JP2006062601A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire having excellent on-ice performance capable of compatibly realizing adequate rigidity distribution of a block and enhancing the edge effect without changing a tread rubber and without increasing the number of sipes. <P>SOLUTION: Elliptical small holes 22 with the major axis thereof being in the tire circumferential direction are formed in a circumferential center portion of a small block 18A demarcated by a transverse sipe 20. The compressive rigidity of the small circumferential center portion is reduced thereby to increase the ground contact pressure of the small block 18 at an edge part, and a high edge effect can be obtained on an icy road. The small holes 22 can minimize the effect on the bending rigidity in the falling-down direction of a small block 18A in comparison with the transverse sipe 20, and reduction of the contact area caused by excessive fall-down deformation can be prevented. In addition, the small holes 22 suck a water film on ice of the contact surface, the water discharging effect can also be improved. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire, and particularly to a pneumatic tire excellent in performance on ice.

  Conventionally, in winter pneumatic tires, in order to improve acceleration and braking performance when starting on ice, lateral sipes have been added to the block part of the tire tread pattern, but the number of sipes has been increased. Although the effect of the edge portion scratching the road surface (hereinafter referred to as the edge effect) and the effect of the sipe portion sucking up the water film on the ice surface (hereinafter referred to as the drainage effect) will increase, the block rigidity will decrease and the contact area on the ice will increase. Since it decreases, there is a problem that the frictional force between the tire and the icy road surface (hereinafter referred to as surface frictional force) decreases.

  If the decrease in surface friction force exceeds the increase in edge effect and drainage effect, the performance on ice will not improve, so there is a limit to improving the performance on ice by adding sipes.

  On the other hand, in the conventional examination, the tread rubber has been improved for the above drainage improvement, and a pneumatic tire having a foam rubber layer on the tread has been developed (for example, Patent Documents 1 to 3). 3).

In recent years, improvement of the sipe shape has been studied so that the reduction of the contact area can be suppressed and the surface friction force can be secured even if the number of sipe is increased, and a three-dimensional sipe shape has been developed (Patent Literature). 4).
Japanese Patent No. 2510533 Patent No. 002518870 Patent No. 002564760 JP 2000-6618

  However, foam rubber is a technique that mainly improves drainage, so that the performance on ice is remarkably improved at a temperature around 0 ° C where a water film is likely to be generated. It was relatively difficult to improve.

  Even if the number of sipes is increased while securing a contact area using a three-dimensional sipe, it is inevitable that the block rigidity is lowered with the increase in the number of sipes, and the small blocks are easily collapsed during tire traveling.

  As a result, handling performance and wear performance on a dry road surface are deteriorated. Therefore, there is a limit to a method for increasing the number of sipes in order to balance with other performances.

  The present invention was made to solve the above problems, and was excellent in on-ice performance capable of achieving both optimization of the rigidity distribution of the block and improvement of the edge effect without changing the tread rubber and increasing the number of sipes. The object is to provide a pneumatic tire.

  The invention according to claim 1 is a pneumatic tire in which a tread is provided with a plurality of blocks defined by a plurality of grooves intersecting with each other. A plurality of small holes having different dimensions in the other direction intersecting with the direction are formed.

  Next, the operation of the pneumatic tire according to claim 1 will be described.

  It is known that when the tire load and the internal pressure conditions are the same, the average contact pressure in the contact surface is substantially equal. Therefore, in order to increase the edge pressure of the block, it is advantageous to lower the contact pressure on the center side of the block, and to increase the edge pressure of the block relatively by causing uneven contact pressure distribution in the block surface. is there.

  The contact pressure of the block depends on the compression rigidity. If the part with high compression rigidity has high contact pressure and the part with low compression rigidity has low contact pressure, the compression rigidity on the center side of the block is lowered. Thus, the block edge pressure can be increased.

  Here, a small hole is provided in the block in order to reduce the compression rigidity on the center side of the block.

  Thereby, the compression rigidity at the edge portion of the block can be ensured while the compression rigidity at the center side of the block is lowered.

  Since the small hole can reduce the influence on the bending rigidity in the collapse direction of the block as compared with the sipe, it is possible to prevent the contact area from being reduced due to the collapse deformation.

  Here, since the small hole in which the dimension in one direction of the opening is different from the dimension in the other direction intersecting with one direction, the bending rigidity in the collapse direction of the block is controlled by the direction of the opening of the small hole, can do.

  In addition, since the small hole sucks up the water film on the ground surface, the drainage effect can be improved. Furthermore, the edge effect of the opening portion of the small hole can be expected.

  The pneumatic tire according to claim 1, wherein the edge effect of the block is increased by increasing the edge pressure of the block, the reduction of the contact area when the block is collapsed, and the drainage effect is further enhanced. Can improve the performance on ice.

  The plurality of grooves intersecting with each other are, for example, a circumferential groove extending along the tire circumferential direction and a lateral groove extending along the tire axial direction. The circumferential groove is inclined with respect to the tire circumferential direction. The lateral groove may be inclined with respect to the tire axial direction.

  The block partitioned by the circumferential groove and the lateral groove is rectangular, but the present invention is not limited to this, and the block shape when the tread is shown in plan view includes the direction of the circumferential groove and the lateral groove, chamfering, notch, etc. By addition, polygons such as rhombuses, hexagons, octagons, etc., substantially U-shapes may be exhibited, and circles, ellipses, etc. may be used.

  Further, in order to prevent local wear caused by uneven distribution of the contact pressure, it is preferable to arrange a plurality of small holes at equal intervals in the tire axial direction of the block.

  The invention according to claim 2 is the pneumatic tire according to claim 1, wherein the block has a small block divided by one or more sipes extending along a tire axial direction. .

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

  By providing a sipe extending along the tire axial direction on the block, the number of edges effective for driving and braking on the icy road increases, and the water film formed between the block and the icy road surface absorbs water. Will improve.

  The sipe may be parallel to the tire axial direction or may be inclined to some extent with respect to the tire axial direction. The inclination angle with respect to the tire axial direction is preferably 40 ° or less, and more preferably 20 ° or less.

  According to a third aspect of the present invention, in the pneumatic tire according to the second aspect, the small hole is formed in a tire circumferential direction central portion of the small block.

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

  Between the sipes, that is, the central portion in the tire circumferential direction of the small block is a part away from the sipes, and the water film is difficult to absorb water by the sipes. For this reason, it is preferable to form a small hole in the tire circumferential direction center portion of the small block, and to absorb the water film which is difficult to absorb water with the sipe, with the small hole.

  The invention according to claim 4 is the pneumatic tire according to claim 2 or claim 3, wherein the depth of the small hole is shallower than the depth of the sipe and deeper than half of the depth of the groove. It is characterized by that.

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

  The depth of the small hole is preferably shallower than the sipe depth in order to ensure appropriate block rigidity, and is preferably deeper than half the groove depth of the groove in order to ensure on-ice performance after wear. .

  According to a fifth aspect of the present invention, in the pneumatic tire according to any one of the first to fourth aspects, the long hole of the small hole is oriented in the tire circumferential direction. It is said.

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

  By directing the long axis of the opening of the small hole in the circumferential direction, the influence on the bending rigidity in the collapse direction (circumferential direction) of the block can be minimized, thus preventing a decrease in the contact area due to excessive collapse deformation. I can do it. Incidentally, it becomes easy to fall down in the circumferential direction by making the long axis of the opening of the small hole face the axial direction.

  A sixth aspect of the present invention is the pneumatic tire according to any one of the first to fifth aspects, wherein a plurality of the small holes are formed in a tire axial direction.

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

  By forming a plurality of small holes in the tire axial direction, the contact pressure can be increased with respect to the entire edge extending in the tire axial direction.

  A seventh aspect of the present invention is the pneumatic tire according to any one of the first to sixth aspects, wherein the small hole has a major axis of 1.0 to 5.0 mm and a minor axis of 0.5. It is characterized by being -2.0 mm.

  Next, the operation of the pneumatic tire according to claim 7 will be described.

  When the long axis of the small hole is less than 1.0 mm, the drainage effect of the small hole sucking up the water film on the ground contact surface is insufficient, so that the performance on ice cannot be improved.

  When the long axis of the small hole exceeds 5.0 mm, the bending rigidity in the block collapse direction is insufficient, so that the ground contact area is reduced, and not only the compression rigidity at the center of the small block but also the compression rigidity near the edge is reduced. Therefore, the edge effect is reduced and the performance on ice cannot be improved.

  If the minor axis of the small hole is less than 0.5 mm, the drainage effect of the small hole sucking up the water film on the ground contact surface is insufficient, so the performance on ice cannot be improved.

  If the minor axis of the small hole exceeds 2.0 mm, the bending rigidity in the block collapse direction is insufficient, so that the ground contact area is reduced and the performance on ice cannot be improved.

  The invention according to claim 8 is the pneumatic tire according to any one of claims 1 to 7, wherein the small hole is elliptical.

  Next, the operation of the pneumatic tire according to claim 8 will be described.

  By making the small hole elliptical, it is possible to prevent stress concentration around the small hole with an angular opening contrast. Moreover, the cross-sectional shape of the pin provided in the mold for forming the small hole becomes an ellipse, which is easy to manufacture.

  As described above, since the pneumatic tire according to the present invention has the above-described configuration, it is possible to improve the performance on ice while achieving both the optimization of the rigidity distribution of the block and the improvement of the edge effect. Have.

  A pneumatic tire 10 according to an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the tread 12 of the pneumatic tire 10 of the present embodiment includes a plurality of circumferential grooves 14 extending along the tire circumferential direction (arrow S direction) and the tire axial direction (arrow W direction). A plurality of rectangular blocks 18 are provided in a tread plan view that is partitioned by a plurality of lateral grooves 16 extending along the horizontal axis.

  In addition, since the internal structure of this pneumatic tire 10 is the same structure as a general pneumatic tire, description of an internal structure is abbreviate | omitted.

  As shown in FIG. 2, in the block 18, linear transverse sipes 20 extending in the tire axial direction and crossing are formed at equal intervals in the circumferential direction, thereby defining a plurality of small blocks 18A.

  A plurality of elliptical small holes 22 are formed at equal intervals along the tire axial direction at the circumferential center of these small blocks 18A.

  The major axis of the elliptical small hole 22 is oriented in the circumferential direction.

  As shown in FIG. 3, when the length of the long axis of the small hole 22 is a and the length of the short axis is b, the length of the long axis is 1.0 to 5.0 mm and the length of the short axis. b is preferably in the range of 0.5 to 2.0 mm, and the ratio a / b is preferably in the range of 2.0 to 5.0, and more preferably in the range of 3.0 to 4.0.

As shown in FIG. 2, the depth d ₁ of the small hole 22 is preferably shallower than the depth d ₀ of the lateral sipe 20 in order to ensure appropriate block rigidity, and in order to ensure on-ice performance after wear. Further, it is preferable that the depth is deeper than half of the groove depth D (same as the height of the block) of the circumferential groove 14.
(Function)
Next, the effect | action of the pneumatic tire 10 of this embodiment is demonstrated.

  In the pneumatic tire 10 of the present embodiment, since the small hole 22 is provided in the circumferential central portion of the small block 18A partitioned by the horizontal sipe 20 to reduce the compression rigidity of the small circumferential central portion, the edge portion of the small block 18A It was possible to increase the contact pressure at the hill and to obtain a high edge effect on the icy road.

  As shown in FIG. 4, when comparing the ground pressure when a braking force or a driving force is applied to a sipe block without a small hole and a sipe block with a small hole, a sipe with a small hole is formed. It can be seen that the attached block has a higher ground pressure P at the edge of the small block.

  The higher the contact pressure at the edge, the higher the ability to cut the water film, that is, the edge effect, which is advantageous for improving the performance on ice.

  The elliptical small hole 22 can minimize the influence on the bending rigidity of the small block 18 </ b> A in the collapse direction as compared with the horizontal sipe 20, and can prevent a reduction in the ground contact area due to excessive collapse deformation.

  Further, since the small hole 22 sucks up the water film on the ice on the ground surface, the drainage effect can be improved.

  Furthermore, the edge effect of the opening part of the small hole 22 can also be expected.

  As described above, the edge effect of the block 18 by increasing the edge pressure of the block 18 is increased, the reduction of the contact area is reduced, and the drainage effect is improved, so that the pneumatic tire 10 of the present embodiment improves the performance on ice. Can do.

  In addition, since the long axis of the elliptical small hole 22 is directed in the circumferential direction, the influence on the bending rigidity in the falling direction of the small block 18A can be minimized, so that reduction of the ground contact area due to excessive falling deformation is prevented. I can do it.

  In addition, when the length a of the long axis of the small hole 22 is less than 1.0 mm, the drainage effect of the small hole 22 sucking up the water film on the ground surface is insufficient, so that the performance on ice cannot be improved.

  When the length a of the long axis of the small hole 22 exceeds 5.0 mm, the bending area in the collapse direction of the block 18 is insufficient and the ground contact area is reduced. Since the compression rigidity in the vicinity decreases, the edge effect decreases and the performance on ice cannot be improved.

  When the length b of the minor axis of the small hole 22 is less than 0.5 mm, the drainage effect of the small hole 22 sucking up the water film on the ground surface is insufficient, so that the performance on ice cannot be improved.

  If the length b of the minor axis of the small hole 22 exceeds 2.0 mm, the bending rigidity in the tilting direction of the block 18 is insufficient, so that the ground contact area is reduced and the performance on ice cannot be improved.

In addition, although the direction of the long axis of the small hole 22 has faced the tire circumferential direction, it may have an angle with respect to the tire circumferential direction. The rigidity against the falling deformation of the small block 18A can be controlled by the direction of the long axis.
(Test example)
In order to confirm the effect of the present invention, one type of tire according to an embodiment to which the present invention was applied and one type of conventional tire were prepared, and the performance on ice was evaluated by actual vehicle running.

  The tire of the example is a tire having the blocks described in the above embodiment, and the conventional tire is a tire having a block in which small holes are not formed, as shown in FIG.

  The tire size was 195 / 65R15, and an internal pressure of 200 kPa was filled.

In the test, a test tire was mounted on a passenger car and a start test and a braking test were performed on an icy road.
-Start test: The accelerator is fully opened from the running state at an initial speed of 10 km / h, and the time (acceleration time) to reach the final speed of 45 km / h is measured and evaluated with the average acceleration calculated from the initial speed, final speed, and acceleration time. Went. The results are expressed as an average speed index with the conventional example being 100, and the larger the index, the better the starting performance.
Brake test: The braking distance from the initial speed of 40 km / h until full braking was applied to the stationary state was measured, and the evaluation was performed using the average deceleration calculated from the initial speed and the braking distance. The results are expressed as an average deceleration index with the conventional example being 100, and the larger the index, the better the braking performance.

試験の結果、本発明の適用された実施例のタイヤは、従来例に対して氷上加速度、及び氷上減速度に優れていることが分かった。

As a result of the test, it was found that the tire of the example to which the present invention was applied was superior in acceleration on ice and deceleration on ice compared to the conventional example.

It is a top view of the tread of the pneumatic tire concerning one embodiment of the present invention. It is a perspective view of the block in which the small hole was formed. It is a top view of a small hole. (A) is explanatory drawing explaining distribution of the ground pressure which acts on a conventional block, (B) is explanatory drawing explaining distribution of the ground pressure which acts on the block of this invention. It is a perspective view of the block of a prior art example.

Explanation of symbols

10 Pneumatic tire 14 Circumferential groove 16 Horizontal groove 18 Block 20 Horizontal sipe 22 Small hole

Claims (8)

A pneumatic tire having a tread having a plurality of blocks defined by a plurality of grooves intersecting each other,
The pneumatic tire according to claim 1, wherein a plurality of small holes having different dimensions in one direction of the opening and dimensions in the other direction intersecting with the one direction are formed in the block. 2. The pneumatic tire according to claim 1, wherein the block has a small block divided by one or more sipes extending along a tire axial direction. The pneumatic tire according to claim 2, wherein the small hole is formed in a tire circumferential direction center portion of the small block. 4. The pneumatic tire according to claim 2, wherein a depth of the small hole is shallower than a depth of the sipe and is deeper than half of the depth of the groove. 5. The pneumatic tire according to any one of claims 1 to 4, wherein the small hole has a long axis of an opening portion facing a tire circumferential direction. The pneumatic tire according to any one of claims 1 to 5, wherein a plurality of the small holes are formed in a tire axial direction. The pneumatic hole according to any one of claims 1 to 6, wherein the small hole has a major axis of 1.0 to 5.0 mm and a minor axis of 0.5 to 2.0 mm. tire. The pneumatic tire according to any one of claims 1 to 7, wherein the small hole has an oval shape.

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