Patent Publication Number: US-8967334-B2

Title: Gear unit at least partially filled with oil

Description:
FIELD OF THE INVENTION 
     The present invention relates to a gear unit at least partially filled with oil. 
     BACKGROUND INFORMATION 
     It is well-known that gear units having oil lubrication are practicable, the oil, i.e., liquid, collecting in the bottom part of the gear-unit interior when the gear unit is not in operation, thus when the gear wheels are stationary, and forming the oil pan there which has an oil level that corresponds to the filling level upon pouring in the oil. During operation of the gear unit, especially at nominal speed of the input shaft and/or output shaft, the gearing parts of the gear unit spray and hurl oil around. In particular, oil is also sprayed out from the gearings engaging with each other. The quantities of oil sprayed around lower the oil level only insignificantly during operation of the gear unit. 
     SUMMARY 
     Example embodiments of the present invention provide a gear unit in which the intention is for as much power as possible to be transmittable per unit volume. 
     Among features of example embodiments of the present invention with respect to the gear unit are that it is a gear unit at least partially filled with oil, a device being provided in the gear unit for lowering the oil level, especially of the oil pan of the gear unit, during operation, the device including at least one temporary storage. 
     This is advantageous because the oil level is lowered significantly, since oil is filled temporarily into a temporary storage, thus, a receptacle. Therefore, churning losses are reducible, and nevertheless, good lubrication is attainable when starting the gear unit, even though a protracted standstill may have taken place beforehand. 
     In example embodiments, the oil level in the temporary storage is higher during operation of the gear unit than the oil level, especially of the oil pan of the gear unit. This offers the advantage that the temporary storage is able to be emptied automatically during standstill of the gear unit. 
     In example embodiments, the temporary storage is located in the interior of the gear unit. This is advantageous because no further housing-forming part, other than the gear housing, is necessary, and the spatial area of the gear unit may be well-utilized. 
     In example embodiments, the temporary storage is in the form of a receptacle whose wall is formed at least partially by a sheet-metal piece \ and/or a plastic piece, especially at least partially together with the inner wall of the housing of the gear unit. This has the advantage that the temporary storage may be produced inexpensively. 
     In example embodiments, the oil level of the gear unit, especially the oil pan of the gear unit, is lower during operation lasting for a minimum duration than the oil level during long-term standstill of the gear unit. The advantage in this case is that churning losses are reducible, and therefore more power is attainable per unit volume due to the substantial lowering of the oil level. 
     In example embodiments, oil from the oil pan of the gear unit is able to be delivered to the temporary storage, especially with the aid of a delivery device, in particular, the temporary storage being disposed in the interior of the gear unit, thus, being surrounded by the gear housing in housing-forming fashion. This is advantageous because it is possible to dispense with an additional housing, and the inner spatial area may be well-used. 
     In example embodiments, the temporary storage is in the form of a receptacle which has openings of the kind that it is able to be emptied through these openings. This offers the advantage that it is able to be emptied automatically during standstill, and therefore the oil level of the oil pan then rises substantially. 
     In example embodiments, the temporary storage is in the form of a receptacle that has openings such that, and the delivery device is conceived and implemented such that the maximum oil flow delivered by the delivery device, especially during operation of the gear unit with the nominal speed of the gear unit, is greater than the oil flow returned from the temporary storage to the oil pan, effected through the openings. The advantage is that the temporary storage fills increasingly during operation and empties during standstill of the gear unit. 
     In example embodiments, the oil level, especially of the oil pan of the gear unit, is lower during operation than the oil level during long-term standstill of the gear unit, in particular, a device being provided for lowering the operational oil level, the device for lowering especially being a device for the temporary storage of oil. The advantage in this context is that when starting the gear unit, the bearings and gearing parts are soaked well by oil, since the oil level is very high at the beginning. In operation, thus, when the oil level is lower, the churning losses are reduced, and the bearings or gearing parts are able to be lubricated from the temporary storage via other delivery device. In operation, these delivery devices are operable without representing an additional energy loss of the gear unit. 
     In example embodiments, a temporary storage is provided to which oil is able to be fed from the oil pan of the gear unit, especially with the aid of a delivery device; in particular, the temporary storage is disposed in the interior of the gear unit, thus, is surrounded by the gear housing in housing-forming fashion. This is advantageous because no additional housing or an additional spatial area is necessary for the temporary storage; rather, the spatial area present in the housing of the gear unit is usable. This holds true especially for a housing which surrounds the gearing parts in essentially cuboidal fashion, a beveled area placed on the cuboid being able to be provided in the area of the input shaft. Advantageously, a cube housing is able to be produced easily and inexpensively, and exhibits great strength accompanied by small wall thickness and small amount of material used. Therefore, a substantially cuboidal interior space is available, minus the rotating area of the gearing parts, as well as the area of the shafts and bearings. This residual spatial area remaining is usable as temporary storage. 
     In example embodiments, the temporary storage is in the form of a receptacle which has openings of the kind that it is able to be emptied through these openings. The advantage in this case is that the temporary storage empties when the gear unit is in the state of rest, particularly with a first time constant. The temporary storage is filled with the aid of the delivery device in the gear unit with such a delivery rate that the delivered oil flow would fill the temporary storage with a second time constant assuming the openings were not present, this second time constant being smaller than the first time constant, especially more than three times smaller or even more than ten times smaller. 
     In example embodiments, the temporary storage is in the form of a receptacle that has openings such that, and the delivery device is implemented such that the maximum oil flow delivered by the delivery device, especially during operation of the gear unit with the nominal speed of the gear unit, is greater than the oil flow returned from the temporary storage to the oil pan, effected through the openings. This offers the advantage that the temporary storage is able to be filled quickly, and thus the oil level of the gear unit is lowered very rapidly after start-up. In particular, it is advantageous to provide the openings to be so small, and to implement the delivery device with a delivery rate, such that the oil flow delivered is at least three times or even ten times greater than the oil flow returned. 
     In example embodiments, the temporary storage has an overflow, especially a height-adjustable overflow, via which excess oil is able to be drained into the oil pan. This is advantageous in that, depending on the variant of the gear unit, adaptation of the oil level is feasible. In addition, adaptation of the lowered oil level as a function of the operating conditions and manufacturing tolerances is made possible. 
     In example embodiments, the delivery device has a baffle plate for catching oil, oil dripping off from the baffle plate being able to be fed via a drainage channel and/or collection channel to the temporary storage. This has the advantage that a part of the delivery means is realizable in an easy manner, and oil which is spraying around may easily be captured. 
     In example embodiments, the drainage channel or collection channel has an opening into which a pipe opens through, from which a ball bearing and/or a gearing may be lubricated. The advantage in this case is that the delivery devices are inexpensive and uncomplicated. 
     In example embodiments, the drainage channel is curved, so that a first portion of the oil dripped off from the baffle plate and caught by the drainage channel flows into a first collection channel, and a second portion of the oil dripped off from the baffle plate and caught by the drainage channel flows into a second collection channel, the temporary storage being fillable from the collection channels, and the collection channels being disposed axially to the side of a gear wheel of the gear unit. The advantage here is that the remaining spatial area, which does not count as part of the rotational area of the gearing parts and is provided in the interior of the cuboidal gear unit, is usable. 
     In example embodiments, at least one partial area of a gearing part of the gear unit is surrounded by a shell, so that oil is only allowed to spray upward; in particular, the shell has an opening at its lower side, thus permitting the shell to be filled from the oil pan, especially when the gear unit is not in operation. The advantage in this context is that more oil is sprayed upward, and thus improved heat dissipation is achievable, since the oil must cover a long distance to the oil pan, the oil being in contact with the housing of the gear unit during the flow back. 
     In example embodiments, the delivery device includes an oil scraper that permits oil to be scraped off from the end face of a rotating gear wheel, and allows the scraped-off oil to be delivered through a pipe to the temporary storage or to a collection channel, the pipe especially being directed upwards, the gear wheel in particular being disposed so that it is at least partially submerged in the oil pan, and the oil scraper in particular being situated above the oil pan. This is advantageous in that a further inexpensive and uncomplicated delivery device is able to be provided. In particular, a conveying effect is attainable in order to convey oil through the pipe into a collection device or a temporary storage, from which, in turn, a pipe leading into the surroundings is able to be fed. Therefore, oil is thus able to be conveyed into the surroundings and cooled there in the cooling airflow streaming past, especially with the aid of the plate cooler situated there. 
     In example embodiments, the pipe includes bores in the gear housing. This is advantageous because oil is able to be conveyed through these bores toward the bearings, e.g., ball bearings. Lubrication of these bearings may therefore be ensured. 
     In example embodiments, a delivery device conveys oil from the interior of the gear unit through a pipe which is attached to the outside of the gear unit, in particular, the pipe returning the oil to the interior of the gear unit. The advantage in this case is that after being brought out, the oil is able to be cooled in the outer area around the gear unit, especially in a cooling airflow which is propelled by a fan impeller. 
     In example embodiments, the pipe on the outside of the gear unit has a gradient, in particular, the oil from a collection device such as a temporary storage or collection channel disposed in the interior of the gear unit flowing outward through the pipe, and from there back again into the oil pan, 
     in particular, the collection device being situated above the oil pan. This offers the advantage that the oil flow is able to be impelled merely by the gradient in the gravitational field, thus, passively. In this context, an energy loss of the gear unit is utilized for raising the oil, for during operation of the gear unit, the oil in its interior is sprayed around, especially upward, as well. A portion of the oil caught there is then conveyed downwards without a further pump, utilizing the gradient, and at the same time, is cooled. 
     In example embodiments, the pipe provided on the outside feeds oil to a plate cooler, and another part of the pipe returns oil from the plate cooler to the oil pan in the interior of the gear unit. The advantage in this instance is that oil is conveyed inexpensively using simple means. 
     In example embodiments, the plate cooler is fastened to the outside of the gear unit and is situated in the cooling airflow. In this case, it is advantageous that an enlarged surface is provided and improved heat dissipation is therefore attainable. In particular, the plate cooler is alignable parallel to the cooling airflow, so that the flow exhibits the least possible turbulence. 
     In example embodiments, the gear unit has an input shaft, 
     a bearing for supporting the input shaft being provided in a housing part of the gear unit, 
     a fan impeller being provided on the input shaft, 
     the housing part being beveled at least in the surface area adjacent to the fan impeller and/or a beveled cowl being mounted on the housing part. 
     This offers the advantage that the cooling airflow is able to be guided as well as possible, and therefore the greatest possible portion of the airflow streams along the housing. In this manner, a powerful cooling airflow for cooling the gear unit is able to be generated by the passively driven fan impeller, thus, driven without separate motor actuator, and great power is able to be generated per unit volume. 
     In example embodiments, cooling fins are provided on the beveled area of the housing part or on the cowl. This has the advantage that the surface is enlarged, thus ensuring improved heat dissipation. In particular, the heat is able to be conducted by air from the housing to the cowl, and from there to the surroundings. Moreover, the beveled housing part or the beveled cowl acts as an air-guide element and reduces turbulence. 
     In example embodiments, cooling fins and/or cooling fingers are provided on the housing part of the gear unit. This is advantageous because the surface is enlarged. In the case of the cooling fingers, an isotropic heat dissipation is even achievable, thus, heat dissipation independent of the installed orientation of the gear unit. 
     In example embodiments, a housing cover, imperviously connectable to a housing part and having cooling fins on its outer side, is provided on the housing of the gear unit. The advantage here is that a large opening is provided in the housing of the gear unit for assembly, maintenance or for oil change. 
     In example embodiments, the cooling fins are aligned corresponding to the direction of the cooling airflow, in particular, the cooling fins being aligned in parallel relative to each other. This is advantageous in that the airflow is able to be developed in a suitable manner, in particular, an air-guide function is feasible. 
     In example embodiments, the input gear stage is a right-angle gear stage. This offers the advantage that a beveled housing is able to be provided, and therefore an improved air-guide function is achievable. 
     In example embodiments, an air-guide containment is provided around the gear unit. This is advantageous because the cooling airflow is able to be passed through between the gear housing and the containment, and thus very good utilization of the cooling airflow is attainable in an easy manner. In addition, further protection is attained for the gear housing, especially for bearing covers, screw plugs and/or oil drain plugs and the like. Such parts are therefore also practicable in plastic instead of steel or cast steel, since the containment may be realized from sheet steel, and thus a metallic protection is provided against the surroundings. 
     In example embodiments, the air-guide containment guides the cooling airflow and, together with the cooling fins and the housing of the gear unit, restricts it to the spatial area provided for the cooling airflow, so that in particular, the cooling airflow absorbs as much of the heat output of the gear unit as possible. Of advantage here is that the airflow is able to be guided such that the best possible cooling of the housing is attainable with the aid of the airflow. 
     In example embodiments, the air-guide containment has passages for the input and output shafts, as well as for the floor mounting of the gear unit, in particular, the air-guide containment moreover having an opening for a sensor. This is advantageous in that the openings are easily realizable, thus, do not have to be sealed off. 
     In example embodiments, a pipe is provided for conducting oil out of the gear-unit interior into the area of the cooling airflow, and a pipe for returning the oil to the gear-unit interior is likewise provided in the area of the cooling airflow, in particular, the pipes being disposed completely or at least partially in the cooling airflow generated by the fan impeller. The advantage in this case is that the oil of the gear unit may be cooled in an easy manner. In particular, the oil only has to be conducted out and in again in a pipe. 
     In example embodiments, the oil conveyed by the pipe for conducting oil out is fed to a plate cooler situated on the housing of the gear unit, especially in the cooling airflow, in particular, the pipe for returning the oil conveying oil from the plate cooler back into the interior of the gear unit. The advantage in this case is that improved heat dissipation is achievable; in particular, the plate cooler is able to be disposed in the cooling airflow and therefore is able to be cooled passively. The oil flow is in contact with the plate cooler for a very long time via a meander-shaped guideway formed in the plate cooler, and is therefore able to emit the greatest possible heat flow to the air. 
     In example embodiments, the spatial area of a shaft bearing disposed in an opening of the gear housing is bounded at least partially with respect to the interior of the gear unit by a delimiting device that has an opening for a shaft supported in the bearing, 
     the lowest point of the opening resulting in a minimum oil level in the spatial area of the bearing. The advantage is thus that in operation, a minimum oil level is ensured in the area of the bearings, and therefore they are well-lubricated. An oil level higher than this minimum oil level is allowed when the gear unit is in the state of rest, and is lowered during operation of the gear unit. The initial lubrication of the bearing is therefore very good, and nevertheless, losses during operation are able to be reduced. 
     In example embodiments, the spatial area is bounded at least partially by the gear housing. This is advantageous because the spatial area is the area of the bearing, which is to be delimited with respect to the gear interior only with the aid of the protection plate. 
     In example embodiments, the delimiting device is a protection plate or a ring. The advantage here is that an inexpensive and uncomplicated delimitation of the spatial area is attainable. 
     In example embodiments, the protection plate is welded or screw-connected to the housing. This is advantageous because a tight connection is able to be produced in an inexpensive and uncomplicated manner. 
     In example embodiments, the ring is provided in a groove, especially a groove going round in the circumferential direction in the housing of the gear unit. This offers the advantage that the minimum oil level is specifiable in an easy manner. It may be that when using such a ring, the protection against spraying oil is not so high as when using a protection plate, but the minimum oil level is reliably adjustable in an easy manner. 
     In example embodiments, the opening encircles the through-going shaft as closely as possible, especially with a clearance of less than 3 mm, particularly of less than 1 mm. 
     This is advantageous because the best possible protection against oil spraying on or oil foam is achievable. 
     In example embodiments, the protection plate is flat, in particular, covers the area of the opening for the bearing. This is advantageous because a simple sheet-metal stamping is usable, in which only the external contour and the openings for the passage of shafts, especially semicircular openings which are provided at the edge area of the protection plate, are necessary. 
     In example embodiments, the housing of the gear unit includes a lower and an upper housing part, the assembly of the gear unit being achievable very easily and inexpensively, 
     a protection plate which substantially surrounds the lower half of the shaft being attached to the lower housing part, 
     a further protection plate which substantially surrounds the upper half of the shaft being attached to the upper housing part. The advantage in this case is that a ring or a protection plate is able to be inserted especially easily. In the same manner, components such as bearings, shafts and gear wheels may be installed without difficulty, for they are easily inserted from above into the corresponding accommodation area. In the case of a ring, the accommodation area is a groove running in the direction of rotation. The protection plate, on the other hand, is insertable from above and is then able to be pressed onto the housing wall. After that, a welded connection and/or screw connection is possible. 
     In example embodiments, the bearings, especially the two bearings of the input shaft of the gear unit, are provided in a housing part, particularly in a substantially cup-shaped housing part, the housing part being screw-connected to a housing part of the gear unit. This offers the advantage that the fitting of the input shaft into a housing part is able to be prefabricated, thus, may be preassembled. Therefore, this unit, including the input shaft, its bearings and associated seal, are able to be stocked in the warehouse and may be installed easily and quickly. In particular, a series of gear units is also able to be produced, which offers great variance using few parts. Namely, the gear unit is realizable as a parallel shaft gear unit if the opening provided in the gear housing for the cup-shaped housing part is occluded and the input shaft is provided at an opening in the side wall of the gear unit. Alternatively, however, the right-angle gear stage may also be provided instead of the occluding part. Thus, a gear unit with input right-angle gear stage or input parallel shaft gear stage may be produced from the same basic housing. 
     In example embodiments, a first bearing is implemented as a bearing pair, a first interspace being formed in the axial direction between the paired individual bearings. This has the advantage that high transverse forces are able to be absorbed, and therefore a particularly stable gear unit is able to be produced. In particular, it is possible to use a pair of individual bearings, preloaded relative to each other, between whose outer rings an interspace is therefore produced. 
     In example embodiments, a second bearing in the axial direction is set apart axially from the first bearing, so that a second interspace is formed. This is advantageous because, again, high transverse forces are able to be absorbed. The greater the distance between the bearings, the higher the absorbable transverse forces. 
     In example embodiments, a first bearing of the input shaft takes the form of a pair of tapered-roller bearings, especially in an X-configuration, preloaded relative to each other, and a second bearing is in the form of a self-aligning roller bearing. This offers the advantage that an especially stable set-up, able to absorb transverse forces, may be produced. 
     In example embodiments, the first and/or second interspace is/are connected by one or more bores to the interior of the gear unit, particularly for the purpose of emptying. The advantage in this instance is that good lubrication is attainable with the gear unit at rest. To that end, it is advantageous to plan the oil level of the gear unit to be suitably high in the state of rest, or the position and the gradient of the bores to be suitably low. For a gear unit in operation, a minimum oil level is again able to be maintained in the interspaces by suitable determination of the height of the bores and of the gradient. In particular, bores without gradient are advantageously usable, as well. A further advantage of the emptying of the interspaces is that no great quantities of oil are present long-term on the input-side seal, and therefore the danger of an oil leak is reducible. 
     In example embodiments, the first and/or second interspace is/are connected by a gap to the interior of the gear unit, especially for the purpose of emptying, the gap being formed between the housing part, particularly the essentially cup-shaped housing part, and the housing part of the gear unit. This is advantageous because a passage for oil may be provided in an easy manner, thus permitting the interspace to be emptied without additional expenditure. 
     In example embodiments, a bore or one of the bores is a radial bore. This is advantageous because a simple and inexpensive bore may be provided for the emptying process. In particular, it may be disposed in the direction of gravity, so that especially effective emptying is achievable. However, to maintain a minimum oil level, a horizontal alignment of the bore is also advantageous. 
     In example embodiments, a bore or one of the bores is an axially directed bore. This is advantageous because emptying to the oil pan situated axially further inside is achievable with little effort. 
     In example embodiments, the radial bore is plugged at its outer end by a stopper. The advantage in this case is that not only is a simple and inexpensive radial bore sufficient for the purpose of emptying, but an access is also created to the area of the bearings. Therefore, sensors, e.g., for determining rotational speed of the input shaft, transverse force or axial force, or perhaps sensors for monitoring the functioning of the bearings, such as temperature sensors or structure-borne noise sensors, may also be disposed in the area of the bearings. The associated signal lines are able to be brought out without special effort through the radial bore and the suitably tightly closing stopper. 
     In example embodiments, an input shaft is sealed off by a shaft sealing ring from the housing part, especially the cup-shaped housing part. This is advantageous, because an oil leak is preventable. 
     In example embodiments, the level of the placement of the bore or of the gap for emptying an interspace determines a minimum oil level for the bearings of the input shaft. This offers the advantage that a minimum oil level may be maintained in an easy and inexpensive manner. 
     LIST OF REFERENCE NUMERALS 
     
         
           1  Housing part 
           2  Fan impeller 
           3  Cooling fins 
           4  Housing cover with cooling fins 
           5  Cooling fins of housing cover  4   
           6  Cooling fins on the beveled housing part 
           7  Output shaft 
           8  Beveled housing area for right-angle gear stage 
           9  Cooling fins 
           41  Rotating flange part, joined in rotatably fixed fashion to output shaft  7   
           42  Air-guide containment 
           50  Discharge pipe 
           51  Feed pipe 
           52  Plate cooler 
           53  Discharge pipe 
           60  Feed pipe 
           61  Feed pipe 
           62  Discharge pipe 
           70  Oil level during operation 
           71  Oil level during standstill 
           72  Bearing 
           73  Shell for bevel wheel 
           74  Shell for bevel pinion 
           80  Temporary storage 
           90  Lateral collection pockets 
           91  Drainage hole for bearing lubrication 
           92  Baffle plate 
           93  Oil-conducting channel 
           100  Pipe 
           101  Scraper 
           120  Gear wheel 
           130  Roof-shaped housing cover 
           131  Protection plate 
           132  Overflow 
           151  Housing cover 
           160  Gear housing 
           161  Gap 
           162  Self-aligning roller bearing 
           163  Gap 
           164  Bore 
           165  Housing part, cup-shaped 
           166  Tapered-roller bearings in X-configuration, preloaded relative to each other 
           167  Flange part 
           168  Shaft sealing ring 
           169  Interspace area between two tapered-roller bearings 
           170  Bore, radial 
           171  Stopper 
           172  Interspace area 
           173  Bore, axial 
       
    
     Example embodiments of the present invention are explained in detail with reference to the Figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a first gear unit according to an example embodiment of the present invention in a front view. 
         FIGS. 2 and 3  show the gear unit according to  FIG. 1  from two different viewing directions. 
         FIG. 4  shows a further gear unit of an example embodiment of the present invention in which, in contrast to  FIGS. 1 through 3 , a containment is additionally provided. 
         FIG. 5  shows a further gear unit of an example embodiment of the present invention having plate cooler  52 , which is attached to the housing of the gear unit. 
         FIG. 6  shows another gear unit of an example embodiment of the present invention, in which oil lines brought out from the gear interior and brought in again are shown. 
         FIG. 7  shows another gear unit according to an example embodiment of the present invention in a lateral view, in which a lateral surface is cut into, the level of the oil during operation and during standstill being illustrated. 
       To that end,  FIG. 8  also shows an oblique view in which conducting channels  93  and a collection pocket  90  can be seen, as well. 
         FIG. 9  shows the gear unit belonging to  FIG. 7  in a top view, thus, with a direction of view from above, that likewise is shown cut into, the cut being into the upper side. 
         FIG. 10  shows a scraper element belonging to the oil-delivery device. 
         FIG. 11  shows the scraper element in an oblique view. 
         FIG. 12  shows the scraper element in a top view. 
         FIG. 13  shows protection plates  132  against spraying oil. 
         FIG. 14  shows protection plates  132  separately, the plates being joined to the gear housing. 
         FIG. 15  shows a housing cover  151  which is roof-like. 
         FIG. 16  shows a horizontal cross-section through the input right-angle gear stage. 
         FIG. 17  shows a top view into a similar section. 
         FIG. 18  shows the view from a different viewing direction. 
     
    
    
     DETAILED DESCRIPTION 
     In the exemplary embodiment according to  FIGS. 1 through 3 , a fan impeller  2  is mounted in rotatably fixed manner on the input shaft. Thus, the fan impeller is operated with a suitably high rotational speed and generates a strong airflow with its fan-impeller blades when the gear unit is operated with the nominal speed. The higher the speed and the torque, the greater the power loss, thus, the heat output to be dissipated to the surroundings, as well. 
     The cooling airflow generated by fan impeller  2  is guided along a beveled housing area  8 . It is produced either by mounting suitably formed sheet-metal pieces and joining them to housing part  1 , or alternatively, by corresponding shaping of housing part  1 , which is possible without special additional effort particularly in the case of a right-angle gear stage to be provided as input. 
     In addition, cooling fins  6  are provided on beveled housing area  8 , and cooling fins  3  and  9  are provided on housing part  1 . 
     A housing cover  4  having cooling fins  5  is also provided on the housing part for assembly and maintenance purposes. 
     In this manner, it is possible to take optimal advantage of the cooling airflow. 
     Output shaft  7  is implemented on both sides, but in other exemplary embodiments, is also feasible on one side. 
     In  FIG. 4 , an air-guide part additionally provided on the gear unit, namely, an air-guide containment  42  is provided. In so doing, a passage for the input shaft and output shaft  7  is provided. In further contrast to  FIGS. 1 through 3 , output shaft  7  is joined in rotatably fixed manner to a rotating flange part  41 . 
     Air-guide containment  42  reduces the drift of the cooling airflow, and therefore leads to more efficient heat dissipation. It also serves as protection against dust deposits on the gear housing, and therefore protects the heat-transfer resistance from the gear housing to the cooling airflow against deterioration. 
     In addition, further parts or components to be cooled may be disposed between the gear housing and the air-guide containment, such as power electronics or cooling devices for cooling oil. The following figures describe exemplary variants for the latter. 
     In  FIG. 5 , attached to housing  1  of the gear unit is a plate cooler  52 , to which oil is fed from the gear interior via one or more feed pipes  50 , and is carried away via one or more discharge pipes  51 . Preferably, the plate cooler includes a base plate having a groove recessed in a meander form, a cover plate being mounted on the base plate. Thus, the oil must flow through the plate cooler in meandering fashion. Alternatively, straight bores may also be arranged in a base element and the oil conducted through the bores, deflection pieces being provided between the end areas of the bores on the base element. 
     On the rear side with respect to the side of the gear unit having the plate cooler, thus the side not visible in  FIG. 5 , a plate cooler  52  having the corresponding pipes may likewise be provided, so that a doubling of the cooling capacity is attainable. 
     Plate cooler  52  is omitted in  FIG. 6 . Feed pipes  60  and  61  are brought together and lead into discharge pipe  62 . Thus, the pipes are exposed directly to the cooling airflow, and particularly if oil flows through them slowly, sufficient cooling capacity may be attained, even without the expenditure of a cooling plate. 
       FIG. 7  shows that level  70  of the oil during operation is lowered compared to level  71  of the oil during standstill. Therefore, upon start-up of the gear unit, good lubrication is available immediately for all bearings, especially the bearings of the input gear stage or bearings  72  of one or more of the intermediate stages of the gear unit as well, since the oil level is so high that the bearings and gearing parts are situated sufficiently deep in the oil pan. Thus, good lubrication is present, even when the gear unit is started after long standstill times. 
     The input stage of the gear unit is arranged as a right-angle gear stage. To that end, provided on the input shaft is a bevel pinion which meshes with a bevel wheel. Churning losses are reduced by a shell  73  for the bevel wheel and a shell  74  for the bevel pinion, which in each case are provided about the lower half of these gearing wheels, for shells ( 73 ,  74 ) are formed such that at least in the area of shells ( 73 ,  74 ), the oil is substantially kept on a circular path during rotational movement of the gearing parts. Therefore, the inner area between the respective shell and gearing part is thus freed of oil, or at least the portion of oil is reduced substantially in this area. 
     Since shells ( 73 ,  74 ) basically surround only the lower half of the gearing parts, oil is only sprayed upwards. Therefore, during the flow-off impelled by gravity, the oil must cover long distances along the inner surface of the housing and/or along a delivery arrangement, which means good heat dissipation from the oil to the gear housing is attainable. At their lower side, shells ( 73 ,  74 ) have at least one opening, so that oil from the oil pan is able to flow back into the spatial area between shell ( 73 ,  74 ) and the gearing part. However, the opening is so small that the oil flow into the spatial area is at least five times or at least ten times less than the oil flow which the gearing part is able to convey out of the spatial area when the nominal speed of the input shaft is reached during operation. 
     Shells ( 73 ,  74 ) are preferably in the shape of a half torus. 
     As  FIG. 8  shows more clearly, with the aid of the oil-delivery arrangement described in greater detail below, during operation, oil is conveyed into a higher-situated temporary storage  80 , so that the oil level drops. Because of this lowering of the oil level during operation, it is possible to reduce the churning losses. That is to say, the gearing parts engage only slightly within the oil pan, in particular, the rapidly rotating gearing parts, such as the gearing parts of the input gear stage and one or more intermediate gear stages, dip less deeply or not at all into the oil pan. 
     Temporary storage  80  has leakages or small openings otherwise provided, so that the temporary storage is emptied automatically. The openings are provided such that the intended lowering of the oil level takes place during operation at nominal value, thus, the oil flow which streams into temporary storage  80  is greater than the oil flow which flows back from temporary storage  80  into the oil pan—at least so long as the oil level in the temporary storage is below a critical value. 
     Therefore, in operation, the temporary storage is thus filled with the aid of the oil-delivery arrangement, and consequently, with rising oil level in temporary storage  80 , the oil level in the gear unit is lowered, especially in the oil pan, so that the power losses are reduced. 
     During operation, the bearings and gearings are lubricated in a manner that the oil squeezed out of the engaging gearings and/or sprayed is caught with the aid of baffle plates  92  and drips off from them into oil-conducting channels  93  that fill lateral collection pockets  90 , from which at least a portion of the oil caught is supplied to the bearings to be lubricated and the gearing parts to be lubricated. 
     As  FIG. 9  shows, to that end, collection pockets  90 , situated on both sides in the gear unit, have drainage holes  91  for the bearing lubrication. The drainage holes discharge into bores in the housing, through which the oil is conducted to the bearing to be lubricated or via conducting channels to the respective gearing part to be lubricated. 
     Oil-conducting channels  93  are curved, so that a portion of the caught oil is conducted into a first, and another portion is conducted into the other collection pocket  90 . 
     Lubrication of the gearing parts and the bearings of the output shaft is not always necessary, since these gearing parts rotate slowly and consequently produce only negligible churning losses. Therefore, dipping of these gearing parts and bearings into the oil pan is not harmful. 
     Preferably, baffle plates  92  and oil-conducting channels  93  are attached to the upper side of the gear housing. 
     The drainage holes are positioned in collection pockets  90  in such a way, and the collection pockets are implemented such that the oil arriving first upon starting the gear unit is used to lubricate the bearings or gearing parts. Only when the caught oil flow exceeds this oil flow necessary for the lubrication is temporary storage  80  filled. 
     In a further exemplary embodiment, temporary storage  80  preferably has an adjustable overflow. To that end, an opening, envisaged in the horizontal direction, may be provided in a side wall of temporary storage  80  and may be covered by a sheet-metal cover part disposed in a manner allowing it to slide in the horizontal direction. The overflow level, and thus also the maximum volume of temporary storage  80 , is therefore adjustable by the sliding of the sheet-metal cover part. 
       FIG. 10  illustrates a further oil-delivery device that shows a scraper  101  which scrapes off oil at an end face of a gear wheel and pushes it into pipe  100 , from which lateral collection pockets  90  are able to be filled, as well. The previously described oil-delivery device, including oil-conducting channels  93 , is additionally effective. In this manner, oil moving along on the gear wheel and sprayed around by the gear wheel is thus able to be caught and used to lubricate bearings or to lower the oil level in operation. 
     Scraper  101  together with pipe  100  are shown separately in  FIG. 11 . Here, it is more apparent that the scraper has a V-shaped recess, at whose pointed end, a borehole is provided, into which pipe  100  leads. 
       FIG. 12  shows the placement of scraper  101  on gear wheel  120 . 
       FIG. 13  shows another gear unit in which, in contrast to the figures described above, instead of housing cover  4 , a housing cover  130  is provided that is roof-shaped. Therefore, oil dripping off from the inner side of this roof-shaped housing cover is able to be led away by oil-conducting channels  93  into collection pockets  90 . Thus, in this manner, it is not oil flung in the horizontal direction as in the case of the baffle plate, but rather oil flung in the vertical direction against the inner side of roof-shaped housing part  130  that is able to be caught and utilized. 
       FIG. 15  shows a housing cover  151  which is V-shaped, thus roof-shaped, the tip of the V pointing upward. In this case, the angle of the roof area, thus, the angle of the respective side of the V with respect to the horizontal is greater than 10°. Preferably, the angle is selected so that the drops sprayed onto the inside of the roof-shaped housing cover move downward laterally on the roof slope under the influence of gravity, in the course of which, they are bound adhesively to the roof, and then drip off into oil-conducting channels  93 . The angle is thus always selected so that the gravitational force is less than the adhesive force for drops sticking adhesively to the surface. In this context, the angle is also essentially a function of the surface tension between oil and housing cover  151 . 
       FIG. 13  also shows protection plate  131 , which is used to protect ball bearings from oil sprayed around or from oil foam driven in the direction of ball bearings. Protection plate  131  is sufficiently wide that even several ball bearings are protectable, especially the ball bearing of the input shaft, of an intermediate shaft and/or of output shaft  7 . Protection plate  131  is secured to the inner side of the housing, and is implemented with openings so large that the rotationally mounted parts belonging correspondingly to the respective ball bearings no contact with protection plate  131 . 
     In  FIG. 13 , a distance sleeve is mounted between the gear wheel and the associated ball bearing on the shaft to maintain a defined distance between the ball bearing and gear wheel. Thus, the distance sleeve is provided in an opening in protection plate  131 . 
     Protection plate  131  has an overflow  132 , so that oil from the oil pan arrives in the area of the protected ball bearings when the oil level of the oil pan is higher than the overflow, thus, especially the overflow edge. 
     Protection plate  131  is welded or screw-fitted to the inner side of the housing, so that the ball bearings are in oil. Especially also in operation, thus, when the oil level in the oil pan falls, there is still a minimum oil level around the ball bearing. In this case, it is also further advantageous that the oil supplied to the gearing parts with the aid of the delivery device accumulates in the spatial area around the ball bearing, which is at least partially bounded by protection plate  131 ; a flow-off of the oil is also provided when the minimum oil level around the ball bearing exceeds overflow  132 . 
     The implementation having protection plate  131  is shown in greater detail in  FIG. 14 . A lower and an upper protection plate  131  are used, the housing of the gear unit likewise being split into a lower and an upper housing part. Lower protection plate  131  is secured, especially screw-fitted, to the lower housing part, and upper protection plate  131  to the upper housing part, as shown in  FIG. 14 , or welded on, as in an alternative exemplary embodiment. 
     In an alternative exemplary embodiment, instead of protection plate  131 , a ring inserted in a groove is provided, which therefore defines an overflow with the aid of the lowest encompassed point. The ring, then, is not able to represent a substantial splash protection, but is able to realize the function of the overflow. 
     In a further exemplary embodiment, an aforementioned protection plate is used in the case of a first bearing, and the aforementioned ring is used in the case of another bearing. 
     In the exemplary embodiment according to  FIGS. 16 ,  17  and  18 , the input right-angle gear stage is shown in greater detail. It is implemented as a bevel-gear stage. 
     A cup-shaped housing part  165  is screw-fitted to gear housing  160  at the axial end, to which, in turn, a flange part  167  is screw-fitted, that accommodates a shaft sealing ring  168  which seals off the gear interior from the outer surroundings. 
     In cup-shaped housing part  165 , two tapered-roller bearings  166 , preloaded relative to each other, are provided in X-configuration, whose axial distancing from each other creates an interspace area  169 . This interspace area  169  is thus bounded by the two tapered-roller bearings  166  and cup-shape housing part  165 . 
     When the gear unit is not in operation, and therefore at high oil level, interspace area  169  is at least partially filled with oil, since it flows into it from the interior of the gear unit. During operation, the oil level of the oil pan in the gear unit is lowered. Interspace area  169  is emptied via a radial bore  170  which leads into interspace  169  and which is closed at its outer radial end by a stopper  171 . An axial bore  173  leads from radial bore  170  back into the interior of the gear unit. The positioning of the bores, especially the height provided relative to the oil pan, makes it possible to maintain a defined minimum oil level in interspace area  169 . The emptying of interspace area  169 , except for this minimum oil level, leads to a decrease in losses, since the bearings are then less surrounded by the oil. 
     A further interspace area  172  between tapered roller bearing  166 , situated axially further inside, and self-aligning roller bearing  162 , via which the input shaft is supported in cup-shaped housing part  165 , is emptied in analogous manner. For that purpose, radial bore  164  is provided, which opens through into an axially inwardly leading gap  163  that is situated between housing  160  of the gear unit and cup-shaped housing part  165 , and widens axially further inwardly into a gap  161 . 
     At its end area situated axially inside, the input shaft bears the bevel pinion, which meshes with a bevel wheel that is supported by bearings provided in housing  160  of the gear unit.