Apparatus for detecting deterioration of NOx selective reduction catalyst

Patent metadata

Field	Value
Publication number	US-9594065-B2
Application number	US-201114110636-A
Country	US
Kind code	B2
Filing date	Apr 12, 2011
Priority date	Apr 12, 2011
Publication date	Mar 14, 2017
Grant date	Mar 14, 2017

Abstract

Apparatus for detecting deterioration of an NOx selective reduction catalyst in an exhaust passage of an internal combustion engine with improved accuracy, includes an NOx purification rate calculation unit for calculating the NOx purification rate in the NOx selective reduction catalyst based on the NOx concentration in the exhaust gas flowing into and out of the NOx selective reduction catalyst. A determination as to whether the NOx selective reduction catalyst is deteriorated is made based on the NOx purification rate at a time when the temperature of the NOx selective reduction catalyst is equal to or higher than a temperature (Tc 0 ) at which the NOx purification rate will start to decrease with a rise in the temperature of the NOx selective reduction catalyst if the degree of deterioration of the NOx selective reduction catalyst is at the upper limit of an allowable range.

First claim

The invention claimed is:

1. An apparatus for detecting deterioration of NOx selective reduction catalyst provided in an exhaust passage of an internal combustion engine, the apparatus comprising:
an ammonia supplying unit that supplies ammonia serving as a reducing agent to said NOx selective reduction catalyst;
a temperature obtaining unit that obtains the temperature of the NOx selective reduction catalyst;
a computer comprising at least one processor configured to:
determine whether the temperature of said NOx selective reduction catalyst is more than a predetermined temperature, wherein the predetermined temperature is a temperature at which a NOx purification rate will start to decrease with a rise in the temperature of said NOx selective reduction catalyst if a degree of deterioration of said NOx selective reduction catalyst is at an upper limit of a predetermined allowable range, wherein the NOx purification rate decrease temperature occurs at a predetermined time when the temperature of the NOx selective reduction catalyst reaches a temperature at which an ammonia oxidizing ability exceeds a NOx reducing ability of the NOx selective reduction catalyst;
based on the temperature of said NOx selective reduction catalyst being more than the predetermined temperature, calculate the NOx purification rate in said NOx selective reduction catalyst based on the NOx concentration in exhaust gas flowing into said NOx selective reduction catalyst and the NOx concentration in exhaust gas flowing out of said NOx selective reduction catalyst; and
determine whether the NOx purification rate calculated at the predetermined time is less than a threshold value, the predetermined time corresponding to when the temperature of the NOx selective reduction catatyst is more than the predetermined temperature, and determine whether or not said NOx selective reduction catalyst is deteriorated based on the determination result.

2. An apparatus for detecting deterioration of NOx selective reduction catalyst according to claim 1 , wherein said computer comprising at least one processor determines whether or not said NOx selective reduction catalyst is deteriorated based on the NOx purification rate calculated by said NOx purification rate calculation unit at a time when the temperature of said NOx selective reduction catalyst is equal to a temperature at which the NOx purification rate will start to decrease with a rise in the temperature of said NOx selective reduction catalyst if said NOx selective reduction catalyst is in an initial condition.

3. An apparatus for detecting deterioration of NOx selective reduction catalyst according to claim 1 , wherein said computer comprising at least one processor determines whether or not said NOx selective reduction catalyst is deteriorated based on the NOx purification rate calculated by said NOx purification rate calculation unit at a time when the temperature of said NOx selective reduction catalyst is higher than said predetermined temperature and not higher than a temperature at which the NOx purification rate in said NOx selective reduction catalyst will become zero if the degree of deterioration of said NOx selective reduction catalyst is at the upper limit of the allowable range.

4. An apparatus for detecting deterioration of NOx selective reduction catalyst provided in an exhaust passage of an internal combustion engine, comprising:
an ammonia supplying unit that supplies ammonia serving as a reducing agent to said NOx selective reduction catalyst;
a temperature obtaining unit that obtains the temperature of the NOx selective reduction catalyst;
a computer comprising at least one processor configured to:
calculate the NOx purification rate in said NOx selective reduction catalyst based on the NOx concentration in exhaust gas flowing into said NOx selective reduction catalyst and the NOx concentration in exhaust gas flowing out of said NOx selective reduction catalyst;
determine a NOx purification rate decrease temperature based on a temperature of the NOx selective reduction catalyst and the NOx purification rate, wherein the NOx purification rate decrease temperature is a temperature at which the NOx purification rate starts to decrease with a rise in the temperature of the NOx selective reduction catalyst, and is when the NOx selective reduction catalyst reaches a temperature at which an ammonia oxidizing ability exceeds a NOx reducing ability of the NOx selective reduction catalyst;
determine that said NOx selective reduction catalyst is deteriorated if the NOx purification rate decrease temperature is lower than a predetermined criterion temperature.

5. An apparatus for detecting deterioration of NOx selective reduction catalyst according to claim 4 , wherein said predetermined criterion temperature is a temperature at which the NOx purification rate will start to decrease with a rise in the temperature of said NOx selective reduction catalyst if the degree of deterioration of said NOx selective reduction catalyst is at the upper limit of an allowable range.

Assignees

• Hagimoto Taiga
• Shibata Daisuke
• Toyota Motor Co Ltd

Inventors

• Hagimoto Taiga
• Shibata Daisuke

Classifications

• F01N11/00

  Monitoring or diagnostic devices for exhaust-gas treatment apparatus · CPC title

• F01N2900/1621

  Catalyst conversion efficiency · CPC title

• G01N31/10 Primary

  using catalysis · CPC title

• F01N2560/021

  for measuring or detecting ammonia NH3 · CPC title

• F01N2550/02

  Catalytic activity of catalytic converters · CPC title