Plasma head and plasma generation device

Abstract

This plasma head includes: a cylindrical external electrode member to which a process gas is circulated; an internal electrode that is accommodated inside the external electrode member and converts the process gas into plasma between the internal electrode and the external electrode member; and a flow regulating unit that is present between the external electrode member and the internal electrode and causes the process gas to flow toward the external electrode member side, or causes the process gas to flow toward the internal electrode side.

Description

Plasma head and plasma generator

[0001] Disclosed herein are plasma heads and plasma generating devices.

[0002] Conventionally, a plasma generating device has been proposed in which, for example, a gas such as air or oxygen is introduced into a cylindrical electrode, a central electrode disposed at the center of the cylindrical electrode is supplied with power, and a plasma flow is generated around the central electrode by a local arc, so that the plasma does not reach the cylindrical electrode, and the workpiece is exposed to this plasma flow for cleaning or sterilizing the surface (for example, Patent Document 1). This device is said to be capable of cleaning or sterilizing the workpiece using plasma.

[0003] Japanese Patent Application Laid-Open No. 2005-288398

[0004] However, in the above-mentioned plasma generating device, for example, dielectric breakdown occurs between the electrodes, causing arc discharge (short circuit), and oxygen is ejected without being converted into radicals. Thus, there is a need for a plasma head that can perform plasma processing more efficiently.

[0005] The present disclosure has been made in consideration of such problems, and has as its main object to provide a plasma head and a plasma generation device that can perform plasma processing with higher efficiency.

[0006] In this disclosure, the following means are adopted to achieve the above-mentioned main object.

[0007] The plasma head of the present disclosure comprises: a cylindrical external electrode member through which a process gas flows; an internal electrode housed inside the external electrode member and converting the process gas into plasma between the external electrode member and the internal electrode; and a rectifying unit located between the external electrode member and the internal electrode and configured to either circulate the process gas toward the external electrode member or circulate the process gas toward the internal electrode.

[0008] This plasma head allows for more efficient plasma processing.

[0009] 1 is a schematic explanatory diagram showing an example of a plasma generation device 10. FIG. 2 is a perspective view and a cross-sectional view of a plasma head 40. FIG. 3 is a cross-sectional perspective view of the plasma head 40 and an explanatory diagram of a rectifying member 55. FIG. 4 is a perspective view and a cross-sectional view of another plasma head 40B. FIG. 5 is a cross-sectional perspective view of another plasma head 40B and an explanatory diagram of a rectifying member 55B.

[0010] This embodiment will be described below with reference to the drawings. FIG. 1 is a schematic explanatory diagram showing an example of a plasma generator 10. FIG. 2 is a perspective view and a cross-sectional view of a plasma head 40. FIG. 3 is a cross-sectional perspective view of the plasma head 40 and an explanatory diagram of a rectifying member 55. FIG. 4 is a perspective view and a cross-sectional view of another plasma head 40B. FIG. 5 is a cross-sectional perspective view of another plasma head 40B and an explanatory diagram of a rectifying member 55B. In this embodiment, the left-right direction (X-axis), the front-back direction (Y-axis), and the up-down direction (Z-axis) are assumed to be the same as those shown in FIG. 1 for convenience. Here, the plasma generator 10 will be described as an atmospheric pressure plasma generator, for example.

[0011] The plasma generator 10 is a device that generates plasma under atmospheric pressure. As shown in Fig. 1, the plasma generator 10 includes an arm robot 12, a control device 20, a power supply device 28, a gas supply device 30, and a plasma head 40. The plasma generator 10 supplies power from the power supply device 28 to the plasma head 40 via a power cable, and supplies a process gas to be converted into plasma from the gas supply device 30 via a supply pipe 31. The plasma generator 10 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 as a robot with six or more axes. 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, if the plasma head 40 can be freely moved, an XYZ robot capable of moving the plasma head 40 may also be used.

[0013] The control device 20 controls each device of the plasma generation device 10. The control device 20 includes a control unit 21, a memory unit 22, a communication unit 23, a display unit 24, and an operation unit 25. The control unit 21 is configured as a microprocessor centered on a CPU and controls the entire plasma generation device 10. The control unit 21 outputs control signals to the arm robot 12, power supply unit 28, gas supply unit 30, plasma head 40, etc. The memory unit 22 is a large-capacity storage medium such as a flash memory, and stores programs for controlling the plasma generation device 10 and job information including the shape of the workpiece W and the surface treatment position. The communication unit 23 is an interface for exchanging information with external devices such as a management server (not shown). The display unit 24 is a display that displays information to the operator. The operation unit 25 is used by the operator to input various information and includes various buttons, levers, etc. In the plasma generating device 10, the arm robot 12, power supply device 28, gas supply device 30, and plasma head 40 are described as being controlled by a single control device 20, but a control unit may be provided for each device, 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.

[0015] The gas supply device 30 supplies a process gas to the outer electrode 41 and the inner electrode 42 of the plasma head 40. The gas supply device 30 may be configured to supply a process gas containing at least one of an inert gas such as nitrogen and an active gas such as oxygen, for example, air, by pressure delivery. The gas supply device 30 includes a supply pipe 31, a supply valve 32, and a gas supply tank (not shown). The supply pipe 31 is a pipe connected between the supply tank of the gas supply device 30 and the plasma head 40. The supply valve 32 controls the supply and stop of the process gas. The gas supply device 30 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 workpiece W supported on a work table with plasma gas 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 unit 13 of the arm robot 12. The base end of the plasma head 40 is attached to the mounting unit 13, and the tip end is covered by a cover 60. A nozzle 49 that irradiates the plasma gas generated by the plasma head 40 is provided below the cover 60. The plasma head 40 includes an external electrode 41, an internal electrode 42, a drive unit 43, a support unit 44, the nozzle 49, and a rectification unit 50.

[0017] The external electrode 41 is a member through which a nozzle 49 is formed and through which a process gas flows. The external electrode 41 is grounded by a grounding member (not shown). As shown in FIGS. 2 and 3 , the external electrode 41 is fixed to a holder 46, which serves as an external electrode member. The holder 46 is a cylindrical member disposed at the tip end of the main body 48 and through which a process gas flows. Since the holder 46 is electrically connected to the external electrode 41, the holder 46 can also be considered part of the external electrode 41. The external electrode 41 has a first member 53 and a second member 57 on the inner side of the holder 46. The first member 53 is a cylindrical member disposed inside the cylindrical holder 46 connected to the external electrode 41. The first member 53 has an outer inclined surface 54 inclined toward the internal electrode 42 at the downstream end in the process gas flow direction. The second member 57 is a cylindrical member disposed inside the cylindrical first member 53. At the downstream end of this second member 57 in the flow direction of the process gas, an outer inclined surface 58 is formed that is inclined toward the rectifying member 55 disposed on the upper side of the internal electrode 42.

[0018] The internal electrode 42 is housed within the external electrode 41 and converts the process gas into plasma between the internal electrode 42 and the external electrode 41. The internal electrode 42 is fixed to a holder 47 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 47 is connected to the power supply 28, is tapered at its tip, and is a member into which the internal electrode 42 can be inserted. Note that, since the holder 47 is electrically connected to the internal electrode 42, the holder 47 can also be considered part of the internal electrode 42. As shown in FIGS. 2 and 3 , an internal member 51 is disposed on the internal electrode 42. The internal member 51 is disposed above a rectifying member 55 disposed above the internal electrode 42. An internal inclined surface 52 inclined toward the second member 57 is formed at the upstream end of the internal member 51 in the process gas flow direction. In the plasma head 40, a voltage is applied to the process gas supplied between the outer electrode 41 and the inner electrode 42, thereby converting the process gas into plasma and generating a plasma gas.

[0019] The drive unit 43 is a motor that rotates a 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. In addition to the external electrode 41, the internal electrode 42, and the nozzle 49, the main body 48 is also provided with the above-mentioned holders 46 and 47, internal member 51, first member 53, rectifying member 55, second member 57, and the like.

[0020] The support part 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 part 44 is removably attached to the attachment part 13. In addition to supporting the main body 48, the support part 44 also supports the supply pipe 31 connected to the gas supply device 30 and the power cable connected to the power supply device 28. The support part 44 rotatably supports the main body 48 by a fixing member 45 arranged below it. The fixing member 45 is a member having a box-shaped wall and houses the upper side of the main body 48. The nozzle 49 is a tip member formed with an outlet for discharging plasma gas. The nozzle 49 is arranged at the lower end of the plasma head 40 so as to face the workpiece W.

[0021] The rectifying section 50 is located between the holder 46 serving as the external electrode member and the internal electrode 42 and controls the flow direction of the process gas. The rectifying section 50 directs the process gas toward the internal electrode 42. The rectifying section 50 is composed of an internal inclined surface 52, an external inclined surface 54, a rectifying plate 56, and an external inclined surface 58. The internal inclined surface 52 formed on the internal member 51 is inclined so as to direct the gas toward the internal electrode 42, upstream of the portion of the internal electrode 42 where the process gas is converted into plasma. The internal inclined surface 52 is formed around the entire outer periphery of the internal member 51. The external inclined surface 54 formed on the first member 53 is inclined so as to direct the gas toward the internal electrode 42, upstream of the portion of the external electrode 41 where the process gas is converted into plasma. The external inclined surface 54 is formed around the entire inner periphery of the end of the first member 53. The outer inclined surface 58 formed on the second member 57 is an inclined surface formed on the upstream side of the portion of the outer electrode 41 where the process gas is converted into plasma, so that the gas flows toward the inner electrode 42. The outer inclined surface 58 is formed around the entire inner periphery of the end of the second member 57. The flow rectifying section 50 circulates the process gas along the outer peripheral surface of the cylindrical inner electrode 42 by at least the inner inclined surface 52, the outer inclined surface 54, and the outer inclined surface 58.

[0022] The rectifying member 55 is a component that converts the process gas into a spiral flow and circulates it between the holder 46 (as an external electrode component) and the internal electrode 42 when the process gas is converted into plasma. As shown in FIG. 3 , the rectifying member 55 is a disc-shaped component that includes a double cylinder consisting of an inner cylinder and an outer cylinder, and multiple rectifying plates 56 are disposed between the cylinders to allow gas to flow. Each rectifying plate 56 is a thin plate, with one end fixed to the inner circumferential wall of the outer cylinder and the other end fixed to the outer circumferential wall of the axially supported inner cylinder. The rectifying plates 56 are arranged in a helical shape with a predetermined inclination angle θ relative to the disc-shaped disc surface. The rectifying plates 56 are inclined to allow gas to flow toward the internal electrode 42 and / or have a curved surface to allow gas to flow toward the internal electrode 42. The rectifying unit 50 uses at least the rectifying plates 56 to circulate the process gas along the outer circumferential surface of the cylindrical internal electrode 42.

[0023] Alternatively, as shown in FIGS. 4 and 5 , the plasma head 40B may include a rectifying section 50B that directs the process gas toward the holder 46, which serves as the external electrode member. The rectifying section 50B is located between the holder 46 and the internal electrode 42 and controls the flow direction of the process gas. This rectifying section 50B directs the process gas toward the holder 46, to which the external electrode 41 is connected. The rectifying section 50B is composed of an internal inclined surface 52B, an external inclined surface 54B, and a rectifying plate 56B. The internal inclined surface 52B formed on the internal member 51B is an inclined surface formed upstream of the portion of the internal electrode 42 where the process gas is converted into plasma, so that the gas flows toward the holder 46. The internal inclined surface 52B is formed around the entire outer periphery of the internal member 51B. The outer inclined surface 54B formed on the first member 53B is an inclined surface formed upstream of the portion of the outer electrode 41 where the process gas is converted into plasma, so that the gas flows toward the holder 46. This outer inclined surface 54B is formed around the entire inner periphery of the end of the first member 53B. The flow rectifying section 50B flows the process gas along the inner periphery of the cylindrical holder 46 by at least the inner inclined surface 52B and the outer inclined surface 54B.

[0024] The flow rectifying member 55B, like the flow rectifying member 55, generates a spiral flow and includes a flow rectifying plate 56B. The flow rectifying plate 56B is a thin plate with one end fixed to the inner peripheral wall of the outer cylinder and the other end fixed to the outer peripheral wall of the journaled inner cylinder. The flow rectifying plate 56B is arranged in a helical shape with a predetermined inclination angle θ relative to the circular disk surface. The flow rectifying plate 56B is inclined to allow gas to flow toward the holder 46 and / or has a curved surface to allow gas to flow toward the holder 46. The flow rectifying unit 50B distributes the process gas along the inner peripheral surface of the cylindrical holder 46 at least by means of the flow rectifying plate 56B.

[0025] Next, the surface modification process of the workpiece W using the plasma generator 10 configured as described above will be described. When a command to start the surface modification process is input from the operation unit 25, the control unit 21 first outputs a command signal to the gas supply device 30 to supply process gas to the plasma head 40. Next, the control unit 21 moves the plasma head 40 to a position facing the workpiece W using the arm robot 12 and rotates the main body 48 using the drive unit 43. Next, the control unit 21 applies a voltage between the external electrode 41 and the internal electrode 42 to convert the process gas into plasma and irradiate it onto the workpiece W. In this process, the plasma head 40 applies a high voltage to the gas between the pair of electrodes to convert the gas into a radical state. However, increasing the voltage or increasing the temperature in the discharge space can cause dielectric breakdown between the electrodes, resulting in a short circuit and oxygen being ejected without being converted into radicals. The plasma head 40 includes a rectifier 50 that adjusts the flow direction of the process gas. This increases the gas flow speed on the electrode surface, thereby further suppressing the occurrence of the short circuit. Effective methods for suppressing this include the rectifier 50, which increases the gas flow speed on the surface of the internal electrode 42, and the rectifier 50B, which increases the gas flow speed on the surface of the holder 46 serving as the external electrode member. Here, the rectifier 50, which directs gas toward the outer surface of the internal electrode 42, is more preferable. The rectifier 50 generates a gas film on the surface of the electrode to further suppress the occurrence of dielectric breakdown between the electrodes, and is more effective than the rectifier 50B because the outer peripheral area of ​​the internal electrode 42 (holder 47) is smaller than the inner peripheral area of ​​the external electrode 41 (holder 46).

[0026] Here, the correspondence between the components of this embodiment and the components of the present disclosure will be clarified. The holder 46 of this embodiment corresponds to an example of an external electrode member of the present disclosure, the internal electrode 42 corresponds to an example of an internal electrode, and the rectification units 50 and 50B correspond to an example of a rectification unit.

[0027] The plasma generator 10 of the present embodiment described above includes a holder 46 as a cylindrical external electrode member through which a process gas flows, an internal electrode 42 housed within the holder 46 and converting the process gas into plasma between the holder 46 and the external electrode 41, and a rectifier 50B located between the holder 46 and the internal electrode 42 and directing the process gas toward the holder 46 or a rectifier 50 directing the process gas toward the internal electrode 42. The presence of the rectifiers 50 and 50B in this plasma head 40 allows the process gas to flow toward the holder 46 or toward the internal electrode 42. When the process gas flows toward the electrode, for example, the process gas can further suppress the occurrence of an electrode short circuit and further reduce the amount of process gas that passes through without being converted into plasma. Therefore, this plasma head allows for more efficient plasma processing.

[0028] The rectifying unit 50 also directs the process gas toward the internal electrode 42. In this plasma head 40, the process gas is directed toward the internal electrode 42, which has a smaller gas contact area, thereby more efficiently preventing electrode short-circuiting and enabling more efficient plasma processing. The rectifying unit 50 also includes an inner inclined surface 52 formed upstream of the portion of the internal electrode 42 where the process gas is converted into plasma, and an inner inclined surface 52 formed upstream of the portion of the external electrode 41 where the process gas is converted into plasma, and both inclined toward the internal electrode 42. This plasma head 40 utilizes the inclined surfaces of the peripheral members of the internal electrode 42 and the external electrode 41 to perform more efficient plasma processing. The rectifying unit 50 also includes one or more rectifying plates 56 arranged upstream of the portion where the process gas is converted into plasma by the internal electrode 42 and the external electrode 41, and inclined to direct the process gas toward the internal electrode 42. In this plasma head 40, more efficient plasma processing can be performed by utilizing the rectifying plate 56. In this case, the rectifying plate 56 may be configured to make the process gas into a spiral flow.

[0029] The rectifying unit 50B may also be configured to direct the process gas toward the holder 46, which serves as the external electrode member. This plasma head 40B allows the process gas to flow toward the holder 46, which allows the process gas to flow relatively easily, thereby enabling more efficient plasma processing. The rectifying unit 50B also includes an inner inclined surface 52B formed upstream of the portion of the internal electrode 42 where the process gas is converted into plasma, and an outer inclined surface 54B formed upstream of the portion of the external electrode 41 where the process gas is converted into plasma, and also toward the holder 46. This plasma head 40B can perform more efficient plasma processing by utilizing the inclined surfaces of the peripheral members of the internal electrode 42 and the external electrode 41. Furthermore, the rectifying unit 50B includes one or more rectifying plates 56B arranged upstream of the portion where the process gas is converted into plasma by the internal electrode 42 and the external electrode 41, and inclined so as to direct the process gas toward the holder 46, which serves as the external electrode member. In the plasma head 40B, more efficient plasma processing can be performed by utilizing the rectifying plate 56B, which may be configured to make the process gas into a spiral flow.

[0030] The plasma generator 10 also includes the above-described plasma head 40 or 40B, a power supply device 28 that supplies power to the external electrode 41 and the internal electrode 42, and a gas supply device 30 that supplies a process gas to the external electrode 41 and the internal electrode 42. Because the plasma generator 10 includes the above-described plasma heads 40 and 40B, it is possible to control the flow direction of the process gas and perform more efficient plasma processing.

[0031] It goes without saying that the plasma head and plasma generation device of the present disclosure are not 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.

[0032] For example, in the above-described embodiment, the rectifying unit 50 includes the inner inclined surface 52, the outer inclined surface 54, the outer inclined surface 58, and the rectifying plate 56. However, as long as the rectifying unit 50 adjusts the flow direction of the process gas, this is not particularly limited, and one or more of these may be omitted, or other inclined surfaces may be included. Furthermore, while the rectifying unit 50 is implemented using parts of the inner member 51, the first member 53, the rectifying member 55, and the second member 57, one or more of these components may be omitted, or other components may be used. In this plasma head 40, by circulating the process gas toward the electrode, the occurrence of a short circuit between the electrodes can be further suppressed, enabling more efficient plasma processing.

[0033] In the above-described embodiment, the rectifying unit 50B includes the inner inclined surface 52B, the outer inclined surface 54B, and the rectifying plate 56B. However, as long as the rectifying unit 50B adjusts the flow direction of the process gas, this is not particularly limited. One or more of these components may be omitted, or other inclined surfaces may be included. Furthermore, while the rectifying unit 50B is implemented using a portion of the inner member 51B, the first member 53B, and the rectifying member 55B, one or more of these components may be omitted, or other components may be used. In this plasma head 40B, by directing the process gas toward the electrode, the occurrence of a short circuit between the electrodes can be further suppressed, enabling more efficient plasma processing.

[0034] In the above-described embodiment, each inclined surface is formed over the entire inner circumference of the cylindrical member or the entire outer circumference of the cylindrical member, but this is not particularly limited to this, and there may be portions where the inclined surface is interrupted.

[0035] In the above-described embodiment, the present disclosure has been described as the plasma generation device 10, but is not particularly limited to this, and may be a plasma head 40, 40B or a rectifying unit 50, 50B.

[0036] This specification also discloses the technical idea of ​​changing "a plasma head according to any one of claims 1 to 3, 5 and 6" in claim 8 of the original application to "a plasma head according to any one of claims 1 to 7."

[0037] The present disclosure is applicable to the technical field of processing the surface of a workpiece.

[0038] REFERENCE SIGNS LIST 10 Plasma generator, 12 Arm robot, 13 Mounting unit, 14 Arm, 15 Drive motor, 16 Base unit, 20 Control device, 21 Control unit, 22 Memory unit, 23 Communication unit, 24 Display unit, 25 Operation unit, 28 Power supply unit, 30 Gas supply device, 31 Supply pipe, 32 Supply valve, 40, 40B Plasma head, 41 External electrode, 42 Internal electrode, 43 Drive unit, 44 Support unit, 45 Fixing member, 46 Holder, 47 Holder, 48 Main body, 49 Nozzle, 50, 50B Rectifying unit, 51, 51B Internal member, 52, 52B Internal inclined surface, 53, 53B First member, 54, 54B External inclined surface, 55, 55B Rectifying member, 56, 56B Rectifying plate, 57 Second member, 58 External inclined surface, 60 cover, W work.

Claims

1. A plasma head comprising: a cylindrical external electrode member through which a process gas flows; an internal electrode housed inside the external electrode member for generating plasma of the process gas between the internal electrode and the external electrode member; and a rectifying portion existing between the external electrode member and the internal electrode for flowing the process gas toward the external electrode member side or for flowing the process gas toward the internal electrode side.

2. The plasma head according to claim 1, wherein the rectifying portion flows the process gas toward the internal electrode side.

3. The plasma head according to claim 2, wherein the rectifying portion includes an inner inclined surface inclined toward the internal electrode side upstream of a site where the internal electrode generates plasma of the process gas and / or an outer inclined surface inclined toward the internal electrode side upstream of a site where the external electrode member generates plasma of the process gas.

4. The plasma head according to claim 2 or 3, wherein the rectifying portion includes one or more rectifying plates disposed upstream of a site where the internal electrode and the external electrode member generate plasma of the process gas and inclined such that the process gas flows toward the internal electrode side.

5. The plasma head according to claim 1, wherein the rectifying portion flows the process gas toward the external electrode member side.

6. The plasma head according to claim 5, wherein the rectifying portion includes an inner inclined surface inclined toward the external electrode member side upstream of a site where the internal electrode generates plasma of the process gas and / or an outer inclined surface inclined toward the external electrode member side upstream of a site where the external electrode member generates plasma of the process gas.

7. The plasma head according to claim 5 or 6, wherein the rectifying portion includes one or more rectifying plates disposed upstream of a site where the internal electrode and the external electrode member generate plasma of the process gas and inclined such that the process gas flows toward the external electrode member side.

8. A plasma generation device comprising: the plasma head according to any one of claims 1 to 3, 5, and 6; a power supply device for supplying power to the external electrode member and the internal electrode; and a gas supply device for supplying the process gas to the external electrode member and the internal electrode.

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