JP6025463B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  In the tire manufacturing method, a low cover (uncrosslinked tire) is obtained by combining a number of members such as treads and sidewalls on the former drum. In the raw cover forming step, 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 employed 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. In this tire, the short fiber reinforced rubber layer is provided on the outer side in the axial direction of the apex of the bead.

  FIG. 11 shows a run flat tire as an example of the conventional tire 62. The tire 62 includes a tread 64, a wing 66, a sidewall 68, a clinch 70, a bead 72, a carcass 74, a load support layer 76, a belt 78, a band 80, an inner liner 82, and a chafer 84.

  In the tire 62, the bead 72 includes a core 86 and an apex 88 that extends radially outward from the core 86. The core 86 has a ring shape and includes a plurality of non-stretchable wires. The apex 88 has a tapered shape that tapers outward in the radial direction, and is made of a highly hard crosslinked rubber. The carcass ply 90 constituting the carcass 74 is bridged between the beads 72 on both sides, and extends along the inside of the tread 64 and the sidewall 68. The carcass ply 90 is wound around the core 86 from the inner side toward the outer side in the axial direction. The end of the carcass ply 90 reaches the vicinity of the tread 64. The structure of the carcass 74 is called an ultra high turn-up structure. The load support layer 76 is located on the inner side in the axial direction of the sidewall 68. The load support layer 76 has a shape similar to a crescent moon. The load support layer 76 is made of a highly hard crosslinked rubber.

  In the tire 62, when the internal pressure is reduced due to puncture, the load support layer 76 supports the vehicle weight. The load support layer 76 allows the tire 62 to travel a certain distance even when the internal pressure is low.

JP 2003-146028 A

  The rigidity of the tire may be adjusted by using a cord having a large outer diameter for the belt. This belt has high rigidity. This belt can contribute to steering stability. However, this belt affects the ride comfort. Moreover, a cord having a large outer diameter causes an increase in mass.

  The rigidity of the tire may be adjusted by increasing the density of the cord included in the belt. This belt has high rigidity. This belt can contribute to steering stability. However, this belt affects the ride comfort. Since the number of cords included in this belt is large, this belt causes an increase in mass.

  A tire having a large thickness may be used to adjust the tire rigidity. This sidewall can contribute to steering stability. However, this sidewall affects ride comfort. Moreover, this side wall causes an increase in mass.

  According to the above-described member containing short fibers, the rigidity of the tire can be adjusted while suppressing an increase in mass. However, the elongation of a member containing a lot of short fibers is small. For this reason, in the tire vulcanization process, when the bladder expands and the raw cover deforms, this member may not be able to follow this 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 the tire 62 shown in FIG. 11 described above, the load support layer 76 is formed using a sheet obtained by extruding the rubber composition. When forming, one end of the sheet and the other end are joined together. In the low cover of the tire 62, the load support layer 76 has a seam.

  As described above, in the vulcanization process of the tire 62, the bladder is expanded and the raw cover is deformed. For example, this deformation causes a shape change in the load support layer 76. As described above, the load support layer 76 has a seam. The strength of the joint portion is smaller than the strength of the seamless portion. For this reason, when the raw cover is deformed, the form is remarkably changed at the joint portion. In the tire 2, the shape of the joint portion may be different from the shape of the seamless portion. This difference in form may affect the durability (also referred to as run-flat durability) of the tire 62 when the internal pressure of the tire 62 is reduced due to puncture.

  An object of the present invention is to provide a pneumatic tire in which an improvement in steering stability is achieved without impairing riding comfort while suppressing an increase in mass. Still another object of the present invention is to provide a pneumatic tire in which an improvement in durability is achieved when the internal pressure of the tire is reduced by puncture while suppressing an increase in mass.

  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 an end of the tread, and a pair of beads each positioned substantially inward in the radial direction from the sidewall. A carcass spanned between one bead and the other bead along the inside of the tread and sidewall, an inner liner positioned inside the carcass, and the carcass radially inward of the tread. And a reinforcing layer positioned between the inner liner and the inner liner. This reinforcing layer is formed by crosslinking a rubber composition containing a base rubber and short fibers.

  Preferably, in this pneumatic tire, the amount of the short fiber is 10 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the base rubber. More preferably, the amount of the short fibers is 30 parts by mass or more with respect to 100 parts by mass of the base rubber.

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

  Preferably, in the pneumatic tire, the reinforcing layer is formed by spirally winding a tape made of the rubber composition in the circumferential direction.

  Preferably, in the pneumatic tire, the width of the tape is 3 mm or more and 25 mm or less, and the thickness of the tape is 0.3 mm or more and 2.0 mm or less.

  Preferably, the pneumatic tire further includes a belt laminated with the carcass inside the tread. The ratio of the width of the reinforcing layer to the width of the belt is not less than 0.2 and not more than 0.95.

  Preferably, the pneumatic tire further includes a pair of load support layers positioned between the carcass and the inner liner on the inner side in the axial direction of the sidewall. Each load supporting layer extends substantially inward in the radial direction from the reinforcing layer. This load support layer is made of a rubber composition equivalent to the rubber composition of the reinforcing layer.

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

  Preferably, in this pneumatic tire, the short fibers in the load supporting layer and the reinforcing layer are oriented in the circumferential direction.

  Preferably, in this pneumatic tire, one load supporting layer, the reinforcing layer, and the other load supporting layer are continuously formed by spirally winding a second tape made of the rubber composition in the circumferential direction. Has been.

  Preferably, in this pneumatic tire, the thickness of the reinforcing layer is not less than 0.5 mm and not more than 2.0 mm.

  Preferably, in this pneumatic tire, the load supporting 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 end of the tread, and each of which is more radial than the sidewalls A pair of beads positioned substantially inside, a carcass extending between one bead and the other bead along the inside of the tread and sidewall, an inner liner positioned inside the carcass, and the above A step of assembling a raw cover, comprising a reinforcing layer positioned between the carcass and the inner liner on the radially inner side of the tread, and the reinforcing layer is made of a rubber composition including a base rubber and short fibers;
(2) The raw cover is put into a mold, and (3) The raw cover is pressurized and heated in a cavity formed between the mold and the core.

  Preferably, in this method for manufacturing a pneumatic tire, the blend amount of the short fibers is 10 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the base rubber. More preferably, the amount of the short fibers is 30 parts by mass or more with respect to 100 parts by mass of the base rubber.

  Preferably, in the method for manufacturing a pneumatic tire, the reinforcing layer is formed by spirally winding a first tape made of the rubber composition in the circumferential direction.

  Preferably, in the method for manufacturing a pneumatic tire, the raw cover further includes a pair of load support layers positioned between the carcass and the inner liner on the inner side in the axial direction of the sidewall. Each load supporting layer extends substantially inward in the radial direction from the reinforcing layer. This load support layer is made of a rubber composition equivalent to the rubber composition of the reinforcing layer.

  Preferably, in this method for producing a pneumatic tire, the amount of the short fibers in the 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. More preferably, the amount of the short fibers is 30 parts by mass or more with respect to 100 parts by mass of the base rubber.

  Preferably, in this pneumatic tire manufacturing method, one load support layer, the reinforcing layer, and the other load support layer are continuously formed by spirally winding a second tape made of the rubber composition in the circumferential direction. Is formed.

  In the pneumatic tire according to the present invention, improvement in steering stability is achieved without impairing the ride comfort while suppressing an increase in mass. In another pneumatic tire according to the present invention, an improvement in durability is achieved when the internal pressure of the tire is reduced by puncture while suppressing an increase in mass.

FIG. 1 is a cross-sectional view showing a part of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view showing a part of the tire of FIG. FIG. 3 is a cross-sectional view taken along line III-III in FIG. FIG. 4 is a schematic diagram showing short fibers of the reinforcing layer of FIG. FIG. 5 is a perspective view showing a part of the tape used for forming the reinforcing layer. FIG. 6 is a schematic view showing a state of manufacturing the tire of FIG. FIG. 7 is a schematic view showing a state different from FIG. 6 of manufacturing the tire of FIG. FIG. 8 is a schematic view showing a state different from FIG. 7 of manufacturing the tire of FIG. 1. FIG. 9 is a schematic view showing a state different from FIG. 8 of manufacturing the tire of FIG. FIG. 10 is a cross-sectional view showing a part of a pneumatic tire according to another embodiment of the present invention. FIG. 11 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 2. In FIG. 1, the vertical direction is the radial direction of the tire 2, the horizontal direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2. In FIG. 1, an alternate long and short dash line CL represents the equator plane of the tire 2. The shape of the tire 2 is symmetrical with respect to the equator plane except for the tread pattern. FIG. 2 shows an equatorial plane portion of the tire 2 of FIG. In FIG. 2, the vertical direction is the radial direction of the tire 2, the horizontal direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2.

  The tire 2 includes a tread 4, a sidewall 6, a bead 8, a carcass 10, a belt 12, an inner liner 14, a reinforcing layer 16, a cushion layer 18, and a chafer 20. The tire 2 is a tubeless type. The tire 2 is mounted on a passenger car.

  The tread 4 has a shape protruding outward in the radial direction. The outer surface of the tread 4 forms a tread surface 22 that contacts the road surface. A groove 24 is carved in the tread surface 22. The groove 24 forms a tread pattern. Although not shown, the tread 4 usually has a base layer and a cap layer. The cap layer is located on the radially outer side of the base layer. The cap layer is laminated on the base layer. The base layer is made of a crosslinked rubber having excellent adhesiveness. A typical base rubber for the base layer is natural rubber. The cap layer is made of a crosslinked rubber having excellent wear resistance, heat resistance and grip properties.

  The sidewall 6 extends substantially inward in the radial direction from the end of the tread 4. The sidewall 6 is joined to the tread 4 at the radially outer end. The sidewall 6 is made of a crosslinked rubber having excellent cut resistance and light resistance. The sidewall 6 prevents the carcass 10 from being damaged.

  The bead 8 is located substantially inward of the sidewall 6 in the radial direction. In the tire 2, the bead 8 includes a first part 26a and a second part 26b. In the tire 2, the first part 26a is located inside the carcass 10 in the axial direction. The second part 26b is located outside the carcass 10 in the axial direction.

  The first part 26a includes a first core 28a and a first apex 30a extending radially outward from the first core 28a. The first core 28a has a ring shape and includes a wound non-stretchable first wire 32a. In the tire 2, the first core 28a is formed by winding the first wire 32a spirally along the circumferential direction. A typical material of the first wire 32a is steel. The first apex 30a is tapered outward in the radial direction. The first apex 30a is made of a highly hard crosslinked rubber.

  The second part 26b includes a second core 28b and a second apex 30b extending radially outward from the second core 28b. The second core 28b is ring-shaped and includes a wound non-stretchable second wire 32b. In the tire 2, the second core 28b is formed by winding the second wire 32b in a spiral shape along the circumferential direction. A typical material of the second wire 32b is steel. The second apex 30b is tapered outward in the radial direction. The second apex 30b is made of a highly hard crosslinked rubber.

  The carcass 10 includes a carcass ply 34. The carcass ply 34 is bridged between the beads 8 on both sides, and extends along the inside of the tread 4 and the sidewall 6. In the tire 2, the end of the carcass ply 34 is sandwiched between the first part 26 a and the second part 26 b of the bead 8. More specifically, the end of the carcass ply 34 is sandwiched between the first core 28a of the bead 8 and the second core 28b.

  Although not shown, the carcass ply 34 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 45 ° to 90 °, and further 75 ° to 90 °. In other words, the carcass 10 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 10 may be formed from two or more carcass plies 34.

  The belt 12 is located on the radially outer side of the carcass 10. The belt 12 is laminated with the carcass 10. The belt 12 reinforces the carcass 10. The belt 12 includes an inner layer 36a and an outer layer 36b. As apparent from FIG. 1, in the axial direction, the width of the inner layer 36a is slightly larger than the width of the outer layer 36b. In the tire 2, the end 38 of the inner layer 36 a is the end of the belt 12.

  Although not shown, each of the inner layer 36a and the outer layer 36b is composed of a large number of cords arranged in parallel and a topping rubber. Each cord is inclined with respect to the equator plane. The absolute value of the tilt angle is usually 10 ° to 35 °. The inclination direction of the cord of the inner layer 36a with respect to the equator plane is opposite to the inclination direction of the cord of the outer layer 36b with respect to the equator plane. A preferred material for the cord is steel. An organic fiber may be used for the cord. The belt 12 may include three or more layers 36.

  The inner liner 14 is located inside the carcass 10. The inner liner 14 forms the inner surface of the tire 2. The inner liner 14 is made of a crosslinked rubber. The inner liner 14 is made of rubber having excellent air shielding properties. A typical base rubber of the inner liner 14 is butyl rubber or halogenated butyl rubber. The inner liner 14 maintains the internal pressure of the tire 2.

  The reinforcing layer 16 is located between the carcass 10 and the inner liner 14 on the inner side in the radial direction of the tread 4. The reinforcing layer 16 extends in the axial direction along the inner liner 14. In the axial direction, the width of the reinforcing layer 16 is smaller than the width of the belt 12. Therefore, the end 40 of the reinforcing layer 16 is located inside the end 38 of the belt 12 in the axial direction.

  In the tire 2, the reinforcing layer 16 is made of a rubber composition crosslinked. This rubber composition contains 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. Two or more kinds of rubbers may be used in combination.

  The rubber composition of the reinforcing layer 16 further includes short fibers. The short fibers can contribute to the strength of the reinforcing layer 16. 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 2, the blending amount of the short fibers contained in the reinforcing layer 16 is preferably 10 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 blend amount of the short fibers to 10 parts by mass or more, the reinforcing layer 16 has an appropriate strength. The reinforcing layer 16 can contribute to the rigidity of the tire 2. The tire 2 is excellent in handling stability. In this respect, the blend amount of the short fibers is more preferably equal to or greater than 25 parts by mass, and particularly preferably equal to or greater than 30 parts by mass. By setting the blending amount of the short fibers to 60 parts by mass or less, the reinforcing layer 16 can be sufficiently bonded to each of the inner liner 14 and the carcass 10. The tire 2 is excellent in durability. In this respect, the blend amount of the short fibers is more preferably equal to or less than 55 parts by weight, and particularly preferably equal to or less than 45 parts by weight.

  Preferably, the rubber composition of the reinforcing layer 16 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 rubber composition of the reinforcing layer 16 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 rubber composition of the reinforcing layer 16 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 reinforcing layer 16, the amount of carbon black is preferably 5 parts by mass or more with respect to 100 parts by mass of the base rubber. In light of the softness of the reinforcing layer 16, 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 rubber composition of the reinforcing layer 16 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 reinforcing layer 16, 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 reinforcing layer 16, the amount of the softening agent is preferably 40 parts by mass or less.

  To the rubber composition of the reinforcing layer 16, stearic acid, zinc oxide, an anti-aging agent, wax, a crosslinking aid, and the like are added as necessary.

  FIG. 3 is a cross-sectional view taken along line III-III in FIG. In FIG. 3, a part of the reinforcing layer 16 is shown. In FIG. 3, the vertical direction is the circumferential direction of the tire 2, and the horizontal direction is the axial direction of the tire 2.

  As shown in the drawing, the reinforcing layer 16 is composed of a large number of short fibers 42 and a matrix 44. In other words, the reinforcing layer 16 is made of fiber reinforced rubber (FRR). These short fibers 42 are dispersed in the matrix 44. The longitudinal direction of these short fibers 42 is substantially along the circumferential direction. In the reinforcing layer 16, the short fibers 42 are oriented in the circumferential direction. The reinforcing layer 16 can contribute to the rigidity of the tire 2.

  FIG. 4 is a schematic view showing the short fibers 42 of the reinforcing layer 16 of FIG. In FIG. 4, the vertical direction is the circumferential direction. What is indicated by the arrow θ is the angle of the short fibers 42. 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 X <b> 2 passes through one end 46 and the other end 48 of the short fiber 42. This angle θ is an angle formed by the longitudinal direction of the short fibers 42 with respect to the circumferential direction. The angle θ is 0 ° or more and 90 ° or less. In FIG. 4, 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 46 to the other end 48.

  From the viewpoint that the reinforcing layer 16 can effectively contribute to the rigidity of the tire 2, the ratio of the number of short fibers 42 having an angle θ of 20 ° or less to the total number of short fibers 42 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 42 exposed in the cross section of the reinforcing layer 16 along the circumferential direction is measured. The angle is measured for 100 randomly extracted short fibers 42. In addition, the case where the ratio of the number of short fibers 42 having an angle θ of 20 ° or less to the total number of short fibers 42 is 90% or more is a state in which the short fibers 42 are oriented in the circumferential direction.

  In the tire 2, the short fibers 42 effectively increase the strength of the reinforcing layer 16. The reinforcing layer 16 is located on the radially inner side of the tread 4. The reinforcing layer 16 can contribute to the rigidity of the tread 4 portion of the tire 2.

  In the tire 2, the reinforcing layer 16 includes a large number of short fibers 42 oriented in the circumferential direction. The reinforcing layer 16 can contribute to the rigidity in the circumferential direction. This reinforcing layer 16 can improve the response felt by the driver operating the steering wheel in the vicinity of a small rudder angle (near the neutral). The reinforcement layer 16 provided between the carcass 10 and the inner liner 14 on the inner side in the radial direction of the tread 4 contributes to the improvement of the response. The tire 2 is excellent in handling stability.

  In the tire 2, since the short fibers 42 included in the reinforcing layer 16 are oriented in the circumferential direction, the influence of the reinforcing layer 16 on the axial rigidity is suppressed. In the tire 2, the riding comfort is appropriately maintained. Moreover, the influence of the short fibers 42 on the mass of the tire 2 is small. In the tire 2, an improvement in steering stability is achieved while suppressing an increase in mass and without impairing riding comfort.

  In the tire 2, the width of the reinforcing layer 16 is appropriately adjusted. This effectively prevents the reinforcing layer 16 from interfering with the carcass 10. Since the occurrence of looseness due to this interference is prevented, the tire 2 is excellent in durability.

  In FIG. 1, a double-headed arrow RW represents the width of the reinforcing layer 16 in the axial direction. A double arrow BW represents the width of the belt 12 in the axial direction.

  In the tire 2, the ratio of the width RW to the width BW is preferably 0.2 or more and 0.95 or less. By setting this ratio to 0.2 or more, the reinforcing layer 16 can effectively contribute to the rigidity of the tire 2. The tire 2 is excellent in handling stability. From this viewpoint, the ratio is more preferably 0.4 or more. By setting this ratio to 0.95 or less, the width of the reinforcing layer 16 is appropriately maintained. Thereby, generation | occurrence | production of the looseness which arises when the reinforcement layer 16 interferes with the carcass 10 is prevented. The tire 2 is excellent in durability. In this respect, the ratio is more preferably equal to or less than 0.7.

  In the tire 2, the average length L (see FIG. 4) of the short fibers 42 is preferably 20 μm or more from the viewpoint that the short fibers 42 effectively increase the strength of the reinforcing layer 16. The reinforcing layer 16 is sufficiently reinforced by the short fibers 42 having an average length L of 20 μm or more. From the viewpoint of dispersibility in the matrix 44, the average length L is preferably 5000 μm or less.

  The average diameter D of the short fibers 42 is preferably 0.04 μm or more. The strength of the reinforcing layer 16 is sufficiently increased by the short fibers 42 having an average diameter D of 0.04 μm or more. From the viewpoint of dispersibility in the matrix 44, the average diameter D is preferably 500 μm or less.

  The aspect ratio (L / D) of the short fibers 42 is preferably 10 or more. The strength of the reinforcing layer 16 is sufficiently increased by the short fibers 42 having an aspect ratio (L / D) of 10 or more. From the viewpoint of dispersibility in the matrix 44, the aspect ratio (L / D) is preferably 500 or less.

  The tire 2 described above is manufactured as follows. 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 surface shape of the tire 2 that is filled with air and whose internal pressure is maintained at 5% of the normal internal pressure.

  In this manufacturing method, the inner liner 14 is wound around the outer surface of the core. The rubber composition of the reinforcing layer 16 is extruded to form the tape 50 shown in FIG. In FIG. 5, the direction indicated by the arrow A is the length direction of the tape 50. This length direction is also the extrusion direction of the tape 50.

  In this manufacturing method, the tape 50 is formed such that the cross-sectional shape thereof is rectangular. As described above, the rubber composition of the reinforcing layer 16 includes the short fibers 42. Therefore, this tape 50 also includes the short fibers 42. Since the tape 50 is formed by extruding the rubber composition, the short fibers 42 are oriented in the extrusion direction of the tape 50, in other words, in the length direction thereof. Here, “oriented in the length direction” means the ratio of the number of short fibers 42 in which the angle formed by the longitudinal direction of the short fibers 42 with respect to the length direction of the tape 50 is 20 ° or less to the total number of short fibers 42. Is 90% or more. The angle formed by the longitudinal direction of the short fibers 42 in the tape 50 with respect to the length direction of the tape 50 is measured by the same method as the method for measuring the angle θ in the reinforcing layer 16 described above. In calculating the ratio, the angle of the short fibers 42 exposed on the surface of the tape 50 is measured.

  In this manufacturing method, the tape 50 is wound on the inner liner 14. Thereby, the reinforcing layer 16 is formed. The state of this formation is shown in FIGS. In these drawings, the left-right direction corresponds to the axial direction of the tire 2, and the up-down direction corresponds to the circumferential direction of the tire 2.

  FIG. 6 shows that the formation of the reinforcing layer 16 is started. In this manufacturing method, the tape 50 is fed from a head (not shown), and the tip of the tape 50 is laminated on the inner liner 14.

  In this manufacturing method, when the leading end of the tape 50 is laminated on the inner liner 14, the rotation of the core is started. Along with this rotation, the head is moved in the axial direction while feeding the tape 50. This is shown in FIG. In FIG. 7, the direction indicated by the arrow B is the rotation direction of the core. This rotational direction B corresponds to the circumferential direction of the tire 2. The direction indicated by arrow C is the moving direction of the head. This moving direction C corresponds to the axial direction of the tire 2.

  In this manufacturing method, since the core is rotated as the head moves, the tape 50 is spirally wound around the inner liner 14 in the circumferential direction. As a result, as shown in FIG. 8, the element 52 forming the reinforcing layer 16 is formed on the inner liner 14 by crosslinking. The element 52 has no seam formed when one sheet is wound and one end of the sheet is joined to the other end.

  In this manufacturing method, the winding pitch of the tape 50 matches the width of the tape 50. As shown in FIG. 7, in this winding, the first edge 54 a of the laminated tape 50 is aligned with the second edge 54 b of the already laminated tape 50. The laminated tapes 50 are joined to the already laminated tapes 50 without a gap. In this manufacturing method, the laminated tape 50 may be wound so as to be overlapped with a part of the already laminated tape 50. The tape 50 may be laminated on the inner liner 14 with a gap from the tape 50 already laminated. The method of winding the tape 50 is appropriately determined in consideration of the specifications of the tire 2 to be manufactured.

  In this manufacturing method, when the element 52 that forms the reinforcing layer 16 is formed, the first part 26 a that forms a part of the bead 8 is combined with the end of the inner liner 14. A carcass ply 34 is formed outside the combination of the first part 26a, the reinforcing layer 16 and the inner liner 14. A second part 26 b forming another part of the bead 8 is combined with the end of the carcass ply 34. Then, the belt 12, the sidewall 6, the tread 4 and the like are combined to obtain a low cover (uncrosslinked tire). In this manufacturing method, the process of assembling the raw cover is referred to as a molding process.

  In this manufacturing method, a large number of elements 52 including the reinforcing layer 16 are combined on the outer surface of the core to obtain a raw cover. As described above, the outer surface of the core is approximated to the inner surface shape of the tire 2 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.

  In this manufacturing method, as shown in FIG. 9, when the mold (symbol M in the figure) is tightened, the raw cover (symbol R in the figure) is connected to the cavity surface 56 of the mold M and the core (in the figure). The pressure is sandwiched between the outer surface 58 of N). The raw cover R is heated by heat conduction from the core N and the mold M. By the pressurization and heating, the rubber composition of each element 52 forming the raw cover R flows. The rubber composition causes a crosslinking reaction by heating, and the tire 2 shown in FIG. 1 is obtained. The tire 2 is formed by pressing and heating the raw cover R in a cavity 60 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 56 of the mold M and the outer surface 58 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 reinforcing layer 16 of the tire 2 is formed by pressing and heating an element 52 made of a rubber composition including short fibers 42 in a cavity 60 formed between a mold M and a core N. . As described above, in this manufacturing method, each element 52 constituting the raw cover R is not stretched in the molding process. Even in the cross-linking step, each element 52 forming the raw cover R is not stretched. For this reason, in this manufacturing method, even if the tape 50 for the reinforcing layer 16 contains a large amount of short fibers to the extent that it breaks without being stretched when the operator picks it with a finger and pulls it, The reinforcing layer 16 is formed, and the raw cover R is obtained. And the tire 2 is obtained from this raw cover R. According to this manufacturing method, the tire 2 including the reinforcing layer 16 containing a large amount of short fibers 42 can be produced with high quality and stability.

  In FIG. 5, the double arrow TT represents the thickness of the tape 50 used for forming the reinforcing layer 16. A double arrow WT represents the width of the tape 50.

  In this manufacturing method, the thickness TT is preferably 0.3 mm or greater and 2.0 mm or less. By setting the thickness TT to 0.3 mm or more, the strength of the tape 50 is appropriately maintained. Moreover, the reinforcing layer 16 formed by the tape 50 can effectively contribute to the rigidity of the tire 2. 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, the influence of the reinforcing layer 16 formed by the tape 50 on the mass of the tire 2 is suppressed. In addition, the formation of a step due to the thickness TT is prevented. According to this tape 50, the reinforcing layer 16 in which the influence on the durability of the tire 2 is suppressed can be formed. In this respect, the thickness TT is more preferably 1.0 mm or less.

  In this manufacturing method, the width WT is preferably 3 mm or more and 25 mm or less. By setting the width WT to 3 mm or more, the productivity of the tire 2 can be appropriately maintained. From this viewpoint, the width WT is preferably 5 mm or more. By setting the width WT to 25 mm or less, the difference in rigidity between the start and end of winding of the tape 50 is appropriately maintained. According to this tape 50, the reinforcing layer 16 can be prevented from inhibiting the durability of the tire 2. From this viewpoint, the width WT is more preferably 15 mm or less.

  In the present invention, the size and angle of each member of the tire 2 are measured in a state where the tire 2 is incorporated in a regular rim and the tire 2 is filled with air so as to have a regular internal pressure. At the time of measurement, no load is applied to the tire 2. In the present specification, the normal rim means a rim defined in a standard on which the tire 2 depends. “Standard rim” in the JATMA standard, “Design Rim” in the TRA standard, and “Measuring Rim” in the ETRTO standard are regular rims. In the present specification, the normal internal pressure means an internal pressure defined in a standard on which the tire 2 relies. “Maximum air pressure” in JATMA standard, “Maximum value” published in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in TRA standard, and “INFLATION PRESSURE” in ETRTO standard are normal internal pressures. In the case of the passenger car tire 2, the dimensions and angles are measured in a state where the internal pressure is 180 kPa. The size and angle of each member of the tire described later are also measured in the same manner as the tire 2.

  FIG. 10 shows a pneumatic tire 92 according to another embodiment of the present invention. In FIG. 10, the vertical direction is the radial direction of the tire 92, the horizontal direction is the axial direction of the tire 92, and the direction perpendicular to the paper surface is the circumferential direction of the tire 92. In FIG. 10, an alternate long and short dash line CL represents the equator plane of the tire 92. The shape of the tire 92 is symmetric with respect to the equator plane except for the tread pattern. A solid line BBL represents a bead base line. The bead base line is a line that defines a rim diameter (see JATMA) of a rim (not shown) on which the tire 92 is mounted.

  The tire 92 includes a tread 94, a sidewall 96, a clinch 98, a bead 100, a carcass 102, a belt 104, a band 106, an inner liner 108, a chafer 110, a reinforcing layer 112, and a load supporting layer 114. The tire 92 is a tubeless type. The tire 92 is attached to a passenger car.

  The tread 94 has a shape protruding outward in the radial direction. The outer surface of the tread 94 forms a tread surface 116 that contacts the road surface. A groove 118 is carved on the tread surface 116. The groove 118 forms a tread pattern. The tread 94 includes a base layer 120 and a cap layer 122. The base layer 120 is made of a crosslinked rubber having excellent adhesiveness. A typical base rubber of the base layer 120 is natural rubber. The cap layer 122 is located on the radially outer side of the base layer 120. The cap layer 122 is laminated on the base layer 120. The cap layer 122 is made of a crosslinked rubber having excellent wear resistance, heat resistance, and grip properties.

  The sidewall 96 extends substantially inward in the radial direction from the end of the tread 94. The sidewall 96 is joined to the tread 94 at the radially outer end. The sidewall 96 is joined to the clinch 98 at the radially inner end thereof. The sidewall 96 is made of a crosslinked rubber having excellent cut resistance and weather resistance. This sidewall 96 prevents the carcass 102 from being damaged.

  The clinch 98 is located substantially inside the sidewall 96 in the radial direction. The clinch 98 is located outside the bead 100 and the carcass 102 in the axial direction. The clinch 98 is made of a crosslinked rubber having excellent wear resistance. The clinch 98 is in contact with a flange of a rim (not shown).

  The bead 100 is located substantially inward of the sidewall 96 in the radial direction. The bead 100 is located inside the clinch 98 in the axial direction.

  In the tire 92, the bead 100 includes a first core 124 a, a second core 124 b, and an apex 126. More specifically, the bead 100 includes a first core 124a, a second core 124b, and an apex 126.

  The first core 124a is located inside the carcass 102 in the axial direction. The first core 124a has a ring shape and includes a wound non-stretchable first wire 128a. In the tire 92, the first core 124a is formed by spirally winding the first wire 128a along the circumferential direction. A typical material of the first wire 128a is steel.

  The second core 124b is located outside the carcass 102 in the axial direction. As is apparent from the drawing, the second core 124 b is covered with the apex 126. The second core 124b has a ring shape and includes a wound non-stretchable second wire 128b. In the tire 92, the second core 124b is formed by winding the second wire 128b spirally along the circumferential direction. A typical material of the second wire 128b is steel. In the tire 92, the second wire 128b is equivalent to the first wire 128a.

  The apex 126 is made of a highly hard crosslinked rubber. The apex 126 is located outside the carcass 102 in the axial direction. As is apparent from the figure, the apex 126 is located between the clinch 98 and the carcass 102. The apex 126 is tapered outward in the radial direction. The outer end of the apex 126 is located outside the outer end of the second core 124b in the radial direction. The outer end of the apex 126 is located outside the outer end of the first core 124a in the radial direction. The outer end of the apex 126 is located inside the outer end of the clinch 98 in the radial direction.

  In the tire 92, the apex 126 has a sufficient size. The bead 100 including the apex 126 sufficiently tightens the tire 92 on the rim. This bead 100 does not require another apex located on the inner side in the axial direction of the carcass 102. The bead 100 can contribute to a reduction in the number of parts constituting the tire 92. Moreover, since the apex 126 has only to be provided outside the carcass 102 in the axial direction, the bead 100 can be easily manufactured. This bead 100 can contribute to the improvement of productivity.

  The carcass 102 includes a carcass ply 130. The carcass ply 130 is bridged between the beads 100 on both sides, and extends along the inside of the tread 94 and the sidewall 96. In the tire 92, the end portion of the carcass ply 130 is sandwiched between the first core 124a and the second core 124b of the bead 100. The carcass 102 has the same configuration as the carcass 10 of the tire 2 shown in FIG.

  In the tire 92, when forming the carcass 102, it is not necessary to turn the carcass ply 90 like the conventional tire 62. In the tire 92, the carcass 102 can be easily formed. The carcass 102 can contribute to the improvement of productivity.

  The belt 104 is located outside the carcass 102 in the radial direction. The belt 104 is laminated with the carcass 102. The belt 104 reinforces the carcass 102. The belt 104 includes an inner layer 132a and an outer layer 132b. As is apparent from FIG. 10, the width of the inner layer 132a is slightly larger than the width of the outer layer 132b in the axial direction. The belt 104 has the same configuration as the belt 12 of the tire 2 shown in FIG.

  The band 106 is located on the radially outer side of the belt 104. In the axial direction, the width of the band 106 is larger than the width of the belt 104. Although not shown, the band 106 is composed of a cord and a topping rubber. The cord is wound in a spiral. The band 106 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, further 2 ° or less. Since the belt 104 is restrained by this cord, lifting of the belt 104 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 108 is located inside the carcass 102. The inner liner 108 forms the inner surface of the tire 92. The inner liner 108 is made of a crosslinked rubber. The inner liner 108 is made of rubber having excellent air shielding properties. A typical base rubber of the inner liner 108 is butyl rubber or halogenated butyl rubber. The inner liner 108 maintains the internal pressure of the tire 92.

  The chafer 110 is located in the vicinity of the bead 100. When the tire 92 is incorporated in the rim, the chafer 110 comes into contact with the rim. By this contact, the vicinity of the bead 100 is protected. In this embodiment, the chafer 110 is made of cloth and rubber impregnated in the cloth. The chafer 100 may be integrated with the clinch 98. In this case, the material of the chafer is the same as that of the clinch 98.

  The reinforcing layer 112 is located between the carcass 102 and the inner liner 108 on the radially inner side of the tread 94. The reinforcing layer 112 extends in the axial direction along the inner liner 108.

  In the tire 92, the reinforcing layer 112 is formed by crosslinking a rubber composition. This rubber composition contains a base rubber and short fibers.

  In the tire 92, a rubber composition equivalent to the rubber composition forming the reinforcing layer 16 of the tire 2 shown in FIG. The base rubber of this rubber composition includes natural rubber, polybutadiene, styrene-butadiene copolymer, polyisoprene, ethylene-propylene-diene terpolymer, polychloroprene, acrylonitrile-butadiene copolymer, and isobutylene-isoprene. Copolymers are exemplified.

  In the tire 92, short fibers equivalent to the short fibers 42 included in the reinforcing layer 16 of the tire 2 shown in FIG. 1 are used for the reinforcing layer 112. Examples of short fibers include organic fibers and paper fibers. From the viewpoint of the strength of the reinforcing layer 112 and the dispersibility of the short fibers in the reinforcing layer 112, the average length L of the short fibers is preferably 20 μm or more and preferably 5000 μm or less. The average diameter D of the short fibers is preferably 0.04 μm or more and more preferably 500 μm or less. The short fiber has an aspect ratio (L / D) of preferably 10 or more and more preferably 500 or less.

  Similar to the reinforcing layer 16 of the tire 2 shown in FIG. 1, the reinforcing layer 112 of the tire 92 includes a large number of short fibers and a matrix. These short fibers are dispersed in a matrix. Although not shown, the longitudinal direction of these short fibers is substantially along the circumferential direction. In the reinforcing layer 112, the short fibers are oriented in the circumferential direction.

  A large number of short fibers oriented in the circumferential direction can contribute to the strength of the reinforcing layer 112. The reinforcing layer 112 can contribute to the rigidity of the tire 92.

  In the tire 92, the short fibers effectively enhance the strength of the reinforcing layer 112. The reinforcing layer 112 is located on the inner side in the radial direction of the tread 94. The reinforcing layer 112 can contribute to the rigidity of the tread 94 portion of the tire 92.

  In the tire 92, the reinforcing layer 112 includes a number of short fibers oriented in the circumferential direction. The reinforcing layer 112 can contribute to the circumferential rigidity. This reinforcing layer 112 can improve the response felt by the driver operating the steering wheel near the small steering angle (near the neutral). The reinforcement layer 112 provided between the carcass 102 and the inner liner 108 on the inner side in the radial direction of the tread 94 contributes to the improvement of the response. The tire 92 is excellent in handling stability.

  In the tire 92, since the short fibers included in the reinforcing layer 112 are oriented in the circumferential direction, the influence of the reinforcing layer 112 on the axial rigidity is suppressed. In the tire 92, the riding comfort is appropriately maintained. Moreover, the influence of the short fibers on the mass of the tire 92 is small. In the tire 92, improvement in handling stability is achieved without impairing riding comfort while suppressing an increase in mass.

  The load support layer 114 is located inside the sidewall 96 in the axial direction. The load support layer 114 is located inside the carcass 102 in the axial direction. The load support layer 114 is located outside the inner liner 108 in the axial direction. As is apparent from the figure, the load support layer 114 extends substantially inward in the radial direction from the reinforcing layer 112. In the tire 92, the reinforcing layer 112 and the load support layer 114 are integrally formed.

  In the tire 92, the load support layer 114 is formed by crosslinking a rubber composition. This rubber composition contains a base rubber and short fibers.

  For the load support layer 114 of the tire 92, a rubber composition equivalent to the rubber composition forming the reinforcing layer 112 is used. The load support layer 114 is made of a rubber composition equivalent to the rubber composition of the reinforcing layer. As the base rubber in the rubber composition of the load support layer 114, natural rubber, polybutadiene, styrene-butadiene copolymer, polyisoprene, ethylene-propylene-diene terpolymer, polychloroprene, acrylonitrile-butadiene copolymer Examples of the polymer and isobutylene-isoprene copolymer are exemplified. Examples of short fibers include organic fibers and paper fibers.

  In the tire 92, the short fibers of the load support layer 114 are equivalent to the short fibers included in the reinforcing layer 112. Therefore, the average length L of the short fibers is preferably 20 μm or more and preferably 5000 μm or less. The average diameter D of the short fibers is preferably 0.04 μm or more and more preferably 500 μm or less. The short fiber has an aspect ratio (L / D) of preferably 10 or more and more preferably 500 or less. The short fibers can effectively contribute to the strength of the load support layer 114 and the dispersibility of the short fibers in the load support layer 114.

  Similar to the reinforcing layer 112, the load support layer 114 of the tire 92 is composed of a large number of short fibers and a matrix. These short fibers are dispersed in a matrix. Although not shown, the longitudinal direction of these short fibers is substantially along the circumferential direction. In the load support layer 114, the short fibers are oriented in the circumferential direction.

  A large number of short fibers oriented in the circumferential direction can contribute to the strength of the load support layer 114. The load support layer 114 can contribute to the rigidity of the tire 92. In the tire 92, when the internal pressure is reduced due to puncture, the load support layer 114 can support the vehicle weight. In addition, the influence of the short fibers contained in the load support layer 114 on the mass of the tire 92 is small. In the tire 92, an increase in mass is suppressed.

  In the tire 92, since the short fibers included in the load support layer 114 are oriented in the circumferential direction, the influence of the load support layer 114 on the deflection of the portion of the sidewall 96 is suppressed. In the tire 92, the riding comfort is appropriately maintained.

  In the tire 92, the load support layer 114 is located between the carcass 102 and the inner liner 108 on the inner side in the axial direction of the sidewall 96. In the tire 92, when the internal pressure is reduced due to puncture, the load support layer 114 can support the vehicle weight. Thereby, even when the internal pressure is low, the tire 92 can travel a certain distance. The tire 92 is a run flat tire. The tire 92 is a side reinforcing type.

  As will be described later, in the tire 92, the thickness of the load support layer 114 and the thickness of the sidewall 96 are appropriately adjusted. In the tire 92, it is not necessary to provide another load support layer between the carcass 102 and the sidewall 96 in addition to the load support layer 114. In other words, the tire 92 does not require a load support layer between the carcass 102 and the sidewall 96. According to the present invention, weight reduction can be achieved. Moreover, the present invention can contribute to a reduction in the number of members constituting the tire 92. According to the present invention, a reduction in production cost can be achieved.

  As described above, the rubber composition of the load support layer 114 is equivalent to the rubber composition of the reinforcing layer 112, and the rubber composition includes short fibers. From the viewpoint that the reinforcing layer 112 and the load support layer 114 have appropriate rigidity, the blending amount of the short fibers contained in the rubber composition is preferably 5 parts by mass or more with respect to 100 parts by mass of the base rubber. Part or more is more preferable, 25 parts by weight or more is more preferable, and 30 parts by weight or more is particularly preferable. From the viewpoint that each of the reinforcing layer 112 and the load supporting layer 114 can be sufficiently bonded to the inner liner 108 and the carcass 102, the blending amount of the short fibers is 60 parts by mass or less with respect to 100 parts by mass of the base rubber. Preferably, 55 parts by mass or less is more preferable, and 45 parts by mass or less is particularly preferable.

  The tire 92 described above is manufactured as follows. In this manufacturing method, a core is prepared as in the manufacturing method of the tire 2 shown in FIG. Although not shown, the core has a toroidal outer surface. This outer surface is approximated to the inner surface shape of the tire 92 in a state where air is filled and the inner pressure is maintained at 5% of the normal inner pressure.

  In the method of manufacturing the tire 92, the rubber composition for the reinforcing layer 112 and the load support layer 114 is extruded to form a tape (also referred to as a strip). Although not shown, this tape has the same configuration as the tape shown in FIG. In this tape, short fibers are oriented in the length direction. From the viewpoint of the productivity of the tire 92, the width of this tape is preferably 5 mm or more, and preferably 30 mm or less. The thickness of this tape is preferably 0.4 mm or more, and preferably 2.5 mm or less.

  In this manufacturing method, the inner liner 108 is formed on the outer surface of the core. A tape is wound spirally around the inner liner 108 in the circumferential direction. Thereby, an element forming one load supporting layer 114 is formed by cross-linking in a portion corresponding to one side wall 96 of the tire 92. In the portion corresponding to the tread 94 of the tire 92, an element forming the reinforcing layer 112 is formed by crosslinking. In the portion corresponding to the other side wall 96 of the tire 92, an element forming the other load supporting layer 114 is formed by crosslinking.

  In this manufacturing method, an element forming one load supporting layer 114, an element forming the reinforcing layer 112, and an element forming the other load supporting layer 114 are formed in succession. In this manufacturing method, the operation is not interrupted in switching from the formation of the element of one load supporting layer 114 to the formation of the element of the reinforcing layer 112. In switching from the formation of the element of the reinforcing layer 112 to the formation of the element of the other load supporting layer 114, the operation is not interrupted. The tire 92 can contribute to an improvement in productivity.

  In this manufacturing method, the first core 124 a forming a part of the bead 100 is combined with the elements forming the load supporting layer 114. A carcass ply 130 is formed on the outer side of the inner liner 108 combined with the elements constituting the reinforcing layer 112 and the load supporting layer 114 and the first core 124a. A second core 124 b forming another part of the bead 100 is combined with the end portion of the carcass ply 130. The apex 126 is combined so as to cover the second core 124b. The belt 104, the sidewall 96, the tread 94, and the like are further combined to obtain a raw cover (uncrosslinked tire).

  In this manufacturing method, a raw cover is obtained by combining a number of members including the reinforcing layer 112 and the load supporting layer 114 on the outer surface of the core. As described above, the outer surface of the core is approximated to the inner shape of the tire 92 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.

  In this manufacturing method, when the mold is tightened, the raw cover is pressed and heated by being sandwiched between the cavity surface of the mold and the outer surface of the core. In this manufacturing method, the raw cover is heated by heat conduction from the core and the mold. The rubber composition of each element constituting the raw cover flows by pressurization and heating. The rubber composition causes a crosslinking reaction by heating, and the tire 92 shown in FIG. 10 is obtained. The tire 92 is formed by pressing and heating the raw cover in a cavity formed between the mold and the core.

  As described above, in this manufacturing method, the raw cover is put into the mold while being combined with the core, and is pressed and heated by being sandwiched between the cavity surface of the mold and the outer surface of the core. In this manufacturing method, the bladder used in the conventional manufacturing method is unnecessary. In this manufacturing method, the raw cover is not stretched in the crosslinking step.

  Each of the reinforcing layer 112 and the load supporting layer 114 of the tire 92 is formed by pressing and heating an element made of a rubber composition containing short fibers in a cavity formed between the mold and the core. Is done. As described above, in this manufacturing method, each element forming the raw cover is not stretched in the molding process. Even in the cross-linking step, the elements forming the raw cover are not stretched. For this reason, in this manufacturing method, a large amount of short fibers are blended in the rubber composition to such an extent that when the operator picks the tape for the reinforcing layer 112 and the load supporting layer 114 with a finger and pulls it, it breaks without stretching. Even then, the raw cover can be molded. And the tire 92 is obtained from this raw cover. According to this manufacturing method, the tire 92 including the reinforcing layer 112 and the load supporting layer 114 containing a large amount of short fibers can be produced with high quality and stability.

  In the tire 92, the load support layer 114 is formed by winding a tape in a spiral shape in the circumferential direction. The load support layer 114 is formed when one sheet is wound and one end and the other end of the sheet are joined together like the load support layer 114 of the conventional tire 92. Absent. The form of the load support layer 114 is not unique. In addition, since the tire 92 can be obtained without extending the low cover, in the method for manufacturing the tire 92, the change in the shape of the load support layer 114 can be effectively suppressed. The load support layer 114 has a uniform shape in the circumferential direction. The load support layer 114 can contribute to the improvement of the durability of the tire 92 when the internal pressure of the tire 92 is reduced by puncture.

  In the tire 92, the hardness of the load support layer 114 is preferably 60 or more and 85 or less. By setting the hardness to 60 or more, when the internal pressure of the tire 92 is reduced due to puncture, the load support layer 114 can effectively contribute to the 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 of the load supporting layer 114 on the deflection of the side wall 96 is suppressed. In the tire 92, the riding comfort is appropriately maintained. From this viewpoint, the hardness is more preferably 80 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.

  In the tire 92, the hardness of the reinforcing layer 112 is preferably 60 or greater and 85 or less. By setting the hardness to 60 or more, the reinforcing layer 112 can effectively contribute to the rigidity of the tread 94 portion. The tire 92 is excellent in handling stability. From this viewpoint, the hardness is more preferably 65 or more. By setting the hardness to 85 or less, excessive rigidity of the tread 94 portion can be suppressed. In the tire 92, the riding comfort is appropriately maintained. From this viewpoint, the hardness is more preferably 80 or less.

  In FIG. 10, the double arrow t represents the thickness of the reinforcing layer 112 on the equator plane. A double-headed arrow H represents a radial distance from the bead base line to the equator of the tire 92. This radial distance H is the height of the cross section of the tire 92. What is indicated by the symbol Ph represents a position on the outer surface of the tire 92 where the radial distance from the bead base line (double arrow Hh in the figure) is half the sectional height H of the tire 92. ing. In other words, the position Ph represents a position corresponding to half the height of the cross section height H of the tire 92. A double-headed arrow e represents the thickness of the load support layer 114 at the position Ph. A double-headed arrow E represents the thickness of the sidewall 96 at the position Ph.

  In the tire 92, the thickness t of the reinforcing layer 112 is preferably 0.5 mm or greater and 2.0 mm or less. By setting the thickness t to 0.5 mm or more, the reinforcing layer 112 can effectively contribute to the rigidity of the tread 94 portion of the tire 92. The tire 92 is excellent in handling stability. In this respect, the thickness t is more preferably equal to or greater than 0.8 mm. By setting the thickness t to 2.0 mm or less, the tread 94 portion is prevented from having excessive rigidity. In the tire 92, the riding comfort is appropriately maintained. From this viewpoint, the thickness t is more preferably 1.3 mm or less.

  In the tire 92, the thickness e of the load support layer 114 is preferably 1 mm or greater and 15 mm or less. By setting the thickness e to be 1 mm or more, when the internal pressure of the tire 92 is reduced due to puncture, the load support layer 114 can effectively contribute to the support of the vehicle weight. In this respect, the thickness e is more preferably 3 mm or more. By setting the thickness e to 15 mm or less, the influence of the load supporting layer 114 on the deflection of the portion of the sidewall 96 is suppressed. In the tire 92, the riding comfort is appropriately maintained. Moreover, since the thickness e is not excessive, the mass of the tire 92 is appropriately maintained. From this viewpoint, the thickness e is more preferably 12 mm or less.

  In the tire 92, the thickness E of the sidewall 96 is preferably 1 mm or greater and 10 mm or less. By setting the thickness E to be 1 mm or more, the sidewall 96 can effectively contribute to the protection of the carcass 102. 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 96 on the bending is suppressed. In the tire 92, the riding comfort is appropriately maintained. In addition, since the thickness E is not excessive, the mass of the tire 92 is appropriately maintained. In this respect, the thickness E is more preferably 7 mm or less.

  In the tire 92, the ratio of the thickness e of the load support layer 114 to the thickness E of the sidewall 96 is preferably 1 or more and 5 or less. By setting this ratio to 1 or more, when the internal pressure of the tire 92 is reduced due to puncture, the load support layer 114 can effectively contribute to the support of the vehicle weight. In addition, since the load support layer 114 effectively contributes to the rigidity of the tire 92, the tire 92 is excellent in steering stability. From this viewpoint, the ratio is more preferably 2 or more. By setting this ratio to 5 or less, the influence of the load supporting layer 114 on the bending of the portion of the sidewall 96 can be suppressed. In the tire 92, the riding comfort is appropriately maintained. From this viewpoint, the ratio is more preferably 3.5 or less.

  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.

[Experiment A]
[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. The raw cover is pressed and heated in a cavity formed between the mold and the core, thereby providing an embodiment having the basic configuration shown in FIG. 1 and the specifications shown in Table 2 below. 1 pneumatic tire (size: 195 / 65R15) was produced. The fact that this tire was manufactured using a core is represented by “A” in this table. For the tire belt, a cord made of steel was used. The configuration of this code was 2 + 2 × 0.23. This is represented by “R” in this table. In this tire, the ratio (RW / BW) of the width RW of the reinforcing layer to the width BW of the belt was 0.6. The width WT of the tape used for forming this reinforcing layer was 10 mm, and its thickness TT was 0.8 mm. The compounding quantity of the short fiber in this reinforcement layer was 40 mass parts. When the tape was pulled in the length direction, the tape broke without stretching. 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 tape was spirally wound in the circumferential direction. The tape feed pitch was made equal to the tape width WT. Therefore, the first edge of the laminated tape was spliced to the second edge of the already laminated tape. This is represented by “1” in this table. This winding structure is called single winding.

[Example 2-10]
A tire of Example 2-10 was manufactured in the same manner as in Example 1 except that the blending amount of the short fibers was as shown in Tables 2 and 3 below. In Example 2-4, when the tape was pulled in the length direction, the tape was slightly elongated (elongation rate was about 3%). This is represented by “S” in this table. In Example 5-10, when the tape was pulled in the length direction, the tape was not stretched but was broken.

[Examples 11-16]
Tires of Examples 11-16 were manufactured in the same manner as Example 1 except that the tape width WT was as shown in Table 4 below.

[Examples 17-22]
Tires of Examples 17-22 were obtained in the same manner as in Example 1 except that the tape thickness TT was as shown in Table 5 below.

[Examples 23-28]
Tires of Examples 23 to 28 were manufactured in the same manner as Example 1 except that the ratio (RW / BW) was as shown in Table 6 below.

[Examples 29-31]
Tires of Examples 29-31 were manufactured in the same manner as Example 1 except that the tape winding structure was as shown in Table 7 below. In the table, “0.5” indicates that the tape is wound with a gap corresponding to half the width WT of the tape between the tape to be laminated and the tape already laminated. It represents that. This winding structure is called 0.5-fold winding. “1.5” indicates that the tape is wound with the feed pitch being 2/3 of the tape width WT. This winding structure is called 1.5-fold winding. “2” indicates that the feed pitch is ½ of the tape width WT and the tape is wound. This winding structure is called double winding. In Examples 31 and 32, the tape is wound so that a part of the laminated tape overlaps a part of the already laminated tape.

[Comparative Example 1-3]
A tire of Comparative Example 1-3 was manufactured in the same manner as in Example 1 except that the reinforcing layer was not provided and the cord configuration and filler in the belt were as shown in Table 1 below. In Comparative Example 2-3, the configuration of the cord included in the belt was 1 × 4 × 0.27. This is represented by “SP” in this table. Comparative Example 1-3 is a conventional tire. In Comparative Example 3, a filler was provided between the carcass and the sidewall. This is represented by “Y” in the table.

[Comparative Example 4-6]
The tire of Comparative Example 4 having the same configuration as Example 4 is manufactured by the conventional manufacturing method, the tire of Comparative Example 5 having the same configuration as Example 5 is manufactured, and the comparative example having the same configuration as Example 1 is manufactured. 6 tires were produced. 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 method.

[Mass of tape]
The mass of the tape used for forming the reinforcing layer was measured. The results are shown in Tables 1 to 7 below as index values with Example 1 as 100. It is shown that the smaller the numerical value, the smaller the mass.

[Mass of tire]
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.

[Maneuvering stability and ride comfort]
The tire was assembled in a 15 × 6JJ rim, and the tire was filled with air so that the internal pressure was 230 kPa. This tire was mounted on a passenger car having a displacement of 2000 cc. 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.

[durability]
A tire was incorporated into a regular rim, and the tire was filled with air so that the internal pressure was 200 kPa. This tire was mounted on a drum-type running test machine, and a vertical load of 7.0 kN was applied to the tire. This tire was run on a drum having a radius of 1.7 m at a speed of 80 km / h. The running time until the tire broke was measured. The results are shown in Tables 1 to 7 below as indices. A larger numerical value is preferable.

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

  As shown in Tables 1 to 7, the manufacturing method of the example has a higher evaluation than the manufacturing method of the comparative example. From this evaluation result, the superiority of the present invention is clear. In Comparative Examples 5 and 6, the raw cover could not be formed because the tape broke during shaping. Therefore, the tires of Comparative Examples 5 and 6 could not be manufactured.

[Experiment B]
[Example 32]
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. The raw cover is pressed and heated in a cavity formed between the mold and the core, thereby having the basic configuration shown in FIG. 10 and the specification shown in Table 8 below. 32 pneumatic tires (size: 245 / 40R18) were 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 load support layer and the reinforcing layer, a tape made of a rubber composition having a short fiber content of 40 parts by mass was used. By winding this tape spirally in the circumferential direction, one load support layer, the reinforcing layer, and the other load support layer were continuously formed. The width of this tape was 10 mm and its thickness was 0.8 mm. When this tape was picked with a finger and pulled in the length direction, the tape immediately broke. 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 load supporting layer and the reinforcing layer was 75. The thickness e of the load supporting layer at a position corresponding to half the height of the cross section of the tire was 10 mm. The sidewall thickness E at this position was 4 mm. Therefore, the ratio of the thickness e to the thickness E (e / E) was 2.5. The thickness t of the reinforcing layer on the equator plane was 0.8 mm.

[Examples 33-39 and Comparative Example 11]
Tires of Examples 33-39 and Comparative Example 11 were obtained in the same manner as in Example 32 except that the blending amount of the short fibers in the rubber composition was as shown in Tables 9 and 10 below. In Comparative Example 11 and Examples 33-35, when the tape was 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. Other than these, the tape broke as soon as it was picked with a finger and pulled in the length direction.

[Examples 40-48]
Tires of Examples 42 to 48 were obtained in the same manner as Example 32 except that the thickness t was as shown in Tables 10, 11 and 12 below.

[Examples 49-56]
Tires of Examples 49-56 were obtained in the same manner as in Example 32 except that the hardness of the load supporting layer (and the hardness of the reinforcing layer) was as shown in Tables 12 and 13 below.

[Comparative Example 10]
A tire of Comparative Example 10 was obtained in the same manner as in Example 32 except that the reinforcing layer was not provided.

[Comparative Example 7]
By a conventional manufacturing method, a pneumatic tire (size: 245 / 40R18) of Comparative Example 7 having the basic configuration shown in FIG. 11 and having the specifications shown in Table 8 below was obtained. This tire is a conventional run flat tire. 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. Thus, it is represented by “C” in this table that the tire was manufactured by the conventional manufacturing method. The hardness of the load support layer of this tire was 75. The thickness e of the load supporting layer at a height Hh that is half the cross-sectional height H of the tire was 12 mm. The side wall thickness E at a height Hh which is half of the cross-sectional height H was 4 mm. Therefore, the ratio of the thickness e to the thickness E (e / E) was 3. This load support layer does not contain short fibers.

[Comparative Example 8-9]
Comparison was made in the same manner as in Comparative Example 7 except that short fibers made of aramid fibers (average outer diameter = 10 μm, average length = 500 μm) were blended into the load support layer, and the blending amounts were as shown in Table 8 below. The tire of Example 8-9 was obtained.

[Tire mass]
The mass of the tire was measured. The results are shown in Tables 8 to 13 below as index values with Comparative Example 7 taken as 100. It is shown that the smaller the numerical value, the smaller the mass.

[durability]
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 8 to 13 below as index values with Comparative Example 7 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 8 to 13 below as indices with a perfect score of 10. Larger numbers are preferable.

[productivity]
The time required to produce one tire was measured. The results (measured time) are shown in the following Tables 8 to 13 as index values with Comparative Example 7 taken as 100. The smaller this number, the higher the evaluation.

  As shown in Tables 8 to 13, 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 9, the raw cover could not be formed because the strip broke during shaping. Therefore, the tire of Comparative Example 9 could not be manufactured.

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

2, 62, 92 ... tire 4, 64, 94 ... tread 6, 68, 96 ... sidewall 8, 72, 100 ... bead 10, 74, 102 ... carcass 12, 78, 104 ... belt 14, 82, 108 ... inner liner 16 ... reinforcing layer 26a, 26b ... part 28a, 28b, 86, 124a, 124b ... core 30a, 30b, 88, 126 ... Apex 42 ... short fiber 44 ... matrix 50 ... tape 56 ... cavity surface 58 ... outer surface 60 ... cavities 76, 114 ... load support layer 112 ... reinforcing layer

Claims (14)

A pneumatic tire manufactured by the core method,
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 substantially radially inward of the sidewall, and the tread And a carcass spanned between one bead and the other bead along the inside of the sidewall, an inner liner located inside the carcass, and the carcass and the inner liner on the radially inner side of the tread And a reinforcing layer located between
The reinforcing layer, Ri Do from those rubber composition comprising a base rubber and the short fibers have been crosslinked,
The pneumatic tire whose compounding quantity of the said short fiber is 55 to 60 mass parts with respect to 100 mass parts of said base rubbers . The pneumatic tire according to claim 1, wherein the short fibers in the reinforcing layer are oriented in the circumferential direction. The pneumatic tire according to claim 1 or 2, wherein the reinforcing layer is made of a first tape spirally wound in a circumferential direction, and the first tape is made of the rubber composition . The width of the first tape is 3 mm or more and 25 mm or less,
The pneumatic tire according to claim 3 , wherein the thickness of the first tape is not less than 0.3 mm and not more than 2.0 mm. It further comprises a belt laminated with the carcass inside the tread,
The pneumatic tire according to any one of claims 1 to 4 , wherein a ratio of the width of the reinforcing layer to the width of the belt is 0.2 or more and 0.95 or less. A pneumatic tire manufactured by the core method,
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 substantially radially inward of the sidewall, and the tread And a carcass spanned between one bead and the other bead along the inside of the sidewall, an inner liner located inside the carcass, and the carcass and the inner liner on the radially inner side of the tread a reinforcing layer positioned between the, in the axial direction inside of each of the above side wall, Bei a respective pair of load support layer positioned between the carcass and the inner liner Eteori,
Each load supporting layer extends inward in the radial direction from the reinforcing layer,
The bead is composed of a first core, a second core and an apex,
The first core is covered with a load support layer, the second core is covered with an apex,
This reinforcing layer consists of a rubber composition containing a base rubber and short fibers,
The load support layer, Ri Do from a rubber composition comparable rubber composition of the reinforcing layer,
The pneumatic tire whose compounding quantity of the said short fiber in the said rubber composition is 45 to 60 mass parts with respect to 100 mass parts of said base rubbers . The pneumatic tire according to claim 6 , wherein the short fibers in the load supporting layer and the reinforcing layer are oriented in the circumferential direction. One load support layer, the reinforcing layer and the other load-bearing layer is composed of a second tape wound spirally in the circumferential direction, the second tape is formed of the rubber composition, according to claim 6 or 7 Pneumatic tire described in 2. The pneumatic tire according to any one of claims 6 to 8 , wherein the reinforcing layer has a thickness of 0.5 mm to 2.0 mm. The pneumatic tire according to any one of claims 6 to 9 , wherein the load supporting layer has a hardness of 60 or more and 85 or less. 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 end of the tread, and each radially inward of the sidewalls. A pair of positioned beads, a carcass spanned between one bead and the other bead along the inside of the tread and sidewalls, an inner liner positioned inside the carcass, and a radius of the tread A step of assembling a raw cover, comprising a reinforcing layer positioned between the carcass and the inner liner on the inner side in the direction, and the reinforcing layer is made of a rubber composition containing a base rubber and short fibers;
The raw cover is put into a mold,
The raw cover, and Nde including a step that is pressed and heated in the formed cavity between the mold and the core,
The manufacturing method of the pneumatic tire whose compounding quantity of the said short fiber is 55 to 60 mass parts with respect to 100 mass parts of said base rubbers . The method for producing a pneumatic tire according to claim 11 , wherein the reinforcing layer is formed by spirally winding a first tape made of the rubber composition in a circumferential direction. 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 end of the tread, and each radially inward of the sidewalls. A pair of positioned beads, a carcass spanned between one bead and the other bead along the inside of the tread and sidewalls, an inner liner positioned inside the carcass, and a radius of the tread A reinforcing layer positioned between the carcass and the inner liner on the inner side in the direction, and a pair of load support layers positioned between the carcass and the inner liner on the inner side in the axial direction of the sidewalls, respectively. It includes a respective load-bearing layer extends almost inward in the radial direction from the reinforcing layer Cage, the bead, the first core is composed of a second core and an apex, the first core is covered with a load support layer, the second core is covered with Apex, this A step of assembling a raw cover, wherein the reinforcing layer is made of a rubber composition containing base rubber and short fibers;
The raw cover is put into a mold,
The raw cover, step a <br/> and Nde contains a that is pressed and heated in the formed cavity between the mold and the core,
The load support layer, Ri Do from a rubber composition comparable rubber composition of the reinforcing layer,
The manufacturing method of the pneumatic tire whose compounding quantity of the said short fiber in the said rubber composition is 45 to 60 mass parts with respect to 100 mass parts of said base rubbers . One load support layer, the reinforcing layer and the other of the load support layer, according to claim 13 which is formed continuously by turning up the second tape made of the rubber composition in the circumferential direction helically A method of manufacturing a pneumatic tire.

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