JP2696298B2 - studless 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 studless tire having good running performance on icy and snowy roads without requiring a stud on a tread surface.

[0002]

2. Description of the Related Art Conventionally, in automobiles running on icy and snowy roads, spike tires having studs embedded in treads have been often used. However, spike tires have a problem that the road surface is shaved with the tip of a stud when traveling on a road during snow removal, and in recent years there has been a tendency to prohibit the use of spike tires. Therefore, studless tires that have improved running performance on ice and snow roads without providing studs on the tread surface have been widely used.In the case of studless tires, in order to improve running performance on ice and snow road surfaces, treads have been used. A block pattern in which a plurality of blocks are arranged is provided, and a plurality of sipes are provided in each block, and arrangement of the blocks and the siping is proposed.

[0003]

However, in general, the performance required for a tire includes starting and acceleration performance, braking performance, cornering performance, climbing performance, etc., and it is required to provide these performances in a well-balanced manner. However, the conventional studless tires described above mainly focus on improving braking performance on icy and snowy roads, and it cannot be said that other performances such as cornering performance are necessarily provided with sufficiently high performance. There was a problem.

[0004] It is an object of the present invention to provide a studless tire having improved running performance on icy and snowy roads, particularly improved cornering performance.

[0005]

In order to achieve the above object, a studless tire according to the present invention comprises a block formed by vertical grooves and horizontal grooves, and has at least one row of blocks extending in the tire circumferential direction. In the studless tire provided with, in the circumferential direction block row, the outer side in the tire rotation axis direction of the block, through the sub-groove shallower than the vertical groove and the lateral groove, the circumferential direction as a long side, and the rotation axis direction as a short side. At least one block is provided in one pitch. Further, on both sides of the grounding center line, the sub-blocks equidistant from the grounding center line are provided so as to be shifted from each other one by one. Further, the ratio of the land area L to the sea area S is expressed as L / S = (0.5 to 0.65) / (0.
5 to 0.35). Further, the land area M within the pitch within one pitch, the surface area m of one sub-block, the width a and the length c of the sub-block, the depth D of the vertical groove or the horizontal groove, the depth d of the sub-groove, the grounding center line Distance e from the sub-block to
In the tread contact width 2T, the following condition is satisfied. m / M = 0.025 to 0.050 a / c = 0.55 to 0.15 d / D = 0.40 to 0.80 0.2 <e / T <0.8

[0006]

[Function] By providing a sub-block, the running performance on ice and snow roads is improved and the lateral rigidity of the tread pattern is increased to prevent skidding, increase the cornering limit speed, and correct the attitude of the vehicle after slipping out Becomes easier,
Driving stability can be improved. If there is no sub-block in one pitch, the effect of preventing the sideslip in that one pitch portion is small, and the effect of preventing the sideslip in the tire circumferential direction becomes non-uniform, which adversely affects the running stability on the icy and snowy road surface. When L / S <0.5 / 0.5 = 1, the land area L is too small, the block is too small, the rigidity of the block is reduced, and the grip force on the road surface is reduced.
When S> 0.65 / 0.35 = 65/35, the sea area S becomes too small and the groove becomes too narrow, so that the snow column cannot be formed sufficiently when traveling on a snowy surface. And the running performance on the snow surface decreases. If m / M <0.025, the sub-blocks are each too small, the lateral rigidity is insufficient, and the effect of improving the steering stability is small. On the other hand, m
When /M>0.05, the sub-blocks are each too large, the deformation amount is small, and the side slip prevention effect is reduced. When a / c <0.055, the sub-block is too thin and rigidity is insufficient. When a / c> 0.15, the deformation of the sub-block is small, and the side slip prevention effect is reduced. Furthermore, d / D <
At 0.40, the sub-groove is too shallow, and the effect as a groove is small.
When /D>0.80, the sub-groove is too deep and the rigidity of the sub-block is reduced.

[0007]

An embodiment will be described with reference to the drawings. 1 and 2, a central longitudinal groove 2 extending in the tire circumferential direction is provided on the equatorial plane of the tread 1, and an intermediate longitudinal groove 3 and an outer longitudinal groove 4 are provided on both sides of the central longitudinal groove 2, respectively. A lateral groove 5 extending in the tire width direction from the tread edge 1a to the other tread end 1a, the central longitudinal groove 2, the intermediate longitudinal groove 3, and the lateral groove 5
, The inner block 6, the middle longitudinal groove 3, the outer longitudinal groove 4, and the lateral groove 5, the outer block 7, the outer longitudinal groove 4, and the tread end 1 a
Thus, the shoulder block 8 is formed by the lateral groove 5. In addition,
Since the intermediate vertical grooves 3 are formed not in a straight line in the circumferential direction but shifted in the width direction, the edges of the inner block 6 and the outer block 7 are formed at the intersections of the intermediate vertical grooves 3 and the horizontal grooves 5 in the circumferential direction. Instead of being located on a straight line, they are arranged offset from each other, increasing the effect of cutting edges on snow and ice surfaces, improving grip performance.

The inner block 6 has a siping 9 having both ends communicating with the central longitudinal groove 2 and the intermediate longitudinal groove 3. The outer block 7 has a siping 10 having both ends communicating with the intermediate longitudinal groove 3 and the outer longitudinal groove 4. The shoulder block 8 is provided with sipes 11 each having both ends communicating with the outer longitudinal groove 4 and the tread end 1a.
Up to five (four in this embodiment) are provided, and no other siping or notch is provided. These sipings increase the contact area between the block surface and the ice and snow road surface, improve the grip performance on the ice and snow road surface, and improve the traction performance on the ice and snow road surface due to the effect of excavating the ice and snow road surface. Further, the effect of the siping can be greatly improved by connecting the siping to the longitudinal groove. If the number of sipings provided in each of the blocks 6, 7, 8 is less than 3, the block rigidity is too high to improve the running performance on ice and snow road surface, and if it exceeds 5, the block rigidity sharply increases. And adversely affect steering stability, especially on a dry road. In addition, it is desirable that the siping is longer than the axial length of the block in order to improve the above effects. In the present embodiment, these effects are improved by forming the central portion of the siping in a wavy shape. ing.

In the circumferential block row of the inner block 6 and the outer block 7, every other inner block 6
The outer block 7 has a long side in the circumferential direction, via sub-grooves 6 a and 7 a (see FIG. 4) formed shallower than the grooves 2, 3, 4 and 5 on the outer side in the tire rotation axis direction. Inner sub-block 12 to prevent sideslip with the rotation axis direction as short side
And an outer sub-block 13. The inner sub-block 12 and the outer sub-block 13 are arranged so as to be shifted from each other by one block in the circumferential direction. In addition, in the circumferential block row of the inner block 6 provided on both sides of the grounding center line OL,
The inner sub-blocks 12 on both sides are provided at positions shifted from each other by one. In the circumferential block row of the outer blocks 7 also provided on both sides of the grounding center line OL, the outer sub-blocks 13 on both sides are provided one by one from each other. It is provided at a shifted position. By providing the inner sub-block 12 and the outer sub-block 13, the running performance on icy and snowy roads is improved, and the lateral rigidity of the tread pattern is increased to prevent skidding, increase cornering limit speed, and start sliding. After that, the attitude of the vehicle can be easily corrected, and steering stability can be improved. A buttress portion 14 which is a transition portion from the tread end 1a of the shoulder block 8 to the side portion 15 is provided.
Is provided with a recess 16 to reduce the rigidity of the shoulder block 8 and prevent wandering during running on a general road and understeer during cornering.

Further, at a contact portion between one tread end 1a and the other tread end 1a, a land area L which is the sum of the surface areas of all the blocks 6, 7, 8, 12, 13 over the entire circumference of the tire; The ratio of the opening area of the grooves 2, 3, 4, 5, 6a, and 7a to the sea area S, which is the sum of the opening areas, is expressed as L / S = (0.5
.About.0.65) / (0.5 to 0.35) (however, the area L + S = 1 of the entire grounding portion). When L / S <0.5 / 0.5 = 1, the land area L is too small, the block is too small, the rigidity of the block is reduced, and the grip force on the road surface is reduced. When L / S> 0.65 / 0.35 = 65/35, Since the sea area S becomes too small and the groove becomes too narrow, the snow column cannot be formed sufficiently when traveling on a snow surface. Therefore, the frictional force with the road surface decreases, and the traveling performance on the snow surface is reduced. descend.

The land area M in the pitch, which is the sum of the surface areas of the blocks 6, 7, 8, 12, 13 within one pitch of the tread pattern, and the inner sub-block 12 or the outer sub-block
The ratio of 13 to the surface area m of one piece is expressed by m / M = 0.025 to 0.050
And If m / M <0.025, each of the inner sub-block 12 and the outer sub-block 13 is too small, resulting in insufficient lateral rigidity and little improvement in steering stability. on the other hand,
When m / M> 0.05, the inner sub-block 12 or the outer sub-block 13 is too large, and the amount of deformation is small.
The side slip prevention effect is reduced. Further, the width a and the length c of the inner sub-block 12 and the outer sub-block 13 are calculated by a / c = 0.05.
5 to 0.15. When a / c <0.055, sub-blocks 12 and 13
However, when a / c> 0.15, the deformation amount of both sub-blocks 12 and 13 becomes small, and the side slip prevention effect is reduced. Further, for the depth D of each of the grooves 2, 3, 4, and 5, the depth d of the sub-grooves 6a and 7a is set to d / D = 0.40 to 0.80. When d / D <0.40, the sub-grooves 6a and 7a are too shallow, and the sub-grooves 6a and 7a have little effect as grooves, and d / D> 0.
At 80, the sub-grooves 6a and 7a are too deep, and the rigidity of the inner sub-block 12 and the outer sub-block 13 decreases. At least one inner sub-block 12 or outer sub-block 13 is provided within one pitch of the tread pattern. If there is no inner sub-block 12 or outer sub-block 13 in one pitch, the anti-skid effect of the one pitch portion is small, and the anti-skid effect in the tire circumferential direction becomes non-uniform. Has a negative effect on stability.

Further, the distance e ₁ from the ground center line OL of the tread 1 to the ground center side ridge line of the inner sub-block 12 and the distance e ₂ from the ground center line OL to the ground center side ridge line of the outer sub-block 13 are: The inner sub-block 12 and the outer sub-block 13 are set within a range of 0.2 <e / T <0.8 with respect to the contact width 2T, which is the distance between the tread ends 1a, 1a. e
When /T≦0.2, the width of the inner block 6 in the tire rotation axis direction is reduced, and the rigidity of the inner block 6 is reduced, which adversely affects traction performance on ice and snow road surfaces, running stability, and the like. When e / T ≧ 0.8, the shoulder block 8
Of the tire in the direction of the rotation axis of the tire becomes smaller and its rigidity is reduced, which adversely affects traction performance on ice and snow road surface, running stability and the like.

Next, Example 1 (see FIG. 4) to which the present invention is applied, Comparative Examples 1 to 3 having sub-blocks and having a structure partially deviating from the present invention, and Comparative Example 4 of a conventional structure Table 1 and Table 2 show the results of the tests using
Shown in In Comparative Example 1 (see FIG. 4), only the groove depth ratio d / D is out of the range of the present invention, that is, d / D = 0.34 <0.40 (lower limit). In Comparative Example 2 (see FIG. 5), the ratio m / M of the inner and outer sub-block surface areas to the land area within one pitch, and the aspect ratio a / c of the inner and outer sub-blocks are out of the range of the present invention. That is, m / M = 0.0145 <0.025 (lower limit), a / M
c = 0.050 <0.055 (lower limit). In Comparative Example 3 (see FIG. 6), the ratio m / M of the inner and outer sub-block surface areas to the land area within one pitch, and the aspect ratio a / c of the inner and outer sub-blocks are out of the range of the present invention. That is, m / M = 0.058> 0.05 (upper limit), a /
c = 0.200> 0.15 (upper limit). Comparative Example 4 (see FIG. 7) has a conventional tread pattern without inner and outer sub-blocks. In Tables 1 and 2, the running performance indicated by an index is based on Comparative Example 4, and the larger the index, the better the performance.

[Table 1] Example Comparative Example 1 Comparative Example 2 L / S 0.58 / 0.42 0.58 / 0.42 0.56 / 0.44 m / M 0.029 0.029 0.0145 a / c 0.100 0.100 0.050 d / D 0.588 0.34 0.588 Sub-block within one pitch number 2 2 2 (e / T) e 1 / T 0.27 0.27 0.29 e 2 / T 0.62 0.62 0.64 ( on-ice performance) turning performance index 105 102 102 slalom time index 106 102 101 (snow performance) handling path passing time (sec) 98.09 101.34 102.22 R35m passage speed (km / h) 32.6 31.2 31.1 Lane change stability score 7 6 6 Controllability after starting 8 7 6

[Table 2] Comparative Example 3 Comparative Example 4 L / S 0.60 / 0.40 0.55 / 0.45 m / M 0.058-a / c 0.200-d / D 0.588-Number of sub-blocks in one pitch 2-(e / T) e ₁ / T 0.25 ー e ₂ / T 0.60 ー (Performance on ice) Turning performance index 101 100 Slalom time index 103 100 (Performance on snow) Handling road passage time (seconds) 101.87 103.40 R35m passage speed (km / h) 30.9 29.3 lanes Change stability score 7 5 Controllability after starting 5 5

As is apparent from Tables 1 and 2, the provision of the sub-block improves the performance on ice and the performance on snow, and the sub-block satisfying the requirements of the present invention provides the sub-block. The performance, especially the cornering performance, is improved.

[0017]

Since the present invention is configured as described above, the following effects can be obtained. By providing a sub-block, while improving the running performance on ice and snow road surface,
By increasing the lateral rigidity of the tread pattern, it is possible to prevent skidding, increase the cornering limit speed, facilitate the correction of the vehicle attitude after slipping, and improve steering stability. When no sub-block exists in one pitch, the side slip prevention effect of the one pitch portion is small, and the side slip prevention effect becomes uneven in the tire circumferential direction,
It adversely affects running stability on ice and snow. L / S <0.
When 5 / 0.5 = 1, the land area L is too small, the block is too small, the rigidity of the block is reduced, the grip force on the ice and snow road surface is reduced, and L / S> 0.65 / 0.35 = 65/35.
In this case, the sea area S becomes too small and the groove becomes too narrow, so that a snow column cannot be formed sufficiently when traveling on a snow surface, so that the frictional force between the road surface and the road surface is reduced and the traveling performance on the snow surface is reduced. Decrease. When m / M <0.025, the sub-blocks are each too small, the lateral rigidity is insufficient, and the effect of improving the steering stability on the ice and snow road surface is small. On the other hand, m / M> 0.05
In the case of 0, the sub-blocks are each too large, the deformation amount is small, and the side slip prevention effect is reduced on the icy and snowy road surface. When a / c <0.055, the sub-block is too thin and the rigidity is insufficient. When a / c> 0.15, the deformation amount of the sub-block is small, and the side slip prevention effect is reduced on the icy and snowy road surface. Further, when d / D <0.40, the sub-groove is too shallow and the effect as a groove is small, and when d / D> 0.80, the sub-groove is too deep and the rigidity of the sub-block decreases.

[Brief description of the drawings]

FIG. 1 is a developed view of a tread according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of the tread developed view of FIG.

FIG. 3A is a sectional view taken along line AA in FIG. 2;
(B) is a sectional view taken along line BB, and (c) is a sectional view taken along line CC.

FIG. 4 is a tread developed view of the example and comparative example 1.

FIG. 5 is a tread developed view of Comparative Example 2.

FIG. 6 is a tread development diagram of Comparative Example 3.

FIG. 7 is a tread developed view of Comparative Example 4.

[Explanation of symbols]

1 tread, 2 central longitudinal groove, 3 intermediate longitudinal groove, 4 outer longitudinal groove, 5 lateral groove 6 inner block, 7 outer block, 8 shoulder block 9, 10, 11 siping, 12 inner sub-block, 13 outer sub-block

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication location B60C 11/12 B60C 11/04 H 11/13 (56) References JP-A-5-112105 (JP) JP-A-5-112104 (JP, A) JP-A-4-349004 (JP, A) JP-A-3-186408 (JP, A) JP-A-4-176712 (JP, A) JP JP-A-63-68407 (JP, A) JP-A-4-197809 (JP, A) JP-A-2-133201 (JP, A) JP-A-3-10910 (JP, A) A) JP-A-6-297916 (JP, A) JP-A-52-44904 (JP, A) JP-A-2-114006 (JP, A) JP-B-7-41776 (JP, B2)

Claims (4)

(57) [Claims] 1. A studless tire having a tread pattern comprising at least one row of blocks extending in the tire circumferential direction, the studless tire including blocks formed by vertical grooves and horizontal grooves. Characterized in that at least one sub-block is provided in one pitch on the outer side in a pitch with a long side in the circumferential direction and a short side in the rotation axis direction via a sub-groove shallower than the vertical groove and the horizontal groove. tire. 2. The studless tire according to claim 1, wherein the sub-blocks equidistant from the grounding center line are provided one by one on both sides of the grounding center line. 3. The land area L and the sea area S are defined as L / S
3. The studless tire according to claim 1 or 2, wherein the ratio is (0.5 to 0.65) / (0.5 to 0.35). 4. A land area M, 1 in a pitch within one pitch
In the surface area m of each sub-block, the width a and the length c of the sub-block, the depth D of the vertical groove or the horizontal groove, the depth d of the sub-groove, the distance e from the grounding center line to the sub-block, and the tread ground width 2T. And the following condition is satisfied.
Or the studless tire according to claim 2 or 3. m / M = 0.025 to 0.050 a / c = 0.55 to 0.15 d / D = 0.40 to 0.80 0.2 <e / T <0.8