Abstract:
A pumping unit is provided with a pump that is partially disposed in a stator of an electric motor. The rotor is at an opposite end from the pump and is connected to the pump shaft to drive it for fluid flow. The pump shaft can be positioned in a central bore of the rotor and connected thereto via a meshing gear.

Description:
RELATED APPLICATIONS 
   This application claims priority to German Application No. DE 103 54 312.0, filed on Nov. 20, 2003, the disclosure of which is incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention concerns a pumping unit, which has a gear pump and an electric motor in a common housing. Such a pumping unit is also designated as a motor-driven pump or a motor-driven pumping unit. 
   2. Description of the Related Art 
   A motor-driven pumping unit is described by German Application DE 100 15 139 A1, shown in  FIG. 1 , and the disclosure of which is incorporated herein by reference. 
   The motor-driven pumping unit comprises an electric motor  1  with a rotor  11  and a stator  12 . The stator  12  has a stator sheet stack  121  and a winding  122 . Rotor  11  has a pot shape and is U-shaped, viewed in axial section. 
   A pump  2  is disposed radially inside rotor  11  and stator  12 . As can be seen, this pump  2  is completely enclosed by rotor  11  or stator  12  of electric motor  1 . 
   In order to produce a drive connection between rotor  11  and pump shaft  21 , land  111  of rotor  1  has a bore with an internal gear, which engages with an external gear of pump shaft  21 . The pump shaft  21  bears a pinion  22 , which meshes with an internal geared wheel  23 , which is disposed eccentrically to the pinion  22  within rotor  11  of electric motor  1 . Side pieces  24  and  25  of pump  2  are disposed axially on both sides of internal geared wheel  23 , and in this pump, pump shaft  21  is mounted in a rotatable manner by friction bearings  241  and  251 . 
   An inlet  5  for introducing the pumping medium is provided in an end side of the housing  4 . An outlet  6  for discharging the pumping medium is provided in the same end side of the housing. 
   The embodiment shown has been found to be easy to produce and is compact. It has been determined, however, that in the case of specific pump data, for example, in the case of a small displaced volume and low pressure, the ratio of motor dimensions to pump dimensions is unfavorable. 
   SUMMARY OF THE INVENTION 
   The object of the invention is to further develop a motor-driven pumping unit of the type described initially in such a way that an optimal and thus cost-favorable structural volume is attained even in the case of small displaced volume and low pressure. 
   The object according to the invention is solved by a pumping unit with the features, and the equivalents thereof, as described herein. 
   The solution according to the invention is based on the knowledge of the inventor that the insufficient structural volume is essentially caused by an unfavorable ratio of motor diameter to motor length. Correspondingly, the inventor has further developed the known embodiment of the pump in such a way that the ratio between motor diameter and motor length can be designed smaller. This possibility is assured in the case of the pumping unit according to the invention by the fact that the rotor of the electric motor is disposed on the end side opposite the pinion and the internal geared wheel of the pump. The drive connection between electric motor and pump will be produced in such a way that the pump is equipped with an extended pump shaft, which projects into the rotor of the electric motor. The rotor of the electric motor is mounted resistant to rotation, preferably cantilevered on a segment of the extended pump shaft. The arrangement of the pump also could be axially shifted next to the rotor of the electric motor onto a common shaft, also designated a tandem structure. 
   Many advantages can be achieved or retained by the embodiment according to the invention, such as, for example, the relatively small structural space necessary for the pumping unit, the forming of the motor and the pump into one integral unit, the cooling of the motor by the pumping medium, which is particularly a hydraulic oil, the comparatively great reduction in sound level, as well as the possibility of being able to separately examine the two units, i.e., pump and motor. In particular, the pumping unit according to the invention is free of any radial packing rings, ventilating fan noise, roller bearings as well as special pump supports and elastic couplings. 
   The rotor of the electric motor is particularly advantageously connected to the pump shaft, resistant to rotation, by means of a meshing gear on its end side or in the region of its end side. The end side of the rotor is particularly considered for the rotation-resistant connection, since it is placed at a distance in relation to the pump, i.e., it is the side placed away from the pump. For example, the pump shaft can be provided with a shaft journal, which bears an external gear that meshes with the rotor of the motor or a disk mounted in the rotor. 
   The pumping unit has an electric motor, a pump and a housing. The electric motor has a rotor and a stator. The rotor has a central bore. The pump conveys the liquid medium and is operably connected to and driven by the electric motor. The pump is at least partially radially inside of the stator. The pump has a shaft and an eccentric internal geared wheel. The shaft has a pinion opposite to and meshing with the eccentric internal geared wheel. The housing encloses the electric motor and the pump. The rotor is on a first end of the pumping unit that is opposite to the pinion and the internal geared wheel of the pump. The rotor is resistant to rotation with respect to the shaft by a segment of the shaft that extends axially into the central bore of the rotor. 
   The pumping unit can have an annular-shaped intermediate space between the rotor and the stator. The housing can have first and second end sides that are axially opposed to each other, where the first end side has an inlet for the liquid medium and the second end side has an outlet for the liquid medium. The medium can flow from the inlet axially along the stator through the annular-shaped intermediate space through the pump and out of the outlet. The pumping unit may also have a meshing gear connected to the rotor on an end of the rotor that is opposite to the pump, where the meshing gear engages with the shaft thereby allowing the rotor to drive the shaft. The pump can be only partially radially inside of a stator winding and the rotor can be inside of the stator sheet stack. The rotor can have a central bore with a first segment of the shaft being disposed through the central bore. At least one spacer sleeve can be positioned between the first segment and the rotor in the central bore. The shaft may have a second segment adjacent to the first segment that has a diameter smaller than the diameter of the second segment. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a cross-sectional view of a motor-driven pumping unit of the prior art; and 
       FIG. 2  shows a cross-sectional view of a motor-driven pumping unit of the present invention. 
   

   DESCRIPTION OF THE INVENTION 
   Referring to  FIG. 2 , pump  2  is no longer completely arranged inside stator  1 . 2  of electric motor  1 , but rather only partly inside it, and in fact exclusively inside one axial end of the stator winding  1 . 2 . 2  and completely outside the axial region of the stator sheet stack  1 . 2 . 1 . 
   The shaft  2 . 1  of pump  2  has two segments or regions, a first segment or region  2 . 1 . 1 , which is allocated to the rotor  1 . 1  of the electric motor, and a second segment or region  2 . 1 . 2 , which is allocated to the pump  2 . The pump shaft  2 . 1  is mounted inside pump  2  in region  2 . 1 . 2 , preferably by means of the friction bearings  2 . 4 . 1  and  2 . 5 . 1  on both sides of the pinion  2 . 2  borne by the pump shaft  2 . 1 . The region  2 . 1 . 1  of the pump shaft  2 . 1 , which is formed with a comparatively smaller diameter than the region  2 . 1 . 2 , is completely enclosed by the rotor  1 . 1  (which is shaped like a hollow cylinder having a central bore  1000 ), and bears rotor  1 . 1 , for example, by means of spacer pieces or spacer sleeves  8  and  9 , which are shown. Rotor  1 . 1  of electric motor  1  is thus mounted cantilevered on pump shaft  2 . 1 . 
   The rigid connection between rotor  1 . 1  and pump shaft  2 . 1  is produced by a connection  7 , which is resistant to rotation. This is formed as an external gear on an axle journal at the end of pump shaft  2 . 1 , which lies opposite the end on the pump side. A meshing disk  10  with an internal gear or locking catch, which is mechanically engaged with rotor  1 . 1 , is shifted onto this axle journal, which has the smallest diameter of pump shaft  2 . 1 . Due to the fact that the internal gear of meshing disk  10  and the external gear of the axle journal engage with one another, the driving power of rotor  1 . 1  is transferred to pump shaft  2 . 1  and thus to the pinion  2 . 2  and the internal geared wheel  2 . 3  which is eccentric to it. 
   The line for the pumping medium through housing  4  is shown by arrows  500 . As can be seen, the pumping medium enters through an inlet  5  for pumping medium in axial direction in a first end side  4 . 1  of housing  4 , is distributed in peripheral direction in an annular channel  11 , which surrounds the first end of the winding  1 . 2 . 2  of stator  1 . 2 , and then flows in the axial direction along stator  1 . 2  through an annular gap between stator  1 . 2  and rotor  1 . 1 . In addition, axial bores  12  are provided in rotor  1 . 1  radially inside the annular gap, and the pumping medium is guided through these bores. After the pumping medium has passed axially through rotor  1 . 1 , it flows into a second annular channel  13  on the other side of rotor  1 . 1 , which surrounds the second axial end of winding  1 . 2 . 2  and pump  2 . 
   The pumping medium is guided from this second annular channel  13  into pump  2 , is compressed therein by means of the gear pump, i.e., the engagement of pinion  2 . 2  in the internal geared wheel  2 . 3 , and conveyed out from housing  4  axially through the outlet  6  for pumping medium. 
   The present invention having been thus described with particular reference to the preferred forms thereof, it will be obvious that various changes and modifications may be made therein without departing from the spirit and scope of the present invention as defined in the appended claims.