:Hi, : :A colleague is developing a new fuel injector system which may have :broad application after some more research. Basically he is pulsing :the injector and can vary the pulse width, when at lower pulsewidths :the predicted mass flow does not appear to follow what it would :assuming a trapezoidal waveform/motion as a standard type petrol :injector does. : :He thinks it may be bounce causing this. He wants to measure either/or :sound and magnetic field via pickups. I said I thought that both are :difficult measurements to interpret with a CRO. He hopes to pickup the :harder sound of the injector seal hitting the metal seat. The motion :is about 0.1mm p-p. The pulse drive supply is believed to be an open :collector/drain driving the injector solenoid, with a reverse biased :diode across the coil. : :Just looking for ideas on detecting bounce. Apparently electrical :detection is difficult because the whole assembly and spring are :connected. Seems to me a distance measurement might be the best way, :unless a microphone can detect the higher harmonic content of seal- :plunger collision.
If the injector solenoid actuates a valve it is the valve which is most likely bouncing, not the solenoid.
In a diesel engine valve bounce can excessively lengthen the period between pre-injection and main injection thus reducing the efficiency of fuel burn and producing poorer CO2 results. You didn't say whether you are talking about petrol or diesel injection but I assume that valve bounce is undesirable in both. Modern diesel engines are now using piezo injectors in preference to solenoid injectors. They are 3 times faster and the injection sequence can be more precisely controlled.
A search for patents pertaining to the problem may provide some clues for you
formatting link
(you may have to register) I haven't studied the text in detail but you can do that. I don't know the equipment used to detect the valve bounce timing graphs but it is probably commercially available.
Essentially, the scheme appears to provide an initial energise pulse to the solenoid and then just prior to the valve reaching the fully open position, re-energising the solenoid again. This purportedly prevents the initial and subsequent bounces and thus reduces the lag between pre-injection and main injection fuel burns.