JP6657707B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  The pneumatic tire includes a tread portion on which a tread pattern having a groove and a land portion defined by the groove is formed. As grooves of the tread pattern, there are a circumferential main groove extending in the tire circumferential direction and a lug groove at least partially extending in the tire width direction. The land portion defined by the plurality of circumferential main grooves is called a row of ribs or blocks. A rib is a continuous land portion that is not separated by lug grooves. Block rows are intermittent land sections that are separated by lug grooves. Increasing the land width, which is the dimension of the land in the tire width direction, improves the rigidity of the land and improves the steering stability of the pneumatic tire. On the other hand, if the land portion width is too large, a phenomenon occurs in which the contact length at the center of the land portion in the tire width direction becomes shorter than the contact length at both ends. The contact length refers to a dimension in a tire circumferential direction of a contact area of the tread portion. If the contact length at the center of the land portion in the tire width direction becomes shorter than the contact length at both ends and the contact shape becomes uneven, the steering stability performance of the pneumatic tire decreases. Further, the contact length at the center of the land portion in the tire width direction is shorter than the contact length at both ends, and the center of the land portion in the tire width direction in the tire circumferential first and rear portions in the contact region of the land portion. When the portion is deformed so as to be depressed, the possibility of occurrence of uneven wear in which both end portions of the land portion in the tire width direction wear more than the center portion increases. Therefore, a technology is known in which the surface of the land portion is projected outward from the reference profile line (reference contour line) in the tire radial direction to improve the steering stability performance and uneven wear resistance performance of the air retirer (see Patent Document 1). ).

  Further, the tread pattern is often constituted by a plurality of pattern elements provided in the tire circumferential direction. The pattern element is the minimum unit of the tread pattern defined by the lug grooves. The plurality of pattern elements provided in the tire circumferential direction are formed with the same or similar design. When a tread pattern includes a plurality of pattern elements, when a pneumatic tire having the tread pattern travels on a road surface, vibrations are periodically generated due to the pattern elements, and noise (pattern noise) may be generated. is there. Further, when the frequency of the noise caused by the pattern element matches the natural frequency of the vehicle equipped with the pneumatic tire, the noise increases due to resonance. A variable pitch method is known as a method for suppressing noise caused by a pattern element. The variable pitch method is a technique for suppressing noise by providing a difference in a pitch length, which is a dimension of a pattern element in a tire circumferential direction, and dispersing the frequency of the noise (see Patent Document 2).

Japanese Patent No. 5387707 JP 05-221206 A

  As disclosed in Patent Literature 1, by protruding the surface of the land portion from the reference profile line outward in the tire radial direction, the steering stability performance of the pneumatic tire is improved. For example, in a pneumatic tire intended to be mounted on a luxury vehicle or a high-performance vehicle, not only steering stability performance but also excellent noise suppression performance is required.

  An aspect of the present invention aims to provide a pneumatic tire that can achieve both steering stability performance and noise suppression performance.

  According to an aspect of the present invention, a pneumatic tire that is rotatable about a rotation axis in a state where the tire is mounted on a vehicle, a tread portion having a tread pattern formed thereon, and provided on both sides in the tire width direction of the tread portion. And a side portion having a display portion indicating a mounting direction with respect to the vehicle, wherein a plurality of the tread portions are provided in a tire width direction, and each of the tread portions extends in a tire circumferential direction. A first shoulder land portion closest to one ground end of the tread portion, and a second shoulder land portion closest to the other ground end of the tread portion, wherein the first shoulder land portion is At least three of the circumferential main grooves are mounted on the vehicle so as to be arranged on the vehicle width direction inner side of the vehicle with respect to the second shoulder land portion and pass through the rotation shaft. An arc-shaped reference profile line passing through an opening end is defined, and the surface of the first shoulder land portion and the surface of the second shoulder land portion respectively protrude outward in the tire radial direction from the reference profile line, and the first shoulder The land portion and the second shoulder land portion each include a plurality of pattern elements having different pitch lengths, and a pitch ratio indicating a ratio between a longest pitch length and a shortest pitch length among the plurality of pattern elements of the first shoulder land portion. Where Pin is the pitch ratio indicating the ratio between the longest pitch length and the shortest pitch length among the plurality of pattern elements of the second shoulder land portion, and the pneumatic tire satisfies the condition of Pin> Pout. Is provided.

  According to the aspect of the present invention, a tread pattern is designed based on a variable pitch method, and a pitch variation structure having a plurality of pattern elements having different pitch lengths is adopted in a tread portion, so that noise occurs during tire running. Is suppressed. Further, by forming the tread pattern so as to satisfy the condition of Pin> Pout, it is possible to achieve both the steering stability performance and the noise suppression performance of the tire. When the pitch ratio is small, the variation in the rigidity of the tread portion in the tire circumferential direction during the running of the tire becomes small, so that the steering stability performance is improved. On the other hand, when the pitch ratio is large, the noise frequency is dispersed, so that the noise suppression performance is improved. In order to improve the steering stability performance of the tire, it is more effective to increase the rigidity of the second shoulder land portion outside the vehicle than to increase the rigidity of the first shoulder land portion inside the vehicle. On the other hand, in order to improve the noise reduction performance for the driver's cab of the vehicle, it is more preferable to reduce the noise generated at the first shoulder land portion inside the vehicle than to reduce the noise generated at the second shoulder land portion outside the vehicle. Is effective. Therefore, by increasing the pitch ratio Pin of the first shoulder land portion and decreasing the pitch ratio Pout of the second shoulder land portion, it is possible to achieve both the steering stability performance and the noise suppression performance of the tire.

  Further, according to the aspect of the present invention, since each of the surface of the first shoulder land portion and the surface of the second shoulder land portion protrudes outward in the tire radial direction from the reference profile line, the surface in the ground region of the first shoulder land portion is provided. The central portion in the tire width direction is prevented from being deformed so as to be depressed in the front and rear portions in the tire circumferential direction, and the ground contact shape of the first shoulder land portion is made uniform. Similarly, the ground contact shape of the second shoulder land portion is also made uniform. Therefore, the steering stability performance and uneven wear resistance performance of the tire can be improved.

  In the aspect of the present invention, it is preferable that an average pitch length of the second shoulder land portion is longer than an average pitch length of the first shoulder land portion.

  Thereby, the steering stability performance of the tire can be further improved. For example, when the vehicle corners leftward, the contact pressure and lateral force received from the road surface by the second shoulder land portion of the tire mounted on the right side of the vehicle increase. By increasing the average pitch length of the second shoulder land, the second shoulder land can withstand a large contact pressure and lateral force. Therefore, the steering stability performance of the tire is improved. The same applies to tires mounted on the left side of the vehicle when the vehicle corners rightward.

  In the aspect of the present invention, the circumferential main groove is provided on a center main groove provided one by one on each side of the tire width direction with respect to a center in the tire width direction, and is provided outside each of the center main grooves in the tire width direction. A shoulder main groove, wherein the tread portion includes a center land portion provided between the two center main grooves, and a first middle land provided between the center land portion and the first shoulder land portion. And a second middle land portion provided between the center land portion and the second shoulder land portion, and a surface of the first middle land portion and a surface of the second middle land portion are respectively provided. Projecting outward from the reference profile line in the tire radial direction, the pitch ratio of the first middle land portion is equal to the pitch ratio of the first shoulder land portion, and the pitch ratio of the second middle land portion is equal to the pitch ratio of the second middle land portion. It is preferably equal to the pitch ratio of the shoulder land portion.

  When four circumferential main grooves are provided in the tire width direction and five land portions are provided in the tire width direction, the pitch ratio of the first middle land portion and the pitch ratio of the first shoulder land portion inside the vehicle are determined. By making the pitch ratio of the second middle land portion outside the vehicle equal to the pitch ratio of the second shoulder land portion, steering stability performance and noise reduction performance are further improved.

  In the aspect of the present invention, the reference profile line is defined so as to pass through all of the open ends of the two center main grooves, and the surface of the center land portion protrudes outward from the reference profile line in the tire radial direction. One of the two open ends of the first center main groove, one open end near the ground contact end, two open ends of the first shoulder main groove, and the surface of the first middle land portion. An arc-shaped first tread profile line including the surface of the first shoulder land portion protrudes outward in the tire radial direction from the reference profile line, and the other of the two open ends of the second center main groove. A second arcuate shape including one open end near the ground contact end, two open ends of the second shoulder main groove, a surface of the second middle land portion, and a surface of the second shoulder land portion. Red profile line, it is preferable to protrude from the reference profile lines on the outer side in the tire radial direction.

  A first tread profile line common to the first middle land portion and the first shoulder land portion is defined, and a second tread profile line common to the second middle land portion and the second shoulder land portion is defined. In addition, the contact property in the tire width direction is improved. Since the first middle land portion and the first shoulder land portion are defined by a single first tread profile line, the ground contact between the first middle land portion and the first shoulder land portion is reduced in the tire width direction. Changes smoothly. Therefore, particularly, the contact property at the first shoulder land portion is improved. Since the second middle land portion and the second shoulder land portion are defined by a single second tread profile line, the contact between the second middle land portion and the second shoulder land portion is reduced in the tire width direction. Changes smoothly. Therefore, particularly, the contact property at the second shoulder land portion is improved. The contact stability of the first middle land portion and the first shoulder land portion is improved, and the contact stability of the second middle land portion and the second shoulder land portion are improved, so that steering stability performance including straight running performance and turning performance, And the uneven wear resistance is further improved.

  In the aspect of the present invention, it is preferable that a maximum protrusion amount of the surface of the center land portion from the reference profile line is 0.2 mm or more and 0.5 mm or less.

  By setting the maximum protruding amount of the center land portion to be 0.2 [mm] or more, the center land portion has more uniform contact pressure at the center portion in the tire width direction and contact pressure at both end portions in the tire width direction. Can be. As a result, the grip force between the center land portion and the road surface increases, so that the steering performance of the vehicle when traveling straight ahead is improved, and the steering stability performance including the straight traveling performance is further improved. In addition, by setting the maximum protrusion amount of the center land portion to 0.5 [mm] or less, the protrusion amount of the center land portion toward the tire radial outside at the center portion in the tire width direction is suppressed. Thereby, the uneven wear resistance performance is further improved.

  In the aspect of the present invention, the maximum protrusion amount of the first tread profile line from the reference profile line and the maximum protrusion amount of the second tread profile line from the reference profile line are not less than 0.6 [mm] 2. 0.0 [mm] or less, and it is preferable that the maximum protrusion amount of the second tread profile line is larger than the maximum protrusion amount of the first tread profile line.

  By setting the maximum protrusion amount of the first tread profile line and the maximum protrusion amount of the second tread profile line to be 0.6 [mm] or more, the first and second middle land portions and the first and second shoulder land portions are provided. In each case, the contact pressure at the center in the tire width direction and the contact pressure at both ends in the tire width direction can be made more uniform. As a result, the grip force between each of the first and second middle land portions and the first and second shoulder land portions and the road surface is increased, so that the steering performance of the vehicle when traveling straight ahead is improved, and the steering stability including the straight traveling performance is improved. The performance is further improved. In addition, by setting the maximum protrusion amount of the first tread profile line and the maximum protrusion amount of the second tread profile line to be 2.0 [mm] or less, the first and second middle land portions and the first and second shoulders. For each of the land portions, the amount of protrusion in the tire radial direction outward at the central portion in the tire width direction is suppressed. Thereby, the uneven wear resistance performance is further improved. Further, since the maximum protrusion amount of the second tread profile line is larger than the maximum protrusion amount of the first tread profile line, the uneven wear resistance is further improved. The second middle land portion and the second shoulder land portion forming the second tread profile line are arranged outside the vehicle. For example, when the vehicle corners to the left, the second middle land portion and the second shoulder land portion of the tire mounted on the right side of the vehicle receive large contact pressure and lateral force from the road surface. The same applies to tires mounted on the left side of the vehicle when the vehicle corners rightward. Therefore, the wear amount of the second middle land portion and the second shoulder land portion arranged outside the vehicle is larger than the wear amount of the first middle land portion and the first shoulder land portion arranged inside the vehicle. By making the maximum protrusion amount of the second tread profile line larger than the maximum protrusion amount of the first tread profile line, even if the second middle land portion and the second shoulder land portion are worn, the rotation axis of the tire and the outside of the vehicle can be used. The difference between the distance to the tread surface and the distance between the rotation axis of the tire and the tread surface inside the vehicle is suppressed. Thereby, the steering stability performance and the uneven wear resistance performance are further improved.

  In the aspect of the present invention, it is preferable that the pitch ratio Pin is 1.4 or more and 1.7 or less, and the pitch ratio Pout is 1.2 or more and 1.5 or less.

  If the pitch ratio Pin is smaller than 1.4, sufficient noise reduction performance may not be obtained. When the pitch ratio Pin is larger than 1.7, sufficient uneven wear resistance may not be obtained. When the pitch ratio Pout is smaller than 1.2, the possibility that noise is generated increases. When the pitch ratio Pout is larger than 1.5, there is a possibility that the steering stability performance is deteriorated. By setting the pitch ratio Pin to 1.4 or more and 1.7 or less and the pitch ratio Pout to 1.2 or more and 1.5 or less, steering stability performance, noise reduction performance, and uneven wear resistance performance can be obtained.

  According to an aspect of the present invention, there is provided a pneumatic tire capable of achieving both steering stability performance and noise suppression performance.

FIG. 1 is a side view showing an example of a vehicle to which the pneumatic tire according to the first embodiment is mounted. FIG. 2 is a view of an example of a vehicle to which the pneumatic tire according to the first embodiment is mounted, as viewed from the rear. FIG. 3 is a sectional view showing a part of the pneumatic tire according to the first embodiment. FIG. 4 is a developed view showing a part of a tread portion of the pneumatic tire according to the first embodiment. FIG. 5 is a development view showing a first shoulder land portion according to the first embodiment. FIG. 6 is a developed view showing a second shoulder land portion according to the first embodiment. FIG. 7 is a diagram illustrating a tread profile line according to the first embodiment. FIG. 8 is a diagram showing a tread profile line in the center land portion among the tread profile lines according to the first embodiment. FIG. 9 is a diagram illustrating tread profile lines of a second middle land portion and a second shoulder land portion among the tread profile lines according to the first embodiment. FIG. 10 is a diagram illustrating a reference profile line according to the first embodiment. FIG. 11 is a diagram illustrating an example of a ground contact shape of the pneumatic tire according to the first embodiment. FIG. 12 is a diagram showing a ground contact shape of a pneumatic tire according to a conventional example. FIG. 13 is a diagram illustrating an example of a tread profile line and a reference profile line according to the second embodiment. FIG. 14 is a diagram illustrating a tread profile line in a center land portion among tread profile lines according to the second embodiment. FIG. 15 is a diagram illustrating an example of a ground contact shape of the pneumatic tire according to the second embodiment.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings, but the present invention is not limited thereto. The components of the embodiments described below can be appropriately combined. In some cases, some components may not be used.

<First embodiment>
A first embodiment will be described. FIG. 1 is a side view illustrating an example of a vehicle 500 on which the tire 1 according to the present embodiment is mounted. FIG. 2 is a view of an example of a vehicle 500 on which the tire 1 according to the present embodiment is mounted, as viewed from the rear. As shown in FIGS. 1 and 2, the vehicle 500 includes a traveling device 501 including the tire 1, a vehicle body 502 supported by the traveling device 501, and an engine 503 for driving the traveling device 501. The tire 1 is a pneumatic tire.

  The traveling device 501 includes a wheel 504 that supports the tire 1, an axle 505 that supports the wheel 504, a steering device 506 for changing the traveling direction of the traveling device 501, and a braking device for decelerating or stopping the traveling device 501. 507.

  The vehicle body 502 has a driver's cab in which a driver boards. An accelerator pedal for adjusting the output of the engine 503, a brake pedal for operating the brake device 507, and a steering wheel for operating the steering device 506 are arranged in the cab. The driver operates an accelerator pedal, a brake pedal, and a steering wheel. The vehicle 500 travels according to the driver's operation.

  The tire 1 is a passenger car tire. Passenger car tires refer to tires defined in Chapter A of JATMA YEAR BOOK 2012 (standard of the Japan Automobile Tire Association). The tire 1 may be a light truck tire defined in Chapter B or a truck and bus tire defined in Chapter C.

  The tire 1 is mounted on a rim of a wheel 504 of the vehicle 500. When mounted on the vehicle 500, the tire 1 rotates on the rotation axis AX and travels on the road surface RS.

  In the following description, a direction parallel to the rotation axis AX of the tire 1 is appropriately referred to as a tire width direction, and a radial direction with respect to the rotation axis AX of the tire 1 is appropriately referred to as a tire radial direction. The rotation direction about AX is appropriately referred to as a tire circumferential direction.

  In the following description, the center of the tire 1 in the tire width direction will be appropriately referred to as a tire center CL. The tire center CL includes a center line on the surface of the tread 10 where the tire equatorial plane and the surface of the tread 10 of the tire 1 intersect. The tire equatorial plane is a plane that passes through the center of the tire 1 in the tire width direction and is orthogonal to the rotation axis AX.

  In the following description, a position far from or away from the tire center CL in the tire width direction is appropriately referred to as a tire width direction outside, and a position near or close to the tire center CL in the tire width direction is appropriately defined as the tire width. Direction inside, and a position far from or away from the rotation axis AX in the tire radial direction is appropriately referred to as a tire radial direction outside, and a position close to or near the rotation axis AX in the tire radial direction is appropriately defined in the tire radial direction inside. ,.

  Further, in the following description, the inside of the vehicle 500 in the vehicle width direction is appropriately referred to as a vehicle inside, and the outside of the vehicle 500 in the vehicle width direction is appropriately referred to as a vehicle outside. The inside of the vehicle refers to a position close to or near the center of the vehicle 500 in the vehicle width direction. The outside of the vehicle refers to a position far from or away from the center of the vehicle 500 in the vehicle width direction of the vehicle 500.

  Vehicle 500 is a four-wheeled vehicle. The traveling device 501 has a left front wheel and a left rear wheel provided on the left side of the vehicle body 502, and a right front wheel and a right rear wheel provided on the right side of the vehicle body 502. The tire 1 includes a left tire 1L mounted on the left side of the vehicle body 502 and a right tire 1R mounted on the right side of the vehicle body 502.

  The tire 1 includes a tread portion 10 on which a tread pattern is formed, and side portions 7 provided on both sides in the tire width direction of the tread portion 10 and having a display portion 600 indicating a mounting direction with respect to the vehicle 500. When the tire 1 runs, the tread portion 10 comes into contact with the road surface RS.

  The tread pattern of the tread portion 10 is an asymmetric pattern. The mounting direction of the tire 1 with respect to the vehicle 500 is specified. The left tire 1L is mounted on the left side of the vehicle 500 such that one designated side portion 7 of the two side portions 7 faces the inside of the vehicle and the other side portion 7 faces the outside of the vehicle. The right tire 1R is mounted on the right side of the vehicle 500 such that one designated side portion 7 of the two side portions 7 faces the inside of the vehicle and the other side portion 7 faces the outside of the vehicle.

  The display section 600 is provided on at least one of the two side sections 7. Side portion 600 includes a serial symbol indicating a mounting direction of tire 1 with respect to vehicle 500. The display unit 600 includes at least one of a mark, a character, a code, and a pattern. As an example of the display unit 600 indicating the mounting direction of the tire 1 with respect to the vehicle 500, a character such as "OUTSIDE" is given, for example. The user can recognize the mounting direction of the tire 1 with respect to the vehicle 500 based on the display unit 600 provided on the side unit 7. Based on display section 600, left tire 1L is mounted on the left side of vehicle 500, and right tire 1R is mounted on the right side of vehicle 500.

  FIG. 3 is a cross-sectional view showing a part of the tire 1 according to the present embodiment. FIG. 3 shows a meridional section passing through the rotation axis AX of the tire 1. The tire 1 is rotatable around a rotation axis AX while being mounted on the vehicle 500. The rotation axis AX of the tire 1 is orthogonal to the tire center CL (tire equatorial plane).

  As shown in FIG. 3, the tire 1 includes a tread portion 10 on which a tread pattern 40 is formed, side portions 7 provided on both sides in the tire width direction of the tread portion 10, and a bead portion 5 connected to the side portion 7. And

  Further, the tire 1 includes a carcass ply layer 2, a belt layer 3, and a bead core 16. The carcass ply layer 2, the belt layer 3, and the bead core 16 function as a strength member (frame member) of the tire 1.

  Further, the tire 1 includes a tread rubber 6, a side rubber 8, a bead filler rubber 22, a rim cushion rubber 24, and an inner liner rubber 26. Tread portion 10 includes tread rubber 6. The side part 7 includes a side rubber 8.

  The carcass ply layer 2 is a strength member that forms the skeleton of the tire 1. The carcass ply layer 2 functions as a pressure vessel when the tire 1 is filled with air. The carcass ply layer 2 includes a carcass cord of an organic fiber and a rubber covering the carcass cord. The carcass ply layer 2 is supported by a bead core 16 of the bead portion 5. The bead cores 16 are arranged on one side and the other side of the carcass ply layer 2 in the tire width direction. The carcass ply layer 2 is folded back at the bead core 16.

  The belt layer 3 is a strength member that holds the shape of the tire 1. The belt layer 3 is disposed between the carcass ply layer 2 and the tread rubber 6. The belt layer 3 includes, for example, a belt cord made of a metal fiber such as steel and rubber covering the belt cord. The belt layer 3 includes a first belt ply 3A and a second belt ply 3B. The first belt ply 3A and the second belt ply 3B are stacked such that the cord of the first belt ply 3A and the cord of the second belt ply 3B intersect. A part of the belt layer 3 is covered with the belt cover layer 30. The belt cover layer 30 includes an organic fiber belt cover cord and rubber covering the belt cover cord.

  The bead portions 5 are strength members for fixing both ends of the carcass ply layer 2. The bead portion 5 fixes the tire 1 to the rim. The bead portion 5 has a bead core 16, a bead filler rubber 22, a rim cushion rubber 24, and a bead reinforcing material. The bead core 16 is a member in which a bead wire is wound in a ring shape. The bead wire is a steel wire. The bead filler rubber 22 is a rubber material disposed in a space formed by folding the end portion of the carcass ply layer 2 in the tire width direction at the position of the bead core 16. The rim cushion rubber 24 comes into contact with a rim on which the tire 1 is mounted. The bead reinforcing member 28 is disposed between the carcass ply layer 2 wound around the bead core 16 and the bead filler rubber 22.

  The side portions 7 are provided on one side and the other side of the tread portion 10 in the tire width direction. The side portion 7 is arranged outside the tread portions T1, T2 of the tread portion 10 in the tire width direction.

  The tread rubber 6 protects the carcass ply layer 2. A tread portion 10 is formed on the tread rubber 6. The side rubber 8 protects the carcass ply layer 2. The side rubbers 8 are arranged on one side and the other side of the tread rubber 6 in the tire width direction. The side portion 7 is formed on the side rubber 8. The inner liner rubber 26 is arranged so as to face the internal space of the tire 1 to be filled with air.

  The tread contact width TW, which indicates the contact width of the tread portion 10, refers to a state in which the tire 1 is assembled to a regular rim, filled with a regular internal pressure, placed vertically on a flat surface, and loaded with a regular load. Means the maximum value of the contact width in the tire width direction, measured in the following manner. That is, the tread contact width TW refers to a distance between the contact end T1 of the tread portion 10 on one side of the tire center CL and the contact end T2 of the tread portion 10 on the other side in the tire width direction.

  The grounding ends T1 and T2 of the tread portion 10 are that the tire 1 is rim-assembled into a regular rim, filled with a regular internal pressure, placed vertically on a flat surface, and placed under a regular load. 10 is the end in the tire width direction of the portion where it comes into contact with the ground.

  The “regular rim” is a rim for which the standard for the tire 1 is defined for each tire 1, and is a standard rim for JATMA, a “Design Rim” for TRA, and a “Measuring Rim” for ETRTO. . However, when the tire 1 is a tire mounted on a new vehicle, a genuine wheel on which the tire 1 is assembled is used.

  The "normal internal pressure" is the air pressure specified for each tire 1 in the standard for the tire 1. The maximum air pressure is JATMA, and the maximum air pressure described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURESURE" for TRA. If the value is ETRTO, it is "INFLATION PRESSURE". However, when the tire 1 is a tire mounted on a new vehicle, the air pressure is displayed on the vehicle.

  The "regular load" is a load specified for each tire 1 according to the standard for the tire 1, and is described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURE SURE" for JATMA and for TRA. If it is the maximum value, ETRTO, it is "LOAD CAPACITY". However, when the tire 1 is a passenger car, the load is set to a load equivalent to 88% of the load determined for each tire 1. When the tire 1 is a tire mounted on a new vehicle, the wheel load is obtained by dividing the front and rear axle weights described in the vehicle verification of the vehicle by the number of tires.

  In the present embodiment, the ground end T1 is arranged inside the vehicle, and the ground end T2 is arranged outside the vehicle.

  FIG. 4 is a developed view showing a part of the tread portion 10 of the tire 1 according to the present embodiment. A tread pattern 40 is formed on a tread portion 10 of the tire 1.

  A plurality of tread portions 10 are provided in the tire width direction, each of which is provided in a circumferential main groove 50 extending in the tire circumferential direction, a plurality of land portions 60 defined by the circumferential main groove 50, and a land portion 60. Lug groove 70 formed. The circumferential main groove 50 and the lug groove 70 are formed in the tread rubber 6. The land portion 60 has a surface 60A (ground contact surface, tread surface) that can contact the road surface RS.

  The circumferential main groove 50 extends in the tire circumferential direction. The circumferential main groove 50 is substantially parallel to a center line (tire equatorial line) where the tire equatorial plane and the tread portion 10 intersect. The circumferential main groove 50 extends linearly in the tire circumferential direction. In addition, the circumferential main groove 50 may be provided in a tire circumferential direction in a wavy shape or a zigzag shape.

  The circumferential main groove 50 has a groove width of 1.0 [mm] or more, has a groove depth of 4.0 [mm] or more, and has at least a part extending in the tire circumferential direction. Say. Generally, the circumferential main groove 50 has a groove width of 6.0 [mm] or more and a groove depth of 7.0 [mm] or more. The circumferential main groove 50 has a treadwear indicator (slip sign) inside. The treadwear indicator indicates the end of wear.

  At least a part of the lug groove 70 extends in the tire width direction. At least a part of the lug groove 70 may be parallel to the tire width direction. The lug groove 70 may be inclined with respect to each of the tire width direction and the tire circumferential direction. At least a part of the lug groove 70 may be connected to the circumferential main groove 50.

  The lug groove 70 is a lateral groove having a groove width of 2.0 [mm] or more, a groove depth of 3.0 [mm] or more, and extending at least partially in the tire width direction. The lug groove 70 may have an open structure penetrating the land portion 60 in the tire width direction, a semi-closed structure having one end terminating in the land portion 60, or both ends terminating in the land portion 60. It may have a closed structure.

  In the present embodiment, four circumferential main grooves 50 are provided in the tire width direction. The circumferential main grooves 50 are center main grooves 51 and 52 provided one each on both sides in the tire width direction with respect to the tire center CL, and shoulder main grooves provided outside the center main grooves 51 and 52 in the tire width direction. 53 and 54. The center main grooves 51 and 52 are provided between the shoulder main groove 53 and the shoulder main groove 54 in the tire width direction.

  In the following description, the center main groove 51 is appropriately referred to as a first center main groove 51, the center main groove 52 is appropriately referred to as a second center main groove 52, and the shoulder main groove 53 is appropriately referred to as a first shoulder. The main groove 53 and the shoulder main groove 54 are appropriately referred to as a second shoulder main groove 54.

  Of the first center main groove 51, the second center main groove 52, the first shoulder main groove 53, and the second shoulder main groove 54, the second shoulder main groove 54 is provided most outside the vehicle, and the second shoulder main groove is provided. A second center main groove 52 is provided outside the vehicle next to 54, a first center main groove 51 is provided outside the vehicle next to the second center main groove 52, and a first shoulder main groove 53 is provided most inside the vehicle. .

  The first center main groove 51 and the first shoulder main groove 53 are provided on the vehicle inner side of the tire center CL. The second center main groove 52 and the second shoulder main groove 54 are provided outside the vehicle with respect to the tire center CL.

  The groove center indicating the center position of the first center main groove 51 in the tire width direction is at least 10 [%] of the tread contact width TW from the tire center CL in the half tread region between the tire center CL and the contact end T1. [%] It is arranged at the position below.

  The groove center indicating the center position of the second center main groove 52 in the tire width direction is at least 10 [%] of the tread contact width TW from the tire center CL in the half tread region between the tire center CL and the contact end T2. [%] It is arranged at the position below.

  The groove center indicating the center position of the first shoulder main groove 53 in the tire width direction is in the half tread region between the tire center CL and the ground contact end T1 and is at least 30% [35] of the tread ground width TW from the tire center CL. [%] It is arranged at the position below.

  The groove center indicating the center position of the second shoulder main groove 54 in the tire width direction is 30% or more of 35% or more of the tread contact width TW from the tire center CL in the half tread region between the tire center CL and the contact end T2. [%] It is arranged at the position below.

  In the present embodiment, five land portions 60 are provided in the tire width direction. The land portion 60 includes a center land portion 61 provided between the first center main groove 51 and the second center main groove 52, and a second land portion 61 provided between the first center main groove 51 and the first shoulder main groove 53. A first middle land portion 62, a second middle land portion 63 provided between the second center main groove 52 and the second shoulder main groove 54, and a first shoulder provided inside the vehicle with respect to the first shoulder main groove 53. A land portion 64 and a second shoulder land portion 65 provided outside the vehicle with respect to the second shoulder main groove 54 are included.

  The first middle land portion 62 is provided between the center land portion 61 and the first shoulder land portion 64 in the tire width direction. The second middle land portion 63 is provided between the center land portion 61 and the second shoulder land portion 65 in the tire width direction.

  Of the first center land portion 61, the first middle land portion 62, the second middle land portion 63, the first shoulder land portion 64, and the second shoulder land portion 65, the second shoulder land portion 65 is provided most outside the vehicle. A second middle land portion 63 is provided outside the vehicle next to the second shoulder land portion 65, a center land portion 61 is provided next to the second middle land portion 63, and a first land portion 61 is provided next to the center land portion 61. The middle land portion 62 is provided outside the vehicle, and the first shoulder land portion 64 is provided most inside the vehicle.

  The center land portion 61 is provided at the tire center CL. The tire center CL (center line) passes through the center land portion 61. The first middle land portion 62 and the first shoulder land portion 64 are provided on the vehicle inner side of the tire center CL. The second middle land portion 63 and the second shoulder land portion 65 are provided outside the vehicle with respect to the tire center CL.

  Of the first center land portion 61, the first middle land portion 62, the second middle land portion 63, the first shoulder land portion 64, and the second shoulder land portion 65, the first shoulder land portion 64 is the tread portion 10 The second shoulder land portion 65 is provided at a position closest to the one grounding end T1 and the position closest to the other grounding end T2 of the tread portion 10.

  The first shoulder land portion 64 is provided between the first shoulder main groove 53 and the ground end T1. The second shoulder land portion 65 is provided between the second shoulder main groove 54 and the ground end T2.

  The tire 1 is mounted on the vehicle 500 such that the first shoulder land portion 64 is disposed inside the vehicle with respect to the second shoulder land portion 65.

  The surface 60A of the land portion 60 that can contact the road surface includes a surface 61A of the center land portion 61, a surface 62A of the first middle land portion 62, a surface 63A of the second middle land portion 63, and a surface 64A of the first shoulder land portion 64. , And a surface 65A of the first shoulder land portion 65.

  The lug groove 70 includes an inclined groove 71 provided on the center land portion 61, an inclined groove 72 provided on the first middle land portion 62, an inclined groove 73 provided on the second middle land portion 63, and a first shoulder land portion. 64 includes an inclined groove 74 provided on the second shoulder land portion 65.

  A plurality of inclined grooves 71 are provided in the center land portion 61 in the tire circumferential direction. One end of the inclined groove 71 is connected to the first center main groove 51, and the other end of the inclined groove 71 ends at the center land portion 61 without being connected to the second center main groove 52. That is, the inclined groove 71 has a semi-closed structure. The inclined groove 71 extends from the first center main groove 51 in a direction inclined with respect to the tire width direction. The inclination angle of the inclined groove 71 with respect to the tire width direction is, for example, not less than 20 [°] and not more than 50 [°].

  A plurality of inclined grooves 72 are provided in the tire circumferential direction in the first middle land portion 62. One end of the inclined groove 72 is connected to the first shoulder main groove 53, and the other end of the inclined groove 72 ends at the first middle land portion 62 without being connected to the first center main groove 51. . That is, the inclined groove 72 has a semi-closed structure. The inclined groove 72 extends from the first shoulder main groove 53 in a direction inclined with respect to the tire width direction. The inclination direction of the inclined groove 72 is the same as the inclination direction of the inclined groove 71. The inclination angle of the inclined groove 72 with respect to the tire width direction is, for example, not less than 20 [°] and not more than 50 [°].

  A plurality of inclined grooves 73 are provided in the second middle land portion 63 in the tire circumferential direction. One end of the inclined groove 73 is connected to the second center main groove 52, and the other end of the inclined groove 73 ends at the second middle land portion 63 without being connected to the second shoulder main groove 54. . That is, the inclined groove 73 has a semi-closed structure. The inclined groove 73 extends from the second center main groove 52 in a direction inclined with respect to the tire width direction. The inclined direction of the inclined groove 73 is the same as the inclined direction of the inclined groove 71 and the inclined direction of the inclined groove 72. The inclination angle of the inclined groove 73 with respect to the tire width direction is, for example, not less than 20 [°] and not more than 55 [°].

  A plurality of inclined grooves 74 are provided in the first shoulder land portion 64 in the tire circumferential direction. One end of the inclined groove 74 extends from the ground contact end T1 to the side portion 7 inside the vehicle, and the other end of the inclined groove 74 is connected to the first shoulder main groove 53 without being connected to the first shoulder main groove 53. Terminates at land 64. That is, the inclined groove 74 has a semi-closed structure. A chamfer 74C is provided at the opening end of the inclined groove 74.

  A plurality of inclined grooves 75 are provided in the second shoulder land portion 65 in the tire circumferential direction. One end of the inclined groove 75 is connected to the second shoulder main groove 54, and the other end of the inclined groove 75 extends to the side portion 7 outside the vehicle from the ground contact end T2. That is, the inclined groove 75 has an open structure. A chamfer 75C is provided at the open end of the inclined groove 75.

  The inclined groove 71 has a semi-closed structure, and the center land portion 61 is not divided by the inclined groove 71. That is, the center land portion 61 is a rib (continuous land portion) in which the surface 61A is continuously connected in the tire circumferential direction.

  The inclined groove 72 has a semi-closed structure, and the first middle land portion 62 is not divided by the inclined groove 72. That is, the first middle land portion 62 is a rib (continuous land portion) in which the surface 62A is continuously connected in the tire circumferential direction.

  The inclined groove 73 has a semi-closed structure, and the second middle land portion 63 is not divided by the inclined groove 73. That is, the second middle land portion 63 is a rib (continuous land portion) in which the surface 63A is continuously connected in the tire circumferential direction.

  The inclined groove 74 has a semi-closed structure, and the first shoulder land portion 64 is not divided by the inclined groove 74. That is, the first shoulder land portion 64 is a rib (continuous land portion) in which the surface 64 </ b> A is continuously connected in the tire circumferential direction.

  The inclined groove 75 has an open structure, and the second shoulder land portion 65 is divided by the inclined groove 75. That is, the second shoulder land portion 65 is a block row (intermittent land portion) in which the surface 65A is interrupted in the tire circumferential direction.

  In the present embodiment, the groove width of the second shoulder main groove 54 is W1, the groove width of the second center main groove 52 is W2, the groove width of the first center main groove 51 is W3, and the groove of the first shoulder main groove 53 is W1. When the width is W4, the groove width W1 is the smallest and the groove width W2 is the largest among the groove widths W1, W2, W3, and W4.

  The ratio [W2 / W1] between the groove width W1 and the groove width W2 is 4 or more and 5 or less. When the groove area ratio of the tread portion 10 between the tire center CL and the ground end T1 is Sin, and the groove area ratio of the tread portion 10 between the tire center CL and the ground end T2 is Sout, the ratio [ Sin / Sout] is 1.1 or more and 1.2 or less. The groove area ratio refers to [groove opening area] / [groove opening area + land area] on the surface of tread portion 10. That is, when it is assumed that there is no groove, the area of the predetermined region of the tread portion 10 is defined as the total area, and the opening area of the groove existing in the predetermined region is defined as the groove area. Groove area] / [total area].

  In the present embodiment, the tread pattern 40 is configured by a plurality of pattern elements provided in the tire circumferential direction. Pattern elements are also called pitches.

  The pattern element (pitch) refers to the minimum unit of the pattern component when the same or similar pattern is repeated along the tire circumferential direction. In other words, the pattern element refers to a portion defined in the tread portion 10 of the tire 1 by one pattern when a plurality of patterns of the same or similar design are provided in the tire circumferential direction. The pattern includes at least one of a lug groove, a sipe, and a calf. The lug grooves and sipes include notches or cuts that do not penetrate the land. The pattern element is defined by two lug grooves 70 arranged in the tire circumferential direction. Note that the pattern element may be partitioned by two sipes arranged in the tire circumferential direction. The pattern element may be defined by a lug groove having a first width arranged in the tire circumferential direction and a lug groove having a second width different from the first width, or may be arranged in the tire circumferential direction. It may be divided by a lug groove and a sipe.

  The sipes are grooves having a groove width of less than 1.5 [mm]. At least a part of the sipe may extend in the tire width direction, or may extend in the tire circumferential direction.

  The center land portion 61 has a plurality of pattern elements 81 partitioned by the inclined grooves 71. In the present embodiment, the pattern element 81 is defined by two adjacent inclined grooves 71 among a plurality of inclined grooves 71 provided in the tire circumferential direction. A plurality of pattern elements 81 are provided in the tire circumferential direction.

  The first middle land portion 62 has a plurality of pattern elements 82 partitioned by the inclined grooves 72. In the present embodiment, the pattern element 82 is defined by two adjacent inclined grooves 72 among a plurality of inclined grooves 72 provided in the tire circumferential direction. A plurality of pattern elements 82 are provided in the tire circumferential direction.

  The second middle land portion 63 has a plurality of pattern elements 83 partitioned by the inclined grooves 73. In the present embodiment, the pattern element 83 is defined by two adjacent inclined grooves 73 among a plurality of inclined grooves 73 provided in the tire circumferential direction. A plurality of pattern elements 83 are provided in the tire circumferential direction.

  The first shoulder land portion 64 has a plurality of pattern elements 84 defined by the inclined grooves 74. In the present embodiment, the pattern element 84 is defined by two adjacent inclined grooves 74 among a plurality of inclined grooves 74 provided in the tire circumferential direction. A plurality of pattern elements 84 are provided in the tire circumferential direction.

  The second shoulder land portion 65 has a plurality of pattern elements 85 partitioned by the inclined grooves 75. In the present embodiment, the pattern element 85 is defined by two adjacent inclined grooves 75 among a plurality of inclined grooves 75 provided in the tire circumferential direction. A plurality of pattern elements 85 are provided in the tire circumferential direction.

  In the present embodiment, the tread pattern 40 is designed based on the variable pitch method. The variable pitch method is a technique for suppressing noise by providing a difference in a pitch length, which is a dimension of a pattern element in a tire circumferential direction, and dispersing the frequency of the noise.

  In the present embodiment, the tread portion 10 adopts a pitch variation structure having a plurality of pattern elements having different pitch lengths. The pitch length refers to the dimension of one pattern element in the tire circumferential direction in a no-load state where the tire 1 is assembled to a prescribed rim, filled with a normal internal pressure, and no load is applied to the tire 1.

  In the present embodiment, in the first shoulder land portion 64, a plurality of pattern elements 84 having different pitch lengths are provided in the tire circumferential direction. In the second shoulder land portion 65, a plurality of pattern elements 85 having different pitch lengths are provided in the tire circumferential direction.

  FIG. 5 is a developed view showing the first shoulder land portion 64 according to the present embodiment. FIG. 6 is a developed view showing the second shoulder land portion 65 according to the present embodiment.

  As shown in FIG. 5, the first shoulder land portion 64 has a plurality of pattern elements 84 having different pitches La. In the example shown in FIG. 5, the first shoulder land portion 64 includes a pattern element 84 having a pitch length La1, a pattern element 84 having a pitch length La2 longer than the pitch length La1, and a pattern having a pitch length La3 longer than the pitch length La2. It has an element 84 and a pattern element 84 having a pitch length La4 longer than the pitch length La3.

  FIG. 5 shows an example in which the number of pitches indicating the total number of types of the pattern elements 84 is four. Note that the number of pitches is not limited to four, and may be any number (number of N). In the example shown in FIG. 5, the pattern element 84 having the pitch length La2 is arranged next to the pattern element 84 having the pitch length La1, and the pattern element 84 having the pitch length La3 is arranged next to the pattern element 84 having the pitch length La2. An example is shown in which a pattern element 84 having a pitch length La4 is arranged next to a pattern element 84 having a pitch length La3. That is, FIG. 5 shows an example in which the plurality of pattern elements 84 are arranged in the tire circumferential direction so that different pitch lengths La are arranged in ascending or descending order in the tire circumferential direction. For example, a pattern element 84 having a pitch length La3 is arranged next to a pattern element 84 having a pitch length La1, a pattern element 84 having a pitch length La2 is arranged next to a pattern element 84 having a pitch length La3, and a pattern element 84 having a pitch length La2. May be arranged next to the pattern element 84 having the pitch length La4. That is, the plurality of pattern elements 84 may be arranged in the tire circumferential direction such that different pitch lengths La are randomly arranged in the tire circumferential direction.

  In the following description, among the pitch lengths La of the plurality of pattern elements 84 of the first shoulder land portion 64, the longest pitch length La is appropriately referred to as the longest pitch length Lamax, and the shortest pitch length La is appropriately shortest. It is called pitch length Lamin. In the example shown in FIG. 5, the longest pitch length Lamax is the pitch length La4, and the shortest pitch length Lamin is the pitch length La1.

  As shown in FIG. 6, the second shoulder land portion 65 has a plurality of pattern elements 85 having different pitch lengths Lb. In the example shown in FIG. 6, the second shoulder land portion 65 includes a pattern element 85 having a pitch length Lb1, a pattern element 85 having a pitch length Lb2 longer than the pitch length Lb1, and a pattern having a pitch length Lb3 longer than the pitch length Lb2. It has an element 85 and a pattern element 85 having a pitch length Lb4 longer than the pitch length Lb3.

  FIG. 6 shows an example in which the number of pitches indicating the total number of types of the pattern elements 85 is four. Note that the number of pitches is not limited to four, and may be any number (number of N). Further, the pitch number of the first shoulder portion 64 and the pitch number of the second shoulder portion 65 may be different. In the example shown in FIG. 6, an example is shown in which the plurality of pattern elements 85 are arranged in the tire circumferential direction such that the pitch lengths Lb are arranged in ascending or descending order in the tire circumferential direction. A plurality of pattern elements 85 may be arranged in the tire circumferential direction so that different pitch lengths Lb are randomly arranged in the tire circumferential direction.

  In the following description, among the pitch lengths Lb of the plurality of pattern elements 85 of the second shoulder land portion 65, the longest pitch length Lb is appropriately called the longest pitch length Lbmax, and the shortest pitch length Lb is appropriately shortest. It is called pitch length Lbmin. In the example shown in FIG. 6, the longest pitch length Lbmax is the pitch length Lb4, and the shortest pitch length Lbmin is the pitch length Lb1.

  The pitch ratio indicating the ratio between the longest pitch length Lamax and the shortest pitch length Lamin among the plurality of pattern elements 84 of the first shoulder land portion 64 is Pin, and the longest pitch length of the plurality of pattern elements 85 of the second shoulder land portion 65. Assuming that a pitch ratio indicating a ratio between Lbmax and the shortest pitch length Lbmin is Pout, the tread pattern 40 is designed so as to satisfy the following expression (1).

Pin> Pout (1)
However,
Pin = Lamax / Lamin (2)
Pout = Lbmax / Lbmin (3)

  In the present embodiment, the pitch ratio Pin is 1.4 or more and 1.7 or less. The pitch ratio Pout is 1.2 or more and 1.5 or less.

  In the present embodiment, the average pitch length Lave of the second shoulder land portions 65 is longer than the average pitch length Laave of the first shoulder land portions 64.

  The average pitch length Laave of the first shoulder land portion 64 is an average value of the pitch length La of the plurality of pattern elements 84. In the present embodiment, the average pitch length Laave is a value obtained by dividing the dimension of the first shoulder land portion 64 in the tire circumferential direction (so-called circumferential length) by the total number of the inclined grooves 74.

  The average pitch length Lbave of the second shoulder land portion 65 is an average value of the pitch length Lb of the plurality of pattern elements 85. In the present embodiment, the average pitch length Lbave is a value obtained by dividing the dimension (so-called circumferential length) of the second shoulder land portion 65 in the tire circumferential direction by the total number of the inclined grooves 75.

  In the present embodiment, the average pitch length Lave of the second shoulder land portions 65 is not less than 1.15 [times] and not more than 1.25 [times] the average pitch length Laave of the first shoulder land portions 64.

  In the present embodiment, the total number of pattern elements 84 in the first shoulder land portion 64 and the total number of pattern elements 85 in the second shoulder land portion 65 are larger.

  FIG. 7 is a diagram showing a tread profile line according to the present embodiment. FIG. 7 shows a meridional section of the tread portion 10 passing through the rotation axis AX. FIG. 8 is an enlarged view of a part of FIG. 7, and is a diagram illustrating a tread profile line of the center land portion 61 among the tread profile lines according to the present embodiment. FIG. 9 is an enlarged view of a part of FIG. 7, and is a diagram showing a tread profile line of the second middle land portion 63 and the second shoulder land portion 65 among the tread profile lines according to the present embodiment.

  Note that the tread profile line and the reference profile line PL0 of the tread portion 10 described below are used when the tire 1 is assembled to a regular rim, filled with a regular internal pressure, and no load is applied to the tire 1. Are the tread profile line and the reference profile line PL0.

  The tread profile line indicates the contour of the surface 60A (ground contact surface, tread surface) of the land portion 60 of the tread portion 10 of the tire 1 in the meridional section of the tread portion 10 passing through the rotation axis AX. In the present embodiment, the tread profile line of the first middle land portion 62 and the tread profile line of the second middle land portion 63 are substantially equal. The tread profile line of the first shoulder land portion 64 and the tread profile line of the second shoulder land portion 64 are substantially equal. In the following description, the tread profile lines of the center land portion 61, the second middle land portion 63, and the second shoulder land portion 65 will be mainly described, and the treads of the first middle land portion 62 and the first shoulder land portion 64 will be described. The description of the profile line is simplified or omitted.

  As shown in FIGS. 7, 8, and 9, in the meridional section of the tread portion 10 passing through the rotation axis AX, an arc-shaped reference profile line PL0 passing through at least three opening ends of the circumferential main groove 50 is defined. Is done. A surface 64A of the first shoulder land portion 64 and a surface 65A of the second shoulder land portion 65 respectively project outward in the tire radial direction from the reference profile line PL0.

  In the present embodiment, each of the surface 61A of the center land portion 61, the surface 62A of the first middle land portion 62, and the surface 63A of the second middle land portion 63 also extends outward from the reference profile line PL0 in the tire radial direction. Protrude.

  In the present embodiment, the maximum protrusion amount E61 of the surface 61A of the center land portion 61 from the reference profile line PL0, the maximum protrusion amount E62 of the surface 62A of the first middle land portion 62 from the reference profile line PL0, the second middle land portion. Each of the maximum protrusion amounts E63 of the surface 63A of the 63 from the reference profile line PL0 is not less than 0.1 [mm] and not more than 1.0 [mm].

  In the present embodiment, the maximum protrusion amount E61 of the surface 61A of the center land portion 61 from the reference profile line PL0 is not less than 0.2 [mm] and not more than 0.5 [mm]. It is more preferable that the maximum protrusion amount E61 is not less than 0.2 [mm] and not more than 0.4 [mm].

  In the present embodiment, the maximum protrusion amount E64 of the surface 64A of the first shoulder land portion 64 from the reference profile line PL0 and the maximum protrusion amount E65 of the surface 65A of the second shoulder land portion 65 from the reference profile line PL0 are 0. 0.3 [mm] or more and 1.0 [mm] or less. It is more preferable that the maximum protrusion amount E64 and the maximum protrusion amount E65 are not less than 0.5 [mm] and not more than 0.7 [mm].

  The maximum amount of protrusion refers to the maximum dimension in the tire radial direction from the reference profile line PL0 to the surface 60A of the land portion 60.

  Note that the amount of protrusion of the surface 64A of the first shoulder land portion 64 from the reference profile line PL0 increases outward from the first shoulder main groove 53 in the tire width direction, and after reaching the maximum protrusion amount E64, the tire width increases. It preferably decreases outward in the direction. Similarly, the amount of protrusion of the surface 65A of the second shoulder land portion 65 from the reference profile line PL0 increases outward from the second shoulder main groove 54 in the tire width direction, and after reaching the maximum protrusion amount E65, the tire It is preferred that it decreases outward in the width direction.

  Next, the reference profile line PL0 will be described with reference to FIG. The reference profile line PL0 is set for each of the target land portions 60. That is, the first reference profile line PL0 is set for the center land portion 61, the second reference profile line PL0 is set for the first middle land portion 62, and the third reference profile line PL0 is set for the second middle land portion 63. Is set, a fourth reference profile line PL0 is set for the first shoulder land portion 64, and a fifth reference profile line PL0 is set for the second shoulder land portion 65.

  In the following description using FIG. 10, reference contour line PL set for second middle land portion 63 will be described.

  As shown in FIG. 10, a second center main groove 52 and a second shoulder main groove 54 are provided on both sides of the second middle land portion 63. The second shoulder main groove 54 has an open end K1 and an open end K2. The second center main groove 52 has an open end K3 and an open end K4.

  The open end K1 is a boundary between the inner wall surface of the second shoulder main groove 54 and the surface 65A of the second shoulder land portion 65. The open end K2 is a boundary between the inner wall surface of the second shoulder main groove 54 and the surface 63A of the second middle land portion 63. The open end K3 is a boundary between the inner wall surface of the second center main groove 52 and the surface 63A of the second middle land portion 63. The open end K4 is a boundary between the inner wall surface of the second center main groove 52 and the surface 61A of the center land portion 61.

  That is, the open end of the circumferential main groove 50 refers to the vertex of a corner formed by the inner wall surface of the circumferential main groove 50 and the surface 60A (ground contact surface, tread surface) of the land portion 60. In addition, when the corner formed by the inner wall surface of the circumferential main groove 50 and the surface 60A of the land portion 60 is chamfered, the open end of the circumferential main groove 50 corresponds to the chamfered surface and the surface 60A. Point of intersection.

  The reference profile line PL0 for the second middle land portion 63 is four of the two circumferential main grooves 50 (the second shoulder main groove 54 and the second center main groove 52) provided on both sides of the second middle land portion 63. Of the two opening ends K1, K2, K3, and K4, a first opening end K2 and a second opening end K3 arranged at the boundary with the surface 63A of the second middle land portion 63, and the remaining two ends. Of the four opening ends K1, K4, the third opening end K4 close to the tire center CL, which is the center of the tread portion 10 in the tire width direction, from the four opening ends K1, K2, K3, K4. Is also an arc drawn with the maximum radius of curvature whose center is located inside the tire radial direction.

  The reference profile line PL0 for the second middle land portion 63 has been described above. For each of the center land portion 61, the first middle land portion 62, the first shoulder land portion 64, and the second shoulder land portion 65, the reference profile line PL0 is set in the same manner as described above.

  Note that the reference profile line PL0 may be an arc-shaped line that passes through all of the open ends of the five circumferential main grooves 50.

  FIG. 11 is a diagram illustrating an example of a contact shape of the tire 1 according to the present embodiment. FIG. 12 is a diagram showing a contact shape of a tire according to a conventional example. The measurement conditions for the contact shape of the tire 1 according to the present embodiment and the measurement conditions for the contact shape of the tire according to the conventional example are the same. In the tread pattern of the tire according to the conventional example, the tread profile line of the tire according to the conventional example matches the reference profile line. That is, the surface of the land portion of the conventional tire does not protrude from the reference profile line. The tread pattern of the conventional tire is the same as the tread pattern 40 described with reference to FIG. As shown in FIG. 12, the contact length of the land portion of the conventional tire is short. As shown in FIG. 11, it can be seen that the contact length of the land portion 60 (61, 62, 63, 64, 65) of the tire 1 according to the present embodiment is long, and the contact area is increased.

  As described above, according to the present embodiment, the tread pattern 40 is designed based on the variable pitch method, and a pitch variation structure having a plurality of pattern elements having different pitch lengths is employed in the tread portion 10, Generation of noise during running of the tire 1 is suppressed. Focusing on the pitch ratio Pin of the first shoulder land portion 64 disposed most inside the vehicle and the pitch ratio Pout of the second shoulder land portion 65 disposed most outside the vehicle, the condition of the expression (1) is satisfied. Thus, by forming the tread pattern 40, it is possible to achieve both the steering stability performance and the noise suppression performance of the tire 1. When the pitch ratio is small, the variation in the rigidity of the tread portion 10 in the tire circumferential direction in the running of the tire 1 becomes small, so that the steering stability performance is improved. On the other hand, when the pitch ratio is large, the noise frequency is dispersed, so that the noise suppression performance is improved. In order to improve the steering stability performance of the tire 1, it is better to increase the rigidity of the second shoulder land portion 65 of the tire 1 outside the vehicle than to increase the rigidity of the first shoulder land portion 64 of the tire 1 inside the vehicle. It is effective. On the other hand, in order to improve the noise reduction performance for the user in the driver's cab, the noise generated on the second shoulder land portion 65 of the tire 1 on the outside of the vehicle is reduced more than the noise on the first tire 1 on the inside of the vehicle. It is more effective to reduce noise generated in the shoulder land portion 64. Therefore, by increasing the pitch ratio Pin of the first shoulder land portion 64 and decreasing the pitch ratio Pout of the second shoulder land portion 65, it is possible to achieve both the steering stability performance and the noise suppression performance of the tire 1.

  According to the present embodiment, each of the surface 64A of the first shoulder land portion 64 and the surface 65A of the second shoulder land portion 65 protrudes outward from the reference profile line PL0 in the tire radial direction. Therefore, the first shoulder land portion 64 is prevented from being deformed such that the center portion in the tire width direction is depressed at the first and second landing portions in the tire circumferential direction in the contact region of the first shoulder land portion 64, and the first shoulder land portion 64 has a uniform contact shape. Be transformed into Similarly, the ground shape of the second shoulder land portion 65 is also made uniform. Therefore, the steering stability performance and uneven wear resistance performance of the tire 1 can be improved.

  According to the present embodiment, the average pitch length Lave of the second shoulder land portions 65 is longer than the average pitch length Laave of the first shoulder land portions 64. Thereby, the steering stability performance of the tire 1 can be further improved. For example, when the vehicle 500 corners leftward, the contact pressure and the lateral force received from the road surface RS by the second shoulder land portion 65 of the right tire 1R mounted on the right side of the vehicle 500 increase. By increasing the average pitch length Lbave of the second shoulder land portion 65, the second shoulder land portion 65 can withstand a large contact pressure and lateral force. Therefore, the steering stability performance of the tire 1 is improved. The same applies to the left tire 1L when the vehicle 500 corners rightward.

  According to the present embodiment, the pitch ratio Pin is 1.4 or more and 1.7 or less, and the pitch ratio Pout is 1.2 or more and 1.5 or less. If the pitch ratio Pin is smaller than 1.4, sufficient noise reduction performance may not be obtained. When the pitch ratio Pin is larger than 1.7, sufficient uneven wear resistance may not be obtained. In addition, when the pitch ratio Pout is smaller than 1.2, the possibility of generating noise increases. When the pitch ratio Pout is larger than 1.5, there is a possibility that the steering stability performance is deteriorated. By setting the pitch ratio Pin to 1.4 or more and 1.7 or less and the pitch ratio Pout to 1.2 or more and 1.5 or less, steering stability performance, noise reduction performance, and uneven wear resistance performance can be obtained.

  In the present embodiment, the maximum protrusion amount E61 of the surface 61A of the center land portion 61 from the reference profile line PL0 is not less than 0.2 [mm] and not more than 0.5 [mm]. Thereby, uneven wear is suppressed and steering stability performance is improved.

  In the present embodiment, the maximum protrusion amount E64 of the surface 64A of the first shoulder land portion 64 from the reference profile line PL0, and the maximum protrusion amount E65 of the surface 65A of the second shoulder land portion 65 from the reference profile line PL0. Is not less than 0.3 [mm] and not more than 1.0 [mm]. Thereby, uneven wear is suppressed and steering stability performance is improved.

  In the present embodiment, the pitch lengths La of the pattern elements 84 of the first shoulder land portions 64 are different from each other, and the pitch lengths Lb of the pattern elements 85 of the second shoulder land portions 65 are different from each other. The pitch lengths of the pattern elements 81 of the center land portions 61 may be different, the pitch lengths of the pattern elements 82 of the first middle land portions 62 may be different, and the pattern elements 83 of the second middle land portions 63 may be different. May have different pitch lengths.

  For example, when the surface 62A of the first middle land portion 62 and the surface 63A of the second middle land portion 63 each protrude outward in the tire radial direction from the reference profile line PL0, a plurality of patterns of the first middle land portion 62 are provided. The pitch ratio indicating the ratio between the longest pitch length and the shortest pitch length of the elements 82 is equal to the pitch ratio Pin of the first shoulder land portion 64, and the longest pitch of the plurality of pattern elements 83 of the second middle land portion 63 The tread pattern 40 may be designed so that the pitch ratio indicating the ratio between the length and the shortest pitch length is equal to the pitch ratio Pout of the second shoulder land portion 65. Thereby, the steering stability performance and the noise reduction performance can be further improved.

  In this embodiment, not only the surface 64A of the first shoulder land portion 64 and the surface 65A of the second shoulder land portion 65, but also the surface 61A of the center land portion 61, the surface 62A of the first middle land portion 62, and the The surface 63A of the second middle land portion 63 also protrudes outward in the tire radial direction from the reference profile line PL0. At least one of the surface 61A of the center land portion 61, the surface 62A of the first middle land portion 62, and the surface 63A of the second middle land portion 63 does not have to project outward from the reference profile line PL0 in the tire radial direction. For example, the surface 61A of the center land portion 61 projects outward in the tire radial direction from the reference profile line PL0, and the surface 62A of the first middle land portion 62 and the surface 63A of the second middle land portion 63 match the reference profile line PL0. Is also good.

  In the present embodiment, four circumferential main grooves 50 are provided, and five land portions 60 are provided. Three circumferential main grooves 50 may be provided, and four land portions 60 may be provided. Two circumferential main grooves 50 may be provided, and three land portions 60 may be provided. Also in this case, the pitch ratio Pin of the land portion 60 closest to the one contact end T1 of the tread portion 10 and the pitch ratio Pout of the land portion 60 closest to the other contact end T2 of the tread portion 10 are expressed by the formula (1). Are satisfied, and the surface 60A of each of the land portions 60 protrudes outward from the reference profile line PL0 in the tire radial direction, so that both the steering stability performance and the noise reduction performance can be achieved.

<Second embodiment>
A second embodiment will be described. In the following description, the same or equivalent components as those of the above-described embodiment are denoted by the same reference numerals, and the description thereof will be simplified or omitted.

  FIG. 13 is a diagram illustrating an example of a tread profile line and a reference profile line according to the present embodiment. FIG. 14 is a diagram illustrating a tread profile line of the center land portion 61 among tread profile lines according to the present embodiment. FIG. 13 and FIG. 14 show meridional sections of the tread portion 10 passing through the rotation axis AX of the tire 1.

  As shown in FIG. 13, the first center main groove 51 has two opening ends K5 and K6 in the tire width direction. The second center main groove 52 has two opening ends K3 and K4 in the tire width direction. The first shoulder main groove 53 has two opening ends K7 and K8 in the tire width direction. The second shoulder main groove 54 has two open ends K1 and K2 in the tire width direction.

  In the present embodiment, the reference profile line PL0 is defined so as to pass through all the open ends K3, K4, K5, K6 of the first and second center main grooves 51, 52. In a meridional section of the tread portion 10 passing through the rotation axis AX of the tire 1, the reference profile line PL0 has an arc shape.

  The surface 61A of the center land portion 61 projects outward in the tire radial direction from the reference profile line PL0.

  Of the two open ends K5 and K6 of the first center main groove 51, one open end K6 near one of the ground ends T1, two open ends K7 and K8 of the first shoulder main groove 53, and An arc-shaped first tread profile line PL1 including a surface 62A of the first middle land portion 62 and a surface 64A of the first shoulder land portion 64 protrudes outward in the tire radial direction from the reference profile line PL0. The first tread profile line PL1 is a common profile line of the first center main groove 51, the first middle land portion 62, and the first shoulder land portion 64. That is, the contour of the surface 62A of the first middle land portion 62 and the contour of the surface 64A of the first shoulder land portion 64 are arranged in the same curve.

  One of the two open ends K3 and K4 of the second center main groove 52, one open end K3 near the other ground end T2, the two open ends K1 and K2 of the second shoulder main groove 54, An arc-shaped second tread profile line PL2 including a surface 63A of the second middle land portion 63 and a surface 65A of the second shoulder land portion 65 protrudes outward in the tire radial direction from the reference profile line PL0. The second tread profile line PL2 is a common profile line for the second center main groove 52, the second middle land portion 63, and the second shoulder land portion 65. That is, the contour of the surface 63A of the second middle land portion 63 and the contour of the surface 65A of the second shoulder land portion 65 are arranged in the same curve.

  As described above, the reference profile line PL0 has an arc shape passing through the opening ends K3, K4, K5, and K6. Assuming that the section height of the tire indicating the distance between the innermost inner end and the outermost outer end of the tire 1 in the tire radial direction is SH, the radius of curvature of the reference profile line PL0 is 5 × SH or more and 20 × It is set in the range of SH or less. The center of the reference profile line PL0 is defined on the tire equatorial plane inward of the reference profile line PL0 in the tire radial direction.

  The first tread profile line PL1 has an arc shape passing through the open ends K6, K7, K8, the surface 62A of the first middle land portion 62, and the surface 64A of the first shoulder land portion 64. Further, the first tread profile line PL1 passes through a point P1 defined on the outer side in the tire width direction from the ground contact end T1. The point P1 is defined at a position outside the tread edge T1 in the tire width direction by a distance of 3% or more and 5% or less of the tread contact width TW. The radius of curvature of the first tread profile line PL1 is smaller than the radius of curvature of the reference profile line PL0. The center of the first tread profile line PL1 is defined inside the first tread profile line PL1 in the tire radial direction and on the tire equatorial plane.

  The second tread profile line PL2 has an arc shape passing through the open ends K1, K2, K3, the surface 63A of the second middle land portion 63, and the surface 65A of the second shoulder land portion 65. Further, the second tread profile line PL2 passes through a point P2 defined outward from the ground contact end T2 in the tire width direction. The point P2 is defined at a position on the outer side in the tire width direction from the ground end T2 by a distance of 3% to 5% of the tread ground width TW. The radius of curvature of the second tread profile line PL2 is smaller than the radius of curvature of the reference profile line PL0. The center of the second tread profile line PL2 is located radially inward of the second tread profile line PL2 on the tire equatorial plane.

  Also in the present embodiment, the pitch ratio Pin of the first shoulder portion 64 is larger than the pitch ratio Pout of the second shoulder land portion 65. Also, the pitch ratio of the first middle land portion 62 and the pitch ratio Pin of the first shoulder land portion 64 are equal, and the pitch ratio of the second middle land portion 63 and the pitch ratio of the second shoulder land portion 65 are equal.

  Also in the present embodiment, the pitch ratio Pin is 1.4 or more and 1.7 or less, and the pitch ratio Pout is 1.2 or more and 1.5 or less.

  As shown in FIG. 14, the maximum protrusion amount E61 of the surface 61A of the center land portion 61 from the reference profile line PL0 is not less than 0.2 [mm] and not more than 0.5 [mm]. It is more preferable that the maximum protrusion amount E61 is not less than 0.3 [mm] and not more than 0.4 [mm].

  As shown in FIG. 13, the maximum protrusion amount E1 of the first tread profile line PL1 from the reference profile line PL0 and the maximum protrusion amount E2 of the second tread profile line PL2 from the reference profile line PL0 are 0.6. It is not less than [mm] and not more than 2.0 [mm]. The maximum protrusion amount E2 of the second tread profile line PL2 is larger than the maximum protrusion amount E1 of the first tread profile line PL1. It is more preferable that the maximum protrusion amounts E1 and E2 be 0.9 [mm] or more and 1.7 [mm] or less.

  FIG. 15 is a diagram illustrating an example of a contact shape of the tire 1 according to the present embodiment. Note that the measurement conditions for the contact shape described with reference to FIGS. 11 and 12 are the same as the measurement conditions for the contact shape of the tire 1 shown in FIG. As shown in FIG. 15, also in the present embodiment, it can be seen that the contact length of the land portion 60 (61, 62, 63, 64, 65) of the tire 1 is long and the contact area is increased.

  As described above, also in the present embodiment, the surface 61A of the center land portion 61, the surface 62A of the first middle land portion 62, the surface 63A of the third middle land portion 63, the surface 64A of the first shoulder land portion 64, And the surface 65A of the second shoulder land portion 65 protrudes outward from the reference profile line PL0 in the tire radial direction, and the pitch ratio Pin and the pitch ratio Pout satisfy the conditions of the expression (1). The reduction performance and the uneven wear resistance performance are improved.

  In the present embodiment, the first tread profile line PL1 and the second tread profile line are defined, and the surface 61A of the center land portion 61, the first tread profile line PL1, and the second tread profile line PL2 are respectively It protrudes outward from the reference profile line PL0 in the tire radial direction. By defining the first tread profile line PL1 and the second tread profile line, the contact property in the tire width direction is improved. That is, since the first middle land portion 62 and the first shoulder land portion 64 are defined by the single first tread profile line PL1, the distance between the first middle land portion 62 and the first shoulder land portion 64 is increased. The contact property changes smoothly in the tire width direction. Therefore, in particular, the ground contact property of the first shoulder land portion 64 is improved. The same applies to the second middle land portion 63 and the second shoulder land portion 65.

  The ground contact property of the first middle land part 62 and the first shoulder land part 64 is improved, and the ground contact property of the second middle land part 63 and the second shoulder land part 65 is improved. Steering stability is further improved, and uneven wear resistance is further improved.

  In the present embodiment, the maximum protrusion amount E61 of the surface 61A of the center land portion 61 from the reference profile line PL0 is determined to be 0.2 [mm] or more and 0.5 [mm] or less. By setting the maximum protrusion amount E61 to 0.2 [mm] or more, the contact pressure at the center in the tire width direction and the contact pressure at both ends in the tire width direction can be made more uniform for the center land portion 61. . As a result, the grip force between the center land portion 61 and the road surface RS is increased, so that the steering performance of the vehicle 500 when traveling straight ahead is improved, and the steering stability performance including the straight traveling performance is further improved.

  In addition, when the maximum protrusion amount E61 is set to 0.5 [mm] or less, the protrusion amount of the center land portion 61 outward in the tire radial direction at the center portion in the tire width direction is suppressed. Thereby, the uneven wear resistance performance is further improved.

  In the present embodiment, the maximum protrusion amount E1 of the first tread profile line PL1 from the reference profile line PL0 and the maximum protrusion amount E2 of the second tread profile line PL2 from the reference profile line PL0 are 0.6 [ mm] to 2.0 [mm], and the maximum protrusion amount E2 of the second tread profile line PL2 is larger than the maximum protrusion amount E1 of the first tread profile line PL1.

  By setting the maximum protrusion amounts E1 and E2 to be equal to or greater than 0.6 [mm], the tires are provided for each of the first and second middle land portions 62 and 63 and the first and second shoulder land portions 64 and 65. The contact pressure at the center in the width direction and the contact pressure at both ends in the tire width direction can be made more uniform. Thereby, the grip force between each of the first and second middle land portions 62 and 63 and the first and second shoulder land portions 64 and 65 and the road surface RS increases, so that the steering performance of the vehicle 500 when traveling straight ahead is improved. The steering stability performance including the straight running performance is further improved.

  Also, by setting the maximum protrusion amounts E1 and E2 to be equal to or less than 2.0 [mm], the first and second middle land portions 62 and 63 and the first and second shoulder land portions 64 and 65 are respectively provided. In addition, the amount of protrusion at the center in the tire width direction outward in the tire radial direction is suppressed. Thereby, the uneven wear resistance performance is further improved.

  Further, since the maximum protrusion amount E2 of the second tread profile line PL2 is larger than the maximum protrusion amount E1 of the first tread profile line PL1, uneven wear resistance is further improved. The second middle land portion 63 and the second shoulder land portion 65 forming the second tread profile line PL2 are arranged outside the vehicle. For example, when the vehicle 500 is cornering in the left direction, the ground pressure and lateral force that the second middle land portion 63 and the second shoulder land portion 65 of the right tire 1R mounted on the right side of the vehicle 500 receive from the road surface RS are large. Become. The same applies to the left tire 1L when the vehicle 500 corners rightward. Therefore, the wear amount of the second middle land portion 63 and the second shoulder land portion 65 is larger than the wear amount of the first middle land portion 62 and the first shoulder land portion 64 arranged inside the vehicle. By making the maximum protrusion amount E2 of the second tread profile line PL2 larger than the maximum protrusion amount E1 of the first tread profile line PL1, even if the second middle land portion 63 and the second shoulder land portion 65 are worn, An increase in the difference between the distance between the rotation axis AX and the surface of the tread portion 10 outside the vehicle and the distance between the rotation axis AX and the surface of the tread portion 10 inside the vehicle is suppressed. Thereby, the steering stability performance and the uneven wear resistance performance are further improved.

  According to the present embodiment, the curvature of the reference profile line PL0 is defined as SH, where the tire section height indicating the distance between the innermost inner end and the outermost outer end of the tire 1 in the tire radial direction is SH. The radius is set in a range from 5 × SH to 20 × SH. By setting the curvature radius of the reference profile line PL0 to be five times or more the tire cross-section height SH, it is possible to suppress the reference profile line PL0 from excessively protruding outward in the tire radial direction. This suppresses the curvature radius of the first tread profile line PL1 and the curvature radius of the second tread profile line PL2 from becoming excessively small, and suppresses a decrease in the contact property of the land portion 60. Further, by setting the radius of curvature of the reference profile line PL0 to be equal to or less than 20 times the tire sectional height SH, the reference profile line PL0 has a shape that appropriately protrudes outward in the tire radial direction. Thereby, the radius of curvature of the first tread profile line PL1 and the radius of curvature of the second tread profile line PL2 are appropriately set, and a decrease in the contact property of the land portion 60 is suppressed.

<Example>
With respect to the tire 1 according to the present embodiment, an evaluation test of steering stability performance, noise reduction performance, and uneven wear resistance performance was performed.

  Tires of Examples 1 to 4 having a tire size of 235 / 40ZR18 (95Y), having the tread pattern 40 shown in FIG. 4, and having the first and second tread profile lines PL1 and PL2 shown in FIG. 1 was produced. In addition, the maximum protrusion amount E61 [mm] of the surface 61A of the center land portion 61 of the tire 1 of the first to fourth embodiments, the maximum protrusion amount E1 [mm] of the first tread profile line PL1, and the second tread profile line PL2. The maximum protrusion amount E2 [mm], the pitch ratio Pin of the first shoulder land portion 64, and the pitch ratio Pout of the second shoulder land portion 65 are as shown in Table 1 below.

  The tires according to the conventional example and the comparative example have the same tread pattern as the tread pattern 40 illustrated in FIG. 4, and have the same tire size as those of the first to fourth examples.

  In the tire according to the conventional example, the surfaces of the plurality of land portions do not protrude from the reference profile line PL0. Further, the pitch ratio Pin and the pitch ratio Pout of the tire according to the conventional example are equal.

  In the tire according to the comparative example, although the surface of the center land portion, the first tread profile line, and the second tread profile line project from the reference profile line PL0, the pitch ratio Pin and the pitch ratio Pout are equal.

  In the tire according to the first embodiment, the surface of the center land portion, the first tread profile line, and the second tread profile line protrude from the reference profile line PL0. Further, the pitch ratio Pin is larger than the pitch ratio Pout. The pitch ratio Pout is 1.2 and the pitch ratio Pin is 1.8. The maximum protrusion amount of the first tread profile line is equal to the maximum protrusion amount of the second tread profile line.

  In the tire according to the second embodiment, the surface of the center land portion, the first tread profile line, and the second tread profile line protrude from the reference profile line PL0. Further, the pitch ratio Pin is larger than the pitch ratio Pout. The pitch ratio Pout is 1.1 and the pitch ratio Pin is 1.6. Note that the maximum protrusion amount of the second tread profile line is smaller than the maximum protrusion amount of the first tread profile line.

  In the tire according to the third embodiment, the surface of the center land portion, the first tread profile line, and the second tread profile line protrude from the reference profile line PL0. Further, the pitch ratio Pin is larger than the pitch ratio Pout. The pitch ratio Pout is 1.1 and the pitch ratio Pin is 1.6. The maximum protrusion amount of the second tread profile line is larger than the maximum protrusion amount of the first tread profile line.

  In the tire according to Example 4, the surface of the center land portion, the first tread profile line, and the second tread profile line protrude from the reference profile line PL0. Further, the pitch ratio Pin is larger than the pitch ratio Pout. The pitch ratio Pout is 1.2, and the pitch ratio Pin is 1.4. The maximum protrusion amount of the first tread profile line is equal to the maximum protrusion amount of the second tread profile line.

  In the tire according to Example 5, the surface of the center land portion, the first tread profile line, and the second tread profile line protrude from the reference profile line PL0. Further, the pitch ratio Pin is larger than the pitch ratio Pout. The pitch ratio Pout is 1.2 and the pitch ratio Pin is 1.6. The maximum protrusion amount of the first tread profile line is equal to the maximum protrusion amount of the second tread profile line.

  Each of the tires 1 according to Examples 1, 2, 3, 4 and 5, the tire according to the conventional example, and the tire according to the comparative example were assembled on a rim of 18 × 8.5J to form an inner pressure of 230 [kPa]. And mounted on a sedan-type test vehicle with a displacement of 2000 [cc], and evaluated for steering stability performance, noise reduction performance, and uneven wear resistance performance.

  In the evaluation test of steering stability performance, a test vehicle equipped with tires was run on a dry road surface, and a sensory evaluation of vehicle stability during straight running and turning was performed. Then, based on the evaluation result, an index evaluation was performed using Conventional Example 1 as a reference (100). This evaluation indicates that the larger the index, the better the steering stability performance.

  In the noise reduction performance evaluation test, a test vehicle travels on a test course having a rough road surface at 100 [km / h], and a test driver performs a sensory evaluation on vehicle interior noise. This evaluation is performed by index evaluation using the conventional example as a reference (100), and the larger the numerical value, the better the noise reduction performance.

  In the evaluation test of the uneven wear resistance performance, the vehicle traveled 1000 [km] on a dry road surface, and the wear amount of the center land portion 61 and the wear amounts of the first and second shoulder land portions 64 and 65 were measured. As the wear amount of the shoulder land portion, an average value of the wear amount of the first shoulder land portion 64 and the wear amount of the second shoulder land portion 65 was calculated. Then, the ratio between the wear amount of the center land portion 61 and the wear amount of the shoulder land portion was calculated. Then, based on the calculation result, an index evaluation was performed using Conventional Example 1 as a reference (100). This evaluation indicates that the larger the index, the better the uneven wear resistance performance.

  According to Table 1, the steering stability of the tires 1 according to Examples 1 to 5 belonging to the technical scope of the present invention is higher than that of the tire according to the conventional example which does not belong to the technical scope of the present invention. It can be seen that the noise reduction performance and the uneven wear resistance performance are excellent.

  In the tire 1 according to the second embodiment, the maximum protrusion amount of the second tread profile line is smaller than the maximum protrusion amount of the first tread profile line. On the other hand, in the tire 1 according to the third embodiment, the maximum protrusion amount of the second tread profile line is larger than the maximum protrusion amount of the first tread profile line. It can be seen that the tire 1 according to Example 3 is superior in uneven wear resistance to the tire 1 according to Example 2.

  In the tire 1 according to the first embodiment, the pitch ratio Pin is larger than 1.7. In the tires 1 according to Examples 2 and 3, the pitch ratio Pout is smaller than 1.2. On the other hand, the tires 1 according to Examples 4 and 5 satisfy the condition that the pitch ratio Pin is 1.4 or more and 1.7 or less and the pitch ratio Pout is 1.2 or more and 1.5 or less. It can be seen that the tires 1 according to Examples 4 and 5 are more excellent in steering stability performance, noise reduction performance, and uneven wear resistance performance.

Reference Signs List 1 tire 2 carcass ply layer 3 belt layer 3A first belt ply 3B second belt ply 5 bead portion 6 tread rubber 7 side portion 8 side rubber 10 tread portion 16 bead core 22 bead filler rubber 24 rim cushion rubber 26 inner liner rubber 28 bead reinforcement Material 30 Belt cover layer 40 Tread pattern 50 Circumferential main groove 51 First center main groove 52 Second center main groove 53 First shoulder main groove 54 Second shoulder main groove 60 Land portion 60A Surface 61 Center land portion 61A Surface 62 1st middle land portion 62A surface 63 2nd middle land portion 63A surface 64 1st shoulder land portion 64A surface 65 2nd shoulder land portion 65A surface 70 lug groove 71 inclined groove 72 inclined groove 73 inclined groove 74 inclined groove 75 inclined groove 81 pattern Element 82 Pattern element 8 Pattern elements 84 pattern elements 85 pattern elements 500 vehicle 501 traveling device 502 body 503 engine 504 wheel 505 axle 506 steering device 507 brake device 600 display unit AX rotational axis CL tire center RS road T1 ground terminal T2 ground terminal TW tread width

Claims (6)

A pneumatic tire that is rotatable around a rotation axis while being mounted on a vehicle,
A tread portion on which a tread pattern is formed,
A side portion provided on both sides in the tire width direction of the tread portion and having a display portion indicating a mounting direction with respect to the vehicle,
A plurality of the tread portions are provided in a tire width direction, each of which is defined by a circumferential main groove extending in a tire circumferential direction and the circumferential main groove, and a first closest to one ground end of the tread portion. A shoulder land portion, and a second shoulder land portion closest to the other ground contact end,
The first shoulder land portion is mounted on the vehicle such that the first shoulder land portion is disposed on the vehicle width direction inner side of the vehicle than the second shoulder land portion,
In a cross section of the tread portion passing through the rotation axis, an arc-shaped reference profile line passing through at least three opening ends of the circumferential main groove is defined,
The surface of the first shoulder land portion and the surface of the second shoulder land portion respectively protrude outward in the tire radial direction from the reference profile line,
Each of the first shoulder land portion and the second shoulder land portion has a plurality of pattern elements having different pitch lengths,
The pitch ratio indicating the ratio between the longest pitch length and the shortest pitch length among the plurality of pattern elements of the first shoulder land portion is Pin,
Pout is a pitch ratio indicating a ratio between the longest pitch length and the shortest pitch length among the plurality of pattern elements of the second shoulder land portion.
And when
Pin> Pout,
Satisfy the conditions,
The average pitch length of the second shoulder land portion is longer than the average pitch length of the first shoulder land portion,
Pneumatic tire. The circumferential main groove includes a center main groove provided one by one on each side of the tire width direction with respect to the center in the tire width direction, and a shoulder main groove provided outside each of the center main grooves in the tire width direction. Including
The tread portion includes a center land portion provided between two center main grooves, a first middle land portion provided between the center land portion and the first shoulder land portion, and the center land portion. A second middle land portion provided between the second shoulder land portion,
The surface of the first middle land portion and the surface of the second middle land portion respectively protrude outward in the tire radial direction from the reference profile line,
The pitch ratio of the first middle land portion is equal to the pitch ratio of the first shoulder land portion,
The pitch ratio of the second middle land portion is equal to the pitch ratio of the second shoulder land portion,
The pneumatic tire according to claim 1 . The reference profile line is defined so as to pass through all the open ends of the two center main grooves,
The surface of the center land portion protrudes outward in the tire radial direction from the reference profile line,
One open end of the two open ends of the first center main groove close to one of the ground ends, two open ends of the first shoulder main groove, and a surface of the first middle land portion; An arc-shaped first tread profile line including the surface of the first shoulder land portion projects radially outward from the reference profile line,
One opening end of the two opening ends of the second center main groove that is closer to the other ground contact end, two opening ends of the second shoulder main groove, and a surface of the second middle land portion; An arc-shaped second tread profile line including the surface of the second shoulder land portion projects radially outward from the reference profile line,
The pneumatic tire according to claim 2 . The maximum protrusion amount of the surface of the center land portion from the reference profile line is not less than 0.2 [mm] and not more than 0.5 [mm].
The pneumatic tire according to claim 3 . The maximum protrusion amount of the first tread profile line from the reference profile line and the maximum protrusion amount of the second tread profile line from the reference profile line are not less than 0.6 [mm] and not more than 2.0 [mm]. And
The maximum protrusion amount of the second tread profile line is larger than the maximum protrusion amount of the first tread profile line,
The pneumatic tire according to claim 3 or 4 . The pitch ratio Pin is 1.4 or more and 1.7 or less,
The pitch ratio Pout is 1.2 or more and 1.5 or less;
The pneumatic tire according to any one of claims 1 to 5 .

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