Catalyst deterioration-detecting system for internal combustion engines

Claim 2

A catalyst deterioration-detecting system for an internal combustion engine having an exhaust system, catalyst means arranged in said exhaust system, oxygen concentration-detecting means arranged in said exhaust system downstream of said catalyst means, for detecting concentration of oxygen in exhaust gases emitted from said engine, and air-fuel ratio control means responsive to an output from said oxygen concentration-detecting means, for controlling an air-fuel ratio of a mixture supplied to said engine, comprising: catalyst deterioration parameter-detecting means for detecting a value of a catalyst deterioration parameter indicative of a degree of deterioration of said catalyst means; operating parameter-detecting means for detecting a value of at least one operating parameter of said engine related to a flow rate of said exhaust gases in said exhaust system; and catalyst deterioration-determining means for determining whether said catalyst means is deteriorated, based on the value of said catalyst deterioration parameter detected by said catalyst deterioration parameter-detecting means and the value of said at least one operating parameter detected by said operating parameter-detecting means.

Claim 3

A catalyst deterioration-detecting system as claimed in claim 1, wherein said catalyst deterioration parameter-detecting means comprises inversion period-detecting means for detecting a value of an inversion period with which said output from said oxygen concentration-detecting means is inverted with respect to a predetermined reference value.

Claim 4

A catalyst deterioration-detecting system as claimed in claim 2, wherein said catalyst deterioration-determining means includes means for correcting the value of said inversion period in dependence on the value of said at least one operating parameter detected by said operating parameter-detecting means.

Claim 5

A catalyst deterioration-detecting system for an internal combustion engine having an exhaust system, catalyst means arranged in said exhaust system, oxygen concentration-detecting means arranged in said exhaust system downstream of said catalyst means, for detecting concentration of oxygen in exhaust gases emitted from said engine, and air-fuel ratio control means responsive to an output from said oxygen concentration-detecting means, for controlling an air-fuel ratio of a mixture supplied to said engine, comprising: catalyst deterioration parameter-detecting means for detecting a value of a catalyst deterioration parameter indicative of a degree of deterioration of said catalyst means; operating parameter-detecting means for detecting a value of at least one operating parameter of said engine related to a flow rate of said exhaust gases in said exhaust system; determination value-setting means for setting a determination value for comparison with the value of said catalyst deterioration parameter detected by said catalyst deterioration parameter-detecting means, based on the value of said at least one operating parameter detected by said operating parameter-detecting means; and catalyst deterioration-determining means for comparing between the value of said catalyst deterioration parameter detected by said catalyst deterioration parameter-detecting means and said determination value set by said determination value-setting means, and for determining that said catalyst means is deteriorated, when the detected value of said catalyst deterioration parameter shows a value indicative of a larger degree of deterioration of said catalyst means than said determination value.

Claim 6

A catalyst deterioration-detecting system for an internal combustion engine having an exhaust system, catalyst means arranged in said exhaust system, oxygen concentration-detecting means arranged in said exhaust system downstream of said catalyst means, for detecting concentration of oxygen in exhaust gases emitted from said engine, and air-fuel ratio control means responsive to an output from said oxygen concentration-detecting means, for controlling an air-fuel ratio of a mixture supplied to said engine, comprising: catalyst deterioration parameter-detecting means for detecting a value of a catalyst deterioration parameter indicative of a degree of deterioration of said catalyst means; operating parameter-detecting means for detecting a value of at least one operating parameter of said engine related to a flow rate of said exhaust gases in said exhaust system; determination value-setting means for setting a determination value for comparison with the value of said catalyst deterioration parameter detected by said catalyst deterioration parameter-detecting means, based on the value of said at least one operating parameter detected by said operating parameter-detecting means; and catalyst deterioration-determining means for comparing between the value of said catalyst deterioration parameter detected by said catalyst deterioration parameter-detecting means and said determination value set by said determination value-setting means, and for determining that said catalyst means is deteriorated, when the detected value of said catalyst deterioration parameter shows a value indicative of a larger degree of deterioration of said catalyst means than said determination value.

Claim 7

A catalyst deterioration-detecting system as claimed in claim 4, wherein said catalyst deterioration parameter-detecting means comprises inversion period-detecting means for detecting a value of an inversion period with which said output from said oxygen concentration-detecting means is inverted with respect to a predetermined reference value, said determination value-setting means setting said determination value for comparison with the value of said inversion period detected by said inversion period-detecting means, based on the value of said at least one operating parameter detected by said operating parameter-detecting means, said catalyst deterioration-determining means comparing between the value of said inversion period detected by said inversion period-detecting means and said determination value set by said determination value-setting means, and determining that said catalyst means is deteriorated, when the detected value of said inversion period is shorter than said determination value.

Claim 8

A catalyst deterioration-detecting system as claimed in claim 5, wherein said determination value-setting means sets said determination value to a smaller value as the value of said at least one operating parameter detected by said operating parameter-detecting means shows a value indicative of a larger value of said flow rate of said exhaust gases.

Claim 9

A catalyst deterioration-detecting system for an internal combustion engine having an exhaust system, catalyst means arranged in said exhaust system, oxygen concentration-detecting means arranged in said exhaust system downstream of said catalyst means, for detecting concentration of oxygen in exhaust gases emitted from said engine, and air-fuel ratio control means responsive to an output from said oxygen concentration-detecting means, for controlling an air-fuel ratio of a mixture supplied to said engine, comprising: air-fuel ratio-determining means for comparing the output from said oxygen concentration-detecting means with a predetermined reference value to thereby determine whether the air-fuel ratio of said mixture supplied to said engine is on a richer side or a leaner side with respect to a stoichiometric air-fuel ratio; air-fuel ratio-retarding control means for changing the air-fuel ratio of said mixture supplied to said engine across said stoichiometric air-fuel ratio upon the lapse of a delay time period after the time said inversion is detected by said inversion-detecting means; catalyst deterioration parameter-detecting means for detecting a value of a catalyst deterioration parameter indicative of a degree of deterioration of said catalyst means; operating parameter-detecting means for detecting a value of at least one operating parameter of said engine related to a flow rate of said exhaust gases in said exhaust system; delay time period-determining means for determining a value of said delay time period, based on said value of said at least one operating parameter detected by said operating parameter-detecting means; and catalyst deterioration-determining means for comparing the value of said catalyst deterioration parameter detected by said catalyst deterioration parameter-detecting means with a predetermined value, and for determining that said catalyst means is deteriorated, when the value of said catalyst deterioration parameter detected by said catalyst deterioration parameter-detecting means shows a value indicative of a larger degree of deterioration of said catalyst means than said predetermined value.

Claim 10

A catalyst deterioration-detecting system for an internal combustion engine having an exhaust system, catalyst means arranged in said exhaust system, oxygen concentration-detecting means arranged in said exhaust system downstream of said catalyst means, for detecting concentration of oxygen in exhaust gases emitted from said engine, and air-fuel ratio control means responsive to an output from said oxygen concentration-detecting means, for controlling an air-fuel ratio of a mixture supplied to said engine, comprising: air-fuel ratio-determining means for comparing the output from said oxygen concentration-detecting means with a predetermined reference value to thereby determine whether the air-fuel ratio of said mixture supplied to said engine is on a richer side or a leaner side with respect to a stoichiometric air-fuel ratio; air-fuel ratio-retarding control means for changing the air-fuel ratio of said mixture supplied to said engine across said stoichiometric air-fuel ratio upon the lapse of a delay time period after the time said inversion is detected by said inversion-detecting means; catalyst deterioration parameter-detecting means for detecting a value of a catalyst deterioration parameter indicative of a degree of deterioration of said catalyst means; operating parameter-detecting means for detecting a value of at least one operating parameter of said engine related to a flow rate of said exhaust gases in said exhaust system; delay time period-determining means for determining a value of said delay time period, based on said value of said at least one operating parameter detected by said operating parameter-detecting means; and catalyst deterioration-determining means for comparing the value of said catalyst deterioration parameter detected by said catalyst deterioration parameter-detecting means with a predetermined value, and for determining that said catalyst means is deteriorated, when the value of said catalyst deterioration parameter detected by said catalyst deterioration parameter-detecting means shows a value indicative of a larger degree of deterioration of said catalyst means than said predetermined value.

Claim 11

A catalyst deterioration-detecting system as claimed in claim 7, wherein said delay time period-determining means sets the value of said delay time period to a larger value as the value of said at least one operating parameter detected by said operating parameter-detecting means shows a value indicative of a larger value of said flow rate of said exhaust gases.

Claim 12

A catalyst deterioration-detecting system as claimed in claim 8, wherein said catalyst deterioration parameter-detecting means comprises inversion period-detecting means for detecting a value of an inversion period with which said output from said oxygen concentration-detecting means is inverted with respect to a predetermined reference value, said catalyst deterioration-determining means comparing between the value of said inversion period detected by said inversion period-detecting means and said predetermined value, and determining that said catalyst means is deteriorated, when the detected value of said inversion period is shorter than said predetermined value.

Claim 13

A catalyst deterioration-detecting system for an internal combustion engine having an exhaust system, catalyst means arranged in said exhaust system, oxygen concentration-detecting means arranged in said exhaust system downstream of said catalyst means, for detecting concentration of oxygen in exhaust gases emitted from said engine, and air-fuel ratio control means responsive to an output from said oxygen concentration-detecting means, for controlling an air-fuel ratio of a mixture supplied to said engine, comprising: catalyst deterioration parameter-detecting means for detecting a value of a catalyst deterioration parameter indicative of a degree of deterioration of said catalyst means; operating parameter-detecting means for detecting a value of at least one operating parameter of said engine related to a flow rate of said exhaust gases in said exhaust system; catalyst deterioration parameter-correcting means for correcting the value of said catalyst deterioration parameter detected by said catalyst deterioration parameter-detecting means, based on the value of said at least one operating parameter of said engine detected by said operating parameter-detecting means; and catalyst deterioration-determining means for comparing the value of said catalyst deterioration parameter corrected by said catalyst deterioration parameter-correcting means with a predetermined value, and for determining that said catalyst means is deteriorated, when the corrected value of said catalyst deterioration parameter shows a value indicative of a larger degree of deterioration of said catalyst means than said predetermined value.

Claim 14

A catalyst deterioration-detecting system for an internal combustion engine having an exhaust system, catalyst means arranged in said exhaust system, oxygen concentration-detecting means arranged in said exhaust system downstream of said catalyst means, for detecting concentration of oxygen in exhaust gases emitted from said engine, and air-fuel ratio control means responsive to an output from said oxygen concentration-detecting means, for controlling an air-fuel ratio of a mixture supplied to said engine, comprising: catalyst deterioration parameter-detecting means for detecting a value of a catalyst deterioration parameter indicative of a degree of deterioration of said catalyst means; operating parameter-detecting means for detecting a value of at least one operating parameter of said engine related to a flow rate of said exhaust gases in said exhaust system; catalyst deterioration parameter-correcting means for correcting the value of said catalyst deterioration parameter detected by said catalyst deterioration parameter-detecting means, based on the value of said at least one operating parameter of said engine detected by said operating parameter-detecting means; and catalyst deterioration-determining means for comparing the value of said catalyst deterioration parameter corrected by said catalyst deterioration parameter-correcting means with a predetermined value, and for determining that said catalyst means is deteriorated, when the corrected value of said catalyst deterioration parameter shows a value indicative of a larger degree of deterioration of said catalyst means than said predetermined value.

Claim 15

A catalyst deterioration-detecting system as claimed in claim 10, wherein said catalyst deterioration parameter-detecting means comprises inversion period-detecting means for detecting a value of an inversion period with which said output from said oxygen concentration-detecting means is inverted with respect to a predetermined reference value, said catalyst deterioration parameter-correcting means correcting the value of said inversion period detected by said inversion period-detecting means, based on the value of said at least one operating parameter detected by said operating parameter-detecting means, said catalyst deterioration-determining means comparing between the value of said inversion period detected by said inversion period-detecting means and said predetermined value, and determining that said catalyst means is deteriorated, when the detected value of said inversion period is shorter than said predetermined value.

Claim 16

A catalyst deterioration-detecting system as claimed in claim 11, wherein said inversion period-correcting means sets the value of said inversion period to a larger value as the value of said at least one operating parameter detected by said operating parameter-detecting means shows a value indicative of a larger value of said flow rate of said exhaust gases.

Claim 17

A catalyst deterioration-detecting system as claimed in any of claims 1-12, wherein said operating parameter-detecting means comprises intake air amount-detecting means for detecting an amount of intake air drawn into said engine.

Claim 18

A catalyst deterioration-detecting system as claimed in claim 13, wherein said intake air amount-detecting means detects parameters representative of rotational speed of said engine and load on said engine.

Claim 19

A catalyst deterioration-detecting system as claimed in claim 13, wherein said intake air amount-detecting means directly detects said amount of intake air drawn into said engine.

Claim 20

A catalyst deterioration-detecting system as claimed in claim 13, wherein said intake air amount-detecting means includes averaging means for averaging said amount of said intake air detected by said intake air amount-detecting means.