JP7617485B2 - tire - Google Patents

Description

This invention relates to tires.

For example, Patent Document 1 shows a pneumatic tire that can improve wet steering stability while maintaining exterior noise performance.

International Publication No. 2018/151108

Incidentally, reducing the groove width and volume of the tread surface is an effective way to improve noise vibration (NV) performance. However, reducing the groove width and volume results in an inability to ensure drainage, which can lead to a deterioration in wet grip performance.

The object of this invention is to provide a tire that can achieve excellent noise performance and wet grip performance.

In order to achieve the above object, a tire according to one aspect of the present invention is a tire having a tread surface with an asymmetric tread pattern with the tire equatorial plane as a boundary, the tread pattern being specified in the direction of the vehicle width when mounted on a vehicle, and the tread pattern is formed by first, second, third and fourth main grooves extending in the tire circumferential direction and arranged in four from the inner side in the vehicle width direction to the outer side in the vehicle width direction, with the groove width of at least the outermost groove in the vehicle width direction narrower than that of the innermost groove in the vehicle width direction, first, second, third, fourth and fifth land portions partitioned by each of the main grooves and extending in the tire circumferential direction like a rib from the inner side in the vehicle width direction to the outer side in the vehicle width direction, five narrow grooves in the tire width direction in the fifth land portion, extending in the tire circumferential direction, at least one narrow groove in the tire width direction and having a narrower groove width than that of the fourth main groove, a first sipe that is the only one in the first land portion and has one end that does not penetrate the first main groove but does not penetrate through the first land portion and the other end that extends outward in the tire width direction and is arranged in the tire circumferential direction, and a tread pattern that extends in the tire width direction in the second land portion and has a narrow groove in the tire width direction. a plurality of second sipes provided in the tire circumferential direction; a plurality of third sipes extending in the tire width direction and provided in the tire circumferential direction in the third land portion; a plurality of fourth sipes extending in the tire width direction and provided in the tire circumferential direction in the fourth land portion; a fifth sipe, one end of which penetrates the narrow groove but does not penetrate through it, and the other end of which extends outward in the tire width direction and is the only fifth sipe provided in the tire circumferential direction on the outer side in the tire width direction of the narrow groove provided in the fifth land portion; and a fifth sipe, one end of which penetrates the fourth main groove in the fifth land portion and the other end of which extends outward in the tire width direction. and fifth lug grooves which extend in the tire circumferential direction, terminate without penetrating the narrow groove, and are provided in a plurality of fifth lug grooves, the second sipes having a number at least twice as many as the third sipes and the fourth sipes, the sipes and grooves provided in the second land portion, the third land portion, and the fourth land portion are provided at an inclination in the same direction with respect to the tire width direction, and the first sipes, the fifth sipes, and the fifth lug grooves have an inclination in the same direction as the sipes and grooves provided in the second land portion, the third land portion, and the fourth land portion.

This invention improves noise performance and wet grip performance.

FIG. 1 is a meridian cross-sectional view of a pneumatic tire according to an embodiment. FIG. 2 is a plan view of a tread surface of the pneumatic tire according to the embodiment. FIG. 3 is a partially enlarged plan view of a tread surface of the pneumatic tire according to the embodiment. FIG. 4 is a partially enlarged plan view of a tread surface of the pneumatic tire according to the embodiment. FIG. 5 is a schematic perspective view of a sipe of a pneumatic tire according to an embodiment. FIG. 6 is a schematic perspective view of another example of a sipe of the pneumatic tire according to the embodiment. FIG. 7 is a table showing the results of a performance test of the pneumatic tire according to the embodiment. FIG. 8 is a table showing the results of a performance test of the pneumatic tire according to the embodiment.

Below, an embodiment of a pneumatic tire according to the present invention will be described in detail with reference to the drawings. Note that the invention is not limited to this embodiment. Furthermore, the components of this embodiment include those that can be substituted and are obvious substitutes while maintaining the identity of the invention. Furthermore, the multiple modified examples described in this embodiment can be combined in any way that is obvious to those skilled in the art.

In the following description, the tire radial direction refers to a direction perpendicular to the tire rotation axis (not shown), which is the rotation axis of the pneumatic tire 1, the tire radial inner side refers to the side toward the tire rotation axis in the tire radial direction, and the tire radial outer side refers to the side away from the tire rotation axis in the tire radial direction. The tire circumferential direction refers to the direction around the tire rotation axis as the central axis. The tire width direction refers to a direction parallel to the tire rotation axis, the tire width inner side refers to the side toward the tire equatorial plane (tire equatorial line) CL in the tire width direction, and the tire width outer side refers to the side away from the tire equatorial plane CL in the tire width direction. The tire equatorial plane CL is a plane that is perpendicular to the tire rotation axis and passes through the center of the tire width of the pneumatic tire 1, and the tire equatorial plane CL coincides with the tire width centerline, which is the center position in the tire width direction of the pneumatic tire 1. The tire width is the width in the tire width direction between the portions located outermost 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 refers to a line that is on the tire equatorial plane CL and extends along the tire circumferential direction of the pneumatic tire 1. Also, a cross section in the tire meridian direction (meridian cross section) refers to a cross section of the tire cut by a plane that includes the tire rotation axis.

The vehicle width direction inner side and vehicle width direction outer side are defined as the directions relative to the vehicle width direction (tire width direction) when the tire is mounted on the vehicle. Specifically, the pneumatic tire 1 is provided with a mounting direction indicator (not shown) that indicates the direction in which the tire is mounted on the vehicle. The mounting direction indicator is, for example, configured by a mark or unevenness attached to the sidewall of the tire. For example, ECER 30 (Article 30 of the Economic Commission for Europe Regulation) requires that a vehicle mounting direction indicator be provided on the sidewall that is on the outer side in the vehicle width direction when mounted on the vehicle. The pneumatic tire 1 of this embodiment has a specified direction relative to the vehicle width direction when mounted on the vehicle.

As shown in FIG. 1, the pneumatic tire 1 of the embodiment has an annular structure centered on the tire rotation axis, and includes a pair of bead cores 11, 11, a pair of bead fillers 12, 12, a carcass layer 13, a belt layer 14, a tread rubber 15, a pair of sidewall rubbers 16, 16, and a pair of rim cushion rubbers 17, 17.

The pair of bead cores 11, 11 have an annular structure formed by multiple windings of bead wire made of steel or organic fiber material around the tire circumferential direction, and form the cores of the left and right bead portions.

A pair of bead fillers 12, 12 are respectively arranged on the radial outer periphery of a pair of bead cores 11, 11 to form a bead portion.

The carcass layer 13 has a single-layer structure consisting of one carcass ply or a multi-layer structure consisting of multiple carcass plies stacked together, and is toroidally stretched between the left and right bead cores 11, 11 to form the tire framework. In addition, both ends of the carcass layer 13 are wrapped around and secured to the outside in the tire width direction so as to envelop the bead cores 11 and the bead fillers 12. In addition, the carcass plies of the carcass layer 13 are formed by coating multiple carcass cords made of steel or organic fiber material (e.g., aramid, nylon, polyester, rayon, etc.) with coating rubber and rolling them, and have a carcass angle (defined as the inclination angle of the carcass cords in the longitudinal direction with respect to the tire circumferential direction) of 80 degrees or more and 95 degrees or less in absolute value.

The belt layer 14 is formed by laminating a pair of cross belts 141, 142 and a belt cover 143, and is arranged around the outer periphery of the carcass layer 13. The pair of cross belts 141, 142 are formed by coating a plurality of belt cords made of steel or organic fiber material with coating rubber and rolling them, and have an absolute belt angle of 20 degrees or more and 55 degrees or less. In addition, the pair of cross belts 141, 142 have belt angles of opposite signs (defined as the inclination angle of the longitudinal direction of the belt cord with respect to the tire circumferential direction), and are laminated with the longitudinal directions of the belt cords crossing each other (so-called cross-ply structure). The belt cover 143 is formed by coating a belt cord made of steel or organic fiber material with coating rubber, and has an absolute belt angle of 0 degrees or more and 10 degrees or less. In addition, the belt cover 143 is, for example, a strip material formed by covering one or more belt cords with a coating rubber, and is formed by winding this strip material spirally multiple times around the outer circumferential surfaces of the cross belts 141, 142 in the tire circumferential direction.

The tread rubber 15 is disposed on the radially outer periphery of the carcass layer 13 and the belt layer 14 to form the tread portion of the tire. The tread rubber 15 also forms a tread surface 15a on the outer peripheral surface of the tread portion that comes into contact with the road surface during running.

A pair of sidewall rubbers 16, 16 are positioned on the outer sides of the carcass layer 13 in the tire width direction to form the left and right sidewall portions.

A pair of rim cushion rubbers 17, 17 are respectively arranged on the radially inner side of the bead cores 11, 11 and the turned-up portion of the carcass layer 13, forming the contact surfaces of the left and right bead portions with the rim flange.

As shown in Figures 1 and 2, the pneumatic tire 1 of the embodiment has a tread pattern 15b on the tread surface 15a. The pneumatic tire 1 of the embodiment shows the tread pattern 15b of an all-season tire. The pneumatic tire 1 of the embodiment shows the tread pattern 15b that is asymmetric in the tire width direction with the tire equatorial plane CL as the boundary.

As shown in FIG. 2, the tread pattern 15b extends along the tire circumferential direction and includes four circumferential main grooves in the tire width direction, the first main groove 21, the second main groove 22, the third main groove 23, and the fourth main groove 24 from the inner side in the vehicle width direction to the outer side in the vehicle width direction. The tread pattern 15b is divided by the four main grooves 21, 22, 23, and 24 and extends in a rib-like manner in the tire circumferential direction, and includes five first land portions 31, second land portions 32, third land portions 33, fourth land portions 34, and fifth land portions 35 in the tire width direction from the inner side in the vehicle width direction to the outer side in the vehicle width direction. The first land portion 31 and the fifth land portion 35 are also called shoulder land portions on the outer side in the tire width direction, and the second land portion 32, the third land portion 33, and the fourth land portion 34 are also called center land portions on the inner side in the tire width direction. The tread pattern 15b includes a first sipe 311 in the first land portion 31. The tread pattern 15b includes a second sipe 321 in the second land portion 32. The tread pattern 15b includes a third sipe 331 in the third land portion 33. The tread pattern 15b includes a fourth sipe 341 in the fourth land portion 34. The tread pattern 15b includes a narrow groove 351, a fifth sipe 352, and a fifth lug groove 353 in the fifth land portion 35. As shown in FIG. 3, the tread pattern 15b also includes a second lug groove 322 in the second land portion 32. As shown in FIG. 4, the tread pattern 15b also includes a third lug groove 332 in the third land portion 33. The tread pattern 15b also includes a fourth lug groove 342 in the fourth land portion 34.

Here, the main groove is a groove that is required to display a wear indicator as specified by JATMA, and generally has a groove width of 4.0 mm or more and a groove depth of 6.5 mm or more. The lug groove is a lateral groove that extends along the tire width direction, generally has a groove width of 1.0 mm or more and less than 6.0 mm, and a groove depth of 3.0 mm or more and less than 6.5 mm, and functions as a groove when the tire is in contact with the ground. The fine groove is a longitudinal groove that extends along the tire circumferential direction, generally has a groove width of 1.0 mm or more and less than 4.0 mm, and a groove depth of 3.0 mm or more and less than 6.5 mm, and functions as a groove when the tire is in contact with the ground. The sipe is a cut formed on the tread surface, generally has a sipe width of less than 1.0 mm and a sipe depth of 2.0 mm or more, and closes when the tire is in contact with the ground.

Groove width is measured as the maximum distance between the left and right groove walls on the tread surface when the tire is mounted on a specified rim, inflated to the specified internal pressure, and in an unloaded state. In configurations where the land portion has a notch or chamfered portion at the edge, the groove width is measured in a cross-sectional view with the groove length direction as the normal direction, based on the intersection point between the tread surface and the extension of the groove wall.

Groove depth is measured as the maximum distance from the tread surface to the bottom of the groove when the tire is mounted on a specified rim, inflated to the specified internal pressure, and in an unloaded state. In addition, if the groove has partial unevenness or sipes at the bottom of the groove, these are excluded from the measurement of the groove depth.

Sipe width is measured as the maximum opening width of the sipes on the land tread when the tire is mounted on the specified rim, inflated to the specified internal pressure, and in an unloaded condition.

The tire contact patch is defined as the contact area between the tire and a plate when the tire is mounted on a specified rim, pressurized to a specified internal pressure, placed perpendicular to a plate in a stationary state, and subjected to a load corresponding to a specified load.

The specified rim refers to the "applicable rim" specified by JATMA, the "design rim" specified by TRA, or the "measuring rim" specified by ETRTO. The specified internal pressure refers to the "maximum air pressure" specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" specified by TRA, or the "inflation pressures" specified by ETRTO. The specified load refers to the "maximum load capacity" specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" specified by TRA, or the "load capacity" specified by ETRTO. However, in JATMA, for passenger car tires, the specified internal pressure is 180 kPa, and the specified load is 88% of the maximum load capacity.

The details of tread pattern 15b are explained below.

2, the first main groove 21, the second main groove 22, the third main groove 23 and the fourth main groove 24 are formed so that the groove width of the fourth main groove 24, which is the outermost in the vehicle width direction, is narrowest compared to the other main grooves 21, 22, 23. The main grooves 21, 22, 23 other than the fourth main groove 24, which is the outermost in the vehicle width direction, are formed so that the groove width is the same or narrower from the inner side in the vehicle width direction to the outer side in the vehicle width direction. The relationship of the groove width of the main grooves includes, for example, that the first main groove 21 has the widest groove width among the four main grooves, the second main groove 22 and the third main groove 23 have the same groove width narrower than the first main groove 21, and the fourth main groove 24 has the narrowest groove width. In the pneumatic tire 1 of the embodiment, it is preferable to obtain the effects of the present disclosure that the fourth main groove 24, which is the outermost in the vehicle width direction, is formed so that the groove width is 75% or less compared to the first main groove 21, which is the innermost in the vehicle width direction.

As shown in FIG. 2, the first sipe 311 of the first land portion 31 is formed with one end penetrating the first main groove 21 and the other end extending outward in the tire width direction. The first sipe 311 is a joint point where one end does not penetrate the first main groove 21. That is, the first sipe 311 is provided at a position where it penetrates the first main groove 21, shifting its position in the tire circumferential direction so that the second sipe 321 penetrating from the second land portion 32 side does not exist opposite on an extension line. A plurality of first sipes 311 are provided in the tire circumferential direction. The first sipes 311 may have uneven pitches in the tire circumferential direction due to pitch variation. This first sipe 311 is the only one formed in the first land portion 31, and no other grooves are formed in the first land portion 31. This is called a sipe base.

In order to obtain the effects of the present disclosure, it is preferable that the first sipe 311 be formed in a three-dimensional shape, like the sipe 101 shown in Figures 5 and 6. The first sipe 311 of the embodiment has the three-dimensional shape of the sipe 101 shown in Figure 6.

The sipe 101 shown in FIG. 5 has an opening 101a that opens to the tread surface 15a formed in a curved shape. The sipe 101 shown in FIG. 5 has sipe walls 101b formed in the tire radial direction facing each other, and at least one of the sipe walls 101b has an unevenness 101c formed thereon. In FIG. 5, the unevenness 101c is formed as a recess (dimple) in one of the sipe walls 101b. The other sipe wall 101b facing the one sipe wall 101b in which the recess is formed may not have an unevenness formed thereon, and may have a protrusion that enters the dimple. In this way, the sipe 101 shown in FIG. 5 is formed in a three-dimensional shape. The sipe 101 shown in FIG. 6 has an opening 101a that opens to the tread surface 15a formed in a curved shape. In addition, the sipe 101 shown in Fig. 6 has sipe walls 101b formed in opposition to each other along the tire radial direction, and each sipe wall 101b is formed into a waveform 101d that meanders (or zigzags) toward the tire radial direction. In this way, the sipe 101 shown in Fig. 6 is formed into a three-dimensional shape.

The second sipes 321 of the second land portion 32 are formed extending in the tire width direction as shown in FIG. 2 and FIG. 3. The second sipes 321 are arranged in a row in the tire circumferential direction. The second sipes 321 may have uneven pitches in the tire circumferential direction due to pitch variations. The second sipes 321 have more than twice the number of the third sipes 331 and the fourth sipes 341. The second lug grooves 322 of the second land portion 32 are formed extending in the tire width direction as shown in FIG. 3. The second lug grooves 322 are arranged in a row in the tire circumferential direction. The second lug grooves 322 may have uneven pitches in the tire circumferential direction due to pitch variations. The second land portion 32 is formed only with the second sipes 321 and the second lug grooves 322.

The second lug groove 322 and the second sipe 321 are formed to be continuous with each other, as shown in FIG. 3. Specifically, the second lug groove 322 has one end penetrating the first main groove 21 or the second main groove 22, and the other end terminating in the second land portion 32. The second sipe 321 has one end penetrating the second main groove 22 or the first main groove 21, and the other end penetrating the other end of the second lug groove 322. That is, when one end of the second lug groove 322 penetrates the first main groove 21, the second sipe 321 has one end penetrating the second main groove 22, and the other end penetrating the other end of the second lug groove 322, so that they are continuous with each other. On the other hand, when one end of the second lug groove 322 penetrates the second main groove 22, the second sipe 321 has one end penetrating the first main groove 21, and the other end penetrating the other end of the second lug groove 322, so that they are continuous with each other.

In addition, the pairs of second lug grooves 322 and second sipes 321 that are formed continuously with each other are formed in a row in the tire circumferential direction. The pairs of second lug grooves 322 and second sipes 321 that are adjacent in the tire circumferential direction are arranged in a staggered manner along the tire circumferential direction. That is, for a pair of second lug grooves 322 and second sipes 321 in which the second lug groove 322 penetrates the first main groove 21 and the second sipe 321 penetrates the second main groove 22, the other pair adjacent in the tire circumferential direction is such that the second lug groove 322 penetrates the second main groove 22 and the second sipe 321 penetrates the first main groove 21. In this way, the pairs of second lug grooves 322 and second sipes 321 that are formed continuously with each other are arranged in a staggered manner along the tire circumferential direction, with pairs adjacent in the tire circumferential direction being replaced in the tire width direction.

In addition, in a pair of second lug grooves 322 and second sipes 321 adjacent to each other in the tire circumferential direction, the second lug grooves 322 are circumferentially biased relative to the second sipes 321. In addition, the pair of second lug grooves 322 and second sipes 321 adjacent to each other in the tire circumferential direction has the bias of the second lug grooves 322 arranged in a staggered manner along the tire circumferential direction. That is, in a pair of second lug grooves 322 and second sipes 321 in which the second lug grooves 322 are arranged in a staggered manner along the tire circumferential direction, the second lug grooves 322 are arranged in a staggered manner along the tire circumferential direction, while the pair of second lug grooves 322 and second sipes 321 in which the second lug grooves 322 are arranged in a staggered manner along the tire circumferential direction of the second sipes 321 are arranged in a staggered manner along the tire circumferential direction. In this way, the pair of second lug grooves 322 and second sipes 321 formed in succession to each other has the bias of the second lug grooves 322 in the pair adjacent to each other in the tire circumferential direction, and the bias of the second lug grooves 322 is exchanged.

In the pneumatic tire 1 of the embodiment, the second land portion 32 may have only the second sipe 321 formed without the second lug groove 322. In this case, as shown in FIG. 2, the second sipe 321 penetrates the first main groove 21 at one end and the second main groove 22 at the other end. That is, in the pneumatic tire 1 of the embodiment, when the second sipe 321 does not have the second lug groove 322, the tire width direction length L1 is 100% of the width B2 of the second land portion 32 (see FIG. 2 and FIG. 3). In addition, in the pneumatic tire 1 of the embodiment, when the second lug groove 322 is present, it is preferable for the tire width direction length L2 of the second lug groove 322 to be 45% or less of the width B2 of the second land portion 32 in order to obtain the effects of the present disclosure (see FIG. 3).

The third sipes 331 of the third land portion 33 are formed extending in the tire width direction as shown in FIG. 2 and FIG. 4. The third sipes 331 are arranged in a row in the tire circumferential direction. The third sipes 331 may have uneven pitches in the tire circumferential direction due to pitch variations. It is preferable for the third sipes 331 to be formed in a three-dimensional shape, as in the sipes 101 shown in FIG. 5 and FIG. 6, in order to obtain the effects of the present disclosure. The third sipes 331 of the embodiment are applied with the three-dimensional shape of the sipes 101 shown in FIG. 5. The third lug grooves 332 of the third land portion 33 are formed extending in the tire width direction as shown in FIG. 4. The third lug grooves 332 are arranged in a row in the tire circumferential direction. The third lug grooves 332 may have uneven pitches in the tire circumferential direction due to pitch variations. Only the third sipes 331 and the third lug grooves 332 are formed in the third land portion 33.

The third lug groove 332 and the third sipe 331 are formed so as to be continuous with each other, as shown in FIG. 4. Specifically, one end of the third lug groove 332 penetrates the second main groove 22, and the other end of the third sipe 331 terminates in the third land portion 33. One end of the third sipe 331 penetrates the other end of the third lug groove 332, and the other end of the third sipe 331 terminates in the third land portion 33. That is, in the set of the third lug groove 332 and the third sipe 331 formed so as to be continuous with each other, the third lug groove 332 penetrates the second main groove 22, and the third sipe 331 that penetrates the third lug groove 332 terminates in the third land portion 33. The sets of the third lug groove 332 and the third sipe 331 formed so as to be continuous with each other are formed in a row in the tire circumferential direction. In addition, in a set of the third lug groove 332 and the third sipe 331 formed continuously to each other, the third lug groove 332 is formed such that the circumferential groove widths W1, W2 are expanded from the other end where the third sipe 331 penetrates to one end where the third lug groove 332 penetrates to the second main groove 22. In order to obtain the effects of the present disclosure, it is preferable that W1/W2 of the circumferential groove widths W1, W2 is 5% or more and 30% or less.

In the pneumatic tire 1 of the embodiment, the third land portion 33 may have only the third sipe 331 formed without the third lug groove 332. In this case, the third sipe 331 may have both ends terminated at the third land portion 33 as shown in FIG. 2, and may have one end penetrating the second main groove 22 and the other end terminating within the third land portion 33. In addition, when the third sipe 331 has the third lug groove 332, one end penetrates the other end of the third lug groove 332 and penetrates the second main groove 22 via the third lug groove 332, and the other end terminates within the third land portion 33. In the pneumatic tire 1 of the embodiment, it is preferable that the third sipe 331 is the only one or the tire width direction length L3 including the third lug groove 332 is 70% or less of the width B3 of the third land portion 33 in order to obtain the effects of the present disclosure (see FIG. 4). In addition, in the pneumatic tire 1 of the embodiment, it is preferable in order to obtain the effects of the present disclosure that the third lug groove 332 has a tire width direction length L4 of 40% or less of the width B3 of the third land portion 33 (see FIG. 4).

The fourth sipes 341 of the fourth land portion 34 are formed extending in the tire width direction as shown in Figures 2 and 4. The fourth sipes 341 are arranged in a row in the tire circumferential direction. The fourth sipes 341 may have uneven pitches in the tire circumferential direction due to pitch variation. The fourth lug grooves 342 of the fourth land portion 34 are formed extending in the tire width direction as shown in Figure 4. The fourth lug grooves 342 are arranged in a row in the tire circumferential direction. The fourth lug grooves 342 may have uneven pitches in the tire circumferential direction due to pitch variation. Only the fourth sipes 341 and the fourth lug grooves 342 are formed in the fourth land portion 34.

The fourth lug groove 342 and the fourth sipe 341 are formed so as to be continuous with each other, as shown in FIG. 4. Specifically, one end of the fourth lug groove 342 penetrates the third main groove 23, and the other end of the fourth sipe 341 terminates in the fourth land portion 34. One end of the fourth lug groove 342 penetrates the other end of the fourth lug groove 342, and the other end of the fourth sipe 341 terminates in the fourth land portion 34. That is, the set of the fourth lug groove 342 and the fourth sipe 341 formed so as to be continuous with each other is such that the fourth lug groove 342 penetrates the third main groove 23, and the fourth sipe 341 that penetrates the fourth lug groove 342 terminates in the fourth land portion 34. The sets of the fourth lug groove 342 and the fourth sipe 341 formed so as to be continuous with each other are formed in a row in the tire circumferential direction. In addition, in a set of the fourth lug groove 342 and the fourth sipe 341 formed continuously with each other, the fourth lug groove 342 is formed such that the circumferential groove widths W3, W4 are expanded from the other end through which the fourth sipe 341 penetrates to one end through which the fourth main groove 23 penetrates. In order to obtain the effects of the present disclosure, it is preferable that W3/W4 is 5% or more and 30% or less.

In the pneumatic tire 1 of the embodiment, the fourth land portion 34 may have only the fourth sipe 341 formed without the fourth lug groove 342. In this case, the fourth sipe 341 includes a configuration in which both ends terminate at the fourth land portion 34, and a configuration in which one end penetrates the third main groove 23 and the other end terminates within the fourth land portion 34, as shown in FIG. 2. In addition, when the fourth sipe 341 has the fourth lug groove 342, one end penetrates the other end of the fourth lug groove 342 and penetrates the third main groove 23 via the fourth lug groove 342, and the other end terminates within the fourth land portion 34. In the pneumatic tire 1 of the embodiment, it is preferable for the fourth sipe 341 to be the only one or the tire width direction length L5 including the fourth lug groove 342 to be 70% or less of the width B4 of the fourth land portion 34 in order to obtain the effects of the present disclosure (see FIG. 4). In addition, in the pneumatic tire 1 of the embodiment, it is preferable in order to obtain the effects of the present disclosure that the fourth lug groove 342 has a tire width direction length L6 of 40% or less of the width B4 of the fourth land portion 34 (see FIG. 4).

2, the narrow groove 351 of the fifth land portion 35 is provided on the tire width direction outer side of the fourth main groove 24 and extends in the tire circumferential direction. The narrow groove 351 is formed with a groove width narrower than the fourth main groove 24. Specifically, in order to obtain the effects of the present disclosure, it is preferable that the narrow groove 351 is formed with a groove width of 20% or less of the fourth main groove 24. At least one narrow groove 351 is provided in the tire width direction. When multiple narrow grooves 351 are provided, about two are preferable in order to suppress the generation of noise.

As shown in FIG. 2, the fifth sipe 352 of the fifth land portion 35 is formed with one end penetrating the narrow groove 351 and the other end extending outward in the tire width direction. The fifth sipe 352 is a joint point where one end does not penetrate the narrow groove 351. That is, the fifth sipe 352 is provided at a position where it penetrates the narrow groove 351, shifting its position in the tire circumferential direction so that it does not face on an extension line when there is a sipe or groove penetrating the narrow groove 351 on the inner side in the tire width direction. The fifth sipe 352 is provided in a plurality of rows in the tire circumferential direction. The fifth sipe 352 may have an unequal pitch in the tire circumferential direction due to pitch variation. This fifth sipe 352 is the only one formed on the outer side in the tire width direction of the narrow groove 351 of the fifth land portion 35, and no other grooves are formed on the outer side in the tire width direction of the narrow groove 351. This is called a sipe base.

In order to obtain the effects of the present disclosure, it is preferable that the fifth sipe 352 be formed in a three-dimensional shape, like the sipe 101 shown in Figures 5 and 6. The fifth sipe 352 of the embodiment has the three-dimensional shape of the sipe 101 shown in Figure 6.

2, the fifth lug groove 353 of the fifth land portion 35 is formed so that one end penetrates the fourth main groove 24 in the fifth land portion 35 and the other end terminates within the fifth land portion 35, and extends in the tire width direction. A plurality of fifth lug grooves 353 are provided side by side in the tire circumferential direction. The fifth lug grooves 353 may have an unequal pitch in the tire circumferential direction due to pitch variation.

In the pneumatic tire 1 of the embodiment, as shown in Figures 2 to 4, the second sipe 321, the second lug groove 322, the third sipe 331, the third lug groove 332, the fourth sipe 341, and the fourth lug groove 342 provided in the second land portion 32, the third land portion 33, and the fourth land portion 34, which are the center land portions, are preferably provided with an inclination in the same direction with respect to the tire width direction in order to obtain the effects of the present disclosure. Also, in the pneumatic tire 1 of the embodiment, as shown in Figure 2, the first sipe 311, the fifth sipe 352, and the fifth lug groove 353 provided in the first land portion 31 and the fifth land portion 35, which are the shoulder land portions, have an inclination in the same direction as the second sipe 321, the second lug groove 322, the third sipe 331, the third lug groove 332, the fourth sipe 341, and the fourth lug groove 342.

As described above, the pneumatic tire 1 of the embodiment has a specified orientation relative to the vehicle width direction when mounted on a vehicle, and has a tread pattern 15b on the tread surface 15a that is asymmetric in the tire width direction with the tire equatorial plane CL as the boundary. The tread pattern 15b includes a first main groove 21, a second main groove 22, a third main groove 23 and a fourth main groove 24 which extend in the circumferential direction of the tire and are provided in four in the tire width direction from the inner side in the vehicle width direction to the outer side in the vehicle width direction, with the groove width at least at the outermost part in the vehicle width direction being narrower than the innermost part in the vehicle width direction; a first land portion 31, a second land portion 32, a third land portion 33, a fourth land portion 34 and a fifth land portion 35 which are partitioned by the main grooves 21, 22, 23 and 24 and extend in the circumferential direction of the tire in a rib shape and are provided in the tire width direction from the inner side in the vehicle width direction to the outer side in the vehicle width direction; at least one narrow groove 351 which extends in the circumferential direction of the tire in the fifth land portion 35 and is provided in the tire width direction and has a groove width narrower than the fourth main groove 24; and a narrow groove 351 which extends in the circumferential direction of the tire and is provided in the tire width direction in the fifth land portion 35, with one end of the first land portion 31 penetrating the first main groove 21 but not penetrating through, and the other end of the narrow groove 351 which is provided in the tire width direction. the first sipe 311 being the only one in the first land portion 31 extending in the tire width direction and provided in multiple numbers in the tire circumferential direction; the second sipe 321 being the only one in the first land portion 31 extending in the tire width direction and provided in multiple numbers in the tire circumferential direction in the second land portion 32; the third sipe 331 being the only one in the first land portion 31 extending in the tire width direction and provided in multiple numbers in the tire circumferential direction in the third land portion 33; the fourth sipe 341 being the only one in the tire width direction and provided in multiple numbers in the tire circumferential direction in the fourth land portion 34; the fifth sipe 352 being the only one on the tire width direction outer side of the narrow grooves 351 in the fifth land portion 35, one end of which penetrates into the narrow groove 351 but does not pass through, and the other end of which extends outward in the tire width direction and terminates without penetrating the narrow groove 351, and which is provided in multiple numbers in the tire circumferential direction. Furthermore, the second sipes 321 have more than twice the number of the third sipes 331 and the fourth sipes 341, the sipes 321, 331, 341 and grooves (322, 332, 342) provided in the second land portion 32, the third land portion 33 and the fourth land portion 34 are inclined in the same direction relative to the tire width direction, and the first sipe 311, the fifth sipe 352 and the fifth lug groove 353 have an inclination in the same direction as the sipes 321, 331, 341 and grooves (322, 332, 342) provided in the second land portion 32, the third land portion 33 and the fourth land portion 34.

With this pneumatic tire 1, in the above configuration, drainage performance is ensured on the inner side in the vehicle width direction, resulting in high wet grip performance, and pitch noise is reduced on the outer side in the vehicle width direction, resulting in noise performance. Specifically, according to this pneumatic tire 1, mainly, the groove width of the first main groove 21 is wide on the inner side in the vehicle width direction, and the groove width of the fourth main groove 24 is narrow on the outer side in the vehicle width direction, thereby achieving both drainage performance and reduction of pitch noise; the number of second sipes 321 in the second land portion 32 is greater than the third land portion 33 and the fourth land portion 34, thereby achieving both drainage performance and reduction of pitch noise; the narrow groove 351 is formed in the fifth land portion 35 on the outer side in the vehicle width direction, and the groove volume is compensated for to compensate for the narrow groove width of the fourth main groove 24, thereby compensating for the drainage performance on the outer side in the vehicle width direction; the fifth lug groove 353 is not allowed to penetrate the narrow groove 351, thereby reducing pitch noise; the fifth sipe 311 and the fifth sipe 352 are configured not to penetrate, and the circumferential position relationship with the other sipes is shifted to reduce pitch noise; and the direction of the inclination angle of the sipes and lug grooves is aligned to improve drainage performance.

In addition, in the pneumatic tire 1 of the embodiment, the second land portion 32 includes a second lug groove 322 having one end penetrating into the first main groove 21 or the second main groove 22 and the other end terminating within the second land portion 32, and the second sipe 321 has one end penetrating into the second main groove 22 or the first main groove 21 and the other end penetrating into the other end of the second lug groove 322.

With this pneumatic tire 1, wet grip performance and noise performance can be achieved at the same time by ensuring the minimum necessary groove volume on the inner side in the vehicle width direction in the second land portion 32 close to the inner side in the vehicle width direction.

In addition, in the pneumatic tire 1 of the embodiment, the second lug grooves 322 and second sipes 321 that are continuous with each other are arranged in a staggered pattern along the circumferential direction of the tire.

With this pneumatic tire 1, the asymmetric tread pattern 15b reduces the difference in drainage performance that occurs when the rotation direction is reversed during tire rotation, thereby improving wet grip performance.

In addition, in the pneumatic tire 1 of the embodiment, the second lug grooves 322 penetrate the second sipes 321 in a biased manner in the circumferential direction of the tire, and the bias is arranged in a staggered pattern along the circumferential direction of the tire.

With this pneumatic tire 1, pitch noise can be reduced by dispersing the period around the tire circumference, thereby improving noise performance.

In addition, in the embodiment of the pneumatic tire 1, the third sipe 331 has one end penetrating the second main groove 22 and the other end terminating within the third land portion 33, and the fourth sipe 341 has one end penetrating the third main groove 23 and the other end terminating within the fourth land portion 34.

With this pneumatic tire 1, noise performance can be improved by preventing pumping noise from leaking out.

In addition, the pneumatic tire 1 of the embodiment includes a third lug groove 332 having one end penetrating into the second main groove 22 in the third land portion 33 and the other end terminating within the third land portion 33, and a fourth lug groove 342 having one end penetrating into the third main groove 23 in the fourth land portion 34 and the other end terminating within the fourth land portion 34. One end of the third sipe 331 penetrates into the other end of the third lug groove 332 and penetrates into the second main groove 22 via the third lug groove 332, and one end of the fourth sipe 341 penetrates into the other end of the fourth lug groove 342 and penetrates into the third main groove 23 via the fourth lug groove 342.

With this pneumatic tire 1, it is possible to achieve both wet grip performance and noise performance by ensuring groove volume within the minimum necessary range.

In addition, in the embodiment of the pneumatic tire 1, the third lug groove 332 is formed with a circumferential groove width that expands from the other end to one end, and the fourth lug groove 342 is formed with a circumferential groove width that expands from the other end to one end.

With this pneumatic tire 1, it is possible to achieve both wet grip performance and noise performance by further ensuring groove volume within the minimum necessary range.

In addition, in the pneumatic tire 1 of the embodiment, the third sipe 331 has a three-dimensional shape.

With this pneumatic tire 1, it is possible to achieve both suppression of uneven wear in the third land portion 33 on the inner side in the tire width direction by ensuring rigidity and ensuring drainage performance.

In addition, in the pneumatic tire 1 of the embodiment, the first sipe 311 and the fifth sipe 352 have a three-dimensional shape.

This pneumatic tire 1 prevents the first land portion 31 and the fifth land portion 35 on the outer side in the tire width direction from collapsing, prevents heel-and-toe wear in the tire circumferential direction between the sipes, reduces pitch noise, and improves noise performance.

In this embodiment, as described above, a pneumatic tire has been described as an example of a tire. However, the present invention is not limited to this, and the configuration described in this embodiment can be arbitrarily applied to other tires within the scope of what is obvious to a person skilled in the art. Examples of other tires include airless tires.

7 and 8 are diagrams showing the results of performance tests of pneumatic tires according to the embodiment. Below, performance evaluation tests conducted on a conventional pneumatic tire, a comparative pneumatic tire, and an example pneumatic tire according to the embodiment will be described. The performance evaluation tests were conducted on noise performance and wet grip performance.

For the noise performance evaluation test, pneumatic tires with tire size 235/50R18 97W were mounted on standard rims with rim size 18x7.5J as specified by JATMA, and were then fitted to a 2WD minivan test vehicle. Air pressure was set to 230kPa for the front and 240kPa for the rear. In the evaluation test, a test driver drove the test vehicle on a test course, and the noise energy at the driver's inner ear was measured and indexed. This evaluation was performed using an index evaluation with the conventional example as the standard (100), and the higher the reciprocal of the value, the better the noise performance.

For the wet grip performance evaluation test, a pneumatic tire with a tire size of 235/50R18 97W was mounted on a standard rim with a rim size of 18x7.5J as specified by JATMA, and was installed on a 2WD minivan as a test vehicle. An air pressure of 220kPa was applied to both the front and rear. In the evaluation test, a test driver drove the test vehicle on a test course with a road surface conforming to the R711 standard, and the wet grip performance was measured and indexed based on the μ-s characteristics. This evaluation was performed using an index evaluation with the conventional example as the standard (100), and the higher the value, the better the noise performance.

In the conventional pneumatic tire, all four main grooves have the same groove width, there are no narrow grooves, the ratio of the second sipe to the third sipe and the fourth sipe is the same, the first sipe is set through the groove, and the fifth lug groove penetrates and is continuous with the fifth sipe.

In the pneumatic tire of Example 1, the first main groove of the four main grooves has the widest groove width, the second and third main grooves have the same groove width narrower than the first main groove, the fourth main groove has the narrowest groove width, has a narrow groove narrower than the fourth main groove, the ratio of the second sipes to the third and fourth sipes is twice as large as the second sipes, the first and fifth sipes are provided penetrating the grooves without penetrating them, and the fifth lug groove is provided penetrating only the fourth main groove. In addition, other characteristic points are specified for the pneumatic tires of Examples 2 to 15.

The pneumatic tires of Comparative Example 1 to Comparative Example 4 differ in some of the regulations from the pneumatic tire of Example 1.

And, as shown by the test results, the pneumatic tire of this embodiment has improved noise performance and wet grip performance compared to the conventional example.

The present disclosure includes the following inventions.
[Invention 1]
A tire having an asymmetric tread pattern on a tread surface, the orientation of which is specified relative to the vehicle width direction when mounted on a vehicle, the tire having an asymmetric tread pattern with the tire equatorial plane as a boundary,
The tread pattern is
First, second, third and fourth main grooves extending in the tire circumferential direction and provided in the tire width direction from the inner side in the vehicle width direction to the outer side in the vehicle width direction, the groove width of at least the outermost groove in the vehicle width direction being narrower than that of the innermost groove in the vehicle width direction;
First, second, third, fourth and fifth land portions are partitioned by the main grooves, extend in a rib shape in the tire circumferential direction, and are provided in the tire width direction from the inner side in the vehicle width direction to the outer side in the vehicle width direction;
At least one narrow groove is provided in the fifth land portion, extending in the tire circumferential direction and in the tire width direction, and has a groove width narrower than that of the fourth main groove;
a first sipe, which is the only one in the first land portion and is provided in the tire circumferential direction, and one end of which does not penetrate through the first main groove and the other end of which extends outward in the tire width direction in the first land portion;
A plurality of second sipes extending in the tire width direction and provided in the tire circumferential direction in the second land portion;
A plurality of third sipes extending in the tire width direction and provided in the tire circumferential direction in the third land portion;
A plurality of fourth sipes extending in the tire width direction and provided in the tire circumferential direction in the fourth land portion;
a fifth sipe, which is the only one on the outer side in the tire width direction of the narrow groove provided in the fifth land portion, and which has one end penetrating the narrow groove but not penetrating therethrough and the other end extending outward in the tire width direction, and which is provided in a plurality of the narrow grooves in the tire circumferential direction;
A plurality of fifth lug grooves are provided in the fifth land portion in the circumferential direction of the tire, each of which has one end penetrating into the fourth main groove and the other end extending outward in the tire width direction and terminating without penetrating into the narrow groove;
Including,
The second sipes have a number that is at least twice as large as the third sipes and the fourth sipes,
The sipes and grooves provided in the second land portion, the third land portion, and the fourth land portion are inclined in the same direction with respect to the tire width direction,
The first sipe, the fifth sipe, and the fifth lug groove have an inclination in the same direction as the sipes and the grooves provided in the second land portion, the third land portion, and the fourth land portion.
tire.
[Invention 2]
The second land portion includes a second lug groove, one end of which penetrates the first main groove or the second main groove and the other end of which terminates within the second land portion,
The second sipe has one end penetrating the second main groove or the first main groove, and the other end penetrating the other end of the second lug groove.
2. The tire according to claim 1.
[Invention 3]
The second lug grooves and the second sipes which penetrate each other are arranged in a staggered manner along the tire circumferential direction.
A tire according to claim 2.
[Invention 4]
The second lug grooves penetrate the second sipes in a circumferential direction of the tire in a biased manner, and the bias is arranged in a staggered manner along the circumferential direction of the tire.
A tire according to claim 3.
[Invention 5]
The third sipe has one end penetrating the second main groove and the other end terminating within the third land portion,
The fourth sipe has one end penetrating the third main groove and the other end terminating within the fourth land portion.
A tire according to any one of claims 1 to 4.
[Invention 6]
a third lug groove having one end penetrating into the second main groove in the third land portion and the other end terminating within the third land portion;
a fourth lug groove having one end penetrating the third main groove in the fourth land portion and the other end terminating within the fourth land portion;
Including,
The third sipe has one end penetrating the other end of the third lug groove and penetrating the second main groove via the third lug groove,
The fourth sipe has one end penetrating through the other end of the fourth lug groove and penetrating through the fourth lug groove into the third main groove.
A tire according to claim 5.
[Invention 7]
The third lug groove is formed such that a circumferential groove width increases from the other end to the one end,
The fourth lug groove is formed such that a circumferential groove width increases from the other end to the one end.
A tire according to claim 6.
[Invention 8]
The tire according to any one of claims 1 to 7, wherein the third sipe has a three-dimensional shape.
[Invention 9]
The tire according to any one of claims 1 to 8, wherein the first sipe and the fifth sipe have a three-dimensional shape.

1. Pneumatic tires (tires)
15b Tread pattern 15a Tread surface 21 First main groove 22 Second main groove 23 Third main groove 24 Fourth main groove 31 First land portion 32 Second land portion 33 Third land portion 34 Fourth land portion 35 Fifth land portion 311 First sipe 321 Second sipe 322 Second lug groove 331 Third sipe 332 Third lug groove 341 Fourth sipe 342 Fourth lug groove 351 Narrow groove 352 Fifth sipe 353 Fifth lug groove

Claims (9)

A tire having an asymmetric tread pattern on a tread surface, the orientation of which is specified relative to the vehicle width direction when mounted on a vehicle, the tire having an asymmetric tread pattern with the tire equatorial plane as a boundary,
The tread pattern is
First, second, third and fourth main grooves extending in the tire circumferential direction and provided in the tire width direction from the inner side in the vehicle width direction to the outer side in the vehicle width direction, the groove width of at least the outermost groove in the vehicle width direction being narrower than that of the innermost groove in the vehicle width direction;
First, second, third, fourth and fifth land portions are partitioned by the main grooves, extend in a rib shape in the tire circumferential direction, and are provided in the tire width direction from the inner side in the vehicle width direction to the outer side in the vehicle width direction;
At least one narrow groove is provided in the fifth land portion, extending in the tire circumferential direction and in the tire width direction, and has a groove width narrower than that of the fourth main groove;
a first sipe, which is the only one in the first land portion and is provided in the tire circumferential direction, and one end of which does not penetrate through the first main groove and the other end of which extends outward in the tire width direction in the first land portion;
A plurality of second sipes extending in the tire width direction and provided in the tire circumferential direction in the second land portion;
A plurality of third sipes extending in the tire width direction and provided in the tire circumferential direction in the third land portion;
A plurality of fourth sipes extending in the tire width direction and provided in the tire circumferential direction in the fourth land portion;
a fifth sipe, which is the only one on the outer side in the tire width direction of the narrow groove provided in the fifth land portion, and which has one end penetrating the narrow groove but not penetrating therethrough and the other end extending outward in the tire width direction, and which is provided in a plurality of the narrow grooves in the tire circumferential direction;
A plurality of fifth lug grooves are provided in the fifth land portion in the circumferential direction of the tire, each of which has one end penetrating into the fourth main groove and the other end extending outward in the tire width direction and terminating without penetrating into the narrow groove;
Including,
The second sipes have a number that is at least twice as large as the third sipes and the fourth sipes,
The second sipes, the third sipes, the fourth sipes, and the grooves provided in the second land portion, the third land portion, and the fourth land portion are inclined in the same direction with respect to the tire width direction, and the first sipes, the fifth sipes, and the fifth lug grooves have an inclination in the same direction as the second sipes, the third sipes, the fourth sipes, and the grooves provided in the second land portion, the third land portion, and the fourth land portion.
tire. The second land portion includes a second lug groove, one end of which penetrates the first main groove or the second main groove and the other end of which terminates within the second land portion,
The second sipe has one end penetrating the second main groove or the first main groove, and the other end penetrating the other end of the second lug groove.
2. The tire of claim 1. The second lug grooves and the second sipes which penetrate each other are arranged in a staggered manner along the tire circumferential direction.
3. The tire of claim 2. The second lug grooves penetrate the second sipes in a circumferential direction of the tire in a biased manner, and the bias is arranged in a staggered manner along the circumferential direction of the tire.
4. The tire of claim 3. The third sipe has one end penetrating the second main groove and the other end terminating within the third land portion,
The fourth sipe has one end penetrating the third main groove and the other end terminating within the fourth land portion.
2. The tire of claim 1. a third lug groove having one end penetrating into the second main groove in the third land portion and the other end terminating within the third land portion;
a fourth lug groove having one end penetrating the third main groove in the fourth land portion and the other end terminating within the fourth land portion;
Including,
The third sipe has one end penetrating the other end of the third lug groove and penetrating the second main groove via the third lug groove,
The fourth sipe has one end penetrating through the other end of the fourth lug groove and penetrating through the fourth lug groove into the third main groove.
6. The tire of claim 5. The third lug groove is formed such that a circumferential groove width increases from the other end to the one end,
The fourth lug groove is formed such that a circumferential groove width increases from the other end to the one end.
7. The tire of claim 6. The tire of claim 1, wherein the third sipe has a three-dimensional shape. The tire of claim 1, wherein the first sipe and the fifth sipe have a three-dimensional shape.

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