Method for determining the idle travel of a piezo-injector with a directly actuated nozzle needle
View Patent ↗A method is disclosed for determining the idle travel of a piezo-injector which has a piezo-actuator and a nozzle needle which is activated directly by the piezo-actuator. A test pulse is applied to the piezo-actuator, which pulse brings about a continuous increase in the piezo-travel. The time period is measured which passes between the starting of the test pulse and the time when the idle travel is overcome. The idle travel of the piezo-injector is then determined from the measured time period.
1. A method for determining an idle travel of a piezo-injector that comprises a piezo-actuator and a nozzle needle actuated by the piezo-actuator, the method comprising:
applying a test pulse to the piezo-actuator that produces a continuous increase of a piezo stroke of the piezo-actuator, wherein the magnitude of the test pulse does not produce a needle stroke within a predefined duration of the test pulse;
wherein the test pulse comprises application of a constant value of current;
measuring the time period that passes between a commencement of the test pulse and a point at which the idle travel is overcome and the piezo-actuator impacts the pin, and
determining the idle travel of the piezo-injector based on the measured time period.
2. The method of claim 1 , wherein the constant value of current is provided by a control device of a motor vehicle.
3. The method of claim 1 , comprising:
obtaining voltage values from the measured time period using a database, and
using the obtained voltage values to control the piezo-actuator during a subsequent fuel injection process.
4. The method of claim 3 , wherein the database is stored in a non-volatile manner in a storage device during the course of manufacturing the motor vehicle.
5. The method of claim 4 , wherein the database stores a plurality of time periods and a respective allocated voltage value for each of a plurality of predefined system pressure values.
6. A common-rail fuel injection system of a motor vehicle, comprising:
a piezo-injector comprising a piezo-actuator and a nozzle needle actuated by the piezo-actuator,
and
a control system configured to:
apply a test pulse to the piezo-actuator that produces a continuous increase of a piezo stroke of the piezo-actuator, wherein the magnitude of the test pulse does not produce a needle stroke within a predefined duration of the test pulse;
wherein the test pulse comprises application of a constant value of current;
measure the time period that passes between a commencement of the test pulse and a point at which the idle travel is overcome and the piezo-actuator impacts the pin; and
determine the idle travel of the piezo-injector based on the measured time period.
7. The system of claim 6 , wherein the control system is configured to determine a magnitude of the test pulse such that it does not produce a needle stroke within a predefined duration of the test pulse, and applying the test pulse with the determined magnitude.
8. The system of claim 6 , wherein the constant value current source is provided by a control device of a motor vehicle.
9. The system of claim 6 , wherein the control system is configured to:
obtaining voltage values from the measured time period using a database accessible by the control system, and
use the obtained voltage values to control the piezo-actuator during a subsequent fuel injection process.
10. The system of claim 9 , wherein the database is stored in a non-volatile manner in a storage device during the course of manufacturing the motor vehicle.
11. The system of claim 10 , wherein the database stores a plurality of time periods and a respective allocated voltage value for each of a plurality of predefined system pressure values.