JPH05104912A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To heighten traveling performance on the icy road surface by providing an inner block with siping groups, each of which is formed of one to five sipings including an intermittent siping, at specified spaces apart between a longitudinal shoulder groove and an inner longitudinal sub-groove. CONSTITUTION:There are provided plural lateral grooves G2 extended to the tread edge E in the direction of intersecting a shoulder groove G1, and a longitudinal sub-groove group 4 formed of two longitudinal sub-grooves which are an inner longitudinal sub-groove G3 and an outer longitudinal sub-groove G4 extended continuously or discontinuously in the tire circumferential direction within the distance M between an outer point P spaced by 3mm to 6mm from the tread edge E and an inner point Q spaced by 0.04 to 0.1 times the tread width TW from the tread edge E. The tread edge E is formed into a square shoulder. In an inner block B1, siping groups, each of which is formed of one to five sipings S including an intermittent siping S1, are provided at specified spaces apart between the longitudinal shoulder groove G1. and the inner longitudinal sub-groove G3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire capable of improving side skid resistance and wandering resistance to improve running performance on icy and snowy roads, and to improve uneven wear resistance to improve durability.

[0002]

2. Description of the Related Art Conventionally, a spike tire in which a chain is attached to a tire or a spike is driven has been used for traveling on an icy road surface or a snowy road surface. However, in recent years, because road surface damage due to spikes and dust scraped off due to the road surface being scraped off, wearing of spiked tires and chains using hard spikes is progressing toward self-restraint, so-called studless without spikes. Tires are increasing.

Such a studless tire has a problem that the running performance on an icy and snowy road surface is inferior to that of the spiked tire, and a side slip is likely to occur particularly when turning on an icy and snowy road surface.

[0004]

In the conventional studless tire, the main purpose is mainly to improve the straight running performance on an icy and snowy road. Therefore, in the tire tread surface, the circumferential length between the central portion and the tread shoulder portion is set. The slippage of the tread shoulder portion occurs due to the difference in thickness, and various attempts have been made to prevent uneven wear and wandering phenomenon caused by the slip.

For example, as shown in FIG. 8 (A), there is a shoulder block a having laterally extending sipes s, and a tread end slanted portion k having a vertical small groove g formed around it. With this structure, the rigidity of the shoulder block a is slightly lowered, and wandering on dry roads can be prevented, but side slippage on ice and snow roads cannot be suppressed.

Although it has been attempted to provide a large number of sipes s on the tread shoulder at small intervals as shown in FIG. 8B, the shoulder block a has a reduced rigidity in the tire circumferential direction, and wandering is reduced. However, there was no effect on the force acting in the tire axial direction, and it was far from being able to improve the skid resistance. Moreover, there is a problem that uneven wear of the toe and heel frequently occurs before and after the siping of the block near both ends of the tread.

Further, as disclosed in Japanese Patent Application Laid-Open No. 56-21905 and as shown in FIG. 8 (C), a plurality of lateral sipes s and one vertical small groove g which circulates in the vicinity of a tread edge e are provided on a shoulder block a. Although the one provided with is proposed, while suppressing the wandering by the sipings,
With respect to the acting force applied from the lateral direction at the time of cornering or the like, the vertical small groove g causes the footing to slightly reduce the lateral slip. However, the above-mentioned proposal is intended to enhance the wandering resistance as well as the driving force and the braking force in the tire circumferential direction, that is, when the vehicle is straight ahead, and the side slip resistance is not particularly taken into consideration and is insufficient.

As described above, in the conventional tires for ice and snow roads, there are some points in which consideration is not given to the side slipperiness during turning.

The inventors of the present invention have earnestly studied in order to enhance the anti-skid resistance and the wandering resistance and to improve the uneven wear resistance. As a result, the installation position is regulated in the vicinity of the shoulder end to form two vertical sub-grooves. It has been found that by providing the shoulder block with siping while controlling its installation position and the number of threads, it is possible to improve the sideslip resistance, wandering resistance and uneven wear resistance.

The present invention is based on the fact that two vertical sub-grooves extending in the circumferential direction are provided in the tread shoulder portion, and that the sipe whose number is regulated is provided in the block located inside the sub-grooves. Improves skidability together,
Moreover, it is an object of the present invention to provide a pneumatic tire that can improve uneven wear resistance and durability.

[0011]

SUMMARY OF THE INVENTION According to the present invention, a tread shoulder portion is continuously formed in the tire circumferential direction, and a distance of 0.2 times or more and 0.3 times or less of a tread width (TW) is separated from a tire equator. Vertical shoulder groove (G1)
A plurality of lateral grooves (G2) crossing the shoulder groove (G1) and extending to the tread edge (E), and an outer point (P) separating a distance of 3 mm or more and 6 mm or less from the tread edge (E) to the tire equator side. An area (M) between the tread edge (E) and an inner point (Q) separating from the tread width (TW) by 0.04 times or more and 0.1 times or less the tire equatorial side. And two vertical sub-grooves, which extend continuously or discontinuously in the tire circumferential direction, and which include an inner vertical sub-groove (G3) on the tire equator side and an outer vertical sub-groove (G4) on the tread edge (E) side. By providing a group of vertical sub-grooves, the inner block (B) surrounded by the vertical shoulder groove (G1), the horizontal groove (G2) and the inner vertical sub-groove (G3) is provided in the tread shoulder portion.
Block row (L1) consisting of 1) and the lateral groove (G
2), an intermediate block row (LM) composed of an intermediate block (BM) surrounded by inner and outer vertical sub-grooves (G3) and (G4), and outer vertical sub-groove (G4) and lateral groove (G2) And an outer block row (LO) consisting of outer blocks (B0) along the tread edge (E), and the inner block (BI), middle block (BM), and outer block (BO). ) The tire meridian tread surface is
The tread edge (E) is formed into a convex curved surface that is smoothly continuous and has an arc of a curvature radius (TR) of 450 to 800 mm, and that the tread surface (F) and the shoulder wall surface (W) form an intersection angle. Formed by square shoulders that intersect with one another, while blocks within said (BI)
The vertical shoulder groove (G1) and the vertical sub-groove (G3) inside
A sipe group consisting of one or more and five or less sipe (S) including intermittent sipe (SI) that is intermittently connected to and from each other, and an interval between adjacent sipe (S) is 8 mm.
It is a pneumatic tire which is provided above and 16 mm or less.

The inner and outer vertical sub-grooves (G3, G4) are
Each groove depth (D1) is the vertical shoulder groove (G1)
0.3 times or more and 1.20 times or less of the groove depth (D0) of
It is desirable that the groove width (WG) is 2.0 mm or more and 4.5 mm or less.

[0013]

Since the tread shoulder portion is provided with the two vertical sub-grooves arranged in the restricted region M near the tread edge E starting from the tread edge E, the edge of the vertical sub-groove is provided in the tire. Since the edge in the circumferential direction is formed and grips in the region M against the acting force in the tire axial direction including during turning, it is possible to prevent the side slip of the tire during turning. Further, by limiting the number of the vertical sub-grooves to two, it is possible to prevent the rigidity of the region M in the axial direction of the tire from being lowered, and to secure the steering stability during straight traveling and turning.

Since the siping S passes continuously or discontinuously between the vertical shoulder groove G1 of the inner block BI and the vertical sub-groove G3 of the inner block BI, the middle block BM and the outer block BO do not have siping and therefore the middle block BM does not have any siping. , Outer block BM, BO
While maintaining the rigidity in the circumferential direction, it becomes extremely easy to follow the block BI on the ice and snow road surface, and the side slip resistance is further improved, and at the same time, the starting force and the braking force at the time of straight running are increased to improve the snow ski road. The driving performance can be improved in a balanced manner.

Further, since the number of sipes S is 5 or less per block, uneven wear and chipping of the blocks caused by the sipes S can be prevented, and the durability of the tread portion is improved.

Moreover, the inner, middle, and outer blocks BI, B
Since the tread surface of M and BO is composed of a convex curved surface of 450 to 800 mm and the tread edge is formed as a square shoulder, uneven wear at the tread edge, which is apt to occur in the past, is prevented. The wandering resistance, which has been a drawback of the square shoulder, is improved by the two vertical sub-grooves having the above-mentioned structure.

The outer block BO and the intermediate block B
Even when M has a narrow width in the tire axial direction,
By discontinuing one or both of the vertical sub-grooves G3 and G4, it is possible to prevent the rigidity of the outer or middle blocks BO and BM from being extremely lowered, improve wear resistance, and further improve durability.

Similarly, by including the intermittent siping SI in the siping forming the siping group LS,
It is possible to prevent an excessive decrease in rigidity of the inner block BI due to the formation of the sipings S ..., Prevent uneven wear and further improve durability.

As described above, according to the invention of the present application, the vertical sub-groove, the siping, and the shape of the tread surface in the tread shoulder portion are organically combined and integrated, so that the wandering property and the skid property are well balanced. Therefore, it is possible to improve the durability and improve the uneven wear resistance.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 to 4, the pneumatic tire 1 includes a vertical shoulder groove G1 that is continuous in the tire circumferential direction in the tread shoulder portion SH, and a plurality of lateral shoulder grooves G2 that intersect the vertical shoulder groove G1 and extend to the tread edge E. , A vertical sub-groove G3 arranged in the vicinity of the tread edge and extending continuously or discontinuously in the tire circumferential direction and extending linearly or in a zigzag shape.
Vertical sub-groove group 4 composed of two vertical sub-grooves 33 of the outer vertical sub-groove G4
And with.

Therefore, the tread shoulder SH has
An inner block row LI consisting of an inner block BI surrounded by the vertical shoulder groove G1, the lateral grooves G2, G2 and an inner vertical sub-groove G3, and surrounded by the lateral grooves G2, G2 and inner and outer vertical sub-grooves G3, G4. The middle block row LM including the middle block BM, the outer vertical sub-groove G4, and the lateral groove G
2, G2 and outer block row L0 along the tread edge E
And the blocks BI, BM, and BO form a block pattern in the tread shoulder portion.

The tread shoulder portions SH are located on both sides of the tread central portion CE through which the tire equator C passes, and form the tread portion 12 together with the tread central portion CE. In the present embodiment, the tread central portion CE has a longitudinal central groove GM substantially on the tire equator C, and a central lateral groove G extending in the tire meridian direction between the longitudinal central groove GM and the longitudinal shoulder groove G1.
P ... are provided, and these grooves G are provided in the central portion CE of the tread.
A central block row LC composed of a central block BC surrounded by M, G1, and GP is formed.

In this embodiment, the vertical shoulder groove G is used.
1, the lateral shoulder groove G2, the vertical central groove GM, and the central lateral groove GP all have the same groove depth DO, but the central lateral groove GP is made shallower so that the central block row LC is ribbed or ribbed from the middle of use. It is also possible to do so.

The pneumatic tire 1 has the tread portion 1
2 has side wall portions 13 and 13 extending inward in the tire radial direction from both ends, and bead portions 15 and 15 located at inner ends in the radial direction of the side wall portion 13, and is provided in each bead portion 15 and 15. A toroidal carcass 17 passing through the side wall portions 13 and 13 and the tread portion 12 is bridged between the bead cores 16 and 16, and a belt layer 19 is arranged radially outside and inside the tread portion 12. ..

The carcass 17 is a so-called radial or semi-radial direction array in which the carcass cords are arranged at an angle of 70 to 90 degrees with respect to the equator C of the tire in this embodiment, and a steel cord is used as the carcass cord. In addition, fiber cords such as nylon, polyester, rayon and aromatic polyamide are adopted.

In the present embodiment, three belt plies are arranged on the belt layer 19 from the carcass 17 side toward the radial outside of the tire. The belt layer 19 has belt cords in which cords of the respective belt plies are inclined with respect to the tire equator C and intersect with each other. The belt cords are made of steel, nylon, polyester, rayon like the carcass 17. Fiber cords such as aromatic polyamide are used.

The vertical shoulder groove G1 is arranged at a distance of 0.2 times or more and 0.3 times or less of the tread width TW, which is the distance between the tread edges E in the tire axial direction, from the tire equator C. On the other hand, the vertical sub-groove group 4 includes an outer point P that separates a distance of 3 mm or more and 6 mm or less from the tread edge E on the tire equator C side, and 0.04 times the tread width TW from the tread edge E. The distance W2 is equal to or more than 0.1 times and is equal to or less than 0.1 times in the region M between the inner point Q and the inner point Q which is separated from the tire equator.

As described above, the vertical sub-groove group 4 is provided in the vicinity of the tread edge E of the tread shoulder portion SH and at the tread edge E.
It is located at a distance from.

The vertical sub-groove group 4 comprises an inner vertical sub-groove G3 on the tire equator C side and an outer vertical sub-groove G4 on the tread edge E side. In the present embodiment, the inner vertical groove G3 is , A straight groove that opens at the lateral grooves G2, G2 and extends continuously. The outer vertical groove G4 is a straight and continuous groove, but a shallow groove portion 20 whose groove bottom is shallower than other positions is provided in the middle portion. As described above, in this example, the sub groove group 4 is formed by the two linear sub grooves G3 and G4 that are continuous in the tire direction.

In the tread shoulder portion SH, the tread surface F of the inner block B1, the middle block BM, and the outer block BO is smoothly continuous and has a radius of curvature of 450 mm or more and 800 mm or less. Is formed into a convex curved surface having a radius of curvature TR.

The tread edge E is formed as a so-called square shoulder where the tread surface F and the buttress wall surface (W) extending from the side wall portion 13 intersect at an intersecting angle.

By forming the tread edge E as a square shoulder in this way, skidding on an ice road can be suppressed, running stability on an ice and snow road can be improved, and shoulder drop wear can be prevented.

The inner and outer vertical sub-grooves G3 and G4 have respective groove depths D1 and D1 which are the groove depth DO of the vertical shoulder groove G1.
0.3 times or more and 1.2 times or less. Further, it is preferable that the groove widths WG and WG of the inner and outer vertical sub-grooves G3 and G4 are 2.0 mm or more and 4.5 mm or less. When there is a difference in height and bottom between the vertical shoulder grooves G1, the groove depth DO at the deepest position is used as a reference. Regarding the groove depth D1 and the groove width WG, the inner and outer vertical sub-grooves G3 and G4 have the same groove depth D1 and groove width WG in this embodiment, but the inner and outer vertical sub-grooves have the same dimensions. Groove depth D between G3 and G4
1 or the groove width WG may be different within the above range.

Even when the inner and outer vertical sub-grooves G3 and G4 have different groove depths D1, the groove depths D are different.
1 is preferably within the above range with respect to the groove depth DO of the vertical shoulder groove G1. Further, the shallow groove portion 20 has a vertical sub-groove G.
No problem will occur as long as the groove depth of 50% of the lower limit value can be secured within the range of 30% or less of the total length of G3.

In the region M, when the distance W3 of the outer point P from the tread edge E is less than 3 mm, the rigidity in the vicinity of the tread edge E of the outer block BO is remarkably reduced and uneven wear occurs. If it exceeds 6 mm, the rigidity of the outer block BO is increased and side slip occurs. Further, the distance W2 of the inner point Q from the tread edge E is 0.
If the inner side exceeds 1 time, the rigidity of the shoulder block 2 in the vicinity of the tread edge E increases, side slippage occurs, and the wandering property deteriorates. On the contrary, when the inner point Q is less than 0.04 times, the distance between the inner and outer vertical grooves G3 and G4 becomes narrower, resulting in the middle block B.
M, the outer block BO becomes narrower and these blocks B
The rigidity of M and BO decreases and uneven wear occurs.

If the groove depth DO is less than 0.3 times the vertical shoulder groove G1, the rigidity of the area M is increased and the grip force in the tire axial direction is decreased, which may cause side slippage. If it exceeds 1.2 times, the rigidity of the region M will be drastically reduced, the steering stability may be degraded, uneven wear may occur, and side slippage may occur.

Further, when the groove width WG is less than 2.0 mm, when a force is applied to the shoulder block 2 in the tire axial direction, side walls of the grooves facing each other may come into contact with each other, so that side slip may not be suppressed. If it exceeds 0.5 mm, uneven wear occurs to impair durability, and the middle and outer blocks BM and BO are narrowed to cause lateral slippage due to excessive reduction in rigidity. Therefore, it is preferable that the groove depth D1 and the groove width WG are within the above ranges.

When the number of the vertical sub-grooves in the region M is one, grip is insufficient with respect to the acting force in the tire axial direction, side slip occurs when turning on an ice / snow road, and camber thrust becomes low. Will be difficult to get over. On the other hand, if the number exceeds three, the rigidity of the shoulder block 2 in the axial direction of the tire becomes small and the steering stability deteriorates.

The vertical sub-grooves G3 and G4 have a groove width WG.
As shown in FIG. 5A, a widened portion WL may be locally provided in a range of 20% or less of the length of each of the vertical sub-grooves G3 and G4. 5 (B), it can be formed in a wavy shape, and as shown in FIG. 5 (C), it can be formed as a zigzag groove having different bending angles at the groove bottom and the groove opening, and in various shapes such as a trapezoid and a triangle. The vertical sub-grooves G3 and G4 having a groove shape can be adopted.

The inclination of the vertical sub-grooves G3 and G4 in the groove depth direction is less than or equal to the inclination angle θ of ± 5 ° with respect to the vertical line N with respect to the tread surface F of the tread portion 12, preferably the vertical line N direction. However, it is good for ensuring the sideslip resistance.

Further, in the inner block BI, one or more and 5 or less connecting the vertical shoulder groove G1 and the inner vertical sub-groove G3, and in this embodiment, a siping consisting of three sipes S. A group LS is provided.

In this embodiment, as shown in FIG. 3, the siping S extends substantially straight at the center of the inner block BI and extends straight in parallel to the lateral groove G2 and has a discontinuity 22 in the middle to form the intermittent siping SI. The siping SM and a pair of side sipes arranged on both sides of the central siping SM, bent in a Z shape, and provided with a shallow bottom portion 23 at an opening opened by the vertical shoulder groove GI and the inner vertical sub-groove G3. SE, SE
Consists of. In this way, the siping group LS includes the intermittent siping SI. Further, the distance between the central siping SM and the side siping SE, that is, the distance L between the adjacent sipes S and S is set to 8 mm or more and 16 mm or less.

Depth D2 of siping S (shown in FIG. 4)
Is preferably not less than 0.5 times and not more than 1.0 times the groove depth D1 of the vertical sub-groove G2, and its groove width WS is preferably not less than 0.3 mm and not more than 1.5 mm. Also, the siping S
Like the vertical sub-grooves G3 and G4, the groove depth D2 thereof may have a shallow shallow groove portion 23 locally, and the groove width WS thereof does not interfere with the locally widening portion. The length of the interrupted portion 22 in the groove longitudinal direction in the intermittent siping SI is preferably 1.0 times or more and 2.0 times or less the groove width WS.

As described above, since the siping S is provided only in the inner block BI and has the inner vertical sub-groove G3 as the groove end, there is no siping in the middle block BM and the outer block B0. It is possible to prevent uneven wear that tends to occur near the edge E.

The siping group L of the block B1 in one
In S, if the number of sipings S exceeds 5, or the siping interval is 8 mm or less, the inner block BI
May decrease in rigidity to cause uneven wear, and block cracks may occur from the siping S. On the contrary, when the siping S is not provided, or when the distance between the sipings exceeds 16 mm, the rigidity of the inner block B1 becomes large, and side slip occurs during traveling.

As described above, the siping group LS having the configuration of the present application
Is to optimize the rigidity of the shoulder block 2 in the axial direction of the tire in cooperation with the vertical sub-groove group 4 so as to reduce side slip and prevent uneven wear during traveling on ice and snowy roads, especially during turning. You can

FIG. 7 shows another example of the vertical sub groove group 4 and the siping group LS. In this example, the vertical sub-groove group 4 includes the vertical sub-groove G3 having the discontinuity 21 and the shallow bottom portions 20 and 2 at the opening ends on both sides.
And an outer vertical sub-groove G4 provided with 0.

Further, the siping group LS provided in the inner block BI has a central siping SM and two sipings arranged on both sides thereof.
It is formed by three sipes S, which are composed of side sipings SE and SE of the book, and in the siping group LS, the side siping SE has a vertical groove GI and an inner vertical sub-groove G3, respectively. The sipe SE on the side portion forms the intermittent sipe S1 by providing the discontinuity portions 22 and 22 between the vertical groove GI and the vertical sub-groove G3 in the end portion facing toward. As described above, in this example, the siping group LS includes the intermittent siping S1.

[0049]

[Specific example] Tire size is 11.00R20 14PR
The tires (Examples 1 to 4) having the configurations shown in FIGS. 1 and 2 were prototyped according to the specifications shown in Table 1 and their performances were tested. For comparison, a conventional configuration (Comparative Examples 1 and 2) and a non-constituent configuration (Comparative Examples 3 to 3)
As for 7), a prototype was also produced and tested. The test method is based on the following conditions.

A) Camber Thrust Using a maneuverability tester, the tire internal pressure was measured at 7.25 KSC and the load was 2840 kg under a camber angle of 6 °.
The larger the value on the positive side, the better.

(B) Steering force The internal pressure of 7.25 KSC was applied to the test tires, the tires were mounted on a 2-D truck, and the tires were judged based on the feeling of driving in the actual vehicle and displayed as an index with Example 3 as 100. .. The larger the value, the better.

C) Rib resistance resistance The tire was rubbed against the curb during actual vehicle running to investigate the situation of occurrence, and the index was set as 100 in Example 3. The larger the value, the better.

(D) Shoulder drop wear A test tire was mounted on an actual vehicle and a 100% paved road averaged 80 km under the load conditions specified in JIS.
/ H is run for 60,000 km, the groove depths of the vertical shoulder groove G1 and the vertical sub-grooves G3, G4 before and after running are measured, and the difference between the measured values before and after running is taken as the wear amount, and the reciprocal thereof is obtained in Example 3. 1
It is indicated by an index of 00. The larger the value, the better.

(E) On-snow-and-snow property The tire was mounted on an actual vehicle under the same conditions as the shoulder drop wear test shown in the item (2), and the braking test on ice-snow and the uphill test were conducted together.

1) Braking test A speed and braking distance measuring device and a test tire were attached to a test vehicle, run at a constant initial speed on a test road surface (normal pressure snow, on ice), and a sudden brake was applied at a fixed position for testing. The braking distance until the car was stopped was measured.

2) Uphill slopes are 4% and 7% in the uphill test
It was conducted in two lanes, and the test vehicle that had been temporarily stopped on the uphill road (normally compressed snow) was started, and it was confirmed whether or not the vehicle could start. As for the method for calculating the uphill acceleration time, the test vehicle was started from the stopped state by the zero start acceleration method, and the uphill acceleration time in the 50 m section was measured. At this time, two gears were used.

Description of road surface Normal pressure snow A road surface that has been compacted with tire rollers and dump trucks. (Studless tires have a friction coefficient of around 0.3) Ice roads that are close to the actual road are aimed at, and water is pierced in the form of snow on the compressed snow. (Friction coefficient of studless tire is around 0.11)

In the evaluation, the reciprocal of the braking distance in the control test is represented by an index with 100 in Example 3, and in the climb test, the reciprocal of the uphill acceleration time is used in Example 3.
Is shown as an index, and the average value of both is shown in Tables 1 and 2. The larger the value, the better.

[0059]

[Table 1]

[0060]

[Table 2]

As a result of the above-mentioned tests, the example has a higher camber thrust and a better steering holding force than the comparative example, so that both the wandering property and the skidability are improved and the rib tear resistance, It was confirmed that the excellent resistance to shoulder drop wear improves wear resistance and enhances steering stability on icy and snowy roads.

Further, as shown in FIGS. 6 and 7, in the example 3, the camber thrust CT with respect to the camber angle CA becomes larger on the positive side than in the comparative examples 1 and 2, and the lateral slip resistance is excellent. Was also confirmed.

[0063]

As described above, the pneumatic tire of the present invention is provided with two vertical sub-grooves in the range regulated from the tread edge at the tread shoulder, and between the vertical shoulder groove and the vertical sub-groove. As the gist is to provide sipings that regulate the number and spacing of the blocks, the wandering property and the skidability are both improved, and the steering stability on ice and snowy roads is improved, and the uneven wear resistance is increased and the durability is improved. Can improve.

Further, in forming the vertical sub-groove, either continuous groove or discontinuous groove can be selected, and by including intermittent siping in the siping group, the rigidity of the block in the shoulder region can be equalized and uneven wear resistance can be obtained. To further improve durability.

The present invention can be applied not only to a new tire but also to a retread tire in which the tread portion is rehabilitated.

[Brief description of drawings]

FIG. 1 is a plan view showing a tire tread portion of an embodiment of the present invention in a developed state.

FIG. 2 is a sectional view taken along the line X-X of the tire in the axial direction of the tire.

FIG. 3 is a perspective view showing a tread shoulder portion.

FIG. 4 is an enlarged sectional view showing the vertical sub-groove.

5A, 5B, and 5C are plan views showing other examples of vertical sub-grooves.

FIG. 6A is a diagram showing a relationship between a camber thrust and a camber angle, and FIG. 6B is a side view schematically showing its action.

FIG. 7 is a perspective view showing a tread shoulder portion of another embodiment.

8A, 8B and 8C are perspective views showing a conventional technique.

[Explanation of symbols]

 3 Vertical sub-groove 4 Vertical sub-groove group B1 Block inside BM Middle block BO Outer block C Tire equatorial line D1, DO Groove depth E Tread edge F Tread surface G1 Vertical shoulder groove G2 Horizontal groove G3 Vertical sub-groove G4 Outer vertical sub-groove LI Block row in LM Middle block row LO Outer block row LS Siping group M area N Vertical line P Outer point Q Inner point S Siping S1 Intermittent siping SH Tread shoulder TR Curvature radius W Wall surface WG groove Width TW tread width

[Procedure amendment]

[Submission date] August 7, 1992

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

Claims (2)

[Claims] 1. A longitudinal shoulder groove (G1) which is continuous with the tread shoulder portion in the tire circumferential direction and is arranged at a distance of 0.2 times or more and 0.3 times or less of the tread width (TW) from the tire equator. And a plurality of lateral grooves (G2) crossing the shoulder groove (G1) and extending to the tread edge (E) and an outer point (P) separating a distance of 3 mm or more and 6 mm or less from the tread edge (E) on the tire equator side. ) And an inner point (Q) separating the tread width (TW) from the tread edge (E) by 0.04 times or more and 0.1 times or less of the tread width (TW) on the tire equator side. And the longitudinal sub-groove (G) on the tire equatorial side that extends continuously or discontinuously in the tire circumferential direction.
3) and a vertical sub-groove group consisting of two vertical sub-grooves including the outer vertical sub-groove (G4) on the side of the tread edge (E), thereby providing the vertical shoulder groove (G1) in the tread shoulder portion. ), A horizontal groove (G2) and an inner vertical sub-groove (G3) surrounded by an inner block row (L1), and the horizontal groove (G2), the inner and outer vertical sub-grooves (G).
3), an intermediate block (B surrounded by (G4)
An outer block row (LO) consisting of an intermediate block row (LM) consisting of M) and an outer vertical sub-groove (G4), lateral groove (G2) and an outer block (B0) along the tread edge (E).
And the inner block (BI), the middle block (BM), and the outer block (BO), the tread surface in the tire meridian direction is smoothly continuous 450 to
A square shoulder formed in a convex curved surface formed of an arc having a radius of curvature (TR) of 800 mm, and the tread edge (E) intersects the tread surface (F) and the shoulder wall surface (W) at an intersecting angle. One or more and five including intermittent siping (SI) that is intermittently formed between the vertical shoulder groove (G1) and the vertical sub-groove (G3) in the inner block (BI) while being formed by A pneumatic tire in which a siping group (LS) including the following sipings (S) is provided with an interval between adjacent sipings (S) being 8 mm or more and 16 mm or less. 2. The inner and outer vertical sub-grooves (G3, G4) have a groove depth (D1) of 0.3 times or more the groove depth (D0) of the vertical shoulder groove (G1). The pneumatic tire according to claim 1, wherein the width is 1.20 times or less and the groove width (WG) is 2.0 mm or more and 4.5 mm or less.