Hydraulic control arrangement for multiple actuators

Abstract

Hydraulic control arrangement for supplying several hydrostatic actuators (1), wherein the control arrangement has a pump whose output is connected to a circulation line (6) which leads into a tank (4), and wherein the control arrangement has a metering orifice (22) and an individual pressure compensator (12) for each actuator (1), characterized in that the individual pressure compensators (12) are connected in series via the circulation line (6), wherein pressure medium can be drawn off from the circulation line (6) for the respective actuator (1) and supplied to the metering orifice (22) via the individual pressure compensators (12).

Description

[0001] The invention relates to a hydraulic control arrangement for several hydrostatic actuators or consumers of a mobile work machine with a neutral circuit according to the preamble of patent claim 1.

[0002] In such control arrangements, the various actuators are fed via a respective valve arrangement from a common circulation line that connects a pump to a tank of the control arrangement. If no actuator requires pressure medium, a continuously circulating volume flow from the pump to the tank—so-called neutral circulation—is possible with minimal energy consumption. Therefore, the pump can be designed as a fixed-displacement pump with simple device and control technology.

[0003] For control arrangements with a bypass line, a first known principle is used, in which the required volume flows of the various actuators are branched off from the bypass line in parallel. The applicant's publication "Hydraulics in Mobile Work Machines" dated January 27, 2014, shows such a control arrangement on page 3 / 7. Its bypass line runs in a small circuit past the various valve arrangements via a (common) pressure compensator, which is opened when the actuators are not actuated, thus enabling low-resistance neutral circulation.

[0004] According to a second principle, the circulation line for the neutral circulation runs through the valve arrangements of the various actuators, so that the valve arrangements are connected in series with each other.

[0005] The applicant's publication "Load-Sensing Control Block in Disc Design SB23-M" RD 66130, dated August 2013, shows this second principle with a fixed-displacement pump and only one actuator on page 3 / 24, bottom left. A directional control valve, in which the metering orifice for determining the actuator speed is integrated, also enables the flow to be redirected to the neutral circuit when the actuator is not to be supplied. The continuous adjustability of the directional control valve also makes it possible to redirect a portion of the flow delivered by the fixed-displacement pump to the neutral circuit that is not required by the actuator, for example, when the actuator is to be moved slowly.

[0006] US 7,284,371 B2 and US 2011 / 0158830 A1 show control arrangements for multiple actuators. These arrangements have a neutral circuit that is routed through the valve arrangements of the various actuators. More specifically, the neutral circuit runs through respective directional control valves, whose valve pistons are in a central position (open center). Although the neutral circuit allows the use of a fixed-displacement pump in such control arrangements, both of these publications provide for variable-displacement pumps.

[0007] Furthermore, it is known from the prior art to integrate an individual pressure compensator into each valve arrangement in a control arrangement for multiple actuators of a mobile work machine having a variable-displacement pump. More specifically, an individual pressure compensator is assigned to each metering orifice, forming a respective flow control valve. This allows a volume flow to the respective actuator that is dependent on the opening cross-section of the metering orifice and independent of the respective actuator's load pressure, thus ensuring a high level of user-friendliness for the driver of the mobile work machine when operating and controlling the actuators.

[0008] In the applicant's publication "LUDV control block in disc design" RD 64125 from February 2011 on page 4 / 24 above and in the aforementioned publication "Load-Sensing Control Block in Disc Design SB23-M" RD 66130 on page 9 / 24 right, such a valve arrangement with an individual pressure compensator for supplying an associated actuator is shown. Each valve arrangement, including the individual pressure compensator, is combined in a valve disc, several of which are grouped into a control arrangement. In both publications, a common pump line of the control arrangement runs through each valve disc, from which a respective channel branches off to the valve arrangement of the respective valve disc.

[0009] A disadvantage of such control arrangements for multiple actuators is that so-called load-sensing lines are required, in which the pressure of the actuator with the highest load is determined. A variable-displacement pump (not shown) is controlled based on this pressure so that it delivers only the required amount of pressure medium. In the first-mentioned publication, this pressure is also required to control the pressure compensators.

[0010] In contrast, the invention is based on the object of creating a control arrangement for several actuators in which the determination of the pressure of the highest-load actuator via corresponding load-sensing lines and shuttle valves spanning the valve arrangements and the corresponding transmission to the pump and, if applicable, to the individual pressure compensators can be omitted.

[0011] This object is achieved by a control arrangement for several actuators of a mobile work machine having the features of patent claim 1.

[0012] The claimed hydraulic control arrangement serves to supply several hydrostatic actuators and has a pump whose output is connected to a circulation line that flows into a tank. Furthermore, the control arrangement has a metering orifice and an individual pressure compensator for each actuator. According to the invention, the individual pressure compensators are connected in series via the circulation line, whereby a portion of the pressure medium from the circulation channel for the respective actuator can be branched off via the individual pressure compensators and fed to the metering orifice arranged downstream of the individual pressure compensator. This allows the unused pressure medium to be passed from each individual pressure compensator to the circulation line. From the last individual pressure compensator, the unused pressure medium is returned to the tank via the circulation line. The actuators are prioritized based on the order of their individual pressure compensators: the individual pressure compensators closest to the pump are given priority.The actuators move independently of the load pressure, even without complex load-sensing lines; thus, a certain opening of the metering orifice results in a certain speed of the actuator.

[0013] Particularly preferably, an inlet and a first outlet of the individual pressure compensator are connected to the circulation line, wherein pressure medium can be branched off to the metering orifice via a second outlet of the individual pressure compensator. A continuously adjustable valve body of the individual pressure compensator is acted upon by the inlet pressure of the metering orifice in the direction of a through position in which the inlet is connected to the first outlet and the second outlet is blocked. In contrast, the valve body of the individual pressure compensator is acted upon by the outlet pressure of the metering orifice in the direction of a branch position in which the inlet is connected to the second outlet and the first outlet is blocked. The system pressure of the pump is set by the individual pressure compensator of the actuator with the highest load pressure at its through control edge. The valve body of the individual pressure compensator is acted upon by a spring in the direction of the through position.

[0014] In a particularly preferred energy-saving development, the pump is a variable-displacement pump. These are controlled as needed, instead of regulating the pressure difference between the pump line or circulation line and the load-sensing signal of the variable-displacement pump, as is the case with the state of the art. Furthermore, hydraulic losses are reduced because the pump pressure can be set to the required value without the Δp lead, which must be reduced at the individual pressure compensators.

[0015] According to a further development, a delivery volume of the variable displacement pump can be adjusted via an electrical control device and via an electrical actuator which, for example, adjusts a control valve of the variable displacement pump.

[0016] For this purpose, according to a first variant, the volumetric flow requirements of the actuators can be stored in the electrical control device as a function of a respective target signal generated by the operator and transmitted to the control device. The control device can then calculate the total demand of all consumers of the control arrangement and adjust the delivery volumetric flow of the variable-displacement pump based on the target signals.

[0017] For this purpose, according to a second variant, the volumetric flow requirements of the actuators can be stored in the electrical control device depending on the setting of the valve bodies of the associated metering orifices, with position sensors being provided on the valve bodies of the metering orifices. The control device can then calculate the total demand of all consumers of the control arrangement and adjust the delivery volumetric flow of the variable-displacement pump depending on the setting of the valve bodies of the metering orifices.

[0018] In a preferred embodiment, the delivery volume of the variable-displacement pump is adjustable depending on the back pressure upstream of a metering orifice located in the circulation line between the last individual pressure compensator and the tank. The control arrangement according to the invention can then also supply additional consumers via additional metering orifices that are not known or stored in the electrical control device, for example, via power beyond or via mechanical directional control valves.

[0019] According to a first variant, a pressure sensor can be connected to the circulation line between the last individual pressure compensator and the measuring orifice, which is electrically connected to the electrical control device.

[0020] Or according to a second variant, the delivery volume of the variable pump is adjusted hydraulically directly via the back pressure.

[0021] A particularly preferred development of the control arrangement according to the invention has a directional control valve for each actuator, which is mechanically coupled to the metering orifice or integrated into it. The directional control valve can operate like a load-sensing directional control valve according to the prior art when sufficient pump pressure is present.

[0022] Preferably, the metering orifice is electrically operated together with the directional control valve.

[0023] In a preferred embodiment, the directional control valve has two working ports connectable to the actuator: an inlet and a tank port. Furthermore, the directional control valve has a closed center position and two working positions for supplying the actuator in two different directions. The metering orifice is coupled to the directional control valve in such a way that it opens a passage in the two working positions of the directional control valve and blocks the passage in the closed position of the directional control valve.

[0024] In order to also allow the actuators to move freely, the above-mentioned directional control valve can be developed into a 4 / 4-way valve which has a release position, wherein the metering orifice is coupled to the 4 / 4-way valve in such a way that it blocks the passage when the 4 / 4-way valve is in the release position.

[0025] A working line directed from the metering orifice to the inlet of the directional control valve can be relieved to the tank when the directional control valve is in the closed position, so that the individual pressure compensator can pass on the entire pressure medium in or into the circulation line when the directional control valve is in the closed position, so that it can be fed to the other actuators.

[0026] If the directional control valve is developed into a 4 / 4-way valve with a free-flow position, the working line must also be able to be relieved to the tank in the free-flow position of the 4 / 4-way valve so that the individual pressure compensator can pass on the entire pressure medium in the circulation line when the directional control valve is in the free-flow position.

[0027] Preferably, the relief via the working line takes place via a relief valve connected to it, which is simply mechanically coupled to the directional control valve or integrated into it.

[0028] Preferably, the relief valve is electrically operated together with the directional control valve.

[0029] In a preferred embodiment, a check valve is provided in the working line between a branch to the relief valve and the inlet. This prevents pressure fluid from the actuator from being forced backward through the directional control valve, the metering orifice, and the individual pressure compensator into the circulation line.

[0030] Preferably, the individual pressure compensator and the metering orifice, and if applicable, the directional control valve, the relief valve, and the check valve are housed in a valve disc. The valve discs are combined in a modular manner to form a valve block of the control arrangement.

[0031] In the following, various embodiments of the invention are described in detail with reference to the figures. Fig. 1 shows a first embodiment of the control arrangement according to the invention with three actuators; Fig. 2 a second embodiment of the control arrangement according to the invention with two actuators (orifice and return of the back pressure to the variable displacement pump via pressure sensor); and Fig. 3 a third embodiment of the control arrangement according to the invention with two actuators (orifice and direct return of the back pressure to the variable displacement pump).

[0032] Fig. Figure 1 shows a first embodiment of the control arrangement according to the invention for supplying three different bidirectionally operable actuators 1, which are designed as differential cylinders. The control arrangement has a variable-displacement pump 2, which draws pressure fluid from a tank 4 and returns it to tank 4 via a circulation line 6.

[0033] The circulation line 6 is formed by channel sections of various valve discs 8, three of which are combined to form a valve block of the control arrangement. Thus, the three valve discs 8 can be designated and differentiated as the valve disc 8 near the pump, the middle valve disc 8, and the valve disc 8 remote from the pump. A closure element 10 is provided on the valve disc 8 remote from the pump, in which a section of the circulation line 6 is formed.

[0034] Each valve disc 8 contains a continuously adjustable individual pressure compensator 12, with the three individual pressure compensators 12 being connected in series in a section of the circulation line 6 extending from the variable displacement pump 2 to the closure element 10. Each individual pressure compensator 12 has an inlet 14, a first outlet 16, and a second outlet 18. The first outlet 16 opens into the circulation line 6, while the second outlet 18 is connected via a working line 20, a metering orifice 22, and a further working line 24 to an inlet 26 of a directional control valve 28 designed as a 4 / 4-way valve. The working line 20, the metering orifice 22, the further working line 24, and the directional control valve 28 are accommodated in the valve disc.

[0035] A valve body of the individual pressure compensator 12 is acted upon by the pressure of the working line 20 toward an end position, referred to as the through position 30, in which the inlet of the individual pressure compensator 12 is connected to its first output 16. Furthermore, the valve body of the individual pressure compensator 12 is acted upon by the pressure of the working line 24 and by the force of a spring 23 toward an end position, referred to as the branch position 34. In this position, the inlet 14 of the individual pressure compensator 12 is connected to its second output 18.

[0036] The directional control valve 28 has two working positions 36, via which the actuator 1 can be moved in different directions. Fig. In the embodiment shown in Figure 1, a load holding valve designed as a check valve is provided in one of the two working lines via which the working connections 37 of the directional control valve 28 are connected to the actuator 1.

[0037] The directional control valve 28 is shown in a closed center position 38. The inlet 26, the two working ports 37, and one tank port of the directional control valve 28 are closed. Furthermore, the directional control valve 28 has a free position 40 in which the two working ports 37 and the tank port are connected to each other, allowing the actuator 1 to move freely. For this purpose, the inlet 26 of the directional control valve 28 is closed.

[0038] Each valve disc 8 has a relief valve 42, via which the working line 24 to the tank 4 can be relieved. Furthermore, a check valve 44 is provided in the working line 24 between the connection of the relief valve 42 and the inlet 26 of the directional control valve 28, which only allows a volume flow to the directional control valve 28.

[0039] The valve bodies of the metering orifice 22, the directional control valve 28, and the discharge valve 42 are continuously adjustable and coupled to one another, so that all three valve bodies constantly move together. For this purpose, an electric actuator 46 is provided, which is supplied with power via a common electric control device 48. The delivery volume of the variable displacement pump 2 is also electrically adjusted via the electric control device 48 – e.g., via an electroproportional controller.

[0040] The directional control valve 28 has the four described switching positions 36, 38, 40, with the metering orifice 22 being designed such that it opens in the two operating positions 36 of the directional control valve 28 and closes in the blocking position 38 and the free position 40. The relief valve 42 is designed in a similar manner, closing in the two operating positions 36 of the directional control valve 28 and opening to the tank 4 in the blocking position 38 and the free position 40.

[0041] Depending on the requirements of the actuator 1, which is defined by the opening of its metering orifice 22, pressure medium is withdrawn from the circulation line 6 via the three individual pressure compensators 12, whereby the individual pressure compensator 12 near the pump or the valve disc 8 near the pump and thus the actuator 1 near the pump has the highest priority, while the individual pressure compensator 12 far from the pump or the valve disc 8 far from the pump and thus the actuator 1 far from the pump has the lowest priority.

[0042] The system pressure is set by the individual pressure compensator 12 of actuator 1 with the highest load pressure at its forward control edge. The total pressure fluid requirement of the control arrangement is known from the sum of the setpoints for the directional control valves 28 and the metering orifices 22. The variable-displacement pump 2 is adjusted via the electrical control device 48 such that only a small excess pressure fluid is generated. This excess pressure is returned to tank 4 via the closure element 10.

[0043] If an actuator 1 with a lower pressure is actuated downstream of the valve disc 8 that determines the system pressure, its individual pressure compensator 12 throttles the pressure medium flow rate of the circulation line 6. If an actuator 1 with a lower pressure is actuated upstream of the valve disc 8 that determines the system pressure, its individual pressure compensator 12 regulates the control pressure drop at its other control edge.

[0044] When the actuators 1 are not actuated, the pressure of the neutral circulation in the circulation line 6 corresponds to the equivalent of the springs 32 of the individual pressure compensators 12. Since in the first embodiment according to Fig. 1 the pressure medium requirement of all actuators 1 is known from the setpoints of the respective metering orifices 22, no further sensors are required. The control arrangement according to Fig. 1 is suitable for valves distributed on the mobile work machine, as no control lines are required.

[0045] If the maximum adjustable flow rate of the variable displacement pump 2 is not sufficient to satisfy all requirements, the actuators 1 are prioritized according to the order of the valve discs 8 - starting with the variable displacement pump 2.

[0046] Fig. Figure 2 shows a second embodiment of the control arrangement according to the invention, wherein only the minimum number of two valve discs 8 is provided. The valve discs 8 correspond to those of the first embodiment according to Fig. 1. Thus, the channels inside the valve discs 8 forming the circulation line 6 correspond to those of the valve discs 8 of the first embodiment. Only the channel section 106 of the valve disc 8 remote from the pump, which is intended for return, is not flowed through by the pressure medium of the circulation, since the closure element 110 of the second embodiment is modified compared to that of the first embodiment. A metering orifice 150 is provided in the closure element 110, with an outlet of the closure element 110 leading directly to tank 4 downstream of the metering orifice 150. Upstream of the metering orifice 150, a pressure sensor 154 is connected to the circulation line 6 via a control line 152. This sensor detects the back pressure (between the individual pressure compensator 12 of the valve disc 8 remote from the pump) upstream of the metering orifice 150 and reports this to the electrical control device 48.This makes it possible to supply further consumers 156 with the control arrangement according to the invention, which are connected to the circulation line 6 on a high-pressure side or pump outlet side and on a low-pressure side.

[0047] The back pressure in front of the measuring orifice 150 is always measured by the pressure sensor 154 and the delivery rate of the variable displacement pump 2 is controlled via the electrical control device 48 so that it always remains at the lowest possible value.

[0048] Fig. Figure 3 shows a third embodiment of the control arrangement according to the invention. This largely corresponds to the second embodiment according to Fig.2. Deviating from this, the back pressure upstream of the metering orifice 150 is fed via the control line 152 directly to a hydraulic adjustment device (e.g., a control piston) of the variable displacement pump 202. This also makes it possible to optimally control the variable displacement pump 202 without knowing the total demand of the actuators 1 or consumers 156.

[0049] Deviating from the embodiments shown, the valve bodies of the metering orifice 22, the directional control valve 28 and the relief valve 42 can also be formed in one piece.

[0050] Deviating from the embodiments shown, the control arrangement according to the invention can also have more than two or three valve discs to supply a correspondingly higher number of actuators.

[0051] A control arrangement is disclosed that serves to supply several hydrostatic actuators. It has a pump whose output is connected to a circulation line that flows into a tank. Furthermore, the control arrangement has a metering orifice and an individual pressure compensator for each actuator. The individual pressure compensators are connected in series via the circulation line. Via the individual pressure compensators, a portion of the pressure medium can be branched off from the circulation channel for the respective actuator and fed to the metering orifice arranged downstream of the individual pressure compensator. This allows the unused pressure medium from each individual pressure compensator to be passed on to the circulation line. From the last individual pressure compensator, the unused pressure medium is returned to the tank via the circulation line. The actuators are prioritized based on the order of their individual pressure compensators: the individual pressure compensators closest to the pump are given priority.The actuators move independently of the load pressure, even without complex load-sensing lines; thus, a certain opening of the metering orifice results in a certain speed of the actuator. List of reference symbols 1 actuator 2; 202 variable displacement pump 4 tanks 6 Circulation line 8 valve discs 10; 110 end element 12 Individual pressure balance 14 Entrance 16 first exit 18 second exit 20 Work management 22 Metering orifice 24 Work management 26 Entrance 28-way valve 30 Pass-through position 32 spring 34 branch position 36 Working position 38 Locking position 40 Release position 42 Relief valve 44 Check valve 46 electric actuator 48 electrical control device 106 Canal Section 150 metering aperture 152 control line 154 pressure sensor 156 additional consumers

Claims

[1] Hydraulic control arrangement for supplying a plurality of hydrostatic actuators (1), wherein the control arrangement has a pump whose output is connected to a circulation line (6) which opens into a tank (4), and wherein the control arrangement has a metering orifice (22) and an individual pressure compensator (12) for each actuator (1), characterized by that the individual pressure compensators (12) are connected in series via the circulation line (6), wherein pressure medium can be discharged from the circulation line (6) for the respective actuator (1) and fed to the metering orifice (22) via the individual pressure compensators (12). [2] Control arrangement according to claim 1, wherein an inlet (14) and a first outlet (16) of the individual pressure compensator (12) are connected to the circulation line (6), and wherein pressure medium can be discharged to the metering orifice (22) via a second outlet (18) of the individual pressure compensator (12), and wherein a continuously adjustable valve body of the individual pressure compensator (12) is acted upon by the inlet pressure of the metering orifice (22) in the direction of a passage position (30) in which the inlet (14) is connected to the first outlet (16), and wherein the valve body of the individual pressure compensator (12) is acted upon by the outlet pressure of the metering orifice (22) in the direction of a branch position (34) in which the inlet (14) is connected to the second outlet (18). [3] Control arrangement according to claim 1 or 2, wherein the pump is a variable displacement pump (2; 202). [4] Control arrangement according to claim 3, wherein a delivery volume of the variable displacement pump (2) is adjustable via an electrical control device (48) and via an electrical actuator (46). [5] Control arrangement according to claim 4, wherein the volume flow requirements of the actuators (1) are stored in the electrical control device (48) as a function of a respective target signal. [6] Control arrangement according to claim 4, wherein the volume flow requirements of the actuators (1) are stored in the electrical control device (48) as a function of the setting of the associated metering orifices (22), and wherein position sensors are provided on the metering orifices (22). [7] Control arrangement according to claim 3, wherein a delivery volume of the variable displacement pump (2; 202) is adjustable as a function of a back pressure in front of a measuring orifice (150) which is arranged in the circulation line (6) between the last individual pressure compensator (12) and the tank (4). [8] Control arrangement according to claim 7, wherein a delivery volume of the variable displacement pump (2) is adjustable via an electrical control device (48) and via an electrical actuator (46), wherein a pressure sensor (154) is provided which is connected to the circulation line (6) between the last individual pressure compensator (12) and the measuring orifice (150) and which is electrically connected to the electrical control device (48). [9] Control arrangement according to claim 7, wherein the delivery volume of the variable displacement pump (202) is hydraulically adjustable via the back pressure. [10] Control arrangement according to one of the preceding claims, with a directional control valve (28) which is mechanically coupled to the metering orifice (22) or integrated therein. [11] Control arrangement according to claim 10, wherein the directional control valve (28) has two working connections (37) connectable to the actuator (1), an inlet (26) and a tank connection, and wherein the directional control valve (28) has a blocking position (38) and two working positions (36), and wherein the metering orifice (22) is coupled to the directional control valve (28) in such a way that it opens a passage in the two working positions (36) of the directional control valve (28) and that it closes off in the blocking position (38) of the directional control valve (28). [12] Control arrangement according to claim 11, wherein the directional control valve (28) is a 4 / 4-way valve having a free position (40), and wherein the metering orifice (22) is coupled to the 4 / 4-way valve in such a way that it shuts off in the free position (40) of the 4 / 4-way valve. [13] Control arrangement according to claim 11, wherein a working line (24) directed from the metering orifice (22) to the inlet (26) of the directional control valve (28) can be relieved to the tank (4) in the blocking position (38) of the directional control valve (28). [14] Control arrangement according to claim 13, wherein the directional control valve (28) is a 4 / 4-way valve having a free position (40), and wherein the metering orifice (22) is coupled to the 4 / 4-way valve in such a way that it shuts off in the free position (40) of the 4 / 4-way valve, wherein the working line (24) can be relieved to the tank (4) in the free position (40) of the 4 / 4-way valve. [15] Control arrangement according to claim 13 or 14, wherein the working line (24) can be relieved via a relief valve (42) which is mechanically coupled to the directional control valve (28) or integrated therein. [16] Control arrangement according to claim 15, wherein a check valve (44) is provided in the working line (24) between a branch to the relief valve (42) and the inlet (26).

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