Method and apparatus for controlling air/fuel ratio in internal combustion engines

Apparatus for controlling the air/fuel ratio of an air/fuel mixture supplied to an internal combustion engine, comprising:

• (a) an airflow meter for producing an output signal indicative of the flow rate of the intake air supplied to said engine;
• (b) an intake air temperature sensor for producing an output signal indicative of the temperature of the intake air of said engine;
• (c) a coolant temperature sensor for producing an output signal indicative of the temperature of the coolant of said engine;
• (d) a gas sensor for producing an output signal indicative of the concentration of a given gas in the exhaust gases of said engine;
• (e) a rotational speed sensor for producing an output signal indicative of the engine rpm;
• (f) fuel injection valves for supplying said engine with fuel in accordance with a driving current;
• and
• (g) controlling means for producing said driving current in accordance with the output signals of said airflow meter, intake air temperature sensor, coolant temperature sensor, gas sensor, and rotational speed sensor, said controlling means including a storage device in which data of correction factors are prestored, said controlling means producing said driving current by:
• (1) selecting a first correction factor from a plurality of predetermined first correction factors prestored in said storage device, in accordance with the output signals of said intake air temperature and said coolant temperature, (2) determining a second correction factor in accordance with said output signal of said gas sensor, (3) determining third correction factors, each of said third correction factors for a different engine operational condition, some of said third correction factors for engine operational conditions in a given region, in which said engine has been operated, being varied to be increased or decreased in accordance with the value of said second correction factor, remaining third correction factors being maintained unchanged, (4) detecting the state of the variation of said third correction factors, (5) modifying all of said third correction factors stored in said storage device in accordance with the result of the detection of the state of the variation of said third correction factors, (6) producing a pulse train signal in accordance with the output signals of said airflow meter, said rotational speed sensor and with said first, second and third correction factors, and (7) producing said driving current in response to said pulse train signal.

Apparatus for controlling the air/fuel ratio of an air/fuel mixture supplied to an internal combustion engine, comprising:

• (a) an airflow meter for producing an output signal indicative of the flow rate of the intake air supplied to said engine;
• (b) an intake air temperature sensor for producing an output signal indicative of the temperature of the intake air of said engine;
• (c) a coolant temperature sensor for producing an output signal indicative of the temperature of the coolant of said engine;
• (d) a gas sensor for producing an output signal indicative of the concentration of a given gas in the exhaust gases of said engine;
• (e) a rotational speed sensor for producing an output signal indicative of the engine rpm;
• (f) fuel injection valves for supplying said engine with fuel in accordance with a driving current;
• and
• (g) a control unit for producing said driving current in accordance with the output signals of said airflow meter, intake air temperature sensor, coolant temperature sensor, gas sensor, and rotational speed sensor;
• said control unit having an analog input port for respectively converting analog signals from said airflow meter, intake air temperature sensor, and coolant temperature sensor into digital signals;
• a digital input port for receiving a digital signal from said gas sensor;
• a rotational number counter for producing an interrupt instruction in synchronization with the rotation of the engine crankshaft, and for producing a digital output indicative of the engine rpm;
• an interrupt control unit for producing an interrupt signal in response to said interrupt instruction;
• a timer circuit for measuring time;
• a read-only memory in which a number of first correction factors have been prestored;
• a random access memory for temporarily storing various data on operations;
• a central processing unit responsive to data from said analog input port, digital input port, rotational number counter, interrupt control unit, timer circuit, read-only memory, and random access memory for producing an output signal;
• a second counter responsive to the output signal of said central processing unit for producing a pulse train signal;
• a driving stage responsive to said pulse train signal for producing said driving current;
• said central processing unit being operated in accordance with a program sequence prestored in said read-only memory, said program has a main routine for determining first, second and third correction factors, and an interrupt routine for determining the pulse width of said pulse train signal in accordance with the rotational speed of said engine, the amount of the intake air and said first to third correction factors, said first correction factor being selected from a plurality of predetermined first correction factors prestored in said read-only memory in accordance with the intake air temperature and coolant temperature;
• said second correction factor being determined in accordance with the detected air/fuel ratio;
• each of said third correction factors being for a different engine operating condition, some of said third correction factors for engine operational conditions in a given region, in which said engine has been operated, being varied to be increased or decreased in accordance with the value of said second correction factor, remaining third correction factors being maintained unchanged;
• all of said third correction factors being uniformly modified in accordance with the state of variation of said third correction factors.

A method of controlling the air/fuel ratio of an air/fuel mixture supplied to an internal combustion engine by a feedback control system, comprising the steps of:

• (a) monitoring operating conditions of said engine;
• (b) determining a first correction factor in accordance with an air/fuel ratio represented by an output signal of a gas sensor which detects the concentration of a given gas in the exhaust gases of said engine;
• (c) determining second correction factors, each of said second correction factors for a different engine operating condition, second correction factors corresponding to a region of said engine operational conditions in which said engine has been operated being changed in accordance with the value of said first correction factor, remaining second correction factors being unchanged;
• (d) detecting the state of variation of said second correction factors;
• (e) modifying all of said second correction factors uniformly throughout the possible entire range of said operating conditions of said engine in accordance with the detected state of variation of said second correction factors;
• and
• (f) determining the air/fuel ratio of the mixture to be supplied to said engine by correcting a standard value, which is obtained on the basis of said engine operating conditions, by said first and second correction factors.

Apparatus for controlling the period of time that injection valves supply fuel to an internal combustion engine to control the air/fuel ratio of an air/fuel mixture supplied to said engine, comprising:

• means for producing condition signals related to operating conditions of said engine;
• means for producing an exhaust signal indicative of the concentration of a given gas in the exhaust gases of said engine;
• memory means for storing correction factors;
• and
• means for:
• (1) determining a first correction factor in accordance with said exhaust signal, (2) determining second correction factors, each of said second correction factors for a different engine operating condition, some of said second correction factors for engine operational conditions in a given region, in which said engine has been operated, being varied to be increased or decreased in accordance with the value of said first correction factor, remaining second correction factors being maintained unchanged, (3) detecting the state of the variation of said second correction factors, (4) modifying all of said second correction factors stored in said storage device in accordance with the result of the detection of the state of the variation of said second correction factors, and (5) producing a driving current for said injection valves in response to said operating conditions and said first and second correction factors.