Piston type energy accumulator

Abstract

The utility model relates to a piston type energy accumulator which is provided with an energy accumulator shell (10) and a separating piston (12) which can be arranged in the energy accumulator shell in a longitudinal moving mode, the separating piston separates two medium spaces (14 and 16) in the energy accumulator shell (10), according to the invention, the energy storage housing (10) is elastically constructed in a sandwich structure from a plurality of individual layers which are partially different from one another in such a way that, under the effect of at least one external force, the energy storage housing permits overall bending from an initial state and returns into the initial state when the respective external force is removed.

Description

Technical Field

[0001] The utility model belongs to the technical field of accumulators, and particularly relates to a piston accumulator. Background Art

[0002] This type of piston accumulator is common in the market. They are widely used in hydraulic equipment, such as for energy storage, for emergency operation, for suppressing mechanical shock or pressure shock, for vehicle suspension, etc.

[0003] A piston accumulator is known from DE10161797C1, which has an accumulator housing, a piston that can move axially in the accumulator housing and separates the gas-side medium space from the fluid-side medium space, a housing cover with a fluid through-opening that terminates the fluid-side medium space, and a stop device that delimits the piston path. The stop device has abutment surfaces that surround the fluid through-opening and are constructed at the piston and at the housing cover. The abutment surfaces abut against each other in the terminal position of the piston close to the housing cover. Among them, the abutment surfaces of the stop device are set as sealing surfaces, and at least one of the abutment surfaces has a convexly arched contour for an uninterrupted linear contact with the other abutment surface. The piston and the housing cover are made of steel, and the steel has a ductility selected accordingly in terms of the best sealing effect at its contact line. Due to this design of the abutment surfaces, the stop device that delimits the piston stroke is constructed with a metal seal having a dual function. The metal seal seals the piston against the fluid through-opening of the fluid-side space in the terminal position of the piston, and the linear contact caused by the arched design of at least one of the abutment surfaces of the metal seal results in a reliable closure due to the high surface pressure of the metal seal assembly, thereby ensuring complete airtightness, more precisely, ensuring complete airtightness over a very large temperature range, which can include a minimum value of -40°C.

[0004] Due to this characteristic design of plastically deforming persistently before possible fracture, such piston accumulators can also be used in harsh outdoor applications under extreme environmental conditions. For example, DE102016003345B4 exemplarily shows such an application in the context of a balancing device for compensating the rotor imbalance of a wind power device, which wind power device consists of at least one of the following:

[0005] - Rotor blades with two piston accumulators extending along their longitudinal directions, the separating pistons of the piston accumulators are respectively pre-tensioned by a compressible medium, and the piston accumulators are interconnected in a medium-guiding manner via an incompressible medium through a fluid pipeline;

[0006] - A control valve that establishes a medium connection between two piston accumulators of a pair of piston accumulators or separates them from each other by switching to a corresponding fluid line;

[0007] - An acceleration sensor;

[0008] - A rotor position sensor; and

[0009] - A control system for evaluating sensor data and manipulating at least a pair of piston accumulators by controlling the control valve.

[0010] With the aid of this balancing device, the corresponding rotor of the wind energy installation can be balanced accordingly during operation, which is usually necessary because especially during operation, imbalances can develop, for example due to the deposition of dirt on the rotor blades or due to non-uniform wind incidence, such as when turbulence occurs during wind operation.

[0011] During the operation of a wind energy installation, the rotor blades are usually also subject to deformation. The deformation is described using a kinematic model that can describe the deformation of the rotor blades, for example based on the assumption of an Euler - Bernoulli bending beam. In this regard, the theoretically determinable deformation at the corresponding rotor blade is consistent with the actual measurement results, which are preferably based on a combination of photogrammetry and laser scanner measurements. In any case, in practice, the deformation of the rotor blades usually occurs in the form of a reversible bending along the longitudinal axis of the rotor, and according to the teaching of DE102016003345B4, the piston accumulators articulated at the rotor blades must be able to follow these deformations, which are generated during operation by changing bending processes caused by changing wind incidence together with the occurring turbulence. Then, despite the ductility mentioned for some components, the piston accumulators, which are usually constructed of solid steel material, still cannot follow the time - varying bending process of the rotor blades, which often leads to failure at the connection points between the piston accumulators and the rotor blades and thus renders the entire imbalance balancing device unusable.

[0012] However, independent of the initial situation in the wind power installation described above, the piston accumulators can also be subject to changing alternating bending stresses, for example, if the piston accumulators are subjected to strong vibrations within the operating range of a hydraulic installation, such as when used in aircraft, rockets, military mission vehicles, agricultural machinery, etc. Summary of the Utility Model

[0013] Starting from the above - mentioned prior art, the present utility model is based on the following task: to further improve a piston accumulator of the above - mentioned type such that reliable operation is ensured even in the case of strong bending stresses, even when interacting with third - party components.

[0014] For this purpose, a piston accumulator is proposed, which has an accumulator housing and a separating piston arranged longitudinally displaceably in the accumulator housing, the separating piston separating two medium spaces from each other in the accumulator housing, wherein the accumulator housing is elastically constructed in a sandwich-structure manner from a plurality of individual layers that are partially different from each other, such that under the action of at least one external force, the accumulator housing allows to bend as a whole starting from an initial state and return to the initial state when the corresponding external force is removed. A piston accumulator is provided that, even when the accumulator housing undergoes large bending under a load, returns without deformation to its initial state when the load is removed, and moreover remains functional even in the bent state. The above sandwich-structure manner contributes decisively to this, by means of which a linear-elastic behavior (Hooke's law) can be achieved for the accumulator housing. In addition, by using a sandwich-structure of a multi-layer technology, an extremely significant weight reduction is achieved, which in combination with third-party components, such as the rotor blades of a wind energy device, results in a particularly favorable operating behavior because only a small mass has to move.

[0015] In a particularly preferred embodiment of the piston accumulator according to the present invention, it is provided that within the scope of the sandwich-structure, the innermost layer of the accumulator housing consists of an airtight first layer, and the layer following outwardly therefrom is formed by a fiber winding. Preferably, the first layer is a thin-walled steel tube in terms of wall thickness, which is preferably manufactured by flow-forming, and the steel tube forms a running surface for the separating piston on its inner circumferential side. In this regard, the steel tube constitutes a steel lining, and even in a deformed state, it forms a smooth running surface for the outer circumferential side of the separating piston together with its guiding and sealing system. In addition, it is ensured in any case that the steel lining is airtight, and if it is intended to replace the internal steel lining with a plastic lining within the scope of improved lightweighting, there is no risk of the working gas penetrating through the plastic or leakage due to resin breakage (so-called fiber breakage in the laminate).

[0016] The corresponding fiber winding following the steel lining for the accumulator housing has a winding direction different from that of the fiber windings preceding it in the winding sequence, respectively. The fibers to be wound are preferably oriented according to the occurring load paths, so that, for example, after a winding at an angle less than 90° in the radial direction around a cylindrical steel lining, another fiber winding can follow, the corresponding fiber orientation of which is between 0° and 45° relative thereto, and subsequently, preferably, winding in the direction of only the radial direction can be carried out again, i.e., in the direction of a load path less than 90°, where the load path is perpendicular to the axial orientation of the tubular steel lining. For example, less than 90° means a winding direction of 87° or 88°. Depending on the strength requirements, additional fiber windings with correspondingly the same or changed orientations can be applied. To influence the strength in different directions, instead of a plurality of individual fibers, fabrics or plies can also be used, which are to be manufactured before contacting the matrix. In any case, when using individual fibers to be wound, a fiber composite material should also be manufactured, which, as a multiphase material or hybrid material, generally consists of at least two main components, namely, the reinforcing fibers to be wound and the matrix in which they are embedded, and the matrix is usually formed by a filler and a bonding material between suitable fibers. To obtain a high-strength fiber composite, carbon materials are preferably used for the current piston accumulator. However, other chemical fibers can also be used, especially chemical fibers made of glass, aramid, and high-strength polyester, etc. Overall, a CFK tube is formed, which has a thin steel lining inside, and overall, the individual fiber layers together with the steel lining form a self-compressive and highly elastic lining composite.

[0017] In another preferred embodiment of the piston accumulator according to the present utility model, it is provided that on at least one free end side of the accumulator housing, the connecting portion is at least partially surrounded by a part of the fiber winding. Preferably, it is further provided herein that the connecting portion is at least partially penetrated by the innermost layer on its cylindrical inner peripheral side, and has an annular receiving groove at the outer peripheral side, and the receiving groove is used for receiving the fiber layers of the respective fiber windings. Particularly preferably, it is provided herein that the receiving groove is at least partially bounded by an inclined surface, at least one inner fiber winding abuts against the inclined surface, and the inclined surface is at least overlapped by a subsequent further outer fiber winding. In this way, the corresponding fiber windings at the free end of the accumulator housing can be connected to the connecting portion with high strength, and the connecting portion is configured as a receiving flange in this regard, which is used for placing a cover member that terminates the accumulator housing at the end side correspondingly. Such a cover member can be adhesively bonded to the free end side of the connecting portion, so that the interior of the accumulator housing is correspondingly sealed with respect to the environment. In addition, if the corresponding cover member is fixedly screwed to the connecting portion, a high-strength connection can also be established. If the cover member is adhesively bonded to the connecting portion, it can be preferably provided that the lining winding is at least partially guided onto the cover member, so as to establish a high-strength connection between the accumulator housing and the cover member in this way. However, if necessary, the cover member (preferably in the middle) requires a connecting portion in the form of a connecting hole generally, so as to connect the interior of the accumulator housing to a fluid circuit, or to ensure that one of the two medium spaces is filled with working gas. However, instead of the cover member, according to the design of the accumulator housing, at least one end of the tube can also be implemented as a hemisphere in the same way, or implemented in the case of using a Klöpperboden. Such a termination side can also be understood as having a fiber winding if possible, so that the interior of the accumulator housing can be correspondingly constructed to be pressure-resistant. In any case, due to the lining design, it is ensured that within a common range, the accumulator housing can absorb bending forces in such a way that relevant bending occurs, and after the bending force is cancelled, the accumulator housing is allowed to reset to the initial state due to the elasticity of the lining composite without permanent deformation.

[0018] In order to achieve a fixed connection between the corresponding fiber winding and the mating connecting portion, it is further provided that a plurality of retaining pins penetrate the lining composite having the fiber winding, the retaining pins have a constant radial spacing relative to each other, and the fiber winding is connected to the connecting portion in a defined manner. Despite this connection, the flexibility of the accumulator housing is not impaired herein. In some embodiments, at least one outer fiber winding is penetrated by a plurality of retaining pins, the retaining pins preferably having a constant spacing relative to each other, and in the radial direction, the retaining pins penetrate the connecting portion.

[0019] In a particularly preferred embodiment of the solution according to the present invention, it is provided that a piston accumulator as described above in the lightweight construction is used for the application in a wind power installation, said piston accumulator being part of a balancing device for compensating the imbalance of a rotor of such an installation, wherein at least one of the rotors is fixedly connected to the accumulator housing of the piston accumulator at discrete fixed points, more precisely in such a way that the accumulator housing can follow the bending path when the rotor bends without being negatively affected in terms of its function. There is no corresponding solution in the prior art. Description of the Drawings

[0020] The piston accumulator according to the present invention will be explained in more detail below with reference to the drawings by way of examples.

[0021] Here, in a schematic and non - to - scale illustration:

[0022] Figure 1 The edge - side end region of the accumulator housing constructed as a sandwich - structured lining composite is shown in the form of a longitudinal sectional view;

[0023] Figure 2 A front - side view of the housing cover for the accumulator housing according to Figure 1 is shown;

[0024] Figure 3 A Figure 1 magnified partial sectional view of the end section of the accumulator housing marked with X in

[0025] Figure 4 is shown schematically according to Figure 1 the possible bending path of the accumulator housing in the case of a bending force introduced in the direction of the arrow;

[0026] Figure 5 and Figure 6 the separating piston for the accumulator housing according to Figure 1 is shown in a side view and in a front - side view;

[0027] Figure 7 A Figure 5 separating piston as shown in Figure 1 is inserted into the accumulator housing according to

[0028] Figure 8 and Figure 7 the application of the piston accumulator according to the design according to Detailed Description of the Invention

[0029] Figure 1The accumulator housing 10 of a piston accumulator is shown in a longitudinal sectional view, and Figure 7 the accumulator housing 10 is shown, which has a separating piston 12 arranged therein so as to be longitudinally movable, which separating piston separates two medium spaces 14, 16 from each other within the accumulator housing 10, and which separating piston is shown in more detail in Figure 5 and Figure 6 Here, one medium space 14 can be used to receive a working gas, for example a working gas in the form of nitrogen, while the other medium space 16 is used to receive a working liquid, for example hydraulic oil. Since the accumulator housing 10 can have a correspondingly large structural length, for example a structural length in the order of 2 meters, the accumulator housing 10 is only shown in the region of its end-side ends in Figure 1 and Figure 7 ; but in the intermediate region, the accumulator housing 10 also corresponds to the edge-side end region design in this regard, which relates to the lining structure of the accumulator housing 10. Accordingly, the accumulator housing 10 is elastically constructed in a sandwich-structure manner from a plurality of individual layers 18, 20, 22 and 24 that are partially different from each other in such a way that, under the action of at least one external force F, the accumulator housing allows bending as a whole starting from the initial state as given in Figure 1 and Figure 7 , according to the simplified illustration in accordance with Figure 4 , and the accumulator housing 10 elastically returns to the initial state again when the corresponding force F is removed. Thus, in this regard, the sandwich-structure manner allows a linearly elastic behavior for the accumulator housing 10.

[0030] Within the scope of the sandwich structure mentioned, the innermost layer 18 of the housing 10 is airtight, and the correspondingly following outer layers 20, 22 and 24 are formed by fiber windings. Such a layer composite results in particular from Figure 3 which figure is a magnified reproduction of the partial section marked X in Figure 1 . According to the illustration in accordance with Figure 7In the illustration, the innermost layer 18 is designed as a thin-walled steel tube in terms of wall thickness. The steel tube is preferably made from a single piece by means of spinning, and the inner circumferential side of the steel tube forms a smooth running surface 26 for the separating piston 12 in this regard. The steel lining 18 extends over the entire length of the accumulator housing 10 up to the free end-side end of the accumulator housing. The corresponding fiber winding for the accumulator housing 10 has a winding direction different from that of the respective preceding fiber winding in the winding sequence. The respective fiber winding is preferably made of a carbon fiber material, and the fiber winding of layer 20 is wound circumferentially onto the steel layer 18, i.e., has a winding direction of less than 90° relative to the longitudinal direction 28 of the accumulator housing 10. In contrast, the subsequent layer 22 can deviate from the above-mentioned winding direction of less than 90° by 0° to 45°; however, there is also the possibility of applying such a layer 22 substantially parallel to the longitudinal direction 28 of the accumulator housing 10 onto the winding 20. Other winding directions are possible here, and it is also possible to apply additional layers according to the respective application case and according to the required rigidity for the overall accumulator housing 10. The outermost layer 24 is again composed of a fiber winding in the same direction as the wound layer 20 (i.e., with a radial winding direction of less than 90°, for example 87° or 88°, relative to the longitudinal direction 28).

[0031] As especially Figure 3As shown additionally, annular connecting parts 30 are present at both ends of the accumulator housing 10, which are constructed as identical components. The annular or columnar connecting parts 30 are penetrated by the steel lining 18 on their inner circumferential side and exit at the free ends of the connecting parts 30 on the end sides. On the outer circumferential side, the respective connecting parts 30 have an annular receiving groove 32 for receiving the fiber layers of the two outermost windings 22 and 24. The receiving groove 32 is bounded on one of its sides by a connecting flange 34 and on its inner side by a fixing inclined surface 36. The connecting flange 34 and the fixing inclined surface 36 both have inclined abutment surfaces 38, 40 extending obliquely on their adjacent sides, and the abutment surfaces together form a cone in a fictitious extension in the direction towards the groove bottom 42. Here, the fixing inclined surface 36 is overlapped by the third layer 22, and in this regard, the third layer abuts directly against the groove bottom 42 of the receiving groove 32. Here, the third layer 22 tapers at its free end side and ends at the foot of the inclined abutment surface 38. The tapered end of the third layer 22 bounds the inclined wall portion 44 of the third layer 22, which together with the inclined abutment surface 38 of the connecting part 30 forms another V-shaped engagement groove 46, which is also designed as an annular groove for engaging the free end of the outer layer 24. In contrast, the second layer 20 following in the winding composite of the steel layer 18 abuts against the inclined surface portion 48 of the fixing inclined surface 36, and in this region, the fixing inclined surface abuts against the innermost layer 18 at the foot side with a small inclination angle. Thus, within the scope of the sandwich structure, a reliable layer composite connection or lining composite connection of the respective layers 18, 20, 22, and 24 in their free regions at the end sides is achieved through the respective connecting parts 30 with the connecting flange 34 and the fixing inclined surface 36.

[0032] At the transition between the steeply extending abutment surface 40 and the relatively flatly extending inclined surface rising surface including the inclined surface portion 48, according to the illustration in accordance with Figure 3 the fixing inclined surface 36 has a substantially horizontally extending peripheral surface or engagement surface 50 for the passage of a plurality of individual preferably metallic retaining pins 52, which are uniformly distributed around the accumulator housing 10 at discrete intervals in the radial direction and fixedly connect the layer composite composed of the respective layers 18, 20, 22, and 22 to the connecting part 30 and thus ensure a reliable layer composite connection.

[0033] The pin clearance portion 54 is located at the free end side of the corresponding connection flange 34 of the connection portion 30, and the pin clearance portions are evenly distributed around the outer circumference of the connection flange 34. The corresponding cover member 56 can be pinned to the mating connection portion 30 through such pin clearance portions 54, and such a cover member 56 exists at each free end of the accumulator housing 10. The mating pins (not shown in detail) are to be arranged along the annular surface 58 provided therefor at the cover member 56, and the virtual inner path of the annular surface is reproduced by the dashed line 60. Additionally, such an annular surface 58 is used for applying an adhesive material on its inner side facing the accumulator housing 10, so as to establish a media-sealed connection between the two media spaces 14, 16 and the environment in this way. Furthermore, within the scope of an embodiment not shown in detail, there is a feasibility that the corresponding cover member 56 is connected to the accumulator housing 10 in a media-sealed and pressure-resistant manner through a fiber winding. In the central region of each cover member 56, there is a connection opening 62, which can be sealedly closed on the gas side of the accumulator housing 10 with the media space 14, while remaining open on the liquid side, so as to connect the other media space 16 to a common hydraulic circuit (not shown). In order to separate the two media spaces 14, 16, i.e., the gas side and the liquid side, in a media-sealed manner, according to the illustration in Figure 7 the separating piston 12 is longitudinally movably inserted into the accumulator housing 10, and the separating piston is shown in detail in Figure 5 and Figure 6 wherein, Figure 6 shows an end view of the separating piston 12 from the right side towards Figure 5 . Therefore, the separating piston 12 has two piston members 13, 15, which are configured as disks with the same outer diameter, and they are fixedly connected to each other at a distance through an elastically yielding piston rod 17, wherein the piston rod 17 allows to bend as a whole from the initial state under the action of at least one external force F, and return to the initial state when the corresponding force F is removed. In this way, as reproduced, for example, in Figure 4 , the double-disk piston assembly of the separating piston 12 is suitable for following the bending path of the accumulator housing 10. Like the two piston members 13, 15, the piston rod 17 is also made of a suitable metallic material, wherein the piston rod 17 is preferably configured to be more elastically bendable than the disks 13, 15. In particular, the piston rod 17 prevents the relatively thin disks for the two piston members 13, 15 from tilting in the accumulator housing 10 within the range guided along the running surface 26, and thereby can hinder the movement process of the separating piston 12.

[0034] A piston member 13 facing a medium space 14 has a guide strip 19 on its outer peripheral side, while another piston member 15 facing another medium space 16 has another guide strip 21 and an annular seal 23 made of a common elastic material. The two annular guide strips 19, 21 are constructed as identical components and are made of a material with good sliding properties, which is preferably temperature-resistant accordingly, such as polytetrafluoroethylene material. The guide strips 19, 21 and the annular seal 23 are all brought into corresponding annular receiving grooves in the mating piston members 13, 15 and slide along the inner peripheral side of the accumulator housing 10 in the form of a running surface 26. In this regard, according to the illustration in Figure 5 , the annular seal 23 is arranged between the two guide strips 19, 21 at the other piston member 15. Due to the disc-shaped arrangement of the two piston members 13, 15, an annular space 25 is formed between the two piston members, and this annular space contains the medium of a medium space 14, especially a medium in the form of working gas. In order to avoid the inclination mentioned for the disc-shaped piston members 13, 15 and to still be able to ensure that the separating piston 12 as a whole can follow the bending trend of the accumulator housing 10 under bending stress, the distance between the two disc-shaped piston members 13, 15 is less than 1 / 3 of the diameter of the corresponding piston members 13, 15. In addition, the disc thickness of the piston member 13 with the guide strip 19 is selected to be less than the disc thickness of the other piston member 15 with the other guide strip 21 and the seal ring 23 for a reliable movement process. For unobstructed operation, it is further stipulated that the piston rod 17 smoothly transitions with its two shoulders 27 facing each other into the free end sides 29, 31 of the two piston members 13 or 15 facing each other. Therefore, the piston rod 17 passes through the corresponding piston members 13, 15 with its end regions facing away from each other, and the piston rod 17 is fixed at the mating piston members 13, 15 along this end region by a threaded section 33 with a common lock nut 35, which is only shown in the illustration in Figure 6 .

[0035] As can be seen from Figure 5 , Figure 6 and Figure 7It can also be seen that the disks of both piston parts 13, 15 are provided with annular recesses 37, which serve firstly to reduce weight and secondly to increase the elasticity of the disks 13, 15. The recesses 37 are designed essentially identically on the facing end sides of the two piston parts 13, 15 and are arranged concentrically with a central recess 39, which receives the correspondingly associated threaded section 33 of the piston rod 17 and the lock nut 35. In addition, on the inner end wall of the piston part 15, there are annular recesses 37, which are widened both on the outer circumference and on the inner circumference, arranged concentrically with these recesses 37. The separating piston 12 designed elastically in this way can also be used in a "normal" accumulator housing 10; an accumulator housing 10 of the type described can also be used with a "conventional" separating piston.

[0036] Figure 4 The energy storage housing 10 is now shown on two bearing seats 64, and a pressing force F is applied from above in the middle at the introduction point 66 so that the energy storage housing 10 is as shown in FIG. Figure 4 bend as shown in . Figure 4 In the embodiment, the accumulator housing 10 is reproduced in an idealized form, in particular without the two end-cap parts 56. If the force F is removed, the accumulator or accumulator housing 10 returns to its position according to Figure 1 and Figure 7 It is self-evident that when the accumulator housing 10 is held fixed at the introduction point 66 and a force is applied from below via the bearing seat 64, the same Figure 4 A similar bend is reproduced in .

[0037] If the piston accumulator is installed within the scope of a balancing device for compensating for rotor imbalances in a wind power plant (e.g. Figure 8 ), then the fixing is achieved along the two bearing seats 64 on one of the two blade sides of the corresponding rotor blade 68. Figure 8 In the drawing, a partially depicted tower of a wind power plant is designated 70. In a manner customary in wind power plants, at the upper end of the tower 70, a machine room 72 (which is also referred to in technical terms as a "nacelle") is arranged rotatably about the tower vertical axis, forward and backward 2 to 3 times. Figure 8 The simplified illustration of FIG. 7 does not show the rotor hub rotatably mounted on the machine chamber 72 for the three rotor blades 68 of the three-blade rotor. A piston accumulator pair is provided in each rotor blade 68, which has an inner piston accumulator 74 and an outer piston accumulator 76. The respective piston accumulators 74, 76 are designed here as follows, that is, Figure 7with a corresponding termination part (Abschlussteil) on the end side as shown, such as the corresponding cover part 56. Here, the corresponding piston accumulators 74, 76 are fixed to the corresponding rotor blades 68 by means of the assigned bearing seats 64.

[0038] The correspondingly internal piston accumulator 74 is arranged in the region of the blade root adjacent to the rotor hub, while the external piston accumulator 76 is offset relative thereto by a distance towards the corresponding blade tip, which distance extends along the longitudinal orientation of the corresponding rotor blade 68. Here it is preferably provided that, corresponding to the smaller installation space available in the corresponding rotor blade 68 near the blade tip, the external piston accumulator 76 is dimensioned more slenderly than the internal piston accumulator 74 of this pair of piston accumulators.

[0039] In the internal piston accumulator 74, the medium space or working space 14 faces the blade root, and this medium space or working space guides a compressible pressure medium, such as a working gas (preferably a working gas in the form of nitrogen); while in the external piston accumulator 76, the working space 14 guiding the compressible medium faces the blade tip. If necessary, the medium space 14 of the internal piston accumulator 74 can also guide ambient air and remain pressureless. In the correspondingly further medium spaces 16 of the piston accumulators 74 and 76 facing each other within the rotor blade 68, an incompressible medium (such as a hydraulic fluid) is provided as a mass movable within the rotor blade 68 concerned for compensating for the imbalance. These fluid-guiding medium spaces 16 facing each other are interconnected by a fluid line 78 (such as a fluid line in the form of a pipe or a hose). Adjacent to the correspondingly internal piston accumulator 74 in the corresponding fluid line 78, a control valve 80 is arranged, such as a control valve in the form of an electromagnetically actuatable switching valve, which can be centrally controlled by a control system 82. In order to transmit the value of the lateral acceleration acting transversely to the rotor axis at the support structure of the wind energy installation to the control system 82, an acceleration sensor 84 is arranged in the tower head or nacelle 72, which acceleration sensor is connected to the control system 82 via a corresponding measurement signal line. In addition, a rotor position sensor 86 is provided, which determines the position of the rotor blade 68 in the form of a rotor speed sensor or a rotor rotational position sensor at the rotor axis and transmits it to the control system 82 via another measurement signal line.

[0040] In order to carry out an imbalance compensation process with the aid of a balancing device, the wind power installation is brought into an initial state in such a way that the rotor speed is increased by a motor to a speed at which the hydraulic liquid in the medium spaces 16 of the pilot fluids of the piston accumulators 74, 76 and in the fluid line 78 between them is displaced outwards towards the blade tips under the action of centrifugal force with the control valve 80 open, and in doing so compresses the working gas in the corresponding fluid space 14 of the external piston accumulator 76, thus bringing it into a loaded state. In order to identify the presence of an imbalance, the wind energy installation must be operated at the critical speed, and in the presence of an imbalance, operation at this speed results in lateral vibrations of the tower and thus in the occurrence of an acceleration signal of the acceleration sensor 84. With the aid of a rotor rotational position sensor at the rotor shaft, it is determined which of the rotor blades 68 has a deviating mass moment of inertia, said rotor rotational position sensor determining the exact position of the rotor blades 68 at any point in time. From the instantaneous value of the lateral acceleration depending on the rotor position, the control system 82 determines which rotor blade 68 has a deviating mass moment of inertia and supplies a control signal to the control valve 80, which partially unloads the considered loaded piston accumulator 76 in order to displace the mass of the incompressible hydraulic liquid in such a way that no lateral acceleration is measured any more. The rotor is then balanced overall.

[0041] It goes without saying that during operation of the rotor blades 68, due to the wind influence, deformations caused by bending forces also occur in the range of turbulence, in particular a corresponding bending of the respective rotor blade 68 in its longitudinal orientation. Due to the above-described piston accumulator solution with a flexurally elastic accumulator housing 10 and / or a flexurally elastic separating piston 12, it is thus possible to absorb the corresponding bending deformations of the rotor blades 68 in all directions, wherein the piston accumulator pair 74, 76 can also function reliably for mass balancing in the event of such bending in order to compensate for the imbalance of the rotor blades 68.

Claims

1. A piston accumulator having an accumulator housing (10) and a separating piston (12) arranged longitudinally displaceably in the accumulator housing, the separating piston separating two medium spaces (14, 16) from each other within the accumulator housing (10), characterized in that The accumulator housing (10) is elastically constructed in a sandwich-structured manner from a plurality of individual layers that are partially different from one another, such that under the action of at least one external force, the accumulator housing allows for overall bending starting from an initial state and returns to the initial state when the corresponding external force is removed.

2. The piston accumulator according to claim 1, wherein The sandwich-structured manner results in a linearly elastic behavior for the accumulator housing (10).

3. The piston accumulator according to claim 1 or 2, characterized in that, Within the scope of the sandwich structure, the innermost layer of the accumulator housing (10) is airtight, and the correspondingly following outer layers are formed by fiber windings.

4. The piston accumulator according to claim 1 or 2, characterized in that, The innermost layer is a thin-walled steel tube that forms a running surface (26) for the separating piston (12) on the inner peripheral side.

5. The piston accumulator according to claim 3, wherein, The respective fiber windings for the accumulator housing (10) have a winding direction different from that of the fiber windings preceding them in the winding sequence.

6. The piston accumulator according to claim 3, wherein, On at least one free end side of the accumulator housing (10), the connecting part (30) is at least partially surrounded by a part of the fiber windings.

7. The piston accumulator according to claim 6, characterized in that, The connecting part (30) is at least partially penetrated by the innermost layer on the cylindrical inner peripheral side of the connecting part and has an annular receiving groove (32) on the outer peripheral side, which is used to receive the fiber layers of the respective fiber windings.

8. The piston accumulator according to claim 7, wherein, The receiving groove (32) is at least partially bounded by a fixing inclined surface (36), at least one inner fiber winding abuts against the fixing inclined surface, and the fixing inclined surface is at least overlaid by a subsequent further outer fiber winding.

9. The piston accumulator according to claim 8, wherein, At least one outer fiber winding is penetrated by a plurality of retaining pins (52), which, when viewed in the radial direction, penetrate the connecting part (30).

10. The piston accumulator according to claim 4, wherein, The steel tube is manufactured by spin forming.

11. The piston accumulator according to claim 9, wherein, The retaining pins have a constant spacing relative to one another.

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