DE102022206509A1 - Hydraulic drive and method for regenerative lowering of an element of a work machine - Google Patents

Abstract

The invention relates to a hydraulic drive for a work machine, which has a hydraulic linear consumer (30) with a first chamber (38) and at least one further hydraulic consumer (32), comprising: a hydraulic machine (4) which can be pivoted to zero and a hydraulic pump (4) mechanically coupled thereto ( 6), a valve block with a first hydraulic valve input connection (24), a second hydraulic valve input connection (25), a first hydraulic consumer connection (34), which can be hydraulically connected or is connected to the first chamber (38) of the linear consumer , and at least one further hydraulic consumer connection, which is hydraulically connectable or connected to the at least one further consumer, wherein the first hydraulic valve input connection (24) is hydraulically connected in a controllable manner to the first hydraulic consumer connection and the second hydraulic valve input connection is hydraulically connected in a controllable manner to the at least one further hydraulic consumer connection, and wherein a hydraulic pump working connection (22) is connected to the second valve inlet connection, and a switching valve (10) which is connected between a hydraulic machine working connection (16) and the first valve input port is connected, and which can be switched into a passage state and into a blocking state, the hydraulic machine working port being 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

The present invention relates to a hydraulic drive and a method for regenerative lowering of an element of a work machine.

Background of the invention

Mobile work machines, such as excavators, telehandlers, reach stackers, and others, have booms with which heavy loads can be lifted and then lowered again after the load has been transported or moved. Depending on the application, the lowering process can take place very quickly and can be positioned less precisely, or it can be carried out more slowly and can be positioned more precisely. As a rule, a load is lowered dissipatively by setting a volume flow via an adjustable aperture, through which the speed can be controlled very well.

Disclosure of the invention

According to the invention, a hydraulic drive for or in a work machine and a method for regenerative lowering of an element of a work machine with the features of the independent patent claims are proposed. Advantageous refinements are the subject of the subclaims and the following description. The embodiments and advantages described below apply equally to the drive and the method.

The proposed drive and control arrangements can expand existing systems in such a way that a regenerative lowering of an active load is possible and the potential energy can be recovered in significant parts. The arrangement can ensure that additional consumers can continue to be controlled. The solution presented can in particular be designed to be modular as a possible platform and transferable to various applications. To realize these advantages, a return line is provided in a hydraulic drive between a linear consumer, e.g. lifting cylinder, and the hydraulic machine in order to return hydraulic fluid (hydraulic fluid, e.g. hydraulic oil) to drive the hydraulic machine, and at the same time a switching valve between the hydraulic machine and the valve block (directional valve arrangement). to block the connection of the hydraulic machine to the valve block. When the switching valve is closed, i.e. the switching valve is in the locked state, hydraulic fluid flowing back from the first consumer can be used to drive the hydraulic machine, which, since it can be pivoted to zero, can also act as a hydraulic motor. Hydraulic power is therefore 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 of a load, such as an element (e.g. boom) of a work machine, which causes a return flow of pressurized hydraulic fluid when lowered.

The hydraulic drive is provided for or in a work machine which has a hydraulic linear consumer and at least one further hydraulic consumer, the linear consumer having a first chamber and being arranged in such a way that a volume flow of pressurized hydraulic fluid into the first chamber causes a movement of a Element (lifting 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 in particular has 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, the pressurization of which causes the same movement (e.g. a boom of an excavator, which is moved by two hydraulic cylinders). For simplicity, these multiple chambers (if any) are collectively viewed as the first chamber within the scope of this description (e.g. as the first chamber, which includes 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 has an adjustable hydraulic machine, which can be pivoted to zero (i.e. a pivot angle of the hydraulic machine can assume both positive and negative values), and a hydraulic pump, the drives of which are mechanically coupled (mechanical energy or power can therefore be transferred between the hydraulic machine and the hydraulic pump). The mechanical coupling takes place in particular via a shaft and/or a gear. A hydraulic machine is a hydraulic machine that can act as both a hydraulic pump and a hydraulic motor, depending on the set (positive/negative) swivel angle. The hydraulic pump can only act as a hydraulic pump, so if it is an adjustable pump it cannot be pivoted to zero.

A valve block, which can also be referred to as a main valve, is provided, which has a first hydraulic valve inlet connection, a second hydraulic valve inlet input connection, a first hydraulic consumer connection (or output connection), which can be hydraulically connected or connected to the first chamber of the linear consumer, and at least one further hydraulic consumer connection (or output connection), which can be hydraulically connected or connected to the at least one further consumer is, has. The first hydraulic valve input port is hydraulically connected to the first hydraulic consumer port in a controllable manner and the second hydraulic valve input port is hydraulically connected to the at least one further hydraulic consumer port in a controllable manner. The term “controllable” refers to the fact that the valve block can be controlled so that the hydraulic connection is adjustable between a closed and an open state. The valve block can, for example, be a single structural unit, for example viewed as a single (main) valve, or can be constructed modularly from several components, for example individual (sub-)valves.

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 at least one further hydraulic consumer connection is provided. The first directional control valve is hydraulically connected to the first valve input port and the at least one second directional control valve is hydraulically connected to the second valve input port. The directional valves of the directional valve arrangement can therefore be supplied with hydraulic fluid independently of one another (i.e. 2-circuit hydrosystem) via the valve input connections, which can be passed on to different consumers through the directional valves. The directional valve arrangement is an example of a modular design of the valve block.

In addition, it can be provided that the first consumer connection, in particular the first directional control valve, can be hydraulically connected to the second valve input connection. For this purpose, a switching 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 connection or summing valve. It is also conceivable that this functionality may be integrated into the first directional control valve. The first directional control valve is then hydraulically connected directly to the second valve input connection. Such configurations can be useful 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, can be hydraulically connected to the first valve inlet connection. For this purpose, a switching 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.

The hydraulic fluid is supplied by the hydraulic machine and the hydraulic pump. The hydraulic pump working connection is (directly) hydraulically connected to the second valve input connection. A switching valve is arranged in the connection between the hydraulic machine working port and the first valve input port or is hydraulically connected between the hydraulic machine working port and the first valve input port, which is in a passage state in which the first valve input port and the hydraulic machine Working port are hydraulically connected, and can be switched into a blocking state in which the first valve input port and the hydraulic machine working port are hydraulically separated. If there is no regenerative lowering or outside 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 using the linear consumer.

Furthermore, the hydraulic machine working connection is hydraulically connected to a return line, which is set up to produce a volume flow of pressurized hydraulic fluid from the first chamber of the linear consumer during the lowering phase when it is connected (i.e. when the first chamber is hydraulically connected to the hydraulic drive is). A suitable means (e.g. valve) can be provided on the linear consumer, which prevents a volume flow outside the lowering phase into the return line. Deviating from this, a return line directional control valve is preferably provided as part of the hydraulic drive (see below).

The hydraulic drive preferably has a control which is set up to control the switching valve during the lowering phase, to switch the valve block to the blocking state (in particular the first directional control valve) to control so that a hydraulic connection from the first valve input connection to the first consumer connection is closed, and to control the hydraulic machine to change the pivot angle so that it can or will be operated as a hydraulic motor. These steps take place simultaneously or at least overlapping. If the first consumer connection or the first directional valve can be hydraulically connected to the second valve input connection, the valve block or the directional valve arrangement (in particular the first directional valve and/or the switching valve and/or the summing valve) is controlled by the control during the lowering phase, so that this connection is closed.

The hydraulic drive preferably has an electrical 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, the hydraulic machine and the hydraulic pump), wherein If necessary, the control is further preferably set up to control the electrical machine and / or an inverter of the electrical machine, in particular so that the electrical machine acts as an electrical generator during the lowering phase. The use of an electric machine to drive the hydraulic machine and the hydraulic pump is advantageous because when the power recovered by the hydraulic machine exceeds the power required by the hydraulic pump, the excess power from the electric machine, which can be operated as a generator, converts into electrical power can be changed. The electrical energy obtained can be stored in a battery, for example.

Preferably, the hydraulic drive has a return line directional control valve which is hydraulically connected to the return line and is hydraulically connectable or connected to the first chamber of the linear consumer and is set up (when connected to the linear consumer) to provide a hydraulic passage between the return line and to close or at least partially open the first chamber in a controllable and/or adjustable manner. The return directional control valve is further preferably a proportional valve. Also more preferably, the control is optionally set up to control the return line directional control valve during the lowering phase and to partially or completely open 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, no hydraulic fluid can flow from the linear consumer to the hydraulic machine working connection outside of the lowering phase. If the return line directional valve is a proportional valve (i.e. has intermediate positions), the volume flow from the linear consumer to the hydraulic machine working connection and thus the lowering speed can be controlled.

The hydraulic drive preferably has a circulation directional control valve which is hydraulically connected to the hydraulic pump working connection and a tank connection of the hydraulic pump and is designed to selectively close a hydraulic passage between the hydraulic pump working connection and the tank connection of the hydraulic pump in a controllable manner or at least partially open. The circulation directional control valve is further preferably a proportional valve. Also more preferably, the control is set up to control 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 additional consumer requires little or no power during the lowering phase, hydraulic neutral circulation losses can be avoided. This configuration is particularly advantageous if 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.

Preferably, if the linear consumer has a second chamber, the hydraulic drive has a compensating directional control valve that is hydraulically connectable or connected to the first chamber and the second chamber and which, when connected, is designed to provide a hydraulic passage between the first Chamber and the second chamber can either be closed or at least partially opened in a controllable manner. The compensating directional control valve is further preferably a proportional valve. Also more preferably, the control is set up to control the compensating directional control valve during the lowering phase and to partially or completely open the hydraulic passage between the first chamber and the second chamber. The second chamber is approximately 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 work machine.

Preferably, the switching valve and/or possibly the control is set up so that outside the lowering phase, the switching valve is or is switched to the open state. The switching valve can, for example, be set up in such a way that it is automatically switched to the open state by a spring or similar if no further control signal is present. Alternatively or additionally, active control could be carried out by the controller.

Preferably, in each case where appropriate, the return line directional valve and/or optionally the control is set up so that outside the lowering phase the hydraulic passage between the first chamber and the return line is closed, and/or is the compensation directional valve and/or optionally the control set up so 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 optionally the control is set up so 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, independently of one another, that the closed position is assumed automatically, for example by a corresponding preload with a spring, if no other control is present, or alternatively or additionally that a corresponding control is carried out by the control.

Further advantages and refinements of the invention result from the description and the accompanying drawing.

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 alone, without departing from the scope of the present invention.

The invention is shown schematically in the drawing using exemplary embodiments and is described in detail below with reference to the drawing.

Character description

• 1 shows a hydraulic drive according to a preferred embodiment of the invention.
• 2 shows a hydraulic drive according to another preferred embodiment of the invention.
• 3 shows the sequence of a preferred embodiment of the method according to the invention.

Detailed description of the drawing

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, that is, they can be driven together. This coupling can take place, for example, via a drive shaft or a gearbox. The speeds of the hydraulic machine 4 and the hydraulic pump 6 are therefore the same or at least have a certain relationship to one another.

The hydraulic machine 4 and the hydraulic pump 6 are preferably driven by an electrical machine 12, which is connected via an inverter 14 to an electrical energy supply, for example a DC voltage system and/or a battery. The inverter 14 can, for example, convert direct current from the electrical power supply into alternating current for the electrical machine when the electrical machine acts as an electric motor, and vice versa convert alternating current into direct current when the electrical machine acts as an electrical generator.

The hydraulic machine 4 is adjustable, i.e. a pivot angle of the hydraulic machine is adjustable. Furthermore, the hydraulic machine 4 can be swiveled to zero, so 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) hydraulic machine working connection 16 and a tank connection 18, which is connected here to a tank 20. In pump operation, the hydraulic machine, for example driven by the electric machine 12, generates a flow of hydraulic fluid (from the tank) from the tank connection 18 to the hydraulic machine working connection 16. In motor operation, a volume flow of hydraulic fluid from the hydraulic machine working connection 16 to the tank connection 18 generates a torque or a 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 electrical machine 12 can also be driven.

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 set up, 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 inlet connection 24 and a second valve inlet connection 25, via which the directional valve arrangement can be supplied with hydraulic fluid. The directional control valve arrangement 8 includes 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 input connection 24 and the at least one second directional control valve 28 is hydraulically connected to the second valve input connection 25 (each in Not shown individually). In general, the directional control valve arrangement can include more than two directional control valves. The directional valve arrangement shown is designed, for example, as a modular directional valve block, which can supply several directional valve sections, which can be supplied with hydraulic fluid via input sections in which the valve input 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 operated or controlled independently of one another. The directional control valves point in 1 For example, each has two consumer connections; in general, the directional control valves can also have a different number of consumer connections independently of one another, that is, in general they have at least one consumer connection. If the valve block is not constructed modularly, but rather as a (at least partially) uniform structural unit, the valve block is set up to implement the functionalities that are described below in connection with the directional control valve arrangement

In the embodiment shown, the first directional control valve 26 and the at least one second directional control valve 28 each have two consumer connections, i.e. hydraulic connections to which hydraulic lines that lead to respective consumers can be connected. The first directional control valve 26 and the at least one second directional control valve 28 are designed to completely or partially open or block hydraulic passages or connections from the valve input connections to the consumer connections, depending on how they are controlled, so that the flow of hydraulic fluid can be controlled to each of the consumer connections or to consumers connected to them.

As already explained above, it can be provided that the first consumer connection 34 can be hydraulically connected to the second valve input connection 25 and/or that the at least one further consumer connection can be hydraulically connected to the first valve input 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).

The hydraulic pump working port 22 is hydraulically connected to the second valve input port 25.

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 an open state (state shown in the figure) and a blocked state. In the open 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, so hydraulic fluid can flow between these ports. In the blocked 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, so no hydraulic fluid can flow between these ports. The switching valve 10 can be actuated electrically or electromagnetically, for example, and in a further advantageous embodiment the switching valve 10 can also be controlled or actuated electro-hydraulically by, for example, so-called pressure control elements.

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. Here, consumer connections of the first directional control valve 26 are hydraulically connected to working connections or chambers of the linear consumer 30. Specifically, a first consumer connection 34 is hydraulically connected to a first chamber 38 and a second consumer connection 36 is hydraulically connected to a second chamber 40. The linear consumer can also be referred to as the first hydraulic consumer or as the hydraulic primary consumer.

Likewise, another hydraulic consumer 32 (also a differential cylinder here as an example) is shown, which is hydraulically connected to the at least one second directional control valve 28. In general, more consumers 32 than those shown can be provided, which are hydraulically connected to corresponding second directional control valves. So at least it's another hyd hydraulic consumer is provided, which can also be referred to as at least a second hydraulic consumer or as a hydraulic secondary consumer.

The linear consumer 30 is set up in such a way, in particular arranged on a work machine in which the hydraulic drive is used, that when hydraulic fluid is fed into the first chamber 38 of the linear consumer by appropriate control of the first directional control valve 26 (and corresponding hydraulic fluid from the second Chamber 40 is passed), a load is lifted (not shown). This can be done, for example, using a boom on the work machine. The load is lifted against the effect of gravity, assuming the machine is in a normal working position. The hydraulic fluid in the first chamber is under a corresponding pressure (caused by the load).

Between the first chamber 38 of the linear consumer 30 and the hydraulic machine working connection 16 of the hydraulic machine 4, a return line directional valve 42, which here is a 2/2-way valve with an intermediate position (proportional valve), is preferably provided. One port of the return line directional valve is hydraulically connected to the first chamber and the other port of the return line directional valve is hydraulically connected to the hydraulic machine working port 16 via a return line 46. The return line 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 at Adjustment in the direction of the open end position, a through opening is increasingly opened or the 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 as the cross section increases. 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, for example, whereby in a further advantageous embodiment the return directional control valve 42 can also be controlled electro-hydraulically by, for example, so-called pressure control elements. can be operated. The closed end position can be a position that is assumed automatically (in particular outside the lowering phase when there is no further control signal, for example, as illustrated, by a biasing element (e.g. spring) that causes a movement into the closed end position.

When the control valve 10 is closed and the return line directional valve 42 is (at least partially) open, pressurized hydraulic fluid is passed from the first chamber 38 of the linear consumer 30 through the return line directional valve 42 and the return line 46 to the hydraulic machine working connection 16, so that the hydraulic machine 4 as Motor can be operated 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 electrical machine 12. Overall, a regenerative lowering of a load lifted by the linear consumer takes place during a lowering phase.

The first directional control valve 26 is controlled during the regenerative lowering so that there is no hydraulic connection between the first valve input connection 24 and the first consumer connection 34. If the first consumer connection 34 can be connected hydraulically 25 to the second valve input connection, this connection is closed during the regenerative lowering, the directional valve arrangement is controlled during the regenerative lowering so that there is no hydraulic connection between the second valve input connection 25 and the first consumer connection 34 exists. Preferably, the first directional control valve 26 is additionally controlled during the regenerative lowering so that there is no hydraulic connection between the first valve input connection 24 and the second consumer connection 36 (if the directional control valve arrangement is set up so that such a connection can be established).

During regenerative lowering (closed control valve 10), the hydraulic supply of the 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 input connection 25.

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

The compensating directional control valve 44 allows hydraulic fluid to be directed between the chambers. In particular, it is possible to direct hydraulic fluid from the first into the second chamber during regenerative lowering, so that a supply via the first directional valve or the directional valve arrangement 8, which is only hydraulically supplied by the hydraulic pump due to the closed switching valve, is not necessary.

During regenerative lowering, the speed of lowering 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.

The compensation directional control valve 44 is designed here as a separate valve. Alternatively, the compensation directional control valve or its functionality could also be integrated in the first directional control valve 26.

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 connection that can be connected or connected to the first chamber being provided on the first directional valve and on the second consumer connection can be omitted). In this case, the compensation directional control valve 44 can be dispensed with.

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

The hydraulic drive can further comprise an (electronic) control 50, which is set up 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 set up to control the electrical machine 12 or the inverter 14, the return line directional control valve 42, the compensation directional control valve 44 and the circulation directional control valve 48, if available. In any case, control can take place via appropriate control lines (not shown).

The controller 50 is set up to control the switching valve 10 during a regenerative lowering or during a lowering phase, so that it is switched to the blocking state, and to control the adjustable hydraulic machine 4 or its pivot angle, so that the hydraulic machine 4 acts as a hydraulic motor. The swivel angle is swiveled through zero so that the Hyd romachine generates a torque on the drive shaft for a given direction of rotation. Furthermore, the return line directional valve 42 is controlled by the controller 50 to switch to an at least partially open position. During the 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 connection 24 and the first consumer connection 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 choice of the open position of the return line directional control valve 42 and, if necessary, the open position of the compensation directional control valve 44.

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.

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

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

In contrast to 1 is the hydraulic pump 6 of the embodiment 2 an adjustable hydraulic pump. Furthermore, no circulation 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, approximately corresponding to a pivot angle of the hydraulic pump 6. In particular, if during a regenerative lowering the at least one further consumer 32 requires little or no hydraulic power, 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, in the hydraulic drive the 2 Neutral circulation losses can be reduced even without a circulation directional control valve.

The controller 50 is in the embodiment 2 preferably set up 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 1 , where the circulation directional control valve is at least partially opened, the control 50 adjusts the pivot angle of the adjustable hydraulic pump to zero or close to zero, ie controls the adjustable hydraulic pump accordingly.

3 shows the sequence of a preferred embodiment of the method according to the invention. Steps that are carried out during a lowering phase are shown here. It is a method for the regenerative lowering of an element of a work machine, which is carried out by a hydraulic drive according to the invention (eg according to 1 until 2 ) is driven. A supply or removal of hydraulic fluid to the linear consumer causes the element to be raised or lowered.

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 inlet 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 overlapping. For a description of the effect of these steps, please refer to the description of 1 until 2 referred. As already explained, the steps mentioned can be carried out or initiated in particular by controlling the hydraulic drive.

Claims (15)

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 the first chamber or from the first chamber causes an element of the work machine to be raised or lowered, comprising an adjustable hydraulic machine (4) which passes through zero is pivotable, and a hydraulic pump (6), the drives of which are mechanically coupled, the hydraulic machine having a hydraulic machine working connection (16) and the hydraulic pump having a hydraulic pump working connection (22); a valve block with a first hydraulic valve input connection (24), a second hydraulic valve input connection (25), a first hydraulic consumer connection (34), which is hydraulically connectable or connected to the first chamber (38) of the linear consumer, and at least a further hydraulic consumer connection which is hydraulically connectable or connected to the at least one further consumer, wherein the first hydraulic valve input connection (24) is hydraulically connected in a controllable manner to the first hydraulic consumer connection (34) and the second hydraulic valve input connection (25) is hydraulically connected in a controllable manner to the at least one further hydraulic consumer connection, and wherein the hydraulic pump working connection (22) is hydraulically connected to the second valve input connection (25); a switching valve (10) which is hydraulically connected between the hydraulic machine working port (16) and the first valve input port (24), and which is in a passage state in which the first valve input port and the hydraulic machine working port are hydraulically connected, and can be switched to a blocking state in which the first valve input port and the hydraulic machine working port are hydraulically separated; wherein the hydraulic machine working connection is hydraulically connected to a return line (46) which is designed to receive a volume flow of pressurized hydraulic fluid from the first chamber (38) of the linear consumer during a lowering phase when this is connected. Hydraulic drive after Claim 1 , the valve block comprises a directional valve arrangement (8) with the first hydraulic valve inlet port (24) and the second hydraulic valve inlet port (25); wherein the directional control valve arrangement (8) comprises a first directional control valve (26), on which the first hydraulic consumer connection (34) is provided, and at least one second directional control valve (28), on which the at least one further hydraulic consumer connection is provided; wherein the first directional control valve (26) is hydraulically connected to the first valve input port (24), wherein the at least one second directional control valve (28) is hydraulically connected to the second valve input port (25). Hydraulic drive after Claim 1 or 2 , comprising a control (50) which is set up 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 input connection (24) to the first consumer connection (24) is closed, and the hydraulic machine (4) is controlled to change the pivot angle so that it can or will be operated as a hydraulic motor. Hydraulic drive according to one of the preceding claims, further comprising an electric machine (12) which is coupled to the hydraulic machine (4) and the hydraulic pump (6); whereby depends on Claim 3 the controller (50) is preferably set up to control the electrical machine (12) and/or an inverter (14) of the electrical machine, in particular so that the electrical machine acts as an electrical generator during the lowering phase. Hydraulic drive according to one of the preceding claims, comprising a return line directional 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 designed to provide a hydraulic to selectively close or at least partially open the passage between the return line (46) and the first chamber (38) in a controllable manner; wherein the return directional control valve (42) is preferably a proportional valve; and/or whereby depending on Claim 3 the control (50) is preferably set up 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 provide a hydraulic passage between the hydraulic pump working connection (22) and the tank connection (23) of the hydraulic pump in a controllable manner to either close or at least partially open; wherein the circulation directional control valve (48) is preferably a proportional valve; and/or whereby depending on Claim 3 the control (50) is preferably set up to control 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 balancing directional control valve (44) which is hydraulically connectable to the first chamber (38) and the second chamber (40) and which, when connected, is adapted to provide a hydraulic passage between the first chamber and to selectively close or at least partially open the second chamber in a controllable manner; wherein the compensating directional control valve (44) is preferably a proportional valve; and/or whereby depending on Claim 3 the control (50) is preferably set up to control the compensation 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 set up so that outside the lowering phase the switching valve is or is switched to the open state. Hydraulic drive according to one of the preceding claims, wherein the return directional valve (42) and / or as dependent on Claim 3 the control (50) is set up so 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 control valve (44) and / or as dependent on Claim 3 the control (50) is set up so 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 control (50) is set up so 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, can be hydraulically connected to the second valve input connection (25); whereby depends on Claim 3 the controller (50) is preferably set up to control the directional control valve arrangement during the lowering phase so 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 in the first chamber or from the first chamber causes the element of the work machine to be raised or lowered, the work machine having a hydraulic drive according to one of the preceding claims; whereby during a lowering phase the switching valve is switched to 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 input 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. Procedure 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 directional control valve (42). Procedure according to one of the Claims 10 or 11 , wherein the linear consumer (30) has a second chamber (40), a hydraulic passage between the first chamber (38) and the second chamber (40) being partially or completely opened during the lowering phase; in particular using a compensating directional control valve (44). Procedure according to one of the Claims 10 until 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). Procedure according to one of the Claims 10 until 13 , wherein outside the lowering phase, the switching valve (10) is switched to the open 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 hyd Ro pump working connection (22) and the hydraulic pump tank connection (23) is closed.

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