JPH0755604B2 - Vehicle tires - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle tire in which the left and right portions of the tread portion with respect to the tread center have different effective ground contact areas.

(Prior Art) Centrifugal force generated during turning of a vehicle is a portion of the tread portion that is outside with respect to the tread center during turning (hereinafter referred to as “outer portion”), especially when the load acting on the shoulder portion of the tread portion is inside. It acts on the tire so as to be larger than that which acts on a portion (hereinafter referred to as “inner portion”) that becomes.

When the load acts on the tread portion as described above, the ground contact pressure and the ground contact length of the outer part become larger than those of the inner part. The applied load is larger than that of the inner part. As a result, so-called shoulder drop wear, in which the shoulder portion of the tread portion is worn more rapidly than other portions, occurs in the outer portion. Further, since the ground contact pressure and the ground contact length of the inner portion are small, the adhesion between the road surfaces, that is, the grip performance is deteriorated.

The shoulder drop wear shortens the life of the tire and causes a decrease in steering stability during turning. In order to prevent such uneven wear, it is necessary to improve the wear resistance of the outer portion. However, in a conventional tire, since wear resistance and grip performance are in a trade-off relationship, it is difficult to improve the wear resistance and the grip performance without deteriorating the other.

From this, it has been proposed to periodically change the mounting state of the tire on the rim or the mounting state of the rim on which the tire is mounted on the vehicle so that the tire is worn uniformly. However, such a reassembling work requires a great deal of time, labor and skill.

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

(Solution Means, Actions, and Effects) A vehicle tire of the present invention includes a tread portion having left and right portions arranged on opposite sides with respect to a tread center, and a shoulder portion arranged adjacent to the tread portion. .

In the above vehicle tire, the present invention is to install the tire on a predetermined rim, maintain the internal pressure of the tire at a predetermined value, and the left and right parts when a predetermined maximum load is applied to the tire. When the ratio of the effective ground contact area of RT is RT and the load is removed from the tire, and the difference between the outer diameter dimension Dc of the tread portion and the outer diameter dimension Ds of the shoulder portion is Dc-Ds, 0.85 <RT <0.98 4.0mm <Dc-Ds <12.0mm.

In the present invention, the predetermined rim, the predetermined internal pressure, and the predetermined maximum load respectively refer to the rim specified as applicable to the tire, the internal pressure specified as the tire to be maintained, and the tire. It is called the maximum allowable load that can be applied. Further, the ratio of the effective ground area referred to in the present invention is the ratio of the small value of the effective ground area to the large value of the effective ground area. Further, in the present invention, the outer diameter dimension Dc of the tread portion refers to the diameter dimension of the position of the tread center when the inner pressure is applied and the load is not applied, and the outer diameter dimension Ds of the shoulder portion is the inner pressure. Is the outer diameter of the widthwise end edge of the ground contact surface when the load is not applied.

The effective ground contact area of the tread part on the left and right with respect to the tread center is to install the tire on a specified rim, fill the tire with air to maintain the internal pressure of the tire at a specified value, and to maintain the specified maximum load of the tire. This can be obtained by determining the area of the region on the one side and the other side of the tread center that can be in contact with the ground within the range of the contact width when the tire is acted on each of the left and right parts over the entire circumference of the tire.

Further, the ratio of the effective ground area is obtained by dividing a small value by a large value among the effective ground areas as described above.
Obtainable.

The tire of the present invention is attached to a vehicle so that the side having a smaller effective ground contact area is on the inside. As a result, the pattern rigidity of the inner part is reduced as compared with that of the outer part, the grip performance of the entire tire at the time of turning of the vehicle is improved, and abrupt ground contact shape change is prevented. As a result, the wear energy (kg / mm) represented by the product of the ground contact pressure and the slip during turning becomes almost the same in the inner part and the outer part.

When the ratio RT of the effective ground contact area is 0.98 or more, the shoulder drop wear of the outer portion is large as in the case of the conventional tire. On the other hand, when the ratio RT of the effective ground contact area is 0.85 or less, the pattern rigidity of the inner portion is excessively lowered, and the inner portion is easily deformed, so that the inner portion is greatly worn. A preferable value of the ratio RT of the effective ground contact area is 0.85 mm <RT ≦ 0.95, and more preferably 0.86 mm <RT ≦ 0.94.

If the difference in outer diameter Dc-Ds is 12 mm or more, the ground contact pressure at the outer part will be significantly lower than that at the inner part and the amount of slip will increase, resulting in greater shoulder drop wear on the outer part. . On the other hand, when the difference Dc-Ds in the outer diameter dimension is 4 mm or less, the wear of the tread center portion increases.

According to the tire of the present invention, by mounting the tire on the vehicle so that the portion having a small effective grounding area is the inside, the grip of the inner portion is improved, and thus the grip of the entire tire is improved, Further, since the wear energy (kg / mm) at the time of turning is almost the same in the inner part and the outer part, the shoulder drop wear of the outer part is reduced. Therefore, it is not necessary to perform the work of reassembling the tire to the rim and the work of reassembling the rim on which the tire is mounted to the vehicle in order to improve the steering stability and evenly wear the tire.

The present invention also includes a tire center and a maximum tire width SW.
Curvature CT of the tread in the central area within 40% of
The ratio of R to the radius of curvature STR of the tread in the outer region that is outside the tire width 52% of the tire maximum width SW and is 72% of the tire maximum width SW inward in the width direction CTR / STR and the tire flatness ratio The tread radius index α represented by is α = 1.3-1.43.

Conventionally, the shape of the tread surface has been formed with a single radius of curvature (tread radius). In this case, the contact pressure in the central region of the tread center and the tread shoulder (hereinafter referred to as "intermediate region") is low, and the amount of slippage is large, so that uneven wear tends to occur in the region. In particular, when the ground contact areas on both sides of the tread center are different and the direction in which the tire is mounted on the vehicle is specified as in the present invention, it is not possible to prevent uneven wear from occurring by changing the position of the tire, which is a large tendency. . Therefore, the inventors have solved this problem by making the radius of curvature of the tread different in the central region and the outer region.

The lowering of the ground contact pressure in this intermediate region is generally higher in a tire having a lower flatness. As a result of the investigation by the inventors of tires having different aspect ratios, the CTR / STR value is 2.6 to 3.4 for tires with an aspect ratio of 50%, 2.2 to 2.8 for tires with an aspect ratio of 60%, and a tire with an aspect ratio of 65%. Then, it was found that the range of 1.9 to 2.6 is effective in preventing uneven wear in the intermediate region. That is, the tread radius index α
By setting the ratio to 1.3 to 1.7, it is possible to prevent a decrease in ground contact pressure and an increase in the amount of slippage in a region between the tread center and the tread shoulder, and to prevent uneven wear in the region. Where α is
If it is less than 1.3, this effect is unlikely to occur, and if it exceeds 1.7, the ground contact pressure in the outer region is lowered and uneven wear is apt to occur.

Therefore, according to the present invention, it is possible to prevent a decrease in the ground contact pressure and an increase in the amount of slippage in the intermediate region between the tread center and the tread shoulder, and it is possible to prevent uneven wear in the region.

(Embodiment) A 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. And a tread pattern 16 including and. The tread pattern 16 has different shapes for the left side portion 20 and the right side portion 22 with respect to the tread center 18. Therefore, the shape and arrangement of the block 24 in the portion 20 and those of the block 26 in the portion 22 are not the same.

The effective ground areas RL and RR of the parts 20 and 22 are such that the effective ground area RL of the part 20 is larger than the effective ground area RR of the part 22, and the effective ground area RR of the part 22 is determined by the effective ground area RL of the part 20. The divided value RR / RL, or the ratio RT, is selected so that 0.85 <RT <0.98 as described above.

The effective ground contact areas RL, RR of the parts 20, 22 are mounted on the standard rim to which the tire 10 should be applied, the internal pressure of the tire 10 is maintained at a predetermined value, and the maximum allowable load is applied to the tire 10. It can be obtained by obtaining the area of the groundable portion existing within the range of the ground contact width W at that time over the entire circumference of the tire for each of the parts 20 and 22. In other words, the effective ground contact areas RL, RR of the parts 20, 22 should be obtained as the sum of the areas within the ground contact width W of the blocks 24, 26 existing within the range of W / 2 from the tread center 18. You can

The outer diameter dimension Dc of the tread portion and the outer diameter dimension Ds of the shoulder portion are selected such that the difference Dc-Ds between them is 4.0 mm <Dc-Ds <12.0 mm.

For the outer diameter dimensions Dc and Ds, measure the length dimension in the outer circumferential direction at the position of the tread center when the load is zero and the length dimension in the outer circumferential direction at the position of the widthwise edge of the grounding surface with a tape measure. , Can be accurately obtained by dividing the measured value by the pi.

The tread pattern 16 is not limited to the example shown in FIG. 2 and may have another shape, for example, the shape shown in FIG. 3, FIG. 4 or FIG.

In Fig. 1, the tire center is sandwiched by the maximum tire width SW
Radius of curvature of the tread within the central area C within 40% of
CTR and the ratio of the curvature radius STR of the tread in the outer area S, which is outside the tire width 52% of the tire maximum width SW in the width direction and is 72% of the tire maximum width SW, CTR / STR and the tire flatness ratio The tread radius index α represented by
Is desirable.

(Experimental example) The tread pattern, the ratio of the effective contact area of the inner part to the effective contact area of the outer part (RR / RL), and the difference in the outer diameter dimension (Dc-Ds) were selected as shown in Table 1. Example 1,
The tires of 2 and Comparative Examples 1 to 10 of 195 / 65R14 were manufactured.

Wear these tires on the front wheels of a passenger car so that the part on the side with the smaller effective contact area is on the inside, and wear amount ML, MR of the outside part and the inside part of the tread part when the passenger car is running. The ratio of the wear amount RL of the outer part to the wear amount MR of the inner part is shown in Table 1 as the wear ratio ML / MR, and the steering stability is shown in Table 1 as the rating.

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

As is clear from Table 1, according to the tires of Examples 1 and 2, the effective contact area ratio RR / RL and the outer diameter dimension difference Dc
Since -Ds is within the predetermined range, there are advantages that the amount of wear on the outer portion and the amount on the inner portion are almost the same, and the steering stability is high.

On the other hand, in the tire of Comparative Example 1, Example 1 of the present invention was used.
Compared with the tires of 2 and 2, the ratio of effective ground contact area is large,
Since the difference between the outer diameters is small, there is a problem that the amount of wear on the outer portion is significantly large and the steering stability is poor.

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

In the tire of Comparative Example 4, compared with the tires of Examples 1 and 2 of the present invention, the ratio of the effective ground contact area and the difference in the outer diameter dimension are small, so that the wear amount of the inner portion is large and the steering stability is poor. , There is a problem.

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

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

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

The tires of Comparative Examples 8 and 9 have a large difference in outer diameter dimension as compared with the tires of Examples 1 and 2 of the present invention, and therefore, there is a problem that the wear amount of the outer portion is large and the steering stability is poor. is there.

The tire of Comparative Example 10 has a smaller ratio of effective ground contact area and a larger difference in outer diameter dimension than the tires of Examples 1 and 2 of the present invention, and therefore, the wear amount of the inner portion is large, and the steering stability is high. There is a problem that it is inferior in sex.

The distributions of the wear energies of the tires of Example 2 and Comparative Examples 1, 5 and 7 are shown in FIG. 6 as I, II, III and IV, respectively.
Indicate. The wear energy has a camber angle of 0.6
And the toe angle is a value when the toe-in 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, 5, and 7, the change in the wear energy in the width direction of the tread portion is small, so the change in the wear amount of each part in the width direction of the tread portion is small.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the tire of the present invention, FIG.
FIG. 3, FIG. 4, FIG. 4 and FIG. 5 are views showing examples of the tread pattern of the tire of the present invention, and FIG. 6 is a view showing distribution of wear energy of the tread portion. 10: tire, 12, 14: tread groove, 16: tread pattern, 18: tread center, C: central area, S: outer area.

Claims (1)

[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 adjacent to the tread portion. Mounted on the rim of the tire, the internal pressure of the tire is maintained at a predetermined value, the ratio of the effective ground area of the left and right parts when a predetermined maximum load is applied to the tire is set to RT, and the load from the tire The difference between the outer diameter Dc of the tread and the outer diameter Ds of the shoulder when the
Assuming Dc-Ds, 0.85 <RT <0.98 4.0mm <Dc-Ds <12.0mm, with the tire center sandwiched between the tire maximum width SW and the tread radius of curvature CTR in the central area within 40% of the tire maximum width, and the tire maximum width. S
Tire width maximum outside of 52% of W and 72% of maximum tire width SW
A vehicle tire having a tread radius index α represented by the product of the ratio CTR / STR of the tread radius of curvature STR in the outer region on the inner side in the width direction and the tire flatness ratio is α = 1.3 to 1.43.