Patent ID: 6885976
Filing Date: 2005-04-26
Classification: F01L,F02D,Y02T

Abstract:
1. A fault determining apparatus for a variable valve timing mechanism driven by an oil pressure of a working oil to change a phase of at least one of an intake cam and an exhaust cam with respect to a crank shaft of an internal combustion engine to change an opening/closing timing of at least one of an intake valve and an exhaust valve, and to control an actual cam phase of said at least one of said intake cam and said exhaust cam in a feedback manner to reach a target cam phase, said fault determining apparatus comprising: fault determining means for determining that said variable valve timing mechanism is faulty when a cam phase difference between said target cam phase and said actual cam phase is not within a first predetermined range; oil temperature parameter detecting means for detecting an oil temperature parameter indicative of a temperature of said working oil; and correcting means for broadening said first predetermined range when said temperature of said working oil is low, wherein said fault determining means is configured to preliminarily determine that said variable valve timing mechanism is faulty when said cam phase difference is not within said first predetermined range, and to definitely determine that said variable valve timing mechanism is faulty when said cam phase difference again goes out of said first predetermined range, and wherein said fault determining apparatus further comprises: a normality determining means for determining that said variable valve timing mechanism is normal when a difference between said target cam phase which is set when said cam phase difference falls under said first predetermined range after said preliminary determination of the fault and said stored preliminary fault determination target cam phase is within a second predetermined range, and for suspending a determination that said variable valve timing mechanism is normal when said cam phase difference is not within said second predetermined range.