JP2015187428A - Dry vacuum pump device and operation method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cause a pump operation speed to promptly reach a target speed irrespectively of the temperature of a pump body, and enable the pump operation speed to return to the target speed even if the operation speed deviates from the target speed by disturbance.SOLUTION: A feedback control system calculates and outputs a current command value I1 for compensating for a rotation speed deviation ΔR between a target rotation speed Rtar of a pump and an actual rotation speed Rdet of a rotor of the pump. The target rotation speed Rtar and a reference temperature Tref are supplied from a control device to a feed-forward compensator 34 in a feed-forward control system and a measured actual temperature Tdet of the pump is also supplied to the feed-forward compensator 34, and the feed-forward compensator 34 outputs a feed-forward compensation value I2. The compensation values I1 and I2 are added up in an adder 35, an addition result is supplied to a power module as a current command value I output to a motor, and a current based on the command value I is supplied to the motor. By adding the compensation value I2 based on the actual temperature Tdet of the pump to the compensation value I1, the rotation speed of the pump can promptly reach the target rotation speed.

Description

  The present invention relates to a dry vacuum pump apparatus that sucks gas from a sealed container such as a vacuum chamber and an operation method thereof. More specifically, the present invention allows the pump operation speed to reach the target speed quickly at the start of pump operation, and allows the difference between the operation speed and the target speed to quickly become zero when there is a disturbance such as load fluctuation. In particular, the present invention relates to a dry vacuum pump device that controls a pump operation speed using an inverter device and an operation method thereof.

  The dry vacuum pump apparatus is widely used as one of semiconductor device manufacturing facilities. The manufacturing process of a semiconductor device has a process of processing a product in a vacuum space, and generally uses a dry vacuum pump device to form the vacuum space. As a configuration of the dry vacuum pump device, a motor is controlled using an inverter device in order to output a desired torque, change a pump operation speed, and / or reduce a rotational speed for energy saving. It is common. In particular, by increasing the frequency of the drive power supplied to the motor from the commercial frequency by the inverter device, the rotor rotational speed can be increased and the exhaust performance of the vacuum pump device can be improved.

  The inverter device provided in the dry vacuum pump device is the speed specified in advance by the inverter device itself, the speed designated by the control device provided in the pump body, and designated by the host device. Speed control is performed so that the vehicle is operated at a target speed given by one of the speeds. In order to perform such speed control, in the conventional example, feedback control is performed via the inverter device so that the difference between the target speed of the vacuum pump device and the actual operation speed becomes zero.

  Further, as an example of a method for feedback control of the pump speed, a method based on PID control is generally used. For example, Patent Document 1 discloses that a vacuum vessel includes a pressure sensor, and PID control is performed by an inverter so that a detected pressure obtained by the pressure sensor becomes a set target pressure. Furthermore, there is also a PID control in which the pump speed becomes the target speed based on the fact that the exhaust speed, which is one of the performance indexes of the vacuum pump apparatus, is proportional to the operating speed of the vacuum pump apparatus.

  In general, it is known that increasing the proportional gain in the feedback control is effective in improving the followability of the pump speed to the target speed. Further, as a general characteristic of feedback control (or PID control), there is always a deviation between the target speed and the actual driving speed. To reduce this deviation, the proportional gain of the feedback control is also increased. Is effective. On the other hand, when the proportional gain is increased, as a general behavior of PID control, there is a problem that the overshoot of the pump operation speed is increased, and thereby the control of the vacuum pump device becomes unstable.

By the way, when constructing the vacuum pump device, it is necessary to consider that the followability of the rotor in the pump main body, that is, the speed response, varies with various factors with respect to the output power supplied from the motor. These factors include, for example, (1) manufacturing variations such as rotor diameter, rotor-to-casing clearance, and shaft distortion, and (2) changes in rotor-to-casing clearance due to pump body temperature rise and lubrication oil Mention may be made of changes in viscosity and (3) quantitative and qualitative changes in the load (gas) to be sucked. In addition, as a factor of the temperature rise of a pump main body, with the compression exhaust of gas at the time of operation of a vacuum pump apparatus, compression heat generate | occur | produces and a pump main body temperature rises, Moreover, exhaust gas is a vacuum pump apparatus. In order to prevent the product from being cooled and accumulated as a product in the pump body, the vacuum pump device itself may be heated.

JP 2012-154315 A

The above factor (1) can be dealt with by measuring the characteristics of components (clearance, mass balance, etc.) in advance and reflecting them as control parameters. In addition, the factor (3) cannot be predicted because it depends on the usage pattern of the user. However, if it can be predicted, it may be reflected in the control parameter.
On the other hand, for the factor (2), it is necessary to reflect the temperature of the casing of the pump body in the control so that the motor power necessary for the target speed can be output. A method has not yet been proposed. In particular, when the pump operation is started, it is required to quickly reach the target temperature, but depending on the casing temperature, it takes a long time to reach the target speed.

  The present invention has been made in view of the above-described problems of the conventional example, and the purpose of the dry vacuum pump device is to operate the pump regardless of the temperature of the pump body in order to bring out stable pump operation performance. Controls the pump speed so that it can quickly reach the target speed at the start, and quickly return to the target speed even when the pump speed deviates from the target speed due to disturbance such as load fluctuation during operation. That is.

In order to achieve the above object, the present invention is a dry vacuum pump device comprising:
Temperature measuring means for measuring the actual temperature of the pump body;
A motor for driving the rotor of the pump body;
An inverter device that supplies electric current for driving the pump body at a predetermined target rotational speed to the motor, and is fed based on a difference between the actual temperature measured by the temperature measuring means and a predetermined reference temperature. There is provided a dry vacuum pump device including a feedforward compensator for calculating a forward compensation value, and an inverter device for compensating a current supplied to the motor based on the calculated feedforward compensation value.

  In the above-described dry vacuum pump device according to the present invention, the device further includes a rotational speed measuring means for measuring the rotational speed of the rotor, and the inverter device further includes a deviation between the measured rotational speed of the rotor and the target rotational speed. A feedback compensator for calculating a feedback compensation value for calibrating the output, an adder for adding the feedforward compensation value and the feedback compensation value to output as an output current command value, and supplying the motor based on the output current command value It is preferable that current output means for outputting the current to be output is provided.

In addition, the feedforward compensator further uses the target rotational speed of the pump body to calculate the feedforward compensation value,
K1 x (actual temperature of pump body-reference temperature of pump body) + K2 x target rotational speed + K3
However, K1, K2, and K3: It is preferable that the calculation is performed with a coefficient determined by the pump body.
In the case of a pump body whose response characteristics do not vary relatively depending on the rotational speed, instead of the above formula, the Feedford compensation value is set.
K1 x (actual pump temperature-pump reference temperature) + K3
You may calculate by.

In order to achieve the above object, the present invention further provides an operation control method in a dry vacuum pump device,
A step of setting a relationship between the feedforward compensation value and the actual temperature of the pump body by an actual machine test,
By actually operating the pump body with a motor, the relationship between the optimum feedforward compensation value of the current to be supplied to the motor to drive the pump at the target rotational speed and the actual temperature of the pump body is obtained. The actual temperature of the pump body is changed, and the optimum feedforward compensation value is obtained for each changed temperature, whereby the relationship between the feedforward compensation value and the actual temperature of the pump body is obtained. Step to get the
Storing the relationship between the acquired feedforward compensation value and the actual temperature of the pump body in the storage medium of the feedforward compensator of the inverter device; and
Driving the pump to evacuate the vacuum vessel, comprising:
Measuring the actual temperature of the pump body;
A feedforward compensation value corresponding to the measured actual temperature is read from the storage medium by the inverter device, and the read feedforward compensation value is calculated from the measured rotational speed of the pump body and the target rotational speed. And adding a current corresponding to the added compensation value to the motor, and a driving step.

  According to the dry vacuum pump device of the present invention, it is possible to perform optimal motor control in accordance with the change in the behavior of the dry vacuum pump device that changes depending on the casing temperature of the pump body. In addition, the time until the pump operation speed reaches the target speed is speeded up and shortened. Furthermore, since the arrival of the vacuum pump device at the target speed is shortened, the tact time during the manufacture of the semiconductor device can be shortened, thereby improving the productivity of the semiconductor device.

FIG. 1 is a schematic configuration diagram of a dry vacuum pump apparatus according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram of a pump body included in the dry vacuum pump apparatus of FIG. FIG. 3 is a block diagram showing an electrical connection relationship of the dry vacuum pump device of FIG. 4 is a block diagram showing a configuration of the arithmetic processing unit of the inverter device shown in FIG. FIG. 5 is a graph showing the relationship between the compensation amount required in the feedforward control and the casing temperature in the dry vacuum pump apparatus of FIG. FIG. 6 is a graph comparing the performance of the control operation of the dry vacuum pump device of FIG. 1 with that of the prior art.

Hereinafter, a dry vacuum pump apparatus according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a dry vacuum pump apparatus 100 according to an embodiment of the present invention. The dry vacuum pump device 100 is connected to a vacuum vessel 50, and the gas in the vacuum vessel 50 is exhausted to the outside through the pump body 10. More specifically, the gas in the vacuum vessel 50 is sucked through the air inlet provided in the casing 11 of the pump body 10 by the pump operation, and the gas is exhausted from the air outlet provided in the casing 11. Thus, the vacuum container 50 is brought into a vacuum state.

  A motor 20 is disposed on a side surface of the pump body 10, and the rotor accommodated in the casing 11 of the pump body is driven by the motor 20. The inverter device 30 is connected to the motor 20 and supplies AC power to the motor 20. Furthermore, the inverter device 30 is connected to the measuring means 15 provided in the casing 11 of the pump body, and various measurement data related to the pump body measured by the measuring means 15 (for example, the temperature of the pump body and the rotor rotational speed). Is input and used for operation control of the pump body 10. A control device 40 is connected to the inverter device 30, and the control device 40 outputs a control signal for pump operation control to the inverter device 30. In addition to the above, the dry vacuum pump device 100 also includes components such as a cooling device for cooling the motor 20 with a coolant medium such as water, but illustration thereof is omitted.

  FIG. 2 is a schematic configuration diagram of the vacuum pump main body 10 in a state coupled to the vacuum vessel 50 shown in FIG. The vacuum pump body 10 can be a positive displacement vacuum pump device, for example. A pair of rotors 12 and 12 'are rotatably disposed in the rotor chamber in the casing 11, and one of the rotor rotating shafts 16 and 16' is coupled to the rotating shaft of the motor 20 (FIG. 1) (if necessary). Through the gear). When the rotation shaft 16 (or 16 ′) of the rotor is rotated by operating the motor, the two rotation shafts 16 and 16 ′ rotate in synchronization via a synchronous gear (not shown), thereby the rotors 12 and 12 ′. Thus, the gas sucked from the intake port 18 is exhausted through the exhaust port 19. Minute gaps are formed between the pair of rotors and between the rotors and the inner peripheral surface of the casing 11, and the rotors 12 and 12 ′ are not in contact with each other but centered on the rotating shafts 16 and 16 ′. It can be rotated.

  FIG. 3 is a block diagram showing an electrical connection relationship of the dry vacuum pump device 100 described in FIG. The dry vacuum pump device performs feedback control by the inverter device 30 so that the difference between the actual operation speed of the pump body 10, that is, the actual rotation speed, and the target rotation speed designated via the control device 40 quickly becomes zero. Execute feedforward control. In order to execute such control, the inverter device 30 receives the target rotational speed Rtar (R-target) and the reference temperature Tref (T-reference) of the rotor of the pump body 10 from the control device 40, and measures the measurement means. 15 (FIG. 1), the actual rotational speed Rdet (R-detected) that is the measured rotational speed of the rotor of the pump body 10 and the actual temperature that is measured from the rotational speed measuring means 151 and the temperature measuring means 152. Receives temperature Tdet (T-detected). In one embodiment, the temperature measuring means 152 measures the temperature of the casing 11 of the pump body 10 and outputs it as the actual temperature Tdet of the pump body. The temperature may be measured and output as an actual temperature.

  The inverter device 30 includes an arithmetic processing unit (CPU) 31 and a power module 32. The arithmetic processing unit 31 processes the data received from the control device 40, the rotation speed measuring unit 151, and the temperature measuring unit 152, calculates the value of the current to be supplied to the motor 20, that is, the output current command I, and the power module 32. Converts the electric power so that the current i actually flowing to the motor 20 is equal to the output current command value I commanded from the arithmetic processing unit 31, and supplies the current i to the motor 20.

FIG. 4 is a block diagram for explaining the processing operation of the arithmetic processing unit 31 in the inverter device 30 of the dry vacuum pump device. In the prior art, as described above, only feedback control is employed. However, in the present invention, not only feedback control by the feedback compensator 33 but also feedforward control by the feedforward compensator 34 is employed. ing.

  In FIG. 4, the subtractor 32 included in the feedback control system receives the target rotation speed Rtar of the pump body designated from the control device 40 (FIG. 3), and measures the rotation speed provided in the pump body 10 from the speed. The rotational speed of the rotor detected by the means 151, that is, the actual rotational speed Rdet is subtracted, and the obtained rotational speed deviation ΔR is input to the feedback compensator 33. The feedback compensator 33 calculates and outputs a current command value I1 that compensates for the input rotational speed deviation ΔR. The feedback control in the feedback compensator 33 is preferably the PID control described above, but is not limited to this, and any feedback control method can be adopted.

On the other hand, for feedforward control, the target forward speed Rtar and the reference temperature Tref are supplied from the control device 40 to the feedforward compensator 34, and the actual temperature Tdet of the pump body is supplied from the temperature measuring means 152. The feedforward compensator 34 outputs a feedforward compensation value I2 based on these inputs.
The target rotational speed Rtar input to the feedforward compensator 34 is used to increase the compensation value in a rotational speed band where the response characteristics are not good. For example, in a multi-stage Roots pump or the like, the response characteristics vary greatly depending on the rotation speed, and therefore the response characteristics are not good depending on the rotation speed. When the pump is driven at a target rotational speed Rtar within a rotational speed band where such response characteristics are not good, a feedforward compensation value is set by a predetermined compensation value set in advance according to the target rotational speed Rtar or the rotational speed band. Increasing I2 improves the pump response characteristics. If the response characteristic is relatively independent of the rotational speed, the target rotational speed Rtar does not necessarily need to be input to the feedforward compensator 34.

  By the way, when the temperature of the pump is low, the viscosity of the bearing grease in the pump body increases, and the sliding resistance of the bearing tends to increase. When actual operation of the pump device is started under these circumstances and the operation speed is to be increased to the rated speed, the speed increase time may become longer if power is supplied as usual. is assumed. Further, when the pump temperature is high, the clearance becomes small due to the difference in thermal expansion between the rotor of the pump body and the casing. When the clearance becomes small, the amount of gas discharged when the rotor makes one rotation increases. In other words, since a larger amount of power is required to rotate the rotor once, it is assumed that the electric power for rotating the rotor at the rated rotation increases. Therefore, feed-forward control is adopted in addition to feedback control, and when the pump temperature is higher or lower than the reference temperature, a large current is input to the motor, thereby shortening the effective operation speed increase time. Is considered possible.

  That is, the operating temperature of the pump is in the range of 0 to 200 ° C. when viewed at the casing temperature. When the pump temperature is low, the grease viscosity of the bearing increases. As a result, the response characteristics deteriorate, and unless a large amount of current is supplied to the motor, it takes time until the pump operating speed reaches the target value. In particular, when the temperature is 40 ° C. or lower, the influence due to an increase in grease viscosity is increased. In addition, when the pump temperature is high, the clearance between the rotor and the casing is narrowed, which also deteriorates the response characteristics, and it takes time until the pump operating speed reaches the target value. In particular, when the temperature is 150 ° C. or higher, the influence due to the narrowing of the clearance becomes large.

Such a decrease in the pump operating speed depending on the actual temperature of the pump can be compensated by increasing the current value to the motor driving the pump, and the actual temperature Tdet of the pump and the current supplied to the motor. The bias value, i.e., the feedforward compensation value I2 is
For example, it can be expressed as shown in FIG. Note that the relationship between the actual pump temperature Tdet and the feedforward compensation value I2 varies depending on the actual dry vacuum pump device, and as shown in FIG. In some cases, the compensation value changes in a substantially linear manner, and in other cases, the compensation value changes in a curve such as a quadratic function. Therefore, a relationship between the actual temperature Tdec and the feedforward compensation value I2 may be determined by performing an actual machine test in advance using an actual dry vacuum pump device.

  More specifically, when the pump body is actually operated by the motor, the relationship between the optimum feedforward compensation value of the current to be supplied to the motor to drive the pump at the target rotational speed and the actual temperature of the pump body. Is obtained by changing the actual temperature Tdet of the pump body and obtaining an optimum feedforward compensation value I2 for achieving the target rotational speed Rtar for each changed temperature. At this time, the reference temperature Tref of the pump is set as a temperature when the feedforward compensation value I2 is minimum based on the result of the actual machine test. Then, the relationship between the temperature of the pump body and the feedforward compensation value I2 obtained in this way is stored in an appropriate storage medium provided in the feedforward compensator 34, and the pump body is actually operated to perform vacuum. It is read and used when the container is evacuated. Instead of storing the obtained relationship in the feedforward compensator 34, it is stored in the control device 40 (FIGS. 1 and 3), and when the pump body is actually driven, the relationship is read from the control device 40. The feed forward compensator 34 may be provided.

The feedforward compensator 34 performs an operation so as to output a feedforward compensation value I2, but the relationship between the actual pump temperature Tdet and the feedforward compensation value I2 is shown in the graph of FIG. 5 as a reference temperature Tref. The feedforward compensation value I2 is calculated by the following mathematical expression when expressed by a substantially linear function.
I2 = K1 x (Tact-Tref) + K2 x Rtar + K3
K1 to K3 are coefficients, and are appropriately determined according to the characteristics of the actual dry vacuum pump. As is apparent from FIG. 5, the coefficient K1 is the slope of the graph, and is a minus sign when the actual temperature Tdet of the pump body is lower than the reference temperature Tref, and a plus sign when it is higher. The coefficient K2 may be zero, and the coefficient K3 is the feedforward compensation value I2 at the reference temperature Tref in FIG.

Returning to FIG. 4, the feedforward compensation value I2 obtained by the feedforward compensator 34 is added to the compensation value I1 from the feedback compensator 33 in the adder 35, and the output current command value I (= I1 + I2) is used as the power. Output to module 32 (FIG. 3). Note that the feedforward compensation value I2 may be added to the feedback compensation value I1 only when the feedforward compensation value I2 is relatively large (for example, 40 ° C. or lower and 150 ° C. or higher).
Thus, in the dry vacuum pump apparatus 100 of the present invention, in addition to the feedback control by the feedback compensator 33, the feedforward compensator 34 performs the feedforward control correlated with the actual pump temperature, thereby providing feedback control. Without increasing the proportional gain, it is possible to realize speed control of the pump main body with excellent stability and responsiveness.

FIG. 6 is a graph comparing the operation performance of the dry vacuum pump apparatus of the present invention with that of the prior art, and shows the tendency when the pump is started when the pump body temperature, that is, the pump actual temperature Tdet is 10 ° C. It is a graph. Here, the performance of the prior art means a case where only feedback control is applied to the inverter, and is shown in the graph of FIG. The graph of FIG.5 (b) has shown the case where feedforward control is also employ | adopted in addition to feedback control based on this invention. In both the graphs of FIGS. 5A and 5B, the vertical axis represents the rotational speed R of the pump body, the horizontal axis represents time, the solid line in each graph represents the target rotational speed Rtar, and the dotted line represents the pump body. The actual rotational speed Rdet of is shown. As apparent from the comparison of the graph of FIG. 5B with the graph of FIG. 5A, according to the present invention, the operation speed reaches the target rotation speed Rtar in a short time from the start t0 of the pump device. It is also possible to reduce the overshoot of the actual rotational speed Rdet. Furthermore, it can be inferred that even if the operating speed deviates from the target rotational speed for some reason during driving, it is possible to return to the target rotational speed in a short time.

  The dry vacuum pump apparatus according to the embodiment of the present invention has been described above, but it goes without saying that various modifications can be made. For example, the calculation of the compensation value in the Feedford compensator is not limited to the above-described linear calculation formula, and as described above, a quadratic function or the like may be used according to the characteristics of the pump body, and feedforward The compensation value may be changed stepwise.

Claims (6)

A dry vacuum pump device,
Temperature measuring means for measuring the actual temperature of the pump body;
A motor for driving the rotor of the pump body;
An inverter device that supplies electric current for driving the pump body at a predetermined target rotational speed to the motor, and is fed based on a difference between the actual temperature measured by the temperature measuring means and a predetermined reference temperature. A dry vacuum pump device comprising: a feedforward compensator for calculating a forward compensation value; and an inverter device for compensating a current supplied to the motor by the calculated feedforward compensation value. The dry vacuum pump device according to claim 1,
The apparatus further comprises a rotational speed measuring means for measuring the rotational speed of the rotor,
The inverter device further includes
A feedback compensator for calculating a feedback compensation value for calibrating a deviation between the measured rotational speed of the rotor and the target rotational speed;
An adder that adds the feedforward compensation value and the feedback compensation value to output as an output current command value;
A dry vacuum pump device comprising: current output means for outputting the current supplied to the motor based on the output current command value. The dry vacuum pump device according to claim 1 or 2, wherein the feedforward compensator further uses the target rotational speed of the pump body to calculate the feedforward compensation value,
K1 x (actual temperature of pump body-reference temperature of pump body) + K2 x target rotational speed + K3
However, K1, K2, and K3: Dry vacuum pump devices that are configured to perform calculations using coefficients determined by the pump body. The dry vacuum pump device according to claim 1 or 2, wherein the feedforward compensator calculates the feedforward compensation value as follows:
K1 x (actual pump temperature-pump reference temperature) + K3
However, K1 and K3: Dry vacuum pump devices that are configured to calculate with a coefficient determined by the pump body. The dry vacuum pump device according to any one of claims 1 to 4, wherein the temperature measuring unit is configured to measure a temperature of the casing of the pump and output the measured temperature as an actual temperature of the pump body. Pump device. An operation control method in a dry vacuum pump device,
A step of setting a relationship between the feedforward compensation value and the actual temperature of the pump body by an actual machine test,
By actually operating the pump body with a motor, the relationship between the optimum feedforward compensation value of the current to be supplied to the motor to drive the pump at the target rotational speed and the actual temperature of the pump body is obtained. The actual temperature of the pump body is changed, and the optimum feedforward compensation value is obtained for each changed temperature, whereby the relationship between the feedforward compensation value and the actual temperature of the pump body is obtained. Step to get the
Storing the relationship between the acquired feedforward compensation value and the actual temperature of the pump body in the storage medium of the feedforward compensator of the inverter device; and
Driving the pump to evacuate the vacuum vessel, comprising:
Measuring the actual temperature of the pump body;
A feedforward compensation value corresponding to the measured actual temperature is read from the storage medium by the inverter device, and the read feedforward compensation value is calculated from the measured rotational speed of the pump body and the target rotational speed. And a driving step comprising: adding a deviation corresponding to the feedback compensation value for calibrating to the motor and supplying a current corresponding to the added compensation value to the motor.

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