Method for controlling fuel supply to internal combustion engines having catalytic means for purifying exhaust gases, at operation in a high speed region

Claim 1

A method for controlling the quantity of fuel being supplied to an internal combustion engine having an intake passage and a catalytic means for purifying detrimental ingredients in exhaust gases emitted from the engine, in a feedback manner responsive to an output from a means for detecting the concentration of an ingredient in the exhaust gases so that the air/fuel ratio of an air/fuel mixture being supplied to the engine is controlled to a theoretical mixture ratio, said catalytic means being of the type being apt to most increase in bed temperature when the air/fuel ratio of the air/fuel mixture assumes said theoretical mixture ratio or a value close thereto, the method comprising the steps of: determining whether or not the engine is operating in a predetermined high speed operating region wherein the rotational speed of the engine is higher than a predetermined value which is a maximum value of the rotational speed of the engine above which the bed temperature of said catalytic means will exceed a predetermined maximum allowable value, if the air/fuel ratio of the air/fuel mixture being supplied to the engine is controlled to said theoretical mixture ratio or a value close thereto, and the absolute pressure in said intake passage is higher than a predetermined value; and (2) interrupting said feedback control and increasing the quantity of fuel being supplied to the engine by a predetermined amount, so that the resultant air/fuel mixture being supplied to the engine has an air/fuel ratio richer than said theoretical mixture ratio, when it is determined in said step (1) that the engine is operating in said predetermined high speed operating region, said predetermined amount being set to larger values as the absolute pressure in said intake passage increases.

Claim 2

A method for controlling the quantity of fuel being supplied to an internal combustion engine having an intake passage and a catalytic means for purifying detrimental ingredients in exhaust gases emitted from the engine, in a feedback manner responsive to an output from a means for detecting the concentration of an ingredient in the exhaust gases so that the air/fuel ratio of an air/fuel mixture being supplied to the engine is controlled to a theoretical mixture ratio, said catalytic means being of the type being apt to most increase in bed temperature when the air/fuel ratio of the air/fuel mixture assumes said theoretical mixture ratio or a value close thereto, the method comprising the steps of: determining whether or not the engine is operating in a predetermined high speed operating region wherein the rotational speed of the engine is higher than a predetermined value which is a maximum value of the rotational speed of the engine above which the bed temperature of said catalytic means will exceed a predetermined maximum allowable value, if the air/fuel ratio of the air/fuel mixture being supplied to the engine is controlled to said theoretical mixture ratio or a value close thereto, and the absolute pressure in said intake passage is higher than a predetermined value; and (2) interrupting said feedback control and increasing the quantity of fuel being supplied to the engine by a predetermined amount, so that the resultant air/fuel mixture being supplied to the engine has an air/fuel ratio richer than said theoretical mixture ratio, when it is determined in said step (1) that the engine is operating in said predetermined high speed operating region, said predetermined amount being set to larger values as the absolute pressure in said intake passage increases.