Abstract:
The invention concerns an exhaust gas recycling device comprising a cooled path ( 5 ) and a non-cooled path ( 6 ) connected through a selective connection means ( 7 ) to a conduit ( 14 ) provided with a valve ( 7 ) including a chamber ( 9 ) connected to the conduit and accommodating a mobile flow regulating element and perforated with a passage orifice ( 16 ) for defining a variable cross-section for allowing through exhaust gases. The cooled and non-cooled paths have each one end opening on to a wall ( 10 ) of the chamber and the regulating element is mounted opposite said wall to be mobile between a first extreme position wherein the passage orifice is opposite the cooled path and a second extreme position wherein the passage orifice is opposite the non-cooled path, the regulating element having an intermediate position wherein the regulating element closes the cooled and non-cooled paths.

Description:
[0001]    The present invention relates to an exhaust gas recirculation device that can be used in particular to reinject some of the exhaust gases into the intake circuit of a combustion engine. 
       BACKGROUND OF THE INVENTION 
       [0002]    An exhaust gas recirculation device generally comprises a cooled path and an uncooled path which are connected by a selective connecting member to a pipe which is connected to the intake circuit of the engine and which is provided with a flow regulating valve. The selective connecting member comprises a chamber into which the cooled and uncooled paths open, and a valve element that can move in the chamber between a position in which the uncooled path is connected and the cooled path is closed off and a position in which the cooled path is connected and the uncooled path is closed off. The valve is mounted between two pipe portions and comprises a body delimiting a chamber into which the pipe portions open, a flow regulating element pierced with a through-orifice being mounted to move in the chamber in order to define a variable cross section through which the exhaust gases can pass. This exhaust gas recirculation device has a structure that is relatively complicated and bulky. 
       SUBJECT OF THE INVENTION 
       [0003]    It would therefore be beneficial to have an exhaust gas recirculation device which is simple and compact. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    For this purpose, the invention provides an exhaust gas recirculation device comprising a cooled path and an uncooled path which are connected by a selective connecting means to a pipe provided with a valve comprising a chamber connected to the pipe and housing a flow regulating element that is able to move and is pierced with a through-orifice so as to define a variable cross section for the passage of the exhaust gases, the cooled and uncoated paths each having an end opening onto a wall of the chamber and the regulating element being mounted facing this wall so as to be able to move between a first extreme position in which the through-orifice faces the cooled path and a second extreme position in which the through-orifice faces the uncooled path, the regulating element having an intermediate position in which the regulating element closes off the cooled and uncoated paths. 
         [0005]    Thus, causing the regulating element to move from its intermediate position into its first extreme position allows the flow of exhaust gases from the cooled path to be regulated, while causing the regulating element to move from its intermediate position into its second extreme position allows the flow of exhaust gases from the uncooled path to be regulated. The flow in the pipe can thus be regulated. Furthermore, when the regulating element is in one of its extreme positions or in its intermediate position, the regulating element selectively connects the cooled and uncooled paths to the pipe. The valve in this way performs a dual function of regulating the flow and of selecting which path is connected to the pipe. Furthermore, the regulating element can be moved in a plane perpendicular to the flow of exhaust gases which means that the means used to move the regulating element are only to a limited extent called upon to be able to withstand the forces exerted on the regulating element by the pressurized exhaust gases. 
         [0006]    According to one particular embodiment, the regulating element is formed of a disk mounted in the chamber to pivot between its two extreme positions. 
         [0007]    The disk can be made to move in a particularly simple way using an electric motor for example. This structure of the valve is particularly compact. 
         [0008]    As a preference, the three positions of the disk are spaced 120° apart. 
         [0009]    This arrangement makes it possible to obtain the largest passage cross section for a given size. 
         [0010]    According to one advantageous feature, the disk and the wall are in contact via at least one first collar surrounding the through-orifice and, as a preference, the disk and the wall are also in contact via at least one second collar symmetric with the first collar with respect to an axis of rotation of the disk. 
         [0011]    Sealing is thus achieved over a relatively small area, namely the edge of the collar, making it easier to obtain a good seal. Furthermore, making several symmetric collars allows the forces with which the disk is pressed against the wall to be spread. 
         [0012]    According to another advantageous feature, the valve comprises a return element for returning the disk to the intermediate position and, as a preference, the return element comprises two torsion springs connected to the disk and to the body so as to exert opposing return torques on the disk. 
         [0013]    The valve is then in the position in which it closes off both paths when no power is applied to it. 
         [0014]    Other features and advantages of the invention will emerge from reading the description which follows of some particular nonlimiting embodiments of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    Reference will be made to the attached drawings, among which: 
           [0016]      FIG. 1  is a schematic view of a combustion engine equipped with an exhaust gas recirculation device, 
           [0017]      FIG. 2  is a view in axial section of a valve according to the invention for the first position of the regulating element, 
           [0018]      FIG. 3  is a view similar to that of  FIG. 2  for a second position of the regulating element, 
           [0019]      FIG. 4  is a view from above of the wall that forms the seat for the regulating element, 
           [0020]      FIG. 5  is a view similar to that of  FIG. 3  of a valve according to an alternative form of embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    With reference to  FIG. 1 , the exhaust gas recirculation device, denoted in general by  1 , is intended to be fitted to a combustion engine  2  being connected, on the one hand, to the burnt gases exhaust pipe  3  and, on the other hand, to the air intake pipe  4 . This arrangement is known per se. 
         [0022]    The recirculation device  1  comprises a cooled path  5  and an uncooled path  6  which are known per se and which are connected, on the one hand, to the exhaust pipe  3  and, on the other hand, to the intake pipe  4  via a valve  7 . 
         [0023]    With reference also to  FIGS. 2 to 4 , the valve  7  comprises a body  8  which delimits a chamber  9  closed by a flange  10  pierced with passages to which the corresponding ends of the cooled  5  and uncooled  6  paths are connected. The flange  10  is fixed to the body  8  removably, for example using screws that cannot be seen in the figures, and forms one wall of the chamber  9 . The flange  10  comprises, on the same side as the chamber  9 , a surface, from which a first collar  11  surrounding the mouth of the cooled path  5 , a collar  12  surrounding the mouth of the uncooled path  6  and a blind collar  13  project, 120° apart from one another. The collars  11 ,  12  and  13  are identical. 
         [0024]    The chamber  9  is connected to the intake pipe  4  by a connecting pipe  14  that opens into the chamber  9 . 
         [0025]    The chamber  9  accommodates a flow regulating element formed of a disk  15  pierced with a through-orifice  16  of a cross section comparable with that of the cooled  5  and uncooled  6  paths. The disk  15  lies facing the collars  11 ,  12 ,  13  and the flange  10 . The disk  15  is secured to one end of a shaft  17 , an opposite end of which is secured to a toothed sector  18  rotated off an electric motor  19 , in this incidence, a DC motor. 
         [0026]    The disk  15  can thus be rotated between two extreme positions, namely:
       a first extreme position (depicted in  FIGS. 2 and 3 ) in which the through-orifice  16  lies facing the collar  11  and therefore the cooled path  5  (the disk  15  therefore uncovers the cooled path  5  and closes off the uncooled path  6 ), and   a second extreme position (not depicted) in which the through-orifice  16  lies facing the collar  12  and therefore the uncooled path  6  (the disk  15  then uncovers the uncooled path  6  and closes off the cooled path  5 ).       
 
         [0029]    Between these two extreme positions, the disk  15  has an intermediate position (not depicted) in which the through-orifice  16  faces the collar  13 , the disk  15  closing off the cooled  5  and uncooled  6  paths. The two extreme positions and the intermediate position are 120° apart. This 120° separation between the positions makes it possible to have the largest passage cross section for a given size. 
         [0030]    The valve  7  comprises a return element returning the disk  15  to the intermediate position. The return element comprises two torsion springs  20 ,  21  which are helical springs coaxial with the shaft  17 , each having one end connected to the toothed sector  18  and one end connected to the body  8  so as to exert on the toothed sector  18 , and therefore on the disk  15 , opposing return torques. 
         [0031]    The shaft  17  is housed in the body  8 , not only such that it can pivot, but also such that it can slide so that the disk  15  can move between two axial positions, namely:
       a seated first position (depicted in  FIG. 3 ) in which the disk  15  is pressed against the collars  11 ,  12 ,  13 , the collars  11 ,  12 ,  13  forming the seat for the disk  15 , and   an unseated second position (depicted in  FIG. 2 ) in which the disk  15  is away from the collars  11 ,  12 ,  13 .       
 
         [0034]    The valve  7  comprises movement means for moving the disk  15  between its seated position and its unseated position. 
         [0035]    The movement means comprise a coil  22  fixed to the body  8  coaxial with respect to the shaft  17  so that it lies facing a plate  23  of magnetic material which undergoes a translational movement as one with the shaft  17 . The coil  22  is connected to electrical power supply means, not depicted, in such a way that when power is applied to the coil  22  it attracts the plate  23  and moves the shaft  17  and the disk  15  towards the seated position of the disk  15 . 
         [0036]    The movement means also comprise a return member for returning the disk  15  to the unseated position. The return means comprises a helical compression spring  24  which is positioned coaxially with respect to the shaft  17  between the body  8  and a plate  25  which is fixed in terms of translation but free to turn with respect to the shaft  17 . In this particular instance, the plate  25  is mounted such that it is free to rotate on a stepped bushing  26  secured to the shaft  17  and bears axially against the shoulder of the bushing  26  and against the plate  23  via sliding shoes or needle thrust bearings. The spring  24  pushes the plate  25  back against an end stop  27  secured to the body  8 . The end stop  27  defines the unseated position of the disk  15 . 
         [0037]    The way in which the valve works will now be described. 
         [0038]    When the combustion engine  2  is not running, the electric motor  19  and the coil  22  are not powered. The spring  24  holds the disk  15  in the unseated position and the torsion springs  20 ,  21  hold the disk  15  in the intermediate position. 
         [0039]    Exhaust gas recirculation is managed in the way known per se by the engine control unit or by some other dedicated unit known per se, to which the electric motor  19  and, at least indirectly, the coil  22 , are connected. 
         [0040]    When the combustion engine  2  is in an exhaust gas recirculation phase, the electric motor  19  is operated in such a way that the disk  15  is brought into one or other of its two extreme positions according to whether it is the cooled path  5  or the uncooled path  6  that is to be connected to the intake pipe  4  by the connecting pipe  14 . It will be understood that, when the disk  15  is in one of its two extreme positions, it allows maximum flow rate because the through-orifice  16  is fully facing one of the two paths  5 ,  6 . By contrast, when the disk  15  is between its intermediate closing-off position and one of its extreme positions, the through-orifice  16  lies only partially facing one of the two paths which means that the disk  15  closes off part of this path. The disk  15  thus reduces the cross sectional area available for the passage of the flow of exhaust gases from the path in question and thus regulates the flow. 
         [0041]    It will be noted that when the disk  15  is in the unseated position and the combustion engine is in the recirculation phase, there is a leakage at the mouth of the path facing which the disk  15  lies for closing this path off. This leakage has a negligible flow rate. 
         [0042]    When the disk  15  pivots between its extreme positions it is not pressed against the collars  11 ,  12 ,  13 . That makes it possible to limit friction and therefore the wearing of the contacting parts. The angular position of the disk  15  is detected in the conventional way. 
         [0043]    Outside of exhaust gas recirculation phases, the electric motor  19  brings the disk  15  into its intermediate position and the coil  22  is powered and keeps the disk  15  in the seated position. 
         [0044]    In order to make the disk  15  move between its various angular positions if there is a return to the recirculation phase, the power supply to the coil  22  is cut off beforehand so that the spring  24  can move the disk  15  into its unseated position, then the electric motor  19  is powered in such a way as to move the disk  15  into the desired position. 
         [0045]    The presence of the collars  11 ,  12 ,  13  makes it possible to simplify the way in which a seal is achieved between the disk  15  and its seat and makes it possible to balance the loads exerted on the disk  15  when the disk is in the seated position. 
         [0046]    The valve  7  performs a dual function of regulating the flow and selecting which path  5 ,  6  is connected to the pipe  14 . Furthermore, since the disk  15  is moved in a plane perpendicular to the flow of the exhaust gases, the means used to move the disk  15  are only to a limited extent called upon to withstand the forces exerted on the disk  15  by the pressurized exhaust gases. 
         [0047]    When the combustion engine  2  is switched off, the supply of power to the coil  22  is cut off so that the spring  24  pushes the disk  15  back into the unseated position. The possibility of particles or agglomerates contained in the exhaust gases sticking the disk  15  to the flange  10  is thus avoided. 
         [0048]    According to an alternative form of embodiment depicted in  FIG. 5 , the return member returning the disk  15  to the unseated position comprises a permanent magnet  27 , of circular shape, fixed around the periphery of the plate  23  facing a magnetic plate  28  which is fixed in terms of translation but free to turn with respect to the body  8 . The magnetic plate  28  is coaxial with the shaft  17  and is fixed to the body  8  by a rotational-guidance bearing and axial needle thrust bearings. The plate  23  is made of magnetic material. 
         [0049]    The permanent magnet  27  has a diameter greater than that of the coil  22 . 
         [0050]    The permanent magnet  27  is associated with an armature  29  through which the magnetic flux generated by the permanent magnet  27  flows so that the permanent magnet  27  generates an attractive force attracting the magnetic plate  28 . 
         [0051]    The armature  29  comprises, in a way known per se, a saturating section restricting the flux generated by the permanent magnet  27  so as to limit the increase in the force of attraction produced by the permanent magnet  27  as the permanent magnet approaches the plate  28 . This makes it easier for the coil  22  to move the disk  15  when this coil is powered in such a way as to move the disk  15  into the seated position in which it is pressed against the collars  11 ,  12 ,  13 . 
         [0052]    Thus, when the coil  22  is powered, it attracts the plate  23  and brings the disk  15  into the seated position. When the supply of power to the coil  22  is cut off, the permanent magnet  27  attracts the plate  28  and carries the disk  15  into the unseated position. 
         [0053]    The difference in diameter between the permanent magnet  27  and the coil  22  is such that the permanent magnet  27  and the coil  22  are separated from one another so that the permanent magnet  27  is subjected little, if at all, to the magnetic field generated by the coil  22 . 
         [0054]    In this alternative form of embodiment, the toothed sector driven by the electric motor  19  is secured to the plate  23 . 
         [0055]    The torsion springs  20 ,  21 , which are helical and coaxial with the shaft  17 , each have an end connected to a part that rotates as one with the shaft  17  and an end connected to the body  8  so as to exert opposing return torques on the shaft  17  and therefore on the disk  15 . 
         [0056]    In this alternative form of embodiment too, the surface of the flange  10  lying on the same side as the chamber  9  is plain and the disk  15  has three projecting collars (only two collars can be seen in  FIG. 5 ): one collar surrounding the through-orifice  16  and two blind collars. 
         [0057]    The way in which the valve according to this alternative form of embodiment works is identical to the mode of operation already described. 
         [0058]    Of course, the invention is not restricted to the embodiment described and alternative forms of embodiment may be applied thereto without departing from the scope of the invention as defined by the claims. 
         [0059]    In particular, the regulating element could have a structure different from that described and could, for example, consist of a sliding plate. 
         [0060]    Furthermore, the paths  5  and  6  could be connected directly to the chamber  9  by connection end pieces arranged externally on the body  8 . 
         [0061]    The collars  11 ,  12 ,  13  are optional. 
         [0062]    The valve  7  may be mounted upstream of the cooled and uncooled paths rather than downstream as depicted in  FIG. 1 . 
         [0063]    During the recirculation phase, provision may be made for the disk  15  to be brought into the seated position once this disk is in the desired angular position connecting one of the paths to the pipe  14  if it is not desirable for there to be any leakage on the other path. If the angular position were to be changed, the disk  15  would be unseated beforehand, and then, once it has been pivoted, returned to its seated position.