JPH0338409A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PURPOSE:To prevent partial wear by forming slits on a land portions in the direction of separating the long axis thereof and also at a predetermined angle relative to the equator of a tire, in the tire having block like tread patters in the title. CONSTITUTION:Sipes 34, 36 are formed in the direction of the long axis 30 of a land portion 28 and within the limit of 35-55 deg. of an average angle theta relative to a direction parallel to the equator 32 of a time, in the land portion 28 divided by a circumferential directional groove 24 and a lateral directional groove 26. According to this construction, force applied to the land portion 28 can be prevented from concentrically appling to a kick-out portion between sipes 34, 36 at the time of braking so that the force can be applied along the sipes 34, 36. Consequently, the force can be dispersed to the whole land portion to be able to prevent partial wear.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pneumatic radial tire for heavy loads, and more particularly to a pneumatic radial tire for heavy loads having a block-shaped tread pattern.

[Conventional technology]

Conventionally, the negative ratio of heavy-duty pneumatic radial tires for all-season or winter use, that is, the area ratio of the grooves to the total area of the grooves and land areas of the tread, has been adjusted to improve driving performance and braking performance. 30% compared to 20% to 30% negative ratio for summer tires
It is said to be as high as ~50%. In addition, heavy-duty pneumatic radial tires for all seasons or winter use have a tread pattern that has a block-shaped land area or a tread pattern that has a land area that is an arrangement of blocks in order to improve driving performance and braking performance. has been done.

Further, if the land portion is large, the rigidity of the land portion increases and the movement of the land portion becomes small, making it impossible to obtain effective driving performance and braking performance for off-road use such as on muddy ground or snow.

For this reason, in order to reduce the rigidity of the land area, 20% or more of the groove depth is
To obtain effective driving performance and braking performance for off-road use by forming multiple cuts (hereinafter referred to as sipes) with a depth of 70% in the land area and promoting the movement of the land area. It has been known.

However, in vehicles that are becoming more versatile, heavy-duty pneumatic radial tires with tread patterns that provide effective driving and braking performance for off-road use are used when driving on dry roads with a high coefficient of friction. There is. Particularly when the vehicle to which the tire is installed is an F/R vehicle, the front-mounted tire has a strong braking force on the ground contact surface, which accelerates the wear of the kick-off portion of the land portion.

Furthermore, as shown in FIG. 5, a plurality of sipes 52 are provided on the land portion 50 in the tire width direction along the left and right direction in FIG.
If they are formed at a predetermined distance in the circumferential direction of the tire (vertical direction in FIG. 5), a force opposite to the traveling direction acts intensively on the kick-out portion 53 between the sipes 52 during braking. do. Therefore, as shown in FIG. 6, the kick-out portion 53 between the sipes 52 of the land portion 50 wears out before other portions. Therefore, uneven wear (heel-ant wear) occurs in the land portion 50 in which the cross-sectional shape seen from the width direction of the tire is sawtooth, resulting in a problem that the appearance, noise resistance performance, and off-road driving performance are deteriorated.

[Problems solved by the invention]

The present invention has been made in consideration of the above facts, and an object of the present invention is to obtain a heavy-duty pneumatic radial tire that can reduce uneven wear of the land portions formed in the tread portion.

[Means and actions to solve the problem]

In the present invention, a belt layer and a tread portion are sequentially wound around the outer periphery of a crown portion of a radial carcass extending in a toroidal shape, and this tread portion has a plurality of circumferential grooves arranged at predetermined intervals in the width direction of the tire. A heavy-duty pneumatic radial tire having a land portion defined by a large number of lateral grooves that intersect with at least a portion of the circumferential groove and are arranged at approximately equal intervals in the circumferential direction of the tire, wherein the land portion It is characterized by having a wavy cut formed in a direction that divides the long axis of the tire and at an angle of 35° to 55° with respect to a direction parallel to the equator of the tire.

Therefore, in the heavy-duty pneumatic radial tire of the present invention, the depth of cut is 3 in the direction parallel to the equator of the tire.
Since it is formed in the direction of 5° to 55°, preferably 45°, the force acting on the land portion during braking does not concentrate on the kick-out portion between the notches formed in the land portion 50. , acting in sequence along the notch. Therefore, it is possible to distribute the force applied to the land portion over the entire land portion from stepping on to kicking off, and uneven wear of the land portion can be reduced.

[Embodiments of the invention]

A first embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

As shown in FIG. 2, in the heavy-duty pneumatic radial tire 10, both longitudinal ends of a radial carcass 12 extending in a toroidal shape are wound around a bead core 14 formed in a ring shape around the tire rotation axis. This radial carcass 12 is covered with an inner liner rubber layer 16. In addition, radial carcass 1
2 is a known structure consisting of an l-ply or a few briars of a rubberized layer with cords arranged in a radial arrangement.

The crown portion 21 of the carcass 12 is a thick tread portion 18. Further, a known non-extensible belt layer 22 is arranged between the tread portion 18 and the radial carcass 12 to reinforce the tread portion 18.

As shown in FIG. 1, in the tread pattern of the tread portion 18, in this embodiment, three circumferential grooves 24 are provided at predetermined intervals in the tire width direction (left-right direction in FIG. 1). They are arranged in a zigzag pattern along the circumferential direction of the tire. Further, a large number of lateral grooves 26 are provided in the circumferential groove 24.
The horizontal grooves 26 intersect with at least a portion of the grooves and are arranged at approximately equal intervals in the circumferential direction of the tire, and the depth of the lateral grooves 26 is set to be slightly shallower than the circumferential grooves 24.

The land portion 28 defined by the circumferential grooves 24 and the lateral grooves 26 has an average angle θ with respect to a direction that separates the long axis 30 of the land portion 28 and parallel to the equator 32 of the tire. in the range of 35° to 55°, preferably 4
Zigzag-shaped sipes 34 and 36 with an angle of 5° are formed.

The depth of the deepest part of the sipe 34.36 is the same as that of each groove 24.36.
Sipe 34 is considered to be 60% to 90% of the depth of Sipe 26.
．． The width of 36 is 0.5 mm to 1.2 mm.

Further, both ends 34A and 34B of the sipe 34 reach either the circumferential groove 24 or the lateral groove 26,
Only one end 36A of the sipe 36 reaches either the circumferential groove 24 or the lateral groove 26.

Next, the operation of this embodiment will be explained.

When the vehicle equipped with the heavy-duty pneumatic radial tire 10 of this embodiment enters a braking state, force acts on the land portion 28 from the road surface. In this case, in the heavy load pneumatic radial tire 10 of the present invention, the sipe is 34.36.
is between 35° and 55°, preferably 4° relative to the tire equator.
It is formed in the direction of 5°. Therefore, the force acting on the land portion 28 during braking does not concentrate on the kicking part between the sipes 34 and 36 of the land portion 28, and the sipe 34
．． 36 in order. Therefore, the entire land portion 28 absorbs the force applied to the land portion 28 from the time of stepping on to the kick-off, and the force can be dispersed, thereby reducing uneven wear of the land portion 28.

Also, due to the sipes 34 and 36 in the land part 28, the land part 28
In addition to reducing the overall rigidity, the rigidity of each part within the land section 28 can be made uniform, and by arranging multiple sipes 34 and 36, the rigidity within the land section is further reduced and driving performance during off-road use is improved. can be done.

Moreover, by making the sipes 34 and 36 into a zigzag shape, the edge component of the pattern that has a high correlation with the snow column shear force, that is, the edge length, increases, and the performance on snow is improved.

Further, by orienting the sipe end in a direction substantially parallel to the equator of the tire, it is possible to prevent stress from being concentrated at the sipe end within the land portion 28 during braking and from generating cracks at this location.

Next, a second embodiment of the present invention will be described with reference to FIGS. 3 and 4.

Incidentally, the same members as in the first embodiment are given the same reference numerals and the explanation thereof will be omitted.

As shown in FIG. 3, in the tread pattern of the tread portion 18, a plurality of circumferential grooves 38 are arranged at predetermined intervals in the width direction of the tire (left-right direction in FIG. 3) in a zigzag pattern along the circumferential direction of the tire. placed in a mold. Further, a large number of lateral grooves 40 intersect with the circumferential groove 38 and are arranged at approximately equal intervals in the circumferential direction of the tire, and a land portion 42 partitioned by these circumferential grooves 38 and lateral grooves 40 is a platform. It is considered to be a base. This land portion 42 has a zigzag shape in the direction dividing the long axis 44 of the land portion 42 and at an angle θ in the range of 35° to 55°, preferably 45° with respect to the direction parallel to the equator 32 of the tire. Sipe 34.36
is formed.

Therefore, the force acting on the land portion 28 during braking is the kick-out portion 3 between the sipes 34 and 36 of the land portion 28, as shown in FIG.
It does not act intensively on 7.

Therefore, uneven wear of the land portion 28 can be reduced.

Therefore, in this embodiment as well, the same effects as in the first embodiment can be obtained.

In the second embodiment, the land portion 42 has a home base shape, but the land portion 42 may have another shape such as a diamond shape instead. Further, in the first and second embodiments, the sipes are of a zigzag shape, but they may be of other wavy shapes instead.

<Experimental example> Second embodiment of the present invention (Fig. 3) and conventional technology (Fig. 5)
Heavy-duty pneumatic radial tire with the tread pattern shown in (tire size 185R14LT8PR)
1 Regular internal pressure 4.5kgf/cfll, front wheel load 580
kg/piece, rear wheel load 780kg/piece) are installed on the one box pan, - 35% on the ship route and 55% on the highway.
Table 1 shows the results of observing the state of wear after driving 20,000 km on a road with a 10% mountain plate.

Table 1 Note that the wear level of the tire of the present invention in Table 1 (symbol Hl in Figure 4) is the wear level of the conventional tire (symbol HO in Figure 6).
It is expressed as an index with 100.

As a result, it was found that the wear level difference of the heavy load pneumatic radial tire of this example was 75% of the wear level difference of the heavy load pneumatic radial tire of the prior art.

The experimental results revealed that the heavy-duty pneumatic radial tire of the present invention described above is particularly excellent.

〔Effect of the invention〕

Since the present invention has the above configuration, it has an excellent effect of reducing uneven wear of the land portions formed in the tread portion.

[Brief explanation of drawings]

FIG. 1 is a plan view showing a tread pattern of a pneumatic radial tire for heavy loads according to a first embodiment of the present invention, and FIG. 2 is a plan view showing a tread pattern of a pneumatic radial tire for heavy loads according to a first embodiment of the present invention. 3 is an enlarged plan view showing a part of the tread pattern of a heavy-duty pneumatic radial tire according to a second embodiment of the present invention; FIG. 4 is a sectional view with hatching partially omitted; FIG. 5 is an enlarged plan view showing a part of the tread pattern of a conventional pneumatic radial tire for heavy loads; FIG. 6 is a sectional view taken along line Vl-VI in FIG. 5; lO...Pneumatic radial tire for heavy loads, 12...
- Carcass, 18... Tread part, 22... Belt layer, 24.38... Circumferential groove, 26.40... Lateral groove, 28... Land part, 34.36... Sipe.

Claims (3)

[Claims] (1) A belt layer and a tread part are sequentially wound around the outer periphery of the crown part of a radial carcass extending in a toroidal shape, and this tread part has a plurality of circumferential grooves arranged at predetermined intervals in the width direction of the tire, and a plurality of circumferential grooves arranged at predetermined intervals in the width direction of the tire. In a heavy-duty pneumatic radial tire having a land portion defined by a large number of lateral grooves that intersect with at least a portion of the directional grooves and are arranged at approximately equal intervals in the circumferential direction of the tire, the land portion 1. A pneumatic radial tire for heavy loads, characterized by having wavy cuts formed in a direction that divides a long axis and at an angle of 35° to 55° with respect to a direction parallel to the equator of the tire. (2) Claim (1) characterized in that the depth of the deepest part of the cut is 60% to 90% of the depth of the groove.
Heavy-duty pneumatic radial tires listed. (3) The pneumatic radial tire for heavy loads according to claim (1), wherein the width of the cut is 0.5 mm to 1.2 mm.