JP2020190230A - Vacuum pump and its operation method - Google Patents

Abstract

To provide a vacuum pump which can properly determine a failure of the pump, and its rough operation method.SOLUTION: This vacuum pump comprises a pump main body, a motor, a drive circuit, and a control part. The pump main body has a rotating shaft. The motor has a rotor core including a permanent magnet, and attached to the rotating shaft, and a stator core having a coil. The drive circuit has a drive part for supplying a drive current for rotating the motor to the coil, and a detection part for detecting an induction voltage which is generated at the coil. The control part controls the drive circuit. A control unit selectively performs a first control mode for supplying the drive current to the motor, and a second control mode for acquiring a time change of the induction voltage at non-electricity carrying for stopping the supply of the drive current to the motor.SELECTED DRAWING: Figure 5

Description

The present invention relates to a vacuum pump and a method of operating the vacuum pump.

Dry pumps such as mechanical booster pumps and screw pumps are volume transfer type vacuum pumps that transfer gas from the intake port to the exhaust port by rotating two pump rotors arranged in the pump chamber inside the casing synchronously in opposite directions. Is. In this type of vacuum pump, there is no contact between both pump rotors and between each pump rotor and casing, etc., and the others are only bearing rolling friction, contact seal friction, gear meshing transmission, oil bath agitation, and eddy current loss. Therefore, the mechanical loss is very small as compared with other vacuum pumps, and there is an advantage that the energy required for driving can be reduced as compared with a vacuum pump having a large frictional work such as an oil rotary vacuum pump.

On the other hand, if the bearings and oil lip seals that rotatably support both pump rotors deteriorate as the operating time increases, the sliding resistance of both pump rotors increases, resulting in deterioration of pump performance and abnormalities during operation. It becomes difficult to maintain the desired pump performance due to an increase in sound and vibration.

Therefore, there is known a technique for determining the presence or absence of an abnormality in a pump by observing the motor current in an operating state and analyzing the frequency component of the motor current. For example, Patent Document 1 discloses a technique in which a sensor for measuring a motor current in an energized state is provided, and a signal pattern representing a pump failure condition is identified by analyzing the frequency of the motor current from the output of the sensor. There is.

Special Table 2018-515706

However, the load current of the motor fluctuates due to changes in pressure and temperature environment, and the pump is easily affected by electrical noise during driving. Therefore, the failure of the pump is properly judged from the change in the current of the motor in the energized state. It's very difficult to do.

In view of the above circumstances, an object of the present invention is to provide a vacuum pump capable of appropriately determining a failure of the pump and an operation method thereof.

In order to achieve the above object, the vacuum pump according to one embodiment of the present invention includes a pump main body, a motor, a drive circuit, and a control unit.
The pump body has a rotating shaft.
The motor has a rotor core including a permanent magnet and attached to the rotating shaft, and a stator core having a coil.
The drive circuit includes a drive unit that supplies a drive current that rotates the motor to the coil, and a detection unit that detects an induced voltage generated in the coil.
The control unit controls the drive circuit. The control unit acquires a time change of the induced voltage in a first control mode in which the drive current is supplied to the motor and a second control mode in which the supply of the drive current to the motor is stopped and no electricity is supplied. Selectively execute the control mode.

The vacuum pump is configured to be capable of detecting the time change of the induced voltage generated in the coil when the motor is de-energized. Since the rotation speed of the motor has a strong correlation with the induced voltage generated by the motor, it is possible to grasp the rotational state of the motor based on the attenuation characteristic of the induced voltage. As a result, it is possible to properly determine whether or not the pump has failed without being affected by electrical noise.

The control unit may be configured to execute the second control mode for a predetermined time when the load current of the motor reaches a predetermined value or less after the execution of the first control mode. As a result, the second operation mode can be executed without deteriorating the pump performance.

The control unit may further have a storage unit that stores data related to the time change of the induced voltage acquired from the detection unit in a time series. As a result, the history of the time change of the induced voltage can be accumulated, and the presence or absence of abnormality or the degree of deterioration of the pump can be determined from the accumulated information.

The control unit determines the presence or absence of an abnormality in the pump body based on the data on the time change of the induced voltage acquired from the detection unit and the past data on the time change of the dielectric pressure stored in the storage unit. It may further have a determination unit for determination.

The operation method of the vacuum pump according to one embodiment of the present invention is
By supplying the drive current to the motor, the rotating shaft of the pump body is rotated,
The supply of the drive current to the motor is stopped, the time change of the rotation speed of the rotating shaft is detected, and the change is detected.
Based on the detected time change of the rotation speed, it is determined whether or not there is an abnormality in the pump body.

The step of detecting the time change of the rotation speed may detect the time change of the rotation speed based on the time change of the induced voltage of the motor.

According to the present invention, it is possible to properly determine the failure of the pump.

It is a schematic block diagram which shows the exhaust system provided with the vacuum pump which concerns on one Embodiment of this invention. It is an overall perspective view of the said vacuum pump. It is a schematic cross-sectional view which shows the internal structure of the said vacuum pump. It is a schematic side sectional view which shows the internal structure of the said vacuum pump. It is a block diagram which shows schematic structure and function of the control unit in the said vacuum pump. It is a figure explaining an example of time change of the rotation speed of a motor. It is a figure which shows an example of the time change of the induced voltage detected when the motor is de-energized. It is a flowchart which shows an example of the processing procedure at the time of operation of the said vacuum pump. It is a flowchart which shows an example of the processing procedure of the failure determination of the said vacuum pump.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an exhaust system 100 including a vacuum pump according to an embodiment of the present invention. The exhaust system 100 includes a main pump 101 as the vacuum pump, an auxiliary pump 102, and a controller 103.

The main pump 101 is typically composed of a dry pump, which is a mechanical booster pump in this embodiment. The main pump 101 has a pump main body 10 and a motor 20 as described later.

The pump main body 10 has an intake port E1 communicating with the inside of the vacuum chamber 1 via the pipe L1 and an exhaust port E2 connected to the auxiliary pump 102 via the pipe L2. The pipe L1 may be provided with a vacuum valve capable of switching communication between the vacuum chamber 1 and the pump body 10 and disconnection thereof. Further, a switchable vacuum valve having the same effect as closing and opening the exhaust port E2 of the pump main body 10 may be arranged in the pipe L2.

The auxiliary pump 102 is connected to the exhaust port E2 of the main pump 101 via the pipe L2, and exhausts the back pressure of the main pump 101. The auxiliary pump 102 typically comprises a dry pump and, in this embodiment, a screw pump. The auxiliary pump 102 is typically started together with the main pump 101 and is always driven at a constant rotation speed. The auxiliary pump 102 may be omitted if necessary.

The controller 103 is configured as a control unit that controls the operations of the main pump 101 and the auxiliary pump 102.

[Vacuum pump configuration]
Subsequently, the details of the main pump 101 will be described. FIG. 2 is an overall perspective view of the main pump 101, FIG. 3 is a schematic cross-sectional view showing the internal structure of the main pump 101, and FIG. 4 is a schematic side sectional view showing the internal structure of the main pump 101. In FIGS. 2 to 4, the X-axis, the Y-axis, and the Z-axis indicate three axial directions orthogonal to each other.

The main pump 101 includes a pump main body 10, a motor 20, and a control unit 30. The main pump 101 is composed of a single-stage mechanical booster pump.

(Pump body)
The pump main body 10 has a first pump rotor 11, a second pump rotor 12, and a casing 13 that houses the first and second pump rotors 11 and 12.

The casing 13 has a first casing portion 131, partition walls 132 and 133 arranged at both ends of the first casing portion 131 in the Y-axis direction, and a second casing portion 134 fixed to the partition wall 133. The first casing portion 131 and the partition walls 132 and 133 form a pump chamber P for accommodating the first and second pump rotors 11 and 12.

The first casing portion 131 and the partition walls 132, 133 are made of an iron-based metal material such as cast iron or stainless steel, and are coupled to each other via a seal ring (not shown). The second casing portion 134 is made of a non-ferrous metal material such as an aluminum alloy.

An intake port E1 communicating with the pump chamber P is formed on one main surface of the first casing portion 131, and an exhaust port E2 communicating with the pump chamber P is formed on the other main surface. An intake pipe that communicates with the inside of a vacuum chamber (not shown) is connected to the intake port E1, and an exhaust pipe (not shown) or an intake port of an auxiliary pump (not shown) is connected to the exhaust port E2.

The first and second pump rotors 11 and 12 are composed of eyebrows type rotors made of an iron-based material such as cast iron, and are arranged so as to face each other in the X-axis direction. The first and second pump rotors 11 and 12 have rotation shafts 11s and 12s parallel to the Y-axis direction, respectively. One end 11s1, 12s1 side of each rotating shaft 11s, 12s is rotatably supported by a bearing B1 fixed to a partition wall 132, and the other end 11s2, 12s2 side of each rotating shaft 11s, 12s is a partition 133. It is rotatably supported by a bearing B2 fixed to. A predetermined gap is formed between the first pump rotor 11 and the second pump rotor 12 and between the pump rotors 11 and 12 and the inner wall surface of the pump chamber P, and each pump rotor 11 is formed. , 12 are configured to rotate mutually and non-contact with the inner wall surface of the pump chamber P.

A rotor core 21 constituting the motor 20 is attached to one end 11s1 of the rotating shaft 11s of the first pump rotor 11, and a first synchronous gear 141 is fixed between the rotor core 21 and the bearing B1. A second synchronous gear 142 that meshes with the first synchronous gear 141 is fixed to one end portion 12s1 of the rotating shaft 12s of the second pump rotor 12. By driving the motor 20, the first and second pump rotors 11 and 12 rotate in opposite directions via the synchronous gears 141 and 142, whereby gas is transferred from the intake port E1 to the exhaust port E2. ..

(motor)
The motor 20 is a brushless DC motor, and in the present embodiment, it is composed of a permanent magnet synchronous type canned motor. The motor 20 includes a rotor core 21, a stator core 22, a can 23, and a motor case 24.

The rotor core 21 is fixed to one end 11s1 of the rotating shaft 11s of the first pump rotor 11. The rotor core 21 has a laminated body of electromagnetic steel plates and a plurality of permanent magnets M attached to the peripheral surface thereof. The permanent magnets M are arranged along the periphery of the rotor core 21 with alternating polarities (N pole, S pole).

In this embodiment, an iron-based material such as a neodymium magnet or a ferrite magnet is used as the permanent magnet material. The arrangement form of the permanent magnets is not particularly limited, and may be a surface magnet type (SPM) in which the permanent magnets are arranged on the surface of the rotor core 21, or an embedded magnet type (IPM) in which the permanent magnets are embedded in the rotor core 21. It may be.

The stator core 22 is arranged around the rotor core 21 and fixed to the inner wall surface of the motor case 24. The stator core 22 has a laminated body of electromagnetic steel plates and a plurality of coils C wound around the laminated body. The coil C is composed of a three-phase winding including a U-phase winding, a V-phase winding, and a W-phase winding, each of which is electrically connected to the control unit 30.

The can 23 is arranged between the rotor core 21 and the stator core 22, and houses the rotor core 21 inside. The can 23 is a bottomed cylindrical member having an opening at one end on the gear chamber G side, which is made of a synthetic resin material such as PPS (polyphenylene sulfide) or PEEK (polyetheretherketone). The can 23 is fixed to the motor case 24 via a seal ring S mounted around the opening end side thereof, and seals the rotor core 21 from the atmosphere (outside air).

The motor case 24 is made of, for example, an aluminum alloy and houses a rotor core 21, a stator core 22, a can 23, and synchronous gears 141 and 142. The motor case 24 is fixed to the partition wall 132 via a seal ring (not shown) to form a gear chamber G. The gear chamber G contains lubricating oil for lubricating the synchronous gears 141 and 142 and the bearing B1. An oil lip seal 150 (see FIG. 3) that prohibits the intrusion of lubricating oil from the gear chamber G into the pump chamber P is mounted between the rotating shaft 11s of the first pump rotor 11 and the partition wall 132. The outer surface of the motor case 24 is typically provided with a plurality of radiating fins.

The tip of the motor case 24 is covered with a cover 25. The cover 25 is provided with a through hole that can communicate with the outside air, and is configured to be able to cool the rotor core 21 and the stator core 22 via a cooling fan 50 arranged adjacent to the motor 20. Instead of or in addition to the cooling fan 50, the motor case 24 may have a water-coolable structure.

(Controller unit)
FIG. 5 is a block diagram schematically showing the configuration and function of the control unit 30. As shown in FIG. 5, the control unit 30 includes a drive circuit 31 and a control unit 32. The control unit 30 is for controlling the drive of the motor 20. The control unit 30 is composed of a circuit board housed in a metal case installed in the motor case 24 and various electronic components mounted on the circuit board.

The drive circuit 31 includes a drive unit 311, a detection unit 312, and a temperature sensor 313.

The drive unit 311 is composed of an inverter circuit having a plurality of semiconductor switching elements (transistors) that generate a drive current that rotates the motor 20 at a predetermined rotation speed (for example, 5000 rpm). These semiconductor switching elements individually control the opening / closing timing by the control unit 32, so that the drive current supplied to the coil C (U-phase winding, V-phase winding, and W-phase winding) of the stator core 22 can be supplied to each of them. Generate.

The detection unit 312 is electrically connected to the coil C of the stator 22. The detection unit 312 detects the magnetic pole position of the rotor core 21 from the waveform of the counter electromotive force generated in the coil C due to the temporal change of the magnetic flux (interlinkage magnetic flux) intersecting with the coil C, and energizes the coil C. It is output to the control unit 32 as a position detection signal for controlling the timing.

Further, the detection unit 312 detects the induced voltage generated in the coil C when the motor 20 is not energized (when the supply of the drive current to the coil C is stopped). When the motor 20 is not energized, the motor 20 is in a free-run state, and an induced voltage is generated in the coil C by the rotation of the permanent magnet M attached to the rotor core 21. The detection unit 312 detects the induced voltage and its temporal change, and outputs the voltage to the control unit 32.

The detection unit 312 is not limited to the case where it is configured as a part of the drive circuit 31, and may be configured by a circuit independent of the drive circuit 31.

The temperature sensor 313 detects the temperature of the drive circuit 31. When the drive circuit 31 is at a predetermined temperature (for example, 90 ° C.) or higher, the drive unit 311 stops supplying the drive current to the coil C. As a result, the motor 20 can be put into a free-run state to prevent a further temperature rise of the motor 20.

The control unit 32 is a control circuit that controls the drive circuit 31, and is typically composed of a computer including a CPU (Central Processing Unit). The control unit 32 acquires the first control mode for supplying the drive current to the motor 20 and the time change of the induced voltage generated in the coil C when the supply of the drive current to the motor 20 is stopped. Selectively execute the operation mode.

The first control mode is an operation mode in which the pump main body 10 is operated by driving the motor 20 by the drive circuit 31, thereby realizing a predetermined pump function. In the first control mode, the control unit 32 outputs a control signal for exciting the coil C of the stator core 22 to the drive circuit 31 based on the magnetic pole position of the rotor core 21 detected by the detection unit 312. In this case, the control unit 32 detects the load torque of the motor 20 from the magnetic pole position of the rotor core 21 acquired by the detection unit 312, and generates a control signal based on the load torque to rotate the motor 20 without stepping out. Then, this is output to the drive circuit 31.

On the other hand, the second control mode is an operation mode for detecting a time change of the induced voltage acting on the coil C when the motor 20 is not energized, and is mainly for determining the presence or absence of a failure of the pump body 10. Will be executed. In the second operation mode, the control unit 32 stops the supply of the drive current to the coil C by the drive unit 311 to put the motor 20 in a non-energized state, and typically rotates as represented by the pump rotors 11 and 12. The rotational energy stored in the component unit (the initial value is when the drive current supply is stopped) is set to be attenuated by the load, and the time change of the induced voltage of the motor 20 detected by the detection unit 312 is acquired. (This is a detection principle similar to the so-called spinning rotor gauge.)

As described above, the rotating shafts 11s and 12s of the pump body 10 are rotatably supported by the bearings B1 and B2 and the oil lip seal 150. When the bearings B1 and B2 and the oil lip seal 150 are normal, the sliding loss of the rotating shafts 11s and 12s by the bearings B1 and B2 and the oil lip seal 150 is stable in the operating state where the motor rotates at a constant rotation speed (for example, 5000 rpm). doing. Therefore, in the free-run state of the main pump 101 in which the power supply to the motor 20 is stopped, as shown by the solid line F1 in FIG. 6, the rotor core 21 and the rotor core 21 and the oil lip seal 150 are subject to sliding loss due to sliding loss of the bearings B1 and B2 and the oil lip seal 150. The rotation speeds of the rotation shafts 11s and 12s decrease with a constant time change (tilt).

On the other hand, if at least one of the bearings B1 and B2 and the oil lip seal 150 has some trouble due to deterioration with time or the like, the sliding resistance with the bearings B1 and B2 or the oil lip seal 150 becomes large. In this case, the rotation speeds of the rotor core 21 and the rotating shafts 11s and 12s in the free-run state decrease with a larger inclination than the time change (F1) in the normal state as shown by the two-dot chain line F2 in FIG. As shown by F3, the time change of the rotation speed fluctuates irregularly.

Therefore, the control unit 32 determines the change in the rotation speed of the rotor core 21 and the rotating shafts 11s and 12s in the free-run state of the main pump 101 based on the time change of the induced voltage generated in the coil C when the motor 20 is not energized. .. The rotation speed of the motor 20 has a strong correlation with the induced voltage. Let the rotation speed (rotation speed) of the motor 20 (rotor core 21) be ω (rad / s) and the induced voltage generated by the motor 20 be E (V). , Is defined as the following equation.
E = Ke × ω
Here, Ke is an induced voltage constant (Vs / rad).

FIG. 7 shows an example of the time change of the induced voltage E detected when the motor 20 is not energized. When the supply of the drive current from the drive circuit 31 to the motor 20 is stopped, the induced voltages Eu, Ev, Ew are applied to the coils C of each of the U, V, and W phases by the electromagnetic action of the permanent magnet M on the rotor core 21 that rotates inertially. Occurs. The waveforms of the induced voltages Eu, Ev, and Ew of each phase are sinusoidal waves whose amplitude and frequency change with time. When the motor 20 is de-energized, the rotation speeds of the rotating shafts 11s and 12s gradually decrease due to the sliding loss of the bearings B1 and B2 and the oil lip seal 150 (see F1 in FIG. 6). The frequencies and magnitudes of the induced voltages Eu, Ev, and Ew also decrease with the passage of time. Therefore, by monitoring the time changes of the induced voltages Eu, Ev, and Ww by the inclinations of these envelopes Ev1 and Ev2, it is possible to determine the presence or absence of abnormalities in the rotational state of the rotating shafts 11s and 12s.

Since the induced voltage E is a physical quantity detected when the motor 20 is not energized, it is not easily affected by electromagnetic noise caused by energization, and therefore the rotational state of the motor 20 can be properly grasped. The magnetic field formed by the permanent magnet M of the rotor core 21 has temperature dependence, and the magnitude of the induced voltage generated in the coil C may vary depending on the environmental temperature. However, when the bearings B1 and B2 and the oil lip seal 150 are normal, the slopes of the envelopes Ev1 and Ev2 representing the temporal change of the induced voltage are constant regardless of the temperature and are not affected by the environmental temperature. It is possible to determine whether or not there is an abnormality in the rotational state of the rotating shafts 11s and 12s. Further, if necessary, a sensor for detecting the temperature of the motor 20 may be separately provided, and the magnitude of the detected induced voltage E may be corrected based on the output of the sensor.

The timing at which the second control mode is executed is not particularly limited, but if the second control mode is inadvertently executed during the exhaust of the vacuum chamber 1, the exhaust time may be delayed and the tact time may be extended. Therefore, it is preferable that the second control mode is executed at a timing at which the pump performance of the main pump 101 is unlikely to be affected.

For example, immediately after the start of operation of the main pump 101, the load current of the motor 20 is relatively high because the inside of the vacuum chamber 1 is at atmospheric pressure. As the internal pressure of the vacuum chamber 1 decreases, the load current of the motor 20 also gradually decreases, and when the vacuum chamber 1 reaches a predetermined degree of vacuum (the ultimate pressure of the main pump 101), the load current of the motor 20 becomes the minimum value. It stays almost constant. In this state, even if the drive of the motor 20 is temporarily stopped, the rotation shafts 11s and 12s of the pump body 10 can be rotated relatively stably by inertia while suppressing the decrease in the degree of vacuum of the vacuum chamber 1. it can.

Therefore, in the present embodiment, the control unit 32 is configured to execute the second control mode for a predetermined time when the load current of the motor 20 reaches a predetermined value or less after the execution of the first control mode. The load current is not more than a predetermined value is, for example, the current value or the power value of the motor 20 when the main pump 101 reaches the ultimate vacuum degree or a pressure in the vicinity thereof. By temporarily suspending the first control mode and executing the second control mode in this state, the induction of the motor 20 that rotates by inertia (free run) while suppressing the deterioration of the degree of vacuum of the vacuum chamber 1 is suppressed. The time change of the voltage can be acquired. Further, the predetermined time during which the second control mode is executed is not particularly limited as long as it is the time required for the detection unit 312 to detect a significant time change of the induced voltage of the motor 20, and is typically not limited. , Hundreds of milliseconds to a few seconds. By returning to the first control mode after the elapse of a predetermined time, it is possible to minimize the deterioration of the pump performance of the main pump 101.

The control unit 32 has a storage unit 321 and a determination unit 322.

The storage unit 321 is typically composed of a non-volatile memory, and stores programs and control parameters of each process executed by the control unit 32. The storage unit 321 further stores data regarding a time change of the induced voltage of the motor 20 acquired from the drive circuit 31 (detection unit 312) in the second control mode.

Data on the time change of the induced voltage of the motor 20 include, for example, the amount of fluctuation of the induced voltage over a predetermined time from the stoppage of energization of the motor 20, specifically, the time change of the amplitude of the induced voltage, the time change of the frequency, and the like. Can be mentioned. The data may be data relating to the time variation of the induced voltage of at least one of the three phases. Further, the data stored in the storage unit 321 may be not only numerical values such as a voltage value and a frequency, but also a waveform itself showing a time change of the induced voltage shown in FIG. 7.

The data regarding the time change of the induced voltage may be stored in the storage unit 321 as history information from the first execution of the second control mode to the present. Thereby, for example, at the time of maintenance of the main pump 101, the life of the main pump 101, the replacement time of parts, and the like can be predicted by referring to the history information.

The determination unit 322 pumps based on the data obtained from the detection unit 312 regarding the time change of the induced voltage when the motor 20 is not energized and the past data regarding the time change of the dielectric pressure stored in the storage unit 321. It is configured to be able to determine the presence or absence of an abnormality in the main body 10.

For example, when the sliding loss of the rotating shafts 11s and 12s increases due to a defect in the bearings B1 and B2 and the oil lip seal 150, the induced voltage changes with time per unit time (hereinafter, also referred to as induced voltage fluctuation). Significant differences appear. Therefore, by storing the induced voltage fluctuation of the main pump 101 in the storage unit 321 as a reference, the bearings B1 and B2 and the oil lip seal 150 are based on the difference from the induced voltage fluctuation in the normal state. It is possible to estimate the presence or absence of defects or the degree of deterioration.

The induced voltage fluctuation in the normal state as a reference may be, for example, the induced voltage fluctuation at the time of shipment or the induced voltage fluctuation acquired at the time of executing the second control mode last time. By using the measured values at the time of shipment or in the past actually obtained from the main pump 101 as the reference, it is possible to make an appropriate failure judgment without being affected by individual differences of the pump.

It should be noted that the malfunction is not limited to the bearings B1 and B2 of the main pump 101 and the oil lip seal 150, and for example, a malfunction of the auxiliary pump 102 may cause a significant difference from the normal state of the induced voltage fluctuation. When the operation of the auxiliary pump 102 is stopped or the pump performance is significantly deteriorated due to a failure or the like, the back pressure of the main pump 101 increases. In this case, even if the bearings B1 and B2 of the main pump 101 and the oil lip seal 150 are in a normal state, the rotational load of the rotating shafts 11s and 12s increases, so that the rotation speed tends to decrease sharply after the motor 20 is stopped. Therefore, by monitoring the induced voltage fluctuation of the motor 20, it is possible to monitor not only the failure of the main pump 101 itself but also the presence or absence of an abnormality in the entire exhaust system 100 including the auxiliary pump 102.

Further, when it is desired to eliminate the influence of the auxiliary pump 102 and the vacuum chamber 1 and monitor the state of only the pump main body 10, the vacuum valve provided in the pipe L1 and the vacuum valve provided in the pipe L2 (not shown) are closed. Then, the second control mode may be executed. Under this condition, the volume up to the pump body 10 and the two vacuum valves and the pressure condition at the time of closing are set as the initial values, so that the disturbance factor is reduced with respect to the time change of the induced voltage acquired from the detection unit 312. As a result, the same effect as that of increasing the signal strength of the pump body 10 is produced, so that it becomes easier to determine the abnormality.

[How to operate the vacuum pump]
Subsequently, the operation method of the main pump 101 configured as described above will be described.

FIG. 8 is a flowchart showing an example of a processing procedure during operation of the main pump 101 executed by the control unit 32.

The exhaust system 100 starts the exhaust operation inside the vacuum chamber 1 when the main pump 101 and the auxiliary pump 102 are activated. When the main pump 101 is started, the control unit 32 controls the drive circuit 31 in the first control mode, and the drive unit 311 is a drive current for rotating the motor 20 at a rated rotation speed (5000 rpm in this embodiment). To generate. By the operation of the motor 20, the first and second pump rotors 11 and 12 rotate, and a predetermined pumping action is performed to discharge the gas in the vacuum chamber 1 sucked from the intake port E1 from the exhaust port E2. The exhaust port E2 of the main pump 101 is exhausted by the auxiliary pump 102, so that the back pressure of the main pump 101 is maintained below the atmospheric pressure.

The control unit 32 determines whether or not the load current of the motor 20 of the main pump 101 is equal to or less than a predetermined value (step 101). When the main pump 101 reaches the ultimate pressure and the load current reaches a predetermined value or less, the first control mode is switched to the second control mode to stop the supply of the drive current from the drive circuit 31 to the motor 20 (step). 102). As a result, the motor 20 is in a free-run state, and the rotor core 21 and the rotating shafts 11s and 12s continue to rotate due to inertia. The detection unit 312 detects the induced voltage fluctuation generated in the coil C of the motor 20 and outputs it to the control unit 32.

The control unit 32 acquires data regarding the induced voltage fluctuation of the motor 20 detected by the detection unit 312 (step 103). The acquired data on the induced voltage fluctuation is stored in the storage unit 321. The detection and acquisition of data on the induced voltage fluctuation is continued until a predetermined time elapses after the energization of the motor 20 is stopped. The auxiliary pump 102 is continuously driven even while the main pump 101 is executing the second control mode.

The control unit 32 switches from the second control mode to the first control mode after a predetermined time has elapsed after stopping the energization of the motor 20, and resumes the energization of the motor 20 from the drive circuit 31 (step). 104, 105). As a result, the exhaust operation of the vacuum chamber 1 by the main pump 101 is restarted.

The second control mode is not limited to the case where the load current of the motor 20 is executed every time the load current becomes equal to or less than the above predetermined value. For example, the second control mode may not be executed until a certain period of time has elapsed since the previous second control mode was executed. In this case, it is possible to prevent deterioration of the pump function due to frequent execution of the second control mode.

FIG. 9 is a flowchart showing an example of a failure determination processing procedure of the main pump 101 executed by the control unit 32. Failure determination of the main pump 101 is typically made during execution of the second control mode. Instead of this, in the second control mode, only the data related to the induced voltage fluctuation may be acquired, and the failure determination may be performed as a task different from the second control mode after returning to the first control mode. ..

The control unit 32 (determination unit 322) determines whether or not there is an abnormality or failure of the pump main body 10 based on the data on the induced voltage fluctuation when the motor 20 is de-energized, which is acquired when the second control mode is executed.

In the present embodiment, when the data related to the induced voltage fluctuation is acquired from the detection unit 312, the past induced voltage fluctuation stored in the storage unit 321 is read out and the difference between them is calculated (steps 201 and 202). If the difference is not more than a predetermined value, it is determined that there is no problem with the bearings B1 and B2 and the oil lip seal 150, and the operation of the main pump 101 is continued as it is.

On the other hand, when it is determined that the above difference is equal to or more than a predetermined value, the bearings B1 and B2 and the oil lip seal 150 may have a high degree of malfunction or deterioration. Therefore, the determination unit 322 determines that the pump body 10 is abnormal. , The data related to the induced voltage fluctuation at that time is stored in the storage unit 321 as an abnormal value (steps 203 and 204).

The predetermined value of the above difference indicating that the value is abnormal is not necessarily limited to the value at which the operation of the main pump 101 needs to be stopped immediately, and is a value suitable for warning that a failure will occur in the near future. You may. In this case, an alarm unit (not shown) may be activated to notify the user of the abnormality of the pump.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made.

For example, in the above embodiment, the vacuum pump (main pump 101) has been described by taking a single-stage mechanical booster pump as an example, but the present invention is not limited to this, and other dry pumps such as a multi-stage roots pump and a screw pump can be used. The present invention is also applicable. Further, the auxiliary pump 102 may be provided with the same failure determination function as the main pump 101.

Further, the vacuum pump according to the present invention may further include a transmission unit capable of transmitting data regarding the induced voltage fluctuation of the motor 20 acquired in the second control mode to an external device. In this case, the external device may be a higher-level computer connected to the vacuum pump or a cloud server connected via a network. As a result, the operating state of the vacuum pump can be managed at a place other than the place where the vacuum pump is installed. Further, even when the vacuum pump is not in operation, it is possible to diagnose the failure of the vacuum pump.

Further, in the above embodiment, in the second control mode, the time change of the rotation speed of the rotating shaft is detected based on the time change of the induced voltage of the motor, but the present invention is not limited to this. For example, a reflective member may be provided at the end of the rotating shaft, and a time change in the rotation speed of the rotating shaft may be detected by using a general-purpose rotation speed measuring device that utilizes periodic light input. If the motor is a synchronous machine, there is an effect that it is not necessary to prepare a separate rotation speed measuring device by using the induced voltage, but if the motor is an induction machine, if the supply of drive current is stopped, the synchronous machine Since the rotating magnetic field based on the rotation of the rotor core is not generated, the induced voltage cannot be used. In such a case, a rotation speed measuring device, more preferably a non-contact type rotation speed measuring device, may be used instead of the detection unit 312.

10 ... Pump body 20 ... Motor 30 ... Control unit 31 ... Drive circuit 32 ... Control unit 100 ... Exhaust system 101 ... Main pump 102 ... Auxiliary pump 311 ... Drive unit 312 ... Detection unit 321 ... Storage unit 322 ... Judgment unit B1, B2 …bearing

Claims (6)

A pump body with a rotating shaft and
A motor having a rotor core including a permanent magnet and attached to the rotating shaft, and a stator core having a coil,
A drive circuit having a drive unit that supplies a drive current for rotating the motor to the coil and a detection unit that detects an induced voltage generated in the coil.
A control unit that controls the drive circuit, the time of the induced voltage when the first control mode for supplying the drive current to the motor and the non-energization when the supply of the drive current to the motor is stopped. A vacuum pump comprising a second control mode for acquiring changes and a control unit for selectively executing. The vacuum pump according to claim 1.
The control unit is a vacuum pump that executes the second control mode for a predetermined time when the load current of the motor reaches a predetermined value or less after the execution of the first control mode. The vacuum pump according to claim 2.
The control unit is a vacuum pump further having a storage unit that stores data related to a time change of the induced voltage acquired from the detection unit in a time series. The vacuum pump according to claim 3.
The control unit determines the presence or absence of an abnormality in the pump body based on the data on the time change of the induced voltage acquired from the detection unit and the past data on the time change of the dielectric pressure stored in the storage unit. A vacuum pump having a determination unit for determination. By supplying the drive current to the motor, the rotating shaft of the pump body is rotated,
The supply of the drive current to the motor is stopped, the time change of the rotation speed of the rotating shaft is detected, and the change is detected.
A method of operating a vacuum pump for determining the presence or absence of an abnormality in the pump body based on the detected time change of the rotation speed. The method for operating a vacuum pump according to claim 5.
The step of detecting the time change of the rotation speed is a method of operating a vacuum pump that detects the time change of the rotation speed based on the time change of the induced voltage of the motor.

Images