Pilot-control electromagnetic valve

Abstract

The invention relates to a valve, in particular a proportional valve, comprising a main plunger for controlling a main volume flow and comprising a pilot-control plunger (12) for controlling a pilot-control volume flow, wherein the main and pilot-control plungers (12) are longitudinally moveably guided in a valve housing (14), and the pilot-control plunger (12) can be actuated by a magnetic device, wherein the position of the main plunger can be adjusted by the pilot-control plunger (12) in that a fluid pressure at the main plunger is communicated, via a fluid connection (18), into the pilot control chamber (20) containing the pilot-control piston (12), which keeps the main plunger in its closed position blocking the main volume flow when the magnetic device is not actuated, and wherein, when the magnetic device is actuated, the pilot-control plunger (12) moves into a position in which the fluid pressure, decoupled from the pressure supply via the main plunger, falls in the pilot-control chamber (20) until the main plunger moves into an open position controlling the main volume flow.

Description

[0001] Pilot-operated solenoid valve

[0002] The invention relates to a valve, in particular a proportional valve, with a main piston for controlling a main volume flow and with a pilot piston for controlling a pilot volume flow, wherein the main and pilot pistons are guided longitudinally displaceably in a valve housing and wherein the pilot piston can be actuated by means of a magnetic device.

[0003] From DE 103 23 595 A1 a valve is known, in particular in the form of a proportional seat valve or slide valve, with a valve housing and at least three fluid connections passing through the valve housing as well as with a main piston guided in the valve housing and a

[0004] A pilot control piston that provides pilot control and is controllable by means of an energizable magnetic device, wherein, when the pilot control is open, fluid flows from one of the two ports controllable by the main piston via a cross-sectional constriction in the main piston and the pilot control to the third port controllable by the pilot piston, and wherein, due to the resulting pressure drop, the main piston moves into a control position, each of the two fluid ports controllable by the fluid quantity. EP 2 880 315 B1 discloses a valve, in particular a pilot-operated proportional directional seat valve, comprising a valve housing having a fluid inlet and a fluid outlet, wherein the fluid flow between this inlet and outlet is controllable by a main piston, wherein a pilot valve chamber is provided on a rear side of the main piston, with a pilot valve closing member movable by an actuating device,with which the fluid flow between the pilot valve chamber and the fluid outlet can be regulated, wherein an inlet orifice is arranged between the fluid inlet and the pilot valve chamber, wherein the opening cross-section of the inlet orifice can be reduced by a control element, wherein the inlet orifice has a plurality of orifice bores, wherein the opening cross-section of at least one of the orifice bores can be reduced by the control element, and wherein the splitting of the inlet orifice into a plurality of orifice bores makes it possible to switch the inlet orifice into a plurality of opening stages.

[0005] Pilot-operated directional valves with electro-hydraulic actuation control the start, stop, and direction of a volume flow, as well as the speed, acceleration, and deceleration of a hydraulic consumer connected to the valve, for example, in the form of a hydraulic working cylinder. Pilot-operated directional valves are generally used where large volume flows need to be controlled with low flow losses. However, low flow losses at high volume flows mean large opening cross-sections and thus large strokes of the main piston. Malfunctions that impair valve function are the flow and friction forces that counteract the switching movement, which depend on the volume flow and pressure differential, i.e., the valve performance. Particularly with mechanical actuation by a spring, usually in the form of a return spring, the rated value of the spring force can be too small compared to the friction force required to return the spool.To meet these requirements for the solenoid system in terms of stroke and force, the solenoid system would either have to be dimensioned accordingly or the valve would have to be hydraulically piloted. As shown above, valves for such applications are known in the state of the art that therefore necessarily require hydraulic pilot control.

[0006] Based on this prior art, the invention seeks to further improve the functional behavior of known valves. This object is achieved by a valve having the features of patent claim 1 in its entirety.

[0007] Because, according to the characterizing part of patent claim 1, the position of the main piston can be adjusted by means of the pilot control piston, in which a fluid pressure acting on the main piston is reported via a fluid connection into a pilot control chamber with the pilot control piston, which, when the magnetic device is not actuated, holds the main piston in its closed position which prevents the main volume flow, and that, when the magnetic device is actuated, the pilot control piston moves into a position in which the fluid pressure, decoupled from the pressure supply via the main piston, in the pilot control chamber falls until the main piston reaches an open position which regulates the main volume flow, an overall improved control quality is created with low pressure losses and avoidance of leaks during operation of the valve according to the invention.

[0008] With the valve solution according to the invention, a linear adjustment of the position of the main piston is achieved via the magnetic force of the magnetic device, while simultaneously compensating for any flow force and sealing friction on the main piston. In this case, it is advantageous that the pilot piston moves against the force (F Federl ) of an energy storage device from the force (F Magnet ) of the magnetic device, taking into account a friction force (F Reib ) the pilot piston is essentially pressure balanced, in which the following applies:

[0009] ^Magnet - ^Federi - F Reib =0- Since the pilot piston is in equilibrium during the opening movement of the main piston to control the main flow between two possible fluid connection points in the valve housing, the stroke of the main piston can be adjusted via the pilot control. This has no equivalent in the state of the art.

[0010] Further advantageous embodiments of the valve according to the invention are the subject of the dependent claims. It is particularly advantageous if the main piston is coupled to a position measuring device for detecting its position. Due to the advantageous control of the main piston via the pilot piston, the valve according to the invention requires a correspondingly small-sized magnetic device with reduced opening cross-sections in the range of the volume flows to be controlled, which requires only small strokes of the main piston. This results in a highly dynamic proportional throttle valve.

[0011] In the following, the valve according to the invention is explained in more detail using an embodiment according to the figures. In principle and not to scale, the longitudinal sections show the

[0012] Figure 1 essential components of the valve;

[0013] Figure 2 in a closed valve position, the front part of the valve according to Figure 1; and

[0014] Figure 3 shows a representation corresponding to Figure 2 with the valve open. The valve shown in the figures is a so-called proportional valve and has a main piston 10 for controlling a main volume flow. Furthermore, a pilot piston 12 is provided for controlling a pilot volume flow, with the main piston 10 and the pilot piston 12 being jointly guided for longitudinal movement in a valve housing 14. As can be seen in particular from Figure 1, the pilot piston 12 is arranged for movement in the valve housing 14 by means of a magnetic device 16.

[0015] The position of the main piston 10 is adjustable by means of the pilot control piston 12, in which a fluid pressure acting on the main piston 10 is reported via a fluid connection 18 into a pilot control chamber 20 with the pilot control piston 12, which, when the magnetic device 16 is not actuated, holds the main piston 10 in its closed position which prevents the main volume flow, as is shown in Figure 2, wherein, when the magnetic device 16 is actuated, the pilot control piston 12 moves into a position in which the fluid pressure, decoupled from the pressure supply via the main piston 10, in the pilot control chamber 20 falls until the main piston 10 reaches an open position which regulates the main volume flow, as is shown in Figures 1 and 3 as an example for one of the possible open positions.

[0016] The pilot piston 12 is against the force F Federlan energy storage device in the form of a compression spring 22 can be actuated by the opposing force ^Magnet of the magnetic device 16, taking into account a friction force F fiejö for the valve, the pilot piston 12 is essentially pressure balanced, in which: F Magnet “ F Spring “ F Friction — 0 or

[0017] The opposing forces F Feder j und F Magnetare indicated in Figure 3 by force arrows 26 and 28, respectively. As can also be seen from the figures, the pilot piston 12 is designed as a hollow piston, which has a first recess 30 on its outer circumference in the manner of an annular groove, which, when the magnetic device 16 is not actuated, establishes the fluid-carrying connection to the main piston 10, as shown in Figure 2.The pilot control piston 12, designed as a hollow piston, has a fluid-carrying channel 32 along its inner circumference, which opens into the pilot control chamber 20 with one free end 34 and which opens into a second annular groove-like recess 38 on the outer circumference of the hollow or pilot control piston 12 via a radially extending channel section 36 of this axially extending channel 32. When the magnetic device 16 is actuated, the second annular groove-like recess 38, as shown in Figures 1 and 3, moves into a tank connection 40 in the valve housing 14 in such a way that a fluid-carrying connection to the tank connection 40 is established, but the first recess 30 is separated from the fluid-carrying connection to the main piston 10. Both the channel section 36 and the tank connection 40 can, as shown, be present in multiple copies.In any case, a changeover valve 42 is connected to the fluid-carrying connection between the main piston 10 and the pilot control chamber 20, which transfers the higher pressure from two fluid connections 44, 46 in the valve housing 14, via which the main volume flow to be controlled is guided, into the pilot control chamber 20 as a signal pressure.

[0018] If the fluid pressure at the fluid connection 44 is greater than at the fluid connection 46, fluid with this higher pressure passes via the fluid connection 44 and a longitudinal channel 50 in the front area of ​​the main piston 10 to the changeover valve 42 with its closing ball 48. The closing ball 48 in question is moved to the right as viewed in the direction of the figures and in doing so closes a radial channel 52 introduced into the main piston 10, which opens into the fluid connection 46 in the valve housing 14. The valve chamber 54 of the changeover valve 42 is in turn connected to a further longitudinal channel 56 in the main piston 10, the free front end of which opens into a fluid chamber 58 in the main piston 10.The fluid chamber 58 is connected to a further fluid chamber 62, which is designed as an annular chamber and is arranged between the valve housing 14 and the main piston 10, via two connecting channels 60 in the main piston 10, which are arranged at an oblique angle of 45° to the longitudinal axis of the valve.Following this, the further fluid chamber 62 merges into an annular chamber 64 arranged in the valve housing 14, and from there a longitudinal channel section 66 leads into a further annular space 67 and then merges into a transverse channel part 68 in the valve housing 14, which has a wider cross-section at its inner end, towards the pilot piston 12, and which, as shown in Figure 2, can be brought into fluid coverage with the annular first recess 30 on the outer circumference of the pilot piston 12, wherein, as shown in Figures 1 and 3, the relevant fluid-conducting connection can be blocked by moving the pilot piston 12 from right to left under the action of the magnetic device 16. It is understood that the respective channels and other connections, as shown, can be accommodated multiple times on the valve body as required.In any case, components 50, 52, 54, 56, 58, 60, 62, 64, 66, 67, 68, and 30 form the fluid connection 18 between the fluid port 44 on the front side of the main piston 10 and the pilot chamber 20 between the main control piston 10 and the pilot piston 12. Thus, the pressure at the fluid port 44 is transmitted or forwarded to the pilot chamber 20 in the closed valve position of the main piston 10.

[0019] If the pressure at the radial connection 46, the additional fluid connection in the valve housing 14, is greater than at the fluid connection 44, as viewed in the direction of the figures, the changeover valve 42 is switched, with the closing ball 48 now assuming its left-hand closed position, closing the channel 50. In this way, fluid at a predeterminable pressure reaches the valve chamber 54 via the fluid connection 46 and the radial channel 52 into the additional longitudinal channel 56, so that the remaining fluid connection 18 to the pilot control chamber 20 is now released via this path. Typically, a fluid pressure from a pressure supply device, such as a hydraulic pump, should be present at the fluid connection 44, and a hydraulic consumer, such as a hydraulic cylinder, should be connected to the fluid connection. Other assignments of the fluid connections 44, 46 are conceivable.

[0020] As can be seen from the figures, the main piston 10 is composed of two components 70, 72, wherein these components, with their mutually facing free end faces, delimit the fluid chamber 58 as seen in the axial displacement direction of the valve pistons 10, 12. A second compression spring 74 acts as a further energy storage device on the free end face of the second component 72, which faces the magnetic device 16. The second compression spring 74, which is supported with its other free end on stationary parts of the valve housing 14, is arranged on the inner circumference of the second compression spring 74 and coaxial with it. The compression spring 22 extends, with one free end supported on a shoulder-shaped interior of the second component 72 and its other free end supported on an annular projection 76 on the pilot piston 12.In this way, both the main piston 10 and the pilot piston 12 are preloaded via the two compression springs 22, 74, whose spring force together amounts to the amount.

[0021] Fl Feder + (x * c) in the above formula.

[0022] The following describes how the movement of the main piston 10 is controlled. The movement of the main piston 10, as viewed in the direction of Figure 2, to the right in a state as shown in Figures 1 and 3, occurs as follows. The pressure present at the respective fluid connection 44 or 46 in front of the main piston 10, which is reported to the pilot piston 12 via the changeover valve 42 and the fluid connection 18, holds the main piston 10 closed by the pressure in the pilot chamber 20 as shown in Figure 2 when the magnetic device 16 is de-energized, via the area difference formed by the opposite end faces of the main piston 10.

[0023] If a force is now generated by the magnetic device 16, when the magnetic force is greater than the frictional force plus the spring force, the pilot piston 12 is moved to the left in the direction of the figures, and the resulting movement of the pilot piston 12 to the left closes off the pressure supply from the main piston 10, in which, as shown in Figures 1 and 3, the closed outer circumference of the pilot piston 12 closes the transverse channel part 68 in the valve housing 14. In the resulting closed position, however, the pilot chamber 20 is connected via the second recess 38 of the fluid-carrying channel 32 in the pilot piston 12 to the tank via the two tank connection bores 40 running radially in the valve housing 14, which at their respective free ends open into a recessed annular channel 78 on the outer circumference of the pilot piston 12 in each of its travel positions.This annular channel 78 transitions into a relief chamber 80, which is controlled to expand in volume as soon as the pilot control piston 12 moves to the left, establishing the fluid-carrying connection from the pilot control chamber 20 via the fluid-carrying components 32, 36, 80, 78 to the respective tank connection 40. Due to the resulting connection of the pilot control volume to the tank, the pressure in the pilot control chamber 20 drops, and a new equilibrium is established at the valve until the valve is completely closed. In particular, the following overall situation arises: The magnetic force is reduced, so that the pilot control piston 12 opens the connection for the pressure supply to the main piston 10. This increases the pilot pressure and thus also the pressure force in the pilot control chamber 20.This causes the main piston 10 to move from right to left again, which results in the spring force of the compression springs 22 and 74 decreasing, so that a new equilibrium is established according to the following formula:.

[0024] ^Magnet “ F Spring 1 “ ^Friction — ^Magnet - (F -Spring + X * c ) — FR e jb = 0.

[0025] The solenoid device 16 is used to actuate the pilot control piston 12 and usually has an energizable coil 81 which moves a solenoid armature 82 from right to left in the energized state, whereby the solenoid armature 82 drives the pilot control piston 12 in a correspondingly positively guided manner via a hollow actuating rod 84 and a coupling 86. For an unhindered movement of the pilot piston 12, it is provided, among other things, that the clutch 86, which is freely movable in a clutch chamber 88 of the valve housing 14, is fluidly connected to the fluid-carrying channel 32 via radial transverse bores 90, so that the pressure in the pilot chamber 20 is also present in the clutch chamber 88 via the channel 32 and the transverse bores 90 (Figure 3), which is passed on in a pressure-compensating manner to the magnetic system of the actuating magnet, in the form of the magnetic device 16, via the hollow actuating rod 84 on the outer circumference and on the inner circumference.The said component 86 is a kind of dead space 89 on the left as viewed in Fig. 2.

[0026] This chamber 89 is filled or emptied via at least one bore 91 in the component 86, so that the dynamics or damping of the valve can be adjusted via the respective bore 91 in the component 86.

[0027] Furthermore, on the second component 72 of the main piston 10, a

[0028] Measuring rod 92 is fixedly arranged, which passes through both the pilot piston 12 and the actuating magnet system in order to open with its other free end region into a position measuring device designated as a whole by 94, which is provided with two measuring coils 96 and can measure the travel movement for the main piston 10 in both directions.

[0029] Such a displacement measuring system is disclosed as an example for a pressure compensator in DE 10 2012 014 250 A1.

[0030] Furthermore, the main piston 10, as shown in particular in the illustration according to Figure 2, has on its free end face a spherically shaped end face 98, formed from a predeterminable radius, which serves to establish a linear relationship between the stroke of the main piston 10 and the opening area generated by it at the fluid connections 44 or 46. Otherwise, the main piston 10 is guided longitudinally movable on the inner circumferential side of the valve housing 14 via stepped annular surfaces, and individual sealing ring systems, regularly in

[0031] Form of O-rings, ensure a fluid-tight demarcation of the individual fluid spaces and fluid sections as specified above.

Claims

Patent claims for a valve, in particular a proportional valve, with a main piston (10) for controlling a main volume flow and with a pilot piston (12) for controlling a pilot volume flow, wherein the main (10) and pilot pistons (12) are guided longitudinally in a valve housing (14) and wherein the pilot piston (12) can be actuated by means of a magnetic device (16), characterized in that the position of a main piston (10) is adjustable by means of a pilot piston (12) in which a (10) The applied fluid pressure is reported via a fluid connection (18) to a pilot chamber (20) with the pilot piston (12), which, when the solenoid device (16) is not actuated, holds the main piston (10) in its closed position, thus preventing the main volume flow, and that, when the solenoid device (16) is actuated, the pilot piston (12) moves to a position in which the fluid pressure, decoupled from the pressure supply via the main piston (10), falls in the pilot chamber (20) until the main piston (10) reaches an opening position that regulates the main volume flow. Valve according to claim 1, characterized in that the pilot piston (12) moves against the force (F) Federl ) of an energy storage device from the force (F Magnet ) the magnetic device (16) can be actuated, taking into account a frictional force (F Reib ) the pilot piston (12) is essentially pressure-balanced, in which the magnet applies Valve according to claim 1 or 2, characterized in that the pilot piston (12) is designed as a hollow piston which has a first recess (30) on its outer circumference which, when the magnetic device (16) is not actuated, forms the fluid-carrying connection to the The main piston (10) forms a fluid-carrying channel (32) with its inner circumference, the free end (34) of which opens into the pilot chamber (20) and which, via a channel section (36) of this channel (32), opens into a second recess (38) on the outer circumference of the hollow piston. When the solenoid device (16) is actuated, the piston retracts into a tank connection (40) in the valve housing (14) such that the first recess (30) is separated from the fluid-carrying connection to the main piston (10). The valve according to one of the preceding claims is characterized in that a switching valve (42) is connected in the fluid-carrying connection between the main piston (10) and the pilot chamber (20). This switching valve directs the higher pressure from two fluid connections (44, 46) in the valve housing (14), through which the main volume flow is routed, into the pilot chamber (20) as the signal pressure.A valve according to one of the preceding claims, characterized in that a fluid chamber (58) is provided in the main piston (10) as part of the fluid connection (18), which opens via at least one connecting channel (60) in the main piston (10) into a further fluid chamber (62) between the valve housing (14) and the main piston (10), which opens via at least one further connecting channel (64, 66, 67, 68) in the valve housing (14) into the first recess (30) in the pilot piston (12) with at least partial overlap. A valve according to one of the preceding claims, characterized in that at least one further connecting channel (78, 80) is arranged in the pilot piston (12) and in the valve housing (14), by means of which the second recess (38) on the pilot piston (12) can be connected to a tank.

7. Valve according to one of the preceding claims, characterized in that the main piston (10) is held in the direction of its closing position by means of a further energy storage device.

8. Valve according to one of the preceding claims, characterized in that the respective energy storage device is formed from a compression spring (22, 74) and that the compression spring (74) for the main piston (10) has a higher spring stiffness than the compression spring (22) for the pilot piston (12).

9. Valve according to one of the preceding claims, characterized in that the main piston (10) has a radius at least partially convex on its free end face (98) to establish a linear relationship between the stroke of the main piston (10) and the opening area it creates at one of the fluid ports (44, 46) in the valve housing (14).

10. Valve according to one of the preceding claims, characterized in that the pilot piston (12) is penetrated by a measuring rod (92) which is connected to the main piston (10) and is part of a displacement measuring device (94) for the main piston (10).

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