JP2017074841A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve braking performance in a moist road surface by making rigidity at a front and back of a tire and drainage performance compatible.SOLUTION: At least one land part 16A provided in a tread part 10 is provided with a lateral groove 20 which crosses the land part. The lateral groove 20, which has a bent part 24 and is formed in a folded shape, includes a first lateral groove part 26 extending from the bent part to communicate with one main groove 16A and a second lateral groove part 28 extending from the bent part to communicate with the other main groove 16B. One groove wall 26A of the first lateral groove part 26 includes a first inclined surface part 40 that is inclined so as to widen a groove width of the first lateral groove part toward a grounding surface 38. One groove wall of the second lateral groove part 28A, or a groove wall 28A at the opposite side of the one groove wall 26A of the first lateral groove part, includes a second inclined surface part 42 which is inclined so as to widen a groove width of the second lateral groove part toward the grounding surface 38.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire.

  The tread portion of the pneumatic tire is provided with a plurality of main grooves extending in the tire circumferential direction, and a plurality of land portions are partitioned by the main grooves. The land portion is generally provided with a groove, and for example, a transverse groove that crosses the land portion may be provided. When such a lateral groove is provided in a direction inclined with respect to the tire width direction, the rigidity of the end portion of the block defined by the lateral groove is lowered, so that the longitudinal rigidity of the tire is lowered. Therefore, in order to improve the front-rear rigidity of the tire, the lateral groove may be formed in a folded shape that is bent in a V shape. If it is a transverse groove with a turn-back configuration, the front and rear rigidity of the tire can be improved by approaching the rectangular shape of the block, but it is difficult to improve drainage performance on wet road surfaces. Therefore, the high level requirement is not sufficiently satisfied in terms of braking performance on wet road surfaces.

  In Patent Document 1, in order to improve braking performance on a wet road surface, the wall surface of the block defined by the horizontal groove is inclined so that the angle formed with the groove bottom of the horizontal groove is an acute angle, and the inclined wall surface is Providing a secondary groove extending from the ground plane is disclosed. However, such sub-grooves cannot be said to have a sufficient effect of improving drainage performance.

  On the other hand, in Patent Document 2, in order to suppress uneven wear while suppressing biting of pebbles and the like, a lateral groove traversing a land portion is connected to a circumferential narrow groove portion and one main groove thereof. A first narrow groove portion and a second narrow groove portion whose other end communicates with the other main groove. Of the groove walls facing each other, the first and second narrow groove portions are opposite to each other. A structure in which an inclined surface is provided is disclosed. However, in the configuration disclosed in Patent Document 2, since the first narrow groove portion and the second narrow groove portion are parallel, the longitudinal rigidity of the tire cannot be improved.

JP 2012-240608 A JP2013-035345A

  An object of this invention is to provide the pneumatic tire which can improve the braking performance on a wet road surface by making the front-rear rigidity and drainage performance of the tire compatible.

  The pneumatic tire according to the present embodiment is a pneumatic tire provided with a plurality of main grooves extending in the tire circumferential direction and a plurality of land portions partitioned by the main grooves in a tread portion. At least one of the land portions is provided. Has a transverse groove that crosses the land portion, and the transverse groove has a bent portion and is bent, and communicates with the one main groove that divides the land portion from the bent portion. A first horizontal groove portion extending from the bent portion and a second horizontal groove portion extending so as to communicate with the other main groove defining the land portion from the bent portion, wherein one groove wall of the first horizontal groove portion is a ground plane A first inclined surface portion that is inclined so as to widen the groove width of the first horizontal groove portion toward the side, and is one groove wall of the second horizontal groove portion, and one groove wall of the first horizontal groove portion; The groove wall on the opposite side widens the groove width of the second lateral groove portion toward the grounding surface side. It is intended to include a second inclined surface which is inclined so that.

  According to this embodiment, the braking performance on a wet road surface can be improved.

The expanded view which shows the tread pattern of the pneumatic tire which concerns on one Embodiment. The principal part enlarged plan view of the tread part of the pneumatic tire. III-III sectional view taken on the line of FIG. IV-IV sectional view taken on the line of FIG. VV sectional view taken on the line of FIG. The principal part enlarged plan view of the tread part which concerns on other embodiment.

  Hereinafter, the present embodiment will be described with reference to the drawings.

  The pneumatic tire according to the embodiment is not illustrated, but the pair of left and right bead portions and sidewall portions and the radially outer ends of the left and right sidewall portions are connected to each other between the sidewall portions. The tread portion 10 is provided, and a general tire structure can be adopted except for the tread pattern.

  As shown in FIG. 1, a plurality of straight main grooves 12 extending in the tire circumferential direction CD are provided on the surface of the tread portion 10. In this example, four main grooves 12 are provided. Specifically, a pair of center main grooves 12A and 12A arranged on both sides of the tire equator CL and a pair of center main grooves 12A and 12A are provided. It is composed of a pair of shoulder main grooves 12B, 12B respectively disposed on the outer side Wo in the tire width direction. Here, the tire width direction is a direction parallel to the tire rotation axis, and is indicated by a symbol W in the drawing. Further, the tire circumferential direction is a circumferential direction around the tire rotation axis, and is indicated by a symbol CD in the drawing. The tire width direction outer side Wo refers to a side away from the tire equator CL in the tire width direction W. In the figure, CL indicates the tire equator plane and corresponds to the center in the width direction W of the tire.

  A plurality of land portions are defined in the tread portion 10 by the main grooves 12. Specifically, the tread portion 10 includes a central land portion 14 formed between the pair of left and right center main grooves 12A and 12A, and a pair of left and right intermediate portions formed between the center main groove 12A and the shoulder main groove 12B. Land portions 16A and 16B and a pair of left and right shoulder land portions 18A and 18B formed on the outer side Wo in the tire width direction of the pair of left and right shoulder main grooves 12B and 12B are provided.

  Here, the tire according to this embodiment is a tire with front and back designation when mounted on the vehicle, that is, a surface mounted on the vehicle inner side and a surface mounted on the vehicle outer side when mounted on the vehicle. Is predetermined. As shown in FIG. 1, the tread pattern is asymmetric with respect to the tire equator CL, and is set so that the right side is disposed outside the vehicle in the vehicle mounting posture and the left side is disposed inside the vehicle in the vehicle mounting posture.

  This embodiment is characterized by the configuration of the intermediate land portion 16A outside the vehicle. In the intermediate land portion 16A, a plurality of lateral grooves 20 that cross the intermediate land portion 16A are provided at intervals in the tire circumferential direction CD. In this example, in the intermediate land portion 16A, the lateral groove 20 and a non-penetrating lateral groove 22 that does not cross the intermediate land portion 16A and terminate in the middle of the land portion 16A are spaced in the tire circumferential direction CD. It is provided alternately.

  As shown in an enlarged view in FIG. 2, the lateral groove 20 has a bent portion 24 and has a bent shape. In this example, the lateral groove 20 is formed in a folded shape that is bent in a V shape in plan view. The lateral groove 20 is a narrow groove that completely divides the intermediate land portion 16A. The groove width of the lateral groove 20 is not particularly limited. In this example, the groove width of the lateral groove 20 is such that when the tire is assembled on a regular rim, the tire is placed vertically on a flat road surface with regular internal pressure filled, and a regular load is applied to contact the ground groove 20. The width of the groove 20 is set such that the opposing groove walls come into contact with each other. That is, the lateral groove 20 is a narrow groove generally called a sipe. Specifically, the groove width a0 (see FIGS. 3 and 4) of the lateral groove 20 may be 0.1 to 1.5 mm, 0.2 to 1.0 mm, or 0.3 to 0.8 mm.

  Here, 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, a standard rim for JATMA, “Design Rim” for TRA, and ETRTO. Would be "Measuring Rim". The normal 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. The maximum air pressure is JATMA, and the table is TRA. “INFLATION PRESSURE” for ETRTO. In addition, the normal load is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. If it is JATMA, it is the maximum load capacity, and if it is TRA, the maximum load described in the above table. If the value is ETRTO, it is “LOAD CAPACITY”, but if the tire is for a passenger car, the load is equivalent to 88% of the load. In the following, unless otherwise specified, the dimensions of each part of the tire are values in a no-load state in which the tire is assembled on a regular rim and filled with a regular internal pressure.

  The lateral groove 20 includes a first lateral groove portion 26 that extends from the bent portion 24 so as to communicate with one main groove 12A that defines the intermediate land portion 16A, and a second main groove 12B that defines the intermediate land portion 16A from the bent portion 24. It is comprised with the 2nd horizontal groove part 28 extended so that it may connect.

  The bent portion 24 is located at the center of the intermediate land portion 16A in the tire width direction W, and has an obtuse angle.

  The first lateral groove portion 26 is a lateral groove portion extending straight from the bent portion 24 toward the center main groove 12A on the tire equator CL side, and communicates with the center main groove 12A. The first lateral groove portion 26 is provided so as to be inclined with respect to the tire width direction W. For this reason, the first lateral groove portion 26 is formed on land portions on both sides of the tire circumferential direction CD in the opening to the center main groove 12A. And an acute corner 30 having an acute angle with the center main groove 12A, and an obtuse corner 32 having an obtuse angle with the first lateral groove 26 and the center main groove 12A. Yes.

  The second lateral groove portion 28 is a lateral groove portion that extends straight from the bent portion 24 toward the shoulder main groove 12B on the outer side Wo in the tire width direction, and communicates with the shoulder main groove 12B. The second lateral groove portion 28 is a lateral groove portion extending in a direction intersecting with the extending direction of the first lateral groove portion 26, and extends from the bent portion 24 to the same side as the first lateral groove portion 26 in the tire circumferential direction CD. ing. The second lateral groove portion 28 is provided so as to be inclined with respect to the tire width direction W. For this reason, the second lateral groove portion 28 is formed on the land portions on both sides in the tire circumferential direction CD in the opening to the shoulder main groove 12B. And an acute angled corner 34 formed by an angle between the main groove 12B and the shoulder main groove 12B, and an obtuse angled corner 36 formed by the second lateral groove 28 and the shoulder main groove 12B having an obtuse angle. Yes.

  As described above, the first lateral groove portion 26 is provided on the tire equator CL side (tread center side, indicated as “Ce side” in FIG. 2), and the second lateral groove portion 28 is disposed on the tire width direction outer side Wo (tread shoulder side, In FIG. 2, “Sh side” is displayed.).

  The first lateral groove portion 26 and the second lateral groove portion 28 are provided with inclined surfaces (tapes) on the opposite groove walls in the tire circumferential direction CD among the opposed groove walls. That is, in the first lateral groove portion 26, one groove wall 26 </ b> A includes a first inclined surface portion 40 that is inclined so as to widen the groove width of the first lateral groove portion 26 toward the ground surface 38 side. Further, in the second lateral groove portion 28, one groove wall 28A of the first lateral groove portion 26 opposite to the one groove wall 26A is directed toward the grounding surface 38 side. 2 The 2nd inclined surface part 42 which inclines so that the groove width of the horizontal groove part 28 may be expanded is provided.

  Specifically, the first inclined surface portion 40 has an acute angle in which an angle formed by the first lateral groove portion 26 and the one main groove (center main groove) 12A is an acute angle among the pair of groove walls of the first lateral groove portion 26. Is provided in the groove wall 26 </ b> A constituting the rectangular corner portion 30. The other groove wall 26B of the first lateral groove portion 26 is not provided with an inclined surface portion (see also FIG. 3).

  The second inclined surface portion 42 has an obtuse angle side where the angle formed by the second lateral groove portion 28 and the other main groove (shoulder main groove) 12B of the pair of groove walls of the second lateral groove portion 28 is an obtuse angle. It is provided in the groove wall 28 </ b> A constituting the corner portion 36. The other groove wall 28B of the second lateral groove portion 26 is not provided with an inclined surface portion (see also FIG. 4).

  As shown in FIG. 3, the first inclined surface portion 40 is chamfered from the ground contact surface 38 of the intermediate land portion 14 toward the groove side. Therefore, the first groove surface 26A of the first lateral groove portion 26 includes a first inclined surface portion 40 that is inclined in a direction away from the other groove wall 26B toward the outer side in the tire radial direction Ko at the opening to the ground contact surface 38, and The first inclined surface portion 40 includes a vertical surface portion 44 that extends along the tire radial direction K from the lower end to the groove bottom.

  On the other hand, as shown in FIG. 4, the second inclined surface portion 42 is formed via a vertical surface portion 46 that falls from the ground contact surface 38 of the intermediate land portion 14 toward the inner radial direction Ki. In other words, the second inclined surface portion 42 is formed so as to incline toward the groove side after being separated from the ground surface 38. Specifically, the one groove wall 28A of the second lateral groove portion 28 includes a first vertical surface portion 46 extending from the ground contact surface 38 along the tire radial direction K, and an inner radial direction Ki from the lower end of the vertical surface portion 46. The second inclined surface portion 42 is inclined in a direction approaching the other groove wall 28B, and the second vertical surface portion 48 extends along the tire radial direction K from the lower end of the second inclined surface portion 42 to the groove bottom.

  Here, the tire radial direction K is a direction perpendicular to the tire rotation axis. The tire radial direction inward Ki refers to a direction approaching the tire rotation axis in the tire radial direction K, and the tire radial direction outward Ko refers to a direction away from the tire rotation axis in the tire radial direction K.

  In this example, the second lateral groove portion 28 is formed with a shallow groove depth at the opening end portion 28E to the other main groove (shoulder main groove) 14B (see FIG. 5). That is, the second lateral groove portion 28 includes a region having a deep groove depth and a shallow region, the opening end portion 28E to the shoulder main groove 14B is set to a shallow region, and a portion 28F on the center side of the opening end portion 28E. Is set in a deep area. In this example, as shown in FIGS. 4 and 5, in the opening end portion 28 </ b> E having a shallow groove depth, the second vertical surface portion 48 is not provided on the one groove wall 28 </ b> A, and the lower end of the second inclined surface portion 42. Corresponds to the bottom of the groove.

  Each dimension in the cross-sectional shape of the lateral groove 20 is not particularly limited. For example, the groove depth h0 (see FIGS. 3 and 4) of the lateral groove 20 may be 3.0 to 10.0 mm, or 5.0 to 8.5 mm. The height h1 of the first inclined surface portion 40 in the first lateral groove portion 26 may be 1.0 to 3.0 mm, or 1.3 to 2.0 mm. The height h2 of the first vertical surface portion 46 in the second horizontal groove portion 28 may be 1.0 to 3.0 mm or 1.3 to 2.0 mm. The total height h3 of the first vertical surface portion 46 and the second inclined surface portion 42 in the second horizontal groove portion 28 may be 1.5 to 5.0 mm, or may be 2.0 to 4.0 mm. The opening width a1 of the first lateral groove portion 26 at the ground contact surface 38 may be 1.5 to 6.0 mm or 2.5 to 5.0 mm. The opening width a <b> 2 at the ground contact surface 38 of the second lateral groove portion 28 may be 1.5 to 6.0 mm, or may be 2.5 to 5.0 mm. The groove depth at the opening end 28E of the second lateral groove portion 26 is the same as h3 in the example shown in FIG. 5, but may be shallower than the groove depth h0 shown in FIG. It may be 0.3 to 0.8 times.

  In this embodiment, as shown in FIGS. 1 and 2, a chamfered inclined surface 50 extending in the tire circumferential direction CD is provided at an edge portion facing the center main groove 12A of the intermediate land portion 16A. An end portion of the inclined surface 50 in the tire circumferential direction CD is connected to the first inclined surface portion 40 of the lateral groove 20 at the acute corner portion 30. Therefore, the connecting portion between the first inclined surface portion 40 and the inclined surface 50 is formed in a shape in which an acute angle 30 is chamfered, and the rigidity improvement effect of the corner portion 30 is enhanced.

  As shown in FIG. 1, the non-penetrating lateral groove 22 provided in the intermediate land portion 16A is the second lateral groove portion 28 from the central portion in the tire width direction W of the intermediate land portion 16A toward the outer side Wo in the tire width direction. Extending substantially parallel to the shoulder main groove 14B.

  In the central land portion 14, non-penetrating lateral grooves 52 are provided at intervals in the tire circumferential direction CD, and no lateral grooves that cross the land portion 14 are provided. Further, in the intermediate land portion 16B on the inner side of the vehicle, straight transverse grooves 54 and non-penetrating transverse grooves 56 that cross the intermediate land portion 16B are alternately provided at intervals in the tire circumferential direction CD. . The pair of left and right shoulder land portions 18A and 18B are also provided with a plurality of lateral grooves 58 across the land portions 18A and 18B at intervals in the tire circumferential direction CD.

  In the present embodiment configured as described above, in the horizontal groove 20 that crosses the intermediate land portion 16A, the horizontal groove 20 is formed in a folded shape that is bent in a V shape, and then the first horizontal groove portion 26 and the second horizontal groove portion. Of the 28 opposing groove walls, the inclined surface portions 40 and 42 are provided on the opposite groove walls in the tire circumferential direction CD, so that both the tire front-rear rigidity and the drainage performance can be achieved, and braking on a wet road surface is possible. The performance can be improved.

  More specifically, by forming the horizontal groove 20 in a turn-back shape, the block shape defined by the horizontal groove 20 can be made closer to a rectangular shape compared to the case where the horizontal groove is simply formed obliquely. Therefore, since the block rigidity is increased, the block is less likely to fall with respect to the front / rear input during braking, and the tire front / rear rigidity can be increased. Thereby, the grounding property at the time of braking / driving is improved, and the braking performance is improved. Note that the approach of the block shape to the rectangular shape is advantageous not only in the longitudinal rigidity but also in the tire width direction, which is advantageous in improving the handling performance.

  Further, by providing the inclined surface portions 40 and 42 in the cut-back lateral groove 20, the groove volume is increased and the drainage performance is improved. For this reason, the braking performance on a wet road surface can be improved in combination with the improvement of the tire longitudinal rigidity.

  In addition, since the inclined surface portions 40 and 42 are provided on the opposite groove walls of the first lateral groove portion 26 and the second lateral groove portion 28 of the lateral groove 20, the block is provided regardless of the rotation direction of the tire. Heel-and-toe wear that is uneven wear can be suppressed.

  According to the present embodiment, the first inclined surface portion 40 is chamfered from the ground contact surface 38 of the land portion 16A, and the second inclined surface portion 42 is formed from the ground contact surface 38 of the land portion 16 in the tire radial direction inward Ki. Since it formed through the vertical surface part 46 which falls in, it has the following effect. In the chamfered first inclined surface portion 40, the drain end performance can be improved by increasing the groove volume while increasing the rigidity of the block end portion to improve the tire front-rear rigidity. On the other hand, in the 2nd inclined surface part 42, since it was set as the 1st stage, the groove | channel volume can be enlarged correspondingly and the improvement effect of drainage performance is high.

  Further, by providing the first lateral groove portion 26 on the tire equator CL side and the second lateral groove portion 28 on the outer side Wo in the tire width direction, the following operational effects can be obtained. That is, since the 2nd inclined surface part 42 which is the inclined surface made into one paragraph is distribute | arranged to the tire width direction outer side Wo, drainage performance can be improved more. In addition, since the second inclined surface portion 42 has one stage, the rigidity is lower than that of the first inclined surface portion 40. Therefore, when the tire is in contact with the ground, the intermediate land portion 16A is located on the outer side Wo in the tire width direction from the tire equator CL side. It becomes easy to extend in the direction CD, and the ground contact area increases. Therefore, it is advantageous for improving handling performance.

  Further, according to the present embodiment, the first inclined surface portion 40 is provided on the groove wall 26 </ b> A constituting the corner portion 30 on the acute angle side among the pair of groove walls of the first lateral groove portion 26, and the second inclined surface portion 42 is provided. Of the pair of groove walls of the second lateral groove portion 28, the groove wall 26A constituting the obtuse angle side corner portion 36 is provided with the following operational effects. That is, the chamfered first inclined surface portion 40 that increases the rigidity is provided in the corner portion 30 on the acute angle side having low rigidity, and the second portion having a lower rigidity than the chamfered shape in the corner portion 36 on the obtuse angle side having high rigidity. By providing the inclined surface portion 42, the difference in rigidity between them can be reduced.

  According to the present embodiment, since the groove depth at the opening end portion 28E to the shoulder main groove 12B is formed shallow in the second lateral groove portion 28, the following operational effects are exhibited. That is, the groove 28 is provided at the opening end 28E to the shoulder main groove 14B while increasing the groove volume and improving the drainage performance by the central portion 28F, which is the deep groove area provided in the second lateral groove 28. By reducing the depth, the rigidity in the tire width direction can be improved. Therefore, both drainage performance and handling performance can be achieved.

  As described above, the pneumatic tire according to the present embodiment can improve the braking performance on the wet road surface while achieving both the front and rear rigidity of the tire and the drainage performance, and has excellent handling performance and suppresses heel and toe wear. be able to.

  In the above-described embodiment, the lateral groove 20 having the above-described unique inclined surface-turning configuration is provided in the intermediate land portion 16A outside the vehicle (that is, the land portion present at a quarter position of the tread contact width). This is because it is advantageous in drainage performance and handling performance by adopting the intermediate land portion 16A outside the vehicle. However, such a lateral groove 20 may be provided in other land portions, and may be provided in at least one land portion.

  Moreover, in the said embodiment, although the said specific turning-back structure with an inclined surface was employ | adopted for all the transverse grooves which cross the said land part 16A provided in the intermediate land part 16A, it is not necessarily in all the transverse grooves which cross a land part. It does not have to be adopted.

  In the above embodiment, the inclined surface 50 extending in the tire circumferential direction CD is provided at the edge portion facing the center main groove 12A of the intermediate land portion 16A. However, as shown in FIG. Good. In the example shown in FIG. 6, the first inclined surface portion 40 provided in the first lateral groove portion 26 is formed with a constant width in the extending direction of the first lateral groove portion 26. Other configurations are the same as those in the above embodiment, and the corresponding parts are denoted by the same reference numerals and description thereof is omitted.

  Although some embodiments have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention.

  In order to show the effects of the above embodiment, pneumatic radial tires for passenger cars of Example 1 and Comparative Examples 1 and 2 (size: 225 / 50ZR17 98Y) were prototyped. The tire of Example 1 is the tire of the above-described embodiment shown in FIGS. 1 to 5, and is an example in which the lateral groove 20 having the turning structure with the unique inclined surface is provided in the intermediate land portion 16A outside the vehicle (h0 = 8.0 mm, h1 = 1.5 mm, h2 = 1.5 mm, h3 = 3.0 mm, a0 = 0.8 mm, a1 = 3.0 mm, a2 = 3.0 mm). The tire of Comparative Example 1 is an example in which the lateral groove is formed as a simple reversing sipe without providing the first inclined surface portion 40 and the second inclined surface portion 42 in the configuration of Example 1 (the depth of the lateral groove) Was constant). In the tire of Comparative Example 2, in the configuration of Example 1, the first inclined surface portion 40 of the first lateral groove portion 26 forms the groove wall on the same side as the second inclined surface portion 42 (that is, the obtuse corner portion 32). This is an example provided in the groove wall 26B (however, the second inclined surface portion 42 is not a single stage, but a simple chamfered shape similar to the first inclined surface portion 40. The depth of the lateral groove is constant). In any example, the configuration other than the lateral groove 20 of the intermediate land portion 16A is the same.

  Each of these tires was mounted on a regular rim and assembled to a vehicle at an internal pressure of 220 kPa, and braking performance on wet road surfaces, handling performance, and heel and toe wear amount (T / H wear rate) were evaluated. Each evaluation method is as follows.

  -Braking performance: A vehicle equipped with each evaluation tire is run on a 1mm water film road surface as a wet road surface, full braking is performed from 100 km / h to 0 km / h, and the reciprocal of the stopping distance at that time is It was displayed as an index with the value of Comparative Example 1 being 100. The larger the index is, the shorter the stop distance is, and the better the braking performance on the wet road surface.

  -Handling performance: A vehicle equipped with each evaluation tire is run on a 1mm water film road surface as a wet road surface, running straight at 60-140 km / h, lane change, slalom, and sensory evaluation, Lap time was also measured to comprehensively evaluate handling performance. The evaluation result of Comparative Example 1 is expressed as an index with 100, and the larger the index, the better the handling performance on wet road surfaces.

  -Heel and toe wear amount: The amount of heel and toe wear (the difference in wear amount between the front side and the rear side in the tire rotation direction with respect to the groove) after the tire was mounted on an actual vehicle and traveled on a general road for 12000 km was examined. The smaller the value, the smaller the amount of heel and toe wear, and the better the heel and toe wear resistance.

  The results are as shown in Table 1. Compared with Comparative Example 1 in which the inclined surface portion is not provided in the cut-back groove, in Example 1 in which the inclined surface portion is provided on the opposite groove wall in the turned-back groove, the heel and toe are provided. The braking performance on wet road surfaces was improved while suppressing wear. Moreover, it was excellent also in the improvement effect of handling performance in Example 1. On the other hand, in Comparative Example 2, although the braking performance was improved by improving the drainage performance by providing the inclined surface portion in the cut-back groove, the effect was low, and the handling performance and the improvement effect of the heel and toe wear were also improved. It was not obtained.

DESCRIPTION OF SYMBOLS 10 ... Tread part, 12A ... Center main groove, 12B ... Shoulder main groove, 16A ... Intermediate land part, 20 ... Horizontal groove, 24 ... Bending part, 26 ... First horizontal groove part, 26A ... One groove wall of the first horizontal groove part , 26 ... second lateral groove, 28A ... one groove wall of the second lateral groove, 28E ... open end of the second lateral groove, 30 ... acute angle of the first lateral groove, 36 ... of the second lateral groove Obtuse corner, 38 ... ground contact surface, 40 ... first inclined surface, 42 ... second inclined surface, 46 ... first vertical surface, CL ... tire equator, CD ... tire circumferential direction, K ... tire radial direction, W ... tire width direction

Claims (5)

In a pneumatic tire provided with a plurality of main grooves extending in the tire circumferential direction and a plurality of land portions partitioned by the main grooves in a tread portion,
At least one of the land portions is provided with a transverse groove that crosses the land portion,
The lateral groove has a bent portion and has a bent shape. The lateral groove extends from the bent portion so as to communicate with one main groove that defines the land portion, and the land extends from the bent portion. A second lateral groove portion extending to communicate with the other main groove defining the portion,
One groove wall of the first horizontal groove portion includes a first inclined surface portion that is inclined so as to widen the groove width of the first horizontal groove portion toward the grounding surface side,
One groove wall of the second lateral groove portion, which is opposite to the one groove wall of the first lateral groove portion, widens the groove width of the second lateral groove portion toward the grounding surface side. Including a second inclined surface portion inclined to
Pneumatic tire.   The first inclined surface portion is formed from a ground contact surface of the land portion, and the second inclined surface portion is formed via a vertical surface portion that falls inward in the tire radial direction from the ground contact surface of the land portion. Pneumatic tire described in 2.   The pneumatic tire according to claim 2, wherein the first lateral groove portion is provided on a tire equator side, and the second lateral groove portion is provided on an outer side in the tire width direction. The first inclined surface portion is a groove wall constituting an acute angle corner portion of the pair of groove walls of the first horizontal groove portion, the angle formed by the first horizontal groove portion and the one main groove being an acute angle. Provided,
Of the pair of groove walls of the second lateral groove portion, the second inclined surface portion is a groove wall that forms an obtuse angle corner portion where the angle formed by the second lateral groove portion and the other main groove is an obtuse angle. The pneumatic tire according to claim 2 or 3, provided.   The pneumatic tire according to any one of claims 2 to 4, wherein the second lateral groove portion is formed with a shallow groove depth at an opening end portion to the other main groove.

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