Methods and systems for fuel rail pressure relief

• US 9,970,379 B2
• Filed: 10/21/2016
• Issued: 05/15/2018
• Est. Priority Date: 02/29/2016
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Zeng, Paul, Stickler, Mark L., Barber, Kwan Jamal
• Primary Examiner(s): SOLIS, ERICK R
• Application Number:
  US15/331,744
• Publication Number:
  US 20170248096A1
• Time in Patent Office: 571 Days
• Field of Search: 123431
• CPC Class Codes: F02D 2041/389 for injecting directly into the cylinder
• CPC Class Codes: F02D 2200/0602 Fuel pressure
• CPC Class Codes: F02D 41/3094 the fuel injection being effected by at least two different injectors, e.g. one in the intake manifold and one in the cylinder
• CPC Class Codes: F02D 41/32 of the low pressure type F02D41/3082 takes precedence
• CPC Class Codes: F02D 41/3863 by controlling the flow out of the common rail, e.g. using pressure relief valves
• CPC Class Codes: F02D 41/3872 characterised by leakage flow in injectors
• CPC Class Codes: F02M 63/005 Pressure relief valves
• CPC Class Codes: F02M 63/0245 between the high pressure pump and the common rail
• CPC Class Codes: F02M 63/025 from the common rail

Abstract

Methods and systems are provided for adjusting operation of fuel injectors of an internal combustion engine to reduce injector ticking noise during direct injection fuel rail pressure release. The method includes first reducing a significant part of the direct injection fuel rail pressure via a mechanical high pressure pump relief valve and only if further pressure relief is required then intermittently activating the direct injector to inject in small amount of fuel. Due to the reduced frequency of activation and small pulse-widths, the impact force transmitted from injectors to cylinder head is small thereby reducing the objectionable ticking noise.

Claims

1. A method, comprising:

during an engine warm idling condition,

maintaining direct injectors disabled until a direct injection fuel rail pressure is reduced by a high pressure pump relief valve; and

then further reducing the direct injection fuel rail pressure via intermittent activation of the direct injectors.

2. The method of claim 1, wherein the warm idling condition includes running the engine below a threshold speed and supplying fuel to the engine via a port injector only.

3. The method of claim 1, wherein the direct injectors are maintained disabled until the direct injection fuel rail pressure is at or below a first threshold pressure.

4. The method of claim 3, wherein the first threshold pressure is a pressure setting of the high pressure pump relief valve.

5. The method of claim 1, wherein the intermittent activation of the direct injector is based on a duration elapsed the direct injectors were disabled.

6. The method of claim 1, wherein the further reducing includes intermittently injecting fuel via the direct injectors until the fuel rail pressure reduces to a second threshold pressure, lower than the first threshold pressure.

7. The method of claim 6, wherein a fuel pulse-width and interval of the intermittently injecting is based on a difference in pressure between the first and second threshold.

8. The method of claim 6, further comprising deactivating the direct injector when the direct injection fuel rail pressure reached the second threshold pressure.

9. The method of claim 1, wherein the high pressure pump relief valve is a mechanically actuated valve.

10. The method of claim 6, further comprising adjusting fueling via the port injector based on the intermittent injection via the direct injector.

11. A method, comprising:

delivering fuel to an engine cylinder via a port injector while maintaining a direct injector disabled;

during a first condition, reducing pressure at a fuel rail of the direct injector by opening a pump relief valve while maintaining the direct injector disabled; and

during a second condition, first reducing pressure at the fuel rail of the direct injector by opening the pump relief valve while maintaining the direct injector disabled, and then further reducing the pressure by intermittently enabling the direct injector.

12. The method of claim 11, wherein during the first condition, the direct injector were disabled for a shorter duration before the pump relief valve is opened, and during the second condition, the direct injectors were disabled for a longer duration before the pump relief valve is opened.

13. The method of claim 11, wherein during the first condition a pressure relief index is smaller, and during the second condition the pressure relief index is higher, wherein the pressure relief index is a measure of a requirement of fuel rail pressure relief based on each of a duration of direct injection deactivation and engine operating conditions.

14. The method of claim 11, further comprising during a third condition, reducing pressure by intermittently enabling the direct injector while maintaining the pump relief valve closed.

15. The method of claim 14, wherein the intermittently enabling of the direct injector during the second condition includes fuel injection with a first pulse width and a first frequency, and the intermittently enabling of the direct injector during the third condition includes fuel injection with a second pulse width and a second frequency, the second pulse width is larger than the first pulse width and the second frequency is higher than the first frequency.

16. The method of claim 14, further comprising adjusting fueling via port injection based on intermittent fueling during each of the first, second and third condition via direct injection.

17. A fuel system comprising:

a first fuel rail coupled to a direct injector;

a second fuel rail coupled to a port injector;

a high pressure pump coupled to a fuel line leading to the first fuel rail;

a fuel tank;

a low pressure fuel pump coupled to the fuel tank;

a pump relief valve coupled upstream of the high pressure fuel pump, between the high pressure fuel pump and the first fuel rail, wherein the pump relief valve is configured to maintain a fixed fuel pressure in the first fuel rail; and

a controller including non-transitory instructions for intermittently activating direct injection only if a further pressure relief below the fixed fuel pressure is requested.

18. The method of claim 17, wherein the pump relief valve is one of a mechanical valve and an electrically actuated valve.

19. The method claim 17, wherein intermittently activating direct injection includes activating fuel injection via direct injection for a certain duration while maintaining port injection active.

20. The method claim 17, further comprises adjusting port injection based on intermittent activation of direct injection.