Pumps – Condition responsive control of pump drive motor – By control of electric or magnetic drive motor
Reexamination Certificate
2001-05-22
2002-10-22
Freay, Charles G. (Department: 3746)
Pumps
Condition responsive control of pump drive motor
By control of electric or magnetic drive motor
C417S045000, C417S410100, C417S420000, C417S423400, C417S423700, C417S423120, C600S003000, C600S016000, C600S017000, C600S151000, C415S118000, C415S203000, C415S900000
Reexamination Certificate
active
06468041
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to magnetically levitated (maglev) apparatus and more specifically to those magnetically levitating an impeller to deliver liquid such as blood.
2. Description of the Background Art
FIG. 7
is a vertical cross section of a maglev liquid pump apparatus as one example of a conventional maglev apparatus and a block diagram of a controller thereof. In
FIG. 7
a magnetically levitated liquid pump apparatus
100
is configured with an electromagnet unit
120
, a pump unit
130
and a motor unit
140
housed in a cylindrical housing
101
. Electromagnet unit
120
has an electromagnet
121
and a magnetic bearing sensor
122
incorporated therein. Housing
101
has on one side a side wall having a center provided with an inlet
102
introducing a liquid. At least three electromagnets
121
and at least three magnetic bearing sensors
122
surround inlet
102
. Electromagnets
121
and magnetic bearing sensors
122
are attached to a partition
103
separating electromagnet unit
120
and pump unit
130
from each other.
In pump unit
130
an impeller
131
is rotatably housed and it has a portion closer to electromagnet unit
120
, or closer to one side, that is supported by electromagnet
121
contactless through partition
103
, and magnetic bearing sensor
122
senses the distance as measured from one side of impeller
131
. Impeller
131
has the other side with a permanent magnet
132
buried therein. Motor unit
140
houses a motor
141
and a rotor
142
. Rotor
142
has a surface facing pump unit
130
and having a permanent magnet
143
buried therein, opposite to permanent magnet
132
buried in impeller
131
, with partition
104
disposed therebetween.
In the liquid pump apparatus thus configured, magnetic bearing sensor
122
provides an output which is in turn input to a sensor circuit
201
included in a controller
200
and sensor circuit
201
detects the distance between one side of impeller
131
and magnetic bearing sensor
122
. Sensor circuit
201
provides an output which is in turn input to a PID compensator
202
to provide PID compensation and PID compensator
202
provides an output which is in turn amplified by a power amplifier
203
and thus applied to electromagnet
121
to control attractive force provided toward the opposite side of impeller
131
.
Furthermore impeller
131
has a portion closer to motor unit
140
that is affected by the attractive force introduced by permanent magnets
132
and
143
and impeller
131
is magnetically levitated by a non-controlled bearing provided by permanent magnets
132
and
143
and a controlled bearing provided by electromagnet
121
. A motor control circuit
205
provides a control signal which is in turn applied to a power amplifier
204
. Power amplifier
204
drives motor
141
and the motor's driving force rotates impeller
131
and blood or any other similar liquid introduced through inlet
102
is output through an outlet (not shown) formed at pump unit
130
.
The
FIG. 7
magnetic bearing sensor
122
is a reluctance sensor using a carrier wave. This reluctance sensor is provided opposite to impeller
131
with the
FIG. 7
partition
103
disposed therebetween. Note that partition
103
is formed of conductive material, particularly titanium for blood pumps owing to its compatibility with blood. The reluctance sensor generates a magnetic field, which introduces an eddy current in the conductive titanium and would thus impair the sensor's sensitivity.
In order to avoid this the carrier wave is adapted to have a low frequency range. This, however, may significantly affect controlling the magnetic bearing. More specifically, a reluctance sensor using a carrier wave provides a detection with a phase delay for down to a frequency approximately two decades lower than that of the carrier wave, e.g., 100 Hz for a carrier wave frequency of 10 kHz. To compensate for this to reliably control the magnetic bearing, PID compensator
202
needs to be constructed to lead a phase to a high frequency range. Consequently PID compensator
202
has a gain increased and a component of the carrier frequency contained in the sensor output causes voltage saturation in a circuit portion internal to PID compensator
202
and thus prevents reliable control.
SUMMARY OF THE INVENTION
Therefore the present invention mainly contemplates a magnetic bearing apparatus capable of removing a carrier wave frequency component used in a magnetic bearing sensor, to provide reliably control.
Generally the present invention provides a magnetically levitated apparatus including: a drive unit driving and thus levitating a body to be levitated; a magnetic position detection circuit using a carrier wave signal to detect a position of the body as the body levitates; a controlled magnetic bearing unit operative in response to an output of the magnetic position detection circuit to support the body without contacting the body; a control circuit operative in response to a signal output from the magnetic position detection circuit to control the controlled magnetic bearing unit, wherein between the magnetic position detection circuit and the body there exists a partition formed of a conductive material; and a filter connected between the magnetic position detection circuit and the control circuit to remove a carrier wave signal output from the magnetic position detection circuit.
Thus in the present invention a filter can remove a carrier wave frequency component from a sensor output before amplification. Thus voltage saturation in the control circuit can be prevented to provide reliable control.
More preferably the magnetic position detection circuit includes: a reluctance sensor provided adjacent to the body and having an inductance varying as the distance between the reluctance sensor and the body varies; and a sensor circuit operative in response to an output of the reluctance sensor to output a signal varying as the inductance varies.
Furthermore the present apparatus further includes a carrier wave generation circuit feeding the magnetic position detection circuit with a carrier wave signal, wherein: the sensor circuit outputs the carrier wave signal with the amplitude varying as the spacing between the magnetic position detection circuit and the body varies; and the filter removes a center frequency of the carrier wave signal.
Furthermore the filter is a band eliminating filter arranged immediately subsequent to the sensor circuit.
Furthermore, the drive unit includes a non-controlled magnetic bearing unit magnetically coupled with the body at one side and a drive unit operative to rotate the body via the magnetic bearing unit, and the controlled magnetic bearing unit is magnetically coupled with the body at the other side.
Furthermore the body is an impeller rotated to output a liquid and the magnetically levitated apparatus configures a magnetically levitated pump.
The magnetically levitated apparatus further includes a drive unit rotatably driving the impeller through magnetic-coupling.
Furthermore the impeller is rotated to output blood and the magnetically levitated apparatus configures a blood pump apparatus.
Furthermore the impeller is rotated to output blood and the magnetically levitated apparatus configures a blood pump apparatus.
More preferably the body is rotated to rotate a vane and the magnetically levitated apparatus configures a turbo molecular pump.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 4891744 (1990-01-01), Yamamoto et al.
patent: 5911558 (1999-06-01), Nakazeki et al.
patent: 6087598 (2000-07-01), Munch
patent: 6126966 (2000-10-01), Nakazeki et al.
patent: 2522168 (1996-10-01), None
Belena John F
McDermott & Will & Emery
NTN Corporation
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