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Apparatus for diagnosing deterioration of NOX absorption-reduction catalyst

a technology of nox absorption reduction and diagnostic equipment, which is applied in the direction of mechanical equipment, machines/engines, exhaust treatment, etc., can solve the problems of deterioration of nox catalyst, impaired degradation of nox absorption performance, etc., to improve accuracy in deterioration diagnosis, reduce the number of checking processes, and facilitate the effect of enhancing productivity

Inactive Publication Date: 2010-08-12
DENSO CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention provides an apparatus for diagnosing deterioration of a NOx catalyst in an exhaust path of an internal combustion engine. The apparatus includes a NOx sensor, a deterioration diagnostic indicator calculating unit, and a deterioration diagnosing unit. The deterioration diagnostic indicator calculating unit calculates a ratio of the amount of NOx emitted from the catalyst to the amount of NOx inflow, or the amount of NOx absorbed in the catalyst. The deterioration diagnosing unit then uses this ratio as a diagnostic indicator to diagnose deterioration of the catalyst. The apparatus can enhance the accuracy of diagnosing NOx catalyst deterioration, increase productivity, and ensure frequent conducting of deterioration diagnosis, by mitigating the impact of catalyst size and operational states.

Problems solved by technology

Therefore, deterioration of the NOx catalyst (degradation in the performance of absorbing NOx) is required to be detected at an earlier occasion.
However, with these configurations, the accuracy in the deterioration diagnosis will be impaired unless the deterioration determining threshold is set according to the catalytic capacity or the engine operating condition (emission gas flow).
However, the configuration of setting the deterioration determining threshold according to the catalytic capacity or the engine operating condition (emission gas flow) may create a drawback.
Specifically, with such a configuration, developing and designing the systems for diagnosing deterioration of NOx catalyst will have to involve time-consuming processes of checking the deterioration determining thresholds, leading to low productivity.
However, with this countermeasure, the frequency of conducting deterioration diagnosis may fall off and thus the required frequency of conducting deterioration diagnosis is unlikely to be ensured.

Method used

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  • Apparatus for diagnosing deterioration of NOX absorption-reduction catalyst
  • Apparatus for diagnosing deterioration of NOX absorption-reduction catalyst
  • Apparatus for diagnosing deterioration of NOX absorption-reduction catalyst

Examples

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first embodiment

[0028]Referring to FIGS. 1 to 4, a first embodiment of the present invention will be described.

[0029]First, referring to FIG. 1, the configuration of an engine control system in general of the first embodiment will be described.

[0030]The engine control system includes an engine 11, i.e. an internal combustion engine. The intake pipe 12 of the engine 11 is provided with an air cleaner 13 disposed most upstream thereof, and an air flow meter14 disposed downstream of the air cleaner 13 to sense the flow volume of intake air (hereinafter referred to as “intake air flow”). A throttle valve 15 and a throttle position sensor 16 that detects a throttle position are disposed downstream of the air flow meter 14.

[0031]Further, a surge tank 17 is disposed downstream of the throttle valve 15. An intake-pipe pressure sensor 18 is disposed at the surge tank 17 to sense the pressure in the intake pipe. The surge tank 17 is provided with an intake manifold 19 which introduces air to the individual c...

second embodiment

[0078]Referring to FIGS. 5 to 8 hereinafter will be described a second embodiment of the present invention. In the second and the subsequent embodiments, the components identical with or similar to those in the first embodiment are given the same reference numerals for the sake of omitting explanation.

[0079]In the first embodiment, the NOx sensor 25 has been disposed upstream of the NOx catalyst 23. However, as shown in FIGS. 5 to 8, in the present embodiment, a NOx sensor 31 is disposed downstream of the NOx catalyst 23, and an O2 sensor 32 or an air-fuel ratio sensor is disposed upstream of the NOx catalyst 23 (downstream of the three-way catalyst 22). In the present embodiment, the NOx sensor 31 is incorporated with an air-fuel ratio detecting function as well as a NOx sensing function. Other hardware configurations are similar to the first embodiments.

[0080]Similar to the first embodiment, in the second embodiment as well, the non-purification factor is calculated, which is a ra...

third embodiment

[0110]With reference to FIGS. 9 and 10, hereinafter will be described a third embodiment of the present invention.

[0111]In the second embodiment described above, the NOx concentration to be sensed downstream of the NOx catalyst 23 has been set to “0” during the period when the output of the O2 sensor 32 upstream of the NOx catalyst 23 is enriched, or the period within a predetermined time from the completion of the NOx purge (rich purge). In this way, the NOx emission from the NOx catalyst 23 has been ensured to be inhibited from being summed.

[0112]The third embodiment shown in FIGS. 9 and 10 makes use of a rich period when the emission gas into the NOx catalyst 23 is richer than the stoichiometric level. Specifically, in this rich period, the output of the NOx sensor 31 during this rich period is subjected to an upper limit guard process with the output of the NOx sensor 31 immediately before the rich period. Using the value resulting from the upper limit guard process, the NOx emi...

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Abstract

An apparatus for diagnosing deterioration of a NOx absorption-reduction catalyst provided at an exhaust path of an engine includes a sensor disposed upstream of the catalyst to sense a NOx concentration in emission gas, a calculating unit calculating a first ratio of emission of NOx to inflow of NOx or a second ratio of absorption of NOx to inflow of NOx, and a diagnosing unit which diagnoses deterioration of the catalyst using the first or second ratio as an indicator. The calculating unit calculates inflow of NOx based on an output of the sensor and either the flow volume of the emission gas or a correlation value of the flow volume of the emission gas, calculates the absorption of NOx based on the amount of rich components required for reducing the NOx, and calculates the emission of NOx based on the difference between the inflow and absorption of NOx.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application is based on and claims the benefit of priority from earlier Japanese Patent Application No. 2009-029220 filed Feb. 11, 2009, the description of which is incorporated herein by reference.BACKGROUND OF THE INVENTION[0002]1. Technical Field of the Invention[0003]The present invention relates to an apparatus for diagnosing deterioration of a NOx absorption-reduction catalyst (hereinafter referred to as an “NOx catalyst”), which apparatus diagnoses deterioration of a NOx catalyst provided at an exhaust path of an internal combustion engine (engine).[0004]2. Related Art[0005]In recent years, so-called lean-burn engines or cylinder injection engines, which control air-fuel ratio to be leaner than a stoichiometric air-fuel ratio (theoretical air-fuel ratio), have been in practical use for the purposes of improving fuel consumption of vehicles. These engines tend to produce more NOx (nitrogen oxides) than normally used engines. The...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): F01N11/00
CPCF01N3/0807F01N11/00Y02T10/47Y02T10/20F01N2560/026Y02T10/12Y02T10/40
Inventor YOSHIKAWA, HISAYO
Owner DENSO CORP