JP2015083453A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire 2 excellent in durability when puncture occurs, and riding comfort.SOLUTION: A side wall 8 of a tire 2 has a rim protector 34 projecting outward of an axial direction. A bead 12 comprises a core 38 and apexes 40. In the tire 2, one apex 40a is a rear side apex, and the other apex 40b is a front side apex, and at the time, about the respective rear side apex 40a and the front side apex 40b, first reference thickness T1 at a first reference position separated by 1.0 mm from an outer end of the core 38 toward an outside in a radial direction, second reference thickness T2 at a second reference position separated by 17.0 mm from an inner end of the core 38 toward the outside in the radial direction, third reference thickness T3 at an intermediate position between the second reference position and a tip end Pr of the rim protector 34 in the radial direction, and a complex elastic modulus, are adjusted.

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. For this support layer, a highly hard crosslinked rubber is used. 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 can support the vehicle weight. Run-flat tires can travel a certain distance even in a puncture state.

  When the run-flat tire runs in a puncture state, the portion located on the inner side (also referred to as the back side) rather than the portion located on the outer side (also referred to as the front side) in the width direction of the vehicle of the tire, Damage tends to concentrate. This is because, in the puncture state, the tire camber angle is in the negative camber, and the temperature of the back side wall is higher than the temperature of the front side wall, so the deflection of the side wall part of the back side is It is thought to be caused by the fact that it is larger than the deflection of the part.

  From the viewpoint of improving durability during puncture (also called run-flat durability), the thickness of the load support layer on the back side is made larger than that on the front side, and the height of the apex on the back side is higher than that on the front side. Is also being considered. An example of such examination is disclosed in Japanese Patent Application Laid-Open No. 2013-071468.

JP 2013-071468 A

  The inventors investigated in detail about the damage situation of the run flat tire which ran in the puncture state. As a result, it was found that there was much damage starting from the bead portion of the tire (specifically, apex and / or clinch). In the run flat tire, it is indispensable to improve the durability of the bead portion in order to further improve the run flat durability while allowing the support layer to function sufficiently.

  The apex having a large thickness can contribute to the durability of the bead portion. However, if an apex having a large thickness is used for the left and right beads, not only the dynamic balance but also the ride comfort deteriorates.

  An apex having a large complex elastic modulus can contribute to the durability of the bead portion. However, when an apex having a large elastic modulus is adopted for the left and right beads, not only the dynamic balance but also the ride comfort deteriorates.

  The clinch having a large thickness can contribute to the durability of the bead portion. However, if the left and right clinches have a large thickness, not only the dynamic balance but also the ride comfort deteriorates.

  A clinch having a large complex elastic modulus can contribute to the durability of the bead portion. However, if the left and right clinches have a large elastic modulus, not only the dynamic balance but also the ride comfort deteriorates.

  An object of the present invention is to provide a pneumatic tire that is excellent in durability during puncture and ride comfort.

The pneumatic tire according to the present invention has a tread whose outer surface forms a tread surface, a pair of sidewalls that extend substantially inward in the radial direction from the end of the tread, and each of which is substantially inward in the radial direction from the sidewall. A pair of clinches positioned at each side, a bead positioned axially inside the clinches, and a carcass spanned between one bead and the other bead along the inside of the tread and the sidewall And a pair of load support layers that are positioned on the inner side in the axial direction than the sidewalls. Each sidewall includes a rim protector that protrudes outward in the axial direction. Each bead includes a core and an apex extending radially outward from the core. A position separated by 1.0 mm radially outward from the outer end of the core is defined as a first reference position, and the thickness of the apex at the first reference position is defined as a first reference thickness T1. The clinch thickness is defined as a first reference thickness S1, and a position separated by 17.0 mm radially outward from the inner end of the core is defined as a second reference position, and the thickness of the apex at the second reference position is defined as a second reference thickness. The thickness of the clinch at the second reference position is defined as a second reference thickness S1, and a radial intermediate position between the second reference position and the tip of the rim protector is defined as a third reference position. The thickness of the apex at the three reference positions is the third reference thickness T3, the thickness of the clinch at the third reference position is the third reference thickness S3, When the tire is the back apex, the other apex is the front apex, the one clinch is the back clinch, and the other clinch is the front clinch, the tire has the following conditions (1) to (8 )
Condition (1) The difference (T1a−T1b) between the first reference thickness T1a of the back-side apex and the first reference thickness T1b of the front-side apex is 0.5 mm or more and 1.2 mm or less.
Condition (2) The difference (T2a−T2b) between the second reference thickness T2a of the back-side apex and the second reference thickness T2b of the front-side apex is 0.5 mm or more and 1.2 mm or less.
Condition (3) The difference (T3a-T3b) between the third reference thickness T3a of the back side apex and the third reference thickness T3b of the front side apex is 0.5 mm or more and 1.2 mm or less.
Condition (4) The ratio (Ea / Eb) of the complex elastic modulus Ea of the back side apex to the complex elastic modulus Eb of the front side apex is 1.4 or more and 1.7 or less.
Condition (5) The difference (S1a−S1b) between the first reference thickness S1a of the back side clinch and the first reference thickness S1b of the front side clinch is 0.5 mm or more and 1.2 mm or less.
Condition (6) The difference (S2a−S2b) between the second reference thickness S2a of the back side clinch and the second reference thickness S2b of the front side clinch is 0.5 mm or more and 1.2 mm or less.
Condition (7) The difference (S3a−S3b) between the third reference thickness S3a of the back side clinch and the third reference thickness S3b of the front side clinch is 0.5 mm or more and 1.2 mm or less.
Condition (8) The ratio (Ma / Mb) of the complex elastic modulus Ma of the back side clinch to the complex elastic modulus Mb of the front side clinch is 1.4 or more and 1.7 or less.

  Preferably, the pneumatic tire satisfies at least two conditions among the above conditions (1) to (8).

  More preferably, the pneumatic tire is one of the above conditions (1) and (2), the conditions (2) and (3), and the conditions (3) and (1). Meet. More preferably, the pneumatic tire satisfies the condition (1), the condition (2), and the condition (3). Particularly preferably, the pneumatic tire further satisfies the condition (4).

  More preferably, the pneumatic tire is one of the above conditions (5) and (6), the conditions (6) and (7), and the conditions (7) and (5). Meet. More preferably, the pneumatic tire satisfies the condition (5), the condition (6), and the condition (7). Particularly preferably, the pneumatic tire further satisfies the condition (8).

  In the pneumatic tire according to the present invention, the thickness of the back-side apex is greater than the thickness of the front-side apex at any of the first reference position, the second reference position, and the third reference position, or the complex elastic modulus of the back-side apex. Ea is larger than the complex elastic modulus Eb of the front apex. Alternatively, the thickness of the back side clinch is greater than the thickness of the front side clinch at any of the first reference position, the second reference position, and the third reference position, or the complex elastic modulus Ma of the back side clinch is greater than the complex elastic modulus Mb of the front side clinch. Is also big. In this tire, the bead portion on the back side has higher rigidity than the rigidity of the bead portion on the front side. For this reason, the durability at the time of puncture is improved by attaching the tire to the vehicle such that the bead portion on the back side is located inside in the width direction of the vehicle. Moreover, the difference (T1a-T1b), the difference (T2a-T2b), the difference (T3a-T3b) and the ratio (Ea / Eb), and the difference (S1a-S1b), the difference (S2a-S2b), the difference (S3a-S3b) ) And the upper limit of the ratio (Ma / Mb) are appropriately adjusted, so that a good riding comfort is maintained. This tire is excellent in durability during puncture and ride comfort.

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 another part of the tire of FIG. 1.

  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 generally symmetric with respect to the equator plane except for the tread pattern. In FIG. 1, a solid line BBL represents a bead base line. The bead base line is a line that defines a rim diameter (see JATMA) of a rim (not shown) on which the tire 2 is mounted. The bead baseline extends in the axial direction.

  The tire 2 includes a tread 4, a wing 6, a sidewall 8, a clinch 10, a bead 12, a carcass 14, a load support layer 16, a belt 18, a band 20, an inner liner 22, and a chafer 24. 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 surface 26. 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.

  The wing 6 is located between the tread 4 and the sidewall 8. The wing 6 is joined to each of the tread 4 and the sidewall 8. The wing 6 is made of a crosslinked rubber having excellent adhesiveness.

  The sidewall 8 extends substantially inward in the radial direction from the end of the tread 4. The radially outer end of the sidewall 8 is joined to the tread 4 and the wing 6. The radially inner end of the sidewall 8 is joined to the clinch 10. The sidewall 8 is made of a crosslinked rubber having excellent cut resistance and weather resistance. The sidewall 8 is located outside the carcass 14 in the axial direction. The sidewall 8 prevents the carcass 14 from being damaged.

  From the viewpoint of preventing damage, the hardness of the sidewall 8 is preferably 50 or more, and more preferably 55 or more. From the viewpoint of riding comfort in a normal state, the hardness is preferably 70 or less, and more preferably 65 or less. In the present application, the hardness is measured with a type A durometer in accordance with the provisions of “JIS K6253”. This durometer is pressed against the cross section shown in FIG. 1, and the hardness is measured. The measurement is made at a temperature of 23 ° C. The hardness of the clinch 10 and the load support layer 16 described later are also measured in the same manner.

  In the tire 2, the sidewall 8 includes a rim protector 34. The rim protector 34 projects outward in the axial direction. The rim protector 34 prevents damage to the flange of the rim on which the tire 2 is mounted. As shown, the rim protector 34 has a top surface 36. The rim protector 34 has a shape that spreads from the top surface 36 toward the carcass 14. Reference numeral Pr denotes a radially inner end of the top surface 36 of the rim protector 34. In the present application, this inner end Pr is the tip of the rim protector 34. When the rim protector 34 has an outwardly tapered shape, the apex of the rim protector 34 is the tip Pr. Usually, the height in the radial direction from the bead base line to the tip Pr is set to 20 mm or more and 30 mm or less.

  The clinch 10 is located substantially inside the sidewall 8 in the radial direction. The clinch 10 is located outside the beads 12 and the carcass 14 in the axial direction. The clinch 10 is made of a crosslinked rubber having excellent wear resistance. The clinch 10 contacts the rim flange.

  From the viewpoint of wear resistance, the hardness of the clinch 10 is preferably 60 or more, and more preferably 65 or more. In light of riding comfort in a normal state, the hardness is preferably 90 or less, and more preferably 80 or less.

  The bead 12 is located inside the clinch 10 in the axial direction. The bead 12 includes a core 38 and an apex 40 that extends radially outward from the core 38. The core 38 is ring-shaped and includes a wound non-stretchable wire. A typical material for the wire is steel. The apex 40 is tapered outward in the radial direction. The apex 40 is made of a highly hard crosslinked rubber. In the tire 2, the radially outer end 42 of the apex 40 is located on the radially outer side with respect to the tip Pr of the rim protector 34.

  In the tire 2, the hardness of the apex 40 is preferably 75 or more and 100 or less. By setting the hardness to 75 or more, the apex 40 contributes to the rigidity of the tire 2 effectively, so that the tire 2 is excellent in steering stability. Further, when the internal pressure of the tire 2 is reduced due to puncture, the apex 40 can effectively contribute to supporting the vehicle weight. In this respect, the hardness is more preferably equal to or greater than 80. By setting the hardness to 100 or less, the influence of the apex 40 on the bending of the portion of the sidewall 8 can be suppressed. In the tire 2, the riding comfort is appropriately maintained. From this viewpoint, the hardness is more preferably 95 or less. The hardness of the apex 40 is measured in the same manner as that of the sidewall 8 and the clinch 10 described above.

  The carcass 14 includes a carcass ply 44. The carcass ply 44 is bridged between the beads 12 on both sides. The carcass ply 44 is along the inside of the tread 4 and the sidewall 8. The carcass ply 44 is folded around the core 38 from the inner side to the outer side in the axial direction. By this folding, a main portion 46 and a folding portion 48 are formed in the carcass ply 44. The end 50 of the folded portion 48 reaches the vicinity of the tread 4. Specifically, the end 50 of the folded portion 48 reaches just below the belt 18. In other words, the folded portion 48 overlaps the belt 18. The carcass 14 has a so-called “super high turn-up structure”. The carcass 14 having an ultra high turn-up structure contributes to the durability of the tire 2 in a punctured state. The carcass 14 contributes to durability in the puncture state.

  Although not shown, the carcass ply 44 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 14 has a radial structure. The cord is made of organic fiber. Preferred organic fibers include polyethylene terephthalate fiber, nylon fiber, rayon fiber, polyethylene naphthalate fiber and aramid fiber.

  The load support layer 16 is located on the inner side in the axial direction of the sidewall 8. The support layer 16 is located on the inner side in the axial direction than the carcass 14. The support layer 16 is sandwiched between the carcass 14 and the inner liner 22. The support layer 16 tapers inward and outwards in the radial direction. This support layer 16 has a similar shape to the crescent moon. The support layer 16 is made of a highly hard crosslinked rubber. When the tire 2 is punctured, the support layer 16 supports the load. The support layer 16 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 16 having a shape different from the shape of the support layer 16 illustrated in FIG.

  A portion of the carcass 14 that overlaps the support layer 16 is separated from the inner liner 22. In other words, the carcass 14 is curved due to the presence of the support layer 16. In the puncture state, a compressive load is applied to the support layer 16, and a tensile load is applied to a region of the carcass 14 that is close to the support layer 16. Since the support layer 16 is a rubber lump, it can sufficiently withstand the compressive load. The cord of the carcass 14 can sufficiently withstand a tensile load. The support layer 16 and the cord of the carcass 14 suppress 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 of the support layer 16 is preferably 60 or more, and more preferably 65 or more. In light of riding comfort in a normal state, the hardness is preferably 90 or less, and more preferably 80 or less.

  The belt 18 is located on the inner side in the radial direction of the tread 4. The belt 18 is laminated with the carcass 14. The belt 18 reinforces the carcass 14. The belt 18 includes an inner layer 52 and an outer layer 54. As apparent from FIG. 1, the width of the inner layer 52 is slightly larger than the width of the outer layer 54 in the axial direction. Although not shown, each of the inner layer 52 and the outer layer 54 is composed of a large number of cords arranged in parallel and a topping rubber. Each cord is inclined with respect to the equator plane. The absolute value of the tilt angle is usually 10 ° to 35 °. The inclination direction of the cord of the inner layer 52 with respect to the equator plane is opposite to the inclination direction of the cord of the outer layer 54 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 18 is preferably 0.7 times or more the maximum width of the tire 2. The belt 18 may include three or more layers.

  The band 20 is located on the radially outer side of the belt 18. In the axial direction, the width of the band 20 is substantially equal to the width of the belt 18. Although not shown, the band 20 is composed of a cord and a topping rubber. The cord is wound in a spiral. The band 20 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 18 is restrained by this cord, the lifting of the belt 18 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 18 and the band 20 constitute a reinforcing layer. The reinforcing layer may be formed only from the belt 18. The reinforcing layer may be configured only from the band 20.

  The inner liner 22 is located inside the carcass 14. The inner liner 22 is joined to the inner surface of the carcass 14. The inner liner 22 is made of a crosslinked rubber. The inner liner 22 is made of rubber having excellent air shielding properties. A typical base rubber of the inner liner 22 is butyl rubber or halogenated butyl rubber. The inner liner 22 holds the internal pressure of the tire 2.

  The chafer 24 is located in the vicinity of the bead 12. When the tire 2 is incorporated in the rim, the chafer 24 comes into contact with the rim. By this contact, the vicinity of the bead 12 is protected. In this embodiment, the chafer 24 is made of cloth and rubber impregnated in the cloth. The chafer 24 may be integrated with the clinch 10. In this case, the material of the chafer 24 is the same as that of the clinch 10.

  In FIG. 1, a two-dot chain line B represents a vehicle body of a passenger car to which the tire 2 is attached. In FIG. 1, the left-right direction is also the width direction of the vehicle. The right side is the vehicle width direction inside (IN side), and the left side is the vehicle width direction outside (OUT side).

  FIG. 2 shows a part 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, a portion of one bead 12a of the tire 2 is shown. FIG. 2 shows a portion of a bead 12a located on the inner side in the width direction of the vehicle when the tire 2 is mounted on a passenger car. Therefore, the right side of FIG. 2 is also the inner side in the width direction of the vehicle.

  In FIG. 2, a solid line L1 is a first reference line extending in the axial direction. A double-headed arrow H1 represents the height in the radial direction from the radially outer end of the core 38 to the first reference line L1. In the present application, this height H1 is 1.0 mm. That is, the first reference line L1 is an imaginary straight line that extends in the axial direction through a position 1.0 mm away from the outer end of the core 38 radially outward (hereinafter referred to as a first reference position). A solid line L2 is a second reference line extending in the axial direction. A double-headed arrow H2 represents the height in the radial direction from the radially inner end of the core 38 to the second reference line L2. In the present application, this height H2 is 17.0 mm. That is, the second reference line L2 is a virtual straight line that extends in the axial direction through a position (hereinafter referred to as a second reference position) that is 17.0 mm away from the inner end of the core 38 radially outward. The solid line LR is a virtual straight line extending in the axial direction through the tip Pr of the rim protector 34. A solid line L3 is a virtual straight line passing through a radial intermediate position between the virtual straight line LR and the second reference line L2 (hereinafter referred to as a third reference position). In the present application, this solid line L3 is referred to as a third reference line.

  In FIG. 2, a double-headed arrow T1 is the first reference thickness of the apex 40 measured along the first reference line L1. That is, the first reference thickness T1 is the thickness of the apex 40 at the first reference position. A double-headed arrow T2 is the second reference thickness of the apex 40 measured along the second reference line L2. That is, the second reference thickness T2 is the thickness of the apex 40 at the second reference position. A double-headed arrow T3 is the third reference thickness of the apex 40 measured along the third reference line L3. That is, the third reference thickness T3 is the thickness of the apex 40 at the third reference position.

  In FIG. 2, a double arrow S1 is the first reference thickness of the clinch 10 measured along the first reference line L1. That is, the first reference thickness S1 is the thickness of the clinch 10 at the first reference position. A double-headed arrow S2 is the second reference thickness of the clinch 10 measured along the second reference line L2. That is, the second reference thickness S2 is the thickness of the clinch 10 at the second reference position. The double arrow S3 is the third reference thickness of the clinch 10 measured along the third reference line L3. That is, the third reference thickness S3 is the thickness of the clinch 10 at the third reference position. In addition, when the protrusion or the hollow is provided in the outer surface of the clinch 10, thickness S1, thickness S2, and thickness S3 are obtained based on the virtual outer surface obtained as there is no protrusion or hollow.

In the present invention, the first reference position, the second reference position, and the third reference position in the apex 40 and the clinch 10 correspond to locations where distortion concentrates when the tire 2 is traveling in a puncture state. The degree of distortion is calculated from analysis by a finite element method (FEM). The conditions for analysis are as follows.
Rim: 17 × 6.0JJ
Internal pressure: 0 kPa
Load: 4.24kN

  As described above, FIG. 2 shows a portion of the bead 12a positioned on the inner side in the width direction of the vehicle when the tire 2 is mounted on a passenger car. In the present application, the bead 12a included in this portion is also referred to as a backside bead. The core 38a that forms part of the bead 12a is also referred to as a back-side core. The apex 40a which forms another part of the bead 12a is also referred to as a back side apex. As shown in FIG. 2, the first reference thickness T1 of the back side apex 40a is represented as “T1a”. The second reference thickness T2 is represented as “T2a”. The third reference thickness T3 is represented as “T3a”. Further, the clinch 10a included in this portion is also referred to as a backside clinch. As shown in FIG. 2, the first reference thickness S1 of the backside clinch 10a is represented as “S1a”. The second reference thickness S2 is represented as “S2a”. The third reference thickness S3 is represented as “S3a”.

  FIG. 3 shows another part of the tire 2 shown in FIG. In FIG. 3, 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. FIG. 3 shows a portion of the other bead 12 b of the tire 2. Also in the bead 12b shown in FIG. 3, the first reference thickness T1, the second reference thickness T2, and the third reference thickness T3 of the apex 40 are defined in the same manner as the bead 12a shown in FIG. Is done. Also in the clinch 10b shown in FIG. 3, the first reference thickness S1, the second reference thickness S2, and the third reference thickness S3 of the clinch 10 are defined in the same manner as the clinch 10a shown in FIG. The

  In the tire 2, the left and right cores 38 have the same configuration except that they are symmetrical with respect to the equator plane. Accordingly, the radial heights of the left and right cores 38 are the same as the center positions of the left and right cores 38. Further, in the tire 2, the positions in the radial direction of the outer ends 42 of the left and right apex 40 are also the same. The positions in the radial direction of the outer ends (symbol PC in FIG. 1) of the left and right clinch 10 are the same.

  FIG. 3 shows a portion of a bead 12b positioned outside in the width direction of the vehicle when the tire 2 is mounted on a passenger car. Therefore, the left side of FIG. 3 is the outside in the width direction of the vehicle. In the present application, the bead 12b included in this portion is also referred to as a front bead. The core 38b forming a part of the bead 12b is also referred to as a front side core. The apex 40b forming another part of the bead 12b is also referred to as a front side apex. As shown in FIG. 3, the first reference thickness T1 of the front-side apex 40b is represented as “T1b”. The second reference thickness T2 is represented as “T2b”. The third reference thickness T3 is represented as “T3b”. Further, the clinch 10b included in this portion is also referred to as a front side clinch. As shown in FIG. 3, the first reference thickness S1 of the front side clinch 10b is expressed as “S1b”. The second reference thickness S2 is represented as “S2b”. The third reference thickness S3 is represented as “S3b”.

  In the tire 2, the configuration of the front apex 40b is the same as that of the conventional tire. Therefore, the first reference thickness T1b of the front side apex 40b is 9.0 mm or greater and 10.0 mm or less. The second reference thickness T2b of the front side apex 40b is 8.0 mm or greater and 9.0 mm or less. The third reference thickness T3b of the front side apex 40b is 6.5 mm or more and 7.5 mm or less. Furthermore, the complex elastic modulus Eb of the front side apex 40b is 15 MPa or more and 100 MPa or less.

  In the tire 2, the configuration of the front side clinch 10b is the same as that of the conventional tire. Therefore, the first reference thickness S1b of the front side clinch 10b is 2.0 mm or greater and 6.0 mm or less. The second reference thickness S2b of the front side clinch 10b is 4.0 mm or greater and 8.0 mm or less. The third reference thickness S3b of the front side clinch 10b is 7.0 mm or greater and 11.0 mm or less. Furthermore, the complex elastic modulus Mb of the front side clinch 10b is 15 MPa or more and 100 MPa or less.

In the present invention, the complex elastic modulus Eb of the front-side apex 40b and the complex elastic modulus Mb of the front-side clinch 10b are 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
Note that the complex elastic modulus Ea of the back side apex 40a and the complex elastic modulus Ma of the back side clinch 10a, which will be described later, are also measured in the same manner as the elastic modulus Eb and the elastic modulus Mb.

In this tire 2, the difference (T1a-T1b) between the first reference thickness T1a of the back side apex 40a and the first reference thickness T1b of the front side apex 40b, the second reference thickness T2a of the back side apex 40a, and the front side apex 40b. Of the second reference thickness T2b (T2a-T2b), the difference between the third reference thickness T3a of the back side apex 40a and the third reference thickness T3b of the front side apex 40b (T3a-T3b), and the back side apex 40a. The ratio (Ea / Eb) of the complex elastic modulus Ea to the complex elastic modulus Eb of the front-side apex 40b, and the difference between the first reference thickness S1a of the back-side clinch 10a and the first reference thickness S1b of the front-side clinch 10b (S1a-S1b ), The difference between the second reference thickness S2a of the back side clinch 10a and the second reference thickness S2b of the front side clinch 10b (S2a− 2b), the difference (S3a-S3b) between the third reference thickness S3a of the back side clinch 10a and the third reference thickness S3b of the front side clinch 10b, and the ratio of the complex elastic modulus Ma of the back side clinch 10a to the complex elastic modulus Mb of the front side clinch 10b. (Ma / Mb) is adjusted appropriately. Specifically, the tire 2 satisfies any of the following conditions (1) to (8).
Condition (1) The difference (T1a-T1b) is 0.5 mm or more and 1.2 mm or less.
Condition (2) The difference (T2a-T2b) is 0.5 mm or more and 1.2 mm or less.
Condition (3) The difference (T3a-T3b) is 0.5 mm or more and 1.2 mm or less.
Condition (4) The ratio (Ea / Eb) is 1.4 or more and 1.7 or less.
Condition (5) The difference (S1a-S1b) is 0.5 mm or more and 1.2 mm or less.
Condition (6) The difference (S2a-S2b) is 0.5 mm or more and 1.2 mm or less.
Condition (7) The difference (S3a-S3b) is 0.5 mm or more and 1.2 mm or less.
Condition (8) The ratio (Ma / Mb) is 1.4 or more and 1.7 or less.

  In the tire 2, the thickness of the back-side apex 40a is greater than the thickness of the front-side apex 40b at any of the first reference position, the second reference position, and the second reference position, or the elastic modulus Ea of the back-side apex 40a is It is larger than the elastic modulus Eb of the front side apex 40b. Alternatively, the thickness of the back side clinch is greater than the thickness of the front side clinch at any of the first reference position, the second reference position, and the third reference position, or the complex elastic modulus Wa of the back side clinch is greater than the complex elastic modulus Mb of the front side clinch. Is also big. In the tire 2, the back side bead 12 a has higher rigidity than the front side bead 12 b. For this reason, the durability at the time of puncture is improved by mounting the tire 2 on the body B of the vehicle so that the portion of the back side bead 12a is positioned inward in the width direction of the vehicle. Moreover, the difference (T1a-T1b), the difference (T2a-T2b), the difference (T3a-T3b) and the ratio (Ea / Eb), and the difference (S1a-S1b), the difference (S2a-S2b), the difference (S3a-S3b) ) And the upper limit of the ratio (Ma / Mb) are appropriately adjusted, so that a good riding comfort is maintained. The tire 2 is excellent in durability during puncture and ride comfort.

  As described above, in the tire 2, the configuration of the front bead 12b is the same as that of the conventional tire. For this reason, in this tire 2, the influence on the riding comfort and the dynamic balance recognized in the conventional tire which employ | adopted the apex which has big rigidity in the right and left bead is suppressed. In the tire 2, the influence on the riding comfort and the dynamic balance recognized in the conventional tire configured such that the left and right clinches have large rigidity is suppressed. According to the present invention, the tire 2 is obtained in which not only the ride comfort but also the dynamic balance is maintained well.

  In the tire 2 that satisfies the condition (1), the difference (T1a−T1b) is not less than 0.5 mm and not more than 1.2 mm. By setting this difference (T1a-T1b) to be 0.5 mm or more, the back-side apex 40a can effectively contribute to durability during puncture. In this respect, the difference (T1a−T1b) is preferably equal to or greater than 0.6 mm. By setting this difference (T1a-T1b) to be 1.2 mm or less, the difference in rigidity between the back-side apex 40a and the front-side apex 40b is appropriately maintained. The tire 2 is excellent in ride comfort. From the viewpoint of improving the dynamic balance, the difference (T1a-T1b) is preferably 1.1 mm or less. In the case where the tire 2 satisfies the condition (1), the second reference thickness T2a of the back side apex 40a is set to the front side apex from the viewpoint that the effect of the condition (1) is effectively reflected in the performance of the tire 2. 40b is equal to or greater than the second reference thickness T2b, the third reference thickness T3a of the back apex 40a is equal to or greater than the third reference thickness T3b of the front apex 40b, and the complex elastic modulus Ea of the back apex 40a is It is equal to or greater than the complex elastic modulus Eb of the front side apex 40b, the first reference thickness S1a of the back side clinch 10a is equal to or more than the first reference thickness S1b of the front side clinch 10b, and the second reference thickness S2a of the back side clinch 10a is It is equal to or more than the second reference thickness S2b of the front side clinch 10b, and the third reference thickness S3a of the back side clinch 10a is the front side clinch 10b. And a third reference thickness S3b least equivalent, and complex elastic modulus Ma of the backside clinch 10a is is preferably at the front side clinch 10b complex elastic modulus Mb least equivalent.

  In the tire 2 that satisfies the condition (2), the difference (T2a−T2b) is not less than 0.5 mm and not more than 1.2 mm. By setting this difference (T2a-T2b) to be 0.5 mm or more, the back-side apex 40a can effectively contribute to durability during puncture. From this viewpoint, the difference (T2a−T2b) is preferably 0.6 mm or more. By setting this difference (T2a−T2b) to be equal to or less than 1.2 mm, the difference in rigidity between the back-side apex 40a and the front-side apex 40b is appropriately maintained. The tire 2 is excellent in ride comfort. From the viewpoint of improving the dynamic balance, the difference (T2a-T2b) is preferably 1.1 mm or less. In the case where the tire 2 satisfies the condition (2), the first reference thickness T1a of the back side apex 40a is the front side apex from the viewpoint that the effect of the condition (2) is effectively reflected in the performance of the tire 2. The third reference thickness T3a of the back side apex 40a is equal to or more than the third reference thickness T3b of the front side apex 40b, and the complex elastic modulus Ea of the back side apex 40a. Is equal to or greater than the complex elastic modulus Eb of the front side apex 40b, the first reference thickness S1a of the back side clinch 10a is equal to or greater than the first reference thickness S1b of the front side clinch 10b, and the second reference thickness S2a of the back side clinch 10a. Is equal to or greater than the second reference thickness S2b of the front side clinch 10b, and the third reference thickness S3a of the back side clinch 10a is equal to or greater than the front side clinch 10b. And a third reference thickness S3b least equivalent, and complex elastic modulus Ma of the backside clinch 10a is is preferably at the front side clinch 10b complex elastic modulus Mb least equivalent.

  In the tire 2 that satisfies the condition (3), the difference (T3a−T3b) is not less than 0.5 mm and not more than 1.2 mm. By setting this difference (T3a-T3b) to be 0.5 mm or more, the back-side apex 40a can effectively contribute to durability during puncture. In this respect, the difference (T3a−T3b) is preferably equal to or greater than 0.6 mm. By setting this difference (T3a−T3b) to be equal to or less than 1.2 mm, the difference in rigidity between the back-side apex 40a and the front-side apex 40b is appropriately maintained. The tire 2 is excellent in ride comfort. From the viewpoint of improving the dynamic balance, the difference (T3a-T3b) is preferably 1.1 mm or less. In the case where the tire 2 satisfies the condition (3), the first reference thickness T1a of the back side apex 40a is the front side apex from the viewpoint that the effect of the condition (3) is effectively reflected in the performance of the tire 2. The second reference thickness T2a of the back side apex 40a is equal to or more than the second reference thickness T2b of the front side apex 40b, and the complex elastic modulus Ea of the back side apex 40a. Is equal to or greater than the complex elastic modulus Eb of the front side apex 40b, the first reference thickness S1a of the back side clinch 10a is equal to or greater than the first reference thickness S1b of the front side clinch 10b, and the second reference thickness S2a of the back side clinch 10a. Is equal to or greater than the second reference thickness S2b of the front side clinch 10b, and the third reference thickness S3a of the back side clinch 10a is equal to or greater than the front side clinch 10b. And a third reference thickness S3b least equivalent, and complex elastic modulus Ma of the backside clinch 10a is is preferably at the front side clinch 10b complex elastic modulus Mb least equivalent.

  In the tire 2 that satisfies the condition (4), the ratio (Ea / Eb) is 1.4 or more and 1.7 or less. By setting the ratio (Ea / Eb) to be 1.4 or more, the back-side apex 40a can effectively contribute to durability during puncture. From this viewpoint, the ratio (Ea / Eb) is preferably 1.5 or more. By setting the ratio (Ea / Eb) to 1.7 or less, the difference in rigidity between the back side apex 40a and the front side apex 40b is appropriately maintained. The tire 2 is excellent in ride comfort. From the viewpoint of improving the dynamic balance, the ratio (Ea / Eb) is preferably 1.6 or less. In the case where the tire 2 satisfies the condition (4), the first reference thickness T1a of the back side apex 40a is the front side apex from the viewpoint that the effect of the condition (4) is effectively reflected in the performance of the tire 2. The second reference thickness T2a of the back side apex 40a is equal to or more than the second reference thickness T2b of the front side apex 40b, and the third reference thickness of the back side apex 40a. T3a is equal to or greater than the third reference thickness T3b of the front side apex 40b, the first reference thickness S1a of the back side clinch 10a is equal to or greater than the first reference thickness S1b of the front side clinch 10b, and the second reference of the back side clinch 10a. The thickness S2a is equal to or greater than the second reference thickness S2b of the front side clinch 10b, and the third reference thickness S3a of the back side clinch 10a is the front side clinch 10b. Chi 10b and the third reference thickness S3b least equivalent, and complex elastic modulus Ma of the backside clinch 10a is is preferably at the front side clinch 10b complex elastic modulus Mb least equivalent.

  In the tire 2 that satisfies the condition (5), the difference (S1a−S1b) is not less than 0.5 mm and not more than 1.2 mm. By setting this difference (S1a-S1b) to be 0.5 mm or more, the back side clinch 10a can effectively contribute to durability during puncture. In this respect, the difference (S1a−S1b) is preferably equal to or greater than 0.6 mm. By setting this difference (S1a-S1b) to be 1.2 mm or less, the difference in rigidity between the back side clinch 10a and the front side clinch 10b is appropriately maintained. The tire 2 is excellent in ride comfort. From the viewpoint of improving the dynamic balance, the difference (S1a-S1b) is preferably 1.1 mm or less. In addition, when the tire 2 satisfies the condition (5), the first reference thickness T1a of the back side apex 40a is set to the front side apex from the viewpoint that the effect of the condition (5) is effectively reflected in the performance of the tire 2. 40b is equal to or greater than the first reference thickness T1b, the second reference thickness T2a of the back side apex 40a is equal to or greater than the second reference thickness T2b of the front side apex 40b, and the third reference thickness T3a of the back side apex 40a. Is equal to or greater than the third reference thickness T3b of the front side apex 40b, the complex elastic modulus Ea of the back side apex 40a is equal to or greater than the complex elastic modulus Eb of the front side clinch 10b, and the second reference thickness S2a of the back side clinch 10a. Is equal to or greater than the second reference thickness S2b of the front side clinch 10b, and the third reference thickness S3a of the back side clinch 10a is the front side clinch 1 b is the third reference thickness S3b least equivalent, and complex elastic modulus Ma of the backside clinch 10a is is preferably at the front side clinch 10b complex elastic modulus Mb least equivalent.

  In the tire 2 that satisfies the condition (6), the difference (S2a−S2b) is not less than 0.5 mm and not more than 1.2 mm. By setting this difference (S2a-S2b) to be 0.5 mm or more, the back side clinch 10a can effectively contribute to durability during puncture. In this respect, the difference (S2a−S2b) is preferably equal to or greater than 0.6 mm. By setting this difference (S2a-S2b) to be 1.2 mm or less, the rigidity difference between the back side clinch 10a and the front side clinch 10b is appropriately maintained. The tire 2 is excellent in ride comfort. From the viewpoint of improving the dynamic balance, the difference (S2a-S2b) is preferably 1.1 mm or less. When the tire 2 satisfies the condition (6), the first reference thickness T1a of the back-side apex 40a is set to the front-side apex from the viewpoint that the effect of the condition (6) is effectively reflected in the performance of the tire 2. The second reference thickness T2a of the back side apex 40a is equal to or more than the second reference thickness T2b of the front side apex 40b, and the third reference thickness of the back side apex 40a. T3a is equal to or greater than the third reference thickness T3b of the front side apex 40b, the complex elastic modulus Ea of the back side apex 40a is equal to or greater than the complex elastic modulus Eb of the front side clinch 10b, and the first reference thickness of the back side clinch 10a. S1a is equal to or greater than the first reference thickness S1b of the front side clinch 10b, and the third reference thickness S3a of the back side clinch 10a is the front side clinch. 0b and the third reference thickness S3b least equivalent, and complex elastic modulus Ma of the backside clinch 10a is is preferably at the front side clinch 10b complex elastic modulus Mb least equivalent.

  In the tire 2 that satisfies the condition (7), the difference (S3a−S3b) is not less than 0.5 mm and not more than 1.2 mm. By setting this difference (S3a-S3b) to be 0.5 mm or more, the back side clinch 10a can effectively contribute to durability during puncture. In this respect, the difference (S3a−S3b) is preferably equal to or greater than 0.6 mm. By setting this difference (S3a-S3b) to be 1.2 mm or less, the rigidity difference between the back side clinch 10a and the front side clinch 10b is appropriately maintained. The tire 2 is excellent in ride comfort. From the viewpoint of improving the dynamic balance, the difference (S3a-S3b) is preferably 1.1 mm or less. In the case where the tire 2 satisfies the condition (7), the first reference thickness T1a of the back side apex 40a is the front side apex from the viewpoint that the effect of the condition (7) is effectively reflected in the performance of the tire 2. The second reference thickness T2a of the back side apex 40a is equal to or more than the second reference thickness T2b of the front side apex 40b, and the third reference thickness of the back side apex 40a. T3a is equal to or greater than the third reference thickness T3b of the front side apex 40b, the complex elastic modulus Ea of the back side apex 40a is equal to or greater than the complex elastic modulus Eb of the front side clinch 10b, and the first reference thickness of the back side clinch 10a. S1a is equal to or greater than the first reference thickness S1b of the front side clinch 10b, and the second reference thickness S2a of the back side clinch 10a is the front side clinch. 0b and the second reference thickness S2b least equivalent, and complex elastic modulus Ma of the backside clinch 10a is it is preferably at the front side clinch 10b complex elastic modulus Mb least equivalent.

  In the tire 2 that satisfies the condition (8), the ratio (Ma / Mb) is 1.4 or more and 1.7 or less. By setting the ratio (Ma / Mb) to 1.4 or more, the back side clinch 10a can effectively contribute to durability during puncture. From this viewpoint, the ratio (Ma / Mb) is preferably 1.5 or more. By setting this ratio (Ma / Mb) to 1.7 or less, the rigidity difference between the back side clinch 10a and the front side clinch 10b is appropriately maintained. The tire 2 is excellent in ride comfort. From the viewpoint of improving the dynamic balance, the ratio (Ma / Mb) is preferably 1.6 or less. When the tire 2 satisfies the condition (8), the first reference thickness T1a of the back side apex 40a is set to the front side apex from the viewpoint that the effect of the condition (8) is effectively reflected in the performance of the tire 2. The second reference thickness T2a of the back side apex 40a is equal to or more than the second reference thickness T2b of the front side apex 40b, and the third reference thickness of the back side apex 40a. T3a is equal to or greater than the third reference thickness T3b of the front side apex 40b, the complex elastic modulus Ea of the back side apex 40a is equal to or greater than the complex elastic modulus Eb of the front side apex 40b, and the first reference of the back side clinch 10a. The thickness S1a is equal to or greater than the first reference thickness S1b of the front side clinch 10b, and the second reference thickness S2a of the back side clinch 10a is the front side clinch 10b. And a second reference thickness S2b equal or Chi 10b, and preferably the third reference thickness S3a of the rear clinch 10a is third reference thickness S3b equal or front clinch 10b.

  The tire 2 preferably satisfies at least two of the above conditions (1) to (8). Thereby, the back side apex 40a and / or the back side clinch 10a can contribute to the durability at the time of puncture effectively. Since the rigidity difference between the back-side apex 40a and the front-side apex 40b and / or the rigidity difference between the back-side clinch 10a and the front-side clinch 10b is appropriately maintained, excellent riding comfort and good dynamic balance are appropriately maintained. The According to the present invention, it is possible to obtain a pneumatic tire 2 that is excellent in durability while appropriately maintaining riding comfort and dynamic balance. From this viewpoint, it is more preferable to satisfy at least three conditions among the conditions (1) to (8), it is more preferable to satisfy at least four conditions, and it is more preferable to satisfy at least five conditions. It is more preferable to satisfy one condition, and it is more preferable to satisfy at least seven conditions. Particularly preferably, all of the above conditions (1) to (8) are satisfied.

  In the tire 2, only the difference in rigidity between the left and right apex 40 may be adjusted to achieve improved puncture durability and ride comfort. In this case, the first reference thickness S1a of the back side clinch 10a is equal to the first reference thickness S1b of the front side clinch 10b from the viewpoint that the effect of the difference in rigidity between the left and right apex 40 is effectively reflected in the performance of the tire 2. The second reference thickness S2a of the back side clinch 10a is equal to or more than the second reference thickness S2b of the front side clinch 10b, and the third reference thickness S3a of the back side clinch 10a is equivalent to the third reference thickness S3b of the front side clinch 10b. Thus, the complex elastic modulus Ma of the back side clinch 10a is preferably equal to or greater than the complex elastic modulus Mb of the front side clinch 10b.

  When adjusting only the rigidity difference between the left and right apex 40 to achieve improved puncture durability and ride comfort (hereinafter referred to as Case 1), this tire 2 includes conditions (1) and (2), It is preferable to satisfy any of the conditions (2) and (3) and the conditions (3) and (1). Thereby, the further improvement of durability at the time of puncture is achieved, maintaining riding comfort and dynamic balance favorably. From this viewpoint, when the tire 2 satisfies the conditions (1) and (2), the third reference thickness T3a of the back side apex 40a is equal to or greater than the third reference thickness T3b of the front side apex 40b, and the back side The complex elastic modulus Ea of the apex 40a is preferably equal to or greater than the complex elastic modulus Eb of the front apex 40b. Thereby, the effects of the conditions (1) and (2) are effectively reflected in the performance of the tire 2. When the tire 2 satisfies the conditions (2) and (3), the first reference thickness T1a of the back side apex 40a is equal to or greater than the first reference thickness T1b of the front side apex 40b. The complex elastic modulus Ea is preferably equal to or greater than the complex elastic modulus Eb of the front apex 40b. Thereby, the effect by these conditions (2) and (3) is reflected in the performance of the tire 2 effectively. When the tire 2 satisfies the condition (3) and the condition (1), the second reference thickness T2a of the back side apex 40a is equal to or greater than the second reference thickness T2b of the front side apex 40b. The complex elastic modulus Ea is preferably equal to or greater than the complex elastic modulus Eb of the front apex 40b. Thereby, the effect by these conditions (3) and (1) is reflected in the performance of the tire 2 effectively.

  In the case 1, the tire 2 may be configured to further satisfy the condition (4) in addition to any two conditions (1) to (3). In this case, from the viewpoint that the effect of each condition is effectively reflected in the performance of the tire 2, when the tire 2 satisfies the conditions (1), (2), and (4), the third of the back side apex 40a. The reference thickness T3a is preferably equal to or greater than the third reference thickness T3b of the front side apex 40b. When the tire 2 satisfies the conditions (2), (3), and (4), the first reference thickness T1a of the back-side apex 40a is preferably equal to or greater than the first reference thickness T1b of the front-side apex 40b. When the tire 2 satisfies the conditions (3), (4), and (1), the second reference thickness T2a of the back side apex 40a is preferably equal to or greater than the second reference thickness T2b of the front side apex 40b.

  Further, in the case 1 described above, the tire 2 more preferably satisfies the conditions (1), (2), and (3). Thereby, the further improvement of durability at the time of puncture is achieved, maintaining riding comfort and dynamic balance favorably. In this case, from the viewpoint that the effect of each condition is effectively reflected in the performance of the tire 2, the complex elastic modulus Ea of the back-side apex 40a is equal to or more than the complex elastic modulus Eb of the front-side apex 40b. Is preferred.

  In the case 1 described above, the tire 2 has a condition (1), a condition (2), a condition (3), and a condition (4), that is, all four conditions indicated by the conditions (1) to (4). It is more preferable to satisfy Thereby, the further improvement of durability at the time of puncture is achieved, maintaining riding comfort and dynamic balance favorably.

  In the tire 2, only the rigidity difference between the left and right clinches 10 may be adjusted to achieve improved puncture durability and riding comfort. In this case, the first reference thickness T1a of the back-side apex 40a is different from the first reference thickness T1b of the front-side apex 40b from the viewpoint that the effect of the rigidity difference between the left and right clinches 10 is effectively reflected in the performance of the tire 2. The second reference thickness T2a of the back-side apex 40a is equal to or more than the second reference thickness T2b of the front-side apex 40b, and the third reference thickness T3a of the back-side apex 40a is the third reference thickness T3a of the front-side apex 40b. It is preferably equal to or greater than the reference thickness T3b, and the complex elastic modulus Ea of the back side apex 40a is preferably equal to or greater than the complex elastic modulus Eb of the front side apex 40b.

  When adjusting only the rigidity difference between the left and right clinches 10 to achieve improvement in durability and riding comfort at the time of puncture (hereinafter referred to as case 2), the tire 2 includes conditions (5) and (6), It is preferable to satisfy any of (6) and condition (7), and condition (7) and condition (5). Thereby, the further improvement of durability at the time of puncture is achieved, maintaining riding comfort and dynamic balance favorably. From this viewpoint, when the tire 2 satisfies the conditions (5) and (6), the third reference thickness S3a of the back side clinch 10a is equal to or greater than the third reference thickness S3b of the front side clinch 10b, and the back side clinch 10a. It is preferable that the complex elastic modulus Ma is equal to or greater than the complex elastic modulus Mb of the front side clinch 10b. Thereby, the effects of the conditions (5) and (6) are effectively reflected in the performance of the tire 2. When the tire 2 satisfies the conditions (6) and (7), the first reference thickness S1a of the back side clinch 10a is equal to or greater than the first reference thickness S1b of the front side clinch 10b, and the complex elastic modulus of the back side clinch 10a. Ma is preferably equal to or greater than the complex elastic modulus Mb of the front side clinch 10b. Thereby, the effects of the conditions (6) and (7) are effectively reflected in the performance of the tire 2. When the tire 2 satisfies the conditions (7) and (5), the second reference thickness S2a of the back side clinch 10a is equal to or greater than the second reference thickness S2b of the front side clinch 10b, and the complex elastic modulus of the back side clinch 10a. Ma is preferably equal to or greater than the complex elastic modulus Mb of the front side clinch 10b. Thereby, the effects of the conditions (7) and (5) are effectively reflected in the performance of the tire 2.

  In the case 2 described above, the tire 2 may be configured to further satisfy the condition (8) in addition to any two of the conditions (5) to (7). In this case, from the viewpoint that the effect of each condition is effectively reflected in the performance of the tire 2, when the tire 2 satisfies the conditions (5), (6) and (8), the third reference of the back side clinch 10a. The thickness S3a is preferably equal to or greater than the third reference thickness S3b of the front side clinch 10b. When the tire 2 satisfies the conditions (6), (7), and (8), the first reference thickness S1a of the back side clinch 10a is preferably equal to or greater than the first reference thickness S1b of the front side clinch 10b. When the tire 2 satisfies the conditions (7), (8), and (5), the second reference thickness S2a of the back side clinch 10a is preferably equal to or greater than the second reference thickness S2b of the front side clinch 10b.

  Furthermore, in the case 2 described above, it is more preferable that the tire 2 satisfies the condition (5), the condition (6), and the condition (7). Thereby, the further improvement of durability at the time of puncture is achieved, maintaining riding comfort and dynamic balance favorably. In this case, the complex elastic modulus Ma of the back side clinch 10a is preferably equal to or more than the complex elastic modulus Mb of the front side clinch 10b from the viewpoint that the effect of each condition is effectively reflected in the performance of the tire 2. .

  In the case 2 described above, the tire 2 has a condition (5), a condition (6), a condition (7), and a condition (8), that is, all four conditions indicated by the conditions (5) to (8). It is more preferable to satisfy Thereby, the further improvement of durability at the time of puncture is achieved, maintaining riding comfort and dynamic balance favorably.

  In the tire 2, there is a difference in rigidity between the left and right bead 12 portions. For this reason, in the vehicle in which the tire 2 is mounted, there is a difference in the size of the cornering force between the tire 2 mounted on the right side of the vehicle and the tire 2 mounted on the left side of the vehicle. In this case, the steering wheel response may deteriorate, and the steering stability may be reduced.

  The present inventors diligently examined the influence of the apex 40 and the clinch 10 on the cornering force of the tire 2. As a result, it has been found that the influence of the rigidity difference between the left and right clinches 10 on the cornering force is smaller than the influence of the rigidity difference between the left and right apex 40 on the cornering force. Therefore, in the tire 2, when adjusting the rigidity of either the apex 40 or the clinch 10 from the viewpoint of improving durability during puncture and riding comfort, the rigidity of the left and right apex 40 is adjusted. Rather, it is preferable to adjust the rigidity of the left and right clinch 10. Thereby, the tire 2 excellent in durability and riding comfort at the time of puncture can be obtained while appropriately maintaining the steering stability. When adjusting the rigidity of the left and right apex 40 to improve the durability and riding comfort during puncture, it is preferable to adjust the rigidity of the left and right clinch 10 as well. Thereby, the durability at the time of puncture and the improvement of riding comfort of the tire 2 are achieved while minimizing the influence on the steering stability due to the difference in rigidity between the left and right apex 40.

  As described above, in the tire 2, by adjusting the thickness or elastic modulus of the apex 40 and / or by adjusting the thickness or elastic modulus of the clinch 10, particularly in the portion of the backside bead 12a. Durability is improved. In a passenger vehicle in which the tire 2 is mounted on the vehicle so that the backside bead 12a portion of the tire 2 is positioned inward in the vehicle width direction, the durability at the time of puncture is maintained without impairing dynamic balance and riding comfort. An improvement in sex is achieved.

  In the present invention, the size and angle of each member of the tire 2 are measured in a state where the tire 2 is incorporated in a regular rim and the tire 2 is filled with air so as to have a regular internal pressure. At the time of measurement, no load is applied to the tire 2. 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. When the tire 2 is for a passenger car, the dimensions and angles are measured with the internal pressure being 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]
A pneumatic tire (run flat tire) of Example 1 having the basic configuration shown in FIG. 1 and having the specifications shown in Table 5 below was obtained. The size of this tire was set to “225 / 45R17”. In Example 1, the first reference thickness T1b of the front side apex was 9.5 mm. The second reference thickness T2b was 8.5 mm. The third reference thickness T3b was 7.0 mm. The complex elastic modulus Eb was 50 MPa. The first reference thickness T1a of the back side apex was 10.5 mm. The second reference thickness T2a was 9.5 mm. The third reference thickness T3a was 8.0 mm. The complex elastic modulus Ea was 80 MPa. In Example 1, the first reference thickness S1b of the front side clinch was 4.0 mm. The second reference thickness S2b was 6.0 mm. The third reference thickness S3b was 9.0 mm. The complex elastic modulus Mb was 50 MPa. The first reference thickness S1a of the back side clinch was 4.0 mm. The second reference thickness S2a was 6.0 mm. The third reference thickness S3a was 9.0 mm. The complex elastic modulus Ma was set to 50 MPa.

[Example 2-55 and Comparative Example 1-17]
The first reference thickness T1a, the second reference thickness T2a, the third reference thickness T3a and the complex elastic modulus Ea of the back side apex, and the first reference thickness S1a, the second reference thickness S2a, the third reference thickness S3a of the back side clinch and By adjusting the complex elastic modulus Ma, the difference (T1a-T1b), the difference (T2a-T2b), the difference (T3a-T3b) and the ratio (Ea / Eb), and the difference (S1a-S1b), the difference (S2a- Tires of Example 2-55 and Comparative Example 1-17 except that S2b), the difference (S3a-S3b), and the ratio (Ma / Mb) were as shown in Table 1-14 below. Got.

[Durability (during puncture)]
The tire was incorporated into a regular rim (size = 17 × 8.0J), and the tire was filled with air to adjust the internal pressure to 250 kPa. This tire was mounted on a drum type running test machine so that the back apex was at a position corresponding to the inner side in the width direction of the vehicle. After installation, a longitudinal load corresponding to 75% of the maximum load load specified by JATMA was applied to the tire. The puncture state was reproduced with the internal pressure of the tire as normal pressure, 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 1-14 below as index values with Comparative Example 1 taken as 100. The larger the value, the better, that is, the run flat durability is excellent.

[Vertical spring evaluation]
The longitudinal spring constant of the tire was measured under the following conditions.
Rim size used: 17 × 8.0J
Internal pressure: 230 kPa
Load: The index when the spring constant of the tire of Load Comparative Example 1 corresponding to 80% of the maximum load load defined by JATMA is 100 is shown in Table 1-14 below. The lower the value, the smaller the vertical spring and the better the ride comfort.

[Dynamic balance]
The tire was assembled in a regular rim (size = 17 × 8.0J), and this tire was filled with air so that the internal pressure was 230 kPa. The tire was attached to a balancer testing machine, and the mass of a weight necessary for dynamic balance was measured. The results are shown in Tables 1-14 below as index values with Comparative Example 1 taken as 100. The lower the number, the better.

[Steering stability]
The tire was assembled in a rim (size = 17 × 8.0 J), and this 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 driving stability. The results are shown in the following Table 1-14 as an index with Comparative Example 1 as 6 points. Larger numbers are preferable. The full score of this evaluation is 10 points.

  As shown in Table 1-14, 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 tire described above can be applied to various vehicles.

2 ... Tire 4 ... Tread 8 ... Sidewall 10, 10a, 10b ... Clinch 12, 12a, 12b ... Bead 14 ... Carcass 16 ... Load support layer 26 ... Tread surface 34 ... Rim protector 38, 38a, 38b ... Core 40, 40a, 40b ... Apex

Claims (8)

A tread whose outer surface forms a tread surface, a pair of sidewalls each extending substantially inward in the radial direction from the end of the tread, and a pair of clinch each positioned substantially inward in the radial direction from the sidewall, A pair of beads positioned axially inward of the clinch, a carcass spanned between one bead and the other bead along the inside of the tread and the sidewall, and each of the sidewalls A pair of load support layers located on the inner side in the axial direction,
Each sidewall has a rim protector that protrudes outward in the axial direction,
Each bead includes a core and an apex extending radially outward from the core,
A position separated by 1.0 mm radially outward from the outer end of the core is defined as a first reference position, and the thickness of the apex at the first reference position is defined as a first reference thickness T1. The clinch thickness is defined as a first reference thickness S1, and a position separated by 17.0 mm radially outward from the inner end of the core is defined as a second reference position, and the thickness of the apex at the second reference position is defined as a second reference thickness. The thickness of the clinch at the second reference position is defined as a second reference thickness S1, and a radial intermediate position between the second reference position and the tip of the rim protector is defined as a third reference position. The thickness of the apex at the three reference positions is the third reference thickness T3, and the thickness of the clinch at the third reference position is the third reference thickness S3.
When one apex is the back apex, the other apex is the front apex, one clinch is the back clinch, and the other clinch is the front clinch,
A pneumatic tire that satisfies any of the following conditions (1) to (8).
Condition (1) The difference (T1a−T1b) between the first reference thickness T1a of the back-side apex and the first reference thickness T1b of the front-side apex is 0.5 mm or more and 1.2 mm or less.
Condition (2) The difference (T2a−T2b) between the second reference thickness T2a of the back-side apex and the second reference thickness T2b of the front-side apex is 0.5 mm or more and 1.2 mm or less.
Condition (3) The difference (T3a-T3b) between the third reference thickness T3a of the back side apex and the third reference thickness T3b of the front side apex is 0.5 mm or more and 1.2 mm or less.
Condition (4) The ratio (Ea / Eb) of the complex elastic modulus Ea of the back side apex to the complex elastic modulus Eb of the front side apex is 1.4 or more and 1.7 or less.
Condition (5) The difference (S1a−S1b) between the first reference thickness S1a of the back side clinch and the first reference thickness S1b of the front side clinch is 0.5 mm or more and 1.2 mm or less.
Condition (6) The difference (S2a−S2b) between the second reference thickness S2a of the back side clinch and the second reference thickness S2b of the front side clinch is 0.5 mm or more and 1.2 mm or less.
Condition (7) The difference (S3a−S3b) between the third reference thickness S3a of the back side clinch and the third reference thickness S3b of the front side clinch is 0.5 mm or more and 1.2 mm or less.
Condition (8) The ratio (Ma / Mb) of the complex elastic modulus Ma of the back side clinch to the complex elastic modulus Mb of the front side clinch is 1.4 or more and 1.7 or less.   The pneumatic tire according to claim 1, wherein at least two of the conditions (1) to (8) are satisfied.   The air according to claim 2, satisfying any one of the condition (1) and the condition (2), the condition (2) and the condition (3), and the condition (3) and the condition (1). Enter tire.   The pneumatic tire according to claim 3, wherein the condition (1), the condition (2), and the condition (3) are satisfied.   The pneumatic tire according to claim 3 or 4, further satisfying the condition (4).   The air according to claim 2, satisfying any one of the conditions (5) and (6), the conditions (6) and (7), and the conditions (7) and (5). Enter tire.   The pneumatic tire according to claim 6, wherein the condition (5), the condition (6), and the condition (7) are satisfied.   The pneumatic tire according to claim 6 or 7, further satisfying the condition (8).

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