Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2001-09-12
2003-09-09
Mullins, Burton (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C324S207250, C310S090500
Reexamination Certificate
active
06617722
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic levitation rotating machine which performs levitation support control of a rotator, provided with a magnetic material as an object to be controlled, so that the rotator is supported in a levitated state at a desired position in a noncontact manner through the utilization of magnetic attraction force or magnetic repulsion force generated by an electromagnet or a permanent magnet. More particularly, the present invention relates to a detection mechanism for detecting the axial displacement and the rotating speed of the rotator.
2. Description of the Related Art
FIG. 10
is a diagram showing a general example of the construction of a conventional magnetic bearing mechanism, and
FIG. 11
is a diagram showing an example of the construction of a control unit for performing levitation support control of the magnetic bearing. In the magnetic levitation rotating machine, a rotator R is driven and rotated by a motor in a noncontact manner, and, in addition, is supported in a levitated state by a radial magnetic bearing and a thrust magnetic bearing. The rotator R is provided with a target member
21
of a magnetic material, and is supported in a levitated state at a radial target levitation position by controlling magnetic attraction force generated from a radial support electromagnet
20
. A radial displacement sensor
11
is provided near the electromagnet
20
. The radial displacement sensor
11
measures the radial displacement (location) of a target magnetic material
19
provided in the rotator R. Further, the rotator R is provided with a thrust disk
18
formed of a magnetic material, and an axial levitation support electromagnet
15
for the rotator R is disposed so as to sandwich the thrust disk
18
thereby. The rotator R provided with the thrust disk
18
is supported in the levitated state at an axial target levitation position by controlling magnetic attraction force generated from the axial levitation support electromagnet
15
.
A target
16
, formed of a magnetic material, for a position sensor is provided at the shaft end of the rotator R, and an axial displacement sensor
13
for the rotator R is provided on the fixed side to measure the axial displacement of the rotator R. The rotator R is provided with a rotating speed detection disk
17
, and a rotating speed detection sensor
14
is provided on the fixed side in its position near the rotating speed detection disk
17
. Here all the displacement sensors
11
,
12
,
13
are sensors utilizing such a phenomenon that magnetic characteristics are changed in response to the displacement of a target (magnetic) material, such as an eddy current sensor or an inductance sensor. The rotating speed detection disk
17
has a concave or a convex, and passage through the concave or the convex is detected by a displacement sensor utilizing the same magnetic properties as described above to detect the rotating speed. In the example of the construction of the conventional magnetic bearing mechanism shown in
FIG. 10
, two sensors
11
,
12
for detecting the radial displacement are shown. In fact, however, two additional sensors are disposed in a direction perpendicular to the paper surface. The sensors can detect a coordinate position within a plane perpendicular to the rotating shaft of the rotator.
In the prior art, as shown in
FIG. 11
, the axial displacement sensor
13
, the rotating speed detection sensor
14
, and the axial levitation support electromagnet
15
are disposed in a hierarchical structure manner on the fixed side of the magnetic bearing mechanism along the axial direction of the rotator R. As shown in
FIG. 11
, a signal, on the axial position (displacement) of the rotator R, obtained by the axial displacement sensor
13
is sent through a sensor signal processor
23
and a compensation circuit
24
provided within the control unit to an exciting current output amplifier
25
that outputs exciting current which is then supplied to the axial levitation support electromagnet
15
to perform excitation, whereby the rotator R is controlled so as to be levitated and supported at an axial predetermined position. Likewise, the output of the rotating speed detection sensor
14
is input into a rotation sensor signal processor
26
, provided within the control unit, where the rotating speed is computed. The rotating speed value thus obtained is compared with a target rotating speed in a rotating speed controlling unit
27
, and a current for driving the motor is supplied from an inverter
28
to the motor (not shown in
FIG. 10
) so that the rotating speed is brought to a predetermined value.
A great feature of the magnetic levitation rotating machine, wherein a rotator is supported in a levitated state by the above-described series of magnetic levitation controls, is such that the rotator, even when located at any position, is supported in a levitated state and rotated in a noncontact manner. Therefore, a noncontact rotating speed detection system should also be used in rotating speed detection means at the time of the application of rotating force by an induction machine or a synchronous machine.
Specifically, in addition to a displacement sensor element for levitation position detection for performing levitation support control of the rotator, a rotating speed detection sensor element should be installed. In the conventional techniques, however, as with the displacement sensor for position detection for magnetic levitation control, rotating speed detection sensors of an eddy current type, induction type, or inductance type, which is an electromagnetic detection method, have been generally used. When the electromagnetic sensor of the conventional type is used, however, for some mechanical arrangement of the sensors, a mutual electromagnetic interference phenomenon occurs. Therefore, the rotating speed detection sensor element and the displacement sensor element for position detection should be provided while leaving a space therebetween.
That is, in order to operate the above structure without any electromagnetic trouble, in
FIG. 10
, a certain space should be provided between the axial displacement sensor
13
and the rotating speed detection sensor
14
and between the rotating speed detection sensor
14
and the axial levitation support electromagnet
15
. Therefore, there is a limitation on a reduction in size of the shaft end portion in the magnetic bearing mechanism.
Further, in the conventional system, as shown in
FIG. 10
, in the detection of the rotating speed, a method has been used wherein a rotating speed detection disk
17
partially provided with a notch is provided at the shaft end of the rotator and the disk is rotated together with the rotator and, in this case, when the notch has passed the front of the rotating speed detection sensor, a pulse signal synchronized with the rotating speed is generated. In this method, however, leaked magnetic flux of the magnetic levitation electromagnet is introduced into a portion around the rotating speed detection disk
17
, and this deteriorates the S/N ratio of the rotating speed detection sensor signal. For this reason, the disposition of the rotating speed detection disk
17
, the axial displacement sensor target
16
, and the thrust disk
18
while leaving a certain space among one another is unavoidably necessary from the viewpoint of structure.
As described above, due to the above-described restrictions, the noncontact-type rotating speed detection sensor, based on an electromagnetic principle, which is provided within the magnetic bearing mechanism for levitating and supporting the rotator, should be provided while leaving a certain space, for example, from the electromagnet and the displacement sensor for position detection constituting the magnetic bearing mechanism. This is an obstacle to a reduction in size of the whole magnetic bearing mechanism.
In the rotating speed detection system of the rotating speed detection sensor, the adoption of a system utili
Miyamoto Matsutaro
Nakazawa Toshiharu
Ooyama Atsushi
Ebara Corporation
Mullins Burton
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