JPH02246806A - Pneumatic tire for heavy load preventing lopsided wear - Google Patents

Abstract

PURPOSE:To reduce lopsided wear concerning the above-mentioned tire for a bus etc. by forming a downstepped level difference area at the end of a tread and providing a cutout with a radial cross section in a (L) or crank shape along the periphery of the tread in the boundary of an adjacent land portion thereto. CONSTITUTION:A downstepped level difference area 3 is formed at the end of a tread and a cutout 4 is formed along the periphery of the tread in the boundary of a land portion 2 thereto. This cutout 4 is formed into a (L) or crank shape. Such constitution permits effective dispersion and relaxation of outer force resulting from the grounding face of the tread end and reduction of lopsided wear as well as avoidance of ribtear etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) Pneumatic radial tires mounted on heavy vehicles such as buses and trucks suffer from significant uneven wear, particularly at the tread ends.

The present invention relates to pneumatic tires mounted on such vehicles, and is intended to effectively reduce and improve uneven wear of the tires.

(Conventional technology) Regarding reducing and improving uneven tread wear, there have been many proposals for adding innovations to the crown shape and pattern, but uneven wear at the edges of the tread (shoulder wear) in particular has not yet been addressed. At present, no accurate preventive measures have been established.

Incidentally, JP-A-58-194606 proposes a tire having a structure in which lateral ribs are formed at the end of the tread in a narrow, substantially annular group in the circumferential direction.
Even in such tires, the ribs themselves were missing due to stone engraving in the circumferential groups, and although it was possible to slow down the progress of uneven wear, it was not possible to prevent it.

(Problems to be Solved by the Invention) It is an object of the present invention to propose a heavy-duty pneumatic tire that can advantageously reduce or prevent uneven wear at the tread edges of the tire without adversely affecting tire performance.

(Means for solving the problem) The uneven wear that occurs on this type of tire naturally depends on driving conditions and road surface conditions, but (when cornering, the edge of the tire's tread gets away from the road surface). It is thought that an excessive external force (lateral force) acts on the area, generating a nucleus that causes uneven wear, and that this is accelerated when driving straight.In order to reduce and improve such uneven wear, it is necessary to We have found that it is extremely effective to alleviate the external forces acting on the system as much as possible.

This invention is based on the above knowledge.

In other words, the present invention provides a heavy-duty pneumatic tire that has a groove on the entire surface of the tread and a land area separated by the groove, in which a stepped area is formed at the end of the tread, and the stepped area and the land area separated by the groove are formed. This is a heavy-duty pneumatic tire that prevents uneven wear and is characterized by having an L-shaped or crank-shaped notch along the tread circumference at the boundary with the connected land area.

Now, in FIG. 1, the main part of the case where this invention is applied to a pneumatic radial tire for heavy loads is shown in cross section of only one side of the tread end. The groove part 1 and the land part 2 are arranged on the entire surface of the tire tread,
Forms tread patterns such as blocks, lips, lugs, or ribs/lugs.

Further, 3 is a stepped region formed at the end of the tread, and 4 is a notch formed along the periphery of the tread at the boundary between the step region 3 and the land portion 2 connected thereto. The bridge is L-shaped to prevent the step area 3 from being damaged by stones etc., and has the role of reducing the ground pressure in that area and reducing the burden of lateral force during cornering along with the step area.

Further, FIGS. 2 and 3 show an example in which the notch 4 is shaped like a crank to further reduce the ground pressure in that area.

The internal structure of the pneumatic tire illustrated in FIGS. 1, 2, and 3 above is the same as that of a heavy-duty pneumatic radial tire for boat fishing, and is not shown here.

(Function) Generally, when a tire moves under load, the ground pressure on its tread surface is almost constant in the width direction of the tread when driving straight, but when cornering in particular, it becomes distributed as shown in Figure 4. Experiments have shown that the local increase in ground pressure caused by such lateral forces is the main cause of uneven wear and tear.

In this invention, first, a step region 3 is provided at the tread end of the tire to help reduce ground contact pressure, and a notch 4 is further provided at the boundary between this step region 3 and the land portion 2, so that the tread end External forces received from the road surface are effectively dispersed and alleviated as shown in FIG. 5, so there is no risk of uneven wear that significantly affects the life of the tire, and rib tears and the like are advantageously avoided.

Here, as for the step C in the step region 3, if the step C is small, the notch 4 will not engage with the ground when traveling straight, and especially if the notch 4 moves in the direction of opening, the notch 4. Stress concentration at the bottom of the groove is likely to occur, and rib tears are likely to occur. Therefore, the lower limit is 1.5 ffIf11, which is a value that allows the surface of the step area to contact the ground with a lateral force of 1/10 when the tire is filled with the regular internal pressure and the tire's regular load is small.
3. It is preferable to set it to about Otnm. On the other hand, regarding the upper limit, in normal driving, the lateral force applied to the tire is 2 times the normal load.
Since it is rare that the load exceeds 710, the step area should touch the ground when a lateral force is input, and in order to bear this lateral force, the surface of the step area should touch the ground with a lateral force of 3/10 of the normal load. , preferably about 0 to 6.0 m.

(Example) Test tires of sizes 11R22, 5, and 14PR (internal pressure 7.OOkgfloa) having the structure shown in Figure 6 (a) (b) (c) (d) were loaded with a normal load of 11 .5), and the axle type is 2D-4.
The wear status of the tire tread surface was investigated after completing the 60,000-mile race (0x). In addition, in this test, Figure 6 (
The tire shown in a) was used as a reference tire. Table the results.
Shown in 1.

Table 1 A rib tear test was conducted in which the vehicle repeatedly ran up and down steps with a height of 10 cm. The results are shown in Table 2, and the tire according to the present invention had a very small crank length at the notch, and no dropout in the step area was observed.

Table 2 In the second embodiment, the width of the step area is not taken into account;
As is clear from the above table, it was confirmed that the tire according to the present invention had an extremely small uneven wear index (the smaller the better). Further, when the tire was observed in detail after running, it was found that the standard tire had localized wear at the edge of the tread as shown in Figure 7(a), whereas the tire according to the present invention had local wear at the edge of the tread as shown in Figure 7(b). ) to (d), the wear was almost uniform.

Next, test tires shown in FIGS. 8(a) and 8(b) were prepared, each of these tires was mounted on the front wheels of a 2D-4 vehicle, and loaded with 100% of the normal carrying load (invention Effects of the Invention According to the present invention, uneven wear at the tread edges can be reduced and the life of the tire can be significantly extended without adversely affecting the running performance of the tire.

[Brief explanation of drawings]

1, 2, and 3 are cross-sectional views of main parts of a heavy-duty pneumatic tire according to the present invention; FIGS. 4 and 5 are diagrams showing the distribution of ground pressure at the tread end of the tire; Figure 6 (a) (b) (c) (d) is a cross-sectional view of the main part of the tire used in the example, Figure 7 (a) (b) (c) (d) is the tire tread surface after the running test. Diagram showing the wear status of
Figures (a) and (b) are sectional views of main parts of the test tire used in the beam tire test. 1...Groove portion 2...Land portion 3...Step area 4...Notch Fig. 1 Fig. 2

Claims (1)

[Scope of Claims] 1. In a heavy-duty pneumatic tire having a groove on the entire surface of the tread and a land area separated by the groove, a stepped area is formed at the end of the tread, and this stepped area A pneumatic tire for heavy loads that prevents uneven wear, characterized in that a notch having an L-shaped or crank-shaped radial cross section along the periphery of the tread is provided at the boundary between the tread and the connected land area.