Adaptive air/fuel ratio controller for internal combustion engine

An adaptive closed loop air/fuel ratio controller for an internal combustion engine having supply means to supply a mixture of fuel and air to the engine and a sensor providing a sensor signal in response to the air/fuel ratio of the mixture supplied to the engine, the means to supply a mixture of air and fuel being characterized by the variations in the air/fuel ratio of the mixture supplied thereby in response to varying engine temperature, the controller including, in combination:

• means effective to sense engine temperature;
• a memory having numbers stored at locations addressable in accordance with an engine operating point determined by at least the value of engine load;
• means effective to recurrently (a) adjust the supply means in accord with the number stored in the memory at the location addressed by the engine operating point at least when the engine first operates at said operating point and, at least at some times, in accord with the sensor signal in a direction to establish a predetermined air/fuel ratio and (b) adjust the number in the memory at the address corresponding to the engine operating point in a direction to cause correspondence with the value of the supply means adjustment and by an amount determined by a time constant having a value varying directly with the value of the sensed engine temperature, whereby the numbers in the memory are each updated substantially to the value producing the predetermined closed loop air/fuel ratio at the respective engine operating point during varying values of engine temperature and whereby the rate of adjustment of the numbers in the memory is greater during engine warmup where engine temperature increases rapidly.

The method of controlling the air/fuel ratio in an internal combustion engine having supply means to supply a mixture of fuel and air to the engine and a sensor providing a sensor signal in response to the air/fuel ratio of the mixture supplied to the engine, the method including the steps of:

• determining the engine operating point;
• adjusting the supply means in accord with a number stored in a memory at a location addressed by the engine operating point at least when the engine first operates at said operating point and, at least at some times, in accord with the sensor signal in a direction to establish a predetermined closed loop air/fuel ratio;
• and
• adjusting the number in the memory at a location addressed by the engine operating point in a direction to cause correspondence with the value of the supply means adjustment and at a rate directly proportional to the value of engine temperature so that the numbers in the memory are each updated substantially to the value producing the predetermined closed loop air/fuel ratio at the respective engine operating point during varying values of engine temperature and at a rate that is greater during colder engine temperatures where the rate of change of temperature is greater.