Internal combustion engine equipped with catalytic converter

Claim 1

An internal combustion engine having a combustion chamber and being operated on a fuel containing sulfur, comprising: fuel supply means for controllably supplying the fuel into an air induction passageway communicating the atmosphere and the combustion chamber to induct air into the combustion chamber; a catalytic converter having therein an oxidation catalyst for oxidizing the unburned constituents contained in the exhaust gases discharged from the combustion chamber, said catalytic converter being connected to the combustion chamber through an exhaust gas passageway; an exhaust gas sensor disposed in the exhaust gas passageway upstream of said catalytic converter and arranged to generate an information signal representing the composition of the exhaust gases passing through the exhaust gas passageway; a control circuit electrically connected between said exhaust gas sensor and said fuel supply means and arranged to control, in response to the information signal, the amount of fuel supplied from said fuel supply means to feed the combustion chamber with an air-fuel mixture having an air-fuel ratio within a range which develops exhaust gases having an air-fuel ratio ranging from 14:1 to 15.5:1, said exhaust gases being discharged into the exhaust gas passageway upstream of said catalytic converter; means for interrupting the electrical connection between said exhaust gas sensor and control circuit to stop the control operation of said control circuit when the temperature in the oxidation catalyst in said catalytic converter is below a predetermined temperature above which at least one of hydrogen sulfide and sulfuric acid is formable; the interrupting means including a switch disposed between said exhaust gas sensor and said control circuit, said switch being operated to (1) close to establish the electrical connection between said exhaust gas sensor and said control circuit and (2) open to interrupt the electrical connection between the same, and a temperature sensor disposed in said catalytic converter and electrically connected to said switch, said temperature sensor being arranged to normally allow the switch to open and to cause the switch to close when the temperature in said oxidation catalyst in said catalytic converter exceeds said predetermined temperature; and secondary air supply means for supplying secondary air into the exhaust gas passageway upstream of said exhaust gas sensor while the electrical connection between said exhaust gas sensor and said control circuit is interrupted, said secondary air supply means including a secondary air source connected through a secondary air supply pipe to the exhaust gas passageway for supplying under pressure secondary air into the exhaust gas passageway, and a first electromagnetic valve disposed in the secondary air supply pipe which is arranged to open to establish the fluid communication between said air source and the exhaust gas passageway and to close to block the fluid communication between the same, said first electromagnetic valve being electrically connected between said switch and said control circuit to close when said switch closes and to open when said switch opens