Control method for electro-hydraulic control valves over temperature range
Patent No. 6,938,592
Issued: September 6, 2005
Inventors: Taylor; Danny R. (Freeville, NY); Quinn, Jr.; Stanley B. (Elmhurst, IL)
In a variable cam timing (VCT) system (10a) which has a feedback control loop wherein an error signal (36) relating to at least one sensed position signal of either a crank shaft position (24a) or at least one cam shaft position (22a) is fed back for correcting a predetermined command signal (12). The system further includes a valve (14) for controlling a relative angular relationship of a phaser (42); and includes a variable force solenoid (20) for controlling a translational movement of the valve (14). An improved control method comprising the steps of: providing a dither signal (38) sufficiently smaller than the error signal (36); as temperature varies, changing at least one parameter relating to the dither signal (38); and applying the dither signal (38) upon the variable force solenoid (20), thereby using the dither signal (38) for overcoming a system hysteresis without causing excessive movement of valve (14).
REFERENCE TO RELATED APPLICATIONS
This application claims an invention which was disclosed in Provisional Application No. 60/389,202, filed Jun. 17, 2002, entitled "IMPROVED CONTROL METHOD FOR ELECTRO-HYDRAULIC CONTROL VALVES OVER TEMPERATURE RANGE". The benefit under 35 USC §119(e) of the United States provisional application is hereby claimed, and the aforementioned application is hereby incorporated herein by reference.
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