JP7487296B2 - Plasma generating device, plasma generating method, and control device - Google Patents

Description

This disclosure relates to a plasma generating device that performs plasma processing using nitrogen.

In the plasma generating device, plasma processing is performed using nitrogen as an inert gas, as described in the following patent document:

Japanese Patent Application Laid-Open No. 10-034343

The objective of this specification is to provide a plasma generator that can appropriately supply nitrogen.

In order to solve the above problems, the present specification discloses a plasma generating device comprising: a plasma head having an electrode for generating plasma; a nitrogen supplying device having a membrane for separating nitrogen gas having a predetermined concentration or more from a nitrogen-containing gas and supplying the nitrogen gas to the electrode; a mixed gas tube connected to the nitrogen supplying device for supplying a mixed gas of the nitrogen gas and air to the plasma head; and a nitrogen gas tube connected to the nitrogen supplying device for supplying nitrogen gas having a predetermined concentration or more to the plasma head, the plasma generating device comprising: a second nitrogen gas supplying path between the nitrogen supplying device and a first nitrogen gas supplying path; and a third nitrogen gas supplying path between the nitrogen gas tube and the second nitrogen gas supplying path, the second nitrogen gas supplying path being branched into the first nitrogen gas supplying path and the third nitrogen gas supplying path; an oxygen concentration detector on the second nitrogen gas supplying path for detecting the oxygen concentration of the nitrogen gas separated by the membrane; and a voltage is applied to the electrode when the nitrogen concentration detected using the oxygen concentration detector reaches a predetermined concentration .

The present specification also discloses a plasma generation method for generating plasma by using a nitrogen supply device that supplies nitrogen gas through a membrane that separates nitrogen gas at a predetermined concentration or higher from a nitrogen-containing gas to supply a mixed gas of nitrogen gas and air through a mixed gas tube to an electrode of a plasma head, and by using the nitrogen supply device to supply nitrogen gas at a predetermined concentration or higher to the electrode of the plasma head through a nitrogen gas tube , wherein a second nitrogen gas supply path is disposed between the nitrogen supply device and a first nitrogen gas supply path, and a third nitrogen gas supply path is disposed between the nitrogen gas tube and the second nitrogen gas supply path, the second nitrogen gas supply path branches into the first nitrogen gas supply path and the third nitrogen gas supply path, an oxygen concentration detector that detects the oxygen concentration of the nitrogen gas separated by the membrane is disposed on the second nitrogen gas supply path, and when the nitrogen concentration detected using the oxygen concentration detector reaches a predetermined concentration, a voltage is applied to the electrode to generate plasma .

The present specification also relates to a control device for a plasma generation device having a plasma head in which an electrode for generating plasma is disposed, the plasma generation device having a membrane for separating nitrogen gas having a predetermined concentration or more from a gas containing nitrogen, the control device including a nitrogen supply device for supplying the nitrogen gas to the electrode, a mixed gas tube connected to the nitrogen supply device for supplying a mixed gas of the nitrogen gas and air to the plasma head, a nitrogen gas tube connected to the nitrogen supply device for supplying nitrogen gas having the predetermined concentration or more to the plasma head, a second nitrogen gas supply path between the nitrogen supply device and a first nitrogen gas supply path, and a control device for controlling the nitrogen gas tube. and a third nitrogen gas supply path between the second nitrogen gas supply path , the second nitrogen gas supply path branching into the first nitrogen gas supply path and the third nitrogen gas supply path, the plasma generating device having an oxygen concentration detector on the second nitrogen gas supply path for detecting the oxygen concentration of the nitrogen gas separated by the membrane, the nitrogen supply device being disposed in the control device, the control device being separate from the plasma head, supplying nitrogen gas from the nitrogen supply device to the plasma head , and applying a voltage to the electrode when the nitrogen concentration detected using the oxygen concentration detector reaches a predetermined concentration .

According to the present disclosure, nitrogen gas is supplied to the electrodes from a nitrogen supply device having a membrane that separates nitrogen gas at a predetermined concentration or higher from a nitrogen-containing gas. This allows nitrogen to be appropriately supplied to the electrodes.

FIG. 1 is a diagram showing a plasma device. FIG. 4 is a schematic diagram showing a gas supply unit. FIG. 2 is a cross-sectional view showing a nitrogen separation device. FIG. 2 is a perspective view showing a plasma head. 1 is a cross-sectional view of the plasma head cut in the X direction and the Z direction at the positions of the electrodes and the plasma passage on the main body side. FIG. FIG. 6 is a cross-sectional view taken along line AA in FIG. 5 . FIG. 1 is a diagram showing a conventional plasma generating device. FIG. 13 is a diagram showing a modified example of a plasma generating device.

Below, an embodiment of the present invention will be described in detail with reference to the drawings as a mode for carrying out the present invention.

As shown in FIG. 1, the plasma device 10 includes a plasma head 11, a robot 13, and a control box 15. The plasma head 11 is attached to the robot 13. The robot 13 is, for example, a serial link type robot (which can also be called an articulated robot). The plasma head 11 is capable of irradiating plasma gas while being held at the tip of the robot 13. The plasma head 11 is capable of moving three-dimensionally in response to the drive of the robot 13.

The control box 15 is mainly composed of a computer, and controls the plasma device 10. The control box 15 has a power supply unit 15A that supplies power to the plasma head 11, and a gas supply unit 15B that supplies gas to the plasma head 11. The power supply unit 15A is connected to the plasma head 11 via a power cable 17. The power supply unit 15A changes the voltage applied to the electrode 73 (see Figures 3 and 4) of the plasma head 11 based on the control of the control box 15.

The gas supply unit 15B is connected to the plasma head 11 via multiple (four in this embodiment) gas tubes 19, and supplies reactive gas, carrier gas, and heat gas to the plasma head 11 under the control of the control box 15. In detail, as shown in FIG. 2, the gas supply unit 15B has a pump 20, a nitrogen separator 22, an air supply path 24, a nitrogen supply path 26, a mixed gas supply path 28, multiple flow regulators 30, a mixer 32, and an oxygen concentration detector 34. The pump 20 sends out compressed air and is connected to one end of the air supply path 24. The compressed air used is factory air used in factories. In other words, the pump 20 is for generating factory air, and factory air is used as the compressed air supplied to the air supply path 24. The other end of the air supply path 24 branches into three. Of the three branched air supply lines 24, the first air supply line 24a is connected to the mixer 32, the second air supply line 24b is connected to the nitrogen separator 22, and the third air supply line 24c is connected to the gas tube 19d.

The nitrogen separation device 22 is a device that separates nitrogen at a predetermined concentration or higher (hereinafter referred to as "nitrogen-rich gas") from air, i.e., gas containing nitrogen, and is composed of a housing 50 and a separation membrane 52, as shown in FIG. 3. The housing 50 is generally cylindrical, and a through hole 54 is formed in the housing 50, penetrating from the inner peripheral surface to the outer peripheral surface. The inside of the housing 50 is filled with a separation membrane 52, which is a hollow fiber-shaped polymer membrane. An air supply channel 24b is connected to one end of the housing 50, and a nitrogen supply channel 26 is connected to the other end of the housing 50.

With this structure, the nitrogen separator 22 separates nitrogen-rich gas from the compressed air sent out from the pump 20 and supplies the nitrogen-rich gas to the nitrogen supply path 26. Specifically, when compressed air is sent in from one end of the housing 50, due to the difference in molecular size between nitrogen and oxygen, the nitrogen passes through the separation membrane 52 inside the housing 50 in the axial direction. On the other hand, oxygen cannot pass through the separation membrane 52 inside the housing 50 in the axial direction and is discharged in the radial direction. For this reason, nitrogen is separated from the compressed air sent in from one end of the housing 50 and sent out from the other end of the housing 50. The pressure of the compressed air sent into the housing 50 is 0.5 MPa. In addition, the gas from which nitrogen has been separated from the compressed air, that is, oxygen, is discharged from the through hole 54 of the housing 50. As a result, nitrogen-rich gas with a concentration of a predetermined concentration or more, for example, 99.9%, is supplied to the nitrogen supply path 26.

In the nitrogen separation device 22, the concentration of the nitrogen-rich gas to be separated is determined according to the length of the housing 50, that is, the capacity of the separation membrane 52 filled in the housing 50. For this reason, for example, in order to separate nitrogen-rich gas with a concentration of 99.9%, a nitrogen separation device 22 having a housing 50 with a length of 1 m or more is required, and the nitrogen separation device 22 is arranged in a vertically extending position inside the control box 15 as shown in FIG. 1. The nitrogen separation device 22 is arranged so that the end of the housing 50 into which compressed air is fed is located at the top and the end of the housing 50 from which rich gas is discharged is located at the bottom. In other words, the nitrogen separation device 22 is arranged inside the control box 15 so that compressed air is supplied from the top of the housing 50 of the nitrogen separation device 22 and rich gas is discharged from the bottom of the housing 50.

In addition, since the housing 50 has an outer diameter of 244 mm and a length of 1080 mm, the nitrogen separator 22 occupies a certain amount of space in the vertical direction inside the control box 15, but does not occupy much space in the horizontal direction. As described above, in the nitrogen separator 22, the gas in which nitrogen is separated from the compressed air, that is, oxygen, is discharged from the through hole 54 of the housing 50. On the other hand, a high-voltage current is passed through the power cable 17 that supplies current from the control box 15 to the electrode 73 of the plasma head 11. For this reason, in order to discharge oxygen, which has high combustion support, to a position away from the power cable 17 through which the high-voltage current is passed, the nitrogen separator 22 is disposed on the rear side inside the control box 15, and the through hole 54 opens to the rear of the control box 15.

As shown in FIG. 2, the end of the nitrogen supply line 26 opposite to the end connected to the nitrogen separation device 22 branches into three. The first nitrogen supply line 26a of the three branched nitrogen supply lines 26 is connected to the mixer 32, the second nitrogen supply line 26 is connected to the gas tube 19b, and the third nitrogen supply line 26c is connected to the gas tube 19c. The mixed gas supply line 28 is also connected to the mixer 32, and the compressed air supplied from the air supply line 24a and the nitrogen-rich gas supplied from the nitrogen supply line 26a are mixed in the mixer 32, and the mixed gas is supplied to the mixed gas supply line 28. The mixed gas supply line 28 is connected to the gas tube 19a.

With this structure, a mixed gas of compressed air and nitrogen-rich gas is supplied from the gas supply unit 15B to the gas tube 19a, nitrogen-rich gas is supplied to the gas tubes 19b and 19c, and compressed air is supplied to the gas tube 19c. In addition, a flow regulator 30a is arranged in the air supply path 24a, a flow regulator 30b is arranged in the nitrogen supply path 26a, a flow regulator 30c is arranged in the nitrogen supply path 26b, a flow regulator 30d is arranged in the nitrogen supply path 26c, and a flow regulator 30e is arranged in the air supply path 24c. This adjusts the flow rate of the gas supplied to each gas tube 19. In other words, the gas supply unit 15B supplies gases such as a mixed gas of compressed air and nitrogen-rich gas, nitrogen-rich gas, and compressed air to the plasma head 11 with the flow rate adjusted.

In addition, an oxygen concentration detector 34 is disposed at a non-branched portion of the nitrogen supply line 26 connected to the nitrogen separator 22. This allows the nitrogen concentration of the nitrogen-rich gas separated by the nitrogen separator 22 to be detected. That is, air contains nitrogen, oxygen, argon, and carbon dioxide as its main components, with the nitrogen content in air being approximately 78%, the oxygen content in air being approximately 21%, the argon content in air being approximately 0.9%, and the carbon dioxide content in air being approximately 0.03%. Therefore, the nitrogen-rich gas separated from the air is mostly nitrogen, except for oxygen. The nitrogen concentration of the nitrogen-rich gas separated by the nitrogen separator 22 is determined by subtracting the oxygen concentration detected by the oxygen concentration detector 34 from 100%. That is, for example, if the oxygen concentration detector 34 detects an oxygen concentration of 0.1%, the nitrogen concentration of the nitrogen-rich gas separated by the nitrogen separator 22 is 99.9 (=100-0.1)%. In this way, in the gas supply unit 15B, nitrogen-rich gas is separated from the compressed air, and the nitrogen concentration of the separated nitrogen-rich gas is managed by the oxygen concentration detector 34.

As shown in FIG. 1, the control box 15 also includes an operation unit 15C having a touch panel and various switches. The control box 15 displays various setting screens and operating states (e.g., gas supply state) on the touch panel of the operation unit 15C. The control box 15 also receives various information through operational input to the operation unit 15C.

As shown in FIG. 4, the plasma head 11 includes a plasma generating unit 60, a heat gas supply unit 62, and the like. The plasma generating unit 60 converts the processing gas supplied from the gas supply unit 15B of the control box 15 into plasma to generate plasma gas. The heat gas supply unit 62 heats the gas supplied from the gas supply unit 15B to generate heat gas. The plasma head 11 of this embodiment ejects the plasma gas generated in the plasma generating unit 60, together with the heat gas generated by the heat gas supply unit 62, onto the workpiece W shown in FIG. 1. The processing gas is supplied to the plasma head 11 from the upstream side to the downstream side in the direction of the arrow shown in FIG. 4. The plasma head 11 may be configured without including the heat gas supply unit 62. That is, the plasma device of the present disclosure may be configured without using heat gas.

5 and 6, the plasma generating unit 60 includes a head main body 71, a pair of electrodes 73, a plasma irradiation unit 75, and the like. FIG. 5 is a cross-sectional view cut in accordance with the positions of the pair of electrodes 73 and a plurality of main body side plasma passages 111 described later, and FIG. 6 is a cross-sectional view taken along line AA in FIG. 5. The head main body 71 is made of highly heat-resistant ceramic, and a reaction chamber 77 for generating plasma gas is formed inside the head main body 71. Each of the pair of electrodes 73 is, for example, cylindrical, and is fixed with its tip protruding into the reaction chamber 77. In the following description, the pair of electrodes 73 may be simply referred to as electrodes 73. The direction in which the pair of electrodes 73 are aligned is referred to as the X direction, the direction in which the plasma generating unit 60 and the heat gas supply unit 62 are aligned is referred to as the Y direction, and the axial direction of the cylindrical electrode 73 is referred to as the Z direction. In this embodiment, the X direction, the Y direction, and the Z direction are perpendicular to each other.

The heat gas supply unit 62 includes a gas pipe 81, a heater 83, a connection unit 85, etc. The gas pipe 81 and the heater 83 are attached to the outer circumferential surface of the head main body 71 and are covered by a cover 87 shown in FIG. 6. The gas pipe 81 is connected to the gas supply unit 15B of the control box 15 via a gas tube 19d (see FIG. 2). As a result, air is supplied from the gas supply unit 15B to the gas pipe 81. The heater 83 is attached midway along the gas pipe 81. The heater 83 heats the air flowing through the gas pipe 81 to generate heat gas.

As shown in FIG. 6, the connecting portion 85 connects the gas pipe 81 to the plasma irradiation portion 75. When the plasma irradiation portion 75 is attached to the head main body portion 71, one end of the connecting portion 85 is connected to the gas pipe 81, and the other end is connected to a heat gas passage 91 formed in the plasma irradiation portion 75. Heat gas is supplied to the heat gas passage 91 via the gas pipe 81.

As shown in FIG. 6, a part of the outer periphery of the electrode 73 is covered by an electrode cover 93 made of an insulator such as ceramics. The electrode cover 93 is generally hollow and cylindrical, with openings formed at both ends in the longitudinal direction. The gap between the inner periphery of the electrode cover 93 and the outer periphery of the electrode 73 functions as a gas passage 95. The downstream opening of the electrode cover 93 is connected to the reaction chamber 77. The lower end of the electrode 73 protrudes from the downstream opening of the electrode cover 93.

In addition, inside the head main body 71, a reaction gas flow path 101 and a pair of carrier gas flow paths 103 are formed. The reaction gas flow path 101 is provided in the approximate center of the head main body 71 and is connected to the gas supply unit 15B via the gas tube 19a (see FIG. 2). As a result, the reaction gas flow path 101 causes the gas supplied from the gas tube 19a, that is, a mixed gas of air and nitrogen-rich gas, to flow into the reaction chamber 77. In addition, the pair of carrier gas flow paths 103 are disposed at positions sandwiching the reaction gas flow path 101 in the X direction. The pair of carrier gas flow paths 103 are connected to the gas supply unit 15B via the gas tubes 19b and 19c (see FIG. 2). As a result, the nitrogen-rich gas supplied from the gas tubes 19b and 19c is supplied to the carrier gas flow path 103. Then, the carrier gas flow path 103 causes the nitrogen-rich gas to flow into the reaction chamber 77 via the gas passage 95.

Oxygen (O2) can be used as the reactive gas (seed gas), so the gas supply unit 15B supplies a mixed gas of air and nitrogen-rich gas to the reactive gas flow passage 101 via the gas tube 19a, and causes it to flow between the electrodes 73 of the reaction chamber 77. Hereinafter, for convenience, this mixed gas may be referred to as the reactive gas, and oxygen may be referred to as the seed gas. In addition, nitrogen may be used as the carrier gas, but a certain concentration or higher of nitrogen is required. For this reason, the gas supply unit 15B supplies nitrogen-rich gas to the carrier gas flow passage 103 via the gas tubes 19b and 19c, and causes the nitrogen-rich gas to flow from each of the gas passages 95 so as to surround each of the pair of electrodes 73. Hereinafter, this nitrogen-rich gas may be referred to as the carrier gas, for convenience.

An AC voltage is applied to the pair of electrodes 73 from the power supply unit 15A of the control box 15. By applying a voltage, for example as shown in FIG. 5, a pseudo arc A is generated between the lower ends of the pair of electrodes 73 in the reaction chamber 77. When the reactive gas passes through this pseudo arc A, the reactive gas is turned into plasma. Therefore, the pair of electrodes 73 generates a discharge of the pseudo arc A, turns the reactive gas into plasma, and generates plasma gas.

In addition, in the downstream portion of the reaction chamber 77 in the head main body 71, a plurality of (six in this embodiment) body-side plasma passages 111 are formed, spaced apart in the X direction and extending in the Z direction. The upstream ends of the plurality of body-side plasma passages 111 open to the reaction chamber 77, and the downstream ends of the plurality of body-side plasma passages 111 open to the lower end surface of the head main body 71.

The plasma irradiation unit 75 includes a nozzle 113, a nozzle cover 115, and the like. The nozzle cover 115 is generally T-shaped in side view from the X direction, and is composed of a nozzle body 117 and a nozzle tip 119. The nozzle 113 is an integral body of the nozzle body 117 and the nozzle tip 119, and is made of highly heat-resistant ceramic. The nozzle body 117 is generally flange-shaped and is fixed to the lower surface of the head body 71 by a bolt 120. The nozzle tip 119 is shaped to extend downward from the lower surface of the nozzle body 117. The nozzle 113 is formed with a plurality of (six in this embodiment) nozzle-side plasma passages 121 that penetrate the nozzle body 117 and the nozzle tip 119 in the vertical direction, that is, in the Z direction, and the plurality of nozzle-side plasma passages 121 are arranged at intervals in the X direction. The plurality of nozzle-side plasma passages 121 are formed at the same positions as the plurality of body-side plasma passages 111 in the Z direction. Therefore, the main body side plasma passage 111 and the nozzle side plasma passage 121 are connected.

The nozzle cover 115 is generally T-shaped when viewed from the side in the X direction, and is composed of a cover body 125 and a cover tip 127. The nozzle cover 115 is an integral part of the cover body 125 and the cover tip 127, and is made of highly heat-resistant ceramic. The cover body 125 is generally plate-shaped with a certain thickness, and a recess 129 is formed in the cover body 125, which opens on the upper surface and is recessed in the Z direction. The cover body 125 is fixed to the lower surface of the head body 71 by a bolt 130 so that the nozzle body 117 of the nozzle 113 is stored in the recess 129. For this reason, the nozzle cover 115 is detachable from the head body 71, and is removed from the head body 71 when replacing the nozzle 113, etc. Furthermore, a heat gas passage 91 is formed in the cover body 125 so as to extend in the Y direction, with one end of the heat gas passage 91 opening into the recess 129 and the other end of the heat gas passage 91 opening into the side surface of the cover body 125. The end of the heat gas passage 91 that opens into the side surface of the cover body 125 is connected to the connection portion 85 of the heat gas supply unit 62 described above.

The cover tip 127 extends downward from the underside of the cover body 125. A through hole 133 is formed in the cover tip 127, penetrating in the Z direction, and the upper end of the through hole 133 is connected to the recess 129 of the cover body 125. The nozzle tip 119 of the nozzle 113 is inserted into the through hole 133. As a result, the nozzle 113 is entirely covered by the nozzle cover 115. The lower end of the nozzle tip 119 of the nozzle 113 and the lower end of the cover tip 127 of the nozzle cover 115 are located at the same height.

When the nozzle 113 is covered by the nozzle cover 115, the nozzle body 117 of the nozzle 113 is located inside the recess 129 of the nozzle cover 115, and the nozzle tip 119 of the nozzle 113 is located inside the through hole 133 of the nozzle cover 115. In this state, there are gaps between the recess 129 and the nozzle body 117, and between the through hole 133 and the nozzle tip 119, and these gaps function as the heat gas output passage 135. Heat gas is supplied to the heat gas output passage 135 via the heat gas passage 91.

In the plasma head 11, the plasma gas generated in the reaction chamber 77 flows together with the carrier gas through the main body side plasma passage 111 and the nozzle side plasma passage 121, and is ejected from the opening 121A at the lower end of the nozzle side plasma passage 121. The flow rates of the carrier gas and the nitrogen-rich gas contained in the reaction gas at the time of plasma gas ejection are controlled within the range of 40 L/min to 80 L/min by the operation of the flow rate regulators 30b, 30c, and 30d, thereby ensuring sufficient ejection of plasma gas. In addition, the heat gas supplied from the gas pipe 81 to the heat gas passage 91 flows through the heat gas output passage 135. This heat gas functions as a shield gas that protects the plasma gas. The heat gas flows through the heat gas output passage 135 and is ejected from the opening 135A at the lower end of the heat gas output passage 135 along the ejection direction of the plasma gas. At this time, the heat gas is ejected so as to surround the plasma gas ejected from the opening 121A of the nozzle side plasma passage 121. In this way, by spraying the heated gas around the plasma gas, it is possible to increase the efficacy of the plasma gas (wettability, etc.), and the effectiveness of the plasma treatment by spraying the plasma gas is improved.

In addition, in the plasma device 10, when the plasma head 11 ejects the plasma gas, the ejection of the plasma gas is managed based on the gas concentration of the carrier gas, that is, the nitrogen concentration of the nitrogen-rich gas. In detail, as described above, in the gas supply section 15B of the control box 15, the nitrogen-rich gas is separated from the air by the nitrogen separator 22. Then, the nitrogen concentration of the nitrogen-rich gas separated by the nitrogen separator 22 is detected using the oxygen concentration detector 34. Then, when the nitrogen concentration detected using the oxygen concentration detector 34 reaches a set concentration, specifically, for example, 99.9%, a voltage is applied to the electrode 73. That is, until the nitrogen concentration reaches 99.9%, the device is in a state of waiting for the nitrogen concentration to rise, and no voltage is applied to the electrode 73. At this time, the touch panel of the operation section 15C of the control box 15 displays that the device is in a state of waiting for the nitrogen concentration to rise. Then, when the nitrogen concentration reaches 99.9%, a voltage is applied to the electrode 73, and the plasma gas is ejected from the plasma head 11. This makes it possible to use a high-concentration nitrogen-rich gas as a carrier gas, enabling appropriate plasma processing.

In addition, when the plasma gas is ejected, the nitrogen concentration detected using the oxygen concentration detector 34 is monitored, and when the nitrogen concentration falls below 99.9%, a warning screen is displayed on the touch panel of the operation unit 15C of the control box 15. This allows the operator to recognize the decrease in the nitrogen concentration of the carrier gas, improving usability. In addition, when the nitrogen concentration of the carrier gas decreases, the operator can decide whether to continue the plasma processing by displaying a warning screen without stopping the ejection of the plasma gas. As a result, for example, when the operator determines that the effect of the decrease in nitrogen concentration on the plasma processing is minor, the plasma processing is continued, thereby preventing the disposal of the workpiece W during plasma irradiation. Note that the nitrogen concentration at which the quality of the workpiece W cannot be guaranteed due to the decrease in nitrogen concentration is set as the minimum concentration, and when the nitrogen concentration detected using the oxygen concentration detector 34 falls below the minimum concentration, the voltage application to the electrode 73 is stopped. This ensures the quality of the plasma processing by the plasma device 10.

Incidentally, the plasma device 10 is an example of a plasma generating device. The plasma head 11 is an example of a head. The control box 15 is an example of a control device. The nitrogen separation device 22 is an example of a nitrogen supply device. The oxygen concentration detector 34 is an example of an oxygen concentration detector. The housing 50 is an example of a cylindrical member. The separation membrane 52 is an example of a membrane. The electrode 73 is an example of an electrode.

As described above, this embodiment provides the following advantages:

In the plasma device 10, nitrogen-rich gas is separated from compressed air by a nitrogen separator 22 having a separation membrane 52, a so-called separation membrane type nitrogen supply device, and the separated nitrogen-rich gas is supplied to the electrode 73. As described above, the nitrogen separator 22 is composed of a cylindrical housing 50 and is arranged inside the control box 15 in a vertically extending position. Therefore, the nitrogen separator 22 occupies a certain amount of space in the vertical direction inside the control box 15, but does not occupy much space in the horizontal direction. This makes it possible to suppress an increase in the installation space of the control box 15. In addition, the nitrogen separator 22, that is, a separation membrane type nitrogen supply device, is relatively inexpensive, and can also suppress an increase in the cost of the plasma device 10.

On the other hand, in the conventional plasma device, as shown in FIG. 7, a nitrogen generator 152 is disposed next to a control box 150, and the control box 150 supplies the nitrogen-rich gas generated by the nitrogen generator 152 to the plasma head 11. The nitrogen generator 152 generally has a built-in PSA (Pressure Swing Adsorption) type nitrogen supply device. The PSA type nitrogen supply device separates nitrogen from air by adsorbing oxygen to an adsorbent, and is a structurally complex and large device. For this reason, a large space needs to be secured in order to install the nitrogen generator 152. In addition, since the PSA type nitrogen supply device is structurally complex and relatively expensive, the user's cost burden is large. For this reason, the plasma device 10 adopts a separation membrane type nitrogen supply device instead of a PSA type nitrogen supply device, which makes it possible to reduce the installation space and the user's cost burden.

The PSA type nitrogen supply device is structurally capable of separating 99.99% nitrogen-rich gas, but the separation membrane type nitrogen supply device cannot separate 99.99% nitrogen-rich gas, and can only separate 99.9% nitrogen-rich gas. However, the plasma device 10 does not require nitrogen-rich gas with a purity as high as 99.99%, and 99.9% nitrogen-rich gas is sufficient to ensure proper plasma processing. For this reason, in consideration of installation space, costs, etc., the plasma device 10 employs a separation membrane type nitrogen supply device rather than a PSA type nitrogen supply device.

The electrode 73 is disposed in the plasma head 11, and the nitrogen separator 22 is disposed in a control box 15 that is separate from the plasma head 11. The control box 15 supplies the plasma head 11 with electric power and the nitrogen-rich gas separated from the air by the nitrogen separator 22. In this way, by disposing the electrode 73 and the nitrogen separator 22 in different devices, each device can be made compact.

The nitrogen separation device 22 is also equipped with an oxygen concentration detector 34, which measures the oxygen concentration of the nitrogen-rich gas separated from the air by the nitrogen separation device 22. This makes it possible to manage the nitrogen concentration of the nitrogen-rich gas based on the oxygen concentration measured by the oxygen concentration detector 34, ensuring appropriate plasma processing.

The nitrogen-rich gas separated by the nitrogen separator 22 is supplied from the gas supply unit 15B to the electrode 73 of the plasma head 11 at a flow rate of 40 L/min to 80 L/min. This allows plasma processing to be performed using a sufficient amount of nitrogen-rich gas.

The nitrogen separation device 22 has a cylindrical housing 50 in which a separation membrane 52 is built. The housing 50 is disposed in a position extending in the vertical direction, and compressed air is supplied from the upper part of the housing 50, causing nitrogen-rich gas to be discharged from the lower part of the housing 50. This makes it possible to prevent the control box 15 in which the nitrogen separation device 22 is disposed from becoming too large.

In addition, factory air used in factories is used as the compressed air supplied to the nitrogen separation device 22. This makes it possible to reduce the need to install a device that generates compressed air specifically for the nitrogen separation device.

The present disclosure is not limited to the above embodiment, and can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. Specifically, for example, the electrode 73 and the nitrogen separator 22 are arranged in different devices, but they may be arranged in one device. In such a case, the device becomes larger, but the gas tube 19 and the like can be arranged in the device. However, in the nitrogen separator 22, as described above, oxygen with high combustion support is discharged from the through hole 54 of the housing 50, and considering that a voltage is applied to the electrode 73, it is desirable to arrange the electrode 73 and the nitrogen separator 22 in different devices.

In the above embodiment, the nitrogen separation device 22 discharges the gas obtained by separating nitrogen from the compressed air, i.e., oxygen, directly from the through-hole 54 of the housing 50, but the oxygen may be diluted to a certain concentration before being discharged.

In addition, in the above embodiment, power and nitrogen-rich gas are supplied to the plasma head 11 from the control box 15, but power may be supplied to the plasma head 11 from a device other than the control box 15. In other words, the power supply unit 15A may be disposed in a device other than the control box 15, and power may be supplied to the plasma head 11 from that device.

In the above embodiment, the oxygen concentration of the nitrogen-rich gas separated by the nitrogen separator 22 is measured using the oxygen concentration detector 34, and the nitrogen concentration of the nitrogen-rich gas is calculated based on the measured oxygen concentration. On the other hand, the nitrogen concentration of the nitrogen-rich gas separated by the nitrogen separator 22 may be directly measured using the nitrogen concentration detector.

In the above embodiment, the nitrogen separator 22 is composed of one housing 50, but a nitrogen separator composed of multiple housings may be used. Specifically, for example, as shown in FIG. 8, a nitrogen separator 162 composed of three housings 160 may be used. In this way, when the nitrogen separator 162 is composed of three housings 160, the outer diameter of the housing 160 is less than half the outer diameter of the housing 50, and the length of the housing 160 is slightly longer than the length of the housing 50. Specifically, the outer diameter of the housing 160 is 109 mm, and the length of the housing 160 is 1110 mm. The pressure of the compressed air sent into the inside of the housing 160 is 0.9 to 1.0 MPa.

10: Plasma device (plasma generator) 11: Plasma head (head) 15: Control box (control device) 22: Nitrogen separator (nitrogen supply device) 34: Oxygen concentration detector 50: Housing (cylindrical member) 52: Separation membrane (membrane) 73: Electrode

Claims (8)

a plasma head having an electrode for generating plasma;
a nitrogen supplying device having a membrane for separating nitrogen gas having a predetermined concentration or more from a nitrogen-containing gas, the nitrogen gas being supplied to the electrode;
a mixed gas tube connected to the nitrogen supply device and supplying a mixed gas of the nitrogen gas and air to the plasma head;
a nitrogen gas tube connected to the nitrogen supply device and supplying nitrogen gas having a concentration equal to or higher than the predetermined concentration to the plasma head;
A plasma generating device comprising:
a second nitrogen gas supply line between the nitrogen supply device and the first nitrogen gas supply line;
a third nitrogen gas supply line between the nitrogen gas tube and the second nitrogen gas supply line;
the second nitrogen gas supply path branches into the first nitrogen gas supply path and the third nitrogen gas supply path,
an oxygen concentration detector is provided on the second nitrogen gas supply line to detect the oxygen concentration of the nitrogen gas separated by the membrane;
A plasma generating device that applies a voltage to the electrodes when the nitrogen concentration detected by the oxygen concentration detector reaches a predetermined concentration . The plasma generating device according to claim 1, further comprising a mixer between the nitrogen supply device and the mixed gas tube for mixing the air and the nitrogen gas. The plasma generating device according to claim 1, further comprising a mixer for mixing the mixed gas with a first nitrogen gas supply line between the nitrogen supply device and the mixed gas tube. 4. The plasma generating device according to claim 1, wherein the nitrogen gas separated by the membrane is supplied from the nitrogen supply device to the electrode at a flow rate of 40 L/min to 80 L/min. The nitrogen supply device has a cylindrical member that incorporates the membrane,
The cylindrical member is disposed in a position extending in a vertical direction,
5. The plasma generating device according to claim 1, wherein air is supplied from an upper portion of the cylindrical member, and the nitrogen gas is discharged from a lower portion of the cylindrical member. The nitrogen supply device is
6. The plasma generating device according to claim 1, wherein the nitrogen gas is separated from factory air used in a factory and the nitrogen gas is supplied. A method for generating plasma, comprising the steps of: using a nitrogen supplying device that supplies nitrogen gas through a membrane that separates nitrogen gas having a predetermined concentration or more from a nitrogen-containing gas, supplying a mixed gas of nitrogen gas and air through a mixed gas tube to an electrode of a plasma head; and using the nitrogen supplying device to supply the nitrogen gas having the predetermined concentration or more to the electrode of the plasma head through a nitrogen gas tube ,
a second nitrogen gas supply line between the nitrogen supply device and the first nitrogen gas supply line;
a third nitrogen gas supply line is disposed between the nitrogen gas tube and the second nitrogen gas supply line;
the second nitrogen gas supply path branches into the first nitrogen gas supply path and the third nitrogen gas supply path,
an oxygen concentration detector for detecting the oxygen concentration of the nitrogen gas separated by the membrane is disposed on the second nitrogen gas supply line;
The plasma generating method includes applying a voltage to the electrodes when the nitrogen concentration detected by the oxygen concentration detector reaches a predetermined concentration, thereby generating plasma . A control device for a plasma generation device including a plasma head in which an electrode for generating plasma is disposed,
The plasma generating device includes:
a nitrogen supplying device having a membrane for separating nitrogen gas having a predetermined concentration or more from a nitrogen-containing gas, the nitrogen gas being supplied to the electrode;
a mixed gas tube connected to the nitrogen supply device and supplying a mixed gas of the nitrogen gas and air to the plasma head;
a nitrogen gas tube connected to the nitrogen supply device and supplying nitrogen gas having a concentration equal to or higher than the predetermined concentration to the plasma head;
a second nitrogen gas supply line between the nitrogen supply device and the first nitrogen gas supply line;
a third nitrogen gas supply line between the nitrogen gas tube and the second nitrogen gas supply line;
Equipped with
the second nitrogen gas supply path branches into the first nitrogen gas supply path and the third nitrogen gas supply path,
The plasma generating device includes:
an oxygen concentration detector is provided on the second nitrogen gas supply line to detect the oxygen concentration of the nitrogen gas separated by the membrane;
The nitrogen supply device is disposed in the control device,
The control device includes:
a control device that is separate from the plasma head, supplies nitrogen gas from the nitrogen supply device to the plasma head , and applies a voltage to the electrode when the nitrogen concentration detected using the oxygen concentration detector reaches a predetermined concentration .

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