Closed loop fuel control for internal combustion engine

Claim 1

A closed loop fuel injection system for proportioning a mixture of air and fuel delivered to an internal combustion engine comprising: (a) sensor means for producing an electrical signal having a magnitude that varies in proportion to the concentration of exhaust gas from said engine; (b) first electrical circuit mean responsive to said electrical signal to compensate for small amplitude, short term disturbances in said electrical signal, said first circuit means having high gain, low stability and restrictive modification capability over said electrical signal, for providing a first circuit signal with an amplitude limited to a small value; (c) second electrical circuit means responsive to said electrical signal to compensate for large amplitude, long term disturbances in said electrical signal, said second circuit means having low gain, high stability, and large modification capability over said electrical signal for providing a second circuit signal with a large amplitude; (d) said first circuit means having a response time that varies directly with and is substantially the same as the time between formation and detection of said air fuel mixture, and being adapted to correct any part of said large amplitude disturbances that is not corrected by said second circuit means; (e) said second circuit means having a response time longer than the response time of said first circuit means, and being adapted to at least partially correct said large amplitude disturbances; (f) means for combining the first and second circuit signals to produce a composite pulse of variable width to fix the proportion of air-fuel in said mixture; (g) means for applying said composite pulse to an injector of said internal combustion engine; (h) wherein said means for combining includes a timing means connected to receive said circuit signals, means for enabling said timing means, said timing means being enabled in response to said enabling means and producing a timing signal having a time period responsive to said first and second circuit signals, said composite pulse of variable width produced by said means for combining, having a variable width responsive to said time period.