Patent Description:
Conventionally, in pneumatic tire (below referred to as tire) mounted on a four-wheel vehicle, for the purpose of improving cornering performance, a structure in which a side reinforcing layer composed of a cloth rubberized with a plurality of cords is provided on tire side portion is known (refer to Patent Literature <NUM>).

Such a side reinforcing layer is provided from an outer tire width direction end of belt layer provided inside the of tread portion of tire radial direction to an outer end of tire radial direction of bead portion. Thus, since the rigidity of tire side portion is improved, the gripping force and responsiveness during cornering of the vehicle can be improved.

<CIT> discloses a pneumatic tire that includes a carcass including at least two sheets of carcass plies, a belt layer, bead apex rubber, two sheets of textile reinforcing layers, and a steel reinforcing layer, and has a flatness ratio of <NUM>% or less. The total number of layers in the carcass plies is <NUM>-<NUM>, the total number of layers in the textile reinforcing layers is <NUM>-<NUM>, and the total number of layers in the steel reinforcing layer is <NUM>-<NUM> on a tire axial direction passing a position of <NUM> outside of the radial direction from a radial direction outermost end portion of a bead core. In a side wall portion at the tire radial direction outside of <NUM>% of a tire cross-sectional height from a bead base line, a tire radial direction height in a rigidity relieving region where the textile reinforcing layers and the steel reinforcing layer are not provided is <NUM>-<NUM>% of the tire cross-sectional height.

<CIT> discloses a pneumatic tire that includes: a carcass having a ply constituted of a ply body and a ply folding-back part and formed by covering a ply cord with rubber; and a bead filler. The pneumatic tire also includes a first reinforcing layer formed by covering a first cord with rubber and a second reinforcing layer formed by covering a second cord with rubber, arranged in order from the inside in the tire width direction between the ply folding-back part and the bead filler, and a third reinforcing layer arranged outside in the tire width direction of the ply folding-back part and made of rubber. The first cord, the second cord and the ply cord have a tensile modulus larger in this order, and the rubber for constituting the third reinforcing layer has a <NUM>% modulus smaller than the rubber for constituting the bead filler.

<CIT> discloses a pneumatic tire includes a buttress reinforcing layer. A carcass includes a first ply and a second ply. The first ply and the second ply each have a main portion that is extended on and between beads on both sides. The buttress reinforcing layer extends along the first ply and the second ply between the first ply and the second ply. An outer end of the buttress reinforcing layer is disposed inward of a shoulder region of a tread in a radial direction. An inner end of the buttress reinforcing layer is disposed at a maximum width position of the tire or disposed outward of the maximum width position of the tire in the radial direction.

<CIT> discloses a pneumatic tire that includes a white letter part which protrudes from white rubber arranged outward in a tire radial direction than an outer edge of a bead filler in the sidewall part and a side reinforcing layer which extends outward in the tire radial direction from a bead part. The outer peripheral edge of the side reinforcing layer is located outward in the tire radial direction relative to the inner circumferential end of the white letter part, and when a length in the tire radial direction from an inner peripheral edge of a bead core to the inner circumferential end of the white letter part is made to be H1, a length in the tire radial direction from the inner peripheral edge of the bead core to the outer peripheral edge of the side reinforcing layer is made to be H2, and a length in the tire radial direction of the white letter part is made to be T, (H2-H1)/T is set equal to or more than <NUM>.

However, with the performance improvement of the vehicle, further improvement of cornering performance, in particular, improvement of controllability in the critical condition of tire performance (gripping force, etc.) during cornering (below, referred to as controllability in critical condition) is required.

In general, by improving the axial force in the small steering angle region at the start of cornering and optimizing the shear deformation of tread portion in the large steering angle region after entering the corner, performance such as gripping force and responsiveness can be expected to be improved.

In addition, in order to improve the controllability in critical condition, it is essential to effectively function the ground contact surface of tread portion. In particular, in order to improve the axial force, it is important to promote the shear deformation of tread portion. As a method for promoting the shear deformation of tread portion, the case rigidity of tire can be increased.

However, when the case rigidity of tire is increased, the damping property of tire (flexibility of tire of tire radial direction) during cornering decreases, so that it becomes difficult to maintain the attitude of the vehicle in the state where the load is applied to tire during cornering. Therefore, the time dependency of the lateral force (Fy) is reduced.

Accordingly, an object of the present invention is to provide a tire in which the improvement of the axial force and the ease of maintaining the attitude of the vehicle during cornering can be achieved at a high level.

According to a first aspect of the invention there is provided a tire (pneumatic tire <NUM>) including a tread portion (tread portion <NUM>) in contacting with a road surface, a tire side portion (tire side portion <NUM>) continuous to the tread portion and positioned inside in a tire radial direction of the tread portion, a bead portion (bead portion <NUM>) continuous to the tire side portion and positioned inside in the tire radial direction of the tire side portion, and a carcass (carcass <NUM>) that forms tire skeleton. The bead portion includes a bead core (bead core <NUM>) and a bead filler (bead filler <NUM>) provided outside in the tire radial direction of the bead core, the carcass includes a body portion (body portion <NUM>) and a folded portion (folded portion <NUM>) continuous to the body portion and folded back to outside in a tire width direction via the bead core, and a part of the body portion and the folded portion are formed by at least a plurality of plies (ply <NUM> a, ply <NUM> b, ply <NUM> a, ply <NUM> b). The carcass include a first reinforcing member (flipper <NUM>) folded back from an inner side in the tire width direction via the bead core to an outer side in the tire width direction to cover the bead core and the bead filler, and a second reinforcing member (insert <NUM>) provided between the bead filler and the first reinforcing member folded outside in the tire width direction. In at least a part of the region where the second reinforcing member is provided, thickness (thickness D1, thickness D2) of a side rubber (side rubber <NUM>) provided on the outside in the tire width direction of the carcass is substantially the same as ply thickness combining the body portion and the folded portion formed by a plurality of plies. A thickness (D1, D2) of the side rubber (<NUM>) at a maximum width position of tire is <NUM>% or more of a sectional width of the tire side portion (<NUM>) at the maximum width position.

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 the pneumatic tire <NUM> taken along tire width direction and tire radial direction. In <FIG>, sectional hatching is not shown.

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

In the present embodiment, the pneumatic tire <NUM> is a four-wheel vehicle, specifically, a tire assumed to be mounted on a passenger vehicle. In particular, the pneumatic tire <NUM> can be suitably used for a four-wheel vehicle such as a sports type vehicle emphasizing cornering performance.

The tread portion <NUM> is a portion in contact with a road surface. On the tread portion <NUM>, a pattern (not shown) is formed according to the use environment of the pneumatic tire <NUM> and the type of vehicle to be mounted.

The tire side portion <NUM> is continuous to the tread portion <NUM> and is positioned inside in the tire radial direction of the tread portion <NUM>. The tire side portion <NUM> is an area from the outer edge of the tire width direction of the tread portion <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 (tire skeleton) of the pneumatic tire <NUM>. In this embodiment, the carcass <NUM> has a radial structure in which carcass cords (not shown) disposed radially along the tire radial direction are coated with a rubber material. The carcass <NUM> has a body portion <NUM> and a folded portion <NUM>.

The body portion <NUM> extends over the tread portion <NUM>, the tire side portion <NUM> and the bead portion <NUM> and the body portion <NUM> is a portion until it is folded back at the bead portion <NUM>.

The folded portion <NUM> is a portion continuous to the body portion <NUM> and folded back to outside in the tire width direction via a bead core <NUM>. The outer end <NUM> e of the folded portion <NUM> in the tire radial direction extends to the inside in the tire radial direction of the belt layer <NUM>. That is, the carcass <NUM> has an envelope structure.

However, the carcass <NUM> may not necessarily have an envelope structure, and for example, it may also have a high-turn-up structure in which the outer end <NUM> e does not reach the belt layer <NUM> but is positioned inside in tire radial direction of the belt layer <NUM>, more specifically, in the vicinity of the maximum width position Wmax (not shown in <FIG>, see <FIG>).

The carcass cord is formed of an organic fiber such as nylon as in the case of a tire for standard four-wheel vehicles. In the present embodiment, the carcass <NUM> is formed of a plurality of plies (carcass plies). The configuration of the carcass <NUM> will be described later.

The belt layer <NUM> is provided inside in the tire radial direction of the tread portion <NUM>. In this embodiment, the belt layer <NUM> includes a pair of crossing belts with crossed steel cords. The belt layer <NUM> may include a reinforcing belt provided at an end of the crossing belt in the tire width direction.

The bead portion <NUM> is continuous to the tire side portion <NUM> and is positioned inside in the tire radial direction of the tire side portion <NUM>. The bead portion <NUM> is annular extending to the tire circumferential direction and is locked to a rim wheel (not shown).

The bead portion <NUM> includes a bead core <NUM> and a bead filler <NUM>.

The bead core <NUM> is formed by twisting a plurality of metal cords. For example, the bead core <NUM> may be formed of steel cords. The number of cords (the number of cores) is not particularly limited, but in this embodiment, the number of cores is about <NUM>.

The bead filler <NUM> is provided outside in the tire radial direction of the bead core <NUM>. The bead filler <NUM> is formed by using rubber harder than other parts formed by rubber. The bead filler <NUM> is provided to fill a space having wedge-shaped in cross-sectional shape formed by the body portion <NUM> and the folded portion <NUM> of the carcass <NUM>.

In this embodiment, a second bead filler <NUM> is provided. The second bead filler <NUM> is provided outside in the tire width direction of the folded portion <NUM> of the carcass <NUM>. The second bead filler <NUM> is also formed of the same member as the bead filler <NUM>.

The pneumatic tire <NUM> also includes a flipper <NUM> and an insert <NUM>.

The flipper <NUM> is provided to cover the periphery of the bead portion <NUM>. Specifically, the flipper <NUM> is folded back from the inside in the tire width direction via the bead core <NUM> to the outside in the tire width direction to cover the bead core <NUM> and the bead filler <NUM>.

The flipper <NUM> has a structure in which a plurality of cords arranged slantingly to the tire radial direction are covered with rubber. An organic fiber such as aramid fiber can be used as the cord.

The flipper <NUM> reinforces the bead portion <NUM>. In this embodiment, the flipper <NUM> constitutes the first reinforcing member.

The insert <NUM> is provided outside in the tire width direction of the bead filler <NUM>. Specifically, the insert <NUM> is provided between the bead filler <NUM> and the flipper <NUM> folded outside in the tire width direction.

The insert <NUM> is also formed by covering a plurality of cords arranged slantingly to the tire radial direction with rubber. The cord may be an organic fiber such as aramid fibers or a metal such as steel.

The insert <NUM> reinforces the tire side portion <NUM> and the bead portion <NUM>. In this embodiment, the insert <NUM> constitutes the second reinforcing member.

The flipper <NUM> and the insert <NUM> may be referred to as a side reinforcing layer or the like.

A rim line <NUM> is provided on an outer side surface of the bead portion <NUM> of tire width direction. The rim line <NUM> is a projection formed along the bead portion <NUM> to confirm that the tire circumferential direction is correctly mounted on the rim wheel. In this embodiment, the rim line <NUM> is provided on the outer side in the tire radial direction about <NUM> from the outer end of a rim flange <NUM>.

<FIG> is a partial cross-sectional view of the pneumatic tire <NUM>. In <FIG>, in order to facilitate identification, the cross section hatching is shown only for a part of the components.

As shown in <FIG>, in this embodiment, the carcass <NUM> is formed by a plurality of plies (carcass plies). Specifically, the body portion <NUM> is formed by two plies. A part of the folded portion <NUM> is formed by <NUM> plies.

More specifically, the body portion <NUM> is formed by a ply <NUM> a and a ply <NUM> b. The folded portion <NUM> is formed by a ply <NUM> a and a ply <NUM> b. The ply <NUM> b terminates near the center of the bead filler <NUM> in the tire radial direction.

The flipper <NUM> has an inner portion <NUM> and an outer portion <NUM>. The inner portion <NUM> is a portion positioned inside the bead portion <NUM> in the tire width direction. The outer portion <NUM> is a portion positioned outside the bead portion <NUM> in the tire width direction.

The tire side portion <NUM> has the maximum width position Wmax at which tire width of the pneumatic tire <NUM>, that is, the width along the tire width direction, becomes maximum. In the present embodiment, the maximum width position Wmax is a position where the width along the tire width direction in pneumatic tire <NUM> which is not rim-assembled is maximum.

<FIG> is a partially enlarged sectional view of the pneumatic tire <NUM>. In <FIG>, as in <FIG>, in order to facilitate identification, only a part of the components is displayed with cross section hatching.

As described above, the body portion <NUM> and the folded portion <NUM> of the carcass <NUM> are formed by a plurality of plies, specifically, two plies, but in at least a part of the region where the insert <NUM> is provided, the thickness of a side rubber <NUM> provided outside in the tire width direction of the carcass <NUM> is substantially the same as the ply thickness obtained by combining the body portion <NUM> and the folded portion <NUM> formed by a plurality of plies.

Specifically, the thickness D1 of the side rubber <NUM> is substantially the same as the thickness of the ply <NUM> a, the ply <NUM> b, the ply <NUM> a and the ply <NUM> b combined. In this embodiment, the ply thicknesses of the ply <NUM> a, the ply <NUM> b, the ply <NUM> a, and the ply <NUM> b are each about <NUM>. Therefore, the thickness D1 is about <NUM>. By substantially the same it is meant that the thickness D1 is within ± <NUM>% of the total thickness of the plurality of plies.

The thickness D1 is the thickness of the side rubber <NUM> at the maximum width position Wmax. The thickness D1, that is, the thickness of the side rubber <NUM> at the maximum width position Wmax, is not less than <NUM>% of the cross-sectional width (D1 + D1 ' in the figure) of tire side portion <NUM> at the maximum width position Wmax. Note that the section width is the total thickness of tire side portion <NUM> along a straight line perpendicular to the outer surface of the tire width direction in tire sectional view as shown in <FIG>.

That is, in the present embodiment, the thickness of the side rubber <NUM> at the maximum width position Wmax is substantially the same as the thickness of the four plies (ply <NUM> a, ply <NUM> b, ply <NUM> a, and ply <NUM> b) forming the carcass <NUM>.

In addition, the thickness D2 of the side rubber <NUM> at the position of the rim line <NUM> is also substantially the same as the ply thickness obtained by combining the ply <NUM> a, the ply <NUM> b, the ply <NUM> a, and the ply <NUM> b. The thickness D2 is not less than <NUM>% of the cross-sectional width (D2 + D2 ' in the figure) of the bead portion <NUM> at the position of the rim line <NUM>.

Note that the section width is the total thickness of the bead portion <NUM> along a straight line perpendicular to the outer surface of the tire width direction in tire sectional view as shown in <FIG>. As shown in <FIG>, a plurality of rim lines <NUM> may be provided, and in such a case, the rim line <NUM> provided on the outermost side of the tire radial direction is used as a reference. The thickness D2 does not include a portion of the rim line <NUM> protruding from the outer surface of the bead portion <NUM> in the tire width direction.

In this embodiment, the thickness D1 and the thickness D2 do not include the thickness of the second bead filler <NUM>. That is, the thickness D1 (thickness D2) is a distance from the tire width direction outer surface of the second bead filler <NUM> to the tire width direction outer surface of the folded portion <NUM> (ply <NUM> a) of the carcass <NUM>.

The positions of the thickness D1 and the thickness D2 in the tire radial direction are provided with the flipper <NUM> (outer portion <NUM>) and the insert <NUM>.

Also, an outer end <NUM> a of an outer portion <NUM> of the flipper <NUM> in the tire radial direction is positioned outside of the tire radial direction than an outer end <NUM> a of an inner portion <NUM> of the flipper <NUM> in the tire radial direction. In addition, the outer end <NUM> a is located outside of the <NUM>% of the section height SH of the pneumatic tire <NUM> in the tire radial direction.

The section height SH is the height of the pneumatic tire <NUM> from the inside edge of the bead portion <NUM> in the tire radial direction to the outside edge of the tread portion <NUM> in the tire radial direction that is not rim assembled. In this embodiment, the outer end <NUM> a is provided at <NUM>% of the section height SH. The position of <NUM>% of the section height SH is based on the inner edge of the bead portion <NUM> in the tire radial direction (hereinafter the same).

The outer end <NUM> a in the tire radial direction of the inner portion <NUM> of the flipper <NUM> is provided at <NUM>% of the section height SH.

An outer end <NUM> a of the insert <NUM> in the tire radial direction is positioned inside in the tire radial direction than at <NUM>% of the section height SH. In this embodiment, the outer end <NUM> a is provided at <NUM>% of the section height SH.

An outer end <NUM> a of the second bead filler <NUM> in the tire radial direction is close to the maximum width position Wmax but is positioned inside in the tire radial direction than the maximum width position Wmax.

According to the embodiment described above, the following effects can be obtained. Specifically, the flipper <NUM> (first reinforcing member) is provided in the bead portion <NUM> of the pneumatic tire <NUM>, and the insert <NUM> (second reinforcing member) is provided between the bead filler <NUM> and the outer portion <NUM> of the flipper <NUM>.

In at least a part of the region where the insert <NUM> is provided, the thickness D1 of the side rubber <NUM> is substantially the same as the ply thickness obtained by combining the body portion <NUM> and the folded portion <NUM> of the carcass <NUM> formed by the plurality of plies.

The thickness of the side rubber <NUM> is thicker than a conventional pneumatic tire of the same kind. Specifically, the thickness (thickness D1 and thickness D2) of the rubber is increased from the maximum width position Wmax to the rim line <NUM>. That is, the thickness of the side rubber <NUM> is increased in at least a part where the flipper <NUM> and the insert <NUM> are provided in the tire radial direction.

By increasing the thickness of the side rubber <NUM> (thicker gauging) and arranging the flipper <NUM> and the insert <NUM>, the longitudinal spring property and the damping property of the pneumatic tire <NUM> can be improved without increasing the case rigidity.

More specifically, the thicker gauging of the side rubber <NUM> improves the longitudinal spring property, and this promotes the shearing deformation of the tire side portion <NUM> which is relatively more easily deformed than the tread portion <NUM>. Since the shape of the carcass <NUM> (cross-sectional shape along the tire width direction and the tire radial direction) is hard to deform, the axial force of pneumatic tire <NUM> during cornering can be improved.

Further, since the damping property of tire (flexibility of tire (carcass <NUM>) in the tire radial direction) during cornering can be optimized by making the thickness gauge of the side rubber <NUM>, the attitude of the vehicle during cornering can be easily maintained.

That is, according to the pneumatic tire <NUM>, the improvement of the axial force during cornering and the ease of maintaining the attitude of the vehicle can be made compatible at a high level. In addition, a high degree of compatibility between the improvement of axial force during cornering and the ease of maintaining the attitude of the vehicle can contribute to the improvement of the controllability in critical condition of tire performance (gripping force, etc.) during cornering.

The case rigidity means rigidity of the carcass <NUM> itself forming tire skeleton (case).

The thickness of the side rubber <NUM> at the maximum width position Wmax is <NUM>% or more of the cross-sectional width of the tire side portion <NUM> at the maximum width position Wmax. The thickness D2 of the side rubber <NUM> at the position of the rim line <NUM> is <NUM>% or more of the sectional width of the bead portion <NUM> at the position of the rim line <NUM>. Therefore, the relative thickness of the side rubber <NUM> is increased from the tire side portion <NUM> to the bead portion <NUM>. Thus, the longitudinal spring property and the damping property of the pneumatic tire <NUM> can be improved more appropriately, and the improvement of the axial force during cornering and the ease of maintaining the attitude of the vehicle can be made compatible in a higher dimension.

In the present embodiment, the thickness of the side rubber <NUM> at the maximum width position Wmax is substantially the same as the thickness of the four plies (ply <NUM> a, ply <NUM> b, ply <NUM> a, and ply <NUM> b) forming the carcass <NUM>. Therefore, the longitudinal spring property and the damping property of the pneumatic tire <NUM> can be more appropriately improved while securing a balance with the case rigidity of the carcass <NUM>. Thus, the improvement of the axial force during cornering and the ease of maintaining the attitude of the vehicle can be made compatible in a higher dimension.

In this embodiment, the outer end <NUM> a of the outer portion <NUM> of the flipper <NUM> in the tire radial direction is positioned outside in the tire radial direction than the outer end <NUM> a in the tire radial direction of the inner portion <NUM> of the <NUM> flipper.

Also, the outer end <NUM> a of the insert <NUM> in the tire radial direction is positioned inside in the tire radial direction than at <NUM>% of the section height SH. Further, the outer end <NUM> a of the second bead filler <NUM> in the tire radial direction is close to the maximum width position Wmax but is located inside in the tire radial direction than the maximum width position Wmax.

Thus, over a wide range of the tire side portion <NUM> in the tire radial direction, characteristics may be imparted to the tire side portion <NUM> that contribute to appropriate improvements in longitudinal spring property and damping property of the pneumatic tire <NUM>. Thus, the improvement of the axial force during cornering and the ease of maintaining the attitude of the vehicle can be made compatible in a higher dimension.

Although the contents of the present invention have been described above with reference to the examples, it will be obvious to those skilled in the art that the present invention is not limited to these descriptions and that various modifications and improvements are possible as claimed.

For example, although the second bead filler <NUM> is provided in the above-described embodiment, the second bead filler <NUM> may not necessarily be provided. In this case, the thickness D1 (thickness D2) of the side rubber <NUM> is a distance from the tire width direction outer surface of the tire side portion <NUM> (bead portion <NUM>) to the tire width direction outer surface of the folded portion <NUM> (ply <NUM> a) of the carcass <NUM>.

In the embodiment described above, the outer end <NUM> a of the insert <NUM> in the tire radial direction is positioned inside in the tire radial direction than at <NUM>% of the section height SH, and the outer end <NUM> a in the tire radial direction of the second bead filler <NUM> is positioned inside the maximum width position Wmax while approaching the maximum width position Wmax, but such a positional relationship is not required.

Claim 1:
A tire (<NUM>) comprising:
a tread portion (<NUM>) for contacting with a road surface;
a tire side portion (<NUM>) continuous to the tread portion (<NUM>) and positioned inside in a tire radial direction of the tread portion (<NUM>);
a bead portion (<NUM>) continuous to the tire side portion (<NUM>) and positioned inside in the tire radial direction of the tire side portion (<NUM>); and
a carcass (<NUM>) that forms a tire skeleton, wherein
the bead portion (<NUM>) includes a bead core (<NUM>) and a bead filler (<NUM>) provided outside in the tire radial direction of the bead core (<NUM>);
the carcass (<NUM>) includes a body portion (<NUM>) and a folded portion (<NUM>) continuous to the body portion (<NUM>) and folded back to outside in a tire width direction via the bead core (<NUM>), and
a part of the body portion (<NUM>) and the folded portion (<NUM>) are formed by at least a plurality of plies (41a, 41b, 42a, 42b), wherein
the carcass comprises:
a first reinforcing member (<NUM>) folded back from an inner side in the tire width direction via the bead core (<NUM>) to an outer side in the tire width direction to cover the bead core (<NUM>) and the bead filler (<NUM>); and
a second reinforcing member (<NUM>) provided between the bead filler (<NUM>) and the first reinforcing member (<NUM>) folded outside in the tire width direction, wherein
in at least a part of the region where the second reinforcing member (<NUM>) is provided, a thickness of a side rubber (<NUM>) provided on the outside in the tire width direction of the carcass (<NUM>) is substantially the same as a ply thickness combining the body portion (<NUM>) and the folded portion (<NUM>) formed by the plurality of plies (41a, 42b, 42a, 42b);
wherein a thickness (D1, D2) of the side rubber (<NUM>) at a maximum width position of tire is <NUM>% or more of a sectional width of the tire side portion (<NUM>) at the maximum width position.