JP7553777B2 - tire - Google Patents

Description

The present invention relates to a tire.

Tires mounted on vehicles have grooves formed in the tread portion to ensure various performance characteristics according to the manner in which the tire is used, and the shape of the grooves is devised to improve performance. For example, in the pneumatic tires described in Patent Documents 1 to 3, circumferential grooves and lug grooves are formed in the tread portion to make the land portion into a block shape in order to improve driving performance on snowy and icy roads, and sipes are further arranged on the block-shaped land portion to increase the edge component and improve performance on ice.

International Publication No. 2008/026255 JP 2015-6882 A JP 2017-88019 A

Among tires, there are so-called studless tires that are required to be driven on snowy and icy roads, and performance on ice and snow is important for studless tires. Methods for improving performance on ice and snow in studless tires include, for example, reducing the groove area on the inside of the tread in the direction of mounting on the vehicle to increase the contact area and enhance the edge effect, thereby improving braking performance on ice, and increasing the groove area on the outside of the direction of mounting on the vehicle to increase the snow column shear force, thereby improving braking performance on snow.

However, even on icy and snowy roads, not only braking performance but also turning performance is required. If the groove area on the outer side in the vehicle mounting direction is increased, the rigidity of the land part decreases, and there is a risk that the land part will collapse during turning, making it difficult to ensure turning performance. For this reason, there was room for improvement in performance on ice and on snow, taking turning performance into consideration.

The present invention was made in consideration of the above, and aims to provide a tire that can more reliably improve performance on ice and on snow.

In order to solve the above problems and achieve the object, the tire according to the present invention comprises at least three circumferential grooves extending in the tire circumferential direction, a plurality of lug grooves extending in the tire width direction, a plurality of land portions defined by the circumferential grooves and the lug grooves, and a plurality of sipes extending in the tire width direction and disposed in the land portions defined on both sides in the tire width direction by the circumferential grooves, the inner sipes being the sipes disposed in the land portions located on the inner side of the tire equatorial plane in the vehicle mounting direction have the same inclination direction in the tire circumferential direction with respect to the tire width direction as the inner lug grooves being the lug grooves defining the land portions, and the outer sipes being the sipes disposed in the land portions located on the outer side of the tire equatorial plane in the vehicle mounting direction have the opposite inclination direction in the tire circumferential direction with respect to the tire width direction as the outer lug grooves being the lug grooves defining the land portions.

In addition, in the above tire, it is preferable that one end of the inner lug groove opens into the circumferential groove and the other end terminates within the land portion, and both ends of the outer lug groove open into the circumferential groove.

In addition, in the above tire, it is preferable that the land portion in which the outer sipes are arranged has a circumferential narrow groove that has a groove depth shallower than the groove depth of the circumferential groove and extends in the tire circumferential direction.

In addition, in the above tire, it is preferable that the circumferential narrow groove has a groove width in the range of 1.5 mm to 4 mm, and a groove depth in the range of 30% to 80% of the groove depth of the circumferential groove.

In addition, in the above tire, it is preferable that the inner lug groove has one or more bends where the extension direction changes.

In addition, in the above tire, it is preferable that the inclination of the inner lug groove in the tire width direction with respect to the tire circumferential direction is within a range of 55° to 75°.

In addition, in the above tire, it is preferable that the inclination of the inner lug groove in the tire width direction relative to the tire circumferential direction is greater than the inclination of the outer lug groove in the tire width direction relative to the tire circumferential direction.

In addition, in the above tire, it is preferable that the inclination of the inner sipes in the tire width direction relative to the tire circumferential direction is within a range of 55° to 75°.

In addition, in the above tire, it is preferable that the inclination of the inner sipe in the tire width direction relative to the tire circumferential direction is greater than the inclination of the outer sipe in the tire width direction relative to the tire circumferential direction.

In addition, in the above tire, it is preferable that the difference in inclination of the inner lug groove and the inner sipe in the tire width direction relative to the tire circumferential direction is 20° or less.

The tire according to the present invention has the effect of more reliably improving performance on ice and on snow.

FIG. 1 is a tire meridian cross-sectional view showing a main portion of a pneumatic tire according to an embodiment. FIG. 2 is a view taken along the line AA in FIG. FIG. 3 is a detailed view of part B in FIG. FIG. 4 is a detailed view of part C in FIG. FIG. 5 is a cross-sectional view taken along line E--E of FIG. FIG. 6 is a table showing the results of the performance evaluation test of pneumatic tires.

Below, an embodiment of a tire according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to this embodiment. Furthermore, the components in the following embodiment include those that are replaceable and easily conceivable by a person skilled in the art, or those that are substantially the same.

[Embodiment]
In the following description, a pneumatic tire 1 will be used as an example of a tire according to the present invention. The pneumatic tire 1, which is an example of a tire, can be filled with air, an inert gas such as nitrogen, or other gases.

In the following description, the tire radial direction refers to a direction perpendicular to the tire rotation axis (not shown), which is the rotation axis of the pneumatic tire 1, the tire radial inner side refers to the side toward the tire rotation axis in the tire radial direction, and the tire radial outer side refers to the side away from the tire rotation axis in the tire radial direction. The tire circumferential direction refers to the direction around the tire rotation axis as the central axis. The tire width direction refers to a direction parallel to the tire rotation axis, the tire width inner side refers to the side toward the tire equatorial plane (tire equatorial line) CL in the tire width direction, and the tire width outer side refers to the side away from the tire equatorial plane CL in the tire width direction. The tire equatorial plane CL is a plane that is perpendicular to the tire rotation axis and passes through the center of the tire width of the pneumatic tire 1, and the tire equatorial plane CL coincides with the tire width centerline, which is the center position in the tire width direction of the pneumatic tire 1. The tire width is the width in the tire width direction between the parts located at the outermost positions in the tire width direction, that is, the distance between the parts farthest from the tire equatorial plane CL in the tire width direction. The tire equatorial line is a line that is on the tire equatorial plane CL and runs along the tire circumferential direction of the pneumatic tire 1. In the following description, the tire meridian section is a section obtained by cutting the tire on a plane that includes the tire rotation axis.

1 is a tire meridian cross-sectional view showing a main part of a pneumatic tire 1 according to an embodiment. The pneumatic tire 1 according to this embodiment has a specified mounting direction relative to the vehicle, that is, a direction when mounted on the vehicle. That is, in the pneumatic tire 1 shown in this embodiment, the side facing the inside of the vehicle when mounted on the vehicle is the inside of the vehicle mounting direction, and the side facing the outside of the vehicle when mounted on the vehicle is the outside of the vehicle mounting direction. Note that the designation of the inside of the vehicle mounting direction and the outside of the vehicle mounting direction is not limited to when mounted on a vehicle. For example, when assembled on a rim, the orientation of the rim relative to the inside and outside of the vehicle in the tire width direction is determined, so when assembled on a rim, the pneumatic tire 1 is specified in the tire width direction relative to the inside of the vehicle mounting direction and the outside of the vehicle mounting direction. In addition, the pneumatic tire 1 has a mounting direction display portion (not shown) that indicates the mounting direction relative to the vehicle. The mounting direction display portion is, for example, configured by a mark or unevenness attached to the sidewall portion 8 of the tire. For example, ECER 30 (Article 30 of the Economic Commission for Europe Regulation) requires that a mounting direction indicator be provided on the sidewall portion 8 that is on the outer side of the vehicle mounting direction when mounted on the vehicle. Also, the pneumatic tire 1 according to this embodiment is a pneumatic tire 1 that is mainly used for passenger cars.

When viewed in a tire meridian section, the pneumatic tire 1 according to this embodiment has a tread portion 2 disposed on the outermost portion in the tire radial direction, and the tread portion 2 has a tread rubber 4 made of a rubber composition. The surface of the tread portion 2, i.e., the portion that comes into contact with the road surface when a vehicle (not shown) equipped with the pneumatic tire 1 is traveling, is formed as a tread contact surface 3, and the tread contact surface 3 constitutes part of the contour of the pneumatic tire 1.

Shoulder portions 5 are located at both outer ends of the tread portion 2 in the tire width direction, and sidewall portions 8 are arranged on the tire radially inward side of the shoulder portions 5. That is, the sidewall portions 8 are arranged on both sides of the tread portion 2 in the tire width direction. In other words, the sidewall portions 8 are arranged in two locations on both sides of the pneumatic tire 1 in the tire width direction, forming the outermost exposed portion of the pneumatic tire 1 in the tire width direction.

Bead portions 10 are located on the radially inner side of each sidewall portion 8 located on both sides in the tire width direction. The bead portions 10 are arranged in two locations on both sides of the tire equatorial plane CL, just like the sidewall portions 8, i.e., a pair of bead portions 10 are arranged on both sides of the tire equatorial plane CL in the tire width direction. Each bead portion 10 is provided with a bead core 11, and a bead filler 12 is provided on the radially outer side of the bead core 11. The bead core 11 is an annular member formed by bundling bead wires, which are steel wires, into a circular ring shape, and the bead filler 12 is a rubber member arranged on the radially outer side of the bead core 11.

The tread portion 2 is provided with a belt layer 14. The belt layer 14 is constructed with a multi-layer structure in which a plurality of belts 141, 142 and a belt cover 143 are laminated, and in this embodiment, two layers of belts 141, 142 are laminated. The belts 141, 142 constituting the belt layer 14 are constructed by coating a plurality of belt cords made of steel or organic fiber materials such as polyester, rayon, and nylon with coating rubber and rolling them, and the belt angle, defined as the inclination angle of the belt cord with respect to the tire circumferential direction, is within a predetermined range (for example, 20° to 55°). The two layers of belts 141, 142 have different belt angles. For this reason, the belt layer 14 is constructed as a so-called cross-ply structure in which the two layers of belts 141, 142 are laminated with the inclination directions of the belt cords crossing each other. In other words, the two-layer belts 141 and 142 are arranged so that the belt cords of the respective belts 141 and 142 cross each other, forming a so-called cross belt.

The belt cover 143 is made by coating multiple belt cover cords made of steel or organic fiber materials such as polyester, rayon, or nylon with coating rubber and rolling them, and the belt angle, defined as the inclination angle of the belt cover cords with respect to the tire circumferential direction, is within a predetermined range (for example, 0° to 10°). The belt cover 143 is, for example, a strip material made of one or more belt cover cords coated with coating rubber, and is constructed by wrapping this strip material in a spiral shape centered on the tire rotation axis from the tire radial outside of the two-layer belts 141 and 142.

A carcass layer 13 containing the cords of the radial ply is provided continuously on the inner side of the belt layer 14 in the tire radial direction and on the tire equatorial plane CL side of the sidewall portion 8. Therefore, the pneumatic tire 1 according to this embodiment is configured as a so-called radial tire. The carcass layer 13 has a single-layer structure consisting of one carcass ply, or a multi-layer structure consisting of multiple carcass plies stacked together, and is toroidally spanned between a pair of bead portions 10 arranged on both sides in the tire width direction to form the tire framework.

In detail, the carcass layer 13 is disposed from one bead portion 10 to the other bead portion 10 of a pair of bead portions 10 located on both sides in the tire width direction, and is wound around the bead core 11 at the bead portion 10 to wrap the bead core 11 and the bead filler 12. The bead filler 12 is a rubber material disposed in a space formed on the tire radial outer side of the bead core 11 by folding the carcass layer 13 at the bead portion 10 in this way. The belt layer 14 is disposed on the tire radial outer side of the portion of the carcass layer 13 located in the tread portion 2 that is stretched between the pair of bead portions 10 in this way. The carcass ply of the carcass layer 13 is formed by coating a plurality of carcass cords made of steel or organic fiber material such as aramid, nylon, polyester, rayon, etc. with coating rubber and rolling them. The carcass cords that make up the carcass ply are arranged in parallel at an angle to the tire circumferential direction, while aligning with the tire meridian direction.

In the bead portion 10, rim cushion rubber 17 is arranged on the tire radial inner side and tire width outer side of the bead core 11 and the turned-up portion of the carcass layer 13, which constitute the contact surface of the bead portion 10 with the rim flange. In addition, an inner liner 16 is formed along the carcass layer 13 on the inner side of the carcass layer 13 or on the inner side of the carcass layer 13 in the pneumatic tire 1. The inner liner 16 forms the tire inner surface 18, which is the inner surface of the pneumatic tire 1.

Figure 2 is a view taken along the line A-A in Figure 1. In the tread portion 2, a plurality of circumferential grooves 30 extending in the tire circumferential direction and a plurality of lug grooves 40 extending in the tire width direction are formed on the tread ground contact surface 3, and a plurality of land portions 20 are defined on the surface of the tread portion 2 by these circumferential grooves 30 and lug grooves 40. In this embodiment, four circumferential grooves 30 are formed side by side in the tire width direction. In detail, the circumferential grooves 30 have four grooves: two inner circumferential grooves 31 arranged on both sides of the tire equatorial plane CL in the tire width direction, and two outer circumferential grooves 35 arranged one on each side of the two inner circumferential grooves 31 in the tire width direction. The groove width of these circumferential grooves 30 is in the range of 3.5 mm to 12 mm, and the groove depth is in the range of 6.0 mm to 10.0 mm.

The land portion 20 defined by the circumferential grooves 30 includes a center land portion 21, a second land portion 22, and a shoulder land portion 23. The center land portion 21 is a land portion 20 located between the inner circumferential grooves 31, and both sides in the tire width direction are defined by the inner circumferential grooves 31. The second land portion 22 is a land portion 20 located between the inner circumferential groove 31 and the outer circumferential groove 35 adjacent in the tire width direction, and the inner part in the tire width direction is defined by the inner circumferential groove 31, and the outer part in the tire width direction is defined by the outer circumferential groove 35. The shoulder land portion 23 is a land portion 20 located outside the outer circumferential groove 35 in the tire width direction, and the inner side in the tire width direction is defined by the outer circumferential groove 35. The second land portion 22 and the shoulder land portion 23 are located on both sides in the tire width direction of the tire equatorial plane CL.

Of the four circumferential grooves 30, the two outer circumferential grooves 35 are each formed to extend linearly along the tire circumferential direction. On the other hand, of the four circumferential grooves 30, the two inner circumferential grooves 31 are each formed in a zigzag shape with at least one of the groove walls on both sides in the groove width direction extending in the tire circumferential direction and oscillating in the tire width direction.

In more detail, when the two inner circumferential grooves 31 are the first inner circumferential groove 31a and the second inner circumferential groove 31b, the first inner circumferential groove 31a has a zigzag groove wall on the outer side in the tire width direction, and the inner side in the tire width direction is formed to extend linearly along the tire circumferential direction. The second inner circumferential groove 31b is formed in a zigzag shape by the entire second inner circumferential groove 31b extending in the tire circumferential direction and oscillating in the tire width direction. Therefore, the second inner circumferential groove 31b has a constant groove width, while both groove walls on both sides in the groove width direction are formed in a zigzag shape.

In this embodiment, the first inner circumferential groove 31a is the inner circumferential groove 31 that is located on the inside of the tire equatorial plane CL in the vehicle mounting direction, out of the two inner circumferential grooves 31 that are located on both sides of the tire equatorial plane CL. Also, the second inner circumferential groove 31b is the inner circumferential groove 31 that is located on the outside of the tire equatorial plane CL in the vehicle mounting direction, out of the two inner circumferential grooves 31 that are located on both sides of the tire equatorial plane CL.

The lug grooves 40 include a center lug groove 41, an inner lug groove 42, an outer lug groove 44, and a shoulder lug groove 45. Of these, the center lug groove 41 is disposed between the two inner circumferential grooves 31. The center lug groove 41 extends in the tire width direction and is inclined in the tire circumferential direction with respect to the tire width direction, with both ends opening into the inner circumferential groove 31. Therefore, the center land portion 21 defined by the inner circumferential groove 31 and the center lug groove 41 is a block-shaped land portion 20 defined on both sides in the tire width direction by the inner circumferential groove 31 and on both sides in the tire circumferential direction by the center lug groove 41.

The inner lug groove 42 is a lug groove 40 arranged on the inner side of the tire equatorial plane CL in the vehicle mounting direction, and is arranged between the first inner circumferential groove 31a and the outer circumferential groove 35 adjacent to the first inner circumferential groove 31a. In other words, the inner lug groove 42 is arranged in the inner second land portion 22a, which is the second land portion 22 located on both sides of the tire equatorial plane CL in the tire width direction, and is located on the inner side of the tire equatorial plane CL in the vehicle mounting direction and is located between the first inner circumferential groove 31a and the outer circumferential groove 35. In this way, the inner lug groove 42, which is a lug groove 40 arranged in the land portion 20 whose both sides in the tire width direction are partitioned by the circumferential groove 30, has one end that opens into the circumferential groove 30 and the other end that terminates within the land portion 20, and is formed by bending at multiple points. That is, the inner lug groove 42 is a lug groove 40 that is open on one side, with one end opening into the circumferential groove 30 and the other end not opening.

Specifically, the inner lug groove 42 has one end opening into the outer circumferential groove 35 and the other end terminating in the inner second land portion 22a, and is bent at two points between the end opening into the outer circumferential groove 35 and the end terminating in the inner second land portion 22a. That is, the inner lug groove 42 opens into the outer circumferential groove 35 that defines the outer side in the tire width direction or the inner side in the vehicle mounting direction of the two circumferential grooves 30 that define both sides of the inner second land portion 22a in the tire width direction. A plurality of inner lug grooves 42 are arranged in the tire circumferential direction in the same form. In addition, since one end of the inner lug groove 42 terminates in the inner second land portion 22a at one of both ends in the extension direction of the inner lug groove 42, the inner second land portion 22a is not divided in the tire circumferential direction by the inner lug groove 42. Therefore, the inner second land portion 22a is a rib-shaped land portion 20 that is continuously formed in the tire circumferential direction.

The outer lug groove 44 is a lug groove 40 that is arranged on the inside and outside of the vehicle mounting direction with respect to the tire equatorial plane CL, and is arranged between the second inner circumferential groove 31b and the outer circumferential groove 35 adjacent to the second inner circumferential groove 31b. The outer lug groove 44 extends in the tire width direction and is inclined in the tire circumferential direction with respect to the tire width direction, with one end opening into the second inner circumferential groove 31b and the other end opening into the outer circumferential groove 35. In this way, the outer lug groove 44 arranged between the second inner circumferential groove 31b and the outer circumferential groove 35 is located on the outside of the vehicle mounting direction with respect to the tire equatorial plane CL, and is a lug groove 40 that defines the outer second land portion 22b, which is the second land portion 22 located between the second inner circumferential groove 31b and the outer circumferential groove 35. Therefore, the outer second land portion 22b is a block-shaped land portion 20 that is defined on both sides in the tire width direction by the second inner circumferential groove 31b and the outer circumferential groove 35, and on both sides in the tire circumferential direction by the outer lug groove 44.

The shoulder lug grooves 45 are arranged on the outer side in the tire width direction of the outer circumferential grooves 35 located on both sides in the tire width direction of the tire equatorial plane CL. Each shoulder lug groove 45 is formed extending in the tire width direction, with the inner end in the tire width direction opening into the outer circumferential groove 35 and the outer end in the tire width direction terminating at the so-called design end, which is the end in the tire width direction of the tread pattern of the tread portion 2. In this way, the shoulder lug grooves 45 formed between the outer circumferential grooves 35 and the design end form a lug groove 40 that defines the shoulder land portion 23 together with the outer circumferential groove 35. Therefore, the shoulder land portion 23 is a block-shaped land portion 20 defined on both sides in the tire circumferential direction by the shoulder lug grooves 45.

The lug grooves 40 thus formed have a groove width in the range of 3.0 mm to 8.0 mm, and a groove depth in the range of 6.0 mm to 9.0 mm.

Furthermore, a circumferential narrow groove 50 extending in the tire circumferential direction is disposed in the outer second land portion 22b located between the second inner circumferential groove 31b and the outer circumferential groove 35. The circumferential narrow groove 50 is a groove that extends in the tire circumferential direction with a groove width narrower than the groove width of the circumferential groove 30.

The circumferential narrow groove 50 is disposed in the tire circumferential direction in the outer second land portion 22b located on the outer side of the tire equatorial plane CL in the vehicle mounting direction, and both ends in the tire circumferential direction open into the outer lug groove 44 that defines the outer second land portion 22b. The circumferential narrow groove 50 is formed with a portion that extends in the tire circumferential direction and bends in the tire width direction. In this embodiment, the circumferential narrow groove 50 is disposed in the outer second land portion 22b in a crank-like shape by bending at two points.

In addition, shoulder narrow grooves 55 extending in the tire circumferential direction are arranged in the shoulder land portion 23 located on the outer side in the tire width direction of the outer circumferential groove 35. One end of the shoulder narrow groove 55 extending in the tire circumferential direction opens into the shoulder lug groove 45, and the other end terminates within the shoulder land portion 23. The shoulder narrow grooves 55 arranged in the shoulder land portion 23 and located on the same side in the tire width direction with respect to the tire equatorial plane CL all have the end portions on the side that open into the shoulder lug groove 45 on the same side in the tire circumferential direction. In other words, the shoulder narrow grooves 55 arranged in the shoulder land portion 23 defined by the same outer circumferential groove 35 all face the same direction in the tire circumferential direction.

The shoulder narrow groove 55 arranged on the inside of the tire equatorial plane CL in the vehicle mounting direction and the shoulder narrow groove 55 arranged on the outside of the tire mounting direction have ends on different sides, one that opens into the shoulder lug groove 45 and the other that terminates within the shoulder land portion 23. In other words, the shoulder narrow groove 55 arranged on the inside of the tire equatorial plane CL in the vehicle mounting direction and the other that terminates on the outside of the tire mounting direction are oriented in opposite directions in the tire circumferential direction.

Furthermore, a plurality of sipes 60 extending in the tire width direction are arranged in each land portion 20. The sipes 60 arranged in the land portion 20 are formed and arranged in a zigzag shape by repeatedly bending and oscillating in the tire circumferential direction while extending in the tire width direction. The ends of each sipe 60 may terminate within the land portion 20, or may open into another groove. By arranging the sipes 60 in each land portion 20 in this manner, the pneumatic tire 1 according to this embodiment can be applied to a studless tire that ensures driving performance on icy and snowy roads, or an all-season tire that ensures driving performance in winter.

The sipes 60 referred to here are formed in the shape of narrow grooves on the tread contact surface 3, and when the pneumatic tire 1 is mounted on a specified rim and the internal pressure is set to a specified internal pressure, the walls constituting the narrow grooves do not come into contact with each other when no load is applied, but when the narrow grooves are located in the contact surface formed on the flat plate when a load is applied vertically on the flat plate, or when the land portion 20 on which the narrow grooves are formed collapses, the walls constituting the narrow grooves, or at least a part of the portion provided on the wall surface, come into contact with each other due to deformation of the land portion 20. In this embodiment, the sipes 60 have a groove width of 1.4 mm or less, and a maximum depth from the tread contact surface 3 within a range of 3.5 mm to 9.0 mm.

The specified rim here refers to the "standard rim" specified by JATMA, the "design rim" specified by TRA, or the "measuring rim" specified by ETRTO. Also, the specified internal pressure refers to the "maximum air pressure" specified by JATMA, the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "INFLATION PRESSURES" specified by ETRTO.

The sipe 60 may be a so-called three-dimensional sipe or a two-dimensional sipe. The three-dimensional sipe here refers to a sipe 60 that has a curved wall surface with amplitude in the width direction of the sipe 60 in both a cross-sectional view with the length direction of the sipe 60 as the normal direction (cross-sectional view including the width direction and depth direction of the sipe 60) and a cross-sectional view with the depth direction of the sipe 60 as the normal direction (cross-sectional view including the width direction and length direction of the sipe 60). The two-dimensional sipe refers to a sipe 60 that has a straight wall surface in any cross-sectional view with the length direction of the sipe 60 as the normal direction (cross-sectional view including the width direction and depth direction of the sipe 60).

Figure 3 is a detailed view of part B in Figure 2. The inner lug groove 42, which defines the inner second land portion 22a, which is the land portion 20 located on the inside of the vehicle mounting direction relative to the tire equatorial plane CL, and is formed by bending at one or more points, is a lug groove 40 having one or more bent portions 43 whose extension direction changes. In this embodiment, the inner lug groove 42 has two bent portions 43, a first bent portion 43a which is a bent portion 43 located on the outer circumferential groove 35 side of the inner lug groove 42, and a second bent portion 43b which is a bent portion 43 located on the end side that terminates within the inner second land portion 22a of the inner lug groove 42. As a result, the inner lug groove 42 has a first extension portion 42a, a second extension portion 42b, and a third extension portion 42c, with the two bent portions 43 as boundaries.

More specifically, the first extension 42a is a portion located between the end of the inner lug groove 42 on the side that opens into the outer circumferential groove 35 and the first bend 43a. The second extension 42b is a portion located between the first bend 43a and the second bend 43b in the inner lug groove 42. The third extension 42c is a portion located between the terminal end 42d, which is the end of the inner lug groove 42 on the side that terminates within the inner second land portion 22a, and the second bend 43b.

The two bent portions 43 of the inner lug groove 42 are the first bent portion 43a and the second bent portion 43b, and the bend direction in the groove width direction of the inner lug groove 42 is the same. In other words, the two bent portions 43 of the inner lug groove 42 have groove walls on the same side in the groove width direction, located on the minor angle side of the bend.

The bend 43 of the inner lug groove 42 has a bend angle of 90° or more. That is, the angle θ1 of the first bend 43a of the inner lug groove 42 is 90° or more, and the angle θ2 of the second bend 43b is also 90° or more. In this case, the bend angle of the bend 43 is an angle on the minor side of the bend. That is, the bend angle of the bend 43 of the inner lug groove 42 is an obtuse angle. The bend angle of the bend 43 is an angle at the center line of the groove width of the inner lug groove 42. The angle θ1 of the first bend 43a is preferably within the range of 90°≦θ1≦130°, and the angle θ2 of the second bend 43b is also preferably within the range of 90°≦θ2≦130°.

The inner lug groove 42 is bent at two bends 43 in this way to form a first extension 42a, a second extension 42b, and a third extension 42c. The first extension 42a extends at an angle close to the tire width direction, and the second extension 42b extends at an angle close to the tire circumferential direction.

In this embodiment, the two bends 43 of the inner lug groove 42 are bent in the same direction, so that the inner lug groove 42, which opens into the outer circumferential groove 35 and extends in the tire width direction, is formed in a shape that turns back toward the outer circumferential groove 35 when viewed as a whole. That is, the inner lug groove 42 is formed such that the third extension portion 42c approaches the outer circumferential groove 35 where the first extension portion 42a opens as it moves from the second extension portion 42b side toward the terminal end portion 42d side.

The first extension portion 42a, the second extension portion 42b, and the third extension portion 42c of the inner lug groove 42 are formed to have different lengths. Specifically, in the inner lug groove 42, the first extension portion 42a is the longest, the second extension portion 42b is the next longest, and the third extension portion 42c is the shortest. That is, the lengths of the first extension portion 42a, the second extension portion 42b, and the third extension portion 42c of the inner lug groove 42 satisfy the relationship: length of the first extension portion 42a > length of the second extension portion 42b > length of the third extension portion 42c.

Multiple inner lug grooves 42 are arranged in the inner second land portion 22a, and the multiple inner lug grooves 42 are arranged side by side in the tire circumferential direction with the same shape. In this way, it is preferable that the inner lug grooves 42 arranged in multiple in the inner second land portion 22a are formed so that the total length L in the tire circumferential direction satisfies the relationship 0.6≦(L/P)≦0.8 with respect to the pitch P between the inner lug grooves 42 adjacent in the tire circumferential direction.

In addition, multiple sipes 60 extending in the tire width direction are arranged in the inner second land portion 22a. The sipes 60 arranged in the inner second land portion 22a, which is the land portion 20 located on the inside of the vehicle mounting direction relative to the tire equatorial plane CL, are provided as inner sipes 61. The inner sipes 61 arranged in the inner second land portion 22a have the same inclination direction in the tire circumferential direction with respect to the tire width direction as the inner lug grooves 42. In other words, the inner sipes 61 extend in the tire width direction and are inclined in the tire circumferential direction with respect to the tire width direction, and the inclination direction in the tire circumferential direction with respect to the tire width direction is the same as the inclination direction in the tire circumferential direction with respect to the tire width direction of the inner lug grooves 42.

Here, the inner lug groove 42 has one or more bends 43, and the extension direction changes at the bends 43, but the part of the inner lug groove 42 that is compared with the inclination direction of the inner sipe 61 is the part of the inner lug groove 42 that extends in a predetermined direction with the longest length. That is, in this embodiment, the inner lug groove 42 has a first extension 42a, a second extension 42b, and a third extension 42c that extend in different directions due to two bends 43, but the first extension 42a has the longest length. Therefore, the part of the inner lug groove 42 that is compared with the inclination direction of the inner sipe 61 is the first extension 42a. That is, the inclination direction of the inner sipe 61 in the tire circumferential direction with respect to the tire width direction is the same as the inclination direction of the first extension 42a that extends in the tire circumferential direction with respect to the tire width direction with respect to the tire width direction in the inner lug groove 42.

In other words, the inclination direction of the inner sipe 61 in the tire width direction relative to the tire circumferential direction is the same as the inclination direction of the inner lug groove 42 in the tire width direction relative to the tire circumferential direction. In other words, the inclination direction of the inner sipe 61 in the tire width direction relative to the tire circumferential direction is the same as the inclination direction of the first extension portion 42a in the tire width direction relative to the tire circumferential direction.

In this way, the inner lug groove 42, which is formed with a tilt direction with respect to the tire circumferential direction in the same direction as the tilt direction of the inner sipe 61, has a tilt θg in the tire width direction with respect to the tire circumferential direction in the range of 55° to 75°. In detail, the inner lug groove 42 has a tilt θg in the tire width direction with respect to the tire circumferential direction of the first extension portion 42a, which is a portion to be compared with the tilt direction of the inner sipe 61, in the inner lug groove 42, in the tire width direction with respect to the tire circumferential direction in the range of 55° to 75°. In this case, the tilt θg of the inner lug groove 42 is the tilt of the center line of the groove width of the inner lug groove 42 in the tire width direction with respect to the tire circumferential direction.

On the other hand, the inclination θs of the inner sipe 61 in the tire width direction relative to the tire circumferential direction is within a range of 55° to 75°. In this case, the inclination θs of the inner sipe 61 is the inclination of a straight line passing through both ends of the inner sipe 61 in the longitudinal direction relative to the tire width direction.

As described above, the inner lug grooves 42 and the inner sipes 61 are formed with the same inclination relative to the tire circumferential direction, and the difference in inclination in the tire width direction relative to the tire circumferential direction is 20° or less. In other words, the difference between the inclination θg of the inner lug groove 42 in the tire width direction relative to the tire circumferential direction and the inclination θs of the inner sipes 61 in the tire width direction relative to the tire circumferential direction is 20° or less.

In addition, the inner sipe 61 has a communicating sipe 65, which is a sipe 60 whose both ends open to the circumferential groove 30 and the inner lug groove 42 and communicate between the circumferential groove 30 and the inner lug groove 42. The communicating sipe 65 opens to the inner lug groove 42 and a circumferential groove 30 different from the circumferential groove 30 on the side where the inner lug groove 42 opens. In other words, the communicating sipe 65 has one end opening to the first inner circumferential groove 31a, which is a circumferential groove 30 different from the circumferential groove 30 on the side where the inner lug groove 42 opens, among the two circumferential grooves 30 that define the inner second land portion 22a, and the other end opening to the inner lug groove 42. In detail, the communicating sipe 65 opens into the inner lug groove 42 at the position of the first bend 43a of the inner lug groove 42, and is formed along an extension line of the first extending portion 42a from the position of the first bend 43a toward the first inner circumferential groove 31a, and the end opens into the first inner circumferential groove 31a. The communicating sipe 65 formed between the inner lug groove 42 and the first inner circumferential groove 31a is formed as a straight sipe 60.

Figure 4 is a detailed view of part C in Figure 2. The outer lug grooves 44 that define the tire circumferential end of the outer second land portion 22b, which is the land portion 20 located on the outer side in the vehicle mounting direction relative to the tire equatorial plane CL, extend in the tire width direction while being inclined in the tire circumferential direction with respect to the tire width direction, and both ends open to the circumferential grooves 30. In other words, the outer lug grooves 44 that define the outer second land portion 22b are arranged so as to be inclined in the tire width direction with respect to the tire circumferential direction.

In this way, the outer lug groove 44, which is arranged at an angle to the tire circumferential direction, has a smaller inclination in the tire width direction relative to the tire circumferential direction than the inner lug groove 42 (see FIG. 3). In other words, the inner lug groove 42 has a larger inclination in the tire width direction relative to the tire circumferential direction than the outer lug groove 44. In this case, the portion of the inner lug groove 42 that is compared with the inclination of the outer lug groove 44 is the first extension portion 42a, which is the longest portion of the inner lug groove 42 whose extension direction changes at the bend portion 43. In other words, the inclination of the first extension portion 42a of the inner lug groove 42 in the tire width direction relative to the tire circumferential direction is larger than the inclination of the outer lug groove 44 in the tire width direction relative to the tire circumferential direction.

In addition, multiple sipes 60 extending in the tire width direction are arranged in the outer second land portion 22b. The sipes 60 arranged in the outer second land portion 22b, which is the land portion 20 located on the outer side of the vehicle mounting direction relative to the tire equatorial plane CL, are provided as outer sipes 62. The outer sipes 62 arranged in the outer second land portion 22b are inclined in the tire circumferential direction with respect to the tire width direction in the opposite direction to the outer lug grooves 44, which are the lug grooves 40 that define the outer second land portion 22b. In other words, the outer sipes 62 extend in the tire width direction and are inclined in the tire circumferential direction with respect to the tire width direction, and the inclination direction of the outer lug grooves 44 in the tire circumferential direction with respect to the tire width direction is opposite to the inclination direction of the outer lug grooves 44 in the tire circumferential direction with respect to the tire width direction. In other words, the inclination direction of the outer sipes 62 in the tire width direction with respect to the tire circumferential direction is opposite to the inclination direction of the outer lug grooves 44 in the tire width direction with respect to the tire circumferential direction.

The outer sipes 62 arranged on the outer second land portion 22b are inclined in the tire width direction relative to the tire circumferential direction less than the inner sipes 61 (see FIG. 3) arranged on the inner second land portion 22a. In other words, the inner sipes 61 are inclined in the tire width direction relative to the tire circumferential direction more than the outer sipes 62, and the inner sipes 61 extend at an angle closer to the tire width direction than the outer sipes 62.

In addition, a circumferential narrow groove 50 having a groove width narrower than the groove width of the circumferential groove 30 is arranged in the outer second land portion 22b. The circumferential narrow groove 50 is formed with a groove width Wn in the range of 1.5 mm to 4 mm. The circumferential narrow groove 50 has one or more bends 51 in which the extension direction changes in the outer second land portion 22b, and thus has a long portion 50a and a short portion 50b with relatively different lengths. In this case, the long portion 50a is relatively longer than the short portion 50b.

In this embodiment, the circumferential narrow groove 50 has two bent portions 51, i.e., the circumferential narrow groove 50 is bent at two points. The two bent portions 51 are bent in opposite directions in the groove width direction of the circumferential narrow groove 50, so that the circumferential narrow groove 50 is formed in a crank shape by extending in the tire circumferential direction and bending at two points. The bent portion 51 of the circumferential narrow groove 50 has an angle of 90° or more on the minor angle side of the bend. That is, the bent portion 51 of the circumferential narrow groove 50 is formed at a right angle or an obtuse angle.

The circumferential narrow groove 50 formed in a crank shape has a short portion 50b between two bent portions 51, and a long portion 50a between each bent portion 51 and the end of the circumferential narrow groove 50 that opens into the outer lug groove 44. In other words, the circumferential narrow groove 50 has two long portions 50a that open into the outer lug grooves 44 adjacent to each other in the tire circumferential direction, and a short portion 50b that is disposed between the ends of the two long portions 50a on the opposite side to the ends that open into the outer lug groove 44. The two long portions 50a are both longer than the short portions 50b, and the long portions 50a are approximately the same length.

The two long portions 50a of the circumferential narrow groove 50 are both inclined toward the tire width direction with respect to the tire circumferential direction, and the inclination angle with respect to the tire circumferential direction is approximately the same for the two long portions 50a. The inclination of the long portions 50a of the circumferential narrow groove 50 toward the tire width direction with respect to the tire circumferential direction is within a range of 5° to 45°.

The short portion 50b of the circumferential narrow groove 50 has an inclination direction in the tire width direction opposite to the tire circumferential direction. The circumferential narrow groove 50 is formed in a zigzag shape that extends in the tire circumferential direction while oscillating in the tire width direction, because the inclination directions in the tire width direction are opposite to each other in the long portion 50a and the short portion 50b.

Figure 5 is a cross-sectional view taken along line E-E of Figure 4. The groove depth Dn of the circumferential narrow groove 50 is shallower than the groove depth Dm of the circumferential groove 30 that defines the outer second land portion 22b, which is the land portion 20 in which the circumferential narrow groove 50 is disposed, and the groove depth Dn of the circumferential narrow groove 50 is within a range of 30% to 80% of the groove depth Dm of the circumferential groove 30. The groove depth Dn of the circumferential narrow groove 50 that is formed shallower than the groove depth Dm of the circumferential groove 30 is preferably within a range of 3.5 mm to 7.0 mm.

The circumferential narrow grooves 50 thus formed have ends that open into the outer lug grooves 44, but the circumferential narrow grooves 50 that open from opposite sides of the outer lug groove 44 in the groove width direction of the outer lug groove 44 open at positions close to the outer lug groove 44 in the tire width direction, or have portions that open at the same position in the tire width direction.

Of the two circumferential grooves 30 that define both sides in the tire width direction of the outer second land portion 22b in which the circumferential narrow grooves 50 are arranged, the second inner circumferential groove 31b that defines the inner side in the tire width direction is formed in a zigzag shape by extending in the tire circumferential direction and oscillating in the tire width direction. The second inner circumferential groove 31b is formed in a zigzag shape with long portions 32 and short portions 33 that are relatively different in length, and the long portions 32 and short portions 33 are alternately arranged with the zigzag bending position as the boundary. In this case, the long portions 32 are relatively longer than the short portions 33.

In this way, the second inner circumferential groove 31b formed in a zigzag shape having the long portion 32 and the short portion 33 has a zigzag period in the tire circumferential direction that is the same as the pitch in the tire circumferential direction between adjacent outer lug grooves 44. Therefore, the long portion 32 and the short portion 33 of the second inner circumferential groove 31b are located in the portion of the second inner circumferential groove 31b that is located between the outer lug grooves 44 adjacent in the tire circumferential direction. As a result, in the portion of the second inner circumferential groove 31b that defines one outer second land portion 22b, one long portion 32 and one short portion 33 are located. In other words, the portion formed by the second inner circumferential groove 31b in one outer second land portion 22b is defined by a set of the long portion 32 and the short portion 33 of the second inner circumferential groove 31b.

The second inner circumferential groove 31b is formed to extend in the tire circumferential direction while oscillating in the tire width direction, so that the long portion 32 and the short portion 33 are inclined in the tire width direction with respect to the tire circumferential direction, and the inclination direction in the tire width direction is opposite to each other. The circumferential narrow groove 50 arranged in the outer second land portion 22b has a long portion 50a inclined in the tire width direction with respect to the tire circumferential direction in the opposite direction to the long portion 32 of the second inner circumferential groove 31b, which is inclined in this way with respect to the tire circumferential direction. In other words, the circumferential narrow groove 50 has two long portions 50a, each of which has an inclination direction in the tire width direction with respect to the tire circumferential direction in the opposite direction to the long portion 32 of the second inner circumferential groove 31b.

The inclination of the long portion 32 of the second inner circumferential groove 31b in the tire width direction relative to the tire circumferential direction is within a range of 5° to 30°. It is preferable that the inclination of the long portion 50a of the circumferential narrow groove 50 in the tire width direction relative to the tire circumferential direction is greater than the inclination of the long portion 32 of the second inner circumferential groove 31b.

When mounting the pneumatic tire 1 according to this embodiment on a vehicle, the pneumatic tire 1 is mounted on a rim wheel and inflated with air inside. At this time, the mounting direction of the pneumatic tire 1 according to this embodiment relative to the vehicle is specified, so it is mounted on the vehicle in the specified direction. That is, it is mounted on the vehicle in the direction specified by the mounting direction indicator attached to the sidewall portion 8. As a result, the pneumatic tire 1 is mounted on the vehicle with the inner second land portion 22a, which is defined by the inner lug groove 42 and in which the inner sipe 61 is arranged, positioned on the inside of the vehicle mounting direction, and the outer second land portion 22b, which is defined by the outer lug groove 44 and in which the outer sipe 62 is arranged, positioned on the outside of the vehicle mounting direction.

When a vehicle equipped with a pneumatic tire 1 travels, the pneumatic tire 1 rotates with the lower part of the tread surface 3 of the tread portion 2 in contact with the road surface. When a vehicle equipped with a pneumatic tire 1 travels on a dry road surface, the vehicle travels by transmitting driving and braking forces to the road surface and generating turning forces mainly due to the frictional force between the tread surface 3 and the road surface.

When driving on a wet road surface, water between the tread surface 3 and the road surface enters the circumferential grooves 30, lug grooves 40, and other grooves and sipes 60, and these grooves drain the water between the tread surface 3 and the road surface while driving. This makes it easier for the tread surface 3 to make contact with the road surface, and the friction between the tread surface 3 and the road surface enables the vehicle to drive.

When driving on a snowy road surface, the pneumatic tire 1 compacts the snow on the road surface with the tread contact surface 3, and the snow on the road surface enters the circumferential grooves 30 and lug grooves 40, compacting the snow in the grooves. In this state, when a driving force or braking force acts on the pneumatic tire 1, or when a force acts in the tire width direction due to the vehicle turning, a shear force acting on the snow in the grooves, known as a snow column shear force, is generated between the pneumatic tire 1 and the snow. When driving on a snowy road surface, this snow column shear force generates resistance between the pneumatic tire 1 and the road surface, allowing the driving force and braking force to be transmitted to the road surface, ensuring snow traction. This enables the vehicle to drive on a snowy road surface.

When traveling on snowy or icy road surfaces, the tire also uses the edge effects of the circumferential grooves 30, lug grooves 40, and sipes 60. In other words, when traveling on snowy or icy road surfaces, the tire also uses the resistance caused by the edges of the circumferential grooves 30, lug grooves 40, and sipes 60 catching on the snow or ice surface. When traveling on icy road surfaces, the sipes 60 absorb water on the surface of the icy road surface, and the water film between the icy road surface and the tread contact surface 3 is removed, making it easier for the icy road surface and the tread contact surface 3 to come into contact. As a result, the resistance between the tread contact surface 3 and the icy road surface increases due to frictional force and edge effects, and the running performance of a vehicle equipped with the pneumatic tire 1 can be ensured.

The circumferential grooves 30, lug grooves 40, and sipes 60 formed in the tread portion 2 contribute to ensuring driving performance when driving on wet road surfaces, snowy road surfaces, and icy road surfaces. For example, in order to improve wet performance, which is the driving performance on wet road surfaces, it is effective to increase the groove area of the tread portion 2. In other words, if the groove area, which is the area of the grooves such as the circumferential grooves 30 and lug grooves 40, is increased, water on the road surface can easily enter the grooves when driving on a wet road surface, so that the drainage of water between the tread contact surface 3 and the road surface can be improved, and wet performance can be improved.

Increasing the groove area is also effective in improving snow performance, which is the driving performance on snowy roads. In other words, when the groove area is increased, the amount of snow that can enter the circumferential grooves 30 and lug grooves 40 when driving on snowy roads can be increased, and the snow column shear force acting on the snow that has entered the grooves can be increased. This improves snow traction when driving on snowy roads, and improves snow performance.

Here, when the groove area of the tread portion 2 is increased, the volume of the land portion 20 defined by the circumferential grooves 30 and the lug grooves 40 decreases with the increase in the groove area. When the volume of the land portion 20 decreases, the rigidity of the land portion 20 decreases, but when the rigidity of the land portion 20 decreases, the land portion 20 becomes more likely to deform and collapse when a load is applied. When the land portion 20 collapses, the contact area of the collapsed land portion 20 is reduced, which may make it difficult to ensure driving performance.

For example, when driving on icy roads, in addition to the edge effect due to the edge components of the grooves, the frictional force caused by the tread contact surface 3 touching the icy road surface is also important. However, if the rigidity of the land portion 20 is reduced by increasing the groove area of the tread portion 2, the land portion 20 will tend to collapse when a load is applied, which will tend to reduce the contact area and may make it difficult to ensure driving performance due to frictional force. For this reason, if the rigidity of the land portion 20 is reduced by increasing the groove area of the tread portion 2, the land portion 20 will tend to collapse when braking while driving on icy roads, which will tend to reduce the contact area and may make it difficult to ensure braking performance on icy roads.

For this reason, one method for achieving both ice performance, which is driving performance on icy roads, and snow performance is, for example, to reduce the groove area on the inside of the tread 2 in the vehicle mounting direction, and increase the groove area on the outside of the vehicle mounting direction. In other words, since a large load acts on the inside of the tread 2 in the vehicle mounting direction when the vehicle is braked, the contact area can be secured by reducing the groove area on the inside of the tread 2 in the vehicle mounting direction, and braking performance on ice can be secured. In addition, the reduced groove area on the inside of the tread 2 in the vehicle mounting direction is compensated for by the outside of the tread 2 in the vehicle mounting direction, and the groove area on the outside of the vehicle mounting direction is increased, thereby securing snow column shear force and ensuring braking performance on snow.

However, the performance required for a pneumatic tire 1 used on snowy and icy roads is not only braking performance but also turning performance. If the groove area on the outer side of the vehicle mounting direction is increased, it may be difficult to ensure turning performance. In other words, when the vehicle turns, a large load acts on the outer part of the pneumatic tire 1 in the vehicle mounting direction, which is located on the outer side in the radial direction of the turn. If the groove area on the outer side of the vehicle mounting direction is increased, the rigidity of the land portion 20 on the outer side of the vehicle mounting direction decreases, so that when a large load acts on the part on the outer side of the vehicle mounting direction when the vehicle turns, the land portion 20 is likely to collapse. This makes it difficult to ensure steering stability when the vehicle turns, and there is a risk that it may be difficult to ensure turning performance.

In contrast, in the pneumatic tire 1 according to this embodiment, the outer sipes 62, which are sipes 60 arranged in the land portion 20 located on the outer side of the vehicle mounting direction relative to the tire equatorial plane CL, are inclined in the tire circumferential direction relative to the tire width direction in the opposite direction to the outer lug grooves 44, so that the rigidity of the land portion 20 located on the outer side of the vehicle mounting direction can be ensured. In other words, in this embodiment, the outer sipes 62 are inclined in the tire width direction relative to the tire circumferential direction in the opposite direction to the outer lug grooves 44, so that the land portion 20 where the outer sipes 62 are arranged can be prevented from having a direction in which the rigidity against the load acting thereon is weak.

In other words, when the inclination direction of the outer sipes 62 is the same as the inclination direction of the outer lug grooves 44, the land portion 20 in which the outer sipes 62 are arranged is likely to ensure rigidity in the extension direction of the outer sipes 62 and the outer lug grooves 44, but it may be difficult to ensure rigidity in a direction close to a direction perpendicular to the extension direction of the outer sipes 62 and the outer lug grooves 44. In this case, when a load acts on the outer second land portion 22b, which is the land portion 20 in which the outer sipes 62 are arranged, in a direction close to a direction perpendicular to the extension direction of the outer sipes 62 and the outer lug grooves 44, the outer second land portion 22b is likely to collapse.

When the inclination direction of the outer sipes 62 is the same as the inclination direction of the outer lug grooves 44, the outer second land portion 22b is likely to have a direction in which its rigidity against load is weak. However, in this embodiment, the outer sipes 62 are inclined in the tire width direction in the opposite direction to the tire circumferential direction relative to the outer lug grooves 44. This makes it possible to prevent the outer second land portion 22b from having a direction in which its rigidity against load is weak, and the rigidity of the outer second land portion 22b can be ensured regardless of the direction of the load, so that the outer second land portion 22b can be prevented from collapsing when a large load is applied when the vehicle is turning. Therefore, it is possible to ensure the steering stability when the vehicle is turning, and the cornering performance can be ensured.

In addition, the inner sipes 61, which are sipes 60 arranged in the land portion 20 located on the inside of the tire equatorial plane CL in the vehicle mounting direction, have the same inclination direction in the tire circumferential direction with respect to the tire width direction as the inner lug grooves 42, so the direction in which the inner sipes 61 exert their edge effect can be aligned with the direction in which the inner lug grooves 42 exert their edge effect. Therefore, the inner sipes 61 can maximize the edge effect in the inner second land portion 22a in which the inner sipes 61 are arranged, together with the inner lug grooves 42. This can enhance the edge effect in the inner second land portion 22a, which is located on the inside of the vehicle mounting direction with respect to the tire equatorial plane CL and is subjected to a large load when the vehicle is braked, and can ensure braking performance on icy road surfaces. As a result, it is possible to more reliably improve ice performance and snow performance.

In addition, the inner lug groove 42 has one end opening into the circumferential groove 30 and the other end terminating within the inner second land portion 22a, so that the rigidity of the inner second land portion 22a can be ensured. This makes it possible to suppress the inner second land portion 22a from collapsing when a large load acts on the inner second land portion 22a located on the inner side of the vehicle mounting direction relative to the tire equatorial plane CL during braking of the vehicle. Therefore, it is possible to suppress a reduction in the contact area during braking of the vehicle, and it is possible to more reliably ensure braking performance on icy road surfaces. In addition, since both ends of the outer lug groove 44 open into the circumferential groove 30, it is possible to increase the snow column shear force in the outer lug groove 44, and it is possible to improve snow traction when driving on a snowy road surface. As a result, it is possible to more reliably improve ice performance and snow performance.

In addition, the outer second land portion 22b, which is the land portion 20 where the outer sipes 62 are arranged, has a groove depth shallower than the groove depth of the circumferential grooves 30 and is arranged with circumferential narrow grooves 50 extending in the tire circumferential direction, so that the snow column shear force can be increased while suppressing a decrease in the rigidity of the outer second land portion 22b. This makes it possible to more reliably improve the running performance when running on snowy roads. In addition, by arranging the circumferential narrow grooves 50 in the outer second land portion 22b, it is possible to increase the edge effect in the tire width direction while suppressing a decrease in the rigidity of the outer second land portion 22b. This makes it possible to more reliably improve the cornering performance by the edge effect in the tire width direction of the circumferential narrow grooves 50 while suppressing the collapse of the outer second land portion 22b when the vehicle turns. As a result, it is possible to more reliably improve the performance on ice and on snow.

In addition, the circumferential narrow grooves 50 have a groove width Wn in the range of 1.5 mm to 4 mm, and a groove depth Dn in the range of 30% to 80% of the groove depth Dm of the circumferential grooves 30. This prevents the rigidity of the land portion 20 in which the circumferential narrow grooves 50 are arranged from becoming too low, while ensuring the snow column shear force of the circumferential narrow grooves 50 and achieving an edge effect. As a result, it is possible to more reliably improve performance on ice and on snow.

In addition, the inner lug groove 42 has one or more bends 43 where the extension direction changes, so that the length can be secured and the groove area can be secured. This allows a lot of snow to enter the inner lug groove 42 when driving on a snowy road surface, and snow column shear force can be secured, so that snow traction can be improved and performance on snow can be improved. In addition, the inner lug groove 42 has one or more bends 43 whereby the length can be secured, so that the edge component of the inner lug groove 42 can be increased and the edge effect can be enhanced. This improves driving performance when driving on an icy road surface. As a result, it is possible to more reliably improve performance on ice and on snow.

In addition, the inclination of the inner lug groove 42 in the tire width direction relative to the tire circumferential direction is within the range of 55° to 75°, so that the running performance on icy road surfaces and snowy road surfaces can be effectively improved. In other words, if the inclination of the inner lug groove 42 in the tire width direction relative to the tire circumferential direction is less than 55°, the inclination of the inner lug groove 42 in the tire width direction is too small, so that it may be difficult to obtain the edge effect in the tire circumferential direction due to the edge component of the inner lug groove 42. In this case, it may be difficult to exert the edge effect due to the edge of the inner lug groove 42 during braking on an icy road surface, and it may be difficult to effectively ensure the braking performance. In addition, if the inclination of the inner lug groove 42 in the tire width direction relative to the tire circumferential direction is greater than 75°, the inclination of the inner lug groove 42 in the tire width direction is too large, so that it may be difficult to efficiently ensure the length of the inner lug groove 42. In this case, it may be difficult to efficiently increase the edge component of the inner lug groove 42, or to obtain snow column shear force in the inner lug groove 42, which may make it difficult to effectively improve driving performance on icy or snowy road surfaces.

In contrast, when the inclination of the inner lug groove 42 in the tire width direction relative to the tire circumferential direction is within the range of 55° to 75°, the edge component of the inner lug groove 42 can be efficiently increased, effectively ensuring snow column shear force, and more reliably exerting the edge effect in the tire circumferential direction due to the edge of the inner lug groove 42. This effectively improves driving performance on icy and snowy road surfaces. As a result, it is possible to more reliably improve performance on ice and on snow.

In addition, the inclination of the inner lug groove 42 in the tire width direction relative to the tire circumferential direction is greater than the inclination of the outer lug groove 44 in the tire width direction relative to the tire circumferential direction, so the edge effect in the tire circumferential direction due to the edge component of the inner lug groove 42 can be more reliably improved. This makes it possible to efficiently exert the edge effect in the tire circumferential direction when braking on an icy road surface at a position inside the vehicle mounting direction of the tire equatorial plane CL, where the ground load tends to be large during braking, and improves braking performance. As a result, it is possible to more reliably improve performance on ice.

In addition, the inclination of the inner sipe 61 in the tire width direction relative to the tire circumferential direction is within the range of 55° to 75°, so that the running performance on icy road surfaces can be effectively improved. In other words, if the inclination of the inner sipe 61 in the tire width direction relative to the tire circumferential direction is less than 55°, the inclination of the inner sipe 61 in the tire width direction is too small, so that it may be difficult to obtain the edge effect in the tire circumferential direction due to the edge component of the inner sipe 61. In this case, it may be difficult to exert the edge effect due to the edge of the inner sipe 61 during braking on an icy road surface, and it may be difficult to effectively ensure the braking performance. In addition, if the inclination of the inner sipe 61 in the tire width direction relative to the tire circumferential direction is greater than 75°, the inclination of the inner sipe 61 in the tire width direction is too large, so that it may be difficult to efficiently ensure the length of the inner sipe 61. In this case, it may be difficult to efficiently increase the edge components of the inner sipes 61, and it may be difficult to effectively improve driving performance on icy roads.

In contrast, when the inclination of the inner sipes 61 in the tire width direction relative to the tire circumferential direction is within the range of 55° to 75°, the edge component of the inner sipes 61 can be efficiently increased and the edge effect of the inner sipes 61 in the tire circumferential direction can be more reliably exerted. This makes it possible to effectively improve driving performance on icy road surfaces. As a result, it is possible to more reliably improve performance on ice.

In addition, the inclination of the inner sipes 61 in the tire width direction relative to the tire circumferential direction is greater than the inclination of the outer sipes 62 in the tire width direction relative to the tire circumferential direction, so the edge effect in the tire circumferential direction due to the edge components of the inner sipes 61 can be more reliably improved. This makes it possible to efficiently exert the edge effect in the tire circumferential direction when braking on an icy road surface at a position inside the vehicle mounting direction of the tire equatorial plane CL, where the ground load tends to be large during braking, and improves braking performance. As a result, performance on ice can be more reliably improved.

In addition, since the difference in the inclination of the inner lug groove 42 and the inner sipe 61 in the tire width direction relative to the tire circumferential direction is 20° or less, the direction in which the edge effect of the inner sipe 61 is exerted can be more reliably brought closer to the direction in which the edge effect of the inner lug groove 42 is exerted. This allows the inner sipe 61 and the inner lug groove 42 to exert the edge effect to the maximum in the inner second land portion 22a where the inner sipe 61 and the inner lug groove 42 are arranged. Therefore, the edge effect of the inner second land portion 22a, which is subjected to a large load when braking the vehicle by being located on the inside of the vehicle mounting direction relative to the tire equatorial plane CL, can be enhanced, and braking performance on icy road surfaces can be improved. As a result, performance on ice can be more reliably improved.

[Modification]
In the above embodiment, the inner lug groove 42 and the inner sipe 61, which have the same inclination direction in the tire circumferential direction relative to the tire width direction, are arranged in the inner second land portion 22a among the multiple land portions 20 arranged side by side in the tire width direction, but the land portion 20 in which the inner lug groove 42 and the inner sipe 61 are arranged may be a land portion 20 other than the inner second land portion 22a. The inner lug groove 42 and the inner sipe 61 may be arranged in any land portion 20 as long as the land portion 20 is located on the inner side in the vehicle mounting direction relative to the tire equatorial plane CL. Also, the inner lug groove 42 and the inner sipe 61 may be arranged in multiple land portions 20 that are different from each other in the tire width direction as long as the land portion 20 is located on the inner side in the vehicle mounting direction relative to the tire equatorial plane CL.

The outer lug groove 44 and the outer sipe 62, which have opposite inclination directions in the tire circumferential direction relative to the tire width direction, are arranged in the outer second land portion 22b among the multiple land portions 20 arranged side by side in the tire width direction, but the land portion 20 in which the outer lug groove 44 and the outer sipe 62 are arranged may be a land portion 20 other than the outer second land portion 22b. The outer lug groove 44 and the outer sipe 62 may be arranged in any land portion 20 located on the outer side of the tire equatorial plane CL in the vehicle mounting direction. The outer lug groove 44 and the outer sipe 62 may be arranged in multiple land portions 20 that are different from each other in the tire width direction, as long as the land portion 20 is located on the outer side of the tire equatorial plane CL in the vehicle mounting direction.

In the above embodiment, the inner lug groove 42 has two bent portions 43, but the number of bent portions 43 of one inner lug groove 42 may be more than two, and one inner lug groove 42 may have one or more bent portions 43. In the above embodiment, the bending directions of the two bent portions 43 of the inner lug groove 42 are the same as the bending direction in the groove width direction of the inner lug groove 42, but the bending directions of the multiple bent portions 43 of one inner lug groove 42 may be different from each other. Regardless of the number of bent portions 43 or the bending direction, the inner lug groove 42 has one or more bent portions 43, and thereby the groove area can be secured while suppressing a decrease in the rigidity of the land portion 20 in which the inner lug groove 42 is arranged.

In addition, in the above-described embodiment, the inner lug groove 42 opens into the circumferential groove 30 that defines the outer side of the land portion 20 in the tire width direction, among the circumferential grooves 30 that define both sides of the inner lug groove 42 in the tire width direction, but the circumferential groove 30 into which the inner lug groove 42 opens may be the circumferential groove 30 that defines the inner side of the land portion 20 in the tire width direction.

In the above embodiment, both ends of the circumferential narrow groove 50 in the length direction are open to the lug groove 40, but both ends of the circumferential narrow groove 50 do not have to be open to the lug groove 40, and it is sufficient that at least one end of the circumferential narrow groove 50 is open to the lug groove 40. In the above embodiment, the circumferential narrow groove 50 has two bent portions 51, but the number of bent portions 51 that the circumferential narrow groove 50 has may be other than two, and the number of bent portions 51 may be, for example, one.

In the above embodiment, the tread portion 2 has four circumferential grooves 30, but the number of circumferential grooves 30 may be other than four. The circumferential grooves 30 may have at least three grooves, and may partition the land portion 20 located on the inner side of the tire equatorial plane CL in the vehicle mounting direction from the land portion 20 located on the outer side of the tire equatorial plane CL in the vehicle mounting direction. The above embodiment and modified examples may be appropriately combined. In the above embodiment, the pneumatic tire 1 is used as an example of a tire according to the present invention, but the tire according to the present invention may be other than the pneumatic tire 1. The tire according to the present invention may be, for example, a so-called airless tire that can be used without filling with gas.

[Example]
6 is a table showing the results of a performance evaluation test of a pneumatic tire. Hereinafter, a performance evaluation test will be described for the above-mentioned pneumatic tire 1, a conventional pneumatic tire, the pneumatic tire 1 according to the present invention, and a comparative pneumatic tire compared to the pneumatic tire 1 according to the present invention. The performance evaluation tests were conducted on braking performance on an icy road surface, braking performance on a snowy road surface, and cornering performance on a snowy road surface.

The performance evaluation test was performed by mounting a pneumatic tire 1 with a tire nominal size of 195/65R15 91Q as specified by JATMA on a JATMA standard rim wheel with a rim size of 15 x 6.5J, mounting the test tire on a front-wheel drive evaluation vehicle with an engine displacement of 1800cc, adjusting the air pressure to 250 kPa for the front wheels and 240 kPa for the rear wheels, and running the evaluation vehicle.

Each test item was evaluated as follows: braking on ice was performed on an ice test course using an evaluation vehicle fitted with test tires, and the reciprocal of the braking distance was expressed as an index, with the conventional example (described below) being set at 100. For braking on ice, the higher the index, the shorter the braking distance on icy roads, indicating superior performance in terms of braking on ice.

For braking on snow, a vehicle fitted with the test tires was used to carry out braking tests on a test course on a snowy road surface, and the reciprocal of the braking distance was evaluated by expressing it as an index, with the conventional example (described below) being set at 100. For braking on snow, the higher the index, the shorter the braking distance on snowy road surfaces, indicating superior performance in terms of braking on snow.

In addition, turning on snow was evaluated by conducting turning tests on a test course on a snowy road surface with an evaluation vehicle fitted with the test tires, and expressing the reciprocal of the turning time during the turning run as an index with the conventional example described below being set at 100. For turning on snow, the higher the index, the higher the turning ability on snowy road surfaces, indicating superior performance in terms of turning on snow.

The performance evaluation test was carried out on nine types of pneumatic tires, including a conventional pneumatic tire, Examples 3, 6, and 7 which are pneumatic tire 1 according to the present invention, a comparative example which is a pneumatic tire compared with pneumatic tire 1 according to the present invention , and Reference Examples 1, 2, 4, and 5. Of these, in the conventional example, the inclination direction of the inner sipe relative to the inner lug groove and the inclination direction of the outer sipe relative to the outer lug groove are both the same. In addition, in the comparative example, the inclination direction of the inner sipe relative to the inner lug groove and the inclination direction of the outer sipe relative to the outer lug groove are both opposite.

In contrast, in Examples 3, 6, and 7, which are examples of the pneumatic tire 1 according to the present invention, the inclination directions of the inner sipes 61 relative to the inner lug groove 42 are all the same, and the inclination directions of the outer sipes 62 relative to the outer lug groove 44 are all opposite. Furthermore, the pneumatic tires 1 according to Examples 3, 6, and 7 and Reference Examples 1, 2, 4, and 5 are different from each other in the form of openings (open/non-opening) at both ends of the inner lug groove 42 relative to the circumferential groove 30, the presence or absence of bending of the inner lug groove 42, the form of openings (open/non-opening) at both ends of the outer lug groove 44 relative to the circumferential groove 30, and the presence or absence of a circumferential narrow groove 50 relative to the land portion 20 on which the outer sipes 62 are disposed, which is located on the outer side in the vehicle mounting direction.

As a result of carrying out a performance evaluation test using these pneumatic tires 1, it was found that the pneumatic tires 1 according to Examples 3 , 6, and 7 can improve the performance in all of braking on ice, braking on snow, and turning on snow compared to the conventional tire, as shown in Figure 6. In other words, the pneumatic tires 1 according to Examples 3, 6, and 7 can more reliably improve the performance on ice and on snow.

REFERENCE SIGNS LIST 1 pneumatic tire 2 tread portion 3 tread ground contact surface 8 sidewall portion 10 bead portion 13 carcass layer 14 belt layer 20 land portion 21 center land portion 22 second land portion 22a inner second land portion 22b outer second land portion 23 shoulder land portion 30 circumferential groove 31 inner circumferential groove 31a first inner circumferential groove 31b second inner circumferential groove 35 outer circumferential groove 40 lug groove 41 center lug groove 42 inner lug groove 42a first extension portion 42b second extension portion 42c third extension portion 42d terminal end portion 43, 51 bend portion 44 outer lug groove 45 shoulder lug groove 50 circumferential narrow groove 55 shoulder narrow groove 60 sipe 61 inner sipe 62 outer sipe 65 Interconnecting sipes

Claims (9)

At least three circumferential grooves extending in a tire circumferential direction;
A plurality of lug grooves extending in a tire width direction;
A plurality of land portions defined by the circumferential groove and the lug groove;
A plurality of sipes extending in the tire width direction and disposed in the land portion defined by the circumferential groove on both sides in the tire width direction;
Equipped with
The inner sipe, which is the sipe arranged in the land portion located on the inner side in the vehicle mounting direction with respect to the tire equatorial plane, has an inclination direction in the tire circumferential direction with respect to the tire width direction in the same direction as the inner lug groove, which is the lug groove that divides the land portion,
an outer sipe, which is a sipe arranged in the land portion located on the outer side of the tire equatorial plane in a vehicle mounting direction, has an inclination direction in the tire circumferential direction with respect to the tire width direction opposite to that of an outer lug groove, which is a lug groove that divides the land portion;
The inner lug groove has one end that opens into the circumferential groove and the other end that terminates within the land portion,
The tire is characterized in that both ends of the outer lug groove are open to the circumferential groove . The tire according to claim 1 , wherein a circumferential narrow groove extending in the tire circumferential direction is arranged in the land portion in which the outer sipes are arranged, the groove depth of which is shallower than the groove depth of the circumferential groove. The tire according to claim 2 , wherein the circumferential narrow groove has a groove width in the range of 1.5 mm to 4 mm, and a groove depth in the range of 30% to 80% of the groove depth of the circumferential groove. The tire according to any one of claims 1 to 3 , wherein the inner lug groove has one or more bends at which an extending direction of the inner lug groove changes. The tire according to any one of claims 1 to 4 , wherein the inner lug groove has an inclination in the tire width direction with respect to the tire circumferential direction within a range of 55° to 75°. The tire according to any one of claims 1 to 5 , wherein the inclination of the inner lug groove in the tire width direction with respect to the tire circumferential direction is greater than the inclination of the outer lug groove in the tire width direction with respect to the tire circumferential direction. The tire according to any one of claims 1 to 6 , wherein the inboard sipe has an inclination in the tire width direction with respect to the tire circumferential direction within a range of 55° to 75°. The tire according to any one of claims 1 to 7 , wherein an inclination of the inner sipe in the tire width direction with respect to the tire circumferential direction is greater than an inclination of the outer sipe in the tire width direction with respect to the tire circumferential direction. The tire according to any one of claims 1 to 8 , wherein a difference in inclination between the inner lug groove and the inner sipe in the tire width direction with respect to the tire circumferential direction is 20° or less.

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