Rotary expansible chamber devices – With removal or accommodation of solid foreign material in... – With filter
Utility Patent
1999-05-04
2001-01-02
Vrablik, John J. (Department: 3748)
Rotary expansible chamber devices
With removal or accommodation of solid foreign material in...
With filter
C418S248000, C418S249000
Utility Patent
active
06168401
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an hydraulic conveying device, in particular for conveying diesel fuel for an internal-combustion engine in motor vehicles, with a housing provided with at least one conveying chamber as well as a displacement unit arranged in the conveying chamber, rotation of the displacement unit resulting in the formation of pump chambers with varying volumes by way of which a fluid is conveyed from a suction connection of the conveying device to a pressure connection of the conveying device.
Hydraulic conveying devices of the type defined in the introduction are known. They are used for example as fuel-conveying pumps in motor vehicles, in order to draw in the contents of a tank and to convey them to an injection unit of the internal-combustion engine. The hydraulic conveying devices are constructed for example in the form of blocking-vane pumps, gear pumps or vane-cell pumps. The hydraulic conveying devices have to ensure that fuel is conveyed continuously out of the tank and is supplied with an increase in pressure of several bar for example to a high-pressure pump of the injection unit. This must be provided for under all operating conditions of the motor vehicle. In particular, if a supply of fuel present in the tank runs out, a so-called empty running of the tank, air is drawn in through the conveying device.
Air is drawn in in this way until fuel still present in supply lines to the internal-combustion engine is used up, and the internal-combustion engine stops as a result of a lack of fuel. The conveying device is dried out as it were by the air flow conveyed through the conveying device in this case, so that as a result of a minimal clearance—required for operating the conveying device—between the movable and stationary parts of the conveying device it is no longer possible to seal off the clearance by the fuel. In particular, when the tank is re-filled with fuel and drawing-in takes place by way of the conveying device, the problem arises that the leakage points inside the conveying device render the build-up of pressure at least difficult, if not actually impossible. In particular, a rapid and reliable supply of fuel to the internal-combustion engine is possible only after a relatively long run-up phase.
SUMMARY OF THE INVENTION
The object of the invention is to provide an hydraulic conveying device of the type defined in the introduction, in which a reliable and rapid run-up is possible in a simple manner in any operating situation, and in particular even at low rotational speeds of the drive.
This object is attained according to the invention by an hydraulic conveying device with a fluid conveying chamber, having a pumping rotor in it and devices which retain fluid in the pumping chamber when fluid supply from the suction connection to the conveying chamber is interrupted. Preferably, such a device comprises a pressure collecting chamber above the conveying chamber. Since the conveying device comprises means which retain a quantity of the fluid to be conveyed in the conveying chamber when a supply of fluid by way of the suction connection is interrupted, it is advantageously possible, even when the supply of a fluid to be conveyed runs out, to prevent the hydraulic conveying device from running dry. The fluid remaining in the conveying device, in particular in a conveying chamber of the conveying device, prevents an interruption of the sealing effect between the moved and fixed parts of the conveying device, so that at all times a sealing film of fluid remains in gaps existing between them as a result of manufacture.
A preferred embodiment of the invention provides a pressure-collecting chamber arranged substantially above the conveying chamber in the fitted position of the blocking-vane pump. In this way, it advantageously becomes possible for fluid remaining in the pressure-collecting chamber to flow back into the conveying chamber as a result of gravity when a supply of fluid is interrupted. The fluid collects in the conveying chamber, so that the conveying chamber lies below a residual-fluid level inside the conveying device. When the conveying device starts up again, fluid is thus immediately available, and can form a sealing film between the moved and stationary parts of the conveying device.
In particular, if the pressure ducts connecting the conveying chamber to the pressure-collecting chamber extend at an angle which ascends to a horizontal line extending through an axis of rotation, a satisfactory return of the residual fluid into the conveying chamber is assisted.
A further preferred embodiment of the invention provides that in blocking-vane pumps pressure outlets of the conveying chamber are connected by at least one fluid connection to spring chambers by way of which vanes are acted upon with a radially acting force by spring members arranged in spring chambers. In this way, it is in an advantageous manner, the residual fluid collecting in the conveying chamber can arrive directly in the spring chambers after the conveying device is started up again, and so the sealing of a clearance (gaps) from the radially movable to stationary parts of the displacement unit can take place immediately. This prevents a pressure build-up in the conveying device from being delayed by possible leakage points in the case of this clearance.
In addition, in a preferred embodiment of the invention, the pressure-collecting chamber is provided with at least one cross-sectional enlargement and/or at least one cross-sectional constriction. This cross-sectional enlargement or cross-sectional constriction respectively can advantageously produce a swirling of the fluid in the pressure-collecting chamber, and the swirling leads to retardation of the speed of flow. This makes it possible for the fluid present in the pressure-collecting chamber not to be pumped away completely through the pressure outlet when the conveying device is switched off following an interruption of the fluid supply. The quantity of fluid remaining in the pressure-collecting chamber is then available for filling the conveying chamber.
In addition, it is preferred if at least one wall, which has at least one through opening for the fluid, is provided inside the pressure-collecting chamber. This causes a banking-up in front of the wall, and, particularly when a fluid to be conveyed suddenly becomes absent, this banking-up leads to the possibility of air, which is conveyed instead of the fluid, then taking up the quantity of residual fluid which remains in the pressure-collecting chamber. This quantity of residual fluid is advantageously banked up at the at least one wall and is available for the return of the quantity of residual fluid into the conveying chamber.
In addition, it is preferred if the pressure-collecting chamber is formed by a free space of a portion of a housing of the conveying device. As a result, in particular if the housing is produced from a die-casting, it is possible to produce even irregular contour sections of the pressure-collecting chamber, for example the cross-sectional enlargements, cross-sectional constrictions, walls, pressure ducts and so forth, in a simple manner by means of known and reliably controllable methods.
Other objects and features of the invention are explained below in embodiments with reference to the accompanying drawings.
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Patent Abstract of Japan No. 6-229377 of Aug. 16, 1994, vol. 18/No. 607.
Otto Dieter
Schenck Kai
Luk Automobiltechnik GmbH & Co. KG
Ostrolenk Faber Gerb & Soffen, LLP
Vrablik John J.
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