JP3502711B2 - 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 a sipe provided on a land portion, and more particularly to a studless tire adapted to improve skidding on ice and snow.

[0002]

2. Description of the Related Art Conventionally, as a studless tire for improving skidding on ice and snow, for example, there is a tire proposed in Japanese Patent Application Laid-Open No. 4-201109. This tire has a structure in which a narrow groove is arranged in the tire circumferential direction in a land portion having a sipe defined on the tread surface, and the land portion is divided into a narrow land portion and a wide land portion. The edge effect of both land areas facing the narrow groove improves skid resistance on ice and snow.

However, in the studless tire having the above-described structure, the wall effect of the narrow land portion and the wall surface of the wide land portion are in contact with each other and the narrow groove is closed in the actual use condition, so that the edge effect is greatly reduced. Therefore, the effect of improving skid was small, and further improvement was required.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a studless tire capable of improving skid resistance on ice and snow.

[0005]

A studless tire of the present invention that achieves the above object is provided with a main groove extending in the tire circumferential direction and a lateral groove extending in the tire width direction on a tread surface, and the main groove and the lateral groove are provided. In a studless tire having a divided land portion and a sipe extending in the tire width direction on the land portion, at least two thin tires extending in the tire circumferential direction at the land portion and having both ends communicating with the lateral groove are provided. Grooves are arranged so that narrow blocks divided between the narrow grooves and wide blocks divided on both sides thereof are arranged, and the width Wa of the narrow blocks in the tire width direction is Wa ≧ 2 mm, The width Wb of the wide block is set to 0.25 W ≦ Wb ≦ 0.40 W with respect to the land width W, and the depth Dt of the narrow groove is 0.33 Db ≦ with respect to the depth Db of the main groove.
When Dt ≦ 0.75Db is set and the width T of the narrow groove in the tire width direction is Dt ≦ Wa, T ≧ 1.2 mm, D
to 1.2mm <T ≦ 0.8Wa time of t> Wa, said Sai
One of the two grooves communicates with the main groove, and the narrow groove is connected to the sipe.
It is characterized in that they are arranged apart from each other.

In another studless tire of the present invention, a main groove extending in the tire circumferential direction and a lateral groove extending in the tire width direction are provided on the tread surface, and a land portion divided by the main groove and the lateral groove is formed. Then, in a studless tire provided with a sipe extending in the tire width direction on the land portion,
At least two narrow grooves that extend in the tire circumferential direction and have one end communicating with the lateral grooves are arranged on the land portion, and are divided into pseudo narrow blocks divided between the narrow grooves and both sides thereof. A pseudo wide block is arranged, and the width Wa ′ of the pseudo narrow block in the tire width direction is Wa ′ ≧ 2 mm,
The width Wb ′ of the pseudo wide block is 0.
25W ≦ Wb ′ ≦ 0.40W, and the extending length Lc of the narrow groove is the length L of the land portion in the extending direction of the narrow groove.
Lc ≧ 0.66Lt with respect to t, the depth Dt ′ thereof is set to 0.33Db ≦ Dt ′ ≦ 0.75Db with respect to the depth Db of the main groove, and the width T of the narrow groove in the tire width direction. When T '≧ 1.2 mm when'Dt' ≤ Wa ', and when Dt'> Wa '1.
The feature is that 2 mm <T ′ ≦ Wa ′.

At least two narrow grooves, both ends of which communicate with the lateral grooves, are arranged in the land portion divided by the main grooves and the lateral grooves as described above, and narrow blocks are provided between the narrow grooves, and wide blocks are provided on both sides of the narrow blocks. By providing blocks and setting the width Wa of the narrow blocks, the width Wb of the wide blocks, the depth Dt of the narrow grooves, and the width T of the narrow grooves within the above ranges, skidding occurs when turning on ice and snow. Even if occurs, it is possible to prevent the narrow wall and the wide block, which are divided by the narrow groove, from facing each other so that the narrow walls are completely in contact with each other, and the narrow groove is always in the open state. be able to. As a result, a high edge effect can be exerted, so that it becomes possible to improve the side slip resistance on ice and snow.

Further, at least two narrow grooves, one end of which communicates with the lateral groove, are arranged in the land portion divided by the main groove and the lateral groove, and the pseudo narrow block divided between the narrow grooves and both sides thereof are provided. And a width of the pseudo narrow block Wa ′, a width of the pseudo wide block Wb ′, an extending length Lc of the narrow groove, and a depth Dt of the narrow groove.
Also, by setting the width T ′ of the narrow groove as described above, it is possible to improve the side slip resistance on ice and snow in the same manner, while the pseudo narrow block and the pseudo wide block are completely formed. Since they are connected to each other without being divided into, it is easy to secure mutual block rigidity effective for suppressing the occurrence of abnormal wear.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The configuration of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows an example of a studless tire of the present invention, 1 is a tread surface,
The tread surface 1 is provided with a plurality of main grooves 2 extending along the tire circumferential direction S and a plurality of lateral grooves 3 communicating with the main grooves 2 and extending in the tire width direction. A large number of land portions 4 are formed of blocks divided by. Each land portion 4 is provided with a plurality of zigzag-shaped sipes 5 extending in the tire width direction.

In FIG. 1, five main grooves 2 are formed on the tread surface 1, one is provided on the tire center CL, and the remaining four are provided at positions symmetrical to each other, two each. The tread surface 1 is provided with 6 rows of blocks. In the land part 4 of the two block rows on each side,
Three sipes 5 are provided on each side of the land, and one of them is connected to the main groove 2. The three sipe 5 are arranged in the land portion 4 of the two block rows in the central portion, and while the central sipe communicates both ends thereof to the main grooves 2 on both sides, the sipe before and after the sipes are one. Is communicated with the main groove 2, and one of the communicating sides is reversed.

According to the present invention, in the studless tire having the above-mentioned structure, the land portions 4 of the two block rows on each side are provided.
At the center portion in the tire width direction, two straight narrow grooves 6 extending along the tire circumferential direction S are provided so that both ends thereof communicate with the lateral grooves 3. These narrow grooves 6 are located between the above-mentioned sipes 5, and are arranged apart from each other without communicating with the sipes 5. A narrow block 4a having a narrow width is defined between the narrow grooves 6, and a wide block 4b having a width wider than that of the narrow block 4a is defined on both sides of the narrow groove 6, respectively. ing.

The width Wa of the narrow block 4a in the tire width direction is set to Wa ≧ 2 mm, and the width Wb of the wide block 4b in the tire width direction is smaller than the land width W of the land portion 4 in the tire width direction. 0.25W ≦ Wb ≦ 0.40
It has a W relationship. Further, the depth Dt of the fine groove 6
Is 0.33 Db ≦ Dt ≦ with respect to the depth Db of the main groove 2.
The width T of the narrow groove 6 in the tire width direction is set to 0.75 Db, and T ≧ 1.2 m when Dt ≦ Wa.
When m and Dt> Wa, 1.2 mm <T ≦ 0.8 Wa.

In this way, the two narrow grooves 6 communicating with the front and rear lateral grooves 2 are made to extend in the tire circumferential direction S in the land portion 4, and the narrow block 4a and the wide blocks 4b are arranged on both sides thereof. , The width Wa of the narrow block 4a, the wide block 4b
By setting the width Wb, the depth Dt of the narrow groove 6, and the width T of the narrow groove 6 in the above ranges, even if skidding occurs on ice and snow during turning, the narrow groove 6 It is possible to prevent the narrow walls 6a and the wide blocks 4b that face each other from completely contacting each other so that the narrow groove 6 is closed, so that the narrow groove 6 can be kept open at all times. Since it is possible to obtain the edge effect, it is possible to improve the lateral slip resistance.

If the width Wa of the narrow block 4a is less than 2 mm, it is difficult to secure the rigidity of the narrow block 4a, and the narrow block 4a is wide block 4b during side skidding.
It becomes difficult to secure the skid resistance effect on snow, and it is difficult to form the vent hole for the narrow block 4a in the mold. The upper limit of the width Wa of the narrow block 4a is preferably 7 mm or less from the viewpoint of the effect on the skid resistance.

The width Wb of the wide block 4b is 0.2.
If it is less than 5 W, the required block rigidity cannot be secured, and conversely, if it is more than 0.40 W, the wide block becomes too large and the narrow block 4a and the narrow groove 6 are effectively arranged. Is difficult and also disadvantageous in terms of skid resistance. The depth Dt of the fine groove 6 is 0.33D
If it is smaller than b, the drainage property and snow bite resistance in the narrow groove 6 are deteriorated, and if it is larger than 0.75 Db, the narrow block 4a and the wide block 4b are brought into contact with each other at the time of skidding to close the narrow groove 6. Both of them cannot obtain a good skid-proof effect on ice and snow.

If the width T of the narrow groove 6 is less than 1.2 mm when Dt ≦ Wa, the narrow block 4a and the wide block 4b come into contact with each other at the time of skidding, and the narrow groove 6 is closed.
The upper limit of the width T of the narrow groove 6 is preferably 4.0 mm or less from the viewpoint of ensuring the rigidity of the entire block group including the narrow blocks 4a and the wide blocks 4b.

The width T of the narrow groove 6 is 1.2 when Dt> Wa.
If it is less than or equal to mm, the narrow groove 6 is closed as described above, and if
If it exceeds 8 Wa, the block rigidity of the narrow block 4a is small, so that buckling or the like occurs in the groove, which causes abnormal wear such as unevenness. FIG. 3 shows another example of the studless tire of the present invention. In the studless tire described above, the land portion 4 formed of a block is formed on the tread surface 1 by the main groove 2 and the lateral groove 3, whereas in this embodiment, the rib is formed by the main groove 2 and the lateral groove 3 on the tread surface 1. The land portions 4A and 4B, which are composed of blocks and blocks, are sectioned and formed.

One main groove 2 provided on the tire center CL and one main groove 2 provided on each side of the main groove 2.
And a total of three main grooves 2 are arranged along the tire circumferential direction S. Between the main grooves 2 on both sides, the land portion 4 formed of a rib is formed between the main grooves 2 on the tire center CL.
A is provided, and the lateral grooves 3 are formed in the land portions 4A as lug grooves alternately from both sides of the land portions 4A at predetermined intervals along the tire circumferential direction S. The lateral groove 3 formed of this lug groove is configured such that its tip end portion overlaps when viewed from the tire circumferential direction. A land portion 4B composed of a block divided by the main groove 2 and the lateral groove 3 is formed outside the tire on both sides of the main groove 2.

Reference numeral 5a denotes a zigzag sipe extending along the tire width direction in the land portion 4A, one of which is a main groove at each portion of the land portion 4A located between the front and rear lateral grooves 3 adjacent to each other on the same side. and three sipes 5a communicating with the 2 and the other is the one sipe 5a communicating with the lateral groove 3, are Oite disposed a predetermined intervals along the tire circumferential direction S. 5b is land 4B
The zigzag sipe extends along the tire width direction, and has the same arrangement as that of the above-described embodiment.

In the present invention, also in the studless tire having the land portions 4A and 4B in which the ribs and the blocks are mixed, the narrow groove 4a is provided by disposing the thin grooves 6 in the land portions 4A and 4B. And the wide block 4b are partitioned and formed, and the width Wa of the narrow block 4a, the width Wb of the wide block 4b, the depth Dt of the narrow groove 6 and the width T of the narrow groove 6 are set in the above ranges. By doing so, the same effect can be achieved. The narrow groove 6 provided in the land portion 4A made of a rib is formed in each portion 4A ₁ of the land portion 4A which is not provided with the sipe 5a located between the adjacent front and rear lateral grooves 3 which are alternately arranged, The front and rear lateral grooves 3 communicate with each other.

FIG. 4 shows still another example of the studless tire of the present invention. In this embodiment, in place of the narrow groove 6 whose both ends communicate with the front and rear lateral grooves 3 in the embodiment of FIG. 3,
It has a configuration in which two straight narrow grooves 6 ′ having only one end communicating with the lateral groove 3 are provided. Pseudo narrow blocks 4a 'that are not completely divided and are divided are formed between the narrow grooves 6', and pseudo wide blocks 4a 'that are wider than the pseudo narrow blocks 4a' are formed on both sides thereof. 4b 'is divided and formed.

The narrow groove 6'herein means a narrow groove whose both ends communicate with the lateral groove 3, one of which is not communicated, that is, the pseudo narrow block 4a 'and the pseudo wide block on one side. 4b 'and a narrow groove which is connected to the horizontal groove 3 or both ends of which are connected to the lateral groove 3, a narrow groove having a discontinuous structure divided into two without arranging the groove in the middle part, that is, the middle The narrow groove in which the pseudo narrow block 4a 'and the pseudo wide block 4b' are connected to each other is one narrow groove 6'of which only one end communicates with the lateral groove 3.

Pseudo narrow block 4 in the tire width direction
Width Wa 'of a', width Wb 'of pseudo wide block 4b', narrow groove 6 '
Has a depth Dt 'of Wa' ≧ 2 mm, 0.25 W, like the narrow block 4a, the wide block 4b, and the narrow groove 6 described above.
≤Wb '≤0.40W, 0.33Db ≤Dt' ≤0.75D
In addition to being set to the relationship of b, the extending length Lc of the narrow groove 6 ′ is equal to the land portion 4B in the extending direction of the narrow groove 6 ′.
(In the land portion 4A, the land portion 4A is not provided with the sipe 5a located between the adjacent front and rear lateral grooves 3 that are alternately arranged.
Lc ≧ 0.66L for the length Lt of each portion 4A ₁ ) of
It is in the range of t. In the case of the fine groove 6 ′ divided into two in the middle part, the length Lc is the total length.

The width T'of the narrow groove 6'in the tire width direction is T'≥1.2 mm when Dt'≤Wa ', and Dt'> Wa '.
At that time, 1.2 mm <T ′ ≦ Wa ′. In this way, the two narrow grooves 6 ′ whose one end communicates with the lateral groove 3 divides the pseudo narrow block 4a ′ and the pseudo wide blocks 4b ′ on both sides thereof, and the pseudo narrow block 4a ′ is arranged as described above. Width Wa ',
By setting the width Wb 'of the pseudo wide block 4b', the length Lc of the narrow groove, the depth Dt 'of the narrow groove, and the width T'of the narrow groove 6', the narrow groove 6 can be used in a normal use state. 'Length Lc of 50
By not closing more than 100%, the same effect as above can be obtained.

Further, since the pseudo-narrow width block 4a 'and the pseudo-wide width block 4b' are connected without being completely divided, mutual blocks necessary for suppressing abnormal wear from occurring in these blocks. It becomes easy to secure rigidity.
Further, since either one of the narrow grooves 6 ′ communicates with the lateral groove 3 and both ends thereof are not closed with respect to the lateral groove, the provision of the narrow groove 6 ′ does not increase noise.

If the length Lt of the fine groove 6'is less than 0.66 Lt, it becomes difficult to secure an edge length for obtaining an effective edge effect. As shown in FIG. 5, the narrow groove 6 ′ can be formed with the groove bottom surface 6′a along the surfaces (tread surface 1) of the land portions 4A and 4B and parallel to the surface. As shown in 6, it may be inclined.

Further, as shown in FIG. 7, a shallow narrow groove c may be provided following the closed end 6'b which does not communicate with the other lateral groove 3 of the narrow groove 6 '. The shallow fine groove c in this case is 0.33Db which is the lower limit of the depth Dt 'of the fine groove 6'.
It is a shallower groove. This narrow groove c is shown in FIG.
The narrow groove 6 ′ and the lateral groove 3 may be provided so as to communicate with each other, or, as shown in FIG. 7B, the narrow groove 6 ′ may be provided so as to communicate only with the narrow groove 6 ′.

Further, in this embodiment, the fine groove 6'is provided in the land portions 4A and 4B in which the block and the rib are mixed, but it is provided in the land portion 4 consisting of only the block as shown in FIG. The studless tire having the land portion divided by the main groove 2 and the lateral groove 3 can be preferably used. In the present invention, in the above-described embodiment, the case where two thin grooves 6 and 6 ′ are arranged has been described, but more thin grooves 6 and 6 ′ may be provided depending on the size of the land portions 4, 4A and 4B. By forming at least two fine grooves 6 and 6 ', the land portion can be divided into a narrow block 4a and a wide block 4b, and a pseudo narrow block 4a' and a pseudo wide block 4b '.

Further, in the above-mentioned embodiment, the land portions 4, 4
The width W of A and 4B is preferably W ≦ 0.33 Wt with respect to the tire ground contact width Wt of the tread surface 1 in order to secure an effective groove area ratio. The lower limit of the land width W is preferably W ≧ 0.13 Wt, from the viewpoint of securing traction and block rigidity during tire braking / driving.

The narrow grooves 6, 6'are preferably arranged such that the extending direction thereof is along the tire circumferential direction S.
The tire can be extended so as to be inclined with respect to the tire circumferential direction S in both directions within a range of 45 °. Also, the narrow groove 6,
The relation between the widths T and T ′ of 6 ′ and the width Tb of the main groove 2 is preferably Tb ≧ 1.5T and Tb ≧ 1.5T ′, respectively.
The width Tb of the main groove 2 in this case means the length of the shortest distance in the main groove 2.

Further, in the above embodiment, the narrow grooves 6 and 6'are provided, but the same studless tire has the narrow groove 6 whose both ends communicate with the lateral groove 3 and the narrow groove 6 whose one end communicates with the lateral groove 3. 'May be mixed and provided.

[0032]

EXAMPLE A test tire having the same tire size of 650R16 and having the configurations shown in FIGS.
The width W of the narrow block 4a or the pseudo narrow block 4a '
a, Wa ', the depths Dt, Dt' of the narrow grooves 6, 6'with respect to the depth Db of the main groove, the widths T, T'of the narrow grooves 6, 6 ', and the land width W.
Wide block 4b or pseudo wide block 4b '
The widths Wb and Wb ′ of the tires and the test tire having the configuration of FIG. 4, the skid resistance on snow when the length Lc of the fine groove 6 ′ with respect to the length Lt of the land portion is changed. When the evaluation test was performed under the measurement conditions shown below, the results shown in FIGS. 8 to 12 (displayed by solid lines) were obtained.

The widths T and T'of the narrow grooves 6 and 6'and the widths Wb and W of the wide block 4b or the pseudo wide block 4b '.
The test tires with different b ′ were subjected to an abrasion resistance evaluation test under the following measurement conditions.
The result shown in No. 1 (indicated by a chain line) was obtained. In the test tire having the configuration shown in FIG. 1, the values other than the above-mentioned changed values are 2.0 mm for the width Wa and 1 for the width Wb.
1 mm, narrow groove depth Dt is 6 mm, narrow groove width T is 1.4 mm, and the relationship between the narrow groove width T and the main groove width Tb is Tb = 4.3T. In the tire, the widths Wa and Wa 'are 2.0 mm, the widths Wb and Wb' are 11 mm, and the fine groove depths Dt and Dt '.
Is 6 mm, narrow groove width T, T'is 1.4 mm, narrow groove width T,
The relationship between T ′ and the width Tb of the main groove is Tb = 4.3T
(T '), the length Lc of the fine groove 6'in the test tire having the configuration of FIG. 4 is 0.8 Lt. The ground contact width Wt of the test tires filled with standard air pressure is 122 mm. Side-slip resistance Each test tire was mounted on a rim with a rim size of 13 x 4.50B, air pressure was set to 200 kPa, and it was mounted on a 1500 cc vehicle. No skidding occurred on an ice-snow road test course with an air temperature of -2 to -5 ℃. The maximum speed was measured, and the result was evaluated by an index value with the conventional tire being 100. The larger the value, the better the skid resistance. Abrasion resistance Each test tire was mounted on a 1500cc vehicle in the same manner as above, and after running 1000km on a test course consisting of a mixed surface of paved roads and ice and snow roads, the amount of wear generated in blocks divided by fine grooves was measured. The measurement was performed, and the result was evaluated by an index value with the conventional tire being 100. The larger the value, the better the abrasion resistance.

In the test tire in which the widths T and T'of the narrow grooves were changed, the uneven wear of the narrow blocks or the pseudo narrow blocks, the widths Wb and W of the wide blocks or the pseudo wide blocks were used.
For the test tires with different b ', the amount of uneven wear of the wide block or the pseudo wide block was measured. From FIGS. 8 to 12, the widths Wa and W of the narrow block or the pseudo narrow block are shown.
a ′ is Wa, Wa ′ ≧ 2 mm, and the width Wb, Wb ′ of the wide block or the pseudo narrow block is 0.25 W ≦ with respect to the land width W.
Wb, Wb ′ ≦ 0.40 W, and the depth Dt of the fine groove,
Dt 'is 0.33Db≤Dt, D with respect to the depth Db of the main groove
Set t '≦ 0.75Db and set the width T, T'of the narrow groove to D
When t, Dt '≤ Wa, Wa', T, T'≥ 1.2 mm, D
When t, Dt '> Wa, Wa' 1.2 mm <T, T'≤ 0.8
Wa, Wa ', and in the case of a narrow groove having one end communicating with each other, the tire of the present invention having a length Lc of Lc≥0.66Lt has a resistance against a (pseudo) narrow block or a (pseudo) wide block. It can be seen that the skid resistance on ice and snow can be improved without lowering the wear resistance.

[0035]

As described above, according to the present invention, at least two fine grooves extending in the tire circumferential direction and having both ends communicating with the lateral groove are provided in the land portion divided by the main groove and the lateral groove. The narrow block divided between the narrow grooves and the wide blocks divided on both sides thereof are arranged, and the width Wa of the narrow block in the tire width direction is Wa ≧ 2 mm and the width Wb of the wide block is landed. 0.25 W ≦ Wb ≦ 0.
When the depth Dt of the narrow groove is set to 0.33 Db ≦ Dt ≦ 0.75 Db with respect to the depth Db of the main groove and the width T of the narrow groove in the tire width direction is Dt ≦ Wa When T ≧ 1.2 mm and Dt> Wa 1.2 mm <T ≦ 0.8 W
Since it is set to a, it is possible to improve the skid resistance on ice and snow.

When a narrow groove is provided such that one of the narrow grooves communicates with the lateral groove, the extending length Lc of the narrow groove is compared with the length Lt of the land portion in the extending direction of the narrow groove. Lc ≧
Also by setting to 0.66 Lt, the skid resistance on ice and snow can be improved.

[Brief description of drawings]

FIG. 1 is a plan view of a main portion of a tread surface showing an example of a studless tire of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a plan view of a main portion of a tread surface showing another example of the studless tire of the present invention.

FIG. 4 is a plan view of a main portion of a tread surface showing still another example of the studless tire of the present invention.

FIG. 5 (a) is a cross-sectional view of a land portion showing a narrow groove communicating with a lateral groove on one side, and FIG. 5 (b) is a narrow groove divided at a central portion and each one of two divided fine grooves communicates with the lateral groove. FIG.

FIG. 6 is a cross-sectional view of a land portion showing another example of the narrow groove of FIG. 5 (a).

7 (a) and (b) are cross-sectional views of land portions showing still another example of the narrow groove of FIG. 5 (a).

FIG. 8 is a width W of a narrow block or a pseudo narrow block.
It is a graph showing the relationship between a, Wa'and skid resistance,
(A) is a graph showing the case of a test tire having the configuration of FIG. 1, (b) is a graph showing the case of a test tire having the configuration of FIG. 3, (c) is a test tire having the configuration of FIG. It is a graph which shows the case of.

FIG. 9 shows the depths Dt, Dt ′ of the fine grooves with respect to the depth Db of the main groove.
And (a) is a graph showing the relationship between skid resistance and (a) is a graph showing the case of a test tire having the configuration of FIG. 1.
(B) is a graph showing the case of the test tire having the configuration of FIG. 3, and (c) is a graph showing the case of the test tire having the configuration of FIG. 4.

FIG. 10 is a graph showing the relationship between the widths T and T ′ of the narrow grooves and the sideslip resistance (solid line) and wear resistance (dashed line),
(A) is a test tire having the configuration of FIG.
3 is a graph showing the case of ≦ Wa, (b) is a test tire having the configuration of FIG. 3, and FIG. 4 is a graph showing the case of Dt ≦ Wa, (c) is the test tire having the configuration of FIG. 'In the test tire having the constitution of FIG. 1, (d) is a graph showing the case of Dt> Wa, (e) is the test tire having the constitution of FIG. 3, and Dt> Wa FIG. 4 is a graph showing the case, FIG.
FIG. 6 is a graph showing a case where Dt ′> Wa ′ in a test tire having the above structure.

FIG. 11 is a graph showing the relationship between the width Wb and Wb ′ of the wide block or the pseudo wide block with respect to the land width W, and the sideslip resistance (solid line) and wear resistance (dashed line).
(A) is a graph showing the case of a test tire having the configuration of FIG. 1, (b) is a graph showing the case of a test tire having the configuration of FIG. 3, (c) is a test tire having the configuration of FIG. It is a graph which shows the case of.

FIG. 12 is a graph showing the relationship between the length Lc of the fine groove and the skid resistance with respect to the length Lt of the land portion.

[Explanation of symbols]

1 tread surface 2 main groove 3 lateral groove 4, 4B block (land portion) 4A rib (land portion) 4a narrow block 4a 'pseudo narrow block 4b wide block 4b' pseudo wide block 5, 5a, 5b
Sipe 6,6 'narrow groove S tire circumferential direction

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B60C 11 / 04,11 / 11,11 / 12

Claims (6)

(57) [Claims] 1. A main groove extending in the tire circumferential direction and a lateral groove extending in the tire width direction are provided on a tread surface to form a land portion divided by the main groove and the lateral groove, and the land portion extends in the tire width direction. In a studless tire provided with a sipe extending to the bottom, at least two narrow grooves extending in the tire circumferential direction at both ends and communicating with the lateral groove at both ends are provided, and a narrow partition defined between the narrow grooves is provided. A wide block and wide blocks divided on both sides thereof are arranged, the width Wa of the narrow block in the tire width direction is Wa ≧ 2 mm, and the width Wb of the wide block is 0. 25 W ≤ Wb ≤
The relationship is 0.40 W, the depth Dt of the narrow groove is set to 0.33Db ≦ Dt ≦ 0.75Db with respect to the depth Db of the main groove, and the width T of the narrow groove in the tire width direction is set to Dt.
T ≧ 1.2 mm when ≦ Wa, 1.2 mm <Dt> Wa
T ≦ 0.8 Wa, and one of the sipes is the main groove
A studless tire in which the narrow groove is arranged so as to be in communication with the sipe and is separated from the sipe . 2. A tread surface is provided with a main groove extending in the tire circumferential direction and a lateral groove extending in the tire width direction to form a land portion divided by the main groove and the lateral groove, and the land portion is provided in the tire width direction. In a studless tire provided with a sipe extending to, the at least two fine grooves extending in the tire circumferential direction and having one end communicating with the lateral groove are provided in the land portion, and a pseudo partition formed between the fine grooves is provided. The narrow block and the pseudo wide block divided on both sides thereof are arranged, and the width Wa ′ of the pseudo narrow block in the tire width direction is Wa ′ ≧ 2 mm,
The width Wb ′ of the pseudo wide block is 0.
25W ≦ Wb ′ ≦ 0.40W, and the extending length Lc of the narrow groove is the length L of the land portion in the extending direction of the narrow groove.
Lc ≧ 0.66Lt with respect to t, the depth Dt ′ thereof is set to 0.33Db ≦ Dt ′ ≦ 0.75Db with respect to the depth Db of the main groove, and the width T of the narrow groove in the tire width direction. When T '≧ 1.2 mm when'Dt' ≤ Wa ', and when Dt'> Wa '1.
Studless tire with 2mm <T '≤ Wa'. 3. One of the sipes communicates with the main groove.
The studless tire according to claim 2, wherein the narrow groove is arranged apart from the sipe . 4. The sipes are arranged on both sides of the land portion, and the sipes are
The studless tire according to claim 1, wherein the narrow groove is provided between the tires. 5. The land portion comprises a block.
The studless tire according to any one of items 4 to 4 . 6. The method according to claim 1, wherein the land portion has ribs.
Studless tire according to any one of.