Pressure balance arrangement with switchable flow-cut function

Abstract

The invention relates to a pressure balance arrangement (10) with a linearly movable control slide (20) which defines a first and a second orifice (21; 22) which can be jointly adjusted by movement of the control slide (20), wherein the second orifice (22) effects a load holding, wherein the control slide (20) is acted upon by a control spring (23) and a pressure at a first control point (11) in the direction of the first end position (41), wherein it is acted upon by a pressure at a second control point (12) in the direction of the second end position (42), wherein a third control point (13) is arranged directly downstream of the first orifice (21) towards the output point (15), wherein the third control point (13) is fluidically connected to the second control point (12) via at least a third orifice (73).According to the invention, a control valve (80) is provided with a closed and an open switching position (81; 82), wherein the second control point (12) is connected via the control valve in the open switching position (82) to a fluid return (96) such that the second orifice (22) is completely closed, regardless of the pressure at the inlet point (14).

Description

[0001] The invention relates to a pressure compensator arrangement according to the preamble of claim 1.

[0002] DE 196 31 803 B4 discloses a pressure compensator arrangement whose control spool forms a first and a second orifice, which are adjusted jointly and in opposite directions when the control spool moves. The first orifice regulates an actual pressure difference between a first control point and an output point to a predetermined target pressure difference, which is defined by the preload of a control spring. The second orifice maintains a load. The first and second orifices are fluidically connected in series, with a third control point arranged between the first and second orifices. It should be noted that the second orifice in DE 196 31 803 B4 is only shown in the figure and not described in the text.

[0003] DE 10 2020 202 985 A1 discloses a pressure compensator assembly that includes a flow boost function. The pressure compensator is adjusted by means of an associated valve so that the first orifice is fully open.

[0004] Reference should also be made to DE 103 03 385 B4, in which pressure compensators with a single orifice are influenced by means of switching valves.

[0005] DE 10 2018 204642 A1 also discloses a known pressure compensator arrangement.

[0006] Within the scope of the present invention, a so-called flow-cut function is to be realized, ie the fluid flow which flows from the inlet point to the connected working connection (main flow) is to be blockable, regardless of the position of the main orifice or the main slide.

[0007] According to claim 1, it is proposed that a control valve be provided with a closed and an open switching position, wherein the second control point is connected to a fluid return via the control valve in the open switching position such that the second orifice is completely closed, regardless of the pressure present at the inlet point. To achieve the desired result, the third orifice with constant flow resistance and the flow resistance of the control valve in the open switching position can be suitably coordinated with one another. It is conceivable that the said flow resistance of the control valve is selected to be considerably smaller than the flow resistance of the third orifice, so that the pressure in the fluid return is essentially established at the first control point. However, this particularly simple solution has the disadvantage that a large amount of pressurized fluid can be lost to the tank when the flow cut function is activated.This fluid loss is particularly significant if the circuit is to function reliably. How to address this problem is explained below.

[0008] The pressure compensator assembly is preferably used with a pressurized fluid, which is most preferably a liquid and in particular hydraulic oil. The fluid return is preferably connected to a tank of an open hydraulic circuit. The fluid return can be a working fluid return, to which the actuators (cylinders, hydraulic motors) of the hydraulic system are also connected. It can be a separate control fluid return, to which only those hydraulic components through which a small fluid flow flows are connected, for example, pilot control valves. At least one continuously adjustable main orifice is preferably connected between the output point and the first control point.

[0009] Advantageous further developments and improvements of the invention are specified in the dependent claims.

[0010] It can be provided that, in the closed switching position of the control valve, direct fluid exchange between the second control point and the fluid return is prevented. Thus, in the closed switching position, the pressure compensator assembly operates as if the flow cut function were not present. In particular, the control of the pressure drop across the main orifice is not adversely affected.

[0011] The second orifice plate can be arranged between the third control point and the output point. This prevents pressure fluid from flowing through the third control point when the third orifice plate is closed. The load is thus reliably maintained by the second orifice plate.

[0012] The third orifice can be configured as part of a 2-way flow control valve. This defines or at least limits the fluid flow through the third orifice, regardless of the pressure at the inlet.

[0013] It can be provided that the 2-way flow control valve comprises an auxiliary pressure compensator fluidically connected in series with the third orifice. The auxiliary pressure compensator is acted upon in an opening direction by an auxiliary spring and by the pressure immediately downstream of the third orifice, and is acted upon in a closing direction by the pressure immediately upstream of the third orifice. This 2-way flow control valve has a particularly simple design. The preload of the auxiliary spring determines the pressure drop at the third orifice or at least limits it upwards. Thus, the fluid flow through the third orifice depends essentially solely on its flow resistance.

[0014] It can be provided that the control valve is biased into the closed position by a return spring, while being movable into the open position by an actuating magnet. With this assignment of the aforementioned switching positions, the actuating magnet only needs to be energized when the flow cut function is to be active, i.e., in rare exceptional cases. The force of the actuating magnet preferably acts directly on the valve spool of the control valve; no pilot valve is provided. The actuating magnet preferably comprises an electromagnet with an electric coil.

[0015] It can be provided that the control valve is biased into the open position by a return spring, while being movable into the closed position by an actuating magnet. This ensures, in particular, that the flow cut function is activated in the event of a power failure. The actuator connected to the pressure compensator assembly is thus no longer hydraulically driven. It can only move under its own weight or external loads. The force of the actuating magnet preferably acts directly on the valve spool of the control valve; no pilot valve is provided.

[0016] It can be provided that at least the third orifice and preferably the entire 2-way flow control valve is located within the control spool. It should be noted that only very small fluid flows flow through the 2-way flow control valve, and its control accuracy does not need to be particularly high. Therefore, a very small 2-way flow control valve can be used without any problems.

[0017] The control valve can be provided as part of a separate auxiliary assembly, which is firmly connected, in particular screwed, to a separate valve housing, with the control spool located in the valve housing. This makes it possible to convert a valve disc without a flow-cut function into a valve disc with a flow-cut function with little effort. This simplifies the series production of the corresponding assemblies because the number of component variants is minimized. The control valve is preferably designed as a cartridge valve, in particular as a screw-in valve.

[0018] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0019] The invention is explained in more detail below with reference to the accompanying drawings. They show: Fig. 1 a hydraulic circuit diagram of a pressure compensator arrangement according to the invention; Fig. 2 an alternative for the 2-way flow control valve in Fig. 1 ; and Fig. 3 a valve disc with the pressure compensator arrangement according to Fig. 1 .

[0020] Fig. 1 shows a hydraulic circuit diagram of a pressure compensator arrangement 10 according to the invention. With the pressure compensator arrangement 10, the difference between the pressure at the first control point 11 and the pressure at the output point 15 (actual pressure difference) is primarily regulated to a constant value (desired pressure difference), which is determined by the preload of the control spring 23. Thus, the speed of movement of the actuator connected to the first and second working connection depends solely on the position of the main slide (No. 53 in Fig. 3 ) and not from the load acting on the actuator. The main slide forms the main aperture 91, which is continuously adjusted by the movement of the main slide. Fig. 3 For the main slide shown, a separate main aperture (No. 91a; 91b in Fig. 3 ) which are provided in Fig. 1 are combined to form a main orifice 91. The first control point 11 is located directly downstream of the main orifice 91, with the output point 15 located directly upstream of the main orifice 91. The actual pressure difference explained above is accordingly the pressure drop across the main orifice 91. The manipulated variable of the control explained above is the setting of the continuously adjustable first orifice 21, which is defined by the movable control slide 20.

[0021] Furthermore, the pressure compensator assembly 10 provides load holding, meaning that no pressure fluid can flow from the output point 15 to the input point 14, particularly if the pressure at the input point 14 is insufficient to support the load acting on the actuator. Load holding is achieved by the second orifice 22.

[0022] The first and second orifices 21; 22 are fluidically connected in series between the inlet point 14 and the outlet point 15, with the first orifice 21 being arranged between the inlet point 14 and the second orifice 22.

[0023] The first and second orifices 21; 22 are formed by a linearly movable control spool 20, so that they are adjusted together when the control spool 20 moves. In the first end position 41 of the control spool 20, which is preloaded by the control spring 23, the second orifice 22 is completely closed, with the continuously adjustable first orifice 21 being as wide open as possible. If the control spool 20 is moved from the first end position 41 towards the opposite second end position 42, the combined flow resistance of the first and second orifices 21; 22 initially decreases comparatively quickly because the second orifice 22 opens quickly. In a middle position 43, the combined flow resistance of the first and second orifices 21; 22 is minimal.

[0024] If the control spool 20 is moved from the center position 43 further towards the second end position 42, the combined flow resistance of the first and second orifice 21; 22 slowly increases because the first orifice 21 closes gently and continuously. In this range, the above-explained control of the pressure difference between the first control point 11 and the outlet point 15 takes place. In this range, the pressure at the third control point 13, which is arranged between the first and second orifice 21; 22, is essentially equal to the pressure at the outlet point 15. This pressure is passed via the 2-way flow control valve 70 to the end face of the control spool 20 opposite the control spring 23, the fluid chamber there forming the second control point 12.

[0025] The front side of the control spool 20, on which the preloaded control spring 23 acts, is also subjected to the pressure of the first control point 11. If the actual pressure difference exceeds the target pressure difference (preload of the control spring), the first orifice 21 closes, reducing the fluid flow through the main orifice 91. As a result, the actual pressure difference decreases. In the opposite case, the first orifice 21 opens, increasing the actual pressure difference.

[0026] Within the scope of the invention, a possibility is to be created to direct the fluid flow from the inlet point 14 to the associated working connection (No. 51; 52 in Fig. 3 ), regardless of the setting of the main shutter 91. The main shutter 91 may be manually operated, the invention being intended, for example, to enable emergency shut-off which occurs automatically when the corresponding emergency is detected.

[0027] The aforementioned shut-off is effected by moving the control slide 20 into the closed position of the second orifice 22 by means of the control valve 80. The control valve 80 has a closed and an open switching position 81; 82. The closed switching position 81 is preloaded by a return spring 83, whereby the open switching position 82 can be set by means of an actuating magnet 84. If the flow cut function is to be active, particularly in the event of a power failure, the two switching positions 81; 82 should preferably be interchanged. Fig. 1 With the assignment of the two switching positions 81; 82 shown, the pressure compensator arrangement 10 behaves in the de-energized state like a pressure compensator arrangement without flow cut function.

[0028] In the closed switching position 81, the pressure compensator assembly 10 carries out the above-explained control of the actual pressure difference at the main orifice 91. Accordingly, the fluid connection between the second control point 12 and the fluid return 96 to the tank 92 is blocked. The corresponding control takes place in the embodiment according to Fig. 1 This only occurs when the actuating magnet 84 is not energized.

[0029] When the actuating magnet 84 of the control valve 80 is energized, the open switching position 82 is set. Starting from the third control point 13, pressurized fluid can flow via the 2-way flow control valve 70, then via the second control point 12, then via the control valve 80, then via the fluid return 96 to the tank 92. At the second control point 12, a pressure is thus established that lies between the pressure of the third control point 13 and the pressure in the tank 92. In order for the flow cut function to be reliably activated or for the second orifice 82 to be completely closed, the pressure of the first control point 12 must be as close as possible to the pressure in the tank so that the control spring 23 can overcome the corresponding pressure force.

[0030] Critical at this point are operating conditions in which a very high pressure is present at the inlet point 14. This can occur if the pressure compensator assembly 10 is part of a valve block by means of which several actuators are supplied with pressurized fluid from a common pump. The pump discharge pressure, which corresponds to the pressure at the inlet point 14, is then determined by the actuator with the highest load, whereby the pressure compensator assembly according to the invention can be assigned to another actuator. If one were to now, as in Fig. 2 If, instead of the 2-way flow control valve 70, only the fixed third orifice 73 were to be connected between the third and second control points 13; 12, a large fluid flow could flow from the inlet point 14 via the control valve 80 to the tank 92 when the flow cut function is activated. The control valve 80 would have to be designed with very low resistance and thus very large in order to achieve the desired low pressure at the second control point 12. Furthermore, this fluid flow would be associated with considerable energy losses.

[0031] To remedy this problem, the third orifice 73 is part of a 2-way flow control valve 70. The fluid flow through the third orifice 73 thus essentially depends only on the preload of the auxiliary spring on the corresponding auxiliary pressure compensator, which is fluidically connected in series with the third orifice 73. The aforementioned fluid flow is essentially independent of the pressure at the inlet point 14. The 2-way flow control valve 70 can be very simple and small, since it is only intended to allow small fluid flows through, and is only effective at high pressures to limit the fluid flow upwards. For the control function of the pressure compensator arrangement 10, the only thing that matters is that the aforementioned fluid flow is sufficient to compensate for small leaks. As a result, the pressures at the second and third control points 12; 13 are essentially the same when the closed position 81 is set on the control valve 80.

[0032] The auxiliary pressure compensator 71 of the 2-way flow control valve 70 is fluidically connected in series with the third orifice 73, and as shown, it can be arranged upstream of the third orifice 73. However, the auxiliary pressure compensator 71 can also be arranged downstream of the third orifice 73. A fourth control point 74 is arranged directly upstream of the third orifice 73 toward the third control point 14. The second control point 12 is arranged directly downstream of the third orifice 73. The auxiliary pressure compensator 71 regulates the pressure difference between the fourth and second control points 74; 12 to the value specified by the preload of the auxiliary spring 72. The pressure at the fourth control point 14 accordingly acts on the auxiliary pressure compensator 71 in the closing direction, while the pressure at the second control point 12 and the preload force of the auxiliary spring 72 act on the auxiliary pressure compensator 71 in the opening direction.

[0033] Also worth mentioning is the shuttle valve 95, which is part of a shuttle valve cascade, by means of which a maximum load pressure is determined from several individual load pressures. The individual load pressure of the pressure compensator arrangement 10 according to the invention is the pressure at the first control point 11. The highest load pressure is used, for example, to regulate the discharge pressure of the pump that delivers pressurized fluid to the inlet point 14.

[0034] Fig. 2 shows an alternative for the 2-way flow control valve in Fig. 1 . Otherwise, this second embodiment of the pressure compensator arrangement 10 is unchanged from the embodiment according to Fig. 1 , so that in this regard, reference is made to the comments on Fig. 1 is referred to.

[0035] The orifice assembly 70' replaces the 2-way flow control valve according to Fig. 1 , wherein the orifice assembly 70' comprises only the third orifice 73. The third orifice 73 preferably has a fixed flow resistance. The orifice assembly 70' preferably comprises a single part which is attached to the Fig. 3 marked with 70' into the control slide (No. 20 in Fig. 3 ) is screwed in.

[0036] Fig. 3 shows a valve disc 50 with the pressure compensator arrangement 10 according to Fig. 1 The valve disc 50 comprises a linearly movable main slide 53, with which a fluid connection to the first and second working ports 51; 52 can be controlled. In the Fig. 3 In the central position of the main slide 53 shown, which is preloaded by the spring 54, both the first and the second working connection 51; 52 are blocked.

[0037] If the main spool 53 is moved to the right from the center position by means of the pilot valves 55 or by means of the hand lever 56, the first working port 51 is fluidically connected to the output point 15, and the second working port 52 is fluidically connected to a fluid return 58. Reference numeral 91a designates the control edge of the main orifice 91, which is assigned to the first working port 51. The pressure at the first working port 51 is reported to the first control point 11 by means of a load-sensing channel system 59 in the main spool 53. The corresponding load signal is the subject of DE 196 31 803 B4, although other load-sensing systems are also known and can also be used within the scope of the present invention.

[0038] If the main spool 53 is moved to the left starting from the center position, the second working port 52 is fluidically connected to the output point 15, wherein the first working port 51 is fluidically connected to a fluid return 58. The reference numeral 91b denotes the control edge of the main orifice 91, which is assigned to the second working port 52. The pressure at the second working port 52 is reported to the first control point 11 by means of the load signaling channel system 59 in the main spool 53. It should be noted that the present valve disc 50 comprises two separate working fluid returns 58, which each connect all valve discs 50 of a valve block perpendicular to the plane of the drawing. Fig. 3 It is understood that the present invention can also be used with a monolithic valve block. The working fluid returns 58 are preferably connected to a tank (No. 92 in Fig. 1 ) of an open hydraulic circuit are permanently fluidically connected.

[0039] The inlet point 14 is formed by a channel which connects all valve discs 50 of the valve block perpendicular to the plane of the Fig. 3 This channel is preferably connected to a pump which draws pressurized fluid from said tank and delivers it under pressure to the inlet point 14. The pressurized fluid is preferably a liquid and most preferably hydraulic oil.

[0040] The two pressure relief valves 57 provide an upper limit for the pressure at the respective working connection 51; 52. Instead of a pressure relief valve 57, a screw plug can be screwed in, so that the respective bore, including the fluid connection to the fluid return 58, is fluid-tightly closed.

[0041] The separate auxiliary assembly 90 is attached to the valve housing 16 of the valve disc 50, in particular by being screwed there. The control valve 80 is accommodated there, in particular, the auxiliary assembly 90 controlling the Fig. 1 explained fluid connections. In this case, a separate control fluid return 93 is used for the connection to the tank. The control fluid return 93 and the control fluid inlet 94 are each bores which connect all valve discs of the valve block perpendicular to the plane of the drawing of the Fig. 3 The control fluid return 93 is connected to the tank separately from the working fluid return 58, so that large fluid flows in the working fluid return 58 do not cause pressure fluctuations in the control fluid return 93. The control fluid inlet 94 is connected to the pump, for example, via an associated pressure regulator. The two pilot valves 55 are preferably fluidically connected to the control fluid return 93 and the control fluid inlet 94.

[0042] Please also note the frontal recess 97 in the control slide 20. There, the 2-way pressure regulator 70 can be optionally Fig. 1 or the aperture assembly 70' to Fig. 2 be recorded. Reference symbol

[0043] 10Pressure compensator arrangement 11First control point 12Second control point 13Third control point 14Input point 15Output point 16Valve body 20Control spool 21First orifice 22Second orifice 23Control spring 24Stop surface 41first end position 42second end position 43middle position 50Valve disc 51First working port 52Second working port 53Main spool 54Spring 55Pilot valve 56Hand lever 57Pressure relief valve 58Working fluid return 59Load sensing channel system 60Threaded hole for check valve 61First hole 62Second hole 63Screw plug 64Through hole 65Hexagon socket 66Screw head 702-way flow control valve 70'Orifice assembly 71Auxiliary pressure compensator 72Auxiliary spring 73Third orifice 74Fourth control point 80Control valve 81Closed switching position 82Open switching position 83Return spring 84Actuating solenoid 90Auxiliary assembly 91Main orifice 91aControl edge of the main orifice, which is assigned to the first working port 91bControl edge of the main orifice, which is assigned to the second working port 92Tank 93Control fluid return 94Control fluid inlet 95Shuttle valve 96Fluid return 97Receiving recess

Claims

1. Pressure balance arrangement (10) having a linearly movable control spool (20) which defines a first and a second orifice (21; 22) that are jointly adjustable by movement of the control spool (20), wherein they are fluidically connected in series between an inlet point (14) and an outlet point (15), wherein, in a first end position (41) of the control spool (20), the first orifice (21) is completely open, wherein, in the first end position (41), the second orifice (22) is completely closed, wherein, in a second end position (22) of the control spool (20) opposite the first end position (21), the first orifice (21) is completely closed, wherein its opening cross section continuously decreases from the first towards the second end position (21; 22), wherein, in the second end position (42), the second orifice (22) is completely open, wherein the control spool (20) is acted upon in the direction of the first end position (41) by a regulating spring (23) and a pressure at a first control point (11), wherein it is acted upon in the direction of the second end position (42) by a pressure at a second control point (12), wherein a third control point (13) is arranged directly downstream of the first orifice (21) towards the outlet point (15), wherein the third control point (13) is fluidically connected to the second control point (12) via at least one third orifice (73), characterized in that a control valve (80) having a closed and an open switching position (81; 82) is provided, wherein the second control point (12) is connected via the control valve in the open switching position (82) to a fluid return (96) in such a way that the second orifice (22) is completely closed no matter what pressure is present at the inlet point (14).

2. Pressure balance arrangement (10) according to Claim 1, wherein, in the closed switching position (81) of the control valve (80), a direct fluid exchange between the second control point (12) and the fluid return (96) is prevented.

3. Pressure balance arrangement (10) according to either of the preceding claims, wherein the second orifice (22) is arranged between the third control point (13) and the outlet point (15).

4. Pressure balance arrangement (10) according to one of the preceding claims, wherein the third orifice (73) is part of a 2-way flow-regulating valve (70).

5. Pressure balance arrangement (10) according to Claim 4, wherein the 2-way flow-regulating valve (70) comprises an auxiliary pressure balance (71) which is fluidically connected in series to the third orifice (73), wherein the auxiliary pressure balance (71) is acted upon in an opening direction by an auxiliary spring (72) and by the pressure directly downstream of the third orifice (73), wherein it is acted upon in a closing direction by the pressure directly upstream of the third orifice (73).

6. Pressure balance arrangement (10) according to one of the preceding claims, wherein the control valve (80) is preloaded into the closed position (81) by a restoring spring, wherein it is movable into the open position (82) by an actuating magnet (84).

7. Pressure balance arrangement (10) according to one of Claims 1 to 5, wherein the control valve (80) is preloaded into the open position (82) by a restoring spring, wherein it is movable into the closed position (81) by an actuating magnet (84).

8. Pressure balance arrangement (10) according to one of the preceding claims, wherein at least the third orifice (73) and preferably the entire 2-way flow-regulating valve (70) are arranged within the control spool (20).

9. Pressure balance arrangement (10) according to one of the preceding claims, wherein the control valve (80) is part of a separate auxiliary assembly (90) which is fixedly connected, in particular screwed, to a separate valve housing (16), wherein the control spool (20) is arranged in the valve housing (16).

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