Air/fuel ratio control system

• US 6,138,504 A
• Filed: 06/04/1998
• Issued: 10/31/2000
• Est. Priority Date: 06/04/1998
• Status: Expired due to Term

• Current Assignee: Esko-Graphics Imaging GmbH (Danaher Corporation)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Lewis, Donald J., Pursifull, Ross Dykstra, Kotwicki, Allan Joseph, Russell, John David
• Primary Examiner(s): MCCALL, ERIC SCOTT
• Application Number:
  US09/090,125
• Time in Patent Office: 880 Days
• Field of Search: 73/116, 73/117.2, 73/117.3, 73/118.1, 73/118.2
• US Class Current: 73/114.33
• CPC Class Codes: F02D 2041/1432 the system including a filter, e.g. a low pass or high pass filter
• CPC Class Codes: F02D 2200/0402 the parameter being determined by using a model of the engine intake or its components
• CPC Class Codes: F02D 41/0072 Estimating, calculating or determining the EGR rate, amount or flow sensors in EGR systems F02M26/45
• CPC Class Codes: F02D 41/182 for the control of a fuel injection device
• CPC Class Codes: F02D 41/32 of the low pressure type F02D41/3082 takes precedence
• CPC Class Codes: G01F 1/34 by measuring pressure or differential pressure
• CPC Class Codes: G01F 1/363 with electrical or electro-mechanical indication G01F1/37 and G01F1/38 take precedence
• CPC Class Codes: G01F 22/02 involving measurement of pressure
• CPC Class Codes: G01F 9/001 with electric, electro-mechanic or electronic means G01F9/008 and G01F9/02 take precedence
• CPC Class Codes: G01F 9/023 with electric, electro-mechanic or electronic means
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A method for controlling the air/fuel ratio of an internal combustion engine uses a manifold pressure sensor and an exhaust gas recirculation system having an orifice and a exhaust pressure sensor located upstream of the orifice. Both the manifold pressure sensor and the exhaust pressure sensor are sampled synchronously with a frequency proportional to the firing frequency of the engine and then filtered to eliminate unwanted frequencies. The sampled signals obtained then have the necessary bandwidth needed for closed loop control of the exhaust gas recirculation flow and engine air/fuel ratio control.

Claims

1. A method for calculating air flow in an internal combustion engine, the method comprising:

sensing an engine speed of the engine;

obtaining discrete pressure measurements from a continuously measured first pressure at a frequency proportional to a firing frequency of the engine;

filtering said obtained discrete pressure measurements with a filter to remove oscillations at frequencies proportional to said firing frequency; and

calculating a mass of gas entering a cylinder of the engine responsive to said filtered discrete pressure measurements and said engine speed.

2. The method recited in claim 1 wherein said first pressure sensor is a manifold pressure sensor.

3. The method recited in claim 1 further comprising the step of determining said frequency from an engine rotation signal.

4. The method recited in claim 1 wherein said step of obtaining discrete pressure measurements further comprises the step of obtaining discrete pressure measurements from a continuously measured first pressure at said first frequency substantially proportional to a dominant frequency of said first pressure measured by said first pressure sensor.

5. The method recited in claim 4 wherein said step of calculating further comprises the steps of:

suspending said calculation during a transition in a flow area; and

creating an open-loop estimate of said mass of gas responsive to said transition and engine operating conditions.

6. The method recited in claim 1 further comprising the steps of:

obtaining second discrete pressure measurements from a continuously measured second pressure at a second frequency proportional to said firing frequency of the engine;

calculating a gas flow estimate responsive to a difference between said discrete pressure measurements and said second discrete pressure measurements.

7. The method recited in claim 6 wherein said second pressure sensor is an exhaust pressure sensor.

8. The method recited in claim 6 further comprising the step of determining said second frequency from an engine rotation signal.

9. The method recited in claim 6 wherein said gas flow is an exhaust gas recirculation flow.

10. The method recited in claim 6 wherein said step of obtaining second discrete pressure measurements further comprises the step of obtaining second discrete pressure measurements from a continuously measured second pressure at said second frequency substantially proportional to a dominant frequency of said second pressure measured by said second pressure sensor.

11. A method for calculating exhaust gas recirculation of an internal combustion engine having an exhaust gas recirculation tube coupled between an intake manifold and an exhaust manifold, an orifice in the tube, a first pressure sensor located upstream of the orifice, and a second pressure sensor located downstream of the orifice, said method comprising:

obtaining first discrete pressure measurements from a continuously measured first pressure of the first sensor at a first frequency proportional to a firing frequency of the engine;

obtaining second discrete pressure measurements from a continuously measured second pressure of the second pressure sensor at a second frequency proportional to said firing frequency of the engine; and

calculating an exhaust gas recirculation flow responsive to a difference between said obtained first discrete pressure measurements and said obtained second discrete pressure measurements.

12. The method recited in claim 11 further comprising the steps of:

filtering said obtained first discrete pressure measurements with a first filter to remove oscillations at frequencies proportional to said firing frequency;

filtering said obtained second discrete pressure measurements with a second filter to remove oscillations at frequencies proportional to said firing frequency; and

calculating said exhaust gas recirculation flow responsive to a difference between said obtained first filtered pressure and said obtained second filtered pressure.

13. The method recited in claim 11 further comprising the step of determining said first freqeucny and said second frequency from an engine rotation signal.

14. The method recited in claim 11 wherein said step of obtaining first discrete pressure measurements further comprises the step of obtaining first discrete pressure measurements from a continuously measured first pressure of the first sensor at said first frequency substantially proportional to a first dominant frequency of said first pressure measured by the first pressure sensor.

15. The method recited in claim 11 wherein said step of obtaining second discrete pressure measurements further comprises the step of obtaining second discrete pressure measurements from a continuously measured second pressure of the second sensor at said second frequency substantially equal to a second dominant frequency of said second pressure measured by the second pressure sensor.