JPH03295285A - Gas laser device - Google Patents

Abstract

PURPOSE:To improve a high frequency motor and a bearing in reliability and service life by a method wherein a high frequency inverter which rotates a high frequency motor is directed to output an output frequency correspondent to a laser output value. CONSTITUTION:A laser output value outputted from a processor 1 is converted into a current instruction value through an output control circuit 2, and the control circuit 2 outputs the converted value. Correlation data between the laser output value of a laser oscillator and the output frequency of a high frequency inverter correspondent to the laser output value are stored in a memory cell 10. Basing on a control program, the processor 1 determines the output frequency of a high frequency inverter 22 corresponding to the laser output value. The high frequency inverter 22 drives a high frequency motor 20a at the outputted frequency, a turbo blower 20 is made to rotate corresponding to the laser output value, and the input power of the high frequency motor 20a is kept nearly constant at both the maximum laser output and a base discharge.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a gas laser device equipped with a mechanism for forcibly cooling laser gas using a blower and a cooler, and in particular, the present invention relates to a gas laser device equipped with a mechanism for forcibly cooling a laser gas using a blower and a cooler. The present invention relates to a gas laser device configured to control.

[Conventional technology]

Gas laser oscillators such as CO2 gas lasers have high efficiency, high output, and good beam characteristics, so they have come to be widely used in metal processing and the like as gas laser devices combined with numerical control devices. In such a gas laser oscillator, in order to improve the oscillation efficiency, it is necessary to sufficiently recool the laser gas that has become hot during laser oscillation. For this reason, the laser gas is constantly circulated within the apparatus through a cooler using a blower such as a turbo blower. Since this blower normally requires high-speed rotation of 10 Krprr1 (rotation for 7 minutes) or more, a high-frequency motor is used and a high-frequency inverter is used as a driving source.

FIG. 3 is a diagram showing an actually measured exhaust curve for a conventional turbo blower. This shows the exhaust curves of the turbo blower at base discharge and at maximum output, which were actually measured based on JISB8345. In the figure, the horizontal axis represents the flow rate, and the vertical axis represents the compression ratio. In FIG. 3, the ventilation resistance curve of the ventilation system during base discharge and maximum output is shown as a quadratic curve. It can be seen that the air blowing resistance curve a during base discharge is on the right side of the air blowing resistance curve at maximum output, and the laser gas flow rate is larger during base discharge at the same compression ratio than at maximum output. In other words, it can be seen that the ventilation piping resistance has decreased.

Note that the relationship between the compression ratio of the turbo blower and the flow rate of the laser gas is represented by a curve CC for a rotational speed of 85 Krpm, a curve d for CC180Krp, and a curve e for 70Krp'm.

To give a further example, the rotation speed is 80 Krpm and the gas pressure is 6.
The values of the laser gas flow rate and high frequency motor input at the time of base discharge and maximum output of the turbo blower under the condition of 2 Torr are as follows.

(a) Laser gas flow rate during base discharge 260j! /sec High frequency motor input 2.4kW (b) Laser gas flow rate at maximum output 180f/sec High frequency motor input 2.1kW In this way, the turbo blower is a constant compression type blower, so during base discharge where the discharge area is narrow, the blower piping resistance increases. The laser gas flow rate becomes maximum.

On the other hand, when the laser output value is maximum, both the discharge area and the ventilation piping resistance are maximum, and the laser gas flow rate is minimum.

[Problem to be solved by the invention]

However, since the turbo blower is a constant compression type blower,
As the resistance of the ventilation piping changed, the amount of laser gas blown also changed. In other words, during base discharge where the discharge area is narrow, the amount of laser gas blowing is maximum, and the load on the high frequency motor is reduced.
In other words, the input power becomes maximum.

Conversely, when the discharge area is at its maximum, the amount of laser gas blown is at its minimum, and the load on the high-frequency motor, that is, its input power, is at its minimum.

In this way, the load on the high-frequency motor changes as the laser output changes, so the value must be determined based on the value when the turbo blower's operating point has the maximum load, that is, the value at base discharge when the laser output does not drop. Ta.

Furthermore, if the high-frequency motor remains under a heavy load such as during base discharge, this places a burden on the high-frequency motor, lowering its reliability and shortening its lifespan. Moreover, the base discharge time becomes a considerable amount of time when the setup and work preparation before starting machining of the workpiece and the maintenance time after machining the workpiece are totaled.

The present invention has been made in view of these points, and an object of the present invention is to provide a gas laser device configured to command an output frequency corresponding to a laser output value to a high-frequency inverter that rotates a high-frequency motor.

Another object of the present invention is to provide a gas laser device in which the human power of the high-frequency motor is maintained at the same level as when the laser output value is maximum even during base discharge when the laser output value is zero. .

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention provides a laser oscillator with a function of forcedly circulating laser gas in a closed loop using a blower and a gas cooler driven by a high-frequency inverter, and a control device that controls the laser oscillator. A gas laser device comprising: a laser output command means for commanding a laser output value of the laser oscillator; an output frequency determining means for determining an output frequency of the high frequency inverter corresponding to the laser output value; A gas laser device comprising an output frequency command means for commanding the high frequency inverter,
provided.

[Effect]

The output frequency determining means reads the laser output value and determines the output frequency in accordance with the laser output. Since the output of the turbo blower increases as the laser output value decreases, the pressure frequency of the turbo blower is reduced. This keeps the input power of the high frequency motor constant. The high frequency inverter rotates the high frequency motor at this output frequency, and the high frequency motor drives the blower to force the laser gas to circulate in a closed loop and cool the laser gas through the cooler.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing the configuration of a gas laser device of the present invention. In the figure, a processor 1 operates based on a control program stored in a ROM (not shown).
The nitrogram stored in the memory 10 is read out to control the operation of the entire gas laser device. The output control circuit 2 has a built-in D/A converter that converts a digital value into an analog output, and converts the laser output value output from the processor 1 into a current command value and outputs the current command value.

After rectifying the commercial power source, the laser power source 3 performs a switching operation to generate a high frequency voltage, and supplies a high frequency current to the discharge tube 4 according to the current command value.

A laser gas 25 circulates inside the discharge tube 4, and when a high frequency voltage is applied from the laser power source 3, a discharge occurs and the laser gas 25 is excited.

By reciprocating between the total reflection mirror 5 and the output mirror 6, the laser beam receives energy from the excited laser gas 25, is amplified, and a part of the laser beam is outputted from the eight mirrors 6 to the outside.

The pressurized laser beam 9 changes direction with a pendulum mirror 7 and is irradiated onto the surface of a workpiece 17 by a condensing lens 8 .

- The memory 10 is a non-volatile memory that stores the program and various parameters, and uses a CMO 5 backed up by a battery.

The memory 10 also stores the laser output value of the laser oscillator,
Correlation data between this laser output value and the output frequency of the high frequency inverter is stored. Based on the control program, the processor 1 determines the output frequency of the high frequency inverter 22 according to the laser output value.

During base discharge when the laser output value of the gas laser device is zero, the ventilation piping resistance is the minimum, the flow rate of the laser gas is the maximum, and the load on the high frequency motor 20a, that is, the human power is the maximum. Conversely, when the laser output value is maximum, the ventilation piping resistance is maximum and the flow rate of laser gas is minimum.
The human power of the high frequency motor 20a is minimized.

Therefore, in order to reduce the number of rotations of the high frequency motor 20a,
The output frequency of the high frequency inverter 22 is reduced to reduce the human power of the high frequency motor 20a during base discharge. From the experiment, the output frequency will be reduced by about 5%. That is, by reducing the rotation speed of the high-frequency motor 20a by about 5%, the input power of the high-frequency motor 20a can be made the same as when the laser output value is the maximum.

A position control circuit 11 controls the rotation of a servo motor 13 via a servo amplifier 12 in response to a command from a processor 1, and controls the rotation of a servo motor 13 via a ball screw 14 and a nut 15.
6 and the position of the workpiece 17. Although the figure shows only one axis of the servo amplifier and servo motor, there are actually a plurality of control axes. Display device 1
8, a CRT or liquid crystal display device is used.

Power sensor 1 that measures the output power of the laser oscillation device
Reference numeral 9 measures the monitor laser output output through a part of the total reflection mirror 5 using a thermoelectric or photoelectric conversion element.

A turbo blower 20 for circulating laser gas is coupled to a high frequency motor 20a and circulates laser gas 25 through coolers 21a and 21b. Cooler 2
1a is a laser gas 25 that has become hot due to laser oscillation.
The cooler 21b removes the heat of compression by the turbo blower 20.

The high frequency inverter 22 rotates the high frequency motor 20a,
The turbo blower 20 is driven, and the vacuum pump 23 is for exhausting gas inside the blowing system.

FIG. 2 is a flowchart for controlling the load of the high frequency motor of the gas laser device of the present invention.

In the figure, the number following S indicates the step number.

[S1] Read the laser output value to the output control circuit 2,
Check whether it is a base discharge, and if it is a base discharge, go to S2.
Otherwise, proceed to S3.

[S2] As explained above, the output frequency of the high-frequency motor 20a is reduced to a value where the input power of the high-frequency motor 20a is approximately the same as when the laser output value is at its maximum.

[S3] Output the output frequency to the high frequency inverter 22.

[S4] The high-frequency inverter 22 drives the high-frequency motor 20a at this output frequency, the turbo blower 20 rotates according to the laser output value, and the input power of the high-frequency motor 20a changes between the maximum laser output value and the base discharge. They become exactly the same.

In the above description, an example has been described in which the input power of the high-frequency motor is switched only when the laser output value is at its maximum and during base discharge. In addition to this, correlation data between the laser output value and the 8-power frequency is stored in memory in advance so that the input power of the high-frequency motor is almost constant, and this correlation data is read out to determine the output frequency of the high-frequency inverter. It can also be configured to determine. by this,
It becomes possible to keep the load on the high-frequency motor constant over a wide range of laser output values. Such correlation data can be obtained by measuring the laser output value and the load current of the high frequency motor.

FIG. 2 is a flowchart for controlling the load of the high-frequency motor of the gas laser device of the present invention, and FIG. 3 is a diagram showing an actually measured exhaust curve in a conventional turbo blower.

〔Effect of the invention〕

As explained above, the present invention is configured to determine the output frequency corresponding to the laser output value and output it to the high frequency inverter, so the turbo blower can be driven even during base discharge or when the laser output value is small. The load on the high-frequency motor used will not increase unnecessarily. Therefore,
The reliability and lifespan of high-frequency motors and bearings are improved.

Further, with the reduction of the motor load during base discharge, it is expected that the laser device will be able to increase its output by setting the operating point of the turbo blower on the high load side.

[Brief explanation of drawings]

Figure 1 shows the configuration of the gas laser device of the present invention. 1 9 0 0a 21a,b 2 3 5 P.U. Output control circuit Power supply for laser electric power tube memory position control circuit power sensor turbo blower high frequency motor Cooler high frequency inverter Vacuum pump laser gas Figure 2 Figure 3

Claims (4)

[Claims] (1) In a gas laser device consisting of a laser oscillator with a function of cooling laser gas by forced circulation in a closed loop using a blower and a gas cooler driven by a high-frequency inverter, and a control device that controls the laser oscillator. , laser output command means for commanding a laser output value of the laser oscillator; output frequency determining means for determining an output frequency of the high frequency inverter corresponding to the laser output value; and an output frequency for commanding the output frequency to the high frequency inverter. A gas laser device comprising: a command means; (2) The output frequency determining means is configured to reduce the output frequency according to a predetermined ratio when the laser output value is zero during base discharge compared to when the laser output value is maximum. The gas laser device according to claim 1. (3) The output frequency determining means reads correlation data between the laser output value stored in a memory in advance and the output frequency of the high frequency inverter corresponding to the laser output value, and determines the output frequency based on the correlation data. 2. The gas laser device according to claim 1, wherein the gas laser device is configured to determine. (4) The gas laser device according to claim 1, wherein the control device is constituted by a numerical control device.