US 8,938,947 B2 · Catalyst degradation detection apparatus

Abstract

A catalyst degradation detection apparatus includes: calculation means for calculating, as an oxygen storage amount of a catalyst, an amount of oxygen stored into or desorbed from the catalyst during a period from when a change that corresponds to a change in an air/fuel ratio occurs in the signal of a pre-catalyst sensor to when the signal of a post-catalyst sensor reaches a criterion value regarding the change in the air/fuel ratio; catalyst degradation determination means for determining of degradation of the catalyst on the basis of the oxygen storage amount; and correction means for correcting the oxygen storage amount calculated for use for determining of degradation of the catalyst more to a decrease side as a measured responsiveness of the post-catalyst sensor becomes more deteriorated relative to a reference value.

A catalyst degradation detection apparatus comprising:

a pre-catalyst sensor that is provided in an exhaust passageway of an internal combustion engine upstream of a catalyst and that outputs a signal based on an oxygen concentration in exhaust gas;
a post-catalyst sensor that is provided in the exhaust passageway downstream of the catalyst and that outputs a signal based on the oxygen concentration in the exhaust gas;
and
an electronic control unit having control logic configured to cause the electronic control unit to:
control an air/fuel ratio of the internal combustion engine such that the air/fuel ratio changes between a rich side and a lean side;
provide a criterion value for determining that a change that corresponds to a change in the air/fuel ratio has occurred in the signal of the post-catalyst sensor;
calculate as an oxygen storage amount of the catalyst an amount of oxygen stored into the catalyst or desorbed from the catalyst during a period from when the change that corresponds to the change in the air/fuel ratio occurs in the signal of the pre-catalyst sensor to when the signal of the post-catalyst sensor reaches the criterion value;
calculate the amount of oxygen that is stored into the catalyst when the air/fuel ratio of the internal combustion engine is changed from the rich side to the lean side by the electronic control unit, as the oxygen storage amount found when oxygen is stored;
calculate the amount of oxygen that is desorbed from the catalyst when the air/fuel ratio of the internal combustion engine is changed from the lean side to the rich side by the electronic control unit, as the oxygen storage amount found when oxygen is desorbed:
determine presence or absence of degradation of the catalyst based on the oxygen storage amount;
measure responsiveness of a change in the signal output by the post-catalyst sensor to a change in the oxygen concentration in the exhaust gas downstream of the catalyst;
measure the responsiveness of the signal output by the post-catalyst sensor to the change in the air/fuel ratio to the lean side when the air/fuel ratio of the internal combustion engine is changed from the rich side to the lean side by the electronic control unit;
measure the responsiveness of the signal output by the post-catalyst sensor to the change in the air/fuel ratio to the rich side when the air/fuel ratio of the internal combustion engine is changed from the lean side to the rich side by the electronic control unit;
correct the oxygen storage amount calculated for use for determining the presence or absence of degradation of the catalyst by determining a corrected oxygen storage amount by reducing the calculated oxygen storage amount more greatly as the responsiveness of the post-catalyst sensor measured by the electronic control unit becomes more deteriorated relative to a reference value;
correct the oxygen storage amount found when oxygen is stored, based on the responsiveness of the post-catalyst sensor to the change in the air/fuel ratio to the lean side;
and
correct the oxygen storage amount found when oxygen is desorbed, based on the responsiveness of the post-catalyst sensor to the change in the air/fuel ratio to the rich side;
wherein
when only one of the responsiveness of the post-catalyst sensor to the change in the air/fuel ratio to the lean side and the responsiveness of the post-catalyst sensor to the change in the air/fuel ratio to the rich side has been measured, the electronic control unit calculates an average value of the oxygen storage amount corrected based on the only one of the responsiveness that has been measured and the oxygen storage amount that corresponds to the responsiveness that has not been measured, and determines the presence or absence of degradation of the catalyst based on comparison of the corrected oxygen storage amount with a predetermined first threshold value and comparison of the average value with a second threshold value that is greater than the first threshold value.

16 more elements

Description16,527 words

Summary6,341 words

#1. Field of the Invention

#The invention relates to a catalyst degradation detection apparatus.

#2. Description of the Related Art

Brief description of the drawings10 figures

#The features, advantages, and technical and industrial significance of this invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

#FIG. 1 is a schematic diagram showing an overall construction of an engine to which a catalyst degradation detection apparatus in accordance with an embodiment of the invention is applied;

#FIG. 2 is a graph showing changes in an output signal of an air/fuel ratio sensor relative to changes in the oxygen concentration in exhaust gas in accordance with the embodiment of the invention;

Detailed description9,787 words

#An embodiment in which the invention is applied to a motor vehicle engine will be described hereinafter with reference to FIG. 1 to FIG. 8. In an engine 1, a throttle valve 13 is provided in an intake passageway 3 leading to a combustion chamber 2 so that the throttle valve 13 can be opened and closed. Air is taken into the combustion chamber 2 through the intake passageway, and fuel injected from a fuel injection valve 4 is supplied into the combustion chamber 2 via the intake passageway 3. A mixture of air and fuel supplied into the combustion chamber 2 burns due to ignition by an ignition plug 5. As the mixture burns within the combustion chamber 2, a piston 6 reciprocates, rotating a crankshaft 7 that is an output shaft of the engine 1.

#After being burned in the combustion chamber 2, the mixture is sent out as an exhaust gas from the combustion chamber 2 into an exhaust passageway 8. The exhaust gas that passes through the exhaust passageway 8 is let out into the outside after harmful components of the exhaust gas, such as HCs, CO, NOx, etc., are removed by a three-way catalyst of a catalytic converter 16. The three-way catalyst has an oxygen storage function in order to effectively remove the foregoing three components from the exhaust gas. While the three-way catalyst is equipped with the oxygen storage function, a stoichiometric air/fuel ratio control of controlling the air/fuel ratio of the mixture so that the oxygen concentration in the catalyst atmosphere converges to the value of oxygen concentration occurring at the time of combustion of the mixture at the stoichiometric air/fuel ratio is performed. Therefore, with the three-way catalyst, the three components of exhaust gas, that is, NOx, HCs and CO, can be effectively removed.

#Besides, the exhaust passageway 8 upstream of the catalytic converter 16 is provided with an air/fuel ratio sensor 17 as a pre-catalyst sensor that outputs a signal based on the oxygen concentration in exhaust gas, and the passageway downstream of the catalytic converter 16 is provided with an oxygen sensor 18 as a post-catalyst sensor that outputs a signal based on the oxygen concentration in exhaust gas.

Facts

Application

13/583,139Filed 24 Feb 2011

Priority

JP 2010-0518559 Mar 2010

Published

US 2012/0324869 A127 Dec 2012

Granted

27 Jan 2015

Term ends

30 Oct 2031

Estimated · how

20 years from earliest known nonprovisional domestic filing plus recorded patent term adjustment, including 248 days of adjustment. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification11 codes

F01N 11/007
Monitoring or diagnostic devices for exhaust-gas treatment apparatus: the diagnostic devices measuring oxygen or air concentration downstream of…
F02D 41/0295
In relation with the state of the exhaust gas treating apparatus: control according to the amount of oxygen that is stored on the exhaust gas…
F02D 41/2454
Characterised by what is learned or calibrated: learning of the air-fuel ratio control
F01N 2550/02
Monitoring or diagnosing the deterioration of exhaust systems: catalytic activity of catalytic converters

Timeline

9 Mar 2010Priority claimedJP 2010-051855
24 Feb 2011Application filedUS 13/583,139
6 Sep 2012Assigned to Toyota Jidosha Kabushiki Kaishaassignment of assignor's interest
27 Dec 2012PublishedUS 2012/0324869 A1
27 Jan 2015GrantedUS 8,938,947 B2
12 Oct 2026TodayWithin its term
30 Oct 2031Term endsEstimated, includes 248 days of adjustment

Catalyst degradation detection apparatus

Life of this patent

Catalyst degradation detection apparatus

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims6

Description16,527 words

Drawings

Classification11 codes

Life of this patent

Description16,527 words