Patent ID: 6082189
Filing Date: 2000-07-04
Classification: F02M

Abstract:
A method of checking a functional operability of a tank venting system of an internal combustion system of a motor vehicle, the tank venting system including:a container for absorbing fuel vapors communicating via a venting line with a fuel tank and via a regeneration line with an intake pipe of an internal combustion engine, and the container having an air intake connected to atmosphere and which is closeable by means of a shut-off valve for checking the tank venting system;a pressure sensor detecting a system pressure of the tank venting system;a tank venting valve in the regeneration line, the tank venting valve being selectively opened for feeding the fuel vapor stored in the container and for build up of a negative pressure in the tank venting system;the method which comprises:temporarily classifying the tank venting system as not serviceable ifthe system pressure does not satisfy a predetermined condition when a negative pressure is increasing in the system with the tank venting valve open and the shut-off valve closed; orthe system pressure does not satisfy a further predetermined condition when the negative pressure is decaying with the tank venting valve closed and the shut-off valve closed;checking operating variables of the motor vehicle, including operating variables of the internal combustion engine and the tank venting system; andaborting the diagnosis if predefined operating variable values are not attained at which a statement about a functional operability of the system is possible;registering chronologically successive pressure values and using the successive pressure values as input variables for a physical model which simulates a pressure variation in the event of a leak in the tank venting system based on a gas mass flow flowing through an opening, and forming a parameter with the physical model which describes a curve variation of the pressure during the diagnosis and which contains information about a leak area;comparing a value representing the leak area with a given threshold value; andevaluating a tightness of the tank venting system on the basis of a result obtained in the comparing step.