JPH0619972B2 - Electronic beam processing machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electron beam processing machine for generating an electron beam from an electron gun and welding a workpiece by the electron beam, and particularly to an electron beam processing machine. The present invention relates to an electron beam processing machine equipped with an electron beam control device capable of interrupting a discharge phenomenon at high speed.

[Conventional technology]

Known examples of electron beam processing machines include Japanese Patent Publication No.
There is one described in Japanese Patent No. 27278. As shown in FIG. 4, this electron beam processing machine includes a power supply device 1, an electron gun 2, an electron discharge device 3, a sensing circuit 4, a timing circuit 5, a ground 6, and a negative power supply device 1. It is composed of a lead 7 on the voltage application side and a lead 8 on the positive ground side. In this electron beam processing machine, when discharge occurs in the electron gun 2, the sensing circuit 4 (transistor is used) connected to the cathode side of the electron discharge device 3 (quadrupole vacuum tube is used) is caused by discharge. Detects overcurrent. For example, 0.6
When the current exceeds the limiting current of A, the output of the sensing circuit 4 is input to the timing circuit 5 for adjusting the cutoff time, and the output from the timing circuit 5 causes the electronic discharge device 3 to be inoperative (that is, the vacuum tube By cutting off between the anode and the cathode), the power supply device 1 is protected from overload.

[Problems to be solved by the invention]

 This conventional example has five problems.

The first problem is that in implementing this conventional example, the power supply device 1 must have a withstand voltage equal to or higher than the voltage generated by itself.

That is, in FIG. 4, in the case of the power supply device 1 that generates, for example, 60,000 V, when the electronic discharge device 3 is in an operating state (conduction between the anode and the cathode of the vacuum tube), the positive lead 8 Is 0 V as a potential at the ground level (for simplicity, the voltage drop in the vacuum tube is not considered.
This point will be described later), and the potential of the negative lead 7 is
It is −60,000 V. However, when the electronic discharge device 3 becomes inoperative, all the voltage generated by the power supply device 1 is applied to the electronic discharge device 3, and the potential of the negative lead 7 becomes + 60,000V. This is due to the counter electromotive force of inductors such as a transformer provided in the power supply device 1. As a result, the power supply device 1 will be damaged unless it has a withstand voltage of 60,000 V or more.

In order to solve this point, the electronic discharge device 3, the sensing circuit 4, and the timing circuit 5 may be connected between the negative lead 7 and the electron gun 2. In this case, these devices and circuits are Since it is always at −60,000 V, a large amount of insulation processing must be performed on the filament tube power supply, the grid power supply, the power supply for the sensing circuit 4 and the timing circuit 5, and the signal transmission path. Further, in general, the transmission of the insulation-processed signal is usually delayed, and the high-speed response shown in the above conventional example cannot be obtained. The processing method for solving this problem is not clearly shown in the above-mentioned conventional example, and can necessarily be implemented only in the circuit shown in FIG. Therefore, when the above-mentioned conventional example is carried out, a huge power supply device 1 is required, which is impractical from an economical point of view, and the device must be upsized.

The second problem is that in the above conventional example, a so-called solid state using a semiconductor as the power discharge device 3 cannot be used, and is effective only by using a vacuum tube. At present, there is no semiconductor element having a withstand voltage of 60,000 V or more per piece, so that it is necessary to connect several semiconductor elements in series to guarantee the withstand voltage. To this end, it is necessary to clarify the balancing of the shared voltage of the semiconductor element, the method of supplying power to the semiconductor element and the method of supplying power to the bias circuit. Therefore, in the above-mentioned conventional example, it is impossible to implement using a semiconductor element.

The third problem is the voltage drop due to the vacuum tube. If the bias voltage is applied to, for example, 20,000 V when the vacuum tube is in the conductive state, the voltage drop between the anode and the cathode between the vacuum is 20,000 V or more, and the power supply device 1 applies the electron gun 2 to the electron gun 2. It is necessary to supply a voltage that is the required acceleration voltage plus the voltage drop of the vacuum tube, which is very inefficient.

A fourth problem is that overload sensing is current only. Normally, when a discharge occurs in the electron gun 2, a rapid increase in the current (beam current) flowing in the high voltage circuit and a decrease in the acceleration voltage are observed. It is not clear which of these changes faster depending on the inside and the state of the electron gun (although they are macro-simultaneously), so if the change in accelerating voltage is not sensed, high-speed protection from overload is not possible. I can't get it.
In this respect, it can be said that the current sensing alone is insufficient.

The fifth problem is the operation and non-operation time in the electronic discharge device 3 (that is, the recovery time and the cutoff time of the high voltage circuit).
Is to be fixed. When the above conventional example is applied to various electron beam processing machines, it is cut off and restored by the characteristics of the electron gun, that is, the range of acceleration voltage and beam current, the arrangement of the electronic optical system, the electrostatic capacity of the electron gun itself, and the like. The time should be set arbitrarily.

In the above-mentioned conventional example, all the components constituting the timing circuit 5 are fixed, which is inconvenient in the above problems.

As described in Japanese Patent Application Laid-Open No. 56-116000, if a semiconductor power control element connected in series is used for the breaker and the signal from the beam current detection circuit is converted into an optical signal, the breaker is cut off. Only the device needs to be insulated, and high speed operation can be maintained. Furthermore, the on-resistance during operation can be made smaller than when a vacuum tube is used.

However, if the circuit breaker is simply configured by the semiconductor power control element group, the surge generated when the power control element group is turned on and off may adversely affect other devices.

An object of the present invention is to provide an electron beam processing machine capable of rapidly interrupting discharge (overload) generated in an electron gun and suppressing generation of surge at the time of interruption.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention relates to an electron beam processing machine including an electron gun for projecting an electron beam onto a workpiece and a power supply device for supplying DC power to the electron gun, which are connected in series. A plurality of semiconductor power control elements, which are inserted in series between the negative output end of the power supply device and the electron gun, and the output voltage of the negative output end of the power supply device. An acceleration voltage detection circuit for detecting, a beam current detection circuit inserted in series between the positive side output end of the power supply device and the ground, a detection output signal of the acceleration voltage detection circuit and a first set value. By comparing the detection output signal of the beam current detection circuit with the first comparison circuit that outputs the overload detection signal when the detection output signal exceeds the first set value, the detection output signal is 2 Overload when the set value is exceeded When the second comparison circuit that outputs a known signal and the cutoff signal is output in response to the overload detection signal from the first comparison circuit or the second comparison circuit and no overload detection signal is generated from any of the comparison circuits A control signal output circuit that outputs a conduction signal; and an optical signal transmission circuit that converts an output signal of the control signal output circuit into an optical signal and transmits the optical signal to a blocking device. Photoelectric conversion means for converting an optical signal of the semiconductor device into an electric signal, a switching control means for sequentially connecting or disconnecting each semiconductor power control element in response to an output signal of the photoelectric conversion means, and a surge generated by each semiconductor power control element. And a surge absorbing means for absorbing the surge absorbing means.

[Action]

According to the present invention having the above-described configuration, the output signal of the control signal output circuit is converted into an optical signal and transmitted to the interruption device, so that the signal transmission speed can be increased and the interruption device can operate at high speed when overloaded. Can be shut off. Further, since each semiconductor power control element of the circuit breaker is sequentially cut off, the surge voltage at the time of cutoff can be made lower than when all the power control elements are cut off at the same time. Moreover, since each power control element is provided with the surge absorbing means, it is possible to suppress application of a high voltage due to a surge to the power supply device or the semiconductor power control element at the time of interruption.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIGS. 1, 2, and 3.

FIG. 1 is a block diagram of an embodiment of the present invention. In FIG. 1, the high voltage circuit of the electron beam processing machine includes a power supply device 1, an electron gun 2, a beam current detection circuit 10 and a high voltage and high speed interruption device 9.

The high-voltage high-speed interrupting device 9 is connected in series between the negative high-voltage applying side lead 7 of the power supply device 1 and the electron gun 2. The occurrence of overload is detected by the beam current detection circuit 10 and the accelerating voltage detection circuit 11, the control circuit 12 receives these feedback signals, and the high-voltage high-speed cutoff device 9 outputs them as an optical signal insulated from the ground through the optical fiber 13. Sent. In response to the optical signal, the high-voltage high-speed circuit breaker 9 repeatedly turns off and turns on the high-voltage circuit at high speed for an arbitrary time, and when the disappearance of the overload is confirmed, the voltage-current of the high-voltage circuit is returned to a steady state.

The drive circuit 14 supplies power to the high-voltage high-speed circuit breaker 9. The drive circuit 14 is composed of an insulating transformer and an inverter as described later.

High voltage and high speed circuit breaker 9, control circuit 12 and drive circuit 14
And the operating principle will be described with reference to FIGS. 2 and 3.

Next, FIG. 2 shows a schematic circuit diagram of the high-voltage high-speed circuit breaker 9, the control circuit 12, and the drive circuit 14.

In this embodiment, a MOSFET 901 is used as a solid state high voltage switching element. MOSFET
901 includes a self-charge voltage dividing circuit mainly composed of a capacitor 902 for the purpose of dividing the voltage of the MOSFET 901 and supplying a gate voltage. For example, 12 sets are connected in series. Only the first-stage MOSFET has a gate. It is driven by the circuit 903. First stage MOSFET by gate circuit 903
Turns on, turns off, and if it turns on,
The second stage MOSFET is turned on by the electric charge of the capacitor 902, and the final stage MOSFET is also turned on in a chain. In the case of turn-off, on the contrary, the MOSFETs in the final stage are turned off in a chained manner, and at the same time, the capacitor 902 is charged. That is, each MOSFET 901 is controlled by the switching control means including the gate circuit 903 and the capacitor 902.
Turn off or turn on sequentially. Therefore, the surge voltage at the time of interruption can be suppressed lower than when the MOSFETs 901 are simultaneously turned off. The time from the turn-on or turn-off of the first-stage MOSFET to the turn-on or turn-off of the final-stage MOSFET is about 0.1 μsec or less in actual measurement.

One block formed by integrating these circuits is called a high-voltage semiconductor module 91, and a necessary withstand voltage is obtained by connecting a plurality of stages in series. Also,
A surge absorber 92 is attached to each of the high-voltage semiconductor modules 91 to protect them from surges.

The high-voltage high-speed circuit breaker 9 including a group of high-voltage semiconductor modules 91 is supplied with turn-on and turn-off signals from the control circuit 12 and electric power from the drive circuit 14 to drive the first-stage MOSFET.

The drive circuit 14 includes an inverter 141 and an isolation transformer 14.
It consists of two. A commercial frequency is set to a high frequency by the inverter 141, high voltage insulation is performed by the insulation transformer 142, and power is supplied to the gate circuit 903. This power is
The signals are sequentially sent to the gate circuit of the next-stage high-voltage semiconductor module 91 by the gate transformer 904 in the gate circuit. As a matter of course, the gate transformer 904 must have a withstand voltage equal to or higher than the voltage generated between the high voltage semiconductor modules.

Next, a method of transmitting an overload generation signal from the beam current detection circuit 10 and the acceleration voltage detection circuit 11 to each high voltage semiconductor module 91 of the high voltage high speed circuit breaker 9 from the control circuit 12 will be described with reference to FIGS. It will be described with reference to the drawings.

When overload occurs, the acceleration voltage drops and the beam current increases. Each set value is Va and Ia
Then, due to the occurrence of overload, the outputs of the acceleration voltage detection circuit 11 and the beam current detection circuit 10 decrease and increase proportionally (Vb and I in FIG. 3).
b). The comparators 121 and 123 for accelerating voltage and beam current in the control circuit 12 compare with the outputs of the respective voltage setters 122 and 124, and output an overload generation signal. With this signal, the multivibrator 125 emits an on / off signal for repeating a predetermined period, and is input to the NOT circuit 127 through the photocoupler 126.

As described above, the acceleration voltage comparator 121 and the beam current comparator 123 detect the overload state and the logical sum is obtained by the multivibrator 125 by monitoring both the fluctuation of the beam current and the fluctuation of the acceleration voltage. This is to detect the overload state as fast as possible. The on / off period of the multivibrator 125 can be arbitrarily set according to the load characteristics of the electron gun. NOT circuit 1
The output of 27 provides the bias of transistor 128,
The light emitting diode 129 emits and turns off depending on whether the transistor 128 is turned on or off. A signal insulated from the high voltage and the signal between the high voltage semiconductor modules by the light emitting diode 129 is sent to the light receiving diode 905 in the high voltage semiconductor module 91 through the optical fiber 5, and the gate circuit 903 causes the first stage MOSFET of the first stage MOSFET to operate. Turn on and turn off.

In the steady state where no overload occurs, the NOT circuit 12
Since the ON signal is always given by 7, the high-voltage high-speed cutoff device 9 is in the conductive state. Further, the electric charge of the capacitor 902 in the high-voltage semiconductor module 91 decreases due to the leakage current between the gate and the source of the MOSFET 901 and the like, so that it is recharged by interrupting the high-voltage circuit for a very short period at a constant cycle. As a result, the function of self-charging partial pressure by the capacitor 902 is satisfied. For example, 42 kW (accelerating voltage 6
When applied to an electron beam welder of 10,000 V and a beam current of 700 mA), the period for charging the capacitor is 10 seconds or more and the interruption time is 100 μsec or less, and it is known that the welding quality is not affected at all. .

Next, the relationship between these signals when an overload occurs
It is shown in the time chart in the figure.

When an overload occurs, for example, if the beam current increases and reaches the comparison setting beam current Ib, the beam current comparator 123 outputs and the multivibrator 125 operates. As described above, the high-voltage high-speed cutoff device 9 is cut off, and a voltage is generated between the anode and the cathode. After the OFF command period t _OFF (set to 3 msec in this embodiment) of the multivibrator 125 is cut off, the multi-vibrator 125 is returned by the _ON command t _ON (set to 400 μsec in this embodiment). At this time, the acceleration voltage of the comparison setting is set. If the acceleration voltage is higher than the value Vb, it is considered that the overload has disappeared, and the steady state is restored. However, in the opposite case, the multivibrator OFF command is repeated again until the predetermined acceleration voltage is reached. It is clear that the total of these interruption times has no effect on the melt-solidification continuity of the work piece since the total time does not exceed 10 ms.

As an effect of the present invention carried out in an electron beam welder of 42 kW (accelerating voltage 60,000 V, beam current 700 mA), firstly, the power supply device 1 was never damaged due to overload, and secondly, The high-speed disconnection of overload has eliminated the welding defects caused by overload, which has been common in the past.

〔The invention's effect〕

As described above, according to the present invention, since the output signal of the control signal output circuit is converted into the optical signal and transmitted to the blocking device, it is possible to increase the signal transmission speed and to prevent overload. The shutoff device can be shut off at high speed. Further, since each semiconductor power control element of the circuit breaker is sequentially cut off, the surge voltage at the time of cutoff can be made lower than when all the power control elements are cut off at the same time. Since the absorbing means is provided, it is possible to suppress the occurrence of a surge at the time of interruption, and it is possible to protect the semiconductor power control element and the power supply device from the surge.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a specific circuit diagram thereof, FIG. 3 is a time chart showing the operation of the embodiment, and FIG. 4 is a block diagram of a conventional example. 1 ... Power supply device, 2 ... Electron gun, 3 ... Electronic discharge device, 4 ... Sensing circuit, 5 ... Timing circuit, 6 ... Grounding, 7
...... Negative high voltage side lead, 8 ...... Positive ground side lead, 9 ...
… High-voltage high-speed circuit breaker, 10 …… Beam current detection circuit, 1
1 ... Acceleration voltage detection circuit, 12 ... Control circuit, 13 ...
Optical fiber, 14 ... Driving circuit, 91 ... High-voltage semiconductor module, 92 ... Surge absorber, 901 ... MOSFET,
902 ... Capacitor, 903 ... Gate circuit, 904
...... Gate transformer, 905 …… Light receiving diode, 12
1 ... Accelerating voltage comparator 122 ... Accelerating voltage comparison / setting device 123 ... Beam current comparator 124
…… Beam current comparison and setting device, 125 …… Vibrator,
126 ... Photo coupler, 127 ... NOT circuit, 12
8 ... Transistor, 129 ... Light emitting diode, 14
1 ... Inverter, 142 ... Isolation transformer.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kiichi Tokunaga 4026 Kuji Town, Hitachi City, Ibaraki Prefecture Hitachi Research Laboratory, Hitachi Ltd. (72) Inventor Masakazu Midorikawa 3-1-1, Saicho Town, Hitachi City, Ibaraki Prefecture Hitachi Ltd., Hitachi Works (72) Inventor Takeo Uehara 3-1-1, Saiwaicho, Hitachi, Ibaraki Hitachi Ltd., Hitachi Works (56) References JP-A-56-116000 (JP, A) )

Claims (1)

[Claims] 1. An electron beam processing machine comprising an electron gun for projecting an electron beam onto a workpiece and a power supply device for supplying DC power to the electron gun, wherein a plurality of semiconductor power control elements connected in series. A cutoff device inserted in series between the negative output end of the power supply device and the electron gun, and an acceleration voltage detection circuit for detecting the output voltage of the negative output end of the power supply device, A beam current detection circuit inserted in series between the positive output end of the power supply device and the ground is compared with a detection output signal of the acceleration voltage detection circuit and a first set value, and the detection output signal is the first When the first comparison circuit that outputs an overload detection signal when the set value is exceeded and the detection output signal of the beam current detection circuit and the second set value are compared, and the detected output signal exceeds the second set value Second comparison that outputs an overload detection signal And a control signal output that outputs a cutoff signal in response to an overload detection signal from the first comparison circuit or the second comparison circuit, and outputs a conduction signal when no overload detection signal is generated from any of the comparison circuits. A circuit, and an optical signal transfer circuit for converting an output signal of the control signal output circuit into an optical signal and transferring the optical signal to the blocking device, wherein the blocking device converts the optical signal from the optical signal transfer circuit into an electrical signal. Photoelectric conversion means, switching control means for sequentially connecting or disconnecting each semiconductor power control element in response to an output signal of the photoelectric conversion means, and surge absorbing means for absorbing surge generated from each semiconductor power control element. An electron beam processing machine characterized by having.