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Circuit for controlling and indicating fuel injector operation

  • US 4,612,597 A
  • Filed: 12/19/1984
  • Issued: 09/16/1986
  • Est. Priority Date: 12/19/1984
  • Status: Expired due to Term
First Claim
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1. A circuit for controlling and indicating the operation of an electromagnetic fuel injector having a coil and an armature moved upon energization of the coil from a deenergized position to a stop position for controlling fuel injection, the circuit comprising in combination:

  • a voltage source,a switching element series coupled with the coil across the voltage source, the switching element having a conductive state wherein the coil is charged by the voltage source and having a nonconductive state;

    a high voltage breakdown device for providing a discharge path for the coil when the switching element is in its nonconductive state;

    means responsive to an injection command signal and the value of the coil current for setting the switching element in its conductive state to charge the coil when the coil current is less than a first value and setting the switching element in its nonconductive state to discharge the coil when the coil current is greater than a second value greater than the first value, the time required for the coil current to first reach the second value in response to an injection command signal being less than the time for the armature to move from its deenergized position to its stop position;

    means for monitoring the duty cycle of the conductive and nonconductive states of the switching element, the duty cycle varying in one direction while the core accelerates from its de-energized position to its energized position and in the opposite direction after the core reaches the stop position; and

    means for generating a signal that indicates operation of the fuel injector at the time at which the duty cycle variation changes its direction.

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