Patent Abstract:
A hydraulic control assembly for a plurality of consumers includes, for each consumer, a supply metering orifice configured to control fluid flow. A flow-sensing fluid-flow-path extends over detection orifices positioned hydraulically in series, whereby a detection orifice is assigned to each supply metering orifice. The fluid-flow-path is connected to a hydraulic pump upstream of the detection orifices, and a control device of the hydraulic pump downstream of the detection orifices. Each detection orifice is configured to close the fluid-flow-path upon detecting a fluid supply deficiency for a corresponding consumer, whereby the control device is configured to interact with the fluid-flow-path such that fluid flow from the hydraulic pump is increased. When no customers have a supply deficiency, the fluid-flow-path over the detection orifices is fully opened, and the control device is configured to reduce fluid flow from the hydraulic pump.

Full Description:
This application claims priority under 35 U.S.C. §119 to patent application no. DE 10 2013 223 288.8, filed on Nov. 15, 2013 in Germany, the disclosure of which is incorporated herein by reference in its entirety. 
     The disclosure proceeds from a hydraulic control assembly. 
     BACKGROUND 
     DE 10 2009 034 616 A1 discloses a control assembly which takes the form of a load-sensing (LS) control. In this control the highest load pressure is signaled to a variable-displacement pump and the latter is controlled in such a way that a pump pressure exceeding the load pressure by a specific pressure differential Δp prevails in a pump line. Individual pressure compensators, which also maintain a constant pressure differential over the supply metering orifices of the hydraulic consumers having a lower load pressure at any given time, are assigned to adjustable supply metering orifices of the LS control for the consumers. The individual pressure compensators are usually arranged upstream of the supply metering orifices and restrict the fluid flow between the pump line and the supply metering orifices to such a degree that irrespective of the pump pressure the pressure upstream of the supply metering orifices still only exceeds the individual load pressure by a specific pressure differential. In the event of a supply deficit the consumer at the highest load pressure becomes slower, because the pump pressure issuing from its supply metering orifice falls and the pressure differential over this supply metering orifice thereby diminishes. 
     In this LS control a highest load pressure is signaled to a pump control of the variable-displacement pump usually via LS signal lines, which are interconnected by way of a shuttle valve cascade. This gives rise to a considerable outlay for mechanical devices, takes up a lot of overall space and is cost-intensive. In order to afford an adequate control pressure gradient at the supply metering orifices in these LS controls, the variable-displacement pump needs to provide an increased control pressure gradient at the individual pressure compensators, particularly in order to be able to compensate for influences on the fluid flow due to temperature changes or due to flow resistances. The control pressure gradient ensures that an adequate pressure differential prevails at the supply metering orifices in all operating states. 
     The Rexroth data sheet RD 66 134 discloses a hydraulic circuit diagram for the LS control explained above. 
     The publication U.S. Pat. No. 5,305,789 A discloses a load-independent flow distribution (LUDV) control. In a LUDV control the individual pressure compensators are arranged downstream of the supply metering orifices and restrict the fluid flow between the supply metering orifices and a load to such a degree that the pressure downstream of all supply metering orifices is equal, preferably equal to or slightly in excess of the highest load pressure. Here nothing changes in the event of a pressure supply deficit on the pressure downstream of the supply metering orifices. The pump pressure increases in the same way upstream of all supply metering orifices, so that the pressure differential varies in the same way at all supply metering orifices if the pump pressure diminishes in the event of a supply deficit, and the flow distribution between the supply metering orifices is maintained. Determination of a maximum load pressure relies on the fact that only the individual pressure compensator at the highest load is fully opened. Only in the fully opened position of the individual pressure compensator is its load pressure connected to a LS signal channel. 
     The Rexroth data sheet RD 64 125 discloses a hydraulic circuit diagram for the generic LUDV control. 
     DE 10 2007 045 803 A1 discloses a control assembly in which positions of valve spools of the individual pressure compensators are measured and the individual pressure compensators control the pressure differential at the supply metering orifice assigned to them. Here a displacement of a hydraulic pump is electrically adjusted as a function of the measuring result. This relies on the fact that only the valve spool of the individual pressure compensator at the highest load is fully opened. 
     The object of the disclosure, on the other hand, is to create a hydraulic control assembly which, in particular, is roughly functionally equivalent to the LS control and/or the LUDV control, which is of simple design, takes up little overall space, has a lower power requirement and is cost-effective. 
     SUMMARY 
     This object is achieved by a hydraulic control assembly. 
     Advantageous developments of the disclosure form the subject matter of the drawings and the claims. 
     According to the disclosure a hydraulic control assembly for consumers is provided. This has a supply metering orifice for each respective consumer for controlling a magnitude of a fluid flow from a hydraulic pump to the respective consumer. For this purpose each respective supply metering orifice is hydraulically connected on the inlet side to the hydraulic pump, in particular directly or indirectly via at least one further valve. A respective consumer is provided on the outlet side of each respective supply metering orifice. A respective detection orifice is advantageously assigned to each respective supply metering orifice. Here the detection orifices are arranged hydraulically in series. A flow-sensing (FS) fluid flow path extends over the detection orifices, starting from the hydraulic pump. The FS fluid flow path can therefore be connected to the hydraulic pump upstream of the detection orifices. The fluid flow path then terminates at a control device, in particular downstream of the detection orifices. The control device here serves to control a magnitude of a fluid flow from the hydraulic pump to the supply metering orifices. Each respective detection orifice is designed in such a way that if the pressure differential over each respective supply metering orifice falls below a specific value (supply deficit) it closes the FS fluid flow path. On attaining or exceeding the specific pressure differential (normal supply) the detection orifice assigned to the supply metering orifice opens the FS fluid flow path. The FS fluid flow path advantageously serves to influence the control device of the hydraulic pump for controlling the fluid flow from the hydraulic pump to the consumers or to the supply metering orifices. In particular, the FS fluid flow path therefore allows the control device to detect whether there is a supply deficit. The FS fluid flow path therefore serves for transmitting an FS signal. 
     This solution has the advantage that the control device of the hydraulic pump no longer uses the highest load pressure to control the fluid flow, as in the prior art explained at the outset, but instead makes the control of the hydraulic pump dependent upon the FS fluid flow path, that is to say whether the latter is opened or closed. If it is opened, that is to say if all detection orifices arranged hydraulically in series are opened, there is no supply deficit to a supply metering orifice or a consumer. If, on the other hand, a detection orifice is closed, the FS fluid flow path is blocked and the control device is able to control the hydraulic pump in such a way, for example, that the supply deficit to the supply metering orifices is counteracted. 
     In the hydraulic control assembly according to the disclosure, therefore, LS signal lines and a shuttle valve cascade, as are provided in the control assemblies explained at the outset in the prior art, can be omitted. This leads to a reduction in the outlay for mechanical devices and to a reduction in the overall space required. Costs are thereby reduced. In addition the hydraulic control assembly according to the disclosure has relatively low energy losses. 
     In a further development of the disclosure the FS fluid flow path influences the control device in such a way that a closure of the FS fluid flow path by at least one of the detection orifices leads to an increase in the fluid flow from the hydraulic pump to the consumers. An opening of the FS fluid flow path by all detection orifices on the other hand advantageously leads to a reduction of the fluid flow from the hydraulic pump to the consumers. 
     Each respective detection orifice may have a valve element for opening and closing the FS fluid flow path. Here the valve element is preferably acted upon in the opening direction by the fluid upstream of the supply metering orifice assigned thereto and in the closing direction by the fluid downstream of the supply metering orifice assigned thereto, and in addition by a spring force of a detection spring, especially an adjustable detection spring. This represents a simple way, in terms of mechanical devices, of closing the FS fluid flow path in the event of a supply deficit to the supply metering orifice, that is to say if the pressure differential over the supply metering orifice falls below a specific value. 
     The spring force of the detection spring of the detection orifice advantageously predefines the pressure differential at which the valve spool of the detection orifice is actuated in the direction of the closing position. 
     A pump control may preferably be provided as control device for adjusting a displacement of the hydraulic pump embodied as a variable-displacement pump. Alternatively it is feasible for the control device to be an inlet pressure compensator of the hydraulic pump embodied as a constant-displacement pump. 
     The pump control has the advantage that the variable-displacement pump can be turned down when the FS fluid flow path is opened and there is therefore no supply deficit at the supply metering orifices. If the FS fluid flow path is closed, on the other hand, the variable-displacement pump can be turned by the pump control in the direction of an increased displacement. The FS fluid flow path also allows the control device to be designed without a volumetric flow regulator. 
     In a further development of the disclosure each respective supply metering orifice may be embodied as a continuously adjustable directional control valve. In a neutral position this may close a fluid connection between the consumer assigned to it and the hydraulic pump, and in switching positions it may open a fluid connection between the consumer assigned to it and the hydraulic pump. The directional control valve therefore serves to adjust an opening cross section. 
     In a preferred embodiment, which may be based, in particular, on a LS control with individual pressure compensators, an individual pressure compensator is assigned to each respective supply metering orifice. Said pressure compensator is preferably used to maintain an approximately constant pressure differential over the supply metering orifice. Besides a respective detection orifice, therefore, a respective individual pressure compensator is additionally provided. Here the individual pressure compensator may be connected to the supply metering orifice on the inlet or outlet side. In contrast to the prior art, the provision of an individual pressure compensator in addition to the detection orifice obviates the need for an excess pressure. 
     In a further development of the disclosure at least one individual pressure compensator is formed together with the assigned detection orifice as an individual valve having a common valve element. All individual pressure compensators are preferably formed as individual valves with the detection orifices assigned to them. This has the advantage that only one valve need be used, which simplifies the mechanical devices needed and is cost-effective. 
     The individual valve may advantageously be connected to the supply metering orifice on the inlet or outlet side. 
     The valve element of each respective individual valve is preferably embodied as a valve spool. This may have a basic position and be displaceable from this position in the direction of first switch switching positions. In addition it may be displaceable in the direction of second switching positions, which adjoin the first switching positions. In the various positions the valve spool may advantageously fulfill the functions of the detection orifice and the individual pressure compensator. The FS fluid flow path may therefore be opened in the first and second switching positions and closed in the basic position. Additionally, in the second switching positions a fluid connection between the hydraulic pump and the consumer may be closed. In the first switching positions the fluid connection between the hydraulic pump and the consumer may then be restricted or fully opened. In the basic position the fluid connection between the hydraulic pump and the consumer is then preferably fully opened. With a normal supply to the supply metering orifice, the pressure differential over the supply metering orifice is controlled by the individual valve in the first and second switching positions, in which the FS fluid flow path is fully opened. Here the pump control may turn the pivotable pump down. In the event of a supply deficit, on the other hand, the valve element of the individual valve is in the basic position, the FS fluid flow path being closed and the fluid connection from the hydraulic pump to the supply metering orifice and to the consumer being fully opened. Here the pump control may then turn the variable-displacement pump in the direction of an increased displacement. 
     In adjusted operation the individual valve and the FS fluid flow path allow the valve spool of the individual valve of the consumer at the highest load to be positioned preferably in the area of its first switching positions, since in contrast to the prior art the hydraulic pump does not deliver any excess pressure. This leads to an energy saving, since a control reserve for so-called extreme situations is no longer necessary. 
     In a further development of the individual valve the valve element may be acted upon in the direction of the basic position by the spring force of the detection spring and by the fluid downstream of the assigned supply metering orifice. The valve element may be acted upon in the direction of the first and second switching positions by the fluid upstream of the supply metering orifice assigned to it. 
     In a further preferred embodiment, which is based in particular on a LUDV control, the control assembly according to the disclosure may be formed with an individual pressure compensator connected to the supply metering orifice on the outlet side. A FS fluid flow path can therefore also be provided in a control assembly which is basically embodied as a LUDV control assembly. 
     In a further preferred embodiment an individual pressure compensator having a valve spool may therefore be connected to each respective supply metering orifice on the outlet side. In a basic position this may close a fluid connection between the supply metering orifice and the assigned consumer and starting from the basic position and moving in the direction of the first switching positions may afford restricted opening of the fluid connection between the supply metering orifice and the assigned consumer. Starting from the first switching positions the valve switch, moving further in the direction of the second switching positions, may fully open the fluid connection between the supply metering orifice and the assigned consumer. 
     The valve spool of each respective individual pressure compensator of the further embodiment may be further acted upon in the direction of the first and second switching positions by the fluid downstream of the supply metering orifice and in the direction of the basic position by the highest load pressure of the consumers. 
     In addition, the individual pressure compensators of the further preferred embodiment may be connected to a common LS line. The valve spool of each respective individual pressure compensator may then afford a restricted connection, downstream of the supply metering orifice, to a consumer line connected to the consumer. In the first switching positions and in the basic position the valve spool may close the connection between the LS line and the consumer line. Via the LS line the valve spool may furthermore be acted upon in the direction of the basic position by the highest load pressure of the consumers. 
     In a further development of the disclosure the pump control may preferably comprise an adjusting cylinder for adjusting the displacement of the variable-displacement pump. Here the adjusting cylinder is preferably controlled by a control valve. 
     A piston of the adjusting cylinder may furthermore define a cylinder chamber, which can be charged with fluid in order to reduce the displacement of the variable-displacement pump. In order to increase the displacement of the variable-displacement pump, fluid can be discharged from the cylinder chamber. For charging fluid, the cylinder chamber is in particular connected directly to the FS fluid flow path, especially through a restricted connection. 
     The control valve may comprise a valve spool, which is acted upon in the direction of a basic position by a spring force of a valve spring, in particular an adjustable spring. It may be acted upon in the direction of switching positions by fluid from an outlet side of the hydraulic pump and therefore acted upon by a pump pressure. In the basic position a fluid connection is preferably opened between the FS fluid flow path and the cylinder chamber, and closed between the outlet side of the hydraulic pump and the cylinder chamber. In the switching positions the fluid connection may be closed between the FS fluid flow path and the cylinder chamber and opened between the outlet side of the hydraulic pump and the cylinder chamber. 
     The FS fluid flow path is advantageously connected via a restrictor to a tank, so that a defined pressure prevails in the FS fluid flow path even when a detection orifice is closed. 
     The hydraulic control assembly may be provided in a valve block. It is feasible for the valve block to be formed from valve plates, the valves for each respective consumer being provided in each respective valve plate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments are explained in more detail below with reference to drawings, of which: 
         FIG. 1  shows a hydraulic circuit diagram of a control assembly according to the disclosure in a first exemplary embodiment, 
         FIG. 2  shows a further hydraulic circuit diagram of the control assembly according to the disclosure, 
         FIG. 3  shows a hydraulic circuit diagram of a portion of the control assembly according to a second exemplary embodiment, 
         FIG. 4  shows a hydraulic circuit diagram of a portion of the control assembly according to a third exemplary embodiment, 
         FIG. 5  shows a hydraulic circuit diagram of a portion of the control assembly according to a fourth exemplary embodiment and 
         FIG. 6  shows a hydraulic circuit diagram of a portion of the control assembly according to a fifth exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     According to  FIG. 1  the hydraulic control assembly  1  comprises a valve block  2 , which comprises valve plates  4 ,  6  and  8 . Each respective valve plate  4  to  8  comprises two working connections A, B for the connection of a hydraulic consumer, such as a hydraulic cylinder, for example. Here the valve plates  4  to  8  are of identical design and each comprise a supply metering orifice  10  and an individual valve  12 . Here each respective individual valve  12  forms an individual pressure compensator, which is connected to the inlet side of the respective supply metering orifice  10 , and a detection orifice according to the disclosure. 
     The design of the supply metering orifices  10  is explained with reference to the valve plate  4 . The supply metering orifice  10  is designed as a continuously adjustable  5 / 4  directional control valve. Here a valve spool of the supply metering orifice  10  is spring-centered in a neutral position  0 . By means of a hydraulic actuator  14  the valve spool can be shifted from the neutral position  0  in the direction of a first switching position a or in the opposite direction from the neutral position  0  in the direction of second switching positions b. If the valve spool is shifted further from the second switching positions b it reaches free-flow or floating positions c. In the first switching position (a) a fluid connection is opened between an inlet line  16 , which extends from a hydraulic pump not represented in  FIG. 1 , and a working line  18  to the working connection B. In addition a fluid connection is opened between a working line  20  connected to the working connection A, and an outlet line  22  connected to a tank (not represented). In the first switching positions (a) a pressure is also picked off downstream of the supply metering orifice  10  via a branch line  24 . The branch line  24  here is connected to the individual valve  12 . In contrast to the first switching positions a, in the second switching positions b of the supply metering orifice  10  the working line  20  is connected to the inlet line  16  and the working line  18  is connected to the outlet line  22 . In the free-flow or floating positions c both working connections  18  and  20  are connected to the outlet line  22  and the inlet line  16  and the branch line  24  are closed. In the neutral position  0  all lines are separated from one another. Control lines  26  and  28  are provided for controlling the hydraulic actuator  14 . Alternatively it is feasible for the supply metering orifice  10  to be actuated electromagnetically or manually. 
     The individual valve  12  is likewise explained in more detail with reference to the valve plate  4 . It is designed as a continually adjustable  4 / 3  directional control valve. A spring force of a detection spring  30  acts upon a valve spool in the direction of a basic position  0 . From the basic position  0  it can be shifted in the direction of first switching positions a. Further to the switching positions a, it can be shifted in the direction of second switching position b. A flow-sensing (FS) fluid flow path  32  extends over the individual valves  10  of the valve plates  4  to  8 . The individual valves  12  are arranged in series in respect of this FS fluid flow path  32 . Here in the basic position  0  of the individual valve  12  the FS fluid flow path  32  is closed and in the first and second switching positions a,b it is opened. The FS fluid flow path  32  is therefore opened only when all valve spools of the individual valves  12  are not in their neutral position  0 . If, on the other hand, one or more of the valve spools of the individual valves  12  is in the basic position  0 , the FS fluid flow path  32  is closed. The FS fluid flow path  32  is connected to the inlet line  16  upstream of the individual valves  12  and extends further over the individual valve  12  of the valve plate  8  to the individual valve  12  of the valve plate  6  and thence to the individual valve  12  of the valve plate  4 . Downstream of the last individual valve  12  of the valve plate  4  the FS fluid flow path  32  is then connected to a pump control (not represented) of a hydraulic pump embodied as a variable-displacement pump. 
     As already explained above, the valve spool of each respective individual valve  12  is acted upon by the spring force of the detection spring  30  in the direction of the basic position  0 . In addition it is acted upon in the direction of the basic position  0  by the fluid in the branch line  24  and therefore by the pressure downstream of the supply metering orifice  10 . In the opposite direction, that is to say in the direction of the first and second switching positions a,b, the valve spool is acted upon, via a control line  34 , by the fluid from the inlet line  16  downstream of the individual valve  12  and upstream of the supply metering orifice  10 . In the basic position  0  the FS fluid flow path  32  is closed and the inlet line  16  to the supply metering orifice  10  is fully opened. In the first switching positions a, on the other hand, the FS fluid flow path  32  is opened and the inlet line  16  to the supply metering orifice is likewise fully opened. In the second switching positions b the FS fluid flow path  32  is then opened again and the inlet line  16  to the supply metering orifice  10  is closed. 
     The hydraulic control assembly according to the disclosure in  FIG. 1  differs from conventional LS control assemblies particularly in the provision of the FS fluid flow path  32 , which can be opened and closed by the detection orifices of the individual valves  12 . The FS fluid flow path  32  therefore serves for transmitting an FS signal, which is explained below, for which reason a load pressure signal, which is relayed to a pump control via LS signal lines and a shuttle valve cascade, for example, is no longer necessary. According to  FIG. 1 , instead of individual pressure compensators the individual valves  12  are provided, which unlike individual pressure compensators have an additional control edge for controlling the FS fluid flow path. 
     In explaining the operating principle of the control assembly  1  in  FIG. 1  it is first assumed that the variable-displacement pump (not shown) is in operation and the supply metering orifices  10  are in their neutral position  0  shown. As a result the valve spools of the individual valves  12  are located in the second switching position b, so that the FS fluid flow path  32  is opened. Fluid is then fed via this path from the inlet line  16  to the pump control of the variable-displacement pump, which serves as FS signal. The FS fluid flow path  32  here interacts with the pump control in such a way that with the FS fluid flow path  32  opened (FS signal open) the variable-displacement pump is turned down. 
     It is next assumed that the supply metering orifice  10  of the valve plate  8  is situated in its second switching position b, so that a consumer connected to the working connections A, B of the valve plate  8  is supplied with fluid via the inlet line  16 . The individual valves  12  of the valve plates  4  and  6  are in the second switching position b. If the consumer connected to the valve plate  8  now has a supply deficit, that is to say the pressure differential over the supply metering orifice  10  is below a predefined pressure differential, the valve spool of the individual valve  12  of the valve plate  8  is shifted into the basic position  0 . The FS fluid flow path  32  is accordingly closed by the individual valve  12  of the valve plate  8 . Therefore no fluid passes from the inlet line  16  to the pump control via the FS fluid flow path  32 . Here the FS fluid flow path  32  interacts with the pump control in such a way that in this case the variable-displacement pump is turned in the direction of an increase in the displacement. In this case the individual valve  12  of the valve plate  8  is fully or almost fully opened in respect of the inlet line  16  to the supply metering orifice  10 , for which reason it has minimal hydraulic losses, in contrast to a conventional LS control assembly of prior art. 
     In the absence of a continuing supply deficit of the consumer connected to the valve plate  8 , the valve spool of the individual valve  12  of the valve plate  8  is moved into its first switching position a. The FS fluid flow path  32  is therefore opened again and at the same time the inlet line  16  to the supply metering orifice  10  of the valve plate  8  is fully or almost fully opened, which again leads to minimal hydraulic losses. The opened FS fluid flow path  32  causes the pivotable pump to be turned down again. 
     It is now assumed that the hydraulic consumers connected to the valve plates  6  and  8  are operated in parallel. For this purpose both the valve spool of the supply metering orifice  10  of the valve plate  6  and the valve spool of the supply metering orifice  10  of the valve plate  8  are situated in the second switching positions b, for example. Here the pressure differential of the supply metering orifices  10  of the valve plates  6  and  8  are adjusted via the individual valves  12 . The consumer connected to the valve plate  6  should be the consumer at the highest load, which is why the individual valve  12  of the valve plate  6  controls the FS fluid flow path  32 . For this purpose its valve spool is situated in the basic position  0  or in the first switching position a. Here the variable-displacement pump is controlled by the pump control so that the necessary pressure differential prevails at the supply metering orifices  10 . The connection in the first valve plate  6  between the inlet line  16  and the supply metering orifice  10  is therefore fully opened, which leads to minimal hydraulic losses. The other individual valve  12  of the valve plate  8  with the consumer at a lower load then controls the pressure differential via the supply metering orifice  10  of the valve plate  8  in the conventional way, in that its valve spool is in the switching positions a or b. The FS fluid flow path  32  is therefore fully opened via the individual valve  12  of the valve plate  8 . 
     The hydraulic control assembly  1  according to the disclosure in  FIG. 1  therefore means that in the absence of a supply deficit to the assigned supply metering orifice  10  each individual valve  12  relays the FS signal via the FS fluid flow path  32 . If there is no overall supply deficit, the FS signal is transmitted via the opened FS fluid flow path  32  to the pump control, which correspondingly turns down the variable-displacement pump. If only one hydraulic consumer is used, the individual valve  12  assigned to this is used for controlling the FS fluid flow path  32  and therefore for controlling the variable-displacement pump, in order to adjust the pump pressure commensurately. If multiple consumers are operated, the individual valve  12  of the consumer at the highest load is used for controlling the FS fluid flow path  32  and therefore for controlling the variable-displacement pump, and the other individual valves  12  are used as conventional individual pressure compensators. 
       FIG. 2  shows a further representation of the hydraulic control assembly  1 . Here the valve plates  4 ,  6  and  8  are represented as blocks. They serve as locators for the portions  36  of hydraulic control assemblies  1  in different embodiments depicted in  FIGS. 3-6 . 
       FIG. 2  also shows examples of hydraulic consumers  38 . Here they are differential cylinders, which are each connected to the working co 0 nnections A, B of the valve plates  4 - 8 . 
     In addition  FIG. 2  shows a variable-displacement pump  40  having a pump control  42 . This comprises an adjusting cylinder  44  with a piston  46 . This defines a cylinder chamber  48 . Via the cylinder chamber  48  fluid is capable of acting on the piston  46  in the direction for turning down the variable-displacement pump  40 . A spring force of a spring  50  acts on the piston  46  in the opposite direction. The pump control  42  further comprises a control valve  52 , which is embodied as a continuously adjustable  3 / 2  directional control valve. A spring force of an adjustable valve spring  54  acts on a valve spool in the direction of a basic position  0 . In the opposite direction to the switching positions a fluid in the inlet line  16  is capable of acting on the valve spool via a control line  56 , the inlet line  16  being connected to the variable-displacement pump  40  on the outlet side. In the basic position  0  a fluid connection between the FS fluid flow path  32  and the cylinder chamber  48  of the adjusting cylinder  44  is opened by the control valve  52 . In the switching positions a, on the other hand, this connection is closed whilst a fluid connection between the inlet line  16  and the cylinder chamber  48  is opened. Here the FS fluid flow path  32  is connected to the control valve  52  downstream of the detection orifices not shown in  FIG. 2 . Also extending from the FS fluid flow path  32  downstream of the detection orifices not shown in  FIG. 2  is a branch line  58 , which is directly connected to the cylinder chamber  48  by a restrictor  60 . A further restrictor  62 , via which the branch line  58  and therefore the FS fluid flow path  32  is connected to a tank  64 , is provided hydraulically in parallel with the restrictor  60 . 
       FIG. 3  represents the portion  36  of a second embodiment of the control assembly  1 . Viewed in conjunction with  FIG. 2 , the portion  36  is provided for the valve plates  4 - 8 . In contrast to the embodiment in  FIG. 1  the supply metering orifice  10  is embodied as a  6 / 3  directional control valve. A valve spool of the metering orifice  10  is spring-centered in a neutral position  0 . It can be shifted from the neutral position  0  in the direction of first switching positions a. In the opposite direction it can be shifted from the neutral position  0  in the direction of second switching positions b. In the first switching positions (a) the inlet line  16  is connected via the supply metering orifice  10  to a connecting line  66 , which again in the first switching position a is connected via the metering orifice  10  to the working line  16  for the working connection A. In addition, in the first switching positions (a) the working line  20  for the working connection B is connected to the outlet line  22 . In the neutral position  0  all lines are separated from one another. In the second switching positions b, on the other hand, the inlet line  16  is again connected via the metering orifice  10  to the connecting line  66 , the latter then being further connected via the metering orifice  10  to the working line  20  for the working connection B. The working line  18  is then connected to the outlet line  22 . 
     The branch line  24  for the individual valve  12  branches off from the connecting line  60 . The fluid downstream of the supply metering orifice  12  therefore continues to act upon the valve spool of the individual valve  12  in the direction of its basic position  0 . In the opposite direction it is acted upon by the fluid from the control line  34  between the individual valve  12  and the supply metering orifice  10 . In contrast to  FIG. 1 , the intention with the individual valve  12  in  FIG. 3  is that in the first switching positions a of the valve spool the inlet line  16  should have a restricted connection to the supply metering orifice  10 . 
     An operating principle of portion  36  of the control assembly  1  according to  FIG. 3  here substantially corresponds to the operating principle of the control assembly in  FIG. 1 . 
     In the operating description of the hydraulic control assembly according to  FIGS. 2 and 3  it is assumed that all supply metering orifices  10  for the consumers  38  are at least partially opened, and that the valve spools of the individual valves  12  are situated in the switching positions a or b. Accordingly the FS fluid flow path  32  is opened, so that the cylinder chamber  48  of the adjusting cylinder  44  is connected to the inlet line  16  via the FS fluid flow path  32 , the branch line  58  and the restrictor  60 . Irrespective of the position of the valve spool of the control valve  52 , therefore, the pressure prevailing on the piston  46  approximates to the feed pressure of the variable-displacement pump  40 . The piston  46  therefore moves in the direction of an enlargement of the cylinder chamber  48 , which leads to turning down of the variable-displacement pump  40 . In their function as individual pressure compensators the individual valves  12  control the pressure differential over the assigned supply metering orifice, in such a way that this remains substantially constant and corresponds to a pressure equivalent of the spring force of the detection spring  30 . If the fluid flow delivered by the variable-displacement pump  40  is no longer sufficient, with the result that at least one supply metering orifice  10  has a supply deficit, the valve spool of that individual valve  12  having a metering orifice  10  with a supply deficit is shifted in the direction of its basic position  0 . The valve spool of the individual valve  12  is therefore shifted into its basic position  0  if the pressure differential of the assigned metering orifice  10  is less than the pressure equivalent of the detection spring  30 . The FS fluid flow path  32  is therefore closed. The FS fluid flow path  32  is then connected to the tank  64  via the branch line  58 . The control valve  52  then adjusts a feed pressure of the variable-displacement pump  40  to the value set by the valve spring  54 , which corresponds in particular to the maximum admissible feed pressure. This in turn leads to an increase in the displacement of the variable-displacement pump  40 , until there is no longer any supply deficit. 
     If the valve spool of a supply metering orifice  10  is situated in the neutral position  0 , the valve spool of the assigned individual valve  12  is shifted into its second switching position b. In this position the FS fluid flow path  32  is opened in respect of this individual valve  12 . If all supply metering orifices  10  are in the neutral position  0 , a displacement of the variable-displacement pump  40  is adjusted to the smallest possible value, so that energy losses are as low as possible when the consumers  38  are at a standstill. 
       FIG. 4  shows a portion  36  of a hydraulic control assembly  1  according to a third exemplary embodiment. Here, in contrast to  FIG. 3 , each respective individual valve  12  is connected to the outlet side of the supply metering orifice  10 . The individual valve  12  is arranged in the connecting line  66 . In the basic position  0  of the individual valve  12  the connecting line  66  is fully opened. In the first switching position a, on the other hand, the opening of the connecting line  66  is restricted and in the switching position b it is closed. The FS fluid flow path  32  is controlled by the individual valve  12 , as in the first and second exemplary embodiments. Fluid acting on the valve spool of the individual valve  12 , via the branch line  24 , which branches off from the connecting line  66  between the individual valve  12  and the supply metering orifice  10 , acts in the direction of the basic position  0 . In the opposite direction fluid is capable of acting thereon via the control line  34 , which branches off from the inlet line  16  upstream of the supply metering orifice  10 . 
     An operating principle of the control assembly according to  FIG. 4  substantially corresponds to the operating principle of the control assembly according to  FIG. 3 . 
       FIG. 5  shows the portion  36  of the control assembly  1  in  FIG. 2  according to a fourth exemplary embodiment. Here this is based on a LUDV control assembly with individual pressure compensator connected on the outlet side. The supply metering orifice  10  is embodied according to  FIGS. 3 and 4 . Instead of a separate individual valve  12 , an individual pressure compensator  68  and a detection orifice  70  are provided separately from one another. Here the individual pressure compensator  68  is arranged in the connecting line  66 . It is designed as a continuously adjustable  3 / 3  direction control valve. Here the valve spool of the individual pressure compensator  68  can be brought into a basic position  0 . From this position it can be shifted in the direction of first switching positions (a) and further thereto on in the direction of second switching positions b. A load pressure signal line  72  is connected to the individual pressure compensator  68 . Branching off from this is a control line  74 , fluid from which acts on the valve spool of the individual pressure compensator  68  in the direction of its basic position  0 . In the opposite direction fluid acts on the valve spool by way of a control line  76 , which branches off from the connecting line  66  between the supply metering orifice  10  and the individual pressure compensator  68 . In its first switching positions a of the individual pressure compensator  68  the connecting line  66  has a restricted opening. In the second switching positions b the connecting line  66  is fully opened and the load pressure signal line  72  additionally has a restricted connection to the connecting line  66 . In the basic position  0  the connecting line  66  is closed and the load pressure signal line  72  is separated from the latter. The individual pressure compensators  68  of the valve plates  4  to  8  in  FIG. 2  therefore together share the load pressure signal line  72 , see also  FIG. 2 , the highest load pressure then prevailing in this line. 
     The detection orifice  70  is designed as a  2 / 2  directional control valve. A valve spool of the detection orifice  40  is acted upon by the spring force of the detection spring  30  in the direction of a basic position  0 . It can be shifted from the basic position  0  in the direction of a switching position (a) against the spring force. In addition to the spring force, fluid from the connecting line  66  between the supply metering orifice  10  and the individual pressure compensator  66  acts on the valve spool by way of a control line  78  in the direction of its basic position  0 . In the opposite direction, that is to say in the direction of the switching position a, fluid from the inlet line  16  upstream of the supply metering orifice  10  is capable of acting on the valve spool via a control line  80 . In the basic position  0  the detection orifice  70  closes the FS fluid flow path  32 . In the switching position a, on the other hand, the FS fluid flow path  32  is opened. 
     In the absence of a supply deficit, the control assembly is used in the normal way according to  FIG. 2  in conjunction with  FIG. 5 . The FS fluid flow path  32  is then opened via the detection orifice  70 . In the event of a supply deficit, however, the detection orifice  70  closes the FS fluid flow path  32 , so that the variable-displacement pump  40  according to the embodiments in  FIGS. 3 and 4  again increases its displacement. Without the detection orifice  70 , in the event of a supply deficit the variable-displacement pump  40  would not receive any information that the fluid flow was insufficient. In the embodiment according to  FIG. 5 , the individual pressure compensator  68 , which is assigned to the consumer at the highest load pressure, is fully opened, which leads to low energy losses as in the preceding embodiments. 
     The portion  36  according to  FIG. 6  in conjunction with  FIG. 2  shows a further embodiment of a control assembly  1 . Here, in contrast to the preceding embodiments, only the supply metering orifice  10  is provided, together with the detection orifice  70 . Here the supply metering orifice  10  is embodied according to  FIG. 3 . The detection orifice  70  is embodied according to  FIG. 5 . Fluid from the connecting line  66  acts on the valve spool of the detection valve  70  in the direction of the basic position  0 , in that a control line  82  branches off from said connecting line. In the opposite direction fluid from the inlet line  16  upstream of the supply metering orifice  10  acts on the valve spool via a control line  84  branching off from said inlet line. 
     If the pressure differential over the supply metering orifice  10  according to  FIG. 6  is less than the pressure equivalent of the detection spring  30 , the FS fluid flow path  32  is closed by the detection valve  70 . The variable-displacement pump  40  in  FIG. 2  is then shifted in the direction of an increase in displacement. 
     A hydraulic control assembly for a plurality of consumers is disclosed. Here a supply metering orifice for controlling a fluid flow is provided for each respective consumer. A detection orifice is assigned to each respective supply metering orifice. Here the detection orifices are arranged hydraulically in series. A flow-sensing (FS) fluid flow path here extends over the detection orifices. Upstream of the detection orifices the fluid flow path is connected to the hydraulic pump and downstream of the detection orifices it is connected to a control device of the hydraulic pump. If a consumer has a fluid supply deficit, the corresponding detection orifice closes the flow-sensing fluid flow path. Here the control device interacts with this FS fluid flow path in such a way that the fluid flow from the hydraulic pump is thereby increased. If none of the consumers has a supply deficit, the FS fluid flow path over the detection orifices is fully opened and the control device reduces the fluid flow from the hydraulic pump. 
     LIST OF REFERENCE NUMERALS 
     
         
           1  control assembly 
           2  valve block 
           4  valve plate 
           6  valve plate 
           8  valve plate 
           10  supply metering orifice 
           12  individual valve 
           14  actuator 
           16  inlet line 
           18  working line 
           20  working line 
           22  outlet line 
           24  branch line 
           26  control line 
           28  control line 
           30  detection spring 
           32  FS fluid flow path 
           34  control line 
           36  portion 
           38  consumer 
           40  variable-displacement pump 
           42  pump control 
           44  adjusting cylinder 
           46  piston 
           48  cylinder chamber 
           50  spring 
           52  control valve 
           54  valve spring 
           56  control line 
           58  branch line 
           60  restrictor 
           62  restrictor 
           64  tank 
           66  connecting line 
           68  individual pressure compensator 
           70  detection orifice 
           72  load pressure signal line 
           74  control line 
           76  control line 
           78  control line 
           80  control line 
           82  control line 
           84  control line 
         A,B working connection 
           0 ^ neutral position, basic position 
         a first switching position 
         b second switching position 
         c free-flow position

Technology Classification (CPC): 5