JPH06147185A - Magnetic levitation type vacuum pump - Google Patents

Abstract

PURPOSE:To provide a magnetic levitation type vacuum pump capable of previously detecting rock of a protecting bearing caused by touch down. CONSTITUTION:Before the start of normal operation of a magnetic leviatation type vacuum pump, an exciting current is supplied to radial electromagnets 20, 24 and axial electromagnets 32, 34 to magnetically levitate a rotor shaft 18 in the non-contact state. A high frequency motor 30 is rotated at the low speed rotational frequency of several thousands [rpm]. In such a condition, the rotation of the high frequency motor 30 and the magnetic levitation of the rotor shaft 18 are stopped and touched down. The amount of time elapsed from the touch-down until the rotation of the rotor shaft 18 is stopped is measured, and if the measured time is shorter than a designated time, it is judged that a protecting bearing is damaged in a large scale, and the replacement is directed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic levitation type vacuum pump, and more particularly to a magnetic levitation type vacuum pump in which lock of a protective bearing due to touchdown is detected in advance to facilitate maintenance.

[0002]

2. Description of the Related Art For example, in an etching process or a CVD process in semiconductor manufacturing, a vacuum pump is used to secure a vacuum state and discharge a process gas. In this case, the use of contact-type vacuum pump of using lubricating _{oil, SiH 4, PH 3, B} 2 H 6, A S H
A magnetic levitation vacuum pump that uses non-contact bearings is used because the lubricating oil may affect process gases such as ₃ .

The magnetic levitation type vacuum pump ensures that a vacuum state is secured by the rotor blades attached to the rotor shaft by rotating the rotor shaft by a high frequency motor while magnetically levitating the rotor shaft in the axial and radial directions. ing. Various controls such as magnetic levitation of the rotor shaft, detection of the position of the rotor shaft, and rotation of the high-frequency motor are controlled by a control unit arranged outside the main body. The controlled part such as an electromagnet is connected to the control part by a connection cable via a connector arranged in the main body.

When an abnormality such as disconnection of a connector occurs during operation of such a magnetic levitation type vacuum pump, the rotor shaft, which was rotating at a high speed in the magnetic levitation state, comes into contact (touchdown), The magnetic levitation vacuum pump may be damaged. Therefore, in the magnetic levitation vacuum pump, a protective bearing is generally arranged to protect the device.

When the protective bearing of the magnetic levitation type vacuum pump is connected to a chamber for etching or the like, when atmospheric air enters the chamber, for example, a vacuum gauge tube for measuring the degree of vacuum in the chamber is damaged. It is also used and protected by the atmosphere when it enters the atmosphere.

[0006]

However, the magnetic levitation type vacuum pump is usually 20,000 [rpm] to 48,000 [r.
Since it rotates at a high speed at a rotation speed of [pm], if touchdown is performed several times due to entry into the atmosphere or the like, the protective bearing will be damaged and it will gradually become difficult to rotate. Then, if the protective bearing is damaged more than a predetermined amount and further touchdown is performed, there is a problem that the bearing finally locks at the time of touchdown.

In particular, there is a case where the rotor shaft and the bearing are seized due to the lock. In this case, not only is disassembly difficult when repairing, but also many replacement parts are required, resulting in a repair cost. Had led to an increase in.
The present invention has been made in view of such problems,
It is an object of the present invention to provide a magnetic levitation vacuum pump capable of detecting lock of a protective bearing due to touchdown in advance.

[0008]

According to a first aspect of the invention, a rotor shaft having magnetism, a high frequency motor for rotating the rotor shaft, and a plurality of protective bearings arranged at a predetermined interval from the rotor shaft. A plurality of magnetic levitation electromagnets that magnetically levitate the rotor shaft, a plurality of position detection sensors that detect the position of the rotor shaft, and the rotor shaft in a non-contact state based on detection signals from the position detection sensors. Control means for controlling the electric current supplied to the plurality of magnetic levitation electromagnets so as to magnetically levitate and hold it in a predetermined position, and the rotor shaft is rotated at a predetermined low speed revolution. Damage determining means for bearing the rotor shaft on the protective bearing, and determining the damage state of the protective bearing from the rotating state of the rotor shaft, and the damage determining means. When the protective bearing by the step is determined to be more damage predetermined, and exchange instruction means for instructing a replacement of the protective bearings, by including the magnetic levitation type vacuum pump to achieve the object.

[0009]

In the magnetic levitation type vacuum pump of the present invention, for example,
By monitoring the rotating state of the protective bearing before starting operation, it is determined whether the protective bearing will be locked or not when the touchdown occurs next time. If the bearing is damaged, a warning such as an alarm is issued to instruct replacement of the protective bearing in advance.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the magnetic levitation type vacuum pump of the present invention will be described in detail below with reference to FIGS. FIG. 1 shows the overall structure of a magnetic levitation type vacuum pump.

This magnetic levitation type vacuum pump is installed in, for example, a semiconductor manufacturing apparatus, and discharges process gas from a chamber or the like. In this example, a plurality of stator blades 12 are arranged inside a cylindrical outer casing 10, and a plurality of rotor blades 14 are arranged between the respective stator blades 12.

The rotor blades 14 are provided on the outer peripheral wall of the rotor 15, and the rotor 15 is fixed to the rotor shaft 18 with bolts 19 so as to rotate in conjunction with the rotor shaft 18 made of a magnetic material. The rotor 15 uses a so-called magnetic bearing, and two pairs of radial electromagnets 20 are arranged above the rotor shaft 18 so as to sandwich the rotor shaft 18, and the two pairs of radial electromagnets are orthogonal to each other. Are arranged as follows. Adjacent to the radial electromagnet 20, the rotor shaft 18
Two pairs of radial sensors 22 are provided so as to face each other across the pair.

Further, two pairs of radial electromagnets 24 are similarly arranged under the rotor shaft 18, and the radial electromagnet 24 is also provided with two pairs of radial sensors 26 adjacent to each other. . These radial electromagnets 20, 24
When the exciting current is supplied to the rotor shaft 18, the rotor shaft 18 is magnetically levitated. During this magnetic levitation, the rotor shaft 18 is detected by the position detection signals from the radial sensors 22 and 26.
The exciting current is controlled so that is held at a predetermined position.

Further, a high frequency motor 30 is arranged between the radial direction sensor 22 and the radial direction sensor 26 inside the exterior body 10 in this embodiment. When the high-frequency motor 30 is energized, the rotor shaft 18 and the rotor blades 14 fixed to the rotor shaft 18 rotate.

A disk-shaped magnetic metal disk 31 is fixed to the lower portion of the rotor shaft 18, and the pair of axial electromagnets 3 sandwiching the metal disk 31 and facing each other are provided.
2, 34 are arranged. Further, an axial sensor 36 is arranged so as to face the cut end of the rotor shaft 18.

The exciting currents of the axial electromagnets 32 and 34 are controlled according to the position detection signal from the axial sensor 36, so that the rotor shaft 18 is held at a predetermined position in the axial direction. . In addition, this rotor shaft 18
A rotation sensor 38 for detecting the number of rotations of the rotor shaft is arranged at the lower end of the.

Further, in order to protect the entire device at the time of touchdown, radial protection bearings 50 are arranged at a predetermined interval above the rotor shaft 18 and at a lower part at a predetermined interval in the axial direction. Bearings 51 are arranged respectively. Each of these parts corresponds to the axial electromagnet 3
Through a connector 44 provided in the vicinity of 2, 34, a cable is connected to a signal processing system including a magnetic bearing controller, a main controller, and the like.

FIG. 2 shows an electrical configuration of the magnetic levitation type vacuum pump. The magnetic levitation vacuum pump mainly includes a system controller 70 using a microprocessor unit (MPU) and the like, and a magnetic levitation controller 8
It is configured by 0.

The system controller 70 monitors the state of the magnetic levitation type vacuum pump and performs various controls such as the judgment operation according to this embodiment.
a, a ROM (Read Only Memory) 70b in which programs and data for executing various controls in the CPU 70a are stored, a RAM (Random Access Memory) 70c used as a working memory, a keyboard interface ( I / F) 70d, display I / F
F70e, I / O 70f, 70g, and 70h are provided, and these are connected to a bus line 70j such as a data bus. Further, a timer 70i for measuring time is connected to the CPU 70a.

The keyboard I / F 70d is connected to a keyboard 74 for performing various operation instructions and other operations.
Further, the display I / F 70e is a CRT or LCD for displaying the operating state from the keyboard 74, the floating state of the rotor shaft 18, and the operating state of the magnetic levitation vacuum pump.
A display device 76 such as is connected.

A magnetic levitation controller 80 is connected to the I / O 70f. This magnetic levitation controller 8
0 is the radial sensor 22, 26 and the axial sensor 3
6 is provided with PIDs (correction circuits) 82a to 82e to which the position detection signals from 6 are respectively input.
Amplifiers 84a and 84e are connected to the respective output terminals of to 82e.

Radial electromagnets 20 and 24 composed of a pair of coils are connected to the output terminals of the amplifiers 84a to 84d. Further, the axial electromagnets 32 and 34 configured as a pair of coils are connected to the output terminal of the amplification unit 84e. This magnetic levitation controller 80 is
The rotor shaft 18 is magnetically levitated in the radial direction by supplying an exciting current to the radial electromagnets 20 and 24, and the rotor shaft 18 is held at a predetermined radial position according to the position detection signals from the radial sensors 22 and 26. As described above, the amplification factors of the amplifiers 84a to 84d are changed to control the exciting current to be supplied.

At the same time, the magnetic levitation controller 80
The rotor shaft 18 is magnetically levitated in the axial direction by supplying an exciting current to the axial electromagnets 32 and 34, and the rotor shaft 18 is held at a predetermined axial position according to a position detection signal from the axial sensor 36. Then, the amplification factor of the amplifier 84e is changed to control the exciting current to be supplied.

A rotation sensor 38 is connected to the I / O 70g, and a pulse signal from the rotation sensor 38 is read by the CPU 70a to detect the rotation speed of the rotor shaft 18. In addition, the I / O 70h includes a high frequency motor 30.
A motor driver 77 for rotating and driving is connected. The motorized hiver 77 converts an AC power source (not shown) into a direct current by a converter, and then supplies it to the high frequency motor 30 as a three-phase alternating current by an inverter again.

Further, a timer 70i for measuring time is connected to the CPU 70a. Next, the operation of determining whether or not the protective bearings 50, 51 need to be replaced by the magnetic levitation type vacuum pump configured as described above will be described.

First Judgment Operation FIG. 3 shows the first judgment operation. First, before starting the normal operation of the magnetic levitation type vacuum pump, the CPU 7
0a instructs the magnetic levitation controller 80 to magnetically levitate the rotor shaft 18 via the I / O 70f.

The magnetic levitation controller 80 includes the CPU 7
0a, the radial electromagnets 20, 24
Then, an exciting current is supplied to the axial electromagnets 32 and 34 to magnetically levitate the rotor shaft 18 (step 31). In this case, in the magnetic levitation controller 80, the PIDs 82a to 82e and the amplification units 84a to 8e are detected by the position detection signals from the radial direction sensors 22 and 26 and the axial direction sensor 36.
The rotor shaft 18 is held at the shaft center by controlling the exciting current by 4e.

The CPU 70a also instructs the motor driver 77 via the I / O 70h to start rotation of the high frequency motor 30. Upon receiving this instruction, the high frequency motor 30 outputs the converted three-phase alternating current to rotate the high frequency motor 30 (step 32). The CPU 70a calculates the number of rotations of the rotor shaft 18 due to the rotation of the high frequency motor 30 as I / O.
It is detected by reading the pulse signal supplied from the rotation sensor 38 via 70g. Then, it is monitored whether or not the detected rotation speed of the rotor shaft 18 has reached a predetermined value, for example, a low rotation speed of several thousand times per minute (step 3).
2).

When the number of rotations of the rotor shaft 18 reaches a predetermined value (step 33; Y), the CPU 70a determines the rotor shaft 1
The magnetic levitation controller 80 is instructed to move the rotor shaft 18 up and down while the rotor 8 is rotating (step 34). In the magnetic levitation controller 80, the exciting currents supplied to the axial electromagnet 32 and the axial electromagnet 34 are alternately changed to alternately press them in the vertical direction.

During this time, the CPU 70a keeps the axial sensor 36
The rotation state of the rotor shaft 18 is monitored by monitoring the position detection signal supplied from the magnetic levitation controller 80 and the I / O 70f (step 35). CP
The U 70a determines whether or not the rotation is abnormal depending on whether or not the vibration width of the rotor shaft 18 exceeds a predetermined value based on the position detection signal from the axial sensor 36 (step 36). If it is determined that the rotation is abnormal (step 36; Y), it is determined that the protective bearing is damaged, and the indicator I /
A request for replacement of the protective bearings 50, 51 is displayed on the display 76 via F70e (step 37), and the first determination operation is ended.

If it is determined that the rotation is abnormal,
The CPU 70a controls so that the normal operation of the magnetic levitation vacuum pump is prohibited until the protective bearings 50 and 51 are replaced. On the other hand, when it is determined that the rotation is not abnormal (step 36; N), the first determination operation is ended and the normal operation is performed.

Second Judgment Operation In this second judgment operation, the protective bearing is magnetically levitated and rotated down at a low rotational speed to touch down the rotor shaft 18 until the rotor shaft 18 stops. Is to determine whether or not replacement is required.

FIG. 4 shows the second judgment operation. First, similarly to the first determination operation, the CPU 70a instructs the magnetic levitation controller 80 to magnetically levitate the rotor shaft 18 (step 41) before starting the normal operation of the magnetic levitation vacuum pump. Motor driver 7
Instructing 7 to rotate the high frequency motor 30 (step 42).

Then, the CPU 70a uses the rotation sensor 38
Rotor shaft 18 detected from the pulse signal supplied from
It is monitored whether or not the number of revolutions has reached a predetermined value of several thousand [rpm] (step 42). When the rotation speed reaches a predetermined value (step 43; Y), the CPU 70a determines that the rotor shaft 1
8 is touched down (step 44). Ie C
The PU 70a stops the rotation of the high frequency motor 30 by instructing the motor driver 77 to stop the supply of the three-phase AC through the I / O 70h, and at the same time, causes the magnetic levitation controller 80 to generate an exciting current through the I / O 70f. The magnetic levitation of the rotor shaft 18 is stopped by instructing to stop the supply of. As a result, the rotor shaft 18 touches down and rotates while being supported by the protective bearings 50 and 51.

At the same time, the PU 70a starts measuring the rotation stop time by the timer 70i (step 4).
5). Then, the CPU 70a monitors from the pulse signal supplied from the rotation sensor 38 via the I / O 70g whether or not the rotation of the rotor shaft 18 has stopped (step 4).
6). When the rotation of the rotor shaft 18 stops (step 4
6; Y), the CPU 70a reads the time required for rotation stop from the timer 70i, and determines whether or not this stop time is less than or equal to a predetermined value (step 47).

When it is determined that the stop time is less than or equal to the predetermined value (step 47; Y), the stop time is short because the protective bearings 50 and 51 are damaged and smooth rotation is not performed. Therefore, the protection bearing replacement request is displayed on the display 76 via the display I / F 70e (step 48), and the first determination operation is ended.

If it is determined that the protective bearings 50, 51 are damaged as in the first determining operation, the CPU 70a causes the magnetic levitation type vacuum pump to operate normally until the protective bearings 50, 51 are replaced. Control so that the operation is prohibited. On the other hand, when it is determined that the rotation is not abnormal (step 47; N), the second determination operation is ended and the normal operation is performed.

In the second judgment operation, the predetermined value of the stop time which is a reference for judging the damage of the protective bearing is previously set to the rotation speed (20000 [Mg. rpm] ~ 48
000 [rpm]) and other various conditions,
The value is stored in the ROM 70b in advance.

As described above, according to this embodiment,
Before starting the normal operation of the magnetic levitation vacuum pump, it detects the damage state of the protective bearing and requests replacement, so the protective bearing may lock due to touchdown, or the rotor may be damaged. It is possible to prevent the occurrence of large damage such as.

The first or second judgment operation for detecting the damage state of the protective bearing does not necessarily have to be performed before the start of the normal operation operation. For example, the judgment operation is performed after the touchdown occurs. Good. Also,
In the embodiment described above, when it is determined that the protective bearing needs to be replaced, the indicator is instructed to request replacement, but the present invention is not limited to this.
For example, a warning device such as a buzzer may be connected to the bus line of the system controller via I / O to notify the replacement request by an alarm sound. Alternatively, a voice synthesizer may be connected via the I / O, and the replacement of the protective bearing may be requested by voice.

Further, in the present invention, after the rotor shaft is rotated in a magnetically levitated state up to a low rotation speed of a predetermined rotation speed,
Touch down the radial sensors 22 and 2 at this time.
6 and the position detection signal of the axial sensor 36, the damage state of the protective bearing may be determined.

[0042]

As is apparent from the above description, according to the magnetic levitation type vacuum pump of the present invention, the lock of the protective bearing due to the touchdown is detected in advance, so that the maintenance can be easily performed. .

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a magnetic levitation vacuum pump of the present invention.

FIG. 2 is a block diagram showing an electrical configuration of the embodiment.

FIG. 3 is a flowchart showing a first judgment operation of the embodiment.

FIG. 4 is a flowchart showing a second judgment operation of the embodiment.

[Explanation of symbols]

 15 rotor 20, 24 radial electromagnet 30 high-frequency motor 32, 34 axial electromagnet 50, 51 protective bearing 70 system controller 80 magnetic levitation controller 77 motor driver

Claims (1)

[Claims] 1. A rotor shaft having magnetism, a high-frequency motor for rotating the rotor shaft, a plurality of protective bearings arranged at a predetermined interval from the rotor shaft, and a plurality of magnetic bearings for magnetically levitating the rotor shaft. A levitation electromagnet, a plurality of position detection sensors for detecting the position of the rotor shaft, and based on a detection signal from the position detection sensor, magnetically levitates the rotor shaft to a predetermined position in a non-contact state,
And control means for controlling the current supplied to the plurality of magnetic levitation electromagnets so as to hold, and the rotor shaft is borne by the protective bearing in a state in which the rotor shaft is rotating at a predetermined low speed revolution, Damage determining means for determining the damage state of the protective bearing from the rotation state of the rotor shaft, and replacement for instructing replacement of the protective bearing when the damage determining means determines that the protective bearing is damaged beyond a predetermined level. A magnetic levitation vacuum pump, comprising: an indicating means.