Hydraulic system for adjusting pitch angle of rotor blade of wind turbine and wind turbine having such hydraulic system

Abstract

The invention relates to a hydraulic system (10) for adjusting a pitch angle of a rotor blade (108) of a wind turbine (100). The hydraulic system (10) comprises a variable pump (12), a hydraulic energy accumulator (14), a dynamic valve (16), a control valve (18), an oil tank (20) and a variable pitch cylinder (22). The invention also relates to a wind turbine having such a hydraulic system (10).

Description

Technical Field

[0001] The invention relates to a hydraulic system for adjusting the pitch angle of a rotor blade of a wind turbine and a wind turbine having such a hydraulic system. Background Art

[0002] Such hydraulic systems are known in the prior art and are also referred to as blade adjustment systems. These hydraulic systems are configured to adjust the aerodynamic angle of attack of one or more rotor blades of a wind turbine, thereby setting the so-called pitch angle. To this end, the rotor blades are rotatably mounted on the rotor of the wind turbine via a pitch bearing and a pitch gearbox. The rotor is in turn rotatably mounted on the nacelle of the wind turbine via a hub. The hydraulic system changes the angle of attack of the rotor blades as a function of the current wind speed, so as to operate the wind turbine with optimal efficiency and, thus, a substantially constant rated power. The angle of attack of the rotor blades is adjusted for a variety of purposes in order to achieve the desired blade lift, for example, to stationary the rotor, to limit the energy supply of the wind to the blades, to perform maintenance work, etc. In other words, the angle of attack is adapted to the wind direction.

[0003] Furthermore, the hydraulic system is also configured to prevent the wind turbine from being damaged in strong winds by turning the rotor blades out of the wind, the so-called feathered position. This interrupts the lift of the rotor blades and the rotor may come to a standstill with the support of the brakes.

[0004] To this end, the hydraulic system usually has a pitch cylinder that engages with the rotor blades and can change the pitch angle of the rotor blades relative to the hub by retracting or extending the pitch cylinder. The pitch cylinder is provided with pressure by a hydraulic accumulator, whereby the hydraulic accumulator can be charged by a suitable and simple device (usually a metering pump) arranged in the nacelle. Since the device is only used to charge the accumulator, the efficiency of the device is not considered in detail in these systems. In addition, since the device is arranged in the nacelle, the heat that it may generate is a problem.

[0005] However, a disadvantage of the known solution is that, since the hydraulic accumulator only supplies pressure to the pitch cylinder, this (high) pressure is also permanently present on the rod side of the pitch cylinder. Furthermore, a correspondingly large accumulator must be selected in order to be able to provide the necessary pressure and the required amount of hydraulic body. Furthermore, the rotary feedthrough required for charging the accumulator is expensive, complex and maintenance-intensive. For reasons of efficiency, it would therefore be desirable to solve the pitch angle adjustment problem in a different way and, if possible, to eliminate the rotary feedthrough. However, due to the heat generated, it is not possible to install a metering pump in the rotating hub. Due to the complex hydraulic design, the use of a variable pump for pure accumulator charging operation is not economical. Furthermore, a variable pump is not suitable for direct control of the pitch cylinder, since it takes a certain amount of time for the variable pump to provide the required flow or pressure after it has been swung out. Summary of the invention

[0006] Therefore, an object of the present invention is to provide an improved hydraulic system for adjusting the pitch angle of rotor blades of a wind turbine. Another object of the present invention is to provide a wind turbine having such a hydraulic system.

[0007] A solution to the above mentioned problem is achieved by a hydraulic system according to claim 1 and a wind turbine according to claim 15. Further preferred embodiments are described in the dependent claims.

[0008] According to the invention, a hydraulic system for adjusting the pitch angle of the rotor blades of a wind turbine is therefore proposed. The hydraulic system comprises a variable pump, a hydraulic accumulator, a dynamic valve, a control valve, an oil tank and a pitch cylinder. Preferably, the control valve is configured as a proportional valve, preferably a slide valve. The variable pump is connected to the control valve via a first connecting line without a rotating oil seal, and the control valve is connected to the oil tank via a second connecting line without a rotating oil seal. The control valve is also connected to the piston side of the pitch cylinder via a third connecting line without a rotating oil seal, and the control valve is connected to the rod side of the pitch cylinder via a fourth connecting line without a rotating oil seal. Thus, in a first switching position of the control valve, the first connecting line is connected to the third connecting line, while in a second switching position of the control valve, the first connecting line is connected to the fourth connecting line, and the second connecting line is connected to the third connecting line. The hydraulic accumulator is connected to the first connecting line via a fifth connecting line, wherein the fifth connecting line leads to the first connecting line at an interface. The dynamic valve is arranged in the fifth connecting line and, in a first switching position, blocks the fifth connecting line in a flow direction from the hydraulic accumulator to the first connecting line. In a second switching position, the dynamic valve releases the fifth connecting line.

[0009] In principle, the hydraulic system according to the invention serves to adjust the pitch angle via the flow provided by the variable pump. The hydraulic accumulator and the dynamic valve serve to compensate for the designed delay in the flow provided by the variable pump. To set the pitch angle, the control valve is switched to the corresponding switching position and the variable pump is swung out. At the same time, the dynamic valve opens, thereby connecting the hydraulic accumulator to the control valve via the fifth connecting line and the first connecting line. As soon as sufficient capacity is obtained via the variable pump, the dynamic valve closes again and disconnects the hydraulic accumulator from the control valve. The capacity will then be provided entirely by the variable pump.

[0010] The advantage of this is that the efficiency is increased by using a variable displacement pump, and the hydraulic system is located in the hub, which significantly reduces the heat generation. In this way, a rotating oil seal can be omitted. In addition, since only the initial supply via the accumulator is required, the hydraulic accumulator can be configured with a smaller storage volume and a higher storage pressure, which significantly improves the overall cost-effectiveness of the accumulator. In addition, this also allows pressure to be applied as needed, so that the rod side of the pitch cylinder is no longer subject to high pressure for a long time.

[0011] Preferably, a first check valve opening in the flow direction from the variable pump to the control valve is arranged upstream of the interface in the first connecting line. When the dynamic valve is in the second switching position, the first check valve prevents the hydraulic oil in the accumulator from flowing in the direction of the variable pump.

[0012] Preferably, the hydraulic accumulator is connected to the fourth connecting line via a sixth connecting line, wherein the control valve blocks the fourth connecting line in the first switching position. This means that when pressure is applied to the piston side of the pitch cylinder, hydraulic oil discharged from the rod side is loaded into the hydraulic accumulator. In this case, preferably, a second non-return valve that opens in the flow direction from the fourth connecting line to the hydraulic accumulator is arranged in the sixth connecting line. This prevents the hydraulic oil from accidentally flowing out of the hydraulic accumulator via the sixth connecting line.

[0013] Preferably, the hydraulic system comprises a control unit. The control unit may also be a higher-level control unit of the wind turbine or an independent control unit of the hydraulic system.

[0014] Preferably, the dynamic valve is preloaded to the first switching position and can be activated by the control unit to switch to the second switching position. Once the pitch angle adjustment is performed, the control unit switches the dynamic valve to the second switching position, thereby connecting the hydraulic accumulator to the control valve via the first connecting pipe line. Once sufficient capacity is provided by the variable pump, the signal from the control unit is interrupted and the dynamic valve is switched to the first switching position due to the preload so as to disconnect the hydraulic accumulator from the first connecting pipeline. The dynamic valve can be configured, for example, as an electromagnetically actuated 2 / 2-way valve, which switches accordingly when energized by the control unit.

[0015] Preferably, the control valve can be switched to the first switching position or the second switching position by the control unit. Also preferably, the control valve can be switched to the accumulator charging position. In the accumulator charging position of the control valve, the first connecting line, the second connecting line, the third connecting line and the fourth connecting line are all blocked. This means that when the control valve is in the accumulator charging position, the hydraulic accumulator can be charged through the fifth connecting line. It is conceivable that the dynamic valve is switched to the second switching position in order to charge the hydraulic accumulator. In addition, the dynamic valve can also be configured so that in the first switching position of the dynamic valve, the check valve can realize the flow from the first connecting line to the hydraulic accumulator.

[0016] Preferably, a first pilot control line branches out from the first connecting line and is connected to the variable pump in such a way that a pilot control pressure signal can be applied to the variable pump. Preferably, a pilot control valve is provided in the first pilot control line, whereby the pilot control valve is configured to block or release the pilot control line. Furthermore, the pilot control valve can be configured to release the pilot pressure signal applied to the variable pump to the oil tank. Preferably, the first pilot control valve is actuated by the control system.

[0017] In the first embodiment, when the control valve is in the accumulator charging position, the pilot control valve for charging the accumulator is opened. This ensures that the variable pump swings out and increases the flow rate according to the pilot pressure signal sent through the first pilot control pipeline at that time. Preferably, the first embodiment is an embodiment with a load pressure signaling circuit.

[0018] In this case, preferably, the hydraulic system has a second pilot control line, whereby the second pilot control line is connected to the first pilot control line via a first shuttle valve. In the first switching position of the control valve, the second pilot control line is connected to the first connecting line or the third connecting line, and in the second switching position of the control valve, the second pilot control line is connected to the fourth connecting line. Therefore, the load pressure applied to the pitch cylinder sends a signal via the second pilot control line and can therefore be transmitted as a pilot pressure signal to the load pressure regulator via the first shuttle valve, thereby operating the variable pump accordingly.

[0019] The hydraulic system includes a third pilot control line, which branches out from the first pilot control line between the control valve and the pilot control valve and leads to the first pilot control line between the pilot control valve and the variable pump through a second shuttle valve. A preload valve is provided in the third pilot control line, whereby the preload valve preloads the pilot pressure signal in the first pilot control line to a defined pressure. This arrangement ensures that the pilot pressure signal always maintains a minimum level, so that the variable pump always swings out to a certain extent.

[0020] Preferably, the first pilot control line is depressurized to the tank via a pressure relief line, whereby a pressure relief element is arranged in the pressure relief line. The pressure relief element is preferably a pressure relief valve. It is also conceivable to provide a leak point as a pressure relief element via a throttle valve or the like. This ensures that the pressure in the first pilot control line is not locked, but decreases over time, so that the variable displacement pump can be safely swung back to the zero position when necessary.

[0021] In a second embodiment, no load pressure signaling circuit is provided, but the system is completely controlled by the control unit. For this purpose, preferably, suitable sensors are provided in the hydraulic system, for example, position sensors on the pitch cylinders. Also preferably, the control system can also use other sensor data of the wind turbine to adjust the pilot pressure signal of the pump. Preferably, the pilot control valve is configured as a proportional 3 / 3 directional control valve so as to block the first pilot control line or connect it to the variable pump, or release the pilot control pressure signal applied to the variable pump to the oil tank, so that the variable pump rotates in the zero direction.

[0022] Preferably, a flow control element is arranged in the third connecting line. Preferably, the flow control element is configured as a pressure valve and a bypass line bypassing the pressure valve in the flow direction from the control valve to the pitch cylinder. This ensures that the piston side of the pitch cylinder can be pressurized unhindered, but the flow can be regulated when pressure is applied on the rod side.

[0023] According to the present invention, a wind turbine is also provided, which is provided with a tower, a nacelle arranged on the tower, and a rotor rotatably mounted on the nacelle via a hub, at least one rotor blade is rotatably arranged on the rotor at a pitch angle relative to the hub, and the wind turbine includes the above-mentioned hydraulic system for adjusting the pitch angle, and the hydraulic system is completely arranged in the hub. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be described in more detail below with reference to the embodiments shown in the accompanying drawings. In the accompanying drawings:

[0025] Figure 1is a side view of a wind turbine;

[0026] Figure 2 is a hydraulic circuit diagram of a hydraulic system according to a first exemplary embodiment of the present invention;

[0027] Figure 3 is a hydraulic circuit diagram of a hydraulic system according to a second exemplary embodiment of the present invention; and

[0028] Figure 4 is a hydraulic circuit diagram of a hydraulic system according to a third exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0029] Figure 1 1 shows a side view of a wind turbine 100 according to the present invention. The wind turbine 100 has a tower 102 and a nacelle 104 attached to the tower 102. A rotor 106 is rotatably mounted on the nacelle 104 via a hub 112. The wind turbine 100 further includes a plurality of rotor blades 108 attached to the rotor 106. In addition, a hydraulic system 10 (see FIG. 1 ) is provided for each rotor blade 108 and is completely disposed in the hub 112. Figures 2 to 4 ), the hydraulic system 10 is configured to adjust the aerodynamic angle of attack of the respective rotor blades 108 of the wind turbine 100. The hydraulic system changes the angle of attack of the rotor blades 108 as a function of the current wind speed in order to operate the wind turbine 100 at optimal efficiency and thus at a substantially constant rated power. To this end, the angular position of the rotor blades 108 relative to the hub 112, the so-called pitch angle, is adjusted by the respective hydraulic system 10 in such a way that the required lift is generated. The hydraulic system 10 is also configured to prevent the wind turbine 100 from being damaged in strong winds by turning the rotor blades 108 out of the wind, into the so-called feathering position. In this way, the lift of the rotor blades 108 is interrupted and the rotor 106 stops rotating.

[0030] Figure 2A first exemplary embodiment of a hydraulic system 10 for adjusting the pitch angle of individual rotor blades 108 according to the invention is shown. The hydraulic system 10 comprises a variable displacement pump 12, a hydraulic accumulator 14, a control valve 18, an oil tank 20 and a pitch cylinder 22. In the exemplary embodiment, the control valve 18 is configured as a proportional three-way controller. The variable displacement pump 12 sucks hydraulic oil through the oil tank 20 in a known manner and is connected to the control valve 18 via a first connecting line 24. The control valve 18 is also connected to the oil tank 20 via a second connecting line 26. The pitch cylinder 22 is connected to the control valve 18 on the piston side via a third connecting line 28. On the rod side, the pitch cylinder 22 is connected to the control valve 18 via a fourth connecting line 30. The control valve can be switched to a first switching position RV1, a second switching position RV2 and an accumulator charging position RV3. In the first switching position RV1, the first connecting line 24 is connected to the third connecting line 28, and the second connecting line 26 and the third connecting line 30 are blocked. In the second switching position, the first connecting line 24 is connected to the fourth connecting line 30, and the second connecting line 26 is connected to the third connecting line 28. In the accumulator charging position RV3, the first connecting line 24, the second connecting line 26, the third connecting line 28 and the fourth connecting line 30 are blocked.

[0031] The hydraulic accumulator 14 is connected via a fifth connecting line 32, which leads to the first connecting line 24 between the variable pump 12 and the control valve 18 at an interface 34. The dynamic valve 16 is arranged in the fifth connecting line 32. The dynamic valve 16 is biased to a first switching position DV1, in which the fifth connecting line 32 is blocked in the flow direction from the hydraulic accumulator 14 to the interface 34. A first check valve 36 is arranged in the first connecting line 24 between the variable pump 12 and the interface 34. The first check valve 36 blocks the flow in the direction of the variable pump 12. In addition, the hydraulic accumulator 14 is connected to the fourth connecting line 30 via a sixth connecting line 38. A second check valve 40 that opens in the direction of the flow to the hydraulic accumulator 14 is arranged in the sixth connecting line 38.

[0032] The dynamic valve 16 can be actuated by a control unit 42 so that it switches to a second switching position DV2, in which the fifth connecting line 32 is released. In the exemplary embodiment, the dynamic valve 16 is therefore configured as an electromagnetically actuated 2 / 2-way valve. The control unit 42 can be an independent control unit 42 of the hydraulic system 10 or can also be part of a higher-level control unit of the wind turbine 100. The control unit 42 is also configured to switch the control valve 18 between a first switching position RV1, a second switching position RV2 and an accumulator charging position RV3. The control unit is also connected to the sensor system 110 of the wind turbine and to the position sensor 64 of the pitch cylinder 22. The control unit 42 processes the sensor data and takes the sensor data into account when controlling the hydraulic system 10.

[0033] A flow control element 62 is provided in the third connecting line 28. In this exemplary embodiment, the flow control element 62 is configured as a pressure valve and a bypass line that bypasses the pressure valve. The hydraulic oil can flow from the control valve 18 to the piston side of the pitch cylinder 22 unimpeded through the flow control element 62, but the flow from the piston side of the pitch cylinder 22 to the control valve 18 is controlled by the pressure valve. As shown in the figure, the pressure in the fourth connecting line 30 acts on the pressure valve on the control side.

[0034] exist Figure 2 In the exemplary embodiment shown, the load pressure signaling circuit for applying a pilot pressure signal to the variable pump 12 is provided with a first pilot control line 44 and a second pilot control line 48. The first pilot control line 44 branches out from the first connecting line 24 between the variable pump 12 and the first check valve 36 and is connected to the variable pump 12 via a load pressure regulator 74. The pilot pressure signal in the first pilot control line 44 determines the extension and contraction of the variable pump 12 by receiving the pilot pressure from the first connecting line 24 via a fourth pilot control line 76 and sending its signal to the variable pump 12 via the load pressure regulator 74. As shown in the figure, the load pressure regulator 74 is configured as a proportional 3 / 2-way valve, wherein the pressure in the fourth pilot control line 76 acts on the load pressure regulator 74 in the opening direction. The pressure in the first pilot control line 44 acts on the load pressure regulator 74 in the closing direction. In addition, the load pressure regulator 74 is preloaded in the closing direction by a spring. Therefore, according to the pilot pressure signal, the pressure signal is transmitted to the variable pump 12 through the load pressure regulator 74 to achieve swing, or the pressure signal is released to the tank 20 through the load pressure regulator 74 .

[0035] A pilot control valve 46 is arranged in the first pilot control line 44, which can be actuated by the control unit 42. As shown in the figure, the pilot control valve 46 in the exemplary embodiment is configured as an electromagnetically actuated 2 / 2-way valve. The pilot control valve 46 is biased to a switching position, which blocks the first pilot control line 44 in the direction of flow to the variable pump 12. The control unit 42 can be used to switch the pilot control valve 46 to the switching position that releases the first pilot control line 44.

[0036] In this exemplary embodiment, in the first switching position RV1 of the control valve 18, the second pilot control line 48 is connected to the third connecting line 28. In the second switching position RV2 of the control valve 18, the second pilot control line 48 is connected to the fourth connecting line 30. In the accumulator charging position RV3 of the control valve 18, the second pilot control line 48 is blocked. The second pilot control line 48 leads to the first pilot control line 44 between the pilot control valve 46 and the variable pump 12 via the first shuttle valve 50.

[0037] The first branch line 70 branches out from the third connecting line 28 between the pitch cylinder 22 and the flow control element 62. The first branch line 70 leads to the fifth connecting line 32 or the sixth connecting line 38. A first emergency valve 66 is arranged in the first branch line 70. In the exemplary embodiment, the first emergency valve 66 is configured as an electromagnetically actuated 2 / 2-way valve. The first emergency valve 66 is biased to a switching position that releases the first branch line 70. The control unit 42 can be used to switch the first emergency valve 66 to a switching position that blocks the first branch line 70.

[0038] The second branch line 72 branches out from the fourth connecting line 30 between the pitch cylinder 22 and the control valve 18. The second branch line 72 leads directly to the second connecting line 26, wherein the second emergency valve 68 is arranged in the second branch line. In the exemplary embodiment, the second emergency valve 68 is configured as an electromagnetically actuated proportional 2 / 2-way valve. The second emergency valve 68 is biased to a switching position that releases the second branch line 72. The control unit 42 can be used to switch the second emergency valve to a switching position that blocks the second branch line 72.

[0039] The first emergency valve 66 and the second emergency valve 68 are provided in a known manner for emergency control of the hydraulic system 10 , for example in the event of a power failure. Therefore, during normal operation, the first emergency valve 66 and the second emergency valve 68 are energized by the control unit 42 .

[0040] The operation of the hydraulic system 10 for setting the pitch angle will now be described.

[0041] In order to adjust the pitch angle by extending the pitch cylinder 22, the control valve 18 is switched to the first switching position RV1 by the control unit 42. At the same time, the control unit switches the dynamic valve 16 to the second switching position DV2, thereby connecting the hydraulic accumulator 14 to the first connecting line 23. At this time, the variable pump 12 has not yet swung out and only provides dp pressure. In the first switching position RV1 of the control valve 18, the first connecting line 24 and the third connecting line 28 connected to the first connecting line 24 are pressurized by the hydraulic accumulator 14, so that the pitch cylinder 22 begins to extend. The load pressure signal of the third connecting line 28 is received by the second pilot control line 48 and fed into the first pilot control line 44 through the first reciprocating valve 50. Therefore, the pilot pressure signal is applied to the variable pump 12, and the variable pump 12 swings out. Once the variable pump 12 supplies a sufficient amount, the dynamic valve 16 is switched to the first switching position DV1 by the control unit 42 due to preloading, and the hydraulic accumulator 14 is disconnected from the first connecting line 24. Now, only the variable displacement pump 12 supplies oil to the pitch cylinder 22. The hydraulic oil discharged from the rod side of the pitch cylinder 22 flows out through the fourth connecting line 30 and is guided to the hydraulic accumulator 14 through the sixth connecting line 38.

[0042] In order to adjust the pitch angle by retracting the pitch cylinder 22, the control valve 18 is switched to the second switching position RV2 by the control unit 42. At the same time, the control unit switches the dynamic valve 16 to the second switching position DV2, thereby connecting the hydraulic accumulator 14 to the first connecting line 23. At this time, the variable pump 12 has not yet swung out and only provides dp pressure. In the second switching position RV2 of the control valve 18, the first connecting line 24 and the fourth connecting line 30 connected to the first connecting line 24 are pressurized by the hydraulic accumulator 14, so that the pitch cylinder 22 begins to retract. The load pressure signal of the fourth connecting line 30 is received by the second pilot control line 48 and fed into the first pilot control line 44 through the first reciprocating valve 50. Therefore, the pilot pressure signal is applied to the variable pump 12, and the variable pump 12 swings out. Once the variable pump 12 supplies a sufficient amount, the dynamic valve 16 is switched to the first switching position DV1 by the control unit 42 due to preloading, and the hydraulic accumulator 14 is disconnected from the first connecting line 24. Now, only the variable displacement pump 12 supplies oil to the pitch cylinder 22. The hydraulic oil exhausted from the piston side of the pitch cylinder 22 flows out through the third connecting line 28 and the flow control element 62 in a controlled manner and is discharged to the oil tank 20 through the second connecting line 26.

[0043] In order to charge the hydraulic accumulator 14, the control valve 18 is switched to the accumulator charging position RV3 by the control unit 42. At the same time, the pilot control valve 46 is switched to the switching position of releasing the first pilot control line 44 by the control unit 42. The dP pressure of the variable pump 12 received from the first connecting line 24 is transmitted to the variable pump 12 as a pilot pressure signal, and the variable pump 12 swings out. Then, the hydraulic accumulator 14 is charged with increasing pressure via the fifth connecting line 32, which is provided via the variable pump 12. As shown in the figure, in order to achieve this purpose, the dynamic valve 16 is configured in such a way that the flow towards the hydraulic accumulator 14 can also be achieved in the first switching position DV1 of the dynamic valve 16. Of course, during the charging operation of the accumulator, the dynamic valve 16 can also be switched to the second switching position DV2 by the control unit 42.

[0044] Figure 3 A second exemplary embodiment of a hydraulic system 10 according to the invention is shown. Figure 2 The exemplary embodiments shown differ in that the load pressure signaling circuit is configured differently.

[0045] In this exemplary embodiment, the load pressure signaling circuit has a third pilot control line 52, which branches off from the first pilot control line 44 between the control valve 18 and the pilot control valve 46. The third pilot control line 52 then flows back into the first pilot control line 44 between the pilot control valve 46 and the variable pump 12 via the second shuttle valve 54. A preload valve 56 is provided in the third pilot control line 52. The pressure in the first pilot control line 44 can be preloaded to a defined pressure level via the preload valve 56, so that an increased pilot pressure signal can be applied to the variable pump 12 compared to the first exemplary embodiment. As a result, the variable pump 12 has a greater swing-out amplitude.

[0046] In addition, the load pressure signaling circuit has a pressure relief line 58, which branches out from the first pilot control line 44 between the variable pump 12 and the first shuttle valve 50. The pressure relief line 58 is connected to the oil tank 20 so as to release any residual pressure that may be trapped in the first pilot control line 44 to the oil tank 20, so that the variable pump 12 can be safely swung back to the zero position. To this end, a pressure relief element 60 is provided in the pressure relief line 58. In this exemplary embodiment, the pressure relief element 60 is configured as a pressure relief valve so as to throttle and reduce the pressure of the first pilot control line 44 to prevent the pilot control pressure signal in the first pilot control line 44 from accidentally collapsing.

[0047] Figure 4A third exemplary embodiment of a hydraulic system 10 according to the invention is shown. The hydraulic system 10 according to the third exemplary embodiment does not have a load pressure signaling circuit. Instead, the pilot control valve 46 is configured as an electromagnetically actuated proportional 3 / 3 directional control valve, which can be controlled by the control unit 42 in the following way: the first pilot control line 44 is blocked or connected to the variable pump 12. In addition, the pilot control valve 46 can also be switched by the control unit 42 to a switching position, in which the pilot pressure signal applied to the variable pump 12 is released to the tank 20. This ensures that there is no residual pressure between the pilot control valve 46 and the variable pump 12 to prevent the variable pump 12 from swinging back.

[0048] It should also be noted that the various elements in the different embodiments may be combined together. For example, it is conceivable that a pressure relief line with a pressure relief element may also be provided in the first or third embodiment. In addition, it should be noted that numbers such as "first" and "second" are only used for distinction and do not specify a mandatory order. Reference numerals list 10. Hydraulic system 12 variable pump 14Hydraulic accumulator 16 Dynamic valve 18. Control valve 20 Fuel Tanks 22 Pitch Cylinder 24 First connecting pipeline 26 Second connecting pipeline 28Third connecting pipeline 30 Fourth connecting pipeline 32 Fifth connecting pipeline 34 interfaces 36First check valve 38 Sixth connecting pipeline 40 Second check valve 42Control Unit 44 First pilot control pipeline 46 pilot control valve 48 Second pilot control pipeline 50 First reciprocating valve 52 Third pilot control pipeline 54 Second reciprocating valve 56 Preload Valve 58 pressure relief line 60 pressure relief element 62 Flow control elements 64 Position Sensors 66 First emergency valve 68 Second emergency valve 70 first branch pipeline 72 Second branch pipeline 74 Load Pressure Regulator 76 Fourth pilot control pipeline First switching position of the DV1 dynamic valve Second switching position of the DV2 dynamic valve First switching position of RV1 control valve Second switching position of RV2 control valve Accumulator charging position of RV3 control valve 100 wind turbines 102 Tower 104 Engine Room 106 rotors 108 rotor blades 110 sensor system 112 wheel hub

Claims

1. A hydraulic system (10) for adjusting the pitch angle of a rotor blade (108) of a wind turbine (100), the hydraulic system (10) comprising a variable displacement pump (12), a hydraulic accumulator (14), a dynamic valve (16), preferably a proportional control valve (18), an oil tank (20) and a pitch cylinder (22), in, The variable pump (12) is connected to the control valve (18) via a first connecting line (24) without a rotating oil seal, the control valve (18) is connected to the oil tank (20) via a second connecting line (26) without a rotating oil seal, the control valve (18) is connected to the piston side of the pitch cylinder (22) via a third connecting line (28) without a rotating oil seal, and the control valve (18) is connected to the rod side of the pitch cylinder (22) via a fourth connecting line (30) without a rotating oil seal, so that in the first switching position (RV1) of the control valve (18), the first connecting line (24) is connected to the third connecting line (28), and so that in the second switching position (RV2) of the control valve (18), the first connecting line (24) is connected to the fourth connecting line (30), and the second connecting line (26) is connected to the third connecting line (28), The hydraulic accumulator (14) is connected to the first connecting line (24) via a fifth connecting line (32), and the fifth connecting line (32) leads to the first connecting line (24) at an interface (34). wherein the dynamic valve (16) is arranged in the fifth connecting pipeline (32), and The dynamic valve (16) blocks the fifth connecting line (32) in the flow direction from the hydraulic accumulator (14) to the first connecting line (24) and releases the fifth connecting line (32) in a second switching position (DV2).

2. The hydraulic system (10) according to claim 1, It is characterized in that A first check valve (36) that opens in the flow direction from the variable displacement pump (12) to the control valve (18) is arranged upstream of the port (34) in the first connecting line (24).

3. The hydraulic system (10) according to claim 1 or 2, It is characterized in that The hydraulic accumulator (14) is connected to the fourth connecting line (30) via a sixth connecting line (38), wherein the control valve (18) blocks the fourth connecting line (30) in the first switching position (RV1), and preferably, wherein a second check valve (40) opening in the flow direction from the fourth connecting line (30) to the hydraulic accumulator (14) is arranged in the sixth connecting line (38).

4. The hydraulic system (10) according to any one of the preceding claims, It is characterized in that The hydraulic system (10) comprises a control unit (42).

5. The hydraulic system (10) according to claim 4, It is characterized in that The dynamic valve (16) is biased to the first switching position (DV1) and can be actuated by the control unit (42) to switch to the second switching position (DV2).

6. The hydraulic system (10) according to claim 4 or 5, It is characterized in that The control valve (18) can be switched to the first switching position (RV1) or the second switching position (RV2) by the control unit.

7. A hydraulic system (10) according to any one of the preceding claims, It is characterized in that The control valve (18) can be switched to an accumulator charging position (RV3), and the first connecting line (24), the second connecting line (26), the third connecting line (28) and the fourth connecting line (30) are all blocked at the accumulator charging position (RV3), wherein when the control valve (18) is in the accumulator charging position (RV3), the hydraulic accumulator (14) can be charged through the fifth connecting line (32).

8. The hydraulic system (10) according to any one of the preceding claims, It is characterized in that A first pilot control line (44) branches off from the first connecting line (24), wherein a pilot control pressure signal can be applied to the variable displacement pump (12) via the first pilot control line (44).

9. The hydraulic system (10) according to claim 8, It is characterized in that Preferably, a proportional pilot control valve (46) is disposed in the first pilot control line (44), and the pilot control valve (46) is configured to block or release the first pilot control line (44) and / or release the pilot control pressure signal applied to the variable pump (12) to the oil tank (20).

10. The hydraulic system (10) according to claim 9, It is characterized in that The pilot control valve (46) can be actuated by the control unit in order to block or release the first pilot control line (44) or to release pressure to the tank (20).

11. The hydraulic system (10) according to any one of the preceding claims 8 to 10, It is characterized in that The hydraulic system comprises a second pilot control line (48), the second pilot control line (48) being connected to the first pilot control line (40) via a first shuttle valve (50), wherein, in the first switching position (RV1) of the control valve (18), the second pilot control line (48) is connected to the first connecting line (24) or the third connecting line (28), and Therein, in the second switching position (RV2) of the control valve (18), the second pilot control line (48) is connected to the fourth connecting line (30).

12. The hydraulic system (10) according to claim 11, It is characterized in that The hydraulic system (10) includes a third pilot control line (52), the third pilot control line (52) branching from the first pilot control line (44) between the control valve (18) and the pilot control valve (46), and leading to the first pilot control line (44) between the pilot control valve (46) and the variable pump (12) through a second shuttle valve (54), wherein a preload valve (56) is arranged in the third pilot control line (52), wherein the preload valve (56) preloads the pilot pressure signal in the first pilot control line (44) to a defined pressure.

13. The hydraulic system (10) according to claim 12, It is characterized in that The first pilot control pipeline (44) releases pressure to the oil tank (20) through a pressure relief pipeline (58), wherein a pressure relief element (60) is arranged in the pressure relief pipeline (58), and the pressure relief element (60) is preferably a pressure relief valve (60).

14. The hydraulic system (10) according to any one of the preceding claims, It is characterized in that A flow control element (62) is arranged in the third connecting pipeline (28), wherein preferably, the flow control element (62) is configured as a pressure valve and a bypass pipeline bypassing the pressure valve along the flow direction from the control valve (18) to the pitch cylinder (22).

15. A wind turbine (100), comprising a tower (102), a nacelle (104) arranged on the tower, and a rotor (106) rotatably mounted on the nacelle (104) via a hub (112), at least one rotor blade (108) being rotatably arranged on the rotor (106) at a pitch angle relative to the hub (112), the wind turbine (100) having a hydraulic system (10) for changing the pitch angle according to any of the preceding claims, the hydraulic system (10) being arranged in the hub (112).

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