JPH0767252B2 - Magnetic bearing control device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic bearing control device that controls the radial position of a magnetically levitated rotating shaft in a magnetic bearing to control its attitude.

<Prior Art> Conventionally, in this type of device, the radial position of the magnetically levitated rotating shaft is detected, and the rotating shaft is driven by an electromagnet in a direction in which the deviation of the detected position from the reference position is eliminated. A loop for controlling the shaft position is formed.

Then, the spring constant is set to a high value in controlling the radial position of the rotary shaft, and thereby the posture of the rotary shaft is stabilized.

However, in magnetic bearings used for turbo molecular pumps, etc., it is desired to reduce external vibration as much as possible. Therefore, in devices used for such applications, the above spring constant is lowered, and therefore control stability is improved. There was a problem of damage.

Therefore, as disclosed in Japanese Patent Laid-Open No. 52-93852, a proposal has been made to insert a band elimination filter centering on the rotation frequency of the rotation axis into the above-mentioned loop for controlling the rotation axis position.

According to these proposals, only the spring constant in the rotation frequency range of the rotating shaft is reduced, so that it is possible to significantly suppress vibration and reduce it while ensuring control stability.

<< Problems to be Solved by the Invention >> However, in these proposed devices, the circuit configuration of the band elimination filter that reduces the spring constant only with respect to the rotation frequency of the rotating shaft becomes complicated, and therefore the manufacturing cost of the device is increased. It has been greatly increased and its reliability has been remarkably reduced, and these are considered to be major factors that hinder the commercialization of the device.

The present invention has been made in view of the above conventional problems,
It is an object of the present invention to provide an inexpensive and highly reliable magnetic bearing control device that can suppress the occurrence of vibration while ensuring control stability.

<< Means for Solving the Problems >> To achieve the above object, the apparatus according to the present invention is configured as shown in FIG.

In the figure, the rotating shaft a is driven in the radial direction by an electromagnet b, and its position is detected by a position detecting means c.

Then, in the comparison means d, the deviation of the detected position by the detection means c from the reference position is obtained, and the energization current to the electromagnet b is controlled by the energization control means e according to the position deviation.

Further, the electromagnet b, the detection means c, the comparison means d, the energization control means e
A band elimination filter g is inserted at an appropriate position of the control loop f formed by (1), and the band elimination filter g is connected to a secondary high-pass filter h that removes frequency components of the rotation axis a that are equal to or lower than the steady rotation speed. And i, which have a proportional output relationship, are connected in parallel.

<< Operation of the Invention >> In the present invention, the above-mentioned spring constant is applied only to the steady rotation frequency of the rotation axis a by the band elimination filter g whose configuration is simplified by the parallel connection of the secondary high-pass filter h and the proportional circuit i. Has been reduced.

<< Description of Embodiments >> Preferred embodiments of an apparatus according to the present invention will be described below with reference to the drawings.

FIG. 2 shows the internal structure of an outer rotor type magnetic bearing type turbo-molecular pump, in which a rotor (rotating shaft) 12 is rotated around a stator 10.

The rotor 12 is housed in a cylindrical outer cylinder 16 in which an exhaust port 14 is formed in the lower part in the figure, and stator blades 18 provided on the inner peripheral surface of the outer cylinder 16 and the inner peripheral surface of the rotor 12 are provided. A pump action is performed by the rotor blades 20 provided.

The rotor 12 is rotationally driven by exciting a motor coil 22 provided in the stator 10 with an inverter (not shown). At that time, magnetic levitation of the rotor 12 is caused by an axial electromagnet 24, and The attitude control is performed by the radial electromagnets 26 and 28, respectively.

Further, in order to control the magnetic levitation and the attitude of the rotor 12, the axial position and the radial position thereof are detected by the axial position sensor 30 and the radial position sensors 32 and 34, respectively.

Here, a control circuit for controlling the magnetic levitation and attitude of the rotor 12 is connected to the connector 38 provided on the lower side of the pump in FIG. 2, and a circuit block for controlling the attitude of the rotor 12 is shown in FIG. The figure shows only one axis.

In the figure, the detection signal of the position sensor 32 (34) is the comparator 42.
Is supplied to one of the comparison inputs, and the other comparison input of the comparator 42 is supplied with a signal corresponding to the reference position of the rotor 12.

The comparator 42 obtains a comparison signal corresponding to the deviation of the detection position attached to the reference position of the rotor 12, and the comparison signal corresponds to the deviation of the rotor detection position from the reference position. The comparison signal of the comparator 42 is given to the phase adjusting circuit 46 via the integrating circuit 44, and the phase adjusting circuit 46
The comparison signal whose phase is adjusted in the advance direction or the delay direction by is given to the power amplification circuit 48.

The electromagnet 26 (28) is energized by the power amplification circuit 48, and as a result, the rotor 12 is drive-controlled to the reference position.

As described above, the position sensor 32 (34), the comparator 42, the integrating circuit 4
4, phase adjustment circuit 46, power amplification circuit 48 and electromagnet 26 (2
8) forms a loop 50 for controlling the position of the rotor 12, and the magnetically levitated rotor 12 has a loop 50 for each axis.
Is controlled to the reference posture.

Here, the inertial axis and the central axis of the rotor 12 do not exactly coincide with each other, and thus the position sensor is not operated during the steady rotation of the rotor 12.
The detection signal obtained at 32 (34) contains a vibration component having the same frequency as the rotation speed.

The vibration component is absorbed by the band elimination filter 52 having the steady frequency of the rotor 12 as the center frequency provided in the loop 50 to reduce the spring constant.

The band elimination filter 52 of the present embodiment is provided on the subsequent stage side of the comparator 42, and has a secondary high-pass filter 54 and a proportional circuit 56.
And are connected in parallel.

Among them, the secondary high-pass filter 54 removes frequency components equal to or lower than the steady rotation speed of the rotor 12, and the proportional circuit 56 has an output proportional to an input.

The phase characteristic of the band elimination filter 52 is shown in FIG. 4 and the gain characteristic thereof is shown in FIG. 5, and as can be understood from both figures, the stability of the position control of the rotor 12 is impaired. It is possible to control the vibration of the rotor 12 without the need.

As described above, according to this embodiment, the band elimination filter 52 that reduces the spring constant only with respect to the rotation frequency of the rotor 12 includes the secondary high-pass filter 54 and the proportional circuit.
The circuit configuration of the device is extremely simplified because it is configured by 56 parallel connections.

Therefore, the manufacturing cost of the device can be remarkably reduced and its reliability can be improved.

As a result, it became possible to commercialize a device with high control stability and low vibration for the first time.

<< Effects of the Invention >> As described above, according to the present invention, a band elimination filter that reduces the spring constant only with respect to the rotation frequency of the rotation shaft is configured by parallel connection of a secondary high-pass filter and a proportional circuit. Therefore, it becomes possible to configure a device having high control stability of the rotary shaft and low vibration at a low cost, and to remarkably improve its reliability.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to the claims of the present invention, FIG. 2 is an explanatory diagram of the internal structure of a magnetic bearing type turbo-molecular pump, and FIG. 3 is a block diagram showing one axis of a control circuit for controlling the attitude of the rotor in FIG. , FIG. 4 is a band elimination filter in FIG.
52 is a phase characteristic diagram, and FIG. 5 is a gain characteristic diagram of the band elimination filter 52 in FIG. 12 ... Rotor 26 (28) ... Electromagnet 32 (34) ... Position sensor 42 ... Comparator 44 ... Integration circuit 46 ... Phase adjustment circuit 48 ... Power amplification circuit 50 ... Loop 52 ... Band elimination filter 54 ... Secondary high-pass filter 56 … Proportional circuit

Claims (1)

[Claims] 1. An electromagnet for driving a rotating shaft in a radial direction, a position detecting means for detecting a radial position of the rotating shaft, a comparing means for obtaining a deviation of a detected position from a reference position, and a position deviation of a current supplied to the electromagnet. An energization control means for controlling the rotation axis is formed, and a loop for controlling the rotation axis position is formed with a secondary high-pass filter that removes frequency components below the steady rotation speed of the rotation axis, and the output is proportional to the input. A magnetic bearing control device, characterized in that a band elimination filter in which a related proportional circuit is connected in parallel is inserted into the loop.