Abstract:
A rotary piston machine, with a driving part and a driven part, which are geared together, is proposed, for which these parts  17  and  18  run on a common stationary main axle  8.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a rotary test machine. Such a rotary piston machine is known (German patent 4241320) as a pump, compressor or motor, for which the ridges of teeth of a rotating driving parts, in order to limit the working spaces, run on a cycloid surface of an also toothed driven part, driving the latter. The aforementioned working spaces, which are increased or decreased in size for their work during the rotation of the parts, in order to produce the delivery action on a medium, are formed between the teeth of the driving and driven parts. 
     It has also already been proposed (patent application DE 103 35 939.7 of Aug. 2, 2003) that a portion of the machine housing be mounted in a “floating manner”, in order to be able to equalize gap losses and the like better by these means. However, such a floating arrangement has the disadvantage that, at the expense of a decrease in the losses through the gap, the danger of imbalances arises. The significance of this disadvantage depends on the practical use of the object, the rpm then actually employed and the pressure aimed for playing an important roll. 
     SUMMARY OF THE INVENTION 
     Compared to the foregoing, the inventive rotary piston machine has the advantage that the invention can be used especially in the delivery system of fuel-burning engines, for example, as a pre-delivery pump for diesel injection installations or as pre-delivery pump or a pressure and supplying pump of gasoline injection installation. The combination as a unit between the engine housing and the machine housing offers the possibility of making such a delivery pump or pressure pump small, since the electric motor can engage the driving part of the rotors directly, without an additional, expensive mounting. The housing can be connected in different ways, for example, as a screw connection between two “pots”, which embrace, on the one hand, the pump and, on the other, the electric motor, or there may be beading between a lid part and a pot part, depending on how this appears to be meaningful for practical use and, above all, for being able to produce advantageously. It is of decisive importance for the invention that the parts, which relate to the electric motor, such as the magnets and the mounting of the rotor, are disposed in the machine housing and that the pump parts, including the inflow and outflow device for the medium, are accommodated in the machine housing. 
     Due to the stationary main axle, a good and especially axially identical guidance of the rotating parts, namely of the rotor of the electric motor, of the driving part and of the driven part, is achieved, so that even if the inner housing were to be mounted in a floating manner, there would be radial matching. Moreover, such an axle can also serve to axially tie in the parts and, last but not least, offer advantages for automatic installation in production on a large scale. The relatively short width of the known bearings is broadened by a multiple for the stationary main axle, especially for the rotor of the electric motor, as a result of which the specific radial forces are reduced corresponding to the larger bearing surface to the benefit of the service life of the rotary piston machine. The length of the service life, as well as the reliability plays an exceptionally significant role especially when used as a fuel pump in the vehicles. 
     It should be pointed out here that the development of a minimum amount of noise is aimed for especially in vehicle construction and when a fuel delivery pump is used in a motor vehicle. The slightest imbalances would already lead to appreciable noise. This makes the problem, on which the invention is based, even clearer. Due to the use of a continuous, stationary main axle, the development of imbalances is prevented. The use of a stationary main axis is also known for fuel delivery pumps of a different type (Robert Bosch GmbH). 
     Admittedly, the claimed bearing bushing has already been proposed earlier. However, it does not belong to the state of the art and plays an appreciable role in connecting the individual distinguishing features of claim  1  and their developments. 
     Such an inventive “electric pump” is not limited in its application to a fuel delivery pump and, instead, depending on its size and efficiency, can be used for liquid media or gaseous media. In such a case, however, significantly higher pressures can be produced than in the case of a known fuel delivery pumps (Robert Bosch GmbH or the like). 
     In accordance with an advantageous development of the invention, there is a change in the rotational position of the working spaces to the suction channel and the pressure channel and, with that, to the working phase of the working spaces in relation to the suction channel and the pressure channel due to the relative rotation of the bearing bushing of the driven part on the main axle. A change in the amount conveyed can be achieved in a simple manner by these means. 
     According to an additional development of the invention, the bearing bushing is connected with a bottom bearing for the driven part, on which the latter is supported on its side averted from the driving part and which is also disposed rotatably on the main axle. In this connection, the bearing bushing and the bottom bearing have the same axle, which rests perpendicularly on the bearing surface, on which the driven part is supported. By rotating this bottom bearing on the main axle within the machine housing, the above-mentioned relative adjustment, from the start of the delivery to the inflow and outflow channels, mentioned above, is shifted relatively, with the result that the delivery performance of the machine is changed. 
     According to an additional advantageous development of the invention, the rotors run in an inner housing, in which the suction channel, which is open towards the rotors, and the pressure channel are disposed. This inner housing is disposed within the rest of the machine housing so that it does not rotate and does not float and, in particular, is secured against rotating with respect to the bottom bearing. In this connection, the inner housing may be disposed in an additional housing bushing and secured there, so that it cannot twist. This housing bushing, in turn, may be mounted in the outer machine housing. 
     In accordance with an additional advantageous development of the invention, the rotors run in a recess (of the inner housing), which is open and cylindrical towards the driven side and closed and spherical towards the driving side. The driving part is supported at this spherical surface, whereas the driven part is held in its working position on the cylindrical side by the bearing bushing and the bottom bearing. 
     According to an additional, advantageous development of the invention, the driving part has an inner, spherical region, at which the driven part is supported with a correspondingly configured front face or supports the bearing bushing of the driven part. By these means, the inner region of the rotors, close to the main axle, which is less effective anyhow, is used as an axial supporting means, so that the more effective sections of the rotors, which lie radially further to the outside, form the working spaces. 
     According to an additional, advantageous development of the invention, the driven part is loaded axially in the direction of the driving part. 
     According to a development of the invention, which is advantageous in this regard, the driven part is put under a load in the direction of the driving part by the force of a spring. Such a force may be of advantage, particularly in the starting phase of such a pump, in order to achieve the tightness between the working flanks of mutually meshing teeth required for the delivery. 
     In accordance with a possible, additional development of the invention in this regard, the pressure channel of the machine is connected with a space between the driven part and the housing (bottom bearing) on the side averted from the driving part. By these means, it is achieved that, when the medium in the pressure channel has reached a certain pressure, the driven part is pressed against the driving part in such a manner, that the above-mentioned tightness between the flanks can be achieved by this pressure. 
     In accordance with an additional, advantageous development of the invention, advanced for itself, the transitions at the rotors between the mutually facing spherical supporting surfaces providing axial support and the surfaces of the teeth, limiting the working space, are rounded off. By means of such a rounding off, on the one hand, a greater tightness is achieved between the boundaries of the working spaces, leading to an improvement in the effective pressure and delivery action of such a pump, and, on the other, the processing of pump parts in these sections of the manufacturing process is simplified, quite apart from the fact that the danger of chip formation by the sharp-edged parts is avoided. The radius of such rounded off edges preferably is at least 1 mm. Basically this radius is independent of the size of the pump parts. 
     According to an additional development of the invention, which is, however, also advanced for itself, short-circuit channels or short-circuit grooves, over which, during the rotation and, in particular, before the suction or pressure channels are opened up, adjacent working spaces can be connected with one another in order to achieve pressure equalization in the working spaces of changing capacity, are disposed in the bottom surface of the rotors. During the rotation of the driven and driving parts and before the suction channel is opened up, the delivery spaces between the parts change, the assigned flanks of the teeth of the one part sliding over corresponding surfaces of the other part, so that the spaces between the teeth, from which the actual working spaces result, act here as harmful spaces. An overpressure would result in the one harmful place and a reduced pressure would result in the adjacent space. Due to the invention, the pressure in the spaces is equalized to the benefit of the efficiency of the pump. 
     Further advantages and advantageous developments of the invention can be inferred from the following description, the drawing and the claims. 
     An example of the object of the invention is described in greater detail in the following and shown in the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows the inventive fuel delivery pump in the longitudinal section corresponding to arrow  1  in  FIG. 2 , 
         FIG. 2  shows a longitudinal section through the delivery pump corresponding to the line II-II in  FIG. 1 , 
         FIG. 3  shows the rotors of the pump, assigned to one another, in a longitudinal section on an enlarged scale, as well as in an exploded representation, and 
         FIG. 4  shows the inner housing of the pump in a longitudinal section. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The fuel delivery pump shown has a rotary piston pump  1  and an electric motor, which drives this pump  1  and is disposed in a motor housing  3 , onto which a housing lid  4  is bolted. In this connection, especially the electric motor is shown in a highly simplified fashion with a rotor  5  and a magnet ring  6 , as well as an axial locking part  7  of the motor housing  3 , which is connected with the motor housing  3 , to which it is sealed. In addition, a stationary axle  8  (main axle) of the rotor  5 , as well as the possible pressure connection  9  for the fuel discharging pipeline are disposed at this locking part  7 . The fuel delivery pump is constructed as an immersion pump, for which the fuel reaches the pump over suction ports  10 , which are only indicated here, in order to leave the pump once again then over the pressure connection  9 . The fuel, within the motor housing  3 , flows around the electric motor  5 ,  6  here. 
     The second fixed bearing  11  of the rotor  5  is disposed at the housing of the pump  1 . The rotor  5  is disposed in an appropriate borehole on the front face of an inner housing  12  of the rotary piston pump  1 . This inner housing  12  is disposed on the outside in a housing bushing  13 , which once again is sealed from the motor housing  3  and clamped partially in the latter and partially within the housing lid  4 . 
     As can be inferred particularly from  FIG. 4 , a recess  14  with a cylindrical section  15  and a spherical section  16  is provided in the inner housing  12 . 
     Two pump rotors work in this recess  14 , namely a driving part  17  and a driven part  18 . The driving part  17  is driven over a positive clutch  20  by the rotor  5  of the electric motor  2  and transfers the rotational movement of the latter to the driven part  18 . Cycloid gearings, which can be recognized in  FIG. 3  and have working surfaces  19 , which appropriately face one another, are provided on the front faces of the driving part  17  and the driven part  18 . By these means, pump working spaces  21 , as can be seen in  FIG. 2 , are formed between the working surfaces  19  and the inner wall of the recess  14 . 
     On the driven side, the recess  14  is closed off by a bottom bearing  22 , which is disposed at an angle to the axis of the recess  14  in order to achieve the necessary conveying angle and which is sealed from the housing bushing  13  at  23 . A journal pin  24  is disposed on this bottom bearing  22  perpendicularly to the front face of the bottom bearing  22  facing the recess  14 . The driven part  18  is mounted over a borehole  25  ( FIG. 3 ) on the bottom bearing  22 . 
     The driven part  18  is supported over a spherical surface  29 , facing the driving part  17 , at a corresponding spherical recess  30  of the driving part  17  ( FIG. 3 ). 
     It can be seen in  FIG. 4  how the delivery process takes place. Fuel is supplied to or removed from the working spaces  21  ( FIG. 2 ) over conveying nodules  31 , which are disposed in the walls of the inner housing  12 . On the pressure side, the fuel is then passed to the underside of the driven part  18 , as a result of which this is put under load in the direction of the driving part  17 . However, the latter functions only when the pump has already generated pressure. 
     All the distinguishing features, presented here, may be essential to the invention individually as well as in any combinations with one another. 
     LIST OF REFERENCE SYMBOLS 
     
         
           1  Rotary piston pump 
           2  Electric motor 
           3  Motor housing 
           4  Housing lid 
           5  Rotor 
           6  Magnet ring 
           7  Locking part (axial) 
           8  Main axle 
           9  Connections 
           10  Suction connection 
           11  Pressure connection 
           12  Inner housing 
           13  Housing bushing 
           14  Recess 
           15  Cylindrical section 
           16  Spherical section 
           17  Driving part 
           18  Driven part 
           19  Working surfaces 
           20  Positive clutch 
           21  Pump working spaces 
           22  Bottom bearing 
           23  Seal 
           24  Journal pin 
           25  Blind borehole 
           26  Helical spring 
           27  Sphere 
           28  Blind borehole 
           29  Spherical surface 
           30  Spherical recess 
           31  Delivery nodules