JP2010116064A - Heavy-duty pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heavy-duty pneumatic radial tire capable of reducing the occurrence of eccentric wear of a land part caused by wiping phenomenon, side force input, and the like, and sufficiently restraining the advancement of the eccentric wear into the land part. <P>SOLUTION: A plurality of circumferential grooves extending in the circumferential direction of the tire are arranged on a tread surface 1. The land part is defined in between two pieces of circumferential grooves mutually adjacent to each other, and recessed parts 9 starting from the top end of at least either one wall of the circumferential grooves are formed within the cross section in the tire width direction. The recessed parts 9 are provided in the tire circumferential direction in a discontinuous manner. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  In particular, the present invention relates to a heavy-duty pneumatic radial tire that can reduce uneven wear at a tread portion of a pneumatic radial tire for heavy-duty vehicles such as trucks and buses.

In heavy-duty pneumatic radial tires, in the rolling contact of the tire, the land portion that receives the compressive force due to the load is perpendicular to the compression direction in the ground plane (tread circumferential direction and / or width). (Direction) The groove wall bulges and deforms due to strain, and then when the land part leaves the road surface, the deformation is returned to cause a slip of the land part with respect to the road surface (wiping).
In particular, the land edge of the tread surface, which is partitioned by a circumferential groove, etc., is deformed more than other areas due to the wiping phenomenon and the side force input in the tire width direction. Uneven wear occurs and the wear develops in the land. Such wear not only impairs the wear life of the tire but also greatly affects steering stability.

  For example, by providing a sipe extending in the tire width direction in the vicinity of the edge of the land to reduce the unevenness of the land in the vicinity of the edge of the land. A technique has been proposed in which the shear force component of the braking force that promotes uneven wear is increased by increasing the amount of deformation in the region, and the progress of uneven wear in the land portion is reduced by causing the sipe-formed region to bear.

  However, by providing such a sipe at the edge of the land, the progress of uneven wear can be reduced, but the rigidity of the area where the sipe is provided becomes low, and a sipe tear is generated or a part of the land is formed. There was a risk of missing.

  Accordingly, an object of the present invention is to reduce the occurrence of uneven wear at the edge of the land due to the wiping phenomenon, side force input, etc. The purpose is to provide a radial tire.

  A pneumatic tire according to the present invention has a plurality of circumferential grooves extending in a tire circumferential direction on a tread surface, and a land portion is defined between two circumferential grooves adjacent to each other. A recess is formed from the upper end of at least one groove wall of the circumferential groove in the cross section in the tire width direction, and the recess is provided discontinuously in the tire circumferential direction.

  Here, the circumferential groove can be extended not only in a linear shape but also in a zigzag shape, a wave shape, a crank shape, or the like.

More preferably, in such a heavy-duty pneumatic radial tire, the maximum depth t of the concave portion from the imaginary line segment connecting the upper end and the groove bottom point of the groove wall of the circumferential groove in the cross section of the tire width direction, And the maximum groove depth D of the circumferential groove is 0 <t ≦ 2 × D × tan α (when α = 0, 0 <t < D / 8) is satisfied.
Here, the groove bottom point of the groove wall refers to a junction point between the groove wall and the groove bottom curve.

  Preferably, the concave portion is 5 to L / 10 mm in the tire circumferential direction (where L is the tire circumferential direction length of the concave portion of the tire ground contact surface of each groove provided with the concave portion, and when 50 <L, 5-10 mm).

  In the pneumatic tire of the present invention, by forming a recess from the upper end of at least one groove wall of the circumferential groove in the cross section in the tire width direction, the groove amount is reduced by reducing the amount of rubber that bulges under load. It is possible to suppress the deformation of the land edge that occurs during the wiping deformation in which the wall expands and returns. As a result, uneven wear that occurs at the land edge can be suppressed.

  In addition, by forming a recess in the groove wall of the circumferential groove, it is possible to reduce the ground pressure at the edge of the land portion when inputting the wibbing phenomenon or side force, thereby suppressing deformation, resulting in uneven wear. Can be suppressed.

  In addition, by providing the recesses in the tire circumferential direction discontinuously, it is possible to suppress a decrease in wear life due to a decrease in the rubber volume of the tread portion, and chipping of a land edge due to a decrease in land rigidity. it can.

Hereinafter, the pneumatic tire of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a partial development view of a tread pattern showing an embodiment of a pneumatic tire according to the present invention, and FIG. 2 is an enlarged end view of a main part showing the inside of a tire width direction cross section of the circumferential groove of FIG. is there.
Since the reinforcing structure inside the tire is the same as that of a general radial tire, the illustration is omitted.

  In the figure, reference numeral 1 denotes a tread surface, and the tread surface 1 has a plurality of circumferential grooves extending in the tread circumferential direction. In the figure, the tread surface 1 is linearly arranged in the tread circumferential direction at equal intervals from the tire equator surface. Two center circumferential grooves 2 extending continuously, and a shoulder circumferential groove 3 adjacent to each side portion of the center circumferential groove 2 are disposed.

  In the figure, the central land portion 4 is disposed between the two center circumferential grooves 2, the intermediate land portion 5 is disposed between the center circumferential groove 2 and the shoulder circumferential groove 3, and the shoulder circumferential groove 3 and the tread side edge. Each of the shoulder land portions 6 is partitioned between the two.

  The central land portion 4 and the intermediate land portion 5 are inclined in the tire circumferential direction and extend to the left in the figure, and both ends do not open in the respective circumferential grooves 2 and 3 ending in the land portions 4 and 5. Sipes 7 and 8 are provided at equal intervals in the tire circumferential direction.

  Here, for example, each of the circumferential grooves 2 and 3 can have a groove width in a range of 10.0 to 19.0 mm and a groove depth in a range of 7.0 to 25.0 mm.

  In this pneumatic tire, at least one groove wall of the circumferential groove, in the figure, from the upper end of both groove walls, for example, a recess 9 is formed with a single arc, and the recess 9 is discontinuous in the tire circumferential direction. Preferably, the pitch is 5 to 10 mm (where L is the length in the tire circumferential direction of the recess on the tire ground contact surface of each groove provided with a recess, and 5 to 10 mm when 50 <L).

  Moreover, it is preferable that the shape of the concave portion 9 is a continuous shape that does not have a bending point, an inflection point, or the like. By using this shape, strain concentration in the circumferential groove due to bending deformation at the time of loading or non-loading is achieved. Can be mitigated and cracks in the circumferential groove can be prevented.

  In such a tire, more preferably, the concave portion 9 has a maximum depth t of the concave portion 9 from an imaginary line segment connecting the upper end and the groove bottom point of the groove wall of the circumferential groove, and the imaginary line segment and the land top of the concave portion 9. The relationship between the angle α formed with the tangent to the surface and the maximum groove depth D of the circumferential groove is 0 <t ≦ 2 × D × tan α (where 0 <t <D / 8 when α = 0) Meet.

  By adopting this configuration, it is possible to improve the uneven wear resistance without greatly impairing the rubber amount of the tread portion 1 and extend the wear life of the tire.

  That is, if t exceeds 2 × D × tan α (D / 8 when α = 0), the uneven wear resistance can be improved, but the conventional groove wall shape having no recess shape is obtained. On the other hand, since the rubber amount is reduced, the tire life tends to be reduced.

  Preferably, the recess 9 is 5 to L / 10 mm in the tire circumferential direction (where L is the length in the tire circumferential direction of the recess 9 on the tire ground contact surface of each groove provided with the recess 9 and 50 <L In this case, by providing a pitch of 5 to 10 mm), uneven wear of the land edge can be suppressed without greatly reducing the land rigidity and the rubber amount.

  Next, tires of Example tires 1 and 2 and comparative tires 1 to 3 having a structure as shown in FIG. 1 and having a size of 295 / 75R22.5 are manufactured as shown in Table 1. Each item was changed to evaluate uneven wear resistance.

In this evaluation, the tires 1 and 2 and the tires 1 to 3 of the comparative example are mounted on a rim having a rim size of 8.25 × 22.5 on a total of 48 steering wheels (front wheels) of 12 vehicles. The inner pressure was set to 690 kPa, the vehicle was run under a load mass of 2800 kg, and a comprehensive evaluation was performed on the presence or absence of uneven wear initial nuclei at the land end and subsequent uneven wear progress.
The uneven wear resistance was evaluated by the average uneven wear area of each land edge except for the tread edge.

From the results of Table 2, the Example tires 1 and 2 have good results in comparison with the comparative example tires 1 to 3 in that both uneven wear resistance at the land edge and wear resistance and durability are compatible. became.
The comparative example tire 2 was removed because about 1/3 of the tire was worn when running 257495 km (160,000 miles), and the comparative example tire 3 was almost all tires when running 128748 km (80,000 miles). The test was stopped because cracks occurred in the vicinity of the bending point and cracks were severe.

It is a partial development view of a tread pattern showing one embodiment of a pneumatic tire of the present invention. It is a principal part expanded end elevation which shows the inside of a tire width direction cross section of the circumferential groove of FIG. It is a principal part expanded end elevation which shows the inside of the conventional tire width direction cross section of a circumferential groove.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread tread 2 Center circumferential groove 3 Shoulder circumferential groove 4 Central land part 5 Middle land part 6 Shoulder land part 7,8 Sipe 9 Concave part

Claims (3)

In a pneumatic tire in which a plurality of circumferential grooves extending in the tire circumferential direction are arranged on the tread surface, and a land portion is defined between two circumferential grooves adjacent to each other,
A heavy-duty pneumatic radial tire characterized by forming a recess from the upper end of at least one groove wall of the circumferential groove in a cross section in the tire width direction and discontinuously providing the recess in the tire circumferential direction. .   In the tire width direction cross section, the angle formed between the maximum depth t of the concave portion from the imaginary line segment connecting the upper end of the groove wall and the groove bottom point of the circumferential groove and the tangent to the land top surface of the concave portion Claim 1 wherein α and the maximum groove depth D of the peripheral groove satisfy a relationship of 0 <t ≦ 2 × D × tan α (where α <0, 0 <t <D / 8). The described pneumatic radial tire for heavy loads.   The concave portion is 5 to 10 mm in the tire circumferential direction (where L is the length in the tire circumferential direction of the concave portion of the tire ground contact surface of each groove provided with the concave portion, and 5 to 10 mm when 50 <L). The heavy-duty pneumatic radial tire according to claim 1, wherein the pneumatic radial tire is provided at a pitch of 5 mm.

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