JP3801031B2 - Vacuum pump control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vacuum pump control device that places a vacuum target space in a vacuum state, and more particularly to a vacuum pump control device that protects the device from application by an excessive voltage.
[0002]
[Prior art]
Conventionally, the vacuum pump control device exhausts the gas existing in the vacuum target space to bring the vacuum target space into a vacuum state. In particular, the vacuum pump control device is used for the purpose of setting the vacuum target space (inside the chamber) to a vacuum state when forming a thin film, vapor deposition, or the like in semiconductor manufacturing such as semiconductor elements and liquid crystals. Normally, such a vacuum pump control device uses a commercial power source (for example, AC 200V) for a factory as a power source in a factory or the like that manufactures semiconductors. Further, the pump of the vacuum pump control device is driven by a motor. The motor is controlled based on the rated voltage of the motor with respect to the motor speed (motor speed) as shown in FIG. A duty ratio of 0 to 100% is assigned, and the motor is driven by duty control.
[0003]
[Problems to be solved by the invention]
However, the voltage of commercial power sources used in factories and the like is not always constant, and the voltage varies depending on the load conditions of machines and facilities that use the same power source.
[0004]
When such a commercial power supply is electrically connected to a vacuum pump control device having a pump and a motor for driving the pump, the following problems arise. That is, when a voltage fluctuation of the commercial power supply, particularly a voltage drop (also referred to as a voltage drop) occurs, the voltage (applied voltage) applied to the motor is also lowered accordingly. When the voltage applied to the motor decreases, the current (motor current) flowing through the coil inside the motor decreases, and the generated torque of the motor decreases. As a result, the rotational speed of the pump driven by the motor becomes unstable, which affects the exhaust performance (vacuum level, exhaust speed, etc.) of the vacuum pump. Therefore, this leads to a deterioration in the quality of the semiconductor or liquid crystal produced in the vacuum target space.
[0005]
Therefore, the present invention has been made in view of the above-described problems, and it is possible to provide a configuration in which stable motor control can be performed even when the voltage for driving the motor fluctuates, and to improve the reliability of the vacuum pump control device. Is a technical issue.
[0006]
[Means for Solving the Problems]
The technical means taken in order to solve the above-mentioned problem is that a voltage is supplied from a power source, and a pump for exhausting air from the vacuum target space is controlled with respect to the vacuum target space by controlling a voltage applied to the motor. In the vacuum pump control device for setting the target space in a vacuum state, the vacuum pump control device includes a voltage detection unit that detects a voltage from the power source and a rotation state detection unit that detects a rotation state of the motor, and is detected by the voltage detection unit. based on the rotational state detected by the voltage and the rotational state detecting means, to control the voltage applied to the motor, further, the upper limit value of the voltage applied to the motor, controlling the relationship between the voltage and the rotating state The factor is determined based on the control factor.
[0007]
According to the above-described means, the voltage applied to the motor is controlled based on the voltage detected by the voltage detecting means and the rotation state detected by the rotation state detecting means. Even when the voltage fluctuates, the applied voltage of the motor can be controlled in consideration of the rotational state of the motor and the voltage from the power source.
[0008]
For example, even if the voltage supplied to the motor is lower than the rated voltage of the motor due to fluctuations in the power supply voltage, the duty ratio is changed according to the rotational state of the motor according to the amount of power reduction from the rated voltage of the motor. As a result, a margin of torque (margin torque) from the minimum drive voltage (motor counter electromotive voltage) of the motor is obtained, and the rotation of the motor is stabilized. As a result, the rise to the predetermined rotational speed during the initial driving of the motor is accelerated, and the rotational speed of the motor is stabilized even in the normal driving state. If the rotation speed of the motor that drives the pump is stabilized, the degree of vacuum in the vacuum target space is not affected by fluctuations in voltage when the motor is driven, and the reliability of the vacuum pump control device is improved.
[0009]
In general, when switching control of a motor with an IGBT or the like, in order to protect the IGBT element and the motor coil from overcurrent, conventionally, the voltage applied to the motor is controlled only by the control factor of the motor speed as shown in FIG. Therefore, when the power supply voltage is lowered, the upper limit value of the applied voltage of the motor is lowered and the rotation is unstable. However, since the upper limit value of the voltage applied to the motor is determined based on the relation between the rotation state and the voltage as a control factor, the motor of the vacuum pump control device due to excessive voltage or the seizure inside the device and Burnout is prevented and reliability is improved.
[0010]
Further, the duty factor can be controlled by determining the duty ratio within a range of a protection voltage for protecting the motor or the internal device from an overcurrent by a simple ratio determined by the rotation state and the power supply voltage.
[0011]
Further, if the rotational state is the rotational speed of the motor, duty control can be performed by detecting the rotational speed of the motor.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0013]
FIG. 1 is an example of a system configuration diagram of a vacuum pump control device (hereinafter referred to as this device) 1. This apparatus 1 can be applied to semiconductor manufacturing apparatuses such as semiconductor elements (for example, ICs, microcomputers, semiconductor sensors, etc.) and liquid crystals used in electronic equipment. In the present apparatus 1, the pump 9 is driven to exhaust the gas existing in the vacuum target space (internal space in the chamber) 20, and the inside of the chamber is evacuated. The apparatus 1 is not limited to this, but is used in a factory or the like, and uses a commercial power source (for example, a voltage of AC 200V) 15 that is a power source for the factory. In the commercial power supply 15, the power supply voltage (power supply voltage) fluctuates in the factory according to the state of the load connected to the power supply.
[0014]
The power supply 15 is connected to a DC converter 2 that converts the AC power supply of the apparatus 1 into DC, and the voltage converted from AC to DC by the DC converter 2 is an IGBT (insulated gate bipolar transistor) circuit 6 described later. Is input. On the other hand, the power supply voltage applied from the power supply 15 to the present apparatus 1 is branched before the DC converter 2 in order to detect voltage fluctuations, and a voltage detector (voltmeter, voltage sensor, etc.) 3 Connected to. The voltage supplied to the apparatus 1 is detected by the voltage detector 3. Then, the power supply voltage of the power supply 15 is input to the servo circuit 5 through the voltage detector 3. The servo circuit 5 includes a PWM circuit for determining a duty ratio therein, compares the rotational speed set by the rotational speed setting device 4 with the rotational speed of the motor 7 at a predetermined timing, and sets the rotational speed by the rotational speed setting device 4. The number of revolutions is controlled so that the number of revolutions is set.
[0015]
The output of the servo circuit 5 is input to the IGBT circuit 6, and the IGBT circuit 6 applies a pseudo AC voltage having a predetermined voltage and frequency set by the rotational speed setting device 4 to the motor 7. A current is passed through the pump 9 to drive the pump 9 at a predetermined rotational speed.
[0016]
The rotation speed setting device 4 has a function capable of arbitrarily setting the rotation speed of the motor 7 or the pump 9 so that the motor rotation speed can be arbitrarily set by changing the resistance value of the variable resistor by a volume or the like (not shown). It has become. The output of the rotation speed setting device 4 is input to the servo circuit 5.
[0017]
As a result, the gas in the chamber 20 is sucked from the pipe connected to the pump 9 and exhausted to the outside of the apparatus 1, and the chamber can be evacuated. In this case, in order to detect the rotation state (for example, the rotation speed) of the motor 7, a motor rotation detector (for example, a rotation speed sensor represented by a hall element, a non-contact rotation switch, etc.) is provided on the rotation shaft of the motor 7. ), And a rotation signal detected by the motor rotation detector is input to the servo circuit 5.
[0018]
Next, the operation of the apparatus 1 will be described.
[0019]
When commercial power is supplied from the power source 15 to the present apparatus 1, 200 V alternating current is first converted into direct current by the direct current converter 2 in the present apparatus 1. The servo circuit 5 has a function of controlling the IGBT circuit 6 so that the set rotational speed is set according to the rotational speed set by the rotational speed setting device 4. In other words, the servo circuit 5 includes a PWM circuit that performs PWM control, and according to the speed deviation between the rotation speed detected by the motor rotation detector 8 and the rotation speed set by the rotation speed setting device 4. The duty ratio by PWM control is determined by the servo circuit 5, and a pseudo AC voltage controlled by the IGBT circuit 6 is applied to the motor 7, whereby a current proportional to the voltage applied to a coil (not shown) inside the motor is obtained. And is driven at a rotational speed that balances the torque of the load connected to the output of the motor 7 (load torque).
[0020]
Therefore, the duty control will be briefly described with reference to FIG. Usually, the rotational speed of the DC motor is proportional to the applied voltage. For example, when driven by a constant rated voltage, the voltage Eb (constant) is applied. When the switching element of the PWM circuit provided in the servo circuit 5 is repeatedly turned on and off at a predetermined period T1 under a constant voltage Eb, the switching element is turned on for one period of time T1. The ratio of the time (ON time) T2 to perform becomes an average voltage. That is, as a result, it corresponds to applying a voltage of (T2 / T1) Eb, and the rotation speed of the motor 7 is determined according to the average voltage.
[0021]
Next, motor control based on motor characteristics will be described. The average voltage applied to the motor 7 is applied to the motor 7 as shown in FIG. 3 in order to protect the elements of the motor 7 and the IGBT circuit 6 from damage or breakage of the internal circuit due to overcurrent generated by the overvoltage. The upper limit value of the voltage is determined according to the change in the rotational speed. The upper limit value of the motor applied voltage is applied to generate a maximum allowable torque when the motor 7 is normally driven with respect to the motor 7, that is, when the motor 7 is in a certain rotation state. Represents the maximum value of the voltage to be generated, is determined by the rotational speed-voltage characteristics of the motor 7 to be used, and is set in proportion to the rotational speed of the motor 7 (= pump rotational speed). The setting of the upper limit value is obtained based on the fact that the minimum drive voltage (back electromotive voltage) of the motor 7 is proportional to the rotational speed of the motor 7.
[0022]
For example, in FIG. 3, assuming that the predetermined rotational speed N1 of the motor 7 and the load torque of the pump 9 at this time is L1, a current balanced with the load torque L1 for driving the pump 9 is caused to flow through the motor 7. Can maintain rotation at a constant rotation speed N1. As a condition for passing a current through the motor 7, the motor 7 is not driven unless a voltage higher than the counter electromotive voltage e, which is a minimum drive voltage proportional to the rotation speed of the motor 7, is applied to the motor 7. For this reason, the upper limit value a of the voltage applied to the motor 7 must be applied with a voltage equal to or higher than the load torque L of the motor 7. As a result, slight fluctuations in the rotational speed in the vicinity of the rotational speed N1 are quickly recovered, and a torque margin (margin torque) that can be maintained at a constant rotational speed is obtained.
[0023]
However, in a factory or the like, the voltage of the power supply 15 does not always maintain the state of c as shown in FIG. 3. For example, the lower limit of the guaranteed voltage of the motor (about 10 to 15% compared to c). There may be a case where the voltage drops to a lowered value. In this way, when the voltage applied to the motor 7 drops to d, as shown in FIG. 6, when the upper limit value of the voltage applied to the motor 7 is determined by a function of only the rotational speed, the motor 7 is The upper limit value a of the guaranteed voltage to be driven actually decreases to b (in this case, the upper limit value a decreases by an amount corresponding to the voltage drop from c to d).
[0024]
For this reason, at the rotation speed N1, the upper limit value of the motor applied voltage is “a” during normal driving, but the upper limit value becomes “b” due to the voltage drop of the power supply 15. The marginal torque (the difference torque at the intersection of a and b in N1) is hardly obtained, and it is difficult to maintain the rotational speed N1 by the output from the servo circuit 5. As a result, when the power supply 15 is lowered, the rotational speed of the motor 7 is likely to fluctuate and a large residual remains.
[0025]
Therefore, in the present embodiment, the voltage of the power source 15 that drives the motor 7 is detected by the voltage detector 3, and the duty ratio for driving the motor 7 is changed by the motor rotation detector 8. Yes. In this case, as shown in FIG. 4, the upper limit value of the voltage applied to the motor 7 is determined by taking the ratio of the rotation speed and the voltage detected by the motor rotation detector 8 and the voltage detector 3 and using this as the control factor. is doing. Thus, as shown in FIG. 2, the duty ratio for driving the motor 7 is T2 / T1 when the correction due to the voltage drop is not performed. However, when the voltage drop is corrected, the duty ratio is changed to T3 / T1. The ratio increases as shown by the broken line.
[0026]
As a result, the voltage applied to the motor 7 is as shown in f of FIG. That is, when the voltage of the power supply 15 is reduced and a voltage drop occurs, the duty ratio is determined by taking the ratio of the rotational speed and the voltage as shown in FIG. 4 even when the rotational speed N1 is slightly reduced. The ratio increases. As a result, the surplus torque with respect to the load torque of the pump 9 is increased, and the torque can be afforded. Therefore, as shown in FIG. 5, when the motor 7 is started from the time of stopping and is increased to the set rotational speed, there is a surplus torque at the time of starting compared to the conventional case, so that the rotational speed rises from the starting time. In addition to being faster, a marginal torque can be obtained without being influenced by fluctuations in the power supply even during normal driving. Further, even when the rotational speed of the motor 7 deviates from the set rotational speed when the motor is driven, the time for recovering to the predetermined rotational speed is shortened, and as a result, the rotational speed is stabilized. Thus, if the rotation speed is stable, the pump 9 can be driven stably, and the reliability of the apparatus 1 is improved.
[0027]
Therefore, even if the power supply voltage of the commercial power supply becomes lower than the rated voltage of the motor 7, it is possible to eliminate the problem that the time until the set rotational speed is reached or the set rotational speed is not reached as in the prior art. The problem that the exhaust performance (vacuum degree, exhaust speed, etc.) with respect to the chamber 20 is reduced can be solved.
[0028]
【The invention's effect】
According to the present invention, since the motor is duty-controlled based on the voltage detected by the voltage detection means and the rotation state detected by the rotation state detection means, the voltage from the power source fluctuates due to external factors. However, the duty ratio can be changed according to the motor rotation state according to the power supply drop from the rated voltage of the motor, and the rise to the predetermined number of rotations at the initial drive of the motor can be made faster. The rotation speed of the motor can be stabilized. Therefore, it is possible to prevent the degree of vacuum in the vacuum target space from being affected by fluctuations in voltage when the motor is driven, and it is possible to improve the reliability of the vacuum pump control device.
[0029]
In this case, the upper limit value of the voltage applied to the motor is controlled based on the relation between the rotation state and the voltage and is controlled based on the control factor. Burn-in and burnout can be prevented, reliability can be improved, and stable rotation can be obtained regardless of fluctuations in power supply voltage.
[0030]
If the control factor is a ratio determined by the rotational state and the voltage, the duty ratio can be easily determined within the allowable voltage range of the motor and IGBT by a simple ratio based on the rotational state of the motor.
[0031]
Further, if the rotational state is the rotational speed of the motor, the control can be performed by detecting the rotational speed of the motor.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a vacuum pump control device according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram for explaining duty control for driving a motor in an embodiment of the present invention.
3 is a graph showing the relationship between the number of rotations of the motor shown in FIG. 1 and the voltage for driving the motor, and the relationship between the number of rotations of the motor and the torque generated by the motor.
FIG. 4 is a graph showing the relationship between the motor speed / power supply voltage and the duty ratio in the duty control of the vacuum pump control apparatus according to the embodiment of the present invention.
FIG. 5 is a comparison diagram with a conventional example showing the stability of the vacuum pump control device in one embodiment of the present invention.
FIG. 6 is a graph showing the relationship between the motor rotation speed and the duty ratio in a conventional example.
[Explanation of symbols]
1 Vacuum pump control device 2 Voltage 3 Voltage detector (voltage detection means)
7 Motor 8 Motor rotation detector (Rotation state detection means)
9 Pump 15 Commercial power (power)
20 chamber (vacuum target space)

Claims (3)

In a vacuum pump control device that is supplied with voltage from a power source and controls a voltage that is applied to a motor for a pump that exhausts air from the vacuum target space with respect to the vacuum target space, thereby bringing the vacuum target space into a vacuum state.
Voltage detecting means for detecting a voltage from the power source;
Rotation state detection means for detecting the rotation state of the motor,
Based on the voltage detected by the voltage detection means and the rotation state detected by the rotation state detection means, the voltage applied to the motor is controlled, and the upper limit value of the voltage applied to the motor is set to the rotation state. And a control factor for the relationship between the voltage and the voltage, and a determination is made based on the control factor.   The vacuum pump control device according to claim 1, wherein the control factor is a ratio determined by the rotation state and the power supply voltage.   The vacuum pump control device according to claim 1 or 2, wherein the rotation state is the number of rotations of the motor.

Images