JP5109734B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire having steering stability performance on a dry road surface and on-snow performance on a snow road surface.

  For pneumatic tires called all-season tires applied to dry and snowy road surfaces, both driving stability on dry road surfaces and snow performance on snowy road surfaces (mainly braking performance and turning performance) must be compatible. Is desired. Conventionally, in this type of pneumatic tire, a rib is formed in the vicinity of the tire equatorial plane in the tread portion by a plurality of circumferential main grooves extending in the tire circumferential direction and a plurality of lateral grooves intersecting the circumferential main groove. A block row is formed on the outer side in the tire width direction. Further, a plurality of sipes are formed in the block row. In this pneumatic tire, the edge component in the tire width direction per unit width of the rib formed in the vicinity of the tire equatorial plane is set to 50% or less of the edge component in the tire width direction per unit width of the block row. Yes. In other words, conventional pneumatic tires have the tread rigidity on the ribs near the tire equator to obtain steering stability on dry roads, while the edge component in the tire width direction is also applied to the outer block in the tire width direction on the snow. The on-snow performance on the road surface is obtained (for example, refer to Patent Document 1).

JP-A-8-48114

  By the way, the sipe formed on the blocks in the block row has an edge effect on the blocks, and generates a grip force by scratching the road surface on a frozen road or a snowy road. Thereby, the on-snow performance on the road surface on snow is obtained. That is, the performance on snow improves by providing many sipes. On the other hand, if the sipe is increased, the block is easily deformed, and the block is greatly deformed on the dry road surface, and the steering stability performance is impaired.

  From this point of view, in conventional pneumatic tires, a large amount of edge component in the tire width direction is given to the block on the outer side in the tire width direction, so that the deformation of the block increases, and the deformation of this block stabilizes the handling on the dry road surface. Performance will be impaired.

  This invention is made | formed in view of the above, Comprising: It aims at providing the pneumatic tire which can make compatible the steering stability performance on a dry road surface, and the performance on snow on a snowy road surface.

  In order to achieve the above object, in the pneumatic tire according to the present invention, a tire includes a plurality of circumferential main grooves extending in the tire circumferential direction and a plurality of lug grooves intersecting in the tire circumferential direction on the tread surface. In a pneumatic tire having a plurality of blocks arranged side by side in the circumferential direction and having a narrow groove-shaped sipe provided on the tread surface of the block so as to intersect the tire circumferential direction, the circumferential main groove In the block provided at least on the outermost side in the tire width direction, the lug groove is bent and provided with at least one bending point within a range of the center 50% of the width in the tire width direction of the block. And each angle θ with respect to the tire circumferential direction on both sides in the tire width direction with the bending point as a boundary is set in a range of 30 [degrees] ≦ θ ≦ 80 [degrees], and one end of the sipe Penetrates the circumferential main groove In addition, the other end is provided to be located within a range of the center 50% of the width in the tire width direction of the block.

  According to this pneumatic tire, because the lug groove is bent and the wedge-shaped portion facing the tire circumferential direction is formed on the block, the edge effect due to the sipe in the tire width direction and the tire circumferential direction is achieved. The braking performance (driving performance) and the turning performance, which are the performance on snow on the road surface, can be improved. In addition, the bending point of the lug groove and the other end of the sipe are located within the range of 50% of the center of the block in the tire width direction. For this reason, the rigidity of the center part of a block becomes high, the fall of the block to the tire circumferential direction and a tire width direction is suppressed on a dry road surface, and the steering stability performance on a dry road surface can be improved. In particular, the bending point of the lug groove is provided within a range of 50% of the center of the block, and each angle θ with respect to the tire circumferential direction on both sides in the tire width direction with the bending point as a boundary is 30 [degrees] ≦ θ ≦ 80 [degrees] is set. For this reason, falling in the tire circumferential direction and the tire width direction can be suppressed with a good balance.

  In the pneumatic tire according to the present invention, each angle θ of the lug groove is set in a range of 40 [degrees] ≦ θ ≦ 70 [degrees].

  According to this pneumatic tire, falling in the tire circumferential direction and the tire width direction can be suppressed with a better balance.

  Moreover, in the pneumatic tire according to the present invention, the sipes are provided on both sides of the block in the tire width direction, and are provided in parallel with portions of the lug grooves on both sides in the tire width direction.

  According to this pneumatic tire, the balance of the edge effect due to the sipe in the tire width direction and the tire circumferential direction can be further improved, and the braking performance (driving performance) and the turning performance, which are on-snow performance on snow, can be further improved.

  Moreover, in the pneumatic tire according to the present invention, the tread portion is divided in the tire circumferential direction by the circumferential main groove and a plurality of inclined lug grooves obliquely intersecting the tire circumferential direction at the center portion in the tire width direction of the tread portion. And a slanted sipe in the form of a narrow groove provided in parallel to the slanted lug groove on the tread surface of the central block.

  According to this pneumatic tire, the tilting in the tire circumferential direction prevents the central block from falling in the tire circumferential direction and the tire width direction, so that the steering stability performance on the dry road surface can be improved. Moreover, the braking performance (driving performance) and the turning performance, which are on-snow performance, can be improved by the inclined sipes provided in parallel with the inclined lug grooves.

  Further, in the pneumatic tire according to the present invention, the groove width is narrower than the circumferential main groove on the outer side in the tire width direction of the outer circumferential main groove on the outermost side in the tire width direction, and extends in the tire circumferential direction. And at least one circumferential sub-groove provided on the outer side in the tire width direction of the circumferential sub-groove and having a larger number in the tire circumferential direction than the lug groove. And an outer lug groove provided.

  According to this pneumatic tire, the snow column shear force is increased by providing the outer lug grooves provided more in the tire circumferential direction than the lug grooves on the outer side in the tire width direction of the circumferential sub-grooves. In addition, braking performance (driving performance) and turning performance, which are snow performance on a snowy road surface, are improved.

  In the pneumatic tire according to the present invention, the width divided in the tire circumferential direction by a plurality of inclined lug grooves that obliquely intersect the tire circumferential direction between the circumferential sub-groove and the circumferential main groove. A laterally outer block is provided, and a slanted sipe with a narrow groove provided in parallel with the inclined lug groove is provided on the tread surface of the laterally outer block.

  According to this pneumatic tire, the tilting lug groove in which the widthwise outer side block obliquely intersects the tire circumferential direction can prevent the tire from falling in the tire circumferential direction and the tire width direction. For this reason, the steering stability performance on a dry road surface can be improved. Moreover, the braking performance (driving performance) and the turning performance, which are on-snow performance, can be improved by the inclined sipes provided in parallel with the inclined lug grooves.

  In the pneumatic tire according to the present invention, the groove bottom sipe having a narrow groove shape provided along the extending direction of the lug groove at the groove bottom of at least one of the lug grooves. Is further provided.

  According to this pneumatic tire, when the tread portion is separated from the road surface, the groove bottom of the lug groove is opened by the groove bottom sipe, so that it is easy to discharge snow clogged in the lug groove. For this reason, the snow drainage effect of the lug groove is enhanced, the grip force for scratching the road surface on a frozen road or a snowy road can be maintained, and the performance on snow can be improved.

  In the pneumatic tire according to the present invention, the lug groove provided with the groove bottom sipe has a groove depth such that at least a part of the groove bottom approaches or separates from the groove bottom of the groove bottom sipe. Is provided with a gradual change.

  According to this pneumatic tire, as the tread portion wears, the lug groove becomes shallow together with the circumferential main groove. However, the lug groove gradually becomes shallow because the groove depth is provided with gradual change. Therefore, it is possible to maintain the steering stability performance on the dry road surface and the snow performance on the snow road surface until the pneumatic tire reaches the end of its life, and it is possible to prevent a situation where it appears as if it has reached the end of its life early.

  In the pneumatic tire according to the present invention, the groove width W2 of the groove bottom sipe is set in a range of 0.15 ≦ W2 / W1 ≦ 0.50 with respect to the groove width W1 of the lug groove. It is characterized by.

  According to this pneumatic tire, the snow removal performance in the lug groove can be further improved.

  In the pneumatic tire according to the present invention, the maximum groove depth D2 of the groove bottom sipe is set in a range of 0.20 ≦ D2 / D1 ≦ 0.90 with respect to the maximum groove depth D1 of the lug groove. It is characterized by being.

  According to this pneumatic tire, the snow removal performance in the lug groove can be further improved.

  The pneumatic tire according to the present invention can achieve both the steering stability performance on the dry road surface and the performance on snow on the snow road surface.

  Embodiments of a pneumatic tire according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. The constituent elements of this embodiment include those that can be easily replaced by those skilled in the art or those that are substantially the same. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

  In the following description, the tire radial direction means a direction orthogonal to the rotational axis of the pneumatic tire, the tire radial inner side is the side toward the rotational axis in the tire radial direction, and the tire radial outer side is in the tire radial direction. The side away from the rotation axis. Further, the tire circumferential direction refers to a direction around the rotation axis as a central axis. Further, the tire width direction means a direction parallel to the rotation axis, the inner side in the tire width direction is the side facing the tire equator plane in the tire width direction, and the outer side in the tire width direction is separated from the tire equator plane in the tire width direction. Say the side.

  1 is a plan view showing a part of a tread portion of a pneumatic tire according to an embodiment of the present invention, FIG. 2 is a sectional view showing a groove bottom sipe, and FIG. 3 is another embodiment of the groove bottom sipe. FIG. 4 is a plan view showing the groove bottom sipe of FIG. 3, FIGS. 5 and 6 are sectional views showing still another embodiment of the groove bottom sipe, and FIG. 7 is a sectional view of the present invention. It is a graph which shows the result of the performance test of the pneumatic tire concerning an embodiment.

  The pneumatic tire 1 is formed with a tread portion 2 that is formed of an elastic rubber member and forms an outline of the pneumatic tire 1 on the outermost side in the tire radial direction. In addition, the tread portion 2, that is, a tread surface 21 that comes into contact with the road surface when a vehicle (not shown) on which the pneumatic tire 1 is mounted travels, has a plurality of (in this embodiment) extending in the tire circumferential direction. Four) circumferential main grooves 3 are provided. A plurality of (three in this embodiment) ribs 4 extending in the tire circumferential direction are provided between the circumferential main grooves 3.

  In this pneumatic tire 1, each rib 4 on the outermost side in the tire width direction is formed with blocks 4 a arranged in parallel in the tire circumferential direction by lug grooves 5 formed so as to intersect the tire circumferential direction. Yes. The tread 21 of the block 4a is provided with a narrow groove-shaped sipe 6 formed so as to intersect the tire circumferential direction.

  The lug groove 5 has a bending point 5a and is bent into a V shape. At least one bending point 5a is provided within a range of the center 50% of the width in the tire width direction of the block 4a. In the lug groove 5, each angle θ with respect to the tire circumferential direction on both sides in the tire width direction with the bending point 5 a as a boundary is set in a range of 30 [degrees] ≦ θ ≦ 80 [degrees]. That is, the lug groove 5 is formed in a range where the bending angle is not less than 60 degrees and not more than 160 degrees.

  The sipe 6 is provided with one end 6a penetrating the circumferential main groove 3 and the other end 6b positioned in the middle of the block 4a. Specifically, the other end 6b of the sipe 6 is located within the center 50% of the width in the tire width direction of the block 4a.

  In this pneumatic tire 1, the lug groove 5 is bent so that a wedge-shaped portion facing in the tire circumferential direction is formed in the block 4 a, and therefore the sipe 6 in the tire width direction and the tire circumferential direction is used. It is possible to balance the edge effect and improve the braking performance (driving performance) and the turning performance, which are the performance on snow on the snow road surface. Moreover, the bending point 5a of the lug groove 5 and the other end 6b of the sipe 6 are located within a range of the center 50% of the block 4a in the tire width direction. For this reason, the rigidity of the center part of the block 4a becomes high, the fall of the block 4a in the tire circumferential direction and the tire width direction on the dry road surface is suppressed, and the steering stability performance on the dry road surface can be improved. In particular, the bending point 5a of the lug groove 5 is provided in the range of 50% of the center of the block 4a, and each angle θ with respect to the tire circumferential direction on both sides in the tire width direction with the bending point 5a as a boundary is 30 [ Degrees] ≦ θ ≦ 80 [degrees]. For this reason, falling in the tire circumferential direction and the tire width direction can be suppressed with a good balance.

  The angle θ at which the lug groove 5 bends is preferably set in a range of 40 [degrees] ≦ θ ≦ 70 [degrees]. According to such a configuration, falling in the tire circumferential direction and the tire width direction can be suppressed with a better balance. In addition, the bending point 5a of the lug groove 5 is not limited to one, and a plurality of bending points 5a may be provided, and a plurality of wedge-shaped portions may be provided.

  The sipes 6 are preferably provided on both sides of the block 4a in the tire width direction and in parallel with the bent lug grooves 5. According to such a configuration, the balance of the edge effect by the sipe 6 in the tire width direction and the tire circumferential direction can be further improved, and the braking performance (driving performance) and turning performance, which are on-snow performance on the snow, can be further improved. The sipe 6 may be provided only on one side of the block 4a in the tire width direction. Further, at least one sipe 6 may be provided in the tire circumferential direction.

  As shown in FIG. 1, the block 4 a described above is preferably formed on each rib 4 on both sides on the outermost side in the tire width direction between the circumferential main grooves 3, but on the outermost side in the tire width direction. It may be formed on at least one rib 4.

  Further, in the pneumatic tire 1 according to the present embodiment, the inclined lug groove 7 formed in the rib 4 of the center region 2a, which is the center portion in the tire width direction of the tread portion 2, is formed so as to obliquely intersect the tire circumferential direction. Thus, blocks 4b divided in the tire circumferential direction are formed. The tread 21 of the block 4b is provided with a slanted sipe 8 in the form of a narrow groove formed in parallel with the slanted lug groove 7. It is sufficient that at least one inclined sipe 8 is provided in the tire circumferential direction. The block 4b is provided with a center groove 9 along the tire equator line.

  According to this configuration, the block 4b provided in the center region 2a of the tread portion 2 can be prevented from falling in the tire circumferential direction and the tire width direction by the inclined lug grooves 7 that obliquely intersect the tire circumferential direction. . For this reason, the steering stability performance on a dry road surface can be improved. In addition, the inclined sipe 8 provided in parallel with the inclined lug groove 7 can improve braking performance (driving performance) and turning performance, which are on-snow performance on snow.

  In addition, the pneumatic tire 1 according to the present embodiment has a shoulder region 2b of the tread portion 2 that is further on the outer side in the tire width direction of the outer circumferential main groove 3 on the outermost side in the tire width direction than the circumferential main groove 3. The groove width is narrow and the circumferential sub-groove 10 is provided extending in the tire circumferential direction. Further, on the outer side in the tire width direction of the circumferential sub-groove 10, there are provided a larger number in the tire circumferential direction than the lug groove 5 through the circumferential sub-groove 10 and intersecting the tire circumferential direction. The outer lug groove 11 is provided.

  The outer lug groove 11 has one end penetrating the circumferential sub-groove 10 and the other end penetrating the tire width direction side end of the tread portion 2. The numbers in the circumferential direction are the same. A closed outer lug groove 11b is formed between the open outer lug grooves 11a, one end of which penetrates the circumferential sub-groove 10 and the other end of which does not penetrate the tire width direction side end of the tread portion 2 and is short. It has been.

  According to such a configuration, the outer lug grooves 11 provided more in the tire circumferential direction than the lug grooves 5 are provided on the outer side in the tire width direction of the circumferential sub-groove 10 in the shoulder region 2b of the tread portion 2. As a result, the snow column shearing force (shear resistance of the snow column created in the outer lug groove 11 by stepping on the snow) increases, and the braking performance (driving performance) and the turning performance, which are on the snow road surface, are improved. it can.

  In addition, as shown in FIG. 1, it is preferable that the circumferential sub-groove 10 and the outer lug groove 11 are provided on both sides in the tire width direction in order to improve performance on snow, but only on one side in the tire width direction. It may be provided. Further, as shown in FIG. 1, the circumferential sub-groove 10 is not limited to a configuration in which one circumferential side sub-groove 10 is provided on one side in the tire width direction, and a plurality of circumferential secondary grooves 10 may be provided.

  In the pneumatic tire 1 according to the present embodiment, the widthwise outer rib 12 is provided between the circumferential main groove 3 and the circumferential subgroove 10. And the width direction outer side rib 12 is formed with the width direction outer side block 12a divided in the tire circumferential direction by the inclined lug groove 13 formed diagonally intersecting the tire circumferential direction. The tread surface 21 of the width direction outer block 12a is provided with a slanted groove-shaped sipe 14 formed in parallel with the slanted lug groove 13. It is sufficient that at least one inclined sipe 14 is provided in the tire circumferential direction.

  According to this structure, the width direction outer side block 12a can suppress the fall in a tire circumferential direction and a tire width direction by the inclined lug groove 13 which cross | intersects diagonally with respect to a tire circumferential direction. For this reason, the steering stability performance on a dry road surface can be improved. In addition, the inclined sipe 14 provided in parallel with the inclined lug groove 13 can improve braking performance (driving performance) and turning performance, which are on-snow performance on snow.

  By the way, in the pneumatic tire 1 according to the present embodiment, the circumferential main groove 3 is formed with the widest groove width on the tread surface 21 of the tread portion 2, and a wear indicator (not shown) indicating a wear limit on the groove bottom. ) Is provided. The lug groove 5 is formed to have a narrower groove width than the circumferential main groove 3, and the inclined lug groove 7, the circumferential auxiliary groove 10, the outer lug groove 11, and the inclined lug groove 13 are equivalent to the lug groove 5. The groove width is as follows. Further, the sipe 6, the inclined sipe 8, and the inclined sipe 14 have a groove width narrower than that of the lug groove 5, and are formed in the range of 0.4 [mm] to 2.0 [mm] in the present embodiment. Further, the lug groove 5, the sipe 6, the inclined lug groove 7, the inclined sipe 8, the circumferential sub-groove 10, the outer lug groove 11, the inclined lug groove 13 and the inclined sipe 14 are not provided with wear indicators.

  Further, as shown in FIG. 2, the pneumatic tire 1 according to the present embodiment is applied to all the lug grooves described above (the lug grooves 5, the inclined lug grooves 7, the outer lug grooves 11, and the inclined lug grooves 13). A groove bottom sipe 15 is provided. The groove bottom sipe 15 is formed in a narrow groove shape along the extending direction of the lug grooves 5, 7, 11, 13. In addition, in FIG. 2, the form which provided the groove bottom sipe 15 in the inclined lug groove 7 provided in the center area | region 2a of the tread part 2 is shown.

  According to such a configuration, when the tread surface 21 of the tread portion 2 is separated from the road surface, the groove bottom B1 of the lug groove 7 (5, 11, 13) is opened by the groove bottom sipe 15, so the lug groove 7 (5, 11, 13) It becomes easy to discharge snow clogged up. For this reason, the snow removal effect of the lug grooves 7 (5, 11, 13) is enhanced, the grip force for scratching the road surface on the frozen road and the snowy road can be maintained, and the performance on snow can be improved.

  The groove bottom sipe 15 described above is preferably provided in all the lug grooves 5, 7, 11 and 13 described above in order to improve the performance on snow. However, in consideration of steering stability performance on a dry road surface. The lug grooves 5, 7, 11, 13 may be selected and provided.

  Further, in the pneumatic tire 1 according to the present embodiment, as shown in FIG. 3, the lug grooves 7 (5, 11, 13) provided with the groove bottom sipe 15 correspond to the groove bottom of the groove bottom sipe 15. The groove depth is gradually changed in such a manner that at least a part of the groove bottom approaches or separates. Specifically, the lug grooves 7 (5, 11, 13) have a minimum groove depth (the shallowest groove depth) at the center in the tire width direction of the rib 4 (block 4b), and both sides from the center in the tire width direction ( For example, the groove bottom B1 is inclined so that the groove depth smoothly changes deeply toward the circumferential main groove 3). On the other hand, the groove bottom sipe 15 has a groove bottom B2 formed at a certain depth. For this reason, the depth position of the groove bottom B1 of the lug groove 7 (5, 11, 13) changes with the inclination of the groove bottom B1, and is minimum at the position of the maximum groove depth D2 of the groove bottom sipe 15. The groove depth becomes the maximum depth D1 at the position of the minimum groove depth of the groove bottom sipe 15. The maximum groove depth D1 of the lug groove 7 (5, 11, 13) and the maximum groove depth D2 of the groove bottom sipe 15 are formed shallower than the groove depth D0 of the circumferential main groove 3, and It is formed in the vicinity of a wear indicator provided at the groove bottom of the circumferential main groove 3.

  When the pneumatic tire 1 is mounted on a vehicle and travels, the tread portion 2 is worn and each groove gradually becomes shallow. When the tread surface 21 of the tread portion 2 is worn to the same depth as the wear indicator provided at the groove bottom of the circumferential main groove 3, the pneumatic tire 1 is replaced at the end of its life. Here, for example, when the maximum groove depth D1 of the lug groove 7 (5, 11, 13) is shallower than the groove depth D0 of the circumferential main groove 3 and is formed at a constant depth, the tread The lug grooves 7 (5, 11, 13) are lost before the tread 21 of the part 2 is worn to the same depth as the wear indicator. For this reason, the steering stability performance on the dry road surface and the snow performance on the snow road surface are deteriorated. In addition, since the lug grooves 7 (5, 11, 13) are eliminated, it may appear as if it has reached the end of its life even though it can still be used.

  In this regard, according to such a configuration, the lug groove 7 (5, 11, 13) becomes shallow together with the circumferential main groove 3 with wear of the tread portion 2, but the lug groove 7 (5, 11, 13) Since the groove depth is provided with gradual change, it becomes gradually shallower. FIG. 4 shows a state in which the circumferential main groove 3 is shallow from the new article to about half in the configuration shown in FIG. As shown in FIG. 4, the lug grooves 7 (5, 11, 13) gradually change from the center in the tire width direction toward both sides in the rib 4 (block 4b) because the groove depth gradually changes. Decrease. For this reason, it is possible to maintain the steering stability performance on the dry road surface and the snow performance on the snow road surface until the pneumatic tire 1 reaches the end of its life, and it is possible to prevent a situation where it appears as if the end of the life has been reached early.

  Further, as shown in FIG. 5, the lug grooves 7 (5, 11, 13) have a minimum groove depth (the shallowest groove depth) on one side in the tire width direction of the rib 4 (block 4b). The groove bottom B1 is provided so as to be inclined so that the groove depth smoothly changes from one direction to the other. On the other hand, the groove bottom sipe 15 has a groove bottom B2 formed at a certain depth. In addition, the lug grooves 7 (5, 11, 13) adjacent to the lug grooves 7 (5, 11, 13) in the tire circumferential direction have a minimum groove depth (most at the other side in the tire width direction of the rib 4 (block 4b)). The groove bottom B1 is inclined and provided so that the groove depth smoothly changes from the other side in the tire width direction toward the one side. Thus, the lug grooves 7 (5, 11, 13) are configured such that the inclination of the groove bottom B1 is staggered in the tire circumferential direction.

  According to this configuration, the lug groove 7 (5, 11, 13) becomes shallow together with the circumferential main groove 3 as the tread portion 2 is worn. In block 4b), it gradually decreases from one side in the tire width direction (or the other in the tire width direction) to the other side (or one side). For this reason, it is possible to maintain the steering stability performance on the dry road surface and the snow performance on the snow road surface until the pneumatic tire 1 reaches the end of its life, and it is possible to prevent a situation where it appears as if the end of the life has been reached early.

  Further, as shown in FIG. 6, the lug grooves 7 (5, 11, 13) have the minimum groove depth (the shallowest groove depth) on both sides in the tire width direction of the rib 4 (block 4b). The groove bottom B1 is provided so as to be inclined so that the groove depth smoothly changes from both sides in the direction toward the center. On the other hand, the groove bottom sipe 15 has a groove bottom B2 formed at a certain depth.

  According to this configuration, the lug groove 7 (5, 11, 13) becomes shallow together with the circumferential main groove 3 as the tread portion 2 is worn. In block 4b), it gradually decreases from both sides in the tire width direction toward the center. For this reason, it is possible to maintain the steering stability performance on the dry road surface and the snow performance on the snow road surface until the pneumatic tire 1 reaches the end of its life, and it is possible to prevent a situation where it appears as if the end of the life has been reached early.

  In the pneumatic tire 1 shown in FIGS. 2, 3, 5, and 6, the groove width W2 of the groove bottom sipe 15 is 0 with respect to the groove width W1 of the lug groove 7 (5, 11, 13). .15 ≦ W2 / W1 ≦ 0.50 is set. According to such a configuration, the snow removal performance of the lug grooves 7 (5, 11, 13) can be further improved. If the groove width W2 of the groove bottom sipe 15 is set in the range of 0.25 ≦ W2 / W1 ≦ 0.35 with respect to the groove width W1 of the lug groove 7 (5, 11, 13), the lug groove 7 The effect of improving the snow removal of (5, 11, 13) can be obtained better. The groove width W2 of the groove bottom sipe 15 is preferably set in a range of 0.4 [mm] ≦ groove width W2 ≦ 2.0 [mm].

  Further, in the pneumatic tire 1 shown in FIGS. 3, 5 and 6, the maximum groove depth D2 of the groove bottom sipe 15 with respect to the maximum groove depth D1 of the lug groove 7 (5, 11, 13) is The range is set to 0.20 ≦ D2 / D1 ≦ 0.90. According to this configuration, the snow removal performance of the lug grooves 7 (5, 11, 13) by the groove bottom sipe 15 can be further improved. If the maximum groove depth D2 of the groove bottom sipe 15 is set in a range of 0.35 ≦ D2 / D1 ≦ 0.70 with respect to the maximum groove depth D1 of the lug groove 7 (5, 11, 13). Further, the effect of improving the snow removal of the lug grooves 7 (5, 11, 13) can be obtained more favorably.

  In the pneumatic tire 1 according to the present embodiment, the pattern of the tread portion 2 described above is arranged point-symmetrically in a plan view as shown in FIG. Therefore, when this pneumatic tire 1 is mounted on a vehicle, any direction in the tire circumferential direction can be set as the traveling direction.

  In the present embodiment, for a plurality of types of pneumatic tires with different conditions, on-snow performance on the road (braking performance and turning performance), steering stability performance on the dry road surface, snow discharge performance on the snow road surface (when new, A performance test for 40% wear on the tread and 70% wear on the tread) was performed (see FIG. 7).

  In performance tests on snow performance (braking performance and turning performance) on snowy road surfaces and steering stability performance on dry road surfaces, pneumatic tires having a tire size of 215 / 60R16 are used. Then, this pneumatic tire was mounted on a regular rim stipulated by JATMA, provided with the highest air pressure stipulated by JATMA, and mounted on a sedan type vehicle having a displacement of 2000 cc produced in Japan. In the evaluation method, on the snow performance (braking performance), the braking distance from 40 [km / h] is measured on the road surface on the snow. Then, based on this measurement result, index evaluation using the conventional example as a reference (100) is performed. This evaluation is preferable as the numerical value increases. In snow performance (turning performance), the lap time during turning of a 30 [m] circle on the snow road surface is measured. Then, based on this measurement result, index evaluation using the conventional example as a reference (100) is performed. This evaluation is preferable as the numerical value increases. Further, in the handling stability performance, the feeling on the handling course which is a dry road surface is evaluated, and the index evaluation based on the conventional example as the standard (3) is performed. This evaluation is preferable as the numerical value increases.

  In the performance test for snow removal performance, a pneumatic tire having a tire size of 215 / 50R17 91W is used. This pneumatic tire was assembled to a rim having a rim size of 17 × 7 JJ, applied with the highest air pressure specified by JATMA, and mounted on a sedan type vehicle with a displacement of 2000 cc produced in Japan. In the evaluation method, feeling on a handling course on a snowy road surface is evaluated, and index evaluation is performed at 40% wear and 70% wear with a new article as a reference (100). This evaluation is preferable as the numerical value increases.

  In the pneumatic tire of the conventional example, the lug groove is not bent (no bending point), and the position of the sipe end is continuous without being defined (sipe continuous). The pneumatic tire of the comparative example is outside the center 50% range in the tire width direction, although the lug groove is bent to have a bending point and the sipe end is located in the block. Further, in the pneumatic tire of the comparative example, each angle θ of the lug groove is 85 degrees. In the pneumatic tires of Examples 1 to 5, the lug groove bending point and the position of the sipe end, the angle θ of the lug groove, the number of the outer lug grooves, the bottom groove sipes, and the lug groove slopes provided with the bottom groove sipes This is a tire in which changes, W1 / W2, and D1 / D2 are optimized.

  As shown in the test results of FIG. 7, in the pneumatic tires of Examples 1 to 5, the performance on snow (braking performance and turning performance) on the snow road surface, the steering stability performance on the dry road surface, the road surface on snow during tread friction, respectively. It can be seen that the snow drainage performance is improved.

  As described above, the pneumatic tire according to the present invention is suitable for achieving both the steering stability performance on a dry road surface and the performance on snow on a snow road surface.

It is a top view which shows a part of tread part of the pneumatic tire concerning embodiment of this invention. It is sectional drawing which shows a groove bottom sipe. It is sectional drawing which shows other embodiment of a groove bottom sipe. It is a top view which shows the groove bottom sipe of FIG. It is sectional drawing which shows other embodiment of a groove bottom sipe. It is sectional drawing which shows other embodiment of a groove bottom sipe. It is a graph which shows the result of the performance test of the pneumatic tire concerning embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 21 Tread surface 2a Center area 2b Shoulder area 3 Circumferential main groove 4 Rib 4a, 4b Block 5 Lug groove 5a Bending point 6 Sipe 6a One end 6b Other end 7 Inclined lug groove 8 Inclined sipe 9 Center groove 10 Circumferential sub-groove 11 Outer lug groove 11a Open outer lug groove 11b Closed outer lug groove 12 Width direction outer rib 12a Width direction outer block 13 Inclined lug groove 14 Inclined sipe 15 Groove bottom sipe B1 Lag groove groove bottom B2 Groove bottom sipe Groove bottom W1 Groove width of lug groove W2 Groove width of groove sipe θ angle

Claims (10)

The tread portion has a plurality of blocks arranged in parallel in the tire circumferential direction by a plurality of circumferential main grooves extending in the tire circumferential direction and a plurality of lug grooves intersecting in the tire circumferential direction on the tread surface, and In a pneumatic tire having a narrow groove-shaped sipe provided across the tire circumferential direction on the tread surface of the block,
In the block provided at least on the outermost side in the tire width direction between the circumferential main grooves, the lug groove has at least one bending point in the range of the center 50% of the width in the tire width direction of the block. And each angle θ with respect to the tire circumferential direction on both sides of the tire width direction with the bending point as a boundary is set in a range of 30 [degrees] ≦ θ ≦ 80 [degrees], A sipe is a pneumatic tire characterized in that one end penetrates the circumferential main groove and the other end is provided within a range of the center 50% of the width in the tire width direction of the block.   2. The pneumatic tire according to claim 1, wherein each angle θ of the lug groove is set in a range of 40 [degrees] ≦ θ ≦ 70 [degrees].   3. The pneumatic tire according to claim 1, wherein the sipes are provided on both sides of the block in the tire width direction and are provided in parallel with portions of the lug grooves on both sides in the tire width direction. A central block divided in the tire circumferential direction by the circumferential main groove and a plurality of inclined lug grooves obliquely intersecting the tire circumferential direction is provided in the tire width direction central portion of the tread portion,
The pneumatic tire according to any one of claims 1 to 3, wherein the tread of the center block has a narrow groove-shaped inclined sipe provided in parallel with the inclined lug groove.   At least one circumferential sub groove provided on the outer side in the tire width direction on the outermost side in the tire width direction, on the outer side in the tire width direction, is narrower than the circumferential main groove and extends in the tire circumferential direction. A groove and an outer lug groove that penetrates the circumferential subgroove on the outer side in the tire width direction of the circumferential subgroove and has a larger number in the tire circumferential direction than the lug groove. The pneumatic tire according to any one of claims 1 to 4, wherein: Between the circumferential sub-groove and the circumferential main groove is provided a width direction outer block divided in the tire circumferential direction by a plurality of inclined lug grooves obliquely intersecting the tire circumferential direction,
The pneumatic tire according to claim 5, further comprising a narrow groove-shaped inclined sipe provided in parallel with the inclined lug groove on the tread surface of the widthwise outer block.   The groove bottom sipe provided in the groove bottom of at least one of the lug grooves among all the lug grooves is provided along the extending direction of the lug groove. The pneumatic tire according to any one of 1 to 6.   The lug groove provided with the groove bottom sipe is provided with a groove depth gradually changed in such a manner that at least a part of the groove bottom approaches or separates from the groove bottom of the groove bottom sipe. The pneumatic tire according to claim 7, wherein   9. The groove width W2 of the groove bottom sipe is set in a range of 0.15 ≦ W2 / W1 ≦ 0.50 with respect to the groove width W1 of the lug groove. Pneumatic tires.   8. The maximum groove depth D2 of the groove bottom sipe is set in a range of 0.20 ≦ D2 / D1 ≦ 0.90 with respect to the maximum groove depth D1 of the lug groove. The pneumatic tire as described in any one of -9.

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