EP2985469B1 - Hydrostatic drive and valve device for same - Google Patents

Description

The invention relates to a hydraulic drive according to the preamble of patent claim 1.

For moving loads, in particular for lifting and lowering, a hydraulic cylinder, in particular a double-acting, is used. This has two piston chambers, which are separated by a piston. An external load acts on a piston rod connected to the piston. Basically, there is a need to be able to recover energy. This can be done, for example, when potential energy of an elevated load when lowering the load is free again.

For this purpose, the document shows DE 10 2012 003 320 A1 a hydrostatic drive in which hydraulic fluid flowing from the hydraulic cylinder can be passed via a valve device to a hydraulic motor and / or a hydraulic accumulator. About the hydraulic motor, a fan of an internal combustion engine can be driven. Pressure medium for driving this hydraulic motor or a hydraulic motor assisting the internal combustion engine can be taken from the hydraulic accumulator. Solutions are also known in which an electric generator or a flywheel can be driven via the outflowing pressure medium or the hydraulic accumulator receiving the pressure medium.

A disadvantage of this concept is that the hydraulic component receiving the outflowing pressure medium-that is to say the hydraulic motor or the hydraulic accumulator-must be designed for the maximum pressure medium volume flow occurring at the maximum speed of movement of the hydraulic cylinder. The same applies to a hydraulic pump of the drive, which is to be designed so that it can be nachgefördert about them in the enlarging piston chamber of the hydraulic cylinder sufficient pressure medium. Although the case of maximum movement speed comparatively rarely occurs, at most about half of the operating time, so hydraulic components large capacity must be kept, the bulk operating time far below their capacity, which adversely affects the cost and efficiency of the drive.

The publication DE 10 2008 034 301 A1 shows in this regard a solution with a regeneration of the effluent from the decreasing piston chamber pressure medium. Here, a direct pressure medium connection of the two piston chambers is proposed, so that a portion of the outflowing pressure medium, bypassing the hydraulic pump, can flow into the other piston chamber. Due to this regeneration, the hydraulic pump can be made smaller, which reduces the cost of the drive and in particular allows the operation of the hydraulic pump with higher efficiency, since the hydraulic pump can work because of their smaller size over a longer period of operation in the range of their maximum delivery volume.

Against this background of the prior art, there is a constant demand to prevent cavitation in the expanding piston chamber or at least to reduce the risk of cavitation.

In contrast, the invention is therefore the object of the invention to provide a generic hydrostatic drive, which is better protected against cavitation, which are reduced as a result, the cost.

In contrast, the invention is therefore the object of the invention to provide a generic hydrostatic drive, which is better protected against cavitation, which are reduced as a result, the cost.

This object is achieved by a hydrostatic drive having the features of patent claim 1.

Advantageous developments are described in the dependent claims.

A hydrostatic drive has a particularly double-acting hydraulic cylinder for moving, in particular for lifting and / or lowering, a load, and for recuperation (recovery) of hydraulic power of the hydraulic cylinder a hydraulic machine and / or a hydraulic accumulator. In particular, potential and / or kinetic energy of the load can be recovered via the hydraulic machine or the storage. In the hydraulic cylinder, two piston chambers are fluidly separated from each other by a piston, of which a piston chamber is fluidically connectable to the hydraulic machine and / or the reservoir via a first pressure medium connection. In addition, the drive has a second pressure medium connection via which the other piston chamber can be supplied with a partial volume flow of a discharge volume flow flowing away from a piston chamber. Furthermore, a third pressure medium connection connected in parallel with the second pressure medium connection is provided. Also via these, the other piston chamber can be supplied with a partial volume flow of the outflow volume flow of the one piston chamber. The third pressure medium connection has a third throttle device with an invention according to the pressure of the other piston chamber adjustable, third opening cross-section. The third pressure medium connection can thus be controlled via the third throttle device.

The movement of the load for a direction of movement of the piston forcibly leads to a reduction of the one piston chamber and to an enlargement of the other piston chamber. The pressure medium flowing out of the one piston chamber is proportionally conducted via the second pressure medium connection into the enlarging other piston chamber, which can be referred to as regeneration of pressure medium. A pressure medium source, in particular a hydraulic pump or a hydraulic accumulator, which is to be provided for providing the pressure medium volume flow for the other piston chamber, therefore no longer has to be designed for the maximum pressure medium volume flow of the other piston chamber due to the maximum movement speed. It can instead be designed smaller, so that investment and operating costs can be saved and the cost of the drive can be reduced. The previously discussed cavitation in the other piston chamber can be prevented according to the invention well over the third throttle device with the adjustable depending on the pressure of the other piston chamber third opening cross-section.

The third opening cross-section can preferably be controlled as a function of the increasing pressure of the other piston chamber, it being possible for the third opening cross-section to be openable as a function of the decreasing pressure of the other piston chamber.

The third throttle device has in a preferred development, in particular an adjustable pressure equivalent, with which the third throttle device, in particular a throttle body or valve body, is loaded in the direction of a control of the third opening cross-section. In this way, cavitation is prevented in the other piston chamber and the pressure in the other piston chamber is less than or equal to the set third pressure equivalent, so that a pressure gain is limited.

The second pressure medium connection proves to be particularly advantageous when the hydraulic cylinder is designed such that the partial volume flow can completely cover the pressure medium volume flow necessary for filling the other piston space. Then, this pressure medium volume flow is completely regenerated from the drain volume flow and it may even be considered to dispense entirely with a hydraulic pump.

Preferably, the hydraulic machine is formed via a hydraulic motor for converting hydraulic energy of the drain volume flow into mechanical energy. The mechanical energy can be used, for example, to drive other hydraulic machines, a generator, a flywheel or supporting the drive of an internal combustion engine. The stored pressure medium energy can be used offset in time if necessary.

The hydraulic machine can be designed with a constant or variable displacement volume.

The hydraulic machine can be designed as an axial piston machine in swash plates or Schrägachsenbauweise.

The swashplate design with adjustable displacement volume running hydraulic machine can be designed with swivel swash plate be, whereby a change between engine and pump operation, or vice versa, is made possible by a simple swinging.

A drive shaft of the hydraulic machine may be connected to a drive shaft of a diesel engine or an electric motor and / or generator or to a mechanical flywheel.

In order to be able to control and / or shut off the first pressure medium connection, in particular the outflow volume flow, the first pressure medium connection of the drive in a preferred development has a first throttle device with an adjustable, first opening cross section.

The first throttle device is preferably designed in such a way that it allows a substantially leak-free load hold in the non-actuated state of the hydraulic cylinder. For this purpose, the first throttle device is preferably designed as a continuously adjustable 2/2-way seat valve that is biased in a blocking position of its valve seat, in particular by a spring and actuated in the direction of flow positions. The actuation can be designed hydraulically, mechanically or electromagnetically.

Preferably, the first throttle device is attached directly to the hydraulic cylinder, in particular flanged, so that it can fulfill the function of a pipe rupture protection.

To move the load is preferably a double-acting differential cylinder. The piston then has a piston surface, of which the piston space is at least partially limited. Preferably, this is larger than another piston surface of the piston, of which the other piston chamber is at least partially limited. The regeneration from the piston chamber with the larger piston surface to the piston chamber with the smaller piston surface thus takes place via the second pressure medium connection.

Preferably, the hydraulic cylinder is designed such that the piston is connected to a piston rod, from which the other piston chamber is penetrated and at which the load acts.

In order to be able to influence the amount of the partial volume flow, the second pressure medium connection of the drive in a preferred development has a second throttle device with a second opening cross section which is adjustable as a function of the pressure of the piston space.

Particularly preferably, the second throttle device is designed such that its pressure drop, more precisely its flow resistance, via the second opening cross-section, at least when it is largely turned on, is low. The same applies preferably for the first opening cross-section of the first throttle device. This can be achieved in a piston chamber via the second pressure medium connection, the pressure gain. In a piston chamber then prevails due to the second pressure medium connection, a higher pressure than without the second pressure medium connection. Although the outflow volume flow is reduced by the partial volume flow, the possibility of the hydromachine and / or the hydraulic accumulator resulting from said pressure increase results smaller because this can now provide a required power or storage capacity at reduced flow rate but elevated pressure.

The lower the already mentioned flow resistance of the first throttle device, the more pressure medium energy is supplied via the drain volume flow of the hydraulic machine and / or the hydraulic accumulator.

In a preferred development, the second opening cross section can be controlled as a function of the increasing pressure of the one piston chamber, wherein it can be opened in dependence on the decreasing pressure of the one piston chamber. Particularly preferably, the second opening portion is controllable in this way in a predetermined interval of the pressure of a piston chamber. In this way, depending on the pressure of a piston chamber and depending on its tendency (rise, sink), the partial volume flow can be reduced or increased. The more the second opening cross-section is opened, the stronger the effect previously discussed pressure boost. At full zugesteuertem second opening cross section, however, the second pressure medium connection according to the invention is completely interrupted and the pressure gain comes to a standstill. In this way it is ensured that a predetermined maximum load can be held by the hydraulic cylinder.

Preferably, the control of the second opening cross-section by the second throttle device - in particular a throttle or valve body of the second throttle device - is loaded in the direction of a Zusteuerung the second opening cross section with the pressure of a piston chamber.

Counteracting the second throttle device in a preferred development, a lower or minimum pressure equivalent, with which it - in particular its throttle or valve body - is loaded in the direction of a control of the second opening cross-section. By way of the lower pressure equivalent, a limit value of the pressure of the one piston chamber can thus be preset, from which the second pressure medium connection is controlled. From this closing point, or from reaching this limit, the second opening cross-section is reduced with increasing pressure, whereby the partial volume flow is throttled.

In a preferred embodiment, the second throttle device is designed such that the second opening cross-section is substantially constant controlled as long as the pressure of a piston chamber is smaller than the lower pressure equivalent. Consequently, in this pressure range, the pressure of one piston chamber has no influence on the partial volume flow, and the advantages of pressure amplification and reduction of the pressure medium volume flow to be supplied by the hydraulic pump are fully realized.

In a preferred development, the second opening cross section can be controlled substantially in proportion to the increasing pressure of the one piston chamber, as long as the pressure of the one piston chamber rises above the lower pressure equivalent. Thus, the pressure gain in this pressure range is increasingly reduced.

In a preferred embodiment, the second throttle device has an upper pressure equivalent, with which it is loaded in the direction of a control of the second opening cross-section and which is greater than the first pressure equivalent. By way of the upper pressure equivalent, a closing pressure is thus established for the pressure of the one piston chamber, from which the second opening cross section has been closed and the partial volume flow has become approximately zero and the pressure boost is thereby switched off.

In the event that the second opening cross-section is closed, when the pressure of the one piston chamber is equal to or greater than the upper pressure equivalent, there is the problem that with continued movement of the piston cavitation threatens in the other piston chamber. For this case, the drive according to the invention, the third pressure medium connection and / or the previously discussed hydraulic pump is provided which can provide this Nachsaugvolumenstrom required and thereby prevents cavitation in the other piston chamber. In addition, the drive can be developed such that the second throttle device has a Restöffnungsquerschnitt as soon as the pressure of a piston chamber is approximately equal to the upper pressure equivalent or greater than this. By means of the residual opening cross section, sufficient pressure medium can then always be fed into the other, enlarging piston space.

Particularly preferably, the residual opening cross-section is designed such that in the other piston chamber a pressure is established which is limited and prevented by cavitation.

Device-technically simple, the lower and / or the upper pressure equivalent is formed via at least one compression spring. Particularly preferably, both mentioned pressure equivalents are formed by a common spring. Of course, other technical solutions, such as electromagnetic or hydraulic, for applying the pressure equivalents or possible.

Preferably, the lower pressure equivalent and / or the upper pressure equivalent is configured adjustable. In the case of the spring, the spring force is preferably adjustable.

In a preferred embodiment, the hydraulic pump is part of the hydrostatic drive. In particular, if the partial volume flow is insufficient to cover the pressure medium volume flow, which is required by the enlarging other piston chamber.

The drive is preferably used in a mobile work machine, since there due to always tight space and the requirement of a low vehicle weight fiction reduction of the hydromachine (due to the described pressure boost) and the hydraulic pump (due to the regeneration described) prove to be particularly advantageous.

A valve device of the hydrostatic drive, which is designed according to at least one of the aspects of the preceding description, is embodied in a further development in a compact block or disk construction. In this case, the valve device has the second throttle device with the second opening cross section, which is adjustable as a function of the pressure of the one piston chamber, via which the second pressure medium connection can be controlled. In addition, it has the second pressure medium connection connected in parallel, third pressure medium connection, via which the other piston chamber with the partial volume flow of the drain volume flow can be supplied. In the third pressure medium connection, the third throttle device is provided with the third opening cross-section which is adjustable as a function of the pressure of the other piston chamber and via which the third pressure medium connection can be controlled.

• Figur 1 einen hydrostatischen Antrieb mit Regeneration, und mit Rekuperation über eine Hydromaschine,
• Figur 2 einen hydrostatischen Antrieb mit Regeneration, und mit Rekuperation über einen Hydrospeicher,
• Figur 3 einen hydrostatischen Antrieb mit druckabhängig gesteuerter Regeneration,
• Figur 4 ein Ausführungsbeispiel eines hydrostatischen Antriebs,
• Figur 5 einen hydrostatischen Antrieb mit einer Regeneration mit Restöffnungsquerschnitt, und
• Figur 6 eine Ventilvorrichtung des Ausführungsbeispiels gemäß Figur 4 .

In the following two embodiments of a hydrostatic drive according to the invention are explained in detail. Show it:

• FIG. 1 a hydrostatic drive with regeneration, and with recuperation via a hydraulic machine,
• FIG. 2 a hydrostatic drive with regeneration, and with recuperation via a hydraulic accumulator,
• FIG. 3 a hydrostatic drive with pressure-controlled regeneration,
• FIG. 4 an embodiment of a hydrostatic drive,
• FIG. 5 a hydrostatic drive with a regeneration with residual opening cross-section, and
• FIG. 6 a valve device of the embodiment according to FIG. 4 ,

It is true that components which are designed to be identical over the drives and shown embodiments, are provided with the same reference numerals.

According to FIG. 1 a hydrostatic drive 1 has a hydraulic cylinder 2 for moving, in particular for lifting and / or lowering a load, which is symbolized by the designation F _L. In the example shown, the hydraulic cylinder raises and lowers the load F _L under the action of gravity in FIG. 1 in the direction of the arrow marked x acts. The hydraulic cylinder 2 has a piston 4 which is received axially displaceably in a housing 6 of the hydraulic cylinder 2. From the piston 4, a cylinder bottom side piston chamber 8 is fluidically separated from a piston rod side, other piston chamber 10 in the housing 6. The piston 4 has on the cylinder bottom side a piston surface 12, of which the one piston chamber 8 is limited in sections, and on the other hand another piston surface 14, of which the other piston chamber 10 is partially limited. On the side of the other piston surface 14, a piston rod 16 is attached to the piston 4, to which the load F _L attacks.

By way of a first pressure medium connection 18, one piston chamber 8 is connected to a working connection of a hydraulic machine 20 designed as a hydraulic motor with an adjustable displacement. The first pressure medium connection 18 has a first throttle device 22 with an adjustable, first opening cross-section, via which the first pressure medium connection 18 can be opened and closed. The other piston chamber 10 is connected to a working port of a hydraulic displacement pump 24 configured with an adjustable displacement volume.

The hydrostatic drive 1 additionally has a second pressure medium connection 26 branching off from the first pressure medium connection, via which the one piston space 8 can be fluidically connected to the other piston space 10 for a so-called regeneration operation. In Regenrationsbetrieb takes place the Pressure medium supply of the other piston chamber 10 partially or completely via the second pressure medium connection 26, that is, a partial flow of the effluent from a piston chamber 8 drain volume flow. In the second pressure medium connection 26 is designed as a simple adjusting throttle second throttle device 28 is arranged. The second throttle device 28 is formed in the first embodiment as a simple adjusting throttle. About them, the second pressure medium connection 26 and thus the partial volume flow can be controlled.

FIG. 2 shows a second example of a hydrostatic drive 101, which substantially according to FIG. 1 is the same, and as a sole difference instead of the hydraulic motor has a hydraulic accumulator 121. Through this, the pressure medium energy of the whole or of the partial volume flow reduced drain volume flow can be stored for later use.

A third example of a hydrostatic drive 201 according to FIG. 3 corresponds largely to that according to FIG. 1 , By way of derogation, a second throttle device 228 is arranged in the second pressure medium connection 26, which has a second opening cross section A _{2 which is} adjustable as a function of the pressure p _A and via which the second pressure medium connection 26 can be actuated and controlled.

The second throttle device 228 is configured in the example as a proportionally adjustable 2/2-way valve. A valve body of the second throttle device 228 is loaded in the direction of a blocking position 228b with the pressure p _A , whereas it is loaded in the direction of an open position 228a with a pressure equivalent, namely the spring force of a spring 230. If the valve body is in the open position 228a, the spring 230 acts with a spring force on the valve body, which corresponds to a lower pressure equivalent p _Au . If the valve body is in the blocking position 228b, the spring 230 acts with a spring force which corresponds to an upper pressure equivalent p _Ao .

The third example according to FIG. 3 takes advantage of the two examples described above (regeneration solution) and combines this with a higher utilization of the recuperable from the piston chamber 8 pressure medium energy. It is the second throttle device 228 designed such that its pressure loss is low. In particular, when the first throttling device 22 is fully opened, the pressure p _B in the other piston chamber 10 is then approximately equal to the pressure p _A in a piston chamber 8. It follows that the pressure p _A increases further. This results in the following a new balance of forces on the piston 4 with an increased compared to the aforementioned examples pressure p _A. Depending on an area ratio i of one piston surface 12 to the other piston surface 14 of 2: 1, the drain volume flow towards the hydraulic motor 20 can be approximately halved with this approach, and the pressure p _A and thus the working pressure of the hydraulic motor 20 can be approximately doubled. Although the hydraulic pressure medium energy supplied to the hydraulic motor 20 via the outflow volume flow is approximately the same as in the preceding examples, the hydraulic motor 20 can be designed to be half as large. As a result, the drive 201 is particularly cost-effective.

It should be noted that the described pressure increase or pressure increase of the pressure p _A in reality somewhat lower fails, as at control edges of the first throttle device 22 but also the second throttle device 28 is a real pressure loss.

With the mentioned pressure amplification of the pressure p _A , there is generally the problem that only a reduced load F _L can be maintained for a maximum permissible pressure p _Amax (for example, 380 bar). Without the pressure _{amplification} described, the ratio F _Lmax = p _Amax * A results ₁₂ , with A ₁₂ as the surface area of a piston surface 12. However, with the pressure _gain the relationship F _Lmax = p _Amax * (A ₁₂ - A ₁₄ ), with A ₁₄ as surface area of the other piston surface 14.

In order to be able to maintain the required maximum load F _Lmax , the second pressure medium connection 26 is controlled as a function of the pressure p _A in a piston chamber 8 when it rises above a certain threshold value. For this purpose, the above-described load of the valve body of the second throttle device 228 serves in the direction of the blocking position 228b with the tapped by a piston chamber 8 pressure p _A. The tap is carried out via a load signaling line 232, between the one piston chamber 8 and the first throttle device 22 of the first Pressure medium connection 18 branches off. The closing of the second pressure medium connection 26, or of the second opening cross-section A ₂ , begins according to the diagram in FIG FIG. 3 right from a closing point to which the pressure p _A in a piston chamber 8 reaches the value of the lower pressure equivalent p _Au . The closing takes place until reaching the upper pressure equivalent p _{Ao in} proportion to the increasing pressure p _A. Then the second opening cross-section A ₂ = 0 and there is neither the described regeneration nor the pressure gain. Between the two pressure equivalents p _Au and p _Ao these two effects steadily decrease with increasing pressure p _A.

The values for the pressure equivalents p _Au , p _Ao , which determine the control behavior of the second throttle device 28, depend on the maximum permissible pressure p _Amax in a piston chamber 8. In addition, an operating strategy plays a role. In order that the pressure p _A does not exceed the value p _Amax at any load F _L despite the above-described pressure boost, the upper pressure equivalent p _Ao can be determined in a simple design as follows:
p _Ao = p _Amax / (1-1 / i), with i as the area ratio of one piston surface 12 to the other piston surface 14 and with p _Amax = F _Lmax / A ₁₂

Theoretically, p _{Ao could} also be designed for the value of the maximum pressure p _Amax . Even then, the pressure p _A in a piston chamber 8 can not statically exceed the value p _Amax , since the pressure p _{A is} tapped via the load reporting line 232 directly in a piston chamber 8 and reported to the second throttle device 228. However, this type of design for p _Ao in dynamic load cases proves to be critical.

If, for example, the maximum pressure p _Amax is 380 bar and the area ratio i = 2, then the value 190 bar results for the upper pressure equivalent p _Ao . In the following, the lower pressure equivalent p _Au is designed so that the second throttle device 228 has a stable control behavior. In the exemplary embodiment shown, this is given when p _{Au is} about 50 bar lower than p _Ao (140 bar).

Notwithstanding the described simple approach, a higher value can be assumed for the upper pressure equivalent p _Ao , because due to a motor control of the hydraulic motor 20, the pressure downstream of the first throttle device 22 is not equal to the pressure p _A. On the one hand, this is due to the fact that the outflow volume flow via the first throttle device 22 requires / generates a pressure gradient. On the other hand, via the hydraulic motor 20 pressure medium flows off, so that mechanical energy can be delivered to a shaft 34. So that the control is stable and in the case of a desired movement of the piston 4, this can take place continuously, a working pressure p _{M is} provided for the hydraulic motor 20, which is below the pressure p _A.

A weakness of in FIG. 3 As shown, it is that at operating times, where the load F _{L is} so large that the second throttle device 228 is controlled (blocking position 228 b), the inlet flow into the other piston chamber 10 must be supplied from another location. In principle, the reserved hydraulic pump 24 could serve this purpose. However, in particular in the case of mobile machines, for example construction machines, the pressure medium volume flow of the hydraulic pump 24 is a limiting factor in parallel operation of a plurality of hydraulic consumers. If, at their maximum utilization, the additional suction volume flow required by the other piston chamber 10 is added and the second pressure medium connection 26 is closed as mentioned, cavitation may occur in the other piston chamber 10 due to the lack of pressure medium supply and / or the other hydraulic consumers due to insufficient supply through the hydraulic pump 24 slower.

To remedy this, the drive 201 according to the invention is according to an in FIG. 4 shown embodiment of a hydrostatic drive 301 is supplemented by a third pressure medium connection 340 which is connected in parallel to the second pressure medium connection 26 and branches off from the first pressure medium connection between the first throttle device 22 and the working port of the hydraulic motor 20.

In the third pressure medium connection 340 according to the invention, a third throttle device 342 is provided, the third opening cross section of which can be controlled as a function of the pressure p _{B of} the other piston chamber 10. More specifically, one is Valve body of the third throttle device 342 in the direction of an open position of the third throttle device 342 with the pressure equivalent of a spring 344 and loaded in the direction of a closed position with the pressure p _{B of} the other piston chamber 10. With decreasing pressure p _{B of} the third opening cross section is thus controlled by the spring 344, whereby the above-described cavitation is prevented by undersupply of the other piston chamber 10. The third throttle device 342 may also be referred to as a suction valve. By pressurizing its valve body in the direction of a closed position, it is additionally prevented that the pressure p _B in the other piston chamber 10 rises above the pressure equivalent of the spring 344 due to the partial volume flow flowing in via the third pressure medium connection 340. In the illustrated embodiment, the spring force / pressure equivalent of the spring 344 is adjustable and adjusted to about 10 bar.

FIG. 5 shows an example according to the example FIG. 3 based example of a hydrostatic drive 401. In this is the Nachsaugung that in the embodiment according to FIG. 4 is made possible via the third pressure medium connection, solved in an alternative way. To simplify the description of the hydrostatic drive 401, reference is made at this point only to the differences from the third example according to FIG FIG. 3 received.

A second throttle device 428 of the second pressure medium connection has instead of the blocking position 228b according to FIG. 3 a constructionally related residual opening position b with a residual opening cross-section A _2R . Thus, in each case, a suction of the partial volume flow in the other piston chamber 10 via the second pressure medium connection 26, which is why the hydraulic pump 24 is no longer with the other piston chamber 10 in pressure medium connection / must be. The residual opening cross-section A _2R is dimensioned such that sufficient pressure medium can flow into the other piston chamber 10 via it, but no pressure buildup takes place in the latter. In the embodiment shown, the dimensioning is selected so that adjusts the pressure p _B ≤ 10 bar in the other piston chamber 10. This is sufficient to prevent cavitation in the other piston chamber 10 due to dynamic movement effects of the piston 4.

To ensure that no pressure medium from the other piston chamber 10 (rod side) to a piston chamber 8 (bottom side) can flow, in the second pressure medium connection 26 between the other piston chamber 10 and the second throttle device 428 to a second throttle device 428 closing check valve 446 installed ,

In the event that the hydraulic motor 20 can also go into pump operation, it is ensured that pressure medium is not conveyed by it directly into the other piston chamber 10, but into the one piston chamber 8, by forming a second pressure medium connection 26 in the first pressure medium connection 18 closing check valve 448 is provided.

Notwithstanding the previously described drives, the hydraulic pump 24 in the example according to FIG. 5 with the one piston chamber 8 and not fluidly connected to the other piston chamber 10.

FIG. 6 FIG. 12 shows a valve device 354 that summarizes the second throttle device 228 and the third throttle device 342. The valve device 354 is also in the embodiment according to FIG. 4 installed. It is designed as a valve block with the connections L, A, X, and B1 and B2. Via the connection A, the second and third pressure medium connection 26 and 340 with the first pressure medium connection 18 according to FIG FIG. 4 connectable. Via the connection X, the load-signaling line 232 can be fluidically connected to the one piston chamber 8. Via the port B1 of the other piston chamber can be connected and via the port B2, the hydraulic pump 24 can be connected. The valve device 354 summarizes in a compact manner the functions of the load pressure-dependent regeneration of pressure medium from one piston chamber 8 in the other piston chamber 10 via the second throttle device 228 and the pressure-controlled Nachsaugung in the other piston chamber 10 via the third throttle device 342 together. In addition to the illustration according to FIG. 4 is a Leakage connection L of the valve device 354 shown, via the spring chambers (not shown) of the springs 230 and 344 are connected to a low pressure level.

In order to be able to control the pressure medium supply of the one piston chamber 8 independently of the displacement volume of the hydraulic pump 24, the hydrostatic drive 401 has a fourth throttle device 450, via which an opening cross section of the pressure medium connection of the hydraulic pump 24 with the one piston chamber 8 can be controlled. A further check valve 452 between the fourth throttle device 450 and the working port of the hydraulic pump 24 is provided, on the one hand to prevent the flow of pressure medium from the one piston chamber 8 to the hydraulic pump 24 and on the other hand to allow the pressure medium supply of a piston chamber 8 by the hydraulic pump 24.

The mentioned pressure medium connections can each be designed as a pressure medium line or pressure medium channel.

Disclosed is a hydrostatic drive with a double-acting hydraulic cylinder for moving a load, wherein one of the piston chambers of the hydraulic cylinder for recuperation of particular potential energy of the load with a hydraulic machine, in particular a hydraulic motor, and / or a hydraulic accumulator is fluidically connectable. In this case, the hydraulic cylinder to a second pressure medium connection, via which the other piston chamber for the regeneration of pressure medium energy with a partial volume flow of a flowing away from a piston chamber drain volume flow can be supplied.

Disclosed is a hydrostatic drive with a hydraulic cylinder for moving a load, a piston chamber with a hydraulic machine and / or a hydraulic accumulator for recuperation of hydraulic energy of the hydraulic cylinder is fluidly connected.

Disclosed is still a valve device for such a drive.

LIST OF REFERENCE NUMBERS

1; 101; 201; 301; 401

hydrostatic drive

2

hydraulic cylinders

4

piston

6

cylinder housing

8th

a piston chamber

10

another piston chamber

12

a piston surface

14

other piston area

16

piston rod

18

first pressure medium connection

20

hydromachine

22

first throttle device

24

hydraulic pump

26

second pressure medium connection

28; 228; 428

second throttle device

228a

Öffnungssstellung

228b

blocking position

230

feather

232

Load-sensing line

34

wave

340

third pressure medium connection

342

third throttle device

344

feather

354

valve device

446, 448

check valve

450

fourth throttle device

452

check valve

A ₂

second opening cross-section

A _2R

second residual opening cross section

p _A

Pressure in a piston chamber

p _Amax

maximum permissible pressure in one piston chamber

p _B

Pressure in the other piston chamber

p _Au

lower pressure equivalent

p _Ao

upper pressure equivalent

Claims (14)

1. Hydrostatic drive having a hydraulic cylinder (2) for moving, in particular lifting and/or lowering, a load (F_L), and having a hydraulic machine (20) and/or a hydraulic accumulator (121) for the recuperation of hydraulic energy from the hydraulic cylinder (2), in particular of potential and/or kinetic energy of the load (F_L), two piston chambers (8, 10) in the hydraulic cylinder (2) being separated from each other fluidically via a piston (4), of which one piston chamber (8) can be connected fluidically via a first pressure medium connection (18) of the drive (301) to the hydraulic machine (20) and/or the hydraulic accumulator (121), and having a second pressure medium connection (26), via which the other piston chamber (10) can be supplied with a partial volume flow of a discharge volume flow flowing away from the one piston chamber (8), characterized by a third pressure medium connection (340) connected in parallel with the second pressure medium connection (26), via which the other piston chamber (10) can be supplied with a partial volume flow of the discharge volume flow, and which has a third throttling device (342), via which the third pressure medium connection (340) can be controlled, wherein the third throttling device (342) has a third opening cross section that can be adjusted as a function of the pressure (p_B) of the other piston chamber (10).
2. Drive according to Claim 1, having a first throttling device (22) with an adjustable, first opening cross section, via which the first pressure medium connection (18) can be controlled.
3. Drive according to Claim 1 or 2, having a second throttling device (28; 228; 428) with a second opening cross section (A₂) that can be adjusted as a function of the pressure (p_A) of the one piston chamber (8), via which the second pressure medium connection (26) can be controlled.
4. Drive according to Claim 3, wherein the second opening cross section (A₂) can be closed as a function of the rising pressure (p_A) of the one piston chamber (8) and/or wherein the second opening cross section (A₂) can be opened as a function of the decreasing pressure (p_A) of the one piston chamber (8).
5. Drive according to Claim 3 or 4, wherein the second throttling device (28; 228; 428) is loaded in the direction of closing the second opening cross section (A₂) with the pressure (p_A) of the one piston chamber (8).
6. Drive according to one of Claims 3 to 5, having a lower pressure equivalent (p_Au), with which the second throttling device (28; 228; 428) is loaded in the direction of opening the second opening cross section (A₂) .
7. Drive according to Claim 6, wherein the second opening cross section (A₂) is opened substantially constantly when the pressure (p_A) of the one piston chamber (A) is lower than the lower pressure equivalent (p_Au) .
8. Drive according to Claim 6 or 7, wherein the second opening cross section (A₂) can be closed substantially proportionally as a function of the pressure (p_A) of the one piston chamber (8) when the pressure (p_A) of the one piston chamber (8) rises above the lower pressure equivalent (p_Au).
9. Drive according to one of Claims 6 to 8, having an upper pressure equivalent (p_Ao), with which the second throttling device (228; 428) is loaded in the direction of opening the second opening cross section (A₂), and which is higher than the lower pressure equivalent (p_Au).
10. Drive according to Claim 9, wherein the pressure (p_A) of the one piston chamber (8) can be limited via the upper pressure equivalent (p_Ao).
11. Drive according to Claim 9 or 10, wherein the second throttling device (428) has a remaining opening cross section (A_2R) when the pressure (p_A) of the one piston chamber (8) is approximately equal to the upper pressure equivalent (p_Au) or higher.
12. Drive according to one of the preceding claims, wherein the third opening cross section can be closed as a function of the rising pressure (p_B) of the other piston chamber (10) and/or wherein the third opening cross section can be opened as a function of the decreasing pressure (p_B) of the other piston chamber (10).
13. Drive according to one of the preceding claims, having an in particular adjustable pressure equivalent (344), with which the third throttling device (342) is loaded in the direction of opening the third opening cross section.
14. Drive according to Claim 3, having a valve device which is implemented in a block or disc design and which has a second throttling device (28; 228; 428) with the second opening cross section (A₂) that can be adjusted as a function of the pressure (p_A) of the one piston chamber (8), via which the second pressure medium connection (26) can be controlled, and which has the third pressure medium connection (340) connected in parallel with the second pressure medium connection (26), via which the other piston chamber (10) can be supplied with a partial volume flow of the discharge volume flow, and which has the third throttling device (342) with the third opening cross section that can be adjusted as a function of the pressure (p_B) of the other piston chamber (10), via which the third pressure medium connection (340) can be controlled.

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