Plasma generation device, control device, and control method

Abstract

This plasma generation device comprises: a plasma head having a pair of electrodes for converting a flowing process gas to plasma by using an applied voltage; and a control device having a main control unit for outputting a signal to a power control unit, and a power control unit for supplying electric power to the plasma head on the basis of the signal received from the main control unit. The main control unit stops the supply of electric power to the power control unit when the state of the power control unit assessed on the basis of a power unit signal from the power control unit is an abnormal state. The power control unit stops the supply of electric power to the plasma head when the state of the main control unit assessed on the basis of a control unit signal from the main control unit is an abnormal state.

Description

Plasma generating device, control device, and control method

[0001] This specification discloses a plasma generation device, a control device, and a control method.

[0002] Conventionally, a plasma generator has been proposed that includes, for example, an oscillator that generates high-frequency radio waves, a circuit that processes the high-frequency radio waves generated by the oscillator, a transmitter that transmits the high-frequency radio waves processed by the circuit, and a plasma generator that generates plasma using the high-frequency radio waves transmitted by the transmitter (see, for example, Patent Document 1). In this device, an operation control unit serving as a main control unit monitors and controls the current in a power supply unit serving as a power control unit, thereby stabilizing the current.

[0003] Japanese Patent Application Laid-Open No. 2001-357999

[0004] However, in the above-mentioned plasma generating device, consideration is given to the case where an abnormality occurs in the power control unit that supplies power to the plasma head, but consideration is not given to the case where an abnormality occurs in the main control unit.

[0005] The present disclosure has been made in consideration of such problems, and a main object of the present disclosure is to provide a plasma generation device, a control device, and a control method that can perform plasma processing more safely.

[0006] In order to achieve the above-mentioned main object, the present disclosure has adopted the following parts.

[0007] The plasma generating device of the present disclosure comprises a control device having a plasma head having a pair of electrodes that converts a flowing process gas into plasma by an applied voltage, a main control unit that outputs a signal to a power control unit, and a power control unit that supplies power to the plasma head based on a signal received from the main control unit, wherein the main control unit stops supplying power to the power control unit when the state of the power control unit determined based on the power unit signal from the power control unit is abnormal, and the power control unit stops supplying power to the plasma head when the state of the main control unit determined based on the control unit signal from the main control unit is abnormal.

[0008] In this plasma generator, if an abnormality occurs in the power control unit, the main control unit stops the power supply to the power control unit, and if an abnormality occurs in the main control unit, the power control unit stops the power supply to the plasma head. Therefore, even if an abnormality occurs in either control unit, plasma processing can be performed more safely.

[0009] 1 is a schematic explanatory diagram showing an example of a plasma generation device 11. FIG. 2 is a perspective view and a cross-sectional view of a plasma head 40. FIG. 3 is a flowchart showing an example of a plasma processing routine. FIG. 4 is an explanatory diagram showing an example of an error notification screen 70. FIG. 5 is a flowchart showing an example of a power management processing routine. FIG. 6 is an explanatory diagram showing an example of signal exchange between a main control unit 21 and a power control unit 22.

[0010] This embodiment will be described below with reference to the drawings. Fig. 1 is a schematic diagram showing an example of a plasma generator 11. Fig. 2 is a perspective view and a cross-sectional view of a plasma head 40. In this embodiment, the left-right direction (X-axis), front-rear direction (Y-axis), and up-down direction (Z-axis) are assumed to be as shown in Fig. 1 for convenience. Here, the plasma generator 11 will be described as an atmospheric pressure plasma generator, for example.

[0011] The plasma generator 11 is a device that generates plasma under atmospheric pressure. As shown in Fig. 1, the plasma generator 11 includes an arm robot 12, a control device 20, a power supply device 28, a gas supply device 29, and a plasma head 40. The plasma generator 11 supplies power from the power supply device 28 via a power cable to the plasma head 40 via the control device 20, and supplies a process gas to be converted into plasma from the gas supply device 29 via a supply pipe. The plasma generator 11 irradiates the workpiece W with plasma gas from the plasma head 40 to perform surface treatment of the workpiece W.

[0012] The arm robot 12 is configured as a moving unit that moves the plasma head 40 to approach and move away from the workpiece W. The arm robot 12 may be configured as, for example, a vertically articulated five-axis robot or a six-axis robot. The arm robot 12 has a mounting unit 13, an arm 14, a drive motor 15, and a base 16. The mounting unit 13 is a portion to which the plasma head 40 can be attached and detached, and is disposed at the tip of the arm 14. The arm 14 is made up of multiple members pivotally supported by joint shafts and freely rotates around the joint shafts to move the plasma head 40 in three-dimensional space in the front-to-back, left-to-right, and up-to-down directions. The drive motor 15 is disposed on each joint shaft and drives the joint shafts to rotate. The base 16 supports and installs the arm 14. Note that, although the arm robot 12 is used as the moving unit here, an XY robot capable of moving the plasma head 40 in the up-to-down direction may also be used, provided that the plasma head 40 can be freely moved.

[0013] The control device 20 controls each device of the plasma generator 11. The control device 20 includes a main control unit 21, a power control unit 22, a memory unit 23, a communication unit 24, a display unit 25, and an operation unit 26. The main control unit 21 is configured as a microprocessor centered on a CPU and is a unit that controls the entire plasma generator 11. The main control unit 21 outputs control signals to the arm robot 12, the power control unit 22, the power supply unit 28, the gas supply unit 29, the plasma head 40, and the like. As will be described in detail later, the main control unit 21 determines the state of the power control unit 22 based on a power unit signal from the power control unit 22. The main control unit 21 outputs a control unit signal to the power control unit. The control unit signal is a periodic signal that has the same voltage as the power unit signal input from the power control unit 22 and a longer period than the power unit signal. The power unit signal and the control unit signal are signals used to detect whether each control unit is operating normally. The power control unit 22 is one of the sub-controllers and is a unit that controls the power supply. The power control unit 22 supplies power to the plasma head 40 based on a signal received from the main control unit 21. The power control unit 22 also inputs the power to be supplied to the plasma head 40 via the main control unit 21. The power control unit 22 determines the state of the main control unit 21 based on a control signal from the main control unit 21. The memory unit 23 is a large-capacity storage medium such as a flash memory, and stores a program for controlling the plasma generator 11 and job information including the shape of the workpiece W and the surface treatment position. The memory unit 23 also stores execution condition information including the execution conditions of the plasma treatment. The execution condition information includes the pressure and flow rate of the process gas, the voltage and current of the supplied power, etc. The communication unit 24 is an interface for exchanging information with an external device such as a management server (not shown). The display unit 25 is a display that displays information to the operator M. The operation unit 26 is used by the operator M to input various information and includes various buttons, levers, etc. The display unit 25 may be a touch panel that also functions as the operation unit 26.In the plasma generating device 11, the arm robot 12, power supply device 28, gas supply device 29, and plasma head 40 are described as being controlled by the main control unit 21 and power control unit 22 of the control device 20, but a control unit may be provided in each device to be controlled, or each control process may be shared among multiple control units.

[0014] The power supply device 28 is a device that supplies power to the external electrode 41 and the internal electrode 42. The power supply device 28 generates high-frequency AC power from, for example, a commercial power source to be supplied to the pair of external electrode 41 and internal electrode 42 of the plasma head 40. The power supply device 28 supplies the generated AC power to the external electrode 41 and internal electrode 42 of the plasma head 40 via the control device 20.

[0015] The gas supply device 29 supplies a process gas to the outer electrode 41 and the inner electrode 42 of the plasma head 40. The gas supply device 29 may be configured to supply, by pressure, air or the like containing at least one of an inert gas such as nitrogen and an active gas such as oxygen as the process gas. The gas supply device 29 includes a supply pipe, a supply valve, and a gas supply tank. The supply pipe is a pipe connected between the supply tank of the gas supply device 29 and the plasma head 40. The supply valve is an electromagnetic valve that starts and stops the supply of the process gas. The gas supply device 29 may also include a heater for heating the process gas supplied to the plasma head 40, if necessary.

[0016] The plasma head 40 irradiates a plasma gas onto the workpiece W supported on a work table to modify the surface of the workpiece W. Examples of surface modification include a modification process that changes the surface from hydrophobic to hydrophilic. The plasma head 40 is removably attached to the mounting portion 13 of the arm robot 12. A nozzle 47 that irradiates the plasma gas generated by the plasma head 40 is provided at the bottom of the plasma head 40. The plasma head 40 includes an external electrode 41, an internal electrode 42, a drive portion 43, a support portion 44, and the nozzle 47.

[0017] The external electrode 41 is a member having a nozzle 47 formed therein and through which the process gas flows. The external electrode 41 is electrically grounded via a brush. As shown in FIG. 2 , the external electrode 41 is fixed to a holder 41 a. The holder 41 a is a cylindrical member disposed at the tip end of the main body 48 and through which the process gas flows. The internal electrode 42 is housed inside the holder 41 a connected to the external electrode 41 and converts the process gas into plasma between the holder 41 and the external electrode 41. The internal electrode 42 is fixed to the holder 42 a and electrically connected to a power cable connected to the power supply 28. A voltage is applied to the process gas using power supplied from the power supply 28. The holder 42 a is connected to the power supply 28 and is formed so that its tip is tapered, allowing the internal electrode 42 to be inserted therein. In the plasma head 40, a voltage is applied to the process gas supplied between the external electrode 41 and the internal electrode 42 to convert the process gas into plasma and generate plasma gas. The nozzle 47 is a tip member having a discharge port formed therein for discharging plasma gas. The nozzle 47 is disposed at the lower end of the plasma head 40 so as to face the workpiece W.

[0018] The drive unit 43 is a motor that rotates the main body 48 at the tip side of the plasma head 40. The plasma head 40 irradiates the workpiece W with plasma gas while rotating the main body 48. The main body 48 is provided with an external electrode 41, an internal electrode 42, a nozzle 47, and the like. The support unit 44 is a member that supports the main body 48 of the plasma head 40 so that it can rotate around its axis. The support unit 44 is removably attached to the attachment unit 13. In addition to supporting the main body 48, the support unit 44 also supports a supply pipe connected to the gas supply device 29, a power cable connected to the power supply device 28, and the like. Note that although the plasma head 40 rotates the main body 48, this rotation may not be necessary.

[0019] Next, a surface modification process for the workpiece W using the plasma generator 11 configured as described above will be described. Fig. 3 is a flowchart showing an example of a plasma processing routine executed by the main control unit 21 of the control device 20. This routine is stored in the memory unit 23 and is executed by the main control unit 21 after an effective input for the plasma processing is made by the operator M. When this routine starts, the main control unit 21 first reads out execution condition information for the plasma processing from the memory unit 23 and acquires the execution conditions (S100). The execution condition information includes the pressure and flow rate of the process gas, the voltage value and current value of the supplied power, etc.

[0020] Next, the main control unit 21 determines whether or not there is an abnormality in the power control unit 22 (S110). The main control unit 21 makes this determination based on the power unit signal, which is a periodic signal output from the power control unit 22 to the main control unit 21. Examples of abnormal states include a freeze state, a circuit failure, or a failure in the I / O signal input / output unit. The main control unit 21 may determine that the power control unit 22 is in an abnormal state when the power unit signal is not input from the power control unit 22 for a first predetermined time. The first predetermined time may be, for example, an empirically determined time period during which an abnormality in the power control unit 22 can be determined. Since the main control unit 21 is a higher-level device, it can more quickly determine the detection of an abnormality in the power control unit 22, which is a lower-level device, using the power unit signal with a short period. If there is no abnormality in the power control unit 22, the main control unit 21 instructs the power control unit 22 to supply power from the power supply device 28 according to the acquired execution conditions and controls the gas supply device 29 to supply process gas, thereby performing plasma processing on the workpiece W (S150). Next, the main control unit 21 determines whether the plasma processing is complete based on, for example, the execution time (S160). If the plasma processing is not complete, the main control unit 21 executes the processing from S110 onward, and if the plasma processing is complete, the main control unit 21 ends this routine.

[0021] On the other hand, if an error occurs in the power control unit 22 in S110, the main control unit 21 stops the power supply to the power control unit 22 (S120). By stopping the power supply to the power control unit 22, the main control unit 21 can safely and reliably stop the power supply to the plasma head 40 from the abnormal power control unit 22. The main control unit 21 then displays an error notification screen 70 on the display unit 25 (S130). FIG. 4 is an explanatory diagram showing an example of the error notification screen 70. The error notification screen 70 includes a notification information display field 71 and a transition instruction input field 72. The notification information display field 71 displays information to be notified to the operator M as a message. The notification information display field 71 displays a message outlining the error state and its error code. The transition instruction input field 72 is a key operated to transition to the next screen, and includes, for example, a setting key operated to display details of the error and a reset key operated to reset the device. When the worker M checks the error notification screen 70, he or she restarts the device or performs maintenance.

[0022] After S130, the main control unit 21 determines whether the abnormal state of the power control unit 22 has been resolved (S140). If the abnormal state has not been resolved, the main control unit 21 executes the processes from S120 onward. That is, the main control unit 21 stops the power supply to the power control unit 22 and notifies the user of the details of the abnormal state. On the other hand, if the abnormal state of the power control unit 22 has been resolved, the main control unit 21 executes the processes from S150 onward. That is, the main control unit 21 supplies power to the power control unit 22 and resumes plasma processing. Note that although the main control unit 21 determines that the abnormal state has been resolved in S140, because the abnormal state of the power control unit 22 is rarely resolved by simple measures, this routine may be terminated after S130. In this way, the main control unit 21 detects the abnormal state of the power control unit 22 based on the power unit signal from the power control unit 22 and stops the high-output power supply to ensure safety.

[0023] Next, the electrode supply management process by the power control unit 22 will be described. FIG. 5 is a flowchart illustrating an example of a power management process routine executed by the power control unit 22. This routine is repeatedly executed during the plasma processing routine after the control device 20 is started. When this routine starts, the power control unit 22 first determines whether or not there is an abnormality in the main control unit 21 based on a control unit signal from the main control unit 21 (S200). The power control unit 22 receives a control unit signal, which is a periodic signal with a longer period than the power unit signal, from the main control unit 21. This control unit signal has the same voltage as the power unit signal. The power control unit 22 determines that the main control unit 21 is in an abnormal state when the periodic control unit signal received from the main control unit 21 is not received for a second predetermined period. The second predetermined period may be set to, for example, an empirically determined time period during which an abnormality in the main control unit 21 can be determined. If there is no abnormality in the main control unit 21, the power control unit 22 supplies power to the plasma head 40 based on the control signal from the main control unit 21 (S230) and ends this routine. The power control unit 22 may output the power supplied from the power supply device 28 directly to the plasma head 40 .

[0024] On the other hand, if an abnormality is detected in the main control unit 21 in S200, the power control unit 22 stops the power supply to the plasma head 40 (S210) and waits until the abnormality is resolved (S220). In this plasma generator 11, the power control unit 22 monitors the main control unit 21 and takes measures such as stopping the power supply when an abnormality occurs in the main control unit 21. If the operator M notices an abnormality in the main control unit 21, for example, due to an abnormal display on the display unit 25, he or she can take measures such as restarting the device or performing maintenance. If the abnormality in the main control unit 21 is resolved in S220, the power control unit 22 resumes the power supply to the plasma head 40 in S230, and this routine ends.

[0025] FIG. 6 is an explanatory diagram showing an example of signal exchange between the main control unit 21 and the power control unit 22. FIG. 6A shows a normal state, FIG. 6B shows an abnormal state of the power control unit 22, and FIG. 6C shows an abnormal state of the main control unit 21. As shown in FIG. 6A, under normal conditions, the power control unit 22 outputs a periodic power unit signal, and the main control unit 21 outputs a periodic control unit signal with the same voltage as the power unit signal but a longer period, thereby monitoring each other. In a conventional plasma generator 11, the main control unit 21, which is a higher-level control unit, may monitor the power control unit 22. However, if the main control unit 21 freezes or the I / O signal input / output unit fails during operation of the plasma generator 11, for example, an abnormality in the power control unit 22 may be falsely detected, the power control unit 22 may not detect that the main control unit 21 is in an abnormal state and may maintain its output state, or the main control unit 21 may not be able to control the power control unit 22, causing the power control unit 22 to continue outputting even when the operation is stopped due to an operation stop operation. In this plasma generator 11, a main control unit 21, which is a control unit, and a power control unit 22, which is a power supply unit, monitor each other using a watchdog signal. The main control unit 21 and the power control unit 22 repeatedly switch the output watchdog signal from Hi to Lo at regular intervals, and if the input watchdog signal does not change state within the regular interval, they determine that there is an abnormality and stop the operation. Therefore, in the plasma generator 11, even if either the main control unit 21 or the power control unit 22 freezes or if either the I / O signal input / output unit of the main control unit 21 or the power control unit 22 fails, the operation can be stopped and an abnormality can be detected.

[0026] Here, the correspondence between the components of this embodiment and the components of the present disclosure will be clarified. The control device 20 of this embodiment is an example of a control device of the present disclosure, the main control unit 21 is an example of a main control unit, the power control unit 22 is an example of a power control unit, the external electrode 41 and the internal electrode 42 are an example of a pair of electrodes, the plasma head 40 is an example of a plasma head, and the plasma generation device 11 is an example of a plasma generation device. Note that in this embodiment, an example of a control method of the present disclosure is also clarified by explaining the operation of the plasma generation device 11.

[0027] The plasma generator 11 of the present embodiment described above includes a plasma head 40 having a pair of electrodes that converts a flowing process gas into plasma by applying a voltage thereto, and a control device 20 having a main control unit 21 that outputs a signal to a power control unit 22 and a power control unit 22 that supplies power to the plasma head 40 based on a signal received from the main control unit 21. The main control unit 21 stops supplying power to the power control unit 22 when the state of the power control unit 22 is determined to be abnormal based on the power unit signal from the power control unit 22, and the power control unit 22 stops supplying power to the plasma head 40 when the state of the main control unit 21 is determined to be abnormal based on the control unit signal from the main control unit 21. In this plasma generator 11, the main control unit 21 stops the power supply to the power control unit 22 when an abnormality occurs in the power control unit 22, and the power control unit 22 stops supplying power to the plasma head 40 when an abnormality occurs in the main control unit 21. Therefore, regardless of whether an abnormality occurs in either control unit, plasma processing can be performed and stopped more safely.

[0028] The power control unit 22 outputs a periodic power unit signal to the main control unit 21, and the main control unit 21 outputs a periodic control unit signal, which has a longer period than the power unit signal, to the power control unit 22. This plasma generator 11 can determine an abnormality using the periodic signal. The power control unit 22 can monitor the main control unit 21 relatively slowly. Furthermore, the power control unit 22 inputs power to be supplied to the plasma head 40 via the main control unit 21, and the main control unit 21 stops power supplied to the plasma head 40 when the power control unit 22 is in an abnormal state. This plasma generator 11 can ensure safety by having the main control unit 21 stop power to the plasma head. Furthermore, the main control unit 21 determines that the power control unit is in an abnormal state when the power unit signal is not input from the power control unit 22 for a first predetermined time, and the power control unit 22 determines that the main control unit 21 is in an abnormal state when the control unit signal is not input from the main control unit 21 for a second predetermined time. In this plasma generator 11, an abnormality in each control unit can be determined as a predetermined time elapses. The first predetermined time may be shorter, longer, or the same as the second predetermined time. The main control unit 21 may output a control unit signal to the power control unit, the control unit signal having the same voltage as the power unit signal input from the power control unit 22. In this plasma generator 11, the voltage can be uniformly controlled.

[0029] It goes without saying that the plasma generation device, control device, and control method of the present disclosure are in no way limited to the above-described embodiments, and can be implemented in various forms as long as they fall within the technical scope of the present disclosure.

[0030] For example, in the above-described embodiment, the main control unit 21 outputs a control unit signal with a long cycle, but this is not limited to this, and the main control unit 21 may output a control unit signal with the same cycle as the power unit signal or a shorter cycle. In this plasma generation device 11, the power supply can also be stopped when an abnormality occurs in the control device 20, making it possible to perform plasma processing more safely.

[0031] In the above-described embodiment, the main control unit 21 determines an abnormality in the power control unit 22 by using a watchdog timer when no power unit signal is input for a first predetermined time, but the present invention is not limited to this, as long as the abnormality determination is based on the input and output of a predetermined signal. Similarly, the power control unit 22 determines an abnormality in the main control unit 21 by using a watchdog timer when no control unit signal is input for a second predetermined time, but the present invention is not limited to this, as long as the abnormality determination is based on the input and output of a predetermined signal.

[0032] In the above-described embodiment, the control signal and the power signal have the same voltage, but this is not limited thereto and they may have different voltages. In consideration of the circuit configuration and operating voltage of the control device 20, it is preferable to use signals of the same voltage.

[0033] In the above-described embodiment, the present disclosure has been described as a plasma generating device 11, but is not limited to this and may be a control device 20, a control method for the plasma generating device 11, or a program therefor.

[0034] This specification also discloses the technical idea of ​​changing "the plasma generator according to claim 1 or 2" in claim 4 as originally filed to "the plasma generator according to any one of claims 1 to 3," and the technical idea of ​​changing "the plasma generator according to claim 1 or 2" in claim 5 as originally filed to "the plasma generator according to any one of claims 1 to 4."

[0035] The present disclosure is applicable to the technical field of processing the surface of a workpiece.

[0036] REFERENCE SIGNS LIST 11 Plasma generator, 12 Arm robot, 13 Mounting unit, 14 Arm, 15 Drive motor, 16 Base unit, 20 Control device, 21 Main control unit, 22 Power control unit, 23 Memory unit, 24 Communication unit, 25 Display unit, 26 Operation unit, 28 Power supply unit, 29 Gas supply device, 40 Plasma head, 41 External electrode, 41a Holder, 42 Internal electrode, 42a Holder, 43 Drive unit, 44 Support unit, 45 Fixing member, 47 Nozzle, 48 Main body, 70 Error notification screen, 71 Notification information display field, 72 Transition instruction input field, M Operator, W Work.

Claims

1. A plasma generation device comprising: a control device having a plasma head having a pair of electrodes that converts a flowing process gas into plasma by an applied voltage; a main control unit that outputs a signal to a power control unit; and a power control unit that supplies power to the plasma head based on a signal received from the main control unit, wherein the main control unit stops supplying power to the power control unit when the state of the power control unit determined based on the power unit signal from the power control unit is abnormal, and the power control unit stops supplying power to the plasma head when the state of the main control unit determined based on the control unit signal from the main control unit is abnormal.

2. The plasma generation device according to claim 1, wherein the power control unit outputs the power unit signal, which is a periodic signal, to the main control unit, and the main control unit outputs the control unit signal, which is a periodic signal having a longer period than the power unit signal, to the power control unit.

3. A plasma generating device as described in claim 1 or 2, wherein the power control unit inputs the power to be supplied to the plasma head via the main control unit, and the main control unit stops the power supplied to the plasma head when the power control unit is in an abnormal state.

4. A plasma generating device as described in claim 1 or 2, wherein the main control unit determines that the power control unit is in an abnormal state when the power unit signal is not input from the power control unit for a first predetermined time, and the power control unit determines that the main control unit is in an abnormal state when the control unit signal is not input from the main control unit for a second predetermined time.

5. The plasma generating device according to claim 1 or 2, wherein the main control unit outputs the control unit signal to the power control unit, the control unit signal having the same voltage as the power unit signal input from the power control unit.

6. A control device used in a plasma generating device equipped with a plasma head having a pair of electrodes that converts a flowing process gas into plasma by an applied voltage, the control device comprising: a main control unit that outputs a signal to a power control unit; and a power control unit that supplies power to the plasma head based on a signal received from the main control unit, wherein the main control unit stops supplying power to the power control unit when the state of the power control unit determined based on the power unit signal from the power control unit is abnormal, and the power control unit stops supplying power to the plasma head when the state of the main control unit determined based on the control unit signal from the main control unit is abnormal.

7. A control method in which a computer controls a plasma generating device comprising: a plasma head having a pair of electrodes that converts a flowing process gas into plasma by an applied voltage; and a control device having a main control unit that outputs a signal to a power control unit and a power control unit that supplies power to the plasma head based on a signal received from the main control unit, the control method comprising: a step in which the main control unit stops supplying power to the power control unit when the state of the power control unit determined based on a power unit signal from the power control unit is abnormal; and a step in which the power control unit stops supplying power to the plasma head when the state of the main control unit determined based on a control unit signal from the main control unit is abnormal.

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