Magnetic rotor bearing

• US 4,763,032 A
• Filed: 11/27/1984
• Issued: 08/09/1988
• Est. Priority Date: 11/29/1983
• Status: Expired due to Term

• Current Assignee: Life Extenders Corporation
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: Bramm, Gunter, Novak, Pavel
• Primary Examiner(s): Skudy, R.
• Application Number:
  US06/675,144
• Time in Patent Office: 1,351 Days
• Field of Search: 308/10, 128/1 D, 128/DIG. 3, 623/3, 417/356, 340/870.32, 340/870.28, 340/870 R, 356/151
• US Class Current: 310/90.5
• CPC Class Codes: A61M 60/122 Implantable pumps or pumping devices, i.e. the blood being pumped inside the patient's body
• CPC Class Codes: A61M 60/148 in line with a blood vessel using resection or like techniques, e.g. permanent endovascular heart assist devices
• CPC Class Codes: A61M 60/216 including a rotating member acting on the blood, e.g. impeller
• CPC Class Codes: A61M 60/221 the blood flow through the rotating member having both radial and axial components, e.g. mixed flow pumps
• CPC Class Codes: A61M 60/237 the blood flow through the rotating member having mainly axial components, e.g. axial flow pumps
• CPC Class Codes: A61M 60/422 the force acting on the blood contacting member being electromagnetic, e.g. using canned motor pumps
• CPC Class Codes: A61M 60/562 for making blood flow pulsatile in blood pumps that do not intrinsically create pulsatile flow
• CPC Class Codes: F16C 2316/18 Pumps for pumping blood
• CPC Class Codes: F16C 2360/44 Centrifugal pumps
• CPC Class Codes: F16C 32/0429 for both radial and axial load, e.g. conical magnets
• CPC Class Codes: F16C 32/0444 Details of devices to control the actuation of the electromagnets

Abstract

The present invention provides a magnetic rotor bearing for suspending a rotor in a contact-free manner, in particular the rotor of an axial- or radial-centrifugal blood pump, comprising a permanent- and electromagnet arrangement which stabilizes the position of, and suspends the rotor in a stator, in particular a housing, and comprises a circuit arrangement connected to at least one position sensor or to the position sensor operating circuit thereof for the rotor. The rotor is suspended in the stator in a stable, contact-free manner by means of a permanent magnet arrangement except for a single geometric adjusting degree of freedom. The position of the rotor is stabilized only within the geometric adjusting degree of freedom not stabilized by the permanent magnet arrangement, by a permanent magnet arrangement located in the rotor and comprising at least one permanent magnet. The permanent magnet arrangement which co-operates with the electromagnet arrangement comprises at least one permanent magnet of the permanent magnet arrangement provided for suspending the rotor and consists in particular, of the permanent magnets of this permanent magnet arrangement positioned in the rotor. The circuit arrangement is a control circuit stabilizing the position of the rotor, during the absence of external forces, in a position of minimum energy requirement of the electromagnet arrangement.

Claims

1. An absolutely-low energy consuming, and relatively-high electromagnetically efficient, magnetic rotor bearing assembly, comprising:

a stator;

a rotor having an axis of rotation that is disposed in the stator;

said rotor has a shaft, wherein the rotor and its shaft are hollow inside, and have a total density selected to be exactly adapted to that of human blood;

permanent first magnet means including a permanent magnet mounted to the rotor cooperative with a permanent magnet mounted to the stator for magnetically suspending said rotor in said stator by magnetic repulsion so that the rotor is free from mechanical contact with the stator and is axially movable by displacement along the axis of rotation, the permanent magnet mounted to the rotor is axially staggered with respect to the permanent magnet mounted to the stator to maximize centering forces;

second magnet means including a permanent magnet mounted to the rotor cooperative with an electromagnet having a field intensity mounted to the stator for stabilizing the rotor against displacement along the axis of rotation; and

means coupled to the second magnet means responsive to a desired value representing an intended axial position of the rotor and including a position sensor providing a signal respresentative of actual axial position of the rotor for providing a field intensity of the electromagnet of the second magnet means such that the rotor is always axially moved from its actual position to the intended axial position in the absence of symmetrical external forces.

2. An absolutely-low energy consuming, and relatively-high electromagnetically efficient, magnetic rotor bearing assembly, comprising:

a stator;

a rotor having an axis of rotation that is disposed in the stator;

permanent first magnet means including a permanent magnet mounted to the rotor cooperative with a permanent magnet mounted to the stator for magnetically suspending said rotor in said stator by magnetic repulsion so that the rotor is free from mechanical contact with the stator and is axially movable by displacement along the axis of rotation, the permanent magnet mounted to the rotor is axially staggered with respect to the permanent magnet mounted to the stator to maximize centering forces;

second magnet means including a permanent magnet mounted to the rotor cooperative with an electromagnet having a field intensity mounted to the stator for stabilizing the rotor against displacement along the axis of rotation;

means coupled to the second magnet means responsive to a desired value representing an intended axial position of the rotor and including a position sensor providing a signal representative of actual axial position of the rotor for providing a field intensity of the elctromagnet of the second magnet means such that the rotor is always axially moved from its actual position to the intended axial position in the absence of symmetrical external forces;

said position sensor includes at least one pulsed radiation barrier having a pulsed radiation transmitting element and a cooperative radiation receiving element; and

further including another pulsed radiation barrier that includes a pulsed radiation transmitting element and a pulsed radiation receiving element, said pulsed radiation barriers being mounted to respective axial ends of the rotor, said pulsed radiation receiving elements providing respective output signals, a subtraction device having an input and an output for subtracting the output signals of the radiation receiving elements of the two pulsed radiation barriers, an integration device having an input and an output for integrating the output signal of the subtraction device, a sample and hold circuit an input of which is connected to the output of the integration device, a first switch coupled between the output of the subtraction device and the input of the integration device, a second switch connected to the integration device for resetting the integration device, a third switch connected between the output of the integration device and the input of the sample and hold circuit, and a control for controlling the duty cycles of the three switches such that the first switch is always closed when the radiation transmitting elements are transmitting, the third switch is closed in each case after the integration of a predetermined number of output signals from the subtraction device, and the second switch is closed as soon as the third switch has been opened.

3. An absolutely-low energy consuming, and relatively-high electromagnetically efficient, magnetic rotor bearing assembly, comprising:

a stator;

a rotor having an axis of rotation that is disposed in the stator;

permanent first magnet means including a permanent magnet mounted to the rotor cooperative with a permanent magnet mounted to the stator for magnetically suspending said rotor in said stator by magnetic repulsion so that the rotor is free from mechanical contact with the stator and axially movable by displacement along the axis of rotation, the permanent magnet mounted to the rotor is axially staggered with respect to the permanent magnet mounted to the stator to maximize centering forces;

second magnet means including a permanent magnet mounted to the rotor cooperative with an electromagnet having a field intensity mounted to the stator for stabilizing the rotor against displacement along the axis of rotation; and

means coupled to the second magnet means responsive to a desired value representing an intended axial position of the rotor and including a position sensor providing a signal representative of actual axial position of the rotor for providing a field intensity of the electromagnet of the second magnet means such that the rotor is always axially moved from its actual position to the intended axial position in the absence of asymmetrical external forces;

said rotor is adapted to operation as a conveying member in a blood pump having a suction side, and further including a power control device, said power control device including a pressure sensor on the suction side of the blood pump, and a characteristic memory having its input connected to the pressure sensor, said memory providing predetermined output signals in response to a predetermined input signal, and a power control device for controlling the pumping power in response to the output signal of the characteristic memory.

4. The assembly of claim 3, wherein the power control device includes an oscillator having a frequency and an output voltage coupled to the asynchronous motor of the blood pump, and means for changing the frequency and output voltage of the oscillator depending on the load and speed of the blood pump.

5. The assembly of claim 4, further including a second characteristic memory connected between the asynchronous motor and the oscillator for changing the operating voltage amplitude of the asynchronous motor depending on the frequency of the oscillator.