JPH06102401B2 - Pneumatic radial tires - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pneumatic radial tire with improved steering stability during high-speed traveling by making the contact pressure distribution on the tread surface uniform.

[Conventional technology]

In a pneumatic radial tire with a wide tread surface contact width, a high rigidity steel cord belt layer can be widely arranged, so that the tread surface rigidity is increased and steering stability can be improved. However, as the contact width increases, the contact pressure distribution on the tread surface becomes uneven, and the grip force on the road surface becomes insufficient.Therefore, the vehicle when switching diagonal lines during high speed driving exceeding 160 km / hr There was a problem that the movement of the car became unstable and the steering stability deteriorated.

As a result of studying the problem of such a radial tire having a wide tread ground width, the present inventors have found that the ground pressure distribution is closely related to the cross-sectional contour shape of the tread.

Conventionally, a tread of a pneumatic radial tire has a single radius of curvature Ra as shown in FIG. 2 (A).
There are two types of arcs, one of which is an arc formed by the above, and the other of which is an arc having a radius of curvature Rb arranged side by side with a center-to-center distance c between these arcs as shown in FIG.

In the case of the former virtual cross-sectional contour shape of FIG. 2 (A) (hereinafter, simply referred to as cross-sectional contour shape), as shown in FIG. 2 (B), the tire circumferential direction extends from the center portion 1 toward the shoulder portion 3. 4 shows a ground contact shape 4 in which the ground contact width is gradually reduced. Generally, as shown in FIG. 2 (C), the inner structure of the pneumatic radial tire T is such that both ends of the carcass layer 11 are wound around the bead cores 12 on the left and right sides from the inside of the tire to the outside thereof, respectively. A belt layer 14 made of steel cord is arranged on the tread portion 13 of 11. Such a radial tire T is shown in FIG. 2 (C).
When the rim R is assembled to the rim R as shown in Fig. 1 and mounted on a vehicle (not shown) and a load P is constantly applied, the shape of the tread portion shown by the dotted line before loading is the center portion 1 as shown by the solid line. The greater the deformation. As a result, the contact pressure distribution of the tread is as shown in FIG.
The ground pressure is large at the shoulder portion 3 and relatively low at the intermediate portion 2. That is, the ground contact pressure depends on the cross-sectional contour shape of the tread portion.

Since the contact pressure distribution becomes non-uniform in this way, the grip force cannot be effectively transmitted to the vehicle body, which causes a problem that steering stability during high-speed traveling deteriorates.

On the other hand, in the latter case of the cross-sectional contour shape of FIG. 3 (A), it is possible to increase the ground contact pressure at the intermediate portion. However, in this case, as shown in FIG. 3 (B), the contact width (contact pressure) in the tire circumferential direction in the center portion 1 is remarkably reduced, and thus the steering stability at the time of high-speed traveling is sufficient as in the above case. Could not be improved.

[Problems to be Solved by the Invention]

An object of the present invention is to provide a pneumatic radial tire with improved steering stability during high-speed running by making the tread contact pressure distribution of a pneumatic radial tire having a wide tread contact width uniform.

[Means for Solving the Problems]

Such an object of the present invention is to wind up both ends of the carcass layer from the tire inside to the outside around the left and right bead cores respectively, and arrange the belt layer made of steel cord on the outer periphery of the carcass layer in the region corresponding to the tread portion. In the radial tire, the virtual cross-sectional contour shape of the tread portion, a center portion formed from an arc having a radius of curvature R ₁ centered on a center line passing through the tread width center, and left and right in the tire width direction from the center line, respectively. At a distance b to
An intermediate portion formed of an arc having a radius of curvature R _{2 and} having a center on each of two lines parallel to the center line, and further formed so as to connect the outer shoulder portions to each other, and substantially the same height as the top a and a top B of the intermediate portion, and the distance b with respect to the ground half width W of the tread portion, 0.3 W <b <the 0.5 W, the radius of curvature R _1, R ₂ can be achieved by setting 0.2 <R ₂ / R ₁ ≦ 0.5.

In the present invention, the "virtual cross-sectional contour shape", which is abbreviated as the cross-sectional contour shape, refers to the contour of the tread outer surface in the tire meridian section when the grooves and sipes provided in the tread are omitted.

In this manner, the virtual cross-sectional contour shape of the tread portion is separated from the center portion formed by an arc having a radius of curvature R ₁ centered on the center line and a distance b from the center line to the left and right in the tire width direction. An intermediate portion formed of an arc having a radius of curvature R ₂ having a center at each position and further outer shoulder portions are formed so as to be connected to each other, and the top portion A of the center portion and the top portion B of the intermediate portion are formed. The contact pressure distribution can be made uniform by setting the heights of and to be substantially the same and setting the relationship between the distance b and the radii of curvature R ₁ and R ₂ within the ranges of the above expressions.

In the present invention, the ground contact width generally refers to a standard air pressure specified by JATMA and a load corresponding to 80% of the maximum load as used in the art.

Hereinafter, the configuration of the present invention will be described in detail with reference to the drawings.

The tire of the present invention, as shown in FIG. 1 (A), has a radius of curvature R ₁ centered on a center line E passing through the center of the tread width.
And a center portion 1 formed of an arc of _{2 and} an arc having a radius of curvature R ₂ having a center on each of two lines parallel to the center line E at a position separated from the center line E by a distance b in the tire width direction. An intermediate portion 2 formed from
Further, the shoulder portions on both outer sides are formed so as to be connected to each other, and the top portion A of the center portion and the top portion B of the intermediate portion have a virtual cross-sectional contour shape that is substantially at the same height.

Further, as shown in FIG. 1 (C), the tire of the present invention, like the conventional radial tire, has both end portions of the carcass layer 11 wound up around the bead cores 12 on the left and right sides from the tire inner side to the outer side to form a carcass. A belt layer 14 made of steel cord is annularly arranged on the tread portion 13 of the layer 11 along the tire circumferential direction.

The cross-sectional contour shape of the tire of the present invention has a radius of curvature R ₁ centered on the center line E of the center portion 1 and a radius of curvature R ₂ centered on a line separated from the center line E of the middle portion 2 by a specific distance b. Since it is formed from an arc, the center of the radius of curvature R ₂ forming the intermediate portion 2 bulges slightly. When formed only from a single arc having a radius of curvature R ₁ centered on the center line E, as shown by the dotted line in FIG.
Becomes a smooth curve and does not swell, whereas
In the present invention, as shown by the solid line, the intermediate portion 2 swells and the load P
The ground pressure increases due to the load. Further, as shown in FIG. 1 (B), the ground contact shape 4 has a large ground contact width in the vicinity of a position separated from the center line E of the center portion 1 and the intermediate portion by a distance b in the tire width direction.

In the present invention, if the center of the radius of curvature R ₂ forming the intermediate portion 2 of the cross-sectional contour shape becomes too close to the center line E, the cross-sectional contour shape becomes similar to that in FIG. Is difficult to make uniform, so the radius of curvature
The center of R ₂ is located parallel to the tire width direction from the center line E at a distance b that is 0.3 times or more the half-contact width W of the tread surface. If the center of the radius of curvature R ₂ is too far apart, the contact pressure of the shoulder portion 3 will be improved in a pattern, and the contact pressure distribution cannot be made uniform, so the contact half width W should be 0.5 or less. To do.

Further, in the present invention, the radius of curvature R _{2 with} respect to the radius of curvature R ₁
The ratio R ₂ / R ₁ must be greater than 0.2. This ratio is 0.
When it is 2 or less, the center of the radius of curvature R ₂ is located in the shoulder portion 3 (the distance b becomes large), and the shoulder portion 3
Cannot be formed with a smooth arc, and the ground contact pressure of the intermediate portion 2 decreases. Further, if the ratio R ₂ / R ₁ is larger than 0.5, the contact pressure distribution tends to have a distribution close to the contour shape of the cross section of FIG. Moreover, since the shape of the shoulder portion 3 is unlikely to be round, the wear resistance performance deteriorates.

Note that the specific sizes of the curvature radii R ₁ and R ₂ may be appropriately selected on the assumption that the above relationship is maintained, and for example, the curvature radius R ₁ is 500 to 1000 mm, and the curvature radius R ₂ is You can choose from the range of 100-500 mm.

In the present invention, a tire is manufactured in consideration of the above-mentioned radius of curvature R ₁ and R ₂ and the distance b from the center line to the center of the radius of curvature R ₂ , and a green tire is manufactured using this mold. Then, it can be easily produced by molding and vulcanizing it according to a conventional method.

Example 1, Conventional Example 1, 2 The carcass layer is composed of 1650D / 2 rayon cord, the belt layer is composed of steel cord, the width thereof is 195 mm, the tire size is 225 / 50R16 (oblateness 50%), The point that the contact half width W is 90 mm is common, and the sectional contour shape, the contact shape, the radii of curvature R ₁ , R ₂ , Ra, Rb, and the distance b from the center line to the center of the radius of curvature R ₂ are as follows. The tire of the present invention and the conventional tires 1 and 2 were manufactured.

Tire of the Invention Cross-sectional contour shape: FIG. 1 (A) Ground contact shape: FIG. 1 (B) R ₁ = 800 mm, R ₂ = 350 mm, b = 35 mm Conventional tire 1 Cross-sectional contour shape: FIG. 2 (A) Ground contact shape : Fig. 2 (B) Ra = 820mm Conventional tire 2 Cross-sectional contour shape: Fig. 3 (A) Ground contact shape: Fig. 3 (B) Rb = 350mm, c = 70mm These 3 types of tires are grounded by the following method The pressure distribution and high speed steering stability were evaluated.

Evaluation method of contact pressure distribution: Each test tire filled with 2.0 kgf / cm ² of air pressure was mounted on a rim with a width of 7 inches, and a load of 440 kg was applied to the tire. The measurement points in the direction and the circumferential direction were obtained, and the ground pressures were evaluated to evaluate the results, and the results are shown in FIGS. 4 (A) to 4 (C).

FIG. 4 (A) shows the case of the conventional tire 1, FIG. 4 (B) shows the case of the conventional tire 2, and FIG. 4 (C) shows the case of the tire of the present invention. From these FIGS. 4 (A) to (C), the conventional tire 1 has a low ground contact pressure in the middle portion, and the conventional tire 2 has a low ground contact pressure in both the center portion and the shoulder portion, and each of them has a ground contact pressure. There is a problem with pressure uniformity. On the other hand, it can be seen that the tire of the present invention shows almost no change in the ground contact pressure in these regions.

High-speed steering stability evaluation method: Each of the test tires used in the evaluation of the above ground contact pressure was set to 2,800cc.
The high-speed steering stability was evaluated by sensory evaluation of the driving performance when the vehicle was mounted on a passenger car and running at a speed of 160-200km / h. The evaluation results are shown by an index with the value of Conventional Tire 1 as the standard (100). The higher the index value, the better.

The results are shown in Table 1.

It can be seen from Table 1 that the tire of the present invention is superior to the conventional tires 1 and 2 in high-speed steering stability.

Comparative Examples 1 to 5 Five types of comparative tires 1 to 1 of the present invention tire 1 of Example 1 in which R ₂ / R ₁ and b are different as shown in Table 2
5 were manufactured respectively.

With respect to these five types of tires, high-speed steering stability was evaluated by the above-described measuring method, and the results are shown in Table 2.

It can be seen from Table 2 that Comparative Tires 1 to 5 all exhibit high-speed steering stability similar to that of Conventional Tire 1, and no improvement effect is recognized.

Example 2 In the tire of the present invention of Example 1, b is 0.39 W (constant)
Then, five types of tires having different ratios R ₂ / R ₁ were manufactured, and the high-speed steering stability (index) was measured by the above-described measuring method. The measurement results are shown in FIG. 5 (A) by plotting the ratio R ₂ / R ₁ on the horizontal axis and the high-speed steering stability (index) on the vertical axis.

It can be seen from FIG. 5 (A) that, when the distance b is satisfied under the conditions specified in the present invention and 0.2 <R ₂ / R ₁ ≦ 0.5 is satisfied, a high level of high-speed steering stability is exhibited.

Example 3 In the tire of the present invention of Example 1, four types of tires were manufactured in which the ratio R ₂ / R ₁ was set to 0.44 (constant) and only b was changed, and high speed steering stability (index ) Was measured. The measurement results are shown in FIG. 5 (B) by plotting b as the horizontal axis and high-speed steering stability (index) as the vertical axis.

From FIG. 5 (B), it can be seen that when the ratio of R ₂ / R ₁ is 0.3W <b <0.5W under the conditions specified in the present invention, a high level of high-speed steering stability is exhibited. .

〔The invention's effect〕

According to the present invention, in a radial tire having a wide ground contact width in which a belt layer made of a steel cord having high rigidity is arranged in the tread portion, the virtual cross-sectional contour shape of the tread portion is an arc having a radius of curvature R ₁ centered on the center line. A center portion formed by the center line, a middle portion formed by an arc having a radius of curvature R _{2 and} having a center at a position parallel to the left and right of the center line in the tire width direction, and a shoulder portion, respectively. Formed by
By setting the relationship between the distance b and the radii of curvature R ₁ and R ₂ within the ranges of the above equations, respectively, the contact pressure distribution can be made uniform and the high-speed steering stability can be improved.

[Brief description of drawings]

FIG. 1 (A) is an explanatory view showing an example of a sectional contour shape of the tire of the present invention, FIG. 1 (B) is an explanatory view showing a ground contact shape of the tire of the present invention of FIG. 1 (A), FIG. C) is a cross-sectional view showing an example of the tire of the present invention, FIGS. 2A and 3A are explanatory views showing cross-sectional contour shapes of comparative tires, respectively.
FIG. 2B and FIG. 3B are explanatory views showing the ground contact shapes of the tires of FIG. 2A and FIG. 3A, respectively.
FIG. 2C is a sectional view showing a deformed state when the tire of FIG. 2A is mounted on a vehicle and a load is applied, FIG. 2D.
Shows the contact pressure distribution at that time, FIGS. 4 (A), 4 (B), and 4 (C) are explanatory views showing the contact pressure distribution of each of the above tires in a graph, and FIG. (A) is the ratio R ₂ / R
₁ is a graph showing the relationship between high-speed steering stability (index), and FIG. 5 (B) is a graph showing the relationship between b and high-speed steering stability (index). 1 ... Center part, 2 ... Intermediate part, 3 ... Shoulder part, 4 ... Ground contact shape, 13 ... Tread part, 14 ... Belt part, E ... Center line.

Claims (1)

[Claims] 1. A pneumatic radial in which both end portions of a carcass layer are respectively wound around left and right bead cores from inside to outside of a tire, and a belt layer made of steel cord is arranged on an outer periphery of the carcass layer in an area corresponding to a tread portion. In the tire, a virtual cross-sectional contour shape of the tread portion, a center portion formed from an arc having a radius of curvature R ₁ centered on a center line passing through the tread width center, and the distance from the center line to the left and right in the tire width direction, respectively. At a position separated by b,
An intermediate portion formed of an arc having a radius of curvature R _{2 and} having a center on each of two lines parallel to the center line, and further formed so as to connect the outer shoulder portions to each other, and substantially the same height as the top a and a top B of the intermediate portion, and the distance b with respect to the ground half width W of the tread portion, 0.3 W <b <the 0.5 W, the radius of curvature R _1, R Pneumatic radial tire with _{2 set} to 0.2 <R ₂ / R ₁ ≦ 0.5.