Abstract:
The invention relates to A device for transforming a rotation of a gear into a translation of a slide, the device including a supporting member provided with a fixed tubular wall translatably connected to the slide by a cam channel, the gear being rotatably mounted on the supporting member and rotatably connected to the slide which is suitable for pivoting about an axis. The gear comprises a ring rotatably mounted on the tubular wall of the supporting member.

Description:
The invention relates to a device for converting a rotational movement of a gearwheel into a translational movement of a slide and to a valve comprising such a device. A valve of this type can for example be used in a motor vehicle combustion engine exhaust gas recirculation circuit. 
     BACKGROUND OF THE INVENTION 
     Document FR 2 914 975 describes such a movement conversion device and the application thereof to an EGR valve. Exhaust gas recirculation systems are known by their abbreviation EGR systems and are used for reinjecting exhaust gases into the intake side of a combustion engine notably with a view to reducing pollutant emissions. 
     OBJECT OF THE INVENTION 
     It is an object of the invention to reduce the cost and size of such a device. 
     BRIEF DESCRIPTION OF THE INVENTION 
     To this end, the invention has conceived of a device for converting a rotational movement of a gearwheel into a translational movement of a slide, the device comprising a support member equipped with a fixed tubular wall translationally connected to the slide by a camway, the gearwheel being mounted so that it can rotate on the support member and being connected in rotation to the slide which is able to pivot about an axis, characterized in that the gearwheel comprises a ring mounted to rotate on the tubular wall of the support member. 
     In such a conversion device, the gearwheel is positioned directly on the tubular wall and this guarantees that these two elements are suitably coaxial with one another. There is therefore no need to cap the support member with a pivot, and this makes the device more compact and simpler to produce. The support member may thus comprise a simple cylinder which acts as a tubular wall. 
     The gearwheel may have a central opening providing access to the slide. 
     Such a central opening can house components more compactly within the device. For example, a position sensor, whether this be a rotary or a linear sensor, can be housed in the central opening without increasing the size on the top of the support member. 
     The device may further comprise the following features, alone or in combination:
         the central opening may provide access to a portion of the slide which portion lies along the axis of pivoting thereof;   the gearwheel may comprise a housing for the rotational drive of the slide;   the drive housing may be defined by two longitudinal walls running parallel to the direction of translational movement of the slide;   the gearwheel may comprise a skirt in the continuation of the ring, the longitudinal walls being attached to the skirt;   the ring may be mounted to rotate on the tubular wall via a rolling bearing;   the tubular wall may comprise a counterbore in which to mount the rolling bearing;   the ring and the gearwheel may be coaxial.       

     Another subject of the invention targets a valve comprising a rotary actuator and a valve shutter which are joined together by a movement conversion device such that the actuator is able to close and open the valve shutter, the movement conversion device being as described hereinabove and the valve shutter forming part of the slide. 
     The valve may comprise the following features, alone or in combination:
         the central opening may provide access to a portion of the slide which portion lies along the axis along which the stem of the valve shutter extends;   the slide may comprise a valve shutter and a bar fixed transversely to the stem of the valve shutter;   the stem of the valve shutter may be fixed in a through-hole in the bar, the gearwheel may comprise a central opening providing direct access to the stem of the valve shutter;   it may comprise a sensor that senses the position of the valve shutter and is arranged in the central opening;   it may also comprise a protective cap, the sensor being mounted on the interior face of the cap.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood in the light of the description which follows of one preferred and nonlimiting embodiment, which description is given with reference to the attached drawings, among which: 
         FIG. 1  is a perspective depiction of a valve comprising a movement conversion device according to the invention, this device being depicted in part section; 
         FIG. 2  is a perspective view in part section of the movement conversion device of  FIG. 1 ; 
         FIG. 3  is a cross sectioned detail of  FIG. 2 ; 
         FIG. 4  is a view of the device of  FIG. 2 , from above; 
         FIG. 5  is a sectional part view of the valve of  FIG. 1 , capped with a cap. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  depicts a valve  1  which, in this example, is an exhaust gas recirculation valve that works in the conventional way. The valve  1  comprises a valve shutter  2  which allows a fluid, in this instance the exhaust gases, to be introduced and metered into a line, in this instance the intake line. 
     Such a valve  1  comprises a motor  3  in mesh with a transmission wheel  4  which is itself in mesh with a gearwheel  5 . The motor  3  is thus able to drive the rotation of the gearwheel  5 . The rotational movement of this gearwheel  5  is moreover converted into a translational movement of the valve shutter  2  by a movement conversion device  6 . The device  6  for this purpose comprises a support member  9  fitted with bearings  7  for longitudinally guiding the stem of the valve shutter  2 . The support member  9  comprises a tubular wall  10  equipped with a camway  11  with which there collaborates a bar  8  fixed to the end of the stem of the valve shutter  2  (by pinning, force-fitting, welding or any other means of attachment). The camway  11  here is formed of two tracks one on each side of the tubular wall  10  (see  FIG. 2 ), it being understood that it could comprise any suitable number thereof. It could thus have just one track or a number of tracks higher than two. 
     This bar  8  is fitted at each of its ends with a follower  12  collaborating with the camway  11  so that as the gearwheel is turned it in turn turns the bar  8  thus causing the translational movement of the valve shutter  2  because of the follower  12  running in the camway  11 . 
     The valve shutter  2  and the bar  8  are fixed relative to one another and together form a slide the translational movement of which responds to the rotational movement of the gearwheel  5 . Any other elements that might be rigidly connected to the valve shutter  2  would also form part of the slide. 
     The valve  1  additionally comprises a linear sensor  13  for determining the longitudinal position of the valve shutter  2 . 
       FIG. 2  shows the support member  9  in isolation from the valve  1 . 
     The gearwheel  5  comprises a toothed portion  14  able to mesh with the transmission wheel  4 . In the present example, this toothed portion extends only over an angular sector that corresponds to the required linear travel of the valve shutter  2 . The toothed portion could of course extend over a different angular sector, or even over the entire periphery of the gearwheel if necessary, depending on the operational range in which the slide  2 ,  8  is intended to operate. 
     The gearwheel  5  also comprises a ring  15  which extends in the direction of the axis of rotation of the gearwheel  5  so that this ring  15  forms a tubular mounting portion. The ring  15  is coaxial with the axis of rotation of the gearwheel  5 . The gearwheel  5  is mounted to rotate on the support member  9  by fitting the ring  15  onto the internal ring of a rolling bearing  16  the external ring of which is itself snugly fitted onto the tubular wall  10  of the support member  9 . The rolling bearing  16  is schematically depicted in the figures. 
     More specifically, in this example, the tubular wall  10  comprises a counterbore  17  into which the rolling bearing  16  is fitted. The optimum profile for the connection between the tubular wall  10  and the rolling bearing  16  is depicted, for this example, in the cross-sectional view that is  FIG. 3 . The counterbore  17  supports the outer ring of the rolling bearing  16  while a clearance  18  separates the tubular wall  10  from the remainder of the rolling bearing  16  to avoid unwanted friction. 
     The gearwheel  5  is thus mounted to rotate on the tubular wall  10  via the rolling bearing  16  so that rotation of the toothed portion  14  is coaxial with the direction of translational movement of the valve shutter  2 . As an alternative, the rolling bearing  16  may be replaced by some other type of pivot connection, a plain bearing or a low-friction ring, for example. The ring  15  of the gearwheel  5  may also be mounted directly on the tubular wall  10  if the materials used, possibly with a surface treatment or coating where appropriate, have a suitable coefficient of friction. 
     The ring  15  of the gearwheel  5  is extended by a skirt  19  designed to collaborate with the bar  8 . This skirt  19  comprises two mutually parallel longitudinal walls  20  running parallel to the direction of translational movement of the valve shutter  2 . The two longitudinal surfaces  20  between them define a housing  21  for the bar  8  (see  FIG. 4 ). Thus the bar  8  is positioned in the housing  21  so that the gearwheel  5  is able to turn the bar  8  via the longitudinal walls  20  and so that the bar  8  is free to slide in the housing  21  in the direction of translational movement of the valve shutter  2 . 
     In consequence, within the valve  1 , the rotation of the gearwheel  5  causes the turning of the bar  8 , the followers  12  of which then roll along the fixed camway  11  (because the support member  9  is fixed in relation to the gearwheel  5  and to the slide  2 ,  8 ), and this jointly leads to the translational movement of the slide  2 ,  8  in the direction of opening or closing the valve shutter  2 . 
     The gearwheel  5  also comprises a central opening  23  providing access to the slide  2 ,  8 . The internal volume of the ring  15  in this instance is hollow and is thus put to use to form an empty space in which additional components of benefit to the operation of the valve  1  can be installed. In addition, this empty space provides access to the slide  2 ,  8  from above, so that components designed for example to collaborate with the stem of the valve shutter  2  or the bar  8  can be installed therein. 
     In the present example, this empty space is put to use for installing a sensor  13 . With reference to  FIGS. 1 and 5 , the valve  1  indeed comprises a position sensor  13  that senses the translational position of the valve shutter  2 . The position of the slide  2 ,  8  (of which in this instance the valve shutter  2  forms a part) is, in this example, registered by a conventional linear position sensor. An example of a linear position sensor is given in document EP1503181. Any type of sensor capable of registering the position of the slide  2 ,  8  can be used. The sensor  13  in this example comprises a guide rod  22  on which there slides a cylinder  24  which is attached to a feeler  25  kept in contact with the valve shutter stem by a spring  26 . The feeler  25  follows the back and forth movements of the valve shutter  2  while a measurement device  27 , generally comprising a Hall-effect probe (see document EP1503181) supplies a signal indicative of the linear position of the feeler  15  and therefore of the valve shutter  2 . The measurement device  27 , the guide rod  22  (with the elements attached to it) are fixed under the cap  28  which is depicted in  FIG. 5  and which incidentally also protects the various components of the valve  1 . Thanks to the housing  21 , such a sensor  13  can be fitted without any appreciable increase in the size of the valve. 
     Alternative forms of embodiment of the invention can be conceivable of without departing from the scope of the invention. In particular, the longitudinal walls  20  may have an alternative shape; they may be produced in any form that allows the bar  8  to be turned as the gearwheel  5  is turned.