JP6147577B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire. Specifically, the present invention relates to a carcass structure of a pneumatic tire.

  A conventional method for forming a carcass ply of a pneumatic tire will be described with reference to FIG. An unvulcanized carcass ply 4 is wound around the outer peripheral surface of the molding drum 2. One end 4a and the other end 4b in the circumferential direction of the carcass ply 4 are joined. Thereby, the carcass ply 4 is formed into a cylindrical shape.

  As a joint structure between the one end 4a and the other end 4b, a so-called overlap joint or a so-called zipper joint is known.

  As shown in FIG. 6A, in the overlap joint, one end 4a side end and the other end 4b side end overlap in the radial direction and are joined. In a tire having a carcass of this overlap joint, when the air pressure acts, the extension of the cord at the overlapping portion becomes non-uniform. For this reason, the phenomenon which dents along this joint part tends to arise. This dent phenomenon is called so-called joint dent. This joint dent impairs the appearance of the tire.

  As shown in FIG. 6B, in the zipper joint, one end 4a and the other end 4b are abutted and joined in the circumferential direction. In the carcass of the zipper joint, one end and the other end of the carcass ply are strongly abutted in the circumferential direction, so that the intervals of the carcass cords are likely to be uneven. This unevenness of the carcass cord also causes joint dent. Moreover, if the butting force between the one end and the other end of the carcass ply is weak, the joining is easily released. This disconnection is called a so-called opening. This mesh opening impairs the durability of the tire.

  Japanese Patent Laying-Open No. 2005-153349 and Japanese Patent Laying-Open No. 2006-168420 propose a joint structure in which the distance between cords is made uniform in a zipper joint. Thereby, generation | occurrence | production of a joint dent is suppressed and the one end and other end of a carcass can be joined more firmly.

JP 2005-153349 A JP 2006-168420 A

  However, even in these improved joint structures, if the butting force between one end and the other end of the carcass ply is too weak, an opening can occur. On the other hand, if this butting force is too strong, joint dents can occur. This joining structure requires high accuracy.

  An object of the present invention is to provide a tire excellent in durability while suppressing generation of joint dent.

The pneumatic tire according to the present invention has a tread whose outer surface forms a tread surface, a pair of sidewalls each extending substantially inward in the radial direction from the end of the tread, and each positioned radially inward of the sidewalls. A pair of beads and a carcass spanned between one bead and the other bead along the inside of the tread and the sidewall are provided.
This carcass is composed of a carcass ply. The carcass ply includes a ply body wound in the circumferential direction and a joint ply positioned between one end and the other end of the ply body in the circumferential direction. The ply body is composed of a cord and a topping rubber arranged in parallel to each other. The joint ply includes a joint body and fins extending in a circumferential direction away from the circumferential ends at a pair of circumferential ends of the joint body. The joint body is composed of a cord and a topping rubber arranged in parallel to each other. The one fin is overlapped and joined to one end of the ply body in the radial direction, and the other fin is overlapped and joined to the other end of the ply body in the radial direction. When the cord interval of the joint bodies arranged in parallel to each other is the interval Pj, the circumferential width Wf of the fin is not less than 2 times and not more than 7 times the interval Pj. The fin thickness Tf is not less than 0.2 times and not more than 0.7 times the thickness Tj of the joint body.

A method for producing a carcass ply for a pneumatic tire according to the present invention includes:
A preparation step of preparing an unvulcanized ply body, an unvulcanized joint ply and a molding drum;
A ply main body is wound around the outer peripheral surface of the forming drum, and a joining step in which one end and the other end in the circumferential direction of the ply main body are joined via an unvulcanized joint ply.
The ply body is composed of a plurality of cords and a topping rubber arranged in parallel to each other. The joint ply includes a joint body and a pair of fins extending in a circumferential direction away from the circumferential ends at a pair of circumferential ends of the joint body. The joint body is composed of a plurality of cords and a topping rubber arranged in parallel to each other.
In this joining step, one fin of the joint ply is overlapped and joined to one end of the ply body in the radial direction. The other fin is overlapped and joined to the other end of the ply body in the radial direction.

  Preferably, the thickness Tf of the pair of fins is formed thinner than the thickness Tj of the joint body.

  Preferably, in this manufacturing method, when the cord interval of the joint bodies arranged in parallel to each other is the interval Pj, the circumferential width Wf of the fin is not less than 2 times and not more than 7 times the interval Pj.

  Preferably, in this manufacturing method, the fin thickness Tf is not less than 0.2 times and not more than 0.7 times the thickness Tj of the joint body.

  In the tire according to the present invention, the occurrence of joint dent is suppressed. And it is suppressed that the durability of a tire is impaired. According to the manufacturing method of the present invention, a carcass ply in which generation of joint dent is suppressed can be easily 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 explanatory view showing a ply body, a joint ply, and a molding drum of the carcass ply for the tire of FIG. FIG. 3 is a cross-sectional view showing a part of the ply body and the joint ply of FIG. FIG. 4 is a cross-sectional view showing the joint ply of FIG. FIG. 5 is an explanatory view showing a conventional molding drum and a carcass ply. FIG. 6A is an explanatory view of a conventional carcass ply overlap joint, and FIG. 6B is an explanatory view of a conventional carcass ply zipper joint.

  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 10. In FIG. 1, the vertical direction is the radial direction of the tire 10, the horizontal direction is the axial direction of the tire 10, and the direction perpendicular to the paper surface is the circumferential direction of the tire 10. In FIG. 1, an alternate long and short dash line CL represents the equator plane of the tire 10. The shape of the tire 10 is symmetrical with respect to the equator plane except for the tread pattern.

  The tire 10 includes a tread 12, a sidewall 14, a bead 16, a carcass 18, a belt 20, a band 22, an inner liner 24, and a chafer 26. The tire 10 is a tubeless type. The tire 10 is attached to a passenger car.

  The tread 12 forms a tread surface 28 that contacts the road surface. The tread 12 is made of a crosslinked rubber. The sidewall 14 extends substantially inward in the radial direction from the end of the tread 12. The radially outer end of the sidewall 14 is joined to the tread 12. The sidewall 14 is made of a crosslinked rubber. The bead 16 is located on the radially inner side of the sidewall 14. The bead 16 includes a core 30 and an apex 32 extending outward from the core 30 in the radial direction. The core 30 includes a wound non-stretchable wire. The apex 32 is made of a highly hard crosslinked rubber.

  The belt 20 is located inside the tread 12 in the radial direction. The belt 20 is laminated with the carcass 18. The belt 20 includes an inner layer 34 and an outer layer 36. Each of the inner layer 34 and the outer layer 36 is composed of a large number of cords arranged in parallel and a topping rubber. The belt 20 may include three or more layers. The band 22 is located on the radially outer side of the belt 20. The band 22 is made of a cord and a topping rubber. The belt 20 is restrained by this cord.

  The inner liner 24 is located inside the carcass 18. The inner liner 24 is made of a crosslinked rubber. For the inner liner 24, rubber having excellent air shielding properties is used. The inner liner 24 holds the internal pressure of the tire 10.

  The chafer 26 is located in the vicinity of the bead 16. When the tire 10 is assembled into the rim, the chafer 26 comes into contact with the rim. By this contact, the vicinity of the bead 16 is protected. The chafer 26 is made of a crosslinked rubber having excellent wear resistance. The chafer 26 may be made of cloth and rubber impregnated in the cloth.

  The carcass 18 includes a carcass ply 38. The carcass ply 38 is stretched between the beads 16 on both sides, and extends along the tread 12 and the sidewalls 14. The carcass ply 38 is folded around the core 30 from the inner side to the outer side in the axial direction. By this folding, the carcass ply 38 is formed with a main portion 38a and a folding portion 38b.

  The carcass ply 38 includes a large number of cords arranged in parallel and a topping rubber. In the tire 2, the absolute value of the angle formed by each cord with respect to the equator plane is 75 ° to 90 °. In other words, the carcass 18 has a radial structure. The cord is made of organic fiber. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers. The carcass 38 may be formed from two or more plies. The carcass ply 38 is formed by using the manufacturing method of the present invention.

  The manufacturing method of the carcass ply 38 of the present invention will be described with reference to FIGS. The aforementioned carcass ply 38 is obtained from the cylindrical carcass ply 40 shown in FIG. The manufacturing method of the cylindrical carcass ply 40 includes a preparation step and a joining step.

  In this preparation step, a molding drum 42, a ply body 44 and a joint ply 46, which are members of the tubular carcass ply 40, are prepared.

  In the joining step, the ply body 44 is wound around the outer peripheral surface of the molding drum 42. A circumferential gap is formed between one end 44 a and the other end 44 b of the ply body 44. The joint ply 46 is disposed in this gap. One end 40a of the ply body 44 and the joint ply 46 are joined. The other end 40b and the joint ply 46 are joined. One end 40 a and the other end 44 b of the ply body 44 are joined via the joint ply 46. In this way, the cylindrical carcass ply 40 is formed.

  Although not shown, a member constituting the bead 16 is disposed at an axial end portion of the outer peripheral surface of the cylindrical carcass ply 40. The end portion of the tubular carcass ply 40 is folded back so as to wrap around the members constituting the bead 16. A member constituting the sidewall 14 is disposed on an inner side in the axial direction of a member constituting the bead 16. A member constituting the belt 20, a member constituting the band 22, and a member constituting the tread 12 are sequentially stacked on the axial center of the outer peripheral surface of the cylindrical carcass ply 40. In this way, a substantially cylindrical green tire is formed.

  This raw tire is molded into a tire 10 in which the tread 12 protrudes radially outward through a temporary molding process and a vulcanization molding process. A carcass ply 38 (carcass 18) along the tread 12 and the sidewall 14 is formed from the cylindrical carcass ply 40 through the temporary molding process and the vulcanization molding process.

  The joining structure of the cylindrical carcass ply 40 shown in FIG. 2 will be described with reference to FIGS. FIG. 3 shows a joining structure in a cross section perpendicular to the axial direction of the cylindrical carcass ply 40 of FIG.

  The ply body 44 includes a plurality of cords 48 and a topping rubber 50 arranged in parallel to each other. The cord 48 extends in the axial direction. A double arrow Tb in FIG. 3 indicates the thickness of the ply body 44. A double-headed arrow Pb indicates the circumferential pitch of the cord 48. In the ply body 44, cords 48 are arranged at a pitch Pb in the circumferential direction.

  As shown in FIG. 4, the joint ply 46 includes a joint body 52 and a pair of fins 54. The fin 54 extends in the circumferential direction away from the circumferential end at the circumferential end of the joint body 52. The joint ply 46 includes a plurality of cords 56 and a topping rubber 58. The plurality of cords 56 are disposed on the joint body 52. The plurality of cords 56 extend in the axial direction in parallel with each other.

  A double arrow Wj in FIG. 4 indicates the circumferential width of the joint body 52. A double arrow Tj indicates the thickness of the joint body 52. A double-headed arrow Wf indicates the circumferential width of the fin 54. The fins 54 protrude from the joint body 52 in the circumferential direction with a width Wf from one end to the other end in the axial direction. A double arrow Tf indicates the thickness of the fin 54. A double-headed arrow Pj indicates the pitch of the cord 56 in the circumferential direction. In the joint body 52, the cords 56 are arranged at a pitch Pj in the circumferential direction.

  For example, a member constituting the fin 54 is obtained by extruding with a roller die or a die having a fin shape. This member is joined to a member constituting the joint body 52. In this way, the joint ply 46 is obtained.

  As shown in FIG. 3, in the joining structure of the cylindrical carcass ply 40, the joint body 52 is sandwiched between one end 44 a and the other end 44 b in the circumferential direction of the ply body 44. The one end 44a and the other end 44b and the joint body 52 are butted in the circumferential direction. One fin 54 is overlapped in the radial direction with the end portion on the one end 44a side of the ply body 44, and the other fin 54 is overlapped in the radial direction with the end portion on the other end 44b side. The fins 54 and the ply body 44 are joined in the radial direction. One end 44a and the other end 44b of the ply body 44 and the joint body 52 are joined in the circumferential direction.

  In the carcass 10 of the tire 2, the fin 54 of the joint ply 46 and the ply main body 44 are superposed and joined in the radial direction, so that the joint strength is excellent. Due to this superposition, the opening of the joint of the cylindrical carcass ply 40 is suppressed. In order to suppress this opening, it is not necessary to attach the one end 44a and the other end 44b of the ply body 44 with a large force. Thereby, the intensity | strength of the circumferential direction of the carcass 10 is made more uniform.

  From the viewpoint of sufficiently obtaining this bonding strength, the fin width Wf is preferably at least twice the pitch Pj of the cord 56, and more preferably at least three times. On the other hand, in the joint ply 46 having the small width Wf, the bending of the fins is difficult to occur. From this viewpoint, the width Wf is preferably not more than 7 times the pitch Pj, more preferably not more than 5 times.

  The fin 54 having a large thickness Tf is excellent in bonding strength with the ply body 44. From this viewpoint, the thickness Tf of the fin 54 is preferably 0.2 times or more, and more preferably 0.3 times or more the thickness Tj of the joint body 52. On the other hand, the fin 54 having a small thickness Tf does not impair the appearance of the tire 2. From this viewpoint, the thickness Tf is preferably 0.7 times or less, more preferably 0.5 times or less of the thickness Tj.

  The material of the topping rubber of the joint ply 46 and the material of the topping rubber of the ply body 44 are the same. Thereby, sufficient joining strength is easy to be obtained. The material of the cord of the joint ply 46 and the material of the cord of the ply main body 44 are the same. Thereby, the intensity | strength of the circumferential direction of the carcass 10 is equalized.

  Further, from the viewpoint of making the strength of the carcass 10 uniform, the pitch Pb of the cord 48 of the ply body 44 and the pitch Pj of the cord 56 of the joint ply 46 are preferably made equal. More preferably, at the joint portion between the ply body 44 and the joint ply 46, the pitch Pc between the cord 48 and the cord 56 is preferably equal to the pitch Pb.

  In the present invention, the dimension of each member of the tire 2 is measured by a cross section cut out from the tire 10 as shown in FIG. In the present specification, the normal rim means a rim defined in a standard on which the tire 10 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 10 depends. “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.

  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 tire having the basic structure shown in FIG. 1 was prototyped. The tire size was “195 / 65R15”. Table 1 shows the ratio (Wf / Pj) between the circumferential width Wf of the joint ply fin and the pitch Pj of the cord and the ratio (Tf / Tj) between the fin thickness Tf and the joint body thickness Tj. It is shown.

[Comparative Example 1]
A tire was obtained in the same manner as in Example 1 except that the carcass was formed of an overlap joint.

[Comparative Example 2]
A tire was obtained in the same manner as in Example 1 except that the carcass was formed by a zipper joint.

[Example 2-3 and Comparative Example 3-6]
Tires were obtained in the same manner as in Example 1 except that the ratio (Wf / Pj) and the ratio (Tf / Tj) were changed as shown in Tables 1 and 2.

[Dent evaluation]
These tires were incorporated into regular rims. This tire was filled with air so as to be 3.0 kPa. This tire was set on an FV (Force Variation) measuring machine. The tire was rotated and the dent amount of the shoulder portion was measured using a distance sensor. This evaluation result was indexed with the evaluation result of Comparative Example 1 as 100. The results are shown in Tables 1 and 2. This index is preferable as the numerical value increases.

[Joint evaluation]
The tire was assembled in a regular rim, and the tire was filled with air until a predetermined high pressure was reached. The air pressure was maintained for a predetermined time. Thereafter, the dent appearance was observed. After the evaluation of the dent appearance, the dent was cut and checked for the occurrence of openings. The results are shown in Tables 1 and 2.

[durability]
A tire was incorporated into a regular rim, and the tire was filled with air to obtain a predetermined internal pressure. This tire was mounted on a drum-type running test machine, and a predetermined longitudinal load was applied to the tire. The tire was run on a drum at a predetermined speed. Tires that were not damaged after running a predetermined distance were indexed 100. For tires damaged in the course of reaching this predetermined distance, the evaluation results were indexed based on the distance traveled until failure. The results are shown in Tables 1 and 2. This index is preferable as the numerical value increases.

  As shown in Tables 1 and 2, the tire of the example has a higher evaluation than the tire of the comparative example. Although not shown in Tables 1 and 2, the productivity of Comparative Example 2 is about 30% lower than that of Comparative Example 1. The productivity of Example 1-3 and Comparative Example 3-6 was equivalent to that of Comparative Example 1. From these evaluation results, the superiority of the present invention is clear.

  The joining structure described above can be widely applied to the carcass ply of a pneumatic tire. The present invention can be applied to various pneumatic tires such as light trucks, small trucks, trucks / buses, and two-wheeled vehicles, as well as the passenger car tires exemplified here.

2, 42 ... Drum 4 ... Carcass ply 10 ... Tire 12 ... Tread 14 ... Side wall 16 ... Bead 18 ... Carcass 20 ... Belt 22 ... Band 24 ... Inner liner 26 ... Chafer 28 ... Tread surface 30 ... Core 32 ... Apex 34 ... Inner layer 36 ... Outer layer 38 ... Carcass ply 40 ... Cylindrical carcass ply 44 ... ply body 46 ... joint ply 48 ... cord 50 ... topping rubber 52 ... joint body 54 ... fin 56 ... cord 58 ... topping rubber

Claims (5)

A tread whose outer surface forms a tread surface, a pair of sidewalls each extending substantially inward in the radial direction from the end of the tread, a pair of beads each positioned radially inward of the sidewalls, the tread and the above A carcass is provided between one bead and the other bead along the inside of the sidewall,
This carcass is made up of carcass plies,
The carcass ply is composed of a ply body wound in the circumferential direction and a joint ply located between one end and the other end in the circumferential direction of the ply body,
This ply body consists of a cord and topping rubber arranged in parallel to each other,
The joint ply includes a joint body and a pair of circumferential ends of the joint body, and a fin extending in the circumferential direction away from the circumferential end,
This joint body consists of a cord and topping rubber arranged in parallel to each other,
This ply body does not include the fins extending in the circumferential direction at one end and the other end in the circumferential direction,
One fin of the joint ply is overlapped and joined to one end of the ply body in the radial direction, and the other fin of the joint ply is overlapped and joined to the other end of the ply body in the radial direction,
When the cord interval arranged parallel to each other of the joint body is the interval Pj,
The circumferential width Wf of the fin is not less than 2 times and not more than 7 times the interval Pj,
A pneumatic tire in which the thickness Tf of the fin is 0.2 to 0.7 times the thickness Tj of the joint body. A preparation step of preparing an unvulcanized ply body, an unvulcanized joint ply and a molding drum;
A ply main body is wound on the outer peripheral surface of the forming drum, and one end and the other end in the circumferential direction of the ply main body are provided with a joining step in which the uncured joint ply is joined therebetween,
This ply body consists of a plurality of cords and topping rubber arranged in parallel with each other,
The joint ply includes a pair of fins extending in a circumferential direction away from the circumferential end at a pair of circumferential ends of the joint body and the joint body,
This joint body consists of a plurality of cords and topping rubber arranged parallel to each other,
This ply body does not include the fins extending in the circumferential direction at one end and the other end in the circumferential direction,
In this joining step, one fin of the joint ply is superposed and joined to one end of the ply body in the radial direction, and the other fin of the joint ply is superposed and joined to the other end of the ply body in the radial direction. A method for manufacturing a carcass ply for a pneumatic tire.   The manufacturing method according to claim 2, wherein a thickness Tf of the pair of fins is formed to be thinner than a thickness Tj of the joint body. When the cord interval arranged parallel to each other of the joint body is the interval Pj,
The manufacturing method according to claim 2 or 3, wherein the circumferential width Wf of the fin is not less than 2 times and not more than 7 times the interval Pj.   The manufacturing method according to claim 3 or 4, wherein the thickness Tf of the fin is not less than 0.2 times and not more than 0.7 times the thickness Tj of the joint body.

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