Internal-combustion engines – Spark ignition timing control – Electronic control
Patent
1999-02-25
2000-05-16
Yuen, Henry C.
Internal-combustion engines
Spark ignition timing control
Electronic control
12340637, F02P 5152
Patent
active
060621990
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND INFORMATION
It is described in, e.g., the handbook.
It is known from the related art, e.g., the handbook Autoelektrik/Autoelektronik am Ottomotor/Bosch [Automotive Electrical and Electronic Systems on the Spark Ignition Engine/Bosch](1st edition, VDI Verlag 1987, ISBN 3-18-419 106-0), that the operation of an internal combustion engine should approach the knock limit as closely as possible for optimum torque. Knocking is an uncontrolled form of combustion which can damage an engine. For this reason, the firing angle is normally set so that there is always a safety margin from the knock limit. However, since the knock limit depends on fuel quality, engine condition and environmental conditions, gasoline consumption may be impaired due to the safety margin of late firing angles. Therefore, there have been many attempts to determine the knock limit during operation and set the firing angle as close to this known limit as possible. To guarantee operation as close to the knock limit as possible, knock sensors are provided to detect knocking and relay an appropriate signal to the control unit. One knock sensor is usually provided for multiple cylinders to detect knocking noises in these cylinders. In internal combustion engines with a large number of cylinders or with an unfavorable arrangement of cylinders, a knock sensor cannot sense all cylinders equally well due to the knock sensor installation site. In such cases, two knock sensors may be used per engine to permit analysis of sounds in all cylinders as much as possible.
SUMMARY OF THE INVENTION
The method of knock control according to the present invention with the characterizing features of the main claim has the advantage in comparison with the known method that knock control can also be performed for all cylinders in multicylinder internal combustion engines even if only one knock sensor is provided for a group of cylinders and not all cylinders are sensed equally well by the knock sensor. In normal operation of an internal combustion engine, knock control is performed for each cylinder individually on the basis of knocking in the individual cylinders. In certain operating ranges, e.g., at a very high rpm, operation is switched to knock control with a lead cylinder. Using only one knock sensor for a group of multiple cylinders also has the advantage that only the signal of one knock sensor need be analyzed, thereby reducing analysis expense and thus freeing up computer capacity. The advantage of selecting at least one cylinder from the group of cylinders as one or more lead cylinders, with the selected cylinder(s) preferably being the cylinder(s) of the cylinder group sensed best by the knock sensor or the cylinder(s) with the highest incidence of knocking, is that knocking in this cylinder or in these cylinders permits knock control for all cylinders. The other cylinders of the cylinder group are guided along the knock limit as guided cylinders on the basis of knocking in the lead cylinder(s). This permits even better knock-free operation of the internal combustion engine at the knock limit. Another advantage is that knocking detected in one of the guided cylinders causes a knock adjustment only in this cylinder. This prevents a firing adjustment, which causes a loss of torque, from being triggered in all cylinders.
It is also advantageous. It is especially advantageous to perform the ignition retard of the guided cylinder in a plurality of steps, so that sudden changes in torque are prevented. It is further advantageous to provide a safety offset in the firing angle ignition retard value for the guided cylinders in comparison with the lead cylinder, because then the knocking tendency in these guided cylinders is reduced in comparison with the lead cylinders operated directly at the knock limit.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows an exemplary diagram of an ignition system for performing a knock control.
FIG. 2 shows firing angle curves of a lead cylinder and a guided cylinder over time.
FIG. 3 shows individual procedural st
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patent: 4625692 (1986-12-01), Kashimura et al.
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patent: 5027775 (1991-07-01), Iwata
Entenmann Robert
Franke Steffen
Haeming Werner
Surjadi Iwan
Unland Stefan
Robert & Bosch GmbH
Vo Hieu T.
Yuen Henry C.
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