Method of detecting a doser valve opening or closing event
View Patent ↗A method of detecting a valve opening or closing event in a solenoid operated reductant injector valve includes applying a voltage to the solenoid to actuate the valve, the voltage having a chopped waveform. A resultant current through the solenoid is sampled at local maxima and minima. Values of a difference between the local maxima and subsequent local minima or between local minima and subsequent local maxima are determined. A rate of change of the difference values are determined and a valve opening or closing event based on the rate of change is determined.
1. A method of detecting a valve opening event or a valve closing event in a reductant injector valve having a solenoid which operates the reductant injector, the method comprising the steps of:
a) applying a voltage to said solenoid to actuate said reductant injector valve, said voltage having a chopped waveform as a result of applying a modulation signal to a voltage drive;
b) sampling a resultant current through the solenoid at local maxima and minima;
c) determining difference values between the local maxima and subsequent local minima or between the local minima and subsequent local maxima;
d) determining a rate of change of said difference values; and
e) determining the valve opening event or the valve closing event based on the rate of change in step d).
2. A method as claimed in claim 1 wherein step e) comprises determining whether a magnitude of the rate of change of said difference values is above a threshold, and if so, determining the valve opening event or the valve closing event.
3. A method as claimed in claim 2 where step e) comprises determining if there is a step increase or decrease in said difference values.
4. A method as claimed in claim 1 where step e) comprises determining if there is a step increase or decrease in said difference values.
5. A method as claimed in claim 1 wherein step b) is performed by synchronising sampling times with the modulation signal with respect to the voltage drive.
6. A method as claimed in claim 1 including determining a valve opening or closing time from said rate of change.
7. A method of detecting a valve opening or a valve closing in a reductant injector valve having a solenoid which operates the reductant injector valve, the method comprising the steps of:
a) applying a voltage to said solenoid to actuate said reductant injector valve, said voltage having a chopped waveform as a result of applying a modulation signal to a voltage drive;
b) sampling a resultant current at local maxima or local minima;
c) forming a plot from the sampling of step b); and
d) analyzing said plot to determine said valve opening or said valve closing;
wherein step b) is performed by synchronising sampling times with the modulation signal with respect to the voltage drive.
8. A method as claimed in claim 7 wherein step d) comprises determining first or second derivatives of said plot and comparing the first or second derivatives values to a threshold.
9. A method as claimed in claim 8 where step d) includes determining a glitch and determining the valve opening therefrom.
10. A method as claimed in claim 7 where step d) includes determining a glitch and determining the valve opening therefrom.