Method and apparatus for controlling air-fuel ratio in an internal combustion engine

• US 4,503,824 A
• Filed: 02/03/1984
• Issued: 03/12/1985
• Est. Priority Date: 09/05/1980
• Status: Expired due to Term

• Current Assignee: Nippondenso Co., Ltd. (DENSO Corporation)
• Original Assignee: Nippondenso Co., Ltd. (DENSO Corporation)
• Inventors: Kawashima, Yutaka, Ninomiya, Masakazu, Suzuki, Atsushi
• Primary Examiner(s): Cox, Ronald B.
• Application Number:
  US06/576,773
• Time in Patent Office: 403 Days
• Field of Search: 123/435, 123/436, 123/443, 123/440, 123/425, 123/419
• US Class Current: 123/436
• CPC Class Codes: F02D 41/1474 by detecting the commutation time of the sensor
• CPC Class Codes: F02D 41/1483 Proportional component
• CPC Class Codes: F02D 41/263 the program execution being modifiable by physical parameters

Abstract

A method for controlling the air-fuel ratio in an internal combustion engine in which the correction of a base air-fuel ratio is carried out on the basis of the determination as to whether the base air-fuel ratio is on the richer or the leaner side of the air-fuel ratio corresponding to optimum specific fuel consumption, the determination being carried out by comparing four driving state indicating signals at different air-fuel ratios with each other, the correction being directed to bringing the base air-fuel ratio closer to the air-fuel ratio corresponding to the optimum specific fuel consumption.

Claims

1. A method for controlling the air-fuel ratio in an internal combustion engine, which comprises the steps of:

obtaining the base air-fuel ratio determined by a base fuel amount and a base intake air amount,

detecting the signal which represents the rotation rate of the engine in operation,

selecting the air-fuel ratio at the richer side of the base air-fuel ratio and the air-fuel ratio at the leaner side of the base air-fuel ratio in the vicinity of the base air-fuel ratio, by regulating the rate of the air flow in a by-pass for the main air path in the engine, said air flow in said by-pass being supplied to the downstream of a throttle valve,

driving the engine using an air-fuel mixture with said selected at least two air-fuel ratios in the richer and the leaner side during predetermined periods,

detecting the signals which represent the engine status while the engine is running with the richer side air-fuel ratio and the engine status while the engine is running with the leaner side air-fuel ratio,

storing the detected signals which represent the engine statuses,

comparing four signals representing four engine statuses detected during four running periods including two running periods with the richer side air-fuel ratio and two running periods with the leaner side air-fuel ratio,

determining, based on the result of said comparison, whether the air-fuel ratio is the value in the richer or the leaner side of the air-fuel ratio corresponding to the maximum specific fuel consumption, and

correcting the base air-fuel ratio by changing the base fuel injection amount, based on the result of said determination, so as to become closer to the air-fuel ratio corresponding to the best specific fuel consumption.

2. A method according to claim 1, wherein the control of the air-fuel ratio is performed by changing the amount of the fuel injection.

3. A method according to claim 1, wherein the control of the air-fuel ratio is performed by regulating the rate of the by-passing air flow through an electromagnetic valve in a by-pass for the main air path.

4. A method for controlling the air-fuel ratio of a running internal combustion engine having an air intake passage containing a throttle valve for controlling the amount of intake air flowing to the engine and a bypass passage for delivering a flow of bypass air to the air intake passage downstream of the throttle valve, the method comprising:

supplying a base fuel amount to the running engine in accordance with the amount of intake air to obtain a predetermined base air-fuel ratio;

producing a signal which represents the rotation rate of the engine;

delivering a dithered flow of bypass air to the intake passage downstream of the throttle valve to produce at least two selected air-fuel ratios in a range between relatively richer and relatively lea ner air-fuel ratio values in the vicinity of the base air-fuel ratio;

detecting the signals which represent the ro tation rates of the engine during successive periods of running at said at least two different selected air-fuel ratios;

storing said detected signals;

comparing said stored signals representing engine rotation rates during at least three running periods, including first and third running periods at a first one of said selected air-fuel ratios and an intermediate second running period at a second one of said selected air-fuel ratios;

determining, based on the result of said comparison, whenever the engine rotation rate during said second running period is either greater than or less than the engine rotation rates during both of said first and third running periods; and

changing the base fuel amount supplied to the engine, in response to such a determination, to correct the base air-fuel ratio so as to become closer to the air-fuel ratio corresponding to an optimum specific fuel consumption for the engine.

5. A method for controlling the air-fuel ratio of a running internal combustion engine according to claim 4, wherein said step of changing the amount of fuel comprises:

changing the base fuel amount supplied to the engine to correct the base air-fuel ration in the relative direction of the first selected air-fuel ratio whenever the engine rotation rate during said second running period is less than the engine rotation rates during both of said first and third running periods, and to correct the base air-fuel ratio in the relative direction of the second selected air-fuel ratio whenever the engine rotation rate during said second running period is greater than the engine rotation rates during both of the first and third running periods.

6. A method for controlling the air-fuel ratio of a running internal combustion engine according to claim 4, wherein the step of supplying a base fuel amount to the engine comprises injecting a base fuel pulse for each ignition, and the step of changing the base fuel amount supplied to the engine comprises changing the amount of each base fuel injection pulse.

7. A method for controlling the air-fuel ratio of a running internal internal combustion engine according to claim 4, wherein the step of supplying a base fuel amount to the engine comprises delivering fuel via a jet in a venturi carburetor, and the step of changing the base fuel amount supplied to the engine comprises regulating the rate of a flow of bleed air through an air bleeding chamber in the fuel path to said jet.

8. A method for controlling the air-fuel ratio of a running internal combustion engine according to claim 4, wherein the step of delivering a dithered flow of bypass air comprises alternately actuating and deactuating an electromagnetic valve in said bypass passage.

9. A method for controlling the air-fuel ratio in a running internal combustion engine according to claim 4, wherein the step of comparing said stored signals representing engine rotation rates comprises comparing signals for first and third running periods at a first selected air-fuel ratio and second and fourth running periods, following the respective first and third running periods, at a second selected air-fuel ratio.

10. A method for controlling the air-fuel ratio of a running internal combustion engine according to claim 9, wherein said step of determining whenever the engine rotation rate during said second running period is either greater than or less than the engine rotation rates during both of the first and third running periods further comprises determining whether the engine rotation rate during the fourth running period is greater than the engine rotation rate during the third running period when the engine rotation rate for the second running period is greater than the engine rotation rates for both the first and third running periods and whether the engine rotation rate for the fourth running period is less than the engine rotation rate for the third running period when the engine rotation rate for the second running period is less than the engine rotation rates for both of the first and third running periods.

11. A method for controlling the air-fuel ratio of a running internal combustion engine according to claim 4, wherein one of said at least two selected air-fuel ratios is the base air-fuel ratio.

12. A method for controlling the air-fuel ratio of a running internal combustion engine according to claim 11, wherein said selected air-fuel ratios include an air-fuel ratio richer than the base air-fuel ratio and an air-fuel ratio leaner than the base air-fuel ratio.

13. A method for controlling the air-fuel ratio of a running internal combustion engine according to claim 12, wherein said step of comparing said stored signals comprises comparing signals from five running periods including three running periods at the base air-fuel ratio, a running period at said richer air-fuel ratio occurring between two of the running periods at the base air-fuel ratio and a running period at the leaner air-fuel ratio occurring between another two of the running periods at the base air-fuel ratio.

14. An apparatus for controlling the air-fuel ratio in an internal combustion engine having an air intake passage, a throttle valve disposed in the air intake passage for controlling the amount of intake air flow to the engine, means for supplying fuel to the engine, and a bypass air passage having an outlet connected to the air intake passage downstream of the throttle valve, wherein the apparatus comprises:

means for controlling the fuel supplying means in accordance with the amount of intake air flow to obtain a predetermined base air-fuel ratio;

a sensor for detecting rotation angles of the engine;

means for shutting and for opening the bypass passage by at least a first selected amount for predetermined periods for supplying selectively alternating flow of bypass air to the intake passage downstream of the throttle valve;

a computer responsive to signals from said rotation angle sensor for controlling the means for shutting and opening the bypass passage to obtain for successive predetermined running periods at least two different selected air-fuel ratios in a range between relatively richer and relatively leaner air-fuel ratio values in the vicinity of said base air-fuel ratio, for comparing signals representing engine rotation rate during at least three running periods, including first and third running periods at a first one of said selected air-fuel ratios and an intermediate second running period at a second one of said selected air-fuel ratios, and for determining from said comparison whenever the engine rotation rate during said second running period is either greater than or less than the engine rotation rates during both of the first and third running periods, and for generating a correction signal in response to each such determination for correcting the base fuel amount so as to make the base air-fuel ratio closer to the air-fuel ratio corresponding to an optimum specific fuel consumption for the engine; and

means for delivering the correction signal from the computer to said means for controlling the fuel supply means.

15. An apparatus according to claim 14, wherein said computer compares said signals representing engine rotation rate for four running periods, including first and third running periods at a first one of said selected air-fuel ratios and second and fourth running periods, following the respective first and third running periods, at a second one of said selected air-fuel ratios.