Volumetric flow supply mechanism

Abstract

The utility model relates to a volumetric flow supply mechanism, in particular for a closed-center LS system (10), having a pressure supply device (12) and a pressure compensator as components of a supply system for fluid supply of a hydraulic consumer (18) that can be connected thereto, characterized in that the pressure compensator is connected to the pressure supply device (12). The pressure supply device (12) provides a volume flow in a demand-oriented manner for supplying the hydraulic consumer (18), in that the pressure compensator is formed by a circulating pressure compensator (14) which leads a possible excess volume flow out of the supply flow, and the volume flow supply device has an adjusting device (38) which adjusts the pressure compensator (14). The regulating device reduces the excess volume flow to a minimum value by actuating the pressure supply device (12).

Description

Technical Field

[0001] The utility model relates to a volume flow supply mechanism, in particular a volume flow supply mechanism for a closed center LS system. The volume flow supply mechanism has a pressure supply device and a pressure compensator as components of a supply system. The supply system is used for fluid supplying a hydraulic consumer connectable thereto. Background Art

[0002] DE102009049548A1 discloses a valve assembly for regulating the pressure of a pressure medium from a pressure medium pump to at least one first consumer, the valve assembly comprising a pre-controlled pressure regulating valve, a main piston loaded by the pressure medium, and a pre-control piston, which can relieve the pressure of a pressure chamber between the piston back side of the main piston and the pre-control piston, the pressure relief valve being connected to the pressure chamber in a flow-conducting manner, the pressure relief valve opening when the pressure medium pressure at the load connection LS indicates that the consumer is deactivated and directing the pressure medium with a low pressure back into the pressure medium container or the pressure medium pump, and closing when the pressure medium pressure at the load connection LS indicates that the consumer is in use.

[0003] In this way, a valve assembly for regulating the pressure of a pressure medium is provided which can further minimize pressure losses when no consumer is connected. In this way, a significant reduction in pressure losses of the valve assembly is achieved compared to known circuits with a circulating pressure compensator.

[0004] DE 10 2013 017 093 A1 discloses a control device, in particular for hydraulically controlling components of a mobile working machine. The control device comprises at least one pressure supply connection and a tank or return connection, two application connections, a control and / or regulating valve connected between the connections, and two control lines capable of controlling at least one of the control and / or regulating valves, wherein a modularly constructed function block is connected to at least one of the control lines. With a suitable design of the modularly constructed function block, a number of further design options of the control device can be modified in concept, and thus the functional reliability can also be regularly increased. Utility Model Content

[0005] Based on this prior art, the object of the present invention is to further improve the known solution while retaining its advantages.

[0006] To this end, the present invention provides a volume flow supply mechanism having a pressure supply device and a pressure compensator as components of a supply system for fluidically supplying a hydraulic consumer connectable thereto. The pressure supply device provides a demand-based volume flow for supplying the hydraulic consumer. The pressure compensator comprises a circulating pressure compensator that diverts any excess volume flow from the supply flow, and the volume flow supply mechanism comprises a regulating device that reduces the excess volume flow to a minimum by actuating the pressure supply device. This provides a structurally simple, cost-effective, robust, and demand-based volume flow supply mechanism for a hydraulic system, such as a closed-center LS system. On the one hand, this demand-based volume flow supply mechanism promotes system stability in the event of oversupply; on the other hand, the resulting excess volume flow causes hydraulic losses, which must be avoided. The solution according to the present invention enables demand-based volume flow supply to the connected hydraulic consumers by means of the regulating device, with any excess volume flow being diverted via the circulating pressure compensator so that the resulting losses can be reduced to the necessary minimum. The respectively used pressure compensator or circuit pressure compensator can be integrated with the preferably respectively used orifice plate or measuring orifice plate in the main control block.

[0007] Advantageously, the pressure supply device comprises a variable-speed hydraulic pump, which is driven by a variable-speed motor, which is controlled by the regulating device. The demand-based regulating device can reduce the losses caused by excess volume flow to the minimum required for system stability.

[0008] In another particularly preferred embodiment of the volume flow supply mechanism according to the present invention, the regulating device includes a controller, preferably in the form of a PID controller, having a predeterminable command variable. The controller's command variable is formed by the output value of a sensor, which detects the pressure value on the outlet side of the circulating pressure compensator in the form of a pressure sensor and / or detects the displacement position of the valve spool of the circulating pressure compensator in the form of a displacement sensor. Preferably, a measuring orifice is connected downstream of the circulating pressure compensator, through which the fluid flows to the tank or return connection and, thus, to the storage tank. The pressure difference across the measuring orifice can be detected by a pressure sensor, and the signal of the pressure sensor serves as the command variable or actual value for the closed-loop control circuit. The speed of the hydraulic pump is then regulated by the regulating device so that, ideally, the command variable corresponds to the setpoint value.

[0009] Accordingly, by means of the regulating device proposed here, the constant Δp is adjusted by measuring the orifice plate so that within the regulating range of the hydraulic pump (n<n max ) within a certain timeframe, a continuous excess volume flow is passed through the circulating pressure compensator. The system is thus oversupplied and operates at a stable operating point. The demand-driven control device can reduce the losses caused by the excess volume flow to the minimum necessary for system stability. The supply system of this design requires only a single pressure sensor, and the pressure detected upstream of the measuring orifice is independent of the load, or load pressure / pump pressure. Another advantage is that the relatively low pressure level of the measuring orifice, compared to the load-related pressure, allows the sensor to detect a smaller pressure range and, therefore, a higher resolution of the pressure range. This results in cost advantages, as the sensor accuracy can be reduced.

[0010] The measuring orifice plate has a damping effect, and the measured variable is independent of the load on the hydraulic consumer. This has a positive impact on the sensor's signal quality and improves control quality. Signal smoothing can be omitted, which in turn improves the response characteristics. The circuit pressure compensator can be dimensioned smaller, as only a small excess volume flow must be discharged during normal operation.

[0011] Furthermore, alternatively or additionally, there is the possibility that the circulating pressure compensator is equipped with a measuring system, with which the position of the slide of the circulating pressure compensator is detected. In this case, the signal of the slide position is used as a control variable (actual value) for a closed-loop control circuit. The speed of the hydraulic pump is then adjusted by the control device so that, ideally, the control variable again corresponds to the command variable (theoretical value). Accordingly, a constant slide position is adjusted using the control device proposed here, which corresponds to the desired excess volume flow through the circulating pressure compensator at the rated pressure to be defined. Accordingly, the system is again in oversupply and operates at a stable operating point. Furthermore, other advantages such as for the pressure sensor solution are also obtained here. A pressure difference ΔP corresponding to the desired pressure is adjusted using the control device proposed here. LS The slide position corresponds to the opening point of the circulating pressure compensator. This allows early detection when the circulating pressure compensator is "out of control".

[0012] The excess volume flow, at a constant slide position, is load-dependent and, accordingly, is greater at higher load pressures than at lower load pressures. Possible ways to reduce or avoid this effect are to provide a large, finer control range in the circulating pressure compensator or, in addition or as an alternative, to use a pressure sensor solution for further compensation within the control device.

[0013] In a particularly preferred embodiment, a bypass line is provided in parallel with the aforementioned measuring orifice, which particularly preferably has at least one spring-loaded non-return valve that leads toward the tank or the return line. This makes it possible to limit the pressure difference across the measuring orifice, particularly in the event of high excess volume flows, for example, in standby mode. This standby mode is used when no consumers are actuated and the hydraulic pump delivers a volume flow Q due to the minimum speed. min . Therefore, the opening pressure of the check valve in the bypass must be above the command variable. This limits the circulating pressure in standby mode and contributes to energy-efficient operation of the pressure supply. Furthermore, limiting this pressure protects the pressure sensor from excessive pressure.

[0014] In another particularly preferred embodiment of the volume flow supply mechanism according to the present invention, at least one additional measuring orifice is connected in parallel with one of the measuring orifices and preferably upstream of the check valve, viewed in the flow direction. The free cross-section of the additional measuring orifice is preferably larger than that of the one measuring orifice. This allows for a fine control range, with flow only flowing through the additional measuring orifice when the opening pressure of the bypass check valve is exceeded. This point can be identified by an inflection point in the volume flow-pressure diagram. Furthermore, an additional bypass can be provided for one or the additional measuring orifice, for example, via a check valve. Consequently, the opening pressure of the bypass check valve for one or the additional measuring orifice is higher than that of the bypass check valve of the one measuring orifice. This results in a change in the volume flow-pressure diagram. The aforementioned fine control range expands the detection range of the sensor device used. Furthermore, further system interventions are conceivable, such as switching one or more valves (electrically or hydraulically-mechanically) above a certain pressure via the measuring orifice.

[0015] Furthermore, the present invention relates to a method for implementing a demand-based volume flow supply, in particular for a closed-center LS system, using the supply device described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The solution according to the present invention is explained in more detail below with the aid of an embodiment. In this case, in the drawings which are schematic and not to scale:

[0017] Figure 1 One embodiment of a volume flow supply mechanism is shown;

[0018] Figure 2 、 Figure 3 Two volume flow diagrams are shown; and

[0019] Figures 4 to 12 Shown relative to Figure 1Changes in implementation methods. DETAILED DESCRIPTION

[0020] Figure 1 A volume flow supply arrangement is shown in the form of a hydraulic circuit diagram, in particular for a so-called closed center LS system, in which a system is Figure 1 10 in the diagram. In technical terms, such a system 10 is also referred to as an LS-MCV (main control valve). Furthermore, the volume flow supply device has a pressure supply device, designated as a whole, 12, and a so-called circulating pressure compensator 14 as a pressure compensator. The pressure supply device 12 and the pressure compensator 14 are components of a supply system, designated as a whole, 16, which is used to supply fluid to a hydraulic consumer, designated as a whole, 18, which can be connected thereto.

[0021] Hydraulic consumer 18 has two hydraulic motors 20 with two possible flow directions. Each hydraulic motor 20 is controlled via an electrically actuated 4 / 3-way proportional bypass valve 22. A directional control valve 24, shown between the assignable hydraulic motor 20 and the proportional valve 22, reports the higher pressure in the supply to the hydraulic motor 20 to an LS (load sensing) line 26. A 2 / 2-way bypass valve 28 and its control line 29 are connected to this line. In the open circuit position shown, each valve 28 has a pressure limiting function 74 and, to this end, establishes a flow-conducting connection between the pressure supply line P and one input of the respective valve 22. The other input of the valve 22 is connected to a tank or return line T, which leads to a storage tank 30, which can also be composed of multiple tank components. The opposite output of the respective proportional valve 22 leads to the control side of the associated hydraulic motor 20. Downstream of the branching point 32 of the bypass valve 28 into which the assignable control line 29 opens, a nonreturn valve 36 is connected in the direction of a central load sensing (LS) line 34 , which opens in the direction of the central LS line 34 and remains in its closed position in the opposite direction.

[0022] The pressure supply device 12 for supplying the hydraulic consumer 18 provides a volume flow to the hydraulic consumer in a demand-driven manner, in that a circuit pressure compensator 14 diverts any excess volume flow from the supply flow provided by the pressure supply device 12 in the pressure supply line P. Furthermore, a regulating device, designated as a whole by 28, is provided which, by actuating the aforementioned pressure supply device 12, helps to reduce the excess volume flow to a minimum.

[0023] If another Figure 1As can be seen, the pressure supply device 12 includes a variable-speed hydraulic pump 40, preferably in the form of a constant-speed pump, which is driven by a variable-speed motor M, for example, in the form of an electric motor, which in turn is controlled by a regulating device 38. The regulating device 38 includes a regulator 42, for example, in the form of a PID regulator. The regulator 42 has a command variable 44 and a manipulated variable 46 on its input side. The command variable 44 represents a setpoint value, and the manipulated variable 46 represents a corresponding actual value. The regulator 42 is connected on its output side to a motor control device 48, for example, in the form of a frequency converter. The frequency converter predetermines the required speed in the electric motor M as a manipulated variable and, therefore, speed-controlledly sets the hydraulic pump 40 to its corresponding delivery rate. The hydraulic pump draws this delivery rate from the storage tank 30 and delivers it to the pressure supply line P.

[0024] The manipulated variable 46 mentioned is formed by the output value of a pressure sensor 50. This pressure sensor 50 detects the pressure value on the outlet side 52 of the circulation pressure compensator 14 and is connected to a branch point 54 which leads via a further tank or return line 56 to the storage tank 30.

[0025] The circuit pressure compensator 14 is connected on the input side to the pressure supply line P, specifically via a further branching point 58, which is provided directly at the output of the hydraulic pump 40. The circuit pressure compensator 14 is designed as a directly controlled, spring-loaded throttle valve in a slide configuration, whose valve element 60, together with an accumulator such as a compression spring 62, is exposed on one side to the LS pressure from the consumer 18 and on the other side to the control pressure in a control line 64, which corresponds to the output or supply pressure of the pressure supply 12, i.e., the corresponding output pressure of the hydraulic pump 40. The aforementioned LS pressure is conveyed from the central LS line 34 to a control side of the circuit pressure compensator 14 via an LS control line 66.

[0026] A corresponding cyclic pressure compensator 14 in the form of a slide can be directly controlled as shown and is available from the copyright holder, for example under the serial number DWM12121ZD, with an integrated pressure limiting function (e.g., designed as a screw-in valve). Such a pressure compensator 14 is infinitely adjustable and, as shown in Figure 1As shown in FIG, it is closed in the normal position. The task of such a pressure compensator 14 is to keep the set volume flow constant regardless of pressure fluctuations. As a regulating valve in combination with a compression spring 62, the compression spring keeps the pressure drop demand-oriented at the same level via an integrated measuring throttle and the connection therewith to the consumer 18. Therefore, with the same measuring throttle area, the volume flow remains the same. If the load pressure in the load sensing system 10 drops to the tank pressure by all consumers 20 in the tank relief, the pressure compensator 14 also opens towards the storage tank 30 via the internal measuring throttle. In this way, such a circulating pressure compensator 14 can be used, for example, when variable loads are lifted or in order to drive the hydraulic motor 20 at the same speed. Instead of a directly controlled circulating pressure compensator 14, in order to realize the Figure 1 Alternatively, a pilot-controlled pressure compensator can also be used for the connection variant, which will be explained in more detail below.

[0027] A measuring orifice 68 is connected to the shown outlet side 52 of the circulation compensator 14 and is connected downstream of the branching point 54 in the direction of the storage tank 30 into the tank or return line 56. In parallel with the measuring orifice 68, a spring-loaded nonreturn valve 72 is connected in the branch line 70 and opens in the direction of the storage tank 30.

[0028] In a preferred embodiment, it can also be provided that a further measuring orifice 74 is connected in parallel with the first measuring orifice 68 in the branch line 70 and upstream of the check valve 72 in the throughflow direction. The cross-section of the further measuring orifice 74 is larger than that of the first measuring orifice 68. However, this configuration is not mandatory. The further measuring orifice 74 can also be arranged downstream of the check valve 72.

[0029] The excess volume flow formed is conducted from the system 10 via the circulation pressure compensator 14 in such a way that a measuring orifice 68 is arranged downstream of the circulation pressure compensator 14, through which the fluid flows to the storage tank 30. The pressure difference across this measuring orifice 68 is detected by means of a pressure sensor 50, and the signal of this pressure sensor 50 is used as a control variable (actual value) 46 for a closed-loop control circuit implemented as a control device 38. The speed of the hydraulic pump 40 is regulated by means of this control device 38 so that, ideally, the control variable 46 as an actual value corresponds to the command variable 44 as a setpoint value. Accordingly, the control variable 46 is used here according to Figure 1The proposed regulating device adjusts the constant Δp via one of the measuring orifices 68 so that within the regulating range (wherein the current rotational speed is always less than the maximum rotational speed of the hydraulic pump 40), a continuous excess volume flow flows through the circulating pressure compensator 14. Accordingly, the supply system is oversupplied and operates at a stable operating point, while the excess volume flow required for system stability is reduced to the necessary minimum value, thereby avoiding hydraulic losses within the supply range. This provides a compromise between system stability and loss avoidance.

[0030] By using second measuring orifice 74 , whose free cross section is preferably larger than the free cross section of first measuring orifice 68 , a fine control range can be achieved and the detection range of the sensor element can be widened by pressure sensor 50 .

[0031] By means of a variable speed assembly, in particular in the form of a constant speed pump, as a hydraulic pump 40, a volume flow can be provided on demand, so that the excess volume flow and the resulting losses via the circulation pressure compensator 14 are reduced to a necessary minimum. Therefore, the excess volume flow is diverted from the system via the circulation pressure compensator 14 in such a way that at least one measuring orifice 68 is provided downstream of the circulation pressure compensator 14, through which the fluid flows to the tank 30. The pressure difference (p) at the measuring orifice 68 is detected by the pressure sensor 50. T =p U = 0 bar). The signal of the pressure sensor 50 serves as the manipulated variable (actual value) for the closed control loop. The speed of the assembly is regulated by the control device so that, ideally, the manipulated variable corresponds to the command variable (setpoint value).

[0032] Accordingly, with the regulating device proposed here, a constant Δp is set via the measuring orifice 68, which must not be equal to Δ PLS , so that in the adjustment range (n <n max，总成 ) a continuous excess volume flow flows through the circulation pressure compensator 14. Accordingly, the system is in oversupply and operates in a stable operating point.

[0033] The losses caused by excess volume flow can be reduced to the minimum necessary for system stability by means of a demand-based control system.

[0034] The system only requires one pressure sensor 50, whereas the so-called eLS system usually requires at least two load-related sensor values, one in the form of pump pressure and the other in the form of LS pressure. In addition, the pressure detected upstream of the measuring orifice 68 is independent of the load or load pressure / pump pressure. Another advantage is that, compared to the load-related pressure range of up to 250 / 350 bar, the relatively low pressure level of the measuring orifice 68 (possibly less than 10 bar, related to the orifice design) makes the pressure range of the sensor smaller and therefore the resolution of the pressure range higher. Therefore, the sensor accuracy can be reduced, which brings cost advantages. The corresponding measuring orifice 68 has a gas damping effect, and the measured variable is independent of the load. This has a positive impact on the signal quality of the sensor 50 and improves the control quality. If necessary, the smoothing of the signal can be omitted, which improves the response characteristics.

[0035] Overall, the circuit pressure compensator 14 can be dimensioned smaller, since only a small excess volume flow has to be discharged during normal operation.

[0036] Additionally, according to Figure 1 In the embodiment of the invention, a bypass valve / check valve 72 with an upstream further measuring orifice 74 is provided in parallel with the measuring orifice 68 in order to limit the pressure difference across the measuring orifice 68 in the event of a high excess volume flow, for example in standby mode. In the corresponding standby mode, no consumer is actuated and the assembly delivers a volume flow Q due to the minimum speed. min，总成 The opening pressure of the check valve 72 in the bypass must be above the command value. This limits the circulating pressure in standby mode and contributes to energy-efficient operation of the assembly. Furthermore, the pressure limitation protects the sensor 50 from excessive pressure.

[0037] Figure 2 and Figure 3 In graphical form, according to Figure 1 The solution shows the volume flow V as a function of the pressure p at the measuring orifice 68 as the controlled variable. Here, a denotes the opening pressure "bypass of the measuring orifice 68 via the non-return valve 72." Furthermore, b denotes the fine control range and c denotes the excess volume flow. The inflection point KS1 is characterized after leaving the fine control range b.

[0038] In accordance with Figure 3 In the figure, another second inflection point KS2 is obtained for the following cases: Figure 1 As shown in the solution of , a bypass with a further measuring orifice 74 is provided next to the first measuring orifice 68. In this way, as in Figure 1The flow only flows through the further measuring orifice 74 when the opening pressure of the bypass check valve 72 is exceeded.

[0039] Therefore, the fine control range b can only be achieved by arranging an additional orifice or measuring orifice 74 upstream or downstream of the bypass valve or non-return valve 72 of the measuring orifice 68, which additional orifice or measuring orifice is preferably larger than the first measuring orifice 68. The flow through the measuring orifice 74 is only achieved when the opening pressure of the bypass valve or non-return valve 72 is exceeded and this point is as shown in FIG. Figure 3 As already explained in

[15] , this can be recognized by the inflection point KS2 in the volume flow-pressure diagram. Once inflection point KS2 is reached, the pressure p at the measuring orifice 68 does not increase further; only the volume flow V increases further. In any case, the detection range of the sensor element, particularly when using pressure sensor 50, is widened by the aforementioned fine control range b.

[0040] Further system interventions are conceivable, for example electrical or hydro-mechanical switching of one or more valves via measuring orifices 68 , 74 above a certain predeterminable pressure.

[0041] The following will especially focus on Figure 1 Further embodiments will be described starting from the solution according to the present invention, but these embodiments will only be described in terms of their differences with those according to the present invention. Figure 1 In this regard, the same structural component will be interpreted in the same manner as for Figure 1 The same reference numerals are also used for the following exemplary embodiments, and the statements made therefor then also apply to the following exemplary embodiments.

[0042] according to Figure 4 The solution is modified in such a way that the circulating pressure compensator 14 now has a displacement measuring system, in particular in the form of a displacement sensor 76, with which the position of the valve slide 60 in each adjustment position of the circulating pressure compensator 14 is detected. The signal of the slide position now serves as the control variable 46 and represents the corresponding actual value for the closed control circuit in the form of a control device 38. By means of a control device 38 of this type, the speed of the hydraulic pump 40 is regulated so that, ideally, the control variable 46 as the actual value again corresponds to the command variable 44 as the setpoint value. Accordingly, the control variable 46 according to the method proposed here is used. Figure 4The regulating device 38 regulates a constant slide position and this slide position corresponds to the desired excess volume flow through the circulating pressure compensator 14 at the rated pressure to be defined. Accordingly, the system is again in oversupply and operates in a stable operating point while avoiding volume losses. The excess volume flow is load-dependent when the slide position is constant, and accordingly the excess volume flow is greater at higher load pressures than at lower load pressures. Possibility of reducing or completely avoiding this effect is to provide the circulating pressure compensator 14 with a large fine control range or to additionally use a pressure sensor 50 for compensation within the regulating system 38. Preferably, the valve core 60 within the circulating pressure compensator 14 has a positive overlap when the spring preload / spring stiffness of the compression spring 62 is adapted. In addition, in Figure 1 The additional metering orifices 68 and 74 shown in FIG. 1 and the non-return valve 72 in the bypass line have been omitted, and the further tank or return line 56 opens as a branch on the outlet side directly into the storage tank 30 for the fluid.

[0043] In accordance with Figure 5 In the embodiment of the invention, a pressure-limiting valve 80 is additionally provided, so that the volume flow discharged via the pressure-limiting valve 80 flows via a downstream metering orifice 68 or a plurality of metering orifices 68, 74 to the tank 30. The pressure-limiting valve 80 opens mechanically when a set pressure value is exceeded; however, an electrical solution is also possible. This arrangement of the pressure-limiting valve 80 and the circuit pressure compensator 14 allows for a demand-based volume flow supply with an additional pressure cutoff, without the use of an additional pressure sensor or pressure switch for detecting the pump / system pressure, without requiring an additional pressure regulator to be used in the system or covering the demand-based control device for the pressure cutoff. The function of the pressure cutoff is as follows: upon reaching a set pressure equal to the set value of the pressure-limiting valve 80, the delivery volume flow of the respective assembly is limited or reduced in order to avoid increased power losses in the system.

[0044] The pressure limiting valve 80 is connected in parallel with the pressure compensator 14 and is fluidically connected to the pressure supply line of the hydraulic pump 40 and to the two measuring orifices 68 and 74. In addition, an additional non-return valve 82 is provided in the bypass with the non-return valve 72 to the second measuring orifice 74, which opens toward the tank 30. Figure 5 The circuit diagram solution can be realized according to Figure 3 Schematic representation of a volume flow-pressure diagram.

[0045] If necessary, the additional measuring orifice 74 with the non-return valve 72 can also be omitted within the scope of the volume flow and pressure to be controlled. Figure 6For comparable purposes, two parallel-connected measuring orifices 74 , 74 ′ can be used, which together lead in the direction of the nonreturn valve 72 .

[0046] In accordance with Figure 7 In the embodiment of the invention, the setpoint speed is transmitted as an input variable to the motor control device 48, which is formed by a conventional frequency converter, for example. The motor control device 48 then predetermines the corresponding speed for the motor M as the manipulated variable and uses a control pump with a hydraulic-mechanical regulating device as the hydraulic pump 40, which is controlled by the pressure difference across the measuring orifice 68, which is hydraulically guided back to the control pump. The relevant pressure difference is extracted upstream of the measuring orifice 68 and the non-return valve 82. In this solution, the additional measuring orifice 74 with the non-return valve 72 is omitted. Otherwise, it is possible to use a control pump according to the invention. Figure 7 The advantageous design scheme as described above can be realized by the solution of the circuit diagram. In addition, the pressure sensor 50 or other sensor devices can be omitted.

[0047] In accordance with Figure 8 In one embodiment, a variable-speed assembly with a speed control device is used. The speed control device of the assembly is implemented in parallel with the control device of a hydraulic pump 40 in the form of a variable displacement pump. The speed control uses the control variable of the variable displacement pump control device, which is proportional to the control angle, as the control variable (actual value) for the closed control loop. The control device regulates the speed of the assembly so that, ideally, the control variable corresponds to the command variable (setpoint value). This approach eliminates the need for a sensor for detecting the rotation angle of the variable displacement pump.

[0048] The prerequisite is a variable displacement pump with an electrical control device, which in particular operates electro-proportionally. Like the controller 42, the controller 42' is preferably a PID controller, which receives a command variable on the input side and a manipulated variable from the pressure sensor 50 on the output side. To control the variable displacement pump, the controller 42' then outputs, for example, an electric current as a manipulated variable, which is proportional to the adjustment angle of such a hydraulic pump 40.

[0049] In accordance with Figure 8 The solution is based on Figure 9 In the embodiment of FIG, the manipulated variable of the controller 42 ′ is supplied as the manipulated variable to the controller 42 for the motor adjusting device 38 .

[0050] In accordance with Figure 10In the embodiment of FIG, a dual-pump assembly is now used, wherein both pumps 40, 40' feed into the same system and at least one of the two pumps is isolated from the system via a non-return valve 84. In at least one of the hydraulic pumps (here, hydraulic pump 40'), a switching valve 86 is additionally provided upstream of the non-return valve 84, which is closed in the direction of the switching valve 86. The pressure difference across the measuring orifice 68 or the measuring orifices 68, 74 is also fed back to the switching valve 86 as a hydraulic signal.

[0051] Here, the switching valve 86 has Figure 11 . If the set pressure is exceeded, as an upper set value e that can be predefined mechanically or electrically, one of the two pumps 40, 40' is connected to a further third pressure level that is below the system pressure; ideally, this pressure level corresponds to the tank pressure in the tank 30. Only when the pressure falls below the lower set value f does the switching valve 86 switch back and omit the connection in the direction of the third pressure level (tank pressure). Accordingly, as in Figure 11 As shown in , the switching valve 86 has a hysteresis g relative to the opening pressure. The speed control device for the two drives M, in particular in the form of constant-current pumps, 40 , 40 ′ is realized in parallel.

[0052] according to Figure 10 The embodiment of the motor M can also be modified accordingly, so that the regulating device 38 for the motor M is omitted and the drive or the motor M (not shown) is operated at a fixed setpoint speed.

[0053] In addition, existence and basis Figure 7 A solution of the type shown in FIG. 1 is quite possible: the regulating device 38 for the motor M is omitted and only a setpoint speed is specified for the motor control 48 for specifying the speed as the manipulated variable or input value.

[0054] according to Figure 12 The embodiment of the embodiment is modified in relation to the previously described solution, so that the pressure difference across the measuring orifice 68 or the measuring orifices 68 , 74 is now detected electronically via a pressure sensor 50 , and the signal of this sensor 50 is used to regulate the speed of the drive in the form of a motor M by means of the already described regulating device 38 . This sensor signal is also used to electrically actuate the switching valve 86 .

[0055] For this purpose, a control device 42' is used again, which receives the (pressure) condition switch-on h and the further (pressure) condition switch-off i as input variables. In addition, the (speed) condition switch-off j can be predetermined as an input condition. The further input variable comes from the output side of the pressure sensor 50, and the control variable (speed) on the output side of the frequency converter 48 is also transmitted to the regulator 42' as a further input variable. Figure 12 The switching valve 86 is an electrically operated switching valve (can also be realized by a normally open valve), which realizes the switching of the Figure 11 The volume flow-pressure diagram of FIG is shown, which has a hysteresis characteristic g as shown. Here, the lower setpoint f corresponds to the (pressure) switch-on condition h, and the upper setpoint e corresponds to the (pressure) switch-off condition i. In this electrically controlled variant, the hysteresis is implemented in the control device 42 ′.

[0056] The switching valve 86 can be designed in various ways and, in the present case, consists of an electromagnetically actuated 2 / 2-way bypass switching valve connected to the tank 30 on the outlet side. However, all variants have in common that, below a pressure value h, the switching valve 86 is in a position in which there is no connection to a pressure level below the system pressure (the pressure of another pump stage). Conversely, when a further pressure value i is exceeded, the switching valve 86 establishes a connection to another pressure level below the system pressure; ideally, this corresponds to the tank pressure. Furthermore, although this is not mandatory, this process can also be coupled to other conditions, such as a speed condition j. A speed control device for the drive M can be implemented in parallel, or the assembly M can be operated at a constant speed.

[0057] All solutions have in common at least that a simple, cost-effective, robust and demand-oriented volume flow supply device for the closed sensor system is realized and that the volume flow of the fluid is provided on demand, reducing any excess volume flow and the associated losses via the circulation pressure compensator 14 to the necessary minimum.

Claims

1. A volume flow supply device having a pressure supply device (12) and a pressure compensator as components of a supply system for fluidly supplying a hydraulic consumer (18) connectable thereto, characterized in that: The pressure supply device (12) provides a volume flow for supplying the hydraulic consumer (18) in a demand-oriented manner, in that the pressure compensator is formed by a circulating pressure compensator (14) which diverts any excess volume flow from the supply flow, and the volume flow supply device has a regulating device (38) which reduces the excess volume flow to a minimum value by actuating the pressure supply device (12).

2. The volume flow supply mechanism according to claim 1, characterized in that The volume flow supply device is a volume flow supply device for a closed center LS system (10).

3. The volume flow supply mechanism according to claim 1, characterized in that The pressure supply device (12) has at least one hydraulic pump (40) which is driven by a motor (M) which is controlled by the regulating device (38).

4. The volume flow supply mechanism according to claim 1 or 2, characterized in that The regulating device (38) comprises a regulator (42) having a predeterminable command variable (44), wherein the regulating variable (46) of the regulator is formed by an output value of a sensor, which detects a pressure value on the outlet side (52) of the circulating pressure compensator (14) in the form of a pressure sensor (50) and / or detects a displacement position of a valve element (60) of the circulating pressure compensator (14) in the form of a displacement sensor (76).

5. The volume flow supply mechanism according to claim 3, characterized in that The regulating device (38) comprises a regulator (42) having a predeterminable command variable (44), wherein the regulating variable (46) of the regulator is formed by an output value of a sensor, which detects a pressure value on the outlet side (52) of the circulating pressure compensator (14) in the form of a pressure sensor (50) and / or detects a displacement position of a valve element (60) of the circulating pressure compensator (14) in the form of a displacement sensor (76).

6. The volume flow supply mechanism according to claim 4, characterized in that The regulator (42) is in the form of a PID regulator.

7. The volume flow supply mechanism according to claim 5, characterized in that The output of the regulator (42) is connected to a motor control unit (48).

8. The volume flow supply mechanism according to claim 7, characterized in that The motor control device (48) is formed by a frequency converter which predetermines the rotational speed of a motor (M) serving as a drive device for the hydraulic pump (40) as a control variable.

9. The volume flow supply mechanism according to any one of claims 1 to 3, characterized in that The circulating pressure compensator (14) is designed as a directly controlled, spring-loaded throttle valve in a slide design, the valve core (60) of which is subjected to the LS pressure from the hydraulic consumer (18) together with the accumulator on one side and to a control pressure corresponding to the output or supply pressure of the pressure supply device (12) on the other side.

10. The volume flow supply mechanism according to claim 9, characterized in that The energy accumulator is a compression spring (62).

11. The volume flow supply device according to any one of claims 1 to 3, characterized in that At least one measuring orifice plate (68) is connected to the outlet side (52) of the circulation pressure compensator (14).

12. The volume flow supply mechanism according to claim 11, characterized in that A bypass line (70) is provided in parallel with the measuring orifice plate (68).

13. The volume flow supply mechanism according to claim 12, characterized in that The bypass line (70) has at least one spring-loaded non-return valve (72) which leads in the direction of the tank or the return line (56).

14. The volume flow supply mechanism according to claim 11, characterized in that At least one further measuring orifice (74) is connected in parallel to one of the measuring orifices (68).

15. The volume flow supply mechanism according to claim 13, characterized in that At least one further measuring orifice (74) is connected in parallel to one of the measuring orifices (68) and upstream of the non-return valve (72) as viewed in the flow direction.

16. The volume flow supply mechanism according to claim 14 or 15, characterized in that The free cross section of the further measuring orifice (74) is dimensioned to be larger than the free cross section of the one measuring orifice (68).

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