JP3132773B2 - Electromagnetic actuator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art For example, in a semiconductor manufacturing process, the following measures are required for a robot used in a clean room in order to maintain high cleanliness.

(1) A dust-producing element is removed, deleted, or replaced by adopting a low-dust-generating and non-dust-generating mechanism.

(2) Incorporation of a dustproof mechanism to prevent outflow and diffusion of internally generated particles.

(3) Improve reliability and maintainability and make maintenance free.

[0006] As a specific method of the above measures, there is the following method.

(1) Internal negative pressure suction. That is, the inside of the robot is negatively pressurized, and a flow of air toward the inside is always formed so that dust does not flow out through the portion opened to the outside.

(2) Magnetic fluid seal. That is, the inside of the robot and the outside are completely separated by the magnetic fluid, and the diffusion of dust from the inside is prevented. In FIG. 9, a magnetic fluid 36 is held in a ring shape between a magnetic pole 34 magnetized by a magnet 33 provided on the inner periphery of a casing 37 and a rotating shaft 35 of a magnetic material to obtain a sealing effect.

(3) AC servo motor. That is, since there is no brush, dust generation is reduced and maintenance is free as compared with the conventional DC servo motor.

[0010]

In a special environment such as space, in a vacuum, in a clean room, or in a liquid, there are problems such as dust generation from the contact portion of the actuator and lubrication of the bearing portion. For example, in the semiconductor manufacturing field, LSI
As the degree of integration increases, manufacturing environments and devices with high cleanliness are required. For this reason, at present, unmanned manufacturing processes are being promoted, but there are problems such as dust generation from the inside of the robot used and maintenance of parts requiring lubrication. At present, in order to cope with these problems, countermeasures such as providing the above-described dustproof mechanism in the motor unit of the robot serving as a dust generation source are taken, but the effect is insufficient.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and it is an object of the present invention to provide a small-size, dust-free, lubrication-free electromagnetic actuator which does not require any measures such as providing a dust-proof mechanism. The purpose is.

[0012]

According to the present invention, there is provided a rotary electromagnetic actuator comprising at least one radial magnetic bearing and one thrust magnetic bearing, wherein a rotary shaft is supported in a non-contact manner. The magnetic pole of the thrust magnetic bearing is provided with a stepping motor and a thrust magnetic bearing common to a stepping motor magnetic pole, and the stepping motor and the thrust magnetic bearing are provided at the center to constitute a drive unit, and the stepping motor and the thrust The magnetic bearing is composed of three or more concentric electromagnets and a disk having radial teeth on the surface, and the magnetic poles of the three or more electromagnets have teeth whose adjacent magnetic poles are shifted in pitch, and the magnetic poles in the direction of the rotation axis. Based on a sensor for detecting the gap and a signal from the sensor, the three or more electromagnets are excited to keep the gap in the rotation axis direction constant. A magnetic bearing control circuit, wherein the magnetic bearing control circuit changes the magnetic pole width stepwise so that the surface areas of the magnetic poles of the three or more electromagnets are equal, and sequentially excites the three or more electromagnets by a pulse signal. In this way, the motor has a function of performing positioning in the rotation direction and controlling the directions of magnetic fluxes generated by the three or more electromagnets so that adjacent magnetic poles always have the same polarity.

[0013]

In the electromagnetic actuator constructed as described above, the rotor, that is, the rotating shaft is supported in a non-contact manner by the magnetic bearing, so that no dust is generated, no lubrication is required, and the atmosphere is contaminated. No maintenance is required. Further, the bearing in which the thrust bearing and the stepping motor are integrated with each other, that is, the drive unit, enables high-precision positioning in the rotation direction, and is compact and can be suitably used in a special environment.

[0014]

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

In FIG. 1, a drive unit 2 comprising a stepping motor and a thrust magnetic bearing is provided at the center of the electromagnetic actuator according to the present invention, and radial magnetic bearings 3, 4 are provided. Further, displacement sensors 5 and 6 and displacement sensors 7 and 7 for detecting gaps in the radial axis direction and the thrust axis direction are provided. The rotor, that is, the rotating shaft 1 is supported in a non-contact manner by the magnetic bearings 3 and 4 and the drive unit 2, and the stepping motor of the drive unit 2 is used to position the rotor in the rotation direction.

In FIG. 2 to FIG. 5, the electromagnet on the stator side of the drive unit 2 is composed of three concentric electromagnets 8, 9 and 10, and each of the electromagnets 8 to 10 can control the magnetic force independently. Has become. The magnetic poles of these electromagnets 8 to 10 include:
The teeth 14, 15 and 16 with radially shifted pitches are respectively formed (half pitch shifted in the example shown), while the radial teeth 13 are provided on the rotating shaft 1 on the rotor side.
Is provided.

The electromagnets 8 to 10 maintain a constant gap in the thrust axis direction, support the rotating shaft 1 in a non-contact manner, and sequentially excite the teeth 14 to 6 radially shifted in pitch to form a disk. The radial teeth 13 on the surface of the surface 13 are sucked to generate a rotational force and to perform positioning. This position holding force is generated by the bias magnetic flux 17 for linearizing the magnetic bearing control system. Also, this magnetic flux 1
The direction of 7 is such that the magnetic flux generated by the electromagnets 8 to 10 is always the same at adjacent magnetic poles.

In FIG. 6, the control device is provided with a magnetic bearing control circuit 19 and a stepping motor control circuit 29.

Electromagnets 8, 9, and 10 are connected to the magnetic bearing control circuit 19 through detection circuits 20, 21, and 22 and drive circuits 23, 24, and 25, respectively. Based on the feedback signal from the sensor 7, the drive circuits 23, 24, 25 excite the electromagnets 8, 9, 10 via the detection circuits 20, 21, 22 to support the rotating shaft 1 in a non-contact manner.

The stepping motor control circuit 29
Is composed of an open-loop three-phase circuit, which inputs pulse signals of each phase to drive circuits 23, 24, and 25, excites electromagnets 8, 9, and 10, and performs rotational positioning. Alternatively, a closed loop system can be configured by detecting the rotational position by an encoder (not shown) and feeding it back to the stepping motor control circuit.

FIG. 7 shows another embodiment of the present invention, in which the widths of the magnetic poles of the three electromagnets 8a, 9a, and 10a of the drive unit 2a are increased so that the magnetic pole areas of the magnetic poles are equal. This is an example in which the configuration is changed step by step, and the other components are configured in the same manner as in FIG. In this embodiment, there is an effect that the rotational torque generated by each of the electromagnets 8a to 10a is made uniform, and that uneven rotation can be avoided. FIG. 8 shows another embodiment of the present invention.
This is an example in which the 0 teeth 14 to 16 are shifted not by a half pitch (see FIG. 3) but by, for example, 0.25 pitch, and the other components are configured in the same manner as FIGS. 1, 2, 3 to 6 and FIG. In this embodiment, the positioning accuracy can be further improved.

[0022]

Since the present invention is constructed as described above, the thrust bearing and the stepping motor are integrated, the rotating shaft is supported in a non-contact manner in combination with the radial bearing, and the rotational positioning is performed. In addition, it is possible to provide a compact, high-accuracy positioning, non-dusting, and non-lubricating actuator.

[Brief description of the drawings]

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

FIG. 2 is a side sectional view showing a driving unit.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a sectional view taken along line BB of FIG. 2;

FIG. 5 is a side view showing the disk.

FIG. 6 is a block diagram showing a control device.

FIG. 7 is a side sectional view showing another embodiment of the present invention.

FIG. 8 is a view corresponding to FIG. 3, showing another embodiment of the present invention.

FIG. 9 is a perspective view showing an example of a conventional dustproof mechanism.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Rotating shaft 2, 2a ... Driving part 3, 4 ... Radial magnetic bearing 5-7 ... Displacement sensor 8-10 ... Electromagnet 11 ... Disk 13 ... Disk teeth 14-16: teeth of electromagnet poles 17: bias magnetic flux 19: magnetic bearing control circuit 20-22: detection circuit 23-25: drive circuit 29: stepping motor control circuit 33 ..Magnet 34 ・ ・ ・ Magnetic pole 35 ・ ・ ・ Rotating shaft 36 ・ ・ ・ Magnetic fluid 37 ・ ・ ・ Casing

Continued on the front page (72) Inventor Genichi Sato 11-1, Haneda Asahimachi, Ota-ku, Tokyo Inside Ebara Works Co., Ltd. (72) Inventor Masao Yongdai 11-1, Haneda Asahi-cho, Ota-ku, Tokyo Stock Association In-house EBARA CORPORATION (56) References JP-A-47-43635 (JP, A) JP-A-63-99742 (JP, A) JP-A-63-69442 (JP, A) Jpn. , U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) H02K 37/24 H02K 7/09

Claims (1)

(57) [Claims] 1. At least one radial magnetic bearing and one
In the case of a rotary electromagnetic actuator that is composed of three thrust magnetic bearings and the rotating shaft is supported in a non-contact manner,
The magnetic pole of the thrust magnetic bearing is provided with a stepping motor and a thrust magnetic bearing in common with a stepping motor magnetic pole, and the stepping motor and the thrust magnetic bearing are provided at the center to constitute a drive unit, and the stepping motor and the thrust magnetic The bearing consists of three or more concentric electromagnets and a disk with radial teeth on the surface, and the magnetic poles of the three or more electromagnets have teeth whose adjacent magnetic poles are shifted in pitch, and have a gap in the rotation axis direction. And a magnetic bearing control circuit that excites the three or more electromagnets based on a signal from the sensor to maintain a constant gap in the rotation axis direction. The magnetic pole width is changed stepwise so that the surface areas of the magnetic poles of the three or more electromagnets become equal, and the three or more electromagnets are sequentially excited by a pulse signal to rotate in the direction of rotation. Positioning is performed, the electromagnetic actuator, characterized in that it has always function of controlling so that homopolar the direction of the magnetic flux generated by the said three or more electromagnets in adjacent magnetic poles.