Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1990-09-17
1992-04-07
Dolinar, Andrew M.
Internal-combustion engines
Charge forming device
Fuel injection system
123492, 123493, F02D 4110
Patent
active
051017954
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to fuel injection systems for internal combustion engines of the type wherein the lengths of fuel injection pulses are based on engine load signals developed from a measurement of intake manifold pressure and wherein compensation is provided for the fuel injection signals during transitions between different dynamic operating conditions such as during acceleration or deceleration.
BACKGROUND OF THE INVENTION
It is known from U.S. Pat. No. 4,534,331 to determine when acceleration enrichment of the engine mixture is appropriate by sequential detection of engine inlet manifold pressure values (representing engine load values) having a predetermined characteristic. For example, acceleration enrichment could be provided when a predetermined number of sequential load values ascended in magnitude according to a specific relationship.
One important condition for the effectiveness of transition compensation during acceleration (or deceleration) is the actuality of the load information which is used to calculate the duration of injection. In a pressure system, the average pressure in the inlet manifold of the engine can, in a static case, be used to calculate load. Thus, in incremental systems, the average pressure is determined, for example by double sensing (at 180.degree. intervals), whereas in segmental systems the average pressure can be obtained by high-frequency integration of pressure over one suction period.
Published European patent publications 0,259,544 and 0,162,469 disclose an acceleration correction of the injection amount, based on the measured pressure in the intake and in dependence on detected intake pressure differences. The correction is an additive one and further dependent on engine parameters, for example, temperature.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved means for obtaining compensation during transition conditions.
In accordance with the present invention, this object is achieved in that inlet manifold pressure values representative of engine load are modified to provide fast acting transition compensation in dependence upon incremental pressure difference values.
This measure has the advantage that it acts equally appropriately both during acceleration enrichment and during leaning out of the fuel air mixture on deceleration.
Advantageously, the pressure difference values are themselves modified by other engine-dependent factors when the measured incremental inlet manifold pressure differences exceed predetermined thresholds.
In a preferred embodiment, above a first threshold of pressure difference, the pressure value representative of engine load is modified additively in accordance with the pressure difference, itself modified by a first engine temperature dependent factor and, above a second threshold of pressure difference, the pressure difference is modified by a second, larger engine temperature-dependent factor.
The aforegoing measures provide transition compensation with a fast-acting response. In addition, slow-acting compensation can be provided by modifying the pressure values slowly in accordance with the running summation of the pressure difference values regulated with a slow time constant.
A further advantage is provided when both the average value of the inlet manifold pressure and the rectified peak value of the inlet manifold pressure over a complete combustion period are established, and wherein, when the peak value exceeds the average value by more than a predetermined threshold, the average value is replaced by the peak value to provide said pressure values modified in dependence upon the incremental pressure difference values to provide transition compensation.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings, in which:
FIG. 1 is a block diagram illustrating part of a control program in accordance with the present invention, involving load calculation;
FIG
REFERENCES:
patent: 4411235 (1983-10-01), Shinoda et al.
patent: 4534331 (1985-08-01), van Belzen et al.
patent: 4643152 (1987-02-01), Yamato
patent: 4747387 (1988-05-01), Takao et al.
Hirschmann Klaus
Junginger Erich
Schnaibel Eberhard
Dolinar Andrew M.
Ottesen Walter
Robert & Bosch GmbH
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