JP3465728B2 - Electric discharge machine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric discharge machining apparatus in which a workpiece and an electrode are immersed in a machining fluid in a machining tank, and more particularly, to an electric discharge machining apparatus in which the machining tank is vertically movable. It relates to the device.

[0002]

2. Description of the Related Art In electric discharge machining, a work piece is machined in a state in which a minute gap between an electrode and a work piece facing each other is insulated by a working liquid mainly composed of water or oil. Therefore, the machining tank of the electrical discharge machine is designed to immerse the electrode on the spindle and the workpiece on the table in the machining fluid stored inside to block and insulate from the surrounding air during electrical discharge machining. When not performing, for example, when working on a table, the electrode and the work piece are exposed from the working liquid to facilitate the work.

In order to immerse the electrode and the workpiece in or out of the working fluid in this way, conventionally, the working fluid is raised or lowered in a state where the working fluid is stored, so that the working fluid level with respect to the table is arbitrary. There has been proposed an electric discharge machine configured to be adjustable in height. For example, the conventional electric discharge machine shown in FIG. 4 has a bed 10 for storing a machining fluid 101.
2, the table 104 on which the workpiece 103 is placed, the gedai 105 that supports the table 104, and the table 104.
Processing tank 107 surrounding the processing tank 107 and the processing tank 107
5, the drive device 108 for moving up and down along with the bed 102,
A machining fluid supply device 109 for feeding the machining fluid 101 therein to a machining tank 107, an electrode 111 fixed to a spindle 110, and a head for moving the spindle 110 so that the electrode 111 faces the workpiece 103 at an arbitrary position. , A column, a movable structure such as a saddle (not shown), and the like.

[0004]

By the way, in this type of electric discharge machining apparatus, when the machining tank 107 descends and its lower part sinks into the machining fluid 101 in the bed 102,
The processing tank 107 receives from the processing liquid 101 buoyancy and a drag force generated when an object moves in the liquid (hereinafter, these forces are collectively referred to as a resistance force). In particular, in the case of an electric discharge machine for machining a large workpiece 103 such as a die, a machining tank 107 having a large bottom area and a depth is used so that the periphery of a table 104 having a large area can be filled with a machining fluid. Therefore, when this sinks into the working fluid 101 in the bed 102, a large amount of the working fluid 101 is pushed away, whereby the working tank 107 receives a very large resistance force on the bottom surface.

The working tank 107 is a uniform speed and the working fluid 101 is
Since it is considered that the processing tank 107 is placed in a uniform flow, the resistance D received at that time is represented by the following equation. _{D = C D · 1/2 · ρV} 2 S (1) ρ: Density C _D of the working fluid: drag coefficient (resistance coefficient) V: uniform flow velocity (uniform velocity of the processing tank) S: uniform flow Area of the object projected on a plane perpendicular to the direction of (processing tank bottom area)

From the above equation, it can be seen that the larger the bottom area or the faster the descending speed, the more the machining tank 107 receives the greater resistance force from the machining fluid 101. Therefore, according to the conventional electric discharge machining apparatus, when the bottom area of the machining tank 107 is large, the descending speed thereof is remarkably reduced, or the force to descend is lost due to the resistance force and is forcibly stopped. In any case, there is a problem in that an unreasonable force acts on the drive device 108 for moving up and down the processing tank 107.

Therefore, an object of the present invention is to provide an electric discharge machining apparatus capable of smoothly lowering the machining tank into the machining liquid in the bed even when the bottom area of the machining tank is large.

[0008]

In order to solve the above-mentioned problems, the present invention provides a processing tank for accommodating a working fluid in a bed, providing a table for placing a workpiece on the working fluid, and surrounding the table. Is installed in the bed so that it can be moved up and down, the machining fluid of the bed is sent to the machining tank, and in the electrical discharge machining device that performs electric discharge machining with the workpiece and the electrode immersed in the machining fluid in the machining tank, A hole is formed on the bottom surface through which the working liquid passes, and the hole is provided with a valve through which the working liquid can pass only from the outside to the inside of the processing tank.

Further, this valve is preferably an elastic plate having one end fixed to the processing tank.

[0010]

According to the electric discharge machining apparatus of the present invention, during electric discharge machining, the valve, preferably the elastic plate, closes the hole in the bottom surface of the machining tank by the pressure based on the self-weight of the machining fluid in the machining tank, so that the machining fluid is discharged from the machining tank. Hold so that it does not leak. Further, when the lower part of the processing tank sinks into the working fluid in the bed during non-working, the valve, preferably the elastic plate, is pushed open by the resistance of the working fluid in the bed to remove the working fluid in the bed. Pass it into the processing tank. Therefore, at this time, the resistance force applied to the processing tank is reduced, and the processing tank smoothly and quickly descends into the processing liquid in the bed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the electric discharge machining apparatus of the present embodiment is configured to machine a workpiece 3 such as a large die, a bed 2 for storing a machining fluid 1 and a workpiece 3.
A table 4 on which the table 4 is placed, a gedai 5 that supports the table 4, a processing tank 7 that surrounds the table 4, a drive device 8 that raises and lowers the processing tank 7 along the geddy 5, and a processing liquid 1 in the bed 2. A machining liquid supply device 9 for feeding the liquid into the machining tank 7 and an electrode 11 fixed to the main shaft 10 are provided. Then, the working liquid 1 is constantly fed from the bed 2 to the working tank 7 by the working liquid supply device 9 so that the workpiece 3, the table 4, and the electrode 11 are immersed by the working liquid 6 in the working tank 7. Has become.

As shown in FIG. 2, the side wall of the processing tank 7 has a double inner and outer structure, and the outer wall 7a is formed higher than the inner wall 7b. Therefore, the working liquid 6 in the working tank 7 exceeds the upper edge of the inner wall 7b, falls between the inner wall 7b and the outer wall 7a, and falls into the bed 2.

As shown in FIG. 3, the bottom surface 7c of the processing tank 7 is provided with four holes 7d through which the processing liquid passes.
In addition, the processing tank 7 is formed so as to block these holes 7d from above.
An elastic plate 13 made of rubber, synthetic resin, metal, or the like is attached to the bottom surface 7c of the above with a bolt 12 at one end thereof. This elastic plate 13 is pressed against the bottom surface 7c by the pressure based on the self-weight of the processing liquid in the processing tank 7,
The processing liquid is configured to block the hole 7d in such a state that the processing liquid does not leak to the outside of the processing tank 7 at all or slightly leaks.
A wiper 14 is provided on the inner peripheral edge of the bottom surface 7c for sealing so as not to leak the working liquid from the gap between the working tank 7 and the gedai 5.

In the electric discharge machining apparatus of the present embodiment constructed as described above, during electric discharge machining, the machining tank 7 is arranged in a raised position, and the lower surface thereof is separated upward from the machining liquid 1 in the bed 2. . In this state, the elastic plate 13 closes the hole 7d of the bottom surface 7c by the pressure of the working liquid 6 in the working tank 7, and holds the working liquid 6 so as not to leak from the working tank 7.

On the other hand, at the time of non-processing, the processing tank 7 is lowered by the drive unit 8. Then, when the lower part of the processing tank 7 comes into contact with the processing liquid 1 in the bed 2, the processing liquid 1 exerts an upward resistance force on the lower surface of the processing tank 7. The resistance force at this time is the buoyancy force corresponding to the sinking depth of the processing tank 7,
It consists of the drag force received from the working liquid 1 when the working tank 7 sinks at a uniform speed. Here, the fact that the processing tank 7 sinks at a uniform velocity is considered to be that the processing tank 7 is placed in a uniform flow with its bottom face perpendicular to the flow direction. In order for the elastic plate 13 to be pushed open when the elastic plate 13 is lowered while receiving a drag force, the relationship between the downward pressure and the upward pressure acting on the elastic plate 13 must be as follows.

Pressure due to the working fluid 6 in the working tank 7 <pressure due to the working fluid 1 in the bed 2 + pressure due to the drag force This can be expressed by the following equation. ρH ₁ <ρH ₂ + D / S (2) ρ: Density of the working fluid H ₁ : Depth from the liquid level in the working bath to the bottom of the working bath H ₂ : From the liquid level in the bed to the bottom of the working bath Depth D: Drag force (buoyancy) S: Area of elastic plate Here, the drag force D is calculated from equation (1) as D = C _D · 1/2 · ρV ² S V: Uniform velocity of the processing tank C _D : Since it can be expressed as a drag coefficient, the equation (2) becomes ρH ₁ <ρH ₂ + C _D · 1/2 · ρV ² (3).

In the equations (2) and (3), H ₁ and H ₂ both represent the liquid level, but the machining fluid 6 is constantly fed from the bed 2 into the machining tank 7 by the feeding device 9. Therefore, as can be seen from FIG. 1, H ₁ is considerably larger than H ₂ . However, the relation of the expression (3) is shown to be established when V becomes a certain value or more, and the elastic plate 13 is pushed open when the relation of the expression (3) is established.

As described above, when descending the processing tank 7 at a uniform and higher speed than a certain value, the elastic plate 1 is expressed by the above equation.
Since the pressure exerted upward from the outside becomes larger than the pressure exerted downward on No. 3 in a short time, the lower surface of the processing tank 7 contacts the liquid surface of the working liquid 1 of the bed 2 and then elastically changes in a blinking manner. The plate 13 is pushed open while bending based on one end. When a gap is created between the elastic plate 13 and the bottom surface 7c, the high-pressure machining liquid 1 in the bed 2 flows into the machining tank 7 at a lower pressure than that through the hole 7d, and works upward in the machining tank 7. The pressure escapes to the inside, the resistance due to the drag decreases, and the processing tank 7 descends smoothly and quickly. In this state, the processing liquid 6 in the processing tank 7 is filled with the holes 7
It increases by the amount of liquid flowing in from d.
Since it is collected in the bed 2 through the space between the heavy walls, the processing tank 7
There is no danger of it overflowing.

When the working tank 7 stops descending, the drag force of the working liquid 1 working on the lower surface of the working tank 7 gradually becomes smaller than the pressure of the working liquid 6 in the working tank 7, and the elastic plate 13 causes the bottom surface 7c of the elastic plate 13. To close the hole 7d and hold the working liquid 6 in the working tank 7.

The present invention is not limited to the above-mentioned embodiment, and the gist of the present invention is, for example, that the number and shape of the holes on the bottom surface of the processing tank are changed, or the configuration of the valve is changed. It is also possible to embody by arbitrarily changing the shape and configuration of each part without departing from the above.

[0021]

As described in detail above, the first aspect of the present invention
According to the electric discharge machining equipment, the machining tank has a hole through which the machining liquid passes and a valve that closes the hole, so that even if the bottom area of the machining tank is large, it can be smoothed into the machining fluid in the bed. It has an excellent effect that it can be lowered to.

According to the electric discharge machine of claim 2,
Since the valve is made of an elastic plate, it is possible to securely block the hole during electrical discharge machining so that the machining liquid does not leak from the machining tank.
Further, when the processing tank is lowered, the holes can be opened to allow the processing liquid to flow into the processing tank, and there is an effect that these two operations can be realized with a simple configuration.

[Brief description of drawings]

FIG. 1 is a side view of an electric discharge machine showing an embodiment of the present invention.

FIG. 2 is an enlarged view showing a side wall structure of a processing tank in the same apparatus.

FIG. 3 is a cross-sectional view showing a main part of the processing tank.

FIG. 4 is a side view showing a conventional electric discharge machine.

[Explanation of symbols]

1 ... Machining liquid in bed, 2 ... Bed, 3 ... workpiece, 4 ... Table, 5 ... Gedai, 6 ... Machining fluid in machining tank, 7 ... Machining tank, 7c ... , 7d ... hole, 8
..Driving device, 9 ... Machining liquid supply device, 10 ...
11 ... Electrode, 13 ... Elastic plate, 14 ... Wiper

Claims (2)

(57) [Claims] 1. A processing liquid is stored in a bed, a table is provided above the processing liquid, and a workpiece is placed on the bed, and a processing tank surrounding the table is arranged in the bed so that the processing liquid can be moved up and down. In an electric discharge machining device that discharges a workpiece and an electrode into a machining fluid in a machining tank and performs electric discharge machining in the machining tank, a hole through which the machining fluid passes is formed on the bottom surface of the machining tank, and the hole is machined. An electric discharge machine equipped with a valve that allows machining fluid to pass only from the outside to the inside of the tank. 2. The electric discharge machining apparatus according to claim 1, wherein the valve comprises an elastic plate having one end fixed to the machining tank.