JPH0455105A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PURPOSE:To restrain the occurrence of a rut wandering phenomenon while excellent high speed, wear-resistance and low fuel cost performance are kept by providing saw-toothed projecting and recess portions in the peripheral direction of a tire on both edges of a tread surface, and disposing sipes on the projecting portions. CONSTITUTION:A reinforcing belt 2 comprises four layers and is formed by 3 metal cord. Plural main grooves 4 are provided on a tread surface 10, and saw-toothed projecting and recess portions 5 are formed in the peripheral direction on both edges thereof by continuously providing a V-shaped groove 8. Further, sipes 11 are disposed on the projecting portion of the projecting and recess portions. When the projecting and recess portions 5 come into contact with the wall surface of a rut, the tip 9 is brought into point-contact with wall surface of the rut, and the contact is performed in such a manner as to increase the reaction force gradually. As the contact pressure is increased, the tip 9 is divided into two parts in the peripheral direction of a tire by the sipes 11, and as the repulsive force is small, the tire will not be pushed back from the wall surface of the rut, but can easily get over the rut. Further, the projecting and recess portions 5 have the biting performance to the wall surface of the rut so as to promote the escape from the rut.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pneumatic radial tire suitable for use in heavy-duty vehicles such as trucks and buses.

[Conventional technology]

In recent years, pneumatic radial tires have come to be used in heavy-duty vehicles such as trucks and buses, demonstrating their excellent high speed performance, wear resistance, and low fuel consumption. In this pneumatic radial tire for heavy-duty vehicles, the reinforcing belt layer of the tread portion is generally made of metal cord in order to withstand the heavy load, and has extremely high rigidity.

However, these heavy-duty pneumatic radial tires with high rigidity in the trend section are filled with even higher internal pressure, so when they are driven on a rutted road surface, they are exposed to excessive pressure from the road surface when escaping from the ruts. A so-called wandering phenomenon occurs in which the handle is taken off by an external force.

(Problems to be Solved by the Invention) The present invention has been made to eliminate such conventional drawbacks, and its purpose is to improve the excellent high speed and wear resistance of heavy-duty pneumatic radial tires. To provide a pneumatic radial tire for heavy loads that is less likely to cause rut wandering while maintaining performance, fuel efficiency, etc.

[Means to solve the problem]

That is, the heavy-duty pneumatic radial tire of the present invention is a heavy-duty pneumatic radial tire in which a reinforcing belt made of metal cord is disposed in the tread portion, and a plurality of leads extending in the circumferential direction of the tire are provided on the tread surface. The tire is characterized in that sawtooth-like uneven portions are provided on both edges of the tread surface along the circumferential direction of the tire, and sipes are provided on the convex portions of the uneven portions.

1 to 3 illustrate a heavy-duty pneumatic radial tire according to an embodiment of the present invention, in which 1 is a trend section, 2 is a reinforcing belt disposed in the circumferential direction of the tread section 1, and 3 is a pneumatic tire for heavy loads according to an embodiment of the present invention. is a carcass. The carcass 3 is made up of at least one layer, and is approximately 90' in the circumferential direction of the tire.
It is made of metal cord or organic fiber cord. The reinforcing belt 2 is composed of at least two layers (four layers in this embodiment), and is mainly composed of metal cords. These reinforcing belts 2 form an angle of 15 to 30 degrees with respect to the tire circumferential direction, and intersect with each other between layers.

On the other hand, the contact surface of the tread portion 1, that is, the trend tread surface 10
A plurality of main grooves 4 extending in the circumferential direction of the tire are provided, forming a rib pattern. This tread surface 1
Sawtooth-like uneven portions 5 are provided on both edges of the tire 0 along the circumferential direction of the tire. The uneven portion 5 is formed by continuously providing a groove 8 in the shape of a 7 in the tire circumferential direction from the tread surface 10 to the shoulder portion 7 in the direction of the rotational axis of the tire. has been done.

Further, on both edges of the tread surface 10, sipes 1 extending in the direction of the tire rotation axis reach the peaks 9 of the convex portions of the uneven portions 5.
1 is provided. The direction of the sipes 11 may be in the tire width direction, and is not necessarily limited to the tire rotation axis direction as in the illustrated embodiment, but may be in an oblique direction.

In this way, the serrated uneven parts 5 are provided on both edges of the tread surface 10 along the tire circumferential direction, and the sipes 11 are arranged on the convex parts of the uneven parts 5, so that the tread surface 10
The rigidity of both edges of the tread surface 1o can be reduced without substantially reducing the ground contact surface.

In the tread surface 10 having such a configuration, when the uneven portion 5 contacts the wall surface of the rut, the tip 9 of the uneven portion 5 comes into point contact with the wall surface of the rut, and the reaction force is initially very small and gradually the reaction is caused. Make contact that increases the force. Moreover, as the contact pressure increases, the tip 9 of the uneven portion 5 is split into two by the sipes 11 in the tire circumferential direction. In such a case, even if the uneven portion 5 is incompressible, the tire will not be pushed back from the wall of the rut because its repulsive force is small.
You can easily get over the ruts. Further, since both edges of the tread surface 5 are formed into sawtooth-like uneven portions 5, the tread has a tendency to bite into the wall surface of the ruts, thereby facilitating escape from the ruts.

Assuming that the aforementioned pinch of the uneven portion 5 is l, and the width of the uneven portion 5 in the tire rotation axis direction is a, a/E is preferably within the range expressed by the following formula.

That is, 0, 1 < a / It < 0, 2 --
If fl)a/(l is within the range of formula 11 above, the stiffness of both edges of the trend tread can be reduced without substantially reducing the tire contact area, thereby preventing the rut wandering phenomenon. becomes less likely to occur.

Further, the width of the sipe 11 in the tire rotation axis direction is greater than or equal to the width a of the uneven portion 5 in the tire rotation axis direction, and the pitch β of the uneven portion 5 is
It is desirable that it be equal to or less than (a<b≦β). Furthermore, the depth h of the uneven portion 5 and the sipe 11 should be greater than or equal to the width a of the uneven portion 5 in the tire rotational axis direction and equal to or less than the width of the sipe 11 in the tire rotational axis direction (a<h≦b). is desirable.

〔Example〕

The present invention tire having the structure shown in FIGS. 1 and 2 and the conventional tire having the tread surface shown in FIG. A test in which the vehicle was equipped with an empty vehicle and drove on a rutted test course at a speed of 80 to 90 km/h while driving straight in the ruts, entering and exiting the ruts, and intentionally hitting the tires against the rut walls. was conducted with 10 test drivers.

The feeling of each test driver at that time was scored using a 10-point system based on the conventional tire, and the average value of the 10 drivers was expressed as the wandering prevention performance.

The above feeling score includes the frequency of wandering, the amount of wandering movement, the speed of wandering movement,
We evaluated things such as the convergence of wandering, the feel of the steering wheel, and the vehicle's behavior in and out of ruts, and the evaluation results are shown in the table.

Note that the tire size is 1000R20.

(Hereinafter, blank spaces) It can be seen from this "table" that the tire of the present invention has extremely excellent wandering prevention performance.

〔Effect of the invention〕

As described above, the present invention provides a heavy-duty pneumatic radial tire in which a reinforcing belt made of a metal cord is disposed in the tread portion and a plurality of main grooves extending in the tire circumferential direction are provided in the tread surface. Sawtooth-like unevenness is provided along the circumferential direction of the tire on both edges, and sipes are placed on the protrusions of the unevenness, thereby achieving the excellent high speed, wear resistance, and low wear resistance that heavy-duty pneumatic radial tires have. The rut-wandering phenomenon becomes even more difficult to occur while maintaining fuel economy, etc., and the driver can drive safely even on rutted roads without the steering wheel getting stuck in the ruts.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the main part of the tread part of a radial tire according to an embodiment of the present invention, FIG. 2 is a plan view of the tread part of the radial tire, and FIG. 3 is a perspective view of the main part of the radial tire. FIG. 4 is a plan view of the tread portion of a conventional pneumatic radial tire. DESCRIPTION OF SYMBOLS 1... Tread part, 2... Reinforcement belt, 4... Main groove, 5... Uneven part, 10... Tread surface, 11...
...Sipe.

Claims (1)

[Claims] In a heavy-duty pneumatic radial tire in which a reinforcing belt made of metal cord is arranged in the tread part and a plurality of main grooves extending in the circumferential direction of the tire are provided on the tread surface, grooves are provided along the circumferential direction of the tire on both edges of the tread surface. A pneumatic radial tire for heavy loads, which is provided with a sawtooth-like uneven portion and sipes are arranged on the convex portion of the uneven portion.