JPH04255453A - Electromagnetic actuator - Google Patents

Abstract

PURPOSE:To obtain a miniature dust-free, lubrication-free actuator having high positioning accuracy by integrating a thrust bearing and a step motor and supporting a rotary shaft with no contact in combination with a radial bearing. CONSTITUTION:Eight electromagnets 13-20, arranged radially with same circumferential interval on the stator B side at a driving section 7, support a rotary shaft 6 without contacting while keeping a constant gap between the electromagnets and a disc 24. When four sets of every other electromagnets 13 and 15, 17 and 19, 14 and 16, 18 and 20 are combined and excited with pulse signals, ring type teeth 21, 22 mutually shifted by single pitch are attracted and rotary force is generated thus performing the positioning. Position holding force is generated from the permanent magnet 23 of the disc 24 and the flux thereof also functions as bias flux for linearizing the magnetic bearing control system.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic actuator that can be used in special environments where dust generation and lubrication are problematic (space, vacuum, clean room, liquid).

0002

2. Description of the Related Art In order to maintain a high degree of cleanliness in, for example, semiconductor manufacturing processes, the following measures are required for robots used in clean rooms.

(1) Adopts low dust generation and no dust generation mechanism,
Eliminate, delete, or replace dust-generating elements.

(2) Incorporating a dustproof mechanism to prevent internally generated particles from flowing out and dispersing.

(3) Improve reliability and maintainability, and aim for maintenance-free operation.

[0006] Specific methods for the above countermeasures include the following methods.

(1) Internal negative pressure suction. That is, the inside of the robot is made to have a negative pressure, and a flow of air is always created inward to prevent dust from flowing out through the part that opens to the outside.

(2) Magnetic fluid seal. That is, the magnetic fluid completely separates the inside and outside of the robot to prevent dust from dispersing from inside. In FIG. 8, a magnetic pole 2 magnetized by a magnet 1 provided on the inner circumference of a casing 5
A magnetic fluid 4 is held in a ring shape between the rotary shaft 3 and the rotating shaft 3 made of magnetic material to obtain a sealing effect.

(3) AC servo motor. That is,
Since there are no brushes, the motor itself generates less dust than conventional DC servo motors and requires less maintenance.

0010

[Problems to be Solved by the Invention] Under special environments such as space, vacuum, clean rooms, and liquids, there are problems such as dust generation from the contact portion of the actuator and the need for lubrication of the bearing portion. For example, in the semiconductor manufacturing field, LSI
As manufacturing technology becomes more highly integrated, highly clean manufacturing environments and equipment are required. For this reason, unmanned manufacturing processes are currently underway, but this poses problems such as dust generation from inside the robots used and maintenance of parts that require lubrication. Currently, in order to deal with these problems, countermeasures such as providing the above-mentioned dust prevention mechanism in the motor section of the robot, which is a source of dust generation, are being taken, but the effects are insufficient.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a dust-free and lubrication-free electromagnetic actuator that is small, has good positioning accuracy, and does not require measures such as providing a dust-proof mechanism. The purpose is

0012

[Means for Solving the Problems] According to the present invention, a rotary electromagnetic actuator is constructed of at least one radial magnetic bearing and one thrust magnetic bearing, and in which a rotor is supported in a non-contact manner. , the thrust magnetic bearing has a motor/radial magnetic bearing part whose magnetic pole is common to the motor magnetic pole, and the bearing part includes eight electromagnets and a disk having two ring-shaped teeth arranged one pitch apart from each other on the surface thereof. The magnetic poles of the eight electromagnets have teeth with radially adjacent magnetic poles shifted by a half pitch, and the eight electromagnets are excited based on a signal from a displacement sensor that detects a gap in the rotation axis direction. to keep the gap in the direction of the rotational axis constant, and
The eight electromagnets are excited by pulse signals to position them in the rotational direction, and a bias magnetic flux for linearizing the magnetic bearing control system is formed in the eight electromagnets, and the magnetic flux is also used as a rotational holding force. The magnetic force of the eight electromagnets is independently excited based on a signal that detects the inclination of the rotor, thereby controlling the inclination of the rotor.

[0013]

[Operation] In the electromagnetic actuator configured as described above, the rotor, that is, the rotating shaft, is supported by magnetic bearings in a non-contact manner, so there is no dust generation, no lubrication is required, and there is no possibility of contamination in the atmosphere. Also, no maintenance is required. Furthermore, the bearing section, that is, the driving section, which integrates the thrust bearing and the stepping motor, enables highly accurate positioning in the rotational direction, and is compact and suitable for use in special environments.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings.

In FIG. 1, in the center of the electromagnetic actuator according to the present invention, a driving section 7 consisting of a stepping motor and a thrust magnetic bearing is provided, and on both sides of the driving section 7 in the direction of the thrust axis, radial magnetic bearings 8, 9 is provided. Further, displacement sensors 10 and 11 and displacement sensors 12 and 13 are provided to detect gaps in the radial axis direction and the thrust axis direction. And rotor A
That is, the rotating shaft 6 is supported in a non-contact manner by magnetic bearings 8 and 9, and is positioned in the rotational direction by a stepping motor of the drive unit 7.

In FIGS. 2 to 4, the electromagnets on the stator B side of the drive unit 7 are composed of eight electromagnets 13 to 20 arranged radially at equal intervals around the circumference, and each electromagnet independently controls the magnetic force. It is now possible to do so. On the surface of the rotating shaft 6 on the rotor A side, a disk 2 is provided with two ring-shaped teeth 21 and 22 facing the electromagnets 13 to 20 and a permanent magnet 23.
4 is provided. The teeth 21 and 22 are shifted from each other by one pitch. On the other hand, the magnetic poles of the electromagnets 13 to 20 are formed with a plurality of (four in the illustrated example) teeth 25 and 26 that are opposed to the teeth 21 and 22, respectively.
5 and 26 are adjacent magnetic poles in the circumferential direction and are shifted by half a pitch from each other. The electromagnets 13 to 20 maintain a constant gap between the electromagnets and the disk 24, and support the rotating shaft 6 in a non-contact manner. In addition, 8 electromagnets 13 to 20
Among them, every other four sets of electromagnets 13 and 15, 17 and 19, 14 and 16, 18 and 20 are combined and excited with a pulse signal to generate the teeth 2 on the surface of the disk 24.
1 and 22, and generates rotational force for positioning. This position holding force is the disc 2
The magnetic flux generated by the permanent magnet 23 of No. 4 also acts as a bias magnetic flux to linearize the magnetic bearing control system.

In FIG. 5, for example, opposing electromagnets 13
~20 magnetic poles 51, 51' include electromagnetic coils 37, 38 for magnetic bearings and stepping motor coils 39, 4.
0, 41, and 42 are wound. The electromagnetic coils 37 and 38 are connected to a magnetic bearing control circuit 44 via a drive circuit 45 and a detection circuit 63.
A displacement sensor 12 that detects a gap in the thrust axis direction is connected via a sensor amplifier 43 to the displacement sensor 12 . The magnetic bearing control circuit 44 controls the magnetic force of the electromagnetic coils 37 and 38 via the drive circuit 45 based on the feedback signal from the displacement sensor 12, and supports the rotating shaft 6 in a non-contact manner. .

The stepping motor coils 39 to 4
1 is a four-phase stepping motor control circuit in an open loop system in which electromagnet magnetic poles 51 and 55, 52 and 56, 53 and 57, 54 and 58 are combined, and are connected through first to fourth drive circuits 47 to 50, respectively. 46. Then, this control circuit 46 firstly controls the first drive circuit 4
The third drive circuit 49 excites the electromagnet magnetic poles 51 and 55, and the third drive circuit 49 excites the electromagnet magnetic poles 53 and 57.
7) generates a closed-loop magnetic flux to generate rotational force, and then the second drive circuit 48 generates a closed-loop magnetic flux to generate rotational force.
, and the fourth drive circuit 50 excites the electromagnet magnetic poles 54 and 58 to similarly obtain rotational force.

Next, the operation will be explained with reference to FIGS. 6 and 7.

In FIG. 6, the outer tooth 2 of the disk 24
1, a gap G is provided between the electromagnet magnetic poles 51 and 5.
2, 53 are opposed, and their four teeth 25-2
5 are shifted by a half pitch from each other, and therefore, in the illustrated state, the pair of electromagnet magnetic poles 51 and 53 are shifted by a half pitch from the teeth 21.

The tooth 21 of the disk 24 becomes the north pole due to the permanent magnet 23, and the magnetic flux 29 constantly flows in the direction of the arrow.In contrast, when the magnetic flux 31 is caused to flow as shown in the figure at the electromagnet magnetic poles 51 and 53, the electromagnet magnetic pole 51 The magnetic flux of the side gap G is
The magnetic fluxes 31 and 29 increase as a sum, and the magnetic flux in the gap G on the other electromagnet magnetic pole 53 side decreases as the difference between the magnetic fluxes 31 and 29.

As a result, a torque T is generated in the direction of the arrow,
The rotating shaft 6 is rotated.

In FIG. 7, similar to FIG. 6, torque T is generated and the rotating shaft 6 is rotated.

FIG. 9 shows magnetic bearing control means for controlling the inclination of the rotor 6. As shown in FIG. The control means is as described in 8 above.
It takes advantage of the fact that each electromagnet can be excited independently. First, the inclination of the rotor is detected from the differential signal of displacement sensors 59 and 60 (radial direction gap detector),
Based on the signal, the electromagnets 61 and 62 are excited via a magnetic bearing control circuit and a drive circuit to correct the inclination θ when the rotor is tilted from Z to Z' axis, for example. By adding this control means to the control device of FIG. 5, a system that can also control the tilt can be constructed.

[0025]

[Effects of the Invention] Since the present invention is constructed as described above, the thrust bearing and the stepping motor are integrated, and combined with the radial bearing, the rotating shaft is supported without contact, and rotational positioning is performed. , it is possible to provide an actuator that is small, has good positioning accuracy, and is dust-free and lubrication-free.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing one embodiment of the present invention.

FIG. 2 is a side sectional view showing a half part of the drive section.

FIG. 3 is a view of the electromagnet in the direction of arrow H.

FIG. 4 is a view of the disk in the direction of arrow D.

FIG. 5 is a block diagram of a control device.

FIG. 6 is a developed view of the teeth on the outer circumferential side showing the principle of generating rotational force.

FIG. 7 is a developed view of the teeth on the inner peripheral side showing the principle of generating rotational force.

FIG. 8 is a perspective view showing an example of a conventional dustproof mechanism.

FIG. 9 is a block diagram showing magnetic bearing control means for controlling the tilt of the rotor.

[Explanation of symbols]

A... Rotor B... Stator G... Gap 6... Rotating shaft 7... Drive section 8, 9... Radial magnetic bearings 10 to 13, 59, 60... Displacement sensor 13-20,
61, 62... Electromagnets 21, 22... Teeth 23... Permanent magnets 25, 26... Teeth 29... Magnetic flux of permanent magnets 31... Magnetic flux of electromagnets 44... Magnetic bearing control circuit 46...Stepping motor control circuit 51-58...
・Electromagnet magnetic pole 63...detection circuit

Claims (2)

[Claims] Claim 1: A rotary electromagnetic actuator comprising at least one radial magnetic bearing and one thrust magnetic bearing, in which a rotor is supported in a non-contact manner,
The thrust magnetic bearing has a motor/radial magnetic bearing part whose magnetic pole is common to the motor magnetic pole, and the bearing part is composed of eight electromagnets and a disk having two ring-shaped teeth mutually shifted by one pitch on the surface. The magnetic poles of the eight electromagnets have teeth that are shifted by half a pitch from the radially adjacent magnetic poles, and the eight electromagnets are each excited based on a signal from a sensor that detects a gap in the direction of the rotation axis. At the same time, the eight electromagnets are excited by a pulse signal to maintain a constant gap in the direction of the rotational axis, and the eight electromagnets are positioned in the rotational direction, and a bias magnetic flux is applied to the eight electromagnets to linearize the magnetic bearing control system. An electromagnetic actuator characterized in that the magnetic flux acts as a rotation holding force. 2. The electromagnetic actuator according to claim 1, wherein the eight electromagnets are independently excited based on a signal that detects the inclination of the rotor to control the inclination of the rotor.