Regulated flow canister purge system

Claim 1

For controlling the purging of a fuel vapor collection canister of an evaporative emission control system associated with the fuel system of an internal combustion engine, a regulated flow canister purge arrangement comprising an electronic vacuum regulator having a vacuum inlet at which engine manifold vacuum is received, an outlet at which is delivered a percentage of the engine manifold vacuum received at the vacuum inlet as determined by an electronic control signal supplied to a control input of the electronic vacuum regulator, a canister purge inlet to which a canister that is to be purged of gaseous fuel vapors is communicated, a canister purge outlet that is communicated to engine manifold vacuum, valve means for controlling flow between said canister purge inlet and said canister purge outlet, and a movable wall for operating said valve means, one side of said movable wall bounding one variable volume chamber and another side of said movable wall bounding another variable volume chamber, biasing means acting on said movable wall so as to cause said valve means to be biased toward blocking flow between said canister purge inlet and said canister purge outlet, and means communicating the outlet of said electronic vacuum regulator with said one variable volume chamber to cause the volumes of said chambers to vary in relation to the percentage of manifold vacuum applied to said one variable volume chamber, characterized in that: vacuum in said another variable volume chamber is caused to be correlated in a predetermined manner with engine manifold vacuum; in that in steady state operating conditions wherein the magnitude of intake manifold vacuum and the value of said control signal are held constant, said valve means operates to allow a corresponding, substantially constant flow rate from said canister purge inlet to said canister purge outlet that is correlated with the intake manifold vacuum and control signal values; in that for a certain steady state value of intake manifold vacuum and a certain steady state value of said control signal, said valve means operates to allow a certain corresponding flow rate from said canister purge inlet to said canister purge outlet; in that in response to a change in intake manifold vacuum from said certain steady state value thereof while said control signal remains unchanged at said certain steady state value thereof, said valve means is re-adjusted such that the flow rate between said canister purge inlet and said canister purge outlet is allowed to continue substantially unchanged at said certain flow rate; and in that in response to a change in said control signal from said steady state value thereof while the magnitude of intake manifold vacuum remains unchanged at said steady state value thereof, said valve means is re-adjusted such that the flow rate between said canister purge inlet and said canister purge outlet is changed from said certain flow rate to an amount correlated with the change in said control signal.