JP2003182311A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate the nonuniformity of the grounding pressure of a tire by defining the shape of blocks for optimizing the height of the blocks, and improve driving stability performance on a dry road surface and driving performance on an icy road. <P>SOLUTION: Each block 18 is formed into such a shape that the height of the block increases gradually from the end toward the center first, then decreases gradually toward center in the tire width direction. As a result, the grounding pressure on the grounding end side and on the center side in the tire width direction can be reduced in comparison with a case of a tire having conventional blocks of which the treading surfaces have a uniform height, so that the grounding pressure can be uniformed in the tire width direction to obtain a high driving stability performance on a dry road surface. Also, by forming each block 18 into such a shape that the height of the block decreases gradually from the end toward the center in the circumferential direction of the tire, the grounding pressure on the center side in the circumferential direction of the tire can be reduced in comparison with a case of a tire having conventional blocks, so that the grounding pressure can be uniformed in the circumferential direction of the tire to obtain a high driving performance on an icy road. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having a block on a tread, and more particularly to a pneumatic tire having excellent steering stability and ice performance.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG.
As shown in (1), the height of the block 100 was usually constant.

The block 1 having such a constant height
As shown in FIG. 8, when 00 touches the dry road surface 102, a frictional force is generated between the block 100 and the dry road surface 102, so that the block 100 deforms to bulge into a barrel shape. Bending works on the ground end of the and the ground end is pushed toward the ground.

Further, since rubber, which is the main material of the tread, is incompressible, the block 100 having a constant height has a large compression rigidity in the vicinity of the center (because it can bulge outward in the vicinity of the side of the block, it is compressed). The rigidity is low.)

Therefore, when the block 100 having a constant height is grounded on the dry road surface 102, the grounding pressure becomes particularly large at the grounding end (block end) and the center of the block as shown in the graph of FIG. Inhomogeneity that becomes large at a portion and becomes relatively small between the grounding end and the central portion of the block occurs.

Therefore, the block 1 having a constant height
At 00, it is difficult for the entire tread to transmit lateral force to the road surface, especially in the small steering angle range (when the slip angle is small) and the large steering angle range (when the slip angle is large), which are important for steering stability. There was a problem.

When the block 100 having such a constant height contacts the ice road surface 104 as shown in FIG. 9, there is almost no frictional force between the block 100 and the ice road surface 104. The block 100 is deformed into a trapezoidal shape in which the tread side is widened, and the ground end of the block 100 does not bend like the case of the dry road surface 102.

Further, since rubber, which is the main material of the tread, is incompressible, the block 100 having a constant height has a large compression rigidity in the vicinity of the center (because it can bulge outward near the side of the block, it is compressed). The rigidity is low.)

Therefore, when the block 100 having a constant height is grounded on the ice road surface 104, the ground pressure becomes particularly large at the central portion of the block as shown in the graph of FIG.

When the ground pressure becomes uneven, the ground area becomes smaller than that when the ground pressure is uniform. Therefore, the block 100 having a constant height is particularly important for driving on ice and during braking. In the above, there is a problem that it becomes difficult for the entire tread surface to transmit the driving force and the braking force to the road surface.

On the other hand, in the conventional study, the tread pattern has been improved in order to improve the grounding characteristics, but in view of the drainage property and other performances,
The current situation is that there are limits.

An invention has been made in which the central portion of the block is made to have a convex shape in the tire circumferential or widthwise cross section, as in Japanese Patent Laid-Open No. 62-279105. It is difficult to obtain a tread shape that is compatible with each other, and it is usually difficult to determine the shape by trial and error.

Further, as in Japanese Unexamined Patent Publication No. 2000-71719, by forming a peripheral ridge whose height gradually decreases toward the block edge and the center of the block in the vicinity of the block edge, the contact pressure is made uniform. Although the invention has been made to improve the performance of a dry road surface with this method alone,
It was difficult to achieve compatibility with ice performance.

[0014]

SUMMARY OF THE INVENTION In consideration of the above facts, the present invention eliminates non-uniformity of ground pressure by defining a shape that optimizes the block height of blocks existing in a tread to improve steering stability, It is also an object of the present invention to provide a pneumatic tire having improved on-ice performance.

[0015]

The invention according to claim 1 is directed to a circumferential groove extending substantially along the tire circumferential direction,
A pneumatic tire having a plurality of blocks defined on the tread by lateral grooves intersecting with the circumferential groove, wherein the tread surface of the block has an end portion when viewed in a cross section along the tire width direction. From the end to the center, the height then gradually decreases toward the center, and when viewed in a cross section along the tire circumferential direction, the height gradually decreases from the end to the center. As described above, at least one of the raised portion and the depressed portion is provided.

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

When a conventional block having a constant height is grounded on a dry road surface, the distribution of the ground pressure in the width direction of the block becomes particularly large at the ground end and becomes large at the center of the block.
Although it is relatively small between the ground contact end and the center of the block (see Fig. 8), when viewed in a cross section along the tire width direction, the height gradually increases from the end to the center. , After that, in the block whose height gradually decreases toward the central portion, the block edge and the block height on the central side of the block become low. The ground contact pressure on the central portion side in the tire width direction can be reduced, and the ground contact pressure can be made uniform in the tire width direction (see FIG. 5).

In the steering stability performance, it is important that the entire tread surface of the block transmits lateral force to the road surface in the small steering angle range and the large steering angle range. However, in the pneumatic tire according to claim 1, Non-uniform contact pressure in the tire width direction of the block on a dry road surface is suppressed, so the ground contact of the block is good when lateral force is input on a dry road surface, which results in high steering stability performance on a dry road surface. To be

Next, when the conventional block having a constant height is grounded on the ice road surface, the distribution of the ground pressure in the circumferential direction of the block is large at the center of the block and relatively small at the ground end (see FIG. 9)), when viewed in a cross section along the tire circumferential direction, a block whose height gradually decreases from the end to the central portion is a ground contact on the ice circumferential surface at the central portion side in the tire circumferential direction. The pressure can be lowered, and the ground contact pressure on the icy road surface can be made uniform in the tire circumferential direction (see FIG. 6).

For the on-ice performance, it is important that the entire tread surface transmits the driving force and the braking force to the icy road surface at the time of driving or braking, but the pneumatic tire according to claim 1 blocks on the icy road surface. Since the non-uniformity of the ground contact pressure in the tire circumferential direction is suppressed, the ground contact of the block at the time of driving or braking on an icy road surface is good, and therefore, high performance on ice can be obtained.

The circumferential groove may be parallel to the tire circumferential direction or may be inclined to some extent with respect to the tire circumferential direction.

The lateral groove may intersect at least with the circumferential groove, may be parallel to the tire width direction, or may be inclined to some extent with respect to the tire width direction.

Further, in order to prevent local wear caused by uneven distribution of the ground contact pressure, it is preferable that the height of the tread changes smoothly, and the block has a cross section in the height direction. At this time, it is preferable that the contour line of the tread surface is constituted by a smooth curve.

According to the invention described in claim 2, in the pneumatic tire according to claim 1, the height is gradually increased from the end portion to the central portion in the tire width direction cross section of any portion in the tire circumferential direction. Then, after that, the height gradually decreases toward the central portion, so that the height gradually decreases from the end portion toward the central portion in any tire circumferential cross section in the tire width direction,
At least one of a raised portion and a depressed portion is provided,
It is characterized by that.

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

In any section in the tire width direction in the tire circumferential direction, the height is gradually increased from the end portion to the central portion, and then the tread shape is gradually reduced toward the central portion. The contact pressure can be made uniform in the tire width direction in the entire block. As a result, steering stability performance can be improved.

In addition, by providing a tread shape in which the height gradually decreases from the end portion to the central portion in any section in the tire circumferential direction in the tire width direction, the ground contact pressure is made uniform in the tire circumferential direction in the entire block. Can be converted. Thereby, the performance on ice can be improved.

According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, the height difference between the highest portion and the lowest portion of the tread in the tire width direction cross section of the block, And the difference in height between the highest part and the lowest part of the tread in the tire circumferential section is 0.1
It is characterized by being within the range of 2.5 mm.

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

Since the deformation of the block is limited under the input of the tire, if the height difference is too large, a portion of the tread surface of the block will not come into contact with the road surface. That is, the ground contact area may be reduced.

Therefore, the upper limit of the height difference is set to 2.5 in order to prevent an extreme reduction in the ground contact area.
mm.

On the other hand, if the height difference is less than 0.1 mm, the effect of lowering the ground contact pressure at the block edges and the central portion of the block is low, and the effect of suppressing uneven ground contact pressure is insufficient.

Therefore, the size of the height difference is set to 0.1 to
It is preferably within the range of 2.5 mm.

The height difference is 0.3 to 1.0.
It is more preferable to set it within the range of mm.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the pneumatic tire of the present invention will be described with reference to FIGS.

As shown in FIG. 2, the tread 12 of the pneumatic tire 10 of this embodiment has a tire circumferential direction (arrow A).
Direction) and a plurality of circumferential grooves 14 extending along the tire width direction (arrow B direction).
A plurality of blocks 18 are formed by 6 and.

Since the internal structure of the pneumatic tire 10 is not different from that of a general pneumatic tire, the description of the internal structure will be omitted.

FIG. 1 is a perspective view of the block 18, FIG. 3 is a sectional view of the block 18 in the tire width direction, and FIG. 4 is a sectional view of the block 18 in the tire circumferential direction. ing.

As shown in FIGS. 1, 3 and 4,
On the tread surface of the block 18, raised portions 20 are formed near the block edges on both sides in the tire width direction.

The raised portion 20 is formed continuously in the tire circumferential direction, and its height is set to be highest at both end portions in the tire circumferential direction and lowest at the central portion in the tire circumferential direction. The block height gradually decreases from both ends in the tire circumferential direction toward the center in the tire circumferential direction.

Further, a depression 22 continuous in the tire circumferential direction is provided between the raised portions 20, and a depression 24 continuous in the tire circumferential direction is provided on the block end side of the raised portion 20 in the tire width direction. It is provided.

The recessed portion 22 and the recessed portion 22 are set to have the highest end portions in the tire circumferential direction and the lowest center portion in the tire circumferential direction, and the block height is from the both end portions in the tire circumferential direction to the center portion in the tire circumferential direction. The taper is gradually decreasing toward the section.

The depression 22, the depression 22 and the raised portion 20 are smoothly connected to each other.

In the block 18 of the present embodiment, the contour shape of the tread when viewed in a cross section along the tire width direction is such that the height gradually increases from the end to the center as shown in FIG. After that, the height is gradually reduced toward the central portion, and the contour shape of the tread when viewed in a cross section along the tire circumferential direction is all higher from the end portion to the central portion as shown in FIG. Is a shape that gradually decreases.

As shown in FIG. 3, the height difference D1 between the highest part and the lowest part of the tread when the block 18 is viewed in a cross section along the tire width direction is in the range of 0.1 to 2.5 mm. It is preferably within the range of 0.3 to 1.0 mm, and more preferably within the range of 0.3 to 1.0 mm.

Further, as shown in FIG. 4, the height difference D2 between the highest portion and the lowest portion of the tread when the block 18 is viewed in a section along the tire circumferential direction is 0.1 to 2.5 mm.
Is preferable, and 0.3 to 1.0 mm is more preferable. (Operation) Next, the operation of the pneumatic tire 10 of the present embodiment will be described.

When a block having a constant height is grounded on a dry road surface, the ground pressure distribution in the width direction of the block is particularly large at the grounding end and large at the center of the block. Although it becomes relatively small between the two, as shown in FIG. 3, when the block 18 is viewed in a cross section along the tire width direction, the height gradually increases from the end portion to the central portion, and then, By adopting a shape in which the height gradually decreases toward the central portion, it is possible to reduce the ground contact pressure on the ground contact end side in the tire width direction and the center part side in the tire width direction in comparison with a block having a constant tread height. As shown in FIG. 5, the ground contact pressure can be made uniform in the tire width direction in the entire block 18.

As a result, the ground contact of the block at the time of lateral force input on a dry road surface is improved, and high steering stability performance on a dry road surface can be obtained.

Further, in the block 18 of this embodiment,
As described above, since it is possible to suppress the unevenness of the ground contact pressure in the tire width direction, it is possible to suppress the occurrence of buckling reduction due to lateral force on a road surface where frictional force acts like a dry road surface and improve the steering stability performance. .

Further, when a block having a constant height is in contact with the ice road surface, the contact pressure distribution in the circumferential direction of the block is large at the center of the block and relatively small at the contact end.
As shown in FIG. 3, when the block 18 is viewed in a cross section along the tire circumferential direction, the tire has a shape in which the height gradually decreases from the end portion toward the center portion, so that the tire has a tread height equal to that of the block. The ground contact pressure on the central portion side in the circumferential direction can be lowered, and as shown in FIG. 6, the ground contact pressure can be made uniform in the tire circumferential direction in the entire block 18.

As a result, the ground contact of the block during driving and braking on an icy road surface is improved, and high on-ice performance is obtained.

In the tire circumferential direction section and the tire width direction section, the height difference of the tread surface of the block 18 is 0.1.
Within the range of 2.5 mm, the contact pressure can be made uniform in the tire width direction and the tire circumferential direction without reducing the contact area of the block 18.

In this embodiment, the circumferential groove 14 extends along the tire circumferential direction (arrow A direction) and the lateral groove 16 extends along the tire width direction (arrow B direction). However, the circumferential groove 14 may be inclined with respect to the tire circumferential direction, and the lateral groove 16 may be inclined with respect to the tire width direction.

Further, although the block 18 of the present embodiment is rectangular, the present invention is not limited to this, and the shape of the block 18 when the tread 12 is viewed in plan is the direction of the circumferential groove 14 and the lateral groove 16, By adding chamfers, notches and the like, the shape may be a rhombus, a hexagon, an octagon, or another polygon, or may be a substantially U-shape, or a circle, an ellipse, or the like. (Test Example) In order to confirm the effect of the present invention, four types of tires of the example to which the present invention is applied, two types of tires of comparative examples, and one type of conventional tire are prepared, and steering stability performance is obtained by running an actual vehicle. The performance on ice was evaluated.

The tire size is 195 / 50R15.
Therefore, the internal pressure of 200 kPa was filled and the vehicle was actually driven.

The block size is 30 m in the tire circumferential direction.
m, tire width direction is 20 mm, and height is 9 mm (average value).

The tire of the conventional example is a tire having blocks having a constant height.

The tires of Examples and Comparative Examples are tires having a raised portion and a depressed portion on the tread like the above-described embodiment.

As shown in FIG. 3, the distance L1 from the block end to the top of the raised portion 20 is 3 mm.

The evaluation is as shown in Table 1 below. The evaluation is a feeling evaluation by a test driver, and is an index display with the conventional tire being 100.
Also, the larger the value, the better the performance.

[0061]

[Table 1] As a result of the test, the tires of Examples 1 to 4 have steering stability performance on a dry road surface as compared with the tires of the conventional example and the comparative example.
And it can be seen that the performance on ice is improved.

[0062]

As described above, since the pneumatic tire of the present invention has the above-mentioned constitution, it is possible to eliminate the unevenness of the ground contact pressure, and to improve the steering stability performance on dry road surface and the ice performance as compared with the conventional one. It has an excellent effect that it can be made.

[Brief description of drawings]

FIG. 1 is a plan view of a tread of a pneumatic tire according to an embodiment of the present invention.

2 is a perspective view of the block shown in FIG. 1. FIG.

FIG. 3 is a sectional view in the tire width direction of the block.

FIG. 4 is a tire circumferential direction sectional view of a block.

FIG. 5 is an explanatory diagram showing a ground contact pressure distribution in a tire width direction cross section of the block.

FIG. 6 is an explanatory diagram showing a ground contact pressure distribution in a tire circumferential cross section of the block.

FIG. 7 is a sectional view of a block of a conventional example.

FIG. 8 is an explanatory diagram showing a contact pressure distribution on a dry road surface in a conventional block.

FIG. 9 is an explanatory diagram showing a contact pressure distribution on an ice road surface in a conventional block.

[Explanation of symbols]

10 pneumatic tires 12 treads 14 circumferential groove 16 lateral groove 18 blocks 20 Raised part 22 Depression 24 Depression

Claims (3)

[Claims] 1. A pneumatic tire having a tread provided with a plurality of blocks defined by circumferential grooves extending substantially along the tire circumferential direction and lateral grooves intersecting with the circumferential grooves. When viewed in a cross section along the tire width direction, the tread surface of the block gradually increases in height from the end portion toward the central portion, and then gradually decreases in height toward the central portion. At least one of a raised portion and a depressed portion is provided so that the height gradually decreases from an end portion toward a central portion when viewed in a cross section along the pneumatic tire. 2. The tire width direction cross-section of any portion in the tire circumferential direction is such that the height is gradually increased from the end portion to the central portion, and then the height is gradually reduced toward the central portion. At least one of the raised portion and the depressed portion is provided so that the height gradually decreases from the end portion toward the central portion in the tire circumferential cross section of any portion of the tire. Pneumatic tire described. 3. The height difference between the highest part and the lowest part of the tread in the tire width direction cross section of the block, and the height difference between the highest part and the lowest part of the tread surface in the tire circumferential cross section, The pneumatic tire according to claim 1 or 2, wherein the pneumatic tires are each in the range of 0.1 to 2.5 mm.