JP6809239B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire capable of improving dry performance and wet performance in a well-balanced manner by devising the shape of a sipe provided in the tread portion.

Conventionally, in the tread pattern of a pneumatic tire, a plurality of sipes are formed on ribs defined by a plurality of main grooves. By providing such a sipe, drainage is ensured and wet performance is exhibited. However, when a large number of sipes are arranged on the tread portion in order to improve the wet performance, there is a drawback that the rigidity of the ribs is lowered and the dry performance is lowered.

Further, in a pneumatic tire, it is necessary to improve the drainage property of the groove and the sipe in order to improve the wet performance. As a method for improving drainage, it has been proposed to provide a chamfered portion on the edge of a sipe provided on the tread portion (for example, Patent Document 1). In this case, since the chamfered portion functions as a drainage channel, the drainage property of the ground contact surface is improved, and it is expected that the wet performance of the tire is improved. However, if a chamfered part is simply added to the sipe, the chamfered part will be crushed due to the deformation of the tread part at the time of touchdown, and the chamfered part will not function effectively as a drainage channel, and sufficient drainage property will be ensured. There is a concern that it cannot be done. Further, depending on the chamfering size, the improvement of dry performance or wet performance may be insufficient.

Japanese Unexamined Patent Publication No. 2016-88469

An object of the present invention is to provide a pneumatic tire capable of improving dry performance and wet performance in a well-balanced manner by devising the shape of a sipe provided on the tread portion.

The pneumatic tire of the present invention for achieving the above object is provided with a plurality of main grooves extending in the tire circumferential direction and a plurality of rows of ribs partitioned by the main grooves in the tread portion, and the vehicle mounting direction is set. In the designated pneumatic tire, each of the vehicle outer region and the vehicle inner region of the tread portion has at least one row of ribs in which a plurality of sipes extending in the tire width direction are formed, and the sipes have at least one edge. The chamfered sipe consists of a chamfered sipe having a chamfered portion and a non-chapeded sipe having no chamfered portion on the edge. Chamfered sipes communicating with either one and communicating with each of the main grooves located on both sides of the rib are alternately arranged in the tire circumferential direction, and the non-chafted sipes are adjacent to at least one side of the chamfered sipe in the tire circumferential direction. The total extension LB _OUT of the non-clamping sipe in the outer region of the vehicle and the total extension LB _IN of the non-clamping sipe in the inner region of the vehicle satisfy the relationship of LB _OUT <LB _IN .

In the present invention, at least one of the ribs in a plurality of rows has a plurality of sipes extending in the tire width direction, and the sipes have a chamfered portion on at least one edge and a chamfered portion on the edge. Since it is composed of non-chamfered sipe, the chamfered sipe provided with the chamfered portion leads to improvement of drainage property at the time of touchdown, and wet performance can be improved. On the other hand, since the non-chamfered sipe without the chamfered portion coexists in the same rib adjacent to the tire circumferential direction of the chamfered sipe, the non-chamfered sipe bears the deformation of the tread portion at the time of touchdown. Contributes to suppressing the collapse of the chamfered portion in the chamfered sipe. Further, in the chamfering sipe, one end thereof is terminated in the rib while the other end communicates with one of the main grooves located on both sides of the rib, and communicates with each of the main grooves located on both sides of the rib. By alternately arranging the chamfered sipe in the tire circumferential direction, a wide ground contact area can be secured around the chamfered sipe, and the crushing of the chamfered portion of the chamfered sipe can be effectively suppressed. This makes it possible to improve the wet performance. Further, the total extension LB _OUT of the non-chamfered sipe in the outer region of the vehicle and the total extension LB _IN of the non-chamfered sipe in the inner region of the vehicle satisfy the relationship of LB _OUT <LB _IN. It works effectively against the load, and the rigidity of the tread portion can be sufficiently secured, which leads to the improvement of the dry performance.

In the present invention, among the non-chamfered sipes, the distance L1 between the non-chamfered sipes closest to the chamfered sipes and the chamfered sipes in the tire circumferential direction is preferably 2 mm to 15 mm. As a result, the crushing of the chamfered portion of the chamfered sipe can be effectively suppressed.

In the present invention, it is preferable that the depth Cd _IN of the chamfered sipe in the inner region of the vehicle and the depth Nd _IN of the non-chamfered sipe in the inner region of the vehicle satisfy the relationship of 1 <Nd _IN / Cd _IN ≤ 1.5. As a result, the crushing of the chamfered portion of the chamfered sipe can be effectively suppressed.

In the present invention, the width Cw of the opening on the ground plane in the chamfered sipe is preferably 1.6 mm to 4.8 mm. As a result, drainage property at the time of touchdown can be ensured.

In the present invention, the width Cw _OUT of the opening on the ground plane in the chamfered sipe of the vehicle outer region and the width Cw _IN of the opening on the ground plane in the chamfered sipe of the vehicle inner region are 1 <Cw _IN / Cw _OUT ≤ 3 It is preferable to satisfy the relationship of 0.0. As a result, it is possible to improve the drainage property in the vehicle inner region, improve the braking performance on the wet road surface, increase the pattern rigidity in the vehicle outer region, and improve the cornering performance on the dry road surface.

In the present invention, it is preferable that the groove area Ga _OUT in the main groove in the vehicle outer region and the groove area Ga _IN in the main groove in the vehicle inner region satisfy the relationship of 1 <Ga _IN / Ga _OUT ≦ 1.4. As a result, it is possible to improve the drainage property in the vehicle inner region, improve the braking performance on the wet road surface, increase the pattern rigidity in the vehicle outer region, and improve the cornering performance on the dry road surface.

In the present invention, the non-chamfered sipe is preferably bent in the tire circumferential direction in the plan view of the tread portion to have a bent portion, and the bending angle of the non-chamfered sipe is preferably 20 ° to 100 °. As a result, the wall surfaces of the non-chamfered sipes support each other in the deformation direction, so that the pattern rigidity can be ensured, which leads to the improvement of the cornering performance on the dry road surface.

In the present invention, the hardness E _OUT of the rib tread rubber having the chamfered sipe in the vehicle outer region and the hardness E _IN of the rib tread rubber having the chamfered sipe in the vehicle inner region satisfy the relationship of E _OUT −E _IN ≧ 3. Is preferable. As a result, the cornering performance on a dry road surface can be improved, the chamfered portion of the chamfered sipe can be suppressed from being crushed, and the braking performance on a wet road surface can be improved.

In the present invention, it is preferable that the radius of curvature TR of the virtual arc forming the tread profile and the radius of curvature RR of the outer contour line of the rib having the chamfer sipe satisfy the relationship of TR> RR. As a result, the drainage property of the rib at the time of touchdown can be improved, and the wet performance can be effectively improved.

In the present invention, 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, JATTA is a standard rim, and TRA is a "regular rim". "Design Rim", or "Measuring Rim" for ETRTO. "Regular internal pressure" is the air pressure defined for each tire in the standard system including the standard on which the tire is based. For JATTA, the maximum air pressure, and for TRA, the table "TIRE LOAD LIMITS AT VARIOUS". The maximum value described in "COLD INFLATION PRESSURES", which is "INFLATION PRESSURE" for ETRTO, but 180 kPa when the tire is a passenger car.

It is a meridian cross-sectional view which shows the pneumatic tire which comprises embodiment of this invention. It is a perspective view which shows a part of the tread part of the pneumatic tire which concerns on this invention. It is a top view which shows a part of the tread part of the pneumatic tire which concerns on this invention. FIG. 3 is a cross-sectional view taken along the line XX of FIG. It is sectional drawing which shows the modification of the non-chamfered sipe formed in the tread portion of the pneumatic tire which concerns on this invention. It is a top view which shows the other modification of the sipe formed in the tread part of the pneumatic tire which concerns on this invention. It is a top view which shows the other modification of the tread part of the pneumatic tire which concerns on this invention. Other modified examples of the non-chamfered sipe formed on the tread portion of the pneumatic tire according to the present invention are shown, and FIGS. (A) to (C) are plan views of each modified example. It is sectional drawing which shows the other modification of the tread part of the pneumatic tire which concerns on this invention. It is a top view which shows the other modification of the tread part of the pneumatic tire which concerns on this invention. It is a top view which shows the other modification of the tread part of the pneumatic tire which concerns on this invention. It is a top view which shows the other modification of the tread part of the pneumatic tire which concerns on this invention. Other modified examples of the chamfered sipe formed on the tread portion of the pneumatic tire according to the present invention are shown, and FIGS. (A) to (D) are cross-sectional views of each modified example.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a pneumatic tire according to an embodiment of the present invention, and FIGS. 2 to 4 show a part of a tread portion of the pneumatic tire. In FIG. 1, CL is the tire equatorial line, in FIGS. 2 and 3, Tc is the tire circumferential direction and Tw is the tire width direction.

As shown in FIG. 1, the pneumatic tire according to the embodiment of the present invention has a designated mounting direction with respect to the vehicle, and IN is inside the tire equatorial line CL with respect to the vehicle when the tire is mounted on the vehicle. (Hereinafter referred to as a vehicle inner region), OUT indicates a region outside the tire equatorial line CL with respect to the vehicle (hereinafter referred to as a vehicle outer region) when the tire is mounted on the vehicle. Further, the pneumatic tire according to the embodiment of the present invention includes a tread portion 1 extending in the tire circumferential direction to form an annular shape, and a pair of sidewall portions 2 and 2 arranged on both sides of the tread portion 1. A pair of bead portions 3 and 3 arranged inside the sidewall portion 2 in the tire radial direction are provided.

A carcass layer 4 is mounted between the pair of bead portions 3 and 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back from the inside to the outside of the tire around the bead core 5 arranged in each bead portion 3. A bead filler 6 made of a rubber composition having a triangular cross section is arranged on the outer periphery of the bead core 5.

On the other hand, a plurality of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 include a plurality of reinforcing cords that are inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged so as to intersect each other between the layers. In the belt layer 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in the range of, for example, 10 ° to 40 °. A steel cord is preferably used as the reinforcing cord of the belt layer 7. At least one belt cover layer 8 is arranged on the outer peripheral side of the belt layer 7 so that the reinforcing cords are arranged at an angle of, for example, 5 ° or less with respect to the tire circumferential direction for the purpose of improving high-speed durability. There is. As the reinforcing cord of the belt cover layer 8, an organic fiber cord such as nylon or aramid is preferably used.

The above-mentioned tire internal structure shows a typical example of a pneumatic tire, but is not limited to this.

As shown in FIGS. 1 and 2, a plurality of main grooves 9 extending in the tire circumferential direction are formed in the tread portion 1. The main groove 9 includes a main groove 9A located on the tire equatorial line CL and a pair of main grooves 9B and 9B located outside the tire width direction. A plurality of rows of ribs 10 are partitioned in the tread portion 1 by these main grooves 9. The rib 10 includes a pair of ribs 10A and 10A located on both sides of the tire equatorial line CL and a pair of ribs 10B and 10B located outside the rib 10A in the tire width direction.

In the aspects of FIGS. 1 and 2, three main grooves 9 are formed in the tread portion 1, but in order to achieve both drainage and securing a ground contact area, the tread portion 1 has 3 main grooves 9. It is preferable to provide ~ 5 main grooves 9.

As shown in FIG. 2, the rib 10 includes a plurality of sipes 11 extending in the tire width direction and a block 20 partitioned by the plurality of sipes 11. These blocks 20 are arranged so as to line up in the tire circumferential direction. On the other hand, the sipe 11 is composed of a chamfered sipe 12 and a non-chamfered sipe 13. The sipe 11 is a narrow groove having a groove width of 0.5 mm to 1.6 mm and a depth of 2.0 mm or more when the rim is not assembled.

As shown in FIG. 3, the chamfered sipe 12 is a sipe having a chamfered portion 14 on at least one of the edges 12a and 12b. In the aspect of FIGS. 2 and 3, the chamfered portion 14 is provided on one edge 12a over the entire length of the chamfered sipe 12, but can also be provided on both side edges 12a and 12b, or the chamfered sipe 12 It may be provided partially or intermittently along the extending direction. Further, in the chamfered sipe 12, one end 12c is terminated in the rib 10, while the other end 12d communicates with one of the main grooves 9 and 9 located on both sides of the rib 10. The chamfered sipes 12 and 12 communicating with the main grooves 9 and 9 located on both sides of the rib 10 are alternately arranged in the tire circumferential direction, and the chamfered sipes 12 are arranged in a staggered manner in the tire circumferential direction as a whole. .. As shown in FIG. 4, the chamfered portion 14 formed on the chamfered sipe 12 has a triangular shape in a cross-sectional view orthogonal to the extending direction of the chamfered sipe 12. The chamfered sipe 12 has a depth of 1 mm or more at a portion other than the chamfered portion 14.

The non-chamfered sipe 13 is a sipe provided in a region within 50 mm in the tire circumferential direction with the chamfered sipe 12 as the center and without a chamfered portion. The non-chamfered sipe 13 is arranged adjacent to at least one side of the chamfered sipe 12 in the tire circumferential direction. In FIGS. 2 and 3, non-chamfered sipes 13 are arranged adjacent to both sides of the chamfered sipes 12 in the tire circumferential direction on the ribs 10A in the vehicle inner region, while non-chamfered sipes 13 are arranged on the ribs 10A in the vehicle outer region. The sipe 13 is arranged adjacent to one side of the chamfered sipe 12 in the tire circumferential direction.

Further, the non-chamfered sipe 13 penetrates the rib 10 in the tire width direction. As a result, there is an effect of suppressing the crushing of the chamfered portion 14 of the chamfered sipe 12 at the time of touchdown. On the other hand, the non-chamfered sipe 13 can be configured as a closed sipe whose both ends end in the rib 10 or a semi-closed sipe in which only one end ends in the rib 10. Further, the non-chamfered sipe 13 may be inclined with respect to the tire width direction, and may be bent or curved.

The rib 10 may be provided with a groove other than the chamfered sipe 12 and the non-chamfered sipe 13. However, since the drainage property in the rib 10 can be sufficiently ensured by the chamfered sipe 12, it is preferable to provide only the chamfered sipe 12 and the non-chamfered sipe 13 from the viewpoint of increasing the ground contact area and improving the braking performance. ..

The hardness of the tread rubber should be small in order to increase the contact area, while the hardness of the tread rubber should be large in order to suppress the crushing of the chamfered portion 14. In order to achieve both of these, the hardness of the tread rubber is preferably 58 to 75 as defined by JIS K6253. In particular, the relationship between the hardness E _OUT of the tread rubber of the rib 10 having the chamfered sipe 12 in the outer region of the vehicle and the hardness E _IN of the tread rubber of the rib 10 having the chamfered sipe 12 in the inner region of the vehicle is E _OUT −E _IN ≧ 3. It is good to meet. This contributes to the improvement of cornering performance on dry road surface and braking performance on wet road surface.

In the above pneumatic tire, the total extension LB _OUT of the non-chamfered sipe 13 in the outer region of the vehicle and the total extension LB _IN of the non-chamfered sipe 13 in the inner region of the vehicle are configured to satisfy the relationship of LB _OUT <LB _IN . .. Here, the total lengths LB _OUT and LB _IN of the non-chamfered sipe 13 are the sum of the sipe lengths of all the non-chamfered sipe 13 formed on the ribs 10 of the vehicle outer region or the vehicle inner region. In particular, it is preferable that the ratio LB _IN / LB _OUT of the total length LB _IN and the total length LB _OUT of the non-chamfered sipe 13 is in the range of 1.2 to 1.8. As a method of increasing the total length LB _IN of the non-chamfered sipe 13 in the vehicle inner region to be larger than the total length LB _OUT of the non-chamfered sipe 13 in the vehicle outer region, the number of non-chamfered sipes 13 is increased in the vehicle inner region. This includes increasing the sipe length of the non-chamfered sipe 13 or increasing the number of ribs to be applied. The sipe length is the length measured at the center of the groove width of the sipe along the extending direction of the sipe.

Further, in addition to satisfying the relationship between the total extension LB _OUT and the total extension LB _IN described above, what is the total extension LA _OUT of the chamfered sipe 12 in the vehicle outer region and the total extension LA _IN of the non-chamfered sipe 13 in the vehicle inner region? LA _OUT satisfy the relationship of ≦ LA _iN, and / or the total length LA ratio _OUT LB _OUT / LA _OUT chamfer sipe 12 on the vehicle outer side region of the total length LB _OUT non chamfered sipe 13 on the vehicle outer side area, the vehicle interior be the total length LA ratio _iN LB _iN / LA _iN chamfer sipe 12 of the vehicle inner area of the total length LB _iN non chamfered sipe 13 in the region that satisfies the relationship of _{LB OUT / LA OUT ≦ LB iN} / LA iN preferable.

In the pneumatic tire described above, at least one of the ribs 10 in the plurality of rows has a plurality of sipes 11 extending in the tire width direction, and the sipes 11 have chamfered portions 14 on at least one of the edges 12a and 12b. Since it is composed of a chamfered sipe 12 and a non-chamfered sipe 13 having no chamfered portion on the edge, the drainage property at the time of touchdown can be improved due to the chamfered sipe 12 provided with the chamfered portion 14, and the wet performance can be improved. It leads to improvement of. On the other hand, since the non-chamfered sipe 13 having no chamfered portion coexists in the same rib 10 adjacent to the tire circumferential direction of the chamfered sipe 12, the non-chamfered sipe 13 has a tread portion 1 when it touches the ground. It bears the deformation and contributes to the suppression of the crushing of the chamfered portion 14 in the chamfered sipe 12.

Further, in the chamfered sipe 12, one end portion 12c thereof terminates in the rib 10, while the other end portion 12d communicates with one of the main grooves 9 located on both sides of the rib 10, and is located on both sides of the rib 10. By alternately arranging the chamfered sipes 12 communicating with each of the main grooves 9 in the tire circumferential direction, a wide ground contact area can be secured around the chamfered sipes 12 and the chamfered portion 14 of the chamfered sipes 12 is crushed. Can be effectively suppressed. This makes it possible to improve the wet performance. Further, the total extension LB _OUT of the non-chamfered sipe 13 in the outer region of the vehicle and the total extension LB _IN of the non-chamfered sipe 13 in the inner region of the vehicle satisfy the relationship of LB _OUT <LB _IN , so that the outer side of the vehicle mounted when turning. It works effectively against a large load, and the rigidity of the tread portion 1 can be sufficiently ensured, which leads to improvement of dry performance.

In the pneumatic tire, as shown in FIG. 3, the concave region of the chamfered sipe 12 including the chamfered portion 14 and the concave region of the non-chamfered sipe 13 closest to the chamfered sipe 12 among the non-chamfered sipe 13 are closest to each other. The distance in the tire circumferential direction at the position to be chamfered is defined as the distance L1. The distance L1 is preferably 2 mm to 15 mm, more preferably 4 mm to 11 mm. By setting the distance L1 appropriately in this way, the non-chamfering sipe 13 can effectively suppress the crushing of the chamfered portion 14 of the chamfered sipe 12. Here, if the distance L1 is smaller than 2 mm, the rigidity of the rib 10 decreases in the region sandwiched between the chamfered sipe 12 and the non-chamfered sipe 13, and the region collapses, making it difficult to secure the ground contact property. Performance tends to deteriorate.

Further, in FIG. 3, the inclination angles of the chamfered sipe 12 and the non-chamfered sipe 13 with respect to the tire circumferential direction are defined as an inclination angle θ _C and an inclination angle θ _N , respectively. At this time, the inclination angle θ _C of the chamfered sipe 12 and the inclination angle θ _N of the non-chamfered sipe 13 may be configured to satisfy the relationship of θ _C −30 ° ≦ θ _N ≦ θ _C + 30 °. By setting the inclination angles θ _C and θ _N in this way, it is possible to effectively suppress the collapse of the chamfered portion 14 of the chamfered sipe 12. The inclination angle θ _N of the non-chamfered sipe 13 is an inclination angle specified within a range equivalent to the length of the chamfered sipe 12 in the tire width direction.

As shown in FIG. 4, in the chamfered sipe 12 and the non-chamfered sipe 13, the depths from the ground plane to the groove bottom of the sipe are defined as the depth Cd and the depth Nd, respectively. At this time, it is preferable that the depth Cd _IN of the chamfered sipe in the inner region of the vehicle and the depth Nd _IN of the non-chamfered sipe in the inner region of the vehicle satisfy the relationship of 1 <Nd _IN / Cd _IN ≦ 1.5. More preferably, 1.1 <Nd _IN / Cd _IN ≤ 1.4 is preferable. By appropriately setting the depth Nd _IN with respect to the depth Cd _IN in this way, it is possible to effectively suppress the crushing of the chamfered portion 14 of the chamfered sipe 12. Here, when the ratio of the depth Nd _{IN to} the depth Cd _IN is larger than 1.5, the rigidity of the rib 10 in the vehicle inner region tends to decrease, the block 20 tends to collapse, and the wet performance tends to decrease.

Further, in FIG. 4, the width of the opening of the chamfered sipe 12 on the ground plane is defined as the width Cw. The width Cw of this opening is measured along a direction orthogonal to the extending direction of the chamfer sipe 12. At this time, the width Cw of the opening may be configured to be 1.6 mm to 4.8 mm. By configuring the chamfered sipe 12 in this way, drainage at the time of touchdown can be ensured. Here, when the width Cw of the opening of the chamfered sipe 12 on the ground contact surface is smaller than 1.6 mm, the effect of improving drainage is small, and when it is larger than 4.8 mm, the ground contact area is small, and in wet performance and dry road surface. Cornering performance tends to deteriorate.

FIG. 5 shows a modified example of the non-chamfered sipe formed on the tread portion of the pneumatic tire according to the present invention. As shown in FIG. 5, the width of the opening on the ground plane of the non-chamfered sipe 13 is defined as the width Nw. The width Nw of this opening is measured along a direction orthogonal to the extending direction of the non-chamfered sipe 13. In FIG. 5, the width Nw of the non-chamfered sipe 13 gradually widens from the bottom toward the opening. By forming the non-chamfered sipe 13 in this way, the burden on the deformation of the tread portion 1 of the non-chamfered sipe 13 increases, and the crushing of the chamfered portion 14 of the chamfered sipe 12 can be effectively borne.

FIG. 6 shows another modification of the sipe formed on the tread portion of the pneumatic tire according to the present invention. As shown in FIG. 6, the opening of the chamfered sipe 12 in the vehicle inner region on the ground plane is wider than the opening on the ground plane of the chamfered sipe 12 in the vehicle outer region. That is, the width Cw _OUT of the opening of the chamfered sipe 12 in the outer region of the vehicle and the width Cw _IN of the opening of the chamfered sipe 12 in the inner region of the vehicle satisfy the relationship of 1 <Cw _IN / Cw _OUT ≤ 3.0. It is configured. By appropriately setting the width Cw _IN with respect to the width Cw _{OUT in} this way, the drainage property in the vehicle inner region is improved, the braking performance on the wet road surface is improved, and the pattern rigidity in the vehicle outer region is enhanced. , It is possible to improve the cornering performance on a dry road surface. Here, when the ratio of the width Cw _{IN to} the width Cw _OUT exceeds 3.0, the rigidity of the block 20 in the vehicle inner region region tends to be excessively small, and the braking performance on a wet road surface tends to deteriorate.

FIG. 7 shows another modification of the tread portion of the pneumatic tire according to the present invention. As shown in FIG. 7, the main groove 9B in the vehicle inner region is formed wider than the main groove 9B in the vehicle outer region. That is, the groove area Ga _OUT of the main groove 9 in the outer region of the vehicle and the groove area Ga _IN of the main groove 9 in the inner region of the vehicle are configured to satisfy the relationship of 1 <Ga _IN / Ga _OUT ≤ 1.4. .. By appropriately setting the groove area Ga _IN with respect to the groove area Ga _{OUT in} this way, the drainage property in the vehicle inner region is improved, the braking performance on the wet road surface is improved, and the pattern rigidity in the vehicle outer region is improved. It becomes possible to improve the cornering performance on a dry road surface. Here, when the ratio of the groove area Ga _{IN to} the groove area Ga _OUT is larger than 1.4, the rigidity of the block 20 in the vehicle inner region region tends to be excessively lowered, and the braking performance on a wet road surface tends to be lowered.

8 (a) to 8 (c) show other modifications of the non-chamfered sipe formed on the tread portion of the pneumatic tire according to the present invention. As shown in FIG. 8A, the non-chamfered sipe 13 is bent in the tire circumferential direction in the plan view of the tread portion 1 to have a bent portion 13a. The bending angle θ1 of the non-chamfered sipe 13 is in the range of 20 ° to 100 °. Here, the bending angle θ1 of the non-chamfered sipe 13 is a portion on the other side with respect to the extension direction of the portion on one side when the non-chamfered sipe 13 has a portion on one side and a portion on the other side with the bent portion 13a as a boundary. Means the tilt angle of. Since the non-chamfered sipe 13 has such a bent portion 13a having a bending angle θ1, the blocks 20 of the ribs 10 divided by the non-chamfered sipe 13 are less likely to be displaced in the lateral direction (tire width direction). That is, since the wall surfaces of the non-chamfered sipe 13 can support each other in an arbitrary deformation direction to secure the pattern rigidity, the cornering performance on a dry road surface can be improved. However, this does not include a form in which the bending angle θ1 is larger than 90 ° and both ends of the non-chamfered sipe 13 communicate with the same main groove 9 among the main grooves 9 on both sides of the rib 10. Further, in addition to the case shown in FIG. 8A, there is a case where the tire has a chevron shape that is convex in the tire circumferential direction as shown in FIG. 8B, and two bent portions 13a are shown in FIG. 8C. It can be illustrated a case where the tires are formed in a stepped shape as a whole.

FIG. 9 shows another modification of the tread portion of the pneumatic tire according to the present invention. In FIG. 9, each rib 10 is formed with a chamfered sipe 12 and a non-chamfered sipe 13 as in the above-described embodiment. In the tire meridional cross-sectional view, assuming an arc R passing through both end points E1, E2, E3, E4 in the tire width direction of the two main grooves 9 located in the center of the tire, an outer contour line defining the tread surface of the rib 10 is assumed. Projects outward in the tire radial direction from the arc R. That is, the radius of curvature TR of the arc R forming the tread profile and the radius of curvature RR of the outer contour line of the rib 10 having the chamfered sipe 12 satisfy the relationship of TR> RR. As a result, the drainage property of the rib 10 at the time of touchdown can be improved, and the wet performance can be effectively improved. The radius of curvature TR and the radius of curvature RR are measured in a state where the tire is rim-assembled on a regular rim and the regular internal pressure is applied.

FIGS. 10 to 12 show other modifications of the tread portion of the pneumatic tire according to the present invention. 10 and 11 show an example in which the above-mentioned chamfered sipe 12 and non-chamfered sipe 13 are applied to the rib 10 partitioned by the four main grooves 9 extending in the tire circumferential direction, and FIG. This is an example applied to the rib 10 partitioned by the main groove 9 of the book. In FIGS. 10 and 11, a pair of main grooves 9A and 9A located on both sides of the tire equatorial line CL and a pair of main grooves 9B and 9B located outside the tire width direction are located on the tire equatorial line CL. Ribs 10A and a pair of ribs 10B and 10B located on the outer side in the tire width direction are partitioned. Further, in FIG. 12, a main groove 9A located near the tire equatorial line CL, a pair of main grooves 9B and 9B located outside the tire width direction, and a pair of main grooves 9C located on the outermost side in the tire width direction are shown. , 9C divides the rib 10A located on the tire equatorial line CL, the pair of ribs 10B and 10B located outside the tire width direction, and the rib 10C located outside the tire width direction of the rib 10B in the vehicle inner region region. Has been done.

In FIG. 10, more non-chamfered sipes 13 are arranged on the ribs 10B in the vehicle inner region than on the ribs 10B in the vehicle outer region. In FIG. 11, the non-chamfered sipe 13 of the rib 10B in the vehicle outer region extends parallel to the tire width direction, while the non-chamfered sipe 13 of the rib 10B in the vehicle inner region is inclined with respect to the tire width direction. doing. In FIG. 12, the chamfered sipe 12 and the non-chamfered sipe 13 are arranged only on the pair of ribs 10B and 10B, and the non-chamfered sipe 13 is arranged on the rib 10B in the vehicle inner region more than the rib 10B in the vehicle outer region. There is. That is, in any of the embodiments shown in FIGS. 10 to 12, the relationship between the total extension LB _OUT of the non-chamfered sipe 13 in the vehicle outer region and the total extension LB _IN of the non-chamfered sipe 13 in the vehicle inner region is LB _OUT <LB _IN . It is configured to meet.

13 (a) to 13 (d) show other modifications of the chamfered sipe formed on the tread portion of the pneumatic tire according to the present invention. As shown in FIG. 13A, in a cross-sectional view orthogonal to the extending direction of the chamfered sipe 12, a chamfered portion 14 is formed on one edge of the chamfered sipe 12, and the cross-sectional shape of the chamfered portion 14 is rectangular. Is. By making the cross-sectional shape of the chamfered portion 14 rectangular in this way, it is possible to secure a sufficient groove volume against deformation of the tread portion 1 at the time of touchdown, and it is possible to improve drainage. On the other hand, as the cross-sectional shape of the chamfered portion 14 of the chamfered sipe 12, in addition to those shown in FIGS. 4 and 13 (a), the contour of a curve that is convex inward in the tire radial direction as shown in FIG. 13 (b). Examples include a case where the tire has a line, a case where the tire has a curved contour line which is convex outward in the radial direction of the tire as shown in FIG. 13 (c), and a case where the tire has a triangular shape as shown in FIG. 13 (d). it can.

In a pneumatic tire having a tire size of 195 / 65R15 and having a plurality of main grooves extending in the tire circumferential direction and a plurality of rows of ribs partitioned by the main grooves in the tread portion, with or without chamfering sipes and non-chatoming. Presence / absence of sipe, ratio of total length LB _IN of non-champed sipe in the vehicle inner region to total length LB _OUT of non-chafted sipe in the outer region of the vehicle (LB _IN / LB _OUT ), distance between chamfered sipe and non-chafted sipe L1 ( mm), the ratio of the depth Nd _IN of the chamfered sipe in the inner region of the vehicle to the depth Cd _IN of the chamfered sipe in the inner region of the vehicle (Nd _IN / Cd _IN ), the width of the opening of the chamfered sipe in the outer region of the vehicle Cw _OUT (Mm), ratio of width Cw _IN of chamfered sipe opening in vehicle inner region to width Cw _OUT of chamfered sipe opening in vehicle outer region (Cw _IN / Cw _OUT ), groove area of main groove in vehicle outer region The ratio of the groove area Ga _IN of the main groove in the vehicle inner region to Ga _OUT (Ga _IN / Ga _OUT ), the bending angle of the non-chafted sipe, the hardness E _OUT of the tread rubber of the rib in the vehicle outer region, and the rib in the vehicle inner region. Conventional example, Comparative Examples 1 to 3 and Examples in which the difference from the hardness E _{IN of the} tread rubber (E _OUT- E _IN ) and the presence or absence of the rib protruding outward in the tire radial direction are set as shown in Tables 1 and 2. I made tires 1-9.

These test tires were evaluated for braking performance on wet road surface and steering stability performance on dry road surface by the following test method, and the results are shown in Tables 1 and 2.

Braking performance on wet roads:
Each test tire is assembled on a wheel with a rim size of 15 x 6J, mounted on a front-wheel drive vehicle with a displacement of 1500cc, and the braking distance is measured from an initial speed of 80km / h to a complete stop on a wet road surface with a water pressure of 230kPa. did. The evaluation result is shown by an index of 100 in the conventional example using the reciprocal of the measured value. The larger the index value, the better the braking performance on a wet road surface.

Steering stability on dry roads:
Each test tire was assembled on a wheel having a rim size of 15 × 6J, mounted on a front-wheel drive vehicle having a displacement of 1500 cc, and a sensory evaluation was carried out by a test driver on a dry road surface at an air pressure of 230 kPa. The evaluation result is shown by an index of 100 in the conventional example. The larger this index value is, the better the steering stability performance on a dry road surface is.

As can be seen from Tables 1 and 2, by devising the shape of the sipe provided in the tread portion, the tires of Examples 1 to 9 have braking performance on a wet road surface and a dry road surface in comparison with the conventional example. At the same time, the steering stability performance was improved.

On the other hand, in Comparative Example 1, since the total length of the non-chamfered sipe in the outer region of the vehicle and the total length of the non-chamfered sipe in the inner region of the vehicle are set to be equal, the effect of improving the steering stability performance on the dry road surface cannot be obtained. Chamfered. In Comparative Example 2, since no sipes were provided on the ribs, the effect of improving the braking performance on a wet road surface could not be sufficiently obtained. In Comparative Example 3, since only the sipes without the chamfered portion were arranged on the ribs, the effect of improving the braking performance on the wet road surface could not be sufficiently obtained, and the effect of improving the steering stability on the dry road surface was small. It was.

1 Tread part 2 Side wall part 3 Bead part 9 Main groove 10 Rib 11 Sipe 12 Chamfered sipe 12a, 12b Edge 12c, 12d End 13 Non-chamfered sipe 14 Chamfered part

Claims (9)

In a pneumatic tire provided with a plurality of main grooves extending in the tire circumferential direction and a plurality of rows of ribs partitioned by the main grooves in the tread portion and a vehicle mounting direction is specified.
Each of the vehicle outer region and the vehicle inner region of the tread portion has at least one row of ribs in which a plurality of sipes extending in the tire width direction are formed, and the sipes are chamfered sipes having chamfered portions on at least one edge. The chamfered sipe consists of a non-chamfered sipe having no chamfered portion at the edge, and the chamfered sipe communicates with one of the main grooves located on both sides of the rib while one end thereof is terminated in the rib. Chamfered sipes communicating with each of the main grooves located on both sides of the rib are alternately arranged in the tire circumferential direction, and the non-chamfered sipes are arranged adjacent to at least one side of the chamfered sipe in the tire circumferential direction, and the vehicle outer region. A pneumatic tire characterized in that the total extension LB _OUT of the non-chamfered sipe and the total extension LB _IN of the non-chamfered sipe in the inner region of the vehicle satisfy the relationship of LB _OUT <LB _IN . The pneumatic tire according to claim 1, wherein the distance L1 in the tire circumferential direction between the non-chamfered sipe closest to the chamfered sipe and the chamfered sipe is 2 mm to 15 mm. Claim 1 or claim 1, wherein the chamfered sipe depth Cd _IN in the vehicle inner region and the non-chamfered sipe depth Nd _{IN in the} vehicle inner region satisfy the relationship of 1 <Nd _IN / Cd _IN ≤ 1.5. The pneumatic tire according to 2. The pneumatic tire according to any one of claims 1 to 3, wherein the width Cw of the opening on the ground contact surface of the chamfered sipe is 1.6 mm to 4.8 mm. The relationship between the width Cw _OUT of the opening on the ground plane in the chamfered sipe of the vehicle outer region and the width Cw _IN of the opening on the ground plane in the chamfered sipe of the vehicle inner region is 1 <Cw _IN / Cw _OUT ≤ 3.0. The pneumatic tire according to any one of claims 1 to 4, wherein the tire meets the above conditions. Claims 1 to 5 characterized in that the groove area Ga _OUT of the main groove in the vehicle outer region and the groove area Ga _IN of the main groove in the vehicle inner region satisfy the relationship of 1 <Ga _IN / Ga _OUT ≤ 1.4. Pneumatic tires listed in any of. Claims 1 to 6 are characterized in that the non-chamfered sipe is bent in the tire circumferential direction in a plan view of the tread portion to have a bent portion, and the bending angle of the non-chamfered sipe is 20 ° to 100 °. Pneumatic tires listed in any of. The feature is that the hardness E _OUT of the rib tread rubber having the chamfered sipe in the outer region of the vehicle and the hardness E _IN of the rib tread rubber having the chamfered sipe in the inner region of the vehicle satisfy the relationship of E _OUT −E _IN ≧ 3. The pneumatic tire according to any one of claims 1 to 7. The air according to any one of claims 1 to 8, wherein the radius of curvature TR of the arc forming the tread profile and the radius of curvature RR of the outer contour line of the rib having the chamfered sipe satisfy the relationship of TR> RR. Chamfered tire.

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