Patent Description:
Conventionally, in tires used for heavy-load vehicles, there has been known a structure in which a wire chafer is arranged such as to cover an outer circumference of a carcass fixed by bead cores to thereby reinforce a bead portion (Patent Document <NUM>).

Patent document <NUM> discloses a heavy duty pneumatic radial tire comprising a bead portion provided with a wire chafer having an outer end located outward over an outer end of a turnup portion of a carcass ply in a radial direction of the tire, and a bead core embedded in the bead portion.

Patent document <NUM> discloses a carcass having a rubber-covered radial arrangement code of <NUM> ply or more extending between the bead cores embedded in the pair of bead parts, and the carcass has a folded part that winds up around the bead core, and the bead that sandwiches the bead core. In a heavy-duty pneumatic radial tire having a bead reinforcement layer consisting of two rubber-covered steel cord layers, which are independent in both inside and outside areas, the bead reinforcement layer located in the outside area of the bead has its tire radius.

Patent document <NUM> discloses a pair of bead portions including at least a bead core, a carcass layer folded between bead cores and folded around the bead core, and folded around the carcass layer in the bead portion. A first wire chafer formed of metal and rubber, a second wire chafer disposed on the inner side in the tread width direction of the carcass layer in the bead portion, the first wire chafer formed of metal and rubber, and a third wire chafer disposed on the inner side in the tread width direction of the second wire chafer and formed of metal and rubber, and is an end portion located on the inner side in the tread width direction of the first wire chafer.

Patent document <NUM> discloses a tire having a bead core having a hexagonal pillar and having a bead portion formed by reinforcing the outside with a steel chafer. A split portion is formed in the steel chafer.

However, in recent years, for heavy-load vehicles such as trucks, there has been a demand for increasing a load amount without increasing the number of tires, and although there has been a demand for improving a load bearing performance per tire, however, it is difficult to meet these demands with a structure of the conventional bead portion. It is to be noted that the larger the load, the greater a deformation amount of a ground-contacted part of the tire becomes, and a carcass wound around a bead core deforms to be pressed against the bead core. At this time, a wire chafer provided on an outer circumference of the carcass acts to press the carcass against the bead core, and as the tire contacts the ground and leaves the ground repeatedly, the carcass is caused to be rubbed by the bead core, and eventually this may lead to break of the carcass. In particular, there is a risk that, when a contour shape of the bead core in a cross-sectional view is polygonal, such as square or hexagonal, the carcass is rubbed by a top part of the bead core, thus is more easily broken.

The present invention aims at providing a tire capable of minimizing the amount of deformation in the bead portion and improving the load-bearing performance.

A tire according to claim <NUM> solves the above-mentioned problem.

Hereinafter, the present invention will be described in detail through embodiments of the invention; however, the following embodiments are not intended to limit the inventions set forth in the claims, and all of combinations of the features described in the embodiments are not necessarily essential to the solving means of the invention, but selectively employed configurations are included.

<FIG> is an example of a cross-sectional view of a tire for heavy-load vehicles. <FIG> is an enlarged cross-sectional view of a bead portion, and <FIG> is a cross-sectional view of a bead core in the bead portion. Hereinafter, a configuration of the tire according to an embodiment will be explained on the basis of the cross-sectional views illustrated in <FIG>. In the following description, as illustrated in <FIG>, directions will be explained as a tire width direction and a tire radial direction. Further, with respect to the tire width direction, the direction is defined such that, in the direction of a paper surface, right and left are defined with a tire center CL as a center line separating to right and left, a tire center Cl side is defined as an inner side, and each end part Tt side of right and left-ground contact surfaces Tm is defined as an outer side, and so on. For convenience of explanation, a direction of rotation of the tire T is specified as shown by the arrows in the figure.

As illustrated in <FIG> and <FIG>, the tire T includes a bead core <NUM>, a carcass <NUM>, a belt layer <NUM> formed of a plurality of belts, a nylon chafer <NUM> and a wire chafer <NUM>, which are formed of mainly cord members, and a bead filler <NUM>, a bead cover rubber <NUM>, a rim cushion rubber <NUM>, a belt under rubber <NUM>, a side rubber <NUM>, a base rubber <NUM>, a tread rubber <NUM>, and inner liner <NUM>, which are formed of mainly rubber members.

The bead core <NUM> is provided in pair on the right and left- sides in the tire T. The bead core <NUM> is formed in a ring shape by winding the bead cord <NUM> a predetermined number of times. The bead core <NUM> is formed to have a contour shape, in a cross-sectional view, for example, to be a polygonal shape such as square or hexagon, or a circular shape and so on. In the present embodiment, as illustrated in <FIG>, an explanation will be given particularly as to a case where the bead core is formed in a hexagonal shape.

The bead core <NUM> may be formed in the hexagonal shape, for example, by winding a bead cord <NUM> with a diameter of <NUM> to <NUM> <NUM> to <NUM> times. For the diameter of the bead cord <NUM>, one size is selected, for example, from the above-mentioned range, such as <NUM> or <NUM>, taking a tire diameter into consideration. The bead cord <NUM> is formed to have a predetermined diameter, for example, by layer twisting or multi twisting of steel strands. The number of turns of the bead core <NUM> may be set from the above-mentioned range on the basis of the diameter of the bead cord <NUM> and the size of the tire T.

The bead core <NUM>, which was formed into the hexagonal shape by having been wound as described above, is arranged so that one top part 12a is on the inner side in the tire width direction and a top part 12d, which is at a diagonal position of the top part 12a, protrudes on the outer side in the tire width direction. The bead core <NUM> may be formed so that an angle α of the top part 12a that protrudes toward the inner side in the tire width direction becomes, for example, <NUM> to <NUM> degrees. In other words, the cross-sectional shape of the bead core <NUM> may be hexagonal, but does not necessarily need to be regular hexagonal. When the bead core <NUM> is arranged in this way, upper and lower- sides 12A; 12B, which extend along the tire width direction, may be formed so that <NUM> to <NUM> bead cords <NUM> are lined up in a row.

The carcass <NUM> is configured, for example, of one or more layers of carcass plies, and is folded back so as to be rolled up from the inner side of the bead cores <NUM> provided on the right and left sides to the outer side, and extends in a toroidal shape between the right and left bead cores <NUM>, so that carcass cords that form the carcass plies extend in the tire radial direction. End parts of the wound-up carcass <NUM> are set, for example, to terminate on the inner side in the tire radius direction inner than a maximum width Wmax of the tire T, or on the outer side in the tire radial direction outer than the maximum width Wmax, or at the maximum width Wmax.

It is preferable to use the carcass cords, which form the carcass <NUM>, having an outer diameter of, for example, about <NUM> to <NUM>. Further, it is also preferable to set the number of driving of the carcass cords into the carcass <NUM> to be <NUM> to <NUM> per unit, for example.

The carcass <NUM> is set so that, when the carcass <NUM> is assembled to a proper rim and a predetermined internal pressure is applied, an angle of an inner circumferential surface side at a side of the bead core <NUM> and above the above-mentioned top part 12a, which is so called the angle β of a case line of the carcass ply, becomes about <NUM> to <NUM> degrees.

The case line of the carcass <NUM> refers to a line passing through a center of the thickness of the carcass <NUM> in the cross section in the tire width direction, and refers to a shape of the carcass <NUM> in the cross section in the tire width direction in an unloaded state, when the tire T is assembled to the proper rim and the predetermined internal pressure is applied. Further, as illustrated in <FIG>, the angle β of the case line refers to an acute side of an angle of intersection of a tangent line f1 set on the carcass <NUM> at the side of the bead core <NUM>, for example, within a range from an end part on the outer side in the tire radial direction of the bead core <NUM> to the top part 12a, and a straight line f2 extending along the tire width direction.

Furthermore, the carcass <NUM> is suitable for tire sizes with a periphery length of about <NUM> to <NUM> between fixing points F, which are fixed by the bead core <NUM> by rim assembly. The fixing point F refers to a position from the most inward in the tire radial direction of one of the bead cores <NUM> of the carcass <NUM> to the most inward in the tire radial direction of the other one of the bead cores <NUM>.

Incidentally, the periphery length of the carcass <NUM> refers to a length of the carcass ply passing through the center of the thickness of the carcass body portion, when there are multiple carcass plies.

The proper rim refers to standard rims (Measuring Rim in the STANDARDS MANUAL by ETRTO and Designing Rim in the YEAR BOOK by TRA) in the applicable size described in industrial standards valid for regions where the tire is produced and used, such as JATMA YEAR BOOK by the Japan Automobile Tyre Association (JATMA) in Japan, STANDARDS MANUAL by the European Tyre and Rim Technical Organisation (ETRTO) in Europe, and YEAR BOOK by the Tire and Rim Association, Inc. (TRA) in the United States of America.

The bead filler <NUM> is provided on the outer side in the tire radial direction of the carcass <NUM> folded back around the bead core <NUM>, so as to fill a space between the folded carcass <NUM>.

Furthermore, the bead cover rubber <NUM> is provided between the bead core <NUM> and the carcass <NUM>. The bead cover rubber <NUM> is arranged such that, for example, it starts at from a start end 21A on the inner side in the tire radial direction of the bead core <NUM>, extends along the inner side in the tire width direction of the bead core <NUM> toward the outer side in the tire radial direction, extends past an end on the outer end in the tire radial direction of the bead core <NUM> and terminates at a terminal end 21B, and wraps a half on the inner side in the tire width direction of the bead core <NUM>. It is preferable to make the bead cover rubber 21by a rubber member containing <NUM> to <NUM>% styrene-butadiene rubber when the polymer is <NUM>. A thickness of the bead cover rubber <NUM> is set so that, when the carcass <NUM> falls down toward the outer side in the tire width direction and is pressed against the bead core <NUM> due to a load applied to the tire T, a predetermined thickness is maintained. For example, the thickness of the bead cover rubber <NUM> may be <NUM> to <NUM>. By forming the bead cover rubber <NUM> in this manner, the bead cover rubber <NUM> can be made highly elastic and the carcass <NUM> can be prevented from contacting the bead core <NUM>.

The wire chafer <NUM> is provided on the inner circumference side of the carcass <NUM> wound around the bead core <NUM>. The wire chafer <NUM> is provided to wrap the carcass <NUM> wound around the bead core <NUM> from the outside, and extends along the carcass <NUM> from the inner circumference side to the outer circumference side of the carcass <NUM>. The wire chafer <NUM> will be described in detail later.

The nylon chafer <NUM> is provided on a further inner circumference side of the wire chafer <NUM> provided on the inner circumference side of the carcass <NUM>. The nylon chafer <NUM> is a member formed by a nylon cord, and as illustrated in <FIG>, in the cross-sectional view, for example, the nylon chafer <NUM> is provided in such a manner that one end 17A starts from the outer side in the radial direction outer than an upper end <NUM> on the outer side in the radial direction of a later-described upper side chafer <NUM> and the other end 17B reaches the lower end of the bead core <NUM>, so as to cover a part of a later-described lower side chafer <NUM>. By providing the nylon chafer <NUM> on the inner circumference side of the wire chafer <NUM> along the carcass <NUM>, fall-down deformation in the bead portion can be suppressed.

The rim cushion rubber <NUM> is provided from an innermost side in the tire radial direction to the outer side in the tire width direction, so as to cover the outer sides of the lower side chafer <NUM> and the nylon chafer <NUM>, whereby the adhesion to the applicable rim and the structure in the bead portion can be protected. On the outer side in the tire radial direction of the rim cushion rubber <NUM>, the side rubber <NUM> is continuously provided along the carcass <NUM>.

At a crown part of the carcass <NUM>, that is. , at a position of the carcass <NUM> corresponding to the tread portion in the tire T, the belt layer <NUM> is provided, which is configured of one or more belt plies (sixteen plies, 16a-16f in the present embodiment). The belt under-rubber <NUM> is provided between end parts of the belt plies 16c; 16d, which protrude in the tire width direction, of the belt layer <NUM>, and the outer circumferential surface of the carcass <NUM>. The base rubber <NUM> and the tread rubber <NUM> formed with a predetermined tread pattern are overlaid on the outer side in the tire radial direction of the belt layer <NUM>.

The base rubber <NUM> and the tread rubber <NUM> extend outwardly in the tire width direction so as to form an outline shape of the tire and cover the outer side in the tire radial direction of the side rubber <NUM>.

The inner liner <NUM> is provided on the inner circumference side of the carcass <NUM>. The inner liner <NUM> extends between the rim cushion rubbers <NUM> provided on the right and left bead portions, covers the entire inner circumference of the carcass <NUM>, and provides airtightness as a pneumatic tire.

As illustrated in <FIG> and <FIG>, the wire chafer <NUM> according to the present embodiment is separated at a side on the inner side in the tire width direction of the bead core <NUM> into the upper side wire chafer <NUM> (hereinafter simply referred to as the upper side chafer) that extends along the carcass <NUM> from the side of the bead core <NUM> toward the outer side in the tire radial direction, and the lower side chafer <NUM> (hereinafter referred to as the "lower side chafer") that extends along the carcass <NUM> from the side of the bead core <NUM> toward the inner side in the tire radial direction. In the following description, the end part on the bead core <NUM> side of the upper side chafer <NUM> is referred to as a lower end <NUM>, and the end part on the opposite side is referred to as the upper end <NUM>. Further, the end of the lower side chafer <NUM> opposite the lower end <NUM> of the upper side chafer <NUM> is referred to as an inner end <NUM>, and the end on the opposite side is referred to as an outer end <NUM>.

<FIG> is a schematic diagram illustrating a crossing state of carcass cords and chafer cords. As illustrated in <FIG>, the upper side chafer <NUM> and the lower side chafer <NUM> are formed such that the chafer cords <NUM> intersect the carcass cords <NUM>, which extend in the tire radial direction, at a predetermined angle θ. The angle θ may be set in a range of <NUM> to <NUM> degrees, for example. By setting the angle θ of the chafer cords <NUM> in this manner, the chafer cords <NUM> act to suppress a restraining force (tension) that tries to pull out the carcass cords <NUM> along with ground contact and a movement of the rubber around the carcass cords <NUM> to antagonize the restraining force, whereby the rigidity at the bead portion can be enhanced.

The above-mentioned separation at the side does not mean that the lower end <NUM> of the upper side chafer <NUM> and the inner end <NUM> of the lower side chafer <NUM> are necessarily included in a range X in which the bead core <NUM> is projected in the tire width direction. For example, there may be a state in which both the lower end <NUM> of the upper side chafer <NUM> and the inner end <NUM> of the lower side chafer <NUM> are included in the aforementioned range X, a state in which only one of the ends is included, or a state in which the both ends are not included. The projected range X refers to a range between a straight line that passes an upper end in the tire radial direction of the bead core <NUM> and extends in the tire width direction and a straight line that passes a lower end in the tire radial direction of the bead core <NUM> and extends in the tire width direction.

In other words, it is sufficient enough that the aforementioned rang X in which the bead core <NUM> is projected. is included in a discontinuous section between the upper side chafer <NUM> and the lower side chafer <NUM>.

For example, a position, at which the wire chafer <NUM> is separated into the upper side chafer <NUM> and the lower side chafer <NUM>, is determined in advance by analysis or the like so that a difference between a maximum value and a minimum value of the tension, which acts on the carcass <NUM> when the tire makes one rotation, is minimized, and the aforementioned discontinuous section may be set to include the determined position.

At this time, with respect to a relationship between the lower end <NUM> of the upper side chafer <NUM> and the inner end <NUM> of the lower side chafer <NUM>, the both ends may be butted with each other, or may be separated by a predetermined distance along the carcass <NUM>. Preferably, a distance L that separates the lower end <NUM> of the upper side chafer <NUM> from the inner end <NUM> of the lower side chafer <NUM> and that forms the discontinuous section, may be about <NUM> to <NUM>, for example. Incidentally, the distance L is a periphery length along the carcass <NUM>.

In the above-described range, when the tire T was grounded and the carcass <NUM> fell down toward the tire width direction, and a force that separates the lower end <NUM> of the upper side chafer <NUM> from the inner end <NUM> of the lower side chafer <NUM> was applied, the rubber interposed between the lower end <NUM> of the upper side chafer <NUM> and the inner end <NUM> of the lower side chafer <NUM> allows the deformation thereof, hence peeling off of the lower end <NUM> of the upper side chafer <NUM> and the inner end <NUM> of the lower side chafer <NUM> from the interposed rubber can be prevented.

More preferably, the inner end <NUM> of the lower side chafer <NUM> may be set lower in the tire radial direction than the top part 12a that faces the tire inner circumference side of the bead core <NUM>. Further, as illustrated in <FIG>, in a case where the bead core <NUM> has a plurality of top parts 12a; 12b; 12f, the inner end <NUM> of the lower side chafer <NUM> may be set equal to or lower than the top part 12b located on the lower side in the tire radial direction.

<FIG> is a diagram illustrating another form of the structure of the bead portion. The structure of the bead portion is not limited to those illustrated in <FIG> and <FIG>. For example, as illustrated in <FIG>, the nylon chafer <NUM> may be provided in place of the bead cover rubber <NUM>. With this, compared to a case where the bead cover rubber <NUM> is arranged between the carcass <NUM> and the bead core <NUM>, a time until the carcass <NUM> contacts the bead core <NUM> can be made longer.

<FIG> are conceptual diagrams illustrating a deformation shape of the bead portion when a load is applied.

As described above, by providing the wire chafer <NUM>, it is possible to prevent, while reinforcing the bead portion, excessive fall-down of the carcass <NUM> and improve the load bearing performance The fall-down of the carcass <NUM> refers to a state in which the carcass <NUM> inclines toward the bead core <NUM>, as illustrated in <FIG>, as the carcass <NUM> fixed by the bead core <NUM> is pushed out, from the ungrounded state illustrated in <FIG>, toward the tire width direction due to the ground contact.

Further, by separating the wire chafer <NUM> into the upper side chafer <NUM> and the lower side chafer <NUM> and providing to avoid the sides of the top parts 12a to 12c of the bead core <NUM>, it is possible to prevent the wire chafer <NUM> from pushing the carcass <NUM> toward the top parts 12a to 12c when the tire T is brought into contact with the ground. This means that the carcass <NUM> is not pushed against the bead core. In other words, a risk that the carcass <NUM> contacts the bead core <NUM> can be reduced.

The lower side chafer <NUM> may be set in such a manner as to extend the inner end <NUM> from more inner side in the tire width direction than the fixing point F of the carcass <NUM>. By setting the position of the lower side chafer <NUM> in this manner, one end side of the lower side chafer <NUM> is brought into a state of being restrained by the bead core <NUM>, thus can support the fall-down of the carcass <NUM> from the outside.

By extending the upper side chafer <NUM> along the carcass <NUM> so as to include the terminal end 21B of the bead cover rubber <NUM> in the tire radial direction, the upper side chafer <NUM> can support, together with the bead cover rubber <NUM>, the fall-down of the carcass <NUM> from the inner circumference side.

As a form of separation, for example, there may be considered a method of separation by overlapping the end part of the upper side chafer <NUM> and the end part of the lower side chafer <NUM>. However, it is conceivable that, due to the deformation during ground contact, a shear force is generated in a range where the upper side chafer <NUM> and the lower side chafer <NUM> overlap, and the rubber interposed between the upper side chafer <NUM> and the lower side chafer <NUM> is peeled off from the upper side chafer <NUM> or from the lower side chafer <NUM>, which causes a structural break. Therefore, it is preferable to separate the wire chafers <NUM> along the carcass <NUM> with a predetermined distance therebetween so that the upper side chafer <NUM> and the lower side chafer <NUM> do not overlap.

As described, by separating the wire chafer <NUM> into the upper side chafer <NUM> and the lower side chafer <NUM> and providing them along the carcass <NUM>, the deformation occurred when subjected to a load can be suppressed and a load amplitude on the carcass <NUM> can be minimized, thus the load bearing performance can be improved. As a result, the durability performance of the tire T can be improved.

Next, the present invention will be described in detail with embodiments, however, the present invention is not limited in any way by these examples. As an embodiment, the structure described above is applied to a tire for a heavy-load vehicle with a tire size of <NUM>/80R63.

Dimensions and a positional relationship of the wire chafer <NUM> (upper side chafer <NUM> and lower side chafer <NUM>), the carcass <NUM>, the bead core <NUM> and other components forming the bead portion may be set as follows. The number of cord driving (per <NUM>) of the upper side chafer <NUM> and the lower side chafer <NUM> is preferably <NUM> to <NUM>. A cord diameter of the upper side chafer <NUM> and the lower side chafer <NUM> is preferably <NUM> to <NUM>. A periphery length of the upper side chafer <NUM> is preferably <NUM> to <NUM>. A periphery length of the lower side chafer <NUM> is preferably <NUM> to <NUM>. A separation distance between the upper side chafer <NUM> and the lower side chafer <NUM> is preferably <NUM> to <NUM>. An angle of the chafer cord <NUM> with respect to the carcass cord <NUM> is preferably <NUM> to <NUM> degrees. The number of cord driving (per <NUM>) of the carcass cords <NUM> in the carcass <NUM> is preferably <NUM> to <NUM>. A diameter of the carcass cord is preferably <NUM> to <NUM>. An angle of the case line is preferably <NUM> to <NUM> degrees. A periphery length of the carcass <NUM> between fixing points A-A is preferably <NUM>,<NUM> to <NUM>,<NUM>. The number of turns of the bead cord <NUM> is preferably <NUM> to <NUM> (<NUM> to <NUM> for an upper side or a lower side). The innermost angle α of the bead core <NUM> is preferably <NUM> to <NUM> degrees. The bead cover rubber <NUM> (percentage when polymer is <NUM>) is preferably <NUM> to <NUM> phr.

The periphery length of the upper side chafer <NUM> is set to <NUM> and the periphery length of the lower side chafer <NUM> is set to <NUM>. The lower end <NUM> of the upper side chafer <NUM> and the inner end <NUM> of the lower side chafer <NUM> are separated by <NUM>. This separation distance is a length of the extension along the carcass <NUM>. The upper side chafer <NUM> and the lower side chafer <NUM> are formed with the chafer cords having a diameter of <NUM> so that the number of chafer cord driving becomes <NUM> to <NUM> per <NUM>. With respect to the upper side chafer <NUM> and the lower side chafer <NUM>, the angle θ at which the chafer cord <NUM> crosses the carcass cord <NUM> extending in the tire radial direction is set to <NUM> degrees (see <FIG>).

With respect to the carcass <NUM>, the carcass cord diameter is set to <NUM>, the number of carcass cord driving is set to <NUM> per <NUM>, and the periphery length from the fixing point F at one end to the fixing point F at the other end is set to <NUM>. Further, the carcass <NUM> is formed so that the angle β of the case line at the side of the bead core <NUM> is set to <NUM> degrees (see <FIG>).

The bead core <NUM> is formed in the hexagonal shape as described above, and the number of windings of the bead wire is set to <NUM>. The bead core <NUM> is so arranged that one part 12a faces the inner side and one top part 12a faces the outer side in the tire width direction. In the state of being arranged in this manner, the sides 12A; 12B extending along the tire width direction of the bead core <NUM> are respectively formed with <NUM> bead wires. Further, the bead core <NUM> is so formed that <NUM> bead wires are aligned in a straight line between the aforementioned top part 12a on the inner side in the tire width direction and the top part 12d facing outward. The angle α of the aforementioned top part 12a of the bead core <NUM>, which faces the inner side in the tire width direction, is <NUM> degrees.

<FIG> is a diagram illustrating a result of analysis, by Finite Element Method (FEM), of change in the load applied to the carcass <NUM>, with the tire configured as described above. In <FIG>, the solid line g1 indicates a change in the load applied to the tire according to the present embodiment, and the dashed line g2 indicates a change in the load applied to the carcass <NUM> when the wire chafer <NUM> is used as a single piece without being separated into the upper side chafer <NUM> and the lower side chafer <NUM> as in the present embodiment.

As illustrated in <FIG>, it has been found that, with the tire according to the present embodiment, the amplitude (load amplitude) of the change in the load applied to the carcass <NUM> becomes smaller compared to the case where the wire chafer <NUM> is not separated. In other words, it has been found that, with the tire T according to the present embodiment, even with the same load, fall-down of the carcass <NUM> becomes small. Therefore, in a state in which the fall-down similar to the case where the wire chafer <NUM> is not separated is allowed, the tire T according to the present embodiment can tolerate a larger load.

Incidentally, in a case where the structure of the bead portion according to the present embodiment is applied to other tire sizes, the same effect can be obtained by analogously changing the relationship of the dimensions and arrangement of the upper side chafer <NUM> and the lower side chafer <NUM>, the carcass <NUM>, and the bead core <NUM>, from the aforementioned range based on the aforementioned <NUM>/80R63. The same effect can be obtained by varying the dimensions and arrangement of the upper side chafer <NUM> and the lower side chafer <NUM>, carcass <NUM>, and bead core <NUM>.

In summary, the present invention can be described as follows. That is, as a configuration of the tire, a tire includes:
a pair of bead cores formed in a polygonal shape in cross-sectional view; a carcass toroidally straddling between the bead cores and folded back around the bead cores; and a wire chafer extending along the carcass so as to cover the carcass folded back around the bead cores from an inner side in a radial direction of a tire, in which, at a side on a tire inner circumference side of the bead core, the wire chafer is provided by being separated into an upper side wire chafer and a lower side wire chafer.

According to this configuration, the amount of deformation (amplitude) of the bead portion can be minimized. Hence, the load bearing performance can be improved without degrading the durability of the tire.

As another configuration of the tire, the upper side wire chafer and the lower side wire chafer may be separated within a range from the upper end to the lower end of the bead core.

Claim 1:
A tire comprising:
a pair of bead cores (<NUM>) formed in a polygonal shape in cross-sectional view;
a carcass (<NUM>) toroidally straddling between the bead cores (<NUM>) and folded back around the bead cores (<NUM>);
a wire chafer (<NUM>) extending along the carcass (<NUM>) so as to cover the carcass (<NUM>) folded back around the bead cores (<NUM>) from an inner side in a radial direction of a tire, the wire chafer (<NUM>) being provided on an inner circumference side of the carcass (<NUM>), and
a nylon chafer (<NUM>) that is provided as a nylon cord, the nylon chafer (<NUM>) being provided at an inner circumference side of the wire chafer (<NUM>),
wherein, at a side on a tire inner circumference side of the bead core (<NUM>), the wire chafer is provided by being separated into an upper side wire chafer (<NUM>) and a lower side wire chafer (<NUM>),
wherein the upper side wire chafer (<NUM>) and the lower side wire chafer (<NUM>) are separated at, as a boundary, a top part of the bead core located on an innermost side in a tire width direction among top parts of the bead core (<NUM>) that face inwardly in the tire width direction, and
wherein a first end (17A) of the nylon chafer (<NUM>) is disposed radially outwards of an upper end (<NUM>) of the upper side wire chafer (<NUM>) in the tire radial direction, and a second end (17B) of the nylon chafer (<NUM>) reaches a lower end of the bead core (<NUM>) so as to cover a part of the lower side wire chafer (<NUM>).