JP4499808B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire in which ice performance is improved by suppressing wiping generated in a shoulder portion of a tread.

  In general, in a pneumatic tire, a block is often formed on a tread. For example, pneumatic tires disclosed in Patent Documents 1 and 2 are known. In the tire of Patent Document 1, the inclination of the block side wall is changed in order to suppress uneven wear. In the tire of Patent Document 2, the inclination of a part of the block side wall is changed in order to suppress noise reduction and anti-hydroplaning performance.

JP 2006-137230 A JP 2006-188214 A

  As shown in FIG. 1, when the pneumatic tire is in contact with the ground, a force (indicated by an arrow in the drawing) directed to the center of the contact surface 100 is applied to each part of the tread. This force is called in-plane contraction force, and a linear main groove extending in the tire circumferential direction is carved, and when the main groove is wide, slipping tends to occur in the closing direction of the main groove. In particular, on ice and snow roads where the friction coefficient between the road surface and the tire is small, a phenomenon occurs in which the main groove closes due to in-plane contraction force (this phenomenon is called a wiping phenomenon).

  Since the contact pressure distribution becomes non-uniform due to the wiping phenomenon, a road surface having a smaller coefficient of friction with the tire is more likely to cause performance deterioration such as a reduction in braking performance. Since the angle formed by the belt cord of the belt layer disposed on the inner side in the tire radial direction from the tread and the tire circumferential direction is about 20 degrees, a wiping phenomenon is likely to occur in a groove extending in the tire circumferential direction.

  In the tires described in Patent Documents 1 and 2, it was not possible to suppress a decrease in braking performance due to wiping. Therefore, an object of the present invention is to improve ice performance by suppressing wiping generated at the shoulder portion of the tread.

The pneumatic tire of the present invention is a pneumatic tire in which a row of blocks is formed in the shoulder portion of the tread and a rotation direction is specified by a main groove extending in the tire circumferential direction and a lateral groove extending inward in the tire width direction from the ground contact end. In the tire,
The side wall on the stepping side of the block includes a triangular prism-shaped first protrusion that is integrally molded, and the tire width direction and the side surface of the first protrusion are opened outward in the width direction with an opening angle θ1.
The side wall on the kicking side of the block has a triangular prism-shaped second projecting portion formed integrally and the tire width direction and the side surface of the second projecting portion open at the inner side in the width direction with an opening angle θ2. ,
The side wall on the inner side in the width direction of the block is provided with a third protrusion having a triangular prism shape that is integrally formed, and the tire circumferential direction and the side surface of the third protrusion are opened at the stepping side with an opening angle θ3. The height D1 of the first protrusion, the height D2 of the second protrusion, and the height D3 of the third protrusion are 12 to 60% of the height D of the block. .

  By providing triangular prism-shaped first to third protrusions on each side wall of the shoulder block except the grounding end side, and by providing each side wall and the side surface of each protrusion to open in a predetermined direction, by wiping The direction of the frictional force acting on the block can be made closer to the tire circumferential direction, and as a result, the longitudinal frictional force generated during braking can be increased, and the braking performance is improved.

  Hereinafter, an embodiment of a pneumatic tire according to the present invention will be described with reference to the drawings. Fig. 2a is a top view of the block of the pneumatic tire according to the present invention, and Fig. 2b is a perspective view of the block viewed from the direction A of Fig. 2a. The block 3 is a block formed in a shoulder portion of the tread, and is formed by a main groove 1 extending in the tire circumferential direction and a lateral groove 2 extending in the tire width direction from the ground contact end E. Note that R is the tire rotation direction, and the tire W is the tire width direction (the right side is the outside in the width direction in FIG. 2a). A block is also formed on the other shoulder portion (not shown), and has the following configuration, and a block and / or a rib is formed in a region sandwiched between the two shoulder portions.

  On the side wall 11 on the stepping side, the side wall 12 on the kick-out side, and the side wall 13 on the inner side in the width direction of the block 3, the first protrusion 21 having a triangular prism shape, the second protrusion 22, and the third protrusion 23 are blocked. 3 and molded integrally. Note that the stepping side is the side of the block 3 that contacts the ground first, and the kicking side is the side facing the stepping side in the circumferential direction.

  The first protrusion 21 of the side wall 11 on the step-in side is provided such that one side surface 21a opens outward in the width direction at an angle (opening angle) θ1 with the tire width direction W. Conversely, the second protrusion 22 of the side wall 12 on the kick-out side is provided such that one side surface 22a forms an angle (opening angle) θ2 with the tire width direction W and opens inward in the width direction. And the 3rd protrusion part 23 of the side wall 13 of the width direction inner side is provided so that one side surface 23a may make the tire circumferential direction R and angle (opening angle) (theta) 3, and it may open in the stepping side. Further, the heights D <b> 1 to D <b> 3 of the protrusions 21, 22, and 23 are lower than the height D of the block 3.

  In FIG. 2a, the effect of each protrusion part 21,22,23 is demonstrated. During braking, a force (downward in the figure) is applied to the block 3 from the kicking side to the stepping side. Since the block 3 is formed by the main groove 1, the corner on the inner side in the width direction (upper left corner in the figure) on the kicking side of the block 3 is the outer corner in the width direction on the kicking side (upper right in the figure). The corner 3) has a lower rigidity, and the block 3 is subjected to a twisting force that rotates counterclockwise.

  With respect to this twisting force, the protrusions 21, 22, and 23 increase the rigidity of the block 3, and the distribution of the contact pressure of the block 3 is made uniform. As a result, the braking performance is improved. Therefore, if the shape of the first projecting portion on the stepping side opens in the opposite direction to the shape illustrated in FIG. 2 such as a shape that opens outward in the width direction, the effect of increasing the rigidity of the block 3 against the twisting force is obtained. Since it is low, the braking performance is not improved so much. Further, when the projecting portion is not a triangular prism shape but a quadrangular prism shape, it is necessary to enlarge the projecting portion in order to obtain the same effect, and the volume of the main groove 1 or the lateral groove 2 is greatly reduced and the drainage performance is impaired. .

  The other shoulder block (not shown) is provided with a projecting portion that is symmetrical to the projecting portions 21 to 23 illustrated in FIG. Further, in order to improve the snow and snow performance, notches may be provided on the side walls 11 to 13 except for the side wall on the grounding end side that is not the protruding portion.

  The frictional force acting on the tire block of the present invention is schematically shown by a friction circle as shown in FIG. 3a. On the other hand, the friction circle acting as a friction force acting on the block having no protrusion is as shown in FIG. In the figure, 200 is a friction circle, F is a friction force, and Fx and Fy are forces obtained by disassembling the friction force F in the tire width direction W and the tire circumferential direction (front-rear direction), respectively. In the block of the present invention, the braking force is improved because the frictional force Fy in the front-rear direction is large.

  The opening angles θ1 and θ2 of the side walls 21a and 22a of the first and second protrusions 21 and 22 are preferably 2 to 8 degrees, and the opening angle θ3 of the side wall 23a of the third protrusion 23 is preferably 2 to 10 degrees. If the opening angles θ1, θ2, and θ3 are small, the effect of the present invention is small. Conversely, if the opening angles θ1, θ2, and θ3 are large, the volumes of the main groove 1 and the horizontal groove 2 are small, and the drainage performance is impaired. Further, it is more possible to determine the opening angles θ1, θ2, and θ3 so that the projecting portions 21, 22, and 23 do not contact the land portion (block or rib) facing the block 3 with the main groove 1 or the lateral groove 2 interposed therebetween. preferable.

  The heights D1 to D3 of the first to third protrusions 21, 22, and 23 are preferably 12 to 60% of the height D of the block 3, and even if D1, D2, and D3 are not equal, they are within this range. Good. When D1 or the like is less than 12% of the height D, the effect of increasing the rigidity of the block 3 is low and the braking performance is not improved so much. If D1 or the like exceeds 60% of the height D, the groove volume of the main groove 1 or the lateral groove 2 becomes too small, and the drainage performance decreases.

  The other side surfaces 21b and 22b of the protrusions 21 and 22 can be provided at an arbitrary angle with respect to the tire width direction W, and the other side surface 23b of the protrusion 23 is provided at an arbitrary angle with respect to the tire circumferential direction. Can do.

  In order to improve the performance on icy and snowy roads, sipes may be provided in the block 3 as appropriate, and in order to obtain further edge effects, notches may be provided in the side walls 11 to 13 of the block 3.

  Example tires and comparative tires according to the present invention were manufactured, and the respective tires were mounted on a sedan type front-wheel drive passenger vehicle and evaluated. The tread pattern is the pattern shown in FIG. 4, and as described above, zigzag cutouts are formed on the side walls of each block. The tire size was 195 / 65R15.

  Example 1 and Comparative Example 2 are tires in which the shoulder block has the protrusions shown in FIG. 2, and Comparative Example 1 is a tire in which the shoulder block does not have the protrusions shown in FIG. It was. The dimensions of each protrusion were as shown in Table 1. In addition, in FIG. 4, each protrusion part is not illustrated.

  In Table 1, the ice braking performance indicates a braking distance (using ABS) from 40 km / h on the ice road surface. The hydroplaning resistance indicates the speed at which hydroplaning always occurs when only one of the front and rear wheels is driven in a wet road with a water depth of 8 mm. Each numerical value is expressed as a numerical value with Comparative Example 1 being 100, and the larger the numerical value, the better the performance.

  According to Table 1, the example tire was able to improve the braking performance on the ice road surface without impairing the drainage performance.

It is a figure which shows the side wall of the main groove of the pneumatic tire which concerns on this invention in the state which earth | grounded. Fig. 2a is a top view of the block of the pneumatic tire according to the present invention, and Fig. 2b is a perspective view of the block as viewed from the direction A in Fig. 2a. FIG. 3a shows a friction circle of a block of a pneumatic tire according to the present invention, and FIG. 3b shows a friction circle of a block of a conventional pneumatic tire. It is a figure which shows the tread pattern which concerns on an Example and a comparative example.

Explanation of symbols

1 Main groove 2 Horizontal groove 3 Block 21-23 Projection

Claims (2)

In the pneumatic tire in which a row of blocks is formed in the shoulder portion of the tread and the rotation direction is specified by the main groove extending in the tire circumferential direction and the lateral groove extending inward in the tire width direction from the ground contact end,
The side wall on the stepping side of the block includes a triangular prism-shaped first protrusion that is integrally molded, and the tire width direction and the side surface of the first protrusion are opened outward in the width direction with an opening angle θ1.
The side wall on the kicking side of the block has a triangular prism-shaped second projecting portion formed integrally and the tire width direction and the side surface of the second projecting portion open at the inner side in the width direction with an opening angle θ2. ,
The side wall on the inner side in the width direction of the block is provided with a third protrusion having a triangular prism shape that is integrally formed, and the tire circumferential direction and the side surface of the third protrusion are opened at the stepping side with an opening angle θ3. It has been,
The first projecting portion of the height D1, the pneumatic height D2 of the second protrusion, the height D3 of the third projecting portion is characterized by a 12 to 60% of the height D of the block tire. The pneumatic tire according to claim 1, wherein the opening angles θ1 and θ2 are 2 to 8 degrees, and the opening angle θ3 is 2 to 10 degrees.

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