JP2021115877A - Heavy-load tubeless tire - Google Patents

Abstract

To provide a heavy-load tubeless tire 12 preventing occurrence of peeling of a chafer 36 at tire production or of a toe lack at rim assembly.SOLUTION: In a heavy-load tubeless tire 12, the inner end PA of a chafer 36 is located at a zone from the intersection a of the axial reference line La of a core 44 with a bead base face 72 to the intersection b of the reference line Lb of a bead part B with a bead inner side face 76. The end PC of an inner liner 32 is located at the zone from a toe PT to the above intersection b. Besides, an insulation 34 is located between the inner end PA of the chafer 36 and the end PC of the inner liner 32. A ratio of an axial direction distance BW from a heel PH to the axial reference line La of the core 44 to the axial direction distance BB from the heel PH to the toe PT is 80% or more and 90% or less.SELECTED DRAWING: Figure 2

Description

The present invention relates to a heavy load tubeless tire.

In heavy-duty tubeless tires mounted on vehicles such as trucks and buses, a chafer made of hard rubber is used for the portion in contact with the rim. For the inner liner, rubber having a low permeability coefficient of a gas such as air is used. Since the inner liner is inferior in adhesiveness, it is joined to the inner surface of the carcass via an insulation having excellent adhesiveness.

FIG. 4 shows the bead portion B of the conventional heavy-duty tubeless tire 2. In the tire 2, the inner liner 4 is arranged so as to overlap the core 6 in the axial direction, for example, in order to prevent the core 6 from rusting due to moisture permeation. In order to protect the inner liner 4, the chafer 8 is arranged inside the inner liner 4 in the axial direction in the toe PT portion of the tire 2. In this tire 2, the toe PT portion is composed of a hard chafer 8.

When assembling the tire 2 to the rim, one bead portion B is fitted into the rim, and then the other bead portion B is fitted into the rim. At this time, the toe PT portion of the bead portion B is strongly pressed against the flange of the rim. The part of the toe PT including the hard chafer 8 is hard. In the tire 2, there is a concern that the force acting on the toe PT portion causes the toe PT portion to be chipped, rather than the toe PT portion being deformed by this force. In order to prevent the occurrence of this toe chipping, the configuration of the toe PT portion has been studied (for example, Patent Document 1 below).

Japanese Unexamined Patent Publication No. 2007-45375

In the manufacture of the tire 2, the bladder is peeled off from the tire 2 when the completed tire 2 is taken out from the mold. In the tire 2 shown in FIG. 4, the chafer 8 forming the inner surface of the bead portion B comes into contact with the bladder. Since the bladder is in close contact with the chafer 8, when the bladder is peeled off from the tire 2, a force acts on the tire 2 so as to peel the chafer 8 from the inner liner 4. Since the inner liner 4 is inferior in adhesiveness, the chafer 8 may be peeled off from the inner liner 4 when the tire 2 is taken out from the mold.

In the tubeless tire disclosed in Patent Document 1 described above, a soft chafer comes into contact with the bladder. When removing the tire from the mold, the bladder may come into close contact with the soft chafer and the soft chafer may come off the inner liner.

The present invention has been made in view of such an actual situation, and an object of the present invention is to provide a heavy-duty tubeless tire in which peeling of a chafer during manufacturing and chipping of a toe during rim assembly are suppressed. ..

The heavy-duty tubeless tire according to the present invention includes a pair of bead portions fitted to the rim. The outer surface of each bead portion is connected to the bead base surface mounted on the seat of the rim and the heel which is the outer end of the bead base surface, and is in contact with the flange of the rim. It has an inner surface of the bead that connects to the toe, which is the inner end. The bead portion comprises a core including a wire extending in the circumferential direction and an apex located on the radial outer side of the core, and a bead and a carcass folded from the inner side to the outer side in the axial direction around the core. A carcass having a ply, an inner liner forming the inner surface of the bead, an insulation located between the inner liner and the carcass, and a chafer forming the bead base surface and the outer surface of the bead. Be prepared. A straight line extending in the axial direction through the heel is a reference line of the bead portion. The cross section of the core includes a cross section of the plurality of wires, and among the plurality of wire cross sections, the wire cross section located inside in the axial direction is the reference cross section, and passes through the axial inner end of the reference cross section in the radial direction. The extending straight line is the axial reference line of the core. The inner end of the chafer is located in a zone of the outer surface of the bead portion from the intersection of the axial reference line of the core and the bead base surface to the intersection of the reference line of the bead portion and the inner surface of the bead. do. The end of the inner liner is located on the outer surface of the bead portion in a zone from the toe to the intersection of the reference line of the bead portion and the inner surface of the bead. The insulation is located between the inner end of the chafer and the end of the inner liner. The ratio of the axial distance from the heel to the axial reference line of the core with respect to the axial distance from the heel to the toe is 80% or more and 90% or less.

Preferably, in this heavy-duty tubeless tire, the inner end of the chafer is located in the zone from the intersection of the axial reference line of the core and the bead base surface to the toe on the outer surface of the bead portion.

Preferably, in this heavy duty tubeless tire, the chafer is stiffer than the inner liner and the insulation.

Preferably, in this heavy load tubeless tire, the complex elastic modulus of the chafer is 12 MPa or more.

Preferably, in this heavy load tubeless tire, the nominal aspect ratio is 70% or less.

In the heavy-duty tubeless tire of the present invention, peeling of the chafer during manufacturing and chipping of the toe during rim assembly can be suppressed.

FIG. 1 is a cross-sectional view showing a part of a heavy-duty tubeless tire according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view showing a bead portion of the tire of FIG. FIG. 3 is an enlarged cross-sectional view showing the shape of the bead portion where toe chipping may occur. FIG. 4 is an enlarged cross-sectional view showing a bead portion of a conventional heavy-duty tubeless tire.

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

In the present invention, the state in which the tire is incorporated in the normal rim, the internal pressure of the tire is adjusted to the normal internal pressure, and no load is applied to the tire is referred to as a normal state. In the present invention, unless otherwise specified, the dimensions and angles of each part of the tire are measured in a normal state.

Regular rims are rims defined in the standards on which the tire relies. The "standard rim" in the JATTA standard, the "Design Rim" in the TRA standard, and the "Measuring Rim" in the ETRTO standard are regular rims.

Regular internal pressure means the internal pressure defined in the standard on which the tire relies. The "maximum air pressure" in the JATTA standard, the "maximum value" in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are normal internal pressures.

Normal load means the load specified in the standard on which the tire relies. The "maximum load capacity" in the JATMA standard, the "maximum value" in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are normal loads.

FIG. 1 shows a part of a heavy-duty tubeless tire 12 (hereinafter, may be simply referred to as “tire 12”) according to an embodiment of the present invention. The tire 12 is mounted on a heavy-duty vehicle such as a truck or a bus. The tire 12 is a tire for trucks and buses.

FIG. 1 shows a part of a cross section of the tire 12 along a plane including a rotation axis of the tire 12. In FIG. 1, the left-right direction is the axial direction of the tire 12, and the vertical direction is the radial direction of the tire 12. The direction perpendicular to the paper surface of FIG. 1 is the circumferential direction of the tire 12. In FIG. 1, the alternate long and short dash line CL represents the equatorial plane of the tire 12. In FIG. 1, the tire 12 is incorporated in the rim R (regular rim).

In FIG. 1, the solid line BBL extending in the axial direction is the bead baseline. This bead baseline is a line that defines the rim diameter (see JATTA, etc.) of the rim R (regular rim). Reference numeral PB is the intersection of the bead baseline and the contact surface of the rim R with the tire 2.

The tire 12 includes a tread 14, a pair of sidewalls 16, a pair of beads 18, a carcass 20, a belt 22, a cushion layer 24, a pair of reinforcing layers 26, a pair of interlayer strips 28, a pair of edge strips 30, and an inner liner 32. , Insulation 34 and a pair of chafers 36.

The tread 14 comes into contact with the road surface on its outer surface 38 (ie, the tread surface 38). Although not shown, the tread 14 includes a base portion and a cap portion located radially outward of the base portion. The base is made of low heat-generating crosslinked rubber. The cap portion is made of crosslinked rubber in consideration of wear resistance and grip performance.

The tread 14 is engraved with a groove 40 (that is, a circumferential groove 40) that extends continuously in the circumferential direction. As a result, the tread 14 is configured with a plurality of land portions 42 arranged in parallel in the axial direction. The tread 14 has a plurality of land portions 42 partitioned by a circumferential groove 40.

Each sidewall 16 runs along the edge of the tread 14. The sidewall 16 extends radially inward from the end of the tread 14. The sidewall 16 is made of crosslinked rubber.

Each bead 18 is located radially inside the sidewall 16. The bead 18 includes a core 44, a cover 46, and an apex 48.

The core 44 extends in the circumferential direction. The core 44 includes a steel wire 50 extending in the circumferential direction. The core 44 is configured by winding the wire 50 around. The cross-sectional shape of the core 44 is a hexagon. The cross-sectional shape may be quadrangular.

In FIG. 1, reference numeral θ is an angle formed by the bottom surface of the core 6 with respect to the axial direction. In the tire 12, this angle θ is 15 ° or more and 25 ° or less. This angle θ is measured on the tire 12 in the normal state.

The cover 46 surrounds the core 44. The cover 46 surrounds the core 44 and bundles the spirally wound wires 50. The cover 46 prevents the bundle of wound wires 50 from being loosened.

The apex 48 is located radially outward of the core 44. Apex 48 is tapered outward in the radial direction.

The apex 48 includes an inner apex 48u and an outer apex 48s. The outer apex 48s is located outside the inner apex 48u in the radial direction. The inner apex 48u and the outer apex 48s are made of crosslinked rubber. The outer apex 48s is softer than the inner apex 48u.

The carcass 20 is located inside the tread 14, sidewall 16 and chafer 36. The carcass 20 bridges between one bead 18 and the other bead 18. The carcass 20 has a radial structure.

The carcass 20 includes at least one carcass ply 52. The carcass 20 of the tire 12 is composed of one carcass ply 52. The carcass ply 52 has a ply body 54 that bridges one core 44 and the other core 44, and a pair of folds that are connected to the ply body 54 and are folded back from the inside to the outside in the axial direction around each core 44. It has a part 56.

Although not shown, the carcass ply 52 contains a large number of parallel cords. These cords are covered with topping rubber. The material of the cord is steel.

The belt 22 is located radially inside the tread 14. The belt 22 is located on the outer side in the radial direction of the carcass 20.

The belt 22 is composed of a plurality of layers 58 laminated in the radial direction. In the tire 12, the belt 22 is composed of three layers 58. In the tire 12, the number of layers 58 constituting the belt 22 is not particularly limited. The configuration of the belt 22 is appropriately determined in consideration of the specifications of the tire 12.

Although not shown, each layer 58 contains a large number of parallel cords. These cords are covered with topping rubber. Each cord slopes with respect to the equatorial plane. The material of the cord is steel.

Each cushion layer 24 is located at the end of the belt 22 between the belt 22 and the carcass 20. The cushion layer 24 is made of crosslinked rubber.

Each reinforcing layer 26 is located at a portion of the bead 18. The reinforcing layer 26 is folded back along the carcass 20 from the inside in the axial direction to the outside around the core 44 inside the carcass 20. The reinforcing layer 26 is connected to a bottom piece 60 located radially inside the core 44, an inner piece 62 connected to one end of the bottom piece 60 and extending substantially outward in the radial direction, and connected to the other end of the bottom piece 60 in the radial direction. It includes an outer piece 64 extending outward. In the axial direction, the inner piece 62 is located inside the ply body 54, and the outer piece 64 is located outside the folded-back portion 56.

Although not shown, the reinforcing layer 26 contains a large number of cords in parallel. These cords are covered with topping rubber. The material of the cord is steel. This reinforcing layer is also called a steel filler.

Each interlayer strip 28 is located between the outer apex 48s of the bead 18 and the chafer 36. The interlayer strip 28 covers the end of the folded-back portion 56 and the outer end of the reinforcing layer 26. The interlayer strip 28 is made of crosslinked rubber.

Each edge strip 30 is located between the outer apex 48s of the bead 18 and the interlayer strip 28. The end of the folded-back portion 56 comes into contact with the edge strip 30. As shown in FIG. 1, the end of the folded-back portion 56 is sandwiched between the edge strip 30 and the interlayer strip 28. The edge strip 30 is made of crosslinked rubber. The edge strip 30 is made of the same material as the interlayer strip 28.

The inner liner 32 is located inside the carcass 20. The inner liner 32 constitutes the inner surface of the tire 12. The inner liner 32 is made of a crosslinked rubber containing butyl rubber or halogenated butyl rubber as a base rubber. The permeability coefficient of gas such as air of this crosslinked rubber is low. The inner liner 32 has excellent air shielding properties. The inner liner 32 holds the internal pressure of the tire 12.

The insulation 34 is located between the inner liner 32 and the carcass 20. The insulation 34 is made of a crosslinked rubber having excellent adhesiveness. The insulation 34 joins the inner liner 32 to the carcass 20.

Each chafer 36 is located axially outward of the bead 18. The chafer 36 is located radially inside the sidewall 16. The chafer 36 comes into contact with the seat S and the flange F of the rim R. The chafer 36 is made of crosslinked rubber in consideration of wear resistance. The chafer 36 is harder than the inner liner 32 and the insulation 34.

In the tire 12, the portion located on the outer side in the radial direction and in contact with the road surface is the tread portion T. The portion fitted to the rim R is the bead portion B. The portion between the tread portion T and the bead portion B is the side portion W. The tire 12 is located between a tread portion T in contact with the road surface, a pair of bead portions B each fitted to the rim R, and a tread portion T and a bead portion B, respectively, in the radial direction. It is provided with a pair of side portions W.

In the tire 12, the tread portion T includes a tread 14, a carcass 20, a belt 22, a cushion layer 24, an inner liner 32, and an insulation 34. The side portion W includes a sidewall 16, a carcass 20, a cushion layer 24, an inner liner 32, and an insulation 34. The bead portion B includes a sidewall 16, a bead 18, a carcass 20, a reinforcing layer 26, an interlayer strip 28, an edge strip 30, an inner liner 32, an insulation 34, and a chafer 36.

The tire 12 is manufactured as follows. In a molding machine (not shown), elements such as a tread 14 are combined to prepare an unvulcanized tire 12 (hereinafter, also referred to as a raw tire). Raw tires are pressurized and heated in a vulcanizer (not shown). The raw tire is put into the mold of the vulcanizer. A bladder located inside the mold is filled with a heating medium (eg, steam). The bladder expands and the raw tire is pressed against the cavity surface of the mold by the expanded bladder. As a result, the raw tire is pressurized and heated in the mold to obtain the tire 12.

FIG. 2 shows the bead portion B of the tire 12 shown in FIG. In FIG. 2, the left-right direction is the axial direction of the tire 12, and the vertical direction is the radial direction of the tire 12. The direction perpendicular to the paper surface of FIG. 2 is the circumferential direction of the tire 12.

As described above, the core 44 of the bead 18 included in the bead portion B is formed by winding the wire 50. As shown in FIG. 2, the cross section 66 of the core 44 includes a cross section 68 of the plurality of wires 50. The cross section 66 of the core 44 has a configuration in which a plurality of cross-sectional rows including cross sections 68 of a plurality of wires 50 arranged in the axial direction are laminated in the radial direction.

In the tire 12, of the cross sections 68 of the plurality of wires 50 included in the cross section 66 of the core 44, the cross section 68 of the wire 50 located inside in the axial direction is the reference cross section 68b. When there are a plurality of cross sections 68 of the wire 50 located inside in the axial direction, the reference cross section 68b is specified in the cross section having the largest number of cross sections 68 of the wire 50 included in the cross section.

In FIG. 2, reference numeral La is a straight line extending in the radial direction through the inner end in the axial direction of the reference cross section 68b. In the tire 12, this straight line La is the axial reference line of the core 44. Reference numeral Lr is a straight line extending in the axial direction through the radial inner end of the reference cross section 68b. In the tire 12, this straight line Lr is the radial reference line of the core 44.

The outer surface 70 of the bead portion B includes a bead base surface 72, a bead outer surface 74, and a bead inner surface 76. The bead base surface 72 and the bead outer surface 74 are shaped by the cavity surface of the mold. The bead inner surface 76 is shaped by the outer surface of the bladder.

The bead base surface 72 forms a radial inner surface of the bead portion B. The bead base surface 72 is placed on the seat S of the rim R. In FIG. 2, reference numeral PH is the outer end of the bead base surface 72. The outer edge PH of the bead base surface 72 is also referred to as a heel. This heel PH is a position on the outer surface 70 of the bead portion B corresponding to the intersection PB of the bead baseline and the contact surface of the rim R with the tire 12 described above. Reference numeral PT is an inner end of the bead base surface 72. The inner end PT of the bead base surface 72 is also referred to as a toe PT. This toe PT corresponds to the boundary between the mold and the bladder in the cavity formed by the mold and the bladder.

In FIG. 2, reference numeral Lb is a straight line extending in the axial direction through the heel PH. In the tire 12, this straight line Lb is the reference line of the bead portion B. As shown in FIG. 2, the reference line Lb of the bead portion B is located inside the core 44 in the radial direction. Reference numeral a symbol a is an intersection of the axial reference line La of the core 44 and the bead base surface 72. In FIG. 2, the axis of the tire 12 is based on a straight line connecting the left and right heel PHs in a state where the distance from one heel PH to the other heel PH matches the rim width, that is, the reference line Lb of the bead portion B. The direction is specified.

The bead outer surface 74 is a part of the side surface of the tire 12. The bead outer surface 74 is connected to the heel PH which is the outer end of the bead base surface 72. The bead outer surface 74 comes into contact with the flange F of the rim R.

The bead inner surface 76 is a part of the inner surface of the tire 12. The bead inner surface 76 is connected to the toe PT, which is the inner end of the bead base surface 72. In FIG. 2, reference numeral r is an intersection of the radial reference line Lr of the core 44 and the inner side surface 76 of the bead. Reference numeral b is an intersection of the reference line Lb of the bead portion B and the inner side surface 76 of the bead. The intersection b is located inside the intersection r in the radial direction.

In this tire 12, the chafer 36 forms a bead base surface 72 and a bead outer surface 74. The inner liner 32 forms the inner side surface 76 of the bead. In FIG. 2, reference numeral PA is the inner end of the chafer 36. Reference numeral PC is the end of the inner liner 32. As shown in FIG. 2, the inner end PA of the chafer 36 and the end PC of the inner liner 32 are located on the outer surface 70 of the bead portion B.

In this tire 12, the inner end PA of the chafer 36 is the reference line Lb and the bead of the bead portion B from the intersection a of the axial reference line La of the core 44 and the bead base surface 72 of the outer surface 70 of the bead portion B. It is located in the zone up to the intersection b with the inner surface 76. The end PC of the inner liner 32 is located in the zone from the toe PT to the intersection b on the outer surface 70 of the bead portion B. Then, the insulation 34 is located between the chafer 36 and the inner liner 32. When the inner end PA of the chafer 36 is located in the zone from the toe PT to the intersection b, the inner end PA of the chafer 36 is located inside the end PC of the inner liner 32 in the radial direction.

In the tire 12, the chafer 36 and the inner liner 32 are joined via an insulation 34 having excellent adhesiveness. The inner liner 32, which is inferior in adhesiveness, constitutes the bead inner surface 76 with which the bladder comes into contact during manufacturing. In this tire 12, the chafer 36 and the inner liner 32 are not directly joined, and the bladder is easily peeled off from the inner side surface 76 of the bead. In this tire 12, not only the peeling of the chafer 36 at the time of manufacturing, which was a concern in the conventional tire 2, but also the peeling of the inner liner 32 can be suppressed. With this tire 12, the occurrence of defects during manufacturing can be suppressed. The tire 12 can contribute to the improvement of productivity.

In the tire 12, the end PC of the inner liner 32 is located inside the reference line Lb of the bead portion B in the radial direction. The inner liner 32 effectively suppresses the infiltration of oxygen and moisture contained in the internal space of the tire 12 into the bead portion B. In this tire 12, for example, rusting of the wire 50 constituting the core 44 and oxidative deterioration of the carcass ply 52 located around the core 44 can be suppressed. Good durability is maintained in the tire 12.

When the tire 12 is assembled to the rim R, one bead portion B is fitted to the rim R, and then the other bead portion B is fitted to the rim R. At this time, the toe PT portion of the bead portion B is strongly pressed against the flange F of the rim R. The zone up to, more specifically, the zone from this intersection r to the intersection b of the reference line Lb of the bead portion B and the inner side surface 76 of the bead comes into contact with the flange F first.

As shown in FIG. 2, in this tire 12, the chafer 36 is not arranged in the zone from the intersection r to the intersection b. An inner liner 32 and an insulation 34, which are softer than the chafer 36, are arranged in this zone. When the tire 12 is incorporated into the rim R, the bead portion B is deformed in this zone, so that the force with which the flange F of the rim R presses the toe PT portion is reduced. With this tire 12, the occurrence of toe chipping at the time of rim R assembly is suppressed.

In FIG. 2, the double-headed arrow BB is the axial distance from the heel PH to the toe PT. The double-headed arrow BW is the axial distance from the heel PH to the axial reference line La of the core 44.

In this tire 12, the ratio (BW / BB) of the axial distance BW from the heel PH to the axial reference line La of the core 44 to the axial distance BB from the heel PH to the toe PT is 80% or more and 90% or less. be.

Since the ratio (BW / BB) is 80% or more, the toe PT portion does not have a sharp shape (also referred to as a smash bead) as shown in FIG. 3 (a), but is shown in FIG. As shown, the shape of the toe PT portion is adjusted so that the angle formed by the bead inner surface 76 with respect to the bead base surface 72 is an obtuse angle. In this tire 12, the volume of the toe PT portion is reduced. Since the interference between the toe PT portion and the flange F is suppressed, the occurrence of toe chipping at the time of rim assembly is suppressed in this tire 12. From this point of view, this ratio (BW / BB) is preferably 83% or more.

Since the ratio (BW / BB) is 90% or less, a sufficient contact area between the bead portion B and the sheet S of the rim R is secured. Since the inner end PA of the chafer 36 is located inside the axial reference line La of the core 44 in the axial direction, the rigidity of the bead portion B is appropriately maintained in this tire 12. In this tire 12, the influence of the volume reduction on the bead 18 tightening force and durability is suppressed. Moreover, in this tire 12, since the occurrence of protrusion at the toe PT portion as shown in FIG. 3B is prevented, the occurrence of toe chipping at the time of rim assembly due to this protrusion can be suppressed. ..

In this tire 12, peeling of the chafer 36 at the time of manufacturing and occurrence of toe chipping at the time of rim assembly are suppressed. With this tire 12, improvements in productivity and rim assembly are achieved. In particular, in this tire 12, improvement in productivity and rim assembly is achieved while suppressing the influence on the bead tightening force and durability.

As shown in FIG. 2, in this tire 12, the inner end PA of the chafer 36 is toeed from the intersection a of the axial reference line La of the core 44 and the bead base surface 72 of the outer surface 70 of the bead portion B. Located in the zone up to PT. In this tire 12, the rigidity of the bead portion is appropriately secured while suppressing the influence of the chafer 36 on the rigidity of the toe PT portion. In this tire 12, the occurrence of toe chipping at the time of rim assembly is suppressed while suppressing the influence on the bead tightening force and durability. From this point of view, the inner end PA of the chafer 36 is located in the zone from the intersection a of the axial reference line La of the core 44 and the bead base surface 72 to the toe PT in the outer surface 70 of the bead portion B. preferable.

As shown in FIG. 2, in the axial direction, the toe PT is located inside the intersection r of the radial reference line Lr of the core 44 and the inner side surface 76 of the bead. In the tire 12, the shape of the toe PT portion is adjusted so that the angle formed by the bead inner surface 76 with respect to the bead base surface 72 is an obtuse angle, and the volume of the toe PT portion is reduced. Since the interference between the toe PT portion and the flange F is suppressed, the occurrence of toe chipping at the time of rim assembly is suppressed in this tire 12. From this viewpoint, it is preferable that the toe PT is located inside the intersection r of the radial reference line Lr of the core 44 and the inner side surface 76 of the bead in the axial direction.

In FIG. 2, the double-headed arrow BR is the axial distance from the heel PH to the intersection r of the radial reference line Lr of the core 44 and the inner side surface 76 of the bead. In the tire 12, the ratio (BW / BR) of the axial distance BW from the heel PH to the axial reference line La of the core 44 with respect to the axial distance BR is preferably 65% or more and 75% or less.

In this tire 12, the complex elastic modulus of the chafer 36 is preferably 12 MPa or more. As a result, the chafer 36 contributes to ensuring the bead tightening force and durability. From the viewpoint of appropriately maintaining the rigidity of the bead portion B, the complex elastic modulus of the chafer 36 is preferably 20 MPa or less.

In this tire 12, the complex elastic modulus E ^* of an element such as the chafer 36 is measured under the following conditions using a viscoelastic spectrometer in accordance with the provisions of JIS K6394. In this measurement, a test piece obtained by pressurizing and heating the rubber composition of each element is used.
Initial distortion = 10%
Amplitude = ± 1%
Frequency = 10Hz
Deformation mode = tensile measurement temperature = 70 ° C

In the tire 12, the inner liner 32, which is softer than the chafer 36, contributes to suppressing the occurrence of toe chipping during rim assembly. From this viewpoint, the ratio of the complex elastic modulus of the inner liner 32 to the complex elastic modulus of the chafer 36 is preferably 60% or less. From the viewpoint of ensuring the rigidity of the inner liner 32, this ratio is preferably 20% or more.

In the tire 12, the insulation 34, which is softer than the chafer 36, contributes to suppressing the occurrence of toe chipping during rim assembly. From this viewpoint, the ratio of the complex elastic modulus of the insulation 34 to the complex elastic modulus of the chafer 36 is preferably 60% or less. From the viewpoint of ensuring the rigidity of the insulation 34, this ratio is preferably 35% or more.

As is clear from the above description, in the heavy-duty tubeless tire 12 of the present invention, peeling of the chafer 36 during manufacturing and occurrence of toe chipping during rim assembly can be suppressed. According to the present invention, it is possible to obtain a heavy-duty tubeless tire 12 in which productivity and rim assembly are improved while suppressing the influence on the bead tightening force and durability. In particular, the present invention exerts a more remarkable effect on the heavy-duty tubeless tire 12 having a nominal aspect ratio of 70% or less. This "nominal of flatness ratio" is a "nominal of flatness ratio" included in the "nominal tire" specified in JIS D4202 "Automobile tires-nominal terms and specifications".

Hereinafter, the present invention will be described in more detail with reference to Examples and the like, but the present invention is not limited to such Examples.

[Example 1]
A heavy-duty tubeless tire (tire size = 245 / 70R19.5) having the basic configuration shown in FIG. 1-2 and having the specifications shown in Table 1 below was obtained.

In this Example 1, the ratio (BW / BB) of the axial distance BW from the heel PH to the axial reference line La of the core to the axial distance BB from the heel PH to the toe PT was 86%. The inner end PA of the chafer was arranged in the zone from the intersection a of the axial reference line La of the core and the bead base surface to the toe PT on the outer surface of the bead portion B. This is represented by "a to PT" in the "PA position" column of the table. The end PC of the inner liner was arranged in the zone from the toe PT to the intersection b of the reference line Lb of the bead portion B and the inner surface of the bead on the outer surface of the bead portion B. This is represented by "PT to b" in the "PC position" column of the table. An insulation was placed between the inner end PA of the chafer and the end PC of the inner liner. The fact that the chafer and the inner liner were not overlapped is indicated by "N" in the "overlap" column of the table.

[Example 2-3 and Comparative Example 1-2]
The tires of Example 2-3 and Comparative Example 1-2 were obtained in the same manner as in Example 1 except that the axial distance BB was changed and the ratio (BW / BB) was set as shown in Table 1 below. ..

[Example 4 and Comparative Example 3]
The tires of Example 4 and Comparative Example 3 were obtained in the same manner as in Example 1 except that the position of the inner end PA of the chafer was changed. In Example 4, the inner end PA of the chafer was arranged in the zone from the toe PT to the intersection b on the outer surface of the bead portion B. In Comparative Example 3, the inner end PA of the chafer was arranged in the zone from the heel PH to the intersection a on the outer surface of the bead portion B. This is represented by "PH to a" in the "PA position" column of the table.

[Comparative Example 4-5]
The tires of Comparative Example 4-5 were obtained in the same manner as in Example 1 except that the position of the inner end PA of the chafer was changed and the chafer and the inner liner were overlapped. In Comparative Example 4, the inner end PA of the chafer was arranged in the zone from the toe PT to the intersection b on the outer surface of the bead portion B. In Comparative Example 5, the inner end PA of the chafer was arranged in the zone from the intersection b to the intersection r between the radial reference line Lr of the core and the inner surface of the bead on the outer surface of the bead portion B. This is represented by "br" in the "PA position" column of the table. The fact that the chafer and the inner liner are overlapped is indicated by "Y" in the "overlap" column of the table.

[Generation of defective products]
50 prototype tires were manufactured. By observing the appearance of the prototype tire, the number of tires in which defects such as peeling of the chafer or inner liner and protrusion of the toe portion (see FIG. 3B) were confirmed was counted. The results are shown in the "Defective" column of Tables 1 and 2 below. "P" in the "content" column of Tables 1 and 2 represents the case where peeling of the chafer or the inner liner is confirmed, and "S" represents the case where the protrusion of the toe portion is confirmed. Since the smash bead shown in FIG. 3A is not a defect, the tire in which the smash bead is confirmed is treated as a normally manufactured prototype tire.

[Rim assembly]
We confirmed the occurrence of toe chipping when incorporating the prototype tire into the rim (size = 19.5 x 7.5) using a tire changer. Three prototype tires were evaluated, and the number of prototype tires that could be incorporated into the rim without the occurrence of toe chipping is shown in Tables 1 and 2 below as an index of rim assembly.

[durability]
The prototype tire was incorporated into a rim (size = 19.5 x 7.5) and filled with air to adjust the internal pressure of the tire to the normal internal pressure. This tire was mounted on a drum tester, a load of 200% of the normal load was applied, and the tire was run on a drum (drum diameter = 1707 mm) at a speed of 20 km / h. The running time until the bead part was damaged was measured. This result is an index with the traveling time of Comparative Example 3 as 100, and is shown in Tables 1 and 2 below. The larger the value, the longer the running time and the better the bead durability.

As shown in Tables 1 and 2, in the examples, it is confirmed that the occurrence of peeling of the chafer during manufacturing and chipping of the toe during rim assembly is suppressed while maintaining good durability. The examples are highly evaluated as compared with the comparative examples. From this evaluation result, the superiority of the present invention is clear. In Comparative Example 1, the occurrence of smash beads was confirmed. Peeling of the chafer or inner liner of Comparative Examples 4 and 5 was confirmed in the overlap between the chafer and the inner liner.

The technique described above for suppressing the peeling of the chafer during manufacturing and the occurrence of toe chipping during rim assembly can be applied to various tires.

2, 12 ... Tire 4, 32 ... Inner liner 6, 44 ... Core 8, 36 ... Chafer 18 ... Bead 26 ... Reinforcing layer 34 ... Insulation 50 ...・ Wire 52 ・ ・ ・ Carcass ply 66 ・ ・ ・ Cross section of core 44 68 ・ ・ ・ Cross section of wire 50 68b ・ ・ ・ Reference cross section 70 ・ ・ ・ Outer surface of bead part B 72 ・ ・ ・ Bead base surface 74 ・ ・ ・Bead outer surface 76 ・ ・ ・ Bead inner surface

Claims (5)

With a pair of beads that fit onto the rim
The outer surface of each bead part
The bead base surface that can be placed on the rim sheet and
A bead outer surface that is connected to the heel, which is the outer end of the bead base surface, and is in contact with the flange of the rim.
It is provided with an inner surface of the bead connected to the toe, which is the inner end of the bead base surface.
The bead part
A bead comprising a core containing a wire extending in the circumferential direction and an apex located radially outward of the core.
A carcass with a carcass ply that folds around the core from the inside to the outside in the axial direction.
The inner liner that forms the inner surface of the bead and
The insulation located between the inner liner and the carcass,
A chafer forming the bead base surface and the bead outer surface is provided.
The straight line extending in the axial direction through the heel is the reference line of the bead portion.
The cross section of the core includes a plurality of cross sections of the wires, and among the plurality of wire cross sections, the wire cross section located inside in the axial direction is the reference cross section, and passes through the axial inner end of the reference cross section in the radial direction. The extending straight line is the axial reference line of the core.
The inner end of the chafer is located in the zone from the intersection of the axial reference line of the core and the bead base surface to the intersection of the reference line of the bead portion and the inner surface of the bead on the outer surface of the bead portion. death,
The end of the inner liner is located on the outer surface of the bead portion in a zone from the toe to the intersection of the reference line of the bead portion and the inner surface of the bead.
The insulation is located between the inner edge of the chafer and the edge of the inner liner.
A heavy-duty tubeless tire in which the ratio of the axial distance from the heel to the axial reference line of the core is 80% or more and 90% or less with respect to the axial distance from the heel to the toe. The tubeless tire for heavy load according to claim 1, wherein the inner end of the chafer is located in a zone from the intersection of the axial reference line of the core and the bead base surface to the toe on the outer surface of the bead portion. .. The heavy-duty tubeless tire according to claim 1 or 2, wherein the chafer is harder than the inner liner and the insulation. The heavy-duty tubeless tire according to any one of claims 1 to 3, wherein the chafer has a complex elastic modulus of 12 MPa or more. The heavy-duty tubeless tire according to any one of claims 1 to 4, wherein the flatness ratio is 70% or less.

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