JPH05338414A - Tire for heavy load - Google Patents

Abstract

PURPOSE:To heighten a stone releasing property and to improve stone biting preventive effect as well as protecting the groove bottoms of longitudinal grooves extending zigzag from a stone. CONSTITUTION:In zigzag longitudinal grooves G1 formed in a tread central region T1, protect blocks 6 protruded and positioned at each of zigzag corner parts K from groove bottoms SG of the longitudinal grooves G1 are provided. Block height H and block width W of the protect block 6 change in accordance with expressions 91), (2). H=AXDoXlcos (L/LoXpi)1... (1), W=BXWoXlcos (L/LoXpi)1... (2), A is a constant of more than 0.3 and less than 0.6, B is a constant of more than 0.2 and less than 0.4; Do is depth of the longitudinal groove; Lo is a distance between corner parts KK in the tire circumferential direction; L is a distance from the corner part K in the tire circumferential direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy-duty tire, and more particularly to a pneumatic tire for trucks / buses having reduced stone trapping.

[0002]

2. Description of the Related Art Recently, as a pneumatic tire for heavy vehicles,
Metal belt cords, which are made of metal carcass cords, are arranged on the outer side of the crown portion of the carcass at relatively shallow angles in the tire circumferential direction, and the tread reinforcing effect of the belts provides rolling, abrasion resistance, puncture resistance, etc. The so-called radial tires that have improved

Further, in this type of tire, a tread pattern having vertical grooves extending in a zigzag pattern in the tire circumferential direction, such as a rib type and a rib lug type, is generally used from the viewpoint of high speed, wet grip resistance and the like. . However, in a tire having such a tread pattern, for example, when getting into a scattered construction site such as crushed stone, stone trapping often occurs in the vertical groove, and when running in the stone trapping state, the bottom of the groove, and thus the belt. This will damage the layers and carcass, greatly reducing tire life. In particular,
The corners of the zigzag vertical groove located in the center area of the tread where the ground contact pressure is large, the groove width is the most easily contracted by the ground load and becomes the bending point, so once stone trapping occurs, the binding force is released strongly. There is a problem that it is hard to be done.

[0004]

As a countermeasure against stone trapping, conventionally, there has been proposed a method in which a vertical groove has a two-step bottom, a method in which a circumferentially continuous projection is formed on the groove bottom of the vertical groove, and the like. .

However, although these methods are effective from the viewpoint of protecting the groove bottom, they are not always sufficient in terms of releasing the trapped stones.

The present invention is basically based on the provision of a protect block in which the block height H and the block width W are gradually reduced toward the adjacent corners at the groove bottom of the zigzag corner which is inferior in the effect of releasing the trapped stones. The purpose of the present invention is to provide a heavy-duty tire that protects the bottom of the groove while improving the stone release property and the stone trapping prevention effect.

[0007]

[Means for Solving the Problems] To achieve the above object
In the heavy load tire of the present invention, the tread of the tread portion is
It is formed in the central area and extends continuously in the tire circumferential direction.
In each zigzag vertical groove, from the groove bottom of the vertical groove to each zigzag
A trapezoidal tech to prevent stones from being raised at the corner
While the protection block is provided, the protection block is
Block height H from groove bottom and tire axial direction at groove bottom
The width W of each block is gradually increased toward the adjacent corners.
And reduce the tire between the zigzag corners
Circumferential distance is Lo, vertical groove width is Wo, vertical groove depth
Is the distance from the corner in the tire circumferential direction.
The block of the protect block at the position separating the separation L
The lock height H and the block width W are expressed by the following equations (1) and (2) H = A × Do × | cos (L / Lo × π) | (1) W = B × Wo × | cos (L / Lo × π) | ... (2) is characterized. Equation (1),
The symbol A in (2) is a constant of 0.3 or more and 0.6 or less,
B is a constant of 0.2 or more and 0.4 or less.

[0008]

[Function] Since the protect block rises from the groove bottom,
Prevents stones trapped in the groove from touching the bottom of the groove and damaging it when touching the ground. Further, since the protect block is compressed at the part in contact with the taken-in stone, it accumulates repulsive force to the outside of the groove and accumulates the stone when the ground contact surface is opened to the protruding side due to tire rolling. It is released by the repulsive force.

In particular, since the protect block has a large rubber volume in the corner portion, the repulsive force is high and the releasing effect can be improved in the corner portion where stone trapping is most likely to occur. Further, the rigidity of the groove bottom at the corner portion is increased and the decrease in groove width at the time of contact with the ground is reduced, so that stone intrusion can be prevented.

Further, in the protect block, since the block height H and the block width W are reduced by a smooth cosine curve along the groove, the groove volume smoothly increases toward the intermediate position between the corners. As a result, when a stone is caught in the corner portion, the stone can be guided to the intermediate position, and the stone can be discharged to the outside so as to be ejected. The synergistic effect of these can greatly improve the stone trapping effect.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a tread portion T of a tire 1 of the present invention. In the figure, the tire 1 has two zigzag-shaped vertical grooves G1 and G1 extending continuously in the tire circumferential direction in the tread central region T1 of the tread portion T, and has a groove bottom SG of the vertical groove G1. Is provided at each corner portion K of the zigzag, and a protect block 6 is provided.

The tread central region T1 means a region between the boundary lines t1 and t1 which are separated from the tire equator C by a distance A which is 0.2 times the tread width TW, and which is the most during tire running. The applied load is high and the occurrence of stone trapping is large.
Therefore, in the present invention, the protect block 6 is provided in the zigzag vertical groove formed at least in the tread central region T1. In this example, the protect block 6 is provided in the tread central area T2 outside the tread central area T1.
A rib pattern tire having a rib pattern having five ribs, which is provided with a zigzag vertical groove G2, but has a lug groove extending from the tread edge instead of the vertical groove G2. It is also possible to adopt a rib rug pattern in which a lug groove is further formed outside the pattern and the vertical groove G2.

In order to maintain drainage and improve grip, the vertical grooves G1 and G2 are formed in zigzag with the same pitch P and the same phase in this example.

The protect block 6 provided in the corner portion K of the vertical groove G1 has a trapezoidal shape that is raised at a small height from the groove bottom SG of the vertical groove G1, and as shown in FIGS. The block height H from the groove bottom SG and the block width W in the tire axial direction at the groove bottom SG respectively decrease in a cosine curve toward the adjacent corners K adjacent in the tire circumferential direction.

That is, the distance in the tire circumferential direction between the corners K, K is Lo, the groove width in the tire axial direction on the tread surface of the vertical groove G1 is Wo, and the groove depth of the vertical groove G1 from the groove bottom SG. In the present invention, the block height H of the protect block 6 at a position Q separated from the corner K by a distance L in the circumferential direction of the tire is represented by a constant A and a groove as shown in FIG. Depth Do and 100 (L / Lo × π)
Equation (1) which is the product of the absolute value of H = A × Do × | cos (L / Lo × π) |

As shown in FIG. 5, the block width W at the position Q is a constant B, a groove width Wo, and cos (L / Lo ×).
Formula (2) which is the product of the absolute value of π) W = B × Wo × | cos (L / Lo × π) | ... is set by Formula (2).

Here, the constant A is 0.3 or more and 0.6 or less, and the constant B is 0.2 or more and 0.4 or less.

Such a protect block 6 is compressed at a portion which comes into contact with a stone taken in the groove at the time of ground contact, like the conventional one in which a protruding rib extending at a constant width and a constant height is provided at the groove bottom. Therefore, the repulsive force to the outside of the groove is accumulated, and when the contact area moves to the protruding area due to the rolling of the tire, the accumulated repulsive force can release the stone to the outside. In particular, in the protect block 6, since the rubber volume is large in the corner portion K, the repulsive force is high, and the effect of discharging stones to the outside can be improved in the corner portion K. Moreover, the rigidity of the groove bottom at the corner K is increased,
Since the reduction of the groove width at the time of contact with the ground can be reduced, the intrusion of stones into the groove can be prevented.

Further, in the protect block 6, the block height H and the block width W are respectively reduced toward the adjacent corner portion K, and the groove volume is increased at the intermediate position R of each corner portion K. Therefore, for example, when a stone is trapped in the corner portion K, the stone M can be guided to the intermediate position R as schematically shown in FIG. 6, and the stone M can be ejected to the outside to prevent the stone from being trapped. The effect can be greatly improved. Note that the block height H and block width W are reduced smoothly by the cosine curve and while changing the reduction rate,
The invitation and the like can be effectively performed.

The side wall 6g of the protect block 6 is
It is inclined so that the width becomes narrower toward the tread surface, and in this example, the difference W-WU between the block upper surface width WU in the tire axial direction on the block upper surface and the block width W on the groove bottom is formed to be substantially constant. is doing. As a result, the cut resistance of the protect block 6 is improved, soil removal and water resistance are improved, and the appearance of the vertical groove G1 is improved.

On the side wall g of the vertical groove G1, the groove bottom SG is formed.
Is inclined so that the width becomes narrower toward the vertical groove G1.
Of each inclination α with respect to the normal passing through the ridge on the tread surface of
The side walls 6g, g and the groove bottom SG are connected to each other by a smooth arc, for example, while being formed to be about 15 degrees, more preferably about 10 degrees (constant).

(Specific Example) A tire having a tire size of 10.00R20 having a tread pattern shown in FIGS. 1 to 5 was prototyped according to the specifications shown in Table 1, and the stone blockability of the tire was measured by a protect block at the groove bottom. It was compared with the one having no width (Comparative Example 1) and the one having a constant height and width of the protect block (Comparative Example 2).

[0023]

[Table 1]

[0024]

As described above, the heavy-duty tire of the present invention is provided with a protect block on the groove bottom of the corner portion of the zigzag vertical groove in which the block height and the block width are gradually reduced at a predetermined rate. Therefore, while protecting the bottom of the groove, the stone release property is enhanced and the stone trapping effect is improved.

[Brief description of drawings]

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

FIG. 2 is an enlarged plan view showing a protect block.

FIG. 3 is a sectional view of a protect block in the tire axial direction.

FIG. 4 is a block height H and a distance L of a protect block.
It is a diagram which shows the relationship with.

FIG. 5 is a diagram showing a relationship between a block width W and a distance L of a protect block.

FIG. 6 is a diagram illustrating a part of the operation of a protect block.

[Explanation of symbols]

 6 Protect block G1 Vertical groove K Corner part SG Groove bottom T Tread part T1 Tread central area

Claims (1)

[Claims] 1. A zigzag-shaped vertical groove formed in a tread central region of a tread portion and extending continuously in a tire circumferential direction,
While providing a trapezoidal protect block for preventing stone trapping which is located at each corner of the zigzag from the groove bottom of the vertical groove, the block height H from the groove bottom of the protect block and the tire at the groove bottom The block width W in the axial direction is gradually reduced toward the adjacent corners, respectively,
The distance in the tire circumferential direction between the zigzag corners is L
o, the groove width of the vertical groove is Wo, and the depth of the vertical groove is Do, the block height H and the block width W of the protect block at a position spaced a distance L from the corner portion in the tire circumferential direction are A heavy-duty tire represented by the following formulas (1) and (2). H = A × Do × | cos (L / Lo × π) | (1) W = B × Wo × | cos (L / Lo × π) | (2) A is 0.3 or more and 0 A constant of 0.6 or less, and B is a constant of 0.2 or more and 0.4 or less.