JP6919666B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire.

Patent Document 1 discloses a pneumatic tire that achieves both drainage performance and uneven wear resistance. In Patent Document 1, a recess is provided in the groove wall of the main groove, and a sipe that communicates with the recess and a shallow groove that avoids the recess and communicates with the recess are provided.

JP-A-2017-43208

The pneumatic tire of Patent Document 1 described above relates to snow performance, which is a running performance on a snowy road, particularly braking performance on a snowy road surface, that is, snow braking performance, and improvement of steering stability performance, that is, snow handling performance on a snowy road surface. Not considered and there is room for improvement. It is also necessary to consider the chipping resistance.

The present invention has been made in view of the above, and an object of the present invention is to provide a pneumatic tire having improved chipping resistance, snow braking performance, snow handling performance, and drainage performance in a well-balanced manner. ..

In order to solve the above-mentioned problems and achieve the object, the pneumatic tire according to an embodiment of the present invention is a pneumatic tire having a tread pattern, and the tread pattern extends in the tire circumferential direction. Provided on the land portion, which is continuous in the tire circumferential direction and is defined by two or more circumferential main grooves and two of the three or more circumferential main grooves. A plurality of lug grooves provided and a sipe provided in the land portion and provided between the adjacent lug grooves are included, and the outer edge of the land portion in the tire width direction is in the tire width direction. It has a zigzag shape with irregularities whose position changes periodically, the inner edge of the land portion in the tire width direction is a straight shape, and the sipe has an edge from the outer edge in the tire width direction to the inner edge in the tire width direction. It is a penetrating sipe that extends continuously up to, and the sipe has a Z-shape having two bent portions, and passes through the midpoint position of the land portion in the tire width direction of the two bent portions. distance in the tire width direction of the bent portion closer to the center line and said center line state, and are ratio 0 to 0.40 to the width of the tire width direction of the land portion, the sipes, the land portion open to the tread.

Before SL sipe has an inner straight portion connected to the tire width direction inner edge, with respect to the tire width direction of the width of the land portion, the ratio of the length of the tire width direction of the inner straight section 0.10 It is preferably 0.40 or less.

The ratio of the distance in the tire circumferential direction between the zigzag convex portions to the length of the zigzag edge between the adjacent lug grooves in the tire circumferential direction is preferably 0.15 or more and 0.55 or less. ..

The ratio of the width of the land portion in the tire width direction to twice the amplitude of the zigzag shape in the tire width direction is preferably 0.03 or more and 0.15 or less.

The sipe has an outer straight section that connects to the outer edge in the tire width direction, and is inside the sipe in the tire width direction with respect to the length of the zigzag edge between adjacent lug grooves in the tire circumferential direction. The ratio of the distance in the tire circumferential direction from the connection point with the circumferential main groove to the inner end point in the tire width direction of the outer straight portion is preferably 0.15 or more and 0.45 or less.

The distance in the tire circumferential direction from the connection point of the sipe with the circumferential main groove on the inner side of the tire width direction to the end point of the outer straight portion on the inner side in the tire width direction with respect to the width of the land portion in the tire width direction. The ratio is preferably 0.15 or more and 0.65 or less.

The sipe has an inner straight portion connected to the inner edge in the tire width direction, and the ratio of the width of the zigzag shape to the length of the inner straight portion in the tire width direction is twice the width of the zigzag shape in the tire width direction. Is preferably 0.15 or more and 0.45 or less.

A plurality of the sipes may be provided between the adjacent lug grooves. It is preferable that the straight portions of the plurality of sipes are parallel to each other.

It is preferable that two or more of the sipes are provided between the adjacent lug grooves, and three or more of the zigzag-shaped protrusions are provided between the adjacent lug grooves.

The ratio of the minimum value of the distance between the convex portions of the zigzag shape to the maximum value of the distance between the convex portions of the zigzag shape is preferably 0.50 or more.

To the connection portion of the adjacent lug groove to the inner circumferential main groove in the tire width direction and the plurality of the sipes provided between the adjacent lug grooves to the inner circumferential main groove in the tire width direction. When the distance in the tire circumferential direction between the connecting portions including the connecting portion and the connecting portions adjacent to each other in the tire circumferential direction is Ls1, Ls2, ..., Lsn (n is a natural number of 3 or more), Ls1 <Lsn is preferable. ..

To the connection portion of the adjacent lug groove to the inner circumferential main groove in the tire width direction and the plurality of the sipes provided between the adjacent lug grooves to the inner circumferential main groove in the tire width direction. The distance in the tire circumferential direction between the connecting portions including the connecting portion and the connecting portions adjacent to each other in the tire circumferential direction is Ls1, Ls2, ..., Lsn (n is a natural number of 3 or more), and the tire width direction of the adjacent lug grooves. Includes a connection portion to the outer circumferential main groove and a connection portion of a plurality of the sipes provided between the adjacent lug grooves to the outer circumferential main groove in the tire width direction , and includes the tire circumferential direction. When the distance in the tire circumferential direction between the convex portions of the connecting portions adjacent to each other is Lz1, Lz2, ..., Lzn (n is a natural number of 3 or more), Ls1 <Lz1 and Lsn> Lzn. Is preferable.

The ratio of the groove depth of the sipe to the groove depth of the circumferential main groove is preferably 0.50 or more and 0.85 or less.

The sipe has a bottom raising portion provided on the inner groove bottom in the tire width direction, and the ratio of the groove depth of the sipe in the bottom raising portion to the groove depth of the sipe is 0.40 or more and 0.70 or less. Is preferable.

It is preferable that the sipe is connected to the maximum amplitude position in the tire width direction of the zigzag edge.

According to the present invention, the effects of improving chipping resistance, snow braking performance, snow handling performance, and drainage performance in a well-balanced manner can be obtained.

FIG. 1 is a cross-sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a development view showing an example of a tread pattern of the pneumatic tire shown in FIG. FIG. 3 is a plan view showing an example of sipe. FIG. 4 is an enlarged view of a part of the middle land portion of the tread pattern shown in FIG. FIG. 5 is an enlarged view of a part of the middle land portion of the tread pattern shown in FIG. FIG. 6A is an enlarged view of a part of the middle land portion of the tread pattern shown in FIG. FIG. 6B is an enlarged view of a part of FIG. 6A. FIG. 7A is a diagram showing another example of the middle land area. FIG. 7B is an enlarged view of a part of FIG. 7A. FIG. 8A is a diagram showing another example of the middle land area. FIG. 8B is an enlarged view of a part of FIG. 8A. FIG. 9 is a cross-sectional view taken along the extending direction of the sipe of FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description of each embodiment, the same or equivalent components as those of the other embodiments are designated by the same reference numerals, and the description thereof will be simplified or omitted. The present invention is not limited to each embodiment. In addition, the components of each embodiment include those that can be easily replaced by those skilled in the art, or those that are substantially the same. The plurality of modifications described in this embodiment can be arbitrarily combined within a range self-evident by those skilled in the art. In addition, the configuration may be omitted, replaced or changed without departing from the gist of the invention.

[Pneumatic tires]
FIG. 1 is a cross-sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment of the present invention. FIG. 1 shows a cross-sectional view of a one-sided region in the tire radial direction. Further, FIG. 1 shows a radial tire for a passenger car as an example of a pneumatic tire.

The cross section in the tire meridian direction is a cross section when the tire is cut on a plane including the tire rotation axis (not shown). Further, the reference numeral CL is a tire equatorial plane, and refers to a plane that passes through the center point of the tire in the tire rotation axis direction and is perpendicular to the tire rotation axis. The tire radial direction means a direction orthogonal to the rotation axis (not shown) of the pneumatic tire 10, the inner side in the tire radial direction is the side toward the rotation axis in the tire radial direction, and the outer side in the tire radial direction is the tire radial direction. Refers to the side away from the axis of rotation. Further, the tire circumferential direction refers to a circumferential direction centered on the rotation axis. The tire width direction means a direction parallel to the rotation axis. The inside in the tire width direction is the side facing the tire equatorial plane CL in the tire width direction, and the outside in the tire width direction is the side away from the tire equatorial plane CL in the tire width direction.

The tire equatorial plane CL is a plane that is orthogonal to the rotation axis of the pneumatic tire 10 and passes through the center of the tire width of the pneumatic tire 10. The tire width is the width in the tire width direction between the portions located outside in the tire width direction, that is, the distance between the portions farthest from the tire equatorial plane CL in the tire width direction. The tire equatorial line is a line on the tire equatorial plane CL along the tire circumferential direction of the pneumatic tire 10. In the present embodiment, the tire equatorial line is designated by the same code "CL" as the tire equatorial plane.

As shown in FIG. 1, the pneumatic tire 10 of the present embodiment includes a tread portion 1 extending in the tire circumferential direction to form an annular shape, and a pair of sidewall portions 2 arranged on both sides of the tread portion 1. 2 and a pair of bead portions 3 and 3 arranged inside the sidewall portions 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 degrees to 40 degrees. As the reinforcing cord of the belt layer 7, a steel cord is preferably used. On the outer peripheral side of the belt layer 7, at least one layer of the belt cover layer 8 formed by arranging the reinforcing cords at an angle of, for example, 5 degrees or less with respect to the tire circumferential direction is arranged 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 tire internal structure described above is a typical example of a pneumatic tire, and is not limited thereto.

[Tread section]
FIG. 2 is a developed view showing an example of a tread pattern of the pneumatic tire 10 shown in FIG. In FIGS. 1 and 2, reference numeral T indicates a tire ground contact end.

As shown in FIG. 2, the pneumatic tire 10 of this example includes four circumferential main grooves 11A, 11B, 12A, and 12B in the tread portion 1. The circumferential main grooves 12A and 12B extend in the tire circumferential direction at positions outside the tire width direction of the tire equatorial plane CL. The circumferential main groove 11A extends in the tire circumferential direction at a position closer to the tire equatorial plane CL than the circumferential main groove 12A. The circumferential main groove 11B extends in the tire circumferential direction at a position closer to the tire equatorial plane CL than the circumferential main groove 12B.

The circumferential main grooves 11A, 11B, 12A and 12B are circumferential grooves having a wear indicator indicating the end of wear, and generally have a groove width of 5.0 [mm] or more and a groove depth of 7.5 [mm] or more. Has a sword. The groove widths and groove depths of the circumferential main grooves 11A, 11B, 12A and 12B are not limited to the above ranges.

Further, the lug groove described later means a lateral groove having a groove width of 2.0 [mm] or more and a groove depth of 3.0 [mm] or more. Further, the sipe described later is a notch formed in the land portion, and generally has a groove width of less than 1.5 [mm].

In FIG. 2, the center land portion Rc is partitioned by the two circumferential main grooves 11A and 11B. Further, the middle land portion Rm is partitioned by the two circumferential main grooves 11A and 12A, and the other middle land portion Rm is partitioned by the two circumferential main grooves 11B and 12B. The outer side of the circumferential main groove 12A in the tire width direction is the shoulder land portion Rs. The outer side of the circumferential main groove 12B in the tire width direction is another shoulder land portion Rs. When there are three main grooves in the circumferential direction, the center land portion Rc is not provided, and the middle land portion Rm on both sides of the equator line CL and the shoulder land portion Rs on the outer side in the tire width direction of the middle land portion Rm are formed. Become a tread part.

The center land portion Rc (hereinafter, may be simply referred to as the land portion Rc) is located on the tire equatorial line CL. The land Rc has a plurality of sipes 15. The sipe 15 extends in the tire circumferential direction and the tire width direction. One end of the sipe 15 is connected to the circumferential main groove 11A, and the other end of the sipe 15 is connected to the circumferential main groove 11B. The sipe 15 is a penetrating sipe that penetrates the land Rc. In this example, the edges on both sides of the land portion Rc have a straight shape.

The middle land portion Rm (hereinafter, may be simply referred to as a land portion Rm) has a plurality of lug grooves 13. The lug groove 13 extends in the tire width direction and the tire circumferential direction. One end of the lug groove 13 opens into the circumferential main groove 11A or 11B. The other end of the lug groove 13 opens into the circumferential main groove 12A or 12B. The land portion Rm has a plurality of sipes 16 between the lug grooves 13 adjacent to each other in the tire circumferential direction. The sipe 16 extends in the tire circumferential direction and the tire width direction. One end of the sipe 16 is connected to the circumferential main groove 11A or 11B, and the other end of the sipe 16 is connected to the circumferential main groove 12A or 12B. The sipe 16 is a penetrating sipe that penetrates the land Rm.

In this example, the outer edge of the land portion Rm in the tire width direction, that is, the edge on the circumferential main groove 12A or 12B side has a zigzag shape. The zigzag shape is a shape having irregularities in which the position in the tire width direction changes periodically. The inner edge of the land portion Rm in the tire width direction, that is, the edge on the circumferential direction main groove 11A or 11B side has a straight shape having no unevenness.

The shoulder land portion Rs (hereinafter, may be simply referred to as the land portion Rs) has a plurality of lug grooves 14A and 14B. The lug grooves 14A and 14B extend in the tire width direction from the inside in the tire width direction to the outside in the tire width direction. The lug grooves 14A and 14B extend from the circumferential main groove 12A or 12B to a position outside the tire ground contact end T. The land portion Rs has a plurality of sipes 17 between the lug groove 14A and the lug groove 14B. The sipe 17 extends in the tire width direction. One end of the sipe 17 is connected to the circumferential main groove 12A or 12B, and the other end of the sipe 17 is connected to the decorative groove 18 outside the tire ground contact end T.

[Z-shaped]
FIG. 3 is a plan view showing an example of the sipe 16. In FIG. 3, one end of the sipe 16 is connected to the circumferential main groove 11A, and the other end is connected to the circumferential main groove 12A. Referring to FIG. 3, the sipe 16 of this example is composed of straight portions ST1, ST2 and ST3, and bent portions C1 and C2. The straight portion ST1 is arranged on the circumferential main groove 11A side, that is, on the inner side in the tire width direction. The straight portion ST1 is connected to the inner edge of the land portion Rm in the tire width direction. The straight portion ST3 is arranged on the main groove 12A side in the circumferential direction, that is, on the outside in the tire width direction. The straight portion ST3 is connected to the outer edge of the land portion Rm in the tire width direction. The length of the straight portion ST1 in the extending direction is shorter than the length of the straight portion ST3 in the extending direction.

One end of the straight portion ST1 is connected to the circumferential main groove 11A, and the other end of the straight portion ST1 is connected to one end of the bent portion C1. The other end of the bent portion C1 is connected to the straight portion ST2. One end of the straight portion ST3 is connected to the circumferential main groove 12A, and the other end of the straight portion ST3 is connected to one end of the bent portion C2. The other end of the bent portion C2 is connected to the straight portion ST2. As described above, by providing the bent portion C1 between the straight portion ST1 and the straight portion ST2 and the bent portion C2 between the straight portion ST2 and the straight portion ST3, the sipe 16 has a substantially Z shape. There is. The Z-shape is a shape including at least two bent portions and the straight portions are connected by the bent portions. The Z-shape may include an S-shape composed of an arc. In the following description, of the straight portion ST1 and the straight portion ST3, the straight portion ST1 close to the equatorial plane CL may be referred to as an inner straight portion, and the straight portion ST3 far from the equatorial plane CL may be referred to as an outer straight portion.

FIG. 4 is an enlarged view of a part of the land portion Rm of the tread pattern shown in FIG. In FIG. 4, among a plurality of lug grooves 13 penetrating the land portion Rm, in the block formed by the adjacent lug grooves 13, the length of the zigzag edge between the adjacent lug grooves 13 in the tire circumferential direction is determined. Let it be L1. Let L2 be the distance between the zigzag-shaped protrusions in the tire circumferential direction. The ratio L2 / L1 of the distance L2 to the length L1 is preferably 0.15 or more and 0.55 or less. If this ratio L2 / L1 is larger than 0.55, the edge effect cannot be sufficiently obtained and the snow performance is not improved, which is not preferable. If this ratio L2 / L1 is smaller than 0.15, the zigzag-shaped unevenness becomes too fine and easily chipped, which is not preferable. The length L1 of the zigzag edge in the tire circumferential direction is measured with reference to the corner of the intersection of the lug groove 13 and the circumferential main groove 12A.

Further, in FIG. 4, the maximum width of the land portion Rm in the tire width direction is W1. Let W2 be the length in the tire width direction from the connection point of the sipe 16 with the circumferential main groove 11A on the inner side in the tire width direction to the end point K1 on the outer side in the tire width direction of the inner straight portion ST1. Of the plurality of lug grooves 13 penetrating the land portion Rm, in the block formed by the adjacent lug grooves 13, the width twice the amplitude in the tire width direction of the zigzag shape is defined as W3. The width W3 is the distance in the tire width direction between the corners 21 and the corners 22 of the opening of the sipe 16.

At this time, the ratio W2 / W1 of the width W2 to the width W1 is preferably 0.10 or more and 0.40 or less. If this ratio W2 / W1 is smaller than 0.10, the edge effect becomes small and the snow performance deteriorates, which is not preferable. If this ratio W2 / W1 is larger than 0.40, the bent portion C1 becomes close to the zigzag portion, and the chipping resistance is inferior, which is not preferable.

The ratio W3 / W2 of the width W3 to the width W2 is preferably 0.15 or more and 0.45 or less. If this ratio W3 / W2 is smaller than 0.15, the edge effect of the zigzag groove becomes small and the snow performance deteriorates, which is not preferable. If this ratio W3 / W2 is larger than 0.45, the drainage property is lowered, the edge effect of the sipe 16 is also reduced, and the snow performance is lowered, which is not preferable.

Further, the ratio W3 / W1 of the width W3 to the maximum width W1 of the land portion Rm in the tire width direction is preferably 0.03 or more and 0.15 or less. If this ratio W3 / W1 is larger than 0.15, the drainage property is hindered and the drainage performance is deteriorated, which is not preferable. If this ratio W3 / W1 is smaller than 0.03, the edge effect is not produced and the snow performance is not improved, which is not preferable.

By the way, in the land portion Rm, two or more sipes 16 are provided between the adjacent lug grooves 13, and three or more zigzag-shaped convex portions are provided between the adjacent lug grooves 13. Is preferable. If the number of sipes 16 between the adjacent lug grooves 13 is less than two, the number of zigzag-shaped convex portions is reduced and the snow performance is not improved, which is not preferable.

Further, in FIG. 4, the straight portions ST3 of each of the plurality of sipes 16 are parallel to each other. Here, parallel means that the angle formed by the two straight lines L16 extending the center lines of the two sipes 16 is within ± 5 °. When the two straight lines L16 are completely parallel, the angle formed by the two straight lines L16 is 0 °.

Further, in FIG. 4, the plurality of lug grooves 13 are parallel to each other. Here, "parallel" means that the angle formed by the two straight lines L13 extending the center lines of the two lug grooves 13 is within ± 5 °. When the two straight lines L13 are completely parallel, the angle formed by the two straight lines L13 is 0 °.

FIG. 5 is an enlarged view of a part of the land portion Rm of the tread pattern shown in FIG. In FIG. 5, the distances between the zigzag-shaped convex portions between the adjacent lug grooves 13 are Lz1, Lz2, ..., Lzn (n is a natural number of 3 or more), respectively. The distance Lz1 and the distance Lzn are distances in the tire circumferential direction measured with reference to the lug grooves 13 which are different from each other. At this time, it is preferable that the ratio Lzmin / Lzmax of the shortest distance Lzmin to the longest distance Lzmax among the distances Lz1 to Lzn is 0.50 or more. That is, it is preferable that the ratio of the minimum value of the distance between the convex portions of the zigzag shape to the maximum value of the distance between the convex portions of the zigzag shape is 0.50 or more. When the ratio Lzmin / Lzmax is 0.50 or more, it means that the distance between the convex portions is not evenly divided. By making the distances between the convex portions different rather than evenly divided, the dispersion of the sound generated when the pneumatic tire 10 touches the road surface is improved, and the pattern noise is improved. The minimum values of the distances Lz1, Lz2, ..., Lzn are 3.0 [mm].

Further, in FIG. 5, the distances in the tire circumferential direction of the connecting portions to the circumferential main groove 11A on the inner side in the tire width direction between the plurality of sipes 16 provided between the adjacent lug grooves 13 are Ls1, Ls2, ... , Lsn (n is a natural number of 3 or more). The distances Ls1, Ls2, ..., Lsn are all the distances in the tire circumferential direction measured with reference to the connection portion of the inner straight portion ST1 to the circumferential main groove 11A. The distance Ls1 and the distance Lsn are distances in the tire circumferential direction measured with reference to the lug grooves 13 which are different from each other. At this time, it is preferable that the relationship between the distance Ls1 and the distance Lsn is Ls1 <Lsn. That is, it is preferable that the distance Lsn at the other end is longer than the distance Ls1 at one end in the tire circumferential direction. By changing the distance of the inner straight portion ST1 of the Z-shaped sipe 16, the edge effect can be exhibited in a wider angle and the snow performance can be improved. The minimum values of the distances Ls1, Ls2, ..., Lsn are 2.5 [mm].

In FIG. 5, the distances in the tire circumferential direction between the convex portions of the connecting portions to the circumferential main groove 12A on the outer side in the tire width direction between the plurality of sipes 16 provided between the adjacent lug grooves 13 are Lz1 and Lz2, respectively. , ..., Lzn (n is a natural number of 3 or more). The distance Lz1 and the distance Ls1 are distances in the tire circumferential direction measured with reference to the same lug groove 13. Since the same lug groove 13 is used as a reference, the distance Lz1 and the distance Ls1 have a relationship between the inside and the outside in the tire width direction, and both are at corresponding positions. Further, the distance Lzn and the distance Lsn are distances in the tire circumferential direction measured with reference to the same lug groove 13. Since the same lug groove 13 is used as a reference, the distance Lzn and the distance Lsn have a relationship between the inside and the outside in the tire width direction, and both are at corresponding positions. At this time, it is preferable that Ls1 <Lz1 and Lsn> Lzn. That is, in the tire circumferential direction, the relationship between the distance Ls1 at the corresponding position and the distance Lz1 is preferably larger at the distance Lz1 at the position outside the tire width direction than at the distance Ls1 at the position inside the tire width direction. Since the distance Lz1 is larger than the distance Ls1, the length of the sipe in the extending direction becomes longer, so that the edge effect becomes larger and the snow performance is improved. Further, in the tire circumferential direction, the relationship between the distance Lsn at the corresponding position and the distance Lzn is preferably smaller for the distance Lzn for the position outside the tire width direction than for the distance Lsn for the position inside the tire width direction. Since the distance Lzn is smaller than the distance Lsn, the length of the sipe in the extending direction becomes longer, so that the edge effect becomes larger and the snow performance is improved.

In FIG. 5, the sipe 16 is connected to the maximum amplitude position of the width W3, which is twice the amplitude of the zigzag edge in the tire width direction. As a result, when stress is applied in the tire circumferential direction, the stress applied to the convex portion that tends to be chipped can be dispersed along the groove wall of the sipe 16, and the chipping resistance is improved. For example, when stress is applied in the tire circumferential direction as shown by arrow YA, the stress can be dispersed along the groove wall of the sipe 16 as shown by arrow YB. This improves the chipping resistance of the convex portion that is easily chipped.

FIG. 6A is an enlarged view showing a part of the land portion Rm of the tread pattern shown in FIG. FIG. 6B is an enlarged view of a part of FIG. 6A. In FIGS. 6A and 6B, the two bent portions C1 and C2 of the sipe 16 are arranged inside the center line RL passing through the center of the land portion Rm in the tire width direction in the tire width direction. Of the two bent portions C1 and C2, the bent portion C2 is located closer to the center line RL than the bent portion C1. The boundary between the bent portion C2 and the straight portion ST3 is the end point K2. Let Db be the distance between the end point K2 and the center line RL in the tire width direction. The ratio Db / W1 of the distance Db to the maximum width W1 of the land portion Rm in the tire width direction is preferably 0 or more and 0.40 or less.

Here, the length in the tire circumferential direction from the connection point 23 of the sipe 16 with the circumferential main groove 11A on the inner side in the tire width direction to the end point K2 on the inner side in the tire width direction of the outer straight portion ST3 is defined as L3. The ratio L3 / L1 of the length L3 to the length L1 is preferably 0.15 or more and 0.45 or less. If the ratio L3 / L1 is larger than 0.45, the number of sipes cannot be increased, which is not preferable because the snow performance is not improved. When the ratio L3 / L1 is smaller than 0.15, the length of the portion connecting the straight portion ST1 and the straight portion ST3 extending from both edge sides of the land portion Rm (that is, the bent portion C1, the straight portion ST2 and the bent portion C2). Is not preferable because the edge effect is reduced and the snow performance is not improved.

Further, the ratio L3 / W1 of the length L3 to the maximum width W1 is preferably 0.15 or more and 0.65 or less. If the ratio L3 / W1 is smaller than 0.15, the edge effect becomes small and the snow performance deteriorates, which is not preferable. If the ratio L3 / W1 is larger than 0.65, the number of sipes cannot be increased, which is not preferable because the snow performance is not improved.

FIG. 7A is a diagram showing another example of the land area Rm. FIG. 7B is an enlarged view of a part of FIG. 7A. In FIGS. 7A and 7B, the bent portions C1 and C2 of the sipes 16A and 16B are arranged inside the center line RL passing through the center of the land portion Rm in the tire width direction in the tire width direction. In the sipe 16A, of the two bent portions C1 and C2, the bent portion C2 is located closer to the center line RL than the bent portion C1. The boundary between the bent portion C2 and the straight portion ST3 is the end point K2. Let Dba be the distance between the end point K2 and the center line RL in the tire width direction. The ratio Dba / W1 of the distance Dba to the maximum width W1 in the tire width direction of the land portion Rm is preferably 0 or more and 0.40 or less.

Further, in the sipe 16B, of the two bent portions C1 and C2, the bent portion C1 is located closer to the center line RL than the bent portion C2. The boundary between the bent portion C1 and the straight portion ST1 is the end point K1. Let Dbb be the distance between the end point K1 and the center line RL in the tire width direction. The ratio Dbb / W1 of the distance Dbb to the maximum width W1 in the tire width direction of the land portion Rm is preferably 0 or more and 0.40 or less.

FIG. 8A is a diagram showing another example of the land portion Rm. FIG. 8B is an enlarged view of a part of FIG. 8A. In FIGS. 8A and 8B, the bent portion C1 of the sipe 16C is arranged inside the center line RL passing through the center of the land portion Rm in the tire width direction in the tire width direction. The bent portion C2 of the sipe 16B is located on the center line RL. More specifically, the end point K2, which is the boundary between the bent portion C2 and the straight portion ST3, is located on the center line RL. In this case, since the distance between the end point K2 and the center line RL in the tire width direction is 0, the ratio Db / W1 = 0. The same applies to the bent portion C2 of the sipe 16D.

Therefore, also in the case of FIGS. 8A and 8B, the land portion Rm of the distance in the tire width direction between the bent portion C2 closer to the center line RL passing through the midpoint position in the tire width direction of the land portion Rm and the center line RL. Satisfies the condition that the ratio of tires to the width in the tire width direction is 0 or more and 0.40 or less. One of the two bent portions C1 and C2 is provided inside the center line RL passing through the midpoint position in the tire width direction of the land portion Rm, and the other one is located on the center line RL. You may be doing it.

As described above, of the two bent portions C1 and C2, the distance between the bent portion of the bent portion closer to the center line RL passing through the midpoint position in the tire width direction of the land portion Rm and the center line RL in the tire width direction. When the ratio of the land portion Rm to the maximum width W1 in the tire width direction is 0 or more and 0.40 or less, the following effects can be obtained. That is, the edge effect is increased by providing the zigzag groove and the substantially Z-shaped sipe 16. If the substantially Z-shaped bending point and the zigzag portion are close to each other, the block rigidity in the vicinity of the zigzag portion decreases, and there is a concern about chipping. Therefore, by providing the bending point of the sipe 16 and the zigzag portion at a position separated from each other, it is possible to achieve both snow performance and chipping resistance.

[Groove depth]
FIG. 9 is a cross-sectional view taken along the extending direction of the sipe 16 of FIG. The ratio DS / Dg of the groove depth DS of the sipe 16 to the groove depth Dg of the circumferential main groove 11A is preferably 0.50 or more and 0.85 or less. If the ratio DS / Dg is larger than 0.85, the block rigidity is lowered and the wear resistance is lowered, which is not preferable. If the ratio DS / Dg is smaller than 0.50, the snow performance deteriorates, which is not preferable.

As shown in FIG. 9, a bottom raising portion 160 is provided at the connecting portion of the sipe 16 to the circumferential main groove 11A. It is preferable that the ratio DS1 / DS of the groove depth DS of the sipe 16 and the groove depth DS1 of the sipe 16 in the bottom raising portion 160 is 0.40 or more and 0.70 or less. If the ratio DS1 / DS is larger than 0.70, the block rigidity is lowered and the wear resistance is lowered, which is not preferable. If the ratio DS1 / DS is smaller than 0.40, the snow performance deteriorates, which is not preferable.

Although the land portion Rm between the circumferential main grooves 11A and 12A has been described above, the same description applies to the land portion Rm between the circumferential main grooves 11B and 12B.

Further, the groove width is measured as the maximum value of the distance between the left and right groove walls at the groove opening in a no-load state in which the tire is mounted on the specified rim and the specified internal pressure is filled. In a configuration in which the land portion has a notch or a chamfered portion at the edge portion, the groove width is set based on the intersection of the tread tread and the extension line of the groove wall in a cross-sectional view with the groove length direction as the normal direction. Be measured. Further, in the configuration in which the grooves extend in a zigzag shape or a wavy shape in the tire circumferential direction, the groove width is measured with reference to the center line of the amplitude of the groove wall.

The tire ground contact end T is a contact surface between the tire and the flat plate when the tire is mounted on the specified rim to apply a specified internal pressure and the tire is placed perpendicular to the flat plate in a stationary state and a load corresponding to the specified load is applied. It is defined as the maximum width position in the tire axial direction in.

Here, the specified rim means an "applicable rim" specified in JATTA, a "Design Rim" specified in TRA, or a "Measuring Rim" specified in ETRTO. The specified internal pressure means the "maximum air pressure" specified in JATTA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified in TRA, or "INFLATION PRESSURES" specified in ETRTO. The specified load means the "maximum load capacity" specified in JATTA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified in TRA, or the "LOAD CAPACITY" specified in ETRTO. However, in JATTA, in the case of a passenger car tire, the specified internal pressure is an air pressure of 180 [kPa], and the specified load is 88 [%] of the maximum load capacity.

[Example]
Tables 1 to 5 are tables showing the results of performance tests of pneumatic tires according to the present invention. In this performance test, different pneumatic tires were evaluated for chipping resistance, snow braking performance, snow handling performance, and drainage performance. In these performance tests, test tires of size 225 / 65R17 102H were mounted on rims of rim size 17 × 7.0J and an air pressure of 230 [kPa] was applied. Further, as a test vehicle, an FF (Front engine Front drive) SUV (Sport Utility Vehicle) vehicle having a displacement of 2500 [cc] was used.

The anti-chipping performance was evaluated by measuring the number of chips on the tread surface after traveling on an off-road road course for 450 laps and indexing it. This evaluation is performed by an index evaluation based on the conventional example (100), and the larger the value, the more preferable.

The snow braking performance was evaluated by indexing the braking distance at a speed of 30 km / h on a snowy road surface. This evaluation is performed by an index evaluation based on the conventional example (100), and the larger the value, the more preferable.

The snow handling performance was evaluated by indexing the feeling of the test driver for steering stability on snowy roads. This evaluation is performed by an index evaluation based on the conventional example (100), and the larger the value, the more preferable.

The drainage performance was evaluated by an index comparing the conventional example with 100 by measuring the speed at which the slip ratio reached 10% and 15% while traveling in a hydropool having a water depth of 10 ± 1 [mm]. This evaluation is performed by an index evaluation based on the conventional example (100), and the larger the value, the more preferable.

In the pneumatic tires of Examples 1 to 32, the inner edge of the land portion Rm in the tire width direction (that is, the center side) has a straight shape, and the edge of the land portion Rm on the outer side in the tire width direction (that is, the shoulder side) is straight. It is a tire having a zigzag shape having irregularities whose position in the tire width direction changes periodically, having a substantially Z-shaped sipe, and having a ratio Db / W1 of 0 or more and 0.40 or less.

In Examples 1 to 32, the settings are as shown in Tables 1 to 5. That is, the ratio W2 / W1 is 0.10 or more and 0.40 or less and not, the ratio L2 / L1 is 0.15 or more and 0.55 or less and not, and the ratio W3 / W1 is 0. .03 or more and 0.15 or less and not, ratio L3 / L1 of 0.15 or more and 0.45 or less and not, ratio L3 / W1 of 0.15 or more and 0.65 or less Yes and no, ratio W3 / W2 is 0.15 or more and 0.45 or less and not, ratio DS / Dg is 0.50 or more and 0.85 or less and not, ratio Those having a DS1 / Dg of 0.40 or more and 0.70 or less and those having a DS1 / Dg of not were prepared.

The conventional pneumatic tire is a tire having a straight-shaped sipe, with both the inner edge in the tire width direction (that is, the center side) and the outer edge in the tire width direction (that is, the shoulder side) of the land portion having a straight shape. .. In addition, for comparison, a pneumatic tire of a comparative example was prepared. In the pneumatic tire of the comparative example, the inner edge of the land portion in the tire width direction (that is, the center side) has a straight shape, and the outer edge of the land portion in the tire width direction (that is, the shoulder side) is periodically positioned in the tire width direction. It is a tire having a zigzag shape having irregularities that change to, and having a straight sipe.

These pneumatic tires were evaluated for chipping resistance, snow braking performance, snow handling performance, and drainage performance by the above evaluation method, and the results are also shown in Tables 1 to 5.

As shown in Tables 1 to 5, when the ratio W2 / W1 is 0.10 or more and 0.40 or less, when the ratio L2 / L1 is 0.15 or more and 0.55 or less, the ratio W3 / W1 is 0. When the ratio L3 / L1 is 0.15 or more and 0.45 or less, when the ratio L3 / W1 is 0.15 or more and 0.65 or less, the ratio W3 / W2 is .03 or more and 0.15 or less. Good results when the ratio DS / Dg is 0.50 or more and 0.85 or less, and the ratio DS1 / DS is 0.40 or more and 0.70 or less. was gotten.

1 Tread part 2 sidewall part 3 bead part 4 carcass layer 5 bead core 6 bead filler 7 belt layer 8 belt cover layer 10 tires 11A, 11B, 12A, 12B circumferential main grooves 13, 14A, 14B lug grooves 15, 16, 16A ~ 16D, 17 Sipe 18 Decorative groove 21, 22 Corner 160 Bottom raising part C1, C2 Bending part CL Tire equatorial plane K1, K2 End point Rc Center land part RL Center line Rm Middle land part Rs Shoulder land part ST1, ST2, ST3 Straight line Part T Tire ground contact end

Claims (16)

Pneumatic tires with a tread pattern
The tread pattern is
Three or more circumferential main grooves extending in the tire circumferential direction,
Of the three or more circumferential main grooves, a land portion that is continuous in the tire circumferential direction and is partitioned by the two circumferential main grooves.
A plurality of lug grooves provided in the land area and
A sipe provided on the land and between adjacent lug grooves.
Including
The outer edge of the land portion in the tire width direction has a zigzag shape having irregularities whose position in the tire width direction changes periodically, and the inner edge of the land portion in the tire width direction has a straight shape.
The sipe is a penetrating sipe that continuously extends from the outer edge in the tire width direction to the inner edge in the tire width direction.
The sipe has a Z-shape with two bends and has a Z-shape.
Of the two bent portions, the distance between the bent portion closer to the center line passing through the midpoint position in the tire width direction of the land portion and the center line in the tire width direction is the distance in the tire width direction of the land portion. Ri der ratio is 0 to 0.40 to the width,
The sipe is a pneumatic tire that opens on the tread surface of the land portion. The sipe has an inner straight section that connects to the inner edge in the tire width direction.
The pneumatic tire according to claim 1, wherein the ratio of the length of the inner straight portion in the tire width direction to the width of the land portion in the tire width direction is 0.10 or more and 0.40 or less. 1 Alternatively, the pneumatic tire according to claim 2. Any one of claims 1 to 3 , wherein the ratio of the width of the zigzag shape to the width in the tire width direction of the land portion is 0.03 or more and 0.15 or less. Pneumatic tires described in. The sipe has an outer straight portion that connects to the outer edge in the tire width direction.
Inside the tire width direction of the outer straight portion from the connection point with the tire width direction inner side of the sipe with respect to the length of the zigzag shape edge between adjacent lug grooves in the tire width direction. The pneumatic tire according to any one of claims 1 to 4 , wherein the ratio of the distances in the tire circumferential direction to the end point is 0.15 or more and 0.45 or less. The distance in the tire circumferential direction from the connection point of the sipe with the circumferential main groove on the inner side of the tire width direction to the end point of the outer straight portion on the inner side in the tire width direction with respect to the width of the land portion in the tire width direction. The pneumatic tire according to claim 5 , wherein the ratio is 0.15 or more and 0.65 or less. The sipe has an inner straight section that connects to the inner edge in the tire width direction.
Any of claims 1 to 6 , wherein the ratio of the width of the inner straight portion in the tire width direction to twice the amplitude of the zigzag shape in the tire width direction is 0.15 or more and 0.45 or less. Pneumatic tires listed in one. The pneumatic tire according to any one of claims 1 to 7 , which has a plurality of the sipes between adjacent lug grooves. The pneumatic tire according to claim 8 , wherein the straight portions of the plurality of sipes are parallel to each other. Two or more of the sipes are provided between the adjacent lug grooves.
The pneumatic tire according to any one of claims 1 to 9 , wherein three or more zigzag-shaped convex portions are provided between the adjacent lug grooves. The method according to any one of claims 1 to 10 , wherein the ratio of the minimum value of the distance between the convex portions of the zigzag shape to the maximum value of the distance between the convex portions of the zigzag shape is 0.50 or more. Pneumatic tires. To the connection portion of the adjacent lug groove to the inner circumferential main groove in the tire width direction and the plurality of the sipes provided between the adjacent lug grooves to the inner circumferential main groove in the tire width direction. anda connecting portion, the tire circumferential direction of the distance between the connecting portions adjacent in the tire circumferential direction Ls1, Ls2, ..., when the Lsn (n is a natural number of 3 or more), claim a Ls1 <Lsn 1 The pneumatic tire according to any one of claims 11. To the connection portion of the adjacent lug groove to the inner circumferential main groove in the tire width direction and the plurality of the sipes provided between the adjacent lug grooves to the inner circumferential main groove in the tire width direction. The distance in the tire circumferential direction between the connecting portions including the connecting portion and the connecting portions adjacent to each other in the tire circumferential direction is Ls1, Ls2, ..., Lsn (n is a natural number of 3 or more).
To the connection portion of the adjacent lug groove to the outer circumferential main groove in the tire width direction and the plurality of the sipes provided between the adjacent lug grooves to the outer circumferential main groove in the tire width direction. When the distance in the tire circumferential direction between the connecting portion and the convex portions of the connecting portions adjacent to each other in the tire circumferential direction is Lz1, Lz2, ..., Lzn (n is a natural number of 3 or more), Ls1 <Lz1. The pneumatic tire according to any one of claims 1 to 12 , which is present and has Lsn> Lzn. The pneumatic tire according to any one of claims 1 to 13 , wherein the ratio of the groove depth of the sipe to the groove depth of the circumferential main groove is 0.50 or more and 0.85 or less. It has a bottom raising portion provided at the groove bottom inside the tire width direction of the sipe.
The pneumatic tire according to any one of claims 1 to 14 , wherein the ratio of the groove depth of the sipe to the groove depth of the sipe at the bottom raising portion is 0.40 or more and 0.70 or less. The pneumatic tire according to any one of claims 1 to 15 , wherein the sipes are connected to the maximum amplitude position in the tire width direction of the zigzag edge.

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