JP2014151848A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire 32 in which the occurrence of a dent is suppressed and which combines driving stability with ride quality.SOLUTION: The pneumatic tire 32 includes a carcass 42 and a pair of load supporting portions 52. The load supporting portions 52 include inner layers 80 and outer layers 82. The inner layer 80 and the outer layer 82 comprise a cross-linked rubber composition including a base material rubber and a short fiber. A carcass ply 68 of the carcass 42 is formed from a number of tapes 70. In the carcass ply 68, the tapes 70 are juxtaposed to each other in a circumferential direction. Each tape 70 includes a body 90 and a pair of side pieces 92. The carcass ply 68 includes a first tape 70a in which the side piece 92 is positioned between the inner layer 80 and the outer layer 82 and a second tape in which the side piece 92 is positioned between the load supporting portion 52 and a side wall 36.

Description

  The present invention relates to a pneumatic tire.

  In the tire manufacturing method, a raw cover (unvulcanized tire) is obtained by combining a number of members such as treads and sidewalls on the former drum. In the raw cover molding process, the diameter of the drum is increased and the shape of the raw cover is adjusted.

  In this manufacturing method, the raw cover is put into a mold. At this time, the bladder is located inside the raw cover. When the bladder is filled with gas, the bladder expands. As a result, the raw cover is deformed. The mold is tightened and the internal pressure of the bladder is increased. The raw cover is pressed between the mold and the bladder. The raw cover is heated by heat conduction from the bladder and the mold. The rubber composition of the raw cover flows by pressurization and heating. The rubber causes a crosslinking reaction by heating, and a tire is obtained.

  The performance of the tire is controlled by adjusting the characteristics of the members constituting the tire. From the viewpoint of improving steering stability, a member containing short fibers may be adopted as a constituent member of the tire.

  The adoption example of the member containing the said short fiber is disclosed by Unexamined-Japanese-Patent No. 2003-146028. In the tire described in this publication, a short fiber reinforced rubber layer is used as a member containing short fibers.

  FIG. 16 shows a run flat tire as an example of the conventional tire 2. 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.

  In the tire 2, the bead 12 includes a core 26 and an apex 28 that extends radially outward from the core 26. The core 26 has a ring shape and includes a plurality of non-stretchable wires. The apex 28 has a tapered shape that tapers outward in the radial direction, and is made of a highly hard crosslinked rubber. The carcass ply 30 constituting the carcass 14 is bridged between the beads 12 on both sides, and extends along the inside of the tread 4 and the sidewall 8. The carcass ply 30 is folded around the core 26 from the inner side toward the outer side in the axial direction. The end 30 e of the carcass ply 30 reaches the vicinity of the tread 4. The structure of the carcass 14 is called an ultra high turn-up structure. The load support layer 16 is located on the inner side in the axial direction of the sidewall 8. The load support layer 16 has a shape similar to a crescent moon. The load support layer 16 is made of a highly hard crosslinked rubber.

  In the tire 2, when the internal pressure is reduced due to puncture, the load support layer 16 supports the vehicle weight. The load supporting layer 16 allows the tire 2 to travel a certain distance even when the internal pressure is low.

JP 2003-146028 A

  In the tire 2 shown in FIG. 16, the load supporting layer 16 having a large thickness is provided from the viewpoint of improving durability (also referred to as run-flat durability) when the internal pressure is reduced by puncture. May be adopted. However, the thick load support layer 16 may cause an increase in mass. In addition, the load support layer 16 affects the rigidity. This load support layer 16 may also reduce riding comfort.

  According to the above-described member containing short fibers, the rigidity of the tire 2 can be adjusted while suppressing an increase in mass. That is, according to this member, there is a possibility of achieving both handling stability and riding comfort. However, the elongation of a member containing a lot of short fibers is small. For this reason, in the vulcanization process of the tire 2, when the bladder is expanded and the raw cover is deformed, the member may not be able to follow the deformation. In the manufacturing method involving deformation of the raw cover, there is a problem that a member containing a large amount of short fibers cannot be employed. In this manufacturing method, there is a limit in achieving both steering stability and ride comfort.

  The carcass ply 30 of the tire 2 is formed, for example, by preparing a plurality of tapes including a large number of cords arranged in parallel and sequentially joining them. When joining, the edge of one tape is superimposed on the edge of the other tape. For this reason, a junction part is thick compared with another part. Since cords are also present at the edge portions of the tape, the cord density at the joined portion is higher than the cord density at the other portions. When the tire 2 having such a carcass ply 30 is filled with air, a dent may be generated at a position corresponding to the joint portion on the side surface of the tire 2. This dent is also called a dent. Dent affects the appearance and uniformity of the tire 2.

  An object of the present invention is to provide a pneumatic tire that achieves both steering stability and ride comfort while suppressing the occurrence of dents.

  The pneumatic tire according to the present invention is formed by being assembled on the outer surface of a toroidal core, and being pressurized and heated in a cavity formed between the mold and the core. The tire includes a tread whose outer surface forms a tread surface, a pair of sidewalls each extending substantially inward in the radial direction from the tread, a pair of clinch each positioned substantially radially inward of the sidewalls, A pair of beads each 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, respectively, from the sidewall And a pair of load support portions positioned on the inner side in the axial direction. The load support portion includes an inner layer and an outer layer positioned on the outer side in the axial direction than the inner layer. The inner layer is made of a crosslinked first rubber composition. The first rubber composition includes a base rubber and short fibers. The outer layer is made of a crosslinked second rubber composition. The second rubber composition includes a base rubber and short fibers. The carcass includes a carcass ply formed from a large number of tapes. In the carcass ply, these tapes are juxtaposed in the circumferential direction. Each tape includes a main body located radially inside the tread, and a pair of side pieces each located inside the sidewall in the axial direction. The carcass ply includes a first tape having a side piece positioned between the inner layer and the outer layer, and a second tape having a side piece positioned between the load support portion and the sidewall. Contains.

  Preferably, in the pneumatic tire, in the carcass ply, the first tape and the second tape are alternately arranged in the circumferential direction.

  Preferably, in this pneumatic tire, the amount of the short fibers in the first rubber composition is 5 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the base rubber. The described pneumatic tire.

  Preferably, in this pneumatic tire, the amount of the short fiber in the first rubber composition is 30 parts by mass or more with respect to 100 parts by mass of the base rubber.

  Preferably, in the pneumatic tire, the short fibers are oriented in the circumferential direction in the inner layer.

  Preferably, in this pneumatic tire, the inner layer is formed by spirally winding a first strip made of the first rubber composition in the circumferential direction.

  Preferably, in this pneumatic tire, the amount of the short fibers in the second rubber composition is 5 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the base rubber.

  Preferably, in the pneumatic tire, the amount of the short fibers in the second rubber composition is 30 parts by mass or more with respect to 100 parts by mass of the base rubber.

  Preferably, in the pneumatic tire, the short fibers are oriented in the circumferential direction in the outer layer.

  Preferably, in this pneumatic tire, the outer layer is formed by spirally winding a second strip made of the second rubber composition in the circumferential direction.

  Preferably, in this pneumatic tire, the thickness of the inner layer positioned on the inner side in the axial direction of the first tape and the outer layer positioned on the outer side in the axial direction at a reference position corresponding to half the height of the cross section. The ratio of the sum of the thickness and the thickness of the load support portion positioned on the inner side in the axial direction of the second tape is 1.0.

  Preferably, in the pneumatic tire, the width of the tape is 20 mm or more and 70 mm or less.

  Preferably, in this pneumatic tire, the hardness of the inner layer is 60 or more and 85 or less.

  Preferably, in the pneumatic tire, the outer layer has a hardness of 60 or more and 85 or less.

A method for manufacturing a pneumatic tire according to the present invention includes:
(1) On the outer surface of the toroidal core, a tread whose outer surface forms a tread surface, a pair of sidewalls each extending substantially inward in the radial direction from the tread, and each of which is substantially inward in the radial direction from the sidewalls A pair of clinches located on the inner side, a pair of beads located on the inner side in the axial direction of 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 portions that are positioned on the inner side in the axial direction than the sidewalls, and the load support portion includes an inner layer and an outer layer that is positioned on the outer side in the axial direction with respect to the inner layer. The inner layer is made of a first rubber composition, the first rubber composition contains a base rubber and short fibers, and the outer layer is a second rubber composition. The second rubber composition includes a base rubber and short fibers, and the carcass includes a carcass ply formed of a large number of tapes. In the carcass ply, these tapes are arranged in parallel in the circumferential direction. Each of the tapes includes a main body positioned radially inward of the tread and a pair of side pieces each positioned axially inward of the sidewall, and the carcass ply includes the inner layer and the A step of assembling a raw cover, including a first tape having a side piece between the outer layer and a second tape having a side piece located between the load support and the sidewall;
(2) a step of inserting the raw cover into a mold;
(3) The raw cover includes a step of pressing and heating in a cavity formed between the mold and the core.

  In the pneumatic tire according to the present invention, each of the inner layer and the outer layer of the load support portion includes short fibers. The tire is assembled on the outer surface of a toroidal core, and is formed by pressing and heating in a cavity formed between the mold and the core. For this reason, in this tire, it is possible to employ an inner layer and an outer layer containing many short fibers, which could not be employed by the conventional manufacturing method. According to the inner layer and the outer layer, the rigidity of the tire can be adjusted while suppressing an increase in mass. That is, the inner layer and the outer layer can contribute to both handling stability and riding comfort.

  The tire carcass ply is formed using a large number of tapes. These tapes are juxtaposed in the circumferential direction. In this tire, of these tapes, the side piece of the first tape is located between the inner layer and the outer layer, and the side piece of the second tape is located between the load support portion and the sidewall. Yes. In this tire, the side piece of the first tape and the side piece of the second tape are not joined. In this carcass ply, the joining portion is not formed on the side piece of the tape as in the conventional carcass ply. In this tire, the occurrence of dent is suppressed. As described above, the inner layer and the outer layer can contribute to both handling stability and ride comfort. According to the present invention, it is possible to obtain a pneumatic tire that achieves both steering stability and riding comfort while suppressing the occurrence of dents.

  In the load supporting layer of the tire, a portion divided into an inner layer and an outer layer by a tape and a portion in which the inner layer and the outer layer are integrated are mixed. The division by the tape can suppress the influence on the rigidity by the load support portion. This tire is excellent in ride comfort. Moreover, the mixture of the portion divided by the tape and the portion not so can suppress the expansion of damage along the carcass ply in the load support layer. This tire is excellent in run-flat durability.

FIG. 1 is a front view showing a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II-II in FIG. FIG. 3 is a cross-sectional view taken along line III-III in FIG. FIG. 4 is a perspective view showing a part of the tape for the carcass ply. FIG. 5 is an enlarged cross-sectional view illustrating a sidewall portion of the tire of FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. FIG. 7 is a schematic view showing the short fibers of the inner layer of FIG. FIG. 8 is a perspective view showing a portion of the first strip for the inner layer. FIG. 9 is a front view schematically showing how the tire of FIG. 1 is manufactured. FIG. 10 is a front view schematically showing a different manufacturing state from FIG. FIG. 11 is a front view schematically showing a different manufacturing state from FIG. FIG. 12 is a front view schematically showing a different manufacturing state from FIG. FIG. 13 is a front view schematically showing a different manufacturing state from FIG. FIG. 14 is a front view schematically showing a different manufacturing state from FIG. FIG. 15 is a front view schematically showing a different manufacturing state from FIG. FIG. 16 is a cross-sectional view showing a part of a conventional tire.

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

  FIG. 1 shows a pneumatic tire 32. In FIG. 1, a double arrow A represents the circumferential direction of the tire 32. In FIG. 1, the direction perpendicular to the paper surface is the axial direction of the tire 32.

  FIG. 2 shows a part of a cross section of the tire 32 taken along the line II-II in FIG. In FIG. 2, the vertical direction is the radial direction of the tire 32, the horizontal direction is the axial direction of the tire 32, and the direction perpendicular to the paper surface is the circumferential direction of the tire 32. In FIG. 2, the alternate long and short dash line CL represents the equator plane of the tire 32. In the illustrated cross section, the shape of the tire 32 is symmetrical with respect to the equator plane except for the tread pattern.

  FIG. 3 shows a part of a cross section of the tire 32 along the line III-III in FIG. FIG. 3 shows a cross section of a portion different from the cross section shown in FIG. In FIG. 3, the vertical direction is the radial direction of the tire 32, the horizontal direction is the axial direction of the tire 32, and the direction perpendicular to the paper surface is the circumferential direction of the tire 32. In FIG. 3, the alternate long and short dash line CL represents the equator plane of the tire 32. In the illustrated cross section, the shape of the tire 32 is symmetrical with respect to the equator plane except for the tread pattern.

  2 and 3, a solid line BBL represents a bead base line. This bead base line is a line that defines a rim diameter (see JATMA) of a rim (not shown) on which the tire 32 is mounted. The bead baseline extends in the axial direction. A double-headed arrow H represents the height in the radial direction from the bead base line to the equator of the tire 32. This height H is the cross-sectional height of the tire 32. The symbol Ph represents the position on the outer surface of the tire 32 where the radial height from the bead base line (double arrow Hh in the figure) is half of the cross-sectional height H. In the tire 32, this position Ph is a reference position corresponding to a half height of the cross-sectional height H.

  The tire 32 includes a tread 34, a sidewall 36, a clinch 38, a bead 40, a carcass 42, a belt 44, a band 46, an inner liner 48, a chafer 50, and a load support portion 52. The tire 32 is a tubeless type. The tire 32 is attached to a passenger car.

  The tread 34 has a shape protruding outward in the radial direction. The outer surface of the tread 34 forms a tread surface 54 that contacts the road surface. A groove 56 is carved on the tread surface 54. The groove 56 forms a tread pattern.

  The tread 34 of the tire 32 includes a base layer 58 and a cap layer 60. The cap layer 60 is located on the radially outer side of the base layer 58. The base layer 58 is made of a crosslinked rubber having excellent adhesiveness. The cap layer 60 is made of a crosslinked rubber having excellent wear resistance, heat resistance, and grip properties.

  The sidewall 36 extends substantially inward in the radial direction from the end of the tread 34. The sidewall 36 is located outside the carcass 42 in the axial direction. The sidewall 36 is joined to the tread 34 at the radially outer end. The sidewall 36 is joined to a clinch 38 at the radially inner end. The sidewall 36 is made of a crosslinked rubber having excellent cut resistance and weather resistance.

  In the tire 32, the hardness of the sidewall 36 is preferably 40 or greater and 75 or less. By setting the hardness to 40 or more, the sidewall 36 can effectively contribute to the rigidity of the tire 32. The tire 32 is excellent in handling stability. In this respect, the hardness is more preferably equal to or greater than 45. By setting the hardness to 75 or less, excessive rigidity of the tire 32 can be effectively suppressed. In the tire 32, the riding comfort is appropriately maintained. From this viewpoint, the hardness is more preferably 65 or less.

  In the present application, the hardness is JIS-A hardness. This hardness is measured with a type A durometer in an environment of 23 ° C. in accordance with the provisions of “JIS-K6253”. More specifically, the hardness is measured by pressing a type A durometer against the cross section shown in FIG.

  The clinch 38 is located substantially inward of the sidewall 36 in the radial direction. The clinch 38 is located outside the bead 40 and the carcass 42 in the axial direction. The clinch 38 contacts the flange of a rim (not shown). The clinch 38 is made of a crosslinked rubber having excellent wear resistance. In the tire 32, the outer end 38e of the clinch 38 is located radially inward from the reference position Ph. Thereby, the influence on the riding comfort by the clinch 38 is suppressed.

  The bead 40 is located on the inner side in the axial direction than the clinch 38. In the tire 32, the bead 40 includes a first core 62 a, a second core 62 b, and an apex 64. More specifically, the bead 40 includes a first core 62a, a second core 62b, and an apex 64.

  The first core 62 a is located on the inner side in the axial direction than the carcass 42. The first core 62a has a ring shape. The first core 62a includes a wound non-stretchable first wire 66a. The first core 62a of the tire 32 is formed by winding the first wire 66a in a spiral shape along the circumferential direction. A typical material of the first wire 66a is steel.

  The second core 62b is located on the outer side in the axial direction than the first core 62a. The second core 62 b is located on the outer side in the axial direction than the carcass 42. The second core 62b has a ring shape. The second core 62b includes a wound non-stretchable second wire 66b. The second core 62b of the tire 32 is formed by winding the second wire 66b in a spiral shape along the circumferential direction. A typical material of the second wire 66b is steel. In the tire 32, a wire equivalent to the first wire 66a is used as the second wire 66b.

  The apex 64 is made of a highly hard crosslinked rubber. The apex 64 is located on the outer side in the axial direction than the carcass 42. As is apparent from the figure, the apex 64 covers the second core 62b and extends substantially outward in the radial direction from the second core 62b. In the tire 32, the outer end 64 e of the apex 64 is located radially inward from the outer end 38 e of the clinch 38.

  In the tire 32, the apex 64 has a sufficient size. The bead 40 including the apex 64 sufficiently tightens the tire 32 to the rim. This bead 40 does not require another apex located axially inward of the carcass 42. The bead 40 can contribute to a reduction in the number of parts constituting the tire 32. In addition, since the apex 64 only needs to be provided on the outer side in the axial direction of the carcass 42, the manufacture of the bead 40 is easy. This bead 40 can contribute to the improvement of productivity.

  The carcass 42 includes a carcass ply 68. The carcass 42 of the tire 32 includes a single carcass ply 68. The carcass 42 may be formed from two or more carcass plies 68. The carcass ply 68 is bridged between the beads 40 on both sides. The carcass ply 68 is along the inside of the tread 34 and the sidewall 36. In the tire 32, the end portion of the carcass ply 68 is sandwiched between the first core 62a of the bead 40 and the second core 62b.

  In the tire 32, when forming the carcass 42, it is not necessary to fold the carcass ply 68 unlike the conventional tire 32. In the tire 32, the carcass 42 can be easily formed. The carcass 42 can contribute to the improvement of productivity.

  Although not shown, the carcass ply 68 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 42 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.

  In FIG. 1, a carcass ply 68 is represented by a dotted line. In the tire 32, the carcass ply 68 is formed from a large number of tapes 70. In the carcass ply 68, these tapes 70 are juxtaposed in the circumferential direction. In the tire 32, at the equator plane, the tapes 70 are juxtaposed so that the width direction thereof coincides with the circumferential direction of the tire 32.

  In FIG. 4, a portion of the tape 70 for the carcass ply 68 is shown. In FIG. 4, the direction indicated by the arrow B is the length direction of the tape 70.

  The tape 70 includes a plurality of cords 72 and a topping rubber 74. As shown in the drawing, these cords 72 are juxtaposed at intervals in the width direction of the tape 70. This interval is equivalent to the cord interval in the carcass ply 30 of the conventional tire 2. Each cord 72 extends in the length direction of the tape 70. The length of the tape 70 is equal to the length from one end of the carcass ply 68 to the other end in the cross section of the tire 32 shown in FIGS.

  The belt 44 is located on the radially outer side of the carcass 42. The belt 44 is laminated with the carcass 42. The belt 44 reinforces the carcass 42. The belt 44 includes a first layer 76 and a second layer 78 located outside the first layer 76. As is apparent from the drawing, the width of the first layer 76 is slightly larger than the width of the second layer 78 in the axial direction. The axial width of the belt 44 is preferably 0.7 times or more the maximum width of the tire 32. The belt 44 may include three or more layers.

  Although not shown, each of the first layer 76 and the second layer 78 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 first layer 76 with respect to the equator plane is opposite to the inclination direction of the cord of the second layer 78 with respect to the equator plane. A preferred material for the cord is steel. An organic fiber may be used for the cord.

  The band 46 is located on the radially outer side of the belt 44. In the tire 32, the axial width of the band 46 is slightly larger than the axial width of the belt 44. Although not shown, the band 46 is made of a cord and a topping rubber. The cord is wound in a spiral. The band 46 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 44 is restrained by this cord, lifting of the belt 44 is suppressed. From the standpoint that the belt 44 is effectively restrained, the axial width of the band 46 is preferably 0.9 to 1.1 times the axial width of the belt 44. In the tire 32, the cord of the band 46 is made of an organic fiber. Examples of preferable organic fibers include nylon fibers, polyethylene terephthalate fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  The inner liner 48 is located inside the carcass 42. The inner liner 48 forms the inner surface of the tire 32. The inner liner 48 is made of a crosslinked rubber. For the inner liner 48, rubber having excellent air shielding properties is used. A typical base rubber of the inner liner 48 is butyl rubber or halogenated butyl rubber. The inner liner 48 holds the internal pressure of the tire 32.

  The chafer 50 is located in the vicinity of the bead 40. When the tire 32 is incorporated into the rim, the chafer 50 contacts the rim. By this contact, the vicinity of the bead 40 is protected. In this embodiment, the chafer 50 is made of cloth and rubber impregnated in the cloth. The chafer 50 may be integrated with the clinch 38. In this case, the material of the chafer 50 is the same as that of the clinch 38.

  The load support portion 52 is located on the inner side in the axial direction than the sidewall 36. The load support portion 52 is located on the outer side in the axial direction than the inner liner 48.

  In the tire 32, the load support portion 52 includes an inner layer 80 and an outer layer 82. Specifically, the load support portion 52 includes an inner layer 80 and an outer layer 82. The outer layer 82 is located on the outer side in the axial direction than the inner layer 80.

  In the cross section shown in FIG. 2, the inner layer 80 is located axially inward of the carcass ply 68. The outer layer 82 is located on the outer side in the axial direction than the carcass ply 68. The load support portion 52 in this cross section is divided into two layers (an inner layer 80 and an outer layer 82) by a carcass ply 68.

  In FIG. 2, the radially inner portion of the inner layer 80 covers the first core 62 a of the bead 40. The inner layer 80 extends from the first core 62a substantially outward in the radial direction. The radially outer portion of the inner layer 80 has a tapered shape. The radially outer end 80 e of the inner layer 80 is located on the inner side in the axial direction from the end 78 e of the second layer 78 of the belt 44.

  In FIG. 2, the radially inner portion of the outer layer 82 has a tapered shape. This inner portion is located between the carcass ply 68 and the apex 64. The radially inner end of the outer layer 82 is located on the radially outer side than the second core 62b. The radially outer portion of the outer layer 82 has a tapered shape. The radially outer end 82 e of the outer layer 82 is located on the inner side in the axial direction from the end 76 e of the first layer 76 of the belt 44.

  In the cross section shown in FIG. 3, the entire load support portion 52 is located on the inner side in the axial direction than the carcass ply 68. In other words, in the load support portion 52 in this cross section, the inner layer 80 and the outer layer 82 are integrated. In the cross section shown in FIG. 3, the structures of the carcass 42 and the load support portion 52 in the side wall 36 are different from those in the cross section shown in FIG. This cross section has the same configuration as that of the cross section shown in FIG. 2 except for the carcass 42 and the load support portion 52.

  In FIG. 3, the radially inner portion of the load support portion 52 covers the first core 62 a of the bead 40. The load support portion 52 extends substantially outward in the radial direction from the first core 62a. The radially outer portion of the load support portion 52 has a tapered shape. The radially outer end 52e of the load support portion 52 is located inside the end 78e of the second layer 78 of the belt 44 in the axial direction.

  In the cross section shown in FIG. 3, the load support portion 52 is not divided by the carcass ply 68. As described above, in the cross section shown in FIG. 2, the load support portion 52 is divided by the carcass ply 68. That is, the load support portion 52 of the tire 32 includes a portion that is divided into the inner layer 80 and the outer layer 82 by the carcass ply 68 and a portion in which the inner layer 80 and the outer layer 82 are integrated.

  In the tire 32, the inner layer 80 is formed by crosslinking the first rubber composition. The first rubber composition includes a base rubber. Examples of the base rubber include natural rubber, polybutadiene, styrene-butadiene copolymer, polyisoprene, ethylene-propylene-diene terpolymer, polychloroprene, acrylonitrile-butadiene copolymer, and isobutylene-isoprene copolymer. Illustrated. From the viewpoint of adhesiveness, natural rubber is preferred as the base rubber. Two or more kinds of rubbers may be used in combination.

  The first rubber composition of the inner layer 80 further includes short fibers. The short fibers can contribute to the strength of the inner layer 80. As this short fiber, an organic fiber is illustrated. Examples of the organic fibers include nylon fibers, rayon fibers, aramid fibers, polyethylene naphthalate fibers, and polyester fibers. From the viewpoint of weight reduction and cost reduction, paper fibers obtained by pulverizing raw material paper made of kraft paper and waste newspaper may be used as the short fibers.

  In the tire 32, the blending amount of the short fibers in the first rubber composition of the inner layer 80 is preferably 5 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the base rubber. By setting the blending amount of the short fibers to 5 parts by mass or more, the inner layer 80 has an appropriate strength. The inner layer 80 can contribute to the rigidity of the tire 32. In this respect, the blend amount of the short fibers is more preferably 10 parts by mass or more. By setting the blending amount of the short fibers to 60 parts by mass or less, the adhesiveness of the inner layer 80 is appropriately maintained. The inner layer 80 in the cross section shown in FIG. 2 can be sufficiently bonded to the carcass ply 68 and the inner liner 48. The inner layer 80 in the cross section shown in FIG. 3 can be sufficiently bonded to the outer layer 82 and the inner liner 48. The tire 32 is excellent in durability. In this respect, the amount of the short fiber is more preferably equal to or less than 55 parts by mass.

  Preferably, the first rubber composition of the inner layer 80 includes sulfur. Rubber molecules are cross-linked by sulfur. Other crosslinking agents may be used with or instead of sulfur. Crosslinking may be performed by an electron beam.

  Preferably, the first rubber composition of the inner layer 80 includes a vulcanization accelerator together with sulfur. A sulfenamide vulcanization accelerator, a guanidine vulcanization accelerator, a thiazole vulcanization accelerator, a thiuram vulcanization accelerator, a dithiocarbamate vulcanization accelerator, and the like can be used.

  The first rubber composition of the inner layer 80 includes a reinforcing material. A typical reinforcement is carbon black. FEF, GPF, HAF, ISAF, SAF, etc. can be used. From the viewpoint of the strength of the inner layer 80, the amount of carbon black is preferably 5 parts by mass or more with respect to 100 parts by mass of the base rubber. From the viewpoint of the softness of the inner layer 80, the amount of carbon black is preferably 50 parts by mass or less. Silica may be used together with or in place of carbon black. Dry silica and wet silica can be used.

  The first rubber composition of the inner layer 80 includes a softener. Examples of preferable softeners include paraffinic process oil, naphthenic process oil, and aromatic process oil. From the viewpoint of the softness of the inner layer 80, the amount of the softening agent is preferably 10 parts by mass or more with respect to 100 parts by mass of the base rubber. In light of the strength of the inner layer 80, the amount of the softening agent is preferably 40 parts by mass or less.

  In addition to the above-mentioned components, the first rubber composition of the inner layer 80 requires compounding agents conventionally used in the rubber industry, such as stearic acid, zinc oxide, anti-aging agents, waxes, crosslinking aids and the like. Depending on the situation, it is further added.

  In the tire 32, the outer layer 82 is formed by crosslinking the second rubber composition. The second rubber composition includes a base rubber. As the base rubber, the base rubber described above with respect to the first rubber composition is preferably used.

  The second rubber composition of the outer layer 82 further includes short fibers. The short fibers can contribute to the strength of the outer layer 82. As this short fiber, the short fiber mentioned above regarding the 1st rubber composition is used suitably.

  In the tire 32, the blend amount of the short fibers in the second rubber composition of the outer layer 82 is preferably 5 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the base rubber. By setting the blending amount of the short fibers to 5 parts by mass or more, the outer layer 82 has an appropriate strength. The outer layer 82 can contribute to the rigidity of the tire 32. In this respect, the blend amount of the short fibers is more preferably 10 parts by mass or more. By setting the blend amount of the short fibers to 60 parts by mass or less, the adhesiveness of the outer layer 82 is appropriately maintained. The outer layer 82 in the cross section shown in FIG. 2 can be sufficiently bonded to the carcass ply 68, the sidewall 36, the clinch 38 and the apex 64. The outer layer 82 in the cross section shown in FIG. 3 can be sufficiently bonded to the carcass ply 68 and the inner layer 80. The tire 32 is excellent in durability. In this respect, the amount of the short fiber is more preferably equal to or less than 55 parts by mass.

  Preferably, the second rubber composition of the outer layer 82 includes sulfur. Rubber molecules are cross-linked by sulfur. Other crosslinking agents may be used with or instead of sulfur. Crosslinking may be performed by an electron beam.

  Preferably, the second rubber composition of the outer layer 82 includes a vulcanization accelerator together with sulfur. As the vulcanization accelerator, the vulcanization accelerator described above with respect to the first rubber composition is used.

  The second rubber composition of the outer layer 82 includes a reinforcing material. A typical reinforcement is carbon black. FEF, GPF, HAF, ISAF, SAF, etc. can be used. From the viewpoint of the strength of the outer layer 82, the amount of carbon black is preferably 5 parts by mass or more with respect to 100 parts by mass of the base rubber. From the viewpoint of the softness of the outer layer 82, the amount of carbon black is preferably 50 parts by mass or less. Silica may be used together with or in place of carbon black. Dry silica and wet silica can be used.

  The second rubber composition of the outer layer 82 includes a softening agent. Examples of preferable softeners include paraffinic process oil, naphthenic process oil, and aromatic process oil. In light of the softness of the outer layer 82, the amount of the softening agent is preferably 10 parts by mass or more with respect to 100 parts by mass of the base rubber. From the viewpoint of the strength of the outer layer 82, the amount of the softening agent is preferably 40 parts by mass or less.

  In addition to the above-mentioned components, the second rubber composition of the outer layer 82 requires compounding agents conventionally used in the rubber industry, such as stearic acid, zinc oxide, anti-aging agents, waxes, and crosslinking aids. Depending on the situation, it is further added.

  In the tire 32, a rubber composition different from the first rubber composition of the inner layer 80 described above may be used as the second rubber composition of the outer layer 82. As this second rubber composition, a rubber composition equivalent to the first rubber composition may be used. From the viewpoint of productivity, the second rubber composition and the first rubber composition are preferably composed of equivalent rubber compositions.

  FIG. 5 shows a part of the tire 32 of FIG. In FIG. 5, the portion where the load support portion 52 is provided is shown enlarged. In FIG. 5, the vertical direction is the radial direction of the tire 32, the horizontal direction is the axial direction of the tire 32, and the direction perpendicular to the paper surface is the circumferential direction of the tire 32. 6 is a cross-sectional view taken along line VI-VI in FIG. In FIG. 6, a part of the inner layer 80 is shown. In FIG. 6, the vertical direction is the radial direction of the tire 32, and the horizontal direction is the circumferential direction of the tire 32.

  As shown in the figure, the inner layer 80 is composed of a large number of short fibers 84 and a matrix 86. In other words, the inner layer 80 is made of fiber reinforced rubber (FRR). These short fibers 84 are dispersed in the matrix 86. The longitudinal direction of these short fibers 84 is substantially along the circumferential direction. In the inner layer 80, the short fibers 84 are oriented in the circumferential direction. The short fibers 84 can effectively contribute to the strength of the inner layer 80.

  FIG. 7 is a schematic view showing the short fibers 84 of the inner layer 80 of FIG. In FIG. 7, the left-right direction is the circumferential direction. What is indicated by an arrow θ is the angle of the short fiber 84. The angle θ is an absolute value of an angle formed by the straight line X1 and the straight line X2. The straight line X1 extends in the circumferential direction. The straight line X2 passes through one end 84a and the other end 84b of the short fiber 84. This angle θ is an angle formed by the longitudinal direction of the short fibers 84 with respect to the circumferential direction. The angle θ is 0 ° or more and 90 ° or less. In FIG. 7, what is indicated by a double arrow L is the fiber length. The fiber length L is obtained by measuring the length from one end 84a to the other end 84b.

  From the viewpoint that the inner layer 80 can effectively contribute to the rigidity of the tire 32, the ratio of the number of short fibers 84 having an angle θ of 20 ° or less to the total number of short fibers 84 is preferably 50% or more. 70% or more is more preferable, and 90% or more is particularly preferable. In calculating the ratio, the angle of the short fibers 84 exposed in the cross section of the inner layer 80 along the circumferential direction is measured. The angle is measured for 100 randomly extracted short fibers 84. When the ratio of the number of short fibers 84 having an angle θ of 20 ° or less to the total number of short fibers 84 is 90% or more, the short fibers 84 in the inner layer 80 are oriented in the circumferential direction. is there.

  In the tire 32, from the viewpoint that the short fibers 84 effectively increase the strength of the inner layer 80, the average length L (see FIG. 7) of the short fibers 84 is preferably 20 μm or more. The inner layer 80 is sufficiently reinforced by the short fibers 84 having an average length L of 20 μm or more. From the viewpoint of dispersibility in the matrix 86, the average length L is preferably 5000 μm or less.

  The average diameter D of the short fibers 84 is preferably 0.04 μm or more. The strength of the inner layer 80 is sufficiently increased by the short fibers 84 having an average diameter D of 0.04 μm or more. From the viewpoint of dispersibility in the matrix 86, the average diameter D is preferably 500 μm or less.

  The aspect ratio (L / D) of the short fiber 84 is preferably 10 or more. The strength of the inner layer 80 is sufficiently enhanced by the short fibers 84 having an aspect ratio (L / D) of 10 or more. From the viewpoint of dispersibility in the matrix 86, the aspect ratio (L / D) is preferably 500 or less.

  Although not shown, the outer layer 82 is composed of a large number of short fibers and a matrix, like the inner layer 80 described above. In other words, the outer layer 82 is made of fiber reinforced rubber (FRR). These short fibers are dispersed in a matrix. The longitudinal direction of these short fibers is substantially along the circumferential direction. In the outer layer 82, the short fibers are oriented in the circumferential direction. The short fibers can effectively contribute to the strength of the outer layer 82.

  From the viewpoint that the outer layer 82 can effectively contribute to the rigidity of the tire 32, when the angle formed by the longitudinal direction of the short fibers with respect to the circumferential direction is represented by an angle θ, the angle θ is 20 ° or less. The ratio of the number of certain short fibers to the total number of short fibers is preferably 50% or more, more preferably 70% or more, and particularly preferably 90% or more. The angle θ and the ratio are obtained in the same manner as the angle θ and the ratio in the inner layer 80 described above.

  As described above, the short fibers 84 of the inner layer 80 are preferably used for the short fibers of the outer layer 82. Accordingly, the average length of the short fibers in the outer layer 82 is preferably 20 μm or more, and preferably 5000 μm or less, like the short fibers 84 of the inner layer 80 described above. The average diameter of the short fibers is preferably 0.04 μm or more, more preferably 500 μm or less. The short fiber has an aspect ratio (L / D) of preferably 10 or more, more preferably 500 or less. Accordingly, the short fibers can sufficiently increase the strength of the outer layer 82, and the short fibers can be well dispersed in the matrix.

  As described above, the inner layer 80 is formed by crosslinking the first rubber composition, and the outer layer 82 is formed by crosslinking the second rubber composition. Therefore, the load support portion 52 of the tire 32 is formed by crosslinking a rubber composition.

  The load support portion 52 can contribute to the rigidity of the tire 32. The load support portion 52 is located between the sidewall 36 and the inner liner 48. In the tire 32, when the internal pressure is reduced due to puncture, the load support portion 52 supports the vehicle weight. Thereby, even when the internal pressure is low, the tire 32 can travel a certain distance. The tire 32 is a run flat tire 32. The tire 32 is a side reinforcing type.

  As described above, the first rubber composition of the inner layer 80 includes short fibers 84, and the second rubber composition of the outer layer 82 also includes short fibers. Therefore, the load support portion 52 includes short fibers. In the tire 32, the short fibers effectively increase the strength of the load support portion 52. The load support portion 52 can contribute to the rigidity of the tire 32. The tire 32 including the load support portion 52 is excellent in steering stability. When the internal pressure of the tire 32 decreases due to puncture, the load support portion 52 supports the vehicle weight. The tire 32 can travel a certain distance even when the internal pressure is low. And since the influence which the short fiber contained in the load support part 52 has on mass is small, in this tire 32, the increase in mass is suppressed. In addition, since the tire 32 can employ the thin load support portion 52, weight reduction is achieved.

  As described above, the short fibers 84 included in the inner layer 80 are oriented in the circumferential direction, and the short fibers contained in the outer layer 82 are also oriented in the circumferential direction. Therefore, the short fibers included in the load support portion 52 are oriented in the circumferential direction. In the tire 32, the influence on the deflection by the load support portion 52 is suppressed. In the tire 32, the riding comfort is appropriately maintained.

  In the tire 32, the inner layer 80 preferably has a hardness of 60 or greater and 85 or less. By setting the hardness to 60 or more, when the internal pressure of the tire 32 is reduced due to puncture, the inner layer 80 can effectively contribute to supporting the vehicle weight. From this viewpoint, the hardness is more preferably 65 or more. By setting the hardness to 85 or less, the influence on the bending by the inner layer 80 is suppressed. In the tire 32, the riding comfort is appropriately maintained. In this respect, the hardness is more preferably equal to or less than 80. The hardness of the inner layer 80 is measured in the same manner as the hardness of the sidewall 36 described above. The same applies to the hardness of the outer layer 82 described later.

  In the tire 32, the outer layer 82 preferably has a hardness of 60 or greater and 85 or less. By setting the hardness to 60 or more, when the internal pressure of the tire 32 is reduced due to puncture, the outer layer 82 can effectively contribute to support of the vehicle weight. From this viewpoint, the hardness is more preferably 65 or more. By setting the hardness to 85 or less, the influence on the bending by the outer layer 82 is suppressed. In the tire 32, the riding comfort is appropriately maintained. In this respect, the hardness is more preferably equal to or less than 80.

  The tire 32 described above is manufactured as follows. In this manufacturing method, the first rubber composition of the inner layer 80 is extruded to form the first strip 88 shown in FIG. In FIG. 8, the direction indicated by the arrow C is the length direction of the first strip 88. This length direction is also the extrusion direction of the first strip 88.

  In this manufacturing method, the first strip 88 is formed so that its cross-sectional shape is rectangular. As described above, the first rubber composition of the inner layer 80 includes the short fibers 84. Accordingly, the first strip 88 also includes the short fiber 84. Since the first strip 88 is formed by extruding the first rubber composition, the short fibers 84 are oriented in the extrusion direction, in other words, in the length direction of the first strip 88. Here, “oriented in the length direction” means that the ratio of the number of short fibers 84 whose longitudinal direction is 20 ° or less with respect to the length direction of the first strip 88 to the total number of short fibers 84 is 90. It means the case where it is more than%. The angle formed by the longitudinal direction of the short fibers 84 in the first strip 88 with respect to the length direction of the first strip 88 is measured by the same method as the method for measuring the angle θ in the inner layer 80 described above. In calculating the ratio, the angle of the short fibers 84 exposed on the surface of the first strip 88 is measured.

  In FIG. 8, the double arrow TS represents the thickness of the first strip 88 used for forming the inner layer 80. A double arrow WS represents the width of the first strip 88.

  In this manufacturing method, the thickness TS is preferably 0.3 mm or greater and 2.0 mm or less. By setting the thickness TS to 0.3 mm or more, the strength of the first strip 88 is appropriately maintained. Moreover, the inner layer 80 formed by the first strip 88 can effectively contribute to the rigidity of the tire 32. In this respect, the thickness TS is more preferably equal to or greater than 0.5 mm. By setting the thickness TS to 2.0 mm or less, formation of a step due to the thickness TS is prevented. In this respect, the thickness TS is more preferably equal to or less than 1.0 mm.

  In this manufacturing method, the width WS is preferably 3 mm or more and 25 mm or less. By setting the width WS to 3 mm or more, the productivity of the tire 32 can be appropriately maintained. From this viewpoint, the width WS is preferably 5 mm or more. By setting the width WS to 25 mm or less, the difference in rigidity between the start and end of winding of the first strip 88 is appropriately maintained. According to the first strip 88, the inner layer 80 having an appropriate shape is obtained. From this viewpoint, the width WS is more preferably 15 mm or less.

  In this manufacturing method, the second rubber composition of the outer layer 82 is extruded to form a second strip. Although not shown, the second strip has a configuration similar to that of the first strip 88 shown in FIG.

  In this manufacturing method, a core is prepared. Although not shown, the core has a toroidal outer surface. This outer surface is approximated to the inner shape of the tire 32 in a state where it is filled with air and its internal pressure is maintained at 5% of the normal internal pressure.

  In this manufacturing method, the inner liner 48 is wound around the outer surface of the core. On the inner liner 48, the first strip 88 described above is spirally wound in the circumferential direction. Thereby, the inner layer 80 which forms a part of the load support portion 52 is formed.

  When the inner layer 80 is formed, the first core 62 a of the bead 40 is combined with the inner layer 80. A state in which the first core 62 is combined with the inner layer 80 is shown in FIG.

  As described above, in the tire 32, the carcass ply 68 is formed using a large number of tapes 70. In this manufacturing method, a large number of tapes 70 shown in FIG. 4 are prepared for forming the carcass ply 68.

  In this manufacturing method, the tape 70 is combined with a raw cover (unvulcanized tire) being formed. When the tape 70 is combined with the raw cover, the width direction of the tape 70 is matched with the circumferential direction of the tire 32 on the equator plane. The length direction of the tape 70 is matched with the axial direction of the tire 32.

  In this manufacturing method, as shown in FIG. 10, the tapes 70 are arranged at intervals in the circumferential direction. This interval is represented by a distance between one tape 70 on the equator plane of the tire 36 and another tape 70 located next to the one tape 70. This interval is appropriately determined according to the specifications of the tape 70. In this manufacturing method, since the carcass ply 68 is formed by using the tape 70 shown in FIG. 4, the distance is preferably equal to or smaller than the width of the tape 70. .

  In this manufacturing method, the central portion of the tape 70 is laminated on the portion corresponding to the inner side in the radial direction of the tread 34. The end portion of the tape 70 is laminated on a portion corresponding to the inner side in the axial direction of the sidewall 36. In the present invention, the central portion of the tape 70 is referred to as a main body 90. The end portion of the tape 70 is referred to as a side piece 92. In the tire 32, the tape 70 forms a part of the carcass ply 68. The tape 70 in the carcass ply 68 of the tire 32 includes a main body 90 positioned on the radially inner side of the tread 34 and a pair of side pieces 92 each positioned on the inner side of the sidewall 36 in the axial direction.

  In this manufacturing method, as shown in FIG. 10, after the tapes 70 are combined, the outer layer 82 is formed. In the present invention, the tape 70 combined before the outer layer 82 is formed is referred to as a first tape 70a.

  When the first tape 70a is combined, the second strip described above is spirally wound in the circumferential direction. Thereby, the outer layer 82 which forms another part of the load support portion 52 is formed. FIG. 11 shows a state where the outer layer 82 is combined with the raw cover that is being formed.

  Once the outer layer 82 is formed, the tape 70 is further combined. In the present invention, the tape 70 combined after the formation of the outer layer 82 is referred to as a second tape 70b.

  In this manufacturing method, when the second tape 70 b is combined with the raw cover, the width direction of the second tape 70 b is matched with the circumferential direction of the tire 32 on the equator plane. The length direction of the second tape 70 b is matched with the axial direction of the tire 32. The main body 90 of the second tape 70 b is laminated on a portion corresponding to the inner side in the radial direction of the tread 34. The side piece 92 of the second tape 70b is laminated on a portion corresponding to the axially inner side of the sidewall 36.

  As shown in FIG. 12, the second tape 70b is arranged at intervals in the circumferential direction, like the first tape 70a. The position where the second tape 70b is disposed is between one first tape 70a and another first tape 70a located next to the first tape 70a. When the second tape 70b is combined with the raw cover, the center in the width direction of the second tape 70b is made to coincide with the center in the circumferential direction of the interval of the first tape 70a described above. In this manufacturing method, since the carcass ply 68 is formed using the tape 70 shown in FIG. 4, the interval between the second tapes 70b is equal to the interval between the first tapes 70a described above.

  As shown in FIG. 13, when the carcass ply 68 is formed by combining the second tape 70 b, the second core 62 b of the bead 40 is combined with the end portion of the carcass ply 68. As shown in FIG. 14, the apex 64 of the bead 40 is further combined. The clinch 38, the sidewall 36, the belt 44, the band 46, and the tread 34 are combined to obtain a raw cover. In this manufacturing method, the process of assembling the raw cover is called a molding process.

  In this manufacturing method, a large number of elements including the carcass ply 68 are combined on the outer surface of the core to obtain a raw cover. In other words, the raw cover is assembled on the outer surface of the core. As described above, the outer surface of the core is approximated to the shape of the inner surface of the tire 32 that is filled with air and whose internal pressure is maintained at 5% of the normal internal pressure. This manufacturing method does not require shaping of the raw cover as in the conventional manufacturing method. In this manufacturing method, the raw cover is not extended in the molding process.

  The raw cover is put into the opened mold. In this manufacturing method, the raw cover is put into the mold while being combined with the core. Therefore, the core is located inside the raw cover put into the mold. After loading, the mold is tightened.

  As shown in FIG. 15, when the mold (symbol M in the figure) is tightened, the raw cover (symbol R in the figure) becomes the cavity surface 94 of the mold M and the outer surface of the core (symbol N in the figure). It is sandwiched between 96 and pressurized. The raw cover R is heated by heat conduction from the core N and the mold M. The rubber composition of the raw cover R flows by pressurization and heating. The rubber composition causes a crosslinking reaction by heating, and the tire 32 shown in FIG. 1 is obtained. The tire 32 is formed by pressing and heating the raw cover R in a cavity formed between the mold M and the core N. In this manufacturing method, the process in which the raw cover R is pressurized and heated is referred to as a crosslinking process.

  As described above, in this manufacturing method, the raw cover R is put into the mold M in a state of being combined with the core N, and is pressed and heated by being sandwiched between the cavity surface 94 of the mold M and the outer surface 96 of the core N. Is done. In this manufacturing method, the bladder used in the conventional manufacturing method is unnecessary. In this manufacturing method, the raw cover R is not extended in the crosslinking step.

  The inner layer 80 forming a part of the load support portion 52 of the tire 32 is formed by pressing and heating an element made of the first rubber composition including the short fibers 84 in the cavity. As described above, in this manufacturing method, the raw cover R is not extended in the molding process. Even in the crosslinking step, the raw cover R is not stretched. For this reason, in this manufacturing method, even if this first strip 88 contains a large amount of short fibers 84 to such an extent that it breaks without being stretched when an operator picks it with a finger and pulls it, The inner layer 80 is formed, and the raw cover R is obtained. And the tire 32 is obtained from this raw cover R. According to this manufacturing method, the tire 32 including the inner layer 80 containing a large amount of short fibers 84 can be produced with high quality and stability.

  The outer layer 82 forming another part of the load support portion 52 of the tire 32 is formed by pressing and heating an element made of the second rubber composition containing short fibers in the cavity. As described above, in this manufacturing method, the raw cover R is not extended in the molding process. Even in the crosslinking step, the raw cover R is not stretched. For this reason, in this manufacturing method, even if this second strip contains a large amount of short fibers to such an extent that it will break without being stretched when the operator picks it with a finger and pulls it, the outer layer 82 is removed from the second strip. And a raw cover R is obtained. And the tire 32 is obtained from this raw cover R. According to this manufacturing method, the tire 32 including the outer layer 82 containing a large amount of short fibers can be produced with high quality and stability.

  As described above, in the tire 32, each of the inner layer 80 and the outer layer 82 of the load support portion 52 includes short fibers. The tire 32 is assembled on the outer surface of the toroidal core, and is formed by being pressurized and heated in a cavity formed between the mold and the core. For this reason, in this tire 32, it is possible to employ the inner layer 80 and the outer layer 82 containing many short fibers, which could not be employed in the conventional manufacturing method. According to the inner layer 80 and the outer layer 82, the rigidity of the tire 32 can be adjusted while suppressing an increase in mass. That is, the inner layer 80 and the outer layer 82 can contribute to both handling stability and ride comfort.

  In the tire 32, the inner layer 80 is formed by spirally winding the first strip 88 in the circumferential direction. The inner layer 80 is formed by winding a sheet and joining one end and the other end of the sheet together like a conventional load support layer 16 formed using a single sheet. There is no seam. The form of this inner layer 80 is not unique. In addition, since the tire 32 can be obtained without extending the low cover R, the form change of the inner layer 80 can be effectively suppressed in the method of manufacturing the tire 32. The inner layer 80 can contribute to improving the uniformity of the tire 32.

  In the tire 32, the outer layer 82 is formed by spirally winding the second strip in the circumferential direction. The outer layer 82 is formed by winding a sheet and joining one end and the other end of the sheet together like a conventional load support layer 16 formed using a single sheet. There is no seam. The form of this outer layer 82 is not unique. In addition, since the tire 32 can be obtained without extending the low cover R, in the method for manufacturing the tire 32, a change in the shape of the outer layer 82 is effectively suppressed. The outer layer 82 has a uniform shape in the circumferential direction. The outer layer 82 can contribute to improvement of run flat durability.

  In this manufacturing method, the carcass ply 68 is formed by combining a large number of tapes 70. In this manufacturing method, a number of first tapes 70 a are combined before the outer layer 82 is formed, and a number of second tapes 70 b are combined after the outer layer 82 is formed. For this reason, in the tire 32 obtained by this manufacturing method, as shown in FIG. 2, the side piece 92 of the first tape 70 a is located between the inner layer 80 and the outer layer 82. As shown in FIG. 3, the side piece 92 of the second tape 70 b is located between the outer layer 82 as a part of the load support portion 52 and the sidewall 36. In other words, the carcass ply 68 of the tire 32 includes the first tape 70 a in which the side piece 92 is positioned between the inner layer 80 and the outer layer 82, and the side between the load support portion 52 and the sidewall 36. And a second tape 70b on which the piece 92 is located.

  In the tire 32, in the carcass ply 68, the first tape 70a and the second tape 70b are preferably arranged alternately in the circumferential direction. Thereby, the influence on the uniformity by the carcass ply 68 is suppressed.

  As described above, in the tire 32, the side piece 92 of the first tape 70a is located between the inner layer 80 and the outer layer 82, and the side piece 92 of the second tape 70b is connected to the load support portion 52 and the side layer. It is located between the wall 36. In the tire 32, the side piece 92 of the first tape 70a and the side piece 92 of the second tape 70b overlap in the axial direction, but the both side pieces 92 are not directly joined. In the tire 32, the joining portion of the tape 70 is not formed on the inner side in the axial direction of the sidewall 36. In the tire 32, generation of dent due to the joint portion is suppressed. According to this manufacturing method, it is possible to obtain the tire 32 having a good appearance in which generation of dents is prevented. As described above, the inner layer 80 and the outer layer 82 can contribute to both handling stability and ride comfort. According to the present invention, it is possible to obtain the pneumatic tire 32 that achieves both steering stability and riding comfort while suppressing the occurrence of dents.

  In the load supporting layer of the tire 32, a portion divided into the inner layer 80 and the outer layer 82 by the tape 70 and a portion in which the inner layer 80 and the outer layer 82 are integrated are mixed. The division by the tape 70 can suppress the influence of the load support portion 52 on the rigidity. The tire 32 is excellent in ride comfort. Moreover, the mixture of the portion divided by the tape 70 and the portion that is not so can suppress the expansion of damage along the carcass ply 68 in the load support layer. The tire 32 is also excellent in run flat durability.

  In FIG. 2, a double-headed arrow e1 represents the thickness of the inner layer 80 at the position Ph. This thickness e1 is the thickness of the inner layer 80 located on the inner side in the axial direction of the first tape 70a forming a part of the carcass ply 68. A double-headed arrow e2 represents the thickness of the outer layer 82 at the position Ph. The thickness e2 is the thickness of the outer layer 82 located on the outer side in the axial direction of the first tape 70a. A double arrow E represents the thickness of the sidewall 36 at the position Ph.

  In FIG. 3, a double-headed arrow e3 represents the thickness of the load support portion 52 at the position Ph. This thickness e3 is the thickness of the load support portion 52 located on the inner side in the axial direction of the second tape 70b forming another part of the carcass ply 68. A double arrow E represents the thickness of the sidewall 36 at the position Ph. In the tire 32, the thickness E is equal to the thickness E in FIG.

  In the tire 32, the ratio of the sum of the thickness e1 and the thickness e2 to the thickness e3 is preferably 1.0. Thereby, the tire 32 in which the portion of the sidewall 36 has a uniform thickness in the circumferential direction is obtained. In the tire 32, the shape of the portion of the sidewall 36 is not unique. The tire 32 is excellent in run flat durability.

  Preferably, in the tire 32, the ratio of the thickness e1 to the thickness e2 is greater than 1. Thereby, the inner side layer 80 can contribute to run flat durability effectively.

  In the tire 32, the thickness e3 is preferably 1 mm or greater and 15 mm or less. By setting the thickness e3 to be 1 mm or more, when the internal pressure of the tire 32 is reduced due to puncture, the load support portion 52 can effectively contribute to support of the vehicle weight. In this respect, the thickness e3 is more preferably 3 mm or more. By setting the thickness e3 to 15 mm or less, the influence of the load support portion 52 on the deflection is suppressed. In the tire 32, the riding comfort is appropriately maintained. Moreover, since the thickness e3 is not excessive, the mass of the tire 32 is appropriately maintained. In this respect, the thickness e3 is more preferably 12 mm or less, and further preferably 10 mm or less.

  In the tire 32, the thickness E is preferably 1 mm or more and 10 mm or less. By setting the thickness E to be 1 mm or more, the sidewall 36 can effectively contribute to the protection of the carcass 42. In this respect, the thickness E is more preferably 2 mm or more. By setting the thickness E to 10 mm or less, the influence of the side wall 36 on the bending is suppressed. In the tire 32, the riding comfort is appropriately maintained. Moreover, since the thickness E is not excessive, the mass of the tire 32 is appropriately maintained. In this respect, the thickness E is more preferably 7 mm or less.

  In the tire 32, it is preferable that the thickness e <b> 3 is thicker than the thickness E of the sidewall 36 from the viewpoint of run-flat durability. Thereby, when the internal pressure of this tire 32 falls by puncture, the load support part 52 can contribute to support of a vehicle weight effectively. From this viewpoint, it is preferable that the ratio of the thickness e3 to the thickness E is larger than 1. This ratio is preferably set to be smaller than 3 from the viewpoint that the influence on the mass and the ride comfort by the load support portion 52 is suppressed.

  In the tire 32, it is preferable that the sum of the thickness e <b> 1 and the thickness e <b> 2 is larger than the thickness E of the sidewall 36 from the viewpoint of run-flat durability. Thereby, when the internal pressure of this tire 32 falls by puncture, the load support part 52 can contribute to support of a vehicle weight effectively. From this viewpoint, it is preferable that the ratio of the sum of the thickness e1 and the thickness e2 to the thickness E is larger than 1. This ratio is preferably set to be smaller than 3 from the viewpoint that the influence on the mass and the ride comfort by the load support portion 52 is suppressed.

  In FIG. 4, the double arrow TT represents the thickness of the tape 70 for the carcass ply 68. A double arrow WT represents the width of the tape 70.

  In this manufacturing method, the thickness TT is preferably 0.3 mm or greater and 2.0 mm or less. When the thickness TT is set to 0.3 mm or more, the tape 70 can be easily formed. In this respect, the thickness TT is more preferably equal to or greater than 0.5 mm. By setting the thickness TT to 2.0 mm or less, formation of a step due to the thickness TT is prevented. In this respect, the thickness TT is more preferably 1.0 mm or less.

  In this manufacturing method, the width WT is preferably 20 mm or greater and 70 mm or less. By setting the width WT to 20 mm or more, the productivity of the tire 32 can be appropriately maintained. From this viewpoint, the width WT is more preferably 30 mm or more. By setting the width WT to 70 mm or less, the influence of the carcass ply 68 on the rigidity of the load support portion 52 can be suppressed. The tire 32 is excellent in run flat durability. From this viewpoint, the width WT is more preferably 50 mm or less.

  In the present invention, the size and angle of each member of the tire 32 are measured in a state where the tire 32 is incorporated in a regular rim and the tire 32 is filled with air so as to have a regular internal pressure. During the measurement, no load is applied to the tire 32. In the present specification, the normal rim means a rim defined in a standard on which the tire 32 relies. “Standard rim” in the JATMA standard, “Design Rim” in the TRA standard, and “Measuring Rim” in the ETRTO standard are regular rims. In the present specification, the normal internal pressure means an internal pressure defined in a standard on which the tire 32 relies. “Maximum air pressure” in JATMA standard, “Maximum value” published in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in TRA standard, and “INFLATION PRESSURE” in ETRTO standard are normal internal pressures. In the case of the passenger car tire 32, the dimensions and angle are measured in a state where the internal pressure is 180 kPa.

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

[Example 1]
A raw cover was formed on the outer surface of the core, and the raw cover was put into the mold while being combined with the core. By pressing and heating this raw cover in a cavity formed between the mold and the core, the raw cover has the basic configuration shown in FIGS. 1 to 3 and the specifications shown in Table 1 below. A pneumatic tire (size: 245 / 40R18) of Example 1 was obtained. This tire is a run flat tire. The fact that this tire was manufactured by the core method is indicated by “A” in this table.

  For the formation of the inner layer, a first strip made of a first rubber composition having a short fiber content of 40 parts by mass was used. The inner layer was formed by winding this first strip spirally in the circumferential direction. The width of this first strip was 10 mm and its thickness was 0.8 mm. When the first strip was picked with a finger and pulled in the length direction, the first strip was immediately broken. This is represented by “B” in this table. Short fibers made of aramid fibers (average outer diameter = 10 μm, average length = 500 μm) were used as the short fibers. The hardness of the inner layer was 75. In forming the outer layer, a strip equivalent to the first strip used for forming the inner layer was used as the second strip. The outer layer was formed by spirally winding this second strip in the circumferential direction.

  For forming the carcass ply, a tape having a width of 40 mm was used. Therefore, the width of the first tape in which the side piece is located between the inner layer and the outer layer is 40 mm, and the width of the second tape in which the side piece is located between the load support portion and the sidewall is 40 mm. . In Example 1, the first tape and the second tape were alternately arranged in the circumferential direction.

  In the cross section shown in FIG. 2, the thickness e1 of the inner layer is 6 mm and the thickness e2 of the outer layer is 4 mm at a reference position corresponding to half the height of the cross section of the tire. . In the cross section shown in FIG. 3, the thickness e3 of the load support portion at this reference position was set to 10 mm. The sidewall thickness E at this reference position was 4 mm. The side wall had a hardness of 60.

[Example 2-10]
A tire of Example 2-10 was obtained in the same manner as in Example 1 except that the blending amounts of the short fibers in the inner layer and the outer layer were as shown in Tables 2 and 3 below. In Example 2-5, when the strips for the inner layer and the outer layer were picked with a finger and pulled in the length direction, the strip was slightly stretched (about 3% elongation). This is represented by “S” in this table. Otherwise, the strip broke as soon as it was picked with a finger and pulled lengthwise.

[Examples 11-19]
Tires of Examples 11-19 were obtained in the same manner as in Example 1 except that the widths of the first tape and the second tape were as shown in Tables 4 and 5 below.

[Example 20-28]
Tires of Examples 20-28 were obtained in the same manner as in Example 1 except that the hardnesses of the inner layer and the outer layer were as shown in Tables 6 and 7 below.

[Comparative Example 4]
In another embodiment, the strip of Example 1 was spirally wound in the circumferential direction to form a load supporting layer corresponding to the load supporting portion, and then the tape of Example 1 was sequentially joined in the circumferential direction to form a carcass ply. In the same manner as in Example 1, a tire of Comparative Example 4 was obtained. The comparative example 4 does not include the cross-sectional portion shown in FIG. A joint portion of the side piece of the tape is formed on the inner side in the axial direction of the sidewall.

[Comparative Example 1]
A pneumatic tire (size: 245 / 40R18) of Comparative Example 1 having the basic configuration shown in FIG. 16 and the specifications shown in Table 1 below was obtained by a conventional manufacturing method. This tire is a conventional run flat tire. In this tire, the load support layer was formed using a sheet. Therefore, this load bearing layer has a seam. In this manufacturing method, the raw cover was shaped in the molding process. In the cross-linking step, the raw cover was expanded using a bladder. In this table, “C” represents that the tire was manufactured by the conventional manufacturing method.

  The load supporting layer of Comparative Example 1 does not contain short fibers. The load supporting layer had a hardness of 75. The sidewall hardness was 60. The thickness e of the load support layer at the reference position Ph corresponding to the height Hh which is half the cross-sectional height H of the tire was 12 mm. The sidewall thickness E at the reference position Ph was 4 mm.

[Comparative Example 2-3]
Comparison was made in the same manner as in Comparative Example 1 except that short fibers made of aramid fibers (average outer diameter = 10 μm, average length = 500 μm) were blended in the load support layer and the blending amounts were as shown in Table 1 below. The tire of Example 2-3 was obtained.

[Tire mass]
The mass of the tire was measured. The results are shown in Tables 1 to 7 below as index values with Comparative Example 1 taken as 100. It is shown that the smaller the numerical value, the smaller the mass.

[Durability (Runflat)]
A tire was incorporated into a regular rim, and the tire was filled with air so that the internal pressure was 180 kPa. This tire was mounted on a drum type traveling tester, and a longitudinal load of 7.5 kN 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 to 7 below as index values with Comparative Example 1 taken as 100. A larger numerical value is preferable.

[Maneuvering stability and ride comfort]
The tire was incorporated into a rim of 18 × 8.5 J, and the tire was filled with air so as to achieve a standard internal pressure. This was installed in a front engine rear wheel drive passenger car with a displacement of 3.0 liters. The driver was driven on the racing circuit to evaluate the driving stability and ride comfort. The results are shown in Tables 1 to 7 below as indices with a perfect score of 10. Larger numbers are preferable.

[Dent level]
A tire was incorporated into a regular rim, and the tire was filled with air so that the internal pressure was 180 kPa. The appearance of the tire was visually observed to confirm the occurrence of dents. The results are shown in Tables 1 to 7 below as indices with a perfect score of 10. The larger the value, the less dent is generated.

[productivity]
The time required to produce one tire was measured. The results (measured time) are shown in the following Tables 1 to 7 as index values with Comparative Example 1 taken as 100. The smaller this number, the higher the evaluation.

  As shown in Tables 1 to 7, 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. In Comparative Example 3, the raw cover could not be formed because the strip broke during shaping. Therefore, the tire of Comparative Example 3 could not be manufactured.

  The method described above can also be applied to the manufacture of various tires.

2, 32 ... Tire 4, 34 ... Tread 8, 36 ... Sidewall 10, 38 ... Clinch 12, 40 ... Bead 14, 42 ... Carcass 16 ... Load support layer 30, 68 ... Carcass ply 52 ... Load support 70, 70a, 70b ... Tape 80 ... Inner layer 82 ... Outer layer 84 ... Short fiber 90 ... Main body 92 ...・ Side

Claims (15)

It is assembled on the outer surface of the toroidal core, and is formed by pressurization and heating in a cavity formed between the mold and the core,
A tread whose outer surface forms a tread surface, a pair of sidewalls each extending substantially inward in the radial direction from the tread, a pair of clinch each positioned substantially radially inward of the sidewalls, and each of which is from a clinch A pair of beads positioned on the inner side in the axial direction, a carcass extending between one bead and the other bead along the inner side of the tread and the sidewall, and each of which is axially inner than the sidewall. And a pair of load support portions located at
The load support portion includes an inner layer and an outer layer positioned on the outer side in the axial direction than the inner layer,
The inner layer consists of a crosslinked first rubber composition,
The first rubber composition includes a base rubber and short fibers,
The outer layer consists of a crosslinked second rubber composition,
This second rubber composition contains a base rubber and short fibers,
The carcass includes a carcass ply formed from a number of tapes,
In this carcass ply, these tapes are juxtaposed in the circumferential direction,
Each tape includes a main body located radially inside the tread and a pair of side pieces each located axially inside the sidewall.
The carcass ply includes a first tape having a side piece positioned between the inner layer and the outer layer, and a second tape having a side piece positioned between the load support portion and the sidewall. Contains pneumatic tires.   The pneumatic tire according to claim 1, wherein in the carcass ply, the first tape and the second tape are alternately arranged in a circumferential direction.   The pneumatic tire according to claim 1 or 2, wherein a blending amount of the short fibers in the first rubber composition is 5 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the base rubber.   The pneumatic tire according to claim 3, wherein a blending amount of the short fibers in the first rubber composition is 30 parts by mass or more with respect to 100 parts by mass of the base rubber.   The pneumatic tire according to claim 3 or 4, wherein the short fibers are oriented in the circumferential direction in the inner layer.   The pneumatic tire according to any one of claims 3 to 5, wherein the inner layer is formed by spirally winding a first strip made of the first rubber composition in a circumferential direction.   The pneumatic tire according to any one of claims 1 to 6, wherein a blending amount of the short fibers in the second rubber composition is 5 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the base rubber.   The pneumatic tire according to claim 7, wherein a blending amount of the short fibers in the second rubber composition is 30 parts by mass or more with respect to 100 parts by mass of the base rubber.   The pneumatic tire according to claim 7 or 8, wherein the short fibers are oriented in the circumferential direction in the outer layer.   The pneumatic tire according to any one of claims 7 to 9, wherein the outer layer is formed by spirally winding a second strip made of the second rubber composition in the circumferential direction. At the reference position corresponding to half the height of the cross section,
The thickness of the load support portion located on the inner side in the axial direction of the second tape, the sum of the thickness of the inner layer located on the inner side in the axial direction of the first tape and the thickness of the outer layer located on the outer side in the axial direction. The pneumatic tire according to claim 1, wherein the ratio to is 1.0.   The pneumatic tire according to any one of claims 1 to 11, wherein the tape has a width of 20 mm to 70 mm.   The pneumatic tire according to any one of claims 1 to 12, wherein the inner layer has a hardness of 60 or more and 85 or less.   The pneumatic tire according to any one of claims 1 to 13, wherein the outer layer has a hardness of 60 to 85. On the outer surface of the toroidal core, a tread whose outer surface forms a tread surface, a pair of sidewalls each extending substantially inward in the radial direction from the tread, and each positioned substantially radially inward of the sidewalls A pair of clinches, a pair of beads each positioned on the inner side in the axial direction than the clinches, a carcass spanned between one bead and the other bead along the inside of the tread and the sidewall, respectively Is provided with a pair of load support portions positioned on the inner side in the axial direction than the sidewall, the load support portion is provided with an inner layer and an outer layer positioned on the outer side in the axial direction than the inner layer, The inner layer is made of a first rubber composition, the first rubber composition contains a base rubber and short fibers, and the outer layer is made of a second rubber composition. The second rubber composition includes a base rubber and short fibers, and the carcass includes a carcass ply formed of a large number of tapes. In the carcass ply, these tapes are juxtaposed in the circumferential direction. Each of the tapes includes a main body positioned radially inward of the tread and a pair of side pieces each positioned inward of the sidewall in the axial direction, and the carcass ply includes the inner layer and the outer side. A step of assembling the raw cover, comprising: a first tape having a side piece positioned between the layers; and a second tape having the side piece positioned between the load support portion and the sidewall;
The raw cover is put into a mold,
A method of manufacturing a pneumatic tire, comprising: a step in which the raw cover is pressurized and heated in a cavity formed between the mold and the core.

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