Abstract:
A sensor device for monitoring a component of interest, including at least one sensor for measuring at least one parameter indicative of condition of the component of interest, signal processing device for processing the signals of the sensor, a housing for at least the signal processing device and a mounting feature for mounting the sensor device close to the component of interest. The mounting feature can include a bolt and bracket having a first portion including an opening for inserting the bolt in an insertion direction and a second portion with a surface parallel to the insertion direction configured to mount the housing.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This is a Non-Provisional Patent Application, filed under the Paris Convention, claiming the benefit of Great Britain (GB) Patent Application Number 1421781.4, filed on 8 Dec. 2014 (08.12.2014), which is incorporated herein by reference in its entirety. 
       FIELD OF THE INVENTION 
       [0002]    The invention relates to a sensor device for monitoring a mechanical component of interest, in particular a train bearing arranged in a train axle box. 
       BACKGROUND OF THE INVENTION 
       [0003]    The invention relates to devices for monitoring the condition of components, in particular of rotating components of vehicles or machinery. When attempting to monitor the condition, it is often difficult to find suitable locations for the required sensor systems such that they can be applied without disassembly of mechanical systems and resultant destruction of the assemblies and components they are intended to monitor. 
         [0004]    Sensor systems should be configured such that they can be quickly and easily installed for a range of condition monitoring tasks. However, increased mounting comfort often leads to an increased distance between the sensor system and the component of interest, such that the quality of the measurement is reduced due to attenuation, increased noise and environmental factors. 
         [0005]    Parameters measured in condition monitoring are typically vibration, acoustic emission or temperature. The longer the transmission path for heat or acoustic waves, the higher the risk that information gets lost. Maximizing the transmission of signals of interest to the sensor is a key factor in maximizing the signal-to-noise ratio. As a consequence, it is preferred to place the sensors as close to the component of interest as is practical. In particular, material interfaces and components between the sensors and the component of interest should be minimized, as each interface can add significantly to an attenuation of signals. Further, the sensor system should have a compact design as the space envelope of suitable mounting sites is often small. 
       SUMMARY OF THE INVENTION 
       [0006]    In view of the above considerations, the invention seeks to provide a sensor device for monitoring a component of interest which can be mounted close to the component of interest, requires small space and does not significantly add to the attenuation in a transmission path of physical quantities to be measured between the component of interest and the sensor. 
         [0007]    The invention relates to a sensor device for monitoring a component of interest. The sensor device includes at least one sensor for measuring at least one parameter indicative of a condition of the component, signal processing device for processing the signals of the sensor, a housing for receiving and protecting the signal processing device, and a mounting feature for mounting the sensor device to the component of interest. 
         [0008]    It is proposed that the mounting feature includes a screw or bolt and a bracket formed as a cast metal part, wherein the bracket has a first portion including an opening for inserting the screw or bolt in an insertion direction and a second portion parallel to the insertion direction, wherein the second portion has a surface configured to mount the housing and/or the sensor. The first portion of the bracket has an end face configured to be pressed directly against a surface of the component of interest by the clamping force generated by the bolt and the second portion protrudes away from the end face. 
         [0009]    The bracket of the sensor device according to the invention ensures that the sensors can be aligned for optimal detection. The second portion of the bracket arranged upright is configured for mounting the sensors and preferably has a flat surface. The coupling of acoustic emission and vibrations is of high quality because acoustic waves entering the bracket via the first portion can be securely guided to the second portion and the sensor. The angled arrangement of the two portions leads to a compact design while at the same time allowing for the insertion of a screw or bolt and fixing tools to tighten the screw or bolt even within very restricted space limits. 
         [0010]    In preferred embodiments of the invention, the sensor is formed as a vibration sensor, an acoustic emission sensor and/or as a temperature sensor. In either case, a substance for improving the transmission of acoustic waves between the component of interest and the sensor can be used at an interface between the bracket and the component on which the bracket is mounted, wherein the substance may be a gel or a paste. 
         [0011]    Preferably, the sensors are placed as close as possible to the base portion of the bracket in order to minimize the influence of external noise. 
         [0012]    Further, it is proposed that the sensor device comprises at least one battery for powering the signal processing device and/or the sensor. In alternative embodiments of the invention, the sensor device can be equipped with a generator assembly such as a thermal generator or a power harvester. 
         [0013]    In a preferred embodiment of the invention, the sensor device comprises a transmitter for wireless communication. This facilitates the use in retrofit applications, because the installation of wires or cables can be avoided. An antenna of the transmitter can be arranged in a protected space if the housing is made of a material permitting the transmission of electromagnetic waves emitted and/or intended to be received by the transmitter. 
         [0014]    In a preferred embodiment of the invention, the component of interest is a bearing of a vehicle, in particular a bearing in a train axle hub. Preferably, the sensor device is configured to be attached close to a loaded zone of a non-rotating ring of a bearing. The inventors have found that there is a statistically better chance of detecting high-frequency vibrations from a bearing, if the sensor is located in the area relatively close to the loaded zone of the bearing and/or approximately in line with the load direction. In the case of a vehicle, such as a train, the load line travels vertically upwards, passing through the center of the bearing. It has been found that placing sensors within +30 degrees of the load line facilitates good signal detection of high-frequency vibrations. Further, it is proposed that the sensor is oriented with regard to the line of maximum stress in order to further improve the signal detection quality. The performance of vibration and acoustic emission sensors has been found to give best performance when the sensors are mounted on the line of maximum stress +25 degrees. These parameters apply in particular to sensor devices designed for application to monitoring train axle boxes. 
         [0015]    Further, it is proposed that the sensor device is configured to be located in a direction of highest stiffness of the system. This direction is likely to ensure a reliable transmission of acoustic waves. 
         [0016]    Further, it is proposed that at least the second portion of the bracket comprises a structure, such as flanges or ridges, increasing the rigidity of the second portion. 
         [0017]    In preferred embodiments of the invention, the bracket is a cast metal part, in particular made of Zamak 5 alloy, which is an alloy as defined in the standard EN12844 with a base metal of zinc and alloying elements of aluminum, magnesium and copper. Zamak alloys are part of the zinc aluminum alloy family, wherein they are distinguished from the other ZA alloys because of their constant aluminum content of 4%. However, other materials with high rigidity can be suitable for the bracket as well. In general, it is important that the material passes vibrations, acoustic emissions and temperature, and does not block or strongly attenuate these quantities. 
         [0018]    Further, it is proposed to provide the surface of the mounting bracket which is configured to contact the sensor in the form of a flat surface, preferably a polished surface optionally equipped with a gel for improving the acoustic coupling and/or a thermally conductive paste. 
         [0019]    Further, it is proposed that a signal processing device is formed as a PCB which is potted or overmoulded in order to protect the electronics from vibration, temperature, fire, foreign object strike corrosion, etc. The electronic parts should fulfil the standards set, e.g., in EN50155 and EN61373. 
         [0020]    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 
         [0021]      FIG. 1  illustrates an axle box equipped with a sensor device according to the invention; 
           [0022]      FIG. 2  is an axial view of the axle box according to  FIG. 1 ; 
           [0023]      FIG. 3  is an exploded view of a sensor device according to a first embodiment of the invention; 
           [0024]      FIG. 4  is a further exploded view of the sensor device according to the first embodiment of the invention; 
           [0025]      FIG. 5  is a first perspective view of the sensor device according to the first embodiment of the invention in an assembled configuration; 
           [0026]      FIG. 6  is a second perspective view of the sensor device according to the first embodiment of the invention; 
           [0027]      FIG. 7  is an exploded view of the sensor device according to a second embodiment of the invention; 
           [0028]      FIG. 8  is a sensor device according to the second embodiment of the invention in an assembled configuration; 
           [0029]      FIG. 9  is a perspective view of a sensor device according to a third embodiment of the invention; 
           [0030]      FIG. 10  is a perspective view of a sensor device according to a fourth embodiment of the invention; 
           [0031]      FIG. 11  is a perspective view of a sensor device according to a fifth embodiment of the invention; 
           [0032]      FIG. 12  is a perspective view of a sensor device according to a sixth embodiment of the invention; 
           [0033]      FIG. 13  is a perspective view of the sensor device according to the sixth embodiment of the invention with a battery cover removed; and 
           [0034]      FIG. 14  is an explosion view of the sensor device according to the sixth embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0035]      FIG. 1  illustrates an axle box  10  for a passenger train comprising a central bore  10   a  for receiving a double-row roller bearing (not shown). A sensor device  12  according to the invention is attached to a flange in a top part of the axle box  10 . 
         [0036]    As illustrated in  FIG. 2 , the sensor device  12  is attached directly in the line of load  13  of the axle box  10  and of the bearing mounted therein such that the sensor device  12  is located very close to a loaded zone of the bearing in a direction of maximum stiffness of the axle box  10 . The sensor device includes a bolt  15  for fastening a body part of the sensor device  12  to the axle box. The mounting position maximizes the transmission of high frequency noise as generated e.g. by defects of the rolling elements passing by the sensor device  12 . 
         [0037]      FIG. 3  is an exploded view of the sensor device  12  according to the invention. The sensor device  12  comprises a housing  14  having a lower housing part  14   a  and a housing cover part  14   b , both made of dielectric plastic material. The housing  14  is provided with a gasket (not shown) or with multiple gaskets in order to protect the electronics arranged therein. 
         [0038]    The sensor device  12  includes a PCB with various electronic components as a signal processing device  16 . In particular, the signal processing device includes a wireless transmitter  18 , the antenna of which is arranged under a protruding portion of the housing cover member  14   b  such that signals sent by the transmitter and/or received by the transmitter are unaffected by the metallic parts of the axle box  10  and of the sensor device  12 . 
         [0039]    Further, the sensor device  12  includes a bracket  20  as a mounting feature with a roughly angular shape, the bracket  20  having a first portion  20   a  with an opening  20   b  for receiving the bolt  15  and a second portion  20   c  extending perpendicular to the first portion  20   a  of the bracket  20 . The opening  20   b  is configured such that the bolt  15  can be fitted into the opening  20   b  in an insertion direction  17 . The second portion  20   c  has a surface extending parallel to the insertion direction  17  and the housing is mounted on the surface using screws. 
         [0040]    Sensors  22   a ,  22   b  formed as temperature and acoustic emission sensors are attached to the signal processing device  16  via a flexible circuit board, and are directly attached to or embedded into a solid base part of the bracket  20  connecting the portions  20   a ,  20   c . The sensors  22   a ,  22   b  are fixed on the bracket by a mounting plate and screws  26   a ,  26   b . Electronic devices such as capacitors for filtering or damping the sensor signals are mounted on the mounting plate as a part of a sensor unit including the sensors  22   a ,  22   b.    
         [0041]    Further, the sensor device  12  includes batteries  28   a ,  28   b  and a cover member  30  of a battery compartment as well as suitable electrodes and gasket rings for sealing the battery compartment. 
         [0042]    The printed circuit board forming the signal processing device  16  is potted on both sides. 
         [0043]    As illustrated in  FIG. 3 , the second portion  20   c  of the bracket  20  is provided with stabilizing ridges following the shape of the batteries  28   a ,  28   b , which increase the rigidity of the bracket. The bracket is a solid cast metal part made of Zamak 5 alloy. 
         [0044]    The sensors  22   a ,  22   b  can be attached to a flat and/or polished portion of the surface of the bracket  20  and/or fitted into a recess machined into the material of the bracket  20 . The location at which the sensors  22   a ,  22   b  are attached to the bracket  20  should be as close as possible to the lower surface of the first part  20   a  of the bracket facing the axle box  10  and the bearing as the component to be monitored. In the embodiment illustrated in  FIGS. 4 and 5 , the sensors  22   a ,  22   b  are arranged axially between the head of the bolt  15  and the axle box  10 . 
         [0045]      FIG. 4  illustrates the assembly with the housing parts  14   a ,  14   b  removed. 
         [0046]      FIGS. 5 and 6  show the sensor device  12  in different perspective views. 
         [0047]    Further embodiments of the invention are illustrated in  FIGS. 7 to 11 . The following description of the further embodiments is limited to differences to the embodiment illustrated in  FIGS. 1 to 6  in order to avoid repetitions. For features which are unchanged the reader is referred to the above description of the embodiment of  FIGS. 1 to 6 . Similar features are provided with the same reference numbers in order to highlight the similarities. 
         [0048]    In the embodiment of  FIGS. 7-8 , the bracket  20  is formed as a sleeve-like body with an opening  20   b  formed as an axial bore and a flat side face  20   d  with smaller bores for mounting the housing  14  using screw. A sensor unit  24  is embedded in a recess in the side face  20   d  and the sensing surfaces of the sensors  22   a ,  22   b  are contact with an inner surface of the recess, wherein the inner surface extends in a direction perpendicular to the axial direction of a bolt  15  for fastening the sensor device  12 . 
         [0049]    The orientation of the battery compartment or power pack of the sensor device  12  in the embodiment of  FIG. 7  is rotated by 90° as compared to the embodiment of  FIGS. 1 and 2 . Further, the battery compartment is arranged on top of the signal processing device  16 . The more massive bracket  20  in the embodiment of  FIG. 7  ensures a transmission of vibrations and heat transfer with low loss. The bolt  15 , which is a standard M16 bolt, has to be about 40 mm longer than in the embodiment of  FIGS. 1-6 . 
         [0050]    In the embodiment of  FIG. 9 , the bracket  20  is formed as a sleeve-like body with an opening  20   b  formed as an axial bore, wherein an end of the bore remote from the side of the component to be monitored has an increased diameter in order to countersink the head of the bolt  15 . 
         [0051]    The embodiment of  FIG. 10  features a generally L-shaped bracket with an angular shape for fixing the sensor device  12  to the axlebox. 
         [0052]    In the embodiment of  FIG. 10 , the bracket  20  of the sensor unit  12  includes an inner surface with a roughly semicircular profile encompassing a screw head of the bolt  15 . The lateral edges of the semicircular profile are formed as ridges increasing the rigidity of the bracket  20 . 
         [0053]    Further embodiments of the invention include spacers to be arranged between the bracket  20  and the axlebox  10 .