Control System for a Diesel Internal Combustion Engine

The invention relates to an arrangement for the electronic closed-loop control and/or open-loop control of a diesel internal combustion engine.

Such an arrangement is described in the journal "Autotechnik", No. 11, 1983, pages 52 and 53 under the title "Elektrisch gesteuerte Pumpendusen fur schnellaufende Direkteinspritzer-Dieselmotoren". The following is disclosed: a pump nozzle for each cylinder comprising an injection nozzle and a solenoid valve, and further different sensors for operating characteristic variables of the internal combustion engine and an electronic control apparatus. The injected quantity of fuel is metered by a solenoid valve which opens and closes in correspondence to signals of the electronic control apparatus. The injection start and the injected quantity can be controlled independently of each other by the metering start and the pulse width, respectively.

A method and arrangement for closed-loop or open-loop control of a diesel internal combustion engine is known from U.S. Pat. No. 4,378,775 wherein the metered quantity of fuel is controlled by means of a solenoid valve with a distribution injection pump.

It has been shown that the course of injection obtainable with the known arrangements can lead to disturbing combustion noises.

The invention solves the problem to minimize noise emissions in arrangements of the above-mentioned type.

The arrangement according to the invention for closed-loop control and/or open-loop control of an internal combustion engine having the features of the main claim affords the advantage with respect to the described state of the art that the course of injection can be electronically controlled in correspondence to the requirements of the internal combustion engine. In this way, the noise emission of the internal combustion engine is substantially reduced.

The invention will be explained in the following with respect to the drawings. A schematic configuration of the arrangement is shown in FIG. 1. FIGS. 2a-c show by example the interrelationship between the drive signal of the solenoid valve, the unit chamber pressure EP and the needle stroke of an injection valve.

An internal combustion engine is identified with 10 in FIG. 1. Operating parameters such as speed N, temperature of the internal combustion engine TM, cooling water temperature TW and further operating characteristic values of the internal combustion engine are detected by means of various sensors and supplied to the control apparatus 20. The control apparatus 20 receives signals from further sensors 24 with reference to the accelerator pedal position FP, charge pressure P, air temperature TL and further characteristic variables. In addition, signals reach the control apparatus which characterize the injection such as injection start, fuel quantity and unit chamber pressure EP. The control apparatus generates output signals for driving the injection pump 40, for example for driving the actuator of the pump piston and of the solenoid valve 30. Furthermore, additional devices 22 such as glow plugs or the exhaust-gas recirculation can be driven by the control device 20. The solenoid valve 30 opens and closes in correspondence to the drive signals and meters the fuel to the pump work chamber of the fuel pump 40 in a clocked manner. From the fuel pump 40, the fuel is pumped into the internal combustion engine 10.

This arrangement can be so configured that the drive signals can be computed simultaneously for all solenoid valves or the arrangement can be so configured that the drive signals can be computed separately for each solenoid valve. In this case, a control can occur with the arrangement which is specific to a cylinder.

FIG. 2a shows the time-dependent course of the drive signal of a metering cycle for the solenoid valve 30. FIG. 2b shows the unit chamber pressure EP and FIG. 2c the needle stroke which corresponds approximately to the course of injection, which is the time-dependent course of the injected fuel quantity for each fixed time duration. The clock frequency as well as the pulse duty factor are variable within wide limits. The pressure build-up in the pump work chamber (unit chamber) is then dependent upon the clock frequency and the pulse duty factor. The pressure build-up in the unit chamber can be influenced within wide limits by repeatedly clocking the solenoid valves in each metering cycle. A uniform build-up of pressure is obtained by means of a first long drive pulse. In this way, a stable injection start is obtained. This is necessary, among other reasons, for low noise emission. A long injection duration can be obtained by means of a corresponding clocking and this above all affords advantages during idle. The clock frequency and the pulse duty factor determine the course of the pressure build-up in the unit chamber and thereby also the course of the injection. Since the drive signals for the solenoid valves are determined in dependence upon operating characteristic variables, the course of injection can be controlled in a closed-loop or an open-loop manner. A specific pulse duty factor and a specific clock frequency or a specific sequence of different pulse duty factors and/or clock frequencies can be pregiven in dependence upon operating conditions such as charge pressure PL, charge temperature TL, speed N and load for each operating condition.

In dependence upon the temperature of the internal combustion engine, it is possible during idle to realize a long injection duration by means of multiple clocking at a low pulse duty factor.

However, a specific unit chamber pressure or a specific time-dependent course of the unit chamber pressure can be pregiven in dependence upon operating characteristic variables. The solenoid valve then functions as an actuator for a control of the unit chamber pressure.

Such an arrangement can be utilized for all injection systems wherein the metering of fuel is influenced by a magnetic valve.