JPS62241709A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PURPOSE:To prevent the eccentric abrasion by dividing a tread part into a pair of outside regions positioned on the outside in the direction of width, center region and a pair of intermediate regions positioned between the outside regions and center region and forming a projection part at least in one intermediate region. CONSTITUTION:As for a pneumatic tire for heavy load, a plurality of main grooves 6 extending in the peripheral direction are formed on the tread part 5, and the tread part 5 is divided into a pair of outside regions 10 positioned on the outside in the direction of width, center region 11 positioned at the center in the direction of width, and a pair of intermediate regions 12 positioned between the both regions 10 and 11. In this case, a projection part 13 which projects outwardly in the radial direction and extends in the circumferential direction is formed at the part having a low set pressure in a train 7 of highland parts in the intermediate region 12. Therefore, the rigidity is improved by increasing the body thickness of the tread 5 in the part where the projection part 13 is formed, and the ground contact pressure of the part is increased, and the drag in the intermediate region 12 is prevented, and the eccentric abrasion is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a heavy-duty pneumatic radial tire with improved uneven wear resistance.

In general, the tread portion of heavy-duty pneumatic radial tires used for trucks, buses, etc. has a ri-diameter tread, and the outer widthwise part and the widthwise center part thereof are respectively The sidewalls and belts have high rigidity due to the internal pressure. Therefore, when the regular internal pressure is filled and the regular cylinder is acting, the ground contact pressure of the tread part of the tire is It is high in the area, and low in the pair of intermediate areas between the @ alignment side area and the central area.

It looks like t. Therefore, when such a heavy-duty pneumatic tire is running, drag occurs in the intermediate region where the ground contact pressure is low, and this region is partially worn, and the wear progresses faster than in other parts.

For this reason, in the case of a rib tie having a plurality of main grooves in the tread portion, there is a problem in that uneven wear such as river wear and rib punching occurs in the ribs located in the intermediate region.

Such a problem arises when the tread portion of a heavy-duty pneumatic radial tire is formed with a plurality of side grooves extending in the circumferential direction. A pair of outer regions located at the center in the width direction, a central region located at the center in the width direction, and a pair of intermediate regions located between the outer region and the center region, and divided into five in the width direction, and at least one of the This can be solved by providing a protrusion in the intermediate region that protrudes radially outward and extends circumferentially.

Since the protrusion that protrudes outward in the radial direction and extends in the circumferential direction is provided in the intermediate region, the wall thickness of the area where the protrusion is provided becomes thicker and the rigidity increases. The stiffness is approximately equal to the stiffness of the region and the center region, and the stiffness is averaged over the entire surface of the tread. As a result, the ground contact pressure of the tread portion becomes uniform throughout, resulting in uneven llj! It is possible to prevent the occurrence of wear and tear.

LL: Hereinafter, a first embodiment of the present invention will be described based on the drawings.

In FIGS. 1 and 2, 1 is a pneumatic tire for freight cargo used for trucks, buses, etc., and this tire 1 extends from one bead to the other bead (not shown) at least 1r! It has a carcass layer 3 of I. In this carcass layer 3, a large number of substantially straight cords are embedded in the equatorial plane 2 of the tire 1. In addition, carcass layer 3
At least two annular belt layers 4 are disposed on the outside in the radial direction, and these belt layers 4 include a large number of belt layers that intersect at a predetermined angle with respect to the equatorial plane 2 and intersect with each other between adjacent layers. A metal cord is buried at 1'. The tire 1 has a tread portion 5 having a radius of curvature (tread radius) of 100 mm, and the tread portion 5 has a plurality of (four in this embodiment) main grooves 6 extending in the circumferential direction and bent in a zigzag manner. are formed, and on both sides of these main grooves 6, land portion rows 7 extending in the circumferential direction are formed.
It is defined by grooves 6. When such a tire l is filled with a regular internal pressure and is run with a regular load applied to it, the ground contact pressure of the pair of outer regions 10 and the center region 11 becomes higher than the ground contact pressure of the pair of intermediate regions 12. It is known empirically from the shape of prints, etc. Here, the outer region 10 refers to a pair of regions located on the outer side in the width direction of the tread section 5, which is divided into five equal parts in the width direction from one tread end 14 to the other tread end 15, Further, the central region 11 is a region located at the center in the width direction, and the intermediate region 12 is a pair of regions located between the outer region IO and the central region 11. In this way, the ground pressure in the outer 11111f1'I region 10 is higher than the ground pressure in the intermediate region 12, and the reason why the ground pressure in the central region 11 is higher than that in the intermediate region 12 is because
This is probably because the central region 11 has high rigidity under the influence of the internal pressure and the belt layer 4. Here, the tire 1
Depending on the type, the ground pressure of the entire intermediate region 12 may be low, or the ground pressure of a part of the intermediate region 12 may be low. Therefore, in the present invention, a protrusion 13 that protrudes radially outward and extends in the circumferential direction is located in a portion of the land section row 7 in the intermediate region 12 where the ground pressure is low (a part or the whole of the intermediate region 12).
will be established. As a result, the wall thickness of the tread portion 5 increases in the portion where the protruding portion 13 is provided, and the rigidity improves, thereby increasing the ground pressure in this portion, and the ground pressure in the intermediate region 12 is lower than that in the outer region 1. , approximately equal to the ground pressure in the central region 11. As a result, dragging in the intermediate region 12 is prevented.
As a result, the rate of menopause becomes uniform throughout the tread portion 5, and uneven menopause caused by river wear, rib punch, etc. can be prevented. In addition,
Depending on the type of tire, the low ground pressure area may extend to part of the outer region 10 and central region 11;
In this case, a protrusion connected to the protrusion 13 of the intermediate region 12 may be provided in the region 1O111, and the protrusion a of the protrusion 13 is preferably in the range of 0.1 mm to 2.0 am. This is because if it is less than 0.1 tsm, the rigidity of the part where the protrusion 13 is provided can hardly be improved, and if it exceeds 2.0 am, only the protrusion 13 will touch the road surface. This is because you will end up hitting one side. A land column within the intermediate area 12 as shown in FIG. When the protrusions 13 are provided throughout, the ground pressure is improved and averaged from the value before the protrusions 13 (shown by the imaginary line) to the value shown by the solid line, as shown in FIG.

Note that uneven wear in the intermediate region 12 may progress due to side force, so the protrusion 13
It may be provided in either one of the two areas.

Next, we will show the results of a wear test.The size of the tires used in this test was TB R10,00R20, and what rims were used? , 50V20, and the tire was filled with the normal internal pressure specified by JIS and a normal load was applied. The tires used were the ribbed tires shown in FIGS. 1 and 2, and the internal structures such as the carcass layer were the same in the conventional tire and the test tire to which the present invention was applied. Further, the protrusion a of the protrusion is 0.3 am. Also, what is the wear of the land rows provided with the protrusions when such conventional tires and test tires are mounted on an actual vehicle and traveled for 50,000 km? compared. the result.

The conventional tire had a wear index of 1oo, and the test tire had a wear index of 70. In addition, in this test, the smaller the wear index, the better.

FIG. 4.5.6 shows a :j'S2 embodiment of the present invention. In this embodiment, each day/section row 7 is divided by a plurality of lateral grooves 21 that are spaced apart in the circumferential direction and carried approximately in the l1il+ direction. In addition, in this tire 1, the ground pressure is low at the outer side in the width direction of the land row 7 located in the intermediate region 12, as shown by the imaginary line in FIG. The protrusion 22 is provided as shown in FIG. 5, and the ground pressure is averaged as shown by the solid line in FIG.

i7's7 and 8 are diagrams showing a third embodiment of the present invention. In this example, the ground pressure of tire 1 is 8th
As shown by the imaginary line in the figure, it is low at the inner side in the width direction of the land row 7 located in the intermediate region 12, so that I'0
．． A gentle mountain-shaped protrusion 23 having a length L is provided as shown in FIG. 7, and the ground pressure is averaged as shown by the solid line in FIG.

Figures 9 and 10 are diagrams showing a fourth embodiment of the invention.

In this example, the ground pressure of Y/R 1 is 10th
As shown by the imaginary line in the figure, the widthwise central part of the land row 7 located in the intermediate region 12 is low, so a gentle mountain-shaped protrusion 24 with a peak is provided in this part as shown in FIG. , the ground pressure is averaged as shown by the solid line in Figure 1O.

As explained above, according to the present invention, the ground contact pressure of the tread portion is made uniform throughout, and uneven wear can be prevented from occurring.

[Brief explanation of drawings]

1 is a plan view of a tread portion of a tire showing a first embodiment of the present invention, FIG. 2 is a sectional view taken along the line II in FIG. 1, and FIG.
Figure 4 is a graph showing the ground pressure distribution, Figure 4 is a plan view of the tread portion of a tire showing a second embodiment of the present invention, Figure 5 is a sectional view taken along the -I1 arrow in Figure 4, and Figure 6. 7 is a sectional view similar to FIG. 2 showing the third embodiment of the present invention, FIG. 71S8 is a graph showing the ground pressure distribution, and FIG. 59 is the fourth embodiment of the present invention. Second example
FIG. 10, which is a cross-sectional view similar to the one shown in the figure, is a graph showing the ground pressure distribution. 10...Outer area 11...Central area 12.
...Intermediate region 13, 22, 23, 24...Protruding portion Patent applicant Brideston Co., Ltd. Agent Patent attorney Ta 1) Toshio Figure 7 Figure 8 □ Tread width direction position □ Figure 9 Figure 10 □ Tread width direction position□

Claims (1)

[Claims] In a heavy-duty pneumatic radial tire in which a plurality of main grooves extending in the circumferential direction are formed in the tread portion, the tread portion is divided into a pair of outer regions located on the outside in the width direction and a central region located in the center in the width direction. , a pair of intermediate regions located between the outer region and the central region are divided into five in the width direction, and at least one of the intermediate regions is provided with a protrusion that protrudes outward in the radial direction and extends in the circumferential direction. A pneumatic radial tire for heavy loads.