EP2401141A1

EP2401141A1 - Hydraulic drive

Info

Publication number: EP2401141A1
Application number: EP10706597A
Authority: EP
Inventors: Werner Kuttruf
Original assignee: Voith Patent GmbH
Current assignee: Voith Patent GmbH
Priority date: 2009-02-25
Filing date: 2010-02-24
Publication date: 2012-01-04
Also published as: WO2010097399A1; DE102009011441A1; DE102009011441B4

Abstract

The invention relates to a hydraulic drive (1) comprising an operating piston (2) guided along an operating direction (7) in a housing (5), wherein the operating piston (2) borders an operating pressure chamber (17) that can be filled with a pressure fluid in order to move the operating piston (2) in the operating direction (7) and additionally borders a control chamber (19), the volume thereof increasing upon movement of the operating piston (2) in the operating direction (7), additionally comprising a control piston (27) guided in a control cylinder (25) that can be moved along a control axis (29) between a neutral position, an inflow position enabling the inflow of pressure fluid into the operating pressure chamber and an outflow position enabling the outflow of pressure fluid out of the operating pressure chamber (17), wherein the control piston borders a piston chamber (33) that is filled with control fluid in order to move the control piston (27) from the neutral position to the inflow position or from the outflow position to the neutral position and that is pressure-connected to the control chamber (19) such that the control piston (27) is returned to the neutral position by the volume change of the control chamber (19).

Description

description

Title: Hydraulic drive

The invention relates to a hydraulic drive with a guided in a housing working piston.

Hydraulic drive devices are known in various designs. These usually have a hydraulic control circuit, with which the controlled variable (travel of the working piston) is set by the specification of a reference variable. In EP 0 296 104 B1, for example, a hydraulic linear servo amplifier is described. In this case, the movement of the piston is controlled by mechanical displacement of a spool by means of an actuating rod. From DE 42 27 563 a controlled hydraulic feed drive is also known. The movement of the piston is controlled by an electrically controlled control valve, wherein the hydraulic control circuit is produced by a displacement measuring system on a pilot cylinder.

Such hydraulic drives come in particular as press and

Punching drives in deep-drawing presses, press stages, cutting presses and other machine tools are used. Usually, large lifting loads between 5 t and 800 t have to be overcome. The loaded components must therefore be designed to be robust. At the same time, a multiplicity of mechanical and / or electrical components must be arranged precisely matched to one another in the known hydraulic drive systems mentioned by way of example.

The invention has for its object to provide a robust, simply constructed hydraulic drive with great flexibility in the arrangement of the components.

This object is achieved by a hydraulic drive according to claim 1. This comprises a working piston guided in a housing along a working direction, the working piston defining a working pressure space which can be filled with a pressure fluid for movement of the working piston in the working direction. The working piston also limits a control chamber whose volume increases in movement of the working piston in the working direction. Further is a guided in a control cylinder control piston is provided, which is displaceable along a control axis between a neutral position, a supply of pressurized fluid into the working pressure space enabling inflow position and a drainage of pressurized fluid from the working pressure space enabling discharge position. Further, a piston chamber is provided, which is filled for movement of the control piston from the neutral position into the inflow position or from the outflow position to the neutral position with a control fluid, and is removed to move the control piston from the neutral position to the outflow control fluid. The piston chamber is also pressure-connected to the control chamber such that the control piston is returned by the change in volume of the control chamber in the neutral position.

The movement of the control piston thus takes place via the control fluid, whereas the movement of the working piston takes place by means of the pressurized fluid. In particular, pressurized fluid and control fluid may be formed by different media and provided with widely different pressures. Thus, for example, the control fluid can be provided in an energy-saving manner from a low-pressure supply and the pressurized fluid as the actual working medium from a high-pressure supply.

In the hydraulic drive according to the invention, the setpoint input thus takes place by the supply / discharge of control fluid in / out of the piston chamber interacting with the control piston. Since the piston chamber is pressure-connected to the control chamber, the supply / discharge of the control fluid can also be done in / from the control room. The volume of control fluid represents the reference variable of the hydraulic control loop. The controlled variable is the travel of the working piston. A feedback of the controlled variable (travel) to the reference variable (control fluid volume) is carried out hydraulically via the associated with the piston movement change in the volume of the control chamber. An additional displacement measuring system on the moving working piston is for the realization of the hydraulic control circuit in the hydraulic drive according to the invention basically not necessary, which simplifies the structure of the hydraulic drive so far. Preferably, only the control piston is designed as a moving component in addition to the actual working piston. The control cylinder may be stationary, in particular connected to the housing or integrated into this integrated. During operation of the device then only small masses during the control operations to move. At the same time, the number of mechanical transitions between different components is reduced and therefore friction forces during the control process are minimized. This allows control with a highly dynamic motion profile. The hydraulic drive therefore has a high fidelity and high response speed. A reduction in the number of moving parts also simplifies the structure in that complex measures for sealing are required only in a few places. In addition, malfunctions are largely avoided by tilting movable components against each other, as can occur, for example, in hydraulic linear actuators with mechanical control via spool. The hydraulic drive according to the invention can therefore be operated with high reliability and robust against interference.

Characterized in that the arrangement of the control cylinder and control piston can be largely independent of the working piston, the structure of the hydraulic drive according to the invention can be flexibly adapted to the available space. For example, with limited axial space conditions, the control cylinder can be arranged parallel to the working piston. It is only crucial that the piston chamber is pressure-connected to the control chamber, which can be realized for example by rigid or flexible pressure lines. Such freedom of design is not possible, for example, in mechanically controlled hydraulic linear drives on principle.

Preferably, the control piston can limit the piston chamber directly. However, it is also conceivable that between the control piston and the piston chamber acting on the control piston Equalizing piston is provided. About the compensating piston, the desired transmission ratio of the working piston and the control piston can be specified, in particular, which can be brought in different positions control piston can be executed as a standard component.

Advantageous embodiments result from the fact that the

Control space limiting hydraulic effective area of the working piston is equal to, smaller than or greater than the piston space limiting hydraulic effective area of the control piston or the intermediate balance piston. Thereby, a 1: 1 hydraulic ratio, a reduction or an arbitrary ratio between the volume of control fluid and the volume of pressurized fluid can be provided. It can thus be realized various translations between working and control piston.

A preferred embodiment of the invention results from the fact that the working piston has a working portion which limits the working pressure chamber and further comprises a working portion remote, designed as a guide piston area, softer limits the control room. The working pressure chamber is thus spatially separated from the control room and not hydraulically pressure-connected. The guide piston can be formed in particular by a guide rod, which is guided for axial alignment of the working piston in the housing and the end face is formed like a piston.

As a further embodiment, control piston and control cylinder can be arranged together with the working piston in the housing of the hydraulic drive.

The control axis of the control piston and the working direction of the working piston preferably run parallel. Alternatively, it is also possible that the control axis extends at an angle to the working direction. As a result, a flexible, adapted to the space requirements of the installation situation arrangement is possible.

It is particularly preferred that the control piston parallel to

Guide piston is arranged in the housing and that the end face of the housing, the control chamber and the piston chamber of the control piston limited together. The guide piston and the control piston thus have such similar axial dimensions that a common arrangement in the housing with a common cover is possible. Such a hydraulic drive is thus extremely compact and robust.

An advantageous embodiment also results from the fact that the

Control cylinder connected to pressure lines is arranged spaced from the housing. The control axis can be arranged at any angle to the working direction. This allows a particularly flexible design of the hydraulic drive. In addition, arrangements can be realized in which only very little space is required for the actual working unit (working piston and housing). All controls can be arranged separately from the work unit. Precise control is still possible.

Particularly preferred is when the control piston has control edges, which cooperate with control edges on the control cylinder for controlling the flow of pressurized fluid such that the flow through the deflection of the control piston from the neutral position along the control axis is continuously adjustable. Since the working piston is moved by filling the working pressure chamber with pressurized fluid, a proportional control of the speed of the piston movement is possible by the arrangement described. During operation of the device, therefore, the working piston can be moved at different speeds depending on the requirement.

Advantageously, a spring means is provided, which acts on the control piston resiliently against the pressure prevailing in the piston chamber pressure so that the control piston is held in the neutral position. The spring means may be formed in particular as a hydraulic spring or as a helical spring. When pressure relief of the control fluid (for example, by appropriate volume change of the control chamber), the control piston thus automatically returns to the neutral position. Thereby, the response speed of the controller can be increased.

For further embodiment of the invention is a control fluid supply provided such that a defined volume of control fluid can be fed into the piston chamber or discharged from the piston chamber. The control fluid supply can be remote from the working piston or its housing and remote from the control piston or its cylinder. The supply of control fluid in the piston or control chamber can be done via rigid or flexible pressure lines.

When hydraulic drive according to the invention various ways of control are possible. In particular, the control fluid supply can be designed as an electrofluidic converter with a piston for outputting a defined volume of control fluid from a control fluid tank. Such a transducer operates on the principle of an "infusion syringe." For example, the volume dispensed may be calibrated once for a particular movement of the piston, allowing for precise control of the working piston.

A further embodiment results from the fact that the control fluid supply includes a low-pressure pump or a low-pressure accumulator for control fluid and an electric directional control valve for controlling the supplied from the low-pressure pump and the low-pressure accumulator to the control chamber volume of control fluid. As a directional control valve, for example, a continuous servo valve can be used.

Further, the control fluid supply comprises a motor driven by a pump over which a predetermined volume in or out of the piston chamber is supplied or removed. It is also grateful that the control fluid supply comprises a motor-driven eccentric piston, via which a predeterminable volume can be supplied to or removed from the piston chamber.

As an advantageous development of a measuring device for determining the volume of the supplied into the control chamber or discharged from the control chamber control fluid is provided. The measured volume values can be used, for example, to set up the hydraulic feedback or to increase the precision of the control. It is also conceivable, a measuring device for determining the

To provide travel of the working piston along the working direction. Since the movement of the working piston changes the volume of the control chamber, a monitoring and / or refinement of the hydraulic feedback is also possible in this way.

As a particularly preferred embodiment of the invention, the pressure of the control fluid is lower than the pressure of the pressurized fluid during operation of the device. The movement of the control piston can therefore be done with little energy and effort. The hydraulic drive acts as a hydraulic booster in this sense.

Advantageously, the pressure fluid and the control fluid is formed by a hydraulic oil, wherein for the provision of pressurized fluid, a high-pressure supply and to provide control fluid, a low pressure supply for hydraulic oil can be provided. The control of the hydraulic drive thus takes place by providing defined volumes of hydraulic oil at low pressure and is associated with only a small amount of energy.

Further details and advantageous embodiments of the invention will become apparent from the following description, with reference to which the embodiments of the invention shown in the figures are described and explained in more detail.

In the drawings:

FIG. 1 shows a longitudinal section through an inventive device

Hydraulic drive with sketched electrofluidic converter as control fluid supply;

Figure 2 is a sketched further embodiment of the control fluid supply in cooperation with a volume measuring device;

FIG. 3 shows a sketched further embodiment of the control fluid supply; and

FIG. 4 shows a sketched further embodiment of the control fluid supply.

The inventive hydraulic drive 1 shown in Figure 1 has a working piston 2 with a working section 3, which is sealingly guided in a housing 5 along a working direction 7. The working piston 2 comprises a piston rod 9 designed to extend in the working direction 7. The region of the working piston 2 facing away from the working direction 7 against the working portion 3 is designed as a guide piston 11. The diameter 15 of the guide piston 11 is smaller than the diameter 13 of the working portion 3. The guide piston 11 is sealingly guided in the guide portion 6 of the housing 5.

The working piston 2 limits with its working section 3 a

Working pressure chamber 17. On the working pressure chamber 17 side facing away from an annular space 4 is present, in which there is preferably a continuous pressure. The work piston 3 delimiting the working pressure chamber 17 has a hydraulic active surface 14 for moving the working piston 2. The control piston 11 delimiting the control chamber has a hydraulic active surface 16.

To supply the working pressure chamber 17 with a pressurized fluid, which is formed here by a hydraulic oil, a high-pressure supply 21 is provided. To receive from the working pressure chamber 17 effluent hydraulic oil, a tank 23 is provided.

In the housing 5, a control cylinder 25 is further arranged, in which a control piston 27 is guided sealingly displaceable along a control axis 29. In the embodiment shown in FIG. 1, the control axis 29 runs parallel to the working direction 7. In principle, the working direction 7 and the control axis 29 can enclose an arbitrary angle. The guide portion 6 of the housing 5, the guide piston 11, the control cylinder 25 and the control piston 27 have similar axial dimensions and are arranged in the housing 5 parallel to each other. The end face 31 of the housing 5 forms a common conclusion of the guide portion 6 and the control cylinder 25. On the side facing away from the working section 3 of the control piston 27 is provided by the control piston 27 preferably separately trained, the control piston 27 fitting, balancing piston 37 is provided.

The control piston 27 has two annular collar-like axial extensions 39, 41. The extension 39 acts against the balance piston 37, which limits a piston chamber 33 with the control cylinder 25. Between the two extensions 39, 41 is a flow space 35. The control piston 27 facing away from end face 52 of the balance piston 37 forms a hydraulic active surface 53 for movement of the balance piston 37 and the control piston 27th

About the diameter of the balance piston 37, the desired gear ratio of the control piston 27 and the guide piston 11 can be given without having to change the size ratios of the guide piston 11 and control piston 27. With suitable size ratios of the guide piston 11 and the control piston 27, the balance piston 37 can also be omitted.

The flow space 35 is connected via a pressure channel 45 with the

Working pressure chamber 17 connected. The piston chamber 33 is connected via the passage 47 to the control chamber 19. The end face 31 of the housing 5 thus forms a common cover for the piston chamber 33 and the control chamber 19th

In the control cylinder 25 are through annular recesses a

Inflow chamber 49 and a return chamber 51 with the control piston 27 limited. In this case, the inlet chamber 49 is connected to the high pressure supply 21, the return chamber 51 to the tank 23rd

The annular collar-like extension 41 of the control piston 27 has a

Control edge 60, which cooperates with a control edge 62 of the inlet chamber 49. Similarly, a control edge 64 is provided on the annular collar-like extension 39 for cooperation with a control edge 66 on the control piston 27.

In the figure 1, the neutral position of the control piston 27 is shown.

In this case, the control edges 60 and 62 or 64 and 66 are aligned with each other. The flow space 35 is thus neither in the neutral position with the inflow chamber 49 still connected to the return chamber 51 pressure-connected. If the control piston 27 is moved downwards from its position shown in FIG. 1, it enters the inflow position. In this case, a gap between the corresponding control edges 60 and 62 opens, whereby the inlet chamber 49 is pressure-connected to the flow space 35. If, on the other hand, the control piston 27 is moved upwards from its neutral position in FIG. 1, the return flow chamber 51 is pressure-connected to the flow space 35 in an analogous manner by opening a gap between the control edges 64 and 66. In this situation, the control piston 27 is in its drainage position.

In the area of the annular collar-like enlargement 41, the control piston 27 has a bottom side 54, on which a arranged between the housing 5 and the control piston 27 spring means 55, which is designed here as a helical spring 56 is supported. In the illustration of Figure 1, the control piston 27 is thereby acted upon by a force up against the pressure prevailing in the piston chamber 33 pressure.

In order to supply the piston chamber 33 or the control chamber 19 with a defined volume of control fluid, a control fluid supply 80 is provided. This is connected via a connecting line 108 with the passage 47, which connects the piston chamber 33 and the control chamber 19. The control fluid supply 80 is formed in FIG. 1 as an electrofluidic converter 81. Here, a control fluid space 87 is provided which is delimited by a piston 83. The piston 83 is driven by a linear electric motor 89. When the piston 83 is moved by the electric linear motor 89 by a defined distance, a defined volume of control fluid is squeezed out of the control fluid chamber 87 and supplied to the piston chamber 33. As such, the electrofluidic transducer 81 operates similarly to an infusion syringe.

Since the piston chamber 33 and the control chamber 19 are pressure-connected via the passage 47, it does not matter if the control fluid directly to the control chamber 19, the piston chamber 33 or one of the two rooms connecting line section or the passage 47 is supplied. During operation of the hydraulic drive 1, the hydraulic control takes place in the manner described below. In Figure 1, the control piston 27 is in its neutral position, the working piston 2 in its initial position. The piston chamber 33 and the control chamber 19 are filled with an initial volume of control fluid. On the hydraulic active surface 53 of the control piston 27 acts in Figure 1, a force down. This is exactly compensated by the force acting on the control piston 27 upward force, which is provided by the spring means 55. The control piston 27 is therefore in its neutral position in the balance of power. To move the working piston 2 by a defined travel in the working direction 7, the piston chamber 33 is supplied by the control fluid supply 80, a defined volume of control fluid. The supply of control fluid increases the pressure on the active hydraulic surface 53 of the balance piston 37 and thus on the control piston 27. This then differs from its neutral position in the direction of the inflow position down , The control fluid supply 80 only has to overcome the counterforce of the spring means 55 and can therefore be designed as an energy-saving low-pressure supply. In the inflow position of the control piston 27 opens a gap between the inlet chamber 49 and the flow space 35 as described above. Then, pressurized fluid flows from the high pressure supply 21 through the inlet chamber 49, through the flow space 35, via the pressure channel 45 and into the working pressure chamber 17th the working piston 2 is moved from its initial position in the working direction 7. The movement path of the working piston 2 along the working direction 7 is just so great that the movement associated with the increase in the volume of the control chamber 19 just corresponds to the volume supplied to the control fluid , As the control room 19 is connected to the piston chamber 33 via the passage 47, the increase in volume of the control chamber 19 compensates the volume supplied to the piston chamber 33. By this volume compensation leaves the force acting on the hydraulic active surface 53 of the balance piston 37 force, and the control piston 27 returns due to the upward force of the spring means 55 back to its neutral position. As a result, a further inflow of pressurized fluid to the working pressure chamber 17 is prevented, and the hydraulic drive reaches a new rest position, in which the control piston 27 is again in its neutral position. In this way, via the volume of the control chamber 19, a hydraulic feedback of the manipulated variable (travel of the working piston 2) with the reference variable (volume of control fluid) is provided. A measuring device for detecting the manipulated variable, for example, a position measurement on the working piston 2, so in principle for the operation of the hydraulic drive is not necessary, but may still be provided for better control of the process.

Upon displacement of the control piston 27 along the control axis 29, the opening width of the gap between the corresponding control edges 60, 62 and 64, 66 is continuously adjustable. Since the opening width of the gaps between inlet chamber 49 and return chamber 51 and the flow space 35 regulates the time flow rate of control fluid, a proportional control of the travel speed of the working piston is possible in this way. The hydraulic over- or reduction between the volume of control fluid and the volume of pressurized fluid is determined by the ratio of the active hydraulic surface 16 in the control chamber 19 and the hydraulic active surface 14 of the working piston 2 in the working pressure chamber 17. The device works insofar as a hydraulic booster on the one hand, on the other hand as a hydraulic ratio.

If the piston chamber 33 or the control chamber 19, a defined volume of control fluid removed, so moves the Control piston 27 from the neutral position in the drainage position described above. As a result, the working pressure chamber 17 is connected via the pressure channel 45, the flow space 35, with the return chamber 51 and with the tank 23. This allows an outflow of pressurized fluid from the working pressure chamber 17 and thus a return movement of the working piston 2 against the working direction 7 due to a pending in the annulus 4 continuous pressure.

To increase the precision of the hydraulic feedback is a

Measuring device 75 for determining the supplied from the control fluid supply 80 in the piston chamber 33 and discharged from the piston chamber 33 volume of control fluid. Furthermore, a control unit 76 is provided, which controls the linear motor 89, evaluates distance measuring signals of the deflection of the linear motor 89 and the output volume measured by the measuring device 75.

When providing a measuring device for detecting the position of the working piston 2, the measuring device 75 can be omitted.

The supply of control fluid for an inventive

Hydraulic drive can be done in different ways. To supply the piston chamber 33 (see Fig. 1) via the connecting line 108 a defined volume of control fluid, a control fluid supply 90 is sketched in Figure 2, which cooperates with a measuring device 75 for the added or removed volume of control fluid and a control unit 76 , The control fluid supply 90 comprises a low-pressure supply or low-pressure source 92 for hydraulic oil, which forms the control fluid here. The flow of hydraulic oil from the low-pressure supply 92 to the piston chamber 33 (see Fig. 1) is controlled by an electrically operable directional control valve 96, which is controlled by the control unit 76 accordingly. A defined volume of control fluid can be provided by the measuring device 75 measuring the volume of control fluid supplied or removed, and the control unit 76 correspondingly activating the directional control valve 96 by comparing the measured values with the defined specifications. The control fluid supply 100 sketched in FIG. 3 has a reservoir 102 for control fluid and a pump 106. The pump 106 is driven by a motor 105. The motor 105 is actuated by an electrical control unit 76 so that a defined volume of control fluid can be made available to the piston chamber 33 (see FIG. 1) or the control chamber 19 (see FIG. Via a measuring system 104, the speed and thus the delivery volume of the pump 106 can be determined.

FIG. 4 shows a further control fluid supply 110. This comprises an eccentric 114 driven by a motor 112, via which a piston 116 is moved up and down. Via the piston 116, a predeterminable volume is fed into the connecting line 108 or removed from the connecting line 108. In addition, a volume compensation 118, in particular for adjusting the initial position of the working piston 2, can be connected to the connecting line 108. Such a control fluid supply 110 finds particular use in comparatively fast, periodically recurring strokes of the working piston 2.

Claims

claims

1. Hydraulic drive (1) comprising a in a housing (5) along a working direction (7) guided working piston (2), wherein the working piston (2) defines a working pressure chamber (17) for movement of the working piston (2) in the working direction ( 7) can be filled with a pressurized fluid, and also delimits a control chamber (19) whose volume increases when the working piston (2) moves in the working direction (7), furthermore comprising a control piston (27) guided in a control cylinder (25) between a neutral position, a supply of pressurized fluid into the working pressure chamber (17) enabling inflow position and a drainage of pressurized fluid from the working pressure chamber (17) enabling drainage position along a control axis (29) is displaceable, wherein a piston chamber (33) is provided, the for moving the control piston (27) from the neutral position into the inflow position or from the outflow position into the neutral position with a control fluid t is, and is so pressure-connected to the control chamber (19) that is returned by the change in volume of the control chamber (19) of the control piston (27) in the neutral position.

2. Hydraulic drive (1) according to claim 1, characterized in that the control piston (27) the piston chamber (33) directly limited.

3. Hydraulic drive (1) according to claim 1, characterized in that between the control piston (27) and the piston chamber (33) a compensating piston (37) is interposed.

4. Hydraulic drive (1) according to claim 1, 2 or 3, characterized in that the working piston (2) has a working portion (3) which limits the working pressure chamber (17) and a guide piston (11) formed area, softer the control room (19) limited.

5. Hydraulic drive (1) according to one of the preceding claims, characterized in that the control piston (27) is arranged parallel to the guide piston (11) in the housing (5) and that the end face (31) of the housing (5) the control chamber (19 ) and the piston chamber (33) bounded together.

6. Hydraulic drive (1) according to one of claims 1 to 4, characterized characterized in that the control cylinder (25) connected to pressure lines from the housing (5) is arranged spaced.

7. Hydraulic drive (1) according to any one of the preceding claims, characterized in that the control piston (27) control edges (60, 64) which cooperate with control edges (62, 66) on the control cylinder (25) for controlling the flow of pressurized fluid in such a way in that the flow is steplessly adjustable by the deflection of the control piston (27) from the neutral position along the control axis (29).

8. Hydraulic drive (1) according to one of the preceding claims, characterized in that a spring means (55) is provided, which acts on the control piston (27) against the in the piston chamber (33) prevailing pressure in the neutral position.

9. hydraulic drive (1) according to one of the preceding claims, characterized in that a control fluid supply (80, 90, 100, 110) is provided such that a defined volume of control fluid in the piston chamber (33) and / or control chamber (19) supplied or can be removed from the piston chamber (33) and / or control chamber (19).

10. hydraulic drive (1) according to claim 9, characterized in that the control fluid supply (80) as an electrofluidic converter (81) with a piston (83) for outputting a defined volume of control fluid from a control fluid tank (87) is formed.

11. hydraulic drive (1) according to claim 9, characterized in that the control fluid supply (90) a low pressure pump and / or a low pressure accumulator (92) for control fluid and an electric directional control valve (96) for controlling the low pressure pump and / or the low pressure accumulator ( 92) to the piston chamber (33) supplied volume of control fluid.

12. Hydraulic drive (1) according to claim 9, characterized in that the control fluid supply (100) via a motor (105) drivable pump (106) via which a predeterminable volume in or out of the piston chamber (133) or zu- can be dissipated.

13. Hydraulic drive (1) according to claim 9, characterized in that the control fluid supply (110) has a motor-driven eccentric piston (116) comprises, over which a specifiable volume in or out of the piston chamber (133) can be added or removed.

14. Hydraulic drive (1) according to one of the preceding claims, characterized in that a measuring device (75) for determining the volume of the in the piston chamber (33) and / or control chamber (19) supplied or from the piston chamber (33) and / or Control space (19) discharged control fluid is provided.

15. Hydraulic drive (1) according to one of the preceding claims, characterized in that a measuring device for determining the travel path of the working piston (2) along the working direction (7) is provided.