JP4220562B2 - Metal bellows tube forming method - Google Patents

Description

  The present invention relates to a forming method for forming a bellows tube (bellows tube) from a metal circular tube, and more particularly to a forming method for forming a bellows tube having a small outer diameter (for example, about 4 mm to 7 mm) by press working.

  A metal bellows tube is a metal tube whose tube wall is formed in a bellows shape, and various methods have been developed as a method for forming a bellows tube from a metal circular tube. Examples of these methods include (1) roll forming method, (2) hydraulic forming method, (3) welding method, and (4) electrodeposition method.

The roll forming method of (1) is a method in which a metal core is placed inside a metal tube, and a roller is pressed against the outside to form, and the minimum outer diameter of the bellows tube that can be formed due to the strength of the metal core etc. Is about 10 mm.
In addition, in the hydraulic forming method (2), an annular mold is placed outside the metal circular tube, and in that state, a liquid such as oil or water is placed inside the metal circular tube, and a high pressure is applied to this. In this method, the tube wall of the metal circular tube is formed into a bellows shape.
The welding method (3) is a method of forming a bellows tube by welding the inner and outer edges of a donut-shaped part obtained by press molding, and has a problem in pressure resistance.
In the method of electrodeposition (4), a round bar made of aluminum is cut out in accordance with the inner shape of the bellows tube to form a mandrel, and a metal film is deposited on the surface of the mandrel to a desired thickness by electrodeposition. To do. Thereafter, the mandrel is removed with a solvent to obtain a bellows-like thin metal film. In this method, since the metal film is formed to a desired thickness, the thickness is limited, and it is difficult to form a bellows tube that requires high pressure strength.

  On the other hand, metal bellows pipes are widely used from general industries to chemical fields, such as valve seals, piping members, vacuum equipment, accelerators, etc. by using expansion, contraction, springiness, and airtightness. Recently, fuel injection devices for automobiles It is also used for other valves. And the bellows pipe used for the valve | bulb of a fuel-injection apparatus is small (for example, outer diameter around 5 mm), and the pressure strength which can endure a pressure of 20 MPa is calculated | required.

However, the above-described conventional forming method has no problem in forming a large bellows tube having a large diameter (for example, 10.0 to 900.0 mm), but it is almost impossible to form a bellows tube having a small diameter. .
This is because, in the roll forming of (1), the core metal also becomes thin according to the diameter and deforms without being able to withstand the pressure of the roller. Therefore, it is necessary to process the circular pipe with high accuracy, and the entire apparatus becomes large and complicated, resulting in expensive equipment. These forming methods are structurally unsuitable for forming a bellows tube having a small diameter.
In addition, the thickness of the metal circular tube used in response to the demand for high pressure strength increases, but any of the above-described conventional forming methods is difficult to process and form this.
Therefore, it is almost impossible to form a bellows tube having a small outer diameter (for example, about 4 mm to 7 mm) and excellent pressure resistance with high accuracy by the conventional molding method.

Recently, a method of forming a bellows tube by compressing a metal tube in the axial direction and generating irregularities due to buckling on the surface has been proposed (see, for example, Patent Document 1).
However, the method described in Patent Document 1 is a method that uses a buckling method by placing a mandrel inside and then compressing the metal tube from the axial end to generate irregularities due to buckling. is there. In addition, when compressing in the axial direction, it is possible to suppress the occurrence of buckling at a portion other than a predetermined location by preliminarily forming a bent bead that is a starting point of buckling on the surface of the metal tube, and more uniform. However, since the end of the tube is compressed in the axial direction, the deformation due to buckling varies, and the shape of the formed collar is not stable.

JP 2005-262308 A

  An object of this invention is to provide the shaping | molding method which can shape | mold the bellows pipe | tube with an outer diameter small diameter (for example, about 4 mm-7 mm) and excellent in pressure-resistant strength with high precision.

  As a result of earnest research to achieve the above-mentioned object, the present inventor uses press work and accurately produces a product with the desired product dimensions in order to accurately form a bellows pipe from a thick, small-diameter metal circular pipe. As a result of further research based on such knowledge, it has been accomplished that the present invention has been completed.

That is, the metal bellows tube molding method of the present invention is a molding method for molding a bellows tube from a metal circular tube by press work,
(1) A metal circular pipe work having annular ridges on the inner surface at equal pitches, an outer mold that can be opened and closed in the radial direction, and inserted into the outer mold and alternately meshed with the annular ridge. An annular ridge that has an equal pitch on the outer surface and is inserted between an inner mold that expands and contracts in the radial direction, and the inner mold is pressed and expanded in the outer mold direction to corrugate the pipe wall of the workpiece The first step of molding
(2) said inner workpiece molded in the first step, to insert the core metal of the inner diameter substantially the same diameter of the fold portions, and and clamped from above and below with openable plate member each fold portion, each plate member A second step of compressing the corrugated pitch interval by pressurizing in the direction of narrowing the mutual interval, and forming the corrugated outer shape from a substantially V-shaped cross section to a substantially U-shaped cross section ;
(3) Insert a mandrel having an outer diameter that matches the inner diameter of the flange portion at the completion of the second step and the target inner diameter to be reduced in the third step, inside the workpiece formed in the second step, The corrugated valley portion is sandwiched between circumferentially spaced split punches on the outside of the workpiece, and the split punch is disposed corresponding to the flange portion that reduces the diameter. A cored bar having a matching outer diameter is disposed, and a cored bar having an outer diameter matching the inner diameter of the flange part is disposed inside the flange part higher than the flange part to be reduced in diameter. Is pressed from the radially outer side to the center direction to reduce the valley portion to a contact with the outer peripheral surface of the core metal having an outer diameter matching the inner diameter of the reduced diameter, and further, the core metal and the workpiece are A third step of moving in the axial direction and reducing the valley portion to a target inner diameter by one pitch ;
(Claim 1).

The outer mold having an annular ridge on the inner surface in the first step determines the outer shape (wave shape) of the bellows tube, and is for setting the workpiece and taking out the molded workpiece after completion of processing in the first step. However, the number of divisions may be any of two divisions, three divisions, four divisions, etc., and the division outer mold is closed to be provided with a shape.
On the other hand, the inner mold expands in the radial direction and pushes the pipe wall of the work placed outside the inner mold to the inner surface side of the outer mold. Like the outer mold, the circumferential direction is divided into a plurality of parts. Has been. As for the number of divisions, a gap is generated between the divided molds by expanding in the radial direction, but it is effective to increase the number of divisions in order to reduce the width of the gap as much as possible. In consideration of molding of the mold, about four divisions are preferable.

  Further, as a method of expanding the inner mold in the direction of the outer mold by pressure (pressing pressure), for example, a tapered hole is formed along the axis of the divided inner mold, and the tapered hole (shaft of the divided inner mold) is formed. By inserting a taper pin into the core and applying a press pressure to the upper end of the taper pin, the divided inner mold can be expanded outward in the radial direction.

  The compression of the corrugated pitch interval in the second step compresses all of the plurality of ridges formed in the first step at the same time. For this purpose, the plate member sandwiching the ridge portion from above and below has a predetermined interval. Are divided so that the workpiece can be attached and detached, and can be opened and closed. There are various methods such as controlling the amount of movement of the pressure member or detecting it with a sensor to complete the compression of the wave-shaped pitch interval. For example, the plate members stacked in advance with a predetermined interval between them When contact is made by pressurization, compression may be completed, and in that case, the apparatus can have a simple structure.

The method of pressing and moving the divided punch in the third step from the radially outer side to the center direction may be any method such as a cam method or a cylinder method. The number of divided punches is not particularly limited as long as the diameter defined by the inner diameter of the punch changes (reduced diameter) by the radial movement of the punch.
The diameter of the third step is reduced to the bellows tube having a substantially U-shaped cross-section by reducing the diameter of the trough formed by narrowing the wave-shaped pitch interval in the second step. The entire shape is molded one pitch (one step) at a time without reducing the diameter. That is, a cored bar having a diameter reduction margin (gap between a corrugated inner diameter at the end of the second process and a corrugated inner diameter at the end of the third process (finished bellows pipe)) to be inserted inside the work and the work Are sequentially moved in the axial direction for each pitch forming to reduce the diameter.
A cored bar having an outer diameter difference corresponding to a diameter reduction allowance inserted into a workpiece is a two-part structure of a large-diameter cored bar and a small-diameter cored bar, or a large-diameter part and a small-diameter part are formed on one shaft. A stepped core may be used.

According to the above means, the metal circle set between the outer mold and the inner mold by expanding the inner mold radially outward with respect to the closed fixed outer mold having the annular ridge in the first step. The pipe work is preformed into a wave shape with a gentle pipe wall by meshing the inner and outer annular ridges. Then, the corrugated portion of the pre-formed gentle wave-shaped tube wall is sandwiched from above and below by the plate members in the second step, and by pressing (pressing) the interval between the plate members, The pitch interval is narrowed, and the wave shape is formed from a substantially V-shaped cross section to a substantially U-shaped cross section. And the workpiece | work where the wave shape became an acute angle is further diameter-reduced to the target internal diameter by the diameter reduction (drawing) operation | movement by the division | segmentation punch of a 3rd process, and all the valley parts are reduced in diameter. This completes the bellows tube.
That is, the tube wall of the metal circular tube is preformed into a gentle wave shape, and then the pre-formed wave shape is formed into a sharp acute wave shape by narrowing the pitch interval, and finally the wave shape trough is formed. Reduce the diameter to finish the desired bellows tube.
And since the trough portion is reduced in diameter by one pitch in the third step, the portions other than the reduced diameter portion in the work are released toward the end in the axial direction, so that the diameter reducing operation is stably performed without being blocked. Is called. Therefore, a bellows tube having a small diameter and a large thickness can be formed with high accuracy.

In the first step, the inner mold arranged on the inner side with respect to the outer mold closed and fixed is expanded outward in the radial direction to form the tube wall of the workpiece into a wave shape, but the inner mold is divided into a plurality of circumferential directions. Therefore, when it expands in the radial direction, a gap is generated in the circumferential direction between the members constituting the inner mold. Therefore, in the case where the inner mold is expanded to form a wave shape, the tube wall portion corresponding to the gap is indirectly stretched by the expansion of the inner mold. However, when the diameter of the bellows tube to be molded is small, for example, when the outer diameter of the workpiece is 5 mm, the wall thickness is 1 mm, and the number of divisions of the inner mold is four, the inner mold is expanded and the inner mold members are The resulting gap is 0.5 mm or less.
Therefore, even if the inner mold is expanded at a certain position, it does not greatly affect the finished product, but when molding a more accurate product, the generated gap is directly pressed by the inner mold. For this purpose, the inner mold or the outer mold (including the work) is rotationally moved in the circumferential direction (Claim 2). For example, when the inner mold is a quadrant mold, the inner mold or the outer mold is rotated 45 degrees clockwise or counterclockwise from the position where the inner mold or the outer mold is first expanded, and the inner mold is expanded at that position.
By performing this operation a plurality of times, the tube wall can be expanded evenly.

Further, the diameter reduction in the third step is performed by moving the divided punch, which is divided into a plurality of circumferential directions in the radial direction, in the same manner as the inner mold in the first step. There is a minute gap between them. Thus, the entire circumference of the pipe wall uniformly reduced in diameter, when increasing the outer径真circularity, by rotating the divided punch or work in the circumferential direction to move the reduced diameter position (claim 3).

  According to the above means, by rotating the divided punch or workpiece in the circumferential direction to reduce the diameter, the reduced diameter position (drawing position) by the divided punch moves in the circumferential direction, and there is no portion that is not directly reduced in diameter by the divided punch. . Thereby, the roundness can be increased.

According to the metal bellows tube forming method of the present invention, a metal bellows tube having a small diameter and a large material thickness, which is difficult to be formed by the conventional method, can be formed with high accuracy by the configuration described in claim 1. .
In addition, according to the configuration of claim 2, it is possible to more uniformly perform the gentle wave shape molding (preliminary molding) in the first step, and as a result, the molding accuracy in the second and third steps thereafter is also stable. A highly accurate bellows tube can be formed.

Furthermore, according to the configuration of the third aspect, a highly accurate bellows tube having a stable outer diameter roundness can be formed.

The method for forming a metal bellows pipe of the present invention includes three steps (a first process, a second process, and a first process) from the work W of a metal circular pipe made of a material to finishing to a target bellows pipe F. By molding in three steps, it is possible to form a bellows tube (for example, 7 mm or less) having a large wall thickness and a small diameter, which has been difficult to mold by the conventional method, with high accuracy. Is.
That is, a metal circular work W (see FIG. 1A) is alternately arranged between an outer mold having annular ridges on the inner surface at equal pitches and an annular ridge inserted inside the outer mold. Engaging annular ridges on the outer surface at equal pitches, inserted between the inner molds that expand and contract in the radial direction, and the inner molds are expanded in the outer mold direction by axial pressure (pressing) The first step of forming the tube wall of the workpiece into a gently corrugated ridge (see FIG. 1B for the shape of the first step processed product), and inside the workpiece W ′ formed in the first step, Insert a core bar having the same diameter as the inner diameter of the flange portion, and sandwich the flange portion from above and below with a plate member that can be opened and closed, and pressurize in a direction to narrow the interval between the plate members to reduce the pitch interval of the wave shape. The second step to be compressed (see FIG. 1C for the shape of the second step processed product) and the second step inside the workpiece W ″ formed in the second step Insert a cored bar that has an inner diameter that matches the inner diameter of the flange at the time of completion and the target inner diameter to be reduced in the third step, and sandwich the corrugated valley on the outside of the work with a split punch. The third step (refer to FIG. 1 (d) for the shape of the third step processed product (finished product F)) is to reduce the diameter to the target inner diameter by moving the punch from the radially outer side to the center direction.

Hereinafter, the first to third steps will be described with reference to the drawings. Note that the illustrated molding apparatus is for conceptually explaining the molding method of the present invention, and a power source and the like not directly related to molding are omitted.
[First step]
This first step is a step of preforming the tube wall of the workpiece W into a gentle wave shape. As shown in FIG. 2, the forming apparatus projects the annular ridges 2 on the inner surface at an equal pitch and has a diameter. The outer die 1 is divided into four parts that can be opened and closed in the direction, and the annular ridges 4 that are alternately meshed with the annular ridges 2 of the outer die 1 are provided at equal pitches on the outer surface and can be expanded and contracted in the radial direction. A split inner mold 3 and a taper pin 5 that expands the inner mold 3 outward in the radial direction are provided. The outer mold is disposed on a base 6 that supports and holds a workpiece. Is arranged above the outer mold 1 and is configured to be detachable with respect to the outer mold 1, and the inner mold 3 is urged in a closing direction by a spring 7.

As shown in FIG. 2 (a), the first step by the above apparatus is as follows. First, the outer mold 1 on the base 6 is opened, the workpiece W is placed at the center, and then, as shown in FIG. 2 (b). The outer mold 1 is closed to hold the workpiece W. Next, as shown in FIG. 2 (c), the inner mold 3 reduced in diameter by a spring is inserted inside the workpiece W. At this time, the annular ridges 4 of the inner mold 3 are positioned between the annular ridges 2 of the outer mold 1 and are arranged so as to engage with each other in a staggered manner. Then, as shown in FIG. 2 (d), the taper pin 5 inserted into the shaft core of the inner mold 3 is pressurized with a press machine, and the inner mold 3 is expanded outward in the radial direction.
As a result, the tube wall of the workpiece W is pressure-bonded to the inner surface of the outer mold 1 which is closed and fixed, and is formed into a wave shape by meshing the annular ridge 2 of the outer mold 1 and the annular ridge 4 of the inner mold 3.

Since the inner mold 3 is a split mold as described above, a slight gap is generated between the mold members when the inner mold 3 is expanded in the radial direction, and the inner mold 3 does not contact the inner surface of the workpiece W. A part arises. Therefore, the inner die 3 is rotated in the circumferential direction so that the outer surface of the inner die 3 corresponds to the portion where the inner die is not in contact with the workpiece W at the previous inner die expansion, and the taper pin 5 is again attached at that position. The inner die 3 is expanded by applying pressure with a press. The operation of rotating the inner die 3 in the circumferential direction is performed several times and the expansion position is moved, so that the peripheral wall of the workpiece W is uniformly formed into a wave shape.
After the molding, as shown in FIG. 3A, the press machine is lifted to release the pressurization of the taper pin 5, the inner mold 3 is contracted radially inward by the contraction force of the spring 7, and the workpiece W Pull away from the inside surface.
Thereafter, the inner mold 3 is moved upward as shown in FIG. 3 (b) to be separated from the outer mold 1, and the outer mold 1 is opened as shown in FIG. '(See Fig. 1 (b)) is taken out.
4 (a), 4 (b), and 4 (c) show the outer mold 1 and the inner mold 3 in each part of the molding operation in the first step (inner mold insertion, molding by expanding the inner mold, and inner mold diameter reduction). It is an enlarged view showing a positional relationship of the workpiece W.

[Second step]
The second step is a step of forming a wave shape that narrows the pitch interval of the gentle (obtuse angle) pre-formed in the first step, and compresses the flange portion of the workpiece W ′ that has finished the first step in the axial direction. Then, the workpiece W ″ in which the wavy pitch interval shown in FIG. 1C is compressed is formed.
In the second step of compressing the pitch of the corrugated ridge portion, a plate member divided into left and right parts is fitted into each corrugated trough portion of the work W ′, and the corrugated trough is placed inside the work W ′. A core metal having the same diameter as the inner diameter of the portion is inserted to regulate the inner diameter, and in this state, the plate members are pressed in the vertical direction to narrow the vertical interval between the plate members, thereby forming a wave-shaped pitch. Compress the interval.
In the apparatus, plate members 9 and 9 ′ having substantially semicircular cutouts that can be fitted into wave-shaped valley portions of the workpiece W ′ move vertically on the bases 8 and 8 ′ that can be opened and closed. A lower mold 10 arranged in a stackable manner, a core 11 inserted inside the workpiece W ′, and an upper mold 13 holding down a pressure block 12 for pressing the plate members 9 and 9 ′ of the lower mold 10; A guide pin 14 for setting the workpiece W ′ on the lower die 10 is provided, and the upper die 13 and the guide pin 14 are configured to move up and down with respect to the lower die 10.

First, as shown in FIG. 5A, the workpiece W ′ is fitted on the guide pin 14, and then the guide pin 14 is lifted into the open lower mold 10 as shown in FIG. As shown in FIG. 5C, the lower mold 10 is closed and the plate members 9 and 9 ′ are fitted into the wave-shaped valley portions of the workpiece W ′. By fitting the plate members 9 and 9 ′ into the corrugated valley portions of the workpiece W ′, the stacked plate members 9 and 9 ′ are held at a wave-shaped pitch interval, and the stacked plate members are between each other. A gap corresponding to the compression allowance is formed in. After the work W ′ is fitted and set to the lower mold 10, the guide pin 14 is lowered as shown in FIG. 5 (d) and detached from the work W ′.
After the guide pin 14 is detached, the upper die 13 is lowered as shown in FIG. 6A, the core metal 11 is inserted inside the work W ′, and the pressure block 12 is moved to the plate members 9 and 9 of the lower die 10. Touch the top of '. The positional relationship among the lower mold 10, the upper mold 13 and the work W ′ at this time is as shown in FIG. 8A, and the plate members 9 and 9 ′ of the lower mold 10 are fitted in the wave-shaped valley portions of the work W ′. A compression allowance S is formed between the stacked plate members in engagement. Further, the outer peripheral surface of the core metal 11 of the upper mold 13 is substantially in contact with the corrugated inner surface (inner diameter of the valley portion) of the work W ′, and the pipe of the work W ′ is compressed when the corrugation is compressed by the pressure block 12. The wall is restricted from bulging and deforming toward the center.

Next, as shown in FIG. 6 (b), the upper die 13 is lowered, and the plate members 9, 9 'in which the lower die 10 is laminated are pressurized by the pressure block 12, and the compression allowance S is made zero. . In the compressed state, as shown in FIG. 8 (b), the plate members 9, 9 'fitted in the valley portions come into contact with each other, and the compression margin S becomes zero, and the deformation due to the compression is caused to bulge inward. Since the deformation is restricted by the metal core 11, the deformation is allowed to bulge out in the outward direction in which the deformation is allowed, that is, in the step portion (relief recess) 15 formed in advance on the plate members 9, 9 ′.
After completion of the compression, the upper die 13 is raised and separated from the lower die 10 as shown in FIG. 6C, and then the guide pins 14 are raised as shown in FIG. Is inserted into the workpiece W ′ supported by the first step, and after the insertion, the lower mold 10 is opened as shown in FIG. 7A, and the guide pin 14 is lowered as shown in FIG. The processed workpiece W ″ is taken out from the guide pin 14.

[Third step]
The third step is a step of reducing the inner diameter of the corrugated valley portion in which the pitch interval is narrowed in the second step to the target inner diameter. A cored bar having an outer diameter that matches the inner diameter of the flange portion and the target inner diameter to be reduced in the third step is inserted, and a corrugated valley portion is provided on the outer side of the workpiece W ″ with a gap in the circumferential direction. A plurality of divided punches are sandwiched, and the divided punches are moved from the radially outer side to the central direction to reduce the diameter to a desired inner diameter, thereby obtaining a finished product (product) F (see FIG. 1D).
As shown in FIG. 9, the apparatus includes a sleeve holder 17 having a sleeve 16 that holds a workpiece W ″ that has been processed in the second step, and a lower metal core having an outer diameter that matches the inner diameter to be reduced. It matches the inner diameter of the lower cored bar holder 19 that holds 18 upright, the four divided punches 20 that are movable in the radial direction to reduce the valley portion of the workpiece W ″, and the inner diameter of the valley portion of the workpiece W ″. An upper cored bar holder 22 is provided that suspends and holds an upper cored bar 21 having an outer diameter, and the sleeve 16 is fitted to the lower cored bar 18 and supported so as to be vertically movable. The punch holder 23 that is horizontally supported through the sleeve 16 is supported in a substantially cross shape in plan view, and the valley portion of the workpiece W ″ is pushed in the center direction by pressing and moving from the radially outer side to the center direction. Reduced to the inner diameter of

  As a mechanism for pressing and moving the divided punch 20 in the radial direction, for example, as shown in FIGS. 11 (a) and 11 (b), it surrounds a workpiece W ″ supported upright by a sleeve 16 on the punch holder 23. Around the periphery, a four-division divided punch 20 is supported by a punch guide 24 so as to be movable in the radial direction, and the divided punch 20 is moved in the radial direction by the rotation of a ring-shaped scroll cam 25 and moves along the valley portion of the workpiece W ″. Push in the center to reduce the diameter.

  In the third step, first, as shown in FIG. 9 (a), the workpiece W "that has been formed in the second step is fitted and set to the sleeve 16, and then the upper core metal as shown in FIG. 9 (b). 21 is inserted into the workpiece W ″, and the lower end of the upper cored bar 21 is brought into contact with the upper end of the lower cored bar 18. At this time, the positional relationship among the sleeve 16, the workpiece W ″, the divided punch 20, the lower metal core 18, and the upper metal core 21 is as shown in FIG. 12A, and the valley portion of the workpiece W ″ corresponding to the divided punch 20. An annular gap S ′ corresponding to the reduction diameter is generated between the inner diameter of the lower cored bar 18 and the outer peripheral surface of the lower cored bar 18. Has not occurred. Therefore, in the diameter reduction by the radial movement of the divided punch 20 performed later, only the valley portion where the divided punch 20 is fitted is reduced in diameter, and the other portions are not deformed.

After the upper mandrel 21 is inserted, as shown in FIG. 9C, the split punch 20 is moved in the radial center direction by the rotation of the scroll cam 25 to reduce the valley portion of the workpiece W ″. The amount of is to make the above-described annular gap S ′ zero, and as shown in FIG. 12 (b), the inside of the valley portion reduced in diameter by the radial movement of the divided punch 20 is the outer peripheral surface of the lower core metal 18. Until it comes into contact with
Then, after the diameter reduction, as shown in FIG. 9D, the divided punch 20 is moved radially outward to be separated from the workpiece W ″ (see FIG. 12C), and the diameter reduction of one valley portion is completed. To do.
Then, in order to reduce the diameter of the next valley portion, as shown in FIG. 9E, the sleeve 16 holding the workpiece W ″ is lowered by one pitch along the lower cored bar 18. The sleeve 16 at this time point. The positional relationship among the workpiece W ″, the divided punch 20, the lower cored bar 18, and the upper cored bar 21 is as shown in FIG.
Thereafter, the diameter reduction by the movement of the divided punch (operation of FIG. 9C), the opening and disengagement of the divided punch 20 (operation of FIG. 9D), and the downward movement of the sleeve 16 (work W ″) (FIG. 9 (FIG. 9). The operation (e) is sequentially repeated to reduce the diameter of all trough portions of the corrugated shape formed on the peripheral wall of the workpiece W ″, and the final diameter reduction processing is completed as shown in FIG. .

  After completing the final diameter reduction, the upper cored bar 21 is detached from the work W ″ as shown in FIG. 10B, and then the sleeve 16 is moved to the lower cored bar 18 as shown in FIG. 10C. The workpiece W ″ is projected upward from the split punch 20 and the workpiece W ″ is taken out from the sleeve 16 to obtain a finished product (metal bellows tube) F. The completed metal bellows tube F is shown in FIG. As shown in d).

  In the third step, the divided punch 20 is moved in the central direction in the radial direction to reduce (squeeze) the valley portion of the workpiece W ″. The divided punch is divided into a plurality of circumferential directions (in the illustrated example, four divisions). Therefore, the entire circumference of the valley portion of the workpiece W ″ is not necessarily reduced in diameter by the divided punch, and a portion where the diameter is not reduced by the divided punch is generated on the circumference. In order to eliminate the occurrence of an unreduced portion due to the divided punch and to reduce the diameter to a substantially perfect circle, the divided punch 20 or the workpiece W ″ is rotated in the circumferential direction in the same manner as in the first step, so that the reduced diameter position is obtained. The position where the divided punch hits the workpiece is moved.The diameter reduction position can be changed, that is, the number of times of position change is arbitrary, so that more uniform diameter reduction can be performed.

The forming method described above is performed for a vertical mold that sets the workpiece in the vertical direction and the apparatus for forming the vertical mold is illustrated. However, in the molding method of the present invention, the axis of the work is parallel to the horizontal line. It goes without saying that a horizontal mold formed in a state of being laid down may be used.
Moreover, the shaping | molding apparatus which shows each operation | movement of the 1st process in this invention, a 2nd process, and a 3rd process is an example to the last, and is not limited by this.

It is a front view which shows the shaping | molding state of each process in the shaping | molding method of this invention, (a) is the workpiece | work (metal circular pipe) W used for shaping | molding, (b) is the workpiece | work W 'at the time of completion of a 1st process, (c ) Shows the workpiece W ″ when the second process is completed, and (d) shows the finished product F when the third process is completed. (A)-(d) is explanatory drawing which shows from the work set of a 1st process to shaping | molding of a waveform. (A)-(c) is explanatory drawing which shows from an inner mold diameter reduction of an 1st process to an outer mold opening. (A)-(c) is an enlarged view which shows the positional relationship of the outer mold | type 1, the inner mold | type 3, and the workpiece | work W at the time of each operation | movement of a 1st process. (A)-(d) is explanatory drawing which shows to the set of the workpiece | work with respect to the lower mold | type of a 2nd process. (A)-(d) is explanatory drawing which shows the waveform compression operation | movement of a 2nd process. (A), (b) is explanatory drawing which shows the process of taking out the molded workpiece | work of a 2nd process. (A), (b) is an enlarged view which shows the state before the compression of a 2nd process, and the state after compression. (A)-(e) is explanatory drawing which shows from the work set of a 3rd process to the diameter reduction of the trough part of the 1st step | paragraph. (A)-(c) is explanatory drawing which shows from the completion of diameter reduction of the last stage of a 3rd process to the taking-out of a workpiece | work. It is explanatory drawing which shows an example of the moving mechanism which performs the diameter reduction operation | movement of the division | segmentation punch of a 3rd process, (a) is before diameter reduction, (b) shows the time of diameter reduction. (A)-(d) is an enlarged view at the time of each operation | movement of a 3rd process.

Explanation of symbols

W ... Work (metal circular pipe)
W ′: Work piece that has been formed in the first step W ″: Work piece that has been formed in the second step
F ... Finished product that completed the third process
1 ... Outer mold that forms a wave shape on the workpiece in the first step
3 ... Inner mold that forms a wave shape on the workpiece in the first step
5 ... Taper pin that expands the inner die 9, 9 '... Plate member that compresses the wave shape in the second step 11 ... Core metal inserted inside the workpiece in the second step 18, 21 ... Inserted into the workpiece in the third step Core to be cut 20 ... Split punch that reduces the trough of the workpiece in the third step

Claims (3)

A molding method in which a small-diameter bellows pipe is formed by press working from a metal circular pipe having a small outer diameter,
(1) A metal circular pipe work having annular ridges on the inner surface at equal pitches, an outer mold that can be opened and closed in the radial direction, and inserted into the outer mold and alternately meshed with the annular ridge. An annular ridge that has an equal pitch on the outer surface and is inserted between an inner mold that expands and contracts in the radial direction, and the inner mold is pressed and expanded in the outer mold direction to corrugate the pipe wall of the workpiece The first step of molding
(2) said inner workpiece molded in the first step, to insert the core metal of the inner diameter substantially the same diameter of the fold portions, and and clamped from above and below with openable plate member each fold portion, each plate member A second step of compressing the corrugated pitch interval by pressurizing in the direction of narrowing the mutual interval, and forming the corrugated outer shape from a substantially V-shaped cross section to a substantially U-shaped cross section ;
(3) Insert a mandrel having an outer diameter that matches the inner diameter of the flange portion at the completion of the second step and the target inner diameter to be reduced in the third step, inside the workpiece formed in the second step, The corrugated valley portion is sandwiched between circumferentially spaced split punches on the outside of the workpiece, and the split punch is disposed corresponding to the flange portion that reduces the diameter. A cored bar having a matching outer diameter is disposed, and a cored bar having an outer diameter matching the inner diameter of the flange part is disposed inside the flange part higher than the flange part to be reduced in diameter. Is pressed from the radially outer side to the central direction to reduce the diameter of the valley until it comes into contact with the outer peripheral surface of the cored bar having an outer diameter matching the inner diameter of the reduced diameter, and further to the cored bar and the workpiece A third step of axially moving the trough portion to a desired inner diameter by one pitch ;
A method for forming a metal bellows tube for high pressure resistance, comprising : 2. The metal for high pressure resistance according to claim 1, wherein the expansion in the first step is performed by rotating one or both of an inner mold and an outer mold in the circumferential direction to move the expansion position. A method for forming a bellows tube. 3. The metal bellows pipe for high pressure resistance according to claim 1 or 2 , wherein the diameter reduction by the divided punch in the third step is performed by rotating the divided punch in the circumferential direction and moving the reduced diameter position . Molding method.

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