CN111089087B

CN111089087B - Assembly for a working hydraulic system, method and working hydraulic system

Info

Publication number: CN111089087B
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: 2024-06-18
Anticipated expiration: 2039-10-23
Also published as: DE102018218165A1; CN111089087A

Abstract

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

Background

Working hydraulic systems with several consumers (Verbraucher), for example hydraulic cylinders and/or hydraulic motors, are known from the prior art. The consumers may be supplied by a hydraulic pump, which may be driven by an internal combustion engine, for example. The consumers can be, for example, hydraulic cylinders to which control valves are assigned, which control the supply to the hydraulic cylinders and thus the movement of the pistons separating one pressure chamber of the hydraulic cylinders from the other pressure chamber of the hydraulic cylinders. The hydraulic cylinder may be installed, for example, in an excavator and designed to lift a load. In order to protect the system from damage, for example due to absorbed excessive loads, a pressure limiting valve can be arranged between the control valve and the pressure chamber of the hydraulic cylinder, which valve opens the pressure medium connection to the tank at too high a 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 (entlassen) the pressure medium from the pressure chamber. At the same time, for example, a further consumer, i.e. a further consumer, can be actuated, the pressure medium connection to the hydraulic pump being opened. It has been shown that in this state, the pressure limiting valve undesirably opens the pressure medium connection to the tank under certain load conditions. As a result, the hydraulic cylinder under load sinks unregulated (unkontrolliert), and the lowering of the load 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 for operating a hydraulic system, which is controllable and controllable at any time. Another object is to provide a method with such an assembly, with which the assembly for the working hydraulic system can be controlled controllably at any time, and also to provide a working hydraulic system with such an assembly.

The task according to the components for the working hydraulic system is achieved according to the following features: the controller recognizes at least one operating state in which the pressure on the pressure side of the first consumer would reach or exceed a safety pressure based on the actuation of the consumer and/or based on the load state of the consumer, and the controller avoids the at least one operating state by means of control measures for at least one of the control valves or for a plurality of the control valves and/or for the hydraulic machine. The task pertaining to the method is achieved according to the following features: a critical operating state is predicted and/or identified, and control measures for at least one or several of the control valves and/or the hydraulic machine are implemented for avoiding or avoiding the critical operating state. And the task concerning the working hydraulic system is achieved according to the working hydraulic system with the assembly according to the invention.

An advantageous development of the invention comprises: at least one pressure sensor is provided, by means of which the controller detects an operating state; wherein the corresponding control valve can be directly or indirectly controlled electronically; wherein the consumers are respectively provided with two working joints; wherein the control valve has a valve element which connects a first working connection of the associated consumer to the hydraulic machine and a second working connection of the associated consumer to the tank in a first or first switching position, and conversely connects a first working connection of the associated consumer to the tank and a second working connection of the associated consumer to the hydraulic machine in a second or second switching position; wherein at least one of the consumers is designed as a hydraulic cylinder; wherein the controller, in order to avoid critical operating states, throttles one or both of the consumers or cuts off a pressure medium connection from the hydraulic machine to one or both of the consumers; wherein the hydraulic machine has a pressure joint and wherein the or at least one pressure sensor is connected to the output side of the pressure joint, the pressure sensor reporting pressure to the controller; wherein the controller electronically controls the volumetric flow of the hydraulic machine; wherein the controller controls the hydraulic machine in order to avoid the critical operating state in such a way that the pressure on the output side of the pressure connection is limited; wherein the controller throttles or intercepts a pressure medium connection between the hydraulic machine and the first consumer in order to avoid the critical operating state when a pressure tapped on an output side of a pressure connection of the hydraulic machine exceeds a predetermined limit pressure; wherein the controller has an input device that controls the position of the control valve; 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.

According to the invention, an assembly for a working hydraulic system is provided, which assembly has at least one consumer. The load consuming device may be, for example, a hydraulic cylinder provided for lifting a load, which hydraulic cylinder may, for example, move a boom (Ausleger) of the excavator. The assembly furthermore has a further hydraulic consumer which is arranged in parallel to the first consumer, in particular in a fluid-like manner. The first and the further consumers are supplied with pressure medium by at least one hydraulic machine, wherein a respective control valve, for example a 4/3-pass control valve (4/3-Wege-Steuerventil), is provided between the hydraulic machine and the respective consumers for controlling the respective consumers. It is conceivable that other hydraulic elements than control valves do not exist which would affect the pressure medium flow. 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, whose task is to open the pressure medium connection to the tank starting from a specific safety pressure on the pressure side. In other words, the assembly has pressure protection on the secondary side.

For example, this can be used for component protection, since damage can occur to the working hydraulic system starting from a specific pressure on the pressure side. The assembly also has a control which controls in particular the control valves of the different consumers and/or the hydraulic machine, for example the delivery rate of the hydraulic machine. The controller is further configured to identify and/or predict a critical operating state in which, based on manipulation of the consumer and/or the hydraulic machine, the pressure of the pressure side connected to the pressure limiting valve will reach or exceed a safety pressure at which the pressure limiting valve is open. If the controller recognizes that a critical operating state exists, it takes (einleiten) control actions involving at least one control valve or a plurality of control valves and/or the hydraulic machine in order to avoid (abwenden) or prevent the critical state.

An advantage of the invention is that by means of such an assembly it is ensured that the consumer, in particular the first consumer having a pressure side to which the pressure limiting valve is connected, can be controlled at any time in a regulated and reliable manner by the controller. In other words, for example, in particular when the load 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, by means of the assembly, the safety of personnel staying in the work area of a work machine equipped with a work hydraulic system having the assembly is increased. In addition, the assembly automatically recognizes, by the control unit, a critical operating state in which the pressure limiting valve is open, i.e. the person operating the working hydraulic system does not have to recognize or predict the critical operating state, and thus misoperations and human errors are less likely to occur.

The critical operating state occurs in particular when the first load is a hydraulic cylinder. The critical operating state also occurs, in particular, when the first hydraulic cylinder lifts a particularly heavy load, i.e. when a relatively high 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 other words, in particular by means of the first control valve, the pressure medium connection from the pressure chamber connected to one pressure limiting valve 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 other words, the pressure chamber of the first hydraulic cylinder is filled (beschicken) with pressure medium and at the same time 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 the case of another consumer, in particular a hydraulic cylinder, the pressure medium connection from the pressure chamber of the other consumer to the hydraulic machine can now likewise be opened. If the pressure in the pressure chamber of the further consumer, which is now connected to the pressure chamber of the first hydraulic cylinder with pressure medium, is high, a pressure increase in the pressure chamber may occur, wherein a pressure limiting valve is connected to the pressure chamber. In other words, by lowering the load and simultaneously opening the pressure medium connection from the other consumer to the hydraulic machine, critical operating conditions may occur. 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 reduced by the hydraulic cylinder drops unregulated downwards.

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 the pressure is not reported to the controller until the pressure is, for example, 10 bar below the safety pressure at which the pressure limiting valve is open, or the pressure sensor may report the pressure on the pressure side to the controller 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 the 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 is reduced, i.e. the pressure limiting valve is not triggered, although the other consumer has a pressure medium connection to the hydraulic machine. The critical operating state can be predicted more precisely by the pressure sensor.

Preferably, a corresponding plurality or one control valve, i.e. the control valve of the first consumer or of the other consumer, can be controlled electronically. In other words, a plurality or one control valve can be controlled in particular electromechanically and/or electrohydraulically. Electromechanical control of one or more control valves may be achieved, for example, through the use of electromagnets. The controller may affect a plurality of or a single control valve by a plurality of electronically controllable control valves or a single electronically controllable control valve. The corresponding control valve can also be hydraulically regulated. For this purpose, for example, a pressure relief valve may 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 load 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 can each have a valve element (Ventilschieber). Furthermore, the respective valve element can preferably have at least three different switching positions. In the first switching position (which is the basic position) of the spring centering, the working connection can preferably be closed, i.e. the pressure side is not connected to the pressure medium, for example a tank and/or a hydraulic machine. The other or other switching position of the spool may connect the first pressure side of the associated consumer with the tank and the second pressure side of the consumer with the hydraulic machine. Instead, a third or third switching position may connect the first pressure side of the associated consumer with the hydraulic machine and the second pressure side with the tank. If the valve element 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 a further switching position, the valve element is moved in a first direction from the basic position. In the third switching position, the spool moves from the basic position in a direction opposite to the first direction.

In particular, this critical operating state occurs when the further consumer is likewise a hydraulic cylinder. In an example of an excavator, the first hydraulic cylinder is, for example, a boom cylinder (Auslegerzylinder) and the second hydraulic cylinder is, for example, an stick cylinder (Stielzylinder). In this example, a critical operating state may occur when the boom cylinder reduces a large load and at the same time a corrective movement is possible 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, some or all of the hydraulic cylinders have pistons. The pistons of the respective hydraulic cylinders may 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 the piston rod. In the example of a boom cylinder, it is possible to fix the hydraulic cylinder to the excavator body and to fix the piston rod, for example, to the boom and to move the boom by moving the piston rod together with the piston in the hydraulic cylinder. For this purpose, the pressure chamber on the piston side is filled with pressure medium, which is discharged from the other pressure chamber, so that the piston rod is either extended from the hydraulic cylinder or retracted into it.

In order to avoid critical operating states, control measures of the control unit can be used to control the first consumer and/or one of the further consumers, for example a hydraulic cylinder, in a throttling manner and/or to interrupt a pressure medium connection from the hydraulic machine to one of the consumers. In other words, when a critical operating condition occurs, a single operation (Einzelbetrieb), i.e., the opening of only one of the control valves, may be taken by the controller. For example, the controller may take control measures, for example, if the pressure side to which the pressure limiting valve is connected is lower than the safety pressure by a certain value, for example 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 is briefly opened for discharging pressure medium from the pressure side. By taking control measures, regulation of the first consumer can be resumed, to the pressure side of which the pressure limiting valve is connected. In order to avoid the critical operating state, the control valve is thus closed, i.e. the control valve of the first consumer is interrupted and/or the control valve of the other consumer is interrupted. As mentioned above, another possibility is to instead disconnect the pressure medium connection, but to throttle the pressure medium connection 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, for example, actuating the first consumer, it is not necessary, for example, to completely disconnect the pressure medium. If the first load is, for example, a hydraulic cylinder and it reduces the load, the pressure medium connection of the other load can be throttled only if the load is lowered at least one specific minimum speed and pressure medium is thereby discharged from the pressure chamber of the hydraulic cylinder.

The assembly may preferably have in particular a further pressure sensor which is connected to the output side of the pressure connection of the hydraulic machine, in particular between the pressure connection of the hydraulic machine and a corresponding control valve of the consumer. The pressure detected by the pressure sensor is also transmitted to the controller. The pressure at the pressure joint of the hydraulic machine is known to the controller by means of the pressure sensor and thus the controller may preferably control the hydraulic machine. That is, the controller may set, for example, the volumetric flow delivered by the hydraulic machine as a function of the pressure on the output side of the pressure fitting of the hydraulic machine. Alternatively or additionally, the hydraulic machine may furthermore have a pressure regulator and/or a pressure feed flow regulator with or without the possibility of exceeding the target value of the pump (u bersteuern), and/or a feed flow regulator with suitable dynamics. Additionally or alternatively, the air pressure or volume supply of the adjustment chamber (STELLKAMMER) of the hydraulic machine may be adjusted.

If the hydraulic machine is electronically controlled, the controller may operate the hydraulic machine in a pressure limiting manner in order to avoid critical operating conditions. In other words, 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, the delivery volume of the hydraulic machine can be limited. In other words, by detecting the pressure of 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 has occurred or has occurred, and can therefore avoid the critical operating state by adjusting the hydraulic machine. One of the advantages is that both control valves can still be operated. The pressure limitation is preferably performed by a hydraulic press.

An additional or alternative control measure for avoiding the critical operating state may be to close the control valve of the first consumer and thereby disconnect the pressure medium connection to the pressure side of the first consumer if the pressure in the pressure connection of the hydraulic machine exceeds a certain value. In other words, the hydraulic machine delivers for example a volume flow required by another consumer, so that the control valve of the first consumer is not opened. In this way, the working hydraulic system can be controlled 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 limited.

If the control valve is actuated by the controller during the control action to avoid a critical state, it is provided that the controller has an algorithm that influences the control valve. For example, the controller may have a data store with algorithms stored thereon. Algorithms for controlling and/or influencing the control valve can determine, for example, how fast and/or when the pressure medium connection is closed and/or how far the pressure medium connection is throttled. In particular, this may be done depending on the pressure transmitted by the pressure sensor to the controller. By means of which an accurate and precise control of the control valve is allowed. Furthermore, algorithms for controlling the hydraulic machine may also be stored on the data storage.

In one embodiment, the working hydraulic system may preferably be an open center working hydraulic system. That is to say, the consumers arranged in parallel have control valves which are open for the oil flow in the intermediate position, so that all the feed flow fed by the hydraulic machine is 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 in a fluid-tight manner between the hydraulic machine and the consumer, which hydraulic control element can be controlled, for example, in an electro-hydraulic manner in proportion, and which hydraulic control element can open a pressure medium connection between the hydraulic machine and the tank in order to limit and/or control the volumetric flow leading from the hydraulic machine to the consumer. The hydraulic control element may be, for example, a control valve, in particular a 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 volumetric flow delivered by the hydraulic machine is directed, for example, by a circulation valve and/or the performance of the hydraulic machine is limited.

The working hydraulic system may furthermore be equipped with a load sensing system (LS system). LS systems are also known as load pressure reporting systems. In an open-center working hydraulic system, a pressure balance (Druckwaage) is connected via a hydraulic control element, which can be a control valve, and the control element can be actuated by the hydraulic control element. Through this manipulation, excess volumetric flow can be discharged to the tank in an open center system. In a closed-center working hydraulic system, the delivery capacity of the hydraulic machine 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 is generated by the volumetric flow supply of the hydraulic machine, is controlled in such a way that the highest pressure prevailing in the working hydraulic system is exceeded by a specific pressure difference. Furthermore, the consumers have a respective individual pressure balance which is set individually, via a respective control valve of the respective consumer, a respective pressure difference.

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

The controller also preferably has input means, such as a pressure sensor and/or an electronic joystick, for reading the driver's wishes. The controller may thus convert driver wishes into movements of the control valve and/or control of the hydraulic machine and/or communicate restrictions or throttles to the pressure medium connection and/or the hydraulic machine to the driver, for example.

Furthermore, the method for controlling a working hydraulic system having such an assembly has the following steps. First, a previously defined critical operating state is identified and/or expected. The above-mentioned different control measures, i.e. throttling and/or closing one or more control valves, are then 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 the 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 the 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 graph which shows, by way of example, the relationship between the normalized pressure on the pressure side of the first consumer connected to the pressure limiting valve 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 further has an excavator body 6 on which a first hydraulic cylinder 8, which may be a first load, is arranged. A piston rod 10 protrudes from the hydraulic cylinder 8 and is fixed to a boom 12. A hinge (Gelenk) is arranged between the excavator body 6 and the boom 12, by means of which hinge a rotational movement of the boom 12 about the hinge is made possible. By means of the movement, i.e. retraction or extension, of the piston rod 10 in the hydraulic cylinder 8, the boom 12 can be moved around the articulation and thus the end of the boom 12 not arranged on the excavator body 6 can be moved downwards or upwards. Thus, the load 4 suspended on the bucket 2 moves upward and downward with the boom 12. Furthermore, at the end of the boom 12 which is not arranged on the excavator body 6, a further hydraulic cylinder 14 is arranged as a further load, the piston rod 16 of which is arranged on the excavator boom (Baggerstiel) 18. Excavator stick 18 is connected to boom 12 by a hinge about which it can rotate. The excavator stick 18 may be rotated by movement of the piston rod 16 about the hinge, which in turn may move the load 4. On the excavator boom 18, a further hydraulic cylinder 22 with a piston rod 20 is arranged, which hydraulic cylinder serves to ensure the movement of the bucket 2. The bucket 2 is likewise connected to the excavator stick 18 by means of a hinge, so that the bucket 2 can be moved by extending or retracting a hydraulic cylinder 22, which hydraulic cylinder 22 is another load.

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, which is not penetrated by the piston rod 10, is high, since the pressure in the pressure chamber counteracts the load 4, which pressure chamber may be 300 bar, for example. By lowering the load 4, undesired movement of the load 4 may occur due to the rotation of the boom 12 about a hinge arranged on the excavator body 6. Thus, boom 12 is not only moved downward, but rather excavator stick 18 is additionally tilted. This may be compensated for, for example, by retracting piston rod 16, which piston rod 16 moves excavator stick 18. The pressure prevailing in the pressure chamber of hydraulic cylinder 14, which is not penetrated by 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 stick 18 at the same time, the control valves, which are explained in detail below in fig. 2, open up a corresponding pressure medium connection to the hydraulic machine and thus also result in a pressure medium connection between the pressure chambers. By simultaneous opening of the control valve, the pressure in the pressure chamber of the first hydraulic cylinder 8, which is penetrated by the piston rod 10, is likewise increased to at least 250 bar. This pressure also acts on the pressure chamber in which a pressure of 300 bar is present, since it has to be additionally compensated for. The area ratio between the faces of the piston facing the pressure chamber in which a pressure of 300 bar is present is larger than the area ratio between the faces acted on by the pressure in the pressure chamber penetrated by the piston rod 10, because the piston rod 10 causes a reduction in area, because it acts on the piston. The area ratio may be, for example, 2:1, that is to say, the area of the piston without the piston rod 10 is twice 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 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 boom 12 and excavator stick 18, a pressure limiting valve opening may occur. If the pressure limiting valve is open, the pressure in the pressure chamber of the load 4 is kept down and thus the cantilever 12 and the load 4 are not decelerated and fall down unregulated until the pressure limiting valve is closed again.

In fig. 2, an assembly 24 of a working hydraulic system is shown, as it is provided for example in the excavator 1 of fig. 1. The assembly 24 includes a first hydraulic cylinder 26 as a first consumer, and a second hydraulic cylinder 28 and a hydraulic motor 30 as other consumers. These components are arranged in fluid parallel. 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 fluidly arranged between the hydraulic machine 32 and the respective consumers 26, 28, 30. In order to center the respective spool of the respective control valve 34, 36, 38 in the basic position or in the intermediate position, a valve spring 40 is arranged in each case on the respective control valve 34, 36, 38 when the latter is not actuated. For actuating the control valves 34, 36, 38, two electromagnetic actuators (Aktor) 42 are each arranged on the respective control valve 34, 36, 38.

Hydraulic cylinders 26, 28 have pistons 44, 46, respectively. The piston 44 of the hydraulic cylinder 26 separates a pressure chamber 48 as one pressure side from a pressure chamber 50 constituting the other pressure side. The pressure chamber 50 is penetrated by a piston rod 52 extending away from the piston 44 and protruding from the hydraulic cylinder 26. In the hydraulic cylinder 28, the piston 46 separates a pressure chamber 54 forming one pressure side from a pressure chamber 56 forming the other pressure side, and the pressure chamber 56 is likewise penetrated by a piston rod 58 extending from the piston 46.

The corresponding control valves 34, 36, 38 are 4/3-way 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 middle position of their spools, i.e. the respective consumers 26, 28, 30 are not connected to the hydraulic machine 32 in the middle position by pressure medium. The control valves 34, 36, the hydraulic cylinders 26, 28 can be switched in such a way that their respective valve element can be displaced in such a way that the pressure chambers 48, 54 each have a respective working connection A1, via which working connection A1 a pressure medium connection with the hydraulic machine 32 is provided. 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 the 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 A2. Depending on the manner of switching the control valve 38, the working connection A1 is connected to either the tank 60 or the hydraulic machine 32, and conversely the working connection A2 is connected to either the hydraulic machine 32 or 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 the safety pressure, the pressure limiting valve 62 opens the pressure medium connection to the tank 60. The hydraulic cylinder 26 may for example correspond to the hydraulic cylinder 8 in fig. 1 and the pressure chamber 48 corresponds to a pressure chamber of the hydraulic cylinder 8 which is not penetrated by a 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 lowering and/or extending the boom 12 of fig. 1. In addition, the pressure of at least one pressure sensor 74 is communicated to controller 66. The pressure sensor is connected to the pressure chamber 48 of the hydraulic cylinder 26 and transmits the measured pressure to the controller 66. Additionally or alternatively, another pressure sensor 76 may communicate pressure to the 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. The controller 66 may also control the control valves 34, 36, 38 via the actuator 42. In addition, the controller 66 has a connection to a hydraulic machine actuator 80. Accordingly, the controller 66 may determine the delivery capacity of the hydraulic machine 32.

When, for example, a load 82 acts on the piston rod 52 of the hydraulic cylinder 26, a critical operating state can occur in the assembly 24, which leads to the opening of the pressure limiting valve 62. In this example, the pressure in the pressure chamber 48 may be 300 bar in order to raise 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 is lowered, 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, the pressure chamber 54 is filled with pressure medium, and the pressure chamber 56 has a pressure medium connection to a tank in order to discharge the pressure medium. In other words, in this state, the pressure chamber 54 and the pressure chamber 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. Thus, the pressure in the pressure chamber 50 is 250 bar. That is, the pressure in pressure chamber 48 increases because it now holds load 84 and additionally compensates for the pressure acting from pressure chamber 50 on piston face 86 of 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 to say that the area of the piston face 88 is twice that of the piston face 86, the pressure increases to 125 bar. That is, the pressure within pressure chamber 48 rises to 425 bar. If this pressure exceeds the safety pressure of the pressure medium connection from which the pressure limiting valve 62 opens 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 assembly through actuator 42 and hydraulic machine actuator 80 such that the critical condition is avoided. The control of the control valves 34, 36, 38 may also take place in accordance with an algorithm, and thus the controller 66 may 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 the controller 66, in other words, the control action implemented by the controller 66, may depend on the pressure in the pressure chamber 48 and/or on the pressures reported by the pressure sensors 74 and 76 to the controller 66 on the output side of the hydraulic machine 32.

Fig. 3 shows, by way of example, a standardized pressure p (see fig. 2) in the pressure chamber 48 or 50 and a standardized opening cross section of the control valve 34(See FIG. 2). This relationship may be stored, for example, on the data storage 86 of the controller 66, see FIG. 2. The pressure p, i.e. the pressure p/p _s, is plotted here, wherein p _s is the safety pressure at which the pressure limiting valve 62 opens the pressure medium connection to the tank 60. Furthermore, open cross section/>Also plotted in a standardized manner, wherein the open cross section refers to the largest possible open cross section/>It can be seen that the larger the pressure p, the more strongly the opening cross section (see fig. 2) of the valve core of the control valve 34 is opened. In this embodiment, the opening cross section/>, of the control valve 34 when the pressure p is 0.75 times the safety pressureIs closed. Furthermore, the opening cross section/>, when the pressure ratio p/p _s = 0.5Only the largest possible opening cross section/>25% Of (C). For example, in another embodiment, p/p _s is equal to/>The relationship between these may be linear.

An assembly for a working hydraulic system is disclosed, the assembly having two hydraulic consumers arranged in fluid parallel 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-tight manner between the hydraulic machine and the respective consumer for controlling the respective consumer. A pressure limiting valve is connected to at least one pressure side of the first consumer, which opens a pressure medium connection to the tank starting from a specific safety pressure. In addition, a control is provided in the assembly, which control is able to control the control valve and the hydraulic machine. The control unit is configured such 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 control measures for at least one of the control valves or for a plurality of the control valves and/or for the hydraulic machine.

Claims

1. An assembly for a working hydraulic system, which assembly has at least two hydraulic consumers (8, 14, 22, 26, 28, 30) arranged in parallel to one another in a fluid-like manner and at least one hydraulic machine (32) for supplying the hydraulic consumers (8, 14, 22, 26, 28, 30), wherein a respective control valve (34, 36, 38) is provided in a fluid-like manner between the hydraulic machine (32) and the respective hydraulic consumer (8, 14, 22, 26, 28, 30) for controlling the respective hydraulic 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 the hydraulic consumers (8, 14, 22, 26, 28, 30) which 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 control valve (34, 36) is provided for controlling the hydraulic machine (32) and the respective hydraulic consumer is provided for controlling the hydraulic consumer (8, 14, 22, 26, 28, 30), and wherein a controller (66, 66) is connected to at least one of the critical pressure sides (48, 50, 54, 56) of the hydraulic consumers (8, 30) is operated on the basis of the critical pressure states (48, 26, 28, 30) and the hydraulic consumer (26, 30) which is operated on the basis of the critical pressure state (48, 26, 30) and the critical state (26, 30) which is characterized by the controller (48, 26, 30) and the critical state (48, 30) and the conditions, 14. 22, 26, 28, 30) may reach or exceed a safety pressure, and the controller (66) may avoid the at least one critical operating state by control measures for at least one of the control valves (34, 36, 38) or for a plurality of the control valves (34, 36, 38) and/or for 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 the critical operating state.

3. The 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. The assembly according to claim 1 or 2, wherein the hydraulic consumers (8, 14, 22, 26, 28, 30) each have two working connections (A1, A2).

5. The assembly according to claim 4, wherein the control valve (34, 36, 38) has a spool connecting a first working connection (A1, A2) of the associated hydraulic consumer (8, 14, 22, 26, 28, 30) with the hydraulic machine (32) and a second working connection (A1, A2) of the associated hydraulic consumer (8, 14, 22, 26, 28, 30) with the tank (60) in one first or first switching position, respectively, and conversely connecting a first working connection (A1, A2) of the associated hydraulic consumer (8, 14, 22, 26, 28, 30) with the tank (60) and a second working connection (A1, A2) of the associated hydraulic consumer (8, 14, 22, 26, 28, 30) with the hydraulic machine (32) in one or second switching position.

6. The assembly according to claim 1 or 2, wherein at least one of the hydraulic consumers (8, 14, 22, 26, 28, 30) is designed as a hydraulic cylinder.

7. The assembly according to claim 1 or 2, wherein the controller (66) is configured to control one or both hydraulic consumers (8, 14, 22, 26, 28, 30) in a throttled manner or to interrupt a pressure medium connection from the hydraulic machine (32) to one or both hydraulic consumers (8, 14, 22, 26, 28, 30) of the hydraulic consumers (8, 14, 22, 26, 28, 30) in order to avoid the critical operating state.

8. An assembly according to claim 2, wherein the hydraulic machine (32) has a pressure joint (77), and wherein the or at least one pressure sensor (74, 76) is connected to the output side of the pressure joint (77), which pressure sensor reports pressure to the controller (66).

9. The assembly of claim 1 or 2, wherein the controller (66) electronically controls the volumetric flow of the hydraulic machine (32).

10. The assembly of claim 8, wherein the controller (66) manipulates the hydraulic machine (32) to avoid the critical operating state such that pressure on the output side of the pressure tap (77) is limited.

11. The assembly according to claim 8, wherein the controller (66) throttles or intercepts the pressure medium connection between the hydraulic machine (32) and the hydraulic consumers (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 claim 1 or 2, wherein the controller (66) has an input device (68, 70) that controls the position of the control valve (34, 36, 38).

13. An assembly according to claim 1 or 2, wherein the working hydraulic system has 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 a working hydraulic system with an assembly according to any one of claims 1 to 13, the method 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 for a plurality of the control valves (34, 36, 38) and/or for the hydraulic machine (32) for avoiding or avoiding the critical operating state.

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