JP2002321508A - Air tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air tire whose tread part converts from a block pattern into a rib pattern and whose traction performance and brake performance at a rib pattern are prevented from deteriorating and whose abrasion resistance performance and partial wear resistance performance are excellent. SOLUTION: Depths of a center longitudinal groove 2 and the second side longitudinal grooves of right and left 4L, 4R on the tread part are maximized, transverse grooves 6L, 6R are formed at a deep grooved part 20A and a shallow grooved part 20B, and the deep grooved part 20A remains as a branch transverse groove at the rib pattern.

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 pneumatic tire having a tread for transforming a block pattern into a rib pattern.

[0002]

2. Description of the Related Art A pneumatic tire having a tread portion transformed from a block pattern to a rib pattern is known. For example, a "tread pattern for a heavy-duty pneumatic tire" disclosed in Japanese Patent Application Laid-Open No. 60-76404 has been proposed. ing. That is, the conventional example disclosed in the above-mentioned publication is described as "a plurality of zigzag and straight flutes arranged continuously in the circumferential direction on the tread tread surface of the tire,
In a pneumatic tire having a tire tread portion forming a block pattern, a tread rubber corresponding to 35 to 75% of the maximum depth of the vertical groove is formed by a large number of horizontal grooves provided in the tire axial direction connecting the vertical grooves. The tread pattern for a pneumatic tire, wherein the horizontal groove disappears at the stage when is worn, and a rib pattern consisting of only a vertical groove is formed. "Met.

[0003]

In the above prior art,
The so-called all-season tread pattern, which has a tread portion transformed from a block pattern to a rib pattern, can be used throughout the year from winter to summer.
However, at the stage where the tread rubber is worn (middle to late wear), the horizontal groove disappears and a rib pattern consisting of only the vertical groove is formed, so that there has been a problem that the traction and braking performance is slightly lowered.

Further, in a pneumatic tire, land portions (edges of blocks, ribs, etc.) during running tend to cause heel-and-toe wear, and pattern noise tends to occur during running, resulting in noise reduction. There were challenges.
The present invention relates to a pneumatic tire which is transformed from a block pattern to a rib pattern, in an initial stage of wear (including when new).
The purpose of the present invention is to provide a pneumatic tire in which heel-and-toe wear is prevented and pattern noise is suppressed while ensuring (maintaining) traction and braking performance over a later period of wear. It is suitable for road driving.

[0005]

According to the present invention, a plurality of longitudinal grooves extending in the circumferential direction are formed at intervals in the tread width direction, and lateral grooves extending in a direction crossing the longitudinal grooves are spaced in the tread circumferential direction. In order to achieve the above-mentioned object, the following technical measures are taken in a pneumatic tire having a tread portion of a block pattern formed in a large number.
That is, the pneumatic tire of the present invention according to claim 1 is:
At the stage where the tread portion corresponding to about half of the maximum depth of the vertical groove is worn, most of the horizontal groove disappears and a part of the horizontal groove is left in the vertical groove as a branch horizontal groove. A tread portion is formed.

As described above, since the lateral grooves remain as the branched lateral grooves even in the latter period of wear (including the middle stage), the traction performance and the brake performance are maintained even in the rib pattern even in the latter period of wear (including the middle period). is there. The pneumatic tire according to the present invention according to claim 2, wherein the longitudinal groove is a center longitudinal groove 2 located at the center of the tread width.
First side vertical grooves 3L, 3R located on the left and right sides of the center vertical groove 2, and second side vertical grooves 4L, 4R located on the left and right sides of the first side vertical grooves 3L, 3R; Left and right shoulder vertical grooves 5L, 5R located outside the left and right of the second side vertical grooves 4L, 4R and at the shoulders of the tread width.
R, and when the tread portion 1 corresponding to about half of the maximum depth of the center vertical groove 2 and the left and right second side vertical grooves 4L, 4R is worn, the left and right first Lateral grooves 6L, 6R, 7L, 7 together with side vertical grooves 3L, 3R and the left and right shoulder vertical grooves 5L, 5R.
Most of R, 8L, 8R, 9L, 9R disappear, and the center longitudinal groove 2 and the left and right second side longitudinal grooves 15L,
15R, a part of the lateral groove is branched into lateral grooves 21L, 21L.
The tread portion 1 of a plurality of rib patterns left as R, 22L, and 22R is formed.

It is recommended that about half of the first and second aspects be 55 to 60% of the maximum depth of the vertical groove (claim 3). Further, the above-mentioned claim 1 or 2
In the above, the branch lateral grooves 21L, 21R, 22L, 22
It is recommended that R is left and right alternately left in the longitudinal direction of the longitudinal grooves 2, 4L, 4R (claim 4). Further, according to claim 1 or 2, the branch lateral grooves 21L, 2L,
1R, 22L, longitudinal groove 2, 4L in which 22R is left,
4R has a zigzag shape alternately left and right in the circumferential direction via the bent portions 14S, 15L, 15R, and has branch lateral grooves 21L, 2L.
Each of 1R, 22L, 22R has a bent portion 14S, 15
It is recommended that the residue be left through L and 15R (claim 5).

Further, in the pneumatic tire according to the present invention, the vertical groove has a center vertical groove 2 located at the center of the tread width and a first vertical groove located on the left and right sides of the center vertical groove 2. The side vertical grooves 3L and 3R and the first side vertical grooves 3
L, 2R, 2L, 4R, 4L
R, and left and right shoulder vertical grooves 5L, 5R located on the shoulders of the tread width on the right and left outside of the second side vertical grooves 4L, 4R, and the center vertical groove 2 and the left and right The groove depths of the second side vertical grooves 4L, 4R are the same or substantially the same, and the left and right first side vertical grooves 3L, 3R and the left and right shoulder vertical grooves 5L,
The groove depth of 5R is 55% to 60% of the groove depth of the center longitudinal groove 2 and the left and right second side longitudinal grooves 4L and 4R, and the center longitudinal groove 2 and the left and right first side grooves are formed. Left and right center horizontal grooves 6L connecting the vertical grooves 3L and 3R,
6R has a step portion 20C in the middle of the longitudinal direction of the groove, and the left and right first side vertical grooves 3L, 3R have the same or almost the same shallow groove portion 20B as the vertical grooves 3L, 3R.
A deep groove 20A whose side is the same or almost the same as the vertical groove 2
The left and right second side vertical grooves 4L and 4R communicate with the left and right first side vertical grooves 3L and 3R and the left and right shoulder vertical grooves 5L and 5R, respectively. , 7R and the left and right second side lateral grooves 8L, 8R each have a stepped portion 20C in the middle of the longitudinal direction of these grooves, and have the left and right first side vertical grooves 3L, 3R side and the left and right shoulder vertical grooves 5L, 5R. The side is the vertical groove 3
The left and right second side vertical grooves 4L, 4R are the same or almost the same deep groove 20A as the vertical grooves 4L, 4R in the shallow groove 20B which is the same or almost the same as L, 3R, 5L, 5R. It is assumed that.

Further, the center vertical groove 2 and the left and right second side vertical grooves 4L, 4R are defined by the bent part 1
4S, 15L, 15R, and alternately zigzag in the circumferential direction, the left and right center lateral grooves 6L, 6R and the left and right first side lateral grooves 7L, 7R, and the left and right second lateral grooves 7L, 7R.
Each of the side lateral grooves 8L and 8R is provided with the bent portion 15
It is recommended to be formed in L, 15R (claim 7). Further, the left and right center blocks 10L and 10R are formed by the center vertical groove 2, the left and right first side vertical grooves 3L and 3R, and the left and right center horizontal grooves 6L and 6R. The first side vertical grooves 3L, 3R and the left and right second side vertical grooves 4L, 4R.
And the left and right shoulder vertical grooves 5L, 5R and the left and right first and second side lateral grooves 7L, 7R, 8L, 8R to form left and right first and second side blocks 11L, 11R.
R, 12L, 12R are formed, and the left and right shoulder vertical grooves 5L, 5R and the left and right shoulder horizontal grooves 9L, 9R connected to the left and right shoulder vertical grooves 5L, 5R.
L and 13R are formed, and the left and right center blocks 1 are formed.
0L, 10R, the left and right first and second side blocks 11L, 11R, 12L, 12R, and the left and right shoulder blocks 13L, 13R have respective sipes 15L, 15R, 16L, 16R, 17 on the tread surfaces.
It is recommended that L, 17R, 18L and 18R are formed (claim 8).

In the above-mentioned claim 8, the left and right center blocks 10L and 10R and the left and right first blocks
Sipe formed on each of the two side blocks 11L, 11R, 12L, 12R is a horizontal sipe 15L, 15R, 16L, 16R, 17L, 17R along a horizontal groove.
It is recommended that the sipes 18L, 18R formed on the left and right shoulder blocks 13L, 13R are horizontal sipes, vertical sipes, or a combination of vertical and horizontal sipes (claim 9). Further, the sipe 15L, 15R, 16L, 16R, 17L, according to claim 8 or 9,
The depth of each sipe of 17R, 18L, 18R is
It is recommended that the depth be 55 to 60% of the groove depth of the left and right center vertical grooves 2 and the left and right second side vertical grooves 4L and 4R (claim 10).

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of a pneumatic tire having a tread portion which can be transformed from a block pattern to a rib pattern according to the present invention will be described. 1 and 2 show a first embodiment. FIG. 1 shows a pneumatic tire having a tread portion 1 in a block pattern. FIG. 2 shows a state in which the tread portion 1 is transformed into a rib pattern. Is shown. In FIG. 1, a tread portion 1 of a block pattern has a plurality of (seven in FIG. 1) longitudinal grooves extending in a circumferential direction at intervals in a tread width direction, and a horizontal groove extending in a direction crossing the longitudinal grooves. By forming a large number at intervals in the tread circumferential direction, the tread portion 1 has a block pattern separated by vertical and horizontal grooves.

More specifically, the plurality of vertical grooves include a center vertical groove 2 at the center (center) of the tread, and left and right first side vertical grooves 3L located on the left and right sides of the center vertical groove 2, 3
R, left and right second side vertical grooves 4L and 4R located on the left and right of the left and right first side vertical grooves 3L and 3R, and left and right outer sides of the left and right second side vertical grooves 4L and 4R. And the left and right shoulder vertical grooves 5L located in the shoulder portion,
5R. On the other hand, a large number of lateral grooves are provided with left and right center lateral grooves 6L and 6R that communicate (communicate) the center longitudinal groove 2 with the left and right first side longitudinal grooves 3L and 3R, and the left and right first lateral grooves.
The left and right first side lateral grooves 7L and 7R which communicate (communicate) the side vertical grooves 3L and 3R with the left and right second vertical grooves 4L and 4R, the left and right second side vertical grooves 4L and 4R, and the left and right shoulder vertical grooves 5L. , 5R, and left and right second shoulder side grooves 9L, 9R communicating (communicating) with the left and right shoulder vertical grooves 5L, 5R.

The left and right center blocks 10L, 1L are formed by a plurality of vertical grooves and a large number of horizontal grooves crossing the vertical grooves.
0R, left and right first and second side blocks 11
The tread portion 1 has a block pattern composed of L, 12L, 11R, 12R and left and right shoulder blocks 13L, 13R. Each of the plurality of vertical grooves may extend in a linear form in the circumferential direction, but in the illustrated form, the center vertical groove 2 and the left and right second side vertical grooves 4
L, 4R have zigzag shapes alternately left and right in the circumferential direction via bent portions 14S, 14L, 14R, respectively, and the left and right center lateral grooves 6L, 6R and the left and right first side lateral grooves 7L, 7R and the left and right second lateral grooves 7L, 7R. Side lateral groove 8L, 8R
Are formed in the bent portions 14S, 14L, 14R.

Further, the left and right center blocks 10L, 1
On the tread surface (ground contact surface) of the 0R, there are lateral sipes 15L and 15R (axial sipes) in the direction along the lateral groove, and traction performance and braking performance, particularly
Improve ice and snow performance. The same applies hereinafter), left and right first and second side blocks 11L, 12L, 11R, 12R.
Each of the horizontal sipes 16L, 17L, 16R, 1
7R is formed, and the left and right shoulder blocks 13L, 1L are formed.
3R is a combination sipe 18L, 18 composed of a horizontal sipe and a vertical sipe (a circumferential sipe, which mainly prevents sideslip at its sipe edge; the same applies hereinafter).
R is formed.

The lateral sipe formed in each of the center block and the first and second side blocks is such that the sipe adjacent to the lateral groove before and after the block is an open sipe, and two semi-open sipe are provided between the open sipe before and after the open sipe. It is sipes. Here, the open sipe means a sipe opening (edge) communicating two vertical grooves,
Semi-open means that only one end of the sipe opening communicates with the vertical groove and the other end is closed. As described above, by forming the lateral sipe by the open sipe in the block, the rigidity of the block edge is softened to prevent uneven wear, and the running performance on ice and snow roads is improved by easily breaking the water film or the ice and snow film. The traction performance and braking performance have been improved.

FIG. 1 shows a pneumatic tire according to the present invention.
As shown in FIG. 2, the left and right side ribs 23 separated from the tread portion 1 of the block pattern shown in (1) by the center vertical groove 2 and the left and right second side vertical grooves 4L and 4R.
L, 23R and left and right shoulder ribs 24L, 24R.
1L, 21R are alternately branched left and right in the circumferential direction in the left and right second side vertical grooves 4L, 4R.
Is transformed into the remaining tread portion 1 of the rib pattern.

That is, about 50% of the maximum depth (50 to 65%, preferably 55%) of the maximum depth of the vertical groove (the center vertical groove 2 and the left and right second side vertical grooves 4L, 4R in the embodiment).
% To 60%) at the stage when the tread portion corresponding to
Most of the lateral grooves and left and right first side vertical grooves 3L, 3L
R and the left and right shoulder vertical grooves 5L, 5R disappear and the vertical grooves (center vertical groove 2 and left and right second side vertical grooves 4L, 4L,
R), a part of the lateral groove (a part of the left and right center lateral grooves 6L, 6R, the left and right first and second side lateral grooves 7L, 7R, 8L, 8R).
Of the rib pattern formed by the left and right side ribs 23L, 23R and the left and right shoulder ribs 24L, 24R (a plurality of ribs, four ribs in the embodiment) left as part of the branch lateral grooves 21L, 21R, 22L, 22R. 1
The left and right side ribs 23L, 2L
Since 3R is formed as a result of the disappearance of the first side vertical grooves 3L and 3R, the wide side ribs 23L which are the sum of the tread surfaces of the center block and the first side block,
23R, and the left and right shoulder ribs 24L and 24R are formed as a result of the disappearance of the left and right shoulder vertical grooves 5L and 5R. Therefore, the wide left and right shoulder ribs 24L obtained by summing the tread surfaces of the second side block and the shoulder block. , 24R.

Center longitudinal groove 2 and left and right second side longitudinal grooves 4
L, 4R have the same groove width and groove depth (including substantially the same), and the left and right first side vertical grooves 3L, 3R
R is the center longitudinal groove 2 and the left and right second side longitudinal grooves 4
L and 4R are formed shallow with respect to the groove width and groove depth, and the left and right shoulder vertical grooves 5L and 5R are formed by the center vertical groove 2 and the left and right second side vertical grooves 4L and 4R. (Including the widths of the first side vertical grooves 3L and 3R) and the groove depth, where the vertical grooves are the center vertical groove 2 and the left and right second side vertical grooves 4L and 4R. The depth is the maximum depth, and the left and right first side vertical grooves 3L, 3L
The groove depths of R and the left and right shoulder vertical grooves 5L, 5R are each set to about half (50-65%, preferably 55-60%) of the maximum depth.

The left and right center sub-grooves 6L and 6R, the left and right first side sub-grooves 7L and 7R, and the left and right second side sub-grooves 8L and 8R are represented by the center lateral groove 6R in FIG. Center vertical groove 2 as described above (the same applies to the left and right second side vertical grooves 4L, 4R)
When the depth of the groove is H, the left and right center horizontal grooves 6L and 6R connecting the center vertical groove 2 and the left and right first side vertical grooves 3L and 3R are provided with step portions 20 in the middle of the groove longitudinal direction.
C, the left and right first side vertical grooves 3L, 3R are formed in a shallow groove portion 20B having the same or substantially the same groove depth H2 as the vertical grooves 3L, 3R. It is formed in a deep groove portion 20A having a depth H1, where H>H1> H2, and H2 is 50 to 6 of H.
It is 5%, preferably 55-60%.

That is, when the tread portion 1 is worn by about half of the maximum depth H of the vertical groove, the deep groove portion 20A in the horizontal groove is substantially branched lateral grooves 21L and 21R in the circumferential direction of the center vertical groove 2. The left and right grooves are formed alternately, and the deep groove portions 20 are formed also in the second side vertical grooves 4L and 4R.
A is substantially alternately formed in the circumferential direction as the branch lateral grooves 22L and 22R. On the other hand, the lateral grooves 6L, 6R, 7
The shallow groove portions 20B at L, 7R, 8L, and 8R (FIG. 1)
Until the tread portion 1 is reduced to about half, the tread portion 1 substantially functions as a tie bar, and the block rigidity is secured.

Further, each of the center longitudinal groove 2 and the left and right second side longitudinal grooves 4L, 4R is provided with a bent portion 14S,
When the shape is zigzag through 4L and 14R,
Each of the deep groove portions 20A, substantially branched lateral grooves 21L, 21
R, 22L, and 22R are bent portions 14S, 14 respectively.
It is formed via L and 14R. FIG.
As shown in (1), the tread portion 1 of the block pattern
Are formed at the center of the tread width, the first side vertical grooves 3L, 3R located on the left and right sides of the center vertical groove 2, and the first side vertical grooves 3L. A second side vertical groove 4L located on the left and right sides of the 3R,
4R, and left and right shoulder vertical grooves 5L, 5R located on the shoulders of the tread width on the right and left outer sides of the second side vertical grooves 4L, 4R. The groove depths of the second side vertical grooves 4L, 4R are the same or substantially the same.
Side vertical grooves 3L, 3R and the left and right shoulder vertical grooves 5
The groove depth of L and 5R is 50% to 65% of the groove depth of the center vertical groove 2 and the left and right second side vertical grooves 4L and 4R.
Desirably, it is 55% to 60%.

Further, the left and right center horizontal grooves 6L and 6R connecting the center vertical groove 2 and the left and right first side vertical grooves 3L and 3R have a stepped portion 20C in the middle of the longitudinal direction of the groove. The first side vertical groove 3L, 3R side is the vertical groove 3
L, 3R, the center vertical groove 2 side is the same or almost the same deep groove 20A as the vertical groove 2 in the shallow groove 20B which is the same or almost the same as the left and right second side vertical grooves 4
L, 4R, the left and right first side vertical grooves 3L, 3R, and the left and right shoulder vertical grooves 5L, 5R, respectively.
Each of the side lateral grooves 8L and 8R has a stepped portion 20C in the middle of the longitudinal direction of these grooves, so that the left and right first side vertical grooves 3
L, 3R side and left and right shoulder vertical grooves 5L, 5R side are the same or substantially the same shallow groove portion 20B as the vertical grooves 3L, 3R, 5L, 5R, and left and right second side vertical grooves 4L, 4R side are the vertical grooves 4L, This is the same or almost the same deep groove 20A as 4R.

Further, as shown in FIG. 1A, the left and right center blocks 10L and 10R are formed by the center vertical groove 2, the left and right first side vertical grooves 3L and 3R, and the left and right center horizontal grooves 6L and 6R. Formed on the left and right first
Side vertical grooves 3L and 3R and the left and right second side vertical grooves 4
L, 4R, the left and right shoulder vertical grooves 5L, 5R and the left and right first and second side lateral grooves 7L, 7R, 8L, 8
First and second left and right side blocks 11 depending on R
L, 11R, 12L, 12R are formed, and the left and right shoulder vertical grooves 5L, 5R and the left and right shoulder horizontal grooves 9L, 9R connected thereto form left and right shoulder blocks 13L, 13R, and the left and right center. Blocks 10L, 10R, the left and right first and second side blocks 11L, 11R, 12L, 12R, and the left and right shoulder blocks 13L, 13R have respective sipes 15L, 15R, 16L, 16 on the block tread surfaces.
R, 17L, 17R, 18L and 18R are formed, and the depth of each sipe is 50 times the groove depth of the left and right center vertical grooves 2 and the left and right second side vertical grooves 4L and 4R.
2 to 65%, preferably 55 to 60%. Therefore, as shown in FIG. 2, the sipes have disappeared in the case of the rib pattern.

FIGS. 3 to 5 show the second to fourth embodiments of the pneumatic tire having the tread portion 1 in a block pattern. The tread portion 1 is worn down to about half the maximum depth of the vertical groove. What transforms into the tread part of the rib pattern is
Since it is almost the same as FIG. 2, the differences will be described below, and the common parts will use the common reference numerals. FIG.
As apparent from (1) and FIGS. 3 to 5,
The forms of the sipes 18L, 18R formed on the tread surfaces of the left and right shoulder blocks 13L, 13R are different.

That is, the sipes 18L, 1L in FIG.
8R is a semi-closed sipe formed by a combination of a horizontal sipe and a vertical sipe (waveform sipe) that open in the shoulder vertical grooves 5L and 5R, respectively. On the other hand, the sipes 18L and 18R shown in FIG. 3 are vertical sipes and are closed sipes (sipes in which both ends of the sipes are closed). Further, the sipes 18L and 18R shown in FIG. 4 are a plurality of horizontal sipes, and are a combination of two closed sipes and one semi-closed sipes.

Further, the sipes 18L and 18R shown in FIG.
Is a short sipe formed by a semi-closed sipe (combination type) with a horizontal sipe and a vertical sipe (however, a straight sipe). In these sipes, since the sipes 18L and 18R shown in FIG. 3 are vertical sipes,
Although advantageous in terms of preventing sideslip, it is inferior in traction performance and braking performance, especially on icy and snowy roads. On the other hand, since the sipes 18L and 18R shown in FIG. 4 are lateral sipes, the traction performance and the braking performance are excellent, but the side slip prevention is slightly inferior.

In this regard, the combined sipes 18L and 18R shown in FIGS. 1 (1) and 5 are advantageous in traction performance, braking performance and anti-skid performance (cornering performance). Sipe 18L, 18 formed in shoulder block 13L, 13R
For R, the sipe depth is 50 to 65% of the depth of the center longitudinal groove 2 and the left and right second side longitudinal grooves 4L, 4R.
Desirably, the content is 55 to 60%.
As represented by (3), a combination of a wide sipe and a narrow sipe may be used.

Next, the tire size 11R22.514
P. For R pneumatic tires, acceleration performance index on snow, braking performance index, heel and toe wear or H /
Table 1 shows the results of experiments conducted on Examples 1 and 2 of the present invention and Conventional Examples 1, 2, and 3 for the amount of T wear and the passing noise index.

[0029]

[Table 1]

However, the temperature at the time of measuring the performance on snow is minus 5
° C, and parentheses in the column of acceleration / braking index are index values when the tread portion is worn by 50%.

[0031]

As described in detail above, according to the present invention, the wear resistance, uneven wear resistance and running noise can be suppressed, and the traction performance and brake performance can be reduced even in the tread portion of the rib pattern. Can be maintained.

[Brief description of the drawings]

FIG. 1 is a first embodiment showing a tread portion in a block pattern, (1) is a partially developed plan view of the tread portion, (2) is an AA enlarged sectional view of (1), (3) () Is an enlarged sectional view of the shoulder sipe.

FIG. 2 is a plan view of a tread portion when the block pattern of FIG. 1 is transformed into a rib pattern.

FIG. 3 is a plan view of a second embodiment showing a tread portion in a block pattern.

FIG. 4 is a plan view of a third embodiment showing a tread portion in a block pattern.

FIG. 5 is a plan view of a fourth embodiment showing a tread portion in a block pattern.

[Explanation of symbols]

 1 tread portion 2 center longitudinal groove 3L, 3R first side longitudinal groove 4L, 4R second side longitudinal groove 5L, 5R shoulder longitudinal groove 6L, 6R center lateral groove 7L, 7R first side lateral groove 8L, 8R second side lateral groove 9L, 9R shoulder lateral groove

Claims (10)

[Claims] 1. A plurality of longitudinal grooves extending in the circumferential direction are formed at intervals in the tread width direction, and a large number of transverse grooves crossing the longitudinal grooves are formed at intervals in the tread circumferential direction. In a pneumatic tire having a tread portion of a block pattern, at a stage where a tread portion corresponding to about half of the maximum depth of the vertical groove is worn, most of the horizontal groove disappears and a part of the horizontal groove becomes a vertical groove. A pneumatic tire characterized in that a plurality of tread portions of a rib pattern left as branch lateral grooves are formed. 2. A plurality of longitudinal grooves extending in the circumferential direction are formed at intervals in the tread width direction, and a large number of transverse grooves crossing the longitudinal grooves are formed at intervals in the tread circumferential direction. In the pneumatic tire having the tread portion of the block pattern, the vertical groove has a center vertical groove (2) located at the center of the tread width and a first side positioned left and right outside the center vertical groove (2). Vertical grooves (3L) and (3R), second side vertical grooves (4L) and (4R) located on the left and right sides of the first side vertical grooves (3L) and (3R), and second side vertical grooves (4L). )
(4R) and left and right shoulder vertical grooves (5L) and (5R) located on the left and right shoulders of the tread width, the center vertical groove (2) and the left and right second side vertical. When the tread portion (1) corresponding to about half of the maximum depth of the grooves (4L) and (4R) is worn, the left and right first side vertical grooves (3L) and (3R) and the left and right shoulder vertical grooves (3R). 5L) (5R) along with the lateral groove (6
L) (6R) (7L) (7R) (8L) (8R) (9
L) (9R) mostly disappears and the center vertical groove (2) and the left and right second side vertical grooves (15L) (1
5R), a part of the lateral groove is a branch lateral groove (21L)
A pneumatic tire, wherein a plurality of tread portions (1) of rib patterns left as (21R), (22L), and (22R) are formed. 3. The method according to claim 1, wherein the half is about half.
A pneumatic tire, wherein the depth is 55 to 60% of the maximum depth of the vertical groove. 4. The branch lateral grooves (21L) (21R) (22)
The pneumatic tire according to claim 1 or 2, wherein the left and right sides (L) and (22R) are alternately left in the longitudinal direction of the longitudinal grooves (2), (4L) and (4R). 5. The branch lateral groove (21L) (21R) (22)
L) The longitudinal groove (2) (4L) in which (22R) remains
(4R) has a zigzag shape alternately left and right in the circumferential direction through the bent portions (14S) (15L) (15R), and each of the branch lateral grooves (21L) (21R) (22L) (22R) has a bent portion ( 3. The pneumatic tire according to claim 1, wherein the pneumatic tire remains through the 14S), (15L), and (15R). 4. 6. A plurality of longitudinal grooves extending in the circumferential direction are formed at intervals in the tread width direction, and a large number of transverse grooves crossing the longitudinal grooves are formed at intervals in the tread circumferential direction. In the pneumatic tire having the tread portion of the block pattern, the vertical groove has a center vertical groove (2) located at the center of the tread width and a first side positioned left and right outside the center vertical groove (2). Vertical grooves (3L) and (3R), second side vertical grooves (4L) and (4R) located on the left and right sides of the first side vertical grooves (3L) and (3R), and second side vertical grooves (4L). )
(4R) and left and right shoulder vertical grooves (5L) and (5R) located on the right and left shoulders of the tread width, the center vertical groove (2) and the left and right second side vertical. The groove depths of the grooves (4L) and (4R) are the same or substantially the same, and the left and right first side vertical grooves (3L) and (3R) and the left and right shoulder vertical grooves (5L)
The groove depth of (5R) is 55 times the groove depth of the center vertical groove (2) and the left and right second side vertical grooves (4L) and (4R).
% To 60%, and the left and right center horizontal grooves (6L) (6R) connecting the center vertical groove (2) and the left and right first side vertical grooves (3L) (3R) are in the longitudinal direction of the groove. And a first longitudinal groove (3L) (3R) on the left and right sides having a step portion (20C) in the middle thereof and a shallow groove portion (20B) which is the same or substantially the same as the longitudinal groove (3L) (3R). The (2) side is the same or almost the same deep groove (20A) as the vertical groove (2), and the left and right second side vertical grooves (4L) and (4R) and the left and right first side vertical grooves (20R) are formed. 3
L) (3R) and the left and right shoulder vertical grooves (5L)
The left and right first side lateral grooves (7L) and (7R) and the left and right second side lateral grooves (8L) that communicate each of the (5R).
Each of (8R) has a step (20C) in the middle of these grooves in the longitudinal direction, and has left and right first side vertical grooves (3L) (3L).
R) side and the left and right shoulder vertical grooves (5L) and (5R) sides are the same or almost the same shallow grooves (20B) as the vertical grooves (3L), (3R), (5L) and (5R), and the left and right second side vertical grooves. (4L) The pneumatic tire, wherein the (4R) side has a deep groove (20A) which is the same as or substantially the same as the vertical groove (4L) (4R). 7. The center vertical groove (2) and the left and right second side vertical grooves (4L) (4R) are bent (14S) (1
5L) and (15R), and alternately zigzag in the circumferential direction. The left and right center lateral grooves (6L) and (6R), the left and right first side lateral grooves (7L) and (7R), and the left and right second side lateral grooves. The pneumatic tire according to claim 6, wherein each of (8L) and (8R) is formed in the bent portion (15L) (15R). 8. The left and right center blocks (10L) (10R) by the center vertical groove (2), the left and right first side vertical grooves (3L) (3R), and the left and right center horizontal grooves (6L) (6R). Are formed, the left and right first side vertical grooves (3L) and (3R), the left and right second side vertical grooves (4L) and (4R), and the left and right shoulder vertical grooves (5L).
(5R) and the left and right first and second side lateral grooves (7
L) (7R) (8L) (8R) to the left and right first and second side blocks (11L) (11R) (12)
L) and (12R) are formed, and the left and right shoulder blocks (13L) and (13R) are formed by the left and right shoulder vertical grooves (5L) and (5R) and the left and right shoulder lateral grooves (9L) and (9R) connected thereto. The left and right center blocks (10L) and (10R), and the left and right first and second side blocks (11L) (11R) (12)
L) (12R), the left and right shoulder blocks (13
L) (13R) on each block tread surface (15L) (15R) (16L) (16R) (17L)
The pneumatic tire according to claim 6 or 7, wherein (17R), (18L), and (18R) are formed. 9. Left and right center blocks (10L) (1
0R) and left and right first and second side blocks (11L)
The sipe formed on each of (11R), (12L), and (12R) is a horizontal sipe (15L) (1
5R) (16L) (16R) (17L) (17R), and the sipe (18L) (18R) formed on the left and right shoulder blocks (13L) (13R) is a horizontal sipe or a vertical sipe or a vertical / horizontal sipe. The pneumatic tire according to claim 8, which is a combination sipe. 10. The sipe (15) according to claim 8 or 9,
L) (15R) (16L) (16R) (17L) (17
The depth of each sipe of R) (18L) (18R) is 55 to 60% of the groove depth of the left and right center vertical grooves (2) and the left and right second side vertical grooves (4L) (4R).
A pneumatic tire characterized in that: