Internal-combustion engines – Charge forming device – Fuel flow regulation between the pump and the charge-forming...
Patent
1999-07-15
2000-11-28
Moulis, Thomas N.
Internal-combustion engines
Charge forming device
Fuel flow regulation between the pump and the charge-forming...
137540, 417186, F02M 3704
Patent
active
061521140
DESCRIPTION:
BRIEF SUMMARY
The invention is based on a overflow valve, which is used as a control valve in an apparatus for pumping fuel. The apparatus has a supply container for fuel for an internal combustion engine of a motor vehicle, a catchment disposed in the supply container, a fuel pumping assembly that aspirates from the catchment and communicates on the pressure side with the engine, a return line from the engine or a direct branch from the pressure line to the supply container, and a fluid entrainment pump communicating with the return line or the branch and disposed in the supply container. By means of the fluid entrainment pump, the fuel is pumped into the catchment, and the overflow valve closes or opens a overflow opening to the fluid entrainment pump.
One such apparatus is known from German Patent Disclosure DE 44 26 667 A1. There the overflow opening is closed by a ball, which rests on a valve seat of the overflow opening. Lateral guidance of the ball is affected via ribs in such a way that the ribs can move only vertically away from or toward the overflow opening. The vertical motion is caused by two compression forces oriented counter to one another. Once compression force is created by fuel that flows through a jet nozzle of the fluid entrainment pump. The other compression force is caused by a spring element. The spring element is L-shaped, and the shorter leg of this shape is fastened in a carrier, so that the other, long leg, as a unilaterally fastened spiral spring, presses against the ball.
ADVANTAGES OF THE INVENTION
The overflow valve of the invention in an apparatus for pumping fuel to the internal combustion engine of a motor vehicle has the advantage that the use of a spirally shaped spring makes extremely precise control of the fluid entrainment pump possible. The spirally shaped spring has a shallow characteristic curve, which can be adjusted so precisely that a very sensitive control of the fluid entrainment pump can be performed. Uncovering of the overflow opening to allow fuel to flow out of the fluid entrainment pump can be adjusted by means of the type of spring and the attendant precision in such a way that a desired pressure in the fluid entrainment pump of between 0.25 and 2.5 bar can be controlled as required, with only extremely negligible deviation.
Advantageous features and refinements are recited in the dependent claims.
One advantageous refinement provides that the spring is integrated in one piece with a securing system. As a result, the labor involved in producing the spring and installing it is kept low. Furthermore, the one-piece nature of the securing system and the spring makes it possible to assure a precision fit by way of the production tool. Jointly manufacturing the spring and securing system means that in the later installation, care need be taken merely for the fastening of the securing system. The location of the spring in the securing system remains assured by adherence to the specified tolerances in manufacture. To that end, the securing system has a base, which is secured to the catchment by means of a seat provided for it. The base has barbs, for instance, to prevent unintended loosening in the seat.
The securing system itself preferably has a frame, in the middle of which the spring is disposed. On the one hand, in this way the frame stabilizes the spring. On the other, a suspension of the spring that makes adequate safety possible in operation is assured. A further advantage of using the frame is the attendant rigidity of the securing system. As a result, the securing system becomes invulnerable to impacts, jarring or other exertions of force of the kind that occur in conventional product ion processes and the attendant transportation and storage. The high rigidity also makes it possible for such machining steps as bending or a heat treatment not to impair the adherence to tolerances. A further advantage is obtained in assembly. The frame itself is simple to grasp and to insert into the seat intended for it. Because the securing system is in one piece, there is no
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Moulis Thomas N.
Robert & Bosch GmbH
Striker Michael J.
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