Internal-combustion engines – Spark ignition timing control – Electronic control
Reexamination Certificate
1999-12-17
2001-04-03
Solis, Erick (Department: 3747)
Internal-combustion engines
Spark ignition timing control
Electronic control
C123S436000, C701S111000
Reexamination Certificate
active
06209519
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to the improvement of the quiet running of an engine by equalizing the torque components of the individual cylinders as to the total torque of an internal combustion engine. Here, the engine can be a spark-ignition engine or a diesel engine. A detection of the actual torque of a cylinder takes place via an evaluation of the time-dependent course of the rotation of the crankshaft or of the camshaft. A torque correction takes place via an intervention on at least one of the variables: injected fuel quantity, air quantity or ignition time point in a spark-ignition engine, exhaust-gas return rate, injection position or cylinder compression. The term “injection position” relates to the angular position of an injection pulse to a reference point such as top dead center of the piston of a cylinder in a combustion stroke.
A method for cylinder equalization is disclosed in U.S. Pat. No. 4,688,535. In this method, segment times are detected to evaluate the time-dependent course of the rotational movement of the crankshaft or camshaft. Segment times are the times in which the crankshaft or camshaft passes through a predetermined angular region assigned to a specific cylinder. The more uniformly the engine runs, the lesser are the differences between the segment times of the individual cylinders. From the above-mentioned segment times, an index for the rough running of the engine can therefore be formed. In the known method, a controller is assigned to each cylinder of the engine and a rough-running actual value specific to a cylinder is supplied to the controller as an input signal. The rough-running values of several cylinders are averaged to form the desired control value. The mean value serves as the desired value. At the output end, the controller influences the cylinder-specific injection time and therefore the cylinder-individual torque contribution such that the cylinder-individual rough-running actual value approaches the desired value.
Rough-running values, which are obtained from rpm signals, are also used for detecting combustion misfires. Quotients are formed as rough-running values LUT in the method disclosed in U.S. Pat. No. 5,861,553. In the numerator of these quotients, differences of sequential segment times are present and the denominator of these quotients contains the third power of one of the participating segment times. This quotient can be weighted with additional factors as well as be provided with a dynamic correction which considers rpm changes of the entire engine. With respect to the formation of rough-running values, U.S. Pat. No. 5,861,553 is incorporated herein by reference. The sum of these rough-running values, which is formed over one camshaft rotation, is equal to zero for a constant engine rpm.
The detection of defects of the transducer wheel system as well as the detection of the component of the rough running which is based on torsion vibrations of the crank drive and on different energy releases in different cylinders, is known from U.S. Pat. No. 5,822,710.
The detected defects and the above-mentioned rough-running component serve to provide a computed correction of the rough-running values for the detection of combustion misfires. For example, in overrun operation with a six-cylinder engine, the segment times (t1, t2, t3) of the three transducer wheel segments are detected. At each segment time, a corrective value (K1, K2, K3) is formed and additively or multiplicatively coupled to the segment time (Kt1=t1*K1 or t1*K1, . . . ). The corrective values are so determined that the results Kti (wherein i=1 to 3) are equal to each other. Such a correction considerably improves the quality of the detection of combustion misfires which is based on the evaluation of rpm fluctuations.
SUMMARY OF THE INVENTION
It is an object of the invention to minimize the real cylinder-individual differences in the combustion between the cylinders with a control concept. The torque components of the cylinders are then of the same magnitude. The real differences here characterize the rough-running component which is based on different combustion but not on torsion vibrations and/or transducer wheel defects.
The electronic control arrangement of the invention is for equalizing torque contributions of different cylinders of an internal combustion engine to the total torque of the engine which can operate in an overrun mode and in a fired mode. The electronic control arrangement includes: means for providing first quantities (Ka) of a rough running of the engine in the overrun mode and second quantities (Kvi) in the fired mode; means for providing third quantities (Ksi) for a rough-running component based on torsion vibrations; means for forming cylinder-individual fourth quantities (Kki) for the rough running from the first, second and third quantities with the fourth quantities being independent of the rough running in the overrun mode and independent of the rough-running component based on the torsion vibrations; and, means for equalizing the torque contributions on the basis of the fourth quantity.
Especially advantageous effects occur during idle and in the lower part-load range because these ranges exhibit especially intense smooth running effects or rough-running effects as a consequence of varying torque components of different cylinders.
The combination of the above features permits a separation of the influences of different causes of rpm fluctuations. These influences are described below as items (a) to (c).
Item (a)
Disturbances, which are caused by defects of the rpm detection system, occur synchronously with the rotation movement of the transducer wheel and are synchronous to the rotational movement thereof because of the coupling of the transducer wheel to the crankshaft. These disturbances are independent of load and can be learned during overrun operation. For example, for an eight-cylinder engine, four corrective values KA, KB, KC and KD can be formed.
Item (b)
Non-uniformities, which are based on torsion vibrations of the crank drive are mostly synchronous to the rotation movement of the camshaft and typically at specific resonance rpms. The vibration components are independent of deterioration and can be computed. The vibration components can also be determined utilizing measurements as an alternative to a computation. For an eight-cylinder engine, there are eight corrective values KS1, . . . ,KS8, which can be stored in a corrective characteristic field of the engine control apparatus.
Item (c)
Differences because of the combustion process, for example, because of varying cylinder charges, are synchronous to the rotation of the camshaft and are dependent upon deterioration because of different wear of the cylinder/piston pairing. In the following, these differences are assigned eight corrective values (Kv1, . . . ,Kv8) in the example of an eight-cylinder engine.
An essential element of the invention is to intervene in the management of the engine based on the above-mentioned corrective values so that the torque components of the different cylinders are equalized.
In this context, the computed correction of the mechanical faults of the segment time detection system (transducer wheel tolerances) is especially important in the detection of the segment times during overrun operation because these would otherwise be controlled out by a controlled intervention. The consequence would be a real physical rough running which would generate a signal of perfect smooth running in combination with the mechanical defects.
According to the invention, corrective values Kvi are learned in fired operation; and, in overrun operation, corrective values Ka, Kb, . . . , et cetera are learned and are coupled to predetermined corrective values Ksi.
What is decisive in the computation of the corrective values is that the different systematic disturbance components are considered separately. What is essential in this context is especially the use of predetermined values for the torsion vibration effects because these ef
Melchior Gerard
Ries-Muller Klaus
Ottesen Walter
Robert & Bosch GmbH
Solis Erick
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