JP2009154764A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire with excellent braking performance by providing a support layer including a short fiber and two cover layers. <P>SOLUTION: The tire 2 includes a pair of beads 8; a carcass 10 laid between both the beads 8; and a pair of composites 16 positioned at a shoulder area 24 of the tire 2, i.e., at an outer side of the carcass 10. The composite 16 includes the support layer and the two cover layers. The support layer is positioned between both the cover layers. The support layer includes the short fiber. Preferably, in the tire 2, thickness of the composite 16 is 1.0 to 3.0 mm. Preferably, in the tire 2, thickness of the cover layer is 0.3 to 0.7 mm. Preferably, in the tire 2, thickness of the support layer is 0.5 to 1.4 mm. Preferably, in the tire 2, thickness of the support layer is thicker than the thickness of the cover layer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire mainly mounted on a passenger car.

  The tire is configured by combining a large number of rubber members. The specifications, combinations, etc. of these rubber members have been studied to improve tire performance.

  The cornering force generated in the tire during turning acts as a centripetal force. A large cornering force is generated in a tire having a large lateral rigidity. This tire can turn stably. This tire is excellent in handling stability.

  Japanese Unexamined Patent Application Publication No. 2005-239070 discloses a tire in which steering stability is improved without increasing the mass. In this tire, a reinforcing body including short fibers is provided in the shoulder region. The short fibers are dispersed in a medium composed of portions other than the short fibers of the reinforcing body. The short fibers are oriented in the axial direction.

JP 2005-239070 A

  In some cases, the contact pressure of the tire in the vicinity of the tread edge (shoulder region) is greater than the contact pressure in the vicinity of the equator (equatorial region). In this tire, the tread cannot sufficiently contribute to the braking performance. Wear is promoted in the tread in the shoulder region. Such a tire is inferior in wear resistance and braking performance.

  If the portion of the equatorial region of the tread is configured to have a large thickness, the ground pressure will be uniform. In this tire, uneven wear of the tread is suppressed, and the tread can contribute to braking performance. This tread affects the mass of the tire. A tire having a large mass causes an increase in rolling resistance and a decrease in steering stability.

  In the tire of the above publication, since the reinforcing body can reinforce the shoulder region, a uniform contact pressure can be obtained. In this tire, uneven wear of the tread is suppressed, and the tread can contribute to braking performance. However, in this tire, there is a possibility that the reinforcing body is peeled off from the rubber member adjacent to the reinforcing body. The durability of such a tire is not sufficient.

  An object of the present invention is to provide a tire having excellent braking performance.

  A pneumatic tire according to the present invention includes a pair of beads, a carcass spanned between both beads, a pair of composites that are shoulder regions of the tire and are located outside the carcass. It has. This composite includes a support layer and two coating layers. This support layer is located between the two coating layers. This support layer contains short fibers.

  Preferably, in this tire, the thickness of the composite is 1.0 mm or more and 3.0 mm or less.

  Preferably, in this tire, the thickness of the coating layer is not less than 0.3 mm and not more than 0.7 mm.

  Preferably, in this tire, the thickness of the support layer is not less than 0.5 mm and not more than 1.4 mm.

  Preferably, in this tire, the thickness of the support layer is larger than the thickness of the covering layer.

  Preferably, in this tire, the loss tangent of the coating layer is 0.05 or more and 0.07 or less.

  Preferably, in the tire, the support layer has a hardness of 50 or greater and 70 or less.

  Preferably, in this tire, the short fibers of the support layer are oriented.

  In this tire, the composite includes a support layer containing short fibers and two coating layers. This composite can effectively contribute to the rigidity of the tire while suppressing an increase in the mass of the tire. In this tire, since a uniform contact pressure can be obtained, uneven wear of the tread can be suppressed, and this tread can effectively contribute to braking performance. This tire is excellent in wear resistance and braking performance. In this tire, the support layer containing short fibers can contribute to the generation of cornering force. This tire is excellent in handling stability. In this tire, since the composite is configured such that the support layer is located between the first coating layer and the second coating layer, the composite is separated from the components of the tire adjacent to the composite. Peeling can be suppressed. This tire is excellent in durability.

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

  FIG. 1 is a cross-sectional view showing a part of a pneumatic tire 2 according to an embodiment of the present invention. In FIG. 1, the vertical direction is the radial direction, the horizontal direction is the axial direction, and the direction perpendicular to the paper surface is the circumferential direction. The tire 2 has a substantially left-right symmetric shape centered on a one-dot chain line CL in FIG. This alternate long and short dash line CL represents the equator plane of the tire 2. The tire 2 includes a tread 4, a sidewall 6, a bead 8, a carcass 10, a belt 12, a band 14, a composite body 16, an inner liner 18 and a chafer 20. The tire 2 is a tubeless type. The tire 2 is mounted on a passenger car. In this specification, the portion of the equator plane of the tire 2 is referred to as an equator region 22. A portion near the end of the tread 4 of the tire 2 is referred to as a shoulder region 24.

  The tread 4 is made of a crosslinked rubber having excellent wear resistance. The tread 4 has a shape protruding outward in the radial direction. The tread 4 includes a tread surface 26. The tread surface 26 is in contact with the road surface. A groove 28 is carved in the tread surface 26. The groove 28 forms a tread pattern. The groove 28 may not be cut in the tread 4.

  The sidewall 6 extends substantially inward in the radial direction from the end of the tread 4. The sidewall 6 is made of a crosslinked rubber. The sidewall 6 absorbs an impact from the road surface by bending. Furthermore, 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. The bead 8 includes a core 30 and an apex 32 that extends radially outward from the core 30. The core 30 has a ring shape. The core 30 includes a plurality of non-stretchable wires (typically steel wires). The apex 32 is tapered outward in the radial direction. The apex 32 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. The carcass ply 34 is folded around the core 30 from the inner side to the outer side in the axial direction.

  Although not shown, the carcass ply 34 includes a plurality of cords arranged in parallel and a topping rubber. The absolute value of the angle formed by each cord with respect to the equator plane is usually 70 ° to 90 °. In other words, the carcass 10 has a radial structure. The cord is usually made of organic fibers. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers. A carcass 10 having a bias structure may be employed.

  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 36 and an outer layer 38. Although not shown, each of the inner layer 36 and the outer layer 38 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 not less than 10 ° and not more than 35 °. The cord inclination direction of the inner layer 36 is opposite to the cord inclination direction of the outer layer 38. A preferred material for the cord is steel. An organic fiber may be used for the cord.

  The band 14 is located inside the tread 4. The band 14 covers the belt 12. The band 14 restrains the belt 12. The band 14 includes a full band 40 and a pair of edge bands 42 that are located radially inside the full band 40 and are spaced apart in the axial direction.

  Although not shown, the full band 40 is composed of a cord and a topping rubber. The cord extends substantially in the circumferential direction and is wound spirally. The full band 40 has a so-called jointless structure. Since the belt 12 is restrained by this cord, lifting of the belt 12 is suppressed. The cord is usually made of organic fibers. Examples of preferable organic fibers include nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  Although not shown, the edge band 42 is made of a cord and a topping rubber. The cord extends substantially in the circumferential direction and is wound spirally. The edge band 42 has a so-called jointless structure. Since the belt 12 is restrained by this cord, lifting of the belt 12 is suppressed. The cord is usually made of organic fibers. Examples of preferable organic fibers include nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  The composite 16 is located in the shoulder region 24. The composite 16 is located outside the carcass 10. The left and right composites 16 are spaced apart in the axial direction. An axially inner portion of the composite 16 is located between the carcass 10 and the belt 12. As shown, the composite 16 is along the carcass 10. This composite 16 is laminated on the carcass 10.

  In the tire 2, the end 44 (inner end) located on the inner side in the axial direction of the composite 16 is located on the inner side in the axial direction of the end 46 of the belt 12. The inner end 44 is located on the inner side in the axial direction of the end 48 of the band 14. In the tire 2, the inner end 44 is sandwiched between the carcass 10 and the belt 12. An end 50 (outer end) located on the outer side in the axial direction of the composite 16 is located on the outer side in the axial direction of the end 46 of the belt 12. The outer end 50 is located outside the end 48 of the band 14 in the axial direction. The outer end 50 is located radially outside the tip 52 of the apex 32.

  FIG. 2 is a cross-sectional view taken along the line II-II in FIG. FIG. 2 shows a part of the composite 16 and the carcass ply 34. In FIG. 2, the left-right direction is the circumferential direction. The composite 16 includes a support layer 54 and two coating layers 56. The support layer 54 is located between the two coating layers 56. In this specification, the coating layer 56 located on the carcass 10 side is the first coating layer 56a, and the coating layer 56 located on the belt 12 side is the second coating layer 56b. As illustrated, in the tire 2, the first covering layer 56 a is laminated on the outside of the carcass ply 34. A support layer 54 is laminated on the outside of the first covering layer 56a. A second coating layer 56 b is laminated on the outer side of the support layer 54. Sidewalls 6 are laminated on the outer side of the second coating layer 56b.

  The support layer 54 is formed by crosslinking a rubber composition containing short fibers. This short fiber reinforces the support layer 54. 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 that the support layer 54 can be effectively reinforced, an aramid fiber is preferable as the organic fiber. In addition, from the viewpoint of weight reduction and cost reduction, paper fibers obtained by pulverizing raw material paper made of kraft paper and newspaper waste paper may be used as the short fibers.

  Examples of the base rubber of the rubber composition constituting the support layer 54 include 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. From the viewpoint of versatility and processability, natural rubber and styrene-butadiene copolymer are preferable as the base rubber. From the viewpoint of low loss tangent, natural rubber and polybutadiene are preferable as the base rubber. In the tire 2, it is particularly preferable that the base rubber is constituted by blending natural rubber and polybutadiene. In this case, the mass ratio ((natural rubber) / (polybutadiene)) of this blend is preferably 20/80 or more, and preferably 60/40 or less.

  From the viewpoint that the support layer 54 can be effectively reinforced, the rubber composition constituting the support layer 54 can contain carbon black as a filler. From the viewpoint of reinforcing properties, the blending amount of the carbon black is preferably 30 parts by mass or more with respect to 100 parts by mass of the base rubber. From the viewpoint that good processability can be maintained, the blending amount of the carbon black is preferably 70 parts by mass or less with respect to 100 parts by mass of the base rubber.

  In the tire 2, a filler other than carbon black may be used in combination with the rubber composition constituting the support layer 54. Examples of other fillers include silica, calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, alumina, clay, talc and magnesium oxide. The rubber composition may also contain chemicals such as a softener, a tackifier, a crosslinking agent such as sulfur, a vulcanization accelerator, a crosslinking aid, and an anti-aging agent. In consideration of the workability and performance of the tire 2, an optimal chemical is blended in the rubber composition in an optimal amount.

  The first coating layer 56 a is formed by crosslinking a rubber composition different from the support layer 54. As will be described later, the loss tangent of the first coating layer 56a is small. In the tire 2, the first coating layer 56a does not include short fibers.

  As the base rubber of the rubber composition constituting the first coating layer 56a, natural rubber, polybutadiene, styrene-butadiene copolymer, polyisoprene, ethylene-propylene-diene terpolymer, polychloroprene, acrylonitrile-butadiene Copolymers and isobutylene-isoprene copolymers are exemplified. From the viewpoint of versatility and processability, natural rubber and styrene-butadiene copolymer are preferable as the base rubber. From the viewpoint of low loss tangent, natural rubber and polybutadiene are preferable as the base rubber. In the tire 2, it is particularly preferable that the base rubber is constituted by blending natural rubber and polybutadiene. In this case, the mass ratio ((natural rubber) / (polybutadiene)) of this blend is preferably 20/80 or more, and preferably 60/40 or less.

  From the viewpoint of processability, the rubber composition constituting the first coating layer 56a can contain carbon black as a filler. From this viewpoint, the blending amount of the carbon black is preferably 20 parts by mass or more with respect to 100 parts by mass of the base rubber. From the viewpoint that the first coating layer 56a having a small loss tangent can be obtained, the blending amount of the carbon black is preferably 30 parts by mass or less with respect to 100 parts by mass of the base rubber.

  In the tire 2, a filler other than carbon black may be used in combination with the rubber composition constituting the first coating layer 56a. Examples of other fillers include silica, calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, alumina, clay, talc and magnesium oxide. The rubber composition may also contain chemicals such as a softener, a tackifier, a crosslinking agent such as sulfur, a vulcanization accelerator, a crosslinking aid, and an anti-aging agent. In consideration of the workability and performance of the tire 2, an optimal chemical is blended in the rubber composition in an optimal amount.

  The second coating layer 56b is formed by crosslinking a rubber composition different from the support layer 54. As will be described later, the loss tangent of the second coating layer 56b is small. In the tire 2, the second coating layer 56b does not include short fibers. In the tire 2, the same rubber composition as the rubber composition constituting the first coating layer 56a can be used for the second coating layer 56b.

  The base rubber of the rubber composition constituting the second coating layer 56b includes natural rubber, polybutadiene, styrene-butadiene copolymer, polyisoprene, ethylene-propylene-diene terpolymer, polychloroprene, acrylonitrile-butadiene. Copolymers and isobutylene-isoprene copolymers are exemplified. From the viewpoint of versatility and processability, natural rubber and styrene-butadiene copolymer are preferable as the base rubber. From the viewpoint of low loss tangent, natural rubber and polybutadiene are preferable as the base rubber. In the tire 2, it is particularly preferable that the base rubber is constituted by blending natural rubber and polybutadiene. In this case, the mass ratio ((natural rubber) / (polybutadiene)) of this blend is preferably 20/80 or more, and preferably 60/40 or less.

  From the viewpoint of processability, the rubber composition constituting the second coating layer 56b can contain carbon black as a filler. From this viewpoint, the blending amount of the carbon black is preferably 20 parts by mass or more with respect to 100 parts by mass of the base rubber. From the viewpoint that the second coating layer 56b having a small loss tangent can be obtained, the blending amount of the carbon black is preferably 30 parts by mass or less with respect to 100 parts by mass of the base rubber.

  In the tire 2, a filler other than carbon black may be used in combination with the rubber composition constituting the second coating layer 56b. Examples of other fillers include silica, calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, alumina, clay, talc and magnesium oxide. The rubber composition may also contain chemicals such as a softener, a tackifier, a crosslinking agent such as sulfur, a vulcanization accelerator, a crosslinking aid, and an anti-aging agent. In consideration of the workability and performance of the tire 2, an optimal chemical is blended in the rubber composition in an optimal amount.

  FIG. 3 is a cross-sectional view taken along line III-III in FIG. In FIG. 3, a part of the support layer 54 is shown. In FIG. 3, the vertical direction is the axial direction. The support layer 54 includes a large number of short fibers 58 and a matrix 60. As shown, these short fibers 58 are dispersed in the matrix 60. The longitudinal direction of these short fibers 58 is substantially along the axial direction.

  FIG. 4 is a schematic view showing the short fibers 58 of the support layer 54 of FIG. In FIG. 4, the vertical direction is the axial direction. In FIG. 4, an angle θ indicates the angle of the short fiber 58. The angle θ is an angle formed by the straight line S1 and the straight line S2. The straight line S1 extends in the axial direction. The straight line S <b> 2 passes through one end 62 and the other end 64 of the short fiber 58. The straight line S2 represents the longitudinal direction of the short fibers 58. The angle θ is −90 ° or more and 90 ° or less. In this paper, the straight line S2 extends downward to the right. In this case, the angle θ is indicated by a positive value. When the straight line S2 extends downward to the left, the angle θ is indicated by a negative value.

  In the present invention, the orientation direction of the short fibers 58 included in the support layer 54 is indicated by an angle formed by the orientation direction with respect to the axial direction (hereinafter, orientation angle). This orientation angle can be obtained by the following method using the above angle θ. First, a sample including the cross section of the support layer 54 shown in FIG. 3 is cut out from the tire 2. Next, this cross section is observed with a stereomicroscope. In this cross-sectional observation, the angle θ of the short fiber 58 is measured. This angle θ is measured for 100 short fibers 58 extracted at random. Next, a relationship (frequency distribution) between the angle and the frequency is obtained. In this relationship, the angle showing the maximum peak is the orientation angle of the short fibers 58.

  The support layer 54 in which the short fibers 58 are oriented in the axial direction can contribute to the improvement of the lateral rigidity of the tire 2. From this viewpoint, the absolute value of the orientation angle is preferably 45 ° or less, more preferably 30 ° or less, and further preferably 15 ° or less. Particularly preferably, this orientation angle is 0 °.

  In the frequency distribution function, the full width at half maximum of the peak represents the orientation of the short fibers 58. As the orientation of the short fibers 58 increases, the half width becomes narrower. By improving the orientation of the short fibers 58, the short fibers 58 can effectively reinforce the support layer 54. From this viewpoint, it is preferable that the half width is small. In the tire 2, the half width is preferably 20 ° or less, more preferably 10 ° or less, and particularly preferably 5 ° or less.

  As described above, in the tire 2, the support layer 54 includes the short fibers 58. The short fibers 58 reinforce the support layer 54. Since the support layer 54 can contribute to the rigidity of the tire 2, the tire 2 can generate a large cornering force when turning. The tire 2 can turn stably. The tire 2 is excellent in handling stability.

  In the tire 2, the short fibers 58 are oriented in the axial direction. The support layer 54 can effectively contribute to improving the lateral rigidity of the tire 2. The tire 2 can generate a large cornering force when turning. The tire 2 can turn stably. The tire 2 is excellent in handling stability.

  As shown in FIG. 2, the first covering layer 56 a is interposed between the support layer 54 and the carcass 10. The first coating layer 56 a can contribute to prevention of peeling due to shear between the composite 16 and the carcass 10. The second coating layer 56 b is interposed between the support layer 54 and the sidewall 6. The second coating layer 56 b can contribute to prevention of peeling due to shearing between the composite 16 and the sidewall 6. In the tire 2, since the composite 16 is configured such that the support layer 54 is located between the first coating layer 56 a and the second coating layer 56 b, the composite 16 and the composite 16 are adjacent to each other. The peeling from the constituent members of the tire 2 to be performed can be suppressed. The tire 2 is excellent in durability.

  As described above, the composite 16 is located in the shoulder region 24. The composite 16 can effectively reinforce the shoulder region 24. By this reinforcement, the shape of the tire 2 can be appropriately maintained. In the tire 2, the contact pressure in the shoulder region 24 is equal to the contact pressure in the equator region 22. The contact pressure of the tire 2 is uniform. In the tire 2, the tread 4 can sufficiently contribute to the braking performance. The tire 2 is excellent in braking performance. In the tire 2 whose contact pressure is uniform, uneven wear of the tread 4 is suppressed. The tire 2 is excellent in wear resistance.

  In the tire 2, the thickness of the support layer 54 is larger than the thickness of the first covering layer 56a. The thickness of the support layer 54 is larger than the thickness of the second coating layer 56b. The support layer 54 can effectively contribute to the lateral rigidity of the tire 2. The tire 2 is excellent in handling stability.

  As described above, from the viewpoint of reinforcing properties, the support layer 54 can contain carbon black. In the tire 2, since the carbon black can reinforce the matrix 60 constituting the support layer 54, peeling between the short fibers 58 and the matrix 60 can be suppressed. The support layer 54 does not hinder the durability of the tire 2.

  In the tire 2, the complex elastic modulus E * r obtained by deforming the support layer 54 in the direction perpendicular to the axial direction is obtained by the complex elastic modulus E * r obtained by deforming the support layer 54 in the axial direction. The ratio to is preferably 10 or more and 20 or less. By setting this ratio to 10 or more, the support layer 54 can effectively contribute to the lateral rigidity of the tire 2. The tire 2 is excellent in handling stability. By setting this ratio to 20 or less, the rigidity of the tire 2 can be appropriately maintained. In the tire 2, riding comfort can be maintained.

In the present invention, the complex elastic modulus E * r, complex elastic modulus E * c and loss tangent of the support layer 54, the loss tangent of the first coating layer 56a, and the loss tangent of the second coating layer 56b are “JIS-K 6394”. Is measured under the conditions shown below using a viscoelastic spectrometer (manufactured by Iwamoto Seisakusho).
Initial strain: 10%
Amplitude: ± 1%
Frequency: 10Hz
Deformation mode: Tensile
Measurement temperature: 70 ° C

  The test piece used for the measurement by a viscoelastic spectrometer is plate-shaped, the length is 45 mm, the width is 4 mm, and the thickness is 2 mm. Measurement is performed by chucking both ends of the test piece. The length of the displacement part of the test piece is 30 mm. This test piece is cut out from the tire 2. Note that, for the measurement of the complex elastic modulus E * r, a test piece cut out from the tire 2 so that the length direction thereof coincides with the axial direction is used. For the measurement of the complex elastic modulus E * c, a test piece cut out from the tire 2 is used so that its length direction coincides with a direction perpendicular to the axial direction. When it is difficult to cut out, this test piece is punched out from a slab obtained by holding the rubber composition constituting the support layer 54 in a mold having a temperature of 160 ° C. for 10 minutes.

  An excessive loss tangent promotes heat generation due to deformation. This heat generation increases the rolling resistance while affecting the durability. From this viewpoint, the loss tangent of the support layer 54 is preferably 0.013 or less. Since heat generation due to deformation is preferably suppressed, the loss tangent of the support layer 54 is preferably as small as possible. The loss tangent of the support layer 54 is preferably 0 or more from the viewpoint that heat generation due to deformation can be suppressed while maintaining a sufficient reinforcing effect. The loss tangent of the support layer 54 is indicated by the loss tangent obtained when the complex elastic modulus E * r is measured.

  In the tire 2, since the loss tangent of the first coating layer 56a is small, heat generation accompanying deformation of the first coating layer 56a can be suppressed. The first covering layer 56a does not hinder the durability of the tire 2. Since the first covering layer 56a can reduce rolling resistance, the tire 2 can contribute to the fuel efficiency of the vehicle.

  An excessive loss tangent hinders the braking performance of the tire 2. From this viewpoint, in the tire 2, the loss tangent of the first coating layer 56a is preferably 0.05 or more. The loss tangent is preferably 0.07 or less from the viewpoint that the first coating layer 56a can contribute to the reduction of rolling resistance while maintaining the durability of the first coating layer 56a.

  In the tire 2, since the loss tangent of the second coating layer 56b is small, heat generation due to deformation of the second coating layer 56b can be suppressed. The second coating layer 56b does not hinder the durability of the tire 2. Since the second covering layer 56b can reduce rolling resistance, the tire 2 can contribute to the fuel efficiency of the vehicle.

  An excessive loss tangent hinders the braking performance of the tire 2. From this viewpoint, in the tire 2, the loss tangent of the second coating layer 56b is preferably 0.05 or more. The loss tangent is preferably 0.07 or less from the viewpoint that the second coating layer 56b can contribute to the reduction of rolling resistance while maintaining the durability of the second coating layer 56b.

  In the tire 2, the support layer 54 preferably has a hardness of 50 or greater and 70 or less. By setting the hardness to 50 or more, the composite 16 including the support layer 54 can effectively reinforce the shoulder region 24. In the tire 2, the tread 4 can sufficiently contribute to the braking performance, and uneven wear of the tread 4 is suppressed. Since the composite 16 can contribute to the generation of cornering force, the tire 2 is excellent in steering stability. From this viewpoint, the hardness is more preferably 55 or more. By setting the hardness to 70 or less, the rigidity of the tire 2 can be appropriately maintained. The tire 2 is excellent in ride comfort. From this viewpoint, the hardness is more preferably 65 or less.

  In the present invention, the hardness is measured by a type A durometer according to JIS-K6253. This hardness is measured under conditions where the temperature is 23 ° C. For this measurement, a test piece formed by crosslinking the rubber composition constituting the support layer 54 is used. This test piece is obtained by holding the rubber composition in a mold having a temperature of 160 ° C. for 10 minutes. The hardness of the 1st coating layer 56a and the 2nd coating layer 56b mentioned later is measured similarly.

  In the tire 2, the hardness of the first coating layer 56a is preferably 50 or greater and 70 or less. By setting the hardness to 50 or more, the composite 16 including the first covering layer 56a can effectively reinforce the shoulder region 24. In the tire 2, the tread 4 can sufficiently contribute to the braking performance, and uneven wear of the tread 4 is suppressed. Since the composite 16 can contribute to the generation of cornering force, the tire 2 is excellent in steering stability. From this viewpoint, the hardness is more preferably 55 or more. By setting the hardness to 70 or less, the first coating layer 56a can effectively contribute to prevention of peeling due to shearing between the composite 16 and the carcass 10. The tire 2 is excellent in durability. Since the rigidity is appropriately maintained, the tire 2 is excellent in ride comfort. From this viewpoint, the hardness is more preferably 65 or less.

  In the tire 2, the hardness of the second coating layer 56b is preferably 50 or greater and 70 or less. By setting the hardness to 50 or more, the composite body 16 including the second coating layer 56b can effectively reinforce the shoulder region 24. In the tire 2, the tread 4 can sufficiently contribute to the braking performance, and uneven wear of the tread 4 is suppressed. Since the composite 16 can contribute to the generation of cornering force, the tire 2 is excellent in steering stability. From this viewpoint, the hardness is more preferably 55 or more. By setting the hardness to 70 or less, the second coating layer 56b can effectively contribute to prevention of peeling due to shear between the composite 16 and the carcass 10. The tire 2 is excellent in durability. Since the rigidity is appropriately maintained, the tire 2 is excellent in ride comfort. From this viewpoint, the hardness is more preferably 65 or less.

  In FIG. 1, a solid line BBL is a bead 8 base line. The bead 8 base line is a line that defines the rim diameter (see JATMA) of the rim on which the tire 22 is mounted. The double arrow line WA is the axial width from the equator plane to the end 46 of the belt 12. A double arrow line WB is an axial width from the equator plane to the inner end 44 of the composite 16. The double arrow line HA is the height in the radial direction from the bead 8 base line to the equator plane. A double arrow line HB is a height in the radial direction from the bead 8 base line to the outer end 50 of the composite 16.

  In the tire 2, the ratio of the width WB to the width WA is preferably 70% or more and 90% or less. By setting this ratio to 70% or more, excessive rigidity due to the composite 16 is suppressed, so that riding comfort can be maintained. In this respect, the ratio is more preferably equal to or greater than 75%. By setting the ratio to 90% or less, the composite 16 can effectively reinforce the shoulder region 24. In the tire 2, the tread 4 can sufficiently contribute to the braking performance, and uneven wear of the tread 4 is suppressed. Since the composite 16 can contribute to the generation of cornering force, the tire 2 is excellent in steering stability. In this respect, the ratio is more preferably equal to or less than 85%.

  In the tire 2, the ratio of the height HB to the height HA is preferably 50% or more and 70% or less. By setting this ratio to 50% or more, excessive rigidity due to the composite 16 is suppressed, so that riding comfort can be maintained. In this respect, the ratio is more preferably equal to or greater than 55%. By setting this ratio to 70% or less, the composite 16 can effectively reinforce the shoulder region 24. In the tire 2, the tread 4 can sufficiently contribute to the braking performance, and uneven wear of the tread 4 is suppressed. Since the composite 16 can contribute to the generation of cornering force, the tire 2 is excellent in steering stability. In this respect, the ratio is more preferably equal to or less than 65%.

  In FIG. 2, a double arrow line TA represents the thickness of the composite 16. A double arrow line TB is the thickness of the support layer 54. A double arrow line TC1 represents the thickness of the first coating layer 56a. A double arrow line TC2 represents the thickness of the second coating layer 56b.

  In the tire 2, the thickness TA is preferably 1.0 mm or greater and 3.0 mm or less. The composite 16 can effectively reinforce the shoulder region 24 by setting the thickness to 1.0 mm or more. In the tire 2, the tread 4 can sufficiently contribute to the braking performance, and uneven wear of the tread 4 is suppressed. Since the composite 16 can contribute to the generation of cornering force, the tire 2 is excellent in steering stability. In this respect, the thickness is more preferably equal to or greater than 1.5 mm. By setting the thickness to 3.0 mm or less, excessive rigidity due to the composite 16 is suppressed, so that riding comfort can be maintained. In this respect, the thickness is more preferably equal to or less than 2.5 mm.

  In the tire 2, the thickness TB is preferably not less than 0.5 mm and not more than 1.4 mm. By setting the thickness to 0.5 mm or more, the support layer 54 can effectively contribute to the lateral rigidity of the tire 2. The tire 2 is excellent in handling stability. In this respect, the thickness is more preferably equal to or greater than 0.8 mm. By setting the thickness to 1.4 mm or less, excessive rigidity due to the support layer 54 is suppressed, so that riding comfort can be maintained. In this respect, the thickness is more preferably equal to or less than 1.1 mm.

  In the tire 2, the thickness TC1 is preferably not less than 0.3 mm and not more than 0.7 mm. By setting this thickness to 0.3 mm or more, the first coating layer 56a can contribute to the reduction of rolling resistance while preventing the composite 16 and the carcass 10 from being peeled off by shearing. In this respect, the thickness is more preferably equal to or greater than 0.4 mm. By setting the thickness to 0.7 mm or less, excessive rigidity due to the first covering layer 56a is suppressed, so that riding comfort can be maintained. In this respect, the thickness is more preferably equal to or less than 0.6 mm.

  In the tire 2, the thickness TC2 is preferably 0.3 mm or greater and 0.7 mm or less. By setting this thickness to 0.3 mm or more, the second coating layer 56b can contribute to the reduction of rolling resistance while preventing the composite 16 and the carcass 10 from being peeled off by shearing. In this respect, the thickness is more preferably equal to or greater than 0.4 mm. By setting the thickness to 0.7 mm or less, excessive rigidity due to the second coating layer 56b is suppressed, so that riding comfort can be maintained. In this respect, the thickness is more preferably equal to or less than 0.6 mm.

  In the tire 2, the blending amount of the short fibers 58 included in the support layer 54 is preferably 0.5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the base rubber. The support layer 54 including 0.5 mass parts or more of short fibers 58 contributes to the steering stability of the tire 2. In this respect, the amount of the short fiber 58 is more preferably 3 parts by mass or more. The tire 2 in which the amount of the short fibers 58 is 50 parts by mass or less is excellent in riding comfort. In this respect, the amount to be blended is more preferably equal to or less than 20 parts by weight.

  In the tire 2, the average length L (see FIG. 4) of the short fibers 58 is preferably 10 μm or more from the viewpoint that the short fibers 58 can effectively reinforce the support layer 54. The support layer 54 is sufficiently reinforced by the short fibers 58 having an average length L of 10 μm or more. In this respect, the average length L is more preferably 50 μm or more, further preferably 100 μm or more, and particularly preferably 300 μm or more. From the viewpoint of dispersibility in the matrix 60, the average length L is preferably 1000 μm or less, more preferably 800 μm or less, and particularly preferably 700 μm or less.

  The average diameter D of the short fibers 58 is preferably 0.05 μm or more. The support layer 54 is sufficiently reinforced by the short fibers 58 having an average diameter D of 0.05 μm or more. In this respect, the average diameter D is more preferably 0.10 μm or more, further preferably 1 μm or more, and particularly preferably 5 μm or more. From the viewpoint of dispersibility in the matrix 60, the average diameter D is preferably 50 μm or less, more preferably 30 μm or less, and particularly preferably 20 μm or less.

  The aspect ratio (L / D) of the short fiber 58 is preferably 10 or more. The support layer 54 is sufficiently reinforced by the short fibers 58 having an aspect ratio (L / D) of 10 or more. In this respect, the aspect ratio (L / D) is more preferably 20 or more. From the viewpoint of dispersibility in the support layer 54, the aspect ratio (L / D) is preferably 300 or less, and more preferably 200 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 the JATMA standard, “maximum value” published in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the TRA standard, and “INFLATION PRESSURE” in the 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.

  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.

[Adjustment of rubber composition C]
40 parts by mass of natural rubber, 60 parts by mass of polybutadiene and 25 parts by mass of carbon black were kneaded in a closed kneader to obtain rubber composition C. Natural rubber is “RSS # 3”. The polybutadiene is “BR150B” manufactured by JSR Corporation. Carbon black is “Seast 3” manufactured by Tokai Carbon Co., Ltd. Table 1 below shows the hardness and loss tangent tan δ of the crosslinked rubber obtained by crosslinking the rubber composition C. This hardness is measured with a type A durometer under conditions where the temperature is 23 ° C. Loss tangent is measured under conditions where the temperature is 70 ° C. and the amplitude is ± 1%.

[Adjustment of rubber compositions A, B, D and E]
Rubber compositions A, B, D, and E were obtained in the same manner as the rubber composition C except that the amount of carbon black was changed as shown in Table 1 below.

[Adjustment of rubber composition R]
40 parts by mass of natural rubber, 60 parts by mass of polybutadiene, 50 parts by mass of carbon black and 10 parts by mass of short fibers were kneaded in a closed kneader to obtain a rubber composition R. Natural rubber is “RSS # 3”. The polybutadiene is “BR150B” manufactured by JSR Corporation. Carbon black is “Seast 3” manufactured by Tokai Carbon Co., Ltd. The short fiber is an aramid fiber. The short fibers have an average length L of 500 μ and an aspect ratio (L / D) of 20. Table 2 below shows the hardness and loss tangent tan δ of the crosslinked rubber obtained by crosslinking the rubber composition R. This hardness is measured with a type A durometer under conditions where the temperature is 23 ° C. Loss tangent is measured under conditions where the temperature is 70 ° C. and the amplitude is ± 1%.

[Adjustment of rubber compositions P, Q, S and T]
Rubber compositions P, Q, S, and T were obtained in the same manner as the rubber composition R except that the amount of carbon black was changed as shown in Table 2 below.

[Example 1]
A pneumatic tire of Example 1 having the basic configuration shown in FIG. 1 and having the specifications shown in Table 5 below was obtained. The tire size is 195 / 65R15. The composite is composed of a support layer, a first coating layer, and a second coating layer. The support layer is formed by crosslinking the rubber composition R. This support layer is sandwiched between the first coating layer and the second coating layer. The first coating layer and the second coating layer are formed by crosslinking the rubber composition C. The ratio of the complex elastic modulus E * r obtained by deforming the support layer in the axial direction to the complex elastic modulus E * c obtained by deforming the support layer in the direction perpendicular to the axial direction (E * r / E * c) is 15. The thickness TB of this support layer is 1 mm. The thickness TC1 of the first coating layer is 0.5 mm. The thickness TC2 of the second coating layer is 0.5 mm.

[Examples 11 to 14]
Tires were obtained in the same manner as in Example 1 except that the thickness TC1 and the thickness TC2 were as shown in Table 5 below.

[Examples 9 to 10 and 15 to 16]
Tires were obtained in the same manner as in Example 1 except that the thickness TB was as shown in Tables 4 and 5 below.

[Example 8]
A tire was obtained in the same manner as in Example 1 except that the thickness TB, the thickness TC1, and the thickness TC2 were as shown in Table 4 below.

[Examples 6 to 7 and Examples 17 to 18]
Tires were obtained in the same manner as in Example 1 except that the rubber compositions constituting the first coating layer and the second coating layer were as shown in Tables 4 and 6 below.

[Examples 4 to 5 and Examples 19 to 20]
A tire was obtained in the same manner as in Example 1 except that the ratio (E * r / E * c) was changed by adjusting the orientation angle of the short fibers contained in the support layer.

[Examples 2 to 3 and 21 to 22]
A tire was obtained in the same manner as in Example 1 except that the rubber composition constituting the support layer was as shown in Table 3, Table 4, and Table 6 below.

[Comparative Example 3]
A tire was obtained in the same manner as in Example 1 except that the composite was composed of only the support layer made of the rubber composition C. The composite is not provided with the first coating layer and the second coating layer. The thickness TB is 2 mm.

[Comparative Example 4]
A tire was obtained in the same manner as in Example 1 except that the composite was composed only of the support layer made of the rubber composition R. The composite is not provided with the first coating layer and the second coating layer.

[Comparative Example 5]
A tire was obtained in the same manner as in Example 1 except that the composite was composed only of the support layer made of the rubber composition P. The composite is not provided with the first coating layer and the second coating layer.

[Comparative Example 6]
A tire was obtained in the same manner as in Example 1 except that the composite was composed of a support layer made of the rubber composition R and a second coating layer made of the rubber composition part C. This composite is not provided with the first coating layer provided on the carcass side. The thickness TC2 is 0.5 mm, and the thickness TB is 1.5 mm.

[Comparative Example 7]
A tire was obtained in the same manner as in Example 1 except that the composite was composed of a support layer made of the rubber composition R and a first coating layer made of the rubber composition part C. This composite is not provided with the second coating layer provided on the belt side. In this tire, the thickness TB is 0.5 mm, and the thickness TC2 is 1.5 mm.

[Comparative Example 1]
A tire was obtained in the same manner as in Example 1 except that the composite was not provided. This comparative example 1 is a commercially available tire.

[Comparative Example 2]
A tire was obtained in the same manner as in Example 1 except that the composite was not provided. The tread of this tire is made of a crosslinked rubber having a small loss tangent. Comparative Example 2 is a commercially available low fuel consumption tire.

[Evaluation of tire mass]
The mass of the prototype tire was measured and evaluated based on this measured value. This evaluation result is represented by an index value with Comparative Example 1 as 100. A larger value indicates a greater tire mass. The results are shown in Table 3, Table 4, Table 5, and Table 6 below.

[Sensory evaluation of tires]
The prototype tire was mounted on a passenger car (FF car) having a displacement of 1800 cc. The internal pressure of this tire was 210 kPa. The size of the wheel is 15 × 6J. This passenger car was subjected to a running test on an asphalt road surface, and a driver's sensory evaluation was performed on handling stability, braking performance, and riding comfort. This result is expressed as an index value with Comparative Example 1 as 100. Larger values indicate better results. The results are shown in Table 3, Table 4, Table 5, and Table 6 below.

[Rolling resistance]
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 rolling resistance tester, and a load of 4.3 kN (80% of the normal load) was applied to the tire. This tire was run at a speed of 80 km / h and the rolling resistance was measured to obtain the reciprocal of this measured value. Evaluation was performed based on the reciprocal. This result is expressed as an index value with Comparative Example 1 as 100. It shows that rolling resistance is so small that this value is large. The results are shown in Table 3, Table 4, Table 5, and Table 6 below.

[Durability evaluation]
A prototype tire was mounted on a rim of a drum durability tester, and high-speed durability was evaluated in accordance with the standard of JIS D 4230. This evaluation result is represented by an index value with Comparative Example 1 as 100. Larger values indicate better results. The results are shown in Table 3, Table 4, Table 5, and Table 6 below.

  As shown in Tables 3, 4, 5, and 6, the tires of the examples have small rolling resistance and are excellent in handling stability and braking performance. Furthermore, the tires of the examples are also excellent in durability. From this evaluation result, the superiority of the present invention is clear.

  The tire according to the present invention can be mounted on various vehicles.

FIG. 1 is a cross-sectional view showing a part of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line II-II in 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 support layer of FIG.

Explanation of symbols

2 ... tyre 4 ... tread 6 ... side wall 8 ... bead 10 ... carcass 12 ... belt 14 ... band 16 ... composite 18 ... inner liner 20 .... Chafer 22 ... Equatorial region 24 ... Shoulder region 26 ... Tread surface 30 ... Core 32 ... Apex 34 ... Carcass ply 36 ... Inner layer 38 ... Outside Layer 40 ... Full band 42 ... Edge band 54 ... Support layer 56, 56a, 56b ... Coating layer 58 ... Short fiber 60 ... Matrix

Claims (8)

A pair of beads, a carcass spanned between both beads, and a pair of composites that are shoulder regions of the tire and located outside the carcass;
The composite includes a support layer and two coating layers,
This support layer is located between both coating layers,
A pneumatic tire in which the support layer includes short fibers.   The tire according to claim 1, wherein a thickness of the composite is 1.0 mm or greater and 3.0 mm or less.   The tire according to claim 1 or 2, wherein the coating layer has a thickness of 0.3 mm or more and 0.7 mm or less.   The tire according to any one of claims 1 to 3, wherein a thickness of the support layer is 0.5 mm or more and 1.4 mm or less.   The tire according to any one of claims 1 to 4, wherein a thickness of the support layer is larger than a thickness of the covering layer.   The tire according to any one of claims 1 to 5, wherein a loss tangent of the coating layer is 0.05 or more and 0.07 or less.   The tire according to any one of claims 1 to 6, wherein the support layer has a hardness of 50 or more and 70 or less.   The tire according to any one of claims 1 to 7, wherein the short fibers of the support layer are oriented.

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