Patent ID: 6188562
Filing Date: 2001-02-13
Classification: B60T,H01F,H01H

Abstract:
A method for recognizing armature drop-off in an electromagnetically actuated device which occurs during a holding state of said device, comprising the steps of:(a) supplying a supply voltage via an on-off switching regulator to a coil of said device until a first magnitude switch on current impulse flows through said coil thereby causing said armature to assume a switch on position and said device to achieve a switch on state,(b) continuously monitoring the current flowing through said coil,(c) when said current reaches said first magnitude switch on current, switching off said supply voltage until the current flowing through said coil reaches a second magnitude which is less than said first magnitude,(d) when said current reaches said second magnitude, supplying said coil with said supply voltage until the current flowing through said coil reaches a third magnitude, said third magnitude being less than said first magnitude and greater than said second magnitude, said second and third magnitudes of said current in said coil being sufficient to retain said armature in said switch on position,(e) when said current reaches said third magnitude, switching off said supply voltage until the current flowing through said coil reaches said second magnitude,(f) continuously repeating steps (d) and (e) as cycles thereby achieving a holding state of said device,(g) monitoring the time periods of said cycles,(h) comparing the time periods of said cycles with a threshold value, said threshold value representing an increase in the time period required due to an armature drop off, and(i) generating an error signal when one of the time periods of said cycles exceeds said threshold value.