Abstract:
A lubrication system is provided for a planetary gear train. The system includes an oil supply that disperses oil to a thrust bearing. The thrust bearing purges the oil radially outward. A strategically placed molded cavity collects and channels the oil from the thrust bearing into the planet bearings. Features in a planet gear carrier and a planet gear face washer can form the oil flow path. The washer can have a further feature for expelling the oil after the planet bearings are lubricated. By using the planet gear end face washer, this arrangement allows for the cavity to be cast rather than machined to thereby reduce the cost of increasing the flow of oil into the planet bearings.

Description:
TECHNICAL FIELD 
     The present invention generally relates to planetary gear trains, and more particularly to a lubrication system utilizing molded oil capturing and channeling features. 
     BACKGROUND OF THE INVENTION 
     Planetary gear trains are supplied with a lubricant such as oil to reduce friction as well as provide protection from wear of components that come into relative contact such as gear teeth and bearing surfaces. Additionally, the lubricant is an acceptable medium to remove heat from such components. Increasing the cooling by increasing the volume of oil through a bearing increases the maximum speed of the bearing. 
     In most planetary gear train applications, the planetary gears have the highest rotational speed. Due to this fact, it is most critical to adequately lubricate the rolling elements or planetary bearings to allow the planetary gears to rotate freely. In applications where the planet rotational speed is relatively low, a passive manner of lubricating the planet bearings is adequate. However, when either the relative speed or the load is high, some designs employ a forced lubrication scheme and inject lubricant into the planetary bearings under pressure. Still others employ a combination of the two foregoing techniques by employing channels that collect the oil and then distribute the oil to the planetary gear system by using the centrifugal force on oil leaving a rotating component. Some such prior art designs utilize features to collect and/or distribute the oil that are machined into a carrier for the planet gears. 
     Any feature that can be cast and not require machining reduces both material and machine time cost. In view of the foregoing, it should be appreciated that it is desirable to provide a lubrication system for collecting and distributing lubricant for planetary gears that utilizes molded oil collection and molded oil channeling or distributing features. This permits a lower system cost than if either or both of these features required machining. 
     Increasing the amount of lubrication to the planet bearings also enables a reduction in size and weight of the planetary gear set. Furthermore, additional desirable features will become apparent to one skilled in the art from the foregoing background of the invention and the following detailed description of the preferred exemplary embodiments and the appended claims. 
     SUMMARY OF THE INVENTION 
     A planetary gear train has a plurality of planet gears rotatably mounted in a carrier. The planet gears mesh with a sun gear. Thrust bearings enable the rotation of the sun gear. Planet gear bearings are positioned between each planet gear and its associated journal pin to enable the rotation of the planet gear around the journal pin. 
     In accordance with the teachings of the present invention, a lubrication system is provided for the planetary gear train which includes an oil supply that disperses oil to the thrust bearings. Each thrust bearing purges the oil radially outward. Strategically placed molded cavities collect and channel the oil from the thrust bearings to the planet bearings. Features in the planet gear carrier and planet gear face washers can form these cavities. By using the planet gear face washers, this arrangement allows for the cavities in the carrier to be cast features, thereby reducing the cost of increasing the flow of oil into the planet bearings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will hereinafter be described in conjunction with the appended drawing figures, wherein like reference numbers denote like elements. 
         FIG. 1  is a cross-sectional view of one-quarter of a planetary gear train without the ring gear. 
         FIGS. 2A  and B are detail drawings of the washer used at planet gear end faces. 
         FIG. 3  is a frontal view of the planetary gear train with the sun gear and the end housing removed but including the ring gear. 
         FIG. 4  is an enlarged view of a molded oil collection cavity on one side of the structure of  FIG. 1 . 
         FIG. 5  is an enlarged view of a molded oil collection cavity on another side of the structure of  FIG. 1 . 
         FIG. 6  is a front view of the carrier for the planetary gear train. 
         FIG. 7  is a side view of the carrier of  FIG. 6 . 
         FIG. 8  is a Section A-A of  FIG. 7  showing the placement of washers on the housing flange of the carrier. 
         FIG. 9  is a Section B-B of  FIG. 7  showing the placement of washers on the carrier flange of the carrier. 
         FIG. 10  is a Section A-A of  FIG. 7  having a housing flange oil inlet cavity of an alternative shape. 
         FIG. 11  is a Section B-B of  FIG. 7  having a carrier side oil inlet cavity of an alternative shape. 
         FIG. 12  is a Section A-A of  FIG. 7  having a housing side oil inlet cavity of another alternative shape. 
         FIG. 13  is a Section B-B of  FIG. 7  having a carrier side oil inlet cavity of another alternative shape. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following detailed description of preferred exemplary embodiments of an apparatus of the invention is not intended to limit the scope of the invention. 
       FIG. 1  is a cross-sectional view of one-quarter of an epicyclical planetary gear train  10  with the ring gear removed to promote easier understanding of the structure depicted by the drawing. Helical planetary gear train  10  is typical of prior art gear trains only in the manner of transmitting mechanical power through the gears. More specifically, gear train  10  includes central sun gear  12  that rotates about longitudinal central axis  14 . Sun gear  12  meshes with four planet gears  15 , one of which is shown in  FIG. 1 . Each planet gear  15  is mounted in planet carrier  16  by means of a journal pin  18  in a manner such that each planet gear  15  is driven by sun gear  12  to rotate independent from any other planet gear  15  in a known manner. Each planet gear  15  rotates about the associated journal pin  18  with minimal friction due to a full complement bearing set that employs cylindrical roller bearings  20  that contact both the inner diameter  19  of planet gear  15  and the outer diameter  22  of journal pin  18 . Sun gear  12  is capable of operation in the range from 0 to 12,000 revolutions per minute in either direction. Thus, gear train  10  is suitable for high-speed applications. 
     Input shaft  23  is connected to sun gear  12  by splines such as spline  24  or any other suitable connection method. Shaft  23  is driven by a source (not shown) such as an alternating current (AC) induction electric motor. Shaft  23  rotates sun gear  12  in either a clockwise or a counterclockwise direction manner about central axis  14 . The rotation of the sun gear drives each planet gear  15  that rotates about each journal pin  18 . Sun gear  12  is contained axially by thrust bearings  25  and  26 . Bearings  25  and  26  serve as friction reducing devices for the axial thrust loading upon sun gear  12  due to the action of meshing helical gears  12  and  15 . End housing  28  supports thrust bearing  25  at sun gear end face  29 . Planet carrier  16  supports the other thrust bearing  26 . 
       FIG. 2A  is a detailed drawing of washer  30  that encircles pin  18  and abuts planet gear end faces  21  and  32 . Washer  30  includes outer circle  31  and inner circle  33 . Washer  30  includes oil inlet feature or scallop  34  and an oil outlet scallop  36  into circle  33  and anti-rotation tang  38  extending from outer circle  31 . Outlet scallop  36  is 180° from inlet scallop  34 .  FIG. 2B  is a section A-A of  FIG. 2A  showing that scallops  34  and  36  extend through washer  30  and that tang  38  bends to be at a 90 degree angle with respect to the other portion of washer  30 . 
       FIG. 3  is a frontal view of entire planetary gear train  10  with the sun gear and end housing removed to promote clarity of what is shown. Ring gear  42  includes teeth  44  extending around the inner surface thereof which mesh with planet gears  15 . Ring gear  42  is mechanically grounded through the use of splines  46  to a non-rotating gear train housing (not shown) so that the ring gear is stationary with respect to central axis  14 . With the ring gear  42  stationary, planet gears  15  therefore orbit about central axis  14  causing the planet carrier  16  to also rotate about central axis  14  in the same direction or same sense. Carrier  16  is the output component of gear train  10  and carrier  16  transmits its motion to some other component through the use of some suitable mechanical connection such as output splines  48 . Reference number  45  designates the carrier thrust bearing pilot. 
     A lubrication system for high-speed planetary gear system  10  facilitates lubrication and cooling of planet gear bearings  20 . Planet gears  15  tend to rotate at higher speed than any of the other components of gear train  10  and thus are most in need of lubrication and cooling. More particularly, a fresh supply of oil from a source (not shown) originates in the center of hollow input shaft  23  as shown in  FIG. 1 . Oil exits input shaft  23  through cross-drilled radial channel  52  and end  54  of shaft  23 . A single or multiple channel(s)  52  can be utilized based upon lubrication volume requirements. Oil is propagated through channel  52  and end  54  by the centrifugal forces generated by the rotation of the input shaft  23 . This oil is directed toward and passes through axial thrust bearings  25  and  26 . As the oil leaves thrust bearings  25  and  26 , it continues outward with 360° of radial velocity due to the centrifugal force imparted upon the oil from the rotation of bearings  25  and  26 . 
       FIG. 4  shows a magnified view of “housing side” flange  58  included in circle  60  of  FIG. 1  which includes a portion of housing  28 . A majority of the oil from thrust bearing  25  is collected by cavity  62  at each planet gear. Cavity  62  is created by cast features in planet carrier  16  and the assembly including planet gear  15  and end face washer  30 . Referring to  FIG. 5 , the other or “carrier side” flange  78  of planetary gear train  10  includes output spline  48 . Oil from thrust bearing  26  is contained between sun gear end face  66  and planet gear end face  21 .  FIG. 5  shows a magnified view of the structure included in circle  68  of  FIG. 1 . Oil from bearing  26  is collected by cavity  70  which is surrounded by cast features in planet carrier  16  and assembly of planet gear  15  end face washer  30 . The volume of the oil collected by cavity  70  can be approximately equal to the volume of the oil collected by cavity  62 . 
     Additionally, cavities  62  and  70  capture oil that is ingested into the mesh between sun gear  12  and the planet gears  15 . The hand of helix of sun gear  12  can be either right or left and the rotation thereof can be either clockwise or counterclockwise. Also, the direction of the torque can be either from sun gear  12  to the planet gears  15  or from the planet gears  15  to the sun gear  12 . The hand of sun gear  12 , the sense of its rotation and the direction of the torque determine whether the side of gear train  10  having end plate  28  or the side having carrier  16  collects the oil. 
     At each end face of planet gear  15 , the collected oil is then funneled into its respective planetary bearing  20  by centrifugal forces and the funnel contour of the cast cavities. This oil enters the planet bearing at the point where washers  30  are located by journal pin  18 . Washers  30  each have an inlet scallop  34  strategically placed at its inner diameter where the cast carrier feature will funnel the oil. This reduces the restriction created by the otherwise close fitting design of washers  30  with journal pin  18  if washers  30  did not include inlet scallop  34 . The oil then is passed through and lubricates and cools planet bearing rollers  20 . 
     At end  58  of planetary gear train  10 , the oil is expelled from planet bearing  20  by means of outlet scallop  36  on the inner diameter of washer  30  and cast feature  72  of  FIG. 1  residing on the outboard side of the planet carrier. Feature  72  also engages tang  38  of washer  30  to hold washer  30  stationary. A similar feature  74  on the other side  78  of the planet gear locks washer  30  into place and is not designed to be a primary source for expelling the lubricant from the planet bearing  20 . Outlet scallop  36  on washer  30  at planet end  21  is blocked by the design of locking cavity  74 . As a result, oil from cavity  70  tends to flow over the surface  22  of journal pin  18  toward exit  72  to lubricate and cool roller bearings  20  and pin  18 . The positions of cast features  72  and  74  could be interchanged but it is important that only one of cavities  72  and  74  allow oil flow to force lubrication of all of bearings  20 . 
       FIG. 6  is a front view of sides  58  and  78  of carrier  16 . This view shows the relationship of spline  48  and scalloped oil exit  54  from the end of input shaft  23  to central axis  14 .  FIG. 6  also shows the relationships of carrier side inlet cavities  70 , oil exits  72 , washer locking cavities  74  and holes  80  for engaging pins  18 . 
       FIG. 7  shows a side view of planet carrier  16 .  FIG. 7  includes Section lines A-A and B-B. Cross members  82  hold carrier  16  together so that non-rotating pins  18  can be maintained in alignment for instance. Dashed lines show many of the previously described features on  FIG. 7 . 
       FIG. 8  shows Section A-A of  FIG. 7 , which depicts the relationships of central axis  14 , housing side oil inlets  62 , oil exit cavities  72 , holes  80  and cross member  82 . Oil inlets  62  are bio-concave or crescent shaped. As planet carrier  16  rotates, each strategically shaped cast cavity  62  collects 90° of the oil that is not lost through the clearance  64  between housing  28  and planet carrier  16  for each respective planet gear  15 . The angle of oil collected is equal to 360 degrees divided by the number of planets. Thus, 360 degrees of oil is collected regardless of the number of planets.  FIG. 8  shows Section A-A with washers  30  included. Inlets  62  funnel the oil toward strategically placed cavities  72  which extend under scallop  36  of washer  30  to surface  20  of journal pin  18  so that the oil exits through  72  and is collected by a housing (not shown). The oil is then directed to a sump by the housing in a known manner. The oil is then returned by a pump through shaft  23  in a known manner. Sun gear  12 , planets  15  and spline  48  as indicated in  FIG. 3  determine the diameter of circle  71 . 
       FIG. 9  shows Section B-B of  FIG. 6 , which depicts the relationships of central axis  14  to pilots  45 , output spline  48 , carrier side inlet cavities  70 , washer locking cavities  74  and cross members  82 . The arrangement and substantially semi-circular cavities  70 , in addition to the rotation of planet carrier  16 , is such that for each one of four planet gears  15 , cavities  70  capture approximately 85° of the radial flow of oil from thrust bearings  26 . The other 5° are used as piloting feature  45  of axial thrust bearing  26  between sun gear  12  and planet carrier  16 .  FIG. 9  shows washers  30 . Features  71  indicate oil-blocking portions of features  74 . 
       FIG. 10  is a Section A-A of  FIG. 7  having a housing side inlet cavity of an alternative substantially triangular shape  92  which is formed by straight edges straight lines forming a funnel toward holes rather than the curved edges of  62 . 
       FIG. 11  is a Section B-B of  FIG. 7  having carrier side inlet cavities  70  of an alternative shape  94  which are also formed by straight lines forming funnels toward washer oil inlet ports. 
       FIG. 12  is a Section A-A of  FIG. 7  having a shaped housing side inlet cavities  62  of another alternative triangular shape  96 . 
       FIG. 13  is a Section B-B of  FIG. 7  having carrier side inlet cavities of another alternative shape  98  that taken together substantially form a substantially square outline or shape. Feature  100  show the portion of carrier  16  that block oil even though washers  30  have outlet scallop  36 . Alternatively outlet scallops  36  could perhaps be removed from washers  30  used on carrier flange  78  in some applications. 
     Thus, the above-described embodiments facilitate reduction in the costs associated with increasing the lube flow to a planet gear roller bearings  20  through the use of cast features. Such cast features are employed in conjunction with other already used components such as face washers having strategically placed inexpensive features or scallops in place of machined features. Such embodiments enable an increase in the speed rating of planet gear roller bearings  20  by increasing the cooling that results from increasing the volume of oil through bearings  20 . 
     While the preferred exemplary embodiments have been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that these preferred exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing a preferred embodiment of the invention. It is understood that various changes may be made in the function and arrangement of elements described in an exemplary preferred embodiment without departing from the spirit and scope of the invention as set forth in the appended claims.