System for detecting deterioration of a three-way catalyst of an internal combustion engine

Claim 1

A system for detecting deterioration of a three-way catalyst of an internal combustion engine having an exhaust passage, said three-way catalyst being arranged in said exhaust passage for purifying noxious components present in exhaust gases, said system comprising: a first HC sensor arranged in said exhaust passage at a location upstream of said three-way catalyst for detecting concentration of hydrocarbons present in exhaust gases and providing a first output signal substantially proportional to the concentration of hydrocarbons at said upstream location; a second HC sensor arranged in said exhaust passage at a location downstream of said three-way catalyst for detecting concentration of hydrocarbons present in exhaust gases and providing a second output signal substantially proportional to the concentration of hydrocarbons at said downstream location; and deterioration-determining means for comparing said first output from said first HC sensor with said second output from said second HC sensor and for determining from results of said comparison whether said three-way catalyst is deteriorated.

Claim 2

A system for detecting deterioration of a three-way catalyst of an internal combustion engine having an exhaust passage, said three-way catalyst being arranged in said exhaust passage for purifying noxious components present in exhaust gases, said system comprising: a first HC sensor arranged in said exhaust passage at a location upstream of said three-way catalyst for detecting concentration of hydrocarbons present in exhaust gases and providing a first output signal substantially proportional to the concentration of hydrocarbons at said upstream location; a second HC sensor arranged in said exhaust passage at a location downstream of said three-way catalyst for detecting concentration of hydrocarbons present in exhaust gases and providing a second output signal substantially proportional to the concentration of hydrocarbons at said downstream location; and deterioration-determining means for comparing said first output from said first HC sensor with said second output from said second HC sensor and for determining from results of said comparison whether said three-way catalyst is deteriorated.

Claim 6

A system for detecting deterioration of a three-way catalyst of an internal combustion engine having an exhaust passage, said three-way catalyst being arranged in said exhaust passage for purifying noxious components present in exhaust gases, an oxygen concentration sensor arranged in said exhaust passage for detecting concentration of oxygen in said exhaust gases, and air-fuel ratio feedback control means for controlling an amount of fuel supplied to said engine in response to an output from said oxygen concentration sensor, said system further comprising: a first HC sensor arranged in said exhaust passage at a location upstream of said three-way catalyst for detecting concentration of hydrocarbons present in exhaust gases and providing a first output signal substantially proportional to the concentration of hydrocarbons; a second HC sensor arranged in said exhaust passage at a location downstream of said three-way catalyst for detecting concentration of hydrocarbons present in exhaust gases and providing a second output signal substantially proportional to the concentration of hydrocarbons; and deterioration-determining means for comparing said first output from said first HC sensor with said second output from said second HC sensor and for determining from results of said comparison whether said three-way catalyst is deteriorated.

Claim 7

A system for detecting deterioration of a three-way catalyst of an internal combustion engine having an exhaust passage, said three-way catalyst being arranged in said exhaust passage for purifying noxious components present in exhaust gases, an oxygen concentration sensor arranged in said exhaust passage for detecting concentration of oxygen in said exhaust gases, and air-fuel ratio feedback control means for controlling an amount of fuel supplied to said engine in response to an output from said oxygen concentration sensor, said system further comprising: a first HC sensor arranged in said exhaust passage at a location upstream of said three-way catalyst for detecting concentration of hydrocarbons present in exhaust gases and providing a first output signal substantially proportional to the concentration of hydrocarbons; a second HC sensor arranged in said exhaust passage at a location downstream of said three-way catalyst for detecting concentration of hydrocarbons present in exhaust gases and providing a second output signal substantially proportional to the concentration of hydrocarbons; and deterioration-determining means for comparing said first output from said first HC sensor with said second output from said second HC sensor and for determining from results of said comparison whether said three-way catalyst is deteriorated.

Claim 8

A system for detecting deterioration of a three-way catalyst of an internal combustion engine having an exhaust passage, said three-way catalyst being arranged in said exhaust passage for purifying noxious components present in exhaust gases, said system comprising: a first HC sensor arranged in said exhaust passage at a location upstream of said three-way catalyst for detecting concentration of hydrocarbons present in exhaust gases; a second HC sensor arranged in said exhaust passage at a location downstream of said three-way catalyst for detecting concentration of hydrocarbons present in exhaust gases; deterioration-determining means for comparing an output from said first HC sensor with an output from said second HC sensor and for determining from results of said comparison whether said three-way catalyst is deteriorated; memory means for storing at least one of a value of said output from said first HC sensor and a value of said output from said second HC sensor when the supply of fuel to said engine is interrupted; and correcting means for correcting at least one of the values of said outputs from said first and second HC sensors by said at least one of said values of said outputs stored, wherein said deterioration-determining means carries out comparison based on said at least one of said values of said outputs corrected by said correcting means.

Claim 9

A system for detecting deterioration of a three-way catalyst of an internal combustion engine having an exhaust passage, said three-way catalyst being arranged in said exhaust passage for purifying noxious components present in exhaust gases, said system comprising: a first HC sensor arranged in said exhaust passage at a location upstream of said three-way catalyst for detecting concentration of hydrocarbons present in exhaust gases; a second HC sensor arranged in said exhaust passage at a location downstream of said three-way catalyst for detecting concentration of hydrocarbons present in exhaust gases; deterioration-determining means for comparing an output from said first HC sensor with an output from said second HC sensor and for determining from results of said comparison whether said three-way catalyst is deteriorated; memory means for storing at least one of a value of said output from said first HC sensor and a value of said output from said second HC sensor when the supply of fuel to said engine is interrupted; and correcting means for correcting at least one of the values of said outputs from said first and second HC sensors by said at least one of said values of said outputs stored, wherein said deterioration-determining means carries out comparison based on said at least one of said values of said outputs corrected by said correcting means.