Patent ID: 6595171
Filing Date: 2003-07-22
Classification: F01L,F02D,Y02T

Abstract:
A valve timing control system for an internal combustion engine, for controlling valve timing by changing a cam phase which is a phase of at least one of an intake cam and an exhaust cam, relative to a crankshaft, the valve timing control system being used together with a degradation-determining system that performs a degradation determination of at least one of an oxygen concentration sensor and an exhaust gas-purifying device each arranged in an exhaust system of the engine, in a state in which an air-fuel ratio of a mixture supplied to the engine is controlled to a predetermined state,the valve timing control system comprising: actual cam phase-detecting means for detecting an actual cam phase; operating condition-detecting means for detecting operating conditions of the engine; target cam phase-setting means for setting a target cam phase in dependence on the detected operating conditions of the engine; control means for performing control such that the actual cam phase becomes equal to the target cam phase; determination means for determining whether or not executing conditions for executing the degradation determination are satisfied; and target cam phase-restricting means for restricting a change in setting of the target cam phase in dependence on the detected operating conditions of the engine by said target cam phase-setting means, when said determination means has determined that the executing conditions for executing the degradation determination are satisfied.