Emission control system with a catalyst

• US 6,295,809 B1
• Filed: 07/12/1999
• Issued: 10/02/2001
• Est. Priority Date: 07/12/1999
• Status: Expired due to Term

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Adams, Karen Marie, Hammerle, Robert Henry, Laing, Paul Matthew
• Primary Examiner(s): Denion, Thomas
• Application Number:
  US09/353,294
• Time in Patent Office: 813 Days
• Field of Search: 602/74, 602/86, 603/01, 602/95, 423/219, 423/235, 423/239.1, 436/55
• US Class Current: 60/286
• CPC Class Codes: B01D 53/9431 Processes characterised by a specific device
• CPC Class Codes: B01D 53/9495 Controlling the catalytic process
• CPC Class Codes: F01N 2560/021 for measuring or detecting ammonia NH3
• CPC Class Codes: F01N 2560/06 the means being a temperature sensor
• CPC Class Codes: F01N 2610/02 the substance being ammonia or urea
• CPC Class Codes: F01N 2610/146 Control thereof, e.g. control of injectors or injection valves
• CPC Class Codes: F01N 2900/08 said parameters being related to the engine
• CPC Class Codes: F01N 3/206 Adding periodically or continuously substances to exhaust gases for promoting purification, e.g. catalytic material in liquid form, NOx reducing agents F01N3/2066 takes precedence
• CPC Class Codes: F01N 3/208 Control of selective catalytic reduction [SCR], e.g. dosing of reducing agent
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies

Abstract

A reductant injection control strategy for controlling an amount of nitrogen oxide reducing agent injected upstream of a selective reduction catalyst uses an ammonia sensor located downstream of the catalyst. An open loop injection quantity is first determined based on operation conditions. Ammonia concentration detected downstream of the catalyst is controlled to a desired value, with the desired value based on catalyst temperature and the open loop injection quantity.

Claims

1. A method for controlling a reductant injection into a catalyst coupled to an internal combustion engine, the method comprising:

determining a temperature region in which the catalyst is operating;

generating a reductant injection quantity based on engine operating conditions;

generating a desired reductant slip based on a catalyst temperature and said reductant injection quantity; and

adjusting said reductant injection quantity so that an actual reductant slip approaches said desired reductant slip, wherein adjusting said reductant injection quantity further comprises determining said actual reductant slip based on a sensor located downstream of the catalyst, and decreasing said reductant infection quantity when said actual reductant slip is greater than said desired reductant slip.

3. The method recited in claim 3 wherein said step of generating said desired value of reductant slip further comprises generating said desired value of reductant slip based on a fraction of said reductant injection quantity.

2. The method recited in claim 3 wherein the reductant is any ammonia generating material.

4. The method recited in claim 3 further comprising the step of generating said desired value of reductant slip based on Nox generated by the engine.

5. The method recited in claim 3 wherein said fraction is based on said catalyst temperature.

6. The method recited in claim 3 wherein said step of generating said reductant injection quantity further comprises the step of generating said reductant injection quantity based on a catalyst temperature and a fraction of an engine out nitrogen oxide production.

7. The method recited in claim 3 further comprising the step of discontinuing said adjustment step based on whether said catalyst temperature is within temperature limits.

8. The method recited in claim 7 wherein said step temperature limits are based on exhaust gas space velocity.