Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Mechanical measurement system
Reexamination Certificate
1999-09-20
2002-08-06
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Mechanical measurement system
C702S033000, C702S098000, C702S105000, C702S183000
Reexamination Certificate
active
06430515
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a method of determining barometric pressure for use in an internal combustion engine of a motor vehicle and, more particularly, to a method of determining barometric pressure based on the manifold absolute pressure and the mass airflow going into the engine, where mass airflow is indicative of a pressure drop between the atmospheric pressure and the manifold absolute pressure.
2. Discussion
Barometric pressure varies with weather conditions and altitude. In a motor vehicle, an accurate determination of barometric pressure is essential for various engine control functions. For instance, precise metering of the amount of air and fuel delivered to the engine is necessary to achieve the desired combustion as well as acceptable vehicle emissions. When the barometric pressure drops, typically the timing needs to be retarded and the fuel mixture richened. In addition, the barometric pressure may also be used to control idle bypass airflow, check for limp-in conditions and other diagnostic functions.
Typically, a barometric pressure sensor is used to measure the atmospheric pressure external to the airflow intake system of an internal combustion engine. In order to save the cost of a barometric sensor, it is desirable to provide a method of determining barometric pressure which may be used for engine control functions associated with a motor vehicle.
SUMMARY OF THE INVENTION
In accordance with the present invention, a method is provided for determining the barometric pressure external to an air intake of an internal combustion engine, comprising the steps of: (a) providing a pressure value indicative of an absolute pressure in the intake manifold of the engine; (b) providing a mass airflow value indicative of an airflow into the engine; (c) characterizing a pressure drop across the intake system based on the mass airflow value; and (d) determining a barometric pressure based on the pressure value and the pressure drop, such that the pressure drop is indicative of the pressure differential between the atmospheric pressure and the pressure in the intake manifold. Furthermore, the determination of the barometric pressure may be triggered when the throttle blade reaches a predetermined throttle threshold position which is a function of the rotational speed of the engine.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from a reading of the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings.
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Coatesworth Timothy A.
Kapolnek Chris D.
Ohl Gregory L.
Sanyal Amit K.
Bacon, Jr. Edwin W.
DaimlerChrysler Corporation
Smith Ralph E.
Tsai Carol S
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