JPH06297917A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To improve heel-and-toe wear and the initial wear and partial wear of a tire so as to improve durability by providing a stepped protruding part in a lug groove. CONSTITUTION:A stepped protruding part 7 is provided in a lug groove 4 partitioning a shoulder block 5 in a tire shoulder S, and it is desirable that the size of the stepped protruding part 7 is 0.5<=D2/D1<=0.9, 0.5<=2/L1<=0.9, 0.4<=W2/W1<=0.9, where D1 is the height of the shoulder block 5, D2 is the height of the stepped protruding part 7, L1 is the lateral length of the lug groove 4, L2 is the lateral length of the stepped protruding part 7, W1 is the width of the lug groove 4, and W2 is the width of the stepped protruding part 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an all-weather radial tire. More specifically, it relates to an all-weather pneumatic radial tire in which uneven wear of a tread portion is prevented and tire durability is improved.

[0002]

2. Description of the Related Art A tread pattern for an all-weather tire of this type is a so-called block type pattern having vertical grooves extending in the tire circumferential direction and vertical block groups separated by horizontal grooves intersecting with the vertical grooves. The shoulder portions, which are common and located on both sides of the tread, are divided by lateral lug grooves having a depth equal to or less than the depth of the vertical grooves to form shoulder blocks. The lug groove is provided with a bridge having a shallower depth than the vertical groove in order to increase the rigidity of the shoulder portion. Here, an example of a conventional all-weather block type tread pattern and an example of a lug groove will be described with reference to FIGS. 4 and 5A and 5B, respectively.

In these figures, the tread T has a vertical groove 1
1 and the lateral groove 12, the blocks 13 constituting the column block group B _T and the shoulder portions S on both sides of the tread T are provided with lateral lug grooves 14 communicating with the longitudinal groove 11.
Shoulder blocks 15 defined by the blocks 13 and the shoulder blocks 1 are formed.
5 at each end of the sipe 16 which is substantially parallel to the lateral groove 12.
It is crushed. And shoulder block 15
In order to prevent the occurrence of uneven wear by suppressing the behavior of the shoulder block 15 at the same time as increasing the rigidity of the shoulder portion S, the lateral groove of FIG.
As shown in (b), a bridge 17 having a depth H _b shallower than the depth H of the other vertical groove 11 is provided, and the shoulder blocks 15 are just bridged to form a connected state.

By the way, pneumatic tires having these block patterns are mainly used for tires which are often driven on snowy roads and unpaved roads because of their excellent driving force and braking force. Since there is a strong demand for improvement in running performance, durability and steering stability for these tires, further improvements in these functions have been attempted. For example, in order to further improve the running performance on the road surface, the shape and size of the block itself are made smaller and the number thereof is increased, and the number of sipes provided on the block is increased to increase the edge component of the block, thereby gripping the road surface. It is well known that greater force is advantageous. On the other hand, on the other hand, even if the same sipes are formed, the depth of the sipes is inclined, and the arrangement, the number, and the position of the sipes are specified to improve the steering stability and wear resistance. 2-241804), and further, by connecting the blocks vertically to each other by a platform that is shallower than the groove depth of the groove that separates the blocks in the approximately central part of the tread from each other, improving snow performance and tire life Attempts have been made (Japanese Patent Laid-Open No. 4-85106).

[0005]

However, if the shape and size of each of these blocks is reduced, the rigidity of that portion inevitably decreases. Therefore, when the tire is driven and braked, the block is deformed in the tire circumferential direction. When it becomes large, uneven wear is likely to occur, and as a result, noise is likely to occur. Further, cracks are generated at the bottoms of the grooves that partition these blocks that are repeatedly subjected to compressive deformation, and further at the bottoms of the sipes, and these cracks tend to propagate and cause bursts, sometimes causing chipping of the blocks. Even if the depth and arrangement of sipes are specified as described above or a platform is provided between the blocks, the heel and toe wear (step wear, uneven wear, intended wear) of the shoulder block of the conventional tire is prevented. The reality is that it has not yet been improved.

In consideration of the above-mentioned circumstances, the present inventor has conducted an earnest study on the function of the bridge of the conventional tire in order to investigate the cause of heel and toe wear of the block pattern, particularly the shoulder block, and as a result, the shoulder The method of providing a bridge in the lug groove of the block tends to give excessive rigidity near the ground contact end of the tread and restrains the behavior of the shoulder block, so the shear stress generated during rolling of the tire is restrained by the bridge. We have come to discover the fact that the heel and toe wear is generated as a result of being concentrated in a region with a high degree of freedom, that is, in the vicinity of the stepping side edge of the shoulder block.

Thus, the present invention has been made based on the above-mentioned findings. By providing a step projection in the lug groove, heel and toe wear is improved and initial wear and uneven wear of the tire are improved. The purpose is to improve the durability of the tire.

[0008]

SUMMARY OF THE INVENTION The present invention, which is adapted to the above object, has a plurality of longitudinal grooves extending in the tire circumferential direction and a tread intersecting the longitudinal grooves in at least the central region of the tread excluding both side regions. Has a plurality of column block groups partitioned by a large number of transverse grooves extending along the width direction of the tread, and the shoulder portions of the columns located on both sides of the tread communicate with the longitudinal grooves with a depth equal to or less than that of the longitudinal grooves. Has a plurality of lateral lug grooves and a shoulder block defined by the vertical grooves, and each block except at least the central region is cut at a depth equal to or smaller than the vertical groove. In a pneumatic radial tire with a large number of lateral sipes formed, divide it by a thin cut into the shoulder lug premises in at least one of the above-mentioned both side areas. Characterized in that a difference projection.
Moreover, it is preferable that the step protrusions satisfy the following conditions. 0.5 ≤ D ₂ / D ₁ ≤ 0.9 0.5 ≤ L ₂ / L ₁ ≤ 0.9 0.4 ≤ W ₂ / W ₁ ≤ 0.9 where D _{1 is the} shoulder block height, D _{2 is the} step protrusion height, L ₁ ; Horizontal length of lug groove, L ₂ ; horizontal length of step protrusion, W ₁ ; width of lug groove top surface, W ₂ ;
The width of the step protrusion.

[0009]

Since the step protrusion is provided in the lug groove of the shoulder block of the tire, the rigidity near the ground contact end and the restraining force of the behavior of the shoulder block are performed within an appropriate range, and as a result, the behavior of the shoulder block is reduced. As a result, the shear stress, which was conventionally concentrated near the edge of the block on the stepping side, is appropriately dispersed. That is, since it is possible to suppress local wear at the block edge, it is possible to reduce step wear due to the difference in the wear speed of the block edge between the stepping side and the kicking side. Further, in the conventional tire bridge, as the wear progresses, the lug grooves are already worn out in the initial stage as compared with other longitudinal grooves and lateral grooves, and the appearance is poor, and the traction force is also substantially reduced. However, the configuration of the present invention is effective because the lug groove remains until the end of the usable wear of the tire by providing the step protrusion.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited thereto.

FIG. 1 is an enlarged schematic view showing a part of a tread pattern of a pneumatic radial tire according to the present invention.

In the figure, 1 is a plurality of vertical grooves extending in the tire circumferential direction, and 2 is a large number of lateral grooves extending along the width direction of the tread T so as to intersect the vertical grooves 1. Reference numeral 3 is a block that constitutes each block group partitioned by the vertical groove 1 and the horizontal groove 2. Further, in the shoulder portions S on both sides of the tread T, a lateral lug groove 4 having a depth equal to or less than that of the vertical groove 1 and a substantially trapezoidal shoulder block 5 which is partitioned by the vertical groove 1 are arranged. There is. Further, at each side end of each block 3 and each shoulder block 5 in the vertical direction, a large number of short laterally sipe 6 cut at a depth equal to or less than that of the vertical groove 1 is formed. The step projection 7, which is a noteworthy configuration in the present invention, is provided in the lug groove 4 of the shoulder S, and the shoulder S is located in at least one of the two side areas.
It is also effective to install it in the lug groove. As shown in FIGS. 1 and 2, the step projection 7 has a rectangular cross-sectional shape, the side wall thereof is provided separately from the shoulder block 5, and the height thereof is equal to that of the shoulder block 5. The outer end 8 of the step projection 7 is hollowed out in a semicircular shape so that the tire chain can be easily fitted thereto, but the invention is not limited to this.

By the way, the preferred shape of the step projection 7 is as follows. That is, the height D ₂ of the step protrusion 7 is preferably within the range of 50 to 90% of the depth D ₁ of the lug groove 4. If it is less than 50%, the low-frequency effect of heel and toe wear of the block edge is insufficient, and if it exceeds 90%, the effect of suppressing the behavior of the shoulder block 5 is low.

The lateral length L ₂ of the step projection 7 is set so as to suppress the behavior of the shoulder block 5 in the conventional bridge 1.
7 is preferably provided in the same range as that in which the lug groove 4 is provided, and thus is preferably in the range of 50 to 90% of the lateral length L ₁ of the lug groove 4. Even in this case, if it is less than 50%, the effect cannot be expected, and if it exceeds 90%, it is pressed against the height of the shoulder block 5 and the protrusion thereof does not exhibit a recessed state, which is not preferable in terms of performance. The starting point of the length of L ₂ is preferably the same as the starting point inside the length of L ₁ .

Next, the vertical width W ₂ of the step projection 7 is preferably within the range of 40 to 90% of the width W ₁ of the upper surface of the lug groove 4. If it is less than 40%, the rigidity of the step protrusion 7 becomes too low, which is not effective, and if it exceeds 90%, the gap between the inclined side wall of the lug groove 4 becomes extremely narrow, and as a rule of thumb when traveling. There is a high possibility that cracks will occur at the groove bottom. Therefore, even if it is in the range of 40 to 90%, as a countermeasure against this, a sloped relief surface F is provided on the side wall of the lug groove 4 in the vicinity of the groove bottom to prevent a crack from occurring by forming a large gap, and at the same time, to perform molding. It is preferable for facilitating demolding at a certain time. As a rule of thumb, the setting requirement of the clearance surface F preferably satisfies the conditions of 0 ° ≦ θ ₁ ≦ 4 ° and 0.2 ≦ D ₃ / D ₁ ≦ 0.4. Here, D ₃ is the depth of the clearance surface F. The inclination angle θ ₂ of the inner wall surface of the shoulder block 5 adjacent to the step protrusion 7 is not particularly limited, but is preferably in the range of 3 ° ≦ θ ₂ ≦ 15 °.

(Comparative Test with Comparative Example) Hereinafter, a comparative test regarding heel-and-toe wear between the invention tire and the comparative tire will be described.

1) Test tire Invented tire; ・ Tire size; 10.00 R 20 ・ Tread pattern; pattern shown in FIG. 1 ・ Shape of step protrusion; L ₁ ; 36 mm, L ₂ ; 25 mm (L ₂ / L ₁ = 0.69). W ₁ ; 11 mm, W ₂ ; 6.6 mm (W ₂ / W ₁ = 0.6). D ₁ ; 16.9 mm, D ₂ ; 14.4 mm, D ₃ ; 4 mm (D ₂ / D ₁ = 0.85, D ₃ / D ₁ = 0.24).

Comparative tires ・ Tire size; 10.00 R 20 ・ Tread pattern; pattern shown in Fig. 4 ・ Bridge shape; shape shown in Fig. 5 (a) ・ Lag groove width (W _L ); 11 mm, lug groove height (H-Hb); 4.
5 mm.

2) Abrasion resistance evaluation method Test tires were attached to all wheels of a large-sized vehicle, and 30,000 paved roads were used.
The heel and toe step difference S (see FIG. 3) was measured after traveling for km and the average value was evaluated. The results are shown in Table 1. In addition,
The heel-and-toe step amount S refers to the difference between the amount of wear on the stepping side and the amount of wear on the side of kicking in the shoulder block 5, as shown in FIG. Margin below

[0020]

[Table 1]

As is clear from Table 1 above, the tire of the present invention is excellent in uneven wear resistance.

[0022]

As described above, according to the present invention, since the step protrusion is provided in the lug groove of the shoulder block of the block pattern tire instead of the conventional bridge, heel and toe wear is caused. The initial wear and uneven wear of the tire are prevented, which improves the tire durability.

[Brief description of drawings]

FIG. 1 is a partially enlarged schematic view of a tread pattern of a pneumatic radial tire according to the present invention.

FIG. 2 is a schematic sectional view of a step protrusion according to the present invention.

FIG. 3 is an explanatory diagram showing a heel-and-toe step difference amount.

FIG. 4 is a schematic diagram showing an example of a tread pattern of a conventional pneumatic radial tire.

5 (a) and (b) are BB line and C of FIG. 4, respectively.
It is a -C line sectional view.

[Explanation of symbols]

 1,11 Vertical groove 2,12 Horizontal groove 3,13 Block 4,14 Lug groove 5,15 Shoulder block 6,16 Sipe 7 Step protrusion 8 Outer end T Tread S Shoulder F Relief surface

Claims (2)

[Claims] 1. A plurality of vertical grooves extending in the tire circumferential direction and a plurality of lateral grooves extending along the width direction of the tread intersecting with the vertical grooves in at least the central region of the tread except for both side regions. Along with the column block group, the shoulder portions of the columns located on both sides of the tread are divided by a plurality of lateral lug grooves communicating with the vertical groove with a depth equal to or less than the vertical groove and the vertical grooves. In a pneumatic radial tire that has a shoulder block, and a large number of lateral sipes cut at a depth equal to or less than the longitudinal groove is formed in blocks other than at least the central region of each of these blocks. A pneumatic radial tire characterized in that a step protrusion is provided by dividing the shoulder lug in at least one of the both side regions by a thin notch. 2. The pneumatic radial tire according to claim 1, wherein the step projections satisfy the following conditions. 0.5 ≤ D ₂ / D ₁ ≤ 0.9 0.5 ≤ L ₂ / L ₁ ≤ 0.9 0.4 ≤ W ₂ / W ₁ ≤ 0.9 where D ₁ ; shoulder block height, D ₂ ; step protrusion height, L ₁ ; Horizontal length of lug groove, L ₂ ; horizontal length of step protrusion, W ₁ ; width of lug groove top surface, W ₂ ;
The width of the step protrusion.