Methods and systems for EGR control

Patent metadata

Field	Value
Publication number	US-9303557-B2
Application number	US-201313965794-A
Country	US
Kind code	B2
Filing date	Aug 13, 2013
Priority date	Aug 13, 2013
Publication date	Apr 5, 2016
Grant date	Apr 5, 2016

Abstract

Methods and systems are provided for using compressor recirculation flow via a venturi to enhance low pressure EGR flow. The opening of a compressor recirculation valve can be adjusted based on EGR flow demand to recirculate cooled compressed air through a venturi while generating vacuum for drawing EGR. The approach allows for concurrent EGR control and surge control.

First claim

The invention claimed is:

1. An engine method, comprising:
adjusting an amount of compressor recirculation flow delivered from downstream of a charge air cooler to a compressor inlet via a venturi based on EGR demand; and
in response to compressor surge, increasing compressor recirculation flow around the compressor through a second recirculation passage parallel to a first recirculation passage, while maintaining the adjusted amount of compressor recirculation flow, the second passage not including a venturi coupled to an EGR passage.

2. The method of claim 1 , wherein the adjusting the amount of flow through the first passage is further based on exhaust pressure.

3. The method of claim 2 , wherein the adjusting includes, in response to EGR demand, opening an EGR valve coupled in the EGR passage upstream of the venturi, and increasing the amount of compressor recirculation flow delivered through the first passage as the EGR demand increases.

4. The method of claim 3 , wherein increasing the compressor recirculation flow includes increasing an opening of a first compressor recirculation valve in the first recirculation passage coupling the charge air cooler to the compressor inlet via the venturi, the first compressor recirculation valve positioned upstream of the venturi, the EGR passage coupled to the first recirculation passage at the venturi.

5. The method of claim 4 , further comprising drawing EGR from the EGR passage into the compressor inlet using vacuum drawn at the venturi.

6. The method of claim 5 , wherein increasing compressor recirculation flow through the second passage includes increasing an opening of a second compressor recirculation valve in the second passage.

7. The method of claim 6 , wherein each of the first and second compressor recirculation valves are continuously variable valves and wherein the EGR valve is an on/off valve.

8. An engine method, comprising:
adjusting compressor recirculation flow through a first passage via a venturi based on EGR flow demand while adjusting compressor recirculation flow through a second passage based on an indication of surge, EGR flow delivered only to the first passage via the venturi.

9. The method of claim 8 , further comprising opening an EGR valve and drawing EGR into a compressor inlet from an EGR passage using vacuum generated at the venturi, wherein in response to the indication of surge, a recirculation valve in the second passage is opened to provide surge control while a position of a compressor recirculation valve in the first passage is held to maintain EGR flow control.

10. The method of claim 9 , wherein the EGR valve is an on/off valve mounted on the venturi and wherein opening the EGR valve includes shifting the EGR valve to an on position.

11. The method of claim 10 , wherein the EGR passage is coupled to the first passage at the venturi, the EGR passage not coupled to the second passage.

12. The method of claim 11 , wherein the compressor recirculation flow through the second passage is not via a venturi.

13. The method of claim 12 , wherein adjusting compressor recirculation flow through the first passage includes adjusting an opening of a first continuously variable compressor recirculation valve based on the EGR flow demand, and wherein adjusting compressor recirculation flow through the second passage includes adjusting an opening of a second continuously variable compressor based on surge.

14. The method of claim 13 , wherein the adjusting includes increasing the opening of the second valve as the indication of surge increases, and increasing the opening of the first valve as the EGR flow demand increases.

15. The method of claim 14 , further comprising mixing the drawn EGR with the compressor recirculation flow upstream of the compressor inlet in the first passage.

16. An engine system, comprising:
an engine including an intake and an exhaust;
a turbocharger including an exhaust turbine driven by an intake compressor;
a charge air cooler coupled downstream of the compressor;
a first compressor recirculation passage including a first valve and a venturi, the first passage coupling an outlet of the charge air cooler to an inlet of the compressor, the venturi positioned downstream of the first valve in the passage;
a second compressor recirculation passage including a second valve, the second passage coupling the outlet of the charge air cooler to the inlet of the compressor, the second passage positioned parallel to the first passage;
an EGR passage including an EGR valve for recirculating exhaust residuals to the engine intake via the first compressor recirculation passage, the EGR passage coupled to the first passage at the venturi; and
a controller with computer readable instructions for,
in response to an EGR demand,
opening the EGR valve;
increasing an opening of the first valve based on the EGR demand to recirculate compressed air through the venturi and generate vacuum at the venturi;
drawing EGR into the engine using the vacuum generated at the venturi; and
in response to an indication of surge, increasing an opening of the second valve while maintaining the opening of the first valve.

17. The system of claim 16 further comprising an air inlet throttle upstream of the compressor inlet, wherein the instructions further comprise instructions to determine an EGR valve position required to provide the EGR demand, and closing the air inlet throttle responsive to the EGR valve position outside a limit.

18. The system of claim 16 , wherein the opening of the first valve is further based on exhaust pressure estimated upstream of an inlet of the EGR passage, the opening of the first valve decreased as the exhaust pressure increases.

19. The system of claim 16 , wherein each of the first and second valves are continuously variable valves and wherein the EGR valve is an on/off valve.

Assignees

• Ford Global Tech Llc

Inventors

• Ulrey Joseph Norman
• Mcconville Gregory Patrick
• Styles Daniel Joseph
• Pursifull Ross Dykstra
• Shelby Michael Howard

Classifications

• F02M25/0722

  Mechanical Engineering · mapped topic

• F02D2250/41

  Control to generate negative pressure in the intake manifold, e.g. for fuel vapor purging or brake booster · CPC title

• F02D41/0007 Primary

  for control of turbo-charged or super-charged engines (control of the pumps per se F02B37/12) · CPC title

• F02M25/0709

  Mechanical Engineering · mapped topic

• F02M25/07

  Mechanical Engineering · mapped topic