Motors: expansible chamber type – With motive fluid valve – Both inlet and exhaust controlled by motive fluid pressure...
Patent
1995-06-02
1997-08-26
Lopez, F. Daniel
Motors: expansible chamber type
With motive fluid valve
Both inlet and exhaust controlled by motive fluid pressure...
91446, F15B 1110
Patent
active
056600968
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a controlled proportional valve with a main slide valve section containing a main slide valve, which section controls a flow of fluid between a pump connection connected to a pump and a tank connection connected to a tank and two work connections connected to a load and which generates a load-sensing signal in dependence on the pressures at the work connections, and with a compensating slide valve section which controls the pressure across the main slide valve section in dependence on the load-sensing signal.
EP 0 411 151 A1 describes a proportional valve of that kind in which the load-sensing signal acts on one side of a compensating slide valve. The pump pressure also acts on that side. The pressure at the output of the compensating slide valve and an auxiliary pressure changeable between two positions acts on the opposite side of the compensating slide valve. This creates a constant pressure drop across the main slide valve section. This pressure drop can be changed over between two fixed values. In one case, the main slide valve section operates normally. In the other case, because of a relatively small pressure drop a more precise control is possible, since a more substantial change in the position of the main slide valve must then be made to achieve the same change in the volume flow in the work connections. The load-sensing signal is also additionally fed to a controller, which controls the output of the pump.
DE 34 36 246 C2 discloses a control arrangement for a hydraulically operated load, in which the load-sensing signal is no longer solely dependent on the pressure in the work connections, but is formed partly by the loading pressure and partly by the compensating pressure, that is, the pressure at the output of the compensating slide valve. In the event of fluctuations in the loading, the volume flow is then no longer held constant but drops as the loading increases and increases as the loading decreases. It is intended in this manner to achieve a more rapid damping of the fluctuations. The pressure of the load-sensing signal is produced by a pressure divider, the throttle of which is manually adjustable, in order to be able to achieve optimal adaptation to each given individual case.
JP 2 262 473 A (Abstract) discloses a hydraulic circuit in which a compensating slide valve is also controlled in dependence on a load-sensing signal. This load-sensing signal is also responsible for regulating the pump output. Part of the load-sensing signal can be tapped off and supplied to the other side of the compensating slide valve.
The present invention is based on the problem of achieving rapid response of the proportional valve, wherein it is desirable for the control means used for that purpose to be capable of being retrofitted in existing proportional valves.
This problem is solved in a controlled proportional valve of the kind mentioned in the introduction in that a control arrangement which controls the pressure of the load-sensing signal to influence the actual volume flow and/or the actual pressure in the work connections is provided.
By changing the load-sensing signal, the differential pressure across the main slide valve section can be influenced. In this way, the volume flow through the main slide valve section is influenced, without the position of the main slide valve having to be changed. Of course, the volume flow can also still be influenced by a change in the position of the main slide valve. Thus, instead of a characteristic that indicates the dependency of the volume flow on the position of the main slide valve, a working range or characteristic range is obtained, since, in addition to the opening formed by the main slide valve, the pressure can also be used for control of the volume flow. When the volume flow requirement is small, the differential pressure across the main slide valve section can be reduced, which results in a marked reduction in power loss and thus in an increase in efficiency. When a higher volume flow is required, it was previously necessary
REFERENCES:
patent: 4020867 (1977-05-01), Sumiyoshi
patent: 5203678 (1993-04-01), Sugiyama et al.
Danfoss A/S
Lopez F. Daniel
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