Valve

Abstract

1. Valve 2. The invention relates to a valve, in particular a proportional pressure control valve, comprising a valve piston (12) which is guided in a longitudinally movable manner in a valve housing (10) for alternately releasing and connecting a utility port (A) to a pressure supply port (P) or a return port (T), and comprising an actuating device (16) for controlling the valve piston (12), which is at least partially designed as a hollow piston (46) and the interior (48) of which can be permanently fluidically connected to the utility port (A) and can be fluidically connected to the pressure supply port (P) or the return port (T) via at least one radial recess (50), and which has a further permanent fluid connection (58) in the form of an aperture (56) which connects the interior (48) of the hollow piston (46) to a control side (60) of the valve piston (12), which control side faces away from the utility port (A), characterised in that the valve piston (12) is stepped on the outer circumferential side in such a way that, with the formation of effective surfaces of different sizes, the outside diameter (dl) in the region of the respective radial recess is greater than the outer diameter (d2) in the region of the control side, and that a pressure measuring channel, which at least partially extends through the hollow piston (64) on the inner circumferential side thereof, interconnects two fluid chambers having the differently sized effective surfaces within the valve housing (10), the pressure measuring channel being part of the further fluid connection (58).

Description

[0001] HYDAC FLUIDTECHNIK GMBH

[0002] Justus-von-Liebig-Straße, 66280 Sulzbach / Saar, Germany

[0003] valve

[0004] The invention relates to a valve, in particular a proportional pressure control valve, with a valve piston guided longitudinally in a valve housing for alternately opening and connecting a service port (A) with a pressure supply port (P) or a return port (T) and with an actuating device for controlling the valve piston, which is at least partially designed as a hollow piston with its interior permanently in fluid connection with the service port (A) and can be brought into fluid connection with the pressure supply port (P) or the return port (T) via at least one radial recess and which has a further permanent fluid connection in the form of an orifice that connects the interior of the hollow piston with a control side of the valve piston that is facing away from the service port (A).

[0005] Proportional pressure control valves are very commonly used in mobile machinery for the electro-hydraulic pilot control of directional control valves. For smaller machines, directly controlled proportional pressure control valves are usually sufficient. However, in large construction or industrial machinery, such as excavators, the directional control valves of the hydraulic system reach piston diameters where pilot control with directly controlled proportional pressure control valves is no longer practical. The large spool valves generate a pilot oil flow during rapid switching that the small pilot valves cannot handle. Furthermore, such proportional pressure control valves are regularly used to control clutches in vehicles. Here, the pressure in a clutch, and thus the engagement force for torque transmission, is controlled via the control pressure at the service port (A), which is proportionally adjustable depending on the flow rate.

[0006] WO2015 / 028108 A1 discloses a generic valve in which the main or valve piston has a hollow channel designed in the form of a blind hole and which opens into the service port (A) of the valve on one free end face, forming a permanent fluid connection, and transitions into an orifice on its other free end face, which establishes a further fluid-carrying connection between the hollow channel and a hollow chamber space in the valve housing serving as a control chamber, which occupies different volumes depending on the position of the main or valve piston.

[0007] Furthermore, in the known valve solution, a control device is provided between the main or valve piston and an actuating solenoid device, which allows the valve piston to be depressurized on its piston side facing the actuating solenoid device in the direction of a tank or return connection in such a way that the main or valve piston moves in the direction of the actuating device under the supply and / or service connection pressure controllable during operation when the latter is unactuated.

[0008] DE 101 33 990 A1 discloses a directional control valve, in particular in the form of a continuously adjustable directional control valve, with a valve body guided in a valve bore of a valve housing, via which a connection between a front-side port and at least one radial port can be opened and closed, wherein the pressure acting at a port is guided to the rear of the valve body via a connecting bore and wherein the pressure is tapped at a distance from the valve body in the area of ​​the front-side port.

[0009] In one embodiment of the known valve solution according to Figure 3, the pressure acting in the area of ​​the service port (A) is transmitted via an internal bore of the piston-shaped valve spool to a rear spring chamber. This internal bore, with a constant diameter, opens into the interior on one side and into the spring chamber on the other via at least one radial bore. To minimize the influence of the flow forces, which are particularly strong in the deflection area of ​​the pressure medium, a channel-like tube is inserted into the radial bore as a throttle. This tube extends through the interior and towards the end face of the valve housing—or, as shown in Figure 3, far beyond it—so that the pressure acting in the spring chamber can be measured at a large axial distance from the openings in the cylinder or radial recesses in the hollow piston section of the valve spool.According to the requirements of this known solution, a directional control valve should be created in which discrepancies occurring in both flow directions at high pressure differentials are minimized. Furthermore, the radial recesses in the valve spool open directly at a transition point between the tube and the valve spool, and the tube transitions into a central bore in the valve spool with a widened cross-section, so that an orifice or throttling function to the spring or control chamber of the valve is thus eliminated.

[0010] Based on this state of the art, the invention aims to further improve the state of the art as defined by the generic term.

[0011] A valve with the features of claim 1 solves this problem in its entirety. According to the characterizing part of claim 1, the valve piston is designed with steps on its outer circumference such that, forming differently sized effective areas, the outer diameter in the region of the respective radial recess is larger than the outer diameter on the control side, and a pressure measuring channel, which at least partially extends through the hollow piston on its inner circumference, connects two fluid chambers with differently sized effective areas within the valve housing as part of the further fluid connection. This allows the valve according to the invention to better compensate for the flow forces occurring during operation. If such a valve is used, for example, to control a clutch, the target pressure of the clutch is controlled via the magnetic force of the valve's actuating solenoid.With conventional valve solutions, when the valve is fully open, an additional flow component is obtained, which creates a kind of pressure cushion within the valve. The back pressure of this cushion affects the magnetic force of the actuating solenoid device in such a way that the actuating solenoid device regulates a pressure that does not correspond to the necessary control pressure for the clutch. This is avoided with the valve solution according to the invention.

[0012] If the regulated pressure p is plotted against the volume flow rate Q in a diagram, this results in a kind of "bathtub" characteristic curve for known valve solutions in this context, where the regulated pressure rises again towards the initial pressure value as the volume flow rate Q increases. With the pressure measuring channel according to the invention, in the form of a pressure sensor tube, which is preferably completely enclosed inside the hollow piston, the actual pressure at a consumer, such as a coupling, can be directly measured and thus better controlled. In particular, the aforementioned "bathtub" effect is avoided; instead, a continuously decreasing characteristic curve is obtained, with the advantage of being able to directly control the respective consumer or coupling.In an advantageous embodiment of the valve according to the invention, the free end of the pressure measuring channel, which is opposite the control side, provides a pressure tap in the region of laminar flow within the valve housing near the consumer connection. Preferably, the pressure measuring channel is designed in the form of a pressure sensor tube, which thus constitutes a fluid-carrying measuring line. Because the pressure tap takes place in the region of laminar flow near the consumer connection, the pressure tapped at the inlet side by means of the tubular pressure measuring channel is independent of any pressure increases caused by the flow.

[0013] In another preferred embodiment of the valve according to the invention, it is provided that the pressure measuring channel

[0014] a single-piece component of the valve piston,

[0015] It is part of an installation kit that can be screwed into the valve piston or connected to it by means of a flared connection.

[0016] From a manufacturing perspective, it is advantageous to insert the mounting kit with the integrated pressure measuring channel into the end of the valve piston cavity. Then, by widening a crimped groove at the transition point between the mounting kit and the tubular pressure measuring channel, a radially circumferential engagement flank is created. This flank acts as a retaining element, engaging at least partially with the adjacent inner wall of the valve piston, thus establishing a secure, and in particular positive-locking, connection between the valve piston and the mounting kit with the pressure measuring channel. In this way, a secure fixation of the mounting kit with the integrated pressure measuring channel can be achieved, even under the typically confined installation conditions within the valve piston.

[0017] Preferably, the pressure measuring channel covers the respective radial recess in the hollow piston with a predefinable radial and axial distance. In a further particularly preferred embodiment of the valve according to the invention, the pressure measuring channel is provided with a further orifice on its side opposite the orifice. For preferably homogeneous fluid flow, the inner diameter of the pressure measuring channel is constant, at least as far as it engages the interior of the hollow piston, and the pressure measuring channel is designed in the manner of a pressure measuring tube or pressure measuring tube. Preferably, the fluid-carrying connection with a throttling point in the form of a measuring line of the pressure measuring channel opens with the orifice in the region of an annular shoulder on the valve piston, which at least partially delimits the control chamber in the valve housing.

[0018] In a further preferred embodiment of the valve according to the invention, one annular shoulder of the stepped valve piston, at which the orifice opens, is guided in the control chamber in the valve housing, which is at least partially enlarged in diameter compared to the valve piston. This control chamber can be separated from a further control chamber in the valve housing by means of the valve piston, in which another annular shoulder of the valve piston is at least partially guided, and the further control chamber is larger in diameter than the first control chamber. By taking into account the differently designed sizes of the individual control chambers, a defined control edge is preferably created at the transition point between the two control chambers, which further improves the switching behavior of the valve.

[0019] In a further preferred embodiment of the valve according to the invention, the additional control chamber is permanently connected to the return port by means of the additional orifice, and an additional gap-like fluid connection between the two control chambers is established, at least when the valve piston reaches its maximum stroke, at which point one control chamber is in fluid-carrying contact with the pressure supply port via the channel-like pressure sensing tube and the orifice. Preferably, the cavity of the valve piston and the pressure sensing tube are arranged concentrically to the axis of travel of the valve piston.

[0020] The described fluid connection from the service port via the pressure measuring channel, the orifices, the control chambers, and finally via the control edge located upstream of the tank or return port, results in a pressure differential at the associated orifice. This differential generates a resulting pressure force from the service port towards the magnetic actuator of the operating device, counteracting it. This prevents the valve piston from reaching its maximum end position, particularly through the use of a mechanical stroke, and ensures instantaneous valve return during dynamic switching operations. The valve switches rapidly from a maximum opening in the area of ​​the control edge, which connects the pressure supply port to the service port, to a stroke range with minimal overlap.

[0021] For the technical implementation of the valve, it is advantageous that the cavity of the valve piston and the pressure sensing channel are arranged concentrically to the axis of travel of the valve piston. Furthermore, it is preferably provided that the inner diameter of the pressure sensing channel, at least at its transition to the cavity of the valve piston, is less than or equal to the free diameter of the smallest radial recess in the hollow piston, designed as a transverse bore. It is also preferably provided that the free axial length of the pressure sensing channel in the cavity of the hollow piston is substantially equal to or greater than half the axial length of the cavity of the hollow piston as seen along the axis of travel of the valve piston. The valve according to the invention is explained in more detail below with reference to embodiments. These are shown in a general and not to-scale representation.

[0022] Figure 1 shows a first embodiment of the valve as a whole in an inactive position, in the form of a longitudinal section view;

[0023] Figure 2 shows, in enlarged form, the lower part of the valve according to Figure 1 in an actuated position and without an associated valve block;

[0024] Figure 3 shows the valve according to Figures 1 and 2 in the form of a switching symbol commonly used in hydraulics; and

[0025] Figures 4 to 6 show further embodiments of valve solutions comparable to the illustration in Figure 2.

[0026] The valve shown in its entirety in Figure 1, in the form of a proportional pressure control valve, has a valve piston 12 that is longitudinally movable within a valve housing 10. This arrangement serves to alternately open and close a service port A with a pressure supply port P or a return port T. As shown in Figure 1, the valve, or rather the valve housing 10, is conventionally mounted in a valve block 14, and the individual ports A, P, and T in the valve housing 10 are accordingly continued in the valve block 14. The service port A leads to a hydraulic consumer, such as a vehicle clutch. The pressure supply port P, on the other hand, is connected to a pressure supply source, for example, a hydraulic pump, and the return port T leads conventionally to a reservoir containing fluid, for example, a hydraulic fluid.The pressure supply source regularly draws fluid from the storage tank to supply the hydraulic consumer via the service port A. Conversely, even when the pressure supply is shut off via the pressure supply port P, the service port A can be fluid-carrying connected to the return port T to prevent the pressure supply to the consumer. Figure 1 shows the valve in its unactuated position, i.e., the pressure supply port P is shut off by means of the valve piston 12, and the fluid connection between the service port A and the return port T is correspondingly opened. While only one service port A is used, the pressure supply port P and the return port T can each also be formed from several bores of a bore series, as shown.

[0027] For the movement of the valve piston 12, an actuating device 16 in the form of a magnetic actuation system is used. The actuating device 16 has a magnetic armature 18 which is longitudinally guided in a magnetic housing in the form of a pole tube 20, which is pressure-tightly sealed to the environment by means of a closing element 22. The cylindrically designed magnetic armature 18 has both a compensating bore 24 extending through it and an anti-stick or anti-adherent disc 26 for unimpeded operation. A coil 30 with a coil winding, which can be supplied with power externally via a connector 32, is used to actuate the magnetic armature 18 in a direction of travel along a longitudinal or actuating axis 28.When the coil 30 is energized via the connector 32, the coil 30 generates a magnetic field that causes the magnetic armature 18, viewed in the direction shown in Figure 1, to move from its upper, unactuated position to an actuated lower position until it contacts the disk 26. In the unenergized state, the magnetic armature 18 is returned to its original position by a return spring 34 in the form of a compression spring, which is located at the lower end of the valve housing 10 in the area of ​​the service port A.

[0028] A rod-shaped actuating element 36, which is inserted upwards into the magnetic armature 18 and rests loosely downwards on the upper free end face of the valve piston 12, is used to actuate the valve piston 12 by means of the magnetic armature 18, and is permanently connected to it. The rod-shaped actuating element 36 is guided longitudinally in the pole tube 20 by means of a sliding bearing bushing 38. The pole tube 20 is also penetrated by a further compensating bore 40, one free end of which opens into an armature chamber 42 and the other free end into a piston chamber 44 of the valve housing 10. Similar to the compensating bore 24 in the magnetic armature 18, the further compensating bore 40 in the pole tube 20 also serves to ensure unimpeded valve operation.

[0029] As can be seen from the enlarged section of Figure 2, which shows the lower half of the valve according to Figure 1, the valve piston 12 is partially designed as a hollow piston 46 and its interior 48 is permanently in fluid contact with the service port A in every valve position. The service port A is centrally located on the lower free end face of the valve housing 10. The service port A can be brought into fluid-carrying contact with the pressure supply port P or the return port T via at least one radial recess 50 in the valve piston 12.In this case, a radial recess 50 is formed from several bores, for example six bores 52, which are arranged equidistant from each other and orthogonally opposite each other to the longitudinal or actuation axis 28, extend circumferentially on the outside of the valve piston 12, and transition radially outwards into a row of bores 54 in the valve piston 12 with a correspondingly increased bore diameter. Furthermore, an orifice 56 with a constant opening cross-section is provided at an upper end point of the valve piston 12, which establishes a further permanent fluid connection 58 between the interior 48 of the hollow piston 46 as part of the valve piston 12 and a control side 60 of the valve piston, which can be actuated simultaneously by the magnetic system 16.The corresponding control side 60 is located on the side of the valve piston 12 facing away from the service port A and is divided into various sections, which will be explained in more detail below. The radial bores 52 in the valve piston 12, which are covered by the pressure measuring tube as part of the pressure sensing channel 62, open into a free rotation with two control edges, which allow for the reciprocal release of the oil flow from the pressure supply port P to the service port A or from the service port A to the tank return port T. This also results in reciprocal flow through the radial recess 50 with its bores 52 in the area of ​​the tube. In this respect, the pressure measuring tube or the fluid channel 62 terminates within the valve piston 12 in this area.

[0030] As can be further seen from the figures, the pressure measuring channel 62, as a pressure signal tube and as part of the further fluid connection 58 in the direction of the service port A, is completely enclosed within the interior 48 of the hollow piston 46 as part of the valve piston 12, wherein the respective radial recess 50, in the form of a row with the bores 52 in the hollow piston 46, is covered by the latter at a predefinable radial distance X and, viewed in the axial direction, at a predefinable distance Y from the free end of the pressure signal tube 62, and wherein the pressure signal channel 62 itself, designed as a type of throttle with a predefinable tube length, is permanently fluid-carrying connected to the orifice 56 arranged in the hollow piston 46. The valve piston 12 has a solid upper piston part 63, which points in the direction of the actuating device 16.The hollow piston 46 itself is designed as a hollow cylindrical piston part 65 of the valve piston 12, which is integrally connected to the solid piston part 63 in the direction of the service port A. The pressure sensing channel 62 is formed by a fluid-carrying channel which, in the manner of a bore with a constant inner diameter, extends through the solid piston part 63 to the level of the orifice 56 along the longitudinal or actuation axis 28, wherein the orifice 56 opens into the pressure sensing channel 62 on one side and transitions into a bore 67 with a larger inner diameter than the orifice 56 on the opposite side, and wherein the pressure sensing channel 62 is in continuous fluid communication with the piston chamber 44 in the valve housing 10 via the bore 67 and the orifice 56.The terms pressure sensing channel 62 or pressure measuring tube are chosen because the pressure channel transmits the fluid pressure prevailing in the cavity 48 of the piston part 65 to the rear of the valve piston 12 via the orifice 56, or rather, measures this pressure. In this respect, the fluid channel 62 also forms a kind of measuring line 84 for the fluid pressure to be measured within the valve.

[0031] As can be seen from Figures 1 and 2, the fluid channel, or rather the pressure sensing channel 62, opens into a tubular or tube-shaped channel section 69, which leads into the interior 48 of the hollow piston 46. The free end of the channel section 69 opens into the interior 48 of the hollow cylindrical piston part 65 along the longitudinal axis 28 and just below the row of bores of the radial recess 50 in the valve piston 12. Furthermore, the channel section 69, which is arranged concentrically to the longitudinal axis 28, is an integral part of the solid piston part 63 and thus of the valve piston 12.

[0032] As can be seen further, particularly from Figure 2, the inner diameter of the pressure sensing channel 62 is constant, at least insofar as it engages the interior 48 of the hollow piston 46. Furthermore, the outer circumference of the pressure sensing channel 62, together with the inner circumference of the valve piston 12, defines an annular space 64 in this area, which is open towards the service port A. In this direction, the annular space 64 is interrupted laterally to the outside after a predefinable axial distance from its base, which is less than half the length of the pressure sensing channel 62, by the respective radial recess 50 in the hollow piston 46, which lies in a horizontal plane. In this way, the valve piston 12 with its fluid connection points and the pressure sensing channel 62 can be manufactured as a whole in a simple manner, for example by machining.

[0033] The further fluid-carrying connection 58 with the respective throttling point in the form of the pressure sensing channel 62 and the orifice 56 opens via the bore 67 onto an annular shoulder 66 on the valve piston 12, which, as part of the control side 60, defines a control chamber 68 in the valve housing 10, forming the piston chamber 44. The annular shoulder 66 is penetrated by at least one hollow channel 70, which is arranged parallel to the longitudinal or actuation axis 28 on an outer side of the valve piston 12, which, viewed diametrically opposite this axis 28, is the orifice 56.In the actuated valve position as shown in Figure 2, where the valve piston 12 is displaced downwards in the direction of view of Figure 2 against the action of the return spring 34 by means of the actuating device 16, the hollow channel 70 opens into a further control chamber 72, thus creating a fluid-carrying connection between the first control chamber 68 and the further control chamber 72. A fluid gap in the form of a control edge 74, formed by a further annular shoulder 76 on the valve piston 12 and an adjacent wall-like shoulder 78, is exposed in the valve housing 10. In the unactuated position of the valve piston 12 as shown in Figure 1, the fluid gap, or control edge 74, is closed, and the two control chambers 68 and 72 are essentially fluid-tightly separated from each other.

[0034] The further annular shoulder 76 on the valve piston 12 is defined by a diameter d2 on the valve piston 12, which lies between a reduction in diameter towards the orifice 56 and a diameter expansion with the piston diameter d1 in the area of ​​the fluid connections P, T. Accordingly, the valve piston 12 has two differently sized pressure or effective surfaces A1, A2 on its outer circumference, due to the different diameters d1, d2 on the outer circumference of the valve piston 12, where d1 is larger than d2. The further control chamber 72 is permanently connected to the return connection T by means of a further orifice 80, wherein the free flow cross-section of the further orifice 80 is dimensioned larger than that of the first orifice 56. For the permanent connection of the further orifice 80 to the return connection T, a drain 82 is arranged adjacent to and segmentally within the valve housing 10.As can be seen from Figure 1, this drain 82, together with the return connection T in the valve housing 10, leads into the corresponding connection point in the valve block 14.

[0035] The cavity in the form of the interior 48 of the hollow piston 46, the annular space 64, and the pressure sensing channel 62 are arranged concentrically to the travel axis in the form of the longitudinal axis 28 of the valve piston 12. Furthermore, the inner diameter of the pressure sensing channel 62, as part of a type of pressure measuring line 84, is, at least at its transition to the cavity or interior 48 of the valve piston 12, less than or equal to the free diameter of a smallest radial recess 50 in the hollow piston 46, which is designed as a transverse bore 52. The free axial length of the pressure sensing channel 62 in the valve piston 12 is essentially equal to half or slightly greater than half of the axial length of the valve piston 12 as seen along the travel axis 28.

[0036] The return spring 34 is supported at its lower free end, in the direction of the service port A, by an inwardly crimped edge of a spring sleeve 88, and at its other free end by a contact ring 90, which is engaged from above by a projecting contact surface 92 of the valve piston 12 in this area. The spring sleeve 88 itself is held in the direction of the service port A by a snap ring 94 in the valve housing 10 and its free end face is flush with the underside of the valve housing 10, which in this area encompasses the service port A. In the area of ​​the contact ring 90, individual bores 96 are provided in the valve piston 12 in a radial direction towards the inside, which can serve for pressure equalization.Above the snap ring fastening with the snap ring 94, the spring sleeve 88 has a circumferential web 98 on its outer circumference, which in this area is arranged in a guide 100 in the valve housing 10 in a lowest position due to the action of the compression spring 34.

[0037] In the unactuated position according to Figure 1, the valve piston 12 fluidly separates the pressure supply port P from the service port A, and this service port A is then connected to the return port T, carrying the fluid. In this unactuated position, the control edge in the form of the fluid gap 74 is closed, and the two control chambers 68 and 72 are thus separated from each other by their respective orifices 56 and 80. In the actuated position according to Figure 2, the pressure supply port P is connected to the service port A, and the return port T is blocked by the outer circumference of the valve piston 12. In this respect, the two control chambers 68 and 72 with their orifices 56 and 80 respectively are fluid-conductingly connected to each other via the fluid gap 74 on the further annular shoulder 76, forming the control edge, and the control edge in this respect controls the fluid flow between the throttle in the form of the measuring line 84 and the orifices 56 and 80.The fluid flow at aperture 56 leads to a pressure loss which exerts different forces on surfaces A1 and A2 and thus counteracts the force exerted by the magnet.

[0038] As can be seen further, and in particular from Figure 2, a fluid pressure P1 prevails at the service port A and a fluid pressure P2 prevails on the control side 60 of the valve piston 12, in particular in the piston chamber 44, whereby pressure equilibrium prevails in the static, unactuated state of the valve, i.e., P1 = P2. In the actuated state, in which the actuating device 16 is energized, the actuating part 36 exerts a force F. M on the valve piston 12, viewed from top to bottom in the direction shown in the figures, wherein a spring force F acts in the opposite direction to this actuating force. Federcounteracts the return spring 34. Taking into account the differently effective pressure surfaces A1, A2, which result from the different diameter values ​​d1 and d2 on the outer circumference of the valve piston 12, the following force formula is obtained:

[0039] F M + 42(d2) * P2 - 41(dl) * PI - F Feder = 0

[0040] In particular, a pressure drop AP can occur via the two orifices 56, 80 during valve operation, such that the pressure P2 in the control chamber 68 with the control side 60 becomes lower than the fluid pressure P1 at the service port A. This results in a pressure force radiating from the service port A towards the magnetic actuation of the actuator 16 and thus acts on the magnetic force F. MOn the contrary. In this way, the valve piston 12 can no longer assume its maximum, lower end position as a mechanical stop, which could lead to a kind of sticking of the valve piston 12 in the deflected position, making return difficult. Rather, by preventing the mechanical stop, as described above, in the manner of a virtual hook, an immediate return of the valve is achieved during dynamic switching operations. This has no equivalent in the prior art. For the desired functionality, it is sufficient to provide the return spring of the 34 with a soft to very soft spring characteristic.

[0041] The modified embodiments according to Figures 4 to 6 are only explained insofar as they differ substantially from the preceding embodiment according to Figures 1 and 2. The same components with the same reference numerals are used as above, and the explanations given for them also apply to the embodiments according to Figures 4 to 6.

[0042] In the embodiment shown in Figure 4, an installation kit 102 is used, which can be inserted into the valve piston 12 as shown. The installation kit 102, in the form of an insert, again has a pressure measuring channel 62 in its center, which passes centrally through the upper solid piston part 63. The fluid channel 62 protrudes from the piston part 63 on its side facing the service port A via a measuring tube 69. The valve piston 12 is again partially designed as a hollow piston 46 in the direction of the service port A, and a fluid cavity in the form of a measuring chamber 104 is created in the valve piston 12 in the direction of the orifice 56. This chamber has a larger inner diameter than the fluid channel 62. The measuring chamber 104 itself has no functional relevance. It is merely designed so that it does not present any additional hydraulic resistance between the service port A and the pressure chamber 68.

[0043] By pressing a circumferential annular groove 106 into the free end face of the insert part or installation kit 102, wherein an annular or flanged groove 106 extends concentrically to the longitudinal axis 28 and to the pressure sensing channel 62, a circumferential outer edge 108 of the annular groove 106 is then, as shown in Figure 4, displaced into the wall area of ​​the adjacent inner wall of the valve piston 12 and thus a retention is created which defines and secures the installation kit 102 on the inner circumferential side of the valve piston 12, whereby the interlocking is also secure when higher pressure differences occur.

[0044] The embodiment shown in Figure 5 corresponds to the embodiment shown in Figure 4, except that the orifice 56 in the connection area between pressure sensing channel 62 and measuring chamber 104 has been moved from a radial position to an axial position, and is therefore no longer located at its previous position in the area of ​​the ring switches 66. This orifice acts as an "axial" damping orifice 110 and increases the stability of the valve during operation. The damping orifice 110 can also be arranged within the pressure sensing channel 62.

[0045] In the further embodiment shown in Figure 6, the construction differs in that the installation kit 102 with the fluid channel 62 is now permanently connected to the valve body in the form of the piston 12 via a threaded section 112 in a releasable manner. To create this threaded connection, the tubular pressure sensor channel 62 has an engagement point 114 on its lower free end face, which faces the service port A, for the engagement of an actuating tool (not shown), for example, in the form of an internal hexagon, which, in conjunction with a corresponding wrench, allows the installation kit 102 to be screwed into and out of the wall of the valve piston 12.

Claims

1. P at e n t a n s p r ü c h e 1. Valve, in particular a proportional pressure control valve, with a valve piston (12) guided longitudinally in a valve housing (10) for alternately opening and connecting a service port (A) to a pressure supply port (P) or a return port (T) and with an actuating device (16) for controlling the valve piston (12), which is at least partially designed as a hollow piston (46) with its interior (48) permanently in fluid connection with the service port (A) and can be brought into fluid connection with the pressure supply (P) or the return port (T) via at least one radial recess (50) and which has a further permanent fluid connection (58) in the form of an orifice (56) which connects the interior (48) of the hollow piston (46) to a control side (60) of the valve piston (12) which is connected to the service port (A) turned away, characterized in that the valve piston (12) is designed with steps on its outer circumference,that, by forming differently sized effective areas, the outer diameter (dl) in the area of ​​the respective radial recess is larger than the outer diameter (d2) in the area of ​​the control side, and that a pressure measuring channel, which at least partially extends through the hollow piston (64) on its inner circumferential side, connects two fluid chambers with the differently sized effective areas within the valve housing (10) as part of the further fluid connection (58).

2. Valve according to claim 1, characterized in that the free end of the pressure measuring channel, which is opposite the control side, passes through a pressure tap in the area of ​​the laminar flow within the valve housing (10) in the vicinity of the consumer connection (A).

3. Valve according to claim 1 or 2, characterized in that the pressure measuring channel 4. A one-piece component of the valve piston is, 5. Part of an installation kit is which can be screwed into the valve piston (10) or connected to it by means of a flared connection.

4. Valve according to one of the preceding claims, characterized in that the pressure measuring channel covers the respective radial recess (50) in the hollow piston (40) with a predefinable radial (X) and axial (Y) distance.

5. Valve according to one of the preceding claims, characterized in that the pressure measuring channel is provided with a further orifice (80) on its side opposite the orifice (56).

6. Valve according to one of the preceding claims, characterized in that the inner diameter of the pressure measuring channel (62), at least as far as it engages in the interior of the hollow piston (46), is constant and that the pressure measuring channel (62) is designed in the manner of a pressure measuring tube.

7. Valve according to one of the preceding claims, characterized in that the fluid-carrying connection (58) opens with a throttling point in the form of a measuring line (84) of the pressure measuring channel (62) with the orifice (56) in the area of ​​an annular shoulder (66) on the valve piston (12), which at least partially limits the control chamber (68) in the valve housing (10).

8. Valve according to one of the preceding claims, characterized in that one annular shoulder (66) of the stepped design Valve piston (12) at which the orifice (56) opens, in which at least partially a control chamber (68) is guided in the valve housing (10) which is at least partially wider in diameter than the valve piston (12), which can be separated from a further control chamber (72) in the valve housing (10) by means of the valve piston (12), in which a further annular shoulder (76) of the valve piston (12) is at least partially guided, and that the further control chamber (72) is larger in diameter than the one control chamber (68).

9. Valve according to one of the preceding claims, characterized in that the further control chamber (72) is permanently connected to the return port (T) by means of a further orifice (80) and that at least when a maximum stroke of the valve piston (12) is reached, in which one control chamber (68) is in fluid-carrying contact with the pressure supply port (P) via the pressure sensing channel (62) and the orifice (56), an additional gap-shaped fluid connection (74) is established between the two control chambers.

10. Valve according to one of the preceding claims, characterized in that the cavity (48) of the valve piston (12) and the pressure sensing channel (62) are arranged concentrically to the travel axis (28) of the valve piston (12).

11. Valve according to one of the preceding claims, characterized in that the inner diameter of the pressure sensing channel (62), at least at its transition to the cavity (48) of the valve piston (12), is smaller than or equal to the free diameter of a smallest radial recess in the hollow piston (46) designed as a transverse bore (52). 22 12. Valve according to one of the preceding claims, characterized in that the free axial length of the pressure sensing channel (62) in the cavity (48) of the hollow piston (46) is substantially equal to or greater than half the axial length of the cavity (48) of the hollow piston (46) seen in the travel axis (28) of the valve piston (12).

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