Methods for reducing raw particulate engine emissions

Patent metadata

Field	Value
Publication number	US-9488093-B2
Application number	US-201414151628-A
Country	US
Kind code	B2
Filing date	Jan 9, 2014
Priority date	Jan 11, 2013
Publication date	Nov 8, 2016
Grant date	Nov 8, 2016

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.

First claim

The invention claimed is:

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.

Assignees

• Ford Global Tech Llc

Inventors

• Ruhland Helmut Hans
• Louven Georg

Classifications

• F02D41/402

  Multiple injections · CPC title

• F02D41/3023

  a mode being the stratified charge spark-ignited mode · CPC title

• F02D41/401

  Controlling injection timing (F02D41/402 takes precedence) · CPC title

• F02D41/064

  at cold start (F02D41/067 takes precedence) · CPC title

• F02D41/062

  for starting (F02D41/061 takes precedence) · CPC title