JP5913247B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire that achieves both wet performance and noise performance.

  In recent years, excellent wet performance is required for pneumatic tires.

  In order to improve wet performance, a pneumatic tire is proposed in which the volume of the main groove extending in the tire circumferential direction is increased. However, such a pneumatic tire has a problem that, when traveling on a dry road surface, a large air column resonance sound is generated by the air passing through the main groove, and noise performance is lowered.

  Patent Document 1 below proposes a pneumatic tire in which fine grooves are provided in a circumferential direction in a chamfered inclined wall portion between a groove wall of a main groove and a ground contact surface. Such a pneumatic tire improves wet performance while suppressing air column resonance noise.

JP 2003-146024 A

  However, the pneumatic tire disclosed in Patent Document 1 has room for further improvement in terms of both wet performance and noise performance.

  The present invention has been devised in view of the actual situation as described above, and provides a pneumatic tire having both wet performance and noise performance based on defining the cross-sectional shape of the groove wall surface of the main groove. This is the main purpose.

The present invention is a pneumatic tire in which a tread portion is provided with a plurality of main grooves continuous in the tire circumferential direction and a land portion, and the tread portion is designated for mounting on a vehicle. The main groove includes an outer shoulder main groove located on the vehicle outer side when the vehicle is mounted, and in a tire meridian section including a tire rotation axis, the outer shoulder main groove includes a groove bottom and a tire axially inner side of the groove bottom. A first groove wall surface located on the outer side in the tire axial direction of the groove bottom and a second groove wall surface that is asymmetric with respect to the first groove wall surface with respect to a reference line in the groove depth direction. The first groove wall surface of the outer shoulder main groove is a concave along a circular arc that forms the groove bottom side and the tread surface side and the center is located outside the tire. a curved portion viewed including the land portion, constituting the first groove wall surface An outer middle land portion and a first outer shoulder land portion constituting the second groove wall surface and extending continuously in the tire circumferential direction, and the outer middle land portion communicates with the outer shoulder main groove. An outer middle sipe is provided, and the first outer shoulder land portion is a rib extending continuously in the tire circumferential direction without a lateral groove communicating with the outer shoulder main groove .

  In the pneumatic tire according to the present invention, it is desirable that a radius of curvature of the concave curved surface portion is 10 to 20 mm.

  In the pneumatic tire according to the present invention, the second groove wall surface of the asymmetric main groove has a second linear portion constituting the groove bottom side and a tread surface side, and is gentler than the second linear portion. It is desirable to include a third linear portion extending with a gentle slope.

  In the pneumatic tire according to the present invention, it is preferable that the length of the third linear portion in the groove depth direction is smaller than the length of the first linear portion in the groove depth direction.

  In the pneumatic tire according to the present invention, it is preferable that only the lateral groove or sipe having a groove width of less than 2 mm communicates with the asymmetric main groove.

In the pneumatic tire according to the aspect of the invention, it is preferable that the outer middle sipe includes a first inclined portion that is inclined with respect to a tire axial direction and a second inclined portion that is inclined in a direction opposite to the first inclined portion. .

In the pneumatic tire of the present invention, the land portion is a second outer side which is divided between an outer shoulder sub-groove extending continuously in the tire circumferential direction on the outer side in the tire axial direction of the outer shoulder main groove and the tread grounding end. The second outer shoulder land portion includes a plurality of outer shoulder lateral grooves extending at least from the tread grounding end in the tire axial direction inside, and the outer shoulder lateral groove extends beyond the outer shoulder sub-groove, It is desirable to include a second outer shoulder transverse groove that terminates in the first outer shoulder land.

  In the pneumatic tire of the present invention, a plurality of main grooves continuous in the tire circumferential direction are provided in the tread portion. In the tire meridian cross section including the tire rotation axis, at least one of the main grooves is a groove bottom, a first groove wall surface located on one side of the groove bottom, and located on the other side of the groove bottom and in the groove depth direction. With respect to the reference line, the first groove wall surface includes an asymmetric main groove having an asymmetric second groove wall surface. Such an asymmetric main groove suppresses resonance vibration of air in the groove and effectively suppresses air column resonance sound.

  The first groove wall surface of the asymmetric main groove includes a first linear portion that constitutes the groove bottom side, and a concave curved surface portion that constitutes the tread surface side and extends along an arc whose center is located outside the tire. Such a first groove wall surface increases the groove volume near the tread surface of the asymmetric main groove and effectively suppresses the hydroplaning phenomenon. In addition, such a first groove wall surface scatters vibrations of air passing through the asymmetric main groove in multiple directions. For this reason, resonance vibration of air in the groove is further suppressed, and air column resonance noise is suppressed.

  Therefore, the pneumatic tire of the present invention achieves both wet performance and noise performance.

It is an expanded view of the tread part of the pneumatic tire of this embodiment. It is AA sectional drawing of FIG. It is an expanded sectional view of an asymmetric main groove. It is an enlarged view of the outer middle land part of FIG. It is an enlarged view of the outer side shoulder land part of FIG. It is an enlarged view of the center land part of FIG. It is an enlarged view of the inner middle land part of FIG. It is an enlarged view of the inner side shoulder land part of FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a tread portion 2 of a pneumatic tire (hereinafter sometimes simply referred to as “tire”) 1 of the present embodiment. The pneumatic tire 1 of the present embodiment is designated for the mounting direction to the vehicle. The left side of the tire 1 in FIG. 1 faces the outside of the vehicle when the vehicle is mounted. FIG. 1 shows a radial tire for a passenger car as the tire 1 of the present embodiment.

  As shown in FIG. 1, the tread portion 2 is provided with a plurality of main grooves 10 extending continuously in the tire circumferential direction. In the present specification, the “main groove” means a groove extending continuously in the tire circumferential direction and having a groove width of 3% or more of the tread ground contact width TW.

  The tread contact width TW is a distance in the tire axial direction between the tread contact ends Te and Te of the tire 1 in a normal state. The normal state is a state in which a tire is assembled on a normal rim (not shown) and filled with a normal internal pressure, and is not loaded.

  The “regular rim” is a rim determined for each tire in a standard system including a standard on which the tire is based. For example, “Standard Rim” for JATMA, “Design Rim” for TRA, ETRTO Then "Measuring Rim".

  The “regular internal pressure” is an air pressure determined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” in the case of ETRTO.

  The “tread contact end Te” is a contact position on the outermost side in the tire axial direction when a normal load is applied to the tire 1 in the normal state and the tire 1 contacts the plane with a camber angle of 0 °.

  The “regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. “JATMA” indicates “maximum load capacity”, and TRA indicates “TIRE LOAD”. The maximum value described in “LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “LOAD CAPACITY” in the case of ETRTO.

  The main groove 10 extends linearly, for example. The groove width W1 of the main groove 10 of the present embodiment is, for example, 4 to 8% of the tread ground contact width TW. Such a main groove 10 exhibits excellent wet performance while maintaining steering stability performance.

  FIG. 2 is a cross-sectional view taken along the line AA in FIG. FIG. 2 shows a tire meridian cross section including the tire rotation axis of the tread portion 2. As shown in FIG. 2, the groove depth d1 of the main groove 10 is, for example, 5 to 10 mm.

  In the present embodiment, the main groove 10 includes a pair of shoulder main grooves 25, 25 and a pair of center main grooves 30, 30. The shoulder main groove 25 is provided on both sides of the tire equator C and closest to the tread ground contact Te. The shoulder main groove 25 includes an outer shoulder main groove 26 positioned on the vehicle outer side when the vehicle is mounted and an inner shoulder main groove 27 positioned on the vehicle inner side when the vehicle is mounted.

  The center main groove 30 is provided on the inner side in the tire axial direction of the outer shoulder main groove 26 and the inner shoulder main groove 27 and on both sides of the tire equator C. The center main groove 30 includes an outer center main groove 31 positioned on the vehicle outer side when the vehicle is mounted, and an inner center main groove 32 positioned on the vehicle inner side when the vehicle is mounted.

  By providing each main groove 10 in the tread portion 2, the center land portion 35, the outer middle land portion 36, the inner middle land portion 37, the outer shoulder land portion 38, and the inner shoulder land portion 39 are divided. Yes.

  As shown in FIG. 2, at least one of the main grooves 10 is an asymmetric main groove 12.

  FIG. 3 shows an enlarged cross-sectional view of the asymmetric main groove 12. As shown in FIG. 3, the asymmetric main groove 12 includes a groove bottom 15, a first groove wall surface 16, and a second groove wall surface 17. The first groove wall surface 16 is located on one side of the groove bottom 15. The second groove wall surface 17 is located on the other side of the groove bottom 15. The second groove wall surface 17 is asymmetric with the first groove wall surface 16 with respect to the reference line 13 in the groove depth direction. Such an asymmetric main groove 12 suppresses resonance vibration of air passing through the asymmetric main groove 12 and effectively suppresses air column resonance sound.

  The first groove wall surface 16 of the asymmetric main groove 12 includes a first linear portion 18 and a concave curved surface portion 19.

  The first linear portion 18 extends linearly on the groove bottom 15 side. For example, the first linear portion 18 of the present embodiment is inclined at an angle θ1 of 10 to 15 ° with respect to the reference line 13 in the groove depth direction. The corner portion 22 between the first linear portion 18 and the groove bottom 15 is provided with a chamfered arc to prevent stress concentration.

  The concave curved surface portion 19 constitutes the tread surface 2 s side of the first groove wall surface 16. The concave curved surface portion 19 is along an arc whose center is located outside the tire. The first groove wall surface 16 including the concave curved surface portion 19 increases the groove volume in the vicinity of the tread surface 2s of the asymmetric main groove 12, and effectively suppresses the hydroplaning phenomenon. Moreover, such first groove wall surface 16 scatters vibrations of air passing through the asymmetric main groove 12 in multiple directions. For this reason, the resonance vibration of the air in the asymmetric main groove 12 is further suppressed, and the air column resonance sound is suppressed.

  The radius of curvature r1 of the concave curved surface portion 19 is preferably 10 mm or more, more preferably 13 mm or more, preferably 20 mm or less, more preferably 17 mm or less. Such a concave curved surface portion 19 balances wet performance and noise performance with a better balance.

  The distance L1 in the tire radial direction from the groove bottom 15 to the inner end 19i in the tire radial direction of the concave curved surface portion 19 is preferably 2.0 mm or more, more preferably 2.5 mm or more, more preferably 4.0 mm or less. More preferably, it is 3.5 mm or less. Thereby, air column resonance sound in the vicinity of the groove bottom 15 is suppressed, and excellent noise performance is exhibited.

  The first groove wall surface 16 including the first linear portion 18 and the concave curved surface portion 19 is desirably provided on the tire equator side. Thereby, a large ground pressure acts on the edge 16e of the first groove wall surface 16, and water easily flows into the concave curved surface portion 19 side of the asymmetric main groove 12 during wet running. Therefore, the hydroplaning phenomenon is effectively suppressed.

  The second groove wall surface 17 includes, for example, a second linear portion 20 and a third linear portion 21.

  The second linear portion 20 extends linearly on the groove bottom 15 side of the second groove wall surface 17. For example, the second linear portion 20 is inclined with respect to the reference line 13 in the groove depth direction. The angle θ2 of the second linear portion 20 with respect to the reference line 13 is preferably 10 ° or more, more preferably 13 ° or more, preferably 20 ° or less, more preferably 17 ° or less. When the angle θ2 is smaller than 10 °, the mold release property of the vulcanization mold during tire production may be deteriorated. On the other hand, when the angle θ2 is larger than 20 °, the drainage performance of the groove is lowered, and the hydroplaning phenomenon may easily occur.

  A corner portion 23 between the second linear portion 20 and the groove bottom 15 is provided with, for example, a chamfered arc. The radius of curvature r2 of the corner portion 23 is, for example, 1.0 to 2.0 mm.

  The third linear portion 21 is continuous with the second linear portion 20 and extends linearly on the tread surface 2s side of the second groove wall surface 17. The third linear portion 21 is inclined more gently than the second linear portion 20. Such third linear portion 21 suppresses uneven wear in the vicinity of the edge 17 e of the second groove wall surface 17.

  The angle θ3 of the third linear portion 21 with respect to the reference line 13 is preferably 35 ° or more, more preferably 40 ° or more, preferably 55 ° or less, more preferably 50 ° or less. Such a third linear portion 21 effectively guides the water film into the groove when the tread 2s is in contact with the water film during wet running. For this reason, the hydroplaning phenomenon is further suppressed.

  The length L3 of the third linear portion 21 in the groove depth direction is desirably smaller than, for example, the length L2 of the first linear portion 18 in the groove depth direction. When the length L3 of the third linear portion 21 in the groove depth direction is larger than the length L2 of the first linear portion 18 in the groove depth direction, between the third linear portion and the concave curved surface portion 19 There is a possibility that resonance vibration of air in the groove is likely to occur.

  As shown in FIG. 2, in the present embodiment, the outer shoulder main groove 26 is formed as the asymmetric main groove 12. Thereby, the water in the asymmetric main groove 12 is effectively discharged outside the tire during wet running. The remaining outer center main groove 31, inner center main groove 32, and inner shoulder main groove 27 are symmetric main grooves 11 in which the groove wall surfaces 14 and 14 are symmetrical to each other. Thereby, the rigidity inside the vehicle of the tread portion 2 is increased, and excellent steering stability performance is exhibited.

  Since the asymmetric main groove 12 includes the concave curved surface portion 19, the rigidity of the land portion in the vicinity of the asymmetric main groove 12 is likely to decrease. For this reason, as shown in FIG. 1, it is desirable that only the lateral grooves or sipes having a groove width of less than 2 mm communicate with the asymmetric main groove 12. Thereby, the rigidity of the land portion near the asymmetric main groove 12 is maintained, and excellent steering stability performance is exhibited. In this specification, the “sipe” is a cut having a width of about 1 mm or less, which is substantially free of width, and is distinguished from a draining groove.

  FIG. 4 shows an enlarged view of the outer middle land portion 36. As shown in FIG. 4, the outer middle land portion 36 is provided between the outer shoulder main groove 26 that is the asymmetric main groove 12 and the outer center main groove 31. The width W4 in the tire axial direction of the outer middle land portion 36 is, for example, 0.09 to 0.13 times the tread ground contact width TW.

  The outer middle land portion 36 is provided with an outer middle sipe 45 that communicates between the outer center main groove 31 and the outer shoulder main groove 26. The outer middle land portion 36 is a rib not provided with a lateral groove having a width larger than that of the sipe. Such an outer middle land portion 36 compensates for a decrease in rigidity due to the asymmetric main groove 12 and exhibits excellent steering stability performance.

  The outer middle sipe 45 includes a first inclined portion 46 that is inclined with respect to the tire axial direction, and a second inclined portion 47 that is inclined in a direction opposite to the first inclined portion 46. Such an outer middle sipe 45 effectively maintains the rigidity of the outer middle land portion 36 in the tire axial direction, and improves the steering stability performance during turning.

  FIG. 5 shows an enlarged view of the outer shoulder land portion 38. As shown in FIG. 5, the outer shoulder land portion 38 is provided on the outer side in the tire axial direction of the outer shoulder main groove 26 that is the asymmetric main groove 12. The width W7 of the outer shoulder land portion 38 in the tire axial direction is, for example, 0.18 to 0.24 times the tread ground contact width TW.

  The outer shoulder land portion 38 is provided with an outer shoulder sub-groove 55. For example, the outer shoulder sub-groove 55 extends linearly continuously in the tire circumferential direction. The groove width W8 of the outer shoulder sub-groove 55 is, for example, 1.0 to 3.0 mm. The groove depth d3 (shown in FIG. 2) of the outer shoulder sub-groove 55 is, for example, 0.5 to 1.5 mm.

  The outer shoulder land portion 38 is divided into a first outer shoulder land portion 56 and a second outer shoulder land portion 57 by an outer shoulder sub-groove 55. The first outer shoulder land portion 56 is provided on the inner side in the tire axial direction. The second outer shoulder land portion 57 is provided on the outer side in the tire axial direction.

  The first outer shoulder land portion 56 is a rib extending continuously in the tire circumferential direction. The first outer shoulder land portion 56 is not provided with a lateral groove communicating with the outer shoulder main groove 26. Such a 1st outer side shoulder land part 56 compensates for the rigidity fall by the asymmetric main groove 12, and exhibits the outstanding steering stability performance.

  The second outer shoulder land portion 57 is a block row divided by horizontal grooves. The second outer shoulder land portion 57 has a width W10 that is greater than the first outer shoulder land portion 56.

  The ratio W9 / W10 between the width W9 in the tire axial direction of the first outer shoulder land portion 56 and the width W10 in the tire axial direction of the second outer shoulder land portion 57 is preferably 0.70 or more, more preferably 0.75. It is above, Preferably it is 0.85 or less, More preferably, it is 0.80 or less. Such first outer shoulder land portion 56 and second outer shoulder land portion 57 exhibit excellent wandering performance while maintaining steering stability performance.

  The second outer shoulder land portion 57 is provided with an outer shoulder lateral groove 58 extending at least from the tread ground contact end Te to the inner side in the tire axial direction.

  The outer shoulder lateral groove 58 includes a first outer shoulder lateral groove 59 and a second outer shoulder lateral groove 60. The first outer shoulder lateral groove 59 communicates with the outer shoulder sub-groove 55 and terminates. The second outer shoulder lateral groove 60 terminates in the first outer shoulder land portion 56 beyond the outer shoulder sub-groove 55. The first outer shoulder lateral grooves 59 and the second outer shoulder lateral grooves 60 are alternately provided in the tire circumferential direction. Such first outer shoulder lateral grooves 59 and second outer shoulder lateral grooves 60 make the rigidity distribution of the outer shoulder land portions 38 uniform, and exhibit excellent wear resistance.

  It is desirable that the outer shoulder lateral groove 58 has a groove width W11 that gradually decreases toward the outer side in the tire axial direction. Thereby, the wind noise generated on the side surface of the outer shoulder land portion 38 on the tread ground contact end Te side is effectively suppressed. For this reason, wet performance and noise performance are balanced.

  FIG. 6 shows an enlarged view of the center land portion 35. As shown in FIG. 6, the center land portion 35 is provided between the outer center main groove 31 and the inner center main groove 32. The center land portion 35 is, for example, a rib continuous in the tire circumferential direction.

  The width W3 of the center land portion 35 in the tire axial direction is, for example, 0.08 to 0.14 times the tread ground contact width TW (shown in FIG. 1 and the same applies hereinafter). The center land portion 35 of the present embodiment has a substantially constant width. The center land portion 35 is asymmetrical with respect to the tire equator C. The center land portion 35 is provided so as to be biased with respect to the tire equator C in a direction toward the vehicle inner side when the vehicle is mounted.

  The center land portion 35 is provided with outer center lug grooves 41 and inner center lug grooves 42 alternately in the tire circumferential direction. The outer center lug groove 41 has one end 41 a communicating with the outer center main groove 31 and the other end 41 b terminating in the center land portion 35. The inner center lug groove 42 has one end 42 a communicating with the inner center main groove 32 and the other end 42 b terminating in the center land portion 35. The outer center lug groove 41 and the inner center lug groove 42 exhibit excellent wet performance while maintaining the rigidity of the center land portion 35.

  The length L4 of the outer center lug groove 41 in the tire axial direction is preferably smaller than the length L5 of the inner center lug groove 42 in the tire axial direction. The outer center lug groove 41 and the inner center lug groove 42 maintain the rigidity of the center land portion 35 on the inner side in the tire axial direction, and exhibit excellent steering stability performance.

  It is desirable that the outer center lug groove 41 and the inner center lug groove 42 each terminate in the center land portion 35 without intersecting the tire equator C. Such outer center lug groove 41 and inner center lug groove 42 further maintain the rigidity of the center land portion 35.

  FIG. 7 shows an enlarged view of the inner middle land portion 37. As shown in FIG. 7, the inner middle land portion 37 is provided between the inner center main groove 32 and the inner shoulder main groove 27. The width W5 in the tire axial direction of the inner middle land portion 37 is, for example, 0.11 to 0.17 times the tread ground contact width TW.

  In the inner middle land portion 37, first inner middle lug grooves 50 and second inner middle lug grooves 51 are alternately provided in the tire circumferential direction. The first inner middle lug groove 50 has one end 50 a communicating with the inner shoulder main groove 27 and the other end 50 b terminating in the inner middle land portion 37. The second inner middle lug groove 51 has one end 51 a communicating with the inner center main groove 32 and the other end 51 b terminating in the inner middle land portion 37. Such first inner middle lug groove 50 and second inner middle lug groove 51 achieve both wet performance and steering stability performance.

  The first inner middle lug groove 50 preferably has a groove width W6 that gradually increases toward the outer side in the tire axial direction. The groove width W6 of the first inner middle lug groove 50 of the present embodiment gradually increases stepwise toward the outer side in the tire axial direction. Such a first inner middle lug groove 50 further improves the wet performance.

  The length L7 of the second inner middle lug groove 51 in the tire axial direction is smaller than the length L6 of the first inner middle lug groove 50 in the tire axial direction. Such a 2nd inner side middle lug groove 51 maintains the rigidity of the inner side middle land part 37, and exhibits the outstanding steering stability performance.

  The inner middle land portion 37 is preferably provided with an inner middle sipe 52 that communicates between the outer end 51o of the second inner middle lug groove 51 in the tire axial direction and the inner shoulder main groove 27. Such an inner middle sipe 52 relaxes the rigidity of the inner middle land portion 37 and suppresses the contact sound between the inner middle land portion 37 and the road surface.

  FIG. 8 shows an enlarged view of the inner shoulder land portion 39. As shown in FIG. 8, the inner shoulder land portion 39 is provided on the outer side in the tire axial direction of the inner shoulder main groove 27. The width W12 in the tire axial direction of the inner shoulder land portion 39 is, for example, 0.16 to 0.24 times the tread ground contact width TW.

  An inner shoulder sub-groove 65 is provided in the inner shoulder land portion 39. For example, the inner shoulder sub-groove 65 extends linearly continuously in the tire circumferential direction. The groove width W13 of the inner shoulder sub-groove 65 is, for example, 1.0 to 3.0 mm. The groove depth d4 (shown in FIG. 2) of the inner shoulder sub-groove 65 is, for example, 0.5 to 1.5 mm.

  The inner shoulder land portion 39 is divided into a first inner shoulder land portion 66 and a second inner shoulder land portion 67 by an inner shoulder sub-groove 65. The first inner shoulder land portion 66 is provided on the inner side in the tire axial direction. The second inner shoulder land portion 67 is provided on the outer side in the tire axial direction.

  The 1st inner side shoulder land part 66 is a rib in which the horizontal groove larger than a sipe is not provided. Such a 1st inner side shoulder land part 66 exhibits the outstanding steering stability performance.

  The second inner shoulder land portion 67 has a larger width W15 than the first inner shoulder land portion 66. The ratio W14 / W15 between the width W14 of the first inner shoulder land portion 66 in the tire axial direction and the width W15 of the second inner shoulder land portion 67 in the tire axial direction is preferably 0.20 or more, more preferably 0.25. It is above, Preferably it is 0.40 or less, More preferably, it is 0.35 or less. Such first inner shoulder land portion 66 and second inner shoulder land portion 67 achieve both wet performance and steering stability performance.

  In the second inner shoulder land portion 67, at least inner shoulder lateral grooves 68 extending inward in the tire axial direction from the tread contact end Te are provided in the tire circumferential direction. The inner end 68 i in the tire axial direction of the inner shoulder lateral groove 68 terminates in the second inner shoulder land portion 67.

  An inner shoulder sipe 69 is preferably provided on the inner side in the tire axial direction of the inner shoulder lateral groove 68. Such an inner shoulder sipe 69 suppresses a contact sound between the inner shoulder land portion 39 and the road surface, and improves noise performance.

  The inner shoulder sipe 69 communicates with the inner end 68 i in the tire axial direction of the inner shoulder lateral groove 68 and extends at least to the first inner shoulder land portion 66. The inner shoulder sipe 69 is inclined at an angle θ4 larger than the inner shoulder lateral groove 68 with respect to the tire axial direction.

  The inner shoulder sipe 69 includes a first inner shoulder sipe 70 and a second inner shoulder sipe 71. The first inner shoulder sipe 70 communicates with the inner shoulder main groove 27. The second inner shoulder sipe 71 terminates in the first inner shoulder land portion 66. The first inner shoulder sipes 70 and the second inner shoulder sipes 71 are provided alternately in the tire circumferential direction. Such first inner shoulder sipe 70 and second inner shoulder sipe 71 make the rigidity distribution of the first inner shoulder land portion 66 and the second inner shoulder land portion 67 uniform.

  Although the pneumatic tire of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above, and can be implemented with various modifications.

A pneumatic tire of size 215 / 60R17 having the basic pattern of FIG. 1 and having the cross-sectional shape of the main groove shown in FIG. 2 was prototyped based on the specifications of Table 1. As Comparative Examples 1 and 2, a tire having the basic pattern shown in FIG. 1 and having all the main grooves being symmetrical main grooves was manufactured. These tires were mounted on the following test vehicles and tested for wet performance and noise performance. The common specifications and test methods for each tire are as follows.
Wearing rim: 17 × 7J
Tire internal pressure: 240kPa
Test vehicle: Front-wheel drive vehicle, displacement 2400cc
Tire mounting position: all wheels

<Wet performance>
The test vehicle is entered while gradually increasing the speed to the following test course, the lateral acceleration (lateral G) of the front wheels of the test vehicle is measured, and the average lateral G of the front wheels at a speed of 55 to 80 km / h is calculated. It was done. The results are displayed as an index with Example 1 as 100. It shows that it is excellent in wet performance, so that a numerical value is large.
Test course: Circulation course with a radius of 100 m Road surface: A water pool with a depth of 6 mm and a length of 6 m is installed on the asphalt road surface

<Noise performance>
Vehicle interior noise was measured when traveling on a dry asphalt road surface at a speed of 60 km / h with the test vehicle. Vehicle interior noise was measured with a microphone located at the head of the driver's seat. The evaluation is performed by the reciprocal of the noise level (db), and is indicated by an index with Example 1 as 100. The larger the value, the better the noise performance.
The test results are shown in Table 1.

  As a result of the test, it was confirmed that the pneumatic tire of the example had both wet performance and noise performance.

2 Tread part 10 Main groove
12 asymmetric main groove 15 groove bottom 16 first groove wall surface 17 second groove wall surface 18 first linear portion 19 concave curved surface portion

Claims (7)

A pneumatic tire provided with a plurality of main grooves continuous in the tire circumferential direction and a land portion in the tread portion,
The tread portion is designated for mounting on the vehicle,
The main groove includes an outer shoulder main groove located on the vehicle outer side when the vehicle is mounted,
In the tire meridian cross section including the tire rotation axis, the outer shoulder main groove is located on the groove bottom, the first groove wall surface located on the inner side in the tire axial direction of the groove bottom, on the outer side in the tire axial direction of the groove bottom, and The first groove wall surface is an asymmetric main groove having an asymmetric second groove wall surface with respect to a reference line in the groove depth direction ,
The first groove wall surface of the outer shoulder main groove includes a first linear portion that forms the groove bottom side, and a concave curved surface portion that forms a tread surface side and that is along a circular arc whose center is located outside the tire. See
The land portion includes an outer middle land portion constituting the first groove wall surface, and a first outer shoulder land portion constituting the second groove wall surface and continuously extending in a tire circumferential direction,
The outer middle land portion is provided with an outer middle sipe communicating with the outer shoulder main groove,
The pneumatic tire according to claim 1, wherein the first outer shoulder land portion is a rib extending continuously in the tire circumferential direction without a lateral groove communicating with the outer shoulder main groove .   The pneumatic tire according to claim 1, wherein a radius of curvature of the concave curved surface portion is 10 to 20 mm.   The second groove wall surface of the asymmetric main groove includes a second linear portion constituting the groove bottom side, and a third linear portion constituting the tread surface side and extending at a gentler slope than the second linear portion. The pneumatic tire according to claim 1 or 2, comprising:   The pneumatic tire according to claim 3, wherein a length of the third linear portion in the groove depth direction is smaller than a length of the first linear portion in the groove depth direction.   The pneumatic tire according to any one of claims 1 to 3, wherein only the lateral groove or sipe having a groove width of less than 2 mm communicates with the asymmetric main groove. The said outer middle sipe includes the 1st inclination part which inclines with respect to a tire axial direction, and the 2nd inclination part which inclines in the opposite direction to the said 1st inclination part. Pneumatic tire. The land portion includes a second outer shoulder land portion that is divided between an outer shoulder sub-groove that continuously extends in a tire circumferential direction on the outer side in the tire axial direction of the outer shoulder main groove, and a tread ground contact end.
Before Symbol The second outer shoulder land portion, a plurality of outer shoulder lateral grooves extending in the inner side in the tire axial direction from at least the tread ground contact edge is provided,
The pneumatic tire according to any one of claims 1 to 6, wherein the outer shoulder lateral groove includes a second outer shoulder lateral groove that exceeds the outer shoulder sub-groove and terminates in the first outer shoulder land portion.

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