Abstract:
A compact hydraulic supply unit has a housing forming a reservoir for a pressure fluid, and includes a housing bottom, a housing cover and a housing middle part therebetween in the form of a profiled tube. An electric motor has a laminated stator core held by the housing middle part, and drives a pump located at the housing bottom. The housing middle part has axially extending internal holding Webs for holding the laminated stator core. The size of the housing middle part is independent of the size of the electric motor, so that, with a low structural height, the housing can be so formed that it accepts a larger volume of pressure fluid.

Description:
FIELD AND BACKGROUND OF THE INVENTION 
     The invention relates to a compact hydraulic aggregate which possesses a housing forming a reservoir for a pressure fluid, which comprises a housing bottom, a housing cover and a housing middle part therebetween in the form of a profiled tube, an electric motor located in the housing whose in stator laminated core is held by the housing middle part and which can be connected to an electricity network via a connection box on the housing cover, and a pump located within the housing in the region of the housing bottom and capable of being driven by the electric motor. 
     Such a compact hydraulic aggregate is known, for example, from DE 35 13 472 C2. In such a hydraulic aggregate, the housing may also be regarded as the housing of the electric motor. The rotor and stator of the electric motor are more or less deeply immersed into the pressure fluid, depending on how much oil has been introduced into the reservoir and how much pressure fluid is specifically received by the hydraulic user or users which are supplied with pressure fluid by the pump. The heat generated by the electric motor and the heat introduced into the reservoir by the pressure fluid is released to the environment via the housing. In some circumstances, the pressure fluid, when flowing back from the hydraulic user, additionally passes through an oil cooler in order to reduce the input of heat into the reservoir. This oil cooler may be directly affixed to the hydraulic aggregate. 
     The housing middle part of the known hydraulic aggregate is of circular cross-sectional form internally in the region of the stator laminated core of the electric motor. An exchange of pressure fluid between the spaces in front of the two end faces of the stator laminated core is evidently to take place via channels in the stator laminated core. 
     In the known compact hydraulic aggregate, the internal diameter of the housing middle part is determined by the external diameter of the stator laminated core, so that, for a given stock of pressure fluid, a particular height of the hydraulic aggregate results, whereby the placement of the hydraulic aggregate adjacent to a machine is sometimes prevented. In addition, the flow cross section is small because of the channels of the stator laminated core accepting the coils. In some circumstances, additional longitudinal channels have to be made in the stator laminated core, which results in an electric motor of special design. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention further to develop a compact hydraulic aggregate having the features of the introductory-mentioned paragraph in such a manner that, especially if additional members are built on, it can be produced cost-effectively. In addition, a low structural length is to be possible for a given pressure fluid storage volume. 
     This object is achieved, according to the invention, in that a compact hydraulic aggregate having the introductory-mentioned features is additionally equipped with features wherein holding webs make the external diameter of the stator laminated core and the internal diameter of the housing middle part independent of one another, as it were, and the housing middle part can be formed independently of the size of the electric motor to suit the desired storage volume of the pressure fluid and in the interests of a small structural length of the hydraulic aggregate. There is a great deal of free space between the holding webs for the completely unobstructed exchange of pressure fluid between the two spaces in front of the end faces of the stator laminated core. The heat generated in the electric motor is guided outward via the holding webs and released to the environment via the outer surface of the housing middle part. 
     Particularly preferably, the housing middle part has the external shape of a polygon, in particular a regular polygon. In this arrangement, a partial surface between two corners should lie diametrally opposite a further partial surface, so that the housing middle part can be well clamped for machining. In addition, a component which is externally angular can be stacked better than a circular component. The holding webs advantageously each extend at the center of an external partial surface of the housing middle part lying between two corners, so that the accumulation of material in the corners does not become too great. 
     An embodiment of the invention is also particularly preferred wherein the housing middle part comprises a further axially extending internal web between two holding webs for the stator laminated core of the electric motor, which further web is broader in the circumferential direction of the housing middle part than the holding webs and serves to secure a monitoring member located externally on the housing. For example, threaded holes can be drilled in the further web to permit the attachment of an oil level display glass. 
     This further holding web is also preferably located at the center of an external partial surface of the polygonal housing middle part, so that a level installation surface for the monitoring member is provided externally. 
     As has already been indicated, the compact hydraulic aggregate can additionally be equipped with an oil cooler which is disposed in the region of the housing bottom, for example even below the housing bottom. Preferably, the fan wheel of this oil cooler is driven by a further electric motor, so that no shaft need be guided out from the housing forming the reservoir. According to a feature of the invention provision is now made, in an advantageous manner, for the supply cable for the electric motor to be guided in an axially extending cable duct of the housing middle part to the housing cover, and especially into the connection box there. The supply cable is thus largely protected against damage. In particular, the cable duct also extends within the housing bottom and the housing cover, so that the cable is not visible at all from outside. 
     A temperature sensor, which can be used, for example, for switching an existing oil cooler on and off or, if no oil cooler is present, switches off the electric motor driving the pump is advantageously disposed in accordance with other features of the invention wherein the electrical connection line of the temperature sensor thus extends freely neither inside nor outside the housing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An example of embodiment of a compact hydraulic aggregate according to the invention is illustrated in the drawing. The invention will now be explained in detail with reference to the figures of this drawing. 
     In the figures: 
     FIG. 1 shows a longitudinal section through the example of embodiment equipped with an oil cooler, an oil level display glass and a temperature sensor, and 
     FIG. 2 shows a section through the housing middle part alone, along the line II—II in FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The compact hydraulic aggregate shown possesses a housing  10 , which on the one hand performs the function of the reservoir for the pressure fluid used for operation and in addition can also be regarded as a housing of an electric motor. This housing has, as essential parts, a housing cover  11 , a housing bottom  12  and a housing middle part  13 . The latter is a section of a profiled pipe produced from an aluminum alloy and has been finally machined. The outside of the housing middle part  13  is formed as a regular sixteen-sided figure with individual partial surfaces  14  between two corners. On the inside of the peripheral wall of the housing middle part  13 , a total of twelve holding webs  15  En extend toward the axis  16  of the housing middle part  13 . These holding webs are grouped in four sets of three holding webs each, the three holding webs  15  of each group being located at the centers of three consecutive outer partial surfaces  14 . Between the four sets of holding webs  15  is, in each case, an outer partial surface  14  on which no holding web  15  is present internally. The holding webs  15  are hollowed out over a particular axial distance from one end face of the housing middle part  13 , so that, on each holding web  15 , a radially inward-pointing partial surface  17  in the shape of a regular cylinder, lying on a regular cylinder with the corresponding partial surfaces  17  of the other holding webs  15 , and an axial bearing shoulder  18  are formed. From one side, the stator laminated core  19  and the stator of an electrical motor  21 , having the coils  20 , are pushed into the housing middle part  13  with pressure fit as far as the bearing shoulder  18 . 
     Inwardly and at the center of one of the partial surfaces  14  between two sets of holding webs  15 , the housing part  13  is provided with a further web  25  extending in the longitudinal direction, this further web  25  extending less far radially inward than the holding webs  15  and being thicker than the holding webs  15  in the circumferential direction of the housing middle part  13 . In the region of the holding web  25 , two holes  26  are drilled opposite one another in the axial direction into the housing middle part  13  and have been provided with a thread. As a result of the web  25 , the holes  26  have become long enough to serve for the attachment of an oil level display glass  27  by means of two screws  28 . The hydraulic aggregate shown is provided for operation in a vertical arrangement in which the axis of the housing middle part  13  extends vertically. The lower screw  28  in this arrangement always dips into the oil internally. Via a blind hole therein, in the manner of communicating tubes, a fluid connection exists between the interior of the housing  10  and the display glass  27 . The upper screw  28  is of exactly the same form as the lower screw  28 , in order that, in the event of a changing fluid level, air can escape from the display glass  27  or flow into the display glass. Because the web  25  is located at the center of a partial surface  14 , the display glass  27  lies flat with corresponding contact surfaces on the corresponding partial surface  14  of the housing middle part  13 , without being unacceptably stressed. The housing middle part  13  has the internal form of a circular regular cylinder between the webs  15  and  25 . 
     At each end surface, the housing middle part  13  has a hollowed-out portion  32  extending from that end surface over a certain axial extent and reaching radially outward into the region of the circumferential wall of the housing middle part  13 , in the region of which the webs  15  and  25  are thus fully hollowed-out. The housing cover  11  engages into one recess  32  and the housing bottom  12  into the other hollowed-out portion, with one centering collar  33  in each case. Located in a circumferential channel of each centering collar  33  is a gasket  34 , by means of which the gap is sealed relative to the housing parts. The housing cover, housing bottom and housing middle part are fixed to one another by radially driven flat-headed screws  35  in the region of the hollowed-out portions  32  and of the centering collars  33  which, as can be seen from the conical apertures  36  in the circumferential wall of the housing middle part  13  visible in FIG. 2, lie at the center of each partial surface  14 . 
     The shaft  40  of the rotor of the electric motor  21  is mounted by means of a bearing journal at each end in a rolling bearing,  41  and  42  respectively, which is inserted into a seating of the housing cover  11  or of the housing bottom  12 . Just above the rolling bearing  42  in the housing bottom  12 , the shaft  40  bears a twist-proof centering ring  43  toward which the radial pistons  44  of individual pump members  45  of a radial piston pump  46  fixed to the housing bottom  12  are urged by a compression spring  47 . In the event of rotation of the shaft  40 , the radial pistons  44  perform suction strokes during which pressure fluid is aspirated from the interior of the housing  10 , and pressure strokes, during which they force the aspirated pressure fluid to a pressure outlet (not shown in detail). 
     Located in the housing cover  11  is a filling aperture  51 , which is closed by a screw closure  52 . In addition, the housing cover  11  comprises a recess  53 , initially open outward in the direction of the axis  16  of the shaft  40 , by which a connection box for the hydraulic aggregate is formed. The connection box  53  is covered by a plate  54  with the interposition of a seal. A connection support produced from an electrically insulating material is fixed on the bottom of the connection box  53  and a plurality of connections are provided thereon for the fixing and connecting of electrical lines. A bundle of lines leads through an aperture  55  in the bottom of the connection box  53  into the interior of the housing  10  to the coils of the electric motor  21 . Also provided in the bottom of the connection box  53  is a through threaded hole  56 , into which a temperature sensor  57  is screwed from the interior of the housing  10 . The connecting lines of the temperature sensor  57  lead directly through the threaded attachment of the temperature sensor screwed into the threaded hole  56  into the connection box  53 , but for which they would hang free in the interior of the housing  10 . A connecting cable for supplying the electric motor  21  can enter the connection box  53  through the screw connection  58 . 
     Below the housing bottom  12  is disposed an oil cooler  65  with an electrically driven fan wheel. The electric motor of the oil cooler is connected to current via cable  64  which is guided from the electric motor into the connection box  53 . To prevent this cable  64 , first, from being externally accessible on the hydraulic aggregate and thus capable of being damaged and making the handling of the hydraulic aggregate more difficult, and secondly to prevent additional sealing points being necessary where the cable runs in the interior of the housing, a duct  66  is provided in the wall of the housing middle part  13  which extends in the axial direction along the housing middle part  13  and is guided externally past the gaskets  34 . In order to sufficient housing material to be available for a duct  66  that is continuous all round, an outward curvature  67  is provided on the housing middle part  13  in the region of a corner between two partial surfaces  14 . Attention is drawn to the fact that this outward curvature  67  is drawn at a different position in FIG. 1 from that shown in FIG. 2, in order to enable it be shown in the sectional view according to FIG.  1 . The outward curvature  67  is continued in the form of corresponding outward curvatures of the housing cover  11  and of the housing bottom  12 , in order to enable the duct  66  also to be extended into these parts. At the housing bottom, the duct  66  opens directly and axially into the oil cooler  65 . In the housing cover  11 , however, the duct  66  angles out of the axial direction into an oblique hole  68  which begins from a wall of the connection box  53 . Prom the connection box  53 , the cable  64  extends through the oblique hole  68  and the longitudinal duct  66  to the oil cooler  65 . It is thus protected against any damage.