JPS6138213Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field of the Invention The present invention relates to a pulse laser generator that repeats at high speed.

Technical background of the invention and its problems The process of optically exciting a laser substance using light emission from a flash lamp to obtain pulsed laser light, and concentrating this laser light to perform seam welding has become widely practiced. In this case, it is known that in order to perform good welding at high speed, it is sufficient to keep the peak output of the laser beam low and, on the other hand, to increase the pulse repetition frequency. On the other hand, in order to cause the flash lamp to emit light repeatedly at high speed, the flash lamp is first discharged with a small DC current, and then a current is supplied from the main power source via a switch element to cause the main discharge. That's what I do. However, in this case, unless the power supply output for supplying the main discharge is greater than the voltage drop of the flash lamp during preliminary discharge, the voltage will not flow into the flash lamp, and as a result, it will not be possible to smoothly transition to the main discharge. Therefore, the power supply output for main discharge must be set high. Therefore, the discharge output becomes very large. Furthermore, if this is repeated at a high speed, the average discharge current will increase and will greatly exceed the allowable power of the flash lamp, resulting in the disadvantage that the repetition frequency will be limited.

It is also possible to reduce the average current by narrowing the pulse width of the pulsed discharge, but in this case, a disadvantage arises in that sufficient penetration depth cannot be obtained in laser welding. Furthermore, in conventional pulsed laser devices, the laser material has not reached a thermal steady state at the start of excitation, so when a plane mirror is used as the resonator mirror, the loss is large. Therefore, as the pulse discharge progresses, the laser material is heated, and the laser output gradually increases, making it difficult to obtain a constant output.

Purpose of the invention It is an object of the present invention to provide a pulse laser generator that can reliably perform pulse lighting of an excitation flash lamp at low voltage and at high speed.

Outline of the invention: At the start of pulse discharge, the output of the DC power supply is set to an output sufficiently higher than the voltage drop of the flash lamp during pre-discharge, and a control means is provided for switching to an output lower than this output at the start of pulse discharge. .

Embodiment of the invention The invention will be explained based on FIG. 1 showing one embodiment. The configuration shown in the figure includes a DC voltage generator 1, a switching circuit 2 that changes the voltage from the generator so that it is supplied with pulses of a predetermined time width, and a laser oscillation circuit that receives the pulse voltage supplied through the switching circuit 2. A backup power source 4 that preliminarily supplies a small DC voltage to the oscillating section 3 via a discharge stabilizing resistor 4a, and a trigger wire 6 wound around the flash lamp 5 in the oscillating section 3 to trigger a trigger. It consists of a trigger power supply 7 that supplies a voltage, and a stabilizing circuit section 8 that detects the voltage supplied to the DC voltage generating section 1 and compares it with a reference voltage to stabilize the voltage supplied to the flash lamp 5. DC voltage generator 1
includes a transformer 9, a rectifier circuit 10, and storage capacitors 12 and 13 arranged in parallel via a smoothing choke coil 11. The primary side of the transformer 9 is connected to an AC input line 16 provided with AC line control thyristors 14 and 15. The switching circuit 2 includes thyristors 19 and 20 as switching elements that are connected in series to the (+) side line of the DC voltage generation section 1 via waveform shaping coils 17 and 18, respectively, and a gate pulse generation circuit for these thyristors. 21 and 22. Charge/discharge capacitors 24 and 25 that share a waveform shaping coil 23 are provided in parallel between the thyristor 19 and the coil 18. Oscillation section 3
is a flash lamp 5, a laser substance 26, a condensing reflector 27 housed therein, and optical resonators 28, 29.
Consists of. Further, the stabilizing circuit section 8 is configured as follows. That is, the DC voltage generator 1
In order to detect the DC voltage of storage capacitors 12 and 13 provided in A comparator 34 which compares the detected voltages, amplifies and outputs the difference voltage, and inputs the amplified difference voltage and connects it to the thyristors 14 and 15 provided in the AC input line 16 to adjust the phase of the AC. It is composed of a gate pulse generation circuit 35 for controlling. Here, the reference voltage generation section 31 is provided with a circuit section 31a that generates two levels of voltage, high and low, and a high voltage line 31b and a low voltage line 31c are respectively input to the comparator 34 through a relay 36. It's getting old. The relay 36 is connected to a power source 37 and a changeover switch 38. Changeover switch 38
is provided between the clock pulse generator 43 connected to the trigger power supply 7 and the pulse delay circuit 44, and has two sets of terminals 39-40 and 41-42, and is connected to one set of terminals 39-44. are doing. The opening and closing operations of the two sets of terminals are the same, and one set of terminals 4
1-42 is closed, the coil 45 of the relay 36
and activates the high voltage line 3 at this relay 36.
Low voltage line 3 from terminals 46-47 connected to 1c
1b, and the other set 39-40 brings the pulse generator 43 and pulse delay circuit 44 into conduction.

Note that the output of the pulse generator 43 is sent to one of the gate pulse generation circuits 21 and to the pulse delay circuit 44.
The outputs are branched and input to the other gate pulse generation circuit 22.

Next, the effect of the above configuration will be explained. The flash lamp 5 achieves the voltage V _S -I _S shown in FIG. A characteristic of 50 is obtained. That is, in a krypton flash lamp with a sealed gas pressure of 700 Torr, when the discharge length is 150 mm, the tube voltage drop V _SO is 200 V at I _SO =100 mA. In the above light emission, the changeover switch 38 is kept open so that the pulse voltage of the main discharge, that is, the voltage charged in the charge/discharge capacitors 24 and 25 is initially higher than the above _VSO , that is, the relay 3
6, the voltage connected to the high voltage line 31b, for example V _DC1 , is selected and set as the reference voltage to the comparator 34. Next, when the selector switch 38 is closed to start pulse emission operation, the reference voltage becomes V _SO
It is set to a lower voltage, for example, the voltage V _DC2 connected to the low voltage line 31c.

The charging and discharging capacitors 24 and 25 cause a voltage drop over time as shown by a curve 51 shown in FIG. 2b. The charging/discharging capacitors 24 and 25, which settle to V _DC2 in a steady state, are connected to one of the thyristors 19 through the waveform shaping coil 17 from the DC voltage generator 1.
After being charged by the on operation of thyristor 1
9 is turned off, and after the delay time of the delay circuit 44, the voltage of the charge/discharge capacitors 24 and 25 flows into the flash lamp 5 through the waveform shaping coil 18 and the other thyristor 20 by the gate firing pulse from the gate pulse generation circuit 22. do. When the above discharge ends, the thyristor 20 is turned off. In this way, the voltage V DC1 of the storage capacitors 12 and 13, which has been accumulated higher than the above V _SO , is the voltage V _DC1 of the low voltage line 31b.
Supplementary charging from the AC input is not performed until the low voltage V _DC2 is set by the switching, and the output voltage gradually decreases with each pulse discharge as shown by the curve 51 shown in FIG. 2B. The discharge current waveform of the flash lamp 5 in this case is the waveform 52a shown in FIG.
52b...52n, the peak output gradually decreases. On the other hand, the voltage drop waveforms of the flash lamps are waveforms 53a, 53b, . . . 5 shown in FIG. 2d.
3n, initially a high voltage is shown, but as the voltage drops as shown in the curve 51, a lower voltage is applied from the charge/discharge capacitors 24 and 25. However, the voltage while the main discharge is not being performed is maintained by the power supply from the backup power source 4. Immediately after the main discharge, the flash lamp voltage drop is determined by the above DC pre-discharge voltage drop V _SO at the pre-discharge steady value, as shown in the recovery characteristics 54a, 54b,...54n of the pre-discharge voltage in Figure 2d. becomes a high voltage, and then gradually returns to the above _VSO , but the pulse repetition rate of the main discharge is high, and the pulse repetition period T is still in the steady state in the middle of the rise of the above return characteristics 54a, 54b, ... 54n. Main discharge voltage V _DC2
The next main discharge pulse is started at the timing when the main discharge is performed when V _S is below. In this way, V _DC1 is set so that at least V _DC1 > V _SO
First, the voltage of the DC voltage generator 1 is set to have constant voltage control characteristics, and then the reference voltage is automatically controlled to constant voltage control from V _DC1 to a lower voltage V _DC2 during continuous pulse operation. The configuration is as follows.

Effects of the invention As described above, the flash lamp is lit only at the start of continuous pulse operation under high voltage, that is, high power, input conditions. Averaging will result in a smaller average input condition. On the other hand, the input power in a steady state is lowered by the applied voltage, and if the average power is kept below the predetermined average input capacity of the flash lamp, the input power can be kept below the rated value from the start of discharge. Thus, under pulsed operating conditions, the average input power is the product of the pulsed discharge voltage, peak discharge current, pulse width, and pulse repetition rate;
Since this maximum value is determined by the flash lamp, the pulse discharge voltage and peak discharge current value must be lowered under conditions where the pulse width is widened and the pulse repetition rate is increased. The present invention enables high-speed repetitive pulse operation under operating voltage conditions lower than that of the conventional method, making it possible to oscillate a pulsed laser output with a relatively wide pulse width and large pulse repetition in the laser output waveform. This means that the laser irradiation conditions can be selected from a wider range of conditions than before in various processes such as seam welding, cutting, drilling, heat treatment, etc. with pulsed laser output, making it easier to set conditions and increase processing speed. It has become possible to improve processing quality.

Note that the DC power supply circuit in the above embodiment is not limited to the above embodiment as long as it can perform voltage stabilization control. Further, the switching circuit is not limited to a capacitor charging/discharging circuit, but may be a DC power switching circuit. In addition, a high first voltage (V
It is clear that the voltage switching between the lower voltage ( _DC1 ) and the lower second voltage ( _VDC2 ) can be implemented by other circuits such as a non-contact circuit, in addition to switching by a relay or the like.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing one embodiment of the present invention;
Figures a to d are operation explanatory diagrams. DESCRIPTION OF SYMBOLS 1...DC voltage generation part, 2... Switching circuit, 3... Oscillation part, 4... Reserve power supply, 5... Flash lamp, 8... Stabilization circuit part, 30... Resistance voltage divider, 31 ...Reference voltage generation section, 31b
...High voltage line, 31c...Low voltage line, 34...
... Comparator, 38... Gate pulse generation circuit.

Claims (1)

[Claims for Utility Model Registration] (1) A DC power supply, a switching circuit that changes the voltage from the DC power supply to be supplied with a pulse width of a predetermined time, a flash lamp that emits light by supplying the pulsed power, and the DC power supply. A supply voltage detection means, a reference voltage generation means, a comparison circuit between the detected voltage of the detection means and the reference voltage of the reference voltage generation means, and a difference signal from the comparison circuit is inputted to determine the supply voltage value of the DC power supply. In a pulsed laser generator comprising a control means for stable control and a preliminary discharge power source that supplies a minute DC voltage to the flash lamp via a DC stabilizing resistor provided in parallel with the switching circuit, the pulse laser generator starts the pulse discharge. It is characterized by comprising main discharge voltage control means that sometimes sets the output of the DC power supply to a constant voltage control output that is sufficiently higher than the voltage drop of the flash lamp during preliminary discharge, and switches to an output voltage lower than this output at the start of pulse discharge. Pulsed laser generator. (2) The main discharge voltage control means has a reference voltage generation means configured to extract at least two types of voltages that are high and low, and one of the voltages is selectively switched and inputted to the comparator circuit. A pulsed laser generator according to claim 1, characterized in that: