A valve, in particular a proportional pressure regulating valve, having a spring-loaded valve piston which is guided in a longitudinally displaceable manner and in a manner actuated by an energizable actuating magnet within a valve housing and which, dependent on its displacement position, establishes or shuts off again a fluid-conducting connection between a pump connection and a working connection and between this working connection and a tank connection in the valve housing, wherein those faces sides of the valve piston which are situated opposite one another are permanently pressurized with the pressure of the tank connection and wherein the valve piston has a pressure-active regulation surface, which can be connected in a fluid-conducting manner to the working connection for the generation of the regulation pressure, and having an annular space in the valve housing, into which annular space the working connection opens in a radial or axial direction.
Such valves are already known. For example, document DE 10 2005 022 693 A1 relates to a valve, in particular a proportional pressure limitation valve, having an electrically actuatable magnet system for the actuation of an actuation part, which cooperates with a valve element, which is guided in a longitudinally displaceable manner in a valve housing and which, in one of its opening positions, releases a fluid-conducting connection path between a fluid inlet and a fluid outlet and which, in its shut position, shuts off said path, wherein an energy store, preferably in the form of a compression spring, is arranged between the actuation part and the valve element at a clearance therefrom, which energy store seeks to hold the valve element in the direction of its closed position, and wherein the actuation part is designed as a guide piston, which has a longitudinal guide for the valve element. The known solution ensures that the valve element with its closure part, which, preferably having a seat design, cooperates with a valve seat in the valve housing, always arrives at its envisaged closed position in an axis-precise manner, so that any angular displacement with leakage in the region of the valve seat is reliably prevented. The known valve in principle functions in a force-controlled manner, and any undesirable dynamic effects occurring during operation of the valve are compensated for by the energy store in the form of the compensation spring.
Another valve in the form of a typical proportional pressure regulating valve is disclosed by document DE 10 2013 014 558 A1. Because, in this known valve solution, the respective differential pressure, which is generated during passage through the additional fluid-conducting connection between the utility connection and the tank connection, acts by means of an actuating device on the valve piston in such a way that said valve piston, counteracting a stop position, from which position the additional fluid-conducting connection is increasingly inhibited, passes into a fully opened open position in which, relative to the stop position, an enlarged opening cross section from the utility connection to the tank connection is achieved, an opportunity is thus created to increase the valve piston stroke without having to tolerate the start-up jump of the so-called P-I characteristic curve. The known valve can thus generate a very large opening cross section when releasing a clutch which is connected to the valve, and nevertheless ensure a rapid disengagement of the clutch. In this way, the clutch of a vehicle for example can be smoothly released, which represents a significant safety aspect, in particular in the case of mobile work machines.
Such proportional pressure regulating valves can be designed such that they generate the maximum regulation pressure without energizing of the actuating magnet system, and in technical terms this is expressed as these valves having a so-called failsafe characteristic curve. With increasing current at the actuating magnet, the regulation pressure drops in a continuous manner, and they are therefore frequently used for applications in which, in the case of a power outage, a safe state is obtained only when the maximum regulation pressure is applied at the consumer. It is thus possible for example to actuate clutches which are pressurized in a de-energized manner. As a general rule however, such valves are very frequently equipped with a pilot control.
On the basis of this prior art, the problem addressed by the invention is to realize, preferably in a cost-effective manner, a proportional pressure regulator with a so-called falling characteristic curve. This problem is solved by a valve having the features of claim 1 in its entirety.
Because, in accordance with the characterizing part of claim 1, the pressure-active regulation surface is formed on the valve piston at the transition point between the annular space and the mouth of the working connection in such a way that, in the de-energized state of the actuating magnet, a maximum regulation pressure can be generated, in which a respective adjustment state is produced between the force of a compression spring of the spring-loaded valve piston and the regulation pressure applied at the regulation surface of the valve piston, the regulation pressure of the valve drops linearly over a settable pressure range with increasing energizing of the actuating magnet system. The valve according to the invention is therefore a solution in which a failsafe pressure regulator is realized in a directly controlled manner.
The regulation pressure is measured only at a diameter jump, which forms a pressure-active regulation surface on the regulation piston or valve piston and namely in the region of the respective working connection in the valve housing. All other piston face sides of the valve piston or regulation piston are by contrast essentially pressurized with the tank pressure. In a de-energized manner, a kind of equilibrium is thus obtained between the spring force of the to this extent spring-loaded valve piston and the regulation pressure applied at the circular ring in the form of the diameter jump on the valve piston. If the actuating magnet system is energized, then a portion of said spring force that increases with increasing current is compensated for by the magnetic force of the actuating magnet system and the regulation pressure drops in a preferably linear manner. In order to realize the solution according to the invention, in a particularly preferable manner, a cost-effectively realizable, so-called oppressive magnet system can preferably be used.
The valve solution according to the invention is explained in detail below with reference to two exemplary embodiments according to the drawings. In said drawings, in schematic and not to scale depictions,
As can also be seen from
A compression spring 30 serves for the spring loading of the valve piston, which compression spring is conically tapered upwards when viewed in the viewing direction of
Viewed in the viewing direction of
The actuating magnet 14 has a coil winding 46 in a manner which is standard and therefore not described in detail, which coil winding can be energized from the outside via a connector part 48. The entire actuating magnet 14 is encapsulated in a pressure-tight manner by means of a housing part 50, and on the inside a longitudinally displaceable keeper 52 is provided, which acts via an operating plunger 54 having direct contact directly on the valve piston 10. The actuating magnet 14 is designed as a so-called oppressive magnet, i.e., when the coil winding 46 is energized, the keeper 52 travels, viewed in the viewing direction of
The regulation pressure PR is measured at the diameter jump at the valve piston 10 in the form of the regulation surface 44, with all other piston face sides being pressurized with the tank pressure. If the actuating magnet 14 is de-energized, a balance is thus obtained between the compression spring 30 and the regulation pressure PR applied at the circular ring, or the regulation surface 44. If the coil winding 46 is now energized, then a portion of the compression spring that increases with increasing current is compensated for by the magnetic force of the actuating magnet 14, and the regulation pressure PR drops, as is depicted in
The valve solution according to the invention thus makes it possible to realize in a cost-effective manner a proportional pressure regulator with a falling characteristic curve according to the exemplary depiction of
The additional embodiment of the valve according to the invention in accordance with
In the embodiment according to
Also in the present exemplary embodiment, the central channel 16 of the hollow piston as a valve piston 10 opens in the radial direction into the transverse channel 18, which is in turn delimited inside the valve piston 10 towards the outside by an annular groove 19. This transverse channel 18 with the annular groove 19 is again arranged in the exemplary embodiment according to
The longitudinal channel 60 is arranged for the purpose of its production as an overall longitudinal bore in the valve housing 12, which discharges upwards in the direction of the spring space 40, with it being closed in a pressure-tight manner in this discharge region by means of a blind plug 62. Because, in principle, the valve piston 10 is only actuated by the regulation pressure PR at the regulation surface 44, it can act very promptly in a regulating manner on a hydraulic control circuit, so that regulating delays or switching delays during operation of the valve are avoided.
Number | Date | Country | Kind |
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10 2015 006 099.6 | May 2015 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2016/000074 | 1/15/2016 | WO | 00 |