Method for operating a dual fuel injection system

Patent metadata

Field	Value
Publication number	US-10337445-B2
Application number	US-201514805068-A
Country	US
Kind code	B2
Filing date	Jul 21, 2015
Priority date	Jul 21, 2015
Publication date	Jul 2, 2019
Grant date	Jul 2, 2019

Abstract

A method of operating an engine with dual fuel injection capabilities to address fuel rail over-pressure due to stagnating hot fuel is shown. The method comprises operating an engine cylinder with only port injection, and selectively activating and deactivating the second injector in response to a rail pressure increase of a fuel rail, the fuel rail coupled to the second injector, and deactivating the second injector in response to a rail pressure decrease of the fuel rail to a lower threshold determined based on engine operating conditions. In this way, degradation of the second injector may be reduced while maintaining a desired level of engine performance.

First claim

The invention claimed is:

1. A method, comprising:
via a controller with computer-readable instructions stored on non-transitory memory,
while operating an engine cylinder with fuel from a first injector,
activating a second injector to inject stagnated fuel from a fuel rail coupled to the second injector into the cylinder in response to a fuel pressure increase at the fuel rail, the stagnated fuel being stagnate due to a condition of fuel flow to the fuel rail being substantially equal to zero; and
deactivating the second injector in response to a fuel pressure decrease at the fuel rail below a lower threshold, the lower threshold adjusted based on one or more engine operating conditions.

2. The method of claim 1 , wherein the activating includes activating the second injector in response to the fuel pressure increase at the fuel rail above an upper threshold.

3. The method of claim 2 , wherein the fuel rail coupled to the second injector is a second fuel rail different from a first fuel rail coupled to the first injector.

4. The method of claim 3 , wherein each of the first and second fuel rails is pressurized by a high pressure fuel pump, and wherein during the activating and deactivating, the fuel flow into the second fuel rail from the high pressure fuel pump is disabled.

5. The method of claim 4 , wherein the lower threshold is adjusted to remain above a pressure at which the fuel flow from the high pressure fuel pump to the second fuel rail is enabled.

6. The method of claim 5 , further comprising, while the second injector is activated, adjusting injection of fuel from the first injector responsive to fuel injected by the second injector.

7. The method of claim 3 , wherein the activating is further based on a coefficient of thermal expansion of the stagnated fuel in the second fuel rail, and wherein the lower threshold is adjusted based on engine pre-ignition history.

8. The method of claim 7 , wherein the lower threshold is adjusted based on an estimated exhaust soot load, the lower threshold increasing with increasing exhaust soot load.

9. The method of claim 7 , wherein the lower threshold is adjusted based on an engine speed-load condition, the lower threshold increasing with increased engine speed and increasing load.

10. The method of claim 9 , wherein the first injector is a port injector, and the second fuel injector is a direct injector.

11. A method for an engine comprising:
while port fueling an engine cylinder with direct injection disabled and stagnated fuel from there being substantially zero fuel flow to a direct injection fuel rail,
activating a direct injector to intermittently direct inject fuel from the direct injection fuel rail into the cylinder, the intermittently direct injecting including initiating direct injection when a direct injection fuel rail pressure rises above an upper threshold and continuing the direct injection until the direct injection fuel rail pressure falls below a lower threshold, the lower threshold adjusted based on engine operating conditions, the engine operating conditions including at least one of exhaust soot level and engine pre-ignition history.

12. The method of claim 11 , wherein continuing the direct injection includes delivering fuel as a single direct injection per cylinder combustion event.

13. The method of claim 12 , wherein the direct injecting includes delivering the fuel as a single direct injection during an intake stroke or a compression stroke.

14. The method of claim 12 , wherein the direct injecting includes delivering the fuel as multiple direct injections in at least one of an intake stroke and a compression stroke.

15. A fuel system for an internal combustion engine, comprising:
a port fuel injector in communication with a cylinder;
a direct fuel injector in communication with the cylinder;
a first fuel rail in communication with the port fuel injector;
a second fuel rail in communication with the direct fuel injector;
a high-pressure fuel pump in communication with each of the first and second fuel rails; and
a control system configured with computer-readable instructions stored on non-transitory memory for:
delivering fuel to the cylinder via the port fuel injector with the direct fuel injector disabled and stagnated fuel from there being no fuel flow to the second fuel rail; and
during a first condition, when a pressure of the stagnated fuel in the second fuel rail exceeds an upper threshold, increasing flow of fuel through the direct fuel injector by activating the direct fuel injector; and
during a second condition, when a pressure of the stagnated fuel in the second fuel rail falls below a lower threshold, decreasing the flow of fuel through the direct fuel injector by deactivating the direct fuel injector.

16. The system of claim 15 , where the first condition includes a bulk fuel flow through the direct fuel injector being zero.

17. The system of claim 16 , wherein the high pressure fuel pump includes a high pressure fuel pump inlet coupled to the first fuel rail, and a high pressure fuel pump outlet coupled to the second fuel rail.

18. The system of claim 17 , wherein both of the first and the second conditions include a bulk fuel flow from the high pressure fuel pump outlet to the second fuel rail being zero.

19. The system of claim 18 , wherein both of the first and the second conditions include a bulk fuel flow from the high pressure fuel pump inlet to the first fuel rail being greater than zero.

20. The method of claim 11 , further comprising adjusting a parameter of a cooling system coupled to the direct injection fuel rail responsive to an increase in the direct injection fuel rail pressure, the parameter including one of a flow rate and temperature of coolant.

Assignees

• Ford Global Tech Llc

Inventors

• Sanborn Ethan D
• Thomas Joseph Lyle
• Dusa Daniel

Classifications

• F02M63/0285

  having more than one common rail · CPC title

• F02M63/023

  Means for varying pressure in common rails (pressure control F02D41/3845) · CPC title

• F02M55/025

  Common rails · CPC title

• F02M43/04

  Injectors peculiar thereto · CPC title

• F02D2200/0812

  Particle filter loading · CPC title