Exhaust gas recirculation control system and method

Claim 1

An exhaust gas recirculation control system for an internal combustion engine having an intake manifold and exhaust manifold, the system comprising: a throttle located in the intake manifold of the engine; a pneumatic exhaust gas recirculation tube coupled between the intake manifold and exhaust manifold of the engine; an electronically controlled vacuum regulator for controlling a valve position of said pneumatic exhaust gas recirculation control valve by converting an electrical signal into a vacuum; an exhaust gas recirculation control valve located in said tube; an orifice located in said tube upstream of said exhaust gas recirculation control valve; a differential pressure sensor for measuring a differential pressure across said orifice indicative of an exhaust gas recirculation flow; and an electronic engine controller for reading said differential pressure sensor, filtering said read differential pressure sensor with a first low pass filter, sensing a throttle position of the throttle, filtering said throttle position with a second low pass filter when said throttle position is opening and filtering said throttle position with a third low pass filter when said throttle position is closing, with said second low pass filter having a lower cut-off frequency than said third low pass filter, generating a desired exhaust gas recirculation flow based on an engine load, an engine speed, and atmospheric pressure, creating an error signal from a difference between said read exhaust gas recirculation flow and said desired exhaust gas recirculation flow, creating an actuation signal for the exhaust gas recirculation control valve based on said error, generating an adjusted actuation signal by adding a function of said filtered throttle position to said actuation signal, and sending said adjusted actuation signal to said vacuum regulator.

Claim 3

A method for controlling exhaust gas recirculation in an internal combustion engine having a throttle, an exhaust gas recirculation control system, said method comprising: sensing an exhaust gas recirculation flow; creating a first signal when the throttle is opening; creating a second signal when the throttle is closing; generating a desired exhaust gas recirculation flow based on an engine load, an engine speed, and atmospheric pressure; creating an error signal from a difference between said sensed exhaust gas recirculation flow and said desired exhaust gas recirculation flow; creating an actuation signal for the exhaust gas recirculation control valve based on said error; and generating an adjusted actuation signal by adding said first signal and said atmospheric pressure to said actuation signal when the throttle is opening and adding said second signal and said atmospheric pressure to said actuation signal when the throttle is closing.

Claim 4

A method for controlling exhaust gas recirculation in an internal combustion engine having a throttle, an exhaust gas recirculation control system, said method comprising: sensing an exhaust gas recirculation flow; creating a first signal when the throttle is opening; creating a second signal when the throttle is closing; generating a desired exhaust gas recirculation flow based on an engine load, an engine speed, and atmospheric pressure; creating an error signal from a difference between said sensed exhaust gas recirculation flow and said desired exhaust gas recirculation flow; creating an actuation signal for the exhaust gas recirculation control valve based on said error; and generating an adjusted actuation signal by adding said first signal and said atmospheric pressure to said actuation signal when the throttle is opening and adding said second signal and said atmospheric pressure to said actuation signal when the throttle is closing.