JP6002182B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire that can reduce passing noise.

  For example, PTL 1 below proposes a pneumatic tire provided with a plurality of main grooves and vertical fine grooves extending continuously in the tire circumferential direction between the main grooves. The vertical narrow groove of Patent Document 1 extends with a constant groove width and groove depth smaller than the main groove. Such a vertical narrow groove has a smaller groove volume than the main groove, and therefore the amount of air passing therethrough is small. Therefore, the running noise generated from the vertical narrow groove is not so large.

JP 2010-132181 A

  However, the pneumatic tire of the cited document 1 has room for further improvement with respect to the air column resonance generated in the main groove during running.

  The present invention has been devised in view of the above-described problems. Based on the improvement of the depth of the vertical narrow groove provided in the land, the air column resonance generated in the adjacent main groove is generated. The main purpose is to provide a pneumatic tire that can be effectively reduced.

  The present invention provides a pneumatic tire including at least a main groove extending continuously in a tire circumferential direction in a tread portion and land portions disposed on both sides of the main groove, wherein the land portion includes a tire circumference. A vertical narrow groove extending continuously in the direction and having a groove width smaller than that of the main groove is provided, and the vertical narrow groove is smaller than the first groove depth and a first portion having a first groove depth. The second portion having the second groove depth is alternately included in the tire circumferential direction.

  In the pneumatic tire of the present invention, it is desirable that a third portion in which the groove depth smoothly changes is provided between the first portion and the second portion.

  In the pneumatic tire of the present invention, it is desirable that a plurality of horizontal sipes are provided in the land portion where the vertical narrow grooves are provided.

  In the pneumatic tire of the present invention, it is preferable that the horizontal sipe intersects the vertical groove.

  In the pneumatic tire of the present invention, it is preferable that the lateral sipe communicates with the second portion of the vertical narrow groove.

  In the pneumatic tire of the present invention, the land portion provided with the vertical narrow groove is disposed between a tire equator and a tread end, and the lateral sipe is an inner portion extending on the tire equator side of the vertical groove. It is desirable to have an outer portion extending on the tread end side of the vertical groove and having a depth smaller than that of the inner portion.

  In the pneumatic tire of the present invention, the main groove includes a shoulder main groove provided on the most tread end side and a center main groove provided on the tire equator side of the shoulder main groove, and the land portion is It is desirable that the land portion including the middle land portion divided by the shoulder main groove and the center main groove and provided with the vertical narrow groove is the middle land portion.

  The pneumatic tire according to the present invention includes at least a main groove extending continuously in the tire circumferential direction in the tread portion and land portions disposed on both sides of the main groove. The land portion is provided with a vertical narrow groove extending continuously in the tire circumferential direction and having a groove width smaller than that of the main groove. Such vertical narrow grooves can, for example, supplement the drainage capacity of the main grooves and exhibit excellent wet performance.

  The vertical narrow grooves alternately include first portions having a first groove depth and second portions having a second groove depth smaller than the first groove depth in the tire circumferential direction. Thereby, the land portion between the first portion and the main groove and the land portion between the second portion and the main groove have different amounts of deformation toward the main groove when grounded. For this reason, as for the main groove in the ground contact surface, the groove wall on the side where the vertical groove is provided is deformed into irregularities, and the sectional area (volume) of the groove is changed in the groove length direction. The main groove having such a grounding shape prevents generation of a standing wave of air passing through the main groove, thereby effectively reducing air column resonance sound.

It is an expanded view of the tread part of the pneumatic tire of one embodiment of the present invention. It is an enlarged view of the middle land part of FIG. It is the sectional view on the AA line of the vertical thin groove of FIG. It is sectional drawing of a main groove and a vertical fine groove when a tread part grounds. It is a top view of the grounding surface when a tread part grounds. FIG. 3 is a cross-sectional view of the horizontal sipe of FIG. 2 taken along line BB. It is an enlarged view of the shoulder land part of FIG. It is an enlarged view of the center land part of FIG.

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 is provided with a main groove 3 extending continuously in the tire circumferential direction and a land portion 4 divided by the main groove 3. The tread portion 2 of the present embodiment has, for example, a substantially point-symmetric tread pattern centered on a point on the tire equator C.

  The main groove 3 includes, for example, a pair of shoulder main grooves 5 and 5 and a pair of center main grooves 6 and 6. Each shoulder main groove 5 is provided, for example, on the most tread end Te side. For example, one center main groove 6 is provided between the shoulder main grooves 5 and 5 and on both sides of the tire equator C.

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

  The “regular rim” is a rim determined 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, If there is "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 groove width W1 of the shoulder main groove 5 and the groove width W2 of the center main groove 6 are, for example, 3.0 to 8.0 of the tread ground contact width TW in order to prevent deterioration in steering stability while exhibiting sufficient wet performance. %. The tread contact width TW is a distance in the tire axial direction between the tread ends Te and Te of the tire 1 in the normal state.

  From the same viewpoint, the groove depth of the shoulder main groove 5 and the groove depth of the center main groove 6 are desirably 2 to 8% of the tread ground contact width TW, for example.

  The land portion 4 is provided, for example, on each side of the tire equator C side, on the outer side in the tire axial direction of the middle land portion 7 divided between the shoulder main groove 5 and the center main groove 6 and the shoulder main groove 5. Further, a center land portion 9 is partitioned between the pair of center main grooves 6.

  FIG. 2 shows an enlarged view of the middle land portion 7. As shown in FIG. 2, the middle land portion 7 is provided with a vertical narrow groove 12 extending continuously in the tire circumferential direction and a plurality of lateral sipes 18 extending in the tire axial direction. In this specification, “sipe” means a cut having a width of 1.5 mm or less.

  The vertical groove 12 is provided, for example, in the substantially central portion of the width in the tire axial direction of the middle land portion 7. The distance L1 in the tire axial direction from the center of the vertical narrow groove 12 to the edge 7e on the inner side in the tire axial direction of the middle land portion 7 is, for example, 0.4 to 0. 0 of the width W4 in the tire axial direction of the middle land portion 7. Six times is desirable.

  The vertical narrow groove 12 extends linearly in the tire circumferential direction, for example. The vertical narrow groove 12 only needs to have a smaller groove width W5 than the main groove 3. Such a vertical narrow groove 12 improves wet performance in a well-balanced manner while preventing a decrease in rigidity of the middle land portion 7. The groove width W5 of the vertical narrow groove 12 is preferably 15% or less, more preferably 12% or less of the groove width W2 of the center main groove 6. The vertical narrow groove 12 may be a sipe.

  FIG. 3 shows a cross-sectional view taken along line AA of the vertical groove 12 of FIG. As shown in FIG. 3, the vertical groove 12 includes a first portion 13 having a first groove depth d1 and a second portion 14 having a second groove depth d2 smaller than the first groove depth d1. Are alternately included in the tire circumferential direction.

  FIG. 4 is a cross-sectional view of the main groove 3 and the vertical narrow groove 12 when the tread portion 2 is grounded. As shown in FIG. 4, when the tread portion 2 comes in contact with the road surface G, the groove wall 3 w of the main groove 3 is deformed to be convex toward the groove center side.

  FIG. 5 shows a plan view of the ground plane 10 when the tread portion 2 is grounded. In FIG. 5, the ground plane 10 is hatched. As shown in FIG. 5, in the present invention, since the vertical narrow groove 12 described above is provided, the first land portion 28 between the first portion 13 and the main groove 3 is replaced with the second portion 14 and the main portion. It is easier to deform in the tire axial direction than the second land portion 29 between the groove 3. Accordingly, the first land portion 28 is deformed larger than the second land portion 29 toward the main groove 3 in the ground contact surface 10.

  For this reason, in the main groove 3 in the ground contact surface, the groove wall 3a on the side where the vertical thin grooves 12 are provided is deformed into irregularities, and the sectional area (volume) of the groove is changed in the groove length direction. As a result of experiments by the inventors, it has been found that the main groove 3 having such a grounding shape effectively prevents generation of a standing wave of 800 to 1000 Hz that causes air column resonance.

  As shown in FIG. 3, the first groove depth d1 of the first portion 13 is preferably 2.0 mm or more, more preferably 2.5 mm or more, preferably 4.0 mm or less, more preferably 3. 5 mm or less. The first portion 13 of the present embodiment extends in the tire circumferential direction at a certain depth. Similarly, the length L3 in the tire circumferential direction of the first portion 13 is 0.6 times or more the width W4 in the tire axial direction of the middle land portion 7 (shown in FIG. 2 and the same applies hereinafter). Preferably it is 0.65 times or more, preferably 0.8 times or less, more preferably 0.75 times or less.

  The second groove depth d2 of the second portion 14 is preferably 0.5 mm or more, more preferably 1.0 mm or more, preferably 2.5 mm or less, more preferably 2.0 mm or less. For example, the second portion 14 of the present embodiment extends in the tire circumferential direction at a constant depth. Such a second portion 14 effectively enhances noise performance while maintaining the rigidity of the middle land portion 7.

  The length L4 of the second portion 14 in the tire circumferential direction is preferably smaller than the length L3 of the first portion. The length L4 of the second portion 14 is preferably not less than 0.75 times, more preferably not less than 0.8 times, preferably not more than 0.9 times, more preferably not less than the length L3 of the first portion 13. Is 0.85 times or less. Thereby, the partial wear of the middle land part 7 is suppressed.

  Between the 1st part 13 and the 2nd part 14, the 3rd part 15 from which a groove depth changes smoothly is provided, for example. The third portion 15 has, for example, an inclined surface 16 that gradually decreases the groove depth from the first portion 13 toward the second portion 14. Such an inclined surface 16 smoothly changes the rigidity of the middle land portion 7 and suppresses uneven wear.

  In FIG. 3, the angle θ1 of the inclined surface 16 is preferably 30 ° or more, more preferably 35 ° or more, preferably 50 ° or less, more preferably 45 ° or less.

  As shown in FIG. 2, the lateral sipe 18 is inclined with respect to the tire axial direction, for example. Such a horizontal sipe 18 is useful for reducing the hitting sound of the middle land portion 7 because the entire edge thereof does not contact the road surface at the same time. The angle θ2 of the lateral sipe 18 with respect to the tire axial direction is preferably 35 ° or more, more preferably 40 ° or more, preferably 55 ° or less, more preferably 50 ° or less.

  The lateral sipe 18 includes a main portion 18a and a sub portion 18b having the angle θ2 increased on the inner side in the tire axial direction of the main portion 18a. Thereby, the land part between the sub-part 18b and the center main groove 6 becomes easy to deform | transform, and generation | occurrence | production of the stationary wave of the air in the center main groove 6 is suppressed effectively.

  The horizontal sipe 18 communicates between the center main groove 6 and the shoulder main groove 5, for example. Moreover, the horizontal sipe 18 intersects the vertical narrow groove 12, for example.

  As shown in FIG. 3, it is desirable that the horizontal sipe 18 communicates with the second portion 14 of the vertical narrow groove 12, for example. Since the groove depth of the second portion 14 is smaller than that of the first portion 13, the lateral sipe 18 communicates with the second portion 14, whereby the rigidity of the middle land portion 7 becomes uniform in the tire circumferential direction, and particularly the vertical portion. Uneven wear at the intersection between the narrow groove 12 and the horizontal sipe 18 is effectively suppressed.

  6 shows a cross-sectional view of the horizontal sipe 18 in FIG. As shown in FIG. 4, the horizontal sipe 18 extends, for example, at the tire equator C side inner portion 20 of the vertical narrow groove 12 and the tread end Te side of the vertical narrow groove 12 and has a depth greater than that of the inner portion 20. And a small outer portion 21. Between the inner part 20 and the outer part 21, an intermediate part 22 having a varying depth is provided. Such a horizontal sipe 18 reduces the rigidity of the middle land portion 7 on the inner side in the tire axial direction, and further facilitates deformation of the groove wall of the center main groove 6. Therefore, the generation of a standing air wave in the center main groove 6 is suppressed.

  The depth d6 of the inner portion 20 is desirably larger than, for example, the first groove depth d1 (shown in FIG. 3 and the same applies hereinafter) of the first portion 13 of the vertical narrow groove 12. Thereby, the groove wall of the center main groove 6 is easily deformed not only in the tire axial direction but also in the tire circumferential direction, and the generation of stationary waves is further suppressed. The depth d6 of the inner part 20 is preferably 4.5 mm or more, more preferably 5.5 mm or more, preferably 8.0 mm or less, more preferably 7.0 mm or less.

  From the same viewpoint, the length L6 in the tire axial direction on the tread surface of the inner portion 20 is preferably 0 of the width W4 in the tire axial direction of the middle land portion 7 (shown in FIG. 2 and the same hereinafter). .25 times or more, more preferably 0.3 times or more, preferably 0.45 times or less, more preferably 0.4 times or less.

  The depth d7 of the outer portion 21 is preferably larger than the second groove depth d2 (shown in FIG. 3) of the second portion 14 of the vertical groove 12. Thereby, the edge of the middle land portion 7 on the outer side in the tire axial direction is easily deformed, and the generation of air column resonance sound in the shoulder main groove 5 is suppressed. The depth d7 of the outer portion 21 is preferably 1.5 mm or more, more preferably 2.5 mm or more, preferably 4.0 mm or less, more preferably 3.5 mm or less.

  In a preferred embodiment, the depth d7 of the outer portion 21 is the same as the first groove depth d1 of the first portion 13 of the vertical narrow groove 12. Such an outer portion 21 makes the middle land portion 7 uniform in rigidity and suppresses uneven wear.

  From the same viewpoint, the length L7 in the tire axial direction on the tread surface of the outer side portion 21 is preferably 0.25 times or more, more preferably 0.3 times or more, the width W4 of the middle land portion 7 in the tire axial direction. Yes, preferably 0.45 times or less, more preferably 0.4 times or less. In a preferred embodiment, the length L7 of the outer portion 21 is the same as the length L6 of the inner portion 20. Such a horizontal sipe 18 makes the middle land portion 7 uniform in rigidity, and can reduce the sound of hitting the road surface of the middle land portion 7 during traveling.

  The intermediate portion 22 has a bottom surface 23 that is inclined with respect to the tread surface 7 s of the middle land portion 7. Such an intermediate portion 22 smoothly changes the rigidity of the middle land portion 7 toward the outer side in the tire axial direction and suppresses uneven wear. The angle θ4 of the bottom surface 23 with respect to the tread surface 7s is preferably 10 ° or more, more preferably 15 ° or more, preferably 25 ° or less, more preferably 20 ° or less.

  As shown in FIG. 2, the middle land portion 7 includes, for example, a plurality of first treads that are partitioned on the inner side in the tire axial direction of the vertical grooves 12 by providing the vertical grooves 12 and a plurality of horizontal sipes 18. 25 and a plurality of second treads divided on the outer side in the tire axial direction of the vertical groove 12.

  The first tread surface 25 and the second tread surface 26 have, for example, a substantially parallelogram shape. The first tread surface 25 and the second tread surface 26 can effectively suppress the hydroplaning phenomenon because the front end portion 27 in the tire circumferential direction cuts the water film during wet running.

  In the present embodiment, the vertical narrow groove 12 and the horizontal sipe 18 described above are provided only in the middle land portion 7, but may be provided in the shoulder land portion 8 or the center land portion 9.

  FIG. 7 shows an enlarged view of the shoulder land portion 8. As shown in FIG. 7, the shoulder land portion 8 is provided with a plurality of shoulder lateral grooves 30 extending in the tire axial direction and a plurality of shoulder sipes 31 provided in a region between the shoulder lateral grooves 30. .

  For example, the shoulder lateral groove 30 extends from the tread end Te inward in the tire axial direction and terminates in the shoulder land portion 8. Thereby, since the air which passes through the inside of the shoulder main groove 5 does not move to the shoulder lateral groove 30, the pumping sound of the shoulder lateral groove 30 is reduced.

  The shoulder lateral groove 30 is provided on the inner side in the tire axial direction of the gently inclined portion 33 and the gently inclined portion 33 extending from the tread end Te at an angle θ6 (not shown) of 0 to 5 ° with respect to the tire axial direction. And a steeply inclined portion 34 that is inclined at an angle θ7 that is larger than the inclined portion 33 with respect to the tire axial direction. In such a shoulder lateral groove 30, the rigidity of the land portion between the steeply inclined portion 34 and the shoulder main groove 5 changes in the tire circumferential direction. For this reason, the groove wall of the shoulder main groove 5 is easily deformed into irregularities, and air column resonance is suppressed.

  In order to exhibit the above-described effect while suppressing uneven wear of the shoulder land portion 8, the angle θ7 with respect to the tire axial direction of the steeply inclined portion 34 is preferably 25 ° or more, more preferably 30 ° or more, preferably It is 45 ° or less, more preferably 30 ° or less.

  For example, one or two shoulder sipes 31 are provided between the shoulder lateral grooves 30, 30 adjacent to each other in the tire circumferential direction. The shoulder sipe 31 extends, for example, from the shoulder main groove 5 to the outer side in the tire axial direction and terminates in the shoulder land portion 8. Such a shoulder sipe 31 makes it easy to deform the groove wall of the shoulder main groove 5 and suppresses the generation of a standing wave in the main groove.

  The shoulder sipe 31 is inclined with respect to the tire axial direction, for example. Such a shoulder sipe 31 changes the rigidity of the shoulder land portion 8 on the inner side in the tire axial direction in the tire circumferential direction. For this reason, the groove wall of the shoulder main groove 5 is easily deformed into irregularities. The angle θ8 of the shoulder sipe 31 with respect to the tire axial direction is preferably 25 ° or more, more preferably 30 ° or more, preferably 45 ° or less, more preferably 30 ° or less.

  The angle θ8 of the shoulder sipe 31 is desirably gradually decreased toward the outer side in the tire axial direction, for example. In a preferred embodiment, the shoulder sipe 31 extends along the shoulder lateral groove 30. Such a shoulder sipe 31 can make the shoulder land portion 8 uniform in rigidity, and can reduce the sound of hitting the road surface of the shoulder land portion 8 during traveling.

  FIG. 8 shows an enlarged view of the center land portion 9. As shown in FIG. 8, the center land portion 9 is, for example, a rib extending continuously in the tire circumferential direction. Such a center land portion 9 effectively enhances steering stability on a dry road surface.

  The center land portion 9 is provided with a plurality of center sipes 36 communicating with the center main groove 6 and terminating in the center land portion 9, for example. The center sipe 36 of this embodiment includes, for example, a first center sipe 37 extending from one center main groove 6 and a second center sipe 38 extending from the other center main groove 6. Moreover, a center sipe pair 39 composed of a first center sipe 37 and a second center sipe 38 adjacent to each other in the tire axial direction is spaced apart in the tire circumferential direction.

  Each center sipe 36 preferably terminates without straddling the tire equator C. Thereby, the difference in rigidity between the center land portion 9 and the middle land portion 7 becomes large, and the cross-sectional area (volume) of the shoulder main groove is likely to change in the groove length direction at the time of ground contact. For this reason, air column resonance is effectively suppressed.

  In order to exhibit the above-described effect while suppressing uneven wear of the center land portion 9, the length L9 of the center sipe 36 in the tire axial direction is preferably 0.2 times or more the width W7 of the center land portion 9, More preferably, it is 0.25 times or more, preferably 0.35 times or less, more preferably 0.3 times or less.

  For example, the center sipe 36 is preferably inclined at an angle θ9 of 30 to 45 ° with respect to the tire axial direction. As a result, the land portion between the center sipe 36 and the center main groove 6 is easily deformed, and generation of a stationary wave in the center main groove is suppressed.

  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 of size 235 / 55R20 having the basic pattern of FIG. 1 was prototyped based on the specifications in Table 1. As a comparative example, a tire in which the vertical narrow groove and the horizontal sipe extend at a constant depth was manufactured. Each test tire was mounted on the following test vehicle and tested for noise performance, wet performance, and steering stability. The common specifications and test methods for each tire are as follows.
Wearing rim: 20 × 8.0J
Tire internal pressure: 230kPa
Test vehicle: 4-wheel drive vehicle, displacement 2500cc
Tire mounting position: all wheels

<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 displayed as an index with the numerical value of Comparative Example 1 being 100. The larger the value, the better the noise performance.

<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 numerical value of Comparative Example 1 being 100. Larger values indicate better wet performance.

<Steering stability>
The driving stability of the test vehicle when traveling on a dry road course was evaluated by 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.
The test results are shown in Table 1.

  As a result of the test, it was confirmed that the pneumatic tires of the examples exhibited excellent noise performance while maintaining wet performance.

2 tread portion 3 main groove 4 land portion 12 vertical narrow groove 13 first portion 14 second portion d1 first groove depth d2 second groove depth

Claims (6)

A pneumatic tire including at least a main groove extending continuously in a tire circumferential direction in a tread portion and land portions arranged on both sides of the main groove,
The land portion is provided with a vertical narrow groove extending continuously in the tire circumferential direction and having a groove width smaller than the main groove,
The longitudinal narrow groove, seen including a first portion having a first groove depth and a second portion having a second groove depth less than said first groove depth, alternately in the tire circumferential direction,
The land portion provided with the vertical narrow groove is provided with a plurality of horizontal sipes,
The pneumatic tire according to claim 1, wherein the horizontal sipe communicates with the second portion of the vertical groove . A pneumatic tire including at least a main groove extending continuously in a tire circumferential direction in a tread portion and land portions arranged on both sides of the main groove,
The land portion is provided with a vertical narrow groove extending continuously in the tire circumferential direction and having a groove width smaller than the main groove,
The vertical narrow grooves alternately include first portions having a first groove depth and second portions having a second groove depth smaller than the first groove depth in the tire circumferential direction,
The land portion provided with the vertical narrow groove is provided with a plurality of horizontal sipes,
The horizontal sipe intersects the vertical narrow groove,
The land portion provided with the vertical narrow groove is disposed between the tire equator and the tread end,
The horizontal sipe has an inner part extending on the tire equator side of the vertical groove and an outer part extending on the tread end side of the vertical groove and having a depth smaller than that of the inner part. And pneumatic tires. A pneumatic tire including at least a main groove extending continuously in a tire circumferential direction in a tread portion and land portions arranged on both sides of the main groove,
The land portion is provided with a vertical narrow groove extending continuously in the tire circumferential direction and having a groove width smaller than the main groove,
The vertical narrow grooves alternately include first portions having a first groove depth and second portions having a second groove depth smaller than the first groove depth in the tire circumferential direction,
The main groove includes a shoulder main groove provided on the most tread end side, and a center main groove provided on the tire equator side of the shoulder main groove,
The land portion includes a middle land portion divided by the shoulder main groove and the center main groove, and the land portion provided with the vertical narrow groove is the middle land portion. tire. The pneumatic tire according to any one of claims 1 to 3, wherein a third portion whose groove depth smoothly changes is provided between the first portion and the second portion . The pneumatic tire according to claim 3 , wherein the middle land portion is provided with a plurality of lateral sipes . The pneumatic tire according to claim 5, wherein the horizontal sipe intersects the vertical narrow groove .

Images