JPH1162963A - Magnetic bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic bearing device to simplify structure, reduce a cost, and increase a natural frequency through shortening of a rotary body. SOLUTION: A magnetic bearing device comprises a plurality of sets of magnetic bearings 3, 4, and 5 to support a rotary body 2 in a state not to make contact with a housing 1; and a built-in type brushless DC motor 6 to rotationally drive the rotary body 2. A plurality of rotation sensors 23 and 24 to output a signal, the intensity of which is changed according to a distance between an opposite surface of the rotary body 2, are arranged at equal intervals in a peripheral direction on one periphery concentrical to the rotary body 2 of the housing 1 positioned facing a lower end face 2a of the rotary body 2. One part 26 to be detected consisting of a recessed part is formed in a position corresponding to the periphery of the lower end face 2a of the rotary body 2. Based on output signals from the rotation sensors 23 and 24, the rotation position of the rotary body 2 and the numbers of revolutions thereof are detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic bearing device for rotating a rotating body with a built-in brushless DC motor.

[0002]

2. Description of the Related Art A magnetic bearing device supports a rotating body in a non-contact manner with respect to a fixed portion by a plurality of sets of magnetic bearings.
A device using a brushless DC motor for rotating a rotating body is known. The brushless DC motor is basically composed of three parts: a permanent magnet field synchronous motor, a rotor position detector, and a drive circuit (such as an inverter). Permanent magnet field synchronous motors have multiple phases (usually 3
Phase) consisting of a stator with armature windings and a rotor using permanent magnets. The stator is provided on the fixed part of the magnetic bearing device, and the rotor is integrated with the rotating body of the magnetic bearing device. Provided. Then, in order to control the armature current, it is necessary to detect the rotation position of the rotor, that is, the rotating body by the rotor position detection unit. Usually, a photoelectric element or a Hall element is used for the rotor position detector. Further, the magnetic bearing device is provided with a rotation speed detecting device for detecting the rotation speed of the rotating body, separately from the rotor position detecting unit of the motor, for controlling the speed of the rotating body.

On the other hand, since the rotating body of the magnetic bearing device is driven to rotate at a very high rotational speed, the rotating body is made as short as possible, the bending natural frequency of the rotating body is increased, and the maximum rotating speed is increased. In addition, it is required to increase the degree of freedom in the steady-state rotation speed region to increase the rotation stability. It should be noted that the more the bending natural frequency of the rotating body is apart from the steady rotation speed, the more stable the rotation.

However, in the conventional magnetic bearing device, as described above, the rotation speed detection device of the rotating body and the rotor position detection portion of the brushless DC motor are required, and therefore the structure is complicated and the cost is high. Further, there is a problem that the length of the rotating body becomes longer due to these factors, and the natural frequency of bending thereof decreases.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, simplify the structure and reduce the cost, and increase the natural frequency of the rotating body by shortening the rotating body. An object of the present invention is to provide a magnetic bearing device.

[0006]

According to a first aspect of the present invention, there is provided a magnetic bearing device comprising: a plurality of sets of magnetic bearings for supporting a rotating body in a non-contact manner with respect to a fixed portion; and a built-in brushless for rotating the rotating body. In a magnetic bearing device provided with a DC motor, a signal that changes according to the distance from the opposed surface of the rotating body is output on one circumference concentric with the rotating body of a fixed portion facing the one end face of the rotating body. A plurality of rotation sensors are arranged at equal intervals in the circumferential direction, and one detected portion formed of a concave portion or a convex portion is formed at a position corresponding to the circumference on the end surface of the rotating body. The detection of the rotational position and the number of rotations of the rotating body are performed based on the output signal of the sensor.

[0007] The number of rotation sensors is equal to the number of phases of the armature winding of the brushless DC motor.

When the rotator rotates, the detected portion on the rotator faces the plurality of rotation sensors on the fixed portion one by one during one rotation. Since the detected portion is formed by a concave portion or a convex portion, the rotation sensor and the rotating body face each other when the rotation sensor faces the detected portion on the end surface of the rotating body and when the rotating sensor faces other portions. The distance to the surface changes, thereby changing the magnitude of the output signal of the rotation sensor. Therefore, the magnitude of the output signal of each rotation sensor changes according to the rotation position of the rotating body, that is, the rotor, and the rotation position of the rotor can be detected based on the output signal. In addition, each time the rotating body makes one rotation, the magnitude of the output signal of each rotation sensor changes once, so that the number of rotations of the rotating body can be detected based on this. That is, both the detection of the rotation position of the rotor and the detection of the rotation speed of the rotating body can be performed using the output of the rotation sensor. Therefore, the structure can be simplified and the cost can be reduced. In addition, since the rotation sensor is disposed at the shaft end, which is an empty space, so as to face the end surface of the rotating body, the rotating body can be shortened and its bending natural frequency can be increased. And by increasing the bending natural frequency, the maximum rotation speed of the rotating body is increased,
The rotational stability can be improved by increasing the degree of freedom in the steady rotational speed region.

According to a second aspect of the present invention, there is provided a magnetic bearing device comprising a plurality of sets of magnetic bearings for supporting a rotating body in a non-contact manner with respect to a fixed portion, and a built-in brushless DC motor for rotating the rotating body. In the method, a plurality of detected portions formed of concave portions or convex portions are formed at equal intervals in a circumferential direction on one circumference concentric with the rotating body on one end face of the rotating body, and are formed on the end face of the rotating body. At a position corresponding to the circumference of the opposed fixed portion, one rotation sensor that outputs a signal whose size changes according to the distance from the facing surface of the rotating body is disposed, and based on an output signal of the rotation sensor, The detection of the rotational position and the number of rotations of the rotating body are performed.

[0010] The number of detected parts is equal to the number of phases of the armature winding of the brushless DC motor. Further, the distance from one rotation detection sensor to the surface of the detection target facing the rotation sensor is different from that of the other detection detection target.

When the rotator rotates, a plurality of detected parts on the rotator sequentially face the rotation sensor on the fixed part side one by one during one rotation. Since the detected portion is formed by a concave portion or a convex portion, the rotation sensor and the rotating body face each other when the rotation sensor faces the detected portion on the end surface of the rotating body and when the rotating sensor faces other portions. The distance to the surface changes, thereby changing the magnitude of the output signal of the rotation sensor. Therefore, the output of the rotation sensor changes three times during one rotation of the rotating body. Also, since the distance from the surface of one detected part facing the rotation sensor to the rotation sensor is different from that of the other detected parts, the output signal of the rotation sensor when this detected part faces the rotation sensor Is different from the magnitude of the output signal of the rotation sensor when another detected portion faces the rotation sensor. Therefore, the rotational position of the rotor can be detected with reference to the one detected portion. Further, since the output signal of the rotation sensor changes three times each time the rotating body makes one rotation, the rotation speed of the rotating body can be detected based on this. That is,
Using the output of the rotation sensor, it is possible to detect both the rotational position of the rotor and the rotational speed of the rotating body. Therefore, the structure can be simplified and the cost can be reduced. In addition, since the rotation sensor is disposed at the shaft end, which is an empty space, so as to face the end surface of the rotating body, the rotating body can be shortened and its bending natural frequency can be increased. By increasing the bending natural frequency, the maximum rotation speed of the rotating body can be increased, the degree of freedom in the steady rotation speed region can be increased, and the rotation stability can be improved.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

1 to 4 show a first embodiment, and FIG. 1 schematically shows the entire configuration of a magnetic bearing device.

As shown in FIG. 1, the magnetic bearing device has a set of a vertical shaft-shaped rotating body (2) supported in a non-contact manner on a bottomed vertical cylindrical housing (1) constituting a fixed portion. Axial magnetic bearings (3) and two sets of upper and lower radial magnetic bearings (4)
(5), and a built-in brushless DC motor (6) that rotationally drives the rotating body (2).

The rotating body (2) is disposed concentrically at the center in the housing (1). A cylindrical body (7) having a bottom opening outside the upper part of the housing (1) is concentrically arranged, and the center of the inner surface of the top wall of the cylindrical body (7) is fixed to the upper end of the rotating body (2). Have been. Then, the cylindrical body (7) rotates integrally with the rotating body (2).

The axial magnetic bearing (3) is arranged so as to sandwich the flange-shaped portion of the rotating body (2) from both sides in the axial direction (up and down direction), and a pair of upper and lower magnets for magnetically attracting this portion to both sides in the axial direction. And the excitation current of the electromagnets (8) and (9) is controlled based on the output of an axial displacement sensor (10) provided on the inner surface of the bottom wall (1a) of the housing (1). Thus, the rotating body (2) is supported at a predetermined position in the axial direction. Each radial magnetic bearing (4) (5) is a rotating body
Two pairs of electromagnets (11) arranged so as to sandwich the target portion on the outer periphery of (2) from both sides in two radial directions (horizontal directions) orthogonal to each other and magnetically attract the target portion to both sides in each radial direction. Housing with (12), (13) and (14)
The radial displacement sensor (1) provided on the inner surface of the peripheral wall (1b) of (1)
5) By controlling the excitation current of the electromagnets (11) to (14) based on the outputs of (16), (17) and (18), the rotating body (2) is supported at a predetermined position in the radial direction. Magnetic bearings (3) (4) (5)
For, a well-known configuration can be adopted, and thus a detailed description is omitted.

FIG. 3 shows an example of the electrical configuration of the brushless DC motor (6).

The motor (6) includes a stator (19) and a rotor (2).
0), a rotation detection device (21) and a drive circuit (22).

The stator (19) is fixed to the inner surface of the peripheral wall (1b) of the housing (1), and the rotor (20) is a rotating body inside the stator (19).
It is fixed to the outer circumference of (2). Although not shown in detail, the stator (19) is provided with a plurality of (three in this example) armature windings. For the rotor (20), an annular permanent magnet having magnetic poles at both ends in one diameter direction is used. The stator (19) and the rotor (20) have the same configuration as that of a known permanent magnet field synchronous motor.

The rotation detecting device (21) detects the rotational position of the rotor (20) and the rotational speed of the rotating body (2). That is, the rotation detecting device (21) serves both as a conventional rotor position detecting unit and a rotational speed detecting device, and is configured as follows, for example.

The lower end surface (2a) of the rotating body (2) is shown in FIG. The lower end of the rotating body (2) is a target made of a conductive material, and a plurality (three in this example) is formed on the inner surface of the bottom wall (1a) of the housing (1) facing the lower end surface (2a). Of the rotation sensors (23), (24), and (25) are fixed. The target may be formed by fixing a conductive material to the lower end of the rotating body (2) made of a suitable material, or may be formed integrally with the lower end of the rotating body (2) made of a conductive material. Is also good. The rotation sensors (23) to (25) are arranged at equal intervals (120 °) in the circumferential direction on one circumference concentric with the rotating body (2). Each of the rotation sensors (23) to (25) outputs a signal whose magnitude changes depending on the distance from the facing surface of the rotating body (2), and for example, a known eddy current displacement sensor is used. One detected portion (26) is formed at a position corresponding to the circumference on the lower end surface (2a) of the rotating body (2). In this example, by forming a recess having a constant depth on the end face (2a),
A detected part (26) is formed, and the bottom surface of each of the rotation sensors (23)
(25a) to be detected (26a).

The drive circuit (22) controls the rotation of the motor (6) by controlling the armature current of the armature winding of the stator (19) based on the output signal of the rotation detection device (21). Is what you do.

When the rotating body (2) rotates, during one rotation,
The detected portion (26) faces the three rotation sensors (23) to (25) once each. Each of the rotation sensors (23) to (25) faces the detected surface (26a) while facing the detected portion (26); otherwise, the end surface of the rotating body (2). (2a). Since the distance from the rotation sensors (23) to (25) to the facing surface is different between when facing the detected portion (26) and at other times, During this operation, the magnitudes of the output signals of the rotation sensors (23) to (25) greatly change. FIG. 4 shows an example of changes in output signals of the three rotation sensors (23) to (25). In FIG. 4, first,
When the detected part (26) faces the first rotation sensor (23) at the time point t1, the output signal of the rotation sensor (23) greatly changes. When the detected part (26) faces the second rotation sensor (24) at the time t2 when the rotating body (2) rotates 120 ° from the time t1, the output signal of the rotation sensor (24) greatly changes. When the detected part (26) faces the third rotation sensor (25) at the time t3 when the rotating body (2) further rotates 120 ° from the time t2, the output signal of the rotation sensor (25) greatly changes. At time t4 when the rotating body (2) makes one rotation from time t1, the detected part (26) again faces the first rotation sensor (23), and the output signal of this rotation sensor (23) changes greatly again. As described above, since the output signals of the corresponding rotation sensors (23) to (25) greatly change depending on the rotation position of the rotating body (2), each rotation sensor (2) is included in the drive circuit (22).
3) Check the change in the output signal from (25) to
(2) That is, the rotational position of the rotor (20) can be detected, and the armature current of the armature winding of the stator (19) is controlled based on the rotational position of the rotor (20). , Rotor
(20) can be driven to rotate. Further, each time the rotating body (2) makes one rotation, the magnitude of the output signal of each of the rotation sensors (23) to (25) changes once, so any one of the rotation sensors in the drive circuit (22). (23) The rotation speed of the rotating body (2) can be detected based on the change in the output signal of (25),
Based on this, the rotation speed of the rotating body (2) can be controlled.

In the above embodiment, the detected portion is formed by forming a concave portion on the end face of the rotating body (2). However, the detected portion can be formed by forming a convex portion. In that case, the top surface of the convex detection portion becomes the detection surface.

FIGS. 5 to 8 show a second embodiment. FIG. 5 shows the overall schematic configuration of the magnetic bearing device, and the same parts as those in the first embodiment are denoted by the same reference numerals. FIG.
Shows an example of the electrical configuration of the brushless DC motor (30). The motor (30) is the same as in the first embodiment.
The vehicle includes a stator (19), a rotor (20), a rotation detector (31), and a drive circuit (32).

The stator (19) and the rotor (20) have the same configuration as that of the first embodiment.

The rotation detecting device (31) is for detecting the rotation position of the rotor (20) and the rotation speed of the rotating body (2), and the specific configuration thereof is the same as that of the first embodiment. The case is different. The drive circuit (32) controls the rotation of the motor (30) by controlling the armature current of the armature winding of the stator (19) based on the output signal of the rotation detection device (31). However, the specific configuration is different in the first embodiment.

The rotation detecting device (31) is configured as follows.

The rotating body (2) has the same structure as in the first embodiment, and its lower end surface (2a) is shown in FIG. A plurality (three in this example) of detected parts (33), (34), and (35) are formed on one circumference concentric with the rotating body (2) on the lower end surface (2a) of the rotating body (2). One rotation sensor (36) is fixed to the inner surface of the bottom wall (1a) of the housing (1) facing the lower end surface (2a) of the rotating body (2). The rotation sensor (36) is the same as the rotation sensors (23) to (25) of the first embodiment. Each detected part (33)-(3
5) has the same configuration as the detected portion (26) of the first embodiment, and the detected surface (33a) in which the bottom surfaces of the detected portions (33) to (35) face the rotation sensor (36), respectively. (34a) and (35a). The depth from the lower end surface (2a) of the rotating body (2) to the detected surfaces (33a) to (35a) is equal to each other for the second detected portion (34) and the third detected portion (35). , The first detected portion (33) is different from these. Therefore, when the first detected portion (33) faces the rotation sensor (36), the distance from the rotation sensor (36) to the detected surface (33a), which is the facing surface, is different from other detected portions (34). (3
5) is different from the distance from the rotation sensor (36) to the detected surfaces (34a) (35a) when the rotation sensor (36) faces the rotation sensor (36). Therefore, the output signal of the rotation sensor (36) is different between when the rotation sensor (36) faces the first detected part (33) and when the rotation sensor (36) faces the other detected parts (34) and (35). Different in size.

When the rotating body (2) rotates, during one rotation,
The three detected parts (33) to (35) are sequentially rotated once by the rotation sensor (3).
Opposite to 6). The rotation sensor (36) is a part to be detected (33) to (35)
During the time when it faces the detected surfaces (33a) to (35a), it faces the end surface (2a) of the rotating body (2) otherwise. The distance from the rotation sensor (36) to the facing surface is different between when facing the detected parts (33) to (35) and at other times, so that the detected parts (33) to (35) When opposing to (35), the magnitude of the output signal of the rotation sensor (36) changes greatly. FIG. 8 shows an example of a change in the output signal of the rotation sensor (36). In FIG. 8, first, at time t
When the first detected portion (33) faces the rotation sensor (36) in 1, the output signal of the rotation sensor (36) changes greatly. When the second detected part (34) faces the rotation sensor (36) at the time t2 when the rotating body (2) rotates 120 ° from the time t1, the output signal of the rotation sensor (36) greatly changes. When the third detected part (35) faces the rotation sensor (36) at the time t3 when the rotating body (2) further rotates 120 ° from the time t2, the output signal of the rotation sensor (36) greatly changes. At time t4 when the rotating body (2) makes one rotation from time t1, the first detected part
(33) again faces the rotation sensor (36), and the output signal of the rotation sensor (36) changes greatly again. Also, as mentioned above,
The magnitude of the output signal of the rotation sensor (36) when facing the first detected portion (33) is the output signal of the rotation sensor (36) when facing the other detected portions (34) and (35). It is different from the size of
In the drive circuit (32), the rotation position of the rotating body (2), that is, the rotor (20) is detected by examining a change in the output signal of the rotation sensor (36) with reference to the first detected portion (33). By controlling the armature current of the armature winding of the stator (19) based on the rotational position of the rotor (20), the rotor (20) can be rotationally driven. Also, each time the rotating body (2) makes one rotation, the magnitude of the output signal of the rotation sensor (36) changes three times, so that in the drive circuit (32), the output signal of the rotation sensor (36) changes. Rotating body based on
The rotation speed of (2) can be detected, and based on this, the rotation speed of the rotating body (2) can be controlled.

The distance from the rotation sensor (36) to the detection surfaces (33a) to (35a) of the detection portions (33) to (35) opposed thereto is determined by each of the detection portions (33) to (36). Can all be different.

Also in the case of the second embodiment, the detected portion can be formed by forming a convex portion on the lower end surface (2a) of the rotating body (2). Further, a part of the detected part may be formed by a concave part, and the rest may be formed by a convex part.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a magnetic bearing device according to a first embodiment of the present invention.

FIG. 2 is a bottom view of a rotating body.

FIG. 3 is a block diagram illustrating an example of an electrical configuration of a brushless DC motor.

FIG. 4 is a time chart showing an example of output signals of three rotation sensors.

FIG. 5 is a schematic longitudinal sectional view of a magnetic bearing device according to a second embodiment of the present invention.

FIG. 6 is a bottom view of the rotating body.

FIG. 7 is a block diagram illustrating an example of an electrical configuration of a brushless DC motor.

FIG. 8 is a time chart showing an example of an output signal of a rotation sensor.

[Explanation of symbols]

 (1) Housing (fixed part) (2) Rotating body (2a) Lower end face of rotating body (3) Axial magnetic bearing (4) (5) Radial magnetic bearing (6) Built-in brushless DC motor (19) Stator ( 20) Rotor (21) Rotation detector (23) (24) (25) Rotation sensor (26) Detected part (26a) Detected surface (30) Built-in brushless DC motor (31) Rotation detector (33) (34) (35) Detected part (33a) (34a) (35a) Detected surface (36) Rotation sensor

Claims (2)

[Claims] 1. A magnetic bearing device comprising: a plurality of sets of magnetic bearings for supporting a rotating body in a non-contact manner with respect to a fixed portion; and a built-in brushless DC motor for driving the rotating body to rotate. 1 concentric with the rotating body of the fixed part facing the
A plurality of rotation sensors that output a signal whose magnitude changes according to the distance from the opposing surface of the rotating body are arranged at equal intervals in the circumferential direction on one circumference, and the circumference of the end face of the rotating body is Is formed at a position corresponding to the above, and the detection of the rotation position and the number of rotations of the rotating body are performed based on the output signal of the rotation sensor. Magnetic bearing device. 2. A magnetic bearing device comprising: a plurality of sets of magnetic bearings that support a rotating body in a non-contact manner with respect to a fixed portion; and a built-in brushless DC motor that drives the rotating body to rotate. A plurality of detected portions formed of concave portions or convex portions are formed on one circumference concentric with the rotating body at equal intervals in the circumferential direction, and the circle of the fixed portion facing the end face of the rotating body is formed. At the position corresponding to the circumference, one rotation sensor that outputs a signal whose magnitude changes according to the distance from the opposing surface of the rotating body is arranged, and the rotation position of the rotating body is detected based on the output signal of the rotating sensor. A magnetic bearing device, wherein the rotation speed is detected.