Adaptive EGR control for internal combustion engines

• US 8,042,528 B2
• Filed: 07/31/2009
• Issued: 10/25/2011
• 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
• Primary Examiner(s): Gimie; Mahmoud
• Application Number:
  US12/533,576
• Publication Number:
  US 20110023847A1
• Time in Patent Office: 816 Days
• Field of Search: 123/568.15, 123/568.22, 123/568.21, 123/568.11, 701/108, 602/76, 606/052, 738/614.2
• 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 an operating condition using a stored map;

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; and

determining a flow degradation factor based on a comparison of an initial calibrated pressure differential for the operating condition with a current value for the operating condition.

2. The method of claim 1 wherein the operating condition comprises 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 of claim 1 further comprising:

generating a diagnostic code when the flow degradation factor exceeds a corresponding threshold.

10. The method of claim 9 wherein the corresponding 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;

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 the operating condition 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; and

an EGR flow diagnostic monitor in communication with the EGR valve, the exhaust back pressure sensor, the MAP sensor and the controller, wherein the EGR flow diagnostic monitor detects flow degradation and generates a diagnostic code when a flow degradation factor exceeds a corresponding threshold.

12. The system of claim 11 wherein the operating condition comprises 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 further comprising:

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

17. A method for controlling an engine having an EGR flow diagnostic monitor, comprising:

determining a flow degradation factor;

comparing the flow degradation factor to a corresponding threshold;

generating a diagnostic code when the flow degradation factor exceeds the corresponding threshold; and

triggering a remedial control action in response to the flow degradation factor exceeding the corresponding threshold.

18. The method of claim 17 wherein the flow degradation factor is determined by comparing an initial calibrated pressure differential for an operating condition with a current value for the same operating condition.

19. The method of claim 17 wherein the corresponding threshold is determined based on a relationship between EGR mass flow and NOx produced during combustion.

20. The method of claim 17 wherein the remedial control action includes storing the diagnostic code in memory.