JPH01216723A - Method for discharging electric charge of capacitor of electrolytic finishing machine - Google Patents

Abstract

PURPOSE:To reduce the power capacity of the parts of circuits by carrying out electric discharge for a certain time via grounding resistance when the charge of a capacitor is below a defined value while carrying out the discharge by stages for each defined electric quantity when the charge is above the defined value. CONSTITUTION:A pulse current is fed to between an electrode 2 and a workpiece 4 from capacitors 22-1-22-n based on a control signal from a machining condition control portion (CPU) 42 via a pulse generator 36, a current wave form setting portion 37, a gate circuit 34 and discharge switches 24-1-24-n. In the method of discharging the electric charge of the capacitors 22-1-22-n, when the residual electric charge thereof is above a voltage which can make a current corresponding to the power rating value of the discharging resistance of an electric charge discharging device 39 flow, the electric charge is discharged by stages for each power quantity which is determined by a CR characteristic. When the residual charge is below a defined value, discharge is carried out for fairly a long defined time. Thereby, the power capacity of using parts can be reduced, while obtaining a gloss surface, etc., in a short time.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for discharging the charge of a capacitor, and particularly to a method for discharging the charge of a capacitor in an electrolytic finishing machine that finishes a three-dimensionally shaped work surface in a short time and with high precision. Intermittent discharge method.

[Conventional technology] Conventional metal processing machines fill the gap between the electrode and the workpiece with an electrolyte such as sodium nitrate or sodium chloride, flow this electrolyte at high speed, and generate electrolysis that inhibits stable electrolytic action. An electrolytic machining machine (Japanese Patent Laid-Open No. 1983-1999) that processes a workpiece by passing a direct current from it to an electrode while removing eluted metal compounds, metal ions, hydrogen gas, etc.
71921 and Japanese Unexamined Patent Publication No. 60-44228) are known.

[Problems to be Solved by the Invention] However, with this electrolytic processing machine, there is a problem with the workpiece, especially when machining with a three-dimensional bottom (meaning machining of a three-dimensional structure formed in the shape of a concave hole). This method has the disadvantage that it is difficult to precisely transfer the electrode, and high-precision surface quality cannot be obtained.

Therefore, Ganto Toyama filed Japanese Patent Application No. 62-117486 for an electrolytic finishing machine that would eliminate these inconveniences. A single pulse is supplied between the electrode and the workpiece by discharging the charge from multiple capacitors charged at a predetermined voltage, and the current density of the supplied pulse is made different between the early and late stages of finishing. was.

By the way, in this electrolytic finishing machine, for example, what is the peak current density of the pulses supplied between the electrode and the workpiece? It has a large current value of about OA/cm2, and this current value is obtained from a plurality of capacitors with large capacitance connected in parallel. Therefore, for example, the amount of charge remaining in the capacitor at the end of finishing machining is often large, and when starting the next machining, if this charge is discharged through a grounded discharge resistor, the discharge resistance will be set to a small resistance value. Because the discharge time is shortened, a large current flows during discharge, and this current may damage the discharge resistor and other circuit components, or may cause circuit safety devices (thermal relays, etc.) to activate, causing the circuit to malfunction. There was the inconvenience of being blocked. Further, there is a problem in that the parts used have to have a large power capacity, which increases the cost.

Therefore, the purpose of the present invention is to reduce the power capacity of circuit components, reduce costs, prevent circuit functions from being cut off, and obtain high-precision surface quality such as a glossy surface in a short time. The object of the present invention is to realize a method for discharging charges of a capacitor in an electrolytic finishing machine.

[Means for Solving the Problems] In order to achieve this object, the present invention provides a simple method of discharging electric charge from a condenser between an electrode and a workpiece, which are disposed opposite to each other at a predetermined gap via a stationary electrolyte. In the apparatus for finishing the workpiece while supplying one pulse and removing electrolytic products generated in the gap, the charge in the capacitor is discharged through a grounded resistor, and the charge in the capacitor is If is less than a predetermined value, it will be discharged for a predetermined time,
If the electric charge of the capacitor exceeds a predetermined value, it is characterized in that it is discharged in stages for each predetermined amount of electricity.

[Function] According to the configuration of the present invention, for example, the residual charge of the capacitor is
If the power capacity of the circuit components used is below a predetermined value, the residual charge is discharged for a predetermined period of time via a grounded resistor, and if the residual charge exceeds a predetermined value, it is discharged in stages, for example, at each predetermined power level. Therefore, the current value flowing through the discharge resistor, discharge circuit, etc. can be kept below the power capacity of the parts used.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail and specifically with reference to the drawings.

1 to 5 show an embodiment of the present invention.

In FIG. 1, an electrolytic finishing machine 1 capable of carrying out the present invention includes an electrode fixing device 3 that fixes an electrode 2, a work fixing device 5 that fixes a work 4, and a servo motor 6 that converts rotational motion into reciprocating motion. A control device 12 consisting of a drive conversion section 7, a power supply device 8 that generates a pulse current, a motor drive control section 9, a machining condition control section 10, an electrolyte flow control section 11, etc., and an input device that inputs various data regarding the workpiece 4. 13,
It consists of an electrolyte filtration device 14 that filters an electrolyte, a processing tank 15, and the like.

The electrode fixing device 3 has an electrode 2 made of, for example, pure copper or graphite attached to the lower end of a rod 16 provided at the bottom thereof, with a gap such that the electrode surface 2a and the processed surface 4a of the workpiece 4 are spaced in a three-dimensional direction. Fix it so that it maintains 17. This electrode fixing device 3 is moved up and down by 60 rotations of a servo motor based on a control signal from the motor drive control section 9, and the electrode surface 2
A and the processed surface 4a are set at a predetermined gap 17.

The workpiece fixing device 5 is a table made of highly insulating granite or ceramics, and the workpiece 4 that has been subjected to die-sinking electrical discharge machining, for example, is fixed to the upper surface of the table using a setting jig, screws, etc. (not shown).

A power supply device 8 that supplies a predetermined pulse current between the electrode 2 and the workpiece 4, and the processing condition control unit 1O that controls the power supply device 8 are configured as shown in FIG. 2, for example.

That is, the power supply device 8 includes a DC power supply section 18 and a charging/discharging section 19, and the DC power supply section 18 includes a transformer 20 and a rectifier 21.
The voltage is lowered to a predetermined value by a transformer 20 and rectified by a rectifier 21 to obtain a direct current, which is supplied to capacitors 22-1 to 22-n, which will be described later.

The charging/discharging unit 19 also includes a plurality of capacitors 22-1 to 22-n that discharge charges between electrodes, and each of these capacitors 22-
Diodes 23-1 to 23-n connected to diodes 1 to 22-n to prevent backflow of charges to the DC power supply section 18 side, and a discharge switch 24-1 that is opened and closed to discharge charges to the discharge side.
24-n, and a charging switch 25 that supplies and disconnects power from the DC power supply section 18 to charge each of the capacitors 22-1 to 22-n to a predetermined value.

The processing condition control unit 10 controls the capacitors 22-1 to 22-n.
a voltage detector 26 that detects the voltage value of , a voltage comparator 28 that compares the voltage value detected by this voltage detector 26 with the output value from the D/A converter 27, and A charging detector 29 that detects the completion and start of charging of the capacitors 22-1 to 22-n based on an output signal, and a current detector 30 that detects the current value of the charge discharged between the electrodes.
A peak hold circuit 31 that holds the peak value of the current detected by the current detector 30, and a current comparator that compares the peak current value held by the peak hold circuit 31 with the output value of the D/A converter 32. 33, a pulse generator 36 that generates a pulse with a predetermined time width, and a current waveform setting device 37 that sets the current waveform of the charge discharged between the poles.
a gate circuit 34 that outputs an opening/closing drive signal to the capacitors 22-1 to 22-n, and a charging voltage setter 35 that sets a charging voltage value to be supplied to each of the capacitors 22-1 to 22-n and outputs the signal to the D/A converter 27. , a current setting device 382 that sets the current value flowing between the poles and outputs the signal to the D/A converter 32; and a charge discharger 39 that discharges the residual charges of the capacitors 22-1 to 22-n. A charge discharge command device 40 outputs a control signal to the charge discharger 39, a contact detector 41 detects contact between the electrode 2 and the workpiece 4, and calculates and processes machining conditions based on the input data of the input device 13. It consists of a CPU 42 and the like for processing. Note that the reference numeral 43 in the figure is a diode that prevents each of the discharge switches 24-1 to 24-n from being destroyed by back electromotive force.

The charge discharger 39 is constructed as shown in FIG. 3, for example. That is, the charge discharger 39 includes a power switch 44 as a switch mechanism and a discharge resistor 45 whose one end is grounded.
It consists of The electromagnetic switch 44 has three main contacts 46-
1 to 46-3, two auxiliary contacts 47-1, 47-2, and an electromagnetic coil 48, and the main contacts 46-1 to 46-3 are
The contact is always non-contact, and comes into contact when the electromagnetic coil 48 is energized and the electromagnetic switch 44 is turned on, and the auxiliary contact 47-
1.47-2 is always in contact and becomes non-contact when the electromagnetic switch 44 is turned on. and main contacts 46-1 to 46
-3 are connected in parallel and one end is connected to the discharge switch 24.
-1 to 24-n, and the other end is connected to the workpiece 4.

Further, the auxiliary contacts 47-L 47-2 are also connected in parallel, with one end connected to the discharge switches 24-1 to 24-n, and the other end connected to the resistor 45. The electromagnetic coil 4
8 is connected to the charge discharge command device 40, and a control signal from the charge discharge command device 40 energizes the electromagnetic coil 48 and turns on the electromagnetic switch 44. In addition, the reference numeral 30 in Fig. 3
a is a current detection resistor of the current detector 30;

The input device 13 inputs various data regarding the workpiece 4 such as the machining area S, finishing machining margin, machining conditions, and the like. The electrolyte filtration device 14 has, for example, a centrifugal separator, a liquid temperature regulator, a filter, a solenoid valve, etc. (not shown), and filters the electrolyte containing electrolytic products generated during processing, and also filters the filtered fresh electrolyte. The electrolytic solution is ejected into the gap 17 from the ejection nozzle 49 (see FIG. 1) disposed so as to be directed toward the gap 17 in response to a control signal from the electrolyte flow control section 11.

Next, an example of the finishing operation performed by the electrolytic finishing machine 1 will be explained with reference to the flowchart shown in FIG.

During finishing, the electrode 2 used, for example, when performing die-sinking electrical discharge machining on the workpiece 4 is fixed to the lower end of the rod 16 of the electrode fixing device 3, and the workpiece 4 is fixed to the workpiece fixing device 5 for electrolytic finishing. Power on the processing machine 1 (50). For example, when a discharge key (not shown) of the input device 13 is pressed, the discharge switches 24-1 to 24-1 are pressed.
24-B turns on, a control signal is output from the charge discharge command device 40 to the charge discharger 39, and this signal causes
The electromagnetic switch 44 of the charge discharger 39 that was turned on in the step (50) is turned off (51) b, the auxiliary contact 47
-1.47-2 is in contact (main contacts 46-1 to 46-3 are not in contact).

When the charge discharger 39 is turned off, the time T1 to Tn during which a predetermined current can flow through the resistor 45 is read from the CPU 42 (52). T1 is the time required to keep the average power consumption of the resistor 45 constant when discharging through the capacitors 22-1 to 22-n, and T1 is the time that can be passed at the maximum charging voltage of the capacitors 22-1 to 22-n (area St in FIG. 5 = time equivalent to electric power), T2~T
n is the time required to obtain the same areas S2 to Sn as the area Sl of T1. Note that this time period T1 to Tn depends on the capacitance C of the capacitors 22-1 to 22-n and the resistance value R of the resistor 45.
This is determined in advance from the discharge characteristics determined by the above and stored in the CPU 42.

Then, based on the TlxTn, a predetermined period T, for example, a time longer than the Ts time required to discharge a predetermined voltage Vs, which will be described later, is calculated (53). Thereafter, from the characteristics shown in FIG. 5(B), voltages Vl-Vn corresponding to T1 to Tn, which are stored in advance in the same manner as T1 to Tn, are read (54).

When the voltages Vl-Vn are read, the voltage detector 26 is activated by the control signal from the machining condition control unit 10.
Detect the voltage Vo (residual charge) of 22-n (55)
It is determined whether this voltage vO is less than or equal to a predetermined value Vs (56). If this judgment (56) is NO, that is, the capacitor 22
If the voltage VO of −1 to 22-n exceeds Vs, select the voltage Vi immediately above Vo from among v1 to Vn read in step (54) and the time Ti corresponding to this voltage Vi.
Select (57). Then, the Ti time charge is discharged (5
8) After a waiting time (59) of L/, T-Ti time, return to step (55), and in step (56)
Repeat until ES is reached.

In other words, the voltage vO of the capacitors 22-1 to 22-n is changed to a voltage Vs through which a current corresponding to the power standard value W of the resistor 45 can flow.
Until then, the charge discharger 39 is sequentially turned on for Ti+1, Ti+2, . . . at a constant period T by the control signal of the charge discharge command device 40, thereby discharging the residual charge. Note that the discharge switches 24-1 to 24-n remain in the on state.

If YES in the step (56), that is, the capacitors 22-1~
When the voltage Vo of 22-n becomes equal to or lower than Vs, a predetermined period of time, e.g.
s Heavy charge discharge (60) L/, the discharge of the residual charge is completed, and the charge discharger 39 is turned on (61) by the control signal of the charge discharge command unit 4o.

Through this series of steps, the discharge of the residual charges in the capacitors 22-1 to 22-n that remained before the start of machining (residual at the end of the previous machining) is completed, and when the residual charges disappear, finishing processing is performed in this state. is started, and first the electrode 2 is lowered and the workpiece 4 is
come into contact with. The contact detector 41 detects this contact (6
2) Then, the CPU 42 stores this point as the machining origin A, and operates the electrolyte filtration device 14 to supply the electrolyte into the machining tank 15 (63). Then, the electrode 2 is raised to a position where the electrode gap δ input using the input device 13 is maintained (64).

When the electrode 2 is set and the electrolyte in the gap 17 is stationary (65), the power supply device 8 is turned on by the control signal from the processing condition control unit 10.
Machining area S of workpiece 4 from capacitors 22-1 to 22-n
For example, the peak current density is 30 to 50 A.
A single pulsed current for improving surface roughness with a pulse-on time of 2 to 10 m5ec is supplied at /Cm2 (66) L/, and after this pulsed current is turned off, the electrode 2 is raised (67).

Then, the ejection nozzle 49 is opened by the electrolyte filtering device 14.
A fresh electrolyte is injected into the gap 17 from the gap 17, and the eluted electrolytic products in the gap are removed by supplying a pulsed current (68). Thereafter, the electrode 2 is lowered (69) and brought into contact with the surface to be machined 4a, and the CPU 42 compares this position with the origin A to measure the machining depth (70).

Steps (64) to (
70) is repeated 71), and when a predetermined machining depth is reached, the condenser 22 is
The pulse current supplied from -1 to 22-n is a pulse current for forming a glossy surface, for example, the peak current density is 30 to 50 A.
/ cm m2, pulse on time 20~60m5e
Switch to a single pulse current of C (72), and perform the same processing as steps (64) to (68) (73) to (77).
) is repeated a predetermined number of times (78), a glossy surface is obtained and all processing is completed (79).

As described above, in the method of discharging charges of the capacitors 22-1 to 22-n in the electrolytic finishing machine 1 according to the present invention, the residual charges of the capacitors 22-1 to 22-n are discharged from the resistor 45 for discharging. Voltage Vs that allows a current corresponding to the power standard value to flow
If the residual charge exceeds the voltage Vs, the charge is discharged in stages until the voltage reaches Vs at each predetermined amount of power determined in advance according to the discharge circuit characteristics of the CR, and if the residual charge is below the voltage Vs, the charge is discharged for a relatively long time. Since the charge is discharged for a certain period of time, the value of the current flowing through each circuit such as the charge discharger 390 circuit and the discharge switches 24-1 to 24-n, or the value of the power consumed by the circuit can always be kept within a certain value, The power capacity of circuit components can be reduced and costs can be reduced, and circuit function interruption can be prevented.

6 to 8 are flowcharts showing other embodiments of the present invention, in which the same steps as in FIG. 4 are given the same reference numerals and their explanations will be omitted. FIG. 6 shows that after selecting (57) L/ the voltages Vi and Ti that are directly above the voltage Vo of the capacitors 22-1 to 22-n in step (57), the formula V i '=V
The discharge voltage vi' is set by i - (Vi+1) (80) L/, and the charge corresponding to this voltage vi' is Ti
It is characterized by time discharge (81).

Moreover, FIG. 7 shows that when the voltage Vo exceeds the voltage Vs,
Discharge the charge for a minimum of 71 hours in the TI-Tn (83
), and FIG. 8 further shows that when the voltage vO exceeds the voltage Vs, V.

-Vs'(Vs' is a preset voltage) is set in the charging voltage setting section 35 of the processing condition control section 10 (8
5) At the same time, a charge completion signal is output from the charge detector 29 to discharge (86) for a time Ts'(Ts' is a preset time), that is, the residual charges in the capacitors 22-1 to 22-n are discharged. and repeats until the voltage Vo drops to Vo - Vs9 (87), discharging the charge every voltage Vs',
It is characterized by discharging charges in stages up to the voltage Vs.

In addition, in the above embodiment, the power storage devices 22-1 to 22-
Although the discharge of the residual charge of When finishing the workpiece by supplying a pulsed current of 100% to remove an oxide film formed on the workpiece surface, and supplying a pulsed current of high current density to form a glossy surface in the latter stage of finishing, Switching of each pulse current (
Of course, it can also be applied to the discharge of charge during switching from a high current density to a low current density pulse current.

In the above embodiment, the electromagnetic switch 44 of the charge discharger 39 has main contacts 46-1 to 46-3 and an auxiliary contact 47-.
1.47-2, but main contacts 46-1 to 46-3
can be omitted (short circuit); in this case, the current carrying capacity of the electromagnetic switch 440 is determined only by the resistor 45 (not affected by the machining current), so the small size of the charge discharger 39,
Capacity can be reduced.

[Effects of the Invention] As explained in detail above, in the method for discharging the charge of the capacitor in the electrolytic finishing machine according to the present invention, when the charge of the capacitor is less than a predetermined value set in advance, the charge is discharged for a predetermined period of time. If it discharges and the charge in the capacitor exceeds a predetermined value,
Since the electric power is discharged in stages for each fixed amount of electricity, ■ the power capacity of the parts used in the circuit can be reduced and costs can be reduced, and ■ the circuit function can be prevented from being cut off unnecessarily.
It has the following effects: high-precision surface quality such as a glossy surface can be obtained in a short time, and quality improvement and mechanization can be achieved in the field of mold processing, where labor saving has been slow.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the electrolytic finishing apparatus of this invention.
Figure 2 is a block diagram of the main parts, Figure 3 is a circuit diagram of the charge discharger, Figure 4 is a flowchart showing an example of finishing operation, and Figures 5 (A) and (B) are for explaining the operation. diagram,
6 to 8 are flowcharts showing other embodiments. DESCRIPTION OF SYMBOLS 1... Electrolytic finishing machine, 2... Electrode, 4... Workpiece, 8... Power supply device, 9... Motor drive control section, 10... Machining condition control section 11... Electrolysis Liquid flow control unit, 12...control device, 13...input device,
14... Electrolyte filtration device 22-1 to 22-n
...Electricity storage device, 39...Charge discharger, 40...Charge discharge command device, 42...CPU. Patent applicant Shigeo Suzuki, representative of Shizuoka Seiki Co., Ltd. Figure 1 Figure 7

Claims (1)

[Claims] (1) A single pulse is supplied between the electrode and the workpiece, which are disposed opposite to each other with a predetermined gap, through a stationary electrolyte, and the electrolytic products generated in the gap are removed. In the apparatus for finishing the workpiece, the charge in the capacitor is discharged through a grounded resistor, and when the charge in the capacitor is less than a predetermined value, it is discharged for a predetermined time, and the charge in the capacitor is lowered to a predetermined value. 1. A method for discharging a charge of a condenser in an electrolytic finishing machine, characterized in that if the amount of electricity is exceeded, the charge is discharged in stages for each predetermined amount of electricity.