JP2016060345A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire improved in steering stability on a dry road surface and in on-snow performance in a well-balanced manner.SOLUTION: Provided is a pneumatic tire 1 in which a pair of shoulder major grooves 3 and a center major groove 4 are formed on a tread part 2 so that a pair of shoulder land parts 7 and a pair of center land parts 8 are divided. A ratio W1/W2 of the shoulder land part 7 width W1 to a center land part 8 width W2 is 1.2-1.6. On the center land parts 8, a plurality of center shallow grooves 12 are formed that extend in an inclined manner from the shoulder major grooves 3 in a tire shaft direction and that end within the center land parts 8. On a shoulder major groove 3 side on the shoulder land parts 7, a shoulder sub groove 28 with a groove width smaller than the shoulder major groove 3 is formed extending continuously in a tire circumferential direction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire with improved handling stability and performance on snow on a dry road surface.

  The following Patent Document 1 proposes a pneumatic tire in which lateral grooves and sipes are provided in a center land portion and a shoulder land portion. In such a tire, lateral grooves and sipes exhibit an edge effect, and exhibit excellent wet performance and on-snow performance.

  However, in the tire of Patent Document 1, the width in the tire axial direction of the center land portion is about half that of the shoulder land portion. For this reason, the tire of Patent Document 1 has a tendency that the center land portion is easily deformed, and in particular, steering stability on a dry road surface tends to be low.

  In addition, since the edge component extending along the tire circumferential direction is only the groove edge of the center main groove and the shoulder main groove in the tire of Patent Document 1, the frictional force in the tire axial direction on snow is small. There was a problem that skidding was likely to occur.

JP 2012-136187 A

  The present invention has been devised in view of the above circumstances, and a main object of the present invention is to provide a pneumatic tire in which handling stability on a dry road surface and performance on snow are improved in a well-balanced manner.

  The present invention relates to a pair of shoulder main grooves extending continuously in the tire circumferential direction on the tread ground end side closest to the tread portion, and a center main extending continuously in the tire circumferential direction on the inner side in the tire axial direction than the shoulder main grooves. By providing a groove, a pneumatic tire in which a shoulder land portion on the outer side in the tire axial direction than each shoulder main groove and a center land portion between the shoulder main groove and the center main groove are separated. The ratio W1 / W2 between the width W1 of the shoulder land portion in the tire axial direction and the width W2 of the center land portion in the tire axial direction is 1.2 to 1.6. A plurality of center shallow grooves extending from the shoulder main groove to the tire axial direction and terminating in the center land portion are provided on the shoulder main groove side. It is characterized in that the shoulder sub groove extending continuously in the tire circumferential direction at smaller groove width than the shoulder main groove is provided.

  In the pneumatic tire of the present invention, it is desirable that the shoulder sub-groove has a groove width of 1.2 to 3.0 mm.

  In the pneumatic tire of the present invention, the center shallow groove is preferably inclined at an angle of 35 to 65 ° with respect to the tire circumferential direction.

  In the pneumatic tire according to the present invention, it is desirable that the angle of the center shallow groove gradually decreases toward the inner side in the tire axial direction.

  In the pneumatic tire of the present invention, it is preferable that the center shallow groove terminates on the inner side in the tire axial direction from the center in the width direction of the center land portion.

  In the pneumatic tire of the present invention, the center shallow groove includes a first center shallow groove and a second center shallow groove having a length in the tire axial direction smaller than that of the first center shallow groove. It is desirable that the shallow grooves and the second center shallow grooves are provided alternately in the tire circumferential direction.

  In the pneumatic tire of the present invention, the length L1 of the first center shallow groove in the tire axial direction is 0.50 to 0.95 times the width W2 of the center land portion, and the second center shallow groove It is desirable that the length L2 in the tire axial direction is 0.50 to 0.90 times the width W2 of the center land portion.

  In the pneumatic tire of the present invention, the angle with respect to the tire circumferential direction at the inner end in the tire axial direction of the second center shallow groove is an angle with respect to the tire circumferential direction at the inner end in the tire axial direction of the first center shallow groove. Is desirable.

  In the pneumatic tire of the present invention, the center shallow groove includes an opening having a width of 1.0 to 2.5 mm, and a groove bottom sipe having a width of less than 1 mm extending inwardly in the tire radial direction from the bottom of the opening. It is desirable to include.

  In the pneumatic tire of the present invention, it is desirable that the shoulder land portion is provided with a plurality of shoulder lug grooves extending at least from the tread ground contact end in the tire axial direction and terminating without reaching the shoulder sub-groove. .

  In the pneumatic tire of the present invention, the shoulder land portion is provided with a connecting sipe that extends from the inner end of each shoulder lug groove in the tire axial direction to the shoulder main groove across the shoulder sub groove. desirable.

  The pneumatic tire according to the present invention has a pair of shoulder main grooves extending continuously in the tire circumferential direction on the tread ground end side most continuously on the tread portion, and continuously in the tire circumferential direction on the inner side in the tire axial direction than the shoulder main grooves. By providing the extended center main groove, the shoulder land portion on the outer side in the tire axial direction from each shoulder main groove and the center land portion between the shoulder main groove and the center main groove are separated.

  The ratio W1 / W2 between the width W1 of the shoulder land portion in the tire axial direction and the width W2 of the center land portion in the tire axial direction is 1.2 to 1.6. As a result, the width of the center land portion where a large contact pressure acts is secured, and the handling stability on the dry road surface is enhanced.

  The center land portion is provided with a plurality of center shallow grooves extending from the shoulder main groove to the tire axial direction and terminating in the center land portion. Such a center shallow groove exhibits an edge effect in the tire circumferential direction and the tire axial direction while maintaining the rigidity of the center land portion. For this reason, on-snow performance is enhanced while maintaining steering stability on a dry road surface.

  In the shoulder land portion, a shoulder sub-groove extending continuously in the tire circumferential direction with a groove width smaller than the shoulder main groove is provided on the shoulder main groove side. Such a shoulder sub-groove increases the frictional force in the tire axial direction on the snow by the edge effect of the groove without impairing the steering stability on the dry road surface, and effectively suppresses the skid on the snow.

  As described above, the pneumatic tire of the present invention can improve the steering stability on the dry road surface and the performance on snow with a good balance.

It is an expanded view of the tread part of the pneumatic tire of this embodiment. It is the sectional view on the AA line of FIG. It is an enlarged view of the center land part of FIG. FIG. 4 is a cross-sectional view of the center shallow groove of FIG. 3 taken along line BB. It is CC sectional view taken on the line of the 1st center shallow groove of FIG. FIG. 4 is a sectional view taken along line DD of the second center shallow groove in FIG. 3. It is an enlarged view of the shoulder land part of FIG. It is the EE sectional view taken on the line of the connection sipe and a shoulder lug groove of FIG. It is the FF sectional view taken on the line of the shoulder sipe of FIG. It is an expanded view of the tread part of the pneumatic tire of a comparative example.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a development view of 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 this embodiment is suitably used for, for example, a passenger car.

  As shown in FIG. 1, the tread portion 2 of the tire 1 is provided with a pair of shoulder main grooves 3 and a center main groove 4.

  The shoulder main groove 3 extends continuously in the tire circumferential direction on the tread ground contact end Te side. The shoulder main groove 3 of the present embodiment is linear along the tire circumferential direction. The shoulder main groove 3 may be, for example, a wave shape or a zigzag shape.

  The “tread grounding end Te” is a flat surface with a normal load applied to a normal tire 1 which is assembled with a normal rim (not shown) and filled with a normal internal pressure, and which is not loaded, with a camber angle of 0 °. This is the contact position on the outermost side in the tire axial direction when the contact is made on the ground.

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

  “Regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. “JAMATA” is the “highest air pressure”, TRA is the table “TIRE LOAD LIMITS AT” The maximum value described in “VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO.

  “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” is “Maximum load capacity”, TRA is “TIRE LOAD LIMITS” The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”, “LOAD CAPACITY” in the case of ETRTO.

  The center main groove 4 is provided on the inner side in the tire axial direction than the shoulder main groove 3. The center main groove 4 extends continuously in the tire circumferential direction. The center main groove 4 has, for example, a linear shape along the tire circumferential direction. The center main groove 4 of this embodiment consists of one, and is provided on the tire equator C. For example, one center main groove 4 may be provided on each side of the tire equator C in the tire axial direction.

  The groove width W3 of the shoulder main groove 3 and the groove width W4 of the center main groove 4 are, for example, 3 to 10% of the tread grounding width TW. The shoulder main groove 3 and the center main groove 4 exhibit excellent wet performance while maintaining the rigidity of the tread portion 2. 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 the normal state.

  FIG. 2 shows a cross-sectional view taken along line AA of FIG. As shown in FIG. 2, the groove depth d1 of the shoulder main groove 3 and the groove depth d2 of the center main groove 4 are preferably 5 to 15 mm, for example, in the case of a tire for passenger cars.

  As shown in FIG. 1, the tread portion 2 is divided into a pair of shoulder land portions 7 and a pair of center land portions 8. Each shoulder land portion 7 is provided on the outer side in the tire axial direction of each shoulder main groove 3. Each center land portion 8 is provided between the shoulder main groove 3 and the center main groove 4. In the present embodiment, each groove and each land portion are formed substantially symmetrical with respect to a point on the tire equator C, but are not necessarily limited to such a mode.

  The ratio W1 / W2 between the width W1 of the shoulder land portion 7 in the tire axial direction and the width W2 of the center land portion 8 in the tire axial direction is in the range of 1.2 to 1.6. Thereby, the width | variety of the center land part 8 where a big ground pressure acts is ensured, and the steering stability on a dry road surface is improved. In order to further enhance the above-described effect, the ratio W1 / W2 is preferably 1.3 to 1.5.

  FIG. 3 shows an enlarged view of the center land portion 8. As shown in FIG. 3, the width W2 of the center land portion 8 in the tire axial direction is, for example, 0.15 to 0.20 times the tread ground contact width TW (shown in FIG. 1, the same applies hereinafter). It is.

  The center land portion 8 is provided with a plurality of center shallow grooves 12. As a desirable aspect, the center land portion 8 is a rib extending continuously in the tire circumferential direction where a drainage groove other than the center shallow groove 12 is not disposed.

  The center shallow groove 12 extends from the shoulder main groove 3 with respect to the tire axial direction and terminates in the center land portion 8. Since the center shallow groove 12 does not completely divide the center land portion 8, it is possible to maintain the rigidity of the center land portion 8 and improve the handling stability on the dry road surface.

  The center shallow groove 12 is inclined at an angle of 35 to 65 ° with respect to the tire circumferential direction, for example. Such a center shallow groove 12 exhibits an edge effect in the tire circumferential direction and the tire axial direction, and improves performance on snow. As a desirable mode, for example, the angle θ1 with respect to the tire circumferential direction of the center shallow groove 12 gradually decreases toward the inner side in the tire axial direction. The center shallow groove 12 increases the edge component in the tire circumferential direction on the inner side in the tire axial direction where a large contact pressure acts. This effectively increases the frictional force in the tire axial direction on snow.

  The center shallow groove 12 is preferably terminated, for example, on the inner side in the tire axial direction from the center 8c in the width direction of the center land portion 8. Thereby, the edge component of the center shallow groove 12 increases, and the performance on snow is further enhanced.

  FIG. 4 shows a cross-sectional view taken along line BB perpendicular to the length direction of the center shallow groove 12 of FIG. As shown in FIG. 4, the center shallow groove 12 includes, for example, an opening 15 that is opened on the tread surface 8 s side of the center land portion 8 and a groove bottom sipe 14 that extends from the bottom of the opening 15 toward the inside in the tire radial direction. Contains. In this specification, “sipe” means a cut having a width of less than 1 mm, and is distinguished from a drainage groove.

  The opening 15 has, for example, a circular arc-shaped contour that protrudes inward in the tire radial direction in a cross section orthogonal to the length direction of the center shallow groove 12.

  The width W6 of the tread surface 8s of the opening 15 is, for example, 1.0 to 2.5 mm, more preferably 1.5 to 2.0 mm. The depth d4 of the opening 15 is, for example, 0.5 to 1.5 mm, more preferably 0.8 to 1.2 mm.

  Such an opening 15 can effectively suppress chipping and uneven wear of the center land portion 8 starting from the edge of the center shallow groove 12. Moreover, the opening 15 increases the volume of the center shallow groove 12 and discharges water between the tread surface of the center land portion 8 and the road surface. For this reason, the tire 1 of the present embodiment can improve not only the performance on snow but also the wet performance and the performance on ice.

  The width W7 of the groove bottom sipe 14 of this embodiment is preferably 0.3 to 0.7 mm. The depth d5 from the tread surface 8s of the center land portion 8 to the bottom 14d of the groove bottom sipe 14 is 4.5 to 6.0 mm, more preferably 5.0 to 5.5 mm. Such a groove bottom sipe 14 is useful for suppressing distortion at the ground contact portion of the center land portion 8 during traveling and suppressing uneven wear.

  As shown in FIG. 3, the center shallow groove 12 includes a first center shallow groove 17 and a second center shallow groove 18 having a smaller length in the tire axial direction than the first center shallow groove 17. The first center shallow grooves 17 and the second center shallow grooves 18 are provided alternately in the tire circumferential direction, for example.

  The length L1 of the first center shallow groove 17 in the tire axial direction is preferably 0.50 times or more, more preferably 0.70 times or more, preferably 0 or more than the width W2 of the center land portion 8 in the tire axial direction. .95 times or less, more preferably 0.90 times or less.

  FIG. 5 shows a cross-sectional view taken along the line C-C along the length direction of the first center shallow groove 17 in FIG. 3. As shown in FIG. 5, the first center shallow groove 17 includes a first portion 19 having a substantially constant depth and a second portion in which the depth gradually decreases from the first portion 19 toward the shoulder main groove 3 side. 20 and so on. Such a first center shallow groove 17 maintains the rigidity of the center land portion 8 on the outer side in the tire axial direction, and helps maintain steering stability on a dry road surface.

  The boundary 22 between the first portion 19 and the second portion 20 is preferably located on the outer side in the tire axial direction from the center 8c in the width direction of the center land portion 8 (shown in FIG. 3). The first portion 19 and the second portion 20 as described above secure the volume of the first center shallow groove 17 and improve the water absorption performance of the sipe.

  As a particularly preferable aspect, the outer end 17 o of the first center shallow groove 17 is formed only by the opening 15. That is, the groove bottom sipe 14 of the first center shallow groove 17 is terminated in front of the shoulder main groove 3 without being communicated with the shoulder main groove 3 while gradually decreasing the depth toward the outer side in the tire axial direction. Is desirable. Such first center shallow grooves 17 can maintain the rigidity of the center land portion 8 on the outer side in the tire axial direction, and can suppress uneven wear.

  As shown in FIG. 3, the length L2 of the second center shallow groove 18 in the tire axial direction is preferably 0.50 times or more, more preferably 0.65, the width W2 of the center land portion 8 in the tire axial direction. It is more than double, preferably 0.90 times or less, more preferably 0.75 times or less.

  The ratio L2 / L1 between the length L2 of the second center shallow groove 18 and the length L1 of the first center shallow groove 17 is preferably 0.65 or more, more preferably 0.70 or more, preferably 0.85 or less, more preferably 0.80 or less. The first center shallow groove 17 and the second center shallow groove 18 improve the steering stability on the dry road surface and the performance on snow with a good balance.

  The angle θ3 of the second center shallow groove 18 with respect to the tire circumferential direction at the inner end 18i in the tire axial direction is larger than the angle θ2 with respect to the tire circumferential direction at the inner end 17i of the first center shallow groove 17 in the tire axial direction. Is desirable. Thereby, at the time of driving | running | working, distortion of the grounding part of the center land part 8 is suppressed more effectively, and the uneven wear is suppressed.

  6 is a cross-sectional view taken along the line DD along the length direction of the second center shallow groove 18 of FIG. As shown in FIG. 6, the second center shallow groove 18 has a bottom surface 23 extending in the tire axial direction at a substantially constant depth. Such a second center shallow groove 18 is useful for suppressing distortion of the ground contact portion of the center land portion 8 and suppressing uneven wear during traveling.

  As a particularly preferable aspect, the outer end 18 o of the second center shallow groove 18 is formed only by the opening 15. That is, it is preferable that the groove bottom sipe 14 of the second center shallow groove 18 is terminated before the shoulder main groove 3 without communicating with the shoulder main groove 3. Such a second center shallow groove 18 can maintain the rigidity of the center land portion 8 on the outer side in the tire axial direction and suppress uneven wear.

  FIG. 7 shows an enlarged view of the shoulder land portion 7. As shown in FIG. 7, the width W1 of the shoulder land portion 7 in the tire axial direction is, for example, 0.18 to 0.32 times the tread contact width TW.

  The shoulder land portion 7 is provided with a shoulder sub-groove 28 extending continuously in the tire circumferential direction on the shoulder main groove 3 side.

  The shoulder sub-groove 28 of the present embodiment extends, for example, in a straight line, but is not limited thereto, and may be a zigzag shape or a wave shape.

  The shoulder sub-groove 28 has a groove width W9 smaller than the shoulder main groove 3. The groove width W9 of the shoulder sub-groove 28 is preferably 2 mm or more, more preferably 2.5 mm or more, preferably 4 mm or less, more preferably 3.5 mm or less.

  As shown in FIG. 2, the groove depth d7 of the shoulder sub-groove 28 is preferably 2 mm or more, more preferably 2.5 mm or more, preferably 4 mm or less, more preferably 3.5 mm or less.

  Such a shoulder sub-groove 28 increases the frictional force in the tire axial direction on the snow by the edge effect of the groove edge without reducing the lateral rigidity of the shoulder land portion 7 and effectively prevents the skid on the snow. Suppress.

  As shown in FIG. 7, the shoulder land portion 7 includes a first shoulder land portion 31 inside the shoulder sub-groove 28 in the tire axial direction and a second shoulder land portion 32 outside the shoulder sub-groove 28 in the tire axial direction. Contains.

  The width W10 of the first shoulder land portion 31 in the tire axial direction is preferably 0.1 to 0.2 times the width W1 of the shoulder land portion 7 in the tire axial direction, for example. As a result, the rigidity of the shoulder land portion 7 on the inner side in the tire axial direction is enhanced, and as a result, the handling stability on the dry road surface is enhanced.

  The second shoulder land portion 32 has a width W11 that is larger than that of the first shoulder land portion 31. The width W11 of the second shoulder land portion 32 is preferably, for example, 0.75 to 0.80 times the width W1 of the shoulder land portion 7.

  The shoulder land portion 7 is provided with, for example, a plurality of shoulder lug grooves 34 spaced in the tire circumferential direction, and shoulder sipes 35 provided between the shoulder lug grooves 34.

  The shoulder lug groove 34 extends at least from the tread ground contact end Te toward the inside in the tire axial direction. The shoulder lug groove 34 terminates without reaching the shoulder sub-groove 28. Such a shoulder lug groove 34 improves wet performance and on-snow performance while maintaining the rigidity of the shoulder land portion 7 on the inner side in the tire axial direction.

  A connecting sipe 36 that extends from the inner end 34 i of the shoulder lug groove 34 to the shoulder main groove 3 across the shoulder sub-groove 28 is preferably provided on the inner side in the tire axial direction of the shoulder lug groove 34. Such a connection sipe 36 suppresses distortion of the ground contact portion on the inner side in the tire axial direction of the shoulder lug groove 34 during traveling, and suppresses uneven wear.

  FIG. 8 is a cross-sectional view taken along the line E-E along the length direction of the connecting sipe 36 of FIG. As shown in FIG. 8, the connection sipe 36 includes a first portion 37 on the shoulder main groove 3 side and a second portion 38 whose bottom surface is raised on the tread grounding end Te side with respect to the first portion 37. . Such a connection sipe 36 suppresses uneven wear of the shoulder land portion 7 in the vicinity of the inner end of the shoulder lug groove 34.

  The first portion 37 has, for example, a substantially constant depth d9 and crosses the shoulder sub-groove 28. The depth d9 of the first portion 37 is, for example, 2.5 to 3.5 mm. As a desirable mode, the first portion 37 has a depth equal to that of the shoulder minor groove 28. As a result, the steering stability on the dry road surface and the performance on snow can be improved in a well-balanced manner.

  The second portion 38 is provided between the first portion 37 and the shoulder lug groove 34. The depth d10 of the second portion 38 is preferably 0.40 times or more, more preferably 0.45 times or more, preferably 0.60 times or less, more preferably 0, greater than the depth d9 of the first portion 37. .55 times or less. Such a second portion 38 serves to improve the steering stability on the dry road surface while maintaining the water absorption performance of the connecting sipe 36.

  As shown in FIG. 7, for example, one or two shoulder sipes 35 are provided between shoulder lug grooves 34 adjacent to each other in the tire circumferential direction. For example, the shoulder sipe 35 extends substantially parallel to the shoulder lug groove 34.

  The shoulder sipe 35 extends, for example, at least from the tread ground contact end Te toward the inside in the tire axial direction. The shoulder sipe 35 is terminated without reaching the shoulder sub-groove 28, for example. As a desirable mode, the inner end 35 i of the shoulder sipe 35 is located on the inner side in the tire axial direction than the inner end 34 i of the shoulder lug groove 34. Such a shoulder sipe 35 suppresses distortion of the ground contact portion of the second shoulder land portion 32 during traveling.

  An angle θ4 of the shoulder sipe 35 with respect to the tire axial direction is, for example, 0 to 15 °. As a desirable mode, it is desirable that the angle θ4 of the shoulder sipe 35 gradually increases toward the inner side in the tire axial direction. Such a shoulder sipe 35 can increase the frictional force in the tire axial direction while improving the traction performance on snow.

  FIG. 9 is a cross-sectional view taken along the line FF along the length direction of the shoulder sipe 35 of FIG. As shown in FIG. 9, the shoulder sipe 35 has, for example, a raised portion 40 having a partially raised bottom surface 39. Such a raised portion 40 can suppress the opening of the shoulder sipe 35 and enhance the edge effect.

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

A pneumatic tire having the basic pattern of FIG. 1 was prototyped based on the specifications in Table 1. As a comparative example, as shown in FIG. 10, a tire without a center shallow groove and a shoulder sub-groove was manufactured. Each test tire was tested for handling stability on a dry road surface, wet performance, and performance on snow. The common specifications for each test tire are as follows.
Tire size: 185 / 65R15
Rim size: 15 x 5.5
Tire internal pressure: 200kPa
Tread contact width TW: 132mm
Shoulder main groove groove width W3 and center main groove groove width W4: 9.0 mm
Shoulder main groove depth d1 and center main groove depth d2: 7.4 mm
The test method is as follows.

<Operation stability on dry road>
The driving stability of the following test vehicle when driving on a dry road test course was evaluated based on the driver's sensuality. A result is a score which sets the comparative example 1 to 100, and shows that steering stability is excellent, so that a numerical value is large.
Test vehicle: Displacement 1500cc, front-wheel drive vehicle Test tire mounting position: all wheels

<Wet performance>
The test vehicle traveled on an asphalt road surface with a radius of 100 m provided with a puddle having a depth of 5 mm and a length of 20 m, and the lateral acceleration (lateral G) of the front wheels was measured. The result is an average lateral G at a speed of 50 to 80 km / h, and is represented by an index with the value of Comparative Example 1 being 100. It shows that wet performance is excellent, so that a numerical value is large.

<Snow performance>
The performance on the snow when running on a snowy road with the test vehicle was evaluated by the driver's sensuality. A result is a score which sets comparative example 1 to 100, and shows that performance on snow is excellent, so that a numerical value is large.
The test results are shown in Table 1.

  As a result of the test, it was confirmed that the pneumatic tire of the example improved the handling stability on the dry road surface and the performance on snow in a well-balanced manner.

2 Tread part 3 Shoulder main groove 4 Center main groove 7 Shoulder land part 8 Center land part 12 Center shallow groove 28 Shoulder sub groove

Claims (11)

A pair of shoulder main grooves extending continuously in the tire circumferential direction at the tread ground end side and a center main groove extending continuously in the tire circumferential direction on the inner side in the tire axial direction than the shoulder main grooves are provided in the tread portion. A pneumatic tire in which a shoulder land portion on the outer side in the tire axial direction than each shoulder main groove and a center land portion between the shoulder main groove and the center main groove are divided,
The ratio W1 / W2 between the width W1 of the shoulder land portion in the tire axial direction and the width W2 of the center land portion in the tire axial direction is 1.2 to 1.6,
The center land portion is provided with a plurality of center shallow grooves extending in the tire axial direction from the shoulder main groove and terminating in the center land portion,
The pneumatic tire according to claim 1, wherein a shoulder sub-groove extending continuously in the tire circumferential direction with a groove width smaller than the shoulder main groove is provided on the shoulder main groove side in the shoulder land portion.   The pneumatic tire according to claim 1, wherein the shoulder minor groove has a groove width of 1.2 to 3.0 mm.   The pneumatic tire according to claim 1 or 2, wherein the center shallow groove is inclined at an angle of 35 to 65 ° with respect to a tire circumferential direction.   The pneumatic tire according to any one of claims 1 to 3, wherein the center shallow groove has an angle with respect to a tire circumferential direction that gradually decreases toward an inner side in the tire axial direction.   The pneumatic tire according to any one of claims 1 to 4, wherein the center shallow groove terminates on the inner side in the tire axial direction from the center in the width direction of the center land portion. The center shallow groove includes a first center shallow groove and a second center shallow groove whose length in the tire axial direction is smaller than that of the first center shallow groove,
The pneumatic tire according to any one of claims 1 to 5, wherein the first center shallow groove and the second center shallow groove are alternately provided in a tire circumferential direction. The length L1 in the tire axial direction of the first center shallow groove is 0.50 to 0.95 times the width W2 of the center land portion,
The pneumatic tire according to claim 6, wherein a length L2 of the second center shallow groove in the tire axial direction is 0.50 to 0.90 times the width W2 of the center land portion.   The angle with respect to the tire circumferential direction at the inner end in the tire axial direction of the second center shallow groove is larger than the angle with respect to the tire circumferential direction at the inner end in the tire axial direction of the first center shallow groove. The described pneumatic tire.   The center shallow groove includes an opening having a width of 1.0 to 2.5 mm, and a groove bottom sipe having a width of less than 1 mm extending from the bottom of the opening to the inside in the tire radial direction. The pneumatic tire according to Crab.   10. The shoulder land portion is provided with a plurality of shoulder lug grooves extending at least inward in the tire axial direction from the tread grounding end and terminating without reaching the shoulder sub-groove. 10. Pneumatic tire.   The pneumatic tire according to claim 10, wherein the shoulder land portion is provided with a connecting sipe that extends from an inner end of each shoulder lug groove in the tire axial direction to the shoulder main groove across the shoulder sub groove.

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