JP4558367B2 - Vacuum pump and control method thereof - Google Patents

Description

  The present invention relates to a vacuum pump and a control method thereof, and more particularly, to a vacuum pump operated by a PWM-controlled motor and a control method thereof.

  A vacuum pump operated by a PWM-controlled motor is used for evacuating a chamber of an inspection apparatus such as an electron microscope or an analyzer, a processing apparatus using an ion beam or the like, or another apparatus. PWM control is control for operating a motor based on a set reference frequency.

The setting of the reference frequency for PWM control will be described in more detail with reference to FIG. FIG. 8 is a diagram showing the relationship between the reference frequency of PWM control and the motor torque generated by the reference frequency. As shown in FIG. 8, when the reference frequency is increased, the torque initially increases. However, after the maximum torque Tp is exceeded, the current is less likely to flow in proportion to the motor inductance. descend.
As a first example, when the reference frequency of PWM control is the reference frequency Fp that generates the maximum torque Tp or a reference frequency within an appropriate range before and after the reference frequency Fp, high torque operation that generates a relatively high torque is performed. be able to. Therefore, when a load is applied to the motor, the motor can be operated with a margin when maintaining rotation or accelerating. For example, it is advantageous when the inside of the chamber is surely evacuated to a predetermined vacuum level within a predetermined time. The appropriate range before and after Fp varies depending on the size of the chamber to be evacuated, the predetermined time to reach a predetermined degree of vacuum, the system configuration, and the like. Conventionally, the reference frequency of PWM control has been within such an appropriate range.
As a second example, when the reference frequency of PWM control is a relatively high reference frequency Fh, current is less likely to flow in proportion to the inductance of the motor, and torque is reduced. Therefore, when a load is applied to the motor, for example, when the motor is accelerated and decelerated, the amount of heat generated by the motor increases, the time required for acceleration and deceleration increases, or the regenerative power generation capacity during deceleration decreases. There is an adverse effect. Therefore, conventionally, the reference frequency of PWM control has not been a relatively high reference frequency Fh.

Further, when a motor operated by PWM control is used, motor vibration due to the reference frequency of PWM control occurs. Specifically, the lower the set reference frequency, the more uneven the rotation of the motor, and the motor operation becomes oscillatory.
For example, even when the reference frequency of the PWM control is the reference frequency of the first example described above, vibration due to the reference frequency is generated although it is slight. Further, when the reference frequency of the PWM control is the reference frequency of the second example described above, controllability is improved as compared with the case of the reference frequency of the first example, and the vibration of the motor caused by the reference frequency of the PWM control. It is possible to perform a vibration reduction operation that reduces noise.

  In relation to this, Patent Document 1 discloses a technique for providing a vacuum pump with a damper or operating the vacuum pump with an inertial force in order to reduce the vibration of the vacuum pump.

JP 2003-120582 A (refer to claim 1 and paragraph 0005)

In the vacuum pump, each of the various vibrations caused by various factors is reduced as much as possible, and the total vibrations of the vacuum pump are reduced by stacking them. Thereby, it becomes possible to further exhibit the performance of an apparatus such as an electron microscope connected to the vacuum pump. Therefore, it is desirable to reduce motor vibration caused by PWM control as much as possible.
Also, when you want to ensure that the chamber is evacuated to a certain degree of vacuum within a certain period of time, or that the degree of vacuum in the chamber that has dropped during rated operation due to sample replacement is restored to a certain degree of vacuum in a short time. It is desirable to generate a relatively high torque when a load is applied to the motor, such as when it is desired to do so.

However, as usual, when the reference frequency of PWM control is the reference frequency of the first example described above, a high torque can be generated when a load is applied, but the load on the motor is reduced during operation of the motor. In this case, the operation of the motor could not be changed so as to reduce the motor vibration caused by the PWM control.
On the other hand, when the reference frequency of the PWM control is the reference frequency of the second example described above, the vibration of the motor caused by the PWM control can be reduced as compared with the conventional vacuum pump. The motor operation could not be changed to increase the torque.

  There is also a demand to change the operation of the motor so that the torque of the motor is changed forcibly or by an external signal or the like regardless of the load on the motor.

Therefore, an object of the present invention is to provide a vacuum pump that can change the operation of a motor in accordance with a load applied to the motor, and a control method therefor.
The present invention also provides a vacuum pump that can change the operation of the motor in accordance with the load applied to the motor, and can reduce the vibration of the motor due to the PWM control, and a control method therefor. It is an object.

  According to the present invention, in an electron microscope or an inspection apparatus or the like, the image is observed or output by the electron microscope, or the inspection is actually performed in the inspection apparatus, a predetermined degree of vacuum is achieved and rated operation is being performed. It is an invention made by paying attention to the fact that the load applied to the motor is relatively small during this specific period.

  In order to achieve the above object, a vacuum pump according to the present invention is a vacuum pump operated by a PWM controlled motor, and includes a motor for operating the vacuum pump and a controller for controlling the motor. The controller includes motor controller means for supplying a drive current based on a reference frequency of PWM control to the motor, reference frequency generating means for generating at least two kinds of reference frequencies, and a rating at which the motor rotates at a rated rotational speed. And a reference frequency switching means for switching the reference frequency of PWM control during operation.

According to the vacuum pump of the present invention configured as described above, one of at least two kinds of reference frequencies generated by the reference frequency generating means is supplied to the motor controller means by the reference frequency switching means, and the supplied reference is supplied. PWM control is performed based on the frequency.
During the rated operation, that is, from the start of the rated operation to the end of the rated operation, for example, if a predetermined vacuum level is achieved, the torque required to maintain the predetermined vacuum level is relatively small, so PWM control It is possible to control the motor by switching the reference frequency to a reference frequency that generates a relatively small torque. When the reference frequency after the switching is higher than the reference frequency before the switching, it is possible to perform a vibration reduction operation in which the vibration of the motor due to the PWM control is further reduced as compared with the conventional case.
In addition, during the rated operation, when the degree of vacuum decreases due to, for example, replacement of the sample, it is desired to restore the degree of vacuum to a predetermined degree of vacuum. When it is desired to recover the degree of vacuum in a relatively short time, a load is applied to the motor, so that it is necessary to generate a relatively large torque. Thus, the reference frequency supplied to the motor controller means is switched by the reference frequency switching means to a reference frequency that generates a relatively large torque. Thereby, high torque operation can be performed and the degree of vacuum can be recovered in a relatively short time.
In addition, the reference frequency may be forcibly switched regardless of the load applied to the motor, or the reference frequency may be switched by a signal from another device.
Thus, the operation of the motor can be changed according to the load applied to the motor.

  In the embodiment of the present invention, preferably, the reference frequency generating means generates a first reference frequency and a torque smaller than the first reference frequency and a second reference frequency higher than the first reference frequency. The reference frequency switching means switches the reference frequency for PWM control from the first reference frequency to the second reference frequency during rated operation.

  In the vacuum pump configured as described above, during the rated operation, for example, if the predetermined degree of vacuum is not achieved, it is desired to achieve the predetermined degree of vacuum in a relatively short time. In this case, since a load is applied to the motor, it is necessary to perform a high torque operation that generates a relatively large torque. Therefore, it is necessary to control the motor at the first reference frequency that generates a relatively large torque. Then, after achieving a predetermined degree of vacuum during rated operation, the torque required to maintain the predetermined degree of vacuum is relatively small, so the motor is controlled at a second reference frequency that generates a relatively small torque. It becomes possible. Thus, the reference frequency supplied to the motor controller means is switched from the first reference frequency to the second reference frequency by the reference frequency switching means. Since the second reference frequency is higher than the first reference frequency, it is possible to further perform a vibration reduction operation for reducing motor vibration caused by PWM control. As a result, the motor operation can be changed according to the load applied to the motor, and the vibration of the motor due to the PWM control can be reduced.

The first reference frequency is, for example, a reference frequency of a conventional vacuum pump. As shown in FIG. 8, the first reference frequency is preferably a reference frequency that generates the maximum torque or a reference frequency in the vicinity thereof. However, other reference frequencies may be used as long as the motor can be accelerated to the rated rotational speed.
The second reference frequency is preferably a reference frequency that generates a minimum torque sufficient to maintain the rated operation of the motor in a state where the degree of vacuum is achieved. As shown in FIG. 8, the smaller the torque generated by the second reference frequency, the higher the second reference frequency can be, and the vibration of the vacuum pump caused by the PWM reference frequency can be reduced. it can. Therefore, the smaller the torque generated by the second reference frequency, the better. However, if the second reference frequency is slightly higher than the first reference frequency, the vibration of the vacuum pump due to the PWM reference frequency can be reduced to some extent, and thereby the overall vibration of the vacuum pump. The performance of the device connected to the vacuum pump can be further exhibited. Therefore, the second reference frequency in the present invention generates a second torque smaller than the first torque generated by the first reference frequency, and includes all the reference frequencies higher than the first reference frequency. . In this case, the torque generated by the second reference frequency may not only maintain the rated rotating motor at the rated rotation speed but also accelerate the motor to the rated rotation speed.
Further, the timing for switching from the first reference frequency to the second reference frequency during the rated operation is arbitrary, and may be simultaneously with the start of the rated operation or after the start of the rated operation. When the reference frequency is not switched, the operation is the same as that of a conventional vacuum pump.

  In an embodiment of the present invention, preferably, the vacuum pump main body has a casing having an air inlet and an air outlet, and the gas inside the air inlet is propelled toward the air outlet to the casing inside the casing. The rotor includes a rotatable rotor and a magnetic bearing portion for magnetically floating the rotor with respect to the casing, and the motor rotates the rotor with respect to the casing.

In the vacuum pump configured as described above, the motor rotates the rotor while the rotor is magnetically levitated with respect to the casing, thereby propelling the gas that has entered the intake port of the casing toward the exhaust port.
Since the rotor is floating with respect to the casing, the rotational resistance of the rotor is almost eliminated, and the minimum torque required to maintain the rotational speed of the motor at the rated rotational speed during rated operation is further reduced. Therefore, the second reference frequency can be set to a higher reference frequency, thereby further reducing the vibration of the vacuum pump.

  In the present invention, it is preferable that the controller further includes pump operation monitoring means for supplying an instruction signal indicating a reference frequency to be applied to the motor controller means. A switching instruction signal for instructing switching to the reference frequency is supplied to the motor controller means. When the motor controller means receives the switching instruction signal from the pump operation monitoring means, the reference signal switching means switches the reference frequency of the PWM control.

In the vacuum pump configured as described above, during the rated operation, when the motor controller means receives the switching instruction signal from the pump operation monitoring means, the PWM control reference frequency, for example, the first reference frequency is set to the second reference frequency. And the motor operating at the first reference frequency is operated at the second reference frequency.
During rated operation, it may not be known whether the motor controller means has achieved a predetermined degree of vacuum. After achieving a predetermined degree of vacuum, or when the degree of vacuum is not a predetermined degree, the motor operation can be performed according to the load applied to the motor by switching the reference frequency of PWM control by the switching instruction signal of the pump operation monitoring means. It is possible to change it reliably.

  In an embodiment of the present invention, preferably, the controller further supplies an operation switching request signal for requesting switching of a reference frequency to be applied to the motor controller means to the pump operation monitoring means at a stored predetermined timing. The pump operation monitoring means supplies a switching instruction signal to the motor controller means when an operation switching request signal is supplied from the timing storage means.

In the vacuum pump configured as described above, during the rated operation, an operation switching request signal is supplied from the timing storage means. For example, the second reference frequency for performing the vibration reduction operation from the first reference frequency for performing the high torque operation. The pump operation monitoring means supplies an instruction signal to the motor controller means, and the reference frequency supplied to the motor controller means is changed from the first reference frequency to the second reference frequency by the reference frequency switching means. The motor that was operating at the first reference frequency is operated at the second reference frequency. The predetermined timing may be the time from the start of rated operation, the time from the start of the motor, or any other timing.
During rated operation, the reference frequency for PWM control can be automatically switched at a predetermined timing in accordance with the load applied to the motor.

  In the embodiment of the present invention, preferably, the controller further includes an external input for inputting an operation switching request signal for requesting the pump operation monitoring unit to switch a reference frequency to be applied to the motor controller unit. The pump operation monitoring means supplies a switching instruction signal to the motor controller means when the operation switching request signal is supplied from the external input means.

In the vacuum pump configured as described above, during the rated operation, the operation switching request signal input by the external input means is supplied, and for example, the second operation for performing the vibration reduction operation from the first reference frequency for performing the high torque operation is performed. When it is requested to switch to the reference frequency, the pump operation monitoring means supplies an instruction signal to the motor controller means, and the reference frequency supplied to the motor controller means is switched from the first reference frequency to the second reference frequency. By means of switching, the motor operating at the first reference frequency is operated at the second reference frequency.
During rated operation, when it becomes impossible to maintain a predetermined degree of vacuum, for example, due to sample exchange, or when a predetermined degree of vacuum is achieved after that, depending on the load applied to the motor, PWM, etc. The control reference frequency can be switched at a desired timing.

  In the embodiment of the present invention, preferably, the reference frequency switching means switches the reference frequency of the PWM control according to the load applied to the motor.

In order to achieve the above object, a vacuum pump control method according to the present invention is a vacuum pump control method operated by a PWM-controlled motor, wherein the motor is controlled by PWM control based on a first reference frequency. During the acceleration operation stage for accelerating to the rated rotational speed and during the rated operation in which the motor rotates at the rated rotational speed, the PWM control based on the second reference frequency different from the first reference frequency from the PWM control based on the first reference frequency. And a rated operation stage after switching for performing rated operation, and a deceleration operation stage for decelerating the motor by PWM control based on the third reference frequency.
In the control method according to the present invention, preferably, the second reference frequency generates a torque smaller than the first reference frequency and is higher than the first reference frequency.
Also by the vacuum pump control method according to the present invention configured as described above, the same special effects as the above-described vacuum pump according to the present invention can be obtained.
The third reference frequency may be the same reference frequency as the first reference frequency or may be different from the first reference frequency.

With the vacuum pump and the control method thereof according to the present invention, the operation of the motor can be changed according to the load applied to the motor.
Further, the operation of the motor can be changed according to the load applied to the motor by the vacuum pump and the control method thereof according to the present invention, and the vibration of the motor due to the PWM control can be reduced.

  Hereinafter, an example of an embodiment of a vacuum pump according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing components of a vacuum pump according to the present invention operated by a PWM controlled motor. As shown in FIG. 1, the vacuum pump 1 includes a vacuum pump body 2 including a motor 16 and a controller 4 that controls the motor 16.

Next, a turbo molecular pump will be described as an example of the vacuum pump body 2 with reference to FIG. FIG. 2 is a longitudinal sectional view of the turbo molecular pump.
The vacuum pump body 2 includes a casing 10 having an intake port 6 provided at an upper portion and an exhaust port 8 provided at a lower portion, and a casing 10 for propelling a gas entering the intake port 6 toward the exhaust port 8. , A rotor 14 that can rotate about the vertical axis 12 with respect to the casing 10, a motor 16 that rotates the rotor 14 relative to the casing 10 to operate the vacuum pump 1, and a rotational speed of the motor 16 Two rotational speed sensors 18a, 18b for detecting the rotor and three magnetic bearing portions 20, 22, 24 for magnetically floating the rotor 14 with respect to the casing 10.

  The casing 10 extends in the vertical direction, and is disposed concentrically on the inner side of the outer cylinder part 10a and the outer cylinder part 10a provided with the intake port 6 and the exhaust port 8, from the vertical center to the lower part of the outer cylinder part 10a. And an extending inner cylinder portion 10b. The intake port 6 is provided in the upper surface of the outer cylinder part 10a, and the exhaust port 8 is provided in the lower side surface of the outer cylinder part 10a. A plurality of stator blades 10c extending inwardly from the outer cylinder portion 10a in a direction perpendicular to the vertical axis 12 are arranged from the vicinity of the intake port 6 to the vicinity of the exhaust port 8. The inner cylinder portion 10b has protective bearings 10d at its upper and lower portions for rotatably supporting the rotor 14 when the rotor 14 is not magnetically levitated.

  The rotor 14 is sucked so as to be fixed to the upper part of the rotor shaft 14a and to surround the inner cylinder portion 10b from above, with the rotor shaft 14a rotatably supported around the vertical axis 12 inside the inner cylinder portion 10b. A rotor body 14b extending downward from the vicinity of the opening 6 to a level near the exhaust opening 8, and extending outwardly from the rotor body 14b perpendicularly to the vertical axis 12 toward the outer cylinder portion 10a, over the entire length of the rotor body 14b. And a plurality of rotor blades 14c provided. The rotor blades 14c and the stator blades 10c are alternately arranged so as to overlap each other with a slight gap. The uppermost rotor blade 14c is disposed above the uppermost stator blade 10c. The rotor blade 14c is shaped so as to knock the gas that has entered from the intake port 6 toward the exhaust port 8 when it rotates. The stator blade 10c is shaped so as to guide the gas knocked down by the rotor blade 14c to the lower rotor blade 14c and prevent the gas from returning toward the intake port 6.

  The motor 16 is a DC brushless motor, and includes a permanent magnet 16a fixed to the rotor shaft 14a, and a plurality of electromagnets 16b arranged on the inner cylinder portion 10b around the permanent magnet 16a and spaced apart from the permanent magnet 16a. Have. The plurality of electromagnets 16 b are connected to the controller 4 (not shown), and under the control of the controller 4, magnetic poles are generated so as to generate a rotating magnetic field that rotates the rotor shaft 14 a provided with the permanent magnet 16 a around the vertical axis 12. Can be switched.

The magnetic bearing portions 20 and 22 are for floating the rotor shaft 14a in the radial direction, and are provided at the upper and lower portions of the rotor shaft 14a. The magnetic bearing portion 24 is for floating the rotor shaft 14a in the thrust direction, and is provided at a lower end portion of the rotor shaft 14a.
The magnetic bearing portion 20 includes a rotor shaft portion 20a formed of a high permeability material such as iron, four electromagnets 20b provided at intervals of 90 degrees on the inner cylinder portion 10b around the rotor shaft portion 20a, and a rotor shaft And a displacement sensor 20c for detecting a radial displacement of 14a. The electromagnet 20b and the displacement sensor 20c are connected to the controller 4 (not shown), and the controller 4 operates the four electromagnets 20b in accordance with the radial displacement of the rotor shaft 14a detected by the displacement sensor 20c. The shaft portion 20a is sucked, and thereby the feedback control can be performed so as to maintain the rotor shaft 14a at a predetermined radial floating position.
Since the magnetic bearing portion 22 has the same configuration as the magnetic bearing portion 20, the same alphabetic symbols as those of the magnetic bearing portion 20 are attached to the components of the magnetic bearing portion 22 similar to the magnetic bearing portion 20, Those descriptions are omitted.
The magnetic bearing portion 24 is provided on the inner cylinder portion 10b so as to be disposed above the metal disk 24a and the metal disk 24a fixed to the rotor shaft 14a, and is operable to attract the metal disk 24a upward. An upper electromagnet 24b, a lower electromagnet 24c provided on the inner cylinder portion 10b so as to be disposed below the metal disk 24a, operable to attract the metal disk 24a downward, and a lower end of the rotor shaft 14a. Displacement sensor 24d. The upper electromagnet 24b, the lower electromagnet 24c, and the displacement sensor 24d are connected to the controller 4 (not shown), and the controller 4 has two electromagnets according to the thrust direction displacement of the metal disk 24a detected by the displacement sensor 24c. Feedback control can be performed so as to actuate 24b and 24c and suck the metal disk 24a, thereby maintaining the rotor shaft 14a at a predetermined thrust levitation position.

  Next, the controller 4 will be described with reference to FIG. 1 again. The controller 4 is connected to the motor 16 and the rotation speed sensor 18a, and can generate at least two kinds of reference frequencies, and a motor controller unit 30 for supplying a drive current based on a reference frequency of PWM control to the motor 16. Reference frequency generator 32, which is connected between motor controller 30 and reference frequency generator 32, and is capable of switching the reference frequency of PWM control during rated operation rotating at the rated speed of motor 16. A frequency switching unit 34 and a pump operation monitoring unit 36 connected to the rotation speed sensor 18b and the motor controller unit 30 and for supplying an instruction signal indicating a reference frequency to be applied to the motor controller unit 30 are provided. .

Specifically, the motor controller unit 30 is connected to the electromagnet 16b of the motor 16 and is connected to the motor amplifier unit 30a for supplying a driving current to the motor 16 and the rotation speed sensor 18a, and supplies a rotation speed signal. The motor driver unit 30c is connected to the motor speed unit 30b, the motor amplifier unit 30a, the motor speed unit 30b, and the reference frequency switching unit 34, and supplies a motor drive signal based on the PWM reference frequency to the motor amplifier unit 30a. And have.
The motor driver 30c can determine whether or not the motor 16 is rotating at the rated rotational speed based on the signal supplied from the rotation speed signal supply unit 30b. In addition, the motor driver unit 30c can supply a drive signal based on the reference frequency supplied from the reference frequency switching unit to the motor amplifier unit 30a.

In this embodiment, the reference frequency generation unit 32 includes a first reference frequency generation unit 32a that generates a first reference frequency and a second reference frequency generation unit 32b that generates a second reference frequency. Yes.
The first reference frequency generated by the first reference frequency generator 32a is an arbitrary reference frequency determined in consideration of the cost and circuit configuration of the first reference frequency generator 32a itself, for example, a conventional vacuum This is the conventional reference frequency used for the pump. When the conventional reference frequency is selected as the first reference frequency, the above-described motor 16 is preferably a conventional or novel motor designed to obtain good torque efficiency based on the conventional reference frequency. As a result, the first reference frequency is the reference frequency that generates the maximum torque of the motor 16 or a reference frequency in the vicinity thereof.

  The second reference frequency generated by the second PWM reference frequency generator 32b is preferably a reference frequency that generates a minimum torque sufficient to maintain the rated rotational speed. However, if the second reference frequency can maintain the rated operation of the motor, generates a torque smaller than the first torque, and is higher than the first reference frequency, it is the other reference frequency. Also good. The second reference frequency is, for example, a reference frequency that is an integral multiple of the first reference frequency.

  The reference frequency switching unit 34 supplies the first reference frequency or the second reference frequency to the motor driver unit 30c based on the instruction signal supplied from the pump operation monitoring unit to the motor driver unit 30c. For example, when the rotational speed of the motor 16 is smaller than the rated rotational speed during acceleration operation and deceleration operation, the reference frequency switching unit 34 uses the first reference frequency generated by the first reference frequency generation unit 32a as a motor driver. It is possible to supply to the part 30c. Further, during the rated operation in which the rotation speed of the motor 16 is the rated rotation speed, the first reference frequency generated by the first reference frequency generator 32a and the second reference frequency generated by the second reference frequency generator 30b. The reference frequency can be supplied to the motor driver unit 30c, and the reference frequency supplied to the motor driver unit 30c can be switched between the first reference frequency and the second reference frequency.

The pump operation monitoring unit 36 is connected to the rotation speed sensor 18b, connected to the rotation speed signal supply unit 36a that supplies a rotation speed signal, the rotation speed signal supply unit 36a, and the motor driver unit 30c, and determines the reference frequency to be applied. And a host unit 36 b for supplying an instruction signal to instruct the motor controller unit 30.
The host unit 36b can determine whether or not the motor 16 is rotating at the rated rotation speed based on the signal supplied from the rotation speed signal supply unit 36a. Further, the host unit 36b, during the rated operation, a first instruction signal for instructing the first reference frequency, a second instruction signal for instructing switching from the first reference frequency to the second reference frequency, and the second It is possible to supply the motor driver unit 30c with a third instruction signal for instructing the second reference frequency and a fourth instruction signal for instructing switching from the second reference frequency to the first reference frequency.

  The controller 4 can further supply an operation switching request signal that is connected to the pump operation monitoring unit 36 and that requests switching of a reference frequency to be applied to the motor controller unit 30 at a stored predetermined timing. A timing storage unit 38 and an external input unit 40 connected to the pump operation monitoring unit 36 and for inputting an operation switching request signal for requesting switching of a reference frequency to be applied to the motor controller unit 30 from the outside. ing.

The timing storage unit 38 is, for example, a timer 38, and the operation switching request signal is, for example, a vibration reduction operation signal that requests to switch the reference frequency of PWM control from the first reference frequency to the second reference frequency. . The timer 38 initially operates in a state where the vibration reduction operation signal is OFF, and the vibration reduction operation signal can be switched ON after a predetermined time stored by a trigger signal (not shown). In the present embodiment, the trigger signal is a signal supplied to the timing storage unit 38 at the start of rated operation.
The external input unit 40 is, for example, a manual changeover switch, and the operation switching request signal is, for example, a vibration reduction operation signal that requests to switch the reference frequency of PWM control from the first reference frequency to the second reference frequency. is there.

Next, a control flow of the motor driver unit 30c will be described with reference to FIG. FIG. 3 is a flowchart showing a control flow of the motor driver unit. Hereinafter, the first reference frequency is referred to as “conventional reference frequency”, the second reference frequency is referred to as “vibration reduction reference frequency”, and the motor operation based on the first reference frequency is referred to as “high torque operation”. The operation of the motor based on the second reference frequency is referred to as “vibration reduction operation”.
In ST50, it is determined whether or not the motor 16 is in rated operation. If it is determined that the motor 16 is in rated operation, the process proceeds to ST52, and it is determined whether the instruction signal from the host unit 36b indicates the vibration reduction reference frequency or the conventional reference low frequency. When it is determined that the instruction from the host unit 36b is the vibration reduction reference frequency, the process proceeds to ST54, and a drive signal based on the vibration reduction reference frequency is supplied to the motor amplifier unit 30a in order to perform the vibration reduction operation.
In ST50, when it is determined that the motor 16 is not in rated operation, that is, in stop, acceleration operation or deceleration operation, and in ST52, when it is determined that the instruction from the host unit 36b is the conventional reference frequency, Proceeding to ST56, in order to perform high torque operation, a drive signal based on the conventional reference frequency is supplied to the motor amplifier 30a.

Next, the control flow of the host unit 36b will be described with reference to FIG. FIG. 4 is a flowchart showing the control flow of the host unit.
In ST60, it is determined whether or not the motor 16 is in rated operation. If it is determined that the motor 16 is in rated operation, the process proceeds to ST62, and it is determined whether the vibration reduction operation signal supplied from the timing storage unit 38 or the external input unit 40 is ON or OFF. If it is determined that the vibration reduction operation signal is OFF, the process proceeds to ST64, and a signal indicating a conventional reference frequency, that is, a first instruction signal is supplied to the motor driver 30c.
If it is determined in ST62 that the vibration reduction operation signal is ON, the process proceeds to ST66, and it is determined whether the previous vibration reduction operation signal was ON or OFF. If it is determined in ST66 that the previous vibration reduction operation signal is OFF, the process proceeds to ST68, and a signal instructing the vibration reduction reference frequency is supplied to the motor driver unit 30c. This signal is also a second instruction signal for instructing switching from the conventional reference frequency to the vibration reduction reference frequency.
If it is determined in ST66 that the previous vibration reduction operation signal is ON, and if it is determined in ST60 that the rated operation is not in progress, that is, the vehicle is stopped, accelerated or decelerated, the process proceeds to ST70. A signal for maintaining the reference frequency is supplied to the motor driver 30c. Specifically, if the host unit 36b previously instructed the conventional reference frequency, a signal indicating the conventional reference frequency, that is, a first instruction signal is supplied to the motor driver unit 30c, and the host unit 36b In the case of indicating the vibration reduction reference frequency, a signal indicating the vibration reduction reference frequency, that is, a third instruction signal is supplied to the motor driver 30c.

Next, three operation sequences of the vacuum pump according to the present invention will be described with reference to FIGS.
First, the operation of the vacuum pump 2 common to the three operation sequences will be described.
When the controller 4 is energized, the magnetic bearings 20, 22, and 24 are operated, and the rotor 14 is levitated in the radial direction and the thrust direction with respect to the casing 10. Next, when the motor 16 is operated, the rotor 14 rotates at a high speed while floating with respect to the housing 10. Gas molecules entering from the intake port 6 are knocked down by the rotor blades 14c, and the gas molecules knocked down are guided to one rotor blade 14c by the stator blade 10c rotating at high speed. The gas molecules are propelled downward while alternately colliding with the rotor blades 14 and the stator blades 10c, and finally exhausted from the exhaust port 8.

Next, with reference to FIGS. 3 to 5, a first operation sequence of the vacuum pump that is always in a vibration reduction operation during the rated operation will be described. The first operation sequence is used, for example, when a chamber to be evacuated is roughed by a back pump in advance and a predetermined degree of vacuum can be achieved at the end of acceleration operation of the vacuum pump according to the present invention.
In this first operation sequence, the timing storage unit 38 does not operate, the vibration reduction operation signal of the external input unit 40 is always ON, and the initial state of the reference frequency instruction from the host unit is the vibration reduction reference frequency. And
During the acceleration operation, the control flow of the host unit 36b proceeds from ST60 to ST70, and the host unit 36b supplies the motor driver unit 30c with a signal that maintains the previous reference frequency, that is, a signal that indicates the vibration reduction reference frequency. The control flow of the motor driver unit 30c proceeds from ST50 to ST56, the instruction supplied from the host unit 36b is ignored, and a drive signal based on the conventional reference frequency is supplied to the motor amplifier unit 30a in order to perform high torque operation. As a result, the motor 16 is automatically accelerated with a high torque regardless of an instruction from the host unit 36b during acceleration operation.
During the rated rotation, the control flow of the host unit 36b proceeds from ST60 to ST62 and ST66. Since the vibration reduction operation signal state remains ON, the control flow of the host unit 36b proceeds from ST66 to ST70, and a signal for maintaining the previous reference frequency, that is, a signal for instructing the vibration reduction reference frequency is sent to the motor driver unit 30c. To supply. The control flow of the motor controller 30c proceeds from ST50 to ST52 and ST54, and supplies a drive signal based on the vibration reduction reference frequency to the motor amplifier 30c. Thereby, the motor 16 performs the vibration reduction operation throughout the rated rotation.
During the deceleration operation, the control flow of the host unit 36b and the motor driver unit 30c proceeds in the same manner as the control flow during the acceleration operation. Accordingly, the motor 16 is automatically decelerated with a high torque regardless of an instruction from the host unit 36b during the deceleration operation.

Next, with reference to FIGS. 3, 4 and 6, a second operation sequence of the vacuum pump which will be in a vibration reduction operation after a predetermined time since the rated operation has been performed will be described. The second operation sequence is used, for example, when the chamber capacity is large and a predetermined degree of vacuum cannot be achieved at the end of the acceleration operation of the vacuum pump according to the present invention.
In the second operation sequence, after a predetermined time from the start of the rated operation, the vibration reduction operation signal supplied from the timing storage unit 38 is switched from OFF to ON, and the external input unit 40 does not operate. The predetermined time is appropriately determined according to the capacity of the chamber and the predetermined degree of vacuum.
During the acceleration operation, similarly to the first operation sequence, the motor 16 is automatically accelerated with a high torque.
When the rated operation is started, the control flow of the host unit 36b proceeds from ST60 to ST62. Since the vibration reduction operation signal is OFF, the control flow proceeds from ST62 to ST64, and a signal indicating the conventional reference frequency is supplied to the motor driver unit 30c. Next, the control flow of the motor driver unit 30c proceeds from ST50 to ST52 and ST56, and a drive signal based on the conventional reference frequency is supplied to the motor amplifier unit 30c. Thereby, the motor 16 performs high torque rated operation.
After a predetermined time from the start of rated operation, the vibration reduction operation signal is turned from OFF to ON. The control flow of the host unit 36b proceeds from ST60 to ST62. Since the vibration reduction operation signal is ON, the control flow proceeds from ST62 to ST66. Since the previous vibration reduction operation signal is OFF, the control flow proceeds from ST66 to ST68, and a signal instructing the vibration reduction reference frequency is supplied to the motor driver unit 30c. This signal is also an instruction signal for instructing switching from the conventional reference frequency to the vibration reduction reference frequency. Next, the control flow of the motor driver unit 30c proceeds from ST50 to ST52 and ST54, and a drive signal based on the vibration reduction reference frequency is supplied to the motor amplifier unit 30a. Thereby, the motor starts the vibration reduction rated operation.
During the subsequent rated operation, the control flow of the host unit 36b proceeds from ST60 to ST62 and ST66. Since the previous vibration reduction operation signal is ON, the control flow proceeds from ST66 to ST70, and a signal for maintaining the previous reference frequency, that is, a signal for instructing the vibration reduction reference frequency is supplied to the motor driver unit 30c. Next, the control flow of the motor driver unit 30c proceeds from ST50 to ST52 and ST54, and a drive signal based on the vibration reduction reference frequency is supplied to the motor amplifier unit 30a. Thereby, the motor continues the vibration reduction rated operation.
During the deceleration operation, similarly to the first operation sequence, the motor 16 is automatically decelerated with a high torque.
In the second operation sequence, if the predetermined time in the timing storage unit 38 is set to 0, the same operation as the first operation sequence is performed.

Next, a third operation sequence of the vacuum pump for switching the vibration reduction operation signal from ON to OFF during rated operation and subsequently switching from OFF to ON will be described with reference to FIGS. 3, 4, and 7. . The third operation sequence is used, for example, when a gas load is applied to the vacuum pump during rated operation and a period in which torque is required occurs.
In the third operation sequence, the timing storage unit 38 does not operate, the vibration reduction operation signal of the external input unit 60 is initially ON, and the first instruction of the reference frequency from the host unit is the conventional reference frequency.
During the acceleration operation, similarly to the first operation sequence, the motor 16 is automatically accelerated with a high torque.
When the rated operation is started, the control flow of the host unit 36b proceeds from ST60 to ST62. Since the vibration reduction operation signal is ON, the control flow proceeds from ST66 to ST70. Since the previous vibration reduction operation signal is ON, the control flow proceeds from ST66 to ST70, and a signal for maintaining the previous reference frequency, that is, a signal indicating the conventional reference frequency is supplied. Next, the control flow of the motor driver unit 30c proceeds from ST50 to ST52 and ST56, and a drive signal based on the conventional reference frequency is supplied to the motor amplifier unit 30a. Thereby, the motor performs a high torque rated operation.

When the vibration reduction operation signal is switched from ON to OFF, the control flow of the host unit 36b proceeds from ST60 to ST62 and ST64, and supplies a signal indicating the conventional reference frequency to the motor driver unit 30c. Next, the control flow of the motor driver unit 30c proceeds from ST50 to ST52 and ST56, and a drive signal based on the conventional reference frequency is supplied to the motor amplifier unit 30a. Thereby, the motor 16 continues the high torque rated operation.
When the vibration reduction operation signal is turned from OFF to ON, the control flow of the host unit 36b proceeds from ST60 to ST62. Since the vibration reduction operation signal is ON, the control flow proceeds from ST62 to ST66. Since the previous vibration reduction operation signal is OFF, the control flow proceeds from ST66 to ST68, and a signal instructing the vibration reduction reference frequency is supplied to the motor driver unit 30c. This signal is also an instruction signal for instructing switching from the conventional reference frequency to the vibration reduction reference frequency. Next, the control flow of the motor driver unit 30c proceeds from ST50 to ST52 and ST54, and a drive signal based on the vibration reduction reference frequency is supplied to the motor amplifier unit 30a. Thereby, the motor 16 starts a vibration reduction rated operation.

During the subsequent rated operation, the control flow of the host unit 36b proceeds from ST60 to ST62 and ST66. Since the previous vibration reduction operation signal is ON, the control flow proceeds from ST66 to ST70, and a signal for maintaining the previous reference frequency, that is, a signal for instructing the vibration reduction reference frequency is supplied. Next, the control flow of the motor driver unit 30c proceeds from ST50 to ST52 and ST54, and a drive signal based on the vibration reduction reference frequency is supplied to the motor amplifier unit 30a. Thereby, the motor 16 continues the vibration reduction rated operation.
When the vibration reduction operation signal is switched from ON to OFF again, the control flow of the host unit 36b proceeds from ST60 to ST62 and ST64, and supplies a signal indicating the conventional reference frequency to the motor driver unit 30c. Next, the control flow of the motor driver unit 30c proceeds from ST50 to ST52 and ST56, and a drive signal based on the conventional reference frequency is supplied to the motor amplifier unit 30a. Thereby, the motor 16 starts a high torque rated operation.
During the deceleration operation, similarly to the first operation sequence, the motor 16 is automatically decelerated with a high torque.
When the reference frequency is instructed in the past, even if the vibration reduction operation signal is turned ON from OFF during acceleration operation or deceleration operation, the signal switched from OFF to ON is ignored and rated operation is started. The vibration reduction rated operation is not automatically performed.

In the above description of the embodiment, the vacuum pump 2 has been described as a turbo molecular pump, but may be a dry pump, an oil rotary pump, or another vacuum pump as long as it is driven by a PWM-controlled motor.
In the above-described embodiment, the reference frequency generation unit 32 generates two reference frequencies. However, the number is not limited to two, and three or more reference frequencies may be generated.
In the above-described embodiment, the first reference frequency generation unit 32a and the second reference frequency generation unit 32b are provided to generate the first reference frequency and the second reference frequency independently of each other. When the second reference frequency is an integer multiple of the first reference frequency, the first reference frequency and the second reference frequency may be generated by a single oscillation circuit.
In the above-described embodiment, the controller 4 includes the pump operation monitoring unit 36, the timing storage unit 38, and the external input unit 40. However, the controller 4 may be omitted if unnecessary according to the operation sequence. . For example, if the motor controller unit 30 is controlled so that the vibration reduction operation is always performed during the rated rotation, the pump operation monitoring unit 36, the timing storage unit 38, and the external input unit 40 can be omitted. For example, if it is not necessary to automatically switch the reference frequency, the timing storage unit 38 can be omitted. For example, if the reference frequency is not switched from the outside, the external input unit 40 is omitted. can do.
In the above-described embodiment, the two rotation speed sensors 18a and 18b are provided. However, only one rotation speed sensor may be provided and shared. However, when the signals of the rotation speed sensors 18a and 18b are compared to confirm the state of the vacuum pump 2, two rotation speed sensors are required.
In the above-described embodiment, the vibration reduction operation signal that requires switching the reference frequency of the PWM control from the first reference frequency to the second reference frequency has been described. However, the first reference frequency is changed from the second reference frequency to the first reference frequency. It may be a signal that requests switching to a frequency, or may be a signal that requests switching between other arbitrary reference frequencies.
In the above-described embodiment, only the case where the timing storage unit 38 is switched from OFF to ON has been described. However, the timing storage unit 38 may be switched from ON to OFF.
Moreover, although the external input part 40 was demonstrated as a manual changeover switch in embodiment mentioned above, if the vibration reduction operation signal switches between OFF and ON, the thing of arbitrary forms may be sufficient. For example, a switch that operates in response to a signal indicating the degree of vacuum, a switch that interlocks with an open / close lid of a chamber such as an electron microscope, and the like may be used.
In the above-described embodiment, the elements of the controller 4 are the motor controller unit 30, the reference frequency generation unit 32, the reference frequency switching unit 34, the pump operation monitoring unit 36, the timing storage unit 38, and the external input unit 40. It is arbitrary how these components are combined to form the embodiment. For example, in the above-described embodiment, one controller is provided for one vacuum pump main body 2. However, for example, a first controller having a first reference frequency generation unit for one vacuum pump main body 2. Then, a second controller having a second reference frequency generation unit may be provided to switch the controller connected to the vacuum pump main body 2.

It is a block diagram which shows the component of the vacuum pump by this invention. It is a longitudinal cross-sectional view of a turbo molecular pump. It is a flowchart which shows the control flow of a motor driver part. It is a flowchart which shows the control flow of a pump driving | operation monitoring part. It is a figure which shows the 1st operation | movement sequence of the vacuum pump by this invention. It is a figure which shows the 2nd operation | movement sequence of the vacuum pump by this invention. It is a figure which shows the 3rd operation | movement sequence of the vacuum pump by this invention. It is a figure which shows the relationship between the reference frequency of PWM control, and the motor torque which generate | occur | produces with the reference frequency.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum pump 2 Vacuum pump main body 4 Controller 6 Intake port 8 Exhaust port 10 Casing 14 Rotor 16 Motor 18 Rotation speed sensor 20 Magnetic bearing part 22 Magnetic bearing part 24 Magnetic bearing part 30 Motor controller part 32 Reference frequency generation part 34 Reference frequency switching Unit 36 pump operation monitoring unit 38 timing storage unit 40 external input unit

Claims (9)

A vacuum pump operated by a PWM controlled motor,
A motor for operating a vacuum pump, and a controller for controlling the motor, the controller comprising:
Motor controller means for supplying a drive current based on a reference frequency of PWM control to the motor;
A reference frequency generating means for generating at least two types of said reference frequency,
Vacuum pump said motor and having a means switching the reference frequency for switching in rated operation, the reference frequency of the PWM control, the reference frequency of the higher frequency from the reference frequency of the low frequency rotating at rated speed. It said reference frequency generation means includes a first of said reference frequency, is possible to generate a second of said reference frequency higher than the first and the first reference frequency to generate a smaller torque than the reference frequency vacuum pump according to claim 1, characterized in that you can. The first reference frequency, a vacuum pump of claim 2 wherein said reference frequency or the reference frequency in the vicinity thereof to generate the maximum torque.   The vacuum pump includes a casing having an air inlet and an air outlet, a rotor rotatable with respect to the casing inside the casing so as to propel the gas that has entered the air inlet toward the air outlet, and the rotor And a magnetic bearing portion for magnetically levitating the casing with respect to the casing, wherein the motor rotates the rotor with respect to the casing. The vacuum pump according to item. Wherein the controller further comprises a pump operation monitoring means for supplying an instruction signal instructing the reference frequency to be applied to said motor controller means, the pump operation monitoring means during rated operation, the reference frequency it is supplied to the motor controller means an instruction signal switching instructing to switch, the motor controller unit, when said received the switching instruction signal from the pump operation monitoring means, switching means said reference signal the reference frequency of the PWM control The vacuum pump according to any one of claims 1 to 4, wherein the vacuum pump is switched. Wherein the controller is further said motor controller means operating changeover request signal for requesting to switch the reference frequency to be applied to the stored predetermined said pump operation monitoring means capable timing storage be provided at the timing Having means,
6. The vacuum pump according to claim 5, wherein the pump operation monitoring unit supplies the switching instruction signal to the motor controller unit when an operation switching request signal is supplied from the timing storage unit. Wherein the controller further comprises an external input means for inputting the operation switch request signal for requesting to switch the reference frequency to be applied to said motor controller means to said pump operation monitoring means from the outside,
6. The vacuum pump according to claim 5, wherein the pump operation monitoring unit supplies the switching instruction signal to the motor controller unit when an operation switching request signal is supplied from the external input unit. It said reference frequency switching means, the vacuum pump according to claim 5, characterized in that switching the reference frequency of the PWM control in accordance with a load applied to the motor. 2. The vacuum pump according to claim 1, wherein the reference frequency generating means generates the at least two types of the reference frequencies by a single oscillation circuit.

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