JPH07172112A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To provide a tire showing an excellent on icy road surface from initial abrasion to intermediate abrasion when the tire is used in winter and having excellent traveling property on a normal road surface after the intermediate abrasion. CONSTITUTION:A block pattern with a plurality of blocks 50 formed by a main grooves 20 extending to a tire circumferential direction, an auxiliary groove shallower than the main grooves 20 extending toward a tire circumferential direction between the main grooves 20 or between the main grooves 20 and a tread end and lateral grooves 40 shallower than the main groove for linking two auxiliary grooves or the auxiliary groove and the main groove is included in a pneumatic tire and a groove bottom sipe 70 practically extending to a direction along extending direction of the lateral groove 40 is provided in a groove bottom of the lateral groove 40 and an enlarged portion 71 is formed in a bottom of the groove bottom sipe.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art A conventional studless tire has a block pattern in which a plurality of blocks are arranged on the tread surface, and by sipe which extends mainly in the tire width direction is arranged in each block, the edge effect is obtained. Shows its performance on ice. In addition, this tire is provided with more grooves and sipes than ordinary tires for paved roads in order to improve the running performance on snowy roads.

At this time, if the lateral groove between the blocks has the same depth as the main groove, the rigidity of the block is lowered and the movement is increased, so that cracks may occur at the bottom of the sipe.
Uneven wear occurs on the block. Therefore, a means is known in which the lateral groove is shallower than the main groove to ensure rigidity, and to improve cracks at the sipe bottom and uneven wear of the block.

[0004]

In recent years, studless tires tend to be used for ice and snow road surfaces in the winter from the initial wear to the middle wear (the middle of the service life due to wear) and to the normal road after the middle wear. For,
High wettability is required even after the middle stage of wear. On the other hand, when the lateral groove is simply made shallow as described above, there is a problem that the lateral groove disappears due to wear after the middle stage of wear, and the wettability on a normal road surface is poor.

In view of the above facts, the present invention is a tire that exhibits excellent on-ice and snow road surface performance during winter use from the early stage to the middle stage of wear, and excellent running performance on normal road after the middle stage of wear. The purpose is to provide.

[0006]

In the pneumatic tire of the present invention, a main groove extending in the tire circumferential direction, a sub-groove shallower than the main groove extending in the tire circumferential direction between the main grooves or between the main groove and the tread end, and There is a block pattern in which a plurality of blocks are formed by two sub-grooves or a lateral groove that is shallower than the main groove that connects the sub-grooves to the main groove. The block pattern of the lateral groove is substantially in the extending direction of the lateral groove. A groove bottom sipe extending in the direction along the groove bottom sipe is provided, and an enlarged portion is formed at the bottom of the groove bottom sipe.

Here, it is preferable that there are at least three main grooves extending in the tire circumferential direction. Further, it is preferable that at least one end of the groove bottom sipe is opened to the main groove including the enlarged portion. Further, when the depth of the main groove is D, the depth of the auxiliary groove is d, the depth of the lateral groove is a, and the depth of the groove bottom sipe is b, the depth b of the groove bottom sipe is set to 3 mm or more, and /D=0.3~
0.8, d / D = 0.3 to 0.8, b / (D−a) ≦
It is preferable to set 1.2.

[0008]

[Action]

According to the pneumatic tire of the present invention, the groove bottom sipe extending substantially in the extending direction of the lateral groove is provided at the groove bottom of the lateral groove, whereby the lateral groove disappears due to wear after the middle period of wear, Even after the rib-based pattern, the groove bottom sipe appears on the tread, and its edge effect ensures excellent wet performance on normal road surfaces. Since it is a sipe, the continuity of the ribs is ensured, and uneven wear is unlikely to occur. Also. By providing the enlarged portion at the bottom of the groove bottom sipe, it is possible to prevent the occurrence of cracks from the sipe bottom. Further, since the sub-grooves between the main grooves or between the main groove and the tread end are shallow with respect to the main groove, the sub-grooves disappear after the middle wear period and a plurality of block rows become one rib, and after the middle wear stage. In the above, the rigidity of the ribs is increased, and maneuverability during normal road surface traveling, especially during high speed traveling, is improved.

By having at least three main grooves, it is important for at least three main grooves to remain even after the middle stage of wear in order to exhibit even higher wettability. Therefore, after the middle stage of wear, the rigidity of the ribs is increased, the maneuverability during normal road traveling, particularly the maneuverability during high-speed traveling is improved, and the wettability is also improved by the sipes appearing in at least three main grooves and ribs. Keeps good. Here, the main groove has a groove width of 6
It has a wide width of ~ 13 mm, and the sub-groove has a narrow width of 2-5 mm.

Further, at least one end of the groove bottom sipe is
By opening in the main groove with the enlarged part of the sipe bottom,
The water on the road surface is quickly drained to the main groove, improving wettability.

The depth of the main groove is D, the depth of the lateral groove is a,
When the depth of the groove bottom sipe is b, the depth of the groove bottom sipe is b
Is 3 mm or more, and b / (D−a) ≦ 1.2, a
By setting /D=0.3 to 0.8 and d / D = 0.3 to 0.8, excellent ice and snow road surface running performance and normal road surface running performance can be exhibited. That is, if the depth b of the groove bottom sipe is less than 3 mm, the wettability after the transverse grooves disappear after the middle stage of wear is poor, and if b / (Da) exceeds 1.2, the rigidity of the block decreases. As a result, maneuverability deteriorates and uneven wear easily occurs. Also, a / D and d / D are 0.3.
If it is less than 0.8, the lateral groove and the auxiliary groove are too shallow to compact the snow, resulting in poor snow performance.If it exceeds 0.8, the rigidity of the block decreases, resulting in poor maneuverability and uneven wear. It will be easier.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS.

The tread 10 of the pneumatic tire 1 according to the present invention shown in FIG. 1 has main grooves 20 formed on the tire equator line L and at a position substantially in the middle of the tread end E. There are a total of three grooves. Further, between the main groove 20 and the tread end E, one sub groove 31, the main groove 20
One sub groove 32 is formed between them. Then, a lateral groove 41 connecting the main groove 20 and the sub groove 31 and a lateral groove 42 connecting the main groove 20 and the sub groove 32 are formed, and a large number of blocks 5 are formed.
0 is partitioned.

The depth a of the lateral groove 41 and the lateral groove 42 leading to the main groove is shallower than the depth D of the main groove 20. In this embodiment, the depth D of the main groove is 20 mm, and the depths of the lateral groove 41 and the lateral groove 42 are: The same is 12 mm. Therefore, a / D =
It is 0.6. Further, the depth of the sub-groove is shallower than the depth D of the main groove, and in this embodiment, it is 12 mm which is the same as the depth of the lateral grooves 41 and 42.
It is said that. The groove width of the main groove 20 that can be placed on the tread is 12 m
m, the groove widths of the auxiliary grooves 31 and 32 are 3 mm and 1 mm, respectively.
The width of the lateral grooves 41, 42 is 8 mm.

The block 50 is formed with one sipe 60 extending in the tire width direction. The sipes referred to herein preferably have a groove width of 1.2 mm or less, and are 0.6 mm in this embodiment.

FIG. 2 is a cross-sectional view of one block row of the tread (here, the block row sandwiched between the main groove 20 and the sub groove 32) viewed from the width direction (the arrow indicates the tire circumferential direction). The bottom of the sipe 60 is provided with an enlarged portion 61, and its radius of curvature R is preferably in the range of 0.5 to 3 mm, and is 1.2 mm in this embodiment. Depth c of sipe 60
Is preferably 0.3 to 1.4 times the depth of the lateral groove 40 (horizontal groove 41 or 42 in FIG. 1), and 12 mm in this embodiment.
Is. This improves the performance on ice in the initial stage of wear.

On the groove bottom of the lateral groove 40, a groove bottom sipe 70 extending along the lateral groove is formed. An enlarged portion 71 is provided at the bottom of the groove bottom sipe 70, and its radius of curvature R is preferably in the range of 0.5 to 3 mm, and in this embodiment, 1.2.
It is set to mm. The groove bottom sipe 71 is open to the main groove 20 including the enlarged portion. The depth b of the groove bottom sipe 71 is 8 m
m, and therefore b / (D−a) = 1.0
Is. That is, the lower end of the sipe 70 is located at the main groove bottom position 21.
Matches The groove bottom sipe is not limited to a linear shape, but may be a zigzag shape or a wavy shape as long as it substantially extends in the extending direction of the lateral groove.

FIG. 3 shows a pneumatic tire 7 of the second embodiment.
The pattern after 0% wear is shown. The lateral grooves 41, 42 and the sub-grooves 31, 32 disappear, but the three main grooves and the groove bottom sipes 71 arranged in a staggered pattern remain. As a result, the wet performance from the middle stage to the final stage of wear is further improved, and the rib rigidity is increased, so that the maneuverability during normal road surface traveling, especially during high speed traveling, is improved.

In this embodiment, each block may be provided with a plurality of sipes or may be provided with circumferentially extending sipes. Further, in this embodiment, three main grooves are used, but two main grooves may be used as shown in FIG. However, it is necessary that at least three main grooves be present in order to exhibit even higher wettability after the middle period of wear.
If the number of ribs exceeds 5, the rib rigidity decreases, which is not preferable.

(Test Example) A comparative test between the tire of the present invention and a comparative tire will be described below.

The tire of the present invention has a tire size of 11R2.
2.5 inventive tires of the above examples were used. As the conventional tire, a tire in which a groove bottom sipe was not formed was used in the examples.

Table 1 shows the results of measurement of the on-ice performance on a new tire and the wet performance on 70% wear when each test tire was filled with normal internal pressure and mounted on all wheels of a 10-ton truck with a constant load. It is shown. Here, the performance on ice was measured by taking a reciprocal of the distance from that position to the stop position measured by applying a sudden brake while traveling at an ice temperature of -5 ° C and 20 km / h. Wet performance was measured by measuring the distance from that position to the stop position on the road surface on which a water film having a thickness of 3 mm was formed, by applying a rapid break during drafting at a speed of 40 km / h, and taking the reciprocal of that. . The result is that the value of the comparative tire is 10
It is shown by an index display with 0, and the larger the value, the better.

[0024]

[Table 1]

From the results shown in Table 1, it is clear that the pneumatic tire of the present invention has improved wet performance after the middle stage of wear without deteriorating the performance on ice when new.

[0026]

Since the pneumatic tire of the present invention has the above-mentioned structure, it exhibits excellent on-ice and snow road surface performance during winter use from the early stage to the middle stage of wear, and wet performance and maneuverability after the middle stage of wear. It also has the effect of being excellent in running performance on a normal road surface.

[Brief description of drawings]

FIG. 1 is a diagram showing a tread pattern of a pneumatic tire according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a tread of a pneumatic tire according to an example of the present invention as seen from the tire width direction.

FIG. 3 70% of a pneumatic tire according to an embodiment of the present invention
It is a figure showing a tread pattern at the time of abrasion.

FIG. 4 is a diagram showing a tread pattern of a pneumatic tire according to another embodiment of the present invention.

[Explanation of symbols]

 10 tread 20 main groove 31, 32 auxiliary groove 40, 41, 42 lateral groove 50 block 60 sipe 61 sipe expansion part 70 groove bottom sipe 71 groove bottom sipe expansion part

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B60C 11/12 B 8408-3D

Claims (4)

[Claims] 1. A main groove extending in the tire circumferential direction, a sub-groove shallower than the main groove extending in the tire circumferential direction between the main grooves or between the main groove and the tread end, and two sub-grooves or sub-grooves and the main groove. Has a block pattern in which a plurality of blocks are formed by a lateral groove that is shallower than the main groove that connects the groove, and a groove bottom sipe that extends substantially in the direction of extension of the lateral groove is provided at the groove bottom of the lateral groove. A pneumatic tire having an enlarged portion formed at the bottom of a sipe. 2. The pneumatic tire according to claim 1, wherein there are at least three main grooves. 3. The pneumatic tire according to claim 1, wherein at least one end of the groove bottom sipe is opened in the main groove including the enlarged portion. 4. When the depth of the main groove is D, the depth of the auxiliary groove is d, the depth of the lateral groove is a, and the depth of the groove bottom sipe is b, the depth b of the groove bottom sipe is 3 mm or more. And a / D = 0.3-0.
8, d / D = 0.3 to 0.8, b / (D−a) ≦ 1.2
The tire according to claim 4, wherein: