Abstract:
A bearing device including a clamping ring for retaining and preloading a bearing in a housing, and a sensor unit for detecting at least one state variable of the bearing. The sensor unit is embedded in a recess of the clamping ring.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This is a United States National Stage Application claiming the benefit of International Application Number PCT/EP2013/056472 filed on 27 Mar. 2013 (Mar. 27, 2013), which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    It is known to use clamping rings for retaining and preloading bearings, in particular split outer rings of bearing, in a housing. Split outer rings or split inner rings are used in particular for double row bearings as applied in heavy load applications such as wind turbines, generators or ship propeller bearings. The invention is applicable to any such bearing structure, in particular to bearing structures used in the latter fields of application. 
       BACKGROUND OF THE INVENTION 
       [0003]    Taper roller bearings or bearings with split rings are often mounted using clamping rings for retaining and preloading a bearing in a housing. In the case of wind turbines, the rotor is supported in a housing via at least two bearings, which are usually formed as large-size cylindrical roller bearings, in particular including at least one double row taper roller bearing in O-configuration. 
         [0004]    Bearing assemblies of this type have to support large angular momenta in directions perpendicular to the rotation axis of the bearing and may therefore be subject to strain deformations. Damages of the rollers or the raceways may cause vibrations and/or heat and it is important to efficiently monitor the devices, in particular using remote systems, in order to be able to timely stop the apparatus and to prevent major damages. 
         [0005]    Sensors for this purpose are usually provided on an outer surface of the housing or of the clamping ring, where the measured values may be degraded as compared to direct measurements due to the lack of direct contact. 
         [0006]    Further, externally mounted sensor units are susceptible to damages due to unintended collisions with the housing and the like. 
       SUMMARY OF THE INVENTION 
       [0007]    It is an object of the invention to solve the above problems of the prior art and to provide a reliable way of integrating a sensor unit in a bearing device as described above. 
         [0008]    The invention starts from a bearing device including a clamping ring for retaining and preloading a bearing ring in a housing and a sensor unit for detecting at least one state variable of the bearing. The state variable may include vibrations, acoustic emissions, temperature, strain or load and the sensor unit may include suitable sensors. 
         [0009]    It is proposed that the sensor unit is embedded in a recess of the clamping ring. 
         [0010]    The embedding in the recess of the clamping ring allows for a more direct contact between the sensor and the bearing, in particular the outer or the inner ring of the bearing, while at the same time protecting the sensor unit from unintended collisions and other detrimental influences from the outside. 
         [0011]    It is further proposed that the bearing device includes the bearing, which may in particular be formed as a large-size roller bearing, with at least one split ring, wherein the clamping ring is configured to abut with an axial end face of the ring or of one part of the split ring. 
         [0012]    The position of the sensor unit in the retaining or clamping ring is particularly suitable for measuring strain deformations of the bearing ring, which are more likely to occur in the outer ring of the bearing. In principle, the invention could also be applied to clamping rings retaining an inner ring of a bearing on an axle or on a shaft. 
         [0013]    The advantages of the invention are most effective when the outer diameter of the ring retained by the clamping ring amounts to at least 300 mm, because the recess may be formed sufficiently small as compared to the overall size of the clamping ring and because the problem of strain deformation is of particular relevance in this case. 
         [0014]    Further, it is proposed that the bearing is formed as a double-row taper roller bearing in O-configuration. 
         [0015]    A further aspect of the invention relates to a wireless transmitter for transmitting signals obtained by the sensor, which may be integrated in the sensor unit. The provision of the wireless transmitter facilitates the monitoring of the apparatus having the bearing assembly and the robustness of the entire assembly may be further increased because communication lines may be avoided. 
         [0016]    Further, it is proposed that the recess opens towards a bearing side of the clamping ring, such that at least one contact plate of the sensor unit is in direct contact with the axial end face of one ring of the bearing. It should be noted that the expressions “axial”, “radial” and “circumferential” refer to the cylindrical coordinates with the rotation axis of the bearing taken as central axis, whereas “axially inward” or “axially outward” refers to the inside and the outside of the housing. 
         [0017]    Preferably, a bottom face of the sensor unit including the contact plate is provided with an O-ring preventing the penetration of oil or other liquids into the contact area between the contact plate and the axial end face of the bearing ring. 
         [0018]    In a preferred embodiment, the sensor unit includes an arc-shaped housing, which is adapted to the curvature of the bearing ring to be monitored, in particular such that the curvature of the housing is at least approximately equal to the curvature of the ring in contact with the contact plate of the sensor unit. The expression “equal” is to be interpreted in a wide sense here, i.e. the shown curvature or a main curvature of the housing should be somewhere close to or inside the range between the curvature of the radially inner face of the bearing ring and the curvature of the radially outer surface of the bearing ring. 
         [0019]    Preferably, the sensor unit includes at least one temperature and/or one acoustic emission and/or one vibration sensor. Further, one or more temperature sensors may be provided. 
         [0020]    A weakening of the clamping ring resulting from the recess may be compensated for by providing a reinforcing structure of the clamping ring in the vicinity of the recess. The reinforcing structure may be a portion with increased thickness or increased width of the clamping ring, reinforcing ribs or the like. 
         [0021]    A further aspect of the invention relates to a control unit for controlling or monitoring an apparatus including a bearing device as described above. The control unit is configured to receive data from the sensor unit, in particular using the wireless transmitter, and to generate status information and/or warning signals based on the received data. 
         [0022]    The above embodiments of the invention as well as the appended claims and figures show multiple characterizing features of the invention in specific combinations. The skilled person will easily be able to consider further combinations or sub-combinations of these features in order to adapt the invention as defined in the claims to his specific needs. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0023]    The invention will now be described in more detail for explanatory, and in no sense limiting, purposes, with reference to the following figures, in which 
           [0024]      FIG. 1  is a sectional view of a bearing arrangement of a wind turbine including two clamping rings according to the invention; 
           [0025]      FIG. 2  is a partial sectional view of a first clamping ring of the assembly of  FIG. 1 ; 
           [0026]      FIG. 3  is a perspective view of a backside of the clamping ring of  FIG. 2 ; 
           [0027]      FIG. 4  is a front side view of the clamping ring of  FIG. 2 ; 
           [0028]      FIG. 5  is a detail of  FIG. 3 ; 
           [0029]      FIG. 6  is a detail of  FIG. 4 ; 
           [0030]      FIG. 7  is a perspective view of the sensor unit in  FIGS. 1-6 ; 
           [0031]      FIG. 8  is a perspective view of the sensor unit in  FIGS. 1-6  without its cover plate; 
           [0032]      FIG. 9  is an exploded view of the sensor unit of  FIGS. 7 and 8 ; and 
           [0033]      FIG. 10  is a schematic view of a circuit board and sensor assemblies of the sensor unit of  FIGS. 8 and 9 , taken out of the housing. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0034]      FIG. 1  is a cross sectional view of a bearing arrangement of a wind turbine including a first clamping ring  10  on the rear side remote from the turbine rotor (not shown) and a second clamping ring  12  on the front side of the housing  14  supporting the shaft  16  of the rotor. The shaft  16  is supported in the housing  14  via a first roller bearing  18  formed as a double rotator roller bearing and a second roller bearing  20  on the front side formed as a single row roller bearing. 
         [0035]    The axially inner sides of the outer rings, i.e. the axial sides facing towards the center of the housing  14  abut with shoulders in the housing and are retained and preloaded on their axially outer sides by the clamping rings  10 ,  12  respectively. 
         [0036]      FIG. 2  is a partial sectional view of the first clamping ring  10  of the assembly of  FIG. 1 . As illustrated, the clamping ring  10  is provided with a recess on the axially inner side facing the axially outer side of the outer ring of the bearing  18  and a sensor unit  24  is fitted into the recess  22 . The bottom surface of the recess is provided with two bores  26 ,  28  and two axially projecting rod-like channels  30 ,  32  are fitted into the bores  26 ,  28 . The first channel  30  of a housing  34  of the sensor unit  24  guides a connector via  36  of the sensor unit  24  axially outside of the clamping ring  10  and a second channel  32  of the housing  34  receives an antenna  38  of the wireless transmitting unit  40  provided in the sensor unit  24 . 
         [0037]      FIG. 3  is perspective view of the backside, i.e. of the axially outer side of the clamping ring  10  of  FIG. 2  and it is illustrated that both the connector wire  36  with a pertinent connector and the antenna  38  protrude over the axial end face of the clamping ring  10 . It is to be noted that the bores for bolts fixing the clamping ring  10  on the housing  14  are not illustrated in  FIGS. 3 and 4 . A total of three sensor units  24  with pertinent and recesses  22  is provided in the clamping ring  10  ( FIG. 4 ). The sensor units  24  are isotopically distributed over the circumference of the clamping ring  10 . 
         [0038]    The recesses  22  and the housing  24  have a basically identical shape such that the housing  34  of the sensor unit  24  can be easily fitted into the recesses  22 . The shape of the recesses  22  and of the housing then viewed from in the axial direction and the curvature of the recess and the housing correspond to the curvature of a circle with a radius corresponding to the respective radial positions with regard to the rotation axis of the bearings  18 ,  20  and of the shaft  16 . 
         [0039]      FIG. 4  is a front side view of the clamping ring of  FIGS. 2 and 3  and it is illustrated that the contact surfaces of the sensor units  24  including various contact plates is arranged essentially flush with the contact surface  42  of the clamping ring  10 , which is supposed to come in contact with the axial end face of the outer ring of the roller bearing  18 . 
         [0040]      FIGS. 5 and 6  are details of  FIGS. 3 and 4 . A reinforcing structure  78  (illustrated with dashed lines) in the form of a portion with increased thickness may be provided in the vicinity of the recess  22  in order to compensate for the loss of rigidity of the clamping ring  10  resulting from the presence of the recess  22 . 
         [0041]    The axial height of the housing  34  corresponds to the depth of the recess  22  such that the contact surface of the sensor unit  24  is pressed against the end axial face of the outer ring of the roller bearing  18  when the clamping ring  10  is mounted to the housing. 
         [0042]      FIG. 7  is a perspective view of the sensor unit  24  of  FIGS. 1-6  as viewed from the side of the bearing  18 . 
         [0043]    The sensor unit  24  is equipped with a temperature sensor, a vibration sensor, an acoustic emission (AE) sensor and a strain sensor in the form of a friction strain gauge and two contact plates  44 ,  46  are provided on the side of the sensor unit  24  facing the outer ring of the bearing  18  in the assembled state in order to establish a good mechanical and thermal contact between the sensors and a bearing  18 . 
         [0044]    The bottom of the recess  22  is provided with two threaded bores engaging with screws  48 ,  50  at the ends of the housing  34  of the sensor unit  24 . A cover part  52  of the sensor unit  24  has rectangular holes receiving the contact plates  44 ,  46  and is fixed on the main part of the housing  34  with four further screws. An overmolded O-ring  54  is provided over the entire circumference of the cover part  52  of the housing  34  and is made of soft elastic material so as to prevent the penetration of oil or other liquids into contact area between the contact plates  44 ,  46  and an axial end face of the bearing outer ring. The cover part  52  with the O-ring  54  serving as a face-seal part is formed in a two-shoot molding process. 
         [0045]      FIG. 8  illustrates the sensor unit  24  with a cover plate  52  removed. A printed circuit board  56  is arranged in the center portion of the housing  34  and a sensor assembly  58 ,  68  is arranged on the lateral sides respectively. 
         [0046]      FIGS. 9 and 10  are exploded views of the sensor unit  24  of  FIGS. 7 and 8  and show the cover part  52  with the O-ring  54 , the circuit board  56  with the sensor assemblies  58 ,  60 . 
         [0047]    The sensor assembly  58  includes an acoustic emission sensor  62 , vibration sensor  64  and a temperature sensor  66 , and the sensors  62 ,  64 ,  66  are mounted on the metallic contact plate  44 . 
         [0048]    The second sensor assembly  60  includes a friction strain gauge  70  so as to enable the measurement of strain deformations of the outer ring of the bearing  18 . The sensor assembly  58  is preloaded against the axial end face of the bearing with two springs  72 ,  74  and the friction strain gauge  70  is preloaded with one spring  76 . 
         [0049]    The sensor assembly and the recesses in the second clamping ring  12  may be identical to the above recess  22  and assembly  24  or dimensionally adapted in an appropriate way.