Patent Description:
The present invention relates to a tire.

<CIT> (Patent Literature <NUM>) has proposed a tire having a shoulder land region provided with a plurality of shoulder sipes. Tires similar with respect to said shoulder land region are also disclosed in <CIT> and <CIT>. It is noted that <CIT> is a state of the art document according to Art. <NUM>(<NUM>) EPC.

Further improvement in braking performance has been demanded of tires provided with shoulder sipes as the one disclosed in Patent Literature <NUM> above. On the other hand, in recent years, vehicles have become noticeably quieter, and it is necessary to give due consideration to noise performance of tires.

The present invention was made in view of the above, and a primary object thereof is to provide a tire with improved braking performance while suppressing deterioration of the noise performance.

The present invention is a tire having a tread portion including:.

By adopting the above configuration, it is possible that the tire of the present invention improves the braking performance while suppressing the deterioration of the noise performance.

An embodiment of the present invention will now be described below in conjunction with accompanying drawings. <FIG> is a developed view of a tread portion <NUM> of a tire <NUM> of the present embodiment. As shown in <FIG>, the tire <NUM> of the present embodiment is suitable for use as a pneumatic tire for passenger cars, for example. However, the present invention is not limited to such an aspect, and may be applied to heavy-duty pneumatic tires and non-pneumatic tires that are not filled with pressurized air.

As shown in <FIG>, the tire <NUM> of the present invention has a tread portion <NUM> of which position for mounting the tire on a vehicle is specified regarding inner and outer sides of the tread portion with respect to the vehicle. The tread portion <NUM> includes a first tread edge T1, which is on the outer side of the vehicle when the tire <NUM> is mounted on the vehicle, and a second tread edge T2, which is on the inner side of the vehicle when the tire <NUM> is mounted on the vehicle. The mounting position to the vehicle is indicated by characters or symbols on a sidewall portion (not shown), for example. However, the tire <NUM> of the present invention is not limited to such a manner.

The first tread edge T1 and the second tread edge T2 are the outermost ground contact positions in a tire axial direction of the tire <NUM> when the tire <NUM> in a standard state is in contact with a flat surface with zero camber angle by being loaded with <NUM>% of a standard tire load.

The term "standard state" refers to a state in which the tire <NUM> is mounted on a standard rim (not shown), inflated to a standard inner pressure, and loaded with no tire load. In the case of tires for which various standards have not been established or non-pneumatic tires, the standard state means a standard state of use according to the purpose of use of the tire loaded with no tire load. In the present specification, unless otherwise specified, dimensions of various parts of the tire are values measured in the standard state. Further, in the present specification, unless otherwise noted, known methods can be applied as appropriate to measure the aforementioned dimensions and composition of materials.

The term "standard rim" refers to a wheel rim specified for the concerned tire by a standard included in a standardization system on which the tire is based, for example, the "normal wheel rim" in JATMA, "Design Rim" in TRA, and "Measuring Rim" in ETRTO.

The term "standard inner pressure" refers to air pressure specified for the concerned tire by a standard included in a standardization system on which the tire is based, for example, the maximum air pressure in JATMA, maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table in TRA, and "INFLATION PRESSURE" in ETRTO.

The term "standard tire load" refers to a tire load specified for the concerned tire by a standard included in a standardization system on which the tire is based, for example, the "maximum load capacity" in JATMA, maximum value listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table in TRA, and "LOAD CAPACITY" in ETRTO. For tires for which various standards have not been established, "standard tire load" refers to the maximum applicable load for the use of the tire according to the above-mentioned standards.

The tread portion <NUM> includes a plurality of circumferential grooves <NUM> extending continuously in a tire circumferential direction between the first tread edge T1 and the second tread edge T2, and a plurality of land regions <NUM> divided by the circumferential grooves <NUM>. The tire <NUM> of the present embodiment is configured as a so-called five-rib tire where the tread portion <NUM> is divided by four circumferential grooves <NUM> into five land regions <NUM>. However, the tire <NUM> of the present invention is not limited to such a mode, but may be configured, for example, as a so-called four-rib tire having the tread portion <NUM> divided into four land regions <NUM> by three circumferential grooves <NUM>.

The circumferential grooves <NUM> include a first shoulder circumferential groove <NUM>. The first shoulder circumferential groove <NUM> is arranged closest to the first tread edge T1 among the multiple circumferential grooves <NUM>. In addition, the circumferential grooves <NUM> include a second shoulder circumferential groove <NUM>, a first crown circumferential groove <NUM> and a second crown circumferential groove <NUM>. The second shoulder circumferential groove <NUM> is arranged closest to the second tread edge T2 among the multiple circumferential grooves <NUM>. The first crown circumferential groove <NUM> is arranged between the first shoulder circumferential groove <NUM> and a tire equator (C). The second crown circumferential groove <NUM> is arranged between the second shoulder circumferential groove <NUM> and the tire equator (C).

It is preferred that a distance L1 from the tire equator (C) to a groove centerline of the first shoulder circumferential groove <NUM> or the second shoulder circumferential groove <NUM> is <NUM>% or more and <NUM>% or less of a tread width TW. It is preferred that a distance L2 from the tire equator (C) to a groove centerline of the first crown circumferential groove <NUM> or the second crown circumferential groove <NUM> is <NUM>% or more and <NUM>% or less of the tread width TW. It should be noted that the tread width TW is the distance in the tire axial direction from the first tread edge T1 to the second tread edge T2 of the tire <NUM> in the standard state.

The land regions <NUM> of the present invention include a first shoulder land region <NUM>. The first shoulder land region <NUM> is demarcated axially outside the first shoulder circumferential groove <NUM> and includes the first tread edge T1. In addition, the land regions <NUM> in the present embodiment include a second shoulder land region <NUM>, a first middle land region <NUM>, a second middle land region <NUM>, and a crown land region <NUM>. The second shoulder land region <NUM> is demarcated axially outside the second shoulder circumferential groove <NUM> and includes the second tread edge T2. The first middle land region <NUM> is demarcated between the first shoulder circumferential groove <NUM> and the first crown circumferential groove <NUM>. The second middle land region <NUM> is demarcated between the second shoulder circumferential groove <NUM> and the second crown circumferential groove <NUM>. The crown land region <NUM> is demarcated between the first crown circumferential groove <NUM> and the second crown circumferential groove <NUM>.

<FIG> shows an enlarged view of the first shoulder land region <NUM>. As shown in <FIG>, the first shoulder land region <NUM> includes a first longitudinal edge <NUM> located on the first shoulder circumferential groove <NUM> side and a shoulder center position (11c), which is the center position in the tire axial direction between the first longitudinal edge <NUM> and the first tread edge T1. Further, the first shoulder land region <NUM> is provided with a plurality of first shoulder sipes <NUM> extending from the first longitudinal edge <NUM> to at least the first tread edge T1.

In the present specification, the term "sipe" means a groove-shaped body having a small width (a concept that includes grooves and sipes), where the width between the two inner walls is <NUM> or less in the area excluding chamfered portions, which will be described later. Further, the area excluding the chamfered portions means the area where the two inner walls extend in a tire radial direction parallel to each other. The term "parallel" means that an angle between the two inner walls is <NUM> degrees or less. The width between the two inner walls in the area excluding the chamfered portions is preferably <NUM> or less, and in a more preferred manner from <NUM> to <NUM>. Furthermore, an overall depth of each of the sipes is <NUM> or more and <NUM> or less, for example. In addition, the sipes may also have a so-called flask bottom with an increased width at the bottom. It should be noted that in the present specification, if one of the groove shaped bodies has a portion with the width exceeding <NUM> over more than <NUM>% of the overall depth thereof, the one of the groove shaped bodies shall be regarded as a groove.

<FIG> shows an enlarged view of one of the first shoulder sipes <NUM>. <FIG> shows a cross-sectional view taken along A-A line of <FIG>. <FIG> shows a cross-sectional view taken along B-B line of <FIG>. As shown in <FIG>, each of the first shoulder sipes <NUM> in the present invention has a chamfered portion <NUM> in the entire lengthwise range from the first longitudinal edge <NUM> to the first tread edge T1. In the present embodiment, the chamfered portion <NUM> is formed by sloped surfaces (20a) provided in both of the two sipe walls, but the chamfered portion <NUM> of the present invention may also be formed by the sloped surface (20a) provided in only one of the two sipe walls.

Each of the chamfered portions <NUM> includes a first chamfered portion <NUM> demarcated between the shoulder center position (11c) and the first longitudinal edge <NUM> and a second chamfered portion <NUM> demarcated between the shoulder center position (11c) and the first tread edge T1. In the present invention, the second chamfered portion <NUM> has a chamfer volume V2 larger than a chamfer volume V1 of the first chamfered portion <NUM>. By adopting the above configuration, it is possible that the tire <NUM> of the present invention improves the cornering performance while suppressing the deterioration of the noise performance. The mechanism is as follows.

<FIG> shows an enlarged cross-sectional view of a conventional sipe (a) without a chamfered portion in a state of contacting a road surface (G). <FIG> shows a state during braking, with an arrow (R) indicating a tire rotational direction and an arrow (A) indicating a tire running direction. As shown in <FIG>, in general, when a large shearing force (braking force in <FIG>) is applied around the sipe (a) without the chamfered portion, such as during braking or cornering, an edge (b) of the sipe (a) is pulled inside a ground contacting surface of the land region, and eventually a surface (c) of the land region in the vicinity thereof is locally lifted from the road surface, and thus sufficient grip may not be exerted. Conventionally, this tends to impair braking performance and the cornering performance.

As shown in <FIG>, in the present invention, each of the first shoulder sipes <NUM> is provided with the chamfered portion <NUM> throughout the entire lengthwise range from the first longitudinal edge <NUM> to the first tread edge T1. Therefore, it is possible that the tire <NUM> of the present invention suppresses the above-described problems and improves the braking performance and the cornering performance. Further, in the present invention, since the chamfer volume V2 of the second chamfered portion <NUM> is relatively large, a sufficient size of the chamfered portion can be secured on the first tread edge T1 side of the first shoulder land region <NUM>. As a result, in the formation range of the second chamfered portion <NUM> of each of the first shoulder sipes <NUM>, a ground contacting property is further improved, therefore, the cornering performance can be expected to be further improved.

Further, in general, as the chamfer volume of a sipe increases, running noise (pumping noise, for example) caused by the increase in the sipe volume tends to increase. In the present invention, the relatively small chamfer volume V1 of the first chamfered portion <NUM> can suppress an increase in noise caused by the increase in the sipe volume due to the chamfered portion <NUM>, thereby, it is possible that the deterioration of the noise performance is suppressed.

<FIG> shows an enlarged cross-sectional view of one of the chamfered portions <NUM>. As shown in <FIG>, each of the chamfered portions <NUM> in the present embodiment includes the sloped surfaces (20a) each inclined to connect a main body (25a) of a respective one of sipe walls <NUM> with a ground contacting surface (<NUM>) of the first shoulder land region <NUM> so that sharp corners are not formed between the sipe walls <NUM> of each of the first shoulder sipes <NUM> and the ground contacting surface (<NUM>) of the first shoulder land region <NUM>. Each of the sloped surfaces (20a) in the present embodiment is planar (that is, straight in the lateral cross-section of the sipe), but each of the sloped surfaces (20a) may be smoothly curved so as to be convex radially outward. Further, an opening width of each of the chamfered portions <NUM> may exceed <NUM>, for example. Each of the chamfered portions <NUM> has a depth (d2) of <NUM>% or more and <NUM>% or less of an overall depth (d1) (shown in <FIG>) of each of the first shoulder sipes <NUM>, for example.

The chamfer volume is defined as follows. That is, in the case that each of the first shoulder sipes <NUM> has the chamfered portion on one of the sipe walls thereof, the chamfer volume is the volume of the portion surrounded by a virtual ground contacting surface (11v) and a virtual sipe wall (25v). The virtual ground contacting surface (11v) is obtained by extending the ground contacting surface (<NUM>) of the first shoulder land region <NUM> in a direction of the opening width of the first shoulder sipe <NUM>. The virtual sipe wall (25v) is obtained by extending the main body (25a) of the sipe wall <NUM> to the virtual ground contacting surface (11v). In the case that both of the two sipe walls <NUM> have the sloped surfaces (20a) as shown in <FIG>, the chamfer volume is the sum of the volumes of the two portions shaded with dots.

Each of the sloped surfaces (20a) of the chamfered portion <NUM> means a surface from the main body (25a) of a respective one of the sipe walls <NUM> to the ground contacting surface (<NUM><NUM>) of the first shoulder land region <NUM>. It should be noted that, when the tire <NUM> in the standard state is in contact with a flat surface with zero camber angle by being loaded with <NUM>% of the standard tire load, an edge of the outer surface of the first shoulder land region <NUM> contacting the plane is a boundary <NUM> between each of the sloped surfaces (20a) and the ground contacting surface (<NUM>). The virtual ground contacting surface (11v) is a virtual surface obtained by extending the ground contacting surface (<NUM>) from the boundary <NUM> in the opening width direction of the sipe. If the ground contacting surface is curved, in a cross-sectional view of each of the first shoulder sipes <NUM>, the virtual ground contacting surface (11v) corresponds to a curved line extending from the boundary <NUM> while maintaining the curvature of the ground contacting surface (<NUM>).

The virtual sipe wall (25v) is a virtual surface obtained by extending the main body (25a) of each of the sipe walls <NUM> from a boundary <NUM> between the main body (25a) and a respective one of the sloped surfaces (20a) to the virtual ground contacting surface (11v). The boundary <NUM> between the main body (25a) of each of the sipe walls <NUM> and a respective one of the sloped surfaces (20a) is a location where the angle of the sipe wall <NUM> with respect to the tire radial direction changes abruptly. It should be noted that if the location where the angle changes abruptly is a region having a substantial width, the position closest to the groove centerline corresponds to the boundary <NUM>.

A more detailed configuration of the present embodiment will be described below. It should be noted that each of the configurations described below is a specific form of the present embodiment. Therefore, it goes without saying that the present invention can achieve the effects described above even if it does not have the configurations described below. Further, even if any one of the configurations described below is applied alone to the tire of the present invention with the features described above, improvement in performance can be expected according to each configuration. Furthermore, when some of the configurations described below are applied in combination, a combined improvement in performance can be expected according to the combined configurations.

As shown in <FIG>, the ground contacting surface (<NUM>) of the first shoulder land region <NUM> in the present embodiment is provided with only sipes and not provided with grooves between the first longitudinal edge <NUM> and the first tread edge T1. Thereby, the cornering performance is further improved. However, the present invention is not limited to such an aspect, and the ground contacting surface (<NUM>) of the first shoulder land region <NUM> may be provided with grooves.

It is preferred that an angle of each of the first shoulder sipes <NUM> (an angle on the acute angle side) with respect to the tire circumferential direction increases continuously from the first longitudinal edge <NUM> to the first tread edge T1. Therefore, the cornering performance and the breaking performance are improved in a good balance.

At the first longitudinal edge <NUM>, an angle θ1 of each of the first shoulder sipes <NUM> with respect to the tire circumferential direction is preferably <NUM> degrees or more, more preferably <NUM> degrees or more, still more preferably <NUM> degrees or more, and preferably <NUM> degrees or less, more preferably <NUM> degrees or less. In the embodiment shown in <FIG>, the angle θ1 is about <NUM> to <NUM> degrees, but the angle θ1 is not limited to this, and may be from <NUM> to <NUM> degrees in another embodiment. The first shoulder sipes <NUM> configured as such can provide a large frictional force in the tire axial direction on the first longitudinal edge <NUM> side, therefore, it is possible that the cornering performance is further improved. On the other hand, at the first tread edge T1, an angle θ2 of each of the first shoulder sipes <NUM> with respect to the tire circumferential direction is <NUM> degrees or more and <NUM> degrees or less, and preferably <NUM> degrees or more and <NUM> degrees or less, for example.

As shown in <FIG>, each of the chamfered portions <NUM> has a cross-sectional area taken perpendicular to a longitudinal direction of the sipe and increasing (continuously in the present embodiment) axially outward. In each of the chamfered portions <NUM> of the present embodiment, the cross-sectional area increases continuously from the first longitudinal edge <NUM> to the first tread edge T1. As a result, uneven wear around the first shoulder sipes <NUM> is suppressed.

From the point of view of improving the noise performance and the cornering performance in a good balance, the chamfer volume V2 of each of the second chamfered portions <NUM> is <NUM> times or more, more preferably <NUM> times or more, and <NUM> times or less, more preferably <NUM> times or less the chamfer volume V1 of each of the first chamfered portions <NUM>.

As shown in <FIG>, each of the two sipe walls <NUM> in the present embodiment includes a sloped surface (20a), therefore, each of the chamfered portions <NUM> includes two sloped surfaces (20a) and these two sloped surfaces (20a) have a symmetrical shape with respect to a sipe centerline in a cross section of the sipe. However, the sloped surfaces (20a) are not limited to such a mode, and these two sloped surfaces (20a) may have different shapes from each other, for example.

Each of the sloped surfaces (20a) has an angle of <NUM> degrees or more and <NUM> degrees or less with respect to the tire radial direction, for example. Further, each of the sloped surfaces (20a) in the second chamfered portions <NUM> has an angle θ3 with respect to the tire radial direction larger than an angle θ4 of each of the sloped surfaces (20a) in the first chamfered portions <NUM> with respect to the tire radial direction. Thereby, it is possible that the cornering performance is further improved.

As shown in <FIG>, the first shoulder land region <NUM> in the present embodiment is provided with a plurality of shoulder terminating sipes <NUM>. Each of the shoulder terminating sipes <NUM> extends at least from the first tread edge T1 toward the first longitudinal edge <NUM> and has a terminating end (30a) as a closed end not connected with other sipes and grooves in the ground contacting surface (<NUM>) of the first shoulder land region <NUM>. Each of the shoulder terminating sipes <NUM> is formed with a chamfered portion <NUM> over the entire lengthwise range thereof from the first tread edge T1 to the terminating end (30a). Further, the chamfered portion <NUM> of each of the shoulder terminating sipes <NUM> has a cross-sectional area taken perpendicular to a longitudinal direction of the sipe and continuously increasing from the terminating end (30a) to the first tread edge T1. It is possible that the shoulder terminating sipes <NUM> configured as such, together with the first shoulder sipes <NUM> described above, improve the cornering performance while suppressing deterioration of the noise performance.

<FIG> shows an enlarged view of the second shoulder land region <NUM>. The second shoulder land region <NUM> in the present embodiment is provided with a plurality of second shoulder sipes <NUM>. Each of the second shoulder sipes <NUM> extends from the second tread edge T2 to the second shoulder circumferential groove <NUM>. Each of the second shoulder sipes <NUM> has a chamfered portion <NUM> formed over the entire lengthwise range from the second shoulder circumferential groove <NUM> to the second tread edge T2.

The configuration of the chamfered portions <NUM> of the first shoulder sipes <NUM> described above can be applied to the chamfered portions <NUM> of the second shoulder sipes <NUM>, and the description here is omitted. By including the second shoulder sipes <NUM> configured as such, the tire <NUM> of the present embodiment can further enhance the above-described effects.

<FIG> shows an enlarged view of the first middle land region <NUM>, the second middle land region <NUM>, and the crown land region <NUM>. As shown in <FIG>, the first middle land region <NUM> is provided with first middle sipes <NUM> each completely crossing the ground contacting surface of the first middle land region <NUM> in the tire axial direction. Further, each of the first middle sipes <NUM> is formed with a chamfered portion <NUM> over the entire lengthwise range thereof. In a more preferred embodiment, the chamfered portion <NUM> of each of the first middle sipes <NUM> has a cross-sectional area taken perpendicular to a longitudinal direction of the sipe and continuously increasing from an axial center of the sipe toward both sides in the tire axial direction. It is possible that the first middle sipes <NUM> configured as such, together with the above-mentioned first shoulder sipes <NUM>, improve the cornering performance and the braking performance in a good balance.

The second middle land region <NUM> is provided with a plurality of outer second middle sipes <NUM> and a plurality of inner second middle sipes <NUM>. Each of the outer second middle sipes <NUM> extends axially outward from the second crown circumferential groove <NUM> to have a terminating end (43a) as a closed end not connected with other sipes and grooves in the ground contacting surface of the second middle land region <NUM>. Each of the inner second middle sipes <NUM> extends axially inward from the second shoulder circumferential groove <NUM> to have a closed terminating end not connected with other sipes and grooves in the ground contacting surface of the second middle land region <NUM>.

Each of the outer second middle sipes <NUM> is formed with a chamfered portion <NUM> over the entire lengthwise range thereof. The chamfered portion <NUM> of each of the outer second middle sipes <NUM> has a cross-sectional area taken perpendicular to a longitudinal direction of the sipe and decreasing (continuously in the present embodiment) from the second crown circumferential groove <NUM> toward the terminating end (43a). On the other hand, the inner second middle sipes <NUM> are not chamfered. It is possible that the outer second middle sipes <NUM> and the inner second middle sipes <NUM> configured as such improve the braking performance while suppressing the uneven wear in the land region.

The crown land region <NUM> is provided with a plurality of crown sipes <NUM>. Each of the crown sipes <NUM> extends from the second crown circumferential groove <NUM> toward the tire equator (C) to have a terminating end (50a) as a closed end not connected with other sipes and grooves within a ground contacting surface (<NUM>) of the crown land region <NUM>, for example. Moreover, each of the crown sipes <NUM> is provided with a chamfered portion <NUM> over the entire lengthwise range thereof. The chamfered portion <NUM> of each of the crown sipes <NUM> has a cross-sectional area taken perpendicular to a longitudinal direction of the sipe and decreasing (continuously in the present embodiment) from the second crown circumferential groove <NUM> toward the terminating end (50a). It is possible that the crown sipes <NUM> configured as such improve the braking performance while suppressing the uneven wear in the land region.

As shown in <FIG>, each of the land regions of the present embodiment is provided with only sipes and is not provided with a groove. Thereby, the cornering performance and the braking performance are still further improved.

Claim 1:
A tire (<NUM>) having a tread portion (<NUM>) comprising:
a first tread edge (T1);
a plurality of circumferential grooves (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) extending continuously in a tire circumferential direction; and
a first shoulder land region (<NUM>), wherein
the circumferential grooves (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) include a first shoulder circumferential groove (<NUM>) extending continuously in the tire circumferential direction closest to the first tread edge (T1) among the circumferential grooves (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>),
the first shoulder land region (<NUM>) is demarcated outside the first shoulder circumferential groove (<NUM>) in a tire axial direction and includes a first longitudinal edge (<NUM>) located on the first shoulder circumferential groove side and a shoulder center position (11c),
the shoulder center position (11c) is a center position in the tire axial direction between the first longitudinal edge (<NUM>) and the first tread edge (T1),
the first shoulder land region (<NUM>) is provided with a plurality of first shoulder sipes (<NUM>) extending from the first longitudinal edge (<NUM>) to at least the first tread edge (T <NUM>),
each of the first shoulder sipes (<NUM>) is provided with a chamfered portion (<NUM>, <NUM>, <NUM>) in an entire lengthwise range from the first longitudinal edge (<NUM>) to the first tread edge (T1),
each of the chamfered portions (<NUM>, <NUM>, <NUM>) includes a first chamfered portion (<NUM>) defined between the shoulder center position (11c) and the first longitudinal edge (<NUM>) and a second chamfered portion (<NUM>) defined between the shoulder center position (11c) and the first tread edge (T1),
characterized in that
the second chamfered portion (<NUM>) has a chamfer volume (V2) larger than a chamfer volume (V1) of the first chamfered portion (<NUM>),
wherein the chamfer volume (V2) of the second chamfered portion (<NUM>) is <NUM> times or more and <NUM> times or less the chamfer volume (V1) of the first chamfered portion (<NUM>).