Methods for reducing raw particulate engine emissions

• US 9,488,093 B2
• Filed: 01/09/2014
• Issued: 11/08/2016
• Est. Priority Date: 01/11/2013
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Ruhland, Helmut Hans, Louven, Georg
• Primary Examiner(s): Dallo, Joseph
• Application Number:
  US14/151,628
• Publication Number:
  US 20140196685A1
• Time in Patent Office: 1,034 Days
• Field of Search: 123/431, 123/575, 123/576, 123/578, 123/435, 123/304, 123/305, 123/491, 12317914-17917, 701/105
• US Class Current: 1/1
• CPC Class Codes: F02B 17/005 having direct injection in the combustion chamber
• CPC Class Codes: F02D 2200/0602 Fuel pressure
• CPC Class Codes: F02D 41/062 for starting F02D41/061 takes precedence
• CPC Class Codes: F02D 41/064 at cold start F02D41/067 takes precedence
• CPC Class Codes: F02D 41/065 at hot start or restart F02D41/067 takes precedence
• CPC Class Codes: F02D 41/3023 a mode being the stratified charge spark-ignited mode
• CPC Class Codes: F02D 41/3076 with special conditions for selecting a mode of combustion, e.g. for starting, for diagnosing
• CPC Class Codes: F02D 41/401 Controlling injection timing F02D41/402 takes precedence
• CPC Class Codes: F02D 41/402 Multiple injections

Abstract

The methods described allow for reducing particulate emissions from a direction injection engine during a starting phase, while also maintaining the engine start phase within a predetermined threshold. In one particular example, the methods comprise adjusting at least one of a fuel release pressure threshold and enrichment factor based on an engine condition; activating a starting device to rotate a crankshaft coupled to an engine cylinder without injecting any fuel; supplying fuel to the cylinder based on the enrichment factor only when a fuel pressure exceeds the fuel release pressure threshold; and stratifying a cylinder charge while adjusting a fuel injection within a compression phase and/or expansion phase of the engine. In this way, an amount of fuel injected may be evaporated in the combustion chamber while preventing a combustion wall wetting, which allows for reduced particulate emissions, particularly at reduced temperatures.

Claims

1. A method for reducing particulate emissions from a direct injection applied-ignition engine during a starting phase, comprising:

adjusting at least one of a fuel release pressure threshold and enrichment factor based on one or more engine conditions;

activating a starting device to rotate a crankshaft coupled to an engine cylinder without injecting any fuel;

before fuel pressure exceeds the fuel release pressure threshold, rotating the crankshaft without injecting any fuel;

supplying fuel to the cylinder based on the enrichment factor only when the fuel pressure exceeds the fuel release pressure threshold; and

stratifying a cylinder charge while adjusting at least one fuel injection within one of a compression phase and expansion phase of the engine.

2. The method of claim 1, wherein the at least one adjusted injection is performed close to ignition top dead center, and wherein the at least one injection is initiated in a crank angle range defined by at least one of:

125°

before ignition top dead center and 75°

after ignition top dead center;

90°

before ignition top dead center and 45°

after ignition top dead center; and

60°

before ignition top dead center and 15°

after ignition top dead center.

3. The method of claim 2, wherein the at least one adjusted injection is initiated during the compression phase.

4. The method of claim 2, wherein the at least one adjusted injection is initiated in the expansion phase.

5. The method of claim 1, wherein a spark timing is advanced as an engine temperature decreases, and wherein the fuel release pressure threshold includes a pressure threshold from a group consisting of 30 bar, 50 bar, and 75 bar.

6. The method of claim 1, wherein the engine is operated during the starting phase with an enrichment factor that falls below an enrichment threshold, and wherein the enrichment factor is defined by a ratio of an actually supplied fuel mass to a fuel mass required for stoichiometric combustion, the enrichment threshold being selected from a group consisting of 3, 1.5, 0.8, 0.6, and 0.4.

7. The method of claim 1, wherein the fuel release pressure threshold decreases and the enrichment factor increases as engine temperatures decrease.

8. The method of claim 7, further including advancing at least one of a fuel injection and spark timing based on the reduced fuel release pressure threshold.

9. The method of claim 1, wherein the fuel release pressure threshold increases and the enrichment factor decreases as engine temperatures increase.

10. The method of claim 9, further including retarding at least one of a fuel injection and spark timing based on the increased fuel release pressure threshold.

11. The method of claim 1, wherein a pilot injection is carried out during an intake phase, and wherein both a fuel injection timing is adjusted and the enrichment factor is further adjusted such that an engine start occurs within a predetermined amount of time.

12. A method for starting an engine from rest, comprising:

injecting no fuel into a rotating engine before fuel pressure reaches a threshold;

only injecting fuel to the rotating engine after fuel pressure reaches the threshold;

adjusting an air-fuel ratio produced by the injected fuel in the engine, the air-fuel ratio enleaned as the threshold is reduced; and

spark-igniting the injected fuel in a stratified mixture.

13. The method of claim 12, further comprising injecting fuel within a window defined by a crank angle that falls within the range of 125°

before ignition top dead center and 75°

after ignition top dead center.

14. The method of claim 12, further comprising enriching the air-fuel ratio as the threshold is increased, and wherein the threshold is based on an engine temperature, the threshold increasing as the engine temperature increases and decreasing as the engine temperature decreases.

15. The method of claim 13, wherein starting the engine from rest includes performing an engine cold start, the engine cold start being indicated by an engine temperature that coincides with an ambient temperature.

16. The method of claim 15, further comprising setting the threshold based on one or more engine conditions, and adjusting the air-fuel ratio responsive to the threshold, the method further including decreasing the threshold to decrease an amount of time for the fuel pressure to reach the threshold while enleaning the air-fuel ratio, and increasing the threshold to increase the amount of time for the fuel pressure to reach the threshold while enriching the air-fuel ratio.

17. A method for regulating an engine start phase, comprising:

activating a starting device to rotate a crankshaft coupled to an engine cylinder while injecting no fuel to build up a fuel pressure;

cranking an engine with no fuel injected while the fuel pressure is below a fuel release pressure threshold;

supplying fuel to the cylinder only when the fuel pressure exceeds the fuel release pressure threshold; and

stratifying a cylinder charge while adjusting a fuel injection within an injection window that straddles a compression phase and expansion phase of the engine.

18. The method of claim 17, wherein the fuel release pressure threshold decreases as temperatures decrease and increases as temperatures increase.

19. The method of claim 18, wherein an enrichment factor defined by a ratio of an actual fuel mass supplied to a fuel mass required for stoichiometric combustion is adjusted to adjust an engine ramp up time, and wherein an air-fuel ratio is increased as the fuel release pressure threshold decreases and decreases as the fuel release pressure threshold increases.

20. The method of claim 19, wherein the injection window comprises a crank angle falling within the range of 125°

before ignition top dead center and 75°

after ignition top dead center.