Automotive evaporative emission leak detection system

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;
• and
• an 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 pump comprises an outlet communicated via the flowpath to the vapor confinement space and an inlet that is selectively communicated to atmosphere via a valve, means causing the valve to be open while the pump operates to pressurize the vapor confinement space to a predetermined superatmospheric pressure, and means causing the valve to be closed when the pressure in the vapor confinement space is at the predetermined superatmospheric pressure.

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;
• and
• an 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;
• wherein a housing containing the flowmeter is disposed in the flowpath, and the housing is constructed and arranged such as to provide two flow branches, one of which contains the flowmeter, and the other of which contains a valve for allowing and disallowing flow through the other branch.

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 leak detection system comprising:

• 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;
• and
• in which the pump comprises an outlet communicated via the flowpath to the vapor confinement space and an inlet that is selectively communicated to atmosphere via a valve, means causing the valve to be open while the pump operates to pressurize the vapor confinement space to a predetermined superatmospheric pressure, and means causing the valve to be closed when the pressure in the vapor confinement space is at the predetermined superatmospheric pressure.

An assembly for use in a leak detection system operatively associated with an evaporative emission control system of an engine powered automotive vehicle for detecting leakage from a portion of a vapor confinement space which is upstream of an inlet of a canister purge valve relative to an engine, the assembly comprising:

• a housing comprising a first port adapted to be communicated to a pump, a second port adapted to be communicated to a vapor confinement space, and two parallel branches in that portion of the flowpath that passes through the housing;
• a flowmeter for measuring flow of gaseous medium through the flowpath;
• and
• a valve for allowing and disallowing flow through one of the two branches.

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 leak detection system comprising:

• 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;
• and
• an electric circuit for selectively operating the pump and for processing the gaseous flow measurement of the flowmeter in accordance with an algorithm that comprises means for causing the electric circuit to detect a first state of stability of the gaseous flow measurement of the flowmeter while the pump is running, means for causing the electric circuit to detect a second state of stability of the gaseous flow measurement of the flowmeter while the pump is not running, and means for causing the electric circuit to process the value of the first state of stability of the gaseous flow measurement of the flowmeter and the value of the second state of stability of the gaseous flow measurement of the flowmeter.

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 performing a leakage detection test 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 method of performing the leak detection test comprising:

• pumping a gaseous medium through a flowpath that communicates the vapor confinement space to atmosphere;
• measuring flow of gaseous medium through the flowpath;
• selectively operating the pump;
• processing the gaseous flow measurement of the flowmeter in accordance with an algorithm that detects a first state of stability of the gaseous flow measurement of the flowmeter while the pump is running and that detects a second state of stability of the gaseous flow measurement of the flowmeter while the pump is not running;
• and
• processing the value of the first state of stability of the gaseous flow measurement of the flowmeter and the value of the second state of stability of the gaseous flow measurement of the flowmeter.

An assembly for use in a leak detection system operatively associated with an evaporative emission control system of an engine powered automotive vehicle for detecting leakage from a portion of a vapor confinement space which is upstream of an inlet of a canister purge valve relative to an engine, the assembly comprising:

• a fluid pumping device;
• a housing comprising a flowpath through which the fluid pumping device conveys gaseous fluid relative to the vapor confinement space incidental to a leakage detection test;
• a flowmeter for measuring flow of gaseous medium through the flowpath;
• the housing comprising plural housing parts in assembly relation cooperatively defining the flowpath;
• a first of the housing parts comprising a first port for the flowpath;
• and
• a second of the housing parts comprising a walled tube forming a portion of the flowmeter;
• wherein the housing further comprises a second port for the flowpath;
• the flow conveyed by the fluid pumping device enters the flowpath at one of the ports and exits the flowpath at the other of the ports;
• and
• the entire flow relative to the vapor confinement space is equal to the entire flow conveyed by the fluid pumping device.

An assembly for use in a leak detection system operatively associated with an evaporative emission control system of an engine powered automotive vehicle for detecting leakage from a portion of a vapor confinement space which is upstream of an inlet of a canister purge valve relative to an engine, the assembly comprising:

• a fluid pumping device;
• a housing comprising a flowpath through which the fluid pumping device conveys gaseous fluid relative to the vapor confinement space incidental to a leakage detection test;
• a flowmeter for measuring flow of gaseous medium through the flowpath;
• the housing comprising a first port for the flowpath;
• and
• the port comprising a walled tube forming a portion of the flowmeter;
• wherein the housing further comprises a second port for the flowpath;
• the flow conveyed by the fluid pumping device enters the flowpath at one of the ports and exits the flowpath at the other of the ports;
• and
• the entire flow relative to the vapor confinement space is equal to the entire flow conveyed by the fluid pumping device.

An assembly for use in a leak detection system operatively associated with an evaporative emission control system of an engine powered automotive vehicle for detecting leakage from a portion of a vapor confinement space which is upstream of an inlet of a canister purge valve relative to an engine, the assembly comprising:

• a fluid pumping device;
• a housing comprising a flowpath through which the fluid pumping device conveys gaseous fluid relative to the vapor confinement space incidental to a leakage detection test;
• a flowmeter for measuring flow of gaseous medium through the flowpath;
• the housing comprising a first port for the flowpath;
• and
• a wall that divides the first port into first and second flow branches each of which conveys a fraction of the total flow through the first port, one of the branches comprising the flowmeter;
• wherein the housing further comprises a second port for the flowpath;
• the flow conveyed by the fluid pumping device enters the flowpath at one of the ports and exits the flowpath at the other of the ports;
• and
• the entire flow relative to the vapor confinement space is equal to the entire flow conveyed by the fluid pumping device.