Abstract:
The metal housing of the case of a contactor includes an annular rib extending continuously opposite the cylindrical periphery of the main stationary core, the rib having an internal diameter respectively greater than that of the ferrule and smaller than that of the housing, so as to ensure the locking of the different parts of the case and the crimping of the housing on the stationary magnet following local deformations exerted on the reduced diameter of the swaged part defining the rib.

Description:
BACKGROUND OF THE INVENTION  
   1. Field of the Invention 
   The invention relates to an electromagnetic contactor for an electric starter motor, said contactor comprising: 
   connection terminals intended for connection to the battery and to the electric motor, 
   a movable core, 
   a main stationary core, 
   an axial air gap provided between the movable core and the main stationary core, 
   a tubular coil to produce a magnetic current in the air gap provided between the movable core and a main stationary core during excitation,
         a magnetic circuit provided with a case constructed with magnetic frame attached to the stationary core,       

   an insulating cap enclosing the contacts of the electric power circuit and having connection terminals,
         said case being composed of a metal bell-shaped housing, an internal ferrule made of magnetic material surrounding the coil, and a washer acting as an additional stationary core through which the movable core passes, and arranged opposite the main stationary core.       

   2. Background Art 
   Starters generally comprise an electromagnetic contactor, the purpose of which is to make it possible for:
         the pinion to engage in the drive ring gear at the moment of starting, as well as its disengaging after starting, and   the electric motor to be supplied with current.       

   The contactor is generally composed of an electromagnet actuating a plunger core which, by moving, closes an electrical circuit for supplying power to the electric motor, and pulls an actuator lever that drives the pinion into the starter ring gear. 
   According to the document FR-A-2795884, a motor vehicle starter (see  FIG. 5 ) has a rotary electric motor M and an output shaft equipped with a pinion  1  to drive a starter ring gear C, integral in rotation with the flywheel of the vehicle to start the combustion engine of the vehicle. The pinion  1  is slidably mounted, by means of complementary splines, on the output shaft between a rest position in which it is disengaged from the ring gear, and an active working position in which it engages with said ring gear. 
   The output shaft is driven in rotation by the electric motor when said motor is electrically powered. This shaft is different from the shaft of the motor M in  FIG. 6  because speed-reduction gearing is located between the two shafts. As a variation, the output shaft is the shaft of the motor M. 
   The electric motor of the starter is also associated with an electromagnet power contactor  2  placed above the electric motor. This contactor  2  comprises a tubular coil  2   a  held by a support, the bottom of which constitutes a bearing  2   c  to guide a movable core  2   b.    
   This contactor  2  has the dual function of supplying the electric motor M with current, and of moving the movable pinion  1  between the two positions of rest and work. The excitation of the electromagnet is controlled, for example, by activating the contact key, which establishes the electrical circuit to the battery, after the closing of the contactor&#39;s main power circuit. 
   The movable core  2   b  of the contactor  2  is mechanically connected by a mechanical connection  4 , comprising a control lever, to a starter drive assembly equipped with a freewheel transmission device. The pinion  1  pertains to the starter drive assembly. 
   The fork-shaped control lever is pivotably mounted on a spindle and the output shaft is mounted in rotation in a housing by means of bearings. 
   The housing is intended to be attached to a fixed part of the vehicle and is open for the passage of the ring gear C. This housing is thus used to attach the starter to the engine of the vehicle. 
   The main power circuit of the contactor is provided with a pair of fixed contacts, and a bridge-shaped movable contact  3  which is attached to a pushrod actuator intended to be moved in translation by the movable core during excitation of the coil. 
   More specifically, the pushrod is intended to be moved by the movable core  2   b  after the axial clearance is closed up, and a second return spring acts on the movable core to draw it back to the rest position. 
   A first return spring, called cutoff spring, pulls the movable contact and pushrod assembly to an open position in order to make an axial interval with the fixed contacts. 
   This rest position of the pushrod is determined by contact of the movable contact  3  with a stationary core having a central hole to guide the pushrod provided with a flange for mounting a spring, called contact pressure spring, acting between this flange and the movable contact. The stationary core is flanged and has a centering seat for centering the support of the coil  2   a.    
   Also provided is a spring  5 , called gear engagement spring, housed inside the movable core  2   b  and engaged with a rod connected by a spindle to the upper end of the fork-shaped control lever to couple this lever to the movable core  2   b.    
   The contactor, generally cylindrical in shape, is situated near the electric motor while extending parallel thereto. It is attached to the above-mentioned housing that supports the output shaft and the pinion slidably mounted on said shaft. In a known way the housing also has the frame of the electric motor M closed by a rear bearing for the mounting in rotation of the shaft of the electric motor M. The housing has a front bearing for the mounting in rotation of the output shaft as an extension of the shaft of the electric motor M by means of a bearing between the ends of the said shafts. 
   In addition to the movable core, the contactor comprises a fixed part of magnetic material, and a cap of insulating material and having connection terminals connected to the fixed contacts. The fixed part of the contactor is composed of a dish-shaped frame designed to be mounted on the housing, and the stationary core separated from the movable core by an axial air gap. The tubular coil coaxially surrounds the movable core with a slight radial clearance, and is housed inside the case. 
   The movable core, under the action of the second return spring, is in a position separated from the stationary core when the coil is not excited. 
   When power is supplied to the coil, i.e., during excitation of the coil, the movable core moves by magnetic attraction toward the stationary core at first against the retraction force of the first return spring. After the closing up of the axial clearance between the movable core and the pushrod, the movable core then moves the pushrod against the force exerted by the second and first return springs. This first return spring is stiffer than the second return spring and is less stiff than the contact pressure spring. 
   This movement continues until the movable contact makes contact with the fixed contacts and power is supplied to the electric motor. The contact pressure spring is then compressed until the movable core comes into contact with the stationary core. 
   At the same time the starter drive assembly is moved, under action from the control lever, toward the ring gear C. 
   In the event the pinion  1  does not directly penetrate the ring gear C, the spring  5  is compressed to allow the fixed contacts to close and supply power to the electric motor, which then turns the pinion so that it can penetrate the ring gear C. 
   The structure of the magnetic circuit of such a contactor is well known, for example from the document DE 101 55 103 or by the above-mentioned document FR A 2 795 884. 
   In  FIG. 1 , the stationary core  10  of the contactor is generally immobilized in rotation with respect to the case  11  attached by one or more deformations of the case&#39;s side wall so as to form serrations  12  that are embedded in cavities  13  made on the periphery or behind the stationary core  10 . When the case is produced by stacking several elements, careless handling of the case can result in a risk of the assembly coming apart. 
   In  FIG. 2 , the cap  14  must also be blocked from rotation with respect to the case  11  in order to withstand a certain tightening torque C on the connection terminals. The serrations  12   a  provided for that purpose are also made by deformation of the material of the end of the case  11 , which are then inserted into the cavities  13   a  of the cap  14 . When a certain tightening torque on the cap  14  is exceeded, said cap can undergo the beginning of rotation movement, with the risk of the serrations  12   a  escaping. This situation could occur in the event of insufficient mechanical rigidity of a case obtained by stamping a thin (0.5 to 1.5 mm) sheet of metal. The risk of ovalization of the case due to the action of a heavy rotation torque is then possible, and the function of immobilizing the case from rotation is no longer ensured. 
   SUMMARY OF THE INVENTION 
   In general, in one aspect, embodiments of the invention remedy the above-mentioned disadvantages. In general, in one aspect, an embodiment of the invention relates to a starter contactor having a reinforced mechanical strength, irrespective of the tightening torque exerted on the connection terminals. 
   A device according to one embodiment of the invention is characterized in that the metal housing of the case comprises an annular rib extending continuously opposite the cylindrical periphery of the main stationary core, said rib having an internal diameter respectively greater than that of the ferrule and smaller than that of the housing, so as to ensure the locking of the different parts of the case. 
   Thus, in one embodiment, the rib provides the locking of the different parts of the case as well as the crimping of the housing on the stationary core following local deformations exerted on the reduced diameter of the swaged part defining the rib. 
   The presence of the rib at the end of the housing of the contactor makes it possible to ensure both a stable support of the ferrule and the washer inside the housing, as well as increasing the rigidity of the case  11 , preventing any deformation due to the torque exerted on the cap when the connection terminals are tightened. 
   Moreover, the rib can serve as a centerer for the stationary core so that the quantity of material of said core can be reduced. With this type of arrangement, the standard type of stationary cores can be used with the case being sized accordingly. The cap is a presser cap acting on the stationary core, which acts on the ferrule. 
   According to one embodiment of the invention, the main stationary core is provided with radial cavities in which serrations of the housing are embedded during the crimping operation. The cap includes at least an axial stud intended to engage in a notch of the stationary core during assembly of the cap on the end of the housing. 
   In one embodiment of the invention, the notch that receives the stud can be the same as a cavity of the stationary core. After assembly, additional serrations are made on the end of the housing to immobilize the insulating cap from rotation. 
   Other aspects and advantages of the invention will be apparent from the following description and the appended claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other advantages and characteristics will be seen more clearly from the following description of one form of embodiment of the invention, given by way of non-limiting example, and represented in the appended drawings in which: 
       FIG. 1  is a partial view of the contactor according to the prior art, where the case is attached to the stationary core; 
       FIG. 2  shows a partial view of the contactor according to the prior art, where the case is attached to the insulating connection cap; 
       FIG. 3  shows a cross sectional view of a case of a contactor according to one embodiment of the invention; 
       FIG. 4  is a view in perspective of the case of  FIG. 3 ; 
       FIG. 5  illustrates a half-view in cross section of the contactor equipped with the case of  FIG. 3 ; 
       FIG. 6  is an axial cross sectional view of a starter of the prior art. 
   

   DETAILED DESCRIPTION  
   Exemplary embodiments of the invention will be described with reference to the accompanying figures. Like items in the figures are shown with the same reference numbers. In embodiments of the invention, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to one of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid obscuring the invention. 
   Embodiments of the invention relate to an electromagnetic contactor for an electric starter motor. 
   In  FIG. 3  the movable core  18  is in the rest position so that the axial air gap between the stationary core  10  and the movable core  18  is at a maximum. 
   In  FIGS. 3 to 5 , the case  11  is formed from several elements, comprising a bell-shaped metal housing  15 , an internal cylindrical ferrule  16  of mild steel, and a washer  17  of magnetic material serving as additional stationary core. 
   The cylindrical shaped housing  15  comprises an end plate  115  with a central hole through which the core  18  passes. This end plate is transversely oriented with respect to the X X axis of the contactor CT and is configured to form, centrally at its inner periphery, an axial protrusion  116  directed in the opposite direction of the washer  17 . The protrusion  116  is annular in shape. Advantageously, this housing  15  is obtained economically by deep drawing. 
   The axis X X constitutes the axis of the coil  22 , the movable core  18  and the pushrod  101  intended to be moved by the movable core  18  via an internal washer  103  integral with the core  18 .  102  is the contact pressure spring,  24  is the first return spring, i.e., the cut-off spring,  121  is the second return spring and  5  is the gear engagement spring. 
   All of these springs are helicoid. 
   It will be noted that the washer  103  of the movable core  18  closes a cavity terminated by a centrally open end plate through which the rod  117  passes, which rod is connected by the pin  118  to the control lever (not shown). The gear engagement spring  5  is supported on this end plate and on a flanged end of the rod  18 . 
   A pan  120  is attached, in this instance by crimping, to the movable core  18 . This pan serves as support for one end of the second return spring  121 . 
   According to one characteristic, the protrusion  116  serves as support for the other end of the spring  121  so that the housing has an additional function. 
   The washer  17  is pressed against the end plate  115  of the housing  15 , and comprises in the central part a circular orifice  19  allowing the axial passage of the movable core  18 . The central protrusion  116  of the end plate  115  also has a circular orifice allowing the axial passage of the core  18 . 
   To provide both functions, i.e., on the one hand, providing stable support of the ferrule  16  and the washer  17  in the housing  15 , and on the other hand, the rigidification of the case  11  avoiding any deformation due to the torque exerted on the cap  14  when the connection terminals  20  are tightened, the cylindrical side wall of the housing  15  undergoes a local swaging in order to form an annular rib  21  opposite the location of the stationary core  10 . By way of example, the swaging is obtained by deformation of the material, resulting in a decrease of the diameter obtained by roll bending the whole outer circumference of the housing  15 . 
   The inside diameter D 1  of the rib  21  is greater than the inside diameter of the ferrule  16 , and smaller than the diameter D 3  of the housing  15 . The thickness H of the rib  21  measured in the axial direction is less than or equal to the thickness of the stationary core  10 . 
   Thus, it can be seen from the description and drawings that the washer  17  is first mounted in the housing  15  in contact with the end plate  115 , then the ferrule is added in the housing  15 , and finally the material of the housing  15  is deformed in contact with the free end of the ferrule  16  to axially block said ferrule and form the swaged part. A case  11  in three parts  15 ,  16 ,  17  is thus obtained, which comprises a subassembly that can be handled and transported. This solution does not require welding operations. 
   Advantageously the ferrule  16  is in close contact at its periphery with the inner periphery of the housing  15 . This is also the case with the washer  17 . These parts  16 ,  17 , as well as the housing  15 , are advantageously made of mild steel so that they are electrical conductors and the magnetic current can flow through these parts when power is supplied to the coil  22 . The washer  17  can have the required thickness. Of course, the housing  15  can undergo a surface treatment to give it an aesthetic appearance. As a variation, the housing  15  is made of non-magnetic material such as an aluminum based material. 
   As a variation, the housing  15 , the ferrule  16  and the washer  17  can have a cross section that is square, rectangular, polygonal or other. 
   The end plate  115  protects the washer  17 , which thus has little susceptibility to corrosion. This is also the case with the ferrule  16 . The thickness of the washer  17  is greater than that of the ferrule  16 . 
   The coil  22  is then mounted, having an annular support  220  with U-shaped cross section. 
   The coil  22 , via its annular support  220 , and the washer  17  are mounted on a support tube  23  forming a bearing for the core  18  and being supported on an annular centering flange  99  and with axial orientation of the stationary core  10 . This flange  99  is extended at one of its ends by a side plate  100  of transverse orientation with respect to the axis X X. 
   This end plate forms a support flange and thus an axial stop for the support  220  and for the tube  23 . 
   The support  23  passes through the orifice  19  of the housing  15  and of the protrusion  116 . A first return spring  24  pulls the movable bridge contact  25  against the stationary core  10 , while making an axial interval with the stationary contacts  26 , only one of which is visible in  FIG. 5 . 
   The side plate  100  in this instance is cylindrical in shape. Its outer periphery is in close contact with the inside periphery of the rib  21 , which thus serves as centerer of the side plate  100  and therefore of the stationary core  10 . The rib  21  therefore also makes it possible to reduce the height of the side plate  100  and thus the quantity of material of the stationary core, making it more economical. 
   Advantageously the inside periphery of the rib  21 , and thus of the swaged part, includes a cylindrical portion, visible in  FIG. 3 , which serves as centerer for the side plate  100 . This portion has the above-mentioned inside diameter of D 1 . Two sloping sides extend on either side of this centering portion to define with said portion the rib  21 . One of these sloping sides, the side  210  adjacent to the free end of the ferrule  16 , makes it possible to tighten this ferrule so that it presses against the washer  17 , which in turn is pressed against the end plate  115 . This sloping side  210  is thus a tightening side. Of course, as a variation the groove has another shape, such as an overall V shape with rounded point and cross section similar to that of the serrations  12  of  FIG. 2 . 
   The outer periphery of the stationary core  10 , i.e., the outer periphery of the side plate  100 , in this instance advantageously includes cavities  13  that lock both the case  11  and the cap  14  on to the stationary core  10 . Several local deformations of the housing  15  can be made on the outside of the reduced diameter of the inner rib  21 , so as to locally force the metal into the cavities  13  of the side plate  100  of the stationary core  10  to block said core from rotation. The local deformations are preferably trapezoidal in shape. 
   Thus the housing is crimped onto the stationary core. 
   The base of the cap  14  is provided with studs  27  intended to engage axially in the notches of the stationary core  10 . In  FIG. 5 , the notches are the same as the cavities  13  receiving the metal forced back during the crimping of the housing  15 . 
   After the final assembly of the contactor CT, local deformations are made of the end of the housing  15  at the cap  14 , in order to create serrations  12   a  to ensure the immobilization of the cap  14  from rotation. These serrations  12   a  are advantageously received in the cavities of the cap as in  FIG. 2 . 
   This cap, by means of its base, exerts a tightening action on the side plate  100  of the stationary core  10 , the cap being tilted at the cavities receiving the serrations  12   a  so that said serrations exert an axial force on the cap. The parts  17 ,  16 ,  100  and  14  are thus tightened between the end plate  115  and the serrations  12   a . Advantageously the metal of the housing  15  is pushed into the cavities  13  after the cap is attached. Of course, this operation can also be performed before attaching the cap, the crimping of material at serrations being performed by press. 
   Thus, it can be seen that the local deformations penetrating into the cavities and the studs  27  make it possible to angularly index the different parts with each other. 
   As a result of the invention, the housing  15  does not have to be thick because of the presence of the rigidification rib  21 . 
   While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.