Hydraulic drive and method for regeneratively lowering an element of a machine

Abstract

The invention relates to a hydraulic drive for a machine which has a hydraulic linear load (30) with a first chamber (38) and at least one additional hydraulic load (32), having: a hydraulic machine (4) which can pivot through zero and a hydraulic pump (6) which is mechanically coupled thereto; a valve block having a first hydraulic valve inlet connection (24), a second hydraulic valve inlet connection (25), a first hydraulic load connection (34) which can be or is hydraulically connected to the first chamber (38) of the linear load, and at least one additional hydraulic load connection which can be or is hydraulically connected to the at least one additional load, wherein the first hydraulic valve inlet connection (24) is controllably hydraulically connected to the first hydraulic load connection, and the second hydraulic valve input connection is controllably hydraulically connected to the at least one additional hydraulic load connection, and wherein a hydraulic pump working connection (22) is connected to the second valve input connection; and a switching valve (10) which is connected between a hydraulic machine working connection (16) and the first valve inlet connection and which can be switched into a passage state and into a blocking state, wherein the hydraulic machine working connection is connected to a return line which is designed to receive a volume flow of pressurized hydraulic fluid from the first chamber during a lowering phase.

Description

[0001] The present invention relates to a hydraulic drive and a method for regeneratively lowering an element of a working machine. Background of the invention

[0002] Mobile machinery, such as excavators, telehandlers, reach stackers, and others, has booms that can lift heavy loads and lower them again after transport or repositioning. Depending on the application, the lowering process can be very fast and less precisely positioned, or slower and more precisely positioned. Generally, lowering a load is achieved dissipatively by adjusting the flow rate through a variable orifice, which allows for very precise control of the speed.

[0003] Patent specifications WO 98 / 13603 A1 and US 9 695 841 B2 are known from the prior art. Disclosure of the invention

[0004] According to the invention, a hydraulic drive for or in a working machine and a method for regeneratively lowering an element of a working machine, comprising the features of the independent claims, are proposed. Advantageous embodiments are the subject of the dependent claims and the following description. The embodiments and advantages described below apply equally to the drive and the method.

[0005] The proposed drive and control arrangements can extend existing systems in such a way that regenerative lowering of an active load is enabled, allowing for the recovery of a significant portion of the potential energy. The arrangement can ensure that additional consumers can still be controlled. In particular, the presented solution can be designed modularly as a potential platform and transferred to various applications. To realize these advantages, a return line is provided between a linear consumer, e.g., a lifting cylinder, and the hydraulic machine in a hydraulic drive system to return hydraulic fluid (e.g., hydraulic oil) to drive the hydraulic machine. Simultaneously, a switching valve is provided between the hydraulic machine and the valve block (directional control valve arrangement) to close the connection between the hydraulic machine and the valve block. When the switching valve is closed, i.e.,With the switching valve in the closed position, the hydraulic fluid flowing back from the first consumer can be used to drive the hydraulic machine, which, since it can pivot freely, can also function as a hydraulic motor. Thus, hydraulic power is converted into mechanical power, which is regenerated via the coupling with the hydraulic pump. Excess power can be converted into electrical energy and stored. Overall, this enables the regeneration of potential energy from a load, such as a component (e.g., a boom) of a machine, which causes a backflow of pressurized hydraulic fluid when lowered.

[0006] The hydraulic drive is intended for use in or for a working machine that has a hydraulic linear actuator and at least one further hydraulic actuator. The linear actuator has a first chamber and is arranged such that a volume flow of pressurized hydraulic fluid into the first chamber causes a movement (raising or lowering, depending on whether the hydraulic fluid flows into or out of the first chamber) of the working machine (e.g., an excavator). The element is, for example, a boom, a lifting platform, or similar component of the working machine. The linear actuator has, in particular, one or more hydraulic cylinders. In principle, it is possible for the linear actuator to have several hydraulic cylinders and thus several chambers, the pressurization of which causes the same movement (e.g., an excavator boom moved by two hydraulic cylinders).For the sake of simplicity, these multiple chambers (if any) are considered together as a single first chamber in this description (e.g., as a first chamber comprising several sub-chambers, one in each hydraulic cylinder). Alternatively, instead of "a first chamber," the phrase "at least one first chamber" could be used.

[0007] The hydraulic drive comprises an adjustable hydraulic machine that is zero-rotational (i.e., the hydraulic machine's rotation angle can assume both positive and negative values) and a hydraulic pump whose drives are mechanically coupled (mechanical energy or power can thus be transferred between the hydraulic machine and the hydraulic pump). This mechanical coupling is achieved, in particular, via a shaft and / or a gearbox. A hydraulic machine is defined as a hydraulic machine that can function as both a hydraulic pump and a hydraulic motor, depending on the set (positive / negative) rotation angle. The hydraulic pump can only function as a hydraulic pump; therefore, if it is an adjustable pump, it is not zero-rotational.

[0008] A valve block, which can also be referred to as a main valve, is provided, comprising a first hydraulic valve inlet port, a second hydraulic valve inlet port, a first hydraulic consumer port (or outlet port) that is hydraulically connectable to the first chamber of the linear consumer, and at least one further hydraulic consumer port (or outlet port) that is hydraulically connectable to the at least one further consumer. The first hydraulic valve inlet port is controllably hydraulically connected to the first hydraulic consumer port, and the second hydraulic valve inlet port is controllably hydraulically connected to the at least one further hydraulic consumer port.The term "controllable" refers to the fact that the valve block can be actuated so that the hydraulic connection between a closed and an open state is adjustable. The valve block can be, for example, a single unit, such as a single (main) valve, or it can be modularly constructed from several components, such as individual (sub-)valves.

[0009] Preferably, the valve block (main valve) comprises a directional control valve assembly having a first and a second hydraulic valve inlet port, and comprising a first directional control valve with the first hydraulic consumer port (or outlet port), and at least one second directional control valve with at least one further hydraulic consumer port. The first directional control valve is hydraulically connected to the first valve inlet port, and the at least one second directional control valve is hydraulically connected to the second valve inlet port. The directional control valves of the directional control valve assembly can therefore be supplied with hydraulic fluid independently of each other via the valve inlet ports (i.e., a two-circuit hydraulic system), which can then be directed to different consumers by the directional control valves. The directional control valve assembly is an example of a modular valve block design.

[0010] Additionally, the first consumer port, in particular the first directional control valve, can be hydraulically connected to the second valve inlet port. For this purpose, a switching valve (e.g., a rotary or proportional valve) or a summing valve can be provided in the valve block, particularly in the directional control valve assembly. The second valve inlet port is then hydraulically connected to the first consumer port, in particular the first directional control valve, via the switching or summing valve. It is also conceivable that this functionality is integrated into the first directional control valve. In this case, the first directional control valve is directly hydraulically connected to the second valve inlet port. Such configurations can be advantageous in order to temporarily provide the linear consumer with the combined hydraulic power of the hydraulic machine and the hydraulic pump.Additionally or alternatively, it may be provided that at least one further consumer connection, in particular the at least one second directional control valve, is hydraulically connectable to the first valve inlet connection. For this purpose, a switching valve (e.g., a switching valve or proportional valve) or a summing valve may again be provided in the valve block, in particular in the directional control valve arrangement, or this functionality may optionally be integrated into the at least one second directional control valve.

[0011] The hydraulic fluid supply is provided by the hydraulic machine and the hydraulic pump. The hydraulic pump's working port is hydraulically connected (directly) to the second valve inlet port. A switching valve is located in the connection between the hydraulic machine's working port and the first valve inlet port, or hydraulically connected between the hydraulic machine's working port and the first valve inlet port. This switching valve can be set to a flow-through state, in which the first valve inlet port and the hydraulic machine's working port are hydraulically connected, and to a closed state, in which the first valve inlet port and the hydraulic machine's working port are hydraulically separated. If no regenerative lowering occurs, or...Outside the lowering phase, the switching valve is in the flow state, so that the hydraulic machine can supply the valve block, especially the directional control valve assembly, with hydraulic fluid, e.g. to lift a load using the linear consumer.

[0012] Furthermore, the hydraulic machine's working connection is hydraulically connected to a return line designed to receive a flow of pressurized hydraulic fluid from the first chamber of the linear actuator during the lowering phase, provided the actuator is connected (i.e., when the first chamber is hydraulically connected to the hydraulic drive). A suitable means (e.g., a valve) can be provided on the linear actuator to prevent a flow of fluid into the return line outside of the lowering phase. Alternatively, a return directional control valve is preferably provided as part of the hydraulic drive for this purpose (see below).

[0013] Preferably, the hydraulic drive includes a control unit configured to actuate the switching valve during the lowering phase, to close it, to actuate the valve block (in particular the first directional control valve) so that a hydraulic connection from the first valve inlet port to the first consumer port is closed, and to actuate the hydraulic machine, changing its swivel angle so that it can be operated as a hydraulic motor. These steps occur simultaneously or at least overlapping. If the first consumer port or the first directional control valve is hydraulically connectable to the second valve inlet port, the control unit actuates the valve block or the directional control valve assembly (in particular the first directional control valve and / or the switching valve and / or the summing valve) during the lowering phase so that this connection is closed.

[0014] Preferably, the hydraulic drive includes an electric machine coupled to the hydraulic machine and the hydraulic pump (to drive them or be driven by them, or mechanically coupled to the drives, e.g., drive shafts, of the hydraulic machine and the hydraulic pump). Optionally, the control system is further preferably configured to control the electric machine and / or an inverter of the electric machine, in particular such that the electric machine acts as an electric generator during the lowering phase. The use of an electric machine to drive the hydraulic machine and the hydraulic pump is advantageous because, if the power recovered by the hydraulic machine exceeds the power required by the hydraulic pump, the excess power can be converted into electrical power by the electric machine, which can be operated as a generator. The recovered electrical energy can, for example, be used to power a power source.stored in a battery.

[0015] Preferably, the hydraulic actuator includes a return directional control valve that is hydraulically connected to the return line and hydraulically connectable to, or connected to, the first chamber of the linear actuator. When connected to the linear actuator, the return directional control valve is configured to selectively close or at least partially open a hydraulic passage between the return line and the first chamber in a controllable and / or adjustable manner. The return directional control valve is more preferably a proportional valve. It is also preferably configured to actuate the return directional control valve during the lowering phase, partially or fully opening the hydraulic passage between the return line and the first chamber. Outside the lowering phase, the passage of the return directional control valve is preferably closed.Accordingly, outside the lowering phase, no hydraulic fluid can flow from the linear consumer to the hydraulic machine's working port. If the return directional control valve is a proportional valve (i.e., has intermediate positions), the flow rate from the linear consumer to the hydraulic machine's working port, and thus the lowering speed, can be controlled.

[0016] Preferably, the hydraulic drive includes a bypass valve that is hydraulically connected to the hydraulic pump's working port and a tank port. This valve is configured to selectively close or at least partially open a hydraulic passage between the working port and the tank port. The bypass valve is more preferably a proportional valve. Equally preferably, the control system is configured to actuate the bypass valve during the lowering phase, partially or fully opening the hydraulic passage between the working port and the tank port. This prevents hydraulic neutral circulation losses if at least one other consumer requires little or no power during the lowering phase. This configuration is particularly advantageous when the hydraulic pump is a constant-displacement pump.

[0017] According to another preferred embodiment, the hydraulic pump is an adjustable hydraulic pump. In this case, neutral circulation losses can be avoided even without a directional control valve.

[0018] Preferably, if the linear actuator has a second chamber, the hydraulic actuator includes a compensating directional control valve that is hydraulically connectable to, or already connected to, the first and second chambers. When connected, this valve is configured to selectively close or at least partially open a hydraulic passage between the first and second chambers. The compensating directional control valve is more preferably a proportional valve. Equally preferably, the control system is configured to actuate the compensating directional control valve during the lowering phase, partially or completely opening the hydraulic passage between the first and second chambers. The second chamber is, for example, the second chamber of a double-acting hydraulic cylinder. The second chamber can be filled with hydraulic fluid from the first chamber, thus eliminating the need for a separate hydraulic fluid supply.Here too (as with the first chamber), the second chamber can again comprise several sub-chambers, for example if the linear consumer comprises several hydraulic cylinders that together effect the movement (raising / lowering) of the element of the working machine.

[0019] Preferably, the switching valve and / or, if applicable, the control system is configured such that outside the lowering phase, the switching valve is or is switched to the open state. The switching valve can, for example, be configured so that a spring or similar device automatically switches it to the open state when no further control signal is present. Alternatively or additionally, active control by the controller could be implemented.

[0020] Preferably, and optionally in each case, the return directional control valve and / or the control system is configured such that, outside the lowering phase, the hydraulic passage between the first chamber and the return line is closed, and / or the compensating directional control valve and / or the control system is configured such that, outside the lowering phase, the hydraulic passage between the first chamber and the second chamber is closed, and / or the bypass directional control valve and / or the control system is configured such that, outside the lowering phase, the hydraulic passage between the hydraulic pump working port and the hydraulic pump tank port is closed. Here, too, it can be provided, independently of each other, that the closed position is assumed automatically, e.g., by a corresponding preload with a spring, if no other control signal is present.Alternatively or additionally, that a corresponding control action is taken by the controller.

[0021] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawing.

[0022] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0023] The invention is schematically illustrated in the drawing using exemplary embodiments and is described in detail below with reference to the drawing. Character description

[0024] Figure 1 shows a hydraulic drive according to a preferred embodiment of the invention. Figure 2shows a hydraulic drive according to another preferred embodiment of the invention. Figure 3 shows the sequence of a preferred embodiment of the method according to the invention. Detailed description of the drawing

[0025] Figure 1 Figure 1 shows a hydraulic drive according to a preferred embodiment of the invention. The hydraulic drive forms an open two-circuit hydraulic system. The hydraulic drive comprises a hydraulic machine 4, a hydraulic pump 6, a valve block, namely, for example, a directional control valve arrangement 8, and a switching valve 10. The hydraulic machine 4 and the hydraulic pump 6, or their respective drive shafts, are mechanically coupled to each other, i.e., they can be driven together. This coupling can be effected, for example, via a drive shaft or a gearbox. The rotational speeds of the hydraulic machine 4 and the hydraulic pump 6 are therefore the same or at least bear a certain ratio to each other.

[0026] The hydraulic machine 4 and the hydraulic pump 6 are preferably driven by an electric machine 12, which is connected via an inverter 14 to an electrical power supply, e.g., a DC system and / or a battery. The inverter 14 can, for example, convert DC current from the electrical power supply into AC current for the electric machine when the electric machine acts as an electric motor, and conversely, convert AC current into DC current when the electric machine acts as an electric generator.

[0027] The hydraulic machine 4 is adjustable, meaning its swivel angle is adjustable. Furthermore, the hydraulic machine 4 can swivel to zero, meaning it can be operated both as a hydraulic pump (e.g., corresponding to positive swivel angles) and as a hydraulic motor (e.g., corresponding to negative swivel angles). Such a hydraulic machine is also referred to as "mooring-capable." The hydraulic machine 4 has a (hydraulic) working port 16 and a tank port 18, which is connected to a tank 20. In pump mode, the hydraulic machine, driven, for example, by the electric motor 12, generates a flow of hydraulic fluid (from the tank) from the tank port 18 to the working port 16. In motor mode, a flow of hydraulic fluid from the working port 16 to the tank port 18 generates a torque.a mechanical power on the drive shaft of the hydraulic machine 4, with which the hydraulic pump 6 can be driven (at least partially), and, if excess mechanical power is generated, e.g. the electric machine 12 can also be driven.

[0028] The hydraulic pump 6 is a constant-displacement pump and has a tank connection 23 (hydraulically connected to tank 20) ​​and a hydraulic pump working connection 22. When driven, the hydraulic pump 6 is designed to pump hydraulic fluid from the tank connection 23 to the hydraulic pump working connection 22.

[0029] The directional control valve assembly 8 has a first valve inlet port 24 and a second valve inlet port 25 through which the directional control valve assembly can be supplied with hydraulic fluid. The directional control valve assembly 8 comprises a first directional control valve 26 and at least one second directional control valve 28, wherein the first directional control valve 26 is hydraulically connected to the first valve inlet port 24 and the at least one second directional control valve 28 is hydraulically connected to the second valve inlet port 25 (neither shown in detail). In general, the directional control valve assembly can comprise more than two directional control valves. The directional control valve assembly shown is implemented as an example in a modular directional control valve block, which can have several directional control valve sections that can be supplied with hydraulic fluid via inlet sections in which the valve inlet ports are provided. Each directional control valve section corresponds to a directional control valve, with respective consumer ports.The directional control valves of the individual directional control valve sections are generally independently operable or controllable. The directional control valves feature in . Figure 1 Each valve has two consumer ports as an example; in general, the directional control valves can also have a different number of consumer ports independently of each other, i.e., they generally have at least one consumer port. If the valve block is not modular but constructed as a (at least partially) unified unit, the valve block is designed to implement the functionalities described below in connection with the directional control valve arrangement.

[0030] In the embodiment shown, the first directional control valve 26 and the at least one second directional control valve 28 each have two consumer ports, i.e., hydraulic ports to which hydraulic lines leading to the respective consumers can be connected. The first directional control valve 26 and the at least one second directional control valve 28 are configured, depending on how they are actuated, to fully or partially open or close hydraulic passages or connections from the valve inlet ports to the consumer ports, so that the flow of hydraulic fluid to each of the consumer ports or to the consumers connected thereto can be controlled.

[0031] As explained above, it may be provided that the first consumer connection 34 is hydraulically connectable to the second valve inlet connection 25 and / or that at least one further consumer connection is hydraulically connectable to the first valve inlet connection (via at least one suitable switching valve and / or at least one suitable summing valve and / or a corresponding functionality of the directional control valves).

[0032] The hydraulic pump working port 22 is hydraulically connected to the second valve inlet port 25.

[0033] The hydraulic machine working port 16 is connected to the first valve inlet port 24 via the switching valve 10. The switching valve 10 can be switched between a flow-through state (state shown in the figure) and a closed state. In the flow-through state, the switching valve 10 is open, i.e., there is an (open) hydraulic connection between the hydraulic machine working port 16 and the first valve inlet port 24, and hydraulic fluid can flow between these ports. In the closed state, the switching valve 10 is closed, i.e., there is no hydraulic connection between the hydraulic machine working port 16 and the first valve inlet port 24, and therefore no hydraulic fluid can flow between these ports. The switching valve 10 can be actuated, for example, electrically or electromagnetically, and in a further advantageous embodiment, the switching valve 10 can also be actuated electro-hydraulically, e.g., by means of a control valve.so-called pressure control elements can be controlled or actuated.

[0034] A hydraulic linear consumer 30, or hydraulic cylinder (here a differential cylinder), is shown, which is hydraulically connected to the first directional control valve 26. Consumer ports of the first directional control valve 26 are hydraulically connected to working ports or chambers of the linear consumer 30. Specifically, a first consumer port 34 is hydraulically connected to a first chamber 38, and a second consumer port 36 is hydraulically connected to a second chamber 40. The linear consumer can also be referred to as the first hydraulic consumer or the primary hydraulic consumer.

[0035] Likewise, another hydraulic consumer 32 (here also an example of a differential cylinder) is shown, which is hydraulically connected to the at least one second directional control valve 28. In general, more than the one shown additional consumer 32 can be provided, which are hydraulically connected to corresponding second directional control valves. Thus, at least one additional hydraulic consumer is provided, which can also be referred to as at least one second hydraulic consumer or as a secondary hydraulic consumer.

[0036] The linear actuator 30 is configured, and in particular arranged on a machine in which the hydraulic drive is used, such that when hydraulic fluid is directed into the first chamber 38 of the linear actuator by appropriate control of the first directional control valve 26 (and correspondingly hydraulic fluid is directed out of the second chamber 40), a load is lifted (not shown). This can be done, for example, by means of a boom of the machine. The load is lifted against the force of gravity, assuming the machine is in its normal working position. The hydraulic fluid in the first chamber is under a corresponding pressure (caused by the load).

[0037] A return directional control valve 42, preferably a 2 / 2-way valve with intermediate position (proportional valve), is provided between the first chamber 38 of the linear consumer 30 and the hydraulic machine working port 16 of the hydraulic machine 4. One port of the return directional control valve is hydraulically connected to the first chamber, and the other port of the return directional control valve is hydraulically connected to the hydraulic machine working port 16 via a return line 46. The return directional control valve 42 is adjustable between a closed end position and an open end position. In the closed end position (position shown in the figure), there is no hydraulic connection between the first chamber and the return line or the hydraulic machine working port. When adjusted towards the open end position, a through-port is increasingly opened.The return directional control valve 42 is opened progressively, establishing a hydraulic connection between the first chamber and the return line or the hydraulic machine's working port, which is released as the cross-section increases. In the open end position, the through-port is fully open. The return directional control valve 42, or its adjustment, is, for example, electrically controllable; that is, the return directional control valve 42 can be actuated electrically or electromagnetically. In a further advantageous embodiment, the return directional control valve 42 can also be controlled or actuated electro-hydraulically by, for example, so-called pressure regulating elements. The closed end position can be a position that is assumed automatically (especially outside the lowering phase when no further control signal is present), for example, as illustrated, by a preload element (e.g., a spring) that causes movement into the closed end position.

[0038] With the control valve 10 closed and the return directional control valve 42 (at least partially) open, pressurized hydraulic fluid from the first chamber 38 of the linear actuator 30 is directed through the return directional control valve 42 and the return line 46 to the hydraulic machine's working port 16, allowing the hydraulic machine 4 to operate as a motor to convert hydraulic energy into mechanical energy (torque, speed). The load is lowered accordingly, thus converting potential energy into mechanical energy. This mechanical energy is used to drive the hydraulic pump 6 or the generator-driven electric machine 12. Overall, during a lowering phase, a regenerative lowering of the load raised by the linear actuator takes place.

[0039] The first directional control valve 26 is controlled during regenerative lowering such that there is no hydraulic connection between the first valve inlet port 24 and the first consumer port 34. If the first consumer port 34 is hydraulically connectable to the second valve inlet port 25, this connection is closed during regenerative lowering, and the directional control valve assembly is controlled during regenerative lowering such that there is no hydraulic connection between the second valve inlet port 25 and the first consumer port 34. Preferably, the first directional control valve 26 is also controlled during regenerative lowering such that there is no hydraulic connection between the first valve inlet port 24 and the second consumer port 36 (if the directional control valve assembly is configured to allow such a connection).

[0040] During regenerative lowering (closed control valve 10), the hydraulic supply of at least one further consumer 32 is ensured by the hydraulic pump 6, which continues to supply the directional control valve arrangement with hydraulic fluid via the second valve inlet port 25.

[0041] A balancing directional control valve 44, which here is a 2 / 2-way valve with intermediate position, is preferably provided and arranged between the first chamber 38 and the second chamber 40. One port of the balancing directional control valve is hydraulically connected to the first chamber (and thus also to the first consumer port), and the other port of the balancing directional control valve is hydraulically connected to the second chamber (and thus also to the second consumer port). Like the return directional control valve 42, the balancing directional control valve 44 is adjustable between a closed end position (no hydraulic connection between the first and second chambers) and an open end position, whereby a passage is progressively opened starting from the closed end position (hydraulic connection with increasing cross-section between the first and second chambers). The balancing directional control valve 44 is, for example, electrically or...The valve can be electromagnetically actuated, and in a further advantageous embodiment, the compensating directional control valve 44 can also be electro-hydraulically controlled or actuated by, for example, so-called pressure regulating elements. The closed end position can be a position that is assumed automatically (especially outside the lowering phase when no further control signal is present, for example, as illustrated, by a preload element (e.g., a spring) that causes movement into the closed end position).

[0042] The compensating directional control valve 44 enables hydraulic fluid to be routed between the chambers. In particular, it allows hydraulic fluid to be routed from the first to the second chamber during regenerative lowering, thus eliminating the need for a supply via the first directional control valve or the directional control valve assembly 8, which, due to the closed switching valve, is only hydraulically supplied by the hydraulic pump.

[0043] During regenerative lowering, the lowering speed can be controlled by appropriately controlling the return directional control valve 42 and / or the compensating directional control valve 44, i.e. by controlling the cross-sections of the respective passages.

[0044] The balancing directional control valve 44 is implemented here as a separate valve. Alternatively, the balancing directional control valve, or its functionality, could also be integrated into the first directional control valve 26.

[0045] Instead of the double-acting hydraulic cylinder shown as a linear consumer, a single-acting hydraulic cylinder can also be used (so that only the first chamber is pressurized with hydraulic fluid, with only the first consumer port, which can be connected to or is connected to the first chamber, being provided on the first directional control valve, and the second consumer port can be omitted). In this case, the compensating directional control valve 44 can be omitted.

[0046] Furthermore, a bypass valve 48, which here is a 2 / 2-way valve with an intermediate position, is preferably provided between the hydraulic pump working port 22 and the tank port 23 of the hydraulic pump 6. One port of the bypass valve is hydraulically connected to the hydraulic pump working port 22 (and thus also to the valve inlet port 24) and the other port of the bypass valve is hydraulically connected to the tank port 23 of the hydraulic pump 6 (and thus also to the tank).The bypass directional control valve 48, like the return directional control valve 42 and the balancing directional control valve 44, is adjustable between a closed end position (no hydraulic connection between the hydraulic pump working port 22 and the tank port 23) and an open end position, whereby a passage is progressively opened starting from the closed end position (hydraulic connection with increasing cross-section between the hydraulic pump working port 22 and the tank port 23). The bypass directional control valve 48 can be actuated, for example, electrically or electromagnetically, and in a further advantageous embodiment, the bypass directional control valve 48 can also be controlled or actuated electro-hydraulically by, for example, so-called pressure regulating elements.If, during a regenerative lowering phase, at least one other consumer 32 requires little or no hydraulic power, the bypass valve 48 can be actuated to assume a partially open position. This is advantageous because it reduces neutral circulation losses. The closed end position can be a position that is assumed automatically (especially outside the lowering phase when no further control signal is present), for example, as illustrated, by a preload element (e.g., a spring) that causes movement into the closed end position.

[0047] The hydraulic drive can further comprise an (electronic) control unit 50, which is configured to control the hydraulic machine 4, the switching valve 10, and the directional control valve assembly 8, or the first directional control valve 26, and optionally at least one second directional control valve 28. The control unit 50 can also be configured, where present, to control the electric machine 12 or the inverter 14, the return directional control valve 42, the balancing directional control valve 44, and the bypass directional control valve 48. In any case, the control can be effected via corresponding control lines (not shown).

[0048] The control unit 50 is configured to actuate the switching valve 10 during regenerative lowering or during a lowering phase, so that it is switched to the closed position, and to actuate the adjustable hydraulic machine 4 and its swivel angle, so that the hydraulic machine 4 acts as a hydraulic motor. The swivel angle is set to zero, so that the hydraulic machine generates torque on the drive shaft for a given direction of rotation. Furthermore, the control unit 50 acts on the return directional control valve 42, switching it to a position that is at least partially open. During regenerative lowering, the control unit 50 also acts on the first directional control valve 26, switching it to a state in which there is no hydraulic connection between the first valve inlet port 24 and the first consumer port 34.The compensating directional control valve 44 is also activated, if necessary, to switch to a position that is at least partially open. The lowering rate can be controlled by appropriately selecting the open position of the return directional control valve 42 and, if necessary, the open position of the compensating directional control valve 44.

[0049] If little or no hydraulic power is required by at least one second consumer 32 during regenerative lowering, the control unit 50 can, if necessary, control the circulation valve 48 to switch it to a position that is at least partially open.

[0050] During regenerative lowering (i.e., during the lowering phase), the control unit 50 can optionally control the electric machine 12 or the inverter 14 to reduce the power output or torque output of the electric machine 12. In particular, if the (regenerated) power output by the hydraulic machine 4 exceeds the power input by the hydraulic pump 6 during regenerative lowering, the electric machine 12 can act as an electric generator.

[0051] Figure 2 shows a hydraulic drive according to another preferred embodiment of the invention. This corresponds essentially to the one in Figure 1 the embodiment shown, so that only differences will be discussed below and otherwise the description of the Figure 1 is referred.

[0052] Unlike the Figure 1 is the hydraulic pump 6 of the embodiment of the Figure 2An adjustable hydraulic pump. Furthermore, no bypass valve is provided.

[0053] Since the hydraulic pump 6 is adjustable, the delivery flow rate of the hydraulic pump (at a given speed) can be adjusted, for example, according to a swivel angle of the hydraulic pump 6. In particular, if during a regenerative lowering process at least one other consumer 32 requires no or only a small amount of hydraulic power, the swivel angle of the hydraulic pump 6 can be adjusted to zero or close to zero, so that no or only a small delivery flow rate is generated. Similarly, in the hydraulic drive of the Figure 2 Neutral circulation losses can also be reduced without a directional control valve.

[0054] The control unit 50 is in the embodiment of the Figure 2preferably designed to control the hydraulic pump 6 or its swivel angle. If, during regenerative lowering, no or only a small amount of hydraulic power is required by the at least one second consumer 32, then, unlike in Figure 1 , where the bypass valve is at least partially opened, the control 50 adjusts the swivel angle of the adjustable hydraulic pump to zero or near zero, i.e., controls the adjustable hydraulic pump accordingly.

[0055] Figure 3 Figure 1 shows the sequence of a preferred embodiment of the method according to the invention. The steps performed during a lowering phase are shown. This is a method for the regenerative lowering of an element of a working machine, which is driven by a hydraulic drive according to the invention (e.g., according to the...). Figures 1 to 2) is driven. The supply or removal of hydraulic fluid to the linear consumer causes the element to rise or fall.

[0056] In step 100, the switching valve is switched to the closed position. In step 110, a volume of hydraulic fluid is directed from the first chamber to the working port of the hydraulic machine, and in step 120, the hydraulic connection from the first valve inlet port to the first consumer port is closed. In step 130, the swivel angle of the hydraulic machine is changed so that it acts as a hydraulic motor. These steps are essentially performed simultaneously or overlapping. For a description of the effect of these steps, refer to the description of the Figures 1 to 2 referred to. As already explained, the aforementioned steps can be carried out or initiated in particular by controlling the hydraulic drive.

Claims

1. Hydraulic drive for a working machine which has a hydraulic linear consumer (30) and has at least one further hydraulic consumer (32), wherein the linear consumer has a first chamber (38) and is arranged in such a way that a volume flow of pressurized hydraulic fluid into the first chamber or out of the first chamber causes an element of the working machine to be raised or lowered, respectively, having an adjustable hydraulic machine (4), which is able to be pivoted through the zero point, and a hydraulic pump (6), whose drives are coupled mechanically, wherein the hydraulic machine has a hydraulic machine working connection (16) and the hydraulic pump has a hydraulic pump working connection (22); a valve block with a first hydraulic valve inlet connection (24), a second hydraulic valve inlet connection (25), a first hydraulic consumer connection (34), which is connectable or connected hydraulically to the first chamber (38) of the linear consumer, and with at least one further hydraulic consumer connection, which is connectable or connected hydraulically to the at least one further consumer, wherein the first hydraulic valve inlet connection (24) is connected hydraulically to the first hydraulic consumer connection (34) in a controllable manner, and the second hydraulic valve inlet connection (25) is connected hydraulically to the at least one further hydraulic consumer connection in a controllable manner, and wherein the hydraulic pump working connection (22) is connected hydraulically to the second valve inlet connection (25); a switching valve (10), which is connected hydraulically between the hydraulic machine working connection (16) and the first valve inlet connection (24) and is switchable into a throughflow state, in which the first valve inlet connection and the hydraulic machine working connection are connected hydraulically, and into a blocking state, in which the first valve inlet connection and the hydraulic machine working connection are separated hydraulically; wherein the hydraulic machine working connection is connected hydraulically to a return line (46), which is configured to receive a volume flow of pressurized hydraulic fluid from the first chamber (38) of the linear consumer, when this is connected, during a lowering phase.

2. Hydraulic drive according to Claim 1, the valve block comprising a directional valve arrangement (8) with the first hydraulic valve inlet connection (24) and with the second hydraulic valve inlet connection (25); wherein the directional valve arrangement (8) comprises a first directional valve (26), at which the first hydraulic consumer connection (34) is provided, and at least a second directional valve (28), at which the at least one further hydraulic consumer connection is provided; wherein the first directional valve (26) is connected hydraulically to the first valve inlet connection (24), wherein the at least one second directional valve (28) is connected hydraulically to the second valve inlet connection (25).

3. Hydraulic drive according to Claim 1 or 2, having a controller (50), which is configured to actuate the switching valve (10) so that it is switched into the blocking state, to actuate the valve block, in particular the first directional valve (26), so that a hydraulic connection from the first valve inlet connection (24) to the first consumer connection (24) is closed, and to actuate the hydraulic machine (4) so that the pivot angle is changed such that it can or is operated as a hydraulic motor, during the lowering phase.

4. Hydraulic drive according to one of the preceding claims, further having an electric machine (12), which is coupled to the hydraulic machine (4) and the hydraulic pump (6); wherein, where there is dependency on Claim 3, the controller (50) is preferably configured to control the electric machine (12) and / or an inverter (14) of the electric machine, in particular so that the electric machine acts as an electric generator during the lowering phase.

5. Hydraulic drive according to one of the preceding claims, having a return line directional valve (42), which is connected hydraulically to the return line (46) and is connectable or connected hydraulically to the first chamber (38) of the linear consumer and is configured to selectively close or at least partially open a hydraulic passage between the return line (46) and the first chamber (38) in a controllable manner; wherein the return line directional valve (42) is preferably a proportional valve; and / or wherein, where there is dependency on Claim 3, the controller (50) is preferably configured to actuate the return line directional valve (42) during the lowering phase so that the hydraulic passage between the return line (46) and the first chamber (38) is partially or fully opened.

6. Hydraulic drive according to one of the preceding claims, having a circulation directional valve (48), which is connected hydraulically to the hydraulic pump working connection (22) and a tank connection (23) of the hydraulic pump and is configured to selectively close or at least partially open a hydraulic passage between the hydraulic pump working connection (22) and the tank connection (23) of the hydraulic pump in a controllable manner; wherein the circulation directional valve (48) is preferably a proportional valve; and / or wherein, where there is dependency on Claim 3, the controller (50) is preferably configured to actuate the circulation directional valve (48) during the lowering phase so that the hydraulic passage between the hydraulic pump working connection (22) and the tank connection (23) of the hydraulic pump is partially or fully opened.

7. Hydraulic drive according to one of the preceding claims, wherein the linear consumer (30) has a second chamber (40); wherein the hydraulic drive has a compensation directional valve (44), which is connectable or connected hydraulically to the first chamber (38) and the second chamber (40) and is configured to selectively close or at least partially open a hydraulic passage between the first chamber and the second chamber in a controllable manner when connected; wherein the compensation directional valve (44) is preferably a proportional valve; and / or wherein, where there is dependency on Claim 3, the controller (50) is preferably configured to actuate the compensation directional valve (44) during the lowering phase so that the hydraulic passage between the first chamber (38) and the second chamber (40) is partially or fully opened.

8. Hydraulic drive according to one of the preceding claims, wherein the switching valve (10) and / or, where there is dependency on Claim 3, the controller (50) are / is configured in such a way that, outside the lowering phase, the switching valve is such that it has been switched into or is switched into the throughflow state.

9. Hydraulic drive according to one of the preceding claims, wherein the return line directional valve (42) and / or, where there is dependency on Claim 3, the controller (50) are / is configured in such a way that, outside the lowering phase, the hydraulic passage between the first chamber (38) and the return line (46) is closed, and / or the compensation directional valve (44) and / or, where there is dependency on Claim 3, the controller (50) are / is configured in such a way that, outside the lowering phase, the hydraulic passage between the first chamber (38) and the second chamber (40) is closed, and / or the circulation compensation valve (48) and / or, where there is dependency on Claim 3, the controller (50) are / is configured in such a way that, outside the lowering phase, the hydraulic passage between the hydraulic pump working connection (22) and the tank connection (23) of the hydraulic pump is closed.

10. Hydraulic drive according to one of the preceding claims, wherein the first consumer connection (34), in particular the first directional valve, is connectable hydraulically to the second valve inlet connection (25); wherein, where there is dependency on Claim 3, the controller (50) is preferably configured to control the directional valve arrangement during the lowering phase so that there is no hydraulic connection between the first consumer connection (34) and the second valve inlet connection (25).

11. Method for regenerative lowering of an element of a working machine which has a hydraulic linear consumer (30) and has at least one further hydraulic consumer (32), wherein the linear consumer has a first chamber (38) and is arranged in such a way that a volume flow of pressurized hydraulic fluid into the first chamber or out of the first chamber causes the element of the working machine to be raised or lowered, respectively, wherein the working machine has a hydraulic drive according to one of the preceding claims; wherein, during a lowering phase, the switching valve is switched into the blocking state (100), a volume flow of hydraulic fluid is directed from the first chamber to the working connection of the hydraulic machine (110), a hydraulic connection from the first valve inlet connection (24) to the first consumer connection (34) is closed (120), and a pivot angle of the hydraulic machine (4) is changed (130) so that it acts as a hydraulic motor.

12. Method according to Claim 11, wherein, during the lowering phase, a hydraulic passage between the first chamber (38) and the return line (46) is partially or fully opened, in particular using a return line directional valve (42).

13. Method according to either of Claims 11 and 12, wherein the linear consumer (30) has a second chamber (40), wherein, during the lowering phase, a hydraulic passage between the first chamber (38) and the second chamber (40) is partially or completely opened, in particular using a compensation directional valve (44).

14. Method according to one of Claims 11 to 13, wherein, during the lowering phase, a hydraulic passage between the hydraulic pump working connection (22) and a tank connection (23) of the hydraulic pump is partially or fully opened, in particular using a circulation directional valve (48).

15. Method according to one of Claims 11 to 14, wherein, outside the lowering phase, the switching valve (10) is switched into the throughflow state, and preferably the hydraulic passage between the first chamber (38) and the return line (46) is closed and / or the hydraulic passage between the first chamber (38) and the second chamber (40) is closed and / or the hydraulic passage between the hydraulic pump working connection (22) and the hydraulic pump tank connection (23) is closed.

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