Rotary expansible chamber devices – With mechanical sealing – Axially movable end wall or end wall portion
Patent
1998-12-17
2000-11-28
Denion, Thomas
Rotary expansible chamber devices
With mechanical sealing
Axially movable end wall or end wall portion
418133, 418268, 418 16, E04C 200
Patent
active
061527165
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a vane pump according to the preamble of claim 1.
Vane pumps of the type referred to here are known. They have a rotor, in the circumferential wall of which slots which receive vanes are formed. The rotor rotates within a contour ring which forms preferably two crescent-shaped delivery spaces, through which the vanes run. When the rotor rotates, spaces of increasing and decreasing size are obtained. When the vane pump is in operation, therefore, suction and discharge regions are obtained. in the case of a contour ring of the type referred to here, there are two separate pump portions, each with a suction and a discharge region.
The discharge region is delimited laterally, on the outlet or delivery side, by means of a sealingly bearing pressure plate and, on the side located opposite the delivery side, for example by the casing of the vane pump.
When a vane pump is stopped while it is running hot, the upper vanes slide, due to gravity, into the slots formed in the rotor. The separation provided between the suction and discharge regions is thereby canceled, and there is virtually a short circuit in one pump portion, namely the upper. On the opposite side, as a consequence of gravity, the vanes slide out of their slots or they remain outside, so that separation is maintained here.
When the fluid, for example hydraulic oil, delivered by the vane pump cools, then, its viscosity increases, so that the movability of the vanes diminishes. When the pump is put into operation, the still separated pump portion admittedly delivers the fluid. However, the delivery capacity is greatly reduced, since there is a hydraulic connection from the delivering lower discharge region to the opposite upper discharge region and, there, to the suction region.
If the discharge regions are sealed off by means of the casing, undesirable leakage often occurs, since the casing is bent away from the rotor by the pressure prevailing within the contour ring and the leakage gap therefore becomes larger. The leakage is reduced by using a further pressure plate, instead of sealing off by means of the casing. This pressure plate is designed essentially identically to the pressure plate on the outlet or delivery side and has ducts which in each case open into the discharge regions of the two pump portions and make a connection with a pressure space formed between the pressure plate and casing.
The problem mentioned, regarding the short circuit when the pump is started up, arises to an increased extent in this embodiment, since, in addition to the connection on the delivery side between the discharge regions, there is also a corresponding hydraulic connection on the side located opposite the delivery side.
The object of the invention is, therefore, to provide a vane pump which has very good cold starting properties and, furthermore, has very little tendency to leakage.
This object is achieved with the aid of a vane pump which comprises the features mentioned in claim 1. The vane pump has two pressure plates bearing sealingly on the rotor, the pressure plate located opposite the delivery side having an orifice which makes a fluid connection between a preferably lower discharge region and a closed-off pressure space. A pressure is thereby built up in this pressure space, said pressure bending the pressure plate somewhat toward the rotor and pressing it sealingly onto the rotor. The pressure built up in the delivery region results in the same way in the pressure plate on the delivery side being subjected to a force which presses this pressure plate sealingly onto the rotor. Furthermore, a short circuit between the two discharge regions via the pressure space is avoided by connecting to the pressure space only one of the two discharge regions in the pressure plate located opposite the delivery side. The other discharge region of the pump is sealed off relative to the pressure space by means of the pressure plate.
In an advantageous embodiment, at least one of the fluid connections in the pressure plate located opposite the del
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patent: 3787151 (1974-01-01), Carlson
patent: 4505654 (1985-03-01), Dean, Jr. et al.
patent: 4772190 (1988-09-01), Merz et al.
patent: 5147183 (1992-09-01), Gettel
patent: 5266018 (1993-11-01), Niemiec
patent: 5924856 (1999-07-01), Murayama et al.
Denion Thomas
Luk Fahrzeug--Hydraulik GmbH & Co. KG
Trieu Thai-Ba
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