WO1984001802A1

WO1984001802A1 - Magnetic bearing

Info

Publication number: WO1984001802A1
Application number: PCT/EP1983/000284
Authority: WO
Inventors: Werner Auer; Rainer Sindlinger
Original assignee: Teldix Gmbh
Priority date: 1982-11-05
Filing date: 1983-10-29
Publication date: 1984-05-10
Also published as: DE3240809A1; JPS60500141A; DE3240809C2

Abstract

The magnetic bearing which is rapidly formed comprises a radially passive storage and an axially active regulation. By using only four sensor devices and three regulating amplifiers, a magnetic bearing is obtained which enables, in addition to the axial regulation, a supplementary regulation on two inclination axes perpendicular to the rotation axis.

Description

Magnetic bearing

The invention relates to a magnetic bearing in which the Luftspal tdiameter is large compared to the axial length of the bearing, in which the rotor is radially passive at least on the rotor side by permanent magnets, in which the axial position of the rotor is actively controlled by a control device, and in which several sensor arrangements for determining the axial position as well as control amplifiers and windings are used to exert forces on the rotor.

A magnetic bearing with these features is known from EU patent application 49 300. A flywheel is mounted there with the help of such a magnetic bearing. According to one exemplary embodiment, the flywheel ring contains two permanent magnet rings on the axial surfaces. With these and with the help of yoke rings on the rotor and stator, magnetic circuits are formed there which have axial air gaps between the rotor and stator. This stabilizes the rotor radially. The rotor carries three segment-shaped windings. The magnetic fluxes generated in this way are also conducted through the air gaps; sector by sector are the Axial forces acting on the rotor can be varied. Each of the windings is assigned a sensor monitoring the axial position of the rotor and a downstream control amplifier.

The rotor is hereby forced into a predetermined axial position.

The invention has for its object to improve the bearing properties of such a magnetic bearing with a small axial expansion compared to the radial expansion.

This is achieved in accordance with the invention in that four sensor arrangements are arranged on axes perpendicular to one another and perpendicular to the axis of rotation and in pairs lying diametrically to the axis of rotation, that three control amplifiers are provided, of which the first and second respectively the difference of the sensor signals diametrically opposed sensor arrangements and the third, the sum of all sensor output signals are supplied and that the outputs of the three control amplifiers are connected to windings and are arranged in such a way that when the first and second amplifiers are actuated on the rotor, restoring torques about the axis on which the associated sensor arrangements are located, each act perpendicular axis and that when the third amplifier is actuated, an axial restoring force acts on the rotor.

In the solution according to the invention, not only is there active regulation in the axial direction, but tilting regulators are additionally created for two axes perpendicular to one another and to the axis of rotation. Starting with four sensor arrangements, the system switches to a three-channel controller, which then again operates at least four windings. It is sufficient to use four sensors per se. However, it is more favorable to form each sensor arrangement from a pair of axially offset sensors and sensors which react in opposite directions to axial rotor movements, and to use their differential signal as the sensor output signal.

There are various arrangements and controls of the windings for generating the required restoring moments and forces possible. This will be discussed in more detail using the exemplary embodiments.

In the case of the bearing according to the invention, by coupling signals into the first and second control amplifiers, it is possible to shift the O point of the control characteristic, i.e. to consciously tilt the axis of rotation to a certain extent, which e.g. is of interest for storage of a flywheel for spacecraft.

According to a development of the invention, the input signals of the first and second control amplifiers are cross-coupled, i.e. a portion of the input signal of one amplifier is superimposed on the input signal of the other amplifier. This has the advantage that sufficient stability can be achieved with simple controllers, since the moments generated about an axis produce a precession angular velocity about the radial axis perpendicular thereto. However, this effect disappears when the machine stops.

This cross-coupling is preferably designed to be speed-dependent, i.e. the cross-coupled portion increases with increasing speed.

The invention is explained in more detail using the exemplary embodiments of the drawing. Show it

1 shows a first embodiment of a control for a magnetic bearing according to the invention, FIG. 2 shows a possible structure of the magnetic bearing, which is regulated as shown in FIG. 1,

3 shows other embodiments for the radial passive bearing, FIG. 4 shows other embodiments for the application of moments and forces, FIG. 5 shows another possibility of control,

Fig. 6 shows an embodiment for the construction of the camp, which can be controlled according to FIG. 5.

In Fig. 1, four sensor arrangements 1-4 are provided, of which the sensor arrangements 1 and 2 lie on an axis (x-axis) perpendicular to the axis of rotation (z-axis) and diametrically to the axis of rotation and on axial movements in their output signals in the same way react. Correspondingly, the sensor arrangements 3 and 4 are arranged on the y axis perpendicular to the x and z axes. In differential amplifiers 5 and 6, differential signals are formed from the output signals of the arrangements 1 and 2 or 3 and 4, a difference occurring when the rotor sensed by the sensor arrangements has a tilting movement about the respectively perpendicular to the axis on which the interconnected sensor arrangements lie. lying axis. The signals then reach windings 16 to 19 via control amplifiers 7 and 8, inverters 9 and 10, summing elements 11 to 14 and power amplifiers 15; each of these windings 16 to 19 is spatially assigned to one of the sensor arrangements 1 to 4 and generates an axial force on the rotor when actuated. All 4 sensor arrangements 1 to 4 are also connected to a summing amplifier 20, the output signal of which also reaches the windings 16 to 19 via a control amplifier 21 and the summing amplifiers 11 to 14 and the power amplifiers 15.

If DC voltage signals are coupled to terminals 22 and 23, the O-point of the tilt controller can be adjusted, so that there is a defined misalignment of the rotor axis.

A magnetic bearing constructed in accordance with FIG. 2 can be regulated with the control circuit shown in FIG. 1. Fig. 2a shows a perspective view and Fig. 2b shows a section.

A rotor, designated 31, of the bearing consists of a radially magnetized permanent magnet ring 32, at the poles of which two pole plate rings 33 and 34 are connected. This rotor is offset axially offset on both sides by U-shaped stator ring segments 35 to 38 or 35 'to 38' made of magnetically highly conductive material; the training is such that the free legs of the U are just opposite the pole plate rings 33 and 34. Segment windings 39 to 42 and 39 'to 42' are wound in the circumferential direction around these ring segments. The two winding groups are controlled by the control device shown in FIG. 1 as a function of distance signals which are generated by sensor arrangements 43 to 46 or 43 'to 46'. It is from the signals of a pair of sensors z. B. 45 and 45 'each formed the difference; this difference signal represents the output signal of one of the sensor arrangements 1 to 4 of FIG. 1. The air gaps between rotor 1 and stator are designated 47 and 47 'or 48 and 48'.

The following mode of operation results from FIGS. 1 and 2.

When tilted about the y axis, the sensor pairs 45 and 45 'and 43 and 43' and the sensor arrangements 1 and 2 of FIG. 1 corresponding to them generate output signals. As a result, the windings 16 and 17 are driven in opposite directions and produce a counterturning morale. In FIG. 2, the winding 16 corresponds to the partial windings 41 and 41 'connected in series, which are wound in opposite directions and support each other in their effect. The same applies to the winding 17 and the partial windings 39 and 39 '. Here the flows of the permanent magnet ring and the electromagnets are superimposed in the air gaps 47 and 47 '.

Accordingly, a tilt about the x-axis is corrected by the other tilt controller 8.

In contrast, if the rotor is axially displaced, all sensor arrangements 1 to 4 emit the same signals. The toggle regulators 7 and 8 receive no signal, but the control amplifier 21, which controls all the windings 16 to 19 (and correspondingly 39 to 42 or 39 'to 42') and generates a restoring force.

Also worth mentioning are the cross coupling lines 24 and 25, via which a portion of the input signals of the control amplifiers 7 and 8 can be coupled into the other control amplifier. The cross-coupled components preferably increase with the speed, which can be realized by an amplifier with an adjustable gain factor in each cross-coupling line. 3a to 3c are other exemplary embodiments of a possible passive radial! Aging shown, here a stator ring 50 is arranged coaxially to a rotor ring 51 and the radial bearing is achieved by repelling magnetic poles of permanent magnets.

4a and 4b accordingly show other embodiments for the application of forces to the rotor ring 60, which here consists of soft iron, on which the rotor-side part 61 of the radial bearing is also indicated. The electromagnets 62 and 62 'must, however, alternatively be activated here. Both solutions allow a relatively large inclination of the rotor.

5 corresponds to the circuitry up to the output of the control amplifiers 7, 8 and 21 that of FIG. 1, which is why the same reference numerals are used. The control amplifiers 7 and 8 responsible for the tilt control are connected via power amplifiers 70 to series-connected but oppositely wound windings 72 and 73 or 74 and 75. The winding pairs 72 and 73 or 74 and 75 are again arranged diametrically to the axis of rotation.

A separate winding 76 is connected to the output of the controller 21, which generates an axial force, while the winding pairs 72 and 73 or 74 and 75 generate tilting moments. This connection can be used, for example, in a magnetic bearing according to FIG. 6. In Fig. 6a, 80 denotes a rotor ring, 81 a stator ring and 82 a passive radial bearing. In an air gap 83 of the rotor ring 80, a radial magnetic field is generated with the help of the magnets 82a and 84, in which an annular coil 85 fixed on the stator side and a sector winding 86 also fixed on the stator side are partially immersed. 6b shows that 4 sector windings 86 and a ring winding 85 are provided. If the ring winding 85, which can correspond to the winding 76 of FIG. 5, is driven, an axial force is exerted on the rotor 80, the direction of which depends on the direction of the current. When the winding 86 is actuated and the diametrically opposite winding is actuated in the opposite direction, on the other hand a moment is generated about an axis perpendicular to the plane of the drawing, the direction of rotation of which depends on the current direction.

In Fig. 5 there is finally a feedback 77 to 79 to the control amplifiers 7 and 8. This results in a "current-controlling" behavior regardless of the coil inductances, i.e. the controller output voltages are converted into proportional forces or tilting moments.

Claims

1. Magnetic bearing in which the air gap diameter is large compared to the axial length of the bearing, in which the rotor is supported radially passively at least on the rotor side by permanent magnets, in which the axial position of the rotor is actively controlled by a control device in which several sensor arrangements for determination of the axial position as well as control amplifiers and windings for exerting forces on the rotor are used, characterized in that four sensor arrangements (1-4) are arranged on axes perpendicular to one another and perpendicular to the axis of rotation and in pairs lying diametrically to the axis of rotation are that three control amplifiers (7, 8, 21) are provided, of which the first (7) and second (2) each have the difference between the sensor signals of diametrically opposite sensor arrangements (1, 2 or 3, 4) and the third (21) the sum of all sensor output signals and that the outputs of the three control amplifiers with windings (16-19; 72-76) connected and arranged in such a way that when the first and second amplifiers are activated

(7 and 8) act on the rotor restoring torques around the axis on which the associated sensor arrangements (1-4) lie, each perpendicular axis and that when the third amplifier (21) is actuated, an axial restoring force acts on the rotor .

2. Magnetic bearing according to claim 1, characterized in that each of the four sensor arrangements (1-4) from a pair of axially offset, reacting in opposite directions to axial rotor movements (39, 39 'to 42, 42')

Sensors exist and that the difference in the output signals of each sensor pair (39, 39 'to 42, 42') serves as the output signal of the sensor arrangement.

3. Magnetic bearing according to claim 1 or 2, characterized in that on the stator, the four sensor arrangements (1-4) assigned four windings (16-19; 72-76) are arranged such that they act on forces in the axial direction exert the rotor, and that at the outputs of the first and second control amplifiers (7 and 8) diametrically opposed windings (16 and 17, or 18 and 19; 72 and 73 or 74 and 75) are switched on in such a way that they opposed to the rotor

4. Magnetic bearing according to claim 3, characterized in that all four windings (16-19) are connected to the output of the third control amplifier (21).

5. Magnetic bearing according to claim 3, characterized in that an additional ring winding (76) is provided and is connected to the third control amplifier (21).

6. Magnetic bearing according to claim 5, characterized in that the diametrically lying windings (72 and 73 or 74 and 75) are connected in series with the opposite winding sense to the control amplifier (7 or 8).

7. Magnetic bearing according to claim 3 or 4, characterized in that the diametrically lying windings (16 and 17 or 18 and 19) are connected in parallel to the first and second control amplifiers (7 and 8), one of these two windings ( 17 or 19) the output signal is supplied inverted and that all windings (16-19) are connected in parallel to the third control amplifier (21).

8. Magnetic bearing according to one of claims 1 to 7, characterized in that each winding consists of two Teilwicklun gene (39, 39 '- 42, 42'), the first or second control amplifier (7 or 8) depending on the Direction of the forces to be generated and their magnetic forces act from different axial directions on a ferromagnetic part of the rotor.

9. Magnetic bearing according to one of claims 1 to 7, characterized in that the four windings (86) are partially immersed in the air gap of a rotor-side radial magnetic field.

10. Magnetic bearing according to one of claims 1 to 9, characterized in that the first and second control amplifier ker (7 and 8) signals for the defined tilting of the barrel axis can be supplied.

11. Magnetic bearing according to one of claims 1 to 10, characterized in that the input signals of the first and second control amplifier (7 or 8) are each also fed to the other control amplifier (8 or 7) (cross coupling).

12. Magnetic bearing according to claim 11, characterized in that the cross coupling is increased with increasing speed of the rotor.