Pumps – Motor driven – Electric or magnetic motor
Reexamination Certificate
2001-06-19
2003-07-08
Walberg, Teresa (Department: 3742)
Pumps
Motor driven
Electric or magnetic motor
C417S044100
Reexamination Certificate
active
06589030
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to fluid pump apparatus and more specifically to those magnetically levitating an impeller to discharge fluid such as blood.
2. Description of the Background Art
FIG. 18
is a vertical cross section of a magnetically levitated (maglev) pump apparatus and a block diagram of a controller thereof. In
FIG. 18
a maglev 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 position sensor
122
incorporated therein. Housing
101
has on one side a side wall having a center provided with an inlet
102
introducing a fluid. At least three electromagnets
121
and at least three position sensors
122
surround inlet
102
.
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 a partition
103
, and position 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
of impeller
131
with a partition
104
posed therebetween.
In the maglev pump apparatus thus configured, position sensor
122
provides an output which is in turn input to a sensor circuit
301
included in a controller
300
and sensor circuit
301
detects the distance between one side of impeller
131
and position sensor
122
. Sensor circuit
301
provides an output which is in turn input to a PID compensator
302
to provide PID compensation and PID compensator
302
provides an output which is in turn amplified by a power amplifier
303
and thus applied to electromagnet
121
to control attractive force exerted 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 exerted 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
and it is rotated by the driving force of a motor
141
to allow blood or any other similar fluid introduced through inlet
102
to be output through an outlet (not shown) formed at pump unit
130
.
In the
FIG. 18
maglev pump
100
when a command is issued to provide levitation via the magnetic bearing, i.e., when attractive force occurs at electromagnet
121
, as shown
FIG. 19
, impeller
13
moves from a position A, corresponding to an internal wall surface closer to motor
140
affected by a significant attractive force created by permanent magnets
132
and
143
configuring magnetic-coupling, to a normal levitation position B. However, because of over-shoot of an excessive response as impeller
131
levitates, impeller
131
exceeds normal position B and impinges against a position C corresponding to an internal wall surface closer to electromagnet unit
120
, as represented in FIG.
19
. Thereafter impeller
131
moves to normal levitation position B. If impeller
131
, a target of position sensor
122
, impinges on a wall surface and have its surface damaged, the sensing function may be impaired.
Furthermore if the apparatus is used as a blood pomp impeller
131
is housed in pump unit
130
having its inner wall surface coated with heparin to prevent formation of thrombosis and if impeller
131
impinges against the inner wall of the pump chamber the coating would be disadvantageously peeled off.
SUMMARY OF THE INVENTION
Therefore a main object of the present invention is to provide a maglev pump capable of preventing an impeller from impinging against an inner wall of a pump chamber when a command is issued to provide magnetic levitation.
The present invention provides a maglev pump including: a pump unit outputting a fluid through revolution of a rotative member in a casing; a drive unit magnetically coupled with the rotative member without contacting the rotative member, to rotate the rotative member; a position detection unit detecting a position of the rotative member as the rotative member levitates; and a controlled magnetic bearing unit operative in response to an output of the position detection unit to support the rotative member without contacting the rotative member, and it is characterized in that it is provided with a control means controlling a command signal of the controlled magnetic bearing unit to allow the rotative member to have a position closer to the drive unit when the rotative member starts magnetic levitation.
Thus in the present invention the rotative member can be prevented from impinging against an internal wall of the housing when a command is issued to provide magnetic levitation. Thus the internal wall of the housing can be protected from damage.
Preferably in magnetic levitation the control means shifts the signal output of the position detection unit gradually to a normal value.
More preferably the control means gradually shifts the signal output from the position detection unit in a direction opposite to a normal value to terminate magnetic levitation.
More preferably the maglev pump configures a blood pump.
More preferably the drive unit is switchable between a mode controlling a revolution rate to be constant and a mode controlling a current to be constant and the control circuit controls a revolution rate to be substantially constant when one of the modes is switched to the other of the modes.
Furthermore the control circuit controls a revolution rate within a tolerance of approximately ±20% when one of the modes is switched the other of the modes.
Furthermore the pump includes an adjustment circuit adjusting the position of the rotative member as the rotative member levitates after the maglev pump has been assembled.
The adjustment circuit periodically moves the rotative member in the casing axially.
Furthermore the adjustment circuit includes: a periodical signal generation circuit generating a periodical signal of a low frequency and applying the periodical signal to a circuit portion of the controlled magnetic bearing unit; and a correction circuit outputting a correction signal to the control circuit to rotate the rotative member in the casing at an axially center position, in response to the output from the position detection unit when the rotative member periodically moves according to the periodical signal output from the periodical signal generation circuit.
The periodical signal generation circuit generates a periodical signal of no more than 1 Hz to periodically move the rotative member.
The present invention in another aspect provides a maglev pump including: a pump unit having in a casing a rotative member rotated to output a fluid; a support supporting the rotative member; a drive unit rotating the rotative member; and a control circuit controlling and thus preventing the rotative member from having a revolution rate varying when a supplied power supply voltage varies while the rotative member is rotating in a mode controlling a current to be constant.
Preferably the control circuit adjusts a value of a command indicative of the mode according to the supplied power supply voltage and a feedback signal proportional to a value of a current fed to the drive unit.
More preferably the power supply voltage is supplied by switching between a direct current voltage converted from an alternating current voltage and a direct current voltage supplied from a battery.
The power supply voltage is a selected and further converted one of the direct current voltage converted from the alternating current and the direct current voltage supplied from the battery.
Still more preferably, the support is coupled with the rotative mem
McDermott & Will & Emery
NTN Corporation
Patel Vinod D.
Walberg Teresa
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