Control for a piezo-electric injector when a foot is raised from the accelerator

Patent metadata

Field	Value
Publication number	US-11828245-B2
Application number	US-202117910146-A
Country	US
Kind code	B2
Filing date	Mar 8, 2021
Priority date	Mar 11, 2020
Publication date	Nov 28, 2023
Grant date	Nov 28, 2023

Abstract

Disclosed is a method for discharging the pressure in a fuel supply rail of an injection system of an engine, the fuel injection rail connected to a fuel tank by piezo-electric injectors, each including a needle and a piezo-electric actuator pressing on a servo valve of the injector. The injection system includes a fuel pressure sensor and an electrical generator transmitting electric current pulses to each actuator. When the accelerator is released, a first electrical command allows determination of a moment of opening of the respective servo valve without triggering an injection. A second electrical command triggers a discharge of fuel from the fuel supply rail to the tank and therefore to discharge the pressure of the supply rail without triggering an injection. The second electrical command charges the piezo-electric actuator between a first voltage level that opens the servo valve, and a second voltage level triggering an injection.

First claim

The invention claimed is:

1. A method for discharging the pressure in a fuel supply rail of an injection system of an engine of a vehicle, said fuel supply rail being connected to a fuel tank by a plurality of piezo-electric injectors, each of the piezo-electric injectors including a needle and a piezo-electric actuator configured to press on a servo valve of the injector, the injection system including a fuel pressure sensor for the supply rail and an electrical generator configured to transmit electric current pulses to the piezo-electric actuator of each of the piezo-electric injectors, said method being implemented during a phase of release of an accelerator for which no request for fuel injection has been made, the method comprising:
comparing, by a computer, on each engine cycle, a defined reference fuel pressure for the fuel supply rail with a measured fuel pressure in the fuel supply rail measured by the pressure sensor, and
when the measured fuel pressure is greater than the defined reference fuel pressure:
sending, by the electrical generator, a first electrical command to the piezo-electric actuator of at least one piezo-electric injector of the plurality of piezo-electric injectors, the first electrical command comprising
an electric charge pulse of a defined first duration determined to cause a complete charge of the piezo-electric actuator of the at least one injector,
an electric discharge pulse of the piezo-electric actuator,
a defined second duration corresponding to the time elapsing between the start of the electric charge pulse and the start of the electric discharge pulse of the piezo-electric actuator of the at least one injector, the defined second duration corresponding to the elapsing time being determined such that the needle of the at least one injector remains immobile,

determining, from a value of a force exerted by the piezo-electric actuator on the servo valve during the first electrical currcnt command, a charge time duration allowing an opening of the servo valve of the at least one injector, and
sending, by the electrical generator, a second electrical command to the piezo-electric actuator of said at least one injector, the second electrical command comprising
an electric charge pulse of a defined third duration,
an electric discharge pulse of the piezo- electric actuator, and
a defined fourth duration corresponding to the time elapsing between the start of the electric charge pulse and the start of the electric discharge pulse of the piezo-electric actuator, the defined fourth duration being determined from the charge time duration of the at least one injector to allow the opening of the servo valve of said at least one injector while keeping the needle immobile, so that the voltage at the terminals of the piezo-electric actuator is higher than a first voltage threshold triggering the opening of the servo valve and lower than a second voltage threshold triggering the opening of the needle, the defined second duration being determined as a function of an engine speed, the pressure in the fuel supply rail, and a desired pressure discharge.

2. The method as claimed in claim 1 , wherein the defined fourth duration being greater than a breakage duration allowing breakage of the inertia of the needle of the at least one injector.

3. The method as claimed in claim 2 , wherein the charge time duration allowing the opening of the servo valve is determined by measuring a voltage applied to the piezo-electric actuator and a quantity value of electric charges transferred from the electrical generator to the piezo-electric actuator of the at least one injector.

4. The method as claimed in claim 2 , wherein the opening of the servo valve is detected when the force exerted by the piezo-electric actuator on the servo valve is at a maximum, the force exerted by the piezo-electric actuator on the servo valve being determined from:
the voltage applied to the piezo-electric actuator,
a capacitance value of the piezo-electric actuator, and
a quantity value of electric charges.

5. The method as claimed in claim 2 , wherein the defined third duration of the second electrical command is equal to the charge time duration of the servo valve, to which a fifth defined duration is added.

6. The method as claimed in claim 2 , wherein at least one time lapse not equal to zero separates the two electrical commands.

7. A non-transitory computer-readable medium on which is stored a computer program, comprising code instructions to implement the method as claimed in claim 2 when said program is executed on a computer that is configured to control the injection system of the engine of the vehicle, said system including the fuel supply rail connected to the fuel tank by the plurality of piezo-electric injectors, each piezo-electric injector including the needle and the piezo-electric actuator configured to press on the servo valve of the injector, the injection system including the fuel pressure sensor for the supply rail and the electrical generator configured to transmit the electric current pulses to the piezo-electric actuator of each injector.

8. The method as claimed in claim 1 , wherein the charge time duration allowing the opening of the servo valve is determined by measuring a voltage applied to the piezo-electric actuator and a quantity value of electric charges transferred from the electrical generator to the piezo-electric actuator of the at least one injector.

9. The method as claimed in claim 8 , wherein the opening of the servo valve is detected when the force exerted by the piezo-electric actuator on the servo valve is at a maximum, the force exerted by the piezo-electric actuator on the servo valve being determined from:
the voltage applied to the piezo-electric actuator,
a capacitance value of the piezo-electric actuator, and
the quantity value of electric charges.

10. The method as claimed in claim 8 , wherein the defined third duration of the second electrical command is equal to the charge time duration of the servo valve, to which a fifth defined duration is added.

11. The method as claimed in claim 8 , wherein at least one time lapse not equal to zero separates the two electrical commands.

12. A non-transitory computer-readable medium on which is stored a computer program, comprising code instructions to implement the method as claimed in claim 8 when said program is executed on a computer that is configured to control the injection system of the engine of the vehicle, said system including the fuel supply rail connected to the fuel tank by the plurality of piezo-electric injectors, each piezo-electric injector including the needle and the piezo-electric actuator configured to press on the servo valve of the injector, the injection system including the fuel pressure sensor for the supply rail and the electrical generator configured to transmit the electric current pulses to the piezo-electric actuator of each injector.

13. The method as claimed in claim 1 , wherein the opening of the servo valve is detected when the force exerted by the piezo-electric actuator on the servo valve is at a maximum, the force exerted by the piezo-electric actuator on the servo valve being determined from:
the voltage applied to the piezo-electric actuator,
a capacitance value of the piezo-electric actuator, and
a quantity value of electric charges.

14. The method as claimed in claim 13 , wherein the defined third duration of the second electrical command is equal to the charge time duration of the servo valve, to which a fifth defined duration is added.

15. The method as claimed in claim 13 , where

Assignees

• Vitesco Tech Gmbh

Inventors

• Drouyer Morgan
• Dussardier Quentin

Classifications

• F02D41/3872 Primary

  characterised by leakage flow in injectors · CPC title

• F02D41/123

  the fuel injection being cut-off · CPC title

• F02D41/2096

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

• F02D2041/2024

  the control switching a load after time-on and time-off pulses · CPC title

• F02D2200/0602

  Fuel pressure · CPC title