Patent Publication Number: US-11662014-B2

Title: Gear unit having a housing

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 15/035,396, which is the national stage of PCT/EP2014/002832, having an international filing date of Oct. 21, 2014, and claims priority to Application No. 10 2013 018 712.5, filed in the Federal Republic of Germany on Nov. 8, 2013, each of which is expressly incorporated herein in its entirety by reference thereto. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a gear unit having a housing. 
     BACKGROUND INFORMATION 
     It is generally known that a housing of a gear unit has bearing mountings in which the bearings for the shafts of the gear unit are able to be accommodated, and the related forces are dissipated. 
     SUMMARY 
     Example embodiments of the present invention provide a gear unit having a housing, which may protect the environment and save resources. 
     Among features of example embodiments of the present invention with regard to the gear unit having a housing are that the housing has a housing top part and a housing bottom part, the housing having a housing top part and a housing bottom part on which the housing top part is mounted, the housing top part being disposed on a first side of a plane and the housing bottom part being disposed on the other side of the plane, in particular, the housing top part being formed in shell-like fashion, especially like half a nutshell, the housing top part having at least a first groove formed on its inner side and extending in a longitudinal direction, especially a first groove formed in one piece, e.g., integrally, on the housing top part, the housing top part having at least one further groove formed on its inner side and extending in a transverse direction, especially a further groove formed in one piece, e.g., integrally, on the housing top part, the transverse direction being aligned perpendicular to the longitudinal direction, in particular, the transverse direction being aligned parallel to the axis of the output shaft of the gear unit and/or the longitudinal direction and the transverse direction being aligned parallel to the plane. 
     An advantage in this case is that with the aid of the further groove, oil sprayed up onto the top wall is able to be collected when it flows off in the longitudinal direction. The oil flowing off in the transverse direction is able to be collected by the first groove. The same holds true for the oil flowing off in each case counter to the longitudinal direction, which is able to be collected by a second further groove. The oil flowing off counter to the transverse direction is also able to be collected by a groove aligned parallel to the first groove. The collection of oil is thus ensured all around. Therefore, the grooves altogether may also be described as a closed oil pocket. 
     Among features with regard to the gear unit having a housing a are that the housing has a housing top part and a housing bottom part, on which the housing top part is mounted, in particular, the housing top part being disposed on a first side of a plane and the housing bottom part being disposed on the other side of the plane, the housing top part being formed in shell-like fashion, especially like half a nutshell, and having an oil pocket closed all around, in particular, in each case a groove for collecting sprayed-around oil thus being disposed all the way around. 
     An advantage in this context is that the groove going all around on the inner wall of the concave, e.g., shell-like housing top part makes it possible to collect oil conducted along the top wall or along the oil-guiding rib structure. 
     The further groove may be located closer than the first groove to the top wall at least partially delimiting the interior space, and/or the further groove may be located further away from the plane than the first groove. This offers the advantage that the oil collected in the further groove flows automatically, e.g., under the mere influence of gravitational force, into the first groove. More oil is therefore available for lubrication. The further groove is thus situated higher in the gravitational field. 
     The first groove may be bounded by a groove wall formed on the housing top part, and by the top wall, and/or the further groove is bounded by a further groove wall formed on the housing top part, and by the top wall. This is considered advantageous because the grooves are able to be produced by suitable shaping of the cast part, and therefore without special expenditure. 
     The further groove may discharge into the first groove, or an end area of the further groove may be open such that oil flows from the further groove into the first groove, especially automatically. An advantage in this case is that the oil collected all the way around is usable for the lubrication of parts to be lubricated. 
     The housing top part may have a top wall at least partially delimiting the interior space of the gear unit, at least one oil-guiding rib structure being disposed on the top wall, especially being formed as an elevation or depression, one rib section of the respective oil-guiding rib structure extending from an area of the top wall having slight or vanishing slope—in terms of actual amount—with respect to the plane, especially horizontal plane, to an area of the top wall having a greater slope with respect to the plane in terms of actual amount. 
     This is considered advantageous because the oil sprayed up onto the top wall is able to be conducted by the oil-guiding rib structure to laterally disposed grooves. In the process, the oil is guided along the top wall by the oil-guiding rib to the laterally disposed groove. 
     The respective oil-guiding rib structure may have two or more rib sections that lead into a collector rib section. This offers the advantage that the oil-guiding structure is able to be implemented while saving on material. 
     The housing top part may have a top wall that at least partially delimits the interior of the gear unit and is curved, especially concave, in such a way in the longitudinal direction, and in the transverse direction such that oil droplets sprayed up toward the top wall drip off in or counter to the transverse direction along the top wall into a groove formed on the inner side of the housing top part, in particular, the amount of the gradient of the top wall, e.g., especially the slope of the top wall relative to the horizontal direction, increasing faster in the transverse direction with increasing distance from the highest point of the top wall, especially from the point of the top wall with vanishing gradient, than in the longitudinal direction. An advantage in this case is that the slope and the slope change in the transverse direction are able to be realized such that oil droplets do not drip off, but rather drain off along the oil-guiding rib structure. 
     The housing top part may have a groove formed on its inner side, especially a groove formed integrally, thus, in one piece on the housing top part, in particular, the amount of the gradient of the top wall, e.g., especially the slope of the top wall relative to the horizontal direction, increasing faster in the transverse direction with increasing distance from the highest surface point of the top wall, e.g., especially from the surface point of the top wall with vanishing gradient, than in the longitudinal direction. This is considered advantageous because a groove is formed as collection pocket for oil on the housing top part, and thus the oil conveyed in the transverse direction is able to be collected from there and supplied to the bearing positions to be lubricated. 
     The collector rib section may supply oil to the groove, in particular, the collector rib section of the oil-guiding rib structure extending from an area of the top wall having a first amount of slope with respect to the plane, especially a horizontal plane, to an area of the top wall having a second amount of slope with respect to the plane, the second amount being greater than the first amount. An advantage in this instance is that oil is allowed to be conducted in an easy manner, and at the same time, the slope is selectable such that the oil is able to be guided along the top wall, thus, without dripping off. 
     The top wall may have a plurality of oil-guiding structures. An advantage in this case is that as great a portion as possible of the oil spraying up onto the top wall is able to be drained off to the groove. 
     The respective oil-guiding structure may be produced as a separate part and joined to the housing top part. This offers the advantage of easy manufacture by forming the oil-guiding structure in the casting mold. 
     The housing top part may be formed in shell-like fashion, especially like half a nutshell, the housing top part having a top wall that at least partially delimits the interior of the gear unit and is curved, especially concave, in the longitudinal direction and in the transverse direction such that oil droplets sprayed up toward the top wall drip off in or counter to the transverse direction along the top wall into a groove formed on the inner side of the housing top part, in particular, the amount of the gradient of the top wall, e.g., especially the slope of the top wall relative to the horizontal direction, increasing faster in the transverse direction with increasing distance from the highest point of the top wall, especially from the point of the top wall with vanishing gradient, than in the longitudinal direction. 
     An advantage in this case is that the top wall is inclined such that oil droplets sprayed by a toothing part, such as a gear wheel, up toward the top wall are drained off to a groove in the housing top part, and from there, are able to be supplied to parts to be lubricated with lubricating oil. 
     Among features of example embodiments of the present invention with regard to the gear unit having a housing are that the housing has a housing top part and a housing bottom part, in particular, the housing top part being formed in shell-like fashion, especially like half a nutshell, the housing top part having a top wall that at least partially delimits the interior of the gear unit and is curved, especially concave, in the longitudinal direction and in the transverse direction, the housing top part having a groove formed on its inner side, especially a groove formed integrally, e.g., in one piece on the housing top part, the amount of the gradient of the top wall, e.g., especially the slope of the top wall relative to the horizontal direction, increasing faster in the transverse direction with increasing distance from the highest surface point of the top wall, e.g., especially from the surface point of the top wall with vanishing gradient, than in the longitudinal direction. 
     An advantage in this case is that the top wall is inclined such that oil droplets sprayed by a toothing part, such as a gear wheel, up toward the top wall are drained off to a groove in the housing top part, and from there, are able to be supplied to parts to be lubricated with lubricating oil. Preferably, the oil droplets are conveyed along the top wall in or counter to the transverse direction, so that the grooves disposed in and/or counter to the transverse direction are supplied with oil. 
     The transverse direction may be aligned parallel to the axis of the output shaft, the longitudinal direction being aligned perpendicular to and/or transverse to the transverse direction, in particular, the longitudinal direction being aligned parallel to the plane defined by an axis of an intermediate shaft and an axis of an output shaft. 
     The top wall may be formed in a manner corresponding to a vault. An advantage in this instance is that the sprayed-up oil droplets are drained off along the vault, in order then to be conducted down along the side into a groove formed on the inner side. 
     Lubricating oil may be supplied from the groove to parts to be lubricated, such as bearings and or toothing part. An advantage in this instance is that because oil is sprayed up onto the top wall, the oil is conveyed into the groove. In addition, with the aid of the pumping action of the gear wheel interacting with the trough, lubricating oil is able to be conveyed into the groove, so that sufficient oil is available for lubricating the parts to be lubricated, such as bearings or meshing gear-tooth parts. 
     A trough for guiding oil and reducing losses due to splashing may surround a circumferential section of a toothing part, particularly a gear wheel, especially in the radial and axial direction, the trough including at least three parts, e.g., at least one bottom plate and two side walls, the bottom plate being screw-connected to the two side walls, the trough being fastened to the housing, the trough having an opening, particularly a channel, especially at its lowest surface area, e.g., particularly at the surface area having the greatest radial distance, in particular, during rotational movement of the gear wheel, oil being conveyed from the oil pan of the gear unit through the opening between the trough and gear wheel, especially to a position higher than the level of the oil pan, the bottom plate and the side walls being stamped bent parts. 
     An advantage in this context is that with the aid of the gear wheel, oil is able to be delivered from the oil pan of the gear unit to a higher-situated location such as a temporary storage or a collecting channel, and thus from there, bearings and meshing gear teeth are able to be lubricated with lubricating oil. In addition, with the aid of the trough that, at least sectionally, correspondingly follows the contour of the gear wheel, therefore the outline of the rotating gear wheel, e.g., the cylindrical spatial area that is contacted by the rotating gear wheel, losses due to splashing are able to be reduced. To that end, the gap between the rotating gear wheel and the trough, especially the bottom plate of the trough, must be made small. The bottom plate is situated, with its surface section facing the gear wheel, at a radial distance that is set apart only slightly from the radial distance of the crowns of the gear teeth of the gear wheel to the axis of the gear wheel. Therefore, the surface section of the bottom plate facing the gear wheel extends substantially in the circumferential direction and in the axial direction, but with the exception of an opening, always has the same radial distance to the axis of the gear wheel, especially to the axis of the shaft to which the gear wheel is joined in rotatably fixed fashion. 
     The construction of the trough from only three parts forming it, namely, bottom plate and side walls, permits an especially cost-effective production by screw-connecting these parts. 
     The distance, particularly the distance in the radial direction, between the bottom plate and the crowns of the gear teeth may be constant in the angle-at-circumference area covered by the trough. This is considered advantageous because a small gap is sufficient as distance in order to achieve the pumping action. Losses due to splashing are therefore able to be reduced. 
     The bottom plate may have tab sections extending in the radial direction, at which the side walls are screw-connected. An advantage in this case is that the tab sections are able to be produced in an easy manner by bending a punching sheet. In addition, the tab section is able to be aligned parallel to the side wall, e.g., perpendicular to the surface section of the bottom plate extending in the circumferential direction and in the axial direction. Therefore, a simple sturdy connection is attainable between the bottom plate and side wall. In the case of a production series of gear units in which gear wheels of different sizes are used, a transmission ratio that is different in each instance is achievable for each gear unit in the production series. Consequently, however, the bottom plate must be secured at a radial distance adjusted in each case, and thus the axially aligned screws of the screw connection between the bottom plate and side wall at different radial distance, accordingly. 
     One side wall may have a marking, at which a bore hole is able to be placed for leading through a screw of the screw connection. An advantage in this instance is that depending on the transmission ratio of the gear unit or size, especially the crown circle diameter, of the gear wheel, a bore hole is able to be placed at the radial distance indicated differently in each case, and thus the trough is able to be disposed at different radial distance. 
     The opening, especially the channel, may be bounded by the bottom plate and the two side walls This is considered advantageous because an oil-conveying opening is able to be produced in an inexpensive and uncomplicated manner. 
     The bottom plate and each side wall may in each instance be formed in one piece, e.g., integrally. This is considered advantageous because each of the three parts is able to be produced as a stamped bent part, e.g., in a very inexpensive and uncomplicated manner. In this context, even the two side walls are able to be similarly implemented. 
     A housing may be provided for a gear unit, the housing having a housing top part and a housing bottom part, the housing top part having a frame-like support section on which wall sections are molded, the frame-like support section being formed integrally, e.g., in one piece, with the wall sections, particularly as a casting, especially as a steel casting. 
     An advantage in this case is that only the support section must contain a lot of material, e.g., also mass, but not the wall sections. Therefore, great forces are able to be transmitted, while saving on material. 
     The greatest wall thickness of the wall sections may be less than the greatest wall thickness of the support section. An advantage in this instance is that the wall sections are able to be implemented with thin wall thickness, making it possible to realize the housing while saving on material. 
     The frame-like support section of the housing top part may have a first and a second transverse rib, in particular, the transverse ribs stretching mainly in the horizontal direction, e.g., in particular, being extended further in the horizontal direction than in any direction transverse to it, the frame-like support section having two first ribs, the two first ribs being set apart from each other and in each case being joined to the first transverse rib, especially at two points set apart from each other, in particular, the first ribs stretching mainly in the vertical direction, e.g., in particular, being extended further in the vertical direction than in any direction transverse to it, the two second ribs being set apart from each other and in each case being joined to the second transverse rib, especially at two points set apart from each other, in particular, the second ribs stretching mainly in the vertical direction, e.g., in particular, being extended further in the vertical direction than in any direction transverse to it. This is considered advantageous because especially high stability is attainable, accompanied by little expenditure for material. The reason is that the frame-like support section has a rectangular shape, in which the rectangle is bent out of the plane of the rectangle at its two opposite sides, so that the bent areas are located substantially in further planes that are perpendicular to the plane, are set apart from each other, and are parallel to each other. 
     Each first rib and each second rib may include a lifting eye at its end area facing away from the respective transverse rib. This is considered advantageous because the forces introduced into the housing during transport are introduced directly into the frame-like support section, and not into wall sections having thin wall thickness. 
     A first rib may be joined at its end area to a bar, especially a support bar, that is joined at its other end to the end area of a second rib, the other rib being joined at its end area to a bar, especially a support bar, that in turn is joined at its other end to the end area of the other second rib, in particular, the two bars being disposed in parallel and set apart from each other. This is considered advantageous because high stability is attainable with the aid of the bracings. 
     A shaft of the gear unit may be supported by a bearing in the housing, a first part of the bearing mounting being located in the housing top part and a second part of the bearing mounting being located in the housing bottom part, the first part of the bearing mounting being implemented as a thickened section, and being joined to that area of the transverse ribs at which the respective rib is also joined. An advantage in so doing is that an additional bracing of the frame-like support section is provided by the thickened areas. 
     A housing cover may close an opening in housing top part  1 , the opening being surrounded by the frame-shaped support section, particularly with clearance, especially so that the frame-shaped support section does not directly contact the opening, but rather is set apart from the opening. An advantage in this case is that gear-unit parts are able to be inspected through the opening and maintenance work is able to be carried out. At the same time, no lubricating oil flows out from the gear unit either, since the opening is located on the upper side of the housing top part. 
     Among features with regard to the gear unit are that it is provided with a housing, a shaft of the gear unit being supported by a bearing in the housing, a first part of the bearing mounting being located in the housing top part and a second part of the bearing mounting being located in the housing bottom part, the first part of the bearing mounting being implemented as a thickened section, and being joined to that area of the transverse ribs at which the respective rib is also joined. 
     This is considered advantageous because high torsional stiffness and high mechanical stability are attainable. 
     Example embodiments of the present invention are explained in greater detail below with reference to the Figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    shows an oblique view of a gear-unit housing according to an example embodiment of the present invention for a gear unit in a first viewing direction, the housing being made up of a housing top part  1  and a housing bottom part  2 . 
         FIG.  2    shows an oblique view of the gear-unit housing in another viewing direction. 
         FIG.  3    shows an oblique view of the gear-unit housing in a third viewing direction. 
         FIG.  4    shows an oblique view of housing bottom part  2 . 
         FIG.  5    shows an oblique view of housing top part  1 . 
         FIG.  6    shows the frame-like support section of housing top part  1 . 
       As a segment from housing top part  1 ,  FIG.  7    shows a side wall section  3 , which is inserted into the frame-like support section. 
       As a segment from housing bottom part  2 ,  FIG.  8    shows a wall section having a wave structure, e.g., especially a concave-convex wall section. 
         FIG.  9    shows oil level  90 . 
         FIG.  10    shows a gear wheel  100  of the gear unit that is mounted in rotatably fixed manner on a shaft  101  supported in the gear-unit housing, and is at least partially surrounded by a trough secured to housing bottom part  2 . 
         FIG.  11    shows the trough itself in oblique view, the trough having side walls  102  and a bottom plate  103 . 
         FIG.  12    shows a side wall  102  of the trough.  FIG.  13    shows bottom plate  103  of the trough. 
         FIG.  14    shows the trough without front side wall  102 , so that the gear wheel is visible in oblique view, a first section being denoted. 
         FIG.  15    shows the first section from  FIG.  14    enlarged, a second section being denoted. 
         FIG.  16    shows the second section from  FIG.  15    enlarged. 
         FIG.  17    shows the housing of the gear unit cut into in the longitudinal direction, so that the curvature of the vault wall, especially the arched profile in the longitudinal direction, is visible. 
         FIG.  18    shows the housing of the gear unit cut into in the transverse direction, so that the curvature of top wall  171 , especially the arched profile in the transverse direction, is visible. 
         FIG.  19    shows a rhombus-like oil-guiding structure implemented as oil-guiding rib structure  210 , oil-guiding rib structure  210  being formed or disposed on the inner side of top wall  171 . 
         FIG.  20    shows oil-guiding rib structure  210  and a gear wheel  10  spraying the oil up toward oil-guiding rib structure  210 . 
         FIG.  21    shows oil-guiding rib structure  210  separately. 
         FIG.  22    shows housing top part  1  cut into such that groove wall  170  extending in the longitudinal direction and groove wall  220  extending in the transverse direction are visible. 
         FIG.  23    shows a section from housing top part  1  cut into differently, so that groove wall  170  extending in the longitudinal direction and groove wall  220  extending in the transverse direction are visible. 
         FIG.  24    shows a section from housing top part  1  again cut into differently, so that groove wall  170  extending in the longitudinal direction and groove wall  220  extending in the transverse direction are visible. 
     
    
    
     DETAILED DESCRIPTION 
     As shown in  FIG.  1   , housing bottom part  2  is disposed below housing top part  1 . Thus, housing top part  1  is situated above housing bottom part  2  in the vertical direction. 
     Housing top part  1  has a frame-like support section, which takes up and conducts the major portion of the forces. The remaining sections of housing top part  1  are formed only for the oil-tight enclosure of the gear-unit interior, e.g., are formed with thinner wall thickness than the support section and join closely to the support section. 
     Consequently, housing top part  1  as well as housing bottom part  2  are formed in shell-like fashion. 
     The frame-like support section of housing top part  1  has a first transverse rib  62 . It extends mainly in the horizontal direction. 
     Two first ribs  61  are set apart from each other, and in each case are joined to first transverse rib  61 , particularly at two points set apart from each other. 
     First ribs  61  stretch mainly in the vertical direction, e.g., are extended further in the vertical direction than in any direction transverse to it. 
     The frame-like support section of housing top part  1  also has a second transverse rib  62 . It extends mainly in the horizontal direction. 
     Two second ribs  61  are set apart from each other, and in each case are joined to second transverse rib  61 , particularly at two points set apart from each other. 
     Second ribs  61  stretch mainly in the vertical direction, e.g., are extended further in the vertical direction than in any direction transverse to it. 
     Each first rib  61  and each second rib  61  has a lifting eye  63  at its end area facing away from the respective transverse rib. Thus, the gear unit is able to be picked up at the lifting eyes by hooks or cable and is easily transportable. The forces occurring during transport are introduced at lifting eyes  63  into the end areas and thus into the frame-like support section. Consequently, the gear-unit housing becomes only negligibly deformed and remains undamaged. 
     A first rib  61  is joined at its end area to a bar  60 , particularly a support bar, which at its other end is joined to the end area of a second rib  61 . In the same manner, the other rib  61  is joined at its end area to a bar  60 , particularly a support bar, that in turn is joined at its other end to the end area of the other second rib  61 . The two bars  60  are disposed in parallel and set apart from each other. 
     As described above, wall sections are conformed to the frame-like support section—formed thus of ribs  61 , transverse ribs  62  and bars  60 —of housing top part  1 , so that the shell-like housing top part is able to be formed in one piece, particularly as a casting. 
     In this connection, the wall sections, especially also two side wall sections  3  and the wall section having a concave-convex wave structure, are thus integrally molded and conformed to the frame-like support section and implemented in one piece. 
     Bars  60  stretch mainly in the horizontal direction, e.g., are extended further horizontally than in any direction transverse to that. 
     The frame-like support section is thus realized by an increase in the wall thickness. 
     In addition, thickened areas are also provided on housing top part  1 , which are intended as bearing mounting for at least one part, especially half, of the circumference of an outer ring of a bearing. These arch-like thickened areas adjoining one another are joined to transverse ribs  62 , especially in each case in that end area in which respective rib  61  is joined. 
     The concave-convex wave structure of the wall sections enlarges the surface area, and therefore reduces resistance to the transfer of heat to the ambient air. In this context, an especially sharp depression is provided as depression  5  for a manipulation area for screw connections. In this case, the screws are connecting screws by which housing top part  1  and housing bottom part  2  are screw-connected. 
     Housing bottom part  2  has a wave structure  6 , particularly a concave-convex wall section, which likewise enlarges the surface area, and therefore reduces resistance to the transfer of heat from the gear-unit interior, especially lubricating oil, to the ambient air. 
     The housing cover is provided to close an opening in housing top part  1 , the opening being surrounded by the frame-shaped support section, especially with clearance. That means that the frame-shaped support section does not directly contact the opening, but rather is set apart from the opening. 
     As shown in  FIG.  10   , gear wheel  100  is joined in rotatably fixed manner to shaft  101 , which is supported in the housing by a bearing. In this context, the bearing is accommodated in a bearing mounting in the housing, a first part of the bearing mounting being located in housing top part  1  and a second part of the bearing mounting being located in housing bottom part  2 . 
     The lower spatial area surrounding gear wheel  100  is enclosed by the trough, the trough having side walls  102  and a bottom plate  103 . Thus, it is able to be fabricated from three parts. 
     Side walls  102  of the trough are secured to bottom plate  103 . At its lowest area, bottom plate  103  has a protuberance  130  directed downward. Protuberance  130  is directed radially away from the gear wheel, and is open at its radially outer end area  131 . Thus, lubricating oil of the gear unit gets from the oil pan of the gear unit through protuberance  130  up to gear wheel  100 . Laterally, e.g., on both sides in the axial direction, the protuberance is closed by a respective tab section  120  of side walls  102 , so that a channel is formed passing through radially to gear wheel  100 . 
     As illustrated in  FIG.  12   , in each case side walls  102  are punched out as a sheet-metal part, and at their axial outer side, have markings which identify the positions of bore holes to be introduced, particularly as a function of the transmission ratio of the gear unit and/or toothing data of gear wheel  100 . 
     Screws are guided through the bore holes, making a screw connection achievable between bottom plate  103  and respective side wall  102 . 
     Therefore, depending on the size or other toothing data, the bottom plate is able to be positioned at an optimal radial distance from the central axis of the gear wheel. 
     Bottom plate  103  is likewise produced as a stamped bent part, and has a U-shaped cross-section. In this context, it is bent such that the distance between the toothing, particularly the crowns of the teeth of the toothing of gear wheel  100  located in the same angle at circumference as bottom plate  103 , is constant. Thus, a narrow gap is provided between these tooth crowns and bottom plate  103 . 
     Consequently, a pumping action develops during rotational movement of gear wheel  100 , since the lubricating oil located in the tooth spaces is moved with greater velocity than the lubricating oil in the channel. In this manner, lubricating oil is thus conveyed through the channel from the oil pan to gear wheel  100  and is then moved along with it. 
     The trough also reduces the losses due to splashing during movement of gear wheel  100 , for the teeth of the toothing of gear wheel  100  dip in the spatial area surrounded by the trough. 
     With the exception of tab sections  120  and protuberance  130 , U-shaped bottom plate  103  is bent circularly in the circumferential direction, so that the distance between the teeth of the toothing of gear wheel  100  and bottom plate  103  is substantially constant in the corresponding angle-at-circumference area. 
     Tab sections  120  are directed radially to the outside, so that respective side wall  102  is able to be pressed in the axial direction onto bottom plate  103 , particularly at its tab sections  120 , and screw-connected. 
     With the aid of the pumping action of gear wheel  100  in interaction with the trough, oil is pumped to a position situated higher than the oil level of the oil pan, and from there is conducted via a temporary storage or directly to the places to be lubricated, such as bearings or engaging gear teeth. Appropriate conduits or pipes are provided for this purpose. 
     Protuberance  130  is able to be produced by bending out from the original form of bottom plate  103 . To that end, a punching sheet is bent in such a way that two areas, bent in the shape of circle segments, are set apart from each other over an area bent substantially in the shape of a rectangle. After that, the areas bent in the shape of circle segments are pressed against each other, and thus form the circular area of bottom plate  103 . At the same time, the areas bent in the shape of circle segments encompass an opening. The area bent in the shape of a rectangle likewise has a centrally located opening and thus forms protuberance  130 . 
     As illustrated in  FIGS.  17  and  18   , top wall  171  is curved, a differently curved profile being present in the longitudinal direction than in the transverse direction. In this case, the inclination is such that oil droplets which, for example, are sprayed by a gear wheel  100  of the gear unit up onto the ceiling, preferably flow off in the transverse direction along top wall  171 . Below top wall  171 , particularly below the end area of top wall  171  situated in the longitudinal direction, a groove is formed whose groove wall  170  extends in the longitudinal direction, e.g., extends further in the longitudinal direction than in the transverse direction or other direction perpendicular to the longitudinal direction. In the same manner, a further groove is located below the end area of top wall  171  disposed counter to the longitudinal direction. 
     Thus, the oil sprayed up onto top wall  171  flows off either in the longitudinal direction or counter to the longitudinal direction to the respective end area of top wall  171 , and drips down into the respective groove. From there, the oil is guided to a bearing to be lubricated or to a toothing part to be lubricated. 
     The groove is formed in one piece on housing top part  1 , e.g., by shaping of the steel casting, and therefore is formed integrally with housing top part  1 . 
     From the highest point of concave top wall  171 , the oil flows off faster in the transverse direction than in the longitudinal direction, because the curvature and gradient are greater in the transverse direction. 
     The top wall is extended further in the longitudinal direction than in the transverse direction. 
     Oil-flow direction  172  on top wall  171  is therefore directed outward, e.g., directed in the longitudinal direction or counter to the longitudinal direction, and consequently the oil droplets are conveyed toward the groove. 
     Therefore, not only is oil conveyed to a higher position, especially into the groove, by the conveying effect of the gear wheel together with the trough, but also the oil spraying around is conveyed into the groove. Consequently, sufficient oil is available for lubrication. 
     As shown in  FIGS.  19  through  21   , top wall  171  has a rhombus-like structure that projects into the interior space and collects the oil sprayed up by gear wheel  100  and conducts it in the transverse direction or counter to the transverse direction to the respective groove. 
     In  FIG.  20   , oil-flow direction  201  along oil-guiding rib structure  210 , as well as oil-spray direction  202  are indicated. 
     Oil-guiding rib structure  210  has a rhombus-like structure whose two adjacent sides pointing in the transverse direction are merged to form a collector rib section that conducts the oil toward the groove and/or has an end section of a kind that the oil drips off into the groove. 
     The rib sections formed as sides of the rhombus extend from the area of vanishing or slight slope of top wall  171  up to an area in which the amount of the slope is greater. From there, the collector rib section extends up to an area in which the amount of the slope is even greater. 
     As illustrated in  FIG.  19   , not just one, but also a further oil-guiding rib structure  210  is shown on top wall  171 . It is assigned to a further gear wheel or is disposed such that upon reversal of the direction of rotation of gear wheel  100 , the area of top wall  171  is sprayed upon which has this further oil-guiding rib structure  210 . 
     Other structures may be used. For example, not just two, but rather a plurality of rib sections are directed to a collector rib section, so that the rib sections form a finger-like structure. 
     In this instance, the rib sections again extend from the area of vanishing or slight slope of top wall  171  up to an area in which the amount of the slope is greater. From there, the collector rib section again extends up to an area in which the amount of the slope is even greater. 
     Alternatively, oil-guiding rib structure  210  may also be realized as a separate part, e.g., not as an elevation formed in the casting mold on housing top part  1  and projecting toward the interior, but rather as a part secured to top wall  171  of the housing top part. 
     As a further alternative, oil-guiding rib structure  210  is implemented not as an elevation, but rather as a depression, such as a groove or the like, in top wall  171  of housing top part  1 . 
     As shown in  FIGS.  22  through  24   , not just two groove walls  170  extending in the longitudinal direction are formed on the inner wall of housing top part  1 , but also two further groove walls  220  extending in the transverse direction, which are located closer to top wall  171 , e.g., especially higher. Therefore, oil droplets moving in the longitudinal direction along the top wall are able to be collected in the groove formed by respective further groove wall  220 . From this higher-situated further groove, the oil flows into the groove formed by groove wall  170 , and is therefore able to be used for lubrication. 
     LIST OF REFERENCE NUMERALS 
       1  housing top part 
       2  housing bottom part 
       3  side wall section 
       4  housing cover 
       5  depression for manipulation area for screw connections 
       6  wave structure, especially concave-convex wall section 
       60  bar 
       61  rib 
       62  transverse rib 
       63  lifting eyes 
       90  oil level 
       100  gear wheel 
       101  shaft 
       102  side wall 
       103  bottom plate 
       120  tab section 
       130  protuberance 
       170  groove wall 
       171  top wall 
       172  oil-flow direction on top wall  171   
       210  oil-guiding rib structure 
       201  oil-flow direction 
       202  oil-spray direction 
       220  further groove wall