JPH0587687B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention generally relates to magnetic bearings that support and rotate a rotor by magnetic force.

[Prior art and its problems]

As a method of supporting a rotor rotating at high speed,
Instead of the conventionally used mechanical bearings, a method is known in which the rotor is supported by magnetic force.

Known magnetic bearings that support the rotor using this magnetic force are equipped with mechanical bearings for supporting the rotor when no magnetic force acts on the rotor. This mechanical bearing avoids close contact between the rotor and stator, and in the case of magnetic bearings using permanent magnets, prevents adhesion between the permanent magnets of the rotor and stator or between the permanent magnets and the yoke. This prevents damage to the rotor and stator in an emergency. As described in British Patent GB2056 579A, by reducing the air gap between the rotor and the mechanical bearing, the shock between the rotor and the mechanical bearing in an emergency can be reduced. However, since the rotor rotates while being supported in a non-contact manner, the gap is limited by manufacturing precision and may interfere with the rotor. On the other hand, when conventionally magnetically levitating a rotor that is in contact with the mechanical bearing, as mentioned above, in order to separate the rotor that is approaching the permanent magnet, it is instantaneous, but the control electromagnetic coil is requires a large current. Because of this current,
The capacity of the power amplifier, which is one of the components of the magnetic force supply source, has increased, and the size of the entire device has had to be increased. Also, British patent
As described in GB2048 195A, there are examples where mechanical bearings are used as part of a temporary fixing mechanism for the rotor, and after use, they are moved and used as normal emergency bearings. This mechanical bearing movement mechanism simply fixes the rotor when no magnetic force is applied to the rotor, and when the rotor is levitating, it requires a large amount of current in the electromagnetic coils, just like in the past.

[Purpose of the invention]

The present invention was made to solve the above problems, and it is possible to reduce the capacity of the power amplifier, which was determined by the maximum current generated in the electromagnetic coil when the rotor levitates, and to reduce the size of the electromagnetic coil. can. An object of the present invention is to provide a magnetic bearing having a rotor movement mechanism using a mechanical bearing.

[Summary of the invention]

The present invention includes a rotor, a moving means for mechanically moving the rotor to a floating position via a rotary bearing that can come into contact with the rotor, and a moving means for mechanically moving the rotor to a floating position by the moving means. This is a magnetic bearing having a magnetic force supply source for magnetically levitation.
That is, a configuration is adopted in which the rotor is first mechanically moved to a stable support position in a state where the rotor is not levitated, and then held by the moving means is released and the rotor is magnetically levitated. Furthermore, since the rotary bearing is provided at a position in contact with the rotor, it is possible to rotate the rotor before the moving means is retracted, and the time required to drive the rotor can be shortened.

〔Effect of the invention〕

The capacity of the power amplifier can be reduced and the number of turns of the electromagnetic coil can be reduced, making it possible to downsize the entire device. Further, since a rotation bearing is provided, the rotor can be moved while being rotated.

[Embodiments of the invention]

Hereinafter, typical embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a single-axis control type magnetic bearing, which is one of the embodiments of the magnetic bearing according to the present invention.

The stator side of the magnetic bearing 1 shown in the figure is a case 2.
and radially magnetized permanent magnets 5a and 5b having releg-shaped yokes fixed to the inner and outer circumferences arranged above and below inside the case 2, and mechanical bearings fixed to the case 2 and serving as rotation bearings to be described in detail later. A pair of hollow fixed shafts 4 provided with grooves for moving mechanisms 10a and 10b and electromagnetic coils 9a and 9b wound in a ring shape at the center of the fixed shaft 4 are sandwiched therebetween. yoke 8a, 8b. On the other hand, the rotor 3 inside the case 2
radially magnetized permanent magnets 6a, 6b having ring-shaped yokes fixed to the inner and outer peripheries, which are arranged above and below the rotor 3 so as to face the radially magnetized permanent magnets 5a, 5b; It is composed of a ring-shaped yoke arranged to face the pair of yokes 8a and 8b, and radially magnetized permanent magnets 7 fixed to the inner and outer peripheries. Magnetic control of the rotor 3 in the axial direction is performed as follows.

The axial displacement of the rotor 3 is detected by a displacement meter 15, this detection signal is processed by a control device (not shown), amplified by a power amplifier (not shown), and applied as a current to electromagnetic coils 9a, 9b. The rotor 3 is floated to a stable position by balancing the force of the permanent magnet and the force of the electromagnet. The radial direction of the rotor 3 is controlled by the permanent magnets 6 placed above and below the rotor 3.
It is actively controlled by the attractive force of the permanent magnets 5a, 5b arranged above and below inside the case 2.

The rotor 3 is attracted to either the top or bottom when no magnetic force is applied to the rotor 3, but if the permanent magnets completely attract each other or the permanent magnet and the yoke, it is difficult to levitate it using the force of the electromagnets. Therefore, it is necessary to provide a certain air gap between the permanent magnets or between the permanent magnets and the yoke. For this reason, mechanical bearings 10a, 10b are arranged above and below the rotor 3.

a movable sleeve 11a fixed to the aforementioned mechanical bearings 10a, 10b, movable in the axial direction of the hollow fixed shaft 4, and threaded on the inside;
11b and a threaded shaft 12 which is threaded inside the fixed shaft 4 at a position corresponding to the threaded portion of the movable sleeve. Furthermore, if the screws of the moving sleeves 11a and 11b are different on the upper and lower sides, that is, if the moving sleeve 11a is a right-handed screw,
The moving sleeve 11b has a left-hand thread, and the upper and lower threads of the threaded shaft 12 are the same thread.

Next, the operation of moving the rotor 3 to the stable floating position will be explained.

When the threaded shaft 12 is rotated in the direction of the arrow 13, the direction of the thread changes in the movable sleeve 11.
a and 11b move in the directions of arrows 14a and 14b, respectively. Therefore, the mechanical bearing 10
a and 10b move in the direction sandwiching the rotor 3,
The rotor 3 is moved to a stable floating position. After the rotor 3 floats, the threaded shaft 12 is rotated in the opposite direction and the mechanical bearings 10a, 10b are moved to a position where they do not interfere with the rotation of the rotor 3 by performing the operation opposite to that described above. .

In this way, in a magnetic bearing having a mechanism for moving the rotor 3 to a stable floating position using the mechanical bearings 10a and 10b, it is possible to suppress the peak current flowing through the electromagnetic coils that occurs when the rotor 3 starts floating. It becomes possible to reduce the capacity of the power amplifier, which was determined by this peak current, and to further reduce the number of turns of the electromagnetic coil.

FIG. 2 shows temporal changes in the current flowing through the electromagnetic coil at the time of starting the levitation of the magnetic bearing combined with a permanent magnet. At the start of levitation, the current value exceeds 10A, but when levitation is stable, almost no current flows. As is clear from FIG. 2, the above-mentioned effects are remarkable, and by using a mechanical bearing in the moving mechanism, the magnetic bearing can avoid damage to the components of the magnetic bearing in the event of an emergency.

The moving mechanism using the mechanical bearing for the rotor described above is not limited to the structure shown in FIG. 1, and any other method may be used as long as the rotor can be moved to the stable floating position. FIG. 3 shows another embodiment of the invention. The magnetic bearing shown in FIG. 1 differs in the number of control axes, and is a two-axis controlled magnetic bearing that controls two axes in the radial direction. FIG. 3 is a sectional view showing only one of the two radial axes, and the magnetic bearing 20 comes out from the N pole of the ring-shaped axially magnetized permanent magnet 25 and is fixed to the case 21. The permanent magnet S
The magnetic flux returning to the poles is increased or decreased by the electromagnetic coils 24a and 24b to levitate the rotor 22 to a stable position.

A mechanism for moving the rotor 22 to a stable floating position is arranged at a position corresponding to a threaded shaft 36 and the threaded portion thereof, and includes movable sleeves 26a and 26b movable in the axial direction of the threaded shaft 36, and the movable sleeve. 26
Support rods 28a and 28 supported by pins a and 26b
b, 30a, 30b and mechanical bearings 32a, 32b, 34a, 34b supported by pins on the support rods.
positioning shafts 27a, 27 with inner rings fixed to both ends;
b, and a grooved shaft 37 that prevents rotation of the moving sleeves 26a, 26b.

The moving sleeves 26a and 26b are threaded in different directions; if the moving sleeve 26a is a right-handed thread, the moving sleeve 26b is a left-handed thread, whereas the threaded shaft 36 is threaded in one direction. It is configured. Figure 3 shows rotor 2
As a mechanism for moving 2 to a stable floating position,
The mechanical bearings 32a, 32b, 34a, 34b
Two positioning shafts with inner rings fixed to both ends are shown for convenience, but in reality at least three are required.

The fourth method of moving the rotor 22 to a stable floating position
This will be explained with a diagram. FIG. 4 shows cross section A in FIG. 3, and the same members are designated by the same reference numerals and detailed explanations will be omitted.

When the threaded shaft 36 is rotated in the direction of arrow 40, the movable sleeves 26a, 26b move in the directions of arrows 39a, 39b in FIG. By the movement of the moving sleeves 26a, 26b, the pin-supported support rods 28a, 28b, 29a, 29
As a result, the positioning shafts 27a, 27b, 27c, 27d supported by pins on the support rods move the same distance in the direction of arrows 38a, 38b, 38c, 38d. The positioning shafts 27a, 27
Mechanical bearings 32 fixed to b, 27c, 27d
a, 32b, 33a, 33b, 34a, 34b,
35a and 35b move the rotor 22 to a stable floating position.

Note that the above-mentioned moving mechanism is not limited to the structure shown in FIGS. 3 and 4, and any other method may be used as long as the rotor can be moved to the stable floating position. The present invention can also be applied to a magnetic bearing having three or more control axes by combining the mechanisms shown in FIGS. 1 and 3.

As mentioned above, in a magnetic bearing that has a mechanism for moving the rotor to a stable floating position using a mechanical bearing, the capacity of the power amplifier can be reduced and the winding of the electromagnetic coil can be made thinner, as shown in Figure 1. , the number of turns can be reduced. Furthermore, since the movement mechanism uses an emergency bearing, it is possible to avoid damage to the components of the magnetic bearing in an emergency, resulting in a compact and highly reliable magnetic bearing as a whole. Further, since the rotary bearing is provided at a position in contact with the rotor, it is possible to rotate the rotor before the moving means is retracted, and the time required to drive the rotor can be shortened.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the magnetic bearing according to the present invention, FIG. 2 is a characteristic diagram showing temporal changes in the current flowing through the electromagnetic coil when the rotor of a conventional magnetic bearing is levitating, and FIG. 3 is a diagram of the present invention. FIG. 4, a cross-sectional view showing another embodiment of the invention, is a detailed view of another cross-section of FIG. 1...Magnetic bearing (single axis control type), 2...Case, 3
...Rotor, 4...Fixed shafts 5a, 5b, 6a, 6b,
7... Ring-shaped permanent magnet, 8a, 8b... Yoke, 9
a, 9b... Electromagnetic coil, 10a, 10b... Mechanical bearing, 11a, 11b... Moving sleeve, 12...
Threaded shaft, 20...Magnetic bearing (2-axis control type), 21
...Case, 22...Rotor, 23a, 23b...Yoke, 24a, 24b...Electromagnetic coil, 25...Ring-shaped permanent magnet, 26a, 26b...Moving sleeve,
27a, 27b...positioning axis, 28a, 28b,
29a, 29b, 30a, 30b, 31a, 31
b...Support rod, 32a, 32b, 33a, 33b,
34a, 34b, 35a, 35b... mechanical bearing,
36...Threaded shaft, 37...Grooved shaft.

Claims (1)

[Scope of Claims] 1. A rotor, a moving means for mechanically moving the rotor to a floating position via a rotary bearing that can come into contact with the rotor, and a moving means for mechanically moving the rotor to a floating position by the moving means. A magnetic bearing comprising: a magnetic force supply source that magnetically levitates a rotor;