JPH04185507A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To prevent partial wear of a tread surface, and peeling-off and cracks of treads by forming the tread from a layered body of two rubber layers, and layering both the right and left side parts, which consist of different kinds of rubber compounds, of the respective rubber layers at the tread center part. CONSTITUTION:The tread 50 of a tire is formed from two layers of rubber layers 51, 52. Besides, the left side parts 51a, 52b and the right side parts 51b, 52b, which consist of different kinds of rubber compounds whose characteristics (for example, hardness) are different, of the respective rubber layers 51, 52 are layered at the tread center part around a tire equator line O, and jointed to be ford. Moreover, at the tread center part around the tire equator line O, jointing parts 51c, 52c of the respective rubber layers 51, 52 are formed in a stepped condition so that the different type rubber compounds may be made up each other in advance. With this constitution, the tread is made into an alternately layering structure where jointing surfaces are engaged with each other for making both the upper and lower surfaces of the respective rubber layers 51, 52 flat respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pneumatic radial tire that prevents uneven wear on the tread surface and cracks in the tread.

[Conventional technology]

The tread surface is the part that receives the most wear when the tire contacts the road surface and rolls under load. When the tire is mounted on a vehicle, the force received from the road surface is different between the outside position (outside) and the inside position (inside) of the vehicle, resulting in different wear phenomena.

Conventionally, in order to prevent such uneven wear phenomenon from occurring, as shown in the cross-sectional view in the width direction of the trend part in Fig. 3,
For example, the tread T is configured by arranging a rubber Ga with a high hardness on the outside side and a rubber Gb with a low hardness on the inside side, so that the left and right portions of the tread T have different hardness in the width direction. In this case, the dissimilar rubbers Ga and Gb are joined by diagonally abutting each other at a part of the trend center near the tire equator 'hAo, thereby forming a joint A.

However, even if the tread T is constructed by arranging dissimilar rubbers Ga and Gb in this way, it is difficult to sufficiently prevent the occurrence of uneven wear, and shearing force acts on the joint A and Peeling or cranking occurs from part A,
There was a problem with it growing.

[Problem to be solved by the invention]

The present invention was made to solve the above-mentioned problems with conventional pneumatic radial tires, and it prevents uneven wear on the tread surface and also prevents peeling or cracking from the tread joint surface. The purpose of this invention is to provide a pneumatic radial tire.

[Means to solve the problem]

The pneumatic radial tire of the present invention is a tire having a tread portion made of a laminate of at least two or more rubber layers, and the tread portion has each rubber layer made of different types of rubber having different physical properties on the left and right sides of the tread center portion. Each joint surface at the joint portion is characterized by a structure in which a left side portion and a right side portion, which are previously formed in a stepped shape, are butted against each other so as to complement each other and are joined.

In this way, in the present invention, since the tread is constructed from a laminate of two or more rubber layers, it is possible to not only make the physical properties of the left side and right side parts of each rubber layer different, but also make the physical properties different between the rubber layers. Because of this, the cushioning properties of the entire tread are increased compared to the case where the tread is constructed from a single rubber layer as in the past, and the tread surface can follow the surface shape of the road surface. The growth of cracks, which is typified by uneven wear and chipping, is significantly reduced. In addition, when overlapping and joining the left side and right side parts of each rubber layer at the tread center part, each joining surface at the joint part is shaped in advance so that the left side and right side complement each other and abut. Since the bonding surfaces are bonded together, there is no unevenness at the bonded portions on any surface of each rubber layer, so stress is not concentrated at the bonded portions. No peeling or cracking occurs at the joint.

Hereinafter, the pneumatic radial tire of the present invention will be explained in detail according to the drawings.

FIG. 1 is an explanatory half-section diagram in the meridian direction showing an example of the pneumatic radial tire of the present invention, and FIG. 2 is an explanatory diagram in the meridian direction cross-section of the entire tread of the pneumatic radial tire.

In FIG. 1, a fiber cord such as a polyester cord extending in a direction intersecting the equatorial plane is used as a carcass cord, and the end of a carcass layer 1o, which is a carcass cord coated with a coating layer made of a rubber compound, is wrapped around an annular bead core 20. The tire is rolled up from the inside to the outside.

An inner liner 3o made of non-breathable rubber such as butyl rubber is arranged inside the carcass layer 10, and
Between the carcass layer 10 and the tread 5o, two belt layers 40 and 41 are disposed in the tire circumferential direction over one circumference of the tire.

The tread 50 has two rubber layers 5 as shown in FIG.
1 and 52. Each of the rubber layers 51 and 52 has a left side portion 51a, 52a and a right side portion 51b, 52b made of different rubber compounds having different physical properties (for example, hardness), which are overlapped at the tread center near the tire equator line O. It is constructed by joining together (
51 = 51 a 151b, 52 = 52 a 152
b).

The left side portions 51a and 52a represent the outer side of the tire when it is mounted on a vehicle, and are made of, for example, a harder rubber compound than the inside right side portions 51b and 52b.

In the tread center area near the tire equator line O, the joint parts 51C and 52c of the respective rubber layers 51 and 52 are formed in a step-like manner so that the different rubber compounds complement each other in advance, so that the joint surfaces are mutually The rubber layers 51 and 52 have an alternately laminated structure with no unevenness on either the upper or lower surfaces. That is, both the upper and lower surfaces of each rubber layer 51 and 52 are flat.

Although the rubber layer 51 and 52 are shown as having a two-layer structure in FIG. 2, a laminated structure of three or more layers may be used. However, in the case of a single layer, it is impossible to completely eliminate cracks from the joints between different types of rubber.
Also, depending on the hardness of the rubber on the left and right parts, uneven wear and cracks cannot be prevented.

EXAMPLES Below, the structure and effects of the pneumatic radial tire of the present invention will be further explained with reference to Examples.

〔Example〕

A pneumatic radial tire of tire size 195/60 R15 was provided with the tread structure shown in FIGS. 1 and 2 above, and this radial tire was evaluated.

That is, the tread 50 has a two-layer structure as shown in the figure, and the left side portion 51 is located on the outside side when the tire is mounted on a vehicle.
a, 52a, a rubber compound with a JIS hardness of 62.8 degrees and a 100% modulus of 143.3 kg/ail;
1b, 52b, JIS hardness 59.8 degrees, 100%
A rubber compound with a modulus of 129.6 kg/a11 is used, and a different type of rubber 51 a is used in the tread center area.
151b and joint 51c between 52a and 152b
and 52C were previously formed in a step-like manner so as to complement each other, and these were joined to form an alternately laminated structure to obtain the tire of the present invention. Note that other conditions such as the carcass layer, heald layer, and rim structure were in accordance with the prior art.

On the other hand, as tread rubber, JIS hardness is 64.8 degrees, 1
Conventional tire I was obtained by using a single rubber compound with a 00% modulus of 85.4 kg/Cll1.

Furthermore, in the trend structure shown in Figure 3, the outside Ga
JIS hardness 62.8 degrees, 100% modulus 143.
3kg/cnf rubber compound, inside Gb
JIS hardness 59.8 degrees, 100% modulus 129.
6kg/a+! A conventional tire (2) was obtained by forming a rubber compound by abutting Ga and Gb joints diagonally against each other.

These three types of radial tires were each filled with an internal pressure of 2.1 kg/crJ,
As a result of evaluating the wear status of the tread surface after running 20,000 km on a tire of the present invention (98% dry), it was found that the wear of the tire of the present invention was uniform throughout the outside and inside sides, and no tread flaking or cracking was observed. There wasn't.

On the other hand, conventional tire I had abnormally progressed wear on the outside surface. In addition, the conventional tire ■ had uneven wear in the tire circumferential direction over a width of 1 to 2 cn+ on the outside from the tread center, and in addition, peeling and cranking were observed at some joints of the trend center. .

〔Effect of the invention〕

As explained above, according to the present invention, the tread is constructed from a laminate of at least two rubber layers, and in each rubber layer, the left side portion and the right side portion, which are made of different rubber compounds having different physical properties, are arranged as a trend center. Since the treads are partially overlapped and bonded, it is possible to prevent uneven wear on the trend surface, and it is also possible to prevent the tread from peeling off or cranking.

[Brief explanation of drawings]

FIG. 1 is an explanatory half-section diagram in the meridian direction showing an example of the pneumatic radial tire of the present invention, FIG. FIG. 2 is an explanatory view of a tread section in a meridian direction of a tire. 10... carcass layer, 20... bead core, 30...
... Inner liner, 40 ... Heald layer, 41 ...
・Belt layer, 50... Tread, 51... Rubber layer,
52...Rubber layer, 51a...Left side portion, 52a...
- Left side part, 51b... Right side part, 52b... Right side part, 51C... Joint part, 52 c-joint part. Agent Patent Attorney Nobuo Ogawa −

Claims (1)

[Claims] A tire having a tread portion made of a laminate of at least two or more rubber layers, the tread portion having a structure in which each rubber layer is made of different rubbers having different physical properties bonded to each other on the left and right sides of the tread center portion, and the bonded A pneumatic radial tire characterized in that each joining surface in the section has a structure in which a left part and a right part, which are previously formed in a step shape, are butted and joined so as to complement each other.