JPH0717215A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PURPOSE:To improve the effect of groove bottom cracking prevention and rib tear prevention in the case that a slender groove is provided at each shoulder end portion of a tread surface. CONSTITUTION:A shallow groove recessed portion 6 whose width W2 is wider than the groove width W1 of a slender groove 4, is formed on the inlet side of the slender groove 4 which is provided at a thread 1 surface shoulder end portion and extends along a tire peripheral direction, and at the same time the slender groove 4 is inclined in a straight line shape toward a tire axial inner side than the normal line R of the tread 1 surface, and at the same time the tip side is bent smoothly toward the tire axial inner side.

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 radial tire in which a thin groove is provided at the shoulder end of the tread surface to prevent uneven wear of the tread.

[0002]

2. Description of the Related Art Pneumatic radial tires for heavy loads (hereinafter referred to as radial tires for heavy loads) slip on the shoulder side due to the difference in radius between the tread center part and the shoulder part during running, but the tread has a high tread. Since it has a rigid structure and is hard to be deformed, there is a problem of uneven wear phenomenon in which the shoulder part is quickly worn.

Conventionally, as a measure to solve this problem, by providing a small groove continuous in the tire circumferential direction along the shoulder end of the tread surface to reduce the rigidity of the shoulder end and make it easier to deform, There is a proposal to prevent uneven wear by releasing slippage based on a radius difference. However, as a countermeasure using this narrow groove, small stones are easily bitten into the narrow groove, and the bitten stone gradually moves to the groove bottom, thereby causing cracks in the groove bottom or forming on the outside of the narrow groove. There is a problem that the so-called rib tear is promoted, that is, the thin ribs are chipped. Further, the thin ribs have a drawback that a rib tear is likely to occur due to a tearing force applied when a tire rides over a rut or a curb is climbed up. Various proposals have been made in the past to solve the problems associated with the provision of the narrow grooves, but in reality, no sufficient solution has been obtained.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heavy-duty pneumatic radial which can further improve the effect of preventing cracks at the groove bottom and preventing rib tears when a thin groove is provided at the shoulder end of the tread surface. To provide tires.

[0005]

Means for Solving the Problems The present invention, which achieves this object, is a heavy-duty pneumatic radial tire having a narrow groove extending along the tire circumferential direction at the shoulder end of the tread surface. A shallow groove recess having a width wider than the groove width of the narrow groove is formed on the inlet side, and the narrow groove is linearly inclined toward the tire axial direction inner side with respect to the normal line of the tread surface, and the tip side Is characterized by being smoothly curved inward in the tire axial direction.

Since the shallow groove concave portion having a width larger than the narrow groove width is provided on the narrow groove inlet side as described above, the stone which is about to be caught in the narrow groove is pushed out, and stone trapping occurs. To reduce. Moreover, the narrow groove is linearly inclined inward in the tire axial direction, and the tip side is smoothly curved inward in the tire axial direction to increase the proximal end strength of the thin rib and concentrate stress. The rib tear can be prevented by not letting it.

The present invention will be described in detail below with reference to the drawings. FIG. 2 shows a tread pattern of the heavy duty radial tire of the present invention, and FIG. 1 shows a cross section of the shoulder end portion thereof. As shown in the figure, on the surface of the tread 1,
A plurality of main grooves 2 are provided along the tire circumferential direction, and a plurality of ribs 3 divided into these main grooves 2 are formed.
Of these ribs 3, the shoulder rib 3 is provided with a thin groove 4 having a total depth G ₁ along the end thereof, and a thin rib 5 is formed on the outer side thereof. The narrow groove 4 reduces the rigidity of the shoulder end portion and contributes to preventing uneven wear.

The narrow groove 4 has a shallow groove recess 6 having a width W ₂ wider than the groove width W ₁ on the inlet side thereof. As a result, the width of the upper surface of the thin rib 5 is W ₃ . The narrow groove 4 inclines inward in the tire axial direction with respect to the normal R of the shoulder surface and extends straight, and then the tip side is smoothly curved inward in the tire axial direction. As described above, the shallow groove concave portion 6 provided on the inlet side of the narrow groove 4 receives the pebbles that are trying to be bitten by the narrow groove 4, prevents the pebbles from entering further, and pushes them out. do. Further, the narrow rib 5 formed on the outer side of the narrow groove 4 has a wider width and a higher rigidity toward the base end side thereof, so that the strength is increased and moreover, the smooth bending of the narrow groove 4 causes stress. Since it does not concentrate, it is possible to prevent rib tear due to the tearing force when riding on the curb.

[0009] In the present invention, the width W ₂ and the depth G ₂ of the shallow recesses 6 are each 2.0 to 5.0 times the width W ₁ of the thin groove 4 (2.0W ₁ ~5.0W ₁₎ Is desirable. The absolute value of the groove width W ₁ of the narrow groove 4 is 1.5 to 5.0.
It is desirable to set in the range of mm. If the width W ₂ and the depth G ₂ are each less than 2.0 W ₁ , the above-mentioned effect due to the shallow groove concave portion cannot be obtained. On the other hand, if it exceeds 5.0 W ₁ , the width of the rib 3 of the shoulder portion cannot be sufficiently secured, and the load of the ground contact pressure on the center portion of the tread increases, so that early wear of the center portion (center wear) is induced. Moreover, the rigidity of the shoulder part is significantly reduced,
The cornering power is reduced and the steering stability deteriorates.

The groove depth G ₁ of the fine groove 4 is the groove depth D of the main groove 2.
0.70 to 1.20 times (0.70D to 1.20D)
Is desirable. If it is less than 0.70D, the uneven wear resistance effect due to the fine groove cannot be obtained. However, the groove depth G ₁
Is too large to exceed 1.20D, the groove bottoms of the narrow grooves 4 will remain even after the buffing during tread rehabilitation.

The inclination angle α formed by the center line A of the straight line portion of the narrow groove 4 and the normal line R of the shoulder surface is preferably 0 to 5 °. By setting the inclination angle α to be 0 or more, the rigidity of the base end portion of the thin rib can be increased. But 5
If it exceeds 50 °, the rigidity of the fine ribs becomes too high, and the fine ribs themselves are likely to wear a step. Further, at the tip of the narrow groove, the distance W ₄ between the straight line B along the tire outer wall surface of the straight line portion of the narrow groove 4 and the tip end portion C is 1.3 to 2 times the groove width W ₁ of the narrow groove ( It is desirable to set it in the range of 1.3W _{1 to} 2W ₁ . By smoothly curving the tip end portion so that the distance W ₄ becomes 1.3 W ₁ or more, the stress concentration at the base end portion of the thin rib can be relaxed, and the rib tear prevention effect can be enhanced. However, if the distance W ₄ is made too large to exceed 1.3 W ₁ , it becomes difficult to form the narrow groove.

The curved portion on the tip side of the thin rib is preferably formed at a position separated from the tread surface by a distance of at least ½ of the groove depth G ₁ . Top width W of thin ribs
₃ should be 1 to 5 mm. If the width W ₃ is less than 1 mm, the effect of uneven wear resistance becomes poor. If it exceeds 5 mm, step wear of the thin rib itself will be caused.

[0013]

Example: Tire size is 10.00R20 14P
The R and tread patterns are the same as those in FIG. 2 except for the narrow groove, and the sectional shape of the narrow groove, the groove width W _{1 of the} narrow groove, and the groove depth G
₁ , inclination angle α, distance W ₄ , shallow groove recess width W ₂ , depth G
_The tires of the present invention and comparative tires 1, 2 and _{3 in} which the upper surface width W ₃ of the thin ribs _{2 and the} thin ribs are different from each other as shown in Table 1 were manufactured.

Each of these four types of tires was mounted on a regular rim specified by JATMA, filled with regular air pressure, and loaded with a regular load, and the highway 70% and the mountain road 15
%, 15% of the general road, after traveling for 30,330 km, the number of stone traps in the tread's narrow groove, the number of groove bottom cracks, and the number of fine rib tears were examined, and the results are shown in Table 1. Indicated.

[0015] From Table 1, as in the comparative tire 1, only the fine groove 4 (FIG. 3) has many stone traps and cracks and many rib tears. Further, in the configuration like the comparative tire 2 in which only the shallow groove concave portion 6 is provided at the entrance of the narrow groove 4 (FIG. 4), stone trapping is reduced, but groove bottom cracking and rib tear cannot be prevented. Further, as in the comparative tire 3, the configuration in which the tip side of the narrow groove 4 is only curved (FIG. 5) cannot prevent the occurrence of stone trapping. On the other hand, in the tire of the present invention, stone trapping, cracks at the groove bottom, and rib tears hardly occur.

[0016]

According to the present invention, a shallow groove recess having a width wider than that of the narrow groove is provided on the inlet side of the narrow groove provided at the shoulder end of the tread surface, so that stone trapping and groove bottom cracking are prevented. Reduce. In addition, the narrow groove is linearly inclined toward the inner side of the shoulder surface in the tire axial direction, and the distal end side is curved, so that the base end strength of the narrow rib is increased and stress is not concentrated. Therefore, the rib tear of the thin rib can be prevented.

[Brief description of drawings]

FIG. 1 is a partially enlarged sectional view of a tread shoulder portion of a tire of the present invention.

FIG. 2 is a plan view showing an example of a tread pattern of the tire of the present invention.

FIG. 3 is a partially enlarged sectional view of a shoulder end narrow groove of a comparative tire.

FIG. 4 is a partially enlarged cross-sectional view showing another example of shoulder end narrow grooves of a comparative tire.

FIG. 5 is a partially enlarged cross-sectional view showing still another example of the shoulder end narrow groove of the comparative tire.

[Explanation of symbols]

 1 Tread 2 Main groove 3 Rib 4 Narrow groove 5 Narrow rib 6 Shallow groove recess

Claims (1)

[Claims] 1. A heavy-duty pneumatic radial tire having a narrow groove extending along the tire circumferential direction at the shoulder end of the tread surface, wherein the width of the narrow groove is wider on the inlet side of the narrow groove. A load that forms a shallow groove concave portion and inclines the narrow groove linearly inward in the tire axial direction with respect to the normal line of the tread surface and smoothly curves the tip side inward in the tire axial direction. Heavy duty pneumatic radial tire.