JP2016147567A - tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire which is excellent in durability and operation stability by suppressing a flat spot.SOLUTION: A filler 24 extends from the radial direction inner side of a first reference line L1 to the radial direction outer side of a third reference line L3 while a tire 2 is included in a normal rim 48 to undergo normal inner pressure with the load of 120% of a normal load applied. In this state, the ratio (Sf/St) of the area Sf of the filler between the first reference line L1 and the third reference line L3 to the area St of the tire 2 between the first reference line L1 and the third reference line L3 is set to 0.3 or below. A tip 36a of an apex 36 is located closer to a core 34 than the first reference line L1.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a tire mounted on a vehicle.

  A tire mounted on a vehicle includes an apex extending radially outward from the core. This apex is made of a highly hard crosslinked rubber. Apex contributes to the improvement of tire rigidity. A high-hardness apex is likely to cause permanent distortion when placed in a constant deformation state for a long time. In a tire having a high apex height, this permanent distortion causes deformation of the sidewall and the tread. This deformation of the tread is called a so-called flat spot. From the viewpoint of suppressing the occurrence of this flat spot, the apex height is preferably set low.

  A tire with a low apex height is disclosed in JP2013-169825A, JP2013-545671A, International Publication No. WO2012 / 18106, and the like. By reducing the height of the apex, the occurrence of flat spots can be suppressed.

  On the other hand, if the apex is too low or too thin, tire durability and steering stability may be impaired. The height and thickness of the apex also affect the durability and handling stability of the tire. Even the tires described in the prior art documents disclose fillers and the like located outside the axial direction of the apex. These tires are a combination of an apex and a filler, and the durability and steering stability of the tire are suppressed from being impaired.

JP2013-169825A Special table 2013-545671 International Publication Number WO2012 / 18106

  However, even with these tires, it is not easy to achieve both the suppression of the occurrence of flat spots, the improvement of durability, and the improvement of steering stability. An object of the present invention is to provide a tire excellent in durability and steering stability while suppressing the occurrence of flat spots.

The pneumatic tire according to the present invention includes a tread, a pair of sidewalls, a pair of clinches, a pair of beads, a carcass, and a pair of fillers. Each sidewall extends substantially inward in the radial direction from the end of the tread. Each clinch is located inside the sidewall in the radial direction. Each bead is located inside the clinch in the axial direction. The bead includes a core and an apex extending radially outward from the core. The carcass extends along the inside of the tread and the sidewall and is bridged between one bead and the other bead. The carcass includes a carcass ply. The carcass ply is folded from the inner side toward the outer side in the axial direction around the core. The carcass ply is formed with a main portion located on the inner side in the axial direction of the bead and a folded portion located on the outer side in the axial direction of the bead. Each filler is located between the clinch and the folded portion in the axial direction.
The regular rim in which this tire is incorporated has a flange. This flange forms a bent outer peripheral surface where the outer edge in the radial direction contacting the clinch is located and bent at the curvature radius Rr. A straight line that extends through the center point Pr of the radius of curvature Rr and inclines in the axial direction at an angle of 45 ° with respect to the axial direction from the radially inner side to the outer side is defined as a first reference line L1, and the center of the core A straight line passing through the first reference line L1 and passing through the first reference line L1 is defined as a second reference line L2, and a straight line symmetrical with the second reference line L2 is defined as a third reference line L3 with the first reference line L1 as an axis of symmetry. The filler extends from the inner side in the radial direction of the first reference line to the outer side in the radial direction of the third reference line in a state where 120% of the normal load is applied by being incorporated into the normal rim and adjusted to the normal internal pressure. ing. In this state, the ratio of the area Sf of the filler between the first reference line L1 and the third reference line L3 to the tire area St between the first reference line L1 and the third reference line L3 (Sf / St) is set to 0.3 or less. The tip of the apex is located closer to the core than the first reference line L1.

  Preferably, the tip of the apex is located radially outward from the flange of the regular rim.

  Preferably, the height of the outer end of the folded portion of the carcass ply is Hp, and the height of the outer end of the filler is Hf. At this time, the height Hp is higher than the height Hf. The ratio ((Hp−Hf) / Hp) of the difference (Hp−Hf) between the height Hp and the height Hf with respect to the height Hp is set to 0.05 or more.

  Preferably, the tire is provided with a strip. This strip is laminated on the apex. This strip extends radially outward from the tip of the apex. The outer end of this strip is located radially outward from the first reference line L1. The thickness of this strip exceeds 0 and is 2 mm or less.

  In the tire according to the present invention, the apex and the filler are arranged at appropriate positions and ranges. Thereby, generation | occurrence | production of a flat spot is suppressed. This tire is also excellent in durability and steering stability.

FIG. 1 is a cross-sectional view showing a part of a pneumatic tire according to an embodiment of the present invention. FIG. 2 shows a part of a regular rim in which the tire of FIG. 1 is incorporated. FIG. 3 is a cross-sectional view showing a part of the tire of FIG. 1 that is incorporated in the regular rim of FIG. 2 and is in use. FIG. 4 is an enlarged explanatory view showing a part of FIG.

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

  FIG. 1 shows a pneumatic tire 2. In FIG. 1, the vertical direction is the radial direction of the tire 2, the horizontal direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2. In FIG. 1, an alternate long and short dash line CL represents the equator plane of the tire 2. A solid line BL represents the bead base line of the tire 2. The bead base line is a line that defines the rim diameter (see JATMA) of the rim. The shape of the tire 2 is symmetrical with respect to the equator plane except for the tread pattern.

  The tire 2 includes a tread 4, a pair of sidewalls 6, a pair of clinch 8, a pair of beads 10, a carcass 12, a belt 14, a band 16, an inner liner 18, a pair of chafers 20, a pair of strips 22, and a pair of pairs. A filler 24 is provided. The tire 2 is a tubeless type. The tire 2 is mounted on a light truck, for example. Here, the tire 2 will be described as an example, but the tire 2 according to the present invention can be widely applied to various vehicles. The tire 2 may be a type including a tube.

  The tread 4 has a shape protruding outward in the radial direction. The tread 4 forms a tread surface 26 that contacts the road surface. A groove 28 is carved in the tread 4. The groove 28 forms a tread pattern. The tread 4 has a base layer 30 and a cap layer 32. The cap layer 32 is located on the outer side in the radial direction of the base layer 30. The cap layer 32 is laminated on the base layer 30. The base layer 30 is made of a crosslinked rubber having excellent adhesiveness. A typical base rubber of the base layer 30 is natural rubber. The cap layer 32 is made of a crosslinked rubber having excellent wear resistance, heat resistance, and grip properties.

  Each sidewall 6 extends substantially inward in the radial direction from the end of the tread 4. A radially outer end of the sidewall 6 is joined to the tread 4. The radially inner end of the sidewall 6 is joined to the clinch 8. This sidewall 6 is made of a crosslinked rubber having excellent cut resistance and weather resistance. This sidewall 6 prevents the carcass 12 from being damaged.

  Each clinch 8 is located substantially inside the sidewall 6 in the radial direction. The clinch 8 is located outside the beads 10 and the carcass 12 in the axial direction. The clinch 8 is made of a crosslinked rubber having excellent wear resistance.

  Each bead 10 is located inside the clinch 8 in the axial direction. The bead 10 includes a core 34 and an apex 36 that extends radially outward from the core 34. The core 34 is ring-shaped and includes a wound non-stretchable wire. A typical material for the wire is steel.

The apex 36 is tapered outward in the radial direction. The apex 36 is made of a highly hard crosslinked rubber. From the viewpoint of suppressing the deformation of the apex 36, the complex elastic modulus E ^* a of the apex 36 is preferably 20 MPa or more. From the viewpoint of suppressing a decrease in riding comfort, the complex elastic modulus E ^* a is preferably 60 MPa or less.

  The height in the radial direction of the apex 36 is set lower than the general height. The position of the tip 36a of the apex 36 is located radially inward from the general position. The apex 36 is called a so-called small apex.

  The carcass 12 includes a first ply 38 and a second ply 40. The first ply 38 and the second ply 40 are bridged between the beads 10 on both sides, and extend along the tread 4 and the sidewall 6. The first ply 38 is folded around the core 34 from the inner side toward the outer side in the axial direction. By this folding, the first ply 38 is formed with a main portion 38a positioned on the inner side in the axial direction of the bead 10 on both sides and a folded portion 38b positioned on the outer side in the axial direction of the bead 10. The second ply 40 is folded around the core 34 from the inner side to the outer side in the axial direction. As a result of the folding, the main portion 40a located on the inner side in the axial direction of the bead 10 on both sides and the folded portion 40b located on the outer side in the axial direction of the bead 10 are formed. The end 38c of the folded portion of the first ply 38 is located outside the end 40c of the folded portion of the second ply 40 in the radial direction.

  The first ply 38 and the second ply 40 are composed of a large number of cords arranged in parallel and a topping rubber. The absolute value of the angle formed by each cord with respect to the equator plane is 75 ° to 90 °. In other words, the carcass 12 has a radial structure. The cord is made of organic fiber. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers. The carcass 12 includes two plies of the first ply 38 and the second ply 40. However, the carcass 12 may include one ply, or three or four or more plies. Also good.

  The belt 14 is located on the inner side in the radial direction of the tread 4. The belt 14 is laminated with the carcass 12. The belt 14 reinforces the carcass 12. The belt 14 includes an inner layer 42 and an outer layer 44. In the axial direction, the width of the inner layer 42 is slightly larger than the width of the outer layer 44. Although not shown, each of the inner layer 42 and the outer layer 44 is composed of a large number of cords arranged in parallel and a topping rubber. Each cord is inclined with respect to the equator plane. The general absolute value of the tilt angle is 10 ° or more and 35 ° or less. The inclination direction of the inner layer cord with respect to the equator plane is opposite to the inclination direction of the outer layer cord with respect to the equator plane. A preferred material for the cord is steel. An organic fiber may be used for the cord. The axial width of the belt 14 is preferably 0.7 times or more the maximum width of the tire. The belt 14 may include three or more layers.

  The band 16 is located on the radially outer side of the belt 14. In the axial direction, the width of the band 16 is larger than the width of the belt 14. Although not shown, the band 16 is composed of a cord and a topping rubber. The cord is wound in a spiral. The band 16 has a so-called jointless structure. The cord extends substantially in the circumferential direction. The angle of the cord with respect to the circumferential direction is 5 ° or less, further 2 ° or less. Since the belt 14 is restrained by this cord, lifting of the belt 14 is suppressed. The cord is made of organic fiber. Examples of preferable organic fibers include nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  The inner liner 18 is located inside the carcass 12. In the vicinity of the equator plane, the inner liner 18 is joined to the inner surface of the carcass 12. The inner liner 18 forms a lumen surface 46 that is the inner surface of the tire 2. The inner liner 18 is made of a crosslinked rubber having excellent air shielding properties. A typical base rubber of the inner liner 18 is butyl rubber or halogenated butyl rubber. The inner liner 18 maintains the internal pressure of the tire.

  Each chafer 20 is located in the vicinity of the bead 10. When the tire 2 is incorporated into the rim, the chafer 20 comes into contact with the rim on the radially inner side. By this contact, the vicinity of the bead 10 is protected. The chafer 20 is formed integrally with the clinch 8. Therefore, the material of the chafer 20 is the same as that of the clinch 8. The chafer 20 may be separate from the clinch 8. The chafer 20 may be made of, for example, a cloth and a rubber impregnated in the cloth.

  Each strip 22 extends radially outward from the apex 36. The strip 22 is positioned between the main portion 40a and the folded portion 40b of the second ply 40 in the axial direction. The strip 22 is positioned between the main part (main part 38a and main part 40a) and the folded part (folded part 38b and folded part 40b) of the carcass ply (first ply 38 and second ply 40) of the carcass 12. doing. The strip 22 is made of a sheet-like crosslinked rubber. The strip 22 is made of a highly hard crosslinked rubber.

  The outer end 22 a in the radial direction of the strip 22 is located radially inward from the outer end 40 c of the second ply 40. The outer end 22a is located between the main portion 40a of the second ply 40 and the folded portion 40b. The outer end 22 a is located on the outer side in the radial direction from the inner end 6 a of the sidewall 6. The radially inner end 22 b of the strip 22 is located radially inward from the tip 36 a of the apex 36. The inner end 22b may be located inside the outer end of the core 34 in the radial direction. The radially inner part of the strip 22 is laminated on the inner side surface of the apex 36 in the axial direction. The radially inner portion of the strip 22 may be stacked on the outer surface of the apex 36 in the axial direction.

The tire 2 having a large complex elastic modulus E ^* s of the strip 22 is excellent in rigidity. Thereby, bending can be suppressed. The strip 22 suppresses deformation of the tire 2. The tire 2 is excellent in durability. From this viewpoint, the complex elastic modulus E ^* s of the strip 22 is preferably 20 MPa or more. On the other hand, in the tire 2 having a small complex elastic modulus E ^* s, a decrease in riding comfort is suppressed. From this viewpoint, the complex elastic modulus E ^* s is preferably 60 MPa or less.

  Each filler 24 is located inside the clinch 8 in the axial direction. The filler 24 is located on the outer side in the axial direction of the folded portion 38 b of the first ply 38. The filler 24 is located on the outer side in the axial direction of the folded portion 40 b of the second ply 40. In other words, the folded portion 38 b and the folded portion 40 b are located between the strip 22 and the apex 36 and the filler 24 in the axial direction. The inner surface in the axial direction of the filler 24 is curved in a direction protruding inward in the axial direction. The filler 24 is tapered toward the radially outer end 24a. The filler 24 is tapered toward the radially inner end 24b.

  The outer end 24 a of the filler 24 is located on the outer side in the radial direction of the tip 36 a of the apex 36. The outer end 24 a is located on the radially outer side of the outer end 8 a of the clinch 8. The outer end 24 a is located between the sidewall 6 and the carcass 12. The outer end 24a may be located on the radially inner side of the outer end 8a. The radially inner end 24 b of the filler 24 is located on the radially inner side of the tip 36 a of the apex 36. The inner end 24b is located inside the inner end of the core 34 in the radial direction. In the tire 2, the filler 24 is covered with the clinch 8. The inner end 24b may be located outside the center of the core 34 in the radial direction.

The filler 24 is made of a highly hard crosslinked rubber. The tire 2 having a large complex elastic modulus E ^* f of the filler 24 is excellent in rigidity. Thereby, bending is effectively suppressed. The filler 24 suppresses deformation of the apex 36. The tire 2 is excellent in durability. From this viewpoint, the complex elastic modulus E ^* f is preferably 15 MPa or more. On the other hand, in the tire 2 having a small complex elastic modulus E ^* f, a decrease in riding comfort is suppressed. From this viewpoint, the complex elastic modulus E ^* f is preferably 75 MPa or less.

  A double arrow Hs in FIG. 1 represents the height of the outer end 22 a of the strip 22. A double arrow Hf represents the height of the outer end 24 a of the filler 24. A double-headed arrow Hp represents the height of the end 38 c of the folded portion of the first ply 38. In the present invention, this height Hp is measured by a carcass ply of which the end of the folded portion is located on the outermost side among the carcass plies folded from the inner side in the axial direction toward the outer side around the core 34. The The height Hs, the height Hf, and the height Hp are measured as a linear distance in the radial direction from the bead base line.

  FIG. 2 shows a part of the rim 48 in which the tire 2 is incorporated. The rim 48 is a regular rim of the tire 2. The rim 48 is a “standard rim” in the JATMA standard. The vertical direction in this figure is the radial direction, the horizontal direction is the axial direction, and the direction perpendicular to the paper surface is the circumferential direction. The rim 48 includes a bump 50, a bead sheet 52, and a flange 54. FIG. 2 shows a cross-sectional shape perpendicular to the circumferential direction, and the bump 50, the bead sheet 52, and the flange 54 make a round shape in the circumferential direction. In the cross section of FIG. 2, the bump 50 is recessed inward in the radial direction at substantially the center in the axial direction. A sheet bead 52 extends from the bump 50 outward in the axial direction. A flange 54 extends radially outward from the outside of the seat bead 52 in the axial direction. The radially outer end of the flange 54 is bent and extends outward in the axial direction.

  The bead sheet 52 includes a sheet surface 56. The sheet surface 56 is formed by the outer peripheral surface of the bead sheet 52. The flange 54 includes a contact surface 58. The contact surface 58 extends radially outward from the seat surface 56. One contact surface 58 in the axial direction and the other contact surface 58 are opposed to each other. When the tire 2 is incorporated into the rim 50, the chafer 20 contacts the seat surface 56, and the clinch 8 contacts the contact surface 58.

  A single arrow Dr in FIG. 2 represents the rim diameter. A double arrow Wr represents the rim width. The rim width Wr is measured as an axial distance from one abutting surface 58 in the axial direction to the other abutting surface 58. A single arrow Rr indicates the radius of curvature of the bent outer peripheral surface 60 that is bent and extended outward from the contact surface 58 in the axial direction. The rim diameter Dr, the rim width Wr, and the radius of curvature Rr are determined by the JATMA standard on which the rim 48 depends.

  Here, the rim 48 of the “standard rim” in the JATMA standard is illustrated, but the seat surface 56 and the contact surface 58 of the rim 48 are also included in “Design Rim” in the TRA standard and “Measuring Rim” in the ETRTO standard. A surface corresponding to the bent outer peripheral surface 60 is formed. A curvature radius corresponding to the curvature radius Rr is also set on the outer peripheral surfaces of the rims.

  FIG. 3 shows a part of the tire assembly 62. The tire assembly 62 includes a tire 2 and a rim 48 in which the tire 2 is incorporated. The tire 2 is filled with air having a normal internal pressure. The tire 2 is loaded with a load F that is 120% of the normal load inward in the radial direction. The tire 2 is deformed by receiving the internal pressure and the load F. The tire 2 is deformed along the shape of the seat surface 56, the contact surface 58 and the bent outer peripheral surface 60 of the rim 48. 3 indicates the position of the outer edge in the radial direction where the outer surface of the tire 2 (the outer surface of the clinch 8) and the flange 54 of the rim 48 are in contact with each other. In the present invention, this point Pb is referred to as a separate separation point. The separate separation point Pb is located on the bent outer peripheral surface 60. The separate separation point Pb is obtained in a state where the load F is applied with a normal internal pressure.

  A double arrow Hr in FIG. 3 represents the height of the flange 54. This height Hr is a height from the bead base line to the radially outer end of the bent outer peripheral surface 60. This height Hr is measured as a linear distance in the radial direction. The point Pr represents the center point of the aforementioned curvature radius Rr. The alternate long and two short dashes line L1 is a straight line extending through the center point Pr so as to incline outward from the radial direction toward the inside in the axial direction. The straight line L1 extends at an angle of 45 ° with respect to the axial direction. The straight line L1 represents the first reference line of the present invention. The point Pc represents the center point of the core 34. The center point Pc is the midpoint between the radially outer end and the inner end of the core 34 and the midpoint between the axially inner end and the outer end. The two-dot chain line L2 is a straight line extending in parallel with the first reference line L1 through the center point Pc. The straight line L2 represents the second reference line of the present invention. An alternate long and two short dashes line L3 represents a straight line extending symmetrically to the second reference line L2 with the first reference line L1 as the axis of symmetry. This straight line L3 represents the third reference line of the present invention. A double arrow Ts represents the thickness of the strip 22. The thickness Ts is measured at a position that intersects the first reference line L1. At the time of measuring Ts, the load F cannot be applied.

  The symbol St in FIG. 4 represents the cross-sectional area of the tire 2 between the first reference line L1 and the third reference line L3. The area St is obtained as an area of a region surrounded by the inner surface 46, the outer surface 64, the first reference line L1, and the third reference line L3 of the tire 2. The outer surface 64 includes an outer surface of the sidewall 6 and an outer surface of the clinch 8. Symbol Sf represents the cross-sectional area of the filler 24 between the first reference line L1 and the third reference line L3. The area Sf is a part of the area St. The area St and the area Sf are obtained by a cross section in a state where the tire 2 is set to a normal internal pressure and the load 2 is applied to the tire 2.

  When the tire assembly 62 rolls while the vehicle is running, the deformed portions such as the tread 4 and the sidewall 6 move in the circumferential direction. Due to the movement of the deformed portion, each part of the tire 2 repeats periodic deformation. This periodic deformation increases the distortion and heat generation of the tire 2. This distortion and heat generation impair the durability of the tire 2.

  The tire 2 is deformed along the flange 54 of the rim 48. In the region exceeding the first reference line L1 inclined at an angle of 45 °, the deformation of the tire 2 becomes large. In particular, the amount of deformation increases in the region between the first reference line L1 and the third reference line L3. In this region, distortion and heat generation tend to increase. In the tire 2, the tip 36a of the apex 36 is closer to the core 34 than the first reference line L1. The tip 36a is located inside the first reference line L1. An increase in the deformation amount of the apec 36 is suppressed. As a result, the occurrence of damage between the apec 36 and the carcass 12 is suppressed.

  When the load F acts on the tire 2, the outer surface 64 of the tire 2 is deformed along the bent outer peripheral surface 60. At this time, the portion of the tire 2 on the side of the lumen surface 46 is stretched to generate tensile stress. On the other hand, the portion on the outer surface 64 side is compressed to generate a compressive stress. Crosslinked rubbers such as the clinch 8 and the filler 24 positioned on the outer side in the axial direction are relatively stronger in compressive stress than tensile stress. Those including cords such as the first ply 38 and the second ply 40 positioned on the inner side in the axial direction are resistant to tensile stress along the extending direction of the cord. The first ply 38 and the second ply 40 are relatively stronger in tensile stress than compressive stress in the radial direction.

  The first ply 38 and the second ply 40 can exhibit high durability against tensile stress. In the tire 2, the carcass 12 is positioned on the inner side in the axial direction by the filler 24. Together with the main part 38a and the main part 40a, the folded part 38b and the folded part 40b are located on the inner side in the axial direction. Generation of compressive stress in the carcass 12 is suppressed. The filler 24 contributes to improving the durability of the tire 2.

  Further, the filler 24 extends from the inside of the first reference line L1 to the outside of the third reference line L3 in the radial direction, and contributes to the improvement of the rigidity of the tire 2. By providing the filler 24, sufficient rigidity can be exhibited even if the apex 36 is a small apex. In the tire 2, the deformation of the sidewall 6 is suppressed.

  When the tire 2 is placed in a certain deformation state, the filler 24 is deformed. As described above, the amount of deformation increases in the region between the first reference line L1 and the third reference line L3 even when placed in a certain deformation state. When the high-hardness filler 24 is thickened, permanent distortion is likely to occur. This permanent distortion causes deformation of the sidewall 6 and the tread 4. This permanent distortion can cause a flat spot. From the viewpoint of suppressing the occurrence of flat spots, the filler 24 is preferably thinned. From this point of view, the ratio of the area Sf to the area St (Sf / St) is set to 0.3 or less in the state where the load F is loaded in the rim 48.

  As shown in FIG. 3, the folded portion 38 b and the folded portion 40 b of the carcass 12 protrude inward in the axial direction along the axially outer side surface of the apex 36 and bend and extend. The lower the height of the apex 36, the smaller the radius of curvature at which the folded portion 38b and the folded portion 40b bend and extend. If this bending radius becomes too small, damage such as looseness is likely to occur between the apex 36 and the carcass 12. From this point of view, like the tire 2, the distal end 36 a of the apex 36 is preferably located radially outside the flange 54 of the rim 48. In the tire 2, the occurrence of damage between the apex 36 and the carcass 12 is suppressed. The tire 2 suppresses generation of flat spots and is excellent in durability.

  As shown in FIG. 1, in the tire 2, the height Hp of the end 38 c of the folded portion 38 b of the first ply 38 is higher than the height Hf of the outer end 24 a of the filler 24. By increasing the distance between the end 38c and the outer end 24a, a sudden change in rigidity in the vicinity of the end 38c can be suppressed. From this viewpoint, the ratio ((Hp−Hf) / Hp) of the difference (Hp−Hf) between the height Hp and the height Hf with respect to the height Hp is preferably 0.05 or more. Preferably it is 0.10 or more.

  The height Hp is higher than the height Hs of the outer end 22a of the strip 22. By increasing the distance between the end 38c and the outer end 22a, a sudden change in rigidity in the vicinity of the end 38c can be suppressed. From this viewpoint, the ratio ((Hp−Hs) / Hp) of the difference (Hp−Hs) between the height Hp and the height Hs with respect to the height Hp is preferably 0.05 or more. Preferably it is 0.10 or more.

  As shown in FIG. 3, the strip 22 extends radially outward from the tip 36 a of the apex 36. The outer end 22a of the strip 22 is located radially outward from the first reference line L1 and the third reference line L3. The strip 22 extends from the radially inner side of the first reference line L1 to the radially outer side of the third reference line L3. The strip 22 contributes to improving the rigidity of the tire 2. By providing this strip 22, the filler 24 can be made thinner than that without the strip 22 and sufficient rigidity can be obtained.

  Since the thickness of the strip 22 is reduced, the difference in tensile stress or compressive stress generated between the main portions 38a and 40a and the folded portions 38b and 40b of the carcass 12 is reduced. Thereby, distortion of the strip 22 is suppressed. From this viewpoint, the thickness Ts of the strip 22 is preferably 2.0 mm or less, more preferably 1.5 mm or less, and particularly preferably 1.0 mm or less.

  In the tire 2, the clinch 8 is formed thicker than the filler 24. In the first reference line L1, the folded portion 38b and the folded portion 40b of the carcass 12 are positioned on the inner side in the axial direction by increasing the thickness of the filler 24 and the clinch 8 together. Thereby, the damage of the folding | returning part 38b and the folding | returning part 40b is suppressed.

  In the tire 2, the inner end 24 b of the filler 24 is located inside the inner end of the core 34 in the radial direction. The inner end side of the filler 24 is sandwiched between the core 34 and the flange 54. The inner end side of the filler 24 is fixed by the core 34 and the flange 54. The sandwiching of the filler 24 contributes to suppression of deformation of the tire 2. From this viewpoint, it is preferable that the inner end of the filler 24 is located inside the outer end of the core 34 in the radial direction.

  In the tire 2, the strip 22 and the filler 24 contribute to improvement of the rigidity of the tire 2. The strip 22 and the filler 24 contribute to an improvement in handling stability. By combining the apex 36 with the strip 22 and the filler 24, the durability is improved and the occurrence of a flat spot is suppressed without impairing the steering stability.

In the present invention, the complex elastic modulus ^{E *} a of the complex elastic modulus ^E * s, the complex elastic modulus ^{E *} f and an apex 36 of the filler 24 of the strip 22, according to the standards of "JIS K 6394", the following It is measured using a viscoelastic spectrometer (trade name “VESF-3” manufactured by Iwamoto Seisakusho Co., Ltd.) depending on the measurement conditions. In this measurement, a plate-like test piece (length = 45 mm, width = 4 mm, thickness = 2 mm) is formed from the rubber composition of the strip 22, filler 24 and apex 36. This test piece is used for measurement.
Initial strain: 10%
Amplitude: ± 2.0%
Frequency: 10Hz
Deformation mode: Tensile
Measurement temperature: 70 ° C

  In the present invention, the size and angle of each member of the tire 2 are measured in a state where the tire 2 is incorporated in a regular rim and the tire 2 is filled with air so as to have a regular internal pressure. Unless otherwise specified, no load is applied to the tire 2 during measurement. In the present specification, the normal rim means a rim defined in a standard on which the tire 2 depends. “Standard rim” in the JATMA standard, “Design Rim” in the TRA standard, and “Measuring Rim” in the ETRTO standard are regular rims. In the present specification, the normal internal pressure means an internal pressure defined in a standard on which the tire 2 relies. “Maximum air pressure” in JATMA standard, “Maximum value” published in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in TRA standard, and “INFLATION PRESSURE” in ETRTO standard are normal internal pressures.

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

[Example 1]
A tire having the configuration shown in FIG. 1 was produced. The tire size was LT265 / 75R16. “A” in the column of the apex position of the apex in the table represents a position radially inward from the first reference line L1 and outside the radially outer end of the rim flange. Between the first reference line L1 and the third reference line L3, the ratio of the filler area Sf to the tire area St (Sf / St) was 0.2. The thickness Ts of the strip at the first reference line L1 was 1.0 mm. The ratio (Hp−Hf) / Hp) of the difference (Hp−Hf) between the height Hp and the height Hf of the outer end of the filler with respect to Hp is the height of the outer end of the folded portion of the carcass ply. 0.22.

[Comparative Example 1]
Conventional commercial tires were prepared. “B” in the column of the apex position of the apex in the table represents a position radially outward from the first reference line L1. This tire does not include strips and fillers. In this tire, the area Sf represents the area of the apex between the first reference line L1 and the third reference line L3. The ratio (Sf / St) represents the ratio of the area of the apex to the area St. This ratio (Sf / St) was 0.4. Other configurations were the same as those in Example 1.

[Comparative Example 2]
A tire was obtained in the same manner as in Example 1 except that the tip position of the apex was changed to “B” as in Comparative Example 1.

[Comparative Example 3]
A tire was obtained in the same manner as in Example 1 except that the ratio (Sf / St) was set as shown in Table 1.

[Example 2]
A tire was obtained in the same manner as in Example 1 except that the ratio ((Hp−Hf) / Hp) was set as shown in Table 1.

[Example 3]
A tire was obtained in the same manner as in Example 1 except that the heat Ts of the strip was set as shown in Table 1.

[Example 4]
A tire was obtained in the same manner as in Example 1 except that the strip was not provided.

[Example 5]
A tire was obtained in the same manner as in Example 1 except that the apex tip position was as shown in Table 2. “C” in the column of apex position of the apex in the table represents a position on the radially inner side of the flange of the rim.

[durability]
A tire was incorporated into a regular rim, and the tire was filled with air to adjust the internal pressure to 550 kPa. This tire was mounted on a drum type running test machine, and a 20 kN longitudinal load was applied to the tire. This tire was run on the drum at a speed of 100 km / h. The tire was run for 30000 km to evaluate the durability. This durability is represented by an index in Table 1. This index is 100 when the race is complete. Tires damaged before completion are represented by an index based on the distance traveled at the time of failure. This index is preferable as the numerical value increases. Further, the tire after running was cut, and it was confirmed whether there was any damage such as peeling at the apex and carcass.

[Flat spot performance]
The tire was incorporated into a regular rim, and the radial force variation (RFV) of the tire was measured according to JASO C607. The air pressure inside the tire is 550 kPa. The initial RFV of this tire was measured. After the measurement of the initial RFV, the tire was pressed against a flat road surface for a predetermined time in a stationary state in which a load of 75% of the maximum load load was applied. Thereafter, the post-load RFV was measured. The difference in RFV was calculated by subtracting the initial RFV from the RFV after loading. The result is expressed as an index with the difference in RFV of Comparative Example 1 as 100. The smaller this index is, the smaller the difference in RFV is, and it is difficult to generate a flat spot.

[Steering stability]
The tires were assembled into regular rims and mounted on the rear wheels of the light truck. The tire was filled with air so that the internal pressure was 550 kPa. Commercial tires were mounted on the front wheels as they were. The front tire was filled with air so that the internal pressure was 340 kPa. With each of these tires loaded with a load of 11.38 kN, the driver was evaluated for steering stability. In this evaluation, the driver made a sensory evaluation by driving this light truck for 5 km. The results are shown in Table 1 below as an index. Steering stability was evaluated with the evaluation result of Comparative Example 1 as 100. These indices are more preferable as the numerical value is larger.

  In the durability test, no damage was confirmed in the tires of Examples 1, 2 and 4. In the tires of Comparative Examples 1 to 3 and Examples 3 and 5, looseness was confirmed at the folded portion of the apex and the carcass.

  As shown in Tables 1 and 2, the tire of the example is superior in flat spot performance as compared with the tire of the comparative example. Further, in the tire of the example, it is suppressed that durability and steering stability are impaired. From this evaluation result, the superiority of the present invention is clear.

  The method described above is widely applied to vehicles including passenger cars and the like, but is particularly suitable for tires loaded with a large load such as light trucks, trucks, buses and the like.

2 ... Tire 4 ... Tread 6 ... Sidewall 8 ... Clinch 10 ... Bead 12 ... Carcass 18 ... Inner liner 20 ... Chafer 22 ... Strip 24 ..Filler 34 ... Core 36 ... Apex 38 ... First ply 40 ... Second ply 46 ... Lumen surface 48 ... Rim 54 ... Flange 56 ... Seat Surface 58 ... Contact surface 60 ... Bent outer peripheral surface 62 ... Tire assembly 64 ... Outer surface

Claims (4)

It includes a tread, a pair of sidewalls, a pair of clinch, a pair of beads, a carcass and a pair of fillers,
Each sidewall extends radially inward from the end of the tread,
Each clinch is located radially inside the sidewall,
Each bead is located axially inside the clinch,
The bead includes a core and an apex extending radially outward from the core;
The carcass extends along the inside of the tread and the sidewall and spans between one bead and the other bead, and the carcass includes a carcass ply, and the carcass ply is around the core. Is folded from the inner side in the axial direction to the outer side, and a main part located on the inner side in the axial direction of the bead and a folded part located on the outer side in the axial direction of the bead are formed,
Each filler is located between the clinch and the folded portion in the axial direction,
The regular rim to be incorporated includes a flange, and the flange has a radially outer edge where the flange contacts the clinch and forms a bent outer peripheral surface that bends at a radius of curvature Rr.
A straight line that extends through the center point Pr of the radius of curvature Rr and inclines in the axial direction at an angle of 45 ° with respect to the axial direction from the radially inner side to the outer side is defined as a first reference line L1, and the center of the core A straight line parallel to the first reference line L1 through the second reference line L2, the first reference line L1 as the axis of symmetry, and a straight line symmetric with the second reference line L2 as the third reference line L3,
The filler extends from the inner side in the radial direction of the first reference line to the outer side in the radial direction of the third reference line in a state where 120% of the normal load is applied by being incorporated into the normal rim and adjusted to the normal internal pressure. The ratio of the filler area Sf between the first reference line L1 and the third reference line L3 to the tire area St between the first reference line L1 and the third reference line L3 (Sf / St) is 0.3 or less,
A pneumatic tire in which the tip of the apex is positioned closer to the core than the first reference line L1.   The tire according to claim 1, wherein a tip of the apex is positioned radially outward from a flange of a regular rim. When the height of the outer end of the folded portion of the carcass ply is Hp and the height of the outer end of the filler is Hf,
This height Hp is higher than the height Hf,
The ratio ((Hp-Hf) / Hp) of the difference (Hp-Hf) between the height Hp and the height Hf with respect to the height Hp is set to 0.05 or more. tire. With strips,
This strip is laminated to the apex,
The strip extends radially outward from the tip of the apex, and the outer end of the strip is located radially outward from the first reference line L1,
The tire according to any one of claims 1 to 3, wherein a thickness of the strip exceeds 0 and is 2 mm or less.

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