Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1988-03-28
1990-05-15
Nelli, Raymond A.
Internal-combustion engines
Charge forming device
Fuel injection system
F02M 5100
Patent
active
049248359
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Because of increasingly stringent legal requirements on the maximum allowable toxic content of the exhaust gas of internal combustion engines, but also from the standpoint of improving the ride in motor vehicles, electronic control units are used with increasing frequency for controlling various engine parameters. For instance, it is known to calculate the fuel requirement electronically from the aspirated air quantity or air flow rate, or from the pressure in the intake tube and the engine speed, and then to trigger an injection apparatus with a corresponding trigger signal. In full-load operation, however, the intake strokes sometimes cause such major pulsations of the air quantity flow rate signal and hence of the load signal, which may be in the form of an injection duration or a fuel quantity signal, that the mixture composition fluctuates, which is disruptive and causes increased toxic emissions. In engine idling, and in particular in overrunning or engine braking in the idling speed range, the phase displacement between the air quantity or engine speed detection, the injection instant and the torque output also becomes preceptable and is often disruptive. Rough engine idling, and engine "bucking" in overrunning, are the result.
German Patent Disclosure Document DE-OS 24 55 482 describes an arrangement for obtaining signals from which trigger signals for the fuel metering are generated in an electronic control unit. The signals serving as input signals for the control unit and relating to engine speed and aspirated air flow rate are supplied to a rectifier having a low-pass filter characteristic, in order to damp any alternating voltage components that may be present and that can arise from factors external to the operation. Since the low-pass filter characteristic of the rectifier remains fixed, or in other words is not adapted to changing engine states, the arrangement does not always function completely satisfactorily. Above all, when there are sudden load changes, filter-dictated delays in fuel metering occur.
SUMMARY OF THE INVENTION
It is the object of an invention to provide a method with which the above-mentioned effect of filter devices can be reduced, if not eliminated completely. This and other objects are attained by means a method for eliminating interfering a.c. components from a fuel injection control signal by means of computing and generating a basic injection duration control signal in dependency on predetermined engine variables such as engine speed, airflow rate, etc., and filtering the basic injection duration control signal by a filter whose damping characteristics for the a.c. components is changed in response to predetermined values of at least one engine variable.
ADVANTAGES OF THE INVENTION
The method according to the invention has the advantage over the known prior art that a filter of variable characteristic is used. A further advantage is that it is not the input signals of the control unit, but rather the output signals calculated from them, that are filtered. A further advantage is that in steady or quasi-steady operation of the engine, the damping characteristic of the filter is derived from a field of characteristics of an at least two-dimensional performance graph, by means of which the damping effect of the filter can be adapted to the momentary operating range of the engine.
The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a device for carrying out an embodiment of the method of the invention;
FIG. 2 is a graph showing a variable damping characteristic of the filter in the device of FIG. 1;
FIG. 3 shows an engine
REFERENCES:
patent: 4051818 (1977-10-01), Volckers
Nelli Raymond A.
Robert & Bosch GmbH
Striker Michael J.
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