Patent Publication Number: US-2012031370-A1

Title: Control of the vanes of a vane cell machine

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to control of the vanes of vane cell engines to reduce the friction between the vanes and the housing runway. 
     Because of their simple construction, vane cell engines are used as compressors and pumps as well as expanders and hydro-motors. Especially when used with gaseous media, vane cell engines with higher revolutions per minute can be operated so that due to the acting centrifugal forces, the vanes can be made to press close to the housing runway without additional radial outward-acting pressure springs. Thus the housing runway gets the task of guiding the vanes along the runway contour. To fulfill this function, the centrifugal forces have at all times to be larger than the counter-acting forces because of the pressure of the medium on to the vane frontal area in order to obtain a complete sealing of the rotating working vanes. The pressing vanes cause considerable friction. By injecting a liquid lubricant this friction can be reduced. 
     Another way to reduce the friction is to steer the vanes instead of by the runway by means of a guidance ring mounted at the lateral wall of the vane cell engine. A corresponding proposal is included in the patent document DE 10 2006 028 807 A1 for a pressure cell engine. An implementation into practice has not become known. On the one hand, laterally arranged guidance rings do offer the possibility of reducing friction;, at the same time they, however, cause the generation of further leakage windows for a medium transition between the cells as well as into the area of the rotor axis. 
     SUMMARY OF THE INVENTION 
     The present invention is based on the task to allow movement of the vanes by means of guidance along a guidance slot link inside the rotor and thus to obtain a reduction of friction at the vane tips as well as simultaneously preventing internal media leakages between the cells. 
     In a rotor divided at a right angle to the rotating axis, as has been described in patent document DE 10 2006 057 003 A1, according to the present invention a control link is mounted at a housing-mounted axle that extends into the rotor that guides the vanes in radial direction against the housing runway. One of the features of the invention is that for guiding the movement of the vanes, the foot area of the vane is equipped with guide elements such as rolls that run in the control link, and that the guide elements are connected by springs to the vanes in such a way that they are pressed by spring force against the control link guide path with the spring force directed opposite to the acting centrifugal forces. (An option is to augment adherence of the guide elements to the control link guide path by magnetic attraction between the guide elements and the control link guide path.) According to the invention, the spring forces are tuned to the centrifugal forces in such a way that when the engine is started the vanes barely touch the housing runway thus granting an easy starting and that afterwards the guide elements or rolls will always run along the control link when the rotor has reached a pre-determined operation speed and a statically determined system of forces has formed. 
     The invention is described by means an embodiment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of an embodiment of the invention; 
         FIG. 2  is another exploded perspective view of said embodiment of the invention; 
         FIG. 3  is a front perspective exploded view of vane parts with expanding spring and bending spring; 
         FIG. 4  is a rear perspective exploded view of vane parts with expanding spring and bending spring; 
         FIG. 5  is a perspective view of vane parts assembled; 
         FIG. 6  is a perspective view of vane parts with control link disc; 
         FIG. 7  is a section view through the rotor with vanes and control link disc; and 
         FIG. 8  is a schematic representation of the geometry of the guiding runway on the control link disc. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The operation principle of a divided rotor is shown in  FIGS. 1 and 2 . Both rotor parts are pressed apart by internal expansion springs, not shown here, so that rotation of the rotor parts relative to each other cannot take place. In the guiding grooves of the rotor, the cell vanes are movably arranged. Each vane consists of the vane parts  3   a  and  3   b  one of which covers the other and which are urged away from each other by expansion springs  9  in milled-out grooves  11   a  and  11   b  in such a way that they, together with the rotor parts, are flush with the housing sides and seal the operating areas against each other. 
     The vanes have at their foot area, adjacent to the rotor center, milled-out grooves  10   a  and  10   b , that together form a housing for bending spring  6 . Bending spring  6  is fixed to vane part  3   b . At the end of the bending spring  6 , roll  7  is attached in such a way that it can run in the control link disc  8 . Furthermore the milled-out grooves  12   a  and  12   b  are placed in the vane parts so that when the vane is assembled, the opening  12  results, for receiving the control link disc  8 ,  FIG. 3 ,  FIG. 4 ,  FIG. 5  and  FIG. 6 . 
     The assembled rotor is shown in  FIG. 7 , wherein rotor part lb is connected to the rotor axle, not shown. Rotor part  1   a  is carried along by rotor part  1   b  via the vanes  3 . 
     In between rotor parts  1   a  and  1   b , control link disc  8  is mounted on the hollow axle  2 . 
     The hollow axle  2  is rigidly connected to the housing  4  via lateral cover  14  and thus provides a housing-mounted control link guidance for rolls  7  running along the guidance runway  5 . In the example shown, the control link contour is a single arc trochoid  13 , offset with respect to the rotor axis by the eccentricity of the vane cell engine, see  FIG. 8 . The mathematical formation law of this trochoid is T(φ) =R−exz*cos (φ), with the eccentricity, exz′ of rotor  1  with regard to the housing  4 , with the radius R and the angle of rotation φ. Other contours are possible if the control link obeys radial closing distances to the housing runway. Through the hollow axis  2 , the rotor shaft can be taken to a bearing situated next to the side/lateral cover. In a particular, specific embodiment, the control disc is situated eccentrically on the control link disc axle with the rotor, of course, being situated eccentrically in the housing, and the respective eccentricities are in opposite directions. 
     By construction, vane  3  is arranged with the bending spring  6  and the roll  7  so that at low rotor rotation speeds, e.g. while starting the engine, roll  7  runs from the inside against the guidance runway  5 , but there is not yet any contact between vane tip and housing, allowing for a smooth starting. When an operation rotation speed, determined by the design, has been reached, the centrifugal forces cause a pressing of the vanes on to the housing runway against to the spring force of bending spring  6 . Thus bending spring  6  secures that roll  7  has at all times contact to guidance runway  5 , at the same time it also draws the vanes kinematically exact on to the determined course of motion of control link disc  8 . In this way, a statically determined system of forces develops itself automatically. Considering the fact that the sealing system can only act dynamically in the housing, the construction parts rotor parts  1   a ,  1   b , vane parts  3   a ,  3   b  and the axial arrangement of control link disc  8  are designed according to the invention with offset divided and working grooves, thus forming an effective labyrinth packing that prevents any media from leaking through.