For car engines with minimized fuel consumption the development now points toward the diesel engine with direct injection with air-distributed fuel. To avoid the disadvantages of this method, the forming of the mixture and the combustion must be optimized. This means that an injection system should provide high injection pressures and small dead volumes. The unit injector - where the injection unit and the nozzle are directly connected without any injection pipe - seems to satisfy these requirements. When designing the cam drive for a unit injector many details have to be taken into consideration. The movable parts of the system should be light with high rigidity so as to ensure precise movement transmission. By using high-grade spring materials with great temperature stability and by critically minimizing the oscillations excited by the cam it is possible to achieve high lift-off speeds. Using a barrel shaped roller with the greatest possible load carrying width and a large roller diameter will permit an increase in load by over 3O% using so-called 'G-cams' and by 2O% using tangent cams. Thus the high pump room pressures required in direct-injection diesel engines can be achieved whilst the cam drive system has a sufficiently long service life. In the unit injector various methods of timing advance can be applied. If timing advance is effected by altering the prestroke, then there usually will be a change in the velocity of fuel delivery requiring a correction of the fuel quantity which will be undergoing an additional dynamic change anyway. Adjustment of the fuel quantity is also required if the injection is timed via a controlled timing plunger. For timing advance by means of an eccentric shaft shifting the swivel centre of the rocker arm the timing was shown to require considerable torque.


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    Title :

    The unit injector as an injection system for diesel engines with direct injection and the particular problems of the cam drive


    Additional title:

    Das Pumpe-Düse-System als Einspritzanlage für direkteinspritzende Dieselmotoren


    Contributors:
    Herzog, P. (author) / Stipek, T. (author)


    Publication date :

    1983


    Size :

    30 Seiten, 26 Bilder, 16 Quellen


    Type of media :

    Conference paper


    Type of material :

    Storage medium


    Language :

    English





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