Method for operating a fuel injection system and fuel injection system comprising fuel injection valves with a piezo direct-drive

Patent metadata

Field	Value
Publication number	US-9556839-B2
Application number	US-201314381745-A
Country	US
Kind code	B2
Filing date	Mar 14, 2013
Priority date	Mar 19, 2012
Publication date	Jan 31, 2017
Grant date	Jan 31, 2017

Abstract

A method for operating a fuel injection system includes detecting the pressure prevailing in a pressure accumulator using a fuel injection valve piezo actuator that includes, in addition to the active piezo region used to actuate the closing element, a passive piezo region that acts as a pressure sensor. Using this pressure sensor, the closing element force acting on the passive piezo region, and therefore the pressure prevailing in the pressure accumulator, can be determined.

First claim

What is claimed is:

1. A method for operating a fuel injection system of an internal combustion engine, wherein the fuel injection system has a pressure reservoir, at least one injection valve with piezo direct-drive in which a piezoelectric actuator is in a direct drive connection with a closure element of the injection valve, a pressure sensor that detects a pressure in the pressure reservoir, and a control and regulating unit, wherein the piezoelectric actuator includes an active piezoelectric region used for actuating the closure element and a passive piezoelectric region that forms the pressure sensor for detecting the pressure in the pressure reservoir, the method comprising:
determining a force acting on the passive piezoelectric region through the closure element, and
determining the pressure in the pressure reservoir based on the determined force acting on the passive piezoelectric region; and
regulating pressure in the fuel injection system based on (a) the pressure in the pressure reservoir determined using the pressure sensor and (b) a setpoint pressure value.

2. The method of claim 1 , wherein the pressure in the pressure reservoir is determined in a phase in which the closure element is in the closed state without activation of the active piezoelectric region.

3. The method of claim 1 , wherein the determination of the force acting on the passive piezoelectric region accounts for an offset force additionally acting on the passive piezoelectric region.

4. The method of claim 3 , wherein the force acting on the passive piezoelectric region is determined based on the equation:
F _ s=A _ p*P _rail− A _ s*P _ low

wherein
F_s=a force exerted on the passive piezoelectric region,
A_p=a surface of a connecting member between the piezoelectric actuator and the closure element or a further connecting member,
P_rail=the pressure in the pressure reservoir,
A_s=an area of the passive piezoelectric region, and and
P_low=low pressure.

5. The method of claim 1 , wherein the force acting on the passive piezoelectric region is determined using a characteristic curve from an electric voltage measured across the passive piezoelectric region.

6. The method of claim 1 , wherein the fuel injection system has a plurality of fuel injection valves, and wherein the pressure in the pressure reservoir is determined at least once before an injection by each injection valve.

7. The method of claim 1 , wherein the fuel injection system has a plurality of fuel injection valves, and wherein the method comprises:
determining respective pressure values for all of the injection valves at the same time, and
calculating the pressure in the pressure reservoir based on an average of determined pressure values of all of the injection valves.

8. The method of claim 1 , comprising:
during a function test on each respective injection valve:
setting a defined pressure in the pressure reservoir,
determining a force using the pressure sensor, and
determining and storing a characteristic curve profile for the respective injection valve.

9. A fuel injection system of an internal combustion engine, comprising:
a pressure reservoir,
at least one injection valve with piezo direct-drive, in which a piezoelectric actuator is in direct drive connection with a closure element of the injection valve,
wherein the piezoelectric actuator includes an active piezoelectric region used for actuating the closure element and a passive piezoelectric region that forms a pressure sensor for detecting the pressure in the pressure reservoir,
wherein the passive piezoelectric region of the piezoelectric actuator is configured to determine a force, and
a control and regulating unit programmed to
determine the pressure in the pressure reservoir based on the determined force acting on the passive piezoelectric region; and
regulate pressure in the fuel injection system based on (a) the pressure in the pressure reservoir determined using the pressure sensor and (b) a setpoint pressure value.

10. The fuel injection system of claim 9 , wherein the piezoelectric actuator has a passive piezoelectric region, which is formed by at least one additional, serially arranged passive piezoelectric layer, which is electrically insulated from the active piezoelectric layers.

11. The fuel injection system of claim 9 , wherein the pressure in the pressure reservoir is determined in a phase in which the closure element is in the closed state without activation of the active piezoelectric region.

12. The fuel injection system of claim 9 , wherein the determination of the force acting on the passive piezoelectric region accounts for an offset force additionally acting on the passive piezoelectric region.

13. The fuel injection system of claim 12 , wherein the force acting on the passive piezoelectric region is determined based on the equation:
F _ s=A _ p*P _rail− A _ s*P _ low

wherein
F_s=a force exerted on the passive piezoelectric region,
A_p=a surface of a connecting member between the piezoelectric actuator and the closure element or a further connecting member,
P_rail=the pressure in the pressure reservoir,
A_s=an area of the passive piezoelectric region, and and
P_low=low pressure.

14. The fuel injection system of claim 9 , wherein the force acting on the passive piezoelectric region is determined using a characteristic curve from an electric voltage measured across the passive piezoelectric region.

15. The fuel injection system of claim 9 , wherein the fuel injection system has a plurality of fuel injection valves, and wherein the pressure in the pressure reservoir is determined at least once before an injection by each injection valve.

16. The fuel injection system of claim 9 , comprising a plurality of fuel injection valves, and wherein the control and regulating unit is programmed to:
determine respective pressure values for all of the injection valves at the same time, and
calculate the pressure in the pressure reservoir based on an average of determined pressure values of all of the injection valves.

17. The fuel injection system of claim 9 , control and regulating unit is programmed to, during a function test on each respective injection valve:
set a defined pressure in the pressure reservoir,
determine a force using the pressure sensor, and
determine and storing a characteristic curve profile for the respective injection valve.

Assignees

• Continental Automotive Gmbh

Inventors

• Zhang Hong
• Schoeppe Detlev

Classifications

• F02D41/2096

  for controlling piezoelectric injectors (drive and control circuit for piezoelectric devices in general H10N30/802) · CPC title

• F02D28/00

  Program control of engines · CPC title

• F02M47/027

  Electrically actuated valves draining the chamber to release the closing pressure · CPC title

• F02D41/3809

  Common rail control systems (common rail apparatus F02M55/025, F02M63/0225) · CPC title

• F02M65/00

  Testing fuel-injection apparatus, e.g. testing injection timing {(testing of ignition F02P17/00; measuring fuel consumption G01F9/00); Cleaning of fuel-injection apparatus} · CPC title