JPS6220408B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a magnetic bearing device, and particularly to improvements in an attraction type magnetic bearing device. [Background Art of the Invention and Problems Therewith] Magnetic bearing devices are conventionally known as bearing devices that support high-speed rotating bodies. Magnetic bearing devices are designed to support a rotating body in a completely non-contact manner using magnetic force, and are broadly classified into repulsion type and attraction type based on how magnetic force is used. By the way, in an attraction type magnetic bearing device, when supporting a rotating body in a completely non-contact manner, it is necessary to finely control the magnetic force of each part by controlling the magnetic flux of each part. Such control is normally performed by detecting the radial and axial positions of the rotating body and increasing or decreasing the magnetic flux at necessary locations based on this. That is, Fig. 1 shows an example of a magnetic bearing device of the so-called inner rotor type, in which the rotor is installed inside the stator and is of the suction type . A magnetic bearing element provided between the rotating shaft 1 and the stationary frame 3 is shown. The magnetic bearing element 2 is composed of an axial bearing element 11 and radial bearing elements 12a, 12b arranged on both sides of the axial bearing element 11. The axial support element 11 includes an annular plate 21 made of a high magnetic permeability material and fixed to the outer periphery of the rotating shaft 1;
An annular permanent magnet 22 is fixed to the inner surface of the stationary frame 3 and is magnetized with the polarity shown, and serves as a magnetic flux supply source that generates a magnetic bearing force mainly in the axial direction. An annular magnetic pole material 23a, which is passed through the peripheral portions of both sides of 21.
23b, and coils 24a, 24b mounted so as to increase or decrease the magnetic flux passing through these annular magnetic pole materials 23a, 23b. The radial bearing elements 12a, 12b are of equal construction; for example, taking element 12a, the rotation axis 1
a ring 26 made of a highly permeable material fixed to the outer periphery of the
An annular permanent magnet 27 is fixed to the inner surface of the stationary frame 3 and is magnetized with the polarity shown, and serves as a magnetic flux supply source that generates magnetic bearing force mainly in the radial direction. The annular magnetic pole material 28 is passed through the circumferential surfaces of both ends of the annular magnetic pole material 28.
a, 28b, and four magnetic poles 29 protruding from the inner surfaces of these magnetic pole materials 28a, 28b at an angle difference of, for example, 90 degrees, as shown in FIG. It is composed of a coil 30. On the other hand, position detectors 32 for detecting the radial position of the rotating shaft 1 are arranged around both ends of the rotating shaft 1, for example, in correspondence with the position of the magnetic pole 29, as shown in FIG. As these position detectors 32, eddy current displacement transducers are usually used. Furthermore, position detectors 33a and 33b are arranged at positions facing both end faces of the rotating shaft 1 to detect the axial position of the rotating shaft 1, and these detectors 33a and 33b are also generally equipped with eddy current displacement sensors. It consists of a converter. In this magnetic bearing device, the support is stabilized as follows. That is, when the position of the rotating shaft 1 moves in the radial direction, the gap length between the position detector 32 located in the moving direction and the rotating shaft 1 becomes smaller, and conversely, the gap length between the position detector 32 located in the moving direction and the rotating shaft 1 becomes smaller. The gap length between the sensor 32 and the rotary shaft 1 increases, resulting in a change in the outputs of both position detectors. Utilizing this phenomenon, a control device (not shown) energizes the coil 30 wound around the magnet 29 so as to reduce the magnetic flux passing through the magnetic pole 29 located in the direction in which the gap length becomes smaller. The coil 30 wound around the magnetic pole 29 is energized so as to increase the magnetic flux passing through the magnetic pole 29 located in the direction in which the gap length is increased, and the magnetic force of the magnetic pole portion generated by this energization is The position of the rotating shaft 1 is shifted to a stable position by the difference between the two positions. Although there are various specific means for biasing, all of them basically adopt the method described above. On the other hand, in the axial direction, the control device uses the fact that the outputs of the position detectors 33a and 33b change depending on the change in the axial direction of the rotary shaft 1 to control the coil 24.
By energizing a and 24b, the axial position of the rotating shaft 1 is moved to a stable position. However, the conventional magnetic bearing device configured as described above has the following problems. That is, in order to perform the stabilization control as described above, a position detector that detects the axial and radial positions of the rotating shaft 1 without contacting the rotating shaft 1 is required. There are various types of position detectors, but
Non-contact gap sensor types, such as eddy current displacement transducers, are exclusively used in terms of responsiveness, durability, and ease of handling. In the case of an eddy current type position detector, in principle, it is necessary to set the area of the displacement surface to be measured to be sufficiently larger than the area of the sensitive surface of the detector. However, in the conventional device, the above-mentioned eddy current type position detectors 33a, 3
3b facing both end surfaces of the rotating shaft 1, and these position detectors 33a, 33b detect the axial position of the rotating shaft 1. As a result, there was a problem in that the rotary shaft 1 had to be made larger in diameter and heavier in terms of position detection. Therefore, in order to solve this problem, as shown in FIG. A position detector 33 is placed on the surface located at
It is conceivable to detect the position in the axial direction by making the sensitive surfaces of a and 33b face each other. In this way, the rotating shaft 1 can be made smaller in diameter and lighter in weight. However, since it is necessary to attach the disc 35 in a special manner, the manufacturing process cannot be avoided.
Furthermore, it is difficult to increase the rotational speed when taking into consideration the centrifugal stress applied to the attachment portion of the disk 35. The above explanation was for an example of an inner rotor type, but even for an outer rotor type, as shown in Fig. 5, the hollow rotating shaft 1a has a sufficiently thin wall thickness. A conductive annular plate 36 is attached to the inner or outer surface of the rotating shaft 1a, and this annular plate 36
Position detector 3 with its sensitive surface facing the axial surface of
3a and 33b are arranged and supported by a stationary column 37, the axial position of the rotating shaft 1a is detected. For this reason, problems similar to those described above were inevitable. [Object of the Invention] The present invention has been made in view of the above circumstances, and its purpose is to detect the axial position of a rotating body using a non-contact gap sensor type position detector. Equipped with a detection system that can perform good detection without affecting the diameter of the rotating body, without attaching a special measuring member to the rotating body, or simply by attaching a measuring member with a sufficiently small diameter. The object of the present invention is to provide a magnetic bearing device that can contribute to realizing high-speed rotation. [Summary of the Invention] The magnetic bearing device according to the present invention includes a non-contact gap sensor type position detector that detects the position in the axial direction, which is arranged so that its sensitive surface is parallel to the outer circumferential surface of the rotating body. The present invention is characterized in that the axial position of the rotating body is detected. More specifically, as shown in Fig. 6, the outer diameter or inner diameter (outer diameter in the figure) of the rotating body R is X ₁
The sensitive surface P intersects _a boundary line _T drawn orthogonally to the ideal rotation _center line S of _the rotating body R at a boundary position that changes from ,
and position detectors E 1 and E 2 are provided so as to face the rotating body R with their sensitive surfaces P facing opposite directions centering on the ideal rotation center line S, and the position detectors E ₁ and E ₂ are
The axial position of the rotating body R is detected by the output obtained by adding the outputs of E ₁ and E ₂ using an adder circuit. [Effects of the Invention] With the arrangement of the position detectors E ₁ and E ₂ as described above, taking the position detector E ₁ as an example, a part of the sensitive surface of the position detector E ₁ is connected to the rotating body R. The remaining portion faces the circumferential surface of the large-diameter X ₁ portion, and the remaining portion faces the circumferential surface of the small-diameter X ₂ portion. Since the distance between the sensitive surface P and the circumferential surface of the _X1 section is narrower than the distance between the circumferential surface of the _X2 section, the output of the position detector _E1 is the overlap width between the sensitive surface P and the _X1 section. It depends on H. Therefore, when the rotating body R is displaced in the direction of _the solid line arrow _Y in FIG. This means that the axial position of R can be detected. However, position detector
The output of E ₁ depends on the gap length g ₁ between it and the rotating body R. However, as in this invention, the position detectors E ₁ and E ₂ are arranged around the ideal rotation center line S.
are placed symmetrically and the outputs of position detectors E ₁ and E ₂ are added by an adder circuit, the gap length can be reduced.
By eliminating the outputs due to g ₁ and g ₂ , it is possible to obtain an output corresponding only to the displacement in the axial direction. In this case, the axial position can be detected by using parts of the rotating body R where the outside diameter changes suddenly, such as stepped parts or ends, so a special measuring member is attached to the rotating body R. It is sufficient to attach only small-diameter members. Therefore, the axial position can be detected without increasing the diameter or weight of the rotating body, and without giving special consideration to centrifugal stress, and as a result, high-speed rotation can be achieved. can contribute to [Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 7 shows an example in which the present invention is applied to a magnetic bearing device of a suction type and external rotation type. That is, 51 in the figure indicates a hollow rotating shaft, and 5
2 indicates a magnetic bearing element provided between the inner surface of the rotating shaft 51 and the stationary part 53. The rotating shaft 51 is made of a conductive non-magnetic material or a paramagnetic material and has a cylindrical shape. The magnetic support element 52 is composed of a rotating element 54 and a stationary element 55. Rotating side element 54
are constituted by rings 62a and 62b made of a high magnetic permeability material and mounted in grooves 61a and 61b formed in two stages in the axial direction on the inner circumferential surface of the rotating shaft 51. On the other hand, the stationary side element 55 includes a cylindrical yoke 63 mounted coaxially with the ideal rotation center line of the rotating shaft 51, and a cylindrical yoke 63 that protrudes from the outer periphery of both ends of the yoke 63 with an angular difference of 90 degrees. Magnetic pole 6 for radial bearing
4a, 64b, coils 65a, 65b for radial support force control wound around these magnetic poles 64a, 64b, respectively, and an annular magnetic pole for axial support protruding annularly from the outer periphery of the central part of the yoke 63. 66, coils 67a and 67b for controlling the axial bearing force, which are attached to both sides of the annular magnetic pole 66 on the outer periphery of the yoke 63;
It is composed of annular permanent magnets 68a and 68b that are attached to both sides of the outer periphery of the yoke 63 with an annular magnetic pole 66 in between and are magnetized to the polarities shown. The yoke 63 is fixed to the stationary part 53 via a support member 70, an induction motor yoke 71, and a support member 72. Therefore, around the rotating shaft 51 and the magnetic pole 64
At positions facing a and 64b, eddy current position detectors 73 for detecting the radial position of the rotating shaft 51 in a non-contact manner are arranged with their sensitive surfaces facing the outer circumferential surface of the rotating shaft 51. These position detectors 73 are supported by a stationary frame 74 via a support member. In addition, at both positions 180 degrees apart in the circumferential direction near the lower end of the rotating shaft 51 in the figure, there are non-contact gap sensor types, that is, eddy current type positions, for detecting the axial position of the rotating shaft 51. Detector 7
As shown in FIG. 8, the position detectors 5a and 75b are arranged so that a part of their respective sensitive surfaces face the outer circumferential surface of the lower end of the rotating shaft 51, and their sensitive surfaces face each other. 75b is also supported by the stationary frame 74 via a support member. In the figure, 80 indicates a stator of an induction motor that applies rotational power to the rotating shaft 51, and 81 indicates a rotor of the motor. Therefore, the output end of the position detector 73 is connected to the coil 65 based on the output of these position detectors 73.
It is connected to a known radial stabilization control device (not shown) which stabilizes the radial direction by energizing the actuators a and 65b. Further, the position detector 7
The output ends of 5a and 75b are connected via a signal processing circuit 82 shown in FIG. 10 to a known axial stabilization control device (not shown) which stabilizes the axial direction by energizing coils 67a and 67b. has been done.
The signal processing circuit 82 includes position detectors 75a and 75b.
The output of the amplified signal is linearized and amplified by the converters 83a and 83b, and the offset voltage of the amplified signal is canceled by applying the output voltage of the bias power supplies 84a and 84b. are added by an adder 86, further amplified by an amplifier 88 via a logarithmic amplifier 87 as necessary, and then introduced into the known axial stabilization control device described above. With such a configuration, the N of the permanent magnet 68a
The magnetic flux emitted from the pole reaches the ring 62a, then passes through the ring 62a in the axial direction, and on the other hand, passes from the inner surface of the ring 62a through the magnetic pole 64a and the yoke 63 to the S pole. , on the other hand, from the end face of the ring 62a to the annular magnetic pole 66,
It passes through the yoke 63 and reaches the S pole. The magnetic flux emitted from the N pole of the permanent magnet 68b similarly passes through two paths. Therefore, the rings 62a, 6
A radial magnetic bearing force acts between the inner surface of the ring 2b and the magnetic poles 64a, 64b, and the ring 62
An axial magnetic bearing force will act between the end faces of a and 62b and the annular magnetic pole 66. At this time, when the rotating shaft 51 attempts to move in the radial direction, the position detector 73 detects this movement, and the radial stabilization control device is actuated thereby to appropriately energize the coils 65a and 65b. The rotating shaft 51 is moved to a stable position by controlling the radial magnetic bearing force of each part. On the other hand, when the rotating shaft 51 is about to move in the axial direction, the axial stabilization control device operates and appropriately biases the coils 67a and 67b to control the axial magnetic bearing force and move the rotating shaft 51 in the axial direction. Move to a stable position. That is, when the rotating shaft 51 is displaced in the axial direction, the overlap width H between the outer circumferential surface of the rotating shaft 51 and the sensitive surfaces of the position detectors 75a, 75b changes, so the outputs of the position detectors 75a, 75b also change. This output also depends on the gap length g between the sensitive surface and the outer peripheral surface of the rotary shaft 51. For example, if we focus on the output of one position detector, it changes as shown in FIG. 9 depending on the axial displacement of the rotating shaft 51. Note that in the figure, J indicates a case where g is large, K indicates a case where g is medium, and L indicates a case where g is small. In any case, when the rotating shaft 51 is displaced in the axial direction, the outputs of the position detectors 75a and 75b change. After this output is linearized by converters 83a and 83b of the signal processing circuit 82,
Bias power supplies 84a and 84b convert the offset voltage into a signal. Both signals are then added by an adder 86. Position detector 75
The gap length between the sensitive surfaces of a and 75b and the rotating shaft 51 is such that as one becomes larger, the other becomes smaller, so the output of the adder 86 does not include the component due to the gap length, and is the gap length of the rotating shaft 51. It corresponds only to axial displacement. The axial stabilization control device then energizes the coils 67a and 67b based on the output signal of the signal processing circuit 82. Therefore, the rotating shaft 51 moves to a stable position in the axial direction,
Here, a completely non-contact magnetic bearing state is realized.
Note that if the induction motor is energized in this state, the rotating shaft 51 can be rotated in a completely non-contact state. In this case, the position detector 75a is arranged such that a part of the sensitive surface faces the portion where the outer diameter of the rotating shaft 51 suddenly changes, that is, in the case of this embodiment, the outer circumferential surface of the end of the rotating shaft 51. , 75b are provided, and the position detectors 75a and 75b are used to detect the axial position of the rotating shaft 51, so there is no need to add any special member to the rotating shaft 51 for detecting the axial position. An axial position detection system can be configured. Therefore, it is possible to prevent the rotating shaft 51 from increasing in size and weight, and there is no need to consider centrifugal stress resistance. In addition, the position detector 75
Since the position signal is obtained by adding the outputs of a and 75b, the output of gap lengths g ₁ and g ₂ can be eliminated, and the adverse effects when using a non-contact gap sensor type position detector can be eliminated. This can be prevented, and the above-mentioned effects can be obtained after all. Note that the present invention is not limited to the embodiments described above. That is, although an eddy current displacement transducer is used as the position detector in the above embodiment, other non-contact gap sensor types, such as a light reflection type or a capacitance type displacement transducer, may be used. Further, in the embodiment described above, a position detector 7 for detecting the axial position is provided outside the hollow rotating shaft 51.
5a and 75b are arranged, but they may be arranged inside. Further, although the above-described embodiment is an example in which the present invention is applied to an outer rotor type magnetic bearing device, the present invention can of course also be applied to an inner rotor type magnetic bearing device. FIG. 11 shows an example in which the present invention is applied to an inner rotor type and five-axis control type. In addition, the member for supporting a stationary element is omitted in the figure. That is, in the figure, 101 indicates a rotating shaft, and this rotating shaft 101 is supported in the axial direction by axial supporting elements 102a and 102b at both ends thereof, and by radial supporting elements 103a and 103b in the center thereof. It is designed to be supported in the radial direction by. The axial support elements 102a and 102b have the same structure; taking the element 102a as an example, an annular plate 104 made of a high magnetic permeability material fixed to the outer periphery of the end of the rotating shaft 101;
A permanent magnet 105 fixed to a stationary part, and a magnetic pole 10 that allows the magnetic flux emitted from the permanent magnet 105 to pass through the periphery of one surface of the annular plate 104.
6a, 106b and these magnetic poles 106a, 106
It is composed of coils 107a and 107b for controlling the axial support force, which are wound around the outer periphery of the shaft. On the other hand, the radial bearing elements 103a and 103b are also configured equally, and taking element 103b as an example,
A ring 108 made of a high magnetic permeability material is fixed to the outer periphery of the rotating shaft 101, an annular permanent magnet 109 is fixed to a stationary part, and the magnetic flux emitted from the permanent magnet 109 is passed through the outer circumferential surface of both ends of the ring 108. magnetic pole materials 110a and 110b to be passed through, magnetic poles 111 protruding from the inner surfaces of these magnetic pole materials 110a and 110b with an angle difference of 90 degrees, and a radial bearing force control device wrapped around the outer periphery of these magnetic poles 111. It is composed of a coil 112 for use. In addition, the rotating shaft 101
An eddy current type position detector 113 for detecting the radial position of the rotary shaft 101 is located at a position relative to each magnetic pole 111 around both ends of the rotary shaft 101, with its sensitive surface facing the outer circumferential surface of the rotary shaft 101. It is located. Further, on the radial side of the annular plate 104 constituting the axial support element 102b, eddy current type position detectors 114a and 114b for detecting the axial position of the rotating shaft 1 are installed on one of its sensitive surfaces. The portions are opposed to the outer circumferential surface of the annular plate 104, and are arranged symmetrically about the ideal rotation center line. The output of the position detector 113 is then introduced into a known radial control device, and the position detector 114
The outputs of a and 114b are introduced into a known axial control device via a signal processing circuit shown in FIG. Note that 120 in the figure indicates an induction motor for applying rotational power to the rotating shaft 101. Even with this configuration, since the position detectors 114a and 114b are provided in the above-mentioned relationship, as is clear from the above description, the rotating shaft 1
The axial position can be detected without attaching a special member to 01 for detecting the axial position. Therefore, the same effects as in the embodiment described above can be obtained. In the above embodiment, the annular plate 104 constituting the axial support element 102b is used to detect the axial position, but as shown in FIG. It is also possible to attach a ring 131 and use this ring 131 to detect the position in the axial direction. In this case, since the position detectors 114a and 114b are provided in the above-described relationship, the axial position can be detected satisfactorily even with the ring 131 having a wall thickness of several mm. Therefore, there is no risk that the rotating body will become larger or heavier due to the provision of the ring 131, and the axial position can be changed without special consideration of centrifugal stress resistance. It can be detected well. Furthermore, it goes without saying that the present invention can be applied to other types of magnetic bearing devices.

[Brief explanation of the drawing]

Figure 1 is a schematic vertical cross-sectional view of a conventional magnetic bearing device.
Figure 2 is a sectional view of the same device taken along line A-A in Figure 1 and viewed in the direction of the arrow, and Figure 3 is a sectional view of the same device taken along line B-B in Figure 1 and viewed in the direction of the arrow. 4 and 5 are views for explaining different ways of providing the axial position detector, and FIG. 6 is a view for explaining the schematic configuration of the main parts of the magnetic bearing device according to the present invention. FIG. 7 is a vertical sectional view of a main part of a magnetic bearing device according to an embodiment of the present invention, FIG. 8 is a diagram for explaining the arrangement of the axial position detector in the same device, and FIG. Figure 10 is a diagram for explaining the output characteristics of the axial position detector.
The figure is a block diagram of a signal processing circuit that processes the output of the axial position detector, FIG. 11 is a schematic longitudinal cross-sectional view of the main part of a magnetic bearing device according to another embodiment of the present invention, and FIG. FIG. 7 is a side view of the main parts of a magnetic bearing device according to yet another embodiment. 51...Rotating shaft, 52 ...Magnetic bearing element, 7
3,113...Radial position detector, 75a,
75b, 114a, 114b... Axial position detectors.

Claims (1)

[Claims] 1. A magnetic support element that non-contact supports a rotating body by magnetic force, a position detection system that detects the radial position and axial position of the rotating body, and outputs of these position detection systems. and a means for controlling the radial magnetic bearing force and the axial magnetic bearing force of the magnetic bearing element based on the above, wherein the position detection system that detects the position in the axial direction The diameter or inner diameter is from X ₁ to X ₂ (however, X ₁ > X ₂ ,
X ₂ ≧ 0) through the boundary that changes to first and second position detectors of a non-contact gap sensor type, which are provided facing the rotating body with their sensitive surfaces facing in opposite directions about the ideal rotation center line; and a circuit for adding the outputs of the second position detector. 2. Claim 1, wherein the position detector is any one of a light reflection type displacement detector, a capacitance type displacement detector, and an eddy current type displacement detector.
This is a magnetic bearing device.