Method and system for engine cold-start control

Patent metadata

Field	Value
Publication number	US-10100767-B2
Application number	US-201514733196-A
Country	US
Kind code	B2
Filing date	Jun 8, 2015
Priority date	Jun 8, 2015
Publication date	Oct 16, 2018
Grant date	Oct 16, 2018

Abstract

Methods and systems are provided for improving engine start roughness. In one example, a method for reducing engine start NVH includes operating the engine with a split fuel injection while advancing injection timing as engine coolant temperature increases. The method allows for a smoother engine start while also reducing false misfire incidences.

First claim

The invention claimed is:

1. A method for an engine, comprising:
starting the engine with fuel delivered as a split injection including a first fuel fraction direct injected earlier during a compression stroke of a combustion cycle and a second fuel fraction direct injected later during the compression stroke of the combustion cycle; and
advancing an average fuel injection timing of the split injection and increasing crank-angle-degrees separating the split injection as the engine temperature at the engine starting increases.

2. The method of claim 1 , wherein advancing the average fuel injection timing includes advancing the injection timing of each of the injections of the split injection.

3. The method of claim 1 , wherein the average fuel injection timing is advanced from an initial injection timing as the engine temperature increases, the initial injection timing based on engine speed and load.

4. The method of claim 1 , wherein the average fuel injection timing is advanced from compression stroke TDC as the engine temperature increases.

5. The method of claim 4 , further comprising maintaining the average fuel injection timing advanced for a number of combustion events since a first combustion event of the engine start.

6. The method of claim 5 , further comprising, after the number of combustion events since the first combustion event, retarding the average fuel injection timing towards compression stroke TDC as engine temperature increases.

7. The method of claim 1 , further comprising, during the starting, retarding spark timing from MBT while the average fuel injection timing is advanced, wherein the average fuel injection timing is an average injection timing of the first and second fuel fractions.

8. The method of claim 1 , wherein the engine starting is an engine cold-start.

9. The method of claim 1 , wherein the engine temperature includes an engine coolant temperature at the engine start, before a first combustion event.

10. A method for an engine, comprising:
during an engine cold-start, cranking the engine with fuel delivered as a split injection at a first average injection timing, wherein the split injection during the engine cold-start includes a first number of compression stroke direct injections; and
during an engine hot-start, cranking the engine with fuel delivered as a split injection at a second average injection timing, the second average injection timing advanced relative to the first average injection timing, wherein the split injection during the engine hot-start includes a second number of compression stroke direct injections, the second number smaller than the first number.

11. The method of claim 10 , wherein during the engine cold-start, fuel is delivered as a split injection at the first average injection timing for a first number of combustion events, and then, as engine coolant temperature increases, advancing fuel injection timing from the first average injection timing towards the second average injection timing.

12. The method of claim 11 , wherein during the engine hot-start, fuel is delivered as a split injection at the second average injection timing for a second number of combustion events, the second number smaller than the first number, and then, as the engine coolant temperature increases, retarding fuel injection timing from the second average injection timing towards the first average injection timing.

13. The method of claim 11 , wherein the first average injection timing is an average injection timing of the first number of compression stroke direct injections, and wherein the second average injection timing is an average injection timing of the second number of compression stroke direct injections.

14. The method of claim 10 , wherein the split injection during the engine cold-start includes multiple compression stroke direct injections, and wherein the split injection during the engine hot-start includes at least a compression stroke direct injection and an intake stroke direct injection.

15. The method of claim 10 , further comprising, during the engine cold-start, cranking the engine with spark timing retarded by a larger amount, and during the engine hot-start, cranking the engine with spark timing retarded by a smaller amount.

16. An engine system, comprising:
an engine including a cylinder;
a direct injector for injecting fuel directly into the cylinder;
a temperature sensor for estimating an engine coolant temperature; and
a controller with computer-readable instructions stored on non-transitory memory for:
during an engine start,
for a number of combustion events since a first combustion event, operating the engine with fuel delivered as multiple compression stroke injections during each combustion event, wherein the number of multiple compression stroke injections is adjusted based on an engine temperature and an alcohol content of an injected fuel, a number of compression stroke injections is increased as the engine temperature or the alcohol content of the injected fuel increases, and with an average injection timing of the multiple compression stroke injections advanced from compression stroke TDC, an amount of injection timing advance increased as the engine coolant temperature increases, and where a duration between injections of the multiple compression stroke injections increases as the engine coolant temperature increases.

17. The system of claim 16 , wherein the controller includes further instructions for, after the number of combustion events, while continuing to operate the engine with fuel delivered as multiple compression stroke injections, retarding the average injection timing of the multiple compression stroke injections towards compression stroke TDC, an amount of injection timing retard increased as the engine coolant temperature increases.

18. The system of claim 17 , wherein the controller includes further instructions for, during the number of combustion events, retarding spark timing from MBT, an amount of spark retard based on the amount of injection timing advance, and after the number of combustion events, adjusting the amount of spark retard based on engine speed and load.

Assignees

• Ford Global Tech Llc

Inventors

• Liu Chingpo
• Dudar Aed M
• Fried Marcus William
• Reichenbach Ron

Classifications

• Y02T10/44

  Cross-Sectional Technologies · mapped topic

• F02B17/005

  having direct injection in the combustion chamber · CPC title

• F02D2200/021

  Engine temperature · CPC title

• F02D41/064 Primary

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

• Y02T10/46

  Cross-Sectional Technologies · mapped topic