Pumps – With condition responsive pumped fluid control – Fluid flow rate responsive
Patent
1997-03-12
1998-09-22
Thorpe, Timothy
Pumps
With condition responsive pumped fluid control
Fluid flow rate responsive
417308, 417310, F04B 4900
Patent
active
058105654
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a regulating device for displacement pumps, in particular vane cell pumps, which have a pressure chamber which is connected via a bore, in which a throttle piston can be displaced against the force of a spring, with a pressure channel connected to an outlet. The throttle piston controls an outlet cross section as a function of the pump speed (rpm) or of the conveyed flow. In addition, a spring-loaded flow control piston, whose front face is connected with the pressure chamber, is present in a housing bore. A rear face of the feed control piston projects into a chamber which contains the outlet pressure downstream of the throttle device. As a function of the differential pressure acting on the two faces, the flow control piston releases a connection between the pressure chamber and a pump inlet channel.
2. Description of the Prior Art
Such a regulating device is known from DE 41 01 210-A1. During an increase in speed (rpm), the throttle piston in this pump is displaced by means of dynamic pressure acting on a front face. In the process a control edge intersects a piston opening connected to a pressure chamber, so that the reduction in the cross section of the opening allows less and less hydraulic oil to flow to an outlet. This arrangement constitutes the throttle device.
The reduction in the cross section of the opening increases the differential pressure acting on the flow control piston, so that the latter regulates a conveyed flow to the pump inlet side so that it becomes gradually less. Since the controllable opening is in the throttle piston, the differential pressure also acts on the back of the piston of the throttle device.
In its base position the throttle piston blocks an opening connected with the pressure chamber or the interior with its front face, for which a comparatively stiff spring is required. During the start-up of the pump it is necessary to overcome this spring force. To this end it is necessary in connection with a double-flow pump to build up a considerably higher pump pressure in one of the pressure zones, so that the pump runs considerably louder because of the different pressures. The piston is furthermore designed as a step piston with a snug fit, which requires a certain manufacturing outlay.
It is the object of the invention to provide a regulating device for a characteristic descending conveyed flow curve with the smallest possible construction outlay, without considerably increasing the power consumption of the pump. In addition, the characteristic descending line is to be independent from the opening path and the differential pressure of the flow control piston in order to avoid a disturbance variable.
SUMMARY OF THE INVENTION
This object is attained by means of the present invention.
The novel throttle device is designed in such a way that, in the area of the bore containing the throttle piston, the pressure chamber is in constant contact with a spring chamber by means of a bypass channel, and the throttle piston controls the cross section of a throttle channel connecting the spring chamber with the outlet chamber.
In accordance with a preferred embodiment it is practical to cast the bypass channel into a bearing housing in the shape of a letter T, wherein the perpendicularly extending channel section is open in the direction toward the bore.
Because of the bypass channel, the effect of the differential pressure is independent of the throttle piston, i.e the differential pressure at the regulating piston cannot act on the throttle piston. This makes the installation of a weaker spring possible, because of which smaller output losses arise.
Finally, in accordance with a more preferred embodiment it is advantageous to influence the start of the movement of the throttle piston, and thus the characteristic conveyed flow curve, by means of a narrow bore in the control plate. A part of the conveyed amount can be diverted toward the pressure chamber in this way.
An exemplary embodiment of the inven
REFERENCES:
patent: 2839003 (1958-06-01), Thrap et al.
patent: 4473341 (1984-09-01), Ohe et al.
Thorpe Timothy
Tyler Cheryl J.
ZF Friedrichshafen AG.
LandOfFree
Regulating device for displacement pumps does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Regulating device for displacement pumps, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Regulating device for displacement pumps will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1617388