JP3179914B2 - Heavy duty tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy-duty tire having improved wet grip and abrasion resistance.

[0002]

2. Description of the Related Art Heavy load tires, particularly bus tires, are required to have improved wet grip properties in order to stabilize running during rainfall.

[0003] On the other hand, it has been demanded that the running cost of trucks and buses be reduced, and that the cost per unit running distance be reduced and that tires having high durability are required.

Conventionally, a heavy-duty tire used for a bus or the like has four ribs or four ribs as shown in FIG. 5 in order to mainly improve the grip force when the road surface is dry and to maintain steering stability. It was formed by the pattern having the above ribs a, b, and c.

[0005]

However, the tires having the above-mentioned pattern do not have sufficient gripping force during rainfall, that is, wet gripping property. Particularly, in the case of a bus running on an urban area with many steep hills, a further wetness is required. Grip power was needed.

In order to solve one end of the above-mentioned problems, there has been proposed a structure in which a lateral groove d is provided at a central portion of the tread of the tread as shown by a dashed line in FIG. 5, but only a lateral groove is provided at random. Then, the request could not be satisfied.

As a result of intensive studies to satisfy the above demands, the inventors have found that a tread pattern is formed as a rib having a small number of longitudinal grooves, that is, a wide rib. Zigzag vertical grooves and small grooves extending from the corners of the zigzag ribs. Also, it is necessary to regulate the width and depth of the small grooves. As a result, the inventors have found that the wet grip property can be improved, and that the durability can be improved by regulating the groove depth of the vertical groove, and the present invention has been completed.

[0008] The present invention can improve the wet grip performance, enhance the driver's reliability, and improve the durability.
It is an object of the present invention to provide a heavy duty tire that can be suitably used as a bus tire.

[0009]

SUMMARY OF THE INVENTION The present invention is directed to a zigzag central longitudinal groove extending circumferentially on a tire equator on a tread surface and a zigzag side extending circumferentially between the central longitudinal groove and a tread edge. And the groove depth of each of the vertical grooves is set to 8.5% or more and 9.5% or less of the tread width, and a depth between the central vertical groove and the side vertical groove is set. The ribs extend from the corners of the zigzag, which are the entrance corners or the exit corners of the inner ribs, and are opened with vertical grooves. By tying the groove with the groove , the rib is traversed, or is provided with a break portion that is cut off near the center of the inner rib, and the groove depth of the small groove is at least open to the vertical groove. Characterized in that it has a deep-bottom portion in the vicinity of the opening where the depth is 80 to 90% of the groove depth of the vertical groove. This is a load tire.

Further, the small groove may be provided with a shallow portion which is 15 to 30% of the groove depth of the vertical groove following the deep portion.

The inner rib may be provided with a siping extending in the axial direction of the tire at the corner of the zigzag where the small groove does not open.

Further, the tread surface is 40 to 50% in the rubber composition.
% Of butadiene rubber.

[0013]

The tread portion has a central longitudinal groove and a lateral longitudinal groove of the above construction. Therefore, on both sides of the tire equator on the tread surface
The inner rib can be formed as a wide width, and the inner and side vertical grooves are all zigzag, so that the wet grip and traction properties are better than conventional tires, and the inner rib is formed wider. It is possible to improve durability.

Each vertical groove has a groove depth of 8.
The range is 5 to 9.5%. In conventional heavy duty tires, the groove depth is 7.5% of the tread width,
By setting it to 8.5% or more as in the present invention, the durability can be increased by 12% or more as compared with the conventional structure. If the depth is more than 9.5%, the movement of the edge of the rib becomes large due to the running of the tire, so that uneven wear occurs and heat generation increases, thereby impairing durability.

The small groove extends from the corner of the zigzag of the rib. By forming the ribs in this manner, the movement of each part of the ribs can be made larger and more uniform than in a conventional pattern in which sipes or lateral grooves are provided from other than corners.
Up to 7% of wet grip property can be improved.

The small groove has a groove depth of 80 to 90% of the groove depth of the vertical groove in the vicinity of the opening opening to the vertical groove. If it is less than 80%, improvement in wet grip properties cannot be expected, and if it exceeds 90%, the movement of the rib due to running becomes large, and uneven wear tends to occur at the edge of the small groove.

Further, the small groove has a groove width of 1.5 to 3 mm. When the thickness is 1.5 mm or less, the movement of the rib is small and the wet grip property is inferior. On the other hand, when it exceeds 3 mm, the movement of the rib becomes large and uneven wear occurs.

When the tread rubber is formed by a rubber composition containing 40 to 50% of butadiene rubber, the wet grip property can be increased by 10% or more by incorporating the butadiene rubber in combination with the effect of the small grooves. It is possible, and the abrasion resistance can be increased by 1.5 to 1.7 times by containing the butadiene rubber. If the content of butadiene rubber is less than 40%, the abrasion resistance cannot be improved, and if it exceeds 50%, the wet grip property is reduced and the rib edges may be chipped.

[0019]

An embodiment of the present invention will be described below with reference to the drawings. 1 and 2, a heavy load tire 1 has a zigzag central vertical groove 3 extending circumferentially on a tire equator C on a tread surface 2, and a zigzag side between the central vertical groove 3 and a tread edge E. And three vertical grooves 3, 4 formed by the vertical grooves 4, and an inner rib 5 is formed between the central vertical groove 3 and the side vertical grooves 4. The ribs 5 are provided with small grooves 6 extending from the zigzag corners P and Q of the vertical grooves 3 and 4.

As shown in FIG. 1, the heavy load tire 1 has a tread portion 12, a sidewall portion 13 extending inward in the tire radial direction from both sides of the tread portion 12, and a bead located inward of the sidewall portion 13 in the tire radial direction. And a carcass 16 that returns the bead core 15 of the bead portion 14 from the tread portion 2 through the sidewall portion 13 from the inside to the outside in the tire axial direction, and the tread portion 12 And a belt layer 17 disposed inside the carcass 16 in the radial direction and a bead apex 18 having a triangular cross section is raised outside the bead core 15 in the tire radial direction.

The bead portion 12 is provided with a tread rubber 9 that forms the tread surface 2 radially outside the belt layer 17.

In the present embodiment, the carcass 16 is composed of a single carcass ply in a radial arrangement inclined at an angle of about 90 ° with respect to the tire equator C. The carcass cord is made of nylon, polyester, aromatic polyamide or the like. Organic fiber cords and, if necessary, steel cords are used.

The belt layer 17 has a thickness of 3 to 4 in this embodiment.
Each of the belt plies has an organic fiber cord such as nylon, polyester, or aromatic polyamide fiber, or a belt cord made of a steel cord, and the second and third belt plies disposed on the outside are The belt cords are arranged so as to cross each other.

The center vertical groove 3 and the side vertical groove 4 have a groove depth GH which is a distance in the tire radial direction from the tread surface 2 to the groove bottom, and a tread which is a distance between the tread edges E and E. The width is 8.5% or more and 9.5% or less of the width TW, which is set deeper than the groove depth of a normal heavy duty tire is 7.5% or less of the tread width. It is preferable that the groove width GW of each of the vertical grooves 3, 4 is in the range of 6 to 10% of the tread width TW.

The inner ribs 5 are provided with small grooves 6 starting from the zigzag corners P and Q of the inner ribs 5. In the present embodiment, the corner P at the corner of the zigzag facing the central vertical groove 3 and the corner at the corner of the zigzag facing the vertical groove 4 located at a position facing the corner P of the corner. A plurality of small grooves 6 are provided so as to cross the inner ribs 5 by connecting with P ′. The small groove 6 has a groove width gw of 1.5 to 3 mm, and has a groove depth GH of 80 to 90 in the vicinity of an opening opening to each of the vertical grooves 3 and 4. %
And a shallow bottom portion 10B is formed following the deep groove portion 10A so that the groove depth gh1 is 15 to 30% of the vertical groove depth GH. . By forming the deep groove portion 10A in the vicinity of the opening and the shallow groove portion 10B following the groove portion, the inner ribs can increase the movement of the corners P and P 'while maintaining the strength thereof, Grip properties and abrasion resistance can be improved.

In this embodiment, the center of the inner rib 5 is defined by starting from the corners Q and Q 'of the protruding corners of the zigzag facing the central and side vertical grooves 3 and 4 of the inner rib 5. Sipings 11 having breaks 12 that break off in the vicinity are alternately arranged. Like the small groove 6, the siping 11 has a groove depth gh of 80 to 90% of the groove depth GH of the vertical grooves 3 and 4 in the vicinity of the opening opening to the vertical groove like the small groove 6.

Further, in this embodiment, the small groove 6 is bent in a Z shape, and the siping 11 is also bent in a U shape.

FIGS. 3 and 4 show another embodiment. In FIG. 3, the corner P at the entry corner facing the central longitudinal groove 3 and the corner Q 'at the exit corner facing the side longitudinal groove 4 are connected by a small groove 6A bent in a Z-shape.

On the other hand, in FIG. 4, the inner rib 5 has corners P at every two pitches facing the central vertical groove 3 and the corners P at every two pitches facing the side vertical groove 4. ′ To the corner P,
There are provided small grooves 6B , which are open at P 'and have a break 7 at the center of the rib 5 inside. The breaks 7 are formed at the corners P1, P 'of the corners of the opposed vertical grooves.
Connect to the siping 11A extending from 1. As described above, the present invention can be modified into various aspects.

The tread rubber 9 contains 40 to 5 in the rubber composition.
It is formed using a rubber containing 0% butadiene rubber.
For heavy duty tires, tread rubber is usually 100
% Natural rubber or (butadiene rubber / natural rubber) is 30 /
A rubber composition having a rubber composition of 70 or less is used. By increasing the butadiene rubber compounding ratio to a high ratio of 40 to 50%, wet grip properties are further enhanced, and by increasing the content of butadiene rubber, abrasion resistance can be further enhanced.

[0031]

As described above, the heavy duty tire of the present invention has the following features.
By providing the above configuration, it is possible to improve wet grip performance, increase braking performance and traction force, thereby improving running safety, and also enhance wear resistance and durability, and can be used for buses. Can be suitably adopted as the tire. By incorporating butadiene rubber within the range regulated by the tread rubber, the wet grip performance and the abrasion resistance can be further improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention.

FIG. 2 is a developed plan view showing the tread pattern.

FIG. 3 is a developed plan view showing another tread pattern.

FIG. 4 is a developed plan view showing another tread pattern.

FIG. 5 is a developed plan view showing a tread pattern of a conventional tire.

[Explanation of symbols]

 2 Tread surface 3 Center longitudinal groove 4 Side longitudinal groove 5 Rib in 6 P, P ', Q, Q' Corner TW Tread

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-134312 (JP, A) JP-A-52-44901 (JP, A) JP-A-54-136002 (JP, A) JP-A-1- 160709 (JP, A) Fully open 61-81403 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60C 11/00-11/12

Claims (4)

(57) [Claims] 1. A zigzag central longitudinal groove extending circumferentially on the tire equator on a tread surface, and a zigzag side longitudinal groove extending circumferentially between the central longitudinal groove and a tread edge. The groove depth of each vertical groove is set to 8.5% or more and 9.5% or less of the tread width, and the inner rib between the central vertical groove and the side vertical groove is replaced with the inner rib. It extends from the corner of the zigzag, which is the entry corner or the exit corner, and is opened by a vertical groove. A small groove having a groove width of 1.5 to 3 mm is formed by connecting the central vertical groove to the side vertical groove . Across the ribs, or with a break that breaks near the center of the inner ribs, and the groove depth of the small groove is at least the groove depth of the vertical groove near the opening that opens to the vertical groove. A heavy duty tire having a deep-bottom portion of 80 to 90%. 2. The heavy duty tire according to claim 1, wherein the small groove has a shallow portion which is 15 to 30% of a groove depth of the vertical groove following the deep portion. 3. The heavy-duty tire according to claim 1, wherein the inner ribs are provided with zigzag corners of the ribs, and extend in the tire axial direction and have a cut-off siping. 4. The heavy duty tire according to claim 1, wherein the tread surface is formed using a tread rubber containing 40% or more and 50% or less of butadiene rubber in a rubber composition.