Method and drive apparatus for driving an electromagnetic actuator

Patent metadata

Field	Value
Publication number	US-9337766-B2
Application number	US-201214343918-A
Country	US
Kind code	B2
Filing date	Aug 2, 2012
Priority date	Sep 20, 2011
Publication date	May 10, 2016
Grant date	May 10, 2016

Abstract

A method of activating an electromagnetic actuator having at least one coil and a movable armature. The method includes the step in which the electromagnetic actuator is demagnetized by passing a sequence of electric current pulses with a current flow direction which alternates from one current pulse to the next and with a current size which decreases from one current pulse to the next, through the at least one coil, in order to reduce or eliminate any residual magnetic flux density in the electromagnetic actuator. The method also includes a step in which a position of the movable armature is determined, after the demagnetization step, by passing a measurement current pulse through the at least one coil.

First claim

The invention claimed is:

1. A method of activating an electromagnetic actuator which has at least one coil and a movable armature, the method comprising the steps of:
demagnetizing the electromagnetic actuator by passing a sequence of electric current pulses which have a current flow direction which alternates and a current size which progressively decreases, from one current pulse to a next current pulse, through the at least one coil, in order to either reduce or eliminate any residual magnetic flux density in the electromagnetic actuator and produce a defined and constant magnetic starting condition in the actuator before determining a position of the movable armature;
determining the position of the movable armature, only after demagnetizing the electromagnetic actuator and achieving the defined and constant magnetic starting condition in the actuator, by passing a measurement current pulse through the at least one coil; and
passing, during the determination step, a measurement current pulse through the at least one coil that has a current size which is smaller than the smallest of the current size of the current pulses during the demagnetization step.

2. The method according to claim 1 , further comprising the step of passing through the at least one coil during the demagnetization step, a first electric current pulse with a first flow direction and a first current size, and a subsequent, second electric current pulse with a second current flow direction different from the first current flow direction and a second current size smaller than the first current size.

3. The method according to claim 2 , further comprising the step of passing through the at least one coil, during the demagnetization step, at least one further electric current pulse with a flow direction opposite to that of an immediately preceding current pulse, and a current size Smaller than that of the immediately preceding current pulse.

4. The method according to claim 1 , further comprising the step of progressively reducing, during the demagnetization step, a duration of the current flow through the at least one coil from one current pulse to the next current pulse through the sequence of electric current pulses.

5. The method according to claim 1 , further comprising the step of passing a movement current pulse through the at least one coil to move the armature, and the movement current pulse having a current size that is larger than the largest of the current size of the current pulses which pass during the demagnetization step.

6. The method according to claim 5 , further comprising the step of carrying out the demagnetization step after passing the movement current pulse through the at least one coil and before the determination step.

7. The method according to claim 1 , further comprising the step of evaluating, during the determination step, a reaction of the at least one coil to the movable armature in the measurement current pulse to determine the position of the movable armature.

8. The method according to claim 1 , wherein the electromagnetic actuator has a first coil and a second coil, the method further comprising the step of passing, during the demagnetization step, the sequence of electric current pulses through a series circuit of the first coil and the second coil, and passing, during the determination step, the measurement current pulse through the series circuit of the first coil and the second coil.

9. A method of activating an electromagnetic actuator which has at least one coil and a movable armature, the method consisting of the steps to:
demagnetizing the electromagnetic actuator by passing a sequence of electric current pulses which have a current flow direction which alternates, and a current size which progressively decreases, from one current pulse to a next current pulse, through the at least one coil, in order to either reduce or eliminate any residual magnetic flux density in the electromagnetic actuator;
determining a position of the movable armature, after the step of demagnetizing the electromagnetic actuator, by passing a measurement current pulse through the at least one coil; and
passing, during the determination step, a measurement current pulse through the at least one coil hat has a current size which is smaller than the smallest of the current size of the current pulses during the demagnetization step.

10. An activating device for activating an electromagnetic actuator comprising:
at least one first and second coil surrounding an armature movement space; and
a movable magnetic armature, being located in and being axially movable within the armature movement space, with respect to a housing of the electromagnetic actuator, by a connecting rod, and the activating device being capable of:
demagnetizing the electromagnetic actuator by passing a sequence of electric current pulses with a current flow direction which alternates, and a current size which progressively decreases, from one current pulse to a next current pulse, through the at least one first and the second coil, in order to either reduce or eliminate any residual magnetic flux density in the electromagnetic actuator and produce a defined and constant magnetic starting condition in the actuator before determining an axial position of the movable armature;

determining the axial position of the movable armature, only after demagnetizing the electromagnetic actuator and achieving the defined and constant magnetic starting condition in the actuator, by passing a measurement current pulse through both of the at least one first and the second coil; and
the activating device, when determining the axial position of the movable armature, passes a measurement current pulse through the at least one first and second coil that has a current size which is smaller than the smallest of the current size of the current pulses during the demagnetization step.

11. The activating device according to claim 10 , wherein activating device further comprises four switching devices;
at least one of the four switching devices comprises a metal oxide semiconductor field-effect transistor; and
the four switching devices further comprises a first high-side switching device (Hss 1 ), a second high-side switching device (Hss 2 ), a first low-side switching device (Lss 1 ) and a second low-side switching device (Lss 2 );
the first high-side switching device and the second high-side switching device are connected upstream in the current flow direction, and the first low-side switching device and the second low-side switching device are connected downstream in the current flow direction so that the current flow direction, through the first and the second coils, connected in series, can be set by selective closing and opening of the four switching devices.

Assignees

• Weinl Florian
• Pantke Michael
• Zahnradfabrik Friedrichshafen

Inventors

• Weinl Florian
• Pantke Michael

Classifications

• H01F7/1844 Primary

  Monitoring or fail-safe circuits (for relays H01H47/002) · CPC title

• H01F13/006

  Methods and devices for demagnetising of magnetic bodies, e.g. workpieces, sheet material (for erasing of information on magnetic record carriers G11B5/00) · CPC title

• H01F2007/185

  with armature position measurement · CPC title

• H02P25/064 Primary

  of the synchronous type · CPC title

• H02P25/06 Primary

  Linear motors · CPC title