JP7365252B2 - Pneumatic tire and its manufacturing method - Google Patents

Description

The present invention relates to a pneumatic tire and a method for manufacturing the same.

In the manufacture of pneumatic tires, tire components such as belts and treads are wound around a forming drum to form a cylindrical tread band. Meanwhile, tire constituent members such as an inner liner and carcass ply are wound around another molding drum to mold a cylindrical carcass band. Beads are attached to both ends of the molded carcass band, and the band is folded back around the beads to form a cylindrical green case.

After the tread band is transported to the radially outer side of the green case, the green case is expanded radially outward and bonded to the inner surface of the tread band, thereby forming a green tire. The molded green tire is vulcanized and molded using a vulcanization molding device to produce a pneumatic tire.

As inner liners for pneumatic tires manufactured in this manner, there are known inner liners that include an inner layer to ensure air impermeability and an outer layer to ensure adhesion to the carcass ply. . For example, Patent Document 1 discloses a pneumatic tire including an inner liner having an inner layer made of a butyl rubber layer and an outer layer made of a tie gum layer.

Japanese Patent Application Publication No. 2015-123935

In the pneumatic tire described in Patent Document 1, when an inner liner having an inner layer and an outer layer is wound, a joint portion is formed in which both circumferential ends of the tire are overlapped and joined. Therefore, the joint portion of the inner liner becomes thicker than the non-joint portion, and uniformity in the circumferential direction of the tire decreases. Therefore, it is desirable to form a joint portion in which both circumferential ends of the tire are butted against each other and joined together.

However, when manufacturing a pneumatic tire, when forming a joint by butting both ends of the inner liner in the tire circumferential direction, when the green case equipped with the inner liner bulges outward in the radial direction, the inner liner There is a risk that cracks may occur from the inner layer at the joint.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic tire and a method for manufacturing the same that can suppress cracks from occurring in the inner layer at a joint portion of an inner liner having an inner layer and an outer layer.

The present invention includes an inner liner having an inner layer constituting the inner surface of the tire and an outer layer disposed on the outer surface side of the tire of the inner layer, and the inner liner includes both ends of the inner layer and the outer layer in the tire circumferential direction. It has a joint portion in which the surfaces are butted and joined, and both end surfaces of the inner layer in the tire circumferential direction are larger in the tire circumferential direction with respect to the thickness direction of the inner liner than both end surfaces of the outer layer in the tire circumferential direction. To provide a pneumatic tire that is inclined.

With this configuration, at the joint part of the inner liner, the inner layer is butted against each other at a greater angle than the outer layer. It is possible to increase the bonding strength by increasing the contact area of the surfaces. Therefore, it is possible to suppress the generation of cracks from the inner layer at the joint portion of the inner liner.

The inner layer is made of a rubber material that has better air impermeability than the outer layer, and the outer layer is made of a rubber material that has better adhesiveness than the inner layer.

With this configuration, the inner liner has an inner layer made of a rubber material that is more air-impermeable than the outer layer, so cracks occur from the inner layer while ensuring air impermeability at the joints of the inner liner. can be restrained from doing so. Furthermore, since the inner liner has an outer layer made of a rubber material with better adhesiveness than the inner layer, it is possible to further suppress the occurrence of cracks at the joint portion of the inner liner.

It is preferable that both end surfaces of the inner layer in the tire circumferential direction and both end surfaces of the outer layer in the tire circumferential direction are spaced apart from each other in the tire circumferential direction.

With this configuration, the outer surface of the inner layer and the inner surface of the outer layer can be brought into contact in the tire circumferential direction between both end surfaces of the inner layer in the tire circumferential direction and both end surfaces of the outer layer in the tire circumferential direction. By increasing the contact area, the bonding strength can be increased, and the occurrence of cracks can be further suppressed.

Both end surfaces of the inner layer and the outer layer in the tire circumferential direction may be formed to be inclined linearly in the tire circumferential direction with respect to the thickness direction of the inner liner.

With this configuration, both end faces in the tire circumferential direction of the inner layer and the outer layer are formed to be inclined linearly, so both end faces in the tire circumferential direction of the inner layer and the outer layer can be formed relatively easily. It is possible to relatively easily prevent cracks from occurring at the joint portion of the inner liner.

Both end surfaces of the inner layer and the outer layer in the tire circumferential direction may be formed to be inclined in a curved shape in the tire circumferential direction with respect to the thickness direction of the inner liner.

With this configuration, both end faces in the tire circumferential direction of the inner layer and the outer layer are formed to be inclined in a curved manner, so that the inner layer and the outer layer of the tire are formed to be inclined in a straight line. It is possible to increase the contact area of each of the circumferential end surfaces to increase the joint strength and to suppress the occurrence of cracks in the joint portion of the inner liner.

The present invention also provides an inner liner having an inner layer constituting the inner surface of the tire and an outer layer disposed on the tire outer surface side of the inner layer, and the inner liner is wound into a cylindrical shape, and the inner layer and the outer layer are wound in a cylindrical shape. Both end surfaces of the outer layer in the tire circumferential direction are butted against each other to form a joint portion, and both end surfaces of the inner layer in the tire circumferential direction are smaller than both end surfaces of the outer layer in the tire circumferential direction in the thickness direction of the inner liner. To provide a method for manufacturing a pneumatic tire that is largely inclined in the tire circumferential direction.

With this configuration, at the joint part of the inner liner, the inner layer is butted against each other at a greater angle than the outer layer. It is possible to increase the bonding strength by increasing the contact area of the surfaces. Therefore, it is possible to suppress the generation of cracks from the inner layer at the joint portion of the inner liner.

According to the pneumatic tire and the method for manufacturing the same according to the present invention, it is possible to suppress cracks from occurring in the inner layer at the joint portion of the inner liner having the inner layer and the outer layer.

FIG. 1 is a meridian half-sectional view of a pneumatic tire according to an embodiment of the present invention. FIG. 3 is a cross-sectional view of the inner liner. FIG. 3 is a sectional view of the joint portion of the inner liner. FIG. 3 is a sectional view of a first modification of the joint portion of the inner liner. FIG. 7 is a sectional view of a second modification of the joint portion of the inner liner. FIG. 7 is a sectional view of a third modification of the joint portion of the inner liner.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a meridian half-sectional view of a pneumatic tire according to an embodiment of the present invention. As shown in FIG. 1, the pneumatic tire 1 according to the embodiment of the present invention has a tread portion 2 in contact with the road surface, and a pneumatic tire that extends inward in the tire radial direction TR from both sides of the tread portion 2 in the tire width direction TW. 1, and a pair of bead portions 4 located inside the pair of sidewall portions 3 in the tire radial direction TR and fixed to the rim of a wheel (not shown). .

The bead portion 4 includes a bead core 6 and a bead filler 7 disposed outside the bead core 6 in the tire radial direction. The bead cores 6 are formed into an annular shape by bundling a plurality of bead wires, and are arranged on both sides of the pneumatic tire 1 in the tire width direction. The bead filler 7 is annularly formed from a rubber material and has a substantially triangular cross section.

A carcass ply 8 is stretched between the pair of bead portions 4, specifically between the pair of bead cores 6. The carcass ply 8 is formed into a band shape by arranging a plurality of wires in parallel and covering them with a rubber material, and is wound around the bead core 6 from the inner side in the tire width direction to the outer side in the tire width direction on both sides in the tire width direction, and is wrapped around the bead filler 7. It extends radially outward along the tire.

An inner liner 20 is provided on the inner side of the carcass ply 8 in the tire radial direction to form the inner surface 1a of the tire and to maintain air pressure. The inner liner 20 is provided over the tread portion 2, the sidewall portions 3, and the bead portions 4. The inner liner 20 has an inner layer 21 that constitutes the tire inner surface 1a and an outer layer 22 that is disposed on the tire outer surface side of the inner layer 21, as shown in FIG. 3, which will be described later.

A first belt ply 10 and a second belt ply 11 disposed outside the first belt ply 10 in the tire radial direction are provided outside the carcass ply 8 in the tire radial direction in the tread portion 2 . The second belt ply 11 is provided so that the outer side in the tire width direction is on the inner side in the tire width direction (tire equator line C1 side) than the first belt ply 10 . The first and second belt plies 10 and 11 are formed into a band shape by arranging a plurality of wires in parallel and covering them with a rubber material, and each wire extends in the tire circumferential direction.

A cap ply 12 is arranged outside the second belt ply 11 in the tire radial direction. The cap ply 12 is for reinforcing the first and second belt plies 10 and 11, and is formed into a band shape by arranging a plurality of wires in parallel and covering them with a rubber material, and each wire extends in the tire circumferential direction. There is.

The pneumatic tire 1 includes a tread rubber 13 provided on the outside in the tire radial direction of the cap ply 12 in the tread portion 2 and forming the outer surface of the tread portion 2, and a tread rubber 13 provided on the outside in the tire radial direction of the cap ply 12 in the bead portion 4 and on the inside of the carcass ply 8 in the tire radial direction and the tire. Rim strip rubber 14 provided on both sides in the width direction and forming the outer surface of the bead portion 4; and side strip rubber 14 provided on the outer side in the tire width direction of the carcass ply 8 in the sidewall portion 3 and forming the outer surface of the sidewall portion 3. Wall rubber 15 is provided.

The pneumatic tire 1 will be further explained with reference to FIGS. 2 and 3.

In FIG. 2, a cross section of the inner liner 20 is shown as a cross section perpendicular to the width direction of the inner liner 20, specifically, a cross section perpendicular to the tire axis C2. As shown in FIG. 2, the inner liner 20 is wound into a cylindrical shape, and one end 20a, which is the tip of the inner liner 20 in the tire circumferential direction TC, and the other end 20b, which is the rear end, are butted together. A joint portion J1 is formed by joining.

In FIG. 3, a cross section of the joint portion J1 of the inner liner 20 is shown in an enlarged manner. The inner liner 20 is formed in a band shape and, as shown in FIG. 3, includes an inner layer 21 that constitutes the inner surface 1a of the tire, and an outer layer 22 that is disposed on the outer surface side of the inner layer 21. The inner layer 21 is made of a rubber material that has better air impermeability than the outer layer 22, and the outer layer 22 is made of a rubber material that has better adhesiveness than the inner layer 21.

The inner layer 21 is made of a rubber material having better air impermeability than the outer layer 22, such as butyl rubber. The outer layer 22 is made of a rubber material with better adhesive properties than the inner layer 21, such as natural rubber. The thickness of the inner layer 21 is set, for example, to 1.5 to 5.0 mm, and the thickness of the outer layer 22 is set, for example, to 1.0 to 2.5 mm.

When the inner liner 20 is wound into a cylindrical shape, one end 20a and the other end 20b are butted and joined. A joint portion J1, in which both end portions 20a and 20b of the inner liner 20 in the tire circumferential direction are butt-joined, is formed to have approximately the same thickness as the non-joint portion 20c excluding the joint portion J1. Thereby, it is possible to improve the uniformity in the tire circumferential direction TC compared to the case where both end portions 20a and 20b of the inner liner 20 in the tire circumferential direction are overlapped and joined.

At the joint portion J1 of the inner liner 20, one end surface 21a and the other end surface 21b in the tire circumferential direction, which are both end surfaces of the inner layer 21 in the tire circumferential direction, are butted and joined together, and the tire circumference, which is both end surfaces of the outer layer 22 in the tire circumferential direction, are butted and joined. The end surface 22a in one direction and the end surface 22b in the other direction are butted and joined.

Both tire circumferential end surfaces 21a and 21b of the inner layer 21 are formed to be inclined in the tire circumferential direction with respect to the thickness direction of the inner liner 20, and both tire circumferential end surfaces 22a and 22b of the outer layer 22 are formed to be inclined in the tire circumferential direction with respect to the thickness direction of the inner liner 20. It is formed to be inclined in the tire circumferential direction with respect to the thickness direction of the tire.

As shown in FIG. 3, both tire circumferential end surfaces 21a and 21b of the inner layer 21 are formed to be linearly inclined in the tire circumferential direction with respect to the thickness direction of the inner liner 20, such as the tire radial direction TR. . Both end surfaces 21a and 21b in the tire circumferential direction of the inner layer 21 have planes extending in the tire circumferential direction from an inner end P1a on the inner surface of the tire to an outer end P1b on the outer surface of the tire with respect to the thickness direction of the inner liner 20. It is formed to be inclined at θ1.

Both end surfaces 22a and 22b of the outer layer 22 in the tire circumferential direction are also formed to be inclined linearly in the tire circumferential direction with respect to the thickness direction of the inner liner 20, such as the tire radial direction TR, as shown in FIG. Ru. Both end surfaces 22a and 22b in the tire circumferential direction of the outer layer 22 have a plane extending in the tire circumferential direction from an end point P2a on the inner surface side of the tire to an outer end P2b on the outer surface side of the tire with respect to the thickness direction of the inner liner 20 at an inclination angle θ2. It is formed at an angle.

Both end surfaces in the tire circumferential direction of the inner liner 20 are provided such that both end surfaces 21a and 21b in the tire circumferential direction of the inner layer 21 and both end surfaces 22a and 22b in the tire circumferential direction of the outer layer 22 are continuous in the thickness direction of the inner liner 20. The outer end P1b of both tire circumferential end surfaces 21a, 21b of the inner layer 21 and the inner end P2a of the tire circumferential end surfaces 22a, 22b of the outer layer 22 are formed to coincide with each other.

In this embodiment, both tire circumferential end surfaces 21a and 21b of the inner layer 21 are more inclined in the tire circumferential direction with respect to the thickness direction of the inner liner 20 than the tire circumferential end surfaces 22a and 22b of the outer layer 22. . Both end surfaces 21a and 21b of the inner layer 21 in the tire circumferential direction are formed to have a larger inclination angle than both end surfaces 22a and 22b of the outer layer 22 in the tire circumferential direction.

The inclination angle θ1 of the tire circumferential end surfaces 21a, 21b of the inner layer 21 is set to be larger than the inclination angle θ2 of the tire circumferential end surfaces 22a, 22b of the outer layer 22. The inclination angle θ1 of the inner layer 21 is set to, for example, 50 to 70 degrees, the inclination angle θ2 of the outer layer 22 is set to, for example, 30 to 60 degrees, and the inclination angle θ1 of the inner layer 21 is set to, for example, 50 to 70 degrees. The angle is set to be larger than the angle θ2.

In the inner liner 20, an inner layer 21 and an outer layer 22 are integrally formed, and both end surfaces 21a and 21b of the inner layer 21 in the tire circumferential direction are closer to each other than the inner liner and the outer layer 22. The tire is cut by a cutting device so as to be formed with a large inclination in the tire circumferential direction with respect to the thickness direction of the tire, and is then supplied to a forming drum and wound into a cylindrical shape. Rim strip rubber 14 and carcass ply 8 are wound in a cylindrical shape on the outer side of the inner liner 20 in the tire radial direction.

In this way, in the pneumatic tire 1, the inner liner 20 having the inner layer 21 and the outer layer 22 is bonded by abutting both end surfaces 21a, 21b and 22a, 22b in the tire circumferential direction of the inner layer 21 and the outer layer 22, respectively. Both end surfaces 21a and 21b of the inner layer 21 in the tire circumferential direction are arranged in the tire circumferential direction with respect to the thickness direction of the inner liner 20 from both end surfaces 22a and 22b of the outer layer 22 in the tire circumferential direction. It is highly sloping.

Next, a method for manufacturing the pneumatic tire 1 will be explained.

When manufacturing the pneumatic tire 1, first, tire constituent members for molding a cylindrical tread band, such as the tread rubber 13 forming the tread portion 2, the first and second belt plies 10, 11, are prepared. . On the other hand, tire constituent members for molding a cylindrical carcass band, such as the inner liner 20 and the carcass ply 8, are prepared.

Then, tire constituent members such as the inner liner 20 and the carcass ply 8 are sequentially wound around the forming drum to form a cylindrical carcass band. In the molding of the carcass band, the inner liner 20 is wound into a cylindrical shape, and a joint portion J1 is formed in which both end surfaces 21a, 21b and 22a, 22b of the inner layer 21 and the outer layer 22 in the tire circumferential direction are butted against each other and joined. . Both end surfaces 21a and 21b in the tire circumferential direction of the inner layer 21 are formed to be more inclined in the tire circumferential direction with respect to the thickness direction of the inner liner 20 than both end surfaces 22a and 22b in the tire circumferential direction of the outer layer 22.

The carcass band is transferred to another forming drum, and then a bead core 6 and a bead filler 7 are assembled on both sides of the carcass band, and the carcass band is folded back around the bead core 6 on both sides in the width direction of the drum to form a cylindrical green. The case is molded.

Meanwhile, tire constituent members such as the first and second belt plies 10, 11 and tread rubber 13 are further wound around another molding drum to mold a cylindrical tread band. After the tread band is conveyed to the radially outer side of the green case, the green case is expanded radially outward in a toroidal shape, and the outer surface of the green case is joined to the inner surface of the tread band to form a carcass tread assembly. Ru.

Next, a pair of sidewall rubbers 15 are wrapped around the carcass tread assembly to form a green tire. The molded green tire is vulcanized and molded by a vulcanization molding machine equipped with a tire vulcanization mold, and a pneumatic tire 1 is manufactured.

Although the pair of sidewall rubbers 15 are wound and molded after the carcass tread assembly is molded, it is also possible to wrap and mold the sidewall rubbers 15 when molding the carcass band.

In this embodiment, the inner liner 20 has an inner layer 21 and an outer layer 22 integrally formed, and the inner liner 20 in which the inner layer 21 and the outer layer 22 are integrally formed is wound around a molding drum. The inner liner 20 is cut into a predetermined length by a cutting device and wound around the molding drum, but it is also possible to cut the inner liner 20 into a predetermined length by a cutting device in advance and wind it around the molding drum.

As described above, the pneumatic tire 1 according to the present embodiment includes the inner liner 20 including the inner layer 21 that constitutes the tire inner surface 1a and the outer layer 22 that is disposed on the tire outer surface side of the inner layer 21. The inner liner 20 has a joint portion J1 in which both end surfaces 21a, 21b and 22a, 22b of the inner layer 21 and the outer layer 22 in the tire circumferential direction are butted against each other and joined. Both end surfaces 21 a and 21 b of the inner layer 21 in the tire circumferential direction are more inclined in the tire circumferential direction with respect to the thickness direction of the inner liner 20 than both end surfaces 22 a and 22 b of the outer layer 22 in the tire circumferential direction.

As a result, at the joint J1 of the inner liner 20, the inner layer 21 is butted against each other at a greater angle than the outer layer 22. By increasing the contact area of both tire circumferential end surfaces of 21, the bonding strength can be increased. Therefore, it is possible to suppress the occurrence of cracks in the inner layer 21 at the joint portion J1 of the inner liner 20.

When a joint J1 is formed by butting and joining both ends 20a and 20b of the inner liner 20 in the tire circumferential direction during manufacture of the pneumatic tire 1, when the green case including the inner liner 20 bulges outward in the radial direction. It is possible to suppress cracks from occurring in the inner layer 21 at the joint portion J1 of the inner liner 20.

Further, the inner layer 21 is made of a rubber material that has better air impermeability than the outer layer 22, and the outer layer 22 is made of a rubber material that has better adhesiveness than the inner layer 21. As a result, the inner liner 20 has the inner layer 21 made of a rubber material that is more air-impermeable than the outer layer 22, so that the inner liner 20 can maintain air impermeability at the joint J1 of the inner liner 20 while maintaining the inner layer 21. It is possible to suppress the occurrence of cracks from 21. Moreover, since the inner liner 20 has the outer layer 22 made of a rubber material with better adhesiveness than the inner layer 21, it is possible to further suppress the occurrence of cracks at the joint portion J1 of the inner liner 20.

Further, both end surfaces 21a, 21b and 22a, 22b of the inner layer 21 and the outer layer 22 in the tire circumferential direction are each formed to be inclined linearly in the tire circumferential direction with respect to the thickness direction of the inner liner 20. As a result, both end surfaces 21a, 21b and 22a, 22b of the inner layer 21 and the outer layer 22 in the tire circumferential direction are formed to be inclined linearly, so that both end surfaces 21a of the inner layer 21 and the outer layer 22 in the tire circumferential direction are formed to be inclined linearly. , 21b and 22a, 22b can be formed relatively easily, and it is possible to relatively easily suppress the occurrence of cracks in the joint portion J1 of the inner liner 20.

Further, in the method for manufacturing the pneumatic tire 1 according to the present embodiment, an inner liner 20 having an inner layer 21 constituting the tire inner surface 1a and an outer layer 22 disposed on the tire outer surface side of the inner layer 21 is prepared. Then, the inner liner 20 is wound into a cylindrical shape, and a joint portion J1 is formed in which both end surfaces 21a, 21b and 22a, 22b of the inner layer 21 and the outer layer 22 in the tire circumferential direction are butted against each other and joined. Both tire circumferential end surfaces 21a and 21b are more inclined in the tire circumferential direction with respect to the thickness direction of the inner liner 20 than the tire circumferential end surfaces 22a and 22b of the outer layer 22.

As a result, at the joint J1 of the inner liner 20, the inner layer 21 is butted against each other at a greater angle than the outer layer 22. By increasing the contact area of both tire circumferential end surfaces of 21, the bonding strength can be increased. Therefore, it is possible to suppress the occurrence of cracks in the inner layer 21 at the joint portion J1 of the inner liner 20.

FIG. 4 is a sectional view of a first modification of the joint portion of the inner liner. FIG. 4 shows a modification of the joint portion of the inner liner in a cross section corresponding to FIG. 3. In FIG. Like the inner liner 30 shown in FIG. 4, both end surfaces 31a, 31b and 32a, 32b of the inner layer 21 and the outer layer 22 in the tire circumferential direction are respectively formed to be inclined in a curved shape. You may also do so.

Regarding the inner liner 30, both end surfaces 31a and 31b of the inner layer 21 in the tire circumferential direction are formed to be inclined in the tire circumferential direction with respect to the thickness direction of the inner liner 30, and both end surfaces of the outer layer 22 in the tire circumferential direction 32a and 32b are formed to be inclined in the tire circumferential direction with respect to the thickness direction of the inner liner 30.

Both end surfaces 31a and 31b of the inner layer 21 in the tire circumferential direction are each formed to be inclined in a curved shape in the tire circumferential direction with respect to the thickness direction of the inner liner 20, and are curved in the tire circumferential direction with respect to the thickness direction of the inner liner 30. A plane shown by a two-dot chain line extending in the direction from the inner end P1a on the inner surface side of the tire to the outer end P1b on the outer surface side of the tire is formed to be inclined at an inclination angle θ1. Both end surfaces 31a and 31b in the tire circumferential direction of the inner layer 21 are each formed in a curved shape extending from the inner surface of the tire toward the outer surface of the tire toward the other side in the tire circumferential direction.

Both end surfaces 32a and 32b of the outer layer 22 in the tire circumferential direction are also formed to be inclined in a curved manner in the tire circumferential direction with respect to the thickness direction of the inner liner 20, and are curved in the tire circumferential direction with respect to the thickness direction of the inner liner 30. A plane shown by a two-dot chain line extending in the direction from an end point P2a on the inner surface side of the tire to an outer end P2b on the outer surface side of the tire is formed to be inclined at an inclination angle θ2. Both end surfaces 32a and 32b of the outer layer 22 in the tire circumferential direction are each formed in a curved shape extending from the inner surface of the tire toward the outer surface of the tire toward the other side in the tire circumferential direction.

Regarding the inner liner 30, both end surfaces 31a and 31b of the inner layer 21 in the tire circumferential direction are more inclined in the tire circumferential direction with respect to the thickness direction of the inner liner 30 than both end surfaces 32a and 32b of the outer layer 22 in the tire circumferential direction. The inclination angle θ1 of both tire circumferential end faces 31a, 31b of the inner layer 21 is set to be larger than the inclination angle θ2 of the tire circumferential end faces 32a, 32b of the outer layer 22.

At the joint J1 where both tire circumferential end portions 30a, 30b are butted and joined, both tire circumferential end surfaces 31a, 31b of the inner layer 21 are butted and joined, and both tire circumferential end surfaces 32a, 32b of the outer layer 22 are butted and joined. They are butted and joined together.

In this way, even in the case where both end surfaces 31a, 32a, 31b, 32b in the tire circumferential direction of the inner layer 21 and outer layer 22 of the inner liner 30 are formed to be inclined in a curved shape, the joint portion J1 of the inner liner 30 Since the inner layer 21 is butted against each other at a greater angle than the outer layer 22, it is possible to suppress the occurrence of cracks in the inner layer 21 at the joint portion J1 of the inner liner 30.

Moreover, since both end surfaces 31a, 32a, 31b, and 32b in the tire circumferential direction of the inner layer 21 and the outer layer 22 are formed to be inclined in a curved manner, compared to the case where they are formed to be inclined in a straight line, The contact area of each of the tire circumferential end surfaces 31a, 32a, 31b, 32b of the inner layer 21 and the outer layer 22 is increased to increase the bonding strength and to suppress the occurrence of cracks at the joint J1 of the inner liner 30. be able to.

FIG. 5 is a sectional view of a second modification of the joint portion of the inner liner. FIG. 5 shows a modification of the joint portion of the inner liner in a cross section corresponding to FIG. 3. In FIG. As shown in the inner liner 40 shown in FIG. 5, both end surfaces 41a, 41b and 42a, 42b of the inner layer 21 and the outer layer 22 in the tire circumferential direction are inclined in a wavy and curved manner, respectively. It may also be formed by

Regarding the inner liner 40, both end surfaces 41a and 41b of the inner layer 21 in the tire circumferential direction are formed to be inclined in the tire circumferential direction with respect to the thickness direction of the inner liner 40, and both end surfaces of the outer layer 22 in the tire circumferential direction are formed so as to be inclined in the tire circumferential direction. 42a and 42b are formed to be inclined in the tire circumferential direction with respect to the thickness direction of the inner liner 40.

Both end surfaces 41a and 41b in the tire circumferential direction of the inner layer 21 are each formed to be inclined in a wavy curved manner in the tire circumferential direction with respect to the thickness direction of the inner liner 20, and A plane shown by a two-dot chain line extending in the tire circumferential direction from an inner end P1a on the tire inner surface side to an outer end P1b on the tire outer surface side is formed to be inclined at an inclination angle θ1. Both end surfaces 41a and 41b of the inner layer 21 in the tire circumferential direction are respectively formed in a wave-like curved shape extending from the inner surface of the tire toward the outer surface of the tire to the other side in the tire circumferential direction.

Both end surfaces 42a and 42b of the outer layer 22 in the tire circumferential direction are also formed to be inclined in a wavy and curved manner in the tire circumferential direction with respect to the thickness direction of the inner liner 40. A plane shown by a two-dot chain line extending in the tire circumferential direction from an end point P2a on the tire inner surface side to an outer end P2b on the tire outer surface side is formed to be inclined at an inclination angle θ2. Both end surfaces 42a and 42b of the outer layer 22 in the tire circumferential direction are each formed in a wavy curved shape extending from the inner surface of the tire toward the outer surface of the tire toward the other side in the tire circumferential direction.

Regarding the inner liner 40, both end surfaces 41a and 41b of the inner layer 21 in the tire circumferential direction are more inclined in the tire circumferential direction with respect to the thickness direction of the inner liner 40 than both end surfaces 42a and 42b of the outer layer 22 in the tire circumferential direction. The inclination angle θ1 of the tire circumferential end surfaces 41a, 41b of the inner layer 21 is set to be larger than the inclination angle θ2 of the tire circumferential end surfaces 42a, 42b of the outer layer 22.

At the joint J1 where the tire circumferential ends 40a and 40b are butted and joined, the tire circumferential end surfaces 41a and the other end surface 41b of the inner layer 21 are butted and joined, and the tire circumferential end surfaces 42a and 40b of the outer layer 22 are joined together. The other end surfaces 42b are butted and joined.

In this way, even in the case where both end surfaces 41a, 42a, 41b, and 42b of the inner layer 21 and the outer layer 22 in the tire circumferential direction are respectively formed to be inclined in a wavy curved manner, at the joint portion J1 of the inner liner 30, Since the inner layer 21 is butted against each other at a greater angle than the outer layer 22, it is possible to suppress the occurrence of cracks in the inner layer 21 at the joint portion J1 of the inner liner 30.

FIG. 6 is a sectional view of a third modification of the joint portion of the inner liner. FIG. 6 shows a modification of the joint portion of the inner liner in a cross section corresponding to FIG. 3. In FIG. Like the inner liner 50 shown in FIG. 6, it is also possible to provide both tire circumferential end surfaces 21a, 21b of the inner layer 21 and tire circumferential end surfaces 22a, 22b of the outer layer 22 separated in the tire circumferential direction TC. It is.

Like the inner liner 50, both end surfaces 21a, 21b of the inner layer 21 in the tire circumferential direction and both end surfaces 22a, 22b of the outer layer 22 in the tire circumferential direction are provided spaced apart in the tire circumferential direction TC. It is also possible to form the outer end P1b of the direction end surfaces 21a, 21b and the inner end P2a of the tire circumferential direction end surfaces 22a, 22b of the outer layer 22 apart in the tire circumferential direction TC.

Regarding the inner liner 50, both end surfaces 21a and 21b of the inner layer 21 in the tire circumferential direction are more inclined in the tire circumferential direction with respect to the thickness direction of the inner liner 50 than both end surfaces 22a and 22b of the outer layer 22 in the tire circumferential direction. , both end surfaces 21a and 21b of the inner layer 21 in the tire circumferential direction are formed to have a larger inclination angle than both end surfaces 22a and 22b of the outer layer 22 in the tire circumferential direction.

At the joint J1, where both tire circumferential ends 50a and 50b are butted and joined, both tire circumferential end surfaces 41a and the other end surface 41b of the inner layer 21 are butted and joined, and the tire circumferential end surfaces 42a and 50b of the outer layer 22 are butted and joined. The other end surfaces 42b are butted and joined.

In this way, when both tire circumferential end surfaces 21a, 21b of the inner layer 21 and tire circumferential end surfaces 22a, 22b of the outer layer 22 are provided spaced apart in the tire circumferential direction TC, the inner layer Since the outer surface 21c of the inner layer 21 and the inner surface 22c of the outer layer 22 can be brought into contact between the circumferential end surfaces 21a, 21b of the tire 21 and the tire circumferential end surfaces 22a, 22b of the outer layer 22, the joint By increasing the contact area at portion J1, the bonding strength can be increased, and the occurrence of cracks can be further suppressed.

In the third modification shown in FIG. 6, both end surfaces in the tire circumferential direction of the inner layer 21 and the outer layer 22, which are linearly inclined, are provided spaced apart in the tire circumferential direction TC. Even in the case where both end surfaces in the tire circumferential direction of the inner layer 21 and the outer layer 22 are inclined in a curved shape, as in the first modification example and the second modification example shown in FIG. It is also possible to provide both circumferential end surfaces separated in the tire circumferential direction TC.

The present invention is not limited to the illustrated embodiments, and various improvements and changes in design are possible without departing from the gist of the present invention.

1 Pneumatic tire 1a Tire inner surface 20, 30, 40, 50 Inner liner 21 Inner layer 21a, 31a, 41a One end surface in the tire circumferential direction of the inner layer 21b, 31b, 41b The other end surface in the tire circumferential direction of the inner layer 22 Outer layer 22a, 32a, 42a One end surface in the tire circumferential direction of the outer layer 22b, 32b, 42b The other end surface in the tire circumferential direction of the outer layer J1 Joint portion

Claims (6)

An inner liner having an inner layer constituting the inner surface of the tire and an outer layer disposed on the outer surface side of the tire of the inner layer,
The inner liner has a joint portion in which both end surfaces of the inner layer and the outer layer in the tire circumferential direction are butted and joined,
In the pneumatic tire, both end surfaces of the inner layer in the tire circumferential direction are more inclined in the tire circumferential direction with respect to the thickness direction of the inner liner than the both end surfaces of the outer layer in the tire circumferential direction. The inner layer is formed from a rubber material that has better air impermeability than the outer layer,
The pneumatic tire according to claim 1, wherein the outer layer is formed from a rubber material with better adhesiveness than the inner layer. The pneumatic tire according to claim 1 or 2, wherein both end surfaces of the inner layer in the tire circumferential direction and both end surfaces of the outer layer in the tire circumferential direction are provided apart from each other in the tire circumferential direction. Any one of claims 1 to 3, wherein both end surfaces of the inner layer and the outer layer in the tire circumferential direction are each formed to be inclined linearly in the tire circumferential direction with respect to the thickness direction of the inner liner. The pneumatic tire described in item 1. Any one of claims 1 to 3, wherein both end surfaces of the inner layer and the outer layer in the tire circumferential direction are each formed to be inclined in a curved shape in the tire circumferential direction with respect to the thickness direction of the inner liner. The pneumatic tire described in item 1. preparing an inner liner having an inner layer constituting the inner surface of the tire and an outer layer disposed on the outer surface side of the tire of the inner layer;
Winding the inner liner into a cylindrical shape and forming a joint portion in which both end surfaces of the inner layer and the outer layer in the tire circumferential direction are butted against each other and joined,
The method for manufacturing a pneumatic tire, wherein both end surfaces of the inner layer in the tire circumferential direction are more inclined in the tire circumferential direction with respect to the thickness direction of the inner liner than both end surfaces of the outer layer in the tire circumferential direction.

Images