JP3751826B2 - Shaft pushing device for hydroform molding - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a shaft pressing device for pressing an opening end of a pipe in an axial direction in hydroforming, in which a pipe is molded by the pressure of a liquid filled inside.
[0002]
[Prior art]
Hydroform molding is a molding method called hydraulic bulge processing, in which a pipe to be molded is inserted into a molding die, and its opening end is blocked by pressing with a shaft pressing device, and the pipe is in that state. This is a processing method in which a liquid such as water (hereinafter referred to as “processing fluid”) is filled inside, the processing fluid is pressurized to expand the pipe from the inside, and is molded into a shape corresponding to the cavity of the molding die. Conventionally, a shaft pushing device conventionally used for hydroforming is a cylinder device having a simple structure, and abuts the front end of the piston against the end of the pipe and pushes it in the axial direction. In such a shaft pushing device, since the front end of the piston receives a large reaction force of the machining fluid, it is necessary to continue to apply a force to counteract it, and the device must be considerably enlarged.
[0003]
In hydroform molding, not only deformation due to the hydraulic pressure inside the pipe, but also a method in which the pipe is positively compressed and deformed by the pressing force of the shaft pressing device at the same time is employed. In this case, not only does the working fluid not leak from the inside of the pipe, that is, a pressing force for compressing and deforming the pipe but also a pressing force for compressing and deforming the pipe, the shaft pressing device is further increased in size. In that case, the molding speed must also be appropriate in order to perform good molding, and the reaction force from the working fluid changes slightly according to the degree of molding from the start of molding. It is necessary to control the pressing force that causes compressive deformation of the pipe while detecting a force change. However, since the pressing force for the end seal is larger than the pressing force for compressive deformation of the pipe, the control is extremely difficult. If the reaction force of the machining fluid received from the front end of the piston can be eliminated or alleviated, the force that presses the end of the pipe will be small, so the shaft pushing device can be miniaturized and the pipe can be compressed and deformed. The control of the pressing force is facilitated even when the is actively used.
[0004]
As a technique for eliminating the reaction force received by the piston, there is a technique described in, for example, Japanese Patent Laid-Open No. 38-17158. The axial pushing device described in this publication has a pipe axial inner cross-sectional area (the area of a section defined by the inner wall surface of the pipe in the axial straight section; in the case of a round pipe, the area of a circle having an inner diameter as a diameter) ) The rear end of the piston is molded so that it has the same axial cross-sectional area as that of), and the rear end protrudes toward the rear of the cylinder. The reaction force elimination chamber is formed separately from the cylinder, filled with machining fluid. It is a shaft pushing device constituted by inserting a rear end portion thereof. According to this axial pushing device, the machining fluid is conducted between the inside of the pipe and the reaction force erasing chamber through the axially penetrating hole provided in the piston. By introducing pressure into the force erasing chamber, it is possible to erase the reaction force from the machining fluid received by the front end of the piston in balance with the force from the machining fluid in the reaction force erasing chamber received by the piston rear end. .
[0005]
This shaft pushing device has an effect that the pushing force that the cylinder has to generate in order to push the pipe end can be reduced by eliminating the reaction force by the above action. However, since the reaction force elimination chamber is provided as a separate body from the cylinder, downsizing of the entire apparatus has not been achieved with the shaft pushing device.
[0006]
[Problems to be solved by the invention]
The present invention was made for the purpose of solving the problems of the shaft pressing device used in the conventional hydroforming molding, and in addition to being able to balance the reaction force received by the piston, It is an object of the present invention to provide a shaft pushing device that can be configured extremely small.
[0007]
[Means for Solving the Problems]
(1) The hydroforming molding shaft pushing device of the present invention is used in hydroforming molding in which a pipe is filled with a machining fluid and the pipe is molded by the fluid pressure, and the opening end of the pipe is pressed in the axial direction. A piston that has a front end in contact with the open end of the pipe, and a cylinder that includes the piston and that applies pressure to the piston in the axial direction. A space that is partitioned by the cylinder and the piston and whose volume changes with the movement of the piston is formed, and a conduction path that connects the space and the inside of the pipe is formed in the piston. and by the working fluid is filled in the conductive path, the space is, that acts as a reaction force balance chamber to provide a resistance to the reaction force from the working fluid to the piston.
[0008]
That is, the shaft pressing device of the present invention is provided with a reaction force balance chamber in the cylinder for balancing the reaction force from the machining fluid received by the piston front end. The conduction path formed in the piston connects the inside of the pipe to be molded and this reaction force balance chamber, so that the fluid pressure inside the pipe is guided to the reaction force balance chamber and the front end of the piston receives. By applying a force against the reaction force from the liquid from the rear, it is possible to balance both forces. Therefore, the force applied from the cylinder to the piston to press the pipe end can be small. In other words, the shaft pushing device of the present invention can be considered as a device in which another cylinder device driven by the hydraulic pressure of the machining fluid is built in the cylinder, that is, a dual-structure cylinder device.
[0009]
In the conventional shaft pushing device described above, the reaction force erasing chamber exists as a separate chamber outside the cylinder, whereas by providing the reaction force balance chamber inside the cylinder, the shaft pushing device of the present invention is In addition to being able to balance the reaction force received by the piston, the shaft pushing device is extremely small.
[0010]
The space serving as the reaction force balance chamber is formed in the piston in the axial direction and has a bottomed hole that opens in the rear end portion, and protrudes forward in the axial direction from the rear end portion of the cylinder and is fitted into the bottomed hole. partitioned by a rod, Ru is configured as being formed within said piston.
[0011]
Here, “axially forward” means the direction in which the piston presses the pipe. That is, it means the direction in which the front end of the piston moves to press the end of the pipe. In addition, the “rear end portion” of the cylinder means a portion of the cylinder that is located rearward in the axial direction (meaning a direction opposite to the “forward in the axial direction”). In the case of a cylindrical cylinder with a bottom, as in a general cylinder device, it means the bottom.
[0012]
In the axial pushing device of this aspect, the bottomed hole formed in the piston functions as another cylinder, and the rod protruding from the cylinder functions as another piston. That is, the cylinder device has a double structure in which a cylinder device is separately provided inside the piston. Since the reaction force balance chamber is present inside the piston, the shaft pushing device of this aspect is an extremely small shaft pushing device.
[0013]
Desirable embodiments, rods inserted into the bottomed hole protrudes axially forwardly from the rear end of the cylinder, that has a part of the cylinder.
[0014]
When performing Hydro foam molding, machining fluid is filled inside the pipe is typically fed into the pipe from the front end of the piston Jiku押device. In the case of the shaft pushing device according to the present invention, since the above-mentioned conduction path is formed in the piston so as to conduct inside the pipe, a supply path branched from the middle of the conduction path to communicate with the outside of the apparatus is provided. Can be supplied from. Then, this supply path is connected to a pressurizing device by an external pipe or the like, and the working fluid may be pressurized by the pressurizing device. In addition, if a gas such as air remains inside the pipe during molding, the molding is adversely affected, so the gas in the pipe needs to be released outside the apparatus. The passage branched from the conduction path can also be used as a discharge path for releasing gas.
[0015]
However, when the machining fluid supply passage or the gas discharge passage is provided in the piston, the piston moves forward in the molding process, so the external device such as the pressurizing device and the piping to the piston are flexible, such as a hose. Shall be. Since such a flexible pipe has a high working fluid pressure, the structure thereof becomes complicated, and the handling thereof becomes complicated. Therefore, in the shaft pushing device of the present invention, in the case of the above aspect in which the reaction force balance chamber is provided inside the piston, the rod is formed with a second conduction path that conducts the space and the outside of the cylinder. It can be configured (corresponding to claim 1 ).
[0016]
In other words, in the shaft pushing device of this aspect, the second conduction path is a machining fluid supply path for supplying the machining fluid from the outside of the cylinder to the reaction force balance chamber and the pipe, or the pipe interior and the reaction force balance. It becomes a discharge path for releasing the gas remaining in the chamber. This second conducting path leads to the outside of the apparatus at the rear of the cylinder. Since the cylinder is fixed without moving during molding, the external piping to the external device such as a pressurizing device may be a fixed piping, which is simple in structure and does not require special consideration in handling. When using this shaft pushing device, the hydroform molding system itself can have a simple configuration.
[0017]
( 2 ) In the case of adopting the above aspect in which the space defined by the bottomed hole drilled in the piston and the rod inserted into the piston and protruding from the cylinder is the reaction force balance chamber, the reaction force balance chamber is generated. The force resisting the reaction force to the piston is proportional to the size of the rod's axial cross-sectional area. Therefore, in the axial pushing device of the present invention of this aspect, the rod can be configured such that its axial cross-sectional area is substantially equal to the axially inner cross-sectional area of the pipe (corresponding to claim 2 ). .
[0018]
The reaction force from the machining fluid in the pipe increases in proportion to the cross-sectional area directly inside the axis of the pipe. When making the pipe axial cross-sectional area equal to the rod axial cross-sectional area, the machining fluid inside the pipe will push the piston backward, and the machining fluid in the reaction force balance chamber will push the piston back forward. The drag force is theoretically equal in magnitude, and both are balanced. Therefore, in the shaft pressing device of the present invention of this aspect, the reaction force is eliminated, and it is only necessary to generate a very small pressing force, and the device itself can be extremely miniaturized.
[0019]
In addition, when the axial cross-sectional area of the rod is small compared to the axial internal cross-sectional area of the pipe, since the drag is small compared to the reaction force, an extra force is required to press the pipe by the difference between the two. If the rod axial cross-sectional area is larger than the pipe axial internal cross-sectional area, the drag is superior to the reaction force. Must be generated. However, even in these cases, when the difference between the cross-sectional areas is not so large, the pressing force required for the shaft pressing device is small, and the objective of downsizing the shaft pressing device is sufficiently achieved.
[0020]
( 3 ) In the shaft pushing device of the present invention, the piston may have a structure in which a front end portion including a front end contacting the pipe can be exchanged according to the outer shape of the pipe (corresponding to claim 3 ). Generally, the front end portion of the piston of the shaft pressing device is inserted into the mold. Therefore, the shape of the front end portion inserted into the mold must be changed depending on the thickness of the pipe to be molded, for example, the outer diameter of a round pipe. In the conventional normal shaft pressing device, the piston is structured so that the front end portion is integrated, so that the shaft pressing device itself has to be replaced when the workpiece is changed. This replacement of the shaft pushing device is complicated and takes a long time. On the other hand, in the shaft pushing device of this aspect, since only the front end portion can be exchanged, it is practical in that it can easily and quickly cope with a change in the molding object. In addition to the reduction, the work with less time loss in the setup change is secured.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings, and an example of the embodiment will be described in detail, and further, after describing a modification thereof, other embodiments will be referred to.
[0022]
<Example Embodiment>
FIG. 1 and FIG. 2 show a main part of a hydroforming molding system using a shaft pressing device according to an embodiment of the present invention. FIG. 1 shows a state before molding, and FIG. 2 shows a state during molding.
[0023]
The present hydroforming molding system mainly includes a shaft pressing device 1 according to an embodiment of the present invention, and a molding die 2 composed of an upper die 2a and a lower die 2b. Although omitted in the drawing, the shaft pressing device 1 is disposed in a pair on both the left and right sides of the mold 2. A pipe 3 serving as a molding is placed on the molding die 2 and used for molding.
[0024]
Briefly speaking, the shaft pushing device 1 includes a piston 10 and a cylinder 20 in which the piston 10 is housed. Although not shown in the drawing, both the mold 2 and the cylinder 20 are fixedly attached to a base (mounting base), and the position of the cylinder 20 is fixed to the mold 2. On the other hand, the piston 10 is displaced. The shaft pushing device 1 is a double-acting cylinder device that is operated by hydraulic pressure, and the piston 10 is roughly divided into a rod-shaped rod portion 10a positioned at the front and a pressure receiving portion 10b receiving the hydraulic pressure positioned at the rear. The two hydraulic chambers 32a and 32b are formed by being sealed by the inner wall surface of the cylinder 20 and the O-rings 31a and 31b, respectively. The cylinder 20 is provided with oil supply passages 33a and 33b that respectively communicate with the outside of the cylinder 20, and hydraulic oil is supplied to the hydraulic chambers 32a and 32b from these. The oil supply passages 33a and 33b are connected to a hydraulic pipe (not shown). The hydraulic pipe is connected to a hydraulic pump (not shown), and the piston 10 is connected to the cylinder 20 by driving the hydraulic pump. Pressure is applied in the axial direction, and forward movement or backward movement becomes possible, and the pressing force of the shaft pressing device 1 is generated.
[0025]
In addition, the rod portion 10a of the piston 10 is formed such that a part thereof, specifically, a front end portion 10c located outside the cylinder 20 is detachable, which will be described in detail later, depending on the pipe to be molded. Can be exchanged. The front end portion 10c is inserted into the mold, and the front end 10d is in contact with the opening end 3a of the pipe 3. The shaft pressing device 1 presses the opening end 3a in the axial direction. Will be.
[0026]
In the axial pushing device 1, a space 41 that is partitioned by the cylinder 20 and the piston 10 and whose volume changes as the piston 10 moves is formed inside the cylinder 20. Specifically, the space 41 has a bottomed hole 11 that is formed in the piston 10 in the axial direction and opens at the rear end, and forms a part of the cylinder 20 and protrudes forward in the axial direction from the rear end of the cylinder 20. It is partitioned by a rod 21 to be inserted into the hole 11 and formed inside the piston 20.
[0027]
In the state where the front end 10 d of the piston 10 is in contact with the opening end 3 a of the pipe 3, a conduction path 42 is formed in the piston 10 to conduct the space 41 and the inside of the pipe 3. More specifically, a through-hole formed in a straight line in the axial direction of the piston 10 conducts the space 41 and the inside of the pipe 3 so that the machining liquid can freely pass therethrough.
[0028]
Further, in the present shaft pushing device 1, the second conducting path 43 that conducts the space 41 and the outside of the cylinder 20 is formed in the rod 21. Specifically, a through hole that penetrates both the rod 21 and the rear part of the cylinder 20 is formed. The second conduction path 43 is connected to a pressurizing apparatus (not shown) (for example, a hydraulic / hydraulic converter or the like), and the processing liquid (mainly water is supplied) via the second conduction path 43. Etc. are used, and a hydraulic pressure can be applied to the inside of the pipe 3.
[0029]
Note that the second conduction path is not necessarily required for the other shaft pushing device (not shown). Similarly, when the second conduction path is provided, the second conduction path is used to pipe the machining fluid. When supplying the inside, it becomes possible to serve as a discharge path for discharging the air remaining inside the pipe to the outside of the system. Incidentally, at the time of molding, the second conduction path may be closed with a valve or the like to apply a hydraulic pressure to the machining fluid.
[0030]
As shown in FIG. 1, before molding, the mold 2 is opened and the pipe 3 is set at a predetermined position. Thereafter, the mold 2 is closed, and then the piston 10 of the shaft pressing device 1 moves forward so that the front end 10 d abuts against the open end 3 a of the pipe 3 in the mold 2. Then, the machining fluid is supplied into the pipe 3 from the second conduction path 42 connected to the pressure device. In a state where the machining liquid is supplied, the space 41 and the conduction path 41 are filled with the machining liquid.
[0031]
By applying a predetermined force to the opening end 3 a of the pipe 3 by the piston 10, the working liquid is prevented from leaking from between the opening end 3 a and the front end 10 d of the piston 10 by the pressurizing device. Pressure. The molding pressure is applied to the pipe 3 from the inside by the hydraulic pressure of the working fluid, and the pipe 3 is deformed by being expanded and pressed against the cavity of the molding die 2 to be molded. The expansion of the pipe 3 is also accompanied by deformation in the axial direction. That is, since the length of the pipe 3 is shortened, the piston 10 is advanced following the retreat of the opening end 3a. Further, the piston may be advanced while pressurizing the pipe by the piston 10 in order to more actively compress and deform.
[0032]
At the time of molding, the piston 10 receives a reaction force from the front end 10d due to the hydraulic pressure of the machining fluid. In the present shaft pushing device 1, the space 41 gives the piston a drag force that eliminates the reaction force. That is, the space 41 functions as a reaction force balance chamber. The fluid pressure inside the pipe 3 is also introduced into the space 41 by the conduction path 42, and the piston is given a force to push back by the fluid pressure in the space 41. Incidentally, in the present axial pushing device 1, the axially inner cross-sectional area of the pipe 3 (corresponding to the area in which the working fluid in the pipe is in contact with the front end 10d of the piston 10 in FIG. 2, the front end of the rod 21 is equivalent to the area in contact with the machining fluid in the space 41), and the reaction force and the resisting force are equal in magnitude. Therefore, the opening end 3a of the pipe 3 is sealed only by applying a small pressing force to the opening end 3a of the pipe 3, and the shaft pressing device can be further downsized.
[0033]
Further, even when a pressing force is further applied to positively use the compression deformation of the pipe, the pressing force is applied by the main shaft pressing device 1. At that time, since the reaction force from the working fluid continues to change during the molding, the pressing force must be changed to follow the change. Since the reaction force from the pipe 3 is balanced with the reaction force by the pressure balance chamber (space 41), the fluid pressure inside the pipe is detected and the value is fed back to control the pressing force of the shaft pressing device. Good hydroform molding is possible with extremely simple control without the need for control.
[0034]
To summarize the axial pushing device 1, it can be considered that another cylinder device in which the rod 21 serves as a piston and the bottomed hole 11 of the piston 10 serves as a cylinder is incorporated in the cylinder device. That is, it is a double cylinder device. Therefore, in order to secure the function as a cylinder device incorporated therein, between the front end portion 10c of the piston 10 and the rod portion 10a main body, the sliding portion between the bottomed hole 11 and the rod 21, the main body of the cylinder 20 of the rod 21 and Each of the connection surfaces is sealed by an O-ring 34. The shaft pushing device 1 can achieve a very small shaft pushing device by adopting a structure of a double cylinder device.
[0035]
<Two modified embodiments>
In the above-described shaft pressing device, the front end portion 10c of the piston 10 is formed to be detachable. Therefore, an embodiment will be described in which the front end portion 10c is replaced in accordance with the cross-sectional shape of the pipe to be molded. FIG. 3 shows a shaft pushing device equipped with a piston front end corresponding to a thick pipe, and FIG. 4 shows a shaft pushing device equipped with a piston front end corresponding to a thin pipe. Since any of the shaft pushing devices 1 shown in FIGS. 3 and 4 has only the front end portion of the piston of the shaft pushing device replaced, detailed description thereof will be omitted.
[0036]
In any of the shaft pushing devices 1, a reaction force is generated on the piston 10 due to the hydraulic pressure inside the pipe 3, and the space 41 formed inside the piston 10 functions as a reaction force balance chamber. Resistance force is applied from the rear of the piston. In the case of the apparatus shown in FIG. 3, since the axial cross-sectional area of the rod 21 is smaller than the axial internal cross-sectional area of the pipe, the drag is smaller than the reaction force. Therefore, an extra pressing force corresponding to the difference must be applied to the open end 3a of the pipe 3. On the contrary, in the case of the apparatus shown in FIG. 4, since the axial cross-sectional area of the rod 21 is larger than that of the pipe, the drag is larger than the reaction force. Therefore, it is necessary to reduce the pressing force by an amount corresponding to the difference.
[0037]
Such adjustment of the pressing force of the shaft pressing device can be performed relatively easily when the difference between the reaction force and the reaction force is not large, so that the effect as a reaction force balance chamber is sufficiently exhibited. . By exchanging only the front end portion of the piston, it is possible to cope with the molding of pipes of various sizes without exchanging the axial pressing device itself. Therefore, the axial pressing device of this embodiment is a very practical device.
[0038]
<Other embodiments>
The shaft pushing device of the above embodiment is merely an example, and the shaft pushing device of the present invention is by no means limited to the above embodiment. The shaft pushing device of the present invention can be implemented in various forms including various modifications and improvements based on the knowledge of those skilled in the art including the above-described embodiment.
[0039]
For example, in the case of the hydroforming molding of the above embodiment, two shaft pressing devices are installed on both sides of the molding die, that is, in a mode of sealing both open ends of the pipe. Instead of this mode, only one open end of the pipe is pressed by the shaft pressing device, and the other open end is brought into contact with the inner wall surface of the molding die, so that hydroform molding using only one shaft pressing device is performed. It becomes possible.
[0040]
In the case of the above-described embodiment, the second conduction path for supplying the machining fluid or discharging the remaining air is formed in both shaft pressing devices. However, if any air discharging means is provided. The second conduction path for supplying and pressurizing the machining fluid may be provided in any one of the shaft pressing devices.
[0041]
Further, the second conduction path of the shaft pushing device is connected to the rear end of the cylinder through the rod. Instead of this aspect, for example, as shown in FIG. 41) and the inside of the pipe can be branched to provide a working fluid supply path 44 that leads from the conduction path 42 to the outside of the piston. The supply path 44 is connected to an external pressurizing device. The processing liquid may be pressurized and the pipe may be formed with the liquid pressure.
[0042]
【The invention's effect】
Unlike the conventional shaft pushing device, the shaft pushing device of the present invention used for hydroforming is provided with a reaction force balance chamber formed in the piston for generating a resistance against the reaction force received from the hydraulic pressure inside the pipe. The cylinder is defined by a bottom hole and a rod that protrudes from the rear end of the cylinder and is inserted into the bottomed hole, and is built in the cylinder. That is, it is configured as a double-structure cylinder device. By adopting such a configuration, the shaft pushing device of the present invention can balance the reaction force received by the piston, and becomes a very compact shaft pushing device.
[Brief description of the drawings]
FIG. 1 is a main part of a hydroforming molding system using a shaft pressing device according to an embodiment of the present invention, and shows a state before molding.
FIG. 2 is a main part of a hydroforming molding system using a shaft pressing device according to an embodiment of the present invention, and shows a state during molding.
FIG. 3 shows a shaft pushing device according to the present invention which is equipped with a piston front end of a type corresponding to a thick pipe.
FIG. 4 shows a shaft pushing device according to the present invention which is equipped with a piston front end corresponding to a thin pipe.
FIG. 5 shows a shaft pushing device according to the present invention having a working fluid supply path that branches off from a conduction path that conducts the reaction force balance chamber and the inside of the pipe and leads to the outside of the piston.
[Explanation of symbols]
1: shaft pushing device 10: piston 10a: rod portion 10b: pressure receiving portion 10c: front end portion 10d: front end 11: bottomed hole 20: cylinder 21: rod 31a, 31b: O-ring 32a, 32b: hydraulic chambers 33a, 33b: Oil supply path 34: O-ring 41: space (reaction force balance room)
42: Conducting path 43: Second conducting path 44: Supply path 2: Mold 2a: Upper mold 2b: Lower mold 3: Pipe (molded article)
3a: Open end

Claims (3)

It is used in hydroform molding that fills the inside of a pipe with a working fluid and molds the pipe by its hydraulic pressure, and is a shaft pressing device for pressing the opening end of the pipe in the axial direction,
A piston whose front end abuts the open end of the pipe;
An internal cylinder, and a cylinder that applies axial pressure to the piston;
In the piston,
A bottomed hole that is drilled in the axial direction inside the piston and opens at the rear end, and is fixed to the cylinder that protrudes forward in the axial direction from the rear end of the cylinder and is inserted into the bottomed hole. A space that is partitioned by a rod that changes in volume as the piston moves,
A conduction path connecting the interior of the pipe and the space;
A second conducting path that conducts the space formed in the rod and the outside of the cylinder;
Formed,
The hydroforming molding shaft pusher, wherein the space functions as a reaction force balance chamber that applies a reaction force against a reaction force from the machining liquid to the piston by filling the space and the conduction path with the machining liquid. apparatus. The hydroforming molding shaft pushing device according to any one of claims 1 to 3, wherein the rod is formed so that a cross-sectional area of the shaft is substantially equal to a cross-sectional area of the pipe.   5. The hydroform molding shaft pushing device according to claim 1, wherein the piston has a structure in which a front end portion including a front end contacting the pipe can be exchanged according to an outer shape of the pipe.

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