Abstract:
Electric motor comprising a rotor and a stator ( 2 ), the stator comprising a body ( 3 ) forming a frame and a windings assembly ( 4, 5 ) housed in slots of the body. The electric motor comprises at least one rod ( 16, 23 ) used to connect, to one another, at least two fixed assembled parts of the electric motor, the rod extending into a housing ( 9 ) formed in the body over the entire length thereof in order to emerge on each side of the body.

Description:
[0001]    The invention relates to the field of electric motors such as those fitted to electromechanical actuators used in aircraft or other vehicles. 
       BACKGROUND OF THE INVENTION 
       [0002]    Numerous electromechanical actuators are found in modern-day aircraft and used for various applications: flight controls, wheel braking, rotational driving of wheels, etc. 
         [0003]    Electromechanical actuators comprise an actuating member and an electric motor designed to drive the actuating member. 
         [0004]    The design of an electric motor for an electromechanical actuator needs to meet specifications at “equipment” level and at “system” level. These specifications, which are dependent on the application in which the electric motor is used, translate into numerous and restrictive requirements that have an impact on the manufacture of the electric motor. 
         [0005]    These requirements in particular include integration requirements (for example requirements relating to the volume of the electric motor or to the integration of power supply or monitoring electrical components into the electric motor), architecture requirements (for example a requirement of inbuilt redundancy which leads to the electric motor being fitted with two separate coils), requirements in terms of mechanical robustness (for example a requirement of resistance to impact, vibrations), etc. 
         [0006]    The electric motor needs to meet all of these requirements, making it relatively complex to manufacture. 
       OBJECT OF THE INVENTION 
       [0007]    The objective of the invention is an electric motor that can be equipped with electrical components and that is robust, compact and relatively simple to manufacture. 
       SUMMARY OF THE INVENTION 
       [0008]    With a view to achieving this objective, there is proposed an electric motor comprising a rotor and a stator, the stator comprising a body forming a frame and a windings assembly housed in slots of the body. According to the invention, the electric motor comprises at least one rod used to connect, to one another, at least two fixed assembled parts of the electric motor, the rod extending into a housing formed in the body over the entire length thereof in order to emerge on each side of the body. 
         [0009]    The use of the rod positioned in the housing formed along the entire length of the body allows simple and robust assembly of the electric motor. This assembly is particularly well suited to attaching to the body an electric board positioned on one face of the body of the stator of the electric motor. 
         [0010]    Further features and advantages of the invention will become apparent from reading the following description of one nonlimiting particular embodiment of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    Reference will be made to the attached drawings, among which: 
           [0012]      FIG. 1  is a perspective view of an electric motor according to a first embodiment of the invention; 
           [0013]      FIG. 2  is a view similar to that of  FIG. 1 , in which a central part of an electric board of the electric motor is not depicted in order to make the inside of a stator of the electric motor visible; 
           [0014]      FIG. 3  is an exploded view of the electric motor of the invention according to the first embodiment; 
           [0015]      FIG. 4  is a perspective view of an electric motor according to a second embodiment of the invention; 
           [0016]      FIG. 5  is a view similar to that of  FIG. 4 , in which a central part of an electric board of the electric motor is not depicted in order to make the inside of a stator of the electric motor visible; 
           [0017]      FIG. 6  depicts a portion of a radial segment used to manufacture a body of the stator of the electric motor according to the second embodiment of the invention; 
           [0018]      FIG. 7  depicts the body of the stator of the electric motor according to the second embodiment of the invention prior to assembly thereof. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    With reference to  FIGS. 1 to 3 , the electric motor  1  according to the first embodiment of the invention comprises a casing of cylindrical overall external appearance (which has not been depicted), inside which a fixed stator  2  and a rotor (not depicted) rotationally driven about an axis X are incorporated. 
         [0020]    The stator  2  comprises a body  3 , a first coil assembly  4  and a second coil assembly  5  which is distinct from and magnetically not coupled to the first coil assembly  4 . 
         [0021]    The body  3  of the stator  2  has a tubular overall shape with an internal surface that is substantially cylindrical in order to accommodate the rotor and an external surface that is substantially cylindrical. The body  3  is made up of a plurality of laminations forming a frame and stacked in an axial direction (in this case along the axis X). 
         [0022]    The body  3  of the stator  2  is made in one piece in this embodiment and comprises a plurality of radial sectors  6  which are evenly distributed about the circumference of the body  3  of the stator  2  and which extend over the entire length of the body  3  of the stator  2 . 
         [0023]    Each radial sector  6  comprises an internal radial rib the terminal surface of which forms a longitudinal portion of the internal surface of the body  3  and an external radial rib  7  the terminal surface of which forms the external surface of the body  3 . 
         [0024]    The internal radial ribs of the radial sectors  6  between them delimit slots  8  which are open at their ends and towards the inside of the body  3 . 
         [0025]    Housings  9  are formed in the body  3  at the periphery of the body  3  and over its entire length parallel to the central axis of the body  3  to open at each end of the body  3 . Each housing  9  is positioned at the level of a radial sector  6  and is formed between the internal surface of the body  3  and the external surface of the body  3  partially inside the rib  7  of the relevant radial sector  6 . 
         [0026]    The first coil assembly  4  and the second coil assembly  5  are housed in the slots  8  of the body  3  of the stator  2 . 
         [0027]    The electric motor  1  additionally comprises a first electric board  11  comprising first electrical components  12  and a second electric board  13  comprising second electrical components. 
         [0028]    The first electrical components  12 , like the second electrical components  13 , comprise Hall-effect sensors intended to measure the position of the rotor in order to control the electric motor  1 . 
         [0029]    This then yields an architecture with inbuilt redundancy (“full duplex” architecture): the electric motor  1  can be driven and therefore can operate despite a fault affecting the first electric board  11  or affecting the second electric board  13 , or affecting the first coil assembly  4  or affecting the second coil assembly  5 . 
         [0030]    The first electric board  11  and the second electric board  13  are electric boards of annular shape the outside diameter of which is substantially equal to the outside diameter of the body  3  of the stator  2  (including the height of the ribs  7 ). The first electric board  11  and the second electric board  13  are each positioned on a different face of the body  3 , being mounted parallel to the said face and placed against winding overhangs  15  of the first coil assembly  4  and of the second coil assembly  5 . 
         [0031]    The body  3  of the stator  2 , the first electric board  11  and the second electric board  13  are assembled using rods  16  (in this instance four rods) which extend through four housings  9  uniformly spaced about the circumference of the body  3  of the stator  2 . 
         [0032]    The length of each rod  16  is greater than that of the body  3  of the stator  2 . Thus, a first end of each rod  16  emerges from the housing  9  in which it is positioned and extends from the relevant face of the body  3  of the stator  2  as far as the first electric board  11 , running alongside the winding overhangs  15 , then extends through a fixing hole  17  formed in the first electric board  11 . Likewise, a second end of each rod  16  emerges from the housing  9  in which it is positioned and extends from the relevant face of the body  3  of the stator  2  as far as the second electric board  13 , running alongside the winding overhangs  15 , then extends through a fixing hole  18  formed in the second electric board  13 . 
         [0033]    The first electric board  11  and the second electric board  13  are fixed to each rod  16  using a nut  19 . 
         [0034]    A spacer piece  20  and a bushing  21  extend around the first end of each rod  16  between the relevant face of the body  3  of the stator  2  and the first electric board  11 . 
         [0035]    Likewise, a spacer piece  20  and a bushing  21  extend around the second end of each rod  16  between the relevant face of the body  3  of the stator  2  and the second electric board  13 . 
         [0036]    It will be noted that the rods  16  are hollow and that electric leads are routed along inside the rods  16  to power the first electric board  11  and the second electric board  13 . 
         [0037]    This then achieves a simple and robust assembly of the body  3  of the stator  2 , of the first electric board  11  and of the second electric board  13 . 
         [0038]    It will be noted that a fifth rod  23 , shorter than the rods  16 , extends through a fifth housing  9 . This fifth rod  23  has two ends each of which emerges onto a different face of the body  3  of the stator  2 . The fifth rod  23  is used to attach to the body  3  two rotation-proofing lugs  25  which are intended to secure the body  3  of the stator  2  and the casing of the electric motor  1  in terms of rotation. Each lug  25  comprises a main section  26  of semicircular cross section, having a flat surface arranged on part of the length of a rib  7  of a radial sector  6 , and a base  27  pierced with a fixing hole. The main section  26  performs the rotation-proofing function. The fixing hole in the base  27  allows the lug  25  to be fixed to the body  3  of the stator  2  using the fifth rod  23  which extends through the fixing hole, and using a nut  28 . 
         [0039]    With reference to  FIGS. 4 to 7 , the electric motor according to a second embodiment of the invention  40  comprises a stator  31  comprising a hollow body  30  of cylindrical external shape. 
         [0040]    The body  30  is made up of a plurality of laminations forming a frame and stacked in an axial direction (in this instance along the axis X). 
         [0041]    In the second embodiment of the invention, the body  30  of the stator  31  of the electric motor  40  is made up of the assembly of distinct radial segments  32  extending over the entire length of the body  30 . Each radial segment  32  comprises a base  33  defining a circular sector and a main section  34 . A groove  35  and a rib  36  are formed on the base  33  of each radial segment  32 . The radial segments  32  are assembled by means of the groove  35  and of the rib  36  of the base  33  of each radial segment  32  to form the body  30  of the stator  31 . 
         [0042]    When the radial segments  32  are assembled, the circular sectors of the bases  33  define the cylindrical exterior shape of the body  30  of the stator  31  and the main sections  34  extend radially towards the inside of the body  30  of the stator  31  and form slots in which a first coil assembly  43  and a second coil assembly  37  are housed. 
         [0043]    The electric motor  40  additionally comprises a first electric board  38  and a second electric board  39  performing the same function as in the first embodiment of the invention. Assembly of the motor  40  is similar to that of the first embodiment except that the electric motor  40  according to the second embodiment further comprises two flat annular fixing rings  41  each positioned against a different face of the body  30  of the stator  31 . The annular fixing rings  41  join together the distinct radial segments  32 . The annular fixing rings  41  have, passing through them, the four rods used to assemble the body  30 , the first electric board  38  and the second electric board  39  and are fixed axially by means of the spacer pieces  42  which extend between each electric board  38 ,  39  and the face of the body  30  of the stator  31  on which this board is positioned. 
         [0044]    In a third embodiment of the invention, the body of the stator is made up of a plurality of laminations forming a frame and stacked in an axial direction (in this instance, along the axis X). 
         [0045]    Each lamination comprises fixing holes. When the laminations are stacked, the fixing holes are positioned facing one another so as to form housings that extend over the entire length of the body. The rods emerge from an upper lamination of the body and from a lower lamination of the body to be fixed to the upper lamination and to the lower lamination using fixing means once again involving nuts. Alternatively, the annular fixing rings of the second embodiment and the spacer pieces may also be used with the rods to assemble the laminations and the electric boards. 
         [0046]    It will be noted here that the rods may also act as end stops for the translational movement of the electric motor or as heat bridges to remove the heat generated by the operation of the motor. 
         [0047]    The invention is not restricted to the particular embodiments which have just been described but rather covers any alternative form that falls within the scope of the invention as defined by the claims. 
         [0048]    Although a motor equipped with two electric boards has been described, the motor could perfectly well comprise a single electric board positioned like one of the first or second electric boards (in an architecture of the simplex type). 
         [0049]    Although it has been indicated that the first electric components and the second electric components comprise Hall-effect sensors intended to measure the position of the rotor in order to control the electric motor  1 , the electric boards may perfectly well comprise different electric components, for example sensors of a different type or alternatively components intended to generate an electrical current flowing through the coils for powering the electric motor. 
         [0050]    The body  3  of the first embodiment may also be in several pieces.