Method and algorithm for diagnosing an NH3 sensor in an SCR system using measurements from two channels of the sensor

• US 9,482,137 B2
• Filed: 12/03/2012
• Issued: 11/01/2016
• Est. Priority Date: 12/01/2011
• Status: Active Grant

• Current Assignee: Cummins Incorporated
• Original Assignee: Cummins Incorporated
• Inventors: Liu, Feng, Geveci, Mert
• Primary Examiner(s): Matthias, Jonathan
• Application Number:
  US13/692,026
• Publication Number:
  US 20130139489A1
• Time in Patent Office: 1,429 Days
• US Class Current: 1/1
• CPC Class Codes: F01N 11/00 Monitoring or diagnostic devices for exhaust-gas treatment apparatus , e.g. for catalytic activity safety, indicating or supervising devices for internal combustion engines F02B77/08; testing of machines G01M13/00
• CPC Class Codes: F01N 11/007 the diagnostic devices measuring oxygen or air concentration downstream of the exhaust apparatus
• CPC Class Codes: F01N 13/0093 the purifying devices are of the same type
• CPC Class Codes: F01N 2550/02 Catalytic activity of catalytic converters
• CPC Class Codes: F01N 2560/021 for measuring or detecting ammonia NH3
• CPC Class Codes: F01N 2560/026 for measuring or detecting NOx
• CPC Class Codes: F01N 2560/14 having more than one sensor of one kind
• CPC Class Codes: F01N 3/106 Auxiliary oxidation catalysts
• CPC Class Codes: F01N 3/2066 Selective catalytic reduction [SCR]
• CPC Class Codes: F02D 2041/1468 the characteristics being an ammonia content or concentration of the exhaust gases
• CPC Class Codes: F02D 41/1441 Plural sensors
• CPC Class Codes: F02D 41/146 the characteristics being an NOx content or concentration
• CPC Class Codes: F02D 41/222 relating to the failure of sensors or parameter detection devices
• CPC Class Codes: G01M 15/102 by monitoring exhaust gases
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A system includes an internal combustion engine providing exhaust gases to an exhaust conduit, an aftertreatment system having an SCR catalyst component and disposed in the exhaust conduit. The system further includes a first NH₃ sensing element preferentially sensitive to NH₃ and a second NH₃ sensing element preferentially sensitive to NO₂ in the exhaust conduit. Both NH₃ sensing elements are positioned downstream of the SCR catalyst component. The system includes a controller having a test conditions module that determines whether an NO₂ concentration downstream of the SCR catalyst component is below a threshold value, an NH₃ diagnostic module that provides a detection comparison value in response to the NO₂ concentration, a first signal from the first NH₃ sensing element, and a second signal from the second NH₃ sensing element. The controller includes a sensor condition module that provides an NH₃ sensor condition value in response to the detection comparison value.

Claims

1. A system, comprising:

an internal combustion engine providing exhaust gases to an exhaust conduit;

an aftertreatment system disposed in the exhaust conduit, the aftertreatment system comprising a selective catalytic reduction (SCR) catalyst component;

a first NH₃ sensing channel operationally coupled to the exhaust conduit at a position downstream of the SCR catalyst component, the first NH₃ sensing channel sensitive to NH₃;

a second NH₃ sensing channel operationally coupled to the exhaust conduit at the position downstream of the SCR catalyst component, the second NH₃ sensing channel more sensitive to NO₂ than the first NH₃ sensing channel, and the first NH₃ sensing channel is more sensitive to NH₃ than the second NH₃ sensing channel; and

a electronic controller operationally coupled to and configured to interpret a first signal from the first NH₃ sensing channel and a second signal from the second NH₃ sensing channel, wherein the first and second NH₃ sensing channels are operationally coupled at a position downstream of the SCR catalyst component, the controller being configured to determine whether an NO₂ concentration at the position downstream of the SCR catalyst component is below a threshold value, the controller being configured to not enable an NH₃ sensor condition diagnostic in response to the NO₂ concentration being above the threshold value and to enable the NH₃ sensor condition diagnostic to provide a detection comparison value in response to the NO₂ concentration being below the threshold value, and further in response to a first signal from the first NH₃ sensing channel and a second signal from the second NH₃ sensing channel, the controller further being configured to provide an NH₃ sensor condition value in response to the detection comparison value.

2. The system of claim 1, wherein the first NH₃ sensing channel and the second NH₃ sensing channel are disposed in a single sensor housing.

3. The system of claim 2, wherein the first NH₃ sensing channel and the second NH₃ sensing channel comprise a differential response to NO₂.

4. The system of claim 1, wherein the controller is further configured to provide the detection comparison value in response to a difference between an NH₃ value from the first signal and an NH₃ value from the second signal.

5. The system of claim 1, wherein the controller is further configured to provide the detection comparison value in response to an NH₃ value from the first signal and an NH₃ value from the second signal.

6. The system of claim 5, wherein the controller is further configured to interpret a healthy sensor state space, and to provide the detection comparison value in response to a comparison of the healthy sensor state space with a position determined from the NH₃ value from the first signal and the NH₃ value from the second signal.

7. The system of claim 1, wherein the controller is further configured to interpret a healthy sensor state space, and to provide the detection comparison value in response to a comparison of the healthy sensor state space with a position determined from an NH₃ value from the first signal and an NH₃ value from the second signal.

8. The system of claim 7, wherein a position within the healthy sensor state space is determined to be a healthy sensor indication, and wherein a position outside the healthy sensor state space is determined to be a failed sensor indication.

9. The system of claim 1, wherein the first NH₃ sensing channel comprises an NH₃ detection element of an NH₃ sensor, and wherein the second NH₃ sensing channel comprises an NO₂ compensation element of the NH₃ sensor.

10. A method, comprising:

performing, with an electronic controller operationally coupled to and configured to interpret a first signal from a first NH₃ sensing channel and a second signal from a second NH₃ sensing channel that are operationally coupled to an exhaust gas conduit downstream of a selective catalytic reduction (SCR) component, the following;

determining whether an amount of NO₂ present in an exhaust gas produced by operation of an internal combustion engine connected to the exhaust gas conduit is below a sensor check threshold value;

in response to the amount of NO, present being above the sensor check threshold value, not enabling an NH₃ sensor condition diagnostic;

in response to the amount of NO₂ present being below the sensor check threshold value, interpreting the first signal from the first NH₃ sensing channel and the second signal from the second NH₃ sensing channel, wherein the first and second NH₃ sensing channels comprise distinct sensitivities to NO₂;

providing a detection comparison value in response to the first signal and the second signal; and

providing an NH₃ sensor condition value in response to the detection comparison value.

11. The method of claim 10, wherein the detection comparison value comprises a difference between the first signal and the second signal, and wherein the providing an NH₃ sensor condition value in response to the detection comparison value comprises determining if the difference exceeds a sensor failed threshold value.

12. The method of claim 10, wherein the determining the amount of NO₂ present is below the sensor check threshold value comprises at least one operation selected from the operations consisting of:

determining that an engine out NO_x amount is below a predetermined amount;

determining that an engine is operating at a low NO_x output operating condition;

determining that an oxidation catalyst is at a low NONO₂ conversion condition;

determining that an oxidation catalyst is below a predetermined temperature; and

determining that an amount of oxygen available in the engine exhaust is below a predetermined level.

13. The method of claim 10, further comprising interpreting a first signal-second signal sensor operation map, and wherein the providing the detection comparison value in response to the first signal and the second signal comprises returning a sensor operating region in response to the first signal, the second signal, and the map.

14. The method of claim 13, further comprising providing the NH₃ sensor condition value as one of a healthy sensor indication and a failed sensor indication in response to the detection comparison value.

15. An apparatus, comprising:

an electronic controller operationally coupled to and configured to interpret a first signal from a first NH₃ sensing channel and a second signal from a second NH₃ sensing channel, wherein the first and second NH₃ sensing channels are operationally coupled to an engine exhaust at a position downstream of a selective catalytic reduction (SCR) component;

the electronic controller further being configured to determine whether an NO₂ concentration at the position downstream of the SCR component is below a threshold value, the electronic controller further being configured to not enable an NH₃ sensor condition diagnostic in response to the NO₂ concentration being above the threshold value and to enable the NH₃ sensor condition diagnostic to provide a detection comparison value based on the first signal and the second signal in response to the NO₂ concentration being below the threshold value, the electronic controller further being configured to provide an NH₃ sensor condition value in response to the detection comparison value.

16. The apparatus of claim 15, wherein the electronic controller is further configured to provide the detection comparison value in response to a difference between the first signal and the second signal.

17. The apparatus of claim 16, wherein the electronic controller is further configured to provide the detection comparison value in response to a magnitude of each of the first signal and the second signal.

18. The apparatus of claim 17, wherein the first NH₃ sensing channel and the second NH₃ sensing channel are disposed in a single sensor housing.

19. The apparatus of claim 18, wherein the first NH₃ sensing channel and the second NH₃ sensing channel comprise a differential response to NO₂.

20. The apparatus of claim 19, wherein the first NH₃ sensing channel comprises an NH₃ detection element of an NH₃ sensor, and wherein the second NH₃ sensing channel comprises an NO₂ compensation element of the NH₃ sensor.