GB1249205A - A control device for a fuel injection device of an internal combustion engine - Google Patents

Abstract

1,249,205. I.C. engine fuel injection systems. DR.-ING. H.C.F. PORSCHE K.G. May 16, 1969 [May 24, 1968], No.24994/69. Heading F1B. [Also in Divisions G1 and H3] A device for controlling an electromagnetically operated fuel injection valve for an I.C. engine comprises means for triggering the discharge of energy in the form of an electric current from an energy storage device through a discharge circuit which includes the electromagnet of the valve, and a control device for limiting the discharge current to a value above the hold current of the electromagnet. In Fig. 1, the energy storage device is a capacitor 1, which is charged via a diode 9 and current-limiting resistor 10 by a D, C. converter 8. A switch 18 operated by an engine cam-shaft (and therefore opening and closing at a rate dependent on engine speed) and acting through a device 17 then switches on a first transistor 11 to discharge the capacitor 1 through the electromagnet of the fuel injection valve 13 thereby opening the injection valve. After a time determined by engine variables 20 (such as load and air in engine temperatures), the device 17 switches off the first transistor 11, thereby re-closing the injection valve 13. A device 14 which measures the voltage across the electromagnet over-rides the first transistor 11 by switching off a second transistor 12 in series with the first transistor if the discharge current has fallen to a predetermined value somewhat higher than the hold current of the electromagnet. This avoids erratic variations of the time of closing of the injection valve 13 which would occur if the latest time of closing were allowed to be dependent on the discharge current falling below the hold current. In other embodiments the first transistor initiates the discharge but does not terminate it. Instead, the second transistor always terminates the discharge (i.e., the discharge current always drops to the abovementioned predetermined value somewhat higher than the hold current, and the effect of the engine variables is to vary the time at which this predetermined value is reached. This may be done by a step-wise variation of the capacitance or by controlling the D.C. converter. A further alternative is to control an infinitely variable or stepwise variable resistor which is connected in series with the electromagnet. A capacitor is connected in parallel with the resistor to prevent the resistor from alternating the initial part of the discharge pulse, thereby ensuring a rapid opening of the injector valve. Fig.9 shows an embodiment in which the energy storage device is an inductor instead of a capacitor. The inductor comprises a transformer 59. On receiving a pulse from the cam-shaft operated switch 53, a device 62 which is also influenced by engine variables 61 switches off a transistor 60 to interrupt the transformer primary current. The resultant inductive back e.m.f. developed at the transformer secondary energizes the electromagnet of the injector valve 57 to open the latter. So in Fig.1, the current to the electromagnet is terminated by an engine variable 56 acting through a device 55 to switch off a first transistor 54, unless it has already been terminated by a device 47 which switches off a second transistor 58 if the current falls to a predetermined value somewhat higher than the hold current. In a modification, Fig. 8 (not shown), the transistors 54, 58 and the device 55 are omitted, the transistor (42) in the primary circuit which is switched off to initiate the electromagnet current being switched on again by the device (47) when the current falls to the predetermined value so as to terminate the current.