Method and apparatus for detecting saturation gas amount absorbed by catalytic converter

• US 5,622,047 A
• Filed: 10/05/1994
• Issued: 04/22/1997
• Est. Priority Date: 07/03/1992
• Status: Expired due to Term

• Current Assignee: Nippondenso Co., Ltd. (DENSO Corporation)
• Original Assignee: Nippondenso Co., Ltd. (DENSO Corporation)
• Inventors: Ikuta, Kenji, Yamashita, Yukihiro, Isomura, Shigenori
• Primary Examiner(s): Hart, Douglas
• Application Number:
  US08/318,599
• Time in Patent Office: 930 Days
• Field of Search: 60/274, 60/276, 60/277, 60/285
• US Class Current: 60/274
• CPC Class Codes: F01N 11/007 the diagnostic devices measuring oxygen or air concentration downstream of the exhaust apparatus
• CPC Class Codes: F01N 2550/02 Catalytic activity of catalytic converters
• CPC Class Codes: F01N 2900/0422 measuring the elapsed time
• CPC Class Codes: F02D 41/1441 Plural sensors
• CPC Class Codes: F02D 41/1477 characterised by the regulation circuit or part of it,(e.g. comparator, PI regulator, output)
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

In an apparatus for detecting a saturation gas amount absorbed by a catalytic converter disposed in an exhaust system of an engine, an air-to-fuel ratio detecting device is disposed in a region of the engine exhaust system downstream of the catalytic converter for monitoring exhaust gas, which has passed through the catalytic converter, to detect an air-to-fuel ratio of an air-fuel mixture causing the exhaust gas. An air-to-fuel ratio changing device serves to change an air-to-fuel ratio of an air-fuel mixture fed to the engine by a correction quantity in a given direction, and serves to maintain changing the air-to-fuel ratio during a correction time. A change increasing device serves to increase the correction quantity and/or the correction time by the air-to-fuel ratio changing device to execute an air-to-fuel ratio changing process again in cases where the air-to-fuel ratio detected by the air-to-fuel ratio detecting device does not vary even when the air-to-fuel ratio changing device executes changing the air-to-fuel ratio. A saturation gas amount calculating device serves to calculate a saturation gas amount absorbed by the catalytic converter on the basis of the correction quantity and the correction time in cases where the air-to-fuel ratio detected by the air-to-fuel ratio detecting device varies when the air-to-fuel ratio changing device executes changing the air-to-fuel ratio.

Claims

1. An apparatus for detecting a saturation gas amount absorbed by a catalytic converter disposed in an exhaust system of an engine, comprising:

air-to-fuel ratio detecting means disposed in a region of the engine exhaust system downstream of the catalytic converter for monitoring exhaust gas, which has passed through the catalytic converter, to detect an air-to-fuel ratio of an air-fuel mixture causing the exhaust gas;

air-to-fuel ratio changing means for, in cases where the air-to-fuel ratio detected by the air-to-fuel ratio detecting means remains in a given range around a stoichiometric ratio during at least a predetermined time, changing an air-to-fuel ratio of an air-fuel mixture fed to the engine by a correction quantity in a given direction, and maintaining said changing-the air-to-fuel ratio during a correction time;

change increasing means for increasing at least one of the correction quantity and the correction time by the air-to-fuel ratio changing means to execute an air-to-fuel ratio changing process again in cases where the air-to-fuel ratio detected by the air-to-fuel ratio detecting means does not vary even when the air-to-fuel ratio changing means executes said changing air-to-fuel ratio; and

saturation gas amount calculating means for calculating a saturation gas amount absorbed by the catalytic converter on the basis of the correction quantity and the correction time in cases where the air-to-fuel ratio detected by the air-to-fuel ratio detecting means varies when the air-to-fuel ratio changing means executes said changing the air-to-fuel ratio.

2. The apparatus of claim 1 wherein the air-to-fuel ratio changing means is operative to change the air-to-fuel ratio in a direction opposite to the given direction after said changing the air-to-fuel ratio.

8. The apparatus of claim 1, wherein the air-to-fuel ratio correcting means comprises skip means for, when the result of said detecting by the downstream air-to-fuel ratio detecting means changes between a rich side and a lean side with respect to a predetermined reference value, changing stepwise the predetermined air-to-fuel ratio in a direction opposite to a direction of said change in the result of said detecting by the downstream air-to-fuel ratio detecting means, and skip quantity setting means for varying a quantity of said stepwise changing by the skip control means in response to the condition of deterioration of the catalytic converter which is determined by the deterioration condition determining means.

3. An apparatus for detecting a saturation gas amount absorbed by a catalytic converter disposed in an exhaust system of an engine, comprising:

means for feeding an air-fuel mixture to the engine;

means for changing an air-to-fuel ratio of the air-fuel mixture from a stoichiometric air-to-fuel ratio to saturate the catalytic converter;

means for detecting whether or not the catalytic converter is saturated by said changing the air-to-fuel ratio by the changing means; and

means for, when the detecting means detects that the catalytic converter is saturated, determining a saturation gas amount absorbed by the catalytic converter in accordance with a degree and a duration of said changing the air-to-fuel ratio by the changing means.

4. A method of detecting a saturation gas amount absorbed by a catalytic converter disposed in an exhaust system of an engine, comprising the steps of:

feeding an air-fuel mixture to the engine;

changing an air-to-fuel ratio of the air-fuel mixture from a stoichiometric air-to-fuel ratio to saturate the catalytic converter;

detecting whether or not the catalytic converter is saturated by said changing the air-to-fuel ratio; and

when the catalytic converter is detected to be saturated, determining a saturation gas amount absorbed by the catalytic converter in accordance with a degree and a duration of said changing the air-to-fuel ratio.

5. An apparatus for detecting a condition of deterioration of a catalytic converter disposed in an exhaust passage of an internal combustion engine, comprising:

upstream air-to-fuel ratio detecting means provided in a region of the exhaust passage upstream of the catalytic converter for detecting an air-to-fuel ratio of an air-fuel mixture causing exhaust gas flowing into the catalytic converter;

downstream air-to-fuel ratio detecting means provided in a region of the exhaust passage downstream of the catalytic converter for detecting an air-to-fuel ratio of an air-fuel mixture causing exhaust gas flowing from the catalytic converter;

air-to-fuel control means for controlling a rate of fuel injection into the engine in response to a result of said detecting by the upstream air-to-fuel ratio detecting means, and for varying the air-to-fuel ratio of the air-fuel mixture causing the exhaust gas flowing into the catalytic converter around a predetermined air-to-fuel ratio at an amplitude and a period;

increasing control means for correcting and increasing at least one of the amplitude and the period of said varying by the air-to-fuel ratio control means during a predetermined time; and

deterioration condition determining means for increasing a degree of said increasing by said increasing control means in cases where the air-to-fuel ratio detected by the downstream air-to-fuel ratio detecting means does not vary although at least one of the amplitude and the period is corrected and increased by the increasing control means, and for, when the air-to-fuel ratio detected by the downstream air-to-fuel ratio detecting means varies, determining a condition of deterioration of the catalytic converter in response to the amplitude and the period which occur as a result of said variation.

6. The apparatus of claim 5, wherein the air-to-fuel ratio control means comprises target air-to-fuel ratio setting means for setting a target air-to-fuel ratio, and feedback means for feedback-controlling the fuel injection rate in response to the result of said detecting by the upstream air-to-fuel ratio detecting means so that the result of said detecting by the upstream air-to-fuel ratio detecting means can be essentially maintained at the target air-to-fuel ratio, the target air-to-fuel ratio varying around the predetermined air-to-fuel ratio at the amplitude and the period.

7. The apparatus of claim 6, wherein the air-to-fuel ratio control means comprises air-to-fuel ratio correcting means for correcting the predetermined air-to-fuel ratio in response to a result of said detecting by the downstream air-to-fuel ratio detecting means.

9. The apparatus of claim 6, wherein the increasing control means comprises means for correcting and increasing at least one of an amplitude and a period of the target air-to-fuel ratio set by the target air-to-fuel ratio setting means.

10. The apparatus of claim 7, wherein the increasing control means comprises means for correcting and increasing at least one of an amplitude and a period of the target air-to-fuel ratio set by the target air-to-fuel ratio setting means.

11. The apparatus of claim 5, wherein the predetermined time used by the increasing control means is set when a total time of operation of the engine increases by each predetermined interval.

12. The apparatus of claim 11, wherein the engine is mounted on a vehicle, and the predetermined time used by the increasing control means is set as a distance traveled by the vehicle.

13. The apparatus of claim 11, further comprising means for canceling said correcting and increasing by the increasing control means after the condition of deterioration of the catalytic converter is determined by the deterioration condition determining means.

14. The apparatus of claim 5, wherein the increasing control means is operative for accumulatively increasing at least one of the amplitude and the period every given interval until the air-to-fuel ratio detected by the downstream air-to-fuel ratio detecting means varies during determination of the condition of deterioration of the catalytic converter by the deterioration condition determining means.

15. The apparatus of claim 14, wherein the increasing control means comprises means for executing said correcting and increasing of at least one of the amplitude and the period when the air-to-fuel ratio detected by the downstream air-to-fuel ratio detecting means is in a predetermined allowable range.

16. A method of detecting a condition of deterioration of a catalytic converter disposed in an exhaust passage of an internal combustion engine, comprising the steps of:

detecting an upstream air-to-fuel ratio of an air-fuel mixture causing exhaust gas flowing into the catalytic converter;

detecting a downstream air-to-fuel ratio of an air-fuel mixture causing exhaust gas flowing from the catalytic converter;

controlling a rate of fuel injection into the engine in response to a result of said detected upstream air-to-fuel ratio, and varying the air-to-fuel ratio of the air-fuel mixture causing the exhaust gas flowing into the catalytic converter around a predetermined air-to-fuel ratio at an amplitude and a period;

correcting and increasing at least one of the amplitude and the period of said varying of the air-to-fuel ratio; and

increasing a degree of said increasing of at least one of the amplitude and the period in cases where the detected downstream air-to-fuel ratio does not vary although at least one of the amplitude and the period is corrected and increased, and when the detected downstream air-to-fuel ratio varies, determining a condition of deterioration of the catalytic converter in response to the amplitude and the period which occur as result of said variation.