JP7102983B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire.

In order to improve the steering stability on a dry road surface, it is conceivable to set a wide land width of the tread portion with the aim of ensuring the tread rigidity. However, in this case, the ground contact pressure at the center of the width direction of the land portion decreases, the ground contact length of the land portion in the tire circumferential direction becomes shorter in the ground contact region, and the end portion of the ground contact length becomes recessed inward to improve the ground contact property. Get worse. Therefore, the steering stability performance on a dry road surface may deteriorate. In addition, the decrease in the ground contact pressure at the center of the land portion in the width direction may reduce the drainage performance and the steering stability performance on a wet road surface.

Conventionally, for example, in Patent Documents 1 to 3, the steering stability performance on a dry road surface and the steering stability performance on a wet road surface are improved by configuring the land contact patch so as to project in the center in the width direction. Is shown.

Japanese Unexamined Patent Publication No. 2013-189121 Japanese Unexamined Patent Publication No. 2016-002890 Japanese Unexamined Patent Publication No. 2014-118123

However, in recent years, as the performance of vehicles has been improved, it has been desired to further improve the steering stability performance on dry road surfaces and the steering stability performance on wet road surfaces.

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 performance on a dry road surface and steering stability performance on a wet road surface.

In order to solve the above-mentioned problems and achieve the object, the pneumatic tire according to one aspect of the present invention has five tires in the tire width direction due to four tire circumferential grooves extending in the tire circumferential direction on the ground contact surface of the tread portion. By forming the land portion of the tire, the center land portion on the equatorial plane of the tire, the first middle land portion on the first side in the tire width direction in the mounting direction of the center land portion with respect to the vehicle, and the first middle land portion. The first side shoulder land part on the first side of the side middle land part, the second side middle land part on the second side opposite to the first side of the center land part in the tire width direction, and the second side. The second side shoulder land portion on the second side of the middle land portion is provided, and the circumferential groove between the first side middle land portion and the first side shoulder land portion is the other three. A pneumatic tire formed as a circumferential groove whose groove width is narrower than that of the book's circumferential groove, and the land width Wcc of the center land portion and the land width Wco of the first side middle land portion are It satisfies the relationship of Wco <Wcc, and the ground contact surface of the first side middle land portion and the first side shoulder land portion is formed so as to project outward in the tire radial direction with respect to the reference profile straddling the circumferential narrow groove. The ground contact surface of the center land portion is formed so as to project outward in the tire radial direction with respect to the reference profile, and the ground contact surface of the second side middle land portion is formed so as to project outward in the tire radial direction with respect to the reference profile. The protrusion amount Hcc of the center land portion and the protrusion amount Hci of the second side middle land portion are Hcc <Hso, with respect to the protrusion amount Hso of the first side middle land portion and the first side shoulder land portion. Satisfy the relationship of Hci <Hso.

Further, in the pneumatic tire according to one aspect of the present invention, it is preferable that the protrusion amount Hcc of the center land portion is in the range of 0.2 mm ≦ Hcc ≦ 0.4 mm.

Further, in the pneumatic tire according to one aspect of the present invention, it is preferable that the protrusion amount Hso of the first side middle land portion and the first side shoulder land portion is in the range of 0.3 mm ≦ Hso ≦ 0.6 mm. ..

Further, in the pneumatic tire according to one aspect of the present invention, the protrusion amount Hcc of the center land portion and the protrusion amount Hso of the first side middle land portion and the first side shoulder land portion are 1.2 ≦ Hso /. It is preferable to satisfy the relationship of Hcc ≦ 2.0.

Further, in the pneumatic tire according to one aspect of the present invention, the relationship between the protrusion amount Hcc of the center land portion and the protrusion amount Hci of the second side middle land portion is 0.9 ≦ Hcc / Hci ≦ 1.1. It is preferable to meet.

Further, in the pneumatic tire according to one aspect of the present invention, one end communicates with one of the circumferential grooves in the tire width direction at the time of contact patch on the ground contact surface of the center land portion, and the other end ends at the center land portion. There is a groove, and on the ground contact surface of the first side middle land portion, there is a groove in which one end communicates with the circumferential narrow groove on the outer side in the tire width direction and the other end ends at the first side middle land portion. However, it is preferable that there is a groove on the ground contact surface of the second side middle land portion, one end communicating with the circumferential groove on the outer side in the tire width direction and the other end ending at the second side middle land portion. ..

Further, in the pneumatic tire according to one aspect of the present invention, with respect to the land width Wcc of the center land portion, the land width Wco of the first side middle land portion and the land portion of the first side shoulder land portion. The width Wso, the land width Wci of the second side middle land portion, and the land width Wsi of the second side shoulder land portion are 0.7 ≦ Wco / Wcc ≦ 0.9, 1.0 ≦ Wso / It is preferable to satisfy the relationships of Wcc ≦ 1.2, 0.7 ≦ Wci / Wcc ≦ 0.9, and 0.9 ≦ Wsi / Wcc ≦ 1.1.

Further, in the pneumatic tire according to one aspect of the present invention, the contact patch of the land portion of the second shoulder is formed so as to project outward in the tire radial direction with respect to the reference profile, and the land portion of the first shoulder is formed. It is preferable that the protrusion amount Hso and the protrusion amount Hsi of the second shoulder land portion satisfy the relationship of 0.9 ≦ Hso / Hsi ≦ 1.1.

Further, in the pneumatic tire according to one aspect of the present invention, the mounting direction with respect to the vehicle is specified, the outside of the vehicle is the first side in the tire width direction, and the inside of the vehicle is the second side in the tire width direction. Is preferable.

According to the present invention, the contact patch of the first side middle land portion and the first side shoulder land portion is formed so as to project outward in the tire radial direction from the reference profile, and the center land portion and the second side middle land portion are in contact with each other. The ground is also formed so as to protrude outward in the tire radial direction from the reference profile, so that the contact patch length, center land portion, and center land portion of the central portion in the tire width direction including the first side middle land portion and the first side shoulder land portion are formed. It is possible to secure the contact patch length of each tire width direction center portion of the two-side middle land portion. Therefore, it is possible to improve the steering stability performance on a dry road surface. In particular, since a circumferential fine groove is provided between the first side middle land portion and the first side shoulder land portion, the ground contact length can be secured at this circumferential fine groove portion. Therefore, it is possible to improve the steering stability performance on a dry road surface. In addition, the ground contact surfaces of the first side middle land portion and the first side shoulder land portion are formed so as to project outward from the reference profile in the tire radial direction, and the ground contact surfaces of the center land portion and the second side middle land portion are also formed, respectively. Since it is formed so as to protrude outward in the tire radial direction from the reference profile, the contact patch of the central part in the tire width direction including the first side middle land part and the first side shoulder land part, the center land part and the second side middle land part. It is possible to increase the ground contact pressure at the center of each part in the tire width direction. For this reason, the water removal action is improved from the central portion in the tire width direction including the first side middle land portion and the first side shoulder land portion to both sides in the tire width direction, and the center land portion and the second side middle land portion are respectively. The water removal action is improved toward both sides in the tire width direction of the central portion in the tire width direction, and the steering stability performance on a wet road surface can be improved. Moreover, according to the present invention, the protrusion amount Hcc of the center land portion and the protrusion amount Hci of the second side middle land portion are Hcc with respect to the protrusion amount Hso of the first side middle land portion and the first side shoulder land portion. The amount of protrusion Hso of the first side middle land part and the first side shoulder land part on the outer side in the tire width direction, which satisfies the relationship of <Hso and Hci <Hso and the ground contact length is reduced in the ground contact region as compared with others, is the tire. By making it larger than the protrusion amount Hcc of the center land part adjacent to the inside in the width direction and the protrusion amount Hci of the second side middle land part, the first side middle land part and the first side shoulder land part and their tire width inside It is possible to suppress a sudden decrease in the ground contact length, improve the ground contact property, and contribute to the improvement of the steering stability performance on a dry road surface and the steering stability performance on a wet road surface. As a result, it is possible to improve the steering stability performance on a dry road surface and the steering stability performance on a wet road surface. Moreover, according to the present invention, the land width Wcc of the center land portion and the land width Wco of the first side middle land portion satisfy the relationship of Wco <Wcc, so that the first side middle land portion and the first side Balance the outward protrusion of the tire radial direction across the circumferential groove of the shoulder land part and the outward protrusion of the center land part in the tire radial direction, and the first side middle land part and the first side shoulder land part. , It is possible to balance the contact length and contact pressure with the center land area. Therefore, the effect of improving the steering stability performance on a dry road surface and the effect of improving the steering stability performance on a wet road surface can be remarkably obtained.

FIG. 1 is a meridional cross-sectional view of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a plan view of a tread portion of a pneumatic tire according to an embodiment of the present invention. FIG. 3 is a detailed view of the tread portion of FIG. FIG. 4 is a chart showing the results of a performance evaluation test of a pneumatic tire according to an embodiment of the present invention.

Hereinafter, embodiments of 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 of this embodiment include those that can be easily replaced by those skilled in the art, or those that are substantially the same. Further, the plurality of modifications described in this embodiment can be arbitrarily combined within a range self-evident by those skilled in the art.

FIG. 1 is a meridional cross-sectional view of a pneumatic tire according to the present embodiment. FIG. 2 is a plan view of the tread portion of the pneumatic tire according to the present embodiment. FIG. 3 is a detailed view of the tread portion of FIG.

In the following description, the tire radial direction means a direction orthogonal to the rotation axis (not shown) of the pneumatic tire 1, and the tire radial inside means the side toward the rotation axis in the tire radial direction and the tire radial outside. Refers to the side away from the rotation axis in the tire radial direction. 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 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, and the tire equatorial plane CL is the center of the pneumatic tire 1 in the tire width direction. The position in the tire width direction coincides with the center line in the tire width direction. The tire equatorial line refers to a line on the tire equatorial plane CL and along the tire circumferential direction of the pneumatic tire 1, and in the present embodiment, the same code "CL" as the tire equatorial plane is attached.

As shown in FIG. 1, the pneumatic tire 1 of the present embodiment has a tread portion 2, shoulder portions 3 on both sides thereof, a sidewall portion 4 and a bead portion 5 sequentially continuous from each shoulder portion 3. ing. 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 a ground contact 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 15 and a bead filler 16. The bead core 15 is formed by winding a bead wire, which is a steel wire, in a ring shape. The bead filler 16 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 15.

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 15 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 7a and 7b are laminated, is arranged on the outer periphery of the carcass layer 6 in the tire radial direction in the tread portion 2, and covers the carcass layer 6 in the tire circumferential direction. Is. The belts 7a and 7b 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 7a and 7b 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 entire belt layer 7. 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 only the end portion of the belt layer 7 in the tire width direction, or has, for example, two reinforcing layers. , The reinforcing layer on the inner side in the tire radial direction 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 the end portion in the tire width direction of the belt layer 7. Even if it is arranged so as to cover only the tires, or for example, it has two reinforcing layers and each reinforcing layer is arranged so as to cover only the end portion of the belt layer 7 in the tire width direction. good. 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.

The internal structure of the pneumatic tire 1 described above shows a typical example of the pneumatic tire 1, but the internal structure is not limited to this.

The pneumatic tire 1 of the present embodiment has a designated mounting direction with respect to the vehicle. That is, when the pneumatic tire 1 of the present embodiment is mounted on a vehicle, the orientation with respect to the outside and the inside of the vehicle is specified in the tire width direction. Although the orientation is not specified in the figure, it is indicated by, for example, an index provided in the sidewall portion 4. Therefore, when mounted on a vehicle, the side facing the outside of the vehicle is the outside of the vehicle (first side), and the side facing the inside of the vehicle is the inside of the vehicle (second side). The designation of the outside of the vehicle and the inside of the vehicle is not limited to the case where the vehicle is mounted on the vehicle. For example, when the rim is assembled, the orientation of the rim with respect to the outside and the inside of the vehicle is determined in the tire width direction. Therefore, when the pneumatic tire 1 is rim-assembled, the orientation with respect to the outside of the vehicle and the inside of the vehicle is specified in the tire width direction.

The ground contact surface 10 of the tread portion 2 is formed with four circumferential grooves 20 extending in the tire circumferential direction and continuous over the entire circumference of the tire side by side in the tire width direction.

The circumferential groove 20 has a groove width of 3.0 mm or more and a groove depth of 6.0 mm or more except for the circumferential groove 20 arranged on the outermost side of the vehicle, and is obliged to display the wear indicator specified in JATTA. It is a groove to have. The circumferential groove 20 arranged on the outermost side of the vehicle is formed as a circumferential groove having a narrower groove width than the other circumferential grooves 20. The groove width of the circumferential fine groove is narrower than the groove width of the other circumferential grooves 20, and is in the range of 1.5 mm or more and 4.0 mm. The groove depth of the circumferential narrow groove is the same as that of the other circumferential grooves 20.

The groove width, sipe width, and land width described below are opened in the ground plane 10 in a no-load state (specified load = 0) in which the pneumatic tire 1 is mounted on the specified rim and filled with the specified internal pressure. It is measured as the maximum value of the dimensions of the open ends of both grooves in the tire width direction. In a configuration in which a notch or chamfer is formed on the groove opening edge, the groove width is measured including the notch or chamfer with the groove opening end as the outer edge of the notch or chamfer. The groove depth and sipe depth are measured as the maximum values of the dimensions from the ground contact surface 10 to the groove bottom in a no-load state (specified load = 0) in which the pneumatic tire 1 is mounted on the specified rim and filled with the specified internal pressure. Will be done.

The specified rim 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.

Two circumferential grooves 20 are arranged on the outer side in the tire width direction with the tire equatorial plane CL as a boundary. On the outside of the vehicle, the circumferential groove 20 near the tire equatorial plane CL is called the outer center groove 21, and the circumferential groove (circumferential narrow groove) 20 outside the tire width direction of the outer center groove 21 is referred to as the outer shoulder groove 23. Call. On the inside of the vehicle, the circumferential groove 20 near the tire equatorial surface CL is called the inner center groove 22, and the circumferential groove 20 on the outer side of the inner center groove 22 in the tire width direction is called the inner shoulder groove 24.

In the present embodiment, the circumferential groove 20 is formed in a zigzag shape in which the outer center groove 21 is bent along the tire circumferential direction at regular intervals on both sides in the tire width direction. The other inner center groove 22, the outer shoulder groove 23, and the inner shoulder groove 24 are formed linearly in the tire circumferential direction. The outer center groove 21 has a triangular chamfered portion having a long portion and a short portion on the ground contact surface 10 formed side by side in the tire circumferential direction at the groove opening end, and the length of the chamfered portion at both groove opening ends. The long and short parts are arranged point-symmetrically to form a zigzag shape.

Further, on the ground contact surface 10 of the tread portion 2, five land portions 30 arranged in the tire width direction are formed by four circumferential grooves 20 (21, 22, 23, 24). The land portion 30 on the tire equatorial plane CL formed between the outer center groove 21 and the inner center groove 22 is referred to as a center land portion 31. On the outside of the vehicle (first side), the land portion 30 formed between the outer center groove 21 and the outer shoulder groove 23 is called the outer middle land portion (first side middle land portion) 32, and the outer shoulder groove 23 The land portion 30 formed on the outer side in the tire width direction is referred to as an outer shoulder land portion (first shoulder land portion) 34. On the inside of the vehicle (second side), the land portion 30 formed between the inner center groove 22 and the inner shoulder groove 24 is called the inner middle land portion (second side middle land portion) 33, and the inner shoulder groove 24 The land portion 30 formed on the outer side in the tire width direction is referred to as an inner shoulder land portion (second shoulder land portion) 35. The outer shoulder groove 23 and the inner shoulder groove 24 are located on the ground contact end T, respectively.

The ground contact end T is both outermost ends in the tire width direction of the ground contact region, and in FIG. 2, the ground contact end T is continuously shown in the tire circumferential direction. In the ground contact area, 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 ground contact surface 10 of the tread portion 2 of the pneumatic tire 1 dried. This is the area that touches the flat road surface.

In the center land portion 31, only the lug groove 51 is formed on the ground contact surface 10. One end of the lug groove 51 communicates with the inner center groove 22 and extends to the CL side of the tire equatorial plane (inside in the tire width direction), and the other end is the tire of the center land portion 31 in the ground contact surface 10 of the center land portion 31. It is provided at the end of the tire equatorial plane CL near the center in the width direction. A plurality of lug grooves 51 are arranged at intervals in the tire circumferential direction. The lug groove 51 has a groove width in the range of 1.5 mm or more and 4.5 mm or less, and a groove depth in the range of 55% or more and 80% or less of the groove depth of the inner center groove 22. The lug groove 51 secures a water removing action as compared with a configuration in which a groove is not formed in the center land portion 31, and contributes to improvement of steering stability performance on a wet road surface. Further, since the lug groove 51 is provided in the ground contact surface 10 of the center land portion 31 at the other end so as not to reach the tire equatorial plane CL, the rigidity of the center land portion 31 is ensured and the road surface is dry. Contributes to the steering stability performance of. Further, the lug groove 51 has an inclination angle with respect to the tire circumferential direction within a range of 110 deg or more and 130 deg or less. The lug groove 51 contributes to suppressing the occurrence of chipping wear by ensuring an inclination angle of 110 deg or more, and contributes to improving steering stability performance on a wet road surface by ensuring 130 deg or less due to the edge effect.

The lug groove 51 preferably has a relationship of 0.30 ≦ L1 / Wcc ≦ 0.60 between the dimension L1 in the tire width direction and the land width Wcc of the center land portion 31. The land width Wcc of the center land portion 31 is a dimension in the tire width direction of the ground contact surface 10 excluding the chamfered portion in the circumferential groove 20, and is also referred to as a ground contact width that can actually touch the road surface. Hereinafter, the definition of the land width of other land areas is the same. The lug groove 51 secures the water removing action by 0.30 ≦ L1 / Wcc and contributes to the improvement of steering stability performance on a wet road surface, and the rigidity of the center land portion 31 by L1 / Wcc ≦ 0.60. Contributes to steering stability performance on dry roads.

The outer middle land portion 32 is formed with only the lug groove 52 and the sipe 41 on the ground contact surface 10.

One end of the lug groove 52 communicates with the outer shoulder groove 23 and extends inward in the tire width direction, and the other end is terminated in the ground contact surface 10 of the outer middle land portion 32. The lug groove 52 is formed so as to extend mainly in the tire width direction in a long shape, and a bent portion is provided at the other end so as to extend mainly in the tire circumferential direction in a short shape. A plurality of lug grooves 52 are arranged at intervals in the tire circumferential direction. The lug groove 52 has a groove width in the range of 1.5 mm or more and 4.5 mm or less, and a groove depth in the range of 55% or more and 80% or less of the groove depth of the outer shoulder groove 23.

The lug groove 52 preferably has a relationship of 0.65 ≦ L2 / Wco ≦ 0.85 between the dimension L2 in the tire width direction and the land width Wco of the outer middle land portion 32. The lug groove 52 secures a water removing action by 0.65 ≦ L2 / Wco and contributes to the improvement of steering stability performance on a wet road surface, and by L2 / Wco ≦ 0.85, the outer middle land portion 32 It secures rigidity and contributes to steering stability performance on dry road surfaces. In particular, since the lug groove 52 is arranged at the outer edge portion in the tire width direction (ground contact end T side) where the contribution of water removal action is high in the outer middle land portion 32, the steering stability performance on a wet road surface is improved. Contribution is high.

The sipe 41 is singly arranged between the end portions of the lug grooves 52 adjacent to each other in the tire circumferential direction, and extends mainly in the tire circumferential direction. The sipe 41 does not communicate with the lug groove 52 and the circumferential groove 20, and is provided so that both ends thereof are terminated within the ground contact surface 10 of the outer middle land portion 32. The sipe 41 has a sipe width in the range of 0.3 mm or more and 1.5 mm or less, and a sipe depth in the range of 3.0 mm or more and 7.0 mm or less. The sipe 41 is closed when the ground contact surface 10 touches the ground. As described above, the sipe 41 is arranged between the lug groove 52 having the dimension L2 in the tire width direction and the end portion of the lug groove 52, so that the arrangement relationship between the lug groove 52 and the circumferential groove 20 is optimized. Therefore, the rigidity of the outer middle land portion 32 is made uniform, which contributes to steering stability performance on a dry road surface.

The inner middle land portion 33 is formed with only the lug groove 53 and the sipe 42 on the ground contact surface 10.

One end of the lug groove 53 communicates with the inner shoulder groove 24 and extends inward in the tire width direction, and the other end is terminated in the ground contact surface 10 of the inner middle land portion 33. The lug groove 53 is formed so as to extend in a long shape mainly in the tire width direction. A plurality of lug grooves 53 are arranged at intervals in the tire circumferential direction. A plurality of lug grooves 53 are arranged at intervals in the tire circumferential direction. The lug groove 52 has a groove width in the range of 1.5 mm or more and 4.5 mm or less, and a groove depth in the range of 55% or more and 80% or less of the groove depth of the outer shoulder groove 23.

The lug groove 53 preferably has a relationship of 0.50 ≦ L3 / Wci ≦ 0.80 between the dimension L3 in the tire width direction and the land width Wci of the inner middle land portion 33. The lug groove 52 secures the water removing action by 0.50 ≦ L3 / Wci and contributes to the improvement of the steering stability performance on the wet road surface, and the inner middle land portion 33 by L3 / Wci ≦ 0.80. It secures rigidity and contributes to steering stability performance on dry road surfaces.

The sipe 42 is provided so that one end communicates with the inner center groove 22 and extends outward in the tire width direction, and the other end ends in the ground contact surface 10 of the inner middle land portion 33. A plurality of sipes 42 are arranged at intervals in the tire circumferential direction. The sipe 42 has a sipe width in the range of 0.6 mm or more and 1.8 mm or less, and a sipe depth in the range of 3.0 mm or more and 7.0 mm or less. The sipe 42 is closed when the ground contact surface 10 touches the ground. The sipes 42 are alternately arranged with respect to the lug grooves 53 in the tire circumferential direction. As a result, as compared with the configuration in which only the lug groove or only the sipe is arranged in the tire circumferential direction, the water removal action is ensured, which contributes to the improvement of the steering stability performance on a wet road surface, and the inner middle land portion 33. It contributes to the improvement of steering stability performance on dry road surface by ensuring the rigidity balance of. In particular, the lug groove 53 is arranged at the outer edge portion in the tire width direction (ground contact end T side) where the contribution of water removal action is high in the inner middle land portion 33, and the sipe 42 contributes to the improvement of rigidity in the inner middle land portion 33. By arranging the tire on the inner edge in the high tire width direction (CL side of the tire equatorial plane), it is possible to effectively enhance the mutual balance between the steering stability performance on a wet road surface and the steering stability performance on a dry road surface.

The sipe 42 preferably has a relationship of 0.20 ≦ L4 / Wci ≦ 0.25 between the dimension L4 in the tire width direction and the land width Wci of the inner middle land portion 33. The sipe 42 secures the water removal action by 0.20 ≦ L4 / Wci and contributes to the improvement of the steering stability performance on the wet road surface, and the rigidity of the inner middle land portion 33 by L4 / Wci ≦ 0.25. Contributes to steering stability performance on dry roads.

The sipe 42 and the lug groove 53 are arranged so as not to overlap each other when viewed in the tire circumferential direction. Specifically, the dimension D1 in the tire width direction between the end of the sipe 42 and the end of the lug groove 53 is 0.05 ≦ D1 / Wci ≦ 0.20 with respect to the land width Wci of the inner middle land 33. It is preferably in the range. As a result, the rigidity of the inner middle land portion 33 is ensured as compared with the configuration in which the two overlap each other when viewed in the tire circumferential direction, which contributes to the improvement of steering stability performance on a dry road surface.

Further, the sipe 42 of the inner middle land portion 33 and the lug groove 51 of the center land portion 31 are inclined in the same direction with respect to the tire circumferential direction. Further, the sipe 42 and the lug groove 51 extend along a mutual extension line, and one ends communicating with the inner center groove 22 are provided so as to face each other with the inner center groove 22 in between. As a result, the sipe 42 and the lug groove 51 secure the water removing action and contribute to the improvement of the steering stability performance on the wet road surface.

The outer shoulder land portion 34 is formed with only the lug grooves 54 and 55 on the ground contact surface 10.

The lug groove 54 intersects the ground contact end T from the outside in the tire width direction and extends inward in the tire width direction, and the extending end extends within the ground contact surface 10 of the outer shoulder land portion 34 without communicating with the outer shoulder groove 23. It is provided at the end. A plurality of lug grooves 54 are arranged at intervals in the tire circumferential direction. The lug groove 54 has a groove width in the range of 1.5 mm or more and 4.5 mm or less, and a groove depth in the range of 55% or more and 80% or less of the groove depth of the outer shoulder groove 23.

The lug groove 54 preferably has a relationship of 0.50 ≦ L5 / Wso ≦ 0.90 between the dimension L5 inside in the tire width direction from the ground contact end T and the land width Wso of the outer shoulder land portion 34. The lug groove 54 secures a water removing action by 0.50 ≦ L5 / Wso and contributes to improvement of steering stability performance on a wet road surface, and L5 / Wso ≦ 0.90 of the outer shoulder land portion 34. It secures rigidity and contributes to steering stability performance on dry road surfaces. The land width Wso of the outer shoulder land portion 34 is a dimension in the tire width direction between the outer edge portion of the outer shoulder groove 23 in the tire width direction and the ground contact end T on the outer side of the vehicle.

The lug groove 55 is provided so that one end communicates with the outer shoulder groove 23 and extends outward in the tire width direction, and the other end ends in the ground contact surface 10 of the outer shoulder land portion 34 without intersecting the ground contact end T. Has been done. A plurality of lug grooves 55 are arranged at intervals in the tire circumferential direction. The lug groove 55 has a groove width in the range of 1.5 mm or more and 4.5 mm or less, and a groove depth in the range of 55% or more and 80% or less of the groove depth of the inner shoulder groove 24. The lug grooves 55 are alternately arranged with respect to the lug grooves 54 in the tire circumferential direction. As a result, as compared with the configuration in which only one of the lug grooves is arranged in the tire circumferential direction, the water removal action is ensured, which contributes to the improvement of steering stability performance on a wet road surface, and the outer shoulder land portion. It secures the rigidity balance of 34 and contributes to the improvement of steering stability performance on a dry road surface.

The lug groove 55 preferably has a relationship of 0.35 ≦ L6 / Wso ≦ 0.55 between the dimension L6 in the tire width direction and the land width Wso of the outer shoulder land portion 34. The lug groove 55 secures a water removing action by 0.35 ≦ L6 / Wso and contributes to improvement of steering stability performance on a wet road surface, and L6 / Wso ≦ 0.55 of the outer shoulder land portion 34. It secures rigidity and contributes to steering stability performance on dry road surfaces.

The lug grooves 54 and 55 are arranged so as to overlap each other when viewed in the tire circumferential direction. Specifically, the dimension D2 in the tire width direction between the ends of the lug grooves 54 and 55 that overlap each other is 0.10 ≦ D2 / Wso ≦ 0.30 with respect to the land width Wso of the outer shoulder land portion 34. It is preferably in the range. As a result, the water removing action is ensured as compared with the configuration in which the two do not overlap each other when viewed in the tire circumferential direction, which contributes to the improvement of the steering stability performance on a wet road surface.

The inner shoulder land portion 35 is formed only with the lug groove 56 and the sipe 43.

The lug groove 56 intersects the ground contact end T from the outside in the tire width direction and extends inward in the tire width direction, and the extending end extends within the ground contact surface 10 of the inner shoulder land portion 35 without communicating with the inner shoulder groove 24. It is provided at the end. A plurality of lug grooves 56 are arranged at intervals in the tire circumferential direction. The lug groove 56 has a groove width in the range of 1.5 mm or more and 4.5 mm or less, and a groove depth in the range of 55% or more and 80% or less of the groove depth of the inner shoulder groove 24.

The lug groove 56 preferably has a relationship of 0.70 ≦ L7 / Wsi ≦ 0.90 between the dimension L7 inside the tire width direction from the ground contact end T and the land width Wsi of the inner shoulder land portion 35. The lug groove 56 secures a water removing action by 0.70 ≦ L7 / Wsi and contributes to the improvement of steering stability performance on a wet road surface, and the inner shoulder land portion 35 by L7 / Wsi ≦ 0.90. It secures rigidity and contributes to steering stability performance on dry road surfaces. The land width Wsi of the inner shoulder land portion 35 is a dimension in the tire width direction between the outer edge portion of the inner shoulder groove 24 in the tire width direction and the ground contact end T inside the vehicle.

The sipe 43 is provided so that one end communicates with the inner shoulder groove 24 and extends outward in the tire width direction, and the other end is terminated in the ground contact surface 10 of the inner shoulder land portion 35 without intersecting the ground contact end T. ing. A plurality of sipes 43 are arranged at intervals in the tire circumferential direction. The sipe 43 has a sipe width in the range of 0.6 mm or more and 1.8 mm or less, and a sipe depth in the range of 3.0 mm or more and 7.0 mm or less. The sipe 43 is closed when the ground contact surface 10 touches the ground. The sipes 43 are alternately arranged with respect to the lug grooves 56 in the tire circumferential direction. As a result, as compared with the configuration in which only the lug groove or only the sipe is arranged in the tire circumferential direction, the water removal action is ensured, which contributes to the improvement of the steering stability performance on a wet road surface, and the inner shoulder land portion 35. It secures the rigidity balance of the tire and contributes to the improvement of steering stability performance on dry road surface.

The sipe 43 preferably has a relationship of 0.40 ≦ L8 / Wsi ≦ 0.60 between the dimension L8 in the tire width direction and the land width Wsi of the inner shoulder land portion 35. The sipe 43 secures the water removal action by 0.40 ≦ L8 / Wsi and contributes to the improvement of the steering stability performance on the wet road surface, and the rigidity of the inner shoulder land portion 35 by L8 / Wsi ≦ 0.60. Contributes to steering stability performance on dry roads.

The sipe 43 and the lug groove 56 are arranged so as to overlap each other when viewed in the tire circumferential direction. Specifically, the dimension D3 in the tire width direction at the end of the mutually overlapping sipes 43 and the lug groove 56 is 0.20 ≦ D3 / Wsi ≦ 0.40 with respect to the land width Wsi of the outer shoulder land portion 34. It is preferable that it is in the range of. As a result, the water removing action is ensured as compared with the configuration in which the two do not overlap each other when viewed in the tire circumferential direction, which contributes to the improvement of the steering stability performance on a wet road surface.

In the pneumatic tire 1 of the present embodiment described above, the land width Wcc of the center land portion 31 and the land width Wco of the outer middle land portion (first side middle land portion) 32 satisfy the relationship of Wco <Wcc. In addition, the ground contact surface 10 of the outer middle land portion 32 and the outer shoulder land portion (first side shoulder land portion) 34 protrudes outward in the tire radial direction with respect to the reference profile PRso straddling the outer shoulder groove (circumferential narrow groove) 23. The ground contact surface 10 of the center land portion 31 is formed so as to project outward in the tire radial direction with respect to the reference profile PRcc, and the ground contact surface 10 of the inner middle land portion (second side middle land portion) 33 is the reference profile PRci. It is formed so as to project outward in the tire radial direction with respect to the protrusion amount Hcc of the center land portion 31 and the protrusion amount Hci of the inner middle land portion 33 with respect to the protrusion amount Hso of the outer middle land portion 32 and the outer shoulder land portion 34. Satisfies the relationship of Hcc <Hso and Hci <Hso.

Here, as shown in FIG. 3, the reference profile PRco of the outer middle land portion 32 and the outer shoulder land portion 34 is in a no-load state in which the pneumatic tire 1 is mounted on the specified rim and filled with the specified internal pressure (specified load =). In the meridional cross-sectional view of 0), it is an arc that passes through three points of the groove opening ends P1o and P2o in the outer center groove 21 and the ground contact end T on the outside (first side) of the vehicle. The ground contact surface 10 of the outer middle land portion 32 and the outer shoulder land portion 34 has a dimension in the tire width direction between the outer groove opening end P2o of the outer center groove 21 in the tire width direction and the ground contact end T on the outer side of the vehicle. In the range including the land width Wco of the outer middle land portion 32 and the land width Wso of the outer shoulder land portion 34, the outer shoulder groove (circumferential narrow groove) 23 from each groove opening end P2o and the ground contact end T on the outer side of the vehicle. It projects outward in the tire radial direction along a gradual curve (or arc) toward the center in the tire width direction. That is, in other words, the protrusion amount Hso of the outer middle land portion 32 and the outer shoulder land portion 34 is the groove opening end P2o which is the end portion of the land portion width Wco in the tire width direction and the end of the land portion width Wso in the tire width direction. This is the difference in protrusion from the reference profile PRso with respect to the ground contact end T on the outside of the vehicle, which is a part.

Further, the reference profile PRcc of the center land portion 31 is a meridional cross-sectional view in a no-load state (specified load = 0) in which the pneumatic tire 1 is mounted on the specified rim and filled with the specified internal pressure, and each groove in the outer center groove 21. Tire width direction at the opening ends P1o, P2o and the inner center groove 22 The arc passing through the three points of the inner groove opening end P1i, or the tire width direction at each groove opening ends P1i, P2i and the outer center groove 21 at the inner center groove 22 It is an arc that passes through three points of the inner groove opening end P2i. The ground contact surface 10 of the center land portion 31 is a dimension in the tire width direction between the inner groove opening end P1o of the outer center groove 21 in the tire width direction and the inner groove opening end P1i of the inner center groove 22 in the tire width direction. In the land width Wcc of the center land portion 31, the groove opening ends P1o and P1i project outward in the tire radial direction in a gradual curve (or arc) toward the central portion in the tire width direction. That is, in other words, the protrusion amount Hcc of the center land portion 31 is the protrusion difference from the reference profile PRcc with respect to the groove opening ends P1o and P1i which are the ends of the land portion width Wcc in the tire width direction.

Further, the reference profile PRci of the inner middle land portion 33 is a meridional cross-sectional view in a no-load state (specified load = 0) in which the pneumatic tire 1 is mounted on the specified rim and filled with the specified internal pressure, and each in the inner center groove 22. It is an arc that passes through three points of the groove opening ends P1i and P2i and the groove opening ends P3i on the inner side in the tire width direction in the groove opening ends P1i and P2i and the inner shoulder groove 24. The ground contact surface 10 of the inner middle land portion 33 is located in the tire width direction between the outer groove opening end P2i of the inner center groove 22 in the tire width direction and the inner groove opening end P3i of the inner shoulder groove 24 in the tire width direction. In the land width Wci of the inner middle land portion 33, which is a dimension, the tires project outward in the tire radial direction from the groove opening ends P2i and P3i toward the central portion in the tire width direction in a gradual curve (or arc). That is, in other words, the protrusion amount Hci of the inner middle land portion 33 is the protrusion difference from the reference profile PRci with respect to the groove opening ends P2i and P3i which are the ends of the land portion width Wci in the tire width direction.

Therefore, according to the pneumatic tire 1, the contact patch 10 of the outer middle land portion 32 and the outer shoulder land portion 34 is formed so as to project outward in the tire radial direction from the reference profile PRso, and the center land portion 31 and the inner middle portion 31 are formed. The contact patch 10 of the land portion 33 is also formed so as to project outward in the tire radial direction from the reference profiles PRcc and PRci, respectively, so that the contact patch of the central portion in the tire width direction including the outer middle land portion 32 and the outer shoulder land portion 34 is also formed. It is possible to secure the contact patch length of the center portion in the tire width direction of each of the length, the center land portion 31 and the inner middle land portion 33. Therefore, it is possible to improve the steering stability performance on a dry road surface. In particular, since the outer shoulder groove 23 which is narrow in the circumferential direction is provided between the outer middle land portion 32 and the outer shoulder land portion 34, the ground contact length can be secured in the portion of the outer shoulder groove 23. .. The ground contact length is a dimension in the tire circumferential direction in the above-mentioned ground contact region. Therefore, it is possible to improve the steering stability performance on a dry road surface. Further, the ground contact surface 10 of the outer middle land portion 32 and the outer shoulder land portion 34 is formed so as to project outward from the reference profile PRso in the tire radial direction, and the ground contact surface 10 of the center land portion 31 and the inner middle land portion 33 is also formed. By being formed so as to project outward in the tire radial direction from the reference profiles PRcc and PRci, respectively, the contact patch of the central portion in the tire width direction including the outer middle land portion 32 and the outer shoulder land portion 34, the center land portion 31 and the inner middle portion are formed. It is possible to increase the contact patch of the central portion of each of the land portions 33 in the tire width direction. Therefore, the water removal action is improved from the central portion in the tire width direction including the outer middle land portion 32 and the outer shoulder land portion 34 to both sides in the tire width direction, and the tires of the center land portion 31 and the inner middle land portion 33 are respectively. Central portion in the width direction The water removing action is improved toward both sides in the tire width direction, and the steering stability performance on a wet road surface can be improved.

Moreover, according to the pneumatic tire 1, the protrusion amount Hcc of the center land portion 31 and the protrusion amount Hci of the inner middle land portion 33 are set with respect to the protrusion amount Hso of the outer middle land portion 32 and the outer shoulder land portion 34. The tire width is the amount of protrusion Hso of the outer middle land portion 32 and the outer shoulder land portion 34 on the outer side in the tire width direction, which satisfies the relationship of Hcc <Hso and Hci <Hso and reduces the ground contact length in the ground contact region as compared with others. By making it larger than the protrusion amount Hcc of the center land portion 31 adjacent to the inner side in the direction and the protrusion amount Hci of the inner middle land portion 33, between the outer middle land portion 32 and the outer shoulder land portion 34 and the inner side in the tire width direction. It is possible to suppress a sudden decrease in the ground contact length, improve the ground contact property, and contribute to the improvement of the steering stability performance on a dry road surface and the steering stability performance on a wet road surface. As a result, it is possible to improve the steering stability performance on a dry road surface and the steering stability performance on a wet road surface.

Moreover, according to the pneumatic tire 1, the land width Wcc of the center land portion 31 and the land width Wco of the outer middle land portion (first side middle land portion) 32 satisfy the relationship of Wco <Wcc. The outer middle land portion 32 and the outer shoulder land portion 34 sandwich the outer shoulder groove 23 in the tire radial direction, and the center land portion 31 protrudes outward in the tire radial direction. The balance between the contact length and the contact pressure between the 32 and the outer shoulder land portion 34 and the center land portion 31 can be adjusted. Therefore, the effect of improving the steering stability performance on a dry road surface and the effect of improving the steering stability performance on a wet road surface can be remarkably obtained.

Further, according to the pneumatic tire 1, when the mounting direction with respect to the vehicle is specified, the outside of the vehicle is the first side in the tire width direction, and the inside of the vehicle is the second side in the tire width direction, the outside of the vehicle. In the region where the ground contact pressure rises during cornering, the ground contact surfaces 10 of the outer middle land portion 32 and the outer shoulder land portion 34 are formed so as to project outward in the tire radial direction from the reference profile PRso, so that the outer middle land portion is formed. The contact length of the central portion of the portion 32 and the outer shoulder land portion 34 in the tire width direction can be secured, the effect of improving the steering stability performance on a dry road surface can be remarkably obtained, and the outer middle land portion 32 and the outer shoulder land portion can be obtained. The contact pressure at the center of the tire width direction of 34 can be increased, the water removal action can be improved from the center of the tire width direction to both sides in the tire width direction, and the effect of improving the steering stability performance on a wet road surface can be remarkably obtained. ..

Further, in the pneumatic tire 1 of the present embodiment, it is preferable that the protrusion amount Hcc of the center land portion 31 is in the range of 0.2 mm ≦ Hcc ≦ 0.4 mm.

According to this pneumatic tire 1, by setting the protrusion amount Hcc of the center land portion 31 to 0.2 mm or more, the contact pressure at the center portion of the center land portion 31 in the tire width direction can be set on both sides in the tire width direction. It can be approached to the ground pressure of. On the other hand, by setting the protrusion amount Hcc of the center land portion 31 to 0.4 mm or less, it is possible to suppress an excessive decrease in the contact pressure on both sides of the center land portion 31 in the tire width direction. As a result, the ground contact property at the center land portion 31 can be improved, the clipping force with the road surface can be enhanced, and the steering stability performance on a dry road surface and the steering stability performance on a wet road surface can be improved.

Further, in the pneumatic tire 1 of the present embodiment, it is preferable that the protrusion amount Hso of the outer middle land portion 32 and the outer shoulder land portion 34 is in the range of 0.3 mm ≦ Hso ≦ 0.6 mm.

According to the pneumatic tire 1, the protrusion amount Hso of the outer middle land portion 32 and the outer shoulder land portion 34 is set to 0.3 mm or more in the tire width direction of the outer middle land portion 32 and the outer shoulder land portion 34. The contact pressure at the center can be brought close to the contact pressure on both sides in the tire width direction. On the other hand, by setting the protrusion amount Hso of the outer middle land portion 32 and the outer shoulder land portion 34 to 0.6 mm or less, the contact pressure on both sides of the outer middle land portion 32 and the outer shoulder land portion 34 in the tire width direction is excessive. The decrease can be suppressed. As a result, the ground contact property of the outer middle land portion 32 and the outer shoulder land portion 34 sandwiching the outer shoulder groove 23 can be improved, and the clipping force with the road surface can be enhanced, and the steering stability performance on the dry road surface and the steering stability performance on the wet road surface can be improved. The steering stability performance can be improved.

Further, in the pneumatic tire 1 of the present embodiment, the protrusion amount Hcc of the center land portion 31 and the protrusion amount Hso of the outer middle land portion 32 and the outer shoulder land portion 34 are 1.2 ≦ Hso / Hcc ≦ 2.0. It is preferable to satisfy the relationship.

According to the pneumatic tire 1, the balance between the ground contact pressure at the center land portion 31 and the ground pressure at the outer middle land portion 32 and the outer shoulder land portion 34 sandwiching the outer shoulder groove 23 is ensured, and both ground contact properties are ensured. As a good condition, the clipping force with the road surface can be increased in the regions of the outer middle land portion 32 and the outer shoulder land portion 34 where the ground pressure rises when cornering outside the vehicle than the center land portion 31, and the maneuvering on a dry road surface can be performed. It is possible to improve the stability performance and the steering stability performance on a wet road surface.

Further, in the pneumatic tire 1 of the present embodiment, it is preferable that the protrusion amount Hcc of the center land portion 31 and the protrusion amount Hci of the inner middle land portion 33 satisfy the relationship of 0.9 ≦ Hcc / Hci ≦ 1.1. ..

According to the pneumatic tire 1, the protrusion amount Hcc of the center land portion 31 and the protrusion amount Hci of the inner middle land portion 33 satisfy the relationship of 0.9 ≦ Hcc / Hci ≦ 1.1, so that the center land portion is satisfied. Excessive fluctuations in ground pressure can be suppressed in 31 and the inner middle land portion 33, these ground contact properties can be improved, the clipping force with the road surface can be increased, and steering stability performance and wetness on dry road surfaces can be enhanced. It is possible to improve the steering stability performance on the road surface.

Further, in the pneumatic tire 1 of the present embodiment, at the ground contact surface 10 of the center land portion 31, one end communicates with one circumferential groove 20 in the tire width direction at the time of ground contact, and the other end ends at the center land portion 31. There is a groove 51, and there is a lug groove 52 on the ground contact surface 10 of the outer middle land portion 32, one end communicating with the outer shoulder groove 23 on the outer side in the tire width direction and the other end ending at the outer middle land portion 32. It is preferable that the ground contact surface 10 of the inner middle land portion 33 has a lug 53 groove having one end communicating with the inner shoulder groove 24 on the outer side in the tire width direction and ending at the inner middle land portion 33 at the other end.

According to the pneumatic tire 1, the center land portion 31, the outer middle land portion 32, and the inner middle land portion 33 are provided with lug grooves 51, 52, 53 whose other ends are terminated at the land portions 31, 32, 33. By doing so, each land portion 31, 32, 33 is formed in a rib shape to secure the land portion rigidity, improve the ground contact property, increase the clipping force with the road surface, and stabilize the steering on a dry road surface. Performance can be improved. Further, since the other ends are provided with lug grooves 51, 52, 53 terminating at the land portions 31, 32, 33, in order to secure the water removal action, the steering stability performance on a dry road surface is maintained and the wetness is maintained. It is possible to improve the steering stability performance on the road surface.

Further, in the pneumatic tire 1 of the present embodiment, with respect to the land width Wcc of the center land portion 31, the land width Wco of the outer middle land portion 32, the land width Wso of the outer shoulder land portion 34, and the inner middle The land width Wci of the land portion 33 and the land width Wsi of the inner shoulder land portion 35 are 0.7 ≦ Wco / Wcc ≦ 0.9, 1.0 ≦ Wso / Wcc ≦ 1.2, 0.7 ≦ It is preferable to satisfy the relationship of Wci / Wcc ≦ 0.9 and 0.9 ≦ Wsi / Wcc ≦ 1.1.

According to the pneumatic tire 1, the land width Wco of the outer middle land portion 32 is formed 0.7 to 0.9 times the land width Wcc of the center land portion 31, and the center land portion 31 has a land width Wco of 0.7 to 0.9 times. The land width Wso of the outer shoulder land 34 is formed 1.0 to 1.2 times the land width Wcc, and the land of the inner middle land 33 is formed with respect to the land width Wcc of the center land 31. The width Wci is formed 0.7 to 0.9 times, and the land width Wsi of the inner shoulder land 35 is formed to be equivalent to the land width Wcc of the center land 31. The ground contact pressure of each middle land portion 32, 33 between the shoulder land portions 34, 35 is weakened with respect to the land portion 31, and the ground contact pressure of each shoulder land portion 34, 35 is increased by that amount, in the tire width direction of the ground contact region. As a whole, the clipping force with the road surface can be enhanced in a well-balanced manner, and the steering stability performance on a dry road surface and the steering stability performance on a wet road surface can be improved.

Further, in the pneumatic tire 1 of the present embodiment, the ground contact surface 10 of the inner shoulder land portion 35 is formed so as to project outward in the tire radial direction with respect to the reference profile PRsi, and the protrusion amount of the first side shoulder land portion It is preferable that Hso and the protrusion amount Hsi of the second shoulder land portion satisfy the relationship of 0.9 ≦ Hso / Hsi ≦ 1.1.

Here, as shown in FIG. 3, the reference profile PRsi of the inner shoulder land portion 35 is a meridional cross-sectional view in a no-load state (specified load = 0) in which the pneumatic tire 1 is mounted on the specified rim and filled with the specified internal pressure. It is an arc that passes through three points of the groove opening ends P3i and P4i in the inner shoulder groove 24 and the ground contact end T inside the vehicle. The ground contact surface 10 of the inner shoulder land portion 35 has a dimension in the tire width direction between the groove opening end P4i on the outer side of the inner shoulder groove 24 in the tire width direction and the ground contact end T on the inner side of the vehicle. In the land width Wsi, the groove opening end P4i and the ground contact end T inside the vehicle protrude outward in the tire radial direction in a gradual curve (or arc) toward the central portion in the tire width direction. That is, in other words, the protrusion amount Hsi of the inner shoulder land portion 35 is the protrusion difference from the reference profile PRsi with respect to the groove opening end P4i which is the end portion of the land portion width Wsi in the tire width direction and the ground contact end T inside the vehicle. ..

Therefore, according to the pneumatic tire 1, the ground contact surface 10 of the inner shoulder land portion 35 is also formed so as to project outward in the tire radial direction from the reference profile PRsi, so that the inner shoulder land portion 35 is formed in the center portion in the tire width direction. The ground contact length can also be secured. Therefore, it is possible to improve the steering stability performance on a dry road surface. Moreover, the contact patch 10 of the inner shoulder land portion 35 is also formed so as to project outward in the tire radial direction from the reference profile PRsi, so that the contact pressure of the inner shoulder land portion 35 in the center portion in the tire width direction can be increased. Therefore, the water removing action of the inner shoulder land portion 35 is improved from the central portion in the tire width direction to both sides in the tire width direction, and the steering stability performance on a wet road surface can be improved. As a result, it is possible to improve the steering stability performance on a dry road surface and the steering stability performance on a wet road surface. Moreover, the protrusion amount Hso of the outer shoulder land portion 34 and the protrusion amount Hsi of the inner shoulder land portion 35 satisfy the relationship of 0.9 ≦ Hso / Hsi ≦ 1.1, so that the outer shoulder land portion 34 and the inner shoulder land portion 34 are satisfied. In the portion 35, excessive fluctuations in the ground contact pressure can be suppressed, these ground contact properties can be improved, the clipping force with the road surface can be increased, and the steering stability performance on a dry road surface and the steering stability on a wet road surface can be enhanced. Performance can be improved.

In this embodiment, performance tests on steering stability performance (also referred to as dry performance) on dry road surfaces and steering stability performance (also referred to as wet performance) on wet road surfaces were conducted for a plurality of types of pneumatic tires under different conditions (also referred to as dry performance). (See FIG. 4).

In the performance evaluation test, a pneumatic tire, which is a test tire with a tire designation of 225 / 50R17 98W size specified by JATTA, is assembled to a regular rim with a rim size of 17 x 75J and filled with an internal pressure of 230 kPa to fill a sedan type test vehicle. It was attached to all the rear wheels of.

The method of evaluating the steering stability performance on a dry road surface is to strike a test course on a dry road surface, and a professional test driver evaluates the feeling of control drive performance, lane change performance, cornering performance, and so on. This evaluation is an index evaluation based on the conventional example (100). This evaluation indicates that the higher the index, the better the steering stability performance on a dry road surface.

As for the evaluation method of steering stability performance on a wet road surface, a test driver on a wet road surface runs on a test course, and a professional test driver evaluates the feeling of control drive performance, lane change performance, cornering performance, and the like. This evaluation is an index evaluation based on the conventional example (100). This evaluation indicates that the higher the index, the better the steering stability performance on wet road surfaces.

In FIG. 4, the pneumatic tires of the conventional example and the first to fifteenth embodiments have a designated mounting direction with respect to the vehicle, and the tire width is provided by four circumferential grooves extending in the tire circumferential direction on the ground contact surface of the tread portion. By forming five land parts in the direction, the center land part on the tire equatorial plane, the outer middle land part on the outside of the vehicle in the center land part, and the outer shoulder land part on the outside of the vehicle in the outer middle land part. And the inner middle land part inside the vehicle in the center land part, and the inner shoulder land part inside the vehicle in the inner middle land part, and the circumferential direction between the outer middle land part and the outer shoulder land part. The groove is formed as a circumferential groove having a narrower groove width than the other three circumferential grooves.

In the pneumatic tire of the conventional example, the ground contact surface of each land portion is on the reference profile, and the width of each land portion is the same. On the other hand, in the pneumatic tires of Examples 1 to 16, the land width Wcc of the center land portion and the land width Wco of the outer middle land portion satisfy the relationship of Wco <Wcc, and the outer middle land portion and the outer side. The ground contact surface of the shoulder land portion is formed so as to project outward in the tire radial direction with respect to the reference profile straddling the circumferential groove, and the ground contact surface of the center land portion is formed so as to project outward in the tire radial direction with respect to the reference profile. The ground contact surface of the inner middle land portion is formed so as to project outward in the tire radial direction with respect to the reference profile, and the protrusion amount Hcc of the center land portion and the inner side are formed with respect to the protrusion amount Hso of the outer middle land portion and the outer shoulder land portion. The protrusion amount Hci of the middle land portion satisfies the relationship of Hcc <Hso and Hci <Hso.

As shown in the test results of FIG. 4, it can be seen that the pneumatic tires of Examples 1 to 16 have improved steering stability performance on a dry road surface and steering stability performance on a wet road surface.

1 Pneumatic tire 2 Tread part 3 Shoulder part 4 Side wall part 5 Bead part 6 Carcus layer 7 Belt layer 7a, 7b Belt 8 Belt reinforcement layer 10 Ground plane 15 Bead core 16 Bead filler 20 Circumferential groove 21 Outer center groove 22 Inner center Groove 23 Outer shoulder groove (circumferential narrow groove)
24 Inner shoulder groove 30 Land 31 Center land 32 Outer middle land (first side middle land)
33 Inner middle land 34 Outer shoulder land 35 Inner shoulder land 41, 42, 43 Sipe 51, 52, 53, 54, 55, 56 Rug groove CL Tire equatorial surface Hcc Center land protrusion amount Hci Inner middle land Hco Outer middle land protrusion Hsi Inner shoulder Land protrusion Hso Outer shoulder Land protrusion P1o, P2o Outer center groove groove opening end P1i, P2i Inner center groove groove opening end P3i, P4i Groove opening end of inner shoulder groove PRcc Center land reference profile PRco Outer middle land reference profile PRso Outer shoulder land reference profile PRci Inner middle land reference profile PRsi Inner shoulder land reference profile T Grounding end Wcc Center land width Wco outer middle land width Wso outer shoulder land width Wci inner middle land width Wsi inner shoulder land width

Claims (9)

By forming five land portions in the tire width direction by four circumferential grooves extending in the tire circumferential direction on the ground contact surface of the tread portion, the center land portion on the tire equatorial plane and the center land portion are formed. The first side middle land portion on the first side in the tire width direction in the mounting direction with respect to the vehicle, the first side shoulder land portion on the first side of the first side middle land portion, and the first side of the center land portion. Has a second side middle land portion on the second side opposite to the tire width direction and a second side shoulder land portion on the second side of the second side middle land portion. A pneumatic tire in which the circumferential groove between the middle land portion and the first shoulder land portion is formed as a circumferential groove having a narrower groove width than the other three circumferential grooves.
Of the circumferential grooves, an arc passing through three points of each groove opening end and the first side ground contact end in the outer center groove forming the first side of the center land portion is used as a reference profile straddling the circumferential narrow groove. ,
An arc that passes through three points of the groove opening end of each groove opening end in the outer center groove and the groove opening end of the inner center groove forming the second side of the center land portion in the circumferential direction groove in the tire width direction, or the inner side. The arc passing through the three points of each groove opening end in the center groove and the groove opening end on the inner side in the tire width direction in the outer center groove is used as the reference profile of the center land portion.
The second side is an arc that passes through three points of each groove opening end in the inner center groove and the groove opening end on the inner side in the tire width direction in the inner shoulder groove on the outer side in the tire width direction of the circumferential groove. As a reference profile for the middle land area
The land width Wcc of the center land portion and the land width Wco of the first side middle land portion satisfy the relationship of Wco <Wcc, and the contact between the first side middle land portion and the first side shoulder land portion. The ground is formed so as to project outward in the tire radial direction with respect to the reference profile straddling the circumferential groove, and the ground contact surface of the center land portion protrudes outward in the tire radial direction with respect to the reference profile of the center land portion. The ground contact surface of the second side middle land portion is formed so as to project outward in the tire radial direction with respect to the reference profile of the second side middle land portion, and the first side middle land portion and the first side are formed. A pneumatic tire in which the protrusion amount Hcc of the center land portion and the protrusion amount Hci of the second side middle land portion satisfy the relationship of Hcc <Hso and Hci <Hso with respect to the protrusion amount Hso of the shoulder land portion. The pneumatic tire according to claim 1, wherein the protrusion amount Hcc of the center land portion is in the range of 0.2 mm ≦ Hcc ≦ 0.4 mm. The pneumatic tire according to claim 1 or 2, wherein the protrusion amount Hso of the first side middle land portion and the first side shoulder land portion is in the range of 0.3 mm ≦ Hso ≦ 0.6 mm. Claims 1 to 3 in which the protrusion amount Hcc of the center land portion and the protrusion amount Hso of the first side middle land portion and the first side shoulder land portion satisfy the relationship of 1.2 ≦ Hso / Hcc ≦ 2.0. Pneumatic tire according to any one of. The invention according to any one of claims 1 to 4, wherein the protrusion amount Hcc of the center land portion and the protrusion amount Hci of the second side middle land portion satisfy the relationship of 0.9 ≦ Hcc / Hci ≦ 1.1. Pneumatic tires. On the ground contact surface of the center land portion, there is a groove in which one end communicates with one of the circumferential grooves in the tire width direction and the other end ends at the center land portion at the time of contact with the first side middle land portion. When touching down on the ground, there is a groove in which one end communicates with the circumferential narrow groove on the outer side in the tire width direction and the other end ends at the first side middle land portion, and the other end touches the ground surface of the second side middle land portion. The pneumatic tire according to any one of claims 1 to 5, wherein sometimes one end communicates with the circumferential groove on the outer side in the tire width direction and the other end has a groove terminated at the second side middle land portion. With respect to the land width Wcc of the center land portion, the land width Wco of the first side middle land portion, the land width Wso of the first side shoulder land portion, and the land portion of the second side middle land portion. The width Wci and the land width Wsi of the second shoulder land portion are 0.7 ≦ Wco / Wcc ≦ 0.9, 1.0 ≦ Wso / Wcc ≦ 1.2, 0.7 ≦ Wci / Wcc ≦ The pneumatic tire according to any one of claims 1 to 6, which satisfies the relationship of 0.9, 0.9 ≦ Wsi / Wcc ≦ 1.1. The arc passing through the three points of the groove opening ends P3i and P4i in the inner shoulder groove 24 and the ground contact end T inside the vehicle is used as the reference profile of the land portion of the second shoulder.
The ground contact surface of the second shoulder land portion is formed so as to project outward in the tire radial direction with respect to the reference profile of the second shoulder land portion, and the protrusion amount Hso of the first shoulder land portion and the first The pneumatic tire according to any one of claims 1 to 7, wherein the protrusion amount Hsi of the land portion of the two-sided shoulder satisfies the relationship of 0.9 ≦ Hso / Hsi ≦ 1.1. The inflator according to any one of claims 1 to 8, wherein the mounting direction with respect to the vehicle is specified, the outside of the vehicle is the first side in the tire width direction, and the inside of the vehicle is the second side in the tire width direction. tire.

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