Apparatus for detecting deterioration of exhaust gas purifying catalysts

A deterioration detection apparatus for detecting deterioration of a catalyst of an engine having an upstream-side catalyst and a downstream-side catalyst provided for purifying exhaust gas, the deterioration detection apparatus comprising:

• a first sensor, provided on an upstream side of the upstream-side catalyst, for detecting an air-fuel ratio of exhaust gas flowing in the upstream side of the upstream-side catalyst;
• a second sensor, provided on a downstream side of the upstream-side catalyst, for detecting an air-fuel ratio of exhaust gas flowing in the downstream side of the upstream-side catalyst;
• a third sensor, provided on a downstream side of the downstream-side catalyst, for detecting an air-fuel ratio of exhaust gas flowing in the downstream side of the downstream-side catalyst;
• a catalyst deterioration diagnosing unit for determining existence and non-existence of a deteriorating state of the upstream-side catalyst based on at least a signal output of the second sensor,
• wherein the catalyst deterioration diagnosing unit controls the air-fuel ratio of the exhaust gas flowing in the downstream side of the downstream-side catalyst in a predetermined range during a period of time to diagnose the deteriorating state of the upstream-side catalyst,
• an upstream-side catalyst temperature determining unit for determining temperature of the upstream-side catalyst;
• and
• a downstream-side catalyst temperature determining unit for determining temperature of the downstream-side catalyst,
• wherein the catalyst deterioration diagnosing unit diagnoses the deteriorating state of the upstream-side catalyst only when the temperatures of the upstream-side catalyst and the downstream-side catalyst are in respective predetermined ranges.

A deterioration detection apparatus for detecting deterioration of a catalyst of an engine having an upstream-side catalyst and a downstream-side catalyst provided for purifying exhaust gas, the deterioration detection apparatus comprising:

• a first sensor, provided on an upstream side of the upstream-side catalyst, for detecting an air-fuel ratio of exhaust gas flowing in the upstream side of the upstream-side catalyst;
• a second sensor, provided on a downstream side of the upstream-side catalyst, for detecting an air-fuel ratio of exhaust gas flowing in the downstream side of the upstream-side catalyst;
• a third sensor, provided on a downstream side of the downstream-side catalyst, for detecting an air-fuel ratio of exhaust gas flowing in the downstream side of the downstream-side catalyst;
• a catalyst deterioration diagnosing unit for determining existence and non-existence of a deteriorating state of the upstream-side catalyst based on at least a signal output of the second sensor,
• wherein the catalyst deterioration diagnosing unit controls the air-fuel ratio of the exhaust gas flowing in the downstream side of the downstream-side catalyst in a predetermined range during a period of time to diagnose the deteriorating state of the upstream-side catalyst, and
• a catalyst deterioration diagnosis inhibition unit for inhibiting the catalyst deterioration diagnosing unit from diagnosing the deteriorating state of the upstream-side catalyst when the third sensor becomes abnormal.

A deterioration detection apparatus for detecting deterioration of a catalyst of an engine having an upstream-side catalyst and a downstream-side catalyst provided for purifying exhaust gas, the deterioration detection apparatus comprising:

• a first sensor, provided on an upstream side of the upstream-side catalyst, for detecting an air-fuel ratio of exhaust gas flowing in the upstream side of the upstream-side catalyst;
• a second sensor, provided on a downstream side of the upstream-side catalyst, for detecting an air-fuel ratio of exhaust gas flowing in the downstream side of the upstream-side catalyst;
• a third sensor, provided on a downstream side of the downstream-side catalyst, for detecting an air-fuel ratio of exhaust gas flowing in the downstream side of the downstream-side catalyst;
• and
• a catalyst deterioration diagnosing unit for determining existence and non-existence of a deteriorating state of the upstream-side catalyst based on at least a signal output of the second sensor,
• wherein the catalyst deterioration diagnosing unit carries out a diagnosis of the deteriorating state of the upstream-side catalyst during a period of time in which the air-fuel ratio of the exhaust gas flowing in the downstream side of the downstream-side catalyst is controlled in a predetermined range, and
• wherein the catalyst deterioration diagnosing unit starts the diagnosis of the deteriorating state of the upstream-side catalyst after a signal output of the third sensor has been sustained in the predetermined range for a predetermined period of time continuously.

for detecting deterioration of a catalyst of an engine having an upstream-side catalyst and a downstream-side catalyst provided for purifying exhaust gas, the deterioration detection apparatus comprising:

• a first sensor, provided on an upstream side of the upstream-side catalyst, for detecting an air-fuel ratio of exhaust gas flowing in the upstream side of the upstream-side catalyst;
• a second sensor, provided on a downstream side of the upstream-side catalyst, for detecting an air-fuel ratio of exhaust gas flowing in the downstream side of the upstream-side catalyst;
• a third sensor, provided on a downstream side of the downstream-side catalyst, for detecting an air-fuel ratio of exhaust gas flowing in the downstream side of the downstream-side catalyst;
• a catalyst deterioration diagnosing unit for determining existence and non-existence of a deteriorating state of the upstream-side catalyst based on at least a signal output of the second sensor,
• wherein the catalyst deterioration diagnosing unit carries out a diagnosis of the deteriorating state of the upstream-side catalyst during a period of time in which the air-fuel ratio of the exhaust gas flowing in the downstream side of the downstream-side catalyst is controlled in a predetermined range,
• an upstream-side catalyst temperature determining unit for determining temperature of the upstream-side catalyst;
• and
• a downstream-side catalyst temperature determining unit for determining temperature of the downstream-side catalyst,
• wherein the catalyst deterioration diagnosing unit diagnoses the deteriorating state of the upstream-side catalyst only when the temperatures of the upstream-side catalyst and the downstream-side catalyst are in respective predetermined ranges.

A deterioration detection apparatus for detecting deterioration of a catalyst of an engine having an upstream-side catalyst and a downstream-side catalyst provided for purifying exhaust gas, the deterioration detection apparatus comprising:

• a first sensor, provided on an upstream side of the upstream-side catalyst, for detecting an air-fuel ratio of exhaust gas flowing in the upstream side of the upstream-side catalyst;
• a second sensor, provided on a downstream side of the upstream-side catalyst, for detecting an air-fuel ratio of exhaust gas flowing in the downstream side of the upstream-side catalyst;
• a third sensor, provided on a downstream side of the downstream-side catalyst, for detecting an air-fuel ratio of exhaust gas flowing in the downstream side of the downstream-side catalyst;
• a catalyst deterioration diagnosing unit for determining existence and non-existence of a deteriorating state of the upstream-side catalyst based on at least a signal output of the second sensor,
• wherein the catalyst deterioration diagnosing unit carries out a diagnosis of the deteriorating state of the upstream-side catalyst during a period of time in which the air-fuel ratio of the exhaust gas flowing in the downstream side of the downstream-side catalyst is controlled in a predetermined range,
• a catalyst deterioration diagnosis inhibition unit for inhibiting the catalyst deterioration diagnosing unit from diagnosing the deteriorating state of the upstream-side catalyst when the third sensor becomes abnormal.

A deterioration detection apparatus for detecting deterioration of a catalyst of an engine having an upstream-side catalyst and a downstream-side catalyst provided for purifying exhaust gas, the deterioration detection apparatus comprising:

• a first sensor, provided on an upstream side of the upstream-side catalyst, for detecting an air-fuel ratio of exhaust gas flowing in the upstream side of the upstream-side catalyst;
• a second sensor, provided on a downstream side of the upstream-side catalyst, for detecting an air-fuel ratio of exhaust gas flowing in the downstream side of the upstream-side catalyst;
• a control unit for effecting an air-fuel ratio feedback control using the air-fuel ratios detected by the first sensor and the second sensor;
• a third sensor, provided on a downstream side of the downstream-side catalyst, for detecting an air-fuel ratio of exhaust gas flowing in the downstream side of the downstream-side catalyst;
• and
• a catalyst deterioration diagnosing unit for determining existence and non-existence of a deteriorating state of the upstream-side catalyst based on at least a signal output of the second sensor,
• wherein the catalyst deterioration diagnosing unit controls the air-fuel ratio of the exhaust gas flowing in the downstream side of the downstream-side catalyst in a predetermined range during a period of time to diagnose the deteriorating state of the upstream-side catalyst.

A deterioration detection apparatus for detecting deterioration of a catalyst of an engine having an upstream-side catalyst and a downstream-side catalyst provided for purifying exhaust gas, the deterioration detection apparatus comprising:

• a first sensor, provided on an upstream side of the upstream-side catalyst, for detecting an air-fuel ratio of exhaust gas flowing in the upstream side of the upstream-side catalyst;
• a second sensor, provided on a downstream side of the upstream-side catalyst, for detecting an air-fuel ratio of exhaust gas flowing in the downstream side of the upstream-side catalyst;
• a control unit for effecting an air-fuel ratio feedback control using the air-fuel ratios detected by the first sensor and the second sensor;
• a third sensor, provided on a downstream side of the downstream-side catalyst, for detecting an air-fuel ratio of exhaust gas flowing in the downstream side of the downstream-side catalyst;
• and
• a catalyst deterioration diagnosing unit for determining existence and non-existence of a deteriorating state of the upstream-side catalyst based on at least a signal output of the second sensor,
• wherein the catalyst deterioration diagnosing unit carries out a diagnosis of the deteriorating state of the upstream-side catalyst during a period of time in which the air-fuel ratio of the exhaust gas flowing in the downstream side of the downstream-side catalyst is controlled in a predetermined range.

A method for detecting deterioration of an upstream side first exhaust emission control catalyst in the presence of a downstream-side second exhaust emission control catalyst, said method comprising:

• determining the temperature of the upstream-side catalyst;
• determining the temperature of the downstream-side catalyst;
• and
• diagnosing the deterioration state of the upstream-side catalyst when the temperatures of the upstream-side catalyst and the downstream-side catalyst are in respective predetermined ranges.