Measuring and testing – Vehicle chassis – Steering
Patent
1995-05-08
1997-03-04
Chilcot, Richard
Measuring and testing
Vehicle chassis
Steering
123435, G01M 1500
Patent
active
056081618
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method of determining the combustion air ratio .lambda. (which is the ratio of the quantity of air supplied, to the minimum quantity of air required for the combustion of one unit of quantity of fuel) of a reciprocating-piston internal combustion engine, particularly an Otto engine.
The methods used at this time to determine the combustion air ratio .lambda. in reciprocating-piston internal combustion engines are based on the determination of the air mass, and the fuel mass, or an evaluation of the chemical composition of the exhaust gas. The disadvantage of these methods is that an exact determination of the combustion air ratio cannot be performed for individual operating cycles, particularly at higher engine rpms. In measurement processes employing a so-called leanness sensor, the problem arises of the considerable temperature dependency of this type of sensor, which leads to erroneous measurements without extensive temperature compensation. Moreover, with the aid of a lambda sensor measurement or leanness sensor measurement, ultimately only averaged values can be detected which may still be sufficient for the regulations and/or controls of the fuel supply system of an internal combustion engine. With the aid of a lambda sensor measurement or leanness sensor measurement, however, it is possible to make more precise statements about the operating-cycle-specific combustion air ratio as a function of the combustion process, which is necessary in particular for the optimization of aggregates as a whole, i.e., reciprocating-piston internal combustion engines, including the aggregates needed for regulation and control.
SUMMARY OF THE INVENTION
The object of the invention is to create a method that permits the determination of the combustion air ratio .lambda. for individual operating cycles.
In the method of the invention, the gradient of the combustion chamber pressure is measured, as a function of the position of the piston in the cylinder, for at least one operating cycle, and the measured signals that represent the gradient of the combustion chamber pressure are digitized, and the digitized measured signals are entered into a programmed evaluation unit in which the value of the combustion air ratio is calculated from the measured gradient of the combustion chamber pressure in an iterative computational process, and the result of calculation is outputted. The basis of evaluation in the evaluation unit is the rule that the energy prior to combustion and the energy following or toward the end of combustion are identical, or at least nearly identical.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates two graphical curves of an equation utilized by the present invention.
FIG. 2 is a graphical representation of a typical dependency of the course of a combustion function on the combustion air ratio.
FIG. 3 is a graphical representation of individual, typical operating cycles in which the average combustion ratio is varied.
DETAILED DESCRIPTION OF THE INVENTION
Evaluation preferably takes place based on the following equation: ##EQU2##
In a useful embodiment, at least one distinction parameter, particularly the distinction parameter of "rich/lean," is additionally entered into the evaluation unit in order to eliminate ambiguity. It is especially advantageous when at least one distinction parameter derived from the measurement of the gradient of the combustion chamber pressure is entered into the evaluation unit.
The method of the invention permits the determination of the combustion air ratio .lambda., independently of the rpm of the engine, for individual operating cycles. An assumption of the invention is that, by means of combustion, the chemical energy level of the gas mixture in the cylinder decreases, and the energy is released as change-in-volume work and wall heat. This conservation of energy is described by Equation 1.1 for the phase from the time of ignition to the end of combustion, where
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Chilcot Richard
FEV Motorentechnik GmbH & Co. Kommanditgesellschaft
McCall Eric S.
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