JP4250377B2 - Power supply for EDM - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power source for an electric discharge machine for finishing, which can stably generate a minute electric discharge.
[0002]
[Prior art]
A conventional power supply for an electric discharge machine will be described with reference to the drawings. FIG. 37 is a diagram showing a basic circuit configuration of a conventional power source for an electric discharge machine shown in, for example, “Electrical discharge machining technology” (Saito, Mori, Takatsuki, Furuya: Nikkan Kogyo Shimbun (1997) p. 75). It is. FIG. 38 is a timing chart showing the operation of the conventional power supply for an electric discharge machine shown in FIG.
[0003]
As shown in FIG. 37, between the electrodes 1 and 2 (in the case of a wire processing machine, a wire and a work, in the case of a sculpture processing machine, a die electrode and a work) are connected to a switching element S (here, an FET (field effect transistor)). Used) and a resistor Rs. By turning on and off the switching element S, a pulsed voltage waveform is applied between the electrodes. Basically, a pulse voltage can be applied in this circuit, but a capacitor Cs may be added in parallel between the electrodes by adding a so-called capacitor discharge concept. Alternatively, even if no capacitor is added, there is a capacitance formed between the electrodes by at least the discharge gap and the dielectric constant of the working fluid.
[0004]
In this case, as shown in FIG. 38, the current waveform is such that a current pulse having a high peak value from the capacitor Cs immediately after the start of discharge, and then a current having a low peak point flows from the DC power source V0 via the resistor Rs. Become.
[0005]
Therefore, the strength of discharge is determined by the capacitor Cs, the resistance Rs, and the voltage value V0. Now, when it is intended to reduce the strength of the discharge, that is, the amount of moving electric charge, these values should be reduced.
[0006]
First, although the applied voltage is V0, a certain amount of voltage is required to cause discharge, and therefore this value cannot be reduced below a certain value.
[0007]
Next, when the resistance Rs is increased, the current flowing through the resistance Rs is decreased. Here, it is known that a current of a certain value or more is necessary for sustaining the discharge arc. Therefore, when the resistance Rs is increased to a certain value or more, the arc can be sustained by the current from the resistance Rs. The discharge current from the resistor Rs becomes zero. That is, the discharge current from the resistor Rs can be made zero by increasing the value of the resistor Rs.
[0008]
Finally, it is the value of the capacitor Cs. If this value is reduced, the discharge current from the capacitor Cs is reduced. However, as described above, there is some floating capacitance between the electrodes, such as capacitance between the electrodes, and this cannot be removed. Therefore, the discharge current from the capacitor Cs has a certain lower limit value, that is, a lower limit value that discharges only with the stray capacitance between the electrodes. That is, by reducing the resistance Rs, the amount of electric charge of the discharge flowing between the electrodes can be reduced, but cannot be less than the stray capacitance between the electrodes.
[0009]
It is not only the capacitance of the discharge gap that exists between the electrodes. Capacitance due to other mechanical structures, or because multiple power supplies are used for processing, when other circuits are connected between the electrodes, stray capacitance of the circuit exists in parallel between the electrodes is doing.
[0010]
Alternatively, there is a floating capacitance in a motor for rotating the electrodes by the profiler. This is shown in FIG. FIG. 39 is a diagram showing a circuit configuration of another conventional power source for an electric discharge machine.
[0011]
Generally, electrostatic capacity other than the electrostatic capacity between the electrodes 1 and 2 is connected via an inductance Lp such as a mechanical structure or a feeder line to another power supply board. Even in the case of the stray capacitance Cp existing through such an inductance Lp, when a DC voltage is applied between the electrodes, it is equivalent to the capacitor Cs. Therefore, a discharge current corresponding to the capacitance of Cs + Cp is generated. Will flow.
[0012]
[Problems to be solved by the invention]
That is, no matter how small the resistance Rs is, the applied voltage is V0, and the charge amount of the discharge current cannot be smaller than V0 × (Cs + Cp). This determined the limit of surface roughness of the conventional electric discharge machining. Even if a small amount of charge is supplied between the discharge electrodes, there is no termination resistor or switch that short-circuits the electrodes, so that charge accumulates between the electrodes, and as a result, only a large discharge can be generated. It was.
[0013]
In some cases, the value of the stray capacitance Cp can be reduced as much as possible by disconnecting other processing power sources connected between the electrodes by a relay or the like at the stage of finishing processing, or by electrically insulating the surface plate for holding the workpiece. The finishing process may be performed with a smaller size. In this case, the discharge charge amount is surely reduced and the surface roughness is improved. However, in the middle of a series of processing procedures, complicated steps such as disconnecting the power source and insulation are necessary. A machining method that can proceed from roughing to finishing without giving any special changes to the power supply or mechanical system (this state is called “non-insulated”) and can achieve better surface roughness. Was needed.
[0014]
The present invention has been made to solve the above-described problems, and can stably generate a very small electric discharge even in a non-insulated state, and thus can obtain a fine surface roughness. The purpose is to obtain a power source.
[0015]
[Means for Solving the Problems]
  A power supply for an electric discharge machine according to the present invention includes a first charge storage element that stores electric charge, a first DC power supply that charges the first charge storage element,By on / off operationA first switching element for causing a charge accumulated in the first charge storage element to flow through the electrode gap to generate a pulsed discharge, a second DC power supply, and the second DC power supply are connected in series. ,By turning on during the period when the first switching element is onAnd a second switching element that draws out the electric charge existing in parallel with the electrode gap or the electrode gap to the second DC power supply.
[0026]
  AlsoThisThe electric power source for an electric discharge machine according to the invention further includes a second charge storage element for storing electric charges in parallel with the second DC power supply.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
A power supply for an electric discharge machine according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 1 of the present invention. In addition, in each figure, the same code | symbol shows the same or equivalent part.
[0028]
In FIG. 1, as in FIG. 39, a capacitance Cs and a water resistance Rw exist between the electrodes 1 and 2. The difference from FIG. 39 is that the capacitor Cq for storing the charge once exists in front of the switch Su, and the resistor Rs is not a resistor for limiting the discharge current, but rather a resistor for charging the capacitor Cq. Is playing a role.
[0029]
Further, it is desirable that the path from the capacitor Cq to the discharge gap has as little impedance as possible. Although a discharge switch Su exists, for example, when an FET is used as this switch, it may be considered that the resistance when ON is sufficiently small. In practice, an inductance Ls such as a feeder line exists in the path. Further, as a feature of this circuit, a switch Sl for short-circuiting the electrodes is provided in parallel between the electrodes.
[0030]
Next, the operation of the electric discharge machine power supply according to Embodiment 1 will be described with reference to the drawings. FIG. 2 is a timing chart showing the operation of the power supply for the electric discharge machine according to Embodiment 1 of the present invention.
[0031]
2, (a) shows the operation timing of the two switches, (b) shows the change in voltage across the capacitor Cq, and (c) shows the voltage applied between the electrodes.
[0032]
Here, it is assumed that no discharge has occurred. First, at time t = 0, it is assumed that the voltage Vs is applied to both ends of the capacitor Cq and the charge Cq × Vs is accumulated. Further, both the switches Su and Sl are assumed to be OFF. In this state, the switch Su is turned on at time t = t1. Then, the electric charge accumulated in the capacitor Cq is applied between the electrodes through a path having a small impedance.
[0033]
First, when the impedance of the path is sufficiently small, a voltage Vp approximately equal to the voltage value Vs stored in the capacitor Cq is instantaneously applied between the electrodes. Actually, the voltage Vp becomes smaller than Vs due to the influence of the impedance Ls of the path.
[0034]
Thereafter, the charge Cq × Vs stored in the capacitor Cq gradually approaches the voltage value Vd divided by the capacitance Cs between the capacitor Cq and the electrode. In other words, a high peak voltage is first applied and gradually decreases. The switch Su discharges the charge and then turns OFF. When the switch S1 is turned ON while the voltage between the electrodes gradually approaches the voltage Vd, the charge accumulated between the electrodes is short-circuited through the switch S1 and the voltage between the electrodes is reduced. The voltage returns to zero.
[0035]
Here, a resistance Rw of water exists between the electrodes, but since this value is generally sufficiently large, it takes a considerable time for the voltage to become zero through the resistance Rw. When the switch Su is turned off, the capacitor Cq starts charging again, and the time constant of this charging is Cq × Rs.
[0036]
Now, consider the case where a discharge occurs. When discharge occurs, the impedance between the electrodes rapidly decreases, the voltage between the electrodes decreases, and a certain arc voltage is obtained. A current flows between the electrodes. At this time, the flowing current is supplied from the capacitor Cq or the resistor Rs while the switch Su is ON, and is as shown in FIG.
[0037]
Here, if the resistance Rs is sufficiently large and the arc cannot be sustained with the current from the resistance Rs, the current that flows is only the current from the capacitor Cq. This means that the amount of current flowing by discharge can be controlled by a known capacitor Cq on the circuit regardless of the timing of the switch Su. As described above, the depth of the discharge trace is determined by the amount of charge of the flowing current. That is, the processing surface roughness can be controlled by the value of the capacitor Cq.
[0038]
For example, in the case of FIG. 37, the discharge charge amount is controlled by the ON time of the switch S. However, when the target charge amount value is reduced, the ON time of the switch S is shortened, and it becomes difficult to open and close the switch S for a very short time due to the switch S, for example, the rising speed of the FET. In the case of the circuit configuration as shown in FIG. 1, the amount of charge can be controlled not by the ON time of the switch Su but by the capacitor Cq and the applied voltage Vs. This is a feature of the first embodiment of the present invention.
[0039]
Here, as for the necessity of the switch Sl, if there is no switch Sl, if the discharge does not occur several times continuously, the voltage is accumulated in the capacitance Cs between the electrodes. When the recharged charge is input, the voltage between the electrodes becomes Vd × n (where Vd × n <Vs). Therefore, when a discharge occurs after that, a normal n-fold charge amount flows and the surface roughness is deteriorated. In other words, it is impossible to achieve the original object of the present invention of always discharging a certain amount of charge.
[0040]
Embodiment 2. FIG.
A power supply for an electric discharge machine according to Embodiment 2 of the present invention will be described with reference to the drawings. FIG. 3 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 2 of the present invention. FIG. 4 is a timing chart showing the operation of the electric discharge machine power supply according to Embodiment 2 of the present invention.
[0041]
In the circuit configuration shown in FIG. 3, the capacitance Cs and the water resistance Rw exist between the electrodes as in FIG. Also, the difference from FIG. 39 is that, similar to FIG. 1, the capacitor Cq for storing the charge is present before the switch Su, and the resistor Rs is not a resistor for limiting the discharge current, but rather the capacitor Cq. Is playing a role of resistance to charge. It is desirable that the path from the capacitor Cq to the discharge gap has as little impedance as possible.
[0042]
The difference from the case of FIG. 1 is that a floating capacitance Cp caused by another circuit or mechanical structure is connected between the electrodes. In many cases, an inductance Lp exists between the floating capacitance Cp and the electrode.
[0043]
First, it is assumed that the voltage across the capacitor Cq is Vs and the voltage between the electrodes is zero at time t = 0. At time t = t1, the switch Su is turned on. Then, current flows from the capacitor Cq between the electrodes. Here, when the resistance component of the path is sufficiently small, a short pulse and a high-peak voltage pulse are applied between the electrodes.
[0044]
At this time, the peak value Vp of the voltage value is approximately the same as the voltage value Vs originally charged in the capacitor Cq if the inductance Ls of this path is sufficiently smaller than the inductance Lp. Even if it is not sufficiently small, a voltage of approximately Vp = Lp / (Lp + Ls) × Vs is applied.
[0045]
The voltage pulse resonates for a while and shows a vibration waveform, and then reaches a certain value Vd. Here, Vd = Vs × Cq / [Cq + Cs + Cp]. Since the capacitor Cq is assumed to be sufficiently smaller than the floating capacitance Cp, the value of Vd is sufficiently smaller than Vs.
[0046]
Now, it is assumed that the resistance Rs connected to the power source is sufficiently large so that the discharge arc cannot be maintained. At this time, when a voltage pulse is applied at time t = t1 and a discharge occurs between the electrodes, a current flows between the electrodes, but the resistance Rs is not large enough to supply a current. This is the amount of charge accumulated in the capacitor Cq at the maximum. That is, the amount of charge flowing between the electrodes can be controlled by the value of the capacitor Cq.
[0047]
Even if the value of the capacitor Cq is decreased, the voltage value applied between the electrodes can be sufficiently increased if the resistance of the discharge path is sufficiently small and the inductance Ls is also sufficiently small. Therefore, a sufficiently high voltage pulse can be applied with a sufficiently small capacitor Cq to cause discharge and to limit the amount of charge of the discharge to be sufficiently small.
[0048]
For example, in the conventional circuit, there is no element Cq for limiting the charge, and voltage is applied between the electrodes by directly storing the charge in the capacitance connected between the electrodes or the parasitic capacitance Cp + Cs. . Therefore, when the voltage between the electrodes becomes high enough to be discharged, the amount of charge accumulated here also increases accordingly, and the amount of charge flows between the electrodes due to the discharge, so a weak discharge can be caused. There wasn't. In the present invention, a high peak voltage can be instantaneously applied by providing an element for accumulating charges outside the switching element and applying it between the electrodes via a path having a small impedance. Here, since the inductance Lp exists up to the large electrostatic capacitance Cp parasitic between the electrodes, the electrostatic capacitance Cp becomes invisible for a sudden voltage pulse.
[0049]
Now, in FIG. 3, there is no switch Sl for short-circuiting the electrodes as in FIG. This is because, as will be described later, the power supply or mechanical structure connected in parallel has a resistance component Rp (dotted line) in some cases, and if no discharge occurs, the amount of charge Cq accumulated between the electrodes. This is because × Vs flows through the resistance component Rp and the potential difference between the poles returns to zero.
[0050]
Embodiment 3 FIG.
A power supply for an electric discharge machine according to Embodiment 3 of the present invention will be described with reference to the drawings. FIG. 5 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 3 of the present invention. FIG. 6 is a timing chart showing the operation of the electric discharge machine power supply according to Embodiment 3 of the present invention.
[0051]
When the resistance component Rp does not exist or is sufficiently large, if it is necessary to short-circuit between the electrodes with a switch in order to operate at high repetition, the electrodes are short-circuited as in the first embodiment. A switch S1 may be provided. This is shown in FIG. 5 and FIG.
[0052]
Compared to the case of the first embodiment, the capacitance between the electrodes is sufficiently large as Cs + Cp. Therefore, the voltage value Vd when reaching a certain value is sufficiently smaller than that in FIG. 2, but still does not discharge. Charge accumulates in Cp and Cs. When the switch Su is turned on many times as it is and a charge amount Cq × Vs is flown each time, the voltage between the electrodes gradually rises and reaches a voltage that can be discharged sometime, and is stored in Cp. A large discharge with a large amount of charge will occur. For this reason, in this circuit, it is desirable that the charge accumulated in Cp and Cs is zeroed every time.
[0053]
Embodiment 4 FIG.
A power supply for an electric discharge machine according to Embodiment 4 of the present invention will be described with reference to the drawings. FIG. 7 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 4 of the present invention.
[0054]
Here, the switch Sl for short-circuiting is used, but when only the switch Sl is present in the short-circuit path, all the accumulated charge energy is consumed by the switch Sl. Load becomes a problem.
[0055]
In this case, as shown in FIG. 7, if a resistor Rl is inserted in series with the switch Sl, a part or most of the energy can be consumed by the resistor Rl, so that the load on the switch Sl that is an FET is small. Become. However, in order to make the repetition sufficiently fast, the resistor Rl must have a small value to some extent.
[0056]
The time constant when the charge is shorted to zero is
(ON resistance of Sl + Rl) × (Cs + Cp)
However, when an FET is assumed as the switch Sl, the ON resistance is generally small enough.
Rl × (Cs + Cp)
You may think. This value needs to be less than the ON time of the switch Sl.
[0057]
Embodiment 5 FIG.
A power supply for an electric discharge machine according to Embodiment 5 of the present invention will be described with reference to the drawings. FIG. 8 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 5 of the present invention.
[0058]
The switch Su or S1 is appropriate to use an FET because it has a high switching speed, needs to be operated at high speed and with high repetition, and has a sufficiently small resistance at the time of ON. When a voltage is applied between the drain and the source of the FET, a current flows from the drain to the source when the FET is turned on, and is interrupted when the FET is turned off. Here, the FET usually has a diode parasitic in the source-drain direction. That is, regardless of whether the switching element is ON or OFF, if the source is at a higher potential than the drain, a current flows from the source to the drain.
[0059]
In the case of the present invention (Embodiment 5), for example, current flows as shown in FIG. 2 and FIG. . In this case, the current should flow from the drain to the source, but a reverse voltage may be applied due to the ringing of the waveform, the source becomes a higher voltage than the drain, and the current may flow backward. In order to prevent this, a diode that prevents backflow is often inserted in series with the FET. FIG. 8 shows a circuit diagram in this case. In FIG. 8, diodes 3 and 4 in series are inserted in both of the switches Su and Sl, but both are not necessarily required. Adjustments should be made to achieve the desired waveform or desired performance.
[0060]
Embodiment 6 FIG.
A power supply for an electric discharge machine according to Embodiment 6 of the present invention will be described with reference to the drawings. FIG. 9 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 6 of the present invention.
[0061]
In the fifth embodiment, the diodes 3 and 4 opposite to the parasitic diode of the FET are inserted in order to prevent the reverse current of the FET. The inter-voltage remains unchanged. In order to positively rectify the waveform oscillating positively or negatively in the positive direction, a diode Ds may be inserted between the electrodes as shown in FIG. At this time, the diode Ds needs to be sufficiently fast.
[0062]
Embodiment 7 FIG.
A power supply for an electric discharge machine according to Embodiment 7 of the present invention will be described with reference to the drawings. FIG. 10 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 7 of the present invention.
[0063]
The capacitor Cq that temporarily stores the amount of charge must discharge the stored charge instantaneously at a high speed, and therefore its frequency response must be sufficiently high. Since the target pulse width is about several tens ns to μs, it is necessary to cope with a frequency of at least 10 kHz, more preferably 1 MHz. An example of such a high-speed capacitor is a film capacitor.
[0064]
When electric charges are discharged from the capacitor Cq at once, ringing may occur due to the inductance of the path, and the voltage across the capacitor Cq may temporarily become negative. In order to avoid this, there is a method of inserting a high-speed diode 5 in parallel with the capacitor Cq as shown in FIG.
[0065]
Embodiment 8 FIG.
A power supply for an electric discharge machine according to Embodiment 8 of the present invention will be described.
[0066]
Now, after the capacitor Cq is discharged and the voltage across the capacitor Cq once becomes zero, it takes some time for the capacitor Cq to be charged again with the voltage of Vs. For example, when Cq and Vs are connected by a resistor Rs, Cq × Rs is the time constant. This value is only a time constant, and it takes more than twice as long until charging is completed.
[0067]
Therefore, when the value of the resistor Rs is increased, it is impossible to perform a high repetition operation. Since the value of the capacitor Cq is often about 0.1 to 10 nF, if the value of the resistor Rs is, for example, 100 kΩ or more, the time constant cannot be sufficiently repeated as 1 ms. Therefore, the value of the resistance Rs needs to be 100 kΩ or less, preferably 10 kΩ or less so that repetition of kHz or more is possible.
[0068]
On the other hand, it is the lower limit value of the resistance Rs. In FIG. 37, in order for the current from the resistance Rs to disappear, the current value from the resistance Rs must be so small that the arc cannot be sustained. Ideally, this current can be estimated by (Vs−Va) / Rs where the arc voltage is Va, and the minimum current value that can be maintained by the arc is around 1 A, although it depends on the conditions. Therefore, the value of the resistance Rs needs to be at least 10Ω, preferably at least 100Ω, at the minimum. In this case, the arc cannot be sustained by supplying current from the resistor Rs, and the amount of discharge charge can be minimized.
[0069]
Embodiment 9 FIG.
A power supply for an electric discharge machine according to Embodiment 9 of the present invention will be described with reference to the drawings. FIG. 11 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 9 of the present invention. FIG. 12 is a timing chart showing the operation of the electric discharge machine power source according to Embodiment 9 of the present invention.
[0070]
According to the eighth embodiment, there is a certain limit on the value of the resistance Rs. Actually, since the subsequent current from the resistor Rs is desired to be zero, the resistor Rs is more than a certain value, and the time required for charging is desired to be as short as possible, that is, the discharge frequency is desired to be as high as possible. Is set to the smallest value. In other words, the lower limit of the value of the resistance Rs for cutting the arc determines the maximum operating frequency.
[0071]
An example of a method for increasing the operating frequency beyond this is shown in FIG. A switch Sr is inserted in series with the resistor Rs. Similarly, an element such as an FET is used for the switch Sr.
[0072]
The operation timing of the switch Sr is shown in FIG. When the switch Su is turned on and charge is flowing from the capacitor Cq, the switch Sr is turned off. Thereafter, when the switch Su is turned off, the switch Sr is turned on and charging via the resistor Rs starts.
[0073]
That is, by changing the resistance value of the charging path with time, when charging the capacitor Cq, the resistance value of the path is lowered to shorten the charging time, and when the capacitor Cq is discharged, the resistance value is sufficiently increased. The subsequent current from the resistor Rs is eliminated.
[0074]
In the case of this method, a resistor having a sufficiently small resistance value may be used as the resistor Rs. Since the time required for charging is shortened as much as the resistor Rs is small, a high repetition operation is possible. In an extreme case, the resistance Rs is not necessary, and only the ON resistance of the switch Sr may be used. However, there is some inductance in the charging path, and if the resistance is too small, waveform disturbance such as ringing may occur.
[0075]
  There is also a heat problem. The energy lost by the resistance by one charge is Cq ×Vs ² / 2 and does not depend on the value of the resistance Rs. Therefore, the amount of heat consumed is the same even when the resistance value of the resistor Rs decreases. On the other hand, if the resistance value becomes too small and is about the same as the ON resistance of the switch Sr, there arises a problem that heat generated in the switch increases due to the ON resistance of the switch Sr. Therefore, the value of the resistor Rs is desirably a large value within the range allowed by the repetition frequency, for example, 1 kΩ or less.
[0076]
In FIG. 12, each operation timing in the circuit configuration using the switches Su and Sl is expressed so that the ON periods do not overlap. However, there is no necessity, and if the switch Su is turned on before the switch Sl and the current can flow from the capacitor Cq within that time, there is no problem even if the ON periods of both pulses overlap thereafter. . Even if the switch Su is turned on for a sufficiently long time, the shape of the current flowing between the electrodes is roughly defined by the capacitor Cq and the inductance Ls between the electrodes. In this state, even if both the switch Su and the switch Sl are turned on, the power source Since there is a large resistance Rs between Vs, almost no current flows.
[0077]
If the switch Su and the switch Sl are designed so that the ON periods thereof overlap, the switch Su need not be switched at high speed, and the circuit design can be easily performed.
[0078]
Embodiment 10 FIG.
A power supply for an electric discharge machine according to Embodiment 10 of the present invention will be described with reference to the drawings. FIG. 13 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 10 of the present invention. FIG. 14 is a timing chart showing the operation of the electric discharge machine power supply according to Embodiment 10 of the present invention.
[0079]
FIG. 13 shows another example of a method for charging the capacitor Cq. In FIG. 13, an inductance Ls is intentionally inserted instead of the resistor Rs. In this case, when the switch Sr is turned ON, the potential difference between both ends of the capacitor Cq approaches Vs while oscillating by resonance between C and L.
[0080]
  As indicated by the dotted line in FIG. 14, when the switch Sr is turned OFF when the voltage reaches around Vs, the capacitor Cq is charged to Vs. At this time, Cq × that occurred in the case of resistance chargingVs ² / 2 loss energy is not generated. Therefore, efficient charging becomes possible.
[0081]
Embodiment 11 FIG.
A power supply for an electric discharge machine according to Embodiment 11 of the present invention will be described.
[0082]
Here, the value of the capacitor Cq is considered. That is, the value of the capacitor Cq is the amount of charge to be discharged. The magnitude of this charge amount determines the surface roughness of the finished surface. The object of the present invention is that the charge of (Cs + Cp) × Vs is inevitably included in the conventional method, but the charge is limited to Cq × Vs, and a smaller amount of charge is controlled and input. Is.
[0083]
Therefore, it is not necessary to use this circuit system unless the capacitor Cq is smaller than Cs + Cp. Of course, it is necessary to perform a machining with a high machining capability even if the surface roughness is poor, by transferring a larger amount of electric charge while sequentially moving from the rough machining to the finishing machining. At present, the value of the capacitor Cp is estimated to be about several tens of nF, but this greatly varies depending on the machine configuration and the like. Therefore, the value of the capacitor Cq may be considered to be approximately 1 μF or less. Even if the value of the capacitor Cq is set to 0FF, there is always a stray capacitance of the circuit. However, since the discharge cannot be sufficiently performed only by the stray capacitance of the circuit, a capacitor Cq for charge accumulation is inserted. There is a need.
[0084]
Embodiment 12 FIG.
A power supply for an electric discharge machine according to Embodiment 12 of the present invention will be described with reference to the drawings. FIG. 15 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 12 of the present invention.
[0085]
In FIG. 15, an inductance Lu is intentionally inserted between the capacitor Cq and the switch Su. This lowers the peak value of the pulse applied between the discharge electrodes, but widens the pulse width. That is, the peak value and the pulse width of the applied pulse can be adjusted by adjusting the inductance Lu.
[0086]
There is a delay time in the discharge, and the discharge does not occur immediately after the voltage is applied. If the width of the voltage pulse is too short, the discharge is difficult to occur. Therefore, even if the peak value is slightly lowered, there are cases where discharge is more likely to occur when the pulse width is increased. Further, since the peak value is lowered, the loss due to switching of the FET is greatly reduced.
[0087]
Embodiment 13 FIG.
A wire electric discharge machine including a power supply for an electric discharge machine according to the present invention will be described with reference to the drawings. FIG. 16 is a diagram showing a configuration of a wire electric discharge machine including a power supply for an electric discharge machine according to the present invention.
[0088]
In the twelfth embodiment, the method of adjusting the pulse width by intentionally inserting the inductance has been described. However, in general, there are not a few inductances Ls connecting the circuit and the electrodes, and as a result, there is a Vs between the electrodes. In many cases, only a voltage pulse having a considerably low value is applied. In this case, on the contrary, it is necessary to make the inductance of the path as small as possible.
[0089]
FIG. 16 is a diagram showing how the discharge electrodes and the power supply are connected when the power supply of the present invention is actually mounted in the case of a wire electric discharge machine. Here, the space between the discharge electrodes refers to the gap between the wire 1 and the workpiece 2. The workpiece 2 is generally fixed on the processing table 6 and power is supplied from the processing table 6 and the power supply terminal 7. Therefore, when there is another machining power supply 20 in addition to the power supply 10 of the present invention, a voltage is applied between the machining table 6 and the power supply terminal 7 as shown in FIG.
[0090]
Similarly, the power supply 10 of the present invention needs to apply a voltage to the machining table 6 and the power supply terminal 7 using some power supply feeder 8. Generally, the inductance from the feed feeder 8 and the feed point to the discharge gap is Ls.
[0091]
First, as to how to reduce the inductance of the power feeder 8, it is effective to use a coaxial cable for the power feeder 8, in addition to making the length of the feeder as short as possible.
[0092]
On the other hand, the coaxial cable has a feature that the cable has a large stray capacitance instead of a small inductance. On the contrary, this stray capacitance is not preferable because it lowers the voltage value applied between the electrodes. If the effect due to the stray capacitance of the cable is greater than the effect due to the reduced inductance, the use of the coaxial cable is disadvantageous. In this case, the inductance is larger than that of the coaxial cable, but it is effective to use a twisted cable having a small stray capacitance or a bundle of many twisted cables.
[0093]
Embodiment 14 FIG.
Another wire electric discharge machine including a power supply for an electric discharge machine according to the present invention will be described with reference to the drawings. 17 and 18 are diagrams showing the configuration of another wire electric discharge machine including the electric discharge machine power supply according to the present invention.
[0094]
In the fourteenth embodiment, how to reduce the inductance from the feeding point of the feeding feeder to the discharge gap will be described. For example, FIG. 17 shows an example in which the feeding point is as close to the work 2 as possible. In this case, since power is directly supplied to the work 2, it is necessary to attach an electrode when the work 2 is mounted, but the inductance is considerably reduced by that amount.
[0095]
Further, as shown in FIG. 18, if the power supply 10 itself is attached to the power supply terminal 7 and only the connection line is extended from there to the work 2, no feeder line is required, and the inductance associated with the connection can be greatly suppressed. .
[0096]
Embodiment 15 FIG.
A power supply for an electric discharge machine according to Embodiment 15 of the present invention will be described with reference to the drawings. FIG. 19 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 15 of the present invention.
[0097]
If it is difficult to sufficiently reduce the inductance Ls, conversely, a method of intentionally increasing Lp can be considered. When a voltage of approximately Vp = Lp / (Lp + Ls) × Vs is applied between the electrodes as described in the second embodiment, the voltage applied between the electrodes increases as Lp is increased. An example is shown in FIG. In addition to Lp, an inductance La is intentionally inserted.
[0098]
However, in this case, the inductance from this other processing power source to the electrode increases, and there is a risk that the processing performance of this processing power source will be reduced. For example, if this power supply is used for roughing, such as a power supply that processes with a large current, the circuit inductance limits how much current can flow between the electrodes, so the processing capability Directly affect. Therefore, a switch Sa that short-circuits the inductance La connected in series may be provided and switched at the stage of processing. Since the switch Sa needs to have a sufficiently small resistance value when turned on, a switch such as a conductor is more suitable than an element such as an FET.
[0099]
Embodiment 16 FIG.
A power supply for an electric discharge machine according to Embodiment 16 of the present invention will be described with reference to the drawings. FIG. 20 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 16 of the present invention.
[0100]
An object of the present invention is to generate a discharge with the smallest possible charge amount in order to improve surface roughness. Therefore, the amount of charge is limited by the capacitor Cq, but there is a limit in practice. First, in order to generate discharge, a certain level of voltage must be applied between the electrodes. When capacitor Cq is reduced, Vs can be increased, but Vs naturally has an upper limit due to the breakdown voltage of the circuit. There is a limit to reducing Ls due to the structure of an actual device.
[0101]
FIG. 20 describes a method for generating a discharge with a charge amount smaller than the charge amount determined by Cq × Vs.
[0102]
First, in the case of this circuit system and when another processing power supply circuit is connected to the outside, the voltage waveform is first applied to a sharp pulse with a short pulse width applied between the electrodes and once to Cp. Therefore, two pulses of the second pulse reflected and returned between the electrodes are often observed. This indicates that a part of the energy of the capacitor Cq has once returned to Cp. A voltage waveform schematic diagram at this time is shown in FIG.
[0103]
Here, as shown in FIG. 20, a path is provided to short-circuit Cp with a resistor Rp. The value of the resistor Rp is very small, or the resistance value may be zero, that is, it may be directly short-circuited. It is necessary to provide a switch Sp for disconnecting the short-circuit path for the operation of other circuits.
[0104]
In an actual apparatus configuration, the base of the feeder line connecting the other electrodes and the discharge electrode is short-circuited. Alternatively, the switch Sp and the resistor Rp may be configured inside another circuit (inside the power supply 20 in FIG. 20). The switch Sp may be electrically opened and closed using a bidirectional switch or the like, or may be mechanically opened and closed using a relay. If a bidirectional switch or the like (or a unidirectional switch depending on the type of the power supply 20) is used, the switch Sp and the resistor Rp can be easily formed inside the power supply 20.
[0105]
FIG. 21B shows a voltage waveform schematic diagram when the short-circuit loop is provided in parallel with the electrodes as described above. The voltage waveform is only the first steep pulse, and the second pulse is not observed. This is because the end of the feeder line is short-circuited, so that the energy that goes up to Cp and reflects is lost. Therefore, if a discharge occurs in the first pulse, a part of the charge amount flows through the short-circuit path, so that the amount of charge flowing is smaller than Cq, and therefore the charge defined by Cq × Vs. It is possible to generate a discharge with a charge amount smaller than that.
[0106]
In FIG. 20, a resistor Rp and a switch Sp are provided between the feeder line and another processing power supply circuit (floating capacitance component Cp), but these are provided between the discharge electrodes and the feeder line. May be provided. The closer the installation location is between the poles, the more the influence of stray capacitance can be eliminated. For example, when the feeder line is composed of a coaxial cable as described above, this also works as a stray capacitance. However, in order to better eliminate this effect, the installation location of the resistor Rp and the switch Sp is between the discharge electrodes. It is better to install between the feeder line. In this case, a mechanical switch using a relay or the like is simple and desirable.
[0107]
In the present embodiment, the wire electric discharge machine has been mainly described, but the present invention can also be applied to other configurations including a sculpted electric discharge machine. That is, even when the stray capacitance Cp and the pole are not connected by a feeder line, the influence of the stray capacitance Cp can be reduced by forming the resistor Rp and the switch Sp near the electrodes.
[0108]
Embodiment 17. FIG.
In the above sixteenth embodiment, the method of reducing the influence of the stray capacitance by short-circuiting the stray capacitance Cp using the resistor Rp and the switch Sp has been described. At this time, the smaller the resistor Rp is, the more the electric charge entering between the electrodes from the stray capacitance Cp can be suppressed. However, when the resistor Rp is extremely small, it is difficult to apply a voltage between the electrodes and there is a possibility that the discharge will not occur. Therefore, more ideally, the switch Sp is in the OFF state and a sufficient voltage is applied between the electrodes until immediately before the discharge, and the switch Sp is in the ON state at the moment of discharge, and the charge of the stray capacitance Cp is caused by the termination resistor. It is desirable to be consumed. Furthermore, in other words, Embodiment 16 can be rephrased as stray capacitance Cp being grounded via resistor Rp. However, if a reverse potential is applied via resistor Rp, it can be more reliably stored in stray capacitance Cp. It can be said that the generated charge can be eliminated. In other words, if the electric charge stored in the stray capacitance Cp is pulled out at the expected timing, an effect more than grounding (short circuit) can be expected.
[0109]
Therefore, in the seventeenth embodiment, a processing power source and a processing method for obtaining better surface roughness by positively eliminating the influence of the stray capacitance Cp as compared with the above-described sixteenth embodiment will be described.
[0110]
A power supply for an electric discharge machine according to Embodiment 17 of the present invention will be described with reference to the drawings. FIG. 22 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 17 of the present invention. FIG. 23 is a timing chart showing the operation of the electric discharge machine power supply according to the seventeenth embodiment of the present invention.
[0111]
As shown in FIG. 22, the power supply 10 including the resistor Rs, the power supply Vs, the capacitor Cq, the switch Su, and the switch Sl is the same as that in the above-described sixteenth embodiment. However, the diode D1 is inserted so that a current does not flow backward from the reverse power supply block 30 described later to the switch Sl. A reverse power supply block 30 including a relay Re, a switch St, a resistor Rp, and a power supply Vt is connected in parallel with the electrodes between the power feeder 9 and the stray capacitance Cp. Depending on the polarity of the applied voltage, the switch St may be used alone, but a relay is also used in combination with the roughing and finishing to reliably eliminate the influence of each circuit. That is, the relay Re is turned off during rough machining, and the relay Re is turned on during finishing machining. Although the switch St is illustrated as using a FET, other circuit elements may be used.
[0112]
As described in the sixteenth embodiment, the connection place may be between the electrodes and between the feeder feeders Lp. When there is no installation place of the reverse power supply block 30, a twist line or the like is drawn from between the electrodes (near) and connected. May be.
[0113]
When the switch Su is turned on, the electric charge stored in the capacitor Cq starts to move to the stray capacitance Cp between the electrodes. At the same time, the voltage between the electrodes starts to rise, and the switch St is turned on when the peak value is reached. At this time, the power source Vs has a positive polarity and the power source Vt has a negative polarity when viewed from the workpiece 2. The charges stored in the stray capacitance Cp and the interelectrode capacitance Cs tend to flow to the power supply Vt via the switch St and the resistor Rp. In the voltage waveform between the electrodes shown in FIG. 23, the dotted line is the waveform when grounded via the resistor Rp as in the sixteenth embodiment, and the solid line is the reverse voltage applied via the resistor Rp as in the seventeenth embodiment. It is a waveform of time. By applying a reverse voltage and extracting the charge from the gap, the voltage waveform becomes a shorter pulse than in the sixteenth embodiment. That is, the inflow of charges from the stray capacitance between the electrodes can be suppressed.
[0114]
Now, if the reverse power supply block 30 is provided with the power supply Vt, the burden on the switch St may be increased. This is because if the switching is not performed at a certain high speed, the inter-electrode voltage may become a high voltage on the negative side.
[0115]
Therefore, similarly to the power supply 10 using the capacitor Cq, the configuration using the capacitor Cr in the reverse power supply block (reverse power supply block 40) is based on FIG. 24 and the operation at that time is shown in the timing chart of FIG. Explained originally.
[0116]
As shown in FIG. 24, the reverse power supply block 40 includes a power supply Vt, a charge limiting capacitor Cr, a charging resistor Rr and a switch St, backflow prevention diodes D3 and D4, and a resistor Rp. The power supply 10 is also added with backflow prevention diodes D1 and D2. It is assumed that charges are stored in advance in the capacitors Cq and Cr. At this time, when the switch Su is turned on, the electric charge starts to move between the capacitor Cq and the electrodes. As shown in FIG. 25, if the switch St is turned on at a slightly delayed timing, a reverse voltage is applied between the electrodes, so that the charge that is being accumulated between the electrodes and in the stray capacitance Cp is applied to the capacitor Cr. It works to flow in. The difference from FIG. 23 is the ON time of the switch St. The amount of charge to be drawn (reverse voltage applied between the electrodes) depends on the capacitor Cr. If the charging resistance Rr is sufficiently large, the ON time of the switch St is no longer relevant. That is, the switch St eliminates the need for high-speed switching. Thereafter, if the switch Sl is turned on, even if a vibration waveform remains between the electrodes, it can be quickly removed. Thus, if the reverse power supply block 40 is configured in the opposite direction to the power supply 10, the loss of the switch St can be reduced, and the circuit configuration can be simplified.
[0117]
Embodiment 18 FIG.
An electric discharge machine power source according to Embodiment 18 of the present invention will be described with reference to the drawings. FIG. 26 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 18 of the present invention. 27 and 28 are timing charts showing the operation of the electric discharge machine power source according to Embodiment 18 of the present invention.
[0118]
In order to increase the processing capability, it is necessary to increase the discharge frequency. In addition, if the time between discharges is short, discharge tends to occur. Therefore, it is possible to increase the probability of discharge by increasing the frequency and further improve the machining capability. Therefore, how to increase the pulse frequency in this circuit is an important technique.
[0119]
In this circuit, there are mainly two factors that hinder the increase in frequency. One is the charging time of the capacitor Cq by the resistor Rs. This is because the resistance Rs has to be increased to some extent in order to stop the supply of the arc current from the resistance Rs. As described in the eighth embodiment, one solution is to reduce the value of the resistor Rs itself by arranging a switch in series with the resistor Rs.
[0120]
The other is the heat generation of the switches Su and Sl, which are FETs that perform discharge and short-circuit between the electrodes. In particular, the switch Su, which is an FET for discharging, has a very steep current, and therefore has a large resistance loss during switching and ON, and generates heat. In order to avoid this, it may be possible to reduce the load on each FET by arranging a number of FETs in parallel.
[0121]
FIG. 26 shows a circuit configuration diagram in the case where a switch is arranged on the resistor Rs using these methods and four FETs are arranged in parallel on the upper and lower sides.
[0122]
Here, the para numbers of the upper and lower FETs that are the switches Su and Sl are not necessarily the same. In some cases, there is a problem of the thermal load of the switch Sr, which is an FET. In this case, a plurality of switches Sr may be arranged in parallel. For example, in FIG. 26, there are two parameters.
[0123]
Next, FIG. 27 shows an example of the operation. When the current peak is high, it is often performed to simultaneously turn on a plurality of FETs, thereby reducing the overall ON resistance and reducing losses in the FETs. FIG. 27 shows an example using such a system, and all four upper FETs are simultaneously turned ON at the pulse generation timing. The four lower FETs are also turned on at the same time when the electrode is short-circuited. The same applies to the charging FET. This method is effective when the current value is high or when it is desired to sufficiently reduce the ON resistance of the path.
[0124]
On the other hand, FIG. 28 shows another example of this operation method. Here, one FET is always used for discharging, such that one of the FETs is turned ON at the generation timing of the pulse, and another FET is turned ON when the next pulse is generated. In the meantime, since no current flows through the other FETs, the substantial frequency applied to one FET can be reduced to a quarter.
[0125]
Since the lower FET performs the same operation, the load on the lower FET is also reduced to a quarter. Since the FET for resistance charging has two parameters, the load is halved. In this way, there is a method of increasing the frequency by shifting the ON timing of each FET. In this method, since all current flows through one FET, it cannot be used if the current value is large and the FET rating is exceeded. However, the current purpose is to generate a very small discharge, the current value is not too high, and if the single ON resistance of the FET can be regarded as sufficiently small, the method as shown in FIG. Is effective.
[0126]
Further, when a plurality of FETs are simultaneously turned on as shown in FIG. 27, it is generally difficult to operate the plurality of FETs at the same timing. If the ON timing of each FET is slightly shifted due to jitter of each gate voltage or the like, the entire turn-on time becomes longer, which is disadvantageous in terms of influence on the elements as well as circuit characteristics. Therefore, also in this sense, the operation shown in FIG. 28 is more advantageous than the operation shown in FIG.
[0127]
Of course, if the number of FETs operating simultaneously is small, simultaneous driving becomes easier, so it is conceivable that the intermediate method of FIGS. 27 and 28, for example, turning on two FETs at different timings. In other words, the driving method needs to be optimized according to the circuit configuration, required performance, and actual use conditions.
[0128]
Embodiment 19. FIG.
An electric discharge machine power supply according to Embodiment 19 of the present invention will be described with reference to the drawings. FIG. 29 shows a circuit configuration of a power supply for an electric discharge machine according to Embodiment 19 of the present invention. FIG. 30 is a timing chart showing the operation of the electric discharge machine power supply according to the nineteenth embodiment of the present invention.
[0129]
In FIG. 26, only the FETs are arranged in parallel, but a plurality of capacitors Cq and resistors Rs may be arranged in parallel. This is shown in FIG.
[0130]
In FIG. 29, the combination of the switch Su, which is the FET on the discharge side, and the capacitor Cq and the resistor Rs is in parallel, and the short-circuit switch Sl is also in parallel.
[0131]
The feature of this method is that the charging time of the capacitor Cq can be made substantially four times longer by charging the four capacitors Cq at different times. Since a sufficiently large value can be selected as the value of the resistor Rs, the switch Sr becomes unnecessary. For this reason, operational difficulties such as the cost of the switch Sr and the malfunction of the switch Sr can be solved.
[0132]
Next, FIG. 30 shows an example of the operation. As with the operation of FIG. 28, one FET is turned on at each discharge timing. At this time, a corresponding one of the four capacitors Cq is discharged. The voltage change of each capacitor Cq in the process in which the four FETs generate pulses while shifting the timing is thus as shown in FIG. Since the potential difference of each capacitor Cq is different at each time, a diode is required between the capacitor Cq and the resistor Rs to prevent backflow.
[0133]
In FIG. 29, four switches S1, which are FETs on the short-circuit side, are also arranged, but there may be any number as well, and should be determined in consideration of the thermal load of each FET.
[0134]
Embodiment 20. FIG.
A power supply for an electric discharge machine according to Embodiment 20 of the present invention will be described with reference to the drawings. FIG. 31 is a timing chart showing the operation of the electric discharge machine power supply according to the twentieth embodiment of the present invention. The configuration of the power supply for the electric discharge machine according to the twentieth embodiment is the same as that of the nineteenth embodiment.
[0135]
Now, in the power supply for the electric discharge machine shown in FIG. 29, in FIG. 30, one capacitor is discharged by one discharge.
[0136]
Now, it is assumed that the values of the four capacitors Cq or the resistance Rs are the same. At this time, if charging of the capacitor Cq is in time (it can be considered that the switch Sr is turned on if it is not in time), it is possible to simultaneously turn on two or a plurality of switches to discharge from the plurality of capacitors.
[0137]
For example, consider operation as shown in FIG. From FIG. 30, the charging time of the capacitor Cq is halved, but it is assumed that the resistor Rs is selected as such. Two switches are turned ON by one discharge, and electric charges from the two capacitors Cq flow. Therefore, in such a driving method, it is possible to generate a discharge with twice the amount of charge as compared with the driving as shown in FIG.
[0138]
As described in the prior art, electric discharge machining often repeats machining several times while increasing the surface roughness.In the beginning, a large current is applied to process at high speed, and the charge amount is gradually reduced to reduce the surface. Increase the roughness. When the operation as shown in FIGS. 30 and 31 is performed, the charge amount of the discharge can be controlled in two stages, and the input charge amount can be switched according to the finishing stage, which is very meaningful in practical use. is there.
[0139]
Since the description has been made on the assumption that the same pulse is output at a high frequency, the value of each capacitor Cq and the value of the resistor Rs in FIG. 29 are the same. In this case, it was shown that the charge amount of discharge can be changed by discharging two or more of them simultaneously as described above. Alternatively, the magnitude of the discharge can be changed by changing the value of the capacitor Cq.
[0140]
Embodiment 21. FIG.
A power supply for an electric discharge machine according to Embodiment 21 of the present invention will be described.
[0141]
When considering changing the strength of the discharge by changing the value of the capacitor Cq, when different Cq and a plurality of switches are simultaneously turned on and combined, the following method is used to reduce the number of capacitors. Can be output.
[0142]
For example, in FIG. 29, it is assumed that the ratio of charge amounts is Cq1: Cq2: Cq3: Cq4 = 1: 2: 4: 8. In this case, a combination of On and OFF of the switches Su1 to Su4 makes it possible to make a combination of 16 levels of charges including 2 to the fourth power, that is, 0.
[0143]
In other words, 15 levels of output can be obtained by using only four capacitors. Thus, the value of the charge amount can be freely changed with a relatively simple circuit configuration.
[0144]
Embodiment 22. FIG.
A power supply for an electric discharge machine according to Embodiment 22 of the present invention will be described with reference to the drawings. FIG. 32 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 22 of the present invention.
[0145]
FIG. 32 is a combination of FIG. 26 and FIG. Each capacitor Cq does not have to be one FET, and if the thermal load of the FET is increased, it may be arranged in parallel as shown in FIG. In other words, the number of capacitors Cq, the number of switches Su, and the number of switches S1 should be determined for different reasons. That is, the number of capacitors Cq probably balances the charging time or the above embodiment. In the case of 20, 20, etc., it should be determined according to the pattern of the charge amount to be output.
[0146]
The number of switches Su and S1 FETs should be determined by the thermal load, and this should be optimized by the circuit configuration, heat dissipation method, actual waveform, and the like. In FIG. 32, the capacitor Cq has 3 parameters, the switch Su has 2 parameters, and 6 switches in total, and the switch Sl has 2 parameters.
[0147]
Embodiment 23. FIG.
A power supply for an electric discharge machine according to Embodiment 23 of the present invention will be described.
[0148]
Until now, discussions have been made on outputting pulses or increasing the frequency, but it is also possible to output pulses in bursts (intermittently) instead of simply increasing the frequency of the pulses.
[0149]
That is, this is a method in which several pulses are continuously generated as a group pulse, and the group pulse is applied again after a pause. Of course, when there is no pause at all, the number of pulses is the largest and the machining capacity is maximized, but electric discharge machining also has problems such as surface accuracy and straightness, and the pulse interval is closely related to the ease of discharge Therefore, burst output has various advantages.
[0150]
First, since the ease of discharge is higher as the pulse interval is shorter, it is better to make the pulse interval as short as possible. The pulse interval is often determined by circuit limit conditions such as the charging time of the capacitor Cq.
[0151]
On the other hand, in order to increase the surface accuracy, the straightness of the surface becomes a big problem. Straightness is thought to be caused by the balance between the force acting between the wire and the workpiece, the discharge reaction force, and the electrostatic force. Since the electrostatic force is determined by the pulse application time, the straightness may be adjusted by adjusting the pulse application time. Therefore, it is understood that it is necessary to adjust the number of pulses within a unit time so as to improve straightness, rather than increasing the number of pulses unnecessarily.
[0152]
As described above, generating pulses in bursts is a very useful technique in electrical discharge machining, especially in the finishing process, but the circuit of the present invention basically allows the pulse generation timing to be freely set by switching FETs. Therefore, it can be said that it is a circuit system suitable for such control.
[0153]
Embodiment 24. FIG.
A power supply for an electric discharge machine according to Embodiment 24 of the present invention will be described with reference to the drawings. FIG. 33 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 24 of the present invention. FIG. 34 is a timing chart showing the operation of the electric discharge machine power supply according to Embodiment 24 of the present invention.
[0154]
In the above embodiments, all the circuits have been shown that apply a positive pulse to the wire side. The main purpose of this circuit is finishing, and applying a positive polarity pulse to the wire side tends to improve surface roughness. Therefore, applying a positive pulse to the wire side is more practical. This is because the nature is high.
[0155]
However, in this case, there is a problem of the electrolytic corrosion effect. That is, there is a problem in that when a voltage is applied between the electrodes in a DC manner, electrolysis occurs and the workpiece and the basic workpiece are corroded. In order to avoid this, it is only necessary to output positive and negative bipolar pulses instead of unipolar pulses so that there is no DC voltage component as a whole.
[0156]
FIG. 33 shows a circuit configuration that can output both plus and minus pulses to the circuit system of FIG. 5 according to the present invention. In FIG. 33, an H-bridge circuit composed of four FETs is basically used.
[0157]
This operation will be described with reference to FIG. As shown in FIG. 34, it is possible to freely apply pulses in both the plus direction and the minus direction by turning on and off the switches Su1, Su2, Sl1, and Sl2.
[0158]
Embodiment 25. FIG.
In the above-described twenty-fourth embodiment, the method of applying bipolar pulses between the electrodes using the H-bridge circuit configuration has been described. In the twenty-fifth embodiment, a method of applying a bipolar pulse using a full bridge circuit configuration will be described.
[0159]
A power supply for an electric discharge machine according to Embodiment 25 of the present invention will be described with reference to FIG. The approximate circuit configuration is the same as that described in the seventeenth embodiment, and a capacitor Cq for generating a pulse with a positive polarity for the workpiece and a switch Su and a pulse with a negative polarity for the workpiece are generated. Capacitor Cr, switch St, capacitor Cq, resistors Rs and Rr for charging capacitor Cr, and diodes D1, D2, D3 and D4 for preventing reverse current.
[0160]
One of the differences from the above-described embodiment 17 is a wiring method between the electrodes. The seventeenth embodiment is based on the concept that the charge entering the stray capacitance Cp is consumed via the resistor Rp immediately before the stray capacitance Cp. That is, the wiring with the power source 10 for supplying electric charge between the electrodes and the wiring with the power source 40 for extracting electric charge from the stray capacitance Cp or between the electrodes are made different. However, since this embodiment 25 has a strong meaning of controlling the voltage waveform applied between the electrodes, the supply of charges between the electrodes and the extraction of charges from the electrodes are performed by the same wiring. I am doing so. For the same reason, the resistor Rp is not used.
[0161]
FIG. 36 is a timing chart showing the operation of the electric discharge machine power supply according to the twenty-fifth embodiment of the present invention. As in the above-described twenty-fourth embodiment, the positive electrode side and the negative-electrode side may be operated independently on only one side, respectively, to create an AC waveform. A method of extracting the voltage and shortening the voltage waveform will be described.
[0162]
As shown in FIG. 36, when the switch Su is turned on, the charge is transferred from the capacitor Cq through the diode D2 and the switch Su between the electrodes. Along with this, the interelectrode voltage rises. When the switch St is turned on with a slight delay, the charge between the electrodes is extracted to the capacitor Cr through the diode D3 and the switch St. Along with this, the voltage between the electrodes also decreases. The switches Sl and Sv are used to return to the initial state (0 V) when a voltage remains between the electrodes or when the waveform vibrates. These switches are not always necessary when capacity is transferred ideally. A resistor may be inserted in place of the switch S1 and the switch Sv. As a result, even if a voltage remains between the electrodes, the time constant of the combined capacitance of the discharge electrode capacitance Cs and the stray capacitance Cp and the inserted resistance can be easily set to 0V.
[0163]
Usually, the electrical discharge machine is basically designed so that the workpiece 2 becomes GND for safety. If the H-bridge configuration as described in the above-mentioned twenty-fourth embodiment is adopted, the power supply becomes floating, so that it is not necessarily a desirable configuration considering the influence on other circuits. However, as in the twenty-fifth embodiment, if the full bridge configuration is used, the power sources Vs and Vt can be grounded, and the circuit can be designed based on the GND standard. In addition, as shown in the above-described eighteenth to twenty-second embodiments, a plurality of switching elements may be arranged in parallel and combined.
[0164]
【The invention's effect】
  A power supply for an electric discharge machine according to the present invention includes a first charge storage element, a first DC power supply for charging the first charge storage element,By on / off operationA first switching element for causing a charge accumulated in the first charge storage element to flow through the electrode gap to generate a pulsed discharge, a second DC power supply, and the second DC power supply are connected in series. ,By turning on during the period when the first switching element is onSince the second switching element that extracts the electrode gap or the electric charge existing in parallel with the electrode gap to the second DC power supply is provided, a very small discharge can be stably generated even in a non-insulated state. As a result, there is an effect that a fine surface roughness can be obtained.
[0175]
  AlsoThisThe electric power source for the electric discharge machine according to the present invention further includes the second charge storage element for storing electric charges in parallel with the second DC power supply, so that it is very small even in a non-insulated state with a simple circuit configuration. It is possible to generate a stable discharge stably and to obtain a fine surface roughness.
[Brief description of the drawings]
FIG. 1 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 1 of the present invention.
FIG. 2 is a timing chart showing the operation of the electric discharge machine power supply according to Embodiment 1 of the present invention.
FIG. 3 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 2 of the present invention.
FIG. 4 is a timing chart showing an operation of a power supply for an electric discharge machine according to Embodiment 2 of the present invention.
FIG. 5 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 3 of the present invention.
FIG. 6 is a timing chart showing an operation of an electric discharge machine power supply according to Embodiment 3 of the present invention.
FIG. 7 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 4 of the present invention.
FIG. 8 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 5 of the present invention.
FIG. 9 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 6 of the present invention.
FIG. 10 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 7 of the present invention.
FIG. 11 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 9 of the present invention.
FIG. 12 is a timing chart showing an operation of a power supply for an electric discharge machine according to Embodiment 9 of the present invention.
FIG. 13 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 10 of the present invention.
FIG. 14 is a timing chart showing an operation of a power supply for an electric discharge machine according to Embodiment 10 of the present invention.
FIG. 15 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 12 of the present invention.
FIG. 16 is a diagram showing a configuration of a wire electric discharge machine including a power supply for an electric discharge machine according to Embodiment 13 of the present invention.
FIG. 17 is a diagram showing a configuration of another wire electric discharge machine including a power supply for an electric discharge machine according to Embodiment 14 of the present invention.
FIG. 18 is a diagram showing a configuration of another wire electric discharge machine including a power supply for an electric discharge machine according to Embodiment 14 of the present invention.
FIG. 19 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 15 of the present invention.
FIG. 20 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 16 of the present invention.
FIG. 21 is a schematic diagram for explaining voltage waveforms applied between discharge electrodes of a power supply for an electric discharge machine according to Embodiment 16 of the present invention;
FIG. 22 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 17 of the present invention.
FIG. 23 is a timing chart showing an operation of a power supply for an electric discharge machine according to Embodiment 17 of the present invention.
FIG. 24 is a diagram showing a circuit configuration of another electric discharge machine power supply according to Embodiment 17 of the present invention;
FIG. 25 is a timing chart showing operation of another electric discharge machine power supply according to Embodiment 17 of the present invention;
FIG. 26 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to an eighteenth embodiment of the present invention.
FIG. 27 is a timing chart showing an operation of a power supply for an electric discharge machine according to Embodiment 18 of the present invention.
FIG. 28 is a timing chart showing another operation of the power supply for the electric discharge machine according to Embodiment 18 of the present invention.
FIG. 29 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 19 of the present invention.
FIG. 30 is a timing chart showing an operation of a power supply for an electric discharge machine according to Embodiment 19 of the present invention.
FIG. 31 is a timing chart showing an operation of a power supply for an electric discharge machine according to Embodiment 20 of the present invention.
FIG. 32 shows a circuit configuration of a power supply for an electric discharge machine according to Embodiment 22 of the present invention.
FIG. 33 is a diagram showing a circuit configuration of a power supply for an electric discharge machine according to Embodiment 24 of the present invention.
FIG. 34 is a timing chart showing an operation of a power supply for an electric discharge machine according to Embodiment 24 of the present invention.
FIG. 35 shows a circuit configuration of a power supply for an electric discharge machine according to Embodiment 25 of the present invention.
FIG. 36 is a timing chart showing an operation of a power supply for an electric discharge machine according to Embodiment 25 of the present invention.
FIG. 37 is a diagram showing a circuit configuration of a conventional power supply for an electric discharge machine.
FIG. 38 is a timing chart showing the operation of a conventional power supply for an electric discharge machine.
FIG. 39 is a diagram showing a circuit configuration of another conventional power source for an electric discharge machine.
[Explanation of symbols]
1 electrode (wire), 2 electrode (work), 3 diode, 4 diode, 5 diode, 6 processing table, 7 feed terminal, 8 feed feeder, 9 feed feeder, 10 power source, 20 power source, Cs capacitance, Cq capacitor , Ls inductance, Rs resistance, Rw water resistance, Sl switch, Su switch, Vs power supply, Sv switch, St switch, Vt power supply.

Claims (2)

A first charge storage element for storing charge;
A first DC power supply for charging the first charge storage element;
A first switching element for generating a pulsed discharge by causing the charge accumulated in the first charge accumulation element to flow through the electrode gap by an on / off operation ;
A second DC power source;
The second DC power supply is connected in series with the second DC power supply, and is turned on while the first switching element is turned on, whereby the electrode gap or the electric charge existing in parallel with the electrode gap is extracted to the second DC power supply. A power supply for an electric discharge machine comprising a second switching element.   The power supply for an electric discharge machine according to claim 1, further comprising a second charge storage element for storing charges in parallel with the second DC power supply.

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