阅读说明：本技术 充气轮胎 (Pneumatic tire ) 是由 植村卓范 于 2019-10-25 设计创作，主要内容包括：本发明提供一种充气轮胎,该充气轮胎能够兼顾在干燥路面上的驾驶稳定性和在潮湿路面上的驾驶稳定性的提高。刀槽花纹(12)的至少一端与主槽(9)相连通,并在刀槽花纹(12)的至少一个边缘具有倒角部(13),倒角部(13)的至少一端朝向主槽(9)开口,在子午线截面中,轮廓线(L1)比基准胎面轮廓线(L0)更向轮胎径向外侧突出,基准胎面轮廓线(L0)的曲率半径TR(mm)和条状花纹(10)的轮廓线(L1)的曲率半径(RR)(mm)满足TR>RR的关系,倒角部(13)设置成跨越条状花纹(10)的轮廓线(L1)的最大突出位置(P),相对于基准胎面轮廓线(L0)的条状花纹(10)的最大突出量(D)(mm)和倒角部(13)的最大宽度(W)(mm)满足0.05mm～2<W×D<1.50mm～2的关系。(The invention provides a pneumatic tire which can improve the driving stability on a dry road surface and the driving stability on a wet road surface at the same time. At least one end of the sipe (12) communicates with the main groove (9), and has a chamfered portion (13) at least one edge of the sipe (12), at least one end of the chamfered portion (13) opens to the main groove (9), in a meridian section, a contour line (L1) protrudes further to the tire radial outside than a reference tread contour line (L0), and a curvature radius TR (mm) of the reference tread contour line (L0) and a curvature radius RR (mm) of a contour line (L1) of the stripe pattern (10) satisfy TR>RR relation, the chamfer part (13) is providedThe maximum protrusion position (P) of the rib (10) is set to be crossed with the contour line (L1), and the maximum protrusion amount (D) (mm) of the rib (10) and the maximum width (W) (mm) of the chamfer part (13) relative to the reference tread contour line (L0) satisfy 0.05mm 2 <W×D<1.50mm 2 The relationship (2) of (c).)

1. A pneumatic tire having, in a tread portion, a plurality of main grooves extending in a tire circumferential direction, a plurality of rows of ribs partitioned by the main grooves, and sipes extending in a tire width direction,

at least one end of the sipe communicates with the main groove and has a chamfered portion at least one edge of the sipe, at least one end of the chamfered portion being open to the main groove,

in meridian section, the contour of the tread defining the sipe having a rib of said sipe and a reference tyreThe radius of curvature TR (mm) of the arc forming the reference tread profile line and the radius of curvature RR (mm) of the arc forming the profile line of the rib are such that TR is satisfied>RR, the chamfer is provided so as to span the maximum projection position of the rib profile, and the maximum projection D (mm) of the rib and the maximum width W (mm) of the chamfer relative to the reference tread profile satisfy 0.05mm²<W×D<1.50mm²The relationship (2) of (c).

2. A pneumatic tire as in claim 1, wherein said chamfered portion is provided to only one edge of said sipe.

3. A pneumatic tire as in claim 1 or 2, wherein said sipes are inclined with respect to the tire circumferential direction.

4. A pneumatic tire as claimed in any one of claims 1 to 3, wherein said sipe has an inclination angle of 40 ° to 80 ° with respect to an acute-angle side in the tire circumferential direction.

5. A pneumatic tyre as claimed in anyone of claims 1 to 4, characterized in that only one end of the sipe terminates inside the strip.

6. A pneumatic tyre as claimed in anyone of claims 1 to 5, characterized in that said sipes are located in a plurality of rows of said strips.

7. A pneumatic tyre as claimed in anyone of claims 1 to 6, wherein at least a portion of the sipe is curved or flexed when viewed from above.

8. A pneumatic tire according to any one of claims 1 to 7, wherein both end portions of the chamfered portion are open toward the main groove.

Technical Field

The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire in which a chamfer shape of a sipe is designed to improve both driving stability on a dry road surface and driving stability on a wet road surface.

Background

Conventionally, in a tread pattern of a pneumatic tire, a plurality of sipes are formed in a rib pattern defined by a plurality of main grooves. By providing such a sipe, drainage can be ensured and driving stability can be exhibited on a wet road surface. However, when a plurality of sipes are provided in the tread portion to improve the driving stability on a wet road surface, the rigidity of the rib is lowered, and thus there is a disadvantage that the driving stability on a dry road surface is lowered.

Further, various proposals have been made for forming sipes in a tread pattern in a pneumatic tire and chamfering the sipe (see, for example, patent document 1). In the case where the sipe is formed and chamfered, there is a possibility that an edge effect is lost depending on the shape of the chamfer, and there is a case where driving stability on a dry road surface or driving stability on a wet road surface cannot be sufficiently improved depending on the size of the chamfer.

Documents of the prior art

Patent document

Patent document 1: japanese Kokai publication Hei-2013-537134

Disclosure of Invention

Problems to be solved by the invention

The present invention aims to provide a pneumatic tire which can achieve both improvement in driving stability on a dry road surface and improvement in driving stability on a wet road surface by designing a chamfered shape of a sipe.

Technical scheme

A pneumatic tire of the present invention for achieving the above object has, in a tread portion, a plurality of main grooves extending in a tire circumferential direction, a plurality of rows of sipes partitioned by the plurality of main grooves, and a sipe extending in a tire width direction, and is characterized in that at least one end of the sipe communicates with the main grooves, and has a chamfered portion at least one edge of the sipe, at least one end of the chamfered portion being open to the main grooves, and in a meridian section, a contour line defining a tread surface of the sipe having the sipe protrudes more outward in a tire radial direction than a reference tread contour line, and a curvature radius (RR) of an arc forming the reference tread contour line and a curvature radius (RR) of an arc forming the contour line of the sipe satisfy TR>RR, the chamfer is provided so as to span the maximum projection position of the rib profile, and the maximum projection D (mm) of the rib and the maximum width W (mm) of the chamfer relative to the reference tread profile satisfy 0.05mm²<W×D<1.50mm²The relationship (2) of (c).

Effects of the invention

In the present invention, at least one end of the sipe communicates with the main groove, and at least one edge of the sipe has a chamfered portion, and therefore, drainage when contacting the ground can be improved, and driving stability on a wet road surface can be improved. At least one end of the chamfered portion is open to the main groove, and in a meridian cross section, a contour line defining a tread surface of a sipe-containing rib projects outward in the tire radial direction from a reference tread contour line, and a curvature radius TR of a circular arc forming the reference tread contour line and a curvature radius RR of a circular arc forming the rib-containing contour line satisfy TR>In relation to RR, the chamfered portion is provided so as to straddle the maximum projecting position of the contour line of the sipe, and therefore, in the sipe-containing rib, the shape projecting outward in the tire radial direction promotes drainage in the rib, whereby the driving stability on a wet road surface is further improved. The maximum protrusion amount D of the rib and the maximum width W of the chamfered portion with respect to the reference tread profile line satisfy 0.05mm²<W×D<1.50mm²Thereby making it possible to improve the driving stability on a dry road surface and the driving stability on a wet road surface in a balanced manner.

In the present invention, it is preferable that the chamfered portion is provided only on one edge of the sipe. Thereby, in the side of the sipe having the chamfered portion, the drainage can be improved due to the chamfered portion, and in the side of the sipe having no chamfered portion, the water film can be removed due to the edge effect. As a result, both the driving stability on dry road surfaces and the driving stability on wet road surfaces can be achieved.

In the present invention, preferably, the sipe is inclined with respect to the tire circumferential direction. Thereby, the edge effect can be improved, and the driving stability on a wet road surface can be effectively improved.

In the present invention, it is preferable that the inclination angle of the acute angle side of the sipe with respect to the tire circumferential direction is 40 ° to 80 °. This can effectively improve the driving stability on a dry road surface.

In the present invention, it is preferred that only one end of the sipe terminates within the bar. This improves the rigidity of the rib pattern and effectively improves the driving stability on a dry road surface.

In the present invention, it is preferable that the sipes are provided in a plurality of rows of the ribs. This can achieve both improvement in driving stability on dry road surfaces and improvement in driving stability on wet road surfaces.

In the present invention, it is preferable that at least a part of the sipe is bent or flexed in a plan view. Thereby, the total number of edges in each sipe can be increased, and the driving stability on a wet road surface can be effectively improved.

In the present invention, it is preferable that both end portions of the chamfered portion open toward the main groove. Thus, the driving stability on a wet road surface can be effectively improved.

Drawings

Fig. 1 is a meridian cross-sectional view showing a pneumatic tire according to an embodiment of the present invention.

Fig. 2 is a plan view showing a part of a tread portion of a pneumatic tire according to an embodiment of the present invention.

Fig. 3 is a meridian cross-sectional view showing the contour shape of the tread portion of the pneumatic tire according to the embodiment of the present invention.

Parts (a) to (d) of fig. 4 are sectional views illustrating a sipe formed on a tread portion of a pneumatic tire according to an embodiment of the present invention, the part (a) of fig. 4 is an X-X direction sectional view of fig. 2, and the parts (b) to (d) of fig. 4 are sectional views of various modifications.

Detailed Description

Hereinafter, the structure of the present invention will be described in detail with reference to the drawings. Fig. 1 shows a pneumatic tire according to an embodiment of the present invention. In fig. 1, CL is the tire centerline.

As shown in fig. 1, a pneumatic tire according to an embodiment of the present invention includes: a tread portion 1 having a ring shape and extending in a tire circumferential direction; a pair of side walls 2, 2 provided on both sides of the tread portion 1; and a pair of bead portions 3, 3 provided on the inner side of the sidewall portions 2 in the tire radial direction.

A carcass layer 4 is mounted between the pair of bead portions 3, 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and the reinforcing cords are folded back from the inner side to the outer side of the tire around bead cores 5 provided in the respective bead portions 3. A bead filler 6 formed of a rubber composition having a triangular cross section is provided on the outer periphery of the bead core 5.

On the other hand, a plurality of belt layers 7 are embedded in the tread portion 1 on the outer circumferential side of the carcass layer 4. These belt layers 7 include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and the reinforcing cords cross each other between the layers. In the belt layer 7, the inclination angle with respect to the tire circumferential direction of the reinforcing cords is set within a range of, for example, 10 ° to 40 °. As the reinforcing cord of the belt layer 7, a steel cord is preferably used. In order to improve high-speed durability, at least one belt cover layer 8 is provided on the outer circumferential side of the belt layer 7, and the belt cover layer 8 is formed by arranging reinforcing cords at an angle of, for example, 5 ° or less with respect to the tire circumferential direction. As the reinforcing cord of the belt cover layer 8, an organic fiber cord of nylon, aramid, or the like is preferably used.

A plurality of main grooves 9 extending in the tire circumferential direction are formed in the tread portion 1. A plurality of rows of ribs 10 are defined in the tread portion 1 by these main grooves 9. In the present invention, the main groove 9 means a groove having a wear indicator.

The tire internal structure described above is a structure showing a typical example of a pneumatic tire, but is not limited thereto.

Fig. 2 shows a part of a tread portion of a pneumatic tire according to an embodiment of the present invention. In fig. 2, Tc denotes the tire circumferential direction, Tw denotes the tire width direction, and P is the maximum protruding position of the rib 10 with respect to the reference tread profile line L0 described later.

As shown in fig. 2, the rib 10 is formed with a plurality of lug grooves 11 extending in the tire width direction and a plurality of sipes 12, 14, 16 extending in the tire width direction. Then, chamfering is performed along the main groove 9 at the edge of the rib 10.

The lug groove 11 is inclined with respect to the tire circumferential direction and has a sharp inflected portion. One end of the lug groove 11 opens into the main groove 9, and the other end of the lug groove 11 terminates in the rib 10. Such lug grooves 11 are formed in the rib 10 at intervals in the tire circumferential direction. In order to improve the driving stability on a wet road, it is preferable that the maximum width of the lug groove 11 is 2mm to 7mm, more preferably 3mm to 6mm, and the maximum depth thereof is 3mm to 8mm, more preferably 4mm to 7 mm.

Each of the sipes 12, 14, 16 is linear, one end of the sipe 12, 14, 16 terminating in a rib 10, the other end of the sipe 12, 14, 16 communicating with the main groove 9 of the adjacent rib 10. Sipes 12, 14 communicating with the respective main grooves 9 on both sides of the rib 10 are arranged in an alternating manner in the tire circumferential direction, and the sipes 12, 14 are arranged alternately in the tire circumferential direction as a whole. Also, the sipes 16 are also provided in the same manner, and the sipes 16 are staggered in the tire circumferential direction as a whole. In the present invention, the sipes 12, 14, 16 are narrow grooves, and the groove width thereof is 1.5mm or less.

Each sipe 12, 14 has opposing edges 12A, 12B and edges 14A, 14B. A chamfered portion 13 is formed on at least one of the edges 12A, 12B, and a chamfered portion 15 is also formed on at least one of the edges 14A, 14B. In the embodiment of fig. 2, the chamfered portions 13 and 15 are formed on the edges 12B and 14B of the sipes 12 and 14, respectively, and have non-chamfered regions where no other chamfered portion is present in the portions facing the chamfered portions 13 and 15 of the sipes 12 and 14. Further, the sipe 16 is not chamfered.

The chamfered portion 13 of the sipe 12 terminates at one end in the tire width direction at the center portion in the tire width direction of the rib 10, but the end is connected to the lug groove 11 and opens to the main groove 9 through the lug groove 11, and the other end of the chamfered portion 13 of the sipe 12 is connected to the opening end of the other lug groove 11 facing the main groove 9 and opens to the main groove 9 through the other lug groove 11. That is, both end portions of the chamfered portion 13 are opened substantially to the main groove 9. Further, one end of the chamfered portion 15 of the sipe 14 is terminated at the center portion in the tire width direction of the rib 10, but the end is connected to the lug groove 11, and opens to the main groove 9 through the lug groove 11, and the other end of the chamfered portion 15 of the sipe 14 opens to the main groove 9.

Fig. 3 shows a contour shape of the tread portion 1 in the pneumatic tire according to the embodiment of the present invention. In fig. 3, when a reference tread contour line L0 formed of an arc (curvature radius: TR) passing through three points (end points E1 to E3) of end points E1, E2, and E3 is assumed in a tire meridian cross-sectional view, a contour line L1 formed of an arc (curvature radius: RR) defining a tread surface of the rib 10 projects outward in the tire radial direction than the reference tread contour line L0, wherein the end points E1, E2 are both end points in the tire width direction of the rib 10 having the sipe 12, and the end point E3 is an end point in the tire width direction in the main groove 9 located on the tire centerline CL side among the main grooves 9 adjacent to the rib 10. The center of the arc forming the reference tread contour line L0 and the arc forming the contour line L1 are both on the inner side in the tire radial direction. The curvature radius TR of the arc forming the reference tread contour line L0 of the tread portion 1 and the curvature radius RR of the arc forming the contour line L1 of the rib 10 satisfy the relationship TR > RR.

Further, in order to easily understand the features of the tread portion 1, the profile shape is enlarged in fig. 3 and does not necessarily match the actual profile shape. When the edges of the rib 10 of the tread portion 1 are chamfered, the intersection points between the extension lines of the groove wall surfaces of the main grooves 9 and the extension lines of the tread surface of the rib 10 in the tire meridian cross section are designated as the end points E1, E2 of the rib 10. Assuming that the reference tread contour line L0 of the rib 10 located on the tire center line CL is defined as a reference, three points, namely, the two end points of the rib 10 in the tire width direction and the end point of one of the main grooves 9 located on both sides of the rib 10 on the inner side in the tire width direction of the rib 10, are defined as a reference, and assuming that the reference tread contour line L0 of the rib 10 located on the outermost side (shoulder portion) in the tire width direction is defined as a reference, three points, namely, the end point of the rib 10 on the inner side in the tire width direction and the two end points of the rib 10 located on the inner side in the tire width direction of the rib 10, are defined as a reference.

In the pneumatic tire described above, the position in the tire width direction where the projection amount of the contour line L1 of the rib 10 with respect to the reference tread contour line L0 is the largest is the maximum projection position P. The chamfered portion 13 of the sipe 12 is provided so as to straddle the maximum projecting position P of the contour line L1 of the rib 10. That is, the chamfered portions 13 are present on both sides in the tire width direction with reference to the maximum projecting position P. On the other hand, the chamfered portion 15 of the sipe 14 ends within the rib 10 without reaching the maximum projecting position P.

The maximum value of the projection amount of the contour line L1 with respect to the reference tread contour line L0 is set to the maximum projection amount d (mm), and the maximum value of the width of the chamfered portion 13 measured in the direction orthogonal to the sipe 12 is set to the maximum width w (mm). At this time, the maximum protrusion amount D of the rib 10 and the maximum width W of the chamfered portion 13 with respect to the reference tread profile line L0 satisfy 0.05mm²<W×D<1.50mm²The relationship (2) of (c). Particularly, preferably, 0.10mm is satisfied²<W×D<1.00mm²The relationship (2) of (c). Also, it is preferable that the maximum of the rib 10 with respect to the reference tread profile line L0 be the maximumThe projection amount D is in the range of 0.1mm to 0.8mm, and preferably, the maximum width W of the chamfered portion 13 is in the range of 0.5mm to 4.0 mm.

In the pneumatic tire described above, the sipe 12 has at least one end communicating with the main groove 9 and the chamfered portion 13 at least one edge 12A, 12B, and therefore, drainage when contacting the ground can be improved and driving stability on a wet road surface can be improved. At least one end of the chamfered portion 13 opens into the main groove 9, and in a meridian cross section, a contour line L1 for defining the tread surface of the rib 10 having the sipe 12 protrudes outward in the tire radial direction from the reference tread contour line L0, and the radius of curvature TR of the arc forming the reference tread contour line L0 and the radius of curvature RR of the arc forming the contour line L1 of the rib 10 satisfy TR>In relation to RR, the chamfered portion 13 is provided so as to straddle the maximum projecting position P of the contour line L1 of the rib 10, and therefore, in the rib 10 having the sipe 12, the shape projecting outward in the tire radial direction promotes drainage in the rib 10, thereby further improving the driving stability on a wet road surface. The maximum protrusion amount D of the rib 10 and the maximum width W of the chamfered portion 13 with respect to the reference tread profile line L0 satisfy 0.05mm²<W×D<1.50mm²Thereby making it possible to improve the driving stability on a dry road surface and the driving stability on a wet road surface in a balanced manner. Wherein when the product of the maximum projection amount D and the maximum width W is 0.05mm²When the maximum protrusion amount D multiplied by the maximum width W is 1.50mm, the driving stability on a wet road surface tends to deteriorate²In the above, driving stability on a dry road surface tends to deteriorate.

In particular, in the case of the embodiment shown in fig. 2, one end of each of the sipes 12, 14, 16 communicates with the lateral groove 11, and therefore, the sipes 12, 14 and the sipe 16 communicate through the lateral groove 11, having a structure in which the sipe substantially penetrates the rib 10, and therefore, the drainage can be improved, and the driving stability on a wet road surface can be improved. Further, since the sipes 16 are provided on the extension lines of the sipes 12 and 14, the improvement of the drainage performance is concerned, and the driving stability on a wet road surface is further improved.

In fig. 2, the chamfered portion 13 is provided only at one edge 12B of the sipe 12, but the present invention is not limited thereto, and the chamfered portion 13 may be provided at two positions of the edges 12A and 12B. When the chamfered portion 13 is provided only at one of the edges 12A, 12B, the side of the sipe 12 where the chamfered portion 13 is located can improve drainage by the chamfered portion 13, and the water film can be removed by the edge effect of the edges 12B, 12A at the other non-chamfered side. As a result, the driving stability on a dry road surface and the driving stability on a wet road surface can be compatible with each other, as compared with the case where the chamfered portions 13 are provided at two positions of the edges 12A, 12B.

Also, the sipe 12 is inclined with respect to the tire circumferential direction. By inclining the sipe 12 with respect to the tire circumferential direction, the edge effect can be improved, and the driving stability on a wet road surface can be effectively improved. The inclination angle of the sipe 12 on the acute angle side with respect to the tire circumferential direction is set as an inclination angle θ. In this case, the inclination angle θ of the sipe 12 is preferably 40 ° to 80 °, and more preferably 50 ° to 70 °. In this manner, by appropriately setting the inclination angle θ of the sipe 12, the driving stability on a dry road surface can be effectively improved. Among them, when the inclination angle θ is less than 40 °, the partial wear resistance is deteriorated, and when it is more than 80 °, the effect of sufficiently improving the driving stability on a wet road surface cannot be obtained. Further, if a so-called variable pitch is adopted in the sipe of the tread portion 1, and a plurality of sipes 12 are provided at irregular intervals in the tire circumferential direction, and their shapes and sizes are different, the inclination angle θ of the sipe 12 is targeted at the inclination angle of the sipe 12 in an intermediate pitch (for example, in the case of three kinds of variable pitches, pitches other than the maximum pitch and the minimum pitch) within the rib 10.

Further, only one end of the sipe 12 in the tire width direction communicates with the main groove 9, but there is no particular limitation, and both ends of the sipe 12 may communicate with the main groove 9. In the case where only one end of the sipe 12 is terminated in the rib 10, the rigidity of the rib 10 can be improved as compared with the case where both end portions of the sipe 12 are communicated with the main groove 9, and therefore the driving stability on a dry road surface can be effectively improved.

Further, the chamfered portions 13 are opened to the main groove 9 substantially at both ends in the tire width direction, but the present invention is not particularly limited, and only one end of the chamfered portion 13 may be opened to the main groove 9. When both ends of the chamfered portion 13 are open to the main groove 9, the steering stability on a wet road surface can be effectively improved as compared with the case where only one end of the chamfered portion 13 is open to the main groove 9.

In the pneumatic tire described above, it is preferable that the sipes 12 are provided in a plurality of rows of the ribs 10 formed in the ribs 10 of the tread portion 1. As described above, by providing the sipes 12 in the plural rows of the ribs 10, it is possible to achieve both improvement of driving stability on dry road surfaces and improvement of driving stability on wet road surfaces. In particular, the sipe 12 may be provided on the rib 10 located on the tire centerline CL and/or on the ribs 10 located on both sides of the rib 10 in the tread portion 1. When the sipe 12 is provided on the sipe 10 located at the tire width direction central portion, a more significant effect can be obtained by the sipe 12 having the chamfered portion 13, as compared to the case where the sipe 12 is provided on the sipe 10 located at the outermost side (shoulder portion) in the tire width direction.

Also, preferably, at least a portion of the sipe 12 is curved or flexed in a top view. The overall shape of the sipe 12 may also be arcuate. As described above, since the sipe 12 has a curved or bent shape in a plan view and does not have a straight shape, the total number of the edges 12A and 12B in the sipe 12 increases, and the driving stability on a wet road surface can be effectively improved. Further, when at least a part of the sipe 12 is bent or flexed in a plan view, the inclination angle θ of the sipe 12 is an angle with respect to the tire circumferential direction of an imaginary line connecting both end portions of the sipe 12 in the tire width direction.

Portions (a) to (d) of fig. 4 illustrate the sectional shapes of sipes formed in a tread portion of a pneumatic tire according to an embodiment of the present invention. In part (a) of fig. 4, when viewed from a cross section orthogonal to the extending direction of the sipe 12, a chamfered portion 13 is formed in one edge 12B of the sipe 12, and the sectional shape of the chamfered portion 13 has a contour line of a curve protruding inward in the tire radial direction. By forming such a cross-sectional shape, the groove volume can be sufficiently secured against deformation of the tread portion 1 when contacting the ground, and the drainage property can be improved. On the other hand, other cross-sectional shapes of the chamfered portion 13 of the sipe 12 include a rectangular shape as shown in fig. 4 (b), a shape having a curved line protruding outward in the tire radial direction as shown in fig. 4 (c), and a triangular shape as shown in fig. 4 (d).

In the above description, an example in which the length of the sipe 12 in the tire width direction and the length of the chamfered portion 13 in the tire width direction are substantially the same is shown (see fig. 2), but the present invention is not particularly limited thereto, and the lengths in the respective tire width directions may be different. Likewise, the lengths in the tire width direction in the sipe 14 and the chamfered portion 15 may also be made different.

Further, in the embodiment of fig. 2, an example is shown in which the chamfered portion 15 of the sipe 14 ends without reaching the maximum projecting position P in the contour line L1 of the rib 10, but the present invention is not limited to this, and the chamfered portion 15 of the sipe 14 may be provided so as to straddle the maximum projecting position P in the contour line L1 of the rib 10. Further, in the embodiment of fig. 2, an example is shown in which the width of the chamfered portion 13 is constant along the extending direction, but the width of the chamfered portion 13 may not be constant from one end to the other end. If the width of the chamfered portion 13 is not constant from one end to the other end, it is preferable that the width of the chamfered portion 13 is greater than or equal to the width of the tire width direction end of the chamfered portion 13 at the maximum projecting position P of the contour line L1 of the rib 10. The arc forming the contour line L1 may be formed by a single or two arcs.

Examples

A pneumatic tire having a tire size of 245/40R19, a tread portion having a plurality of main grooves extending in the tire circumferential direction, a plurality of rows of ribs partitioned by the main grooves, and a sipe extending in the tire width direction, wherein the sipe has at least one end communicating with the main grooves and has a chamfered portion at least one edge, the chamfered portion has at least one end opening into the main grooves, and the position of the chamfered portion (both sides or one side), the inclination angle theta of the sipe with respect to the tire circumferential direction, the presence or absence of a termination of one end portion of the sipe in the rib, the number of rows of the ribs having the sipe, the overall shape of the sipe (straight line or curved), the number of rows of the ribs having the sipe, the product of the maximum projection amount D and the maximum width W, the arrangement position of the chamfered portion (both sides or one side), and the inclination angle theta of the sipe with respect to the tire circumferential direction as shown in Table 1 are set, The tires of the conventional examples, comparative examples 1 and 2, and examples 1 to 8 were set with or without openings to the main grooves at both ends of the chamfered portion.

In table 1, when the position of the chamfered portion is "not over", it means that the chamfered portion is provided at a distance from the maximum projecting position of the contour line of the rib in the tire width direction, whereas when the position of the chamfered portion is "over", it means that the chamfered portion is present on both sides in the tire width direction with reference to the maximum projecting position of the contour line of the rib. In the tires of the conventional examples, comparative examples 1 and 2, and examples 1 to 8, the contour line of the tread surface defining the sipe-having rib projects further outward in the tire radial direction than the reference tread contour line, and the maximum projecting position of the contour line of the rib is located at the tire width direction central portion of the rib.

For these test tires, sensory evaluations were made by the test driver regarding the driving stability on dry road surfaces and the driving stability on wet road surfaces, and the results thereof are summarized in table 1.

Sensory evaluation was performed on steering stability on a dry road surface and steering stability on a wet road surface under the condition that each test tire was assembled to a wheel having a rim size of 19 × 8.5J and mounted on a vehicle and the air pressure was 260 kPa. The evaluation results are shown as an index with the conventional example set to 100. The larger the index value, the more excellent the driving stability on a dry road surface or the driving stability on a wet road surface.

As is clear from table 1, the tires of examples 1 to 8 improved both driving stability on dry road surfaces and driving stability on wet road surfaces by designing the shape of the chamfered portion formed in the sipe.

On the other hand, the product of the maximum protrusion amount D and the maximum width W of the tire of comparative example 1 is smaller than the range specified in the present invention, and therefore the effect of improving the driving stability on a wet road surface cannot be sufficiently obtained, and the product of the maximum protrusion amount D and the maximum width W of the tire of comparative example 2 is larger than the range specified in the present invention, and therefore the effect of improving the driving stability on a dry road surface cannot be obtained.

Description of the reference numerals

1 tread part

2 side wall part

3 bead portion

9 Main groove

10 stripe pattern

11 horizontal groove

12. 14, 16 sipes

13. 15 chamfer part

L0 reference Tread Profile

L1 outline

P maximum projected position

CL tire centerline