Heavy-duty tire

Abstract

To provide a heavy-duty tire 2 capable of improving reading performance of an RFID tag 52 while suppressing the influence of incorporating the RFID tag 52 on durability.SOLUTION: A tire 2 comprises: a pair of beads 10; a carcass 12; a tread 4; a pair of side walls 6; and a tag member 24 that includes an RFID tag 52. Each bead 10 includes an apex 36. The apex 36 includes inner and outer apexes 38 and 40. Each side wall 6 includes inner and outer sides 60 and 62. The inner end of the inner side 60 is held between the outer apex 40 and the outer side 62. The tag member 24 is positioned between the inner and outer sides 60 and 62. The volume resistivity of the inner side 60 is higher than that of the outer side 62.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a heavy duty tire. [Background technology]

[0002] It has been proposed to embed RFID (Radio Frequency Identification) tags in tires in order to manage data such as tire manufacturing management, customer information, driving history, etc. Various studies have been conducted on technology for embedding RFID tags in tires (for example, Patent Document 1 listed below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-046057 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a heavy-duty tire that can achieve improved RFID tag reading performance while suppressing the impact on durability caused by the incorporation of an RFID tag. [Means for solving the problem]

[0005] The heavy-duty tire according to the present invention comprises a pair of beads, a carcass spanning the pair of beads, a tread positioned radially outward of the carcass, a pair of sidewalls positioned axially outward of the carcass, and a tag member including an RFID tag. Each of the pair of beads comprises a core and an apex. The apex comprises an inner apex positioned radially outward of the core and an outer apex positioned radially outward of the inner apex. Each of the pair of sidewalls comprises an inner side portion and an outer side portion positioned axially outward of the inner side portion. The inner end of the inner side portion is sandwiched between the outer apex and the outer side portion. The tag member is positioned between the inner side portion and the outer side portion. The volume resistivity of the inner side portion is higher than that of the outer side portion. [Effects of the Invention]

[0006] The present invention can provide a heavy-duty tire that can achieve improved RFID tag reading performance while suppressing the impact on durability caused by the incorporation of an RFID tag. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a cross-sectional view showing a portion of a heavy-duty tire according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing a portion of the tire of FIG. [Figure 3] FIG. [Figure 4] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. [Figure 5] FIG. 3 is a cross-sectional view showing a portion of the tire of FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, the present invention will be described in detail based on preferred embodiments, with appropriate reference to the drawings.

[0009] The tire of the present invention is mounted on a rim. The inside of the tire is filled with air, and the internal pressure of the tire is adjusted. A tire mounted on a rim is also called a tire-rim assembly. A tire-rim assembly includes a rim and a tire mounted on the rim.

[0010] In the present invention, a state in which a tire is mounted on a standard rim, the internal pressure of the tire is adjusted to a standard internal pressure, and no load is applied to the tire is referred to as a standard state.

[0011] In the present invention, unless otherwise specified, the dimensions and angles of each part of the tire are measured in a normal state. The dimensions and angles of each part of the tire's meridian cross section, which cannot be measured when the tire is mounted on a regular rim, are measured on a cut surface of the tire obtained by cutting the tire along a plane including the rotation axis. In this measurement, the tire is set so that the distance between the left and right beads matches the distance between the beads of the tire mounted on a regular rim. Note that the tire configuration, which cannot be confirmed when the tire is mounted on a regular rim, is confirmed on the cut surface.

[0012] A genuine rim is a rim specified in the 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 all genuine rims.

[0013] Normal tire pressure refers to the pressure specified in the standard on which the tire is based. The "maximum tire pressure" in the JATMA standard, the "maximum tire pressure" listed in the TRA standard's "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURE" and the "INFLATION PRESSURE" in the ETRTO standard are normal tire pressures.

[0014] Normal load refers to the load specified in the standard on which the tire is based. The "maximum load capacity" in the JATMA standard, the "maximum value" listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are normal loads.

[0015] In the present invention, the crosslinked rubber is a crosslinked product of a rubber composition obtained by pressurizing and heating the rubber composition. The rubber composition is a material obtained by mixing raw rubber components and chemicals in a kneader such as a Banbury mixer. The crosslinked rubber is also called vulcanized rubber, and the rubber composition is also called unvulcanized rubber.

[0016] Examples of raw rubber components include natural rubber (NR), butadiene rubber (BR), styrene butadiene rubber (SBR), isoprene rubber (IR), ethylene propylene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), and butyl rubber (IIR). Examples of chemicals include reinforcing agents such as carbon black and silica; softeners such as process oil; plasticizers; zinc oxide; wax; lubricants such as stearic acid; antioxidants; processing aids; sulfur; and vulcanization accelerators. The selection of raw rubber components and chemicals, the content of the selected chemicals, etc., are determined appropriately depending on the specifications of each element to which the rubber composition is applied, such as the tread and sidewall. In the present invention, unless otherwise specified, a rubber composition commonly used in tires is used.

[0017] Although not described in detail, in the present invention, the volume resistivity of the elements constituting the tire is controlled by a known method of adjusting the content of carbon black. The carbon black is not particularly limited, and carbon blacks commonly used in the tire industry, such as GPF, FEF, HAF, ISAF, and SAF, can be used.

[0018] In the present invention, the volume resistivity of the elements constituting the tire is measured in accordance with the double ring electrode method specified in JIS K6271. The measurement temperature is set to 25°C. A sheet (thickness = 1 mm) made of the same material as the element to be measured is used for the measurement.

[0019] In the present invention, the carbon black content of the elements constituting a tire is measured by thermogravimetric analysis (TGA) in accordance with JIS K6226-1. A test piece to be analyzed is sampled from the tire. The carbon black content is expressed as the ratio of the amount of carbon black contained in this test piece to the total amount of the test piece.

[0020] In the present invention, the complex modulus of an element made of crosslinked rubber among elements constituting a tire is measured in accordance with the provisions of JIS K 6394. The measurement conditions are as follows. Initial strain = 10% Dynamic strain = ±1% Frequency = 10 Hz Mode = Decompression mode Temperature=70℃ In this measurement, a test piece (length 40 mm x width 4 mm x thickness 1 mm) is sampled from the tire. The longitudinal direction of the test piece is aligned with the circumferential direction of the tire. If it is not possible to sample a test piece from the tire, the test piece is sampled from a sheet of crosslinked rubber (hereinafter also referred to as a rubber sheet) obtained by pressing and heating the rubber composition used to form the element to be measured at a temperature of 170°C for 12 minutes. In the present invention, the complex modulus is expressed as the complex modulus at 70°C.

[0021] In the present invention, the tread portion of a tire is the portion of the tire that comes into contact with the road surface. The bead portion is the portion of the tire that fits onto the rim. The sidewall portion is the portion of the tire that bridges between the tread portion and the bead portion. A tire has the following portions: a tread portion, a pair of bead portions, and a pair of sidewall portions.

[0022] [Findings that form the basis of the present invention] Data recorded on RFID tags is read via radio waves from an RFID reader. The reading performance of an RFID tag is affected by the conductivity of the elements surrounding the RFID tag. To achieve good reading performance, when embedding an RFID tag in a tire, it is recommended to place the RFID tag away from metal elements such as steel cords.

[0023] Tires undergo repeated deformation and recovery. If an RFID tag is embedded in a tire, there is concern that a unique distortion may occur in the tire. To minimize the impact of the RFID tag on durability, it is being considered to place the RFID tag in a location on the tire where movement is minimal.

[0024] From the perspective of durability and readability, in the case of heavy-duty tires, it is considered to place RFID tags in the least moving part of the zone from the folded end of the carcass ply to the widest point of the tire. However, the sidewall in this area is thick, and sufficient readability is currently not achieved. While it is possible to improve readability by thinning the sidewall or reducing its conductivity, there is a concern that this would reduce durability.

[0025] Therefore, the inventors have conducted extensive research into whether it is possible to improve the reading performance of RFID tags while suppressing the impact on durability caused by incorporating an RFID tag by making the sidewall two-layered, and have completed the present invention, which is described below.

[0026] [Outline of the embodiment of the present invention] The present invention is a heavy-duty tire comprising a pair of beads, a carcass spanning the pair of beads, a tread positioned radially outward of the carcass, a pair of sidewalls positioned axially outward of the carcass, and a tag member including an RFID tag, wherein each of the pair of beads comprises a core and an apex, and the apex comprises an inner apex positioned radially outward of the core and an outer apex positioned radially outward of the inner apex, and each of the pair of sidewalls comprises an inner side portion and an outer side portion positioned axially outward of the inner side portion, the inner end of the inner side portion is sandwiched between the outer apex and the outer side portion, the tag member is positioned between the inner side portion and the outer side portion, and the volume resistivity of the inner side portion is higher than the volume resistivity of the outer side portion.

[0027] The heavy-duty tire of the present invention can achieve improved RFID tag readability while suppressing the impact on durability caused by the incorporation of an RFID tag. The mechanism by which the tire achieves this effect has not been clarified, but is presumed to be as follows.

[0028] In the tire of the present invention, the inner side portion, which has a high volume resistivity, reduces the electrical conductivity of the entire sidewall. Because the tag member is disposed between the inner side portion and the outer side portion, this tire allows the RFID tag to be positioned closer to the tire's outer surface, compared to conventional tires in which the sidewall is constructed from a single member. This sidewall contributes to improving the RFID tag's readability. Furthermore, the inner side portion, located between the RFID tag and the carcass, has low electrical conductivity. This reduces the impact of the carcass on the RFID tag's readability. This tire can improve the reading performance of RFID tags. The inner sidewall is positioned so that its inner edge is sandwiched between the outer apex and outer sidewall. This tire allows the RFID tag to be placed in an appropriate position with minimal movement and distortion. This tire can minimize the impact of the RFID tag on durability. Because the volume of the inner sidewall relative to the sidewall is kept within an appropriate range, the impact of the inner sidewall on durability is also minimized. This tire can improve RFID tag reading performance while minimizing the impact on durability caused by the built-in RFID tag.

[0029] Preferably, the carcass includes a carcass ply, the carcass ply including a ply body that spans between the pair of beads and a pair of folded-up portions that are continuous with the ply body and folded up at the beads, and the RFID tag is located radially outward from an end of the folded-up portion and radially inward from a maximum width position of the tire. In this case, the tire can reduce the risk of reading errors due to RFID tag failure and can improve RFID tag reading performance.

[0030] Preferably, the tag member includes the RFID tag and a protector covering the RFID tag, and the carbon black content CBu of the inner side portion, the carbon black content CBs of the outer side portion, and the carbon black content CBp of the protector satisfy the following relational expression: CBp≦CBu <CBs In this case, the tire can improve the reading performance.

[0031] Preferably, the tag member has a thickness of 1.0 mm or more and 2.5 mm or less. In this case, the tire can be prevented from being affected by the tag member on durability, and the reading performance of the RFID tag can be improved.

[0032] Preferably, the inner side portion is disposed so as to straddle the maximum width position of the tire in the radial direction, thereby improving the reading performance of the tire.

[0033] Preferably, the volume resistivity of the inner side portion is 1.0×10 10 Ω·cm or more. In this case, the tire's reading performance can be improved.

[0034] Preferably, the carbon black content CBu of the inner side portion is 0.6 times or less the carbon black content CBs of the outer side portion, whereby the tire can achieve improved readability.

[0035] Preferably, the inner side portion located axially inside the RFID tag is thicker than the outer side portion located axially outside the RFID tag, thereby improving the reading performance of the tire.

[0036] As described above, the present invention provides a heavy-duty tire that can improve RFID tag readability while minimizing the impact on durability of the built-in RFID tag. This will be explained in detail below using the heavy-duty tire shown in Figure 1 as an example.

[0037] [Details of the embodiment of the present invention] 1 shows a part of a tire 2 according to one embodiment of the present invention. This tire 2 is mounted on vehicles such as trucks and buses. This tire 2 is a heavy-duty tire.

[0038] FIG. 1 shows a part of a cross section (hereinafter referred to as a meridian cross section) of a tire 2 taken along a plane including the rotation axis of the tire 2. The direction indicated by the double-headed arrow AD is the axial direction of the tire 2. The axial direction of the tire 2 means a direction parallel to the rotation axis of the tire 2. The direction indicated by the double-headed arrow RD is the radial direction of the tire 2. The direction perpendicular to the plane of FIG. 1 is the circumferential direction of the tire 2. A dashed line EL extending in the radial direction represents the equatorial plane of the tire 2. Figure 2 shows a part of the cross section shown in Figure 1. Figure 2 shows the bead portion of a tire 2.

[0039] The direction from the equatorial plane toward the edge of the tread surface, which will be described later, is the outer side in the axial direction of the tire 2, and the direction from the edge of the tread surface toward the equatorial plane is the inner side in the axial direction of the tire 2. The direction indicated by the arrow RD1 is the radially outer side of the tire 2, and the direction indicated by the arrow RD2 is the radially inner side of the tire 2.

[0040] The tire 2 shown in Figures 1 and 2 is mounted on a rim R (regular rim). The solid line BBL extending in the axial direction is the bead base line, which defines the rim radius (see JATMA, etc.).

[0041] The tire 2 includes a tread 4, a pair of sidewalls 6, a pair of chafers 8, a pair of beads 10, a carcass 12, a belt 14, a pair of reinforcing layers 16, a pair of cushion layers 18, a pair of interlayer strips 20, an inner liner 22, and a tag member 24.

[0042] The tread 4 is located radially outward of the carcass 12. The tread 4 includes a tread surface 26. The tire 2 comes into contact with the road surface at the tread surface 26 of the tread 4. Grooves 28 are formed in the tread 4. The position indicated by the symbol TE is the end of the tread surface 26 . In a tire, if the edge of the tread surface cannot be identified visually, the position on the outer surface of the tire corresponding to the axially outer edge of the contact patch obtained by applying a normal load to a tire in a normal state, setting the camber angle to 0°, and contacting the tire with a flat surface is used as the edge of the tread surface.

[0043] The position indicated by the symbol Eq is the equator. The equator Eq is the intersection of the tread surface 26 and the equatorial plane. If the grooves 28 are on the equatorial plane, the equator is determined based on a virtual tread surface obtained assuming that the grooves 28 are not present. The radial distance from the bead base line to the equator Eq obtained in the tire 2 in a normal state is the section height of this tire 2 (see JATMA, etc.).

[0044] The tread 4 comprises a base portion 30 and a cap portion 32. The base portion 30 is made of a cross-linked rubber with low heat buildup. The cap portion 32 is located radially outward of the base portion 30. The cap portion 32 is made of a cross-linked rubber that takes into consideration wear resistance and grip performance. The cap portion 32 includes the tread surface 26. 1, the position indicated by the symbol BE is the radially inner end of the base portion 30. The position indicated by the symbol CE is the radially inner end of the cap portion 32.

[0045] 1 , the inner end CE of the cap portion 32 is located radially inside the inner end BE of the base portion 30. The inner end BE of the base portion 30 is covered by the cap portion 32. The inner end CE of the cap portion 32 is the radially inner end TRE of the tread 4. The inner end TRE of the tread 4 is located between the sidewall 6 and the cushion layer 18.

[0046] Each sidewall 6 is continuous with an end of the tread 4. The sidewall 6 is located axially outward of the carcass 12. The sidewall 6 is made of crosslinked rubber. The radially outer end SG of the sidewall 6 is located radially outside the inner end TRE of the tread 4. The radially inner end SU of the sidewall 6 is located near the rim R. The radially inner end SU of the sidewall 6 is located radially outside the radially outer end FG of the rim R.

[0047] The position indicated by the symbol PW is the axial outer end (hereinafter referred to as the outer end PW) of the tire 2. If the outer surface of the tire 2 has decorations such as patterns or letters, the outer end PW is determined based on a virtual outer surface obtained assuming that there is no decoration. The tire 2 has its maximum width at the outer end PW. The outer end PW is also called the maximum width position. The axial distance from the first outer end PW to the second outer end PW (not shown) of the tire 2 in a normal state is the section width of the tire 2 (see JATMA, etc.).

[0048] 1, the length indicated by the double-headed arrow H is the radial distance from the bead base line to the maximum width position PW. The radial distance H is also called the radial height of the maximum width position PW. In the tire 2 in a normal state, the ratio of the radial height H at the maximum width position PW to the cross-sectional height is equal to or greater than 0.40 and is equal to or less than 0.60.

[0049] Each chafer 8 is located radially inward of the sidewall 6. The chafer 8 contacts the rim R. The position indicated by the symbol CG is the radially outer end of the chafer 8. The chafer 8 is made of cross-linked rubber in consideration of wear resistance. The complex modulus of elasticity of the chafer 8 is 10 MPa or more and 15 MPa or less.

[0050] An outer end CG of the chafer 8 is located radially outward of an inner end SU of the sidewall 6. The outer end CG of the chafer 8 is covered by the sidewall 6. The outer end CG of the chafer 8 contacts a bead 10 (more specifically, an outer apex, which will be described later). 2, the length indicated by the double-headed arrow C is the radial distance from the bead base line to the outer end CG of the chafer 8. The radial distance C is also called the radial height of the chafer 8.

[0051] Each bead 10 is located axially inward of the chafer 8. The beads 10 are located radially inward of the sidewall 6.

[0052] The bead 10 includes a core 34 and an apex 36 . The core 34 extends in the circumferential direction. Although not shown, the core 34 includes a wound steel wire. The core 34 has a generally hexagonal cross-sectional shape. The apex 36 is located radially outward of the core 34. The apex 36 extends radially outward from the core 34. The apex 36 tapers outward. The radially outer end AG of the apex 36 is located radially outward of the outer end CG of the chafer 8. The outer end AG of the apex 36 is located radially inward of the maximum width position PW.

[0053] 2, the length indicated by the double-headed arrow L is the radial distance from the bead base line to the outer end AG of the apex 36. The radial distance L is also called the radial height of the apex 36. In this tire 2, in order to achieve a good balance between the rigidity of the bead portion and the deflection of the tire 2, the ratio (L / H) of the radial height L of the apex 36 to the radial height H of the maximum width position PW is adjusted to be in the range of 0.55 or more and 0.95 or less. From the same viewpoint, the ratio (L / C) of the radial height L of the apex 36 to the radial height C of the chafer 8 is adjusted within the range of 1.08 to 1.54.

[0054] The apex 36 includes an inner apex 38 and an outer apex 40. The inner apex 38 is located radially outward of the core 34. The outer apex 40 is located radially outward of the inner apex 38.

[0055] The inner apex 38 tapers outward. A radially outer end UAG of the inner apex 38 is located radially inward of the outer end CG of the chafer 8. The outer end UAG of the inner apex 38 is included in the inner surface of the apex 36. The inner apex 38 is made of hard crosslinked rubber. The complex modulus of elasticity of the inner apex 38 is 60 MPa or more and 90 MPa or less.

[0056] The outer apex 40 is thick near the outer end UAG of the inner apex 38. From this thicker portion, the outer apex 40 tapers inward and then outward. A radially inner end SAU of the outer apex 40 is located near the core 34. A radially outer end SAG of the outer apex 40 is located near the tag member 24. The inner end SAU and outer end SAG of the outer apex 40 are included in the outer surface of the apex 36. The outer end SAG of the outer apex 40 is also the outer end AG of the apex 36. The outer end SAG of the outer apex 40 is also included in the inner surface of the apex 36. The outer apex 40 is made of crosslinked rubber and is softer than the inner apex 38. The complex modulus of elasticity of the outer apex 40 is 3.0 MPa or more and 6.0 MPa or less.

[0057] The apex 36 of the tire 2 further includes an edge strip 42 . The edge strip 42 is located axially outward of the outer apex 40 and forms part of the outer surface of the apex 36. The edge strip 42 is located radially between the outer end CG of the chafer 8 and the inner end SAU of the outer apex 40. The edge strip 42 is made of crosslinked rubber and is softer than the chafer 8 and harder than the outer apex 40. The complex elastic modulus of the edge strip 42 is 7.0 MPa or more and 12 MPa or less.

[0058] The carcass 12 is located inside the tread 4, the pair of sidewalls 6, and the pair of chafers 8. The carcass 12 bridges between the pair of beads 10. The carcass 12 of the tire 2 has a radial structure.

[0059] The carcass 12 includes at least one carcass ply 44. The carcass 12 of the tire 2 is configured with one carcass ply 44. The carcass ply 44 is turned up at each bead 10.

[0060] The carcass ply 44 includes a ply body 46 and a pair of turned-up portions 48. The ply body 46 spans between a pair of beads 10, i.e., between a first bead 10 and a second bead 10 (not shown). Each turned-up portion 48 is continuous with the ply body 46 and turned up at the bead 10. The turned-up portions 48 of the tire 2 are turned up at the bead 10 from the axially inner side to the axially outer side. Ends FE of the turned-up portions 48 are located radially inward of the outer ends UAG of the inner apex 38. Ends FE of the turned-up portions 48 are in contact with the edge strip 42. The bead 10 is sandwiched between the ply body 46 and the turned-up portions 48. The inner ends SU of the sidewall 6 described above are located radially inward of the ends FE of the turned-up portions 48.

[0061] Although not shown, the carcass ply 44 includes a number of carcass cords arranged in parallel. These carcass cords are covered with a topping rubber. Each carcass cord intersects with the equatorial plane. The angle that the carcass cord makes with the equatorial plane is between 70° and 90°. The carcass cords of this tire 2 are steel cords.

[0062] 2 is the radial distance from the bead base line to the end FE of the turned-up portion 48. The radial distance N is also called the radial height of the turned-up portion 48. In the tire 2, the ratio (N / H) of the radial height N of the folded-back portion 48 to the radial height H of the maximum width position PW is set in the range of 0.25 to 0.45.

[0063] The belt 14 is located radially outside the carcass 12. The belt 14 is located radially inside the tread 4. The belt 14 includes four belt plies 50. The four belt plies 50 are, from the radially inner side, a first belt ply 50A, a second belt ply 50B, a third belt ply 50C, and a fourth belt ply 50D. These belt plies 50 are arranged in the radial direction. Among the four belt plies 50, the first belt ply 50A is located at the radially innermost position. The fourth belt ply 50D is located at the radially outermost position. The second belt ply 50B has the widest width, and the fourth belt ply 50D has the narrowest width.

[0064] Although not shown, each belt ply 50 includes a number of parallel belt cords. These belt cords are covered with a topping rubber. Each belt cord is inclined with respect to the equatorial plane. The belt cords of this tire 2 are steel cords.

[0065] Each reinforcing layer 16 is positioned between the carcass 12 and the chafer 8 . The reinforcing layer 16 is located outside the carcass 12 and is turned up at the bead 10. The reinforcing layer 16 is arranged so as to wrap around the radially inner portion of the bead 10 from the radially inner side of the carcass 12. The inner end RN of the reinforcing layer 16 is located between the ply body 46 and the inner liner 22 in the axial direction. The inner end RN of the reinforcing layer 16 is located between the outer end UAG of the inner apex 38 and the core 34 in the radial direction. The outer end RG of the reinforcing layer 16 is located between the turned-up portion 48 and the chafer 8 in the axial direction. The outer end RG of the reinforcing layer 16 is located between the end FE of the turned-up portion 48 and the core 34 in the radial direction.

[0066] Although not shown, the reinforcing layer 16 includes a large number of reinforcing cords arranged in parallel. These reinforcing cords are covered with a topping rubber. The reinforcing cords of this tire 2 are steel cords.

[0067] Each cushion layer 18 is located at an end of the belt 14, between the belt 14 and the carcass 12. A radially inner end CU of the cushion layer 18 is located radially inside the inner end TRE of the tread 4. The cushion layer 18 is made of a soft crosslinked rubber.

[0068] Each interlayer strip 20 is located axially between the chafer 8 and the apex 36 (specifically, the outer apex 40). The radially outer end IG of the interlayer strip 20 is located radially inward of the outer end CG of the chafer 8. The interlayer strip 20 and the edge strip 42 cover the end FE of the turned-up portion 48 , and the interlayer strip 20 and the chafer 8 cover the outer end RG of the reinforcing layer 16 axially outside the turned-up portion 48 . The interlayer strip 20 is made of crosslinked rubber and has a rigidity similar to that of the edge strip 42. The complex modulus of elasticity of the interlayer strip 20 is 7.0 MPa or more and 12 MPa or less.

[0069] The inner liner 22 is positioned inside the carcass 12. The inner liner 22 is joined to the inner surface of the carcass 12 via insulation (not shown) made of crosslinked rubber. The inner liner 22 forms the inner surface of the tire 2. The inner liner 22 is made of crosslinked rubber that has excellent air barrier properties.

[0070] The tag member 24 is built into the sidewall 6. The tag member 24 of this tire 2 is built into only one of the pair of sidewalls 6. The tag member 24 may be built into both sidewalls 6. From the viewpoint of suppressing a decrease in durability, it is preferable that the tag member 24 is built into only one of the pair of sidewalls 6. Multiple tag members 24 may be provided at intervals in the circumferential direction, but from the viewpoint of suppressing a decrease in durability, it is sufficient that one tag member 24 is provided in only one of the sidewalls 6.

[0071] Fig. 3 is a plan view of the tag member 24. Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 3. The tag member 24 is plate-shaped and is long in the length direction and short in the width direction. 2, in the tire 2, the tag member 24 is arranged such that a first end 24s in the width direction thereof is located on the radially outer side of the tire 2 and a second end 24u is located on the radially inner side of the tire 2. In the tire 2, the first end 24s of the tag member 24 is also called an outer end, and the second end 24u is also called an inner end.

[0072] The tag member 24 includes an RFID tag 52. In FIG. 3, the RFID tag 54 is shown by a solid line for ease of explanation, and is entirely covered with a protective body 54. The tag member 24 includes the RFID tag 52 and the protective body 54 that entirely covers the RFID tag 52. The RFID tag 52 is located at the center of the tag member 24. The protective body 54 is made of cross-linked rubber. In this tire 2, the formation of a good communication environment is taken into consideration, and the protective body 54 is made of cross-linked rubber that has high electrical resistance. The volume resistivity of the protective body 54 is 1.0×10 10 Ω·cm or more. The protector 54 of the tire 2 has a rigidity similar to that of the outer apex 40. The complex elastic modulus of the protector 54 is equal to or greater than 3.0 MPa and equal to or less than 6.0 MPa.

[0073] The RFID tag 52 is a small, lightweight electronic component. Although not described in detail, the RFID tag 52 is a small, lightweight electronic component consisting of a semiconductor chip 56 that integrates a transmitter / receiver circuit, a control circuit, memory, and other components, and an antenna 58. When the RFID tag 52 receives an interrogation radio wave, it uses the received signal as electrical energy and transmits the data stored in the memory as a response radio wave. This RFID tag 52 is a type of passive radio frequency identification transponder.

[0074] The RFID tag 52 of this tire 2 includes a semiconductor chip 56 and a pair of antennas 58. The semiconductor chip 56 is located between the pair of antennas 58. Each antenna 58 extends from the semiconductor chip 56 in the length direction of the tag member 24.

[0075] The tag member 24 is a plate-shaped member in which the RFID tag 52 is covered with crosslinked rubber. In the tag member 24, the RFID tag 52 is arranged so that its length direction coincides with the length direction of the tag member 24. The length TL of the tag member 24 before being embedded in the tire 2 is 60 mm or more and 80 mm or less. The width TW is 10 mm or more and 20 mm or less. The length GL of the RFID tag 52 is 30 mm or more and 50 mm or less.

[0076] 2, the position indicated by the symbol TU is the radially inner end of the RFID tag 52 (specifically, the semiconductor chip 56). The position indicated by the symbol TS is the radially outer end of the semiconductor chip 56, i.e., the radially outer end of the RFID tag 52. In the present invention, when the inner end TU of the RFID tag 52 in the tire 2 is located radially outward from a reference position (hereinafter referred to as the reference position), the RFID tag 52 is located radially outward from the reference position. When the outer end TS of the RFID tag 52 in the tire 2 is located radially inward from the reference position, the RFID tag 52 is located radially inward from the reference position.

[0077] The sidewall 6 of the tire 2 includes an inner side portion 60 and an outer side portion 62. Each of the inner side portion 60 and the outer side portion 62 is made of crosslinked rubber. The complex elastic modulus of the inner side portion 60 is 2.0 MPa or more and 3.5 MPa or less. The outer side portion 62 is harder than the inner side portion 60. The difference between the complex elastic modulus of the outer side portion 62 and the complex elastic modulus of the inner side portion 60 is preferably 0.5 MPa or more and 1.5 MPa or less. The rigidity of the outer side portion 62 is the same as the rigidity of the outer apex 40, or the rigidity of the outer side portion 62 is lower than the rigidity of the outer apex 40.

[0078] A radially outer end USG of the inner side portion 60 is located radially outward from the inner end BE of the base portion 30. A radially inner end USU of the inner side portion 60 is located radially inward from the outer end AG of the apex 36 (more specifically, the outer end SAG of the outer apex 40). The inner side portion 60 contacts the outer apex 40, the carcass 12, the cushion layer 18, and the cap portion 32 from the radially inner side to the radially outer side.

[0079] The outer side portion 62 is located axially outward of the inner side portion 60. A radially outer end SSG of the outer side portion 62 is the outer end SG of the sidewall 6. An inner end SSU of the outer side portion 62 is the inner end SU of the sidewall 6. The radially outer end SSG of the outer side portion 62 is located radially outward from the outer end USG of the inner side portion 60. The radially inner end SSU of the outer side portion 62 is located radially inward from the inner end USU of the inner side portion 60. The outer side portion 62 covers the entire inner side portion. The inner end SSU of the outer side portion 62 is located radially inward from the outer end CG of the chafer 8. The outer side portion 62 contacts the chafer 8, outer apex 40, inner side portion 60, and cap portion 32 from the radially inner side to the outer side. The outer side portion 62 contains carbon black. The volume resistivity of the outer side portion 62 is 1.0×10 10 Preferably, the volume resistivity of the outer side portion 62 is less than 1.0×10 8 Ω·cm or less.

[0080] The portion from the outer end SG of the sidewall 6 to the inner end USU of the inner side portion 60 (hereinafter referred to as the outer portion of the sidewall 6) is made up of the inner side portion 60 and the outer side portion 62, while the portion from the inner end USU of the inner side portion 60 to the inner end SU of the sidewall 6 (hereinafter referred to as the inner portion of the sidewall 6) is made up of only the outer side portion 62. The outer portion of the sidewall 6 has a two-layer structure, while the inner portion of the sidewall 6 has a single-layer structure. The inner end USU of the inner side portion 60 is the boundary between the outer portion having a two-layer structure and the inner portion having a single-layer structure.

[0081] In this tire 2, the inner end USU of the inner side portion 60, which is the boundary between the outer portion having a two-layer structure and the inner portion having a single-layer structure, is sandwiched between the outer apex 40 and the outer side portion 62. The tag member 24 is located between the inner side portion 60 and the outer side portion 62. The volume resistivity of the inner side portion 60 is higher than the volume resistivity of the outer side portion 62.

[0082] In this tire 2, the inner side portion 60, which has a high volume resistivity, reduces the electrical conductivity of the entire sidewall 6. Since the tag member 24 is disposed between the inner side portion 60 and the outer side portion 62, the tire 2 can position the RFID tag 52 closer to the outer surface of the tire 2, compared to conventional tires in which the sidewall 6 is configured from a single member. This sidewall 6 can contribute to improving the reading performance of the RFID tag 52. The conductivity of the inner side portion 60 located between the RFID tag 52 and the carcass 12 is low. This reduces the influence of the carcass 12 on the reading performance of the RFID tag 52. This tire can improve the reading performance of the RFID tag 52. The inner side portion 60 is disposed such that its inner end USU is sandwiched between the outer apex 40 and the outer side portion 62. In this tire 2, the RFID tag 52 can be disposed in an appropriate position with little movement and distortion. In this tire 2, the impact of the RFID tag 52 on durability can be suppressed. Because the volume of the inner side portion 60 in the sidewall 6 is kept within an appropriate range, the impact of the inner side portion 60 on durability is also suppressed. The tire 2 can achieve improved readability of the RFID tag 52 while suppressing the effect on durability due to the incorporation of the RFID tag 52.

[0083] For example, as shown in FIG. 2, the RFID tag 52 of this tire 2 is located radially outward from the end FE of the folded-back portion 48 and radially inward from the maximum width position PW of the tire 2. As a result, the RFID tag 52 is disposed in a portion of the tire 2 that is less prone to movement and distortion. Since failure of the RFID tag 52 is suppressed, the risk of read errors due to such failure is reduced. Since the RFID tag 52 is disposed away from the end FE of the folded-back portion 48, the tire 2 can improve the read performance of the RFID tag 52. From the viewpoint of being able to reduce the risk of read errors due to failure of the RFID tag 52 in the tire 2 and being able to improve the read performance of the RFID tag 52, the RFID tag 52 is preferably located radially outward from the end FE of the folded-back portion 48 and radially inward from the maximum width position PW of the tire 2. It is more preferable that the RFID tag 52 be located radially outward from the outer end CG of the chafer 8 and radially inward from the maximum width position PW of the tire 2.

[0084] As shown in FIG. 1 , the outer end USG of the inner side portion 60 is located radially outward from the maximum width position PW. The inner end USU of the inner side portion 60 is located radially inward from the maximum width position PW. In other words, the inner side portion 60 is disposed so as to straddle the maximum width position PW in the radial direction. This allows the tire 2 to increase the volume ratio of the inner side portion 60 to the sidewall 6. Because the inner side portion 60 has a high volume resistivity, the tire 2 can effectively reduce the electrical conductivity of the entire sidewall 6. The reduced electrical conductivity contributes to improving the reading performance of the RFID tag 52. The tire 2 can improve the reading performance of the RFID tag 52. From this perspective, it is preferable that the inner side portion 60 be disposed so as to straddle the maximum width position PW in the radial direction. In this case, it is more preferable that the inner end USU of the inner side portion 60 is located radially inward from the outer end SAG of the outer apex 40 and radially outward from the outer end CG of the chafer 8. When the inner end USU of the inner side portion 60 is located radially inward of the outer end SAG of the outer apex 40 and radially outward of the outer end CG of the chafer 8, it is more preferable that the RFID tag 52 be located radially outward of the inner end USU of the inner side portion 60 and radially inward of the maximum width position PW of the tire 2, from the viewpoint of achieving improved reading performance of the RFID tag 52 while suppressing the impact on durability due to the incorporation of the RFID tag 52.

[0085] As previously mentioned, the volume resistivity of the components that make up a tire is controlled by the known method of adjusting the carbon black content. As shown in FIG. 2, the RFID tag 52 is surrounded by a protective body 54 that covers the RFID tag 52, an inner side portion 60, and an outer side portion 62 that sandwich the tag member 24 therebetween. In the tire 2, it is preferable that the carbon black content CBu of the inner side portion 60, the carbon black content CBs of the outer side portion 62, and the carbon black content CBp of the protector 54 satisfy the following relational expression. CBp≦CBu <CBs This achieves a good balance of electrical conductivity among the protective body 54, the inner side portion 60, and the outer side portion 62, which are positioned around the RFID tag 52. The tire 2 can effectively suppress the influence of the carcass 12 on the reading performance of the RFID tag 52.

[0086] The carbon black content CBu of the inner side portion 60 is preferably 0.6 times or less the carbon black content CBs of the outer side portion 62. This effectively suppresses the influence of the carcass 12 on the reading performance of the RFID tag 52. From this viewpoint, it is more preferable that the carbon black content CBu of the inner side portion 60 is 0.5 times or less the carbon black content CBs of the outer side portion 62. From the viewpoint of suppressing the influence of the inner side portion 60 on durability, it is preferable that the carbon black content CBu of the inner side portion 60 is 0.1 times or more the carbon black content CBs of the outer side portion 62.

[0087] The carbon black content CBp of the protector 54 is the same as the carbon black content CBu of the inner side portion 60, or the carbon black content CBp of the protector 54 is lower than the carbon black content CBu of the inner side portion 60. When the carbon black content CBu of the inner side portion 60 is 0.6 times or less the carbon black content CBs of the outer side portion 62, from the viewpoints of improving the reading performance of the RFID tag 52 and suppressing a decrease in durability, the carbon black content CBp of the protector 54 is preferably 0.5 times or more and 1.0 times or less the carbon black content CBu of the inner side portion 60, and more preferably 0.6 times or more and 1.0 times or less.

[0088] The volume resistivity of the inner side is 1.0 x 10 10 It is preferable that the volume resistivity of the inner side portion is 1.0×10 or more. This effectively suppresses the influence of the carcass 12 on the reading performance of the RFID tag 52. The tire 2 can improve the reading performance of the RFID tag 52. From this viewpoint, the volume resistivity of the inner side portion is 1.0×10 12 It is more preferable that the resistivity is Ω·cm or more.

[0089] Fig. 5 shows a part of the cross section of the tire 2 shown in Fig. 2. Fig. 5 shows the cross section of the part where the tag member 24 is arranged. The length indicated by the double arrow TP in Fig. 5 is the thickness of the tag member 24. This thickness TP is represented by the maximum thickness of the tag member 24 measured at the portion including the RFID tag 52 (more specifically, the semiconductor chip 56) in the cross section shown in Fig. 5.

[0090] The RFID tag 52 is covered with a protective body 54. Because the protective body 54 has low conductivity, covering the RFID tag 52 with the protective body 54 contributes to improved readability. On the other hand, if the tag member 24 is thick, a thin outer side portion 62 is formed. In this case, there is a concern that the surface distortion increases, increasing the risk of superficial cracks (SFCs), which affect the appearance quality. The thickness TP of the tag member 24 takes into consideration readability and SFC resistance. In this tire 2, the thickness TP of the tag member 24 is preferably 1.0 mm or more, and more preferably 1.4 mm or more, from the viewpoint of improving the reading performance of the RFID tag 52. From the viewpoint of reducing the risk of SFC occurrence, the thickness TP of the tag member 24 is preferably 2.5 mm or less, and more preferably 2.3 mm or less.

[0091] The position indicated by the symbol GC in Fig. 5 is the reference position of the RFID tag 52 in the cross section shown in Fig. 5. The reference position GC is the center of the line segment connecting the outer end TS and inner end TU of the RFID tag 52. The solid line NL is a normal to the side surface of the tire 2 that passes through this reference position GC. If there is decoration on the outer surface of the tire 2, the normal NL is identified on the aforementioned imaginary outer surface. 5, the length indicated by the double-headed arrow Tus is the thickness of the inner side portion 60. This thickness Tus is the thickness of the inner side portion 60 located axially inside of the RFID tag 52. The length indicated by the double-headed arrow Tss is the thickness of the outer side portion 62. This thickness Tss is the thickness of the outer side portion 62 located axially outside of the RFID tag 52. The thicknesses Tus and Tss are measured along the normal line NL.

[0092] In this tire 2, the inner side portion 60 located axially inside the RFID tag 52 is thicker than the outer side portion 62 located axially outside the RFID tag 52. This allows the inner side portion 60 to contribute to improving the reading performance of the RFID tag 52. From this viewpoint, it is preferable that the inner side portion 60 located axially inside the RFID tag 52 is thicker than the outer side portion 62 located axially outside the RFID tag 52. On the other hand, since the outer side portion 62 is thinner than the inner side portion 60, there is a concern that the risk of damage to the tag member 24 increases. However, by arranging the RFID tag 52 radially inward of the maximum width position PW, in other words, by arranging the RFID tag 52 in a portion of the tire 2 that is less prone to movement and distortion, the tire 2 can reduce the risk of damage to the tag member 24 even if the outer side portion 62 is thinner than the inner side portion 60. In this case, the thin outer side portion 62 can contribute to improving the reading performance of the RFID tag 52. From this perspective, it is more preferable that the inner side portion 60, which is located axially inward of the RFID tag 52, is thicker than the outer side portion 62, which is located axially outward of the RFID tag 52, and that the RFID tag 52 is located radially inward of the maximum width position PW.

[0093] The thickness Tus of the inner side portion 60 located axially inside the RFID tag 52 is preferably 1.5 times or more the thickness Tss of the outer side portion 62 located axially outside the RFID tag 52. This enables the tire 2 to improve the reading performance of the RFID tag 52. From the viewpoint of reducing the risk of damage to the tag member 24, the thickness Tus is preferably 2.0 times or less the thickness Tss.

[0094] 5, the solid line NLa is a normal to the outer surface of the tire 2 that passes through the outer end SAG of the outer apex 40. The length indicated by the double arrow Tusa is the thickness of the inner side portion 60 measured along the normal line NLa.

[0095] In the tire 2, the thickness Tusa of the inner side portion 60 at the outer end SAG of the outer apex 40 is preferably the same as or thicker than the thickness Tus of the inner side portion 60 located axially inside of the RFID tag 52. This allows the inner side portion 60 to effectively contribute to improving the reading performance of the RFID tag 52. From this perspective, the thickness Tusa of the inner side portion 60 at the outer end SAG of the outer apex 40 is preferably 1.0 times or more, and more preferably 1.1 times or more, the thickness Tus of the inner side portion 60 located axially inside of the RFID tag 52. From the viewpoint of effectively suppressing the influence of the inner side portion 60 on durability, the thickness Tusa is preferably 1.5 times or less the thickness Tus.

[0096] 2, the solid line NLw is a normal line to the outer surface of the tire 2 that passes through the maximum width position PW. The length indicated by the double-headed arrow Tusw is the thickness of the inner side portion 60 measured along this normal line NLw. The thickness Tusw is the thickness of the inner side portion 60 at the maximum width position PW.

[0097] In this tire 2, the thickness Tus of the inner side portion 60 located inside the RFID tag 52 is preferably the same as or thicker than the thickness Tusw of the inner side portion 60 at the maximum width position PW. This allows the thinner inner side portion 60 at the maximum width position PW to promote deformation of the tire 2, and the thicker inner side portion 60 at the arrangement position of the RFID tag 52 can effectively contribute to improving the reading performance of the RFID tag 52. From this perspective, the thickness Tus of the inner side portion 60 located inside the RFID tag 52 is preferably 1.0 times or more, and more preferably 1.1 times or more, the thickness Tusw of the inner side portion 60 at the maximum width position PW. From the viewpoint of effectively suppressing the influence of the inner side portion 60 on durability, the thickness Tus is preferably 1.5 times or less the thickness Tusw.

[0098] As is clear from the above description, according to the present invention, a heavy-duty tire 2 can be obtained that can achieve improved RFID tag reading performance while suppressing the impact on durability caused by the incorporation of an RFID tag. [Industrial Applicability]

[0099] The technology described above, which can improve the reading performance of RFID tags while suppressing the impact on durability caused by incorporating RFID tags, can be applied to various types of tires.

[0100] [Note] The present invention includes the following aspects.

[0101] [1] A tire comprising a pair of beads, a carcass spanning the pair of beads, a tread positioned radially outward of the carcass, a pair of sidewalls positioned axially outward of the carcass, and a tag member including an RFID tag, wherein each of the pair of beads comprises a core and an apex, the apex comprising an inner apex positioned radially outward of the core and an outer apex positioned radially outward of the inner apex, each of the pair of sidewalls comprising an inner side portion and an outer side portion positioned axially outward of the inner side portion, the inner end of the inner side portion being sandwiched between the outer apex and the outer side portion, the tag member being positioned between the inner side portion and the outer side portion, and the volume resistivity of the inner side portion being higher than the volume resistivity of the outer side portion. [2] A heavy-duty tire as described in [1] above, wherein the carcass comprises a carcass ply, the carcass ply comprising a ply body spanning a pair of the beads and a pair of folded-up portions connected to the ply body and folded up at the beads, and the RFID tag is located radially outward from the end of the folded-up portion and radially inward from the maximum width position of the tire. [3] The heavy-duty tire according to the above-mentioned [1] or [2], wherein the tag member comprises the RFID tag and a protective body covering the RFID tag, and the carbon black content CBu of the inner side portion, the carbon black content CBs of the outer side portion, and the carbon black content CBp of the protective body satisfy the following relational expression: CBp≦CBu <CBs [4] The heavy-duty tire according to the above [3], wherein the tag member has a thickness of 1.0 mm or more and 2.5 mm or less. [5] The heavy-duty tire according to any one of [1] to [4] above, wherein the inner side portion is disposed so as to straddle the maximum width position of the tire in the radial direction. [6] The volume resistivity of the inner side portion is 1.0 × 10 10 The heavy-duty tire according to any one of [1] to [5] above, having a resistance of Ω·cm or more. [7] The heavy-duty tire according to any one of the above [1] to [6], wherein the carbon black content CBu of the inner side portion is 0.6 times or less the carbon black content CBs of the outer side portion. [8] A heavy-duty tire according to any one of [1] to [7] above, wherein the inner side portion located axially inside the RFID tag is thicker than the outer side portion located axially outside the RFID tag. [Explanation of symbols]

[0102] 2. Tires 4. Tread 6. Sidewall 8. Chafer 10 Bead 12. Carcass 24 Tag member 26 Tread surface 30 Base 32 Cap part 34 cores 36 Apex 38···Inner apex 40...Outer apex 44···Carcass ply 46···Ply body 48... Folded part 52... RFID tags 54 Protective body 60...Inner side 62 Outer side

Claims

1. A tire comprising: a pair of beads; a carcass spanning the pair of beads; a tread positioned radially outward of the carcass; a pair of sidewalls positioned axially outward of the carcass; and a tag member including an RFID tag, Each of the pair of beads includes a core and an apex, the apex includes an inner apex located radially outward of the core, and an outer apex located radially outward of the inner apex, Each of the pair of side walls includes an inner side portion and an outer side portion located axially outward of the inner side portion, an inner end of the inner side portion is sandwiched between the outer apex and the outer side portion, the tag member is located between the inner side portion and the outer side portion; The volume resistivity of the inner side portion is higher than the volume resistivity of the outer side portion. Heavy duty tires.

2. the carcass comprises a carcass ply; The carcass ply includes a ply body that spans between the pair of beads, and a pair of turn-up portions that are connected to the ply body and turned up at the beads, the RFID tag is located radially outward from an end of the folded-up portion and radially inward from a maximum width position of the tire; 2. The heavy duty tire according to claim 1.

3. the tag member includes the RFID tag and a protective body that covers the RFID tag, the carbon black content CBu of the inner side portion, the carbon black content CBs of the outer side portion, and the carbon black content CBp of the protective body satisfy the following relational expression:

2. The heavy duty tire according to claim 1. CBp≦CBu<CBs

4. The thickness of the tag member is 1.0 mm or more and 2.5 mm or less.

4. The heavy duty tire according to claim 3.

5. The inner side portion is disposed so as to straddle the maximum width position of the tire in the radial direction.

2. The heavy duty tire according to claim 1.

6. The volume resistivity of the inner side portion is 1.0×10 １０ Ω cm or more, 2. The heavy duty tire according to claim 1.

7. the carbon black content CBu of the inner side portion is 0.6 times or less the carbon black content CBs of the outer side portion; 2. The heavy duty tire according to claim 1.

8. the inner side portion located axially inside the RFID tag is thicker than the outer side portion located axially outside the RFID tag; The heavy duty tire according to any one of claims 1 to 7.

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