JPH08132826A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PURPOSE: To prevent the occurrence of the biased abrasion irregularly abraded in the peripheral direction by arranging fine grooves driftingly in the tire peripheral direction from oblique lines at part of land sections among the fine grooves arranged at the land sections on the oblique lines inclined to the one direction side or the other direction side against the equatorial plane of a tire having a directional pattern. CONSTITUTION: The acute angle portions 12, 13 of pattern blocks 10, 11 formed by fine grooves 8, 8', 9, 9' and main grooves 2 are drifted by a half of the oblique line interval in the tire peripheral direction. The acute angle portions 12, 13 are surrounded by land sections having high rigidity, and the movement of these portions is suppressed small when a tire is rotated. In the adjacent land sections 3, 4 and 6, 7, the acute angle portions 13 of the pattern blocks 11 of the land sections 3, 7 and the acute angle portions 12 of the pattern blocks 11 of the land sections 4, 6 are adjacently located across the main grooves 12, and the biased abrasion resistance of the tread pattern center portion is improved.

Description

Detailed Description of the Invention

[0001]

[Industrial field of application] Radial tires mounted and used in heavy-duty vehicles such as trucks and buses are equipped with a so-called directional tread pattern on the tire treads, and the uneven wear resistance of the treads is Regarding improvement.

[0002]

2. Description of the Related Art In order to improve running performance on a wet road surface, in a pneumatic tire for heavy loads such as trucks and buses, a plurality of main grooves extending substantially along the equatorial plane of the tire are provided. , A tire equipped with a so-called directional tread pattern that is composed of narrow grooves that are arranged on the diagonal line that is inclined in one direction and the other direction with respect to the equatorial plane of the tire across the main grooves has been tried. There is. In such a directional tread pattern, generally, when the tire is grounded on the road surface, the central portion of the tire tread in the axial direction of the tire is grounded first, and then gradually grounded in the direction of both ends. The rotation direction of the tire is designated so that the tire comes into contact with the ground in a direction in which the diagonal lines of the one direction and the other direction intersect.
Therefore, when the tire travels on the wet road surface, the water that has entered between the tire and the road surface is arranged in each land portion on the oblique line that is inclined in one direction and the other direction with respect to the equator surface as the tire rotates. Along the narrow groove, the tire tread portion is swept away from the central portion of the tire tread portion to both ends and quickly discharged from the tire tread edge. It has also been experimentally confirmed that a tire having a directional tread pattern having such characteristics can provide extremely excellent drainage characteristics when traveling on a wet road surface.

[0003]

However, in such a directional tread pattern, when the tire rolls from the tip of the acute angle portion of the pattern block formed by the main groove and the narrow groove inclined to the main groove. Local wear due to local movement of the pattern block is promoted, and uneven wear is likely to occur in which the tire tread wears unevenly in the tire circumferential direction, especially for heavy loads with high ground pressure. The radial tires have been closed up, and the practical use thereof has not yet been sufficiently advanced.

Therefore, in view of the above situation, an object of the present invention is to provide a heavy-duty pneumatic radial tire provided with a directional tread pattern for preventing uneven wear that is worn in an uneven shape in the tire circumferential direction. That is.

[0005]

To achieve the above object, in a heavy duty pneumatic radial tire according to the present invention, a plurality of main grooves are substantially formed on a tire tread as described in claim 1. A plurality of land portions are formed between adjacent main grooves that extend along the tire equatorial plane, and are arranged and adjacent to each of the land portions on the oblique lines that are inclined in one direction with respect to the tire equatorial plane. Each one of the main grooves adjacent to each other is arranged in each land portion on the oblique line that is inclined in the other direction with respect to the tire equatorial plane, and one narrow groove that opens in each of the main grooves is arranged in the tire circumferential direction. A pneumatic radial tire for heavy load having a tread pattern in which a plurality of the other narrow grooves open in the tire circumferential direction are designated and whose rotation direction is designated, and which is on a diagonal line inclined in the one direction and the other direction. Fine arrangement on each land Trying to comprising the down - narrow groove on the land portion of the inner identified partially Toreddopata arranged offset from oblique line in the circumferential direction of the tire.

[0006]

In the directional pattern of the present invention, on the land portion of a part of the narrow grooves arranged in each land portion on the slant line which is inclined in one direction side or the other direction side with respect to the tire equatorial plane. Since the narrow grooves are displaced from the diagonal line in the tire circumferential direction, the acute angle portion of the pattern block formed by intersecting the main groove and the narrow groove is adjacent to each other through the main groove as compared with the conventional tire. The number of places to do decreases. Based on detailed experiments by the inventors who confirmed the movement of the pattern block at the ground contact portion when rolling the tires by means of an anti-road surface tester, etc., the sharp-angled parts of the pattern blocks formed on adjacent land parts When the tires are adjacent to each other via the main groove (FIG. 6, (a)), the movement of the acute angle portion increases at the moment when the tire rolls and the acute angle portion separates from the road surface, and a large slip occurs. It was confirmed that when the periphery of the portion was surrounded by a highly rigid land portion (FIG. 6, (b)), the movement of the acute angle portion was small and the occurrence of slip was significantly suppressed. Therefore, according to the present invention, by arranging a part of the narrow grooves arranged in each land portion on the slanted line in the tire circumferential direction from the slanted line, the pattern block is arranged. Since the number of adjacent portions of the acute angle portion is reduced, it is possible to appropriately reduce the portion that causes a large slip, that is, the portion that locally wears quickly and becomes the core of uneven wear.

It should be noted that the amount by which one of the narrow grooves provided on each of the adjacent land portions on one of the diagonal lines is displaced in the tire circumferential direction is at least the groove width of the narrow groove and is the It is preferable that the narrow grooves are not arranged on the same diagonal line. When the amount of shift is less than the groove width of the narrow groove, the sharp-angled parts of the pattern blocks formed in the adjacent land parts come too close to each other, and the movement of the sharp-angled parts during tire rolling becomes large. Slip locally occurs, which is disadvantageous for uneven wear.

Further, when the narrow groove is displaced in the tire circumferential direction as described in claim 1, in order to maintain the excellent drainage performance on the wet road surface, which is a feature of the directional pattern, as much as possible, The position of the narrow groove in at least two or more land portions among the fine grooves arranged in each land portion on the oblique line inclined in a predetermined direction with respect to the tire equatorial plane so that the directional pattern is configured in advance. Is preferably left on the diagonal line. If there are less than two land areas where fine grooves are maintained on the same diagonal line, no directional pattern is formed.

[0009]

EXAMPLES Examples will be described below. FIG. 1 shows a tread plan view of a tire 1 of Example 1 in which the present invention is applied to a radial tire having a tire size of 11R22.5. FIG.
In, the main groove 2 having a groove width of 11 mm and a groove depth of 15 mm is provided along the equatorial plane XX of the four tires, and the land portions 3, 4, 5, 6, 7 are divided into the respective main grooves. Has been formed. On the left and right of the equatorial plane XX of the tire, a slanted line A-A and a slanted line B- which are inclined at 45 degrees with respect to the equatorial plane.
B is temporarily installed in the tire circumferential direction at a constant slant line interval, and
-Thin groove 8 with a groove width of 3 mm and a groove depth of 9 mm in the land portions 3 and 4 on A
Is slanted to the upper left in the figure, and fine grooves 8'having the same groove width and groove depth are slanted to the upper right in the land portions 6 and 7 on the slanted line BB. Then, in the left area of the tire equatorial plane of the land portion 5 arranged in the center of the tire tread portion, the diagonal line A
-A narrow groove 9 corresponding to the narrow groove 8 provided in the land portion on A
However, they are arranged at the same size as the narrow groove 8 and at the same upper left slant as the narrow groove 8 and shifted in the circumferential direction by a distance of 1/2 of the diagonal line interval in the circumferential direction of the diagonal line AA. Further, in the right area of the tire equatorial plane of the land portion 5, a narrow groove 9'corresponding to the narrow groove 8'provided in the land portion on the diagonal line B-B is formed in the same manner as the narrow groove 9, It is arranged so as to be inclined to the right by a distance of ½ of the distance between the diagonal lines in the circumferential direction of the diagonal line BB in the circumferential direction.

Since the first embodiment is constructed as described above, the sharp-angled portions 12, 13 of the pattern blocks 10, 11 formed by the narrow grooves 8, 8 ", 9, 9" and the main groove 2 are In the adjacent land portions 4, 5 and 5, 6, the acute angle portion 1
Nos. 2 and 13 are circumferentially displaced from each other in the tire circumferential direction by a distance ½ of the diagonal line interval. Therefore, the periphery of the acute-angled portions 12 and 13 is surrounded by the land portion having a high composition, and the movement of this portion during rolling of the tire is suppressed to be small. On the other hand, in the adjacent land portions 3, 4 and 6, 7, the acute angle portion 13 of the pattern block 11 of the land portions 3 and 7 and the acute angle portion 12 of the pattern block 11 of the land portions 4 and 6 are mainly formed. The grooves 2 are adjacent to each other with the groove 2 interposed therebetween. Therefore, in Example 1, the uneven wear resistance of the central portion of the tread pattern is particularly improved.

Next, a second embodiment shown in FIG. 2 will be described. In Example 2, three treads of the same tire size as those in Example 1 are provided with the main grooves 2 having the same dimensions as in Example 1 along the equatorial plane. The land portions 3, 4, 6, and 7 are formed by these main grooves 2. Equatorial plane of tire X
-A slant line A-A and a slant line B-B inclined to the equatorial plane in the direction of 45 degrees with respect to the equatorial plane are provisionally provided in the tire circumferential direction at a constant slant line interval, and on the land portion 4 on the slant line A-A. A narrow groove 8 having the same size as that of the first embodiment is provided so as to be inclined to the upper left in the figure, and a narrow groove 8 ′ having the same groove width and groove depth as the narrow groove 8 is provided in the land portion 6 on the diagonal line BB. It is provided with an inclination to the right. In the land portion 3 located at the left end of the tire tread portion, the diagonal line A-A
Fine groove 9 corresponding to the fine groove 8 provided on the upper land portion 4
However, they are arranged at the same size as the narrow groove 8 and at the same upper left slant as the narrow groove 8 and shifted in the circumferential direction by a distance of 1/2 of the diagonal line interval in the circumferential direction of the diagonal line AA. Further, in the land portion 7 located at the right end of the tire tread portion, similarly to the narrow groove of the land portion 3, a narrow groove corresponding to the narrow groove 8 ′ provided in the land portion 6 on the diagonal line BB. 9 "is the same size as the narrow groove 8" and the narrow groove 8 "
With the same inclination to the upper right, they are arranged so as to be displaced in the circumferential direction by a distance ½ of the diagonal line interval in the circumferential direction of the diagonal line BB.

Since the second embodiment is constructed as described above, the sharp-angled portions 12, 13 of the pattern block 11 formed by the narrow grooves 8, 8 ", 9, 9" and the main groove 2 are adjacent to each other. In the matching land portions 3, 4 and 6, 7, they are arranged in the tire circumferential direction so as to be displaced from each other in the circumferential direction by a distance of 1/2 of the diagonal line interval,
The periphery of the acute-angled portions 12, 13 is surrounded by the land portion having high rigidity, and the movement of these portions during rolling of the tire is suppressed to be small. On the other hand, in the adjacent land portions 4 and 6, the land portion 4
The acute angle portion 13 of the pattern block 11 and the acute angle portion 13 of the pattern block 11 of the land portion 6 are adjacent to each other with the main groove 2 interposed therebetween. Therefore, in Example 2, the tire was excellent in uneven wear resistance of both end portions of the tire tread surface portion.

Further, FIG. 3 shows a plan view of the tread surface of the tire according to the third embodiment. In Example 3, the tread pattern is composed of four main grooves and five land portions, and the narrow grooves of the land portions 4, 5, and 6 at the center of the tread portion are the conventional directional patterns. In the land portions 3 and 7 arranged at both ends of the tire tread portion, the narrow grooves having the same shape as those of the first and second embodiments, which are inclined to the upper left and the upper right, respectively, are maintained. It is arranged so as to be displaced in the tire circumferential direction by a distance ½ of the diagonal line interval. Therefore, the tire of Example 3 is also a tire excellent in uneven wear resistance of both end portions of the tire tread portion, as in Example 2.

Next, in order to verify the effect of the present invention, the tires of Example 1 and Example 2, the tire size, the main groove,
The tires of the comparative example having the conventional directional tread pattern shown in FIG. 4 were prototyped for several tires and the uneven wear actual vehicle test was carried out with the dimensions such as narrow grooves and tire tread width being the same as those of the embodiment. .

The test direction and test conditions are as follows: A test tire having a JIS standard internal pressure is mounted on the left and right front wheels of a normal truck carrying a load whose load per tire is the JIS standard load. The wear state of the pattern block formed on each land portion of the tire tread surface was observed and measured after traveling for km. In particular, in order to confirm the state of occurrence of so-called heel and toe uneven wear at the acute angle portion of the pattern block, the acute angle portions 12 and 13 of the pattern block and the pattern block facing the acute angle portions 12 and 13 via a narrow groove. The difference in the amount of wear between the obtuse angle portion 14 (the end of the pattern block where the main groove and the narrow groove are intersected to define an obtuse angle) is determined by a normal method using a normal depth gauge. (FIG. 5), and those having a large step were evaluated as having large uneven wear. Specifically, all the step differences measured for the acute angle portions 12 and 13 of the pattern block at six positions on the tire circumference were averaged to obtain the uneven wear generation amount (average step difference, mm) of the corresponding tire.

The test results show that, as shown in Table 1 below, the tires of the comparative examples produced uneven wear of 2 to 3 mm at the average step, whereas the tires of Examples 1 and 2 had almost no step. Therefore, uneven wear was not observed.

[0017]

[Table 1]

In the above embodiment, the slant lines which are inclined in one direction and the other direction with respect to the equatorial plane of the tire are straight lines, but the slant lines may be arc-shaped curves instead of straight lines. In this case, the narrow grooves arranged in diagonal lines are also formed in an arc shape in the longitudinal direction.

Furthermore, in the above-mentioned embodiments, the tread pattern is constructed symmetrically with respect to the tire equator line (plane) with respect to the left and right lines (plane). However, in view of the gist of the present invention, the equator is as described above. The present invention is also applied to a tire having a so-called left-right asymmetric pattern in which the line (plane) is not a symmetrical reference line but the reference line is displaced to the left or right from the equator line (plane) by a certain distance. Is applicable.

[0020]

In the heavy duty pneumatic radial tire of the present invention, the acute angle portion of the pattern block formed by the main groove forming the directional tread pattern and the narrow groove diagonally traversing the main groove is the circumference of the tire. Since it is appropriately distributed in the direction, the rigidity is low in the adjacent land portions, and the portion where the acute angle portion that is easy to move in the ground contact surface when the tire rolls is adjacent is reduced, and the core of uneven wear is generated by the directional pattern. It can be reduced appropriately without losing the drainage performance, which is a feature of.

[Brief description of drawings]

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

FIG. 2 is a plan view of a tread surface of a tire according to a second embodiment of the present invention.

FIG. 3 is a plan view of a tread surface of a tire according to a third embodiment of the present invention.

FIG. 4 is a plan view of a tread surface of a tire having a conventional directional pattern.

FIG. 5 is a diagram showing a method of measuring a heel & toe wear step.

FIG. 6 (a). The state where the acute-angled parts of the pattern block adjoin is shown. (B). The state where the acute angle part of the pattern block is surrounded by the land is shown.

[Explanation of symbols]

 1 tire 2 main groove 3 land part 4 land part 5 land part 6 land part 7 land part 8, 8 "narrow groove 9, 9" narrow groove 10 pattern block 11 pattern block 12 pattern block acute angle part 13 acute part of pattern block 14 obtuse part of pattern block

Claims (1)

[Claims] 1. A plurality of main grooves extending substantially along the tire equatorial plane on a tire tread surface, a plurality of land portions formed between adjacent main grooves, and inclined in one direction with respect to the tire equatorial plane. A plurality of one narrow groove arranged in each of the land portions on the diagonal line and opening in each of the adjacent main grooves is arranged in the tire circumferential direction, and the narrow groove inclined in the other direction with respect to the tire equatorial plane. A plurality of the other thin grooves arranged in each land portion and opening in each of the adjacent main grooves are arranged in the tire circumferential direction,
A pneumatic radial tire for heavy load equipped with a tread pattern in which a rotation direction is designated, in which a part of the narrow grooves arranged in each land portion on the slant line inclined in the one direction and the other direction is specified. A pneumatic radial tire for heavy load, comprising a tread pattern in which a narrow groove on a land portion is displaced from the diagonal line in a tire circumferential direction.