A Microinjector for DI-Gasoline Applications

This paper introduces a new microinjector designed for optimizing gasoline direct-injecting engines. The basic idea for the construction of this microinjector was to develop a new kind of valve with an extremely high lifting speed. Generally, the latter can be realized by integrating a piezoelectric stack actuator in the injector in combination with small masses for the accelerated parts. Due to the material properties of piezoceramics, this solution requires an actuator which is comparatively long in size. But it is desirable to keep the actuator as short as possible in order to reduce the production costs and to additionally increase the lifting speed of the valve. To adapt the specifications of the actuator to the requirements of the valve, this present microinjector operates with a new, miniaturized stroke amplifying unit. The miniaturization allows the integration of the unit into the injector tip without extending the outside diameter of 7 mm. Simulations have been performed to demonstrate the high dynamic performance of the injector as well as to optimize the stiffness of the mechanical parts that are directly involved in the opening/closing procedure. Injection quantity measurements have also been performed with the first prototypes, using a hydraulic test bench.