Patent ID: 6283097
Filing Date: 2001-09-04
Classification: F02M

Abstract:
In an automotive vehicle having an engine for powering the vehicle, a fuel tank for storing volatile fuel that is to be combusted in combustion chamber space of the engine, and an evaporative emission control system comprising a vapor confinement space for confining volatile fuel vapor and a canister purge valve that is periodically operated to purge vapor from the vapor confinement space to the engine for entrainment with combustible mixture that is to be combusted in the engine combustion chamber space, and a leak detection system operatively associated with the evaporative emission control system for detecting leakage from a portion of the vapor confinement space which is upstream of an inlet of the canister purge valve relative to the engine, the improvement in said leak detection system which comprises:a pump for pumping a gaseous medium;a flowpath providing communication between the pump and the vapor confinement space;a flowmeter for measuring flow of gaseous medium through the flowpath;the flowmeter comprising an electric circuit element disposed in the flowpath to be exposed to flow of gaseous medium through the flowpath;the electric circuit element having a predetermined temperature vs. electric current characteristic that enables the electric circuit element to provide a signal correlated to flow of gaseous medium through the flowpath; andan electric circuit to which the electric circuit element is operatively connected for supplying electric current to the electric circuit element and for creating a signal representative of electric current flow through the electric circuit element, and hence of flow of gaseous medium through the flowpath;in which the flowpath comprises a tubular wall through which the flow of gaseous medium passes, and the thermistor comprises a body which is disposed internally of the tubular wall;said electric circuit element comprises a thermistor; andthe electric circuit and the thermistor form an assembly, the electric circuit is disposed externally of the tubular wall, and leads extend from the electric circuit to the body of the thermistor.