JPS6237246B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic bearing that supports a rotating body without mechanical contact by using the attractive force of an electromagnet or a permanent magnet.

Conventionally, there has been a device of this type as shown in FIG. In the figure, 1 is a rotor, 2 is a rotating magnetic pole for a thrust magnetic bearing, 3a and 3b are electromagnets for a thrust magnetic bearing, 4 is a radially magnetized ring-shaped permanent magnet, 5a is a fixed magnetic pole for a radial magnetic bearing, and 5b is a radial magnetic bearing. Rotating magnetic pole for magnetic bearing, 6
is a stator, 7 is a position sensor, 8 is a position sensor circuit, 9 is an operational amplifier, 10 is a phase compensation circuit, 11
is a power amplifier.

The rotor 1 is equipped with magnetic poles 2, 5b, and the stator 6 is equipped with electromagnets 3a, 3b, and a magnetic pole 5a.The rotor 1 is rotated around its axis by the attractive force that acts between them, and is attached to the stator 6. On the other hand, it is supported in a predetermined relative position without mechanical contact.

FIG. 2 is an explanatory diagram showing the operation of the thrust magnetic bearing shown in FIG. 1. The same reference numerals as in FIG. The magnetic flux that comes out from the north pole and returns to the south pole passes through the rotating magnetic pole 2, separates in the vertical direction, and passes through the air gap to the thrust magnetic bearing magnets 3a, 3.
It flows into the iron core b, passes through the air gap again, reaches the rotating magnetic pole 2, and returns to the S pole. At a position (position in the thrust direction) where the air gap between the iron core of the electromagnet 3a and the rotating magnetic pole 2 (hereinafter referred to as the upper air gap) and the air gap between the iron core of the electromagnet 3b and the rotating magnetic pole 2 (hereinafter referred to as the lower air gap) are equal. If the rotor 1 exists, the magnitudes of the magnetic fluxes in the upper gap and the lower gap (consider only the magnetic flux shown by the solid line) are equal to each other, and the vertical (thrust direction) attractive forces acting on the rotor 1 are balanced. However, this equilibrium point is unstable, and if the rotor 1 moves downward even slightly, the attractive force due to the magnetic flux in the lower air gap becomes stronger, causing the rotor 1 to move further downward.
That is, the relationship between the position of the rotor 1 in the thrust direction and the attractive force by the permanent magnet 4 attached to the rotor 1 is a positive feedback relationship. So electromagnet 3
By controlling the suction forces of a and 3b, the relationship between the position of the rotor 1 and the total suction force is a negative feedback relationship, thereby stabilizing position control in the thrust direction.

The displacement of the rotor 1 in the thrust direction is detected by the two position sensors 7, an electric signal determined by the displacement is generated, and the outputs of the two position sensors 7 are averaged by the position sensor circuit 8 and the operational amplifier 9. It passes through a phase compensation circuit 10 and a power amplifier 11 to excite the coils of the electromagnets 3a and 3b. Electromagnet 3
The magnetic flux generated by a and 3b is generated in the direction shown by the dotted arrow in FIG. 2, and is added to the magnetic flux (solid arrow) by the permanent magnet 4 in the upper gap, and reduces the magnetic flux by the permanent magnet 4 in the lower gap.

Therefore, for example, when the rotor 1 moves downward, the output voltage from the position sensor 7 increases and the magnetic flux generated by the electromagnets 3a and 3b increases, and as a result, the magnetic flux in the upper air gap increases and the magnetic flux in the lower air gap increases. The rotor 1 is sucked upward, and the thrust direction position of the rotor 1 is maintained at a predetermined position by such negative feedback feedback control.

The phase compensation circuit 10 is for improving the characteristics of the above-mentioned feedback control. For example, by inputting a voltage proportional to the displacement from the operational amplifier 9,
A voltage that is the sum of the voltage proportional to this displacement and the time derivative of the displacement, that is, the voltage proportional to the speed is generated and input to the power amplifier 11. When feedback control is performed using a signal to which a voltage proportional to the speed is added, damping can be applied to the motion of the rotor 1 in the thrust direction.

Next, with respect to the displacement of the rotor 1 in the radial direction, a restoring force is passively exerted by the attractive force of the ring-shaped permanent magnet 4. That is, when the magnetic poles of the electromagnets 3a and 3b facing the magnetic pole 2 try to move away from their opposing positions, a force acts to pull them back to their original opposing positions. However, the electromagnets 3a and 3b
Since the restoring force in the radial direction that acts between the magnetic pole of
A magnetic pole 5a is provided on the stator 6 to form a radial magnetic bearing.

Since the conventional magnetic bearing control device is configured as described above, it has the disadvantage that only the restoring force due to the magnetic attraction force acts in the radial direction, and no damping force acts. If the displacement of the rotor 1 in the radial direction is x and the time is t, then the movement of the rotor 1 in the radial direction is most simply md ² x/dt ² =-k ₁ dx/dt-k ₂ x...(1) It can be expressed by Here, m, k ₁ and k ₂ are each constant, md ² x/dt ² is the force that gives acceleration to the rotor 1 in the radial direction, -k ₁ dx/dt is the force that gives damping to the motion of the rotor 1, -k ₂ x is the restoring force due to magnetic attraction. In the structure shown in Figure 1, the magnetic attraction force generates only a restoring force -k ₂ x, but does not generate a damping force, so the value of the constant k ₁ in equation (1) above is relatively small and As a result, the displacement x changes vibrationally, and the rotor 1 has a constant m and a constant
The disadvantage is that it vibrates greatly at a period determined by k ₂ and that it is difficult to dampen the amplitude of this vibration.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and it dynamically couples the motion of the rotor 1 in the thrust direction and the radial direction, and generates a signal proportional to the speed in the radial direction. Another object of the present invention is to provide a magnetic bearing control device that can also apply damping force in the radial direction by providing feedback to the thrust magnetic bearing control device.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a block diagram showing an embodiment of the present invention, in which the same reference numerals as in FIG. 1 indicate the same or corresponding parts, 7a is a position sensor corresponding to 7 in FIG. 9a is an operational amplifier corresponding to 9 in FIG.
7a, 8a, and 9a are collectively referred to as a thrust position sensor device, 7b is an upper radial direction position sensor, 7c is a lower radial direction position sensor, which is similar to the position sensor 7 in FIG. 1, and 8b is a position sensor. A position sensor circuit similar to the circuit 8a, 9b a three-input operational amplifier, 10a and 10b phase compensation circuits corresponding to 10 in FIG. 1, and 12 a sensor support hardware.

In order to couple the motion of the rotor 1 in the radial direction and the thrust direction, the center of gravity of the rotor is shifted from the geometric center. The spring constant of the upper radial magnetic bearing and the lower radial magnetic bearing (Equation (1)
The motion in the radial direction and the motion in the thrust direction can also be coupled by making the constants k ₂ ) different from each other.

7b, 7c, and 8b in FIG. 3 are collectively referred to as a radial position sensor device, and the output of this radial position sensor device is phase-compensated by a phase compensation circuit 10b, and then sent to the thrust direction via an operational amplifier 9b. Feedback is provided to the control loop. This generates a magnetic damping force by the thrust magnetic bearing, which is coupled with the radial motion and becomes a damping force against the radial motion, sufficiently damping the radial vibration.

As described above, according to the present invention, a damping force in the radial direction is generated by feeding back an electric signal representing displacement in the radial direction to the thrust magnetic bearing control system, so it is not necessary to separately provide an actuator in the radial direction. Therefore, an inexpensive and highly reliable device can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a conventional device.
FIG. 2 is an explanatory diagram showing the operation of the device shown in FIG. 1;
FIG. 3 is a block diagram showing one embodiment of the present invention. 1... Rotor, 2... Rotating magnetic pole for thrust magnetic bearing, 3a, 3b... Electromagnet for thrust magnetic bearing, 4
...Ring-shaped permanent magnet, 5a, 5b...Magnetic pole for radial magnetic bearing, 6...Stator, 7a, 7b, 7c...
Position sensor, 8a, 8b...Position sensor circuit, 9
a, 9b... operational amplifier, 10a, 10b... phase compensation circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1. In a magnetic bearing control device that controls a rotor rotating around an axis to be supported by a magnetic bearing at a predetermined relative position with respect to a stator without mechanical contact, a change in the thrust direction of the rotor with respect to the stator a thrust position sensor device that detects an electric signal determined by a radial position sensor device for detecting an electric signal determined by the radial displacement of the rotor with respect to the stator; A magnetic bearing control device characterized by comprising means for controlling the thrust magnetic bearing electromagnet and applying braking to the movement in the radial direction in addition to a position control output.