JP5015421B2 - Pneumatic tire - Google Patents

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, a lateral sipe has been added to a block portion of a tire tread pattern in order to improve acceleration and braking performance when starting on ice (see, for example, Patent Document 1). ).
JP-A-5-310010 (FIG. 1 etc.)

  However, as the number of sipes is increased in order to improve the performance on ice, the force that the edge part scratches the road surface (hereinafter referred to as the edge effect) and the effect that the sipe part absorbs the water film on the ice surface (hereinafter referred to as the drainage effect) increase. As the block rigidity decreases and the contact area on the ice decreases, 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.

  In particular, the water film generated in the block tread is mainly discharged out of the tread by sipes. Therefore, the central part in the circumferential direction of the small block partitioned by sipes is poor in drainage, and a water film tends to accumulate.

  The present invention has been made to solve the above-mentioned problems, and improves drainage at the center in the circumferential direction of a small block partitioned by sipe, and changes on tread rubber, performance on ice without increasing the number of sipe It is an object to provide a pneumatic tire capable of improving the above.

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 each other, and the sipe extending in the tire axial direction has a sipe extending in the tire circumferential direction. A plurality of small blocks that are divided by being arranged on the tire, and a row of a plurality of independent circular small holes that are arranged in the tire axial direction is formed on the small blocks. The row of small holes is arranged at least in the center of the small block in the tire circumferential direction, and the small hole has a depth greater than half the groove depth of the groove extending in the tire circumferential direction. Yes.

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

In the pneumatic tire according to claim 1, by forming a plurality of independent circular small hole rows in the small blocks partitioned by the sipe, a water film between the sipe generated when traveling on an icy road surface that is difficult to remove by the sipe is formed. It can be sucked up by a plurality of independent small holes in a row, and the performance on ice can be improved without changing the tread rubber or increasing the number of sipes.

The invention of claim 2 is the pneumatic tire according to claim 1, wherein the number of small holes per unit area, the axially central portion of the small blocks is greater than both sides, it is characterized by.

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

Between sipes of small blocks, the removal effect is small portion of the water film by a sipe, i.e., the number of small holes are set larger in the tire axial direction sides compared in the tire axial direction central portion, taken in the sipe on icy road The difficult water film is efficiently sucked up at the portion where the number of small holes per unit area is large , and the performance on ice is improved.

According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, in the small block, the depth of the small hole disposed in the central portion in the axial direction is disposed on both sides in the axial direction. It is characterized by being deeper than the depth of the small hole.

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

  Deep holes can absorb more water than shallow holes.

  Therefore, it is preferable to dispose a deep small hole in the central portion in the axial direction of the small block that is difficult to remove by sipe to improve water absorption performance.

According to a fourth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects, at least one of a shape and a size of the small hole is different in the small block. It is characterized by that.

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

  By varying at least one of the shape and size of the small hole, the distribution of water absorption performance in the small block can be changed.

According to a fifth aspect of the present invention, in the pneumatic tire according to any one of the first to fourth aspects, in the small block, the number of the small holes per unit area is the small size during braking. The block is characterized in that the downstream side in the direction in which the force received from the road surface is larger than the upstream side.

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

For example, at the time of braking, the block falls down and deforms due to the force received from the road surface. At this time, in the small block, the contact pressure is high on the upstream side in the direction in which the force is applied, the contact pressure is low on the downstream side, or floats off the road surface, and the water film becomes thick in the downstream side. Therefore, in the small block, and many downstream of the input of the number of small holes per unit area, it is preferable to increase the downstream side of the water uptake capacity.

  As described above, since the pneumatic tire of the present invention has the above-described configuration, it has an excellent effect that the performance on ice can be improved without changing the tread rubber or increasing the number of sipes.

[First Embodiment]
A pneumatic tire 10 according to a first 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 circular small holes 22 are formed at equal intervals along the tire axial direction at the center in the circumferential direction of these small blocks 18A.

  The diameters of these small holes 22 are all the same.

  The diameter of the small hole 22 is preferably in the range of 0.5 to 2.0 mm.

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 an appropriate block rigidity, and in order to ensure the performance on ice after wear, It is preferable to be deeper than half of the groove depth D (same as the height of the block).
(Function)
Next, the effect | action of the pneumatic tire 10 of this embodiment is demonstrated.

  In the pneumatic tire 10 of the present embodiment, a row of small holes 22 is formed in the small blocks 18A partitioned by the horizontal sipe 20, and a water film between the horizontal sipe that is difficult to be removed by the horizontal sipe 20 when traveling on an icy road surface. Since the plurality of small holes 22 in the row absorbs, the performance on ice can be improved without changing the tread rubber and increasing the number of sipes.

  Furthermore, since the small hole 22 can minimize the influence on the bending rigidity in the falling direction of the small block 18A as compared with the horizontal sipe 20, it is possible to prevent the contact area from being reduced due to excessive falling deformation.

In addition, the edge effect of the opening part of the small hole 22 can also be expected.
[Second Embodiment]
A pneumatic tire 10 according to a second embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same structure as 1st Embodiment, and the description is abbreviate | omitted.

As shown in FIG. 3 (C), in the pneumatic tire 10 of the present embodiment, the number of small holes 22 per row is set to double (that is, the density is double) than in the first embodiment. The performance on ice can be improved as compared with the first embodiment.
[Third Embodiment]
A pneumatic tire 10 according to a third embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same structure as embodiment mentioned above, and the description is abbreviate | omitted.

As shown in FIG. 3D, in the block 18 of the pneumatic tire 10 of the present embodiment, a plurality (the same number as in the first embodiment) are provided in the central portion in the circumferential direction of the small block 18A as in the first embodiment. The small holes 22 are formed in a row in the tire axial direction, but are not equally spaced in the tire axial direction, but are formed so that the number in the tire axial center is larger per unit area than on both sides in the tire axial direction. ing.

  Among the small blocks 18 </ b> A, the center portion in the tire axial direction is a place far from the circumferential groove 14, so that it is more difficult for the horizontal sipe 20 to drain the water film than both sides in the tire axial direction.

For this reason, it is preferable to increase the number per unit area of the small holes 22 on the center side in the tire axial direction of the small block 18A as in the present embodiment.

Thereby, performance on ice can be improved rather than 1st Embodiment with the same number of the small holes 22.
[Fourth Embodiment]
A pneumatic tire 10 according to a fourth embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same structure as embodiment mentioned above, and the description is abbreviate | omitted.

As shown in FIG. 3 (E), in the block 18 of the pneumatic tire 10 of the present embodiment, the rows of small holes 22 similar to those of the third embodiment are symmetric with respect to the circumferential center of the small block 18A. Since one row is provided, the performance on ice can be improved as compared with the third embodiment.
[Fifth Embodiment]
A pneumatic tire 10 according to a fifth embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same structure as embodiment mentioned above, and the description is abbreviate | omitted.

As shown in FIG. 3 (F), in the block 18 of the pneumatic tire 10 of the present embodiment, two rows of small holes 22 arranged in the same manner as in the third embodiment are formed. The rows are arranged closer to the downstream side in the direction in which the force from the road enters (that is, the number of small holes 22 per unit area in the small block 18A is upstream on the input downstream side (right side of the drawing)). is set larger than the side.).

For example, at the time of braking, the water film on the downstream side of the input of the small block 18A that falls and deforms due to the input from the road surface and absorbs water at the portion where the number of the small holes 22 is large , so that it is equidistant in the tire axial direction. The performance on ice can be improved as compared with the case of the above.
[Sixth Embodiment]
A pneumatic tire 10 according to a sixth embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same structure as embodiment mentioned above, and the description is abbreviate | omitted.

This embodiment is a modification of the fifth embodiment. As shown in FIG. 3G, the small hole row on the downstream side of the input is compared with the small hole row on the upstream side, and the small hole 22 on the center side in the tire axial direction. A large number is set. For this reason, performance on ice can be improved rather than 5th Embodiment.
[Seventh Embodiment]
A pneumatic tire 10 according to a seventh embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same structure as embodiment mentioned above, and the description is abbreviate | omitted.

  This embodiment is a modification of the sixth embodiment, and as shown in FIG. 3 (H), the diameter of the small hole 22 on the tire axial direction center side is larger than the diameter of the small hole 22 on both sides in the tire axial direction. Is set.

Therefore, the water absorption at the center side in the tire axial direction of the small block 18A is increased, and the performance on ice can be improved as compared with the sixth embodiment.
[ Reference example ]
A pneumatic tire 10 according to a reference example will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same structure as embodiment mentioned above, and the description is abbreviate | omitted.

This reference example is a modification of the sixth embodiment, and as shown in FIG. 3I, the small hole 22 is not circular but has an L shape.

(Test example)
In order to confirm the effect of the present invention, seven types of tires of the examples to which the present invention was applied, one type of reference tire, and one type of conventional tire were prepared, and the performance on ice was evaluated by actual vehicle running. went.

  Example 1: A pneumatic tire having the blocks described in the first embodiment (see FIGS. 2 and 3B).

  Example 2: A pneumatic tire having the block (see FIG. 3C) described in the second embodiment.

  Example 3: A pneumatic tire having the blocks (see FIG. 3D) described in the third embodiment.

  Example 4: A pneumatic tire having the blocks (see FIG. 3E) described in the fourth embodiment.

  Example 5: A pneumatic tire having the blocks described in the fifth embodiment (see FIG. 3F).

  Example 6: A pneumatic tire having the blocks described in the sixth embodiment (see FIG. 3G).

  Example 7: A pneumatic tire having the blocks described in the seventh embodiment (see FIG. 3H).

Reference example : A pneumatic tire having the block described in the reference example (see FIG. 3I).

  Conventional example: A pneumatic tire having a block in which small holes are not formed (see FIGS. 5 and 3A).

  In addition, between Examples 4-8, the total area of each small hole is set equally.

  The tire size was 195 / 65R15, and the internal pressure was 200 kPa.

In the test, a braking test was performed on an icy road with a test tire mounted on a passenger car.
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 excellent in the deceleration on ice compared to the conventional example.

It is a top view of the tread of the pneumatic tire concerning a 1st embodiment of the present invention. It is a perspective view of the block in which the small hole was formed. (A)-(I) is a top view of a block. It is a top view of the small hole formed in the block of Example 7. It is a perspective view of the block of a prior art example.

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

Claims (5)

A pneumatic tire having a tread having a plurality of blocks defined by a plurality of grooves intersecting each other,
The block includes a plurality of small blocks divided by a plurality of sipes extending in the tire circumferential direction extending along the tire axial direction,
The small block is formed with a row of a plurality of independent small holes arranged in the tire axial direction,
The row of the plurality of independent circular small holes is disposed at least in the tire circumferential direction center of the small block,
The pneumatic tire according to claim 1, wherein the small hole has a depth larger than half of a groove depth of the groove extending in the tire circumferential direction. 2. The pneumatic tire according to claim 1, wherein the number of the small holes per unit area is greater in the axial central portion of the small block than on both sides. The depth of the small hole arrange | positioned at an axial direction center part in the said small block is deeper than the depth of the said small hole arrange | positioned at an axial direction both sides, The Claim 1 or Claim 2 characterized by the above-mentioned. Pneumatic tire. The pneumatic tire according to any one of claims 1 to 3, wherein at least one of a shape and a size of the small hole is different in the small block. The number of the small holes per unit area in the small block is larger on the downstream side in the direction in which the force received by the small block from the road surface during braking is larger than the upstream side. The pneumatic tire according to any one of claims 4 to 4.

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