JPS60190697A - Control system of magnetic bearing in turbo molecular pump - Google Patents

Abstract

PURPOSE:To eliminate a battery for protecting the rotor shaft of a turbo molecular pump by feeding the power regenerated from a motor to respective bearing upon interruption of power to a motor for driving the rotor shaft. CONSTITUTION:The power source section 8 of a turbo molecular pump is comprised of a stabilized power source 20, a magnetic bearing control circuit 22, a power interruption detector 23 and a capacitor 24 for storing the regenerative power and feeding to a magnetic bearing control circuit 22. Upon power interruption, regenerative power from the motor is fed to respective bearing. Consequently, abrupt contact between the rotor shaft and the dry bearing simultaneous with power interruption can be avoided to prevent the impact and the vibration resulting in the elimination of a battery for protecting the rotor shaft.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a control system for a magnetic bearing that supports a rotor shaft of a turbo-molecular pump in a floating state.

(Prior Art) FIG. 1 shows a magnetic levitation type turbomolecular pump previously developed by the applicant.

This pump has a high-frequency motor 3 installed on the outer periphery of a rotor shaft 2 that passes through the rotor housing 1 up and down. An electromagnet 4 is disposed, and a permanent magnet 5 is disposed on the bottom of the rotor shaft 2 to attract the rotor shaft 2 downward.
An electromagnet 6 is provided on the periphery of the outer housing 10 facing this permanent magnet.

And Den Wtl? By energizing Ei 6, the rotor shaft 2 and the rotor assembly R held thereon become in a floating state against its own weight and the attractive force of the permanent magnet 5, and by exciting the electromagnet 4 w1, the rotor shaft 2 and the rotor assembly R held thereon are brought into a floating state. Retained. In other words, each electromagnet 4.degree. 6 constitutes a magnetic bearing, and the rotor shaft 2 is supported in a non-contact manner.

The high-frequency motor 3 and the electric current 4.6 are connected to a power supply unit 8 via a connector 7 provided in the exterior housing, and receive power from the power supply unit 8 to levitate the rotor shaft 2. drive to rotate at high speed.

In addition, 11 is a magnetic sensor for detecting the separation distance between the electromagnet 4 and the outer circumference of the rotor shaft, and 12 is a magnetic sensor for detecting the floating position of the rotor shaft 2. The detection output of each of these sensors causes the electromagnet 4, 6 is feedback-controlled to maintain the rotor shaft 2 at its axial center and at a predetermined floating position.

Further, dry bearings 9 and 10 for protection are provided on the upper and lower sides of the outer circumference of the rotor @2. The dry bearings 9 and 10 are normally in a non-contact state, and the electric 11if! When the power supply from 8 is cut off, the rotor shaft 2 falls onto dry bearings 9 and 10 and is supported by these.

However, the O-ta assembly R is not the driver of the motor! It has a very large moment of inertia compared to the 1 herk required for IJ7.

Moreover, the rotation speed of rotor assembly R is 50 in pure air.
Since the rotor shaft 2 rotates at an extremely high speed and in a non-contact state at 00Or, p, and m, if the power supply is cut off during rotation, the rotor shaft 2 will rapidly move to the protective dry bearings 9, 10.
Contact with the machine may cause vibrations accompanied by loud noises, seizure, wear, etc., which may significantly shorten the life of the machine.

As a countermeasure for this, a battery is built into the power supply section 8, and the circuit is backed up and maintained with this battery, but maintenance is required.

It involves the hassle of replacing it.

(Objective of the Invention) The object of the present invention is to eliminate the need for the above-mentioned battery, and to enable the rotor shaft to be mounted on the dry bearing 1 ring with a bearing in a state where the rotation of the rotor shaft has decreased to a certain level in the event of a power outage. .

(Structure of the Invention) In order to achieve the above object, the present invention provides a system for supplying electric power regenerated from the motor to each bearing when the input power to the rotational drive motor for the 1st and 2nd axes is cut off. It is characterized by

(Embodiment) FIG. 2 shows a control system for a magnetic bearing according to the present invention. The configuration of the rotor driving portion of the turbo molecular pump is the same as that of the conventional one, so the same parts will be described with the same reference numerals.

In the figure, the power supply unit 8 includes a stabilizing power supply device 20, a motor rotation control device 21, a magnetic bearing control circuit 22, a power failure detector 23 that detects a power failure of an external power source (AC200V), and a power failure detector 23 that stores regenerated power. Supplied to the magnetic bearing control circuit 22
It is equipped with a capacitor 24 for

During normal operation, that is, when external power is supplied, the rotational power 11 is supplied to the motor rotation control device 21, and the drive minnow JI2 is supplied to the magnetic bearing control circuit 22 via the capacitor 24. .

Therefore, while the external power supply is being supplied, the motor 3 continues to rotate at the required rotation speed, and the magnetic bearing consisting of the electromagnets 4 and 6 operates, and the rotor shaft is positioned in accordance with the detection outputs of the sensors 11 and 12. Avoid levitating 2.

When the external power supply is cut off in such a state, the power failure detector 23 detects this and sends a regeneration command signal (A') to the motor rotation control device 21.

Upon receiving this signal, the motor rotation control circuit 21 switches and regenerates the regenerated power (Ia) from the motor 3 to the stabilized power supply device 20. This regenerated power is then sent from the stabilized power supply device 20 to the bearing control circuit 22 via the condenser (24), whereby each magnetic bearing 4 and 6 is moved to a position corresponding to the detection output of each sensor 11, 12 when rotating the rotor. Axis 2
maintain the state in which it is held.

Note that the rotor shaft 2 gradually slows down due to resistance due to the regenerative braking action of the motor 3, and eventually stops rotating. Since the power is still being supplied for an extended period of time, the magnetic bearing maintains its original function even though the rotation speed decreases, and the rotation either stops completely or rotates extremely rapidly. At a low speed, the magnetic force sufficient to hold the rotor shaft 2 disappears, and as a result, the rotor shaft 2 is transferred onto the protective dry bearings 9, 10 without any impact or the like. .

The type of motor mentioned above is an induction motor.

The motor may be either a synchronous motor or a DC motor, and these motors can be used as a generator for regenerative power.

(Effects of the invention) Since the control system of Mokubimei is configured as described above,
Unlike conventional magnetic bearings, the rotor shaft does not suddenly come into contact with the dry bearing at the same time as a power outage, and the rotor shaft is transferred to the dry bearing at an extremely low rotation speed or when it has stopped. There is no seizure, wear and tear, and wear and tear on rotating parts can be prevented.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the configuration of a turbo molecular pump and a power supply section, and Fig. 2 is an explanatory diagram showing the electrical configuration of the present invention. 2...Rotor 3...Motor 4.6... - Electromagnet (magnetic bearing) 20... Stabilized power supply device 21... Motor rotation control circuit 22... Magnetic bearing control circuit 23... Power outage detector I +, 'I 2... Drive power (Ia ), I'(a)...Applicant for regenerative power and above, and Iko Seiki Co., Ltd. Agent Mogami Nidebe ζPa.

Claims (1)

[Claims] (1) A turbo molecular pump in which the rotor shaft is supported in a floating state in the radial and axial directions by magnetic bearings, and the rotor shaft is rotatably supported by a protective dry bearing when the magnetic bearing is powered off. A control system for magnetic bearings in a turbo molecular pump, characterized in that when the input power to the motor for rotationally driving the rotor shaft is cut off, the electric power regenerated from the motor is supplied to each bearing.