Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1997-04-28
1998-08-18
Miller, Carl S.
Internal-combustion engines
Charge forming device
Fuel injection system
123495, 417366, 417543, F02M 3704, F04B 1100
Patent
active
057945942
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention is based on a fuel injection pump, in particular a distributor injection pump for internal combustion engines.
A fuel injection pump of this kind is disclosed in EP 0 633 398 A1. The movable wall which divides the storage chamber from the drive mechanism chamber and can be embodied as a membrane or as a movable piston, is used to reduce the sudden loading of the storage chamber by the fuel, which has been previously brought to injection pressure and is sent into the storage chamber at the end of the feed stroke that effects the injection, by virtue of the fact that the movable wall yields to the pressure surge against the drive mechanism chamber, which is under a lower pressure, and offsets the outflow quantity. At the same time, during the intake stroke of the pump piston, the filling process of the pump work chamber is positively supported by the simultaneous volume change in the intake chamber and drive mechanism chamber. The pressure difference in the storage chamber and the drive mechanism chamber, which acts on this pump piston during its intake stroke, powers the pump piston in the intake stroke direction and obviates the need for a separate spring for returning the pump piston from its top dead center position to its bottom dead center position after the pressure or filling stroke.
Because of the great pressure difference between the pressure in the storage chamber (storage pressure) and the pressure in the drive mechanism chamber (lubrication pressure), the movable wall is optimally designed only for pressure fluctuations in the storage chamber, but cannot compensate for pressure fluctuations in the drive mechanism chamber, but rather contributes to the development of pressure oscillations in the drive mechanism chamber. The result is cavitations in the lubricating fluid, which leads to incomplete lubrication of the drive mechanism.
ADVANTAGES OF THE INVENTION
The fuel injection pump according to the invention, has the advantage over the prior art that because of the vacuum chamber according to the invention, which is defined by a membrane, pressure oscillations in the drive mechanism chamber owing to compression or expansion of the vacuum chamber can be compensated for, by means of which cavitation is prevented in the drive mechanism chamber and its filling with lubricating fluid is improved. The vacuum chamber is integrated into the fuel injection pump and does not require any additional installation space.
Advantageous improvements and updates of the fuel injection pump are possible by means of measures set forth herein.
According to a preferred embodiment of the invention, the membrane, together with the movable wall, encloses the vacuum chamber wherein the membrane is preferably fastened to the movable wall, which in the case of a metal wall, is carried out by soldering. This has the advantage that because of the soldering process for connecting the metal membrane and the movable metal wall, a vacuum automatically occurs between the two connected pieces when cooling takes place. The tempering of the membrane can be carried out with the soldering process. A structural change of the design of the fuel injection pump is not required since in comparison to series pumps, only the movable wall has to be provided with a membrane.
According to an advantageous embodiment of the invention, the vacuum chamber is enclosed by two shells that rest on each other and are joined to each other at the edges, which together constitute a pressure capsule with two effective membrane surfaces. With this embodiment of the vacuum chamber, the effective work surfaces for the compensation of pressure oscillations are considerably greater due to the double-sided membrane surfaces.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is explained in detail in the ensuing description in conjunction with preferred embodiments represented in the drawings.
FIG. 1 shows a schematic representation of a longitudinal cross-section through a prior art fuel injection pump,
FIGS. 2 and 3 respectively show
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Greigg Edwin E.
Greigg Ronald E.
Miller Carl S.
Robert & Bosch GmbH
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