Patent Application
20140326336
The invention relates to a valve, in particular a pressure regulating valve for controlling the pressure of a medium flowing through the valve, having a main stage and a pilot stage that controls the main stage and is itself controlled by means of an energizable actuating device against the action of a return device, and having a pressure relief stage of the valve.
Valves, in particular for oil hydraulic systems, such as pressure regulating valves for controlling a pressure of a medium flowing through the valve are sufficiently well known. U.S. Pat. No. 4,316,599, for example, describes a proportional pressure regulating valve, which supplies an essentially constant output pressure with a variable input pressure. The output pressure of the pressure regulating valve to be controlled is preselected by a current signal originating from a corresponding control electronics for an actuating magnet of a magnetic system. Proportional pressure regulating valves in this regard are preferably designed as directly controlled piston slide valves in a three-way embodiment. Valves in this regard are used in oil hydraulic systems, for example, for controlling clutches in manual transmissions or automatic transmissions for a targeted influence on the pressure buildup and dissipation of pressure on hydraulic consumers, for remote setting of the pressure or for pilot control of hydraulic valves and hydraulic actuators in a variety of designs.
DE 10 2005 006 321 A1 discloses a valve, in particular a proportional pressure limiting valve, having a valve housing with at least two fluid connections, wherein the valve can be connected to a hydraulic drive system at a predefinable load pressure. The valve is also suitable for use in hydraulic systems with fluid media of a low viscosity due to the fact that a valve piston, which is operatively connected to a pilot seat by means of an energy accumulator, can be controlled by means of a control device, and the applied consumer pressure on a fluid connection acts at least on the valve piston in such a way that a fluid flow between the two other fluid connections in both directions within the valve housing is possible, depending on the applied consumer pressure and the actuating force of the control device so far. A main stage of the valve can be controlled by a pilot stage in the direction opposite the action of a return device by means of an energizable actuating device. The valve also has a pressure relief stage in its pilot stage.
DE 10 2007 015 077 A1 discloses a slide valve for hydraulic systems such as proportional pressure limiting valves or pressure compensators, having a valve housing which is preferably designed in the form of a screw-in cartridge, in which a valve slide is axially displaceable and has an inflow opening through which fluid flows into the valve housing, and having at least one outflow opening which is formed in the wall of the valve housing and can be closed by the valve slide, depending on the axial position of the valve slide, or can be released for the outflow of fluid out of the valve housing. To reduce cavitation phenomena with the slide valve, it is provided that an annular groove cut into the inside wall of the valve housing is present, said annular groove being positioned with respect to its axial position at the height of the at least one outflow opening, such that a control edge of the valve slide overruns the annular groove in its movement out of the position that closes the outflow opening and into the release position. In some applications of the hydraulic or pneumatic system, a fail-safe behavior of valves is desired in this regard, which means that in the event of a malfunction of the control of a valve, in particular in a failure of an energizable actuating device for the valve, the valve assumes a predefinable function, and in particular a valve element of the valve assumes a predefinable switch position. It is therefore possible to select the functions or operating points of the hydraulic system that are desired in a hydraulic system. One example that can be mentioned here is hydraulic or pneumatic switch elements in cooling systems because when their control fails, the cooling system in this regard nevertheless maintains its function.
DE 44 42 085 A1, EP 0 030 083 A2, U.S. Pat. No. 4,750,704 and DE 30 42 015 A1 each have pilot-controlled proportional pressure regulating valves having a pressure relief stage.
Starting from this prior art, the object of the present invention is to provide a valve, in particular a pressure regulating valve or a pressure limiting valve for controlling a pressure of a medium flowing through the valve which has a predefinable fail-safe behavior.
According to the invention, this object is achieved by a valve having the features of patent claim 1 in its entirety.
Due to the fact that the pressure relief stage of the pilot stage of the valve has a surface area modification device, it is possible for the valve according to the invention to enable a fail-safe function due solely to the media pressure on the valve and preferably to a media pressure of the pilot stage and an implementation of the media pressure by the surface area modification device, and a valve element of the valve, in particular a fail-safe switch position achieved due to the surface area modification device in operative connection to the pilot stage. The inventive design of the pilot stage together with the pressure relief stage, which is formed as a surface area modification device, ensures a predefinable fail-safe behavior of the valve in the event of a failure of the energizable actuating device of the valve.
In a particularly preferred exemplary embodiment of the valve, the surface area modification device has a first, larger pressure-active surface area and a second, comparatively smaller pressure-active surface area. A media pressure, which is influenced by the pilot stage, acts on both pressure-active surface areas, which form a surface area difference, so that the main stage of the valve is controlled by the pilot stage of the valve merely through the action of the media pressure to achieve a fail-safe behavior because of the predefinable surface area difference within the surface area modification device. It may also be advantageous to design the surface area modification device with the help of at least one aperture in the pilot stage. A fail-safe function is thus easily and completely integrated into the valve according to the invention.
A valve element of the main stage is advantageously moved into, and held in a predefinable position, which is determined by at least the difference in surface area of the pressure-active surface areas and a media pressure at a pressure source connection for the valve. The valve element of the main stage may also be moved by the action of the aperture and a media pressure at the pressure source connection for the valve into the predefinable position and held there. The media pressure at the pressure source connection for the valve is determined by the force FN of the actuating device, the force FR of the return device and the surface area difference F1−F2 of the pressure-active surface areas according to the formula:
The pressure at the connection changes with the magnetic force [and] the pressure is limited independently of the volume flow.
The valve opens on reaching the pressure of the pressure stage.
With the inventive valve, it is particularly advantageous that, contrary to the prior art, from which a “falling characteristic line” of the solenoid current plotted as a function of the media pressure on a pressure source connection of a valve is known only for so-called “pulling magnets,” with the inventive valve, it is possible for a “pushing” magnet” to also generate a “falling characteristic line” in this regard. In the case of the inventive valve, the actuating device for actuation of the pilot stage thus exerts a compressive force on an actuating tappet of the pilot stage to achieve the aforementioned characteristic line curve.
The actuating device is particularly preferably formed by an energizable coil device whose solenoid armature applies a compressive force to the actuating tappet of the pilot stage, so that with an increase in the solenoid current, the pressure on the pressure source connection of the valve drops independently of the volume flow.
In a particularly preferred exemplary embodiment of the valve, the pressure-active surface areas of the surface area modification device according to the invention are formed by diameter steps on the actuating tappet
of the pilot stage, which is arranged on the actuating tappet at an axial spacing and, together with the bordering walls of a guide for a valve seat, forms a guide for the actuating tappet. This yields a particularly simple structural solution for integrating the inventive fail-safe function into the valve. No additional components are needed on the inventive valve to enable the fail-safe function, but instead the components present are used to implement the function in this regard. This yields a particularly inexpensive design of the inventive valve, which can be produced easily and rapidly.
The first, larger pressure-active surface area of the surface area modification device advantageously forms a conical valve seat together with the guide for the actuating tappet. The pilot pressure limiting valve may also be designed as a slide. When the actuating device is actuated, the valve seat permits a medium to flow from the surface area modification device belonging to the pilot stage to a tank connection for the valve.
The first, larger pressure-active surface area is advantageously situated on a free end of the actuating tappet facing away from the actuating device. In a particularly preferred exemplary embodiment of the valve as an energy accumulator, the return device is preferably formed as a helical compression spring, which is supported on the free end of the actuating tappet and on a receptacle in the guide for the actuating tappet. The guide and the return device may also be situated in the axial area of the valve element of the main stage.
It may also be advantageous for the return device to be designed as an energy accumulator and preferably as a helical compression spring and to be situated between the first, larger and the second, smaller pressure-active surface areas of the surface area modification device, wherein the helical compression spring may be supported at least indirectly on a receptacle for the guide of the actuating tappet and on the second, smaller pressure-active surface area. This embodiment of the inventive valve has the advantage in particular that its axial length is reduced and the valve has a very compact design.
The inventive valve may have a pressure limiting function or a pressure regulating function and is thus designed in particular preferably as a pressure limiting valve or as a pressure regulating valve.
The invention is explained in greater detail below on the basis of the drawings. The drawings show in schematic diagrams which are not drawn to scale:
In a schematic longitudinal section, which is not drawn to scale,
The surface area modification device 15 has a first, larger pressure-active surface area F1 and a second, smaller pressure-active surface area F2 opposite the former. The pressure-active surface areas F1, F2 together form a surface area difference F1−F2. A media pressure pv, which is influenced by the pilot stage 7, acts on the pressure-active surface areas F1, F2. It may also be advantageous to provide the surface area modification device 15 with an aperture, in particular in the form of a damping aperture 17, which is upstream from the actual modification device 15 in the direction of fluid flow.
Through the action of the surface area modification device 15, a valve element 19 of the main stage 5 is kept in a position determined by at least the surface area difference F1−F2 of the pressure-active surface areas F1, F2 and/or by the action of at least the first aperture 17 and of the media pressure p on a pressure source connection 21 of the valve 1, in particular when the actuating device 9 is not actuated. The media pressure p on the pressure source connection 21 of the valve 1 is determined here by the force FN of the actuating device 9, the force FR of the return device 11 and the surface area difference F1−F2 of the pressure-active surface areas F1, F2 according to the formula
When the magnet is not actuated, the valve element automatically assumes the throttle position on reaching the maximum pressure, this being required to achieve the maximum pressure at the given volume flow.
For actuation of the pilot stage 7, the actuating device 9 applies the force FN in the form of a compressive force FD to an actuating tappet 23 of the pilot stage 7, where preferably FN=FD. The actuating device 9 has an energizable coil device 25, in which, when energized, a solenoid armature 27 applies the compressive force FD to the actuating tappet 23 of the pilot stage 7. With an increase in the volume flow of the medium 3, which is passed through the valve 1, the pressure p of the medium on the pressure source connection 21 drops. The pressure-active surface areas F1, F2 are formed by diameter steps 29, 31 on the actuating tappet 23 of the pilot stage 7 and are arranged at an axial spacing on the actuating tappet 23. The wall parts of the actuating tappet 23, which border the pressure-active surface areas F1, F2, form a valve seat 39 and/or a valve sealing surface 37 together with the bordering walls 33 of a guide 35 on the housing side for the actuating tappet 23.
The first, larger pressure-active surface area F1 of the surface area modification device 15 forms the conical valve seat 39 together the guide 35 of the actuating tappet 23. On actuation of the actuating device 9, the valve seat 39 enables a medium to flow from the surface area modification device 15 belonging to the pilot stage 7 to a tank connection T which leads out of the housing at the location T by way of a connecting line (not shown in greater detail here). Then there is a drop in pressure on the rear end of the valve element 19, which is at the rear on the pressure source connection 21. The first, larger pressure-active surface area F1 is arranged on a free end region 41 of the actuating tappet 23 facing away from the actuating device 9. The return device 11 is designed as an energy accumulator and preferably as a helical compression spring 43. The helical compression spring 43 is supported on the one free end of the actuating tappet 23 and on a receptacle 45 in a sleeve 67, which is described in greater detail below. The return device 11 or the helical compression spring 43 acts on the actuating tappet 23 with a force FR in the opposite direction of action from the compressive force FD of the solenoid armature 27 of the actuating device 9 and of the surface area modification device 15.
The valve 1 may be designed as a pressure regulating valve, but in the exemplary embodiment shown here it is designed as a pressure limiting valve 49. The pressure limiting valve 49 is embodied in the manner of a directional control slide valve or as a pilot control for directional control valves, also for rapid-switching directional control valves for digital hydraulics. The valve element 19, which is designed in the manner of a cylindrical hollow piston, is axially displaceable in a longitudinal guide 51 for a cylindrical valve housing 53 in a sealed design. The valve element 19 controls the flow of a medium between the axial central pressure source connection 21 in the valve housing 53 and a tank connection T formed by radial openings 55 in the valve housing 53. Of the radial openings 55, two are shown, arranged diametrically to the longitudinal axis 75 of the valve 1. The valve element 19 is held in a position in which it blocks the radial openings 55 by a generously dimensioned helical compression spring 56. On its one free end 57 facing the actuating tappet 23, the helical compression spring 56 is supported in an annular receptacle 59 in a pilot stage housing part 61. At its other free end 63, the helical compression spring 56 is in contact with a circular disk-shaped
bottom 65 of the valve element 19. In its unactuated starting position, the helical compression spring 56 is centered radially in the valve element 19 over approx. 4/5 of its total axial extent. The valve element 19 is therefore in the shape of a piston designed with long dimensions. The helical compression spring 56 serves as an adjusting element for the valve element 19 and serves to establish a position of the valve element 19 in the valve housing 53, which reflects a balance of forces between the force acting on the end surface of the piston, this force being created due to a pressure difference by means of the pilot oil flow through the aperture 89, and the adjusting force of the helical spring 56.
In the exemplary embodiment of the valve 1 shown in
The valve element 19 also has a stop 83 on its axial end opposite the bottom 65. The stop 83 is formed by a snap ring 84, which is placed in a circumferential groove 85 in the valve element 19. The snap ring 84 protrudes, with approximately half of its cross section on the periphery, beyond the outside circumference of the valve element 19 and is in contact with the inside circumference of the longitudinal guide 51 with an annular stop face 87. The stop face 87 has the same radius as the snap ring and is formed by a reduction in the inside diameter of the circular cross section of the longitudinal guide 51. In the axial area of the longitudinal guide 51, where the pressure source connection 21, the openings 55 and essentially the valve element 19 are located, the inside diameter is smaller than in the axial region of the longitudinal guide 51 between the stop face 87 and the pilot stage housing part 61.
An aperture 89 is arranged centrally in the bottom 65 of the valve element 19; the media pressure p prevailing on the pressure source connection 21 is transferred to the side of the bottom 65 that faces away from the pressure source connection 21 through this aperture. A media chamber 95 is situated between the bottom 65 of the valve element 19 and the pilot stage housing part 61, so it is connected to another media chamber 97 of the surface area modification device 15 in a media-carrying design, which is accomplished by means of a tapping channel 91 carried in parallel and at a radial spacing from the longitudinal axis 75 in the pilot stage housing part 61 and a transverse channel 93 into which the tapping channel 91 opens. The media chamber 97 is bordered by the bordering wall 33 and the pressure-active surface areas F1, F2 formed by the actuating tappet 23. The aperture 17 is arranged centrally in the transverse channel 93 at the transition from the transverse channel 93 to the media chamber 97. The transverse channel 93 opens into the media chamber 97 in any position of the actuating tappet 23 and is closed with a sealing body 94 in a media-tight seal on its end allocated to the valve housing 53. The media pressure pv of the pilot stage 7 prevails in the media chamber 97. Based on the longitudinal axis 75 of the valve 1, the outflow channel 99 is arranged in the pilot stage housing part 61 diametrically opposite the aperture 17. The outflow channel 99 is formed in the manner of a stepped bore with a diameter that is reduced toward the wall section 77 of the sleeve 67. The outflow channel 99 opens into the additional media chamber 97 via transverse channels 100 situated on the free end of the sleeve 67, and a media flow in the outflow channel 99 is controlled as a function of the position of the end region 41 of the actuating tappet 23 to the inside edge 81. In the exemplary embodiment shown in
In actuation of the actuating tappet 23, the valve seat 39 is opened and the medium 3 can flow from the media chambers 95 and 97 to the outflow channel 99 and to the leakage oil connection L. This in turn results in a pressure drop in the media chambers 95, 97, so that the valve element 19 is acted upon by a smaller force acting in the direction opposite the media pressure p on the pressure source connection 21. The medium 3 can thus also flow from the pressure source connection 21 to the tank connection because the valve element 19 moves upward in the direction of view in
The actuating tappet 23 has a media channel 101, which runs centrally, leading from the interior of the sleeve 67 to an armature space 103 for the solenoid armature 27. In actuation of the actuating tappet 23 by the solenoid armature 27, the armature space 103 is thus equalized in pressure to the extent that the pressure of the leakage oil connection of the pilot stage 7 prevails therein. The valve housing 53 is secured in a nonsealing manner via a plug connection in a pole pipe socket 105. The pilot stage housing part 61 protrudes through the pole pipe socket 105 with its section forming the guide 35 for the actuating tappet 23. The pole pipe socket 105 is provided with a peripheral edge 109, which faces the valve housing 53. The peripheral edge 109 has a much smaller wall thickness than the additional wall thicknesses of the pole pipe socket 105 and is flange-connected to the valve housing in the area of a conical constriction 111 in the outside diameter of the valve housing 53.
The valve 1 shown in
The valve 201, which is shown partially in
In the direction of view in
On its end 335 opposite the end region 241, the actuating tappet 223 is guided slidingly with a seal in an opening 337 belonging to the guide 235 in the pole pipe socket 305. The cross-sectional area of the end 335 defines the second, smaller pressure-active surface area F2. The helical compression spring 243 closing the valve seat 239 and forming the return device 211 is arranged in the media chamber 297. Its one end 257 is supported on a receptacle 247 of the guide 235 of the actuating tappet 223. The other end 263 of the helical compression spring 243 is releasably secured in a form-fitting manner by means of a centering sleeve 339 placed around the actuating tappet 223 and a form-fitting element between the actuating tappet 223 and the centering sleeve 339 on the actuating tappet 223. The bordering walls 233 of the guide 235, which partially define the surface area modification device 215, are formed by parts of the pole pipe socket 305 and parts of the pilot stage housing part 261.
According to the detail V in
and decreases with an increase in the solenoid current through the actuating element (9).
In contrast with the exemplary embodiment shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2011 110 257.8 | Jun 2011 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2012/001139 | 3/14/2012 | WO | 00 | 1/10/2014 |
