CN111089087A

CN111089087A - Assembly for a working hydraulic system, method and working hydraulic system

Info

Publication number: CN111089087A
Application number: CN201911011985.7A
Authority: CN
Inventors: B.塞莱斯; S.奥施曼
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2018-10-24
Filing date: 2019-10-23
Publication date: 2020-05-01
Also published as: DE102018218165A1

Abstract

The invention relates to an assembly for a working hydraulic system, comprising two hydraulic consumers which are arranged in parallel and in a fluid-conducting manner. For supplying the consumers, the assembly furthermore has a hydraulic machine, wherein a respective control valve is arranged in a fluid manner between the hydraulic machine and the consumer for controlling the respective consumer. A pressure-limiting valve is connected to at least one pressure side of the first consumer, which pressure-limiting valve opens a pressure medium connection to the tank starting from a specific safety pressure. Furthermore, a controller is provided in the assembly, which controller is capable of controlling the control valve and the hydraulic machine. The control unit is configured in such a way that it recognizes an operating state in which the pressure on the pressure side of the first consumer reaches or exceeds a safety pressure on the basis of the actuation of the consumer and/or on the basis of the load state of the consumer. If this occurs, the controller avoids the operating state by means of control measures for the control valve and/or the hydraulic machine.

Description

Assembly for a working hydraulic system, method and working hydraulic system

Technical Field

The present invention relates to an assembly for a working hydraulic system according to the preamble of claim 1. Furthermore, the invention relates to a method and a working machine.

Background

From the prior art, working hydraulic systems with a plurality of consumers (verbrauer), for example hydraulic cylinders and/or hydraulic motors, are known. The consumers may be supplied by a hydraulic pump, which may be driven by the combustion engine, for example. The consumer can be, for example, a hydraulic cylinder to which a control valve is assigned, which controls the supply to the hydraulic cylinder and thus the movement of the piston separating one pressure chamber of the hydraulic cylinder from the other pressure chamber of the hydraulic cylinder. The hydraulic cylinder may for example be mounted in an excavator and designed to lift a load. In order to protect the system against damage, for example due to excessive loads absorbed, a pressure limiting valve may be arranged between the control valve and the pressure chamber of the hydraulic cylinder, which pressure limiting valve opens a pressure medium connection to the tank at an excessive pressure in the pressure chamber of the hydraulic cylinder. However, it is possible that the excavator, for example, wishes to reduce the load and for this purpose a pressure medium connection is formed between the pressure chamber in the hydraulic cylinder and the hydraulic pump in order to discharge (entrassen) the pressure medium from the pressure chamber. At the same time, it is possible, for example, to actuate a further consumer, i.e. the pressure medium connection to the hydraulic pump of the further consumer is opened. It has been shown that in this state the pressure limiting valve undesirably opens the pressure medium connection to the tank in certain load states. As a result, the hydraulic cylinder under load sinks in an unregulated (unontroller) manner, and the load reduction cannot be controlled.

Disclosure of Invention

In contrast, the object of the present invention is to provide a technically simple and cost-effective assembly for a device of a working hydraulic system, which assembly is controllable and controllable at all times. A further object is to provide a method having such an assembly, with which the assembly for a working hydraulic system can be controllably controlled at any time, and also to provide a working hydraulic system having such an assembly.

The object according to the invention is achieved by a component for a working hydraulic system according to the features of claim 1. The object is achieved according to the features of claim 14 with respect to the method and according to the features of claim 15 with respect to the working hydraulic system.

Advantageous developments of the invention are the subject matter of the dependent claims.

According to the invention, an assembly for a working hydraulic system is specified, which has at least one consumer. The load can be, for example, a hydraulic cylinder provided for lifting a load, which can move, for example, a boom of an excavator (auslegger). Furthermore, the assembly has a further hydraulic consumer, which is arranged in particular fluidically in parallel to the first consumer. The first consumer and the further consumer are supplied with pressure medium by at least one hydraulic machine, wherein a respective control valve, for example an 4/3 through control valve (4/3-Wege-Steuervetentil), is provided between the hydraulic machine and the respective consumer for controlling the respective consumer. It is conceivable that there are no other hydraulic components that influence the flow of the pressure medium than the control valve. On the pressure side of the first consumer, i.e. in particular between the first consumer and the control valve of the first consumer, a pressure-limiting valve is connected, the task of which is to open a pressure medium connection to the tank starting from a specific safety pressure on the pressure side. In other words, the assembly has a pressure protection of the secondary side.

This can be used, for example, for component protection, since damage can occur on the working hydraulic system starting from a specific pressure on the pressure side. The assembly also has a control unit which controls, in particular, the control valves of the various consumers and/or the hydraulic machine, for example, the delivery volume of the hydraulic machine. The controller is also configured to identify and/or predict a critical operating state in which, on the basis of the actuation of the consumer and/or the hydraulic machine, the pressure on the pressure side connected to the pressure-limiting valve will reach or exceed a safety pressure at which the pressure-limiting valve opens. If the controller recognizes that a critical operating state exists, it takes (einleiten) control measures relating to the at least one control valve or control valves and/or the hydraulic machine in order to avoid (abwenden) or prevent the critical state.

One advantage of the invention is that it is ensured by means of such an assembly that a consumer, in particular a first consumer having a pressure side to which a pressure-limiting valve is connected, can be controlled by the control device in a regulated and reliable manner at all times. In other words, for example, in particular when the consumer is configured to lift a heavy load, a regulated reduction of the load can be achieved without the pressure-limiting valve forming a pressure medium connection to the tank, since the pressure on the pressure side exceeds the safety pressure. Furthermore, the safety of persons staying in the working area of a working machine equipped with a working hydraulic system having the assembly is increased by the assembly. Furthermore, the assembly automatically identifies, by means of the controller, critical operating states in which a pressure-limiting valve opening can occur, i.e. the person operating the working hydraulic system does not need to identify or predict the critical operating state, so that incorrect operation and human errors are less likely to occur.

The critical operating state is generated in particular when the first consumer is a hydraulic cylinder. Furthermore, the critical operating state occurs in particular when the first hydraulic cylinder lifts a particularly heavy load, i.e. a relatively large pressure is already present on the pressure side to which the pressure limiting valve is connected and the load is slowly lowered (ablassen). The pressure side of the hydraulic cylinder may furthermore be a pressure chamber. In this way, the pressure medium connection from the pressure chamber to which the pressure-limiting valve is connected to the tank is opened, and the pressure medium connection from the other pressure chamber of the hydraulic cylinder to the hydraulic machine is opened, in particular by means of the first control valve. In other words, the pressure chamber of the first hydraulic cylinder is filled with (bechcken) pressure medium and at the same time the pressure medium is discharged from the other pressure chamber of the hydraulic cylinder to the tank, so that the piston rod of the hydraulic cylinder can be retracted (einfahren). In a further consumer, in particular a hydraulic cylinder, the pressure medium connection from the pressure chamber of the further consumer to the hydraulic machine can now likewise be opened. If the pressure in the pressure chamber of the further consumer, which now has a pressure medium connection with the pressure chamber of the first hydraulic cylinder, is high, a pressure rise in this pressure chamber can occur, wherein a pressure limiting valve is connected to this pressure chamber. In other words, a critical operating state may occur by lowering the load and simultaneously opening the pressure medium connection from the other consumer to the hydraulic machine. If the pressure-limiting valve is opened in this state, i.e. the pressure in the pressure chamber drops rapidly, it may happen that the load held and/or lowered by the hydraulic cylinder drops downward unregulated.

Preferably, at least one pressure sensor is provided in a component of the working hydraulic system, which pressure sensor measures the pressure, in particular on the pressure side of the first consumer to which the pressure limiting valve is connected, and transmits it to the control unit, so that the control unit can detect the operating state of the working hydraulic system. In other words, the pressure sensor is connected between the pressure side of the consumer and the control valve. The pressure sensor may determine the pressure on the pressure side and may report this pressure to the controller. Here, the pressure sensor of the controller can only report the critical pressure. For example, the pressure sensor may be configured such that it does not report the pressure to the control unit until it is, for example, 10 bar below the safety pressure at which the pressure limiting valve opens, or the pressure sensor may report the pressure on the pressure side to the control unit at short intervals, in particular continuously, during operation of the working hydraulic system. The pressure sensor allows the controller to better detect and/or predict critical operating conditions. When one consumer reduces the load and the other consumer opens a pressure medium connection to the hydraulic machine, a critical operating state does not always occur, but the consumer may also reduce a smaller and/or less heavy load, so that the pressure on the pressure side becomes lower, i.e. the pressure limiting valve does not trigger, despite the other consumer having a pressure medium connection to the hydraulic machine. The critical operating state can be predicted more accurately by the pressure sensor.

Preferably, a corresponding plurality or one of the control valves, i.e. the control valve of the first consumer or of the further consumer, can be electronically controlled. In other words, the control valves or the control valves can be controlled in an electromechanical and/or electrohydraulic manner. Electromechanical control of one or more control valves may be achieved, for example, by using electromagnets. The controller can influence a plurality of or one control valve by a plurality of or one electronically controllable control valves. The corresponding control valve can also be hydraulically adjusted. For this purpose, for example, a pressure relief valve can be used.

The consumers are preferably designed such that they each have two working connections. Depending on the switching position of the respective control valve, the working connection of the respective consumer preferably forms a pressure medium connection of the respective pressure side to the tank and/or the hydraulic machine. In other words, the consumer has at least two pressure sides, which in the hydraulic cylinder can be, for example, pressure chambers with corresponding working connections.

The control valves of the respective consumers may each have a valve cartridge (Ventilschieber). Furthermore, the respective valve element can preferably have at least three different switching positions. In the first, spring-centered switching position (which is the basic position), the service coupling can preferably be closed, i.e. the pressure side has no pressure medium connection to, for example, a tank and/or a hydraulic machine. Another switching position of the spool or other switching positions can connect the first pressure side of the associated consumer with the tank and the second pressure side of the consumer with the hydraulic machine. A third or third switching position can, on the contrary, connect the first pressure side of the associated consumer with the hydraulic machine and the second pressure side with the tank. If the valve slide is continuously adjustable, a plurality of switching positions can be provided in which the respective pressure side has a pressure medium connection to the tank or the hydraulic machine. In the further switching position, the valve element is moved in the first direction starting from the basic position. In the third switching position, the valve element is displaced from the basic position in the direction opposite to the first direction.

In particular, such critical operating states occur when the further consumer is likewise a hydraulic cylinder. In an example of the excavator, the first hydraulic cylinder is, for example, a boom cylinder (Auslegerzylinder) and the second hydraulic cylinder is, for example, an arm cylinder (Stielzylinder). In this example, critical operating states may occur when the boom cylinder reduces large loads and at the same time enables a corrective movement with the stick cylinder, for example in order to compensate for fluctuations.

Preferably, at least the first hydraulic cylinder, or if there are other hydraulic cylinders on the working hydraulic system, a part of the hydraulic cylinders or all the hydraulic cylinders have pistons. The piston of the respective hydraulic cylinder can separate the two pressure chambers from each other. A piston rod protruding from the hydraulic cylinder may be arranged on the piston. The piston rod can be extended from or retracted into the hydraulic cylinder by movement of the piston. If the hydraulic cylinder is a differential cylinder, it has in particular two pressure chambers, one of which is penetrated by a piston rod. In the example of a boom cylinder, a hydraulic cylinder may be fixed to the excavator body and a piston rod, for example, fixed to the boom and the boom moved by moving the piston rod in the hydraulic cylinder together with the piston. For this purpose, the pressure chamber on the piston side is filled with pressure medium, and the pressure medium is discharged from the other pressure chamber, so that the piston rod either extends out of the hydraulic cylinder or retracts into it.

In order to avoid critical operating states, the control measures of the controller can be used to control the first consumer, for example a hydraulic cylinder, and/or one of the further consumers in a throttled manner and/or to interrupt the pressure medium connection from the hydraulic machine to one of the consumers. In other words, when a critical operating condition occurs, a single run (einzelbertrib), i.e., the opening of only one of the control valves, may be assumed by the controller. For example, the control unit can take control measures, for example, if the pressure on the pressure side to which the pressure limiting valve is connected is lower than the safety pressure by a certain value, for example by 10%. Another possibility is that the control unit takes control measures when a critical operating state is reached, i.e. when the pressure-limiting valve opens briefly to discharge pressure medium from the pressure side. By taking control measures, the regulation of the first consumer can be restored, the pressure side of which is connected to a pressure-limiting valve. In order to avoid critical operating states, the control valves are therefore closed, i.e. the control valve of the first consumer is interrupted and/or the control valve of the further consumer is interrupted. As already mentioned, another possibility is to throttle the pressure medium connection instead of disconnecting it, in particular as a function of the actuation of the first consumer and/or as a function of the pressure prevailing in the pressure chamber. In other words, if the pressure on the pressure side to which the pressure-limiting valve is connected is reduced by actuating the first consumer, for example, it is not necessary to completely disconnect the pressure medium connection. If the first consumer is, for example, a hydraulic cylinder and it lowers the load, the pressure medium connection of the other consumer can only be throttled if the load is lowered at least one specific minimum speed and the pressure medium is thus discharged from the pressure chamber of the hydraulic cylinder.

The hydraulic machine may also have a pressure regulator and/or a pressure delivery flow regulator, for example, with or without a target value exceeding (ü bersteuern) the pump, and/or a delivery with suitable dynamics.

If the hydraulic machine is electronically controlled, the controller may operate the hydraulic machine in a pressure-limited manner in order to avoid critical operating conditions. In other words, the delivery volume of the hydraulic machine can be limited, for example, if the control valve of the first consumer, for example a hydraulic cylinder, forms a pressure medium connection from the pressure chamber to which no pressure-limiting valve is connected to the hydraulic machine. In other words, by detecting the pressure on the pressure side of the first consumer to which the pressure limiting valve is connected and/or the pressure at the pressure connection of the hydraulic machine, the controller can estimate whether a critical operating state occurs or has already occurred and can thus be avoided by the regulation of the hydraulic machine. One advantage of this is that both control valves can still be operated. The pressure limitation is preferably performed by means of a hydraulic press.

An additional or alternative control measure for avoiding the critical operating state can be to close the control valve of the first consumer and thus to disconnect the pressure medium connection to the pressure side of the first consumer when the pressure in the pressure connection of the hydraulic machine exceeds a certain value. In other words, the hydraulic machine delivers the volume flow required by, for example, another consumer, so that the control valve of the first consumer is not opened. This makes it possible to control the working hydraulic system simply and reliably. Instead of not opening the control valve of the first consumer, the pressure medium connection can also be throttled, i.e. the control valve can be actuated in such a way that the pressure medium connection is present in a limited manner.

If the control valve is actuated by the controller during a control measure to avoid a critical state, it is provided that the controller has an algorithm which influences the control valve. For example, the controller may have a data store on which the algorithm is stored. The algorithm for controlling and/or influencing the control valve may determine, for example, how fast and/or when the pressure medium connection is closed and/or how much the pressure medium connection is throttled. In particular, this may be done depending on the pressure transmitted by the pressure sensor to the controller. This algorithm allows for accurate and precise control of the control valve. In addition, algorithms for controlling the hydraulic machine can also be stored on the data memory.

In one embodiment, the working hydraulic system may preferably be an open center working hydraulic system. In other words, the consumers arranged in parallel have control valves which are open for the oil flow in the intermediate position, so that all the transport flows transported by the hydraulic machine are guided through all the control valves. Furthermore, in this assembly, the spools are arranged in parallel with each other. Furthermore, a hydraulic control element is preferably arranged fluidically between the hydraulic machine and the consumer, which hydraulic control element can be actuated, for example, in an electrohydraulic manner proportionally, and which hydraulic control element can open a pressure medium connection between the hydraulic machine and a tank in order to limit and/or control the volume flow which is conducted from the hydraulic machine to the consumer. The hydraulic control element may be, for example, a control valve, in particular an 2/2-way control valve.

In another design example, the working hydraulic system may be a closed-center working hydraulic system, i.e. the control valve is closed in an intermediate position and the volume flow delivered by the hydraulic machine is directed, for example, by means of a circulating valve and/or the performance of the hydraulic machine is limited.

The working hydraulic system can furthermore be equipped with a load sensing system (LS system). LS systems are also known as load pressure reporting systems. In open-center working hydraulic systems, a pressure balance (Druckwaage) is connected to the hydraulic control unit, which may be a control valve, and can actuate the control unit. By this manipulation, it is possible to discharge the excess volume flow to the tank in an open central system. In a closed center-working hydraulic system, the delivery capacity of the hydraulic machines is matched to the current demand of one or more consumers. In this system, the pressure in the pressure connection of the hydraulic machine, which pressure is generated by the volume flow feed of the hydraulic machine, is controlled in such a way that the highest pressure occurring in the working hydraulic system is exceeded by a certain pressure difference. Furthermore, the consumers have respective individual pressure balances which are set individually, via the respective control valves of the respective consumers, the respective pressure differences.

Furthermore, the working hydraulic system can be equipped with a throughflow distribution (LUDV) which is independent of the load pressure. The hydraulic machine also provides the volumetric flow required by the consumer. However, in contrast to the LS system, a pressure balance is arranged downstream of the hydraulic machine, i.e. downstream of the hydraulic machine and between the hydraulic machine and the control valve, so that the pressure difference across the control valve, i.e. from the hydraulic machine to the consumers, is the same for all consumers.

The control device also preferably has an input device, for example a pressure sensor and/or an electronic control lever, for reading the driver's wishes. The controller can thus convert the driver's intention into a movement of the control valve and/or a control of the hydraulic machine and/or communicate, for example, a restriction or throttling of the pressure medium connection and/or the hydraulic machine to the driver.

Furthermore, the method for controlling a working hydraulic system having such an assembly has the following steps. First, a critical operating state, as previously defined, is identified and/or anticipated. After this, the different control measures mentioned above, namely throttling and/or closing one or more control valves, are taken in order to close and/or limit the pressure medium connection between the consumer and the hydraulic machine and/or the tank and/or to implement an influence on the hydraulic machine, whereby critical operating states can be avoided or avoided.

Drawings

Preferred embodiments of the invention are explained in more detail below with the aid of schematic drawings.

Fig. 1 schematically shows an excavator, by means of which the occurrence of critical operating states is exemplarily explained;

FIG. 2 illustrates components of a working hydraulic system according to one embodiment;

fig. 3 shows a diagram which shows an example of the relationship between the normalized pressure on the pressure side of the first consumer to which the pressure-limiting valve is connected and the normalized opening cross section of the pressure medium connection.

Detailed Description

Fig. 1 shows an excavator 1, which lifts a load 4 upwards on a bucket 2. The excavator 1 also has an excavator body 6 on which a first hydraulic cylinder 8 is arranged, which may be a first consumer. A piston rod 10 projects from the hydraulic cylinder 8 and is fixed to a boom 12. Between the excavator body 6 and the boom 12, a joint (Gelenk) is arranged, by means of which a rotational movement of the boom 12 about the joint is made possible. By moving, i.e. retracting or extending, the piston rod 10 in the hydraulic cylinder 8, the boom 12 can be moved about the articulation, and thus the end of the boom 12 not arranged on the excavator body 6, downward or upward. Thus, the load 4 suspended on the bucket 2 moves up and down with the boom 12. Furthermore, at the end of boom 12 not arranged on excavator body 6, another hydraulic cylinder 14 is arranged as another consumer, whose piston rod 16 is arranged on excavator stick (baggertilel) 18. The excavator stick 18 is connected to the boom 12 by a hinge so that it can rotate about the hinge. The excavator stick 18 may be rotated by movement of the piston rod 16 about the hinge, which may in turn cause the load 4 to move. On the excavator stick 18, a further hydraulic cylinder 22 with a piston rod 20 is arranged, which cylinder serves to ensure the movement of the bucket 2. The bucket 2 is also connected to the excavator stick 18 by an articulation, so that the bucket 2 can be moved by extending or retracting a hydraulic cylinder 22, which cylinder 22 is another consumer.

If the load 4 is lowered, the piston rod 10 of the hydraulic cylinder 8 is retracted into the hydraulic cylinder 8, as indicated by the arrow in fig. 1. By means of the load 4 held by the hydraulic cylinder 8, the pressure in the pressure chamber of the hydraulic cylinder 8 not penetrated by the piston rod 10 is high, because the pressure in the pressure chamber counteracts the load 4, which may be 300 bar, for example. By lowering the load 4, undesired movements of the load 4 may occur due to the rotation of the boom 12 about the hinge arranged on the excavator body 6. Thus, the boom 12 not only moves downward, but the excavator stick 18 additionally tilts. This can be compensated for, for example, by retracting the piston rod 16, which piston rod 16 moves the excavator stick 18. The pressure prevailing in the pressure chamber of the hydraulic cylinder 14 not penetrated by the piston rod 16 is, for example, 250 bar. Since the pressure chambers of the first hydraulic cylinder 8, which are penetrated by the piston rod 10, and the pressure chambers of the hydraulic cylinder 14, in which a pressure of 250 bar prevails, have a pressure medium connection for the purpose of moving the boom 12 and the excavator boom 18 by simultaneous movement, the control valve explained in detail in fig. 2 below opens a corresponding pressure medium connection to the hydraulic machine and thus also leads to a pressure medium connection between the pressure chambers. By simultaneous opening of the control valves, the pressure in the pressure chamber of the first hydraulic cylinder 8, which is traversed by the piston rod 10, likewise increases to at least 250 bar. This pressure also acts on the pressure chamber in which a pressure of 300 bar is present, since it must additionally compensate for the pressure. The area ratio between the faces of the piston facing the pressure chamber in which the pressure of 300 bar is present is larger than the area ratio between the faces on which the pressure in the pressure chamber penetrated by the piston rod 10 acts, because the piston rod 10 reduces the area because it acts on the piston. The area ratio may be, for example, 2: 1, that is, the area of the piston without the piston rod 10 is twice as large as the area on which the piston rod 10 is mounted. Thus, the pressure in the pressure chamber, in which the pressure is 300 bar, is increased by 125 bar, i.e. by half of 250 bar. This means that the pressure in the pressure chamber is now 425 bar. The pressure limiting valve arranged in the pressure chamber of the hydraulic cylinder 8 can be opened, for example, from a safety pressure of 410 bar. That is, with simultaneous movement of the boom 12 and excavator stick 18, pressure limiting valve opening may occur. If the pressure limiting valve is opened, the pressure in the pressure chamber holding the load 4 drops, and therefore the cantilever 12 and the load 4 drop downward without being decelerated and regulated until the pressure limiting valve closes again.

Fig. 2 shows a component 24 of a working hydraulic system, as is provided, for example, in excavator 1 of fig. 1. Assembly 24 includes a first hydraulic cylinder 26 as a first consumer, and a second hydraulic cylinder 28 and hydraulic motor 30 as other consumers. These components are arranged in parallel in a fluid manner. In addition, the assembly 24 has a hydraulic machine 32 configured to supply the

consumers

26, 28, 30.

Respective control valves

34, 36, 38 are arranged in a fluid-tight manner between the hydraulic machine 32 and the

respective consumers

26, 28, 30. In order to center the respective valve spool of the

respective control valve

34, 36, 38 in the basic or neutral position, a valve spring 40 is arranged on the

respective control valve

34, 36, 38 when it is not actuated. For actuating the

control valves

34, 36, 38, two electromagnetic actuators (Aktor) 42 are respectively arranged on the

respective control valve

34, 36, 38.

Hydraulic cylinders

26, 28 have

pistons

44, 46, respectively. Piston 44 of hydraulic cylinder 26 separates a pressure chamber 48, which is one pressure side, from a pressure chamber 50, which constitutes the other pressure side. Pressure chamber 50 is intersected by a piston rod 52 extending away from piston 44 that protrudes from hydraulic cylinder 26. In hydraulic cylinder 28, piston 46 separates a pressure chamber 54 forming one pressure side from a pressure chamber 56 forming the other pressure side, which pressure chamber 56 is likewise traversed by a piston rod 58 extending from piston 46.

The

corresponding control valves

34, 36, 38 are 4/3 pass-control valves, respectively. The

control valves

34, 36, 38 may be switchable or continuously adjustable. The

control valves

34, 36, 38 are each closed in the center position of their valve slide, i.e., the

respective consumers

26, 28, 30 have no pressure medium connection to the hydraulic machine 32 in the center position. The

control valves

34, 36, the

hydraulic cylinders

26, 28 can be switched in such a way that their respective valve disks can be displaced in such a way that each

pressure chamber

48, 54 has a respective working connection a1, via which working connection a1 has a pressure medium connection to the hydraulic machine 32. If the

respective control valve

34, 36 is switched in this way, the

respective pressure chamber

50, 56 with the respective working connection a2 has a pressure medium connection to the tank 60. The

control valves

34, 36 of the

hydraulic cylinders

26, 28 also have at least one further switching position in which the

pressure chambers

48, 54 are connected to a tank 60 and, correspondingly, the

pressure chambers

50, 56 have a pressure medium connection to the hydraulic machine 32. The hydraulic motor 30 likewise has two working connections a1 and a 2. Depending on the manner of switching of the control valve 38, the working connection a1 is connected either to the tank 60 or to the hydraulic machine 32, and conversely the working connection a2 is connected either to the hydraulic machine 32 or to the tank 60. This affects the rotational direction of the hydraulic motor 30.

Pressure chambers

48 and 50 of hydraulic cylinder 26 are connected to respective

pressure limiting valves

62 and 64. When the pressure in the pressure chamber 48 exceeds a safety pressure, the pressure-limiting valve 62 opens a pressure medium connection to the tank 60. Hydraulic cylinder 26 may, for example, correspond to hydraulic cylinder 8 in fig. 1 and pressure chamber 48 corresponds to the pressure chamber of hydraulic cylinder 8 not traversed by the piston rod.

In addition, the assembly 24 has a controller 66. The controller 66 is connected to an input device 68 and an input device 70. The

input devices

68 and 70 may be operated by the driver and communicate the driver's intent to the controller 66, such as to lower and/or extend the boom 12 of FIG. 1. In addition, the pressure of the at least one pressure sensor 74 is communicated to the controller 66. Which is connected to pressure chamber 48 of hydraulic cylinder 26 and communicates the measured pressure to controller 66. Additionally or alternatively, another pressure sensor 76 may communicate pressure to controller 66. Which measures the pressure at the output side of the pressure connection 77 of the hydraulic machine 32. In other words, the pressure sensor 76 is arranged between the pressure connection 77 of the hydraulic machine 32 and the

control valves

34, 36, 38. Controller 66 may also control

valves

34, 36, 38 via actuator 42. In addition, the controller 66 has a connection to a hydraulic machine actuator 80. From this, the controller 66 may determine the delivery capacity of the hydraulic machine 32.

A critical operating state, which leads to the opening of the pressure-limiting valve 62, can occur in this assembly 24 when, for example, a load 82 acts on the piston rod 52 of the hydraulic cylinder 26. In this example, the pressure in the pressure chamber 48 may be 300 bar in order to lift the load 84. For example, the load 84 acting on the piston 58 is so great that the pressure in the pressure chamber 54 is about 250 bar. If the load 82 decreases, the pressure chamber 48 has a pressure medium connection to the tank 60 and the pressure chamber 50 has a pressure medium connection to the hydraulic machine 32. That is, the pressure chamber 50 is filled with the pressure medium, and the pressure medium is discharged from the pressure chamber 48. The load 84 is now lifted. That is to say, the pressure chamber 54 is filled with pressure medium and the pressure chamber 56 has a pressure medium connection to the tank in order to discharge the pressure medium. In other words, in this state, the

pressure chambers

54 and 50 and the hydraulic machine 32 have a pressure medium connection. That is, the pressure in the

pressure chambers

50, 54 may be the same. The pressure in the pressure chamber 50 is thus 250 bar. That is to say, the pressure in the pressure chamber 48 increases, since it now holds the load 84 and additionally compensates for the pressure acting from the pressure chamber 50 on the piston face 86 of the piston 44. If the area ratio of the piston face 88 to the piston face 86 facing the pressure chamber 48 is, for example, 2: 1, that is, the area of the piston face 88 is twice that of the piston face 86, the pressure increase is 125 bar. That is, the pressure in the pressure chamber 48 rises to 425 bar. If this pressure exceeds the safety pressure from which the pressure-limiting valve 62 opens the pressure medium connection to the tank 60, the load 82 acting on the piston rod 52 may press the piston 44 downwards, whereby the load 82 may drop downwards in an unregulated manner.

Controller 66 may identify the critical operating condition and control the components via actuator 42 and hydraulic actuator 80 such that the critical condition is avoided. The control of the

control valves

34, 36, 38 can also take place according to an algorithm, and the controller 66 can therefore also have a data memory 90, on which at least one algorithm is stored, for example for controlling the

control valves

34, 36, 38 and/or for controlling the hydraulic machine 32. The algorithm selected by controller 66, in other words, the control measures implemented by controller 66, may be dependent upon the pressure in pressure chamber 48 and/or upon the pressure at the output side of hydraulic machine 32 as reported to controller 66 by

pressure sensors

74 and 76.

Fig. 3 shows an exemplary normalized pressure p (see fig. 2) in the

pressure chamber

48 or 50 and a normalized opening cross section of the control valve 34

(see fig. 2). This relationship may be stored, for example, on a data store 86 of the controller 66, see fig. 2. In this case, the pressure p is plotted in a standardized manner, i.e. the pressure p/p is plotted_sWherein p is_sIs a safety pressure at which the pressure-limiting valve 62 opens a pressure medium connection to the tank 60. Furthermore, the cross section is opened

Also drawn in a standardized manner, wherein the open cross-section is referenced to the largest possible open cross-section

. It can be seen that the greater the pressure p, the more strongly the opening cross section (see fig. 2) that the valve spool of the control valve 34 opens is also limited. In this embodiment, the valve is controlled when the pressure p is 0.75 times the relief pressure34 open cross section

Is turned off. Further, the pressure ratio p/p_sOpen cross section at =0.5

Only the maximum possible open cross section

25% of the total. For example, in another embodiment, p/p_sAnd

the relationship between may be linear.

The invention relates to an assembly for a working hydraulic system, comprising two hydraulic consumers which are arranged in parallel in a fluid manner with respect to a hydraulic cylinder. For supplying the consumers, the assembly furthermore has at least one hydraulic machine, wherein a respective control valve is arranged in a fluid manner between the hydraulic machine and the respective consumer for controlling the respective consumer. A pressure-limiting valve, which opens a pressure medium connection to the tank starting from a specific safety pressure, is connected to at least one pressure side of the first consumer. Furthermore, a controller is provided in the assembly, which controller is capable of controlling the control valve and the hydraulic machine. The control unit is configured in such a way that it recognizes at least one operating state in which the pressure on the pressure side of the first consumer reaches or exceeds a safety pressure on the basis of the actuation of the consumer and/or on the basis of the load state of the consumer. If this occurs, the controller avoids at least one operating state by controlling measures for at least one of the control valves or a plurality of the control valves and/or the hydraulic machine.

Claims

1. Assembly for a working hydraulic system, having at least two hydraulic consumers (8, 14, 22, 26, 28, 30) arranged in parallel to one another and at least one hydraulic machine (32) for supplying the consumers (8, 14, 22, 26, 28, 30), wherein a respective control valve (34, 36, 38) is arranged in a fluid-tight manner between the hydraulic machine (32) and the respective consumer (8, 14, 22, 26, 28, 30) for controlling the respective consumer (8, 14, 22, 26, 28, 30), and wherein a pressure limiting valve (62, 64) is connected to at least one pressure side (48, 50, 54, 56) of a first consumer (8, 14, 22, 26, 28, 30), which pressure limiting valve opens a pressure medium connection to a tank (60) starting from a specific safety pressure of the pressure side (48, 50, 54, 56), wherein a controller (66) is provided for controlling the control valves (34, 36, 38) and the hydraulic machine (32), characterized in that the control unit (66) identifies at least one operating state in which a pressure on the pressure side (48, 50, 54, 56) of the first consumer (8, 14, 22, 26, 28, 30) reaches or exceeds a safety pressure on the basis of an actuation of the consumer (8, 14, 22, 26, 28, 30) and/or on the basis of a load state of the consumer (8, 14, 22, 26, 28, 30), and the controller (66) avoids the at least one operating state by controlling measures for at least one of the control valves (34, 36, 38) or a plurality of the control valves (34, 36, 38) and/or the hydraulic machine (32).

2. The assembly of claim 1, wherein at least one pressure sensor (74, 76) is provided by which the controller (66) detects an operating condition.

3. Assembly according to any one of claims 1 or 2, wherein the respective control valve (34, 36, 38) is directly or indirectly electronically controllable.

4. Assembly according to any one of claims 1 to 3, wherein the consumers (8, 14, 22, 26, 28, 30) each have two working connections (A1, A2).

5. Assembly according to claim 4, wherein the control valves (34, 36, 38) each have a spool which, in a first or first switching position, connects the first working connection (A1, A2) of the relevant consumer (8, 14, 22, 26, 28, 30) with the hydraulic machine (32) and the second working connection (A1, A2) of the relevant consumer (8, 14, 22, 26, 28, 30) with the tank (60), and conversely, which, in one or second switching position, connects the first working connection (A1, A2) of the relevant consumer (8, 14, 22, 26, 28, 30) with the tank (60) and the second working connection (A1, A2) of the relevant consumer (8, 14, 22, 26, 28, 30) with the hydraulic machine (32).

6. Assembly according to any one of claims 1 to 5, wherein at least one of the consumers (8, 14, 22, 26, 28, 30) is designed as a hydraulic cylinder.

7. Assembly according to one of claims 1 to 6, wherein the controller (66) controls one or both of the consumers (8, 14, 22, 26, 28, 30) in a throttled manner or blocks a pressure medium connection from the hydraulic machine (32) to one or both of the consumers (8, 14, 22, 26, 28, 30) in order to avoid critical operating states.

8. An assembly according to any one of claims 1 to 7, wherein the hydraulic machine (32) has a pressure joint (77), and wherein the or at least one pressure sensor (74, 76) is connected to an output side of the pressure joint (77), which pressure sensor reports pressure to the controller (66).

9. The assembly of any one of claims 1 to 8, wherein the controller (66) electronically controls the volumetric flow of the hydraulic machine (32).

10. An assembly according to any one of claims 8 or 9, wherein the controller (66) operates the hydraulic machine (32) so as to limit the pressure on the output side of the pressure connection (77) in order to avoid the critical operating state.

11. An assembly according to any one of claims 8-10, wherein the controller (66) throttles or shuts off the pressure medium connection between the hydraulic machine (32) and the first consumer (8, 14, 22, 26, 28, 30) in order to avoid the critical operating state when the pressure tapped on the output side of the pressure connection of the hydraulic machine (32) exceeds a predetermined limit pressure.

12. The assembly of any one of claims 1 to 11, wherein the controller (66) has an input device (68, 70) that controls the position of the control valve (34, 36, 38).

13. The assembly according to any one of claims 1 to 12, wherein the working hydraulic system has valve spools arranged in parallel with each other and a hydraulic control element is arranged fluidly between the hydraulic machine and the tank.

14. Method for controlling (66) a working hydraulic system with an assembly according to any one of claims 1 to 13, having the steps of:

-predicting and/or identifying a critical operating state,

-implementing control measures for at least one of the control valves (34, 36, 38) or a plurality of the control valves (34, 36, 38) and/or the hydraulic machine (32) for avoiding or circumventing the critical operating state.

15. A working hydraulic system having an assembly according to any one of claims 1 to 13.