JPH09328004A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve H/T wear resistance without losing on-snow traveling performance by providing an uneven wear preventing land part opened in a siping for its one side and having an auxiliary siping extended in a direction intersecting this siping and having a specified length. SOLUTION: The land part 4 of a tread surface is composed of a block 5 with vertical and horizontal grooves 2 and 3. A plurality of sipings 6 extended in a tire axial direction are formed in the block 5, and for the block 5, an uneven wear preventing block 5a having an auxiliary siping 7 opened in the siping 6 for its one end, extended in a direction intersecting the same and having a length of 1 to 3mm is provided. Thus, when a braking force is applied, the deformation easily occurs in the surface parts of small book pieces 8 formed by the siping 6, a grounding pressure distribution is made uniform and thereby H/T wear resistance is improved without losing on-snow traveling performance. Further, preferably, the auxiliary siping 7 is formed to have a width of 0.2 to 0.7mm.

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 uneven wear resistance while maintaining running performance on WET, ice roads and the like.

[0002]

2. Description of the Related Art Conventionally, in order to improve running performance on wet roads, snowy roads, etc., a block pattern in which blocks are separated from each other on a tread surface is preferably used. Further, each block is generally parallel to the tire axial direction. It is common for multiple extending sipes to be formed. These sipings increase the coefficient of friction of the block and improve the running performance on the ice and snow road.

In addition, a studless tire developed as a winter tire has sufficient flexibility even at low temperatures in order to further improve running performance on a frozen road while ensuring sufficient snow road performance based on a block pattern or the like. A soft tread rubber that can be held is used.

[0004]

However, in a pneumatic tire having siping provided on the land portion such as a block as described above, although the running performance on a snow and ice road can be improved, the braking force and the driving force acting on the tire can be improved. The contact pressure distribution on the surface of the block b is likely to be non-uniform due to force, etc., resulting in so-called heel and toe wear (hereinafter referred to as H / T wear), resulting in poor uneven wear resistance. There is a problem.

Such H / T wear is considered to be caused by the braking force that frequently acts, and especially occurs in tires used for taxis in which braking is repeated. Further, the occurrence of H / T wear is remarkable even in a studless tire having a relatively soft tread rubber. Such H / T wear remarkably deteriorates running performance on icy roads and snowy roads, and also impairs the appearance of the tire appearance.

Generally, when the braking force F acts on the tire, as shown in FIG. 5 (a), the first contact portion c of the block b is first grounded to be compressed and deformed, but the rear contact portion d of the block b is grounded. After that, since the traveling speed inside the tire becomes slower than the road surface speed, the shearing force F in the block instantaneously acts on the first portion c of the block, and particularly the first portion c of the block tends to rise.

When the block b is provided with the siping e, the first-arrival side of each of the small block pieces b1 to b4 divided by the siping e also tends to float up from the road surface. Thereby, each of the small block pieces b1 to b4
It is considered that the grounding pressure of the rear landing portion increases and, due to the slippage that occurs when the vehicle comes off the road surface in that state, a large amount of wear energy acts and H / T wear as shown in FIG. 5B occurs. .

In order to suppress the H / T wear by keeping the ground pressure on the surface of the block constant, it is conceivable to eliminate the siping or decrease the depth of the siping. There is a problem that the road performance is greatly deteriorated.

The present invention has been devised in view of the above problems, and in addition to the conventional siping, an auxiliary siping of a small length which has one end open to the siping and extends in a direction intersecting with the siping is provided. The object of the present invention is to provide a pneumatic tire which is basically formed to improve the H / T wear resistance without impairing the running performance on snow and ice and can solve the above problems.

[0010]

[Means for Solving the Problems] Claim 1 of the present invention
The invention described is a pneumatic tire having a land portion in which the tread portion has a siping extending substantially parallel to the tire axial direction, wherein the land portion has one end open to the siping and intersects with the siping. The length that extends in the direction is 1
A pneumatic tire including an uneven wear preventing land portion having an auxiliary siping of up to 3 mm.

The siping is defined as "substantially parallel to the tire axial direction" as including the siping formed at an angle of ± 15 degrees or less with respect to the tire axial direction.

According to the second aspect of the invention, the siping width of the auxiliary siping is 0.2 to 0.5 mm,
Moreover, the intersection angle θ with the main siping is 45 to 90.
It is characterized by being °.

Further, the invention according to claim 3 is characterized in that the land portion is a block spaced in the tire circumferential direction.

As described above, according to the present invention, in addition to the conventional siping, one end of the siping is opened to the siping and a small length of the auxiliary siping extending in a direction intersecting with the siping is formed, whereby the ground contact pressure of the land portion is formed. Since the distribution can be made close to uniform, the H / T wear resistance can be improved without impairing the running performance on wet roads and ice and snow roads.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the pneumatic tire of the present invention has a vertical groove 2 extending in the tire circumferential direction, and the vertical groove 2
An example is shown in which the land portion 4 of the tread surface is constituted by blocks 5 which are spaced apart in the tire circumferential direction by the lateral groove 3 extending in the direction intersecting with.

In this example, the block 5 has a substantially rhombic shape, and as shown in FIGS. 1 and 2, a plurality of sipes 6 extending in the tire axial direction are formed. Also,
One end of the block 5 is open to the siping 6, and the length extending in a direction intersecting with the siping 6 is 1 to 3 mm.
Uneven wear prevention block 5a having auxiliary siping 7
In this embodiment, all the blocks 5 are configured by the uneven wear prevention block 5a.

Each of the vertical groove 2 and the horizontal groove 3 extends in a straight line shape and includes various shapes other than those shown in the drawing, such as a wavy or zigzag bent shape. The groove width measured on the tread surface when filled with the normal internal pressure is preferably 6 to 20 mm, and the groove depth is preferably 8 to 20 mm.

The siping 6 formed on the block 5
Has a groove width of 1.0 mm or less, preferably 0.3 to
1.0 mm, groove depth sh (shown in FIG. 2) is 0.4 to 1.0 times the height H of the block 5, preferably 0.5 to
It is desirable to set 0.8 times. In addition, siping 6
It is preferable to provide a plurality of blocks per block, and in this example, three blocks are provided. Then, the siping 6 needs to be substantially parallel to the tire axial direction in order to enhance the snow biting effect and the like by the edge effect, and particularly to improve the running performance on the icy and snowy road.

In the present specification, the siping 6 being “substantially parallel” to the tire axial direction is defined as including the siping 6 arranged at an angle of ± 15 degrees or less with respect to the tire axial direction.

Further, in this example, the siping 6 is a semi-open type whose one end terminates inside the block 5 as shown in FIGS. 1 and 2, and the ends of the siping 6 are alternately arranged in the axial direction of the tire. However, the present invention is not limited to this. For example, siping 6 has blocks 5 at both ends.
A full open type that reaches the end of the block 5 and a closed type in which both ends end together inside the block 5 can be appropriately adopted.

When the siping 6 is a semi-open or closed type, the length SL of the siping 6 (see FIG. 2).
Is preferably 0.5 times or more of W of the block width.

Next, the auxiliary siping 7 is formed such that one end thereof is opened to the siping 6 and the length L (shown in FIG. 2) extending in a direction intersecting with the siping 6 is 1 to 3 mm. In this example, one end terminates inside the block.

When one end of the auxiliary siping 7 does not open to the siping 6, and when the length L of the auxiliary siping 7 is less than 1 mm, the ground pressure of each block segment divided by the siping 6 is constant. However, it is difficult to suppress H / T wear sufficiently.

The length L of the auxiliary siping 7 is 3
If it exceeds mm, the rigidity of the block 5 is deteriorated, the cornering performance is deteriorated, and the block surface is liable to be chipped with rubber or the like, and the effect of keeping the ground contact pressure at a constant level is not reached.

As described above, by providing the uneven wear prevention block 5a having the auxiliary siping 7 in addition to the siping 6, the small block piece 8 which is divided by the siping 7 even when the braking force is applied. , 8 ... are easily deformed, and as a result, the ground pressure distribution of each small block piece 8 can be made even close to each other.
The H / T wear resistance can be improved without impairing the running performance on the snowy road.

The auxiliary siping 7 has a siping width of 0.2 to 0.7 mm, more preferably 0.2 to 0.7 mm.
It is preferably 0.5 mm. This siping width is 0.
If it exceeds 5 mm, the effect of equalizing the ground contact pressure on the block surface tends to decrease. The siping width is 0.
If the thickness is less than 2 mm, the processing becomes difficult and the productivity is poor. The auxiliary siping 7 can be appropriately formed by molding at the same time as vulcanizing the tire with a mold or by cutting the vulcanized tire with a tool.

The auxiliary siping 7 preferably has an intersection angle θ (shown in FIG. 2) with the siping 6 of 45 to 90 °, which is about 90 ° in this example. If the intersecting angle θ is less than 45 °, a sharp portion is generated between the siping 6 and the auxiliary siping 7, which tends to cause the rubber chipping of the block, which is not preferable.

The depth of the auxiliary siping 7 can be set variously, but is preferably set to 1.0 mm or more, and the upper limit can be set to the maximum groove depth of the vertical groove 2 or the horizontal groove 3. Preferably, the depth of the auxiliary siping 7 is 50% to 100% of the maximum groove depth.

Further, it is desirable to provide a plurality of auxiliary sipings 7 (2 to 3 in this example) for one of the sipings 6. In this example, the auxiliary sipings on the first-arrival side extending toward the first-arrival side of the block 5 are provided. 7a and a rear arrival side auxiliary siping 7b that is adjacent to the first arrival side auxiliary siping 7a and extends toward the rear arrival side of the block 5 are illustrated.

When a plurality of auxiliary sipings 7 are provided on one siping 6, the distance between the auxiliary sipings is 5 mm.
It is desirable to keep a distance. In addition, in this example, in each block 5, the first-side and the second-side auxiliary sipings 7a and 7b are arranged in the tire circumferential direction.

This example is preferable in that there is no great difference in block rigidity between the first-arriving side and the last-arriving side of the block 5 and the contact pressure on the surface of the block can be further equalized.

FIG. 3 shows an uneven wear prevention block 5 of the present invention.
7a shows another embodiment of a. In FIG. 3 (A), the sipe 6 exemplifies a semi-open type in which a wavy shape extends in the tire axial direction and both are open at one block edge. Also in this example, the auxiliary siping 7 is
The first arrival side auxiliary siping 7a and the last arrival side auxiliary siping 7b are illustrated, and these are alternately arranged in one siping 6.

In this example, the auxiliary siping 7 is
An example is shown in which the wavy siping 6 is arranged at approximately the apex position P of the amplitude and is arranged so as to extend inward of the amplitude. By arranging the siping 6 and the auxiliary siping 7 as described above, the ground pressure can be made uniform without lowering the rigidity of the block, the H / T wear can be suppressed, and the siping length can be substantially increased. Driving performance on ice and snow can be further improved.

In FIG. 3B, the sipe 6 exemplifies a full open type in which a straight portion 6a and a wavy portion 6b are combined to extend in the tire axial direction, and both are open at both block edges. ing. The corrugated portion 6b
Alternatively, a zigzag portion or the like may be provided.

FIG. 4 shows another embodiment of the present invention,
Land portion 4 on the tread edge side does not reach vertical groove 2 Lug groove 1
A rib 9 having 0 is illustrated. The rib 9 is also formed with the siping 6 and the auxiliary siping 7 is arranged so that the rib 9
Is configured as an uneven wear prevention rib 9a.

Although the description has been centered on the tread pattern, the pneumatic tire of the present invention can be preferably used for a radial tire having a radial structure carcass and a belt layer for tightening the outside of the carcass. Further, it can be preferably used as a studless tire used for winter.

[0037]

[Example] The tire size is 195 / 65R15,
In addition, regarding the auxiliary siping of the tire having the block pattern of the configuration shown in FIG. 1, prototypes were made according to the specifications shown in Table 1 (Examples 1 to 7, comparative examples, conventional examples), and snow / ice performance and H / T wear resistance I did a test. The auxiliary sipings of Examples 1 and 2 extend from the siping toward the first-arrival side of the block.

In the test, a test tire was mounted on the front wheels of a domestically produced front-wheel drive vehicle, and the speed was 80 km / h on the test course.
In addition to running the car at a speed of 20km / h with a 0.4G brake every 1km, the process was repeated until the mileage reached 3000km.

After the test, as shown in FIG. 5B, the H / T wear amount (h1 to h4 at the approximate center of the block width) of each block in an arbitrary block row was measured over the entire circumference of the tire, The average is calculated, and the average is calculated as 100
It was indicated by an index. The larger the value, the smaller the H / T wear amount and the better. Table 1 shows the test results.
Shown in

[0040]

[Table 1]

As a result of the test, it was confirmed that the tires of the examples can reduce the H / T wear in comparison with the comparative examples and the conventional examples. Then, each of the test tires was mounted on an actual vehicle and traveled on an icy road and a snowy road, respectively, but the driver's feeling could not discriminate the difference in running performance.

[0042]

The pneumatic tire of the present invention has, in addition to the siping extending in the tire axial direction, by forming the auxiliary siping of a small length which has one end open to the siping and extends in a direction intersecting with the siping. Since the contact pressure distribution on the land can be made to be close to uniform, the H / T wear resistance can be improved without impairing the running performance on snow and ice.

[Brief description of drawings]

FIG. 1 is a development view of a tread pattern showing an embodiment of the present invention.

FIG. 2 is a perspective view showing an enlarged example of the block.

3 (A) and 3 (B) are plan views of blocks showing another embodiment of the present invention.

FIG. 4 is a development view of a tread pattern showing another embodiment of the present invention.

5A and 5B are cross-sectional views illustrating a conventional technique.

[Explanation of symbols]

 2 Vertical groove 3 Horizontal groove 4 Land portion 5 Block 5a Uneven wear prevention block 6 Siping 7 Auxiliary siping 9 Rib

Claims (3)

[Claims] 1. A pneumatic tire having a tread portion having a land portion formed with siping extending substantially parallel to the tire axial direction, wherein one end of the land portion is open to the siping and intersects with the siping. A pneumatic tire comprising an uneven wear preventing land portion formed with auxiliary siping having a length extending in the direction of 1 to 3 mm. 2. The pneumatic tire according to claim 1, wherein the auxiliary siping has a siping width of 0.2 to 0.5 mm and an intersecting angle θ with the siping is 45 to 90 °. 3. The pneumatic tire according to claim 1, wherein the land portion is a block spaced in the tire circumferential direction.