Patent Description:
This application claims priority on <CIT>.

For heavy duty tires, the application of a technology for suppressing radial growth of a tire has been considered in order to prevent occurrence of uneven wear. For example, in the tire disclosed in PATENT LITERATURE <NUM> below, a band including a band cord extending substantially in a circumferential direction is adopted in order to suppress radial growth of the tire.

PATENT LITERATURE <NUM>: International Publication No. <CIT>.

A tire in accordance with the preamble of claim <NUM> is known from <CIT>. Related tires are described in <CIT>, <CIT>, <CIT> and <CIT>.

When a tire expands, for example, each side portion thereof stretches in the radial direction. When a band is used in order to prevent occurrence of uneven wear, the band suppresses the stretch of each side portion. Depending on the degree of suppression, there is a concern that specific strain may occur in each side portion.

A large load acts on each bead portion of a heavy duty tire. In a low-flatness tire having a nominal aspect ratio of <NUM>% or less, each side portion is shorter than that in a high-flatness tire. Each side portion of the low-flatness tire is likely to be influenced by strain generated in a bead portion thereof.

The use of a band is effective for preventing occurrence of uneven wear. When a band is used for a low-flatness tire, strain is likely to occur in each side portion thereof. There is a concern that damage due to strain may occur in the side portion; in other words, the durability of the tire may decrease.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a heavy duty tire that can ensure durability and improve uneven wear resistance.

The object is solved by a tire having the features of claim <NUM>. Sub-claims are directed to preferred embodiments of the invention.

A heavy duty tire according to an aspect of the present invention has a nominal aspect ratio of <NUM>% or less. The tire includes: a tread that comes into contact with a road surface; a pair of sidewalls that are each connected to an end of the tread and located inward of the tread in a radial direction; a pair of chafers that are each located inward of the sidewall in the radial direction and come into contact with a rim; a pair of beads that are each located inward of the chafer in an axial direction; and a band that is located inward of the tread in the radial direction and includes a spirally wound band cord. At least three circumferential grooves are formed on the tread, whereby at least four land portions are formed in the tread. Among the at least three circumferential grooves, a circumferential groove located on each outer side in the axial direction is a shoulder circumferential groove, and a land portion located outward of the shoulder circumferential groove in the axial direction is a shoulder land portion. The band includes a full band having ends opposed to each other across an equator plane, and a pair of edge bands located outward of the ends of the full band in the radial direction. An outer surface of each chafer has a fitting recess into which a flange of the rim fits. A ratio of a distance in the axial direction from the shoulder circumferential groove to the end of the full band, to a width in the axial direction of the shoulder land portion, is not less than <NUM>% and not greater than <NUM>%.

Preferably, in the heavy duty tire, the fitting recess has a concave curved surface whose contour in a meridian cross-section of the tire is an arc. The concave curved surface has a radius of not less than <NUM> and not greater than <NUM>.

Preferably, in the heavy duty tire, a ratio of a width of the tread to a cross-sectional width of the tire is not less than <NUM> and not greater than <NUM>.

Preferably, in the heavy duty tire, a ratio of a width of the band to a width of the tread is not less than <NUM> and not greater than <NUM>.

Preferably, in the heavy duty tire, each end of the full band is located outward of the shoulder circumferential groove in the axial direction.

Preferably, in the heavy duty tire, a distance in the axial direction from the end of the full band to an inner end of the edge band is not less than <NUM>.

According to the present invention, a heavy duty tire that can ensure durability and improve uneven wear resistance is obtained.

In the present invention, a state where a tire is fitted on a normal rim, the internal pressure of the tire is adjusted to a normal internal pressure, and no load is applied to the tire is referred to as a normal state.

In the present invention, unless otherwise specified, the dimensions and angles of each component of the tire are measured in the normal state. The dimensions and angles of each component in a meridian cross-section of the tire, which cannot be measured in a state where the tire is fitted on the normal rim, are measured in a cross-section of the tire obtained by cutting the tire along a plane including a rotation axis, with the distance between right and left beads being made equal to the distance between the beads in the tire that is fitted on the normal rim.

The normal rim means a rim specified in a standard on which the tire is based. The "standard rim" in the JATMA standard, the "Design Rim" in the TRA standard, and the "Measuring Rim" in the ETRTO standard are normal rims. A rim in the present invention means a normal rim unless otherwise specified.

The normal internal pressure means an internal pressure specified in the standard on which the tire is based. The "highest air pressure" in the JATMA standard, the "maximum value" recited in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are normal internal pressures.

In the present invention, the "nominal aspect ratio" is the "nominal aspect ratio" included in "tyre designation" specified in JIS D4202 "Automobile tyres-Designation and dimensions".

In the present invention, a tread portion of the tire is a portion of the tire that comes into contact with a road surface. A bead portion is a portion of the tire that is fitted to a rim. A side portion is a portion of the tire that extends between the tread portion and the bead portion. The tire includes a tread portion, a pair of bead portions, and a pair of side portions as portions thereof.

The rim includes a seat (a member denoted by reference sign S in <FIG>) and a flange (a member denoted by reference sign F in <FIG>). When the tire is fitted to the rim, the inner circumferential surface of the bead portion is placed on the seat, and the outer surface of the bead portion comes into contact with the flange.

In the present invention, the number of cords included per <NUM> of a tire element, including aligned cords, is represented as the density of cords included in this element (unit: ends/<NUM>). Unless otherwise specified, the density of the cords is obtained in a cross-section of the element obtained by cutting the element along a plane perpendicular to the longitudinal direction of the cords.

<FIG> shows a part of a heavy duty tire <NUM> (hereinafter, also referred to simply as "tire <NUM>") according to an embodiment of the present invention. The tire <NUM> is mounted to a vehicle such as a truck and a bus. The nominal aspect ratio of the tire <NUM> is not greater than <NUM>%. In other words, the tire <NUM> has a nominal aspect ratio of <NUM>% or less. The tire <NUM> is a low-flatness tire.

<FIG> shows a part of a cross-section (hereinafter, also referred to as meridian cross-section) of the tire <NUM> along a plane including the rotation axis of the tire <NUM>. In <FIG>, the right-left direction is the axial direction of the tire <NUM>, and the up-down direction is the radial direction of the tire <NUM>. The direction perpendicular to the surface of the drawing sheet of <FIG> is the circumferential direction of the tire <NUM>. An alternate long and short dash line CL represents the equator plane of the tire <NUM>.

In <FIG>, the tire <NUM> is fitted on a rim R. The rim R is a normal rim. The interior of the tire <NUM> is filled with air to adjust the internal pressure of the tire <NUM>. The tire <NUM> fitted on the rim R is also referred to as a tire-rim assembly. The tire-rim assembly includes the rim R and the tire <NUM> fitted on the rim R.

In <FIG>, a position indicated by reference sign PW is an outer end in the axial direction of the tire <NUM>. In the case where decorations such as patterns and letters are present on the outer surface of the tire <NUM>, the outer end PW is specified on the basis of a virtual outer surface obtained on the assumption that the decorations are not present.

In <FIG>, a length indicated by reference sign WA is the maximum width of the tire <NUM>, that is, the cross-sectional width (see JATMA or the like) of the tire <NUM>. The cross-sectional width WA of the tire <NUM> is the distance in the axial direction from one outer end PW to the other outer end PW. Each outer end PW is a position (hereinafter, maximum width position) at which the tire <NUM> has the maximum width.

The tire <NUM> includes a tread <NUM>, a pair of sidewalls <NUM>, a pair of chafers <NUM>, a pair of beads <NUM>, a carcass <NUM>, a pair of cushion layers <NUM>, an inner liner <NUM>, an insulation <NUM>, a pair of steel fillers <NUM>, a pair of interlayer strips <NUM>, a pair of edge strips <NUM>, and a reinforcing layer <NUM>.

The tread <NUM> comes into contact with a road surface at an outer surface thereof. The outer surface of the tread <NUM> is a tread surface <NUM>. In <FIG>, reference sign PC represents the point of intersection of the tread surface <NUM> and the equator plane CL. The point of intersection PC corresponds to the equator of the tire <NUM>.

In <FIG>, reference sign PE represents an end of the tread surface <NUM>. A length indicated by reference sign WT is the width of the tread <NUM>. The width WT of the tread <NUM> is the distance in the axial direction from one end PE of the tread surface <NUM> to the other end PE of the tread surface <NUM>. When the ends PE of the tread surface <NUM> cannot be identified from the appearance, the position on the tread surface <NUM> corresponding to each outer end in the axial direction of a ground-contact surface obtained when the normal load is applied as a vertical load to the tire <NUM> in the normal state with a camber angle of the tire <NUM> being set to <NUM>° and the tire <NUM> is brought into contact with a road surface that is a flat surface, is used as each end PE of the tread surface <NUM>.

The tread <NUM> is formed from a crosslinked rubber. The tread <NUM> includes a cap layer and a base layer which are not shown. The cap layer is formed from a crosslinked rubber for which wear resistance and grip performance are taken into consideration, and forms the tread surface <NUM>. The base layer is formed from a crosslinked rubber that has low heat generation properties, and is located inward of the cap layer.

In the tire <NUM>, at least three circumferential grooves <NUM> are formed on the tread <NUM>. On the tread <NUM> of the tire <NUM> shown in <FIG>, four circumferential grooves <NUM> are formed. These circumferential grooves <NUM> are aligned in the axial direction and continuously extend in the circumferential direction.

Among the four circumferential grooves <NUM> formed on the tread <NUM>, the circumferential groove <NUM> located on each outer side in the axial direction is a shoulder circumferential groove <NUM>. The circumferential groove <NUM> located inward of the shoulder circumferential groove <NUM> in the axial direction is a middle circumferential groove <NUM>. In the tire <NUM>, the four circumferential grooves <NUM> include a pair of the middle circumferential grooves <NUM> and a pair of the shoulder circumferential grooves <NUM>.

In the tire <NUM>, from the viewpoint of contribution to drainage performance and traction performance, the groove width of each middle circumferential groove <NUM> is preferably not less than <NUM>% and not greater than <NUM>% of the width WT of the tread <NUM>. The groove depth of each middle circumferential groove <NUM> is preferably not less than <NUM> and not greater than <NUM>. The groove width of each shoulder circumferential groove <NUM> is preferably not less than <NUM>% and not greater than <NUM>% of the width WT of the tread <NUM>. The groove depth of each shoulder circumferential groove <NUM> is preferably not less than <NUM> and not greater than <NUM>.

Each sidewall <NUM> is connected to an end of the tread <NUM>. The sidewall <NUM> is located inward of the tread <NUM> in the radial direction. The sidewall <NUM> is formed from a crosslinked rubber. The sidewall <NUM> protects the carcass <NUM>.

Each chafer <NUM> is located inward of the sidewall <NUM> in the radial direction. The chafer <NUM> comes into contact with the rim R. The chafer <NUM> is formed from a crosslinked rubber for which wear resistance is taken into consideration.

Each bead <NUM> is located inward of the chafer <NUM> in the axial direction. The bead <NUM> is located inward of the sidewall <NUM> in the radial direction. The bead <NUM> includes a core <NUM> and an apex <NUM>.

The core <NUM> extends in the circumferential direction. The core <NUM> includes a wound wire made of steel. The core <NUM> has a substantially hexagonal cross-sectional shape.

The apex <NUM> is located radially outward of the core <NUM>. The apex <NUM> includes an inner apex 34u and an outer apex <NUM>. The inner apex 34u extends radially outward from the core <NUM>. The outer apex <NUM> is located radially outward of the inner apex 34u. The inner apex 34u is formed from a hard crosslinked rubber. The outer apex <NUM> is formed from a crosslinked rubber that is more flexible than the inner apex 34u.

The carcass <NUM> is located inward of the tread <NUM>, the pair of sidewalls <NUM>, and the pair of chafers <NUM>. The carcass <NUM> extends on and between one bead <NUM> and the other bead <NUM>. The carcass <NUM> includes at least one carcass ply <NUM>. The carcass <NUM> of the tire <NUM> is composed of one carcass ply <NUM>.

The carcass ply <NUM> is turned up around each core <NUM> from the inner side toward the outer side in the axial direction. The carcass ply <NUM> has a ply body 36a which extends from one core <NUM> to the other core <NUM>, and a pair of turned-up portions 36b which are connected to the ply body 36a and turned up around the respective cores <NUM> from the inner side toward the outer side in the axial direction. An end of each turned-up portion 36b of the tire <NUM> is located at the same position as that of a conventional tire.

The carcass ply <NUM> includes a large number of carcass cords aligned with each other, which are not shown. These carcass cords are covered with a topping rubber. Each carcass cord intersects the equator plane CL. An angle of the carcass cords relative to the equator plane CL is not less than <NUM>° and not greater than <NUM>°. The carcass <NUM> has a radial structure. Steel cords are used as the carcass cords.

Each cushion layer <NUM> is located between the reinforcing layer <NUM> and the carcass <NUM> at an end of the reinforcing layer <NUM>. The cushion layer <NUM> is formed from a flexible crosslinked rubber.

The inner liner <NUM> is located inward of the carcass <NUM>. The inner liner <NUM> forms an inner surface of the tire <NUM>. The inner liner <NUM> is formed from a crosslinked rubber that has a low gas permeability coefficient. The inner liner <NUM> maintains the internal pressure of the tire <NUM>.

The insulation <NUM> is located between the carcass <NUM> and the inner liner <NUM>. The insulation <NUM> is joined to the carcass <NUM> and is joined to the inner liner <NUM>. In other words, the inner liner <NUM> is joined to the carcass <NUM> via the insulation <NUM>. The insulation <NUM> is formed from a crosslinked rubber for which adhesiveness is taken into consideration.

Each steel filler <NUM> is located at a bead <NUM> portion (that is, a bead portion). The steel filler <NUM> is turned up around the core <NUM> from the inner side toward the outer side in the axial direction along the carcass ply <NUM>.

In the tire <NUM>, one end (hereinafter, inner end) of the steel filler <NUM> is located between the outer end of the inner apex 34u and the core <NUM> in the radial direction. The other end (hereinafter, outer end) of the steel filler <NUM> is located between the end of the turned-up portion 36b and the core <NUM> in the radial direction. In the radial direction, the outer end of the steel filler <NUM> is located inward of the inner end thereof.

The steel filler <NUM> includes a large number of filler cords aligned with each other, which are not shown. In the steel filler <NUM>, the filler cords are covered with a topping rubber. Steel cords are used as the filler cords.

Each interlayer strip <NUM> is located between the outer apex <NUM> of the bead <NUM> and the chafer <NUM>. The interlayer strip <NUM> covers the end of the turned-up portion 36b and the outer end of the steel filler <NUM>. The interlayer strip <NUM> is formed from a crosslinked rubber.

Each edge strip <NUM> is located between the outer apex <NUM> of the bead <NUM> and the interlayer strip <NUM>. The end of the turned-up portion 36b is interposed between the edge strip <NUM> and the interlayer strip <NUM>. The edge strip <NUM> is formed from a crosslinked rubber. The material of the edge strip <NUM> of the tire <NUM> is the same as the material of the interlayer strip <NUM>.

The reinforcing layer <NUM> is located inward of the tread <NUM> in the radial direction. The reinforcing layer <NUM> is located between the carcass <NUM> and the tread <NUM>. The reinforcing layer <NUM> includes a belt <NUM> and a band <NUM>.

The belt <NUM> includes a plurality of belt plies <NUM> aligned in the radial direction. Each belt ply <NUM> is disposed such that both ends thereof are opposed to each other across the equator plane CL. The belt <NUM> of the tire <NUM> includes three belt plies <NUM>. Among the three belt plies <NUM>, the belt ply <NUM> located on the inner side in the radial direction is a first belt ply 42A. The belt ply <NUM> located outward of the first belt ply 42A is a second belt ply 42B. The belt ply <NUM> located outward of the second belt ply 42B is a third belt ply 42C. The belt <NUM> includes the first belt ply 42A, the second belt ply 42B, and the third belt ply 42C. The belt <NUM> is composed of the three belt plies <NUM>. The belt <NUM> may be composed of two belt plies <NUM>.

As shown in <FIG>, an end 42Ae of the first belt ply 42A is located outward of the shoulder circumferential groove <NUM> in the axial direction. An end 42Be of the second belt ply 42B is located outward of the shoulder circumferential groove <NUM> in the axial direction. An end 42Ce of the third belt ply 42C is located outward of the shoulder circumferential groove <NUM> in the axial direction.

In <FIG>, a length indicated by reference sign W1 is the width in the axial direction of the first belt ply 42A. A length indicated by reference sign W2 is the width in the axial direction of the second belt ply 42B. A length indicated by reference sign W3 is the width in the axial direction of the third belt ply 42C. The width in the axial direction of each belt ply <NUM> is the distance in the axial direction from one end 42e of the belt ply <NUM> to the other end 42e of the belt ply <NUM>.

In the tire <NUM>, the second belt ply 42B has the largest width W2 in the axial direction. The first belt ply 42A has the width W1 in the axial direction equal to the width W3 in the axial direction of the third belt ply 42C. The width W1 in the axial direction of the first belt ply 42A may be larger than the width W3 in the axial direction of the third belt ply 42C. The width W1 in the axial direction of the first belt ply 42A may be smaller than the width W3 in the axial direction of the third belt ply 42C.

In the tire <NUM>, from the viewpoint of ensuring the stiffness of the tread portion, the ratio (W1/WT) of the width W1 in the axial direction of the first belt ply 42A to the width WT of the tread <NUM> is preferably not less than <NUM> and preferably not greater than <NUM>. The ratio (W2/WT) of the width W2 in the axial direction of the second belt ply 42B to the width WT of the tread <NUM> is preferably not less than <NUM> and preferably not greater than <NUM>. The ratio (W3/WT) of the width W3 in the axial direction of the third belt ply 42C to the width WT of the tread <NUM> is preferably not less than <NUM> and preferably not greater than <NUM>.

An end 38e of the belt <NUM> of the tire <NUM> is represented as an end 42e of the belt ply <NUM> having the largest width in the axial direction among the plurality of belt plies <NUM> included in the belt <NUM>. As described above, in the tire <NUM>, the second belt ply 42B has the largest width in the axial direction. The end 38e of the belt <NUM> of the tire <NUM> is represented as the end 42Be of the second belt ply 42B. In the tire <NUM>, the end 38e of the belt <NUM> is also an end 26e of the reinforcing layer <NUM>.

The band <NUM> includes a full band <NUM> and a pair of edge bands <NUM>. As shown in <FIG>, the full band <NUM> has ends 44e opposed to each other across the equator plane CL. The pair of edge bands <NUM> are disposed so as to be spaced apart from each other in the axial direction with the equator plane CL therebetween.

In the tire <NUM>, each edge band <NUM> is located between the tread <NUM> and the full band <NUM>. The edge band <NUM> is located outward of the end 44e of the full band <NUM> in the radial direction. In the axial direction, an inner end 46ue of the edge band <NUM> is located inward of the end 44e of the full band <NUM>. In the tire <NUM>, the position of the outer end 46se of the edge band <NUM> coincides with the position of the end 44e of the full band <NUM> in the axial direction. In the axial direction, an outer end 46se of the edge band <NUM> may be located outward of the end 44e of the full band <NUM>. The edge band <NUM> overlaps the end 44e of the full band <NUM> in the radial direction. In the axial direction, the outer end 46se of the edge band <NUM> is located inward of the end 38e of the belt <NUM>. In the axial direction, the outer end 46se of the edge band <NUM> of the tire <NUM> is located inward of the end 42Ce of the third belt ply 42C.

<FIG> shows the configuration of the reinforcing layer <NUM>. In <FIG>, the right-left direction is the axial direction of the tire <NUM>, and the up-down direction is the circumferential direction of the tire <NUM>. The direction perpendicular to the surface of the drawing sheet of <FIG> is the radial direction of the tire <NUM>. The front side of the drawing sheet of <FIG> is the outer side in the radial direction, and the back side of this drawing sheet is the inner side in the radial direction.

As shown in <FIG>, each belt ply <NUM> included in the belt <NUM> includes a large number of belt cords <NUM> aligned with each other. In <FIG>, for convenience of description, the belt cords <NUM> are represented by solid lines, but the belt cords <NUM> are covered with a topping rubber <NUM>. The belt cords <NUM> of the tire <NUM> are steel cords. In the tire <NUM>, the density of the belt cords <NUM> in each belt ply <NUM> is not less than <NUM> ends/<NUM> and not greater than <NUM> ends/<NUM>.

The belt cords <NUM> in each belt ply <NUM> are tilted relative to the circumferential direction. The direction in which the belt cords <NUM> included in the first belt ply 42A are tilted (hereinafter, the tilt direction of first belt cords 48A) is the same as the direction in which the belt cords <NUM> included in the second belt ply 42B are tilted (hereinafter, the tilt direction of second belt cords 48B). The tilt direction of the first belt cords 48A may be opposite to the tilt direction of the second belt cords 48B. The tilt direction of second belt cords 48B is opposite to the direction in which the belt cords <NUM> included in the third belt ply 42C are tilted (hereinafter, the tilt direction of third belt cords 48C).

In <FIG>, an angle θ1a is an angle (hereinafter, first tilt angle θ1a) of the first belt cords 48A relative to the equator plane CL. An angle θ2a is an angle (hereinafter, second tilt angle θ2a) of the second belt cords 48B relative to the equator plane CL. An angle θ3a is an angle (hereinafter, third tilt angle θ3a) of the third belt cords 48C relative to the equator plane CL.

In the tire <NUM>, each of the first tilt angle θ1a, the second tilt angle θ2a, and the third tilt angle θ3a is preferably not less than <NUM>° and preferably not greater than <NUM>°. From the viewpoint of effectively restraining movement of the tire <NUM> and ensuring shape stability of the ground-contact surface, the first tilt angle θ1a is preferably not less than <NUM>° and preferably not greater than <NUM>°. The second tilt angle θ2a is preferably not less than <NUM>° and preferably not greater than <NUM>°. The third tilt angle θ3a is preferably not less than <NUM>° and preferably not greater than <NUM>°.

As shown in <FIG>, the full band <NUM> and the pair of edge bands <NUM> included in the band <NUM> each include a spirally wound band cord <NUM>. In <FIG>, for the convenience of description, the band cords <NUM> are represented by solid lines, but each band cord <NUM> is covered with a topping rubber <NUM>.

In the tire <NUM>, the band cords <NUM> are steel cords or cords formed from an organic fiber (hereinafter, organic fiber cords). In the case where organic fiber cords are used as the band cords <NUM>, examples of the organic fiber include nylon fibers, polyester fibers, rayon fibers, and aramid fibers. In the tire <NUM>, as the band cord <NUM> of the full band <NUM> and the band cords <NUM> of the edge bands <NUM>, the same cord may be used, or different cords may be used. The band cords <NUM> used for the full band <NUM> and the edge bands <NUM> are determined according to the specifications of the tire <NUM>.

As described above, the full band <NUM> includes the spirally wound band cord <NUM>. The full band <NUM> has a jointless structure. In the full band <NUM>, an angle of the band cord <NUM> relative to the circumferential direction is preferably not greater than <NUM>° and more preferably not greater than <NUM>°. The band cord <NUM> of the full band <NUM> extends substantially in the circumferential direction.

The density of the band cord <NUM> in the full band <NUM> is not less than <NUM> ends/<NUM> and not greater than <NUM> ends/<NUM>. The density of the band cord <NUM> in the full band <NUM> is represented as the number of cross-sections of the band cord <NUM> included per <NUM> width of the full band <NUM> in a cross-section of the full band <NUM> included in the meridian cross-section.

As described above, each edge band <NUM> includes the spirally wound band cord <NUM>. The edge band <NUM> has a jointless structure. In the edge band <NUM>, an angle of the band cord <NUM> relative to the circumferential direction is preferably not greater than <NUM>° and more preferably not greater than <NUM>°. The band cord <NUM> of the edge band <NUM> extends substantially in the circumferential direction.

The density of the band cord <NUM> in the edge band <NUM> is not less than <NUM> ends/<NUM> and not greater than <NUM> ends/<NUM>. The density of the band cord <NUM> in the edge band <NUM> is represented as the number of cross-sections of the band cord <NUM> included per <NUM> width of the edge band <NUM> in a cross-section of the edge band <NUM> included in the meridian cross-section.

<FIG> shows a part of the cross-section of the tire <NUM> shown in <FIG>. <FIG> shows the tread portion of the tire <NUM>. In <FIG>, the right-left direction is the axial direction of the tire <NUM>, and the up-down direction is the radial direction of the tire <NUM>. The direction perpendicular to the surface of the drawing sheet of <FIG> is the circumferential direction of the tire <NUM>.

In the tire <NUM>, each of the end 42Be of the second belt ply 42B and the end 42Ce of the third belt ply 42C is covered with a rubber layer <NUM>. Two rubber layers <NUM> are further disposed between the end 42Be of the second belt ply 42B and the end 42Ce of the third belt ply 42C, each of which is covered with the rubber layer <NUM>. In the tire <NUM>, an edge member <NUM> including four rubber layers <NUM> in total is formed between the end 42Be of the second belt ply 42B and the end 42Ce of the third belt ply 42C. The edge member <NUM> is formed from a crosslinked rubber. The edge member <NUM> contributes to maintaining the interval between the end 42Be of the second belt ply 42B and the end 42Ce of the third belt ply 42C. In the tire <NUM>, a change of the positional relationship between the end 42Be of the second belt ply 42B and the end 42Ce of the third belt ply 42C due to running is suppressed. The edge member <NUM> is a part of the reinforcing layer <NUM>. The reinforcing layer <NUM> of the tire <NUM> includes a pair of edge members <NUM> in addition to the belt <NUM> and the band <NUM>.

As described above, at least three circumferential grooves <NUM> are formed on the tread <NUM>. Accordingly, at least four land portions <NUM> are formed in the tread <NUM>. As shown in <FIG> and <FIG>, in the tire <NUM>, five land portions <NUM> are formed by forming four circumferential grooves <NUM> on the tread <NUM>. In the present invention, the boundary between the outer surface of each land portion <NUM> and each circumferential groove <NUM> is represented as an end of the land portion <NUM>. The end of the land portion <NUM> is also a reference point for the groove width of the circumferential groove <NUM> and defines the groove opening of the circumferential groove <NUM>.

Among the five land portions <NUM> formed in the tread <NUM>, the land portion <NUM> located on each outer side in the axial direction is a shoulder land portion <NUM>. The shoulder land portion <NUM> is located outward of the shoulder circumferential groove <NUM> in the axial direction and includes the end PE of the tread surface <NUM>. In <FIG>, a length indicated by reference sign WS is the width in the axial direction of the shoulder land portion <NUM>. The width WS in the axial direction is the distance in the axial direction from the inner end of the shoulder land portion <NUM> to the outer end of the shoulder land portion <NUM> (in other words, the end PE of the tread surface <NUM>).

The land portion <NUM> located inward of the shoulder land portion <NUM> in the axial direction is a middle land portion <NUM>. The shoulder circumferential groove <NUM> is present between the middle land portion <NUM> and the shoulder land portion <NUM>. In <FIG>, a length indicated by reference sign WM is the width in the axial direction of the middle land portion <NUM>. The width WM in the axial direction is the distance in the axial direction from the inner end of the middle land portion <NUM> to the outer end of the middle land portion <NUM>.

The land portion <NUM> located inward of the middle land portion <NUM> in the axial direction is a center land portion 60c. The middle circumferential groove <NUM> is present between the center land portion 60c and the middle land portion <NUM>. In the tire <NUM>, the center land portion 60c is located on the equator plane CL. In <FIG>, a length indicated by reference sign WC is the width in the axial direction of the center land portion 60c. The width WC in the axial direction is the distance in the axial direction from one end of the center land portion 60c to the other end of the center land portion 60c which is not shown.

In the tire <NUM>, the five land portions <NUM> include the center land portion 60c, a pair of the middle land portions <NUM>, and a pair of the shoulder land portions <NUM>.

In the tire <NUM>, the width WC in the axial direction of the center land portion 60c is not less than <NUM>% and not greater than <NUM>% of the width WT of the tread <NUM>. The width WM in the axial direction of each middle land portion <NUM> is not less than <NUM>% and not greater than <NUM>% of the width WT of the tread <NUM>. The width WS in the axial direction of each shoulder land portion <NUM> is not less than <NUM>% and not greater than <NUM>% of the width WT of the tread <NUM>.

As described above, the full band <NUM> has the ends 44e opposed to each other across the equator plane CL. The full band <NUM> extends in the axial direction from the equator plane CL toward each end 44e.

In the tire <NUM>, the full band <NUM> effectively restrains movement of the tread portion. A change of the shape of the tire <NUM>, for example, a change of the contour (hereinafter, also referred to as case line) of the carcass <NUM>, is suppressed, so that the ground-contact shape of the tire <NUM> is less likely to change.

Furthermore, in the tire <NUM>, each edge band <NUM> is located outward of the end 44e of the full band <NUM> in the radial direction. The edge band <NUM> holds the end 44e of the full band <NUM>. Fluctuation of the tension of the band cord <NUM> included in the full band <NUM> is suppressed, so that a break of the band cord <NUM> due to the fluctuation of the tension is less likely to occur. The full band <NUM> of the tire <NUM> can stably exhibit the function of suppressing a shape change. The edge band <NUM> is narrower than the full band <NUM>. Therefore, tension fluctuation as in the full band <NUM> is less likely to occur in the band cord <NUM> of the edge band <NUM>. A break is less likely to occur in the band cord <NUM> of the edge band <NUM>.

In the tire <NUM>, the full band <NUM> and the edge bands <NUM> suppress a shape change of the tire <NUM> due to running. The band <NUM> contributes to improvement of uneven wear resistance.

A large load acts on each bead portion of a tire. As described above, the tire <NUM> is a low-flatness tire. Each side portion of the tire <NUM> is shorter than each side portion of a high-flatness tire having a nominal aspect ratio greater than <NUM>%. Each side portion of the tire <NUM> is likely to be influenced by strain generated in a bead portion thereof. In addition, the band <NUM> suppresses stretch of each side portion when the tire <NUM> expands. Each side portion of the tire <NUM> is in a situation where specific strain is likely to occur therein. In the tire <NUM>, the band <NUM> is used in order to improve uneven wear resistance, but there is a concern that damage due to strain may occur in each side portion.

As shown in <FIG>, in the tire <NUM> fitted on the rim R, the outer surface of each chafer <NUM> comes into contact with the rim R.

<FIG> shows a part of the cross-section of tire <NUM> shown in <FIG>. <FIG> shows the bead portion of the tire <NUM>. In <FIG>, the right-left direction is the axial direction of the tire <NUM>, and the up-down direction is the radial direction of the tire <NUM>. The direction perpendicular to the surface of the drawing sheet of <FIG> is the circumferential direction of the tire <NUM>. In <FIG>, a solid line BBL extending in the axial direction is a bead base line. This bead base line is a line that defines the rim diameter (see JATMA or the like) of the rim R.

As shown in <FIG>, in the tire <NUM>, a recess <NUM> is provided on the outer surface of each chafer <NUM>. The recess <NUM> extends in the circumferential direction. The recess <NUM> overlaps the core <NUM> of the bead <NUM> in the axial direction. As shown in <FIG>, in the radial direction, the core <NUM> is located between a tangent point PS and a tangent point PU described later.

In <FIG>, a solid line LB is a straight line that is tangent to the outer surface of the tire <NUM> on the radially outer side and the radially inner side of the recess <NUM>. A position indicated by reference sign PS is the tangent point between the solid line LB and the outer surface of the tire <NUM> on the radially outer side of the recess <NUM>. A position indicated by reference sign PU is the tangent point between the solid line LB and the outer surface of the tire <NUM> on the radially inner side of the recess <NUM>. The solid line LB is a straight line that is tangent to the outer surface of the tire <NUM> at each of the tangent point PS and the tangent point PU. The portion between the tangent point PS and the tangent point PU is the recess <NUM>, and the recess <NUM> is referred to as a fitting recess. The solid line LB is also referred to as a recess reference line.

The fitting recess <NUM> has a concave curved surface <NUM> whose contour in the meridian cross-section is an arc. In <FIG>, a position indicated by reference sign BC is the center of the arc representing the contour of the concave curved surface <NUM>. Reference sign Rb indicates the radius of this arc.

The fitting recess <NUM> further has an outer boundary portion <NUM> and an inner boundary portion <NUM>. The outer boundary portion <NUM> connects the concave curved surface <NUM> and the tangent point PS on the radially outer side of the concave curved surface <NUM>. In the meridian cross-section, the contour of the outer boundary portion <NUM> is represented by an arc, and this arc is tangent to the arc of the concave curved surface <NUM> at the boundary (not shown) between the concave curved surface <NUM> and the outer boundary portion <NUM>. This arc is tangent to the contour line of the outer surface of the tire <NUM> at the tangent point PS. The inner boundary portion <NUM> connects the concave curved surface <NUM> and the tangent point PU on the radially inner side of the concave curved surface <NUM>. In the meridian cross-section, the contour of the inner boundary portion <NUM> is represented by an arc, and this arc is tangent to the arc of the concave curved surface <NUM> at the boundary (not shown) between the concave curved surface <NUM> and the inner boundary portion <NUM>. This arc is tangent to the contour line of the outer surface of the tire <NUM> at the tangent point PU.

In the tire <NUM>, the outer surface of each chafer <NUM> has the fitting recess <NUM> extending in the circumferential direction. As shown in <FIG>, when the tire <NUM> is fitted onto the rim R, the flange F of the rim R fits into the fitting recess <NUM>.

In the tire <NUM>, since the flange F fits into the fitting recess <NUM>, the bead portion is less likely to move with respect to the rim R. Deformation of the bead portion is suppressed, so that strain generated in the bead portion is reduced. The reduction of the strain generated in the bead portion contributes to reduction of strain generated in the side portion. In the tire <NUM>, the risk of occurrence of damage, caused by strain, in the side portion is reduced.

In the tire <NUM>, even though the band <NUM> is provided, the required durability is ensured. As described above, the band <NUM> contributes to improvement of the uneven wear resistance of the tire <NUM>. In the tire <NUM>, the durability is ensured, and the uneven wear resistance is improved.

As described above, the fitting recess <NUM> of the tire <NUM> has the concave curved surface <NUM> whose contour in the meridian cross-section is an arc. In the tire <NUM>, the radius Rb of the arc representing the contour of the concave curved surface <NUM> (hereinafter, the radius Rb of the concave curved surface <NUM>) is preferably not less than <NUM> and not greater than <NUM>.

When the radius Rb is set to be not less than <NUM>, the flange F fits snugly into the fitting recess <NUM>. In the tire <NUM>, the bead portion is sufficiently held by the rim R, so that deformation of the bead portion is suppressed. Since the strain generated in the bead portion is reduced, the influence of the strain, generated in the bead portion, on the side portion is also reduced. In the tire <NUM>, the durability is improved. From this viewpoint, the radius Rb is more preferably not less than <NUM> and further preferably not less than <NUM>.

When the radius Rb is set to be not greater than <NUM>, the flange F comes into sufficiently close contact with the fitting recess <NUM>. Movement of the bead portion with respect to the flange F is suppressed, so that the strain generated in the side portion is reduced. In the tire <NUM>, the durability is improved. From this viewpoint, the radius Rb is more preferably not greater than <NUM> and further preferably not greater than <NUM>.

In <FIG>, reference sign PB indicates the position at which the length from the recess reference line LB to the fitting recess <NUM> is at its maximum, that is, the bottom of the fitting recess <NUM>. A length indicated by a double-headed arrow D is the distance from the recess reference line LB to the bottom PB of the fitting recess <NUM>. The length D is the depth of the fitting recess <NUM>. A length indicated by a double-headed arrow W is the distance from the tangent point PS to the tangent point PU. The distance W is the width of the fitting recess <NUM>.

In the tire <NUM>, from the viewpoint that the flange F comes into sufficiently close contact with the fitting recess <NUM> and movement of the bead portion with respect to the flange F is effectively suppressed, the ratio (DAV) of the depth D of the fitting recess <NUM> to the width W of the fitting recess <NUM> is preferably not less than <NUM> and more preferably not less than <NUM>. From the viewpoint that the flange F fits snugly into the fitting recess <NUM> and deformation of the bead portion is effectively suppressed, the ratio (DAV) is preferably not greater than <NUM> and more preferably not greater than <NUM>.

From the viewpoint of reduction of the strain generated in the side portion, the depth D of the fitting recess <NUM> is preferably not less than <NUM> and preferably not greater than <NUM>.

In the tire <NUM>, the ratio (WT/WA) of the width WT of the tread <NUM> to the cross-sectional width WA is preferably not less than <NUM> and not greater than <NUM>. When the ratio (WT/WA) is set to be not less than <NUM>, the internal volume of the tire <NUM> is appropriately maintained. The band <NUM> effectively suppresses radial growth of the tire <NUM>. Since the ground-contact shape of the tire <NUM> is less likely to change, good uneven wear resistance is achieved in the tire <NUM>. From this viewpoint, the ratio (WT/WA) is more preferably not less than <NUM>. When the ratio (WT/WA) is set to be not greater than <NUM>, the holding force of the band <NUM> is appropriately maintained. Since damage caused due to concentration of strain on the side portion is prevented, the tire <NUM> has good durability. From this viewpoint, the ratio (WT/WA) is more preferably not greater than <NUM>.

In <FIG>, a length indicated by reference sign WB is the width of the band <NUM>. The width WB of the band <NUM> is the distance in the axial direction from one end 40e of the band <NUM> to the other end 40e of the band <NUM>. In the case where the outer end 46se of the edge band <NUM> is located outward of the end 44e of the full band <NUM> in the axial direction, the width WB of the band <NUM> is represented as the distance in the axial direction from the outer end 46se of one edge band <NUM> to the outer end 46se of the other edge band <NUM>.

In the tire <NUM>, the ratio (WB/WT) of the width WB of the band <NUM> to the width WT of the tread <NUM> is preferably not less than <NUM> and not greater than <NUM>. When the ratio (WB/WT) is set to be not less than <NUM>, the band <NUM> effectively suppresses radial growth of the tire <NUM>. Since the ground-contact shape of the tire <NUM> is less likely to change, good uneven wear resistance is achieved in the tire <NUM>. From this viewpoint, the ratio (WB/WT) is more preferably not less than <NUM>. When the ratio (WB/WT) is set to be not greater than <NUM>, the holding force of the band <NUM> is appropriately maintained. Since an increase in strain due to the holding by the band <NUM> is prevented, the risk of occurrence of damage in the side portion is reduced. The tire <NUM> has good durability. From this viewpoint, the ratio (WB/WT) is more preferably not greater than <NUM>.

As described above, the full band <NUM> has the ends 44e opposed to each other across the equator plane CL. The full band <NUM> extends in the axial direction from the equator plane CL toward each end 44e. Each end 44e of the full band <NUM> is located outward of the shoulder circumferential groove <NUM> in the axial direction. The full band <NUM> is located inward of the shoulder circumferential groove <NUM> in the radial direction.

In the tire <NUM>, the full band <NUM> effectively suppresses deformation near the shoulder circumferential groove <NUM>. Since a shape change of the tire <NUM> is suppressed, the ground-contact shape of the tire <NUM> is less likely to change. In the tire <NUM>, occurrence of uneven wear is suppressed. From this viewpoint, each end 44e of the full band <NUM> is preferably located outward of the shoulder circumferential groove <NUM> in the axial direction.

In <FIG>, a length indicated by reference sign SF is the distance in the axial direction from the shoulder circumferential groove <NUM>, that is, the inner end of the shoulder land portion <NUM>, to the end 44e of the full band <NUM>.

In the tire <NUM>, the ratio (SF/WS) of the distance SF in the axial direction from the shoulder circumferential groove <NUM> to the end 44e of the full band <NUM>, to the width WS in the axial direction of the shoulder land portion <NUM>, is not greater than <NUM>%. Accordingly, the end 44e of the full band <NUM> is located at an appropriate distance from the end of the tread <NUM> which moves actively in a running state. Since fluctuation of the tension of the band cord <NUM> is suppressed, occurrence of a break of the band cord <NUM> is suppressed in the tire <NUM>. The full band <NUM> of the tire <NUM> contributes to suppression of a shape change. From this viewpoint, the ratio (SF/WS) is more preferably not greater than <NUM>% and further preferably not greater than <NUM>%.

When the ratio (SF/WS) is set to be not less than <NUM>%, the end 44e of the full band <NUM> is located at an appropriate distance from the shoulder circumferential groove <NUM>, specifically, the bottom 30b of the shoulder circumferential groove <NUM>. In the tire <NUM>, occurrence of damage starting from the bottom 30b of the shoulder circumferential groove <NUM> is suppressed. Since the width of the full band <NUM> is ensured, the full band <NUM> contributes to suppression of a shape change of the tire <NUM>. From this viewpoint, the ratio (SF/WS) is more preferably not less than <NUM>%.

In <FIG>, a length indicated by reference sign We is the distance in the axial direction from the end 44e of the full band <NUM> to the inner end 46ue of the edge band <NUM>.

In the tire <NUM>, the distance We in the axial direction from the end 44e of the full band <NUM> to the inner end 46ue of the edge band <NUM> is preferably not less than <NUM>. Accordingly, the edge band <NUM> effectively holds the end 44e of the full band <NUM>. Fluctuation of the tension of the band cord <NUM> included in the full band <NUM> is suppressed, so that occurrence of a break of the band cord <NUM> due to the fluctuation of the tension is suppressed. The full band <NUM> of the tire <NUM> can more stably exhibit the function of suppressing a shape change. From this viewpoint, the distance We in the axial direction is preferably not less than <NUM>.

In the tire <NUM>, the position of the inner end 46ue of the edge band <NUM> is determined as appropriate in consideration of involvement in occurrence of damage starting from the bottom 30b of the shoulder circumferential groove <NUM>. Therefore, a preferable upper limit of the distance We in the axial direction is not set. From the viewpoint of effectively suppressing occurrence of damage starting from the bottom 30b of the shoulder circumferential groove <NUM>, in the axial direction, the inner end 46ue of the edge band <NUM> is preferably located outward of the bottom 30b of the shoulder circumferential groove <NUM>, and more preferably located further outward of the shoulder circumferential groove <NUM>. In the tire <NUM>, in the axial direction, the inner end 46ue of the edge band <NUM> may be located inward of the bottom 30b of the shoulder circumferential groove <NUM>. In this case, in the axial direction, the inner end 46ue of the edge band <NUM> is more preferably located further inward of the shoulder circumferential groove <NUM>.

In the tire <NUM>, each end 44e of the full band <NUM> is located inward of each end 38e of the belt <NUM> in the axial direction. The belt <NUM> is wider than the full band <NUM>. The belt <NUM> holds each end 44e of the full band <NUM>. The belt <NUM> contributes to suppression of fluctuation of the tension of the band cord <NUM> included in the full band <NUM>. Occurrence of a break of the band cord <NUM> due to fluctuation of the tension is suppressed, so that the full band <NUM> can stably exhibit the function of suppressing a shape change. From this viewpoint, each end 44e of the full band <NUM> is preferably located inward of each end 38e of the belt <NUM> in the axial direction.

In the tire <NUM>, the first belt ply 42A, the second belt ply 42B, and the third belt ply 42C which are included in the belt <NUM> have a width larger than the width of the full band <NUM>. The belt <NUM> effectively holds each end 44e of the full band <NUM>. The belt <NUM> contributes to suppression of fluctuation of the tension of the band cord <NUM> included in the full band <NUM>. Occurrence of a break of the band cord <NUM> due to fluctuation of the tension is suppressed, so that the full band <NUM> can stably exhibit the function of suppressing a shape change. From this viewpoint, the first belt ply 42A, the second belt ply 42B, and the third belt ply 42C which are included in the belt <NUM> preferably have a width larger than the width of the full band <NUM>.

A force acts on the full band <NUM> of the tire <NUM> so as to spread from the inner side toward the outer side in the radial direction. Due to this force, tension is generated in the band cord <NUM> of the full band <NUM>. In the tire <NUM>, the belt <NUM> is located radially inward of the full band <NUM>.

In the tire <NUM>, the belt <NUM> reduces the force acting on the full band <NUM>, so that the tension of the band cord <NUM> included in the full band <NUM> is appropriately maintained. The belt <NUM> contributes to suppression of fluctuation of the tension of the band cord <NUM>. Since the belt <NUM> is wider than the full band <NUM>, fluctuation of the tension of the band cord <NUM> is effectively suppressed. In the tire <NUM>, a break is less likely to occur in the band cord <NUM> of the full band <NUM>. The full band <NUM> can stably exhibit the function of suppressing a shape change. From this viewpoint, in the tire <NUM>, the belt <NUM> is preferably located inward of the full band <NUM> in the radial direction. More preferably, the belt <NUM> is located inward of the full band <NUM> in the radial direction, and the belt <NUM> has a width larger than the width of the full band <NUM>.

<FIG> shows a meridian cross-section of a heavy duty tire <NUM> (hereinafter, also referred to simply as "tire <NUM>") according to another embodiment of the present invention. <FIG> shows a tread portion of the tire <NUM>. In <FIG>, the right-left direction is the axial direction of the tire <NUM>, and the up-down direction is the radial direction of the tire <NUM>. The direction perpendicular to the surface of the drawing sheet of <FIG> is the circumferential direction of the tire <NUM>.

The tire <NUM> has the same configuration as the tire <NUM> shown in <FIG> except that the configuration of the reinforcing layer <NUM> of the tire <NUM> shown in <FIG> is different. Therefore, in <FIG>, the same components as those of the tire <NUM> in <FIG> are designated by the same reference signs, and the description thereof is omitted.

In the tire <NUM> as well, a reinforcing layer <NUM> is located inward of the tread <NUM> in the radial direction. The reinforcing layer <NUM> is located between the carcass <NUM> and the tread <NUM>. The reinforcing layer <NUM> includes a belt <NUM> and a band <NUM>.

The belt <NUM> of the tire <NUM> includes four belt plies <NUM>. The four belt plies <NUM> include a first belt ply 80A located on the inner side in the radial direction, a second belt ply 80B located outward of the first belt ply 80A in the radial direction, a third belt ply 80C located outward of the second belt ply 80B in the radial direction, and a fourth belt ply 80D located outward of the third belt ply 80C in the radial direction. As shown in <FIG>, an end 80Ae of the first belt ply 80A, an end 80Be of the second belt ply 80B, an end 80Ce of the third belt ply 80C, and an end 80De of the fourth belt ply 80D are located outward of the shoulder circumferential groove <NUM> in the axial direction.

In the tire <NUM>, the second belt ply 80B has the largest width in the axial direction, and the fourth belt ply 80D has the smallest width in the axial direction. The first belt ply 80A has a width in the axial direction equal to the width in the axial direction of the third belt ply 80C. The width in the axial direction of the first belt ply 80A may be larger than the width in the axial direction of the third belt ply 80C.

In the tire <NUM>, from the viewpoint of ensuring the stiffness of the tread portion, the ratio of the width in the axial direction of the first belt ply 80A to the width WT of the tread <NUM> is preferably not less than <NUM> and preferably not greater than <NUM>. The ratio (W2/WT) of the width W2 in the axial direction of the second belt ply 80B to the width WT of the tread <NUM> is preferably not less than <NUM> and preferably not greater than <NUM>. The ratio (W3/WT) of the width W3 in the axial direction of the third belt ply 80C to the width WT of the tread <NUM> is preferably not less than <NUM> and preferably not greater than <NUM>. The ratio (W4/WT) of a width W4 in the axial direction of the fourth belt ply 80D to the width WT of the tread <NUM> is preferably not less than <NUM> and preferably not greater than <NUM>.

The band <NUM> includes a full band <NUM> and a pair of edge bands <NUM>. The full band <NUM> has ends 82e opposed to each other across the equator plane CL. The pair of edge bands <NUM> are disposed so as to be spaced apart from each other in the axial direction with the equator plane CL therebetween. In the tire <NUM>, the fourth belt ply 80D which forms a part of the belt <NUM> is located between the pair of edge bands <NUM>.

In the tire <NUM>, each edge band <NUM> is located between the tread <NUM> and the full band <NUM>. The edge band <NUM> is located outward of the end 82e of the full band <NUM> in the radial direction. In the axial direction, an inner end 84ue of the edge band <NUM> is located inward of the end 82e of the full band <NUM>. In the axial direction, an outer end 84se of the edge band <NUM> is located outward of the end 82e of the full band <NUM>. The edge band <NUM> overlaps the end 82e of the full band <NUM> in the radial direction. In the axial direction, the outer end 84se of the edge band <NUM> is located inward of an end 76e of the belt <NUM>. In the axial direction, the outer end 84se of the edge band <NUM> of the tire <NUM> is located inward of the end 80Ce of the third belt ply 80C.

<FIG> shows the configuration of the reinforcing layer <NUM>. In <FIG>, the right-left direction is the axial direction of the tire <NUM>, and the up-down direction is the circumferential direction of the tire <NUM>. The direction perpendicular to the surface of the drawing sheet of <FIG> is the radial direction of the tire <NUM>. The front side of the drawing sheet of <FIG> is the outer side in the radial direction. The back side of the drawing sheet of <FIG> is the inner side in the radial direction.

As shown in <FIG>, each belt ply <NUM> included in the belt <NUM> includes a large number of belt cords <NUM> aligned with each other. The belt cords <NUM> are covered with a topping rubber <NUM>. The belt cords <NUM> are steel cords. The density of the belt cords <NUM> in each belt ply <NUM> is not less than <NUM> ends/<NUM> and not greater than <NUM> ends/<NUM>.

The belt cords <NUM> in each belt ply <NUM> are tilted relative to the circumferential direction. The tilt direction of first belt cords 86A is the same as the tilt direction of second belt cords 86B. The tilt direction of the second belt cords 86B is opposite to the tilt direction of third belt cords 86C. The tilt direction of the third belt cords 86C is the same as the tilt direction of fourth belt cords 86D. The tilt direction of the first belt cords 86A may be opposite to the tilt direction of the second belt cords 86B, and the tilt direction of the fourth belt cords 86D may be opposite to the tilt direction of the third belt cords 86C. In the tire <NUM>, from the viewpoint of obtaining a ground-contact surface whose shape change is suppressed, the tilt direction of the second belt cords 86B is preferably opposite to the tilt direction of the third belt cords 86C.

In <FIG>, an angle θ1b is a tilt angle (hereinafter, first tilt angle θ1b) of the first belt cords 86A relative to the equator plane CL. An angle θ2b is a tilt angle (hereinafter, second tilt angle θ2b) of the second belt cords 86B relative to the equator plane CL. An angle θ3b is a tilt angle (hereinafter, third tilt angle 03b) of the third belt cords 86C relative to the equator plane CL. An angle θ4b is a tilt angle (hereinafter, fourth tilt angle θ4b) of the fourth belt cords 86D relative to the equator plane CL.

In the tire <NUM>, each of the first tilt angle θ1b, the second tilt angle θ2b, the third tilt angle θ3b, and the fourth tilt angle θ4b is preferably not less than <NUM>° and preferably not greater than <NUM>°. From the viewpoint of effectively restraining movement of the tire <NUM> and ensuring shape stability of the ground-contact surface, the first tilt angle θ1b is preferably not less than <NUM>° and preferably not greater than <NUM>°. The second tilt angle θ2b is preferably not less than <NUM>° and preferably not greater than <NUM>°. The third tilt angle θ3b is preferably not less than <NUM>° and preferably not greater than <NUM>°. The fourth tilt angle θ4b is preferably not less than <NUM>° and preferably not greater than <NUM>°.

As shown in <FIG>, the full band <NUM> and the pair of edge bands <NUM> included in the band <NUM> each include a spirally wound band cord <NUM>. The band cord <NUM> is covered with a topping rubber <NUM>.

In the tire <NUM>, the band cords <NUM> are steel cords or organic fiber cords. In the case where organic fiber cords are used as the band cords <NUM>, examples of the organic fiber include nylon fibers, polyester fibers, rayon fibers, and aramid fibers.

The band cord <NUM> of the full band <NUM> extends substantially in the circumferential direction. The density of the band cord <NUM> in the full band <NUM> is not less than <NUM> ends/<NUM> and not greater than <NUM> ends/<NUM>. The band cord <NUM> of the edge band <NUM> extends substantially in the circumferential direction. The density of the band cord <NUM> in the edge band <NUM> is not less than <NUM> ends/<NUM> and not greater than <NUM> ends/<NUM>.

In the tire <NUM> as well, as shown in <FIG>, each of the end 80Be of the second belt ply 80B and the end 80Ce of the third belt ply 80C is covered with a rubber layer <NUM>. Two rubber layers <NUM> are further disposed between the end 80Be of the second belt ply 80B and the end 80Ce of the third belt ply 80C, each of which is covered with the rubber layer <NUM>. In the tire <NUM>, an edge member <NUM> including four rubber layers <NUM> in total is formed between the end 80Be of the second belt ply 80B and the end 80Ce of the third belt ply 80C. The edge member <NUM> is formed from a crosslinked rubber. The edge member <NUM> contributes to maintaining the interval between the end 80Be of the second belt ply 80B and the end 80Ce of the third belt ply 80C. In the tire <NUM>, a change of the positional relationship between the end 80Be of the second belt ply 80B and the end 80Ce of the third belt ply 80C due to running is suppressed.

As described above, the full band <NUM> has the ends 82e opposed to each other across the equator plane CL. The full band <NUM> extends in the axial direction from the equator plane CL toward each end 82e.

In the tire <NUM>, the full band <NUM> effectively restrains movement of the tread portion. A change of a case line is suppressed, so that the ground-contact shape is less likely to change.

Furthermore, in the tire <NUM>, each edge band <NUM> located outward of the end 82e of the full band <NUM> in the radial direction holds the end 82e of the full band <NUM>. Fluctuation of the tension of the band cord <NUM> included in the full band <NUM> is suppressed, so that a break of the band cord <NUM> due to the fluctuation of the tension is less likely to occur. The full band <NUM> of the tire <NUM> can stably exhibit the function of suppressing a shape change.

Although not shown, in the tire <NUM> as well, the outer surface of each chafer <NUM> has a fitting recess <NUM> extending in the circumferential direction. When the tire <NUM> is fitted onto the rim R, the flange F fits into the fitting recess <NUM>.

In the tire <NUM>, since the flange F fits into the fitting recess <NUM>, the bead portion is less likely to move with respect to the rim R. Deformation of the bead portion is suppressed, so that strain generated in the bead portion is reduced. The reduction of the strain generated in the bead portion contributes to reduction of strain generated in the side portion. In the tire <NUM> as well, the risk of occurrence of damage, caused by strain, in the side portion is reduced.

As described above, the full band <NUM> has the ends 82e opposed to each other across the equator plane CL. The full band <NUM> extends in the axial direction from the equator plane CL toward each end 82e. Each end 82e of the full band <NUM> is located outward of the shoulder circumferential groove <NUM> in the axial direction. The full band <NUM> is located inward of the shoulder circumferential groove <NUM> in the radial direction.

In the tire <NUM>, the full band <NUM> effectively suppresses deformation near the shoulder circumferential groove <NUM>. Since a shape change of the tire <NUM> is suppressed, the ground-contact shape of the tire <NUM> is less likely to change. In the tire <NUM>, occurrence of uneven wear is suppressed. From this viewpoint, each end 82e of the full band <NUM> is preferably located outward of the shoulder circumferential groove <NUM> in the axial direction.

In <FIG>, a length indicated by reference sign SF is the distance in the axial direction from the shoulder circumferential groove <NUM> to the end 82e of the full band <NUM>.

In the tire <NUM>, the ratio (SF/WS) of the distance SF in the axial direction from the shoulder circumferential groove <NUM> to the end 82e of the full band <NUM>, to the width WS in the axial direction of the shoulder land portion <NUM>, is preferably not greater than <NUM>%. Accordingly, the end 82e of the full band <NUM> is located at an appropriate distance from the end of the tread <NUM> which moves actively in a running state. Since fluctuation of the tension of the band cord <NUM> is suppressed, occurrence of a break of the band cord <NUM> is suppressed in the tire <NUM>. The full band <NUM> of the tire <NUM> contributes to suppression of a shape change. From this viewpoint, the ratio (SF/WS) is more preferably not greater than <NUM>% and further preferably not greater than <NUM>%.

When the ratio (SF/WS) is set to be not less than <NUM>%, the end 82e of the full band <NUM> is located at an appropriate distance from the shoulder circumferential groove <NUM>, specifically, the bottom 30b of the shoulder circumferential groove <NUM>. In the tire <NUM>, occurrence of damage starting from the bottom 30b of the shoulder circumferential groove <NUM> is suppressed. Since the width of the full band <NUM> is ensured, the full band <NUM> contributes to suppression of a shape change of the tire <NUM>. From this viewpoint, the ratio (SF/WS) is more preferably not less than <NUM>%.

In <FIG>, a length indicated by reference sign We is the distance in the axial direction from the end 82e of the full band <NUM> to the inner end 84ue of the edge band <NUM>.

In the tire <NUM>, the distance We in the axial direction from the end 82e of the full band <NUM> to the inner end 84ue of the edge band <NUM> is preferably not less than <NUM>. Accordingly, the edge band <NUM> effectively holds the end 82e of the full band <NUM>. Fluctuation of the tension of the band cord <NUM> included in the full band <NUM> is suppressed, so that occurrence of a break of the band cord <NUM> due to the fluctuation of the tension is suppressed. The full band <NUM> of the tire <NUM> can more stably exhibit the function of suppressing a shape change. From this viewpoint, the distance We in the axial direction is preferably not less than <NUM>.

In the tire <NUM>, the position of the inner end 84ue of the edge band <NUM> is determined as appropriate in consideration of involvement in occurrence of damage starting from the bottom 30b of the shoulder circumferential groove <NUM>. Therefore, a preferable upper limit of the distance We in the axial direction is not set. From the viewpoint of effectively suppressing occurrence of damage starting from the bottom 30b of the shoulder circumferential groove <NUM>, in the axial direction, the inner end 84ue of the edge band <NUM> is preferably located outward of the bottom 30b of the shoulder circumferential groove <NUM>, and more preferably located further outward of the shoulder circumferential groove <NUM>. In the tire <NUM>, in the axial direction, the inner end 84ue of the edge band <NUM> may be located inward of the bottom 30b of the shoulder circumferential groove <NUM>. In this case, in the axial direction, the inner end 84ue of the edge band <NUM> is more preferably located further inward of the shoulder circumferential groove <NUM>.

In the tire <NUM>, each end 82e of the full band <NUM> is located inward of the end 76e of the belt <NUM> in the axial direction. The belt <NUM> is wider than the full band <NUM>. The belt <NUM> holds each end 82e of the full band <NUM>. The belt <NUM> contributes to suppression of fluctuation of the tension of the band cord <NUM> included in the full band <NUM>. Occurrence of a break of the band cord <NUM> due to fluctuation of the tension is suppressed, so that the full band <NUM> can stably exhibit the function of suppressing a shape change. From this viewpoint, the end 82e of the full band <NUM> is preferably located inward of the end 76e of the belt <NUM> in the axial direction.

In the tire <NUM>, the second belt ply 80B is located radially inward of the full band <NUM>. The second belt ply 80B reduces the force acting on the full band <NUM>, so that the tension of the band cord <NUM> included in the full band <NUM> is appropriately maintained. The second belt ply 80B contributes to suppression of fluctuation of the tension of the band cord <NUM>. Since the second belt ply 80B is wider than the full band <NUM>, fluctuation of the tension of the band cord <NUM> is effectively suppressed. In the tire <NUM>, a break is less likely to occur in the band cord <NUM> of the full band <NUM>. The full band <NUM> can stably exhibit the function of suppressing a shape change. From this viewpoint, at least one belt ply <NUM> of the plurality of belt plies <NUM> included in the belt <NUM> is preferably located inward of the full band <NUM> in the radial direction. The at least one belt ply <NUM> located inward of the full band <NUM> more preferably has a width larger than the width of the full band <NUM>.

In the tire <NUM>, the first belt ply 80A and the second belt ply 80B are located inward of the full band <NUM> in the radial direction. The first belt ply 80A and the second belt ply 80B contribute to suppression of fluctuation of the tension of the band cord <NUM>. Since the first belt ply 80A and the second belt ply 80B are wider than the full band <NUM>, fluctuation of the tension of the band cord <NUM> is more effectively suppressed. In the tire <NUM>, a break is less likely to occur in the band cord <NUM> of the full band <NUM>. The full band <NUM> can stably exhibit the function of suppressing a shape change. From this viewpoint, at least two belt plies <NUM> of the plurality of belt plies <NUM> included in the belt <NUM> are more preferably located inward of the full band <NUM> in the radial direction. The at least two belt plies <NUM> located inward of the full band <NUM> further preferably have a width larger than the width of the full band <NUM>.

In the tire <NUM>, in the radial direction, the second belt ply 80B is located inward of the full band <NUM>, and the third belt ply 80C is located outward of the full band <NUM>. In the tire <NUM>, the full band <NUM> is interposed between the second belt ply 80B and the third belt ply 80C. As described above, the second belt ply 80B is wider than the full band <NUM>. The third belt ply 80C is also wider than the full band <NUM>. The plurality of belt plies <NUM> included in the belt <NUM> of the tire <NUM> include two belt plies <NUM> having a width larger than the width of the full band <NUM>, and the full band <NUM> is interposed between the two belt plies <NUM> having a large width. In the tire <NUM>, fluctuation of the tension of the band cord <NUM> included in the full band <NUM> is more effectively suppressed, so that a break is less likely to occur in the band cord <NUM> of the full band <NUM>. The full band <NUM> of the tire <NUM> can stably exhibit the function of suppressing a shape change. From this viewpoint, in the tire <NUM>, preferably, the plurality of belt plies <NUM> included in the belt <NUM> include two belt plies <NUM> having a width larger than the width of the full band <NUM>, and the full band <NUM> is interposed between the two belt plies <NUM> having a large width.

In the tire <NUM>, the first belt ply 80A, the second belt ply 80B, and the third belt ply 80C have a width larger than the width of the full band <NUM>. In the radial direction, the first belt ply 80A and the second belt ply 80B are located inward of the full band <NUM>, and the third belt ply 80C is located outward of the full band <NUM>. The pair of edge bands <NUM> are located outward of the third belt ply 80C in the radial direction. As described above, each edge band <NUM> is located outward of the end 82e of the full band <NUM> in the radial direction. The edge band <NUM> overlaps the end 82e of the full band <NUM> via the third belt ply 80C in the radial direction.

In the tire <NUM>, the full band <NUM> can stably exhibit the function of suppressing a shape change, and improvement of uneven wear resistance is achieved. From this viewpoint, preferably, in the tire <NUM>, the plurality of belt plies <NUM> included in the belt <NUM> include the first belt ply 80A located on the inner side in the radial direction, the second belt ply 80B located outward of the first belt ply 80A in the radial direction, and the third belt ply 80C located outward of the second belt ply 80B in the radial direction, the first belt ply 80A, the second belt ply 80B, and the third belt ply 80C have a width larger than the width of the full band <NUM>, the first belt ply 80A and the second belt ply 80B are located inward of the full band <NUM> in the radial direction, the third belt ply 80C is located outward of the full band <NUM> in the radial direction, and each edge band <NUM> located outward of the full band <NUM> overlaps the end 82e of the full band <NUM> via the third belt ply 80C in the radial direction.

As is obvious from the above description, according to the present invention, a heavy duty tire that can ensure durability and improve uneven wear resistance is obtained. The present invention exhibits a remarkable effect in a low-flatness heavy duty tire having a nominal aspect ratio of <NUM>% or less.

The following will describe the present invention in further detail by means of examples, etc., but the present invention is not limited to the examples, but can be modified within the scope of the appended claims.

A heavy duty pneumatic tire (tire size = <NUM>/50R22. <NUM>) having the basic structure shown in <FIG> and having specifications shown in Table <NUM> below was obtained.

The reinforcing layer of Example <NUM> has the configuration shown in <FIG>. The fact that each end of the full band is located outward of the shoulder circumferential groove in the axial direction is represented as "OUT" in the cell for "full band end" in Table <NUM> below. The fact that the band has edge bands is represented as "Y" in the cell for "edge band" in Table <NUM>.

In Example <NUM>, the ratio (WT/WA) of the width WT of the tread to the cross-sectional width WA was <NUM>. The ratio (WB/WT) of the width WB of the band to the width WT of the tread was <NUM>. The radius Rb of the arc representing the contour of the concave curved surface of the fitting recess provided on the outer surface of each chafer was <NUM>.

In Example <NUM>, the distance We in the axial direction from the end of the full band to the inner end of the edge band was <NUM>. The ratio (SF/WS) of the distance SF in the axial direction from the shoulder circumferential groove to the end of the full band, to the width WS in the axial direction of the shoulder land portion, was <NUM>%.

A tire of Comparative Example <NUM> was obtained in the same manner as Example <NUM>, except that no edge band and no fitting recess were provided and each end of the full band was located inward of the shoulder circumferential groove in the axial direction.

A tire of Comparative Example <NUM> was obtained in the same manner as Example <NUM>, except that no edge band and no fitting recess were provided.

A tire of Comparative Example <NUM> was obtained in the same manner as Example <NUM>, except that no fitting recess was provided.

Tires of Examples <NUM> and <NUM> were obtained in the same manner as Example <NUM>, except that the width WT of the tread was changed such that the ratio (WT/WA) was set as shown in Tables <NUM> and <NUM> below.

A tire of Example <NUM> was obtained in the same manner as Example <NUM>, except that the width WT of the tread and the width WB of the band were changed such that the ratio (WT/WA) and the ratio (WB/WT) were set as shown in Table <NUM> below.

Tires of Examples <NUM> and <NUM> were obtained in the same manner as Example <NUM>, except that the radius Rb of the concave curved surface was set as shown in Table <NUM> below.

In Examples <NUM> and <NUM>, the position of the bottom PB of the fitting recess and the depth D of the fitting recess were set in the same manner as Example <NUM>.

A tire of Example <NUM> was obtained in the same manner as Example <NUM>, except that a reinforcing layer having the configuration shown in <FIG> was used.

In Example <NUM>, similar to Example <NUM>, the distance We in the axial direction from the end of the full band to the inner end of the edge band was <NUM>. The ratio (SF/WS) of the distance SF in the axial direction from the shoulder circumferential groove to the end of the full band, to the width WS in the axial direction of the shoulder land portion, was <NUM>%.

A test tire was fitted onto a rim (<NUM>×<NUM>) and inflated with air to adjust the internal pressure of the tire to a normal internal pressure. The tire was caused to run on a drum tester at a speed of <NUM>/h for <NUM>, and a profile of the case line on the inner side of the shoulder circumferential groove was obtained. The profile of the case line was compared with the profile of the case line before running to confirm a change in profile before and after running. The results are represented as indexes according to the following ratings in Tables <NUM> and <NUM> below. A higher value represents that a change in profile is reduced. In the running test, a normal load was applied to the tire.

The strain generated on the surface of a side portion when a tire expanded was measured. The tire was fitted onto a rim (<NUM>×<NUM>) and inflated with air to adjust the internal pressure of the tire to <NUM>% of a normal internal pressure. Accordingly, the state of the tire was adjusted to a reference state. The tire in the reference state was further inflated with air to adjust the internal pressure of the tire to the normal internal pressure to expand the tire. Accordingly, the state of the tire was adjusted to a normal state. The peak value of the strain in the radial direction generated on the surface of the side portion was measured in the process of adjusting the state of the tire from the reference state to the normal state. The result is represented as an index with the result of Example <NUM> being regarded as <NUM>, in Tables <NUM> and <NUM> below. A higher value represents that the strain generated on the surface of the side portion is smaller.

As shown in Tables <NUM> and <NUM>, in the Examples, a profile change is suppressed, the strain generated in the side portion is reduced, durability is ensured, and uneven wear resistance is improved. From the evaluation results, advantages of the present invention are clear.

Claim 1:
A heavy duty tire (<NUM>) having a nominal aspect ratio of <NUM>% or less, the heavy duty tire (<NUM>) comprising:
a tread (<NUM>) that comes into contact with a road surface;
a pair of sidewalls (<NUM>) that are each connected to an end of the tread (<NUM>) and located inward of the tread (<NUM>) in a radial direction;
a pair of chafers (<NUM>) that are each located inward of the sidewall (<NUM>) in the radial direction and come into contact with a rim (R);
a pair of beads (<NUM>) that are each located inward of the chafer (<NUM>) in an axial direction; and
a band (<NUM>) that is located inward of the tread (<NUM>) in the radial direction and includes a spirally wound band cord, wherein
at least three circumferential grooves (<NUM>) are formed on the tread, whereby at least four land portions (<NUM>) are formed in the tread (<NUM>),
among the at least three circumferential grooves (<NUM>), a circumferential groove located on each outer side in an axial direction is a shoulder circumferential groove (<NUM>),
a land portion located outward of the shoulder circumferential groove (<NUM>) in the axial direction is a shoulder land portion (<NUM>),
the band (<NUM>) includes a full band (<NUM>) having ends opposed to each other across an equator plane, and a pair of edge bands (<NUM>) located outward of the ends of the full band (<NUM>) in the radial direction, and
an outer surface of each chafer (<NUM>) has a fitting recess (<NUM>) into which a flange (F) of the rim (R) fits,
characterized in that
a ratio (SF/WS) of a distance (SF) in the axial direction from the shoulder circumferential groove (<NUM>) to the end (44e) of the full band (<NUM>), to a width (WS) in the axial direction of the shoulder land portion (<NUM>), is not less than <NUM>% and not greater than <NUM>%.