JP6831270B2 - Power control device for high frequency power supply, control method for high frequency power supply, and light source for laser machining system - Google Patents

Description

The present invention relates to a laser processing system.

Laser machining systems are widely used as industrial machining tools. FIG. 1 is a block diagram of a laser processing system. The laser processing system 10R includes a light source 20R and a processing machine 40. The processing machine 40 receives the laser pulse 50 generated by the light source 20R and irradiates the object 2 with the laser pulse 50.

The processing machine 40 includes an optical system 42, a stage 44, and a processing control device 46. The object 2 is placed on the stage 44 and fixed as needed. The optical system 42 receives the laser pulse 50 and irradiates the object 2 with the laser pulse 52. The stage 44 positions the object ₂ in response to the position control signal S2 from the processing control device 46, and scans the irradiation positions of the object 2 and the laser pulse 52 relative to each other. The stage 44 can be uniaxial, biaxial (XY) or triaxial (XYZ).

The machining control device 46 comprehensively controls the laser machining system 10R. Processing controller 46 Specifically, intermittently outputting the shot instruction S ₁ to the light source 20R. The machining control unit 46 generates a position control signal S ₂ for controlling the stage 44 according to the data (recipe) describes the processing.

Light source 20R in response to the shot instruction _{S 1} from the machining control unit 46, it generates a laser pulse 50. The light source 20R includes a DC power supply 22, a high frequency power supply 24, a laser device 26, and a light source side control device 28. The laser device 26 is a CO ₂ laser or the like. The DC power supply 22 generates a DC voltage V _DC . The high frequency power supply 24 boosts the DC voltage V _DC and applies an AC high voltage V _DRV to the discharge electrode 27 of the laser device 26.

Light source-side control unit 28 is responsive to the shot instruction S _1, thereby intermittently operating the high frequency power supply 24. During the operation period (excitation period) of the high-frequency power supply 24, the laser device 26 emits light, and during the stop period of the high-frequency power supply 24, the laser device 26 stops emitting light.

The high-frequency power supply 24 includes a high-frequency inverter 25, and the high-frequency inverter 25 is composed of a semiconductor switch such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), a bipolar transistor, and an IGBT (Insulated Gate Bipolar Transistor). The light source side control device 28 switches the semiconductor switch at high speed during the excitation period.

Inductance is intentionally or parasitically introduced into the high frequency power supply 24. When a semiconductor switch is switched at high speed, energy corresponding to the current flowing through the inductance is stored in the inductance. This inductance sometimes causes an overvoltage to be applied to the semiconductor switch.

If an overvoltage exceeding the withstand voltage is applied to the semiconductor switch, reliability is impaired. Therefore, a snubber circuit is connected to the semiconductor switch to appropriately absorb the energy of the inductance. Generally, a snubber circuit includes a snubber capacitor connected in parallel with a semiconductor switch, and by drawing a current flowing through the semiconductor switch into the snubber capacitor, an increase in voltage between both ends of the semiconductor switch is suppressed. The electric charge stored in the snubber capacitor is discharged via a discharge resistor.

Here, if the charging speed of the snubber capacitor continues to exceed the discharging speed, the voltage of the snubber capacitor continues to rise, and an overvoltage may be applied to the semiconductor switch. In the technique of Patent Document 1, in order to solve this problem, a discharge switch is provided in parallel with the discharge resistor, and when the voltage of the snubber capacitor exceeds the threshold value, the discharge switch is turned on to turn on the snubber capacitor. It is configured to forcibly reduce the voltage of.

A method of monitoring the voltage of the snubber capacitor or the voltage applied to the semiconductor switch and stopping the high-frequency power supply when a predetermined threshold value is exceeded is also conceivable.

Japanese Patent No. 3991450 JP 2015-195677

In the snubber circuit of Patent Document 1, if the state in which the energy to be absorbed is large continues, the time for the discharge switch to conduct is long. This means that the discharge switch generates heat, so it may not be sufficient for protection.

Further, in the prior art, protection processing is performed based on the voltage of the snubber capacitor, which is effective in protecting the semiconductor switch. However, if the output power of the high-frequency power supply 24 continues to be large, the decrease in reliability of the discharge electrode 27 of the laser device may become more problematic than the semiconductor switch.

The present invention has been made in view of the above problems, and one of the exemplary purposes of the present invention is to provide a light source having improved reliability by an approach different from the conventional one.

One aspect of the present invention relates to a power supply control device that controls a high frequency power source that intermittently supplies an AC voltage to a laser device. The power control device has a determination unit that generates a flag indicating permission or prohibition of the operation of the high-frequency power supply based on the history of the shot command instructing the operation or stop of the high-frequency power supply, and the shot command instructs the operation and the flag. Provided is a drive control unit that operates a high frequency power supply when indicates permission.

The history of shot commands correlates with the energy generated per predetermined time in the past. According to this aspect, it is determined whether or not the state of the high frequency power supply or the laser device is safe based on the history of the shot command, and the laser emission is permitted only when it is safe, so that the reliability is further improved. be able to.

The shot command is a binary signal that takes the first state when instructing the operation and the second state when instructing the stop, and the determination unit is based on the comparison result of the moving average and the threshold value of the duty ratio of the shot command. , You may generate a flag.

Another aspect of the invention relates to a light source for a laser processing system. The light source includes a laser device, a high-frequency power source that intermittently supplies an AC voltage to the laser device, and any of the above-mentioned power supply control devices that control the high-frequency power source.

It should be noted that any combination of the above components or components and expressions of the present invention that are mutually replaced between methods, devices, systems, and the like are also effective as aspects of the present invention.

According to certain aspects of the invention, reliability can be enhanced.

It is a block diagram of a laser processing system. It is a block diagram of the laser processing system which concerns on embodiment. It is an operation waveform diagram of the light source of FIG. It is a functional block diagram which shows the structural example of the determination part.

Hereinafter, the present invention will be described with reference to the drawings based on preferred embodiments. The same or equivalent components, members, and processes shown in the drawings shall be designated by the same reference numerals, and redundant description thereof will be omitted as appropriate. Further, the embodiment is not limited to the invention but is an example, and all the features and combinations thereof described in the embodiment are not necessarily essential to the invention.

FIG. 2 is a block diagram of the laser processing system 10 according to the embodiment. The outline of the laser processing system 10 is the same as that of the laser processing system 10R of FIG. 1, and includes a light source 20 and a processing machine 40. The processing machine 40 irradiates the object 2 with the laser pulse 52 to process the object 2. The type of the object 2 is not particularly limited, and the type of processing includes, but is not limited to, drilling, cutting, and the like. Since the configuration of the processing machine 40 is as described with reference to FIG. 1, it is omitted.

The light source 20 includes a DC power supply 22, a high frequency power supply 24, a laser device 26, and a light source side control device 30.

The DC power supply 22 generates a DC voltage V _DC of several hundred V (for example, 500 V). The configuration of the DC power supply 22 is not particularly limited, but may include a bank capacitor, a power supply device, a filter, and the like. The power supply device may be a converter or a charging circuit that stabilizes the voltage _VDC of the bank capacitor to a target value.

The light source side control device 30 is under the control of the machining control device 46, and controls the DC power supply 22 and the high frequency power supply 24 in response to various control commands, control data, and the like from the machining control device 46.

The light source side control device 30 includes a system controller 32 and a power supply control device 34. The system controller 32 integrally controls the entire light source 20 in response to a control command from the machining control device 46.

The discharge electrode 27 is provided in a chamber filled with a mixed gas such as CO _2, and is equivalently represented as a series capacitor. The high-frequency power supply 24 intermittently supplies a rectangular wave AC voltage V _DRV to the discharge electrode 27 of the laser device 26. This drive voltage V _DRV is applied between the discharge electrodes 27 via an inductance (not shown), and an _AC high-frequency voltage VAC is generated between both ends of the discharge electrode 27 by the series resonance of the inductance and the capacitance. This capacitance changes before and after the start of discharge. That is, the capacitance before the start of discharge is the capacity of the gas sandwiched between the two discharge electrodes. The discharge electrode is embedded in an insulator, and the capacitance after the start of discharge is the capacitance of the insulating portion around the electrode. The high frequency power supply 24 may include an input capacitor, a full bridge (H bridge) type high frequency inverter 25, and a step-up transformer T ₁ . The high-frequency inverter 25 includes a plurality of semiconductor switches and a snubber circuit connected in parallel with each semiconductor switch. High-frequency inverter 25, an AC voltage to a DC voltage V _DC and the amplitude is applied to the primary winding of the step-up transformer T _1.

The secondary winding of the step-up transformer T _1, a high frequency voltage V _AC with an amplitude corresponding to the winding ratio is generated. For example, when _V DC = 500V, the turns ratio is 4, the amplitude of the RF voltage _{V AC} becomes 2 kV. The step-up transformer T ₁ may be omitted and the DC voltage V _DC may be set to several kV. During the operating period of the high-frequency power supply 24, the high-frequency inverter 25 switches at a high frequency, so that a high-frequency drive voltage _VDRV is applied to the discharge electrode 27, and the laser device 26 emits light. During the stop period of the high frequency power supply 24, the excitation of the laser device 26 is stopped, and therefore the laser device 26 is in a non-light emitting state.

Power controller 34, based on the shot instruction S ₁ from the machining control unit 46 controls the operation and stop of the high-frequency power supply 24. Shot command S ₁ is intermittently signal designating stop period and the operation period, it may be an optical signal, it may be an electric signal.

The power supply control device 34 includes a determination unit 36 and a drive control unit 38. Determining unit 36, operation of the high frequency power source 24, based on the history of the shot instruction S ₁ for instructing the stop permission of the operation of the high frequency power source 24 generates a flag S ₃ indicating the prohibition. Drive control unit 38, the shot command S ₁ is to direct the operation period, and when the flag S ₃ shows successful, the high-frequency inverter 25 and the switching in accordance with the driving signal S _4, to operate the high-frequency power supply 24. Drive control unit 38, when the flag S ₃ indicates prohibition, even shot command S ₁ is had instructed operation period, without generating a driving signal S _4, to stop the high frequency power source 24.

For example shot command S ₁ is the first state when directing the operation period, which is a binary signal which takes a second state when instructing to stop. If the shot command S ₁ is an electrical signal, the first state is a high level, the second state may be a low level.

Determining unit 36, based on the history of the shot instruction S _1, may generate an estimate correlated with power consumption of the light source 20 per predetermined time interval (energy). The estimate of the energy exceeds a predetermined threshold, the flag S ₃ may be set to disabled.

Determining unit 36, as an estimate of the energy, may calculate the moving average of the time ratio of the operation period of the shot command S ₁ (duty ratio). Then, the flag S ₃ may be generated based on the comparison result between the moving average value and the determination threshold value. When the repetition frequency is constant, the duty ratio corresponds to the on-time.

As the moving average, a simple moving average may be used, or a weighted moving average may be used. Alternatively, the determination unit 36 may be implemented by using a low-pass filter or an integrator in terms of hardware.

The length of the predetermined time interval may be appropriately determined according to the protection target. For example, when the purpose is to protect the overvoltage of a semiconductor switch, the length of a predetermined time interval may be determined based on the time constant of the snubber capacitor of the snubber circuit. When the purpose is to protect the semiconductor switch or the discharge electrode 27 from overheating, the heat relaxation time of the target may be taken into consideration.

For example, when a semiconductor switch is to be protected, the length of a predetermined time interval, in other words, the length of the time window of the moving average processing may be about 1 ms to 10 ms.

The above is the configuration of the light source 20. Next, the operation will be described. FIG. 3 is an operation waveform diagram of the light source of FIG.

Shot command S ₁ is a pulse signal having a predetermined repetition frequency, the operation period of the high-level high-frequency power source 24, i.e., it instructs the emission period of laser apparatus 26, low level stop period of the high frequency power source 24, i.e. lasers Indicates the stop period of the device 26. That length of the high level shot command S ₁ is represents the length of the operation period of the high frequency power source 24.

In before time t _0, the laser processing system 10 is normal, the length of the high level shot command S ₁ is adjusted in a normal range according to the recipe. The drive control unit 38 outputs the drive signal S ₄ during the operation period instructed by the shot command S ₁ to cause the laser device 26 to emit light.

After time t _0, an abnormal state is indicated. The abnormal state is assumed to be a state in which an abnormality has occurred in the machining control device 46 or other parts, or is affected by noise. Shot command S ₁ on-time in an abnormal state (duty ratio), taking the normal range greater than the power consumption of the high frequency power source 24, it is power supplied to the laser device 26 increases. Determining unit 36, based on the shot instruction S _1, estimates the amount of energy introduced during a predetermined period.

When the duty ratio of the shot command S ₁ is greater condition persists, the estimated value of the energy input in a predetermined time period is gradually increased. The estimated value of the energy exceeds the threshold value TH at time t _1, a transition to a low level flag S ₃ designates prohibition. Thus after time t _1, the power supply control unit 34, also as a shot instruction S ₁ is to direct the operation period, it is masked, the high-frequency power source 24 does not supply the driving signal S _4.

The threshold value TH may be defined in consideration of the withstand voltage and heat resistance of the portion of the light source 20 to be protected. For example, in an application in which the withstand voltage of the semiconductor switch of the high-frequency inverter 25 is a problem, the threshold value TH may be set so that the voltage across the semiconductor switch does not exceed the withstand voltage. In an application in which the heat generation of the semiconductor switch is a problem, the semiconductor The threshold value TH may be set so that the temperature of the switch does not exceed the permissible value. In an application in which the reliability of the discharge electrode 27 of the laser device 26 is a problem, the threshold value TH may be set so that the discharge electrode 27 does not deteriorate.

The above is the operation of the light source 20 and the laser processing system 10 according to the embodiment. According to the laser processing system 10, based on the history of the shot instruction S _1, the state of the high frequency power supply 24 and laser device 26 it is determined whether the safety or not, only if it is safe, emission of the laser is allowed. That is, it is possible to prevent the reliability of the device from being lowered due to excessive energy input, so that the reliability can be further improved.

FIG. 4 is a functional block diagram showing a configuration example of the determination unit 36. The determination unit 36 includes a duty ratio detection unit 60, a moving average processing unit 62, and a comparison unit 64. These functional blocks can be realized by software processing, but may be implemented by hardware. The duty ratio detection unit 60 measures the high level section (operating period) T _ON of the shot command S ₁ and the repetition period T _P , respectively, and calculates the duty ratio S ₅ = (T _ON / T _P ) which is the ratio between them. .. The time may be measured with a digital counter.

The moving average processing unit 62 calculates the moving average value S ₆ of the duty ratio S ₅ . The comparison unit 64 compares the moving average value S ₆ with the threshold value S ₇ and generates a flag S ₃ indicating the comparison result.

In the determination unit 36, the moving average value S ₆ represents the amount of energy per predetermined period. Therefore, the process of FIG. 3 can be realized.

The power supply control device 34 according to the embodiment has (i) a protection method for forcibly discharging when the voltage of the snubber capacitor exceeds the threshold value, and (ii) a high frequency when the voltage between both ends of the semiconductor switch exceeds the threshold value. It can be used in combination with a protection method for stopping the power supply 24, (iii) a protection method for stopping the high frequency power supply 24 when the temperature of the semiconductor switch or other parts exceeds the threshold value. By using these in combination, the reliability of the light source 20 can be further improved.

In the embodiment, the shot command S ₁ is described for binary signals platform, the signal format of the shot command S ₁ is not limited. For example shot command S ₁ may be a serial data or parallel data, and data that specifies the length of the on time T _ON, and the data that specifies the length of the off time T _OFF, may contain.

In the embodiment, to calculate the moving average of the duty ratio shot command S ₁ is defined not limited thereto. For example analyzes the history of the pattern shot command S _1, may generate a flag S ₃ by the more sophisticated signal processing.

The present invention has been described using specific terms and phrases based on the embodiments, but the embodiments show only one aspect of the principles and applications of the present invention, and the embodiments are claimed. Many modifications and arrangement changes are permitted within the range not departing from the idea of the present invention defined in the scope.

2 ... Object, 10 ... Laser processing system, 20 ... Light source, 22 ... DC power supply, 24 ... High frequency power supply, 25 ... High frequency inverter, 26 ... Laser device, 27 ... Electrode, 28, 30 ... Light source side control device, 32 ... System controller, 34 ... Power control device, 36 ... Judgment unit, 38 ... Drive control unit, 40 ... Processing machine, 42 ... Optical system, 44 ... Stage, 46 ... Processing control device, 50, 52 ... Laser pulse, S ₁ ... Shot command, S ₂ ... position control signal, S ₃ ... flag, S ₄ ... drive signal.

Claims (4)

A power supply control device that controls a high-frequency power supply that intermittently supplies AC voltage to a laser device.
Based on the history of shot commands instructing the operation and stop of the high-frequency power supply, an estimated value having a correlation with the power consumption of the light source per predetermined time interval is generated, and when the estimated value is smaller than the threshold value, the above-mentioned A determination unit that indicates permission to operate the high-frequency power supply and generates a flag indicating prohibition when the estimated value is larger than the threshold value .
When the shot command indicates operation and the flag indicates permission, the drive control unit that operates the high-frequency power supply and
A power control device characterized by comprising. The shot command is a binary signal that takes a first state when instructing an operation and a second state when instructing a stop.
The power supply control device according to claim 1, wherein the estimated value is a moving average of the duty ratio of the shot command . Laser device and
A high-frequency power supply that intermittently supplies AC voltage to the laser device,
The power supply control device according to claim 1 or 2, which controls the high frequency power supply.
A light source for a laser processing system, which comprises. A method of generating a high-frequency power supply that intermittently supplies AC voltage to a laser device.
A step of generating a shot command instructing the operation and stop of the high-frequency power supply, and
A step of generating an estimated value that correlates with the power consumption of the light source per predetermined time interval based on the history of the shot command .
A step of generating a flag indicating permission for operation of the high frequency power supply when the estimated value is smaller than the threshold value and prohibition when the estimated value is larger than the threshold value .
When the shot command indicates operation and the flag indicates permission, the step of operating the high frequency power supply and
A control method characterized by comprising.

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