JPH07186626A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To provide a pneumatic radial tire which can improve the drive feeling, steering stability on a wet road surface, and the traveling performance on a snow road. CONSTITUTION:A pneumatic radial tire has two center main grooves 1, center land part 2, two middle main grooves 3, center land part 4, and a middle main groove shoulder land part 5, and the center land part 4 is divided to a plurality of center blocks 41 by lug grooves 6, and the shoulder land part 5 is divided to a plurality of shoulder blocks 51 by lug grooves 7. A main siplng 8 divides the center land part 2 to a plurality of center blocks 21, and a main siping 9 divides the center block 41 to two center small blocks 42, and a main siping 10 divides ths shoulder block 51 to the shoulder small blocks 52.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire which is provided with a groove extending at least in a circumferential direction on a tread and which is suitable for running on a snowy road surface.

[0002]

2. Description of the Related Art An annular tread, and a pair of sidewalls extending inward in the tire radial direction from both ends of the tread,
In a pneumatic radial tire having an annular bead provided at the inner end of the sidewall, generally, a tread surface is provided with a tread pattern including circumferential grooves, lug grooves extending in the tread width direction, and sipings. ,
The drainage performance is improved, the steering stability on wet roads is ensured, and the running performance on mud and snowy roads is ensured. For example, the conventional tread pattern shown in FIG. 2 has two central main grooves a extending in the circumferential direction at a central portion of the tread, and two central main grooves a extending outward in the tread width direction of the central main groove a. Sub-grooves b, two sub-grooves c provided in the shoulders at both ends of the tread and extending in the circumferential direction, and a lug groove d extending in the tread width direction having both ends open to the central main groove a and the sub-main groove b. A lug groove e extending in the tread width direction with both ends open to the sub-main groove b and the sub-groove c, and a plurality of blocks f formed by the central main groove a, the sub-main groove b, the sub-groove c and the lug groove e. Siping g is provided.

[0003]

However, in the above-mentioned conventional tread pattern, the number of sipes per block is small and the rigidity of the block f is high, so that there is a problem that the performance on snow is insufficient. Therefore,
In order to reduce the rigidity of the block f and improve the snow performance, if the number of sipes per block is increased over the entire tread, the rigidity of the block f decreases too much,
There is a problem that the running performance and wear resistance of the muddy road surface and the steering stability on the dry road surface are deteriorated. Also,
Increase the number of sipes per block in one part of the tread (eg, the central part) and increase the number of other sipes (eg, the central part)
The number of sipes per block in the shoulder part) is reduced, the rigidity of part of the block (center part) is lowered to improve snow performance, and the other part (shoulder part)
It is possible to maintain the running performance and wear resistance on the mud road surface, and the steering stability on dry road surface by keeping the height of the block high, but some (center part) blocks and other parts Since the rigidity of the blocks of the (shoulder portion) is different, there is a problem that the riding comfort performance deteriorates.

An object of the present invention is to provide a pneumatic radial tire having improved riding comfort performance, steering stability on wet road surfaces, and snow performance without deteriorating steering stability on dry road surfaces.

[0005]

In order to achieve the above object, a pneumatic radial tire of the present invention comprises an annular tread, and a pair of sidewalls continuous at both ends of the tread,
A pneumatic radial tire having a bead at an inner end of a sidewall, at least 2 provided on a tread.
The main groove extending in the circumferential direction of the book, and the center land portion extending in the circumferential direction on the tread equatorial portion formed between the two main grooves extending across the tread equatorial portion, and the land portion other than the center land portion. A lug groove that is provided and has one end that opens to the main groove and the other end that opens to the other main groove or tread end to divide the land into a plurality of blocks, and the center land that has both ends on both sides. Main siping that opens in the main groove and divides the center land portion into multiple center blocks, and provided in the center block, one end opens in one of the main grooves on both sides, and the other end ends in the center block. It is provided in each block of the auxiliary siping and the land part other than the center land part, one end opens to the main groove, and the other end opens to the main groove, lug groove or tread end part, and each block is two small blocks. Main siping to be divided into Provided click, one end opening to the main grooves or lug grooves, in which the other end is provided with an auxiliary sipes terminating in the small blocks. According to this configuration, the land portion is divided by the lug groove, so that the rigidity of the land portion is reduced and the snow running performance is improved, and the drainage performance is improved by the lug groove to ensure the steering stability of the wet road surface. To do. In addition, the center land portion is divided into a plurality of center blocks by main siping to reduce rigidity, improve snow running performance, and improve ride comfort.
Further, by providing the auxiliary siping, the rigidity is made uniform between the center block and the blocks of other parts, and the riding comfort is improved. Also, by dividing each block into small blocks by main sipings provided on land parts other than the center land part, the rigidity of the blocks will be reduced, improving running performance on snow and improving riding comfort. By providing the auxiliary siping, it is possible to further reduce the rigidity of each block, further improve the running performance on snow, and improve the riding comfort. In addition, four main grooves extending in the circumferential direction provided on the tread, and provided on a block forming a central land portion between the main groove on the equator side and the main groove on the shoulder side,
Provided on the main siping that opens both ends to the main grooves on both sides to divide the central land block into two small blocks, and on the block that constitutes the shoulder land part between the main groove on the shoulder side and the tread end And one end is opened to the main groove on the shoulder side, and the other end is opened to the lug groove or the tread end to divide the shoulder land block into two small blocks. .

[0006]

Embodiments of the present invention will be described with reference to the drawings. In FIG. 1, a tread T is provided with two center main grooves 1 provided on the center side in the width direction and extending in the tire circumferential direction.
(1A, 1B), a center land portion 2 formed between two center main grooves 1, and two middle circumferentially extending tires provided on the tread end TO side with respect to the center main groove 1. The main grooves 3 and 3, the central land portion 4 formed between the center main groove 1 and the middle main groove 3, and the shoulder land portion 5 formed between the middle main groove 3 and the tread end TO. I have it.

The central land portion 4 is divided into a plurality of central blocks 41 by lug grooves 6 which are arranged so that both ends are open to the center main groove 1 and the middle main groove 3. Further, the shoulder land portion 5 is divided into a plurality of shoulder blocks 51 by a lug groove 7 having one end opening to the middle main groove 3 and the other end reaching at least the tread end TO. The above lug grooves 6,7
Has a groove width of 1.5 mm or more and less than 5 mm and a groove depth of 50% or more of the groove depths of the center main groove 1 and the middle main groove 3.

According to this structure, the central land portion 4 and the shoulder land portion 5 are divided into the central block 41 and the shoulder block 51 by the lug grooves 6 and 7, respectively, and the rigidity of the central land portion 4 and the shoulder land portion 5 decreases. As a result, the running performance on snow is improved, and the drainage performance is improved by the lug grooves 6 and 7 to ensure the steering stability on wet road surfaces. If the lug grooves 6 and 7 are not opened to the center main groove 1 or the middle main groove 3, or if the groove width of the lug grooves 6 and 7 is less than 1.5 mm, the rigidity of the central block 41 and the shoulder block 51 is high. As a result, the running performance on snow deteriorates, the drainage performance deteriorates, the steering stability on wet road surfaces deteriorates, and the riding comfort performance also decreases. When the groove width of the lug grooves 6 and 7 is 5 mm or more, the rigidity of each block becomes too high, the driving stability of the dry road surface deteriorates, and the wear resistance performance deteriorates.

The center land portion 2 is provided on the center block 21 and a main siping 8 which is open at both ends to the center main grooves 1A and 1B on both sides and divides the center land portion 2 into a plurality of center blocks 21. One center main groove 1A
Auxiliary siping 81A which is open at the other end and extends to the equator side of the tread T and ends in the center block 21, and one end is opened at the other center main groove 1B and the other end is at the equator side of the tread T. The auxiliary siping 81B extends and terminates in the center block 21. The main siping 8 is provided at an angle of more than 20 degrees and less than 70 degrees with respect to the equatorial plane of the tread, and two adjacent sipings 8A and 8B have different inclination directions. 8A and the siping 8B rising to the left are alternately arranged, and the center main grooves 1A and 1B are provided with widened portions 10A and 10B, respectively, and the widened portions 10A and 10B have 2
One end of each of the sipes 8A and 8B of the book is opened, and the center block 21 is formed in a substantially triangular shape. In addition, the auxiliary siping 81 (81A, 81B) is to the equatorial plane of the tread.
Main siping 8 with an angle of more than 20 degrees and less than 70 degrees
Is provided in the middle of the opening position to the main groove 1.

According to this structure, the main siping 8 divides the center land portion 2 into a plurality of center blocks 21 to reduce the rigidity, improve the snow running performance, and improve the riding comfort. The center block when the main siping 8 is inclined at an angle of 20 degrees or less with respect to the tire width direction
The lateral rigidity of 21 will decrease excessively, and the driving stability of dry road surface will decrease.If it exceeds 70 degrees, the lateral rigidity of center block 21 will become excessively high, and the running performance on snow will increase. Is reduced. In addition, auxiliary siping 81A, 81B
By providing the center block 21 and other parts,
That is, the central block 41 of the central land portion 4 and the shoulder land portion 5
The rigidity between the shoulder block 51 and
Improves ride comfort.

In the central land portion 4, one end is opened to the center main groove 1 and the other end is opened to the middle main groove 3 or the lug groove 6, and each central block 41 is divided into two central small blocks 42, 42. The main siping 9 that is divided into two parts, and the auxiliary siping 91 that is provided in each central small block 42 and has one end that opens to the center main groove 1 or the middle main groove 3 and the other end that terminates in the central small block 42. It is provided. The main siping 9 of the central block 41 may have one end opened to the middle main groove 3 and the other end opened to the center main groove 1 or the lug groove 6, and the auxiliary siping 91 is connected to the lug groove 6. It may be opened. In the shoulder land portion 5, one end is opened to the middle main groove 3 and the other end is opened to the lug groove 7 to divide the shoulder block 51 into shoulder small blocks 52, and to each shoulder small block 52. An auxiliary siping 101 is provided, one end of which opens into the middle main groove 3 and the other end of which terminates in the shoulder small block 52.

According to this structure, the central block 41 and the shoulder block 51 are connected to the central small block 42 and the small shoulder by the main grooves 1 and 3 or the main sipes 9 and 10 whose ends are open to the main groove 1 or 3 and the lug groove 6. Since it is divided into blocks 52 to reduce the rigidity of the central block 41 and the shoulder blocks 51, it is possible to improve the running performance on snow and improve the riding comfort. In addition, when one end of the main sipings 9 and 10 is not opened to the main grooves 1 and 3 or the lug groove 6, the rigidity of the central block 41 and the shoulder block 51 is high, the running performance on snow deteriorates, and the riding comfort is reduced. become worse. Further, by providing the auxiliary sipings 91 and 101, the central block 41 and the shoulder block 51
It is possible to further reduce the rigidity of the vehicle to further improve the running performance on snow and improve the riding comfort. By installing these auxiliary sipings 91 and 101, the running performance on snow and riding comfort are improved by the tread pattern. Since the amount is large, the selection range of the material of the tread rubber is widened, and other performances are less likely to be deteriorated. When both ends of the auxiliary sipings 91 and 101 are opened in the main groove or the like, the rigidity of the central block 41 and the shoulder block 51 is excessively reduced, and the running performance on dry road surfaces is reduced. Further, each shoulder block 52 is provided with an auxiliary siping 102 having one end opened to the tread end and the other end terminating inside the shoulder block 52. Auxiliary siping 102
By providing the shoulder block 52, the rigidity of the shoulder block 52 can be reduced, the traveling performance on snow can be further improved, and the riding comfort can be improved.

Next, an example tire to which the present invention is applied,
Experimental results using comparative example tires having other structures will be described. The tire size is 225 / 60ZR16, the size is 7J × 16, and the tire is mounted on the rim. The internal pressure is 2.0 kg / cm ^2.
The results are shown in Tables 1 and 2 after being run on a domestically produced FR vehicle (4,000 cc). Example tire: A tire with a tread pattern having the structure shown in FIG. Comparative tire I: A tire in which the main siping of the center land portion is halved (only the main siping inclined in one direction) as compared with the tire of the embodiment. Comparative tire II: A tire in which auxiliary siping of the central land portion is extended and both ends are opened in the main groove, as compared with the tire of the embodiment. Driving stability and ride comfort tests are sensory evaluations by the driver. In the braking test, when running at a speed of 60 km / h, all four wheels were braked to lock them, and the braking distance was measured five times. The maximum and minimum three times were averaged. In the abrasion resistance test, the occurrence of uneven wear was checked after running 20,000km on a general road (highway / general road = 70/30). The index display is based on Comparative Example Tire I (10
0), and the larger the value, the better the performance.

[Table 1] Steering Stability Steering Stability Ride Comfort Uneven Wear Resistance (Dry) (Wet) Comparative Example Tire I 100 100 Hard (100) Good Example Tire 95 95 105 Good (110) Good Good Comparative Example Tire II 90 105 Good (115) Wear occurred in the central land Note: The wear generated in the comparative tire II was heel and toe wear with a maximum depth of 1.5 mm that occurred in the central land. The steering stability on the wet road surface of the example tire has improved tenacity. [Table 2] On-snow pressure test On-ice test Steering stability Braking test Steering stability Braking test Comparative tire I 100 100 100 100 100 Example tire 100 101 105 102 Comparative tire II 105 105 102 110 104

From the results shown in Tables 1 and 2, when the main siping of the center land portion is reduced, the steering stability and riding comfort on wet road surfaces deteriorate, and the steering stability on ice sheets deteriorates. Further, when the auxiliary siping of the central land portion is extended and both ends are opened in the main groove, the rigidity of the block is excessively lowered, the steering stability on the dry road surface is deteriorated, and the uneven wear resistance is deteriorated.

[0016]

Since the present invention is constructed as described above, it has the following effects. Since the land part is divided by the lug groove, the rigidity of the land part is reduced and snow running performance is improved, and the drainage performance is improved by the lug groove, and steering stability on wet road surfaces is secured. In addition, the center land portion is divided into a plurality of center blocks by main siping to reduce rigidity, improve snow running performance, and improve ride comfort. Further, by providing the auxiliary siping, the rigidity is made uniform between the center block and the blocks of other parts, and the riding comfort is improved.
Also, by dividing each block into small blocks by main sipings provided on land parts other than the center land part, the rigidity of the blocks will be reduced, improving running performance on snow and improving riding comfort. By providing the auxiliary siping, it is possible to further reduce the rigidity of each block, further improve the running performance on snow, and improve the riding comfort. Further, by providing this auxiliary siping, the snow running performance and riding comfort are greatly improved by the tread pattern, the selection range of the material of the tread rubber is widened, and other performances are less likely to deteriorate.

[Brief description of drawings]

FIG. 1 is a development view of a tread pattern showing an embodiment of the present invention.

FIG. 2 is a development view of a tread pattern showing a conventional tire.

[Explanation of symbols]

T tread, TO tread end 1 center main groove, 2 center land part, 3 middle main groove, 4 center land part 5 shoulder land part, 6,7 lug groove, 8,9,10 main siping 81,91,101 auxiliary siping

Claims (2)

[Claims] 1. A pneumatic radial tire having an annular tread, a pair of sidewalls continuous at both ends of the tread, and a bead at an inner end of the sidewall, in at least two circumferentially extending main tires provided on the tread. A center land portion extending in the circumferential direction on the tread equatorial portion formed between the groove and two main grooves extending across the tread equatorial portion and a land portion other than the center land portion, and one end of which is the main groove. Lug groove that opens at the other end to the other main groove or the tread end and divides the land part into multiple blocks, and the center land part, and both ends open to the main grooves on both sides. Main siping that divides the land portion into a plurality of center blocks, and auxiliary siping that is provided in the center block, one end opens in one of the main grooves on both sides, and the other end ends in the center block, Each side block is provided in each block of the land part other than the center land part, one end of which opens into the main groove and the other end of which opens into the main groove, lug groove or tread end part.
It is characterized by comprising main siping divided into individual small blocks, and auxiliary siping provided on each small block, one end of which is opened to the main groove or the lug groove and the other end is terminated in the small block. Pneumatic radial tire. 2. A block that constitutes a central land portion between four main grooves extending in the circumferential direction provided on the tread, and the main groove on the equator side and the main groove on the shoulder side, and both ends thereof are on both sides. The main siping that opens into the main groove of the central land part is divided into two small blocks, and the block that forms the shoulder land part between the main groove on the shoulder side and the tread end is provided with one end. Is opened to the main groove on the shoulder side, and the other end is opened to the lug groove or the tread end portion, and main siping for dividing the block of the shoulder land portion into two small blocks is provided. Pneumatic radial tire as described.