JP2018154164A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire 2 having improved riding comfort and durability during run-flat running. SOLUTION: In this tire 2, the length of Apex 38 is 20 mm or less. The buffer layer 24 is located between the carcass 12 and the clinch 8 in the axial direction. In the radial direction, the position of the inner end 48 of the buffer layer 24 coincides with the position of the outer end 50 of the core 36, or the inner end 48 of the buffer layer 24 is located outside the outer end 50 of the core 36. .. The outer end 52 of the buffer layer 24 is located near the outer end 34 of the clinch 8 in the radial direction. The cushioning layer 50 is arranged so as to cover the portion where the tire 2 and the rim R are in contact with each other. The loss tangent of the buffer layer 24 is lower than the loss tangent of the clinch 8, and the hardness of the buffer layer 24 is lower than the hardness of the clinch 8. [Selection diagram] Fig. 2

Description

  The present invention relates to a pneumatic tire.

  In recent years, run-flat tires having a load support layer inside a sidewall have been developed and are becoming popular. This run flat tire is called a side reinforcement type. In this type of run-flat tire, when the internal pressure is reduced by puncture, the support layer supports the vehicle weight. Run-flat tires can travel a certain distance even in a puncture state. Various studies have been conducted on run-flat tires. An example of this study is disclosed in Japanese Patent Application Laid-Open No. 2015-067256.

JP2015-0667256

  A load is periodically applied to the tire in the running state. As a result, deformation and restoration are repeated. In a run flat tire, the degree of deformation of the bead portion is large, and damage occurs not in the side wall portion but in the bead portion during running in a puncture state (hereinafter also referred to as run flat running). There is.

  An apex having a large width contributes to the rigidity of the bead portion. By adopting this apex, deformation of the bead portion can be suppressed. Suppression of deformation contributes to damage prevention. The apex is laminated on the core. For this reason, the width of the apex is limited by the width of the core. If the apex width is adjusted, the rigidity may not be sufficiently controlled.

  A long apex also contributes to the rigidity of the bead portion. Apex usually has a tapered shape. For this reason, the contribution to the rigidity by the tip portion of the apex is surprisingly small. With a long apex, deformation of the bead portion may not be sufficiently suppressed.

  In a tire, stress tends to concentrate on a portion that contacts the rim. This part is easily heated by deformation and restoration repeated in the run-flat running. Heat generation may impair durability.

  In the run-flat tire, a highly hard crosslinked rubber is used for the support layer. For this reason, compared with the tire which does not have this support layer, this tire is inferior to riding comfort.

  An object of the present invention is to provide a pneumatic tire in which ride comfort and durability in run-flat running are improved.

  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, a pair of load support layers, and a pair of buffer layers. Each sidewall extends substantially inward in the radial direction from the end of the tread. Each clinch extends substantially inward in the radial direction from the end of the sidewall, and the outer end of the clinch is located inside the maximum width position of the tire in the radial direction. Each bead is located axially inward of the clinch, and the bead includes a core and an apex, and the apex extends from the core substantially outward in the radial direction. Is 20 mm or less in length. The carcass is stretched between one bead and the other bead along the inside of the tread and the sidewall. Each load supporting layer is located inside the sidewall in the axial direction. Each buffer layer is located between the carcass and the clinch in the axial direction, and in the radial direction, the position of the inner end of the buffer layer coincides with the position of the outer end of the core, or The inner end of the buffer layer is located outside the outer end of the core. The ratio of the radial distance from the bead base line to the outer end of the buffer layer to the radial distance from the bead base line to the outer end of the clinch is 85% or more and 105% or less. The position where the radial direction height of the outer surface of the tire is 14 mm from the bead base line is defined as a first point P1, and the position of the outer surface of the tire where the radial direction height from the bead base line is 20 mm is the first point P1. When it is set as two points P2, the said buffer layer has overlapped with each of the said 1st point P1 and the 2nd point P2 in the radial direction. The loss tangent of the buffer layer is lower than the loss tangent of the clinch, and the hardness of the buffer layer is lower than the hardness of the clinch.

  Preferably, in the pneumatic tire, a ratio of a radial distance from the bead base line to the inner end of the buffer layer to a radial distance from the bead base line to the outer end of the core is 150% or less.

  Preferably, in this pneumatic tire, the hardness of the buffer layer is lower than the hardness of the apex.

  Preferably, in this pneumatic tire, the loss tangent of the buffer layer is equal to or lower than the loss tangent of the load support layer.

  Preferably, in the pneumatic tire, when the normal of the outer surface of the tire at the second point P2 is a reference normal, each of the buffer layer and the clinch measured along the reference normal The thickness is 1 mm or more.

  More preferably, in the pneumatic tire, the load support measured along the reference normal is a total thickness of the buffer layer and the clinch measured along the reference normal. The ratio to the layer thickness is 80% or more and 120% or less.

  In the pneumatic tire according to the present invention, a small apex is employed. In this tire, the apex is disposed outside the region where distortion is concentrated in the puncture state. In this tire, the deformation of the apex is effectively suppressed.

  In this tire, a buffer layer is provided between the carcass and the clinch. This buffer layer has a low loss tangent compared to clinch. This buffer layer is disposed in an appropriate position and in an appropriate size in consideration of a region where strain is concentrated. In this tire, heat generation due to deformation of the bead portion is effectively suppressed. In particular, in this tire, heat generation between the contact surface with the rim and the carcass can be suppressed. Further, the buffer layer is arranged such that the position of the carcass in the bead portion is located on the inner side in the axial direction than that of the conventional tire without the buffer layer. This carcass is less likely to concentrate distortion. In this tire, damage at the bead portion is prevented. In this tire, a sufficient traveling distance is ensured even when the internal pressure is reduced by the puncture.

  In this tire, the buffer layer is softer than the clinch. This buffer layer contributes to cushioning of the bead portion during normal running. With this tire, a good ride comfort is achieved. Further, in this tire, the buffer layer is prevented from protruding greatly from the clinch in the radial direction. In this tire, the influence on the riding comfort by the buffer layer is effectively suppressed. This tire is excellent in ride comfort.

  This tire is excellent in ride comfort and durability in run-flat running. ADVANTAGE OF THE INVENTION According to this invention, the pneumatic tire in which the improvement in riding comfort and durability in run-flat running was achieved is obtained.

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.

  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. The shape of the tire 2 is symmetrical with respect to the equator plane except for the tread pattern.

  In FIG. 1, a tire 2 is incorporated in a rim R. This rim R is a regular rim. The tire 2 is filled with air. Thereby, the internal pressure of the tire 2 is adjusted to the normal internal pressure.

  Unless otherwise specified, the dimensions and angles of the members of the tire 2 are measured in a state where the tire 2 is incorporated in a normal rim and the tire 2 is filled with air so as to have a normal internal pressure. At the time of measurement, no load is applied to the tire 2. When the tire 2 is for a passenger car, the dimensions and angles are measured in a state where the internal pressure is 180 kPa.

  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.

  In the present specification, the normal load means a load defined in a standard on which the tire 2 depends. “Maximum value” published in “Maximum load capacity” in the JATMA standard, “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the TRA standard, and “LOAD CAPACITY” in the ETRTO standard are normal loads.

  In FIG. 1, a solid line BBL is a bead base line. This bead base line is a line that defines the rim diameter (see JATMA) of the rim R on which the tire 2 is mounted. The bead baseline extends in the axial direction.

  In FIG. 1, the symbol PW represents a specific position on the outer surface of the tire 2. The tire 2 exhibits the maximum axial width at the position PW. This position PW is the maximum width position of the tire 2. When the outer surface of the tire 2 is provided with irregularities such as grooves and dimples, the aforementioned position PW is determined based on a virtual outer surface obtained by assuming that there are no irregularities, that is, a profile. In the present invention, the tire 2 is incorporated into the rim R, and the tire 2 is filled with air so as to have a normal internal pressure, and the outer surface of the tire 2 in a state where no load is applied to the tire 2 is the profile. Based on.

  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 pair of load support layers 14, a belt 16, a band 18, an inner liner 20, a pair of chafers 22, and A pair of buffer layers 24 are provided. The tire 2 is composed of a number of parts. The tire 2 is a tubeless type. The tire 2 is mounted on a passenger car.

  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 portion of the sidewall 6 is joined to the tread 4. The radially inner portion 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.

  In this tire, the hardness Hs of the sidewall 6 is preferably 50 or greater and 75 or less. By setting the hardness Hs to 50 or more, the sidewall 6 contributes to the rigidity. In the tire 2, the side wall 6 is flexibly bent. In this respect, the hardness Hs is more preferably equal to or greater than 55. By setting the hardness Hs to 75 or less, the influence of the sidewall 6 on the rigidity can be suppressed. The tire 2 is excellent in ride comfort. In this respect, the hardness Hs is more preferably equal to or less than 70.

  In the present invention, the hardness of each part constituting the tire 2 is measured by a type A durometer in accordance with the provisions of “JIS K6253”. The durometer is pressed against the cross section shown in FIG. 1, and the hardness is measured. The measurement is made at a temperature of 70 ° C. In the present invention, the hardness measured at a temperature of 70 ° C. is expressed as “hardness”.

  Each clinch 8 extends from the end of the sidewall 6 substantially inward in the radial direction. The clinch 8 is located outside the beads 10 and the carcass 12 in the axial direction. As shown in FIG. 1, the clinch 8 is located outside the buffer layer 24 in the axial direction. The clinch 8 is made of a crosslinked rubber having excellent wear resistance. The clinch 8 contacts the flange F of the rim R.

  In the tire 2, the hardness Hc of the clinch 8 is preferably 60 or more and 85 or less. By setting the hardness Hc to 60 or more, the clinch 8 contributes to the rigidity. In the tire 2, the deformation of the bead 10 is suppressed. In this respect, the hardness Hc is more preferably equal to or greater than 65. By setting the hardness Hc to 85 or less, the influence of the clinch 8 on the rigidity can be suppressed. The tire 2 is excellent in ride comfort. In this respect, the hardness Hc is more preferably equal to or less than 80. The hardness Hc of the clinch 8 is measured in the same manner as the hardness Hs of the sidewall 6 described above.

  In the tire 2, the clinch 8 is harder than the sidewall 6. In other words, the hardness Hc of the clinch 8 is larger than the hardness Hs of the sidewall 6. In the tire 2, the clinch 8 contributes to wear resistance, and the sidewall 6 contributes to riding comfort. From the viewpoint of the balance between the rigidity with the clinch 8 and the rigidity of the sidewall 6, the difference between the hardness Hc of the clinch 8 and the hardness Hs of the sidewall 6 is preferably 3 or more, and more preferably 20 or less.

  In FIG. 1, a double-headed arrow HW is a radial distance from the bead base line to the maximum width position PW of the tire 2. A double-pointed arrow HC is a radial distance from the bead base line to the outer end 34 of the clinch 8.

  In the tire 2, the outer end 34 of the clinch 8 is located inside the maximum width position PW of the tire 2 in the radial direction. In other words, the ratio of the distance HC to the distance HW is less than 100%. In the tire 2, the influence on the riding comfort by the clinch 8 is effectively suppressed. In this respect, the ratio is preferably 90% or less, and more preferably 85% or less. From the viewpoint that the clinch 8 effectively contributes to rigidity, this ratio is preferably 50% or more, and more preferably 55% or more.

  In the tire 2, the loss tangent (tan δ) Tc of the clinch 8 is preferably 0.08 or less. Thereby, the heat generation of the clinch 8 due to the tire 2 being repeatedly deformed is suppressed. The clinch 8 contributes to the durability of the tire 2. From this viewpoint, the loss tangent Tc is more preferably 0.07 or less, and more preferably 0.06 or less. Since the loss tangent Tc is preferably as small as possible, the preferable lower limit of the loss tangent Tc is not set. In the present invention, the loss tangent measured at a temperature of 70 ° C. is expressed as “loss tangent”.

In the present invention, the loss tangent (tan δ) of each part constituting the tire 2 is measured in accordance with the provisions of “JIS K 6394”. The measurement conditions are as follows.
Viscoelastic spectrometer: "VESF-3" from Iwamoto Seisakusho
Initial strain: 10%
Dynamic strain: ± 1%
Frequency: 10Hz
Deformation mode: Tensile Measurement temperature: 70 ° C

  Each bead 10 is located inside the clinch 8 in the axial direction. The bead 10 includes a core 36 and an apex 38. The core 36 has a ring shape and includes a wound non-stretchable wire. A typical material for the wire is steel. The apex 38 is located outside the core 36 in the radial direction. The apex 38 extends from the core 36 substantially outward in the radial direction. The apex 38 is tapered outward in the radial direction. The apex 38 is made of a highly hard crosslinked rubber. The apex 38 is harder than the clinch 8. The apex 38 contributes to the rigidity of the bead 10 portion.

  In FIG. 1, the symbol PA represents the radially outer end of the apex 38. Reference symbol PB represents the axial center of the bottom of the apex 38. A double arrow LA represents the length of a line segment connecting the outer end PA and the center PB. The length LA is the length of the apex 38.

  In the tire 2, the length LA of the apex 38 is 20 mm or less. In conventional tires, the apex has a length of 40 mm to 50 mm. The apex 38 is smaller than the conventional apex. If the apex 38 is too small, the rigidity of the portion of the bead 10 is insufficient, and the steering stability may be impaired. From this viewpoint, the length LA is preferably 5 mm or more.

  In the tire 2, the hardness Ha of the apex 38 is preferably 75 or more and 95 or less. When the hardness Ha is set to 75 or more, the apex 38 contributes to rigidity. In the tire 2, the deformation of the bead 10 is suppressed. In this respect, the hardness Ha is more preferably equal to or greater than 80. By setting the hardness Ha to 95 or less, the influence of the apex 38 on the rigidity can be suppressed. In the tire 2, good riding comfort is maintained. From this viewpoint, the hardness Ha is more preferably 90 or less. The hardness Ha of the apex 38 is measured in the same manner as the hardness Hs of the sidewall 6 described above.

  In the tire 2, the loss tangent Ta of the apex 38 is preferably 0.08 or less. Thereby, the heat generation of the apex 38 due to the tire 2 being repeatedly deformed is suppressed. The apex 38 contributes to the durability of the tire 2. From this viewpoint, the loss tangent Ta is more preferably 0.07 or less, and more preferably 0.06 or less. Since the loss tangent Ta is preferably as small as possible, a preferable lower limit of the loss tangent Ta is not set. This loss tangent Ta is measured in the same manner as the loss tangent Tc of the clinch 8 described above.

  The carcass 12 includes a first ply 40 and a second ply 42. The first ply 40 and the second ply 42 are bridged between the beads 10 on both sides, and extend along the tread 4 and the sidewall 6. The first ply 40 is folded around the core 36 from the inner side to the outer side in the axial direction. As a result of the folding, a main portion 40a and a pair of folded portions 40b are formed in the first ply 40. The first ply 40 includes a main portion 40a and a pair of folded portions 40b. The second ply 42 is folded around the core 36 from the inner side in the axial direction to the outer side. By this folding, the main portion 42a and a pair of folding portions 42b are formed in the second ply 42. The second ply 42 includes a main portion 42a and a pair of folded portions 42b. The end of the folded portion 40b of the first ply 40 is located outside the end of the folded portion 42b of the second ply 42 in the radial direction. The end of the folded portion 40b of the first ply 40 is located near the position PW in the radial direction, specifically, outside the position PW. The carcass 12 has a so-called “high turn-up (HTU) structure”.

  Although not shown, each of the first ply 40 and the second ply 42 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 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 may be formed from a single ply. The carcass 12 may be formed from three or more plies.

  The load support layer 14 is located inside the sidewall 6 in the axial direction. The support layer 14 is located on the inner side in the axial direction than the carcass 12. The support layer 14 is sandwiched between the carcass 12 and the inner liner 20. The support layer 14 tapers inward in the radial direction and also tapers outward. This support layer 14 has a similar shape to the crescent moon. The support layer 14 is made of a crosslinked rubber. When the tire 2 is punctured, the support layer 14 supports the load. The support layer 14 allows the tire 2 to travel a certain distance even in a puncture state. The tire 2 is also called a run flat tire. The tire 2 is a side reinforcing type. The tire 2 may include a support layer 14 having a shape different from the shape of the support layer 14 shown in FIG.

  A portion of the carcass 12 that overlaps the support layer 14 is separated from the inner liner 20. In other words, the carcass 12 is curved due to the presence of the support layer 14. In the puncture state, a compressive load is applied to the support layer 14, and a tensile load is applied to a region of the carcass 12 that is close to the support layer 14. Since the support layer 14 is a rubber lump, it can sufficiently withstand the compressive load. The cord of the carcass 12 can sufficiently withstand a tensile load. The support layer 14 and the cord of the carcass 12 suppress the vertical deflection of the tire 2 in a punctured state. The tire 2 in which the vertical deflection is suppressed is excellent in handling stability in the puncture state.

  From the viewpoint of suppressing vertical deflection in the puncture state, the hardness Hi of the support layer 14 is preferably 60 or more, and more preferably 65 or more. The hardness Hi is preferably 80 or less, and more preferably 75 or less, from the viewpoint of maintaining the internal pressure, that is, the riding comfort in the normal state. The hardness Hi of the support layer 14 is measured in the same manner as the hardness Hs of the sidewall 6 described above.

  In the tire 2, the loss tangent Ti of the support layer 14 is preferably 0.06 or less. Thereby, heat_generation | fever of the support layer 14 by the tire 2 deform | transforming repeatedly is suppressed. The support layer 14 contributes to the durability of the tire 2. From this viewpoint, the loss tangent Ti is more preferably 0.05 or less, and more preferably 0.04 or less. Since the loss tangent Ti is preferably as small as possible, the preferable lower limit of the loss tangent Ti is not set. This loss tangent Ti is measured in the same manner as the loss tangent Tc of the clinch 8 described above.

  The belt 16 is located inside the tread 4 in the radial direction. The belt 16 is laminated with the carcass 12. The belt 16 reinforces the carcass 12. The belt 16 includes an inner layer 44 and an outer layer 46. As apparent from FIG. 1, the width of the inner layer 44 is slightly larger than the width of the outer layer 46 in the axial direction. Although not shown, each of the inner layer 44 and the outer layer 46 is composed of a plurality 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 cord of the inner layer 44 with respect to the equator plane is opposite to the inclination direction of the cord of the outer layer 46 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 16 is preferably 0.7 times or more the maximum width of the tire 2. The belt 16 may include three or more layers.

  The band 18 is located on the radially outer side of the belt 16. In the tire 2, the width of the band 18 is larger than the width of the belt 16 in the axial direction. Although not shown, the band 18 is composed of a cord and a topping rubber. The cord is wound in a spiral. The band 18 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, and further 2 ° or less. Since the belt 16 is restrained by this cord, lifting of the belt 16 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 belt 16 and the band 18 constitute a reinforcing layer. The reinforcing layer may be formed only from the belt 16. A reinforcing layer may be formed only from the band 18.

  The inner liner 20 is located inside the carcass 12. The inner liner 20 is joined to the inner surface of the carcass 12 on the radially inner side of the tread 4. On the inner side in the axial direction of the sidewall 6, the inner liner 20 is bonded to the inner surface of the support layer 14. The inner liner 20 is made of a crosslinked rubber having excellent air shielding properties. A typical base rubber of the inner liner 20 is butyl rubber or halogenated butyl rubber. The inner liner 20 holds the internal pressure of the tire 2.

  Each chafer 22 is located in the vicinity of the bead 10. When the tire 2 is incorporated into the rim R, the chafer 22 contacts the rim R. By this contact, the vicinity of the bead 10 is protected. In this embodiment, the chafer 22 is integral with the clinch 8. Therefore, the material of the chafer 22 is the same as that of the clinch 8. The chafer 22 may be made of cloth and rubber impregnated in the cloth.

  Each buffer layer 24 is located between the carcass 12 and the clinch 8 in the axial direction. As is apparent from FIG. 1, the buffer layer 24 extends from the vicinity of the core 36 along the carcass 12 substantially outward in the radial direction.

  In the tire 2, a crosslinked rubber having hardness Hk and loss tangent Tk arranged as follows with respect to the hardness Hc and loss tangent Tc of the clinch 8 is used for the buffer layer 24. The hardness Hk is measured in the same manner as the hardness Ha of the sidewall 6 described above. This loss tangent Tk is measured in the same manner as the loss tangent Tc of the clinch 8 described above.

  In the tire 2, the loss tangent Tk of the buffer layer 24 is lower than the loss tangent Tc of the clinch 8. The hardness Hk of the buffer layer 24 is lower than the hardness Hc of the clinch 8. The buffer layer 24 is made of a crosslinked rubber that is softer than the crosslinked rubber of the clinch 8 and hardly generates heat.

  FIG. 2 shows a portion of the bead 10 of the tire 2 shown in FIG. In FIG. 2, 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. 2, the symbol P <b> 1 represents a specific position on the outer surface of the tire 2. In the tire 2, the height in the radial direction from the bead base line to the position P1 is 14 mm. This position P1 is a position on the outer surface of the tire 2 where the radial height from the bead baseline is 14 mm. In the present invention, this position P1 is referred to as a first point. The symbol P2 represents a specific position on the outer surface of the tire 2 like the position P1. In the tire 2, the height in the radial direction from the bead base line to the position P2 is 20 mm. This position P2 is a position on the outer surface of the tire 2 where the radial height from the bead baseline is 20 mm. In the present invention, this position P2 is referred to as the second point. The symbol P3 represents a specific position on the outer surface of the tire 2 as with the position P1 and the position P2. In the tire 2, the height in the radial direction from the bead base line to the position P3 is 17 mm. This position P3 is a position on the outer surface of the tire 2 where the radial height from the bead baseline is 17 mm. In the present invention, this position P3 is referred to as a third point.

  In the present invention, at the first point P1, the second point P2, and the third point P3, the tire 2 is incorporated into the rim R, and the tire 2 is filled with air so as to have a normal internal pressure. It is determined by a profile based on the outer surface of the tire 2 obtained in an unapplied state.

  In FIG. 2, a solid line L1 is a straight line that passes through the first point P1 and extends in the radial direction. The solid line L2 is a straight line extending in the radial direction through the second point P2. The solid line L3 is a straight line extending in the radial direction through the third point P3.

  In the tire 2, the buffer layer 24 overlaps each of the first point P1 and the second point P2 in the radial direction. The buffer layer 24 also overlaps with the third point P3 in the radial direction. The buffer layer 24 overlaps the zone from the first point P1 to the second point P2 in the radial direction. The buffer layer 24 intersects the region from the straight line L1 to the straight line L2. The buffer layer 24 is located in the region from the straight line L1 to the straight line L2.

  The tire 2 is used by being fitted to the rim R. In this state of use, the bead 10 portion of the tire 2 is in contact with the rim R. As a result, a contact surface is formed between the tire 2 and the rim R.

  In the tire 2, the zone from the first point P1 to the second point P2 corresponds to the radially outer portion of the contact surface. The tire 2 is firmly fixed to the rim R on the inner side in the radial direction from this portion. The tire 2 is released from the rim R outside the portion in the radial direction. For this reason, distortion tends to concentrate near this portion. When the tire 2 is punctured and the internal pressure is reduced, the tire 2 itself supports the vehicle weight. At this time, a large load is applied to the tire 2. For this reason, when the vehicle travels in a state where the tire 2 is punctured and the internal pressure is reduced, that is, in the run flat traveling, a large load is applied to the bead 10 portion of the tire 2 and distortion tends to be particularly concentrated.

  In the tire 2, a small apex 38 is employed. In the tire 2, the apex 38 is disposed outside the region where distortion is concentrated in the puncture state. In the tire 2, deformation of the apex 38 is effectively suppressed in the run-flat running state.

  In the tire 2, as described above, the buffer layer 24 is provided between the carcass 12 and the clinch 8. Since the buffer layer 24 has a loss tangent lower than that of the clinch 8, the buffer layer 24 hardly generates heat. For this reason, heat generation in the portion of the bead 10 including the buffer layer 24 is considerably suppressed.

  In the tire 2, the buffer layer 24 is disposed so as to cover a portion where the tire 2 and the rim R are in contact with each other when the tire 2 is combined with the rim R. During the run-flat running, the buffer layer 24 is provided particularly in a portion where distortion is likely to concentrate, so that the heat generation suppressing effect by the buffer layer 24 is sufficiently exhibited.

  In FIG. 1, a double arrow HKu represents a radial distance from the bead base line to the radially inner end 48 of the buffer layer 24. A double-headed arrow Hbc represents a radial distance from the bead base line to the radially outer end 50 of the core 36.

  In the tire 2, the position of the inner end 48 of the buffer layer 24 coincides with the position of the outer end 50 of the core 36 in the radial direction, or the inner end 48 of the buffer layer 24 is the outer end 50 of the core 36. It is located outside. In other words, the ratio of the radial distance HKu from the bead base line to the inner end 48 of the buffer layer 24 to the radial distance Hbc from the bead base line to the outer end 50 of the core 36 is 100% or more. In the tire 2, the buffer layer 24 does not overlap with the core 36 in the axial direction. The axially outer portion of the core 36 is composed of the clinch 8 that is harder than the buffer layer 24. In the tire 2, the position of the core 36 with respect to the rim R is stably maintained in the traveling state. Since the core 36 is difficult to move with respect to the rim R, the deformation of the bead 10 portion is effectively suppressed in the tire 2. Since heat generation is suppressed, the durability can be further improved. From this viewpoint, this ratio is preferably 105% or more. If the inner end 48 of the buffer layer 24 moves away from the core 36 in the radial direction, the volume of the buffer layer 24 decreases, and the heat generation suppressing effect of the buffer layer 24 may be reduced. From the viewpoint of exhibiting the heat generation suppressing effect by the buffer layer 24, this ratio is preferably 150% or less, and more preferably 145% or less. As will be described later, the buffer layer 24 contributes to ride comfort. Also from this viewpoint, this ratio is preferably 150% or less, and more preferably 145% or less.

  In the tire 2, the buffer layer 24 is disposed at an appropriate position and in an appropriate size in consideration of a region where strain is concentrated. In the tire 2, heat generation due to deformation of the bead 10 portion is effectively suppressed. In particular, in the tire 2, heat generation between the contact surface with the rim R and the carcass 12 is suppressed. The bead 10 portion of the tire 2 is hardly damaged.

  In the tire 2, the buffer layer 24 includes the carcass 12, in particular, the folded portion 40 b of the first ply 40 and the folded portion 42 b of the second ply 42 than the folded portion in the conventional tire in which the buffer layer 24 is not provided. Is also arranged on the inside in the axial direction. More specifically, the use of the buffer layer 24 allows the folded portion 40b of the first ply 40 to have the bead 10 of the tire 2 in the region from the straight line L1 to the straight line L2, as shown in FIG. It is arranged at the approximate center of the part. In the tire 2, the carcass 12. Specifically, it is possible to prevent a force in the compression direction or the tensile direction from acting on the folded portion 40 b of the first ply 40. The carcass 12 is less likely to concentrate distortion. In the tire 2, the carcass 12 is hardly damaged.

  In the tire 2, damage at the bead 10 is prevented. In the tire 2, a sufficient traveling distance is ensured even when the internal pressure is reduced due to puncture. The tire 2 is excellent in durability during run-flat running.

  As described above, in the tire 2, the buffer layer 24 is softer than the clinch 8. The buffer layer 24 contributes to the cushioning property of the bead 10 during normal running. In the tire 2, good riding comfort is achieved.

  In FIG. 1, a double-headed arrow HKs is a radial distance from the bead base line to the radially outer end 52 of the buffer layer 24. This distance HKs is also referred to as the radial height of the buffer layer 24.

  In the tire 2, the outer end 52 of the buffer layer 24 is located near the outer end 34 of the clinch 8 in the radial direction. Specifically, in the tire 2, the ratio of the radial distance HKs from the bead base line to the outer end 52 of the buffer layer 24 to the radial distance HC from the bead base line to the outer end 34 of the clinch 8 is 85%. It is more than 105%. By setting the ratio of the distance HKs to the distance HC to be 105% or less, the buffer layer 24 is prevented from projecting greatly from the clinch 8 in the radial direction. In the tire 2, the rigidity of the side wall 6 is properly maintained. In other words, in the tire 2, the influence on the riding comfort by the buffer layer 24 is effectively suppressed. In this respect, the ratio is preferably equal to or less than 100%. By setting the ratio of the distance HKs to the distance HC to 85% or more, the volume of the buffer layer 24 is sufficiently secured. The buffer layer 24 contributes to improvement of cushioning properties and suppression of heat generation. In the tire 2, good riding comfort and durability in run-flat traveling can be obtained. From this viewpoint, the ratio is preferably 90% or more.

  The tire 2 is excellent in ride comfort and durability in run-flat running. According to the present invention, it is possible to obtain the pneumatic tire 2 in which improvement in riding comfort and durability in run-flat traveling is achieved.

  In the tire 2, the loss tangent Tk of the buffer layer 24 is preferably 0.05 or less. Thereby, the buffer layer 24 effectively contributes to suppression of heat generation due to deformation of the bead 10 portion. The tire 2 is excellent in durability during run-flat running. From this viewpoint, the loss tangent Tk is more preferably 0.04 or less, and further preferably 0.03 or less. Since the loss tangent Tk is preferably as small as possible, the preferable lower limit of the loss tangent Tk is not set.

  As described above, in the tire 2, the buffer layer 24 is less likely to generate heat than the clinch 8. Specifically, the difference (Tk−Tc) between the loss tangent Tk of the buffer layer 24 and the loss tangent Tc of the clinch 8 is preferably −0.01 or less. Thereby, the buffer layer 24 effectively contributes to suppression of heat generation due to deformation of the bead 10 portion. The tire 2 is excellent in durability during run-flat running. In this respect, the difference is more preferably −0.02 or less. Since the loss tangent Tk is preferably as small as possible relative to the loss tangent Tc of the clinch 8, the lower limit of this difference is not set.

  In the tire 2, the buffer layer 24 is less likely to generate heat than the apex 38. Specifically, the difference (Tk−Ta) between the loss tangent Tk of the buffer layer 24 and the loss tangent Ta of the apex 38 is preferably −0.01 or less. Thereby, the buffer layer 24 effectively contributes to suppression of heat generation due to deformation of the bead 10 portion. The tire 2 is excellent in durability during run-flat running. In this respect, the difference is more preferably −0.02 or less. Since the loss tangent Tk is preferably as small as possible relative to the loss tangent Ta of the apex 38, the lower limit of this difference is not set.

  In the tire 2, the loss tangent Tk of the buffer layer 24 is preferably equal to the loss tangent Ti of the load support layer 14 or lower than the loss tangent Ti of the load support layer 14. In other words, the difference (Tk−Ti) between the loss tangent Tk of the buffer layer 24 and the loss tangent Ti of the load supporting layer 14 is preferably 0.00 or less. Thereby, the heat generation suppression effect by the buffer layer 24 is further enhanced. The tire 2 is further excellent in durability during run-flat running. In this respect, the difference is more preferably −0.01 or less. In this case, since the loss tangent Tk is preferably as small as possible relative to the loss tangent Ti of the support layer 14, the lower limit of this difference is not set.

  In the tire 2, the hardness Hk of the buffer layer 24 is preferably 55 or greater and 80 or less. By setting the hardness Hk to 55 or more, the buffer layer 24 has appropriate rigidity. In the tire 2, the degree of deformation of the bead 10 portion is appropriately maintained. In this respect, the hardness Hk is more preferably equal to or greater than 60. When the hardness Hk is set to 80 or less, the buffer layer 24 contributes to cushioning properties. In the tire 2, good riding comfort is maintained. In this respect, the hardness Hk is more preferably equal to or less than 75.

  As described above, in the tire 2, the buffer layer 24 is softer than the clinch 8. Specifically, the difference (Hk−Hc) between the hardness Hk of the buffer layer 24 and the hardness Hc of the clinch 8 is preferably −5 or less. Thereby, the buffer layer 24 contributes effectively to the cushioning property of the bead 10 portion during normal running. In the tire 2, a good riding comfort can be obtained. In this respect, the difference is more preferably −10 or less. From the viewpoint of preventing strain concentration due to the difference in rigidity between the buffer layer 24 and the clinch 8, this difference is preferably −20 or more.

  In the tire 2, the hardness Hk of the buffer layer 24 is preferably lower than the hardness Ha of the apex 38. In other words, the buffer layer 24 is preferably softer than the apex 38. Specifically, the difference (Hk−Ha) between the hardness Hk of the buffer layer 24 and the hardness Ha of the apex 38 is preferably −5 or less. Thereby, the buffer layer 24 contributes effectively to the cushioning property of the bead 10 portion during normal running. With this tire, good riding comfort can be obtained. In this respect, the difference is more preferably −10 or less. From the viewpoint of preventing concentration of distortion due to the difference in rigidity between the buffer layer 24 and the apex 38, this difference is preferably −20 or more.

  In the tire 2, the hardness Hk of the buffer layer 24 is preferably equal to the hardness Hi of the load support layer 14 or lower than the hardness Hi of the load support layer 14. In other words, the difference (Hk−Hi) between the hardness Hk of the buffer layer 24 and the hardness Hi of the load support layer 14 is preferably 0 or less. Thereby, the buffer layer 24 contributes effectively to the cushioning property of the bead 10 portion during normal running. With this tire, good riding comfort can be obtained. In this respect, the difference is more preferably −5 or less. From the viewpoint of preventing strain concentration due to the difference in rigidity between the buffer layer 24 and the support layer 14, this difference is preferably −20 or more.

  In the tire 2, the buffer layer 24 is harder than the sidewall 6. Specifically, the difference (Hk−Hs) between the hardness Hk of the buffer layer 24 and the hardness Hs of the sidewall 6 is preferably 3 or more. Thereby, the buffer layer 24 contributes to the rigidity of the bead 10 portion. In the tire 2, the bead 10 is flexibly bent. In the tire 2, good steering stability is maintained. From this viewpoint, the difference is preferably 5 or more. This difference is preferably 10 or less from the viewpoint that the influence on the riding comfort by the buffer layer 24 is suppressed.

  In FIG. 2, a solid line LT is a normal line of the outer surface of the tire 2. This normal LT passes through the second reference point P2. In the present invention, the normal LT of the outer surface of the tire 2 at the second reference point P2 is referred to as a reference normal.

  In FIG. 2, a double arrow t represents a length from the outer surface of the tire 2 to the carcass 12. This length t is the thickness of the outer portion of the carcass 12 of the tire 2 at the second reference point P2. The double arrow tk is the thickness of the buffer layer 24 at the second reference point P2. The double arrow tc is the thickness of the clinch 8 at the second reference point P2. The thickness t, the thickness tk, and the thickness tc are measured along the reference normal line LT. The thickness t is equal to the sum of the thickness tk and the thickness tk (tk + tc). This thickness t is a total thickness of the thickness tk of the buffer layer 24 and the thickness tc of the clinch 8 measured along the reference normal line LT. A double arrow tL represents the thickness of the load support layer 14 measured along the reference normal line LT.

  In the tire 2, the thickness tk of the buffer layer 24 is preferably 1 mm or more. By setting the thickness tk to be 1 mm or more, the buffer layer 24 effectively contributes to suppression of heat generation in the bead 10 portion. In this respect, the thickness tk is more preferably 2 mm or more. The thickness tk is preferably 5 mm or less. By setting the thickness tk to 5 mm or less, the influence of the buffer layer 24 on the rigidity of the bead 10 is suppressed. In the tire 2, the rigidity of the bead 10 is appropriately maintained. In this respect, the thickness tk is more preferably 4 mm or less.

  In the tire 2, the thickness tc of the clinch 8 is preferably 1 mm or more. By setting the thickness tc to 1 mm or more, the rigidity of the clinch 8 is appropriately maintained. In the tire 2, the clinch 8 effectively prevents the bead 10 from being worn away by contact with the rim R. The tire 2 is excellent in wear resistance. From this viewpoint, the thickness tc is more preferably 2 mm or more. The thickness tc is preferably 5 mm or less. By setting the thickness tc to 5 mm or less, the influence of the clinch 8 on the rigidity of the bead 10 portion can be suppressed. In the tire 2, the rigidity of the bead 10 is appropriately maintained. In this respect, the thickness tc is more preferably 4 mm or less.

  In the tire 2, the ratio of the thickness tk to the thickness t is preferably 15% or more and 85% or less. By setting the ratio to 15% or more, the buffer layer 24 effectively contributes to suppression of heat generation in the bead 10 portion. By setting this ratio to 85% or less, the influence of the buffer layer 24 on the rigidity of the bead 10 portion can be suppressed. In the tire 2, the rigidity of the bead 10 is appropriately maintained. In addition, when this ratio is in the range of 33% to 67%, even if this ratio is different, it is confirmed that the tire 2 has equivalent performance if the other configurations are equivalent. .

  In the tire 2, the ratio of the total thickness t to the thickness tL is preferably 80% or more and 120% or less. By setting this ratio to 80% or more, the balance between the thickness of the outer portion of the carcass 12 and the thickness of the load support layer 14 is adjusted, and the force in the compression direction is prevented from acting on the carcass 12. . Since the carcass 12 is prevented from being damaged, the tire 2 is excellent in durability. In this respect, the ratio is more preferably equal to or greater than 90%. By setting this ratio to be equal to or less than 120%, the balance between the thickness of the outer portion of the carcass 12 and the thickness of the support layer 14 is adjusted, and a force in the tensile direction is prevented from acting on the carcass 12. Even in this case, since the carcass 12 is prevented from being damaged, the tire 2 is excellent in durability. In this respect, the ratio is more preferably equal to or greater than 110%. In addition, when this ratio is in the range of 90% to 110%, even if this ratio is different, it is confirmed that the tire 2 has equivalent performance if the other configurations are equivalent. Yes.

  In FIG. 2, the double arrow ti represents the thickness of the load support layer 14. The thickness ti is measured along a straight line passing through the position PW and extending in the axial direction. In the present invention, the thickness ti is the thickness of the support layer 14 at the maximum width position PW of the tire 2.

  In the tire 2, the thickness ti of the support layer 14 is preferably 6 mm or more from the viewpoint that when the tire 2 is punctured, the load support layer 14 contributes to load support. From the viewpoint of riding comfort in a normal state, the thickness ti of the support layer 14 is preferably 15 mm or less.

  In the manufacture of the tire 2, a plurality of rubber members are assembled to obtain a raw cover (unvulcanized tire 2). This raw cover is put into a mold. The outer surface of the raw cover is in contact with the cavity surface of the mold. The inner surface of the raw cover contacts the bladder or the core. The raw cover is pressurized and heated in the mold. The rubber composition of the raw cover flows by pressurization and heating. The rubber causes a crosslinking reaction by heating, and the tire 2 is obtained.

  In the manufacture of the tire 2, the buffer layer 24 may be formed using a sheet made of a rubber composition for the buffer layer 24. The buffer layer 24 may be formed by spirally winding a strip made of a rubber composition. The buffer layer 24 may be formed from a molded product prepared by extruding the rubber composition to have a cross-sectional shape. The buffer layer 24 is formed by an optimum method in consideration of the size and shape of the buffer layer 24.

  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. 1-2 was manufactured. The size of this tire is 245 / 45RF19. The specifications of Example 1 are as shown in Table 1 below.

  The buffer layer is disposed so as to overlap with the zone from the first point P1 to the second point P2 in the radial direction. This is represented by “Y” in the columns of the first point (14 mm), the third point (17 mm), and the second point (20 mm) in the table.

  The loss tangent Tk and hardness Hk of the buffer layer in Table 1 are measured at a temperature of 70 ° C. The sidewall hardness Hs measured at a temperature of 70 ° C. was 60. The loss tangent Tc of clinch measured at a temperature of 70 ° C. was 0.06. The hardness Hc of the clinch measured at a temperature of 70 ° C. was 75. The loss tangent Ta of the apex measured at a temperature of 70 ° C. was 0.06. The Apex hardness Ha measured at a temperature of 70 ° C. was 80. The loss tangent Ti of the load support layer measured at a temperature of 70 ° C. was 0.04. The hardness Hi of the load support layer measured at a temperature of 70 ° C. was 70.

[Comparative Example 1]
Comparative Example 1 is a conventional tire. In this comparative example 1, no buffer layer is provided.

[Example 2-3 and Comparative Example 2]
By changing the loss tangent Tk of the buffer layer, the difference between the loss tangent Tk and the loss tangent Tc (Tk−Tc), the difference between the loss tangent Tk and the loss tangent Ta (Tk−Ta), and the loss tangent Tk and the loss tangent Ti The tires of Example 2-3 and Comparative Example 2 were obtained in the same manner as in Example 1 except that the difference (Tk-Ti) was changed as shown in Table 1 below.

[Example 4-5 and Comparative Example 3-4]
By changing the hardness Hk of the buffer layer, the difference between the hardness Hk and the hardness Hc (Hk−Hc), the difference between the hardness Hk and the hardness Ha (Hk−Ha), and the hardness Hk and the hardness Hi The tires of Example 4-5 and Comparative Example 3-4 were obtained in the same manner as in Example 1 except that the difference (Hk-Hi) was changed as shown in Table 2 below.

[Examples 6-7 and Comparative Example 5]
Examples 6-7 and Comparative Example 6 were compared with Example 6-7 except that the radial distance HC from the bead baseline to the outer edge of the clinch was changed and the ratio (HC / HW) was as shown in Table 3 below. The tire of Example 5 was obtained.

[Examples 8-11 and Comparative Example 6]
Example 8-11 and Example 8-11 were the same as Example 1 except that the radial distance HKs from the bead base line to the outer edge of the buffer layer was changed and the ratio (HKs / HC) was changed as shown in Table 4 below. A tire of Comparative Example 6 was obtained.

[Examples 12-13 and Comparative Examples 7-8]
Example 12-13 and Example 12-13 except that the radial distance HKu from the bead base line to the inner end of the buffer layer was changed and the ratio (HKu / Hbc) was changed as shown in Table 5 below. The tire of Comparative Example 7-8 was obtained. In Comparative Example 8, the buffer layer did not overlap with the first point P1 in the radial direction. This is indicated by “N” in the column of the first point (14 mm) in the table. In Comparative Example 8, the thickness tk is not obtained.

[Comparative Example 9]
A tire of Comparative Example 9 was obtained in the same manner as in Example 1 except that the apex length LA was as shown in Table 5 below.

[Examples 14-15]
Tires of Examples 14-15 were obtained in the same manner as Example 1, except that the thickness tL of the load support layer was changed and the ratio ((tk + tc) / tL) was changed as shown in Table 6 below.

[Examples 16-17]
Tires of Examples 16-17 were obtained in the same manner as in Example 1 except that the thickness tk and the thickness tc were as shown in Table 6 below.

[Durability (Runflat)]
The tire was assembled in a rim (size = 19 × 8 J), and the tire was filled with air to adjust the internal pressure to 180 kPa. This tire was mounted on a drum-type running test machine, and a vertical load corresponding to 80% of the maximum load load of this tire was applied to the tire. A puncture state was reproduced by setting the internal pressure of the tire to normal pressure (measured pressure was 0 kPa), and the tire was run on a drum having a radius of 1.7 m at a speed of 80 km / h. The distance traveled until the tire broke was measured. The results are shown in Tables 1-6 below as indices. The larger the value, the better the run flat durability, which is preferable.

[Ride comfort]
The tire was assembled in a rim (size = 19 × 8 J), and the tire was filled with air so that the internal pressure was 230 kPa. This tire was mounted on a passenger car having a displacement of 4300 cc. The driver was driven on the racing circuit to evaluate the ride comfort. The results are shown in Tables 1-6 below as indices. Larger numbers are preferable.

  As Table 1-6 shows, in the tire of an Example, evaluation is high compared with the tire of a comparative example. From this evaluation result, the superiority of the present invention is clear.

  The technology relating to the buffer layer described above can be applied to various tires.

2 ... Tire 4 ... Tread 6 ... Side wall 8 ... Clinch 10 ... Bead 12 ... Carcass 14 ... Support layer 16 ... Belt 24 ... Buffer layer 26 .... Tread surface 28 ... Groove 34 ... Radial outer end 36 of clinch 8 36 ... Core 38 ... Apex 40 ... First ply 40a ... Main part 40b ... Folded part 42 ... second ply 42a ... main portion 42b ... folded portion 48 ... radially inner end of buffer layer 24 50 ... radially outer end of core 36 52 ... buffer layer 24 Radial outer edge

Claims (6)

A tread, a pair of sidewalls, a pair of clinch, a pair of beads, a carcass, a pair of load support layers and a pair of buffer layers,
Each sidewall extends radially inward from the end of the tread,
Each clinch extends radially inward from the end of the sidewall, and the outer end of the clinch is positioned inward of the maximum width position of the tire in the radial direction.
Each bead is located axially inward of the clinch, the bead has a core and an apex, and the apex extends from the core substantially outward in the radial direction. Is 20 mm or less in length,
The carcass is stretched between one bead and the other bead along the inside of the tread and the sidewall,
Each load supporting layer is located inside the sidewall in the axial direction,
Each buffer layer is positioned between the carcass and the clinch in the axial direction, and in the radial direction, the position of the inner end of the buffer layer coincides with the position of the outer end of the core, or The inner end of the buffer layer is located outside the outer end of the core,
The ratio of the radial distance from the bead base line to the outer end of the buffer layer to the radial distance from the bead base line to the outer end of the clinch is 85% or more and 105% or less,
The position where the radial direction height of the outer surface of the tire is 14 mm from the bead base line is defined as a first point P1, and the position of the outer surface of the tire where the radial direction height from the bead base line is 20 mm is the first point P1. When two points P2
The buffer layer overlaps each of the first point P1 and the second point P2 in the radial direction,
A pneumatic tire in which the loss tangent of the buffer layer is lower than the loss tangent of the clinch, and the hardness of the buffer layer is lower than the hardness of the clinch.   The pneumatic tire according to claim 1, wherein a ratio of a radial distance from the bead base line to the inner end of the buffer layer to a radial distance from the bead base line to the outer end of the core is 150% or less. .   The pneumatic tire according to claim 1 or 2, wherein the hardness of the buffer layer is lower than the hardness of the apex.   The pneumatic tire according to any one of claims 1 to 3, wherein a loss tangent of the buffer layer is equal to or lower than a loss tangent of the load support layer. When the normal of the outer surface of the tire at the second point P2 is a reference normal,
The pneumatic tire according to any one of claims 1 to 4, wherein each of the buffer layer and the clinch measured along the reference normal has a thickness of 1 mm or more.   The ratio of the total thickness of the buffer layer thickness and the clinch thickness measured along the reference normal to the load support layer thickness measured along the reference normal is 80%. The pneumatic tire according to claim 5, which is 120% or less.

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