Heavy-duty tires

Abstract

To provide a heavy-duty tire 2 that achieves weight reduction while maintaining good durability. [Solution] The tire 2 comprises a carcass 12, a pair of sidewalls 6, a pair of chafers 8, and a pair of reinforcing layers 22. The carcass 12 comprises a carcass ply 38. The carcass ply 38 comprises a ply body 40 and a pair of folded portions 42. The reinforcing layer 22 comprises a fiber reinforcing layer 48. The fiber reinforcing layer 48 consists of a single fiber reinforcing ply 52. ​​The sidewall 6 and the chafer 8 are joined at a boundary 54 that spans between the radial inner end SU of the sidewall 6 and the radial outer end CG of the chafer 8. The chafer 8 covers the radial inner end SU of the sidewall 6. The sidewall 6 is softer than the chafer 8.

Description

Technical Field

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

Background Art

[0002] Heavy-duty tires mounted on vehicles such as trucks and buses support a large load. A large load acts on the bead portion of the tire. In order to prevent damage to the bead portion and improve the durability of the tire, it has been proposed to provide a reinforcing layer in the bead portion. For example, the bead portion of the tire disclosed in Patent Document 1 is provided with an inner reinforcing layer in which steel cords are embedded and two outer reinforcing layers in which organic fiber cords are embedded.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a heavy-duty tire that can achieve weight reduction while maintaining good durability.

Means for Solving the Problems

[0005] The heavy-duty tire according to the present invention comprises a pair of beads, a carcass spanning between the pair of beads, a pair of sidewalls located axially outward of the carcass, a pair of chafers located radially inward of the sidewalls and in contact with the rim, and a pair of reinforcing layers located between the carcass and the chafers. The bead comprises a core and an apex located radially outward of the core. The carcass comprises a carcass ply. The carcass ply comprises a ply body spanning between the pair of beads and a pair of folded portions connected to the ply body and folded back by the bead. The reinforcing layer comprises a fiber reinforcing layer located axially outward of the folded portions. The fiber reinforcing layer consists of a single fiber reinforcing ply containing a number of parallel fiber reinforcing cords. The fiber reinforcing cords are organic fiber cords. The sidewall and the chafer are joined at a boundary spanning between the radially inward end of the sidewall and the radially outward end of the chafer. The chafer covers the radially inward end of the sidewall. The sidewall is softer than the chafer. [Effects of the Invention]

[0006] This invention provides a heavy-duty tire that achieves weight reduction while maintaining good durability. [Brief explanation of the drawing]

[0007] [Figure 1] This is a cross-sectional view showing a part of a heavy-duty tire according to one embodiment of the present invention. [Figure 2] This is a cross-sectional view showing a portion of the tire in Figure 1. [Figure 3] This is a cross-sectional view showing a portion of a tire that is not mounted on a rim. [Figure 4] This is an explanatory diagram of the carcass cord, metal reinforcement cord, and fiber reinforcement cord in the bead section. [Figure 5] This graph shows the relationship between the angle of the fiber reinforcement cord and the strain at the end of the folded section. [Modes for carrying out the invention]

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

[0009] The tire of this invention is mounted on a rim. Air is filled inside the tire, and the internal pressure of the tire is regulated. A tire mounted on a rim is also called a tire-rim assembly. A tire-rim assembly comprises a rim and a tire mounted on this rim.

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

[0011] In this invention, unless otherwise specified, the dimensions and angles of each part of the tire are measured under normal conditions. The dimensions and angles of each part of the tire in the meridional cross-section, which cannot be measured when the tire is mounted on a standard rim, are measured at the tire's cross-section, obtained by cutting the tire along a plane containing the axis of rotation. In this measurement, the tire is set so that the distance between the left and right beads matches the distance between the beads in a tire mounted on a standard rim. The tire's structure, which cannot be confirmed when the tire is mounted on a standard rim, is confirmed at the aforementioned cross-section.

[0012] A genuine rim refers to a rim defined 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 considered genuine rims.

[0013] Regular tire pressure refers to the internal pressure specified in the tire's standard. The "maximum air pressure" in the JATMA standard, the "maximum value" listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are all considered regular tire pressures.

[0014] The normal load means the load defined in the standard on which the tire relies. The "maximum load capacity" in the JATMA standard, the "maximum value" published in "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 100% modulus means the stress at 100% elongation. Among the elements constituting the tire, the 100% modulus of the element made of crosslinked rubber is measured at a temperature atmosphere of 23°C using a tensile tester in accordance with the provisions of JIS K6251. In this measurement, strip pieces (length 35 mm × width 6 mm × thickness 1 mm) are sampled from the tire, and dumbbell test pieces are prepared using these strip pieces. The length direction of the strip pieces is made to coincide with the circumferential direction of the tire. When strip pieces cannot be sampled from the tire, dumbbell test pieces are prepared from a sheet-like crosslinked rubber (hereinafter also referred to as a rubber sheet) obtained by pressurizing and heating the rubber composition used for forming the element to be measured at a temperature of 170°C for 12 minutes.

[0016] In the present invention, among the elements constituting the tire, the loss tangent (tanδ) of the element made of crosslinked rubber is measured using a viscoelastic spectrometer in accordance with the provisions of JIS K6394. The measurement conditions are as follows. Initial strain = 10% Dynamic strain = ±1% Frequency = 10 Hz Mode = elongation mode Temperature = 70°C In this measurement, test pieces (length 40 mm × width 4 mm × thickness 1 mm) are sampled from the tire with their length direction made to coincide with the circumferential direction of the tire. When test pieces cannot be sampled from the tire, test pieces are sampled from the aforementioned rubber sheet. The loss tangent of the present invention is represented by the loss tangent at 70°C.

[0017] In the present invention, the tread portion of a tire is the portion of the tire that contacts the road surface. The bead portion is the portion of the tire that is fitted to a rim. The sidewall portion is the portion of the tire that bridges between the tread portion and the bead portion. A tire includes, as portions, a tread portion, a pair of bead portions, and a pair of sidewall portions.

[0018] [Findings on which the present invention is based] The bead portion of a tire includes the folded-back portion of a carcass ply. Strain tends to concentrate at the ends of the folded-back portion. In a tire, deformation and restoration are repeated. It is conceivable that damage (ply turn-up loose; PTL) in which the carcass cord peels off from the rubber occurs at the ends of the folded-back portion. As described above, a large load acts on the bead portion of a heavy-duty tire. The risk of occurrence of PTL is higher than that of a passenger car tire. In order to suppress the occurrence of PTL and improve durability, it is considered to provide a fiber reinforcing layer in the bead portion of a heavy-duty tire assumed to be used in a harsh environment. The fiber reinforcing layer is usually composed of two reinforcing plies and is arranged so as to cover the ends of the folded-back portion. The bead portion of a tire includes a chafer. Since the chafer contacts the rim, it is composed of crosslinked rubber having a relatively high modulus. When the bead portion has a fiber reinforcing layer, the chafer is located between the fiber reinforcing layer and the rim. Since the fiber reinforcing layer contacts the chafer in a region where the shear strain is large, it is conceivable that a loose occurs between the fiber reinforcing layer and the chafer before the above-described PTL occurs. The loose affects the durability of the tire. Due to environmental considerations, weight reduction is required for tires. When the fiber reinforcing layer is composed of one reinforcing ply for weight reduction, the shear strain concentrates between the fiber reinforcing layer and the chafer, and the risk of occurrence of a loose increases. Therefore, the present inventor has earnestly studied to obtain a heavy-duty tire capable of achieving weight reduction while maintaining good durability, and has completed the present invention described below.

[0019] [Summary of Embodiments of the Invention] The present invention relates to a tire comprising a pair of beads, a carcass spanning between the pair of beads, a pair of sidewalls located axially outward of the carcass, a pair of chafers located radially inward of the sidewalls and in contact with the rim, and a pair of reinforcing layers located between the carcass and the chafers, wherein the beads comprise a core and an apex located radially outward of the core, and the carcass comprises carcass plies. The carcass ply comprises a ply body spanning between a pair of beads and a pair of folded portions connected to the ply body and folded back by the beads; the reinforcing layer comprises a fiber reinforcing layer located axially outward of the folded portions, the fiber reinforcing layer consists of a single fiber reinforcing ply containing a number of parallel fiber reinforcing cords, the fiber reinforcing cords are organic fiber cords, the sidewall and the chafer are joined at a boundary spanning between the radially inner end of the sidewall and the radially outer end of the chafer, the chafer covers the radially inner end of the sidewall, and the sidewall is softer than the chafer, making it a heavy-duty tire.

[0020] The heavy-duty tire of the present invention can achieve weight reduction while maintaining good durability. Although the mechanism by which the tire achieves this effect has not been fully elucidated, it is presumed to be as follows.

[0021] A reinforcing layer located between the carcass and the chafer is a fiber-reinforced layer, positioned axially outward at the folded portion. The fiber-reinforced layer restrains the folded portion. This fiber-reinforced layer can contribute to reducing the risk of PTL (Potentially Toxic Litter) formation. The fiber-reinforced layer consists of a single nylon reinforcing ply. This fiber-reinforced layer is lighter than conventional fiber-reinforced layers composed of multiple nylon reinforcing plies. This fiber-reinforced layer can contribute to reducing the weight of the tire. The sidewall and chafer are joined at the boundary spanning the radial inner end of the sidewall and the radial outer end of the chafer, with the chafer covering the radial inner end of the sidewall. This positions the sidewall between the fiber reinforcement layer and the chafer. The sidewall is softer than the chafer. This sidewall mitigates the shear strain that occurs between the fiber reinforcement layer and the chafer. Despite the fiber reinforcement layer being composed of a single nylon reinforcement ply, the occurrence of looseness due to shear strain between the fiber reinforcement layer and the chafer, which was observed in conventional tires, is suppressed. The tire can achieve weight reduction while maintaining good durability.

[0022] Preferably, the line segment connecting the radially inner end of the sidewall and the radially outer end of the chafer is the boundary reference line segment, and the entire boundary is located axially inward from the boundary reference line segment. In this case, the sidewall can effectively contribute to mitigating the shear strain that occurs between the fiber reinforcement layer and the chafer. The occurrence of looseness caused by shear strain is suppressed. The tire can maintain good durability.

[0023] Preferably, the core has a bottom surface positioned opposite the rim seat, the axial outer end of the bottom surface is the reference point of the core, and the inner end of the sidewall is located radially outward from the reference point of the core. In this case, the sidewall is prevented from being positioned in the zone where the tire contact pressure with the rim is maximum. Damage such as chafer cracks and rim chafing is suppressed. The sidewall can effectively contribute to mitigating shear strain that occurs between the fiber reinforcement layer and the chafer. The tire can maintain good durability.

[0024] Preferably, the chafer has a recess on its contact surface with the rim, and the recess is located axially outward from the core. In this case, the strain caused by the rim contacting the chafer is reduced. Since the rim fits into the recess, the movement of the bead is suppressed. Loose and PTL caused by shear strain between the fiber reinforcement layer and the chafer are effectively suppressed. The tire can maintain good durability.

[0025] More preferably, in the meridional cross-section of the tire, the shape of the recess is represented by an arc, and the radius of the arc is 20 mm or more and 30 mm or less. In this case, the rim fits well into the recess, so the movement of the bead is effectively suppressed. Loose and PTL caused by shear strain between the fiber reinforcement layer and the chafer are effectively suppressed. The tire can maintain good durability.

[0026] More preferably, a straight line passing through the midpoint of the recess and extending axially is the recess reference line, and the radial inner end of the sidewall is included in the recess reference line or located radially outside the recess reference line. In this case, the boundary between the sidewall and the chafing is positioned appropriately. This suppresses the influence of the sidewall on the rigidity of the contact portion with the rim. Since the rigidity of the contact portion with the rim is appropriately maintained, the tire can reduce the risk of damage such as chafing cracks and rim chafing. The tire can maintain good durability.

[0027] Preferably, the radially outer end of the chafer is located radially inward from the end of the folded portion. In this case, the boundary between the sidewall and the chafer is positioned away from the tire's widest point. This reduces the risk of chafer cracking and allows the tire to maintain good durability.

[0028] Preferably, the radial distance from the bead baseline to the radially outer edge of the chafer is 18 mm or more. In this case, the boundary between the sidewall and the chafer is positioned appropriately. This reduces the risk of rim chafing occurring in the tire. The tire can maintain good durability.

[0029] Preferably, the loss tangent of the sidewall is lower than the loss tangent of the chafer. In this case, the occurrence of damage caused by heat generation in the sidewall is suppressed, and the tire can maintain good durability.

[0030] Thus, according to the present invention, a heavy-duty tire can be obtained that achieves weight reduction while maintaining good durability. This will be explained in detail below using the heavy-duty tire 2 shown in Figure 1 as an example.

[0031] [Details of the Embodiments of the Invention] Figure 1 shows a part of a heavy-duty tire 2 according to one embodiment of the present invention. This tire 2 is mounted on vehicles such as trucks and buses.

[0032] Figure 1 shows a portion of the cross-section of tire 2 (hereinafter referred to as the meridian cross-section) along the plane containing the rotation axis of tire 2. Figure 2 shows a portion of the cross-section shown in Figure 1. Figure 2 shows the bead portion B of tire 2. The direction indicated by the double arrow AD is the axial direction of tire 2. The axial direction of tire 2 means the direction parallel to the rotation axis of tire 2. The direction indicated by the double arrow RD is the radial direction of tire 2. The direction perpendicular to the plane of paper in Figure 1 is the circumferential direction of tire 2. The dashed line EL extending radially represents the equatorial plane of tire 2.

[0033] In the axial direction, the direction away from the equatorial plane is the axial outward direction of tire 2, and the direction towards the equatorial plane is the axial inward direction of tire 2. The direction indicated by arrow RD1 is the radial outward direction of tire 2, and the direction indicated by arrow RD2 is the radial inward direction of tire 2.

[0034] The tire 2 shown in Figures 1 and 2 is mounted on rim R (regular rim). The solid line BBL extending axially is the bead baseline. The bead baseline is the line that defines the rim diameter of rim R (see JATMA, etc.).

[0035] The rim R comprises a seat S and a flange F. The bead portion B is placed on the seat S, and the bead portion B is pressed against the flange F. The position indicated by the symbol FG is the radial outer end of the rim R.

[0036] This tire 2 comprises 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 cushioning layers 16, a pair of interlayer strips 18, an inner liner 20, and a pair of reinforcing layers 22.

[0037] The tread 4 is located radially outward of the carcass 12. The tread 4 has a tread surface 24. The tire 2 contacts the road surface at the tread surface 24. Grooves 26 are cut into the tread 4.

[0038] The position indicated by the symbol Eq is the equator. Equator Eq is the intersection of the tread surface 24 and the equatorial surface. If there is a groove 26 on the equatorial surface, the equator is determined based on a virtual tread surface obtained by assuming that there is no groove 26. The radial distance from the bead baseline to equatorial Eq obtained in a normal tire 2 is the cross-sectional height of the tire 2 (see JATMA, etc.).

[0039] The position indicated by the symbol TE is the edge of the tread surface 24. In the case of a tire where the edge of the tread surface is not identifiable by appearance, the position on the outer surface of the tire corresponding to the axial 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 bringing the tire into contact with a plane is used as the edge of the tread surface.

[0040] The tread 4 is made of cross-linked rubber. Although not shown, the tread 4 comprises a base portion and a cap portion. The base portion is made of low-heat-generating cross-linked rubber. The cap portion is located radially outward from the base portion. The cap portion is made of cross-linked rubber that takes into consideration wear resistance and grip performance. The cap portion includes the tread surface 24.

[0041] Each sidewall 6 is connected to the end of the tread 4. The sidewalls 6 are located axially outward of the carcass 12. The sidewalls 6 are made of cross-linked rubber. The 100% modulus of the sidewalls 6 is between 1.5 MPa and 2.3 MPa. The loss tangent of the sidewalls is between 0.02 and 0.06.

[0042] The position indicated by the symbol PW is the axial outer end of tire 2 (hereinafter referred to as outer end PW). If there are decorations such as patterns or letters on the outer surface of tire 2, outer end PW is determined based on a hypothetical outer surface obtained assuming there are no decorations. Tire 2 shows its maximum width at outer end PW. 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) obtained in a normal state of tire 2 is the cross-sectional width of this tire 2 (see JATMA, etc.).

[0043] The radial outer end SG of the sidewall 6 of this tire 2 is located radially outside the maximum width position PW. The radial inner end SU of the sidewall 6 is located radially inside the maximum width position PW. This sidewall 6 is positioned across the maximum width position PW. The inner end SU of the sidewall 6 is located radially inside the end FE of the folded portion 42, which will be described later. This inner end SU of the sidewall 6 is located radially inside the outer end FG of the rim R.

[0044] In Figure 2, the length indicated by the double arrow H is the radial distance from the bead baseline to the maximum width position PW. The radial distance H is also called the radial height of the maximum width position PW. In a tire 2 in its normal state, the ratio of the radial height H at the maximum width position PW to the cross-sectional height is between 0.40 and 0.60.

[0045] Each chafer 8 is located radially inward of the sidewall 6. The chafer 8 is in contact with the rim R. The chafer 8 is made of cross-linked rubber with wear resistance in mind. The 100% modulus of the chafer 8 is between 5.8 MPa and 7.2 MPa. Although not detailed here, the loss tangent of the chafer 8 is higher than that of the sidewall 6.

[0046] The radial outer end CG of the chafer 8 is located radially outside the inner end SU of the sidewall 6. This outer end CG of the chafer 8 is located radially outside the outer end FG of the rim R. In Figure 2, the length indicated by the double arrow C is the radial distance from the bead baseline to the radial outer end CG of the chafer 8. The radial distance C is also called the radial height of the chafer 8. The position indicated by the symbol RR is the outer end of the contact surface between the rim R and the tire 2. Position RR is also called the separation point. The separation point RR is identified in the normal state of the tire 2.

[0047] Each bead 10 is located radially inward of the sidewall 6. The bead 10 is located axially inward of the sidewall 6. The bead 10 is located axially inward of the chafer 8.

[0048] Bead 10 consists of a core 28 and an apex 30. The core 28 extends in the circumferential direction. In Figure 2, the position indicated by the symbol CRS is the radial outer end of the core 28. The position indicated by the symbol CRU is the radial inner end of the core 28. The position indicated by the symbol CAS is the axial outer end of the core 28. The position indicated by the symbol CAU is the axial inner end of the core 28.

[0049] Although not shown, the core 28 includes wound steel wire. The cross-sectional shape of the core 28 is determined by winding the wire in a regular manner. As a result, in the cross-section of the core 28, multiple cross-sectional units consisting of multiple wire cross-sections arranged in parallel in the axial direction are stacked in multiple layers in the substantially radial direction. The core 28 of this tire 2 has a hexagonal cross-sectional shape. The core 28 may also have a square cross-sectional shape. In this invention, the cross-sectional shape of the core 28 is determined based on the shape represented by a line circumscribing the cross-section of the core 28, taking into account the presence of steps due to the irregular alignment of the wire cross-sections.

[0050] The core 28 of this tire 2 has approximately six sides 29. For example, as shown in Figure 2, one of the six sides 29, side 29b, is positioned to face the seat S of the rim R. In this invention, of the multiple sides 29 that make up the core 28, the side 29b that is positioned to face the seat S of the rim R is the bottom surface of the core 28. The core 28 has a bottom surface 29b that is positioned to face the seat S of the rim R.

[0051] In Figure 2, the symbol BU represents the vertex formed by the bottom surface 29b and the side surface 29 located axially inward of the two side surfaces 29 adjacent to the bottom surface 29b. Vertex BU is the axially inward end of the bottom surface 29b and is also the radially inward end CRU of the core 28, as mentioned above. Vertex BS represents the vertex formed by the bottom surface 29b and the side surface 29 located axially outward of the two side surfaces 29 adjacent to the bottom surface 29b. Vertex BS is the axially outward end of the bottom surface 29b and is also called the reference point of the core 28. In Figure 2, the solid line LA is a straight line extending axially through the reference point BS and is called the first core reference line. The solid line LR is a straight line extending radially through the reference point BS and is called the second core reference line.

[0052] Apex 30 is located radially outward from core 28. Apex 30 extends radially outward from core 28. Apex 30 tapers outward. The radially outward end AG of apex 30 is located radially inward from the maximum width position PW.

[0053] In Figure 2, the length indicated by the double arrow L is the radial distance from the bead baseline to the outer end AG of the apex 30. The radial distance L is also called the radial height of the apex 30. In this tire 2, from the perspective of balancing the rigidity of the bead section B and the deflection of the tire 2, the ratio (L / H) of the radial height L of the apex 30 to the radial height H of the maximum width position PW is set in the range of 0.55 to 0.95.

[0054] The apex 30 comprises an inner apex 32 and an outer apex 34. The inner apex 32 is located radially outward from the core 28. The outer apex 34 is located radially outward from the inner apex 32.

[0055] The inner apex 32 tapers outward. The radial outer end UAG of the inner apex 32 is located radially outside the outer end CG of the chafer 8. The inner apex 32 is made of cross-linked rubber. The inner apex 32 is harder than the chafer 8. Specifically, the ratio of the 100% modulus of the inner apex 32 to the 100% modulus of the chafer 8 is between 1.5 and 2.3.

[0056] The outer apex 34 is thicker near the outer end UAG of the inner apex 32. From this thicker portion, the outer apex 34 tapers inward and then outward. The radial inner end SAU of the outer apex 34 is located radially inward of the outer end FG of the rim R. The radial outer end SAG of the outer apex 34 is also the outer end AG of apex 30. The outer apex 34 is made of cross-linked rubber. The outer apex 34 is softer than the chafer 8. Specifically, the ratio of the 100% modulus of the outer apex 34 to the 100% modulus of the chafer 8 is between 0.38 and 0.65.

[0057] The apex 30 of this tire 2 further includes an edge strip 36. The edge strip 36 is located axially outward of the outer apex 34 and forms part of the outer surface of the apex 30. The edge strip 36 is located radially between the outer end SAG and the inner end SAU of the outer apex 34. The edge strip 36 is made of cross-linked rubber. The edge strip 36 is softer than the chafer 8 and harder than the outer apex 34.

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

[0059] The carcass 12 comprises at least one carcass ply 38. The carcass 12 of this tire 2 is composed of one carcass ply 38. The carcass ply 38 is folded over at each bead 10.

[0060] The carcass ply 38 comprises a ply body 40 and a pair of folded portions 42. The ply body 40 spans between a pair of beads 10. Each folded portion 42 is connected to the ply body 40 and is folded over at the bead 10. The folded portions 42 of this tire 2 are folded over at the bead 10 from the axially inward to the outward direction. The end FE of the folded portion 42 is located radially inward of the outer end UAG of the inner apex 32. The end FE of the folded portion 42 is located radially between the outer and inner ends of the edge strip 36. The end FE of the folded portion 42 is in contact with the edge strip 36.

[0061] The carcass ply 38 contains numerous parallel carcass cords. Although not shown, these carcass cords are covered with topping rubber. Each carcass cord intersects the equatorial plane. The angle that the carcass cords make with respect to the equatorial plane is between 70° and 90°. The carcass cords of this tire 2 are steel cords.

[0062] In Figure 2, the length indicated by the double arrow N is the radial distance from the bead baseline to the end FE of the folded portion 42. The radial distance N is also called the radial height of the folded portion 42. The ratio (N / H) of the radial height N of the folded portion 42 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 outward of the carcass 12. The belt 14 is located radially inward of the tread 4. The belt 14 comprises at least two belt plies 44 arranged radially. The belt 14 of this tire 2 comprises four belt plies 44. The four belt plies 44, from radially inward, are the first belt ply 44A, the second belt ply 44B, the third belt ply 44C, and the fourth belt ply 44D. The second belt ply 44B has the widest width, and the fourth belt ply 44D has the narrowest width.

[0064] Although not shown in the illustration, each belt ply 44 contains numerous parallel belt cords. These belt cords are covered with 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 cushion layer 16 is located between the belt 14 and the carcass 12 at the end of the belt 14. The cushion layer 16 is made of soft cross-linked rubber.

[0066] Each interlayer strip 18 is located axially between the sidewall 6 and the apex 30 (specifically, the outer apex 34). The outer end of the interlayer strip 18 is located radially outward of the outer end of the edge strip 36. Together with the edge strip 36, the interlayer strip 18 covers the end FE of the folded portion 42. On the axially outward side of the folded portion 42, the interlayer strip 18, together with the sidewall 6, covers the end of the reinforcing layer 22 that is located on the outer surface side of the tire 2 (the second end RS, described later).

[0067] The interlaminar strip 18 is made of cross-linked rubber. The interlaminar strip 18 is softer than the chafer 8 and harder than the outer apex 34. The interlaminar strip 18 has a stiffness comparable to that of the edge strip 36. Having a stiffness comparable to that of the edge strip 36 means that the ratio of the 100% modulus of the interlaminar strip 18 to the 100% modulus of the edge strip 36 is in the range of 0.8 to 1.2.

[0068] The inner liner 20 is located inside the carcass 12. The inner liner 20 is bonded to the inner surface of the carcass 12 via an insulation (not shown) made of cross-linked rubber. The inner liner 20 constitutes the inner surface of the tire 2. The inner liner 20 is made of cross-linked rubber with excellent air-shielding properties.

[0069] Each reinforcing layer 22 is located between the carcass 12 and the chafer 8. The reinforcing layer 22 is folded over along the carcass 12 by the bead 10. The reinforcing layer 22 is positioned to wrap around the radially inner portion of the bead 10 from the radially inner side of the carcass 12. The inner end of the reinforcing layer 22 on the inner side of the tire 2 (hereinafter referred to as the first end RF) is located radially inward of the outer end UAG of the inner apex 32, between the inner liner 20 and the ply body 40. The outer end of the reinforcing layer 22 on the outer side of the tire 2 (hereinafter referred to as the second end RS) is located radially inward of the outer end AG of the apex 30, between the apex 30 and the sidewall 6. This second end RS is located radially outward of the first end RF. The reinforcing layer 22 of this tire 2 is a cord reinforcing layer containing a large number of parallel reinforcing cords. This reinforcing layer 22 comprises a metal reinforcing layer 46 and a fiber reinforcing layer 48.

[0070] The metal reinforcement layer 46 is located between the carcass 12 and the fiber reinforcement layer 48. The metal reinforcement layer 46 is folded over along the carcass 12 at the bead 10. The inner side end of the metal reinforcement layer 46 on the tire 2 side (hereinafter referred to as the first end MF) is the first end RF of the reinforcement layer 22. The outer side end of the metal reinforcement layer 46 on the tire 2 side (hereinafter referred to as the second end MS) is located between the folded portion 42 and the fiber reinforcement layer 48. The second end MS of the metal reinforcement layer 46 is located radially inward of the end FE of the folded portion 42. In this tire 2, the second end MS of the metal reinforcement layer 46 is located radially outward of the first end MF. The second end MS may be located radially inward of the first end MF. The radial position of this second end MS may coincide with the radial position of the first end MF.

[0071] The metal reinforcement layer 46 comprises at least one metal reinforcement ply 50. The metal reinforcement layer 46 of this tire 2 is composed of one metal reinforcement ply 50.

[0072] The metal reinforcement ply 50 contains numerous parallel metal reinforcement cords. Although not shown, these metal reinforcement cords are covered with topping rubber. The material of the metal reinforcement cords in this tire 2 is steel. The metal reinforcement cords are steel cords. The metal reinforcement layer 46 is also called the steel reinforcement layer, and the metal reinforcement ply 50 is also called the steel reinforcement ply.

[0073] The fiber reinforcement layer 48 is located axially outward of the folded portion 42. In this tire 2, the reinforcement layer 22 is located between the carcass 12 and the chafer 8, and the metal reinforcement layer 46 is located between the carcass 12 and the fiber reinforcement layer 48. In this tire 2, the fiber reinforcement layer 48 is located between the metal reinforcement layer 46 and the chafer 8. On the axial outward side of the folded portion 42, the fiber reinforcement layer 48 is located between the metal reinforcement layer 46 and the sidewall 6. On the radial outward side of the second end MS of the metal reinforcement layer 46, the fiber reinforcement layer 48 is located between the interlayer strip 18 and the sidewall 6.

[0074] The inner surface end of the fiber reinforcement layer 48 of the tire 2 (hereinafter referred to as the first end FF) is located radially inward of the first end MF of the metal reinforcement layer 46. The first end FF of the fiber reinforcement layer 48 of the tire 2 is located radially inward of the axial inner end CAU of the core 28 and axially inward of the radial inner end CRU of the core 28. The outer surface end of the fiber reinforcement layer 48 of the tire 2 (hereinafter referred to as the second end FS) is the second end RS of the reinforcement layer 22. The second end FS of the fiber reinforcement layer 48 of the tire 2 is located radially between the outer end AG of the apex 30 and the end FE of the folded portion 42. More specifically, the second end FS is located radially between the radial outer end of the interlayer strip 18 and the end FE of the folded portion 42.

[0075] The fiber reinforcement layer 48 of this tire 2 comprises a fiber reinforcement ply 52. ​​The fiber reinforcement ply 52 contains a number of parallel fiber reinforcement cords. Although not shown, these fiber reinforcement cords are covered with topping rubber. The fiber reinforcement cords of this tire 2 are cords made of organic fibers (hereinafter referred to as organic fiber cords). The fiber reinforcement layer 48 consists of a single fiber reinforcement ply 52 containing a number of parallel fiber reinforcement cords, and the fiber reinforcement cords are organic fiber cords. Examples of organic fiber cords that can be used as fiber reinforcement cords include nylon fiber cords, rayon fiber cords, polyester fiber cords, and aramid fiber cords. Among these, nylon fiber cords are preferred. The fiber reinforcement layer 48, in which the organic fiber cord is a nylon fiber cord, is also called a nylon fiber reinforcement layer, and the fiber reinforcement ply 52 is also called a nylon fiber reinforcement ply.

[0076] As mentioned above, the reinforcing layer 22 located between the carcass 12 and the chafer 8 includes a fiber reinforcing layer 48. The fiber reinforcing layer 48 is positioned axially outward of the folded portion 42. The fiber reinforcing layer 48 restrains the folded portion 42. This fiber reinforcing layer 48 can contribute to reducing the risk of PTL formation. The fiber reinforcing layer 48 of this tire 2 consists of a single fiber reinforcing ply 52. ​​This fiber reinforcing layer 48 is lighter than conventional fiber reinforcing layers composed of multiple fiber reinforcing plies. This fiber reinforcing layer 48 can contribute to reducing the weight of the tire 2. The sidewall 6 and the chafer 8 are joined at a boundary 54 that spans the radial inner end SU of the sidewall 6 and the radial outer end CG of the chafer 8. The chafer 8 then covers the radial inner end SU of the sidewall 6. As a result, the sidewall 6 is positioned between the fiber reinforcement layer 48 and the chafer 8. The sidewall 6 is softer than the chafer 8. This sidewall 6 mitigates the shear strain that occurs between the fiber reinforcement layer 48 and the chafer 8. Despite the fiber reinforcement layer 48 being composed of a single fiber reinforcement ply 52, the occurrence of looseness due to shear strain between the fiber reinforcement layer 48 and the chafer 8, which was observed in conventional tires, is suppressed. This tire 2 can achieve weight reduction while maintaining good durability.

[0077] In Figure 2, the solid line LSC represents the line segment connecting the radial inner end SU of the sidewall 6 and the radial outer end CG of the chafer 8. The line segment LSC is the portion of the straight line passing through the inner end SU and the outer end CG that lies between the inner end SU and the outer end CG, and is also called the boundary reference line segment.

[0078] The boundary 54 between the sidewall 6 and the chafer 8 of this tire 2 is located radially outward from the boundary reference line segment LSC. In other words, the entire boundary 54 is located axially inward from the boundary reference line segment LSC. This allows the sidewall 6 to effectively contribute to mitigating the shear strain that occurs between the fiber reinforcement layer 48 and the chafer 8. The occurrence of looseness caused by shear strain is suppressed. This tire 2 can maintain good durability. From this viewpoint, it is preferable that the entire boundary 54 between the sidewall 6 and the chafer 8 is located axially inward from the boundary reference line segment LSC.

[0079] As mentioned above, the sidewall 6 and the chafer 8 are joined at the boundary 54 that spans the space between the inner end SU of the sidewall 6 and the outer end CG of the chafer 8. The inner end SU of the sidewall 6 is the inner end of the boundary 54, and the outer end CG of the chafer 8 is the outer end of the boundary 54. As shown in Figure 2, the outer end CG of the boundary 54 is located radially outside the separation point RR, and the inner end SU of the boundary 54 is located radially inside the separation point RR.

[0080] The boundary 54 has an inwardly curved shape. Since the flange F of the rim R also has a curved shape in a similar direction, the chafer 8 located between the sidewall 6 and the rim R can have a substantially uniform thickness. When the rim R contacts the chafer 8, the load acting on the boundary 54 is distributed across the entire boundary 54. As a result, the sidewall 6 can effectively contribute to mitigating the shear strain that occurs between the fiber reinforcement layer 48 and the chafer 8. The occurrence of looseness caused by shear strain is suppressed. This tire 2 can maintain good durability. From this viewpoint, it is preferable that the boundary 54 between the sidewall 6 and the chafer 8 has an inwardly curved shape. In this case, it is more preferable that the shape of the boundary 54 is represented by an arc.

[0081] When tire 2 is mounted on rim R, tire 2 comes into contact with rim R. This creates contact pressure between tire 2 and rim R. In a tire in a normal state, the zone from the first core reference line LA to the second core reference line LR corresponds to the zone where the contact pressure is maximum. If, for example, a soft sidewall 6 is located in this zone, there is a risk of increased risk of damage such as chafer cracks or damage to the rim chafing.

[0082] In this tire 2, as shown in Figure 2, the inner end SU of the sidewall 6 is located radially outward from the reference point BS of the core 28. This prevents the sidewall 6 from being positioned in the zone where the contact pressure is maximum. This tire 2 suppresses the occurrence of damage such as chafer cracks and rim chafing. The sidewall 6 can stably perform its function. In other words, the sidewall 6 can effectively contribute to mitigating the shear strain that occurs between the fiber reinforcement layer 48 and the chafer 8. The occurrence of looseness caused by shear strain is suppressed. This tire 2 can maintain good durability. From this viewpoint, it is preferable that the inner end SU of the sidewall 6 is located radially outward from the reference point BS of the core 28.

[0083] Figure 3 shows a cross-section of the bead portion B. This cross-section is part of the meridional cross-section of tire 2, along the plane containing the axis of rotation. The bead portion B of tire 2 shown in Figure 3 is not assembled to the rim R.

[0084] As mentioned above, the chafer 8 is in contact with the rim R. The chafer 8 has a contact surface 56 with the rim R. As shown in Figure 3, a recess 58 is provided on this contact surface 56. The chafer 8 of this tire 2 has a recess 58 on the contact surface 56 with the rim R. The recess 58 overlaps with the core 28 in the axial direction. When the tire 2 is mounted on the rim R, the rim R (specifically, the flange F of the rim R) fits into the recess 58. This reduces the distortion caused by the rim R contacting the chafer 8. Because the rim R fits into the recess 58, the movement of the bead portion B is suppressed. The occurrence of looseness and PTL caused by shear strain between the fiber reinforcement layer 48 and the chafer 8 is effectively suppressed. This tire 2 can maintain good durability. From this viewpoint, it is preferable that the chafer 8 has a recess 58 on the contact surface 56 with the rim R, and that the recess 58 is located axially outward from the core 28.

[0085] In the cross-section shown in Figure 3, the shape of the recess 58 is represented by a single arc. The arrow Rp in Figure 3 is the radius of the arc representing the shape of the recess 58. The position indicated by the symbol PC is the center of this arc.

[0086] In this tire 2, there are no particular restrictions on the shape of the recess 58, as long as the rim R fits into the recess 58 and the movement of the bead portion B is suppressed. However, from the viewpoint of ensuring that the rim R fits sufficiently into the recess 58 and that the movement of the bead portion B is effectively suppressed, it is preferable that the shape of the recess 58 in the meridional cross-section of the tire 2 be represented by an arc. This effectively suppresses the generation of looseness and PTL caused by shear strain between the fiber reinforcement layer and the chafer. This tire can maintain good durability. When the shape of the recess 58 is represented by an arc, from the viewpoint of more effectively suppressing the generation of looseness and PTL, it is preferable that the radius Rp of the arc representing the shape of the recess 58 be 20 mm or more and 30 mm or more, and more preferably 20 mm or more and 25 mm or less.

[0087] In Figure 3, the position indicated by the symbol M is the midpoint of the recess 58. The midpoint M is the position where the length of the contour line representing the shape of the recess 58 is halved. In the case of this tire 2, the shape of the recess 58 is represented by an arc, so the midpoint M of the recess 58 is the position where the length of this arc is halved. The solid line ML in Figure 3 is a straight line that passes through the midpoint M of the recess 58 and extends in the axial direction. In this invention, this straight line ML is the recess reference line.

[0088] If the inner end SU of the sidewall 6 is located radially inward of the recessed reference line ML, the volume of the sidewall 6 present in the contact area between the bead portion B and the rim R increases. Since the sidewall 6 is soft, there is a concern that the rigidity of the contact area with the rim R will decrease, increasing the risk of damage such as chafer cracks and rim chafing.

[0089] However, the inner end SU of the sidewall 6 of this tire 2 is included in the recess reference line ML, as shown in Figure 3. In other words, the radial position of the inner end SU of the sidewall 6 coincides with the radial position of the recess reference line ML. This positions the boundary 54 between the sidewall 6 and the chafing 8 appropriately. The influence of the sidewall 6 on the rigidity of the contact portion with the rim R is suppressed. This tire 2 can maintain appropriate rigidity at the contact portion with the rim R. This tire 2 can reduce the risk of damage such as chafing cracks and rim chafing. This tire 2 can maintain good durability. From this viewpoint, it is preferable that the radial inner end SU of the sidewall 6 is included in the recess reference line ML, or located radially outside the recess reference line ML.

[0090] Chafer 8 is harder than sidewall 6. There is a concern that the risk of chafer cracking increases as the outer edge CG of Chafer 8 approaches the maximum width position PW.

[0091] However, the outer end CG of the chafer 8 of the tire 2 is located radially inward of the end FE of the folded portion 42. As a result, the boundary 54 between the sidewall 6 and the chafer 8 is positioned away from the maximum width position PW of the tire 2. This reduces the risk of chafer cracking in the tire 2. The tire 2 can maintain good durability. From this viewpoint, it is preferable that the outer end CG of the chafer 8 is located radially inward of the end FE of the folded portion 42.

[0092] The radial height C of the chafer 8 is preferably 18 mm or more. This ensures that the boundary 54 between the sidewall 6 and the chafer 8 is positioned appropriately. This reduces the risk of rim chafing occurring in the tire 2. The tire 2 can maintain good durability. From this viewpoint, the radial height C of the chafer 8 is more preferably 25 mm or more. From the viewpoint of reducing the risk of chafer cracking and rim chafing occurring, the radial height C of the chafer 8 is preferably 32 mm or less.

[0093] From the viewpoint of ensuring that the tire 2 maintains good durability, it is preferable that the radial inner end SU of the sidewall 6 is included in the recess reference line ML or located radially outside the recess reference line ML, the radial outer end CG of the chafer 8 is located radially inside the end FE of the folded portion 42, and the radial height C of the chafer 8 is 18 mm or more.

[0094] At the boundary between the sidewall 6 and the chafer 8, the sidewall 6 is sandwiched between the reinforcing layer 22 and the chafer 8. Since the sidewall 6 is softer than the chafer 8, the amount of deformation of the sidewall 6 is greater than that of the chafer 8. There is a concern that damage may occur due to heat generation in the sidewall 6. However, the loss tangent of the sidewall 6 of this tire 2 is lower than the loss tangent of the chafer 8. The occurrence of damage due to heat generation in the sidewall 6 is suppressed. The tire 2 can maintain good durability. From this viewpoint, it is preferable that the loss tangent of the sidewall 6 is lower than the loss tangent of the chafer 8. In this case, the difference between the loss tangent of the chafer 8 and the loss tangent of the sidewall 6 is preferably greater than 0, and 0.04 or more.

[0095] In the bead portion B of this tire 2, the folded portion 42, the metal reinforcing layer 46, and the fiber reinforcing layer 48 are located on the axially outer side of the bead 10. As described above, the folded portion 42 includes carcass cords, the metal reinforcing layer 46 includes metal reinforcing cords, and the fiber reinforcing layer 48 includes fiber reinforcing cords.

[0096] Figure 4 is an explanatory diagram of the carcass cord 60, metal reinforcement cord 62, and fiber reinforcement cord 64 in bead section B. Figure 4 is an image diagram of each cord viewed from the axial outside toward bead section B, and shows each cord unfolded on a plane. The arrangement of the carcass cord, metal reinforcement cord, and fiber reinforcement cord in bead section B will be explained using Figure 4. Although the folded section 42, metal reinforcement layer 46, and fiber reinforcement layer 48 each contain numerous cords, for the sake of explanation, each cord is shown individually, and the arrangement of the carcass cord 60, metal reinforcement cord 62, and fiber reinforcement cord 64 is shown with the intersection positions of the cords aligned.

[0097] In Figure 4, the vertical direction corresponds to the radial direction of tire 2, and the horizontal direction corresponds to the circumferential direction of tire 2. In Figure 4, the dashed line ABL is a straight line extending in the circumferential direction and is a reference line for identifying the slope of each code. The angle that each code makes with respect to the circumferential direction is expressed as an angle from 0 to 180 degrees counterclockwise.

[0098] The carcass cord 60 shown in Figure 4 extends radially. The metal reinforcement cord 62 is inclined relative to the carcass cord 60. In Figure 4, the direction in which the metal reinforcement cord 62 inclins relative to the carcass cord 60 is clockwise. The fiber reinforcement cord 64 is inclined to the same side as the metal reinforcement cord 62 relative to the carcass cord 60. In other words, in Figure 4, the direction in which the fiber reinforcement cord 64 inclins relative to the carcass cord 60 is clockwise.

[0099] Figure 5 is a graph showing the relationship between the angle of the fiber reinforcement cord 64 and the strain at the end FE of the folded portion 42. The data showing this relationship was calculated by a simulation using the Finite Element Method (FEM). The simulation model is a tire 2 based on the configuration shown in Figure 2, in which the carcass 12 consists of one carcass ply 38, the metal reinforcement layer 46 consists of one metal reinforcement ply 50, and the fiber reinforcement layer 48 consists of one fiber reinforcement ply 52. ​​The tire 2 is in a normal state, and the tire size is 295 / 80R22.5. The angle of the fiber-reinforced cord 64 shown on the horizontal axis of the graph in Figure 5 (θf in Figure 7) is the value when the circumferential direction is used as the reference direction.

[0100] As shown in Figure 4, the angle (inferior angle) of the metal reinforcing cord 62 with respect to the circumferential direction is "θ4". In the simulation, θ4 is set to 25°. The angle θf (=θ3+θ4) of the fiber reinforcing cord 64 is set to a value greater than θ4 (25°), and in the simulation, it is varied up to 170° as shown in Figure 5.

[0101] In Figure 5, when the angle θf of the fiber reinforcement cord 64 is less than 90°, it means that the fiber reinforcement cord 64 is inclined on the same side as the metal reinforcement cord 62 with respect to the carcass cord 60, and when the angle θf of the fiber reinforcement cord 64 is greater than 90°, it means that the fiber reinforcement cord 64 is inclined on the opposite side (different side) from the metal reinforcement cord 62 with respect to the carcass cord 60.

[0102] As shown in Figure 5, the strain at the end FE of the folded portion 42 is suppressed more effectively when the angle θf is less than 90° compared to when the angle θf exceeds 90°. In other words, from the viewpoint of more effectively suppressing the generation of PTL, it is preferable that the fiber reinforcement cord 64 is inclined to the same side as the metal reinforcement cord 62 with respect to the carcass cord 60. In this case, the angle θf of the fiber reinforcement cord 64 is preferably 45° or more, and more preferably 60° or more and 70° or less.

[0103] The inclination angle of the metal reinforcing cord 62 relative to the carcass cord 60 is the angle between the carcass cord 60 and the metal reinforcing cord 62. In other words, the inclination angle is the angle (inferior angle) between the carcass cord 60 and the metal reinforcing cord 62, and is defined as the first angle θ1. The inclination angle of the fiber reinforcing cord 64 relative to the carcass cord 60 is the angle between the carcass cord 60 and the fiber reinforcing cord 64. In other words, the inclination angle is the angle (inferior angle) between the carcass cord 60 and the fiber reinforcing cord 64, and is defined as the second angle θ2.

[0104] The angle between the metal reinforcing cord 62 and the fiber reinforcing cord 64, that is, the angle (inferior angle) between the metal reinforcing cord 62 and the fiber reinforcing cord 64, is defined as the third angle θ3. In this embodiment, the second angle θ2 formed by the carcass cord 60 and the fiber reinforcing cord 64 is smaller than the first angle θ1 formed by the carcass cord 60 and the metal reinforcing cord 62.

[0105] The smaller the angle between two chords, the wider the range in which one chord intersects with the other, and the greater the reinforcing effect of one chord on the other. In this embodiment, the second angle θ2 between the carcass cord 60 and the fiber reinforcing cord 64 is relatively small (smaller than θ1). Therefore, the reinforcing effect of the fiber reinforcing cord 64 on the carcass cord 60 is enhanced.

[0106] Preferably, the absolute value of the difference between the second angle θ2 formed by the carcass cord 60 and the fiber reinforcement cord 64 and the third angle θ3 formed by the fiber reinforcement cord 64 and the metal reinforcement cord 62 is 20° or less (|θ2-θ3|≦20°). More preferably, the absolute value of the difference between the second angle θ2 and the third angle θ3 is 15° or less (|θ2-θ3|≦15°). As described above, the second angle θ2 is relatively small, and in a configuration where the absolute value of the difference is 20° or less, the difference between the second angle θ2 and the third angle θ3 becomes small. In other words, the third angle θ3 also becomes relatively small. The reinforcing effect of the carcass cord 60 by the metal reinforcing cord 62 and the reinforcing effect of the metal reinforcing cord 62 by the fiber reinforcing cord 64 are enhanced.

[0107] The third angle θ3 is preferably 15° or greater (θ3 ≥ 15°). This configuration reduces the absolute value of the difference between the second angle θ2 and the third angle θ3. In other words, a configuration is obtained in which both the second angle θ2 and the third angle θ3 are small. For example, the first angle θ1 is 65°, the second angle θ2 is 30°, and the third angle θ3 is 35°.

[0108] The metal reinforcing cord 62 is inclined relative to the carcass cord 60, and the fiber reinforcing cord 64 is inclined relative to the carcass cord 60 on the same side as the metal reinforcing cord 62 (see Figure 4). The second angle θ2 between the carcass cord 60 and the fiber reinforcing cord 64 is smaller than the first angle θ1 between the carcass cord 60 and the metal reinforcing cord 62. The absolute value of the difference between the second angle θ2 and the third angle θ3 between the fiber reinforcing cord 64 and the metal reinforcing cord 62 is 20° or less. And the third angle θ3 is 15° or more. The fiber reinforcement layer 48 consists of a single fiber reinforcement ply 52, and the fiber reinforcement cords 64 of the fiber reinforcement layer 48 are inclined to the same side as the metal reinforcement cords 62, thereby suppressing strain concentration at the end FE of the folded portion 42 (see Figure 5). Furthermore, the second angle θ2 is smaller than the first angle θ1, that is, the second angle θ2 is relatively small. The absolute value of the difference between the second angle θ2 and the third angle θ3 is 20° or less, and since these differences are small, the third angle θ3 is also relatively small. In particular, a configuration is obtained in which the third angle θ3 is 15° or more, thereby reducing the aforementioned difference. Thus, a configuration is obtained in which both the second angle θ2 and the third angle θ3 are small. As described above, the smaller the angle between the two cords (the narrow angle), the wider the range in which one cord intersects the other cord, and the greater the reinforcing effect of one cord on the other cord. Therefore, according to the above configuration, the concentration of strain at the end FE of the folded portion 42 is suppressed, and the reinforcing effect of the carcass cord 60 by the fiber reinforcing cord 64, the reinforcing effect of the carcass cord 60 by the metal reinforcing cord 62, and the reinforcing effect of the metal reinforcing cord 62 by the fiber reinforcing cord 64 are enhanced. Since the deformation of the bead portion B is suppressed, even though the fiber reinforcing layer 48 is composed of a single fiber reinforcing ply 52, the occurrence of looseness and PTL caused by shear strain between the fiber reinforcing layer 48 and the chafer 8 is effectively suppressed. The tire 2 can achieve weight reduction while maintaining good durability.

[0109] As is clear from the above description, according to the present invention, a heavy-duty tire 2 can be obtained that achieves weight reduction while maintaining good durability. [Industrial applicability]

[0110] The technologies described above, which achieve weight reduction while maintaining good durability, can be applied to various types of tires.

[0111] [Note] The present invention includes the following embodiments.

[0112] [1] A tire comprising a pair of beads, a carcass spanning the pair of beads, a pair of sidewalls located axially outward of the carcass, a pair of chafers located radially inward of the sidewalls and in contact with the rim, and a pair of reinforcing layers located between the carcass and the chafers, wherein the bead comprises a core and an apex located radially outward of the core, the carcass comprises a carcass ply, the carcass ply comprising a ply body spanning the pair of beads and a ply body connected to the ply body and folded at the bead A heavy-duty tire comprising a pair of folded portions that are returned, wherein the reinforcing layer comprises a fiber-reinforcing layer located axially outward of the folded portions, the fiber-reinforcing layer consists of a single fiber-reinforcing ply comprising a number of parallel fiber-reinforcing cords, the fiber-reinforcing cords being organic fiber cords, the sidewall and the chafer being joined at a boundary spanning between the radially inner end of the sidewall and the radially outer end of the chafer, the chafer covering the radially inner end of the sidewall, and the sidewall being softer than the chafer. [2] The heavy-duty tire according to [1] above, wherein the line segment connecting the radial inner end of the sidewall and the radial outer end of the chafer is the boundary reference line segment, and the entire boundary is located axially inward of the boundary reference line segment. [3] The heavy-duty tire according to [1] or [2] above, wherein the core has a bottom surface positioned opposite to the rim seat, the axial outer end of the bottom surface is a reference point of the core, and the inner end of the sidewall is located radially outward from the reference point of the core. [4] The heavy-duty tire according to any one of [1] to [3] above, wherein the chafer has a recess on the contact surface with the rim, and the recess is located axially outward from the core. [5] The heavy-duty tire described in [4] above, wherein in the meridional cross-section of the tire, the shape of the recess is represented by an arc, and the radius of the arc is 20 mm or more and 30 mm or less. [6] The heavy-duty tire according to [4] or [5] above, wherein a straight line passing through the midpoint of the recess and extending in the axial direction is the recess reference line, and the radial inner end of the sidewall is included in the recess reference line or located radially outside the recess reference line. [7] The heavy-duty tire according to any of [1] to [6] above, wherein the radial outer end of the chafer is located radially inward of the end of the folded portion. [8] A heavy-duty tire according to any of the above [1] to [7], wherein the radial distance from the bead baseline to the radial outer end of the chafer is 18 mm or more. [9] A heavy-duty tire according to any of the above [1] to [8], wherein the loss tangent of the sidewall is lower than the loss tangent of the chafer. [Explanation of Symbols]

[0113] 2... Tires 4. Tread 6. Sidewall 8. Chafer 10...bead 12...Carcass 14. Belt 22. Reinforcement layer 24...Tread surface 28 cores 30...Apex 32...Inner apex 34...Outer apex 38...Carcass ply 40-ply main body 42...Folded section 46. ​​Metal reinforcement layer 48. Fiber reinforcement layer 50... Metal reinforced ply 52... Fiber-reinforced ply 54...boundary 56...Contact surface 58... recessed 60...carcass cord 62... Metal reinforcement cord 64... Fiber reinforced cord

Claims

1. A tire comprising a pair of beads, a carcass spanning the pair of beads, a pair of sidewalls located axially outward of the carcass, a pair of chafers located radially inward of the sidewalls and in contact with the rim, and a pair of reinforcing layers located between the carcass and the chafers, The bead comprises a core and an apex located radially outward from the core. The carcass comprises a carcass ply, The carcass ply comprises a ply body that spans between a pair of beads, and a pair of folded portions that are connected to the ply body and folded back by the beads. The reinforcing layer comprises a fiber reinforcing layer located on the axially outer side of the folded portion, The fiber-reinforced layer consists of a single fiber-reinforced ply containing a large number of parallel fiber-reinforced cords. The aforementioned fiber-reinforced cord is an organic fiber cord. The sidewall and the chafer are joined at the boundary spanning the radial inner end of the sidewall and the radial outer end of the chafer. The chafer covers the radial inner end of the sidewall, The sidewall is softer than the chafer. Heavy-duty tires.

2. The line segment connecting the radial inner end of the sidewall and the radial outer end of the chafer is the boundary reference line segment. The entire boundary is located axially inward of the boundary reference line segment. A heavy-duty tire according to claim 1.

3. The core has a bottom surface that is positioned opposite the rim's seat, The outer axial end of the bottom surface is the reference point of the core, The inner end of the sidewall is located radially outward from the reference point of the core. A heavy-duty tire according to claim 1.

4. The chafer has a recess on the contact surface with the rim, The recess is located axially outward from the core. A heavy-duty tire according to claim 1.

5. In the meridional cross-section of the tire, the shape of the recess is represented by an arc. The radius of the aforementioned arc is 20 mm or more and 30 mm or less. The heavy-duty tire according to claim 4.

6. A straight line passing through the midpoint of the recess and extending in the axial direction is the recess reference line. The radial inner end of the sidewall is included in the recess reference line, or is located radially outside the recess reference line. The heavy-duty tire according to claim 4.

7. The radial outer end of the chafer is located radially inward from the end of the folded portion. A heavy-duty tire according to claim 1.

8. The radial distance from the bead baseline to the radial outer end of the chafer is 18 mm or more. A heavy-duty tire according to claim 1.

9. The loss tangent of the sidewall is lower than the loss tangent of the chafer. A heavy-duty tire according to any one of claims 1 to 8.

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