JPH09315109A - Pneumatic studless tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure the control stability in of running on a general road without sacrifycing the running performance of studless tire on an icy road. SOLUTION: This tire is provided with a bead core 1, a carcass ply 2 made of a radial cord layer, a belt 3 made of one or more cord layer arranged at the outside of a crown part in the radial direction, and a tread rubber layer 4 arranged at the outside in the radial direction. The tread rubber layer is formed of an outer rubber layer 41 arranged outside in the radial direction and an inner rubber layer 42 arranged inside in the radial direction, both having different rubber characteristics. The hardness Hd, complex mudulus of elasticity E' and tangent of loss angle tanδ of the inner rubber layer 42 are respectively 140-170, 250-420 and 270-350 when the hardness Hd, complex mudulus of elasticity E' and tangent of loss angle tanδ of the outer rubber layer 41 are 100 respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly to a bead core provided on a pair of left and right bead portions and a bead core extending from a crown portion to both bead portions through both side portions. A carcass consisting of a radial cord layer wound around a core and moored at the bead portion.
Air for a passenger vehicle including a ply, a belt made of one or more cord layers arranged radially outside the crown portion of the carcass ply, and a tread rubber layer arranged radially outside the belt. Studless tires.

[0002]

The most important performance required for a studless tire is that it can safely drive without slipping when traveling on ice and snow roads. Therefore, in a studless tire, a rubber that forms a tread rubber layer is generally made of a softer compound than a tire for running on a general road so as to easily bite on a snowy road surface. Further, generally, the tread rubber layer of a studless tire is provided with a large number of sipes for the same purpose. As a result, the rigidity of the tread portion of a studless tire is considerably lower than that of a tire for running on ordinary roads. As a matter of course, studless tires do not only drive on ice and snow roads, but also on general roads. At such times, studless tires tended to be evaluated as having extremely poor steering stability performance for drivers familiar with tire performance for ordinary road use.

An object of the present invention is to solve the above-mentioned problems of the prior art and to secure the steering stability performance when traveling on a general road without sacrificing the performance of the studless tire on the snow and snow road surface. To provide tires.

[0004]

In order to achieve the above object, a pneumatic tire of the present invention comprises a bead core provided on a pair of left and right bead portions, and both bead portions from a crown portion through both side portions. And a carcass ply made of a radial cord layer wound around the bead core and anchored to the bead portion, and one or more cord layers disposed radially outside the crown portion of the carcass ply. (1) The tread / rubber layer, which is made of different rubber material, is arranged on the outer side in the radial direction. (2) the hardness Hd of the rubber of the outer rubber layer, the complex elastic modulus E ′ and the loss tangent of the outer rubber layer and the inner rubber layer arranged radially inward. The air having a hardness Hd of the inner rubber layer of 140 to 170, a complex elastic modulus E ′ of 250 to 420, and a loss tangent tan δ of 270 to 350, where tan δ is 100. It is a studless tire with a core.

To achieve the above object, in the pneumatic studless tire of the present invention, the foaming rate of the inner rubber layer is 0 to 10 when the foaming rate of the rubber of the outer rubber layer is 100. Or, in the cross section including the tire rotation axis, the level of the boundary surface between the outer rubber layer and the inner rubber layer is the same as the level of the platform provided in the groove provided in the tread rubber layer. It is preferable.

[0006] It is difficult to obtain a rubber compound that satisfies both the studless tire's safe running performance on ice and snow roads and the steering stability performance on ordinary roads. A soft compound for studless tires was adopted with an emphasis on safe driving performance, and as a result, the steering stability performance on ordinary roads tended to be sacrificed. In the pneumatic tire of the present invention, as described above, the tread / rubber layer is made of different rubber materials, and is formed by the outer rubber layer arranged on the outer side in the radial direction and the inner rubber layer arranged on the inner side in the radial direction. When the hardness Hd of the outer rubber layer, the complex elastic modulus E ′, and the loss tangent tan δ are 100, the hardness Hd of the rubber of the inner rubber layer is 140 to 170 and the complex elastic modulus E ′ is 250.
To 420, the loss tangent tan δ is 270 to 350, and preferably the foaming rate of the inner rubber layer is 0 to 10 when the foaming rate of the rubber of the outer rubber layer is 100, and in the cross section including the tire rotation axis. The level of the boundary surface between the outer rubber layer and the inner rubber layer is the same as the level of the platform provided in the groove provided in the tread rubber layer. In other words, in the pneumatic tire of the present invention,
Studless only on the parts that are involved in the snow and ice road surface performance.
It means that the tire compound is used. As a result, it is possible to obtain a tire having high rigidity in the tread portion and ensuring steering stability performance when traveling on a general road.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a tire according to an embodiment of the present invention and a conventional tire will be described with reference to the drawings. All tire sizes are 225/55 R1
It is 6.

A tire according to an embodiment of the present invention shown in FIG. 1 has a bead core 1 provided at a pair of left and right bead portions.
And a carcass ply 2 consisting of two radial cord layers extending from the crown part to both bead parts through both side parts, wound around a bead core 1 and moored to the bead part, and a carcass ply. A belt 3 composed of four cord layers arranged radially outward of the crown portion of No. 2
And a tread / rubber layer 4 arranged radially outside the belt 3. The tread rubber layer 4 is made up of an outer rubber layer 41, which is made of different rubber materials, and which is arranged on the outer side in the radial direction and an inner rubber layer 42, which is arranged on the inner side in the radial direction. When the hardness Hd of the rubber of the outer rubber layer 41, the complex elastic modulus E ′, the loss tangent tan δ, and the foaming ratio of the rubber are respectively 100, the hardness Hd of the rubber of the inner rubber layer 42 is 164, the complex elastic modulus E Is 402, the loss tangent tan δ is 286, and the foaming rate of the rubber is 0. In the cross section including the tire rotation axis,
Level L of the boundary surface between the outer rubber layer 41 and the inner rubber layer 42
1 is the same as the level L2 of the platform P provided in the groove G provided in the tread rubber layer 4.

In the pneumatic tire of the conventional example, the tread / rubber layer 4 is formed of a single rubber layer, and the rubber layer has a rubber hardness Hd, a complex elastic modulus E ', a loss tangent tan δ, and a foamed rubber. Example 1 above except that the value of the modulus is the same as the hardness Hd of the outer rubber layer 41, the complex elastic modulus E ′, the loss tangent tan δ, and the foaming rate of the rubber.
It is almost the same as the pneumatic tire of.

For the pneumatic tires of the examples according to the present invention and the pneumatic tires of the conventional examples described above, a comparative test was carried out on the safe running performance on ice and snow roads and the steering stability performance when running on a general road. The test conditions were such that a test tire mounted on a regular rim 7J-16 and filled with a regular internal pressure of 2.5 kg / cm ² was mounted on a vehicle and traveled on a test course. The test result is a feeling evaluation by the test driver. The evaluation result is displayed with a maximum score of 10, and the larger the evaluation score is, the better the performance is.

As a result of the test of the safe running performance on ice and snowy roads, the tires of the examples according to the present invention and the tires of the conventional examples were both 6.5. According to the test result of the steering stability performance on the general road, the tire of the example according to the present invention was 6.0, and the tire of the conventional example was 5.0.

[0012]

From the above evaluation results, the pneumatic tires of the examples based on the present invention have the same safe driving performance on ice and snow roads as the pneumatic tires of the conventional examples, and the steering stability performance on general roads is excellent. It turns out that it is relatively excellent.

[Brief description of drawings]

FIG. 1 is a meridional section schematic view of a pneumatic tire according to the present invention.

[Explanation of symbols]

1 bead core 2 carcass ply 3 belt 4 tread rubber layer 41 outer rubber layer 42 inner rubber layer G groove provided in tread rubber layer L1 level of boundary surface between outer rubber layer 41 and inner rubber layer 42 L2 platform level P platform

Claims (3)

[Claims] 1. A bead core provided on a pair of left and right bead parts, and a radial extending from the crown part to both bead parts through both side parts, wound around the bead core and moored to the bead part. A carcass ply composed of a cord layer, a belt composed of one or more cord layers arranged radially outside the crown portion of the carcass ply, and a tread rubber layer arranged radially outside the belt. (1) The tread / rubber layer is formed of an outer rubber layer disposed on the outer side in the radial direction and an inner rubber layer disposed on the inner side in the radial direction, which are made of different rubber materials. (2) When the hardness Hd of the outer rubber layer, the complex elastic modulus E ′, and the loss tangent tan δ are 100, the hardness H of the rubber of the inner rubber layer is d is 140 to 170, complex elastic modulus E ′ is 250 to 420, and loss tangent tan δ is 27.
Pneumatic studless tire characterized by 0 to 350. 2. The pneumatic studless tire according to claim 1, wherein the foaming rate of the inner rubber layer is 0 to 10 when the foaming rate of the rubber of the outer rubber layer is 100. 3. In the cross section including the tire rotation axis, the level of the boundary surface between the outer rubber layer and the inner rubber layer is the same as the level of the platform provided in the groove provided in the tread rubber layer. Claim 1 characterized by the above.
The pneumatic studless tire according to 1 to 2.