JPH03182810A - Pneumatic tire for truck and bus - Google Patents

Abstract

PURPOSE:To maximize each friction coefficient on an icy surface of respective central parts and shoulder parts in tread parts in a tire with block patterns, by forming the central parts and the shoulder parts in the tread parts from rubber with different dynamic elastic modulus in a particular region respectively. CONSTITUTION:The tread patterns of a tire are formed from a large number of blocks 3 which are partitioned by plural main grooves 1 extending in a circumferential direction of the tire and plural sub-grooves 2 which cross the main grooves 1. Sipes 4 extending in a tire cross direction are disposed in the respective blocks 3 respectively. With this constitution, tread central parts are formed from a rubber component with 90-110kgf/cm<2> dynamic elastic modulus to obtain the maximum friction coefficient on an icy surface approximately 10kgf/cm<2> ground contact pressure. Tread shoulder parts are formed from a rubber component with 60-80kgf/cm<2> dynamic elastic modulus to obtain the maximum friction coefficient on an icy surface at approximately 6-7kgf/cm<2> ground contact pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pneumatic tire for trucks and buses that has improved performance on snowy and icy roads.

[Conventional technology]

Conventionally, the tread of a snow tire, which generally uses soft tread rubber, is divided into three areas: a center part and shoulder parts on both sides. A pneumatic tire for passenger cars has been proposed that is made of rubber with low hardness and exhibits excellent traction performance not only on snowy and icy roads but also on non-snowy and icy roads (Japanese Unexamined Patent Publication No. 37503/1983). ).

However, pneumatic tires for trucks and buses have a significantly larger difference in ground pressure between the center and shoulder areas when loaded than tires for passenger cars.
As with the above-mentioned passenger car tires, it has not been possible to achieve a satisfactory improvement in snow and ice road performance simply by varying the rubber hardness of the tread portion.

[Problem to be solved by the invention]

The object of the present invention is to provide a truck that can improve performance on snowy and icy roads even when the difference in ground pressure between the center part and the shoulder part of the tread part when loaded is extremely large.
Our goal is to provide bus tires.

[Means to solve the problem]

An object of the present invention is to provide a pneumatic tire having a block pattern in which blocks divided by grooves are formed on the tread surface and sipes in the width direction of the tire are formed in the blocks. While setting the elastic modulus E to 90 to 110 Kgf/cm2,
The dynamic elastic modulus of the shoulder rubber is 60 to 80K.
gf/cm”.

In the present invention, the dynamic elastic modulus E° refers to a value measured using a viscoelastic spectrometer (for example, manufactured by Harumoto Seisakusho) under conditions of a temperature of 0° C., a frequency of 20 Hz, and an amplitude of 10±2 z.

In addition, in the present invention, the center portion of the tread portion refers to
Centered on the tread center line, it refers to an area corresponding to 20% to 3oχ of the tread development width W on each side, corresponding to a total of 40χ to 60χ, and the shoulder section refers to an area of 20% to 60χ of the tread development width W at both ends of the tread. This refers to the N range corresponding to 3 oz.

FIG. 1 shows an example of the tread pattern of the truck/bus tire of the present invention.

As shown in the figure, the L/Red pattern consists of a large number of blocks 3 divided by a plurality of main grooves 1 extending in the circumferential direction of the tire and a plurality of sub grooves 2 intersecting with these main grooves 1. . Sipes 4 extending in the tire width direction are formed in each of the blocks 3.

According to research conducted by the present inventors, such trunk
The coefficient of friction on ice due to the tread of a lotus tire varies significantly depending on the dynamic elastic modulus E' of the rubber composition constituting the tread and the ground pressure. For example, the second
As shown in the figure, dynamic elastic modulus E' 50 Kgf/cm
In the case of rubber with a dynamic elastic modulus E of 70 Kgf/cm2, the coefficient of friction on ice reaches its maximum at a ground pressure of approximately 2.5 Kgf/cm2, as shown in curve A. Then, the coefficient of friction on the ice is about 6-7 Kgf as in the curved mouth.
Furthermore, for rubber with a dynamic modulus of elasticity E of 100 Kgf/cm, the friction coefficient of ice becomes maximum at a ground pressure of approximately 10 Kgf/cm, as shown in curve C. It becomes the maximum.

On the other hand, when loaded, there is a significant difference in the ground pressure of truck and bus tires between the center and shoulder areas, which is a big difference when compared to passenger-width tires. For example, a truck/lotus tire with tire size 10.00 R20 has an air pressure of 7.25 h/c- and a tire size of 7.007 R20.
Examining the ground pressure when attached to the X20 rim and applying a load of 2,700 Kgf, the average ground pressure at the center is approximately 10 Kgf/cm, while the average ground pressure at the shoulder is There is a difference of 5 to 7 Kgf/cm.

The present invention is based on the above-mentioned knowledge, and by constructing the center portion of the tread from a rubber composition having a dynamic elastic modulus of E'90 to 110 hf/cm, the elasticity of approximately 10 KBf/cm is achieved.
cm'' ground pressure to obtain the maximum coefficient of friction on ice, and the shoulder part has a dynamic elastic modulus E°60-80Kgf/
cm” of rubber composition, approximately 6 to 7 cm.
The maximum coefficient of friction on ice can be obtained with a ground pressure of Kgf/cm2. For this reason, in the tire of the present invention, when loaded, the coefficient of friction on ice between the center portion and the shoulder portion is maximized, and the frictional force of the entire tread surface is increased. Therefore, traction on ice is increased, and performance on snowy and icy roads can be significantly improved.

In the tire of the present invention, it is further preferable that the sipe, which is formed by a thin cut in the width direction of the tire, provided in the block,
It is preferable to provide them at intervals of 7 to 15 mm in the tire width direction. By arranging the sipes at such intervals, it is possible to further increase the maximum frictional force on ice of the block under the load during loading, and this can contribute to improving the snow and ice road performance of the block.

〔Example〕

Two types of rubber compositions A and B with different dynamic elastic moduli E shown in the table were prepared as tread rubbers, and the following two types of truck and bus tires were created by using these for treads. .

The size of these tires is the same 10.00
It was set to R20.

Tread pattern: Figure 1 Block size: 40mm x 50mm Sipe spacing: 12mm spacing Center part (25x of tread development width on each side around the tread center, total 502): Rubber composition Product A: Shoulder portion (25x each of the tread development width): Rubber composition B. In the tire of the present invention, the entire tread portion is coated with rubber composition A.
The tires had the same structure except that they were constructed from scratch (see the margins below on this page). The braking performance on ice of these two types of tires was evaluated according to the following procedure. As a result, the braking performance on ice of the tire of the present invention was 103 when expressed as an index based on the reciprocal of the measured value, with the measured value of the comparison tire set as 100, and it was found that the performance on icy and snowy roads was improved.

丞±Gufeng Hill Test: Braking when a 10-ton flat-body car was fitted with test tires and was driven at a speed of 20 km/hr on ice floes at -10 degrees Celsius in temperatures below -12 degrees Celsius. The distance was measured.

〔Effect of the invention〕

As explained above, according to the present invention, in a truck/bus tire having a block pattern, the center portion and the shoulder portion of the tread portion are each made of rubber having a dynamic elastic modulus E′ in a specific range different from each other. By making the dynamic elastic modulus E° of the center part larger than that of the shoulder part, the coefficient of friction on ice of the image part can be maximized even if there is a difference in ground pressure between the center part and the shoulder part during loading. This can improve performance on snowy and icy roads.

[Brief explanation of drawings]

Fig. 1 is a plan view showing an example of the tread pattern of the tire of the present invention, and Fig. 2 is a graph showing the relationship between the friction coefficient and ground pressure of rubber compositions with different dynamic elastic moduli E''.1.・・Main groove, 2・・Minor groove, 3・・Block, 4・
...Suib.

Claims (1)

[Claims] Forming blocks divided by grooves on the tread surface,
In a pneumatic tire having a block pattern in which the blocks are formed with sipes in the tire width direction, the dynamic elastic modulus E' of the rubber at the center of the tread is 90 to 110 kg.
A pneumatic tire for trucks and buses that has a dynamic elastic modulus E' of 60 to 80 Kgf/cm^2 in addition to a dynamic elastic modulus E' of the shoulder rubber.