Failure diagnosis device of emission control system

Patent metadata

Field	Value
Publication number	US-2016265461-A1
Application number	US-201615064809-A
Country	US
Kind code	A1
Filing date	Mar 9, 2016
Priority date	Mar 13, 2015
Publication date	Sep 15, 2016
Grant date	—

Abstract

In a failure diagnosis device of an emission control system that utilizes an electrode-based PM sensor to diagnose a failure of a particulate filter, some embodiments may be to suppress reduction of accuracy of diagnosis of a failure due to in-cylinder rich control. The failure diagnosis device of the emission control system performs a measurement process. The measurement process includes a sensor recovery process of removing PM depositing between the electrodes of the electrode-based PM sensor, a process of starting application of the predetermined voltage to the electrodes of the PM sensor after completion of the sensor recovery process, and a process of obtaining an output value of the PM sensor after elapse of a predetermined time period since the start of application of the predetermined voltage to the electrodes of the PM sensor.

First claim

What is claimed is:

1 . A failure diagnosis device for an emission control system, wherein the emission control system includes a particulate filter that is placed in an exhaust conduit of an internal combustion engine and that is configured to trap PM in exhaust gas; an exhaust gas purification device that is placed upstream of the particulate filter in the exhaust conduit and that is configured to purify the exhaust gas by utilizing a non-combusted fuel component included in the exhaust gas; and a supplier that is configured to perform in-cylinder rich control of changing an air-fuel ratio of an air-fuel mixture subjected to combustion in the internal combustion engine to a rich air-fuel ratio which is lower than a stoichiometric air-fuel ratio, so as to supply the non-combusted fuel component to the exhaust gas purification device,
the failure diagnosis device comprising: a PM sensor that is provided to detect an amount of PM flowing out of the particulate filter, the PM sensor including electrodes opposed to each other across an insulating layer and being configured to output an electric signal relating to a value of electric current flowing between the electrodes under application of a predetermined voltage to the electrodes; and a controller comprising at least one processor configured to perform a process of diagnosing a failure of the particulate filter, based on an output value of the PM sensor, wherein the controller is programmed to:
perform a measurement process, the measurement process including a sensor recovery process of removing PM depositing between the electrodes of the PM sensor, a process of starting application of the predetermined voltage to the electrodes of the PM sensor after completion of the sensor recovery process, and a process of obtaining an output value of the PM sensor after elapse of a predetermined time period since the start of application of the predetermined voltage;
diagnose a failure of the particulate filter by comparing the obtained output value of the PM sensor with a predefined reference value;
predict whether the in-cylinder rich control is performed in the predetermined time period, before the measurement process, or during the measurement process, or both before and during the measurement process; and
perform the measurement process or continue the measurement process when it is predicted that the in-cylinder rich control is not performed in the predetermined time period, and either do not perform the measurement process or stop the measurement process when it is predicted that the in-cylinder rich control is performed in the predetermined time period.

2 . The failure diagnosis device of the emission control system according to claim 1 , wherein
the exhaust gas purification device includes an NO X storage reduction catalyst that is configured to store NO X from the exhaust gas when an air-fuel ratio of the exhaust gas is a lean air-fuel ratio higher than the stoichiometric air-fuel ratio and to reduce NO X stored in the NO X storage reduction catalyst when the air-fuel ratio of the exhaust gas is a rich air-fuel ratio lower than the stoichiometric air-fuel ratio, the supplier performs the in-cylinder rich control to reduce NO X stored in the NO X storage reduction catalyst, when a NO X storage amount of the NO X storage reduction catalyst becomes equal to or greater than a first NO X storage amount, and the controller is further programmed to predict that the in-cylinder rich control is performed in the predetermined time period when the NO X storage amount of the NO X storage reduction catalyst is equal to or greater than a second NO X storage amount which is smaller than the first NO X storage amount, while predicting that the in-cylinder rich control is not performed in the predetermined time period when the NO X storage amount of the NO X storage reduction catalyst is less than the second NO X storage amount.

3 . The failure diagnosis device of the emission control system according to claim 1 , wherein
the exhaust gas purification device includes an NO X storage reduction catalyst that is configured to store NO X from the exhaust gas when an air-fuel ratio of the exhaust gas is a lean air-fuel ratio higher than the stoichiometric air-fuel ratio and to reduce NO X stored in the NO X storage reduction catalyst when the air-fuel ratio of the exhaust gas is a rich air-fuel ratio lower than the stoichiometric air-fuel ratio, the supplier performs the in-cylinder rich control to remove a sulfur component from the NO X storage reduction catalyst when a sulfur poisoning amount of the NO X storage reduction catalyst becomes equal to or greater than a first poisoning amount, and the controller is further programmed to predict that the in-cylinder rich control is performed in the predetermined time period when the sulfur poisoning amount of the NO X storage reduction catalyst is equal to or greater than a second poisoning amount which is smaller than the first poisoning amount, while predicting that the in-cylinder rich control is not performed in the predetermined time period when the sulfur poisoning amount of the NO X storage reduction catalyst is less than the second poisoning amount.

4 . The failure diagnosis device of the emission control system according to claim 1 , wherein
the exhaust gas purification device includes a selective catalytic reduction catalyst that is configured to adsorb NH 3 included in the exhaust gas and to reduce NO X from the exhaust gas using the adsorbed NH 3 as a reducing agent, and an NH 3 producing catalyst that is placed upstream of the selective catalytic reduction catalyst and is configured to produce NH 3 when an air-fuel ratio of the exhaust gas is equal to or lower than the stoichiometric air-fuel ratio, the supplier performs the in-cylinder rich control to produce NH 3 by the NH3 producing catalyst when an NH 3 adsorption amount of the selective catalytic reduction catalyst becomes equal to or less than a first NH 3 adsorption amount, and the controller is further programmed to predict that the in-cylinder rich control is performed in the predetermined time period when the NH 3 adsorption amount of the selective catalytic reduction catalyst is equal to or less than a second NH 3 adsorption amount which is larger than the first NH 3 adsorption amount, while predicting that the in-cylinder rich control is not performed in the predetermined time period when the NH 3 adsorption amount of the selective catalytic reduction catalyst is greater than the second NH 3 adsorption amount.

Assignees

• Toyota Motor Co Ltd

Inventors

• Nishijima Hirokazu
• Kidokoro Toru
• Takaoka Kazuya

Classifications

• F01N2560/05

  the means being a particulate sensor · CPC title

• F01N3/2066

  Selective catalytic reduction [SCR] · CPC title

• F01N3/0828

  characterised by the absorbed or adsorbed substances · CPC title

• F01N2570/18

  Ammonia · CPC title

• F01N2570/14

  Nitrogen oxides · CPC title