JP2008044530A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of improving the problem of partial wear which cannot be coped with by a design change. <P>SOLUTION: In the pneumatic tire having at least two grooves 1 continuous in the circumferential direction in a tread T and having ribs or a block train continuous in the tire circumferential direction, each rib or block train is formed by using at least two kinds of rubber, and rubber 2 having high rupture strength on the outer side 4 and rubber 3 having low rupture strength on the inner side 5 of the tire axial direction of each rib and block train are arranged. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire.

  Conventionally, there has been a problem that uneven wear in the tire axial direction occurs when the vehicle travels violently such as on a circuit.

  In particular, in a pneumatic tire having at least two circumferentially continuous grooves in the tread portion and having ribs or block rows that are continuous in the tire circumferential direction, the rib or block row There is a problem in that the wear amount differs between the left and right ends of the block, and each rib or block row wears in a sawtooth-like uneven wear state.

  This problem has been addressed by changing the groove wall angle, changing the profile pattern and design, etc., but the actual situation is that it has not been fully improved.

In addition, for the purpose of improving uneven wear resistance, hydroplaning resistance, wet handling stability, etc., two or more rubber compositions having different blends by blending a fluorine-based additive on one side, Although it has been proposed to be arranged in a central region or a region sandwiching the central region (see Patent Documents 1 and 2), uneven wear that occurs in each rib or block row, which is problematic in the present invention, is proposed. It could not be improved.
Japanese Patent Laid-Open No. 11-78413 JP-A-11-78415

  An object of the present invention is to provide a pneumatic tire capable of improving the problem of uneven wear that cannot be dealt with by design changes in view of the above-described points.

The pneumatic tire of the present invention that achieves the above-described object has the following configuration (1).
(1) In a pneumatic tire having at least two circumferentially continuous grooves in a tread portion and having ribs or block rows that are continuous in the tire circumferential direction, each rib or block row has at least two types. A pneumatic tire characterized by comprising rubber and having a high breaking strength on the outside in the tire axial direction of each rib / block row and a rubber having a low breaking strength on the inside.

  In addition, in the pneumatic tire of the present invention, more specifically, preferably, the pneumatic tire has any one of the following configurations (2) to (4).

(2) The distance from the outer end position of each rib block block to the boundary surface in the width direction of the rubber having a high breaking strength disposed outside in the tire axial direction and the rubber having a low breaking strength disposed inside, The pneumatic tire according to (1) above, wherein the pneumatic tire is located at a position of 5 to 70% when the total length of each rib block is 100.

(3) In each rib / block row, the difference between the breaking strengths of the rubber having a high breaking strength arranged on the outer side in the tire axial direction and the rubber having a low breaking strength arranged on the inner side is 3% or more. (2) The pneumatic tire according to the description.

(4) In each rib block block, the rubber disposed at the outermost side in the tire axial direction has a 20 ° C. hardness of 43 to 85, the rubber disposed at the innermost side has a 20 ° C. hardness of 40 to 82, and The pneumatic according to any one of (1) to (3) above, wherein the rubber disposed at the innermost side has a 20 ° C. hardness of 3 to 20 lower than that of the rubber disposed at the outermost side. tire.

  According to the first aspect of the present invention, there is provided a pneumatic tire that can improve the problem of uneven wear that cannot be dealt with by design changes.

Hereinafter, the pneumatic tire of the present invention will be described in more detail.
FIG. 1 is a meridional section of a tread portion showing an embodiment of a pneumatic tire according to the present invention.

  As shown in FIG. 1, the pneumatic tire of the present invention has at least two circumferentially continuous grooves 1 in the tread portion T, and a rib or block row (hereinafter, referred to as “circumferential tire circumferential direction”). In these pneumatic tires, each rib or block row is formed by using at least two kinds of rubber, and each rib / block row is A rubber 2 having a high breaking strength is arranged on the outer side 4 in the tire axial direction, and a rubber 3 having a low breaking strength is arranged on the inner side 5.

  In FIG. 1, 6 is a tire ground contact width, 7 is a tread central portion, 8 is a carcass, 9 is a belt layer, and 10 is a belt cover layer.

  In the pneumatic tire of the present invention, the rubber 2 having a high breaking strength is arranged on the outer side in the tire axial direction of each rib / block row, and the rubber 3 having a low breaking strength is arranged on the inner side 5. The mounting position for the right wheel or for the left wheel is determined separately.

  The pneumatic tire of the present invention can satisfactorily suppress the occurrence of sawtooth uneven wear in the tire width direction by using at least two kinds of rubbers having different breaking strengths. .

  In the pneumatic tire of the present invention, more specifically, preferably, from the outer end position of each rib block row, a rubber having a high breaking strength disposed outside in the tire axial direction and a breaking strength disposed inside. The distance to the boundary surface in the width direction of the low rubber is at a position of 5 to 70% when the total length of each of the rib blocks is 100. Unbalanced wear can be prevented in a well-balanced manner. More preferably, the position is 30 to 60%.

  In each rib / block row, the difference between the breaking strength (breaking strength X) of the rubber having high breaking strength arranged on the outer side in the tire axial direction and the breaking strength (breaking strength Y) of the rubber having low breaking strength arranged on the inner side is more According to the various findings of the present inventors, it is preferable that there is a difference of 3% or more in that the effects of the present invention are remarkably exhibited.

The 3% is a difference value obtained by the following formula. The upper limit of the difference value is preferably 50%.
Difference value of breaking strength (%) = {(XY) / Y} × 100

  Preferably, in each rib block row, the rubber disposed at the outermost side in the tire axial direction has a 20 ° C. hardness of 43 to 85, and the rubber disposed at the innermost side has a 20 ° C. hardness of 40 to 82. In addition, the 20 ° C. hardness of the rubber arranged on the innermost side is 3 to 20 lower than the 20 ° C. hardness of the rubber arranged on the outermost side. In particular, with this configuration, the hardness of the outer rubber having a high breaking strength is higher than that of the inner rubber having a low breaking strength, so that the cornering power can be increased, and as a result, the steering angle can be reduced. Thus, the slip angle can be reduced and the occurrence of uneven wear can be suppressed. If the hardness difference is less than 3, the effect is not so remarkable, and if the hardness difference exceeds 20, it is not preferable because peeling easily occurs from the boundary surface between the two rubbers.

  FIG. 2 is a meridional section of a tread portion showing another embodiment of the pneumatic tire according to the present invention. In particular, the boundary between the adjacent rib block block row is located at the bottom position of the groove 1. Further, the combination boundary surface of the rubber 2 having a high breaking strength and the rubber 3 having a low breaking strength in the rib / block row is configured to be inclined in the tire width direction. When configured in this way, the boundary area is large and the two rubbers are less likely to be peeled off, and the effect of preventing the occurrence of uneven wear due to the use of two or more types of rubber is well balanced in the entire region in the tire width direction. It can be demonstrated.

  In the pneumatic tire of the present invention, the production of rubber having different values of breaking strength is not particularly limited, but the type of oil added to the rubber in the kneading process may be appropriately changed, or carbon It can be manufactured with good control by appropriately changing the grade and type of black.

  Furthermore, rubbers having different hardness values can be manufactured with good control by appropriately changing the mixing conditions, kneading conditions, kneading method, and the like.

  In order to manufacture the pneumatic tire according to the present invention, in the tread manufacturing process, two or more kinds of rubbers having different breaking strengths, more preferably different hardnesses, are extruded in parallel in each rib / block row unit. It can be manufactured by molding the entire tread.

  In the present invention, it is important to use a combination of rubbers having different breaking strengths and rubbers having different hardnesses at 20 ° C. The absolute value of the breaking strength of each rubber and the absolute value of the hardness at 20 ° C. Although not necessarily limited, in each rib block block, the breaking strength of the rubber used on the outside is preferably 15 to 25 MPa, more preferably 18 to 23 MPa, and the breaking strength of the rubber used on the inside is preferably 10 -20 MPa, more preferably 13-18 MPa.

  Hereinafter, specific examples and effects of the pneumatic tire of the present invention will be described with reference to examples. Each parameter is based on the following measurement method.

(1) Rubber breaking strength:
JIS K6251 vulcanized rubber and thermoplastic rubber-determined by the method of determining tensile properties.

(2) Rubber hardness:
It was obtained by the hardness test method of JIS K6253 vulcanized rubber and thermoplastic rubber, and the hardness of the rubber at 20 ° C. was obtained.

(3) Evaluation of uneven wear amount:
After a predetermined run, the left and right ends of the land portion of the rib block were measured with calipers, and the difference in the amount of wear was measured.

  The evaluation was carried out as a relative evaluation with the reference tire as 100, and it was judged that 105% or more had an effect, assuming that a larger score was better (small difference).

Examples 1-6, Conventional Example 1, Comparative Examples 1-3
A total of 10 types of pneumatic tires of Examples 1 to 6, the conventional example 1, and the comparative examples 1 to 3 of the present invention having the tread cross-sectional shape as shown in FIG. 1 and the specifications as shown in Table 1. (Tire size 245 / 35ZR20) was manufactured.

  The division position shown in Table 1 means the distance from the outer end position of each rib block to the boundary surface between the rubber having high breaking strength and the rubber having low breaking strength in the width direction of the rib block. It is a value expressed as a percentage when the length is 100, and the tread central portion indicates a region of ½ of the tire ground contact width with the tire center line at the center, and the tread end portions indicate the tread central portion. It points out the area | region of both outer sides of.

  Note that the contact width refers to when the tire is filled with air pressure corresponding to the maximum load capacity in the air pressure-load capacity correspondence table stipulated in the JATMA 2006 Yearbook and a load of 80% of the maximum load capacity is applied. The grounding width (length) measured in the tire axial direction.

  Each tire is mounted after it has been mounted on an imported vehicle (displacement of 2.5 liter class) with the outer and inner sides in the tire axial direction as in the spirit of the present invention and traveled 20 times on a 3 km circuit. The difference between the left and right ends of the amount of wear was measured by measuring the left and right ends of the land portion of the rib block with calipers and evaluated.

  The evaluation results are as shown in Table 1, and it can be seen that Examples 1 to 6 of the present invention all have excellent uneven wear resistance.

FIG. 1 is a meridional section of a tread portion showing an embodiment of the pneumatic tire of the present invention. FIG. 2 is a meridional section of a tread portion showing another embodiment of the pneumatic tire of the present invention.

Explanation of symbols

T: tread portion 1: groove 2: rubber having high breaking strength 3: rubber having low breaking strength 4: outer side in the tire axial direction 5: inner side in the tire axial direction 6: tire contact width 7: central portion of the tread 8: carcass 9: Belt layer 10: belt cover layer

Claims (4)

  In a pneumatic tire having at least two circumferentially continuous grooves in the tread portion and having ribs or block rows continuous in the tire circumferential direction, each rib or block row uses at least two types of rubber. A pneumatic tire characterized in that a rubber having a high breaking strength is arranged on the outer side in the tire axial direction of each rib / block row and a rubber having a low breaking strength is arranged on the inner side.   The distance from the outer end position of each rib block row to the boundary surface in the width direction of the rubber with high breaking strength arranged outside in the tire axial direction and the rubber with low breaking strength arranged inside is the rib. The pneumatic tire according to claim 1, wherein the pneumatic tire is located at a position of 5 to 70% when the entire length of the block is 100.   The air according to claim 1 or 2, wherein, in each rib block row, the difference between the breaking strength of a rubber having a high breaking strength arranged on the outer side in the tire axial direction and a rubber having a low breaking strength arranged on the inner side is 3% or more. Enter tire.   In each rib block row, the 20 ° C. hardness of the rubber arranged at the outermost side in the tire axial direction is 43 to 85, the 20 ° C. hardness of the rubber arranged at the innermost side is 40 to 82, and The pneumatic tire according to any one of claims 1 to 3, wherein the 20 ° C hardness of the arranged rubber is 3 to 20 lower than the 20 ° C hardness of the rubber arranged on the outermost side.

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