JPH11189015A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the breakage of a tire, and enhance the performance on ice, in the pneumatic tire in which circumferential sipes are formed in the block. SOLUTION: The water film between a tire and an ice surface is efficiently discharged by forming a plurality of circumferential sipes 48 in a block 34 for enhancing the performance on ice. Denoting by s and d respectively the length of the side 48 in the circumferential direction of a tire and the distance between the circumferential sipes 48, the following relationship is to be satisfied: 0.5<=s/d<=2.5. Thus, the rigidity of the slender region 49 between the circumferential sipes 48 can be sufficiently secured, and the occurrence of crack from the end of the sipe can be restrained by preventing the breakage of the block.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire capable of improving performance on ice without causing a chip in a block, and more particularly to a truck and a bus, a light truck, a light truck, a construction vehicle, an industrial vehicle, and the like. A pneumatic tire suitable for being mounted on a heavy-duty vehicle.

[0002]

2. Description of the Related Art Conventionally, a circumferential sipe is formed in a block of a pneumatic tire, and a water film generated between the tire and a road surface during braking on ice is discharged by the circumferential sipe to shorten a braking distance. An intended pneumatic tire has been proposed (for example, Japanese Patent Application Laid-Open No. 5-330318).

[0003]

There is a method of increasing the number of circumferential sipes in order to improve the performance on ice.

However, when the number of circumferential sipes is increased in order to improve the performance on ice, there is a problem that a chip is generated due to a lateral force during cornering.

The present invention has been made in consideration of the above-described circumstances, and an object of the present invention is to improve performance on ice without causing chipping of a block in a pneumatic tire having a circumferential sipe formed in a block.

[0006]

As a result of repeated experiments and studies, the inventors have found that the ratio s / d between the tire circumferential length s of the circumferential sipe and the distance d between the circumferential sipe is within a certain range. It was found that by setting, the performance on ice could be improved without causing block chipping.

[0007] The invention described in claim 1 has been made in view of the above fact, and is a pneumatic tire having a block in a tread divided by a circumferential groove and a width groove. At least two or more circumferential sipes extending along the circumferential direction of the tire, one end of which is open in the width-directional groove and the other end of which is terminated in the block, are formed. Is s and the interval between the circumferential sipes is d, 0.5 ≦ s /
It is characterized by satisfying d ≦ 2.5.

In the pneumatic tire according to the first aspect, since a plurality of circumferential sipes extending along the tire circumferential direction are formed in the block, these circumferential sipes are formed between the tire and the road surface. Since the film is discharged, high performance on ice is obtained.

When a plurality of circumferential sipes are provided in the block, if the ratio s / d between the tire circumferential length s of the circumferential sipes and the interval d between the circumferential sipes is not appropriate, the blocks are sandwiched by the circumferential sipes. The rigidity of the slender area is no longer ensured, and a crack is generated from the other end of the circumferential sipe (the part that terminates in the block). This crack is connected to the crack in the adjacent circumferential sipe, resulting in a chipped block. Evolve.

In the present invention, the ratio s / d between the tire circumferential length s of the circumferential sipe and the interval d between the circumferential sipe is set to 0.5 ≦ s / d ≦ 2.5. The rigidity of the elongated region sandwiched between the sipe ends is sufficiently ensured, and the occurrence of cracks from the ends of the sipe can be suppressed to prevent the chipping of the block.

Here, if the ratio s / d is less than 0.5, the length s in the circumferential direction of the tire in the circumferential direction sipe becomes short, and high ice performance cannot be obtained.

On the other hand, if the ratio s / d exceeds 2.5, the tire circumferential dimension of the elongated region becomes too long, the rigidity against lateral force is reduced, and the chip is likely to be chipped.

The ratio s / d is set to 1.0 ≦ s / d ≦ 2.
More preferably, 0 is set. The invention according to claim 2 is
The pneumatic tire according to claim 1, wherein a pair of widthwise sipes extending along a tire width direction having both ends opened in the circumferential groove are formed in a central portion in the tire circumferential direction of the block, A narrow region in which the length in the tire circumferential direction is shorter than the wide region on both sides in the tire circumferential direction of the pair of width sipe is formed between the pair of width sipe, and the circumferential sipe is formed in the wide region. Has been characterized.

[0014] In the pneumatic tire according to the second aspect, the narrow region has a shorter length in the tire circumferential direction than the wide regions arranged on both sides in the tire circumferential direction. The rigidity in the circumferential direction decreases. For this reason, when the block receives a frictional force in the tangential direction of the outer periphery of the tire (for example, during driving or braking), the narrow region having a small rigidity in the circumferential direction of the tire has a wider deformation (falling) in the circumferential direction of the tire. Larger than the area, so that one of the pair of widthwise sipes is closed and the other is opened, and the edge effect of the narrow area is reliably obtained, thereby improving the braking performance and the driving performance.

According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, the other end of the circumferential sipe has a dimension in a groove width direction larger than a portion other than the other end. It is characterized by having an enlarged portion.

In the pneumatic tire according to the third aspect, the enlarged portion provided at the other end of the circumferential sipe has a larger dimension in the groove width direction than the portion other than the other end, that is, a larger volume. The amount of water discharged between the road surface and tires can be increased,
The performance on ice can be further improved.

Furthermore, since the enlarged portion can reduce the concentration of stress at the other end of the circumferential sipe, the effect of preventing the occurrence of cracks at the other end can be obtained. This improves the effect of preventing block chipping. The shape of the enlarged portion is preferably circular.

According to a fourth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects, the dimension of the block in the tire circumferential direction is L, and the dimension of the block in the tire width direction is W. 15mm ≦ L ≦ 40m
m, 20 mm ≦ W ≦ 40 mm.

In the pneumatic tire according to the fourth aspect, since the circumferential dimension L of the block is set to 15 mm ≦ L ≦ 40 mm, the effect of preventing the chipping of the block can be reliably obtained, and the effective ice and snow performance can be obtained. Is obtained.

It should be noted that the tire circumferential dimension L of the block is 1
If it is less than 5 mm, the block rigidity in the tire circumferential direction is insufficient,
Blocking is likely to occur due to input along the tire circumferential direction at the time of driving, braking, or the like.

On the other hand, when the circumferential dimension L of the block is 4
If it exceeds 0 mm, the number of blocks arranged in the circumferential direction of the tread tire decreases. For this reason, the ground plane (footprint)
The total amount of edge components extending in the tire width direction of the block in the inside decreases, and effective ice and snow performance cannot be obtained.

The dimension W in the tire width direction of the block is 2
If it is less than 0 mm, the contact pressure per unit area of the block increases because the contact area of the block becomes too small,
Heel and toe wear is likely to occur.

On the other hand, the dimension W of the block in the tire width direction is 4
If it exceeds 0 mm, the number of blocks arranged in the tire width direction of the tread decreases. For this reason, the ground plane (footprint)
The total amount of edge components extending in the tire circumferential direction of the block in the inside decreases, and cornering performance on ice deteriorates.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS.

The pneumatic tire 10 according to the present embodiment is
This is a general radial tire having a cord angle of approximately 90 ° with respect to the tire circumferential direction, and illustration and description of the internal structure are omitted.

As shown in FIG. 1, the pneumatic tire 1
0 tread 12, a circumferential groove 14, a circumferential groove 16, a circumferential groove 1 extending along the tire circumferential direction (the direction of arrow A).
8, the circumferential groove 20, the circumferential groove 22, the width groove 24, the width groove 26, and the width groove 2 extending along the tire width direction.
8, the width direction groove 30 and the width direction groove 32 are formed, and these are used for the block 34, the block 36, the block 38,
A shoulder block 40 and a rib 42 are defined.

The rib 42 has a constant width, and is formed with a vent ridge 44 extending along the tire width direction and the circumferential direction.

Since the blocks 34, 36 and 38 have substantially the same structure, the block 3
4 will be described with reference to FIG.

The circumferential dimension L (average value) of the block 34 is preferably 15 mm ≦ L ≦ 40 mm.

The dimension W of the block 34 in the tire width direction is
(Average value) is preferably 20 mm ≦ W ≦ 40 mm.

The block 34 is provided with a pair of parallel lateral sipes 46 extending substantially along the tire width direction at substantially the center in the tire circumferential direction.

The longitudinal ends of these lateral sipes 46 are connected to the circumferential grooves 14 and 16, respectively.
The block 34 is formed by the pair of lateral sipes 46.
Are divided into three regions in the tire circumferential direction.

The area sandwiched between the pair of lateral sipes 46 is a narrow area 34A, and the area on both sides in the tire circumferential direction of the narrow area 34A is wider than the narrow area 34A in the tire circumferential direction. The area 34B is set.

Here, the tire circumferential average length TS of the narrow region 34A and the tire circumferential average length T of the wide region 34B are shown.
It is preferable that the relationship with L is 0.1 ≦ TS / TL ≦ 0.8.

The width of the narrow region 34A in the tire width direction is preferably 50 to 90% of the width of the wide region 34B.

Thus, a side force is applied to the wide area 34B, and the load of the narrow area 34A is reduced, thereby preventing a crack which is likely to be generated near the widthwise end of the bottom of the lateral sipe 46 by the side force input. be able to.

In the wide area 34B, three circumferential sipes 48 extending in the tire circumferential direction are formed.
One end of the circumferential sipe 48 is connected to the width direction groove 24, and the other end is terminated shortly before reaching the lateral sipe 46. In the present embodiment, at the other end of the circumferential sipe 48, a circular hole-shaped enlarged portion 48A whose dimension in the groove width direction is larger than the groove width dimension of the circumferential sipe 48 is formed.

The block 34 of this embodiment has a tire circumferential dimension L (average value) of 35 mm and a tire width dimension W
(Average value) is 25 mm.

The average length T of the narrow region 34A in the tire circumferential direction.
The ratio TS / TL of S to the tire circumferential average length TL of the wide area 34B is 0.23.

The size of the narrow region 34A in the tire width direction is 85% of the size of the wide region 34B in the tire width direction.

The depth of the width direction sipe 46 is 50 to 100% of the depth of the main groove (circumferential groove and width direction groove). In this embodiment, the depth of the main groove is 20 mm and the width direction sipe is The depth of 46 is 11 mm.

The depth of the circumferential sipe 48 is 30 to 100% of the depth of the main groove (the circumferential groove and the width direction groove). In the present embodiment, the depth of the circumferential sipe 48 is 11 mm.

Next, the operation of this embodiment will be described. As shown in FIG. 3, at the time of driving or braking, the block 34 of the pneumatic tire 10 which is in contact with the road surface 50 is deformed by a frictional force F in a tangential direction of the tire outer periphery. Narrow area 34A
Is shorter in the tire circumferential direction than the wide region 34B, the narrow region 34A has lower rigidity in the tire circumferential direction than the wide region 34B, and the narrow region 34A is deformed in the wide region 34B.
B is larger than B.

Therefore, the block 34 receiving the frictional force F
Now, one of the two lateral sipes 46 is closed,
The other is open and the edge effect of the opened lateral sipe 46 is greater than when only one lateral sipe is inserted. Further, since the plurality of circumferential sipes 48 provided in the block 34 discharge a water film generated between the pneumatic tire 10 and the road surface 50 in the tire circumferential direction, high on-ice performance is obtained. In the present embodiment, since the enlarged portion 48A is provided at the other end of the circumferential sipe 48, the amount of water film generated between the pneumatic tire 10 and the road surface 50 can be increased, and the enlarged portion 48A The performance on ice can be further improved with respect to those not provided with.

In the pneumatic tire 10 of the present embodiment, the ratio s / d of the tire circumferential length s of the circumferential sipe 48 to the interval d between the circumferential sipe is 0.5 ≦ s / d ≦.
Since 2.5 is satisfied, the rigidity of the elongated region 49 sandwiched between the circumferential sipe 48 and the circumferential sipe 48 is sufficiently ensured, and the distortion of the circumferential sipe 48 at the other end in the block can be suppressed. Can be. For this reason, crack generation from the other end inside the block of the circumferential sipe 48 can be suppressed, and the chipping of the block can be prevented. Further, an enlarged portion 48A is provided at the other end in the block of the circumferential sipe 48, and the enlarged portion 48A relieves stress concentration at the other end in the block of the circumferential sipe 48. It is even higher.

In the above embodiment, the enlarged portion 48A is formed at the other end of the circumferential sipe 48 formed in the block 34. However, in some cases, the enlarged portion 48A is formed as shown in FIG. You don't have to.

In the above embodiment, the number of the horizontal sipes 46 formed in the block 34 is two, but depending on the case, it may be one as shown in FIG. 5, or may be three or more. . Further, the circumferential sipe 48 may have a zigzag shape or a waveform.

Further, the tread of the narrow region 34A is changed to the wide region 3
It may be set lower than the tread surface of 4B. by this,
The tread of the narrow area 34A and the tread of the wide areas 34B on both sides are different in distance from the center of rotation of the tire. Moreover, since the narrow area 34A has a smaller ground contact area than the wide area 34B, the narrow area 34A slips on the road surface when the tire rotates. Therefore, the narrow region 34
A, wear progresses faster than the wide areas 34B on both sides,
When the wear of the block 34 progresses, the wide areas 34 on both sides
Projection from the tread surface of B is prevented.

That is, the narrow region 34A does not protrude from the wide regions 34B on both sides, and the ground pressure of the wide region 34B does not decrease, so that the edge effect can be maintained until the end of wear.

In the present invention, the blocks 34,
The shapes of the 36, 38 and the shoulder block 40 are not limited to the shapes shown in FIG. (Test Example 1) A plurality of tires (three circumferential sipes were formed on a block) having different ratios s / d between the tire circumferential length s of the circumferential sipes and the spacing d between the circumferential sipes were prototyped. Then, the occurrence rate of chipping of the blocks was examined.

In the test, the prototype tire was mounted on a vehicle having a loading load of 10 tons, and the vehicle was made to perform a steady circular turn (speed: 20 km / h) with a radius of 30 meters on an asphalt road surface, and the ratio of blocks having chips was examined. It was determined by the following equation (1). Chipping occurrence rate (%) = (number of chipping occurrence blocks / total number of blocks) × 100 (1) Note that the test results are as shown in the graph of FIG. It can be seen that it is preferable to set the ratio s / d to the distance d between the circumferential sipes to 2.5 or less in order to prevent block chipping. (Test Example 2) One kind of conventional tire, three kinds of tires of the example, and three kinds of tires of the comparative example were prepared, and the performance on ice and the occurrence rate of chipping of blocks were compared.

Next, the test method will be described. Performance on ice: tires mounted on a vehicle with a loading capacity of 10 tons,
The braking distance on ice (ice temperature -2 ° C) was measured in a loaded state. The result shows that the reciprocal of the braking distance of the conventional tire is 10
The index is 0, and the larger the value, the better the performance on ice.

Block chipping occurrence rate: Same as in Test Example 1 above. Next, the test tire will be described.

Example 1 This is a pneumatic tire described in the above embodiment in which three circumferential sipes are formed in a block (see FIG. 1).

Example 2 This is a pneumatic tire in which four circumferential sipes are formed in a block. Example 3: A pneumatic tire in which five circumferential sipes are formed in a block.

Conventional example: A pneumatic tire in which one circumferential sipe is formed in a block. Comparative Example 1: A pneumatic tire having five circumferential sipes formed on a block.

Comparative Example 2: A pneumatic tire having three circumferential sipes formed on a block. Comparative Example 3: A pneumatic tire having five circumferential sipes formed on a block.

Each tire has a tire size (11).
R22.5) and the block shape (dimension) are the same,
The number of circumferential sipes, the tire circumferential length s of the circumferential sipes, and the tire width direction dimension d of the elongated region are different from each other as shown in Table 1 below.

[0059]

[Table 1]

It is apparent from the test results in Table 1 that the tires of Examples 1 to 3 to which the present invention is applied are improved in on-ice performance while preventing chipping of blocks.

[0061]

As described above, the pneumatic tire according to the first aspect has the above-mentioned structure, and therefore has an excellent effect that the chip on the block can be prevented and the performance on ice can be improved. .

Since the pneumatic tire according to the second aspect has the above-described structure, the edge effect in the narrow region can be reliably obtained, and thus the pneumatic tire has an excellent effect that the braking performance and the driving performance can be improved.

Since the pneumatic tire according to the third aspect has the above configuration, the performance on ice can be further improved.
Further, the effect of preventing the block from being chipped can be further enhanced.

Further, since the pneumatic tire according to the fourth aspect has the above-described structure, the effect of preventing block chipping can be reliably obtained, and effective ice and snow performance can be obtained.
It has an excellent effect.

[Brief description of the drawings]

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

FIG. 2 is an enlarged plan view of a block.

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

FIG. 4 is a plan view of a block according to another embodiment.

FIG. 5 is a plan view of a block according to still another embodiment.

FIG. 6 is a graph showing a relationship between a ratio s / d and a chipping occurrence rate of a block.

[Explanation of symbols]

 Reference Signs List 10 pneumatic tire 12 tread 14 circumferential groove 16 circumferential groove 18 circumferential groove 20 circumferential groove 22 circumferential groove 24 width groove 26 width groove 28 width groove 30 width groove 34 block 34A narrow area 34B wide Area 36 Block 37 Block 46 Width Sipe 48 Circumferential Sipe 48A Enlarged Part

Claims (4)

[Claims] 1. A pneumatic tire having a block in a tread divided by a circumferential groove and a width direction groove, wherein the block has one end opening in the width direction groove and the other end ending in the block. At least two or more circumferential sipes extending along the circumferential direction of the tire are formed. When the length of the circumferential sipes in the tire circumferential direction is s and the interval between the circumferential sipes is d, 0. 5 ≦ s / d ≦
A pneumatic tire, satisfying 2.5. 2. A pair of widthwise sipes extending along the tire widthwise direction, both ends of which are opened in the circumferential groove, are formed at a central portion in the tire circumferential direction of the block,
A narrow region in which the circumferential length of the tire is shorter than a wide region on both sides in the tire circumferential direction of the pair of width sipe is formed between the pair of width sipe, and the circumferential sipe is formed in the wide region. The pneumatic tire according to claim 1, wherein the pneumatic tire is formed. 3. An end portion of the circumferential sipe has an enlarged portion whose dimension in a groove width direction is larger than a portion other than the other end. The pneumatic tire as described. 4. A tire circumferential dimension of the block is L,
When the width of the block in the tire width direction is W, 1
4. The pneumatic tire according to claim 1, wherein 5 mm ≦ L ≦ 40 mm and 20 mm ≦ W ≦ 40 mm are satisfied. 5.