JPH08232955A - Magnetic bearing - Google Patents

Abstract

PURPOSE: To easily form a closed space to store a control coil without requiring complicated structure and to facilitate manufacturing of a large bearing in simple structure by forming the cylindrical space by a bias core and a yoke. CONSTITUTION: It is possible to displace a rotation axis in the radial direction by magnetizing a control valve 7 by an electric current output from a power amplifier 19 in accordance with a detection signal of a displacement sensor 3. Hereby, the control electric current is made to flow by an opposite phase to generate it in the opposite direction of a control magnetic flux to make downward attraction force work. On such a magnetic bearing in such constitution, a cylindrical closed space is formed by a casing 100 on the outside of a control core 9, stator seal rings 11a, b, c, d and two yokes 4, 5, and as a radial control coil 7 is arranged here, it is hard for a working fluid to intrude into the control coil 7. Consequently, it is not necessary to make it in can structure and it is easy to manufacture a large bearing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic bearing, and more particularly to a magnetic bearing suitable for use in applications where leakage of a working fluid to the outside is not desired, for example, rotary fluid machines such as pumps and turbo centrifugal compressors. .

[0002]

2. Description of the Related Art FIGS. 10 to 12 show a conventional rotary drive device equipped with a magnetic bearing, and a motor unit 30 for rotary drive.
Radial magnetic bearing portions 31 and 32 are provided on both sides of, respectively. The radial bearing portions 31 and 32 are cores (iron cores) 33 and 34 that project in the radial direction toward the rotary shaft.
A plurality of exciting coils 37 and 38, which are composed of coils 35 and 36 wound around this, are arranged in the circumferential direction, and based on a signal from a sensor 40 that detects the radial position of the rotating shaft 39, The position of the rotary shaft in the radial direction is controlled to be constant by adjusting the currents flowing through these coils. Since this bearing has a structure in which the radial magnetic poles are arranged in the circumferential direction as described above, a so-called cylindrical thin metal plate surrounds the entire radial bearing magnetic pole in order to prevent the working fluid from entering the exciting coil. It uses a can structure.

A thrust bearing 41 is provided at one end of the bearing device to keep the axial position constant in response to a load applied in the axial direction. On the side where the rotary shaft 39 is coupled with the driven shaft, the inside of the bearing is protected from the outside at the inner side of the casing penetrating side.
Alternatively, in order to prevent the lubricating fluid inside the bearing from leaking to the outside, a mechanical seal 42 or a non-contact annular seal is arranged.

This radial bearing is controlled by the control circuit shown in FIG. This control circuit includes a compensating circuit 42 for phase compensating the signal from the sensor 40 for detecting the displacement of the rotary shaft, a detecting circuit 43 for rectifying the signal of the phase compensating circuit 42, and an exciting coil for amplifying the detected signal. Three
It is composed of a power amplifier 44 for supplying a current to 7, 38.

[0005]

In such a conventional magnetic bearing, there is a problem that it is difficult to apply the can structure as described above to a large-sized bearing, and another magnetic bearing that can be used for a large-sized bearing is used. The development of a magnetic bearing with a structure was awaited. In addition, the structure is complicated because a mechanical or non-contact annular seal is used on the coupling end side with the driven shaft.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a magnetic bearing which has a simple structure and can be used for a large bearing.

[0007]

In order to solve the above-mentioned problems, the present invention has a stator arranged around a rotary shaft, and a magnetic force is applied to the rotary shaft from the stator to drive the rotary shaft in a radial direction. In a magnetic bearing that applies a force to keep the position of the axis of a rotating shaft constant, the stator extends along the axial direction, and at least three or more position control cores are arranged on the circumference. Control coils wound around the position control core, a pair of disk-shaped yokes fixed to the end portions of the core, and a cylindrical bias magnetic flux permanent magnet connecting the inside of the control core of the yoke. It is composed of.

According to the present invention, a pair of rotor yokes are inserted into the rotary shaft so as to face the stator yoke, and the rotor yokes are connected to form a magnetic circuit. As described above, the sleeve of the magnetic material is inserted into the rotating shaft.

The present invention is also characterized in that a radial groove is provided in the stator yoke between the control coils.

Further, according to the present invention, a cylindrical non-magnetic seal ring is arranged along the rotation axis between the stator yokes,
The seal ring, the yoke, and the bearing casing form a closed space that houses the control core, the control coil, and the bias permanent magnet, and fluid flowing through the bearing gap does not enter the coil portion. And

Further, according to the present invention, a cylindrical non-magnetic seal ring is arranged along the rotation axis between the stator yokes,
Further, a seal disk is arranged on the outer surface of the yoke, and the yoke, the seal ring, the seal disk, and the bearing casing form a closed space for housing the control core, the control coil, and the bias permanent magnet. However, it is characterized in that the fluid flowing through the bearing gap does not enter the coil portion.

Further, the present invention is characterized in that at least one of the surfaces of the stator and the rotating shaft facing each other is provided with irregularities whose surface position changes along the axial direction or the circumferential direction. To do.

Further, the present invention is characterized by comprising a magnetic powder supply device and means for supplying magnetic powder into a gap between the stator and the rotary shaft.

Further, the present invention is characterized in that the magnetic powder supply device mixes the magnetic powder as a fluid and transfers it to the gap between the stator and the rotary shaft.

Further, the present invention is characterized in that the gap between the seal ring of the stator and the sleeve of the rotary shaft is smaller than the gap between the stator yoke and the rotor yoke.

Further, the present invention is characterized in that the inner surface of the seal ring of the stator facing the rotation axis has a multi-arc shape.

[0017]

According to the present invention, a pair of disk-shaped stator yokes are arranged at both ends in the axial direction, and these are connected to the cylindrical permanent magnet for bias by the arc-shaped plate control core. Since the cylindrical space for accommodating the control coil is formed by the permanent magnet for bias and the stator yoke, the control core around which the exciting coil for radial direction control is wound is arranged in this space, and this is placed in an appropriate lid shape. By covering with the member (or bearing casing), a closed space for the control coil is formed. That is, according to the configuration of the magnetic bearing described above,
Structurally, a closed space for the control coil is easily formed.
The magnetic field formed by the control core with the control coil or the bias permanent magnet is guided to the stator yoke along the control core or the bias permanent magnet, and is rotated on the inner surface of the yoke and the outer surface of the rotary shaft or the rotary shaft. It flows between the outer surfaces of the child yoke to the outer surface of the rotating shaft or the magnetic portion of the outer surface of the rotor yoke. The magnetic flux generated by the permanent magnet for bias is uniformly formed in the circumferential direction in the gap portion between the stator yoke and the rotor yoke, whereas the magnetic flux generated by the control core is arbitrarily formed in the circumferential direction. Therefore, the combined magnetic flux becomes non-uniform in the circumferential direction, and the magnetic force in the radial direction acts on the rotor.

Further, by providing a radial groove in the stator yoke, the control magnetic flux generated by the control core and the control coil is prevented from flowing in the yoke in the circumferential direction, and the rotary shaft is effectively turned in the radial direction. Flow to. Therefore, the magnetic flux density in the gap between the stator yoke and the rotor yoke is increased,
The controllability can be enhanced.

Further, since the rotor yoke is connected and the sleeve made of a magnetic material is inserted into the rotating shaft so as to form a magnetic circuit, the magnetic flux generated by the permanent magnet for bias is provided in the gap between the stator yoke and the rotor yoke. The magnetic flux density by the control core can be increased, and the controllability can be improved.

Further, by providing the concavities and convexities on the surfaces of the stator and the rotating shaft which face each other, the flow of the working fluid is hindered and the working fluid is retained in the space between the stator and the rotating shaft.

Further, by supplying the magnetic powder to this space, the flow of the working fluid is similarly disturbed and the same sealing action is performed.

Further, by making the gap between the rotary shaft sleeve and the stator seal ring narrower than the other gaps, the load of the rotary shaft is supported at this portion when the bearing is stopped in an emergency, so that the magnetic bearing is damaged. Is prevented.

Further, by providing the stator seal ring with a multi-arc groove, the working fluid in the bearing gap can be retained.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic bearing according to an embodiment of the present invention will be described below with reference to the drawings.

1 and 2 show a magnetic bearing according to an embodiment of the present invention. FIG. 1 shows a cross section taken along the axial direction, and FIG. 2 shows a cross section taken along line AA. A non-contact sensor 3 which is basically composed of a rotary shaft 1 made of a magnetic material and a cylindrical stator 2 surrounding the rotary shaft 1 and which detects a relative displacement of the rotary shaft is provided. The stator 2 is fixed to the casing 100.

The stator 2 has disk-shaped yokes 4 and 5 at both ends.
The control electromagnet 6 between the yokes 4 and 5 and the bias magnetic flux permanent magnet 8 are arranged outside the permanent magnet 8. The control electromagnet 6 is composed of a control coil 7 and a core 9. The control coil 7 is wound around four arc-plate-shaped control cores 9 arranged at equal intervals on the circumference. The permanent magnet 8 has a cylindrical shape and is magnetized in the axial direction, and generates a uniform magnetic flux in the axial direction along the circumferential direction. Both ends of the control core 9 and the permanent magnet 8 are fixed to the inner ends of the yokes 4 and 5. Inside the permanent magnet 8, a cylindrical seal ring 11a made of a non-magnetic material is attached by fixing both ends to the inner surfaces of the yokes 4 and 5.

A cylindrical rotor yoke 1 is provided on the outer surface of the rotary shaft 1.
2, 14 and the sleeve 13 are fitted and fixed. This rotor yoke has a portion 12 corresponding to the stator yoke,
14 is made of a magnetic material, and the sleeve 13 corresponding to the seal ring 11a is also made of a magnetic material.

Next, the configuration of the control circuit for this magnetic bearing will be described.
This will be described with reference to FIGS. 1 and 2. The control circuit includes a sensor amplifier 17 that amplifies a signal from the sensor 3 that detects the displacement of the rotating shaft, a compensation circuit 18 that phase-compensates the signal of this sensor amplifier, and a signal of this phase compensation circuit that amplifies the radial magnetic pole. And a power amplifier 19 for supplying a current to the. In this embodiment, two sets of the sensors 3 are provided so as to be orthogonal to each other in a plane orthogonal to the axis, and two control circuits are provided accordingly. Then, the control coils 7 located at positions opposite to each other with the axis interposed therebetween are connected in series with the phases reversed, and the output terminals from the respective power amplifiers 19 are controlled so as to correspond to the sensor 3 as shown in FIG. It is connected to the coil 7.

Next, the operation of the magnetic bearing configured as described above will be described. First, a magnetic flux Φ ₁ is generated from the bias magnetic flux permanent magnet 8 in a direction opposite to the radial direction at a position where the yokes 12 and 14 of the rotary shaft 1 face each other as shown in FIG. On the other hand, when a current is applied to the control coil 7, as shown in FIG. 4, a magnetic flux Φ ₂ having the same direction is generated at, for example, a vertically opposed portion of the rotary shaft 1. These individually exert a suction force on the rotation axis from both sides and do not give a radial displacement.

However, when both coils are excited at the same time, both the bias magnetic flux Φ ₁ and the control magnetic flux Φ ₂ act, and these magnetic fluxes strengthen each other above the rotary shaft and weaken each other below the rotary shaft. As a result, upward suction force remains. That is, the rotating shaft 1 can be displaced in the radial direction by exciting the control coil 7 with the current output from the power amplifier 19 according to the detection signal of the displacement sensor 3. In order to exert a downward attraction force in the figure, the control current may be passed in the opposite phase so as to be generated in the direction opposite to the control magnetic flux Φ ₂ in FIG.

In the magnetic bearing having such a configuration, the bearing casing 100 outside the control core 9, the stator seal rings 11a, b, c and d and the two yokes 4 and 5 form a cylindrical closed space. Since the radial control coil 7 is arranged here, it is difficult for the working fluid to enter the control coil. Therefore, it is not necessary to use a can structure, and it is easy to manufacture a large bearing.

FIG. 5 illustrates that the magnetic bearing of the present invention has a sealing effect. On the outer surfaces of the yoke sleeves 12, 13, 14 on the rotor side, there are provided ridges 15 extending in the circumferential direction at predetermined intervals in the axial direction.
Concavities and convexities are alternately formed in the axial cross section. On the other hand, on the inner peripheral surfaces of the yokes 4 and 5 and the seal ring 11a, the ridges 16a and 16b extending toward the surfaces of the sleeves 12, 13 and 14 are arranged at the same pitch as the irregularities of the sleeves.
It is formed so that there is a slight gap between its tip and each of the concave and convex surfaces of the sleeves 12, 13, and 14. A working fluid having an appropriate viscosity is supplied to the cylindrical space between the rotary shaft 1 and the stator 2.

The unevenness formed by the convex portions 15 and 16a, 16b has a resistance action against the flow of the working fluid in this space, and holds the working fluid in this space. As a result, the fluid is always secured in this space, stable rotation is performed, and the sealing of the portion penetrating the bearing casing on the drive shaft side or the like is simplified, and the weight and cost can be reduced.

FIG. 6 shows a magnetic bearing according to the second embodiment of the present invention and is a sectional view taken along the line BB in FIG. The yokes 4 and 5 of the stator 2 have a structure in which slits 21 are formed along the axial direction that penetrate both end faces and open to the outer surface. With this slit 21, the yoke 4,
Since the magnetic resistance in the circumferential direction of 5 is large, it is prevented that the control magnetic flux Φ ₂ bypasses the sleeve of the rotary shaft 1 and is closed in the yoke, and the control force is reduced.

FIGS. 7 and 8 show a third embodiment of the present invention, which is a flow of the working fluid flowing through the narrow gap between the stator 2 and the rotary shaft 1 in the embodiment of FIG. It has been devised to increase resistance. That is, the yoke 5 on the upstream (supply) side of the working fluid of the stator 2
An insertion hole 22 for the magnetic powder is formed at the end of the magnetic powder, which is connected via a supply pipe 23 to a pressure feed pump 24 and a magnetic powder container 26 containing a magnetic powder 25 mixed with a fluid.

In the magnetic bearing having such a structure, when the pressure pump 24 is operated, the magnetic powder is supplied from the upstream side of the working fluid and mixed into the working fluid. This further acts according to the magnetic flux between the stator 2 and the rotating shaft 1 to distribute as shown in FIG. 8 to impede the flow of the working fluid and hold the working fluid in this space.

FIG. 9 shows a fourth embodiment of the present invention, in which the central seal ring 11 of the stator 2 and the corresponding sleeve 13 of the rotary shaft 1 have good slidability, that is, a small friction coefficient. They are made of a material, and no ridges or grooves are provided on these surfaces, and the surfaces of them are smoothly finished. And the gap between them is fixed to the stator yokes 4, 5
And a little smaller than that of the rotor yokes 12 and 14 at both ends. As a result, even if the magnetic bearing itself loses its function due to, for example, abnormal vibration, the seal ring 11 and the sleeve 13 come into contact with each other to prevent damage to the magnetic bearing.

Incidentally, also in this example, the seal ring 1
A spiral groove may be provided on the opposing surfaces of 1 and the sleeve 13 to enhance the sealing effect. Further, on both or one of these surfaces, an appropriate shape, for example, a multi-arc shape may be used to increase the bearing effect, or a polygonal recess or protrusion may be provided to increase the sealing effect. Good.

[0039]

As described above, according to the present invention, since the cylindrical space is formed by the bias core and the yoke, a closed space for housing the control coil can be provided without requiring a complicated structure. It is easily formed, has a simple structure, and is easy to manufacture large bearings. By forming a plurality of circumferential grooves on the opposing surfaces of the stator and the rotating shaft, the flow resistance of the working fluid is increased to maintain the flow in this space, and stable rotation and a simple seal structure can be obtained.

[Brief description of drawings]

FIG. 1 is a front sectional view of a first embodiment of the present invention.

FIG. 2 is a view on arrow AA of FIG.

FIG. 3 is a schematic diagram showing a magnetic flux distribution by the biasing permanent magnet of the above embodiment.

FIG. 4 is a schematic diagram showing a magnetic flux distribution by the control coil of the above embodiment.

FIG. 5 is a schematic diagram showing the configuration of means for increasing the sealing effect of the above embodiment.

FIG. 6 shows a second embodiment of the present invention, which is indicated by B in FIG.
FIG.

FIG. 7 is a front sectional view showing a third embodiment of the present invention.

FIG. 8 is an enlarged view showing a main part of FIG.

FIG. 9 is a front sectional view showing a fourth embodiment of the present invention.

FIG. 10 is a front sectional view showing a conventional magnetic bearing / motor.

11 is a side sectional view of FIG.

FIG. 12 is a schematic diagram showing the arrangement of the sensors in FIG.

13 is a schematic diagram showing the configuration of the conventional control circuit of FIG.

[Explanation of symbols]

 1 Rotation axis 2 Stator 3 Sensor 4, 5 Stator yoke 6 Control electromagnet 7 Control coil 8 Bias magnetic flux permanent magnet 9 Control core 10 Bias magnetic flux permanent magnet 11a Inner seal ring 11c, 11d Side seal ring 12, 14 Rotation Child yoke 13 Sleeves 15, 16a, 16b Convex strip 17 Sensor amplifier 18 Compensation circuit 19 Power amplifier 21 Slit 22 Magnetic powder insertion hole

Claims (10)

[Claims] 1. A magnetic bearing in which a stator is arranged around a rotary shaft, and a magnetic force acts on the rotary shaft from the stator to apply a driving force in a radial direction to keep the rotary shaft at a constant axis. The stator extends along the axial direction and has at least three control cores arranged on the circumference, control coils wound around the cores, and fixed to the end portions of the cores. A pair of disc-shaped stator yokes and a tubular shape that connects the insides of the control coils of the yokes to each other,
A magnetic bearing comprising an axially magnetized permanent magnet for bias magnetic flux. 2. The magnetic bearing according to claim 1, wherein a radial groove is provided in the stator yoke between the control coils. 3. A pair of rotor yokes are inserted into the rotary shaft so as to face the stator yoke,
The magnetic bearing according to claim 1, further comprising a sleeve made of a magnetic material inserted into the rotating shaft so as to connect the rotor yoke to form a magnetic circuit. 4. A cylindrical non-magnetic seal ring is arranged between the stator yokes along a rotation axis, and the seal ring,
The control core is provided by the yoke and the bearing casing,
The magnetic bearing according to claim 1, wherein a closed space for accommodating the control coil and the biasing permanent magnet is formed to prevent fluid flowing through a bearing gap from entering a coil portion. 5. A cylindrical non-magnetic seal ring is arranged between the stator yokes along a rotation axis, and a seal disk is arranged on an outer side surface of the yoke, and the yoke, the seal ring, The sealing disk and the bearing casing form a closed space for accommodating the control core, the control coil, and the biasing permanent magnet, and a fluid flowing through the bearing gap is prevented from entering the coil portion. The magnetic bearing according to claim 1. 6. The concavo-convex whose surface position changes along the axial direction or the circumferential direction is formed on at least one of the surfaces of the stator and the rotating shaft which face each other. Magnetic bearing described in. 7. The magnetic bearing according to claim 1, further comprising a magnetic powder supply device, and means for supplying magnetic powder to a gap between the stator and the rotary shaft. 8. The magnetic bearing according to claim 7, wherein the magnetic powder supplying device mixes the magnetic powder as a fluid and transfers the mixed magnetic powder to a gap between the stator and the rotary shaft. 9. The magnetic bearing according to claim 3, wherein the gap between the seal ring of the stator and the sleeve of the rotary shaft is smaller than the gap between the stator yoke and the rotor yoke. 10. The magnetic bearing according to claim 9, wherein an inner surface of the seal ring of the stator facing the rotation axis has a multi-arc shape.