JP2015098237A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire which is excellent in transient characteristic of turning travel and steering stability.SOLUTION: A pneumatic tire 2 includes a tread 4, a side wall 6, a bead 10, a bead 12, and a carcass 14. The bead 10 is a strand bead which includes a core 34 that is positioned inside a vehicle attachment direction, with a bead wire wound in ring by a plurality of times in axial direction and radial direction, and an apex 36 extending in radial direction from the core 34 toward outside. The bead 12 is a cable bead which includes a core 38 that is positioned outside the vehicle attachment direction and made from a wire material wound in spiral at a core and around the core, and an apex 40 which extends outward in the radial direction from the core 38.

Description

  The present invention relates to a pneumatic tire.

  A tire having high rigidity can withstand a large lateral force during cornering. This tire is excellent in steering stability during turning. However, tires with high rigidity tend to be inferior in transient characteristics during turning. In particular, transient characteristics are likely to deteriorate rapidly in the grip limit region during high-speed turning. On the other hand, a tire having a relatively small rigidity is easily deformed and thus has excellent transient characteristics. However, it is difficult for this tire to exhibit sufficient rigidity against a large lateral force. This tire tends to be inferior in handling stability in turning.

  Patent Document 1 discloses a tire in which a bead core on the inner side (hereinafter referred to as a back side) and a bead core on an outer side (hereinafter referred to as a front side) are different from each other. The axial width of the bead core is made different between the back side and the front side while making the total number of bead wires wound. In this tire, the axial width of the bead core on the back side is made larger than the axial width of the bead core on the front side. In the tire set as a negative camber, the rigidity of the bead portion on the back side is increased to improve the handling stability, the straight running stability, and the riding comfort. On the other hand, the durability of the bead portion is improved by making the total number of the bead wires on the back side the same as the total number of the bead wires on the front side.

JP 2009-1226 A

  The tire of Patent Document 1 is mounted on a four-wheel vehicle. In a turning traveling of a four-wheeled vehicle, the front bead portion is deformed in a direction away from the rim in a tire positioned on the outer side in the turning radius direction. Since the bead portion of the tire is made of a strand bead, it contributes to an improvement in tire rigidity. However, in this tire, the rigidity of the bead portion on the front side is smaller than the rigidity of the bead portion on the back side, so that the steering stability during turning is poor. Furthermore, since the bead portion on the front side is made of a strand bead, the transient characteristics are likely to deteriorate rapidly in the grip limit region in high-speed turning traveling. This tire is inferior in turning performance.

  An object of the present invention is to provide a pneumatic tire that is excellent in transient characteristics and steering stability during cornering.

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 substantially inward in the radial direction from the end of the sidewall. A pair of beads extending along the tread and the inside of the sidewall, and a carcass spanned between one and the other of the pair of beads.
The one bead is a strand bead including a core in which a bead wire is wound in a ring shape a plurality of times in the axial direction and the radial direction, and an apex extending outward from the core in the radial direction. The other bead is a cable bead including a core made of a core and a wire wound in a spiral around the core, and an apex extending radially outward from the core.

  Preferably, the pneumatic tire includes a chafer positioned in the vicinity of each of the pair of beads. The chafer has a bottom surface that contacts the rim. When the angle between the bottom surface of the chafer on the strand bead side and the axial direction is a toe angle θ1, and the angle between the bottom surface of the chafer on the cable bead side and the axial direction is a toe angle θ2, the toe angle θ1 is larger than the toe angle θ2.

  Preferably, the toe angle θ1 on the strand bead side is 20 ° or more and 30 ° or less. The toe angle θ2 on the cable bead side is 10 ° or more and 15 ° or less.

  Preferably, the pneumatic tire includes a chafer positioned in the vicinity of each of the pair of beads and contacting the rim, and a toe strip. The tow strip is located between the bead and the chafer. The ratio H1 / Hs between the height Hs from the bead toe Pt on the strand bead side to the radially outer end of the core and the height H1 from the bead toe Pt to the radially outer end of the toe strip is 0.8 or more and 1.2. It is below. The ratio W1 / Ws between the width Ws from the bead toe Pt on the strand bead side to the axially outer end of the core and the width W1 from the bead toe Pt to the axially outer end of the toe strip is 0.8 or more and 1.2 or less. Has been. The ratio H2 / Hc between the height Hc from the bead toe Pt on the cable bead side to the radially outer end of the core and the height H2 from the bead toe Pt to the radially outer end of the toe strip is 0.8 or more and 1.2. It is below. The ratio W2 / Wc of the width Wc from the bead toe Pt on the cable bead side to the axially outer end of the core and the width W2 from the bead toe Pt to the axially outer end of the toe strip is 0.8 or more and 1.2 or less. Has been. This tow strip is made of a crosslinked rubber. The rubber hardness of the toe strip on the strand bead side is larger than the rubber hardness of the toe strip on the cable bead side.

  Preferably, the rubber hardness of the toe strip on the strand bead side is 80 or more and 90 or less. The rubber hardness of the toe strip on the cable bead side is 50 or more and 70 or less.

  Preferably, a tread pattern is formed on the tread surface. This tread pattern is formed point-symmetrically with respect to the equator plane on the tread surface.

  The pneumatic tire according to the present invention is excellent in steering stability during turning. In addition, this tire is excellent in transient characteristics during turning. This tire can improve turning performance.

FIG. 1 is a cross-sectional view illustrating 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. FIG. 4 is an explanatory diagram showing the core of FIG. FIG. 5A is an explanatory diagram showing the usage state of the tire of FIG. 1, and FIG. 5B is an explanatory diagram showing another usage state 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 tire 2 is attached to a vehicle. The right side of the tire 2 in FIG. 1 shows the back side when the tire 2 is mounted on a four-wheel vehicle. The left side of the tire 2 shows the front side at this time.

  The tire 2 includes a tread 4, a sidewall 6, a clinch 8, a bead 10, a bead 12, a carcass 14, a belt 16, a band 18, an edge band 20, an inner liner 22, a chafer 24, a chafer 26, a toe strip 28, and the like. A tow strip 30 is provided. The tire 2 is a tubeless type. The bead 10, chafer 24 and tow strip 28 are located on the back side when mounted on the vehicle. The bead 12, chafer 26 and tow strip 30 are located on the front side when mounted on the vehicle.

  The tread 4 has a shape protruding outward in the radial direction. The tread 4 forms a tread surface 32 that contacts the road surface. Although not shown, the tread 4 has a base layer and a cap layer. The cap layer is located on the radially outer side of the base layer. The cap layer is laminated on the base layer. The base layer is made of a crosslinked rubber having excellent adhesiveness. A typical base rubber for the base layer is natural rubber. The cap layer is made of a crosslinked rubber having excellent wear resistance, heat resistance and grip properties. Although not shown, the tread surface 32 may have grooves. By forming the groove, a tread pattern is formed on the tread surface 32.

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

  The clinch 8 is located substantially inside the sidewall 6 in the radial direction. On the back side, the clinch 8 is located on the outer side in the axial direction of the tire 2 than the bead 10 and the carcass 14. On the front side, the clinch 8 is located on the outer side in the axial direction of the tire 2 than the bead 12 and the carcass 14. The clinch 8 is made of a crosslinked rubber having excellent wear resistance. The clinch 8 comes into contact with the rim when the rim is assembled.

  The bead 10 is located on the back side when mounted on the vehicle. The bead 10 is located on the inner side in the axial direction of the clinch 8 on the back side. The bead 10 includes a core 34 and an apex 36 that extends radially outward from the core 34. The apex 36 is tapered outward in the radial direction. The apex 36 is made of a highly hard crosslinked rubber.

  The bead 12 is located on the front side when mounted on the vehicle. The bead 12 is located on the inner side in the axial direction of the front side clinch 8. The bead 12 includes a core 38 and an apex 40 that extends radially outward from the core 38. The apex 40 is tapered outward in the radial direction. The apex 40 is made of a highly hard crosslinked rubber.

  The carcass 14 includes a first ply 42 and a second ply 44. The first ply 42 and the second ply 44 are bridged between the bead 10 and the bead 12 and extend along the tread 4 and the sidewall 6. The first ply 42 is folded around the core 34 and the core 38 from the inner side to the outer side in the axial direction. By this folding, the main portion 42a and the folding portion 42b are formed in the first ply 42 (see FIGS. 2 and 3). The second ply 44 is folded around the core 34 and the core 38 from the inner side to the outer side in the axial direction. By this folding, the main portion 44a and the folding portion 44b are formed in the second ply 44 (see FIGS. 2 and 3). The end of the folded portion 42 b of the first ply 42 is located radially outside the end of the folded portion 44 b of the second ply 44.

  Although not shown, the first ply 42 and the second ply 44 are composed of a large number of cords arranged in parallel and a topping rubber. The absolute value of the angle formed by each cord with respect to the equator plane CL is 75 ° to 90 °. In other words, the carcass 14 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 14 may be formed from a single ply.

  The belt 16 is located inside the tread 4 in the radial direction. The belt 16 is laminated with the carcass 14. The belt 16 reinforces the carcass 14. The belt 16 includes an inner layer 46 and an outer layer 48. As shown in FIG. 1, the outer layer 48 is superimposed on the radially outer side of the inner layer 46. In the axial direction, the width of the inner layer 46 is slightly larger than the width of the outer layer 48.

  Although not shown, each of the inner layer 46 and the outer layer 48 includes a plurality of cords arranged in parallel and a topping rubber. Each cord is inclined with respect to the equatorial plane CL. The absolute value of the tilt angle is usually 10 ° to 35 °. The inclination angle of the cord of the inner layer 46 with respect to the equator plane CL is different from the inclination angle of the cord of the outer layer 48 with respect to the equator plane CL. The inclination direction of the cord of the inner layer 46 with respect to the equator plane CL is opposite to the inclination direction of the cord of the outer layer 48 with respect to the equator plane CL. 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 axial direction, the width of the band 18 is larger than the width of the belt 16. Although not shown, the band 18 is composed of a cord and a topping rubber. The cord is wound in a spiral. This band 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 edge band 20 is laminated on the outer side of the belt 16 in the radial direction and on the end of the belt 16. The edge band 20 is laminated on the inner side in the radial direction of the band 18 and at the end of the band 18. Although not shown, the edge band 20 is made of a cord and a topping rubber. The cord is wound in a spiral. This band 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 end of the belt 16 is restrained by this cord, the 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 inner liner 22 is located inside the carcass 14. In the vicinity of the equator plane CL, 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.

  As shown in FIG. 2, the chafer 24 is located in the vicinity of the bead 10. The chafer 24 includes a bottom surface 24a facing radially inward. As shown in FIG. 3, the chafer 26 is located in the vicinity of the bead 12. The chafer 26 includes a bottom surface 26a that faces radially inward. When the tire 2 is assembled in a rim (not shown), the back side chafer 24 and the chafer 26 come into contact with the rim. By this contact, the vicinity of the bead 10 and the bead 12 is protected. At this time, the bottom surface 24a and the bottom surface 26a abut against the seat surface of the rim. In the tire 2, the chafer 24 and the chafer 26 are respectively integrated with the clinch 8. Therefore, the material of the chafer 24 and the chafer 26 is the same as that of the clinch 8. The chafer 24 and the chafer 26 may be made of cloth and rubber impregnated in the cloth.

  As shown in FIG. 2, the core 34 of the bead 10 is formed by winding a rubberized bead wire 52 in a ring shape with a predetermined number of rows in the axial direction and a predetermined number of piles in the radial direction. . This bead 10 is called a strand bead. The strand bead referred to in the present invention includes a single winding bead having a core in which a single bead wire is wound in a ring shape. The bead wire 52 is a non-stretchable wire. A typical material for non-stretchable wire is steel. The core 34 is formed by winding one bead wire 52 in a ring shape, but may be formed by winding two or more bead wires 52 in a ring shape.

  Pt in FIG. 2 indicates a bead toe on the bead 10 side of the tire 2. A double arrow Hs indicates a height from the bead toe Pt to the radially outer end of the core 34. A double-headed arrow H1 indicates the height from the bead toe Pt to the radially outer end of the toe strip 28. The height Hs and the height H1 are measured as radial distances. A double-headed arrow Ws indicates the width from the bead toe Pt to the outer end of the core 34 in the axial direction. A double-headed arrow W1 indicates the width from the bead toe Pt to the outer end in the axial direction of the toe strip 28. The width Ws and the width W1 are measured as axial distances.

  The toe strip 28 is located in the vicinity of the bead 10. The toe strip 28 is located between the chafer 24 and the core 34. The toe strip 28 extends along the chafer 24. The toe strip 28 extends from the vicinity of the bead toe Pt in the radial direction to the vicinity of the radially outer end of the core 34. The toe strip 28 extends from the vicinity of the bead toe Pt in the axial direction to the vicinity of the outer end of the core 34 in the axial direction. The toe strip 28 is made of a crosslinked rubber.

  A two-dot chain line L1 in FIG. 2 indicates a straight line extending in the axial direction through the bead toe Pt on the bead 10 side. A two-dot chain line L <b> 2 indicates a straight line along the bottom surface 24 a of the chafer 24. A double arrow θ1 indicates an angle formed by the straight line L1 and the straight line L2. This angle θ1 is referred to as a toe angle on the bead 10 side.

  As shown in FIGS. 3 and 4, the core 38 of the bead 12 includes a core 54 and a plurality of wires 56. The core 54 has a circular cross section, and has an annular shape in the circumferential direction. As shown in FIG. 4, a plurality of wires 56 are wound around the core 54 in a spiral shape. This bead 12 is called a cable bead. The core 54 is made of, for example, mild steel. The wire 56 is made of, for example, a plated piano wire.

  Pt in FIG. 3 indicates a bead toe on the bead 12 side of the tire 2. A double arrow Hc indicates the height from the bead toe Pt to the radially outer end of the core 38. A double-headed arrow H2 indicates the height from the bead toe Pt to the radially outer end of the toe strip 30. The height Hc and the height H2 are measured as radial distances. A double-headed arrow Wc indicates a width from the bead toe Pt to the outer end in the axial direction of the core 38. A double-headed arrow W2 indicates the width from the bead toe Pt to the outer end of the toe strip 30 in the axial direction. The width Wc and the width W2 are measured as axial distances.

  The toe strip 30 is located in the vicinity of the bead 12. The toe strip 30 is located between the chafer 26 and the core 38. The toe strip 30 extends along the chafer 26. The toe strip 30 extends from the vicinity of the bead toe Pt in the radial direction to the vicinity of the radially outer end of the core 38. The toe strip 30 extends from the vicinity of the bead toe Pt in the axial direction to the vicinity of the outer end of the core 38 in the axial direction. The toe strip 30 is made of a crosslinked rubber.

  3 indicates a straight line extending in the axial direction through the bead toe Pt on the bead 12 side. An alternate long and two short dashes line L4 indicates a straight line along the bottom surface 26a of the chafer 26. A double-headed arrow θ2 indicates an angle formed by the straight line L3 and the straight line L4. This angle θ2 is referred to as a toe angle on the bead 12 side.

  FIG. 5A and FIG. 5B show the usage state of the tire 2 when the four-wheel vehicle is traveling at a high speed. FIG. 5A shows a state of a tire 2 (hereinafter referred to as an outer wheel tire 2) located on the outer side in the turning radius direction. FIG. 5B shows a state of the tire 2 (hereinafter referred to as the inner ring tire 2) located on the inner side in the turning radius direction. Each arrow IN in FIG. 5A and FIG. 5B indicates the back side. An arrow OUT indicates the front side. An arrow F indicates the direction of the lateral force F during turning.

  In the outer wheel tire 2 of FIG. 5A, a bead 12 that is a cable bead is located on the front side. The side wall 6 on the bead 12 side rotates in a direction away from the flange 58a. Since the bead 12 includes the core 38, the bead 12 can easily rotate with respect to the rim 58 even in a grip limit region for high-speed turning. By this rotation, the front side wall 6 is smoothly deformed even in the grip limit region. This smooth deformation contributes to improvement of transient characteristics. The outer tire 2 contributes to improvement of transient characteristics particularly in the grip limit region. The outer wheel tire 2 contributes to an improvement in the turning traveling speed.

  In the outer ring tire 2, a bead 10 that is a strand bead is located on the back side. In this turning traveling, the bead 10 is pressed against the flange 58a. The bead 10 is supported by the rim flange 58a. Whether the side wall 6 on the back side is a strand bead or a cable bead, there is no significant difference in deformation.

  In high-speed turning traveling, a large load is applied to the tire 2. Most of this load is applied to the outer tire 2. The load applied to the outer ring tire 2 is much larger than that applied to the inner ring tire 2. In particular, in high-speed turning traveling, the load applied to the outer wheel tire 2 is large. The outer wheel tire 2 greatly contributes to an improvement in turning traveling speed and an improvement in transient characteristics.

  In the inner tire 2 of FIG. 5B, the bead 10 is located on the back side. The side wall 6 on the bead 10 side rotates in a direction away from the flange 58a. Since the bead 10 includes the core 34, it is relatively difficult to rotate with respect to the rim 58. Since the rotation is small, deformation of the side wall 6 on the back side is suppressed. The sidewall 6 contributes to improvement of the rigidity of the tire 2. The improvement in the rigidity of the tire 2 contributes to the improvement in the grip force. The tire 2 can generate a lateral force F effectively.

  As described above, most of the load is applied to the outer tire 2 in high-speed turning. The inner wheel tire 2 does not require an improvement in performance in the grip limit region of high-speed turning traveling as compared with the outer wheel tire 2. Even if the bead 10 of the inner ring tire 2 is made of a strand bead, excessive characteristics in the grip limit region are not deteriorated.

  In the inner tire 2, the bead 12 is located on the outer side in the mounting direction. In this turning traveling, the bead 12 is pressed against the flange 58 a of the rim 58. The bead 12 is supported by the rim flange 58a. Whether the front-side sidewall 6 is a strand bead or a cable bead, there is no significant difference in the manner of deformation.

  As shown in FIGS. 5A and 5B, the tire 2 is mounted on the vehicle with the bead 10 positioned on the inner side in the mounting direction and the bead 12 positioned on the outer side in the mounting direction. This vehicle improves the stability of high-speed turning. The tire 2 can contribute to improvement of turning performance.

  5A, the front side (OUT side) sidewall 6 rotates in a direction away from the rim flange 58a. In the inner tire 2 of FIG. 5B, the rear side (IN side) sidewall 6 rotates in a direction away from the rim flange 58a. The outer ring tire 2 and the inner ring tire 2 have different bead types located on the side of the sidewall 6 that rotates away from the rim flange 58a. Generally, a cable bead is easier to rotate in a direction away from the rim flange 58a than a strand bead.

  In the tire 2, the toe angle θ1 on the bead 10 side is set larger than the toe angle θ2 on the bead 12 side. Thereby, the ease of rotation of the side wall 6 on the bead 10 side and the side wall 6 on the bead 12 side is adjusted. Thereby, the deformation amount of the inner wheel tire 2 and the deformation amount of the outer wheel tire 2 are adjusted. The tire 2 is provided with different beads 10 and beads 12 and is prevented from being deteriorated in stability during turning.

  In the outer tire 2 of FIG. 5A, the sidewall 6 on the bead 12 side rotates in a direction away from the rim flange 58a. In the outer ring tire 2 having a large toe angle θ 2, the front side wall 6 is easy to rotate with respect to the rim 58. By this rotation, the sidewall 6 is smoothly deformed. This smooth deformation contributes to improvement of transient characteristics. From this viewpoint, the toe angle θ2 is preferably 10 ° or more, and more preferably 12 ° or more.

  On the other hand, in the outer tire 2 having a small toe angle θ <b> 2, the front side wall 6 is difficult to rotate with respect to the rim 58. Deformation of the front side wall 6 is suppressed. This contributes to improving the rigidity of the sidewall 6. The improvement of the rigidity of the sidewall 6 contributes to the improvement of the grip force. In the tire 2, a high cornering force can be generated. The tire 2 contributes to the improvement of steering stability during turning. From this viewpoint, the toe angle θ2 is preferably 15 ° or less, and more preferably 13 ° or less.

  In the inner tire 2 of FIG. 5B, the sidewall 6 on the bead 10 side rotates in a direction away from the rim flange 58a. In the inner tire 2 having a large toe angle θ 1, the rear side wall 6 is easy to rotate with respect to the rim 58. The rear side wall 6 is easily deformed. Thereby, the deformation amount of the inner wheel tire 2 and the deformation amount of the outer wheel tire 2 are adjusted. From this viewpoint, the toe angle θ1 is preferably 20 ° or more, and more preferably 23 ° or more.

  On the other hand, in the outer tire 2 having a small toe angle θ1, the rear side wall 6 is difficult to rotate with respect to the rim 58. Deformation of the rear side wall 6 is suppressed. This contributes to improving the rigidity of the tire 2. The improvement of the rigidity of the sidewall 6 contributes to the improvement of the grip force. From this viewpoint, the toe angle θ1 is preferably 30 ° or less, and more preferably 28 ° or less.

  In the tire 2, the toe angle θ1 and the toe angle θ2 are set within a predetermined range, and the toe angle θ1 is set to be larger than the toe angle θ2, thereby improving the steering stability and the transient characteristics in high-speed turning. , More is being planned.

  In the tire 2, the rubber hardness of the toe strip 28 on the bead 10 side is set larger than the rubber hardness of the toe strip 30 on the bead 12 side. Thereby, the bead 10 is made harder to rotate and the bead 12 is made easier to rotate.

  In the outer ring tire 2 with the rubber hardness of the toe strip 30 being small, the front side wall 6 is smoothly deformed. This smooth deformation contributes to improvement of transient characteristics. From this viewpoint, the rubber hardness of the tow strip 30 is preferably 70 or less, more preferably 65 or less. On the other hand, in the outer ring tire 2 in which the rubber hardness of the toe strip 30 is large, deformation of the front side wall 6 is suppressed. This improvement in the rigidity of the sidewall 6 contributes to an improvement in gripping force. From this viewpoint, the rubber hardness of the tow strip 30 is preferably 50 or more, and more preferably 55 or more.

  In the tow strip 30, the ratio H2 / Hc between the height H2 and the height Hc shown in FIG. 3 is preferably 0.8 or more and 1.2 or less. Moreover, it is preferable that ratio W2 / Wc of width W2 and width Wc shall be 0.8 or more and 1.2 or less.

  In the inner ring tire 2 in which the rubber hardness of the toe strip 28 is small, the side wall 6 on the back side is smoothly deformed. Thereby, the deformation amount of the inner wheel tire 2 and the deformation amount of the outer wheel tire 2 are adjusted. From this viewpoint, the rubber hardness of the tow strip 28 is preferably 90 or less, and more preferably 88 or less. On the other hand, in the inner ring tire 2 in which the rubber hardness of the toe strip 28 is large, deformation of the sidewall 6 on the back side is suppressed. This improvement in the rigidity of the sidewall 6 contributes to an improvement in gripping force. From this viewpoint, the rubber hardness of the tow strip 28 is preferably 80 or more, and more preferably 82 or more.

  In the tow strip 28, the ratio H1 / Hs between the height H1 and the height Hs shown in FIG. 2 is preferably 0.8 or more and 1.2 or less. Moreover, it is preferable that ratio W1 / Ws of width W1 and width Ws shall be 0.8 or more and 1.2 or less.

  In the tire 2, the rubber hardness of the tow strip 28 and the rubber hardness of the tow strip 30 are set within a predetermined range, and the rubber hardness of the tow strip 30 is increased so that the rubber hardness of the tow strip 30 is increased. Further improvements in steering stability and transient characteristics during travel are being made.

  The tire 2 can improve the turning performance of both the inner and outer wheels by arranging the tire 2 on the back side and the front side utilizing the characteristics of different beads. The tire 2 can improve the performance of the outer ring without impairing the performance of the inner ring. The performance of the inner ring can be improved without impairing the performance of the outer ring. By combining the bead 10 and the bead 12, high-speed turning performance is improved for both the inner and outer wheels.

  The tire 2 having no rotational directionality can be used as the forward rotation direction in any circumferential direction. The tire 2 can be mounted on the vehicle with any direction in the circumferential direction as a forward rotation direction. For example, one tire 2 can be mounted as a right wheel tire or a left wheel tire of a four-wheeled vehicle such as a passenger car. From this viewpoint, it is preferable that a tread pattern having no rotational directionality is formed on the tread surface 32. For example, a tread pattern that is point-symmetric with respect to a point on the equator plane CL of the tread surface 32 is preferably formed. The tread pattern including grooves intersecting with the circumferential direction is also preferably formed point-symmetrically with respect to a point on the equator plane CL.

  In the present invention, the dimension and angle of each member of the tire 2 are measured in a cut section as shown in FIG. These dimensions and angles are measured without being incorporated into the rim.

  The rubber hardness referred to in the present invention is measured by pressing a type A durometer against a test piece cut out from the tire 2 under a condition of 23 ° C. in accordance with the provisions of “JIS-K 6253”.

  In this specification, the normal rim means a rim defined in a standard on which a tire depends. “Standard rim” in the JATMA standard, “Design Rim” in the TRA standard, and “Measuring Rim” in the ETRTO standard are regular rims. In this specification, the normal internal pressure means an internal pressure defined in a standard on which the tire depends. “Maximum air pressure” in JATMA standard, “Maximum value” published in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in TRA standard, and “INFLATION PRESSURE” in ETRTO standard are normal internal pressures.

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

[Example 1]
The tire shown in FIG. 1 was prepared. The size of the tire was “330 / 710R18”. Table 1 shows the bead structure of the tire, the toe angle, and the rubber hardness of the toe strip. In Table 1, “front side” indicates the vehicle mounting direction outside, and “back side” indicates the vehicle mounting direction inside. “C” in “bead structure” indicates a cable bead, and “S” indicates a strand bead. The “toe angle” indicates the toe angle θ1 or the toe angle θ2 of the present invention. “Toe strip hardness” indicates the rubber hardness of the tow strip.

[Comparative Example 1-2]
Conventional tires were prepared. This tire was the same as Example 1 except that the bead structure and the toe angle were as shown in Table 1.

[Example 2-3]
A tire was obtained in the same manner as in Example 1 except that the toe angle and the toe strip hardness were as shown in Table 1.

[Example 11-10]
A tire was obtained in the same manner as in Example 1 except that the toe angle was set as shown in Table 2.

[Example 9-17]
A tire was obtained in the same manner as in Example 1 except that the rubber hardness of the tow strip was changed as shown in Table 3.

[Transient characteristics]
A tire was incorporated into a regular rim, and air was filled into the tire so as to achieve a regular internal pressure. This tire was mounted on a racing vehicle having a displacement of 4 liters. The driver was allowed to drive this vehicle on the racing circuit and evaluate the transient characteristics. The results are shown in Tables 1 to 3 below. The value of this result is indicated by an index with Comparative Example 1 as the reference value 100. A larger value is more preferable.

[Maximum lateral acceleration]
A lateral acceleration sensor was attached to the vehicle. The racing circuit was circulated a predetermined number of times, and the lateral acceleration generated at a preselected corner was measured. The maximum value of the lateral acceleration from the start of turning to the end of turning at this corner was obtained. The maximum values of the obtained lateral acceleration are shown in Tables 1 to 3. These values are indicated by indexes with Comparative Example 1 as the reference value 100. A larger value is more preferable.

[Swivel speed]
The racing circuit was circulated a predetermined number of times, and the corner turning speed was measured. This turning speed was obtained as an average speed from the start of turning to the end of turning at this corner. The turning speeds are shown in Tables 1 to 3. These values are indicated by indexes with Comparative Example 1 as the reference value 100. A larger value is more preferable.

[Comprehensive evaluation]
High-speed turning performance was comprehensively evaluated from the transient characteristics, maximum lateral acceleration and turning speed. The results are shown in Tables 1 to 3. These values are indicated by indices with Comparative Example 1 as the reference value 0. A larger value is more preferable.

  As shown in Tables 1 to 3, the pneumatic tire of the example has a higher evaluation than the pneumatic tire of the comparative example. From this evaluation result, the superiority of the present invention is clear.

  The pneumatic tire described above can be widely used as a tire for general passenger cars, including a race-specific tire. This tire can be widely applied to vehicles equipped with inner and outer wheels in cornering.

DESCRIPTION OF SYMBOLS 2 ... Tire 4 ... Tread 6 ... Side wall 8 ... Clinch 10, 12 ... Bead 14 ... Carcass 16 ... Belt 18 ... Band 20 ... Edge band 22 ... Inner liner 24, 26 ... Chafer 28, 30 ... Toe strip 32 ... Tread surface 34, 38 ... Core 36, 40 ... Apex 42 ... First ply 44 ... Second ply 46 ... Inner layer 48 ... Outer layer 52 ... Bead wire 54 ... Core 56 ... Wire 58 ... Rim

Claims (6)

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, a pair of beads each extending substantially inward in the radial direction from the end of the sidewall, and the tread And a carcass bridged between one and the other of the pair of beads along the inside of the sidewall,
This one bead is a strand bead including a core in which a bead wire is wound in a ring shape in the axial direction and the radial direction a plurality of times, and an apex extending radially outward from the core,
A pneumatic tire, which is a cable bead, in which the other bead includes a core including a core and a wire wound in a spiral around the core, and an apex extending radially outward from the core. A chafer located near each of the pair of beads;
This chafer has a bottom that contacts the rim,
When the angle between the bottom surface of the chafer on the strand bead side and the axial direction is a toe angle θ1, and the angle between the bottom surface of the chafer on the cable bead side and the axial direction is a toe angle θ2, the toe angle The tire according to claim 1, wherein θ1 is larger than a toe angle θ2. The strand bead side toe angle θ1 is 20 ° or more and 30 ° or less,
The tire according to claim 2, wherein a toe angle θ2 on the cable bead side is 10 ° or more and 15 ° or less. A chafer and a toe strip that are located near each of the pair of beads and abut against the rim;
This tow strip is located between the bead and the chafer,
The ratio H1 / Hs between the height Hs from the bead toe Pt on the strand bead side to the radially outer end of the core and the height H1 from the bead toe Pt to the radially outer end of the toe strip is 0.8 to 1.2 Has been
The ratio W1 / Ws between the width Ws from the bead toe Pt on the strand bead side to the axially outer end of the core and the width W1 from the bead toe Pt to the axially outer end of the toe strip is made 0.8 to 1.2. And
The ratio H2 / Hc between the height Hc from the bead toe Pt on the cable bead side to the radially outer end of the core and the height H2 from the bead toe Pt to the radially outer end of the toe strip is 0.8 to 1.2 Has been
The ratio W2 / Wc of the width Wc from the bead toe Pt on the cable bead side to the axially outer end of the core and the width W2 from the bead toe Pt to the axially outer end of the toe strip is made 0.8 to 1.2. And
This tow strip is made of crosslinked rubber,
The tire according to any one of claims 1 to 3, wherein a rubber hardness of the toe strip on the strand bead side is larger than a rubber hardness of the toe strip on the cable bead side. The strand bead side toe strip has a rubber hardness of 80 or more and 90 or less,
The tire according to claim 4, wherein a rubber hardness of the toe strip on the cable bead side is 50 or more and 70 or less. A tread pattern is formed on the tread surface,
The tire according to any one of claims 1 to 5, wherein the tread pattern is formed point-symmetrically with respect to the equator plane on the tread surface.

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