JPH01260301A - Position detector for magnetic bearing - Google Patents

Abstract

PURPOSE:To detect the floating position of a rotor noncontactingly, by detecting a change in magnetic resistance generated by the movement of the rotor in the radial direction thereof by a Hall element. CONSTITUTION:The magnetic flux 511 forms a magnetic circuit A directly passing through a Hall element 521 from a yoke 501 to a return to the perma nent magnet 511 through a yoke 505 and a magnetic circuit B passing through an aluminum case 7 from the yoke 501 to reach a magnetic ring 12 and again passing through the aluminum case 7 to return to the yoke 505. The Hall ele ment 521 outputs the voltage corresponding to the magnetic flux passing through the magnetic circuit A. That is, the magnitude of magnetic resistance can be detected according to the size of the gap delta between the magnetic ring 12 and the aluminum case 7 by the Hall element 521. By controlling electromagnets 3, 4 for a magnetic bearing on the basis of the detection output, the gap deltacan be kept at a predetermined value.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a position detection device for a magnetic bearing. The present invention relates to a magnetic bearing position detection device that detects the position of magnetic levitation in a non-contact manner.

[Prior Art] A turbo-molecular pump has several or several stages of turbine blades attached to a spindle shaft supported by rolling bearings, and is rotated at a constant rpm to obtain an ultra-high vacuum.

Such turbomolecular pumps have recently come to be used in semiconductor manufacturing equipment. In this application, it is necessary to flow various trace gases to treat the surface of the semiconductor sea urchin 11, and therefore a pump that can operate under a wide range of vacuum conditions from medium vacuum to high vacuum is required.

FIG. 5 is a sectional view showing an example of a recent turbo-molecular pump, and FIG. 6 is a diagram showing an example of a position sensor built into the turbo-molecular pump.

First, a turbo molecular pump will be explained with reference to FIGS. 5 and 6. In FIG. 5, the turbomolecular pump is covered with a case, and this case includes an inner case 31.
, a lower outer case 32 and an upper outer case 33. The inner case 31 is formed as a hollow interior with closed upper and lower ends, and a flange 34 is formed in the middle outer periphery of the peripheral wall and a wiring passage 35 is formed in the lower part.

Inside the inner case 31 are a spindle shaft 36 and an upper radial magnetic bearing 37 that supports the spindle shaft 36.
Lower radial magnetic bearing 38. a thrust magnetic bearing 39;
Upper radial magnetic bearing 37° Lower radial magnetic bearing 38
Radial position sensors 40 and 41 for detecting the position of magnetic levitation by the spindle shaft 36 and a motor 42 for rotating the spindle shaft 36 are housed. Furthermore, emergency dry bearings 43 and 44 are attached to the upper and lower ends of the inner case 31, and thrust magnetic bearings 3 are attached to the lower part of the inner case 31.
A thrust position sensor 45 is provided for detecting the position of magnetic levitation by 9.

A fin rotor 47 having moving blades 46 on its outer periphery is detachably fixed to the upper end of the spindle shaft 36 protruding from the inner case 31, and a low vacuum is generated on the outer periphery of the cylindrical portion 48 of the fin rotor 47. A thread groove 49 is provided for this purpose.

The lower outer case 32 is formed on the upper opening into which the lower half of the inner case 31 fits, and has a power introduction terminal 50 at the lower part of the peripheral wall.
and a non-reactive gas introduction hole 51 are provided. The exhaust hole 52 provided in the upper part of the peripheral wall is connected to the flange 3 of the inner case 31.
4, and an exhaust port flange 54 is provided on the outside.

Inside the lower outer case 32, a space 55 connected to the power introduction part and the exhaust hole 52 are installed between the fitting surfaces of the inner case 31 and the lower outer case 32 so as to fit externally into the inner case 31. It is sealed by an O-ring 56. The non-reactive gas supplied into the space 55 from the introduction hole 51 flows into the inside of the inner case 31 from the passage hole 57 provided at the lower part of the inner case 31 and the wiring passage 35 and fills the inside of the inner case 31. The non-reactive gas flowing out through the gap of the upper dry bearing 43 passes through the cylindrical part 48 of the fin rotor 47 and the annular space of the inner case 31, and flows into the cylindrical part 48.
The air flows out into the exhaust hole 52 through a constriction portion 58 provided at the lower end of the exhaust hole 52 .

Although the above-mentioned constricted portion 58 is effective by reducing the diameter of the inner diameter portion of the lower end of the cylindrical portion 48, it can also be constructed by increasing the outer diameter portion of the inner case 31. .

The upper outer case 33 is formed into a cylindrical shape, and its lower end is externally fitted into the cylindrical wall 32a on the lower outer case 32, and this fitting portion is
It is sealed with a ring 59, and the rotor blade 4 is provided on the inner peripheral surface.
A stator blade 60 facing the stator blade 6 and a stator 61 facing the thread groove 49 are attached. A ring-shaped notch 6 is formed in the fin rotor 47 at the attachment part to the spindle shaft 36.
2 is provided. This notch 62 is the fin rotor 47
This is provided to prevent a centrifugal force from acting on the fin rotor 47 due to the rotation of the fin rotor 47, which causes the fin rotor mounting portion to expand and a gap from forming in the taper portion. An appropriate radius is provided to alleviate stress concentration.

[Problems to be Solved by the Invention] The radial position sensor 40 shown in FIG. 5 needs to detect displacement of the rotation axis of the spindle shaft 36 in a non-contact manner. For this purpose, a sixth radial position sensor 40 is used.
An eddy current position detection device 400 as shown in the figure is used. This eddy current position detection device 400 is constructed by winding an insulated thin copper wire 401 around a resin core several times to several thousand times in a ring shape to form a coil, and molding the outer periphery of the coil with resin. However, if such an eddy current position detection device 400 is used in a high vacuum, there is a risk that gas or the like will be generated from the mold resin. For this reason, it is necessary to take measures such as covering the coil with a stainless steel vibrator. However, when the coil is coated with a stainless steel vibrator, the whole becomes thicker, and in order to make it thinner, the number of turns of the coil must be reduced. However, when the number of turns of the coil is reduced, the coil current increases for a constant load, so there has been a problem that the load capacity of the magnetic bearing becomes small when the power supply capacity is constant.

Therefore, the main object of the present invention is to provide a position detection device for a magnetic bearing that can detect the position of magnetic levitation by using changes in magnetic flux density of a magnetic loop made by permanent magnets, without using eddy currents. It is.

[Specific means for solving the problem] The invention according to claim 1 provides a spindle whose outer diameter surface is covered with an insulating member for sealing, and which rotates around a fixed axis of a spindle equipped with an electromagnet. A magnetic bearing position detection device for magnetically supporting a rotor made of a magnetic material, for non-contact detection of the gap between the magnetically supported rotor and a fixed spindle shaft. a pair of yokes that are arranged to face each other with a predetermined gap;
Consists of a permanent magnet installed in the gap between the yoke and the spindle axis center, and a Hall element installed in the gap between the yoke and the rotor side to detect changes in magnetic resistance caused by changes in the gap between the rotor and the rotor axis. .

The invention according to claim 2 is a spindle housing whose inner diameter surface is covered with a sealing insulating member and which magnetically supports a rotor made of a magnetic material rotating inside the spindle housing, which is equipped with an electromagnet. A magnetic bearing position detection device for non-contact detection of a gap between a rotor and a housing due to magnetic support, comprising a pair of magnetic bearings fixed to the housing and facing each other with a predetermined gap. a permanent magnet provided on the side of the yoke far from the rotor, and a Hall element provided in the gap between the yoke and the rotor side for detecting a change in magnetic resistance caused by a change in the gap between the rotor and the housing. configured.

[Function] The position detection device for a magnetic bearing according to the invention of claims 1 and 2 rotates with an outer rotor or an inner rotor, and the magnetic flux generated by the permanent magnet provided in the yoke is transmitted between the yoke and the rotor. The change in magnetic resistance caused by the radial movement of the rotor is detected by the Hall element.
The floating position of the rotor can be detected without contact.

[Embodiment of the Invention] FIG. 1 is a sectional view of a main part of a vacuum spindle to which an embodiment of the invention is applied.

First, with reference to FIG. 1, the structure of a vacuum spindle to which an embodiment of the present invention is applied will be described. A spindle shaft 1 made of a non-magnetic material is attached to a base 14. A motor electromagnet 2 for rotating the outer rotor 8 is provided approximately at the center of the spindle shaft 1, and magnetic bearing electromagnets 3.4 for magnetically levitating the outer rotor 8 are provided on both sides of the motor electromagnet 2. At the same time, a sensor 5.6 is provided for detecting a gap between the outer rotor 8 and the spindle shaft. Electromagnets for these motors2. Magnetic bearing electromagnet 3゜4 and sensor 5,
6 is covered with an aluminum case 7. One end of the aluminum case 7 is fixed to the base 14.

Note that the interior of the aluminum case 7 is on the atmospheric pressure side.

The outer rotor 8 rotates around the aluminum case 7 while being magnetically levitated. Electromagnet for motor of outer rotor 8 2. A motor rotor 9 is provided on the inner surface facing each of the magnetic bearing electromagnet 3. Magnetic bearing rotor parts 10 and 11 and magnetic rings 12 and 13 are arranged.

In the vacuum spindle configured as described above, the outer rotor 8 is rotated by the driving force of the motor electromagnet 2 while being magnetically levitated by the magnetic bearing electromagnet 3.4, and the gap between the outer rotor 8 and the spindle shaft is detected by the sensors 5 and 6. The electromagnetic force of the magnetic bearing electromagnets 3 and 4 is controlled by a control circuit (not shown).

FIG. 2 is a sectional view taken along the line -H shown in FIG. 1, and FIG. 3 is an enlarged view of the main parts of the sensor.

Next, a sensor according to an embodiment of the present invention will be described with reference to FIGS. 2 and 3. The sensor 5 includes yokes 501 to 508 divided into four in the circumferential direction, and each of the yokes 501 to 504 and the yokes 505 to 508 are arranged facing each other with a predetermined gap in the axial direction. That is,
yoke 505 for yoke 501. yoke 506 for yoke 502 . Yoke 507 against yoke 503
The yoke 508 is arranged to face the yoke 504, and each form a pair. These yokes 501 to 508 are attached to and integrated with an insulating member 530 and fixed to the spindle shaft 1. York 501-5
Permanent magnets 511 to 514 are attached to the gaps on the spindle shaft 1 side of each of 08, and Hall elements 521 to 524 are attached to the gaps between the yokes on the magnetic ring 12 side.

In the sensor 5 configured as described above, for example, the magnetic flux generated by the permanent magnet 511 passes directly from the yoke 501 to the Hall element 521 and then to the permanent magnet 5 via the yoke 505.
01, and a magnetic circuit B that passes from the yoke 501, passes through the aluminum case 7, reaches the magnetic ring 12, passes through the aluminum case 7 again, and returns to the yoke 505. Then, the Hall element 521 outputs a voltage according to the magnetic flux passing through the magnetic circuit A. Now, when the distance δ between the magnetic ring 12 and the aluminum case 7 is large, more of the magnetic flux generated by the permanent magnet 511 passes through the magnetic circuit A, and the output voltage of the Hall element 521 increases. Conversely, when the interval δ is small, the magnetic flux passing through the magnetic circuit B increases, and the output voltage of the Hall element 521 becomes small.

That is, depending on the size of the distance δ between the magnetic ring 12 and the aluminum case 7, the magnitude of magnetic resistance can be detected by the Hall element 521, and based on the detection output, the magnetic bearing shown in FIG. By controlling the electromagnets 3 and 4, the distance δ can be controlled to a predetermined value.

FIG. 4 is a sectional view showing another example of a turbomolecular pump to which an embodiment of the present invention is applied.

The turbo-molecular pump shown in FIG. 4 has a so-called inner rotor type structure with a rotor 78 provided inside, and is constructed in substantially the same manner as the turbo-molecular pump shown in FIG. 1 described above. That is, a motor rotor 79 is arranged on the circumferential surface of the central part of the rotor 78, and magnetic bearing rotor parts 80, 81 and a magnetic ring 82 are arranged on both sides of the motor rotor 79.
．． 83 is provided. An aluminum case 77 is provided to cover the rotor 78, and the motor rotor 79
A motor electromagnet 72 is arranged in a portion facing the magnetic bearing rotor portions 80, 81, a magnetic bearing electromagnet 73, 74 is arranged in a portion facing the magnetic bearing rotor portions 80, 81, and a sensor 75° 76 is placed opposite the magnetic ring 82, 83. will be provided. Note that the outside of the aluminum case 77 is at atmospheric pressure.

Sensors 75, 76 are constructed almost similarly to those shown in FIGS. 2 and 3 above, but in this embodiment, permanent magnets 751, 761 are provided far from rotor 78, and Hall elements 752 and 762 are provided on the rotor 78 side. In this way, even if a turbo molecular pump is configured with an inner rotor type, the rotor 78 and aluminum case 77
The gap between the two can be detected well.

[Effects of the Invention] As described above, according to the present invention, the magnetic flux generated by the permanent magnet provided in the yoke passes through the magnetic circuit created by the yoke and the rotor, and the magnetic resistance caused by the change in the gap between the rotor and the spindle axis is reduced. By detecting changes in the rotor using a Hall element, the floating position of the rotor can be detected without contact (without using eddy currents as in conventional methods).

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a turbo-molecular pump to which an embodiment of the present invention is applied. FIG. 2 is a sectional view taken along the line -H shown in FIG. 1. FIG. 3 is a sectional view showing essential parts of an embodiment of the present invention. FIG. 4 is a sectional view showing another example of a turbomolecular pump to which an embodiment of the present invention is applied. FIG. 5 is a sectional view showing the structure of a turbo-molecular pump, which is an application example of a conventional vacuum spindle. FIG. 6 is a diagram showing an example of a position sensor using a conventional eddy current method. In the figure, 1 is the spindle shaft, 2.72 is the electromagnet for the motor, 3.4.73.74 is the electromagnet for the magnetic bearing, 5, 6
．． 75.76 is a sensor, 7.77 is an aluminum case, 8 is an outer rotor, 12.13° 82.83 is a magnetic ring, 78 is a rotor, 501 to 508 are yokes, 511 to 5
14,751°761 is a permanent magnet, 521-524,7
52.762 is a Hall element, and 530 is an insulating member. Patent Applicant: NCH N. Toyo Bearing Hanging Figure 2 Figure 3 Seal = 22222 Atsushi S Figure A9 Morning

Claims (3)

[Claims] (1) In a device whose outer diameter surface is covered with a sealing insulating member and which magnetically supports a rotor made of a magnetic material that rotates around a fixed shaft of a spindle equipped with an electromagnet, the magnetic support A magnetic bearing position detection device for non-contact detection of a gap between a rotor and a fixed spindle shaft, the magnetic bearing position detection device being fixed to the spindle shaft and facing each other with a predetermined gap. a pair of yokes; a permanent magnet provided in a gap between the yokes on the spindle axis center side; and a permanent magnet provided in the gap between the yokes on the rotor side to detect changes in magnetic resistance caused by changes in the gap with respect to the rotor axis. Position detection device for magnetic bearings equipped with a Hall element for (2) In a spindle housing whose inner diameter surface is covered with a sealing insulating member and which magnetically supports a rotor made of a magnetic material rotating inside the spindle housing, the rotor is magnetically supported. and a magnetic bearing position detection device for detecting a gap between the housing and the housing in a non-contact manner, the pair of yokes being fixed to the housing and facing each other with a predetermined gap therebetween. , a permanent magnet provided on a side of the yoke far from the rotor, and a Hall element provided in a gap of the yoke on the rotor side for detecting a change in magnetic resistance caused by a change in the gap between the rotor and the housing. , position detection device for magnetic bearings. (3) The pair of yokes are each divided in the circumferential direction, and each of the divided members is magnetically separated by an insulating member, and the Hall element is provided for each of the divided members. A position detection device for a magnetic bearing according to claim 1 or 2.