JPH09182400A - Permanent magnet motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a permanent magnet motor in which a motor is integrated with a fully passive type magnetic bearing with the simple formation of a device and the simple formation of a control means to stably operate. SOLUTION: This motor is provided with a rotor 10 having a rotor magnet 9 disposed in an annular form with a magnetic pole being properly arranged in the axial direction and a stator 7 having an annular stator magnet 6 with the same magnetic pole as the rotor magnet 9 disposed opposite to the rotor magnet 9 in the axial direction and (n) sets (n>=2) of polyphase stator winding 5 for generating a rotating field. The rotor magnet 9 is constituted so as to form a pair of the strength of magnetic force of (n) sets or the existence of of the magnetic force in the circumferential direction, and therefore, a resultant rotating field generated by the stator magnet 6 and the stator winding 5 affects the rotor magnet 9 to repel the rotor 10 and to rotate it in synchronism with the rotating field.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact magnetic bearing and a motor for rotating at high speed in an environment such as a turbo molecular pump in vacuum where bearings cannot be lubricated.

[0002]

2. Description of the Related Art In a conventional magnetic bearing device, active type suction control by feedback control or a combination of partially passive type bearing and active type bearing is generally used. Also, as an all-passive magnetic bearing that does not require control,
Those using a superconducting material have been proposed.

[0003]

The drawbacks of such an active bearing are as follows. (1) The control system is complicated. (2) An exciting current is required to levitate the rotating body. (3) When a trouble such as a power failure occurs, control is lost. On the other hand, for all-passive magnetic bearings that use superconducting materials, (4) a separate system for cooling the superconducting materials is required.
The point is that the device configuration becomes large. Although some technologies for integrating the magnetic bearing and the motor have been proposed, all of them are for active control, and no technology for integrating the passive magnetic bearing and the motor has been published so far. SUMMARY OF THE INVENTION It is an object of the present invention to provide a permanent magnet motor in which an all-passive magnetic bearing and a motor are integrated so that the device configuration and the control means configuration are simple and stable operation is possible.

[0004]

The present invention has been made to solve the above problems, and the invention described in claim 1 is
A rotor having a rotor magnet arranged in an annular shape with magnetic poles aligned in the axial direction, and an annular stator magnet arranged in the rotor magnet with the same magnetic pole as the rotor magnet facing in the axial direction, and a rotating magnetic field is generated. a rotor provided with n sets (n ≧ 2) of multi-phase stator windings, and the rotor magnet forms n sets of magnetic force strength pairs or presence / absence of magnetic force in the circumferential direction. The permanent magnet motor is configured such that the combined rotating magnetic field of the stator magnet and the stator winding acts on the rotor magnet to repel the rotor and rotate in synchronization with the rotating magnetic field.

With this structure, the repulsion of the magnets between the stator and the rotor causes a bearing action in the axial direction, and at the same time, by energizing the stator windings, the same pitch is provided between the rotors. N sets of magnetic force peaks and valleys are formed, which fit into each other. Furthermore, if a rotating magnetic field is formed in the stator winding by energization, a torque for rotating the rotor is generated due to the fit between the peaks and valleys of the magnetic force. As a result, it became possible to integrate the all-passive magnetic bearing and the motor to levitate and drive the rotating body with a simple structure.

According to a second aspect of the present invention, the rotor magnet and the stator permanent magnet have mutually different diameters, and repulsive forces exert a centripetal force toward the rotor. The permanent magnet motor according to claim 1, wherein a centripetal force is always exerted on the shaft center, and a radial bearing action is also performed. The invention according to claim 3 is the permanent magnet motor according to claim 1 or 2, wherein the rotor magnet has a plurality of divided portions arranged at equal intervals in the circumferential direction. The invention according to claim 4 is the permanent magnet motor according to any one of claims 1 to 3, wherein a plurality of pairs of the rotor and the stator are provided.

[0007]

Embodiments of the present invention will be described in detail with reference to FIGS. This motor includes a rectangular or cylindrical motor frame 1, a stator housing 2 that covers both ends of the motor frame 1, and a rotating shaft 4 that passes through a center hole of the stator housing 2. Stator winding 5 and permanent magnet 6
A stator 7 composed of a rotor disk 8 on the rotating shaft 4.
A rotor 10 having a magnet 9 arranged therein is provided. Reference numeral 11 denotes an auxiliary bearing that supports the rotating shaft when it is stationary.

As shown in FIG. 3, the stator permanent magnet 6 has a uniform annular donut shape, is uniformly magnetized in the axial direction, and is fitted between the outer ring 2a and the inner ring 2b of the stator housing 2. Has been done. A surface of the stator permanent magnet 6 facing the rotor magnet 9 is called a stator magnetic pole 6a.
Is a single pole of N pole or S pole (N pole in the illustrated example). In the annular space in the vicinity of the stator magnet 6 of the stator housing 2 (the back side in this example), n sets (n phases) of multiple phases (three phases in this example) are provided.
≧ 2, four pairs in the illustrated example) of the stator windings 5 (U ₁ ,
_{U 2, U 3, U 4} , V 1, ····, W 4) have been uniformly arranged as shown in FIG. Each stator winding 5 (U ₁ ,
(U ₂ , U ₃ , U ₄ , V ₁ , ..., W ₄ ) are connected as shown in FIG. 5, and the windings of each phase are connected to the DC power supply 13 via the transistor 12. By controlling this transistor, a current as shown in FIG. 6 is supplied. In this example, the stator winding has three phases of U, V and W, but the same applies to the case of three or more phases.

On the other hand, the rotor 10 is, as shown in FIG.
A permanent magnet 9 having a shape obtained by dividing an annular ring is attached to a rotor disk 8 fitted on a rotary shaft with a single pole (N pole in the illustrated example) facing the stator magnetic pole 6a facing each other. Therefore, when the surfaces facing each other are called rotor magnetic poles 9a, the rotor magnetic poles form n sets of "presence / absence" of magnetic force along the circumferential direction. It should be noted that instead of such a divided shape, an annular magnet that is magnetized with strength in the circumferential direction may be used.

In this example, as shown in FIG. 7, the rotor magnet 9 and the stator magnet 6 are made to have different diameters (in this example, the rotor magnet is large). As a component of the homopolar repulsive force with 6, the centripetal force always acts toward the axial center. The same effect can be obtained by making the stator magnet 6 larger. Further, the magnetic pole surface can have various shapes depending on the required repulsive force. In this example, two pairs of the rotor 10 and the stator 7 as described above are provided above and below.

By making only the same poles of the permanent magnets face each other in this way, a centripetal force and an axial levitation force can always be obtained at the same time, but when stationary, the permanent magnets 6, 9 from the Earnshaw theorem.
It is not possible to raise the surface stably only. However,
When the rotor 10 rotates, it can be stably levitated by the gyro effect of the rotating body. The present invention also utilizes this principle. Since it is not possible to stably levitate when stationary, an auxiliary bearing 11 that supports it in the radial direction is required. However, if the repulsive force between the permanent magnets is sufficiently large in the axial direction, it is possible to levitate without the auxiliary bearing.

The principle of rotation of the present invention is shown in FIG. The stator magnet 6 and the rotor magnet 9 are uniformly magnetized before assembly, but when assembled, the lines of magnetic force are deformed by mutual influence of magnetic force (repulsive force), and the strength of the surrounding magnetic field is also deformed. Here, the rotor magnetic pole 9a has n sets of magnetic forces in the circumferential direction, and the magnetic force has n sets of peaks and troughs (see FIG. 8A).

The phase of the stator winding 5 (U phase in FIG. 8A) located at the valley of the rotor 10 is the stator magnetic pole 6.
When current is applied in the direction in which the magnetic force of a increases, n sets of peaks of the magnetic force due to the combined magnetic field of the stator permanent magnet 6 and the winding 5 can be formed in the stator magnetic pole 6a, and the peaks and valleys of the rotor magnetic pole 9a and the stator magnetic pole 6a. The mountains and valleys fit together, increasing the axial levitation force, and at the same time, the force for fixing in the rotational direction acts (see FIG. 8B).

When the phase to be further energized in this state is switched from the U phase to the V phase, as shown in FIG.
a and the magnetic poles of the magnetic poles of the rotor 9a deviate from each other, and the repulsive force increases the axial levitation force, and at the same time, a rotational force, that is, torque is generated in the rotor 7, and the magnetic force peaks and valleys meet at the next position. Rotate until it reaches a stable position.
Therefore, if the phases to be energized are sequentially switched as shown in FIG. 6, the rotor 7 rotates continuously, and by rotating, the gyro effect of the rotating body stabilizes the rotor 7 in both radial and axial directions. To surface. As a result, the auxiliary bearing 11 becomes unnecessary when the rotational speed exceeds a certain value.

This motor is a synchronous motor in principle because the rotation of the rotor 10 is synchronized with the switching of the energization of the stator winding 5. Therefore, smooth rotation can be achieved by detecting the position angle of the rotor 10 and switching the energization switching timing. As a means for detecting the position angle of such a rotor, it is possible to use a sensor such as a hall element or a counter electromotive voltage waveform generated by rotation between non-energized phase terminals, as in the case of a general brushless DC motor.

However, in the motor of this method, even if the energization timing and the rotation of the rotor are out of synchronization without being synchronized, the motor falls into the next peak of the magnetic force. It will not immediately stall and stop. Therefore, as an energizing method, it is possible to start the rotation without detecting the position angle of the rotor like the inverter of the induction machine.

[0017]

The present invention integrates a motor with an all-passive magnetic bearing that uses normal magnets and uses permanent magnets. (1) No special control other than driving the motor is required. Therefore, even if a power failure occurs, the rotating body will remain floating and will not be damaged due to being out of control unlike the conventional active control. (2) The repulsive force of the permanent magnet is used, so that the levitation force can be applied to the rotating body even when the rotating body is not energized, and the exciting current for attracting and floating the rotating body unlike the conventional active control is unnecessary. Is. (3) Since no superconducting material is used, no cooling device is required. (4) The all-passive magnetic bearing and the motor are integrated so that the rotating body can be levitated and driven with a simple structure.

Further, the bearing of the present invention is not only suitable for a device that rotates at a high speed in a vacuum (eg, turbo molecular pump) as an application of the present motor, but also supports a rotating body which is usually required as a feature of the present motor. Can be applied to various rotating machines because it is simple and can be used.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of an embodiment of the present invention.

FIG. 2 is a view taken in the direction of arrows II-II in FIG.

FIG. 3 is a view taken in the direction of arrows III-III in FIG. 1;

FIG. 4 is a view taken in the direction of arrows IV-IV in FIG. 1;

FIG. 5 is a connection diagram of the embodiment of FIG.

FIG. 6 is a graph showing a current flowing through each phase of FIG.

7 is a diagram showing the axial force on the rotor of the embodiment of FIG.

FIG. 8 is a schematic diagram illustrating the operation of the embodiment of FIG.

[Explanation of symbols]

 5 Stator winding 6 Stator magnet 7 Stator 9 Rotor magnet 10 Rotor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noboru Aoki 4-2-1 Motofujisawa, Fujisawa-shi, Kanagawa Inside the EBARA Research Institute, Inc. (72) Inventor Shizaburo Shibayama 4-2-1, Fujisawa, Kanagawa No. 1 Stock company Ebara Research Institute

Claims (4)

[Claims] 1. A rotor having a rotor magnet arranged in a ring shape with magnetic poles aligned in the axial direction, and an annular stator magnet arranged in the rotor magnet such that the rotor magnet and the same magnetic pole face each other in the axial direction. A rotor provided with n sets (n ≧ 2) of multi-phase stator windings that generate a rotating magnetic field, and the rotor magnet has n sets of magnetic force strengths or presence / absence of magnetic force in the circumferential direction. The composite rotating magnetic field of the stator magnet and the stator winding acts on the rotor magnet to repel the rotor and rotate in synchronization with the rotating magnetic field. And a permanent magnet motor. 2. The rotor magnet and the permanent magnet of the stator have different diameters in mutually facing portions, and centripetal force toward the axial center is applied to the rotor by mutual repulsive force. Permanent magnet motor. 3. The rotor magnet according to claim 1, wherein a plurality of divided portions are arranged at equal intervals in the circumferential direction.
A permanent magnet motor according to claim 1. 4. The permanent magnet motor according to claim 1, wherein a plurality of pairs of the rotor and the stator are provided.