Method of recognizing the impingement of a reciprocating armature in an electromagnetic actuator

• US 5,691,680 A
• Filed: 07/22/1996
• Issued: 11/25/1997
• Est. Priority Date: 07/21/1995
• Status: Expired due to Fees

• Current Assignee: FEV Motorentechnik GmbH
• Original Assignee: FEV Motorentechnik GmbH
• Inventors: Kather, Lutz, Schrey, Ekkehard
• Primary Examiner(s): Hecker, Stuart N.
• Application Number:
  US08/683,973
• Time in Patent Office: 491 Days
• Field of Search: 318/128, 318/135, 335/228, 335/253, 335/256, 335/266, 335/268, 361/159, 361/167, 361/187
• US Class Current: 335/256
• CPC Class Codes: H01F 2007/185 with armature position measurement
• CPC Class Codes: H01F 2007/1861 using derivative of measured variable
• CPC Class Codes: H01F 7/1844 Monitoring or fail-safe circuits for relays H01H47/002

Abstract

A method of recognizing armature impingement in an electromagnetic actuator having an electromagnet including a solenoid, an armature movable toward and away from the electromagnet and return means for exerting a force on the armature. The method includes the steps of maintaining a solenoid current at a predetermined magnitude I_max during a predetermined period T_A for capturing the armature at the electromagnet; switching off the solenoid current at a moment t₁ upon lapse of the period T_A ; upon lapse of a period T₁ running from moment t₁, oscillating the solenoid current between a lower holding current threshold I_H1 and an upper holding current threshold I_H2 ; detecting a current course from moment t₁ ; and deriving a signal from such current course.

Claims

1. A method of recognizing armature impingement in an electromagnetic actuator having an electromagnet including a solenoid, an armature movable toward and away from the electromagnet and return means for exerting a force on the armature, comprising the following steps:

(a) maintaining a solenoid current at a predetermined magnitude I_max during a predetermined period T_A for capturing the armature at the electromagnet;

(b) switching off the solenoid current at a moment t₁ upon lapse of the period T_A ;

(c) upon lapse of a period T₁ running from moment t₁, oscillating the solenoid current between a lower holding current threshold I_H1 and an upper holding current threshold I_H2 ;

(d) detecting a current course from moment t₁ ; and

(e) deriving a signal from said current course.

2. The method as defined in claim 1, further comprising the step of detecting the magnitude I_p of the solenoid current at the end of period T₁.

3. The method as defined in claim 1, further comprising the step of detecting a moment t_p which is subsequent to moment t₁ and at which the solenoid current decreases to the magnitude of said lower holding current threshold I_H1.

4. The method as defined in claim 1, wherein said oscillating step comprises the step of switching on the solenoid current for predetermined consecutive clock periods T_f and detecting the maximum values of the solenoid current at the end of the clock periods.

5. The method as defined in claim 1, further comprising the step of detecting a first current curve representing the course of an actual solenoid current passing through the electromagnet and comparing said first current curve with a second current curve representing the course of a predetermined desired solenoid current for the electromagnet.