Further Development of Solenoid Operated Gas Injectors with Fast Opening and Closing

The existing state of the art in solenoid operated injectors technology promotes their use mainly for gasoline manifold injection in spark ignition engines. The attempts to use such injectors for direct fuel injection are hampered by slower and less repeatable dynamic response, as compared with hydraulically or mechanically operated diesel injectors. Also, the impact of the solenoid overheating and the resulting loss of power, is considered detrimental for such injectors when installed in the cylinder head of an engine. The next (third) generation of solenoid operated injectors is dealing with all these disadvantages. First, it is using a special inductive driving circuit for the solenoid to boost the opening of the injector needle by amplifying the supply voltage, but only for a very short instant of time. Second, it is utilizing the differential angle in the conical needle seat to reduce the unbalanced pressure force acting on the injector needle when closed; this allows the injector to open at higher gas pressure or to use a stronger return spring to accelerate its closing. The paper explains the principles of these improvements and simulates the injector's behaviour on a computer.