Valve

Abstract

The utility model relates to a valve, in particular to a proportional valve, which is provided with a main piston (10) for controlling the volume flow of a main body and a pilot control piston (12) for controlling the volume flow of pilot control, the main piston (10) and the pilot control piston (12) can be guided in a valve shell (14) in a longitudinal movement manner, and the pilot control piston (12) can be controlled by means of a magnet device (16). The utility model is characterized in that the position of the main piston (10) can be adjusted by means of the pilot control piston (12) in such a way that a fluid pressure acting on the main piston (10) is transmitted via a fluid connection (18) into a pilot control chamber (20) having the pilot control piston (12), the pilot control piston holds the main piston (10) in its closed position that blocks the volume flow of the main body in an actuation position when the magnet arrangement (16) is actuated, and the pilot control piston (12) in an initial position when the magnet arrangement is not actuated, in this position, the fluid pressure decreases in the pilot control chamber (20) in the direction of the tank side (T) in a decoupled manner from the pressure supply via the main piston (10) until the main piston (10) reaches an open position which regulates the volume flow of the main body.

Description

Technical Field

[0001] The utility model relates to a valve, in particular a proportional valve, which has a main piston for controlling the main volume flow rate and a pilot control piston for controlling the pilot control volume flow rate. The main piston and the pilot control piston are guided longitudinally movable in the valve housing, and the pilot control piston can be actuated by means of a magnet device. Background Art

[0002] A valve, in particular a valve in the form of a proportional seat valve or a spool valve, is known from DE10323595A1. The valve has a valve housing and at least three fluid interfaces passing through the valve housing, and has a main piston guided in the valve housing and a pilot control piston for realizing pilot control. The pilot control piston can be actuated by means of an energizable magnet device. When the pilot control device is opened, fluid flows from one of the two interfaces controllable by the main piston through a cross-sectional constriction in the main piston and the pilot control device to a third interface controllable by the pilot control piston. And due to the resulting pressure drop, the main piston reaches a corresponding control position for controlling the two fluid interfaces by the fluid volume.

[0003] A valve, in particular a pilot-controlled proportional reversing seat valve, is known from EP2880315B1. The valve has a valve housing having a fluid inlet and a fluid outlet. The fluid flow between the inlet and the outlet can be adjusted by a main piston. A pilot control valve chamber is provided on the back side of the main piston. The pilot control valve chamber has a pilot control valve closing member movable by a manipulating device. By means of the pilot control valve closing member, the fluid flow between the pilot control valve chamber and the fluid outlet can be adjusted. An inlet throttle plate is arranged between the fluid inlet and the pilot control valve chamber. The opening cross-section of the inlet throttle plate can be reduced by a control element. The inlet throttle plate has a plurality of throttle holes, and the opening cross-section of at least one of the throttle holes can be reduced by the control element. And dividing the inlet throttle plate into a plurality of throttle holes can realize switching the inlet throttle plate into a plurality of opening levels.

[0004] Such a pilot-controlled directional valve uses electrohydraulic actuation to control the start, stop, and direction of the volumetric flow rate, as well as the speed, acceleration, and deceleration of a hydraulic consumer, such as a hydraulic working cylinder, connected to the valve. The pilot-controlled directional valve is used in principle where large volumetric flow rates are to be controlled with small flow losses. However, small flow losses at high volumetric flow rates mean a large opening cross-section and thus a large stroke of the main piston. The disturbances affecting the valve function are the flow forces and frictional forces that are dependent on the volumetric flow rate and the pressure difference, i.e., the valve power, and act against the switching movement. Especially in the case of mechanical actuation by a spring, usually in the form of a return spring, the measured value of the spring force relative to the frictional force may be too small for returning the piston slide valve. To meet the requirements for the magnet system in terms of stroke and force, the magnet system must either be dimensioned correspondingly large or the valve must be pilot-controlled hydraulically. As shown above, valves known for such application cases in the prior art necessarily have hydraulic pilot control devices. Summary of the Invention

[0005] Starting from the prior art, the object of the present invention is to further improve the known valve in terms of its functional characteristics.

[0006] Due to the characteristic part of the valve according to the invention, the position of the main piston can be adjusted by means of a pilot control piston in such a way that the fluid pressure acting on the main piston is transmitted via a fluid connection structure to a pilot control chamber having the pilot control piston. In the case of actuation of the magnet device, the pilot control piston holds the main piston in its closed position blocking the main volumetric flow rate in the actuated position, and in the case of non-actuation or non-energization of the magnet device, the pilot control piston moves into an initial position in which the fluid pressure drops towards the reservoir side in the pilot control chamber decoupled from the pressure supply via the main piston until the main piston reaches the open position for regulating the main volumetric flow rate. Thus, overall, an improved regulation quality is provided, while reducing the pressure loss and avoiding leakage during operation of the valve according to the invention.

[0007] In a preferred embodiment of the valve according to the invention, it is hereby provided that the magnet device has an actuating magnet acting in a tensile manner, which preferably, in the case of energization, overcomes an accumulator (F 磁体弹簧) serves to move the pilot control piston from its initial position to its actuating position, in which the main piston remains in its closed position. Thus, when de-energized, the pilot control piston is in its initial position facing the front of the main piston, whereby the pilot control chamber is disconnected from the pressure supply device and open towards the reservoir. If a pressure is formed on the main piston at this time on the inlet side, this fluid pressure presses the main piston into the open position and releases the pilot fluid connection structure in order to conduct the main flow between the two fluid connection sites in the valve housing, which fluid guiding connection sites preferably engage axially into the valve housing on the one hand and radially into the valve housing on the other hand. In order to obtain the "open-without-current variant" described in this way, a pull-acting actuating magnet is used instead of a push magnet. This results in a solution for stroke adjustment proportional to the magnetic force (current) by means of a pull-constructed actuating magnet, which actuating magnet produces a valve variant that opens without current and which, for the desired linear adjustment of the position of the main piston by magnetic force, results in a descending linear valve characteristic curve by means of compensation for the flow forces and sealing friction on the main piston.

[0008] In a preferred embodiment of the valve according to the present invention it is hereby specified that, under the action of the force (F 弹簧 ) of the accumulator in combination with the force (F 致动器 ) acting in the same direction of the magnet arrangement, the pilot control piston is placed in its actuating position, and the pilot control piston is substantially pressure-balanced taking into account the frictional force (F 摩擦 ), in such a way that the following applies: F 致动器 - F 弹簧 - F 摩擦 = 0.

[0009] The spring acts on the pull-acting actuating magnet in an operative connection, which spring is designed as a magnet spring and has a force (F 磁 ) similar to the magnetic force (F 磁体弹簧 ) and the resulting resultant force is called actuation (F 致动器 ), with the following formula:

[0010] F 致动器 = F 磁体弹簧 - F 磁 .

[0011] Since the pilot control piston is in force equilibrium during the opening movement of the main piston for controlling the main volume flow between the two feasible fluid connection sites in the valve housing, the stroke of the main piston can thus be adjusted by the pilot control.

[0012] Other advantageous embodiments of the valve according to the present invention are the subject of the dependent claims. Particularly advantageously, the main piston is coupled to a displacement measuring device for detecting its position. Since the main piston is advantageously actuated by the pilot control piston, the valve according to the present invention with a magnet device of correspondingly small dimensions is sufficient within the range of the volume flow rate to be controlled even with a reduced opening cross-section, for which only a small stroke of the main piston is required. In this way, a highly dynamic proportional throttle valve is obtained. Description of the Drawings

[0013] The valve according to the present invention will be described in detail below with reference to the embodiments with the aid of the drawings. In this case, a longitudinal sectional view is shown in principle and not to scale:

[0014] Figure 1 The main components of the valve as a whole are shown;

[0015] Figure 2 The front part of the valve in the closed valve position according to Figure 1 is shown; and

[0016] Figure 3 The view corresponding to Figure 2 when the valve is open is shown. Detailed Description of the Embodiment

[0017] The valve shown in the drawings is a so-called proportional valve and has a main piston 10 for controlling the main volume flow. In addition, there is a pilot control piston 12 for controlling the pilot control volume flow, wherein the main piston 10 and the pilot control piston 12 are guided together longitudinally displaceably in the valve housing 14. As can be seen in particular from Figure 1 the pilot control piston 12 is actuated displaceably in the valve housing 14 by means of a magnet device 16.

[0018] The position of the main piston 10 can be adjusted by means of the pilot control piston 12 in such a way that the fluid pressure acting on the main piston 10 is transmitted via a fluid connection structure 18 into a pilot control chamber 20 having the pilot control piston 12, which pilot control piston holds the main piston 10 in its closed position preventing the main volume flow when the magnet device 16 is actuated, energized (as shown in Figure 2 ), while in the case where the magnet device 16 is not actuated, de-energized, the pilot control piston 12 moves from the energized actuation position shown in Figure 2 to the initial position according to Figure 3 in the viewing direction of the drawing looking to the left, in which the fluid pressure substantially decoupled from the pressure supply provided by the main piston 10 drops continuously in the pilot control chamber 20 until the main piston 10 reaches the open position for adjusting the main volume flow, as shown in Figure 3As shown by way of example in one of the possible opening positions. Whenever the directions "right" and "left" are mentioned, this means the directions seen in the viewing direction of the accompanying drawings.

[0019] The position of the main piston 10 is therefore adjusted by means of the pilot control piston 12. In this context, the force balance on the pilot control piston 12 must be taken into account, which, apart from any manufacturing tolerances, is almost pressure-balanced and therefore pressure-free. This results in the following formula relationship:

[0020] F 致动器 –F 弹簧 –F 摩擦 =F 致动器 –(F1 弹簧 +x*c)-F 摩擦 =0, where

[0021] in

[0022] F 致动器 =F 磁体弹簧 -F 磁 ,in

[0023] F 摩擦 = friction due to the movement of the pilot control piston 12,

[0024] c = average spring rate of the springs used,

[0025] F1 弹簧 = the force of the pressure spring 22 acting on the pilot control piston 12 at the end, and

[0026] F 磁体弹簧 =Compression spring 23 a acting on the actuating magnet 17 and acting in the direction of the actuating position of the pilot control piston 12 .

[0027] In the direction of action opposite to the actuation direction of its extension, an additional compression spring 24 can act on the actuating magnet 17, for which purpose it serves to overcome the so-called dead current, i.e. to provide such a current until the actuating magnet 17 as a whole has overcome the spring force and has begun to move. This prevents possible obstructions in the operation of the valve.

[0028] Below, in Figure 1 The force arrows in FIG. 1 indicate the individual forces occurring, in particular the spring forces, together with their directions of action. Here, the spring force F acting on the pilot control piston 12 at the end side is 弹簧 The magnetic force for the actuating magnet 17 is indicated by arrow 26, the magnetic force for the actuating magnet 17 is indicated by arrow 28, and the spring force F acting on the actuating magnet 磁体弹簧 This is indicated by arrow 29 .

[0029] Furthermore, as can be seen from the drawings, the pilot control piston 12 is configured as a hollow piston which has, on its outer circumference, a first recess 30 in the form of an annular shoulder which, in the case of actuation or energization of the magnet device 16 (depending on the Figure 2 view), establishes a connection for the pilot fluid to the main piston 10 in the operating position and, in the case of the magnet device 16 remaining unactuated or de-energized (depending on the Figure 3 view), reaches the initial position under the action of the two pressure springs 23, 24 and prevents the aforesaid connection for the pilot fluid. The pilot control piston 12, configured as a hollow piston, has a channel 32 for the pilot fluid along its inner circumference which opens out with its free end 34 into the pilot control chamber 20 and, via a radially extending channel section 36 of the axially extending channel 32, into an annular second recess 38 on the outer circumference of the hollow or pilot control piston 12 which, in the case of the magnet device 16 being unactuated (depending on the Figure 3 view), reaches a connection structure for the pilot fluid leading to the tank connection 40, at which time the connection of the first recess 30 to the pilot fluid connection to the main piston 10 is disconnected. All so-called fluid guiding structures, such as the channel section 36 and the tank connection 40, can be present in plurality as shown, where, for the sake of simpler representation, usually only one fluid guiding structure is provided with a reference numeral.

[0030] In the connection structure of the pilot fluid between the main piston 10 and the pilot control chamber 20, a valve seat-sealed switching valve 42 is connected. When the valve is "energized" and closed, the switching valve transfers the correspondingly higher pressure among the two fluid ports 44, 46 in the valve housing 14 as the conveying pressure into the pilot control chamber 20, and guides the main volume flow rate to be adjusted via the fluid ports. If the fluid pressure on the end-side axial fluid port 44 is greater than the fluid pressure on the radial fluid port 46 arranged transversely thereto, the fluid with the higher pressure reaches the switching valve 42 with its closing ball 48 via the fluid port 44 and the longitudinal channel 50 with the introduced transverse hole 51, in the front region of the main piston 10 constructed in a valve seat-sealed manner. Such a closing ball 48 moves to the right in the viewing direction of the drawing and closes the radial channel 52 introduced in the main piston 10, and this radial channel leads out to the fluid port 46 in the valve housing 14. Another longitudinal channel 56 is connected to the valve chamber 54 of the switching valve 42 and introduced in the main piston 10, and the other longitudinal channel leads out to the fluid chamber 58 in the main piston 10 with its free end-side end. Through at least two connecting channels 60 arranged at an inclination of 45° to the longitudinal axis of the valve in the main piston 10, the fluid chamber 58 is connected to another fluid chamber 62, and the other fluid chamber is constructed as an annular chamber and arranged between the valve housing 14 and the main piston 10. Immediately thereafter, the other fluid chamber 62 guides the fluid to transition into the annular chamber 64 arranged in a diameter-expanded manner in the valve housing 14, and from there, longitudinal channel segments 66 are respectively guided to the other annular chambers 67 in an opposing manner, and then transition into the transversely arranged channel portion 68 in the valve housing 14, and the transversely arranged channel portion is widened in a groove shape in the cross-section towards the pilot control piston 12 at its inner free end and according to the attached Figure 2 figure illustration partially overlaps the annular first recess 30 on the outer periphery of the pilot control piston 12 in terms of fluid, wherein as long as the pilot control piston 12 moves from its non-energized initial position (according to Figure 3 ) to the right from left in the case of the energized electromagnetic device 16 and reaches its right-side operating position (according to Figure 2 ), the above-mentioned connection of the pilot fluid is achieved. Subsequently, the valve is in its closed position where the fluid path between the interface parts 44, 46 is blocked.

[0031] It should be understood that, as described above, a plurality of corresponding channels and other connections as shown can be provided on the valve as required to ensure reliable fluid guidance. When the magnet device 16 is energized, in any case, the components 50, 52, 54, 56, 58, 60, 62, 64, 66, 67, 68 and 30 constitute a feasible fluid connection structure 18 between the fluid interfaces 44, 46 at the main piston 10 and the pilot control chamber 20 between the main control piston 10 and the pilot control piston 12. In this regard, in the closed valve position of the main piston 10, the corresponding higher pressure on the fluid interface 44 or 46 is continuously conveyed or transmitted into the pilot control chamber 20 as long as the pilot control piston 12 occupies its energized operating position on the right side shown in Figure 2 . Otherwise, in the unoperated, current-free open position of the magnet device 16, the above-described fluid guiding connection structure 18 between the first recess 30 and the transverse channel portion 68 is interrupted in such a way that the pilot control piston 12 occupies its initial position on the left side shown in Figure 3 . However, the pressure in the pilot control chamber 20 is connected to the substantially pressure-free tank side T via the tank interface 40 (see Figure 1 ), so that the main piston 10 can occupy its open position (according to Figure 3 ), in which a main fluid connection is established between the fluid interfaces 44 and 46 in two feasible fluid directions.

[0032] If the pressure on the radial interface 46, which is the additional fluid interface in the valve housing 14, is greater than the pressure on the fluid interface 44, the switching valve 42 is switched in the viewing direction of the drawing in such a way that the closing ball 48 now occupies its closing position on the left side, closing the channel 50. Thus, the fluid with a preset pressure reaches the said further longitudinal channel 56 via the fluid interface 46 and the radial channel 52 and the valve chamber 54, so that in this regard, when the pilot control piston 12 occupies its energized operating position on the right side shown in Figure 2 , the remaining part of the fluid connection structure 18 to the pilot control chamber 20 is now released via such a path. Usually, there should be fluid pressure from a pressure supply device, such as a hydraulic pump, on the fluid interface 44, and a hydraulic consumer, such as a hydraulic cylinder, should be connected to this fluid interface 46. Other layouts of the fluid interfaces 44, 46 in the case of using such a proportional valve can be envisaged. In particular, when the magnet device 16 acts together with an electronic open-loop control device or a closed-loop control device not shown in detail, the valve is suitable as a so-called load valve due to its valve seat tightness, and with this load valve, the load can also be controlled to be reduced.

[0033] As can be further derived from the attached drawings, the main piston 10 consists of two components 70, 72, wherein the components 70, 72 define a fluid chamber 58 in the axial movement direction of the valve pistons 10, 12 when viewed from their free end sides facing each other. A second pressure spring 74 acts as an additional energy accumulator on the free end side of the second component 72 facing the magnet device 16. The second pressure spring is supported at its other free end on a stationary part of the valve housing 14 and is designed as a pressure spring that applies a pre-tightening force to the main piston 10 in its closing direction. A pressure spring 22 extends coaxially with the second pressure spring on the inner peripheral side facing the second pressure spring 74. The pressure spring is supported at one of its free ends on a shoulder-shaped shoulder inside the second component 72 and at its other free end on an annular protrusion 76 on the pilot control piston 12. In this way, the main piston 10 is pre-tightened by the corresponding spring force of the pressure spring 74, while the pilot control piston 12 is pre-tightened by the spring 22.

[0034] From now on, how to adjust the movement of the main piston 10 will be described below. When viewed Figure 2 in the viewing direction, the main piston 10 moves into the state preset as in Figure 3 (i.e., moves to the left), and the following is how it is done. The pressure applied to the corresponding fluid interfaces 44 or 46 in front of the main piston 10 (this pressure is conveyed to the pilot control piston 12 through the switching valve 42 and the fluid connection structure 18) in the case of the magnet device 16 being energized is first used to hold the main piston 10 through the pressure in the pilot control chamber 20 (according to Figure 2 the view) by the area difference formed by the opposite end sides of the main piston 10. Here, according to Figure 2 the view, the pilot control piston 12 is in valve seat sealing contact with the valve housing 14 through an annular valve seat 77, so that in the closed state of the valve, there will be no inadvertent leakage flow from the pilot control chamber 20 towards the tank interface 40.

[0035] If the force generated by the magnet device 16 (open without current) is now cancelled, then in the case of at least including the pressure spring 23 acting between the pilot control piston 12 and the actuating magnet 17 of the magnet device 16, the pilot control piston 12 moves from the position shown in the viewing direction of the attached drawings to its initial position on the left side (according to Figure 3)。In the initial position on the left side, the recess 30 on the outer periphery of the pilot control piston 12 is closed by the corresponding housing part of the valve housing 14. Similarly, the corresponding transverse channel 68 is closed (preferably in a fluid-tight manner) by the adjacent outer periphery of the pilot control piston 12, and the transverse channel can be connected to the fluid chamber 58 in a fluid-guiding manner and thus to the corresponding pressure-introducing side at the main piston 10. In addition, the main piston 10 is held in the direction of its closed position by an external second pressure spring 74.

[0036] However, the fluid pressure in the pilot control chamber 20 must necessarily drop in this regard. As described above, the pilot control chamber 20, which is now disconnected from the pressure supply from the side of the main piston 10, can now be held without pressure via the fluid-guiding channel 32 inside the pilot control piston 12 in the direction of the reservoir connection 40. In this way, a fluid connection is established from the pilot control chamber 20 via the fluid-guiding channel 32 to the laterally extending channel section 36 of the corresponding channel 32. In addition to entering the pilot control piston 12 at the end side, there is also another permanent fluid connection structure to the pilot control chamber 20 via the transverse channel guide 75, and the transverse channel guide leads out with one of its free ends into the channel 32 of the pilot control piston 12. Since the pilot control piston 20 is in its initial position with no current and open, the second recess 38 in the valve housing 14 is opened (aufsteuern) to the left by means of the pressure spring 23, and the fluid can overflow from there via the annular shoulder recess 79 in the valve housing 14 into the pressure relief chamber 80, which is formed by the widened annular recess in the valve housing 14. Therefore, when the valve seat 77 is released, the fluid under pressure on the side of the pilot control chamber 20 then flows out from this pressure relief chamber 80 into the annular channel 78, which is recessed into the pilot control piston 12 with a preset length, such that in each possible movement position of the pilot control piston 12, the annular channel 78 coincides conductively with the reservoir connection 40. The fluid in the annular channel 78 is then placed on the reservoir side T of the valve device via the corresponding reservoir connection 40, so that the pilot control chamber 20 is completely depressurized in this regard. Then, depending on the fluid pressure applied to the main piston 10 respectively, the main piston is opened against the spring action of the pressure springs 22 and 74, and thus a new equilibrium appears in the opened valve.

[0037] In contrast, if the actuating magnet 17 of the magnet device 16 is energized, the assigned actuating magnet 17 or the magnet armature Figure 1 moves, in the direction of observation, to its right movement position or stop position against the action of the additional pressure spring 24 and the magnet spring 23. For this purpose, the magnet device 16 has an energizable coil 81, which, when energized, correspondingly moves the actuating magnet 17 or the magnet armature from its position in Figure 1The initial position shown in [reference] is moved to its actuating position to the right. If the power supply to the coil 81 is cancelled via the common plug connection 82 on the magnet device 16, then the two pressure springs 23, 24 are allowed to return unhindered to Figure 1 the initial position shown, which corresponds to Figure 3 the position of the pilot control piston 12 in [reference], i.e., "open on no current".

[0038] Thus, in this initial position of the magnet device 16, according to Figure 3 the view of [reference], the pilot control piston 12 is also in its initial position on the left side, and as already explained, the pilot control chamber 20 is no longer supplied with fluid having a presettable pressure from the side of the main piston 10 thereafter. The fluid pressure in the pilot control chamber 20 also acts in principle on the back side of the main piston 10, such that as long as the pilot control piston 12 occupies the position according to Figure 2 of [reference], the main piston 10 is reliably held due to the area conversion. Thus, the actuating position or the energized position corresponds to a reliable closed position for the main piston 10. In addition, the fluid reaches the back side of the pilot control piston 12 through the fluid guiding channel 32 of the pilot control piston 12 in order to thereby establish a pressure balance for the movable components; only according to the view according to Figure 2 of [reference], the valve seat sealing closure of the fluid path from the pilot control chamber 20 in the direction of the tank connection 40 is now effected via the valve seat 77, wherein the above-mentioned closure of the fluid path is leak-proof sealed.

[0039] In addition, the main piston 10 has on its free left end side an end side 98 with a convex spherical shape, which is formed by a presettable radius that serves to establish a linear relationship between the stroke of the main piston 10 and the opening area produced by it at the fluid connections 44 or 46. Otherwise, the main piston 10 is guided longitudinally displaceably on the inner peripheral side of the valve housing 14 by a stepped annular surface, wherein the above-mentioned inclined surface forms a further valve seat 100, such that in this regard the main piston 10 effects the valve seat sealing closure between the fluid connection sites 44, 46 in its closed position (according to Figure 1 and 2 ). The individual sealing ring systems, which are not described in detail and are usually in the form of common O-ring seals, ensure the fluid-tight delimitation of the individual fluid chambers and fluid paths from one another as given before.

[0040] In particular, as Figure 1 shown, the valve body can be taken as a whole according to Figure 2 and Figure 3is loaded into the valve block 102 in a common manner, the valve block having interface parts 44, 46 for guiding fluid. Through the fluid connection structure 104 which is partly guided in the valve block 102, there is a permanent fluid connection between the tank interface 40 and the tank side T of the entire valve device. In addition, by Figure 1 it can be seen that the connection channel 60 is surrounded on the outside by the circumferential part of the valve housing 14. As can be further derived from Figure 1 the flange 106 is placed on the valve block 102 from the outside and fixedly connected to the valve block in a common manner. In addition, the individual components of the valve housing 14 are fixedly screwed to the flange on the inner circumferential side of the flange 106 through the threaded section 108.

Claims

1. A valve having a main piston (10) for controlling a main volume flow rate and a pilot control piston (12) for controlling a pilot control volume flow rate, wherein the main piston (10) and the pilot control piston (12) are guided longitudinally displaceably in a valve housing (14), and the pilot control piston (12) can be actuated by means of a magnet device (16). Characterized in that the position of the main piston (10) can be adjusted by means of the pilot control piston (12) in such a way that the fluid pressure acting on the main piston (10) is conveyed via a fluid connection structure (18) into a pilot control chamber (20) having the pilot control piston (12), and in the case where the magnet device (16) is actuated, the pilot control piston holds the main piston (10) in its closed position blocking the main volume flow rate in the actuated position, and in the case where the magnet device (16) is not actuated, the pilot control piston (12) moves into an initial position, in which the fluid pressure drops towards the tank side (T) in the pilot control chamber (20) decoupled from the pressure supply via the main piston (10) until the main piston (10) reaches the open position for adjusting the main volume flow rate.

2. The valve according to claim 1,[[]] Characterized in that the magnet device (16) has an actuating magnet (17) acting in a tensile manner, which moves the pilot control piston (12) from its initial position into its actuated position in the case of energization, in which the main piston (10) is held in its closed position.

3. The valve according to claim 1 or 2,[[]] Characterized in that Under the force F of the accumulator 弹簧 and in combination with the force F acting in the same direction of the magnet device (16), 致动器 the pilot control piston (12) can be placed in its actuating position, and the pilot control piston (12) is pressure-balanced considering the frictional force F 摩擦 in such a way that the following applies: F 致动器 - F 弹簧 - F 摩擦 = 0.

4. The valve according to claim 1 or 2,[[]] Characterized in that the pilot control piston (12) is configured as a hollow piston having a first recess (30) on its outer periphery, which establishes a guiding fluid connection to the main piston (10) in the case where the magnet device (16) is actuated and forms a guiding fluid channel (32) with its inner periphery, the channel leading out into the pilot control chamber (20) with one of its free ends (34) and leading out into a second recess (38) on the outer periphery of the hollow piston through a channel section (36) of the channel (32), and the hollow piston is in fluid connection with a tank interface (40) in the valve housing (14) in the case where the magnet device (16) is not actuated, and thereby the connection of the first recess (30) to the guiding fluid to the main piston (10) is disconnected.

5. The valve according to claim 1 or 2,[[]] Characterized in that a switching valve (42) is connected in the guiding fluid connection structure between the main piston (10) and the pilot control chamber (20), which continues to convey the correspondingly higher pressure of two fluid interfaces in the valve housing (14) as a conveying pressure into the pilot control chamber (20), and the main volume flow rate is guided through the two fluid interfaces.

6. The valve according to claim 1 or 2,[[]] Characterized in that A fluid chamber (58) is provided in the main piston (10) as part of the fluid connection structure (18), and the fluid chamber leads out into another fluid chamber (62) between the valve housing (14) and the main piston (10) via at least one connection channel (60) in the main piston (10). The other fluid chamber leads out into a first recess (30) in the pilot control piston (12) via at least one other connection channel in the valve housing (14) with at least partial overlap.

7. The valve according to claim 4, characterized in that at least one other connection channel is arranged in the pilot control piston (12) and in the valve housing (14), by means of which the second recess (38) on the pilot control piston (12) can be connected to the tank interface (40).

8. The valve according to claim 1 or 2, characterized in that the main piston (10) is held by means of another accumulator in the direction of its closed position.

9. The valve according to claim 1 or 2, characterized in that the respective accumulator is formed by a pressure spring (22, 74), and the pressure spring for the main piston (10) has a greater spring stiffness than the pressure spring for the pilot control piston (12), and the pressure spring for the main piston (10) surrounds the pressure spring for the pilot control piston.

10. The valve according to claim 1 or 2, characterized in that the main piston (10) has a radius at least partially in a convex spherical shape on its free end side (98) for establishing a linear relationship between the stroke of the main piston (10) and the opening area achievable by it at one of the fluid interfaces in the valve housing (14).

11. The valve according to claim 1 or 2, characterized in that the valve is a proportional valve.

12. The valve according to claim 1, characterized in that the magnet device (16) has an actuating magnet (17) acting in a tensile manner, which, when energized, moves the pilot control piston (12) from its initial position to its actuating position against the action of the accumulator, in which the main piston (10) is held in its closed position.

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