JP7225669B2 - Heavy duty pneumatic tire - Google Patents

Description

The present invention relates to heavy duty pneumatic tires.

FIG. 3 shows the portion of the bead 4 (hereinafter also referred to as bead portion B) of the conventional heavy-duty pneumatic tire 2 . This bead portion B is fitted to a rim R (regular rim).

In this tire 2, the carcass ply 6 is folded back around the bead 4 from the inner side to the outer side in the axial direction. The carcass ply 6 includes a ply body 8 and a folded portion 10. - 特許庁

In this tire 2 , the bead 4 has a core 12 and an apex 14 . In this tire 2 , the apex 14 includes a first apex 16 and a second apex 18 softer than the first apex 16 . As shown in FIG. 3, the outer end 16a of the first apex 16 is located radially outside the end 10a of the folded portion 10. As shown in FIG.

This tire 2 is provided with a filler 20 in order to secure the rigidity of the bead portion B. As shown in FIG. Although not shown, this filler 20 is composed of a large number of parallel steel cords and a topping rubber.

The filler 20 is positioned between the folded portion 10 and the chafer 22 . As shown in FIG. 3, the inner end 20a of the filler 20 is positioned inside the core 12 of the bead 4 in the radial direction. Outer end 20b of filler 20 is located inside end 10a of folded portion 10 . This filler 20 does not have a structure folded around the bead 4 like a conventional filler (hereinafter also referred to as normal filler). This filler 20 is also called a short filler.

This tire 2 is mounted on a vehicle such as a truck or a bus. Since a large load acts on the bead portion B of the tire 2, it is important to improve the durability of the bead portion B, that is, the bead durability. In heavy-duty pneumatic tires, it has been studied to improve the bead durability by adjusting the configuration of the bead portion B to control the rigidity (for example, Patent Document 1 below).

JP 2015-157524 A

For example, the rigidity of the bead portion B is increased by increasing the number of turns of the wire 24 in the core 12 configured by winding the wire 24, increasing the volume of the apex 14 located radially outside the core 12, or the like. If it is improved, the bead durability can be improved. However, in this case, there is a concern that the mass of the tire 2 will increase and heat generation accompanying movement of the bead portion B, that is, energy loss will increase. Increased energy loss increases rolling resistance. An increase in rolling resistance of the tire 2 affects fuel efficiency of the vehicle.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a heavy-duty pneumatic tire that achieves improved bead durability and reduced rolling resistance while achieving weight reduction. aim.

A preferred heavy-duty pneumatic tire according to the present invention includes a pair of beads, a ply body spanning between one bead and the other bead, and a ply body connected to the ply body and extending from the axially inner side to the outer side around the bead. a carcass ply having a turn-up portion that is turned back into itself; and a pair of fillers that are positioned axially outside the turn-up portion and that include metal cords. The bead includes a core, a first apex surrounding the core, and a second apex radially outward of the first apex. The circumference of the first apex has a rounded contour. The first apex is stiffer than the second apex. A depression is provided in the zone between the maximum width position and the edge of the turn-up portion of the tire side surface.

Preferably, in this heavy-duty pneumatic tire, when the position on the side surface corresponding to the outer edge of the contact surface between the side surface of the tire and the flange of the rim to which the tire is fitted is defined as the flange contact end, In the radial direction, the outer end of the first apex is positioned inside the end of the folded portion and outside the flange contact end.

Preferably, in this heavy duty pneumatic tire, the radial distance from the radial inner end of the core to the outer end of the first apex is 15 mm or more and 45 mm or less.

Preferably, in this heavy duty pneumatic tire, the distance from the axial inner end of the core to the carcass ply is 1 mm or more.

Preferably, in this heavy-duty pneumatic tire, the minimum thickness from the ply body to the recess is measured along a line segment indicating the minimum thickness, obtained from the ply body without the recess. The ratio to the virtual thickness to the virtual side is 0.3 or more and 0.7 or less.

Preferably, in this heavy duty pneumatic tire, the radial distance from the end of the folded portion to the inner end of the recess is 10 mm or more and 20 mm or less.

Preferably, in this heavy duty pneumatic tire, the recess includes a bottom portion and an outer boundary portion positioned radially outward of the bottom portion. The profile of the outer boundary portion is represented by an outwardly convex arc, and the arc has a radius of 40 mm or more.

Preferably, in this heavy duty pneumatic tire, the recess includes a bottom portion and an inner boundary portion positioned radially inward of the bottom portion. The profile of the inner boundary portion is represented by an outwardly convex arc, and the arc has a radius of 40 mm or more.

Preferably, in this heavy duty pneumatic tire, the bottom profile is represented by an inwardly convex circular arc, or the bottom profile is represented by a straight line.

Preferably, in this heavy-duty pneumatic tire, the first end of the filler is located inside the bead baseline in the radial direction, and the second end of the filler is located between the end of the folded portion and the bead baseline. located between

In the heavy-duty pneumatic tire of the present invention, depressions are provided in the zone between the maximum width position and the end of the folded portion on the side surface. This recess contributes to a reduction in mass and suppresses movement of the rubber in the portion radially outside the end of the folded portion. Since the movement of the turn-up portion is suppressed, damage such as ply turn-up loose is less likely to occur with this tire. This suppression of movement also suppresses the heat generated due to deformation.

Further, in this tire, the core is surrounded by a rigid first apex having a rounded outer periphery. Since the collapse of the bead portion due to the action of the load is suppressed, this tire has good bead durability.

In this tire, the radial height of the first apex is low. In this tire, a sufficient area that can contribute to bending can be secured in the side portion, and the contour of the ply body extending along the apex can be easily set. In this tire, since protrusion of the side surface in the axial direction outward is suppressed, the amount of strain acting on the dent is reduced. In this tire, damage such as cracks in dents is less likely to occur. In this tire, the above-described effects of the dents are fully exhibited. Moreover, since the first apex is configured with a small volume, the influence of this first apex on rolling resistance is effectively suppressed.

In this tire, improvement in bead durability and reduction in rolling resistance are achieved while reducing weight. According to the present invention, it is possible to obtain a heavy-duty pneumatic tire that achieves improved bead durability and reduced rolling resistance while achieving weight reduction.

FIG. 1 is a cross-sectional view showing a portion of a heavy-duty pneumatic tire according to one embodiment of the present invention. 2 is a partial cross-sectional view showing a bead portion of the tire of FIG. 1. FIG. FIG. 3 is a partial cross-sectional view showing a bead portion of a conventional heavy-duty pneumatic tire.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

In the present invention, a state in which the tire is mounted on a 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, the dimensions and angles of each portion of the tire are measured under normal conditions unless otherwise specified.

In the present invention, the regular rim means a rim defined in the standard on which the tire relies. A "standard rim" in the JATMA standard, a "design rim" in the TRA standard, and a "measuring rim" in the ETRTO standard are regular rims.

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

In the present invention, the normal load means the load defined in the standard on which the tire relies. "Maximum load capacity" in the JATMA standard, "maximum value" in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and "LOAD CAPACITY" in the ETRTO standard are normal loads.

FIG. 1 shows part of a heavy-duty pneumatic tire 32 (hereinafter sometimes simply referred to as "tire 32") according to one embodiment of the present invention. This tire 32 is mounted, for example, on heavy-duty vehicles such as trucks and buses.

FIG. 1 shows part of a cross-section of this tire 32 along a plane containing the axis of rotation of the tire 32 . In FIG. 1 , the horizontal direction is the axial direction of the tire 32 and the vertical direction is the radial direction of the tire 32 . The direction perpendicular to the paper surface of FIG. 1 is the circumferential direction of the tire 32 . In FIG. 1 , the dashed-dotted line CL represents the equatorial plane of the tire 32 .

In FIG. 1, the axially extending solid line BBL is the bead baseline. This bead baseline is a line that defines the rim diameter (see JATMA, etc.) of the rim (regular rim).

In FIG. 1, the symbol PW is the outer end of the tire 32 in the axial direction. The outer edge PW is specified based on a virtual side surface obtained by assuming that the side surface 34 of the tire 32 has no decoration such as a pattern or letters. The axial distance from one outer end PW to the other outer end PW is the maximum width of the tire 32, that is, the cross-sectional width of the tire 32 (see JATMA, etc.). The outer end PW is the position where the tire 32 exhibits the maximum width (hereinafter also referred to as the maximum width position of the tire 32).

The tire 32 includes a tread 36 , a pair of sidewalls 38 , a pair of beads 40 , a pair of chafers 42 , a carcass 44 , a belt 46 , a pair of cushion layers 48 , an innerliner 50 and a pair of fillers 52 .

The tread 36 contacts the road surface at its outer surface 54 . The outer surface 54 of the tread 36 is the tread surface. The aforementioned side surface 34 continues to the end of this tread surface 54 and extends radially inward.

The tread 36 has a base portion 56 and a cap portion 58 . The tire 32 is provided with a pair of base portions 56 . These base portions 56 are spaced apart in the axial direction. Each base portion 56 covers an end portion of belt 46 . The base portion 56 is made of crosslinked rubber. The cap portion 58 is positioned radially outside the base portion 56 . The cap portion 58 covers the pair of base portions 56 and the entire belt 46 . The outer surface of this cap portion 58 forms the tread surface 54 described above. The cap portion 58 is made of crosslinked rubber.

In this tire 32 , at least three circumferential grooves 60 are cut in the tread 36 . Thereby, at least four circumferential land portions 62 are formed on the tread 36 .

Each sidewall 38 joins the edge of the tread 36 . Sidewalls 38 extend radially inward from the ends of tread 36 . The sidewalls 38 are made of crosslinked rubber. The outer surface of sidewall 38 constitutes side surface 34 of tire 32 .

Each bead 40 is positioned radially inward of the sidewall 38 . Bead 40 comprises core 64 and apex 66 .

The core 64 extends circumferentially. Core 64 includes steel wire 68 wound around it. Core 64 has a substantially hexagonal cross-sectional shape. In this tire 32, the core 64 is positioned radially outside the bead baseline. In the cross section of this core 64 , the corner indicated by symbol PA is the radial inner end of this core 64 , and the corner indicated by symbol PB is the axial inner end of this core 64 . Note that the corners of the core 64 are specified based on the outline of the bundle of wires 68 included in the cross section of the core 64 .

Apex 66 is located radially outward of core 64 . Apex 66 extends radially outward from core 64 . In this tire 32 , the apex 66 includes a first apex 70 and a second apex 72 . Each of the first apex 70 and the second apex 72 is made of crosslinked rubber. First apex 70 is stiffer than second apex 72 . This apex 66 is composed of a hard first apex 70 and a soft second apex 72 .

In this tire 32, the hardness of the first apex 70 is set within a range of 83 or more and 98 or less. The hardness of the second apex 72 is set within a range of 45 or more and 65 or less. In the present invention, "hardness" is measured using a type A durometer under a temperature condition of 23°C in accordance with JIS K6253.

A first apex 70 surrounds the core 64 . In other words, core 64 is surrounded by first apex 70 . The second apex 72 is located radially outside the first apex 70 . The second apex 72 extends radially outward from the first apex 70 . The second apex 72 tapers radially outward.

As shown in FIG. 1, in this tire 32, the outer circumference of the first apex 70 has a rounded contour. This first apex 70 is round. Therefore, the contact surface of the second apex 72 with the first apex 70, that is, the bottom surface 74 of the second apex 72 has a radially outward convex shape in the cross section shown in FIG. .

Each chafer 42 is positioned axially outside the bead 40 . The chafer 42 is positioned radially inward of the sidewall 38 . A chafer 42 contacts the rim. The chafer 42 is made of crosslinked rubber. In this tire 32 , the outer end 76 of the chafer 42 is located radially inside the outer end 78 of the second apex 72 , that is, the outer end 78 of the apex 66 .

In FIG. 1, the symbol PT is the toe of the tire 32. As shown in FIG. The outer surface of chafer 42 from this toe PT to inner edge 80 of sidewall 38 forms part of side surface 34 .

Carcass 44 is located inside tread 36 , sidewalls 38 and chafer 42 . Carcass 44 comprises at least one carcass ply 82 . The carcass 44 of this tire 32 consists of one carcass ply 82 .

Although not shown, the carcass ply 82 includes a large number of parallel carcass cords. These carcass cords are covered with a topping rubber. Each carcass cord intersects the equatorial plane. In this tire 32, the angle formed by the carcass cords with respect to the equatorial plane is 70° or more and 90° or less. The carcass 44 of this tire 32 has a radial structure. In this tire 32, the material of the carcass cords is steel. A cord made of organic fibers may be used as the carcass cord.

In this tire 32, the carcass ply 82 is folded back around each bead 40 (specifically, the core 64) from the axially inner side to the outer side. The carcass ply 82 consists of a ply body 84 that spans one bead 40 and the other bead 40, and a pair of ply bodies 84 connected to the ply body 84 and folded back around each bead 40 from the inner side to the outer side in the axial direction. and a folded portion 86 . In this tire 32 , the ends 88 of the turned-up portions 86 are located radially between the outer ends 76 of the chafers 42 and the inner ends 80 of the sidewalls 38 .

The belt 46 is positioned radially inward of the tread 36 . This belt 46 is located radially outside the carcass 44 .

In this tire 32, the belt 46 consists of four layers 90 laminated in the radial direction. In this tire 32, the number of layers 90 forming the belt 46 is not particularly limited. The configuration of the belt 46 is appropriately determined in consideration of the specifications of the tire 32 .

Although not shown, each layer 90 includes a number of belt cords arranged side by side. These belt cords are covered with a topping rubber. In this tire 32, the material of the belt cord is steel.

In each layer 90 the belt cords are inclined with respect to the equatorial plane. Belt cords in one layer 90 cross belt cords in other layers 90 laminated on this one layer 90 .

In this tire 32, of the four layers 90, the second layer 90B located between the first layer 90A and the third layer 90C has the largest axial width. The radially outermost fourth layer 90D has the smallest axial width.

Each cushion layer 48 is located between this belt 46 and the carcass 44 at the end portion of the belt 46 . The cushion layer 48 is made of crosslinked rubber.

The inner liner 50 is positioned inside the carcass 44 . The inner liner 50 forms the inner surface of the tire 32 . This inner liner 50 is made of a crosslinked rubber having excellent air shielding properties. The inner liner 50 retains the internal pressure of the tire 32 .

Each filler 52 is located in a portion of bead 40 . This filler 52 is located outside the bead 40 in the axial direction. As shown in FIG. 1, filler 52 is located between turnup 86 and chafer 42 .

Although not shown, the filler 52 includes a large number of parallel metal cords. In this tire 32, the material of the metal cord is steel. In this tire 32, the metal cords included in the filler 52 are steel cords. The metal cord in the filler 52 is covered with a topping rubber.

In this tire 32, the first end 92 (also referred to as the inner end) of the filler 52 is located inside the bead baseline in the radial direction. A first end 92 of the filler 52 is located radially between the bead baseline and the toe PT. In the tire 32, the first end 92 of the filler 52 is arranged in the axial direction at a position equivalent to the position of the inner end PA of the core 64, that is, the corner PA. A second end 94 (also referred to as an outer end) of the filler 52 is located radially inside the end 88 of the folded portion 86 . The second end 94 of the filler 52 is located radially between the end 88 of the turnup 86 and the bead baseline. This filler 52 is a short filler.

The tire 32 may be configured such that the filler 52 is folded around the bead 40 . In this case, the first end 92 of the filler 52 is positioned radially outward of the core 64 and axially outward of the ply body 84 . The second end 94 of the filler 52 is positioned in the same location as the second end 94 of the short filler described above. The filler 52 having such a structure is also called normal filler. From the viewpoint of weight reduction, the above-described short filler is preferable as the filler 52 in the tire 32 .

FIG. 2 shows a portion of the cross-section of tire 32 of FIG. FIG. 2 shows the bead 40 portion of the tire 32 (hereinafter also referred to as bead portion B). 2, the horizontal direction is the axial direction of the tire 32, and the vertical direction is the radial direction of the tire 32. As shown in FIG. The direction perpendicular to the paper surface of FIG. 2 is the circumferential direction of the tire 32 .

This tire 32 is provided with a recess 96 in the side surface 34 . In this tire 32 , the recess 96 is provided in the sidewall 38 forming part of the side surface 34 . As shown in FIG. 2, the recess 96 has an inwardly convex shape. This recess 96 extends continuously in the circumferential direction.

In FIG. 2, reference PS is the outer edge of the recess 96. In FIG. Reference PU is the inner end of this recess 96 . In this tire 32, the outer end PS of the recess 96 is located inside the maximum width position PW in the radial direction. The inner end PU of the recess 96 is positioned radially outside the end 88 of the folded portion 86 . In this tire 32 , the depression 96 is provided in the zone between the maximum width position PW and the end 88 of the folded portion 86 in the side surface 34 .

When a load is applied to the tire 32 mounted on the rim, the rubber moves in the tire 32 toward the vicinity of where the end 88 of the cuff 86 and the second end 94 of the filler 52 are located. In keeping with this movement, the ply body 84 moves axially outward. As described above, in this tire 32 , the depression 96 is located in the zone between the maximum width position PW and the end 88 of the folded portion 86 . This recess 96 restrains the movement of the rubber in the vicinity of where the end 88 of the folded portion 86 and the second end 94 of the filler 52 are located, and restrains the movement of the ply body 84 . This recess 96 suppresses the movement of the rubber in the portion radially outside the end 88 of the folded portion 86 when a load acts on the tire 32 .

In this tire 32, the recess 96 provided in the zone between the maximum width position PW and the end 88 of the folded portion 86 of the side surface 34 contributes to the reduction of mass. As described above, this recess 96 suppresses movement of the rubber in the portion radially outside the end 88 of the folded portion 86 . Since the movement of the folded-back portion 86 is suppressed, the tire 32 is less susceptible to damage such as plies, turn-ups, and looses. This suppression of movement also suppresses the heat generated due to deformation.

In this tire 32, the periphery of the core 64 is surrounded by a rigid first apex 70 having a rounded outer periphery. Since the collapse of the bead portion B due to the action of the load is suppressed, this tire has good bead durability.

In this tire 32, the radial height of the first apex 70 is low. In this tire 32 , the sidewall 38 portion, that is, the side portion S, can sufficiently secure a region that can contribute to bending, and the contour of the ply body 84 extending along the apex 66 can be easily set. In this tire 32, since the protrusion of the side surface 34 in the axial direction outward is suppressed, the amount of strain acting on the recess 96 is reduced. In this tire 32, damage such as cracks in the dents 96 is less likely to occur. In this tire 32, the above-described effects of the depressions 96 are fully exhibited. Moreover, since the first apex 70 is configured with a small volume, the influence of the first apex 70 on rolling resistance is effectively suppressed.

In this tire 32, improvement in bead durability and reduction in rolling resistance are achieved while reducing weight.

The dotted line VL in FIG. 2 is a virtual side surface obtained when the side surface 34 does not have the recess 96 . This virtual side VL is a part of the above-described virtual side used for specifying the maximum width position PW. A solid line NL is the normal line of the ply body 84 . The double arrow TA is the thickness from the ply body 84 to the recess 96 measured along this normal NL. In this tire 32 , this thickness TA is represented by the minimum thickness from the ply body 84 to the recess 96 . A double-headed arrow TB is a virtual thickness from the ply body 84 to the virtual side surface VL measured along the line segment indicating this minimum thickness TA, that is, the normal line NL.

In this tire 32, the ratio of the minimum thickness TA to the virtual thickness TB is preferably 0.3 or more, and preferably 0.7 or less. By setting this ratio to 0.3 or more, an increase in strain in the vicinity of the bottom of this recess 96 is suppressed, and the minimum thickness TA is configured to a required thickness. In this tire 32, the occurrence of damage such as cracks in the recesses 96 is suppressed. From this point of view, this ratio is more preferably 0.4 or more. By setting this ratio to 0.7 or less, movement of the rubber rim forming the sidewall 38 toward the flange LF side when a load is applied is suppressed. In this tire 32 , the recesses 96 effectively suppress the movement of the rubber in the portion radially outside the end 88 of the folded portion 86 . In this tire 32, the bead durability is effectively improved and the rolling resistance is effectively reduced. From this point of view, this ratio is more preferably 0.6 or less.

In FIG. 2 , the double arrow DU is the radial distance from the end 88 of the folded portion 86 to the inner end PU of the recess 96 . A double arrow DS is the radial distance from the maximum width position PW to the outer end PS of the recess 96 .

In this tire 32, the radial distance DU from the end 88 of the folded portion 86 to the inner end PU of the recess 96 is preferably 10 mm or more, and preferably 20 mm or less. By setting the distance DU to 10 mm or more, the recess 96 is arranged with an appropriate distance from the end 88 of the folded portion 86, so interference between the recess 96 and the folded portion 86 is prevented. Concentration of strain on the end 88 of the folded portion 86 is suppressed, and the effects of the recesses 96 are fully exhibited, so that in this tire 32, the bead durability is effectively improved and the rolling resistance is effective. significantly reduced. By setting the distance DU to 20 mm or less, the recess 96 having a sufficient size is secured in the zone between the maximum width position PW and the end 88 of the folded portion 86 . In this case as well, the effects of the depressions 96 are sufficiently exhibited, so that the tire 32 effectively improves the bead durability and effectively reduces the rolling resistance.

In this tire 32, the radial distance DS from the maximum width position PW to the outer end PS of the recess 96 is preferably 10 mm or more, and preferably 20 mm or less. By setting the distance DS to 10 mm or more, the recess 96 is arranged with a proper gap from the maximum width position PW. In this tire 32, the sidewall 38 at the maximum width position PW has an appropriate thickness, so good cut resistance is maintained. By setting the distance DS to 20 mm or less, the recess 96 having a sufficient size is secured in the zone between the maximum width position PW and the end 88 of the folded portion 86 . Since the effect of the depressions 96 is sufficiently exhibited, the tire 32 effectively improves the bead durability and effectively reduces the rolling resistance.

In this tire 32, of the side surface 34, the portion radially inward from the maximum width position PW consists of the aforementioned recess 96, the outer portion 98 extending radially outward from the outer end PS of the recess 96, and the recess 96. an inner portion 100 extending radially inward from the inner end PU.

The aforementioned imaginary side VL is located between the outer portion 98 and the inner portion 100 . An outer end PU of the recess 96 is a boundary between the outer portion 98 and the virtual side surface VL. The inner end PU of this recess 96 is the boundary between the inner portion 100 and this imaginary side VL. In this tire 32, the profile of the imaginary side VL and the profile of the outer portion 98 meet at the boundary PS. The profile of this virtual side VL and the profile of the inner portion 100 meet at the boundary PU.

In this tire 32 , the recess 96 comprises a bottom 102 , an outer boundary 104 and an inner boundary 106 .

An outer boundary 104 spans the bottom portion 102 and the aforementioned outer portion 98 . The profile of outer boundary 104 meets the profile of outer portion 98 at outer edge PS. This outer end PS is also the boundary between the outer boundary portion 104 and the outer portion 98 .

An inner boundary 106 spans the bottom 102 and the inner portion 100 previously described. The profile of the inner border 106 meets the profile of the inner part 100 at the inner end PU. This inner end PU is also the boundary between the inner boundary portion 106 and the inner portion 100 .

In FIG. 2, reference PSb is the outer edge of the bottom portion 102 . Reference PUb is the inner end of this bottom portion 102 . In this tire 32 , the outer boundary portion 104 is located radially outside the bottom portion 102 . The profile of bottom 102 meets the profile of outer boundary 104 at outer edge PSb. This outer end PSb is the boundary between the bottom portion 102 and the outer boundary portion 104 . An inner boundary 106 is located radially inward of the bottom 102 . The profile of the bottom 102 meets the profile of the inner boundary 106 at the inner end PUb. This inner end PUb is the boundary between the bottom portion 102 and the inner boundary portion 106 .

In the cross section of this tire 32 shown in FIG. 2, the profile of the outer boundary 104 is represented by an outwardly convex arc. In this FIG. 2, arrow Rs is the radius of the arc representing the profile of this outer boundary 104 .

In this tire 32, the radius Rs of the arc representing the profile of the outer boundary portion 104 is preferably 40 mm or more. As a result, concentration of strain on the outer boundary portion 104 is suppressed. In this tire 32, the effects of the depressions 96 are sufficiently exhibited, so that the bead durability is effectively improved and the rolling resistance is effectively reduced. Note that the upper limit of this radius Rs is appropriately determined in consideration of the configuration of the profile of the side surface 34 .

In the cross section of this tire 32 shown in FIG. 2, the profile of the inner boundary 106 is represented by an outwardly convex arc. In this FIG. 2, the arrow Ru is the radius of the arc representing the profile of this inner boundary 106 .

In this tire 32, the radius Ru of the arc representing the profile of the inner boundary portion 106 is preferably 40 mm or more. As a result, concentration of strain on the inner boundary portion 106 is suppressed. In this tire 32, the effects of the depressions 96 are sufficiently exhibited, so that the bead durability is effectively improved and the rolling resistance is effectively reduced. Note that the upper limit of the radius Ru is appropriately determined in consideration of the configuration of the profile of the side surface 34 .

In this tire 32, the radius Rs of the arc representing the profile of the outer boundary portion 104 is 40 mm or more from the viewpoint that the depressions 96 effectively contribute to the improvement of bead durability and the reduction of rolling resistance. More preferably, the radius Ru of the arc representing the profile is 40 mm or more.

In this tire 32, the profile of the bottom portion 102 is represented by an inwardly convex arc. This effectively distributes the force acting on the bottom portion 102 over the entire bottom portion 102 . In this tire 32, strain is concentrated on a specific portion of the bottom portion 102, and damage such as cracks is prevented from occurring. In this tire 32, the effects of the depressions 96 are sufficiently exhibited, so that the bead durability is effectively improved and the rolling resistance is effectively reduced.

In FIG. 2, arrow Rb is the radius of the arc representing the profile of bottom 102 . In this tire 32, the radius Rb is the radial distance DU from the end 88 of the folded portion 86 to the inner end PU of the recess 96 and the radial distance DS from the maximum width position PW to the outer end PS of the recess 96. , and the radius Rs of the arc representing the profile of the outer boundary portion 104 and the radius Ru of the arc representing the profile of the inner boundary portion 106 are considered. From the viewpoint of preventing damage due to stress concentration in the bottom portion 102, the radius Rb is preferably 40 mm or more.

Although not shown, in this tire 32 the profile of the bottom 102 of the recess 96 may be represented by a straight line instead of an arc. In this case, the profile of bottom 102 may not meet the profile of outer boundary 104 at outer edge PSb. The profile of this bottom portion 102 may not meet the profile of the inner boundary portion 106 at the inner end PUb. Even if the profile of the bottom portion 102 were represented by a straight line, the forces acting on the bottom portion 102 would be effectively distributed over the bottom portion 102 to prevent damage from occurring in this bottom portion 102 . In the tire 32, the profile of the bottom portion 102 of the recess 96 is preferably represented by a circular arc from the viewpoint of more fully exhibiting the effects of the recess 96. As shown in FIG.

In FIG. 2, the symbol PN is the intersection of the normal NL and the recess 96. In FIG. This intersection point PN is the location on the recess 96 where the thickness from the ply body 84 to the recess 96 exhibits the minimum thickness, ie, the minimum thickness position. Reference character PC is the center position of the recess 96 . This center position PC is specified at a position where the length of the recess 96 is half as measured in the cross section shown in FIG.

In this tire 32, the minimum thickness position PN of the recess 96 is located outside the center position PC of this recess 96 in the radial direction. In this tire 32 , forces acting on the depression 96 are effectively distributed over the depression 96 . In this tire 32, strain is concentrated on a specific portion of the dent 96, and damage such as cracks is prevented from occurring. In this tire 32, the effects of the depressions 96 are sufficiently exhibited, so that the bead durability is effectively improved and the rolling resistance is effectively reduced. From this point of view, it is preferable that the minimum thickness position PN of the recess 96 be located outside the center position PC of the recess 96 in the radial direction.

In this tire 32 , the center position PC of the recess 96 is radially located between the outer end 78 of the apex 66 and the outer end 76 of the chafer 42 . In this tire 32 , the recesses 96 effectively suppress the movement of the rubber in the portion radially outside the end 88 of the folded portion 86 . In this tire 32, the bead durability is effectively improved and the rolling resistance is effectively reduced. From this point of view, the center position PC of the recess 96 is preferably located radially between the outer end 78 of the apex 66 and the outer end 76 of the chafer 42 .

In FIG. 2, the double arrow HW indicates the radial distance from the bead baseline to the maximum width position PW. A double arrow HB is the radial distance from the inner end PU of the recess 96 to the outer end PS.

In this tire 32, the ratio of the radial distance HB to the radial distance HW is preferably 0.45 or more and preferably 0.65 or less. By setting this ratio to 0.45 or more, the size of the recess 96 is sufficiently secured. This recess 96 effectively suppresses movement of the rubber in the portion radially outside the end 88 of the folded portion 86 . In this tire 32, the bead durability is effectively improved and the rolling resistance is effectively reduced. From this point of view, this ratio is more preferably 0.50 or more. By setting this ratio to 0.65 or less, the size of the recess 96 is appropriately maintained. In this tire 32, the influence of the depressions 96 on the rigidity is effectively suppressed. From this point of view, this ratio is more preferably 0.60 or less.

In this tire 32 , the outer end 108 of the first apex 70 is located inside the end 88 of the folded portion 86 in the radial direction. In this tire 32, concentration of strain on the end 88 of the folded portion 86 is suppressed. In the tire 32, a sufficient area that can contribute to bending can be secured in the side portion S, and the contour of the ply body 84 extending along the apex 66 can be easily set. In this tire 32, since the protrusion of the side surface 34 in the axially outward direction is effectively suppressed, the amount of strain acting on the depression 96 is sufficiently reduced. In this tire 32, since damage such as cracks in the depressions 96 is unlikely to occur, the above-described effects of the depressions 96 are fully exhibited. Moreover, since the protrusion of the side surface 34 in the axially outward direction is suppressed and the first apex 70 is configured with a small volume, the tire 32 can reduce the rolling resistance. From this point of view, it is preferable that the outer end 108 of the first apex 70 be located inside the end 88 of the folded portion 86 in the radial direction.

In FIG. 2, PF is a position on the side surface 34 corresponding to the radially outer edge of the contact surface between the tire 32 and the flange LF of the rim, ie, the flange contact edge. In this tire 32, the outer end 108 of the first apex 70 is located radially outside the flange contact end PF. In this tire 32, the rigidity of the first apex 70 is appropriately maintained, and protrusion of the side surface 34 at the outer portion of the flange contact end PF is effectively suppressed. Good bead durability is effectively maintained in this tire 32 . From this point of view, the outer end 108 of the first apex 70 is preferably located radially outside the flange contact end PF.

In FIG. 2, the double arrow HA is the radial distance from the radially inner end PA of the core 64 to the outer end 108 of the first apex 70 . A double arrow DB is the distance from the axial inner end PB of the core 64 to the carcass ply 82 . This distance DB is represented by the shortest distance.

In this tire 32, the radial distance HA from the radial inner end PA of the core 64 to the outer end 108 of the first apex 70 is preferably 15 mm or more, and preferably 45 mm or less. By setting the distance HA to 15 mm or more, the rigidity of the first apex 70 is appropriately maintained, and protrusion of the side surface 34 at the outer portion of the flange contact end PF is effectively suppressed. Good bead durability is effectively maintained in this tire 32 . From this point of view, the distance HA is more preferably 20 mm or longer, more preferably 25 mm or longer. By setting the distance HA to 45 mm or less, the tire 32 can sufficiently secure a region in the side portion S that can contribute to bending, and the contour of the ply body 84 extending along the apex 66 can be easily set. In this tire 32, since the protrusion of the side surface 34 in the axially outward direction is suppressed, the amount of strain acting on the recess 96 is reduced. In this tire 32, the occurrence of damage such as cracks in the dents 96 is suppressed, so the effects of the dents 96 are fully exhibited. From this point of view, the distance HA is more preferably 40 mm or less, more preferably 35 mm or less.

In this tire 32, the distance DB from the axial inner end PB of the core 64 to the carcass ply 82 is preferably 1 mm or more. By setting the distance DB to 1 mm or more, it is possible to prevent the carcass ply 82 from rubbing against the core 64 under the load applied during running. In this tire 32, cutting of the carcass cords near the axial inner end PB of the core 64 is effectively prevented. From this point of view, the distance DB is preferably 1.5 mm or more. From the viewpoint that the first apex 70 is configured with an appropriate volume and the influence of the first apex 70 on rolling resistance is suppressed, the distance DB is preferably 5 mm or less.

By the way, when the nominal aspect ratio of the tire 32 is 65% or less and the nominal cross-sectional width is 385 or more, in this tire 32, with respect to the axial width of the tread 36, the bead base line, the equatorial plane and the carcass The carcass height, expressed as the radial height to the intersection with the inner surface of 44, is low. In this tire 32, the area where the action of the load can be absorbed by bending (that is, the area that can contribute to the above-mentioned bending) is narrower than that of a normal tire. Therefore, it is difficult to ensure sufficient bead durability with this tire 32 .

As described above, the radial height of the first apex 70 of this tire 32 is low, and the side surface 34 is provided with a recess 96 in the zone between the maximum width position PW and the end 88 of the turnup portion 86. . This first apex 70 and recess 96 contribute to the deflection of tire 32 . The recess 96 suppresses the movement of the rubber in the portion radially outside the end 88 of the folded portion 86 and also contributes to the reduction of mass. Therefore, even if the nominal aspect ratio of the tire 32 is 65% or less and the nominal cross-sectional width is 385 or more, the tire 32 can improve bead durability while achieving weight reduction. , and reduced rolling resistance.

As is clear from the above description, according to the present invention, it is possible to obtain a heavy-duty pneumatic tire that achieves improved bead durability and reduced rolling resistance while achieving weight reduction.

The embodiments disclosed this time are illustrative in all respects and are not restrictive. The technical scope of the present invention is not limited to the above-described embodiments, but includes all modifications within the scope of equivalents to the configuration described in the claims.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited only to these Examples.

[Example 1]
A heavy-duty pneumatic tire (tire size=11R22.5) having the basic configuration shown in FIGS. 1 and 2 and the specifications shown in Table 1 below was obtained.

In this Example 1, the outer end of the first apex was arranged radially between the end of the folded portion and the flange contact end PF. In Table 1, "in" means that the outer end of the first apex is positioned inside the end of the folded portion, and that the outer end of this first apex is positioned outside the flange contact end. It is represented by "out".

In Example 1, the radial distance HA from the radially inner end PA of the core to the outer end of the first apex was set to 30 mm. A distance DB from the axial inner end PB of the core to the carcass ply was set to 1.5 mm.

In this Example 1, the minimum thickness TA from the ply body to the recess is obtained assuming no recess from the ply body, measured along a line segment (i.e., normal NL) indicating this minimum thickness TA. The ratio (TA/TB) to the virtual thickness TB up to the virtual side VL was set to 0.5.

[Comparative Example 1]
Comparative Example 1 is the conventional tire (tire size=11R22.5) shown in FIG. In this Comparative Example 1, the apex consisted of a conventional apex. The sides are not recessed.

[Comparative Example 2]
A tire of Comparative Example 2 was obtained in the same manner as in Example 1, except that no depression was provided on the side surface.

[Example 2]
A tire of Example 2 was obtained in the same manner as in Example 1, except that the outer end of the first apex was arranged radially outside the end of the folded portion. In Table 1, "out" indicates that the outer edge of the first apex is located outside the edge of the folded portion.

[Example 3]
A tire of Example 3 was obtained in the same manner as in Example 1, except that the outer end of the first apex was arranged radially inward of the flange contact end. In Table 1, "in" indicates that the outer edge of the first apex is located inside the flange contact edge.

[Example 4-5]
Tires of Examples 4 and 5 were obtained in the same manner as in Example 1, except that the distance DB was set as shown in Table 2 below.

[Example 6-9]
Tires of Examples 4 and 5 were obtained in the same manner as in Example 1, except that the distance HA was set as shown in Table 2 below.

[PTL resistance performance]
As bead durability, PTL (ply turn-up loose) resistance performance was evaluated. For this evaluation, the tire was mounted on a rim (size = 22.5 x 8.75) and the inside of the tire was inflated. The internal pressure of the tire was adjusted to 1000 kPa. The tire was mounted on a bench tester with a drive drum. A vertical load of 76.53 kN was applied to the tire, and the tire was run at 20 km/h, and the running time until the bead was damaged and the occurrence of PTL were confirmed. The results are shown in Tables 1 and 2 below as an index with the tire of Example 1 set to 100. A larger value indicates less occurrence of PTL and better bead durability.

[Rolling resistance coefficient (RRC)]
The tire was mounted on a rim (size = 22.5 x 8.75), and the inside of the tire was filled with air. The internal pressure of the tire was adjusted to 800 kPa. This tire was mounted on a rolling resistance tester. A longitudinal load of 26.72 kN was applied to the tire, and the tire was run at 80 km/h to measure the rolling resistance. The results are shown in Tables 1 and 2 below as indices with Example 1 being 100. The larger the numerical value, the smaller the rolling resistance, which is preferable.

[CBU resistance performance]
CBU (casing break-up) resistance performance was evaluated as bead durability. In this evaluation, the tire was mounted on a rim (size = 22.5 x 8.75), and 300 cc of water was poured into the tire and air was filled. The internal pressure of the tire was adjusted to 800 kPa. It was allowed to stand for two weeks in an atmosphere adjusted to 80°C. After this pretreatment, the inside of the tire was filled with 300 cc of water and air, and the internal pressure was adjusted to 1000 kPa. The tire was mounted on a bench tester with a drive drum. A longitudinal load of 76.53 kN was applied to the tire, and the tire was run at 20 km/h to check the running time until the bead was damaged and the occurrence of CBU. The results are shown in Tables 1 and 2 below as an index with the tire of Example 1 set to 100. A larger value indicates less occurrence of CBU and better bead durability.

[Ozone crack resistance performance]
The tire was allowed to stand for two weeks in an atmosphere adjusted to 80°C. After this pretreatment, this tire was mounted on a rim (size=22.5×8.75) and the inside of the tire was filled with air. The internal pressure of the tire was adjusted to 800 kPa. The tire was mounted on a bench tester with a drive drum. A vertical load of 26.72 kN was applied to the tire, and the tire was run at 40 km/h in an atmosphere adjusted to an ozone concentration of 50 pphm to confirm the occurrence of ozone cracks. The results are shown in Tables 1 and 2 below as an index with the tire of Example 1 set to 100. A larger value indicates that ozone cracks are less likely to occur.

As shown in Tables 1 and 2, in the example, a round apex is adopted as the first apex and a recess is provided on the side surface, thereby reducing weight while improving bead durability and rolling resistance. It is confirmed that the reduction of Examples are evaluated higher than Comparative Examples. From this evaluation result, the superiority of the present invention is clear.

The technique for improving bead durability and reducing rolling resistance while achieving weight reduction as described above can be applied to various tires.

2, 32... tire 4, 40... bead 6, 82... carcass ply 8, 84... ply body 10, 86... folded portion 10a... end of folded portion 10 12, 64 ... core 14, 66 ... apex 16 ... first apex 16a ... outer end of first apex 16 18 ... second apex 20, 52 ... filler 20a ... Inner end 20b of filler 20 Outer end of filler 20 22, 42 Chafer 24, 68 Wire 34 Side 36 Tread 38 Sidewall 44 Carcass 54: Outer surface of tread 36 (tread surface)
70 First apex 72 Second apex 74 Bottom surface of second apex 72 76 Outer end of chafer 42 78 Outer end of second apex 72 ( outer edge of apex 66)
80... Inner end of sidewall 38 88... End of folded portion 86 92... First end of filler 52 94... Second end of filler 52 96... Recess 98... Outside part Reference Signs List 100 inner portion 102 bottom portion 104 outer boundary portion 106 inner boundary portion 108 outer end of the first apex 70

Claims (12)

a pair of beads;
a carcass ply having a ply body that bridges between one bead and the other bead, and a folded portion connected to the ply body and folded back from the inner side to the outer side in the axial direction around the bead;
a pair of fillers located outside the folded portion in the axial direction and including metal cords;
a pair of sidewalls positioned axially outward of the ply body and forming side surfaces of the tire;
a pair of chafers positioned radially inward of the sidewalls and in contact with the rim;
with
the bead comprises a core, a first apex surrounding the core, and a second apex radially outward of the first apex;
the circumference of the first apex has a rounded profile;
the first apex is harder than the second apex;
an outer end of the second apex is sandwiched between the ply body and the sidewall and is in contact with the sidewall;
the outer end of the chafer is positioned radially inside the outer end of the second apex;
A recess is provided in a zone between the maximum width position and the end of the folded portion on the side surface of the tire,
A heavy-duty pneumatic tire , wherein the center position of the recess is radially positioned between the outer end of the second apex and the outer end of the chafer. When the position on the side surface corresponding to the outer edge of the contact surface between the side surface of the tire and the flange of the rim to which the tire is fitted is defined as the flange contact end,
2 . The heavy duty pneumatic tire according to claim 1 , wherein the outer end of the first apex is positioned radially inside the end of the folded portion and outside the flange contact end. The heavy duty pneumatic tire according to claim 1 or 2, wherein the radial distance from the radial inner end of the core to the outer end of the first apex is 15 mm or more and 45 mm or less. The heavy duty pneumatic tire according to any one of claims 1 to 3, wherein the distance from the axial inner end of the core to the carcass ply is 1 mm or more. The ratio of the minimum thickness from the ply body to the recess to the virtual thickness from the ply body to the virtual side surface obtained without the recess, measured along the line segment indicating the minimum thickness, is The heavy-duty pneumatic tire according to any one of claims 1 to 4, which is 0.3 or more and 0.7 or less. The heavy duty pneumatic tire according to any one of claims 1 to 5, wherein the radial distance from the end of the folded portion to the inner end of the recess is 10 mm or more and 20 mm or less. the recess comprises a bottom and an outer boundary located radially outward of the bottom;
The heavy-duty pneumatic tire according to any one of claims 1 to 6, wherein the profile of the outer boundary portion is represented by an outwardly convex circular arc, and the radius of the circular arc is 40 mm or more. the recess comprises a bottom and an inner boundary located radially inward of the bottom;
The heavy duty pneumatic tire according to any one of claims 1 to 7, wherein the profile of the inner boundary portion is represented by an outwardly convex circular arc, and the radius of the circular arc is 40 mm or more. A heavy duty pneumatic tire according to claim 7 or 8, wherein the bottom profile is represented by an inwardly convex arc. A heavy duty pneumatic tire according to claim 7 or 8, wherein the bottom profile is linear. 11. Radially, the first end of the filler is located inside the bead baseline, and the second end of the filler is located between the end of the folded portion and the bead baseline. The heavy duty pneumatic tire according to any one of 1. The inner end of the recess is radially positioned between the end of the folded portion and the outer end of the chafer, and the outer end of the recess is radially positioned between the outer end of the second apex and the maximum width position. The heavy-duty pneumatic tire according to any one of claims 1 to 11 , located between and.

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