JP2013052872A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance uneven wear resistance while maintaining drainage performance.SOLUTION: The pneumatic tire 1 includes asymmetrical tread patterns to be mounted on a vehicle in a specified direction. A lateral groove 4 includes: an inside shoulder lateral groove 11; an outside shoulder lateral groove 12; an inside middle lateral groove 13; and a center lateral groove 14. The inside shoulder lateral groove 11 includes: a first inside shoulder lateral groove 11A that terminates without reaching an inside shoulder vertical groove 3A; and a second inside shoulder lateral groove 11B which is opened in the inside shoulder vertical groove 3A. The outside shoulder lateral groove 12 terminates without reaching an outside shoulder vertical groove 3B. The second inside shoulder lateral groove 11B, the inside middle lateral groove 13, and the center lateral groove 14 form an inside long lateral groove 33 continuing smoothly via an inside center vertical groove 3C and the inside shoulder vertical groove 3A. An arrangement pitch P1 of the inside long lateral groove 33 is larger than an arrangement pitch P2 of the outside shoulder lateral groove 12.

Description

  The present invention relates to a pneumatic tire capable of improving uneven wear resistance while maintaining drainage performance.

  Conventionally, a pneumatic tire is proposed in which a tread portion is provided with a longitudinal groove extending in the tire circumferential direction and a transverse groove extending in a direction intersecting with the longitudinal groove (see, for example, Patent Document 1 below). In such a pneumatic tire, the vertical groove and the horizontal groove can smoothly guide the water film interposed between the road surface and the tread surface, and drainage performance can be improved.

  In the pneumatic tire, in order to further improve the drainage performance, the lateral groove communicates with the longitudinal groove, and the water in the longitudinal groove is guided to the outside in the tire axial direction through the lateral groove.

JP 2003-285610 A

  However, if the horizontal groove is communicated with the vertical groove, the tread rigidity of the portion decreases, and there is a problem that uneven wear tends to occur at the shoulder portions of the tread portion on both outer sides in the tire axial direction where the ground pressure increases when turning. . This uneven wear tends to occur more easily on the outside of the vehicle where the ground contact pressure during turning is greater than on the inside of the vehicle, on both sides in the tire axial direction.

  The present invention has been devised in view of the above circumstances, and has as its main object to provide a pneumatic tire capable of improving uneven wear resistance while maintaining drainage performance.

  According to the first aspect of the present invention, the tread portion includes at least two longitudinal grooves extending in the tire circumferential direction and lateral grooves extending in a direction intersecting with the longitudinal grooves, and the mounting direction to the vehicle is A pneumatic tire having a specified left-right asymmetric tread pattern, wherein the longitudinal groove includes an inner shoulder longitudinal groove disposed on the innermost side of the vehicle and an outer shoulder longitudinal groove disposed on the outermost side of the vehicle, The lateral groove includes an inner shoulder lateral groove extending between the inner shoulder longitudinal groove and the grounded end on the vehicle inner side, and an outer shoulder lateral groove extending between the outer shoulder longitudinal groove and the grounded end on the vehicle outer side. The lateral groove extends from the outside of the ground contact end inside the vehicle to the inside in the tire axial direction and terminates without reaching the inside shoulder longitudinal groove, and the inside groove of the vehicle A second inner shoulder lateral groove extending from the outer side of the grounding end to the tire axial direction inside and opening at the inner shoulder longitudinal groove, the outer shoulder lateral groove extending from the outer side of the grounding end outside the vehicle to the tire axial direction inner side. It extends without extending to the outer shoulder longitudinal groove, and the longitudinal groove extends between the tire equator and the inner shoulder longitudinal groove, and between the tire equator and the outer shoulder longitudinal groove. An outer center longitudinal groove extending in the tire circumferential direction, the lateral groove extending from the inner center longitudinal groove to the inner shoulder longitudinal groove, and from the inner center longitudinal groove over the tire equator to the tire equator. A center transverse groove that terminates without reaching the outer center longitudinal groove, the second inner shoulder transverse groove, the inner middle transverse groove, and the center transverse groove; Forms an inner long horizontal groove that smoothly continues through the inner center vertical groove and the inner shoulder vertical groove, and the inner long horizontal groove arrangement pitch P1 is the arrangement pitch P2 of the outer shoulder horizontal groove 12 It is characterized by being larger than.

  The invention according to claim 2 is the pneumatic tire according to claim 1, wherein the arrangement pitch P1 of the inner long lateral groove is 170 to 220% of the arrangement pitch P2 of the outer shoulder lateral groove. is there.

  The invention according to claim 3 is the pneumatic tire according to claim 1 or 2, wherein a groove depth of the inner shoulder lateral groove is smaller than a groove depth of the outer shoulder lateral groove.

  In the present specification, unless otherwise specified, the dimensions of each part of the tire are values specified in a normal state in which a rim is assembled on a normal rim and a normal internal pressure is filled.

  The “regular rim” is a rim determined for each tire in a standard system including a standard on which a tire is based. For example, JATMA is a standard rim, TRA is “Design Rim”, and ETRTO If present, it means "Measuring Rim".

  The “regular internal pressure” is the air pressure defined by the standard for each tire. If JATMA, the maximum air pressure, if TRA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” Then, “INFLATION PRESSURE” is set, but when the tire is for a passenger car, the pressure is uniformly set to 180 kPa.

  The pneumatic tire according to the present invention has at least two longitudinal grooves extending in the tire circumferential direction on the tread portion and lateral grooves extending in a direction intersecting with the longitudinal grooves, and the right and left of which the mounting direction to the vehicle is designated. It has an asymmetric tread pattern.

  The longitudinal groove includes an inner shoulder longitudinal groove disposed on the innermost side of the vehicle and an outer shoulder longitudinal groove disposed on the outermost side of the vehicle. The lateral groove includes an inner shoulder lateral groove extending between the inner shoulder longitudinal groove and the ground contact end on the vehicle inner side, and an outer shoulder lateral groove extending between the outer shoulder longitudinal groove and the ground contact end on the vehicle outer side.

  The inner shoulder lateral groove extends from the outside of the ground contact end on the vehicle inner side to the tire axial direction inner side and terminates without reaching the inner shoulder vertical groove, and from the outer side of the vehicle inner ground end to the tire axial direction. A second inner shoulder lateral groove extending inward and opening at the inner shoulder longitudinal groove. Since the first inner shoulder lateral groove terminates without reaching the inner shoulder longitudinal groove, it is possible to suppress a decrease in the tread rigidity of the shoulder portion on the inner side of the vehicle and improve uneven wear resistance. On the other hand, since the second inner shoulder lateral groove communicates with the inner shoulder longitudinal groove, the water in the inner shoulder longitudinal groove can be smoothly guided to the inside of the vehicle, and drainage performance can be exhibited.

  Further, the outer shoulder lateral groove extends from the outer side of the ground contact end on the outer side of the vehicle to the inner side in the tire axial direction and ends without reaching the outer shoulder vertical groove. Such an outer shoulder lateral groove can form a tread portion on the outer side of the vehicle where the contact pressure during turning is greatest in a rib shape continuous in the tire circumferential direction, and can improve uneven wear resistance.

  Further, the longitudinal groove includes an inner center longitudinal groove extending between the tire equator and the inner shoulder longitudinal groove, and an outer center longitudinal groove extending between the tire equator and the outer shoulder longitudinal groove in the tire circumferential direction. The lateral groove includes an inner middle lateral groove extending between the inner center longitudinal groove and the inner shoulder longitudinal groove, and a center lateral groove that terminates from the inner center longitudinal groove beyond the tire equator without reaching the outer center longitudinal groove. .

  Further, the second inner shoulder lateral groove, the inner middle lateral groove, and the center lateral groove form an inner long lateral groove that smoothly continues through the inner center longitudinal groove and the inner shoulder longitudinal groove. Such inner long lateral grooves can smoothly guide the water film from the tire equator side to the ground contact end on the inner side of the vehicle, and can greatly improve drainage performance. In addition, since the inner long lateral groove is provided on the inner side of the vehicle having a relatively small ground pressure compared to the outer side of the vehicle, the tread surface on the outer side of the vehicle having a large ground pressure is worn over a wide range as in the prior art. It is possible to suppress the deterioration of uneven wear resistance.

  Furthermore, the arrangement pitch P1 of the inner long horizontal grooves is larger than the arrangement pitch P2 of the outer shoulder horizontal grooves 12. Thereby, it can suppress that tread rigidity inside a vehicle falls too much, and can improve uneven wear-proof performance. Therefore, the pneumatic tire of the present invention can improve uneven wear resistance while maintaining drainage performance.

It is an expanded view of the tread part of the pneumatic tire of this embodiment. It is AA sectional drawing of FIG. FIG. 2 is a partially enlarged view of the inside of the vehicle in FIG. 1. FIG. 2 is a partially enlarged view of the vehicle outside in FIG. 1. 3 is a development view of a tread portion of a pneumatic tire of Comparative Example 1. FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIGS. 1 and 2, a pneumatic tire (hereinafter, simply referred to as “tire”) 1 according to the present embodiment includes a longitudinal groove 3 extending in a tire circumferential direction and a longitudinal groove 3 extending in a tread portion 2. It is configured as a summer tire for a passenger car having a lateral groove 4 extending in a direction intersecting with the groove 3 and having a left-right asymmetric tread pattern in which the mounting direction to the vehicle is specified.

  Further, the direction of mounting on the vehicle is clearly indicated by letters (for example, “INSIDE” and / or “OUTSIDE”) on the sidewall portion of the tire 1 (not shown).

  The longitudinal groove 3 is composed of at least two and four in this embodiment, and is formed as a straight groove extending linearly along the tire circumferential direction. Such straight grooves can smoothly guide the water film interposed between the road surface and the tread surface in the tire circumferential direction during straight traveling and turning, and can improve drainage performance. Preferably, the groove width W1 of the longitudinal groove 3 is preferably set to, for example, about 3.5 to 6.5% of the tread width TW, and the groove depth D1 is set to about 4 to 4.8% of the tread width TW. . The tread width TW is a tire axial distance between the ground contact ends 2i and 2o in a normal state.

  The longitudinal groove 3 includes an inner shoulder longitudinal groove 3A disposed on the innermost side of the vehicle, an outer shoulder longitudinal groove 3B disposed on the outermost side of the vehicle, and an inner center longitudinal portion extending between the tire equator C and the inner shoulder longitudinal groove 3A. The groove 3C includes an outer center longitudinal groove 3D extending in the tire circumferential direction between the tire equator C and the outer shoulder longitudinal groove 3B.

  By these vertical grooves 3A, 3B, 3C and 3C, the tread portion 2 is divided into an inner shoulder land groove 3A and an outer shoulder vertical groove 3B and the vehicle outer side which are divided by the inner shoulder vertical groove 3A and the ground contact end 2i inside the vehicle. The outer shoulder land portion 5B divided by the ground contact end 2o, the inner middle land portion 5C divided by the inner center longitudinal groove 3C and the inner shoulder longitudinal groove 3A, the inner center longitudinal groove 3C and the outer center longitudinal groove 3D. The center land portion 5D to be divided and the outer middle land portion 5E to be divided by the outer center vertical groove 3D and the outer shoulder vertical groove 3B are formed.

  Further, the inner shoulder vertical groove 3A and the outer shoulder vertical groove 3B are preferably arranged on the tire equator C side rather than the conventional tire. The inner shoulder vertical groove 3A and the outer shoulder vertical groove 3B can exhibit drainage performance during turning and straight travel, and increase the width of the inner and outer shoulder land portions 5A and 5B to increase lateral tread rigidity. It is possible to improve uneven wear resistance and steering stability. Preferably, the distance L1 from the tire equator C of the groove center line 3Ac of the inner shoulder longitudinal groove 3A and the distance L2 from the tire equator C of the groove center line 3Bc of the outer shoulder longitudinal groove 3B are, for example, 23 of the tread width TW. About 5 to 28.5% is desirable.

  The lateral groove 4 is provided in the inner shoulder lateral groove 11 provided in the inner shoulder land portion 5A, the outer shoulder lateral groove 12 provided in the outer shoulder land portion 5B, the inner middle lateral groove 13 provided in the inner middle land portion 5C, and the center land portion 5D. And the outer middle lateral groove 15 provided in the outer middle land portion 5E.

  These lateral grooves 11, 12, 13, 14, and 15 can guide the water film in the tire axial direction, and can improve drainage performance. Preferably, the groove width W2 of the lateral groove 4 is set to, for example, about 1.3 to 2.5% of the tread width TW, and the groove depth D2 is set to about 2.7 to 4.6% of the tread width TW. desirable.

  As shown in an enlarged view in FIG. 3, the inner shoulder lateral groove 11 of the present embodiment is smooth between the inner shoulder longitudinal groove 3A and the ground contact end 2i on the vehicle inner side while gradually increasing the angle α1 with respect to the tire circumferential direction. Inclined and extended. Such an inner shoulder lateral groove 11 can smoothly drain the water film to the grounding end 2i side inside the vehicle. The angle α1 is preferably about 65 to 80 °.

  The inner shoulder lateral groove 11 of the present embodiment has an inner end 11Ai in the tire axial direction that opens without reaching the inner shoulder longitudinal groove 3A and the first inner shoulder lateral groove 11A and the inner shoulder longitudinal groove 3A. The second inner shoulder lateral groove 11B is included.

  11 A of such 1st inner side shoulder horizontal grooves can suppress the fall of the tread rigidity of 5 A of inner side shoulder land parts, and can improve uneven wear-proof performance. Further, the second inner shoulder lateral groove 11B can take in the water in the inner shoulder longitudinal groove 3A and smoothly guide it to the grounding end 2i side inside the vehicle, thereby improving drainage performance.

  As shown in FIG. 4 in an enlarged manner, the outer shoulder lateral groove 12 extends between the outer shoulder vertical groove 3B and the ground contact end 2o on the outer side of the vehicle, and extends while gradually decreasing the angle α2 with respect to the tire circumferential direction. Such outer shoulder lateral grooves 12 can smoothly guide the water film to the ground contact end 2o outside the vehicle, similarly to the inner shoulder longitudinal grooves 3A. Preferably, the angle α2 is about 70 to 85 °.

  The outer shoulder lateral groove 12 of the present embodiment terminates without the inner end 12i in the tire axial direction reaching the outer shoulder vertical groove 3B. As a result, the outer shoulder lateral groove 12 can increase the tread rigidity by forming the outer shoulder land portion 5B where the ground contact pressure becomes the largest at the time of turning in a substantially rib shape, thereby improving the wear resistance performance and the H / T wear resistance performance. Can improve.

  Thus, the tire 1 of the present embodiment can improve the uneven wear resistance performance while maintaining the drainage performance by configuring the inner shoulder lateral grooves 11 and the outer shoulder lateral grooves 12 as described above. The second inner shoulder lateral groove 11B is opened by the inner shoulder longitudinal groove 3A to enhance drainage. The inner shoulder land portion 5A provided with the second inner shoulder lateral groove 11B has a relatively small ground pressure compared to the outer shoulder land portion 5B during turning, so that the drainage performance is improved and the deterioration of uneven wear resistance performance is suppressed. sell.

  In order to effectively exhibit such an action, the shortest distance L3 between the inner end 11Ai on the tire equator side of the first inner shoulder lateral groove 11A and the inner shoulder vertical groove 3A is preferably a tread width TW (see FIG. 1) is preferably 1.5% or more, more preferably 3% or more. When the shortest distance L3 is reduced, the rigidity of the inner shoulder land portion 5A is lowered, and there is a possibility that the uneven wear resistance performance is lowered. On the contrary, when the shortest distance L3 is increased, the first inner shoulder lateral groove 11A is excessively shortened, and the drainage performance may be deteriorated. From such a viewpoint, the shortest distance L3 is preferably 6% or less of the tread width TW, more preferably 5% or less.

  From the same viewpoint, the shortest distance L4 between the inner end 12i on the tire equator side of the outer shoulder lateral groove 12 and the outer shoulder longitudinal groove 3B is preferably 1.5% or more of the tread width TW (shown in FIG. 1), More preferably, it is 3% or more, preferably 6.5% or less, more preferably 5.5% or less.

  Further, as shown in FIG. 2, the groove depth D2a of the inner shoulder lateral groove 11 is preferably smaller than the groove depth D2b of the outer shoulder lateral groove 12. As a result, the tread portion 2 can increase the tread rigidity of the inner shoulder land portion 5A, which has a smaller tread rigidity than the outer shoulder land portion 5B, so that the tread rigidity of each of the land portions 5A, 5B can be made substantially uniform. Performance and steering stability performance can be improved.

  In this case, the groove depth D2a of the inner shoulder lateral groove 11 is preferably 100% or less, more preferably 95% or less of the groove depth D2b of the outer shoulder lateral groove 12. If the groove depth D2a is large, the above-described action may not be expected. Conversely, when the groove depth D2a is reduced, the drainage performance of the inner shoulder lateral groove 11 may be reduced. From such a viewpoint, the groove depth D2a is preferably 85% or more, more preferably 90% or more of the groove depth D2b.

  As shown in FIG. 3, the inner shoulder land portion 5A is preferably provided with an inner shoulder short sipe 16 that connects the inner end 11Ai of the first inner shoulder lateral groove 11A and the inner shoulder vertical groove 3A. Such a short inner shoulder sipe 16 can alleviate distortion generated between the first inner shoulder lateral groove 11A and the inner shoulder longitudinal groove 3A, and can effectively exhibit uneven wear resistance. From the same viewpoint, as shown in FIG. 4, it is preferable that the outer shoulder land portion 5B is provided with an outer shoulder short sipe 17 that connects the inner end 12i of the outer shoulder lateral groove 12 and the outer shoulder vertical groove 3B. .

  Further, as shown in FIG. 3, the inner shoulder land portion 5A is spaced from the inner shoulder vertical groove 3A to the vehicle inner side between the first inner shoulder lateral groove 11A and the second inner shoulder lateral groove 11B. An inner shoulder sipe 18 is provided which extends from the position to the inside of the vehicle and terminates beyond the grounding end 2i inside the vehicle. Such an inner shoulder sipe 18 can alleviate distortion at the time of grounding of the inner shoulder land portion 5A, and can further improve uneven wear resistance.

  The inner shoulder land portion 5A extends in the tire circumferential direction between the inner shoulder longitudinal groove 3A and the inner end 18i of the inner shoulder sipe 18 in the tire axial direction, and both ends thereof are the first and second inner shoulders. Preferably, two circumferential sipes 22, 22 are provided that terminate without intersecting the lateral grooves 11A, 11B. Such circumferential sipes 22 and 22 effectively relieve distortion and the like in the lateral direction acting on the inner shoulder land portion 5A during turning. Further, the uneven wear resistance of the inner shoulder land portion 5A in which forces in various directions act in cooperation with the inner shoulder sipe 18 can be further improved.

  Further, the tread portion 2 is connected to the outer end 11Ao on the vehicle inner side of the first inner shoulder lateral groove 11A adjacent to the tire circumferential direction from the outer end 11Bo on the inner side of the second inner shoulder lateral groove 11B in the vehicle. An inner shoulder joint groove 21 extending in the circumferential direction is preferably provided. Such an inner shoulder joint groove 21 can effectively relieve distortion of the inner shoulder land portion 5A, and can further improve uneven wear resistance.

  As shown in FIG. 4, the outer shoulder land portion 5 </ b> B extends between the outer shoulder lateral grooves 12 and 12 adjacent to each other in the tire circumferential direction from the position separated from the outer shoulder vertical groove 3 </ b> B to the vehicle outer side, In addition, an outer shoulder sipe 23 is provided that terminates without reaching the grounding end 2o outside the vehicle. Such an outer shoulder sipe 23 can effectively relieve distortion generated in the outer shoulder land portion 5B, and can further improve uneven wear resistance. Moreover, since the outer shoulder sipe 23 terminates without reaching the grounding end 2o outside the vehicle, it is possible to effectively suppress H / T wear that tends to occur at the grounding end 2o.

  In order to effectively exhibit such an action, the distance L5 between the outer end 23o of the outer shoulder sipe 23 on the vehicle outer side and the grounding end 2o on the outer side of the vehicle is preferably 1.5 mm or more, more preferably 3 mm or more. desirable. If the distance L5 is small, the above H / T wear may not be sufficiently suppressed. On the contrary, when the distance L5 is increased, there is a possibility that the distortion generated in the outer shoulder land portion 5B cannot be sufficiently relaxed. From such a viewpoint, the distance L5 is preferably 8 mm or less, and more preferably 6 mm or less.

  Further, the outer shoulder land portion 5B is provided with an outer shoulder slot 24 extending from the position separated from the ground contact end 2o on the vehicle outer side to the vehicle outer side. The outer shoulder slot 24 of the present embodiment is provided on the vehicle outer side of the outer shoulder sipe 23. Such an outer shoulder slot 24 can effectively relieve distortion generated in the outer shoulder land portion 5B, and can preferably improve uneven wear resistance. Moreover, since the outer shoulder slot 24 is provided at a position separated from the ground contact end 2o to the vehicle outer side, the above-described H / T wear can be effectively suppressed.

  Further, the tread portion 2 extends from the outer end 12o on the outer side of the outer shoulder lateral groove 12 in the tire circumferential direction outside the ground contact end 2o on the outer side of the vehicle, and extends outside the outer shoulder slot 24 adjacent to the tire circumferential direction. An outer shoulder joint groove 25 that connects the end 24o and the outer end 12o of the outer shoulder lateral groove 12 is provided. Such an outer shoulder joint groove 25 can also effectively relieve distortion generated in the outer shoulder land portion 5B.

  As shown in FIG. 3, the inner middle lateral groove 13 extends between the inner shoulder longitudinal groove 3A and the inner center longitudinal groove 3C, and an angle α3 with respect to the tire circumferential direction is smaller than the angle α1 of the inner shoulder lateral groove 11. It is inclined. Such an inner middle lateral groove 13 can smoothly guide a water film interposed between the inner middle land portion 5C that is grounded during straight travel and turning, and can improve drainage performance. The angle α3 is preferably about 55 to 65 °.

  Further, the inner middle lateral groove 13 extends from the inner shoulder longitudinal groove 3A to the inside in the tire axial direction and terminates without reaching the inner center longitudinal groove 3C, and from the inner shoulder longitudinal groove 3A to the tire axial direction. And a second inner middle lateral groove 13B extending inward and opening at the inner center longitudinal groove 3C. Two first inner middle lateral grooves 13A are provided between second inner middle lateral grooves 13B and 13B adjacent in the tire circumferential direction. As described above, the inner middle lateral groove 13 is configured such that the number of the long second inner middle horizontal grooves 13B is smaller than the number of the short first inner middle horizontal grooves 13A, thereby forming the inner middle land portion 5C. The drainage performance can be enhanced without excessively reducing the tread rigidity.

  Further, the inner middle land portion 5C communicates with inner ends 13Ai and 13Ai of the first inner middle lateral grooves 13A and 13A in the tire axial direction, extends in the tire circumferential direction, and opens at the second inner middle lateral groove 13B. A middle narrow groove 26 is formed. Such an inner middle narrow groove 26 can smoothly guide the water film in the tire circumferential direction, and can discharge the water film from the first inner middle lateral groove 13A to the inner shoulder vertical groove 3A, thereby improving drainage performance. To help. The groove width W3 of the inner middle narrow groove 26 is preferably about 0.5 to 1.5% of the tread width TW, and the groove depth D3 is preferably about 0.5 to 1.3% of the tread width TW.

  The center lateral groove 14 terminates from the inner center longitudinal groove 3C beyond the tire equator C without reaching the outer center longitudinal groove 3D. Further, the angle α4 of the center lateral groove 14 with respect to the tire circumferential direction extends with an inclination smaller than the angle α3 of the inner middle lateral groove 13 and the angle α1 of the inner shoulder lateral groove 11. Such a center lateral groove 14 can guide the water film interposed between the center land portion 5D having the highest ground pressure and the road surface to the inner center longitudinal groove 3C during straight traveling. The angle α4 is preferably about 35 to 50 °.

  Further, the center land portion 5D includes a first center sipe 31 extending inward in the tire axial direction from the inner center longitudinal groove 3C and terminating in the vicinity of the tire equator C, and extending inward in the tire axial direction from the outer center longitudinal groove 3D. A second center sipe 32 that terminates near the tire equator C is provided. One first center sipe 31 is provided between the center lateral grooves 14 and 14 adjacent in the tire circumferential direction, while two second center sipes 32 are provided. Thereby, the center land portion 5D can substantially uniform the tread rigidity in the tire axial direction, and can improve the uneven wear resistance performance, and can improve the ground contact property of the center land portion 5D and improve the straight running stability.

  In the present embodiment, the second inner shoulder lateral groove 11B, the inner middle lateral groove 13 (in this embodiment, the second inner middle lateral groove 13B), and the center lateral groove 14 form the inner center longitudinal groove 3C and the inner shoulder longitudinal groove 3A. It is formed as an inner long lateral groove 33 that smoothly continues through. Such an inner long lateral groove 33 can smoothly guide the water film from the tire equator C side to the ground contact end 2i inside the vehicle, and can greatly improve drainage performance. Moreover, since the inner long lateral groove 33 is provided on the inner side of the vehicle having a relatively small ground pressure compared to the outer side of the vehicle, the tread surface on the outer side of the vehicle having a large ground pressure is worn over a wide range as in the prior art. And the deterioration of uneven wear resistance can be suppressed.

  As shown in FIGS. 3 and 4, the arrangement pitch P <b> 1 of the inner long lateral grooves 33 is preferably larger than the arrangement pitch P <b> 2 of the outer shoulder lateral grooves 12. Thereby, it can suppress that tread rigidity inside a vehicle falls too much, and can improve uneven wear-proof performance. The arrangement pitches P1 and P2 are measured at the grounding end 2i inside the vehicle or the grounding end 2o outside the vehicle.

  The arrangement pitch P1 of the inner long lateral grooves 33 is preferably 170% or more, more preferably 185% or more of the arrangement pitch P2 of the outer shoulder lateral grooves 12. When the arrangement pitch P1 is reduced, the tread rigidity inside the vehicle may be excessively reduced. On the contrary, when the arrangement pitch P1 is increased, there is a possibility that improvement of drainage performance cannot be expected. From such a viewpoint, the arrangement pitch P1 is preferably 220% or less, more preferably 210% or less of the arrangement pitch P2.

  As shown in FIG. 4, the outer middle lateral groove 15 extends between the outer shoulder longitudinal groove 3B and the outer center longitudinal groove 3D, and an angle α5 with respect to the tire circumferential direction is greater than the angle α2 of the outer shoulder lateral groove 12. It has a small slope. Such an outer middle horizontal groove 15 can also smoothly guide a water film interposed between the outer middle land portion 5E that is grounded during straight travel and turning and the road surface, and can improve drainage performance. The angle α5 is preferably about 45 to 65 °.

  The outer middle lateral groove 15 extends from the outer shoulder longitudinal groove 3B inward in the tire axial direction and terminates without reaching the outer center longitudinal groove 3D, and from the outer shoulder longitudinal groove 3B to the tire shaft. And a second outer middle lateral groove 15B that extends inward in the direction and terminates on the inner side in the tire axial direction from the first outer middle lateral groove 15A. The first and second outer middle lateral grooves 15A and 15B are arranged adjacent to each other in the tire circumferential direction.

  Further, the first outer middle horizontal groove 15A and the second outer middle horizontal groove 15B are provided at a position that is smoothly connected to the outer shoulder horizontal groove 12 via the outer shoulder vertical groove 3B. As a result, the first and second outer middle lateral grooves 15A and 15B can guide the water film to the outer shoulder lateral groove 12 and discharge it to the grounding end 2o outside the vehicle.

  The outer middle land portion 5E has an outer middle narrow portion extending continuously in the tire circumferential direction through the inner end 15Ai in the tire axial direction of the first outer middle lateral groove 15A and longitudinally passing through the second outer middle lateral groove 15B. A groove 36 is provided. Such an outer middle narrow groove 36 guides the water film in the tire circumferential direction and can discharge the water film to the first and second outer middle lateral grooves 15A and 15B, which is useful for enhancing drainage performance. . Preferably, the groove width W4 of the outer middle narrow groove 36 is, for example, about 0.5 to 1.5% of the tread width TW, and the groove depth D4 (shown in FIG. 2) is 0.5 to 1 of the tread width TW. % Is desirable.

  The outer middle land portion 5E includes a first outer middle sipe 37 and an outer shoulder longitudinal groove 3B extending between the outer center longitudinal groove 3D and the outer middle narrow groove 36 at substantially the same inclination as the outer middle lateral groove 15. A second outer middle sipe 38 extending from the position separated inward in the tire axial direction at substantially the same inclination as the outer middle lateral groove 15 and terminating without reaching the outer middle narrow groove 36 is provided. The first outer middle sipes 37 are provided two fewer than the second outer middle sipes 38 between the second outer middle lateral grooves adjacent in the tire circumferential direction. As a result, the outer middle land portion 5E can substantially equalize the tread rigidity between the vehicle inner region and the vehicle outer region where the tread rigidity is likely to be lowered by the second outer middle lateral groove 15B, thereby improving uneven wear resistance. Can be increased.

  Further, the outer middle land portion 5E is preferably provided with an outer middle short sipe 40 that connects the inner end 15Bi of the second outer middle lateral groove 15B in the tire axial direction and the outer center longitudinal groove 3D. Such an outer middle short sipe 40 can relieve distortion generated between the second outer middle lateral groove 15B and the outer center longitudinal groove 3D, and can effectively exhibit uneven wear resistance.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

Tires having the basic structure shown in FIG. 1 and having longitudinal grooves and lateral grooves shown in Table 1 were manufactured, and their performance was evaluated. For comparison, a tire in which the inner shoulder lateral groove and the outer shoulder lateral groove shown in FIG. 5 were reversed left and right was also manufactured and evaluated in the same manner. The common specifications are as follows.
Tire size: 225 / 55R17 97V
Rim size: 17 × 7.0JJ
Tread width TW: 194mm
Vertical groove:
Groove width W1: 8.5mm
Groove depth D1: 9.0 mm
Ratio (W1 / TW): 4.4%
Ratio (D1 / TW): 4.6%
Inner shoulder flutes:
Distance from tire equator of groove center line L1: 50.5mm
Ratio (L1 / TW): 26.0%
Outer shoulder flutes:
Distance L2 from the tire equator of the groove center line: 50.4mm
Ratio (L2 / TW): 26.0%
Horizontal groove:
Groove width W2: 4.9 mm
Groove depth D2: 7.5 mm
Ratio (W2 / TW): 2.5%
Ratio (D2 / TW): 3.9%
Inner middle narrow groove:
Groove width W3: 2.1mm
Groove depth D3; 1.0 mm
Ratio (W3 / TW): 1.1%
Ratio (D3 / TW): 0.5%
Outer middle narrow groove:
Groove width W4: 2.8 mm
Groove depth D4: 2.0 mm
Ratio (W4 / TW): 1.4%
Ratio (D4 / TW): 1.0%
The test method is as follows.

<Drainage performance>
Each test tire was assembled on the rim, filled with 230 kPa of internal pressure, mounted on all wheels of an FF vehicle with a displacement of 3500 cc, and a puddle with a water depth of 5 mm and a length of 20 m was provided on a 100 m radius asphalt road The test course was entered while gradually increasing the speed, and the average lateral acceleration of the front and rear wheels at a speed of 50 to 80 km / h was measured. The results are displayed as an index with the average lateral acceleration of Example 1 as 100. The larger the value, the better.

<Uneven wear resistance>
Each test tire is assembled to the above rim under the above conditions, mounted on the above test vehicle, traveled on a dry asphalt road surface for 8000 km, and the difference between the amount of wear on the outer shoulder land and the amount of wear on the inner shoulder land is measured. It was done. The measurement was performed at three locations on the tire circumference, and all average values were measured. The results are expressed as an index with the value of Example 1 as 100 with respect to the reciprocal of each average value. The larger the value, the better.

<H / T wear resistance>
Each test tire is assembled to the above rim under the above conditions, mounted on the above test vehicle, traveled on a dry asphalt road surface for 8000 km, and the outer shoulder land portion has a corner between the lateral groove adjacent to the tire circumferential direction and the tread surface. The difference between the wear amount (average value) at the portion and the wear amount at the center portion of the tread between the lateral grooves was measured. The measurement was performed at three locations on the tire circumference, and all average values were measured. The results are expressed as an index with the value of Example 1 as 100 with respect to the reciprocal of each average value. The larger the value, the better.

  As a result of the test, it was confirmed that the tire of the example can improve the uneven wear resistance while maintaining the drainage performance.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Vertical groove 3A Inner shoulder vertical groove 3B Outer shoulder vertical groove 4 Horizontal groove 11 Inner shoulder horizontal groove 11A First inner shoulder horizontal groove 11B Second inner shoulder horizontal groove 12 Outer shoulder horizontal groove

Claims (3)

The tread portion has at least two longitudinal grooves extending in the tire circumferential direction, and lateral grooves extending in a direction intersecting with the longitudinal grooves.
Moreover, it is a pneumatic tire having a left-right asymmetric tread pattern in which the mounting direction to the vehicle is specified,
The longitudinal groove includes an inner shoulder longitudinal groove disposed on the innermost side of the vehicle and an outer shoulder longitudinal groove disposed on the outermost side of the vehicle,
The lateral groove includes an inner shoulder lateral groove extending between the inner shoulder longitudinal groove and the ground contact end on the vehicle inner side, and an outer shoulder lateral groove extending between the outer shoulder longitudinal groove and the ground contact end on the vehicle outer side,
The inner shoulder lateral groove extends from the outside of the ground contact end on the vehicle inner side to the tire axial direction inner side and terminates without reaching the inner shoulder longitudinal groove; and
A second inner shoulder lateral groove extending from the outside of the ground contact end inside the vehicle inward in the tire axial direction and opening at the inner shoulder longitudinal groove;
The outer shoulder lateral groove extends from the outside of the ground contact end on the outer side of the vehicle to the inside in the tire axial direction and terminates without reaching the outer shoulder longitudinal groove,
The longitudinal groove includes an inner center longitudinal groove extending between the tire equator and the inner shoulder longitudinal groove, and an outer center longitudinal groove extending between the tire equator and the outer shoulder longitudinal groove in the tire circumferential direction,
The lateral groove is an inner middle lateral groove extending between the inner center longitudinal groove and the inner shoulder longitudinal groove, and
Comprising a center lateral groove that terminates from the inner center longitudinal groove over the tire equator without reaching the outer center longitudinal groove;
The second inner shoulder lateral groove, the inner middle lateral groove, and the center lateral groove form an inner long lateral groove that smoothly continues through the inner center longitudinal groove and the inner shoulder longitudinal groove,
The pneumatic tire is characterized in that the inner long lateral groove pitch P1 is larger than the outer shoulder horizontal groove pitch P2.   2. The pneumatic tire according to claim 1, wherein the arrangement pitch P <b> 1 of the inner long lateral groove is 170 to 220% of the arrangement pitch P <b> 2 of the outer shoulder lateral groove.   The pneumatic tire according to claim 1 or 2, wherein a groove depth of the inner shoulder lateral groove is smaller than a groove depth of the outer shoulder lateral groove.

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