JP2018203201A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire which combines belt durability with vehicle motion performance.SOLUTION: A pneumatic tire 1 comprises a carcass layer 3, a first belt layer 7 which is provided in a tire radial direction-outside of the carcass layer 3, and a second belt layer 8 which is provided in a tire radial direction-outside of the first belt layer 7. An end of the first belt layer 7 is folded to the second belt layer 8 side, and wraps an end of the second belt layer 8. A cord of the first belt layer 7 is inclined to a left upper side with respect to a tire rotation direction, and a cord of the second belt layer 8 is inclined to a right upper side with respect to the tire rotation direction when the pneumatic tire 1 is mounted to a left wheel. Inclination directions of the cords of the first belt layer 7 and the second belt layer 8 are inverted when the pneumatic tire 1 is mounted to a right wheel. The cord of the first belt layer 7 is coated with a rubber material. The coating rubber material shows a modulus of elasticity of 9.0 MPa to 16.0 MPa when given a frequency of 15 Hz and a distortion of 1%.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire.

  Conventionally, a belt having a fold belt structure is known as a belt provided in a pneumatic tire (for example, Patent Document 1 and Patent Document 2). The fold belt structure is a structure in which a tire radius inner belt layer is folded and a tire radius outer belt layer is included. According to such a fold belt structure, the end of the tire radius outer belt layer is suppressed by the tire radius inner belt layer, and the belt durability is improved. In order to make this belt durability act reliably, it is necessary to suppress the diameter growth of the tire radius inner belt layer. Therefore, the tire described in Patent Document 1 increases the belt durability by setting the inclination angle of the cord of the tire radius inner belt layer to a high angle with respect to the tire width direction.

  By the way, when traction is applied to the tire, the tire radius inner belt layer and the tire radius outer belt layer are shear-deformed into a substantially parallelogram shape in a plane. At this time, when the cord of the tire radius inner belt layer is formed in the short diagonal direction of the parallelogram, compression deformation occurs. When the tire radius inner belt layer is formed at a high angle with respect to the tire width direction, cords are formed in the short diagonal direction of the parallelogram, and compression deformation occurs at the end of the tire radius inner belt layer. In such a case, the cord may break due to fatigue due to compressive deformation, or the rubber covering the cord may peel off.

  Therefore, when the tire described in Patent Document 2 is mounted on the left wheel, the cord of the tire radius inner belt layer is inclined upward to the tire rotation direction, and the cord of the tire radius outer belt layer is left Tilt up. Moreover, when the tire described in Patent Document 2 is attached to the right wheel, the inclination direction is reversed. As described above, the tire described in Patent Document 2 specifies the tire mounting direction and the inclination direction of the tire radius inner belt layer, and suppresses the amount of compressive deformation input to the tire radius inner belt layer.

JP 2006-315523 A Patent No. 5519233

  However, in the inclination direction of the belt layer described in Patent Document 2, the lateral force (cornering force) generated in the tire is reduced, which may impair the vehicle movement performance. In this regard, Patent Document 2 describes that if the inclination direction of the belt layer is reversed, vehicle motion performance is improved. However, if the belt inclination direction is reversed, the belt durability is lowered. Thus, belt durability and vehicle motion performance are a trade-off, and a belt structure that achieves both belt durability and vehicle motion performance has been desired.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a pneumatic tire in which both belt durability and vehicle motion performance in a fold belt structure are compatible.

  A pneumatic tire according to the present invention includes a carcass layer, a first belt layer provided on the outer side in the tire radial direction of the carcass layer, and a second belt layer provided on the outer side in the tire radial direction of the first belt layer. . The pneumatic tire has a fold belt structure in which the end portion of the first belt layer is folded back to the second belt layer side and wraps around the end portion of the second belt layer. When a pneumatic tire is attached to the left wheel, the cord of the first belt layer is inclined upward to the left with respect to the tire rotation direction, and the cord of the second belt layer is inclined upward to the right with respect to the tire rotation direction. . When a pneumatic tire is attached to the right wheel, the cord of the first belt layer is inclined upward to the right with respect to the tire rotation direction, and the cord of the second belt layer is inclined upward to the left with respect to the tire rotation direction. To do. The cord of the first belt layer is covered with a rubber material. The elastic modulus when applying a frequency of 15 Hz and a strain of 1% to the coated rubber is 9.0 MPa to 16.0 MPa.

  According to the present invention, both belt durability and vehicle motion performance are compatible.

FIG. 1 is a cross-sectional view in the tire width direction along the tire radial direction of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a plan view showing a belt structure when the pneumatic tire according to the embodiment of the present invention is attached to the left wheel of the vehicle. FIG. 3 is a plan view showing a belt structure when the pneumatic tire according to the embodiment of the present invention is attached to the right wheel of the vehicle.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, the same portions are denoted by the same reference numerals, and description thereof is omitted.

  With reference to FIG. 1, the structure of the pneumatic tire 1 which concerns on this embodiment is demonstrated. As shown in FIG. 1, the pneumatic tire 1 includes a pair of bead portions 2, a carcass layer 3 that forms a skeleton of the pneumatic tire 1, and a tread portion 4 that has a ground contact surface in contact with a road surface.

  The bead part 2 has a bead core 2a and a bead filler 2b. The carcass layer 3 extends in a toroidal shape between the bead cores 2a.

  At least two bead cores 2a are spaced apart in the tire width direction. The bead core 2a is formed by winding a single bead wire 5 a plurality of times in an annular shape. The bead core 2 a supports the cord tension of the carcass layer 3 generated by the internal pressure of the pneumatic tire 1.

  The bead filler 2b is a rubber material for reinforcing the bead core 2a, and is disposed in a space formed by folding both end portions of the carcass layer 3 outward in the tire width direction at the position of the bead core 2a.

  The carcass layer 3 is formed by two carcass plies 3a and 3b. The carcass plies 3a and 3b have a plurality of cords (for example, organic fiber cords and metal cords), and these cords are covered with a rubber material. A steel cord is provided between the carcass ply 3a and the carcass ply 3b.

  A belt layer 6 is formed between the carcass layer 3 and the tread portion 4. A plurality of belt layers 6 are formed so as to overlap along the tire circumferential direction. The belt layer 6 includes a first belt layer 7, a second belt layer 8, and a belt protective layer 9. The first belt layer 7 is provided on the outer side in the tire radial direction of the carcass layer 3. The second belt layer 8 is provided on the outer side in the tire radial direction of the first belt layer 7. The belt end portion 7 b of the first belt layer 7 is folded back toward the second belt layer 8 and wraps around the end portion of the second belt layer 8. Thus, the belt layer 6 of this embodiment uses a fold belt structure. When the belt end portion 7b presses the end portion of the second belt layer 8, deformation of the second belt layer 8 to the outer side in the tire radial direction is suppressed, and durability of the pneumatic tire 1 is improved. The belt protective layer 9 is formed so as to cover the belt end portion 7b.

  The first belt layer 7, the second belt layer 8, and the belt protective layer 9 have a plurality of cords. These cords are formed of organic fibers such as aramid, polyethylene, and nylon. These cords may be formed of glass fiber or steel fiber. The cord of the belt protective layer 9 is preferably formed so as to be parallel to the tire equator line CL. Thereby, the protrusion deformation of the pneumatic tire 1 when a centrifugal force acts on the pneumatic tire 1 is reduced, and it is possible to prevent uneven wear and excessive heat generation from an imbalance of the ground pressure.

  Next, the details of the belt layer 6 will be described with reference to FIG. In FIG. 2, an arrow C indicates the tire rotation direction. The tire rotation direction is one of the tire circumferential directions, and is the direction in which the tire rotates when the vehicle moves forward.

As shown in FIG. 2, when the pneumatic tire 1 is mounted on the left wheel of the vehicle, the cord 7a of the first belt layer 7 is inclined upward to the left with respect to the tire rotation direction. Further, the cord 8a of the second belt layer 8 is inclined upward to the right with respect to the tire rotation direction. Thus, the cord 7a and the cord 8a are formed so as to cross each other. The inclination angle θ ₁ of the cord 7a with respect to the tire equator line CL is preferably 15 degrees to 55 degrees. The inclination angle theta ₂ with respect to the tire equator line CL code 8a is preferably 45 degrees from 15 degrees. In addition, the inclination angle θ ₁ of the cord 7a with respect to the tire equator line CL is preferably smaller than the inclination angle θ ₂ of the cord 8a with respect to the tire equator line CL. In other words, the inclination angle of the cord 7a with respect to the tire width direction is preferably larger than the inclination angle of the cord 8a with respect to the tire width direction.

  The cord 7a and the cord 8a are covered with a rubber material. The rubber material is not particularly limited, but is natural rubber, for example. A rubber material is impregnated between the cords 7a and 7a. A rubber material is also impregnated between the cord 8a and the cord 8a.

As shown in FIG. 3, when the pneumatic tire 1 is mounted on the right wheel of the vehicle, the cord 7a of the first belt layer 7 is inclined upward to the tire rotation direction. Further, the cord 8a of the second belt layer 8 is inclined upward to the left with respect to the tire rotation direction. That is, when the pneumatic tire 1 according to this embodiment is mounted on a vehicle, the inclination directions of the cord 7a and the cord 8a are reversed between the left wheel and the right wheel. The inclination angle theta ₂ of the inclination angle theta ₁ and codes 8a code 7a shown in FIG. 3, because it is merely the inverse of the angle shown in FIG. 2, the description thereof is omitted.

[Example]
Examples of the present invention will be described in detail using Tables 1 and 2 below. Tables 1 and 2 are collectively referred to as a table below.

Tires having the basic structure shown in FIG. 1 and having different elastic moduli of the coated rubber were made on the basis of the specifications in the table. Only in the tire of Comparative Example 2, the inclination direction is reversed. The cord 7a was coated with a rubber material, and the elastic modulus of the coated rubber was measured using a spectrometer at room temperature under a dynamic strain of 1% and a frequency of 15 Hz. A belt fatigue endurance test and a tire axial force test were performed on the left wheel of each tire. The common specifications for each tire are as follows.
Size: 245 / 45R17
Inclination angle of the cord 7a with respect to the tire equator line CL: 25 degrees Inclination angle of the cord 8a with respect to the tire equator line CL: 25 degrees Material of the cord 7a: aramid fiber Material of the cord 8a: aramid fiber Rim size: 9J
Internal pressure: 180 kPa
Load: 5kN

[Belt fatigue test]
In the tire drum tester, a slip angle of 0 degree, a camber angle of 2 degrees (assuming an actual vehicle negative camber), and a driving force of 3 kN were loaded on each tire. Thereafter, the inner cord in the tire width direction of the belt end portion 7b corresponding to the inner side of the actual vehicle was dissected and taken out, and the rate of decrease in cord strength from the time of a new article was evaluated. The results are shown as an index with the decrease rate of Comparative Example 1 as 100. The numbers in the table indicate that the smaller the performance, the higher the performance. The cord strength is the tensile strength per cord.

[Tire axial force test]
In the tire flat belt testing machine, the camber angle is 2 degrees (assuming an actual vehicle negative camber), the slip angle is swept from 0 degrees to the actual vehicle right turn direction, and the lateral force change rate generated according to the slip angle change is calculated. evaluated. The results are shown as indexes with the lateral force change rate of Comparative Example 1 as 100. The numbers in the table indicate that the higher the performance, the higher the performance.

  As shown in the above table, the rate of decrease in cord strength of the tire of Comparative Example 2 is improved as compared with the tire of Comparative Example 1. This is because by reversing the inclination directions of the cord 7a and the cord 8a, a tensile force is applied to the cord 7a on the inner side of the vehicle at the time of traction so that the cord 7a and the cord 8a are hardly affected by the compressive strain. Thus, if the inclination direction is reversed, the tire durability is improved. However, as shown in the table, in the tire of Comparative Example 2, the lateral force change rate is lowered, and the steering stability is lowered.

  As shown in each example, when the elastic modulus of the covering rubber is increased, the rate of decrease in cord strength and the rate of change in lateral force are improved as compared with the tire of Comparative Example 1. This is because by increasing the coating rubber elastic modulus, the in-plane rigidity of the first belt layer 7 is increased, and the compression deformation of the cord 7a that is weak against compression deformation can be suppressed. Thereby, the durability of the belt layer 6 is improved. Further, since the deformation of the tread rubber that generates the tire axial force is increased by suppressing the deformation amount of the belt layer 6, the tire axial force is improved. Thereby, vehicle motion performance is also improved. In particular, when the elastic modulus of the covering rubber is increased to 13.0 as in Example 4, the cord strength lowering effect is exceeded as compared with the tire of Comparative Example 2. By increasing the elastic modulus of the covering rubber in this way, the tires of the respective examples have a cord strength higher than that of the tire of the comparative example 2 in which the inclination direction is reversed even in the same inclination direction as the tire of the comparative example 1. Can be improved, and both belt durability and vehicle motion performance can be achieved.

  As shown in the tire of Comparative Example 3, when the coated rubber elastic modulus is increased to 17.0 MPa, the cord strength reduction rate and the lateral force change rate are not improved as compared with the tire of Example 4. This is because as the rigidity of the covering rubber increases, the ground contact area decreases and the steering stability deteriorates.

[Action / Effect]
As described above, in this embodiment, the elastic modulus of the covering rubber that covers the cord 7a of the first belt layer 7 is increased. The elastic modulus when a frequency of 15 Hz and a strain of 1% are applied to the coated rubber is preferably 9.0 MPa to 16.0 MPa. Thereby, the in-plane rigidity of the 1st belt layer 7 increases, the compression deformation of the code | cord | chord 7a weak to a compression deformation can be suppressed, and the durability of the belt layer 6 improves. Further, by suppressing the deformation amount of the belt layer 6, the shear deformation of the tread rubber that generates the tire axial force increases, the tire axial force is improved, and the vehicle motion performance is also improved. Thus, the pneumatic tire 1 according to the present embodiment can achieve both belt durability and vehicle motion performance.

In the embodiment, the inclination angle θ ₁ of the cord 7a with respect to the tire equator line CL and the inclination angle θ ₂ of the cord 8a with respect to the tire equator line CL have been described as 25 degrees, but are not limited thereto. The inclination angle θ ₁ may be 15 degrees to 55 degrees, and the inclination angle θ ₂ may be 15 degrees to 45 degrees. In addition, the inclination angle θ ₁ is preferably smaller than the inclination angle θ ₂ . As a result, the lateral force change rate is improved and the steering stability is improved. Further, the diameter growth can be suppressed by bringing the cord 7a and the cord 8a closer to the tire circumferential direction. The elastic modulus of the covering rubber of the cord 7a is preferably larger than the elastic modulus of the covering rubber of the cord 8a.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Bead part 2a Bead core 2b Bead filler 3 Carcass layer 3a, 3b Carcass ply 4 Tread part 5 Bead wire 6 Belt layer 7 1st belt layer 7a Cord 7b Belt end 8 Second belt layer 8a Cord 9 Belt protective layer

Claims (5)

The carcass layer,
A first belt layer provided on the outer side in the tire radial direction of the carcass layer;
A second belt layer provided on the outer side in the tire radial direction of the first belt layer, and an end portion of the first belt layer is folded back to the second belt layer side, and an end portion of the second belt layer Is a pneumatic tire that uses a fold belt structure
When the pneumatic tire is attached to the left wheel, the cord of the first belt layer is inclined leftward with respect to the tire rotation direction, and the cord of the second belt layer is right with respect to the tire rotation direction. Tilted up,
When the pneumatic tire is attached to a right wheel, the cord of the first belt layer is inclined upward to the tire rotation direction, and the cord of the second belt layer is inclined with respect to the tire rotation direction. Tilt to the left,
The cord of the first belt layer is covered with a rubber material,
A pneumatic tire characterized by having an elastic modulus of 9.0 MPa to 16.0 MPa when a frequency of 15 Hz and a strain of 1% are applied to the coated rubber. The cord of the first belt layer is formed of organic fibers,
The rubber material is impregnated between the cords of the first belt layer,
The pneumatic tire according to claim 1, wherein an inclination angle of the cord of the first belt layer with respect to the tire equator line is 15 degrees to 55 degrees. The cord of the second belt layer is formed of organic fiber or steel fiber,
The pneumatic tire according to claim 1 or 2, wherein an inclination angle of the cord of the second belt layer with respect to the tire equator line is 15 degrees to 45 degrees. The inclination direction of the cord of the first belt layer and the inclination direction of the cord of the second belt layer intersect,
The inclination angle of the cord of the first belt layer with respect to the tire equator line is smaller than the inclination angle of the cord of the second belt layer with respect to the tire equator line. Pneumatic tire. The carcass layer is formed from two carcass plies,
The pneumatic tire according to claim 1, wherein a steel cord is provided between the carcass plies.

Images