JP6878946B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire.

Pneumatic tires have grooves formed on the tread surface mainly to ensure drainage, but the grooves on the tread surface cause noise when the vehicle is running. In addition, if the number of grooves is too large, the rigidity of the land portion may decrease and the steering stability may decrease. For this reason, some conventional pneumatic tires are designed to achieve both contradictory performances by devising the groove arrangement form.

For example, in the pneumatic tire described in Patent Document 1, the number of circumferential grooves arranged outside the vehicle from the tire equator line is larger than the number of circumferential grooves arranged inside the vehicle from the tire equator line. By making the total groove width of the circumferential groove arranged on the outside larger than the total groove width of the circumferential groove arranged inside the vehicle from the tire equator line, it is caused by the tread pattern while maintaining the wet performance. We are trying to improve the noise. Further, in the pneumatic tire described in Patent Document 2, three main grooves extending in the tire circumferential direction are provided, two narrow grooves are provided on both sides of the center main groove, and each of the two side main grooves is provided. By providing a narrow groove on the outside in the tire width direction and widening the width of the side main groove on the outside of the vehicle to the width of the side main groove on the inside of the vehicle, the steering stability performance is improved while maintaining drainage. ..

Japanese Patent No. 35027221 Japanese Patent No. 5482938

Here, since vehicles used in snowy areas other than snowy areas have few opportunities to travel on snowy roads, they travel on snowy roads by attaching tire chains to so-called summer tires without using studless tires during snowfall. Sometimes. When the tire chains are attached to the tires and the vehicle travels on a snowy road surface in this way, the tire chains are often attached only to the wheels that are the driving wheels, not to the wheels that are not the driving wheels. In this case, when traveling straight, it is possible to travel on a snowy road surface without any problem, but when turning on a snowy road surface, wheels to which tire chains are not attached may slip sideways.

That is, since the summer tire has a low grip force on the snowy road surface, when a lateral force, that is, a force in the tire width direction is applied between the tread surface and the road surface by turning, this tire width is applied. When the force in the direction exceeds the grip force between the tread surface and the road surface, slippage occurs between the tread surface and the road surface, and skidding may occur. For example, when the vehicle is a front-wheel drive vehicle, tire chains are often attached to the front wheels, which are the driving wheels, and tire chains are not attached to the rear wheels, which are not the driving wheels. In this case, the rear wheels may slip sideways when turning on a snowy road surface.

As a method for suppressing skidding when traveling on a snowy road surface, it is conceivable to arrange many circumferential grooves having a wide groove width to improve the snow removal action and edge effect of the grooves, but the circumference having a large groove width. When many directional grooves are arranged, the rigidity of the land portion decreases. In this case, the grip force between the tread surface and the snowy road surface is improved due to the snow removal action and the edge effect of the groove, but the rigidity of the land portion is lowered, and as a result, the steering stability may be lowered. is there. Therefore, it has been extremely difficult to effectively improve the steering stability on a snowy road surface.

The present invention has been made in view of the above, and an object of the present invention is to provide a pneumatic tire capable of improving steering stability on a snowy road surface.

In order to solve the above-mentioned problems and achieve the object, the pneumatic tire according to the present invention is a pneumatic tire whose mounting direction with respect to the vehicle is specified, is formed on the tread surface, and extends in the tire circumferential direction. It is provided with a main groove of one or more and four or more rows of land portions defined by the main groove, and the main groove is the innermost outermost main groove located on the innermost side of the main groove in the vehicle mounting direction. The groove width Win of the tire and the groove width Wout of the outermost outermost main groove located on the outermost side in the vehicle mounting direction have a relationship of Win <Wout, and the inner outermost main groove of the land portion is used. Circumferential fine grooves extending in the tire circumferential direction are formed in the two rows of adjacent land portions, which are grooves extending in the tire circumferential direction and include the main groove and the circumferential fine groove. The number is characterized in that there are more regions inside the vehicle mounting direction than the tire equatorial plane than in regions outside the vehicle mounting direction from the tire equatorial plane.

Further, in the pneumatic tire, the groove width Win of the inner outermost main groove is within the range of 4 mm or more and 8 mm or less, and the groove width Wout of the outer outermost main groove is within the range of 8 mm or more and 16 mm or less. It is preferable that the groove width Win of the inner outermost main groove and the groove width Wout of the outer outermost main groove have a relationship of (Wout / Win) ≧ 1.4.

Further, in the pneumatic tire, in the circumferential fine groove, the relationship between the distance Lsub between the circumferential fine groove and the innermost outermost main groove and the groove depth Hsub of the circumferential fine groove is Lsub>. It is preferably Hsub.

Further, in the pneumatic tire, in the circumferential fine groove, the groove depth Hsub of the circumferential fine groove is 50% or more and 100% of the groove depth of the main groove closest to the circumferential fine groove. It is preferably 3 mm or more.

Further, in the pneumatic tire, the inner shoulder land portion, which is the land portion located on the outer side in the tire width direction of the inner outermost main groove, and the outer side of the outer outermost main groove in the tire width direction. A plurality of lug grooves extending in the tire width direction are provided in each of the outer shoulder land portion, which is the land portion located in, and the lug groove provided in the inner shoulder land portion is provided in the outer shoulder land portion. It is preferable that the number of lug grooves is larger than that of the lug grooves.

The pneumatic tire according to the present invention has an effect that the steering stability on a snowy road surface can be improved.

FIG. 1 is a cross-sectional view of the meridian showing a main part of the pneumatic tire according to the embodiment. FIG. 2 is a plan view of the tread portion of the pneumatic tire shown in FIG. FIG. 3 is a view taken along the arrow AA of FIG. 2, which is a schematic view of the innermost outermost main groove and the circumferential narrow groove. FIG. 4 is a schematic view showing the action of the main groove and the circumferential narrow groove when turning on a snowy road surface. FIG. 5 is a chart showing the results of performance tests of pneumatic tires.

Hereinafter, embodiments of the pneumatic tire according to the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment. In addition, the components in the following embodiments include those that can be easily conceived by those skilled in the art, or those that are substantially the same.

In the following description, the tire radial direction means a direction orthogonal to the rotation axis of the pneumatic tire 1, 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. Refers to the side away from the axis of rotation. Further, the tire circumferential direction means a circumferential direction with the rotation axis as the central axis. The tire width direction means a direction parallel to the rotation axis, the inside in the tire width direction is the side toward the tire equatorial plane (tire equatorial line) CL in the tire width direction, and the outside in the tire width direction is in the tire width direction. The side away from the tire equatorial surface CL. The tire equatorial plane CL is a plane that is orthogonal to the rotation axis of the pneumatic tire 1 and passes through the center of the tire width of the pneumatic tire 1. The tire width is the width in the tire width direction between the portions located outside in the tire width direction, that is, the distance between the portions farthest from the tire equatorial plane CL in the tire width direction. The tire equatorial line is a line on the tire equatorial plane CL along the tire circumferential direction of the pneumatic tire 1. In the present embodiment, the tire equatorial line is designated by the same code "CL" as the tire equatorial plane.

FIG. 1 is a cross-sectional view of the meridian showing a main part of the pneumatic tire 1 according to the embodiment. Here, the pneumatic tire 1 shown in FIG. 1 is designated with respect to a vehicle, that is, a direction when the tire 1 is mounted on the vehicle. That is, in the pneumatic tire 1 shown in FIG. 1, the side facing the inside of the vehicle when mounted on the vehicle is the inside in the vehicle mounting direction, and the side facing the outside of the vehicle when mounted on the vehicle is the outside in the vehicle mounting direction. The designation of the inside in the vehicle mounting direction and the outside in the vehicle mounting direction is not limited to the case where the vehicle is mounted on the vehicle. For example, when the rim is assembled, the directions of the rim with respect to the inside and the outside of the vehicle are determined in the tire width direction. Therefore, when the rim is assembled, the pneumatic tire 1 is the inside and the vehicle in the vehicle mounting direction in the tire width direction. Mounting direction The orientation with respect to the outside is specified. Further, the pneumatic tire 1 has a mounting direction display unit (not shown) indicating a mounting direction with respect to the vehicle. The mounting direction display portion is composed of, for example, marks and irregularities attached to the sidewall portion 4 of the tire. For example, ECE R30 (Article 30 of the European Economic Commission for Europe) requires that a mounting direction display unit be provided on the sidewall portion 4 which is outside the vehicle mounting direction when the vehicle is mounted. Further, the pneumatic tire 1 according to the present embodiment is a pneumatic tire 1 mainly used for a passenger car.

The pneumatic tire 1 according to the present embodiment has a tread portion 2, shoulder portions 3 on both sides thereof, a sidewall portion 4 and a bead portion 5 which are sequentially continuous from each shoulder portion 3. Further, the pneumatic tire 1 includes a carcass layer 6, a belt layer 7, and a belt reinforcing layer 8.

The tread portion 2 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 outer peripheral surface thereof serves as the contour of the pneumatic tire 1. The outer peripheral surface of the tread portion 2 is a surface that can come into contact with the road surface mainly during traveling, and is configured as the tread surface 10.

The shoulder portion 3 is a portion on both outer sides of the tread portion 2 in the tire width direction. Further, the sidewall portion 4 is exposed to the outermost side in the tire width direction of the pneumatic tire 1. Further, the bead portion 5 has a bead core 51 and a bead filler 52. The bead core 51 is formed by winding a bead wire, which is a steel wire, in a ring shape. The bead filler 52 is a rubber material arranged in a space formed by folding back the end portion of the carcass layer 6 in the tire width direction at the position of the bead core 51.

In the carcass layer 6, each end portion in the tire width direction is folded back from the inside in the tire width direction to the outside in the tire width direction by a pair of bead cores 51, and is hung in a toroid shape in the tire circumferential direction to form a tire skeleton. It is a thing. The carcass layer 6 is formed by coating a plurality of carcass cords (not shown) arranged side by side with an angle in the tire circumferential direction while having an angle with respect to the tire circumferential direction along the tire meridian direction with a coated rubber. The carcass cord is made of, for example, organic fibers such as polyester, rayon and nylon. The carcass layer 6 is provided with at least one layer.

The belt layer 7 has a multi-layer structure in which at least two layers of belts 71 and 72 are laminated, and is arranged outside the outer circumference of the carcass layer 6 in the tire radial direction in the tread portion 2 to cover the carcass layer 6 in the tire circumferential direction. Is. The belts 71 and 72 are formed by coating a plurality of cords (not shown) arranged side by side at a predetermined angle (for example, 20 ° to 30 °) with respect to the tire circumferential direction with a coated rubber. The cord consists of, for example, steel or organic fibers such as polyester, rayon and nylon. Further, the overlapping belts 71 and 72 are arranged so that their cords intersect with each other.

The belt reinforcing layer 8 is arranged outside the outer circumference of the belt layer 7 in the tire radial direction and covers the belt layer 7 in the tire circumferential direction. The belt reinforcing layer 8 is formed by coating a plurality of cords (not shown) arranged side by side in the tire width direction substantially parallel to the tire circumferential direction with coated rubber. The cord is made of, for example, steel or an organic fiber such as polyester, rayon or nylon, and the angle of the cord is within ± 5 ° with respect to the tire circumferential direction. The belt reinforcing layer 8 shown in FIG. 1 is arranged so as to cover the end portion of the belt layer 7 in the tire width direction. The configuration of the belt reinforcing layer 8 is not limited to the above, and is not specified in the drawing, but has a configuration arranged so as to cover the entire belt layer 7, or has, for example, two reinforcing layers and is inside in the tire radial direction. The reinforcing layer is formed larger in the tire width direction than the belt layer 7 and is arranged so as to cover the entire belt layer 7, and the reinforcing layer on the outer side in the tire radial direction is arranged so as to cover only the end portion of the belt layer 7 in the tire width direction. Alternatively, for example, it may have two reinforcing layers, and each reinforcing layer may be arranged so as to cover only the end portion of the belt layer 7 in the tire width direction. That is, the belt reinforcing layer 8 overlaps at least the end portion of the belt layer 7 in the tire width direction. Further, the belt reinforcing layer 8 is provided by winding, for example, a strip-shaped strip material having a width of about 10 mm in the tire circumferential direction.

FIG. 2 is a plan view of the tread portion 2 of the pneumatic tire 1 shown in FIG. The tread surface 10 of the tread portion 2 is formed with three main grooves 31 extending along the tire circumferential direction arranged side by side in the tire width direction. The three main grooves 31 are an inner outermost main groove 33 located on the innermost side in the vehicle mounting direction, an outer outermost main groove 34 located on the outermost side in the vehicle mounting direction, and an inner outermost main groove 34 in the tire width direction. It has a center main groove 32 arranged between the groove 33 and the outermost outermost main groove 34. Of these, the center main groove 32 is located on the tire equatorial plane CL, the inner outermost main groove 33 is located inside the tire equatorial plane CL in the vehicle mounting direction, and the outer outermost main groove 34 is. It is located outside the vehicle mounting direction from the tire equatorial plane CL.

Further, the inner outermost main groove 33 and the outer outermost main groove 34 are both arranged inside in the tire width direction with respect to the ground contact end T which is both outermost ends in the tire width direction of the ground contact region. In FIG. 2, the ground contact end T is continuously shown in the tire circumferential direction. In the ground contact region, when the pneumatic tire 1 was rim-assembled on the specified rim, the specified internal pressure was applied, and 70% of the specified load was applied, the tread surface 10 of the tread portion 2 of the pneumatic tire 1 dried. This is the area that touches the flat road surface. The specified rim in this case is a "standard rim" specified by JATTA, a "Design Rim" specified by TRA, or a "Measuring Rim" specified by ETRTO. The specified internal pressure is the "maximum air pressure" specified by JATTA, the maximum value described in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or "INFLATION PRESSURES" specified by ETRTO. The specified load is the "maximum load capacity" specified by JATTA, the maximum value described in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "LOAD CAPACITY" specified by ETRTO.

The main grooves 31 formed on the tread surface 10 all have a groove width within a range of 4 mm or more and 16 mm or less, and a groove depth within a range of 6 mm or more and 15 mm or less. Further, in each main groove 31, the groove width Win of the inner outermost main groove 33 is within the range of 4 mm or more and 8 mm or less, and the groove width Wce of the center main groove 32 is within the range of 6 mm or more and 14 mm or less. The groove width Wout of the outer outermost main groove 34 is within the range of 8 mm or more and 16 mm or less.

Further, the inner outermost main groove 33 and the outer outermost main groove 34 have a relationship of Win <Wout between the groove width Win of the inner outermost main groove 33 and the groove width Wout of the outer outermost main groove 34. More specifically, the groove width Win of the inner outermost main groove 33 and the groove width Wout of the outer outermost main groove 34 have a relationship of (Wout / Win) ≥ 1.4. The groove width Win of the inner outermost main groove 33 and the groove width Wout of the outer outermost main groove 34 are preferably in the range of 1.6 ≦ (Wout / Win) ≦ 2.2.

Further, on the tread surface 10, four rows of land portions 20 are defined by three main grooves 31. The four rows of land portions 20 have an inner center land portion 21, an outer center land portion 22, an inner shoulder land portion 23, and an outer shoulder land portion 24. Of these, the inner center land portion 21 is located between the center main groove 32 and the inner outermost main groove 33, and both sides in the tire width direction are defined by the center main groove 32 and the inner outermost main groove 33. It is the land area 20. Further, the outer center land portion 22 is located between the center main groove 32 and the outer outermost main groove 34, and both sides in the tire width direction are defined by the center main groove 32 and the outer outermost main groove 34. It is the land part 20. Further, the inner shoulder land portion 23 is located on the outer side of the inner outermost main groove 33 in the tire width direction, and the inner side in the tire width direction is the land portion 20 defined by the inner outermost main groove 33. Further, the outer shoulder land portion 24 is located on the outer side of the outer outermost main groove 34 in the tire width direction, and the inner side in the tire width direction is the land portion 20 defined by the outer outermost main groove 34. All of these land portions 20 are formed as rib-shaped land portions 20 extending in the tire circumferential direction.

Further, of the four rows of land portions 20, the inner center land portion 21 and the inner shoulder land portion 23, which are two rows of land portions 20 adjacent to each other via the inner outermost main groove 33, extend in the tire circumferential direction. At the same time, circumferential fine grooves 36 are formed in which the groove width is narrower than the groove width of the main groove 31. That is, the inner center land portion 21 is formed with an inner circumferential fine groove 37 which is a circumferential fine groove 36 arranged inside the inner outermost main groove 33 in the tire width direction, and the inner shoulder land portion 23 is formed. Is formed with an outer circumferential fine groove 38 which is a circumferential fine groove 36 arranged on the outer side in the tire width direction of the inner outermost main groove 33.

Of these, the inner circumferential groove 37 is arranged near the center of the inner center land portion 21 in the tire width direction. Further, the outer circumferential narrow groove 38 is arranged at a position closer to the inner outermost main groove 33 than the central position in the tire width direction of the inner shoulder land portion 23, and is located closer to the ground contact end T inside the vehicle mounting direction. It is located inside in the tire width direction. The circumferential groove 36 has a groove width of 1.5 mm or more and 3 mm or less.

FIG. 3 is a view taken along the arrow AA of FIG. 2, which is a schematic view of the innermost outermost main groove 33 and the circumferential narrow groove 36. In both of the two circumferential fine grooves 36, the relationship between the distance Lsub between the circumferential fine groove 36 and the inner outermost main groove 33 and the groove depth Hsub of the circumferential fine groove 36 is Lsub> Hsub. .. That is, in the inner peripheral direction fine groove 37, the relationship between the distance Lsub between the inner peripheral direction fine groove 37 and the inner outermost main groove 33 and the groove depth Hsub of the inner peripheral direction fine groove 37 is Lsub> Hsub. In the outer circumferential fine groove 38, the relationship between the distance Lsub between the outer circumferential fine groove 38 and the inner outermost main groove 33 and the groove depth Hsub of the outer circumferential fine groove 38 is Lsub> Hsub. There is. In this case, the distance Lsub between the circumferential fine groove 36 and the inner outermost main groove 33 is the edge located on the inner outermost main groove 33 side of the edges of the opening of the circumferential fine groove 36 and the innermost outermost groove 36. It is the distance in the tire width direction from the edge of the opening of the outer main groove 33, which is located on the circumferential narrow groove 36 side.

Further, in the circumferential fine groove 36, the groove depth Hsub of the circumferential fine groove 36 is within a range of 50% or more and 100% or less of the groove depth Hg of the main groove 31 closest to the circumferential fine groove 36. Moreover, it is 3 mm or more. That is, since the main groove 31 having the shortest distance from the outer peripheral groove 38 is the inner outermost main groove 33, the outer peripheral groove 38 has a groove depth Hsub but a groove of the inner outermost main groove 33. The depth is within the range of 50% or more and 100% or less of Hg, and is 3 mm or more. Further, in the inner peripheral direction fine groove 37, when the main groove 31 closest to the inner peripheral direction fine groove 37 is the inner outermost main groove 33, the groove depth Hsub of the inner peripheral direction fine groove 37 is inside. The depth Hg of the outermost main groove 33 is within the range of 50% or more and 100% or less, and is 3 mm or more. When the main groove 31 closest to the inner circumferential narrow groove 37 is the center main groove 32, the groove depth Hsub of the inner circumferential narrow groove 37 is the groove depth Hg of the center main groove 32 (not shown). It is within the range of 50% or more and 100% or less of (omitted) and 3 mm or more.

The pneumatic tire 1 according to the present embodiment is a vehicle due to the tire equatorial surface CL on the tread surface 10 by forming the circumferential groove 36 in the inner center land portion 21 and the inner shoulder land portion 23 as described above. The number of circumferential grooves 30 is larger in the region inside the vehicle mounting direction than in the tire equatorial plane CL than in the region outside the mounting direction. The circumferential groove 30 in this case is a groove extending in the tire circumferential direction, and refers to a groove including a main groove 31 and a circumferential fine groove 36. That is, in the region outside the tire equatorial plane CL in the vehicle mounting direction, one outer outermost main groove 34 is arranged as the circumferential groove 30, whereas the region inside the tire equatorial plane CL in the vehicle mounting direction is provided. Is provided with a total of three circumferential grooves 30, one inner outermost main groove 33 and two circumferential narrow grooves 36. For this reason, the number of circumferential grooves 30 is larger in the region inside the vehicle mounting direction than in the tire equatorial plane CL than in the region outside the tire equatorial plane CL on the tread surface 10 in the vehicle mounting direction.

When the circumferential groove 30 is located on the tire equatorial plane CL, the circumferential groove 30 on the tire equatorial plane CL is also included in the circumferential groove 30 in the region outside the vehicle mounting direction in the region inside the vehicle mounting direction. It is not included in the circumferential groove 30. Therefore, when comparing the number of the circumferential grooves 30 in the region outside the vehicle mounting direction and the circumferential grooves 30 in the region inside the vehicle mounting direction, the center main groove 32 in the present embodiment is in which region. It is not included in the circumferential groove 30.

Further, the inner shoulder land portion 23 and the outer shoulder land portion 24 are each provided with a plurality of lug grooves 40 extending in the tire width direction. That is, the inner shoulder land portion 23 is provided with an inner shoulder lug groove 41 as a lug groove 40 extending in the tire width direction, and the outer shoulder land portion 24 is provided with an outer shoulder lug groove 42 as a lug groove 40 extending in the tire width direction. Is provided. Of these, the inner end of the inner shoulder lug groove 41 in the tire width direction is connected to the outer circumferential fine groove 38 formed in the inner shoulder land portion 23, and the outer end in the tire width direction is the tread portion 2. The tread surface 10 is opened at the design end E, which is the outer end in the tire width direction. Further, in the outer shoulder lug groove 42, the inner end in the tire width direction is terminated in the outer shoulder land portion 24, and the outer end in the tire width direction is opened at the design end E. The inner shoulder lug groove 41 and the outer shoulder lug groove 42 are inclined in the tire circumferential direction while extending in the tire width direction, respectively.

Here, the design end E is the outermost end in the tire width direction of the ground contact end T and is the outermost end in the tire width direction of the tread portion 2, and is the outermost end in the tire width direction in which a groove is formed in the tread portion 2. In FIG. 2, the design end E is continuously shown in the tire circumferential direction. That is, the tread portion 2 is a dry and flat road surface, and the region on the design end E side of the ground contact end T is a region that does not normally touch the road surface.

The number of the inner shoulder lug groove 41 and the outer shoulder lug groove 42 provided are different from each other, and the number of the inner shoulder lug groove 41 is larger than that of the outer shoulder lug groove 42. In other words, the number of pitches of the inner shoulder land portion 23 and the outer shoulder land portion 24 with the lug groove 40 as a boundary is larger in the inner shoulder land portion 23 than in the outer shoulder land portion 24. Regarding the number of pitches between the inner shoulder land portion 23 and the outer shoulder land portion 24, the number of pitches of the inner shoulder land portion 23 is 64 pitches or more, and the difference from the number of pitches of the outer shoulder land portion 24 is 8 pitches or more. Is preferable.

Further, the inner shoulder land portion 23 is provided with a recess 45 near the outer end (design end E) of the tread portion 2 in the tire width direction. The recess 45 is formed in a circular dimple shape, and a plurality of recesses 45 are formed between adjacent inner shoulder lug grooves 41. In the present embodiment, four recesses 45 are provided between adjacent inner shoulder lug grooves 41, and the four recesses 45 are arranged in two rows in the tire width direction and two rows in the tire circumferential direction. It is provided.

Further, a plurality of sipes 60 are formed on the land portion 20. Here, the sipe 60 is a notch formed in the tread surface 10, generally has a sipe width of less than 1.5 mm and a sipe depth of 4 mm or more, and is closed at the tire contact patch. The sipe width is measured as the maximum value of the opening width of the sipe 60 on the tread surface of the land portion 20 in a no-load state in which the pneumatic tire 1 is mounted on the specified rim and filled with the specified internal pressure. The tire contact patch is air when the pneumatic tire 1 is mounted on the specified rim to apply the specified internal pressure and is placed perpendicular to the flat plate in a stationary state and a load corresponding to the specified load is applied. It is defined as the contact surface between the tire 1 and the flat plate.

The sipe 60 includes an inner outermost main groove penetrating sipe 61, an outer outermost main groove penetrating sipe 62, a center sipe 63, an inner shoulder sipe 64, and an outer shoulder sipe 65. Of these, the inner outermost main groove penetrating sipe 61 is a sipe 60 formed so as to extend in the tire width direction while being inclined in the tire circumferential direction and straddling the inner outermost main groove 33. That is, the inner outermost main groove penetrating sipe 61 is located in the tire width direction of the inner circumferential groove 37 in the inner center land portion 21 from the position inside the outer peripheral groove 38 in the inner shoulder land portion 23 in the tire width direction. It is formed so as to penetrate the innermost outermost main groove 33 toward the outer position.

Further, the outer outermost main groove penetrating sipe 62 is a sipe 60 formed so as to extend in the tire width direction while being inclined in the tire circumferential direction and straddling the outer outermost main groove 34. Specifically, the outer outermost main groove penetrating sipe 62 is the outer outermost main groove from the position of the inner end portion in the tire width direction in the outer center land portion 22 to the position near the outer outermost main groove 34 in the outer shoulder land portion 24. It is formed through the main groove 34. In the outer outermost main groove penetrating sipe 62, the portions formed on the outer center land portion 22 are divided into the center main groove 32 and the outer outermost main groove 34, each of which defines the outer center land portion 22 at both ends. It is connected and bent in the tire circumferential direction in the outer center land portion 22. Further, one end of the portion formed in the outer shoulder land portion 24 of the outer outermost main groove penetrating sipe 62 is connected to the outer outermost main groove 34, and the other end is terminated in the outer shoulder land portion 24.

Further, the center sipe 63 is formed in a region between the inner circumferential narrow groove 37 and the center main groove 32 in the inner center land portion 21 while being inclined in the tire circumferential direction and extending in the tire width direction at one end. Is connected to the center main groove 32, and the other end is terminated in the inner center land portion 21. Further, the inner shoulder sipe 64 is formed in a region outside the inner circumferential groove 37 in the inner shoulder land portion 23 in the tire width direction while being inclined in the tire circumferential direction and extending in the tire width direction at both ends. It ends within the inner shoulder land portion 23. Further, the outer shoulder sipe 65 is formed on the outer shoulder land portion 24 so as to extend in the tire width direction while being inclined in the tire circumferential direction, and both ends thereof are terminated in the outer shoulder land portion 24.

When the pneumatic tire 1 configured as described above is mounted on the vehicle and traveled, the pneumatic tire 1 rotates while the portion of the tread surface 10 located on the lower side and facing the road surface is in contact with the road surface. To do. When traveling on a dry road surface with a vehicle equipped with the pneumatic tire 1, the driving force and braking force are transmitted to the road surface and a turning force is generated mainly by the frictional force between the tread surface 10 and the road surface. It runs by letting it run. Further, when traveling on a wet road surface, water between the tread surface 10 and the road surface enters the main groove 31, the lug groove 40, etc., and the water between the tread surface 10 and the road surface is drained through these grooves. Run while running. This makes it easier for the tread surface 10 to come into contact with the road surface, and the frictional force between the tread surface 10 and the road surface allows the vehicle to travel.

Further, when traveling on a snowy road surface, the pneumatic tire 1 compacts the snow on the road surface with the tread surface 10, and the snow on the road surface enters the main groove 31 and the lug groove 40, so that these snows are also grooved. It will be in a state of being compacted inside. In this state, a driving force or a braking force acts on the pneumatic tire 1, or a force acts in the tire width direction due to the turning of the vehicle, so that the shearing force acts on the snow in the groove. , So-called snow column shear force is generated, and resistance is generated between the pneumatic tire 1 and the road surface due to the snow column shear force, so that the driving force and braking force can be transmitted to the snow road surface, and the vehicle is on the snow. It is possible to drive on the road surface.

Further, when traveling on a snowy road surface, the edge effect of the main groove 31, the lug groove 40, and the sipe 60 is also used. That is, when traveling on a snowy road surface, the edge of the main groove 31 and the lug groove 40 and the edge of the sipe 60 are caught on the snow surface, and the resistance is also used. As a result, the tread surface 10 has a large resistance to the snowy road surface due to the frictional force and the edge effect, and the running performance of the vehicle equipped with the pneumatic tire 1 can be ensured.

Further, in the pneumatic tire 1 according to the present embodiment, the groove width Win of the inner outermost main groove 33 and the groove width Wout of the outer outermost main groove 34 have a Win <Wout relationship, and the innermost outermost groove 33. The groove width Wout of the outer outermost main groove 34 is larger than the groove width Win of the outer main groove 33. As a result, when turning on a snowy road surface, the snow accumulated on the road surface can be removed by the outer outermost main groove 34.

That is, when the vehicle is turning, a force acting toward the outside in the turning direction acts on the vehicle due to the centrifugal force. Therefore, when the vehicle is turning, the wheels located inside in the turning radius direction are located outside in the turning radius direction. A larger load acts on the located wheels. Therefore, in order to ensure steering stability when the vehicle is turning, the grip force between the wheels located outside in the turning radius direction and the road surface is made so that skidding is unlikely to occur even if a large load is applied. Becomes important.

Explaining the relationship between the pneumatic tire 1 used for the wheels located outside in the turning radial direction and the road surface, the pneumatic tire 1 is located between the pneumatic tire 1 and the road surface in the turning radial direction with respect to the road surface. A force acting in the outward direction acts. That is, a force acts in the direction outward in the vehicle mounting direction between the pneumatic tire 1 used for the wheel located outside in the turning radial direction and the road surface, and the vehicle is applied to the pneumatic tire 1 from the road surface. Wearing direction A force acts inward.

Further, on a snowy road surface, uncompacted snow is often piled up on top of compacted snow as a vehicle travels. For this reason, when turning on a snowy road surface, the road surface on which uncompacted snow is piled up with respect to the pneumatic tire 1 used for the wheels located outside in the turning radial direction, which is important when turning. , The vehicle travels while moving relative to the inside from the outside in the vehicle mounting direction. At that time, in the pneumatic tire 1 according to the present embodiment, the groove width Wout of the outer outermost main groove 34 is larger than the groove width Win of the inner outermost main groove 33. Therefore, in the pneumatic tire 1 according to the present embodiment, more snow accumulated on the road surface without being compacted can be allowed to enter the outer outermost main groove 34, and the outer outermost main groove 34 allows more snow to enter. , This snow can be eliminated.

FIG. 4 is a schematic view showing the actions of the main groove 31 and the circumferential narrow groove 36 when turning on a snowy road surface. FIG. 4 is shown in a state where the tread surface 10 faces the lower side on the drawing and faces the road surface 100 in order to explain the action of the main groove 31 and the circumferential fine groove 36 formed on the tread surface 10. It is a partial sectional view. When the vehicle turns on the road surface 100 on which the snow 105 is piled up, the road surface 100 moves relative to the tread surface 10 of the pneumatic tire 1 used for the wheels on the outer side in the turning direction in the inward direction in the vehicle mounting direction. Therefore, the snow 105 on the road surface 100 easily enters the outer outermost main groove 34 located on the tread surface 10 on the outer side in the vehicle mounting direction.

The snow 105 that has entered the outer outermost main groove 34 is compressed by the load acting on the vicinity of the outer outermost main groove 34. As a result, a snow column shearing force is generated between the snow 105 on the road surface 100 and the inside of the outermost main groove 34, and resistance in the tire width direction can be generated between the pneumatic tire 1 and the road surface 100. it can. At that time, since the groove width Wout of the outer outermost main groove 34 is larger than the groove width Win of the inner outermost main groove 33, a large amount of snow 105 enters the outer outermost main groove 34. As a result, the outer outermost main groove 34 can generate a larger snow column shearing force, and can generate a large resistance in the tire width direction between the pneumatic tire 1 and the road surface 100.

Further, when the snow 105 that has entered the outermost main groove 34 moves to a position other than the ground contact region on the circumference of the tread surface 10 due to the rotation of the pneumatic tire 1, the centrifugal force of the pneumatic tire 1 It is discharged from the outermost main groove 34 due to the above. Specifically, the snow 105 that has entered the outer outermost main groove 34 moves from the outer outermost main groove 34 to the rear in the traveling direction of the vehicle with the rotation of the pneumatic tire 1. It is discharged. As a result, the snow 105 on the road surface 100 is discharged from the ground contact area of the tread surface 10 to the outside of the ground contact area by the outer outermost main groove 34. At that time, since the groove width Wout of the outer outermost main groove 34 is larger than the groove width Win of the inner outermost main groove 33, a large amount of snow 105 can be discharged from the road surface 100.

When the vehicle turns, the road surface 100 from which a large amount of uncompressed snow 105 has been removed further moves inward in the vehicle mounting direction. Since the inner outermost main groove 33 and the two circumferential narrow grooves 36 are arranged inside the outer outermost main groove 34 in the vehicle mounting direction, the road surface 100 from which a large amount of snow 105 has been removed can be seen. When the vehicle is relatively moved inward in the vehicle mounting direction, the inner outermost main groove 33 and the circumferential fine groove 36 can exert an edge effect. That is, the edge effect of the main groove 31 and the circumferential narrow groove 36 on the snow surface can be more effective in the compressed snow 105 than in the uncompressed snow 105. Therefore, a large amount of uncompressed snow 105 is discharged by the outer outermost main groove 34, and the road surface 100 on which the compressed snow surface is exposed faces the inner outermost main groove 33 and the circumferential narrow groove 36. In this case, the innermost outermost main groove 33 and the circumferential fine groove 36 can exert a large edge effect on the road surface 100. As a result, the pneumatic tire 1 can generate a large resistance in the tire width direction with the road surface 100 due to the edge effect of the inner outermost main groove 33 and the circumferential narrow groove 36.

At that time, the inner outermost main groove 33 and the two circumferential fine grooves 36 are provided in a form in which two circumferential fine grooves 36 are arranged on both sides of the inner outermost main groove 33 in the tire width direction. ing. Therefore, while the snow 105 exerts an edge effect on the road surface 100 in which the snow is compressed, the snow 105 that has not been removed by the outer outermost main groove 34 can be removed by the inner outermost main groove 33, or the innermost. The outer main groove 33 can generate a snow column shearing force. As a result, it is possible to remove the snow 105 that has not been compressed even in the area inside the tire equatorial plane CL in the vehicle mounting direction, effectively exert the edge effect, and generate the snow column shearing force. , A large resistance in the tire width direction can be generated between the pneumatic tire 1 and the road surface 100.

Further, in the region of the tread surface 10 inside the vehicle mounting direction from the tire equatorial plane CL, more circumferential grooves 30 are formed than in the region outside the vehicle mounting direction from the tire equatorial plane CL, so that the vehicle mounting direction It is possible to secure the rigidity of the land portion 20 in the region outside the vehicle mounting direction while exerting a large edge effect in the inner region. As a result, steering stability can be ensured regardless of the road surface conditions such as a dry road surface and a snowy road surface.

Further, in the region inside the vehicle mounting direction from the tire equatorial plane CL, the groove width Win of the inner outermost main groove 33 is made smaller than the groove width Wout of the outer outermost main groove 34, and the tire of the inner outermost main groove 33 By arranging the two circumferential fine grooves 36 on both sides in the width direction, it is possible to prevent the width of the land portion 20 in the tire width direction from becoming too small as the number of the circumferential grooves 30 increases. .. As a result, the rigidity of the land portion 20 can be ensured as much as possible even in the region inside the vehicle mounting direction, and the steering stability can be ensured more reliably regardless of the road surface condition. In other words, by effectively arranging the circumferential grooves 30, it is possible to secure the performance on snow with a smaller number of grooves than before, so that the deterioration of the land portion 20 can be suppressed, regardless of the road surface condition. Steering stability can be ensured. As a result, due to the large resistance in the tire width direction generated between the pneumatic tire 1 and the road surface 100, skidding can be suppressed and the steering stability on a snowy road surface can be improved.

In addition, since it is possible to suppress a decrease in the rigidity of the land portion 20 and secure steering stability regardless of the road surface condition, it is necessary to secure steering stability on a dry road surface, which is often used for so-called summer tires. Can be done. Further, when increasing the number of the circumferential grooves 30 located in the region inside the vehicle mounting direction with respect to the tire equatorial plane CL, the circumferential groove 30 is not composed of only the circumferential fine grooves 36, but is the outermost inside. Since the main groove 33 is also used, the drainage property when traveling on a wet road surface can be ensured by the inner outermost main groove 33. As a result, it is possible to improve the steering stability on a snowy road surface without deteriorating the steering stability on a dry road surface or a wet road surface.

Further, since the inner outermost main groove 33, the outer outermost main groove 34, and the circumferential narrow groove 36 can ensure steering stability on a snowy road surface, when traveling on a snowy road surface with a vehicle equipped with summer tires, Even when the tire chains are attached only to the drive wheels, it is possible to suppress skidding of the wheels without the tire chains. For example, when the vehicle is a front-wheel drive vehicle, it is possible to suppress skidding of the rear wheels even if the tire chains are attached only to the front wheels that are the driving wheels and the tire chains are not attached to the rear wheels that are not the driving wheels. it can. As a result, the steering stability can be improved even when the pneumatic tire 1 is a summer tire and the vehicle has wheels to which tire chains are not attached and travels on a snowy road surface.

Further, since the groove width Win of the innermost outermost main groove 33 is within the range of 4 mm or more and 8 mm or less, the snow column shearing force is exerted at the time of touchdown or the snow is compressed without significantly reducing the rigidity of the land portion 20. It is possible to remove snow that has not been removed. Further, since the groove width Wout of the outer outermost main groove 34 is within the range of 8 mm or more and 16 mm or less, more snow is discharged by the outer outermost main groove 34 without significantly reducing the rigidity of the land portion 20. It snows, and the edge effect can be ensured in the inner outermost main groove 33 and the circumferential fine groove 36. Further, since the groove width Win of the inner outermost main groove 33 and the groove width Wout of the outer outermost main groove 34 have a relationship of (Wout / Win) ≥ 1.4, the inner outermost main groove 33 and the circumferential direction Snow removal for effectively exerting the edge effect in the narrow groove 36 can be performed more reliably by the outer outermost main groove 34. As a result, the steering stability on the snowy road surface can be improved more reliably.

Further, when the groove width Win of the inner outermost main groove 33 and the groove width Wout of the outer outermost main groove 34 are within the range of 1.6 ≦ (Wout / Win) ≦ 2.2, the tire equator The rigidity of the land portion 20 can be ensured in a well-balanced manner on the outside in the vehicle mounting direction and the inside in the vehicle mounting direction from the surface CL. That is, when the groove width Win of the inner outermost main groove 33 and the groove width Wout of the outer outermost main groove 34 are (Wout / Win) <1.6, the groove width Win of the inner outermost main groove 33 Since the groove width Wout of the outermost main groove 34 is too narrow, the rigidity of the land portion 20 located outside the tire equatorial plane CL in the vehicle mounting direction is higher than that of the land located inside the vehicle mounting direction CL. It may be too large for the rigidity of the portion 20. In this case, the land portion 20 located inside the vehicle mounting direction from the tire equatorial plane CL is likely to wear with respect to the land portion 20 located outside the vehicle mounting direction from the tire equatorial plane CL, and uneven wear may occur. There is. When the groove width Win of the inner outermost main groove 33 and the groove width Wout of the outer outermost main groove 34 are (Wout / Win)> 2.2, the groove width Win of the inner outermost main groove 33 Since the groove width Wout of the outer outermost main groove 34 is too wide, the width of the land portion 20 adjacent to the outer outermost main groove 34 in the tire width direction becomes narrower, and the rigidity of the land portion 20 is low. It can be too much. In this case, it may be difficult to effectively improve the steering stability.

On the other hand, when the groove width Win of the inner outermost main groove 33 and the groove width Wout of the outer outermost main groove 34 are within the range of 1.6 ≦ (Wout / Win) ≦ 2.2, the outer side The groove width Wout of the outermost main groove 34 can be widened within an appropriate range with respect to the groove width Win of the inner outermost main groove 33. As a result, the rigidity of the land portion 20 located outside the vehicle mounting direction from the tire equatorial plane CL can be ensured in a well-balanced manner within an appropriate range with respect to the rigidity of the land portion 20 located inside the vehicle mounting direction. As a result, the steering stability on the snowy road surface can be improved more reliably.

Further, since the relationship between the distance Lsub between the circumferential fine groove 36 and the inner outermost main groove 33 and the groove depth Hsub of the circumferential fine groove 36 is Lsub> Hsub, the circumferential fine groove 36 is provided. It is possible to suppress a decrease in the rigidity of the land portion 20 due to the above. That is, when the relationship between the distance Lsub between the circumferential fine groove 36 and the inner outermost main groove 33 and the groove depth Hsub of the circumferential fine groove 36 is Lsub ≦ Hsub, the inner outermost part in the land portion 20. The width of the portion partitioned by the main groove 33 and the circumferential narrow groove 36 in the tire width direction may be too narrow, and the rigidity of this portion may become too low. In this case, due to the fact that the rigidity of the land portion 20 becomes too low, it becomes difficult to improve the steering stability when the vehicle turns, and the portion of the land portion 20 having low rigidity tends to be worn. As a result, uneven wear may easily occur.

On the other hand, when the relationship between the distance Lsub between the circumferential fine groove 36 and the innermost outermost main groove 33 and the groove depth Hsub of the circumferential fine groove 36 is Lsub> Hsub, the inside in the land portion 20. The width of the portion partitioned by the outermost main groove 33 and the circumferential narrow groove 36 in the tire width direction can be secured, and the rigidity of this portion can be secured. As a result, even when the circumferential fine grooves 36 are provided on both sides of the inner outermost main groove 33 in the tire width direction, it is possible to suppress a decrease in the rigidity of the land portion 20 due to the provision of the circumferential fine grooves 36. Therefore, it is possible to suppress that it becomes difficult to improve the steering stability and that uneven wear is likely to occur. As a result, it is possible to more reliably improve the steering stability on a snowy road surface without causing uneven wear.

Further, in the circumferential fine groove 36, the groove depth Hsub of the circumferential fine groove 36 is 50% or more and 100% or less of the groove depth of the main groove 31 closest to the circumferential fine groove 36, and 3 mm. As described above, the edge effect due to the provision of the circumferential groove 36 can be more reliably exhibited. That is, when the groove depth Hsub of the circumferential fine groove 36 is less than 50% or less than 3 mm of the groove depth of the main groove 31, the groove depth Hsub of the circumferential fine groove 36 is shallow. Therefore, even if the circumferential fine groove 36 is provided, the portion of the land portion 20 partitioned by the circumferential fine groove 36 may not easily fall down when the vehicle turns, and the edge effect may not be exhibited easily.

Here, the edge effect due to the formation of the groove on the tread surface 10 will be described. When the groove is formed on the tread surface 10, when a force in the groove width direction acts on the land portion 20 partitioned by the groove, Due to this force, the land portion 20 collapses slightly in the groove width direction. When the land portion 20 collapses, the ground contact range of the collapsed land portion 20 becomes smaller, so that the ground contact pressure of the grounded portion of the land portion 20 becomes higher. That is, when the land portion 20 collapses, the ground contact pressure becomes locally high, so that a large force can be applied to the snow due to this high pressure, and a large edge effect can be exhibited. If the groove depth Hsub of the circumferential narrow groove 36 is too shallow, the portion of the land portion 20 partitioned by the circumferential fine groove 36 is unlikely to fall down when the vehicle turns, so that the ground contact pressure is large against the snowy road surface. It becomes difficult to do so, and it may be difficult to exert the edge effect.

On the other hand, when the groove depth Hsub of the circumferential fine groove 36 is 50% or more and 100% or less and 3 mm or more of the groove depth of the main groove 31 closest to the circumferential fine groove 36. , The portion of the land portion 20 partitioned by the circumferential groove 36 can be easily collapsed when the vehicle turns. As a result, the ground contact pressure of the land portion 20 with respect to the road surface 100 can be locally increased, and the edge effect due to the provision of the circumferential groove 36 can be more reliably exhibited by the high ground pressure. As a result, the steering stability on the snowy road surface can be improved more reliably.

Further, since the number of the inner shoulder lug grooves 41 is larger than that of the outer shoulder lug grooves 42, the edge effect of the land portion 20 located inside the tire equatorial plane CL in the vehicle mounting direction can be improved. As a result, traction performance and braking performance on a snowy road surface can be ensured, and snow performance can be improved. Further, since the number of the outer shoulder lug grooves 42 is smaller than that of the inner shoulder lug grooves 41, the rigidity of the outer shoulder land portion 24 can be ensured. As a result, a large load is likely to be applied when the vehicle turns, and the rigidity of the outer shoulder land portion 24, which is important for ensuring the rigidity, can be secured, so that the steering stability can be improved more reliably. As a result, the steering stability on the snowy road surface can be improved more reliably.

In the pneumatic tire 1 according to the above-described embodiment, three main grooves 31 are formed and four rows of land portions 20 are provided, but the number of main grooves 31 and land portions 20 is other than this. It may be provided in. That is, three or more main grooves 31 may be formed, and four or more rows may be provided for the land portion 20. It is preferable that the number of the main groove 31 and the land portion 20 is appropriately set based on the desired performance and the like.

Further, in the pneumatic tire 1 according to the above-described embodiment, the inner circumferential groove 37 is arranged near the center of the inner center land portion 21 in the tire width direction, but the inner circumferential groove 37 is inside. It may be arranged at a position other than the vicinity of the center of the center land portion 21. The inner peripheral groove 37 may be arranged at a position closer to the inner outermost main groove 33 than the center in the tire width direction of the inner center land portion 21, for example. When the inner peripheral groove 37 is arranged at a position closer to the inner outermost main groove 33, the inner center land portion 21 is outside the vehicle mounting direction than the inner part of the inner outermost main groove 33 in the vehicle mounting direction. Since the rigidity of this portion is higher, the steering stability when the vehicle is turning can be improved more reliably.

Further, in the pneumatic tire 1 according to the above-described embodiment, the distance Lsub between the inner peripheral groove 37 and the inner outermost main groove 33 and the distance Lsub between the outer peripheral groove 38 and the inner outermost main groove 33 are Lsub. Although the relative relationship with is not particularly specified, the relative relationship of these distances Lsub may be specified. For example, the distance Lsub between the inner peripheral groove 37 and the inner outermost main groove 33 may be larger than the distance Lsub between the outer peripheral groove 38 and the inner outermost main groove 33. When the distance Lsub between the inner peripheral groove 37 and the inner outermost main groove 33 is larger than the distance Lsub between the outer peripheral groove 38 and the inner outermost main groove 33, the outer side of the inner shoulder land portion 23 The rigidity of the portion between the inner peripheral groove 37 and the inner outermost main groove 33 in the inner center land portion 21 is larger than the rigidity of the portion between the circumferential groove 38 and the inner outermost main groove 33. Therefore, the steering stability when the vehicle is turning can be improved more reliably.

Further, in the pneumatic tire 1 according to the above-described embodiment, the main groove 31 and the circumferential fine groove 36 all extend along the tire circumferential direction, but the main groove 31 and the circumferential fine groove 36 are strictly. It does not have to extend along the tire circumferential direction. The main groove 31 and the circumferential narrow groove 36 may be formed in a zigzag shape or a wavy shape that oscillates in the tire width direction while extending in the tire circumferential direction.

Further, in the pneumatic tire 1 according to the above-described embodiment, the land portion 20 is all formed in a rib shape, but the land portion 20 is provided with a lug groove 40 between adjacent main grooves 31. , The land portion 20 may be formed in a so-called block shape in which the land portion 20 is divided in the tire circumferential direction.

〔Example〕
FIG. 5 is a chart showing the results of performance tests of pneumatic tires. Hereinafter, the performance evaluation test of the above-mentioned pneumatic tire 1 with respect to the pneumatic tires of the conventional example and the comparative example and the pneumatic tire 1 according to the present invention will be described. In the performance evaluation test, a test was conducted on the feeling on snow, which is the feeling when driving on a snowy road surface.

In the performance evaluation test, the tire nominal of 185 / 65R15 size specified by JATTA is assembled to the rim wheel of the JATMA standard rim, the air pressure is adjusted to the maximum air pressure specified by JATTA, and the exhaust is exhausted. The test run was carried out by mounting it on a test vehicle with a front wheel drive (front engine / front drive) having an amount of 1200 cc. The evaluation method of feeling on snow, which is a test item, is an index in which a test driver performs a sensory evaluation when a test vehicle runs on a test course made on snow, and the evaluation result is set to 100 in the conventional example described later. expressed. The larger the value of the index, the higher the steering stability on the snowy road surface, and the better the feeling on the snow.

The evaluation test compares the conventional pneumatic tire, which is an example of the conventional pneumatic tire 1, the pneumatic tires 1 according to the present invention, Examples 3 and 4, and the pneumatic tire 1 according to the present invention. Seven types of pneumatic tires, Comparative Examples 1 and 2 and Reference Examples 1 and 2, which are pneumatic tires, were used. Among these pneumatic tires 1, in the conventional pneumatic tire, the groove width Wout of the outer outermost main groove 34 and the groove width Win of the inner outermost main groove 33 are the same size, and the tire equator. The number of circumferential grooves 30 is the same in the region outside the vehicle mounting direction and the region inside the vehicle mounting direction from the surface CL, and the land portion 20 is not provided with the circumferential narrow grooves 36.

Further, in the pneumatic tire of Comparative Example 1, the number of circumferential grooves 30 is larger in the region inside the vehicle mounting direction than in the region outside the vehicle mounting direction than the tire equatorial plane CL, but the outermost tire is inside. The groove width Win of the main groove 33 is larger than the groove width Wout of the outermost outermost main groove 34, and the circumferential narrow grooves 36 are arranged on the shoulder (Sh) land portions on both sides in the tire width direction. Further, in the pneumatic tire of Comparative Example 2, although the circumferential groove 36 is arranged in the inner shoulder (Sh) land portion 23 and the inner center (Ce) land portion 21, the tire is mounted on the vehicle from the equatorial plane CL. The number of circumferential grooves 30 is larger in the region outside the vehicle mounting direction than in the region inside the direction.

On the other hand, in Examples 3 and 4, which are examples of the pneumatic tire 1 according to the present invention, the groove width Wout of the outer outermost main groove 34 is larger than the groove width Win of the inner outermost main groove 33. The number of circumferential grooves 30 is larger in the area inside the vehicle mounting direction than in the area outside the vehicle mounting direction than the tire equatorial plane CL, and the circumferential groove 36 is on the inner shoulder (Sh) land. It is arranged in the portion 23 and the inner center (Ce) land portion 21. Further, in the pneumatic tires 1 according to Examples 3 and 4 and Reference Examples 1 and 2, the ratio of the groove width Wout of the outer outermost main groove 34 to the groove width Win of the inner outermost main groove 33 and the circumferential direction The relative relationship between the distance between the narrow groove 36 and the inner outermost main groove 33 and the groove depth Hsub of the circumferential fine groove 36, the number of pitches of the inner shoulder land portion 23 and the number of pitches of the outer shoulder land portion 24. The relative relationship with each is different.

As a result of conducting an evaluation test using these pneumatic tires 1, as shown in FIG. 5, the pneumatic tires 1 according to Examples 3 and 4 are charged on snow as compared with the conventional examples and Comparative Examples 1 and 2. It turns out that the ring improves. That is, the pneumatic tire 1 according to the third and fourth embodiments can improve the steering stability on a snowy road surface.

1 Pneumatic tire 2 Tread part 3 Shoulder part 4 Side wall part 5 Bead part 6 Carcus layer 7 Belt layer 8 Belt reinforcement layer 10 Tread surface 20 Land part 21 Inner center land part 22 Outer center land part 23 Inner shoulder land part 24 Outside Shoulder land 30 Circumferential groove 31 Main groove 32 Center main groove 33 Inner outermost main groove 34 Outer outermost main groove 36 Circumferential narrow groove 37 Inner circumferential narrow groove 38 Outer circumferential narrow groove 40 Rug groove 41 Inner shoulder lug Groove 42 Outer shoulder lug groove 45 Recess 60 Sipe

Claims (4)

Pneumatic tires with a specified mounting direction for the vehicle
Three or more main grooves formed on the tread surface and extending in the tire circumferential direction,
With four or more rows of land defined by the main groove,
With
The main groove has a groove width Win of the innermost outermost main groove located on the innermost side in the vehicle mounting direction and a groove width Wout of the outermost outermost main groove located on the outermost side in the vehicle mounting direction. , Win <Wout,
Of the land portions, two rows of land portions adjacent to each other via the inner outermost main groove are formed with circumferential fine grooves extending in the tire circumferential direction.
In the circumferential fine groove, the relationship between the distance Lsub between the circumferential fine groove and the innermost outermost main groove and the groove depth Hsub of the circumferential fine groove is Lsub> Hsub.
It is a groove extending in the tire circumferential direction, and the number of circumferential grooves including the main groove and the circumferential narrow groove is inside the vehicle mounting direction from the tire equatorial plane rather than the region outside the vehicle mounting direction from the tire equatorial plane. Pneumatic tires characterized by more areas. The groove width Win of the innermost outermost main groove is within the range of 4 mm or more and 8 mm or less.
The groove width Wout of the outer outermost main groove is within the range of 8 mm or more and 16 mm or less.
The pneumatic tire according to claim 1, wherein the groove width Win of the inner outermost main groove and the groove width Wout of the outer outermost main groove have a relationship of (Wout / Win) ≥ 1.4. In the circumferential fine groove, the groove depth Hsub of the circumferential fine groove is 50% or more and 100% or less of the groove depth of the main groove closest to the circumferential fine groove, and 3 mm or more. The pneumatic tire according to claim 1 or 2. Of the land portions, the inner shoulder land portion, which is the land portion located outside the inner outermost main groove in the tire width direction, and the land portion located outside the outer outermost main groove in the tire width direction. A plurality of lug grooves extending in the tire width direction are provided on the outer shoulder land portion.
The pneumatic tire according to any one of claims 1 to 3 , wherein the lug groove provided on the inner shoulder land portion has a larger number than the lug groove provided on the outer shoulder land portion.

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