JP3311530B2 - 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 a discharge gap for electric discharge machining, a discharge gap state, or a discharge state or a discharge machining state (hereinafter referred to as a "discharge state of a discharge gap"). A discharge state detection circuit for a discharge gap, particularly a discharge state detection circuit when a high-frequency AC voltage source is used as a power supply for the finishing processing, and various controls for processing by a detection signal of the discharge state detection circuit, for example, servo feed The present invention relates to an electric discharge machine for performing control.

[0002]

2. Description of the Related Art FIG. 7 is a schematic block diagram of an example of a conventional circuit for detecting a discharge state in a discharge gap and a circuit for performing servo feed control for electric discharge machining based on a signal detected by the circuit. shows the FIG, 30 is present inventors engaged Waru finishing up machining power source for the development of which will be described later, 1 wire electrode or piercing and wire EDM
A die electrode for engraving, 3 is a workpiece, 31 is a voltage dividing circuit for detecting a discharge gap voltage, and 32 is an operational amplifier that amplifies the detected divided voltage after half-wave or full-wave rectification as necessary. An inverting amplifier circuit; 33, an integrating circuit for rectifying and integrating the amplified voltage;
34 is an inverting amplification circuit for integrating voltage, a gain adjustment circuit for adjusting a servo gain (gain) by adjusting a variable resistor 34A,
35 is a sample and hold amplifier for the amplified voltage whose gain has been adjusted, 36 is an A / D converter for converting the sampled and held amplified voltage into a digital signal, and 37 is an input / output circuit of the converted digital signal to the next-stage NC device. 38. A circuit isolating photocoupler comprising a light emitting element and a light receiving element,
Is a control device having a built-in microcomputer such as an NC controller or a microcomputer for electric discharge machining capable of simultaneously controlling four or three axes of two or more axes, 39 is a motor driver, 40 is XY two axes, Z
This is a two-axis servo motor for shaft or, further, taper processing.

[0003] Reference numeral 30 denotes a finishing power supply for performing a finishing work almost finally in electric discharge machining, and will be described in detail later in particular. For example, the following patent application 1 relates to the prior application of the present applicant. . [Application date] Patent application filed on February 18, 1994 [Reference number] P94-004 [Application number] 1994 Patent application No. 59,777 [Title of the invention] Power supply circuit for wire electric discharge machining and power supply Circuit device 2. [Application Date] Patent application filed on March 23, 1994 [Reference number] P94-032 [Application number] 1994 Patent Application No. 92,836 [Title of Invention] Wire electric discharge machining method and wire electric discharge machining A finishing power supply comprising a high-frequency AC voltage source described in a power supply circuit or the like, which can have a pause for each cycle as necessary, and the output high-frequency AC voltage has a frequency of about 1
At a high frequency of about MHz or more, a working fluid (not shown) is applied to a fine discharge gap between the working electrode 1 and the work piece 3 in which the working fluid flows and intervenes between the two, and discharges, and a semi-finishing process up to the previous stage. In this way, finishing processing is performed mainly for improving the surface roughness (approximately 3.5 to 1 μm Rmax or more) of the processed surface of the workpiece 3 finished to approximately the predetermined size and shape accuracy.

[0004] Thus, the above-mentioned finishing, the first roughing or first-cutting up to the finishing, the next middle- or second-cutting, or the further semi-finishing or third-cutting There are various types of discharge state detection circuits or detection adjustment circuits for the discharge gap of the servo feed control for machining in machining, and one example thereof has a configuration as shown in FIG. The discharge gap voltage is from the voltage dividing circuit 31 to the A / D conversion circuit 36.
The digital signal is converted into a digital signal corresponding to a desired gain, sent to a control device 38 via a photocoupler 37 and calculated, and input to an NC device in the control device 38 by an input setting means 38A according to a processing purpose or the like. According to the deviation from the input desired set voltage or reference voltage, usually zero deviation, zero feed servo, zero method servo in which the feed direction is reversed, or the deviation zero according to the processing speed of the set processing conditions The drive control signal is supplied to the driver 39 of the servo motor 40 so that the machining feed of the servo control system such as the deceleration servo in which the feed speed is set is performed.

[0005]

By the way, in finishing machining using such a high-frequency AC voltage source, the discharge gap, the structure around the discharge gap, and the floating capacitance of the machining voltage source power supply circuit and the like are included. If the value is not appropriately reduced according to the purpose of the finishing process, a discharge of a high discharge peak current due to charging / discharging of the stray capacitance will be mixed. Roughness (approximately 3.5-1 μm Rmax or more) will not be achieved. Also, as described above, if the stray capacitance is not sufficiently small, the applied high-frequency AC voltage is attenuated, otherwise the processing efficiency is poor or the processing efficiency is easily reduced significantly. Therefore, it is necessary to avoid the finish efficiency of the finishing process for improving the surface roughness because the process efficiency is lowered.

However, according to the finishing circuit provided with the discharge state detecting circuit for servo feed control of the conventional example shown in FIG. 7, the discharge gap between the electrode and the workpiece and its surroundings, the high-frequency AC voltage source 30, Even if the stray capacitance of the power supply circuit and the like from the voltage source 30 to the discharge gap can be reduced as desired by devising it, servo control for machining power supply and machining feed is provided in the discharge gap. As a discharge state detecting circuit for use, an electronic circuit in a box of a normal power supply unit from the voltage dividing circuit 31 to the A / D conversion circuit 36 is connected, and not only the electronic circuit but also its circuit configuration and structure are used. However, it has a stray capacitance of approximately 100 to 1000 PF, and the stray capacitance of the detection circuit portion is an obstacle to the finishing process for improving the surface roughness by the high-frequency AC voltage source described above. A. And, in the finishing electric discharge machining using such a high-frequency AC voltage source as a machining power source, as described above, a high voltage of about 1 MHz or more, and a high voltage which is substantially high in machining efficiency as described later, for example, , And a lead wire such as a coaxial cable of a discharge state detection circuit is drawn out of the discharge gap, and a power supply (box) including the detection circuit and the control device 38 is provided. ), There is no major problem that a nearby control circuit including the detection circuit may cause noise interference such as a malfunction, and the detection signal circuit is large. There is a problem that it is necessary to increase the capacity of the element, for example, the resistance of the voltage dividing circuit 31 on the input side, and to take a considerably large cooling means.

[0007] Incidentally, before Symbol discharge gap, and as the stray capacitance of the discharge gap around it the wire electric discharge machining, or usually small, or while easily reduced, so-called ram to use electrodes of total type such as In the case of a die-cut electric discharge machine, the stray capacitance not only increases according to the facing or machining area, but also has a considerable stray capacitance due to the structure of insulatingly supporting the electrode or its support on the machining head or the like. For example, for example, the electrode may be a simple-shaped small-diameter rod-shaped electrode, and the target shape processing may be performed by a relative control movement in a direction perpendicular to the opposite direction between the electrode and the workpiece, or in a processing liquid. 0.1 ~ of metal, alloy, carbon or silicon etc.
As the electric discharge machining in which powder having a size of about 3.0 μmφ is mixed by about several percent, the length of the electric discharge gap during machining is widened, or a wire loop for canceling the capacitance is inserted in series with the electric discharge circuit. Instead of a wire loop, a high-permeability magnetic circuit (for example, see JP-A-59-42222) can be used.
It is not limited to wire electric discharge machining. Further, the discharge condition detection signal of the present invention are those which can also be used to control of as an output 38B of the controller 38 processing power and processing pulses.

Accordingly, the present invention provides a circuit for detecting a discharge state of a discharge gap which has a small stray capacitance and is suitable for finishing, and a high-frequency high-frequency current source as a machining power source for finishing. , detection never give rise to various noise impairments to the control circuit and the like of the circuit near and preferred configuration of the discharge state detection subjecting Hisage the circuit, and the detection circuit detects a signal by a variety for processing To provide an electric discharge machine capable of performing finishing, for example, a high-frequency AC voltage source for the purpose of improving surface roughness under good servo feed control by performing control, for example, servo feed control in particular. It is in.

[0009]

SUMMARY OF THE INVENTION The above-mentioned object of the present invention is as follows.
(1) a high-frequency coupling transformer having primary and secondary windings wound around a ring core, and a current pulse supply circuit for intermittently supplying high-frequency current pulses to the primary winding;
A finishing machining voltage supply circuit for supplying a high-frequency AC voltage induced in the secondary winding to a discharge gap between the machining electrode and the workpiece to perform finishing machining; A discharge state detecting circuit connected directly in parallel to the gap, wherein the light emitting output of the light emitting element is converted into an electric signal by a light receiving element for photoelectric conversion to obtain a discharge state detecting signal of the discharge gap; A plurality of discharge state detection circuits are provided in parallel with the discharge gap, and a discharge state other than the discharge state detection circuit having the series circuit is used when a finishing processing voltage supply circuit for the high-frequency AC voltage is used in processing. Electrical discharge machining in which a mechanical open / close switch for disconnecting the detection circuit from the discharge gap is provided between the discharge gap and a discharge state detection circuit other than the discharge state detection circuit having the series circuit. It is achieved by the location. The object of the present invention is to provide (2) a processing voltage pulse supply circuit for intermittently supplying at least a normal processing voltage pulse with a pause time as a processing power source, and a high-frequency AC voltage to a processing electrode and a processing electrode. A voltage supply circuit for finishing machining to supply to the discharge gap between the bodies, wherein the discharge state detection circuit is connected to and separated from the discharge gap as necessary by an on-off switch provided as necessary, A series circuit of a light emitting element and a light emitting element are directly connected in parallel to the discharge gap, and a light emitting output of the light emitting element is converted into an electric signal by a light-to-electric signal conversion light receiving element to obtain a discharge state detection signal of the discharge gap. And at least one discharge state detection circuit having a voltage detection circuit connected in parallel to the discharge gap different from the discharge state detection circuit including the light emitting element. Then, in the finishing process of controlling the machining feed and other control elements by the obtained discharge state detection signal, in the voltage pulse supply circuit other than the high-frequency AC voltage supply circuit, and in the discharge gap other than the discharge state detection circuit including the light emitting element. This is achieved by providing an electric discharge machining apparatus configured to disconnect the connected discharge state detection circuit from the electric discharge gap by a mechanical open / close switch. The object of the present invention is to provide (3) a resistor in series with the light-emitting element, a current-limiting voltage-dividing resistor provided at a position close to the discharge gap, and a detection circuit side of a power supply device separated from the discharge gap. This is achieved by the electric discharge machining apparatus according to the above (1) or (2), which has a discharge state detection circuit formed by a series connection with a second voltage dividing resistor. The object of the present invention is as described above. (4) The voltage-dividing resistor for limiting the current is:
The resistance value is selected so that a sufficiently large partial pressure value is applied to the divided voltage value of the second voltage-dividing resistor, and the current-limiting voltage-dividing resistor is brought into contact with a machining fluid supplied to a discharge gap. This is achieved by the electric discharge machining apparatus according to (3), further including a discharge state detection circuit configured to be disposed in the machining tank so as to be cooled. The object of the invention described above is
(5) The above (1), (2), which has a discharge state detection circuit in which a rectifying element is connected in reverse polarity in parallel with the light emitting element.
This is achieved by using the electric discharge machine described in (3) or (4). The object of the present invention described above is to provide (6) a discharge state detecting circuit in which the light emitting element is a light emitting diode and the light receiving element is a phototransistor or a photodiode. ) Or (5)
This is achieved by the electric discharge machining device described in (1). The object of the present invention is that the detection signal of the discharge state detection circuit is a discharge gap detection signal of a servo feed control device that controls a discharge gap by feeding. ), (3), (4), (5), or (6)
This is achieved by the electric discharge machining device described in (1).

[0010]

Since the electric discharge machining apparatus of the present invention has the above-described configuration, the electric discharge state detecting circuit connected to the electric discharge gap is only a series circuit portion in which a resistor and a light emitting element of a photocoupler are connected in series. An integrating circuit and an amplifying circuit subsequent to the photocoupler, or further a sample-and-hold amplifying circuit and an A / D converter, are insulated from a discharge gap by the photocoupler. Since the discharge state detection circuit of another discharge gap provided separately is separated by a mechanical open / close switch, the stray capacitance by the discharge state detection circuit provided for the discharge gap can be minimized, Furthermore, since the voltage-dividing resistor on the side near the discharge gap at the input of the detection circuit is a high resistance that suppresses the discharge due to the stray capacitance of the detection circuit, it is preferable to perform finishing processing. While a control, machined surface in a predetermined fine surface roughness rather rough, and has enabled efficient processing. Further, as described above, it is possible to configure a high-efficiency electric discharge machine capable of safely and reliably using a high-frequency AC voltage having a large noise disturbance as a machining power supply at the time of finishing machining. .

[0011]

FIG. 1 shows a discharge gap detecting circuit 41-47 according to an embodiment of the present invention in parallel with a discharge gap detecting circuit 31-37 of FIG. A mechanical open / close switch 49 switches between a high-frequency AC voltage source 30 for finishing and a normal intermittent voltage pulse source 5 for roughing, medium machining, medium finishing, etc. 1 shows an embodiment provided so as to be connectable.

FIG. 2 shows that the mechanical opening / closing switches 48 and 49 are switched so that a discharge gap between the electrode 1 and the workpiece 3 is formed.
A high-frequency AC voltage source 30 is connected as a finishing power supply, and a circuit according to one embodiment of the present invention is connected as a discharge state detecting circuit. Reference numeral 41 denotes a light-emitting element 41A such as various light-emitting diodes and various light-emitting elements. A light sensor, a photocoupler, or a photoelectric conversion element including a light receiving element 41B such as a conductive element, a photodiode, or a phototransistor. The light emitting element 41A and the light receiving element 41B are electrically insulated. Is connected in series with a resistor 41C such as a non-inductive resistor and connected directly to the discharge gap, of course, via a lead wire or the like, but in parallel. 43A is an integrating circuit of the output of the photocoupler 41, 42 is an inverting amplifier circuit,
4 is a gain adjustment circuit for further inverting and amplifying and adjusting the servo gain by adjusting the variable resistor 44A, 43B is an integration circuit, 45 is a sample and hold amplifier circuit, 46 is an A / D converter, and 47 is an input / output circuit. Although there is a slight difference in configuration between the circuits 43A to 47 and the above-described conventional detection circuits 32 to 37, they are substantially the same, and the digital signals detected and adjusted are controlled by an NC control device or the like. Input to the control device 38 having a predetermined operation such as an input signal of the input means 38A, and outputs a drive control signal to the driver 39 of the servomotor 40. Or a control signal 38B for controlling a processing condition such as a supply condition of a processing liquid supply device according to a detection signal.
Is output.

In the drawing, an element 41D connected in parallel to the light emitting element 41A is a rectifying element,
When A is a light-emitting diode, a similar light-emitting diode may be used. In order to protect the light-emitting element 41A against withstand voltage against reverse voltage and to use a high-frequency AC voltage source as a processing power supply, This is for keeping the positive and negative voltage drops the same and keeping the emission characteristics good.

According to the above construction, only the high-frequency AC voltage source 30 as a power source for finishing is connected to the discharge gap formed by the electrode 1 and the workpiece 3 during finishing. A voltage pulse source 5 for intermittently supplying a voltage pulse with an idle time by controlling on / off of a normal type electronic switch element used up to a stage such as a semi-finishing process before the finishing process is mechanically opened and closed. The discharge state detecting circuit which is completely separated from the discharge gap by the switch 49, and which is usually provided with one or more units, is only connected to the discharge state detecting circuit of the present invention by the mechanical open / close switch 48. , Discharge gap 41C
Since only the series circuit of the discharge gap and the light emitting element 41A are connected in parallel, the floating capacitance around the discharge gap and at least the floating capacitance due to the circuit around the discharge gap is in the minimum state. The discharge with a high peak current value due to the stray capacitance and the discharge energy per discharge are not greater than a predetermined value, so that the machined surface is not roughened. Existence does not mean that the high-frequency AC voltage or the finishing pulse is unexpectedly attenuated or the like to lower the machining efficiency, and on the other hand, the discharge state can be detected without increasing the stray capacitance, and the finishing process is performed. Can be processed by controlling the feeding of the workpiece 3 suitably or as desired, so that the drum characteristics of the processing surface of the workpiece 3 and the variation of the processing shape due to the pre-processing stage can be reduced. Can be processed while controlling the Nozomu, quickly processed surface roughness out finishing about 3.5~1μmRmax to desired, it will be able to ensure.

That is, in the case of the machining circuit shown in FIG. 7, the presence of the stray capacitance of the discharge state detection circuits 31 to 37 causes not only poor machining efficiency but also a machining surface roughness of 3.5 to 1 μmR.
Max or higher surface roughness finish cannot be performed. Therefore, conventionally, for surface roughness finish of approximately 3.5 to 1 μm Rmax or higher, the discharge state detection circuits 31 to 37 are controlled by a mechanical switch or the like. The workpiece is cut off from the discharge gap, and is processed at a certain constant speed set in the NC device of the control device 38. However, in such processing of processing feed at a constant speed other than the servo control, a drum on the processing surface of the workpiece 3 is not used. This was a problem because it was not possible to perform processing for controlling the variation in characteristics and shapes as desired.

Thus, the power supply for processing is switched to the intermittent voltage pulse source 5 by switching by the open / close switch 49,
When rough machining or medium machining is to be performed, the discharge state detection circuit is switched to the conventional detection circuits 31 to 37 by the open / close switch 48 as shown in FIG. In other cases, the discharge state detection circuits 41 to 47 of the present invention are used as they are, or the circuits 41 to 47 do not hinder the processing such as roughing. In this state, a connection configuration for operating the conventional detection circuits 31 to 37 may be adopted.

FIG. 2 shows a specific example of the intermittent voltage pulse source 5 and the high-frequency AC voltage source 30 in which the electric discharge machining in FIG. 1 is wire electric discharge machining. Positioning guide 2 spaced apart
A wire electrode, which is reciprocated and moved in the axial direction while applying a predetermined tension between A and 2B, 3 is attached to a work stand 4 mounted on an xy cross table (not shown), and is substantially perpendicular to the axial direction of the wire electrode. The workpieces are opposed to each other via a minute discharge gap, and a discharge is generated by a machining voltage such as an intermittent voltage pulse applied between the two under the machining fluid supply by a machining fluid supply unit (not shown). Processing is performed. Then, the first process up to at least the second cut of roughing and dimensional accuracy
The processing voltage for the processing of the processing step, that is, the intermittent voltage pulse is supplied from the voltage pulse source 5 for wire electric discharge machining in the illustrated embodiment as the power supply connection lines 11A and 11B.
Preferably, a stranded wire having a small floating capacitance component is used for a lead wire near the discharge gap via a coaxial or shielded wire having a small floating inductance component. Is applied to

A plurality of voltage pulse sources 5 are connected to the DC voltage source 6A in accordance with the current capacity.
The most usual conventional intermittent voltage pulse generation / supply circuit 6 comprising a series circuit of an electronic switch element 6B such as a T transistor, a current limiting resistor 6C, and a reverse voltage prevention rectifier 6D is arranged in parallel with the discharge gap. Power supply connection line 11A,
11B, the intermittent voltage pulse is generated as desired by the control of the switch element 6B by the pulse control device 7. That is, the control device portion of the switch device 6B of the control device 7 includes a predetermined ON time signal τ _ON and OFF which is selected and set in advance, except when the switch device 6B is changed and controlled by the discharge state detection signal of the discharge gap. The time signal τ _OFF is regularly and alternately repeated to control the supply of the voltage pulse, and the ON time signal of the switching element 6B is applied to the discharge gap from the start of application of the voltage pulse to the start of discharge in the discharge gap. The measurement of the on-time signal is started from the start of the discharge in the discharge gap after the start of the application of the voltage pulse so that the discharge duration increases as a function of the discharge start delay period, that is, the discharge duration of each discharge pulse is set to a fixed value, and the measurement There is a control for turning off the switch element 6B upon completion and shifting to the off time. In the following description, mainly the latter case will be described. Obtain, but the present invention is not construed as being limited thereto.

The voltage pulse source 5 includes, in addition to a machining voltage pulse supply circuit 6 for turning on and off the switch element 6B, a discharge current amplitude Ip of a discharge pulse from the circuit 6.
And a pulse current amplification circuit or current pulse supply circuit 8 for further increasing the processing speed by increasing the processing average current, comprises a variable DC voltage source 8A, a switch element 8B, and a reverse voltage prevention rectifier 8C. And is provided in parallel with the circuit 6. The current pulse supply circuit 8 outputs a steep rising high current when the control device 7 turns on the switch element 8B so that a so-called resistance-free circuit having no so-called current limiting resistor in the series circuit or the switch element 8B. A circuit 8 in which a current limiting resistor is not inserted in addition to a minute detection resistor for operating a current controller 7A of a switch element 8B provided in a control device 7 for preventing damage, In the wire electric discharge machining, the on-time signal of 6B or the on-time signal from the start of the discharge is within several tens μS at most, and usually several μS.
Since it is within S, even if the switch element 8B is turned on during the on-time signal that operates by detecting the start of discharge in the gap by the voltage pulse applied by the circuit 6, the switch element 8B or at least the current of the circuit 8 Although there is a case where the circuit 8 can be prevented from being damaged even if the current limiting resistor is not provided in the circuit 8 due to the transition time to the operation in the saturation region, etc., the operation region of the switch element 8B is referred to as an unsaturated region or at least a circuit region. If the condition is set such that the range in which the current 8 is sufficiently smaller than the saturation current value of the switch element 8B (usually a fraction) is the operation region, there is no problem of breakage of the switch element 8B, and the switch element 8B is not damaged. This is preferable because the current-off characteristic of the circuit 8B or 8B becomes sharp and steep.

The above-described current pulse supply circuit 8 serves as the voltage pulse source 5 together with the voltage pulse supply circuit 6 as the workpiece 3
First, rough processing for forming a processing groove, that is, a first cut processing step, and a second cut processing step for performing processing for obtaining the size and shape accuracy of processing after the first cut processing step, that is, an intermittent voltage pulse as a processing voltage The gate input is connected to the control device 7 by a changeover switch 8E, and is used in the first processing step used.
For example, the control related to the circuit 6 as described above is performed. After the completion of the second cut processing as the first processing, the processing using the high-frequency AC voltage as the second processing is performed. When shifting to one or two finishing processing steps (for example, a third cutting processing step or a further force cutting processing step) of the surface roughness processing, the voltage pulse supply circuit 6 is cut off by an open / close switch 49 as necessary, and The changeover switch 8E is switched to the high-frequency intermittent pulse gate signal circuit 8D side so that the current pulse supply circuit 8 functions as the high-frequency current pulse generation circuit 10.

At this time, the discharge state detecting circuit is controlled by the open / close switch 48 from the circuits 31 to 37 to the circuits 41 to 4
7 and the high-frequency current pulse generation circuit 10
And a high-frequency coupling transformer 13 provided between the discharge gaps and a circuit switching open / close switch 14 for shifting from the first processing step for obtaining the dimensional and shape accuracy to the second processing step for finishing the processing surface roughness and the like. The high-frequency AC voltage source 30 constituted by the circuit device 12 housed in a box-shaped box having the following configuration and switching is used as follows.

The high-frequency coupling transformer 13 converts each intermittent high-frequency current pulse output from the high-frequency current pulse generating circuit 10 into a one-cycle high-frequency AC voltage. A primary winding 13B and a secondary winding 13C are provided on a ring core 13A of magnetic susceptibility.
The winding ratio is 1: 1 to 3, preferably 1: 1 to 2, and the number of turns is 1 to 5 turns of the primary winding, preferably 1 to 2 turns, 1 to 12 turns of the secondary winding, preferably 1 to 1 turn. Like four turns,
In order to obtain a high frequency AC voltage for finishing processing, which has a small number of turns for each high frequency response and is rather high and has a small current, the number of turns of the secondary winding is equal to that of the primary winding. It is wound so as to be as described above.

Next, the high-frequency current pulse generation circuit 10
And the power supply connection lines 11A and 11B between the discharge gaps composed of the wire electrode 1 and the workpiece 3 and the circuit device 12
The connection and switching configuration of the primary winding 13B will be described.
The open / close switch for connecting / disconnecting the secondary winding 13C to / from the discharge gap and the open / close switch for connecting / disconnecting the secondary winding 13C to / from the output of the high-frequency current pulse generation circuit 10 are connected to both ends of the output of the high-frequency current pulse generation circuit 10 and the wire electrodes 1 Power supply circuit open / close switches 14A, 14B provided in the circuit portions of the power supply connection lines 11A, 11B connected between the power supply connection lines 11A, 11B and the power supply circuit open / close switches 14A, 14 respectively.
The primary winding on / off switch 14C inserted in one or both of the connection circuits during connection to both of the output lines on the high frequency current pulse generation circuit 10 side from B, and the both ends of the output of the secondary winding are A secondary winding on / off switch 14D inserted in one or both connection circuits during connection to both the wire electrode 1 and the workpiece 3 on the discharge gap side of the power supply circuit on / off switches 14A and 14B; The two power supply circuit on / off switches 14A and 14B and the primary and secondary winding on / off switches 14C and 14D are the former on / off switch 14.
When A and 14B are on, the latter on / off switch 14C,
This object is achieved by opening and closing the power supply circuit on / off switches 14A and 14B off and turning on the primary and secondary winding on / off switches 14C and 14D. At this time, a power supply circuit for finishing processing by a high-frequency AC voltage used in the second processing step which is the object of the present invention is configured.
It should be noted that the drawing shows a case in which one open / close switch is provided for each of the primary winding and the secondary winding, and a case where the number of changeover switches provided is the smallest. It goes without saying that various switching circuit configurations can be achieved depending on the number of switches.

FIG. 3 shows the processing power supply circuit of FIG. 2 as a power supply circuit for finishing processing in the second processing step, that is, the open / close switch 49 is turned off, the gate signal circuit 8D is turned on by the changeover switch 8E, and the high-frequency current Pulse generation circuit 10
Function, the power supply circuit on / off switches 14A, 14B are turned off, the transformer primary and secondary winding on / off switches 14C, 1C,
The timing chart in the case where each of the 4Ds is turned on is shown as an almost ideal waveform for two cycles, and “a” is output from the intermittent pulse gate signal circuit 8D to turn on / off the switch element 8B. The high-frequency gate signal b is output from the high-frequency current pulse generation circuit 10 based on the gate signal, and the primary winding 13
The current pulse supplied to B, c is a high-frequency AC voltage induced in the secondary winding 13C based on the pulse current and applied to the discharge gap, and a discharge gap when a discharge occurs in the discharge gap based on the application of the high-frequency AC voltage. The voltage waveform d is an example of the discharge current in the discharge gap. The waveform shaping of the generated high-frequency AC voltage by combining the current pulse generating circuit 10 and the coupling transformer 13 (usually, a steep and smooth sinusoidal waveform, or a continuous waveform of AT _OFF = 0) is performed. It is effective to insert a desired inductance in series into the secondary winding 13C and the discharge circuit in the discharge gap. For this purpose, a coil having a predetermined inductance is connected in series, or the electrode 1 or the guide 2A is connected. , 2B, a magnetic core having a high magnetic permeability may be provided so as to surround the wire electrode 1.

In the finishing processing to which the present invention is applied, the gate signal of the intermittent pulse output from the gate signal circuit 8D is T _ON = 100 nS, T
_OFF = 1.0 μS, approximately T _ON = 50 nS-10
T _OFF = 500n at μS order or less of about 00nS
S is about 10 μs or several tens of μs, and it is preferable to use AT _OFF as long as the AC voltages of C are mutually connected.
The condition is set so that ≧ 0. The output current pulse waveform b of the high-frequency current pulse generation circuit 10
Is that the gate signal a is turned off before the switch element 8B or at least the current in the circuit 8 enters the saturation region operation state of the rising current sufficiently smaller than the saturation current value of the switch element 8B, and the switch element 8B or the circuit 8 Is shown as having occurred at a high speed.

[0026] In addition, high-frequency AC voltage of the secondary winding 13C of the previous Symbol Figure 2, according to a recent test, an outer diameter of about 55mm
φ, inner diameter of about 30 mmφ, ferrite toroidal core such as high permeability Mn-Zn ferrite or Ni-Zn ferrite (for example, TDK PC50 [or PC30] T4
0 × 16 × 24), a Teflon-based resin-coated conductive wire having a cross section of about 3.5 mm ²
B: 1 turn, secondary winding 13C: 2 turns,
The output of the DC voltage source 8A is about 60V and the output is about 150-
170 V, the output of the voltage source 8A is about 25 V,
0-65V, finishing processing (third cut and force cut) for improving the surface roughness, which is the second processing step described above.
When a discharge occurs in the first half-wave of one cycle of the AC voltage, as shown in the discharge current waveform d, a high-frequency high-frequency AC voltage which is preferably applicable to the following is obtained. Then, a discharge occurs, but the finishing can be advanced at a value where the average machining current is smaller than about 1 A. For example, the positive and negative about 150-170V,
A high-frequency AC voltage of about 1 MHz, a processing surface finished to about 10 to 13 μmRmax up to the second cut processing of the first processing step is processed by a third cut of the second processing step to obtain about 3.5 μmRmax or It can be finished more than that, and it is about 1.5μ
It is finished to about mRmax.

The discharge state detection circuit is switched to the discharge state detection circuits 41 to 47 of the present invention having a very small floating capacitance by the open / close switch 48, and the voltage pulse supply circuit in the voltage pulse source 5 is switched. 6 is an open / close switch 49
This makes it possible to reduce the absorption and attenuation of the high-frequency AC voltage, and to allow the finishing to proceed under suitable servo control. In addition, when the pause time AT _OFF between the high-frequency AC voltages c is set to be shorter or more nearly continuous, when the average voltage of the discharge gap is detected to be equal to or lower than a predetermined level, or when a predetermined setting is made. Period (every 100 μS to 10 ms), for example, 10 to 100 μ
It is natural for safety that it is necessary to stop the ON / OFF of the switch element 8B for about s.

In the above-described processing using the intermittent voltage pulse source 5, a normal voltage pulse supply circuit 6 is used.
In addition, a current pulse supply circuit 8 for significantly increasing the discharge current amplitude (Ip) is additionally used, and a discharge with a high discharge current amplitude is performed as in the case of charging and discharging a capacitor. It is not necessary to switch the state detection circuit to the detection circuits 41 to 47 having small stray capacitances. However, the circuit 6 and the circuit 8 are configured to be detachable and freely connectable, and the normal voltage pulse supply circuit 6 is used. A third cut of the second processing step by supplying a minute voltage pulse;
Further, in the case of performing a finishing process such as forcing the workpiece surface to a roughened surface, the switching to the detection circuits 41 to 47 having a small stray capacitance of the discharge state detection circuit of the present invention is useful and effective. It is already clear that FIG. 4 is an explanatory block diagram of an embodiment similar to FIG. 1 having a more preferable and improved discharge gap detection circuit 41 to 47 of the present invention. The difference from FIG. An input resistor 41 in series with the light emitting element 41A of the input section photocoupler 41 of the detection circuits 41 to 47
C is a power supply device provided with a large-capacity, high-resistance voltage-dividing resistor 41C-1 provided at a position close to the discharge gap, and detection circuits 41 to 47, a control device 38, and the like separated from the discharge gap. And the voltage dividing resistor 4 provided on the control unit side.
The machining fluid is supplied to the electric discharge machine main body, and the left side of the one-dot broken line 50 in FIG. The right side of the dashed line 50 is the power supply unit and the control unit side, but the mechanical open / close switch 48 is
It can be provided at an appropriate position such as the machine body side on the left side of 50 . That is, in the configuration of FIG.
To 47 are connected to the discharge gap, and the discharge finish machining for obtaining the machining surface roughness is performed by the high-frequency AC voltage source 30 as shown in FIG. 2, the frequency of the high-frequency AC voltage is about 1 MHz or higher, Since the positive-negative peak-to-peak voltage is a high voltage of about 350 to 500 V, the input resistance 41C of the detection circuits 41 to 47 has a resistance of about 3 KΩ and a rated capacity of about 20 W. Is required with a cooling means such as a cooling fan, and is not long enough to require an installation space.
When the detection circuit lead wire is routed to a power supply device or control unit with 47, various circuits such as a control circuit nearby will cause various malfunctions and other noise disturbances, and the machining control operation and machining will be skillful. It was not uncommon to say that it did not progress. Therefore, in the present invention, the input resistance 41C is set to a high resistance value, for example, about 2.5 KΩ, and a large capacity, for example, about 20 KΩ.
A voltage dividing resistor 41C-1 for limiting current of W and a second resistor 41C-2 having a low resistance value, for example, 100Ω and a small capacity, for example, 1 to 2W, are divided into two parts and are configured in series. And, the former voltage-dividing resistor 41C-1 for limiting the current is immersed in the machining fluid in the machining tank containing the machining part such as the discharge gap for cooling, and the machining tank or The processing fluid to be supplied to the processing section is cooled by a configuration in which the processing liquid is jetted if necessary. By doing so, the second voltage-dividing resistor 41C-2 provided in the detection circuit does not require a special space, and the discharge gap voltage is sufficiently divided (about 1/26), so that the detection circuit , No noise disturbance occurs in nearby control circuits and the like. FIG. 5 is an explanatory view showing an example of a state in which the current-limiting voltage dividing resistor 41C-1 is provided in the machining tank portion of the wire electric discharge machine main body. The work stand 4 on which the workpiece 3 is placed is: The workpiece 3 is provided in a processing tank attached to a cross table on a bed (not shown), and the workpiece 3 is immersed in a processing liquid as required, and a processing liquid injection nozzle 18A including guides 2A and 2B, Wire discharge machining such as cutting and cutting is performed by the wire electrode 1 that moves between 18B. One of the output terminals of the power supply for electric discharge machining (positive electrode side) is on the work stand 4 and the other is the nozzle 18A. The terminal 18A is connected to a power supply (not shown) that contacts the wire electrode 1 via terminals 19A and 19B.
Thus, the voltage dividing resistor 41C-1 is preferably a non-inductive and water-resistant cement resistor, metal clad resistor, or enamel resistor, etc.
And one of the terminals 41C-1A is connected to the work stand 4 (or the terminal 19B of the nozzle 18B), and the other terminal 41C-1B is connected to a power supply. One terminal 21B of the coaxial cable 21 for transmitting a detection signal between the device or the control unit and the processing machine main body, and the other terminal 2 of the coaxial cable 21
1A is connected to the terminal 19B (or the work stand 4) of the nozzle 18B. The partial pressure resistor 41C-1 is immersed and cooled in a processing liquid in a processing tank, or a nozzle 1 as shown in the drawing.
8A, 18B, a pipeline 22 branched from the machining fluid supply pipe 22
A (or an independently provided pipe line) cools as desired by the jet processing liquid of the cooling nozzle 23 supplied. 6A and 6B show a modification of the voltage dividing resistor circuit of the detection circuit. As described above, the voltage dividing resistor circuit of the present invention is provided between the input / output terminals of the detection circuit (19B or 21A and 41C). -1B or 21B) or the line voltage is reduced, so that the machine body side output terminals 21A and 21A are connected as shown in FIG.
A voltage dividing resistor 41C-1C is connected between 1B, or is divided in parallel with a series circuit of a resistor 41C-2 at the other end of the coaxial cable 21 and a light emitting element 41A as shown in FIG. A configuration in which the piezoresistors 41C-2C are connected to reduce the input voltage of the detection circuit is also effective.

As described above, the electric discharge machine according to the present invention has been described with reference to the illustrated embodiment. However, the present invention may be modified in various ways without departing from the spirit of the present invention described in the appended claims. In addition, it can be implemented. For example, in FIG. 2, in the case of a power supply circuit for wire electric discharge machining in which the current pulse supply circuit 8 is not provided, a resistance reducing circuit for short-circuiting the current limiting resistor 6D of the intermittent voltage pulse generating circuit 6 is provided. Alternatively, the gate signal circuit 8D may be switched and connected to the gate signal circuit of the switch element 6B. The gate signal circuit 8D can be provided not only as a part of the pulse control device 7 but also internally. Further, in the control device 7, the stored switching control data can be read out or the like to perform the switching operation by software.
Furthermore, in order to further increase the high-frequency AC voltage for finishing processing, for example, to 2 MHz, two sets of current pulse supply circuits 8 are provided in parallel, for example, each having τ _ON = 10.
At 0 ns, two sets of 1 MHz high frequency (current) pulse generating circuits of τ _OFF = 900 ns have a phase difference of about 180 ° (π), and one cycle of the high frequency AC voltage is about 50
It may be adjusted so as to be completed within 0 ns. Further, as the high-frequency AC voltage source, a normal, for example, transistor-inverter-type high-frequency AC voltage source is used, and this is connected to the discharge gap via a matching circuit. Such a configuration change can be made in each part of the present invention.

Since the electric discharge machining apparatus of the present invention has the above-described configuration, the discharge state detection circuit connected to the discharge gap at the time of finishing machining connects the resistor and the light emitting element of the photocoupler in series. Only the serial circuit portion described above, the integrating circuit and the amplifying circuit after the photocoupler, or further the sample-hold amplifying circuit and the A / D converter are insulated from the discharge gap by the photocoupler. Other detection circuits etc. provided separately as necessary are
Since it is separated by the mechanical opening / closing switch, the stray capacitance by the discharge state detection circuit provided for the discharge gap can be minimized, and the finished surface is preferably servo-controlled, so that the machining surface is not roughened. Efficient processing can be performed with a predetermined fine surface roughness. Further, according to the present invention, a resistor in series with the light emitting element is provided with a current-limiting voltage dividing resistor provided at a position close to the discharge gap and a second resistor provided on a detection circuit side of a power supply device separated from the discharge gap. The high-frequency AC voltage source is discharged without causing a high-frequency high-voltage noise disturbance in the discharge state detection circuit and the power supply device and the control unit in which the circuit is provided. It can be used safely and effectively as a power source for finishing.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a discharge state detection circuit according to the present invention.

FIG. 2 is a circuit diagram showing a detailed example of a power supply circuit portion for electric discharge machining in FIG. 1;

FIG. 3 is a partial timing chart when the circuit of FIG. 2 is operated as a power supply circuit for finishing processing.

FIG. 4 is a block diagram showing an embodiment of the improved discharge state detection circuit of the present invention.

FIG. 5 is an explanatory diagram showing a configuration of a portion of the embodiment of the present invention.

FIGS. 6A and 6B are circuit explanatory diagrams showing modified examples of portions of the embodiment of the present invention.

FIG. 7 is a block diagram of a conventional discharge state detection circuit.

[Explanation of symbols]

1, wire electrode, machining electrode 2A, 2B, positioning guide 3, workpiece 4, work stand 5, voltage pulse source for wire electric discharge machining 6, voltage pulse generation and supply circuit 6A, DC voltage source 6B, electronic switch Element 6C, current limiting resistor 6D, reverse voltage prevention rectifier 7, pulse control device 8, current / current pulse supply circuit 8A, variable DC voltage source 8B, electronic switch element 8C, reverse voltage prevention rectifier 8D, gate signal circuit 8E, changeover switch 10, high-frequency current pulse generation circuits 11A and 11B, power supply connection line 12, circuit device 13, high-frequency coupling transformer 13A, ring core 13B, primary winding 13C, secondary windings 14A, 14B, 14C, 14D, open / close switch 18A, 18B, machining fluid injection nozzle 19A, 19B, terminal 20, resistance mount 21, coaxial cable 22, Working fluid supply pipe 23, cooling nozzle 30, finishing power supply 31, voltage divider circuits 32, 42 for detecting discharge gap voltage, inverting amplifier circuits 33, 43A, 43B, integrating circuits 34, 44, gain adjusting circuits 35, 45, Sample hold amplifiers 36, 46, A / D converters 37, 41, 47, photocoupler 38, control device 39, motor driver 40, servo motor 41A, light emitting element 41B, light receiving element 41C, resistors 41C-1, 41C-2. , 41C-1C, 41C-2
C, voltage dividing resistor 41D, rectifier 48, 49, open / close switch

──────────────────────────────────────────────────続 き Continuation of the front page Examiner Takayuki Kanzaki (56) References JP-A-5-177435 (JP, A) JP-A-56-163830 (JP, A) JP-A-5-2875731 (JP, A) JP-A-51-85593 (JP, A) JP-A-4-250920 (JP, A) JP-A-2-30422 (JP, A) JP-A-6-8049 (JP, A) JP-A-63-200920 (JP) JP, A) JP-B-60-13769 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23H 1/02

Claims (7)

(57) [Claims] 1. A high-frequency coupling transformer having primary and secondary windings wound around a ring core, and a current pulse supply circuit for intermittently supplying a high-frequency current pulse to the primary winding, A finishing machining voltage supply circuit for supplying a high-frequency AC voltage induced in the secondary winding to a discharge gap between the machining electrode and the workpiece to perform finishing, and connecting a series circuit of a resistor and a light emitting element to the discharge gap; A plurality of discharge state detection circuits, which are directly connected in parallel to each other, and convert a light emission output of the light emitting element into an electric signal by a light receiving element of photoelectric conversion to obtain a discharge state detection signal of the discharge gap. A discharge state detection circuit is provided in parallel with the discharge gap, and when a finishing machining voltage supply circuit for the high-frequency AC voltage is used in machining, a circuit other than the discharge state detection circuit having the series circuit is provided. Mechanical off switch for disconnecting the electricity state detection circuit from the discharge gap, discharge machining apparatus, characterized in that provided between the discharge state detecting circuit other than the discharge state detection circuit having the above-mentioned series circuit and the discharge gap. 2. A processing voltage pulse supply circuit for intermittently supplying at least a voltage pulse for normal processing with a pause time as a processing power source, and a high-frequency AC voltage applied to a discharge gap between the processing electrode and the workpiece. And a voltage supply circuit for finishing machining to be supplied.The discharge state detection circuit is connected to and separated from the discharge gap as necessary by an on-off switch provided as necessary, and is connected in series with the resistor and the light emitting element. A discharge state detection circuit in which a circuit is directly connected in parallel with the discharge gap, and a light emission output of the light emitting element is converted into an electric signal by a light-receiving element of photoelectric conversion to obtain a discharge state detection signal of the discharge gap. And at least one discharge state detection circuit having a voltage detection circuit connected in parallel to the discharge gap different from the discharge state detection circuit including the light emitting element. At the time of finishing processing in which machining control and other control elements are controlled by the discharge state detection signal, it is connected to a voltage pulse supply circuit other than the high-frequency AC voltage supply circuit and a discharge gap other than the discharge state detection circuit including the light emitting element. An electric discharge machining apparatus characterized in that the electric discharge state detecting circuit is configured to be separated from the electric discharge gap by a mechanical open / close switch. 3. A current dividing voltage dividing resistor provided in a position close to the discharge gap and a second voltage dividing provided on a detection circuit side of a power supply device separated from the discharge gap by connecting a resistor in series with the light emitting element. 3. The electric discharge machining apparatus according to claim 1, wherein the electric discharge machining apparatus is configured by a series connection with a resistor. 4. The current-limiting voltage-dividing resistor according to claim 2, wherein
The voltage dividing resistor is selected to have a relationship of applying a sufficiently large voltage dividing value to the voltage dividing value of the voltage dividing resistor, and the current limiting voltage dividing resistor is brought into contact with the machining fluid supplied to the discharge gap for cooling. The electric discharge machining device according to claim 3, wherein the electric discharge machining device is arranged in a machining tank portion so as to perform the operation. 5. The electric discharge machining apparatus according to claim 1, wherein a rectifying element is connected in parallel with the light emitting element with a reverse polarity. 6. The electric discharge machining apparatus according to claim 1, wherein the light emitting element is a light emitting diode, and the light receiving element is a phototransistor or a photodiode. 7. A discharge gap detection signal of a servo feed control device for controlling a discharge gap by feeding a discharge gap detection signal of the discharge state detection circuit.
The electric discharge machine according to 5 or 6.