JPH04228308A - Steel radial tire for heavy load - Google Patents

Abstract

PURPOSE:To suppress the movement of rubber during the travel of a tire so as to suppress heating and reduce abnormal wear by disposing lug grooves at a tread shoulder part, and providing each lug groove with a raised part. CONSTITUTION:Lug grooves 2 extended toward the tire equator C from the tread edge E are provided at a tread shoulder part 5, and each lug groove 2 is provided with a raised part 4 raised from the groove bottom 3.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention provides lug grooves in the tread shoulder and protrusions in the lug grooves to suppress the movement of rubber during tire running, suppress heat generation, and reduce abnormal wear. Regarding Uru heavy duty steel radial tires.

0002

[Prior Art] Heavy-duty steel radial tires used for buses, large trucks, etc. have been designed to improve durability by reducing heat generation, running stability, and driving force.
As shown in Fig. 5, there are lug grooves a in the tread shoulder part sh.
A traction pattern with a block type is formed by providing a traction pattern.

0003

[Problem to be Solved by the Invention] However, when the lug grooves a are provided as described above, the rubber forming the block b is destroyed by the impact that the block b receives from the road surface while driving, and the surface is gouged out, creating a recess. Otherwise, abnormal wear such as so-called block punching occurs, such as the edge of block b becoming sagging or chipping.

[0004] Such block punching appears conspicuously in tires in which the pitch between lug grooves is made uneven as a measure to reduce noise.

In addition, in order to prevent the occurrence of block punching, as shown in FIG.
There are tires in which a rib h is provided on the tire and the shoulder part sh is continuous in the circumferential direction of the tire, but the ribbing results in insufficient heat dissipation and the durability of the tread part decreases due to heat generation.

As a result of intensive research to solve the above-mentioned problems, the inventor discovered that punching of the lugs or blocks could be reduced by providing a raised portion in the lug groove located in the tread shoulder portion, and completed the present invention. It was.

[0007] The present invention improves heat resistance and running stability by providing a raised part in the lug groove located at the tread shoulder part and regulating the height and length of the raised part in the axial direction of the tire. The object of the present invention is to provide a heavy-duty steel radial tire that can suppress the occurrence of punching of lugs or blocks and increase the durability of the tread portion without degrading the durability.

[0008]

[Means for Solving the Problems] The present invention provides a load bearing comprising a lug groove extending from the tread edge toward the tire equator, and a protrusion protruding from the groove bottom located in the tread shoulder portion of the lug groove. It is a heavy duty steel radial tire.

[0009]

[Function] Since the tire has lug grooves extending from the tread edge toward the tire equator, running stability is good and heat generation is suppressed. Furthermore, since the lug grooves are provided with protuberances that are located in the tread shoulders and protrude from the groove bottom, the tire has a tread pattern in which the lug grooves are arranged with pitch variations for the purpose of reducing noise. This also eliminates the sagging of the lugs or blocks, suppresses chipping of the lugs or blocks, that is, punching, and increases the durability of the tread portion.

[0010] When the height H from the groove bottom to the top of the raised part and the lengths L1 and L2 from the top of the raised part to the groove bottom are respectively regulated, the block punching resistance performance and heat generation property are balanced. This improves the durability of the parts without compromising running stability.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In the figure, a heavy-duty steel radial tire 1 has lug grooves 2 extending from a tread edge E toward the tire equator C, and the lug grooves 2 are provided with protrusions 4 that protrude from the groove bottom 3.

[0012] The steel radial tire 1 for heavy loads is
The tire has sidewall portions 13, 13 extending inward in the radial direction of the tire from both ends of the tread portion 12 where the lug grooves 2 are present, and bead portions 15, 15 located at the inner ends of the sidewall portion 13 in the radial direction. A toroidal steel radial carcass 17 passing through the sidewall parts 13, 13 and the tread part 2 is bridged between the bead cores 16, 16 provided in each of the bead parts 15, 15, and the radially outer side thereof and the tread part. A belt layer 19 is disposed within 12.

The carcass 17 is a so-called radial or semi-radial arrangement in which carcass cords are arranged at an angle of 70 degrees to 90 degrees with respect to the equator C of the tire, and steel cords are used as the carcass cords. will be adopted.

In this embodiment, the belt layer 19 has four belt plies arranged from the carcass 17 side toward the outside in the radial direction of the tire.

Each belt ply of the belt layer 19 also includes belt cords arranged at an angle and intersecting each other,
Steel is mainly used for the belt cord.

[0016] On the outer peripheral surface of the tread portion 12, first vertical grooves G1, G1, which are bent in a zigzag manner and have a small groove width, are provided on both sides of the tire equator C. Further, the tread portion 12 is provided with a plurality of lug grooves 2 extending from the tread edge E toward the tire equator C, bending in a zigzag shape, and communicating with the first longitudinal groove G1.

In this embodiment, two first vertical grooves G1, G
A plurality of central lateral grooves F that connect between 1 and bend in a Z-shape.
1... and a joint groove 21 that connects the lug grooves 2, 2 and forms a side longitudinal groove G2 that goes around the tread surface 12A in a zigzag shape in the tire equator direction together with the intermediate part of the lug groove 2. In addition, in this embodiment, the center line L of the vertical groove G2 on the side portion extends from the tire equator C by a distance that is 1/4 times the tread width TW, which is the distance in the tire axial direction between the tread edges E, E.
Therefore, the center line L connects the tread surface 12A to the center line L sandwiching the tire equator C, the tread crown portion 22 on the inside of L, and the center line L. L and the tread shoulder portion 5 between the tread edge E.

Further, the tread surface 12A has a first longitudinal groove G1.
, G1 between the first longitudinal groove G1, G1 and the central horizontal groove F.
1, a crown block row CH consisting of S-shaped crown blocks CB surrounded by F1, a first vertical groove G1, a joint groove 21, a first vertical groove G1 and a joint groove 21 of the lug groove 2; an intermediate block row MH consisting of hexagonal intermediate blocks MB surrounded by a portion between the intermediate blocks MB, the joint groove 21, the lug grooves 2, 2 in the region of the tread shoulder portion 5, and the tread edge E. Shoulder block row S consisting of pentagonal shoulder blocks SB
H is formed, and these blocks CB, MB, and SB form a block pattern.

The lug groove 2, the first vertical groove G1, the central lateral groove F1 and the joint groove 21 have groove depths Do of approximately the same dimensions in this embodiment, and the groove depth Do in this embodiment. Grip force is increased by making 0.08 to 0.12 times the tread width TW. Further, sipes 23 are provided on the outer surfaces of the crown block CB, intermediate block MB, and shoulder block SB.

Furthermore, in this embodiment, between the adjacent lug grooves 2, 2, the groove pitches P1, P2, P3, which are the distances between the centers, are not equal, but the adjacent groove pitches P1, P2 and P2, P3 are not equal.
3 gives different so-called pitch variations. The difference between the maximum value and the minimum value of groove pitches P1 to P3 is 0.05 to 0.12 of the average pitch of groove pitches P1 to P3.
Preferably, the range is twice as large, and the arrangement is random. By arranging the lug grooves 2 with pitch variations in this manner, the impact sound caused by the blocks colliding with the road surface during running is dispersed, and noise can be reduced. Note that the groove pitch may be uniform over the entire area.

The raised portion 4 is provided at the tread shoulder portion 5 of the lug groove 2 as described above. The raised part 4 is the top part 6
is approximately flat, and the height H from the groove bottom 3 to the top 6 of the lug groove 2 is 0.28 times or more the groove depth D of the lug groove 2 and 0.
50 times or less, and the length L1 of the top part 6 in the tire axial direction is 0.05 times or more and 0.25 times or less of the tread width TW, and the length L2 of the raised part 4 at the groove bottom 3 in the tire axial direction is set to be at least 0.10 times and at most 0.25 times the tread width TW, and the length L2 at the groove bottom 3 is set at least the length L1 at the top. Therefore, the cross section of the raised portion 4 in the tire axial direction has a trapezoidal or rectangular shape.

Note that the raised portion 4 is located at the tire equator C at its top 6.
It is preferable that the distance N of the side edge P from the tire equator C is at least 0.25 times and at most 0.3 times the tread width TW.

The top portion 6 of the raised portion 4 is continuous with the groove wall 8 of the lug groove 2, ie, the side wall of the shoulder block SB, as shown in FIG. 3 in terms of its shape in the width direction.

If the height H of the raised portion 4 is less than 0.28 times the groove depth D, the punching resistance will deteriorate, and if it exceeds 0.5 times, the heat resistance will be poor, and the running stability and wet grip will deteriorate. Sexuality decreases.

[0025] The length L1 of the top portion 6 is 0.0 of the tread width TW.
If it is less than 05, the bridging between the shoulder blocks SB on both sides of the lug groove 2 will be insufficient, resulting in a decrease in punching resistance. On the other hand, if it exceeds 0.25 times, the running stability and grip performance will deteriorate, the worn appearance of the tread surface will be poor, and the manufacturing cost will increase.

Furthermore, the length L2 at the groove bottom 7 is the tread width T.
If it is less than 0.1 times W, the punching resistance will be poor;
If it exceeds 5 times, running stability and grip performance will deteriorate, heat resistance will be poor, and durability will decrease.

The raised portions 4 may be provided in all the lug grooves 2 or may be provided every two pitches, but in order to improve the block punching resistance, it is preferable to provide them in all the lug grooves 2.

[Specific example] ■ The heat generating tire size is 285/75R24.5 and the size shown in Fig. 1
The tread pattern has a tread pattern shown in FIG. Tires formed to each dimension 0.25 times the tread width TW (
Concrete example) was prototyped, and 8.
The vehicle was run at a speed of 80 kg/H with a load of 2.550 kg under an internal pressure of 0 kg/cm2, and the heat generation temperature was investigated over substantially the entire tread area.

For comparison, there is a conventional structure in which no raised portion is provided in the lug groove (Comparative Example 1, the structure shown in FIG. 5), and a structure in which the tread shoulder part is ribbed (Comparative Example 2, shown in FIG. 6). (configuration) and also tested it.

The test results are shown graphically in FIG. In the figure,
The horizontal axis indicates temperature measurement points in the tire axial direction. Further, the buttress is the vicinity of the opening end of the side wall of the lug groove, and in Comparative Example 2, it is located at the corresponding position.

As a result of the test, the heat generation temperature of the specific example was lower than that of Comparative Example 2, especially in the shoulder region, and there was no significant difference over the entire area compared to Comparative Example 1. It was found that the heat generation property was not impaired.

(2) Punching Resistance Performance Durability tests were conducted on the tire of the specific example described above and the tire of Comparative Example 1 in section (2).

The test was conducted using an indoor tire running tester, and the punching incidence was measured at each stage of tread surface wear. The test results are shown in Table 1.

The punching occurrence rate is expressed as a percentage of the number of shoulder blocks in which punching has occurred with respect to all the shoulder blocks SB constituting the shoulder block row SH. Further, the wear stage of the tread is expressed as a percentage of the ratio of the wear amount to the wear limit, and the wear amount was determined by measuring the remaining depth of the lug groove.

[0035] As a result of the test, it was found that the block punching of the example was significantly reduced and the durability was improved compared to Comparative Example 1 in which no raised portion was provided.

[0036]

[Effects of the Invention] As described above, the heavy-duty steel radial tire of the present invention has raised portions located in the tread shoulder portions of the lug grooves, and also regulates the height and length of the raised portions in the axial direction of the tire. Therefore, the occurrence of block punching can be suppressed and the durability of the tread portion can be increased without deteriorating heat resistance, running stability, and grip performance.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a developed tread surface of a tire according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a cross section of the tire taken along the line X-X.

FIG. 3 is a sectional view showing a cross section of the tire taken along the Y-Y line.

FIG. 4 is a graph showing the relationship between the position of the tread portion and the heat generation temperature.

FIG. 5 is a developed plan view showing a conventional tread pattern.

FIG. 6 is a developed plan view showing a conventional tread pattern.

[Explanation of symbols]

2 Lug groove 3 Groove bottom 4 Raised part 5 Tread shoulder part 6 Top C Tire equator D Groove depth E Tread edge H Height of raised part L1 Top length L2 Length at groove bottom

Claims (2)

[Claims] 1. A steel radial tire for heavy loads, comprising a lug groove extending from the tread edge toward the tire equator, and a protrusion protruding from the bottom of the lug groove located at the tread shoulder portion. 2. The raised portion has a height (H) from the bottom to the top of the groove that is 0.28 times or more and 0.50 times or less than the groove depth (D) of the lug groove, and the raised portion The length (L1) in the axial direction of the tire at the top of the tread width (TW) is 0.
05 times or more and 0.25 times or less, and the length (L2) in the tire axial direction at the groove bottom of the raised portion is 0.10 times or more and 0.25 times or less of the tread width (TW), and the groove bottom The length (L2) at the top is the length (L2) at the top (
The heavy-duty steel radial tire according to claim 1, wherein the steel radial tire has a temperature of L1) or more.