JP2017210077A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire 22 which achieves improvement in its durability by preventing rib tear.SOLUTION: This pneumatic tire 22 comprises a tread 24, a pair of side walls 26, a pair of beads 30, a carcass 32, a belt 34 and pair of cushion layers 40. The tread 24 comprises a base layer 54 and a cap layer 56 covering the base layer 54. The tread 24 comprises a main groove 48M extending in a circumferential direction. The main groove 48M overlaps with a part of a radial end 72 of the belt 34. A ratio of a thickness of the tire 22 which is measured along a normal line of the carcass 32 passing through the end of a tread surface 46 to a thickness of the tire 22 which is measured along an equatorial plane is 1.4 or more and 1.8 or less. An end 72 of the belt 34 is positioned on the normal line of the carcass 32 or positioned closer to an axial inside than the normal line of the carcass 32.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire. Specifically, the present invention relates to a heavy duty pneumatic tire mounted on a truck, a bus or the like.

  FIG. 3 shows a part of a conventional heavy-duty pneumatic tire 2 mounted on a vehicle such as a truck or a bus. FIG. 3 shows a cross section of the tread 4 portion of the tire 2.

  The tire 2 steps on the road surface in the tread 4. The tread 4 is usually provided with a main groove 6 extending in the circumferential direction from the viewpoint of drainage. A plurality of ribs 8 are formed on the tread 4 by carving a plurality of main grooves 6 aligned in the axial direction in the tread 4.

  The tire 2 supports the vehicle body. A load acts on the tire 2. In the tire 2 mounted on a truck, a bus or the like, the load acting on the tire 2 is considerably large.

  In the tread 4, the main groove 6 portion has a smaller thickness than the rib 8 portion. Distortion tends to concentrate on the bottom of the main groove 6. For this reason, when a wrinkle enters this bottom, the wrinkle becomes large, and the rib 8 may be torn in some cases. Thus, the damage that the rib 8 is torn is also referred to as “rib tear”. Such damage tends to occur in the heavy load tire 2 where a large load acts. In particular, rib tears are likely to occur in the ribs 8s located on the outer side in the axial direction, that is, the shoulder ribs 8s.

  Various studies have been made to prevent the occurrence of damage such as rib tears and improve durability. An example of this examination is disclosed in JP-A-2015-174469.

JP2015-174469A

  The tread 4 is generally composed of a base layer 10 and a cap layer 12 covering the base layer 10. The main groove 6 is cut into the cap layer 12. For this reason, the cap layer 12 is considerably thin at the bottom of the main groove 6. The cap layer 12 is made of a crosslinked rubber having excellent wear resistance, heat resistance, and grip properties. However, with the thin cap layer 12, it is not easy to prevent the occurrence of rib tears.

  In FIG. 3, a solid line LT is a carcass normal. The symbol PC is the intersection of this normal LT and the outer surface of the carcass 14. The normal line LT is orthogonal to the tangent line of the carcass 14 at the intersection point PC, and is a straight line passing through the end PT of the tread surface 16.

  A belt 18 is provided on the inner side in the radial direction of the tread 4. The end 20 of the belt 18 is usually located near the end PT of the tread surface 16. Specifically, the end 20 of the belt 18 is disposed on the outer side in the axial direction than the normal line LT of the carcass 14. The existence of the belt 18 is an obstacle to securing the thickness of the cap layer 12 at the bottom of the main groove 6 located on the outer side in the axial direction.

  An object of the present invention is to provide a pneumatic tire that prevents the occurrence of rib tear and has improved durability.

  The pneumatic tire according to the present invention includes a tread, a pair of sidewalls, a pair of beads, a carcass, a belt, and a pair of cushion layers. The tread includes a base layer and a cap layer that covers the base layer. The cap layer includes a tread surface that contacts the road surface. Each sidewall extends substantially inward in the radial direction from the end of the tread. Each bead is located radially inward of the sidewall. The carcass is stretched between one bead and the other bead along the inside of the tread and the sidewall. The belt is located between the tread and the carcass. Each cushion layer is located between the belt and the carcass. The tread includes a main groove extending in the circumferential direction. The main groove overlaps with an end portion of the belt in the radial direction. The ratio of the tire thickness measured along the carcass normal passing through the end of the tread surface to the tire thickness measured along the equator plane is 1.4 or more. 8 or less. The end of the belt is on the normal line of the carcass or located on the inner side in the axial direction from the normal line of the carcass.

  Preferably, in the pneumatic tire, the ratio of the thickness of the tire measured along the normal of the carcass to the radial distance from the end of the belt to the tread surface is 1.4 or more. 6 or less.

  Preferably, in the pneumatic tire, the ratio of the thickness of the tire measured along the normal line of the carcass to the thickness of the cushion layer is 6.0 or more and 12.0 or less.

  Preferably, in the pneumatic tire, the bottom of the main groove is located between the end of the belt and the end of the cushion layer located inside the end of the belt in the axial direction.

  Preferably, in this pneumatic tire, a ratio of the thickness of the cap layer to the thickness of the tread is 0.4 or more and 0.7 or less on a virtual straight line extending in the radial direction through the bottom of the main groove. is there.

  In the pneumatic tire according to the present invention, the thickness of the tire, which is measured along the normal line of the carcass passing through the end of the tread surface, is sufficiently secured, and the end of the belt is relative to the normal line of the carcass. Is placed in the proper position.

  In this tire, the tread has an appropriate thickness at the bottom of the main groove. In this tire, the bottom of the main groove is hardly damaged. Since the occurrence of rib tear is prevented, this tire is excellent in durability. According to the present invention, it is possible to obtain a pneumatic tire that prevents the occurrence of rib tears and achieves improved durability.

FIG. 1 is a cross-sectional view showing a part of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view showing a part of the tire of FIG. FIG. 3 is an enlarged cross-sectional view showing a part of a conventional pneumatic tire.

  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 22. In FIG. 1, the vertical direction is the radial direction of the tire 22, the horizontal direction is the axial direction of the tire 22, and the direction perpendicular to the paper surface is the circumferential direction of the tire 22. In FIG. 1, the alternate long and short dash line CL represents the equator plane of the tire 22. The shape of the tire 22 is symmetrical with respect to the equator plane except for the tread pattern.

  The tire 22 includes a tread 24, a pair of sidewalls 26, a pair of clinch 28, a pair of beads 30, a carcass 32, a belt 34, an inner liner 36, an insulation 38, a pair of cushion layers 40, a pair of chafers 42, and A pair of fillers 44 is provided. The tire 22 is a tubeless type. The tire 22 is attached to a truck, a bus or the like. The tire 22 is for heavy loads.

  The tread 24 has a shape protruding outward in the radial direction. The tread 24 forms a tread surface 46 that contacts the road surface. In FIG. 1, symbol PT is an end of the tread surface 46.

  As shown in FIG. 1, a groove 48 is cut in the tread 24 of the tire 22. The groove 48 forms a tread pattern.

  In the tire 22, the tread 24 includes a plurality of main grooves 48M. Each main groove 48M extends continuously in the circumferential direction. In FIG. 1, a double-headed arrow W represents the width of the main groove 48M. A double arrow D represents the depth of the main groove 48M.

  In the tire 22, the width W of the main groove 48 </ b> M is preferably set to 1% or more and 7% or less of the ground contact width from the viewpoint of drainage and securing the rigidity of the tread 24. The depth D of the main groove 48M is preferably 10.0 mm or more, and more preferably 12.0 mm or more, from the viewpoint of drainage and securing the rigidity of the tread 24. The depth D is preferably 22.0 mm or less, and more preferably 20.0 mm or less.

  In the present invention, the ground contact width is determined by applying a normal load to the tire 22 in a state where the tire 22 is incorporated in a normal rim (not shown) and the tire 22 is filled with air so as to have a normal internal pressure. It is represented by the maximum axial width of the contact surface obtained by setting the angle to 0 ° and grounding the tire 22 on a flat surface.

  In the present specification, the normal rim means a rim defined in a standard on which the tire 22 relies. “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 22 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.

  In the present specification, the normal load means a load defined in a standard on which the tire 22 relies. “Maximum value” published in “Maximum load capacity” in JATMA standard, “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in TRA standard, and “LOAD CAPACITY” in ETRTO standard are normal loads.

  In the tire 22, a plurality of main grooves 48 </ b> M are carved in the tread 24, thereby forming a plurality of land portions 50 arranged in parallel in the axial direction. The axial width of each land portion 50 is appropriately determined in consideration of the width, number, position, etc. of the main groove 48M.

  In the tire 22, each of these land portions 50 is configured by a single unit extending continuously in the circumferential direction. Such a land portion 50 is also referred to as a rib 52. The land portion 50 of the tire 22 includes a rib 52 extending in the circumferential direction. In the tire 22, the rib 52c positioned on the equator plane is also referred to as a center rib. The ribs 52s located outside in the axial direction are also referred to as shoulder ribs. The rib 52m located between the center rib 52c and the shoulder rib 52s is also referred to as a middle rib. In the tire 22, the land portion 50 may be configured by a plurality of blocks arranged in parallel in the circumferential direction by carving a plurality of grooves 48 extending substantially in the axial direction in the land portion 50.

  In the tire 22, the tread 24 has a base layer 54 and a cap layer 56. Specifically, the tread 24 of the tire 22 includes a base layer 54 and a cap layer 56. That is, the tread 24 is composed of two members.

  The cap layer 56 is located on the radially outer side of the base layer 54. The cap layer 56 is laminated on the base layer 54. The cap layer 56 covers the base layer 54. The base layer 54 is made of a crosslinked rubber having excellent adhesiveness. A typical base rubber of the base layer 54 is natural rubber. The cap layer 56 is made of a crosslinked rubber having excellent wear resistance, heat resistance, and grip properties.

  In the tire 22, the outer surface of the cap layer 56 is the tread surface 46 described above. The cap layer 56 has a tread surface 46. Further, as shown in FIG. 1, the main groove 48 </ b> M is cut in the cap layer 56. The main groove 48M does not cut the base layer 54. A cap layer 56 is located between the main groove 48M and the base layer 54.

  Each sidewall 26 extends substantially inward in the radial direction from the end of the tread 24. A radially outer portion of the sidewall 26 is joined to the tread 24. A radially inner portion of the sidewall 26 is joined to the clinch 28. The sidewall 26 is made of a crosslinked rubber having excellent cut resistance and weather resistance. This sidewall 26 prevents the carcass 32 from being damaged.

  Each clinch 28 is located substantially inside the sidewall 26 in the radial direction. The clinch 28 is located outside the bead 30 and the carcass 32 in the axial direction. The clinch 28 is made of a crosslinked rubber having excellent wear resistance. Although not shown, the clinch 28 contacts the rim flange.

  Each bead 30 is located inside the clinch 28 in the axial direction. As described above, the clinch 28 is positioned substantially inside the sidewall 26 in the radial direction. The bead 30 is located radially inward of the sidewall 26.

  The bead 30 includes a core 58 and an apex 60 that extends radially outward from the core 58. The core 58 is ring-shaped and includes a wound non-stretchable wire. A typical material for the wire is steel. The apex 60 is tapered outward in the radial direction. The apex 60 is made of a highly hard crosslinked rubber.

  The carcass 32 includes a carcass ply 62. In the tire 22, the carcass 32 includes a single carcass ply 62. The carcass 32 may be formed from two or more carcass plies 62.

  In the tire 22, the carcass ply 62 is stretched between the beads 30 on both sides, and extends along the inside of the tread 24, the sidewall 26, and the clinch 28. The carcass ply 62 is folded around the respective cores 58 from the inner side to the outer side in the axial direction. By this folding, the carcass ply 62 is formed with a main portion 62a and a pair of folded portions 62b. The carcass ply 62 includes a main portion 62a and a pair of folded portions 62b.

  Although not shown, the carcass ply 62 includes 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 32 has a radial structure. The cord material is steel. That is, the carcass ply 62 includes a steel cord.

  In the tire 22, the end of the folded portion 62 b is located between the outer end of the apex 60 and the core 58 in the radial direction. A large load acts on the bead 30 portion of the tire 22. The distortion tends to concentrate on the end of the folded portion 62b. In the tire 22, an inner side wall 64, an intermediate layer 66, and a strip 68 are further provided in the bead 30 portion. These suppress the concentration of distortion at the end of the folded portion 62b.

  The belt 34 is located inside the tread 24 in the radial direction. The belt 34 is laminated with the carcass 32. The belt 34 is located between the tread 24 and the carcass 32. The belt 34 reinforces the carcass 32. In the tire 22, the belt 34 includes a first layer 70a, a second layer 70b, a third layer 70c, and a fourth layer 70d. The first layer 70 a constitutes a radially inner portion of the belt 34. The second layer 70b is located on the radially outer side of the first layer 70a. The third layer 70c is located on the radially outer side of the second layer 70b. The fourth layer 70d is located on the radially outer side of the third layer 70c. In this tire 22, the belt 34 is composed of four layers. The belt 34 may be composed of three layers or may be composed of two layers. In the tire 22, the end 72 of the second layer 70b and the end 74 of the third layer 70c are covered with a cover rubber 76 (see FIG. 2).

  Although not shown, each of the first layer 70a, the second layer 70b, the third layer 70c, and the fourth layer 70d is made of a large number of cords arranged in parallel and a topping rubber. The material of each cord is steel. That is, the belt 34 includes a steel cord. In each layer, the cord is inclined with respect to the equator plane. The absolute value of the angle formed by this cord with respect to the equator plane is 15 ° to 70 °.

  As is apparent from FIG. 1, in the tire 22, the second layer 70b is the most of the first layer 70a, the second layer 70b, the third layer 70c, and the fourth layer 70d constituting the belt 34 in the axial direction. It has a large width. In the tire 22, the layer having the largest axial width among the plurality of layers constituting the belt 34, that is, the end 72 of the second layer 70 b is the end of the belt 34. In the tire 22, the axial width of the belt 34 is represented by the axial width of the second layer 70b.

  In the tire 22, the end 72 of the belt 34 is positioned in the vicinity of the end PT of the tread surface 46 in the axial direction. The belt 34 contributes to the rigidity of the tread 24 portion of the tire 22. In the tire 22, the tread surface 46 is in sufficient contact with the road surface. From this point of view, the belt 34 needs a certain axial width. However, when the belt 34 has a large axial width, the end 72 of the belt 34 is close to the outer surface of the tire 22. In this case, the volume of rubber that wraps around the end 72 of the belt 34 becomes insufficient, and damage may occur at the end 72 of the belt 34. From this point of view, the axial width of the belt 34 needs to be maintained appropriately.

  In FIG. 1, the arrow WT is the axial length from the equator plane to the end PT of the tread surface 46. This length WT corresponds to half of the axial width of the tread surface 46. The arrow WB is the axial length from the equator plane to the end 72 of the belt 34. This length WB corresponds to half the axial width of the belt 34.

  In the tire 22, the ratio of the width WB to the width WT, that is, the ratio of the axial width of the belt 34 to the axial width of the tread surface 46 is preferably 0.65 or more, and preferably 0.90 or less. By setting this ratio to 0.65 or more, the belt 34 can effectively contribute to the rigidity of the tread 24. In this respect, the ratio is more preferably equal to or greater than 0.70. By setting this ratio to 0.90 or less, the end 72 of the belt 34 is disposed at an appropriate position. As a result, a sufficient volume of rubber for wrapping the end 72 of the belt 34 is secured. In the tire 22, damage at the end 72 of the belt 34 is effectively suppressed. In this respect, the ratio is more preferably equal to or less than 0.85.

  The inner liner 36 is located inside the carcass 32. The inner liner 36 is made of a crosslinked rubber having excellent air shielding properties. A typical base rubber of the inner liner 36 is butyl rubber or halogenated butyl rubber. The inner liner 36 maintains the internal pressure of the tire 22.

  The insulation 38 is sandwiched between the carcass 32 and the inner liner 36. The insulation 38 is made of a crosslinked rubber having excellent adhesiveness. The insulation 38 is firmly joined to the carcass 32 and is also firmly joined to the inner liner 36. The insulation 38 prevents the inner liner 36 from being peeled off from the carcass 32.

  Each cushion layer 40 is laminated with the carcass 32 in the vicinity of the end 72 of the belt 34. As shown in FIG. 1, the portion of one end 78 of the cushion layer 40 is located between the belt 34 and the carcass 32. The cushion layer 40 is made of a soft crosslinked rubber. The cushion layer 40 absorbs stress at the end 72 of the belt 34. The cushion layer 40 suppresses the lifting of the belt 34.

  Each chafer 42 is located in the vicinity of the bead 30. Although not shown, when the tire 22 is incorporated in the rim, the chafer 42 contacts the rim. By this contact, the vicinity of the bead 30 is protected. In this embodiment, the chafer 42 is integral with the clinch 28. Accordingly, the material of the chafer 42 is the same as that of the clinch 28. The chafer 42 may be made of a cloth and rubber impregnated in the cloth.

  Each filler 44 is located near the bead 30. The filler 44 is laminated with the carcass 32. The filler 44 is folded around the core 58 of the bead 30 on the radially inner side of the carcass 32. Although not shown, the filler 44 is composed of a large number of cords arranged in parallel and a topping rubber. Each cord is inclined with respect to the radial direction. The cord material is steel. The filler 44 can suppress the collapse of the bead 30 portion. The filler 44 contributes to the durability of the tire 22. In the tire 22, the end of the filler 44 is covered with a cover rubber 80.

  FIG. 2 shows a part of the tire 22 of FIG. In FIG. 2, the vertical direction is the radial direction of the tire 22, the horizontal direction is the axial direction of the tire 22, and the direction perpendicular to the paper surface is the circumferential direction of the tire 22.

  As described above, in the tire 22, the tread 24 includes the plurality of main grooves 48M. These main grooves 48M are arranged in parallel in the axial direction. In the present invention, of the plurality of main grooves 48M provided in the tread 24, the main groove 48M positioned on the outer side in the axial direction is referred to as a shoulder main groove 48MS. As shown in FIG. 2, the shoulder main groove 48MS overlaps with the end 72 portion of the belt 34 in the radial direction.

  In the present invention, the length of the end 72 of the belt 34 from the end 72 of the belt 34 (the length indicated by the double arrow W45 in FIG. 2) corresponds to 45% of the axial length WB. It means a zone from the position (position indicated by reference sign P45 in FIG. 2) to the end 72 of the belt 34.

  In FIG. 2, the double arrow WS is the axial length from the equator plane to the bottom of the shoulder main groove 48M. The ratio of this length WS to the axial length WB from the equator plane to the end 72 of the belt 34 is 0.6 or more and 0.9 or less. More specifically, this ratio is 0.7 or more and 0.8 or less.

  In FIG. 2, the solid line LT is a normal line of the carcass 32. Reference sign PC is an intersection of the normal LT and the outer surface of the carcass 32. The normal line LT is orthogonal to the tangent line of the carcass 32 at the intersection point PC, and is a straight line passing through the end PT of the tread surface 46. A double-pointed arrow TS represents the thickness of the tire 22 measured along the normal line LT of the carcass 32 that passes through the end PT of the tread surface 46. A double-headed arrow TQ is the thickness of the tire 22 measured along the equator plane.

  In the tire 22, the thickness TS measured along the normal line LT of the carcass 32 passing through the end PT of the tread surface 46 is sufficiently secured. Specifically, the ratio of the thickness TS measured along the normal line LT to the thickness TQ measured along the equator plane is 1.4 or more. By setting this ratio to 1.4 or more, the rubber volume at the end 72 of the belt 34 is sufficiently secured. In the tire 22, the end 72 of the belt 34 can be disposed sufficiently away from the tread surface 46. In the tire 22, the tread 24 having an appropriate thickness can be formed at the bottom portion of the shoulder main groove 48MS. In the tread 24, the bottom of the shoulder main groove 48MS is hardly damaged. Moreover, since rubber having a sufficient volume is secured at the end 72 of the belt 34, the shoulder rib 52s having sufficient rigidity is formed. In the tire 22, even if an excessive force acts on the bottom of the shoulder main groove 48MS, the shoulder rib 52s suppresses deformation at the bottom. In the tire 22, occurrence of damage at the bottom is more effectively suppressed. In the tire 22, rib tear is unlikely to occur. The tire 22 is excellent in durability.

  In the tire 22, the ratio of the thickness TS to the thickness TQ is 1.8 or less. By setting this ratio to 1.8 or less, the rubber volume covering the end 72 of the belt 34 is appropriately maintained. In the tire 22, heat accumulation at the end 72 of the belt 34 is suppressed. Since heat does not accumulate easily, loose-like damage is unlikely to occur at the end 72 of the belt 34. In the tire 22, good durability is maintained.

  In the tire 22, the end 72 of the belt 34 is disposed at an appropriate position with respect to the normal line LT of the carcass 32. Specifically, the end 72 of the belt 34 is on the normal line LT of the carcass 32 or is located on the inner side in the axial direction from the normal line LT of the carcass 32. In the tire 22, the movement of the end 72 of the belt 34 in the running state is more effective than the conventional tire 2 in which the end 72 of the belt 34 is disposed on the axially outer side than the normal line LT of the carcass 32. It can be suppressed. In the tire 22, although the rubber volume at the end 72 of the belt 34 is sufficiently secured, damage at the end 72 is effectively suppressed. In addition, as compared with the conventional tire 2, disposing the end 72 of the belt 34 away from the tread surface 46 effectively contributes to securing the thickness of the bottom portion of the shoulder main groove 48MS. In the tire 22, the tread 24 having an appropriate thickness can be easily formed in the bottom portion of the shoulder main groove 48MS. In the tire 22, occurrence of damage at the bottom of the shoulder main groove 48MS is more effectively suppressed. In the tire 22, rib tear is unlikely to occur. The tire 22 is excellent in durability.

  As described above, in the tire 22, the thickness TS of the tire 22 measured along the normal LT of the carcass 32 passing through the end PT of the tread surface 46 is sufficiently secured, and the belt 34 The end 72 is disposed at an appropriate position with respect to the normal line LT of the carcass 32.

  In the tire 22, the tread 24 has an appropriate thickness at the bottom of the main groove 48M. In the tire 22, the bottom of the main groove 48M is hardly damaged. Since the occurrence of rib tear is prevented, the tire 22 is excellent in durability. According to the present invention, it is possible to obtain the pneumatic tire 22 in which the occurrence of rib tear is prevented and the improvement in durability is achieved.

  In FIG. 2, a double-headed arrow TE is a radial distance from the end 72 of the belt 34 to the tread surface 46. A double arrow TR is the thickness of the cushion layer 40. This thickness TR is represented by the maximum thickness among the thicknesses measured along the normal line of the inner surface of the cushion layer 40. The cushion layer 40 tapers substantially inward in the axial direction from the position indicating the thickness TR, and the cushion layer 40 tapers outward substantially in the axial direction from the position indicating the thickness TR.

  In the tire 22, one end 78 of the cushion layer 40 is positioned on the inner side in the axial direction from the bottom of the shoulder main groove 48MS. The cushion layer 40 effectively absorbs stress acting on the end 72 portion of the belt 34. In the tire 22, the movement of the end 72 is effectively suppressed. In the tire 22, damage such as loose is effectively suppressed. Since the shoulder main groove 48MS overlaps the cushion layer 40 in the radial direction, the cushion layer 40 effectively absorbs stress acting on the bottom of the shoulder main groove 48MS. In the tire 22, damage is unlikely to occur at the bottom of the shoulder main groove 48MS. From this point of view, in the tire 22, one end 78 of the cushion layer 40 is preferably located on the inner side in the axial direction from the bottom of the shoulder main groove 48MS.

  In the tire 22, the ratio of the thickness TS measured along the normal LT of the carcass 32 passing through the end PT of the tread surface 46 with respect to the distance TE is preferably 1.4 or more, and preferably 1.6 or less. By setting this ratio to 1.4 or more, the cushion layer 40 having a sufficient thickness can be configured. The cushion layer 40 effectively absorbs the stress at the end 72 of the belt 34. In the tire 22, loose damage is unlikely to occur at the end 72 of the belt 34. In the tire 22, good durability is maintained. By setting this ratio to 1.6 or less, the end 72 of the belt 34 can be disposed sufficiently away from the tread surface 46. In the tire 22, a tread 24 having an appropriate thickness is formed at the bottom of the shoulder main groove 48MS. In the tire 22 having the tread 24, the bottom of the shoulder main groove 48MS is hardly damaged. In the tire 22, rib tear is unlikely to occur. The tire 22 is excellent in durability.

  In the tire 22, the ratio of the distance TE to the thickness TQ measured along the equator plane is preferably 0.8 or more, and preferably 1.2 or less. By setting this ratio to 0.8 or more, the end 72 of the belt 34 can be disposed sufficiently away from the tread surface 46. In the tire 22, a tread 24 having an appropriate thickness is formed at the bottom of the shoulder main groove 48MS. In the tire 22 having the tread 24, the bottom of the shoulder main groove 48MS is hardly damaged. In the tire 22, rib tear is unlikely to occur. The tire 22 is excellent in durability. In this respect, the ratio is more preferably equal to or greater than 0.82 and still more preferably equal to or greater than 0.84. By setting this ratio to 1.2 or less, the cushion layer 40 having a sufficient thickness can be configured. The cushion layer 40 effectively absorbs the stress at the end 72 of the belt 34. In the tire 22, loose damage is unlikely to occur at the end 72 of the belt 34. In the tire 22, good durability is maintained. From this viewpoint, the ratio is more preferably 1.18 or less, and further preferably 1.08 or less.

  In the tire 22, the ratio of the thickness TS measured along the normal line LT of the carcass 32 passing through the end PT of the tread surface 46 to the thickness TR is preferably 6.0 or more, and preferably 12.0 or less. . By setting this ratio to 6.0 or more, the thickness TR of the cushion layer 40 is appropriately maintained, so that the end 72 of the belt 34 can be disposed sufficiently away from the tread surface 46. In the tire 22, a tread 24 having an appropriate thickness is formed at the bottom of the shoulder main groove 48MS. In the tire 22 having the tread 24, the bottom of the shoulder main groove 48MS is hardly damaged. In the tire 22, rib tear is unlikely to occur. The tire 22 is excellent in durability. By setting this ratio to 12.0 or less, the cushion layer 40 having a sufficient thickness can be configured. The cushion layer 40 effectively absorbs the stress at the end 72 of the belt 34. In the tire 22, loose damage is unlikely to occur at the end 72 of the belt 34. In the tire 22, good durability is maintained.

  In the tire 22, the ratio of the thickness TR to the thickness TQ measured along the equator plane is preferably 0.1 or more, and preferably 0.3 or less. By setting this ratio to 0.1 or more, the cushion layer 40 having a sufficient thickness can be configured. The cushion layer 40 effectively absorbs the stress at the end 72 of the belt 34. In the tire 22, loose damage is unlikely to occur at the end 72 of the belt 34. In the tire 22, good durability is maintained. In this respect, the ratio is more preferably equal to or greater than 0.11 and still more preferably equal to or greater than 0.13. By setting this ratio to 0.3 or less, the thickness TR of the cushion layer 40 is appropriately maintained, so that the end 72 of the belt 34 can be disposed sufficiently away from the tread surface 46. In the tire 22, a tread 24 having an appropriate thickness is formed at the bottom of the shoulder main groove 48MS. In the tire 22 having the tread 24, the bottom of the shoulder main groove 48MS is hardly damaged. In the tire 22, rib tear is unlikely to occur. The tire 22 is excellent in durability. In this respect, the ratio is more preferably equal to or less than 0.24, and still more preferably equal to or less than 0.22.

  In FIG. 2, the double arrow TG is the thickness of the tread 24 at the bottom of the shoulder main groove 48MS. A double arrow TC is the thickness of the cap layer 56 at the bottom of the shoulder main groove 48MS. The thickness TG and the thickness TC are measured along a virtual straight line that passes through the bottom of the shoulder main groove 48MS and extends in the radial direction.

  In the tire 22, the ratio of the thickness TC of the cap layer 56 to the thickness TG of the tread 24 is preferably 0.4 or more on a virtual straight line extending in the radial direction through the bottom of the shoulder main groove 48MS, and 0.7 or less. Is preferred. By setting this ratio to 0.4 or more, the cap layer 56 having a sufficient thickness is formed at the bottom of the shoulder main groove 48MS. In the tire 22, the cap layer 56 prevents damage at the bottom of the shoulder main groove 48MS. In the tire 22, damage is unlikely to occur at the bottom of the shoulder main groove 48MS. In the tire 22, rib tear is unlikely to occur. The tire 22 is excellent in durability. By setting this ratio to 0.7 or less, the thickness of the base layer 54 is appropriately maintained. As described above, the base layer 54 is made of a crosslinked rubber having excellent adhesiveness. In the tire 22, the cap layer 56 is sufficiently bonded to the belt 34 through the base layer 54. In the tire 22, damage is unlikely to occur between the tread 24 and the belt 34. The tire 22 is excellent in durability.

  In the tire 22, the thickness TC of the cap layer 56 at the bottom of the shoulder main groove 48MS is preferably 3.5 mm or more, and preferably 7.5 mm or less. By setting the thickness TC to be 3.5 mm or more, the cap layer 56 contributes to preventing the occurrence of damage at the bottom of the shoulder main groove 48MS. In the tire 22, damage is unlikely to occur at the bottom of the shoulder main groove 48MS. In the tire 22, rib tear is unlikely to occur. The tire 22 is excellent in durability. By setting the thickness TC to 7.5 mm or less, the cushion layer 40 having a sufficient thickness can be configured. The cushion layer 40 effectively absorbs the stress at the end 72 of the belt 34. In the tire 22, loose damage is unlikely to occur at the end 72 of the belt 34. In the tire 22, good durability is maintained.

  In FIG. 2, a double-headed arrow D is an axial distance from the end 72 of the belt 34 to the normal line LT of the carcass 32 passing through the end PT of the tread surface 46. The double arrow TB is the thickness of the base layer 54 measured along the normal line LT of the carcass 32.

  As described above, in the tire 22, the end 72 of the belt 34 is on the normal line LT of the carcass 32 or is located on the inner side in the axial direction from the normal line LT of the carcass 32. Therefore, in the tire 22, the distance D is 0 mm or more. As a result, in the tire 22, the movement of the end 72 of the belt 34 in the running state is greater than that of the conventional tire 22 in which the end 72 of the belt 34 is disposed on the outer side in the axial direction than the normal line LT of the carcass 32. Effectively suppressed. In the tire 22, although the rubber volume at the end 72 of the belt 34 is sufficiently secured, damage at the end is effectively suppressed. In addition, as compared with the conventional tire 22, disposing the end 72 of the belt 34 away from the tread surface 46 effectively contributes to securing the thickness of the bottom portion of the shoulder main groove 48MS. In the tire 22, the tread 24 having an appropriate thickness can be easily formed in the bottom portion of the shoulder main groove 48MS. In the tire 22, occurrence of damage at the bottom of the shoulder main groove 48MS is more effectively suppressed. In the tire 22, rib tear is unlikely to occur. The tire 22 is excellent in durability. From this viewpoint, the distance D is preferably 3 mm or more, and more preferably 5 mm or more. The large distance D affects the axial width of the belt 34. From the viewpoint that a belt 34 having an appropriate axial width is obtained and this belt 34 effectively contributes to the rigidity of the portion of the tread 24, the distance D is preferably 30 mm or less, and more preferably 20 mm or less.

  In the tire 22, since the end 72 of the belt 34 is disposed away from the tread surface 46, the cap layer 56 having a sufficient volume can be formed between the base layer 54 and the main groove 48 </ b> M. For this reason, unlike the conventional tire 2, a recess in which the shape of the bottom of the main groove 6 is reflected in the base layer 10 is not formed. In the tire 22, the outer surface of the base layer 54 is generally flat. Specifically, as shown in FIG. 2, the boundary between the base layer 54 and the cap layer 56 extends linearly from the equator plane toward the end 72 of the belt 34.

  As shown in FIG. 2, the base layer 54 covers the entire belt 34. In the tire 22, the width of the belt 34 in the axial direction is smaller than that of the conventional tire 2 in which the end 72 of the belt 34 is disposed outside the normal line LT of the carcass 32 in the axial direction. Moreover, the cushion layer 40 has a smaller thickness TR than the conventional tire 2. For this reason, in the tire 22, the volume of the base layer 54 covering the end 72 of the belt 34 is smaller than that of the conventional tire 2. Since the volume of the base layer 54 is small at the end 72 of the belt 34, in the tire 22, substantially the entire shoulder rib 52 s is constituted by the cap layer 56. Such a configuration contributes to the rigidity of the shoulder rib 52s. In the tire 22, even if an excessive force acts on the bottom of the shoulder main groove 48MS, the shoulder rib 52s suppresses deformation at the bottom. In the tire 22, occurrence of damage at the bottom is more effectively suppressed. In the tire 22, rib tear is unlikely to occur. The tire 22 is excellent in durability.

  In the tire 22, the base layer 54 measured along the normal LT of the carcass 32 from the viewpoint that substantially the entire shoulder rib 52s is constituted by the cap layer 56 and the shoulder rib 52s having appropriate rigidity is obtained. The ratio of the thickness TB to the thickness TS measured along the normal LT of the carcass 32 passing through the end PT of the tread surface 46 is preferably 0.1 or less.

  In the present invention, the size and angle of each member of the tire 22 are measured in a state where the tire 22 is incorporated in a regular rim and filled with air so as to have a regular internal pressure unless otherwise specified. During the measurement, no load is applied to the tire 22. In the case of the passenger car tire 22, unless otherwise specified, the dimensions and angles are measured in a state where the internal pressure is 180 kPa.

  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]
The tire shown in FIG. 1 was manufactured. The size of this tire is 11R22.5. In Example 1, as shown in the “Configuration” column of Table 1, the configuration shown in FIG. 2 was adopted as the configuration of the end portion of the belt. In Example 1, the belt was configured such that the end thereof was positioned on the inner side in the axial direction from the normal line LT of the carcass. This is indicated by “in” in the “belt end position” column of Table 1.

  In Example 1, the ratio of the tire thickness TS measured along the carcass normal LT passing through the end of the tread surface to the tire thickness TQ measured along the equator plane (TS / TQ ) Was 1.38. The ratio of the thickness TS to the radial distance TE from the end of the belt to the tread surface (TS / TE) was 1.52. The ratio of the thickness TS to the thickness TR of the cushion layer (TS / TR) was 7.85. On the imaginary straight line extending in the radial direction through the bottom of the shoulder main groove MS, the ratio (TC / TG) of the cap layer thickness TC to the tread thickness TG was 0.5. The ratio (WB / WT) of the axial length WB from the equator plane to the belt end to the axial length WT from the equator plane to the end PT of the tread surface was 0.80.

[Example 2]
Example except that the end of the belt is arranged on the normal LT of the carcass and the ratio (TS / TE), ratio (TS / TR) and ratio (WB / WT) are as shown in Table 1 below. In the same manner as in Example 1, a tire of Example 2 was obtained. The fact that the end of the belt is arranged on the normal line LT of the carcass is indicated by “on” in the “belt end position” column of Table 1.

[Comparative Example 1]
The configuration of the end portion of the belt is the configuration shown in FIG. 3, and the end of the belt is disposed on the axially outer side from the normal line LT of the carcass, and the ratio (TS / TQ), ratio (TS / TE), ratio A tire of Comparative Example 1 was obtained in the same manner as in Example 1 except that (TS / TR) and ratio (WB / WT) were as shown in Table 1 below. The adoption of the configuration shown in FIG. 3 at the end of the belt is shown as “FIG. 3” in the “Configuration” column of Table 1. The fact that the end of the belt is arranged on the outer side in the axial direction from the normal line LT of the carcass is represented by “out” in the “belt end position” column of Table 1.

[Example 3-6 and Comparative Example 2-3]
Example 3-6 and Comparative Example were the same as Example 1 except that the ratio (TS / TQ), ratio (TS / TE) and ratio (WB / WT) were as shown in Table 2 below. A 2-3 tire was obtained.

[Example 7-12]
Tires of Examples 7-12 were obtained in the same manner as Example 1 except that the ratio (TS / TE) and ratio (TS / TR) were as shown in Table 3 below.

[Examples 13-15]
Tires of Examples 13-16 were obtained in the same manner as in Example 1 except that the ratio (TC / TG) was as shown in Table 4 below.

[durability]
The tire was assembled in a rim (size = 22.5 × 8.25), and the tire was filled with air so that the internal pressure was 720 kPa. This tire was mounted on the driving wheel of a truck (2-DD-44 car). A load (10 tons) was loaded on the truck bed and this truck was run on the circuit course. After traveling 10,000 km, the tires were collected and checked for the occurrence of damage such as rib tear and loose. If damage was found, the number and size of the damage was confirmed. The results are shown in the following Table 1-4 as an index with Comparative Example 1 taken as 100. The larger the value, the less the occurrence of damage and the better the durability.

  As shown in Table 1-4, the tire of the example has a higher evaluation than the tire of the comparative example. From this evaluation result, the superiority of the present invention is clear.

  The technology for preventing the occurrence of rib tear as described above can be applied to various tires.

2, 22 ... Tire 4, 24 ... Tread 6, 48M, 48MS ... Main groove 8, 8s, 52, 52c, 52m, 52s ... Rib 10, 54 ... Base layer 12, 56 ... Cap layer 14, 32 ... Carcass 16, 46 ... Tread surface 18, 34 ... Belt 20 ... End of belt 18 26 ... Side wall 28 ... Clinch 30 ... Bead 40 ... Cushion layer 48 ... Groove 50 ... Land part 62 ... Carcass ply 70a, 70b, 70c, 70d ... Layer 72 ... End of second layer 70b (end of belt 34) )
74: end of the third layer 70c 78 ... one end of the cushion layer 40

Claims (5)

It includes a tread, a pair of sidewalls, a pair of beads, a carcass, a belt, and a pair of cushion layers.
The tread includes a base layer and a cap layer covering the base layer,
The cap layer has a tread surface that comes into contact with the road surface,
Each sidewall extends radially inward from the end of the tread,
Each bead is located radially inward of the sidewall,
The carcass is stretched between one bead and the other bead along the inside of the tread and the sidewall,
The belt is located between the tread and the carcass;
Each cushion layer is located between the belt and the carcass,
The tread has a main groove extending in the circumferential direction,
The main groove overlaps with the end portion of the belt in the radial direction;
The ratio of the tire thickness measured along the carcass normal passing through the end of the tread surface to the tire thickness measured along the equator plane is 1.4 or more. 8 or less,
A pneumatic tire in which an end of the belt is on a normal line of the carcass or is located on an inner side in an axial direction from the normal line of the carcass.   The ratio of the thickness of the tire measured along the carcass normal to the radial distance from the belt end to the tread surface is 1.4 or more and 1.6 or less. The described pneumatic tire.   The pneumatic tire according to claim 1 or 2, wherein a ratio of the thickness of the tire measured along the normal of the carcass to the thickness of the cushion layer is 6.0 or more and 12.0 or less. .   The bottom of the main groove is located between the end of the belt and the end of the cushion layer located inside the end of the belt in the axial direction. The described pneumatic tire.   5. The ratio of the thickness of the cap layer to the thickness of the tread is not less than 0.4 and not more than 0.7 on a virtual straight line extending in the radial direction through the bottom of the main groove. The pneumatic tire according to Crab.

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