Abstract
After the successful introduction of a direct injection Diesel engine in the passenger car segment by one European car manufacturer, all important car manufacturers have or will have in the near future Diesel cars equipped with DI engines in their program.
New types of fuel injection systems, so-called Common Rail Systems, are in preparation for further improvement of the engine behavior of cars with direct injection engines regarding noise, exhaust emissions, fuel consumption and driveability and to reduce the costs. The first generation of these systems use solenoid actuators in the injector and have limitations in pressure capability and overall efficiency.
The paper describes an advanced Common Rail System of the second generation, in which -- for the first time -- a piezo actuator is used for controlling the injection. Aside from this main feature, the system also works with higher injection pressure (³1500 bar) and a new high pressure pump with flow control on the low pressure side.
The paper describes the function and advantages of the system, for example:
- extremely short delay and switching time of the piezo actuator in the injector
- precise control and stability of smallest injection quantities for pilot injection
- satisfactory shot to shot behavior of injection quantities in whole map
- injection rate control capability
- reduced losses due to the demand controlled high pressure pump (reduced fuel consumption and lower fuel temperatures)
- high injection pressure for further optimizing engine emissions
- significant lower power consumption in the ECU by using the piezo instead of a solenoid.
This new injection system is a basis to fulfill the Euro III emission levels and, together with further improvements on the engine combustion and after-treatment side, is already a step toward Euro IV levels.