JP2011161676A - Method for producing motorcycle raw tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the uniformity of a tire by eliminating creasing at both tread rubber ends etc. <P>SOLUTION: A method for producing a motorcycle raw tire includes an expansion process for expanding a raw tire body between bead cores by expanding a core former making a convex arc surface with its peripheral surface resembling a tread surface and pushing up the raw tire body, a band forming process for forming band ply on the expanded part of the raw tire body supported by the core former by winding belt-like ply spirally, and a joining process for densely joining a tread rubber body, the band ply, and the raw tire body together by winding a belt-like tread rubber material once on the band ply and carrying out stitch down. The expansion of the core former is carried out through the expansion of an airbag. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a raw tire for a motorcycle that eliminates wrinkles and the like at both ends of a tread rubber to improve tire uniformity.

  In the conventional method for producing a green tire, as shown in FIG. 8, a tread ring c for forming a tread is separately formed on the radially outer side of a cylindrical green tire main body b with a bead core d held by a 2nd drum a. Arrange. Then, while the bead cores d are brought close to each other, the raw tire body b is bulged between the bead cores d and d by filling with an internal pressure so that the bulging portion is brought into pressure contact with the inner peripheral surface of the tread ring c. The tire body b and the tread ring c are joined together.

  On the other hand, in a motorcycle tire, the tread portion is formed with a convex arcuate profile with a small radius of curvature because of the characteristic of turning the vehicle body into a large bank. Accordingly, in order to form the tread ring c of this type of tire, as shown in FIG. 9A, a profile deck e whose outer peripheral surface is approximated to the arc shape of the tread surface is used, and along the outer peripheral surface. The band ply f and the tread rubber g are sequentially laminated.

  At this time, in the band ply f, there is no particular problem because a narrow band ply obtained by rubberizing the band cord is spirally wound along the outer peripheral surface of the profile deck e.

  However, in the tread rubber g, a wide belt-shaped rubber material g1 is wound around and formed into a cylindrical shape, and then the cylindrical tread rubber body is attached to the tire while rotating the profile deck e using a known stitcher h. It is brought into close contact with the band ply f by being pressed against the profile deck e from the equator side toward the tread end side and narrowing inward in the radial direction. For this reason, as shown in FIG. 9B, wrinkles j are generated at both ends of the tread rubber g due to narrowing inward in the radial direction. Then, when the tread ring c having the wrinkles i is bonded to the raw tire body b, as shown in FIG. 9 (C), the tread rubber edge is generated with a wavy (meandering) k or a concave portion m where no rubber is formed. Reduces appearance quality and lowers uniformity.

  In addition, in the following Patent Document 1, a rubber material for tread rubber is not extruded from a rubber extruder into a flat plate shape, but is extruded from a rubber extruder with an arc-shaped cross-sectional shape that matches the outer peripheral surface of the profile deck, It has been proposed that this rubber material is wound around the profile deck as it is.

  However, it is difficult to carry out the above-described method because it is difficult to handle, such as transfer, storage, sticking to a profile deck, etc., of a rubber material having a circular arc section extruded from a rubber extruder.

JP 2004-074647 A

  Therefore, the present invention uses a core former having a convex arcuate outer peripheral surface approximating a tread surface and capable of expanding and contracting, to swell the raw tire body in a toroid shape, and the raw tire supported by the core former. Based on the direct formation of band ply and tread rubber on the bulging part of the main body, it is possible to suppress the occurrence of undulations, dents, etc. at the tread rubber edge when the tread rubber and raw tire body are bonded together An object of the present invention is to provide a method for manufacturing a raw tire for a motorcycle that can suppress deterioration in appearance quality and uniformity.

In order to solve the above-mentioned problem, the invention of claim 1 of the present application is arranged such that the carcass ply extends from the tread portion through the sidewall portion to the bead core of the bead portion, inside the tread portion and radially outward of the carcass ply. And a tread rubber that is disposed on the radially outer side of the band ply and has an outer surface forming a convex arc-shaped tread surface.
A raw tire main body forming step of forming a cylindrical raw tire main body including a carcass cylindrical body in which a sheet-like carcass ply is wound around a forming drum and bead cores are attached to both ends thereof;
Using a core former capable of expanding and contracting with an outer peripheral surface having a convex arc surface approximating the tread surface, and expanding the core former to push up the raw tire main body, the raw tire main body is moved between the bead cores. A bulging step for bulging in a shape along the convex arc surface;
A band ply is affixed to a bulging portion of a raw tire body supported by the core former by applying a narrow band ply with rubberized band cords while spirally winding the tire around the tire circumferential direction. Forming a band, and
On the band ply, a belt-shaped tread rubber material is wound once to form an annular tread rubber body, and the annular tread rubber body is stitched down and pressed toward the core former. And a joining step of closely joining the tread rubber body, the band ply and the green tire body,
The diameter of the core former is increased by expansion of an air bag disposed inside the core former.

In the invention of claim 2, the core former is
A first segment having a large circumferential width and having both circumferential end surfaces inclined inwardly as a first sliding surface inclined in a direction to reduce the circumferential width inward in the radial direction;
The first segments are alternately arranged in the circumferential direction, the circumferential width is small, and both end faces in the circumferential direction are inclined in the direction of increasing the circumferential width inward in the radial direction and the first segment. A second segment that is an outwardly inclined second slide surface that can slidably contact the slide surface;
In addition, the first slide surface has a guide groove extending in the radial direction, and the second slide surface is guided by the guide groove and abuts against the radial outer end of the guide groove in the expanded diameter state. And the stopper which contact | abuts to the radial direction inner end of the said guide groove in the diameter reducing state protruded.

  As described above, the present invention does not form a tread ring separately, but the raw tire body is bulged by a core former having a convex arc-shaped outer peripheral surface that approximates the tread surface, and on this bulged portion. The band ply and the tread rubber are directly formed.

  Since the bulging portion is supported by the core former, the bulging portion is stably maintained in a shape approximate to the tread surface without any deformation or misalignment. Therefore, the band ply and the tread rubber can be formed with high accuracy. The tread rubber is stuck to the green tire body while being squeezed radially inward by stitching down. At this time, compared with the conventional case where a tread ring from a wrinkle that has been narrowed down in advance is pasted to the raw tire body, the tread rubber edge can be reduced and the occurrence of dents can be reduced. Can be improved.

  It is also conceivable that the core former is enlarged or reduced by a mechanical method such as a cylinder or a link mechanism. However, due to mechanical constraints, a sufficient expansion / contraction stroke cannot be secured, and the tread shape and size of the green tire that can be formed are greatly limited. However, by performing expansion / contraction of the core former with the air bag, a sufficient stroke can be secured, and raw tires for motorcycles of various tread shapes and sizes can be formed.

1 is a side view showing an example of a raw tire production line for carrying out a method for producing a raw tire for a motorcycle according to the present invention. It is sectional drawing which expands and shows the principal part of a shaping drum. It is sectional drawing which shows notionally the diameter expansion state and core diameter state of a core former. (A), (B) is sectional drawing and the exploded perspective view which show the guide groove and stopper which were provided in the 1st, 2nd slide surface. (A), (B) is sectional drawing explaining a bulging process and a band formation process. (A), (B) is sectional drawing explaining a joining process. It is sectional drawing which shows an example of the green tire manufactured by the manufacturing method of this invention. It is sectional drawing which shows the manufacturing method of the conventional raw tire. (A) is sectional drawing explaining the conventional tread ring formation process, (B), (C) is a partial perspective view of the tread rubber which shows the problem.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 7 is a schematic cross-sectional view of a raw tire 1 before vulcanization manufactured by the method for manufacturing a raw tire for a motorcycle according to the present invention. In FIG. 7, the raw tire 1 extends from a tread portion 2 to a sidewall. A carcass 6 extending through the part 3 to the bead core 5 of the bead part 4, a band layer 7 arranged inside the tread part 2 and radially outside the carcass 6, and arranged radially outside the band layer 7. In addition, the outer surface includes a tread rubber G forming a tread surface 2S having a convex arc shape.

  The carcass 6 is formed from at least one carcass ply 6A having a carcass cord arranged at an angle of, for example, 60 to 90 degrees with respect to the tire circumferential direction, in this example, one carcass ply 6A. As the carcass cord, for example, an organic fiber cord such as nylon, polyester, or rayon is used. The carcass ply 6A has folded portions 6b that are folded from the inner side to the outer side in the tire axial direction around the bead core 5 at both ends of the ply body portion 6a straddling the bead cores 5 and 5, and the ply body portion 6a. A bead apex rubber 8 for bead reinforcement extending in a radially outward direction from the bead core 5 is disposed between the bent portion 6b and the folded portion 6b.

  The band layer 7 is formed of at least one band ply 7A having a band cord spirally wound in the tire circumferential direction, in this example, one band ply 7A. The band ply 7A is formed by spirally winding a long and narrow band-shaped ply P obtained by rubberizing a band cord. As the band ply 7A, for example, the above-mentioned organic fiber cord is preferably adopted, but for example, a high modulus organic fiber cord such as aromatic polyamide, or a metal cord such as a steel cord can also be adopted.

  If desired, a breaker ply (not shown) in which breaker cords are inclined and arranged at an angle of, for example, 10 or more with respect to the tire circumferential direction can be interposed between the carcass 6 and the band layer 7. As this breaker ply, the same ply material as the carcass ply 6A can also be used.

  A tread rubber G whose outer surface forms the tread surface 2S is laminated on the outer side in the radial direction of the band layer 7. The tread surface 2S is curved into a convex arc shape having a small curvature radius from the tire equator C to the tread end TE, and the contour shape (raw tread profile) approximates the tread profile of the tire after vulcanization molding. Formed.

  FIG. 1 shows an example of a raw tire production line for carrying out the production method of the raw tire 1, and the production method will be described together with this raw tire production line.

  The raw tire production line receives a forming drum 12 that forms a cylindrical raw tire main body 11 including a carcass cylindrical body 11A having bead cores 5 attached to both ends, and the raw tire main body 11 is received from the forming drum 12. A shaping drum 13 that holds and holds the green tire main body 11 held between the bead cores 5 and 5 in a toroidal shape.

  The forming drum 12 is a conventional so-called 1st drum having a well-known structure, and a central drum 12a that can be reduced in diameter, and a drum 12b that is disposed on both sides of the drum 12b and has a turn-up bladder (not shown). With. In this molding drum 12, a sheet-like carcass ply 6A is wound on the central drum 12a, and bead cores 5 are extrapolated on both sides thereof. The carcass ply 6A protruding from the bead core 5 is folded back by a turn-up bladder provided on the drum 12b on the side, thereby forming a carcass cylinder 11A to which the bead core 5 is attached. That is, the raw tire body forming step S1 is performed. The carcass cylindrical body 11A is appropriately attached with tire constituent members such as an inner liner rubber and a side wall rubber to form the cylindrical raw tire main body 11.

  The green tire body 11 is transferred to a shaping drum 13 via a conventional transfer device (not shown) having a known structure.

  The shaping drum 13 has a bead holding means 15 having bead lock rings 14 on both sides in the tire axial direction for holding the bead portion of the green tire main body 11, and a core former 16 capable of expanding and contracting the diameter. Shaping means 17 is provided for expanding the raw tire body 11 between the bead cores 5 and 5 in a toroidal shape by expanding the former 16.

  As shown in FIG. 2, the bead lock ring 14 is supported by a support shaft 18 so as to be able to move in and out of the axial direction around the tire equator C and to be rotatable. In addition, a seating portion 14 a that seats and holds the bead portion of the green tire body 11 is provided at the radially outer end of the bead lock ring 14.

  The shaping means 17 includes the core former 16 having an outer peripheral surface 16S that forms a convex arcuate surface 19 that approximates the tread surface 2S and capable of expanding and contracting, and a diameter expanding means 20 that expands the core former 16. Have.

  As shown conceptually in FIG. 3, the core former 16 includes a plurality of segments 21 divided in the circumferential direction. The segment 21 includes a first segment 21 </ b> A having a large circumferential width, The circumferential width is small and the first segments 21A are composed of second segments 21B arranged alternately in the circumferential direction. Both end surfaces in the circumferential direction of the first segment 21A are formed as inwardly inclined first slide surfaces 22A that incline in the direction of decreasing the circumferential width inward in the radial direction. Further, both end surfaces in the circumferential direction of the second segment 21B are formed as second slide surfaces 22B having an outward inclination that is inclined in the direction of increasing the circumferential width inward in the radial direction. The core former 16 forms one annular body in which the first and second segments 21A and 21B are arranged side by side in the circumferential direction and the outer peripheral surface is continuous in the circumferential direction in the diameter-expanded state Re. In the reduced diameter state Rr, the second segment 21B moves backward inward in the radial direction with respect to the first segment 21A, whereby the core former 16 can be reduced in diameter.

  The first and second segments 21A and 21B are radially inward and outward while the first and second slide surfaces 22A and 22B are in surface contact with each other between the enlarged diameter state Re and the reduced diameter state Rr. Move to slide. At this time, as shown in an enlarged view in FIG. 4A, the first slide surface 22A is formed with a guide groove 23 extending in the radial direction, and the second slide surface 22B has The stopper 24 is guided by the guide groove 23 and contacts the radially outer end 23o of the guide groove 23 in the expanded diameter state Re and contacts the radially inner end 23i of the guide groove 23 in the reduced diameter state Rr. Is projected. As a result, the expanded diameter state Re and the reduced diameter state Rr are regulated.

  Further, as shown in an exaggerated manner in FIG. 4B, when the diameter is reduced, the stopper 24 is configured so that the first segment 21B can move inward in the radial direction following the second segment 21B. A narrow neck portion 24a extending from the slide surface 22B is formed in a stepped shape having a wide head portion 24b at the tip thereof. The guide groove 23 also has a stepped shape in which a narrow portion 23a through which the neck portion 24a passes is provided with a wide portion 23b through which the head portion 24b passes, and each step is engaged with each other, thereby forming a second segment 21B. Following this, the first segment 21B can move radially inward.

  In each segment 21, side plate pieces 25 extending inward in the radial direction are arranged at both ends in the axial center direction in this example. Further, the support shaft 18 is attached with a disk-shaped side wall 26 that can rotate integrally with the support shaft 18, and each side plate piece 25, that is, each segment 21 is attached by a guide 26 a such as a linear bearing provided on the side wall 26. Guides radially in and out.

  Next, an air bag 30 is used as the diameter expanding means 20. In this example, the airbag 30 has a cylindrical shape made of elastic rubber, and both side edges thereof are fixed to the outer peripheral surface of a disk-shaped mounting member 31 fixed to the support shaft 18. And the diameter expansion state which forms the said tread part 2 from the diameter-reduced state Rr used as the diameter of the said core former 16 smaller than the said cylindrical raw tire main body 11 by expansion | swelling of the said airbag 30 by pressurized air. The diameter is expanded to Re.

  Such an air bag 30 has a simple structure and can be disposed in a small space, and can ensure a large expansion / contraction stroke. Therefore, it is possible to efficiently form raw tires for motorcycles having various tread shapes and sizes. In addition to the cylindrical shape, the airbag 30 may have various shapes such as a donut shape.

  Next, in the manufacturing method of the green tire 1, after performing the green tire main body forming step S1 for forming the green tire main body 11 using the forming drum 12, as shown in FIG. The core former 16 is expanded in diameter with respect to the raw tire main body 11 whose bead portion is held by the ring 14, and the raw tire main body 11 is pushed up, so that the raw tire main body 11 extends along the convex arc surface 19, that is, the tread. A bulging step S2 is performed to bulge in a shape approximate to the surface 2S. And in this bulging state, band formation process S3 and joining process S4 are performed in order.

  In the band forming step S3, as shown in FIG. 5B, a narrow belt-like ply P in which a band cord is rubberized is formed on the bulging portion of the raw tire body 11 supported by the core former 16. The band ply 7 </ b> A is formed by being attached while being spirally wound along the tire circumferential direction.

  In the joining step S4, as shown in FIGS. 6 (A) and 6 (B), an annular tread rubber body G2 is first wound on the band ply 7A by winding the belt-like tread rubber material G1 once. While forming, this annular tread rubber body G2 is stitched down. In stitch down, a conventional stitch roller h is used to sequentially press the tread rubber body G2 toward the core former 16 from the tire equator C side toward the tread end TE side while rotating the tread rubber body G2. As a result, the tread rubber body G2, the band ply 7A and the green tire body 11 are closely joined. At this time, since the tread rubber body G2 is stuck to the raw tire main body 11 while being narrowed down, it is possible to reduce the waviness of the tread rubber edge and the occurrence of a dent.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  Based on the manufacturing method of the present invention, motorcycle tires having tire sizes of 190 / 50ZR17 and 160 / 60ZR17 were prototyped according to the specifications shown in Table 1, the uniformity of each sample tire, and the waviness at the tread rubber edge of the raw tire (meandering) ) And compared the occurrence rate of defective products. As Comparative Example 1, a tire was formed based on the conventional method shown in FIG. In Comparative Example 2, mechanical methods such as a cylinder and a link mechanism other than the air bag were adopted as the diameter expansion means, but the core former could not be expanded or contracted with the necessary stroke due to dimensional constraints, and the tire was formed. I couldn't.

(1) Waves at the tread rubber edge (meander):
As shown in FIG. 9C, after the tread ring was attached to the green tire body, the amplitude of the wavy k generated at the edge portion of the tread rubber was measured, and the maximum value was described. The smaller the value, the better the appearance quality.

(2) Defective product incidence:
Due to the wrinkles of the tread rubber, a recess was formed on the outer surface of the tire, and the defective product occurrence rate at which the tire became defective was measured for 200 tires produced.

(3) Uniformity Using an uniformity tester, LFV, RFV, and lateral blur were measured for 200 tires in accordance with JASO C607 (automotive tire uniformity test method), and the average value and standard The deviation (σ) was compared. In the measurement, standard rims of various sizes were used, and the internal pressure was 200 kPa.

  As shown in the table, it can be confirmed that the embodiment can improve the edge undulation, defective product generation rate and uniformity due to the tread rubber as compared with the comparative example 1.

DESCRIPTION OF SYMBOLS 1 Raw motorcycle 2 Tread part 2S Tread surface 3 Side wall part 4 Bead part 5 Bead core 6A Carcass ply 7A Band ply 11 Raw tire main body 11A Carcass cylindrical body 12 Molding drum 16 Core former 19 Convex arc surface 21A 1st Segment 21B Second segment 22A First slide surface 22B Second slide surface 23 Guide groove 24 Stopper 30 Airbag G Tread rubber G1 Tread rubber material G2 Tread rubber body P Strip ply S1 Raw tire body forming step S2 Swelling Process S3 Band formation process S4 Joining process

Claims (2)

A carcass ply extending from the tread part through the sidewall part to the bead core of the bead part, a band ply arranged inside the tread part and radially outside the carcass ply, and arranged radially outside the band ply; A method for producing a raw tire for a motorcycle comprising a tread rubber having an outer surface having a convex arc-shaped tread surface,
A raw tire main body forming step of forming a cylindrical raw tire main body including a carcass cylindrical body in which a sheet-like carcass ply is wound around a forming drum and bead cores are attached to both ends thereof;
Using a core former capable of expanding and contracting with an outer peripheral surface having a convex arc surface approximating the tread surface, and expanding the core former to push up the raw tire main body, the raw tire main body is moved between the bead cores. A bulging step for bulging in a shape along the convex arc surface;
A band ply is affixed to a bulging portion of a raw tire body supported by the core former by applying a narrow band ply with rubberized band cords while spirally winding the tire around the tire circumferential direction. Forming a band, and
On the band ply, a belt-shaped tread rubber material is wound once to form an annular tread rubber body, and the annular tread rubber body is stitched down and pressed toward the core former. And a joining step of closely joining the tread rubber body, the band ply and the green tire body,
The diameter of the core former is increased by the expansion of an air bag disposed inside the core former. The core former is
A first segment having a large circumferential width and having both circumferential end surfaces inclined inwardly as a first sliding surface inclined in a direction to reduce the circumferential width inward in the radial direction;
The first segments are alternately arranged in the circumferential direction, the circumferential width is small, and both end faces in the circumferential direction are inclined in the direction of increasing the circumferential width inward in the radial direction and the first segment. A second segment that is an outwardly inclined second slide surface that can slidably contact the slide surface;
In addition, the first slide surface has a guide groove extending in the radial direction, and the second slide surface is guided by the guide groove and abuts against the radial outer end of the guide groove in the expanded diameter state. The raw tire manufacturing method for a motorcycle according to claim 1, wherein a stopper that abuts against a radially inner end of the guide groove in a reduced diameter state is projected.

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