JP2020164107A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire having both wet braking performance and on-ice braking performance.SOLUTION: In an objective pneumatic tire, the dimension (d1) of a first portion (262a) in a tire radial direction is 50% or more of a deepest groove depth (D), and that (d3) of a third portion (266a) in the same direction as above is also 50% or more of the deepest groove depth (D). An angle (θ1) formed by the tire radial direction and the first portion (262a) is smaller than the angle (θ2) formed by the above direction and a second portion (262b), and the angle (θ3) formed by the above direction and a third portion (266a) is smaller than the angle (θ4) formed by the above direction and a fourth portion (266b). Besides, the angles (θ1, θ3) are both 0° or more and 5° or less, and the angles (θ2, θ4) are both 2° or more and 10° or less.SELECTED DRAWING: Figure 2

Description

The present invention relates to a pneumatic tire that has both wet braking performance and on-ice braking performance.

Conventionally, the hardness of the cap tread rubber has been lowered in order to improve the braking performance, but there has been a concern that the block rigidity may be lowered due to the hardness reduction of the cap tread rubber. For this reason, attempts have been made to make the groove depth relatively small in order to suppress a decrease in block rigidity.

For example, in a tire having a groove on the tread tread of the tire, the groove is partitioned by a pair of groove walls and a groove bottom, and each of the groove walls is a tire from the center of the opening width w of the groove. It consists of two or more surfaces with different inclination angles with respect to the vertical line drawn on the rotation axis of the tire, and the inclination angle of the innermost surface in the tire radial direction is larger than the inclination angle of the outermost surface of the two or more surfaces. Also disclosed is a tire in which the ratio u / w of the opening width w to the width u of the groove bottom is 0.3 or more and 0.5 or less (Patent Document 1).

According to Patent Document 1, in particular, by setting the ratio u / w of the opening width w to the width u of the groove bottom of the groove bottom 3 to 0.3 or more, the inclination angle of the groove wall with respect to the tire radial direction is determined. If it is within the range, the groove depth becomes relatively small. As a result, the inner portion of the land portion 5 of the tread 6 in the tire radial direction is strengthened, and the rigidity of the land portion 5 is increased (0016, 0017). Therefore, in the technique disclosed in Patent Document 1, relatively high braking performance is expected due to the excellent rigidity of the land portion 5.

Japanese Unexamined Patent Publication No. 2014-151747

As described above, the technique disclosed in Patent Document 1 achieves the improvement of the land rigidity, but the ultimate purpose is to improve the appearance and reduce the road noise. In recent years, it has been required to improve various braking performances at the same time. For example, in a studless tire, it is an issue to achieve both wet braking performance and braking performance on ice. However, there is no disclosure about applying the technique disclosed in Patent Document 1 as it is to a studless tire, and it is unclear whether the technique achieves both wet braking performance and on-ice braking performance.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pneumatic tire having both wet braking performance and on-ice braking performance.

In the pneumatic tire according to the present invention, a land portion is formed by disposing a circumferential main groove and a width direction groove on the tread surface.
In a cross-sectional view parallel to the equator of the tire
The profile of the width direction groove arranged between the two land portions adjacent to each other in the tire circumferential direction is the first wall surface, the bottom surface continuous with the first wall surface, and the first wall surface of the bottom surface. The first wall surface including the second wall surface continuous on the opposite side is composed of a first portion far from the bottom surface and a second portion continuous with the first portion and close to the bottom surface. ,
The second wall surface is composed of a third portion far from the bottom surface and a fourth portion close to the groove bottom continuous with the third portion.
The tire radial dimension d1 of the first portion is 50% or more of the deepest groove depth D, and the tire radial dimension d3 of the third portion is 50% or more of the deepest groove depth D.
The angle θ1 formed by the tire radial direction and the first portion is smaller than the angle θ2 formed by the tire radial direction and the second portion, and the angle θ3 formed by the tire radial direction and the third portion is It is smaller than the angle θ4 formed by the tire radial direction and the fourth part.
The forming angle θ1 is 0 ° or more and 5 ° or less, the forming angle θ2 is 2 ° or more and 10 ° or less, the forming angle θ3 is 0 ° or more and 5 ° or less, and the forming angle θ4 is 2 ° or more. It is 10 ° or less.

In the pneumatic tire according to the present invention, the shapes of the two wall surface profile lines facing the tire circumferential direction of the width groove are improved in a cross-sectional view parallel to the tire equatorial plane. As a result, according to the pneumatic tire according to the present invention, both wet braking performance and on-ice braking performance can be achieved at the same time.

FIG. 1 is a plan view showing an example of a tread pattern of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a part of a cross section cut along the line AA'of FIG. 1, and is a cross-sectional view showing a peripheral portion of a groove in the width direction.

Hereinafter, embodiments of the pneumatic tire according to the present invention (basic and additional embodiments 1 to 5 shown below) will be described in detail with reference to the drawings. It should be noted that these embodiments do not limit the present invention. In addition, the components of the above-described embodiment include those that can be easily replaced by those skilled in the art, or those that are substantially the same. Further, the various embodiments included in the above-described embodiments can be arbitrarily combined within a range of self-evident by those skilled in the art.

[Basic form]
The basic form of the pneumatic tire according to the present invention will be described below.

In the following description, the tire radial direction means a direction orthogonal to the rotation axis of the pneumatic tire, the inner side in the tire radial direction is the side toward the rotation axis in the tire radial direction, and the outer side in the tire radial direction is the tire radial direction. The side away from the axis of rotation. The tire circumferential direction refers to a circumferential direction centered on the rotation axis. Further, the tire width direction means a direction parallel to the above rotation axis, the inside in the tire width direction is the side toward the tire equatorial plane CL (tire equatorial line) in the tire width direction, and the outside in the tire width direction is the tire width direction. Refers to the side away from the tire equatorial plane CL. The tire equatorial plane CL is a plane that is orthogonal to the rotation axis of the pneumatic tire and passes through the center of the tire width of the pneumatic tire.

FIG. 1 is a plan view showing an example of a tread pattern of a pneumatic tire according to an embodiment of the present invention. The pneumatic tire 1 shown in the figure has a tread portion 10. The tread portion 10 is made of a rubber material (tread rubber) and is exposed on the outermost side of the pneumatic tire 1 in the tire radial direction, and the surface thereof serves as the contour of the pneumatic tire 1. The surface of the tread portion 10 is formed as a tread surface 12 which is a surface that comes into contact with the road surface when a vehicle (not shown) equipped with the pneumatic tire 1 travels.

As shown in FIG. 1, the tread surface 12 has four circumferential main grooves 14, 16, 18, and 20 extending seamlessly in the tire circumferential direction, and one extending seamlessly in the tire circumferential direction. Circumferential narrow grooves 22, five types of widthwise grooves 24, 26, 28, 30, 32 inclined with respect to the tire circumferential direction, and lug grooves 34, 36 located on the outermost side in the tire width direction, respectively. Five types of circumferential termination grooves 38, 40, 42, 44, 46 and sipe 48, which extend from the width groove and terminate in the land, are provided, respectively, and the tread pattern shown in the figure is formed. There is.

In the present embodiment, the circumferential main groove means a groove having a groove width of 3 mm or more and a groove depth of 4 to 12 mm. The circumferential narrow groove means a groove having a groove width of 1.6 to 3 mm and a groove depth of 1 to 12 mm. The groove in the width direction means a groove having a groove width of 1.6 to 10 mm and a groove depth of 1 to 12 mm. The lug groove means a groove having a groove width of 1.6 to 10 mm and a groove depth of 1 to 12 mm. The circumferential end groove means a groove having a groove width of 0.5 to 10 mm and a groove depth of 0.5 to 12 mm. Further, the sipe means a groove having a groove width of 0.3 to 1.6 mm and a groove depth of 1 to 12 mm.

The tread pattern shown in FIG. 1 is asymmetric in the tire width direction with respect to the tire equatorial plane CL. The circumferential main grooves 14, 20 and the circumferential fine grooves 22 are grooves having the same width and extending in the tire circumferential direction, and the circumferential main groove 16 is a combination of a plurality of grooves having the same width inclined with respect to the tire circumferential direction. It is a groove. Further, the circumferential main groove 18 is a groove in which a plurality of groove portions whose width gradually changes in the tire circumferential direction are combined.

The width direction groove 24 communicates with the circumferential main groove 14, is somewhat wide on the outermost side in the tire width direction, extends substantially in the tire width direction, and is convex upward in FIG. It is a groove that is curved by a minute. The width direction groove 26 is a groove that communicates with the circumferential main grooves 14 and 16 and that the outer portion in the tire width direction is wider than the inner portion and extends inclined with respect to the tire width direction. .. When the outer end of the width direction groove 26 in the tire width direction is extended, it coincides with the inner end of the width direction groove 24 in the tire width direction.

The width direction groove 28 is a groove that communicates with the circumferential direction main grooves 16 and 18, has the same width, and extends in an inclined direction opposite to the width direction groove 26 with respect to the tire width direction. Both ends of the width direction groove 30 are terminated in the land portion between the circumferential direction main grooves 18 and 20, and the width direction groove 30 penetrates the circumferential direction fine groove 22 and extends at an equal width and inclined with respect to the tire width direction. It is a groove. The inclination direction of the width direction groove 30 with respect to the tire width direction is opposite between the width direction grooves 30 and 30 adjacent to each other in the circumferential direction.

The width direction groove 32 is a groove that communicates with the circumferential main groove 20, is somewhat wide on the outermost side in the tire width direction, and extends substantially in the tire width direction, and is convex downward in FIG. It is a groove that is somewhat curved.

The lug groove 34 is arranged between the width groove 24 and 24 on one side in the tire width direction, and the main wide portion extends substantially in a spiral shape, and the width is narrow from this wide portion to both sides in the tire circumferential direction. It is a groove extending so as to communicate with the widthwise groove 24. The lug groove 36 is arranged between the width groove 32, 32 on the other side in the tire width direction, and the main wide portion extends substantially in a spiral shape, and the width is narrow from this wide portion to both sides in the tire circumferential direction. It is a groove extending so as to communicate with the widthwise groove 32. The spiral direction of the wide portion of the lug groove 36 is the same as the spiral direction of the wide portion of the lug groove 34.

The circumferential end groove 38 is a groove in which a narrow portion extends from the width direction groove 24 to one side in the tire circumferential direction and becomes wide in the middle to terminate in the land portion. When the outer end in the tire width direction of the wide portion of the circumferential end groove 38 is extended in the tire width direction, it coincides with the inner end in the tire width direction of the lug groove 34. The circumferential end groove 40 is a groove extending from the width direction groove 24 to one side in the tire circumferential direction (the direction opposite to the extending direction of the narrow portion of the circumferential end groove 38) and terminating in the land portion. .. The circumferential end groove 42 is a groove that extends from the width direction groove 26 to one side in the tire circumferential direction (the same direction as the extension direction of the circumferential end groove 40) and terminates in the land portion. The circumferential end groove 44 is a groove that extends from the width direction groove 32 to one side in the tire circumferential direction (the direction opposite to the extending direction of the circumferential fine groove 40) and terminates in the land portion. In the circumferential end groove 46, the narrow portion extends from the width direction groove 32 to one side in the tire circumferential direction (the direction opposite to the extending direction of the narrow portion of the circumferential end groove 38) and is wide in the middle. It is a groove that ends in the land. When the outer end in the tire width direction of the wide portion of the circumferential end groove 46 is extended in the tire width direction, it coincides with the inner end in the tire width direction of the lug groove 36.

As shown in FIG. 1, by arranging the circumferential main groove 14 to 20, the circumferential fine groove 22, the width direction groove 24 to 32, the lug groove 34 and 36, and the circumferential end groove 38 to 46, as shown in FIG. Eight types of land areas 50 to 64 are formed on the tread surface 12.

Based on the above premise, in the present embodiment, the land portion 54 will be focused on and described below.
FIG. 2 is a part of a cross section cut along the line AA'of FIG. 1, and is a cross-sectional view showing a peripheral portion of a groove in the width direction. That is, FIG. 2 is a cross-sectional view showing a circled portion X of FIG. 1 including a width direction groove 26, and in FIG. 2, two land portions, that is, blocks 54a and 54b are formed on the left and right sides of the width direction groove 26. Has been done.

In the example shown in FIG. 2, the profile of the widthwise groove 26 arranged between the two blocks 54a and 54b adjacent to each other in the tire circumferential direction is a bottom surface 264 continuous with the first wall surface 262 and the first wall surface 262. And a second wall surface 266 which is continuous on the side opposite to the first wall surface 262 of the bottom surface 264.

The first wall surface 262 is composed of a first portion 262a far from the bottom surface 264 and a second portion 262b close to the bottom surface 264 continuous with the first portion 262a. Further, the second wall surface 266 is composed of a third portion 266a far from the bottom surface 264 and a fourth portion 266b close to the groove bottom 264 continuous with the third portion 266a.

Then, as shown in FIG. 2, the tire radial dimension d1 of the first portion 262a is 50% or more of the deepest groove depth D, and the tire radial dimension d3 of the third portion 266a is the deepest groove depth D. 50% or more of. Here, it is assumed that the groove depths D, d1 and d3 are all measured in the tire radial direction from the opening of the groove 26. The deepest groove in the present embodiment means the groove having the deepest depth in the entire tread pattern of FIG. 1, and in the example shown in FIG. 1, the circumferential grooves 14, 18 and 20 correspond to the deepest groove.

Further, as shown in FIG. 2, the angle θ1 formed by the tire radial direction and the first portion 262a is smaller than the angle θ2 formed by the tire radial direction and the second portion 262b, and the tire radial direction and the third portion 262a are formed. The angle θ3 formed by the portion 266a is smaller than the angle θ4 formed by the tire radial direction and the fourth portion 266b. In the cross-sectional view shown in FIG. 2, in the case of the curves of the first portion 262a to the fourth portion 266b, the straight line connecting both end points in the tire circumferential direction of each portion and the tire radial direction form. Let the angles be the angles θ1 to θ4.

Further, in the example shown in FIG. 2, the forming angle θ1 is 0 ° or more and 5 ° or less, the forming angle θ2 is 2 ° or more and 10 ° or less, the forming angle θ3 is 0 ° or more and 5 ° or less, and the forming angle is formed. θ4 is 2 ° or more and 10 ° or less.

(Action, etc.)
In the pneumatic tire according to the present embodiment, as shown in FIG. 2, the tire radial dimension d1 is 50% or more of the deepest groove depth D. As a result, when the four end points A1 to A4 on the first wall surface 262 and the second wall surface 266 are set as fixed points (that is, the opening size, groove bottom size, and groove depth of the width direction groove 26 in the tire circumferential direction). (Assuming that is constant), by setting d1 / D ≧ 50, a sufficient capacity of the groove 26 in the width direction can be secured. Similarly, the tire radial dimension d3 is set to 50% or more of the deepest groove depth D. As a result, when the above four end points A1 to A4 are set as fixed points, the capacity of the groove 26 in the width direction can be sufficiently secured by setting d3 / D ≧ 50. Excellent drainage performance can be obtained by increasing the capacity of the width direction groove 26 based on the shapes (tire radial dimensions) of the two facing wall surfaces 262 and 266 as described above (action 1).

Further, in the pneumatic tire according to the present embodiment, as shown in FIG. 2, the angle θ1 formed is smaller than the angle θ2 formed. As a result, when the four end points A1 to A4 on the first wall surface 262 are fixed points, the angle θ1 formed by the first portion having a relatively large tire radial dimension is set to a relatively small tire radial dimension. By making the angle θ2 formed by the portion 2 smaller, it is possible to secure a larger capacity of the groove 26 in the width direction as compared with the case where θ1 ≧ θ2. Similarly, the angle θ3 formed is smaller than the angle θ4 formed. As a result, when the four end points A1 to A4 are fixed points, the angle θ3 formed by the third portion having a relatively large tire radial dimension is formed by the angle formed by the fourth portion having a relatively small tire radial dimension. By making it smaller than θ4, it is possible to secure a larger capacity of the groove 26 in the width direction as compared with the case of θ3 ≧ θ4. Excellent drainage performance can be obtained by increasing the capacity of the widthwise groove 26 based on the shapes (inclination angles) of the two facing wall surfaces 262 and 266 as described above (action 2).

Further, in the pneumatic tire according to the present embodiment, as shown in FIG. 2, the angles θ1 and θ3 formed are set to 0 ° or more and 5 ° or less. By setting the angles θ1 and θ3 to be formed at 0 ° or more, the rigidity of the blocks 54a and 54b can be increased and an excellent edge effect can be obtained when the end points A1 to A4 are set as fixed points (action 3). ).

On the other hand, by setting the angles θ1 and θ3 to be formed at 5 ° or less, the capacity of the groove 26 in the width direction can be sufficiently secured when the end points A1 to A4 are set as fixed points, which is excellent. Drainage performance can be achieved (action 4).

In addition, in the pneumatic tire according to the present embodiment, as shown in FIG. 2, the angles θ2 and θ4 formed are 2 ° or more and 10 ° or less. By setting the angles θ2 and θ4 to be formed at 2 ° or more, the rigidity of the blocks 54a and 54b can be increased and an excellent edge effect can be obtained when the end points A1 to A4 are set as fixed points (action 5). ).

On the other hand, by setting the angles θ2 and θ4 to be formed at 10 ° or less, the capacity of the groove 26 in the width direction can be sufficiently secured when the end points A1 to A4 are set as fixed points, which is excellent. Drainage performance can be achieved (action 6).

As described above, according to the pneumatic tire according to the present embodiment, excellent wet braking is caused by the actions 1, 2, 4, 6 related to the improvement of drainage performance and the actions 3, 5 related to the improvement of the edge effect. It is possible to achieve both performance and excellent braking performance on ice.

As for the above actions 1 to 6, by adopting the following configuration, each of the above-mentioned effects is produced at a higher level (further).
That is, for the above-mentioned action 1, it is preferable that d1 / D ≧ 60 (d3 / D ≧ 60), and it is more preferable that d1 / D ≧ 70 (d3 / D ≧ 70).
Regarding the above action 2, it is preferable that θ1 / θ2 <0.9 (θ3 / θ4 <0.9), and more preferably θ1 / θ2 <0.8 (θ3 / θ4 <0.8). ..
Regarding the above-mentioned action 3, it is preferable that the forming angles θ1 and θ3 are both 1 ° or more, and it is more preferable that both the forming angles θ1 and θ3 are 1.5 ° or more.
Regarding the above-mentioned action 4, it is preferable that the forming angles θ1 and θ3 are both 4 ° or less, and it is more preferable that both the forming angles θ1 and θ3 are 3.5 ° or less.
Regarding the above-mentioned action 5, it is preferable that the forming angles θ2 and θ4 are both 3 ° or more, and it is more preferable that both the forming angles θ2 and θ4 are 4 ° or more.
Regarding the above-mentioned action 6, it is preferable that the forming angles θ2 and θ4 are both 9 ° or less, and it is more preferable that both the forming angles θ2 and θ4 are 8 ° or less.

As described above, the pneumatic tire according to the present embodiment has the above-mentioned effect by improving the shapes of the two wall surface profile lines facing the tire circumferential direction of the width direction groove in the cross-sectional view parallel to the tire equatorial plane. Combined with 1 to 6, wet braking performance and on-ice braking performance can be compatible at a high level.

Although not shown, the pneumatic tire of the present embodiment shown above is a bead portion and a sidewall portion from the inside to the outside in the tire radial direction in the tire meridional cross-sectional view, as in the conventional pneumatic tire. And has a tread section. Then, the pneumatic tire has, for example, a carcass layer extending from the tread portion to the bead portions on both sides and wound around a pair of bead cores in a cross-sectional view of the tire meridian, and a tire radial outer side of the carcass layer. A belt layer or the like, which is sequentially formed in the tire, is provided.

Further, the pneumatic tire of the present embodiment undergoes each of the usual manufacturing processes, that is, a tire material mixing process, a tire material processing process, a green tire molding process, a vulcanization process, an inspection process after vulcanization, and the like. It is obtained through the process. In the case of manufacturing the pneumatic tire of the present embodiment, in particular, a convex portion corresponding to a desired circumferential main groove or land portion as shown in FIG. 1 is formed on the inner wall of the vulcanization die. Vulcanization is performed using this mold.

[Additional form]
Next, additional embodiments 1 to 5 which can be optionally implemented with respect to the basic embodiment of the pneumatic tire according to the present invention will be described.

(Additional form 1)
In the basic form, of the two land portions (blocks 54a and 54b) shown in FIG. 2, the tire circumferential dimension L1 of the land portion (block 54a) on the first wall surface side is the land portion on the second wall surface side. It is preferable that the size (block 54b) is larger than the tire circumferential dimension L2 (additional form 1).

Here, as shown in FIG. 1, the tire circumferential dimensions L1 and L2 of the blocks 54a and 54b are basically measured at the same positions in the tire width direction. This is because, in FIG. 2, a plurality of widthwise grooves 26 arranged and arranged adjacent to each other in the tire circumferential direction have substantially the same shape and extend so as to be inclined with respect to the tire width direction. However, when the extending directions of the widthwise grooves 26 adjacent to each other in the tire circumferential direction differ by 8 ° or more from the tire width direction, the above tire circumferential dimensions L1 and L2 are the tire widths of the blocks 54a and 54b, respectively. Measurements shall be made at the innermost position, the outermost position, and the intermediate position in the direction, and the average of them shall be adopted.

By setting L1 / L2 in this way, the rigidity of one block 54a can be intentionally increased with respect to the rigidity of the other block 54b. As a result, the required block (for example, block 54a) among the blocks 54a and 54b located on both sides of the groove 26 in the width direction in FIG. 2 can have a relatively excellent edge effect, and the wet braking performance and the braking on ice can be provided. It is possible to achieve both performance and performance at a higher level. In addition, in the form in which the additional form 1 is added to the basic form, particularly in the tire in which the rotation direction is specified, the excellent edge effect due to the increase in rigidity is emphasized on the block on one side of the tire circumferential direction of the width direction groove. It is effective when it is intended to have a target.

(Additional form 2)
In the form in which the additional form 1 is added to the basic form, in FIG. 2, the tire radial dimension d1 of the first portion 262a is larger than the tire radial dimension d3 of the third portion 266a (additional form). 2) is preferable.

The additional form 2 is a form premised on the additional form 1. As described above, the additional form 1 is a form in which the block 54a has a relatively excellent rigidity among the blocks 54a and 54b. On the premise of this, in the additional form 2, the tire radial dimension d1 of the first portion 262a located on the side of the block 42a having a relatively large rigidity is located on the side of the block 62b having a relatively small rigidity. The portion 266a of No. 3 is made larger than the tire radial dimension d3. By setting d1> d3, when the end points A1 to A4 are set as fixed points, the block 54b among the blocks 54a and 54b can be provided with relatively excellent rigidity. From the above, in combination with the additional forms 1 and 2, the rigidity of the blocks 54a and 54b located on both sides of the width direction groove 26 in the tire circumferential direction can be sufficiently ensured, and an excellent edge effect can be obtained. Can be done. As a result, both wet braking performance and on-ice braking performance can be more efficiently achieved at a high level.

(Additional form 3)
In the basic form or the form in which at least the additional form 1 is added to the basic form, it is preferable that the angle θ1 formed is smaller than the angle θ3 formed (additional form 3) in FIG.

By setting θ1 <θ3, the rigidity of one block 54b can be intentionally increased with respect to the rigidity of the other block 54a. As a result, it is possible to give a relatively excellent edge effect to the required block (for example, block 54b) among the blocks 54a and 54b located on both sides of the widthwise groove 26 in FIG. 2, and by extension, the wet braking performance and the ice. It is possible to achieve both braking performance at a higher level. In addition, in the form in which the additional form 3 is added to the basic form, particularly in the tire in which the rotation direction is specified, the excellent edge effect due to the increase in rigidity is emphasized on the block on one side of the tire circumferential direction of the width direction groove. It is effective when it is intended to have a target.

Further, as described above, in the additional form 1, the block 54a has a higher rigidity than the block 54b, and in the additional form 3, the block 54b has a higher rigidity than the block 54a. Therefore, in the form in which both of the additional forms 1 and 3 are added to the basic form, it is possible to give excellent rigidity to both the block 54a and the block 54b, in particular, regardless of the tire in which the rotation direction is specified. It is effective when it is intended.

(Additional form 4)
In the basic form and the like, as shown in FIG. 2, it is preferable that at least one sipe is formed in the land portion (for example, blocks 54a and 54b) (additional form 4). By forming a sipe on the land, the rigidity of each block can be adjusted, and in particular, the contact surface with the frozen road can be increased to increase the frictional force, which in turn can further improve the braking performance on ice. .. It should be noted that such a configuration is particularly effective for studless tires.

(Making test tires)
The tire size is 195 / 65R15 91Q, which includes general components (inner liner, carcass layer, belt layer, belt cover layer, and tread rubber layer) not shown, and has the tread pattern shown in FIG. Further, test tires (conventional example, comparative examples 1 and 2, and Examples 1 to 5) that satisfy the conditions shown in Table 1 below were produced as pneumatic tires. In addition, all of these test tires have a land portion formed by arranging a circumferential main groove and a width direction groove on the tread surface, and a cross-sectional view parallel to the tire equatorial plane. The profile of the width groove arranged between the two land portions adjacent to each other in the tire circumferential direction is opposite to the first wall surface, the bottom surface continuous with the first wall surface, and the first wall surface on the bottom surface. A second portion comprising a second wall surface continuous on the side, the first wall surface being composed of a first portion far from the bottom surface, and a second portion close to the bottom surface continuous with the first portion. The wall surface is composed of a third portion far from the bottom surface and a fourth portion close to the groove bottom continuous with the third portion (FIG. 2).

In Table 1, D is the groove depth of the circumferential main groove 16 shown in FIG. 1, d1 is the tire radial dimension of the first portion 262a shown in FIG. 2, and d2 is the second dimension shown in FIG. The tire radial dimension of the portion 262b, d3 is the tire radial dimension of the third portion 266a shown in FIG. 2, and d4 is the tire radial dimension of the fourth portion 266b shown in FIG. Further, in Table 1, θ1 is the angle formed by the tire radial direction shown in FIG. 2 and the first portion 262a, and θ2 is the angle formed by the tire radial direction shown in FIG. 2 and the second portion 262b. θ3 is the angle formed by the tire radial direction shown in FIG. 2 and the third portion 266a, and θ4 is the angle formed by the tire radial direction shown in FIG. 2 and the fourth portion 266b. Further, in Table 1, L1 is the tire circumferential dimension of the land portion (block 54a) on the first wall surface side shown in FIG. 1, and L2 is the land portion (block 54b) on the second wall surface side shown in FIG. This is the tire circumferential dimension.

(Evaluation of wet braking performance)
Each test tire produced in this way is assembled to a wheel with a rim size of 15 x 6.5J, the air pressure is 250 kPa for the front wheels and 250 kPa for the rear wheels, and it is mounted on a front engine front drive type passenger car with a displacement of 1800 cc. , Wet (WET) braking performance was evaluated.

Specifically, on a wet road surface having a water film of 1 mm, the distance from an initial velocity of 100 km / h to braking and stopping was measured. Then, the reciprocal of the measured value was used, and an index (conventional example of 100) was used for comparison. The results are also shown in Table 1. This evaluation shows that the larger the index, the shorter the distance to stop, and the better the wet braking performance (see Table 1).

(Evaluation of braking performance on ice)
Similar to the above-mentioned evaluation of wet braking performance, each test tire is assembled to a wheel with a rim size of 15 x 6.5J, the air pressure is 250 kPa for the front wheels and 250 kPa for the rear wheels, and the displacement is 1800 cc. The braking performance on ice was evaluated on the test course.

Specifically, on an icy road surface, the distance from an initial velocity of 40 km / h to braking and stopping was measured. Then, the reciprocal of the measured value was used, and an index (conventional example of 100) was used for comparison. The results are also shown in Table 1. This evaluation shows that the larger the index, the shorter the distance to stop, and the better the braking performance on ice (see Table 1).

As is clear from Table 1, it belongs to the technical scope of the present invention (improvements have been made to the shapes of the two wall profile lines facing the tire circumferential direction of the width groove in a cross-sectional view parallel to the tire equatorial plane). The pneumatic tires of Examples 1 to 5 have better wet braking performance and ice braking performance than the pneumatic tires of the conventional example and Comparative Examples 1 and 2 which do not belong to the technical scope of the present invention. It can be seen that both are achieved at a high level.

1 Pneumatic tire 10 Tread part 12 Tread surface 14, 16, 18, 20 Circumferential main groove 22 Circumferential narrow groove 24, 26, 28, 30, 32 Width groove 34, 36 Lag groove 38, 40, 42, 44 , 46 Circumferential end groove 48 Sipe 50, 52, 54, 56, 58, 60, 62, 64 Land 54a, 54b Block 262 First wall surface 262a First part 262b Second part 264 Bottom surface 266 Second Wall surface 266a 3rd part 266b 4th part A1, A2, A3, A4 End point CL Tire equatorial plane

Claims (6)

In a pneumatic tire in which a land portion is formed by arranging a circumferential main groove and a width direction groove on the tread surface.
In a cross-sectional view parallel to the equator of the tire
The profile of the widthwise groove arranged between the two land portions adjacent to each other in the tire circumferential direction is the first wall surface, the bottom surface continuous with the first wall surface, and the first wall surface of the bottom surface. A second wall surface that is continuous on the opposite side, a first portion that includes the first wall surface that is far from the bottom surface, and a second portion that is continuous with the first portion and is close to the bottom surface. ,
The second wall surface is composed of a third portion far from the bottom surface and a fourth portion close to the groove bottom continuous with the third portion.
The tire radial dimension d1 of the first portion is 50% or more of the deepest groove depth D, and the tire radial dimension d3 of the third portion is 50% or more of the deepest groove depth D.
The angle θ1 formed by the tire radial direction and the first portion is smaller than the angle θ2 formed by the tire radial direction and the second portion, and the angle θ3 formed by the tire radial direction and the third portion is It is smaller than the angle θ4 formed by the tire radial direction and the fourth portion.
The forming angle θ1 is 0 ° or more and 5 ° or less, the forming angle θ2 is 2 ° or more and 10 ° or less, the forming angle θ3 is 0 ° or more and 5 ° or less, and the forming angle θ4 is 2 ° or more. Pneumatic tires characterized by being 10 ° or less. The first aspect of claim 1, wherein the tire circumferential dimension L1 of the land portion on the first wall surface side of the two land portions is larger than the tire circumferential dimension L2 of the land portion on the second wall surface side. Pneumatic tires. The pneumatic tire according to claim 2, wherein the tire radial dimension d1 of the first portion is larger than the tire radial dimension d3 of the third portion. The pneumatic tire according to any one of claims 1 to 3, wherein the forming angle θ1 is smaller than the forming angle θ3. The pneumatic tire according to any one of claims 1 to 4, wherein at least one sipe is formed on the land portion. The pneumatic tire according to any one of claims 1 to 5, which is a studless tire.