Method for manufacturing tire

A method for manufacturing a tire includes forming a belt layer by bonding strip materials adjacent in the circumferential direction on the molding surface located on the outer circumferential side of the rigid core. Along the profile in the width direction of an outer circumferential surface of the rigid core, the rigid core is moved so that the molding surface is brought close to the strip material to be bonded, and the strip material is bonded to the molding surface extending in the longitudinal direction while rotating the rigid core in a direction in which the circumferential angle of the rigid core with respect to the longitudinal direction of the strip material changes, so that variation in the bonding margin, due to the position of the rigid core in the width direction, between strip materials that have been adjacently bonded to the molding surface in the circumferential direction is reduced.

TECHNICAL FIELD

The present technology relates to a method for manufacturing a tire, and more specifically, relates to a method for manufacturing a tire in which when forming a belt layer by sequentially arranging and attaching a large number of strip materials to the outer circumferential surface of a rigid core in a circumferential direction, and bonding strip materials that are adjacent in the circumferential direction, it is possible to suppress bonding disorder between the strip materials due to the circumferential length of the outer circumferential surface of the rigid core that varies depending on the position of the rigid core in the width direction.

BACKGROUND

A pneumatic tire is manufactured by vulcanizing an unvulcanized green tire formed by laminating tire components on a molding surface of the outer circumference of a cylindrical forming drum. In the belt layer serving as the tire components, a plurality of reinforcing cords aligned at a predetermined inclination angle with respect to the tire circumferential direction is coated with unvulcanized rubber. The belt layer is formed, for example, by applying a plurality of strip materials with a plurality of aligned reinforcing cords coated with unvulcanized rubber to the molding surface on the outer circumference of the forming drum in the circumferential direction, and bonding strip materials adjacent in the circumferential direction together (see Japan Unexamined Patent Publication No, H11-099564).

One method of forming a green tire is a method of sequentially laminating tire components on the outer circumference of a rigid core having an outer circumferential surface shape corresponding to the shape of the tire inner circumferential surface of the finished tire (for example, see Japan Unexamined Patent Publication No. 2012-171183). Tires typically have a profile in which the circumferential length varies depending on the position in the tire lateral direction. As a result, the outer circumferential surface of the rigid core also has a profile in which the circumferential length varies depending on the position in the width direction. Therefore, when the strip materials forming the belt layer are sequentially and simply extended in the width direction of the rigid core at a predetermined inclination angle with respect to the circumferential direction of the rigid core, and are arranged and bonded in the circumferential direction of the rigid core, depending on the position of the rigid core in the width direction, the overlap between adjacent strip materials in the circumferential direction is excessively large or excessively small, so that a variation occurs in the bonding margin between adjacent strip materials. The variation in the bonding margin adversely affects the quality of the manufactured tire, so there is room for improvement.

SUMMARY

The present technology provides a method for manufacturing a tire in which when forming a belt layer by sequentially arranging and attaching a large number of strip materials to the outer circumferential surface of a rigid core in a circumferential direction, and bonding strip materials that are adjacent in the circumferential direction, it is possible to suppress bonding disorder between the strip materials due to the circumferential length of the outer circumferential surface of the rigid core that varies depending on the position of the rigid core in the width direction.

A method for manufacturing a tire according the present technology is provided, comprising sequentially bonding a large number of strip materials on a molding surface located on an outer circumferential side of a rigid core having an outer circumferential surface with a profile in which a circumferential length changes at a position in a width direction, in manner of extending the strip materials in a width direction of the rigid core at an inclined direction with respect to a circumferential direction of the rigid core, and arranging and bonding the strip materials in the circumferential direction, so that a belt layer is formed by bonding together the strip materials that are adjacently bonded in the circumferential direction; forming a green tire having the belt layer; and vulcanizing the green tire, wherein, the rigid core is relatively moved along the profile that is preliminarily known so that the molding surface is brought close to the strip material to be bonded to the molding surface, and the strip materials to be bonded are extended in the longitudinal direction and bonded to the molding surface while relatively turning the rigid core in a direction in which a circumferential angle with respect to the longitudinal direction of the strip materials to be bonded changes, so that variation in bonding margin, due to the position in the width of the rigid core, between the strip materials to be bonded adjacent to each other in the circumferential direction is reduced.

According to the present technology, along the profile in the width direction of the outer circumferential surface of the rigid core that is preliminarily known, the rigid core is relatively moved so that the molding surface is brought close to the strip material to be bonded to the molding surface, and the strip material is bonded to the molding surface in a manner of extending in the longitudinal direction while relatively rotating the rigid core in a direction in which the circumferential angle of the rigid core with respect to the longitudinal direction of the strip material changes, and thus variation in the bonding margin, due to the position in the width direction of the rigid core, between strip materials that are adjacent in the circumferential direction and bonded to the molding surface is reduced. Therefore, this is advantageous to prevent the strip materials adjacent in the circumferential direction from excessively overlapping with each other, and also prevent gaps generated between adjacent strip materials. Accordingly, it is possible to suppress bonding disorder between the strip materials due to the circumferential length of the outer circumferential surface of the rigid core that varies depending on the position in the width direction. This contributes to improved quality of the manufactured tire.

DETAILED DESCRIPTION

Hereinafter, a method for manufacturing a tire according to the present technology will be described based on embodiments illustrated in the drawings.

According to the present technology, a tire20is manufactured by forming a green tire19using a forming device1illustrated inFIGS.1and2and vulcanizing the formed green tire19. Note that the present technology is not limited to a typical pneumatic tire, and may be applied to the manufacturing of various tires20such as solid tires or the like. The rigid core2illustrated inFIGS.1to3that is formed from metal or the like is used for forming the green tire19. The rigid core2has an outer circumferential surface shape corresponding to the shape of the tire inner circumferential surface of the completed tire20. Therefore, as illustrated inFIG.3, the outer circumferential surface2bof the rigid core2has a profile in which the circumferential length changes depending on the position of the rigid core2in the width direction. In general, the rigid core2has a profile in which the central portion of the rigid core2in the width direction protrudes further toward outer circumferential side than both end portions. The rigid core2is composed of, for example, a plurality of segments divided in the circumferential direction about a center shaft2a, and a support rod for supporting the segments from inside.

The width direction W and the circumferential direction L of the rigid core2correspond to the width direction and the circumferential direction of the green tire19and the completed tire20, respectively. The dot-dash line CL in the figures indicates the tire axis (the axis of the center shaft2a), and the dot-dash line Z indicates the revolution axis passing through the center of the rigid core2in the width direction W and orthogonal to the dot-dash line CL.

The forming device1includes a freely moving arm3for moving the rigid core2to an arbitrary position, a bonding unit4for bonding a strip material16, and a control unit10for controlling the operations of the freely moving arm3and the bonding unit4. Examples of the freely moving arm3include industrial robots and the like. The center shaft2aof the rigid core2is held on the tip end portion of the freely moving arm3, and the rigid core2is able to rotate about the center shaft2a. In addition, the rigid core2is able to rotate about the revolution axis Z.

In this embodiment, the bonding unit4(base frame5) is installed in a fixed state on the floor, and the rigid core2is movable; however, the rigid core2may be installed in a fixed state in a predetermined position and the bonding unit4is movably installed. Alternatively, the bonding unit4and the rigid core2may be movably installed. In other words, in the present technology, it is sufficient that the bonding unit4and the rigid core2are relatively movable.

The bonding unit4includes: a base frame5, a pair of pressing rollers6attached to the base frame5, and a movement mechanism7that horizontally moves the pressing rollers6in a direction toward or away from each other. The movement mechanism7includes, for example, a ball screw and a servo motor that rotates the ball screw. Alternatively, a fluid cylinder or the like may be used as the movement mechanism7. Each of the pressing rollers6may be configured to independently move horizontally, or may be configured to move horizontally in synchronization with each other.

The bonding unit4further includes a pressing body8that moves vertically between the pressing rollers6, and guides9disposed in the vicinity of each of the pressing rollers6. Each guide9is spaced apart in the axial direction of the rotation shaft, and has an externally fitted guide roller. Each guide9is disposed on the outer side (side in the direction in which the pressing rollers6are separated away from each other) of the adjacent pressing roller6, and is capable of moving horizontally along with the adjacent pressing rollers6.

Next, a procedure for manufacturing the tire20according to the present technology will be described.

As illustrated inFIG.4, predetermined tire components (such as an innerliner12, a carcass layer14, and the like) are sequentially bonded to the outer circumferential surface2bof the rigid core2illustrated inFIGS.1and2. More specifically, the innerliner12and the carcass layer14are laminated and bonded sequentially to the outer circumferential surface2bof the rigid core2to form a cylindrical shape. On both sides of the rigid core2in the width direction, a ring-shaped bead member13is disposed on the carcass layer14, and the carcass layer14is folded back around the bead core13aof each of the bead members13. In addition, unvulcanized side rubber17is laminated and bonded to both end portions of the carcass layer14in the width direction. Other tire components are also bonded as needed. Note that inFIGS.5to8, tire components other than a belt layer15(strip material16) are omitted and not illustrated.

Next, the cylindrical belt layer15is formed on the outer circumferential surface (molding surface14a) of the cylindrical carcass layer14that is bonded to the outer circumferential side of the rigid core2. As illustrated inFIG.5, the belt layer15is formed by bonding a plurality of strip materials16. In the belt layer15, a plurality of reinforcing cords16aaligned at a predetermined inclination angle with respect to the tire circumferential direction is coated with unvulcanized rubber. The forming device1is used to form the belt layer15.

Each of the strip materials16is formed by coating, with unvulcanized rubber, the plurality of reinforcing cords16athat are aligned in parallel. Therefore, first, the strip materials16are sequentially arranged one by one over the pair of pressing rollers6. At this time, as illustrated inFIG.1, the pair of pressing rollers6are at positions close to each other, and the pressing body8is at a position where it does not project above the respective pressing rollers6.

Each guide9is located at a position outside of the adjacent pressing roller6(on a side in a direction in which the pressing rollers6are separated from each other). The strip material16disposed is inserted between the pressing roller6and the guide9in such a manner to span over the pair of pressing rollers6. The central portion M of the strip material16in longitudinal direction is set above the pressing body8, and the strip material16is disposed between guide rollers of each of the guides9. The separation distance between the guide rollers of the guides9is set to be slightly greater than the strip width H of the strip material16; however, both are substantially of the same dimension.

The shape data of the rigid core2is inputted to the control unit10, and the data of the profile of the outer circumferential surface2bhaving a circumferential length that varies at the width direction position is also inputted to the control unit10. In addition, various data such as shape data (length, width, thickness) of the tire components used (12,13,14,15, and the like), specification data of the green tire19to be molded, and the like are also inputted.

Next, by cooperation of the rigid core2with the bonding unit4, the strip material16is bonded to the outer circumferential surface14aof the carcass layer14layered on the outer circumferential side of the rigid core2. In other words, the outer circumferential surface of the carcass layer14becomes the molding surface14ato which the strip material16is bonded.

In order to form the belt layer15, a plurality of strip materials16are sequentially bonded to the molding surface14a, extending in the width direction of the rigid core2in a direction oblique (inclination angle a) to the circumferential direction of the rigid core2. Then, the strip materials16bonded to the molding surface14aare bonded to each other in the circumferential direction to form the belt layer15.

Here, the outer circumferential surface2bof the rigid core2has a profile having a circumferential length that varies at the width direction position as described above. The innerliner12and the carcass layer14bonded sequentially to the outer circumferential surface2bare members having a constant thickness, and thus the molding surface14ato which the strip material16is bonded has a profile having a circumferential length (length in the circumferential direction) that varies at the width direction position in the same manner as the outer circumferential surface2b.

Therefore, the belt layer15is formed by actuating the rigid core2and the bonding unit4along the profile of the outer circumferential surface2bof the rigid core2that is inputted to the control unit10and preliminarily known. As illustrated inFIG.6, the pressing body8is moved upward of the strip material16which spans over the pair of pressing rollers6. Accordingly, the central portion M of the strip material16in the longitudinal direction is pressed against the molding surface14aand bonded at the central portion of the rigid core2in the width direction.

Next, as illustrated inFIG.7, the rigid core2is moved downward so as to bring the molding surface14ain proximity with the strip material16to be bonded to the molding surface14a, and the strip material16is bonded to the molding surface14ain a manner of extending in the longitudinal direction while turning the rigid core2about the revolution axis Z. More specifically, with the downward movement of the rigid core2, the rigid core2is turned in a direction in which the circumferential angle of the rigid core2with respect to the longitudinal direction of the strip materials16to be bonded changes, so that the variation in the bonding margin, due to the position in the width direction of the rigid core2(the bonding length in the circumferential direction of the opposing end surfaces of the strip materials16adjacent in the circumferential direction), between the strip materials16that are to be bonded adjacent to each other in the circumferential direction of the molding surface14ais reduced. Adjacent strip materials16are brought essentially in contact and bonded, and thus the bonding margin is neither plus nor minus, but is close to zero.

At both end portions in the width direction in the range corresponding to the tread of the rigid core2, the circumferential length of the molding surface14ais shorter than that of the central portion in the width direction. Therefore, when bonding the strip material16, the rigid core2is turned so that the inclination angle a is greater at both end portions in the width direction than in the central portion in the width direction.

Then, along with the turning of the rigid core2, the pair of pressing rollers6are horizontally moved in a direction away from each other. As a result, the strip material16to be bonded is sandwiched between the molding surface14aand the pressing rollers6, and the strip material16is extended in the longitudinal direction and pressed against and bonded to the molding surface14a.

For example, when it is set in advance to use N strip materials16having the same specification (strip width H) to form the belt layer15, the rigid core2would be turned as described below. The circumferential length K of the molding surface14aat the position in the width direction of the rigid core2illustrated inFIG.8can be predetermined. Then, in a case where the strip material16is bonded at an inclination angle a with respect to the circumferential direction of the rigid core2, the length t of the strip material16in the circumferential direction of the rigid core2at the position in the width direction is t=H/Sin(a). Then, the circumferential length K=the length t×N, so the following Equation (1) is introduced.
Inclination anglea=Sin−1(H·N/K)  (1)

Thus, when bonding each of the strip materials16to the molding surface14a, the rigid core2is turned so that the inclination angle a of the strip material16satisfies Equation (1) above, depending on the position in the width direction of the rigid core2.

In this embodiment, the profile of the rigid core2has a symmetrical shape with respect to the center in the width direction, and thus, after bonding the central portion M in the longitudinal direction of the strip material16to be bonded to the molding surface14aat the central portion in the width direction of the rigid core2, the strip material16is bonded from the central portion M in the longitudinal direction toward both ends in the longitudinal direction. This is advantageous to complete the bonding of the strip materials16in a shorter time.

In a case where the profile of the rigid core2is asymmetrical with respect to the center in the width direction, after bonding the central portion M in the longitudinal direction of the strip material16to be bonded to the molding surface14aat the central portion in the width direction of the rigid core2, for example, the strip material16is bonded to the molding surface14afrom the central portion M in the longitudinal direction toward one end in the longitudinal direction. Then, the strip material16may be bonded to the molding surface14astarting from the central portion M in the longitudinal direction toward the other end in the longitudinal direction.

By bonding the plurality of strip materials16to the molding surface14ain this manner, the belt layer15illustrated inFIG.9is formed. In a case of forming a plurality of belt layers15on the green tire19, another belt layer15is formed on the outer circumferential side of the belt layer15by the same process.

In this embodiment, the movement in the strip width direction of the portion of the strip material16in close proximity to that bonded to the molding surface14ais regulated by the guides9. Therefore, even when the strip material16is bonded to the molding surface14awhile the rigid core2is turned, it is advantageous to prevent defects that the strip material16already bonded to the molding surface14ais deviated.

Next, in order to form the green tire19illustrated inFIG.10, necessary tire components such as a belt reinforcing layer, unvulcanized tread rubber18, and the like are sequentially bonded to the outer circumferential surface of the belt layer15. In this way, a green tire19having a belt layer15is formed.

Next, as illustrated inFIG.11, the green tire19and the rigid core2are disposed inside a vulcanization mold11ainstalled in a vulcanization device11, and the vulcanization mold11ais closed. Then, by vulcanizing the green tire19under predetermined conditions inside the closed vulcanization mold11a, the tire20illustrated inFIG.12(the pneumatic tire20in this embodiment) is completed. After removed from the vulcanization mold11a, the completed tire20is separated from the rigid core2.

In a case of manufacturing a tire20integrated with the wheel, the wheel may be used as the rigid core2, for example. When manufacturing a tire20having such a configuration, it is not necessary to separate the completed tire20from the rigid core2(wheel) after vulcanizing the green tire19.

In the forming device1described above, the belt layer15is formed such that the rigid core2is disposed above the bonding unit4; however, as in the case of the forming device1illustrated inFIG.13, the belt layer15may be formed such that the rigid core2is disposed below the bonding unit4. In the forming device1, the bonding unit4(base frame5) is installed in a fixed state of being suspended downward from the support surface, and the rigid core2is movable by the freely moving arm3.

The forming device1has a configuration in which the vertical position relationship of the rigid core2and the bonding unit4of the forming device1illustrated inFIG.1is reversed, and the other configurations are substantially the same. However, the forming device1has a support roller9aon the outer side of each guide9. The strip material16is inserted between the pressing roller6and the guide9so as to span over the pair of pressing rollers6, and both end portions of the strip material16in the longitudinal direction are supported by the support rollers9a.

In addition, in the forming device1, the pair of pressing rollers6can be moved vertically. The configuration that allows the pair of pressing rollers6to move vertically is not essential, and may be adopted as necessary.

In order to form the belt layer15using the forming device1, the same method described in the above embodiment may be used. When bonding the strip material16to the outer circumferential surface14aof the carcass layer14bonded to the outer circumferential side of the rigid core2, the pair of pressing rollers6are moved downward as necessary. This makes it easier to adhere the strip material16to the outer circumferential surface14a.

In another forming device1illustrated inFIGS.14and15, the rigid core2is able to rotate about a center shaft2afixed to a supporting column2cerected on the floor. In other words, the rigid core2is installed on the floor surface in a fixed state (a state in which the rigid core2is unable to move in a plane). The bonding unit4is installed in a manner movable to any arbitrary position by the freely moving arm3. The bonding unit4is able to turn about a revolution axis Z that extends vertically through the center of the pressing body8when viewed in a plan view. Note that the rigid core2is fixed so that it is unable to turn about the revolution axis Z.

In the procedure of manufacturing the tire20using this forming device1, similar to the previous embodiment, the belt layer15is formed by actuating the rigid core2and the bonding unit4along the profile of the outer circumferential surface2bof the rigid core2that is inputted to the control unit10and preliminarily known; however, in this embodiment, the bonding unit4is moved. Thus, as illustrated inFIG.16, the pressing body8is moved upward of the strip material16in a state in which the strip material16spans over the pair of pressing rollers6. Accordingly, the central portion M of the strip material16in the longitudinal direction is pressed against the molding surface14aand bonded at the central portion of the rigid core2in the width direction.

Next, the bonding unit4is moved upward so that the molding surface14ais in close contact with the strip material16that is to be bonded to the molding surface14a, and while turning the bonding unit4about the revolution axis Z of the rigid core2, the strip material16is bonded to the molding surface14ain a manner of extending in the longitudinal direction. More specifically, with the upward movement of the bonding unit4, the revolution axis Z of the bonding unit4is made to coincide with the revolution axis Z of the rigid core2in a direction in which the angle of the circumferential direction of the rigid core2with respect to the longitudinal direction of the strip material16to be bonded changes, and the bonding unit4is turned about that revolution axis Z, so that the variation in the bonding margin, due to the position in the width direction of the rigid core2(the bonding length in the circumferential direction of the opposing end surfaces of the strip materials16adjacent in the circumferential direction), between the strip materials16that are to be bonded adjacent to each other in the circumferential direction of the molding surface14ais reduced. Adjacent strip materials16are brought essentially in contact and bonded, and thus the bonding margin is neither plus nor minus, but is close to zero.

At both end portions in the width direction in the range corresponding to the tread of the rigid core2, the circumferential length of the molding surface14ais shorter than that of the central portion in the width direction. Therefore, when bonding the strip material16, the bonding unit4is turned such that the inclination angle a is larger at both end portions in the width direction than at the center in the width direction.

Then, as illustrated inFIG.17, with the rotation of the bonding unit2, the pair of pressing rollers6are horizontally moved in a direction away from each other. As a result, the strip material16to be bonded is sandwiched between the molding surface14aand the pressing rollers6, and the strip material16is extended in the longitudinal direction and pressed against the molding surface14aand bonded.

By bonding a large number of strip materials16to the molding surface14ain this manner, the belt layer15illustrated inFIG.9is formed. The subsequent steps are the same as in the previous embodiment. Note that the arrangement described in the previous embodiment may be similarly applied to this embodiment as well.

In the present technology, while moving the rigid core2relatively so that the molding surface14amoves close to the strip material16, and bonding the strip material16to the molding surface14in a manner of extending in the longitudinal direction while relatively turning the rigid core2, variation in the bonding margin due to the position in the width direction of the rigid core2is reduced between the strip materials16that are to be bonded adjacent to the molding surface14ain the circumferential direction. Therefore, this is advantageous to prevent the strip materials16bonded to the molding surface14aand adjacent to each other in the circumferential direction from excessively overlapping in the circumferential direction, or to prevent gaps in the circumferential direction between adjacent strip materials16from occurring. Therefore, it is possible to suppress bonding disorder between the strip materials16due to the circumferential length of the outer circumferential surface2aof the rigid core2that varies depending on the position in the width direction. This also contributes to improved quality of the manufactured tire20.