JPH02225103A - Tire for vehicle - Google Patents

Abstract

PURPOSE:To have compatibility between a grip property and an abrasion resistance property by specifying respectively a ratio between effective ground areas in the left and right of a tread part, and a difference in respective outer diameter dimensions of the tread part and shoulder part when a prescribed maximum load is eliminated from a tire. CONSTITUTION:In a tire 10, there is a tread pattern including a plurality of grooves 12 extending in a tire circumferential direction and a plurality of grooves extending in the direction crossing therewith. And in the tread pattern, left and right parts 20, 22 in relation to a tread center 18 are formed in respective shapes different from each other. In this occasion, the ratio RT between respective effective ground areas RL and RR of left and right parts 20, 22 in the condition when a prescribed maximum load is applied on the tire 10, is set so as to satisfy 0.85<RT<0.98. In addition, a difference Dc-Ds between respective outer diameter dimensions Dc and Ds of a tread part and a shoulder part, is set so as to satisfy 4.0mm<Dc-Ds<12.0mm.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a vehicle tire in which the effective ground contact area of the left and right portions of the tread portion with respect to the tread center are different.

(Prior Art) Centrifugal force generated when a vehicle turns is applied to the portion of the tread portion that is outside with respect to the tread center when turning (hereinafter referred to as “
"The outer part." ) In particular, the area where the load acting on the shoulders of the tread is on the inside (hereinafter referred to as the "inside area").

) acts on the tire in a manner that is larger than that acting on the tire.

When the load acts on the tread as described above, the ground contact pressure and ground contact length of the outer parts become larger than those of the inner parts, so the burden of maintaining the road surface on the outer parts and the burden on the outer parts are reduced. The applied load becomes larger than that of the inner part.

As a result, so-called shoulder-drop wear occurs in the outer portions of the tread, in which the shoulder portions of the tread wear more rapidly than other portions. Also,
Because the ground pressure and ground length of the inner part are small,
The adhesion between the road surface and the road surface, that is, the grip performance is reduced.

The shoulder drop wear shortens the life of the tire and causes a decrease in steering stability when turning. In order to prevent such uneven wear, it is necessary to improve the wear resistance of the outer parts. However, in conventional tires, wear resistance and grip performance are in an antinomic relationship, and it has been difficult to improve wear resistance and grip performance without reducing the other.

For this reason, it has been proposed to periodically change the state of the mounting of the tire on the rim or the state of the mounting of the rim to the vehicle so that the tire wears uniformly. However, such recombination work requires a great deal of time, effort, and skill.

(Problems to be Solved by the Invention) An object of the present invention is to provide a vehicle tire that can improve grip performance and wear resistance of a tread portion without reducing the other.

(Solution Means, Actions, Effects) A vehicle according to the present invention, which includes a tread part having left and right parts arranged on opposite sides with respect to the tread line, and a shoulder part arranged next to the tread part. When the tire is mounted on a predetermined rim, the internal pressure of the tire is maintained at a predetermined value, and a predetermined maximum load is applied to the tire, the ratio of the effective ground contact area of the left and right parts is RT. and when the difference between the outer diameter dimension Dc of the tread portion and the outer diameter dimension Ds of the shoulder portion when the load is removed from the tire is Dc−Ds, 0.85<RT<
0.98 4.0mm<Dc-Ds<12.0mm.

In the present invention, the predetermined rim, predetermined internal pressure, and predetermined maximum load refer to the rim, the internal pressure that can be applied to the tire, the internal pressure that should be maintained, and the tire, respectively. The maximum allowable load that can be applied to a Moreover, the ratio of effective ground contact area as used in the present invention refers to the ratio of a small value of effective ground contact area to a large value of effective ground contact area. Furthermore, in the present invention, the outer diameter dimension Dc of the tread portion is 0.
1 refers to the diameter at the center of the tread when the internal pressure is applied and the load is not applied, and the outer diameter Ds of the shoulder portion is the width of the ground contact surface when the internal pressure is applied and the load is not applied. This refers to the outer diameter dimension at the position of the directional edge.

The effective ground contact area of the left and right parts of the tread with respect to the tread center is determined by installing the tire on the specified rim, filling the tire with air to maintain the internal pressure of the tire at the specified value, and applying a specified maximum load to the tire. This can be obtained by determining the area of the area on one side and the other side of the tread center that can make contact with the ground within the range of the ground contact width when applied, for each left and right portion over the entire circumference of the tire.

In addition, the ratio of effective ground contact area can be calculated by dividing the smaller value by the larger value of the effective ground contact area as described above.
Obtainable.

The tire of the present invention is mounted on a vehicle so that the side with the smaller effective ground contact area is on the inside.

As a result, the pattern rigidity of the inner portion is lowered than that of the outer portion, improving the grip of the entire tire when the vehicle turns, and preventing sudden changes in the contact shape. As a result, wear energy (kg/mm) expressed as the product of ground pressure and slip during turning becomes almost the same between the inner and outer parts.

When the ratio RT of the effective ground contact area is 0.98 or more, shoulder drop wear at the outer portion becomes large, similar to conventional tires. On the other hand, if the ratio RT of the effective ground contact area is 0.85 or less, the pattern rigidity of the inner part becomes too low F, and the inner part becomes easily deformed, so that the wear of the inner part increases.

A preferable value of the ratio RT of effective ground contact area is 0.85 mm<
RT≦0.95, more preferably 0.86 mm<RT≦0.94.

If the difference in outer diameter dimensions Dc-Ds is 12 mm or more, the ground pressure of the outer part will be significantly lower than that of the inner part, and the amount of slip will increase, so shoulder drop wear of the outer part will increase. . On the other hand, the difference in outer diameter dimensions Dc-Ds
If the distance is less than 4 mm, wear at the center of the tread will increase.

According to the tire of the present invention, by mounting the tire on a vehicle so that the part with the smaller effective ground contact area is on the inside, the grip of the inside part is improved, so the grip of the entire tire is improved. Furthermore, since the wear energy (kg/mm) during turning is approximately the same between the inner and outer parts, shoulder drop wear at the outer parts is reduced. Therefore, handling stability is improved, and there is no need to reassemble the tire onto the rim or reassemble the rim with the tire mounted on the vehicle in order to wear the tire uniformly.

Furthermore, sandwich the tire center and set the tire tire maximum width SW 4.
Radius of curvature CT of the tread within the central region within 0%
R and the ratio CTR/S of the radius of curvature STR of the tread in the outer region that is outside in the width direction from 52% of the tire maximum width SW and inside in the width direction from 72% of the tire maximum width SW
It is desirable that the tread radius index α, which is the product of TR and tire aspect ratio, is 1.3 to 1.7.

Conventionally, the shape of the tread surface has been formed with a single radius of curvature (tread radius). In this case, the ground contact pressure in the central region between the tread center and the tread shoulder (hereinafter referred to as the "intermediate region") is low, and the amount of slip increases, which tends to cause uneven wear in this region. . In particular, when the ground contact area on both sides of the tread center is different as in the present invention, and the direction in which the tire is installed on the vehicle is specified, it is necessary to change the position of the tire (because it is not possible to prevent the occurrence of JiR wear, the tendency to Therefore, the inventors solved this problem by making the radius of curvature of the tread different between the central region and the outer region.

In general, tires with a low aspect ratio tend to have a higher tendency to decrease ground pressure in this intermediate region. The inventors investigated tires with different aspect ratios and found that the CTR/STR values were 2.6 to 3.4 for tires with an aspect ratio of 50% and 2.2 to 2.4 for tires with an aspect ratio of 60%. 8. It has been found that for a tire with an aspect ratio of 65%, having an aspect ratio in the range of 1.9 to 2.6 is effective in preventing occurrence of uneven wear in the intermediate region. That is, by setting the tread radius index α to 1.3 to 1.7, a decrease in ground contact pressure and an increase in slip I in the area between the tread center and the tread shoulder are prevented, and uneven wear in this area is prevented. prevent. Here, if α is less than 1.3, this effect is difficult to produce, and if it exceeds 1 or 7, the ground pressure in the outer region decreases and uneven wear tends to occur.

(Example) The tire 10 of the present invention shown in FIGS. 1 and 2 has a plurality of grooves 12 extending in the circumferential direction of the tire, and a plurality of grooves 14 communicating with the grooves and extending in a direction intersecting the grooves. It has a tread pattern 16 including. The tread button 16 has different shapes at a left part 20 and a right part 22 with respect to the tread center 18. Therefore, the shape and arrangement of blocks 24 within site 20 and those of blocks 26 within site 22 are not the same.

The effective ground contact areas RL and RR of parts 20 and 22 are:
The effective ground contact area RL of part 20 is the effective ground contact area M of part 22.
It is larger than RR, and the effective ground contact area RR of the part 22 is
The value RR/R divided by the effective ground contact area RL of part 20
As described above, L, that is, the ratio RT is selected so that 0.85<RT<0.98.

The effective ground contact area RL and RR of the portion 20.22 are the tire 1
0 to the standard rim that should be applied to this, and tire 10
When the internal pressure of the tire 10 is maintained at a predetermined value and the maximum allowable load is applied to the tire 10, the area of the points that can make contact with the ground within the range of the contact width W is determined for each part 20.22 over the entire circumference of the tire. This can be obtained by In other words, the effective ground contact areas RL and RR of the portion 20.22 can be obtained as the sum of the areas of the portions within the ground contact width W of the blocks 24.26 existing within a range of W/2 from the tread center 18. Can be done.

Outer diameter dimension Dc of tread part and outer diameter dimension D of shoulder part
s is selected to a value such that the difference DC-Ds between the two satisfies 4.0 mm<Dc-Ds<12.0 mm, as described above.

The outer diameter dimensions DC and Ds are measured by measuring the length in the outer circumferential direction at the tread center position and the outer circumferential length at the widthwise edge of the ground contact surface when the load is zero, respectively. However, it can be obtained accurately by dividing the measured value by pi.

The tread pattern 16 is not limited to the example shown in FIG.
Other shapes may also be used, such as those shown in FIGS. 3, 4, or 5.

In Figure 1, the tire maximum width S when sandwiching the tire center is
The radius of curvature CTR of the tread in the central region C within 40% of W, and the tread in the outer region S which is outside in the width direction from 52% of the tire maximum width SW and inside in the width direction from 72% of the maximum tire width SW. The ratio C of the radius of curvature STR of
It is desirable that the tread radius index α, which is the product of TR/STR and tire aspect ratio, is 1.3 to 1.7.

(Experimental example) The tread pattern, the ratio of the effective ground contact area of the inner part to the effective ground contact area of the outer part (RR/RL), and the difference in outer diameter dimensions (Dc-Ds) were selected as shown in Table 1. 1.195/65 for Examples 1 and 2 and Comparative Examples 1 to 10
I made R14 tires.

The wear, IIML, and MR of the outer and inner parts of the tread when these tires are mounted on the front wheels of a passenger car and the passenger car is run with the part with the smaller effective ground contact area on the inside. The ratio of the wear fiRL of the outer part to the wear amount MR of the inner part is determined as the wear ratio M L
/M R is shown in Table 1, and steering stability is shown in Table 1 as a score.

In Table 1, the pattern column indicates the drawing number indicating the tread pattern used. The amount of wear is shoulder drop wear. The higher the score, the higher the steering stability.

As is clear from Table 1, according to the tires of Examples 1 and 2, the effective ground contact area ratio RR/RL and the outer diameter difference Dc-Ds are within predetermined ranges, so that This has the advantage that the amount of wear is almost the same as that of the inner part, and the steering stability is improved.

On the other hand, in the tire of Comparative Example 1, the tire of Example 1 of the present invention
Compared to tires 2 and 2, the ratio of effective ground contact area is larger
Since the difference in outer diameter dimensions is small, there are problems in that the amount of wear on the outer parts is significantly large and the steering stability is poor.

The tires of Comparative Examples 2 and 3 have a smaller difference in outer diameter than the tires of Examples 1 and 2 of the present invention, so there is a problem in that the steering stability is inferior.

Compared to the tires of Examples 1 and 2 of the present invention, the tire of Comparative Example 4 has a smaller difference in effective ground contact area ratio and outer diameter dimension, so the amount of wear on the inner part is large and the steering stability is poor. , there is a problem.

The tire of Comparative Example 5 has a larger ratio of effective ground contact area than the tires of Examples 1 and 2 of the present invention, so there is a problem in that the amount of wear on the outer portion is significantly increased.

The tire of Comparative Example 6 has a problem in that the ratio of effective ground contact area is smaller than that of the tires of Examples 1 and 2 of the present invention, so that the amount of wear on the inner portion is large.

Since the tire of Comparative Example 7 has a larger ratio of effective ground contact area than the tires of Examples 1 and 2 of the present invention, there are problems in that the amount of wear on the outer part is significantly large and the steering stability is poor. .

The tires of Comparative Examples 8 and 9 had a large difference in outer diameter compared to the tires of Examples 1 and 2 of the present invention, so there were problems in that the amount of wear on the outer parts was large and the steering stability was poor. be.

Compared to the tires of Examples 1 and 2 of the present invention, the tire of Comparative Example 10 has a smaller ratio of effective ground contact area and a larger difference in outer diameter dimensions, so the amount of wear on the inner part is greater and the handling stability is lower. The problem is that it is inferior.

The abrasion energy distributions of the tires of Example 2 and Comparative Examples 1.5 and 7 are shown in FIG. 6 with reference numerals 1. and 7, respectively. Indicated by II, I and ■. The wear energy is a value when the camber angle is plus 0.6 degrees and the toe angle is 1 degree.

As is clear from FIG. 6, according to the tire of the present invention,
Compared to the tires of Comparative Examples 1 and 5.7, the change in abrasion energy in the width direction of the tread portion is smaller, so the change in the amount of wear at each portion in the width direction of the tread portion is smaller.

/ /

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the tire of the present invention, and FIG.
FIG. 3, FIG. 4, and FIG. 5 are views showing examples of the tread pattern of the tire of the present invention, respectively, and FIG. 6 is a view showing the distribution of abrasion energy in the tread portion. 10: Tire, 12.14:) Red Groove, 16: Tread Pattern, 18 Ni Red Center, C: Central Area, S: Outer Area.

Claims (1)

[Scope of Claims] (1) A vehicle tire including a tread portion having left and right portions disposed on opposite sides with respect to a tread center, and a shoulder portion disposed next to the tread portion, RT the ratio of the effective ground contact areas of the left and right parts when the tire is mounted on a predetermined rim, the internal pressure of the tire is maintained at a predetermined value, and a predetermined maximum load is applied to the tire.
and when the difference between the outer diameter dimension Dc of the tread portion and the outer diameter dimension Ds of the shoulder portion when the load is removed from the tire is Dc−Ds, 0.85<RT<0.98 4. A vehicle tire in which 0mm<Dc-Ds<12.0mm. (2) 40% of the tire maximum width SW across the tire center
The radius of curvature CTR of the tread in the central region within
The product of the ratio CTR/STR of the tread curvature radius STR in the outer region which is outside in the width direction from 52% of the tire maximum width SW and inside in the width direction from 72% of the tire maximum width SW, and the tire aspect ratio. The vehicle tire according to claim 1, wherein the expressed tread radius index α is 1.3 to 1.7.