Fluid sprinkling – spraying – and diffusing – Unitary injection nozzle and pump or accumulator plunger
Patent
1998-11-17
2000-06-27
Kashnikow, Andres
Fluid sprinkling, spraying, and diffusing
Unitary injection nozzle and pump or accumulator plunger
239 90, 239 91, 239 93, 239 95, 2391022, 2395332, 2395334, 2395338, F02M 4702, B05B 108
Patent
active
060796367
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a fuel injection valve with a piezoelectric or magnetostrictive actuator.
BACKGROUND INFORMATION
A fuel injection valve with a piezoelectric actuator is described in, for example, German Published Patent Application No. 195 00 706. In this fuel injection valve, the piezoelectric or magnetostrictive actuator controls a working piston that acts upon a stroke piston via a hydraulic path transformer. The stroke piston is connected in a positive-locking manner via a needle valve to a valve closing member provided on a spray-discharge opening. The piezoelectric or magnetostrictive actuator is thus connected via the hydraulic path transformer in a force-locking manner to the valve closing member. If a suitable electric voltage is applied to the actuator, it expands and displaces the working piston accordingly. Even a relatively small displacement of the working piston is transformed by the hydraulic path transformer into a significantly larger displacement of the stroke piston so that the valve closing member releases the spray-discharge opening with a suitable cross-section. A fuel injection valve of a similar construction type is also described in German Patent No 43 06 073. This publication describes a housing-side mounting of the actuator in a special spherical disk support which achieves in the case of a small non-parallelism of the actuator end, a full-surface abutment of the piezoelectric actuator on the pressure piston acted upon by it.
Conventional fuel injection valves have the disadvantage that the injection pressure is predetermined by the fuel pressure generated by the fuel pump in the fuel intake line and thus the available injection pressure is limited. Moreover, there is the disadvantage of a non-negligible mass inertia of the stroke piston, the needle valve and the valve closing member. The response time of the fuel injection valve is determined by the mass inertia of these elements.
SUMMARY OF THE INVENTION
A fuel injection valve according to the present invention has the advantage that the fuel is injected with a relatively high injection pressure. For this purpose, an additional compression of the fuel takes place with a pump piston that can be activated using a piezoelectric or magnetostrictive actuator so that the fuel pressure prevailing in a fuel pressure line between the pump piston and a spray-discharge nozzle is significantly greater than the fuel pressure prevailing in the fuel intake line. The actuation of the spray-discharge nozzle takes place hydraulically in that the spray-discharge nozzle opens if the fuel pressure prevailing in the fuel pressure line exceeds a predetermined threshold. In this manner, the piezoelectric or magnetostrictive actuator provides both an increase of the injection pressure, as well as a hydraulic actuation of the spray-discharge nozzle. Thus, two functions are combined in an extremely compact unit.
Moreover, due to the compact type of construction, relatively short intake paths arise for the fuel so that cavitation problems are avoided. The fuel volume to be compressed by the pump piston is relatively small and is limited only to the volume of the relatively short practicable fuel pressure line as well as the volume within the spray-discharge nozzle which is likewise practicable with very small dimensions. The damage space allocated to the pump piston is thus relatively small so that a relatively small stroke of the pump piston suffices.
The thermal linear expansion compensation of the actuator required in conventional fuel injection valves can be entirely eliminated since the spray-discharge nozzle is actuated hydraulically instead of mechanically via a stroke piston and a needle valve. Slight temperature-dependent displacements of the pump piston due to a temperature-dependent linear expansion of the actuator connected to the pump piston are thus not harmful to the function of the fuel injection valve according to the present invention. The modular design of the fuel injection valve accordin
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patent: 5845852 (1998-12-01), Waldman
patent: 5884848 (1999-03-01), Crofts et al.
Haag Gottlob
Rembold Helmut
Stutzenberger Heinz
Evans Robin O.
Kashnikow Andres
Robert & Bosch GmbH
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