JP4995520B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  The pneumatic tire includes a pair of beads and a carcass bridged between the beads. The carcass ply is usually folded from the inside to the outside around the bead. By folding, a main body and a pair of folded portions are formed on the ply. Such a carcass structure is referred to as a “1-0 structure”. The structure of the carcass having two plies folded back from the inside to the outside around the bead is called “2-0 structure”.

  This tire is obtained by vulcanizing a green tire. This green tire is obtained by assembling carcass plies, beads and other parts in a former. In the assembly, a carcass ply is wound on the former drum. A pair of beads are fitted on the carcass ply. The vicinity of the end of the carcass ply is folded around the bead.

  In this tire, the folded portion is laminated with the main body outside the main body. The end of the folded portion is located outside the main body. Since the tire is greatly strained on the outside, a large stress is applied to this end. It is not preferable that the end is located outside the main body in terms of durability of the tire. The end is a discontinuity point. When this end is located outside the main body, a minute step may be formed on the sidewall. The level difference impairs the appearance of the tire.

Japanese Patent Application Laid-Open No. 11-42908 discloses a tire provided with a carcass ply that is folded around the bead from the outside to the inside. The end of the ply is located inside the main body of the ply. This ply contributes to durability, appearance, steering stability, light weight, and the like.
JP-A-11-42908

  The tire described in the above publication is excellent in various performances. However, in the green tire assembly for this tire, the process of folding the ply around the bead from the outside to the inside is complicated. The productivity of this tire is low. Complex processes are also a cause of quality variation. An object of the present invention is to achieve both high productivity and high tire quality.

  A pneumatic tire according to the present invention includes a tread whose outer surface forms a tread surface, first and second sidewalls extending substantially inward in the radial direction from the end of the tread, and substantially radially inward of the sidewall. And first and second beads having a core and a carcass. The carcass includes first and second plies. The first ply extends along the tread and the first sidewall and is folded from the outside to the inside around the core of the first bead. The second ply extends along the tread and the second sidewall and is folded from the outside to the inside around the core of the second bead.

  Preferably, in the first ply, one end is located inside the first sidewall and the other end is located inside the tread. In the second ply, one end is located inside the second sidewall and the other end is located inside the tread.

  Preferably, the first ply and the second ply overlap. The overlap width Wo is 10 mm or more.

  Preferably, the tire further includes a belt positioned between the tread and the carcass. The overlap width Wo is smaller than the belt width Wb.

The tire manufacturing method according to the present invention includes:
(1) a step in which the first and second carcass plies are wound apart from each other on the drum;
(2) a step in which a first bead is fitted to the first carcass ply and a second bead is fitted to the second ply;
(3) The first carcass ply is bent at the first bead to form the main body and the folded portion, and (4) The second carcass ply is bent at the second bead to form the main body and the folded portion. And a step of laminating the main body with the main body of the first carcass ply.

  In the tire according to the present invention, the first ply and the second ply folded around the core from the outside to the inside contribute to various performances of the tire. In this tire, since the carcass is constituted by two plies which are separate members, the production thereof is easy.

  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. FIG. 2 is an enlarged view of a main part where the tire 2 of FIG. 1 is shown. 1 and 2, 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. 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 first sidewall 6, a second sidewall 8, a first bead 10, a second bead 12, a carcass 14, a belt 16, a band 18, an inner liner 20, and a chafer 22. . The tire 2 is a tubeless type. The tire 2 is mounted on a passenger car.

  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 24. The tread surface 24 is in contact with the road surface. A groove 26 is carved in the tread surface 24. The groove 26 forms a tread pattern. The groove 26 may not be cut in the tread 4.

  The first sidewall 6 extends substantially inward in the radial direction from one end of the tread 4. The second sidewall 8 extends substantially inward in the radial direction from the other end of the tread 4. These sidewalls 6 and 8 are made of a crosslinked rubber. The sidewalls 6 and 8 absorb the impact from the road surface by bending. Further, the side walls 6 and 8 prevent the carcass 14 from being damaged.

  The first bead 10 is located substantially inward in the radial direction from the first sidewall 6. The second bead 12 is located substantially inward of the second sidewall 8 in the radial direction. Each of the beads 10 and 12 includes a core 28 and an apex 30 that extends radially outward from the core 28. The core 28 has a ring shape. The core 28 includes a plurality of non-stretchable wires (typically steel wires). The apex 30 has a tapered shape that tapers outward in the radial direction. The apex 30 is made of a highly hard crosslinked rubber.

  The carcass 14 includes a first ply 32 and a second ply 34. The first ply 32 extends along the tread 4 and the first sidewall 6. The first ply 32 is folded around the core 28 of the first bead 10 from the outside to the inside. A main body 36 and a folded portion 38 are formed in the first ply 32 by folding. The folded portion 38 is inside the main body 36 in the axial direction. The second ply 34 extends along the tread 4 and the second sidewall 8. The second ply 34 is folded from the outside to the inside around the core 28 of the second bead 12. A main body 40 and a folded portion 42 are formed on the second ply 34 by folding. The folded portion 42 is inside the main body 40 in the axial direction. In the carcass 14, there is one ply (32 or 34) around one core 28. The carcass 14 does not include a ply folded around the core 28 from the inside to the outside. Such a structure of the carcass 14 is referred to as a “0-1 structure”.

  In the first ply 32, one end 44 is inside the first sidewall 6 and the other end 46 (see FIG. 2) is inside the tread 4. This end 46 is located on the left side of the equator plane CL. In the second ply 34, one end 48 is inside the second sidewall 8 and the other end 50 (see FIG. 2) is inside the tread 4. This end 50 is on the right side of the equator plane CL. The vicinity of the end 46 of the first ply 32 overlaps with the vicinity of the end 50 of the second ply 34. The first ply 32 is joined to the second ply 34. The first ply 32 is integrated with the second ply 34 by bonding.

  Although not shown, the first ply 32 and the second ply 34 are made of a cord and a topping rubber. The absolute value of the angle formed by the cord with respect to the equator plane is usually 70 ° to 90 °. In other words, the carcass 14 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.

  The belt 16 is located between the tread 4 and the carcass 14. The belt 16 is laminated with the carcass 14. The belt 16 reinforces the carcass 14. As apparent from FIG. 2, the belt 16 includes an inner ply 52 and an outer ply 54. Although not shown, each of the inner ply 52 and the outer ply 54 is made of a cord and a topping rubber. The cord is inclined with respect to the circumferential direction. The absolute value of the tilt angle is not less than 10 ° and not more than 35 °. The cord inclination direction of the inner ply 52 is opposite to the cord inclination direction of the outer ply 54. The belt 16 has a so-called cross-ply structure. A preferred material for the cord is steel. An organic fiber may be used for the cord.

  The band 18 is located between the belt 16 and the tread 4. The band 18 covers the belt 16. Although not shown, the band 18 is made of a fabric and rubber impregnated in the fabric.

  The inner liner 20 is joined to the inner peripheral surface of the carcass 14. The inner liner 20 is made of a crosslinked rubber. The inner liner 20 is made of rubber having excellent air shielding properties. The inner liner 20 plays a role of maintaining the internal pressure of the tire 2.

  The chafer 22 is located in the vicinity of the bead (10 or 12). When the tire 2 is incorporated into the rim, the chafer 22 comes into contact with the rim. By this contact, the vicinity of the core 28 is protected. The chafer 22 is usually made of cloth and rubber impregnated in the cloth. A chafer 22 made of a single rubber may be used.

  In the tire 2, the end 44 of the first ply 32 is located inside the main body 36. Therefore, no large stress is applied to the end 44. Similarly, no large stress is applied to the end 48 of the second ply 34. The tire 2 is excellent in durability. Since the end 44 of the first ply 32 is located inside the main body 36, a step due to the end 44 is unlikely to occur in the first sidewall 6. Similarly, the second sidewall 8 is unlikely to have a step due to the end 48. The tire 2 is excellent in appearance.

  In FIG. 2, the width of the overlap between the first ply 32 and the second ply 34 is indicated by an arrow Wo. The width Wo is measured in the axial direction. The width Wo is preferably 5 mm or more. In the tire 2 having the width Wo of 5 mm or more, the first ply 32 and the second ply 34 are firmly joined. The firm joining contributes to the strength of the tire 2. In this respect, the width Wo is more preferably 10 mm or more, and particularly preferably 20 mm or more. From the viewpoint of light weight of the tire 2, the width Wo is preferably smaller than the width Wb (see FIG. 1). The width Wb is an axial width of the belt 16. Specifically, the width Wo is preferably 100 mm or less.

  In the tire 2, the cord of the first ply 32 does not reach the second sidewall 8. Similarly, the cord of the second ply 34 does not reach the first sidewall 6. When the vehicle equipped with the tire 2 travels, the frequency band of noise generated from the tire 2 is different from that of the conventional tire. The tire 2 is excellent in silence.

  An end 46 (see FIG. 2) of the first ply 32 does not reach the second sidewall 8. Accordingly, the step due to the end 46 does not occur in the second sidewall 8. The end 50 (see FIG. 2) of the second ply 34 does not reach the first sidewall 6. Accordingly, the step due to the end 50 does not occur in the first sidewall 6. Since the first ply 32 and the second ply 34 are short, the tire 2 is lightweight.

  In FIG. 1, what is indicated by an arrow H is the height of the ends 44 and 48 from the base line BL. The height H is preferably 5 mm or more. The carcass 14 having a height H of 5 mm or more can withstand the internal pressure when the tire 2 is filled with air. In this respect, the height H is more preferably 15 mm or more. From the viewpoint of light weight, the height H is preferably 60 mm or less.

  FIG. 3 is an explanatory view showing an assembly process of a green tire for the tire 2 of FIG. In the assembly process, as shown in FIG. 3A, the first ply 32 and the second ply 34 are wound on the drum 56 of the former. The first ply 32 is separated from the second ply 34. As shown in FIG. 3B, the first bead 10 is fitted on the first ply 32, and the second bead 12 is fitted on the second ply 34. The first ply 32 is bent at the first bead 10 as indicated by the arrow A1. By this bending, the main body 36 and the folded portion 38 are formed in the first ply 32 as shown in FIG. The second ply 34 is bent at the second bead 12 as indicated by arrow A2. By this bending, the main body 40 and the folded portion 42 are formed on the second ply 34 as shown in FIG. The main body 40 of the second ply 34 overlaps the main body of the first ply 32. The second ply 34 is joined to the first ply 32 due to the adhesiveness of the unvulcanized rubber. The second ply 34 may be vulcanized and bonded to the first ply 32 by means such as electron beam irradiation. Other parts are assembled to obtain a green tire. In this green tire, the first ply 32 is folded around the core 28 of the first bead 10 from the outside to the inside. The second ply 34 is folded from the outside to the inside around the core 28 of the second bead 12. The green tire is pressurized and heated in a mold, and the tire 2 is obtained. The tire 2 has a “0-1 structure”.

  If one ply from the first bead 10 to the second bead 12 is used, this ply is inserted between the drum 56 and the beads 10 and 12 in order to achieve the “0-1 structure”. Need to be done. This insertion requires a complicated device. When this device is used for insertion, the tire quality varies. In the present invention, since the first ply 32 is a separate member from the second ply 34, the “0-1 structure” can be easily obtained. This manufacturing method is excellent in productivity. In this manufacturing method, variations in the quality of the tire 2 are suppressed.

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

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

[Example 1]
A pneumatic tire having the structure shown in FIG. 1 was produced. The size of this tire is “205 / 45ZR17”. This tire has a carcass of “0-1 structure”. The carcass includes a first ply and a second ply. The first ply and the second ply are folded from the outside to the inside around the core. The first ply and the second ply are overlapped. The overlap width Wo is 20 mm. The height H of the end of the folded portion is 45 mm. The belt width Wb is 178 mm.

[Example 3]
A tire of Example 3 was obtained in the same manner as Example 1 except that the end height H was 15 mm.

[Examples 2, 4 and 5]
Tires of Examples 2, 4 and 5 were obtained in the same manner as Example 1 except that the width Wo 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 the carcass was formed from one ply. The ply extends from one bead to the other. The ply is folded from the outside to the inside around the core. This carcass has a “0-1 structure”.

[Comparative Example 2]
A tire of Comparative Example 2 was obtained in the same manner as in Example 1 except that a “1-0 structure” carcass was provided. This carcass has one ply. The ply extends from one bead to the other. The ply is folded from the inside to the outside around the core.

[Evaluation of silence]
The tire was attached to a rim of “17 × 7-JJ”, and the tire was filled with air so that the internal pressure was 230 kPa. This tire was mounted on a passenger car having a displacement of 2500 cc. This passenger car was run on a rough asphalt road surface at a speed of 60 km / h. The driver was evaluated for road noise. The results are shown in Table 1 below. Larger numbers are preferable.

[Evaluation of Uniformity]
RFV and LFV were measured according to the conditions of the uniformity test defined in “JASO C607: 2000”. The average value of the results of measuring 20 tires is shown in Table 1 below.

[Evaluation of steering stability]
The tire was attached to a rim of “17 × 7-JJ”, and the tire was filled with air so that the internal pressure was 230 kPa. This tire was mounted on a passenger car having a displacement of 2500 cc. This passenger car was run on a racing circuit. The driver was asked to evaluate the response characteristics and limit behavior. The results are shown in Table 1 below. Larger numbers are preferable.

[Measurement of mass]
The mass of the tire was measured. This result is shown in Table 1 below as an index when Comparative Example 1 is set to 100.

  As shown in Table 1, the tire of each example is excellent in quietness, uniformity, steering stability, and productivity. 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 an enlarged view of a main part in which the tire of FIG. 1 is shown. FIG. 3 is an explanatory view showing an assembly process of a green tire for the tire of FIG.

Explanation of symbols

2 ... Pneumatic tire 4 ... Tread 6 ... First sidewall 8 ... Second sidewall 10 ... First bead 12 ... Second bead 14 ... Carcass 16 ... Belt 18 ... Band 28 ... Core 32 ... First ply 34 ... Second ply 36, 40 ... Main body 38, 42 ... Folded part 56 ... Drum

Claims (4)

A tread whose outer surface forms a tread surface, first and second sidewalls extending substantially inward in the radial direction from the end of the tread, and a first core having a core that is positioned substantially inward in the radial direction from the sidewall. A first and second bead and a carcass;
This carcass has first and second plies,
The first ply extends along the tread and the first sidewall and is folded from the outside to the inside around the core of the first bead,
The second ply extends along the tread and the second sidewall and is folded from the outside to the inside around the core of the second bead ;
The first ply and the second ply overlap at the central portion of the tread, and the overlap portion is in a range between two adjacent circumferential grooves, and is positioned below the groove. A pneumatic tire with an overlap width Wo of 10 mm or more . In the first ply, one end is located inside the first sidewall, and the other end is located inside the tread,
The tire according to claim 1, wherein in the second ply, one end is located inside the second sidewall and the other end is located inside the tread. The tire according to claim 1 or 2 , further comprising a belt positioned between the tread and the carcass and having a width Wb, wherein the width Wo is smaller than the width Wb. The first and second carcass plies are wound apart from each other on the drum;
The first bead is fitted to the first carcass ply and the second bead is fitted to the second ply;
The first carcass ply is bent at the first bead to form the main body and the folded portion, and the second carcass ply is bent at the second bead to form the main body and the folded portion, and the main body is and Nde including a step to be laminated to the body of the first carcass ply in the central portion of the tread,
The tire manufacturing method in which the laminated portion is disposed in a range between two circumferential grooves adjacent to each other in the tread, is not positioned below the groove, and an overlap width Wo is 10 mm or more .

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