JP6308616B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  In recent years, there has been a strong demand for lower fuel consumption of vehicles. In pneumatic tires, rolling resistance is reduced. The weight reduction of the tire contributes to reduction of rolling resistance. In this tire, the thickness of the rubber of the sidewall is made thinner than that of the conventional tire to reduce the weight. The rigidity of the tire is likely to be lower than that of the conventional tire. This reduction in rigidity affects ride comfort and handling stability.

  Japanese Patent Application Laid-Open No. 2010-149677 discloses a tire including a strip apex. The strip apex extends along the carcass. The strip apex is located between the carcass ply and the bead apex. This strip apex increases the rigidity of the tire. In this tire, the rubber thickness of the sidewall is reduced without impairing the ride comfort and the handling stability.

  Japanese Unexamined Patent Application Publication No. 2006-96178 discloses a tire including a sheet-like sub-apex. This sub-apex is composed of a sub-apex outside the axial direction and a sub-apex inside. This secondary apex is located between the carcass ply and the bead apex. By providing this sub-apex, peeling at the interface between the carcass ply and the bead apex is suppressed. As a result, the durability of the bead portion is improved without impairing the handling stability and the ride comfort.

JP 2010-149677 A JP 2006-96178 A

  In these pneumatic tires, the bead apex is formed to be tapered toward the radially outward tip. The bead apex is thinner at the tip than at the core at the core. The rigidity of the tip portion of the bead apex is smaller than the rigidity of the root portion. The tip portion of the bead apex is easier to deform than the root portion.

  In the tire disclosed in Japanese Patent Laid-Open No. 2010-149677, the strip apex is located on the inner side in the axial direction of the bead apex. The strip apex extends from the radially inner side to the outer side of the tip of the bead apex. The strip apex and the bead apex are laminated to increase the rigidity. By laminating a strip apex having high rigidity, the rigidity of the tip portion of the bead apex can be sufficiently obtained. On the other hand, the rigidity of the base portion of the strip apex becomes too large. It is necessary to adjust the rigidity in consideration of the balance between handling stability and ride comfort. In this tire, when the driving stability is improved, the riding comfort is easily impaired, and when the riding comfort is improved, the steering stability is easily impaired. With this tire, it is not easy to further improve both handling stability and ride comfort.

  In the tire disclosed in Japanese Patent Application Laid-Open No. 2006-96178, the sub-apex is superimposed on the bead apex from the tip to the base of the bead apex. In this tire, by using the sub-apex having high hardness, the rigidity is improved, but the ride comfort is impaired. On the other hand, using a sub-apex with low hardness improves riding comfort but impairs rigidity. Further, the ride comfort can be improved by reducing the length in which the sub-apex and the bead apex are laminated. However, from the viewpoint of suppressing peeling at the interface between the carcass ply and the bead apex, the stacked length cannot be reduced. Even with this tire, it is not easy to further improve both handling stability and ride comfort.

  An object of the present invention is to provide a pneumatic tire that is excellent in riding comfort and handling stability while reducing rolling resistance.

  The pneumatic tire according to the present invention has 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 each positioned radially inward of the sidewalls. A pair of beads, a carcass spanned between one bead and the other bead along the inside of the tread and the sidewall, and a pair of strip apex respectively positioned on the radially outer side of the bead It has. The bead includes a core and an apex extending outward in the radial direction from the core. The apex is tapered toward the radially outward tip. The strip apex includes a leading end laminated portion and an inner laminated portion extending radially inward from the leading end laminated portion. The tip laminated portion and the inner laminated portion are laminated on the apex. The tip of the apex is laminated on the tip lamination portion. The tip stacking portion extends radially outward from the tip of the apex. The rigidity of the tip laminated portion is made larger than the rigidity of the inner laminated portion.

  Preferably, the strip apex is made of a rubber sheet. The rubber hardness of the tip laminated portion is larger than the rubber hardness of the inner laminated portion. Preferably, the strip apex includes an outer portion that extends radially outward from the tip laminated portion. The rubber hardness of this outer portion is made larger than the rubber hardness of the tip laminated portion.

  Preferably, the strip apex includes a first rubber sheet extending from the inner laminated portion to the tip laminated portion, and a second rubber sheet laminated on the first rubber sheet and positioned at the tip laminated portion.

  Preferably, the radial width of the second rubber sheet is 15 mm or more and 25 mm or less. The radial width in which the second rubber sheet and the apex are laminated is smaller than the radial width of the second rubber sheet. And this radial direction width is made into 5 mm or more and 15 mm or less.

  Preferably, the ratio HT / HE of the height HT from the bead base line to the inner end of the tip laminated portion with respect to the height HE from the bead base line to the tip of the apex is 0.5 or more and 0.9 or less. Has been.

  Preferably, the ratio HS / HE of the height HS from the bead base line to the inner end of the strip apex with respect to the height HE from the bead base line to the tip of the apex is 0.4 or more and 0.8 or less. Has been.

  In the pneumatic tire according to the present invention, by providing the strip apex, the thickness of the sidewall can be reduced while maintaining rigidity. By providing the strip apex, the tire can be reduced in weight. The strip laminated portion of the apex of the strip apex is laminated on the apex of the apex, thereby improving the rigidity in the vicinity of the apex of the apex. Excessive rigidity is suppressed in the vicinity of the portion where the inner laminated portion is laminated on the apex. In this tire, local deformation of the sidewall is suppressed while suppressing an excessive rigidity. In this tire, both ride comfort and handling stability can be improved.

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 a partially enlarged cross-sectional view of the tire of FIG. FIG. 3 is a partial enlarged cross-sectional view of a pneumatic tire according to another embodiment of the present invention.

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

  FIG. 1 shows a pneumatic tire 2. In FIG. 1, the vertical direction is the radial direction of the tire 2, the horizontal direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2. In FIG. 1, an alternate long and short dash line CL represents the equator plane of the tire 2. A straight line BL represents a bead base line. This bead base line corresponds to a line that defines a rim diameter (see JATMA) of a normal rim to which the tire 2 is mounted. The tire 2 is attached to a vehicle such as a passenger car.

  The tire 2 includes a tread 4, a sidewall 6, a clinch 8, a bead 10, a carcass 12, a belt 14, a band 16, an edge band 18, an inner liner 20, and a chafer 22. The tire 2 further includes a strip 24 as a strip apex. The tire 2 is a tubeless type.

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

  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 12 from being damaged.

  The clinch 8 is located substantially inside the sidewall 6 in the radial direction. The clinch 8 is located outside the beads 10 and the carcass 12 in the axial direction. The clinch 8 is made of a crosslinked rubber having excellent wear resistance. When the tire 2 is assembled to the rim, the clinch 8 comes into contact with the flange of the rim.

  The bead 10 is located on the radially inner side of the sidewall 6. The bead 10 is located inside the clinch 8 in the axial direction. The bead 10 includes a core 34 and an apex 36 that extends radially outward from the core 34. The core 34 has a ring shape. The core 34 includes a wound non-stretchable wire. A typical material for the wire is steel. The apex 36 is tapered outward in the radial direction. The apex 36 is thinner from the core 34 toward the tip 36a. The apex 36 is made of a highly hard crosslinked rubber.

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

  Each of the first ply 38 and the second ply 40 includes a plurality of cords arranged in parallel and a topping rubber. The absolute value of the angle formed by each cord with respect to the equator plane is 75 ° to 90 °. In other words, the carcass 12 has a radial structure. The cord is made of organic fiber. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers. The carcass 12 may be formed from a single ply.

  1 indicates the outermost end in the axial direction of the carcass 12. The distance from one outermost end PW in the axial direction to the other outermost end PW is the maximum width of the carcass 12. The outermost end PW is determined in a state in which the tire 2 is incorporated in a normal rim and is filled with air having a normal internal pressure.

  The belt 14 is located on the inner side in the radial direction of the tread 4. The belt 14 is laminated with the carcass 12. The belt 14 reinforces the carcass 12. The belt 14 includes an inner layer 42 and an outer layer 44. As apparent from FIG. 1, the width of the inner layer 42 is slightly larger than the width of the outer layer 44 in the axial direction. Although not shown, each of the inner layer 42 and the outer layer 44 is composed of a large number of cords arranged in parallel and a topping rubber. Each cord is inclined with respect to the equator plane. The general absolute value of the tilt angle is 10 ° or more and 35 ° or less. The inclination direction of the cord of the inner layer 42 with respect to the equator plane is opposite to the inclination direction of the cord of the outer layer 44 with respect to the equator plane. A preferred material for the cord is steel. An organic fiber may be used for the cord. The axial width of the belt 14 is preferably 0.7 times or more the maximum width of the tire 2. The belt 14 may include three or more layers.

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

  The belt 14 and the band 16 constitute a reinforcing layer 46. The reinforcing layer 46 may be formed only from the belt 14. The reinforcing layer 46 may be formed only from the band 16.

  The edge band 18 is located radially outside the belt 14 and in the vicinity of the end of the belt 14. Although not shown, the edge band 18 is made of a cord and a topping rubber. The cord is wound in a spiral. The edge band 18 has a so-called jointless structure. The cord extends substantially in the circumferential direction. The angle of the cord with respect to the circumferential direction is 5 ° or less, and further 2 ° or less. Since the end of the belt 14 is restrained by this cord, the lifting of the belt 14 is suppressed. The cord is made of organic fiber. Examples of preferable organic fibers include nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  The inner liner 20 is located inside the carcass 12. The inner liner 20 is joined to the inner surface of the carcass 12. The inner liner 20 is made of a crosslinked rubber having excellent air shielding properties. A typical base rubber of the inner liner 20 is butyl rubber or halogenated butyl rubber. The inner liner 20 holds the internal pressure of the tire 2.

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

  The strip 24 is laminated on the outside of the apex 36 in the radial direction. The strip 24 extends from the radially inner side of the tip 36a of the apex 36 to the radially outer side of the tip 36a. The strip 24 is laminated between the carcass 12 and the apex 24 in the axial direction. The strip 24 is formed into a sheet shape. The strip 24 goes around in the circumferential direction. The strip 24 is made of a highly hard crosslinked rubber.

  As shown in FIG. 2, the strip 24 includes an inner laminated portion 48, a tip laminated portion 50, and an outer portion 52. The inner laminated portion 48 is located on the radially inner side of the tip laminated portion 50. The tip laminated portion 50 extends radially outward from the inner laminated portion 48. The outer portion 52 extends outward in the radial direction from the tip stack portion 50. The inner laminated portion 48, the tip laminated portion 50, and the outer portion 52 extend continuously in the radial direction.

  The inner laminated portion 48 extends in a semi-annual direction from the inner end 48a to the outer end 48b. In the tire 2, the inner end 48 a is also the inner end 24 a of the strip 24. The inner end 48 a and the outer end 48 b are located radially inward from the tip 36 a of the apex 36. The entire surface on the outer side in the axial direction of the inner laminated portion 48 is laminated on the inner side surface in the axial direction of the apex 36. The rubber hardness of the inner laminated portion 48 is made smaller than the rubber hardness of the tip laminated portion 50. The rubber hardness of the inner laminated portion 48 is, for example, 60 or more and less than 80.

  The inner end 50a of the tip stacked portion 50 is located radially inward from the tip 36a. The outer end 50b of the tip stacked portion 50 is located on the radially outer side from the tip 36a. In the tip stacking section 50, the tip 36a of the apex 36 is stacked. In the tip stacking portion 50, the region from the inner end 50 a to the position where the tip 36 a is stacked is stacked on the inner side surface in the axial direction of the apex 36. The rubber hardness of the tip laminated portion 50 is made larger than the rubber hardness of the inner laminated portion 48. The rubber hardness of the tip laminated portion 50 is, for example, 75 or more and 90 or less.

  The outer portion 52 is located radially outward from the tip 36a of the apex 36 in the radial direction. The outer portion 52 is laminated on the outer surface of the main portion 40a of the second ply 40. In the radial direction, the inner end 52a of the outer portion 52 is located on the outer side in the radial direction of the tip 36a. The outer end 52b is located more radially outward than the end 38e of the first ply 38 and the end 40e of the second ply 40. The outer end 52 b is laminated between the second ply 40 and the sidewall 6. The rubber hardness of the outer portion 52 is made larger than the rubber hardness of the tip laminated portion 50. The rubber hardness of the outer portion 52 is, for example, 80 or more and 100 or less.

  A double arrow HE in FIG. 2 represents the height of the apex 36. The height HE of the apex 36 is measured as the distance from the bead base line to the tip 36a. A double arrow HS represents the height of the inner end 24 a of the strip 24. The height HS of the inner end 24a is measured as a distance from the bead base line to the inner end 24a. A double-headed arrow HT represents the height of the inner end 50 a of the tip stacking portion 50. This height HT is measured as a distance from the bead base line to the inner end 50a. The height HE, the height HS, and the height HT are measured as a linear distance in the radial direction.

  Since the tire 2 includes the strip 24, the deformation of the sidewall 6 is suppressed. The rigidity of the tire 2 is increased. In the tire 2, the rubber thickness of the sidewall can be reduced without impairing the ride comfort and the handling stability. In the tire 2, the thickness of the sidewall 6 is less than 4 mm at the maximum width position of the carcass 12. Usually, the thickness of the sidewall 6 is 4 mm or more, and the tire 2 includes the thin sidewall 6.

  Since the distal end 36a of the apex 36 is laminated on the tip laminated portion 50 and the tip laminated portion 50 extends radially outward from the tip 36a, the rigidity in the vicinity of the distal end 36a is improved. The local deformation | transformation is suppressed because the taper front-end | tip 36a is laminated | stacked on the front-end | tip laminated | stacking part 50 whose hardness is large compared with the inner side laminated part 48. FIG. The tire 2 is excellent in steering stability because local deformation of the sidewall 6 is suppressed.

  On the other hand, an inner laminated portion 48 having a hardness lower than that of the tip laminated portion 50 is laminated on the apex 36. Thereby, it is suppressed that the rigidity of tire 2 is excessive. By providing the inner laminated portion 48 and the tip laminated portion 50, the rigidity of the tire 2 is moderately improved while suppressing the rigidity of the tire 2 from being excessive.

  In the rolling tire 2, the sidewall 6 is deformed by an external force. In the sidewall 6, the position of the maximum width of the carcass 12, that is, the vicinity of the outermost end PW, is particularly easily deformed. In the tire 2, the outermost end PW is located on the outer side portion 52 in the radial direction. Since the outer portion 52 has a higher hardness than the inner laminated portion 48, local deformation of the sidewall 6 is further suppressed.

  In the tire 2, the outer portion 52 is provided on the outer side in the radial direction of the tip laminated portion 50, so that the rigidity in a range where the apex 36 and the strip 24 extend is made uniform as compared with the conventional tire. In the tire 2, local deformation of the sidewall 6 is further suppressed.

  In the tire 2, the outermost end PW is located on the outer side portion 52 in the radial direction, but is not limited thereto. The outermost end PW may be located at the tip stack portion 64 in the radial direction. Since the leading end stacking portion 64 is harder than the inner stacking portion 48, local deformation of the sidewall 6 can be suppressed.

  The rigidity of the tire 2 can be increased by increasing the width in which the strip 24 and the apex 36 are stacked. The tire 2 having high rigidity is excellent in handling stability. From this viewpoint, the ratio HS / HE of the height HS from the bead base line to the inner end 24a of the strip 24 to the height HE from the bead base line to the tip 36a of the apex 36 is preferably 0.8 or less. Yes, more preferably 0.7 or less.

  On the other hand, the tire 2 having a large ratio HS / HE is excellent in ride comfort. From this viewpoint, the ratio HS / HE is preferably 0.4 or more, and more preferably 0.5 or more.

  The rigidity of the tire 2 can be increased by increasing the width in which the tip stacking portion 50 and the apex 36 are stacked. The tire 2 having high rigidity is excellent in handling stability. From this point of view, the ratio HT / HE of the height HT from the bead base line to the inner end 50a of the tip laminated portion 50 with respect to the height HE is preferably 0.9 or less, more preferably 0.8 or less. is there. On the other hand, the tire 2 having a large ratio HT / HE is excellent in ride comfort. From this viewpoint, the ratio HT / HE is preferably 0.5 or more, and more preferably 0.6 or more.

  FIG. 3 shows a tire 54 according to another embodiment of the present invention. The configuration of the tire 54 will be described with reference to FIG. The tire 54 includes a strip 56 in place of the strip 24 of the tire 2. Other configurations of the tire 54 are the same as those of the tire 2. Here, a configuration different from the tire 2 will be described. The description of the same configuration as the tire 2 is omitted. The same configuration as the tire 2 will be described using the same reference numerals.

  The tire 54 includes a strip 56 as a strip apex. The strip 56 includes a first strip 58 and a second strip 60 stacked on the outer side in the axial direction of the first strip 58.

  The first strip 58 is formed in a sheet shape. The first strip 58 is made of a highly hard crosslinked rubber. The first strip 58 is made of a rubber sheet. The radially inner end 58 a of the first strip 58 is laminated between the carcass 12 and the apex 36. The inner end 58a is located radially inward from the tip 36a of the apex 36. This inner end 58 a is also the inner end 56 a of the strip 56. The radially outer end 58 b is stacked between the carcass 12 and the sidewall 6. The first strip 58 is laminated on the main portion 40 a of the second ply 40. The outer end 58b is located radially outward from the tip 36a of the apex 36.

  The second strip 60 is formed into a sheet shape. The second strip 60 is made of a highly hard crosslinked rubber. The hardness of the second strip 60 may be greater than or equal to the hardness of the first strip 58. The second strip 60 is made of a rubber sheet. The radially inner end 60 a of the second strip 60 is located radially inward from the tip 36 a of the apex 36. The inner end 60 a is located radially outward from the inner end 58 a of the first strip 58. The outer end 60 b of the second strip 60 is located radially outward from the tip 36 a of the apex 36. The outer end 60 b is located radially inward from the outer end 58 b of the first strip 58.

  A double-headed arrow Ha in FIG. 3 represents the radial width of the second strip 60. The width Ha is measured as a distance from the inner end 60a to the outer end 60b. This width Ha is measured along the outer surface of the second strip 60. A double-headed arrow Hb indicates a radial width in which the second strip 60 and the apex 36 are stacked. The width Hb is measured as the distance from the inner end 60a to the tip 36a of the apex 36. This width Hb is measured along the outer surface of the second strip 60. The width Ha and the width Hb are measured in a cross section cut out from the tire 54 as shown in FIG.

  The strip 56 includes an inner laminated portion 62 and a tip laminated portion 64. The inner laminated portion 62 is a portion of the first strip 58 from the inner end 58 a of the first strip 58 to the inner end 60 a of the second strip 60. The tip stacking portion 64 is a portion where the first strip 58 and the second strip 60 are stacked. The inner end 60a of the second strip 60 corresponds to the inner end 64a of the leading end laminated portion 64, and the inner end 60b corresponds to the outer end 64b.

  Since the first strip 58 and the second strip 60 are laminated at the tip laminated portion 64, the rigidity of the tip laminated portion 64 is made larger than the rigidity of the inner laminated portion 62. The tip end 36 a of the apex 36 is stacked on the tip stacking portion 64. The rigidity in the vicinity of the tip 36a is improved. The taper tip 36a is stacked on the tip stacking portion 64, so that local deformation is suppressed.

  On the other hand, since the inner side laminated part 62 is laminated | stacked on the apex 36, it is suppressed that the rigidity of the tire 54 is excessive. By providing the inner laminated portion 62 and the tip laminated portion 64, the rigidity of the tire 2 is moderately improved while suppressing the rigidity of the tire 54 from being excessive. The strip 56 can reinforce the tire 2 similarly to the strip 24.

  In the tire 54, the outermost end PW is located at the front end laminated portion 64 in the radial direction. Thereby, the local deformation | transformation of the side wall 6 is suppressed more. In the tire 54, the provision of the strip 56 makes the rigidity in a range in which the apex 36 and the strip 56 extend uniform, as compared with the conventional tire. In the tire 54, local deformation of the sidewall 6 is suppressed.

  From the viewpoint of improving steering stability, the ratio HS / HE of the height HS from the bead base line to the inner end 56a (58a) of the strip 56 with respect to the height HE from the bead base line to the tip 36a of the apex 36 is , Preferably 0.8 or less, more preferably 0.7 or less. On the other hand, from the viewpoint of improving riding comfort, the ratio HS / HE is preferably 0.4 or more, and more preferably 0.5 or more.

  From the viewpoint of improving the handling stability, the ratio HT / HE of the height HT from the bead base line to the inner end 64a (60a) of the tip laminated portion 64 with respect to the height HE is preferably 0.9 or less, More preferably, it is 0.8 or less. On the other hand, from the viewpoint of improving riding comfort, the ratio HT / HE is preferably 0.5 or more, and more preferably 0.6 or more.

  The tire 54 having a large width Ha of the second strip 60 is excellent in steering stability. From this viewpoint, the width Ha is preferably 15 mm or more, and more preferably 20 mm or more. On the other hand, the tire 54 having a small width Ha is excellent in ride comfort. From this viewpoint, the width Ha is preferably 25 mm or less, and more preferably 20 mm.

  The tire 54 having a large radial width Hb in which the second strip 60 and the apex 36 are stacked has excellent steering stability. From this viewpoint, the width Hb is preferably 5 mm or more, and more preferably 10 mm or more. On the other hand, the tire 54 having a small width Hb is excellent in ride comfort. From this viewpoint, the width Hb is preferably 15 mm or less, and more preferably 10 mm or less.

  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 hardness is measured with a type A durometer in accordance with the provisions of “JIS K6253”. The durometer is pressed against the cross section shown in FIG. 1, and the hardness is measured. The measurement is made at a temperature of 23 ° C.

  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 “245 / 45R19”. In this tire, the thickness of the sidewall (sidewall gauge) at the position where the maximum width of the carcass is 3.5 mm. The height HE of the apex was 35 mm. This tire was provided with a strip apex. The rubber hardness of the outer end portion, the rubber hardness of the tip laminated portion, and the rubber hardness of the inner laminated portion were as shown in Table 1.

[Comparative Example 1]
Conventional tires were prepared. This tire did not have a strip apex. The thickness of the sidewall was 4.5 mm. This tire had the same configuration as that of Example 1 in other configurations.

[Comparative Example 2]
A tire was obtained in the same manner as Comparative Example 1 except that the thickness of the sidewall was 3.5 mm.

[Comparative Example 3]
A tire was obtained in the same manner as in Comparative Example 2 except that the apex height HE was 40 mm.

[Comparative Example 4]
A single rubber sheet was used as the strip apex. The rubber hardness of this rubber sheet was 80. Otherwise, a tire was obtained in the same manner as in Example 1.

[Comparative Example 5]
The rubber hardness of the outer part, the tip laminated part, and the inner laminated part of the strip apex was all set to 80. Otherwise, a tire was obtained in the same manner as in Example 1.

[Example 2-5]
A tire was obtained in the same manner as in Example 1 except that the rubber hardness of the outer portion of the strip apex was set as shown in Table 2.

[Examples 6-8 and Comparative Example 6]
A tire was obtained in the same manner as in Example 1 except that the rubber hardness at the tip laminated portion of the strip apex was set as shown in Table 3.

[Examples 9-11 and Comparative Example 7]
A tire was obtained in the same manner as in Example 1 except that the rubber hardness of the inner laminated portion of the strip apex was set as shown in Table 4.

[Example 12]
A tire having the structure shown in FIG. 3 was prepared. The size of this tire was “245 / 45R19” as in Example 1. In this tire, the thickness of the sidewall (sidewall gauge), the height of the apex HE, the first strip and the second strip were set as shown in Table 5 to obtain a tire.

[Comparative Example 8]
A tire was obtained in the same manner as in Example 12 except that the second strip was not provided.

[Examples 13-15 and Comparative Example 9]
A tire was obtained in the same manner as in Example 12 except that the width Ha of the second strip was changed as shown in Table 5.

[Examples 16-17 and Comparative Example 10-11]
A tire was obtained in the same manner as in Example 12 except that the width Hb in which the second strip and the apex were laminated was set as shown in Table 6.

[mass]
The mass of these tires was measured. The results are shown in Tables 1 to 6 below as indices based on the tire of Comparative Example 1. The smaller this value, the lighter and more preferable.

[Rolling resistance]
Using a rolling resistance tester, the rolling resistance coefficient was measured under the following measurement conditions.
Rim used: 19 × 8.0J
Internal pressure: 210 kPa
Load: 5.9kN
Speed: 80km / h
The results are shown in Tables 1 to 6 below as indices based on Comparative Example 3. A smaller numerical value is preferable.

[Ride comfort and handling stability]
These tires were mounted on a passenger car having a displacement of 4600 cm ² (cc). The driver was allowed to drive the passenger car on a test course to evaluate ride comfort and handling stability. The results are shown in Tables 1 to 6 below as indices based on Comparative Example 5. The evaluation result is preferably as the numerical value is larger.

  As shown in Tables 1 to 6, 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 pneumatic tire mounted on a vehicle, including a general tire for a passenger car.

2, 54 ... Tire 4 ... Tread 6 ... Sidewall 8 ... Clinch 10 ... Bead 12 ... Carcass 14 ... Belt 16 ... Band 18 ... Edge Band 20 ... Inner liner 22 ... Chafer 24, 56 ... Strip 26 ... Tread surface 28 ... Groove 30 ... Base layer 32 ... Cap layer 34 ... Core 36 ... Apex 38 ... first ply 40 ... second ply 42 ... inner layer 44 ... outer layer 46 ... reinforcing layer 48, 62 ... inner laminate 50,64 ... tip Laminated part 52 ... outer part 58 ... first strip 60 ... second strip

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 positioned radially inward of the sidewalls, the tread and the above A carcass spanned between one bead and the other bead along the inside of the sidewall, and a pair of strip apex, each positioned radially outward of the bead,
The bead includes a core and an apex extending radially outward from the core, the apex being tapered toward the radially outward tip;
The strip apex includes a tip laminate portion and an inner laminate portion extending radially inward from the tip laminate portion,
This tip lamination part and the inner lamination part are laminated on the apex,
The tip of the apex is laminated to this tip lamination part,
This tip stacking part extends radially outward from the tip of the apex,
The strip apex is made of rubber sheet,
A pneumatic tire in which the rubber hardness of the tip laminated portion is larger than the rubber hardness of the inner laminated portion . The strip apex includes an outer portion extending radially outward from the tip stack portion,
The tire according to claim 1, wherein the rubber hardness of the outer portion is made larger than the rubber hardness of the front end laminated portion. 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 positioned radially inward of the sidewalls, the tread and the above A carcass spanned between one bead and the other bead along the inside of the sidewall, and a pair of strip apex, each positioned radially outward of the bead,
The bead includes a core and an apex extending radially outward from the core, the apex being tapered toward the radially outward tip;
The strip apex includes a tip laminate portion and an inner laminate portion extending radially inward from the tip laminate portion,
This tip lamination part and the inner lamination part are laminated on the apex,
The tip of the apex is laminated to this tip lamination part,
This tip stacking part extends radially outward from the tip of the apex,
The strip apex is made of rubber sheet,
The strip apex is composed of a first rubber sheet and a second rubber sheet laminated on the first rubber sheet ,
A pneumatic tire in which the tip laminated portion is formed by laminating a first rubber sheet and a second rubber sheet, and the inner laminated portion is formed by the first rubber sheet . The radial width of the second rubber sheet is 15 mm or more and 25 mm or less,
The tire according to claim 3, wherein a radial width in which the second rubber sheet and the apex are laminated is smaller than a radial width of the second rubber sheet and is 5 mm or more and 15 mm or less. The ratio HT / HE of the height HT from the bead base line to the inner end of the tip laminated portion with respect to the height HE from the bead base line to the tip of the apex is set to 0.5 to 0.9. The tire according to any one of claims 1 to 4 . The ratio HS / HE of the height HS from the bead base line to the inner end of the strip apex to the height HE from the bead base line to the tip of the apex is set to 0.4 to 0.8. The tire according to any one of claims 1 to 5 .

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