JP2018075935A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire 72 achieving prevention of generation of rust in a core 26 of a bead 8 and a carcass cord.SOLUTION: A chafer 20 of a tire 72 includes a first chafer 52 and a second chafer 54. The first chafer 52 is positioned outside in an axial direction of a bead 8. The second chafer 54 is joined to an inner liner 14 and the first chafer 52, respectively. A first joint portion 56 of the second chafer 54 and the inner liner 14 is positioned inside in the axial direction of a core 26 of the bead 8, and a second joint portion 58 of the second chafer 54 and the first chafer 52 is positioned inside in a radial direction of the core 26. The second chafer 54 is formed of a rubber composition. The rubber composition contains a base material rubber and polypropylene powder.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire. More particularly, the present invention relates to a heavy duty pneumatic tire mounted on a bus, truck, or the like.

  The tire is provided with an inner liner. This inner liner is located inside the tire and plays the role of maintaining the internal pressure.

  The inner liner is made of a crosslinked rubber produced using a rubber composition. The rubber composition of the inner liner usually contains butyl rubber as the base rubber. Butyl rubber is known as a rubber that is less permeable to gases such as air. On the other hand, it is also known that this butyl rubber may impair the adhesion of the rubber member.

  Regarding the inner liner, various studies have been made from the viewpoint of the leak resistance performance and durability of the tire. An example of this study is disclosed in Japanese Patent Application Laid-Open No. 2004-168244.

JP 2004-168244 A

  When the tire is incorporated into the rim, the bead portion of the tire is placed on the rim seat. When the tire is filled with air, the bead portion slides axially outward along the seat. This bead portion contacts the flange of the rim. This completes the incorporation of the tire into the rim.

  In heavy-duty tires, a rim configured such that the seat is inclined with respect to the axial direction may be used. In this rim, the inclination angle of the seat is usually 15 °. When the tire is installed in the rim, the toe part of the tire will be lifted off the seat. Since a gap is formed between the tire and the seat, moisture and oxygen may penetrate into the tire from this gap.

  A core exists in the bead portion of the tire. Steel wire is usually used for the core. For this reason, when moisture penetrates, rust may be generated in the core.

  A carcass ply is also located in the bead portion of the tire. The carcass ply includes a carcass cord. In heavy duty tires, steel cords are generally used as carcass cords. When moisture or the like permeates, rust may be generated on the carcass cord.

  In the case of a heavy-duty tire, a filler may be employed in this portion from the viewpoint of reinforcing the bead portion. This filler is usually arranged to cover the radially inner part of the core. Such a filler is also referred to as a normal filler. This normal filler also includes a cord, and a steel cord is used as this cord. For this reason, when moisture etc. permeate, there is a possibility that rust also occurs in the cord of the normal filler.

  The occurrence of rust leads to a decrease in strength. The carcass cord is thinner than, for example, the wire that forms the core. For this reason, if the strength is reduced due to the occurrence of rust, the carcass cord may be broken.

  From the viewpoint of weight reduction, the filler may be configured so as to cover a part of the core in the radial direction rather than the entire inner part. The filler having such a configuration is also referred to as a sheet filler. When the sheet filler is employed, a portion where no filler exists is formed between the outer surface of the tire and the core. For this reason, in particular, in a tire employing a sheet filler, there is a problem that moisture or the like easily penetrates to the core or carcass cord, and rust is likely to occur in the core or carcass cord, as compared with a tire employing a normal filler.

  In order to prevent the occurrence of rust, an inner liner may be disposed at a location where gas (moisture) penetrates. However, as described above, the inner liner is inferior in adhesiveness. For this reason, there exists a possibility that an inner liner may peel depending on the arrangement | positioning location of an inner liner. This peeling hinders the durability of the tire.

  As is apparent from the above description, the actual situation is that the technology for preventing the occurrence of rust in the core and the carcass cord has not been sufficiently established.

  An object of the present invention is to provide a pneumatic tire in which rust generation prevention is achieved in a bead core and a carcass cord.

  The pneumatic tire according to the present invention includes a pair of beads, a carcass, an inner liner, and a pair of chafers. The carcass is bridged between one bead and the other bead. The inner liner is located inside the carcass. Each chafer is located in the vicinity of each bead and is configured to contact the rim when the tire is incorporated into the rim. The bead has a ring-shaped core. The chafer includes a first chafer and a second chafer. The first chafer is located outside the bead in the axial direction. The second chafer is joined to each of the inner liner and the first chafer. The first joint portion between the second chafer and the inner liner is located inside the core in the axial direction, and the second joint portion between the second chafer and the first chafer is the radius of the core. It is located inside the direction. The second chafer is made of a rubber composition. The rubber composition includes a base rubber and polypropylene powder.

  Preferably, the pneumatic tire further includes tie gum. The tie gum extends along the carcass outside the inner liner. The end of the tie gum is located between the second chafer and the core.

  Preferably, in the pneumatic tire, the outer end of the second chafer is defined as a fitting end at a point corresponding to the inner end in the axial direction of the contact surface between the tire and the rim on the outer surface of the tire. Is positioned outside the fitting end in the axial direction.

  Preferably, in the pneumatic tire, the first chafer is located radially inward of the second chafer in the second joint portion. The inner end of the first chafer is located inside the fitting end in the axial direction.

  Preferably, in this pneumatic tire, the thickness of the chafer at the fitting end is 1.5 mm or more and 3.0 mm or less.

  Preferably, in the pneumatic tire, in the rubber composition, the amount of the polypropylene powder is 10 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the base rubber.

  Preferably, in this pneumatic tire, the complex elastic modulus of the first chafer is 8.0 MPa or more.

  In the pneumatic tire according to the present invention, the second chafer is such that the first joint portion with the inner liner is located on the inner side in the axial direction from the core, and the second joint portion with the first chafer has a radius smaller than the core. It arrange | positions so that it may be located inside a direction. In this tire, the second chafer is located in a portion where there is a high possibility that a gap is formed between the tire and the rim when the tire is incorporated into the rim.

  In this tire, the rubber composition for the second chafer contains polypropylene powder. Although this second chafer is not as much as the inner liner, it permeates moisture and the like more than the conventional chafer.

  The core of the bead typically includes a non-stretchable wire, but a typical material for this wire is steel. In heavy duty tires, steel cords are usually used as carcass cords.

  As described above, in this tire, the second chafer is located in a portion where a gap is likely to be formed between the tire and the rim when the tire is incorporated into the rim. Since the second chafer prevents the penetration of moisture and the like into the inside of the tire, in this tire, the occurrence of rust in the bead core and the carcass cord is prevented. ADVANTAGE OF THE INVENTION According to this invention, the pneumatic tire in which generation | occurrence | production prevention of the rust in the bead core and the carcass cord was achieved was obtained.

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 an enlarged cross-sectional view showing a part of a pneumatic tire according to another embodiment of the present invention.

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

  FIG. 1 shows a pneumatic tire 2. Specifically, FIG. 1 shows a part of a cross section of the tire 2 along a plane including the central axis of the tire 2. In FIG. 1, the vertical direction is the radial direction of the tire 2, the left-right 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.

  The tire 2 includes a tread 4, a pair of sidewalls 6, a pair of beads 8, a carcass 10, a belt 12, an inner liner 14, a tie gum 16, a pair of fillers 18, and a pair of chafers 20. The tire 2 is a tubeless type. The tire 2 is attached to a truck, a bus or the like. The tire 2 is for heavy loads.

  The tread 4 has a shape protruding outward in the radial direction. The tread 4 forms a tread surface 22 that contacts the road surface. A groove 24 is carved in the tread 4. The groove 24 forms a tread pattern. The tread 4 is made of a crosslinked rubber. In the tread 4, wear resistance, heat resistance, and grip properties are taken into consideration.

  Each sidewall 6 extends substantially inward in the radial direction from the end of the tread 4. The sidewall 6 is located outside the carcass 10 in the axial direction. This sidewall 6 is made of a crosslinked rubber having excellent cut resistance and weather resistance. The sidewall 6 prevents the carcass 10 from being damaged.

  Each bead 8 is located radially inward of the sidewall 6. A part of the chafer 20 is located outside the bead 8 in the axial direction. The bead 8 includes a core 26 and an apex 28.

  The core 26 has a ring shape. The core 26 includes a wound non-stretchable wire 30. Specifically, the core 26 is configured by covering a bundle 32 of wound non-stretchable wires 30 with a wrapping rubber 34. A typical material for the wire 30 is steel.

  The apex 28 extends radially outward from the core 26. As is apparent from FIG. 1, the apex 28 tapers radially outward. The apex 28 is made of a highly hard crosslinked rubber.

  The carcass 10 includes a carcass ply 36. In the tire 2, the carcass 10 includes a single carcass ply 36. The carcass 10 may be formed from two or more carcass plies 36.

  In the tire 2, the carcass ply 36 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 36 is folded around the cores 26 from the inner side to the outer side in the axial direction. By this folding, the carcass ply 36 is formed with a main portion 36a and a pair of folded portions 36b. The carcass ply 36 includes a main portion 36a and a pair of folded portions 36b.

  Although not shown, the carcass ply 36 includes a large number of carcass cords arranged in parallel and a topping rubber. The absolute value of the angle formed by each carcass cord with respect to the equator plane is 75 ° to 90 °. In other words, the carcass 10 has a radial structure. The carcass cord is made of steel. The carcass ply 36 includes a steel cord.

  In the tire 2, the end of the folded portion 36 b is located between the outer end of the apex 28 and the core 26 in the radial direction. As described above, the tire 2 is mounted on a truck, a bus or the like. A large load acts on the bead 8 portion of the tire 2. The distortion tends to concentrate at the end of the folded portion 36b. In the tire 2, an intermediate layer 38 and a strip 40 are further provided in the bead 8 portion. These suppress the concentration of distortion at the end of the folded portion 36b.

  The belt 12 is located on the inner side in the radial direction of the tread 4. The belt 12 is laminated with the carcass 10. The belt 12 reinforces the carcass 10. In the tire 2, the belt 12 includes a first layer 12a, a second layer 12b, a third layer 12c, and a fourth layer 12d. In the tire 2, the belt 12 is composed of four layers. The belt 12 may be composed of three layers or may be composed of two layers.

  As is clear from FIG. 1, in the tire 2, the second layer 12b is the most of the first layer 12a, the second layer 12b, the third layer 12c, and the fourth layer 12d constituting the belt 12 in the axial direction. It has a large width. In the tire 2, the layer having the largest axial width among the plurality of layers constituting the belt 12, that is, the end of the second layer 12 b is the end of the belt 12. In the tire 2, the axial width of the belt 12 is represented by the axial width of the second layer 12b. The axial width of the belt 12 is preferably 0.7 times or more the maximum width of the tire 2.

  Although not shown, each of the first layer 12a, the second layer 12b, the third layer 12c, and the fourth layer 12d is composed of a large number of cords arranged in parallel and a topping rubber. The material of each cord is steel. The belt 12 includes a steel cord. In each layer 12, the cord is inclined with respect to the equator plane. The absolute value of the angle formed by this cord with respect to the equator plane is 12 ° to 70 °.

  The inner liner 14 is located inside the carcass 10. The inner liner 14 is joined to the inner surface of the carcass 10 via a tie gum 16. The inner liner 14 is made of a crosslinked 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. In other words, the inner liner 14 contributes to the leak resistance performance of the tire 2. In the tire 2, the end of the inner liner 14 is located radially inward of the core 26. Thereby, the internal pressure holding effect by the inner liner 14 is sufficiently ensured.

  The tie gum 16 is sandwiched between the carcass 10 and the inner liner 14. The tie gum 16 is made of a crosslinked rubber having excellent adhesiveness. The tie gum 16 is firmly bonded to the carcass 10 and is also firmly bonded to the inner liner 14. The tie gum 16 prevents the inner liner 14 from being peeled from the carcass 10. A typical base rubber of the tie gum 16 is natural rubber.

  Each filler 18 is located near the bead 8. The filler 18 is laminated with the carcass 10. The filler 18 is folded around the core 26 of the bead 8 on the radially inner side of the carcass 10. As shown in FIG. 1, the filler 18 is disposed so as to cover substantially the entire radially inner portion of the core 26. This filler 18 is also referred to as a normal filler. Although not shown, the filler 18 is composed of a large number of cords arranged in parallel and a topping rubber. Each cord is inclined with respect to the radial direction. The cord material is steel. The filler 18 suppresses the fall of the bead 8 portion. The filler 18 contributes to the durability of the tire 2. In the tire 2, the end of the filler 18 is covered with a cover rubber 42.

  Each chafer 20 is located in the vicinity of each bead 8. The chafer 20 extends substantially inward in the radial direction from the end of the sidewall 6. A part of the chafer 20 is located outside the beads 8 and the carcass 10 in the axial direction. The chafer 20 extends substantially inward in the axial direction from the position of the heel H of the tire 2. A part of the chafer 20 is located inside the bead 8 in the radial direction. The chafer 20 further extends substantially outward in the radial direction from the position of the toe T of the tire 2. A part of the chafer 20 is located inside the bead 8 in the axial direction. As shown in FIG. 1, the axially outer portion of the chafer 20 is joined to the radially inner portion of the sidewall 6. The axially inner portion of the chafer 20 is joined to the radially inner portion of the inner liner 14. In the tire 2, the chafer 20 is made of a crosslinked rubber.

  FIG. 2 shows a portion of the bead 8 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.

  FIG. 2 also shows a rim 44 in which the tire 2 is incorporated. The rim 44 is a regular rim. The tire 2 is incorporated into the rim 44, and the inside of the tire 2 is filled with air so that the internal pressure of the tire 2 becomes a normal internal pressure.

  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 present specification, the normal load means a load defined in a standard on which the tire 2 depends. “Maximum value” published in “Maximum load capacity” in the JATMA standard, “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the TRA standard, and “LOAD CAPACITY” in the ETRTO standard are normal loads.

  In the present invention, unless otherwise specified, 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 case of the passenger car tire 2, the dimensions and angle may be measured in a state where the internal pressure is 180 kPa.

  The rim 44 includes a pair of fitting portions 46. The bead 8 portion of the tire 2 is fitted to each fitting portion 46. The fitting portion 46 includes a seat 48 and a flange 50.

  In the rim 44 shown in FIG. 2, the seat 48 is inclined with respect to the axial direction. The inclination angle of the seat 48 is normally set to 15 °. The rim 44 in which the inclination angle of the seat 48 is set to 15 ° is also referred to as a 15 ° tapered rim. This inclination angle is represented by the inclination angle of the surface of the seat 48 on the chafer 20 side.

  In the tire 2, the cross section of the core 26 of the bead 8 has a hexagonal shape. The cross section of the core 26 has six corners. In FIG. 2, for convenience of explanation of the present invention, symbols a, b, c, d, e, and f are attached to these corners. In the core 26, the corner b is the inner end in the axial direction of the core 26.

  In the tire 2, the surface connecting the corner portion a and the corner portion f is the bottom surface of the core 26. This bottom surface faces the sheet 48. The core 26 of the tire 2 includes a bottom surface that faces the seat 48 of the rim 44 when the tire 2 is incorporated into the rim 44. The cross section of the tire 2 shown in FIG. 2 is along a plane including the central axis of the tire 2. The bottom surface extends substantially in the axial direction in the cross section of the tire 2. The corner portion a is the inner end in the axial direction of the bottom surface, and the corner portion f is the outer end in the axial direction of the bottom surface.

  In FIG. 2, the symbol CE represents one end of the contact surface between the tire 2 and the rim 44, specifically, a point on the outer surface of the tire 2 corresponding to the inner end in the axial direction of the contact surface. . As shown in FIG. 2, in the axial direction, the tire 2 does not contact the rim 44 at a portion inside the point CE in the axial direction. A gap is formed between the tire 2 and the rim 44 at a portion on the inner side in the axial direction from the point CE. In the present invention, the point CE corresponding to the inner end in the axial direction of the contact surface between the tire 2 and the rim 44 on the outer surface of the tire 2 is referred to as a fitting end.

  As shown in FIG. 2, the position of the fitting end CE substantially coincides with the position of the corner a of the core 26 in the axial direction. In other words, in a state where the tire 2 is incorporated in the rim 44 and the tire 2 is filled with air so as to have a normal internal pressure, the fitting end CE corresponds to the corner portion a of the core 26 in the axial direction. It is formed at a point on the outer surface of the tire 2.

  As is clear from FIG. 2, a part of the chafer 20 of the tire 2, specifically, the chafer 20 positioned between the heel H and the toe T is placed on the seat 48 of the rim 44. The flange 50 is brought into contact with another part of the chafer 20, specifically, an axially outer portion of the chafer 20. In the tire 2, the chafer 20 is configured to come into contact with the rim 44 when the tire 2 is incorporated into the rim 44.

  In the tire 2, the chafer 20 includes a first chafer 52 and a second chafer 54. Specifically, the chafer 20 includes a first chafer 52 and a second chafer 54. In other words, the chafer 20 is composed of two members.

  The first chafer 52 is positioned substantially inside the sidewall 6 in the radial direction. The first chafer 52 is located outside the bead 8 in the axial direction. Specifically, the first chafer 52 is located outside the bead 8, the carcass 10, and the filler 18 in the axial direction. In the tire 2, the first chafer 52 is made of a crosslinked rubber having excellent wear resistance.

  The first chafer 52 contacts the flange 50 of the rim 44. The symbol DE represents the other end of the contact surface between the tire 2 and the rim 44, specifically, a point on the outer surface of the tire 2 corresponding to the axially outer end of the contact surface. As shown in FIG. 2, this point DE is located on the outer surface of the first chafer 52. When a load acts on the tire 2, distortion tends to concentrate in the vicinity of this point DE. For this reason, it is preferable that the first chafer 52 has a certain degree of rigidity in order to suppress deformation of the portion of the bead 8 and maintain good durability. From this viewpoint, in the tire 2, the complex elastic modulus E * of the first chafer 52 is preferably 8.0 MPa or more. If the rigidity of the first chafer 52 is too high, the riding comfort of the tire 2 may be impaired. From the viewpoint of good riding comfort, the complex elastic modulus E * is preferably 30 MPa or less.

In the present invention, the complex elastic modulus is measured in accordance with the provisions of “JIS K 6394”. In this measurement, a plate-shaped test piece (length = 45 mm, width = 4 mm, thickness = 2 mm) is used. This test piece may be cut out from the tire 2, or a sheet may be prepared from the rubber composition and cut out from the sheet. The measurement conditions are as follows. In addition, although the loss tangent of the tie gum 16 is mentioned later, this loss tangent is also measured similarly to this complex elastic modulus.
Viscoelastic spectrometer: "VESF-3" from Iwamoto Seisakusho
Initial strain: 10%
Dynamic strain: ± 1%
Frequency: 10Hz
Deformation mode: Tensile Measurement temperature: 70 ° C

  The second chafer 54 is located between the inner liner 14 and the first chafer 52. The second chafer 54 is joined to each of the inner liner 14 and the first chafer 52. In the present invention, the joint portion 56 between the second chafer 54 and the inner liner 14 is referred to as a first joint portion. The joint portion 58 between the second chafer 54 and the first chafer 52 is referred to as a second joint portion. In the tire 2, the first joint portion 56 is located on the inner side in the axial direction of the core 26 of the bead 8. The second joint portion 58 is located on the radially inner side of the core 26.

  In the tire 2, the second chafer 54 is made of a rubber composition. Specifically, the second chafer 54 is made of a crosslinked rubber made from a rubber composition. In the tire 2, the second chafer 54 is composed of a crosslinked rubber different from the crosslinked rubber forming the first chafer 52.

  In the tire 2, the rubber composition for the second chafer 54 includes a base rubber. A preferred base rubber of the rubber composition is a diene rubber. Specific examples of the diene rubber include natural rubber (NR), polyisoprene (IR), polybutadiene (BR), acrylonitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR), and polychloroprene (CR). . Two or more kinds of rubbers may be used in combination. In the tire 2, from the viewpoint of adhesiveness, natural rubber is preferable as the main component of the base rubber.

  The rubber composition for the second chafer 54 can include a reinforcing agent. A typical reinforcing agent is carbon black. A preferred carbon black is a furnace black such as FEF, GPF, HAF, ISAF, or SAF. From the viewpoint of the strength of the second chafer 54, the furnace black is more preferably FEF (for example, N550 based on ASTM D1765) and GPF (for example, N660 based on ASTM D1765). In the tire 2, silica may be used together with carbon black. In this case, dry silica and wet silica are used.

  In the tire 2, from the viewpoint of the strength of the second chafer 54, the amount of 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 the influence on the rolling resistance by the second chafer 54 is suppressed, the amount of carbon black is preferably 60 parts by mass or less.

  The rubber composition for the second chafer 54 includes polypropylene powder. This polypropylene powder may be one dried after polymerization, or one obtained by freeze-pulverizing one dried after polymerization. There is no restriction | limiting in particular in the manufacturing method of this polypropylene powder.

  In the tire 2, the polypropylene powder has a particle size of 1 μm or more. From the viewpoint of being easily dispersed without being unevenly distributed in the rubber composition, the particle size of the polypropylene powder is preferably 500 μm or less, more preferably 300 μm, and particularly preferably 100 μm or less.

  The rubber composition for the second chafer 54 includes a filler, a softener, a tackifier, a crosslinking agent such as sulfur, a vulcanization accelerator, a crosslinking aid, and an anti-aging agent in addition to the reinforcing agent and the polypropylene powder. Or other chemicals. In consideration of the workability and performance of the tire 2, an optimal chemical is blended in the rubber composition in an optimal amount.

  As described above, in the tire 2, the rubber composition for the second chafer 54 includes polypropylene powder. The inventors have investigated the water permeability coefficient of various rubber compositions, and have unexpectedly found that the rubber composition containing polypropylene powder can suppress the transmission of moisture and the like. The second chafer 54 of the present invention is based on this finding.

In the tire 2, the moisture permeability coefficient of the second chafer 54 is less than 5000 × 10 ⁻¹⁰ (cm ³ · cm / cm ² · sec · cmHg). Specifically, this transmission coefficient ranges from 3000 × 10 ⁻¹⁰ (cm ³ · cm / cm ² · sec · cmHg) to 4000 × 10 ⁻¹⁰ (cm ³ · cm / cm ² · sec · cmHg). is there. On the other hand, the transmission coefficient of the inner liner 14 is about 2000 × 10 ⁻¹⁰ (cm ³ · cm / cm ² · sec · cmHg), and the transmission coefficient of the conventional chafer 20 is 15000 × 10 ⁻¹⁰ (cm ³ · cm / cm ² · sec · cmHg). That is, in the second chafer 54 of the present invention, although not as much as the inner liner 14, the permeation of moisture and the like is suppressed as compared with the conventional chafer. The permeation coefficient is measured according to JIS K 7126 “Testing method for gas permeability of plastic film and sheet”.

  As described above, in the tire 2, the second chafer 54 has the first joint portion 56 with the inner liner 14 positioned on the inner side in the axial direction from the core 26, and the second joint portion with the first chafer 52. It arrange | positions so that 58 may be located in the radial inside rather than this core 26. FIG. As apparent from FIG. 2, in the tire 2, when the tire 2 is assembled into the rim 44, the second chain is formed in a portion where a gap is likely to be formed between the tire 2 and the rim 44. The fur 54 is located.

  In the tire 2, the second chafer 54 is located on the inner side in the radial direction of the core 26 including the bundle 32 of the steel wires 30 and the carcass ply 36 including the steel cord. In the tire 2, the second chafer 54 prevents moisture and the like from penetrating into the tire 2, thereby preventing rust from occurring in the core 26 and the carcass cord as seen in the conventional tire. That is, according to the present invention, it is possible to obtain the pneumatic tire 2 in which prevention of rust generation in the core 26 and the carcass cord of the bead 8 is achieved.

  As described above, in the tire 2, in the rubber composition for the second chafer 54, the main component of the base rubber is preferably natural rubber. The second chafer 54 is sufficiently joined to the inner liner 14. The second chafer 54 is also sufficiently joined to the first chafer 52. The second chafer 54 is difficult to peel off from the tire 2. The second chafer 54 contributes to the durability of the tire 2. From this viewpoint, when the base rubber contains natural rubber as a main component, the ratio of the weight of the natural rubber to the weight of the base rubber is preferably 70% by weight or more, and more preferably 80% by weight or more.

  In the tire 2, as described above, the polypropylene powder contained in the rubber composition for the second chafer 54 effectively contributes to the suppression of permeation of moisture and the like. For this reason, in order to suppress permeation of moisture and the like, the base rubber of this rubber composition does not need to contain butyl rubber such as butyl rubber and halogenated butyl rubber used for the base rubber of the inner liner 14. According to the present invention, it is possible to obtain the second chafer 54 in which the permeation of moisture and the like is effectively suppressed while maintaining good adhesiveness. From this viewpoint, in the tire 2, the second chafer 54 is Therefore, it is preferable that the base rubber of the rubber composition does not contain a butyl rubber.

  In the tire 2, in the rubber composition for the second chafer 54, the amount of the polypropylene powder is preferably 10 parts by mass or more and preferably 40 parts by mass or less with respect to 100 parts by mass of the base rubber. By setting the amount of the polypropylene powder to 10 parts by mass or more, the second chafer 54 effectively contributes to suppression of permeation of moisture and the like. From this viewpoint, the amount of the polypropylene powder is more preferably 15 parts by mass or more. By setting the amount of the polypropylene powder to 40 parts by mass or less, the strength of the second chafer 54 is appropriately maintained. From this viewpoint, the amount of the polypropylene powder is more preferably 35 parts by mass or less.

  As shown in FIG. 2, the outer end 60 of the second chafer 54 is located outside the fitting end CE in the axial direction. In the tire 2, the second chafer 54 is located in a portion where there is a high possibility that a gap is formed between the tire 2 and the rim 44. Since the second chafer 54 is disposed so as to block the entry path of moisture and the like into the inside of the tire 2, the permeation of moisture and the like into the inside of the tire 2 is effectively suppressed. In the tire 2, the occurrence of rust in the core 26 and the carcass cord is prevented. From this point of view, in the tire 2, it is preferable that the outer end 60 of the second chafer 54 is located outside the fitting end CE in the axial direction.

  When the tire 2 is assembled into the rim 44, the bead 8 portion of the tire 2 is slid the seat 48 of the rim 44 outward in the axial direction. In the tire 2, the first chafer 52 is positioned radially inward of the second chafer 54 at the second joint portion 58 between the second chafer 54 and the first chafer 52. Therefore, when the portion of the bead 8 slides on the seat 48, the first chafer 52 may be peeled off from the second chafer 54, or the second chafer 54 may be peeled off from the first chafer 52. Effectively prevented. In the tire 2, in the tire 2, the first chafer 52 is connected to the second chafer from the viewpoint that damage caused by the second joint portion 58 can be suppressed when the tire 2 is fitted to the rim 44. It is preferable to be located on the radially inner side of the fur 54. From the viewpoint that the portion of the bead 8 can smoothly slide on the seat 48, as shown in FIG. 2, the inner end 62 of the first chafer 52 is inward of the fitting end CE in the axial direction. More preferably it is located.

  In the tire 2, the first chafer 52 is located on the radially inner side of the second chafer 54 in the second joint portion 58 from the viewpoint of smooth fitting to the rim 44 and prevention of occurrence of rust. More preferably, the fitting end CE is located between the inner end 62 of the first chafer 52 and the outer end 60 of the second chafer 54 in the axial direction.

  In FIG. 2, a double arrow LL is an axial distance from the inner end 62 of the first chafer 52 to the outer end 60 of the second chafer 54. This distance LL is also the axial length of the second joint portion 58. A double-headed arrow L1 is an axial distance from the fitting end CE to the inner end 62 of the first chafer 52. A double-headed arrow L2 is an axial distance from the fitting end CE to the outer end 60 of the second chafer 54.

  In the tire 2, the distance LL is preferably 10 mm or more and 20 mm or less. By setting the distance LL to be equal to or greater than 10 mm, a second joining portion 58 in which the first chafer 52 and the second chafer 54 are sufficiently joined is obtained. In the tire 2, it is effectively prevented that the first chafer 52 is peeled off from the second chafer 54 and the second chafer 54 is peeled off from the first chafer 52. The tire 2 is excellent in durability. From this viewpoint, the distance LL is more preferably 12 mm or more. By setting the distance LL to 20 mm or less, the second joint portion 58 including the second chafer 54 having a sufficient thickness is obtained. The second joint portion 58 effectively suppresses the transmission of moisture and the like. In the tire 2, the occurrence of rust in the core 26 and the carcass cord is prevented. From this viewpoint, the distance LL is more preferably 18 mm or less.

  In the tire 2, the distance L1 is preferably 5 mm or more and 10 mm or less. By setting the distance L1 to be 5 mm or more, the first chafer 52 effectively contributes to smooth fitting to the rim 44. From this viewpoint, the distance L1 is more preferably 6 mm or more. By setting the distance L1 to be 10 mm or less, the second bonding portion 58 effectively contributes to suppression of permeation of moisture and the like. From this viewpoint, the distance L1 is more preferably 9 mm or less.

  In the tire 2, the distance L2 is preferably 5 mm or more and 10 mm or less. By setting the distance L2 to be 5 mm or more, the second chafer 54 effectively contributes to suppression of permeation of moisture and the like. From this viewpoint, the distance L2 is more preferably 6 mm or more. By setting the distance L2 to 10 mm or less, the strength of the second joint portion 58 is appropriately maintained. In this respect, the distance L2 is more preferably 9 mm or less.

  In FIG. 2, a double-headed arrow t is the thickness of the chafer 20 at the fitting end CE. In the tire 2, the thickness t of the chafer 20 is preferably 1.5 mm or more and 3.0 mm or less. When the thickness t is set to 1.5 mm or more, the chafer 20 effectively contributes to suppression of permeation of moisture and the like. In this respect, the thickness t is more preferably 1.7 mm or more. By setting the thickness t to 3.0 mm or less, the influence of the chafer 20 on the durability of the tire 2 can be effectively suppressed. In this respect, the thickness t is more preferably 2.8 mm or less. In the tire 2, the chafer 20 has a substantially uniform thickness t particularly from the fitting end CE toward the toe T of the tire 2.

  In the tire 2, the inner end 64 of the second chafer 54 is positioned on the outer side in the radial direction than the corner portion b of the core 26, that is, the axially inner end of the core 26. In the tire 2, the second chafer 54 contributes to suppression of permeation of moisture and the like also on the inner side in the axial direction of the core 26. In the tire 2, generation of rust in the core 26 and the carcass cord is effectively prevented. From this point of view, in the tire 2, it is preferable that the inner end 64 of the second chafer 54 is located radially outside the axially inner end of the core 26. Specifically, the inner end 64 of the second chafer 54 is preferably disposed such that the radial distance from the inner end 64 in the axial direction of the core 26 to the inner end 64 is 3 mm or more and 15 mm or less. .

  As shown in FIG. 2, in the tire 2, the end portion of the inner liner 14 has a shape that tapers radially inward.

  As described above, in the tire 2, the second chafer 54 contributes to suppression of permeation of moisture and the like. For this reason, even if the joint portion of the inner liner 14 and the second chafer 54 is tapered like the tire 2, good leakage resistance performance is prevented while preventing rust from occurring in the core 26 and the like. Can be maintained. In addition, by forming the end portion of the inner liner 14 in a shape that tapers inward in the radial direction, air is effectively prevented from being caught in the end portion in the manufacture of the tire 2. The inner liner 14 having an end portion that is tapered inward in the radial direction suppresses the influence on the mass of the tire 2. The second chafer 54 contributes to the manufacture of the high-quality tire 2 and the weight reduction of the tire 2.

  In the tire 2, the inner end 64 portion of the second chafer 54 has a shape that tapers outward in the radial direction. As described above, the end portion of the inner liner 14 has a shape that tapers radially inward. In the tire 2, each of the second chafer 54 and the inner liner 14 has a tapered shape at the first joint portion 56 between the second chafer 54 and the inner liner 14. In the tire 2, the influence on the mass of the tire 2 by the first joint portion 56 is suppressed to be small.

  In the tire 2, a portion of the inner end 64 of the second chafer 54 has a tapered shape radially outward from the end of the inner liner 14, and an end portion of the inner liner 14 is formed of the second chafer 54. It is preferable to have a tapered shape radially inward from the inner end 64. This prevents a portion having a specific thickness from being formed in the portion constituted by the inner liner 14 and the second chafer 54, that is, the first joint portion 56. In the tire 2, the portion constituted by the inner liner 14 and the second chafer 54 is constituted with a substantially uniform thickness as a whole. The portion constituted by the inner liner 14 and the second chafer 54 contributes to the suppression of the transmission of moisture and the like as a whole.

  When the tire 2 is incorporated in the rim 44, a force in the compression direction acts on a portion located between the core 26 and the rim 44. In this state, since the tire 2 is held for a long time, the shape of this portion is stored in this compressed state. When the shape is memorized in this way, the action against the force in the compression direction in this portion disappears. This loss of action affects the durability of the tire 2. In the tire 2, the tie gum 16 extends along the carcass 10 outside the inner liner 14, and an end portion 66 of the tie gum 16 is located between the second chafer 54 and the core 26. The loss tangent of the tie gum 16 is smaller than that of a member made of a rubber composition containing, for example, butyl rubber in the base rubber. In the tie gum 16, even when the shape is changed by the action of a force in the compression direction, the shape is easily recovered. In other words, since the action against the force in the compression direction continues, deformation of the bead 8 portion that affects the durability can be suppressed. In the tire 2, good durability is maintained. From this point of view, in the tire 2, the end 66 of the tie gum 16 is preferably located between the second chafer 54 and the core 26.

  In the tire 2, the loss tangent of the tie gum 16 is preferably 0.15 or less. By setting the loss tangent to 0.15 or less, the tie gum 16 effectively suppresses deformation of the bead 8 portion. The tire 2 is excellent in durability. From this viewpoint, the loss tangent is more preferably 0.10 or less. Note that the lower the loss tangent, the better. The lower limit of the loss tangent is not set.

  FIG. 3 shows a part of a cross section of a pneumatic tire 72 according to another embodiment of the present invention. In FIG. 3, the vertical direction is the radial direction of the tire 72, the horizontal direction is the axial direction of the tire 72, and the direction perpendicular to the paper surface is the circumferential direction of the tire 72.

  The tire 72 has the same configuration as that of the tire 2 shown in FIG. Therefore, in this FIG. 3, the same code | symbol is attached | subjected to the member same as the member of the tire 2 of FIG. 1, and the description is abbreviate | omitted.

  In the tire 72, one end 76 of the filler 74 is located on the radially inner side of the core 26. The filler 74 extends from the one end 76 along the chafer 20 substantially outward in the radial direction. As shown in FIG. 3, the filler 74 does not cover the entire radially inner portion of the core 26, like the filler 18 of the tire 2 shown in FIG. It covers a part of the inner part in the direction. Such a filler 74 is also referred to as a sheet filler.

  Although not shown, this filler 74 is also composed of a large number of cords arranged in parallel and a topping rubber, like the filler 18 of the tire 2 shown in FIG. Each cord is inclined with respect to the radial direction. The cord material is steel. The filler 74 suppresses the fall of the bead 8 portion. This filler 74 contributes to the durability of the tire 72. In the tire 72, the other end of the filler 74 is covered with the cover rubber 42.

  In the tire 72 as well, the chafer 20 includes a first chafer 52 and a second chafer 54 as in the tire 2 shown in FIG. In the second chafer 54, the first joint portion 56 with the inner liner 14 is positioned on the inner side in the axial direction from the core 26, and the second joint portion 58 with the first chafer 52 is radially inward from the core 26. It arrange | positions so that it may be located in. In the tire 72, the second chafer 54 is located in a portion where there is a high possibility that a gap will be formed between the tire 72 and the rim when the tire 72 is incorporated into the rim.

  In the tire 72, the rubber composition for the second chafer 54 includes polypropylene powder. The second chafer 54 suppresses the permeation of moisture and the like as compared with the conventional chafer, although not as much as the inner liner 14.

  In the tire 72, since the second chafer 54 prevents moisture and the like from penetrating into the tire 72, rust is prevented from occurring in the core 26 and the carcass cord of the bead 8. From the viewpoint that the generation of rust can be more reliably suppressed, the second chafer 54 is preferably configured such that the inner end 60 thereof is positioned on the outer side in the axial direction than the one end 76 of the filler 74.

  As apparent from FIG. 3, in the tire 72, since a sheet filler is used as the filler 74, a portion where the filler 74 does not exist is formed between the outer surface of the tire 72 and the core 26. However, in the tire 72, the second chafer 54 is disposed so as to overlap with a portion where the filler 74 does not exist. In the tire 72, the second chafer 54 effectively suppresses the transmission of moisture and the like. In the tire 72, although the sheet filler is used as the filler 74, the occurrence of rust in the core 26 and the carcass cord of the bead 8 is prevented. The present invention has a more remarkable effect in the tire 72 in which a sheet filler is used as the filler 74.

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

[Example 1]
The tire shown in FIG. 1-2 was manufactured. The size of this tire is 11R22.5. In Example 1, a normal filler was employed.

  In Example 1, in the rubber composition for the second chafer, natural rubber (RSS # 3) and styrene butadiene rubber (trade name “SBR1500” manufactured by JSR) were used as the base rubber. This base rubber does not contain butyl rubber. This is indicated by “N” in the “butyl rubber” column of Table 1. In Example 1, the ratio of the mass of the natural rubber to the mass of the base rubber was set to 80% by mass. The trade name “NOVATEC PP” manufactured by Nippon Polypro Co., Ltd. was used as the polypropylene powder. The amount of the polypropylene powder was set to 20 parts by mass with respect to 100 parts by mass of the base rubber.

  The inner end of the first chafer was disposed on the inner side in the axial direction than the fitting end CE. This is indicated by “in” in the “first chafer end” column of Table 1. The outer end of the second chafer was disposed on the outer side in the axial direction than the fitting end CE. This is represented by “out” in the “second chafer end” column of Table 1. The length LL of the second joint portion was set to 15 mm. The thickness t of the chafer at the fitting end CE was set to 2.0 mm. The complex elastic modulus E * of the first chafer was 8.0 MPa.

[Example 2-5]
A tire of Example 2-5 was obtained in the same manner as in Example 1 except that the amount of polypropylene powder was as shown in Table 1 below.

[Comparative Example 1]
A tire of Comparative Example 1 was obtained in the same manner as in Example 1 except that a conventional chafer was used as the chafer. This comparative example 1 is a conventional tire. The complex elastic modulus E * of the chafer of Comparative Example 1 was 8.0 MPa.

[Reference Example 1]
In the rubber composition for the second chafer, the same procedure as in Example 1 was performed except that the natural rubber of the base rubber was replaced with a butyl rubber (halogenated butyl rubber: trade name “Bromobutyl 2255” manufactured by EXXON). A tire of Reference Example 1 was obtained. The use of butyl rubber as the base rubber is indicated by “Y” in the “butyl rubber” column of Table 1.

[Example 6]
A tire of Example 6 was obtained in the same manner as Example 1 except that the sheet filler shown in FIG.

[Example 7-8]
The tires of Examples 7-8 were the same as Example 6 except that the positions of the inner end of the first chafer and the outer end of the second chafer with respect to the fitting end CE were as shown in Table 2 below. Got.

[Comparative Example 2]
A tire of Comparative Example 2 was obtained in the same manner as Example 6 except that a conventional chafer was used as the chafer. This Comparative Example 2 is also a conventional tire. The complex elastic modulus E * of the chafer of Comparative Example 2 was 8.0 MPa.

[Examples 9-12]
Tires of Examples 9-12 were obtained in the same manner as in Example 6 except that the length LL was changed as shown in Table 3 below.

[Examples 13-16]
Tires of Examples 13-16 were obtained in the same manner as in Example 6 except that the thickness t was as shown in Table 4 below.

[Example 17]
A tire of Example 17 was obtained in the same manner as in Example 6 except that the complex elastic modulus E * of the first chafer was changed as shown in Table 4 below.

[Durability (WET)]
The tire was assembled in a rim (size = 7.50 × 22.5), water (about 300 cc) was put inside the tire, and then the tire was filled with air to set the internal pressure to a normal internal pressure. This tire was mounted on a drum-type running test machine, and a vertical load three times the normal load 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. This running was continued until the tire was damaged. After running, the tires were disassembled, the moisture content of the topping rubber of the carcass ply was measured, and it was confirmed whether rust was generated on the core and the carcass cord or whether fretting occurred on the carcass cord. The results are shown in Tables 1-4 below as indices. Regarding the moisture content, the smaller the numerical value, the less the moisture content, which is preferable. Regarding rust or fretting, the larger the value, the more rust or fretting is suppressed, which is preferable.

[Durability (DRY)]
The tire was assembled in a rim (size = 7.50 x 22.5), and the tire was filled with air to set the internal pressure to a normal internal pressure. In this evaluation, water is not introduced into the tire. This tire was mounted on a drum-type running test machine, and a vertical load three times the normal load 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 distance traveled until the tire was damaged (ply turn loose = PTL) was measured. After running, the tire was disassembled, and the bead deformation angle (angle β shown in FIG. 6 of JP-A-2003-07326) was measured, and the presence or absence of the inner liner was confirmed. The results are shown in Tables 1-4 below. The results for the distance traveled until damage occurs are shown in the index. The larger the value, the longer the travel distance and the better the durability. With respect to the deformation angle, measured values are shown. A smaller numerical value is preferable because deformation of the bead portion is suppressed. Regarding peeling, “Y” indicates that peeling was confirmed, and “N” indicates that this peeling was not confirmed. If there was no peeling, but cracking was observed, “crack” is written in the peeling column.

  As shown in Table 1-4, 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.

  The technology related to the chafer described above can be applied to various types of tires.

2, 72 ... tire 4 ... tread 6 ... sidewall 8 ... bead 10 ... carcass 14 ... inner liner 16 ... tie gum 18, 74 ... filler 20 ... Chafer 26 ... Core 28 ... Apex 30 ... Wire 36 ... Carcass ply 44 ... Rim 48 ... Seat 50 ... Flange 52 ... First chafer 54 ... Second chafer 56: first joining portion 58 ... second joining portion 60 ... outer end of second chafer 54 62 ... inner end of first chafer 52 66 ... tie gum 16 ends 76 ... one end of filler 74 78 ... other end of filler 74

Claims (7)

It has a pair of beads, carcass, inner liner and a pair of chafers,
The carcass is stretched between one bead and the other bead,
The inner liner is located inside the carcass;
Each chafer is located near each bead and is configured to contact the rim when the tire is incorporated into the rim,
The bead has a ring-shaped core,
The chafer has a first chafer and a second chafer,
The first chafer is located axially outside the bead;
The second chafer is joined to each of the inner liner and the first chafer;
The first joint portion between the second chafer and the inner liner is located on the inner side in the axial direction of the core, and the second joint portion between the second chafer and the first chafer is the radius of the core. Located inside the direction,
The second chafer is made of a rubber composition,
A pneumatic tire, wherein the rubber composition includes a base rubber and polypropylene powder. It also has tie gum,
The tie gum extends along the carcass outside the inner liner,
A pneumatic tire, wherein an end of the tie gum is located between the second chafer and the core. When a point corresponding to the axially inner end of the contact surface between the tire and the rim on the outer surface of the tire is a fitting end,
The pneumatic tire according to claim 1 or 2, wherein an outer end of the second chafer is positioned outside the fitting end in an axial direction. In the second joint portion, the first chafer is located radially inward of the second chafer,
The pneumatic tire according to claim 3, wherein an inner end of the first chafer is positioned on an inner side of the fitting end in the axial direction.   The pneumatic tire according to claim 3 or 4, wherein a thickness of the chafer at the fitting end is 1.5 mm or more and 3.0 mm or less.   The pneumatic tire according to any one of claims 1 to 5, wherein, in the rubber composition, the amount of the polypropylene powder is 10 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the base rubber. The pneumatic tire according to any one of claims 1 to 6, wherein the complex elastic modulus of the first chafer is 8.0 MPa or more.

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