JP2011202516A - Operation control device and operation control method for vacuum pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a vacuum pump from stopping during a manufacturing process by detecting the state of the products deposited in the casing of the vacuum pump during the startup of the vacuum pump, and according to the state, outputting a maintenance signal for attracting the attention of the user of the maintenance of the vacuum pump.SOLUTION: This operation control device 9 for controlling the operation of a vacuum pump with a pump rotor which is rotatably disposed in a casing includes a frequency converter 11 for controlling the rotational speed of the pump rotor. The frequency converter 11 includes a calculation part 14 for calculating an integral value by integrating a motor output torque during the startup of the vacuum pump and a storage parts 15 for storing a reference value corresponding to the integral value and a preset threshold.

Description

  The present invention relates to an operation control device and an operation control method for a vacuum pump, and more particularly to an operation control device and an operation control method for a vacuum pump used to evacuate a chamber of a semiconductor manufacturing apparatus or the like.

  In a semiconductor manufacturing apparatus, a vacuum pump is widely used for exhausting a gas used in a semiconductor manufacturing process from the chamber and for creating a vacuum environment in the chamber. As such a vacuum pump, a positive displacement type vacuum pump provided with a roots type or screw type pump rotor is known.

  In general, a positive displacement vacuum pump includes a pair of pump rotors disposed in a casing and a motor for rotationally driving the pump rotor. A minute clearance is formed between the pair of pump rotors and between the pump rotor and the inner surface of the casing, and the pump rotor is configured to rotate without contact with the casing. The pair of pump rotors rotate in opposite directions while being synchronized with each other, whereby the gas in the casing is transferred from the suction side to the discharge side, and the gas is exhausted from a chamber or the like connected to the suction port.

  Some gases used in semiconductor manufacturing processes include components that solidify or liquefy when the temperature of the gas decreases. Usually, the vacuum pump described above generates compression heat in the process of transferring gas, so the vacuum pump in operation is at a certain high temperature. For this reason, while the vacuum pump is maintained at a high temperature, even when the gas containing the above-described components is exhausted using the vacuum pump, the components in the gas are not solidified or liquefied, and good vacuum exhaust is performed. Done.

  However, when the operation of the vacuum pump is stopped and the temperature of the vacuum pump gradually decreases, the components contained in the gas remaining in the casing solidify, and this solidified product (reaction product) is transferred between the pump rotors and between the pump rotors. Deposits in the gap between the pump rotor and casing. And as this product builds up, not only does the vacuum pump start up, but also overloading the vacuum pump during operation of the vacuum pump stops the vacuum pump during the manufacturing process, The process will be very damaging.

  The applicant compares the measured state change amount when the rotation speed of the rotor of the vacuum pump is changed with the normal state change amount, and the measured state change amount is larger or smaller than the normal state change amount by a predetermined amount. A failure diagnosis device for a vacuum pump has been proposed in which a factor causing a pump stop is predicted in advance to prevent damage to a semiconductor wafer or the like due to a sudden vacuum pump stop (Patent Document) 1).

  In addition, when the operation of the vacuum pump is stopped, the applicant rotates the pump rotor in the forward direction and / or the reverse direction according to a predetermined timing pattern after the pump stop is started, and then stops the pump rotor, thereby Even when the solidified or liquefied product in the pump is prevented from rotating the pump rotor, the product can be effectively removed when the vacuum pump is stopped, and the vacuum pump can be started normally. A vacuum pump operation control device and a method for stopping operation have been proposed (see Patent Document 2).

JP 2005-9337 A JP 2009-97349 A

  In the invention described in Patent Document 1, for example, a state change amount from when the pump is started to when it reaches the rated rotation is measured to predict in advance a factor that causes the pump to stop. For this reason, it is necessary not only to increase the rotational speed of the pump to the rated rotational speed at the time of starting the pump, but also to predict the factor that causes the pump to stop until the rotational speed of the pump is increased to the rated rotational speed.

  In addition, the invention described in Patent Document 2 enables the vacuum pump to start normally by effectively removing the product accumulated in the casing when the vacuum pump is stopped. It is not intended to output a maintenance signal in anticipation of a vacuum pump failure at the time of startup.

  The present invention has been made in view of the above circumstances, and detects a situation in which a product is accumulated in a casing of a vacuum pump when the vacuum pump is started. An object of the present invention is to provide a vacuum pump operation control device and an operation control method for preventing a vacuum pump from stopping during a manufacturing process by outputting a maintenance signal to be evoked.

  An operation control device for a vacuum pump according to the present invention is an operation control device for controlling the operation of a vacuum pump having a pump rotor rotatably arranged in a casing, wherein a frequency converter for controlling the rotation speed of the pump rotor is provided. The frequency converter includes a calculation unit that integrates the motor output torque when the vacuum pump is started to calculate an integral value, a storage unit that stores a reference value corresponding to the integral value and a preset threshold value, respectively. Have

  For example, comparing the integrated value of the motor output torque and the reference value corresponding to the integrated value immediately after the start of operation of the vacuum pump until the rotational speed of the vacuum pump reaches a predetermined rotational speed, A maintenance signal is output according to the difference from the threshold.

  After starting the operation of the vacuum pump, the rotation speed of the vacuum pump is maintained at a predetermined rotation speed, the vacuum pump is operated for a predetermined time, and the motor output torque during the rotation of the vacuum pump at the predetermined rotation speed is increased. The integrated value may be compared with a reference value corresponding to the integrated value, and a maintenance signal may be output according to the difference between the two and the threshold value.

  The motor output torque is obtained from, for example, a current supplied to the motor. As a result, even when the current signal that is the basis for torque calculation fluctuates instantaneously due to the influence of noise, etc., the calculation result is integrated for a certain period of time, so that the influence of fluctuation of the current signal is suppressed and a maintenance signal is output. be able to.

  The operation control method for a vacuum pump according to the present invention is an operation control method for controlling the operation of a vacuum pump having a pump rotor rotatably disposed in a casing, and integrating the motor output torque when the vacuum pump is started. A value is calculated, a reference value corresponding to the integral value is compared with the integral value to obtain a difference between the two, and according to a difference between the difference between the two and a threshold value that is set in advance and stored in the storage unit Output a maintenance signal.

  According to the present invention, the situation in which the product is accumulated in the casing of the vacuum pump is detected at the time of starting the vacuum pump, and a maintenance signal that alerts the user to the maintenance of the vacuum pump is output according to this situation. Therefore, it is possible to prevent the vacuum pump from being stopped during the manufacturing process.

It is a vertical front view which shows the structural example of the vacuum pump to which the operation control apparatus and operation control method of the vacuum pump which concern on this invention are applied. It is a vertical side view of FIG. It is a circuit block diagram of an operation control apparatus. FIG. 4A is a graph showing the relationship between the rotational speed of the pump rotor and time when the rotational speed of the pump rotor is linearly increased at the start of operation of the vacuum pump, and FIG. 4 (a) is a graph showing the relationship between pump output torque and time during normal and product accumulation when the rotation speed is increased as shown in FIG. 4 (a). FIG. 4 (c) shows the rotation of the pump rotor. FIG. 5 is a graph showing the relationship between the integral value (torque integral value) of pump output torque and the time when the speed is increased as shown in FIG. FIG. 5A shows the relationship between the rotational speed of the pump rotor and the time when the pump rotor is operated for a predetermined time while maintaining the rotational speed of the pump rotor at a predetermined rotational speed after the operation of the vacuum pump is started. FIG. 5 (b) is a graph showing the relationship between pump output torque and time during normal and product accumulation when the rotational speed of the pump rotor is increased as shown in FIG. 5 (a). FIG. 5C shows the integrated value (torque integrated value) and time of the pump output torque when the pump rotor rotational speed is increased as shown in FIG. It is a graph which shows the relationship.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment, an operation control device and operation control method for a vacuum pump used for exhausting gas in a chamber of a semiconductor manufacturing apparatus will be described. However, the operation control device and operation control method according to the present invention will be described. The applied vacuum pump is not limited to this.

  FIG. 1 is a longitudinal front view showing a configuration example of a vacuum pump to which an operation control device and an operation control method for a vacuum pump according to the present invention are applied, and FIG. 2 is a longitudinal side view of FIG. As shown in FIGS. 1 and 2, the vacuum pump mainly includes a pair of pump rotors 1, a casing 2 having an exhaust chamber 7 in which the pump rotor 1 is accommodated, and a motor 3 that rotationally drives the pump rotor 1. Has been. The casing 2 includes an intake port (not shown) for sucking gas and an exhaust port (not shown) for discharging gas. Each pump rotor 1 is fixed to two rotating shafts 4 rotatably supported by bearings 5.

  A motor rotor (not shown) is fixed to one rotating shaft 4, and a motor stator (not shown) is disposed around the motor rotor. The motor 3 is composed of the motor rotor and the motor stator. In this embodiment, an induction motor is used as the motor 3. A timing gear 6 that meshes with each other is fixed to the ends of the two rotating shafts 4, and the pair of pump rotors 1 rotate in opposite directions while being synchronized with each other. A minute gap is formed between the pair of pump rotors 1 and between the pump rotor 1 and the inner surface of the exhaust chamber 7 of the casing 2, so that each pump rotor 1 rotates without contact with the casing 2. It has become.

  In the vacuum pump having the above-described configuration, by driving the motor 3 to rotate the pair of pump rotors 1, the gas sucked from the suction ports (not shown) of the casing 2 is exhausted as each pump rotor 1 rotates. To the side and exhausted from an exhaust port (not shown) of the casing 2. The gas in the chamber connected to the suction port of the casing 2 is evacuated by continuously transferring the gas from the suction side to the exhaust side. This chamber is, for example, a chamber incorporated in a semiconductor manufacturing apparatus.

  The vacuum pump is provided with an operation control device 8 having a frequency converter 11 in order to control the rotational speed of the motor rotor of the motor 3. The operation control device 8 is disposed between the three-phase power source 9 and the motor 3.

  As shown in FIG. 3, the operation control device 8 includes an earth leakage breaker (ELB) 10 that connects the three-phase power source 9 to the frequency converter 11. A circuit breaker (CB) may be used instead of the earth leakage breaker (ELB). The frequency converter 11 includes a rectifier 12 connected to a three-phase power source 9 via an earth leakage breaker (ELB) 10, a power transistor unit 13 that supplies driving power for rotating the motor rotor of the motor 3 to the motor 3, and A current detector 17 for detecting a current supplied to the motor stator of the motor 3 and a frequency conversion control unit 16 for controlling the frequency converter 11 are provided. The frequency conversion control unit 16 includes a calculation unit 14 for calculating the motor output torque, a storage unit 15 for storing a reference value and a threshold value, and an A / A for taking in the signal of the current detector 17 into the calculation unit 14. D converter 18.

  Thus, when the operation start switch (not shown) of the vacuum pump is operated and the operation of the vacuum pump is started, the frequency converter 11 starts supplying drive power to the motor 3, and the motor 3 The motor rotor starts rotating. As the motor rotor of the motor 3 rotates, the pair of pump rotors 1 rotate in opposite directions in synchronization with each other. Simultaneously with the start of operation of the vacuum pump, the current supplied to the motor 3 is taken into the computing unit 14 via the current detector 17 and the A / D converter 18.

  Here, when the pump rotor 1 is rotated when the product is accumulated on the inner surface of the casing 2 (hereinafter, referred to as product deposition), the product accumulated between the inner surface of the casing 2 and the pump rotor 1 is The frictional force is generated. For this reason, compared with the case where the pump rotor 1 is rotated when the product is not deposited on the inner surface of the casing 2 (hereinafter referred to as normal), a larger motor output torque is required to rotate the pump rotor 1. It becomes.

For example, as shown in FIG. 4 (a), at operation start of the vacuum pump, the linearly increasing the rotational speed of the pump rotor 1, as shown in FIG. 4 (b), in the pump startup t _1, The time t when the pump output torque T ₂ at the time of product deposition becomes larger than the pump output torque T ₁ at the normal time (T ₂ > T ₁ ) and the rotational speed of the pump rotor 1 reaches the predetermined rotational speed N _{1. Also in 2} , the pump output torque during product deposition is larger than the pump output torque during normal operation. Therefore, as shown in FIG. 4 (c), at time t ₂ where the rotational speed reaches a predetermined rotational speed N ₁ of the pump rotor 1, the integral value of the pump output torque during normal computed from the pump startup t ₁ (torque integral value) integral value of the pump output torque during product deposition than _{I 1} becomes larger in the (torque integral _{value) I 2 (I 2> I} 1), the difference between them [Delta] I (= _{I 2} -I ₁₎ occurs.

Therefore, the pump in this example, by driving the vacuum pump in the normal, as shown in FIG. 4 (a), which is calculated from the time the pump starts when increasing the rotation speed of the pump rotor 1 to a predetermined rotational speed N ₁ was The integral value of the output torque (torque integral value) is stored in the storage unit 15 as a reference value, and further, the difference ΔI between the integral value of the pump output torque at the normal time and the integral value of the pump output torque at the product accumulation is obtained. A corresponding threshold value, for example, a first threshold value V ₁ and a second threshold value V ₂ (> V ₁ ) larger than the first threshold value V ₁ are set in advance and stored in the storage unit 15.

Then, at the start of operation of the vacuum pump used for evacuating the chamber, the rotational speed of the pump rotor 1 is increased along the straight line shown in FIG. At this time, the calculation unit 14, sequentially calculates the integral value of perform calculations the motor output torque of the original to the motor output torque current values taken from the current detector 17 from the pump startup t _1. Then, at the time t _{2 when} the rotational speed of the pump rotor 1 reaches a predetermined rotational speed N ₁ , the reference value stored in the storage unit 15, in this example, the integral value of the pump output torque at normal time (Integral value of torque) I ₁ and the integrated value of the motor output torque calculated by the calculating unit 14, for example, the integrated value of the motor output torque calculated by the calculating unit 14 are shown in FIG. If it is equal to the integral value of the pump output torque, a comparison is made with the integral value (torque integral value) I ₂ to find the difference ΔI (I ₂ −I ₁ ) between the _two .

When the difference ΔI is equal to or less than the first threshold value V ₁ (ΔI ≦ V ₁ ), the amount of the product accumulated in the casing 2 of the vacuum pump is such that the operation of the vacuum pump is not supported. Assuming that the rotational speed of the pump rotor 1 of the vacuum pump is increased to the rated rotational speed. When the difference ΔI exceeds the first threshold value V ₁ but is equal to or less than the second threshold value V ₂ (V ₁ <ΔI ≦ V ₂ ), the amount of product accumulated in the casing 2 of the vacuum pump is Although there is no support for the operation of the vacuum pump, it is better to perform the maintenance, and a maintenance signal is issued to the user to prompt the maintenance and the rotation speed of the pump rotor 1 of the vacuum pump is increased to the rated rotation speed Let When the difference ΔI exceeds the second threshold value V ₂ (ΔI> V ₂ ), it is assumed that the amount of the product accumulated in the casing 2 of the vacuum pump is supported by the operation of the vacuum pump. Stop operation.

  In this way, by detecting the situation in which the product is accumulated in the casing of the vacuum pump at the time of starting the vacuum pump, according to this situation, by outputting a maintenance signal that alerts the user to maintain the vacuum pump, It is possible to prevent the vacuum pump from stopping during the manufacturing process.

  Further, by obtaining the motor output torque from the current supplied to the motor 3 and integrating the calculation result for a certain time, even if the current signal that is the basis of the torque calculation fluctuates instantaneously due to the influence of noise or the like, the current signal The maintenance signal can be output while suppressing the influence of fluctuations.

  In this example, two threshold values are provided. However, only the first threshold value may be provided, and three or more threshold values may be provided to determine the amount of product accumulated in the casing 2 of the vacuum pump (steps). ) May be output. Further, the maintenance signal is not limited to signal output, but may be displayed on a display device or output by communication such as RS232C. Further, although the current detector 17 measures the motor output torque current, the current input to the power transistor unit 13 may be measured. The same applies to the following examples.

On the other hand, as shown in FIG. 5A, when the pump rotor 1 is operated for a predetermined time T while maintaining the rotational speed of the pump rotor 1 at the predetermined rotational speed N ₂ after the operation of the vacuum pump is started. 5 (b) as shown in, at pump startup _{t 1,} becomes larger in the pump output torque _{T 2} of the time the product deposited than the pump output torque _{T 1} of the normal _(T 2> T _1), the pump Even while the rotor 1 is rotated at the predetermined rotational speed N ₂ (t _{3 to} t ₄ ), the pump output torque during product deposition becomes larger than the pump output torque during normal operation. Therefore, as shown in FIG. 5 (c), at time t ₄ when maintained over the rotational speed of the pump rotor 1 in a predetermined time T in a predetermined rotational speed N _2, the rotational speed is a predetermined rotational speed N of the pump rotors 1 The integral value (torque integral value) I ₄ of the pump output torque at the time of product deposition is larger than the integral value (torque integral value) I ₃ of the pump output torque at the normal time calculated from the time t ₃ when reaching _2. (I ₄ > I ₃ ), and a difference ΔI (= I ₄ −I ₃ ) occurs between the two.

Therefore, by driving the normal time of the vacuum pump, as shown in FIG. 5 (a), after the start of operation of the vacuum pump, to maintain the rotational speed of the pump rotor 1 at a predetermined rotational speed N _2, pump rotors 1 the when operated for a predetermined time T, the integral value the rotational speed of the pump rotor 1 is calculated from the time reaches the predetermined rotational speed N ₂ of the pump output torque (torque integral value) in the storage unit 15 as the reference value stored, further threshold value corresponding to the difference ΔI between the integral value of the pump output torque during the integration value and product deposition of pump output torque during the normal, for example than the first threshold V ₃ and the first threshold value V ₃ A large second threshold value V ₄ (> V ₃ ) may be set in advance and stored in the storage unit 15.

In this case, the vacuum pump used for evacuating the chamber is driven, and the rotational speed of the pump rotor 1 is set to a predetermined time T after the start of operation of the vacuum pump, as shown in FIG. maintaining a predetermined rotational speed _{N 2.} At this time, the calculation unit 14, the current rotational speed of the integrated value of the pump rotors 1 based on the current value taken from the detector 17 performs the calculation of motor output torque the motor output torque reaches the predetermined rotational speed N ₂ sequentially computed from the time t _3. Then, at time t ₄ when maintained constant over the rotational speed of the pump rotor 1 in a predetermined time T, the reference value stored in the storage unit 15, in this example, the integral value of the pump output torque during normal (Torque The integral value) I ₄ and the integrated value of the motor output torque calculated by the calculating unit 14, for example, the integrated value of the motor output torque calculated by the calculating unit 14 are shown in FIG. If it is equal to the integral value of the output torque, it is compared with the integral value (torque integral value) I ₄ to obtain the difference ΔI (I ₄ −I ₃ ) between the two.

When the difference ΔI is equal to or less than the first threshold value V ₃ (ΔI ≦ V ₃ ), the amount of the product accumulated in the casing 2 of the vacuum pump is such that the operation of the vacuum pump is not supported. Assuming that the rotational speed of the pump rotor 1 of the vacuum pump is increased to the rated rotational speed. If the difference ΔI exceeds the first threshold V ₃ but is less than or equal to the second threshold V ₄ (V ₃ <ΔI ≦ V ₄ ), the amount of product deposited in the casing 2 of the vacuum pump is Although there is no support for the operation of the vacuum pump, it is better to perform the maintenance, and a maintenance signal is issued to the user to prompt the maintenance and the rotation speed of the pump rotor 1 of the vacuum pump is increased to the rated rotation speed Let When the difference ΔI exceeds the second threshold value V ₄ (ΔI> V ₄ ), it is assumed that the amount of product accumulated in the casing 2 of the vacuum pump is supported by the operation of the vacuum pump. Stop operation.

  Also by this, the situation where the product is accumulated in the casing of the vacuum pump is detected at the time of starting the vacuum pump, and according to this situation, a maintenance signal that alerts the user to maintain the vacuum pump is output, It is possible to prevent the vacuum pump from stopping during the manufacturing process.

Predetermined rotational speed N ₂ and the predetermined time T in this case is defined in advance as an optimal value, for example, by experiment or the like.

  Although one embodiment of the present invention has been described so far, it is needless to say that the present invention is not limited to the above-described embodiment, and may be implemented in various forms within the scope of the technical idea. For example, a direct current motor may be used as the motor 3.

DESCRIPTION OF SYMBOLS 1 Pump rotor 2 Casing 3 Motor 4 Rotating shaft 7 Exhaust chamber 8 Operation control apparatus 11 Frequency converter 13 Power transistor part 14 Calculation part 15 Memory | storage part 16 Frequency conversion control part 17 Current detector

Claims (6)

In an operation control device for controlling the operation of a vacuum pump provided with a pump rotor rotatably arranged in a casing,
A frequency converter for controlling the rotational speed of the pump rotor;
The frequency converter includes a calculation unit that integrates motor output torque to calculate an integral value when the vacuum pump is started, and a storage unit that stores a reference value corresponding to the integral value and a preset threshold value. An operation control device for a vacuum pump.   Compare the integrated value of the motor output torque and the reference value corresponding to the integrated value between immediately after the start of operation of the vacuum pump and until the rotational speed of the vacuum pump reaches a predetermined rotational speed, and the difference between the two and the threshold value The operation control device for a vacuum pump according to claim 1, wherein a maintenance signal is output in accordance with the difference between the operation control device and the vacuum pump.   After starting the operation of the vacuum pump, the rotation speed of the vacuum pump is maintained at a predetermined rotation speed, the vacuum pump is operated for a predetermined time, and the motor output torque during the rotation of the vacuum pump at the predetermined rotation speed is increased. 2. The operation control device for a vacuum pump according to claim 1, wherein an integrated value is compared with a reference value corresponding to the integrated value, and a maintenance signal is output in accordance with a difference between the integrated value and the threshold value. In an operation control method for controlling the operation of a vacuum pump provided with a pump rotor rotatably arranged in a casing,
Integrate the motor output torque when starting the vacuum pump to calculate the integral value,
Compare the reference value corresponding to the integral value and the integral value to obtain the difference between them,
A method for controlling operation of a vacuum pump, comprising: outputting a maintenance signal according to a difference between the difference between the two and a threshold value set in advance and stored in a storage unit.   Compare the integrated value of the motor output torque and the reference value corresponding to the integrated value between immediately after the start of operation of the vacuum pump and until the rotational speed of the vacuum pump reaches a predetermined rotational speed, and the difference between the two and the threshold value 5. The operation control method for a vacuum pump according to claim 4, wherein a maintenance signal is output in accordance with a difference between the operation and the vacuum pump.   After starting the operation of the vacuum pump, the rotation speed of the vacuum pump is maintained at a predetermined rotation speed, the vacuum pump is operated for a predetermined time, and the motor output torque during the rotation of the vacuum pump at the predetermined rotation speed is increased. 5. The operation control method for a vacuum pump according to claim 4, wherein an integrated value is compared with a reference value corresponding to the integrated value, and a maintenance signal is output in accordance with a difference between the integrated value and the threshold value.

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