ADAPTIVE EGR CONTROL FOR INTERNAL COMBUSTION ENGINES

• US 20110023847A1
• Filed: 07/31/2009
• Published: 02/03/2011
• Est. Priority Date: 07/31/2009
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Yu, Songping, Gates, Freeman Carter, Farahmand, Sassan
• Granted Patent: US 8,042,528 B2
• Time in Patent Office: Days
• US Class Current: 123/568.21
• CPC Class Codes: F02D 2041/141 using a feed-forward control element
• CPC Class Codes: F02D 2200/0406 Intake manifold pressure
• 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 41/1448 the characteristics being an exhaust gas pressure
• CPC Class Codes: F02D 41/2451 characterised by what is learned or calibrated
• CPC Class Codes: F02D 41/2464 Characteristics of actuators
• CPC Class Codes: F02M 26/23 Layout, e.g. schematics
• CPC Class Codes: F02M 26/35 with means for cleaning or treating the recirculated gases, e.g. catalysts, condensate traps, particle filters or heaters
• CPC Class Codes: F02M 26/47 the characteristics being temperatures, pressures or flow rates
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A system and method for controlling an internal combustion engine having an EGR valve determine a base valve position to deliver a target flow using a stored map and adjust the base position in response to differential pressure across an orifice in the EGR flow to move the valve to a position different from the base position to provide the target flow.

Claims

1. A method for controlling an internal combustion engine having an EGR valve, the method comprising:

determining a base valve position to deliver a target EGR flow for current operating conditions using a stored map; and

adjusting the base valve position in response to differential pressure across an orifice in the EGR flow to move the valve to a position different from the base position to provide the target flow.

2. The method of claim 1 wherein the current operating conditions comprise engine speed and load.

3. The method of claim 1 further comprising:

determining differential pressure based on a difference between exhaust back pressure and manifold absolute pressure.

4. The method of claim 1 wherein the orifice comprises an EGR valve gasket.

5. The method of claim 1 wherein the orifice comprises a sharp edge orifice.

6. The method of claim 1 wherein the EGR flow is an EGR mass flow, the method further comprising:

determining an actual EGR mass flow based on the differential pressure across the orifice;

determining a difference between the actual EGR mass flow and the target EGR mass flow; and

determining an EGR base valve position adjustment based on the difference.

7. The method of claim 6 wherein the orifice is positioned upstream of the EGR valve and the actual EGR mass flow is determined according to:

mass flow=K*sqrt(exhaust backpressure−

MAP)

where K is an empirically determined constant, MAP represents a current manifold absolute pressure.

8. The method of claim 6 wherein the orifice is positioned downstream of the EGR valve and the actual EGR mass flow is determined according to:

mass flow=K*sqrt(exhaust back pressure−

MAP)*MAP

where K is an empirically determined constant and MAP represents a current manifold absolute pressure.

9. The method 6 further comprising:

generating a diagnostic code when the difference exceeds a corresponding threshold.

10. The method of claim 9 wherein the threshold is determined based on a relationship between EGR mass flow and NOx produced during combustion.

11. A system comprising:

a diesel fuel engine having an intake manifold and an exhaust manifold with an exhaust gas recirculation passage coupled therebetween;

an EGR valve positioned in the exhaust gas recirculation passage;

a flow restricting orifice positioned within the exhaust gas recirculation passage;

an exhaust backpressure sensor positioned upstream of the EGR valve;

a MAP sensor coupled to the intake manifold; and

a controller in communication with the EGR valve, the exhaust backpressure sensor and the MAP sensor, the controller determining a base valve position to deliver a target EGR mass flow for current operating conditions using a stored map, and adjusting the base valve position in response to differential pressure across the orifice to move the EGR valve to a position different from the base valve position to provide the target flow.

12. The system of claim 11 wherein the current operating conditions comprise engine torque.

13. The system of claim 11 wherein the controller determines differential pressure based on a difference between exhaust back pressure and manifold absolute pressure.

14. The system of claim 11 wherein the orifice comprises an EGR valve gasket.

15. The system of claim 11 wherein the orifice is positioned downstream of the EGR valve.

16. The system of claim 11 wherein the orifice is positioned upstream of the EGR valve.

17. The system of claim 11 further comprising:

a differential pressure sensor for measuring pressure immediately upstream and downstream of the orifice.

18. A computer readable storage medium having stored data representing instructions executable by an engine controller to control EGR flow in an internal combustion engine, the computer readable storage medium comprising:

instructions that determine a base EGR valve position to deliver a target EGR flow based on current operating conditions using a stored map; and

instructions that adjust the base valve position in response to differential pressure across an orifice in the EGR flow to move the valve to a position different from the base position to provide the target EGR flow.

19. The computer readable storage medium of claim 18 further comprising:

instructions that determine an actual EGR mass flow based on the differential pressure across the orifice;

instructions that determine a difference between the actual EGR mass flow and a target EGR mass flow; and

instructions that determine an EGR base valve position adjustment based on the difference.

20. The computer readable storage medium of claim 19 further comprising:

instructions for generating a diagnostic code when the difference exceeds a corresponding threshold.