valve

Abstract

A valve, in particular a proportional valve, comprising a main piston (10) for controlling a main volume flow and a pilot piston (12) for controlling a pilot volume flow, the main piston (10) and the pilot piston (12) being guided longitudinally movably in a valve housing (14), the pilot piston (12) being controllable by a solenoid device (16), characterized in that the position of the main piston (10) is controllable by the pilot piston (12), which, depending on its moving position, either transmits the fluid pressure present in the main piston (10) via a fluid communication (18) to a pilot chamber (20) or interrupts the fluid communication (18) and connects the pilot chamber (20) to a tank side or to a low pressure side (T) via another fluid communication (19), in which a valve means (21) is introduced which closes in a seat-tight manner as soon as the fluid communication (18) between the main piston (10) and the pilot chamber (20) is established.

Description

[Technical field]

[0001] The invention relates to a valve, in particular a proportional valve, which has a main piston for controlling a main volume flow and a pilot piston for controlling a pilot volume flow, the main piston and the pilot piston being guided longitudinally movably in a valve housing, the pilot piston being controllable by a solenoid device. [Background technology]

[0002] From German patent application DE 10323595 A1 a valve, in particular in the form of a proportional seat valve or piston valve, is known which has a valve housing, at least three fluid ports passing through the valve housing, a main piston guided in the valve housing and a pilot piston which is controllable by an energizable solenoid device and which operates a pilot control, whereby when the pilot control is opened, fluid from one of both ports which can be controlled by the main piston passes through a cross-sectional narrowing in the main piston and the pilot control to a third port which can be controlled by the pilot piston, and on the basis of the resulting pressure drop the main piston reaches a respective control position in which it can control both fluid ports with a fluid quantity.

[0003] From European patent application EP 2 880 315 B1 a valve, in particular a pilot-controlled proportional directional valve, is known which has a valve housing with a fluid inlet and a fluid outlet, the flow of fluid between which can be adjusted by a main piston, a pilot valve chamber with a pilot valve closing member which can be moved by an operating device is provided on the rear side of the main piston, the pilot valve closing member allowing the flow of fluid between the pilot valve chamber and the fluid outlet to be adjusted by means of this pilot valve closing member, an inlet orifice is arranged between the fluid inlet and the pilot valve chamber, the opening cross section of which can be reduced by a control element, the inlet orifice has a plurality of orifice holes, the opening cross section of at least one of which can be reduced by the control element, and by dividing the inlet orifice into a plurality of orifice holes it is possible to switch the inlet orifice into a plurality of opening stages.

[0004] Such pilot-controlled electrohydraulically operated directional valves control the start, stop and direction of the volume flow as well as the speed, acceleration and deceleration of a hydraulic consumer, for example in the form of a hydraulic working cylinder, connected to the valve. Pilot-controlled directional valves are primarily used for controlling large volume flows with low flow losses. However, large volume flows with low flow losses mean a large opening cross section and thus a large stroke of the main piston. The obstacles that impair the function of the valve are the volume flow and the pressure difference, i.e. the flow and friction forces which interfere with the switching action depending on the valve performance. In particular in the case of mechanical actuation by a spring, usually in the form of a return spring, the design value of the spring force may be too small compared to the friction forces to return the piston valve. In order to meet the stroke and force requirements for such a solenoid system, it would be necessary to design the solenoid system with correspondingly large dimensions or to pilot the valve hydraulically. Valves with hydraulic pilot control are therefore necessarily known in the prior art for such applications, as mentioned above. Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention is to proceed from this prior art and further improve the known valve with regard to its functional behavior. This object is achieved by a valve which has as a whole the features of patent claim 1. [Means for solving the problem]

[0006] According to the characterizing part of claim 1, the position of the main piston can be controlled by a pilot piston, which, depending on its displacement position, either transmits the fluid pressure present in the main piston to a pilot chamber via a fluid communication or blocks this fluid communication and connects the pilot chamber via another fluid communication with the tank side or the low pressure side, and a valve means is introduced into the fluid communication, which closes in a seat-tight manner as soon as the fluid communication between the main piston and the pilot chamber is established, so that the pilot control with the pilot piston is seat-tightly sealed in the valve in the possible operating or displacement positions. Due to the above-mentioned seat-tight sealing of the pilot chamber with the pilot piston, the valve according to the invention can be used particularly advantageously as a so-called load valve. This load valve maintains a set and adjustable position without leakage even in the high load range, so that it is ensured that the load acting fluidly on the valve cannot be lowered unintentionally, which would otherwise pose a significant safety risk. In the closed position the valve is leak-tight and in the open position controls the volume flow.

[0007] In a preferred embodiment of the valve according to the invention, the valve means is formed by a valve seat, which consists of a reciprocally abuttable sealing surfaces of the outer periphery of the pilot piston and the inner periphery of the adjacent wall of the valve housing. In particular, the reciprocable sealing surfaces can consist of inclined surfaces with different inclinations, so that within the framework of the valve seat to be manufactured, a linear sealing abutment or sealing edge occurs between the pilot piston and the valve housing, which results in an increased sealing pressure during operation and thus an improved sealing of the valve seat.

[0008] In another preferred embodiment of the valve according to the invention, the sealing surface of the pilot piston is located at the transition between two different diameters of the pilot piston, the larger of which defines an annular recess in the pilot piston and the smaller diameter is formed by an annular groove which, in the closed state of the valve seat, at least partially grips from the inside an annular recess in the valve housing. In this way, the valve seat can be produced in a manner advantageous from the viewpoint of production technology.

[0009] In another preferred embodiment of the valve according to the invention, a recess in the pilot piston is engaged by a passage portion which transitions into the fluid communication passage of the pilot piston, said passage opening on one side into the pilot chamber, in this way the pilot chamber can be connected to the movable component of the valve in a particularly flow-friendly manner.

[0010] In another preferred embodiment of the valve according to the invention, when the pilot piston moves and at the same time blocks the fluid communication from the main piston to the pilot chamber via the valve seat opened thereby, the fluid communication is opened via the recess and the annular groove to the groove-like annular passage on the outer circumference of the pilot piston, into which a tank connection, which is always guiding the fluid on the tank side, is opened. It is further preferred that between the annular groove and the annular passage, a guide with an enlarged diameter of the pilot piston is guided along an assignable inner circumference of the valve housing in each movement position of the pilot piston. In this way, a reliable guidance of the pilot piston inside the valve housing is achieved and at the same time a very compact design is achieved for the moving components inside said valve housing.

[0011] In another particularly preferred embodiment of the valve according to the invention, a dynamic seal is present on the side of the valve housing at a settable distance from the closed valve seat towards the solenoid device, which dynamic seal surrounds the outer periphery of the pilot piston with a settable preload, by means of which complete sealing of the pilot piston in the valve housing is achieved, and a leak-tight seal is achieved by the valve seat or the dynamic seal in both directions corresponding to the control pressure, i.e. towards the pilot chamber and towards the solenoid device.

[0012] An annular relief groove is preferably provided around the outer periphery of the pilot piston along a settable distance to allow pressure-free and therefore unhindered operation of the pilot piston within the valve housing.

[0013] Particularly preferably, in the valve according to the invention, a further valve seat is provided between the main piston and the valve housing as a further seat-tight valve means, and a third valve seat is provided, which is formed by a closing ball and the adjacent wall of the main piston. In this way, the main part of the valve, in particular formed by the main piston, is also designed seat-tight, which is particularly advantageous, in particular if the valve is designed as a loading valve. By combining various seat-tight valve means and kinematic seals, it is ensured that no leakage of the volume flow occurs. The valve according to the invention is designed for pressure closure, and the valve closes automatically due to its basic design. It is also particularly suitable for use as a loading valve. When an equilibrium is reached between the spring force acting on the main piston and the magnetic force by the solenoid, the main piston of the valve remains in a controllable position, thereby controlling the main volume flow between the two fluid ports in the valve housing. For such a control characteristic, it is advantageous for the pilot valve to have an overall negative overlap, and for the first valve means to form a control edge between the pilot piston and the valve housing, which exerts a particularly fine adjustment effect on the control process of the main piston during the valve operation.

[0014] In the following, the valve according to the invention will be explained in more detail on the basis of an embodiment shown in the drawings, which are principle longitudinal sections and are not drawn to scale. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a vertical cross-sectional view of the main components of the valve in an energized state. [Diagram 2] FIG. 2 is a longitudinal cross-sectional view of the front of the valve shown in FIG. 1 in a closed position. [Diagram 3] FIG. 3 is a longitudinal section corresponding to FIG. 2, of the valve in an open position. [Figure 4] FIG. 4 is an enlarged view of the portion marked X in FIGS. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The valve shown is a so-called proportional valve and has a main piston 10 for controlling the main volume flow. Furthermore, a pilot piston 12 is present for controlling the pilot volume flow, both main piston 10 and pilot piston 12 being guided so as to be longitudinally displaceable in a valve housing 14. As can be seen in particular in Figure 1, the pilot piston 12 is controlled so as to be displaceable in the valve housing 14 by a solenoid device 16.

[0017] As shown in Fig. 2, when the solenoid device 16 is energized, the position of the main piston 10 can be adjusted by means of the pilot piston 12, by which the fluid pressure of the main piston 10 is transmitted through the fluid communication 18 to the pilot chamber 20 comprising the pilot piston 12, so that the closed position of the main piston 10 preventing the main volume flow is maintained, so that when the solenoid device 16 is de-energized, the pilot piston 12, moving from the energized operating position shown in Fig. 2, moves to the left side of the figure to the initial position shown in Fig. 3. In that position, the fluid pressure of the pilot chamber 20, which is substantially isolated from the pressure supply through the main piston 10, decreases until the main piston 10 reaches the open position in which the main volume flow is adjusted, as shown by the example of one possible open position shown in Fig. 3. When "right" and "left" are mentioned in the description, they refer to the direction when looking at the figure.

[0018] The position of the main piston 10 is adjusted with the aid of the pilot piston 12. In this way, the balance of forces at the pilot piston 12 is taken into account, which is approximately pressure balanced, apart from any possible manufacturing tolerances, and therefore no compressive forces are present. In this case, the relationship according to the following formula arises: F アクチュエータ -F バネ -F 摩擦 =F アクチュエータ -(F1 バネ +x*c)-F 摩擦 =0 however,

[0019]

number

[0020] The solenoid 17 with the solenoid armature can be acted upon by an additional compression spring (not shown) in a direction opposite to the direction of its suction action, which compression spring is used to provide a so-called dead current until the solenoid 17 as a whole overcomes the spring force and starts to move, thus preventing possible disturbances in the valve operation.

[0021] In the following, the individual forces that occur, particularly the spring forces, are shown by force arrows in FIG. 1 together with their directions of action. The spring force F acting on the end face side of the pilot piston 12 is バネ is indicated by arrow 23b, the magnetic force on the solenoid 17 is indicated by arrow 28, and the spring force F acting on the solenoid 17 is indicated by arrow 29. 磁気バネ is indicated by arrow 29a.

[0022] As can further be seen from the figure, the pilot piston 12 is designed as a hollow piston and has a first recess 30 in the form of an annular step on its outer periphery, which in a defined operating position creates a fluid communication 18 to the main piston 10 when the solenoid device 16 is operated or energized, according to the representation in Fig. 2, and reaches an initial position under the action of a compression spring 23a and blocks such fluid communication, according to the representation shown in Fig. 3, when the solenoid device 16 remains de-energized. The pilot piston 12, designed as a hollow piston, has a fluid communication passage 32 along its inner periphery. The fluid communication passage 32 opens with one free end into the pilot chamber 20 and leads via a radially extending passage section 36 of the axially extending passage 32 to a second annular recess 38 on the outer periphery of the hollow or pilot piston 12. When the solenoid device 16 is not operated, the pilot piston 12, according to the representation of Fig. 3, has the first recess 30 disconnected from fluid communication with the main piston 10 and in fluid communication with the tank connection 40. All the above mentioned fluid connections, as well as the flow passage portion 36 and the tank connection 40, can be multiple as shown, but for the sake of simplicity and clarity, usually only one fluid connection is given one reference number. Furthermore, in addition to the compression spring 23a, of which only the spring chamber between the solenoid armature 17 and the fixed end housing part of the valve housing 14 is shown for the sake of simplicity, other energy storage means can also be used, oriented in the same direction as the compression spring.

[0023] A seat-tight changeover valve 42 is connected in the fluid communication between the main piston 10 and the pilot chamber 20. When the valve is "energized" and closed, this changeover valve 42 transmits the higher pressure of the two fluid ports 44, 46 in the valve housing 14, through which the main volume flow to be controlled is guided, as a signal pressure to the pilot chamber 20. If the fluid pressure at the axial fluid port 44 on the end face is higher than the fluid pressure at the radial fluid port 46 arranged transversely thereto, the fluid with the higher pressure reaches the changeover valve 42 with a closing ball 48 via the fluid port 44 and the longitudinal passage 50 in the front region of the main piston 10, which is designed seat-tight in this respect. Such a closing ball 48 moves to the right as viewed in the direction of view of the figure and seat-tightly closes the radial passage 52 arranged obliquely in the main piston 10 and opening into the fluid port 46 in the valve housing 14.

[0024] The valve chamber 54 of the switching valve 42 is connected to a further longitudinal passage 56, which is also provided in the main piston 10 and opens at its free end into a fluid chamber 58 in the main piston 10. The fluid chamber 58 is connected via at least two communicating passages 60 in the main piston 10, which are arranged perpendicularly to the longitudinal axis of the valve, to a further fluid chamber 62 arranged as an annular chamber between the valve housing 14 and the main piston 10. The further fluid chamber 62 then flows in fluid communication into an annular chamber 64 arranged with an enlarged diameter in the valve housing 14, from which a longitudinal passage section 66 designed as a high-pressure passage closed at one free end by a plug 69 leads to a crescent-shaped annular chamber 67, which is introduced in fluid communication in the form of an arc into a portion of the lower segment of the valve housing 14.

[0025] As shown in particular in Figure 4, the crescent-shaped annular chamber 67 is constantly in fluid communication with a transverse passage portion 68 arranged radially in the valve housing 14, which at its inner free end is enlarged in cross section in the shape of a groove towards the pilot piston 12 and partially overlaps in fluid communication with the first annular recess 30 in the outer periphery of the pilot piston 12, which partially fluidly overlaps with the first annular recess 30 in the outer periphery of the pilot piston 12, according to the representation according to Figure 2. Such fluid communication is established as soon as the solenoid device 16 is energized and the pilot piston 12 moves from the initial de-energized position shown in Figure 3 from left to right and reaches the right-hand operating position shown in Figures 1 and 2. The valve is then in a closed position blocking the fluid path between the fluid ports 44, 46.

[0026] As previously explained, it is understood that each of the illustrated flow passages and other connections can be multiplexed in the valve as necessary to ensure reliable fluid communication. In any case, the components 50, 52, 54, 56, 58, 60, 62, 64, 66, 67, 68, 30 provide possible fluid communication 18 between the fluid ports 44, 46 in the main piston 10 and the pilot chamber 20 between the main piston 10 and the pilot piston 12 as long as the solenoid device 16 is energized and assumes the right-hand operating position shown in Figures 1, 2 and 4. Otherwise, the solenoid device 16 is not operated and is not energized in the open position, and the pilot piston 12 assumes the initial position shown on the left in Figure 3, thereby blocking the fluid communication 18 between the first recess 30 and the transverse flow passage portion 68. Thus, in the closed valve position of the main piston 10, the higher pressure at the fluid port 44 or 46, respectively, is transmitted or communicated to the pilot chamber 20 via the inner fluid communication passage 32 of the pilot piston 12, as long as the pilot piston 12 assumes the right energized operating position shown in Figures 1, 2 and 4. Otherwise, in the non-operated and non-energized position of the solenoid device 16, such fluid communication 18 between the first recess 30 and the transverse passage portion 68 is blocked by the pilot piston 12 assuming the left initial position shown in Figure 3. Thus, the pressure in the pilot chamber 20 is switched to the substantially pressureless tank side T via the tank connection 40 and another fluid communication 19, and the main piston 10 can assume one of the open positions shown in Figure 3, in which a main fluid communication is established between the fluid ports 44 and 46 in both possible fluid directions, as will be explained in more detail below.

[0027] If the pressure in the further fluid port in the valve housing 14, the radial fluid port 46, is greater than the pressure in the fluid port 44, the switching valve 42 is switched by the closing ball 48 taking up the closed position, which closes the left-hand flow passage 50 as viewed in the direction of view of the figure. In this way, fluid with a settable pressure reaches the further longitudinal flow passage 56 via the fluid port 46 and the radial flow passage 52 as well as the valve chamber 54. If the pilot piston 12 then takes up the energized right-hand operating position shown in FIG. 2, the remaining fluid communication 18 is opened through this path towards the pilot chamber 20. Normally, the fluid pressure from a pressure supply device, such as a hydraulic pump, is present in the fluid port 44, and a hydraulic consumer, such as a hydraulic cylinder, is connected to the fluid port 46. Within the scope of the use of such proportional valves, other assignments of the fluid ports 44, 46 are conceivable. This valve is particularly suitable as a so-called load valve, which can be reduced in a controlled manner on the basis of its seat tightness, especially if the actuating solenoid device 16 cooperates with an electronic control or electronic adjustment, not shown in detail.

[0028] As can be further seen from the figure, the main piston 10 is composed of two components 70, 72, which define a fluid chamber 58 at their mutually facing free end faces as viewed in the axial movement direction of the valve pistons 10, 12. A second compression spring 74 acts on the free end face of the second component 72, which faces the solenoid device 16, as another energy storage means. This compression spring 74 is supported at its other free end on a stationary part of the valve housing 14 and is designed as a compression spring, biasing the main piston 10 in its closing direction. Arranged coaxially on the inner periphery of the second compression spring 74, the compression spring 22 extends therefrom and is supported at one free end on an internal stepped shoulder of the first component 70 and at the other free end on an annular projection of the pilot piston 12. In this way, both the main piston 10 and the pilot piston 12 are biased by the respective spring forces of the two compression springs 74 and 22.

[0029] In the following, it will be explained how the movement of the main piston 10 is controlled. The movement of the main piston 10 to the left in the observation direction of Fig. 2, i.e. to the state shown in Fig. 3, is carried out as follows. The pressure present in the respective fluid port 44 or 46 upstream of the main piston 10 is transmitted to the pilot piston 12 via the changeover valve 42 and the fluid communication 18, and when the solenoid device 16 is energized, the pressure in the pilot chamber 20 first holds the main piston 10 in the closed state due to the area difference formed by the opposing end faces of the main piston 10, according to the representation shown in Fig. 2. In this case, according to the representations of Figs. 2 and 4 in particular, the pilot piston 12 is in tight-seat contact with the valve housing 14 via the annular valve seat 23, so that leakage flows cannot unintentionally flow out of the pilot chamber 20 towards the tank connection 40 when the valve is closed.

[0030] When the force exerted by the solenoid device 16 is no longer generated (de-energized opening), the pilot piston 12 moves to an initial position shown in FIG. 3, to the left as viewed in the direction of view of the figure, taking into account the compression spring 23a acting at least between the solenoid housing 14 and the solenoid 17 of the solenoid device 16. In such an initial position to the left, the recess 30 in the outer periphery of the pilot piston 12 is closed by the corresponding housing part of the valve housing 14 and separated from the high-pressure chamber 67. Similarly, the respective lateral flow passage 68, which can be in fluid communication with the fluid chamber 5 and thus with the respective pressure inlet side of the main piston 10, is closed, preferably in a fluid-tight manner, by the adjacent outer periphery of the pilot piston 12. Furthermore, the main piston 10 is biased towards the closed position by an outer second compression spring 74.

[0031] The pilot chamber 20 thus separated from the pressure supply from the main piston 10 side can be kept unpressurized through the fluid communication passage 32 in the pilot piston 12 towards the tank connection 40, due to the inevitable drop in pressure in the pilot chamber 20. In this way, fluid communication is established from the pilot chamber 20 through the fluid communication passage 32 to the respective transversely extending passage portion 36 of the fluid communication passage 32. Since the pilot piston 20 is in the initial position shown in FIG. 3, which is open when not energized, the second recess 38 in the valve housing 14 is operated to open to the left by the compression spring 23a acting on the pilot piston 12, and the fluid can flow from there through the opened valve seat 23 and the annular groove 31 into the annular recess 33 in the valve housing 14, i.e. into the relief chamber or groove-like annular passage 78 formed by the axially enlarged annular recess in the valve housing 14 towards the tank side. Thus, the pilot piston 12 is mounted therein and carries with it an annular passage 78, the front end of which engages with the fluid-guiding annular recess 33, while the rear end of the annular passage 78 still fluidly communicates with the respective tank connection 40, at least with reduced overlap. When the valve seat 23 is opened, from this relief chamber or annular passage 78, the pressurized fluid from the pilot chamber 20 side flows into the annular passage 78. This annular passage 78 is provided in the pilot piston 12 with a settable length such that in all possible positions of movement of the pilot piston 12, the annular passage 78 still at least partially overlaps and is in fluid communication with the tank connection 40. The fluid present in the annular passage 78 is then sent to the tank side T of the valve arrangement via the respective tank connection 40, so that the pilot chamber 20 is completely depressurized. Depending on the fluid pressure present in the respective main piston 10, the main piston 10 is operated open against the spring action of the compression springs 22 and 74, and a new equilibrium is created with the valve open. In particular, each tank connection 40 opens into an enlarged annular space 73, which is guided longitudinally through the valve housing 14 via a low-pressure side connecting passage 77 to establish fluid communication with the tank side T.

[0032] If, on the other hand, the solenoid 17 of the solenoid arrangement 16 is energized again, the corresponding solenoid 17 or solenoid armature is moved against the action of the magnetic spring 23a to a moving or resting position to the right as viewed in the direction of view in Fig. 1. For this, the solenoid arrangement 16 has an energizable coil 81 which, when appropriately energized, moves the solenoid 17 or solenoid armature to its operating position to the right from the initial position shown in Fig. 1. For this, the solenoid arrangement 16 has an energizable coil 81 which, when appropriately energized, moves the solenoid 17 or solenoid armature to its operating position to the right from the initial position shown in Fig. 1. If the coil 81 is no longer energized via a conventional plug connection 82 provided in the solenoid arrangement 16, at least the compression spring 23a allows an unhindered return to the illustrated initial position, i.e. "de-energized open", which corresponds to the position of the pilot piston 12 shown in Fig. 3.

[0033] In this initial position of the solenoid device 16, the pilot piston 12 is also in the left initial position according to the representation according to FIG. 3, and as already explained, the pilot chamber 20 is no longer supplied with fluid at a settable pressure from the side of the main piston 10. The fluid pressure present in the pilot chamber 20 also acts essentially on the rear surface of the main piston 10, so that as long as the pilot piston 12 takes the position shown in FIG. 2, the main piston 10 is kept securely closed due to the area ratio. The operating or energized position therefore corresponds to the position in which the main piston 10 is securely closed. Furthermore, the fluid reaches the rear surface of the pilot piston 12 via the fluid communication passage 32 of the pilot piston 12 and establishes a pressure balance for the moving components. Then, according to only the representations according to FIGS. 2 and 4, a seat-tight interruption of the fluid path from the pilot chamber 20 to the tank connection 40 is achieved by the valve seat 23. Such an interruption of the fluid path is leak-tight.

[0034] The first valve means 21 formed by the valve seat 23 comprises sealing surfaces 24, 25 which can come into contact with each other between an outer circumferential portion 35 of the pilot piston 12 and an inner circumferential portion of the adjacent wall of the valve housing 14, as can be seen in particular from the representation in FIG. 4.

[0035] The sealing surface 24 of the pilot piston 12 is located at the transition point 29 between two different diameters D1, D2 of the pilot piston, the larger of which D1 defines an annular recess in the pilot piston 12 and the smaller diameter D2 is formed by an annular groove 31 which at least partially grips an annular recess in the valve housing from the inside in the closed state of the valve seat 23. For the closed position of the valve seat 23, the pilot piston 12 moves from the initial position shown in Fig. 3 to the right according to the representations of Figs. 2 and 4 to a rest position associated with the valve housing 14. The sealing surface 24 of the pilot piston 12 thus abuts against a corresponding inclined sealing surface 25 of the valve housing 14. To open the valve seat 23, i.e. to establish a fluid communication between the chambers 38, 31, 33, 78, the pilot piston 12 moves in the opposite direction until it assumes the "de-energized open" position illustrated in Fig. 3.

[0036] 4, between the annular groove 31 and the annular groove 78 there is a guide 41 for the enlarged pilot piston 12, which guides in each movement position along an assignable inner circumferential portion 27 of the valve housing 14. In this way, a seat-tight and therefore fluid-tight seal is provided in every case between the pilot chamber 20 and the rear region 83 of the valve with the solenoid device 16 via the closed valve seat 23.

[0037] Furthermore, as can be seen from the figure, at the side of the valve housing 14, at a settable distance from the closed valve seat 23 towards the solenoid device 16, there is a dynamic seal 43 which surrounds the outer periphery 39 of the pilot piston 12, preferably with a settable preload. The pilot piston 12 is sealed by the dynamic seal 43, in particular towards the tank connection 40 and thus towards the tank side T, since the pressurized fluid in the main piston 10 can reach the opposite side, i.e. the rear region 83, where the solenoid device 16 is located, through the flow passage 32 in the pilot piston 12. In this rear region 83, in particular an operating rod 84 of the solenoid device 16 engages and acts on one free end face of the movable pilot piston 12.

[0038] The dynamic seal 43 consists of a sliding ring seal 85, preferably in the form of, for example, a segmented Teflon ring, which is held under prestress by an elastomeric O-seal ring 87, which presses the sliding ring seal 85 against the outer periphery 39 of the pilot piston 12 with a settable prestress. The dynamic seal 43, preferably in the form of such a sliding seal, is accommodated in an assigned groove-like recess in the valve housing 14, which can consist of several parts, as shown, as is customary in valve technology. The above-mentioned distance between the annular recess 33 and the dynamic seal 43 is in this region in any case less than four times the diameter of the pilot piston 12 and more than twice the diameter. In particular, this distance should be 2.7 times the diameter. This distance provides a kind of overlap between the transition to the annular recess 33 and the beginning of the dynamic seal 43, which is necessary in order to keep leakage at a low level if no built-in seal is provided. In order to ensure particularly unhindered operation and to further improve the sealing, the pilot piston 12 is provided in this region with a small annular relief groove 45 on its outer periphery. As already explained, a further valve seat 49 is provided between the main piston 10 and the valve housing 14 as a further seat-tight valve means 47, and a third valve seat 53 is formed by the closing ball 48 in addition to the adjacent wall of the main piston 10 as a third seat-tight valve means 51, so that the three seat-tight valve means 21, 47, 51 used at different locations provide a particularly advantageous loading valve.

[0039] Furthermore, the main piston 10 has, at its left free end face, a ball-shaped end face 98 of a settable radius, which serves to establish a linear relationship between the stroke of the main piston 10 and the opening area at the fluid port 44 or 46 formed by this stroke. Otherwise, the main piston 10 is guided longitudinally movably on the inner periphery of the valve housing 14 via a stepped annular surface. Such an inclined surface forms a further valve seat 49, which results in a second seat-tight valve means 47. In this way, as a whole, a seat-tight shutoff is achieved between the fluid ports 44 and 46, as long as the main piston 10 assumes the closed position shown in Figs. 1, 2 and 4. The individual sealing ring system, which will not be described in detail, usually in the form of conventional O-sealing rings, defines the individual fluid chambers and fluid sections in a fluid-tight manner from one another, as described above.

[0040] As can be seen in particular from Figure 1, a measuring rod 92 is fixedly arranged on the second component 72 of the main piston 10, which passes through both the pilot piston 12 and the solenoid arrangement 16 and opens in the area of ​​its other free end into a displacement measuring device, generally designated 94. This displacement measuring device is equipped with two measuring coils 96, so that the displacement movement of the main piston 10 can be measured technically recorded in both directions. Such a displacement measuring device is described in German patent application DE 10 2012 014 250 A1 by way of example of a pressure balance.

Claims

1. A valve, in particular a proportional valve, comprising a main piston (10) for controlling a main volume flow and a pilot piston (12) for controlling a pilot volume flow, the main piston (10) and the pilot piston (12) being guided longitudinally movably in a valve housing (14), the pilot piston (12) being controllable by a solenoid device (16), the position of the main piston (10) being controllable by the pilot piston (12), the pilot piston (12) being A valve characterized in that, depending on the movement position, the fluid pressure present in the main piston (10) is transmitted to a pilot chamber (20) through a fluid communication (18), or the fluid communication (18) is cut off and the pilot chamber (20) is connected to a tank side or a low pressure side (T) through another fluid communication (19), and a valve means (21) is introduced into the fluid communication (19), and the valve means (21) closes its seat tightly as soon as the fluid communication (18) between the main piston (10) and the pilot chamber (20) is established.

2. 2. The valve according to claim 1, wherein the valve means (21) is formed by a valve seat (23) consisting of sealing surfaces (24, 25) that can abut against each other on an outer circumferential portion (35) of the pilot piston (12) and an inner circumferential portion (27) of an adjacent wall of the valve housing (14).

3. 3. The valve according to claim 1, wherein the sealing surface (24) of the pilot piston (12) is located at a transition point (29) between two different diameters (D1, D2) of the pilot piston (12), the larger of the diameters (D1) defining an annular recess (38) in the pilot piston (12) and the smaller diameter (D2) being formed by an annular groove (31) which at least partially grips an annular recess (33) in the valve housing (14) from the inside when the valve seat (23) is closed.

4. 3. The valve according to claim 1, wherein a recess (38) in the pilot piston (12) is engaged with a flow path portion (36) that transitions into a fluid communication flow path (32) of the pilot piston (12), and the fluid communication flow path (32) is open on one side to the pilot chamber (20).

5. 3. A valve according to claim 1 or 2, characterized in that when the pilot piston (12) moves and simultaneously blocks the fluid communication (18) from the main piston (10) to the pilot chamber (20) via the valve seat (23) opened thereby, the fluid communication is opened via the recess (38) and the annular groove (31) to a groove-shaped annular passage (78) on the outer periphery (39) of the pilot piston (12), and a tank connection (40) for constantly conducting fluid from the tank side (T) opens into the annular passage (78).

6. 3. A valve according to claim 1 or 2, characterized in that between the annular groove (31) and the annular flow passage (78), the enlarged diameter guide (41) of the pilot piston (12) is guided along an assignable inner circumferential portion (27) of the valve housing (14) in each movement position of the pilot piston (12).

7. 3. A valve according to claim 1 or 2, characterized in that a dynamic seal (43) is present on the side of the valve housing (14) at a settable distance from the closed valve seat (23) towards the solenoid device (16), the dynamic seal (43) surrounding the outer periphery (39) of the pilot piston (12) with a settable preload.

8. 3. A valve according to claim 1 or 2, characterized in that the pilot piston (12) is provided with an annular relief groove (45) on its outer periphery (39) along a settable distance.

9. 3. A valve according to claim 1 or 2, characterized in that as a further seat-tight valve means (47), a further valve seat (49) is provided between the main piston (10) and the valve housing (14).

10. 3. A valve according to claim 1 or 2, characterized in that a third seat-tight valve means (51) is provided, which is a third valve seat (53) formed by a closing ball (48) and an adjacent wall of the main piston (10).

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