Abstract:
A pinion shaft bearing arrangement including a pinion shaft, which is mounted by means of at least two rolling bearings in a pinion shaft housing, the pinion shaft bearing housing being a bearing cartridge, having running surface formed on the inner circumference for the rolling elements of the rolling bearings. The pinion shaft housing is sealed in the direction of the pinion shaft by means of a sealing element, and a first lubricant channel is provided in the region between the rolling bearings and a second lubricant channel is provided in the region in front of the sealing element.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is the U.S. national stage application pursuant to 35 U.S.C. §371 of International Application No. PCT/EP2012/065808, filed Aug. 13, 2012, which application claims priority of German Application No. 102011082014.0, filed Sep. 1, 2011. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a pinion shaft bearing arrangement including a pinion shaft, which is mounted in a pinion shaft housing by means of at least two roller bearings, where the pinion shaft bearing housing is a bearing assembly with bearing surfaces, formed on the inner periphery, for the rolling elements of the roller bearings. 
       BACKGROUND OF THE INVENTION 
       [0003]    Such a pinion shaft bearing arrangement is used, for example, as a drive unit of a differential. In this case two drivable axles of for example, a motor vehicle are driven by the drive unit. Hence, the pinion shaft bearing arrangement is used for the final drive. For this purpose, the pinion shaft bearing arrangement is coupled, as well-known, directly or indirectly by way of an intermediate transmission to a drive unit, such as an internal combustion engine or an electric motor. 
         [0004]    Such a pinion shaft bearing arrangement is known, for example, from the German Patent No. 37 05 607 A1. In this case, the pinion shaft bearing arrangement includes not only the pinion shaft that bears the pinion, for example, a toothed bevel gear, but also a pinion shaft housing, in which the pinion shaft is rotatably mounted by means of two roller bearings, tapered roller bearings that are usually tightened against each other. Each roller bearing has an inner ring, seated on the pinion shaft, The outer ball races are formed by the pinion shaft housing itself, which for this purpose is formed as a bearing assembly, so that no separate outer rings are provided, In the case of the pinion shaft bearing arrangement known from the prior art German Patent No. 37 065 607 A1 a separate sealing sleeve is flange-mounted on the pinion shaft housing on the side facing away from the pinion. 
         [0005]    The sealing sleeve seals tightly, on the one hand, in the direction of the pinion shaft housing by means of a sealing element and, on the other hand, in the direction of the pinion shaft itself, respectively, a coupling sleeve, which is slid over said pinion shaft, by means of an additional sealing element, namely a lip seal. An additional sealing element seats tightly toward the housing of the differential. in order to make sure that the pinion shaft bearings are lubricated, a collecting groove is provided in the differential housing. When the differential gears rotate, the lubricant collects in said collecting groove, from which the lubricant flows into the area between to the two roller bearings by way of a duct, which initially extends radially in the differential housing and then extends radially in the pinion shaft housing. From this area between the two roller bearings the lubricant passes into the volume area, which is closed off by means of the flange-mounted sealing sleeve, behind the pinion shaft housing and flows back into the differential housing by way of a discharge duct, which is axially open at the rear section of the pinion shaft housing and which runs through and issues radially from the pinion shaft housing. The discharge duct in turn empties into a section of the duct that continues its course through the differential housing. The design of this pinion shaft bearing arrangement is very complex, in particular with respect to the lubrication, 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    The object of the present invention is to provide a pinion shaft bearing arrangement that is simplified compared to the above described state of the art. 
         [0007]    In order to solve this problem, the invention provides that the pinion shaft housing is tightly sealed in the direction of the pinion shaft by means of a sealing element and that a first lubricant duct extends into the region between the roller bearings; and a second lubricant duct extends into the region in front of the sealing element. 
         [0008]    The pinion shaft housing is sealed directly by means of a sealing element in the direction of the pinion shaft, be it either the shaft itself or a shaft component attached to said shaft. That is, the pinion shaft housing is extended, when viewed from the direction of the differential, beyond the rear roller bearings to such an extent that it is possible to integrate a sealing element in this region. The use of an additional component, such as a sealing sleeve or the like, which is arranged on the pinion shaft housing, is not necessary, because both the radial definition and axial sealing are provided solely by means of the one-piece pinion shaft housing in the form of the bearing assembly. 
         [0009]    Lubrication is provided by means of two lubricant ducts, where in this case a first lubricant duct also extends into the region between the two roller bearings. however, the second duct, which carries the lubricant away, extends directly into the region between the rear (when viewed from the direction of the differential) roller bearing and the sealing element, which is located downstream of said roller bearing and where the lubricant is received. This means that consequently the entire routing of the lubricant is accomplished exclusively in the self-supporting bearing assembly; and even more advantageous is the fact that additional components are not required for the pinion shaft bearing arrangement. 
         [0010]    In an embodiment, both lubricant ducts open out on the end face of the pinion shaft housing. That is, the lubricant is supplied directly at the end face. The same applies to the return flow into the differential housing. Thus, the lubricating oil enters into the feed duct in the region of the front side of the housing. Such an arrangement is easily possible, since sufficient lubricating oil is circulated in the housing when the differential is running, so that an adequate amount can always enter. Even the return flows again directly into the differential housing from the front side. 
         [0011]    However, as an alternative, it is also conceivable that the first duct, i.e., the feed duct, opens out on the peripheral surface; and the second duct opens out on the front side of the pinion shaft housing. Therefore, the first duct can open out radially or may have at least one radially emptying opening section. However, the second return duct ends in any event on the front side. However, the actual configuration, respectively routing of the ducts, depends ultimately on how the pinion shaft housing, i.e., the bearing assembly, is attached to the downstream component, for example, the differential. Hence, it depends on whether a small amount of radial installation space for forming a radially emptying feed duct is still provided or whether this feed duct is supposed to open out primarily on the front side. 
         [0012]    The lubricant bores are arranged circumferentially in such a way that they are offset by at least 45°, preferably by 90°, relative to each other; and, of course, a greater circumferential offset is conceivable, depending on the respective installation situation. 
         [0013]    The sealing element itself, by means of which the pinion shaft housing is tightly sealed toward the pinion shaft, is for example, a radial shaft sealing ring. This radial shaft sealing ring can seal either directly toward the pinion shaft or toward a tightening nut, by means of which the two roller bearings are prestressed. In this case the roller bearings, for example, tapered roller bearings, can be tightened either directly against the pinion, i.e., for example, the bevel gear. However, as an alternative, an adjusting washer can also be inserted in this area. 
         [0014]    The self-supporting bearing assembly is designed as a one-piece component. That is, the entire pinion shaft housing is defined only by the one component. For easy mounting it is expedient to form a radially extending mounting flange, by means of which the pinion shaft housing is screwed, for example, to the differential housing. From this mounting flange, a relatively short dimensioned axial section of the housing can still extend in the direction of the differential housing and can extend a ways into said differential housing, so that by implication it is also possible to provide, for example, a radially open inlet duct in this region. In any case, there is no need to provide any collecting grooves or ducts that extend into the differential housing itself, because the oil feed system, respectively the ducts run only in the pinion shaft housing, i.e., the bearing assembly, and communicate, for example, with the downstream differential. 
         [0015]    In an embodiment, a sensor element, in particular, a resolver, which interacts with the pinion shaft, can be arranged externally on the pinion shaft housing. The embodiment as a one-piece component makes it possible to provide externally a matching recess or the like, in which a sensor element can be arranged, because there is no need whatsoever to provide on the pinion shaft housing some kind of attachment point for a sealing sleeve and the like that would be restrictive in some way for the arrangement of an external component. This means that a radial recess, in which a sensor element can be used, for example, can be formed without difficulty. 
         [0016]    In addition to the pinion shaft bearing arrangement itself, the invention also relates to a drive system, having an electric motor with an outputting hollow motor shaft, a pinion shaft bearing arrangement of the type described above as well as a differential, which is driven by means of the pinion shaft, which is driven by the electric motor. In this case, the pinion shaft is arranged concentrically in the motor shaft; and the bearing assembly is tightly sealed and connected to a differential housing, enclosing the differential, by means of a sealing element. 
         [0017]    Such a drive system is used, for example, as a drive unit of a motor vehicle. it serves as a drive in electric vehicles or hybrid vehicles. The electric motor can drive the pinion shaft directly or by means of a transmission, which is downstream of said electric motor or is coupled to the pinion shaft, which in turn drives the differential, which then branches out to the driven axles. In the drive system according to the invention, the pinion shaft is now accommodated in the interior of the hollow motor shaft and can be rotated separately relative to the motor shaft. In this case the pinion shaft is moved, as stated, by means of the electric motor, the motion of which is coupled to said pinion shaft. The pinion shaft itself is coupled directly to the differential, That is, no transmission is interposed. Said transmission can be arranged, if such a transmission is to be provided, on the other side of the electric motor, so that the electric motor is positioned between the differential and the transmission. 
         [0018]    The pinion shaft housing of the pinion shaft bearing arrangement is supported directly by the differential housing, which accommodates the differential, respectively its corresponding components. That is, the pinion shaft housing is attached to the differential housing. This means that in this case a closed module is produced that is closed outwards, respectively toward the electric motor by means of the other two housings, i.e., the differential housing and the pinion shaft housing, both housing being connected to each other, As a result of this perfect seal, which is achieved by such an arrangement, the electric motor is consequently totally in the “dry” area. This means that there is absolutely no flow of lubricant into, respectively through the electric motor, because the differential housing and the pinion shaft housing completely define and limit the lubricant space required to lubricate the differential as well as the pinion shaft bearing. For this purpose suitable sealing elements, namely, on the one hand, the sealing element in the pinion shaft housing, where the sealing element seals toward the pinion shaft, as well as an additional sealing element, for example, an O-ring, which tightly seals the connecting interface between the pinion shaft housing and the differential housing, are provided. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    One embodiment of the invention is shown in the drawings and described in detail below. The drawings show in: 
           [0020]      FIG. 1  is a schematic sketch elucidating the principle of a drive system according to the invention; 
           [0021]      FIG. 2  is an enlarged detail view of the region between the electric motor and the differential with the pinion shaft bearing arrangement inserted in-between; 
           [0022]      FIG. 3  is a 90° sectional view of the pinion shaft bearing arrangement;  FIG. 4  is a longitudinal sectional view of the pinion shaft bearing arrangement; and, 
           [0023]      FIG. 5  is a perspective view of the pinion shaft bearing arrangement. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]      FIG. 1  is a schematic sketch elucidating the principle of an inventive drive system  1 , having an electric motor  2 , a differential  3 , a pinion shaft bearing arrangement  4  and a transmission  5  that may or may not be shown. 
         [0025]    Electric motor  2  includes motor housing  6 , stator  7  and rotor  8 , which is connected to hollow motor shaft  9 , which is rotated, therefore, by means of rotor  8  during normal operation. Motor shaft  9  extends into transmission  5 , for example, a shiftable transmission having a plurality of gear stages. 
         [0026]    Pinion shaft  10  of pinion shaft bearing arrangement  4  is driven by means of the transmission; and the pinion shaft (see  FIG. 1 ) runs through entire hollow motor shaft  9 . That is, it comes from transmission  5  and extends as far as into differential  3 . Pinion shaft bearing arrangement  4  includes not only pinion shaft  10  with the pinion, which in this case is configured as toothed bevel gear  11 , but also pinion shaft housing  12 , in which pinion shaft  10  is mounted by means of bearings, which are not shown in detail. This feature will be discussed in detail 
         [0027]    Finally, differential  3  includes differential housing  13 , in which, of course, not only central differential drive gear  14 , with which bevel gear  11  meshes, but also other additional components, in particular, outputting drive shafts  15  and the like are arranged. 
         [0028]    During normal operation, when stator  7  is supplied with current, rotor  8  and with it motor shaft  9  are rotated. The rotation of motor shaft  9  is given via transmission  5  translated to pinion shaft  10 , by means of which the differential operates due to bevel gear  11  meshing with differential drive gear  14 ; and output shafts  15 , which lead to corresponding drive axles, are rotated. 
         [0029]    It is clear that the result is a design, where electric motor  2  is also arranged to between differential  3  and transmission  5 , which, of course, can also be screwed directly to motor housing  6 . This means that the output end of motor shaft  9  in the illustrated embodiment runs to the right into transmission  5 , whereas pinion shaft  10 , which is driven by means of the transmission, runs through hollow motor shaft  9  back in the opposite direction into differential  3 , which may be found on the other side of electric motor  2 . 
         [0030]    As shown in  FIG. 1  and  FIG. 2 , pinion shaft housing  12  (which is shown in  FIG. 1  only as a simple sketch) is supported on differential housing  13 , respectively attached to the housing. it is clear from  FIG. 2 , which depicts a more concrete embodiment, that for this purpose pinion shaft housing  12  has radial flange  16 , which in the installed position rests axially against corresponding mounting section  17  of the differential housing  13  and is screwed there by means of connecting screws  18 . Differential housing  13  in turn is supported on motor housing  6 . 
         [0031]    For this purpose there are also mounting screws  19  that connect differential housing  13  to motor housing  6 . Therefore, the whole drive system is defined externally, with respect to electric motor  2  and differential  3 , by motor housing  6  and differential housing  13 . 
         [0032]    A key component is, as described above, pinion shaft bearing arrangement  4 . Pinion shaft  10  is rotatably mounted in pinion shaft housing  12  by means of two roller bearings  20 ,  21 . The roller bearings  20 ,  21  are axially secured relative to each other by means of tightening nut  22 , which is screwed on pinion shaft  10 . According to  FIG. 2 , the roller bearings are tightened against bevel gear  11 , but can also be tightened against an adjusting washer, which may be found between them. 
         [0033]    Pinion shaft housing  12  is designed as a one-piece bearing assembly, in which bearing surfaces  23 ,  24  for tapered rollers  25 ,  26  of two roller bearings  20 ,  21  are formed. This means that, save for two inner rings  27 ,  28 , there are no separate outer rings that have to be integrated. Rather, the roller bearing receives the self-supporting bearing assembly. 
         [0034]    Pinion shaft bearing arrangement  4  is tightly sealed in the direction of differential housing  13  by means of first sealing element  29  in the form of an O-ring. O-ring  30  is located in a corresponding receiving groove on the inner periphery of mounting section  17  of differential housing  13 ; and it seals radially in the direction of the outer periphery of pinion shaft housing  12  having a leading annular collar that engages with differential housing  13 . This means that a first sealing level is achieved in this region. A second sealing level is achieved by means of second sealing element  31  in the form of radial shaft sealing ring  38 , which seals between pinion shaft housing  12  and pinion shaft  10 , respectively, tightening nut  22 , which is securely mounted on pinion shaft  10 . That is, the result of this arrangement is a closed and sealed space that is formed, respectively defined, by the interior of differential housing  13  and pinion shaft housing  12 . 
         [0035]    This seal is necessary to ensure that entire electric motor  2  is arranged completely in the “dry” area, thus ensuring that no lubricating fluid, which is in the interior of differential housing  13 , can pass into the region of electric motor  2 . 
         [0036]    In order to ensure that not only differential  3  itself, but also roller bearing of pinion shaft housing  12  is lubricated by means of the lubricating fluid, for example, an oil, which may be found in differential housing  13 , two ducts, namely feed duct  32  and discharge duct  33 , are formed in pinion shaft housing  12  (see  FIG. 3 ). In the illustrated example, feed duct  32  opens out close to end face  34  of pinion shaft housing  12 . Therefore, the feed duct has an opening region on the front as well as a radial opening region, so that oil that is necessarily splashed about, respectively is conveyed, upon rotation of the differential components, can pass into feed duct  32 . Feed duct is designed in such a way that it extends obliquely in the direction of pinion shaft  10  and angles off toward the end. At the same time, this area is closed outwards by means of ball  35 . Feed duct  32  empties (see  FIG. 3 ) in the region between roller bearings  20 ,  21 , so that consequently any lubricating oil that is supplied in this way is introduced precisely into this region, in which it is needed. 
         [0037]    Discharge duct  33 , which opens out on end face  34  and is circumferentially offset preferably by 90° relative to feed duct  32 , runs as far as up into the region between second sealing element  31 , i.e., radial shaft sealing ring  38  and adjacent roller bearing  24 . In the assembled situation, discharge duct  33  extends in such a way that it extends virtually into the deepest region of pinion shaft housing  12 , where the lubricating oil collects, so that the lubricating oil can be discharged there. Hence, the lubricating oil is removed from a region “behind” second roller bearing  24 . Such an arrangement ensures a reliable lubrication of the pinion shaft bearing. At the same time it is ruled out that the lubricating oil can pass into the region of the electric motor, because the conditions for a perfect seal toward the electric motor side have been met, on the one hand, statically by means of O-ring  30  on the axial flange of the bearing assembly and, on the other hand, dynamically by means of radial shaft sealing ring  38 . Since it involves here a longitudinal sectional view, only discharge duct  33  can be seen. However,  FIG. 4  shows recess  36 , which is formed on the outside of pinion shaft housing  12 . The recess has a sensor element  37 , in the illustrated example, a resolver, hence, a rotary encoder. Rotary encoder interacts in a well-known manner with pinion shaft  10  and detects the rotation of the pinion shaft, so that corresponding signals can be directly picked off in this area. The resolver, which is also shown in the perspective view according to  FIG. 5 , extends, for example, by approximately 90°. Therefore, the resolver is a curved component which can be easily integrated, even though relatively little installation space is provided. Another advantage is that the resolver, which is disposed outside pinion shaft housing  12 , is also arranged in the dry area toward electric motor  2 , because, as described above, this region is completely sealed by means of sealing element  29  and  31 . 
         [0038]    As described above, transmission  5  is optional in this respect. If it is provided, then it may also be arranged with its housing directly on motor housing  6 . The transmission has its own lubrication. This means that no lubricant ducts extend from differential  3  to transmission  5 . In this case, the lubricant ducts would have to be routed necessarily through electric motor  2 . If no transmission  5  is available, it would be necessary to provide a direct meshing between motor shaft  9  and pinion shaft  10 , and this meshing would then be provided inside motor housing  6 . 
       List of Reference Numerals 
       [0039]      1  drive device 
         [0040]      2  electric motor 
         [0041]      3  differential 
         [0042]      4  pinion shaft bearing arrangement 
         [0043]      5  transmission 
         [0044]      6  motor housing 
         [0045]      7  stator 
         [0046]      8  rotor 
         [0047]      9  motor shaft 
         [0048]      10  pinion shaft 
         [0049]      11  bevel gear 
         [0050]      12  pinion shaft housing 
         [0051]      13  differential housing 
         [0052]      14  differential drive gear 
         [0053]      15  output shafts 
         [0054]      16  radial flange 
         [0055]      17  mounting section 
         [0056]      18  connecting screws 
         [0057]      19  mounting screws 
         [0058]      20  roller bearing 
         [0059]      21  roller bearing 
         [0060]      22  tightening nut 
         [0061]      23  bearing surfaces 
         [0062]      24  bearing surfaces 
         [0063]      25  tapered rollers 
         [0064]      26  tapered rollers 
         [0065]      27  inner ring 
         [0066]      28  inner ring 
         [0067]      29  sealing element 
         [0068]      30  O-ring 
         [0069]      31  sealing element 
         [0070]      32  feed duet 
         [0071]      33  discharge duct 
         [0072]      34  end face 
         [0073]      35  ball 
         [0074]      36  recess 
         [0075]      37  sensor element 
         [0076]      38  radial shaft seal