The invention relates to a device consisting of at least one regulating piston, which is guided longitudinally movably in a housing having at least two ports for fluid, and which interacts with a control edge of the housing at a port, which supplies the other port with fluid in regulating positions of the regulating piston via a fluid connection while aiming at pulling [the piston] in the direction of a closing position blocking this fluid connection due to occurring flow forces.
From DE 10 2014 004 796 A1 a proportional pressure regulating valve is known having a generic device having a longitudinally movable regulating piston guided in a valve housing, which piston is used to selectively connect ports present in the valve housing, such as a
So-called flow forces act on this regulating process, due to the existing pressures and the volume flows to be managed at the ports, acting on the valve piston or regulating piston of the device, wherein these flow forces are regularly caused by a pressure drop at the assignable control edge or regulating edge in the housing, for example, in the range of a pump supply connection or pressure supply connection (P) for the load port (A), wherein this pressure drop causes a force in the direction of the device connected to the solenoid operating system, which aims at moving the regulating piston in the direction of its closed position, which further reduces the pre-defined pressure.
For certain applications, such as in coupling applications, however, a quick “filling” of the coupling is necessary for their targeted operation, i.e. controlled valves of this type are generally not particularly suitable. This can be remedied by the use of so-called pilot operated valves (DE 10 2012 015 356 A1), these valves show an increased leakage due to the pilot oil flowing toward the tank or return, however, resulting in increased power losses. Another option is increasing the magnetic force of the solenoid operating system, which increases the space requirement and results in increased costs both in the production and in the operation of the valve.
Based on this prior art, the present invention addresses the problem of providing a device which is particularly suitable to be used in pressure regulating proportional valves and does not have the disadvantages described above and can be produced and operated inexpensively and is of compact design. A device having the features of claim 1 in its entirety solves this problem.
Because, according to the characterizing part, the regulating piston changes its shape from its basic outer cylindrical shape in the area of the control edge of the housing, for a flow force compensation such that an effective flow surface for fluid is created, which causes a compensating force on the regulating piston against the flow force, which aims at pulling the regulating piston into an open position opposite to the locking position, a counterforce to the flow force is generated in the operation of the device according to the force formula F=P×A.
As the control edge or regulating edge is “shifted” and the fluid pressure on the change in shape in the form of a circular ring on the regulating piston as a compensation surface regularly remains constant, the flow force still acts in the direction of the solenoid operating system, but at the same time the newly generated counterforce acts as flow force compensation on the regulating piston via the surface or change in shape in the direction of one of the ports in the housing, in particular in the form of a load port. In this way it is possible to reduce the flow forces occurring during the operation of the device or the valve in a structurally simple and cost-effective manner. Advantageously, in the device according to the invention, therefore, the inlet pressure is used to compensate the flow force. The pressure level occurring there is generally higher than that on the return side of the device, such that larger volume flows can be more easily managed in a regulating manner. Advantageously, the fluid flowing through the device is deflected by 90° in the area of the control edge or regulating edge and the change in shape in the regulating piston such that the fluid impulse occurring can rest against the whole area of the change in shape or the compensating surface thus created.
If the device according to the invention is used in an advantageous manner for a directly controlled valve, the flow force compensation produced in this way permits the use of smaller solenoid operating systems, which regularly show an improved, prompt actuation behavior.
Further advantageous embodiments of the solution according to the invention are the subject of the other dependent claims.
Below, the device according to the invention will be presented in more detail based on an application for a 3-way pressure control proportional valve. In the schematic figures, which are not to scale,
The solenoid 14 has a coil winding 16 in a coil body 18 as customary and therefore not described in greater detail, wherein the coil winding 16 of the operating coil can be supplied with a control current via a connector part 20. In the direction of the valve housing 10, the coil body 18 adjoins a pole plate 22, the free end face of which is encompassed by a flange plate 24, which is to mount the pressure regulating valve to a valve block, not shown. In that way the pressure regulating valve shown in
A magnet armature 26, which has a pressure equalization channel 28, is guided longitudinally movably in the coil body 18 to allow an obstacle-free reciprocating motion of the armature 26 in the solenoid in a pressure-balanced manner. Viewed in the direction of
In the displacement position of the regulating piston 12 shown in
In the pertinent position of the regulating piston 12, the load port A is connected to the tank or return port T via a groove 38 in the regulating piston 12 in a fluid-conveying manner, which groove is permanently connected to the fluid chamber 36 in a fluid-conveying manner and the axial length of which is smaller than the length of the inner wall area of the valve housing 10 between the port P and the port T. In this position, the pressure supply port P is disconnected from the load port A because the regulating piston 12 has passed over the control edge or regulating edge 34; a displacement position, as is apparent from
In the de-energized state, therefore, the pressure supply or pump port P is closed and the load port A is connected to the tank port or return port T. If a current signal is then applied to the coil winding 16 of the solenoid 14 via the connector part 20, the solenoid 14 presses on the regulating piston 12 in the direction of the load connection A with a force corresponding to the magnitude of the control current. As a result, the regulating piston 12 is moved to the right against the return spring 32 and the fluid (oil) flows from the pressure supply port or pump port P to the load port A. Depending on the type of load, not shown, for example in the form of a motor vehicle clutch, a counter pressure then builds up at the load port A, which acts on the surface of the regulating piston at the valve and generates a counterforce to the magnetic force of the solenoid, which moves the regulating piston 12 back into the opposite direction of control. In this way, the inflow from the pressure supply or pump connection P to the load port A is reduced until the pressure applied to the load port A corresponds to the magnetic force and thus to the pressure value specification based on the current signal.
If the load now no longer requires pressurized fluid, as is the case when the clutch is at the stop, the cylindrical regulating piston 12 moves further back and closes the drilled inlet holes 40 of the pressure supply or pump port P as shown in the prior art
Owing to pressure flow and volume flow acting on the regulating piston 12, so-called flow forces also act on this regulating process. These flow forces cause a pressure drop at the control edge or regulating edge 34 (cf.
This is where the invention comes in, which generates a counterforce to the flow force due to its structural design, which will be explained in more detail below, in particular with reference to the illustration of
As is apparent in particular from the illustration according to
The change in shape 48 consists in particular of a discontinuity in diameter, preferably of an offset 56 in the regulating piston 12, which is set back from a free end face 58 of the regulating piston 12 in the region of its groove 38 away from the latter in the direction of the port A. The effective flow surface 52 forms an annular surface and is arranged in abutment with the control edge or regulating edge 34 in a regulating position of the housing 19 or in its extension, wherein the fluid connection between the two ports P, A is actuated.
The change in shape 48 in the regulating piston 12 forms an annular fluid control chamber 60, which during regulating operation is subject to a lower fluid pressure on the return side 62 of the device than the pressure present at the port P in the valve housing 10, wherein the respective pressures to be actuated are greater than the tank pressure or the ambient pressure.
As can be further seen from the illustration according to
According to the invention, the discontinuity in diameter in the form of the step 56 is formed by two different diameters in the regulating piston 12, the smaller diameter opening into the recess or channel 38 in the regulating piston 12 mentioned above.
To compensate for the flow force by a counterforce, a surface 52 has been added to the regulating piston 12, below the control edge or regulating edge 34. In this arrangement the input pressure at the pump port or pressure supply port P can be used to compensate for the flow force. The surface 52 at the port P can be used to generate the counterforce to the flow force according to the force formula F=P×A. Because the control edge or regulating edge 34 is “shifted” in this way but the pressure on the annulus 52 remains constant, the flow force continues to act in the direction of the solenoid 14, the newly generated counterforce [acts] via the surface 52 at the regulating piston 12 in the direction of load port A, however. Thus, while the flow force tries to pull the regulating piston 12 in a closed position, the counterforce generated counteracts by moving or pulling the regulating piston 12 to an opening position. The associated horizontal pressure characteristic curve is reproduced in
The device according to the invention does not need to be limited to applications using direct-controlled compact pressure regulators, such as the proposed valve. Such a flow force management in the way of compensation can also be easily implemented using slide valves. Furthermore, two ports, which are to be connected to each other in a fluid-conveying manner in a regulating manner, are sufficient to be able to perform the flow-force compensation in the frame outlined. In that regard, the device according to the invention can basically be applied anywhere where ports are to be connected to each other and separated again in a regulatory manner in a fluid-conveying manner via a regulating piston. In particular, by using the flow force compensation according to the invention, solenoids can be built more compactly, which improves the actuation behavior and helps to save costs and installation space. This is without parallel in the prior art.
Number | Date | Country | Kind |
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10 2016 007 881.2 | Jun 2016 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2017/000707 | 6/19/2017 | WO | 00 |