JPH04110211A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To raise the frictional force on an icesnow road, in a studless tire, by distributing non-metal short fibers of specified means diameter and mean length and orienting its longitudinal direction along the surface of blocks, and satisfying the specific relation between the dynamic Young's modulus on the surface and that in the central portion of blocks. CONSTITUTION:An extrusion molding process is carried out in such a way that non-metal short fibers, for example, natural fiber like cotton fiber having 1mum or more mean diameter and 100mum or more means length, are distributed within tread rubber, and the longitudinal direction of the short fibers is oriented along the surface of blocks 16 in the tread portion. And further, the dynamic Young's modulus E1 on the surface of a block 16 and the dynamic Young's modulus E2 in the central portion of the block 16, are determined so as to satisfy the relations 1.03<=E1<E2 and 3MPa<=E2<=20MPa.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention - reduces the frictional force (
This product relates to studless pneumatic tires with improved braking and driving performance.

[Conventional technology]

Conventionally, there has been a proposal for an automobile tire whose performance on ice is improved by uniformly dispersing short metal fibers in the tread rubber (Japanese Patent Application Laid-open No. 34206/1983). However, since the rubber hardness of this automobile tire was relatively high, the effect of improving friction on ice was insufficient. In addition, short metal fibers scatter as tires wear out, causing pollution and becoming a major environmental problem.On the other hand, the tread rubber is made of closed-cell foam rubber, and the short fibers are distributed randomly around the closed-cell foam. There is a proposal for a compounded foam rubber composition (Japanese Patent Application Laid-open No. 63-895
Publication No. 47). However, since short fibers are randomly mixed in this foamed rubber composition, there is a problem in that the effect of improving friction on ice is small, even though short fibers are mixed therein.

[Problem to be solved by the invention]

The purpose of the present invention is to provide a pneumatic tire that improves frictional force (braking performance, driving performance) on icy roads, especially on ice, without impairing running performance on shipping routes (dry roads, wet roads). be.

[Means to solve the problem]

That is, the pneumatic tire of the present invention has an average diameter of 1 μm.
As described above, non-metallic short fibers with an average length of 100 μm or more are blended into the tread rubber, and the longitudinal direction of the short fibers is oriented along the surface of the block in the trend section, and the dynamic Young's modulus of the block surface is , and the dynamic Young's modulus E2 at the center of the block are expressed by the following (Equation 11 and Equation (2) 1.03
≦Ei/E! ... (113 (MPa)
)≦E2≦20 (MPa ) =·(2).

This type of tread rubber allows both block rigidity and adhesion effect to be achieved at a high level, thereby improving on-ice frictional force.

Here, the short fibers have an average diameter of less than 1 μm and an average length of 10 μm.
If it is less than 0 μm, the dispersion in the rubber will be random, making it impossible to achieve both high level of block rigidity and adhesion effect.
Not only is the ice and snow performance insufficient, but the performance on regular roads is also inadequate.

The short fibers preferably have an average length of N.

0-5000μm, more preferably 1000-3000μm
μm, and the ratio of fiber length/fiber diameter is 10 to 1000
It's better to have twice as much. The type of short fiber is not particularly limited as long as it is a non-metallic fiber, and natural fibers such as cotton and silk, and chemical fibers such as cellulose and polyamide are used.

On the other hand, the ratio of the dynamic Young's modulus of the rubber inside and outside the block is E1/
When Ez < 1.03, the short fibers cannot be oriented along the block surface, resulting in insufficient friction performance on ice.

However, from the viewpoint of ease of mixing short fibers, E t / E
It is preferable that z≦3.0. Et/EZ>
This is because it is difficult to provide an orientation of 3.0 due to the mixing process of rubber and short fibers.

Furthermore, if E2 is outside the stipulations of equation (2), it becomes difficult for the block rigidity to exhibit good performance as a tire, especially when running on general roads.

Hereinafter, a pneumatic tire according to the present invention will be explained with reference to the drawings.

FIG. 1 is an explanatory half-sectional view in the meridian direction of a pneumatic tire with improved wear on ice according to the present invention. In this figure, the pneumatic tire A of the present invention has a pair of left and right bead portions 1.
1, a pair of left and right sidewall portions 12 connected to these ped portions 11, and a tread portion 13 disposed between these sidewall portions 12. A carcass layer 14 is mounted between the pair of left and right bead portions 11, and a belt layer 15 is arranged to surround the outer periphery of the carcass layer 14 in the tread portion 13. 10 is the tread surface.

FIG. 2 is an explanatory plan view of the tread portion of the pneumatic tire shown in FIG. 1, and FIG. 3 is a cross-sectional view taken along the line --'. Second
As shown in the figure and FIG. 3, the non-metallic short fibers 17 are
The tread rubber is oriented in the tire circumferential direction E, E'' along the ground contact surface a and the side surfaces of the blocks 16 of the tread portion 13.The tread rubber is made by reducing the content of carbon blank and making the heath rubber as soft as possible. The binding effect is enhanced, and the resulting decrease in block rigidity is compensated for by orienting the short fibers 17.

The aforementioned orientation of the short fibers 17 may be performed during extrusion molding of the tread portion. That is, the short fibers 17 having a certain length/diameter ratio tend to line up in the flow direction of the rubber when blended into the rubber. Such a tendency is also observed when unvulcanized tread rubber flows along the mold due to the protrusions of the mold when the tire is vulcanized. Therefore, the short fibers 17 are oriented along the protrusions of the mold, and as a result, the short fibers 17 are oriented along the contact surface a and the side surfaces of the blocks 16 of the tire tread portion 13. However, if the short fibers 17 are too short, they will be randomly arranged in the rubber and will not be oriented. Therefore, short fibers need to have an average diameter of 1 μm or more and an average length of 100 μm or more, preferably an average length of 100 to 5000 μm,
More preferably, the length/
It is preferable that the diameter ratio is 10 to 1000. As the short fibers, for example, natural fibers such as cotton and silk, chemical fibers such as cellulose fibers, and polyamide fibers can be used. In this way, by orienting the short fibers along the ground contact surface and side surfaces of the tread block, the dynamic Young's moduli inside and outside the block are brought into the relationship of (1) and (2) described above, and thereby the tread block 16 is The circumferential stiffness of the tire can be made thicker than the tire radial stiffness. This produces an adhesion effect and improves the frictional force on ice.

Conventional examples, working examples, and comparative examples are shown below.

1. Various types of tires with a tire size of 185/70 R1385Q, whose tread portions were composed of the compounding contents (parts by weight) shown in Table 1, were prepared, and these tires (conventional example, Examples 1 to 2)
, Comparative Examples 1 to 3) were evaluated as follows. The results are shown in "Table 1".

The test vehicle used was a 1600cc FF vehicle.

4 above: The vehicle was driven on an ice floe at an initial speed of 30 @/h, and the braking distance was measured and expressed as an index with the conventional tire (conventional example) set as 100. The larger the value, the better the braking.

Driving performance on snowy roads: A pitching test was conducted at a 5% (2,9') gradient on a smooth, compacted snow road made by repeatedly braking with a passenger car, and a pitching test was performed over a 30m section using the zero starting method. Acceleration time was measured and expressed as an index compared to conventional tires. The larger the value, the better the drive performance.

( ): The feeling of each tire was scored by five test drivers using a 10-point system, and the results (average values) are shown as an index relative to conventional tires. The larger the value, the better the steering stability.

t (·): After running for 20,000 hours on a dry road surface under the conditions of design normal load and air pressure specified by JATMA, the amount of wear of each tire was expressed as an index relative to the amount of wear of conventional tires. The larger the value, the better the wear resistance.

Young (and ) (MPa): Samples were cut from the surface and inside of the tread block of each test tire in the circumferential direction (same as the tire circumferential direction) relative to the tire rotation axis, and measured using a viscoelastic spectrometer manufactured by Toyo Seiki ■. A sample with a length between chucks of 20n, a width of 5mm, and a thickness of 2mm was subjected to a frequency of 20Hz, an initial strain of 10%, a dynamic strain of ±2%,
Measurement was performed at a temperature of 0°C. The larger the value, the greater the rigidity.

(Below is the margin) Note) Book 1 short fiber lol! A: Cellulose short fiber (Santoweb D manufactured by Mitsubishi Monsando Kasei ■).

*2 Short fiber B: carbon short fiber, average length 5 μm, diameter 1 μ-0 *3 Adhesive aid: hexamethoxymethylmelamine (Regimen 3520 manufactured by Mitsubishi Monsando Kasei ■).

*4 Foaming agent: dinitrosopentamethylenetetramine (Cellular D manufactured by Eiwa Kasei Kogyo ■).

*5 Urea-based auxiliary agent: Urea compound (5 in cell paste manufactured by Eiwa Kasei Kogyo ■).

In "Table 1", the conventional example is a conventional studless tire and does not contain short fibers.

Example 1.2 is a short fiber-containing tire defined by the present invention, which can achieve both ice and snow performance and general performance.

Comparative Example 1.2 contains short fibers, but since the average length is below the standard and the short fibers are randomly arranged, the elastic modulus of the surface and center of the block are almost the same, and the ice and snow performance is not improved. However, Comparative Example 2 is foam rubber + staple fiber.

In comparison with Example 1, Comparative Example 3 is a tire that is simply made soft without blending short fibers, and has fair ice and snow performance, but - performance on sea routes is degraded.

〔Effect of the invention〕

As described above, in the present invention, non-metallic short fibers having an average diameter of 1 μm or more and an average length of 100 μm or more are blended into the tread rubber, and the longitudinal direction of the short fibers is aligned along the surface of the block in the trend section. The dynamic Young's modulus E1 of the surface of the block and the dynamic Young's modulus E2 of the center of the block are determined by the following (Equation 11 and (2) 21.03≦E1/E2... (1) 3 ( MPa
)≦E2≦20 (MPa) = - (21) is satisfied, so it is possible to significantly improve the frictional force on ice and snow roads without impairing the running performance on -ship routes (dry roads, wet roads) Furthermore, since non-metallic short fibers are used, it does not cause pollution problems.

[Brief explanation of drawings]

FIG. 1 is an explanatory half-sectional view in the meridian direction of a pneumatic tire according to the present invention, FIG. 2 is an explanatory plan view of the trend part of the pneumatic tire according to the present invention, and FIG. It is a diagram. 10...Tread surface, 11...Bead portion, 12.
・・Side wall, 13-)-Red part, 14-・・
Carcass layer, 15... Heald layer, 16... Block, 17... Short fiber.

Claims (1)

[Scope of Claims] Non-metallic short fibers having an average diameter of 1 μm or more and an average length of 100 μm or more are blended into the tread rubber, and the longitudinal direction of the short fibers is oriented along the surface of the blocks of the tread portion, The dynamic Young's modulus E_1 of the surface of the block and the dynamic Young's modulus E_2 of the center of the block are expressed by the following equations (1) and (2): 1.03≦E_1/E_2 (1) 3 [MPa] ≦E_2≦20 [MPa]... A pneumatic tire that satisfies (2).