Claims
- 1. An air-to-fuel ratio control system for an internal combustion engine comprising:
- a sensor, disposed in the exhaust pipe of an engine, for producing a sensor output signal having a signal level indicative of the air-to-fuel ratio of mixture supplied to said engine;
- a comparison circuit, connected to said sensor, for producing a comparison output signal the signal level of which is stepwise changed between two constant levels each time said signal level of said sensor output signal reaches a constant level predetermined with reference to a desired air-to-fuel ratio;
- an integration circuit, connected to said comparison circuit, for producing an integration output signal the signal level of which is increased and decreased with the time lapse while said signal level of said comparison output signal is kept at one and the other between said two constant levels, respectively;
- a correction circuit, connected between said comparison circuit and said integration circuit, for stepwise correcting said signal level of said integration output signal in synchronism with the level change of said comparison output signal such that said signal level of said integration output signal is abruptly decreased and increased by a predetermined level when the changing direction of said integration output signal is reversed from the increasing to decreasing directions and from the decreasing to increasing directions, respectively; and
- mixture supply means for supplying said engine with the mixture having an air-to-fuel ratio corrected in accordance with said signal level of said integration output signal.
- 2. An air-to-fuel ratio control system according to claim 1 further comprising:
- detection means for producing a detection output signal while at least one operating parameter of said engine is in a predetermined range; and
- a hold circuit, connected to said detection means and said integration circuit, for holding said signal level of said integration output signal at a predetermined constant level irrespective of the level change of said comparison output signal while said detection output signal is produced, whereby correcting the air-to-fuel ratio of mixture is prevented.
- 3. An air-to-fuel ratio control system according to claim 2, wherein said detection means includes:
- an engine temperature detector, adapted to detect the temperature of said engine, for producing said detection output signal while said temperature is lower than a predetermined engine temperature.
- 4. An air-to-fuel ratio control system according to claim 2, wherein said detection means includes:
- an exhaust temperature detector, adapted to detect the temperature of exhaust gases flowing through said exhaust pipe, for producing said detection output signal while said temperature is lower than a predetermined exhaust temperature.
- 5. An air-to-fuel ratio control system according to claim 2, wherein said detection means includes:
- a throttle detector, adapted to detect the opening angle of throttle valve of said engine, for producing said detection output signal while said throttle valve is closed.
- 6. An air-to-fuel ratio control system according to claim 1, wherein said correction circuit includes inverter means for proportionally inverting said signal level of said comparison output signal, and wherein said integration circuit includes:
- an amplifier having a non-inverting input terminal and an inverting input terminal, said non-inverting input terminal being connected to receive the output signal of said inverter means and said inverting input terminal being connected to receive said comparison output signal; and
- a capacitor, connected across the inverting input terminal and the output terminal of said amplifier.
- 7. An air-to-fuel ratio control system according to claim 6 further comprising:
- a temperature detector, adapted to detect the temperature of said engine, for producing a detection signal while the temperature of said engine is lower than a predetermined temperature; and
- a hold circuit, connected to said temperature detector and said integration circuit, for holding said level of said integration output signal at a predetermined constant level irrespective of the level change of said comparison output signal while said detection signal is produced, whereby correcting the air-to-fuel ratio of mixture is prevented.
- 8. An air-to-fuel ratio control system according to claim 7, wherein said hold circuit includes:
- comparator means for comparing said signal level of said integration output signal with said predetermined constant level at which said integration output signal is held; and
- switching means, adapted to be switched to a first switch condition while said detection signal is not generated and to a second switch condition while said detection signal is generated, for applying said comparison output signal to said integration circuit during said first switch condition and applying the output signal of said comparator means to said integration circuit during said second switch condition, whereby said integration circuit keeps changing said signal level of said integration output signal to said predetermined constant level while said switching means is switched to said second switch position.
- 9. An air-to-fuel ratio control system according to claim 8, wherein said mixture supply means includes a fuel injection device adapted to control fuel supply amount by a pulse signal which is corrected in accordance with said integration output signal, and wherein said integration circuit is adapted to control the integrating operation thereof in accordance with said pulse signal.
- 10. An air-to-fuel ratio control system according to claim 1, wherein said comparison circuit includes delay means for delaying said comparison output signal such that durations of one and the other between said two constant levels of said comparison output signal are increased and decreased by a predetermined constant time interval, respectively, whereby the air-to-fuel ratio of mixture to be supplied to said engine is corrected to the one other than said desired ratio.
Priority Claims (3)
Number |
Date |
Country |
Kind |
50-683201 |
Jun 1975 |
JPX |
|
50-70295 |
Jun 1975 |
JPX |
|
50-89857 |
Jul 1975 |
JPX |
|
Parent Case Info
This is a continuation of application Ser. No. 688,390 now abandoned filed May 20, 1976.
US Referenced Citations (6)
Non-Patent Literature Citations (1)
Entry |
"Electronic Closed Loop Controls for Automobiles", John F. Cassidy, Jr., from Automotive Electronics, 2/74. |
Continuations (1)
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Number |
Date |
Country |
Parent |
688390 |
May 1976 |
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