JP2014121979A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that can reduce rolling resistance while maintaining steering stability performance.SOLUTION: A pneumatic tire T includes a belt layer 5 formed by laminating a plurality of belt plies 5a and 5b in a peripheral side of a carcass layer 4 of a tread portion 3. The belt plies 5a and 5b are formed of a belt cord 5c coated with a belt topping rubber 50. In the belt topping rubber 50, a loss tangent tan δ is within a range of 0.10 to 0.30, and a hardness in an inside region IN which is the vehicle inner side when attached to the vehicle, is set to be lower than a hardness in an outside region OUT which is the vehicle outside when attached to the vehicle.

Description

  The present invention relates to a pneumatic tire in which a belt layer formed by laminating a plurality of belt plies is disposed on the outer peripheral side of a carcass layer in a tread portion.

  Conventionally, in a pneumatic tire, improvement in steering stability performance and reduction in rolling resistance have been demanded. For the purpose of increasing the cornering power and improving the steering stability performance, the shoulder portion was reinforced with a belt or the rubber hardness was increased, but such a reinforced structure increases the weight. There is a concern about the increase in rolling resistance due to. For this reason, it has been a challenge to improve both the steering stability performance and the reduction of rolling resistance.

  Patent Document 1 below discloses a pneumatic tire that can improve the durability of the belt without lowering the steering stability performance by changing the elastic modulus of the topping rubber constituting the belt in the tire width direction. Has been.

  Patent Document 2 below discloses a pneumatic tire in which the topping rubber of the belt layer is made of rubber having a shoulder portion with a higher loss tangent than the center portion. According to this pneumatic tire, the rubber constituting the belt layer is large in the front-rear direction such as during braking by using a rubber having a loss tangent higher than that of the center portion in the shoulder portion having a large contribution of the energy loss rate. When the force acts on the tire, energy required for braking by increasing the energy loss of the shoulder portion can be effectively obtained, so that the braking performance can be improved without impairing other performance.

  However, although the pneumatic tire of Patent Document 1 can prevent a decrease in steering stability performance, no consideration is given to a reduction in rolling resistance, and there is a concern about an increase in rolling resistance. Moreover, since the pneumatic tire of patent document 2 has rubber | gum with a high loss tangent arrange | positioned at a shoulder part, there exists a tendency for rolling resistance to increase.

JP 2006-123867 A JP 2006-315501 A

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a pneumatic tire capable of reducing rolling resistance while maintaining steering stability performance.

  The above object can be achieved by the present invention as described below. That is, the pneumatic tire according to the present invention is a pneumatic tire in which a belt layer formed by laminating a plurality of belt plies is disposed on the outer peripheral side of the carcass layer of the tread portion. The belt topping rubber has a loss tangent within a range of 0.10 to 0.30, and the hardness of the in-side region that is the inside of the vehicle when the vehicle is mounted is the same as that when the vehicle is mounted. It is set lower than the hardness of the out-side region that is the outside of the vehicle.

  In general, lowering the loss tangent of rubber can reduce energy loss, which is advantageous for reducing rolling resistance. However, if the loss tangent is lowered, the hardness decreases accordingly, the cornering power decreases, and the steering stability tends to deteriorate. The belt topping rubber of the present invention has a loss tangent in the range of 0.10 to 0.30, and the hardness of the in-side region is set lower than the hardness of the out-side region, so it greatly affects the cornering power. Since the loss tangent in the entire region can be lowered while maintaining the hardness of the out-side region being high, the rolling resistance can be reduced while maintaining the steering stability performance.

  In the pneumatic tire of the present invention, it is preferable that the difference in hardness between the belt-topping rubber in the in-side region and the out-side region is 2 or more.

  Regarding the physical properties of rubber, it is known that there is a certain degree of correlation between loss tangent and hardness. For this reason, the loss tangent of the in-side region can be made sufficiently low by making the hardness of the in-side region 2 or more lower than the hardness of the out-side region, effectively reducing rolling resistance while maintaining steering stability performance. it can.

  In the pneumatic tire of the present invention, it is preferable that a difference in hardness between the belt-topping rubber in the in-side region and the out-side region is 5 or less.

  By reducing the hardness difference between the in-side region and the out-side region, the difference in loss tangent can also be reduced and the loss tangent in the entire region can be lowered, so that rolling resistance can be reduced while maintaining steering stability performance. .

  In the pneumatic tire of the present invention, a belt reinforcement layer comprising a reinforcement ply that covers at least both ends of the belt layer is disposed on the outer peripheral side of the belt layer, and the reinforcement ply covers the reinforcement cord with a reinforcement topping rubber. The reinforced topping rubber has a loss tangent in the range of 0.15 to 0.40, and the hardness of the out side region is set to be 5 or more higher than the hardness of the in side region. Is preferably characterized.

  Reinforced topping rubber has less influence on rolling resistance than belt topping rubber and has a greater influence on cornering power, so the reinforcement topping rubber is set so that the hardness of the out side region is higher than the hardness of the in side region Thus, the cornering power can be increased and the steering stability performance can be improved while suppressing an increase in rolling resistance.

Tire meridian half sectional view showing an example of the pneumatic tire of the present invention The enlarged view which shows the principal part of the pneumatic tire of this invention Sectional drawing which shows the principal part of the pneumatic tire in another embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a tire meridian sectional view schematically showing an example of a pneumatic tire according to the present invention, and CL represents a tire equator. FIG. 2 is a cross-sectional view schematically showing a belt layer and a belt reinforcing layer provided in the tire, but the codes in the drawing are conceptually described, and the actual arrangement pitch becomes denser.

  The pneumatic tire T includes a pair of bead portions 1, a sidewall portion 2 that extends from the bead portion 1 to the outer side in the tire radial direction, a tread portion 3 that is connected to each tire radial direction outer end of the sidewall portion 2, and A pneumatic radial tire for a passenger car including a toroidal carcass layer 4 provided between a pair of bead portions 1 and a belt layer 5 disposed on the outer peripheral side of the carcass layer 4.

  Each of the pair of bead portions 1 is provided with an annular bead core 1a and a bead filler 1b made of hard rubber disposed on the outer side in the tire radial direction of the bead core 1a. The carcass layer 4 is constituted by a carcass ply formed by arranging carcass cords extending in a direction substantially orthogonal to the tire circumferential direction, and both ends thereof are folded back so as to sandwich the bead core 1a and the bead filler 1b. For the carcass cord, organic fibers such as polyester, rayon, nylon, and aramid, and steel fibers are preferably used.

  The belt layer 5 is constituted by a plurality of (in this embodiment, two layers) belt plies 5a and 5b formed by arranging belt cords 5C extending obliquely with respect to the tire circumferential direction. Are stacked such that the belt cords 5C intersect in opposite directions. The belt plies 5a, 5b are formed by covering a plurality of belt cords 5C arranged in parallel with belt topping rubber from both sides. For the belt cord 5C, the above-described organic fibers can be adopted, but steel fibers are preferable for enhancing the circumferential rigidity.

  In the present invention, the belt topping rubbers of the belt plies 5a and 5b are configured as follows. The belt plies 5a and 5b have a configuration in which a plurality of belt cords 5C are embedded in a belt topping rubber 50. The belt topping rubber 50 is a belt topping rubber in an in-side region IN which is the inside of the vehicle when the vehicle is mounted. The physical properties of 51 are different from the physical properties of the belt topping rubber 52 in the out-side region OUT, which is the outside of the vehicle when the vehicle is mounted. In the present embodiment, an example in which the in-side region IN and the out-side region OUT are divided by the tire equator CL is shown.

  In the present invention, the belt topping rubbers 51 and 52 have a loss tangent tan δ within a range of 0.10 to 0.30. Further, the hardness of the belt topping rubber 51 in the in-side region IN is set to be lower than the hardness of the belt topping rubber 52 in the out-side region OUT. As a result, the loss tangent in the entire region including the in-side region IN and the out-side region OUT can be reduced while maintaining the hardness of the out-side region OUT that greatly affects the cornering power. Rolling resistance can be reduced.

  The loss tangent tan δ of the belt topping rubber 51 in the in-side region IN is preferably 0.10 to 0.25, and more preferably 0.10 to 0.20. On the other hand, the loss tangent tan δ of the belt topping rubber 52 in the out-side region OUT is preferably 0.15 to 0.30, and more preferably 0.15 to 0.25. The difference in loss tangent tan δ between the belt topping rubber 51 and the belt topping rubber 52 is preferably 0.15 or less. Accordingly, the loss tangent tan δ of the belt topping rubber 52 in the out-side region OUT can be brought close to the loss tangent tan δ of the belt-topping rubber 51 in the in-side region IN.

  The hardness of the belt topping rubber 51 in the in-side region IN is preferably 50 to 70, and more preferably 60 to 70. On the other hand, the hardness of the belt topping rubber 52 in the out-side region OUT is preferably 55 to 75, and more preferably 65 to 75. The difference in hardness between the belt topping rubber 51 and the belt topping rubber 52 is preferably 2 or more. By making the hardness of the in-side region IN 2 or more lower than the hardness of the out-side region OUT, the loss tangent tan δ of the in-side region IN can be sufficiently lowered, so that the rolling resistance is effectively maintained while maintaining the steering stability performance. Can be reduced. Further, the difference in hardness between the belt topping rubber 51 and the belt topping rubber 52 is preferably 5 or less. By setting the hardness difference between the in-side region IN and the out-side region OUT to 5 or less, the difference in loss tangent tan δ can also be reduced, and the loss tangent tan δ in the entire region including the in-side region IN and the out-side region OUT can be obtained. Since it can be lowered, rolling resistance can be reduced while maintaining steering stability performance. In addition, the rubber hardness in this invention is the value measured at 25 degreeC according to the durometer hardness test (type A) of JISK6253.

  On the outer peripheral side of the belt layer 5, a belt reinforcing layer 6 made of a reinforcing ply formed by arranging reinforcing cords extending substantially parallel to the tire circumferential direction may be provided as necessary. The belt reinforcing layer 6 is disposed so as to cover at least both end portions of the belt layer 5, and can prevent the belt layer 5 from being lifted by a centrifugal force during high-speed running, thereby improving high-speed durability.

  In the present embodiment, an example in which a cap ply 7 and an edge ply 8 are provided as reinforcing plies is shown. The cap ply 7 covers the entire width of the belt layer 5, and the edge ply 8 covers both ends of the belt layer 5 in the tire width direction.

  The reinforcing ply (the cap ply 7 and the edge ply 8) is formed by winding a belt-shaped member covered with a reinforcing topping rubber by aligning reinforcing cords and spirally wound around a forming drum. As the reinforcing cord, organic fibers such as polyester, rayon, nylon, and aramid are preferably used.

  The cap ply 7 and the edge ply 8 have a form in which a plurality of reinforcing cords 6C are embedded in a reinforcing topping rubber 60. The reinforcing topping rubber 60 reinforces the in-side region IN that is the inside of the vehicle when the vehicle is mounted. The physical properties of the topping rubber 61 are different from the physical properties of the reinforcing topping rubber 62 in the out-side region OUT which is the outside of the vehicle when the vehicle is mounted.

  In the present invention, as the reinforcing topping rubber 61 and the reinforcing topping rubber 62, those having the same physical properties as the belt topping rubber 51 and the belt topping rubber 52 may be used. However, the reinforcing topping rubbers 61 and 62 have a loss tangent tan δ in the range of 0.15 to 0.40, and the hardness of the out-side region OUT is set to be 5 or more higher than the hardness of the in-side region IN. It is preferable. By setting the hardness of the reinforced topping rubber 62 in the out-side region OUT to be 5 or more higher than the hardness of the reinforced topping rubber 61 in the in-side region IN, the cornering power is increased and the steering stability performance is suppressed while suppressing an increase in rolling resistance. Can be improved.

  The loss tangent tan δ of the reinforcing topping rubber 61 in the in-side region IN is preferably 0.15 to 0.35, and more preferably 0.15 to 0.25. On the other hand, the loss tangent tan δ of the reinforcing topping rubber 62 in the out-side region OUT is preferably 0.20 to 0.40, and more preferably 0.20 to 0.30. Further, the difference in loss tangent tan δ between the reinforced topping rubber 61 and the reinforced topping rubber 62 is preferably 0.20 or less, and more preferably 0.10 or less. As a result, the loss tangent tan δ of the reinforcing topping rubber 62 in the out-side region OUT can be brought close to the loss tangent tan δ of the reinforcing topping rubber 61 in the in-side region IN.

  The hardness of the reinforcing topping rubber 61 in the in-side region IN is preferably 60 to 80, and more preferably 70 to 80. On the other hand, the hardness of the reinforcing topping rubber 62 in the out-side region OUT is preferably 65 to 85, and more preferably 75 to 85. Further, the hardness difference between the reinforcing topping rubber 61 and the reinforcing topping rubber 62 is preferably 5 or more, and more preferably 10 or more. As a result, the cornering power can be sufficiently increased to improve the steering stability performance.

[Another embodiment]
(1) In the above-described embodiment, the in-side region IN and the out-side region OUT are separated by the tire equator CL, and the in-side region IN: out-side region OUT is set to 50:50 in the tire width direction. showed that. However, the in-side region IN: out-side region OUT is not limited to this, and can be appropriately set in the range of 40:60 to 60:40.

  (2) In the above-described embodiment, the belt reinforcing layer 6 is provided on the outer peripheral side of the belt layer 5, but the belt reinforcing layer 6 is not necessarily provided.

  (3) In the above-described embodiment, an example in which one cap ply 7 and one edge ply 8 are provided as the belt reinforcing layer 6 is shown. However, the configuration of the belt reinforcing layer 6 is not limited thereto. For example, as shown in FIG. 3, the belt reinforcing layer 6 includes (a) only one cap ply 7, (b) only two cap plies 7, or (c) two cap plies 7 and an edge ply. 8 may be composed of one sheet.

  (4) In the above-described embodiment, the cornering power is increased by setting the hardness of the reinforcing topping rubber 62 in the out-side region OUT to 5 or more higher than the hardness of the reinforcing topping rubber 61 in the in-side region IN. . As a method for increasing the cornering power, it is conceivable that the number of ends of the reinforcing cord 6C of the cap ply 7 in the out-side region OUT is larger than the number of ends of the reinforcing cord 6C of the cap ply 7 in the in-side region IN. At this time, it is preferable that the number of ends of the in-side region IN is 15 to 30, the number of ends of the out-side region OUT is 20 to 35, and the difference between the numbers of both ends is 5 or more.

  (5) In the present invention, it is possible to further improve the steering stability performance by using an asymmetric pattern tread having a plurality of main grooves.

  Examples that specifically show the structure and effects of the present invention will be described below. The size of the tire used for the evaluation is 195 / 65R15, and the tire structure and the rubber composition in each example are common except for the structure of the belt layer and the bell reinforcing layer described below. The evaluation items are as follows.

(1) Cornering power Using a drum tester having a diameter of 2500 mm, the cornering force generated in the test tire was measured, and the cornering power at a slip angle of 2 ° was determined. Index evaluation is performed with the result of Conventional Example 1 or Conventional Example 2 as 100, and the larger the value, the greater the cornering power and the better the steering stability performance.

(2) Rolling resistance coefficient The rolling resistance was measured with a rolling resistance tester to determine the rolling resistance coefficient. Index evaluation is performed with the result of Conventional Example 1 or Conventional Example 2 as 100, and the smaller the value, the lower the rolling resistance.

Conventional Example 1
A pneumatic tire in which a belt layer formed by laminating a plurality of belt plies is disposed on the outer circumferential side of the carcass layer in the tread portion, and the belt plying rubber of the belt ply has high hardness throughout the conventional example. It was set to 1. Table 1 shows the results of the above evaluation using such a pneumatic tire.

Example 1
A pneumatic tire in which a belt layer formed by laminating a plurality of belt plies is disposed on an outer peripheral side of a carcass layer in a tread portion, and a belt tangent rubber of the belt ply has a loss tangent of 0.10 to 0.00. A sample having a hardness in the range of 30 and the hardness of the in-side region set lower than the hardness of the out-side region was defined as Example 1. Table 1 shows the results of the above evaluation using such a pneumatic tire.

Comparative Example 1
In contrast to Example 1, the configuration of the belt-topping rubber in the in-side region and the out-side region was reversed as Comparative Example 1. Table 1 shows the results of the above evaluation using such a pneumatic tire.

Conventional example 2
Conventional example 2 is a cap ply provided on the outer peripheral side of the belt layer of conventional example 1, and the reinforced topping rubber of the cap ply has a high hardness throughout. Table 2 shows the results of the above evaluation using such a pneumatic tire.

Example 2
A cap ply is provided on the outer peripheral side of the belt layer of Example 1, and the reinforced topping rubber of the cap ply has a loss tangent in the range of 0.15 to 0.40, and the hardness of the out side region is in the in side region. Example 2 was set to be 5 or more higher than the hardness. Table 2 shows the results of the above evaluation using such a pneumatic tire.

Comparative Example 2
In contrast to Example 2, the configuration of the belt-topping rubber and the reinforced topping rubber in the in-side region and the out-side region was changed to Comparative Example 2. Table 2 shows the results of the above evaluation using such a pneumatic tire.

Example 3
Compared to Example 2, the reinforced topping rubber has a high hardness in the entire region, the hardness difference between the in-side region and the out-side region is increased, the tangent loss is increased in the entire region, and the tangent between the in-side region and the out-side region Example 3 in which the difference in loss was increased was designated as Example 3. Table 2 shows the results of the above evaluation using such a pneumatic tire.

Example 4
In contrast to Example 3, the number of ends of the reinforcement cord of the cap ply in the in-side region was made smaller than the number of ends of the reinforcement cord of the cap ply in the out-side region was designated as Example 4. Table 2 shows the results of the above evaluation using such a pneumatic tire.

Example 5
In contrast to Example 3, the in-side region: out-side region was set to 60:40 as Example 5. Table 2 shows the results of the above evaluation using such a pneumatic tire.

  As shown in Table 1, Example 1 was able to reduce rolling resistance while maintaining cornering power as compared with Comparative Example 1. Similarly, as shown in Table 2, Examples 2 to 5 were able to reduce rolling resistance while maintaining cornering power as compared with Comparative Example 2. Further, in Example 3, the rolling resistance was slightly increased as compared with Example 2, but the cornering power could be increased. In Example 4, the cornering power was slightly lower than that in Example 3, but the rolling resistance could be reduced by reducing the weight. In Example 5, compared with Example 3, the in-side region was wide, so the cornering power was low, but the rolling resistance could be reduced.

3 Tread part 4 Carcass layer 5 Belt layer 5a Belt ply 5b Belt ply 5C Belt cord 6 Belt reinforcing layer 6C Reinforcing cord 7 Cap ply 8 Edge ply 50 Belt topping rubber 51 Belt topping rubber in the inner side region 52 Belt topping in the outer side region Rubber 60 Reinforced topping rubber 61 Reinforced topping rubber in the in-side area 62 Reinforced topping rubber in the out-side area IN In-side area OUT Out-side area T Pneumatic tire

Claims (4)

In the pneumatic tire in which a belt layer formed by laminating a plurality of belt plies is disposed on the outer peripheral side of the carcass layer of the tread portion,
The belt ply is formed by covering a belt cord with a belt topping rubber,
The belt topping rubber has a loss tangent in the range of 0.10 to 0.30, and the hardness of the in-side region that is the inside of the vehicle when the vehicle is mounted is the hardness of the out-side region that is the outside of the vehicle when the vehicle is mounted Pneumatic tire characterized by being set lower than.   2. The pneumatic tire according to claim 1, wherein a difference in hardness of the belt topping rubber between the in-side region and the out-side region is 2 or more.   The pneumatic tire according to claim 1 or 2, wherein a difference in hardness of the belt topping rubber between the in-side region and the out-side region is 5 or less. A belt reinforcement layer made of a reinforcement ply that covers at least both ends of the belt layer is disposed on the outer peripheral side of the belt layer,
The reinforcing ply is formed by covering a reinforcing cord with a reinforcing topping rubber,
The reinforced topping rubber has a loss tangent within a range of 0.15 to 0.40, and a hardness of the out side region is set to be 5 or more higher than a hardness of the in side region. The pneumatic tire according to any one of claims 1 to 3.

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