JPS5921153B2 - Glow discharge device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a glow discharge device, and more particularly to a glow discharge device having means for spatially and temporally controlling glow discharge.

Conventionally, there is an ion nitriding apparatus as shown in FIG. 1 as an example of this type of apparatus.

In the figure, 1 is a discharge furnace, 2 is a gas cylinder that supplies gas such as nitrogen to the discharge furnace 1, 3 is a vacuum pump, 4 is a main power source, 5 is a cock for adjusting and supplying gas flow rate, and 6 is an anode , 1 is a cathode, which is the object to be treated here. 8
is a temperature sensor that detects the temperature of the object T to be processed.

9 is an anode terminal connected to one end of the main power supply 4, 10 is a cathode terminal connected to the other end of the main power supply 4, 11 is a temperature detection terminal, 121, 122 and 123 are electrical insulators, and 13 is a discharge furnace. 1 is a furnace wall, 14 is a stabilizing resistor for stabilizing the discharge, and 15 is a switch for opening and closing the main power source.

Next, the operation will be explained.

First, a gas containing nitrogen is supplied from the gas cylinder 2 to the discharge furnace 1 while being evacuated by the vacuum pump 3 as indicated by the arrow so as to maintain the gas atmosphere at a low pressure (0.5 to 10 Torr). In this state, the main power supply 4 connects the anode 6 and cathode 1.
When a DC voltage is applied between (the object to be treated), discharge breakdown occurs between the electrode 6 and T, and glow discharge occurs later. Nitrogen in the atmosphere is ionized by glow discharge and has a high kinetic energy, which causes it to become a cathode. Collisions with the surface of the (processed object). The kinetic energy of this ion collision is converted into thermal energy and heats the cathode T (workpiece). When the cathode 7 (workpiece) is heated in this way, the cathode T (
The surface of the object) is nitrided. Furthermore, the temperature of the cathode 7 (workpiece) is controlled by detecting the temperature of the cathode □ (workpiece) from the temperature sensor 8VC and feeding it back to the main power supply 4 to control the current flowing to the glow discharge. It's getting old. Conventional ion nitriding equipment using glow discharge is configured as described above, so when glow discharge is generated on the workpiece, it is possible to spread the glow discharge over the entire surface and uniformly ion nitride the entire surface, but glow discharge The drawback is that it is not possible to spatially control so-called glow discharge, which can occur only in a limited area of the object to be treated. In addition, a switch 15 is required to start and stop glow discharge, and starting and stopping large current glow discharge has the disadvantage that the capacity of the switch becomes large and the cost increases. This invention was made to eliminate the drawbacks of the conventional ones, and includes a movable auxiliary electrode for causing preliminary glow discharge between the anode and cathode (workpiece) in the discharge furnace. By controlling at least one of the discharge current, atmospheric gas pressure, and cathode temperature, and applying a voltage with a pulsating waveform that crosses at least the minimum glow ± maintenance voltage between the anode and the cathode,
It is an object of the present invention to provide a glow discharge device that can generate glow discharge in a limited portion of a workpiece and can perform ON/OFF control.

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 2, the discharge furnace 1, gas cylinder 2, hexagram, and vacuum pump 3 are the same as those in FIG. 1, and are therefore omitted. Here, only the glow discharge portion (anode and cathode portions) and the power supply circuit are illustrated. In Figure 2, 4 is the main power supply and commercial AC power supply 1
6. It is composed of an isolation transformer Trl for making the primary side and the secondary side electrically independent, and a full-wave rectifier circuit 17.

18 is an auxiliary power supply circuit connected to the secondary side of the high voltage transformer Tr2, 19 is a thyristor, 20 is a gate circuit and temperature control circuit of the thyristor, 21 is a current limiting resistor for controlling the current, and 22 is a main electrode This is an auxiliary electrode provided between an anode 6 and a cathode 7, which are movable three-dimensionally relative to the main electrodes 6 and 7.

Note that part A of the cathode 7, which acts as an object to be treated, indicates a part where glow discharge does not occur, and part B indicates a part where glow discharge is desired to occur. Next, the operation of this device will be explained.

First, the auxiliary electrode 22 is moved to the vicinity of the portion B of the object to be treated where the surface treatment is to be performed by performing electric discharge. Continuing,
Transformer Tr, Vc, anode 6 and cathode 7 (object to be treated)
The maximum value Vmax of the voltage applied between the anode and the cathode is lower than the discharge breakdown voltage value between the anode and the cathode, and the minimum glow sustaining voltage V.
It is set to be higher, that is, to satisfy the condition of VO<VnlaX<EB. Furthermore, in this state, when the thyristor 19 is turned ON by the gate circuit 20, a high voltage from the auxiliary power supply 18 is applied to the auxiliary electrode 22. Then, a small preliminary glow discharge is generated between the auxiliary electrode 22 and the B section of the cathode 7, which is limited by the current limiting resistor 21. Due to the induction, a main glow discharge occurs between the anode 6 and the cathode 7, and the surface of the B portion is treated. Next, temperature sensor 8V
The temperature of part B of the object 7 to be processed is detected from C, and instructions of 0N and 0FF are given to the gate circuit of the thyristor 19 to open and close the thyristor 19. Then, the output waveform of the main power supply 4 in FIG. 2 is a full-wave rectified waveform 25 as shown in FIG. Main glow 7 discharge is 0N-0FF
It is possible to control the temperature of part B. To explain in more detail, the discharge area S of glow discharge is determined by the atmospheric gas pressure P, the temperature T1 of the cathode (workpiece), the glow discharge current 1, and the proportionality constant determined by the type of gas and the cathode material is k. Then, these relationships become the following formula:

Follow me? 1), the discharge area S can be limited by controlling the temperature T1, the glow discharge current 1, or the gas pressure P. Further, since the glow discharge is induced by the plasma generated by the preliminary glow discharge, the glow discharge spreads at the discharge position including the preliminary glow discharge.

Therefore, when the auxiliary electrode is moved to a portion (processing surface) where discharge is desired, a glow discharge having a glow discharge area S is generated at that portion. In this way, only a partial glow discharge can be obtained by controlling the discharge area S and variable control of the position of the auxiliary electrode.

In addition, glow discharge tends to migrate to areas where the distance between the electrodes is short, so if the glow discharge is turned on continuously, the glow discharge induced by the preliminary glow discharge of the auxiliary electrode will spread to the area near the auxiliary electrode. There may be a transition from the treated surface (for example, B surface) to a portion where the spacing between electrodes is short (for example, A surface).

In order to prevent this migration of glow discharge, in practice, the voltage applied to the main electrode is made into a pulsating waveform, and the glow discharge is maintained on the treated surface B near the auxiliary electrode by cutting off the glow discharge for each pulsating waveform. be able to. For example, suppose that the gate circuit 20 outputs an ON instruction signal 24 from point f to point g, as shown in the upper part of FIG. 3a. Then, the voltage value of the full-wave rectified waveform 25 in FIG. 3a is the minimum glow maintenance voltage V. A main glow discharge occurs at a point h when the voltage is higher than that, and the point decreases every cycle, and the main glow discharge disappears at a point 1 when the voltage value of the full-wave rectified waveform 25 first becomes less than o after passing a point g. . Therefore, a glow current having a waveform 26 flows between the main electrodes to control the temperature of the B portion of the object. However, when implementing the present invention, the conditions under which this glow discharge can be spatially controlled vary depending on the pressure of the discharge gas, the spatial positions of portions A and B of the object 7, ultraviolet rays, etc. , these conditions will also be considered. In the above embodiment, the voltage waveform of the main power source 4 is shown as a full-wave rectified waveform, but the voltage waveform of the main power supply 4 is at least the minimum voltage ±maintenance voltage as shown in FIG. 3b.

It may be a pulsating flow waveform 27 that crosses the . In this case, the glow current has a waveform 28. Furthermore, an AC waveform 29 as shown in FIG. 3c may be used. In the case of an AC waveform, either of the main electrodes 6 and 7 can serve as a cathode, so if two objects to be processed are used as electrodes, there is an effect that two objects to be processed can be processed at the same time. The glow current in this case has a waveform 30. Although not shown, the voltage waveform of the main power source 4 may be half-wave rectified. Further, in the above embodiments, the case of surface treatment of electrodes has been described, but other glow discharge devices, such as cleaning devices, may be used, and the same effects as in the above embodiments can be obtained. As described above, according to the present invention, the voltage waveform of the main power supply is made into a pulsating waveform that crosses at least the minimum glow maintenance voltage, and the auxiliary electrode is movable between the main electrodes and the auxiliary electrode is used to perform a preliminary glow discharge. Since a power source is provided and at least one of the glow discharge current, atmospheric gas pressure, and temperature of the main electrode to be treated is controlled, the glow discharge can be spatially controlled, and the glow discharge can be started and stopped. is also easy, 0N, 0FF
Can be controlled.

[Brief explanation of drawings]

Figure 1 is a sectional view showing a conventional glow discharge surface treatment device.
FIG. 2 is a block diagram of a glow discharge surface treatment apparatus according to an embodiment of the present invention, and FIG. 3 is a diagram showing current and voltage waveforms of the glow discharge surface treatment apparatus of the present invention. In the figure, 1 is a discharge furnace, 2 is a sponge, 3 is a vacuum pot, 4 is a main power supply, 6 is an anode, 7 is a cathode (workpiece),
8 is a temperature sensor, 18 is an auxiliary power supply circuit, 20 is a gate circuit, 22 is an auxiliary electrode, Tr, Tr2 is a transformer, M
ax is the peak voltage value of the output waveform of the main power supply 4, and VO is the minimum glow maintenance voltage value.

Claims (1)

[Claims] 1. A pair of main electrodes facing each other with a predetermined gap therebetween, an auxiliary electrode provided between the main electrodes and movable relative to the main electrode, and the pair of main electrodes. A main power supply is connected to the main electrode and applies a voltage with a pulsating waveform that crosses at least the minimum glow maintenance voltage between the main electrodes to generate and reduce glow discharge at predetermined intervals, and a preliminary glow is connected between the auxiliary electrode and the main electrode. A glow discharge device comprising: an auxiliary power source for causing discharge; and means for controlling at least one of glow discharge current, atmospheric gas pressure, and temperature of one of the main electrodes. 2. The glow discharge device according to claim 1, wherein the output voltage waveform of the main power source is an alternating current, full-wave rectification, or half-wave rectification voltage waveform. 3. The glow discharge device according to claim 1 or 2, wherein the output of the auxiliary power source is controlled to be turned on or off.