Fuel feedback control system for internal combustion engine

Claim 3

A system as claimed in claim 1, in which said fifth means includes means for raising said reference value and the value of said current flow to said exhaust sensor immediately when the feedback control is stopped by said fourth means.

Claim 4

A system as claimed in claim 2, in which said sixth means includes means for gradually dropping said reference value even during a first condition where the value of said output of said exhaust sensor is higher than said reference value.

Claim 5

A system as claimed in claim 3, in which said sixth means includes means for decreasing the dropping rate of said reference value during said first condition as compared with that during a second condition where the value of said output of said exhaust sensor is lower than said reference value.

Claim 6

A system as claimed in claim 1, in which said engine temperature is the temperature of an engine coolant.

Claim 7

A system as claimed in claim 5, in which said fourth means includes means for stopping the feedback control when the engine coolant temperature is below a predetermined level and initiating the feedback control when the engine coolant temperature is not lower than the predetermined level.

Claim 8

A system as claimed in claim 6, in which said predetermined level of the engine coolant temperature is 10° C.

Claim 11

An internal combustion engine having an exhaust pipe, comprising: an exhaust sensor operatively disposed in said exhaust pipe to sense the concentration of a component of engine exhaust gas passing through the exhaust pipe to produce an information output signal; an exhaust gas purifying device disposed in the exhaust pipe to purify the exhaust gas passing through the exhaust pipe; means for deciding a basic fuel supply amount to the engine in accordance with engine operating parameters; means for correcting said basic fuel supply amount in response to a control signal depending upon the deviation between an reference value and the value of said information output signal so as to maintain the air-fuel ratio of mixture at a preset value; means for supplying a current flow to said exhaust sensor; means for varying said reference value in response to the information output signal to said exhaust sensor; means for controlling the initiation and stop of the feedback control in accordance with the relationship between said reference value and the value of said information output signal of said exhaust sensor which output signal is generated in response to said current flow supplied to said exhaust sensor; means for controlling the initiation and stop of the feedback control in accordance with engine temperature; means for varying said reference value and the value of said current flow to said exhaust sensor immediately when the feedback control is stopped in response to said engine temperature; means for varying said reference value with the lapse of time while the feedback control is stopped in response to said engine temperature.

Claim 12

An internal combustion engine having an exhaust pipe, comprising: an exhaust sensor operatively disposed in said exhaust pipe to sense the concentration of a component of engine exhaust gas passing through the exhaust pipe to produce an information output signal; an exhaust gas purifying device disposed in the exhaust pipe to purify the exhaust gas passing through the exhaust pipe; means for deciding a basic fuel supply amount to the engine in accordance with engine operating parameters; means for correcting said basic fuel supply amount in response to a control signal depending upon the deviation between an reference value and the value of said information output signal so as to maintain the air-fuel ratio of mixture at a preset value; means for supplying a current flow to said exhaust sensor; means for varying said reference value in response to the information output signal to said exhaust sensor; means for controlling the initiation and stop of the feedback control in accordance with the relationship between said reference value and the value of said information output signal of said exhaust sensor which output signal is generated in response to said current flow supplied to said exhaust sensor; means for controlling the initiation and stop of the feedback control in accordance with engine temperature; means for varying said reference value and the value of said current flow to said exhaust sensor immediately when the feedback control is stopped in response to said engine temperature; means for varying said reference value with the lapse of time while the feedback control is stopped in response to said engine temperature.

Claim 13

An internal combustion engine as claimed in claim 9, in which said exhaust gas purifying device is a three-way catalytic converter which functions to oxidize CO and HC and reduce NO x .

Claim 14

An internal combustion engine as claimed in claim 10, in which said preset value of the air-fuel ratio is stoichiometric air-fuel ratio.

Claim 15

An internal combustion engine as claimed in claim 11, in which said exhaust sensor is an oxygen sensor for sensing the concentration of oxygen contained in the exhaust gas passing through the exhaust pipe.