Main bearing unit

Abstract

The invention describes a main bearing unit (1) of a wind turbine drivetrain (2), comprising: a tapered roller bearing (10) arranged between a housing (11) of the main bearing unit (1) and a low speed shaft (20) of the drivetrain (2); a press-fit connection between the inner surface (11S) of the housing (11) and the outer surface (102S) of the bearing cup (102); and means (3, 16) that facilitate an axial displacement ([delta] P) of the bearing cup (102) in order to restore a preload force (F preload) on the bearing (10). The invention also describes a method for restoring a preload force (Fpreload) in a bearing (10) of such a main bearing unit (1).

Description

Background Art

[0001] In existing types of wind turbine drive systems, the low-speed shaft (or "main shaft") is rotated by the aerodynamic rotor and is connected to the drive end of the gearbox. The aerodynamic rotor includes rotor blades mounted to a hub, which in turn is connected to the drive end of the low-speed shaft. The low-speed shaft is supported within the housing by a bearing arrangement. In a well-known construction, this comprises a pair of matched tapered roller bearings, with the "upwind" bearing being mounted around the front or drive end of the main shaft and the "downwind" bearing being mounted around the rear or non-drive end of the shaft. The tapered roller bearings comprise an inner ring ("cone"), an outer ring ("cup") and tapered rollers, which are arranged in a cage between the cone and the cup. The purpose of the bearings is to support the weight of the aerodynamic rotor at all times. In a matched pair, the load direction on the front bearing is "downward" while the load direction on the rear bearing is "upward".

[0002] Bearings are typically preloaded because trouble-free bearing operation requires a minimum preload to be maintained throughout the life of the wind turbine. In existing configurations, bearing life can often exceed the service life of the wind turbine, making it unnecessary to initiate maintenance procedures to replace the main bearing unit or restore bearing preload. Instead, established practice is to design the main bearing unit based on the expected service life of the corresponding wind turbine.

[0003] However, the service life of today's wind turbines has increased significantly, from 20 years (older wind turbines) to 25-35 years (modern wind turbines), and it is expected that major components (such as the main bearing unit) should have a correspondingly extended service life or "fatigue life".

[0004] It is known to preload wind turbine main bearing units during assembly to a level that includes allowances for assembly tolerances, measurement tolerances, settlement, creep, wear, and relaxation over the expected service life of the bearing. Because these allowances are chosen to account for rare, worst-case scenarios, even conservative preload levels are already quite large, and a significant portion of service-limiting fatigue damage is caused by bearing preload. However, it is generally not possible to extend the service life of the main bearing unit by reducing the initial preload level to mitigate preload-induced fatigue, as insufficient preload leads to other types of wear that inevitably cause premature fatigue damage.

[0005] Therefore, the longer service life of wind turbines leads to problems with the main bearing units, as the bearing preload level can avoid maintenance problems during the "short" wind turbine service life (about 20 years), but the preload level cannot be reduced to extend the bearing service life to match the "long" wind turbine service life (e.g. 25-35 years).

[0006] One way to increase the fatigue life or service life of a main bearing is to make it larger, i.e. by increasing the overall size of the rollers, raceways, bearing housing etc. However, the cost of designing the main bearing unit for the longer service life of modern wind turbines significantly increases the cost of the wind turbine. Summary of the Invention

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to overcome the above-mentioned problems.

[0008] This object is achieved by the claimed main bearing unit; by the claimed method of restoring a preload force in a bearing of a main bearing unit; and by the claimed wind turbine.

[0009] Although the main bearing unit of the present invention can be used in various types of transmission systems, it is particularly suitable for use in the transmission system of a wind turbine. The main bearing unit of the present invention can be used in a direct drive generator connected to the main shaft. In the following, without limiting the present invention in any way, it can be assumed that the main bearing unit is constructed for use in a wind turbine transmission system, the transmission system including a low speed shaft arranged to drive a high speed unit, the high speed unit including a gearbox and a generator. The bearing arrangement can be assumed to include a pair of matching tapered roller bearings, using a suitable configuration (for example an "O" configuration), with the front bearing at the drive end and the rear bearing at the non-drive end. In this configuration, the front face of the bearing is oriented "outward" and the back face of the bearing is oriented "inward", that is, the back face of the rear bearing cup and cone is oriented towards the drive end of the main shaft; the back face of the front bearing cup and cone is oriented towards the non-drive end of the main shaft.

[0010] According to the present invention, a main bearing unit of a wind turbine transmission system comprises: one or more tapered roller bearings, which are arranged between the housing of the main bearing unit and the low-speed shaft of the transmission system; a press-fit connection, which is between the inner surface of the housing and the substantially cylindrical outer surface of the bearing cup; and axial displacement means, i.e. means for applying an axial force to the back surface of the bearing cup to achieve axial displacement of the bearing cup in order to restore the preload force on the bearing.

[0011] The advantages of the main bearing unit of the present invention are that the construction is economical to manufacture and allows the bearing preload force to be restored at any time during the service life of the main bearing unit. As will be explained below, the bearing preload can be restored in a direct manner without intervention from the non-drive end of the main bearing unit.

[0012] Another advantage of the main bearing arrangement of the present invention is that the design elements or devices used to facilitate the preload recovery procedure only need to occupy an advantageously small amount of space. In particular, the area "rearward" of the bearing, such as the area downwind of the rear bearing, can be completely unaffected by any aspect of the bearing preload, whether by permanently installed parts or tools deployed during the preload recovery procedure. As a result, the distance between the rear bearing and the coupling / gearbox can be advantageously short, so that the drive system can be implemented in an advantageously compact form. Compact drive systems are generally desirable for a variety of reasons. For example, structural vibrations transmitted from the gearbox and generator through the main bearing unit to the nacelle bedplate can be significantly reduced in a configuration where there is only a short distance between the rear bearing and the coupling / gearbox. Drive system designs that can shorten the distance between the rear main bearing and the gearbox can take advantage of this by increasing the distance between the front and rear bearings (which in turn advantageously reduces bearing loads).

[0013] According to the present invention, a method for restoring a preload force in a bearing of such a main bearing unit comprises the steps of: releasing the press-fit force between the housing and the outer surface of the bearing cup; applying an axial force to the back surface of the bearing cup to axially displace the bearing cup from its initial position to a final position; and subsequently fixing the bearing cup in its final position.

[0014] According to the present invention, a wind turbine includes a drive train having an embodiment of the present invention's main bearing unit. The costs associated with manufacturing and maintaining the main bearing unit can be kept advantageously low. This is because the initial preload force does not need to be excessively high, as the preload force can be restored at any time during the wind turbine's service life. Furthermore, since no part of the drive train needs to be disassembled, the preload restoration procedure can be performed at relatively low cost. Manufacturing costs can also be kept low because there is no need to form trapezoidal threads around the rotor shaft to receive corresponding threaded locking nuts.

[0015] Particularly advantageous embodiments and features of the invention are given by the dependent claims, as shown in the following description. Features from different claim categories can be combined as appropriate to give further embodiments not described herein.

[0016] In the following, for the purposes of discussion, the axis of rotation of the drive train should be considered to be "horizontal" (in wind turbines, the drive train is typically tilted a few degrees to avoid collisions between the rotor blades and the tower), and any reference to a "vertical" face of a bearing ring or other part should be understood to be vertical relative to the horizontal axis of rotation.

[0017] For simplicity, the method of restoring the preload force of the present invention is described with respect to the rear bearing, but it should be understood that it is also applicable to the front bearing.

[0018] In a particularly preferred embodiment of the invention, the main bearing unit includes an additional annular component, which is arranged in the housing so that it abuts the back of the bearing cup. This additional annular component is referred to herein as a "preload ring" because its purpose is to help maintain and restore the bearing preload force. The preload ring is sized to fit tightly in the housing and abut the back of the bearing cup. The preload ring can be held in place by appropriate housing features. For example, in a particularly preferred embodiment of the invention, the housing includes a flange, which protrudes radially inwardly into the interior of the housing and is positioned at a certain distance from the back of the bearing cup. The preload ring fits tightly in the gap between the flange and the bearing cup, and this tight fit can be achieved in a variety of ways, as will be explained below.

[0019] The press fit between the housing flange and the preload ring ensures that the preload ring is pressed against the bearing cup in the axial direction, so that the preload ring continuously applies the desired preload force to the bearing cup and supports axial bearing loads during turbine operation. In a particularly preferred embodiment of the present invention, the vertical outer face of the preload ring is in direct contact with the vertical back face of the bearing outer ring or cup. Preferably, the contact surface of the preload ring substantially matches the annular shape of the back face of the bearing cup, so that the outer face of the preload ring is in full contact with the back face of the bearing cup. The outer diameters of the back face of the bearing cup and the preload ring can be substantially the same, so that the cylindrical outer surface of each of these annular components is in direct contact with the cylindrical inner surface of the housing. The inner diameters of the back face of the bearing cup and the preload ring can also be substantially the same. Alternatively, the inner diameter of the preload ring can be slightly smaller than the inner diameter of the back face of the bearing cup.

[0020] As shown above, the bearing arrangement of a wind turbine drivetrain typically includes a pair of matched tapered roller bearings, with a front bearing at the drive end of the shaft and a rear bearing at the non-drive end of the shaft. A housing flange, preload ring, and axial adjustment device may be deployed at the rear bearing. Alternatively or additionally, a mirrored configuration of housing flange, preload ring, and axial adjustment device may be deployed at the front bearing.

[0021] When equipped with a preload ring as described above, the main bearing unit of the present invention is designed so that when the main bearing unit is initially assembled, the preload ring is placed on the bearing to apply the required preload force. Thereafter, during the service life of the wind turbine, the preload force may decrease slightly due to factors such as settlement, creep, wear, relaxation, etc. As described above, even a slight degradation of the preload force can significantly reduce the life of the bearing. The main bearing unit of the present invention is designed so that during the service life of the wind turbine, the bearing preload can be restored in a relatively straightforward manner by axially displacing the preload ring and thereby also axially displacing the bearing cup, and then securing the preload ring in its new position. In this way, the preload force is restored by displacing the bearing cup relative to the fixed bearing cone.

[0022] In a particularly preferred embodiment of the present invention, axial displacement is achieved by deploying one or more sets of shims. A shim set should be understood to include a plurality of shims of equal thickness. For example, each shim in a shim set can be 0.5 mm (or 0.2 mm, 0.1 mm, etc.) thick, so that the shim set can be used to displace the bearing cup by 0.5 mm (or 0.2 mm, 0.1 mm, etc.). Preferably, the shims are made of a resilient material such as steel.

[0023] For clarity, the following description will assume that the main bearing unit is implemented to include a preload ring. In a preferred embodiment of the present invention, the housing of the main bearing unit includes a plurality of openings positioned to coincide with the "bearing side" of the housing flange, for example, immediately adjacent the housing flange downwind and immediately adjacent the preload ring upwind. Each opening is shaped to receive a number of shims, which can be inserted into the space between the housing flange and the preload ring. For example, when the main bearing unit is initially assembled, the bearing preload force can be achieved by the preload ring alone, or in combination with shims from a first shim set. Over the life of the wind turbine, a reduction in the bearing preload force can be addressed by axially displacing the preload ring by a predetermined amount, thereby creating a slight gap upwind of the preload ring, and inserting shims from an appropriate shim set to "fill" the gap. In this embodiment, the outer surface of the shims is preferably polished to a smooth surface to facilitate insertion and removal. The thicker shim arrangement now holds the preload ring in its new position, where it again applies the desired preload force to the bearing cup. In this embodiment, the step of axially displacing the preload ring can be accomplished by first releasing the press fit between the bearing cup and the housing, and then using one or more hydraulic tools to apply pressure to the preload ring to displace it (and the bearing cup) in the axial direction. To this end, the housing can include appropriate openings (e.g., alternating with shim recesses) so that a hydraulic tool can be positioned in each opening upwind of the preload ring. Preferably, during the preload recovery procedure, the spindle (along with the bearing cone) is rotated to ensure that the axial displacement of the bearing cup is uniform and does not cause damage to the bearing rollers and raceways.

[0024] The desired axial displacement can be achieved by removing the gasket rather than by inserting the gasket. To this end, in another preferred embodiment of the present invention, the inwardly protruding housing flange includes an annularly arranged axial through-holes or holes to receive a corresponding number of axial displacement devices, such as threaded fasteners, such as stud bolts, each fastener having a shaft or shank extending to the preload ring. Each of these can be inserted into the hole from the upwind side of the housing flange and extend through the hole so that its end face contacts the upwind side of the preload ring. In a preferred embodiment of the present invention, the hole has an internal thread over at least part of its length to engage with the threaded fastener. At the upwind side of the housing flange, the fastener can terminate in a hexagonal head so that it can be turned using a torque wrench. In this embodiment, the gasket can have the shape of a washer, which is placed between the head of the fastener and the upwind side of the housing flange. When the main bearing unit is initially assembled, the bearing preload force can be achieved by placing a stack of shims (or a single shim of sufficient thickness) under each fastener head and tightening the fasteners so that their outer ends exert the desired preload force on the preload ring (which transfers the preload force to the bearing cup).

[0025] During the life of the wind turbine, a reduction in bearing preload force can be addressed by removing the threaded fasteners and replacing the previous shim(s) with a slightly thinner shim or shim stack. After completing this step for all fasteners, tighten the fasteners again. For example, a 0.5 mm shim can be removed from under each fastener head and replaced with a 0.3 mm shim to move the preload ring (and bearing cup) 0.2 mm in the downwind direction. In this case, the press fit between the bearing cup and the housing is also released in the initial step; during the preload recovery procedure, the main shaft (together with the bearing cone) is preferably rotated to ensure that the axial displacement of the bearing cup is uniform and does not cause damage to the bearing rollers and raceways.

[0026] The embodiments described above may be combined. For example, the annular arrangement of stud bolts may be provided with an initial shim arrangement for setting the preload force during manufacture of the main bearing unit. The housing may also have an annular arrangement of openings so that additional shims can be added as needed during the service life of the wind turbine.

[0027] The preload ring described above can be used to evenly distribute the axial force on the vertical surface of the bearing cup, so that the preload ring facilitates the displacement of the bearing cup during the preload recovery procedure. However, the method of the present invention can also be implemented without such a preload ring: instead, in embodiments where the shim is carried by the stud bolt, the end of the stud can directly apply the required axial force to the end face of the bearing cup; in embodiments where the shim is inserted into a recess in the housing, the shim can be directly inserted between the housing flange and the end face of the bearing cup to achieve the desired axial press fit force.

[0028] For the initial step of releasing the press fit between the bearing cup and the housing, the housing of the main bearing unit preferably includes several channels arranged to deliver pressurized fluid to one or more areas between the inner surface of the housing and the outer surface of the bearing cup. A hydraulic system can be deployed to establish a fluid cushion in the extremely confined space at each of these areas. For example, the hydraulic system can include a pressurized fluid supply and a hose for delivering pressurized fluid to each area. The pressurized fluid effectively breaks the press fit between the inner surface of the housing and the bearing, facilitating uniform axial displacement of the bearing (by adding or removing shims, as described above) when rotating the main shaft and bearing inner ring. During the preload recovery procedure, the front and rear bearings must continue to support the weight of the aerodynamic rotor; that is, the load direction is downward in the front main bearing and upward in the rear bearing. In a preferred embodiment of the present invention, the channels are arranged so that multiple fluid cushions, with individually adjusted hydraulic pressure levels, can be established around the rear bearing as needed. For example, a "thicker" fluid cushion in the upper area of ​​the rear bearing can facilitate displacement of that bearing. The pressure level is carefully chosen to ensure that during axial displacement of the rear bearing, it continues to perform its function of supporting the aerodynamic rotor.

[0029] Alternatively or additionally, the outer shell of the main bearing unit may be heated to achieve expansion, thereby reducing the interference fit between the bearing cup and the outer shell. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Other objects and features of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings. However, it should be understood that the drawings are for illustration purposes only and are not intended to limit the scope of the present invention.

[0031] Figure 1 A main bearing unit of a wind turbine drive train is shown;

[0032] Figure 2-4 The figure shows a first embodiment of the main bearing unit of the present invention;

[0033] Figure 5-7 The figure shows a first embodiment of the main bearing unit of the present invention;

[0034] Figure 8 and 9 illustrates the stages during the preload recovery procedure of the present invention;

[0035] Figure 10 Another embodiment of the present invention is shown;

[0036] Figure 11 A rear bearing in a prior art main bearing unit is shown.

[0037] In the drawings, like numbers refer to like objects throughout. Objects in the drawings are not necessarily drawn to scale. DETAILED DESCRIPTION

[0038] Figure 1 A cross section through a portion of a wind turbine drive train 2 is shown, illustrating a main bearing unit 1 positioned around a low-speed shaft 20 and a coupling interface 22 at the downwind end of the shaft 20 for connection to the next stage of the drive train 2. The main bearing unit 1 is positioned around the low-speed shaft 20 and comprises a pair of matched tapered roller bearings 10 enclosed in a bearing housing 11. In this exemplary embodiment, the housing 11 is secured to a seat plate 24 having a flat bottom, which is intended to be mounted to the top of a wind turbine tower (indicated by the dashed lines). Each bearing 10 comprises a tapered roller 103 disposed between an inner race or "cone" 101 and an outer race or "cup" 102.

[0039] Figure 2-4 An embodiment of the main bearing unit 1 of the present invention is illustrated in which shims 15A are added during a preload recovery procedure. Figure 2 The rear bearing 10 is shown arranged adjacent to a fixed annular ring 14, which is arranged around the non-drive end of the main shaft 20, and the housing 11 of the main bearing unit 1. A seal 18 is provided to prevent contaminants from entering or leaving the bearing space. The inner surface of the bearing inner ring or cone 101 fits tightly around the low-speed shaft 20, i.e., there is a press-fit connection between the bearing cone 101 and the low-speed shaft 20.

[0040] Figure 2 The preload ring 14 is shown as a press fit between the bearing cup 102 and the inwardly projecting housing flange 115, in this case achieved by a stack of shims 15 A. One or both of these shims 15A may have been inserted during the preload recovery procedure, as will be explained below.

[0041] Figure 3is a simplified view of section Ⅰ-Ⅰ of the main bearing unit 1 (looking in the upwind direction) to illustrate how the housing 11 can be designed to receive shims 15A and also to receive the hydraulic jack 30 during the preload recovery procedure. The outer diameters of the preload ring 14 and the bearing cup 102 are indicated by dotted lines. The figure shows an annular arrangement of shim insertion openings 110, in this case eight shim insertion openings 110 are arranged around the housing 11 so that (in this case) a set of eight (preferably identical) shims 15A can be inserted. The insertion openings 110 can be arranged equidistantly as shown, although this is not strictly necessary. The figure shows an annular arrangement of tool openings 111, in this case eight such recesses or openings are arranged around the housing 11 so that the hydraulic jack 30 can be placed to apply a force in the downwind direction to the preload ring 14 (and the bearing cup). During this step, the main shaft 20 is rotated together with the bearing cone 101. Using a Figure 2 The hydraulic circuit 3 shown in FIG. 3 facilitates this step by creating a fluid cushion between the bearing cup 102 and the housing 11. The hydraulic circuit 3 includes a pump 34, a control valve assembly 35, various sensors 33, a controller 31, and a power source 32. A hydraulic line 36 delivers pressurized fluid through a passage 11P in the housing 11, thereby creating a fluid cushion at one or more areas between the housing 11 and the bearing cup 102. This is done to facilitate Figure 4 The axial displacement of the bearing cup 102 shown in FIG. 1 is caused when the hydraulic jack 30 is actuated to apply a force F to the preload ring 14. 轴向 , the preload ring 14 is displaced and thereby also the bearing cup 102 by the desired amount ΔP, as shown in the enlarged portion. The displacement ΔP - which may be only about a few millimeters or even less - can be monitored using a suitable sensor device 38 as shown. For example, a proximity sensor 38 (placed in a suitable opening in the seal 18 and having a wire leading to the controller 31 of the hydraulic system 3) can be deployed to determine the progress of the axial displacement step so that the hydraulic jack 30 can be actuated in a very precise manner. At least three sensors 38 may be sufficient to measure the axial displacement ΔP and may be used to ensure that the front face of the bearing cup is perpendicular to the axis of rotation. As shown, further proximity sensors 39 may be arranged against the back face of the bearing cone. These sensors 39 can be used to measure the elongation of the shaft 20. The difference between the measured values ​​reported by the sensors 38, 39 can be used to determine the degree of compression of the bearing 10 (the roller 103 behaves like a spring element), thereby allowing the preload force F to be determined. 预加载After displacing the bearing cup 102 and preload ring 14, appropriate shims 15 are inserted to fill the newly created gap, thereby securing the bearing cup 102 in its new position. The hydraulic tool 30 is removed from the housing 11, and the controller 31 controls the relevant system components 34, 35 to remove the fluid cushion between the housing 11 and the bearing cup 102, thereby completing the preload recovery procedure.

[0042] Figure 5-7 An embodiment of the main bearing unit of the present invention is illustrated wherein the shims 15B are removed during the restoration preload procedure. Figure 7 is a simplified view of section II-II of the main bearing unit 1 (seen in the upwind direction) to illustrate how the housing 11 may be designed with an inwardly projecting housing flange 115 having an annular arrangement of holes 112 (twelve in this case) to receive the threaded stud bolts 16, and further annular arrangement of larger holes 114 (a matching number in this exemplary case), each of which is wide enough to allow a hydraulically operated tool to apply a force to the preload ring 14, as shown. Figure 6 Initially, as shown in Figure 5 As shown in FIG, one or more washers 15B are placed under the head 160 of each bolt 16, and the total thickness of the washers should be appropriate. Tighten the stud bolt 16 so that the end of the bolt applies an axial force F to the preload ring 14. 轴向 , to generate the desired preload force F on the bearing 10 预加载 This is usually done at the manufacturing plant. In a pre-load recovery procedure performed sometime during the life of the wind turbine, a procedure such as Figure 2 The hydraulic system 3 described in the embodiment of the present invention is used to establish a fluid cushion as described above between the housing 11 and the bearing cup 102, and to control the hydraulic jack 30 to push the preload ring 14 (and the bearing cup 102) in the downwind direction by the desired amount ΔP, as shown in FIG. Figure 6 . Subsequently, the stud bolt 16 can be removed and the previous set of shims 15B can be replaced with a thinner shim or thinner shim stack to reduce the shim depth by the axial displacement amount ΔP. The stud bolt 16 is now tightened again and the hydraulic jack 30 can be removed. The controller 31 is actuated to remove the fluid cushion between the housing 11 and the bearing cup 102, thereby completing the preload recovery procedure.

[0043] In an alternative approach, a set of stud bolts can be used to push the preload ring to the leeward side to achieve the desired increase in bearing preload force. For example, after removing a shim from under the bolt head, the stud bolts can be simultaneously rotated using appropriate equipment to achieve the desired axial displacement of the bearing cup.

[0044] As explained above, in the mirror image configuration, the main bearing unit 1 can also be equipped with a preload ring, which is placed to restore the preload force on the front bearing. The figure also shows some channels in the main shaft, which are used at the manufacturing plant to set the initial preload force F of the bearing. 预加载 The fluid cushion is established when the fluid is applied, which is familiar to the skilled person.

[0045] Figure 8 and Figure 9 The method of the present invention for restoring bearing preload is illustrated, in this case for Figure 2-7 The rear bearing described in. During the service life of the wind turbine, the bearing preload of the rear bearing is monitored at regular intervals. From the measured shaft extension ΔL, the bearing preload force can be calculated (from its initial value F 预加载 ) reduction. Figure 8 Schematic diagram showing the initial bearing preload force F 预加载 and reduced bearing preload force F 低 (As shown by the shorter arrow). Figure 9 In the process of axially displacing the bearing cup 102 from its initial position P0 to its final position P1 (as shown above in Figure 2-7 After the bearing preload force F is restored 预加载 With the initial bearing preload force F 预加载 The wind turbine can continue to operate without risk of damaging the bearing 10. These figures show the preload ring 14 being arranged adjacent the back of the bearing cup 102, but it will be appreciated that the axial force F 轴向 Can be applied directly to the bearing cup back 102F.

[0046] Figure 10 Another embodiment of the present invention is shown in the figure, showing a partial cross section of the upper and lower parts of the main bearing unit. Here, the initial existing bearing preload force F 预加载 The upper portion of the figure shows a stud bolt 16 which is arranged in an axial hole 112 formed in a flange 115 and is tightened to apply an axial force F to the back face 102F of the bearing cup. 轴向 Here, a shim set 15B is arranged below the stud bolt head 160. This shim set 15B can be used to achieve a preload force F during the manufacturing phase of the main bearing unit. 预加载 The lower part of the figure shows a shim set 15A arranged between the housing flange 115 and the bearing cup back 102F. These shims 15A may have been added during a preload recovery procedure during the life of the wind turbine. Of course, such a combination of shim sets 15A, 15B may also be used as described above. Figure 2-9The embodiment of the deployment preload ring 14 described in is implemented.

[0047] Figure 11 The rear bearing 70 of a prior art main bearing unit 7 is shown, along with the elements associated with preloading the rear bearing 10. The position of the bearing cup 703 is secured by housing features. The position of the bearing cone 701 on the low-speed shaft is secured by a lock nut 77 and a press-fit ring 79. The shaft 20 and the lock nut 77 each have matching trapezoidal threads. During assembly of the prior art main bearing unit 7 at the manufacturing facility, after the housing 71 is positioned around the shaft and bearing 70, bearing preload can be achieved by stretching the shaft 20 (e.g., using a hydraulic tool) while securing the position of the rear bearing 70 relative to the housing 71, in a procedure known to those skilled in the art. To this end, the press fit between the rear bearing inner race 701 and the shaft 20 is relieved, for example, by forcing pressurized fluid through a channel to form a fluid "cushion" between the contact surfaces of the inner race 701 and the shaft 20. To this end, as shown, a suitable configuration of conduits or channels is provided in the body of the main shaft 20. During the preloading procedure, the main shaft 20 and the bearing inner ring 701 must be rotated relative to the housing 71 in order to avoid damaging the bearing rollers 703 and raceways, and the tooling for this procedure is constructed to facilitate this rotation. After deactivating the shaft stretching tool and removing the fluid cushion to restore the press fit between the shaft 20 and the bearing inner ring 701, the new position of the bearing 70 is secured by the restored press fit and by turning the locking nut 77 about the low speed shaft 20. The main bearing unit 7 can now be transported to the wind turbine for installation in the nacelle. During the service life of the wind turbine, the bearing preload force F can be restored by removing the press fit ring 79, turning the locking nut 77 the appropriate amount, and replacing the press fit ring 79. 预加载However, due to the large dimensions involved, forming the desired precision of the trapezoidal threads around the shaft 20 and locking nut 77 is both challenging and very expensive, and this aspect of the drivetrain design significantly increases overall manufacturing and maintenance costs. While the same method of stretching the shaft 20 can be used to restore bearing preload at a later stage in the wind turbine's lifespan, installing the necessary tools in an operating drivetrain is difficult. Disassembling the necessary equipment and transporting it to the wind turbine site for installation in the nacelle would be prohibitively difficult. Furthermore, the main shaft 20 must be rotated during the preloading procedure explained above, but is now enclosed in the housing 11. Therefore, the tools used at the manufacturing plant (for stretching the shaft 20 and creating the fluid cushion in the press-fit area between the shaft and the bearing) cannot be simply deployed in the nacelle of an operating wind turbine. Furthermore, it is necessary to provide some method of retaining the rear bearing in its new position on the shaft. For example, the rear bearing could be retained in its new position on the shaft by rotating the trapezoidal thread nut 77 on the shaft. However, this solution is difficult to implement. Alternatively, the main bearing unit 7 may be equipped with an adjustable locking device, such as an arrangement of fasteners between the shaft 20 and the inner race 701 of the rear bearing 70. Any such fastener arrangement would have to be accessible to a technician during the preloading procedure, and the necessary redesign of the main bearing unit 7 would significantly increase the overall cost.

[0048] While the invention has been disclosed in the form of preferred embodiments and variations thereon, it will be appreciated that numerous modifications and variations can be made thereto without departing from the scope of the invention. For example, the position of the preload ring relative to the bearing can be exploited by attaching the seal directly to the preload ring, eliminating the need for housing features to support the seal.

[0049] For the sake of clarity, it is to be understood that the use throughout this application of "a" or "an" does not exclude a plurality, and "comprising" does not exclude other steps or elements.

Claims

1. A main bearing unit (1) of a wind turbine transmission system (2), comprising - a tapered roller bearing (10) arranged between the housing (11) of the main bearing unit (1) and the low-speed shaft (20) of the transmission system (2); - a press-fit connection between an inner surface (11S) of the housing (11) and an outer surface (102S) of the bearing cup (102); and - means (3, 16) which promote an axial displacement (ΔP) of the bearing cup (102) in order to restore the preload force (F 预加载 ).

2. Main bearing unit according to the preceding claim, comprising a preload ring (14) arranged adjacent to the bearing cup back face (102F).

3. Main bearing unit according to the preceding claim, wherein - a preload ring (14) is arranged to abut the bearing cup back face (102F) at the non-drive end of the low speed shaft (20); and / or - A preload ring (14) is arranged to abut the bearing cup back face (102F) of the bearing (10) at the drive end of the low speed shaft (20).

4. A main bearing unit according to any one of the preceding claims, wherein: The position of the bearing cup (102) is fixed by an inwardly protruding housing flange (115) and a set of spacers (15A, 15B).

5. A main bearing unit according to any one of the preceding claims, comprising an annularly arranged opening (110) in the housing (11), and wherein: Each shim (15A) of the shim set is arranged in an opening (110).

6. Main bearing unit according to the preceding claim, wherein: Gasket (15A) - extends between the inwardly projecting housing flange (115) and the back face of the bearing cup (102F), or - extending between the inwardly projecting housing flange (115) and a preload ring (14), the preload ring (14) being arranged to abut the bearing cup back face (102F).

7. A main bearing unit according to any one of the preceding claims, comprising an annularly arranged threaded holes (112) formed in the flange (115) to receive a set of adjusting screws (16), and wherein The end face of each adjusting screw (16) - Apply force (F) to the back side of the bearing cup (102F) 轴向 ),or - Apply force (F) to the preload ring (14) 轴向 ), the preload ring (14) is arranged to abut the back side (102F) of the bearing cup.

8. Main bearing unit according to the preceding claim, wherein Each shim (15B) of the shim set is arranged around the axis (20) of the adjusting screw (16).

9. A main bearing unit according to any one of the preceding claims, adapted to facilitate relief of the radial force (F) exerted by the inner surface of the housing (18) on the outer surface (102S) of the bearing cup (102) during a bearing preload recovery procedure. pfit ).

10. A main bearing unit according to any one of the preceding claims, comprising several channels (11P) arranged to promote the formation of a fluid cushion between the inner surface of the housing (11) and the outer surface (102S) of the bearing cup (102).

11. Main bearing unit according to the preceding claim, wherein The channels (11P) are arranged to facilitate the formation of several individually configurable fluid cushions.

12. A method for restoring a preload force (F 预加载 ), comprising the steps of - Release the press fit force (F) between the housing (11) and the outer surface (102S) of the bearing cup pfit ) - Apply an axial force (F) to the back of the bearing cup (102F) 轴向 ) to achieve a displacement (ΔP) of the bearing cup (102) from its initial position (P0) to a final position (P1); and then - Fixing the bearing cup (102) in its final position (P1).

13. The method according to the preceding claim, wherein Release the press fit force (F) between the housing (11) and the outer surface (102S) of the bearing cup pfit ) step includes establishing a fluid cushion between the housing (11) and the outer surface (102S) of the bearing cup.

14. The method according to any one of claims 12 to 13, wherein The shim set is adjusted by inserting shims (15A) of an additional shim set between the inwardly projecting housing flange (115) and the preload ring (14) and / or the bearing cup.

15. The method according to any one of claims 12 to 14, wherein The shim set is adjusted by removing a set of shims (15B) from between the adjusting screw (16) and the inwardly projecting housing flange (115).

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