Patent ID: 6257184
Filing Date: 2001-07-10
Classification: F01L,F02D,Y02T

Abstract:
An apparatus for diagnosing a hydraulic variable valve timing mechanism which changes a rotational phase of a cam shaft with respect to an engine crank shaft by oil pressure to thereby change a valve timing, said apparatus comprising:phase detection means for detecting said rotational phase;diagnosis means for comparing the rotational phase detected by said phase detection means with a target value for said rotational phase to diagnose a fault of said hydraulic variable valve timing mechanism and then outputting a fault judgment signal;estimation means for estimating a time period for where a response delay in the rotational phase occurs with respect to the change in said target value in accordance with operating conditions; anddiagnosis prohibition means for prohibiting diagnosis by said diagnosis means for the duration of the time period for where said response delay estimated by said estimation means occurs.