Pilot Controlled Solenoid Valve

Abstract

The valve comprises a main piston (10) and a pilot piston (12), the main piston and the pilot piston being guided longitudinally movably in a valve housing (14), the pilot piston being actuable by an electromagnetic device, the position of the main piston being adjustable by the pilot piston, the fluid pressure acting on the main piston sends a signal via a fluid connection (18) to a pilot chamber (20) having the pilot piston, the pilot piston holding the main piston in a closed position blocking the main volume flow when the electromagnetic device is in a deactivated position, and when the electromagnetic device is activated the pilot piston moves to a predetermined position and the fluid pressure in the pilot chamber drops until it reaches an open position disconnected from the pressure supply via the main piston and in which the main piston activates the main volume flow.

Description

[Technical field]

[0001] The invention relates to a valve, in particular a proportional valve, which comprises a main piston for actuating a main volume flow and a pilot piston for actuating a pilot volume flow, the main piston and the pilot piston being guided longitudinally movably in a valve housing, the pilot piston being actuable by an electromagnetic device. [Background technology]

[0002] DE 10 2004 11 2005 A1 discloses in particular a valve in the form of a proportional seat valve or piston valve, which comprises 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 controllable by an energizable electromagnetic device which activates a pilot control, such that when the pilot control is opened, the fluid passes from one of the two ports controllable by the main piston, via a cross-sectional narrowing in the main piston and the pilot control, to a third port controllable by the pilot piston, and due to the resulting pressure drop the main piston reaches a respective control position in which both fluid ports can be controlled by a fluid volume.

[0003] Patent document 2 discloses a valve, particularly a pilot-controlled proportional directional seat valve, having a valve housing with a fluid inlet and a fluid outlet, the fluid flow between the inlet and the outlet being controllable by a main piston, a pilot valve chamber having a pilot valve closing member that can be moved by an actuator on the rear side of the main piston, the pilot valve closing member being capable of operating the fluid flow between the pilot valve chamber and the fluid outlet, an inlet orifice being arranged between the fluid inlet and the pilot valve chamber, the opening cross section of the inlet orifice being reducible by a control element, the inlet orifice having a plurality of orifice holes, at least one of the opening cross sections of which can be reducible by the control element, and wherein the inlet orifice is divided into a plurality of orifice holes, making it possible to switch the inlet orifice into a plurality of opening stages.

[0004] Such pilot-controlled electrohydraulically actuated directional control 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 actuating cylinder, connected to the valve. Pilot-controlled directional control valves are primarily used for controlling volume flows with low flow losses. However, a high volume flow rate and low flow losses means a large opening cross section and therefore a large stroke of the main piston. Disturbances that impair the valve function are the fluid and friction forces that oppose the switching action and depend on the volume flow rate and the pressure difference, i.e. the valve performance. In particular, in the case of mechanical actuation by a spring, usually in the form of a return spring, the set value of the spring force may be too small compared to the friction force for resetting the piston valve. In order to meet the stroke and force requirements for such an electromagnetic system, it is necessary either to design the electromagnetic system with correspondingly large dimensions or to hydraulically pilot control the valve. As mentioned above, valves are known in the prior art for such applications that are necessarily equipped with a hydraulic pilot control. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] DE 10323595 A1 [Patent Document 2] European Patent No. 2880315 Summary of the Invention [Problem to be solved by the invention]

[0006] 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]

[0007] According to the characterizing feature of claim 1, the position of the main piston is adjustable by means of a pilot piston, the fluid pressure acting on the main piston sends a signal via a fluid connection to a pilot chamber with the pilot piston, when the solenoid device is not activated the pilot piston holds the main piston in a closed position blocking the main volume flow, when the solenoid device is activated the pilot piston moves to a predetermined position and the fluid pressure in the pilot chamber drops until it reaches an open position in which it is disconnected from the pressure supply via the main piston and activates the main volume flow, thereby providing an improved control quality with an overall low pressure loss while preventing leakage during operation of the valve according to the invention.

[0008] According to the solution of the valve according to the invention, the linear adjustment of the position of the main piston, in particular via the magnetic force of the electromagnetic device, is achieved by the balance of the fluid forces and the seal friction occurring on the main piston. In this case, the pilot piston is controlled by the force of the electromagnetic device (F magnet ) by the power of the energy storage means (F spring1 ), and the pilot piston operates against the friction force (F friction ) is essentially in pressure equilibrium, and Fmagnet -F spring1 -F friction Advantageously, =0 applies. During the opening movement for actuating the main volume flow between the two possible fluid port positions in the valve housing, the pilot piston is in a state of force equilibrium, so that the stroke of the main piston can be adjusted via the pilot control. This has no equivalent in the prior art.

[0009] 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 connected to a displacement measuring device for detecting the position. Due to the advantageous control of the main piston via the pilot piston, the valve according to the invention suffices for an electromagnetic device of correspondingly small dimensions, with a reduced opening cross section in the region of the volume flow to be controlled, for which only a small stroke of the main piston is necessary. In this way, a highly dynamic proportional throttle valve is obtained.

[0010] In the following, the valve according to the invention is explained in more detail on the basis of an embodiment according to the drawings, which are principal longitudinal sections and are not drawn to scale. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a longitudinal cross-sectional view of the main components of the valve. [Diagram 2] FIG. 2 is a longitudinal sectional view of the front part of the valve according to FIG. 1 in the closed position. [Diagram 3] FIG. 3 is a longitudinal section corresponding to FIG. 2, of the valve in an open position. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The valve shown in the figures is a so-called proportional valve and has a main piston 10 for controlling the main volume flow. Furthermore, there is a pilot piston 12 for controlling the pilot volume flow, both of which are guided so that they can be longitudinally displaced in a valve housing 14. As can be seen in particular in Figure 1, the pilot piston 12 is arranged in the valve housing 14 so that it can be displaced by an electromagnetic device 16.

[0013] The position of the main piston 10 can be adjusted by means of a pilot piston 12, for which the fluid pressure acting on the main piston 10 sends a signal via a fluid connection 18 to a pilot chamber 20 with the pilot piston 12, which holds the main piston 10 in a closed position blocking the main volume flow, as shown in figure 2, when the solenoid device 16 is not activated, and when the solenoid device 16 is activated, the pilot piston 12 moves into position and the fluid pressure drops in the pilot chamber 20 until it reaches an open position in which the main piston 10 is disconnected from the pressure supply via the main piston 10 and the main piston 10 activates the main volume flow, as shown in figure 1 and 3. This is shown exemplarily for one of the possible open positions.

[0014] The pilot piston 12 is actuated by a force F of an energy storage means in the form of a compression spring 22. spring1 The force F of the electromagnetic device 16 against magnet The pilot piston 12 is operated by a friction force F friction is substantially in pressure equilibrium, and the following equation applies: F magnet -F spring1 -F friction =0, or

number

[0015] As can be further seen, the pilot piston 12 is configured as a hollow piston and, according to the representation of Fig. 2, has on its outer circumference a first recess 30 in the form of an annular groove that establishes fluid communication with the main piston 10 when the solenoid device 16 is not activated. The pilot piston 12 configured as a hollow piston has along its inner circumference a passage 32 which opens at one free end 34 into the pilot chamber 20 and, via a radially extending channel portion 36 of this axially extending passage 32, into an annular second recess 38 on the outer circumference of the hollow piston or pilot piston 12. When the solenoid device 16 is activated, the hollow piston 12 enters a tank port 40 in the valve housing 14, as shown in Figs. 1 and 3, so that fluid communication with the tank port 40 is established, but the first recess 30 is isolated from the fluid communication with the main piston 10. Both the passage portion 36 and the tank port 40 can be present in multiples as shown. In each case, a changeover valve 42 is connected in the fluid communication between the main piston 10 and the pilot chamber 20, which transmits the higher pressure from each of the two fluid ports 44, 46 in the valve housing 14 through which the main volume flow is conducted to the pilot chamber 20 as signal pressure.

[0016] If the fluid pressure at the fluid port 44 is higher than that at the fluid port 46, the fluid with the higher pressure reaches the changeover valve 42 with a closing ball 48 via the fluid port 44 and a longitudinal passage 50 in the front region of the main piston 10. Such a closing ball 48 moves to the right as viewed in the direction of the figure and closes a radial passage 52 provided in the main piston 10 and opening into the fluid port 46 in the valve housing 14. A further longitudinal passage 56, again in the main piston 10, is connected to the valve chamber 54 of the changeover valve 42, the free end face of which opens into a fluid chamber 58 in the main piston 10. The fluid chamber 58 is connected via two communicating passages 60 arranged in the main piston 10 at an inclination angle of 45° to the longitudinal axis of the valve with another fluid chamber 62 formed as an annular chamber and arranged between the valve housing 14 and the main piston 10. Subsequently, another fluid chamber 62 fluidly transitions to an annular chamber 64 arranged in the valve housing 14, from which a longitudinal flow passage section 66 leads to another annular chamber 67, which then transitions to a transverse channel portion 68 in the valve housing 14. This transverse channel portion 68 expands in cross section at its inner end towards the pilot piston 12 and can be in fluid communication with a first annular recess 30 in the outer periphery of the pilot piston 12, as shown in FIG. 2, but such fluid communication can be interrupted by the movement of the pilot piston 12 from right to left under the action of the electromagnetic device 16, as shown in FIGS. 1 and 3. It is understood that the respective flow passages and other connections can be accommodated in the valve body in multiples as shown, if necessary. In any case, the components 50, 52, 54, 56, 58, 60, 62, 64, 66, 67, 68 and 30 form the fluid connection 18 between the fluid port 44 at the end face of the main piston 10 and the pilot chamber 20 between the main piston 10 and the pilot piston 12. Thus, the pressure at the fluid port 44 in the closed position of the main piston 10 is transmitted or signaled to the pilot chamber 20 .

[0017] If the pressure at the other fluid port in the valve housing 14, the radial port 46, is greater than the pressure at the fluid port 44, the changeover valve 42 is switched to assume the closed position on the left side, as viewed in the illustrated direction, in which the closing ball 48 closes the flow passage 50. In this way, fluid with a predeterminable pressure reaches the valve chamber 54 and the other longitudinal flow passage 56 via the fluid port 46 and the radial flow passage 52, and the remaining fluid connection 18 to the pilot chamber 20 is released via such a path. Normally, fluid pressure is present at the fluid port 44 from a pressure supply device, such as a hydraulic pump, and a hydraulic consumer, such as a hydraulic cylinder, is to be connected to the fluid port. Other arrangements of the fluid ports 44, 46 are also conceivable.

[0018] 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 free end faces facing each other when viewed in the axial movement direction of the valve pistons 10, 12. A second compression spring 74, as another energy storage means, is engaged with the free end face of the second component 72 facing the electromagnetic device 16, and the second compression spring 74 is supported at its other free end on a fixed part of the valve housing 14. The compression spring 22 extends coaxially with the second compression spring 74 on the inner peripheral surface of the second compression spring 74, and is supported at one free end on an internal stepped shoulder of the second component 72 and at the other free end on an annular projection 76 of 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, and the sum of their spring forces is given by the following equation using the notation of the above equation: Fl spring +(x*c)

[0019] 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 right in the direction of looking at Fig. 2, to the state specified in Fig. 1 and Fig. 3, is performed as follows: The pressure present in the respective fluid port 44 or 46 upstream of the main piston 10 is sent as a signal via the changeover valve 42 and the fluid connection 18 to the pilot piston 12, which holds the main piston 10 in a closed state via the area difference formed by the opposing end faces of the main piston 10 by the pressure in the pilot chamber 20, as shown in Fig. 2, when the solenoid device 16 is de-energized.

[0020] If a magnetic force is generated by the solenoid device 16 and is greater than the friction force plus the spring force, the pilot piston 12 moves to the left in the direction of view of the figure, and by this movement of the pilot piston 12 to the left, the pressure supply from the side of the main piston 10 is cut off. To this end, the closed outer periphery of the pilot piston 12 closes the transverse channel portion 68 in the valve housing 14, as shown in Figures 1 and 3. However, in such a closed position, the pilot chamber 20 is connected to the tank via the second recess 38 of the passage 32 in the pilot piston 12 and through both tank connection holes 40 extending radially in the valve housing 14. These tank connection holes 40 open at their free ends into a concave annular passage 78 in the outer periphery of the pilot piston 12 in each movement position. This annular passage 78 transitions into a relief chamber 80 whose volume increases as soon as the pilot piston 12 moves to the left, thereby establishing fluid communication from the pilot chamber 20 to the respective tank port 40 via the fluid communication components 32, 36, 80, 78. This connection of the pilot control volume to tank reduces the pressure in the pilot chamber 20 and establishes a new equilibrium for the valve until the valve is fully closed.

[0021] In particular, the following overall situation arises: the magnetic force decreases and the pilot piston 12 opens the connection for the pressure supply of the main piston 10. The pilot pressure then increases and with it the pressure in the pilot chamber 20. As a result, the main piston 10 moves again from right to left, which results in a decrease in the spring forces of the compression springs 22 and 74 and a new equilibrium is created: F magnet -F spring1 -F friction =F magnet -(F1 spring +x*c)-F friction =0

[0022] The solenoid device 16 is used to control the pilot piston 12 and usually has an energizable coil 81 which, when energized, moves an armature 82 from right to left, which in turn forces the pilot piston 12 through a hollow operating rod 84 and a coupling 86. In this case, for smooth movement of the pilot piston 12, the coupling 86, which is guided so as to be freely movable in a connecting chamber 88 of the valve housing 14, is fluidly connected to the flow passage 32 through a radial cross hole 90, so that the pressure in the pilot chamber 20 is also present in the connecting chamber 88 through the flow passage 32 and the cross hole 90 (FIG. 3) and is thus transmitted in a pressure-compensating manner to the magnet system of the operating magnet, in the form of the solenoid device 16, on the outer and inner sides via the hollow operating rod 84. The above-mentioned component 86 is on the left side in the direction of view in FIG. 2 as a kind of dead space 89.

[0023] This space 89 can be filled or evacuated via at least one hole 91 in the component 86 to adjust the dynamics or damping of the valve via the respective hole 91 in the component 86 .

[0024] Furthermore, a measuring rod 92 is fixedly arranged on the second component 72 of the main piston 10. This measuring rod 92 passes through both the pilot piston 12 and the actuating electromagnetic system 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 and can measure the displacement of the main piston 10 in both directions.

[0025] Such a displacement measuring system is disclosed, for example, in DE 10 2012 014 250 A1 for a pressure compensation valve.

[0026] Furthermore, the main piston 10, as shown in particular in Fig. 2, has at its free end face a convexly formed end surface 98, formed with a predefinable radius which serves to establish a linear relationship between the stroke of the main piston 10 and the opening area of ​​the fluid port 44 or 46 produced by said stroke. The main piston 10 is otherwise guided longitudinally movably on the inner periphery of the valve housing 14 via a stepped annular surface, and a respective sealing ring system, usually in the form of O-sealing rings, provides the fluid-tight separation of the respective fluid chambers and sections as described above.

Claims

1. A valve, in particular a proportional valve, comprising a main piston (10) for actuating a main volume flow and a pilot piston (12) for actuating a pilot volume flow, The main piston (10) and the pilot piston (12) are guided in a valve housing (14) so ​​as to be longitudinally movable; The pilot piston (12) is actuated by an electromagnetic device (16); The position of the main piston is adjustable by means of the pilot piston (12), and the fluid pressure acting on the main piston sends a signal via a fluid connection (18) to a pilot chamber (20) having the pilot piston (12), and when the electromagnetic device (16) is not activated, the pilot piston (12) holds the main piston (10) in a closed position blocking the main volume flow. When the electromagnetic device (16) is activated, the pilot piston (12) moves to a predetermined position, 1. A valve, characterized in that the fluid pressure in the pilot chamber (20) is disconnected from the pressure supply via the main piston (10) and drops until the main piston (10) reaches an open position in which it operates the main volume flow.

2. The pilot piston (12) is driven by the force of the energy storage means (F ｓｐｒｉｎｇ１ ) of the electromagnetic device (16) against the force (F ｍａｇｎｅｔ ), and the pilot piston (12) is operated by a friction force (F ｆｒｉｃｔｉｏｎ ) is substantially in pressure equilibrium, and F ｍａｇｎｅｔ -F ｓｐｒｉｎｇ１ -F ｆｒｉｃｔｉｏｎ 2. A valve according to claim 1, characterized in that: = 0 applies.

3. The pilot piston (12) is configured as a hollow piston, and the pilot piston (12) has, on its outer periphery, a first recess (30) that establishes fluid communication with the main piston (10) when the electromagnetic device (16) is not activated, and on its inner periphery, a flow path (32) is formed; One free end (34) of the flow passage (32) opens into the pilot chamber (20) and opens into a second recess (38) in the outer periphery of the hollow piston through a channel portion (36) of the flow passage (32); 3. The valve of claim 1 or 2, wherein the hollow piston enters a tank port (40) in the valve housing (14) such that the first recess (30) is isolated from fluid communication to the main piston (10) when the electromagnetic device (16) is activated.

4. 2. The valve according to claim 1, wherein a changeover valve (42) is connected in fluid communication between the main piston (10) and the pilot chamber (20), and the changeover valve transmits the higher pressure of two fluid ports (44, 46) in the valve housing (14) through which the main volume flow is conducted to the pilot chamber (20) as a signal pressure.

5. a fluid chamber (58) within the main piston (10) as part of the fluid connection (18); the fluid chamber (58) opens to another fluid chamber (62) between the valve housing (14) and the main piston (10) through at least one communicating passage (60) in the main piston (10); 4. The valve of claim 3, wherein the other fluid chamber (62) opens at least partially onto the first recess (30) in the pilot piston (12) through at least one other communicating passage (64, 66, 67, 68) in the valve housing (14).

6. 4. The valve according to claim 3, wherein at least one further communication passage (78, 80) is arranged in the pilot piston (12) and the valve housing (14), and the at least one further communication passage (78, 80) connects the second recess (38) in the pilot piston (12) to a tank.

7. 2. A valve according to claim 1, characterized in that the main piston (10) is held towards the closed position by a separate energy storage means.

8. 3. The valve according to claim 2, wherein each of the energy storage means is formed of a compression spring, and the compression spring for the main piston surrounds the pilot piston with a spring stiffness higher than that of the compression spring for the pilot piston.

9. 5. The valve of claim 4, wherein the main piston (10) has a free end face (98) formed at least partially convex and having a radius to establish a linear relationship between the stroke of the main piston (10) and the opening area created in at least one of the fluid ports (44, 46) in the valve housing (14).

10. 2. The valve according to claim 1, wherein a measuring rod (92) passes through the pilot piston (12), the measuring rod (92) being connected to the main piston (10) and being part of a displacement measuring device (94) for the main piston (10).

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