Abstract
1. Device and valve for flow force compensation. 2. A device comprising at least one regulating piston (12), which is guided longitudinally movable in a housing (10) having at least two ports (A, P, T) for fluid, and which interacts with a control edge (56), following a step function, of the housing (10) at a pressure supply port (P), which supplies another port (A) serving as utility port in regulating positions of the regulating piston (12) with fluid, the pressure of which can be preset, via a fluid connection and thereby aims at pulling towards a closed position blocking this fluid connection due to occurring flow forces, wherein the regulating piston (12) has a change of shape (60) from its general outer basic shape in the area of the control edge (56) of the housing (10) for a flow force compensation such that a flow contact surface for fluid is provided, which causes a compensating force acting against the flow force to be introduced into the regulating piston (12), which force aims at pulling the regulating piston (12) into an open position opposite from the blocked position, is characterized in that the change of shape (60) also follows a step function, the function graph of which has at least one step more than the number of steps required to form the control edge (56).
Claims
1. A device comprising at least one regulating piston (12), which is guided longitudinally movable in a housing (10) having at least two ports (A, P, T) for fluid, and which interacts with a control edge (56), following a step function, of the housing (10) at a pressure supply port (P), which supplies another port (A) serving as utility port in regulating positions of the regulating piston (12) with fluid, the pressure of which can be preset, via a fluid connection and thereby aims at pulling towards a closed position blocking this fluid connection due to occurring flow forces, wherein the regulating piston (12) has a change of shape (60) from its general outer basic shape in the area of the control edge (56) of the housing (10) for a flow force compensation such that a flow contact surface for fluid is provided, which causes a compensating force acting against the flow force to be introduced into the regulating piston (12), which force aims at pulling the regulating piston (12) into an open position opposite from the blocked position, characterized in that the change of shape (60) also follows a step function, the function graph of which has at least one step more than the number of steps required to form the control edge (56).
2. The device according to claim 1, characterized in that the respective step on the regulating piston (12) forms an annular surface (62, 64, 66), which is concentric with the longitudinal axis (R) of the regulating piston (12) and perpendicular thereto.
3. The device according to claim 1, characterized in that the individual, adjacent annular surfaces (62, 64, 66) of the steps on the regulating piston (12) are spaced apart from each other by shoulder surfaces (68, 70), which are concentric with the longitudinal axis (R) and parallel thereto.
4. The device according to claim 1, characterized in that the respective annular surface (62, 64, 66), viewed in the direction of the outer circumference of the regulating piston (12), is smaller than or equal to the respective inwardly adjoining annular surface (62, 64, 66).
5. The device according to claim 1, characterized in that the respective shoulder surfaces (68, 70), viewed in the direction of the outer circumference of the regulating piston (12), in parallel to the longitudinal axis (R) of the regulating piston (12), has a smaller height than or the same height as the innermost shoulder surface (82).
6. The device according to claim 1, characterized in that the function graph has more than two steps and the shoulder surface (68) arranged at the outermost part on the regulating piston (12) is followed by a shoulder surface (70) of the same height for one step.
7. The device according to claim 1, characterized in that the innermost shoulder surface (82) on the regulating piston (12) merges into at least one fluid passage point (44) in the regulating piston (12).
8. The device according to claim 1, characterized in that the step for forming the control edge (56) at the pressure supply port (P) is formed by a transition point between at least one associated fluid passage point (74) in the housing (10) and the inner wall (76) of this housing (10), along which wall (76) the regulating piston (12) is guided in a movable manner.
9. The device according to claim 1, characterized in that in the closing direction of the regulating piston (12) for closing the respective passage point (74) with the control edge (56) in its one direction of movement in this direction, the step sequence of the control edge (56) and the change of shape (60) on the regulating piston (12) is ascending, viewed from the outside to the inside, and descending in the opposite direction of movement, viewed from the inside to the outside.
10. The device according to claim 1, characterized in that the steps of the change of shape (60) on the regulating piston (12) merge into an internal recess (78) on the outer circumference of the regulating piston (12), which recess (78) merges out at the opposite end into a further step (80), which interacts with a control edge (58) of a tank port (T).
11. The device according to claim 1, characterized in that the control edge (58) at the tank port (T) is formed by at least one assigned passage point (72) in the valve housing (10).
12. The device according to claim 1, characterized in that the length of the internal recess (78), viewed in parallel to the longitudinal axis (R) of the regulating piston (12), corresponds to the direct distance between two adjacent control edges (56, 58) of the pressure supply port (P) and the tank port (T).
13. The device according to claim 1, characterized in that at least one further fluid passage point (42) merges into the inner recess (78) on the regulating piston (12), which fluid passage point (42) is connected to the one at least one fluid passage point (44) in the regulating piston (12) via a central recess (40) in the regulating piston (12) in a fluid-conveying manner.
14. The device according to claim 1, characterized in that an orifice device (52) in the regulating piston (12) is connected to the respective further fluid passage point (42), which orifice device (52) connects the central recess (40) of the regulating piston (12), which is permanently connected to the utility port (A) in the valve housing (10) in a fluid-conveying manner, to a further central recess (48) in the regulating piston (12) in a fluid-conveying manner, with which further central recess (48) a control device for the regulating piston (12) engages at least in part.
15. The device according to claim 1, characterized in that the outer diameter of the regulating piston (12) is uniform outside the inner recess (78) and the change of shape (60) having the step function, which outer diameter is interrupted, preferably by inserted sealing strips and/or guide strips.
16. A valve, in particular a proportional pressure relief valve, which supplies a consumer with a predeterminable consumer pressure and preferably can be connected to a hydraulic drive system, comprising a valve housing (10) having at least two fluid connections (A, P, T), a device for the flow force compensation according to claim 1 and a control device for moving the regulating piston (12) between the individual regulating positions.
Description
[0024] Further advantages and features of the invention result from the figures and the description of the drawing below. The above-mentioned features and the further cited features can be implemented individually or in any combination at a device according to the invention and a valve according to the invention. The features shown in the figures are to be understood purely schematic and not to scale. In the Figures:
[0025] FIG. 1a shows a longitudinal section through an exemplary valve formed according to the invention;
[0026] FIG. 1b shows an enlarged view of the form of the change of shape used for flow force compensation;
[0027] FIG. 2a shows a longitudinal section of a part of a housing of the valve according to FIG. 1a having the device for flow force compensation according to the invention;
[0028] FIG. 2b shows an enlarged view of the form of a change of shape used for flow force compensation;
[0029] FIG. 2c shows an enlarged view of the form of an alternative change of shape used for flow force compensation similar to the solution according to FIG. 1b;
[0030] FIG. 3a shows a partial perspective view of a further embodiment of a device for flow force compensation according to the invention, shown fora regulating piston, as used in the valve according to FIG. 1a;
[0031] FIG. 3b shows an enlarged view of the form of a change of shape used for flow force compensation according to FIG. 3a; and
[0032] FIG. 3c shows an enlarged view of an alternative form of a change of shape used for flow force compensation, as used for a regulating piston according to FIG. 3a.
[0033] FIG. 1a shows a longitudinal section of a valve formed as a 3-way proportional pressure regulating valve having a regulating piston 12 longitudinally guided in a valve housing 10. The regulating piston 12, which has a valve pilot control 14, is used for the optional connection of ports formed in the valve housing 10, a pressure supply port P, a utility port A and a tank port T. The utility port A is incorporated into the valve housing 10 in the axial longitudinal direction at the left end, as viewed in the direction on FIG. 1a. The pressure supply port P and the tank port Tare each incorporated radially into the valve housing 10 in the form of individual holes arranged in a circular and annular manner. The regulating piston 12 rests against a first compression spring 16, acting as an energy storage. In doing so, one free end of the first compression spring 16 rests against the piston 12, which has a hollow-drilled hole in this end. The other end of the first compression spring 16 rests against the recess of an orifice seat body 18. The orifice seat body 18, which is stationarily arranged in the valve body 10, has a longitudinal drilled hole 20, which forms a valve seat for a seat cone 22 at one end, wherein a damping orifice 24 is provided at the opposite end. The seat cone 22 is clamped between a second 26 and a third compression spring 28 having different spring stiffnesses, wherein the spring tension of the third compression spring 28 can be adjusted via a spindle drive 30. If the seat cone 22 is lifted from the orifice seat body 18, form its pilot seat, against the action of the third compression spring 28 caused by the pressure conditions in the valve, wherein the lifting off is supported by the second compression spring 26, a fluid-conveying connection is established from the damping orifice 24 via the pilot seat into transverse ducts 32 in the orifice seat body 18. The transverse ducts 32 merge into at least one longitudinal duct 34, which is routed to the tank port T. To form the individual longitudinal duct 34, the valve housing 10 is encompassed by a cartridge-like additional housing part 36. Depending on the pressure setting via the mechanical valve pilot control 14, in any case the pressure-limiting valve opens towards the tank port T, as soon as a presettable pressure threshold value is exceeded, to protect the hydraulic circuit, including the machines and equipment connected thereto, from damaging pressure peaks or a correspondingly damaging increase in pressure.
[0034] The utility port A is connected to the pressure supply port P in a fluid-conveying manner via the regulating piston 12 resting against the first pressure spring 16, as shown in FIG. 1a, or, when the regulating piston 12 moves in the longitudinal direction into at least one further regulating position, in which the regulating piston 12 moves in the direction of a stop 38 in the valve housing 10, is connected to the tank port T. For this purpose, the regulating piston 12 has a central recess 40, which extends from the end of the regulating piston 12 assigned to the utility port A, to the fluid passage points 42 arranged in an annular manner on the regulating piston 12. In the respective further regulating position of the regulating piston 12, the fluid passage points 42 serve to establish a fluid connection from the utility port A to the tank port T. Further fluid passage points 44, offset from the fluid passage points 42 in the direction of the utility port A, are formed on the regulating piston 12, which further fluid passage points 44 serve to establish the fluid connection from the utility port A to the pressure supply port P in the regulating position of the regulating piston 12, shown in FIG. 1a. A connecting part 46 and a further central recess 48, with which the first compression spring 16 engages, are adjoined to the central recess 40 of the regulating piston 12. A further longitudinal drilled hole 50 is incorporated in the connecting part 46 of the regulating piston 12. An orifice device 52 is inserted into the further longitudinal drilled hole 50, such that a fluid-conveying connection between the central recess 40, which adjoins the utility port A, and the further central recess 48, which adjoins an inner space 54 between the regulating piston 12 and the orifice seat body 18, is guaranteed in every movement position of the regulating piston 12.
[0035] To control the pressure supply port P, the regulating piston 12 passes over a control edge 56 formed on the valve body 10. To control the tank port T, the control piston 12 passes over another control edge 58, which is also formed on the valve body 10. In the area of the control edge 56 of the valve body 10, the regulating piston 12 has a change of shape 60 from its other outer basic shape, which is cylindrical in the embodiment shown. The form of the change of shape 60 in detail can be seen in FIG. 1b, which shows the area marked X in FIG. 1a in 10-fold magnification. The change of shape 60 follows a step function, whose function graph has three steps and thus two steps more than the single-step control edge 56. On the regulating piston 12, the steps form a first annular surface 62, a second annular surface 64 and a third annular surface 66, each of which extends concentrically to the longitudinal axis R (cf. FIG. 2a) of the regulating piston 12 and perpendicular thereto. The individual, adjacent annular surfaces 62, 64, 66 are spaced apart from one another by a first shoulder surface 68 and a second shoulder surface 70, which are concentric with the longitudinal axis R (cf. FIG. 2a) of the regulating piston 12 and extend parallel thereto. From the outer circumference of the regulating piston 12 the first annular surface 62 and the second annular surface 64 have approximately the same radial extension, whereas the third annular surface 66 has a greater radial extension. The two shoulder surfaces 68 and 70 are, viewed in the direction of the outer circumference of regulating piston 12, of approximately the same height. For this special form of the change of shape 60, the fluid for flow force compensation acts on the annular surfaces 62 to 66 with different radial extensions, thereby ensuring an optimized transmission of force to the regulating piston 12 and a good flow of fluid through the fluid space defined by the change of shape 60, past the control edge 56. Particularly preferably the radial extension of the individual annular surfaces 62 to 66 is selected such that the annular surfaces 62 to 66 having different diameters each have the same surface area.
[0036] FIG. 2a shows a longitudinal section through a valve housing 10 of a device formed according to the invention, as it is a component of the valve according to FIG. 1a, with the regulating piston 12 longitudinally moveable in the housing 10. The valve housing 10 has a total of three ports for fluid, the utility port A axially introduced into the valve housing 10 and, the pressure supply port P formed radially on the valve housing 10, and the tank port T. The control edges 56, 58 of the pressure supply port P and the tank port T are each formed by several radially incorporated passage points 72, 74 in the valve housing 10. The passage points 72 assigned to the tank port Tare arranged along a circular annulus on the valve body 10, as are the further passage points 74 assigned to the pressure supply port P. The respective step for forming the control edge 56 at the pressure supply port P is formed by a transition point between the further passage points 74 in the valve body 10 and the inner wall 76 of the valve body 10, along which the regulating piston 12 is guided in a movable manner.
[0037] As the enlarged illustration of FIG. 2b shows, the control edge 56 is formed single stepped and the change of shape 60 on the regulating piston 12 is formed two stepped. The radially outer first annular surface 62 has a smaller extension in the radial direction than the adjacent second annular surface 64. The annular surfaces 62, 64, which are concentric with the longitudinal axis R of the regulating piston 12 and perpendicular thereto, are spaced apart from each other by a first shoulder surface 68, which is concentric with the longitudinal axis R and parallel thereto. To the second annular surface 64 adjoins the second shoulder surface 70, which merges into the further fluid passage point 44 in the regulating piston 12. When the regulating piston 12 passes over the control edge 56, the further fluid passage points 44 release the fluid connection from the pressure supply port P to the utility port A via the internal recess 78 of the regulating piston 12. Correspondingly, when the regulating piston 12 passes over the other control edge 58, the fluid connection from the utility port A to the tank port Tis released via the central recess 40 and the fluid passage points 42, 44.
[0038] The steps of the change of shape 60 on the regulating piston 12 merge into an internal recess 78 of the regulating piston 12, which internal recess 78 is arranged radially opposite from the inner wall 76 of the valve body 10 and merges into a further step 80 at the axially opposite end, which further step 80 interacts with the further control edge 58 of the tank port T.
[0039] In the direction of the longitudinal axis R, the orifice device 52 in the regulating piston 12 is connected to the respective fluid passage point 42, which orifice device 52 is shown in FIG. 1a and not shown in FIG. 2a for reasons of simplicity, and connects the central recess 40 of the regulating piston 12, which is permanently connected to the utility port A in the valve housing 10 in a fluid-conveying manner, to the further central recess 48 in the regulating piston 12 in a fluid-conveying manner. A control device for the regulating piston 12 not shown in FIG. 2a engages with the further central recess 48 in the regulating piston 12. The actuation system is preferably part of a solenoid system, not shown; but actuation by means of a pneumatic or another fluidic actuator or a mechanical actuation system would also be feasible.
[0040] An alternative form of a change of shape 60 having three steps is shown in FIG. 2c. A first annular surface 62, a second annular surface 64 and a third annular surface 66 are spaced apart from each other by a first shoulder surface 68 and a second shoulder surface 70, wherein a third shoulder surface 82 merges into the further fluid passage 44. The radially inner, third annular surface 66 has the greatest extension in the radial direction.
[0041] FIG. 3a shows a perspective side view of the regulating piston 12, which is rotationally symmetrical to the longitudinal axis R, with the fluid passages 42, 44 formed in the regulating piston 12 and arranged in the area of the internal recess 78. In FIG. 3a it is clearly visible that the regulating piston 12 has the same outer diameter outside the inner recess 78 and the change of shape 60 arranged adjacent to the further fluid passage points 44 and with the step function, which outer diameter is interrupted by radially circumferential constrictions 84 representing pressure relief grooves. The regulating piston 12 is tapered at the end assigned to the utility port A, shown in FIG. 3a below. The constrictions 84 are formed at regular axial distances on the outer circumference of the regulating piston 12.
[0042] FIG. 3b shows the form of the change of shape 60 following a step function in detail. For the 3-stepped change of shape 60, the first annular surface 62, the first shoulder surface 68, the second annular surface 64 and the second shoulder surface 70 each have the same extension in the radial respectively axial direction. The third annular surface 66, viewed in the direction of the outer circumference of the regulating piston 12, is larger than the annular surfaces 62, 64, which adjoin towards the outside. In addition to the constriction 84 in the regulating piston 12, it can be further easily seen from the illustration in FIG. 3b that the regulating piston 12 has a slight curvature inside in the area of the inner recess 78 in the drawing, which results from the graphic representation when a drilled hole is incorporated at the location of a shoulder surface.
[0043] The alternative form of the change of shape 60 shown in FIG. 3c differs from the form shown in FIG. 3b in that one step and thus one annular surface and one shoulder surface fewer are provided, so that from the outer circumference of regulating piston 12 a first annular surface 62, a first shoulder surface 68 and a second annular surface 64 having a greater radial extension than the first annular surface 62 are formed.
[0044] Different requirements for flow force compensation are due to different viscosities of the fluids used, the operating temperature and the pressures used as well as the form of the regulating piston 12, which is arranged in the valve body 10 in a movable manner. The different forms of the change of shape 60 on the regulating piston 12 shown in FIGS. 1b, 2b, 2c, 3b and 3c permit an optimized flow force compensation adapted to the respective control situations via the annular surfaces 62 to 66, which in conjunction form the flow contact surface for the fluid. When passing over the assigned control edge 56, a flow through space for fluid is formed in accordance with the step function that determines the change of shape 60. In the embodiments shown, the control edge 56 has a single step in each case, but step functions having more than one step at the control edge 56 are also conceivable. Due to different radial and axial extensions of the annular surfaces 62 to 66 and of the shoulder surfaces 68, 70, 82, different function graphs of the step function are specified and besides a different action of the flowing fluid, a different flow behavior is achieved at the change of shape 60 and at the control edge 56.
