Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
1999-05-05
2001-04-03
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S479000
Reexamination Certificate
active
06209521
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for operating a fuel supply system for an internal combustion engine, in particular of a motor vehicle, in which the fuel is conveyed into a storage chamber and a pressure is produced in the storage chamber, in which an actual value of the pressure in the storage chamber is measured, and in which the pressure in the storage chamber is controlled to a setpoint value. In addition, the present invention relates to a fuel supply system for an internal combustion engine, in particular of a motor vehicle. The system includes a pump for delivering fuel into a storage chamber and for producing a pressure in the storage chamber, a pressure sensor for measuring an actual value of the pressure in the storage chamber, a pressure-control valve for influencing the pressure in the storage chamber, and a control unit that is provided with means by which the pressure in the storage chamber is controllable to a setpoint value.
BACKGROUND INFORMATION
Such a fuel supply system is known, for example, in connection with internal combustion engines having direct injection. There, the fuel in the storage chamber is made available under a high pressure. The pressure in the storage chamber is controlled to the desired setpoint value with the aid of the pressure-control valve. To inject the fuel into a combustion chamber of the internal combustion engine, an injection valve belonging to the combustion chamber is opened, and the injected fuel is then ignited with the aid of a spark plug. In internal combustion engines having direct injection, the injection valves are arranged in such a way that the fuel is not injected into an intake manifold or the like, but rather is injected directly into the combustion chambers.
The quantity of fuel to be injected is adjusted with the aid of the period of time the respective injection valve is open. At the same time, this period of time is a function of the pressure in the storage chamber. The greater the pressure, the shorter is the period of time for the injection of the same quantity of fuel. To take into account the pressure in the storage chamber when ascertaining the period of time for injecting, a pressure sensor which measures the actual value of the pressure in the storage chamber is allocated to the storage chamber.
If this pressure sensor is defective, thus if incorrect or no values at all are being measured by the pressure sensor, then, because of this, the period of time, and consequently the proportioning of the fuel quantity to be injected, is falsified.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a method and a fuel-supply system which permit correct injection of fuel, even given a defect in the pressure sensor.
This objective is achieved by the present invention in a method or a fuel-supply system, in that the closed-loop control of the pressure in the storage chamber is superseded by an open-loop control, that is, that the control unit is provided with means by which the closed-loop control of the pressure in the storage chamber is able to be superseded by an open-loop control.
Thus, for example, if the pressure sensor is defective, then the closed-loop control, by which the pressure in the storage chamber is adjusted to the desired setpoint value, is replaced by an open-loop control. With the aid of the open-loop control, it is then possible to take the pressure in the storage chamber into account during the proportioning of the fuel quantity to be injected, at least in so far that a largely correct injection continues to be assured. Thus, the actual values of the pressure in the storage chamber measured by the defective pressure sensor are no longer taken into account in the closed-loop control of the fuel quantity to be injected. Instead, this closed-loop control is superseded, so that the pressure in the storage chamber to be taken into account during the proportioning of the fuel quantity to be injected is then furnished by the open-loop control.
In an advantageous embodiment of the present invention, a fault in the closed-loop control of the pressure in the storage chamber is recognized, and after the recognition of a fault, the closed-loop control is interrupted, and the open-loop control is enabled. In this context, a defect in particular of the pressure sensor can be detected by a plausibility control. For example, the signal driving the pressure-control valve can be compared to the signal emitted by the pressure sensor. If these signals deviate substantially from one another over a longer period of time, then a fault can be inferred from this. After the detection of a fault with respect to the closed-loop control of the pressure in the storage chamber, the closed-loop control can then be superseded by the open-loop control. In this manner, it is assured that the necessity of replacing the closed-loop control by the open-loop control is detected reliably, and that the replacement as such is then carried out reliably.
In an advantageous further embodiment of the present invention, the closed-loop control of the pressure in the storage chamber is superseded by an observer model. Thus, the open-loop control superseding the closed-loop control features an observer model. The observer model ascertains the prevailing, present operating state of the internal combustion engine from a plurality of input signals. An output signal representing a characteristic variable of the internal combustion engine is then generated as a function of this operating state. This output signal can then be used, for example, to simulate the pressure in the storage chamber in the event of a defect in the pressure sensor. Thus, with the aid of the observer model, it is possible to implement the open-loop control to be employed in the event of a defect in the closed-loop control of the pressure in the storage chamber.
It is particularly expedient if the observer model carries out a temperature compensation. In particular, the temperature of the pressure-control valve influencing the pressure in the storage chamber rises relatively strongly during the operation of the internal combustion engine, and especially when the pressure-control valve is in the driven, open state. The result is that the cross-section of the pass-through opening of the pressure-control valve likewise changes. This, in turn, changes the quantity of the fuel flowing through the pressure-control valve, which has a direct effect on the pressure in the storage chamber, and thus on the quantity of fuel to be injected.
When the pressure sensor is functioning correctly, these changes are compensated by a setpoint/actual value comparison of the desired pressure and the actual pressure in the storage chamber, and by the provided closed-loop control of the pressure in the storage chamber. On the other hand, if the pressure sensor is defective, then during the open-loop control superseding the closed-loop control, a temperature compensation is implemented with the aid of the observer model. In so doing, for example, the observer model determines, from a plurality of input signals, an output signal which corresponds to the temperature or to the temperature changes of the pressure-control valve. From this signal, it is then possible to infer the resulting change in the cross-section of the pass-through opening of the pressure-control valve, from which a corresponding compensation can be derived. This temperature compensation can then be taken into account when driving the pressure-control valve, and thus when proportioning the quantity of fuel to be injected.
In another advantageous embodiment of the present invention, a supply voltage which is combined with a temperature-dependent factor is provided for the open-loop control of the pressure in the storage chamber. The supply voltage is applied to the pressure-control valve. If the supply voltage is changed by the temperature-dependent factor, then the changing temperature of the pressure-control valve can be compensated in this manner.
In yet another advantageous embo
Grob Ferdinand
Mentgen Dirk
Rembold Helmut
Stutzenberger Heinz
Gimie Nahmoud M
Kenyon & Kenyon
Robert & Bosch GmbH
Yuen Henry C.
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