Main bearing housing of a wind turbine

Abstract

A main bearing housing for supporting a main rotor shaft of a wind turbine, wherein the main bearing housing defines a first end, a second end, and a bottom plate region located between the first end and the second end. The main bearing housing includes a first bearing device positioned at the first end of the main bearing housing and a second bearing device positioned at the second end of the main bearing housing, wherein the bottom plate region includes a first oil reservoir positioned at the first bearing device and a second oil reservoir positioned at the second bearing device. Advantageously, embodiments of the present invention provide that the bearings of the main bearing housing are lubricated by a lubrication system that includes reservoirs positioned at each of the front and rear bearings of the main rotor shaft. Thus, the front and rear bearings are supplied with oil at suitable lubrication points and are part of the lubrication system that supplies oil to other components in the wind turbine that require oil lubrication, such as the gearbox and / or generator bearings. Accordingly, the front and rear bearings of the main bearing housing do not require a separate lubrication system, such as a grease-based system, and thus simplify the overall lubrication requirements of the nacelle.

Description

Technical Field

[0001] The present invention relates to a main bearing housing of a wind turbine and, in particular, to aspects of lubrication 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 even larger rotor disk diameters in an effort to increase the energy capture potential and thereby reduce the average cost of energy production. This principle has contributed to the year-on-year increase in the global installed capacity 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 is accompanied by its challenges, as the wind turbine tower has to be taller, the blades have to be longer and stronger, and the nacelle has to be larger and heavier. The central part of the wind turbine can be considered as the main rotor shaft, as it carries the hub and the rotor blades and utilizes the rotational energy generated by these blades such that it can be converted into electrical energy by a generator. The main rotor shaft and thus the bearing means supporting the main rotor shaft must therefore be incredibly robust to withstand the huge forces generated during the energy production process.

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

[0005] In view of this background, 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 supporting a main rotor shaft of a wind turbine, wherein the main bearing housing defines a first end, a second end, and a base plate region located between the first end and the second end. The main bearing housing includes a first bearing means positioned at the first end of the main bearing housing and a second bearing means positioned at the second end of the main bearing housing, wherein the base plate region includes a first oil sump positioned at the first bearing means and a second oil sump positioned at the second bearing means.

[0007] The advantage of the present invention is that the bearings of the main bearing housing are lubricated by a lubrication system that includes reservoirs positioned at each of the front and rear bearings of the main rotor shaft. Thus, the front and rear bearings are supplied with oil at suitable lubrication points and are part of the lubrication system that supplies oil to other components in the wind turbine that require oil lubrication, such as the gearbox and / or generator bearings. Accordingly, the front and rear bearings of the main bearing housing do not require a separate lubrication system, such as a grease-based system, and thus simplify the overall lubrication requirements of the nacelle.

[0008] Since the first oil reservoir and the second oil reservoir are positioned at the bearing means, oil from the bearing means can be simply collected in the reservoir during use. The oil reservoir and the bearing means can be configured and arranged such that the bearing means is lubricated by the fluid in the reservoir during use. This is advantageous in the event that, for example, the circumferential supply of oil to the bearing means fails due to a malfunction of the lubrication pump. In addition to any oil supplied circumferentially around the bearing means, it also serves as a supplementary lubrication point for the bearing means.

[0009] The main bearing may also include an overflow sump located between the first reservoir and the second reservoir, and wherein the overflow sump, the first reservoir, and the second reservoir are all connected to a fluid discharge system. The fluid discharge system may include a first discharge passage connected to the first reservoir and a second discharge passage connected to the second reservoir, and wherein the first discharge passage and / or the second discharge passage is defined by the main bearing housing. The advantage of this arrangement is that the oil passages are integral with the main bearing housing in that they are defined by the main bearing housing rather than being provided by a separate network of external pipes or hoses. The term "integral" means that these passages are defined by drilled parts or holes that are casting features of the main casting of the main bearing housing. In this regard, one or more ports of the first discharge passage and the second discharge passage may be defined by the main bearing housing. Thus, the outlet can lead directly into a suitable valve workpiece directly attached to the main bearing housing without the need for additional hose connections. For this purpose, the fluid discharge system may include a discharge control valve that can be operated to selectively discharge fluid from one or both of the first oil reservoir and the second oil reservoir. The control valve can be operated periodically to provide more effective cleaning of the oil reservoir contents. The discharge passage may also include an input from a collector sump.

[0010] Optionally, the oil sump may include one or more baffles that help prevent the oil in the sump from being aerated due to sloshing that may occur during the movement of the wind turbine during use. At least one of the one or more baffles may be a component cast integrally with the main bearing housing. Some baffles may be features cast into the main bearing housing casting. Alternatively, at least one of the one or more baffles may be formed as a component separate from but attached to the main bearing housing. This provides flexibility regarding how the oil sump is configured.

[0011] One or both of the oil sumps may include an overflow device configured to allow fluid to overflow from the respective oil sump. The overflow device may include an overflow channel configured with an overflow inlet at or near the bottom plate of the sump and located at a position between the overflow inlet and the upper edge of the sump sidewall and spaced from each of the overflow inlet and the upper edge of the sump sidewall. In other words, the overflow outlet is at a position above the overflow inlet and below the upper edge of the sump sidewall. Those skilled in the art will understand that the terms "above" and "below" should be understood to refer to when the sump is in its normal orientation during use.

[0012] Advantageously, since the overflow channel is supplied with oil from a position near the bottom of the sump, debris and sediment at the bottom of the sump tend to be entrained by the flow of the oil and thus tend not to be collected at the bottom of the sump. Accordingly, the lubrication system can more effectively clean the oil because the debris and sediment are caused to circulate around the lubrication system. This is in contrast to known sump designs in which, when the sump is full, the oil will simply overflow over the top of the sump sidewall.

[0013] In other words, the overflow outlet is at a position above the overflow inlet and below the upper edge of the sump sidewall. Those skilled in the art will understand that the terms "above" and "below" should be understood to refer to when the sump is in its normal orientation during use.

[0014] 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 bore defined in the material of the sump sidewall. This can be a particularly convenient way to integrate such a function into the sump.

[0015] 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 can cause the oil to overflow from the sump more quickly, which can more effectively entrain larger particles in the oil flow. More than one overflow channel may be provided as respective tower structures.

[0016] In another embodiment, the overflow channel may include a laterally elongated channel extending between the overflow wall and the sidewall of the reservoir. The overflow channel can thus extend across the width of the reservoir. It is contemplated that this embodiment can reduce the likelihood of particles floating in different regions of the reservoir bottom tray.

[0017] The reservoir may include a drain channel. The drain channel may be separate from or combined with the overflow channel. In one embodiment, the drain channel is connected to and extends from the overflow channel. The drain channel may be connected to a return channel that supplies oil back to the oil sump of the lubrication system, and the main bearing housing forms part of the oil sump of the lubrication system.

[0018] It should be understood that the preferred and / or alternative features of the first aspect of the present invention may be combined with other aspects of the present invention. The present invention in its various aspects is defined in the following independent claims and the advantageous features are defined in the following dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 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:

[0020] Figure 1 is a view of a wind turbine that can incorporate an embodiment of the present invention;

[0021] Figure 2 is Figure 1 a schematic system-level view of the wind turbine;

[0022] Figure 3 is Figure 1 and Figure 2 a perspective view of the main bearing housing of the wind turbine;

[0023] Figure 4 is a schematic cross-sectional view through Figure 3 the main bearing housing, showing an embodiment of the present invention;

[0024] Figure 5 is a schematic view of a lubrication system for supplying lubricating fluid to Figure 4 the main bearing housing;

[0025] Figure 6 is a plan view showing the bottom plate area of Figure 4 the main bearing housing; and

[0026] Figure 7 and Figure 8 are a perspective view and a side view, respectively, of an alternative embodiment of the oil reservoir.

[0027] Note that like or similar features in different drawings are denoted by the same reference numerals. DETAILED DESCRIPTION

[0028] Referring to Figure 1 , the wind turbine 2 includes a nacelle 4 supported on a generally vertical tower 6, which in turn is mounted to a foundation 8. The foundation 8 may be on land or wholly or partly underwater. The nacelle 4 houses a plurality of functional components, some of which are schematically illustrated by way of example in Figure 2 . Such a configuration is well known to the person skilled in the art.

[0029] Here, the nacelle 4 is shown as housing at least in part a main rotor assembly 10, a gearbox 12 and a generator 14. For the sake of brevity, some typical components have been omitted from Figure 2 as they are not central to the present discussion, such as a power converter and a yaw drive. However, the presence of such components is implicit and such components will be well understood by the person skilled in the art.

[0030] The main rotor assembly 10 includes a hub 16 coupled to a main rotor shaft 18, which is rotatably supported by main bearing means 20 housed within a main bearing housing 22. In this embodiment, the main bearing means 20 includes a front bearing means 24 and a rear bearing means 26. The hub 16 is connected to a plurality of rotor blades 27, although typically three blades in a HAWT. These blades 27 are acted upon by the wind and thus apply a torque from the hub 16 to the main rotor shaft 18, which causes the main rotor shaft to rotate within the main bearing housing 22. From now on, in the present discussion, the front bearing means and the rear bearing means may be referred to simply as "bearings".

[0031] 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 as connected to another flange 29 associated with the hub 16 such that the two flanges form a connection between the hub 16 and the main rotor shaft 18. Thus, the flange 18a may be considered to be at the hub connection end of the main rotor shaft 18.

[0032] The output portion 18b of the shaft 18 provides an input drive to the gearbox 12. The gearbox 12 increases the rotational speed of the main rotor shaft 18 via internal gears (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 electrical power. The electrical power generated by the generator 14 can then be converted by other components (not shown here) as required before being supplied to the electrical grid (e.g., or indeed any power-consuming device).

[0033] 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.

[0034] 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.

[0035] 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 .

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] Still seeFigure 4 It should be understood that the main bearing housing 22 includes a bottom plate region 40 that extends between the front and rear ends of the main bearing housing 22 and includes different functional features, structures, and configurations involved in the lubrication of the front bearing 24 and the rear bearing 26. More specifically, a first oil reservoir 42 is positioned at the front bearing 24, and a second oil reservoir 44 is positioned at the rear bearing 26. The two oil reservoirs 42, 44 are positioned and configured such that lubricating oil sprayed, delivered, or otherwise provided at the front bearing device 24 and the rear bearing device 26 deposits 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.

[0041] Contrary to known lubrication methods for main shaft bearings, it will be understood 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 The lubrication system 50 is schematically shown in to provide further background of the present invention.

[0042] As can be seen, the lubrication system 50 includes a series of lubricated subsystems that are supplied with lubricating fluid from a tank 52. Although various types of lubricating fluids can be used, for simplicity, from now on the general term "oil" will be used to refer to a liquid form of lubricating fluid that can be used for circulating lubrication (i.e., stored in a suitable reservoir or tank and pumped repeatedly from there around the system to various consumption units).

[0043] The lubricating fluid is drawn from the tank 52 by a pump 54 and is directed along a suitable fluid supply network 56 to the lubricant consumption subsystems, which are generally the main bearing housing 22, the gearbox 12, and the generator 14. A fluid return network 57 returns the fluid from each of the main bearing housing 22, the gearbox 12, and the generator 14 to the tank 52, where the fluid can be recirculated again by the pump 54 to the fluid supply network 56.

[0044] Also shown in the fluid supply network 56 here are a filter unit 58 and an oil heater 60, as these are common components in oil-based lubrication systems that can be used under various environmental conditions. It should be noted at this point that the lubrication system 50 is shown in in a simplified form, and thus various common components, such as check valves, branch points, pressure gauges, etc., are omitted for the purpose of clarity. Figure 5 in a simplified form, and thus for the purpose of clarity, various common components, such as check valves, branch points, pressure gauges, etc., are omitted.

[0045] 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 62a and 62b here) supply lubricating oil to the main bearing housing 22.

[0046] More specifically, the first supply line 62a supplies lubricating fluid to the front bearing 24, and the second supply line 62b supplies lubricating fluid to the rear bearing 26. Although not shown herein, it should be understood that the two supply lines 62a and 62b may supply lubricating oil to one or more delivery nozzles that may be appropriately spaced around the bearing assembly for optimal oil delivery. The supply lines 62a and 62b are also shown in Figure 4 as pointing to the top of each bearing assembly 24, 26.

[0047] Thus, the oil sprayed through the nozzles onto the front bearing assembly 24 and the rear bearing assembly 26 is used for lubrication and then flows into the respective oil reservoirs 42, 44 and from the oil reservoirs into the fluid return network 57. Further details of the oil reservoirs will be described in more detail in the following discussion.

[0048] At this point, it should be understood that a significant benefit associated with the above arrangement is that the main bearing housing 22 is included in the fluid lubrication system 50 having the gearbox 12 and the generator 14. In known systems, this is not the case, where the gearbox 12 and optionally the generator 14 are typically lubricated with lubricating oil by a pumping system, while the main bearing housing 22 is typically lubricated with a different medium (usually grease). Thus this represents a simplification of the known method of lubricating the power train components of a wind turbine.

[0049] The discussion will now focus on more specific features of the main bearing housing 22 that serve to provide optimal lubrication to the front bearing assembly 24 and the rear bearing assembly 26.

[0050] Referring again to Figure 4 , it has been described above that the bottom plate region 40 of the main bearing housing 22 includes a first oil reservoir 42 located at the first bearing assembly 24 and a second oil reservoir 44 located at the rear bearing assembly 26. Each oil reservoir 42, 44 is configured and arranged such that it provides a reservoir for lubricating oil at a certain depth such that the bottom of the bearing assemblies 24, 26 is at least partially immersed or submerged in the lubricating oil. This is shown in 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 as being collinear with the roller elements in the bearings 24, 26. The oil level overflow in the two oil reservoirs to the respective bearings is also shown in the plan view of Figure 6 . In this discussion, for simplicity, in cases where they have common features, they will be collectively referred to as the two oil reservoirs. Similarly, the common features of the two oil reservoirs will use the same reference numerals.

[0051] Each oil reservoir 42, 44 can be considered to include a bottom plate disk 61 surrounded by a side wall 63. The exact configuration of the side wall can vary depending on the shape and configuration of the bottom plate region 40 of the main bearing housing 22. For example, if the bottom plate region 40 has a substantial curvature due to the cylindrical shape of the main bearing housing 22, then the reservoir can be a feature cast into the bottom plate region 40 of the main bearing housing 22 such that the side wall is sectionally defined by the inner surface of the main bearing housing 22 itself. Another possibility is that the bottom plate region 40 is relatively flat and thus the oil reservoirs 42, 44 can be separate components placed on and fixed to the bottom plate region 40. Thus, in this case, the oil reservoirs 42, 44 can be box-shaped components having a bottom plate disk 61 or base surrounded by one or more wall sections which together define the boundary walls of the oil reservoir for containing the lubricating oil therein.

[0052] It should be noted that, in Figure 4 and Figure 6 the illustrated embodiment, the oil reservoirs 42, 44 are defined in part by the lateral curved surface of the bottom plate 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. While the axially inner end wall section 64 is positioned towards the center of the bottom plate region 40 of the main bearing housing 22, the outer end wall section 66 is located behind the respective bearing devices 24, 26.

[0053] As Figure 4 shown, during normal operation, the oil level in the oil reservoirs 42, 44 reaches a certain depth during operation such that a portion of the respective bearing device is immersed in the 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 at or near the bottom plate disk 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. Thus, 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 portion of the side wall section 82. The normal orientation can also be with respect to the depth direction of the reservoir (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.

[0054] 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.

[0055] 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 .

[0056] 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 .

[0057] In this embodiment, the tower structure 84 is located in a generally middle position along the lateral extent of the inner wall section 64, which can be clearly seen in Figure 6 . This is an elegantly simple solution, but it will be understood that other configurations are possible. For example, the tower structure 84 can be positioned closer to the left or right side of the inner wall section 64. Another option is that more than one tower structure can be provided with associated overflow channels. Another option is that a single tower structure with an associated overflow channel can be supplied by more than one overflow inlet.

[0058] As can be seen from the illustration in Figure 4 , the lubricating oil from the bottoms or floor pans 70 of the reservoirs 42, 44 flows into the overflow inlets 78 and upward through the overflow channels 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, after being sprayed into the bearing device through the nozzles, the oil level in the overflow channels 76 increases until the oil flows out through the overflow outlets 80. When the overflow outlets 80 are at a position lower than the inner wall section 64, the oil in the overflow channels 76 leaves the overflow outlets 80 and exits the reservoirs 42, 44.

[0059] 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.

[0060] The main bearing housing 22 also includes a drain system 90 that is configured to drain the lubricating oil from the reservoirs 42, 44 and the collector sump 86.

[0061] In the illustrated embodiment, as will be described, the drain system 90 includes a network of fluid channels that are integral with the structure of the main bearing housing 22 in the sense that they are part of the casting. 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 channels can also be implemented as pipes or hoses external to the main bearing housing 22.

[0062] The function of the drain system 90 is to provide a permanently open drain for the collector sump 86, but a selective drain function for each of the two reservoirs 42, 44. Thus, in this way, the contents of the reservoirs 42, 44 can be emptied from time to time to allow the lubricating oil in the reservoirs to be recycled back to the tank 52 and the filter 58.

[0063] To this end, each of the two storage tanks 42, 44 includes a main discharge passage 92 that connects the respective storage tank to the discharge system 90. In the illustrated embodiment, the main discharge passage 92 is an extension of the overflow passage 76 and is thus supplied from the overflow inlet 78. As can be seen, the main discharge passage 92 extends downwardly from the overflow passage 76 and terminates at a respective discharge outlet 94 defined in the lower side of the main bearing housing 22.

[0064] In addition to the main discharge passage 94, each storage tank 42, 44 is also provided with a secondary discharge passage 96. The secondary discharge passage 96 is configured to collect oil that overflows from the axially outer end wall sections 66 of each storage tank 42, 44 and supply the overflowed oil to the main discharge passage 92. Thus, each secondary discharge passage 96 is connected to a respective overflow outlet 94. In the illustrated embodiment, it will be noted that the secondary discharge passage 96 is connected to the respective discharge outlet 94 via a connection or junction 97 to the main discharge passage 92. Another passage 99 extends from the junction 97 to the discharge outlet 94.

[0065] Both discharge 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 discharge 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 storage tank 42, 44 through the respective discharge outlet and into the fluid return network 57.

[0066] It should be noted that in the illustrated embodiment, the collector sump 86 also includes a respective discharge passage 100. Here, the collector discharge passage 100 is implemented as an integral passage or bore in the main bearing housing 22 that extends downwardly from the collector sump 86 and terminates at a connector 102. The connector 102 provides an interface to the fluid return system 57. Thus, in this embodiment, the oil discharge path from the collector sump 86 is not valve-controlled. Optionally, the collector discharge passage 100 can be valve-controlled.

[0067] In this embodiment, the control valve 98 is a single three-way valve. Although it is contemplated that the same function can be achieved by separate two-way valves, 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 electrical connection for control input purposes. Thus, a single three-way valve is more cost-effective than using separate valves to control the flow from each drain passage. It is contemplated that in the normal operating mode, the control valve 98 will close the communication between the reservoirs 42, 44 and the fluid return network 57 such that the reservoirs 42, 44 will be filled with oil to a predetermined depth. Then, the control valve 98 is periodically operated to drain oil from each reservoir 42, 44. The reservoir drain can be performed on one reservoir at a time or on both reservoirs simultaneously. It is contemplated that the 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 this function can be integrated into the main control system.

[0068] As another alternative improvement, the reservoirs 42, 44 may include baffles 104. As shown in the illustrated embodiment, the baffles 104 are located in each reservoir 42, 44 and extend vertically from the bottom plate disc 70 so as to divide the volume of the reservoir into compartments. Thus, the baffles 104 serve to reduce the sloshing of the oil within the reservoir as the wind turbine sways during operation.

[0069] The upper edge of the baffle 104 may extend to a point near the expected maximum oil levels L1, L2 in the reservoir, which can improve efficiency.

[0070] To allow oil to circulate within the reservoirs 42, 44, the baffles 104 may be provided with suitable holes. These holes may take the form of holes or perforations in the baffle 104 to allow oil to pass through. Alternatively or additionally, holes may be defined at the lower edge of the baffle such that a gap 106 exists between the bottom plate disc 70 and the baffle 104. Thus, the oil in the reservoirs 42, 44 can flow beneath the baffle 104, but the baffle still effectively prevents excessive sloshing of the oil within the reservoirs 42, 44.

[0071] It is contemplated that some or all of these baffles 104 may be an integral part of the main bearing housing 22 as they are part of a single casting. Alternatively, in another embodiment, the baffles 104 may be separate components that are fixed to the reservoirs 42, 44 after the main bearing housing 22 is manufactured. Optionally, these baffles 104 may reach edge-to-edge across the width of the reservoirs 42, 44 as shown herein, but this is not essential and it is contemplated that in other embodiments there may be a gap between either or both of the lateral edges of these baffles 104 and the side walls of the reservoirs 42, 44.

[0072] Figure 7 and Figure 8 An alternative design of the reservoir 110 is shown in Figure 8 , which has many similarities with the above-described reservoirs 42, 44, and can thus also be used in the main bearing housing 22. Thus, the reservoir 110 includes a bottom plate disk 112 and upwardly extending side walls 114. The side walls 114 in this arrangement are rectangular in form, but it should be noted that this is not necessary.

[0073] When considering the orientation that will be taken when the reservoir 110 is located in the main bearing housing 22 as described above, the side walls 114 of the reservoir 110 include a first axially inner side wall section 116 and a second axially outer side wall section 118.

[0074] The overflow device 120 is positioned adjacent to the inner side wall section 116. It will be noted that, contrary to the tower-like structure of the overflow device 74 of the previous embodiment, the overflow device 120 in this embodiment includes an elongated overflow channel 122 that extends transversely across the front of the reservoir. Thus, the overflow channel 122 is defined by a shallow box-like structure that is defined by the inner end wall section 116 and another end wall or 'overflow wall' 124. The height of the other 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, its upper edge 117).

[0075] The overflow inlet 130 is defined at the bottom of the reservoir 110, between the bottom plate disk 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 the flow of the previous embodiment, as the oil flows through the overflow inlet 130 into the overflow channel 122, which is at a very low position in the reservoir 110. The oil then travels upward through the overflow channel 122 and exits through the overflow outlet 128. Thus, it is noted that, similar to the previously shown 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 located between the upper edge of the side wall and the overflow inlet 130.

[0076] As in Figure 4 and Figure 6 the previous embodiments, the reservoir 110 of this embodiment includes a plurality of baffles 132. However, for clarity, only two baffles 132 are shown herein. However, as Figure 8 shown, one of these baffles 132 includes a plurality of holes or perforations 134 to allow oil to pass through the holes or perforations, and the other of these baffles 132 includes a gap 136 that is defined between the lower edge 138 of the baffle 132b and the bottom plate disk 112 of the reservoir 110.

[0077] It should be noted that, depending on the construction of the reservoir, the inner end wall section 116 can in fact be defined by a baffle 132 having an opening towards its bottom edge, or by a baffle defining a lower clearance at the bottom plate disc 112 of the reservoir 110.

[0078] Although the reservoirs of Figure 7 and Figure 8 have been described separately, for the sake of clarity, it is stated here that the reservoir of the illustrated embodiment can be used for the main bearing housing 22, just as in the case of the main bearing housing in the embodiment of Figures 4 to 6 , in place of the illustrated reservoir configuration described herein.

[0079] It should be noted that the above discussion describes different variations of the illustrated embodiment and modifications that can be made by a person skilled in the art, which variations and modifications are not considered to fall outside the scope of the invention defined by the appended claims. Other options are also possible.

Claims

1. A main bearing housing (22) for supporting a main rotor shaft (18) of a wind turbine, wherein, the main bearing housing defines a first end, a second end, and a bottom plate region (40) located between the first end and the second end, and the main bearing housing includes: a first bearing device (24) positioned at the first end of the main bearing housing, a second bearing device (26) positioned at the second end of the main bearing housing, wherein the bottom plate region (40) includes a first oil reservoir (42) positioned at the first bearing device and a second oil reservoir (44) positioned at the second bearing device, wherein the first bearing device (24) is configured to be at least partially immersed in the oil held in the first oil reservoir (42), and the second bearing device (26) is configured to be at least partially immersed in the oil held in the second oil reservoir (44).

2. The main bearing housing according to claim 1, the main bearing housing further including an overflow pool (86) located between the first oil reservoir and the second oil reservoir, and wherein, the overflow pool, the first oil reservoir, and the second oil reservoir are all connected to a fluid discharge system (90).

3. The main bearing housing according to claim 2, wherein, the fluid discharge system (90) includes a first discharge passage connected to the first oil reservoir and a second discharge passage connected to the second oil reservoir, and wherein the first discharge passage and / or the second discharge passage is defined by the main bearing housing.

4. The main bearing housing according to claim 3, wherein, one or more outlet holes (94) of the first discharge passage and the second discharge passage are defined by the main bearing housing.

5. The main bearing housing according to claim 2, wherein, the fluid discharge system includes a discharge control valve (98), the discharge control valve being selectively operable to discharge fluid from one or both of the first oil reservoir and the second oil reservoir.

6. The main bearing housing according to claim 5, wherein, the fluid discharge system (90) includes a first discharge passage connected to the first oil reservoir and a second discharge passage connected to the second oil reservoir, and wherein the first discharge passage and / or the second discharge passage is defined by the main bearing housing, one or more outlet holes (94) of the first discharge passage and the second discharge passage are defined by the main bearing housing, and the discharge control valve is directly coupled to the main bearing housing so as to engage with the one or more outlet holes.

7. The main bearing housing according to claim 1, wherein, the first oil reservoir and / or the second oil reservoir includes one or more baffles (104).

8. The main bearing housing according to claim 7, wherein, at least one of the one or more baffles is integral with the main bearing housing.

9. The main bearing housing according to claim 7 or 8, wherein, At least one of the one or more baffles is formed as a component separate from but attached to the main bearing housing.

10. The main bearing housing according to claim 1, wherein, the first oil reservoir and / or the second oil reservoir includes a boundary wall (63) and an overflow passage (76) to allow lubricating fluid to overflow from the respective oil reservoir through the boundary wall, the overflow passage having an inlet opening (78) and an overflow opening (80), wherein the inlet opening is located at a position lower than the overflow opening.

11. The main bearing housing according to claim 10, wherein, the inlet opening is positioned adjacent to the bottom plate of the oil reservoir.

12. The main bearing housing according to claim 10 or 11, wherein, the overflow opening is located at an upper portion of the boundary wall.

13. A wind turbine, the wind turbine comprising: a main shaft rotatably supported by the main bearing housing (22) according to any one of the preceding claims; a gearbox (12) coupled to the main shaft; and a lubrication system (50) including: a tank (52) for lubricating fluid; a lubrication pump (54) for pumping lubricating fluid from the tank; and a fluid pipeline network (56) for delivering lubricating 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.

14. The wind turbine according to claim 13, wherein, the lubrication points on the main bearing housing direct lubricating fluid to the first bearing device and the second bearing device.

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