JPH0648116A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To improve stability, controllability and wandering resistant performance without impairing the durability of even a flat tire by forming the tread surface of the tire out of two circular arcs having a different radius, and connecting the tread surface and butt-less surface via a circular arc having the prescribed radius. CONSTITUTION:A tire having a maximum breadth between 195mm and 225mm, and an aspect ratio between 0.6 and 0.75, is assembled into a rim, and regarding the standard tread surface 5A thereof at the time of supplying the standard internal pressure, the standard tread surface 5A is formed so that an equator surface A crossing a tire equator surface C comes to a center, and points off both sides of a position at 3/10 of tread width WT are taken as B. A central area M between the points B are formed out of a circular arc of a radius R1 between 700mm and 850mm passing the point A with a center on the surface C, and a shoulder area S between the point B and a tread end E is formed out of a circular of a radius between 1/3XR1 and 1/2.5XR1. Furthermore, a tread end is formed out of a circular arc with a radius between 30mm and 50mm, extending from a point E to the butt-less surface of a side wall section. Consequently, stability, controllability responsiveness and wandering resistant performance can be improved without impairing the durability of even a flat tire.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire having improved handling stability, handling response and wandering resistance in a flat tire.

[0002]

2. Description of the Related Art A so-called radial arrangement tire in which carcass cords are arranged substantially at right angles to the equatorial plane of the tire is widely used because it is superior in wear resistance and steering stability as compared with a tire having a bias structure.

However, when a carcass having a radial arrangement is used as a tire for a commercial vehicle having a low flatness ratio, since the tire is a flat tire, the radius of curvature in the axial direction of the tire forming the tread surface becomes large and the tread surface becomes flat. It will be.

[0004]

By flattening the tread surface in this way, the tire touches the road surface,
As shown in FIG. 4, the ground contact surface has an hourglass shape, and the protrusion P appears especially in the shoulder region, and the ground pressure becomes large at this protrusion, resulting in poor steering stability and uneven wear. Easy and inferior in durability.

Further, when there is a rut on the road surface, there is a problem that the rudder cannot be removed completely and the wandering resistance is poor.

The inventor cannot eliminate the above-mentioned protruding portion of the ground contact surface, which is a factor that deteriorates the steering stability, when the tread surface is formed of an arc having a single radius as in the conventional case. Further, it has been known that, in order to eliminate the protruding portion P, the tread surface must be formed by a multi-dimensional curve other than an arc such as a da circle or a parabola in the tire axial direction shape of the tread surface. .

Further, it has been found that in order to improve the anti-wandering performance, the connection portion between the tread surface and the buttress surface, which has not been considered in the past, should be improved.

The inventor of the present invention has two different tread surfaces with different radii.
Formed by two arcs, and based on connecting the tread surface and the buttress surface with an arc having a regulated radius, even a flat tire without impairing durability,
It is an object of the present invention to provide a pneumatic radial tire capable of improving steering stability and wandering resistance.

[0009]

The present invention has a maximum tire width of 195 mm or more and 225 mm or less and an aspect ratio of 60.
A pneumatic radial tire used for commercial vehicles of up to 75%, wherein a standard tread surface when the pneumatic radial tire is assembled into a rim and filled with standard internal pressure, the tread surface being a tire equatorial plane (C). Center area (M) between 3/10 points (B) and (B) that separates a distance of 3/10 times the tread width (WT) from the equatorial point (A) at the intersection with the center of the equatorial point (A). And the shoulder region (S) located between the 3/10 point (B) and the tread edge (E), and the central region (M) has a center on the tire equatorial plane (C). And the shoulder region (S) has a center at the equatorial plane (C) of the tire, and is formed at the 3/10 point ((1) of the first circular arc (S1) having a radius (R1) of 700 mm or more and 850 mm or less). In B), it is connected to the first circular arc (S1) and The radius (R1) of the arc (S1)
Is formed by a second arc (S2) having a radius (R2) that is ⅓ times or more and 1 / 2.5 times or less, and the second arc (S2) is 30 at the tread edge.
A pneumatic radial tire having a radius of not less than 50 mm and having a radius of not less than 50 mm and smoothly connecting to a third arc (S3) extending to the buttress surface of the sidewall portion.

[0010]

In the central region M of the tread surface, a normal tire is formed by an arc having a radius of about 300 mm, whereas in the present application, the radius is more than twice that of 700.
It is formed by the first circular arc S1 of mm or more, which expands the ground contact surface on the tread surface in the tire axial direction, thereby increasing the ground contact area, reducing the ground contact pressure, and improving the steering stability and handling. Increase responsiveness.
When the radius of the first circular arc S1 is less than 700 mm, protrusions P as shown in FIG. 4 appear on both sides of the ground contact surface, resulting in poor steering stability and response at the time of handling. As shown, the ground contact surface at the corner is insufficient and the ground contact pressure increases, resulting in poor wear resistance.

Further, in the shoulder region S, the first
Since it is formed by the second arc S2 having a radius R2 that is ⅓ times or more and 1 / 2.5 times or less of the radius R1 of the arc S1 of FIG. Protrusions P appearing on both sides as shown in FIG.
In addition to the above, the contact pressure can be equalized by forming a rectangular shape with rounded corners as shown in FIG.

If the radius R2 of the second arc S2 is less than 1/3 of the radius R1 of the first arc S1, the corner roundness becomes large as shown in FIG. Wears and is inferior in wear resistance. Conversely, if it exceeds 1 / 2.5 times,
The protrusions P shown in FIG. 3 remain on the ground contact surface, and a high ground pressure is generated at the protrusions, resulting in poor responsiveness during handling.

Further, since the tread surface is formed by the two arcs S1 and S2 whose radial centers are located on the tire equator surface, the shape of the tread surface can be easily set. Manufacturing is simple and economically available.

Further, the second arc extends to the buttress surface and has a radius (R of 30 mm or more and 50 mm or less).
It smoothly connects from 3) to the third arc. As a result, even a flat tire can be easily pulled out of the rut, and the wandering resistance is improved. The radius (R
If 3) is less than 30 mm, it becomes difficult for the rut to get over.
If it exceeds 0 mm, the maximum width of the tire becomes large, and in a vehicle equipped with the tire, the width of the vehicle body is widened, which is not preferable.

As described above, according to the present invention, by organically integrating the above-mentioned components, even a flat tire can improve steering stability and wandering resistance.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1 exemplifying a case where the pneumatic radial tire 1 is assembled to a standard rim J and is filled with air having a standard internal pressure, for example, 6.0 kg / cm ² , the pneumatic radial tire 1 has a bead core 2 on both sides. Bead parts 3 and 3,
Side wall portions 4 and 4 extending outward from the bead portion 3 in the radial direction and both ends thereof are joined together, and the outer surface is a tread surface 5A.
And a troid-shaped carcass 6 which is folded back from the inside of the bead core 2 toward the outside thereof. Further, in the tread portion 5, a belt layer 7 is arranged outside the carcass 6, and a bead apex 8 is provided between the main body portion of the carcass 6 and its folded portion, while the tire 1 has a so-called standard rim. The bottom surface 3A of the bead portion 3 is fitted to the bead seat portions 13, 13 of J to be mounted on the rim J.

Further, the pneumatic radial tire 1 has a standard maximum width W of the tire of 195 mm or more and 225 mm or less when mounted on the standard rim J and the radial direction of the bead portion 3 with respect to the standard maximum width W. It is formed as a tire for a commercial vehicle having an aspect ratio H / W, which is a ratio of a tire length H that is a distance from an inner end to an outer end of the tread surface 5A, of 60 to 75%.

The carcass 6 is composed of a single or plural carcass plies comprising a so-called radial direction cord array in which the carcass cords are arrayed at an angle of about 70 ° to 90 ° with respect to the tire equatorial plane C. In this case, four carcass cords are formed by overlapping, and as the carcass cord, organic fibers such as nylon, rayon, and aromatic polyamide are adopted.

The belt layer 7 is composed of a single or a plurality of belt plies 7A and 7B in this embodiment, and each of the plies 7A and 7B is an organic fiber such as nylon, rayon, aromatic polyamide fiber or a steel cord. The belt cord made of is arranged at a relatively shallow angle with respect to the equatorial plane C of the tire, and the cords of the plies are arranged in opposite directions.

Further, the pneumatic radial tire 1 has a standard tread surface 5A, as shown in FIG.
3/10 points B, B that are separated by 3/10 times the tread width WT, which is the distance between the equatorial point A intersecting the tire equatorial plane C and the edge of the tread portion 5 from the equatorial point A on both sides. It is divided into a central region M located between them and a shoulder region S located between the 3/10 point B and the tread edge E.

In the central region M, the center is on the equatorial plane C of the tire and 700 mm or more and 85 passing through the equatorial point A.
It is formed by a first arc S1 having a radius R1 of 0 mm or less. By making the radius of the arc S1 of the central region M about twice or more as large as that of a normal tire, the ground contact surface L expands in the tire axial direction. As a result, the ground contact pressure is reduced and the steering stability is improved. However, if the radius R1 exceeds 850 mm, the central region M becomes nearly flat, and uneven wear is likely to occur, resulting in poor durability.

On the other hand, in the shoulder region S, the center is on the tire equatorial plane C, and it is connected to the first arc S1 at the 3/10 point B, and the radius R1 of the first arc S1 is smaller than the radius R1. It is formed by a second arc S2 having a radius R2 that is 1/3 times or more and 1 / 2.5 times or less.

First circular arc S1, second circular arc S2 and third circular arc S2
The relationship between the circular arcs is shown in a diagram as shown in FIG. In FIG. 5, it is preferable that the dimensional difference K between the point D where the extension line of the second arc S2 intersects the tire equatorial plane C and the equator point A is 3 mm or less, and the dimensional difference K approaches 0. Is more preferable.

The second arc S2 is a tread edge E
In the above, the third arc S3 is smoothly connected to the third arc S3 extending to the buttress surface 9 of the sidewall portion 4, and the third arc S3 has a radius R3 of 30 mm or more and 50 mm.

[0025]

[Examples] Tires having tire sizes of 205 / 60R17.5 and having the configuration shown in FIG. 1 (Examples 1 to 3)
Was prototyped and its performance was tested. In addition, the tires (Comparative Examples 1 to 6) not having the constitution of the present application were also tested to compare their performances. The test conditions are as follows.

A) Straight running stability, handling responsiveness,
And wandering resistance 1.5t for each test tire with an internal pressure of 6.0kg / cm ²
It was mounted on a small truck of on-product and loaded with a specified maximum load on the truck, traveled on a general road, judged by the driver's feeling, and displayed as an index with Example 1 being 100. The larger the value, the better, and a value of 100 or more is a passing value.

(B) High-speed durability It is mounted on the same vehicle as in 1), loaded with a maximum load, and traveled on the test course at a speed of 100 km / H until the tread surface cracked. Was expressed as an index with Example 3 being 100. The larger the value, the better. The test results are shown in Table 1.

[0028]

[Table 1]

As a result of the test, it was confirmed that the straight-line stability, handling responsiveness and wandering resistance of the example were improved in a well-balanced manner and the high-speed durability could be maintained as compared with the comparative example. did it.

[0030]

As described above, in the pneumatic radial tire of the present invention, in the flat tire, the first circular arc forming the central region of the tread surface, the second circular arc forming the shoulder region, and the second circular arc. The third arc that extends to the buttress surface and is provided with a third arc, and the radius of each arc is regulated. Therefore, even with a flat tire, the steering stability that deteriorates the durability and the responsiveness during handling are improved. In addition, the wandering resistance can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a diagram schematically showing the shape of the tread surface.

FIG. 3 is a plan view showing the shape of the ground contact surface.

FIG. 4 is a plan view showing a shape of a ground contact surface of a conventional tire.

FIG. 5 is a plan view showing the shape of a ground contact surface of a conventional tire.

[Explanation of symbols]

 4 Sidewall 5A Tread surface 9 Buttress surface A Equatorial point B 3/10 points C Tire equatorial surface M Central area R1 Radius of first arc R2 Radius of second arc R3 Radius of third arc S Shoulder area S1 1st circular arc S2 2nd circular arc S3 3rd circular arc WT tread width

Claims (1)

[Claims] 1. The maximum tire width is 195 mm or more and 225 mm.
The following is a pneumatic radial tire used for a commercial vehicle having an aspect ratio of 60 to 75%, wherein the standard tread surface when the pneumatic radial tire is assembled into a rim and filled with standard internal pressure is the tread surface. 3/1, which is 3/10 times the tread width (WT) away from the equatorial point (A) centering on the equatorial point (A) intersecting the tire equatorial plane (C).
The central area (M) between 0 points (B) and (B), and 3/1
It is divided into 0 point (B) and a shoulder area (S) located between the tread edges (E), and the central area (M).
Is formed by a first arc (S1) centered on the tire equatorial plane (C) and having a radius (R1) of 700 mm or more and 850 mm or less, while the shoulder region (S) is the tire equatorial plane (C). Centered at 3/10 points (B)
Is connected to the first circular arc (S1), and is 1/3 or more of the radius (R1) of the first circular arc (S1) and 1 /
A second circular arc (S with a radius (R2) of 2.5 times or less
2) and the second arc (S2) is
A pneumatic radial tire having a radius of 30 mm or more and 50 mm at the tread edge and smoothly continuing to a third arc (S3) extending to the buttress surface of the sidewall portion.