Electricity: electrical systems and devices – Control circuits for electromagnetic devices – Including means for using – or compensating for – the induced...
Reexamination Certificate
1999-03-01
2001-01-16
Fleming, Fritz (Department: 2836)
Electricity: electrical systems and devices
Control circuits for electromagnetic devices
Including means for using, or compensating for, the induced...
C361S154000
Reexamination Certificate
active
06175484
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to solenoid driver circuits and, more particularly, to an improved energy recovery circuit configuration wherein any plurality of solenoid injector driver circuits are coupled together in parallel arrangement such that solenoid coil energy (back EMF) recaptured from one driver circuit can be used to recharge the power level of any plurality of other solenoid driver circuits.
BACKGROUND ART
Electronically controlled fuel injection systems must be capable of high speed operation and must have consistently reproducible stroke characteristics. High speed solenoid operation is therefore imperative as slow acting solenoids result in erroneous quantities of fuel being delivered to each cylinder at an inappropriate timing advance which can adversely affect the performance of the engine. A fuel injection solenoid control system can provide advantageous control of engine operation over the entire range of engine speeds by delivering a regulated voltage for a variable duration of time. This results in the solenoid opening the fuel injector for a substantially standard time duration to deliver a substantially standard pre-selected quantity of fuel to each individual cylinder. Typically, the rise time of current flow through the solenoid is a function of the voltage applied. The reproducibility of the stroke characteristics versus the control signal applied to the solenoid improves with higher voltages applied to the solenoid. However, higher voltages typically require higher voltage supplies that add to the expense of the overall driver circuit.
In a typical fuel injection system for a multi-cylinder engine, a fuel injection solenoid is provided for each engine cylinder and power to each solenoid must be supplied and removed for each compression stroke. Typically, the energy stored in the solenoid during energization is transformed into heat by a diode and resistor combination placed in the flyback current path of each solenoid when power is removed from the solenoid. The magnitude of the energy disposed of in this manner is significant and directly results in an increase to the cost of the system.
U.S. Pat. No. 5,717,562 which issued to the present assignee addresses some of the drawbacks associated with the prior art solenoid driver circuits and discloses an energy saving solenoid driver circuit which recovers power normally dissipated by the flyback current path in a conventional solenoid driver. More particularly, the solenoid driver circuit disclosed in U.S. Pat. No. 5,717,562 provides the advantages of a high voltage solenoid driver while eliminating many of the circuit components of the high voltage power supply traditionally associated with such high voltage solenoid drivers, and such driver circuit primarily recaptures solenoid coil energy (back EMF) when power is disconnected from the solenoid coil, that is, when fuel injection for that particular stroke is complete. Also, the high voltage capacitor associated with the driver circuit disclosed in U.S. Pat. No. 5,717,562 is only charged from the back EMF associated with the particular injector solenoid coil located in that particular driver circuit, and such back EMF is not utilized to recharge any high voltage capacitors associated with the other solenoid injector driver circuits in a typical fuel injection system.
It is therefore desirable to provide an energy recovery circuit configuration wherein the high voltage capacitors associated with a plurality of solenoid injector driver circuits can be recharged simultaneously from the back EMF associated with any one or a plurality of the injector solenoid coils associated with such driver circuits, and that such recharging of at least some of the high voltage capacitors can take place even while the injector solenoid coils for some of the driver circuits are being powered by their capacitors for fuel injection to particular cylinders.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF THE INVENTION
In accordance with the teachings of the present invention, a plurality of solenoid driver circuits are coupled together such that the high voltage capacitors associated respectively with such driver circuits are connected in parallel with each other, each solenoid driver circuit including a high voltage select switch, a select switch and a modulation switch. One or more electronic controllers are coupled to the plurality of driver circuits and control the opening and closing of the various switches such that the back EMF created by a solenoid coil in one driver circuit can be recaptured and used to not only charge the high voltage capacitor associated with that particular driver circuit, but such energy can likewise be utilized to recharge other high voltage capacitors associated with other driver circuits, even while such other driver circuits are active and the solenoid coils of such other driver circuits are energized to control fuel delivery to the engine.
Although it is generally preferred that each fuel injector be driven by its own solenoid injector driver circuit, it is also recognized and anticipated that any plurality of fuel injectors associated with any plurality of cylinders, within limits, may be driven by a single solenoid driver circuit. In this situation, the solenoid driver circuit may include additional solenoid coils positioned in parallel with each other, each solenoid coil being associated with a specific fuel injector. Regardless of the number of solenoid coils associated with a particular driver circuit, the high voltage capacitors associated with each of these solenoid driver circuits, even though each driver circuit may control more than one fuel injector, may still be coupled to each other in accordance with the teachings of the present invention so as to gain the benefits thereof. In this regard, the respective high voltage capacitor recovery times may vary depending upon how many injector solenoid coils are being driven by each respective solenoid driver circuit.
The present circuit configuration therefore enables the high voltage supply of one driver circuit to charge one or more of the high voltage supplies associated with other driver circuits so as to maintain the various high voltage supplies at a desired voltage level thereby improving the current rise time. In addition, the various high voltage supplies can be simultaneously recharged from a plurality of different solenoid injector driver circuits depending upon the timing of the fuel injection sequence associated with the particular engine involved, and depending upon which solenoid injector driver circuits are recovering power through the flyback current path at or near the same time.
REFERENCES:
patent: 5532526 (1996-07-01), Ricco et al.
patent: 5717562 (1998-02-01), Antone et al.
patent: 5757224 (1998-05-01), Antone et al.
patent: 5877931 (1999-03-01), Groppo et al.
Caruthers Michael A.
Davis Errol W.
Lee Chien C.
Love William J.
Caterpillar Inc.
Fleming Fritz
Haverstock Garrett & Roberts
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