Patent Description:
Conventionally, in the pneumatic tire (hereinafter abbreviated as tire) for four-wheel vehicles such as passenger vehicles, and particularly in the tire for high-performance four-wheel vehicles (including vehicles for racing), a structure having a reinforcing belt (also called a spiral belt), in which a reinforcing cord is wound along the tire circumferential direction, is disposed on the outside of the tire radial direction of a pair of crossing belts is widely used (see Patent Literature <NUM>.

Thus, in particular, the diameter growth in which the tire expands in the tire radial direction during high-speed traveling is effectively suppressed, and high-speed durability can be enhanced.

According to the tire described above, the diameter growth of the tire during high-speed traveling can be suppressed. On the other hand, particularly in the case of a high-performance four-wheel vehicle, there is a demand for further improving a cornering force (CF) at a low slip angle (SA) in such a tire.

Thus, in particular, the cornering force of the rear tire to which the steering angle is not given can be effectively increased, and the lap time of the racecourse can be improved.

Accordingly, an object of the present invention is to provide a tire in which the cornering force generated at a low slip angle is further enhanced while improving high-speed durability.

According to the present invention, there is a tire (pneumatic tire <NUM>) according to claim <NUM>.

Further preferred features are defined in the dependent claims.

Embodiments will be described below with reference to the drawings. The same functions and configurations are denoted by the same or similar reference numerals, and description thereof will be omitted as appropriate.

<FIG> is a sectional view of the pneumatic tire <NUM> according to the present embodiment. Specifically, <FIG> is a cross-sectional view of pneumatic tire <NUM> taken along tire width direction and tire radial direction. In <FIG>, the sectional hatching is partially omitted (hereinafter the same). A tire equatorial line CL represents the center of the pneumatic tire <NUM> in tire width direction and tire circumferential direction.

As shown in <FIG>, the pneumatic tire <NUM> includes a tread <NUM>, a tire side portion <NUM>, the carcass <NUM>, a crossing belt layer <NUM>, a bead portion <NUM> and the spiral belt <NUM>.

The pneumatic tire <NUM> is a pneumatic tire for a four-wheel vehicle such as a passenger vehicle and can be suitably used especially for a high-performance four-wheel vehicle (including vehicles for racing).

The tread <NUM> is a portion in contact with the road surface. On the tread <NUM>, a pattern (unillustrated) corresponding to the use environment of the pneumatic tire <NUM> and the type of vehicle to be mounted is formed.

A circumferential groove <NUM> extending along the tire circumferential direction is formed in the tread <NUM>. The circumferential groove <NUM> is a linear groove extending in parallel with the tire circumferential direction. In this embodiment, three circumferential grooves <NUM> are formed including on the tire equatorial line CL.

A widthwise groove (lug groove) extending to the tire width direction may be formed and may communicate with the circumferential groove <NUM>.

The tire side portion <NUM> is continuous to the tread <NUM> and positioned inside the tire radial direction of the tread <NUM>. The tire side portion <NUM> is an area from the outer edge of the tire width direction of the tread <NUM> to the upper edge of the bead portion <NUM>. The tire side portion <NUM> is sometimes referred to as a sidewall.

The carcass <NUM> forms the skeleton of the pneumatic tire <NUM>. The carcass <NUM> has a radial structure in which a carcass cord <NUM> (not shown in <FIG>, see <FIG>) arranged radially along the tire radial direction is covered with a rubber material. However, the carcass <NUM> is not limited to a radial structure, and may be a bias structure in which the carcass cords <NUM> are arranged so as to cross each other in the tire radial direction.

The crossing belt layer <NUM> is disposed inside the tire radial direction of the tread <NUM>. The crossing belt layer <NUM> is provided between the carcass <NUM> and the spiral belt <NUM>.

The crossing belt layer <NUM> is formed by a pair of crossing belts, specifically, a crossing belt <NUM> and a crossing belt <NUM>. That is, the crossing belt layer <NUM> is disposed inside the tire radial direction of the spiral belt <NUM>.

The crossing belt <NUM> is in contact with the carcass <NUM> and is disposed outside the tire radial direction of the carcass <NUM>. The crossing belt <NUM> is in contact with the crossing belt <NUM> and is disposed outside the tire radial direction of the crossing belt <NUM>.

The bead portion <NUM> is continuous to the tire side portion <NUM> and is positioned inside tire radial direction of tire side portion <NUM>. The bead portion <NUM> is annular and the carcass <NUM> is folded from the inside of the tire width direction to the outside of the tire width direction via the bead portion <NUM>.

The spiral belt <NUM> is disposed inside the tire radial direction of the tread <NUM>. In this embodiment, the spiral belt <NUM> constitutes the reinforcing belt.

The spiral belt <NUM> is provided in an area of <NUM>% or more of the overall width TW of the tread in the tire width direction. The spiral belt <NUM> may be provided in an area of <NUM>% or more of the overall width TW, if possible.

The overall width TW is based on the condition that the pneumatic tire <NUM> is assembled to an appropriate rim wheel, the pneumatic tire <NUM> is set to a normal internal pressure, and the pneumatic tire <NUM> is loaded with a normal load.

The normal internal pressure is the air pressure corresponding to the maximum load capacity of the JATMA (Japan Automobile Tire Manufacturers Association) YearBook in Japan, and the normal load is the maximum load capacity (maximum load) corresponding to the maximum load capacity of the JATMA YearBook. In addition, ETRTO in Europe, TRA in the U. , and other tire standards in each country correspond to it.

Next, the internal structure of the pneumatic tire <NUM> will be further described. <FIG> is a top view (tread surface view) showing a part of the carcass <NUM>, the crossing belt layer <NUM> and the spiral belt <NUM> of the pneumatic tire <NUM>.

As shown in <FIG>, the carcass <NUM> is of radial construction and has a carcass cord <NUM> disposed radially along the tire radial direction. The carcass cord <NUM> can be made of an organic fiber such as nylon, similar to the tire for general high-performance four-wheel vehicles.

The crossing belt <NUM> forming the crossing belt layer <NUM> is provided outside the carcass <NUM>. The crossing belt <NUM> has a belt cord <NUM> a inclined with respect to the tire width direction.

The crossing belt <NUM> forming the crossing belt layer <NUM> is provided outside the crossing belt <NUM>. The crossing belt <NUM> also has a belt cord <NUM> a inclined with respect to the tire width direction.

The belt cord <NUM> a is inclined in a direction opposite to the belt cord <NUM> a with the tire width direction as a reference (alternatively, the tire equatorial line CL may be used as a reference.

In the present embodiment, the angle θ1 between the belt cord <NUM> a and the tire width direction is approximately <NUM> degrees. Although the belt cord <NUM> a is inclined in the direction opposite to the belt cord <NUM> a, the angle θ2 between the belt cord <NUM> a and the tire width direction is also approximately <NUM> degrees.

The belt cord <NUM> a and the belt cord <NUM> a are formed of organic fiber or steel. In the case of organic fibers, for example, polyester or Kevlar can be used.

The spiral belt <NUM> has a spiral cord <NUM> wound in tire circumferential direction. Specifically, the spiral belt <NUM> has the spiral cord <NUM> wound so as to be substantially parallel to the tire circumferential direction.

The angle formed by the spiral cord <NUM> with the tire circumferential direction (tire equatorial line CL) is preferably ± <NUM> degrees or less, and more preferably ± <NUM> degrees or less.

The spiral cord <NUM> is formed of organic fiber or steel. Although the material of the spiral cord <NUM> and the material of the belt cord <NUM> a and the belt cord <NUM> a may be the same, they are preferably different from each other in consideration of the performance required for the pneumatic tire <NUM>. Specifically, the spiral cord <NUM> is preferably stronger than the belt cord <NUM> a and the belt cord <NUM> a. In the case of organic fibers, for example, Kevlar can be used.

In this embodiment, the tensile elongation at break of the spiral cord <NUM> is preferably <NUM> cN/dtex or more. The elongation at break of the spiral cord <NUM> is preferably <NUM>% or less. The tensile elongation at break and the elongation at break are measured by the corresponding JIS measurement method.

Further, in the present embodiment, the arrangement interval (may be referred to as arrangement density) of the spiral cords <NUM> in the tire width direction is <NUM> cords/cm or more.

Next, the structure of the spiral belt <NUM> will be further described. <FIG> is a perspective view of a part of the spiral belt <NUM>.

As shown in <FIG>, the spiral belt <NUM> comprises a plurality of cord units <NUM>. Specifically, the spiral belt <NUM> is formed by winding the cord units <NUM>, in which a plurality of spiral cords <NUM> are arranged along the tire width direction, around the tire circumferential direction.

In this embodiment, the cord unit <NUM> has two spiral cords <NUM> spaced in tire width direction. The cord unit <NUM> may be referred to as a two-strip winding (number of the spiral cords <NUM> included in the cord unit <NUM>).

The size of the cord unit <NUM> in the tire width direction, specifically, the unit width W is preferably <NUM>% or less of the overall width TW (see <FIG>) of the tread <NUM>. Although the lower limit of the unit width W is not particularly limited, it is considered that the unit width W is actually <NUM>% or more of the overall width TW in consideration of the ease of manufacturing the cord unit <NUM>.

The spiral belt <NUM> formed by the cord unit <NUM> may be called a mono-spiral belt (MSB). The spiral belt <NUM> is formed by winding the cord unit <NUM> having two spiral cords <NUM> a plurality of times in tire circumferential direction.

That is, the cord unit <NUM> is wound a plurality of times around the tire circumferential direction from one end toward the other end in the tire width direction.

The width of the cord unit <NUM> in the tire width direction, that is, the unit width W is narrower than the width GW (see <FIG>) of the circumferential groove <NUM> in the tire width direction. The ratio of the width GW to the unit width W (GW/W) is <NUM> to <NUM>.

The spiral cord <NUM> is preferably twisted depending on a material (organic fiber or steel). The organic fiber (Kevlar) is preferably twisted at about <NUM> to <NUM> times/cm.

The number of the spiral cords <NUM> to be driven is <NUM> pieces/mm<NUM> or less for the cross sectional area of the cord unit <NUM>, specifically, the product of the unit width W and the unit height H.

According to the embodiment described above, the following effects can be obtained. In the pneumatic tire <NUM>, the spiral belt <NUM> has the spiral cord <NUM> wound in the tire circumferential direction. The tensile elongation at break of the spiral cord <NUM> is <NUM> cN/dtex or more. Further, the elongation at break of the spiral cord <NUM> is <NUM>% or less.

The spiral belt <NUM> having the spiral cord <NUM> having high elasticity effectively suppresses pantograph deformation of the crossing belt layer <NUM>. Furthermore, the spiral belt <NUM> effectively suppresses deformation of the crossing belt layer <NUM> in the tire circumferential direction, specifically deformation of a shoulder part of the tread <NUM> when lateral force is input to the pneumatic tire <NUM>. That is, the shearing rigidity in the crossing belt layer <NUM> is improved.

Thus, at a low slip angle (SA), specifically, in a region where SA is <NUM> degrees or less, a larger cornering force (CF) than that of a conventional similar tire can be generated, and the cornering performance of a vehicle mounted with the pneumatic tire <NUM> is greatly improved. In particular, the cornering force of the rear tire to which the steering angle is not given can be effectively enhanced.

Further, since the tensile elongation at break of the spiral cord <NUM> is high and the elongation at break is low, particularly, the amount of distortion due to repetition of compression and tension of the spiral belt <NUM> at the time of high-speed rolling of the pneumatic tire <NUM> can be effectively suppressed.

Thus, failure caused by heat generation of rubber around the spiral belt <NUM> and the spiral belt <NUM> can be prevented.

Furthermore, the width (unit width W) of the cord unit <NUM> in the tire width direction is narrower than the width GW of the circumferential groove <NUM> in the tire width direction. Therefore, the cord unit <NUM> has high followability to the shape of the circumferential groove <NUM>, and the gauge (rubber thickness) between the groove bottom part of the circumferential groove <NUM> and the cord unit <NUM> is easily made uniform after manufacturing. Thus, the rigidity distribution in the vicinity of the circumferential groove <NUM> is made uniform, and uneven wear in the vicinity of the circumferential groove <NUM> can be suppressed. Further, uniformity of gauge and rigidity distribution may also contribute to high speed durability.

The spiral belt <NUM> is formed by winding the cord units <NUM>, in which a plurality of the spiral cords <NUM> are arranged along the tire width direction, around the tire circumferential direction. Therefore, since the cord units <NUM> can be wound along the tire circumferential direction, the spiral belt <NUM> can be easily manufactured (time reduction), and strength required for the spiral belt <NUM> can be easily secured.

That is, according to the pneumatic tire <NUM>, the cornering force generated at a low slip angle can be further enhanced while improving high-speed durability.

In this embodiment, the spiral cord <NUM> is formed of an organic fiber such as Kevlar or steel. The arrangement interval of the spiral cords <NUM> in the tire width direction is <NUM> cords/cm or more. Further, the spiral belt <NUM> is provided in an area of <NUM>% or more of the overall width TW of the tread <NUM> in the tire width direction.

Therefore, the improvement of the tensile elongation at break of the spiral cord <NUM> and the suppression of elongation at break can be made compatible in a high dimension. This can further enhance the high-speed durability of the pneumatic tire <NUM> and the cornering force at a low slip angle.

In this embodiment, the belt cord <NUM> a and the belt cord <NUM> a are made of organic fiber or steel. Thus, the pantograph deformation of the crossing belt layer <NUM> can be further suppressed. This can further enhance the high-speed durability of the pneumatic tire <NUM> and the cornering force at a low slip angle.

Although the contents of the present invention have been described above with reference to the examples, the present invention is not limited thereto but only by the appended claims.

For example, in the embodiment described above, the spiral cord <NUM> is wound so as to be substantially parallel to the tire circumferential direction, but the spiral cord <NUM> may be wound at a certain angle.

Specifically, the angle formed by the spiral cord <NUM> and the tire circumferential direction (tire equatorial line CL) may be ± <NUM> degrees or less. That is, the angle between the spiral cord <NUM> and the tire width direction may be ± <NUM> degrees or more.

For example, in the above-described embodiment, the cord unit <NUM> is a two-strip winding (two spiral cords <NUM>), but as long as the unit width W < the width GW is satisfied, the number of the spiral cords <NUM> included in the cord unit <NUM> may be slightly increased.

Alternatively, the spiral belt <NUM> may be formed by winding one rubber-coated spiral cord <NUM> along the tire circumferential direction without using the cord unit <NUM>.

The spiral belt <NUM> and the spiral cord <NUM> may also be referred to as a circumferential belt and a circumferential cord.

Claim 1:
A tire (<NUM>) comprising at least:
a tread (<NUM>) in contact with a road surface; and
a reinforcing belt (<NUM>) disposed inside in a tire radial direction of the tread, wherein
a circumferential groove (<NUM>) extending along the tire circumferential direction is formed on the tread,
the reinforcing belt has a reinforcing cord (<NUM>) wound around a tire circumferential direction,
the tensile strength at break of the reinforcing cord is <NUM> cN/dtex or more,
the reinforcing cord has an elongation at break of <NUM>% or less,
the reinforcing belt is formed by a cord unit (<NUM>) in which a plurality of the reinforcing cords (<NUM>) are arranged along the tire width direction and are wound around the tire circumferential direction, and
the width (W) of the cord unit (<NUM>) in the tire width direction is narrower than the width (GW) of the circumferential groove in the tire width direction,
a ratio (GW/W) of the width (GW) of the circumferential groove to the unit width (W) is <NUM> or more to <NUM> or less, and
a number of the reinforcing cords (<NUM>) driven is <NUM> pieces/mm<NUM> or less for the cross sectional area of the cord unit (<NUM>) as the product of the unit width (W) and a unit height (H) of the cord unit (<NUM>),
wherein a crossing belt layer (<NUM>) formed by a pair of crossing belts (<NUM>, <NUM>) is disposed inside in the tire radial direction of the reinforcing belt,
the crossing belt layer (<NUM>) has a belt cord inclined with respect to tire width direction, and
the belt cord is formed of an organic fiber or steel.