Pumps – One fluid pumped by contact or entrainment with another – Jet
Patent
1999-02-24
2000-12-26
Freay, Charles G.
Pumps
One fluid pumped by contact or entrainment with another
Jet
137 37, 137 42, F04F 544
Patent
active
061649228
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a pump for conveying a medium, in particular hydraulic oil, and comprising a flow controller for controlling the flow of medium conveyed by the pump through a discharge channel releasable by a flow-control valve.
Such pumps are known and are used, for example, in motor vehicles for power-steering and/or brake-servo systems as well as for hydraulic suspension systems or the like. This involves pumps which are driven directly by the internal-combustion engine and which thus have a volume flow variable as a function of the rotational speed of the engine or a conveying capacity dependent upon the rotational speed. In those cases in which the consumer connected to the pump requires only a specific maximum volume flow, a flow-control valve is provided which limits the flow of medium delivered by the pump to the consumer. If the conveying capacity of the pump exceeds the maximum volume flow, the flow-control valve opens a discharge channel, by way of which the medium conveyed by the pump flows back to the suction side of the pump. It has been found that in many cases damage is caused at high rotational speeds by cavitation. In addition, there is an irregular suction performance of the pump.
SUMMARY OF THE INVENTION
An object of the invention is to provide a pump as described which does not have this drawback.
The invention provides a pump for conveying a medium and comprising a flow controller for controlling the flow of medium conveyed by the pump, the flow controller comprising a discharge channel releasable by a flow-control valve, a flow divider for dividing the discharge jet flowing into the discharge channel and extending into the discharge channel, the flow divider being spaced from an orifice of the discharge channel facing the flow-control valve. In this way it is possible to prevent the adverse effects of cavitation almost completely.
Preferably, the flow divider is constructed as a moulded part which is provided with an incident-flow projection. The discharge jet released by the flow-control valve strikes the incident-flow projection at high speed and can be deflected thereby in such a way that cavitation can be virtually eliminated. It is thus possible to prevent damage by cavitation in a simple manner.
In a further embodiment of the pump the flow divider is constructed in the form of a pin which is preferably cylindrical and which is arranged in such a way that it is struck by the discharge jet. Other objects and features of the outer face of the pin are used to deflect the discharge jet. In this way, drawbacks resulting from cavitation can be prevented in a simple and inexpensive manner.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is explained in greater detail below with reference to the accompanying drawing, in which:
FIG. 1 is a cross-section through an area of a pump, and
FIG. 2 is a longitudinal section along the line II--II of FIG. 1.
DESCRIPTION OF A PREFERRED EMBODIMENT
The sectional illustration in FIG. 1 shows a cut-away view of a flow controller for a pump 1 provided with a flow-control valve arranged at a right angle to the plane of FIG. 1 and situated in a suitable valve bore 3 in housing 5 of the pump 1. The valve bore 3 is intersected by a discharge channel 7 which is, for example, also formed by a bore. It is also possible to form the discharge channel 7 during casting when manufacturing the housing 5.
A discharge edge 11, which is covered by a flow-control piston (not shown) of the flow-control valve in one operating position and is released in another operating position, is formed in the region of the orifice 9 of the discharge channel 7 opening into the valve bore 3.
The operation of a flow-control valve is known in principle, so that only the following will be noted here: The flow-control piston of the flow-control valve closes the discharge channel 7 in the stationary state of the pump and also in a first operating phase in which the desired volume flow for a consumer has not yet been reached. The flow-control pi
REFERENCES:
patent: 676239 (1901-06-01), Labadie
patent: 1494351 (1924-05-01), Gillard
patent: 2803116 (1957-08-01), Tilney
patent: 3736072 (1973-05-01), Turner et al.
patent: 3922113 (1975-11-01), Turner
patent: 4347047 (1982-08-01), Shiozawa
patent: 4989807 (1991-02-01), Foreman et al.
Breuer Peter
Nguyen Van Doan
Freay Charles G.
Luk Fahrzeug--Hydraulik GmbH & Co. KG
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