Apparatus and method for detecting deterioration of NOx catalyst in diesel engine

Claim 1

An apparatus comprising: a diesel engine having an exhaust pipe; NO x catalyst disposed in the exhaust pipe; means for supplying hydrocarbons into the exhaust pipe as hydrocarbons for reduction so that NO x exhausted from said diesel engine can be reduced and purified by the NO x catalyst disposed in the exhaust pipe; a rotational speed sensor, for measuring a rotational speed of said diesel engine; a load sensor, for detecting a load on said diesel engine; means for determining an amount of hydrocarbons in exhaust gas from said NO x catalyst; and deterioration detecting means for determining an operating condition of the diesel engine on a basis of signals from the rotational speed sensor and the load sensor, and for determining an extent of deterioration of the NO x catalyst on a basis of a change in the amount of hydrocarbons in the exhaust gas from the NO x catalyst during a period of time when the operating condition meets a predetermined condition, wherein said means for determining comprises a hydrocarbon sensor, provided in said exhaust pipe downstream of said NO x catalyst, and wherein said deterioration detecting means memorizes an amount of hydrocarbons which are exhausted from said NO x catalyst, initially measured by the hydrocarbon sensor, as a base amount of hydrocarbons, and compares a predetermined value with a difference between the base amount of hydrocarbons and an amount of hydrocarbons subsequently measured by the hydrocarbon sensor to determine the extent of deterioration of the NO x catalyst.

Claim 2

An apparatus comprising: a diesel engine having an exhaust pipe; NO x catalyst disposed in the exhaust pipe; means for supplying hydrocarbons into the exhaust pipe as hydrocarbons for reduction so that NO x exhausted from said diesel engine can be reduced and purified by the NO x catalyst disposed in the exhaust pipe; a rotational speed sensor, for measuring a rotational speed of said diesel engine; a load sensor, for detecting a load on said diesel engine; means for determining an amount of hydrocarbons in exhaust gas from said NO x catalyst; and deterioration detecting means for determining an operating condition of the diesel engine on a basis of signals from the rotational speed sensor and the load sensor, and for determining an extent of deterioration of the NO x catalyst on a basis of a change in the amount of hydrocarbons in the exhaust gas from the NO x catalyst during a period of time when the operating condition meets a predetermined condition, wherein said means for determining comprises a hydrocarbon sensor, provided in said exhaust pipe downstream of said NO x catalyst, and wherein said deterioration detecting means memorizes an amount of hydrocarbons which are exhausted from said NO x catalyst, initially measured by the hydrocarbon sensor, as a base amount of hydrocarbons, and compares a predetermined value with a difference between the base amount of hydrocarbons and an amount of hydrocarbons subsequently measured by the hydrocarbon sensor to determine the extent of deterioration of the NO x catalyst.

Claim 4

An apparatus comprising: a diesel engine having an exhaust pipe; NO x catalyst disposed in the exhaust pipe; means for supplying hydrocarbons into the exhaust pipe as hydrocarbons for reduction so that NO x exhausted from said diesel engine can be reduced and purified by the NO x catalyst disposed in the exhaust pipe; a rotational speed sensor, for measuring a rotational speed of said diesel engine; a load sensor, for detecting a load on said diesel engine; means for determining an amount of hydrocarbons in exhaust gas from said NO x catalyst; and deterioration detecting means for determining an operating condition of the diesel engine on a basis of signals from the rotational speed sensor and the load sensor, and for determining an extent of deterioration of the NO x catalyst on a basis of a change in the amount of hydrocarbons in the exhaust gas from the NO x catalyst during a period of time when the operating condition meets a predetermined condition, wherein said means for determining comprises a hydrocarbon sensor, provided in said exhaust pipe downstream of said NO x catalyst, and wherein said deterioration detecting means calculates an amount of hydrocarbons exhausted from said NO x catalyst based on said operating condition at a time when a variation of the operating condition is judged to be held within a predetermined range over a predetermined time, and compares a predetermined value with a difference between thus calculated amount of hydrocarbons and an amount of hydrocarbons measured by the hydrocarbon sensor to determine the extent of deterioration of the NO x catalyst.

Claim 5

An apparatus comprising: a diesel engine having an exhaust pipe; NO x catalyst disposed in the exhaust pipe; means for supplying hydrocarbons into the exhaust pipe as hydrocarbons for reduction so that NO x exhausted from said diesel engine can be reduced and purified by the NO x catalyst disposed in the exhaust pipe; a rotational speed sensor, for measuring a rotational speed of said diesel engine; a load sensor, for detecting a load on said diesel engine; means for determining an amount of hydrocarbons in exhaust gas from said NO x catalyst; and deterioration detecting means for determining an operating condition of the diesel engine on a basis of signals from the rotational speed sensor and the load sensor, and for determining an extent of deterioration of the NO x catalyst on a basis of a change in the amount of hydrocarbons in the exhaust gas from the NO x catalyst during a period of time when the operating condition meets a predetermined condition, wherein said means for determining comprises a hydrocarbon sensor, provided in said exhaust pipe downstream of said NO x catalyst, and wherein said deterioration detecting means calculates an amount of hydrocarbons exhausted from said NO x catalyst based on said operating condition at a time when a variation of the operating condition is judged to be held within a predetermined range over a predetermined time, and compares a predetermined value with a difference between thus calculated amount of hydrocarbons and an amount of hydrocarbons measured by the hydrocarbon sensor to determine the extent of deterioration of the NO x catalyst.

Claim 7

An apparatus comprising: a diesel engine having an exhaust pipe; NO x catalyst disposed in the exhaust pipe; means for supplying hydrocarbons into the exhaust pipe as hydrocarbons for reduction so that NO x exhausted from said diesel engine can be reduced and purified by the NO x catalyst disposed in the exhaust pipe; a rotational speed sensor, for measuring a rotational speed of said diesel engine; a load sensor, for detecting a load on said diesel engine; means for determining an amount of hydrocarbons in exhaust gas from said NO x catalyst; and deterioration detecting means for determining an operating condition of the diesel engine on a basis of signals from the rotational speed sensor and the load sensor, and for determining an extent of deterioration of the NO x catalyst on a basis of a change in the amount of hydrocarbons in the exhaust gas from the NO x catalyst during a period of time when the operating condition meets a predetermined condition, wherein said means for determining an amount of hydrocarbons in exhaust gas from said NO x catalyst comprises: an oxidation catalyst, disposed in the exhaust pipe downstream of and at a predetermined distance from the NO x catalyst; a first temperature sensor located in the exhaust pipe upstream of the oxidation catalyst and disposed between the NO x catalyst and the oxidation catalyst; and a second temperature sensor located in the exhaust pipe downstream of the oxidation catalyst; and wherein said deterioration detecting means determines the extent of deterioration of the NO x catalyst on a basis of a change in a temperature difference in accordance with signals from the first and second temperature sensors during a period of time when the operating condition meets a predetermined condition.

Claim 8

An apparatus comprising: a diesel engine having an exhaust pipe; NO x catalyst disposed in the exhaust pipe; means for supplying hydrocarbons into the exhaust pipe as hydrocarbons for reduction so that NO x exhausted from said diesel engine can be reduced and purified by the NO x catalyst disposed in the exhaust pipe; a rotational speed sensor, for measuring a rotational speed of said diesel engine; a load sensor, for detecting a load on said diesel engine; means for determining an amount of hydrocarbons in exhaust gas from said NO x catalyst; and deterioration detecting means for determining an operating condition of the diesel engine on a basis of signals from the rotational speed sensor and the load sensor, and for determining an extent of deterioration of the NO x catalyst on a basis of a change in the amount of hydrocarbons in the exhaust gas from the NO x catalyst during a period of time when the operating condition meets a predetermined condition, wherein said means for determining an amount of hydrocarbons in exhaust gas from said NO x catalyst comprises: an oxidation catalyst, disposed in the exhaust pipe downstream of and at a predetermined distance from the NO x catalyst; a first temperature sensor located in the exhaust pipe upstream of the oxidation catalyst and disposed between the NO x catalyst and the oxidation catalyst; and a second temperature sensor located in the exhaust pipe downstream of the oxidation catalyst; and wherein said deterioration detecting means determines the extent of deterioration of the NO x catalyst on a basis of a change in a temperature difference in accordance with signals from the first and second temperature sensors during a period of time when the operating condition meets a predetermined condition.

Claim 10

An apparatus comprising: a diesel engine having an exhaust pipe; NO x catalyst disposed in the exhaust pipe; means for supplying hydrocarbons into the exhaust pipe as hydrocarbons for reduction so that NO x exhausted from said diesel engine can be reduced and purified by the NO x catalyst disposed in the exhaust pipe; a rotational speed sensor, for measuring a rotational speed of said diesel engine; a load sensor, for detecting a load on said diesel engine; means for determining an amount of hydrocarbons in exhaust gas from said NO x catalyst; and deterioration detecting means for determining an operating condition of the diesel engine on a basis of signals from the rotational speed sensor and the load sensor, and for determining an extent of deterioration of the NO x catalyst on a basis of a change in the amount of hydrocarbons in the exhaust gas from the NO x catalyst during a period of time when the operating condition meets a predetermined condition, wherein said means for determining an amount of hydrocarbons in exhaust gas from said NO x catalyst comprises: an oxidation catalyst, disposed in the exhaust pipe downstream of and at a predetermined distance from the NO x catalyst; a first temperature sensor located in the exhaust pipe upstream of the oxidation catalyst and disposed between the NO x catalyst and the oxidation catalyst; and a second temperature sensor located in the exhaust pipe downstream of the oxidation catalyst; and wherein said deterioration detecting means calculates a difference between temperatures at said first and second temperature sensors determined from the operating condition of the diesel engine at a time when a variation of the operating condition is judged to be held within a predetermined range over a predetermined time, and compares a thus calculated difference with an actual difference between temperatures detected by said first and second temperature sensors, to determine the extent of deterioration of the NO x catalyst.

Claim 11

An apparatus comprising: a diesel engine having an exhaust pipe; NO x catalyst disposed in the exhaust pipe; means for supplying hydrocarbons into the exhaust pipe as hydrocarbons for reduction so that NO x exhausted from said diesel engine can be reduced and purified by the NO x catalyst disposed in the exhaust pipe; a rotational speed sensor, for measuring a rotational speed of said diesel engine; a load sensor, for detecting a load on said diesel engine; means for determining an amount of hydrocarbons in exhaust gas from said NO x catalyst; and deterioration detecting means for determining an operating condition of the diesel engine on a basis of signals from the rotational speed sensor and the load sensor, and for determining an extent of deterioration of the NO x catalyst on a basis of a change in the amount of hydrocarbons in the exhaust gas from the NO x catalyst during a period of time when the operating condition meets a predetermined condition, wherein said means for determining an amount of hydrocarbons in exhaust gas from said NO x catalyst comprises: an oxidation catalyst, disposed in the exhaust pipe downstream of and at a predetermined distance from the NO x catalyst; a first temperature sensor located in the exhaust pipe upstream of the oxidation catalyst and disposed between the NO x catalyst and the oxidation catalyst; and a second temperature sensor located in the exhaust pipe downstream of the oxidation catalyst; and wherein said deterioration detecting means calculates a difference between temperatures at said first and second temperature sensors determined from the operating condition of the diesel engine at a time when a variation of the operating condition is judged to be held within a predetermined range over a predetermined time, and compares a thus calculated difference with an actual difference between temperatures detected by said first and second temperature sensors, to determine the extent of deterioration of the NO x catalyst.

Claim 13

A method of detecting deterioration of an NO x catalyst for a diesel engine in which a hydrocarbon is supplied into an exhaust pipe as a hydrocarbon for reduction, and NO x exhausted from said diesel engine is reduced and purified by the NO x catalyst disposed in the exhaust pipe; said method comprising the steps of: determining an operating condition of the diesel engine; and determining an extent of deterioration of the NO x catalyst on a basis of a change in an amount of hydrocarbon in exhaust gas from said NO x catalyst during a period of time when the operating condition meets a predetermined condition, wherein said step of determining an operating condition comprises: determining an operating condition of the diesel engine on a basis of a rotational speed of said diesel engine and a load on said diesel engine, and wherein said step of determining an extent of deterioration comprises the steps of: measuring an amount of hydrocarbon by a hydrocarbon sensor in the exhaust pipe downstream of the NO x catalyst; memorizing an amount of hydrocarbon initially measured as a base amount of hydrocarbon; and comparing a predetermined value with a difference between the base amount of hydrocarbon and an amount of hydrocarbon subsequently measured to determine the extent of deterioration of the NO x catalyst.

Claim 14

A method of detecting deterioration of an NO x catalyst for a diesel engine in which a hydrocarbon is supplied into an exhaust pipe as a hydrocarbon for reduction, and NO x exhausted from said diesel engine is reduced and purified by the NO x catalyst disposed in the exhaust pipe; said method comprising the steps of: determining an operating condition of the diesel engine; and determining an extent of deterioration of the NO x catalyst on a basis of a change in an amount of hydrocarbon in exhaust gas from said NO x catalyst during a period of time when the operating condition meets a predetermined condition, wherein said step of determining an operating condition comprises: determining an operating condition of the diesel engine on a basis of a rotational speed of said diesel engine and a load on said diesel engine, and wherein said step of determining an extent of deterioration comprises the steps of: measuring an amount of hydrocarbon by a hydrocarbon sensor in the exhaust pipe downstream of the NO x catalyst; memorizing an amount of hydrocarbon initially measured as a base amount of hydrocarbon; and comparing a predetermined value with a difference between the base amount of hydrocarbon and an amount of hydrocarbon subsequently measured to determine the extent of deterioration of the NO x catalyst.

Claim 16

A method of detecting deterioration of an NO x catalyst for a diesel engine in which a hydrocarbon is supplied into an exhaust pipe as a hydrocarbon for reduction, and NO x exhausted from said diesel engine is reduced and purified by the NO x catalyst disposed in the exhaust pipe; said method comprising the steps of: determining an operating condition of the diesel engine; and determining an extent of deterioration of the NO x catalyst on a basis of a change in an amount of hydrocarbon in exhaust gas from said NO x catalyst during a period of time when the operating condition meets a predetermined condition, wherein said step of determining an operating condition comprises: determining an operating condition of the diesel engine on a basis of a rotational speed of said diesel engine and a load on said diesel engine, and wherein said step of determining an extent of deterioration comprises: measuring an amount of hydrocarbon actually exhausted from said NO x catalyst; calculating an amount of hydrocarbon exhausted from said NO x catalyst based on the operating condition of the diesel engine at a time when a variation of the operating condition is judged to be held within a predetermined range over a predetermined time; and comparing a predetermined value with a difference between thus calculated amount of hydrocarbon and thus measured amount of hydrocarbon, to determine the extent of deterioration of the NO x catalyst.

Claim 17

A method of detecting deterioration of an NO x catalyst for a diesel engine in which a hydrocarbon is supplied into an exhaust pipe as a hydrocarbon for reduction, and NO x exhausted from said diesel engine is reduced and purified by the NO x catalyst disposed in the exhaust pipe; said method comprising the steps of: determining an operating condition of the diesel engine; and determining an extent of deterioration of the NO x catalyst on a basis of a change in an amount of hydrocarbon in exhaust gas from said NO x catalyst during a period of time when the operating condition meets a predetermined condition, wherein said step of determining an operating condition comprises: determining an operating condition of the diesel engine on a basis of a rotational speed of said diesel engine and a load on said diesel engine, and wherein said step of determining an extent of deterioration comprises: measuring an amount of hydrocarbon actually exhausted from said NO x catalyst; calculating an amount of hydrocarbon exhausted from said NO x catalyst based on the operating condition of the diesel engine at a time when a variation of the operating condition is judged to be held within a predetermined range over a predetermined time; and comparing a predetermined value with a difference between thus calculated amount of hydrocarbon and thus measured amount of hydrocarbon, to determine the extent of deterioration of the NO x catalyst.

Claim 19

A method of detecting deterioration of an NO x catalyst for a diesel engine in which a hydrocarbon is supplied into an exhaust pipe as a hydrocarbon for reduction, and NO x exhausted from said diesel engine is reduced and purified by the NO x catalyst disposed in the exhaust pipe; said method comprising the steps of: determining an operating condition of the diesel engine; and determining an extent of deterioration of the NO x catalyst on a basis of a change in an amount of hydrocarbon in exhaust gas from said NO x catalyst during a period of time when the operating condition meets a predetermined condition, wherein said step of determining an extent of deterioration comprises: measuring a temperature on an upstream side of an oxidation catalyst which is disposed in said exhaust pipe downstream of and at a predetermined distance from the NO x catalyst; measuring a temperature on a downstream side of said oxidation catalyst; determining an operating condition of the diesel engine; and determining the extent of deterioration of the NO 0 catalyst on a basis of a change in temperature difference between said temperature on a downstream side and said temperature on an upsstream side during a period of time when thus determined operating condition meets a predetermined condition.

Claim 20

A method of detecting deterioration of an NO x catalyst for a diesel engine in which a hydrocarbon is supplied into an exhaust pipe as a hydrocarbon for reduction, and NO x exhausted from said diesel engine is reduced and purified by the NO x catalyst disposed in the exhaust pipe; said method comprising the steps of: determining an operating condition of the diesel engine; and determining an extent of deterioration of the NO x catalyst on a basis of a change in an amount of hydrocarbon in exhaust gas from said NO x catalyst during a period of time when the operating condition meets a predetermined condition, wherein said step of determining an extent of deterioration comprises: measuring a temperature on an upstream side of an oxidation catalyst which is disposed in said exhaust pipe downstream of and at a predetermined distance from the NO x catalyst; measuring a temperature on a downstream side of said oxidation catalyst; determining an operating condition of the diesel engine; and determining the extent of deterioration of the NO 0 catalyst on a basis of a change in temperature difference between said temperature on a downstream side and said temperature on an upsstream side during a period of time when thus determined operating condition meets a predetermined condition.

Claim 22

A method of detecting deterioration of an NO x catalyst for a diesel engine in which a hydrocarbon is supplied into an exhaust pipe as a hydrocarbon for reduction, and NO x exhausted from said diesel engine is reduced and purified by the NO x catalyst disposed in the exhaust pipe; said method comprising the steps of: determining an operating condition of the diesel engine; and determining an extent of deterioration of the NO x catalyst on a basis of a change in an amount of hydrocarbon in exhaust gas from said NO x catalyst during a period of time when the operating condition meets a predetermined condition, wherein said step of determining an extent of deterioration comprises: determining an operating condition of the diesel engine; measuring a temperature on an upstream side of an oxidation catalyst which is disposed in said exhaust pipe downstream of and at a predetermined distance from the NO x catalyst; measuring a temperature on a downstream side of said oxidation catalyst; calculating a difference between said temperature on an upstream side and said temperature on a downstream side based on thus determined operating condition of the diesel engine at a time when a variation of the operating condition is judged to be held within a predetermined range over a predetermined time; and comparing thus calculated temperature difference with an actual difference between said temperature on an upstream side and said temperature on a downstream side, to determine the extent of deterioration of the NO x catalyst.

Claim 23

A method of detecting deterioration of an NO x catalyst for a diesel engine in which a hydrocarbon is supplied into an exhaust pipe as a hydrocarbon for reduction, and NO x exhausted from said diesel engine is reduced and purified by the NO x catalyst disposed in the exhaust pipe; said method comprising the steps of: determining an operating condition of the diesel engine; and determining an extent of deterioration of the NO x catalyst on a basis of a change in an amount of hydrocarbon in exhaust gas from said NO x catalyst during a period of time when the operating condition meets a predetermined condition, wherein said step of determining an extent of deterioration comprises: determining an operating condition of the diesel engine; measuring a temperature on an upstream side of an oxidation catalyst which is disposed in said exhaust pipe downstream of and at a predetermined distance from the NO x catalyst; measuring a temperature on a downstream side of said oxidation catalyst; calculating a difference between said temperature on an upstream side and said temperature on a downstream side based on thus determined operating condition of the diesel engine at a time when a variation of the operating condition is judged to be held within a predetermined range over a predetermined time; and comparing thus calculated temperature difference with an actual difference between said temperature on an upstream side and said temperature on a downstream side, to determine the extent of deterioration of the NO x catalyst.