Method for operating a piezo injector

Patent metadata

Field	Value
Publication number	US-10018138-B2
Application number	US-201515316627-A
Country	US
Kind code	B2
Filing date	Jun 1, 2015
Priority date	Jun 13, 2014
Publication date	Jul 10, 2018
Grant date	Jul 10, 2018

Abstract

The present disclosure relates to fuel injectors. The teachings may be embodied in a method for characterizing a hydraulic coupling element. The fuel injector may have a piston to pressurize a hydraulic medium and a pin connecting the piston to a piezoactuator. The method may include applying a charging current to the piezo actuator low enough that the leakage flow prevents a pressure differential and the nozzle needle remains closed; discharging the piezo actuator with a current high enough to release the mechanical connection between the piston and the pin; detecting when the piston impacts on the pin; and characterizing the coupling element based on the time between discharge and impact.

First claim

What is claimed is:

1. A method for controlling a piezo fuel injector including a hydraulic coupling element with a piston placing a hydraulic medium under pressure and a piezo actuator with a pin connecting said piston to the piezo actuator, wherein the coupling element converts a translational stroke of the piezo actuator into a pressure differential to open a nozzle needle of the piezo fuel injector, the method comprising:
applying a charging current to the piezo actuator, the charging current selected so that a leakage flow produced by the coupling element prevents development of a pressure differential and the nozzle needle remains closed;
discharging the piezo actuator with an actuating current sufficient to release a mechanical connection between the piston and the pin;
generating a signal when the piston impacts on the pin;
detecting the signal;
measuring an elapsed time from a start of discharging until the signal is detected;
determining a characteristic of the coupling element based on the measured time; and
controlling the actuation of the fuel injector based on the determined characteristic of the coupling element.

2. The method as claimed in claim 1 , wherein the measured time is used to monitor wear of the coupling element.

3. A method for testing a piezo fuel injector including a hydraulic coupling element with a piston placing a hydraulic medium under pressure and a piezo actuator with a pin connecting said piston to the piezo actuator, wherein the coupling element converts a translational stroke of the piezo actuator into a pressure differential to open a nozzle needle of the piezo fuel injector, the method comprising:
applying a charging current to the piezo actuator, the charging current selected so that a leakage flow produced by the coupling element prevents development of a pressure differential and the nozzle needle remains closed;
discharging the piezo actuator with an actuating current sufficient to release a mechanical connection between the piston and the pin;
generating a signal when the piston impacts on the pin;
detecting the signal;
measuring an elapsed time from a start of discharging until the signal is detected; and
determining a characteristic of the coupling element based on the measured time;
wherein the characteristic of the coupling element represents a degree of mechanical wear of the coupling element.

4. The method as claimed in claim 3 , further comprising controlling a actuation of the fuel injector based on the degree of mechanical wear of the coupling element.

5. A piezo fuel injector comprising:
a piezo actuator driven by a current source;
a hydraulic coupling element driven by the piezo actuator and converting extension of the piezo actuator into a pressure differential;
a nozzle needle actuated by the pressure differential;
a gap defined between the coupling element and a housing wall, the gap allowing a fuel to flow past the coupling element to the nozzle needle;
wherein the current source generates a charging current selected so low-enough that a leakage flow around the coupling element keeps the pressure differential low enough to prevent opening of the nozzle needle;
and the current source discharges the piezo actuator with an actuating current sufficient to release a mechanical connection between at least a part of the coupling element and the piezoactuator; and
a processor measuring an elapsed time from a start of discharging until impact of the coupling element on the piezo actuator, determining a characteristic of the coupling element based on the measured time, and operating the fuel injector based on the determined characteristic.

6. A piezo fuel injector as claimed in claim 5 , further comprising a pin;
wherein the coupling element comprises a piston with a loose mechanical connection to the pin.

7. A piezo fuel injector as claimed in claim 6 , wherein the piston moves in a pressure cylinder against a spring arranged in the pressure cylinder; and
wherein extension of the piezoactuator moves the piston against the force of the spring to pressurize a fuel and the nozzle needle opens in response to the pressurization.

Assignees

• Continental Automotive Gmbh

Inventors

• Gargiso Tany
• Kramel Manfred
• Wiehoff Hans-Joerg

Classifications

• F02M65/005

  Measuring or detecting injection-valve lift, e.g. to determine injection timing · CPC title

• G01M15/042

  by monitoring a single specific parameter not covered by groups G01M15/06 - G01M15/12 · CPC title

• F02D41/2467

  for injectors · CPC title

• F02D2041/2055

  with means for determining actual opening or closing time · CPC title

• F02D2041/2058

  using information of the actual current value · CPC title