JPH10241890A - Inductively coupled plasma device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain plasma frame output of large output with its superior stability and high efficiency by providing a third nozzle for axially introducing a plasma gas to the inside of an insulation tube on an axial end face on the internal side of the insulation tube of a grounding electrode. SOLUTION: A gas introducing part 4 and a grounding electrode 5A are arranged on the top of an electric insulation tube 1. The grounding electrode 5A is provided with an axial gas introducing port 5a and an axial main nozzle 5c communicating therewith and supplying gas axially to the inside of the electric insulation tube 1. A flow rate of plasma gas supplied respectively from a diameter direction gas introducing port 4a and a circumferential gas introducing port 4b of a gas introducing port 4 and an axial gas introducing port 5a of a grounding electrode 5A can be individually adjusted by a gas flow rate adjusting valve 11. Thus, by introducing gas supplied axially, a heat movement quantity is increased axially of a plasma, and a stable plasma frame with its large heat output can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inductively coupled plasma apparatus for generating arc plasma using high frequency inductive coupling.

[0002]

2. Description of the Related Art An inductively coupled plasma apparatus is obtained by winding a high-frequency induction coil coaxially around an electric insulating tube, applying a high-frequency current to the high-frequency induction coil, and converting the gas introduced into the inside of the electric insulating tube into a plasma. This is an apparatus that uses plasma as a heat source for melting and the like. FIG. 10 is a partial sectional view showing a basic configuration of a conventionally used inductively coupled plasma device. In the figure, reference numeral 1 denotes a cylindrical electric insulating tube formed using quartz. The electric insulating tube 1 has a double structure of an inner cylinder 1a and an outer cylinder 1b, and is used by cooling a not-shown refrigerant through a gap. Reference numeral 2 denotes a high-frequency induction coil wound around the outside of the electrically insulating tube 1 coaxially.
It is wound four turns. Reference numeral 3 denotes a high frequency power supply. Above the electrical insulating tube 1, a gas introduction unit 4 having a nozzle that blows out in the circumferential direction of the insulating tube and a nozzle that blows out in the radial direction of the insulating tube, and a ground electrode 5 are arranged. The gas of the type and flow rate selected by operating the gas flow control valve 7 is supplied from the gas introduction unit 4 to the inside of the electric insulating tube 1 through the gas supply tube 6. The ground electrode 5 is of a water-cooled type and is grounded to the earth side and capacitively coupled to the high-frequency induction coil 2.

FIG. 11 is a cross-sectional view showing a detailed structure of the gas introduction section 4 of the inductively coupled plasma apparatus shown in FIG. The gas inlet 4 surrounding the ground electrode 5 is provided with a radial gas inlet 4a and a circumferential gas inlet 4b. The radial gas inlet 4a communicates with a radial ring-shaped gas blowing nozzle 4c in which nozzle holes that open radially into the electrically insulating tube 1 are arranged and distributed on the peripheral surface. The direction gas inlet 4b is connected to the gas insulating tube 1
Nozzle holes that open obliquely close to the circumferential direction into the inside of the nozzle are connected to a circumferential ring-shaped gas blowing nozzle 4d that is distributed and arranged on the circumferential surface. That is, the gas sent through the gas supply pipe 6 is introduced into the inside of the electric insulating tube 1 through the radial gas inlet 4a and the circumferential gas inlet 4b, and the gas is supplied to the radial ring gas blowing nozzle 4c and the circumferential ring. The gas is supplied in a radial direction and a circumferential direction from the gas blowing nozzle 4d. In addition, the flow rate of the gas introduced from these two gas introduction ports is configured to be individually adjustable by a gas flow control valve 11 incorporated in a branch pipe. Also, the type of gas to be introduced and the mixing ratio of the gas are shown in FIG.
As shown in FIG. 1, selection and adjustment are performed by operating a gas flow control valve 7 connected to a gas supply device.

[0004] The generation of atmospheric pressure arc plasma in the inductively coupled plasma apparatus having the above configuration is performed in the following procedure. First, helium gas is introduced as an ignition gas from a gas inlet 4 provided at the upper end of the electric insulating tube 1, and an output voltage of the high frequency power supply 3 is applied to the high frequency induction coil 2.
The helium gas introduced into the electric insulating tube 1 is discharged by a capacitive coupling electric field formed between the high-frequency induction coil 2 and the ground electrode 5. Subsequently, a plasma gas such as argon is introduced into the inside of the electric insulating tube 1 to maintain the discharge, and then the introduction of the helium gas is gradually stopped to thereby stop the electric insulating tube 1.
The concentration of argon gas in the gas is increased, and the plasma is transferred to arc plasma. After shifting to arc plasma, the high-frequency induction coil 2
Energy is supplied to the plasma by the high-frequency induction electric field generated by the plasma. The plasma in this state is generally called an inductively coupled plasma, and the obtained plasma depends on the strength and shape of the electric field and the gas flow.

[0005]

When high-frequency inductively coupled plasma is used as a heat source in a melting process or the like, a method of irradiating an object to be processed with a plasma frame ejected from a plasma generating source (hereinafter referred to as a plasma torch) is the most common. is there. The amount of heat of the plasma flame spouted from the plasma torch not only depends on the power input to the plasma,
It also has a strong dependence on gas flow. Flow rates of gas (hereinafter abbreviated as r gas) supplied in the radial direction from the radial ring-shaped gas blowing nozzle 4c and gas (hereinafter abbreviated as θ gas) supplied in the circumferential direction from the circumferential ring-shaped gas blowing nozzle 4d The larger the ratio (hereinafter abbreviated as r / θ flow rate ratio), the larger the amount of heat of the plasma frame. This is because the directivity of the r gas in the axial direction is strong, and in order to increase the thermal output of the plasma frame, it is necessary to operate under the condition of a large r / θ flow ratio.

[0006] However, the r / θ flow rate ratio also greatly affects the stability of the plasma. This is because the power injected into the plasma depends on the electrical conductivity of the plasma generation region, and the plasma cannot be maintained under gas flow conditions that impair the stability of the electrical conductivity in this generation space.
Therefore, the flow rate of the r gas cannot be increased without limitation.

When the input power is increased, the plasma is stabilized and the flame output is increased. However, since the temperature of the plasma is increased, the loss due to heat conduction to the wall of the electrically insulating tube is increased, and the overall heat balance is reduced. The proportion of the amount of heat of the plasma frame is reduced. When using plasma as a heat source, high energy efficiency is required to reduce running costs, but in our measurements,
More than half of the plasma input power is lost in the torch. The plasma torch is cooled for thermal protection of the components, and heat loss is inevitable. However, it is desired to reduce the loss as much as possible.

SUMMARY OF THE INVENTION An object of the present invention is to provide an inductively coupled plasma apparatus which solves the above-mentioned problems of the prior art and is excellent in stability and can obtain a high-efficiency, large-output plasma flame output. .

[0009]

In order to achieve the above object, the present invention provides an electric insulating tube, a high-frequency induction coil wound around the electric insulating tube, and a gas introduced into the electric insulating tube in a circumferential direction. A gas introduction section having a first nozzle to be introduced and a second nozzle to be introduced radially and arranged at one end of the electric insulating pipe, and a high-frequency induction coil extending from the end on the gas introducing section side to the inside of the electric insulating pipe. And an inductively coupled plasma apparatus that uses a plasma gas introduced into the insulating tube, a high-frequency current flowing through a high-frequency induction coil to convert the gas into plasma, and (1) insulation of the ground electrode. A third nozzle for introducing the plasma gas into the insulating tube in the axial direction is provided on the axial end face on the tube inner side.

(2) Further, in the inductively coupled plasma apparatus of (1), the plasma gas is inclined with respect to the axial direction on the axial end face of the ground electrode inside the insulating tube, adjacent to the third nozzle. At least one fourth nozzle to be introduced
It shall be provided individually. (3) Alternatively, in the inductively coupled plasma apparatus of (1), a gas rectifying plate is provided in the plasma gas introduction path inside the ground electrode of the third nozzle.

(4) In the inductively coupled plasma apparatus of (1) to (3), a thin cylindrical portion is provided coaxially with the high-frequency induction coil on the axial end face of the ground electrode facing the inside of the electrically insulating tube. Shall be arranged. If the third nozzle is provided as in the above (1), the gas is introduced in the direction of the central axis of the plasma formed inside the electric insulating tube, and this gas has strong directivity in the axial direction. Therefore, the velocity component in the axial direction of the plasma gas increases, and the amount of the plasma flame blown out from the plasma torch increases. That is, a plasma frame having a large heat output can be obtained.

Further, the stability of the plasma with respect to such a gas flow in the direction of the central axis is extremely good. That is,
The electric field strength is E [V / m] and the plasma conductivity is σ [mho /
m], the power injection amount P into the plasma [W / m ³ ]
Is

[0013]

[Number 1] is given by P = σE ² (1), since in the central axis from the principle of generation of an inductively coupled plasma induced electric field E (theta) is zero, the power injection volume P is also zero. Therefore, even if a low-temperature gas is introduced on the central axis and the conductivity of the plasma near the central axis fluctuates or becomes unstable, there is no significant effect on the vicinity of the wall of the electrically insulating tube related to the maintenance of plasma formation. The plasma is stable.

That is, if the third nozzle as in the above (1) is provided, a stable plasma can be obtained with a large thermal output of the plasma frame. In addition, the viscosity of the gas that has been turned into plasma is about five times that of the gas at room temperature. For this reason, the gas introduced in the axial direction hardly spreads after entering the plasma, and passes through the center of the plasma as an airflow having a width substantially equal to the diameter of the nozzle. As described above, since power is not injected into the gas introduced on the central axis itself and is not heated, heating of the gas introduced in the axial direction depends on heat transfer from the plasma. Therefore, the larger the gas flow diameter of the gas introduced in the axial direction, the larger the contact area with the plasma and the greater the amount of heat transfer. Further, when the radial spread increases, the power injection due to the induced electric field also increases, and the heating amount also increases. As a result, heating of the gas flowing in the axial direction is promoted, and the heat output of the plasma flame is increased. On the other hand, if the nozzle of the gas introduced in the axial direction is large in diameter, the viscosity coefficient of the plasma is large as described above. Becomes That is, the flow of the gas introduced in the axial direction needs to have an appropriate amount of spread.

Therefore, a fourth nozzle for introducing the plasma gas obliquely to the axial direction is provided adjacent to the third nozzle as in the above (2), or (3)
If a gas rectifying plate is provided in the plasma gas introduction path as described above, the spread of the gas flow in the axial direction introduced from the end face of the ground electrode and the directivity can be adjusted, so that the plasma stability can be improved. Effectively heated plasma can be obtained without any loss.

If the thin cylindrical portion is arranged on the axial end face as in the above (4), the distance between the nozzle for introducing gas in the axial direction and the generated plasma is reduced. The gas flow is more easily controlled since it is further separated according to the length of the cylindrical portion. In addition, since the surface area of the electrode in contact with the plasma is reduced, heat loss to the ground electrode is reduced, resulting in a more efficient inductively coupled plasma device.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION

<First Embodiment> FIG. 1 is a sectional view of a main part showing a basic structure of a first embodiment of an inductively coupled plasma device according to the present invention. In the figure, reference numeral 1 denotes an electric insulating tube having a double structure composed of an inner cylinder 1a and an outer cylinder 1b made of quartz, and has an inner diameter of 59 mm. Reference numeral 2 denotes a high-frequency induction coil wound around the outer periphery of the electric insulating tube 1 and has a diameter of 90 mm and a number of turns of 3 turns. The high-frequency induction coil 2 is connected to a vacuum tube self-excited high-frequency power supply (not shown) having a maximum voltage of 10 kV, a maximum output of 75 kW, and a frequency of 4 MHz for supplying a high-frequency induction current.
A gas inlet 4 and a ground electrode 5 </ b> A are arranged above the electric insulating tube 1. Among them, a gas inlet 4a for supplying gas in the radial direction to the inside of the electrically insulating tube 1 and a gaseous ring-shaped gas outlet are provided in the gas inlet 4 in the same manner as in the conventional example shown in FIG. A nozzle 4c, a circumferential gas inlet 4b for supplying gas in the circumferential direction, and a circumferential ring gas blowing nozzle 4d are provided. On the other hand, the ground electrode 5A
Is provided with an axial gas inlet 5a and an axial main nozzle 5c communicating with the axial gas inlet 5a to supply gas to the inside of the electrically insulating tube 1 in the axial direction. A radial gas inlet 4a and a circumferential gas inlet 4b of the gas inlet 4;
An axial gas inlet 5a of the ground electrode 5A is connected to a gas supply pipe 6 connected to a plasma gas supply source (not shown).
Are connected via a gas flow control valve 11 so that the flow rate of the plasma gas supplied from each inlet can be individually adjusted by each gas flow control valve 11. Cooling water is flowed in a passage between the inner tube 1a and the outer tube 1b made of quartz, and the tube surface is cooled to protect the electrically insulating tube 1 from heat of plasma generated in the tube. . Although not shown, the ground electrode 5A is grounded to the ground side in a water-cooled manner and is capacitively coupled to the high-frequency induction coil 2.

FIGS. 2 and 3 show the results of measuring the characteristics of the inductively coupled plasma apparatus shown in FIG. 1, and are characteristic diagrams showing the heat balance when plasma is formed by supplying argon gas. 2 shows that the radial flow rate introduced from the radial gas inlet 4a of the gas inlet 4 is 35 [l / min].
The heat generated when argon plasma was formed with the circumferential flow rate introduced from the circumferential gas inlet 4b being 10 [l / min] and the axial flow rate being introduced from the axial gas inlet 5a of the ground electrode 5A being zero. The balance is shown for various input power amounts. As can be seen in the figure, the plasma flame output increases with increasing input power,
Since the ratio of the loss of the electric insulation tube, that is, the amount of heat loss to the wall of the electric insulation tube increases, the ratio of the plasma flame output to the whole decreases with the increase of the input power. The sharp rise in the loss of the electric insulating tube is due to the plasma temperature rising due to an increase in the input power.

FIG. 3 shows that the flow rate in the radial direction is 35 [l / min] and the flow rate in the circumferential direction is 10 [l / min], as in the case of FIG. (L /
2] shows the heat balance when an argon flow rate is introduced to form an argon plasma with respect to various input power amounts. As can be seen from the figure, the output of the plasma flame is increased as compared with the case of FIG. It is shown that by introducing the gas supplied in the axial direction, the amount of heat transfer of the plasma in the axial direction is increased, and a stable plasma flame having a large heat output is obtained.

<Second Embodiment> FIG. 4 is a sectional view of a main part showing a basic structure of a second embodiment of the inductively coupled plasma device according to the present invention. The difference between the configuration of the present embodiment and the configuration of the first embodiment is that the ground electrode 5B has an axial gas inlet 5b and an axial gas inlet 5b in addition to the axial main nozzle 5c communicating therewith. An axial sub-nozzle 5d for supplying gas to the inside of the electric insulating tube 1 with a slight inclination in the axial direction in communication therewith is provided, and the axial gas inlet 5b is connected to the gas flow control valve 11. In that it is connected to the gas supply pipe 6 via

Therefore, in this configuration, the flow rate supplied from the axial main nozzle 5c in the axial direction and the flow rate supplied from the axial sub-nozzle 5d with a slight inclination with respect to the axial direction by operating the gas flow control valve 11 Can be adjusted to control the radial spread of the plasma gas supplied as the axial gas flow, so that the heating of these gases is effectively promoted without impairing the stability of the plasma. As a result, a plasma frame having a large heat output can be obtained.

<Third Embodiment> FIG. 5 is a sectional view of a main part showing a basic configuration of a third embodiment of the inductively coupled plasma device according to the present invention. The difference between the configuration of the present embodiment and the configuration of the first embodiment is that the axial gas inlet 5a of the ground electrode 5C is wide open inside the electric insulating tube 1 and has a large axial direction for supplying gas in the axial direction. The gas rectifying plate 13 is provided near the large-diameter nozzle 5e in the axial direction of the path, communicating with the large-diameter nozzle 5e.

Therefore, in the present configuration, the gas distribution plate 13 adjusts the velocity distribution of the gas in the axial direction when it enters the inside of the electric insulating tube 1, so that the gas introduced in the axial direction can be heated. It is possible to obtain a plasma frame which is effectively promoted, maintains plasma stably, and has a large heat output. <Fourth Embodiment> FIG. 6 is a sectional view of a main part showing a basic configuration of a fourth embodiment of the inductively coupled plasma device according to the present invention. The difference of the configuration of the present embodiment from the configuration of the first embodiment is that the ground electrode 5D is coaxial with the high-frequency induction coil on the axial end face facing the inside of the electric insulating tube 1 and the thin cylindrical portion 14 is provided.
It is provided with.

Therefore, in this configuration, the gas supplied in the axial direction from the axial main nozzle 5c is supplied to the thin cylindrical portion 1
Since the gas is supplied into the plasma after flowing through the inside of the nozzle 4, the space between the plasma in the axial direction main nozzle 5c and the plasma is increased, and the control of the gas flow in the axial direction becomes easier. In addition, since the contact surface area of the ground electrode 5D in contact with the plasma is reduced, heat loss at the ground electrode 5D can be reduced.

FIG. 7 is a characteristic diagram showing a heat balance when plasma is formed by supplying argon gas in the inductively coupled plasma apparatus shown in FIG. This figure shows the same gas flow conditions as in FIG. 3 of the first embodiment, that is, a radial flow rate of 35 [l / min], a circumferential flow rate of 10 [l / min],
In addition, it is a measurement result of a heat balance when an argon plasma is formed at an axial flow rate of 15 [l / min]. As can be seen, the plasma flame output is further increased and the ground electrode loss is significantly reduced as compared to the characteristics of the first embodiment of FIG. That is, in this configuration, a loss can be reduced, plasma can be stably maintained, and a plasma frame having a large thermal output can be obtained.

<Fifth Embodiment> FIG. 8 is a sectional view of a main part showing a basic structure of a fifth embodiment of the inductively coupled plasma device according to the present invention. This embodiment is characterized in that the ground electrode 5E is provided with an axial main nozzle 5c and an axial sub-nozzle 5d as in the second embodiment, and a thin cylindrical portion 14A is formed on the axial end face as in the fourth embodiment. The point is that it is provided. Therefore, in this configuration, by adjusting the flow rate from the axial main nozzle 5c and the axial sub-nozzle 5d, the radial spread of the gas flow in the axial direction can be controlled. Since the distance from the plasma is increased, the control of the gas flow becomes easier, and the loss of the ground electrode is greatly reduced. That is, in this configuration,
The heating of the gas in the axial direction is effectively promoted without impairing the stability of the plasma, and a plasma flame having a large heat output can be obtained.

<Sixth Embodiment> FIG. 9 is a sectional view of a main part showing a basic configuration of a sixth embodiment of the inductively coupled plasma device according to the present invention. This embodiment is characterized in that the ground electrode 5F is provided with an axial main nozzle 5c as in the first embodiment,
A thin cylindrical portion 14B is provided on the axial end surface as in the embodiment,
Further, as in the third embodiment, a gas flow regulating plate 13A is provided near the outlet of the thin cylindrical portion 14B. Therefore, in this configuration, the flow of the gas in the axial direction is introduced into the plasma by adjusting the velocity distribution, so that the introduced gas can be effectively heated, the plasma can be stably maintained, and the heat of the plasma flame can be maintained. The output can be increased.

[0028]

As described above, in the present invention, the inductively-coupled plasma device is configured as described in (1) the first aspect of the present invention, so that the plasma torch frame can be maintained without impairing the stability of the plasma. It is possible to increase the output, and it is possible to generate a high-efficiency, high-efficiency, high-power plasma flame output with excellent stability. Thus, an inductively coupled plasma device can be obtained.

(2) According to the second, third or fourth aspect, the gas introduced into the plasma is heated more efficiently, so that the stability is excellent and the efficiency is high. It is more suitable as an inductively coupled plasma apparatus capable of generating an output plasma flame output.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing a basic configuration of a first embodiment of an inductively coupled plasma apparatus of the present invention.

FIG. 2 is a characteristic diagram showing a heat balance when an argon plasma is formed without introducing an axial gas in the inductively coupled plasma apparatus of the first embodiment.

FIG. 3 is a characteristic diagram showing a heat balance when an argon plasma is formed while introducing an axial gas in the inductively coupled plasma apparatus of the first embodiment.

FIG. 4 is a sectional view of a main part showing a basic configuration of a second embodiment of the inductively coupled plasma apparatus of the present invention.

FIG. 5 is a sectional view of a main part showing a basic configuration of a third embodiment of the inductively coupled plasma device of the present invention.

FIG. 6 is a sectional view of a main part showing a basic configuration of a fourth embodiment of the inductively coupled plasma device of the present invention.

FIG. 7 is a characteristic diagram showing a heat balance of the inductively coupled plasma apparatus according to the fourth embodiment when argon plasma is formed.

FIG. 8 is a sectional view of a main part showing a basic configuration of a fifth embodiment of the inductively coupled plasma device of the present invention.

FIG. 9 is a sectional view of a main part showing a basic configuration of a sixth embodiment of the inductively coupled plasma device of the present invention.

FIG. 10 is a partial cross-sectional view showing a basic configuration of a conventional inductively coupled plasma device.

11 is a partial cross-sectional view showing a configuration of a gas supply unit of the conventional inductively coupled plasma device of FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 electrical insulating tube 2 high-frequency induction coil 4 gas inlet 4 a radial gas inlet 4 b circumferential gas inlet 4 c radial ring gas outlet nozzle 4 d circumferential ring gas outlet nozzle 5 A, 5 B, 5 C ground electrode 5 D, 5 E , 5F Ground electrode 5a, 5b Axial gas inlet 5c Axial main nozzle 5d Axial sub-nozzle 5e Axial large diameter nozzle 6 Gas supply pipe 11 Gas flow control valve 12 Plasma 13, 13A Gas rectifying plate 14 Thin cylindrical portion 14A , 14B Thin cylinder

Claims (4)

[Claims] An electric insulating tube, a high-frequency induction coil wound around the electric insulating tube, a first nozzle for introducing gas into the electric insulating tube in a circumferential direction, and a second nozzle for introducing gas in a radial direction. A gas introduction portion disposed at one end of the electric insulation tube, and a ground electrode disposed coaxially with the high-frequency induction coil from the end on the gas introduction portion side to the inside of the electric insulation tube. In an inductively coupled plasma apparatus that uses a plasma gas to introduce a plasma gas into a high-frequency induction coil and convert the gas into plasma, an axial end face of the ground electrode on the inner side of the insulating tube introduces the plasma gas into the insulating tube in the axial direction. Third
An inductively coupled plasma device comprising: a nozzle. 2. The inductively coupled plasma apparatus according to claim 1, wherein the plasma gas is inclined with respect to the axial direction on an axial end face of the ground electrode inside the insulating tube, adjacent to the third nozzle. An inductively coupled plasma device comprising at least one fourth nozzle to be introduced. 3. The inductively coupled plasma apparatus according to claim 1, further comprising a gas rectifying plate in a plasma gas introduction path inside the ground electrode of the third nozzle. 4. The inductively coupled plasma device according to claim 1, further comprising a thin cylindrical portion formed coaxially with the high frequency induction coil on an axial end face of the ground electrode facing the inside of the electric insulating tube. An inductively coupled plasma device.