Abstract:
An electro-hydraulic unit ( 10 ) in particular for an automotive vehicle anti-locking wheel device, includes two separate parts:
       an electronic control ( 13 ) within which is located particularly an electronic card ( 14 ), winding ( 17 ) as well as an electric motor ( 15 ) provided with a rotor and a stator, the motor being adapted to drive a pump, and   a hydraulic unit ( 11 ), including the pump and a plurality of valves ( 12 ), the whole electronically directed by the control ( 13 ),
 
the electro-hydraulic unit being characterized in that it further includes a ferromagnetic circuit ( 22 ) common at least partially to the stator and to the winding ( 17 ).

Description:
FIELD OF THE INVENTION 
   The present invention relates to an electro-hydraulic unit, and more particularly to such a unit used in an anti-lock device for the wheels of an automotive vehicle. 
   The electro-hydraulic units used in wheel anti-lock systems are conventionally constituted by three separate parts:
         an electric motor, which drives a pump,   a hydraulic block, which comprises the pump and a certain number of valves, pressure detectors, and   an electronic control comprising among other things an electronic card and winding each controlling a valve. The assembly formed by one winding and its valve is called an electrovalve.       

   BACKGROUND OF THE INVENTION 
   An example of a unit of this type is described in EP 0 645 875. 
   Among the conditions which must be satisfied by these electro-hydraulic units, can be cited minimum size, sealing against external moisture and the cost of production. 
   The present invention has principally for its object to propose an electro-hydraulic unit whose size is substantially less than known units of the prior art. 
   It is for example already known, from FR 2 710 699, to position the electric motor and the electronic control in a same and single housing. However, the housing thus made has even greater size, because each portion is juxtaposed or inserted in another but retains all the same assembly of the usual components. 
   There is also known from EP 0 769 437 an electro-hydraulic unit in which, to reduce the number of parts, there is provided a ferrocircuit common to the winding (of the electrovalves) and to the stator (of the motor). However, this ferrocircuit is made by assembly on the one hand of the rear portion of the cover of the motor and on the other hand by the hydraulic block itself. It is thus a matter of a common ferrocircuit but made in two separate parts. According to this document, the hydraulic block is at least magnetizable as to its winding. However, it is not disclosed how to render magnetizable the hydraulic block. 
   In fact, two solutions are possible to have a magnetized hydraulic block: either the block is made of iron, or magnetic elements are added to it. The production of a hydraulic block of iron is unthinkable without substantial increase of cost. Thus, such a block is too long and too costly to machine. This is moreover the reason for which the hydraulic blocks known at present are made exclusively of aluminum. Aluminum is thus a metal which can be easily machined and above all rapidly, with conventional tools. However, given the shape and complexity of present hydraulic blocks, it is not conceivable to make them by molding. 
   On the other hand, it is much too costly to add either a magnetic material or a magnetic element inserted in an aluminum hydraulic block to render it magnetic. These techniques are too troublesome. 
   SUMMARY OF THE INVENTION 
   The object of the present invention is thus to reduce the size of the electro-hydraulic unit, particularly by using common constituents without modifying the hydraulic block. 
   To this end, the present invention relates to an electro-hydraulic unit in particular for automotive vehicle wheel anti-lock devices, said electro-hydraulic unit being of the type comprising two separate parts:
         an electronic control within which is located particularly an electronic card, winding as well as an electric motor provided with a rotor and a stator, said motor being adapted to drive a pump, and   a hydraulic unit, comprising the pump and a plurality of valves, the whole electronically directed by the control,
 
the said electro-hydraulic unit comprising moreover:
   a magnetic circuit common at least partially to the stator and the winding,
 
said unit being characterized in that the ferrocircuit is independent of the hydraulic unit and has at its periphery an annular flange housing the winding, said annular flange ensuring simultaneously a function of mechanically holding the winding and a function of magnetic conduction for these winding.
       

   Thanks to this arrangement, not only is it possible to integrate the motor into the control, but it is moreover possible to use in common certain components belonging to the ferrocircuit (magnetic circuit) and because of this the number of pieces comprising the electro-hydraulic unit is reduced, without modifying corresponding the hydraulic unit (already sufficiently complex and ponderous in itself). The size of this unit is also reduced. 
   According to an important aspect of the invention, the ferrocircuit ensures a function of magnetic conduction both for the stator and for the winding. 
   Surprisingly, it has been observed that there is no or little magnetic diaphony between the stator and the winding. More exactly, the motor controls do not disturb the electrovalve controls (constituted by the assembly of the winding of their metallic frames and a valve secured to the hydraulic block) and vice versa. Moreover, the same is true for diaphony between the electrovalves, which does not exist when these latter are simultaneously controlled. 
   Preferably, the ferrocircuit has at its periphery an annular flange permitting enclosing the magnetic field produced by the winding on the active portion of the valve. Thus, the electrovalves are disposed as close as possible to the motor block, which permits decreasing the size of the electro-hydraulic unit. It will be noted that the ferrocircuit ensures simultaneously a function of mechanically holding the winding at a function of magnetic conduction for these winding. 
   Preferably, it is possible to arrange the electrovalves (winding+valve+ferrocircuit) at the periphery of the motor, which reduces at least the axial size of the electro-hydraulic unit. 
   Preferably, the ferrocircuit is a part that is easy to make from a metallic plate forming a stator and having an annular flange at its external periphery. It is however necessary to consider that this part can be made by other processes than stamping. For example, a machining process permitting producing all the magnetic circuit in a single part is also envisageable. Such a machining (or fritting) also permits positioning the annular flange suitably whilst offering moreover possibilities of adaptation for winding or motors of different sizes. 
   Preferably, the motor has a collector (called external collector) positioned in the housing opposite that the hydraulic block, which permits particularly reducing the length of the electrical connections between the electronic card and the brushes. Moreover, such a motor with external collector has the possibility of supporting the brushes directly by the housing or by the electronic card; this was not the case previously and required the use of an intermediate plastic part called a brush carrying plate. 
   The ferrocircuit, according to the invention, being made from a single metallic part, may preferably be provided with suitable joints to ensure sealing between the hydraulic unit and the control. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects, characteristics and advantages of the present invention will become apparent from the description which follows, by way of non-limiting example, with reference to the accompanying drawings, in which: 
       FIG. 1  is a schematic cross-sectional view, showing the electro-hydraulic unit according to the invention, 
       FIG. 2  is a schematic cross-sectional view of the magnetic circuit (ferrocircuit) according to the invention, and 
       FIGS. 3   a  to  3   c  are schematic views showing a modified embodiment of the ferrocircuit according to the invention,  FIG. 3   c  being a cross-section on the line III-III of  FIG. 3   b.    
   

   DETAILED DESCRIPTION OF THE INVENTION 
   According to the embodiment shown in  FIGS. 1 and 2 , the electro-hydraulic unit  10  according to the invention comprises two parts, namely:
         a hydraulic unit  11  comprising a pump (not shown) and a plurality of valves  12 , and   an electronic control  13  comprising particularly an electronic card  14 , a motor  15  driving the pump, connections  16 , a plurality of winding  17  controlling the valves  12 . This control is a housing of compact shape.       

   The electric motor  15  is provided in conventional manner with a rotor  19  and a stator and is of the type with an external collector  18  (which is to say located opposite the hydraulic unit  11 ). As a modification, this motor could also have a collector disposed between the hydraulic unit  11  and the control. 
   The motor according to the invention thus comprises a wound rotor  19 , in rotation within an annular part called the stator. This stator carries, in a known manner, magnets  21  and has a ferromagnetic circuit  22  permitting closing the magnetic field of these magnets. 
   According to the invention, the ferromagnetic circuit  22  permits not only closing the lines of the field about the stator but also closing at least partially the lines of the magnetic field through the winding  17 . 
   To this end, the ferrocircuit  22  of the stator surrounds the winding  17  forming an annular flange  23  at its external periphery. 
   Because of this, at least one portion of this ferrocircuit is provided by a same and single metallic frame common at least in part to the stator and to the winding. The annular flange  23  receives the winding  17  and the associated valves  12 . 
   In  FIGS. 1 and 2 , a second annular metallic part  24  opposite said annular flange  23  completes the magnetic circuit surrounding each winding  17  to provide a U shaped magnetic circuit, enclosing optimally the lines of force about the winding. In this case, this second annular metallic part  24  can if desired be mounted with the annular flange  23  or being pre-mounted on the hydraulic block. In this latter case, the annular part  24  permits holding the valves in the hydraulic block by covering their shoulder. Because of this, it is possible no longer to place the valves in the hydraulic block, these latter are thus retained in place by the part  24  which also permits positioning them correctly. This part  24  thus has a double function. On the one hand, it serves to enclose correctly the field lines about the winding, and on the other hand it permits the positioning and holding of these winding (valves) in the hydraulic block. 
   It will be noted however that as a modification it is possible to provide a so-called monolithic ferrocircuit, in a single piece, of U shape, enclosing the lines of force. Such a ferrocircuit is shown by way of modification in  FIGS. 3   a  to  3   c . As will be seen best from  FIG. 3   c , the ferrocircuit  22  has a central branch  220  and two end branches  221 . Each of these end branches  221  is provided with an opening  222  adapted to receive one end of the winding  17  (shown in broken lines by way of example). Such a ferrocircuit has the advantage of being able to be produced from a stamped steel sheet according to the shape shown in  FIG. 3   b . There is thus provided a plurality of elements  250  (interconnected) which once bent along the bend lines A and B will take a U shape such as shown in  FIG. 3   c . The ferrocircuit according to this modified embodiment thus has the advantage of being able to be produced from a flat blank. As shown in  FIG. 3   b , the blank can be bent on itself and held in position by interlocking of the plates  260  and  270 . Once closed on itself, the ferrocircuit according to this modified form of the invention, has the shape shown in  FIG. 3   a . Of course, the form and spacing of each element  250  can be different from those shown, without thereby departing from the scope of the present invention. 
   The ferrocircuit  22  performs simultaneously a function of mechanically holding the winding and a function of magnetic conduction for these same winding. This same ferrocircuit  22  of course performs a function of magnetic conduction for the stator. 
   Surprisingly, it has been observed that there is little or no magnetic diaphony between the motor  15  and the winding  17 . More exactly, the magnetic diaphony between these two members is insufficient to disturb their respective functioning. It has also been observed that this diaphony no longer exists between the winding because they function simultaneously. 
   Preferably, the ferrocircuit according to the invention, being made of a single metallic piece, can be provided with suitable joints  26  to ensure sealing between the hydraulic unit and the control. This ferrocircuit also permits confining any possible loss of lubricant from the pump in a retention region  27  between the hydraulic block  11  and the control  13 . 
   The provision of a ferrocircuit common at least in part to the stator and to the winding, permits substantially decreasing at least the axial dimensions of the electro-hydraulic unit, because it is thus possible to have the electrovalves (valve+winding+ferrocircuit) at the periphery of the motor and not to interpose the electrovalves between the motor and the hydraulic unit. Moreover, this ferrocircuit is an element independent of the hydraulic unit, which does not require, according to the invention, any modification. 
   The operation of the electro-hydraulic unit according to the invention is explained below. 
   This electrovalve is constituted by a winding  17  through which is engaged a valve  12  (cartridge containing a valve—not shown) whose movement is controlled by the winding. Thus, upon command by the electronic control  13 , the valve is actuated and the hydraulic pressure prevailing in the hydraulic circuit (not shown) is modified. This electrovalve thus permits regulating the pressure in a hydraulic circuit with which it is associated. In general, there is at least one hydraulic circuit per vehicle wheel so as to be able to regulate, wheel by wheel, the braking pressure (when this electro-hydraulic unit is employed in a wheel and a locking device). 
   It is to be noted that one of the advantages arising from the so-called external position of the collector is, among other things, the possibility of being able to support the brushes  25  of the motor  15  via the housing  20  or the electronic card  14  (in the illustrated example) and not to create a plastic part to ensure this function as is at present the case in all the wheel anti-locking electro-hydraulic units known until now. Thus, in the prior art, the motor is an element separate from the hydraulic unit and from the control (electro-hydraulic unit in three parts). Another advantage of this reverse collector is that it enormously simplifies the connection  16  of the motor because the brushes  25  of the motor are nearer the electronic card  14 , whilst according to the prior art the motor connection has to be pass through all the space of the hydraulic unit to be connected to the electronic card (electro-hydraulic unit in three parts). 
   If the arrangement of the electrovalves at the periphery of the motor permits substantially decreasing the dimensions of the electro-hydraulic unit, it is however possible to arrange these electrovalves between the motor and the hydraulic block without departing from the scope of the present invention. In this case, the form of the ferrocircuit  22  is different from that shown but there is still a first part forming a stator and a second part (in continuity with the first) enclosing at least partially the winding. 
   It will however be noted that when the electrovalves are disposed at the periphery of the motor, it is possible to have them in greater number than when they are placed below the motor. Because of this, when the electro-hydraulic unit is associated with an anti-locking and/or anti-skid device for the wheels and/or with a device for controlling the stability of the vehicle, the arrangement of the electrovalves at the periphery of the motor is preferable because it permits more easily housing the eight to twelve necessary electrovalves. 
   Of course the present invention is not limited to the embodiment described above. Thus, the use of a ferrocircuit common at least in part to the stator and to the winding can be used in all types of motor (with external collector, internal collector . . . ).