WO2014183941A1

WO2014183941A1 - Variable-speed drive having two pumps and a differential cylinder

Info

Publication number: WO2014183941A1
Application number: PCT/EP2014/057468
Authority: WO
Inventors: Udo Froehlich
Original assignee: Robert Bosch Gmbh
Priority date: 2013-05-13
Filing date: 2014-04-14
Publication date: 2014-11-20
Also published as: DE102013008047A1

Abstract

The invention relates to a linear actuator having a double pump (23, 24) and a differential cylinder (9), the annular chamber (48) or piston rod chamber of which is delimited by an annular surface (A1) or piston rod surface of a piston and is connected to a first pump (23), and the piston bottom chamber (50) of which is delimited by a piston bottom surface (A2) of the piston and is connected to a second pump (24). Both pumps are driven by a common variable-speed electric motor (26). The ratio of the annular surface area to the piston bottom surface area is equal to the ratio of the delivery volume of the first pump to the delivery volume of the second pump. According to a first variant, this is achieved by adjusting the rotational speeds of the two pumps by means of a gear unit (26). According to a second variant, this is achieved by designing a pump having an adjustable delivery volume. According to a third variant this is achieved in that, at a constant pump speed, the ratio of the displacement volumes of the pumps corresponds to the ratio of the cylinder surface areas.

Description

Variable speed drive with two pumps and one differential cylinder

description

The invention relates to a variable-speed drive with two pumps and with a differential cylinder.

With double-sided operation of a Differenziaizylinders with a variable speed drive, it is known from the prior art to connect a first pump to the annulus and a second pump to the piston head space of Differenziaizylinders, both pumps are driven by a common variable speed electric motor. It is essential that the ratio of geometric

Displacement volumes of the pump (eg 10.6 cc and 18 cc) with the area ratio of the Differenziaizylinders (eg 0 80/0 125) matches. (eg 10.6 / 18 = (125 ² -80 ² ) / 125 ² ) This represents the least expensive solution and is therefore also carried out. Disadvantage of such drives from the prior art is that the selection of meaningful sizes of Differenziaizylinders by the requirement of the same ratio of its surfaces (ring surface and piston surface) is very limited to the ratio of the delivery volumes of the pump. In contrast, the invention is based on the object, a drive with two

To create pumps and with a differential cylinder whose design is flexible.

This object is achieved by a drive with the features of

Claims 1 or 4. Both claimed drives have a differential cylinder whose annular space or piston rod space is bounded by an annular surface or piston rod surface of a piston and connected to a first pump, and whose piston bottom space is bounded by a piston bottom surface of the piston and connected to a second pump. Thus, the drive is a linear actuator. Both pumps are driven by a common variable speed electric motor. The ratio of the annular surface to the piston bottom surface is equal to the ratio of the delivery volume of the first pump to the delivery volume of the second pump.

In order to be free in the selection of the differential cylinder, the requirement for the same ratio of cylinder surfaces and volume flows according to a first inventive concept by adjusting the rotational speeds of the two pumps is realized by a transmission. In this case, the ratio of the speed of the first pump to the speed of the second pump is realized via the transmission. Then the pumps can have the same nominal delivery volume and they can in particular be identical, whereby the assembly cost is reduced.

According to a first variant of the first concept, the transmission is driven directly on the input side by an output shaft of the electric motor. The transmission has two output shafts, each driving a pump. Thus, the two pumps are mechanically connected in parallel.

According to a second variant of the first concept, only one of the pumps is driven directly by the output shaft of the electric motor, wherein the transmission in turn is driven directly by this pump. The transmission has exactly one output shaft, which drives the other pump. Thus, the electric motor, the one pump, the transmission and the other pump are mechanically connected in series.

Via the gearbox, an increase in the rotational speed of the second pump relative to the electric motor and the first pump or a reduction in the rotational speed of the first pump relative to the electric motor and the second pump can be generated realized. In order to be free in the selection of the differential cylinder, the requirement for equal ratio of volume flows to cylinder surfaces according to a second inventive concept, a pump with adjustable delivery volume is installed, so that the ratio of the volume flows can be adjusted. The other pump can be a constant pump for device simplification.

According to a first variant of the second concept, both pumps are synchronously driven via a one-piece shaft or two mutually coupled shaft sections, the second pump being a variable displacement pump which is permanently adjustable such that the ratio of the annular surface to the piston bottom surface is equal to the ratio of the delivery volume of the first Pump to the delivery volume of the variable is.

According to a second variant of the second concept, both pumps are synchronously driven by a one-piece shaft or two coupled shaft portions, wherein the first pump is a variable that is permanently adjustable so that the ratio of the annular surface to the piston bottom surface equal to the ratio of the delivery volume of the variable to the delivery volume of the second pump.

In particular, in the second concept, both pumps can be arranged in a common housing and thus form a compact double pump.

A preferred development of both concepts of the drive according to the invention has a first working line, via which the first pump is connected to the annular space, and a second working line, via which the second pump is connected to the piston bottom space. A high-pressure accumulator is connected to the first working line or directly to the annulus or to the second working line or directly to the piston bottom space

connected. This allows an emergency function in which the differential cylinder is moved with the pressure medium of the previously loaded high-pressure accumulator. It is particularly preferred if the high-pressure accumulator is connected via an emergency line directly to the piston bottom space, and when the high pressure accumulator is connected via a boost line to the second working line. Thus, the emergency function in the direction of extension of the differential cylinder is possible and also a boost function allows, over which the differential cylinder can be extended faster than a supply of the piston head space via the second pump alone.

If the drive according to the invention has a charging line, over which the first

Working line is connected to the boost line or directly to the high-pressure accumulator, and if in the charging line to the boost line opening check valve is arranged, the high-pressure accumulator for emergency function on the first pump, the first

Working line and the charging line to be recharged. When the charging line is connected to the boost line, the high pressure accumulator is recharged via the boost line.

A particularly preferred development has a low-pressure line which connects a respective low-pressure connection of the pumps. Then it is to compensate for the difference in volume of the two spaces in the operation of the drive

Niederduckspeicher necessary, which is connected to the low pressure line.

In this case, a further low-pressure line is preferred over which the

Niederduckspeicher is connected to the second working line, wherein in the further low-pressure line to the second working line opening check valve is provided. This is a slow-down in the speed-boost mode possible without the piston in the room

Cylinder creates a negative pressure. Furthermore, it can thus, when the high-pressure accumulator - as described above - via the first pump, the first working line, the charging line (and boost line) is charged, at the same time the revolving second pump via the low pressure line connecting the pumps, the other low pressure line and the second working line pressure medium circulate or circulate without pressure.

In a particularly preferred application of the drive according to the invention, the differential cylinder is coupled to at least one adjustable rotor blade of a wind turbine, wherein the annular surface of the differential cylinder in the direction of reducing an angle of attack (pitch) of the at least one rotor blade and the piston bottom surface of the differential cylinder in the direction of increasing the pitch (pitch) acts.

In the following, various embodiments of the invention will be described in detail with reference to FIGS. Show it: 1 shows a simplified circuit diagram of a first embodiment of the drive according to the invention,

2 shows a simplified circuit diagram of a second embodiment of the drive according to the invention,

FIG. 3 shows a simplified circuit diagram of a third exemplary embodiment of the drive according to the invention,

FIG. 4 shows a simplified circuit diagram of a fourth exemplary embodiment of the drive according to the invention,

5 shows a detailed circuit diagram of a drive according to the invention according to one of the four exemplary embodiments of FIGS. 1 to 4 for a rotor blade adjustment of a wind power plant in a normal mode, FIG.

FIG. 6 shows the circuit diagram of the drive according to FIG. 5 in a normal mode with refilling function;

7 shows the circuit diagram of the drive according to FIG. 5 in a speed boost mode with maximum speed, FIG.

8 shows the circuit diagram of the drive according to FIG. 5 in the speed boost mode with minimum speed, FIG.

9 shows the circuit diagram of the drive according to FIG. 5 in the speed-boost mode during deceleration, FIG.

Figure 10 shows the circuit diagram of the drive according to Figure 5 in an emergency function with maximum

Force,

Figure 1 1 shows the circuit diagram of the drive according to Figure 5 in the emergency function with low force, and

Figure 12 shows the circuit diagram of the drive according to Figure 5 when loading the

High-pressure accumulator.

FIG. 1 shows a simplified circuit diagram of a first exemplary embodiment of the drive according to the invention. He has a variable speed electric motor 26, at the output of a gear 18 is coupled. This is on the output side on the one hand to a first

Drive shaft 40 of a first pump 23 and on the other hand to a second drive shaft 42 of a second pump 24 is coupled. In this case, the transmission 18 is designed such that the first drive shaft 40 always rotates slower than the second drive shaft 42. The two Pumps 23, 24 are identical constant pumps, wherein the first pump 23 always has a smaller delivery volume than the second pump 24 due to the slower drive.

The first pump 23 is connected via a first working line 44 to an annular space 48 of a differential cylinder 9, while the second pump 24 is connected via a second working line 46 to a piston head space 50 of the differential cylinder 9. The annular space 48 is delimited by an annular surface A1 of a piston of the differential cylinder 9, while the piston head space 50 is delimited by a piston bottom surface A2 of the piston. According to the invention, the transmission 18 is designed such that the

Speed ratio of the first drive shaft 40 to the second drive shaft 42 and thus the delivery volume flow ratio of the first pump 23 to the second pump 24 the

Area ratio of the annular surface A1 to the piston bottom surface A2 corresponds.

Figure 2 shows a simplified circuit diagram of a second embodiment of the drive according to the invention. This corresponds largely to the first embodiment shown in FIG 1. Deviating from the first embodiment, the required or

desired speed ratio of the two pumps 23, 24 realized in that between a drive shaft of the first pump 23 and the drive shaft 42 of the second pump 24, a transmission 1 18 is arranged. The first pump 23 is driven directly by the electric motor 26, while the second pump 24 is indirectly from the electric motor 26 via the first

Pump 23 and the transmission 1 18 is driven. According to the invention, the transmission 1 18 is designed such that the speed ratio of the first drive shaft 40 to the second drive shaft 42 and thus the delivery volume flow ratio of the first pump 23 to the second pump 24 corresponds to the area ratio of the annular surface A1 to the piston bottom surface A2.

FIG. 3 shows a third exemplary embodiment of the drive according to the invention. In this case, the electric motor 26, the working lines 44, 46 and the differential cylinder 9 correspond to those of the two preceding embodiments. Notwithstanding the preceding embodiments, the volume flow ratio of the two pumps 223, 224 required by the area ratio A1 to A2 is realized in that the first pump 223 is a constant displacement pump, while the second pump 224 is a variable displacement pump whose volume is correspondingly greater than the first Pump 223 is set to increase. In this case, the electric motor 26, the fixed displacement pump 223 and the variable displacement pump 224 are mechanically "in series" connected.

Figure 4 shows a fourth embodiment of the drive according to the invention, which is in principle similar to the third embodiment. The working lines 44, 46 and the differential cylinder 9 correspond to those of the previous embodiments. Notwithstanding the third embodiment, the first pump 323 is a variable displacement pump and the second pump 324 is a constant displacement pump, wherein the delivery volume of the first pump 323 is set reduced in the required manner. In this case, the electric motor 26, the variable displacement pump 323 and the fixed displacement pump 324 are mechanically "in series" connected.

Figures 5 to 12 each show a detailed circuit diagram of a

Drive according to the invention according to one of the four previous embodiments in an application for a Rotorblattverstelleinnchtung m for one or more rotor blades of a (not shown in detail) wind turbine. The two pumps shown correspond to those of one of the preceding embodiments 23, 24; 223, 224; 323, 324. The first pump 23; 223; 323 is connected via the first working line 44 with the annular space 48 of the Differenziaizylinders 9, while the second pump 24; 224; 324 is connected via the second working line 46 with the piston head space 50 of the Differenziaizylinders 9. In the first working line 44 is one of the first pump 23; 223; 323 provided to the annular space 48 hydraulically unlockable check valve 4a, while in the second working line 46 one of the second pump 24; 224; 324 to the piston head space 50 opening hydraulically entprechbares check valve 5 is provided. Low pressure side, the two pumps 23, 24; 223, 224; 323, 324 via a

Low pressure line 52 connected to each other. Between the low-pressure line 52 and the first working line 44, a non-return valve 19 opening from the low-pressure line 52 to the first working line 44 is provided. In the low pressure line 52 open via a common filter 22 and a common check valve 21 leakage lines of the two pumps 23, 24; 223, 224; 323, 324. At the low pressure line 52 is a

Low pressure accumulator 28 connected. The low-pressure accumulator 28 is connected via a further low-pressure line 54 to the second working line 46. In this case, in the further low-pressure line 54, a non-return valve 20 opening from the low-pressure accumulator 28 to the second working line 46 is provided. A high pressure accumulator 27 is connected via an emergency line 56 to the piston head space 50 of the Differenziaizylinders 9. Here, a flow control valve 7 and a hydraulically releasable check valve 2 are arranged in the emergency line 56, the opening direction of the high-pressure accumulator 27 is directed to the piston head space 50. Furthermore, a pressure sensor 35 is provided on the emergency line 56 in the vicinity of the differential cylinder 9. The emergency line 56 and thus the high-pressure accumulator 27 are connected via a boost line 58 to the second working line 46. In this case, the boost line 48 opens in the vicinity of the Differenziaizylinders 9 in the second working line 46. In the boost line 58 a standard open shut-off valve 29, a hydraulically lockable check valve 1, a throttle 6 and a check valve 15 are arranged. The opening directions of the two check valves 1, 15 are directed from the high-pressure accumulator 27 to the second working line 46. To the boost line 58 is in the vicinity of the high-pressure accumulator 27 a

Pressure sensor 37 connected. The high-pressure accumulator 27 is above a

Pressure relief valve 1 1 to the further low-pressure line 54 relieved. Parallel to a standard closed shut-off valve 8 is provided.

Between the annular space 48 and the check valve 4a, a charging line 60 is connected to the first working line 44, which opens into the boost line 58 between the shut-off valve 29 and the check valve 1. In this case, a check valve 17 opening from the first working line 44 to the boost line 58 is provided in the charging line 60. Between the charging line 60 and the low pressure line 52, a pressure limiting valve 33 is arranged, via which the charging line 60 to the low pressure line 52 is relieved. In parallel, a hydraulically releasable check valve 3 is provided, whose

Opening direction of the charging line 60 is directed to the low pressure line 52.

The second working line 46 is connected via a pressure relief valve 10 to

Low pressure line 52 relieved. In this case, the pressure limiting valve 10 on the input side between the Differenziaizylinder 9 and the pilot-operated check valve 5 and a check valve 16 between the second pump 24; 224; 324 and the pilot-operated check valve 5 connected to the second working line 46.

Furthermore, a pressure booster 31 is provided, the input side on the one hand with the low pressure line 52 and on the other hand via a respective pressure to the translator 31st opening check valve 13, 14 is connected to the two working lines 44, 46. In this case, between the two check valves 13, 14 on the one hand and the

Pressure Translator 31 on the other hand, a throttle 36 and serving as a shut-off valve seat 32 is provided.

The annular space 48 can be connected to the low-pressure accumulator 28 via a further emergency line 62 and via a section of the further low-pressure line 54. For this purpose, a flow control valve 34, designed as a 2/2-way valve shut-off valve 30 and a hydraulically releasable check valve 4 are arranged in the further emergency line 62, wherein the opening direction of the check valve 4 is directed from the annular space 48 to the low pressure accumulator 28.

The actuation of the hydraulically releasable check valves 2, 4, 4a and 5 is carried out jointly via a designed as a 3/2 way valve fail-safe valve 38. On the input side, the fail-safe valve 38 is supplied with control pressure medium, the optional from

High-pressure accumulator 27 or over the further low-pressure line 54 from

Low-pressure accumulator 28 can be tapped.

The two hydraulically releasable check valves 1 and 3 can be unlocked together via a 3/2-way seat valve 12, wherein the input-side control pressure means of the 3/2-way seat valve 12 can be tapped either from the low pressure line 52 or from the charging line 60.

The arrows drawn in FIGS. 5 to 12 indicate the size and direction of the volume flows.

In Figure 5, the drive is shown in normal operation. In the illustration, the differential cylinder 9 extends. If the direction of rotation of the electric motor 26 were reversed, the direction of the volume flows also reversed, and the differential cylinder 9 introduced.

FIG. 6 normal operation as in FIG. 5, but with refilling function of FIG

High-pressure accumulator 27. At the theoretically tight seat valves used, it is possible that practically creates some leakage. This leakage leads to a decrease in the pressure in the high-pressure accumulator 27, which jeopardizes its function and thus the safety of the system. So that any leakages do not compromise safety is one

Recharging device consisting of the check valve 13 and 14, pressure booster 31, directional seat valve 32, throttle 36 and pressure sensor 37 executed. If an excessively low accumulator pressure is detected on the pressure sensor 37 in the normal operating mode on the high-pressure accumulator 27, the directional seat valve 32 is switched to the illustrated position. As a result, oil flows from the higher pressure side (in this case from the second working line 46 - with the Differenziaizylinder 9 retracting the first working line 44 could be the higher pressure side) via the check valve 13, the throttle 36 and the directional control valve 32 for

Compressor 31. In this, the volume flow with input pressure (from the second working line 46) translated into a smaller volume flow with outlet pressure and the high-pressure accumulator 27 is supplied. The inlet pressure (from the second working line 46) has a pressure level corresponding to the friction of the system (at least 40 bar). Of the

Input pressure (from the second working line 46) forms the drive of the pressure booster 31 which has a maximum transmission ratio. The input pressure (from the second working line 46) multiplied by the transmission ratio of

Pressure reducer 31 must be greater than the maximum pressure in the high-pressure accumulator 27. By removing the amount of oil (from the second working line 46) for the purpose of accumulator pressure increase 27, the extension speed of the differential cylinder decreases 9. The drop in speed is increased by increasing the speed of the electric motor 26th (see Figures 1 to 4) balanced. So that a small amount of oil is removed, the

Raising the speed of the electric motor 26 thus remains moderate, a throttle 36 is introduced in the pressure path.

FIG. 7 shows the maximum speed of the differential cylinder 9 in the speed boost mode. In order to introduce as little forces as possible into the wind turbine structure in the event of sudden strong gusts of wind, the differential cylinder 9 is moved out quickly over a short distance. For this purpose, the 3/2-way seat valve 12 is switched to the position shown. As a result, the hydraulically releasable check valves 1 and 3 are unlocked. From the high-pressure accumulator 27 now oil flows through the boost line 58

High pressure on the shut-off valve 29, the check valve 1, the throttle 6 and the

Check valve 15 to Differenziaizylinder 9. The throttle 6 prevents it, that the Differentialiaizylinder 9 inflowing amount of oil is too large. At the same time, the pumps 23, 24; 223, 224; 323, 324 brought by the electric motor 26 to maximum speed. Thereby flows to the Differenziaizylinder 9 of the pump 24; 224; 324 via the hydraulically releasable check valve 5, oil to, whereby its speed is further increased.

FIG. 8 shows the minimum speed of the differential cylinder 9 in the speed boost mode. This occurs when the process is initiated as described above, wherein the direction of rotation of the electric motor 26 is reversed. Oil then flows from

Differenziaizylinder 9 via the check valve 5 to the pump 24; 224; 324 and thus reduces their speed. The speed in the speed boost mode can be adjusted continuously between maximum speed (according to FIG. 7) and minimum speed (according to FIG. 8) by changing the direction of rotation and speed of the electric motor 26.

In order to leave the speed-boost mode, the differential cylinder 9 must be braked. Figure 9 shows this deceleration in speed boost mode. For this purpose, the 3/2-way seat valve 12 is de-energized. It then assumes the drawn position. As a result, the hydraulically releasable check valves 1, 3 are closed. The

Pressure conditions in Differenziaizylinder 9 reverse, it is braked. This process can be superimposed on the pump drive. Depending on the direction of rotation of the electric motor 26, the extension movement is decelerated until the speed set by the electric motor 26 is reached and is then continued at this speed in the extension direction. In the other case, the Differenziaizylinder 9 is braked to the state and it reverses its direction of movement and then moves with that of the electric motor 26th

predetermined speed. In emergency or dangerous situations, the rotor blade on the

Rotor blade adjustment m are spent in its safe position. FIG. 10 shows an emergency function with maximum force. This drives the Differenziaizylinder 9. It must be ensured that the Differenziaizylinder 9 can always reach this position. For this purpose, 27 high pressure oil is stored in the high-pressure accumulator. In order to extend the Differenziaizylinder 9 in an emergency, the fail-safe valve 38 is drawn in the

Switched position, thereby the hydraulically releasable check valves 2, 4, 4a, 5 are depressurized and oil flows from the high-pressure accumulator 27 via the flow control valve 7 and the hydraulically releasable check valve 2 to Differenziaizylinder 9. Am

Flow control valve 7, the speed is specified. The outflowing oil flows over Flow control valve 34, shut-off valve 30 to the low pressure accumulator 28. The downstream flow control valve 34 is set to a higher cylinder speed than arranged in the flow control valve 7. When the differential cylinder 9 tensile forces act the flow control valve 34, the cylinder speed.

Figure 1 1 shows the emergency function with low power. This is only possible if the pressure sensor 35 measures a sufficiently small pressure. , To save little oil from the

High-pressure accumulator 27 can be seen, the shut-off valve 30 is switched to its illustrated position. As a result, the path of the outflowing oil changes in the manner shown. The outflowing oil is thus under pressure and flows to the high-pressure accumulator 27. The pressure in the differential cylinder 9 is now approximately constant. In the piston head space 50, it is slightly lower by the control pressure difference at the flow control valve 7. Of the

Differential cylinder 9 extends with less force, since only the area difference A2- Aleffective. From the high-pressure accumulator 27 less oil is removed.

To restore the operating state after emergency or emergency function, the high-pressure accumulator 27 must be refilled. FIG. 12 shows how the

High-pressure accumulator 27 is reloaded. For this purpose, the shut-off valve 30 is switched to its illustrated position and the pumps 23, 24; 223, 224; 323, 324 are driven by the electric motor 26 in a drawn manner. In this case, the first pump 23, 223, 323 conveys oil to the high-pressure accumulator 27, while it is supplied by the low-pressure accumulator 28. The second pump 24; 224; 324 pumps or circulates the oil without pressure. Of the

Differential cylinder 9 is held in the extended position, so that the rotor blade is low in resistance and thus low in force.

Notwithstanding the second embodiment shown in Figure 2, the electric motor 26 and the second pump 24 drive directly, with a reduction gear between the second pump 24 and the first pump 23 is provided. Notwithstanding the drive shown in FIGS 5 to 12 may instead of the

Druckübersetzter 31 also be used an electric motor with a pump.

Disclosed is a linear actuator with a double pump and a differential cylinder whose annular space or piston rod space of an annular surface or piston rod surface a piston is limited and connected to a first pump, and whose piston bottom space is bounded by a piston bottom surface of the piston and connected to a second pump. Both pumps are driven by a common variable speed electric motor. The ratio of the ring area to

Piston bottom surface is equal to the ratio of the delivery volume of the first pump to the delivery volume of the second pump. In a first variant, this is done by

Adjustment of the speeds of the two pumps realized by a gear. According to a second variant, this is realized in that a pump with adjustable

Delivery volume is executed. According to a third variant, this is realized in that at the same pump speed, the ratio of the displacement volume of the pump corresponds to the ratio of the cylinder surfaces.

LIST OF REFERENCES

1 hydraulically operated check valve

2 hydraulically operated check valve

3 hydraulically operated check valve

4 hydraulically operated check valve

4a hydraulically operated check valve

5 hydraulically operated check valve

6 throttle

7 flow control valve

8 shut-off valve

9 differential cylinders

10 pressure relief valve

1 1 pressure relief valve

12 3/2-way seated valve

13 check valve

14 check valve

15 check valve

16 check valve

17 check valve

18 gears

19 check valve

20 check valve

21 check valve

22 filters

23 slower driven pump

24 faster driven pump

26 electric motor

27 high-pressure accumulator

28 low-pressure accumulator

29 shut-off valve

30 shut-off valve

31 pressure intensifier 32 directional seat valve

33 pressure relief valve

34 flow control valve

35 pressure sensor

36 throttle

37 pressure sensor

38 fail-safe valve

40 first drive shaft

42 second drive shaft

44 first working line

46 second working line

48 annulus

50 piston bottom space

52 low pressure line

54 more low pressure line

56 emergency line

58 boost line

60 charging line

62 more emergency line

1 18 gearbox

223 Constant pump with lower delivery volume

224 Variable displacement pump with larger delivery volume

323 Variable displacement pump with low adjusted delivery volume

324 Constant pump with larger delivery volume

A1 ring surface

A2 piston bottom surface

m rotor blade adjustment

Claims

claims

1. drive with a differential cylinder (9), the annular space (48) of a

Ring surface (A1) is limited and with a first pump (23) is connected, and whose piston bottom space (50) of a piston bottom surface (A2) is limited and connected to a second pump (24), wherein the two pumps (23, 24 ) by a common variable speed electric motor (26) are driven, characterized by a transmission (18, 1 18) via which a speed ratio of a rotational speed of the first pump (23) to a rotational speed of the second pump (24) can be generated, the area ratio (A1 / A2) of the annular surface (A1) corresponds to the piston bottom surface (A2).

2. Drive according to claim 1, wherein the transmission (18) on the input side of

Electric motor (26) is driven, and wherein the transmission (18) has two output shafts, each driving a pump (23, 24).

3. Drive according to claim 1, wherein one of the pumps (23) from the electric motor (26).

is driven, and wherein the transmission (1 18) is driven by the pump (23), and wherein the transmission (1 18) has an output shaft which drives the other pump (24).

4. drive with a differential cylinder (9), the annular space (48) of a

Ring surface (A1) is limited and with a first pump (223, 323) is connected, and whose piston bottom space (50) of a piston bottom surface (A2) is limited and with a second pump (224, 324) is connected, the two

Pumps (223, 224, 323, 324) of a common variable speed

Electric motor (26) are driven, characterized in that the pumps (223, 224; 323, 324) are driven synchronously, wherein one of the two pumps is a variable displacement pump (224; 323).

5. Drive according to one of the preceding claims, wherein both pumps (23, 24;

223, 224; 323, 324) have a common or two directly coupled shafts and have a common or two directly coupled housing and a Form double pump whose ratio of the geometric displacement volumes corresponds to the ratio of the cylinder effective areas.

6. Drive according to one of the preceding claims with a first

Working line (44), via which the first pump (23, 223, 323) is connected to the annular space, and with a second working line (46), via which the second pump (24, 224, 324) communicates with the piston head space (50). is connected, wherein a high-pressure accumulator (27) to the first working line (44) or directly to the

Annulus (48) or to the second working line (46) or directly to the

Piston floor space (50) is connected.

7. Drive according to claim 6, wherein the high-pressure accumulator (27) via a

Emergency line (56) is connected directly to the piston head space (50), and wherein the high-pressure accumulator (27) via a boost line (58) to the second

Working line (46) is connected.

8. Drive according to claim 7 with a charging line (60) via which the first

Working line (44) with the boost line (58) or with the high-pressure accumulator (27) is connected, wherein in the charging line (60) for opening a boost line check valve (17) is arranged.

9. Drive according to one of the preceding claims with a

Low pressure line (52), which connects the two pumps with each other, wherein the low pressure line (52), a low pressure accumulator (28) is connected.

10. Drive according to claim 9 with a further Niederduckleitung (54) via which the Niederduckspeicher (28) to the second working line (46) is connected, wherein in the further low-pressure line (54) to the second working line (46) opening check valve (20 ) is provided.

1 1. Wind turbine with a rotor having a plurality of rotor blades, each having one or a common Rotorblattverstelleinrichtung (m), and having a drive according to one of the preceding claims, the differential cylinder (9) is coupled to the at least one Rotorblattverstelleinrichtung (m), wherein the Ring surface (A1) in the direction of reducing an angle of attack of the at least one rotor blade and the piston bottom surface (A2) in the direction of increasing the angle of attack acts.