Pumps – Motor driven – Electric or magnetic motor
Patent
1989-11-13
1991-06-11
Smith, Leonard E.
Pumps
Motor driven
Electric or magnetic motor
417572, F04B 3504
Patent
active
050228307
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an internal tank/fuel pump unit with a vertically disposed, cylindrical unit housing, which has an open lower end, in which is inserted a base plate, which contains a suction channel, which runs from the outer surface of the base plate and terminates in a suction orifice in the inner surface of the base plate.
With the known internal tank pumps of this type, gas bubbles are formed under the pump on the outer surface of the base plate, especially when the fuel is heated strongly. The gas bubbles can interfere with the pumping operation or cause it to be brought to a complete stop. One of the causes of the formation of such gas bubbles may lie therein that, in the known pumps, because of the construction and arrangement of the base plate, local regions of different pressures which favor the formation of gas bubbles, arise in the fuel on its way along the base plate to the suction channel and the suction orifice.
The DE-U No. 8,603,736 discloses a fuel pump, in which a screen, which has a convexly curved shape, for example, is disposed in front of the base plate. This screen is intended to prevent the formation of a gas-bubble cushion at the outer surface of the screen. Such a gas-bubble cushion would interfere with the transport of the fuel, since it may be expected that the gas bubbles formed, because of their lower specific gravity, can rise along the outer surface of the screen towards the edge of the screen and then furthermore upwards along the outer surface of the pump. However, it has turned out that such a screen, if anything, promotes the formation of gas bubbles because of its flow resistance.
In principle, the same disadvantages also occur in the construction according to the French Publication No. 980,744, in which a suction basket, which has rounded edges at the periphery and is furnished with slits, is provided ahead of the base plate. In this construction, the base plate has a plane middle region, which contains the suction orifice. Adjoining the middle region is an inclined edge region, so that, even if the suction basket is omitted, the gas bubbles necessarily formed at higher temperatures and collected on the underside of the base plate, do not migrate towards the outside but are carried along by the aspirated fuel and reach the central suction orifice.
It is an object of the invention to provide an internal tank/fuel pump unit of the generic type, in which the tendency to form gas bubbles is reduced and the entry of gas bubbles into the suction channel is largely avoided.
In the inventive internal tank pump, there are in the path of the fuel flowing to the suction orifice no corners or edges, which can lead to pressure jumps in the flow. Accordingly, the tendency to form gas bubbles is reduced appreciably. Because of the convex shape of the outer surface of the base plate or the insert, the gas bubbles, which nevertheless are formed especially at high temperatures, can bead away radially towards the outside and then upwards along the outer surface of the unit housing. Due to the proposed shape of the suction channel, an adequate cross section for the suction channel or for the flow path of the fuel to the suction channel can be ensured despite the convexly curved shape of the outer surface of the base plate or of the insert, while the distance from the base of the fuel tank is kept as small as possible.
Preferably, the edge surrounding the suction channel is highly rounded off, in order to prevent as far as possible a pressure jump as the fuel flows around this edge.
Two embodiments of the invention are described in the following with reference to the drawings.
FIG. 1 shows a partial longitudinal section of an internal tank/fuel pump unit with a base plate constructed pursuant to the invention.
FIG. 2 shows a plan view of the unit represented in FIG. 1 from below, that is, in the direction of the base plate, on a smaller scale.
FIG. 3 shows a section similar to that of FIG. 1, with an insert placed on a conventional base plate.
FIG. 4 is a partial longitudinal sect
REFERENCES:
patent: 2474009 (1949-06-01), Molyneux
patent: 2485980 (1949-10-01), McClure
patent: 3964836 (1976-06-01), Navelsaker
patent: 4466781 (1984-08-01), Kemmner et al.
patent: 4619588 (1986-10-01), Moore
patent: 4629399 (1986-12-01), Friebe
patent: 4784587 (1988-11-01), Takei et al.
Attenni Johann
Weber Rainer J.
Audi AG
Savio, III John A.
Smith Leonard E.
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