WO2010025729A1

WO2010025729A1 - Axial piston machine and reverse osmosis device

Info

Publication number: WO2010025729A1
Application number: PCT/DK2009/000199
Authority: WO
Inventors: Asger Meng Larsen; Ove Thorbøl HANSEN; Palle Olsen
Original assignee: Danfoss A/S
Priority date: 2008-09-06
Filing date: 2009-09-04
Publication date: 2010-03-11
Also published as: DE102008046168A1; DE102008046168B4

Abstract

The invention relates to an axial piston machine comprising a cylinder drum that has at least two cylinders, a piston (20) in each cylinder, said piston contacting a swashplate (23) at a sliding surface, a valve arrangement that comprises a stationary connection element and a valve element rotating with the cylinder drum, wherein the connection element comprises a pump inlet opening (30) connected to an inlet connection (33) and a pump outlet opening (31) connected to a high-pressure connection. The use of such a machine in a reverse osmosis device is intended to achieve a good level of efficiency. To this end, the connection element comprises a motor inlet opening (32) that is connected to a high-pressure return connection and has a connection to each cylinder over a prescribed first rotary angle range of the cylinder drum.

Description

Axial piston machine and reverse osmosis device

The invention relates to an axial piston machine with a cylinder drum having at least two cylinders, a piston in each cylinder, which bears with a sliding surface on a swash plate, a valve assembly having a stationary connection element and a cylinder drum with the rotating valve element, wherein the Connection element has a pump inlet connected to an inlet port and a pump outlet port connected to a high-pressure port.

Furthermore, the invention relates to a reverse osmosis device having a pump and a membrane unit, which has a membrane, an inlet and a concentrate outlet on one side of the membrane and a permeate outlet on the other side of the membrane.

An axial piston machine of the type mentioned is known for example from DE 102 23 844 A1. The shoes are usually held by a hold-down in contact with the swash plate. When the cylinder drum rotates, the sliding shoes are moved upwards parallel to the axis of the cylinder drum on one half of the swash plate, so that the piston reduces a volume in the cylinder formed in the cylinder drum and moves downwards in the other half of the swash plate, so that he increases the volume again. The piston thus performs a pressure stroke in the first half of the swash plate and a suction stroke in the other half of the swash plate. The pump inlet opening and the pump outlet opening are expediently designed kidney-shaped, so that they can be swept by an opening in the valve element designed as a valve element, when the cylinder drum rotates. If such an axial piston machine is used as a pump in conjunction with a reverse osmosis device, then the high-pressure port is connected to the inlet of the membrane unit. Water to be purified, which is supplied to the membrane unit, then stands at an elevated pressure on one side of the membrane. Part of this water passes through the membrane and can be removed as permeate on the other side of the membrane. On the side of the membrane, on which the entrance is arranged, the concentration in the water increases, so that here a concentrate forms. This concentrate is still under increased pressure.

It has therefore been proposed to operate with the concentrate a motor or a turbine which is arranged on the same shaft as the pump, see US 6,139,740 or US 6,468,431 B1.

However, here an additional device is required, namely the operable with the concentrate drive motor.

The invention has for its object to be able to operate a reverse osmosis device as economically as possible.

This object is achieved in that one uses an axial piston machine of the type mentioned, in which the connecting element has an engine inlet opening which is connected to a Hochdruckrücklaufan- conclusion and is in communication with each cylinder over a predetermined first rotation angle range of the cylinder drum.

Such axial piston machine then works, so to speak, at the same time as a pump and as a motor. However, the drive power of the engine is not sufficient to provide the pump power available, so that an additional drive for the cylinder drum is required. However, this can be done by the membrane unit of the reverse osmosis device use backflowing concentrate to power the machine. The concentrate flowing back from the membrane unit thus acts to drive a piston, while another piston provides the pumping power. However, the concentrate is not fed into the cylinder over the entire "suction stroke" of the piston, but only over the predetermined first rotation angle range, so that liquid can be supplied via the inlet port over the remainder of the "suction stroke".

It is preferred that the motor inlet opening is arranged in the direction of rotation of the cylinder drum between the pump outlet opening and the pump inlet opening. This ensures that fresh liquid from the inlet connection, which is last fed in, is first returned to the high-pressure connection, as in the case of a subsequent pressure stroke of the piston.

Advantageously, a valve device is provided which releases an outlet channel from the cylinder over a predetermined second rotation angle range of the cylinder drum. This makes it possible to at least largely remove the concentrate that has been used previously for driving the cylinder drum from the cylinder and replaced by fresh liquid. The operation of the membrane unit of the reverse osmosis device is therefore not disturbed by increasing the concentration in the concentrate beyond predetermined limits.

Preferably, the outlet channel opens into the cylinder at a predetermined axial distance from the valve arrangement. If the outlet channel is released, one can then generate a flow, ie the incoming fresh liquid can then drive the concentrate previously used to drive the cylinder drum out of the outlet channel. A duty cycle of a cylinder looks like this: when the piston has reached the lowest point of the swash plate, it is moved in a further rotation of the cylinder drum to the valve assembly and displaces liquid from the cylinder into the pump outlet opening. From there, the liquid reaches the entrance of the membrane unit. The concentrate flowing back from the membrane unit, which is still under a relatively high pressure, which is only slightly smaller than the pressure at the pump outlet opening, then acts on the piston when the piston has exceeded the highest point of the swash plate and again moved away from the valve assembly. In this case, the concentrate provides a part of the drive power, because the piston acted upon by a pressure from the valve arrangement generates a drive torque on the cylinder drum via the lo swash plate.

As the cylinder barrel continues to move, the valve means opens the outlet channel so that upon further movement of the piston away from the valve assembly, the increase in volume is now replenished by fresh fluid which is later circulated through the membrane unit.

15 kehrosmosis should be cleaned.

Preferably, the valve device has a discharge opening in the swash plate, which lies opposite the pump inlet opening, and the outlet channel passes through the sliding surface. When the cylinder over the

20 valve assembly is in communication with the pump inlet opening, then it is connected through the piston with the discharge opening in the swash plate, so that the concentrate through the piston, ie through the outlet channel, can flow. You can then feed more fresh water into the cylinder, as it in and of itself

25 stroke would be possible, the piston is still running on the remaining path over the swash plate. If the piston then again performs a pressure stroke after passing through the lowest point of the swash plate, then substantially fresh water is pumped into the pump outlet opening, so that the concentration of salts or other

3 o ren in the permeate undesirable substances can not increase beyond a predetermined level. It is preferred that the outflow opening is arranged congruent to the pump inlet opening. The more accurate the mapping between the drain port and the pump inlet port, the better the filling of the cylinder with fresh water.

In an alternative embodiment, it is provided that the valve device has a pin projecting into the cylinder drum, which covers the outlet channel formed in the cylinder drum or releases it in the predetermined second rotational angle range of the cylinder drum. Also in this embodiment, the valve device comprises a stationary element, namely the pin, and a rotating element, namely the cylinder drum. Due to the rotation of the cylinder drum, the outlet channel is then automatically released in the predetermined second rotation angle range of the cylinder drum and otherwise locked.

In a further alternative it can be provided that the valve device has a pin connected to the cylinder drum, which protrudes into the swash plate. In this case, the valve function will be arranged for example in the swash plate.

In a further embodiment it can be provided that the valve device has a sealing wall which bears against the outside of the cylinder drum and covers the outlet channel or releases it in the predetermined second rotation angle range of the cylinder drum. Again, the valve device has a stationary element, namely the sealing wall and a rotating element, namely the cylinder drum. Due to the rotation of the cylinder drum, the outlet channel is released or locked in the correct position.

In the last three embodiments, it is advantageous if the outlet channel extends radially. In this case, the outlet channel can be made relatively easily. The term "radial" is not to be understood in a mathematically rigorous sense. The exhaust duct needs only from radially inside run radially outward. So it can also have an angle not equal to 90 ° to the axis of rotation of the cylinder drum and does not even have to cut this axis of rotation.

In a preferred embodiment, it is provided that the connection element projects into the cylinder drum. In this case, one has greater freedom in designing the connection geometry, i. during the supply and removal of the liquid in the various pressure stages.

Preferably, the low-pressure connection is preceded by a feed pump. The feed pump does not need to generate much pressure. It merely serves to displace the concentrate from the cylinder as far as necessary. For this purpose, a comparatively low pressure suffices.

Preferably, the engine inlet port is connected via a throttle with a low pressure region. It is difficult, in particular with changing quantities of permeate consumption at the membrane unit, to set the return flow of the concentrate correctly. Theoretically, as much concentrate should get to the engine intake port as the volume of the cylinder increases as the piston moves as the cylinder passes over the engine intake port. Through the throttle you can then ensure that an excess of concentrate can flow into the low pressure range. Nevertheless, the drive power of the concentrate is maintained.

Alternatively or additionally, it may be provided that the swash plate has a variable angle. When the angle is changed, so does the stroke of the piston in the cylinder and thus the volume that is released or displaced with each stroke of the piston in the cylinder. This also makes it possible to adapt to the refluxing concentrate. It is preferred that a control device for changing the angle is provided, wherein the control device is connected to a sensor. The sensor can, for example, measure the permeate consumption at the membrane unit or the salt or dirt concentration on the concentrate side of the membrane.

The object is achieved in a reverse osmosis device of the type mentioned above in that the pump is formed as described above, wherein the pump outlet is connected to the input and the motor inlet opening to the concentrate outlet.

In this way it is possible to use the pressure which is still present at the permeate outlet of the membrane unit for driving the axial piston machine without requiring an additional machine.

Preferably, a difference in length between the pump outlet opening and the motor inlet opening in the direction of rotation is adapted to the membrane. If one proceeds from a steady state operation in which a constant amount of permeate is always taken from the permeate outlet, then one can easily calculate what the difference between the volume that promotes the piston in the cylinder in a pressure stroke, and Volume that can still flow back from the permeate outlet of the membrane. If, for example, 25% of the fresh water is taken off as permeate, then only 75% can flow off again through the concentrate outlet. Accordingly, in this case it would be sufficient to dimension the motor inlet opening so that the piston is acted upon over 75% of the piston movement from the concentrate outlet. The then released in the engine inlet opening by the movement of the piston volume in the cylinder then corresponds exactly to the amount of liquid that flows back from the concentrate outlet. Preferably, the membrane unit has a consumption sensor which is coupled to an adjusting device. In this case, even with changing consumption volumes, it is possible to ensure that the cylinder is filled but not overfilled when the piston in the cylinder starts to move.

In this case, it is preferable for the adjusting device to act on a throttle which connects the motor inlet opening to a low-pressure region. Excess concentrate can then flow through the throttle to the low pressure area, where you can set the throttle so that the necessary to operate the cylinder drum pressure is maintained. As an adjustable throttle and a valve can be viewed, which can be opened or closed by the adjustment.

It can also be provided that the adjusting device acts on the angle of inclination of the swashplate. In this case, the stroke height of the piston in the cylinder is changed, so that one can thereby also influence the working volume in the cylinder, which is released by the piston or which is displaced.

The invention will be described below with reference to preferred embodiments in conjunction with a drawing. Herein show:

1 is a schematic representation of a reverse osmosis device,

2 shows an axial piston machine in longitudinal section,

3 is a perspective view of a connection plate,

4 is a perspective view of a valve plate, 5 is a schematic representation of a swash plate with piston and shoe,

Fig. 6 is an illustration for explaining the operation of a

Reverse osmosis device,

7 is a modified embodiment of FIG. 6,

Fig. 8 shows a further embodiment of an axial piston machine in a schematic representation and

Fig. 9 shows a further embodiment of an axial piston machine in a schematic representation.

1 shows a reverse osmosis device 1 with a membrane unit 2, which has a membrane 3. The membrane unit has an inlet 4 and a concentrate outlet 5 on one side of the membrane 3. On the other side of the membrane 3, a permeate outlet 6 is arranged, can be removed at the purified water.

For the sake of simplicity, it is assumed in the following that saline water is to be desalinated with the aid of the membrane unit 2, which is removed from a supply 7. The desalinated water is released at the permeate outlet 6. Water with a higher salt concentration is released at the concentrate outlet 5. However, the reverse osmosis device 1 is not limited to use in connection with salt water. Other liquids, especially water, which are provided with other loads can be cleaned with the reverse osmosis device 1 accordingly. Reverse osmosis requires increased salt water pressure. This increased pressure is generated by an axial piston machine 8, which will be described in more detail in connection with FIGS. 2 to 5. The axial piston machine 8 acts here mainly as a pump. It is driven by a motor 9 shown schematically, for example, an electric motor or an internal combustion engine. A feed pump 10 may be connected upstream of the axial piston machine in order to produce a sufficient filling of the axial piston machine 8, as will be explained below.

The concentrate, which is present at the concentrate outlet 5, has an elevated pressure which is only a few bar below the pressure at the high-pressure connection 11 of the axial piston machine 8. In order to utilize this pressure, the concentrate outlet 5 of the membrane unit 2 is connected to a high-pressure return connection 12 of the axial piston machine 8 via a line 13. From the line 13, a branch line 14 can branch off, in which a throttle 15 is arranged. The throttle 15 may be adjustable. For this purpose, for example, a sensor 16 may be provided at the permeate outlet 6 of the membrane unit 2, which adjusts the throttle 15 as a function of the outflow quantity of the permeate. The throttle 15 may also be formed by a valve which is alternately opened and closed, for example.

The axial piston machine 8 also has an outflow connection 37, which is connected to a low-pressure region, for example the supply 7.

The axial piston machine 8 will be explained in more detail in connection with FIGS. 2 to 5. It is largely constructed in the manner of a conventional axial piston machine, ie it has a housing 17 in which a cylinder drum 18 is rotatably mounted. In the cylinder drum 18 at least one cylinder 19 is arranged, whose axis is parallel to the Axle of the cylinder drum 18 extends. In the cylinder 19, a piston 20 is arranged, which is movable in the direction of a double arrow 21 back and forth.

The piston 20 is supported by a sliding shoe 22 on a swash plate 23. A hold-down 24 holds the shoe 22 with its sliding surface 25 in abutment against the swash plate 23. When the cylinder drum 18 rotates, the piston 20 is moved from its top dead center shown in Fig. 2 in a bottom dead center and back again.

The cylinder barrel 18 is connected to a valve plate 26. For this purpose, each cylinder 19 is provided with a bushing 27 which is inserted in the valve plate 26. These sockets 27 do not necessarily have to be present. Such axial piston machines can have many different designs. The valve plate 26 has a control port 28 for each cylinder 19.

The valve plate 26 bears against a connection plate 29, which is shown in greater detail in FIG.

The connection plate 29 has three control openings, which are also referred to as "control" because they have an arcuate course. In detail, the connection plate 29 has a pump inlet opening 30 and a pump outlet opening 31, as is known from conventional axial piston machines. In addition, an engine intake port 32 is provided in the rotational direction of the cylinder barrel 18 between the pump outlet port 31 and the pump inlet port 30.

The pump outlet port 31 communicates with the high-pressure port 11. The engine intake port 32 communicates with the high-pressure return port 12. The pump inlet port 30 communicates with an inlet port 33 of the axial piston engine. In Fig. 5, the swash plate 23 is shown with a piston 20 and the associated shoe 22. It can be seen that in the swash plate 23, a drain opening 34 is provided. The piston 20 is, as can be seen from Fig. 2, hollow. It has an outlet channel 35, which passes through the sliding surface 25 and communicates with the hollow interior 36. Accordingly, when the piston 20 overflows the drainage port 34, liquid may flow out of the cylinder 19 through the drainage port 34. The discharge opening 34 is connected to the discharge connection 37 of the axial piston machine 8.

From FIG. 5, it can be seen that the drainage opening 34 is positioned so that it coincides angularly with the pump inlet opening 30. Thus, when a control port 28 reaches the pump inlet port 30, salt water supplied to the input port 33 of the axial piston engine 8 displaces the fluid previously contained in the cylinder 19 through the drain port 37 into a low pressure region such as reservoir 7.

This function will now be explained in more detail with reference to FIG. 6. Shown is a piston 20 in nine different positions a-i, these positions being represented by the position of the associated cylinder 19 associated control port 28 with respect to the pump inlet port 30, the pump outlet port 31 and the engine inlet port 32. The cylinder drum 18 rotates counterclockwise with respect to FIG. 6.

When the piston 20 with its control opening 28 reaches the beginning of the pump outlet opening 31 (a), it is in its bottom dead center, ie the associated cylinder 19 is filled with the largest possible amount of salt water. As the cylinder drum 18 continues to rotate (bd), the piston 20 is turned up and displaces the cylinder 19 located amount of salt water through the pump outlet 31 and the high pressure port 11 to the inlet 4 of the membrane unit 2. The salt water passes partly through the membrane 3 and can be removed via the permeate 6.

Concentrate 5 is still at relatively high pressure at concentrate exit 5. This concentrate is supplied to the engine intake port 32 via the high-pressure return port 12. This concentrate pushes the piston 19 (f, g) down the swash plate 23, by cooperating sliding shoe 22 and swash plate 23 of the piston, which coincides with the motor inlet port 32 stands, works by motor, ie it generates a driving torque on the cylinder drum 18. This allows one to partially convert the energy of the concentrate into a rotational energy, in other words to recover part of the energy. The length of the engine inlet opening 32 may be selected so that it is adapted to the consumption of permeate. For example, if 25% of the salt water supplied to the inlet is taken off as permeate at the permeate outlet 6, then an amount of 75% salt water fed in at the concentrate outlet 5 is available. Accordingly, for example, the length of the engine intake port 32 in the direction of rotation of the cylinder drum 18 may be dimensioned to provide the cylinder with concentrate over 75% of the length of the piston movement.

When the control port 28 reaches the pump inlet port 30 (position h), then fresh salt water is supplied by the feed pump 10 again. Through the drain opening 34, the concentrate located in the cylinder 19 can flow out (i), so that again fresh salt water is pumped to the inlet 4 of the membrane unit 2 during the subsequent pump stroke of the piston 20.

FIG. 7 shows an embodiment modified from FIG. 6, in which the line 13 between the concentrate outlet 5 and the high pressure return line running connection 12, the line 14 branches off with the throttle 15. The throttle 15 ensures that concentrate is always present in the engine inlet opening 32 with a sufficient pressure, but too much concentrate can flow off via the branch line 14.

An alternative, not shown, is to change the inclination of the swash plate 23 to adjust the stroke of the piston 20 to the amount of the refluxing concentrate.

Fig. 8 shows a further embodiment of an axial piston machine 8. Elements which correspond to those of Figures 1 to 7 are provided with the same reference numerals. 8a shows a schematic section through the axial piston machine 8, FIG. 8b shows a plan view of the valve plate 29 and FIG. 8c shows a section A-A according to FIG. 8a.

The position and the control of the outflow channel 35 have changed. For the controlled opening of the outflow channel 35, a valve device is also provided here with a stationary element and a rotating element. The stationary element is formed by a pin 38. The movable element is formed by the cylinder drum 18. The pin 38 is arranged in a central bore 39 in the cylinder drum 18 and lies with its peripheral wall 40 sealingly against the wall of the bore 39.

The outlet channel 35 extends substantially radially from the cylinder 19 into the bore 39. The pin 38 has a recess 41 in its peripheral wall 40. Thus, if the mouth of the outlet channel 35 comes into the region of the recess 41, then the outlet channel 35 is released. Otherwise, the outlet channel 35 is blocked by the pin 38. In the cylinder 19, the mouth of the outlet channel 35 is still surrounded by an extension 42 axially in both directions. This extension 42 allows the outflow of concentrate from the cylinder 19 before the piston 20 has passed the outlet channel 35.

One can also provide the arrangement in reverse. In this case, the cylinder barrel 18 is provided with a pin similar to the pin 38. This pin then projects into the swash plate, wherein the valve function can be arranged in the swash plate. The projecting into the swash plate 23 pin can then have either on its front side or on its peripheral side corresponding openings, which, since the pin rotates with the cylinder drum 18, can serve as valve elements.

In one embodiment, not shown, one can also omit the pin 38 and make the control of the outlet channel 35 through the piston 20.

In both cases, the concentrate displaced from the cylinder 19 is discharged into the housing, not shown, of the axial piston machine 8 and must be removed therefrom.

In a further embodiment, not shown in detail, it is also possible to use a sealing wall surrounding the cylinder drum 18 instead of the pin 38, whereby in this case the outlet channel 35 is guided essentially radially outwardly from the cylinder 19. The sealing wall may then also have a recess corresponding to the recess 41 of the pin 38. If the outlet channel 35 comes into the region of this recess, then it is released. Otherwise it is covered by the sealing wall.

You can also equip the swash plate 23 with a variable inclination (not shown). You may have to in this case move the outlet channel 35 or you have to decouple the pin 38 of the swash plate 23.

The outlet channel 35 may have different shapes. It can be designed, for example, as an annular channel or as an ellipse. He may also have a throttle groove.

It is also possible to provide the extension not in the cylinder 19, but on the piston 20. The effect is otherwise the same.

Fig. 9 shows a further embodiment of an axial piston machine 8, in which elements which correspond to those of Figures 1 to 8, are provided with the same reference numerals. FIG. 9a shows a longitudinal section through the machine, and FIG. 9b shows a section A-A from FIG. 9a.

The arrangement of the outlet channels 35 corresponds to those of FIG. 8. Has changed the valve assembly. The valve assembly now has a pin 43 which projects into the cylinder drum 18. The cylinders 19 can therefore be closed at the end by a cover plate 44. The pin 43 also has a recess 41 on its peripheral wall 40, which releases the outlet channel 35 in a rotational angle range of the cylinder drum 18.

The pin 43 forms here the connection element. The cylinder drum 18 forms the valve element here. The pin 43 has at its end 45, which is inserted into the cylinder barrel 18, three recesses, which form a pump outlet 31, an engine inlet port 32 and a pump inlet opening 30. These openings 30-32 are separated by sealing zones 46-48. In the pin 43, there are three channels, namely a high-pressure channel 49, which is connected to the pump outlet opening 31, a low-pressure channel 50, which communicates with the pump inlet opening. connected to the motor 30 and a recognizable only in Fig. 9b engine passage 51 which is connected to the engine inlet port 32.

Claims

claims

An axial piston machine having a cylinder drum having at least two cylinders, a piston in each cylinder, which bears with a sliding surface on a swash plate, a valve assembly having a stationary connection element and a cylinder drum with the rotating valve element, wherein the connecting element with a Inlet port connected pump inlet port and having a pump outlet connected to a high-pressure port, characterized in that the connection element (29, 43) has an engine inlet port (32) which is connected to a high-pressure return port (12) and with each cylinder (19) via a predetermined first rotation angle range of the cylinder drum (18) is in communication.

2. axial piston machine according to claim 1, characterized in that the motor inlet opening (32) in the direction of rotation of the cylinder drum (18) between the Pumpenauslassöffnung (31) and the pump inlet opening (30) is arranged.

3. Axial piston machine according to claim 1 or 2, characterized in that a valve device (22, 23, 38, 43) is provided, the over a predetermined second rotation angle range of the cylinder drum (18) an outlet channel (35) from the cylinder (19) free - gives.

4. Axial piston machine according to claim 3, characterized in that the outlet channel (35) opens into the cylinder (19) at a predetermined axial distance from the valve arrangement.

5. axial piston machine according to claim 3 or 4, characterized in that the valve device has a drain opening (34) in the Swash plate (23) facing the pump inlet opening (30), and the outlet channel (35) passes through the sliding surface (25).

5 6. Axialkolbenmaschine according to claim 5, characterized in that the discharge opening (34) is arranged congruent to the pump inlet opening (30).

7. Axial piston machine according to claim 3 or 4, characterized marked records that the valve device has a in the cylinder drum (18) projecting pin (38, 43) which covers the in the cylinder drum (18) formed outlet channel (35) or in predetermined second rotational angle range of the cylinder drum (18) releases. 5

8. Axial piston machine according to claim 3 or 4, characterized in that the valve device has a with the cylinder drum (18) connected pin which projects into the swash plate (23). 0

9. Axial piston machine according to claim 3 or 4, characterized in that the valve device has an outside of the cylinder drum (18) abutting the sealing wall which covers the outlet channel or in the predetermined second rotation angle range of the cylinder drum (18) releases. 5

10. axial piston machine according to one of claims 7 to 9, characterized in that the outlet channel (35) extends radially.

11. Axial piston machine according to one of claims 1 to 10, characterized o characterized in that the connecting element (43) projects into the cylinder drum (18).

12. axial piston machine according to one of claims 1 to 11, characterized in that the inlet port (33) is preceded by a feed pump (10).

5 13. Axialkolbenmaschine according to any one of claims 1 to 12, characterized in that the motor inlet opening (32) via a throttle (15) with a low pressure region (7) is connected.

14. Axial piston machine according to one of claims 1 to 13, dadurch0 characterized in that the swash plate (23) has a variable

Has angle.

15. Axial piston machine according to claim 14, characterized in that a control device for changing the angle vorgese-5 is hen, wherein the control device with a sensor (16) is connected.

A reverse osmosis device comprising a pump and a membrane unit having a diaphragm, an inlet and a concentrate outlet on one side of the membrane and a permeate outlet on the other side of the membrane, characterized in that the pump is an axial piston machine according to one of the claims 1 to 14, the pump outlet opening (31) being connected to the inlet (4) and the motor inlet opening (32) being connected to the concave outlet (5).

17. Reverse osmosis device according to claim 16, characterized in that a length difference between the pump outlet opening (31) and the motor inlet opening (32) is adapted in the direction of rotation to the o membrane (3).

18. reverse osmosis device according to claim 16 or 17, characterized in that the membrane unit (2) has a consumption sensor (16) which is coupled to an adjusting device.

19. reverse osmosis device according to claim 18, characterized in that the adjusting device acts on a throttle (15) which connects the motor inlet opening (32) with a low pressure region (7).

20. reverse osmosis device according to claim 18, characterized in that the adjusting device acts on the inclination angle of the swash plate (23).