Wind turbine main bearing housing

Abstract

A main bearing housing for a wind turbine, the main bearing housing comprising a bearing arrangement having a sump located in a floor region of the main bearing housing. The sump comprises a floor pan surrounded by side walls and comprises an overflow arrangement configured to allow fluid to overflow from the sump. The overflow arrangement comprises an overflow channel configured with an overflow inlet at or near the floor pan of the sump and an overflow outlet located in a position between the overflow inlet and an upper edge of the sump side wall. An advantage of the present invention is that, since the overflow channel is supplied with oil from a position close to the bottom of the sump, debris and sediment at the bottom of the sump tend to be entrained by the flow of oil and therefore tend not to collect at the bottom of the sump. As a result, the lubrication system is able to clean the oil more effectively because the debris and sediment are caused to circulate around the lubrication system.

Description

Technical Field

[0001] The present invention relates to a main bearing housing of a wind turbine and in particular to lubrication aspects of the housing. Background Art

[0002] In order to capitalize on economies of scale, there has been a general trend to design wind turbines with ever larger rotor disk diameters in an effort to increase energy capture potential, thereby reducing the average cost of energy production. This rationale has led to a year-on-year increase in installed capacity worldwide in an effort to rebalance the energy production mix away from non-renewable energy sources (such as oil and gas) and towards renewable energy sources (such as wind and solar).

[0003] However, the upward trend in wind turbine size comes with its challenges, as wind turbine towers have to be taller, blades have to be longer and stronger, and nacelles have to be larger and heavier. The centerpiece of a wind turbine can be considered the main rotor shaft, as it carries the hub and rotor blades and harnesses the rotational energy generated by these blades so that it can be converted into electrical energy by a generator. The main rotor shaft, and therefore the bearing arrangement that supports it, must therefore be incredibly robust to withstand the enormous forces generated during energy production.

[0004] In one known arrangement, the main rotor shaft extends through a bearing arrangement comprising a front bearing supporting the end of the shaft close to the hub (i.e. the "front" or "front" end), and a rear bearing supporting the end of the shaft away from the hub (i.e. the "rear" or "rear" end). The bearings are used to ensure that the main rotor shaft can rotate smoothly and also transfer axial loads and bending moments to the bedplate or foundation frame. This arrangement generally effectively decouples the gearbox of the wind turbine from the axial forces and bending forces of the main rotor shaft, so that only torque is transferred to the gearbox. In order to ensure effective lubrication of each of the front bearing and the rear bearing, in a typical known arrangement, the bearings are provided with suitable lubrication arrangements.

[0005] It is against this background that the present invention has been devised. Summary of the invention

[0006] According to a first aspect, an embodiment of the present invention provides a main bearing housing for a wind turbine, the main bearing housing comprising: a bearing arrangement having a sump located in a floor region of the main bearing housing. The sump comprises a floor pan surrounded by side walls and comprises an overflow arrangement configured to allow fluid to overflow from the sump. The overflow arrangement comprises an overflow channel configured with an overflow inlet and an overflow outlet, the overflow inlet being located at or near the floor pan of the sump, the overflow outlet being located in a position between the overflow inlet and an upper edge of the sump side wall and spaced apart from each of the overflow inlet and the upper edge of the sump side wall.

[0007] In other words, the overflow outlet is located above the overflow inlet and below the upper edge of the sump side wall. The skilled person will understand that the terms "above" and "below" should be understood to refer to the sump when it is in its normal orientation in use.

[0008] An advantage of the present invention is that, because the overflow passage is fed with oil from a location close to the bottom of the sump, debris and sediment at the bottom of the sump tends to be entrained by the flow of oil and therefore tends not to collect at the bottom of the sump. As a result, the lubrication system is able to clean the oil more effectively because the debris and sediment are forced to circulate around the lubrication system. This is in contrast to known sump designs in which the oil will simply overflow over the top of the sump sidewalls when the sump is full.

[0009] In one embodiment, the reservoir is located at the bearing arrangement. Positioned in this way, oil from the bearing arrangement can be simply collected in the reservoir. In use, the reservoir and the bearing arrangement can be configured and arranged so that the bearing arrangement is lubricated by the fluid in the reservoir. This is advantageous in the event of a failure in the circumferential oil supply to the bearing arrangement, for example due to a failure of a lubrication pump. It can also serve as a supplementary lubrication point for the bearing arrangement in addition to any oil supplied around the circumference of the bearing arrangement.

[0010] The overflow channel may take various configurations. In one embodiment, the overflow channel may be an integral part of the sump sidewall. For example, the overflow channel may be a channel or borehole defined in the material of the sump sidewall. This may be a particularly convenient way to integrate such a function into the sump.

[0011] In one embodiment, the overflow channel may be defined by a columnar tower structure. The tower structure may be integral with the sump sidewall or may be separate from the sump sidewall. As a single tower structure, the overflow channel provides a single overflow point from the sump, and this may cause the oil to overflow from the sump more quickly, which may more effectively entrain larger particles in the oil flow. More than one overflow channel may be provided as a corresponding tower structure.

[0012] In another embodiment, the overflow channel may include a transverse elongated channel extending between the overflow wall and the side wall of the sump. The overflow channel may thus extend across the width of the sump. It is envisaged that such an embodiment may reduce the likelihood of particles floating in different areas of the sump floor pan.

[0013] The sump may include a drain passage. The drain passage may be separate from or combined with the overflow passage. In one embodiment, the drain passage is connected to the overflow passage and extends away from the overflow passage. The drain passage may be connected to a return passage that feeds oil back to an oil tank of the lubrication system, the main bearing housing forming part of the oil tank of the lubrication system.

[0014] A control valve may be provided to control the flow of fluid through the drain passage. The control valve may be operated periodically to provide more effective cleaning of the sump oil contents. The drain passage may also include an input from a collector sump.

[0015] Optionally, the oil sump may include one or more baffles that help prevent the oil in the sump from becoming aerated due to sloshing that may occur during movement of the wind turbine during use. At least one of the one or more baffles may be an integrally cast component with the main bearing housing.

[0016] Alternatively, at least one of the one or more baffles may be a component separate from but attached to the main bearing housing.

[0017] It will be appreciated that preferred and / or optional features of the first aspect of the invention may be combined with other aspects of the invention.The invention in its various aspects is defined in the appended independent claims and advantageous features are defined in the appended dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0019] Figure 1 is a view of a wind turbine that may incorporate embodiments of the present invention;

[0020] Figure 2 yes Figure 1 A schematic system level view of a wind turbine;

[0021] Figure 3 yes Figure 1 and Figure 2 A perspective view of a main bearing housing of a wind turbine;

[0022] Figure 4 It passes through Figure 3 A schematic cross-sectional view of a main bearing housing of FIG. 1 , illustrating an embodiment of the present invention;

[0023] Figure 5 Yes Figure 4 A schematic diagram of a lubrication system for supplying lubricating fluid to a main bearing housing;

[0024] Figure 6 It shows Figure 4 A plan view of the bottom plate area of ​​the main bearing housing; and

[0025] Figure 7 and Figure 8 A perspective view and a side view, respectively, of an alternative embodiment of an oil sump.

[0026] Note that identical or similar features in different drawings are indicated by the same reference numerals. DETAILED DESCRIPTION

[0027] See also Figure 1 , the wind turbine 2 comprises a nacelle 4 supported on a generally vertical tower 6, which itself is mounted to a foundation 8. The foundation 8 may be on land, or fully or partially underwater. The nacelle 4 houses a number of functional components, some of which are located in Figure 2 Such a configuration is well known to technicians.

[0028] Here, the nacelle 4 is shown as at least partially housing the main rotor arrangement 10, the gearbox 12 and the generator 14. For the sake of brevity, some typical components have been removed from the illustration. Figure 2 Omitted from the discussion, as they are not central to the present discussion, such as power converters and yaw drives. However, the presence of such components is implicit and such components will be well understood by those skilled in the art.

[0029] The main rotor arrangement 10 comprises a hub 16 coupled to a main rotor shaft 18, which is rotatably supported by a main bearing arrangement 20 housed in a main bearing housing 22. In this embodiment, the main bearing arrangement 20 comprises a front bearing arrangement 24 and a rear bearing arrangement 26. The hub 16 is connected to a plurality of rotor blades 27, although three blades are typical in a HAWT. These blades 27 are acted upon by the wind and therefore torque is applied by the hub 16 to the main rotor shaft 18, which torque causes the main rotor shaft to rotate within the main bearing housing 22. From now on, in this discussion, the front bearing arrangement and the rear bearing arrangement may be simply referred to as "bearings".

[0030] The input or "forward" portion of the main rotor shaft 18 includes a hub connection flange 18a by which the main rotor shaft 18 is connected to and driven by the hub 16. Here, the flange 18a is shown connected to another flange 29 associated with the hub 16, so that the two flanges form a connection between the hub 16 and the main rotor shaft 18. Therefore, the flange 18a can be considered to be at the hub connection end of the main rotor shaft 18.

[0031] The output portion 18b of the shaft 18 provides input drive to the gearbox 12. The gearbox 12 steps up the rotational speed of the main rotor shaft 18 via an internal gear (not shown) and drives a high-speed gearbox output shaft 28. The high-speed output shaft 28 in turn drives the generator 14, which converts the rotation of the high-speed output shaft 28 into electricity. The electrical energy generated by the generator 14 can then be converted by other components (not shown here) as required before being supplied to the grid (for example, or indeed any electrical consumption device).

[0032] At this point it should be noted that although in the present embodiment two support bearings 24, 26 are shown providing support to the main rotor shaft 18 in a forward position and a rearward position, it is also known to omit the arrangement of the rearward bearing and, instead, rear support for the main rotor shaft 18 may be provided, for example, by the gearbox 12.

[0033] The main bearing housing 22 is supported on a base frame 30, which may also be referred to as a bedplate. Although not shown here, the base frame 30 may be coupled to a yaw drive at an upper portion of the wind turbine tower 6 to yaw the base frame 30 and thus the entire nacelle 4 relative to the tower 6 in order to enable the orientation of the hub 16 to be adjusted relative to the wind direction.

[0034] The base frame 30 is typically a cast component, for example made of iron / steel, and has the function of transferring the main shaft loads from the shaft 18 through the bearings 24 , 26 , the main bearing housing 22 and the base frame 30 into the wind turbine tower 6 .

[0035] Figure 3 , Figure 4 and Figure 6 A more practical implementation of the main bearing housing 22 and main rotor shaft 18 is shown to provide a better understanding of the configuration of these related components. Note that the general form and configuration of the main bearing housing 22 is for illustrative purposes only and is not intended to limit the invention as defined in the appended claims.

[0036] See first Figure 3 and Figure 4 , the main rotor shaft 18 is tapered along its length to provide a relatively larger circumference at the front end 32 of the shaft 18 and a relatively smaller circumference at the rear end (not shown) of the shaft 18. It should be noted that the main rotor shaft 18 does not have to be tapered.

[0037] A front bearing 24 and a rear bearing 26 are located between the main rotor shaft 18 and the main bearing housing 22, respectively at a forward position and a rearward position along the length of the shaft 18. The front bearing 24 and the rear bearing 26 are thus clamped or sandwiched between the shaft 18 and the main bearing housing 22 and enable the shaft 18 to rotate freely relative to the main bearing housing 22 about a rotor axis R extending through the center of the main rotor shaft 18 during operation of the wind turbine.

[0038] The exact form and configuration of the front bearing 24 and the rear bearing 26 is not critical to the present invention. It should be noted that, as shown in schematic form, the bearings are shown as plain roller bearings for convenience. However, in applications such as this, the bearings will likely be configured as tapered roller bearings and / or tapered roller bearings to more effectively handle the axial thrust on the shaft 18.

[0039] Still see Figure 4 It should be appreciated that the main bearing housing 22 includes a floor area 40 that extends between the front and rear ends of the main bearing housing 22 and includes various functional features, structures, and configurations involved in the lubrication of the front and rear bearings 24, 26. More specifically, a first oil reservoir 42 is located at the front bearing 24, and a second oil reservoir 44 is located at the rear bearing 26. The two oil reservoirs 42, 44 are located and configured so that lubricating oil injected, delivered, or otherwise provided at the front and rear bearing arrangements 24, 26 is deposited in the respective oil reservoirs under the influence of gravity so that the oil in the oil reservoirs can lubricate the bottom ends of the bearings.

[0040] In contrast to known lubrication methods for main shaft bearings, it will be appreciated that in the illustrated embodiment the main bearing housing 22 forms part of a fluid-based lubrication system 50 rather than the grease-based method typical in the art. Figure 5 A lubrication system 50 is schematically shown in FIG. 5 to provide further background to the present invention.

[0041] As can be seen, the lubrication system 50 includes a series of lubricated subsystems that are supplied with lubrication fluid from a tank 52. Although various types of lubrication fluids may be used, for simplicity, the generic term "oil" will be used from now on to refer to lubrication fluids in liquid form that can be used for circulating lubrication (i.e., stored in a suitable reservoir or tank and from which they are repeatedly pumped around the system to the various consumable units).

[0042] Lubricating fluid is drawn from tank 52 by pump 54 and directed along a suitable fluid supply network 56 to the lubricant-consuming subsystems, which are generally the main bearing housing 22, the gearbox 12, and the generator 14. A fluid return network 57 returns fluid from each of the main bearing housing 22, the gearbox 12, and the generator 14 to tank 52, where it can be recirculated again to the fluid supply network 56 by pump 54.

[0043] Also shown here in the fluid supply network 56 are a filter unit 58 and an oil heater 60, as these are common components in oil-based lubrication systems that can be used in a variety of environmental conditions. Figure 5 The schematic diagram is shown in simplified form and therefore various common components such as check valves, tapping points, pressure gauges, etc. have been omitted for the sake of clarity.

[0044] The fluid supply network 56 includes supply lines 62 that supply lubricating oil to the main bearing housing 22, the gearbox 12, and the generator 14. Two of the supply lines, labeled herein 62a and 62b, provide lubricating oil to the main bearing housing 22.

[0045] More specifically, a first supply line 62a provides lubricating fluid to the forward bearing 24 and a second supply line 62b provides lubricating fluid to the rear bearing 26. Although not shown here, it should be understood that both supply lines 62a and 62b can supply lubricating oil to one or more delivery nozzles that can be appropriately spaced around the bearing arrangement for optimal oil delivery. Supply lines 62a and 62b are also located at Figure 4 24 , 26 are shown pointing toward the top end of each bearing arrangement 24 , 26 .

[0046] Thus, oil injected through the nozzles into the front and rear bearing arrangements 24, 26 is used for lubrication and subsequently flows into the respective oil reservoirs 42, 44 and from there into the fluid return network 57. Further details of the oil reservoirs will be described in more detail in the following discussion.

[0047] At this point it should be appreciated that a significant benefit associated with the above arrangement is that the main bearing housing 22 is included in the fluid lubrication system 50 with the gearbox 12 and the generator 14. This is not the case in known systems, where the gearbox 12 and optionally the generator 14 are typically lubricated with lubricating oil via a pumping system, while the main bearing housing 22 is typically lubricated with a different medium, usually grease. This therefore represents a simplification of the known methods of lubricating power train components of a wind turbine.

[0048] The discussion will now focus on more specific features of the main bearing housing 22 that function to provide optimal lubrication to the forward and rear bearing arrangements 24 and 26 .

[0049] See again Figure 4 It has been described above that the floor region 40 of the main bearing housing 22 includes a first oil sump 42 located at the first bearing arrangement 24 and a second oil sump 44 located at the rear bearing arrangement 26. Each oil sump 42, 44 is configured and arranged such that it provides a reservoir for lubricating oil at a depth such that the bottom of the bearing arrangement 24, 26 is at least partially immersed or submerged in the lubricating oil. Figure 4 , where the oil levels ( L1 and L2 , respectively) in each of the first oil reservoir 42 and the second oil reservoir 44 are indicated to be in line with the roller elements in the bearings 24 , 26 . Figure 6 The plan view of the oil level in the two oil reservoirs is also shown to overflow to the corresponding bearings. In this discussion, for simplicity, they will be collectively referred to as the two oil reservoirs when they have common features. Likewise, the common features of the two oil reservoirs will use the same reference numerals.

[0050] Each oil sump 42, 44 may be considered to include a floor pan 61 surrounded by side walls 63. The exact configuration of the side walls may vary depending on the shape and configuration of the floor region 40 of the main bearing housing 22. For example, if the floor region 40 has a substantial curvature due to the cylindrical shape of the main bearing housing 22, then the sump may be a feature cast into the floor region 40 of the main bearing housing 22 such that the side walls are defined in sections by the inner surface of the main bearing housing 22 itself. Another possibility is that the floor region 40 is relatively flat and therefore the oil sump 42, 44 may be a separate component placed on the floor region 40 and secured thereto. Thus, in this case, the oil sump 42, 44 may be a box-like component having a floor pan 61 or base surrounded by one or more wall segments that together define the boundary walls of the oil sump that contain the lubricating oil therein.

[0051] It should be noted that in Figure 4 and Figure 6 In the illustrated embodiment, the oil reservoirs 42, 44 are defined in part by the lateral curved surface of the floor region 40 and in part by the end walls. Thus, the side wall 63 of each oil reservoir 42, 44 is defined in part by an axially inner end wall section 64 and an axially outer end wall section 66. Whereas the axially inner end wall section 64 is located towards the center of the floor region 40 of the main bearing housing 22, the outer end wall section 66 is located behind the respective bearing arrangement 24, 26.

[0052] like Figure 4 As shown, during normal operation, the oil level in the oil reservoirs 42, 44 reaches a certain depth during operation so that a portion of the corresponding bearing arrangement is immersed in oil. However, in order to recirculate the lubricating oil around the lubrication system, the main bearing housing 22 includes an overflow device 74. As will be discussed in more detail, the overflow device 74 includes an overflow channel 76, which is configured with an overflow inlet 78 located at or near the bottom plate 70 of the reservoir 42, 44 and an overflow outlet 80 located at a position between the overflow inlet 78 and the upper edge 82 of the inner side wall section. Therefore, with reference to the normal orientation of the main bearing housing 22, the overflow outlet 80 is above the overflow inlet 78, but below the overall level of the upper extent of the side wall section 82. The normal orientation can also be relative to the depth direction of the reservoir (such as Figure 482 and 84. The overflow outlet 80 is considered as being in the direction of the overflow inlet 78 (shown as the reference numeral "D" in the figure). Here, the dimension 'D' is represented by a vertical arrow aligned with the direction of gravity, that is, acting downward toward the center of the earth. Therefore, when considered in the depth direction, the overflow outlet 80 is located above the overflow inlet 78, and when considered in this same reference system, the overflow outlet 80 is also located below the storage tank side wall section 82. Reference to the overflow outlet 80 being "between" the storage tank side wall 82 and the overflow inlet 78 and spaced apart from the storage tank side wall 82 and the overflow inlet 78 should also be made along the same reference direction. It is conceivable that a relatively small spacing between the overflow outlet 80 and the storage tank side wall section 82 will be sufficient because the storage tanks 42, 44 will overflow from the overflow outlet 80 before the storage tank overflows from the side wall. A height difference of 1 cm is considered acceptable, but higher flow rates can be achieved with a larger height difference; for example, a height difference between 5 cm and 10 cm. It should be noted that in use it is possible to mount the sump 42, 44 so that the sump is inclined relative to a horizontal reference plane. In such a case, even if the overflow outlet 80 and the sump side wall section 82 are at the same height when considered with reference to the sump itself, the inclination of the sump means that the overflow outlet 80 and the sump side wall section 82 will actually be at different vertical heights when considered in the direction of gravity. When the sump is inclined in this manner, the surface of the oil in the sump will be truly horizontal and will therefore first flow out of the overflow outlet 80 before the oil overflows from the sump side wall section 82.

[0053] The advantage of this configuration is that it allows the lubricating oil to overflow from the bottom of the reservoir 42, 44, which typically collects debris and particles (such as small metal fragments). Therefore, the oil flowing from the reservoir 42, 44 through the overflow inlet 78 into the overflow channel 76 tends to entrain debris therein, thus serving as a cleaning mechanism for the reservoir 42, 44.

[0054] The overflow device 74 can be configured in different ways. Figure 4 and Figure 6 An implementation is shown in Figure 7 and Figure 8 An alternative approach is depicted in .

[0055] Stay Figure 4 and Figure 6 In the embodiment shown, it should be noted that in this illustrated embodiment, the inner sidewall section 64 and the main bearing housing 22 are a common cast component, and the overflow passage 76 is an integral part of the inner sidewall section 64. More specifically, Figure 6 As can be seen in FIG. 8 , the overflow passage is defined by a tower structure 84 that extends upwardly from the floor region 40 of the main bearing housing 22 .

[0056] In this embodiment, the tower structure 84 is located approximately midway along the lateral extent of the inner sidewall section 64, which can be Figure 6 . This is an elegantly simple solution, but it will be appreciated that other configurations are possible. For example, the tower structure 84 may be located closer to the left or right side of the inner sidewall section 64. Another option is that more than one tower structure with associated overflow channels may be provided. Another option is that a single tower structure with associated overflow channels may be fed by more than one overflow inlet.

[0057] like Figure 4 As can be seen in the inset in FIG. 6 , lubricating oil from the bottom or bottom plate pan 70 of the reservoirs 42, 44 flows into the overflow inlet 78 and upward through the overflow channel 76 due to the pressure of the lubricating oil above it in the reservoirs 42, 44. As the reservoirs 42, 44 are filled with lubricating oil, the oil level in the overflow channel 76 increases after being sprayed into the bearing arrangement through the nozzle, to the extent that the oil flows out through the overflow outlet 80. When the overflow outlet 80 is at a lower position than the inner side wall section 64, the oil in the overflow channel 76 leaves the overflow outlet 80 and leaves the reservoirs 42, 44.

[0058] The oil overflows from the reservoirs 42, 44 into a collector sump 86 located between the two reservoirs. In this embodiment, the collector sump 86 is part of the floor area 40 of the main bearing housing 22.

[0059] The main bearing housing 22 also includes a drain system 90 that is configured to drain lubrication oil from the sumps 42 , 44 and the collector sump 86 .

[0060] In the illustrated embodiment, the drain system 90 comprises a network of fluid passages which are integral to the structure of the main bearing housing 22 in the sense that they are part of the casting, as will be described. This is a particularly convenient way of forming the drain system 90, as it reduces the number of hose connections required to connect the main bearing housing 22 to the lubrication system 50. However, one or more of these passages may also be implemented as pipes or hoses external to the main bearing housing 22.

[0061] The function of the drain system 90 is to provide a permanently open drain for the collector sump 86, but to provide a selective drain function for each of the two sumps 42, 44. Thus, in this way, the contents of the sumps 42, 44 can be purged from time to time to allow the lubricating oil in the sumps to be recirculated back to the tank 52 and filter 58.

[0062] To this end, each of the two reservoirs 42, 44 includes a main drain passage 92 that connects the respective reservoir to the drain system 90. In the illustrated embodiment, the main drain passage 92 is an extension of the overflow passage 76 and is therefore fed from the overflow inlet 78. As can be seen, the main drain passage 92 extends downwardly from the overflow passage 76 and terminates at a respective drain outlet 94 defined in the underside of the main bearing housing 22.

[0063] In addition to the main drain passage 94, each sump 42, 44 is provided with a secondary drain passage 96. The secondary drain passage 96 is configured to collect oil overflowing from the axially outer end wall section 66 of each sump 42, 44 and to feed the overflowing oil to the main drain passage 92. Thus, each secondary drain passage 96 is connected to a respective overflow outlet 94. In the illustrated embodiment, it will be noted that the secondary drain passage 96 is connected to the respective drain outlet 94 via a connection or junction 97 to the main drain passage 92. A further passage 99 extends from the connection 97 to the drain outlet 94.

[0064] Both drain outlets 94 are connected to a control valve 98. The control valve 98 is configured to selectively close or open either or both of the drain outlets 94. The outlet of the control valve 98 discharges into the fluid return network 57. Thus, the control valve 98 controls the flow of lubricating oil from each sump 42, 44 through the respective drain outlet and into the fluid return network 57.

[0065] It should be noted that in the illustrated embodiment, the collector sump 86 also includes a corresponding drain passage 100. Here, the collector drain passage 100 is implemented as an integral passage or bore in the main bearing housing 22 extending downwardly from the collector sump 86 to terminate at a connector 102. The connector 102 provides an interface to the fluid return system 57. Thus, in this embodiment, the drain path from the collector sump 86 is not valve controlled. Alternatively, the collector drain passage 100 may be valve controlled.

[0066] In this embodiment, the control valve 98 is a single three-way valve. Although it is envisioned that the same function can be achieved by a separate two-way valve, a single valve is particularly beneficial because such a valve tends to be much more compact than the equivalent use of two valves. Moreover, a single three-way valve has only a single fluid control mechanism, a single fluid connection to the main bearing housing, and a single electronic connection for control input purposes. Therefore, a single three-way valve is more cost-effective than using separate valves to control the flow from each discharge channel. It is envisioned that in a normal operating mode, the control valve 98 will close the communication between the storage tanks 42, 44 and the fluid return network 57, so that the storage tanks 42, 44 will be filled with oil to a predetermined depth. Then, the control valve 98 is periodically operated to discharge oil from each storage tank 42, 44. The storage tank discharge can be performed one storage tank at a time or both storage tanks at the same time. It is envisioned that control of the control valve 98 is achieved by the same computer control system that controls other components of the lubrication system. This can be a control system separate from the main control system for other wind turbine subsystems, or the function can be integrated into the main control system.

[0067] As another optional improvement, the storage tanks 42, 44 may include baffles 104. As shown in the illustrated embodiment, the baffles 104 are located in each storage tank 42, 44 and extend vertically from the bottom plate 70 to divide the volume of the storage tank into compartments. Thus, the baffles 104 play a role in reducing the oil in the storage tank from sloshing as the wind turbine sways during operation.

[0068] The upper edge of the baffle 104 may extend to a point near the expected maximum oil level L1 , L2 in the sump, which may improve efficiency.

[0069] In order to allow oil to circulate in the reservoirs 42, 44, the baffle 104 may be provided with suitable apertures. These apertures may take the form of holes or perforations in the baffle 104 to allow oil to pass through. Alternatively or additionally, the apertures may be defined at the lower edge of the baffle so that there is a gap 106 between the bottom plate 70 and the baffle 104. Thus, the oil in the reservoirs 42, 44 is able to flow under the baffle 104, but the baffle is still effective in preventing excessive sloshing of the oil in the reservoirs 42, 44.

[0070] It is contemplated that some or all of the baffles 104 may be an integral component with the main bearing housing 22 in that they are part of a single casting. Alternatively, in another embodiment, the baffles 104 may be separate components that are secured to the receptacles 42, 44 after the main bearing housing 22 is manufactured. Optionally, the baffles 104 may extend edge to edge across the width of the receptacles 42, 44, as shown here, but this is not essential and it is contemplated that in other embodiments a gap may be left between either or both lateral edges of the baffles 104 and the sidewalls of the receptacles 42, 44.

[0071] Figure 7 and Figure 8 , an alternative design of a reservoir 110 is shown which has many similarities to the reservoirs 42, 44 described above and can therefore also be used in the main bearing housing 22. Thus, the reservoir 110 includes a bottom plate pan 112 and an upwardly extending side wall 114. The side wall 114 in this arrangement is rectangular in form, but it should be noted that this is not necessary.

[0072] When considered in the orientation that the sump 110 would assume when located in the main bearing housing 22 as described above, the sidewall 114 of the sump 110 includes a first axially inner sidewall section 116 and a second axially outer sidewall section 118 .

[0073] The overflow device 120 is located adjacent to the inner side wall section 116. It will be noted that, in contrast to the tower-like structure of the overflow device 74 of the previous embodiment, the overflow device 120 in this embodiment comprises an elongated overflow channel 122 extending transversely across the front of the sump. The overflow channel 122 is thus defined by a shallow box-like structure defined by the inner end wall section 116 and a further end wall or 'overflow wall' 124. The height of the further end wall defines the height of the overflow outlet 128, which is lower than the height of the inner end wall section 116 (more specifically, the upper edge 117 thereof).

[0074] An overflow inlet 130 is defined at the bottom of the sump 110, between the bottom plate 112 and the lower edge of the inner wall section 116. Thus, the flow of oil through the overflow device 120 is very similar to that of the previous embodiment, in that the oil flows into the overflow channel 122 through the overflow inlet 130, which is at a very low position in the sump 110. The oil then travels upward through the overflow channel 122 and exits the overflow outlet 128. Note therefore that, similar to the previously illustrated embodiment, the overflow outlet 128 is positioned above the overflow inlet 130 but below the upper edge of the side wall. In other words, the overflow outlet 128 is between the upper edge of the side wall and the overflow inlet 130.

[0075] As in Figure 4 and Figure 6 As in the previous embodiment, the storage tank 110 of this embodiment includes a plurality of baffles 132. However, for the sake of clarity, only two baffles 132 are shown here. Figure 8 As shown, one of the baffles 132 includes a plurality of holes or perforations 134 to allow oil to pass therethrough, and another of the baffles 132 includes a gap 136 defined between a lower edge 138 of the baffle 132 b and the bottom plate 112 of the sump 110 .

[0076] It should be noted that, depending on the configuration of the tank, the inner end wall section 116 may actually be defined by a baffle 132 having an opening toward its bottom edge, or by a baffle defining a lower gap at the floor pan 112 of the tank 110 .

[0077] Although already alone Figure 7 and Figure 8 For the avoidance of doubt, it is stated that the tank of this illustrated embodiment may be used with the main bearing housing 22, as Figures 4 to 6 The main bearing housing in the embodiment of the present invention is the same, instead of the reservoir configuration shown in the description.

[0078] It should be noted that the above discussion describes different variations on the illustrated embodiments and modifications that may be made by a skilled person, which variations and modifications are not considered to fall outside the scope of the present invention as defined by the appended claims. Other options are also possible.

Claims

1. A main bearing housing (22) for a wind turbine, the main bearing housing comprising: Bearing assembly (24, 26), an oil sump (42, 44; 110) located in the bottom plate region of the main bearing housing (22), The oil sump (42, 44; 110) comprises a bottom plate (61; 112) surrounded by side walls (63; 114), and the oil sump comprises an overflow device (74, 120) configured to allow oil to overflow from the oil sump (42, 44; 110), wherein the overflow device (74; 120) comprises an overflow channel (76; 122), the overflow channel being provided with an overflow inlet (78; 130) and an overflow outlet (80; 128), the overflow inlet being located at or near the bottom plate (61, 112) of the oil storage tank (42, 44; 110), the overflow outlet being located between the overflow inlet (78; 130) and an upper edge (82) of the side wall and being spaced apart from each of the overflow inlet and the upper edge of the side wall in the direction of gravity, The oil sump (42, 44; 110) includes a drain passage (92), and the overflow passage (76; 122) forms a fluid path between the overflow inlet (78; 130) and the overflow outlet (80; 128) that bypasses the drain passage (92).

2. The main bearing housing according to claim 1, wherein: The overflow channel (76; 122) is an integral part of the side wall (63; 114) of the oil sump.

3. The main bearing housing according to claim 1 or 2, wherein: The overflow channel (76) is defined by a cylindrical tower structure (84).

4. The main bearing housing according to claim 1 or 2, wherein: The overflow channel (122) includes a transversely elongated channel extending between an overflow wall (124) and the side wall (114).

5. The main bearing housing according to claim 1, wherein: The drain passage (92) is connected to the overflow passage (76) and extends away from the overflow passage.

6. The main bearing housing according to claim 1 or 5, wherein: The exhaust passage (92) also includes an input from the collector sump (86).

7. The main bearing housing according to claim 6, wherein: The overflow outlet (80; 128) is configured to allow oil to overflow into the collector sump (86).

8. The main bearing housing according to claim 1, wherein: The drain passage (92) also includes an input from a secondary drain passage (96) that collects spilled oil from a second region of the oil sump.

9. The main bearing housing according to claim 1, wherein: The discharge passage (92) is connected to the return passage (57) via a discharge outlet (94).

10. The main bearing housing according to claim 9, wherein: The discharge outlet (94) is defined at a surface of the main bearing housing.

11. A main bearing housing according to claim 9 or 10, wherein: A control valve (98) controls the flow of oil through the discharge passage (92) to the return passage (57).

12. The main bearing housing according to claim 11, wherein: The control valve (98) is directly attached to the main bearing housing and engages the drain outlet (94).

13. The main bearing housing according to claim 12, wherein: The control valve (98) is a three-way valve and is engaged with the drain outlet (94) and another drain outlet (94) associated with a corresponding drain passage (92) of the second oil sump (44).

14. The main bearing housing according to claim 1, wherein: The oil sump (42, 44; 110) includes one or more baffles (104; 132).

15. The main bearing housing according to claim 14, wherein: At least one of the one or more baffles (104; 132) is a component cast integrally with the main bearing housing (22).

16. A main bearing housing according to claim 14 or 15, wherein: At least one of the one or more baffles (104; 132) is formed as a component separate from but attached to the main bearing housing (22).

17. A wind turbine, comprising: a main shaft rotatably supported by a main bearing housing (22) according to any one of the preceding claims; a gear box (12) coupled to the main shaft; and a lubrication system (50), the lubrication system comprising: a tank (52) for lubrication fluid; a lubrication pump (54) for extracting lubrication fluid from the tank; and a fluid conduit network (56) for delivering lubrication fluid from the lubrication pump to one or more lubrication points on the main bearing housing and one or more lubrication points on the gearbox.

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