Hydraulic drive and method for regeneratively lowering an element of a machine
Patent Information
- Application Number
- EP2023735286
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-06-28
- Filing Date
- 2023-06-26
- Publication Date
- 2025-05-07
- Estimated Expiration
- 2043-06-26
Smart Images
Figure 1.1
Abstract
Description
[0001] Hydraulic drive and method for regenerative lowering of an element of a work machine
[0002] Description
[0003] The present invention relates to a hydraulic drive and a method for regeneratively lowering an element of a work machine.
[0004] Background of the invention
[0005] Mobile work machines, such as excavators, telehandlers, reach stackers, and others, have booms that can be used to lift heavy loads and then lower them again after transporting or moving the load. Depending on the application, the lowering process can be very fast and less precise, or slower and more precise. Typically, the lowering of a load occurs dissipatively by adjusting the flow rate via an adjustable orifice plate, which allows for very precise control of the speed.
[0006] Disclosure of the invention
[0007] According to the invention, a hydraulic drive for or in a work machine and a method for regeneratively lowering an element of a work machine are proposed, having the features of the independent patent claims. Advantageous embodiments are the subject of the subclaims and the following description. The embodiments and advantages described below apply equally to the drive and the method.
[0008] The proposed drive and control arrangements can extend existing systems in such a way that a regenerative lowering of an active load is enabled and a significant portion of the potential energy can be recovered. The arrangement can ensure that additional consumers can continue to be controlled. The solution presented can, in particular, be designed modularly as a possible platform and transferred to various applications. To realize these advantages, a return line is provided in a hydraulic drive between a linear consumer, e.g., a lifting cylinder, and the hydraulic machine to return hydraulic fluid (hydraulic fluid, e.g., hydraulic oil) to drive the hydraulic machine, and at the same time, a switching valve is provided between the hydraulic machine and the valve block (directional valve arrangement) to block the connection between the hydraulic machine and the valve block. When the switching valve is closed, ieWhen the switching valve is in the closed state, hydraulic fluid flowing back from the first consumer can be used to drive the hydraulic machine, which, since it has zero-turn pivoting capability, can also act as a hydraulic motor. Hydraulic power is thus 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 an element (e.g., a boom) of a work machine, which causes a return flow of pressurized hydraulic fluid during lowering.
[0009] The hydraulic drive is provided for or in a work machine which has a hydraulic linear consumer and at least one further hydraulic consumer, wherein the linear consumer has a first chamber and is arranged such that a volume flow of pressurised hydraulic fluid into the first chamber causes a movement of an element (raising or lowering, depending on whether the hydraulic fluid flows into or out of the first chamber) of the work machine (e.g. excavator). The element is, for example, a boom, a lifting platform or similar of the work machine. The linear consumer has, in particular, one or more hydraulic cylinders (hydraulic cylinders). In principle, it can be provided that the linear consumer has several hydraulic cylinders and thus several chambers whose pressurisation causes the same movement (e.g. a boom of an excavator which is moved by two hydraulic cylinders).For the sake of simplicity, these multiple chambers (if present) are collectively referred to as the first chamber in this description (e.g., as the first chamber comprising multiple sub-chambers, one in each hydraulic cylinder). Alternatively, the phrase "at least one first chamber" could be used instead of "a first chamber." The hydraulic drive comprises an adjustable hydraulic machine capable of zero-angle pivoting (i.e., the pivot angle of the hydraulic machine can assume both positive and negative values), and a hydraulic pump whose drives are mechanically coupled (mechanical energy or power can therefore be transferred between the hydraulic machine and the hydraulic pump). The mechanical coupling is achieved, in particular, via a shaft and / or a gear. A hydraulic machine is a hydraulic machine that can function both as a hydraulic pump and as a hydraulic motor, depending on the set (positive / negative) pivot angle.The hydro pump can only act as a hydraulic pump, so if it is an adjustable pump, it cannot be swiveled to zero.
[0010] A valve block, which can also be referred to as a main valve, is provided, which has a first hydraulic valve input port, a second hydraulic valve input port, a first hydraulic consumer port (or output port) that is hydraulically connectable or connected to the first chamber of the linear consumer, and at least one further hydraulic consumer port (or output port) that is hydraulically connectable or connected to the at least one further consumer. The first hydraulic valve input port is controllably hydraulically connected to the first hydraulic consumer port, and the second hydraulic valve input 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 controlled so that the hydraulic connection can be adjusted between a closed and an open state. The valve block can be a single unit, e.g., a single (main) valve, or it can be modularly constructed from multiple components, e.g., individual (sub)valves.
[0011] The valve block (main valve) preferably comprises or is a directional control valve arrangement which has the first and a second hydraulic valve inlet connection and which has a first directional control valve, on which the first hydraulic consumer connection (or output connection) is provided, and at least one second directional control valve, on which the at least one further hydraulic consumer connection is provided. The first directional control valve is hydraulically connected to the first valve inlet connection and the at least one second directional control valve is hydraulically connected to the second valve inlet connection. The directional control valves of the directional control valve arrangement can therefore be supplied with hydraulic fluid via the valve inlet connections independently of one another (i.e. 2-circuit hydraulic system), which fluid can be passed on to various consumers via the directional control valves. The directional control valve arrangement is an example of a modular design of the valve block.
[0012] Additionally, it can be provided that the first consumer connection, in particular the first directional control valve, is hydraulically connectable to the second valve input connection. For this purpose, an on / off valve (e.g., a switching valve or proportional valve) or a summing valve can be provided in the valve block, in particular in the directional control valve arrangement. The second valve input connection is then hydraulically connected to the first consumer connection, in particular the first directional control valve, via the on / off or summing valve. It is also conceivable for this functionality to be integrated into the first directional control valve, if necessary. In this case, the first directional control valve is hydraulically connected directly to the second valve input connection. Such configurations can be expedient in order to be able to temporarily make the combined hydraulic power of the hydraulic machine and the hydraulic pump available to the linear consumer.Additionally or alternatively, it can be provided that the at least one further consumer connection, in particular the at least one second directional control valve, is hydraulically connectable to the first valve input connection. For this purpose, a connecting valve (e.g., a switching valve or proportional valve) or a summing valve can be provided in the valve block, in particular in the directional control valve arrangement, or this functionality can optionally be integrated into the at least one second directional control valve.
[0013] The hydraulic fluid is supplied by the hydraulic machine and the hydraulic pump. The hydraulic pump working connection is hydraulically connected (directly) to the second valve input connection. A switching valve is arranged in the connection between the hydraulic machine working connection and the first valve input connection, or is hydraulically connected between the hydraulic machine working connection and the first valve input connection. This switching valve can be switched into a pass-through state, in which the first valve input connection and the hydraulic machine working connection are hydraulically connected, and into a blocking state, in which the first valve input connection and the hydraulic machine working connection are hydraulically separated. If no regenerative lowering occurs, oroutside the lowering phase, the switching valve is in particular in the open state, so that the hydraulic machine can supply the valve block, in particular the directional valve arrangement, with hydraulic fluid, e.g. for lifting a load by means of the linear consumer.
[0014] Furthermore, the hydraulic machine working connection is hydraulically connected to a return line, which is configured to receive a volume flow of pressurized hydraulic fluid from the first chamber of the linear consumer during the lowering phase, if the latter is connected (i.e., if the first chamber is hydraulically connected to the hydraulic drive). A suitable means (e.g., a valve) can be provided on the linear consumer to prevent a volume flow into the return line outside of the lowering phase. Alternatively, a return-line directional control valve is preferably provided as a component of the hydraulic drive (see below).
[0015] The hydraulic drive preferably has a controller that is configured to control the switching valve during the lowering phase, to switch it to the blocking state, to control the valve block (in particular the first directional control valve) so that a hydraulic connection from the first valve input port to the first consumer port is closed, and to control the hydraulic machine to change the pivot angle so that it can be or is operated as a hydraulic motor. These steps take place simultaneously or at least overlapping. If the first consumer port or the first directional control valve is hydraulically connectable to the second valve input port, the valve block or the directional control valve arrangement (in particular the first directional control valve and / or the sequence valve and / or the summing valve) is controlled by the controller during the lowering phase so that this connection is closed.
[0016] The hydraulic drive preferably comprises an electric machine which is coupled to the hydraulic machine and the hydraulic pump (in order to drive them or to be driven by them, or is mechanically coupled to the drives, e.g. drive shafts, of the hydraulic machine and the hydraulic pump), wherein optionally the control 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 electrical energy recovered can, for example,stored in a battery.
[0017] The hydraulic drive preferably has a return directional control valve that is hydraulically connected to the return line and is hydraulically connectable or connected to the first chamber of the linear consumer and is configured (when connected to the linear consumer) 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 further preferably a proportional valve. Likewise, the controller is optionally configured to actuate the return directional control valve during the lowering phase, partially or completely opening the hydraulic passage between the return line and the first chamber. Outside of the lowering phase, the passage of the return directional control valve is preferably closed.Accordingly, outside of 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.
[0018] The hydraulic drive preferably has a circulation directional control valve that is hydraulically connected to the hydraulic pump working connection and a tank connection of the hydraulic pump and is configured to controllably close or at least partially open a hydraulic passage between the hydraulic pump working connection and the tank connection of the hydraulic pump. The circulation directional control valve is more preferably a proportional valve. Likewise, the control is preferably configured to actuate the circulation directional control valve during the lowering phase to partially or completely open the hydraulic passage between the hydraulic pump working connection and the tank connection. In the event that the at least one further consumer requires little or no power during the lowering phase, hydraulic neutral circulation losses can be avoided. This configuration is particularly advantageous when the hydraulic pump is a fixed displacement pump.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 circulation directional control valve.
[0019] Preferably, if the linear consumer has a second chamber, the hydraulic drive has a compensating directional valve that is hydraulically connectable or connected to the first chamber and the second chamber and that, when connected, is configured to controllably close or at least partially open a hydraulic passage between the first chamber and the second chamber. The compensating directional valve is further preferably a proportional valve. Likewise, the controller is preferably configured to actuate the compensating directional valve during the lowering phase to partially or completely open the hydraulic passage between the first chamber and the second chamber. The second chamber is, for example, the second chamber of a double-acting hydraulic cylinder. The second chamber can be filled accordingly with hydraulic fluid from the first chamber, so that no further supply of hydraulic fluid is necessary.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 which together cause the movement (raising / lowering) of the element of the working machine.
[0020] Preferably, the switching valve and / or, if applicable, the control system is configured such that, outside of the lowering phase, the switching valve is or will be switched to the open state. The switching valve can, for example, be configured such that a spring or similar automatically switches it to the open state when no further control signal is present. Alternatively or additionally, active control could be provided by the control system.
[0021] Preferably, in each case if necessary, the return line directional control valve and / or if necessary the control is set up such that outside the lowering phase the hydraulic passage between the first chamber and the return line is closed, and / or the compensation directional control valve and / or if necessary the control is set up such that outside the lowering phase the hydraulic passage between the first chamber and the second chamber is closed, and / or the circulation directional control valve and / or if necessary the control is set up such that outside the lowering phase the hydraulic passage between the hydraulic pump working connection and the hydraulic pump tank connection is closed. Here too, it can be provided in each case, independently of one another, that the closed position is assumed automatically, e.g. by appropriate preload with a spring, if no other control is present, oralternatively or additionally, that a corresponding control is carried out by the control system.
[0022] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.
[0023] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.
[0024] The invention is illustrated schematically in the drawing using exemplary embodiments and is described in detail below with reference to the drawing.
[0025] Character description
[0026] Figure 1 shows a hydraulic drive according to a preferred embodiment of the invention.
[0027] Figure 2 shows a hydraulic drive according to another preferred embodiment of the invention.
[0028] Figure 3 shows the sequence of a preferred embodiment of the method according to the invention.
[0029] Detailed description of the drawing
[0030] Figure 1 shows a hydraulic drive according to a preferred embodiment of the invention. The hydraulic drive forms an open 2-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 drive shafts, are mechanically coupled to one another, i.e., they can be driven jointly. This coupling can be achieved, for example, via a drive shaft or a gear. The rotational speeds of the hydraulic machine 4 and the hydraulic pump 6 are therefore equal or at least have a certain relationship to one another.
[0031] The hydraulic machine 4 and the hydraulic pump 6 are preferably driven by an electric machine 12, which is connected to an electrical power supply, e.g., a DC voltage system and / or a battery, via an inverter 14. The inverter 14 can, for example, convert direct current from the electrical power supply into alternating current for the electric machine when the electric machine acts as an electric motor, and conversely, convert alternating current into direct current when the electric machine acts as an electric generator.
[0032] The hydraulic machine 4 is adjustable, i.e. the swivel angle of the hydraulic machine is adjustable. Furthermore, the hydraulic machine 4 can be swiveled through to zero, i.e. 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) hydromachine working connection 16 and a tank connection 18, which is connected here to a tank 20. In pump mode, the hydromachine, driven e.g. by the electric machine 12, generates a flow of hydraulic fluid (from the tank) from the tank connection 18 to the hydromachine working connection 16. In motor mode, a volume flow of hydraulic fluid from the hydromachine working connection 16 to the tank connection 18 generates a torque ora mechanical power on the drive axle of the hydraulic machine 4, with which the hydraulic pump 6 can be driven (at least partially) and, if excess mechanical power is generated, for example, the electric machine 12 can also be driven.
[0033] The hydraulic pump 6 here is a fixed-displacement pump and has a tank connection 23 (here hydraulically connected to the tank 20) and a hydraulic pump working connection 22. The hydraulic pump 6 is configured, when driven, to pump hydraulic fluid from the tank connection 23 to the hydraulic pump working connection 22. The directional valve arrangement 8 has a first valve input connection 24 and a second valve input connection 25, via which the directional valve arrangement can be supplied with hydraulic fluid. The directional valve arrangement 8 comprises a first directional valve 26 and at least one second directional valve 28, wherein the first directional valve 26 is hydraulically connected to the first valve input connection 24 and the at least one second directional valve 28 is hydraulically connected to the second valve input connection 25 (each not shown in detail). In general, the directional valve arrangement can comprise more than two directional valves.The directional valve arrangement shown is exemplified as a modular directional valve block comprising a plurality of directional valve sections that can be supplied with hydraulic fluid via inlet sections in which the valve inlet connections are provided. Each directional valve section corresponds to a directional valve with respective consumer connections. The directional valves of the individual directional valve sections can generally be actuated or controlled independently of one another. In Figure 1, the directional valves each have, by way of example, two consumer connections; in general, the directional valves can also have a different number of consumer connections independently of one another, i.e., they generally have at least one consumer connection.If the valve block is not modular but constructed as a (at least partially) uniform unit, the valve block is designed to implement the functionalities described below in connection with the directional valve arrangement.
[0034] 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 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 controlled, to fully or partially open or block hydraulic passages or connections from the valve input ports to the consumer ports, so that the flow of hydraulic fluid to each of the consumer ports or to consumers connected thereto can be controlled.
[0035] As already explained above, it can be provided that the first consumer connection 34 is hydraulically connectable to the second valve input connection 25 and / or that the at least one further consumer connection is hydraulically connectable to the first valve input connection (via at least one suitable connection valve and / or at least one suitable summing valve and / or a corresponding functionality of the directional control valves).
[0036] The hydraulic pump working port 22 is hydraulically connected to the second valve input port 25.
[0037] The hydraulic machine working port 16 is connected to the first valve input port 24 via the switching valve 10. The switching valve 10 can be switched into a through state (state shown in the figure) and a blocking state. In the 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 input port 24, thus hydraulic fluid can flow between these ports. In the blocking 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 input port 24, thus no hydraulic fluid can flow between these ports. The switching valve 10 can be actuated electrically or electromagnetically, for example, whereby in a further advantageous embodiment, the switching valve 10 can also be actuated electro-hydraulically, e.g.so-called pressure control elements can be controlled or actuated.
[0038] 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.
[0039] Likewise, a further hydraulic consumer 32 (here, for example, also a differential cylinder) is shown, which is hydraulically connected to the at least one second directional control valve 28. Generally, more than the additional consumers 32 shown can be provided, which are hydraulically connected to corresponding second directional control valves. Thus, at least one further hydraulic consumer is provided, which can also be referred to as at least one second hydraulic consumer or as a secondary hydraulic consumer.
[0040] The linear consumer 30 is configured, in particular arranged on a work machine in which the hydraulic drive is used, such that when hydraulic fluid is directed into the first chamber 38 of the linear consumer 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 work machine. The load is lifted against the effect of gravity, assuming a normal working position of the work machine. The hydraulic fluid in the first chamber is under a corresponding pressure (caused by the load).
[0041] Between the first chamber 38 of the linear consumer 30 and the hydraulic machine working connection 16 of the hydraulic machine 4, a return directional control valve 42, which here is a 2 / 2-way valve with intermediate position (proportional valve), is preferably provided. One connection of the return directional control valve is hydraulically connected to the first chamber, and the other connection of the return directional control valve is hydraulically connected to the hydraulic machine working connection 16 via a return line 46. The return directional control valve 42 is adjustable between a closed end position and an open end position, wherein 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 connection, and upon adjustment towards the open end position, a through opening is increasingly opened orthe return directional control valve 42 is increasingly opened so that a hydraulic connection exists between the first chamber and the return line or the hydraulic machine working connection and is released with increasing cross-section. In the open end position, the through opening is completely open. The return directional control valve 42 or its adjustment is, for example, electrically controllable, i.e. the return directional control valve 42 can be actuated electrically or electromagnetically, wherein in a further advantageous embodiment the return directional control valve 42 can also be opened or actuated electro-hydraulically, for example by so-called pressure control elements. The closed end position can be a position that is assumed automatically (in particular outside the lowering phase, when no further control signal is present), for example, as illustrated, by a preload element (e.g. spring) that causes a movement into the closed end position.
[0042] When the control valve 10 is closed and the return directional control valve 42 is (at least partially) open, pressurized hydraulic fluid is directed from the first chamber 38 of the linear consumer 30 through the return directional control valve 42 and the return line 46 to the hydraulic machine's working port 16, so that the hydraulic machine 4 can be operated as a motor to convert hydraulic energy into mechanical energy (torque, speed). The load is reduced accordingly, so that potential energy is converted into mechanical energy. The mechanical energy is used to drive the hydraulic pump 6 or the generator-operated electric machine 12. Overall, a regenerative lowering of a load lifted by the linear consumer takes place during a lowering phase.
[0043] The first directional control valve 26 is controlled during regenerative lowering such that no hydraulic connection exists between the first valve input port 24 and the first consumer port 34. If the first consumer port 34 is hydraulically connectable to the second valve input port 25, this connection is closed during regenerative lowering, and the directional control valve arrangement is controlled during regenerative lowering such that no hydraulic connection exists between the second valve input port 25 and the first consumer port 34. Preferably, the first directional control valve 26 is additionally controlled during regenerative lowering such that no hydraulic connection exists between the first valve input port 24 and the second consumer port 36 (if the directional control valve arrangement is configured to allow such a connection).
[0044] 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 valve arrangement with hydraulic fluid via the second valve inlet connection 25.
[0045] Furthermore, a compensating directional control valve 44 is preferably provided, which here is a 2 / 2-way valve with an intermediate position, which is arranged between the first chamber 38 and the second chamber 40. One connection of the compensating directional control valve is hydraulically connected to the first chamber (and thus also to the first consumer connection), and the other connection of the compensating directional control valve is hydraulically connected to the second chamber (and thus also to the second consumer connection). The compensating directional control valve 44, like the return directional control valve 42, is adjustable between a closed end position (no hydraulic connection between the first and second chambers) and an open end position, wherein a passage is increasingly opened starting from the closed end position in which the passage is closed (hydraulic connection with an increasing cross-section between the first and second chambers). The compensating directional control valve 44 is, for example, electrically or.Electromagnetically actuated, whereby in a further advantageous embodiment, the compensating directional control valve 44 can also be controlled or actuated electro-hydraulically, for example, by so-called pressure control elements. The closed end position can be a position that is automatically assumed (particularly outside the lowering phase, when no further control signal is present), for example, as illustrated, by a biasing element (e.g., spring) that causes a movement into the closed end position.
[0046] The compensating directional valve 44 allows hydraulic fluid to be directed between the chambers. In particular, during regenerative lowering, hydraulic fluid can be directed from the first chamber to the second chamber, eliminating the need for a supply via the first directional valve or the directional valve assembly 8, which is hydraulically supplied only by the hydraulic pump due to the closed switching valve.
[0047] During regenerative lowering, the speed of the lowering can be controlled by appropriately controlling the return directional control valve 42 and / or the compensating directional control valve 44, ie by controlling the cross sections of the respective passages.
[0048] The compensating directional control valve 44 is designed as a separate valve here. Alternatively, the compensating directional control valve or its functionality could also be integrated into the first directional control valve 26.
[0049] 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 supplied with pressurized hydraulic fluid, whereby only the first consumer connection, which is connectable or connected to the first chamber, is provided on the first directional control valve, and the second consumer connection can be omitted). In this case, the compensating directional control valve 44 can be omitted.
[0050] Furthermore, a bypass directional control 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 directional control 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 directional control valve is hydraulically connected to the tank port 23 of the hydraulic pump 6 (and thus also to the tank).The bypass directional valve 48, like the return directional valve 42 and the compensating directional 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, with a passage being increasingly opened starting from the closed end position in which the passage is closed (hydraulic connection with increasing cross-section between the hydraulic pump working port 22 and the tank port 23). The bypass directional valve 48 can be actuated electrically or electromagnetically, for example. In a further advantageous embodiment, the bypass directional valve 48 can also be controlled or actuated electro-hydraulically, for example by so-called pressure control elements.If, during a regenerative lowering of the at least one further consumer 32, no or only a small amount of hydraulic power is required, the circulation directional control valve 48 can be controlled to assume an at least partially open position. This is expedient because it allows neutral circulation losses to be reduced. The closed end position can be a position that is assumed automatically (particularly outside the lowering phase, when no further control signal is present), for example, as illustrated, by a biasing element (e.g., spring) that causes a movement into the closed end position.
[0051] The hydraulic drive can further comprise an (electronic) controller 50 configured to control the hydraulic machine 4, the switching valve 10, and the directional control valve arrangement 8 or the first directional control valve 26, and optionally the at least one second directional control valve 28. Furthermore, the controller 50 can be configured to control, where present, the electric machine 12 or the inverter 14, the return directional control valve 42, the compensating directional control valve 44, and the circulation directional control valve 48. In any case, control can be effected via corresponding control lines (not shown). The controller 50 is configured to control the switching valve 10 during a regenerative lowering or during a lowering phase, so that it is switched to the locked state, and to control the adjustable hydraulic machine 4 or its swivel angle, so that the hydraulic machine 4 acts as a hydraulic motor.The swivel angle is swung through zero, so that the hydraulic machine generates a torque on the drive shaft for a given direction of rotation. Furthermore, the controller 50 controls the return directional control valve 42 to switch to an at least partially open position. During regenerative lowering, the controller 50 also controls the first directional control valve 26 to switch to a state in which there is no hydraulic connection between the first valve input port 24 and the first consumer port 34. Likewise, if necessary, the compensating directional control valve 44 is controlled to switch to an at least partially open position. The lowering speed can be controlled by a suitable selection of the open position of the return directional control valve 42 and, if necessary, the open position of the compensating directional control valve 44.
[0052] If no or only little hydraulic power is required by the at least one second consumer 32 during the regenerative lowering, the controller 50 can optionally control the circulation valve 48 to switch to an at least partially open position.
[0053] During regenerative lowering (i.e., during the lowering phase), the controller 50 may, if necessary, 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 power output (regenerated) by the hydraulic machine 4 exceeds the power absorbed by the hydraulic pump 6 during regenerative lowering, the electric machine 12 may act as an electric generator.
[0054] Figure 2 shows a hydraulic drive according to another preferred embodiment of the invention. This essentially corresponds to the embodiment shown in Figure 1, so only differences will be discussed below, and otherwise reference is made to the description of Figure 1.
[0055] In contrast to Figure 1, the hydraulic pump 6 in the embodiment of Figure 2 is an adjustable hydraulic pump. Furthermore, no bypass directional control valve is provided. Since the hydraulic pump 6 is adjustable, the delivery volume flow of the hydraulic pump (at a given speed) can be adjusted, for example, in accordance with a pivot angle of the hydraulic pump 6. In particular, if the at least one additional consumer 32 requires little or no hydraulic power during regenerative lowering, the pivot angle of the hydraulic pump 6 can be adjusted to zero or close to zero, so that no or only a small delivery volume flow is generated. Accordingly, neutral circulation losses in the hydraulic drive of Figure 2 can be reduced even without a bypass directional control valve.
[0056] In the embodiment of Figure 2, the controller 50 is preferably configured to control the hydraulic pump 6 or its pivot angle. If no or only little hydraulic power is required by the at least one second consumer 32 during the regenerative lowering, unlike in Figure 1, where the circulation directional control valve is at least partially opened, the controller 50 can adjust the pivot angle of the adjustable hydraulic pump to zero or close to zero, i.e., control the adjustable hydraulic pump accordingly.
[0057] Figure 3 shows the sequence of a preferred embodiment of the method according to the invention. It shows steps performed during a lowering phase. This method is for the regenerative lowering of an element of a work machine driven by a hydraulic drive according to the invention (e.g., as shown in Figures 1 to 2). The supply or discharge of hydraulic fluid to or from the linear consumer causes the element to be raised or lowered, respectively.
[0058] In step 100, the switching valve is switched to the blocking state. In step 110, a volume flow 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 input port to the first consumer port is closed. In step 130, the pivot angle of the hydraulic machine is changed so that it acts as a hydraulic motor. These steps are essentially carried out simultaneously or overlappingly. For a description of the effect of these steps, reference is made to the description of Figures 1 to 2. As already explained, the aforementioned steps can be carried out or initiated, in particular, by the control of the hydraulic drive.
Claims
Claims 1. Hydraulic drive for a work machine, which has a hydraulic linear consumer (30) and at least one further hydraulic consumer (32), wherein the linear consumer has a first chamber (38) and is arranged such that a volume flow of pressurized hydraulic fluid into or out of the first chamber causes an element of the work machine to be raised or lowered, comprising an adjustable hydraulic machine (4) which can be pivoted through zero, and a hydraulic pump (6), the drives of which are mechanically coupled, 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 input port (24), a second hydraulic valve input port (25), a first hydraulic consumer port (34) which is hydraulically connectable or connected to the first chamber (38) of the linear consumer, and at least one further hydraulic consumer port which is hydraulically connectable or connected to the at least one further consumer, wherein the first hydraulic valve input port (24) is controllably hydraulically connected to the first hydraulic consumer port (34) and the second hydraulic valve input port (25) is controllably hydraulically connected to the at least one further hydraulic consumer port, and wherein the hydraulic pump working port (22) is hydraulically connected to the second valve input port (25);a switching valve (10) hydraulically connected between the hydraulic machine working port (16) and the first valve input port (24), and switchable into a pass-through state, in which the first valve input port and the hydraulic machine working port are hydraulically connected, and into a blocking state, in which the first valve input port and the hydraulic machine working port are hydraulically separated; wherein the hydraulic machine working port is hydraulically connected to a return line (46) configured to receive a volume flow of pressurized hydraulic fluid from the first chamber (38) of the linear consumer, when connected, during a lowering phase; 2. Hydraulic drive according to claim 1, the valve block comprises a directional valve arrangement (8) with the first hydraulic valve input connection (24) and the second hydraulic valve input connection (25); wherein the directional valve arrangement (8) comprises a first directional valve (26), on which the first hydraulic consumer connection (34) is provided, and at least one second directional valve (28), on which the at least one further hydraulic consumer connection is provided; wherein the first directional valve (26) is hydraulically connected to the first valve input connection (24), wherein the at least one second directional valve (28) is hydraulically connected to the second valve input connection (25).
3. Hydraulic drive according to claim 1 or 2, comprising a controller (50) which is designed to control the switching valve (10) during the lowering phase, to switch it to the blocking state, to control the valve block, in particular the first directional control valve (26), so that a hydraulic connection from the first valve inlet connection (24) to the first consumer connection (24) is closed, and to control the hydraulic machine (4) to change the pivot angle so that it can be or is operated as a hydraulic motor.
4. Hydraulic drive according to one of the preceding claims, further comprising an electric machine (12) coupled to the hydraulic machine (4) and the hydraulic pump (6); wherein, as far as dependent 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 such that the electric machine acts as an electric generator during the lowering phase.
5. Hydraulic drive according to one of the preceding claims, comprising a return-line directional control valve (42) which is hydraulically connected to the return line (46) and is hydraulically connectable or connected 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 control valve (42) is preferably a proportional valve; and / or wherein, as far as dependent on claim 3, the controller (50) is preferably configured to control the return line directional control valve (42) during the lowering phase to partially or completely open the hydraulic passage between the return line (46) and the first chamber (38).Hydraulic drive according to one of the preceding claims, comprising a circulation directional control valve (48) which is hydraulically connected to the hydraulic pump working connection (22) and a tank connection (23) of the hydraulic pump and is designed to controllably 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; wherein the circulation directional control valve (48) is preferably a proportional valve; and / or wherein, as far as dependent on claim 3, the controller (50) is preferably designed to actuate the circulation directional control valve (48) during the lowering phase to partially or completely open the hydraulic passage between the hydraulic pump working connection (22) and the tank connection (23) of the hydraulic pump.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 compensating directional control valve (44) which is hydraulically connectable or connected to the first chamber (38) and the second chamber (40) and which, when connected, is configured to controllably selectively close or at least partially open a hydraulic passage between the first chamber and the second chamber; wherein the compensating directional control valve (44) is preferably a proportional valve; and / or wherein, as far as dependent on claim 3, the controller (50) is preferably configured to actuate the compensating directional control valve (44) during the lowering phase to partially or completely open the hydraulic passage between the first chamber (38) and the second chamber (40).Hydraulic drive according to one of the preceding claims, wherein the switching valve (10) and / or, as dependent on claim 3, the control (50) is configured such that outside the lowering phase the switching valve is or will be switched to the pass-through state. Hydraulic drive according to one of the preceding claims, wherein the return directional control valve (42) and / or, as dependent on claim 3, the controller (50) is configured such that, outside the lowering phase, the hydraulic passage between the first chamber (38) and the return line (46) is closed, and / or the compensating directional control valve (44) and / or, as dependent on claim 3, the controller (50) is configured such that, outside the lowering phase, the hydraulic passage between the first chamber (38) and the second chamber (40) is closed, and / or the circulation directional control valve (48) and / or, as dependent on claim 3, the controller (50) is configured such 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.Hydraulic drive according to one of the preceding claims, wherein the first consumer connection (34), in particular the first directional control valve, is hydraulically connectable to the second valve input connection (25); wherein, as far as dependent on claim 3, the controller (50) is preferably configured to control the directional control valve arrangement during the lowering phase such that there is no hydraulic connection between the first consumer connection (34) and the second valve input connection (25). Method for the regenerative lowering of an element of a work machine which has a hydraulic linear consumer (30) and at least one further hydraulic consumer (32), wherein the linear consumer has a first chamber (38) and is arranged such that a volume flow of pressurized hydraulic fluid into or out of the first chamber causes a lifting or lowering.causes a lowering of the element of the work machine, wherein the work machine has a hydraulic drive according to one of the preceding claims; wherein during a lowering phase the switching valve is switched to the blocking state (100), a volume flow of hydraulic fluid is conducted 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 pivoting angle of the hydraulic machine (4) is changed (130) so that it acts as a hydraulic motor. Method according to claim 10, wherein during the lowering phase a hydraulic passage between the first chamber (38) and the return line (46) is partially or completely opened; in particular using a return line directional control valve (42). Method according to one of claims 10 or 11, 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 compensating directional control valve (44). Method according to one of claims 10 to 12, 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 completely opened; in particular using a circulation directional control valve (48).Method according to one of claims 10 to 13, wherein outside the lowering phase, the switching valve (10) is switched to the pass-through 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.