JP3351894B2 - Heavy duty pneumatic tires - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy-duty pneumatic tire used for heavy vehicles such as trucks and buses.

[0002]

2. Description of the Related Art A heavy-duty pneumatic tire conventionally used for a good road generally has a plurality of rib grooves continuously or linearly or zigzagly extending in a circumferential direction of a tire tread surface. There is a so-called rib pattern and a so-called block pattern in which the whole or a part of the tire tread surface portion is composed of a block and a groove surrounding the block. Live patterns are generally used in areas with little snow in winter, while tires with block patterns are so-called all-season tires that can be used throughout the year for vehicles running in areas with heavy snow in winter. Often used as a mounting. Also, it is preferably applied to a drive shaft requiring particularly large traction. In recent years, as a result of progress in tire pattern design technology accompanying increased vehicle performance and rigorous use conditions, the rib pattern has an unsatisfactory drainage between the road surface and the tire tread during running in rain as described later. It has been pointed out that, especially for small and light-duty tires such as passenger car tires, a tread pattern combining a wedge-shaped rib groove and a block to improve drainage and wet operability.
An improved technique is disclosed in JP-A-1-136801 and the like. On the other hand, in the case of the block pattern, uneven wear of the heel and toe due to the difference in the amount of wear between the front end and the rear end of the block when the front wheels are mounted on the vehicle is likely to occur. Frequent tire location changes.

[0003]

However, when the technology devised for the tire for a small vehicle is directly applied to the tire for a heavy vehicle to which the present invention is applied, uneven wear of the block occurs as the running wear of the tire progresses. Turned out to be unusable. Therefore, in the case of heavy-duty tires in which the value of the external force acting on the tires during running is extremely large, it is a fact that the conventional rib tires and block tires are still used together according to the use conditions. Although good performance can be exhibited in terms of tire running noise and steering stability on dry road surfaces, in the case of running in the rain, the road surface and the tire are rotated with the rotation of the tire from the front in the tire traveling direction, that is, from the side where the tire is depressed. Water penetrates between the ground contact surface and a part of the water is discharged through the rib groove in the rear direction of the tire, that is, on the kicking side as the tire rotates, but on the stepping side due to poor drainage efficiency. Water accumulates in front of the tire and the water film layer penetrates deeply from the front between the tire tread surface and the road surface, causing a decrease in the contact area with the road surface and a decrease in the coefficient of friction of the tire contact surface. Driving performance at the time of the door there was a difficult surface to say that fully satisfied. In addition, there are still unsatisfactory aspects in the traction performance at the time of starting or cornering in running in rain and the traction in running in shallow snow.

On the other hand, in the case of the block pattern, the traction performance at the time of starting and the running performance on a snowy road surface in comparison with the rib tire are good, but the wet performance still has an insufficient surface and the inside of the block is further increased. In addition, there is a problem that uneven wear (so-called heel & toe wear) easily occurs.

Accordingly, an object of the present invention is to provide a heavy-duty pneumatic tire which has the advantages of both a rib tire and a block tire, has excellent wettability, and has less uneven block wear.

[0006]

In order to achieve the above object, in the pneumatic tire for a heavy vehicle according to the first aspect of the present invention, the pneumatic tire is continuous with a tire tread portion in a substantially circumferential direction. Pneumatic retiree having a plurality of main grooves extending in a direction extending from and extending through a plurality of lug grooves intersecting the main grooves, and a plurality of blocks formed in a central portion of the tread, wherein the main grooves are formed in an equatorial plane. It is arranged on both sides, has its start end in the tire rotation direction near the tread equatorial plane, extends rearward in the tire rotation direction while tilting with respect to the tire circumferential direction, and opens at the lug groove or rib groove at the tread end portion In the plurality of lug grooves crossing the main groove, the groove depth is shallower than the main groove except for the tread end portion, and furthermore, on both wall surfaces of the main groove, the depth is the same as the shallow portions of the plurality of lug grooves. Multiple sipes (small grooves) It is characterized by providing. or,
In the second case according to claim 2, in addition to the features described in claim 1, a plurality of sipes (narrow grooves) provided on both wall surfaces of the main groove and having a depth equal to a shallow portion of the plurality of lug grooves crossing the main groove are provided. ), The direction of the angle of inclination formed with the circumferential direction of the tire is opposite to the direction of the angle of the main groove.

[0007]

In the tread pattern according to the present invention, the tread end extends from the front in the tire rotation direction to the rear in the tire rotation direction while being inclined in the circumferential direction of the tire starting from the front in the tire rotation direction. Or the main groove that opens into the groove provided at the end, so that water that has entered the front tread side of the rotation of the tire during running on rainy weather can be quickly applied to both sides of the tire tread through the main groove. And at the same time, the water remaining in the main groove with the rotation of the tire is discharged to the rear of the rotation of the tire. Therefore, in the case of the conventional rib tire, the discharge efficiency is remarkably improved as compared with the case where almost no water is discharged to both sides of the tire tread. For this reason, the range in which the water film enters between the road surface and the tire tread is narrowed, the area where the tire tread directly contacts the road surface (actual contact area) is increased, and the wet performance of the tire is improved. or,
The plurality of lugs formed by the plurality of lug grooves crossing the main groove can provide high traction performance which is an advantage of the block pattern.

Further, the depth of the block (strictly speaking, the depth of the lug groove crossing the main groove) and the depth of the sipe cut in the block on the main groove side are made smaller than the main groove by a predetermined depth, so that the block is formed. The rigidity of the block can be increased, the movement of the block on the ground contact surface during tire running decreases, and uneven wear of the block,
The occurrence of abnormal wear from the sipes can be prevented.
In addition, when the wear of the tire progresses because the depth of the block and the sipe is smaller than that of the main groove, the block and the sipe disappear and the main groove becomes a tread pattern mainly, and the uneven wear and
Further correct abnormal wear.

Furthermore, as described in claim 2, the inclination angle of the sipe with respect to the circumferential direction of the tire on the tread surface is opposite to the inclination angle of the main groove so as to be opposite to each other. With respect to the direction, it is expected that the frictional force is improved by the edge effect provided by the ridge line of the groove or the sipe, thereby improving the operability of the tire.

[0010]

Embodiments will be described with reference to the drawings.
FIG. 1 shows a tire size 11R22.5,1 according to the present invention.
It is a top view of the tread part (1) at the time of a new 4PR. In FIG. 1, the vicinity of the equatorial plane of the tire (a range extending over 10% of the tread width W on each side of the equatorial plane (2) of the tire).
The tire has a starting point (3) forward (downward in the figure) in the tire rotation direction, and extends rearward in the tire rotation direction (upward in the figure) while being inclined with respect to the circumferential direction of the tire, and extends to the tread end (4). Main grooves (7) are formed at every other pitch of the lug grooves, and are opened in the lug grooves (6) of the Y-shaped groove (5) engraved in the groove. The main grooves have a length of about four pitches of the lug grooves (6) and are arranged at every other pitch of the lug grooves as described above, so that adjacent main grooves overlap with each other in the longitudinal direction. are doing. Also, a large number of blocks (9) formed by lug grooves (8) that delimit each main groove are arranged at the center of the tread. At the end of the block formed by these blocks and the Y-groove (5) at the tread end (4), a plurality of sipes (10) are provided with an inclination that is opposite to the inclination direction of the main groove with respect to the tire circumferential direction. Engraved in the direction. Further, the depth of the lug groove and the sipe is set in the range of 40 to 60% of the depth of the main groove depending on the installation location in the tread portion.

According to the present invention, since the new tret pattern is formed, when the tire runs and wears to approximately 50% of the depth of the main groove, it changes to the pattern shown in FIG. I do. At this point, part of the lug groove and all of the sipe have disappeared, leaving the main groove and part of the lug groove. Further, as the wear progresses due to running and reaches the end of the tire wear life, the pattern shown in FIG. 3 is formed. At this point, most of the lug grooves and a part of the Y groove disappeared, and a pattern was formed by a part of the Y groove and the main groove which were left in the same manner as a part of the lug groove slightly left in the center of the tread. −
Is configured.

Due to the above-described structure of the tread pattern and the change of the tread pattern with the progress of the traveling time, excellent drainage performance is ensured from the time of new article to the end of traveling, and from the time of new article to the middle of wear. In addition to the good tracing effect characteristic of the block pattern, the sipe effect is expected to improve steering stability. Further, uneven wear of the block is suppressed, the frequency of tire position replacement can be reduced, and the tire wear life can be improved.

Next, in order to verify the effects of the present invention, three types of tires of the above-described embodiment, a conventional rib pattern, and a conventional block pattern were trial-produced at a tire size of 11R22.5, 14PR. A braking test was carried out on a test course road of asphalt pavement sprinkled with water to reproduce rainy weather when mounted on a predetermined large test vehicle. Fig. 4 shows the results.
As shown in FIG. 5, the above three types of tires were expressed as a relationship of Wet μ (coefficient of friction on a wet road) with respect to each vehicle traveling speed. From this, it can be seen that the performance of the tire of the present invention is good by about 10%. Also, in order to confirm the uneven wear resistance, the tire of the present invention and the conventional block pattern were mounted on a test vehicle with the same tire size as above, and after traveling 40,000 km on a general road, the inside of the tread portion was measured. The degree of uneven wear of the heel and toe of each block (difference in groove depth between the stepped end and the kick-out end) of the blocks was compared. As a result, as shown in FIG. 5, in the tire of the present invention, the occurrence of uneven wear is reduced to approximately 30%.

[0013]

The pneumatic tire for heavy load according to the present invention has the above-described structure, and is particularly excellent in drainage performance in rainy weather, has good wet performance, and blocks at least until the middle stage of wear. It has high traction performance comparable to the pattern, and can exhibit ideal performance for a good road tire that prevents uneven wear, which was a disadvantage of the block pattern.

[Brief description of the drawings]

FIG. 1 is a plan view of a tread portion when a tire of the present invention is new.

FIG. 2 is a plan view of a tread portion when the tire of the present invention is worn by 50%.

FIG. 3 is a plan view of a tread portion at the end of wear of the tire of the present invention.

FIG. 4 is a diagram showing test results of wet road running performance.

FIG. 5 is a view showing the results of an uneven wear resistance evaluation test.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tread part 2 Equatorial plane of tire 3 Starting point 4 Tread end part 5 Y-shaped groove 6 Lug groove 7 Main groove 8 Lug groove dividing main groove 9 Block 10 Sipe

Claims (2)

(57) [Claims] 1. A tire tread portion includes a plurality of main grooves extending substantially continuously in a circumferential direction, and a plurality of blocks formed by a plurality of lug grooves crossing the main grooves are formed in a central portion of the tread. A pneumatic tire, wherein the main grooves are disposed on both sides of an equatorial plane, have a starting end in the tire rotational direction near the tread equatorial plane, and extend rearward in the tire rotational direction while being inclined with respect to the tire circumferential direction. While opening at the lug groove or rib groove at the tread end portion, the plurality of lug grooves crossing the main groove have a groove depth shallower than the main groove excluding the tread end portion, and furthermore, both the main groove A pneumatic tire for heavy load , wherein a plurality of sipes (narrow grooves) having the same depth as a shallow portion of the plurality of lug grooves are provided on a wall surface. 2. An inclination angle direction of a plurality of sipes (narrow grooves) provided on both wall surfaces of the main groove and having a depth equivalent to a shallow portion of a plurality of lug grooves crossing the main groove and formed in the tire circumferential direction. The pneumatic tire for heavy load according to claim 1, wherein the pneumatic tire is in a direction opposite to the angle direction.