Apparatus for abnormal diagnosis of variable valve timing mechanism

An abnormality diagnosis apparatus that diagnoses an abnormality of an adjustable valve mechanism, which changes a phase of a cam shaft for opening and closing a valve in an internal combustion engine relative to a crankshaft of the internal combustion engine and thereby varies an opening-closing characteristic of the valve, said abnormality diagnosis apparatus comprising:

• a fluid actuator that takes advantage of a pressure difference between two pressure chambers and thereby changes a phase difference between the cam shaft and the crankshaft;
• a fluid control valve that switches over a state between a supply and a discharge of a working fluid to and from each of the two pressure chambers of said fluid actuator;
• a control unit that outputs a control signal to said fluid control valve to switch over the state between the supply and the discharge of the working fluid;
• a sensor that actually measures a phase difference between the cam shaft and the crankshaft;
• a computation module that computes a pressure difference between the two pressure chambers in response to at least the control signal output from said control unit and calculates a phase difference between the cam shaft and the crankshaft from the computed pressure difference;
• and
• a determination module that compares the actual phase difference measured by said sensor with the calculated phase difference and determines that at least one of said fluid actuator and said fluid control valve is abnormal when a difference between the calculated phase difference and the measured phase difference is not less than a preset value.

An abnormality diagnosis apparatus that diagnoses an abnormality of an adjustable valve mechanism, which varies a moving characteristic of a valve in an internal combustion engine, said abnormality diagnosis apparatus comprising:

• a receiver that receives an input control signal for varying the moving characteristic of the valve;
• a calculator that computes a physical behavior of the adjustable valve mechanism according to a physical model and thereby calculates a theoretical value of a parameter relating to the moving characteristic of the valve, which is varied by the adjustable valve mechanism, in response to the input control signal;
• an observer that observes a value of the parameter relating to the moving characteristic of the valve, which is varied by the adjustable valve mechanism, in response to the input control signal;
• and
• a detector that detects the abnormality of the adjustable valve mechanism, based on the difference between the theoretical value and the observed value.

An abnormality diagnosis method that diagnoses a abnormality of an adjustable valve mechanism, which varies an moving characteristic of a valve in an internal combustion engine, said abnormality diagnosis method comprising the steps of:

• inputting a control signal for varying the moving characteristic of the valve;
• computing a physical behavior of the adjustable valve mechanism according to a physical model and thereby calculating a theoretical value of a parameter relating to the moving characteristic of the valve, which is varied by the adjustable valve mechanism, in response to the input control signal;
• detecting an observed value of the parameter relating to the moving characteristic of the valve, which is varied by the adjustable valve mechanism, in response to the input control signal;
• and
• determining whether the adjustable valve mechanism is abnormal or normal, based on the theoretical value and the observed value.

An abnormality diagnosis method that diagnoses an abnormality of an adjustable valve mechanism, which changes a phase of a cam shaft for opening and closing a valve in an internal combustion engine relative to a crankshaft of the internal combustion engine and thereby varies an opening-closing characteristic of the valve, said abnormality diagnosis method comprising the steps of:

• providing a fluid control valve that switches over a state between a supply and a discharge of a working fluid to and from each of two pressure chambers included in a fluid actuator, which takes advantage of a pressure difference between the two pressure chambers and thereby changes a phase difference between the cam shaft and the crankshaft;
• outputting a control signal to said fluid control valve to switch over the state between the supply and the discharge of the working fluid;
• actually measuring a phase difference between the cam shaft and the crankshaft with a sensor;
• computing a pressure difference between the two pressure chambers in response to at least the control signal;
• calculating a phase difference between the cam shaft and the crankshaft from the computed pressure difference;
• and
• comparing the actual phase difference measured by the sensor with the calculated phase difference and determining that at least one of the fluid actuator and the fluid control valve is abnormal when a difference between the calculated phase difference and the measured phase difference is not less than a preset value.