Fuel injection systems
Various embodiments include a method for operating an internal combustion engine with a fuel injection system including a piezo actuator comprising: stopping the discharge phase of the actuator during an injection cycle; measuring a voltage profile at the actuator; comparing a feedback signal at the actuator with a setpoint value; varying the discharge time of the actuator in successive injection cycles until the feedback signal corresponds to the setpoint value; defining a servo valve closing time as a defined offset with respect to the optimized discharge time; and using the defined servo valve closing time to set an injection quantity of fuel for future injection cycles.
1. A method for operating an internal combustion engine with a fuel injection system including a piezo actuator, the method comprising:
carrying out an injection process and stopping the discharge phase of the piezo actuator;
measuring a voltage profile at the piezo actuator;
evaluating the voltage profile to detect a voltage rise after the end of the discharge phase by comparing a feedback signal at the piezo actuator with a setpoint value;
varying the discharge time of the piezo actuator in successive injection cycles until the feedback signal corresponds to the setpoint value to obtain an optimized discharge time;
defining a servo valve closing time as a defined offset with respect to the optimized discharge time; and
using the defined servo valve closing time to set an injection quantity of fuel for future injection cycles.
2. The method as claimed in claim 1 , wherein an amplitude of the voltage rise at the piezo actuator is measured as a voltage rise.
3. The method as claimed in claim 1 , wherein the said method is carried out during the driving operation of a vehicle having a piezo-driven fuel injector.
4. A fuel injection system comprising:
a piezo-driven injector injecting fuel into combustion chamber; and
a control unit programmed to:
carry out an injection process and stopping the discharge phase of the piezo actuator;
measure a voltage profile at the piezo actuator;
evaluate the voltage profile to detect a voltage rise after the end of the discharge phase by comparing a feedback signal at the piezo actuator with a setpoint value;
vary the discharge time of the piezo actuator in successive injection cycles until the feedback signal corresponds to the setpoint value to obtain an optimized discharge time;
define a servo valve closing time as a defined offset with respect to the optimized discharge time; and
use the defined servo valve closing time to set an injection quantity of fuel for future injection cycles.