JP2000266566A - Method for discriminating rotary position of vacuum variable condenser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need for measuring data for each vacuum variable condenser or the adjustment of the part constant of a circuit by miniaturizing the detection circuit of the rotary position of the vacuum variable condenser and extending a mechanical life. SOLUTION: In the method for discriminating the rotary position of a vacuum variable condenser 5, a code wheel 14 with a slit according to the rotation of the rotary shaft of a vacuum variable condenser 5, the presence or absence of the slit of the code wheel 14 is detected without any contact for outputting a signal for detecting the presence or absence of the slit, and the number of the slit presence/absence detection signals is counted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining a rotation position when a rotation axis of a vacuum variable capacitor in a high-frequency automatic matching device used in a semiconductor manufacturing apparatus or the like is rotated by a stepping motor.

[0002]

2. Description of the Related Art As an apparatus for manufacturing semiconductors, liquid crystals, and the like,
There is an apparatus using plasma generated by high-frequency power. FIG. 1 is a functional explanatory diagram of an apparatus using plasma generated by high-frequency power. In FIG. 1, a high-frequency power supply 1 is a power supply for generating high-frequency power, and supplies a high-frequency power to a plasma load device 3 via a coaxial cable 4 which is a transmission line of the high-frequency power and a high-frequency automatic matching device 2. It is. The plasma load device 3 is a device that generates plasma using high-frequency power supplied from the high-frequency power supply 1 and uses the plasma for applications such as etching and CVD.

The high-frequency automatic matching device 2 automatically adjusts the impedance between the transmission line of the high-frequency power and the plasma load device 3 in order to efficiently supply the high-frequency power supplied from the high-frequency power source 1 to the plasma load device 3. It is a device to match. Transmission line of high frequency power and plasma load device 3
If the impedance is not matched, the reflected wave power is generated in the plasma load device 3, so that high-frequency power cannot be efficiently supplied to the plasma load device 3.

[0004] In order to match the impedance, a method of converting the impedance by a capacitor and an inductor is generally known. Normally, since the impedance of the plasma load device 3 is not constant, the impedance is matched using a variable impedance element such as a vacuum variable capacitor 5 (hereinafter, referred to as a variable capacitor 5) or a variable inductor.

In the high-frequency automatic matching device 2 shown in FIG.
The impedance is converted using two variable capacitors and two inductors. In such a circuit configuration, in order to convert the impedance, the capacitance of the variable capacitor may be changed according to the impedance of the plasma load device 3. Depending on the oscillation frequency of the high-frequency power supply 1, there is also a circuit configuration using a fixed capacitor, a variable inductor, or the like.

Here, the variable condenser 5 has a structure in which the inside is evacuated and the capacitance is changed by rotating the rotating shaft. FIG. 2 is a rotation position / capacitance correspondence diagram showing an example of the capacitance with respect to the rotation position of the rotary shaft of the variable condenser 5 (hereinafter, referred to as the rotation position of the variable condenser 5). Therefore, if the rotation axis of the variable condenser 5 is connected to the rotation axis of the motor, the rotation axis of the motor can be rotated to change the capacitance of the variable condenser 5. There are various types of motors such as a DC motor and a servo motor, and a stepping motor 6 is widely used in the high-frequency automatic matching device 2.

Therefore, if the rotating shaft of the variable condenser 5 and the rotating shaft of the stepping motor 6 are connected by using the coupling 7, the rotating shaft of the variable condenser 5 rotates in accordance with the rotation of the rotating shaft of the stepping motor 6, and the static The capacitance can be changed. Here, assuming that the rotational position of the variable condenser 5 when the impedance is matched is determined or set in advance, the rotational axis of the variable condenser 5 is rotated by the difference between the rotational position and the current rotational position. Then, the impedance can be matched. That is, if the high-frequency automatic matching device 2 detects the rotation position of the rotation shaft of the stepping motor 6 (hereinafter, referred to as the rotation position of the stepping motor 6), the rotation position of the variable condenser 5 can be known. Further, impedance can be matched by controlling the rotational position of the stepping motor 6.

FIG. 3 shows the arrangement of the prior art when the rotation position detecting circuit 17 comprising the multi-rotation potentiometer 8 and the gears 9 and 10 used in the prior art is mounted so that the rotational position of the variable condenser 5 can be determined. FIG. In the prior art, as shown in FIG. 3, the rotational position of the variable condenser 5 is detected using the multi-rotation potentiometer 8 and the gears 9 and 10. The rotation shaft of the variable condenser 5 is connected to the rotation shaft of the stepping motor 6 by using a coupling 7,
By rotating the rotating shaft of the stepping motor 6, the rotating shaft of the variable capacitor 5 is rotated to change the capacitance. The coupling 7 uses an insulating material to insulate the variable condenser 5 from the stepping motor 6.

A support plate 11 made of an insulating material electrically insulates the variable condenser 5 from the fixed plate 12 and fixes the variable condenser 5 to the fixed plate 12. The fixing plate 12 fixes the stepping motor 6 and the support plate 11.

Gears 9 and 10 are attached to the rotation shaft of the stepping motor 6 and the rotation shaft of the multi-rotation potentiometer 8, respectively.
The stepping motor 6 and the multi-rotation potentiometer 8 are arranged so that the gears of the two gears 9 and 10 mesh with each other. When the rotation shaft of the stepping motor 6 rotates, the two gears 9 are rotated. , 10 rotate the rotary shaft of the multi-rotation potentiometer 8.

The multi-rotation potentiometer 8 is an element whose resistance changes as the rotation shaft rotates. Therefore, the rotation axis of the multi-rotation potentiometer 8 rotates according to the rotation of the rotation axis of the stepping motor 6, and the resistance value changes. That is, when the rotation axis of the variable condenser 5 rotates,
The resistance value of the multi-turn potentiometer 8 changes.

FIG. 4 is a voltage detection circuit diagram for detecting a voltage that changes according to the resistance value of the potentiometer 8. A point A in FIG. 4 is a detection point of a voltage that changes according to the resistance value of the multi-rotation potentiometer 8, and a B point is a voltage detection point after the detection voltage at the A point is amplified using an amplifier circuit. As the amplifier circuit, for example, a non-inverting amplifier circuit using an OP amplifier can be used. FIG. 5 is a diagram showing the relationship between the variable position and the detected voltage, showing an example of the detected voltage at points A and B in FIG. The dotted line in FIG. 5 is the detected voltage at point A, and the solid line is the detected voltage at point B.

A conventional procedure for determining the rotational position of the variable condenser 5 from point A or point B in FIG. 4 will be described below with reference to FIG. To determine the rotational position of the variable condenser 5,
(1) A / D conversion of the voltage at point A to a digital value, and (2) a method of converting the voltage at point A by an amplifier circuit so that the voltage at point B becomes a reference voltage. There is.

(1) In the case of the method of converting the voltage at point A into a digital value by A / D conversion, the voltage at point A and the rotational position of variable condenser 5 are determined in order to determine the rotational position of variable condenser 5. The correlation data is stored in the control circuit of the high-frequency automatic matching device 2. In this case, an A / D converter is connected instead of the amplifier circuit of FIG. 4 in order to A / D convert the voltage at the point A. If the correlation data is stored, the next time the voltage at point A is detected,
Can be determined.

(2) In the case of a method of converting the voltage at point A by an amplifier circuit so that the voltage at point B becomes the reference voltage, the voltage at point B is specified as shown by the solid line in FIG. The output voltage of the amplifier circuit in FIG. For example, when the reference voltage when the rotation position of the variable condenser 5 is 10 rotations is determined to be 10 [V], and when the detection voltage at the point A when the rotation position of the variable condenser 5 is 10 rotations is 5 [V], The amplification factor of the amplifier circuit may be doubled, and the detection voltage at the point B may be set to 10 [V]. If the voltage at the point B is set to a specific reference voltage in this way, when the voltage at the point B is detected next time, the rotational position of the variable condenser 5 is compared with the previously adjusted reference voltage. Can be determined. In addition, as shown in FIG.
Since the solid line (the detected voltage at point B) is proportional, if the voltage at point B is adjusted only for one point, the other points can be calculated in proportion. For example, when the voltage at the point B detected next time is 2
In the case of [V], it can be determined that the rotation position of the variable condenser 5 is two rotations.

[0016]

The high-frequency automatic matching device 2 used in a semiconductor manufacturing apparatus or the like is often required to be miniaturized. However, in the prior art, the first problem is that the detection circuit including the multi-rotation potentiometer 8 and the gears 9 and 10 is used to detect the rotational position of the variable condenser 5, so that the volume of the detection circuit becomes large. There was a disadvantage. Further, since the gears 9 and 10 cannot be downsized for the following reasons, the detection circuit cannot be downsized.

Since the high-frequency automatic matching device 2 is required to match impedance at high speed, the variable capacitor 5
Needs to be changed at high speed. Therefore, it is necessary to rotate the rotation shaft of the stepping motor 6 at high speed. However, when the rotating shaft of the multi-rotation potentiometer 8 is rotated at a high speed, a load is applied to the rotating shaft of the multi-rotation potentiometer 8, sliding contacts, and the like. For that, the rotation axis,
In order to reduce the load on the sliding contacts and the like, it is necessary to reduce the load on the multi-rotation potentiometer 8 by increasing the gear ratio and reducing the rotation speed of the rotation shaft of the multi-rotation potentiometer 8 with respect to the rotation speed of the rotation shaft of the variable condenser 5. There is. That is,
It is necessary to make the gear 10 attached to the multi-rotation potentiometer 8 larger than the size of the gear 9 attached to the stepping motor 6.

Since the rotation angle of the rotary shaft of the variable condenser 5 is larger than the rotation angle of the rotary shaft of the multi-rotation potentiometer 8, the gear ratio is increased and the multi-rotation potentiometer 8 is rotated.
It must be designed to meet the specifications of

As a second problem, since the rotating shaft of the multi-rotation potentiometer 8 is rotated to change the resistance value, the performance deteriorates due to wear of the contact portion. Therefore, there is a disadvantage that the mechanical life is short.

As a third problem, in order to determine the rotational position of the variable condenser 5, as described above, (1) the method of A / D converting the voltage at the point A in FIG. (2) A is set so that the voltage at point B in FIG.
There is a method of converting the magnitude of the voltage at a point by an amplifier circuit. However, as shown below, if the variable condenser 5 is different, it is necessary to perform data measurement or adjustment of component constants, and there is a disadvantage that the number of work steps increases. Was.

(1) In the case of the method of A / D converting the voltage at the point A in FIG. 4 to a digital value, the detection accuracy of the multi-rotation potentiometer 8 and the dimensional accuracy of the gears 9 and 10 vary. Therefore, even if the rotational position of the variable condenser 5 is the same, the detection voltage at the point A varies. Therefore, every time the variable condenser 5 is different, it is necessary to measure the data of the correlation between the voltage at the point A and the rotational position of the variable condenser 5.

(2) In the case of a method of converting the voltage at point A by an amplifier circuit so that the voltage at point B in FIG. 4 becomes the reference voltage, the amplifier circuit shown in FIG. 4 is required. It is necessary to adjust to a constant number of parts. For example, when a non-inverting amplifier circuit using an OP amplifier is used as an amplifier circuit, it is necessary to adjust component constants such as a resistance value. Even in this case, since the detection accuracy of the multi-rotation potentiometer 8 and the dimensional accuracy of the gears 9 and 10 vary, the detection voltages at the points A and B vary even when the rotation position of the variable condenser 5 is the same. Occurs. Therefore, every time the variable condenser 5 is different, the detection voltage at the point B becomes the reference voltage.
It is necessary to adjust the component constants of the amplifier circuit.

The present invention reduces the volume of a component.
Further, by enabling the rotational position of the variable condenser 5 to be determined by non-contact means, the high-frequency automatic matching device 2
To reduce the mechanical life of the
It is an object of the present invention to eliminate the need for data measurement or adjustment of circuit component constants.

[0024]

According to the first aspect of the present invention, as shown in FIGS. 7 to 9 described later, a code wheel 14 having a slit is rotated in accordance with the rotation of a rotary shaft of a vacuum variable condenser 5. The presence / absence of a slit in the code wheel 14 is detected in a non-contact manner, and a slit presence / absence detection signal is output. In spite of the fact that the slit presence / absence detection signal gives an instruction to rotate the rotation axis of the vacuum variable condenser 5, This is a method of determining the rotational position of the vacuum variable capacitor in which the position where the slit is not changed while indicating whether or not the slit is present is the origin position of the vacuum variable capacitor 5.

In the invention of claim 2 at the time of filing, the code wheel 14 having a slit is rotated in accordance with the rotation of the rotation axis of the vacuum variable condenser 5.
4. A method of determining the rotational position of the vacuum variable capacitor, which detects the presence or absence of the slit in a non-contact manner, outputs a slit presence / absence detection signal, counts the number of the slit presence / absence detection signals, and determines the rotational position of the vacuum variable capacitor 5. It is.

The invention of claim 3 at the time of application is based on claim 2 at the time of application.
The number of slit presence / absence detection signals described in (1) is counted using a 3-bit counter, and the rotational position of the vacuum variable capacitor 5 is determined.

[0027]

FIG. 6 is a block diagram showing an embodiment of the present invention when determining the rotational position of the variable condenser 5. FIG.

The rotational position detecting circuit 17 is a detecting circuit comprising a photosensor circuit 13 and a code wheel 14 which will be described later, detects the presence or absence of a slit in the code wheel 14 by non-contact means, and converts the detection signal into a pulse signal. Output.

The 3-bit counter 18 is a pulse counter that outputs 3-bit count data, and can count the number of pulses in the range of 000 to 111 in binary. That is, the pulse number can be counted in the range from 0 to 7 in decimal. The count value is output to the control circuit 19 at regular time intervals. Here, the cycle time during which the count value is output from the 3-bit counter 18 to the control circuit 19 is shorter than the cycle time of the pulse signal output from the photosensor circuit 13 when the stepping motor 6 rotates at the maximum speed. . By doing so, the amount of change in the count value output every fixed period of time is a maximum of ± 1 pulse. For example,
There are 200 slits on the code wheel 14,
When the stepping motor 6 rotates at a maximum of 10 rotations / second, the cycle time of the pulse signal output from the photo sensor circuit 13 is 500 μsec. Therefore, the cycle time for outputting the count value from the 3-bit counter 18 to the control circuit 19 is set to 250 μsec.

Next, a description will be given by converting the count value of the 3-bit counter 18 into a decimal number. When the stepping motor 6 rotates so that the capacitance of the variable condenser 5 increases, the rotation is forward rotation, and when the stepping motor 6 rotates in the reverse direction, the rotation is reverse rotation. Every time the count value is changed from 0 → 1 → 2 → 3 → 4
→ 5 → 6 → 7 → 0 → 1 → 2... When the motor rotates in the reverse direction, the count value changes from 0 → 7 → 6 → 5 every time one pulse is input from the rotation position detection circuit 17. → 4 → 3 → 2 → 1 →
0 → 7 → 6...

The target rotational position setting circuit 20 is a circuit for setting the rotational position of the variable condenser 5 so that the capacitance matches the impedance (hereinafter, the set rotational position is referred to as a target rotational position). Note that the target rotational position is obtained or set in advance.

The control circuit 19 is a circuit having the following functions. A function for obtaining the current rotational position of the variable condenser 5 (hereinafter referred to as the current rotational position) based on the count value input from the 3-bit counter 18. The target rotation position set by the target rotation position setting circuit 20 is compared with the current rotation position, and the driver circuit 21 is driven by the difference between the target rotation position and the current rotation position so that the rotation position of the variable condenser 5 becomes the target rotation position. Function to output rotation command signal to A function of outputting a rotation command signal to the driver circuit 21 so that the rotation shaft of the stepping motor 6 rotates in an arbitrary direction.

The driver circuit 21 is a circuit for rotating the rotation shaft of the stepping motor 6 in accordance with the rotation command signal input from the control circuit 19.

Next, in the block diagram of FIG.
The operation of determining the rotational position of the variable condenser 5 will be described. First, the variable condenser 5 is rotated in the direction of the minimum rotation position in order to determine the minimum rotation position serving as a reference point of the rotation position. When the variable condenser 5 is rotated in the direction of the minimum rotation position, it stops mechanically at the minimum rotation position. At this time, the detection signal output from the photosensor circuit 13 does not change between High and Low even though the control circuit 19 supplies the rotation command signal to the driver circuit 21. Therefore, the count value output from the 3-bit counter 18 does not change. Accordingly, since it is known that the variable condenser 5 is stopped, it can be determined that the variable condenser 5 is the minimum rotation position of the variable condenser 5 serving as a reference point. By rotating the variable condenser 5 in the direction of the maximum rotation position in the same manner, the maximum rotation position can be determined. This maximum rotation position may be used as the reference point. In order for the control circuit 19 to recognize the rotation position when the minimum rotation position or the maximum rotation position is reached as a reference point, the current rotation position is set to a specific numerical value such as 0.

The control circuit 19 compares the target rotational position with the current rotational position and controls the driver circuit 21 to rotate the stepping motor 6 by the difference.
And outputs a rotation command signal.

When the stepping motor 6 rotates, a pulse signal is output from the photo sensor circuit 13, so that
The count value of the 3-bit counter 18 changes. This count value is input to the control circuit 19 at regular intervals.
Note that the amount of change in the count value every fixed period is a maximum of ± 1 pulse.

The control circuit 19 calculates the current rotational position from the change amount of the rotational position calculated by (newly input count value)-(previously input count value).
When the amount of change is -7, the amount of change is +1. When the amount of change is +7, the amount of change is -1. The current rotation position when the change amount of the rotation position is +1 is (previous current rotation position +1). The current rotational position when the change amount of the rotational position is -1 is (previous current rotational position -1).

By repeating the above, the variable condenser 5 can be set to the target rotational position. Note that the target rotation position is not constant, and the target rotation position setting circuit 2
May be changed by 0. For example, when the impedance of the plasma load device 3 changes, it is necessary to change the capacitance of the variable condenser 5 in order to match the impedance. That is, it is necessary to change the target rotation position of the variable condenser 5.

The control power supply of the high frequency automatic matching device 2 is turned off.
If, for example, the function of maintaining the current rotational position of the variable condenser 5 does not exist, the current rotational position of the variable condenser 5 may be determined again by the above-described method.

[0040]

The operation of each mechanism and circuit shown in FIGS. 7 to 11 will be described below with reference to FIG. FIG.
FIG. 2 is a configuration diagram of the present invention when a rotation position detection circuit 17 including a photo sensor circuit 13 and a code wheel 14 is attached so that the rotation position of the variable condenser 5 can be detected. The rotation axis of the variable condenser 5 uses the coupling 7,
When the rotation axis of the stepping motor 6 is connected to the rotation axis of the stepping motor 6, the rotation axis of the variable condenser 5 is rotated to change the capacitance. The coupling 7 insulates the variable condenser 5 from the stepping motor 6 using an insulating material. The supporting plate 15 made of an insulating material includes a variable condenser 5 and a fixing plate 16.
Are electrically insulated from each other, and the variable condenser 5 is fixed to the fixing plate 1.
Fix to 6. The fixing plate 16 fixes the stepping motor 6 and the support plate 15.

The code wheel 14 is fixed to the rotation shaft of the stepping motor 6. The photo sensor circuit 13
The code wheel 14 is installed immediately below the slit so that the presence or absence of the slit can be detected.

FIG. 8 is an explanatory diagram of a code wheel shape for explaining the shape of the code wheel 14. As shown in FIG. 8, the code wheel 14 has a shape of a concentric disk with a slit along the circumference, and can reflect light in a portion without the slit.

The photo sensor circuit 13 is a circuit that detects reflected light of light emitted by the light emitting unit at the light receiving unit, and changes the detection signal between High and Low in accordance with the level of the reflected light. It outputs two detection signals of phase A and phase B shifted in phase. The photosensor circuit 13 is, for example, an HED manufactured by HP (Hewlett-Packard).
R-8000 can be used.

FIG. 9 is an explanatory diagram of the operation of the photosensor circuit for explaining the operation of the photosensor circuit 13. FIG. 9 (a)
When the portion of the code wheel 14 where there is no slit reaches just above the photosensor circuit 13, the light emitted from the photosensor circuit 13 is reflected, and the detection signal becomes High, as shown in FIG. The portion of the code wheel 14 where the slit is present as shown in FIG.
, The light emitted from the photosensor circuit 13 is not reflected, and the detection signal becomes low. A photo sensor circuit 13 of the opposite logic may be used.

In this way, when the rotation shaft of the stepping motor 6 rotates, the code wheel 14
Also rotates, the detection signal of the photo sensor circuit 13 is
It is output as a High and Low pulse signal. When the rotation axis of the stepping motor 6 is not rotating,
Since the code wheel 14 also does not rotate, the photo sensor 1
The detection signal of No. 3 remains High or Low.

As described above, since the detection signal output from the photosensor circuit 13 can be treated as a pulse signal, the rotational position of the variable condenser 5 can be determined by counting the number of pulses.

The 3-bit counter 18 calculates a binary number from 000 to 111 (decimal number from 0 to 7) based on two detection signals of the A phase and the B phase output from the photo sensor circuit 13.
Is a circuit that counts the number of pulses in the range. The 3-bit counter 18 is, for example, a MACH21 manufactured by MACH.
0-12JC can be used.

FIG. 10 illustrates a counting operation for explaining the operation of the 3-bit counter 18 counting the pulse signal based on two detection signals of the phase A and the phase B output from the photosensor circuit 13 with the phases shifted. FIG. 1
0 (a) is a pulse signal diagram showing two detection signals of A phase and B phase outputted from the photo sensor circuit 13,
FIG. 10B is a count operation diagram illustrating the count operation of the 3-bit counter 18.

When the code wheel 14 is rotated by the rotation of the stepping motor 6, two detection signals of the A-phase and the B-phase whose phases are shifted are output from the photo sensor circuit 13 as shown in FIG. You. When the stepping motor 6 rotates forward, compared with the A-phase detection signal,
The phase of the detection signal of the B-phase detection signal is advanced.
When the stepping motor 6 rotates in the reverse direction, the phase of the detection signal of the A phase is ahead of the phase of the detection signal of the B phase.

When the rotation direction changes from the forward rotation to the reverse rotation, when the level of the A-phase detection signal changes (L
ow → High and High → Low), and the B-phase detection level becomes High. When the rotation direction changes from the reverse rotation to the normal rotation, when the level of the A-phase detection signal changes (Low → High and High → Low), the B-phase detection level becomes Low.

As shown in FIG. 10 (b), the 3-bit counter 18 uses two detection signals of phase A and phase B to detect
The number of pulses is counted. For example, when the stepping motor 6 rotates forward, when the A-phase pulse signal rises, the B-phase is High.
Do one. When the A-phase pulse signal falls, B
Since the phase is Low, the count number is not changed.
That is, the count number is incremented by 1 both when the A-phase pulse signal rises and when it falls.

When the rotation direction of the stepping motor 6 changes from the forward rotation to the reverse rotation, when the A-phase pulse signal rises, the count number is incremented by one because the B-phase is High. When the A-phase pulse signal falls,
Since the phase B is High, the count number is decremented by one. That is, the count number is not changed both when the A-phase pulse signal rises and when it falls.

From the operation described with reference to FIG. 10B, the number of pulses can be counted in the following case in the same manner as described above. When the stepping motor 6 rotates in the reverse direction, the count number is decremented by one. When the rotation direction of the stepping motor 6 changes from forward rotation to reverse rotation, the count number is not changed.

As described above, the three-bit counter 18
From the relationship between the two detection signals of the phase and the B phase, the amount of change in the pulse signal and the rotation direction of the code wheel 14 can be determined. The fact that the rotation direction of the code wheel 14 can be determined means that the rotation directions of the stepping motor 6 and the variable condenser 5 can be determined.

FIG. 11 is a circuit diagram of an embodiment of the present invention showing a specific circuit example of the block diagram of FIG. However, FIG.
Is a circuit example excluding the variable condenser 5 and the code wheel 14. Note that the control circuit 19 uses the CPU 22 for control by software, and only the CPU 22 as a main component is described for simplifying the circuit. In addition, in the driver circuit 21, only the motor driver 23, which is a main component, is described in order to simplify the circuit. Further, since FIG. 11 is an example of a circuit using two stepping motors 6, the photo sensor circuit 13 and the motor driver 23 correspond to each of the two stepping motors 6.
Used.

PORT4, PORT5 and F of CPU 22
RT1A, FRT1B, PORT6, PORT7, and PO
RT8, FRT2A, and FRT2B are signal output terminals for controlling the motor driver 23, and ADC1 and ADRT
C2 is an input terminal of a signal indicating the target rotation position sent from the target rotation position setting circuit 20, and PORT0 and PORT0
RT1 and PORT2 are input terminals for a signal indicating the count value sent from the 3-bit counter 18, and POR
T3 is an output terminal of a signal for controlling the 3-bit counter 18. The CPU 22 is, for example, an H made by Hitachi, Ltd.
D64775368CP10 can be used. This CPU2
Reference numeral 2 includes a storage unit in addition to the calculation unit and the control unit, and stores software and data such as the rotational position of the variable condenser 5.

M1, M2, M3, M4, and M5 of the motor driver 23 are input terminals for signals for setting the excitation mode of the stepping motor 6, and CLK is a signal for commanding the number of operation pulses of the stepping motor 6. CWB is an input terminal of a signal indicating the operation direction of the stepping motor 6, RESET is an input terminal of a reset signal, and A and A (inverted), B and B (inverted) PG and SG are GND terminals of a power supply, and VRE is an input terminal of a phase excitation signal of the stepping motor 6.
F is a reference voltage input terminal. Where M
4 and M5 are connected to 5V because they are not related to the excitation mode used in the present invention. Motor driver 23
For example, STK672-050 manufactured by Sanyo Electric Co., Ltd. can be used.

D0, D1, and D2 of the 3-bit counter 18
Is an output terminal of a signal indicating the count value, and RCK
Is a selection signal input terminal for determining which of the two photosensor circuits 13 receives a pulse signal, and A1 and B1 are pulse signal input terminals.

A and B of the photo sensor circuit 13 are pulse signal output terminals, and a 5 V input terminal is a 5 V input terminal. The stepping motor 6 operates by inputting a control signal from the driver circuit 21.

With the circuit as shown in FIG. 11, it is possible to constitute hardware for determining the rotational position of the variable condenser 5 described above. Further, since the CPU 22 is used, it is possible to control the rotational position of the variable condenser 5 by programming the above-described method.

[0061]

(1) In the present invention, the photo sensor circuit 13 and the code wheel 14 are used as the rotational position detecting circuit 17, and the photo sensor circuit 13 is smaller than the multi-rotation potentiometer 8 and has a smaller code length. Since the wheel 14 is attached to the rotating shaft of the stepping motor 6, the volume of the components can be reduced as compared with the prior art. (2) Since the rotational position of the variable condenser 5 is determined by a non-contact means, there is no mechanical wear of the detection circuit and the life is extended. (3) In the present invention, the rotational position of the variable condenser 5 is determined based on the High and Low pulse signals output from the photo sensor circuit 13. Since this pulse signal has a pulse number determined according to the rotational position of the variable condenser 5, even if the variable condenser 5 is different, the data of the correlation between the rotational position of the variable condenser 5 and the output signal required in the prior art is required. There is no need for measurement or adjustment of circuit component constants.

[Brief description of the drawings]

FIG. 1 is a functional explanatory view of an apparatus using plasma generated by high-frequency power.

FIG. 2 is a rotation position / capacitance correspondence diagram showing an example of capacitance with respect to a rotation position of a variable condenser 5;

FIG. 3 is a prior art configuration in which a rotation position detection circuit 17 including a multi-rotation potentiometer 8 and gears 9 and 10 used in the prior art is attached so that the rotation position of the variable condenser 5 can be determined. FIG.

FIG. 4 is a voltage detection circuit diagram for detecting a voltage that changes according to a resistance value of the potentiometer 8;

FIG. 5 is a correspondence diagram between a variable condenser rotation position and a detected voltage, showing an example of detection voltages at points A and B in FIG. 4 with respect to the rotation position of the variable condenser 5;

FIG. 6 is a block diagram showing an embodiment of the present invention when determining the rotational position of the variable condenser 5;

FIG. 7 shows a rotation position detecting circuit 17 comprising a photo sensor circuit 13 and a code wheel 14;
FIG. 4 is a configuration layout diagram of the present invention when attached so as to detect the rotational position of the present invention.

FIG. 8 is an explanatory diagram of a code wheel shape for explaining the shape of the code wheel 14;

FIG. 9 is an explanatory diagram of the operation of the photosensor circuit for explaining the operation of the photosensor circuit 13;

FIG. 10 is a diagram showing a state in which a 3-bit counter 18 outputs a phase A and a phase B shifted from the phase output from the photosensor circuit 13;
It is a count operation explanatory view explaining the operation which counts a pulse signal by two detection signals of a phase.

FIG. 11 is a circuit diagram of an embodiment of the present invention, showing a specific circuit example of the block diagram of FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 High frequency power supply 2 High frequency automatic matching device 3 Plasma load device 4 Coaxial cable 5 Vacuum variable capacitor (varicon) 6 Stepping motor 7 Coupling 8 Multi-rotation potentiometer 9 Gear 10 Gear 11 Support plate 12 Fixed plate 13 Photosensor circuit 14 Code wheel 15 Support plate 16 Fixed plate 17 Rotational position detection circuit 18 3-bit counter 19 Control circuit 20 Target rotation position setting circuit 21 Driver circuit 22 CPU 23 Motor driver A Voltage detection point B Voltage detection point V Power supply voltage

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01G 5/013 G01D 5/30 B H02P 8/38 H01G 5/02 A // G01D 5/30 H02P 8 / 00S (72) Inventor Eiji Kaneko 2-1-1, Tagawa, Yodogawa-ku, Osaka-shi F-term in Daihen Co., Ltd. (Reference) 2F069 AA83 BB40 DD22 DD27 GG04 GG07 HH13 2F103 CA01 CA03 DA01 DA13 EA02 EA12 EB12 EB16 EB32 ED21 FA12 5H303 AA06 BB02 BB06 BB14 DD03 DD23 DD27 EE03 FF04 GG04 GG11 HH05 KK08 LL02 5H580 AA03 BB08 BB10 EE10 FA04 FA13 FA14 FB03 GG04 HH08

Claims (3)

[Claims] 1. A code wheel having a slit is rotated in accordance with the rotation of a rotary shaft of a vacuum variable condenser, the presence or absence of a slit in the code wheel is detected in a non-contact manner, and a slit presence / absence detection signal is output. The position where the detection signal does not change while indicating either the presence or absence of the slit is the origin position of the vacuum variable capacitor even though the command to rotate the rotary axis of the vacuum variable capacitor is given. A method for determining the rotational position of a vacuum variable capacitor. 2. A code wheel having a slit is rotated in accordance with the rotation of the rotary shaft of the vacuum variable condenser, the presence or absence of the slit in the code wheel is detected in a non-contact manner, and a slit presence / absence detection signal is output. A method for determining the rotational position of a vacuum variable capacitor, which counts the number of detection signals and determines the rotational position of the vacuum variable capacitor. 3. The method according to claim 2, wherein the number of slit presence / absence detection signals is counted using a 3-bit counter to determine the rotational position of the vacuum variable capacitor.