GB1279079A - Compensating fuel metering for exhaust gas recirculation - Google Patents

Abstract

1279079 Regulating I C engines GENERAL MOTORS CORP 19 April 1971 [21 May 1970] 25840/71 Heading F1B I.C. engine has a throttle-controlled air inlet passage, a fuel delivery system, and a valvecontrolled exhaust gas re-circulation passage connecting the inlet passage to an exhaust passage, the fuel system controlling fuel delivery in accordance with the pressure existing downstream of the throttle valve, the amount of fuel delivered tending to increase as the absolute pressure downstream of the throttle increases, and the fuel system also including a control means which tends to reduce the amount of fuel delivered as the amount of exhaust gas re-circulated increases, to compensate for the partial pressure due to the exhaust gas. The air inlet includes two passages 14 each having a butterfly-type throttle valve 16, the valves being mounted on a common spindle 18. Exhaust gas to be re-circulated enters a passage 24 from an inlet 72, and the amount which passes to the inlet passages 14, via an outlet passage 28, is controlled by a butterfly-type valve 36, mounted on a spindle 38. This spindle projects through the wall of the gas re-circulation passage and carries a lever 44 on which is a cam follower roller 68, which engages a series of cam surfaces 70a, b, c, d and e formed on a plate 56. Two bolts 52 pass through a slot 54 along the plate, the plate being slidable over the bolts. A third bolt 58 is also slidable along the slot and is connected by a link 62 to a lever 64 mounted on the throttle spindle 18. The lever 44 is spring- biased to rotate anti-clockwise, as seen in Fig.2 (not shown) and the plate 56 is biased leftwards by a spring 66. As the throttles 16 move in the opening direction, the plate 56 is moved to the right so that the cam surfaces move past the roller 68. For the first 5 degrees of movement of the throttles, the valve 36 remains closed. Cam portion 70b then begins to open the valve 36 which reaches its fully open position when the throttles have opened 14-20 degrees. The roller 68 then moves down cam surface 70d so that valve 36 is closed when the throttles have opened 34 degrees. A second cam surface 87 formed on the plate 56 engages a roller 90 mounted on a lever 88 which controls a unit 92 to vary an impedance in a fuel metering circuit. The metering circuit includes a solenoid-operated injection nozzle which sprays fuel on to the back of an inlet valve. The solenoid is energized when a transistor in parallel with the solenoid coil is cut-off. The period of time for which the transistor is cut-off is determined by a circuit which applies a negative going voltage pulse to the base of the transistor, the impedance 92 being part of this circuit.