Patent Description:
In order to manage data regarding manufacturing management, customer information, running history, etc., of tires, incorporation of radio frequency identification (RFID) tags into tires has been proposed. Therefore, various studies have been conducted for the technology to incorporate an RFID tag into a tire (for example, <CIT>). Further prior art tires are disclosed in <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; and <CIT>.

For heavy duty pneumatic tires which are mounted on vehicles such as trucks and buses, there are cases where an RFID tag is placed in a bead portion, not in a side portion, in consideration of breakage due to external damage.

In the case where an RFID tag is placed in a bead portion, the risk of breakage due to external damage can be reduced as compared to the case where an RFID tag is placed in a side portion. Meanwhile, the risk of breakage due to strain during load application may be increased depending on the position in the bead portion at which the RFID tag is placed.

Moreover, in the case of incorporating an RFID tag into a tire, the RFID tag may be covered with a covering rubber and placed in a bead portion. In this case, the durability of the bead portion against strain during load application may be decreased depending on the hardness of the covering rubber.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a heavy duty pneumatic tire in which reduction of the risk of damage to an RFID tag is achieved while an effect on the durability of a bead portion is taken into consideration.

The above object is satisfied by claim <NUM>, such a heavy duty pneumatic tire according to an aspect of the present invention includes:.

Preferably, in the pneumatic tire, the tag assembly is located between the outer apex and the chafer in the axial direction.

Preferably, in the pneumatic tire, a distance in the radial direction from the bead base line to the outer end of the inner apex is not less than <NUM>% and not greater than <NUM>% of the distance in the radial direction from the bead base line to the end of the turned-up portion.

Preferably, in the pneumatic tire, the complex elastic modulus of the inner apex is not less than <NUM> MPa and not greater than <NUM> MPa.

Preferably, in the pneumatic tire, a ratio of a thickness of the RFID tag to a total thickness of the covering rubber is not less than <NUM> and not greater than <NUM>.

Preferably, in the pneumatic tire, the total thickness of the covering rubber is not less than <NUM> and not greater than <NUM>.

Preferably, in the pneumatic tire, a complex elastic modulus of the covering rubber is lower than a complex elastic modulus of the chafer.

Preferably, in the pneumatic tire, the complex elastic modulus of the covering rubber is not less than <NUM> MPa and not greater than <NUM> MPa.

In the heavy duty pneumatic tire of the present invention, reduction of the risk of damage to the RFID tag is achieved while an effect on the durability of a bead portion is taken into consideration.

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.

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.

<FIG> shows a part of a heavy duty pneumatic tire <NUM> (hereinafter, sometimes 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. In <FIG>, the tire <NUM> is fitted on a rim R (normal rim). The tire <NUM> shown in <FIG> is in a normal state.

<FIG> shows a part of a cross-section (hereinafter, 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>. In <FIG>, an alternate long and short dash line CL represents the equator plane of the tire <NUM>.

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

In <FIG>, a solid line BBL is a bead base line extending in the axial direction. The bead base line BBL is a line that defines the rim diameter (see JATMA or the like) of the rim R (normal rim).

In <FIG>, reference character PC indicates the point of intersection of the inner surface of the carcass <NUM> and the equator plane CL. A double-headed arrow HC indicates the distance in the radial direction from the bead base line BBL to the point of intersection PC. The distance HC in the radial direction is the cross-sectional height of the carcass <NUM>.

The tread <NUM> comes into contact with a road surface at an outer surface <NUM> thereof, that is, a tread surface <NUM> thereof. The tread <NUM> has the tread surface <NUM> which comes into contact with a road surface. The tread <NUM> is formed from a crosslinked rubber. The tread <NUM> has a plurality of land portions <NUM> demarcated by grooves <NUM> continuously extending in the circumferential direction, that is, circumferential grooves <NUM>.

Each sidewall <NUM> is connected to an end of the tread <NUM>. The sidewall <NUM> extends radially inward from the end of the tread <NUM>. An inner end <NUM> of the sidewall <NUM> is located on a side surface of the tire <NUM>. The sidewall <NUM> is formed from a crosslinked rubber. In the tire <NUM>, a complex elastic modulus E*s of the sidewall <NUM> is preferably not less than <NUM> MPa and not greater than <NUM> MPa.

In the tire <NUM>, complex elastic moduli E* of components of the tire <NUM> such as the sidewall <NUM> are measured using a viscoelasticity spectrometer ("VES" manufactured by Iwamoto Seisakusho) under the following conditions according to the standards of JIS K6394. In this measurement, a test piece obtained by pressurizing and heating a rubber composition for each component is used. <MAT> <MAT> <MAT> <MAT> <MAT>.

Each bead <NUM> is located radially inward of the sidewall <NUM>. 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 steel wire which is not shown. The core <NUM> has a substantially hexagonal cross-sectional shape.

The apex <NUM> is located outward of the core <NUM> in the radial direction. The apex <NUM> includes an inner apex 40u and an outer apex <NUM>. Each of the inner apex 40u and the outer apex <NUM> is formed from a crosslinked rubber.

The inner apex 40u is located on the core <NUM> side, and extends radially outward from the core <NUM>. The outer apex <NUM> is located outward of the inner apex 40u in the radial direction. An outer end <NUM> of the inner apex 40u is located between an outer end <NUM> and an inner end <NUM> of the outer apex <NUM> in the radial direction.

In the cross-section shown in <FIG>, the inner apex 40u is tapered radially outward. Forming the inner apex 40u in such a shape and locating the outer end <NUM> of the inner apex 40u on the radially outer side with respect to an inner end <NUM> of the steel reinforcing layer <NUM> are suitable for both reducing strain around the inner end <NUM> of the steel reinforcing layer <NUM> during load application and ensuring ride comfort of the tire <NUM>.

The outer apex <NUM> has a maximum thickness around the outer end <NUM> of the inner apex 40u. The outer apex <NUM> is tapered radially outward from a portion having the maximum thickness, and is tapered radially inward from the portion having the maximum thickness. The outer end <NUM> of the outer apex <NUM> is also an outer end of the apex <NUM>.

A complex elastic modulus E*b of the outer apex <NUM> is lower than a complex elastic modulus E*a of the inner apex 40u. In other words, the outer apex <NUM> is softer than the inner apex 40u.

The ratio of the complex elastic modulus E*a of the inner apex 40u to the complex elastic modulus E*b of the outer apex <NUM> is not less than <NUM> and not greater than <NUM>. When the above ratio is maintained in this range, strain generated in a bead portion during load application can be reduced, so that a decrease in the durability of the bead portion can be avoided and deterioration of the ride comfort of the tire <NUM> can be avoided.

In the tire <NUM>, it is sufficient that the complex elastic modulus E*a of the inner apex 40u is, for example, not less than <NUM> MPa and not greater than <NUM> MPa. The complex elastic modulus E*a of the inner apex 40u is preferably not less than <NUM> MPa and not greater than <NUM> MPa, and more preferably not less than <NUM> MPa and not greater than <NUM> MPa.

When the complex elastic modulus E*a of the inner apex 40u is set so as to be not less than <NUM> MPa and not greater than <NUM> MPa, strain is less likely to be generated in the bead portion during load application. As a result, the durability of the bead portion can be kept good.

In <FIG>, a double-headed arrow HA indicates the distance in the radial direction from the bead base line BBL to the outer end <NUM> of the apex <NUM>. The distance HA in the radial direction is the height in the radial direction of the apex <NUM>. A double-headed arrow HU indicates the distance in the radial direction from the bead base line BBL to the outer end <NUM> of the inner apex 40u. The distance HU in the radial direction is the height in the radial direction of the inner apex 40u. A double-headed arrow HS indicates the distance in the radial direction from the bead base line BBL to the inner end <NUM> of the outer apex <NUM>.

In the tire <NUM>, the ratio of the height HA in the radial direction of the apex <NUM> to the cross-sectional height HC of the carcass <NUM> is preferably not less than <NUM>% and not greater than <NUM>%. The ratio of the height HU in the radial direction of the inner apex 40u to the cross-sectional height HC of the carcass <NUM> is preferably not less than <NUM>% and not greater than <NUM>%. The ratio of the distance HS in the radial direction from the bead base line BBL to the inner end <NUM> of the outer apex <NUM> to the cross-sectional height HC of the carcass <NUM> is preferably not less than <NUM>% and not greater than <NUM>%.

The carcass <NUM> is located inward of the tread <NUM> and the sidewalls <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> includes a large number of carcass cords aligned with each other, which are not shown. These carcass cords are covered with a topping rubber. The material of each carcass cord is steel. The carcass cords intersect the equator plane CL. In the tire <NUM>, the carcass <NUM> has a radial structure. An angle of the carcass cords with respect to the equator plane CL is preferably not less than <NUM>° and not greater than <NUM>°.

In the tire <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> includes a ply body <NUM> which extends between one core <NUM> and the other core <NUM>, and a pair of turned-up portions <NUM> each of which is connected to the ply body <NUM> and turned up around the core <NUM> from the inner side toward the outer side in the axial direction. An end <NUM> of the turned-up portion <NUM> is located inward of the outer end <NUM> of the inner apex 40u in the radial direction.

In <FIG>, a double-headed arrow HF indicates the distance in the radial direction from the bead base line BBL to the end <NUM> of the turned-up portion <NUM>. The distance HF in the radial direction is the height in the radial direction of the turned-up portion <NUM>.

In the tire <NUM>, the ratio of the height HF in the radial direction of the turned-up portion <NUM> to the cross-sectional height HC of the carcass <NUM> is preferably not less than <NUM>% and not greater than <NUM>%.

In the tire <NUM>, the height HU in the radial direction of the inner apex 40u is preferably not less than <NUM>% and not greater than <NUM>% of the height HF in the radial direction of the turned-up portion <NUM>. This case is suitable for ensuring good ride comfort and workability at the time of rim fitting while reducing strain generated in the bead portion during load application.

If the height HU in the radial direction of the inner apex 40u is less than <NUM>% of the height HF in the radial direction of the turned-up portion <NUM>, it is difficult to reduce strain generated in the bead portion during load application. On the other hand, if the height HU in the radial direction of the inner apex 40u exceeds <NUM>% of the height HF in the radial direction of the turned-up portion <NUM>, the flexibility of the entire side portion of the tire <NUM> may be deteriorated, resulting in poor ride comfort and workability at the time of rim fitting.

The belt <NUM> is located inward of the tread <NUM> in the radial direction. The belt <NUM> is located radially outward of the carcass <NUM>. The belt <NUM> is stacked on the carcass <NUM>.

The belt <NUM> includes a plurality of layers <NUM> stacked in the radial direction. The belt <NUM> of the tire <NUM> includes four layers <NUM>. In the tire <NUM>, the number of layers <NUM> included in the belt <NUM> is not particularly limited. The configuration of the belt <NUM> is determined as appropriate in consideration of the specifications of the tire <NUM>.

Each layer <NUM> includes a large number of belt cords aligned with each other, which are not shown. Each belt cord is inclined relative to the equator plane CL. The material of each belt cord is steel.

In the tire <NUM>, among the four layers <NUM>, a second layer 56B located between a first layer 56A and a third layer 56C has a largest width in the axial direction. A fourth layer 56D located on the outermost side in the radial direction has a smallest width in the axial direction.

Each cushion layer <NUM> is located between the belt <NUM> and the carcass <NUM> at an end portion of the belt <NUM>. The cushion layer <NUM> is formed from a 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 an excellent air blocking property.

Each steel reinforcing layer <NUM> is located in a portion at the bead <NUM>. The steel reinforcing layer <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>, the carcass ply <NUM> is located between the steel reinforcing layer <NUM> and the bead <NUM>. The steel reinforcing layer <NUM> is in contact with the carcass ply <NUM>.

The steel reinforcing layer <NUM> includes a large number of filler cords aligned with each other, which are not shown. In the steel reinforcing layer <NUM>, the filler cords are covered with a topping rubber. The material of each filler cord is steel.

In the tire <NUM>, one end <NUM> (hereinafter, inner end) of the steel reinforcing layer <NUM> is located between the outer end <NUM> of the inner apex 40u and the core <NUM> in the radial direction. When the inner end <NUM> of the steel reinforcing layer <NUM> is located at such a position, strain is less likely to be generated around the inner end <NUM> during load application. Another end <NUM> (hereinafter, outer end) of the steel reinforcing layer <NUM> is located between the end <NUM> of the turned-up portion <NUM> and the core <NUM> in the radial direction. As shown in <FIG>, in the tire <NUM>, the outer end <NUM> of the steel reinforcing layer <NUM> is located outward of the inner end <NUM> thereof in the radial direction. The carcass ply <NUM> is located between the steel reinforcing layer <NUM> and the core <NUM>.

Each chafer <NUM> is located outward of the steel reinforcing layer <NUM> in the axial direction. The chafer <NUM> is located radially inward of the sidewall <NUM>. An outer end <NUM> of the chafer <NUM> is located outward of the inner end <NUM> of the sidewall <NUM> in the radial direction. The boundary between the chafer <NUM> and the sidewall <NUM> extends between the outer end <NUM> of the chafer <NUM> and the inner end <NUM> of the sidewall <NUM>. The chafer <NUM> comes into contact with the rim R.

The chafer <NUM> is formed from a crosslinked rubber. A complex elastic modulus E*c of the chafer <NUM> is preferably not less than <NUM> MPa and not greater than <NUM> MPa.

In the tire <NUM>, the complex elastic modulus E*c of the chafer <NUM> is higher than the complex elastic modulus E*b of the outer apex <NUM>. In other words, the chafer <NUM> is harder than the outer apex <NUM>.

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 <NUM> of the turned-up portion <NUM> and the outer end <NUM> of the steel reinforcing layer <NUM>. The interlayer strip <NUM> is formed from a crosslinked rubber. A complex elastic modulus E*d of the interlayer strip <NUM> is preferably not less than <NUM> MPa and not greater than <NUM> MPa.

In the tire <NUM>, the complex elastic modulus E*d of the interlayer strip <NUM> is higher than the complex elastic modulus E*b of the outer apex <NUM>. In other words, the interlayer strip <NUM> is harder than the outer apex <NUM>.

Each edge strip <NUM> is located between the outer apex <NUM> of the bead <NUM> and the interlayer strip <NUM>. A portion at the end <NUM> of the turned-up portion <NUM> is in contact with the edge strip <NUM>. As shown in <FIG>, the end <NUM> of the turned-up portion <NUM> is interposed between the edge strip <NUM> and the interlayer strip <NUM>. The edge strip <NUM> is formed from a crosslinked rubber. A complex elastic modulus E*f of the edge strip <NUM> is preferably not less than <NUM> MPa and not greater than <NUM> MPa. In the tire <NUM>, the edge strip <NUM> is formed from the same material as that of the interlayer strip <NUM>.

In the tire <NUM>, the complex elastic modulus E*f of the edge strip <NUM> is higher than the complex elastic modulus E*b of the outer apex <NUM>. In other words, the edge strip <NUM> is harder than the outer apex <NUM>.

<FIG> shows the portion at the bead <NUM> (hereinafter, also referred to as bead portion B) of the tire <NUM> shown in <FIG>. 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>, the tag assembly <NUM> is provided in one bead portion B. The tag assembly <NUM> may be provided in each of both bead portions B. In this case, the tire <NUM> includes a pair of the tag assemblies <NUM>.

The tag assembly <NUM> includes an RFID tag <NUM>. Although not described in detail, the RFID tag <NUM> is a small and lightweight electronic component that is composed of an antenna and a semiconductor obtained by making a transmitter/receiver circuit, a control circuit, a memory, etc., into a chip. Upon receiving interrogation radio waves, the RFID tag <NUM> uses the radio waves as electrical energy and transmits various data in the memory as response radio waves. The RFID tag <NUM> is a type of passive radio frequency identification transponder.

As shown in <FIG>, in the tire <NUM>, the entirety of the RFID tag <NUM> is covered with a covering rubber <NUM>. The tag assembly <NUM> includes the RFID tag <NUM> and the covering rubber <NUM> covering the RFID tag <NUM>. The covering rubber <NUM> is formed from a crosslinked rubber.

In the tire <NUM>, the tag assembly <NUM> is located between the outer apex <NUM> and the chafer <NUM> in the axial direction. The tag assembly <NUM> is in contact with the edge strip <NUM> which is located axially outward of the outer apex <NUM>. The tag assembly <NUM> is in contact with the edge strip <NUM> from the axially outer side of the edge strip <NUM>. In addition, the RFID tag <NUM> included in the tag assembly <NUM> is located outward of the end <NUM> of the turned-up portion <NUM> in the radial direction.

In the tire according to the embodiment of the present invention, it is sufficient that the above tag assembly is located outward of the outer apex in the axial direction, and the tag assembly may be located outward of the chafer in the radial direction.

In <FIG>, a double-headed arrow HR indicates the distance in the radial direction from the bead base line BBL to the radially innermost position of the RFID tag <NUM>. The distance HR in the radial direction is the installation height in the radial direction of the RFID tag <NUM>. Similar to <FIG>, a double-headed arrow HF indicates the height in the radial direction of the turned-up portion <NUM>.

The position in the radial direction of the tag assembly <NUM> in the tire <NUM> is a position at which the installation height HR in the radial direction of the RFID tag <NUM> is not less than <NUM>% and not greater than <NUM>% of the height HF in the radial direction of the turned-up portion <NUM>.

If the installation height HR in the radial direction of the RFID tag <NUM> is less than <NUM>% of the height HF in the radial direction of the turned-up portion <NUM>, breakage is likely to occur around the end <NUM> of the turned-up portion <NUM>, so that the bead portion B may have poor durability. In addition, since the steel carcass cords are close to the RFID tag <NUM>, the RFID tag <NUM> may have poor readability of electronic information.

On the other hand, if the installation height HR in the radial direction of the RFID tag <NUM> exceeds <NUM>% of the height HF in the radial direction of the turned-up portion <NUM>, the position of the RFID tag <NUM> corresponds to a position where strain is likely to be generated during load application (during tire running), and the RFID tag <NUM> is likely to be broken during load application.

<FIG> shows the tag assembly <NUM> in <FIG>. In <FIG>, a double-headed arrow L indicates the length of the tag assembly <NUM>. A double-headed arrow T is the thickness of the tag assembly <NUM>. In <FIG>, the left side is the inner surface side of the tire <NUM>, and the right side is the outer surface side of the tire <NUM>. In <FIG>, the upper side is the tread <NUM> side of the tire <NUM>, and the lower side is the bead <NUM> side of the tire <NUM>. Therefore, <FIG> shows a part of the meridian cross-section of the tire <NUM>.

The size of the tag assembly <NUM> is set as appropriate on the basis of the RFID tag <NUM>, and the length L of the tag assembly <NUM> is generally set in the range of not less than <NUM> and not greater than <NUM>. The thickness T of the tag assembly <NUM> is generally set in the range of not less than <NUM> and not greater than <NUM>.

A production method for the tire <NUM> includes.

In the production method for the tire <NUM>, first, an unvulcanized tire <NUM> (hereinafter, also referred to as green tire) is prepared (step (<NUM>)).

In the production method for the tire <NUM>, components such as the tread <NUM> are combined on a forming machine which is not shown. At least, the chafers <NUM>, the inner liner <NUM>, the steel reinforcing layers <NUM>, the interlayer strips <NUM>, and the carcass ply <NUM> are wound in an overlapping manner to form a tubular formed body. The beads <NUM> are fitted to the tubular formed body. Then, the edge strips <NUM> are attached to the beads <NUM>. The beads <NUM> may be fitted to the tubular formed body after the edge strips <NUM> are attached to the beads <NUM>.

The RFID tag <NUM> is sandwiched between two sheets formed from an unvulcanized rubber composition for the covering rubber <NUM>, to prepare an unvulcanized tag assembly <NUM>. The unvulcanized tag assembly <NUM> is attached to a predetermined position on the edge strip <NUM> and/or the outer apex <NUM> of the bead <NUM>.

A portion that is outward of each core <NUM> is turned up around the core <NUM>, and a portion between the right and left cores <NUM> is shaped into a toroid shape while the distance between the right and left cores <NUM> is decreased. Accordingly, the carcass ply <NUM> is turned up around each core <NUM>. The belt <NUM>, the tread <NUM>, etc., are attached to obtain a green tire.

The prepared green tire has the same configuration as the tire <NUM> shown in <FIG>, except for the point that the green tire is in an unvulcanized state and has not been shaped.

The green tire is pressurized and heated (step (<NUM>)). In the production method for the tire <NUM>, the green tire is placed into a mold of a vulcanizing machine which is not shown. The green tire is pressurized and heated in the mold. Thus, the tire <NUM> is obtained.

In the tire <NUM>, the RFID tag <NUM> is placed at a portion that is between the outer apex <NUM> and the chafer <NUM> and is radially outward of the end <NUM> of the turned-up portion <NUM>. Specifically, the RFID tag <NUM> is installed at a position at which the installation height HR in the radial direction of the RFID tag <NUM> is not less than <NUM>% and not greater than <NUM>% of the height HF in the radial direction of the turned-up portion <NUM>. At this position, strain generated when a load is applied is small. In the tire <NUM>, the RFID tag <NUM> is placed at a portion where strain is small. In the tire <NUM>, the RFID tag <NUM> is less likely to be damaged.

In the tire <NUM>, a complex elastic modulus E*g of the covering rubber <NUM> is preferably not less than <NUM> MPa and not greater than <NUM> MPa.

If the complex elastic modulus E*g of the covering rubber <NUM> is less than <NUM> MPa, the covering rubber <NUM> is excessively deformed during load application, so that the risk of damage to the RFID tag <NUM> is increased. On the other hand, if the complex elastic modulus E*g of the covering rubber <NUM> exceeds <NUM> MPa, breakage is likely to occur around the end <NUM> of the turned-up portion <NUM>, so that the bead portion B may have poor durability.

Preferably, the complex elastic modulus E*g of the covering rubber <NUM> is lower than the complex elastic modulus E*c of the chafer <NUM>. In other words, the covering rubber <NUM> is softer than the chafer <NUM>.

In the tire <NUM>, reduction of the risk of damage to the RFID tag <NUM> is achieved while an effect on the durability of the bead portion B is taken into consideration.

In the tire <NUM>, as already described, the tag assembly <NUM> is installed at the position at which the installation height HR in the radial direction of the RFID tag <NUM> is not less than <NUM>% and not greater than <NUM>% of the height HF in the radial direction of the turned-up portion <NUM>. In addition, the height HU in the radial direction of the inner apex 40u is preferably not less than <NUM>% and not greater than <NUM>% of the height HF in the radial direction of the turned-up portion <NUM>.

As for the installation height HR in the radial direction of the RFID tag <NUM> and the height HU in the radial direction of the inner apex 40u, the installation height HR in the radial direction of the RFID tag <NUM> may be higher, or the height HU in the radial direction of the inner apex 40u may be higher, but the height HU in the radial direction of the inner apex 40u is preferably higher. This case is more suitable for reducing the risk of breakage of the RFID tag <NUM>.

In the tire <NUM>, the interlayer strip <NUM> preferably covers the end <NUM> of the turned-up portion <NUM> in the axial direction, and the interlayer strip <NUM> is preferably located outward of the RFID tag <NUM> in the axial direction. In this case, the complex elastic modulus E*d of the interlayer strip <NUM> is preferably lower than the complex elastic modulus E*c of the chafer <NUM> and higher than the complex elastic modulus E*g of the covering rubber <NUM>. In this case, the interlayer strip <NUM> contributes to protection of the RFID tag <NUM>, so that the risk of damage to the RFID tag <NUM> is reduced.

In the tire <NUM>, from the viewpoint of reducing the risk of damage to the RFID tag <NUM>, the ratio (E*d/E*c) of the complex elastic modulus E*d of the interlayer strip <NUM> to the complex elastic modulus E*c of the chafer <NUM> is preferably not less than <NUM> and preferably not greater than <NUM>. From the same viewpoint, the ratio (E*d/E*g) of the complex elastic modulus E*d of the interlayer strip <NUM> to the complex elastic modulus E*g of the covering rubber <NUM> is preferably not less than <NUM> and preferably not greater than <NUM>.

In <FIG>, double-headed arrows TM1 and TM2 are thicknesses of the covering rubber <NUM>. The thicknesses TM1 and TM2 are represented as smallest thicknesses between the RFID tag <NUM> and the surface of the covering rubber <NUM> in the meridian cross-section of the tire <NUM> at the tag assembly <NUM>. The thickness TM1 is the smallest distance in the tire axial direction between the RFID tag <NUM> and a surface 80a on the tire outer surface side of the covering rubber <NUM>. The thickness TM2 is the smallest distance in the tire axial direction between the RFID tag <NUM> and a surface 80b on the tire inner surface side of the covering rubber <NUM>.

In the tire <NUM>, the sum of the thickness TM1 and the thickness TM2 is defined as a total thickness of the covering rubber <NUM>.

In the tire <NUM>, the ratio (TR/[TM1 + TM2]) of a thickness TR of the RFID tag <NUM> to the total thickness (TM1 + TM2) of the covering rubber <NUM> is preferably not less than <NUM> and not greater than <NUM>. When the above ratio (TR/[TM1 + TM2]) satisfies the above range, good readability of electronic information and good durability of the bead portion B can be ensured.

In the tire <NUM>, the thickness TR of the RFID tag <NUM> is the maximum thickness in the axial direction of the tire <NUM>.

The thickness TR of the RFID tag <NUM> in the tire <NUM> is, for example, about <NUM>.

In the tire <NUM>, the total thickness (TM1 + TM2) of the covering rubber <NUM> is preferably not less than <NUM> and not greater than <NUM>.

If the total thickness of the covering rubber <NUM> is less than <NUM>, the insulation properties by the covering rubber <NUM> are decreased, so that the readability of electronic information may be deteriorated. On the other hand, if the total thickness of the covering rubber <NUM> exceeds <NUM>, the thickness of the covering rubber <NUM> is excessively large and presses the outer apex <NUM> toward the inner side, so that a desired apex thickness cannot be ensured and the durability of the bead portion B may be deteriorated.

In the tire <NUM>, from the viewpoint of ensuring insulation properties and being able to read electronic information in a satisfactory manner, each of the thicknesses TM1 and TM2 of the covering rubber <NUM> is preferably not less than <NUM> and not greater than <NUM>.

The thicknesses TM1 and TM2 of the covering rubber <NUM> are normally substantially equal to each other, but do not necessarily have to be substantially equal to each other.

As is obvious from the above description, in the heavy duty pneumatic tire <NUM> of the present invention, reduction of the risk of damage to the RFID tag <NUM> is achieved while an effect on the durability of the bead portion B is taken into consideration.

The embodiments disclosed above are merely illustrative in all aspects and are not restrictive. The technical scope of the present disclosure is not limited to the above-described embodiments, and all changes which come within the range of equivalency of the configurations recited in the claims are therefore intended to be included therein.

Hereinafter, the present invention will be described in further detail by means of examples, etc., but the present invention is not limited to these examples.

A heavy duty pneumatic tire (tire size = <NUM>/80R22. <NUM>) having the structure shown in <FIG> and having specifications shown in Table <NUM> below was obtained.

A tire of Example <NUM> was obtained in the same manner as Example <NUM>, except that the total thickness of the covering rubber was changed as shown in Table <NUM>.

Tires of Examples <NUM> and <NUM> were obtained in the same manner as Example <NUM>, except that the complex elastic modulus E*g of the covering rubber was changed as shown in Table <NUM>.

A tire of Example <NUM> was obtained in the same manner as Example <NUM>, except that the complex elastic modulus E*a of the inner apex 40u and the complex elastic modulus E*b of the outer apex <NUM> were changed as shown in Table <NUM>.

Tires of Examples <NUM> and <NUM> were obtained in the same manner as Example <NUM>, except that the ratio (distance HU/distance HF (%)) of the height HU in the radial direction of the inner apex 40u to the height HF in the radial direction of the turned-up portion <NUM> was changed as shown in Table <NUM>.

A tire of Example <NUM> was obtained in the same manner as Example <NUM>, except that the ratio (distance HR/distance HF (%)) of the installation height HR in the radial direction of the RFID tag <NUM> to the height HF in the radial direction of the turned-up portion <NUM> was changed as shown in Table <NUM>.

Tires of Comparative Examples <NUM> and <NUM> were obtained in the same manner as Example <NUM>, except that the ratio (distance HR/distance HF (%)) of the installation height HR in the radial direction of the RFID tag <NUM> to the height HF in the radial direction of the turned-up portion <NUM> was changed as shown in Table <NUM>.

Tires of Comparative Examples <NUM> and <NUM> were obtained in the same manner as Example <NUM>, except that the complex elastic modulus E*b of the outer apex <NUM> or the complex elastic modulus E*a of the inner apex 40u was changed as shown in Table <NUM>.

In the tire of Comparative Example <NUM>, the ratio of the complex elastic modulus E*a of the inner apex 40u to the complex elastic modulus E*b of the outer apex <NUM> was <NUM>.

A test tire was fitted onto a rim (size = <NUM>×<NUM>) and inflated with air to adjust the internal pressure of the tire to a normal internal pressure. The tire was heated in an atmosphere of dry air adjusted to <NUM> for <NUM> days. The tire was cooled to room temperature, and then mounted to a drum tester. A load of <NUM> kN was applied to the tire, and the tire was caused to run on a drum (radius = <NUM>) at a speed of <NUM>/h. The running time was measured until the bead became damaged. The results are shown as indexes in Tables <NUM> and <NUM> below. A higher value indicates that the durability is better.

A test tire was fitted onto a rim (size = <NUM>×<NUM>) and inflated with air to adjust the internal pressure of the tire to a normal internal pressure. Whether radio waves emitted from the RFID tag were received was measured using a reading device. The results are shown in Tables <NUM> and <NUM> below. The results are indicated as "∘" for the case where radio waves were successfully received, and indicated as "×" for the case where radio waves were not successfully received.

A test tire was fitted onto a rim (size = <NUM>×<NUM>) and inflated with air to adjust the internal pressure of the tire to a normal internal pressure. The tire was mounted to a drum tester. A load of <NUM> kN was applied to the tire, and the tire was caused to run on a drum (radius = <NUM>) at a speed of <NUM>/h. After running for <NUM> thousand km, the tire was disassembled and checked for damage to the RFID tag. <NUM> tires were evaluated, and the rate of damage to the RFID tag was obtained. The reciprocal of the rate of damage was calculated and used as an index of safety degree. The results are shown as indexes in Tables <NUM> and <NUM> below. A higher value indicates that the risk of damage to the RFID tag is lower.

Test tires were each fitted onto a rim (size = <NUM>×<NUM>) and inflated with air to adjust the internal pressure of the tire to a normal internal pressure. The tires were attached to all the wheels of a test vehicle (one occupant), and the vehicle was driven on a test course having a dry asphalt road surface. The driver made evaluations (sensory evaluations) for ride comfort at that time. The results are shown as indexes in Tables <NUM> and <NUM> below. A higher value indicates that the ride comfort is better.

As shown in Tables <NUM> and <NUM>, each Example has good durability and has low risk of damage to the RFID tag. From the evaluation results, advantages of the present invention are clear.

Claim 1:
A heavy duty pneumatic tire (<NUM>) comprising:
a pair of beads (<NUM>) each including a core (<NUM>) and an apex (<NUM>) located outward of the core (<NUM>) in a radial direction;
a carcass (<NUM>) extending on and between one bead (<NUM>) and the other bead (<NUM>);
a pair of chafers (<NUM>) each located outward of the bead (<NUM>) in an axial direction; and
a tag assembly (<NUM>) including an RFID tag (<NUM>) and a covering rubber (<NUM>) covering the RFID tag (<NUM>), wherein
the apex (<NUM>) includes an inner apex (40u) located on the core (<NUM>) side and an outer apex (<NUM>) located outward of the inner apex (40u) in the radial direction,
a ratio of a complex elastic modulus (E*a) of the inner apex (40u) to a complex elastic modulus (E*b) of the outer apex (<NUM>) is not less than <NUM> and not greater than <NUM>, wherein said complex elastic modulus is measured using a viscoelasticity spectrometer according to the standards of JIS K6394, in which measurement a test piece obtained by pressurizing and heating a rubber composition for each component is used, under the following conditions: initial strain = <NUM>%, amplitude = ±<NUM>%, frequency = <NUM>, deformation mode = tension, measurement temperature = <NUM>;
the carcass (<NUM>) includes at least one carcass ply (<NUM>),
the carcass ply (<NUM>) includes a ply body (<NUM>) extending between one core (<NUM>) and the other core (<NUM>) and a pair of turned-up portions (<NUM>) each connected to the ply body (<NUM>) and turned up around the core (<NUM>) from an inner side toward an outer side in the axial direction,
an outer end (<NUM>) of the inner apex (40u) is located outward of an end (<NUM>) of the turned-up portion (<NUM>) in the radial direction,
the tag assembly (<NUM>) is located outward of the outer apex (<NUM>) in the axial direction, and the tire being characterized in that
a distance (HR) in the radial direction from a bead base line (BBL) to the RFID tag (<NUM>) is not less than <NUM>% and not greater than <NUM>% of a distance (HF) in the radial direction from the bead base line (BBL) to the end (<NUM>) of the turned-up portion (<NUM>), and in that a ratio (TR/[TM1 + TM2]) of a thickness (TR) of the RFID tag (<NUM>) to a total thickness (TM1 + TM2) of the covering rubber (<NUM>) is not less than <NUM> and not greater than <NUM>.