JPH1094826A - Manufacture of tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the manufacturing cost of a tube high in close contactness by shortening a manufacturing process. SOLUTION: On a flat plate which becomes the stock of the tube, recessed parts 2 are provided near both end faces (joined surface obtained when forming a cylindrical body by rounding the flat plate) in the longitudinal direction. These recessed parts 2 extend almost in parallel to the end face of the flat plate, and become hollow in the plate thickness direction of the flat plate. Also, on both end faces of the flat plate, as a means for clinch coupling, a recessed part is formed on one end face, and on the other end face, a projecting part is formed. When forming the cylindrical body by bending with a coupling jig a work (flat plate stock) 5 on which recessed parts 2, recessed part and projecting part have been formed, the recessed parts 2 of the work 5 are strongly pressed between projections 8a, 9a provided on the punches 8, 9 of the coupling jig and recesses 11a provided on a mandrel 11, and are deformed. Consequently, the close contactness of both end faces of the work 5 is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a tube formed by bending a flat plate.

[0002]

2. Description of the Related Art As a prior art, Japanese Patent Publication No. 63-6293 is known.
There is a method for forming a cylindrical body disclosed in Japanese Patent Application Laid-Open No. H10-260, 1988. In this molding method, a flat molded material is rolled to form a primary molded product (cylindrical material) in which both end surfaces are abutted in a non-joined state, and the primary molded product is ironed with a punch and a die to form a desired cylinder. It is a method of forming a body. According to this method, since the cylindrical body is plastically deformed (iron-formed) to form the cylindrical body, a dimensional change due to springback after the forming can be substantially eliminated. As a result, it is possible to obtain a product having high adhesion of the bonding surfaces (both end surfaces).

[0003]

However, the above-described manufacturing method requires a post-processing step associated with ironing.
Specifically, lubrication treatment to prevent seizure during ironing, burr is generated on the end face of the cylindrical body by ironing, the deburring step of removing the burr, the cleaning step after the deburring step, etc. There is a problem that the number of manufacturing steps increases due to the post-processing step, and the cost increases. Further, in severe processing such as ironing, there is a problem that the life of a mold used is shortened. The present invention has been made based on the above circumstances, and an object of the present invention is to provide a method for manufacturing a pipe in which a manufacturing process is shortened to reduce costs.

[0004]

According to the first aspect of the present invention, near the both end surfaces of the flat plate to be the mating surface after bending,
A strain absorbing portion for absorbing the strain generated in the flat plate at the time of bending is formed beforehand in the state of the flat plate, and thereafter, the bending is performed. Thereby, the distortion at the time of bending is absorbed, so that it is possible to obtain a product (pipe) having high adhesion without forming a gap on the joining surfaces (both end surfaces). In addition, according to this manufacturing method, the post-processing step after bending is unnecessary only by forming the strain absorbing portion in the state of the flat plate, so that the manufacturing process is compared to the conventional ironing method. The cost can be reduced, and the cost can be reduced accordingly. Note that the distortion generated during the bending process means a contraction deformation generated on the outer peripheral side of the plate thickness at both ends and a bulging deformation generated on the inner peripheral side of the plate thickness when the flat plate is rounded.

According to the second aspect of the present invention, the strain absorbing portion is
It is a concave portion which is depressed in the thickness direction of the flat plate along the end face of the flat plate. Since the recess can be easily formed by press molding, the problem that the life of the mold is shortened can be avoided. The flat plate may be bent so that a concave portion is formed on the outer peripheral surface of the cylindrical body (tube) (accordingly, the bulge of the concave portion protrudes on the inner peripheral surface of the cylindrical body). The tube may be bent so that a concave portion is formed on the inner peripheral surface (therefore, the bulge of the concave portion protrudes on the outer peripheral surface of the cylindrical body). When the concave portion is formed on the inner peripheral surface of the cylindrical body, the cross-sectional area (volume) inside the tube is not reduced by the concave portion, and the inside of the tube can be effectively used.

According to the third aspect of the present invention, the flat plate has a concave portion on one end surface and a convex portion on the other end surface, and the flat plate is bent to fit the convex portion into the concave portion. Together form a tube. As described above, even when the concave portion and the convex portion are provided on both end surfaces, the deformation of the concave portion and the convex portion during the bending process can be prevented by the action of the strain absorbing portion. Can be prevented.

According to the fourth aspect of the present invention, the strain absorbing portions are formed at three or more positions including the vicinity of both end surfaces of the flat plate and at substantially equal positions in the circumferential direction when the flat plate is bent. After that, bending is performed. Thereby, since the distortion at the time of bending can be absorbed substantially uniformly over the entire circumference of the pipe, the inner and outer diameter accuracy of the pipe can be improved without performing post-processing such as ironing.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a method for manufacturing a pipe according to the present invention will be described with reference to the drawings. (First Embodiment) FIG. 1 is a process diagram showing a flat plate processing process. First, a flat plate 1 (for example, a steel plate having a thickness of about 3 mm) serving as a tube material is cut into a predetermined length to form an elongated rectangular shape (see FIG. 1A). The tube manufactured by the manufacturing method of the present embodiment is, for example, a motor yoke.

Next, both end faces in the longitudinal direction of the flat plate 1 (flat plate 1)
Is formed by press working in the vicinity of a surface that will be a mating surface when the cylindrical body is formed by rolling up the cylindrical body. The recess 2 is provided so as to extend substantially parallel to the end face of the flat plate 1 as shown in FIG. 1A, and as shown in FIG. Depressed in the thickness direction. However, recess 2
Means that not only the surface of the flat plate 1 is depressed,
Is formed in a state in which a bulge due to the concave portion 2 protrudes on the back surface of the substrate. Subsequently, as means for performing clinch bonding, two concave portions 3 (not necessarily two) are formed on one end surface of the flat plate 1 and the convex portions 4 corresponding to the concave portions 3 are formed on the other end surface. Are formed in two places (see FIG. 1C).

Next, a flat plate material (hereinafter, referred to as a work 5) obtained through the steps from FIG. 1A to FIG. 1C is mounted on a connecting jig as shown in FIGS. To produce tubes. The coupling jig includes an upper mold stand 7 to which the die 6 is fixed, a lower mold stand 10 having a fixed punch 8 and a movable punch 9, and a core metal 11. The upper die table 7 is provided so as to be slidable in the vertical direction together with the die 6. The die 6 has a substantially semicircular inner peripheral surface. The inner diameter of the virtual circle when the circle whose inner peripheral surface is a part is imagined is provided to be the same as the outer diameter of the pipe as a product.

The fixed punch 8 has an arc-shaped inner peripheral surface forming a part of the virtual circle, and a projection 8a corresponding to the recess 2 of the work 5 is provided on the inner peripheral surface. The movable punch 9 is held in a vertically slidable state between the fixed punch 8 and the guide 12, and is urged upward by a spring 13 interposed between the movable punch 9 and the lower die table 10. The movable punch 9 has an arc-shaped inner peripheral surface forming a part of the virtual circle similarly to the fixed punch 8, and a projection 9a corresponding to the recess 2 of the work 5 is provided on the inner peripheral surface. ing.

The core metal 11 has a cylindrical shape, and the outer diameter thereof is provided to be the same as the inner diameter of a pipe as a product. Core 11
Are formed at two locations on the outer peripheral surface corresponding to the swelling of the work 5 (projection by the recess 2). The projections 8 provided on the fixed punch 8 and the movable punch 9
The recesses 11 a and 9 a are formed slightly larger than the recesses 2 formed in the work 5, and the recesses 11
a is formed slightly larger than the bulge formed on the work 5.

First, a description will be given of a bending process to a substantially cylindrical shape (not shown). First, the work 5 is started to bend (round) along the outer peripheral surface of the metal core 11 in a state where the one concave portion 2 provided in the work 5 is aligned with the one concave portion 11a of the metal core 11. 5 is bent (rounded) to the vicinity of the other dent 11a of the cored bar 11
do. Next, a not-shown bent into a substantially cylindrical shape is set together with the cored bar 11 with the recess 2 of the work 5 aligned with the projection 9a of the movable punch 9 (see FIG. 2). At this time, the other concave portion 2 of the work 5 is opposed to the projection 8a of the fixed punch 8. Subsequently, the upper mold table 7 is lowered. The die 6 comes into contact with the work 5 by the lowering of the upper die table 7. When the upper mold table 7 is further lowered, the work 5 is pushed by the die 6 to push down the movable punch 9. As the movable punch 9 descends, the other end of the work 5 is bent along the outer peripheral surface of the cored bar 11 while being supported by the fixed punch 8.

Thereafter, as shown in FIG. 3, when the lower end surface of the movable punch 9 comes into contact with the upper surface of the lower die table 10, the other end of the work 5 is sandwiched between the fixed punch 8 and the metal core 11. Then, the concave portion 3 and the convex portion 4 provided on both end surfaces of the work 5 are combined to form a cylindrical body (tube). At this time, the projections 8a, 9a of the fixed punch 8 and the movable punch 9 and the depression 11 of the core 11
a, each of the recesses 2 of the work 5 is strongly pressed and
Since the deformation of the work 5 becomes gentle (from the shape shown by the broken line in FIG. 4 to the shape shown by the solid line), the both end surfaces of the work 5 are extruded from each other, and the work 5 is joined in a state in which both end surfaces (joining surfaces) are in close contact. it can. The distortion of the work 5 caused when the work 5 is rounded, that is, the deformation of the end face of the work 5 due to the tensile stress acting on the outer peripheral side of the work 5 and the compressive stress acting on the inner peripheral side of the work 5, Since the light is absorbed by the recessed portion 2 provided, the adhesion of the bonding surface can be improved.

Hereinafter, the operation of the recess 2 provided in the work 5 will be described with reference to FIGS. When the work 5 is rounded, a tensile stress acts on the outer peripheral side of the work 5 and a compressive stress acts on the inner peripheral side of the work 5. Therefore, the outer peripheral side of the end face of the work 5 is pulled, and the inner peripheral side of the end face of the work 5 is compressed.
b, the end faces 5
A gap is created between a and 5b. On the other hand, when the depression 2 formed in the work 5 is strongly pressed between the projections 8a, 9a of the fixed punch 8 and the movable punch 9 and the depression 11a of the metal core 11, the shape of the depression 2 becomes Protrusions 8a, 9a and depression 1
Deformation follows the shape of 1a (from the shape shown by the broken line in FIG. 4 to the shape shown by the solid line). Thereby, as shown in FIG.
As shown in FIG. 5, the insufficient portion 5 c of the outer peripheral side of the work 5 is supplemented by the deformed portion 5 d, and the remaining portion 5 e of the inner peripheral side of the work 5 is absorbed by the deformed portion 5 f. Then, a cylindrical body can be formed in a state where both end surfaces 5a and 5b of the work 5 are in close contact with each other.

(Effects of the present embodiment) According to the present embodiment, distortion of the work 5 caused when the work 5 is rounded, that is, tensile stress acting on the outer peripheral side of the work 5 and acting on the inner peripheral side of the work 5. The deformation of the end face of the work 5 due to the compressive stress can be absorbed by the recess 2 provided in the work 5 in advance, so that there is almost no gap in the joint surface, and a pipe with good adhesion can be manufactured. Further, in the manufacturing method of the present embodiment, the post-processing steps after the bending (the lubrication processing, the deburring step, the cleaning step, etc.), which have been conventionally required, are only required to form the recess 2 in the flat state. Is unnecessary, so that the manufacturing process can be shortened as compared with the conventional ironing method, and the cost can be reduced accordingly. Furthermore, since it is not necessary to perform severe processing such as ironing, the problem that the life of the mold is shortened can be avoided.

When the clinch connection (connection between the concave portion 3 and the convex portion 4) is performed as in this embodiment, the thickness of the flat plate 1 is 3 mm.
In this case, the upper end of the plate thickness is usually said to be 3 mm because deformation such as the end face of the clinch portion is scraped at the time of the clinch insertion connection is performed. If the method of obtaining the adhesiveness of the end face by strongly pressing between each of the projections 8a, 9a of FIG. 9 and the depression 11a of the cored bar 11, the clinch portion at the time of clinch insertion coupling even if a work 5 of 3 mm or more is used. It is possible to prevent deformation of the end face.

(Second Embodiment) FIG. 6 is a sectional view showing a final manufacturing process of a pipe. In this embodiment, the connecting portion 5A of the work 5
It is an example showing a method for improving the bonding strength between (the concave portion 3 and the convex portion 4). The fixed punch 8 fixed to the lower mold base 10 includes
A protrusion 8b is provided at a position corresponding to the joint 5A of the work 5. The projection 8b allows the connecting portion 5 of the workpiece 5
A is strongly pressed between the metal core 11 and the protrusion 8b
As shown in FIG. 7 (an enlarged cross-sectional view of a main part in FIG. 6), the material of the connecting portion 5A (the portion forming the convex portion 4) moves toward the end face side of the connecting portion 5A. Thereby, the contact pressure (the contact pressure between the concave portion 3 and the convex portion 4) at the end face of the joint portion 5A is improved, so that the adhesion of the joint portion 5A is improved, and a tube having a high joint strength can be obtained.

(Third Embodiment) FIG. 8 is a half end view of the work 5. In the above embodiment, the concave portion 2 which is depressed toward the inner peripheral side of the work 5 is provided, but the concave portion 2 which expands toward the outer peripheral side of the work 5 may be provided as shown in FIG. In this case, since the cross-sectional area (volume) inside the pipe can be increased, the inside of the pipe can be effectively used.

(Fourth Embodiment) FIG. 9 is an end view of a work 5. This embodiment shows an example in which three or more concave portions 2 including the concave portions 2 near both end surfaces of the work 5 are provided. A plurality of recesses 2 (six in FIG. 9) are provided at substantially equal positions in the circumferential direction of the work 5. In this case, since the distortion at the time of bending can be absorbed substantially uniformly over the entire circumference of the pipe, the accuracy of the inner and outer diameters of the pipe can be improved without performing post-processing such as ironing. Therefore, the effect is large when the tube is used as a yoke of a motor.

[Brief description of the drawings]

FIG. 1 is a process chart showing a flat plate processing step.

FIG. 2 is a process cross-sectional view showing one manufacturing process of the pipe.

FIG. 3 is a process sectional view showing a final manufacturing process of the tube.

FIG. 4 is a diagram illustrating the operation of a recess provided in a work.

FIG. 5 is a diagram illustrating the operation of a recess provided in a work.

FIG. 6 is a process sectional view showing a final manufacturing process of the pipe (second embodiment).

FIG. 7 is an enlarged sectional view of a main part of FIG. 6 (second embodiment).

FIG. 8 is a half sectional view of a work (third embodiment).

FIG. 9 is an end view of a work (fourth embodiment).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flat plate 2 Depression part (strain absorption part) 3 Depression part 4 Convex part

Claims (4)

[Claims] 1. A method for producing a pipe by bending a flat plate, comprising:
A method for manufacturing a pipe, comprising: forming a strain absorbing portion for absorbing strain generated in the flat plate at the time of bending, in a flat state in advance, and thereafter performing bending. 2. The tube according to claim 1, wherein the strain absorbing portion is provided to extend substantially parallel to an end face of the flat plate, and is a concave portion which is depressed in a thickness direction of the flat plate. Method. 3. The flat plate has a concave portion on one end surface and a convex portion on the other end surface. The flat plate is bent and the convex portion is fitted into the concave portion to form a tube. The method for producing a pipe according to claim 1, wherein the pipe is formed. 4. After forming the strain absorbing portions at three or more locations including near both end faces of the flat plate and at substantially equal positions in the circumferential direction when the flat plate is bent, bending is performed. The method for producing a pipe according to any one of claims 1 to 3, wherein the pipe is processed.