JP2011093388A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire improved in controllability and stability and drainage performance, while maintaining uneven-wear resistance excellent. <P>SOLUTION: At least four pieces of main grooves 1a-1d extending in the tire circumferential direction are arranged in a tread part T which is asymmetrical between both sides of a tire equator CL, plural rows of land parts 10-50 are partitioned by the main grooves 1a-1d, plural pieces of inclined grooves 31, 21 inclined with respect to the tire circumferential direction are arranged at the center land part 30 and the middle land part 20 positioned on the vehicle inner side, one ends of respective inclined grooves 31, 21 open to the main groove 1b positioned between the land parts 30, 20 while the other ends are ended inside the land parts 30, 20, bottomed parts 21a, 31a are formed on the end side of at least one of the inclined grooves 31, 21, start points of the bottomed parts 21a, 31a are set at positions of 10-30% of the length of respective inclined grooves 21, 31 from open ends of respective inclined grooves 21, 31, and the depth of respective inclined grooves 21, 31 at the bottomed parts 21a, 31a is 20-40% of the depth of the main groove 1b. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pneumatic tire having a tread pattern that is asymmetrical on both sides of the tire equator, with the orientation of the tire front and back being specified when the vehicle is mounted, and more specifically, steering stability, drainage performance, and resistance to resistance on dry road surfaces. The present invention relates to a pneumatic tire that can achieve both uneven wear properties.

  A pneumatic tire usually includes a plurality of main grooves extending in the tire circumferential direction in a tread portion. These main grooves have a relatively large cross-sectional area and support drainage performance. Moreover, it is possible to further improve drainage performance by providing a plurality of lug grooves extending in the tire width direction in the tread portion and communicating these lug grooves with the main groove.

  However, when the land portion partitioned by the main groove is subdivided into a large number of blocks by the lug grooves, there is a disadvantage that not only the steering stability on the dry road surface is lowered, but also that the blocks are likely to be unevenly worn. In contrast, a plurality of inclined grooves are provided in the intermediate land portion located between the center land portion and the shoulder land portion, and one end of each inclined groove is opened to the main groove on the outer side in the tire width direction while the other end is opened. It is proposed to terminate in the middle land portion (see, for example, Patent Documents 1 to 4).

  When such a one-end closed type inclined groove is provided in the intermediate land portion located between the center land portion and the shoulder land portion, it is possible to suppress the occurrence of uneven wear, but the effect of improving drainage performance is The current situation is not always sufficient. In addition, providing an inclined groove in the intermediate land portion is also a factor of reducing the steering stability on the dry road surface.

JP 2004-262212 A JP 2004-17863 A JP 2006-123706 A International Publication No. WO2006 / 059560 Pamphlet

  An object of the present invention is to provide a pneumatic tire that can improve steering stability and drainage performance on a dry road surface while maintaining good uneven wear resistance.

  In order to achieve the above object, a pneumatic tire according to the present invention is a pneumatic tire having a tread pattern that is asymmetric on both sides of the tire equator, with the tire front and back mounting orientations specified when the vehicle is mounted. And at least four main grooves extending in the direction. The main grooves define a plurality of rows of land portions, and a plurality of first grooves that are inclined with respect to the tire circumferential direction in the center land portion located on the tire equator. An inclined groove is provided, and a plurality of second inclined grooves that are inclined in the same direction as the first inclined groove are provided in an inner intermediate land portion located on the vehicle inner side of the center land portion, and one end of each first inclined groove is centered The other end is terminated in the center land portion while opening in the main groove located between the land portion and the inner intermediate land portion, and one end of each second inclined groove is positioned between the center land portion and the inner intermediate land portion. Opening in the main groove The other end is terminated in the inner intermediate land portion, and a bottom-up portion is formed in a region on the terminal end side of at least one of the first inclined groove and the second inclined groove, and the starting point of the bottom-up portion is inclined. It is set at a position of 10% to 30% of the length of each inclined groove from the opening end of the groove, and the depth of each inclined groove at the bottom raised portion is located between the center land portion and the inner intermediate land portion. It is characterized by being 20% to 40% of the depth of the groove.

  The present invention pays attention to a pneumatic tire having a tread pattern that is asymmetric on both sides of the tire equator, with the tire front and back mounting orientations specified when the vehicle is mounted. In addition, by skillfully combining the structure and the structure, it is possible to achieve a balance between steering stability on a dry road surface, uneven wear resistance, and drainage performance.

  That is, in the present invention, the center land portion is provided with a first-end-closed first inclined groove, while the inner intermediate land portion is provided with a one-end-closed-type second inclined groove inclined in the same direction as the first inclined groove. By opening one end of the first inclined groove and the second inclined groove into a common main groove located between the center land portion and the inner intermediate land portion, the drainage performance can be improved while maintaining good uneven wear resistance. It becomes possible to raise effectively. In addition, since the bottom raised portion is formed with a predetermined size in the region on the terminal side of at least one of the first inclined groove and the second inclined groove, the first inclined groove or the second inclined groove is provided. The rigidity of the land part can be secured and the driving stability on the dry road surface can be improved.

  In the present invention, a plurality of lug grooves extending in the tire width direction are provided in the shoulder land portions located on the vehicle inner side and the vehicle outer side, respectively, and these lug grooves are not communicated with the main groove adjacent to each shoulder land portion. It is preferable to do. In particular, the starting point on the tire equator side of the lug groove is preferably set to a position 5% to 20% of the width of the shoulder land portion from the tire equator side edge of the shoulder land portion. By preventing the lug groove on the shoulder land from communicating with the main groove, the shoulder land is secured, improving steering stability on dry roads, and suppressing heel and toe wear, improving uneven wear resistance. can do.

  The average inclination angle a with respect to the tire width direction of the lug groove arranged in the shoulder land portion inside the vehicle and the average inclination angle b with respect to the tire width direction of the lug groove arranged in the shoulder land portion outside the vehicle are 0 ° to 25 °, respectively. It is preferable that Thereby, the drainage capacity to the tire side can be enhanced, and further, the effect of reducing noise during tire rolling can be obtained.

  It is preferable that the number of sipes in the shoulder land portion outside the vehicle is smaller than the number of sipes in the shoulder land portion inside the vehicle. By relatively reducing the number of sipes in the shoulder land portion outside the vehicle, it is possible to improve the handling stability on the dry road surface.

  The average inclination angle α with respect to the tire circumferential direction of the contour line forming an acute angle with respect to the edge of the center land portion of the first inclined groove is 25 ° to 50 °, and is acute with respect to the edge of the inner intermediate land portion of the second inclined groove. It is preferable that the average inclination angle β of the contour line forming the tire circumferential direction is 20 ° to 40 °. The drainage performance is improved by making the average inclination angles α, β of the first inclined groove and the second inclined groove smaller than the respective upper limit values, and the uneven wear resistance is improved by making them larger than the respective lower limit values. it can.

  The average tire inclination angle α with respect to the tire circumferential direction of the contour line forming an acute angle with respect to the edge of the center land portion of the first inclined groove and the tire periphery of the contour line forming an acute angle with respect to the edge of the inner intermediate land portion of the second inclined groove. The relationship with the average inclination angle β with respect to the direction is preferably α> β. Thereby, drainage performance can be improved, ensuring the rigidity of a center land part.

  The inclination angle of the contour line forming an acute angle with respect to the edge of the center land portion of the first inclined groove with respect to the tire circumferential direction is gradually decreased from the opening end of the first inclined groove to at least a central position in the groove length direction, and the second inclined groove It is preferable that the inclination angle with respect to the tire circumferential direction of the contour line forming an acute angle with respect to the edge of the inner middle land portion of the inner slope is gradually reduced from the opening end of the second inclined groove to at least the center position in the groove length direction. Thereby, the outstanding drainage performance can be exhibited.

  The minimum distance γ1 from the edge on the side opposite to the edge where the first inclined groove of the center land portion is open to the first inclined groove is 10% to 40% of the width of the center land portion, The minimum distance γ2 from the edge on the side opposite to the edge on which the second inclined groove opens to the second inclined groove is preferably 10% to 40% of the width of the inner intermediate land portion. The drainage performance can be improved by making the minimum distances γ1, γ2 of the first inclined groove and the second inclined groove smaller than the respective upper limit values, and the uneven wear resistance can be improved by making the minimum distances larger than the respective lower limit values. .

  It is preferable to provide a plurality of chamfered portions on the edge of the center land portion outside the vehicle. Thereby, uneven wear resistance can be improved. Here, in order to obtain the effect of improving uneven wear resistance, the maximum width of the chamfered portion is 10% to 30% of the width of the center land portion, and the maximum depth of the chamfered portion is determined from the wear indicator of the main groove. It is preferable that the maximum width position of the chamfered portion is arranged between the end of the pair of inclined grooves adjacent to the tire circumferential direction and the open end.

  It is preferable that the outer intermediate land portion located on the vehicle outer side of the center land portion has a rib structure continuous in the tire circumferential direction. Thereby, the cornering property can be improved by making up for a decrease in rigidity caused by the first inclined groove and the second inclined groove provided to improve drainage performance.

  Furthermore, in the present invention, the groove area ratio of the entire ground contact area of the tread portion is 25% to 40%, and the groove area ratio in the outer ground contact area from the tire equator of the tread portion to the ground contact end outside the vehicle is It is preferable that the ratio of the groove area ratio in the inner ground contact region from the tire equator of the tread portion to the ground contact edge inside the vehicle is 1.03 to 1.20. As a result, it is possible to achieve both a high level of handling stability and drainage performance on a dry road surface.

It is an expanded view which shows the tread pattern of the pneumatic tire which consists of embodiment of this invention. It is a top view which expands and shows the center land part and inner side intermediate land part in FIG. It is sectional drawing which shows the state which notched the 1st inclination groove | channel or the 2nd inclination groove | channel along the groove width centerline. It is a perspective view which shows the principal part of a center land part. It is a side view which shows the principal part of a center land part.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. 1 shows a tread pattern of a pneumatic tire according to an embodiment of the present invention, FIG. 2 shows a center land portion and an inner intermediate land portion in FIG. 1, and FIG. 3 shows a first inclined groove or a second inclined groove. 2 shows a state cut along the center line of the groove width, shows a state where the first inclined groove in FIG. 2 is cut out at the center position, and FIGS. 3 and 4 show the main part of the center land portion, respectively. is there. The pneumatic tire of the present embodiment is designated with the tire front and back mounting orientation when the vehicle is mounted, and the vehicle outer side is indicated by OUT and the vehicle inner side is indicated by IN.

  As shown in FIG. 1, four main grooves 1a, 1b, 1c, and 1d extending in the tire circumferential direction are sequentially formed in the tread portion T from the vehicle inner side to the vehicle outer side, and these main grooves 1a to 1d form five rows. Land portions 10, 20, 30, 40, and 50 are partitioned. That is, the inner shoulder land portion 10 is located in the shoulder region inside the vehicle, the inner intermediate land portion 20 is located between the main grooves 1a and 1b, and the center land portion 30 is located on the tire equator CL between the main grooves 1b and 1c. The outer middle land portion 40 is located between the main grooves 1c and 1d, and the outer shoulder land portion 50 is located in the shoulder region outside the vehicle. The main grooves 1a to 1d have a groove width of 5.0 mm to 15.0 mm and a groove depth of 7.0 mm to 9.0 mm.

  A plurality of inclined grooves 31 (first inclined grooves) that are inclined with respect to the tire circumferential direction are formed in the center land portion 30 at intervals in the tire circumferential direction. One end of each inclined groove 31 opens into the main groove 1 b located between the center land portion 30 and the inner intermediate land portion 20, and the other end terminates in the center land portion 30. These inclined grooves 31 may have a constant groove width, but it is desirable that the groove width be narrower toward the end as shown in the figure. A raised portion 31 a is formed in a region on the terminal side of each inclined groove 31. As shown in FIG. 2, the starting portion of the bottom raised portion 31 has a shape that is recessed in an arc shape in order to prevent the occurrence of cracks. The center land portion 30 is formed with a plurality of sipes 32 communicating only with the main groove 1b, and the inclined grooves 31 and the sipes 32 are alternately arranged along the tire circumferential direction. Furthermore, a plurality of chamfered portions 33 are formed on the outer edge of the center land portion 30 on the vehicle. Each chamfered portion 33 has a pair of inclined surfaces forming a triangle. These chamfered portions 33 are disposed so as to be positioned between a pair of inclined grooves 31 adjacent to each other in the tire circumferential direction.

  A plurality of inclined grooves 21 (second inclined grooves) that are inclined in the same direction as the inclined grooves 31 are formed in the inner intermediate land portion 20 at intervals in the tire circumferential direction. One end of each inclined groove 21 opens into the main groove 1 b located between the center land portion 30 and the inner intermediate land portion 20, and the other end terminates in the inner intermediate land portion 20. These inclined grooves 21 may have a constant groove width, but it is desirable that the groove width be narrower toward the end side as shown. A raised portion 21 a is formed in a region on the terminal side of each inclined groove 21. As shown in FIG. 2, the starting portion of the bottom raised portion 21 has a shape that is recessed in an arc shape in order to prevent the occurrence of cracks. Further, a plurality of sipes 22 communicating only with the main groove 1b are formed in the inner intermediate land portion 20, and the inclined grooves 21 and the sipes 22 are alternately arranged along the tire circumferential direction.

  A narrow groove 41 extending in the tire circumferential direction is formed in the outer intermediate land portion 40. The narrow groove 41 has a groove width of 0.5 mm to 3.0 mm, a groove depth of 0.5 mm to 2.5 mm, and is shallower and narrower than the main grooves 1a to 1d. The outer intermediate land portion 40 is not divided by a groove extending in the tire width direction, and has a rib structure continuous in the tire circumferential direction.

  The inner shoulder land portion 10 is formed with a plurality of lug grooves 11 extending in the tire width direction and a plurality of sipes 12 extending in the tire width direction. These lug grooves 11 and sipes 12 are alternately arranged at intervals in the tire circumferential direction. The lug groove 11 and the sipe 12 are not in communication with the main groove 1 a adjacent to the inner shoulder land portion 10.

  A plurality of lug grooves 51 extending in the tire width direction are formed in the outer shoulder land portion 50 at intervals in the tire circumferential direction. These lug grooves 51 are not in communication with the main groove 1 d adjacent to the outer shoulder land portion 50.

  In the pneumatic tire having the above-described tread pattern, the central land portion 30 is provided with the one-end closed inclined groove 31, while the inner intermediate land portion 20 is inclined in the same direction as the inclined groove 31. It is possible to effectively improve drainage performance by opening one end of the inclined grooves 21 and 31 into the common main groove 1d located between the center land portion 30 and the inner intermediate land portion 20. Become. Particularly, the drainage capacity based on the main groove 1d is enhanced by arranging the inclined groove 21 and the inclined groove 31 so as to be substantially point-symmetric so that the opening end of the inclined groove 21 and the opening end of the inclined groove 31 face each other. be able to. Further, since the inclined grooves 21 and 31 do not divide the land portions 20 and 30, the uneven wear resistance is also excellent. In addition, since the bottom raised portions 21a and 31a are formed in the regions on the terminal side of the inclined grooves 21 and 31, the rigidity of the land portions 20 and 30 provided with the inclined grooves 21 and 31 is secured, and the steering stability on the dry road surface is ensured. Can be improved. Therefore, it is possible to effectively improve the steering stability and drainage performance on the dry road surface while maintaining the uneven wear resistance.

  In the pneumatic tire described above, the starting points of the raised portions 21a, 31a of the inclined grooves 21, 31 are set to positions 10% to 30% of the length of the inclined grooves 21, 31 from the opening ends of the inclined grooves 21, 31. Yes. That is, as shown in FIG. 3, the length L0 from the open end of the inclined grooves 21 and 31 to the starting point of the raised portions 21a and 31a is 10% to 30% of the length L1 of the inclined grooves 21 and 31. Yes. When the length L0 is less than 10% of the length L1, the drainage performance decreases, and conversely, when the length L0 exceeds 30% of the length L1, the steering stability on the dry road surface decreases. However, the length L0 from the opening end of the inclined grooves 21 and 31 to the starting point of the raised portions 21a and 31a and the length L1 of the inclined grooves 21 and 31 are measured along the groove width center line of the inclined grooves 21 and 31. Dimensions.

  Further, the depth D0 of the inclined grooves 21 and 31 at the bottom raised portions 21a and 31a is 20% to 40% of the depth D1 of the main groove 1b located between the center land portion 30 and the inner intermediate land portion 20. It has become. When the depth D0 is less than 20% of the depth D1, the drainage performance is lowered. Conversely, when the depth D0 exceeds 40% of the depth D1, the driving stability on the dry road surface is lowered. This depth D0 is applied in the entire area of the raised portions 21a and 31a.

  As described above, it is desirable to provide the bottom raised portions 21a and 31a in both the inclined grooves 21 and 31, but the bottom raised portion may be provided in only one of the inclined grooves 21 and 31.

  In the pneumatic tire, a plurality of lug grooves 11 and 51 extending in the tire width direction are provided in the shoulder land portions 10 and 50 located on the vehicle inner side and the vehicle outer side, respectively. , 50 to prevent the main grooves 1a, 1d adjacent to each other, thereby ensuring the rigidity of the shoulder land portions 10, 50, improving the handling stability on the dry road surface, and suppressing the heel and toe wear. And uneven wear resistance can be improved.

  Here, the starting point of the lug grooves 11, 51 on the tire equator CL side is set to a position 5% to 20% of the width of the shoulder land portions 10, 50 from the edge of the shoulder land portions 10, 50 on the tire equator CL side. Good. That is, as shown in FIG. 1, the distance W11 from the edge on the tire equator CL side of the shoulder land portion 10 to the starting point on the tire equator CL side of the lug groove 11 is 5% to 20% of the width W10 of the shoulder land portion 10. It is good to make it. The distance W51 from the edge on the tire equator CL side of the shoulder land portion 50 to the start point on the tire equator CL side of the lug groove 51 is preferably 5% to 20% of the width W50 of the shoulder land portion 50. When the distances W11 and W51 are less than the respective lower limit values, the steering stability on the dry road surface is lowered due to the rigidity reduction of the shoulder land portions 10 and 50, and conversely when the upper limit values are exceeded, the drainage performance is degraded. The widths W10 and W50 of the shoulder land portions 10 and 50 are dimensions in the tire width direction from the edge on the tire equator CL side of the shoulder land portions 10 and 50 to the tread design end.

  The average inclination angle a with respect to the tire width direction of the lug groove 11 arranged in the shoulder land portion 10 inside the vehicle and the average inclination angle b with respect to the tire width direction of the lug groove 51 arranged in the shoulder land portion 50 outside the vehicle are each 0. It is better to set the angle to 25 ° (see Fig. 1). Thereby, the drainage capacity to the tire side can be enhanced, and further, the effect of reducing noise during tire rolling can be obtained. When these average inclination angles a and b exceed 25 °, the drainage capacity is reduced, and noise during tire rolling increases. The average inclination angles a and b of the lug grooves 11 and 51 are the average inclination angles from the starting point of the lug grooves 11 and 51 on the tire equator CL side to the center position in the length direction of the lug grooves 11 and 51. This is because the above part greatly affects the function of the lug grooves 11 and 51.

  The number of sipes in the shoulder land portion 50 outside the vehicle may be smaller than the number of sipes in the shoulder land portion 10 inside the vehicle. More specifically, when sipe is provided on both the shoulder land portion 50 outside the vehicle and the shoulder land portion 10 inside the vehicle, the number of sipes is relatively reduced in the shoulder land portion 50 outside the vehicle. Alternatively, the sipe 12 is provided on the shoulder land portion 10 inside the vehicle, while the sipe is not provided on the shoulder land portion 50 outside the vehicle. Thus, the steering stability on the dry road surface can be improved by relatively reducing the number of sipes in the shoulder land portion 50 outside the vehicle.

  In the pneumatic tire, as shown in FIG. 2, the inclination angle of the contour line forming an acute angle with respect to the edge of the center land portion 30 of the inclined groove 31 is at least a groove from the opening end position P0 of the inclined groove 31. The inclination angle with respect to the tire circumferential direction of the contour line that gradually decreases to the longitudinal center position P1 and forms an acute angle with the edge of the inner intermediate land portion 20 of the inclined groove 21 is at least the groove length from the opening end position P0 of the inclined groove 21. It gradually decreases to the direction center position P1. Thereby, a favorable water flow is formed and it becomes possible to exhibit the outstanding drainage performance.

  The average inclination angle α with respect to the tire circumferential direction of the contour line forming an acute angle with respect to the edge of the center land portion 30 of the inclined groove 31 is set in a range of 25 ° to 50 °, and the edge of the inner intermediate land portion 20 of the inclined groove 21 is set. The average inclination angle β with respect to the tire circumferential direction of the contour line forming an acute angle with respect to the tire angle is set in the range of 20 ° to 40 °. Here, the average inclination angles α and β are average inclination angles from the opening end position P0 of each inclined groove to the center position P1 in the groove length direction. When the average inclination angles α and β are larger than the upper limit values, the resistance of water flowing in the groove is increased, so that the drainage performance is deteriorated. On the other hand, when the average inclination angles α and β are smaller than the respective lower limit values, uneven wear due to chipping tends to occur near the opening end. Further, the average inclination angle α of the inclined groove 31 and the average inclination angle β of the inclined groove 21 satisfy the relationship of α> β. By satisfying α> β, the drainage performance can be improved while ensuring the rigidity of the center land portion 31.

  In FIG. 2, the minimum distance γ1 from the edge on the side opposite to the edge where the inclined groove 31 of the center land portion 30 opens to the inclined groove 31 is in the range of 10% to 40% of the width W30 of the center land portion 30. The minimum distance γ2 from the edge on the opposite side to the edge where the inclined groove 21 of the inner intermediate land portion 20 opens to the inclined groove 21 is in the range of 10% to 40% of the width W20 of the inner intermediate land portion 20 It is good to set to. Thereby, both drainage performance and uneven wear resistance can be achieved. Here, if the minimum distances γ1 and γ2 are smaller than the respective lower limit values, chipping is likely to occur when a large lateral G occurs as in circuit running, and conversely if it is larger than the respective upper limit values, it is difficult to ensure drainage performance. Become.

  As shown in FIG. 2, a plurality of chamfered portions 33 are intermittently provided at the vehicle outer edge of the center land portion 30. By providing such chamfered portions 33, uneven wear resistance is improved. can do. When a large lateral G is generated as in circuit running, a portion near the end of the inclined groove 31 in the center land portion 30 is deformed, and only that portion does not come into contact with the ground, so that it tends to remain without being worn. Therefore, by selectively providing the chamfered portion 33 at a portion other than the vicinity of the end of the inclined groove 31 in the center land portion 30, uneven wear due to the inclined groove 31 can be suppressed.

  The maximum width Wmax of the chamfered portion 33 is preferably set in a range of 10% to 30% of the width W30 of the center land portion 30. If the maximum width Wmax of the chamfered portion 33 is less than 10% of the width W30 of the center land portion 30, the effect of suppressing the uneven wear by the chamfered portion 33 becomes insufficient. Conversely, if it exceeds 30%, the rigidity of the center land portion 30 is increased. Is likely to cause uneven wear due to a significant decrease in the.

  As shown in FIG. 5, the maximum depth Hmax of the chamfered portion 33 is preferably set to 10% or more of the effective depth D of the main groove 1c. The effective depth D of the main groove 1c is the depth from the wear indicator 2 arranged in the main groove 1c to the tread. If the maximum depth Hmax of the chamfered portion 33 is less than 10% of the effective depth D of the main groove 1c, the effect of suppressing uneven wear becomes insufficient.

  The maximum width position of the chamfered portion 33 is preferably disposed between the terminal end and the open end of the pair of inclined grooves 31 and 31 adjacent in the tire circumferential direction. That is, as shown in FIG. 2, a portion having a maximum width Wmax of the chamfered portion 33 is defined in a region X defined between the terminal ends of the pair of inclined grooves 31, 31 adjacent in the tire circumferential direction and the opening end. It is good to arrange. Thereby, uneven wear can be effectively suppressed.

  In the pneumatic tire described above, the outer intermediate land portion 40 located on the vehicle outer side of the center land portion 30 has a rib structure continuous in the tire circumferential direction, so that the inclined grooves 21 and 31 provided for improving the drainage performance are provided. The cornering property can be improved by compensating for the lowering of rigidity of the land portions 20 and 30 caused by the above.

In the pneumatic tire described above, the groove area ratio of the entire ground contact region of the tread portion T is set to 25% to 40%, and the outer ground contact region from the tire equator CL of the tread portion T to the ground contact end outside the vehicle. the ratio of the groove area ratio groove area ratio in the inner contact region from the tire equator CL of the tread portion T for (R _out) to the ground terminal of the vehicle interior _{(R in) (R in /} R out) 1.03 It should be set to ˜1.20. That is, the groove area ratio of the inner ground contact area that greatly contributes to drainage performance is relatively increased, and the groove area ratio of the outer ground contact area that significantly contributes to steering stability on the dry road surface is relatively decreased. . As a result, it is possible to achieve both a high level of handling stability and drainage performance on a dry road surface. The ground contact area is a ground contact area on the tire circumference formed when the tread portion of the pneumatic tire is grounded under conditions of an air pressure of 250 kPa and a load of 4 kPa.

In a pneumatic tire having a tread pattern in which the tire size is 205 / 55R16, the mounting direction of the front and back of the tire when the vehicle is mounted is specified, and the tire has a tread pattern that is asymmetric on both sides of the tire equator, as shown in FIG. Four main grooves extending in the circumferential direction are provided, and five rows of land portions are defined by these main grooves, and a plurality of first inclinations are inclined at the center land portion located on the tire equator with respect to the tire circumferential direction. A groove is provided, and a plurality of second inclined grooves inclined in the same direction as the first inclined groove are provided in an inner intermediate land portion located on the vehicle inner side of the center land portion, and one end of each first inclined groove is connected to the center land portion. The other end is terminated in the center land portion while opening in the main groove located between the center land portion and the inner intermediate land portion, and one end of each second inclined groove is located between the center land portion and the inner intermediate land portion. Open the other end of the groove The first intermediate slope portion is terminated in the side intermediate land portion, a bottom raised portion is formed in a region on the terminal end side of the first inclined groove and the second inclined groove, and a plurality of chamfered portions are provided at the outer edge of the vehicle in the center land portion. Groove bottom-up start position (L0 / L1 × 100%), bottom-up start position of second inclined groove (L0 / L1 × 100%), depth at bottom-up portion of first inclined groove (D0 / D1 × 100%) , Depth at the bottom raised portion of the second inclined groove (D0 / D1 × 100%), start position of the vehicle inner shoulder lug groove (W11 / W10 × 100%), start position of the vehicle outer shoulder lug groove (W51 / W50) × 100%), vehicle inner shoulder lug groove inclination angle a (°), vehicle outer shoulder lug groove inclination angle b (°), shoulder land sipe number (IN / OUT), first inclination groove average inclination Angle α (°), average inclination of second inclined groove Slope angle β (°), minimum distance from the first inclined groove to the main groove edge (γ1 / W30 × 100%), minimum distance from the second inclined groove to the main groove edge (γ2 / W20 × 100%), chamfering Maximum width (Wmax / W30 × 100%), maximum depth of chamfered portion (Hmax / D × 100%), groove area ratio (%) of tread part, ratio of groove area ratio (R _in / R _out ) Tires of Examples 1 to 16 were prepared in the manners shown in Tables 1 and 2. For comparison, a pneumatic tire is provided with inclined grooves in the inner intermediate land portion and the outer intermediate land portion, with one end of each inclined groove opened to the main groove on the shoulder side and the other end terminated in the land portion (conventional example) ) Was prepared.

  About these tires, the following evaluation methods evaluated steering stability on a dry road surface, drainage performance (wet performance), uneven wear resistance, and noise performance. The results are shown in Tables 1 and 2.

Steering stability on dry roads:
Each test tire was assembled on a wheel with a rim size of 16 × 6.5 J, mounted on a passenger car with a displacement of 1800 cc with an air pressure of 250 kPa, and traveled on a test course consisting of a dry road surface, and sensory evaluation was performed by a test driver. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the steering stability on the dry road surface.

Drainage performance:
Each test tire is mounted on a wheel with a rim size of 16 × 6.5J and mounted on a passenger car with a displacement of 1800 cc with an air pressure of 250 kPa, turning while drawing a circle with a radius of 100 m, and in a pool with a depth of 5 mm provided in the turning circuit The maximum lateral acceleration when entering was measured. The evaluation results are shown as an index with the conventional example being 100. A larger index value means better drainage performance.

Uneven wear resistance:
Each test tire was assembled on a wheel with a rim size of 16 × 6.5J and mounted on a passenger car with an air pressure of 250 kPa and a displacement of 1800 cc. After running 10 circuits on a 2 km circuit consisting of a dry road surface, The state of wear was visually observed, and uneven wear resistance was evaluated by a five-point method using the conventional example as a reference (3). An evaluation result means that uneven wear resistance is excellent, so that a score is large.

Noise performance:
Each test tire is mounted on a wheel with a rim size of 16 × 6.5J, mounted on a passenger car with a displacement of 1800cc with an air pressure of 250 kPa, run on a test course consisting of a dry road surface, and a sensory evaluation by a test driver is carried out. The noise performance was evaluated by a five-point method with reference (3). An evaluation result means that noise performance is excellent, so that a score is large.

  As is apparent from Tables 1 and 2, the tires of Examples 1 to 16 improve the steering stability and drainage performance on the dry road surface while maintaining the uneven wear resistance equal to or higher than that of the conventional example. I was able to.

1a, 1b, 1c, 1d Main groove 10, 20, 30, 40, 50 Land part 11, 51 Lug groove 12, 22, 32, 52 Sipe 21, 31 Inclined groove 41 Narrow groove T Tread part

Claims (15)

  In a pneumatic tire having a tread pattern that is asymmetric on both sides of the tire equator, the tire front and back mounting directions are specified when the vehicle is mounted, and at least four main grooves extending in the tire circumferential direction are provided in the tread portion. And a plurality of first inclined grooves that are inclined with respect to the tire circumferential direction are provided in the center land portion located on the tire equator, and located on the vehicle inner side of the center land portion. A plurality of second inclined grooves inclined in the same direction as the first inclined groove are provided in the inner intermediate land portion, and one end of each first inclined groove is located between the center land portion and the inner intermediate land portion. The other end of each second inclined groove is opened in a main groove located between the center land portion and the inner intermediate land portion, while the other end is opened in the inner intermediate land portion. Terminate these first tilts A bottom raised portion is formed in a region on the terminal side of at least one of the grooves and the second inclined groove, and the starting point of the bottom raised portion is 10% to 30% of the length of each inclined groove from the opening end of each inclined groove. %, And the depth of each inclined groove at the bottom raised portion is 20% to 40% of the depth of the main groove located between the center land portion and the inner intermediate land portion. Pneumatic tires.   A plurality of lug grooves extending in the tire width direction are provided in the shoulder land portions located on the vehicle inner side and the vehicle outer side, respectively, and these lug grooves are not communicated with the main grooves adjacent to the shoulder land portions. The pneumatic tire according to claim 1.   The starting point on the tire equator side of the lug groove is set to a position of 5% to 20% of the width of the shoulder land portion from the edge on the tire equator side of the shoulder land portion. Pneumatic tire.   The average inclination angle a with respect to the tire width direction of the lug groove disposed in the shoulder land portion on the vehicle inner side and the average inclination angle b with respect to the tire width direction of the lug groove disposed on the shoulder land portion on the outer side of the vehicle are respectively 0 ° to 25 °. The pneumatic tire according to claim 2, wherein   The pneumatic tire according to claim 2, wherein the number of sipes in the shoulder land portion outside the vehicle is smaller than the number of sipes in the shoulder land portion inside the vehicle.   An average inclination angle α with respect to the tire circumferential direction of the contour line forming an acute angle with respect to the edge of the center land portion of the first inclined groove is 25 ° to 50 °, and with respect to the edge of the inner intermediate land portion of the second inclined groove The pneumatic tire according to any one of claims 1 to 5, wherein an average inclination angle β with respect to a tire circumferential direction of a contour line forming an acute angle is 20 ° to 40 °.   An average inclination angle α with respect to the tire circumferential direction of the contour line that forms an acute angle with respect to the edge of the center land portion of the first inclined groove and an outline that forms an acute angle with respect to the edge of the inner intermediate land portion of the second inclined groove. The pneumatic tire according to claim 1, wherein a relationship with an average inclination angle β with respect to the tire circumferential direction is α> β.   An inclination angle of a contour line forming an acute angle with respect to an edge of a center land portion of the first inclined groove with respect to a tire circumferential direction is gradually decreased from an opening end of the first inclined groove to at least a central position in the groove length direction, and the second The inclination angle with respect to the tire circumferential direction of the contour line forming an acute angle with respect to the edge of the inner intermediate land portion of the inclined groove is gradually decreased from the opening end of the second inclined groove to at least a central position in the groove length direction. The pneumatic tire according to claim 1.   The minimum distance γ1 from the edge of the center land portion opposite to the edge on which the first inclined groove opens to the first inclined groove is 10% to 40% of the width of the center land portion, and the inner intermediate land The minimum distance γ2 from the edge opposite to the edge on the side where the second inclined groove is open to the second inclined groove is 10% to 40% of the width of the inner intermediate land portion. Item 10. The pneumatic tire according to any one of Items 1 to 8.   The pneumatic tire according to claim 1, wherein a plurality of chamfered portions are provided at an edge of the center land portion outside the vehicle.   The pneumatic tire according to any one of claims 1 to 10, wherein a maximum width of the chamfered portion is 10% to 30% of a width of the center land portion.   The pneumatic tire according to any one of claims 1 to 11, wherein a maximum depth of the chamfered portion is 10% or more of an effective depth from a wear indicator of a main groove to a tread surface.   The pneumatic tire according to any one of claims 1 to 8, wherein the maximum width position of the chamfered portion is disposed between a terminal end and an open end of a pair of inclined grooves adjacent to each other in the tire circumferential direction.   The pneumatic tire according to any one of claims 1 to 13, wherein an outer intermediate land portion located on the vehicle outer side of the center land portion has a rib structure continuous in a tire circumferential direction.   The groove area ratio of the entire contact area of the tread portion is 25% to 40%, and from the tire equator of the tread portion to the groove area ratio in the outer contact area from the tire equator of the tread portion to the ground contact end outside the vehicle. 2. The pneumatic tire according to claim 1, wherein the ratio of the groove area ratio in the inner ground contact region to the ground contact end on the inner side of the vehicle is 1.03 to 1.20.

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