Magnetically levitated pump and controlling circuit

Details Magnetically levitated pump and controlling circuit Magnetically levitated pump and controlling circuit

2001-10-24

2003-09-30

Freay, Charles G. (Department: 3746)

Pumps

Condition responsive control of pump drive motor

By control of electric or magnetic drive motor

C417S044100, C417S423700, C415S900000

Reexamination Certificate

active

06626644

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to magnetically levitated (maglev) pumps and controlling circuits, and more specifically to clean pumps employing a magnetic bearing, such as maglev pumps for use in artificial hearts and other similar medical equipment, and controlling circuits.
2. Description of the Background Art
FIGS. 16A and 16B
show a conventional maglev pump. More specifically,
FIG. 16A
is a vertical cross section thereof and
FIG. 16B
is a cross section thereof taken along a line XVIB—XVIB.
A shown in
FIG. 16A
, the maglev pump
1
is configured by a motor unit
10
, a pump unit
20
and a magnetic bearing unit
30
. In pump unit
20
internal to a casing
21
a pump chamber
22
is provided and therein an impeller
23
rotates. As shown in
FIG. 16B
, impeller
23
has a plurality of vanes
27
formed spirally.
Casing
21
is formed of a non-magnetic member and impeller
23
includes a non-magnetic member
25
having a permanent magnet
24
constituting a non-controlled magnetic bearing, and a soft magnetic member
26
corresponding to a rotor of a controlled magnetic bearing. Permanent magnet
24
is divided in a direction of a circumference of impeller
23
and adjacent magnets are magnetized to have opposite magnetic poles. Opposite to that side of impeller
23
having permanent magnet
24
, a rotor
12
is provided external to pump chamber
22
, supported by a bearing
17
.
Rotor
12
is driven by a motor
13
to rotate. Rotor
12
is provided with the same number of permanent magnets
14
as permanent magnets
24
of impeller
23
to face permanent magnets
24
and also create attractive force. Adjacent permanent magnets
14
are also magnetized to have opposite magnetic poles.
Opposite that side of impeller
23
having soft magnetic member
26
, at least three electromagnets
31
and at least three positional sensors
32
are provided circumferentially in magnetic bearing unit
30
to attain balance with the attractive force of permanent magnets
24
and
14
in pump chamber
22
to maintain impeller
23
at a center of casing
21
. Electromagnet
31
has a geometry of the letter C and position sensor
32
is a magnetic sensor.
In maglev pump
1
thus configured an attractive force acts axially between permanent
14
buried in rotor
12
and permanent magnet
24
provided to impeller
23
. This attractive force contributes to magnetic-coupling, which rotatably drives impeller
23
and also provides radial supporting stiffness. To achieve balance with the attractive force, C-shaped electromagnet
31
has a coil passing electric current to levitate impeller
23
.
When rotor
12
is rotated by a driving force provided by motor
13
formed by motor rotor
15
and motor stator
16
, permanent magnets
14
and
24
form magnetic-coupling and impeller
23
thus rotates to suck a fluid through a suction port
60
and discharge the fluid through an outlet
70
. Since impeller
23
is isolated from rotor
12
by casing
21
and is also not contaminated by electromagnet
31
, maglev pump
1
discharges a fluid (blood if the pump is used for blood pump) maintained clean.
FIG. 17
shows the
FIGS. 16A and 16B
maglev pump and a circuit controlling the same. In
FIG. 17
, a maglev pump
200
is shown in a perspective view, at seen at a suction port
60
shown in
FIG. 16A
, and an axis of rotation of impeller
23
is surrounded by three electromagnets M
1
-M
3
and three sensors S
1
-S
3
. Sensors S
1
-S
3
provides their respective outputs which are inputs to sensor amplifiers H
1
-H
3
, respectively, amplified thereby and thus output to an operation circuit
202
.
Operation circuit
202
performs an operation on sensor outputs amplified by sensor amplifiers H
1
-H
3
and outputs to a phase compensation circuit
203
a voltage a proportional to a gap between electromagnet M
1
and impeller
23
, a voltage b proportional to a gap between electromagnet M
2
and impeller
23
, and a voltage c proportional to a gap between electromagnet M
3
and impeller
23
.
Phase compensation circuit
203
includes proportional plus derivative circuits PD
1
-PD
3
and integral circuits I
1
-I
3
. Proportional plus derivative circuit PD
1
and integral circuit I
1
receive control voltage a. Proportional plus derivative circuit PD
2
and integral circuit I
2
receive control voltage b. Proportional plus derivative circuit PD
3
and integral circuit I
3
receive control voltage c. An output of proportional plus derivative circuit PD
1
and that of integral circuit I
1
are added together and thus output to a limit circuit LM
1
. An output of proportional and derivative circuit PD
2
and that of integral circuit I
2
are added together and thus output to a limit circuit LM
2
. An output of proportional plus derivative circuit PD
3
and that of integral circuit I
3
are added together and thus output to a limit circuit LM
3
. If limit circuits LM
1
-LM
3
receive a signal of positive voltage they pass the signal and if they receive a signal of negative voltage then they compulsorily set the signal to be 0V. Limit circuits LM
1
-LM
3
have their respective output signals input to power amplifiers A
1
-A
3
, respectively. Power amplifiers A
1
-A
3
amplify the output signals, respectively, to drive their respective electromagnets M
1
-M
3
. Thus the control circuits allow an operation to be performed based on the outputs of sensors S
1
-S
3
individually for electromagnets M
1
-M
3
to drive electromagnets M
1
-M
3
.
FIG. 18
is a block diagram showing another example of the circuit controlling the maglev pump. The
FIG. 17
control circuit includes phase compensation circuit
203
having proportional plus derivative circuits PD
1
-PD
3
and integral circuits I
1
-I
3
independently provided for electromagnets M
1
-M
3
, whereas the
FIG. 18
control circuit, does not have an independent phase compensation circuit for each electromagnet. More specifically, it is provided with a phase compensation circuit for each mode of movement of an impeller controlled by a magnetic bearing. Herein, impeller
23
has separate modes of movement including a translative movement in the direction of an axis of translative movement of the impeller, and rotative movements around the axis of translative movement of the impeller, orthogonal to each other relative to the axis, i.e., a pitching movement and a yawing movement.
With reference to
FIG. 18
, separation circuit
204
performs an operation on sensor signals output from sensor amplifiers H
1
-H
3
and outputs the impeller
23
translative movement parameter z, pitching movement parameter &thgr;x and yawing movement parameter &thgr;y. Phase compensation circuit
205
, as well as the
FIG. 17
phase compensation circuit
203
, considers each mode of movement and it is configured by proportional plus derivative circuits PD
1
-PD
3
and integral circuits I
1
-I
3
providing their respective outputs which are fed through a distributor
206
for distribution to electromagnets M
1
-M
3
to pass electric current to electromagnets M
1
-M
3
via limit circuits LM
1
-LM
3
and power amplifiers A
1
-A
3
.
If the
FIG. 16A
maglev pumps
1
is used as a mobile pump or it is buried in a human body in the form of a blood pump, the entirety of the pump would move while impeller
23
rotates. Furthermore, the
FIG. 16A
impeller
23
in the form of a disc pitches and yaws as it rotates, and the entirety of the pump is thus affected by gyroscopic moment, disadvantageously resulting in precession, swaying around.
If impeller
23
is rotating and pitching and yawing movements are applied to the pump, a gyroscopic moment proportional to the movements' speed acts on impeller
23
. This gyroscopic moment results in impeller
23
being affected by a gyroscopic moment having an axis of rotation orthogonal to a rotative movement, such as pitching, applied to the pump as disturbance and impeller
23
thus displaces in pump chamber
22
, and triggered thereby is a precession of a low frequency in the direction opposite

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