JPH10129212A - Radial tire for small-sized truck - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radial tire for a small-sized truck improving wandering performance. SOLUTION: In a radial tire for a small-sized truck provided with a carcass 1, main belt 2 made by a two-layer chord layer formed by burying a parallel steel chord in a coating rubber, belt reinforcing layer 3 of single layer, pair of peripheral direction grooves 7 extended in a peripheral direction with a space of about 25% or less a tread width apart from a tire equator line, and a tread pattern having a central rib 4, the belt reinforcing layer 3 is made by a chord layer formed by burying a plurality of the parallel steel chords in the coating rubber, this chord direction is 70 to 90 degrees relating to the peripheral direction, a width of this sectional direction is 20 to 80% tread width, a crown radius R1 of the central rib is 20 to 90% crown radius R2 in this both side part, between the main belt 2 and the belt reinforcing layer 3, a rubber layer 6 is arranged over almost a total width of the belt reinforcing layer 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial tire for a small truck, and more particularly to a radial tire for a small truck having improved wandering performance when the small truck is empty.

[0002] Here, to describe the terminology used herein, a "M _100" is a physical property value of a rubber by the test method of the rubber shown in JIS-K6301, was stretched rubber 100% It is a tensile stress at that time, and is one of the general ones showing physical properties of rubber. Sometimes referred to as 100% modulus.

[0003]

2. Description of the Related Art Conventionally, radial tires for light trucks have been known to have a problem in wandering when running on a rut. For example, a design in which a crown R is reduced or a lateral narrow groove is arranged in a tread shoulder portion is used. The technique was taken.

[0004]

However, when the crown R is reduced as described above, early wear of the shoulder portion becomes a problem, and when a narrow lateral groove is arranged in the tread shoulder portion, the light truck becomes empty. At times, there was a problem that the effect could not be exhibited because the shoulder portion hardly touched the ground.

SUMMARY OF THE INVENTION The present invention has been made as a result of studying to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a small truck radial wobbling performance improved for a small truck. To provide tires.

[0006]

In order to achieve the above object, a radial tire for a small truck according to the present invention is provided with a carcass comprising at least one radial cord layer and a crown portion radially outside of the carcass, At least two steel cords laid in parallel in a covering rubber
A main belt including a plurality of cord layers, and at least one belt reinforcing layer disposed radially outside the main belt;
A tread disposed radially outward of the belt reinforcing layer; and a pair of circumferential grooves extending circumferentially continuously from the tire equator line disposed on the tread at an interval of about 25% or less of the tread width. And a tread pattern having a tread central rib separated by the pair of circumferential grooves and a tread pattern having both side areas, (1) the belt reinforcing layer is formed of a plurality of parallel steel sheets. A cord layer is formed by embedding a lude in a covering rubber, the cord direction is 70 to 90 degrees with respect to the circumferential direction, and the width in the cross-sectional direction is 20 to 80 of the tread width.
(2) The crown radius R1 of the central rib is 20 to 90% of the crown radius R2 of the both sides,
(3) Between the main belt and the belt reinforcing layer, a rubber layer is disposed over substantially the entire width of the belt reinforcing layer.

Further, the cross-sectional shape of the rubber layer is a convex lens shape whose thickness is gradually reduced from the center of the tread in the width direction of the tire.
More preferred because wandering performance is improved if it is formed of rubber having 40 to 100% of the M ₁₀₀ value of _100.

In order to improve the wandering performance, it is necessary to increase the camber stiffness (ratio of camber thrust to camber angle) of the tire. However, the radial tire has a smaller camber stiffness than the bias tire and has a smaller wandering performance. Is disadvantaged. It is known that the crown radius should be reduced in order to increase the camber stiffness. That is, the contact pressure in the center area of the tread may be made higher than the contact pressure in the both side sections of the tread. However, when the crown radius is reduced, there is a problem that the wear resistance, which is one of the important characteristics of the truck tire, is particularly deteriorated, so that it cannot be changed significantly.
Since the camber stiffness increases substantially in proportion to the load, wandering is a problem particularly when the vehicle is empty. In the present invention, since the crown radius of the rib in the central area of the tread is reduced, the contact pressure in the central area of the tread is increased even when the load applied to the tire is small,
As a result, camber stiffness is increased and wandering performance is improved.

According to the present invention, a rubber layer is further disposed radially outside the main belt in the central region of the tread, and a plurality of steel cords arranged in parallel in the radial direction are embedded in the covering rubber. Since the belt reinforcing layer whose cord direction is 70 to 90 degrees with respect to the circumferential direction is disposed, there is an effect that the ground pressure in the central area is increased and camber stiffness is increased.

Note that the groove wall of the circumferential groove on the side forming the tread center rib is continuously connected from the crown radius of the center rib as shown in FIG. 1, and the boundary between the groove side wall and the center rib may not be clear. .

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A tire according to an embodiment of the present invention and a conventional tire will be described with reference to the drawings. FIG. 1 is a partial cross-sectional view in the width direction of a tire according to an embodiment of the present invention. A main belt composed of two cord layers embedded in the main belt, a single belt reinforcing layer disposed radially outside the main belt, and approximately 23% of the tread width from the tire equator line disposed on the tread. A radial tire for a light truck, comprising a tread pattern having a pair of circumferential grooves extending continuously in the circumferential direction at an interval of% and a central rib divided by the circumferential grooves.

FIG. 2 is a partial cross-sectional view of the conventional tire in the width direction. The crown radius of the center rib is continuously connected to the crown radii of both sides, and the rubber layer 6 and the belt reinforcing layer 3 are also arranged. Not what it is. Other structures and materials are the same as those of the tire of the embodiment. The tire size is 195 / 85R16 and the rim size is 5
1 / 2J. And the tread width TW is 133 mm
The belt reinforcement layer uses a steel cord arranged in a cord direction at 90 degrees to the circumferential direction.
The rubber layer used had a convex lens shape.

Next, in order to confirm the effects of the present invention, six types of tires were prototyped as shown in Table 1. For these tires, indoor camber stiffness was measured, and a feeling evaluation of wandering performance in an actual vehicle was performed. The camber stiffness in the room was evaluated by setting the average value per camber angle of 1 degree when the camber angle was sequentially increased to 10 degrees with an internal pressure of 5.75 kgf / cm ² and a load of 750 kgf as 100 for a conventional tire.
Feeling evaluation of the wandering performance of the actual vehicle was based on the condition that an Isuzu Elf 2-ton vehicle was used with the empty vehicle (front axle weight about 1500k).
gf, rear axle weight of about 1200 kgf) and evaluated by traveling on a rutted road. In the evaluation, the feeling was evaluated assuming that the conventional tire was ± 0, and in 0.25 points, +0.25 points were different (improved) and +1 points were considerably different (improved). All the results are shown in Table 1.

[0014]

[Table 1]

[0015]

As can be seen from Table 1, the radial tires for small trucks according to the embodiments of the present invention have a greater camber stiffness than the pneumatic radial tires of the conventional example and the comparative example, and have a wandering feeling in a real vehicle. It is clear that the evaluation is also good.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of an embodiment of the radial tire for a small truck of the present invention.

FIG. 2 is a partial sectional view showing a conventional radial tire for a small truck.

[Explanation of symbols]

 E Equatorial line TW Tread width 1 Carcass 2 Main belt 3 Belt reinforcement layer 4 Tread center rib 5 Tread both sides area 6 Rubber layer 7 Circumferential groove

Claims (2)

[Claims] 1. A carcass comprising at least one radial cord layer, and at least two cord layers disposed on a radially outer side of a crown portion of the carcass and having a parallel steel cord embedded in a covering rubber. A main belt, at least one belt reinforcement layer disposed radially outside the main belt, a tread disposed radially outside the belt reinforcement layer, and a tire equatorial line disposed on the tread. A tread pattern having a pair of circumferential grooves extending continuously in the circumferential direction at an interval of about 25% or less of the tread width, a central rib and both side sections divided by the pair of circumferential grooves; (1) The belt reinforcing layer comprises a cord layer in which a plurality of parallel steel cords are embedded in a covering rubber. The cord direction is 7
0 to 90 degrees, the width in the cross-sectional direction is 20 to 80% of the tread width, and (2) the crown radius R1 of the central rib is 20 to 90% of the crown radius R2 of the both sides.
(3) between the main belt and the belt reinforcing layer,
A radial tire for a light truck, wherein a rubber layer is disposed over substantially the entire width of the belt reinforcing layer. 2. A cross-sectional shape of the rubber layer is gradually convex shape to reduce the thickness toward the tread center in the tire width direction, the rubber layer is 40 to 100% of the M ₁₀₀ of the coating rubber of the main belt light truck radial tire for according to claim 1, characterized in that it is formed of rubber having a M ₁₀₀ values.