Abstract:
A camshaft adjusting device having improved lubricant management including adjusting gearing for adjusting the angular position of a camshaft is proposed, the adjusting gearing having an input shaft, which can be coupled to a crankshaft, an output shaft, which can be coupled to the camshaft and an adjusting shaft, which can be coupled to an actuator. The adjusting gearing defines a rotational axis and the gearing forms a gearing interior, in which the input shaft, the output shaft and the adjusting shaft are operatively interconnected. The camshaft adjusting device has a lubricant supply for supplying the gearing interior with a lubricant and the lubricant supply is designed to form a lubricant sump in the gearing interior, the sump being radially outwards situated relative to the rotational axis.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is the United States National Stage Application pursuant to 35 U.S.C. §371 of International Patent Application No. PCT/DE2014/200458, filed on Sep. 9, 2014 and claims priority to German Patent Application No. 10 2013 220 220.2 filed on Oct. 8, 2013, which applications are incorporated by reference in their entireties. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a camshaft adjusting device. 
       BACKGROUND OF THE INVENTION 
       [0003]    Camshaft adjusting devices are used for the adjustment of the angular position of the crankshaft relative to the camshaft of an internal combustion engine. Such camshaft adjusters typically comprise a drive member, which is coupled to the crankshaft by means of, for example, a chain or a belt; an output member, which is usually coupled to the camshaft in a torsion proof manner; and an adjusting shaft, which makes it possible to adjust an angular position of the output member relative to the drive member. 
         [0004]    The drive shaft, the adjusting shaft and the output shaft come into operative connection with each other in a transmission, so that the net result is mechanical friction in the transmission due to the bearing arrangements and the mutual engagement. In order to reduce the mechanical friction, it is customary to lubricate the transmission of the camshaft adjuster with oil. 
         [0005]    For example, the publication DE 10 2005 059 860 A1 discloses a lubricant circuit of a camshaft adjuster. In the lubricant circuit a lubricant is fed to the camshaft adjuster by way of the camshaft and is discharged again through the outlet ports that are located radially on the outside. In order to control the amount of lubricant in the camshaft adjuster and to avoid flooding the camshaft adjuster, it is proposed to form a flow element in a flow channel, which acts as a throttle or a diaphragm, in order to adjust the lubricant flow. 
       SUMMARY OF THE INVENTION 
       [0006]    The object of the present invention is to propose a camshaft adjusting device that exhibits an improved lubricant management. 
         [0007]    This engineering object is achieved by means of a camshaft adjusting device exhibiting the features disclosed in the patent claims. Preferred or advantageous embodiments of the invention will be apparent from the dependent claims, the following description and the accompanying figures. 
         [0008]    A camshaft adjusting device, which is designed, in particular, for an engine, especially for an internal combustion engine, of a vehicle, is proposed within the scope of the invention. Optionally, the camshaft adjusting device comprises a camshaft, wherein the camshaft is designed to control the valves of the engine. 
         [0009]    The camshaft adjusting device has a variator, wherein in this case it is particularly preferred that said variator be designed as a triple shaft transmission. The variator comprises an input shaft, an output shaft and an adjusting shaft. The input shaft can be coupled, for example, to the crankshaft of the motor by means of a chain or a belt. The output shaft is preferably coupled or can be coupled to the camshaft in a torsion proof manner. In particular, the input shaft forms a drive member; and the output shaft, an output member. In contrast, the adjusting shaft can be coupled or is coupled to an actuator. The actuator can be arranged with respect to the motor in such a way that it is rigidly mounted in the housing or can be arranged to rotate with said motor. The actuator may be implemented, for example, as a motor, in particular, an electric motor or as a brake. Optionally the camshaft adjusting device comprises the actuator. 
         [0010]    The variator is designed to adjust an angular position of the camshaft. In particular, the variator is designed to change the angular position of the camshaft relative to the angular position of a crankshaft of the engine. As an alternative or in addition, the variator is designed to adjust the angular position between the input shaft and the output shaft. By adjusting the angular position it is preferably possible to move the opening times and/or closing times of the valves of the engine in the direction of “early” or “late.” 
         [0011]    The variator, in particular, the input shaft and/or the output shaft and/or the adjusting shaft define(s) a common axis of rotation of the variator. 
         [0012]    The variator forms an internal gear chamber, wherein the input shaft, the output shaft and the adjusting shaft come into operative connection with each other in the internal gear chamber. In particular, the variator is designed as a summation transmission, wherein in this case it is particularly preferred that a rotary motion of the adjusting shaft be added to the rotary motion of the input shaft; and in this way the angular position is adjusted. 
         [0013]    The camshaft adjusting device, in particular, the variator, has a lubricant supply unit for supplying the internal gear chamber with a lubricant. In particular, the lubricant is designed as an oil, especially as a transmission oil. The lubricant supply unit is designed as a continuous supply unit, so that the lubricant is continuously supplied to and removed from the internal gear chamber. 
         [0014]    It is proposed within the scope of the invention that the lubricant supply unit be designed to form a lubricant sump, in particular, a lubricant jacket, which is disposed radially outside of the axis of rotation, in the internal gear chamber. In other words, the lubricant supply unit is dimensioned in such a way that the lubricant sump is formed in an annular space around the axis of rotation by the lubricant for lubricating the variator. It is particularly preferred that when the camshaft adjusting device is running, the lubricant sump be constant, in particular, in relation to the radial extension. In particular, the lubricant sump is designed so as to be speed independent of the radial expansion in the normal operating mode of the camshaft adjusting device, thus, for example, when the engine is running in idle or at higher operating speeds of the engine. In particular, when the system is running, the lubricant sump assumes a design specified target state that is speed independent. It is particularly preferred that the variator be designed in such a way that the input shaft, the output shaft and/or the adjusting shaft draw(s) lubricant from the lubricant sump and distribute(s) the lubricant in the internal gear chamber. 
         [0015]    As a result, the invention takes a different approach to supplying lubricant to the variator. In this case the lubricant supply unit ensures that during the normal operating mode there is always a radially external lubricant sump that makes sure that the variator is undersupplied and at the same time oversupplied with the lubricant. It is particularly preferred that when the camshaft adjusting device, in particular, the variator, is running, the lubricant sump is designed to be constant. 
         [0016]    In order to emphasize the inventive idea, it is claimed that the lubricant sump is formed due to flywheel forces, in particular, centrifugal forces that act on the lubricant. The centrifugal forces are generated by the rotation of the variator or parts thereof. It is particularly preferred that in the normal operating mode the variator rotates, on average, at an angular velocity that corresponds to the angular velocity of the input shaft and/or the output shaft. Rotating the variator at this average angular velocity has the effect of generating the centrifugal force, which in turn results in the lubricant sump being generated. 
         [0017]    In a preferred embodiment of the invention the lubricant sump is dimensioned in the radial extent in such a way that at least one sliding bearing point and/or at least one rolling bearing point and/or at least one engagement point between two of the three shafts is and/or are covered with lubricant, where in this case the three shafts are formed by the input shaft, the output shaft and the adjusting shaft. This design emphasizes the aspect that it is not absolutely necessary to arrange all of the friction relevant points in the variator in the lubricant sump, because the relative motion of the three shafts in relation to each other causes the lubricant to be drawn from the lubricant sump and to be distributed in the variator, in particular, in the internal gear chamber. The lubricant level and, thus, the radial position of the inner surface of the lubricant sump has to be selected, in particular, in such a way that, on the one hand, the transmission members and the bearing arrangements are sufficiently immersed in the lubricant sump, but, on the other hand, it is possible to avoid unnecessary churning losses due to a lubricant level that is too high. 
         [0018]    In a particularly preferred embodiment of the invention the lubricant supply unit comprises a lubricant feed line and a lubricant discharge line, where in this case the lubricant discharge line comprises a lubricant overflow, which defines the radial expansion of the lubricant sump in the direction of the axis of rotation. As a result, the lubricant overflow ensures that the internal gear chamber is not inundated with the lubricant. The lubricant overflow can be designed by choice, in particular, as one or more outlet ports out of the internal gear chamber, in particular, as an outlet gap out of the internal gear chamber. For example, the lubricant overflow is designed as at least one outlet port, oriented in the axial direction, out of the internal gear chamber. For example, in open systems, as used, for example, in chain drives, the lubricant overflow may lead into the chain case, so that the lubricant can flow out and can be returned there into the oil circuit. In closed systems, for example, in the case of belt drives, it is possible to provide, for example, return lines in the cylinder head of the motor. 
         [0019]    It is particularly preferred that the lubricant discharge line exhibit a lubricant outflow, where in this case the lubricant outflow is designed radially outside of the lubricant sump. The lubricant outflow ensures that, for example, the unwanted dirt particles or other impurities in the lubricant do not permanently settle in the internal gear chamber, but rather are removed from the radially external bottom of the lubricant sump through the lubricant outflow out of the internal gear chamber, in particular, are flooded out through the lubricant outflow. For example, the lubricant outflow may be implemented as one or more outlet ports, extending in the radial direction, and/or as one or more outlet ports, extending in the axial directions. It is particularly preferred that the variator comprise a plurality of outlet ports as the lubricant outflow, with the outlet ports being preferably distributed at regular intervals in the circumferential direction about the axis of rotation. Preferably an intermediate angle between the outlet ports of the lubricant outflow is selected so as to be smaller than 60°, in particular, less than 50°. The distribution in the direction of rotation makes it possible to achieve that the lubricant can run off automatically through the lubricant outflow when the variator has stopped running. On the one hand, this arrangement has the advantage that after the variator has been shut down for a prolonged period of time, no uncooled, and, as a result, viscous or sticky lubricant remains in the variator and/or that the lubricant does not accumulate in an angle segment of the variator, thus producing in this way an imbalance when the variator is started up again. 
         [0020]    In the configuration of the lubricant supply unit it is preferred that the volumetric flow rate QZ of the lubricant in the lubricant feed line be designed to be preferably on average greater than the volumetric flow rate QZ of the lubricant outflow, so that QZ&gt;QA holds true. In this way it is ensured that when the camshaft adjusting device is running, the lubricant accumulates in the internal gear chamber; and that the lubricant sump is formed. It is particularly preferred that the lubricant supply unit be adjusted in such a way that QA≦0.9*QZ holds true. The volumetric flow rates may be checked, for example, by means of a standardized test procedure; and, in so doing, a differential pressure of 5 bar and an oil viscosity of 30 cSt, for example, are reached. 
         [0021]    In addition, it is, however, preferred that the sum of the mass flows of the lubricant outflow QA and the lubricant overflow QU be preferably designed to be on average greater than or equal to the volumetric flow rate of the lubricant feed line QZ, so that QA+QU≧QZ holds true. In this way both the formation of the lubricant sump as well as its limit in the radial direction is ensured radially inwards in the direction of the axis of rotation. 
         [0022]    When viewed in terms of design, the lubricant feed line may be assigned a radius RZ; the lubricant outflow, a radius RA; and the lubricant overflow may be assigned a radius RU in relation to the axis of rotation. In order to form the lubricant sump in the manner described, it is preferred that RZ&lt;RU&lt;RA hold true. 
         [0023]    In the event that there are a plurality of ports in the lubricant outflow, the lubricant overflow and the lubricant feed line, an average radius is used; and this radius can be calculated, for example, according to the following formula: 
         [0000]        R =(1 /A )·∫ r·A ( r )· dr  
 
         [0000]    where
   R averaged radius, thus, RZ, RU or RA   A total area of the respective ports, thus, AZ, AU, AA   r radius as the distance from the axis of rotation   A(r) radius dependent area of the respective ports   
 
         [0028]    Taking into consideration the notations that have been introduced, but independently of the formula, it is preferred that the total area AZ of the ports of the lubricant feed lines into the internal gear chamber and the total area AA of the ports of the lubricant outflow out of the internal gear chamber satisfy the following relation: 
         [0000]        AA≦ 0.9 *AZ.    
         [0029]    Furthermore, it is preferred that the total area AZ of the ports of the lubricant feed lines into the internal gear chamber and the total area AU of the ports of the lubricant overflow out of the internal gear chamber satisfy the following relation: 
         [0000]        AU≧ 2.0 *AZ.    
         [0030]    In this case it is preferably assumed that the total areas form in each instance the size of the lubricant feed line and the lubricant outflow, respectively, with the size determining the volumetric rate of flow. 
         [0031]    In principle, the variator may be designed as a swashplate gear mechanism, an eccentric gear mechanism, a planetary gear unit, a cam gear mechanism, a multi-articulated gear mechanism or coupled gear mechanism respectively, a friction gear mechanism, a helical gear mechanism with a threaded spindle as the speed increasing stage or as a combination of individual designs in a multi-stage design. 
         [0032]    In a particularly preferred embodiment in terms of design, the variator is designed as a wave gear, where in this case said wave gear comprises a rolling bearing and a deformable steel bushing, which has external gear teeth and which is disposed on the rolling bearing. It is particularly preferred that the lubricant sump be installed in such a way that the rolling bearing with the outer ring, but not with the inner ring, and/or the steel bushing is and/or are immersed at least in sections in the lubricant sump. In this preferred embodiment the rapidly rotating component, i.e. the inner ring, of the rolling bearing, is kept out of the lubricant, so that the lubricant sump is not disrupted by churning losses. However, it is ensured by the immersion of the outer ring or the steel bushing that sufficient lubricant is fed to the rolling bearings and, as a result, also to the inner ring. 
         [0033]    In particular, it should hold true for the radius of the inner ring Ri in relation to the radius RU of the ports of the lubricant overflow: 
         [0000]        Ri≦ 0.9 *RU.    
         [0034]    In a specific embodiment of the invention it is provided that the lubricant is fed through the axially extending passage ports in the camshaft, with said passage ports terminating in the radius RZ in the internal gear chamber. Furthermore, it is preferably provided that the lubricant outflow is designed as a plurality of outlet ports, which extend in the axial direction and which are located at the level of the outermost region of a bearing arrangement between the input shaft and the output shaft in the internal gear chamber. Furthermore, it is preferably provided that the lubricant overflow is designed as a plurality of outlet ports or as a circumferential, preferably continuous lubricant gap, with said outlet ports or lubricant gap being disposed with respect to the radius RU between the inner ring and the outer ring of the rolling bearing. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0035]    Additional features, advantages and effects of the invention will become apparent from the following description of preferred exemplary embodiments of the invention as well as the accompanying figures, in which: 
           [0036]      FIG. 1  is a schematic diagram of a camshaft adjusting device according to one exemplary embodiment of the invention; 
           [0037]      FIG. 2  is a cross-sectional view of the variator of the camshaft adjusting device in  FIG. 1 ; 
           [0038]      FIG. 3  is the same view as in  FIG. 2  the variator with a lubricant sump; 
           [0039]      FIG. 4  is an alternative embodiment of the variator in  FIG. 2 ; and, 
           [0040]      FIG. 5  is a plan view of the variator in  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0041]      FIG. 1  shows in a diagrammatic representation a camshaft adjusting device  1  for an engine, in particular, an internal combustion engine of a vehicle, as a first exemplary embodiment of the invention. The camshaft adjusting device  1  comprises a camshaft  2 , which has a plurality of cams  3 , which are designed to actuate the valves of the engine. 
         [0042]    The drive of the camshaft  2  is provided by way of a drive gear  4 , which is coupled to a crankshaft (not shown) of the engine by means of a chain, a belt or a transmission. A variator  5  is interposed between the drive gear  4  and the camshaft  2 . Said variator allows an angular adjustment of the camshaft  2  to be effected in a controlled fashion relative to the drive gear  4  and, as a result, relative to the crankshaft (not shown). In order to control the variator  5 , this variator is coupled to an electric motor  6  by means of a motor shaft  13 , which is arranged so as to be stationary relative to the variator  5 . That is, said motor shaft does not rotate along with said variator. 
         [0043]    The camshaft adjusting device  1  comprises a lubricant supply unit  7 , which introduces, starting from an oil pan or more specifically an oil tank  8 , transmission oil as a lubricant into the camshaft  2  through a motor oil pump  9  and optionally a motor oil filter  10  by means of a rotary transmitter (not shown) for oil. The lubricant is fed through a lubricant feed line  11  from the camshaft  2  into the variator  5 , in order to lubricate the variator  5  and is then discharged again from the variator  5  through a lubricant discharge line  12 , so that the lubricant supply unit  7  is designed as a lubricant circuit. 
         [0044]      FIG. 2  shows the variator  5  in a cross-sectional view taken along an axis of rotation D, which is defined, for example, by the camshaft  2  or the motor shaft  13  ( FIG. 1 ). 
         [0045]    The variator  5  is also designed as a so-called wave gear (also called a harmonic drive gear). The wave gear  5  is also referred to as an ellipto-centric gear or in English a strain wave gear (SWG). The variator  5  has an input shaft  14 , which is coupled in a torsion proof manner to the drive gear  4  or is formed by this drive gear. Furthermore, the variator  5  has an output shaft  15 , which is connected to the camshaft  2  in a torsion proof manner. In contrast, an adjusting shaft  16  is connected to the motor shaft  13  in a torsion proof manner. The adjusting shaft  16  has a generator section  17 , which has a cross section that is perpendicular to the axis of rotation D and which is designed so as to be not round, in particular, is designed to be elliptical. A rolling bearing  18  is disposed on said generator section in such a way that the inner ring  19  of the rolling bearing  18  rests on a shell surface of the generator section  17 ; and the outer ring  20  bears a deformable, cylindrical steel bushing  21  with external gear teeth. The steel bushing  21  is also referred to as a flex spline. The steel bushing  21  is designed with a cross section, which is perpendicular to the axis of rotation D, and is designed elliptical as well. 
         [0046]    The input shaft  14  bears internal gear teeth  22 , which mesh with the external gear teeth of the steel bushing  21 . Even the output shaft  15  bears internal gear teeth  23 , which also mesh with the external gear teeth of the steel bushing  21 . By rotating the adjusting shaft  16  at an angular velocity that is different from the angular velocity of the input shaft  14  it is possible to adjust the input shaft  14  and the output shaft  15  in terms of the angular position to each other. Such a harmonic drive gear is also described, for example, in the publication DE 10 2005 018 956 A1. 
         [0047]    The input shaft  14 , the output shaft  15  and the adjusting shaft  16  come into operative connection in an interaction region  28  in a radius RG by means of the internal gear teeth  22 ,  23  and the external gear teeth of the steel bushing  21 . In addition, the variator  5  has a sliding bearing section  24  in a radius RL between a carrier of the internal gear teeth  23  of the output shaft  15  and the input shaft  14 . 
         [0048]    The variator  5  forms an internal gear chamber  25 , which is formed by the input shaft  14 , on the one hand, by a supporting member  26  and, on the other hand, by a cover  27 , where in this case the rolling bearing  18  and the interaction region  28  of the external gear teeth of the steel bushing  21  and the internal gear teeth  22  and  23  are disposed in the internal gear chamber  25  of the sliding bearing section  24 . 
         [0049]    The lubricant feed line  11  comprises one or more axially oriented outlet ports  29 , which are arranged on an end face S of the output shaft  15  at a distance RZ from the axis of rotation D. The outlet ports  29  are supplied with lubricant through the channels in the camshaft  2 . In the normal operating mode the lubricant issues from the outlet ports  29  and is distributed in the internal gear chamber due to the rotation of the output shaft  15 , where in this case the end face S acts as a lubricant guide surface. The lubricant is fed through the outlet ports  29  into the internal gear chamber  25 . 
         [0050]    The lubricant discharge line  12  is divided into a lubricant outflow  30  and a lubricant overflow  31 . The lubricant outflow  30  is located at a distance RA from the axis of rotation D. The lubricant overflow  31  is disposed at a distance RU from the axis of rotation D. 
         [0051]    The outlet ports  29 , the lubricant outflow  30  and the lubricant overflow  31  as well as the distances RA, RZ and RU are dimensioned in such a way that a lubricant sump  32  is formed in the internal gear chamber  25 , as is shown in a highly schematic form in  FIG. 3 , superimposed on the cross sectional view of the variator  5 . It can be seen that the lubricant sump  32  extends from the radial outer side of the internal gear chamber  25  up to a radially outer edge of the lubricant overflow  31 . The sliding bearing section  24  as well as the interaction region  28  of the internal gear teeth  22 ,  23  and the external gear teeth of the steel bushing  21  and the outer ring  20  of the rolling bearing  18  are disposed in this region of the lubricant sump  32 . Thus, by generating the lubricant sump  32  it is ensured that both the sliding bearing section  24  and the interaction region  28  are supplied with sufficient lubricant. In contrast, the inner ring  18  is arranged outside of the lubricant sump  32 , in order to avoid unnecessary churning of the lubricant. 
         [0052]    If the volumetric flow rates of the lubricant supply unit  7  are taken into consideration, then the volumetric flow rate QZ of the lubricant feed line  11  is adjusted by the configuration of the outlet ports  29  and other flow-relevant components in such a way that said volumetric flow rate is always less than or equal to the volumetric flow rate of the lubricant discharge line  12  that is made up of the volumetric flow rate QA of the lubricant outflow  30  and the volumetric flow rate QU of the lubricant overflow  31 . 
         [0053]    In particular, it is provided that the volumetric flow rate QA of the lubricant outflow  30  is less than the volumetric flow rate QZ of the lubricant feed line  11 . In this way it is ensured in the normal operating mode that, first, the lubricant sump  32  is filled until it reaches the radially outer edge of the lubricant overflow  30  and then flows out with certainty, so that an overflow of the internal gear chamber  25  is prevented. This arrangement achieves the objective that when the variator  5  is running, the radial expansion of the lubricant sump  32  is always constant, irrespective of the angular velocity of the input shaft  14 . 
         [0054]      FIG. 4  shows an additional exemplary embodiment of the variator  5 , where, in contrast to the exemplary embodiment in the preceding figures, the lubricant outflow  30  is divided into two different axial outflow ports, with one of the outflow ports being disposed in the supporting member  26  and the other outflow port being disposed in the cover  27 . The flow of the lubricant is indicated in schematic form by the arrows. 
         [0055]      FIG. 5  shows a plan view of the variator  5 , in order to illustrate the external ports of the lubricant discharge line  12 . The lubricant outflows  30 , which are provided as passage ports out of the internal gear chamber  25 , for example, into a chain case of the motor, can be seen in the circumferential direction. An intermediate angle beta is provided in each instance between the passage ports of the lubricant outflows, so that the internal gear chamber  25  may idle when the variator  5  is shut down. In contrast, the lubricant overflow  31  is designed as an annular gap between the cover  27  and a circular collar of the generator section  17 . 
         [0056]    The variables of the variator  5  satisfy preferably at least one condition or any selection of the following conditions or all of the following conditions:
       RZ&lt;RU&lt;RA.   RA≧1.00*RG and/or RA≧1.00*RL, in particular, RA≧1.05*RG and/or RA≧1.05*RL.   QZ&gt;QA, preferably 0.9*QZ&gt;QA.   The total area AA of the ports of the lubricant outflow  30  is less than the total area of the AZ of the outlet ports  29  of the lubricant feed line  11 , in particular, AA≦0.9*AZ holds true.   The total area AU of the ports of the lubricant overflow  31  is greater than the total area of the AZ of the outlet ports  29  of the lubricant feed line  11 , in particular, AU≧2.0*AZ holds true.   QU&gt;QZ−QA, where QZ=QA+QU holds true.   Ri≧1.0*RU, preferably Ri≦0.9*RU.       
 
       LIST OF REFERENCE NUMERALS 
       [0064]      
         [0000]    
       
         
               
               
             
           
               
                   
               
             
             
               
                 1 
                 camshaft adjusting device 
               
               
                 2 
                 camshaft 
               
               
                 3 
                 cam 
               
               
                 4 
                 drive gear 
               
               
                 5 
                 variator 
               
               
                 6 
                 electric motor 
               
               
                 7 
                 lubricant supply unit 
               
               
                 8 
                 oil tank 
               
               
                 9 
                 motor oil pump 
               
               
                 10 
                 motor oil filter 
               
               
                 11 
                 lubricant feed line 
               
               
                 12 
                 lubricant discharge line 
               
               
                 13 
                 motor shaft 
               
               
                 14 
                 input shaft 
               
               
                 15 
                 output shaft 
               
               
                 16 
                 adjusting shaft 
               
               
                 17 
                 generator section 
               
               
                 18 
                 rolling bearing 
               
               
                 19 
                 inner ring 
               
               
                 20 
                 outer ring 
               
               
                 21 
                 steel bushing 
               
               
                 22 
                 internal gear teeth 
               
               
                 23 
                 internal gear teeth 
               
               
                 24 
                 sliding bearing section 
               
               
                 25 
                 internal gear chamber 
               
               
                 26 
                 supporting member 
               
               
                 27 
                 cover 
               
               
                 28 
                 interaction region 
               
               
                 29 
                 axially oriented outlet ports 
               
               
                 30 
                 lubricant outflow 
               
               
                 31 
                 lubricant overflow 
               
               
                 32 
                 lubricant sump 
               
               
                 D 
                 axis of rotation 
               
               
                 QA, QU, QZ 
                 volumetric flow rates 
               
               
                 RA, RZ, RO, RG, RL 
                 radii 
               
               
                 AA, AZ, AU 
                 total areas