Internal-combustion engines – Charge forming device – Auxiliary control of carburetor fuel metering
Patent
1978-08-10
1981-02-24
Myhre, Charles J.
Internal-combustion engines
Charge forming device
Auxiliary control of carburetor fuel metering
123445, 123446, F02B 3300
Patent
active
042520983
ABSTRACT:
The invention is disclosed in the preferred embodiment as an electronic feedback carburetor system wherein, in the closed-loop mode of operation, an oxygen sensor monitors the oxygen concentration of the exhaust gases and supplies a signal to an electronic control unit which in turn causes a command signal to be supplied to the carburetor for adjusting the air/fuel ratio to a commanded value. The electronic control unit contains unique circuitry which selectively provides closed-loop and open-loop modes of operation depending upon the condition of other input signals to the electronic control unit. The circuitry contains integrator and stability circuits which are both utilized in the closed-loop mode to develop from the oxygen sensor signal a composite signal which provides for closely regulated control of the air/fuel ratio about a desired operating point at or in the vicinity of stoichiometric. This composite signal provides, in response to a change in state of the oxygen sensor, a predetermined amount of change in the command signal to the carburetor which is maintained for a time interval equal to the transport time of the mixture from the carburetor through the engine to the oxygen sensor. With the engine running under a fairly steady state condition the amount of correction and the duration thereof are sufficient to cause the sensor to switch back to its original state, and in this way the air/fuel ratio is closely regulated about the desired operating point. Where the engine experiences a more dynamic change in its operation, additional correction is made after the termination of the transport time interval. Extreme transient conditions cause interruption of the closed-loop mode of operation in favor of the open-loop mode; the open-loop mode also prevails during initial running of the engine after starting. When the system mode changes from closed-loop to open-loop, the integrator signal is locked in the integrator so that when the closed-loop operation resumes, the system can more rapidly attain the desired operating point. The closed-loop circuitry also contains a programming device which provides programming capability without requiring change to the layout of the circuit on a circuit board. There is also a fault detection circuit which provides for fault detection, such as might be occasioned by a failed oxygen sensor. Additional features are also disclosed.
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Tomczak Lawrence W.
Vorndran John R.
Chrysler Corporation
Myhre Charles J.
Nelli Raymond A.
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