Abstract:
A connector for an electric motor including a magnetic ring which is the seat of a magnetic field tied to operating parameters of the motor. A magnetic flux conduction member forms a flux concentrator interposed, when a connector is fixed on the motor, between the magnetic ring and a Hall-effect sensor to measure the magnetic flux conducted by the magnetic flux conduction member. The electric motor can be used with geared motors for window-lifting systems, seat actuation systems or sunroof systems, in the automobile field.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to the field of electric motors, in particular geared motors for automobile accessories, which are used for example in window-lifting systems, seat actuation systems or sunroof systems. 
   The invention is more precisely aimed at a connector for an electric motor, said motor comprising a magnetic ring which is the seat of a magnetic field tied to operating parameters of the motor. 
   The motors or geared motors to which the invention applies are associated with a control system which uses motor speed and/or position parameters. These parameters are fed to the control system by a Hall-effect sensor associated with the magnetic ring, which is adapted so as to deliver to the sensor a magnetic field dependent on the speed and/or position of the motor shaft. 
   Generally, the electronic control devices of such motors or geared motors comprise a circuit board secured to the casing of the motor, said board comprising motor electrical supply connections and the Hall-effect sensor. This sensor is fixed on a board part formed of a rigid strip that penetrates into the casing of the motor up to a region neighboring the magnetic ring, in such a way that the sensor is located in the vicinity of said ring. 
   It can readily be seen that the presence of such an electronic control module on the casing of the motor is incompatible with a high degree of standardization of motors, since such a configuration of the motor and of its casing is not suited to an application in which the speed and/or position sensor is dispensed with, and in which the electronic control device of the motor is located remotely some distance away from the motor. 
   SUMMARY OF THE INVENTION 
   A main aim of the invention is to remedy this drawback, and to propose a connector for an electric motor, which makes it possible to transport information of magnetic type to an electronic processing device and is capable of amalgamating with this function the conventional functions for the electrical supply of the motor. 
   With this aim, a connector according to the invention comprises at least one magnetic flux conduction member forming a flux concentrator interposed, when the connector is fixed on the motor, between the magnetic ring and a Hall-effect sensor adapted so as to measure the magnetic flux conducted by the magnetic flux conduction member. 
   According to one embodiment, the magnetic flux conduction member exhibits an elongate part, an end of the elongate part exhibiting a smaller section than the mean section of the elongate part, neighboring the Hall-effect sensor. 
   According to a further embodiment, the section of said end decreases progressively in the neighborhood of the Hall-effect sensor. 
   According to a further embodiment, the elongate part of the magnetic flux conduction member is made of soft steel. 
   According to other characteristics of the invention:
         the magnetic flux conduction member comprises at least one metal pin adapted so that a part of said pin, when the connector is fixed on the motor, lies in the vicinity of the magnetic ring;   the magnetic flux conduction member comprises two metal pins whose free ends are disposed symmetrically with respect to an axial plane (P) of the magnetic ring;   the connector furthermore comprises at least two electrical power contacts linked to a supply source for the motor;   the electrical contacts comprise a part made of brass;   at least one of said electrical power contacts is disposed so as to constitute a part of the magnetic flux conduction member;   said power contact constituting a part of the magnetic flux conduction member is connected, when the connector is fixed on the motor, to a metal pad secured to the motor and a part of which lies in the vicinity of the magnetic ring;   said power contact constituting a part of the magnetic flux conduction member is made of steel;   the magnetic flux conduction member is secured to the power contact;   the magnetic flux conduction member is affixed to the power contact;   the connector is secured to a printed circuit on which the Hall-effect sensor is disposed;   the connector is adapted so as to be fixed in a detachable manner on the electric motor.       

   The invention is also aimed at a geared motor for automobile accessories, such as a window or a seat, comprising a rotor shaft equipped with a magnetic ring, characterized in that it comprises a connector as described above. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments of the invention will now be described with regard to the appended drawings, in which: 
       FIG. 1  is an end-on view in partial section of a geared motor equipped with a connector according to a first embodiment of the invention; 
       FIG. 2  is a diagrammatic cross section along the line  2 — 2  of  FIG. 1  representing the magnetic flux conduction member and the magnetic ring; 
       FIG. 3  is a view similar to  FIG. 1  according to a second embodiment of the invention; 
       FIG. 4  is a cross section similar to  FIG. 2 , along the line  4 — 4  of  FIG. 3 ; 
       FIG. 5  is a partial sectional end-on view of a third embodiment of the invention; 
       FIG. 6  is a sectional diagrammatic side view of the embodiment of  FIG. 5 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Represented in  FIG. 1  is a geared motor  1  including a motor  2  and a reduction gear  3 , the motor  2  being equipped with an electronic control device  4  which includes a printed circuit board  5 . 
   The motor  2  includes a stator  6  forming a shroud in which permanent magnets (not represented) are housed and supporting by way of a bearing  7  an end  8 A of a rotor shaft  8  of a rotor  9 . In a known manner, the latter includes windings coiled around stacked laminations. A commutator  10  is linked electrically to the rotor  9  and receives by way of brushes  11  the motor supply current transmitted to the motor  2  at the level of supply lugs  12 . 
   The geared motor  1  further includes a casing  20  rigidly fixed to the stator  6  and supporting by way of a second bearing assembly, not represented, a second end of the rotor shaft  8 . The rotor shaft  8  span situated on the same side as the second shaft end is configured as a threaded rod forming a worm screw, which drives a set of gears of the reduction gear  3 . A magnetic ring  21  is fixed on the rotor shaft  8  in a region neighboring the supply lugs  12 . 
   The casing  20  exhibits an aperture  22  near the supply lugs  12  that receives in a detachable manner an electrical connector  30  into which the printed circuit board  5  of the electronic control device  4  is fixed. The printed circuit board  5  supports an electronic circuit able to deliver a supply current for the motor  2 . The connector  30  is held in position by a releasable fastener of conventional type (not illustrated). The current delivered by the electronic circuit travels through power tags  31  secured to the printed circuit board  5 , each of the power tags  31  being connected fixedly to an end  32 A of a contact  32  of a “stirrup” type, that is one end of the power contact  32  includes an elastic clip having two inwardly arched symmetric contact portions. 
   The printed circuit board  5  additionally supports a Hall-effect sensor  33  intended to receive a magnetic flux indicative of the speed and/or position of the rotor shaft  8  and to transmit to the electronic control device  4  an electrical signal indicative of these operating parameters of the motor  2 . 
   The connector  30  also includes a magnetic flux conduction member including, in the embodiment of the invention represented in  FIG. 1 , of two parallel metal pins  35 , one end of which is fixed to the printed circuit board  5  in the vicinity of the Hall-effect sensor  33 . The other end  35 A constituting the free end of the pin  35  is situated, when the connector  30  is inserted into the aperture  22  of the corresponding casing  20  and held by the fastener, near a periphery of the magnetic ring  21 . The two free ends  35 A are preferably disposed symmetrically with respect to an axial plane P of the magnetic ring  21 . 
   The relative position of the metal pins  35  and of the magnetic ring  21  is more clearly apparent in  FIG. 2 . The magnetic ring  21  generates a magnetic field of constant strength whose direction varies with the angular position of the rotor shaft  8 , and therefore the magnetic flux conducted by the pins  35  of the magnetic ring  21  to the Hall-effect sensor  33  is dependent on an angular position of the rotor shaft  8 . The electrical signal delivered by the Hall-effect sensor  33  therefore affords access to the speed and/or angular position of the rotor shaft  8 . Preferably, the pins  35  forming magnetic flux conduction members are made of steel. 
   Represented in  FIG. 3  is a geared motor  101  of the same type as above, whose motor  102  includes a rotor shaft  108  on which a magnetic ring  121  is fixedly mounted. A connector  130  includes a printed circuit board  105  forming part of an electronic control device  104  of the electric motor  102  and supporting a pair of supply tags  131  situated in proximity to a Hall-effect sensor  133 . The connector  130  is fixed in a detachable manner to the casing  120  of the geared motor  101  by conventional releasable fastener (not represented). The connector  130  includes contacts  132  of “stirrup” type, fixed by one of their ends  132 A to the supply tags  131  and intended to be connected by a second end  132 B to motor supply lugs  112 . 
   In this embodiment of the invention, and as will be more clearly seen in  FIG. 4 , the two lugs  112  each exhibit a part  140  overlapping the magnetic ring  121  oblique with respect to the direction of coupling of the contacts  132 , and which lies in the vicinity of the magnetic ring  121  in an almost tangential manner. The two parts  140  are preferably symmetric with respect to the axial plane P of the magnetic ring  121 . Likewise, the supply tags  131  include a part  131 A partially overlapping the Hall-effect sensor  133 , so that the lugs  112 , the contacts  132  and the supply tags  131  fulfil the flux concentrator function and constitute a member for conducting the magnetic flux of the magnetic ring  121  to the Hall-effect sensor  133 . 
   Preferably, the contacts  132  are made of steel, a material of this type offering an acceptable compromise between the qualities of electrical and magnetic conduction, and exhibiting excellent mechanical properties. 
   It is readily understood that the two embodiments of the invention which have just been described make it possible to design geared motors with a high degree of standardization. Specifically, it is not necessary to secure a printed circuit board carrying a Hall-effect sensor to the motor in order to achieve the position and/or speed sensor functions, and hence to modify the casing of a standard motor. Thus, one and the same motor can be used regardless of the application of the geared motor, and regardless of the type of sensor required (speed/position), only the connector having to be modified. 
     FIGS. 5 and 6  represent a geared motor according to a third embodiment of the invention. A connector  230 , represented only partially, includes, as in the other embodiments, a printed circuit board  205  that supports a Hall-effect sensor  233 . 
   Magnetic flux conduction pins  241  each exhibit an end near a Hall-effect sensor part  233 A and  233 B, respectively. The other end of the pins  241  can, for example, come into contact with a respective lug  212 . As in the embodiment of  FIG. 3 , the lugs  212  supplies the magnetic ring  221  mounted on a rotor  209 . The magnetic flux of the magnetic ring  221  can thus be conducted from the magnetic ring  221  up to the Hall-effect sensor  233 . 
   As represented in  FIG. 6 , the magnetic flux conduction pins  241  exhibit an elongate part. This elongate part exhibits an end neighboring the sensor  233  of reduced section, that is to say of smaller section than the mean section of the elongate part. This reduced section can for example be obtained by using flat pins of reduced width at the level of this end. The reduced section makes it possible to concentrate the magnetic flux at the level of the Hall-effect sensor  233 . The amplitude of the magnetic flux conducted by the pins  241  up to the Hall-effect sensor  233  is thus increased. Similar pins of reduced section may of course be used in the previous embodiments of the invention. 
   Pins whose section decreases progressively toward the Hall-effect probe are preferably used. The flux losses in proximity to the Hall-effect probe are thus reduced. The pins  241  are preferably made of soft iron, steel, nickel or ferrite. A material exhibiting high magnetic permeability is generally used. 
   According to a variant, supply tags  242  electrically link an electrical supply harness  208  to the lugs  212 . The supply tags  242  are preferably made of copper or brass so as to ensure high conduction of the electric current between the supply harness  208  and the lugs  212 . 
   The supply tags  242  and the pins  241  can be fixed at the same level as the lugs  212 . Each supply tag  242  can also be fitted to a pin, for example by soldering, by adhesive bonding or by riveting. It is also possible to use other means of mechanical fixing or simply to stack a tag on top of a pin, retaining them by their respective ends. 
   The invention, which makes it possible to conduct magnetic information to a remote sensor, renders a single geared motor configuration adaptable to various applications, the standardization of the geared motor being offset by the diversification of the connection engineering, thereby achieving a considerable saving with regard to the complete system.