Tire manufacturing method

Abstract

To provide a tire manufacturing method capable of reducing residual air around an overlap joint part included in a tire constituent member.SOLUTION: A tire manufacturing method includes a stitching process of pressing a press roller against an outer peripheral surface of a second tire constituent member while rotating a rotary support, for crimping the second tire constituent member to an outer peripheral surface of a cylindrical first tire constituent member supported by the rotary support. At an overlap joint part included in the first tire constituent member, when an end located relatively outside a radial direction is called an outer end, and an end located relatively inside the radial direction is called an inner end. In the stitching process, the rotary support is rotated along a predetermined direction so that the press roller passing through the overlap joint part goes from an outer peripheral surface of the outer end to an outer peripheral surface of the inner end.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a tire manufacturing method that includes a stitching process. [Background technology]

[0002] A known method for manufacturing pneumatic tires is to mold a green tire (unvulcanized tire) through a stitching process. In the stitching process, a pressure roller is pressed against the outer peripheral surface of a cylindrical first tire component supported by a molding drum while the molding drum is rotating, in order to press the second tire component onto the outer peripheral surface of the second tire component (see, for example, Patent Document 1).

[0003] Even when a stitching process is performed, air may remain between the first tire constituent member and the second tire constituent member. Such remaining air may cause defective tire molding, so it is desirable to reduce it as much as possible. The inventors' investigation revealed that air tends to remain around the overlap joint portion included in the first tire constituent member, and that taking measures to prevent this can achieve significant improvements. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-117173 Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure has been made in consideration of the above-described circumstances, and its purpose is to provide a tire manufacturing method that can reduce air remaining around an overlap joint portion included in a tire constituent member. [Means for solving the problem]

[0006] The tire manufacturing method of the present disclosure includes a stitching step of pressing a pressure roller against an outer peripheral surface of a cylindrical first tire constituent member supported by a rotary support member while rotating the rotary support member, in order to press a second tire constituent member onto an outer peripheral surface of the second tire constituent member, In the overlap joint portion included in the first tire constituent member, when an end portion located relatively radially outward is referred to as an outer end portion and an end portion located relatively radially inward is referred to as an inner end portion, In the stitching step, the rotary support is rotated in a predetermined direction so that the pressure roller passing through the overlap joint portion moves from the outer peripheral surface of the outer end portion to the outer peripheral surface of the inner end portion. [Brief explanation of the drawings]

[0007] [Figure 1] A half cross-sectional view showing the process of forming a green tire [Figure 2] A longitudinal cross-sectional view of the forming drum along the arrow XX in Figure 1(C) [Figure 3] Enlarged view of the main part of Figure 2 [Figure 4] Cross-section showing the overlap joint [Figure 5] Schematic diagram showing a process for forming a belt-like ply DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of a tire manufacturing method according to the present disclosure will be described with reference to the drawings.

[0009] FIG. 1 is a half-sectional view that schematically shows an example of a green tire molding process. First, as shown in FIG. 1(A), an inner liner rubber 1, a rim strip rubber 2, and a carcass ply 3 (a belt-like ply 60, described later) are wound in this order on a molding drum D1. This forms a cylindrical green case 10A that forms a carcass band. Next, as shown in FIG. 1(B), on a molding drum D2, beads 4 are assembled on both sides of the green case 10A, and the carcass ply 3 is folded back around the beads 4. This forms a cylindrical green case 10B that has been turned up.

[0010] Then, as shown in Fig. 1(C), in the forming drum D3, a sidewall rubber 5 having a predetermined cross-sectional shape is wound around the outer peripheral surface of the green case 10B in the tire circumferential direction. Subsequently, the sidewall rubber 5 is pressure-bonded to the green case 10B by a stitching process described later. This forms a cylindrical green case 10C with the sidewall rubber 5 attached. In this embodiment, the steps in Figs. 1(A) to 1(C) are performed on separate forming drums D1 to D3, but are not limited to this and can also be performed using a common forming drum.

[0011] As shown in FIG. 1(D), belt plies 6, 7, tread rubber 8, etc. are wound in this order on a building drum D4. This forms a cylindrical tread band 20. Then, as shown in FIG. 1(E), on a building drum D5, the green case 10C is expanded and deformed into a toroidal shape and combined with the tread band 20 disposed radially outward. The unvulcanized green tire thus formed is vulcanized and molded using a tire vulcanization mold (not shown) to produce a pneumatic tire.

[0012] The attachment of the sidewall rubber 5 shown in FIG. 1(C) will be described in detail with reference to FIGS. 2 to 4. FIG. 2 is a longitudinal cross-sectional view of the forming drum D3 taken along the arrow XX in FIG. 1(C), showing the state before the stitching step is performed. FIG. 3 is an enlarged view of the area surrounded by the rectangular frame RF in FIG. 2. Although the outer peripheral surface of the forming drum D3 is depicted as flat in FIG. 3, it is actually gently curved. The forming drum D3, which is a rotary support, is configured to be rotatable about an axis 10. The rotation of the forming drum D3 is driven by a drive unit 11. The speed and timing of the rotation of the forming drum D3 are controlled by a control unit 12.

[0013] The forming drum D3 is configured to be expandable and contractible, and the mechanism for this is conventionally known. The forming drum D3 has a cylindrical outer circumferential surface, onto which a green case 10B is fitted. After the forming drum D3 is inserted in a contracted state into the cylindrical green case 10B, the forming drum D3 is expanded in diameter, and the green case 10B is supported in a fitted state by the forming drum D3. A sidewall rubber 5 supplied from a supply device (not shown) is wound around the outer circumferential surface of the green case 10B. The sidewall rubbers 5 are arranged in pairs as shown in Figure 1(C).

[0014] The pressure roller 13 is disposed so as to face the outer peripheral surface of the forming drum D3. The pressure roller 13 is supported by a moving device (not shown) via a displacement cylinder 14 (e.g., an air cylinder). The displacement cylinder 14 functions as an actuator that displaces the pressure roller 13 toward the sidewall rubber 5. The moving device is configured to be movable along the axial direction of the forming drum D3. The operation of the displacement cylinder 14 and the moving device is controlled by a control device 12. The pressure roller 13, the displacement cylinder 14, and the moving device are provided in pairs corresponding to a pair of sidewall rubbers 5.

[0015] Once the sidewall rubber 5 has been wound around the outer peripheral surface of the green case 10B, the stitching process is carried out. In the stitching process, in order to press the sidewall rubber 5 (corresponding to the second tire constituent member) onto the outer peripheral surface of the cylindrical green case 10B (corresponding to the first tire constituent member) supported by the forming drum D3, the forming drum D3 is rotated while the pressing roller 13 is pressed against the outer surface of the sidewall rubber 5. At this time, the displacement cylinder 14 extends, and the pressing roller 13 is pressed against the sidewall rubber 5 with a corresponding pressure. The pressing roller 13 is rotatably mounted on the tip of the rod of the displacement cylinder 14, and therefore rotates drivenly.

[0016] Fig. 3 shows the periphery of the overlap joint portion 30 (of the carcass ply 3) included in the green case 10B. Fig. 4 shows the overlap joint portion 30 in isolation. In the overlap joint portion 30 included in the green case 10B (hereinafter simply referred to as "joint portion 30"), the end portion located relatively radially outward is referred to as the outer end portion 31, and the end portion located relatively radially inward is referred to as the inner end portion 32. In the joint portion 30, the outer end portion 31 and the inner end portion 32 are overlapped with each other, forming a step, which causes the outer peripheral surface to rise.

[0017] Through research by the present inventors, it was found that the main reason why air remains between the green case 10B and the sidewall rubber 5 even after the stitching process is that the pressure roller 13 jumps over a step when it rides up onto the joint portion 30, and as a result, the pressure roller 13 does not press sufficiently against the side 30s of the joint portion 30. It was also found that such a jumping phenomenon of the pressure roller 13 occurs particularly noticeably when the pressure roller 13 moves relatively to the right in Fig. 3 (in other words, from position P2 to position P1 via the joint portion 30).

[0018] Therefore, in the stitching process of this embodiment, the forming drum D3 is rotated in a predetermined direction so that the pressure roller 13 passing through the joint portion 30 moves from the outer peripheral surface of the outer end portion 31 to the outer peripheral surface of the inner end portion 32. That is, in FIG. 3, the forming drum D3 is rotated in the R1 direction (see FIG. 2) so that the pressure roller 13 moves relatively to the left side of FIG. 3 (in other words, from position P1 to position P2 via the joint portion 30). If the positional relationship between the outer end portion 31 and the inner end portion 32 is reversed, the forming drum D3 is rotated in the R2 direction (see FIG. 2). As a result, the pressure roller 13 that rides over the joint portion 30 moves along the outer peripheral surface of the outer end portion 31, thereby suppressing the jumping phenomenon of the pressure roller 13. As a result, residual air around the joint portion 30 is reduced, and ultimately, the occurrence of tire molding defects (poor inflation) can be suppressed.

[0019] To prevent the jumping phenomenon of the pressure roller 13, it is also effective to reduce the hardness of the pressure roller 13 to reduce the recoil when pressing the joint portion 30. From this viewpoint, the hardness of the pressure roller 13 is preferably 55 or less, and more preferably 50 or less. Furthermore, from the viewpoint of imparting the required durability to the pressure roller 13, the hardness of the pressure roller 13 is preferably 40 or more. This hardness of the pressure roller 13 refers to the hardness measured with an A-type durometer in accordance with JIS K6301.

[0020] As described above, the green case 10B includes the carcass ply 3. In this embodiment, the joint portion 30 is a formed ply joint portion where one end and the other end are overlapped with each other when the carcass ply 3 is formed into a cylindrical shape. In other words, the joint portion 30 is a joint portion that is generated when a belt-like ply (a belt-like ply 60 described later) is wound around the forming drum D1 to form a cylindrical shape, as shown in FIG. 1(A). When the belt-like ply is wound, the starting end becomes the inner end portion 32, and the terminal end becomes the outer end portion 31. Such a formed ply joint portion is formed at one location in the circumferential direction of the cylindrical carcass ply 3.

[0021] FIG. 5 is a schematic diagram showing the process of forming the belt-shaped ply 60. As described above, the cylindrical carcass ply 3 is formed by winding the belt-shaped ply 60 around the forming drum D1. The belt-shaped ply 60 is formed from a plurality of strip-shaped plies 50. The strip-shaped ply 50 is formed by cutting a topping sheet 40 supplied from a calender roll (not shown) or the like to a predetermined length by a cutting device 41. This predetermined length is set to a dimension corresponding to the width of the carcass ply 3. The topping sheet 40 is formed by topping unvulcanized rubber onto a plurality of aligned carcass cords 3C.

[0022] The formed strip-shaped ply 50 is fed in a direction parallel to the cutting direction by the cutting device 41, and the rear end of the preceding strip-shaped ply 50 in the feeding direction is overlapped with the front end of the succeeding strip-shaped ply 50 in the feeding direction. Then, with the ends of the strip-shaped plies 50 overlapped, the crimping device 51 moves in the width direction, thereby joining the multiple strip-shaped plies 50. A predetermined number of strip-shaped plies 50 are joined together to form a belt-shaped ply 60 having a predetermined length. A joint 61 formed by overlapping the ends of the strip-shaped plies 50 when forming the belt-shaped ply 60 in this manner is called a cut ply joint.

[0023] In the example of Figure 5, a rubber tape 62 is applied after the strip-shaped ply 50 is joined. The rubber tape 62 is interposed between the belt-shaped ply 60 (i.e., the carcass ply 3 in Figure 1(A)) wound around the forming drum D1 and the inner liner rubber 1. The rubber tape 62 is arranged in the buttress region, which expands greatly during vulcanization molding. The buttress region is the radially outer region of the tire sidewall, and is a part that does not come into contact with the ground during normal driving on flat paved roads. By disposing the rubber tape 62 in the buttress region, it is possible to prevent the carcass cord 3C from pressing against the inner liner rubber 1.

[0024] In this embodiment, an example has been shown in which the forming drum D3 is rotated in a predetermined direction (direction R1 in FIG. 2 ) based on the aspect of the joint portion 30, which is a formed ply joint portion. However, this joint portion 30 may also be a cut ply joint portion. However, in a formed ply joint portion, the step tends to be larger than in a cut ply joint portion due to the presence of the rubber tape 62 between the outer end portion 31 and the inner end portion 32, and therefore the jumping phenomenon of the pressure roller 13 is more likely to occur. Therefore, in order to enhance the effect of reducing residual air, it is preferable that the joint portion 30 is a formed ply joint portion.

[0025] In the stitching process, the rotation speed of the forming drum D3 may be temporarily reduced when the pressure roller 13 passes through the joint portion 30. This increases the effectiveness of suppressing the jumping phenomenon of the pressure roller 13, and more effectively suppresses residual air. The rotation of the forming drum D3 is controlled by the control device 12. The control device 12 can determine the timing at which the pressure roller 13 passes through the joint portion 30 based on the relative positions of the pressure roller 13 and the joint portion 30. If the circumferential position of the joint portion 30 is always constant when the green case 10B is supported by the forming drum D3 (for example, if the joint portion 30 is always located directly above the shaft 10 as shown in Figure 3), the position information of the joint portion 30 can be temporarily input to the control device 12.

[0026] The circumferential position of the joint portion 30 may be detected by a detector, and the timing for temporarily reducing the rotational speed of the forming drum D3 may be controlled based on the detection result. By constantly determining the position of the joint portion 30, it is possible to deal with situations where the circumferential position of the joint portion 30 is not constant. In this case, it is preferable to rotate the green case 10B one or more times before or while winding the sidewall rubber 5 to detect the position of the joint portion 30. A non-contact distance sensor 15 capable of detecting the distance to an object, such as a laser displacement meter, is preferably used as the detector. Formed ply joints and cut ply joints can be distinguished based on the size and length of the step.

[0027] The circumferential position of the joint portion 30 may be detected by a detector based on a mark M (see FIG. 4) that has been applied in advance, and the timing for temporarily reducing the rotational speed of the forming drum D3 may be controlled based on the detection result. Such a mark M may be applied to the outer peripheral surface of the carcass ply 3 (belt-like ply 60), for example, in the process shown in FIG. 5 or FIG. 1(A). In this case, a camera 16 capable of detecting the mark M may be used as the detector. Although a triangular mark M is used in FIG. 4, the shape of the mark is not limited to this. The color of the mark M may be a color different from the color of the carcass ply 3 (usually black).

[0028] Alternatively, the orientation of the joint portion 30 (i.e., the positional relationship between the outer end portion 31 and the inner end portion 32) may be detected by a detector, and the forming drum D3 may be rotated in a predetermined direction based on the detection result. This method can also handle situations where the orientation of the joint portion 30 is not constant. For example, it is possible to detect the orientation of the triangle of the mark M using the camera 16 as a detector, and detect the orientation of the joint portion 30 based on that. In this case, the control device 12 rotates the forming drum D3 in the R1 direction (see FIG. 2) if the orientation of the triangle of the detected mark M is the orientation shown in FIG. 4, and rotates the forming drum D3 in the R2 direction (see FIG. 2) if the orientation is opposite to that shown in FIG. 4.

[0029] As described above, the tire manufacturing method of this embodiment includes a stitching process in which the pressing roller 13 is pressed against the outer peripheral surface of the sidewall rubber 5 while rotating the building drum D3 in order to press the sidewall rubber 5 (corresponding to the second tire constituent member) against the outer peripheral surface of the cylindrical green case 10B (corresponding to the first tire constituent member) supported by the building drum D3. In the overlap joint portion 30 included in the green case 10B, the end located relatively radially outward is referred to as the outer end 31, and the end located relatively radially inward is referred to as the inner end 32. In the stitching process, the building drum D3 is rotated in a predetermined direction (direction R1 in FIG. 2 ) so that the pressing roller 13 passing through the overlap joint portion 30 moves from the outer peripheral surface of the outer end 31 to the outer peripheral surface of the inner end 32. This suppresses the jumping phenomenon of the pressing roller 13 and reduces air remaining around the overlap joint portion 30.

[0030] In this embodiment, the green case 10B as the first tire constituent member includes the carcass ply 3, and the overlap joint portion 30 is a formed ply joint portion where one end and the other end of the carcass ply 3 are overlapped with each other when the carcass ply 3 is formed into a cylindrical shape. By rotating the forming drum D3 in a predetermined direction based on the aspect of the formed ply joint portion, which tends to have a larger step compared to the cut ply joint portion, the effect of reducing residual air can be enhanced.

[0031] In the stitching process, the rotation speed of the forming drum D3 may be temporarily reduced when the pressure roller 13 passes through the overlap joint portion 30. This method can enhance the effect of suppressing the jumping phenomenon of the pressure roller 13 and more effectively suppress residual air. In this case, the circumferential position of the overlap joint portion 30 may be detected by a detector (for example, a distance sensor 15 or a camera 16), and the timing of temporarily reducing the rotation speed of the forming drum D3 may be controlled based on the detection result. This makes it possible to deal with situations where the circumferential position of the joint portion 30 is not constant.

[0032] The hardness of the pressure roller 13 measured by a type A durometer conforming to JIS K6301 is preferably equal to or less than 55. This reduces the reaction force when pressing the joint portion 30, and more effectively prevents the pressure roller 13 from jumping.

[0033] In this embodiment, a stitching process for crimping the sidewall rubber 5 onto the outer peripheral surface of the carcass ply 3 contained in the green case 10B has been described, but this is not limited thereto, and the method disclosed herein can also be adopted in a stitching process for crimping other tire constituent members.

[0034] The tire manufacturing method of the present disclosure is not limited to the above-described embodiment, and various improvements and modifications are possible within the scope of the gist thereof. [Explanation of symbols]

[0035] 3 Carcass ply 5 Sidewall rubber (second tire component) 10B Green case (first tire component) 13 Pressure roller 15 Distance sensor (detector) 16 Camera (detector) 30 Overlap joint 31 Outer edge 32 Inner end D3 Forming drum (rotating support)

Claims

1. a stitching step of pressing a pressure roller against an outer peripheral surface of a cylindrical first tire constituent member supported by a rotary support member while rotating the rotary support member in order to press a second tire constituent member onto an outer peripheral surface of the second tire constituent member, In the overlap joint portion included in the first tire constituent member, when an end portion located relatively radially outward is referred to as an outer end portion and an end portion located relatively radially inward is referred to as an inner end portion, a tire manufacturing method in which, in the stitching step, the rotating support is rotated in a predetermined direction so that the pressing roller passing through the overlap joint portion moves from the outer peripheral surface of the outer end portion to the outer peripheral surface of the inner end portion, and the rotational speed of the rotating support is temporarily reduced when the pressing roller passes through the overlap joint portion.

2. the first tire component includes a carcass ply; 2. The tire manufacturing method according to claim 1, wherein the overlap joint portion is a molded ply joint portion formed by overlapping one end portion and the other end portion of the carcass ply with each other when the carcass ply is molded into a cylindrical shape.

3. 2. The tire manufacturing method according to claim 1, further comprising the steps of: detecting the circumferential position of the overlap joint portion with a detector; and controlling the timing of temporarily reducing the rotational speed of the rotary support body based on the detection result.

4. 4. The tire manufacturing method according to claim 1, wherein the hardness of the pressing roller measured with an A-type durometer in accordance with JIS K6301 is 55 or less.

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