Tire for heavy load

Abstract

To provide a tire for a heavy load, in which durability of a bead part can be enhanced.SOLUTION: A tire 2 for a heavy load comprises: a pair of beads 10; a carcass 12 having a folded-back part 52 hung between the pair of beads 10 and folded back from insides toward outsides in axial direction by the beads 10; a one-layered steel reinforcement layer 20 having a first outside part 201 positioned outside in the axial direction of the folded-back part 52; and a one-layered fiber reinforcement layer 26 having a second outside part 261 positioned outside in the axial direction of the first outside part 201. The carcass 12 has a plurality of carcass cords 49, and the steel reinforcement layer 20 has a plurality of steel cords 21. The fiber reinforcement layer 26 has a plurality of fiber cords 27. The steel cords 21 incline with respect to the carcass cords 49, and the fiber cords 27 incline to the same side as the steel cords 21 incline, with respect to the carcass cords 49.SELECTED DRAWING: Figure 7

Description

[Technical field]

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

[0002] Heavy-duty pneumatic tires mounted on heavy vehicles such as trucks and buses support a relatively large load. In order to prevent damage to the beads and improve their durability, multiple reinforcing layers are provided to reinforce the beads (see, for example, Patent Document 1). The tire disclosed in Patent Document 1 has a carcass folded up at the beads, one steel reinforcing layer, and two fiber reinforcing layers. The reinforcing layers distribute strain in the beads and improve durability. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-50717 Summary of the Invention [Problem to be solved by the invention]

[0004] The heavy-duty pneumatic tire disclosed in Patent Document 1 has two fiber reinforcement layers, and therefore, when a relatively large load is repeatedly applied to the tire, there is a possibility that the two fiber reinforcement layers may peel off. An object of the present invention is to provide a heavy duty tire that enables the durability of the bead portion to be increased. [Means for solving the problem]

[0005] The heavy-duty tire of the present invention has a pair of beads, a carcass having a folded-up portion that spans between the pair of beads and is folded back from the axially inner side to the axially outer side at each of the beads, a single steel reinforcing layer having a first outer portion located axially outward of the folded-up portion, and only a single fiber reinforcing layer having a second outer portion located axially outward of the first outer portion, wherein the carcass has a plurality of carcass cords, the steel reinforcing layer has a plurality of steel cords, and the fiber reinforcing layer has a plurality of fiber cords, the steel cords are inclined relative to the carcass cords, and the fiber cords are inclined to the same side as the steel cords relative to the carcass cords. Effect of the Invention

[0006] According to the heavy duty tire of the present invention, it is possible to suppress damage caused by peeling in the fiber reinforcing layer, which is a reinforcing layer, and to increase the durability of the bead portion. [Brief description 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. [Diagram 2] FIG. 2 is an enlarged view of a portion of the cross section shown in FIG. [Diagram 3] 11 is a graph showing the relationship between the position of the inner end of the fiber reinforcement layer and the deformation amount of a shoulder portion. [Figure 4] 11 is a graph showing the relationship between the position of the inner end of the fiber reinforcement layer and the deformation amount of the toe portion. [Diagram 5] 1 is a graph showing the relationship between the position of the outer end of the fiber reinforcement layer and the strain at the end of the turned-up portion of the carcass ply. [Figure 6] 1 is a graph showing the relationship between the position of the outer end of a fiber reinforced layer and the strain at the outer end of the fiber reinforced layer. [Figure 7] FIG. 2 is an explanatory diagram of a plurality of types of codes. [Figure 8] 1 is a graph showing the relationship between the angle of a fiber cord and the distortion at the end of a turned-up portion of a carcass ply. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] [Details of the embodiment of the present invention] The present invention will now be described based on preferred embodiments with reference to the drawings.

[0009] The heavy duty tire (hereinafter also simply referred to as "tire") of the present invention is mounted on a rim. Air is filled inside the tire, and the internal pressure of the tire is adjusted. The tire mounted on the rim is also called a tire-rim assembly. The tire-rim assembly has 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 in the meridian section that cannot be measured when the tire is mounted on a regular rim are measured on the tire section 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 is the same as the distance between the beads on the tire mounted on a regular rim. The tire configuration that cannot be confirmed when the tire is mounted on a regular rim is confirmed on the aforementioned section.

[0012] A genuine rim is a rim that is 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 genuine rims.

[0013] Normal tire pressure means the internal pressure specified in the standard on which the tire is based. 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 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 "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are normal loads.

[0015] The tire has a tread portion, a pair of bead portions, and a pair of sidewall portions. The tread portion 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, and the sidewall portion is the portion of the tire that connects between the tread and the bead.

[0016] 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 distortion = 10% Dynamic distortion = ±1% Frequency = 10Hz Mode = Decompression mode Temperature=70℃

[0017] For this measurement, a test piece (length 40 mm x width 4 mm x thickness 1 mm) is sampled from the tire. The length 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-like 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 represented as the complex modulus at 70°C.

[0018] [Details of the embodiment of the present invention] FIG. 1 shows a portion of a heavy-duty tire 2 (hereinafter, also simply referred to as "tire 2") according to one embodiment of the present invention. This tire 2 is mounted on a heavy vehicle such as a truck or a bus. The tire 2 shown in FIG. 1 is mounted on a rim R (regular rim). FIG. 1 mainly shows a cross section of a first axial side of the tire 2. In the cross section shown in FIG. 1, the omitted left side of the tire 2 (opposite the first axial side) is defined as the second axial side.

[0019] FIG. 1 shows a portion of a cross section (referred to as a "meridian cross section") of a tire 2 taken along a plane including the rotation axis of the tire 2. In FIG. 1, the left-right direction is the axial direction of the tire 2, and the up-down direction 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. The axial direction includes not only the direction along the rotation axis of the tire 2, but also the direction parallel to the rotation axis. In each drawing, the axial direction is indicated by an arrow "AD" and the radial direction is indicated by an arrow "RD". Fig. 2 is an enlarged view showing a part of the cross section shown in Fig. 1. Fig. 2 shows a bead portion of a tire 2. Note that in Fig. 2, the rim R is omitted.

[0020] 1, a dashed line CL extending in the radial direction represents the equatorial plane of the tire 2. A solid line BBL extending in the axial direction in Figures 1 and 2 is a bead base line. The bead base line is a line that defines the rim diameter of the rim R (see JATMA, etc.).

[0021] The tire 2 has 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 cushion layers 16, a strip layer 18, a pair of steel reinforcing layers 20, a pair of interlayer strips 22, an inner liner 24, and a pair of fiber reinforcing layers 26.

[0022] The tread 4 is located radially outward of the carcass 12. The tread 4 comes into contact with the road surface at a tread surface 30. Grooves 32 are formed in the tread 4. The tread 4 has a base portion 34 and a cap portion 36 located radially outward of the base portion 34. The base portion 34 is made of a cross-linked rubber with low heat generation. The cap portion 36 is made of a cross-linked rubber with consideration given to wear resistance and grip performance. The cap portion 36 includes the tread surface 30.

[0023] The position indicated by the symbol PC in Fig. 1 is the equator. The equator PC is the intersection point between the tread surface 30 and the equatorial plane. When the groove 32 is located on the equatorial plane, as in the tire 2 shown in Fig. 1, the equator PC is determined based on a virtual tread surface obtained assuming that the groove 32 does not exist. The radial distance from the bead base line BBL to the equator PC obtained in the tire 2 in a normal state is the section height of the tire 2 (see JATMA, etc.).

[0024] The sidewalls 6 are continuous with both ends of the tread 4. The sidewalls 6 are located radially inward of the tread 4. The sidewalls 6 are located axially outward of the carcass 12. The position indicated by the symbol PS is the inner end of the sidewall 6. The sidewall 6 is made of a crosslinked rubber having good cut resistance, and has a complex elastic modulus of 2.0 MPa or more and 6.0 MPa or less.

[0025] The position indicated by the symbol PW is the axial outer end of the tire 2 (hereinafter also referred to as the "outer end PW"). If there is a decoration such as a pattern or lettering on the outer surface, the outer end PW is identified based on a virtual outer surface obtained assuming that there is no decoration. The maximum width of the tire 2 is defined at the outer end PW. The outer end PW obtained for the tire 2 in a normal state is also called the maximum width position. The axial distance from the outer end PW on the first axial side to the outer end PW on the second axial side (not shown) obtained for the tire 2 in a normal state is the cross-sectional width of the tire 2 (see JATMA, etc.).

[0026] 1, the length indicated by the symbol H is the radial distance from the bead base line BBL 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 of 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.

[0027] The chafer 8 is located on the radially inner side of the sidewall 6. The chafer 8 contacts the rim R. The position indicated by the symbol PB is the radially outer end of the chafer 8. The chafer 8 is made of a crosslinked rubber in consideration of wear resistance. The complex elastic modulus of the chafer 8 is 10 MPa or more and 15 MPa or less. The chafer 8 is harder than the sidewall 6.

[0028] The bead 10 is located axially inward of the chafer 8. The bead 10 is located radially inward of the sidewall 6. The bead 10 has a core 38 and an apex 40. The core 38 extends in the circumferential direction. The core 38 includes wound steel wire. The core 38 has a generally hexagonal cross-sectional shape. The apex 40 is located radially outside the core 38 and extends radially outward from the core 38. The apex 40 tapers outward. An outer end PA of the apex 40 is located radially outside an outer end PB of the chafer 8.

[0029] The apex 40 has an inner apex 42 and an outer apex 44. The inner apex 42 is located radially outward of the core 38. The outer apex 44 is located radially outward of the inner apex 42.

[0030] The inner apex 42 is tapered radially outward. The inner apex 42 is made of a hard crosslinked rubber. The complex elastic modulus of the inner apex 42 is 60 MPa or more and 90 MPa or less.

[0031] The outer apex 44 is thick near the outer end PU of the inner apex 42. The outer apex 44 tapers radially inward from this thickened portion and then tapers radially outward. An inner end PG1 of the outer apex 44 is located near the core 38. An outer end PG2 of the outer apex 44 becomes the outer end PA of the apex 40.

[0032] The outer apex 44 is made of a crosslinked rubber. The outer apex 44 is softer than the inner apex 42. The complex elastic modulus of the outer apex 44 is equal to or greater than 3.0 MPa and equal to or less than 6.0 MPa.

[0033] The apex 40 further has an edge strip 46. The edge strip 46 is located axially outward of the outer apex 44 and constitutes a part of the outer surface of the apex 40. The edge strip 46 is located radially between the outer end PB of the chafer 8 and the inner end PG1 of the outer apex 44. The edge strip 46 is made of a crosslinked rubber. The edge strip 46 is softer than the chafer 8 and harder than the outer apex 44. The complex elastic modulus of the edge strip 46 is 7.0 MPa or more and 12 MPa or less.

[0034] 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 has a radial structure. The carcass 12 has at least one carcass ply 48. The carcass 12 shown in Figures 1 and 2 is made of one carcass ply 48. The carcass ply 48 is turned up at the bead 10.

[0035] The carcass ply 48 (see FIG. 2 ) has a ply body 50 and a pair of turn-up portions 52. The ply body 50 bridges between a pair of beads 10, i.e., between the bead 10 on a first axial side and the bead 10 on a second axial side (not shown). Each turn-up portion 52 is connected to the ply body 50 and turned up at the bead 10. The turn-up portion 52 is turned up at the bead 10 from the inside toward the outside in the axial direction. An end PF of the turn-up portion 52 is located radially inward of the outer end PB of the chafer 8. The bead 10 is sandwiched between the ply body 50 and the turn-up portion 52.

[0036] FIG. 7 is an explanatory diagram of a plurality of cords. For ease of explanation, FIG. 7 shows only three representative cords of each type. A carcass ply 48 (carcass 12) has a plurality of carcass cords 49 arranged in parallel. These carcass cords 49 are covered with a topping rubber. Each carcass cord 49 intersects with the equatorial plane. The material of the carcass cords 49 is steel. A steel cord is used as the carcass cord 49.

[0037] 1 and 2, the dimension indicated by the symbol h3 is the radial distance from the bead base line BBL to the end PF of the turned-up portion 52. The radial distance h3 is also called the radial height of the end PF of the turned-up portion 52. The ratio (h3 / H) of the radial height (h3) of the end PF of the folded-back portion 52 to the radial height H of the maximum width position PW is equal to or greater than 0.25 and is equal to or less than 0.45.

[0038] 1 has four belt plies 54. The belt 14 has a first belt ply 54A, a second belt ply 54B, a third belt ply 54C, and a fourth belt ply 54D. These belt plies 54 are arranged in the radial direction. In the case of the tire 2 shown in FIG. 1, the second belt ply 54B has the widest width, and the fourth belt ply 54D has the narrowest width.

[0039] Although not shown, each belt ply 54 includes a number of belt cords arranged in parallel. Each belt cord is inclined with respect to the equatorial plane. The belt cord is made of steel. Steel cords are used as the belt cords.

[0040] The cushioning layer 16 is located between the belt 14 and the carcass 12 at the end of the belt 14. The cushioning layer 16 is made of a soft crosslinked rubber.

[0041] The strip layer 18 is located between the carcass 12 and the belt 14 on the radially inner side of the tread 4. The strip layer 18 is located between the cushion layer 16 on the first side in the axial direction and the cushion layer 16 (not shown) on the second side in the axial direction. The strip layer 18 is made of crosslinked rubber.

[0042] The steel reinforcing layer 20 is located between the bead 10 and the chafer 8. The steel reinforcing layer 20 is located between the carcass 12 and the fiber reinforcement layer 26. The steel reinforcing layer 20 has a shape folded back at the bead 10. That is, as shown in Fig. 2, the steel reinforcing layer 20 has a first outer portion 201 located axially outward of the folded back portion 52 of the carcass 12, and a portion extending from the first outer portion 201 to surround a radially inner portion of the bead 10. More specifically, the steel reinforcing layer 20 has a first outer portion 201, a first inner portion 202 located axially inside the ply body 50 of the carcass 12, and a first curved portion 203 connecting the first outer portion 201 and the first inner portion 202. An inner end 20s and an outer end 20f of the steel reinforcing layer 20 are each located between the end PF of the turned-up portion 52 and the core 38 in the radial direction.

[0043] In the case of the embodiment shown in FIG. 2, the end PF of the folded-back portion 52 is located higher than the outer end 20 f of the steel reinforcing layer 20 . Conversely, although not shown, the outer end 20f of the steel reinforcing layer 20 may be located higher than the end PF of the folded-back portion 52.

[0044] In either case, as will be explained later, the outer end PR1, which is the axially outer end of the fiber reinforcement layer 26, is located higher than the outer end 20f of the steel reinforcement layer 20 and the end PF of the folded-back portion 52. When the outer end 20f of the steel reinforcement layer 20 is located higher than the end PF of the folded-back portion 52, the outer end PR1 of the fiber reinforcement layer 26 is located 5 mm or more higher than the outer end 20f. This allows the fiber reinforcement layer 26 to cover the steel reinforcement layer 20, increasing the durability of the bead portion.

[0045] The steel reinforcing layer 20 includes a plurality of first filler cords arranged in parallel. The material of the first filler cords is steel. That is, the steel reinforcing layer 20 has a plurality of steel cords 21 (see FIG. 7). In the steel reinforcing layer 20, the steel cords 21 are covered with a topping rubber. Only one steel reinforcing layer 20 having a plurality of parallel steel cords 21 is provided on a first axial side of the tire 2 (see FIG. 2). Although not shown, only one steel reinforcing layer having a plurality of parallel steel cords is provided on a second axial side of the tire 2.

[0046] 2, the outer end 20f of the steel reinforcement layer 20 is located between the turned-up portion 52 and the fiber reinforcement layer 26 in the axial direction. The outer end 20f is located radially inside the end PF of the turned-up portion 52. The inner end 20s is located between the inner liner 24 and the ply body 50 in the axial direction. The radial position of the inner end 20s may be approximately the same as the radial position of the outer end 20f, but the inner end 20s may be located radially outside or inside the outer end 20f.

[0047] The interlayer strip 22 is located between the fiber reinforcement layer 26 and the apex 40 in the axial direction. The interlayer strip 22 covers the end PF of the turned-up portion 52 and the outer end 20f of the steel reinforcement layer 20. The interlayer strip 22 contacts the apex 40 on the radially outer side of the end PF of the turned-up portion 52. The interlayer strip 22 contacts the fiber reinforcement layer 26 on the radially outer side of the outer end 20f of the steel reinforcement layer 20. The interlayer strip 22 is made of a crosslinked rubber. The interlayer strip 22 is harder than the sidewall 6 and softer than the chafer 8. The complex elastic modulus of the interlayer strip 22 is 7.0 MPa or more and 12 MPa or less.

[0048] The inner liner 24 is positioned inside the carcass 12. The inner liner 24 is joined to the inner surface of the carcass 12 via an insulation (not shown) made of crosslinked rubber. The inner liner 24 constitutes the inner surface of the tire 2. The inner liner 24 is made of crosslinked rubber with excellent air barrier properties.

[0049] The fiber reinforcement layer 26 is located between the steel reinforcement layer 20 and the chafer 8. The fiber reinforcement layer 26 has a shape that is folded back at the bead 10 for a small dimension from the axially outer side toward the axially inner side. That is, the fiber reinforcement layer 26 has a second outer portion 261 that is located axially outer of the first outer portion 201 of the steel reinforcement layer 20, and a portion that extends from the second outer portion 261 and surrounds a radially inner portion of the bead 10. More specifically, the fiber reinforcement layer 26 has a second outer portion 261 and a second curved portion 262. The second curved portion 262 is located circumferentially and axially inward of the first curved portion 203 of the steel reinforcement layer 20. The second curved portion 262 is connected to the second outer portion 261.

[0050] An inner end PR2, which is an axially inner end of the fiber reinforcement layer 26, is located axially inside of the ply body 50, between the inner liner 24 and the steel reinforcement layer 20. The inner end PR2 of the fiber reinforcement layer 26 is located radially inside of the inner end 20s of the steel reinforcement layer 20. The inner end PR2 of the fiber reinforcement layer 26 is located radially inside of the inner end PG1 of the outer apex 44.

[0051] The fiber reinforcement layer 26 includes a plurality of second filler cords arranged in parallel. The material of the second filler cords is fiber, particularly organic fiber. That is, the fiber reinforcement layer 26 has a plurality of fiber cords 27 (see FIG. 7). The organic fiber is preferably nylon fiber. In the fiber reinforcement layer 26, the fiber cords 27 are covered with a topping rubber. Only one fiber reinforcement layer 26 having a plurality of parallel fiber cords 27 is provided on a first axial side of the tire 2 (see FIG. 2). Although not shown, only one fiber reinforcement layer having a plurality of parallel fiber cords is provided on a second axial side of the tire 2.

[0052] Fig. 3 is a graph (simulation result) showing the relationship between the position of the inner end PR2 of the fiber reinforced layer 26 and the deformation (amount of movement) of the shoulder portion 19s (see Fig. 1). Fig. 4 is a graph (simulation result) showing the relationship between the position of the inner end PR2 of the fiber reinforced layer 26 and the deformation (amount of lift) of the toe portion 19t (see Fig. 1). A to E shown on the horizontal axis in Figs. 3 and 4 indicate positions around the bead 10 in Fig. 2. In order to reduce the amount of displacement in the shoulder portion 19s and the toe portion 19t, as shown in Figures 3 and 4, the position of the inner end PR2 of the fiber reinforcement layer 26 is preferably between A and C, and more preferably close to B.

[0053] As shown in FIG. 2, the inner end PR2 of the fiber reinforcement layer 26 is preferably located radially inward of a first line S1 defined below and radially outward of a second line S2 defined below. First line S1: An imaginary straight line that passes through the axially innermost position 381 (position B) of the core 38 and is parallel to the bead baseline BBL. Second line S2: An imaginary straight line that passes through the radially innermost position 382 (position C) of the core 38 and is parallel to the bead baseline BBL.

[0054] With this configuration, the second curved portion 262 of the fiber reinforcement layer 26 is present radially inward of the core 38. According to the fiber reinforcement layer 26 having the second curved portion 262, when the carcass ply 48 (ply body 50) is subjected to tension in the radially outward direction, the fiber reinforcement layer 26 is able to resist the tension, improving the durability of the bead portion. Furthermore, the presence of the fiber reinforcement layer 26 (the second curved portion 262) on the radially inner side of the core 38 stabilizes the bead portion when the tire 2 is fitted onto the rim R, improving the uniformity performance.

[0055] The second outer portion 261, which is the axially outer portion of the fiber reinforcement layer 26, is located axially between the steel reinforcement layer 20 and the interlayer strip 22, and the chafer 8. The second outer portion 261 contacts the chafer 8. The contact surface between the second outer portion 261 and the chafer 8 constitutes a part of the outer surface of the fiber reinforcement layer 26 (or the inner surface of the chafer 8).

[0056] An outer end PR1 of the fiber reinforced layer 26 is located radially outward of an inner end PR2 thereof. The outer end PR1 of the fiber reinforced layer 26 is located radially between an end PF of the folded-back portion 52 and an outer end PA of the apex 40 (see FIG. 1). An outer end PR1 of the fiber reinforcement layer 26 is located radially inward of an outer end PB of the chafer 8 in the radial direction.

[0057] The outer end PR1 of the fiber reinforcement layer 26 is preferably located radially outward of a third line S3 defined below and a fourth line S4 defined below. Third line S3: An imaginary straight line that passes through the radially outermost position (end PF) of the folded-back portion 52 of the carcass 12 and is parallel to the bead baseline BBL. Fourth line S4: an imaginary straight line that passes through the radially outermost position (outer end 20f) of the steel reinforcing layer 20 and is parallel to the bead baseline BBL

[0058] Fig. 5 is a graph showing the relationship between the position of the outer end PR1 of the fiber reinforcement layer 26 and the strain at the end PF of the turned-up portion 52 of the carcass ply 48. Fig. 6 is a graph showing the relationship between the position of the outer end PR1 of the fiber reinforcement layer 26 and the strain at the outer end PR1 of the fiber reinforcement layer 26. The data shown in these graphs are calculated by a simulation using the Finite Element Method (FEM). The simulation model is based on the configuration shown in Fig. 2, and is a tire with only one steel reinforcing layer 20 and one fiber reinforcing layer 26, in the normal state. The tire size is 295 / 80R22.5.

[0059] The vertical axis of the graph shown in FIG. 5 represents the strain at the end PF of the carcass ply 48, and the horizontal axis represents the distance h2 in the radial direction from the bead base line BBL to the outer end PR1 of the fiber reinforced layer 26. The vertical axis of the graph shown in FIG. 6 represents the strain at the outer end PR1 of the fiber reinforced layer 26, and the horizontal axis represents the distance h2 in the radial direction from the bead base line BBL to the outer end PR1 of the fiber reinforced layer 26.

[0060] A radial distance h3 from the bead base line BBL to the end PF of the turn-up portion 52 is 42 mm in each case. As shown in FIG. 5, the distance h2 is preferably 45 mm or greater. As shown in FIG. 6, the distance h2 is preferably equal to or less than 65 mm. From the above, when the distance h3 is 42 mm, it is preferable to set the distance h2 to be equal to or greater than 45 mm and equal to or less than 65 mm.

[0061] From these results, it is preferable that the dimension h1 between the end PF of the folded-back portion 52 and the outer end PR1 of the fiber reinforced layer 26 is 3 mm or more and 23 mm or less, and more preferably 5 mm or more and 15 mm or less. With this configuration, it is possible to suppress the concentration of stress at the end PF of the folded-back portion 52 and the outer end PR1 of the fiber reinforced layer 26, respectively, and to suppress the increase in distortion.

[0062] As described above, the inner end PR2 of the fiber reinforced layer 26 is located radially inward from the first line S1 and radially outward from the second line S2, and the outer end PR1 of the fiber reinforced layer 26 is located radially outward from the third line S3 and the fourth line S4. With this configuration, although there is only one fiber reinforcement layer 26, it wraps around the bead 10 inward in the axial direction and further extends radially outward beyond the third line S3 and the fourth line S4 on the axially outer side of the bead 10. As a result, the single fiber reinforcement layer 26 contributes to improving the rigidity of the bead portion.

[0063] [About the placement of multiple types of codes] Fig. 7 is an explanatory diagram of the multiple types of cords, namely, carcass cords 49, fiber cords 27, and steel cords 21. Fig. 7 is an image diagram of the various cords as viewed from the axial outside toward the bead portion including the bead 10, and is also a diagram of the various cords developed on a plane. The carcass cord 49 passing the axial outside of the bead portion is provided along the radial direction. The direction perpendicular to the direction in which the carcass cord 49 extends (the left-right direction in Fig. 7) is the "circumferential direction (the tangential direction to the circumferential direction)".

[0064] As shown in Fig. 7, the steel cords 21 are inclined with respect to the carcass cords 49. In the case of Fig. 7, the direction in which the steel cords 21 are inclined with respect to the carcass cords 49 is the clockwise direction. The fiber cords 27 are inclined to the same side as the steel cords 21 with respect to the carcass cords 49. That is, in the case of Fig. 7, the direction in which the fiber cords 27 are inclined with respect to the carcass cords 49 is the clockwise direction.

[0065] Fig. 8 is a graph showing the relationship between the angle of the fiber cord 27 and the strain at the end PF of the turned-up portion 52 of the carcass ply 48. Data showing this relationship is calculated by a simulation using the finite element method (FEM). The simulation model is based on the configuration shown in Fig. 2, and is a tire having only one steel reinforcing layer 20 and only one fiber reinforcing layer 26, in the normal state. The tire size is 295 / 80R22.5. The angle of the fiber cord 27 (θn in FIG. 7) shown on the horizontal axis of the graph in FIG. 8 is a value based on the circumferential direction.

[0066] As shown in Fig. 7, the angle (minor angle) of the steel cord 21 when the circumferential direction is used as a reference is "θ4". In the simulation, θ4 is set to 25°. The angle θn (=θ3+θ4) of the fiber cord 27 is set to a value larger than θ4 (25°), and is changed up to 170° in the simulation, as shown in Fig. 8.

[0067] 8, when the angle θn of the fiber cord 27 is less than 90°, the fiber cord 27 is inclined to the same side as the steel cord 21 with respect to the carcass cord 49. When the angle θn of the fiber cord 27 exceeds 90°, the fiber cord 27 is inclined to the opposite side (different side) to the steel cord 21 with respect to the carcass cord 49.

[0068] Although there is only one fiber reinforcement layer 26, the fiber cords 27 of the fiber reinforcement layer 26 are inclined to the same side as the steel cords 21. Therefore, distortion at the end PF of the carcass ply 48 is suppressed, as shown in Fig. 8. According to Fig. 8, the angle θn of the fiber cord 27 is preferably 45° or more, and more preferably 60° or more and 70° or less.

[0069] As described above, since the fiber reinforcement layer 26 that serves as the reinforcing layer of the bead 10 is only one layer, it is possible to prevent damage due to peeling in the fiber reinforcement layer 26. Moreover, as is clear from the result shown in Fig. 8, the fiber cord 27 is configured to incline on the same side as the steel cord 21 with respect to the carcass cord 49, thereby suppressing distortion at the end (end PF) of the folded-back portion 52 of the carcass 12, and making it possible to increase the rigidity of the bead portion having the bead 10.

[0070] [About the angles of various cords] The inclination angle of the steel cord 21 with respect to the carcass cord 49 is an included angle between the carcass cord 49 and the steel cord 21. In other words, the inclination angle is an angle (minor angle) formed between the carcass cord 49 and the steel cord 21, and this angle is defined as a "first angle θ1." The inclination angle of the fiber cord 27 with respect to the carcass cord 49 is an included angle between the carcass cord 49 and the fiber cord 27. In other words, the inclination angle is an angle (minor angle) formed between the carcass cord 49 and the fiber cord 27, and this angle is defined as a "second angle θ2."

[0071] The included angle between the steel cord 21 and the fiber cord 27, that is, the angle (minor angle) between the steel cord 21 and the fiber cord 27 is defined as a "third angle θ3". In this embodiment, the second angle θ2 between the carcass cords 49 and the fiber cords 27 is smaller than the first angle θ1 between the carcass cords 49 and the steel cords 21.

[0072] Here, the smaller the angle (included angle) between the two cords, the wider the area over which one cord crosses the other cord, and the greater the reinforcing effect of one cord on the other cord. In the present embodiment, the second angle θ2 between the carcass cord 49 and the fiber cord 27 is relatively small (compared to θ1), and the reinforcing effect of the carcass cord 49 by the fiber cord 27 is enhanced.

[0073] The absolute value of the difference between the second angle θ2 between the carcass cords 49 and the fiber cords 27 and the third angle θ3 between the fiber cords 27 and the steel cords 21 is preferably 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 the absolute value of the difference is 20° or less, so that the difference between the second angle θ2 and the third angle θ3 is small. That is, the third angle θ3 is also relatively small. The reinforcing effect of the steel cords 21 on the carcass cords 49 and the reinforcing effect of the fiber cords 57 on the steel cords 21 are enhanced.

[0074] The third angle θ3 is preferably 15° or more (θ3≧15°). This configuration reduces the absolute value of the difference between the second angle θ2 and the third angle θ3. In other words, the second angle θ2 is small, and the third angle θ3 is also small. As an example of the angles, the first angle θ1 is 65°, the second angle θ2 is 30°, and the third angle θ3 is 35°.

[0075] As described above, the steel cords 21 are inclined with respect to the carcass cords 49, and the fiber cords 27 are inclined with respect to the carcass cords 49 on the same side as the steel cords 21 (see FIG. 7). The second angle θ2 between the carcass cords 49 and the fiber cords 27 is smaller than the first angle θ1 between the carcass cords 49 and the steel cords 21. The absolute value of the difference between the second angle θ2 and the third angle θ3 between the fiber cords 27 and the steel cords 21 is 20° or less. And, the third angle θ3 is 15° or more. Although the fiber reinforcement layer 26 is only one layer, the fiber cords 27 of the fiber reinforcement layer 26 are inclined to the same side as the steel cords 21, so that distortion at the end PF of the carcass ply 48 is suppressed (see FIG. 8). 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 the difference is small, the third angle θ3 is also relatively small. In particular, by setting the third angle θ3 to 15° or more, a configuration is obtained in which the difference is small. From the above, a configuration is obtained in which the second angle θ2 is small and the third angle θ3 is also small. As described above, the smaller the angle (included angle) between the two cords, the wider the range in which one cord crosses the other cord, and the stronger the reinforcing effect of one cord on the other cord. Therefore, according to the above configuration, distortion at the end PF of the carcass ply 48 is suppressed, and the reinforcing effect of the fiber cords 27 on the carcass cords 49, the reinforcing effect of the steel cords 21 on the carcass cords 49, and the reinforcing effect of the fiber cords 57 on the steel cords 21 are enhanced.

[0076] [Regarding flange fit of the bead part of the rim] As described above (see FIG. 1), the tire 2 is mounted on the rim R (regular rim). The chafer 8 in contact with the rim R is located axially outside the fiber reinforcement layer 26. The chafer 8 has a recess 70 in contact with a part of the rim R (flange). The recess 70 has a concave curved shape in a meridian cross section (see FIG. 2). The recess 70 is composed of a recessed groove that is provided continuously in the circumferential direction.

[0077] As described above, the fiber reinforcement layer 26 (second outer portion 261) is only one layer, and compared to a case where there are two layers, the portion including the chafer 8 has a higher ability to conform to a part of the rim R (flange) when elastically deformed. The flange fit of the rim R by the recess 70 is improved compared to a case where there are two fiber reinforcement layers. The recessed portion 70 can reduce stress caused by deformation of the bead portion when the tire 2 runs on a road surface. The recessed portion 70 is in close contact with a part of the rim R (flange), thereby enhancing the effect of reducing the stress.

[0078] In a meridian cross section of the tire 2, the recess 70 has a shape along a single circular arc on the bottom side of the recess 70. The recess 70 has a cross-sectional circular arc shape, and the radius of curvature r of the arc is 20 mm or more and 30 mm or less. The radius of curvature r being 30 mm or less can have a function of suppressing collapse of the carcass 12 when an internal pressure load is applied. The radius of curvature r being 20 mm or more makes it difficult for stress concentration to occur in the recess 70.

[0079] The following describes the thickness T between the second outer portion 261 of the fiber reinforcement layer 26 and the axially outer side surface 8f of the chafer 8, which is the bead outer side surface, in the region of the chafer 8 where the recess 70 is formed. Note that the thickness T is a thickness dimension along the normal direction of the fiber reinforcement layer 26 (its axially outer surface) in the meridian cross section of the tire 2 shown in FIG.

[0080] The chafer 8 has a position 8p where the thickness T is a maximum thickness Tmax and a position 8q where the thickness T is a minimum thickness Tmin. The difference between the maximum thickness Tmax and the minimum thickness Tmin is preferably 2 mm or more. Also, the difference is preferably 7 mm or less.

[0081] If the difference is 2 mm or more, when a load acts on the bead portion and the bead portion deforms, the fit with the flange of the rim R is improved, and as a result, the stress on the bead portion is alleviated. In order to prevent the occurrence of cracks due to deterioration of the bead portion, the minimum thickness Tmin is preferably 2 mm or more, and more preferably 7 mm or less.

[0082] As shown in Fig. 2, the outer end PR1 of the fiber reinforcement layer 26 is located radially inward of the radially outer end PD of the interlayer strip 22. The outer end PR1 of the fiber reinforcement layer 26 is located radially inward of the radially outer end PE of the edge strip 46. Even if the outer end PR1 of only one fiber reinforcement layer 26 is located radially inward as described above, the chafer 8 has the recess 70, which makes it possible to reduce the stress generated by the deformation of the bead portion. In other words, the recess 70 allows the outer end PR1 of the fiber reinforcement layer 26 to be located radially inward, making it possible to shorten the fiber reinforcement layer 26, which leads to weight reduction.

[0083] As is clear from the above description, according to the present invention, a heavy duty tire 2 capable of enhancing the durability of the bead portion can be obtained. [Industrial Applicability]

[0084] The above-described technology that enables the durability of the bead portion to be increased can be applied to various tires.

[0085] [Additional Notes] The present invention includes the following aspects. (1) A heavy-duty tire has a pair of beads, a carcass spanning the pair of beads and having a folded-up portion folded back from the axially inner side to the axially outer side at each of the beads, a single steel reinforcing layer having a first outer portion located axially outward of the folded-up portion, and only a single fiber reinforcing layer having a second outer portion located axially outward of the first outer portion, wherein the carcass has a plurality of carcass cords, the steel reinforcing layer has a plurality of steel cords, and the fiber reinforcing layer has a plurality of fiber cords, the steel cords are inclined relative to the carcass cords, and the fiber cords are inclined to the same side as the steel cords relative to the carcass cords.

[0086] (2) The heavy-duty tire according to (1) above, wherein an angle between the carcass cord and the fiber cord is smaller than an angle between the carcass cord and the steel cord.

[0087] (3) The heavy-duty tire according to (2) above, wherein an absolute value of a difference between an angle formed between the carcass cord and the fiber cord and an angle formed between the fiber cord and the steel cord is 20° or less.

[0088] (4) The heavy-duty tire according to (3) above, wherein the angle between the fiber cord and the steel cord is 15° or more.

[0089] (5) A heavy-duty tire according to any one of (1) to (4), further comprising a chafer located axially outward of the fiber reinforcement layer and in contact with the rim, the chafer having a recess in contact with a portion of the rim. (6) The heavy duty tire according to (5) above, wherein the recess has an arcuate cross section with a radius of curvature of 20 mm or more and 30 mm or less.

[0090] (7) The heavy-duty tire according to any one of (1) to (6), wherein the bead has a core, an axially inner end of the fiber reinforcement layer is located radially inner than a first line defined below and radially outer than a second line defined below, and an axially outer end of the fiber reinforcement layer is located radially outer than a third line defined below and a fourth line defined below. First line: An imaginary straight line that passes through the innermost axial position of the core and is parallel to the bead baseline. Second line: an imaginary straight line that passes through the innermost position in the radial direction of the core and is parallel to the bead baseline Third line: a virtual straight line that passes through the radially outermost position of the folded portion and is parallel to the bead baseline. Fourth line: an imaginary straight line that passes through the radially outermost position of the steel reinforcing layer and is parallel to the bead baseline [Explanation of symbols]

[0091] 2. Heavy duty tires 8. Chafer 10 Bead 12. Carcass 20...Steel reinforcement layer 20f...Outer end (the outermost position in the radial direction of the steel reinforcing layer) 201... First outer part 21 Steel cord 26...Fiber reinforcement layer 261...Second outer part 27 Textile cord 38 Core 381...Innermost axial position of core 382...Innermost radial position of core 49 Carcass cord 52... Folded part 57 Textile cord 70...Concave PR1...Outer end (axially outer end of the fiber reinforcement layer) PR2... Inner end (axially inner end of the fiber reinforcement layer) PF··· end (the outermost radial position of the folded part) R...Rim S1...First line S2: Second line S3: Third line S4...Fourth line θ1: First angle (angle between the carcass cord and the steel cord) θ2: Second angle (angle between the carcass cord and the fiber cord) θ3: Third angle (angle between fiber cord and steel cord)

Claims

1. A pair of beads; a carcass having a folded-up portion that spans between a pair of the beads and is folded up from an inner side toward an outer side in the axial direction at each of the beads; a steel reinforcing layer having a first outer portion located axially outward of the folded portion; Only one fiber reinforced layer having a second outer portion located axially outside the first outer portion; having The carcass has a plurality of carcass cords, The steel reinforcing layer includes a plurality of steel cords, The fiber reinforcement layer has a plurality of fiber cords, The steel cord is inclined with respect to the carcass cord, The fiber cord is inclined to the same side as the steel cord with respect to the carcass cord. Heavy duty tires.

2. an angle between the carcass cord and the fiber cord is smaller than an angle between the carcass cord and the steel cord; 2. A heavy duty tire according to claim 1.

3. an absolute value of a difference between an angle formed between the carcass cord and the fiber cord and an angle formed between the fiber cord and the steel cord is 20° or less; 3. A heavy duty tire according to claim 2.

4. The angle between the fiber cord and the steel cord is 15° or more.

4. A heavy duty tire according to claim 3.

5. a chafer located axially outward of the fiber reinforcement layer and in contact with the rim; the chafer has a recess that contacts a portion of the rim; 3. A heavy duty tire according to claim 1 or 2.

6. The recess has a cross-sectional arc shape with a radius of curvature of 20 mm or more and 30 mm or less.

6. A heavy duty tire according to claim 5.

7. The bead has a core, The axially inner end of the fiber reinforcement layer is located radially inner than a first line defined below and radially outer than a second line defined below, The axially outer end of the fiber reinforcement layer is located radially outward from a third line defined below and a fourth line defined below.

3. A heavy duty tire according to claim 1 or 2. First line: a virtual straight line passing through the innermost position of the core in the axial direction and parallel to the bead baseline Second line: an imaginary straight line that passes through the innermost position in the radial direction of the core and is parallel to the bead baseline Third line: a virtual straight line that passes through the radially outermost position of the folded portion and is parallel to the bead baseline Fourth line: an imaginary straight line that passes through the radially outermost position of the steel reinforcing layer and is parallel to the bead baseline

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