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

• Current Assignee: General Motors Corporation (General Motors Company)
• Original Assignee: General Motors Corporation (General Motors Company)
• Inventors: Hamren, Glen C.
• Primary Examiner(s): Gellner, Michael L.
• Application Number:
  US06/683,342
• Time in Patent Office: 636 Days
• Field of Search: 123/490, 361/152
• US Class Current: 361/152
• CPC Class Codes: F02D 2041/2027 Control of the current by pulse width modulation or duty cycle control
• CPC Class Codes: F02D 2041/2055 with means for determining actual opening or closing time
• CPC Class Codes: F02D 2041/2058 using information of the actual current value
• CPC Class Codes: F02D 2041/2075 Type of transistors or particular use thereof
• CPC Class Codes: F02D 2200/063 Lift of the valve needle
• CPC Class Codes: F02D 41/20 Output circuits, e.g. for controlling currents in command coils

Abstract

A circuit for controlling and indicating the operation of an electromagnetic fuel injector is described in which the injector current is regulated to a predetermined value by switching the injector coil current on and off in response to the coil current value relative to the predetermined value. Operation of the injector is sensed by sensing the change in direction in the duty cycle of the switched coil current as the duty cycle varies while the injector armature moves toward and strikes its stop position.

Claims

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.

2. 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 transistor series coupled with the coil across the voltage source, the transistor having an on state wherein the coil is charged by the voltage source and having an off state;

a Zener diode coupled in parallel with the transistor for providing a discharge path for the coil when the transistor is in its off state;

a current sensing resistor coupled in series with the coil, the voltage across the resistor being a measure of the coil current;

means responsive to an injection command signal and the voltage across the current sensing resistor for biasing the transistor to its on state to charge the coil when the voltage across the current sensing resistor represents a coil current less than a first value and biasing the transistor to its off state to discharge the coil when the voltage across the current sensing resistor represents a coil current greater than a second value that is 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 it deenergized position to its stop position;

means for monitoring the on and off states of the transistor, the on state varying relative to the off state in one direction while the core accelerates from its deenergized 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 variation of the on state relative to the off state changes its direction.