side b1 of the block B induces a peeling phenomenon of floating from the road surface. And this peeling phenomenon
It has been found that the ground contact pressure is increased non-uniformly and the wear of the block B on the rear side b2 is accelerated. In order to suppress H / T wear, in addition to suppressing slippage with the road surface at the start of stepping, it is necessary to prevent this separation phenomenon. For that purpose, the first-arrival side of the block must be deformed. In addition to making it easier, it was found that it is necessary to avoid the stress concentration on the rear side and suppress the peeling phenomenon.

That is, the present invention employs a drum-shaped block provided with widening portions on both sides of the constricted portion and sipes the block, and effectively prevents slippage at the time of stepping and the isolation phenomenon. An object of the present invention is to provide a studless tire that can be suppressed and can improve H / T wear resistance while maintaining snow-ice running performance.

[0007]

In order to achieve the above object, in a studless tire of the present invention, a tread portion is provided with a plurality of block rows, which are blocks arranged in the tire circumferential direction, arranged in the tire axial direction. A tire having a block pattern, wherein the block has a constricted portion with a minimum block width in the tire axial direction, and an increase in width on the first-come-first side in which the block width gradually increases from the constricted part toward a road surface first-come-first side in the tire circumferential direction. Portion and a thickening portion on the rear-end side in which the block width gradually increases toward the rear-end side of the road surface in the tire circumferential direction, and the block has a leading edge and a trailing edge in the tire circumferential direction, respectively. When the leading edge and the trailing edge are parallel to the tire axis and the leading edge and the trailing edge of the block of the adjacent block row adjacent to this block in the tire axial direction are displaced from each other in the tire circumferential direction. At the same time, the blocks are provided with sipes extending at an angle of 5 degrees or less with respect to the tire axial direction, and the ratio A / H between the length A of the blocks in the tire circumferential direction and the height H of the blocks is 1.6. It is set to ~ 2.8.

[0008]

In general, the ground pressure distribution of the block when the vertical force P acts depends on the lateral elastic modulus of the rubber and the block shape. Further, as shown in FIGS. 6A to 6C, in the contact pressure distribution, when the contact pressure q at the center of the block is the highest and the contact pressure q decreases toward the contact end (block peripheral edge), the block peripheral edge The shearing force .tau. Is the largest, and therefore, a block having such a contact pressure distribution is the most efficient in transmitting the force from the tire to the road surface. From the behavior experiments by the present inventors in various block shapes, when the ratio A / H between the block length A and the block height H in the tire circumferential direction is in the range of 1.6 to 2.8, the ground contact is achieved. It is possible to obtain a pressure distribution, which reduces block deformation and enhances the load supporting ability, and it is possible to efficiently transmit the driving force and the braking force to the road surface by the high shearing force τ at the block periphery.

Further, the block shape is an hourglass shape in which widening portions are provided on both sides of the constricted portion. Therefore, as shown in FIG. 5, in the thickening portion on the trailing side, the external force F is dispersed so as to escape laterally from the side surface of the block. On the contrary, in the thickening portion on the first-arrival side, the external force F acts so as to be concentrated inward from the side surface of the block, thereby increasing the apparent rigidity of the thickening portion on the first-arrival side, and at the thickening portion on the latter-arrival side. The separation phenomenon on the first-arrival side is suppressed in cooperation with the distribution of external force.

Further, the sipe further enhances the effect of suppressing the peeling phenomenon, and at the start of stepping on the block, the sipe opens so that the first-arriving side of the block follows the road surface to reduce the slip amount and suppress the toe wear. To do.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a studless tire 1 (hereinafter referred to as tire 1
Is a pair of bead portions 13 through which the bead core 12 passes.
And a tread portion 15 that extends from each bead portion 13 outward in the tire radial direction and a tread portion 15 that connects the outer ends of the bead portion 13 and has an outer peripheral surface that forms a tread surface 2. Formed as.

In the tire 1, a carcass 16 folded around the bead core 12 from the tread portion 15 to the sidewall portion 14 is bridged between the bead portions 13 and 13, and the carcass 16 is radially outward of the carcass 16. In addition, the belt layer 17 is wound inside the tread portion 15.

The carcass 16 is formed by one or more carcass plies in which carcass cords are arranged at an angle of 70 to 90 degrees with respect to the tire equator C, in this example, one carcass ply. The carcass cord is a steel cord. Besides, organic fiber cords such as nylon, rayon and polyester are adopted.

The belt layer 17 is composed of two belt plies in which belt cords are arranged at an angle of 0 to 30 degrees with respect to the tire equator C, and in the present example, the cords cross each other. Place them in different directions. Similar to the carcass cord, a metal fiber cord such as steel and an organic fiber cord such as nylon, polyester, or rayon are used as the belt cord.

On the tread surface 2, as shown in FIG.
A plurality of vertical grooves 3 extending in the tire circumferential direction, four in this example.
A, 3A, 3B, and 3B (generally referred to as vertical groove 3) are provided. Also, on the tread surface 2, these vertical grooves 3, 3
An inner lateral groove 4A for partitioning the spaces, and an outer lateral groove 4B for partitioning the outermost vertical groove 3B and the tread edge E.
A lateral groove 4 consisting of

The vertical groove 3 and the horizontal groove 4 form a block pattern composed of a plurality of blocks 5. In this example, the block pattern includes an inner block row R1 in which the inner blocks 5A are arranged in the tire circumferential direction on the tire equator C, and an inner block row R2, R2 in which the inner blocks 5B are arranged outside thereof. Block 5C outside on the outside
And an outer block row R3 and R3 arranged side by side, and one or more sipes 10 are formed in each block 5.

The lateral groove 4 extends substantially parallel to the tire axial direction. Therefore, when the tire rolls, the block 5 is the side on which the block 5 first reaches the road surface. Rear edge e2 in the tire circumferential direction
Are substantially parallel to the tire axial direction. As a result, the edge effect on the road surface, the snow biting effect, etc. are enhanced. Here, “substantially parallel” means an angle of 5 degrees or less with respect to the tire axial direction.

As shown in an enlarged view in FIGS. 3 and 4, the block 5 has tire widths on both sides in the tire circumferential direction of the constricted portion 6 having the smallest block width in the tire axial direction, as seen from the tire width. Has a drum-like shape provided with a first-incoming-side thickening portion 7 and a rear-incoming-side thickening portion 9 in which the tire width gradually increases toward the latter-arriving side. That is, the maximum widths Wa1 and Wa2 of the increased width portions, which are the block widths at the leading edge e1 and the trailing edge e2.
Are larger than the block minimum width Wc, which is the block width at the constricted portion 6, respectively.

As a result, as shown in FIG. 5, the external force F is dispersed outward in the thickening portion 9 on the trailing side, and the external force F is concentrated inward in the thickening portion 6 on the leading side. As a result, the apparent rigidity of the widened portion 6 is increased, and the interaction between these effectively suppresses the peeling phenomenon on the first-arrival side. Therefore, in order to ensure the effect of suppressing the peeling, the maximum widths Wa1 and Wa2 of the thickened portions are 1.
It is preferably 20 times or more, more preferably 1.40 or more. In this example, the maximum widths Wa1 and Wa2 of the widened portion are set to be substantially equal to each other. Also the ratio W
For a / Wc, the average value of each block in the ground plane is used.

Blocks 5A and 5B in the above are shown in FIG.
As shown in FIG. 5, both side edges e3 and e4 are formed in a left-right symmetrical shape with a bent line in a V shape, thereby improving straightness. As shown in FIG. 4, the outer block 5C has a left-right asymmetry in which the side edge e3 on the inner side in the tire axial direction is formed into a V-shaped bending line and the outer side edge e4 is formed on a straight line in the circumferential direction. The outer block 5C is arranged in symmetrical positions across the tire equator C, thereby maintaining straightness.

The leading edge e1 and the trailing edge e2 of the block 5 are compared with the leading edge e1 and the trailing edge e2 of the block 5 of the adjacent block row R which is adjacent to the block 5 on both sides in the tire axial direction. , Are displaced from each other in the tire circumferential direction.
This ensures that the vertical groove 3 secures the necessary groove width, and in this example, the land ratio, which is the ratio of the total block surface area to the total area of the tread surface 2, is 0.55 to 0.6.
It is set to about 5 to maintain snow and ice performance. Therefore, in order to increase the vertical groove width, it is preferable that the position displacement length L1 be ⅓ to ½ times the pitch length L2 of the block arrangement.

Each block 5 has a ratio A of a length A in the circumferential direction on the tread surface of the block and a height H of the block.
/ H is 1.6 to 2.8, and as shown in FIGS. 6 (A) to 6 (C), the ground pressure p at the center of the block is the highest and the ground pressure p goes toward the ground end (the block periphery). Form a drum-shaped contact pressure distribution that decreases. Therefore, it is possible to enhance the load supporting ability and efficiently transmit the driving force and the braking force to the road surface by the high shearing force τ generated at the peripheral edge of the block. When the ratio A / H is less than 1.6, the rigidity becomes too small, and when it exceeds 2.8, the rigidity becomes too large and the force transmission efficiency deteriorates.

In this example, the vertical groove 3 and the horizontal groove 4 have the same groove depths GD1 and GD2, so that the groove depth G
D1 and GD2 match the block height H. When the groove depths GD1 and GD2 are different from each other, the lateral groove depth G
D2 is defined as the block height H, and when the lateral groove depth GD2 on the first-arriving side and the lateral groove depth GD2 on the last-arriving side in one block 5 are different, the average value thereof is used. It is defined as the block height H. The groove wall surface of the block 5 is inclined at an angle of about 5 to 15 degrees with respect to the normal line to the tread surface 2, in this example, about 10 degrees.

The sipes 10 provided on each block 5
Is a narrow groove having a groove width of 1.0 mm or less, and is substantially parallel to the tire axial direction, and more specifically, extends linearly at an angle of 5 degrees or less with respect to the tire axial direction, and In the example, both ends of the sipe are opened at the block side edges e3 and e4. The depth SD of the sipe 10 is, for example, 0.5 to 1.0 times the block height H, further enhancing the peeling suppression effect, and at the time of starting the stepping of the block, the portion of the leading edge e1 of the block. To soften and reduce slippage with the road surface in this part to suppress toe wear. The sipes 10 may have both ends of the sipes terminated within the block 5, or only one end thereof may terminate within the block.

[0025]

SPECIFIC EXAMPLE A tire having a tire size of 5.60R13 and having the configuration shown in FIG. 1 and the pattern shown in FIG. 2 was prototyped according to the specifications shown in Table 1 (Example 1), and its snow and ice performance and H resistance / T wear performance was tested. The tires having the pattern shown in FIG. 7 (Comparative Examples 1, 2 and 3) and the tire having the pattern shown in FIG. 8 (Comparative Example 4) were also tested and their performances were compared.

The test was conducted as follows. 1) Friction coefficient-slip ratio characteristic (μ-s characteristic) This was carried out by an indoor drum test. As shown in FIG. 9, pressure snow S was adhered to the surface of the rotating disk R to make the test tire T a speed of 40 km / h and a tire internal pressure. 1.9kg / cm ² , load 340kg
The friction coefficient-slip characteristics are obtained as shown in FIG. 10 by running on the rotating disc R under the condition of 10 and the tire rotation stops and the slip ratio of 10% is obtained.
Judgment was made based on the lock μ which is a coefficient of friction of 0%. Table 1
The numerical values shown in are shown as indices with Comparative Example 1 being 100. The larger the value, the better.

2) H / T wear test A test tire was mounted on the front wheels of an all-wheel-drive vehicle, and 1500 was applied from 90 km / h to 50 km / h on the test course.
After decelerating every m and running for 300 km, the difference δ between the maximum amount of wear at both circumferential edges of the block and the minimum amount of wear at the center of the block was measured, and Comparative Example 1
It is indicated by an index of 00. The larger the value, the less the H / T wear and the better. The test results are shown in Table 1.

[0028]

[Table 1]

[0029]

Since the studless tire of the present invention is constructed on the way, it is possible to improve the H / T wear resistance while maintaining the running performance on ice and snow.

[Brief description of drawings]

FIG. 1 is a meridional sectional view of a tire showing an embodiment of the present invention.

FIG. 2 is a development view of a tread pattern illustrating the tread surface.

FIG. 3 is a perspective view showing an enlarged example of inner blocks.

FIG. 4 is a perspective view illustrating an enlarged outer block.

FIG. 5 is a diagram illustrating the operation of the block of the present invention.

FIG. 6A is a schematic cross-sectional view showing deformation of a block at the time of grounding.

FIG. 6B is a diagram showing a ground pressure distribution at that time.

FIG. 6 (C) is a diagram showing a shear force distribution at that time.

FIG. 7 is a schematic development view of a tread pattern of a specific example used in the comparative experiment of Table 1.

FIG. 8 is a schematic development view of a tread pattern of a specific example used in the comparative experiment of Table 1.

FIG. 9 is a perspective view showing an outline of a testing machine for measuring μ-s characteristics.

FIG. 10 is a graph illustrating μ-s characteristics.

FIG. 11 is a cross-sectional view illustrating a conventional technique.

[Explanation of symbols]

 5, 5A, 5B, 5C Block 6 Constricted part 7 Widening part on the first arrival side 9 Widening part on the last arrival side 10 Sipe 15 Tread part e1 First arrival edge e2 Rear arrival edge R, R1, R2, R3 Block row

Claims (1)

[Claims] 1. A tire having a block pattern in which a plurality of block rows composed of blocks spaced in a tire circumferential direction are arranged in a tire axial direction in a tread portion, wherein the blocks have a block width in the tire axial direction. The smallest constricted portion, the first-increasing width portion where the block width gradually increases from the constricted portion toward the road surface first-arriving side in the tire circumferential direction, and the block width gradually increases toward the road surface last-arriving side in the tire circumferential direction. It has a drum shape with a widened portion on the trailing side, and the leading edge and trailing edge in the tire circumferential direction of the block are substantially parallel to the tire axis, and the leading edge and trailing edge are The blocks of the adjacent block rows adjacent to each other in the tire axial direction are displaced from each other in the tire circumferential direction with respect to the leading edge and the trailing edge of the blocks and extend to the blocks at an angle of 5 degrees or less with respect to the tire axial direction. A studless tire provided with sipes and having a ratio A / H between the length A of the block in the tire circumferential direction and the height H of the block of 1.6 to 2.8.