Abstract:
This invention details a lubrication system for an automatic transmission, specifically the bearings of the planetary pinion gears. The planetary carriers have grooves formed in spider and flange sections thereof to carry the lubricating material from the inner diameter of the planetary carrier to the inner diameter of each pinion gear bearing mounted in the planetary carrier. The invention further includes two thrust washers that are assembled on opposing sides of each pinion gear that have axially and radially extending slots that further carry the oil between the inner diameter of the planetary carrier and the outer diameter of the planetary carrier. Lastly, the invention discloses a method for lubricating the pinion gears of the planetary carrier.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application 60/555,141 filed Mar. 22, 2004. 
     
    
     TECHNICAL FIELD  
       [0002]     This invention relates to a means of lubricating a hybrid electro-mechanical transmission, and more particularly the pinion gear bearing components of the planetary carrier.  
       BACKGROUND OF THE INVENTION  
       [0003]     Power transmissions require oil or other lubricating materials to carry away thermal energy dissipated by the power transmission components. This is especially true for electromechanical transmissions having an electric motor housed inside the transmission. The lubricating oil originates in an oil reserve and is directed by a pump that distributes the oil centrifugally throughout the transmission. The operating temperatures of the bearing components supporting the planetary gear loads can be of considerable concern. To ensure sufficient lube oil flow to the intended internal components, the transmission design has to be carefully considered to provide sufficient oil flow to components along the entire length of the transmission.  
         [0004]     An electro-mechanical transmission is described and commonly assigned U.S. Provisional Ser. No. 60/531,528 entitled “Two-Mode Compound-Split, Hybrid Electro-Mechanical Transmission Having Four Fixed Ratios,” Schmidt et al., filed Dec. 19, 2003 and hereby incorporated by reference in its entirety.  
       SUMMARY OF THE INVENTION  
       [0005]     The present invention is a hybrid electromechanical automatic transmission with a lubrication system that provides the appropriate cooling to the planetary carrier and its components. More specifically, this invention includes a supply of lubricating oil (or transmission fluid), which travels through the main shaft of the transmission from the reservoir and towards the planetary carrier. The main shaft has radial apertures to direct the lubricating oil from the main shaft towards the planetary carrier. A sun gear shaft, which encircles the main shaft and receives the lubricating oil from the main shaft, is also included. The sun gear shaft has radial apertures as well to direct the lubricating oil towards the planetary carrier. A seal and/or bushing is included between the sun gear and the main shaft and is operative to support the sun gear and substantially prevent the lubricating oil from flowing away from the planetary carrier.  
         [0006]     The planetary carrier assembly consists of the planetary carrier, several pinion gears, pinion bearings and thrust washers. The planetary carrier is made of a spider and flange section, which encase the pinion gears. Thrust washers are on both sides of the pinion gears to react any thrust loading. The spider section has an annular machined groove (or first groove), which catches and directs the lubricant into a pocket which abuts a radially extending formed groove (or second groove) at the inner most diameter of the planetary carrier. A first thrust washer—containing both radially and axially extending grooves—receives the lubricating oil and directs the lube oil towards the pinion bearings. After flowing along the pinion bearings, a second thrust washer—located adjacent to the flange section of the planetary carrier—transfers the lubricating oil from the planetary carrier. This ensures that the majority of the lube oil is used for pinion bearing lubrication.  
         [0007]     In one aspect of the present invention, the grooves in the planetary carrier are formed in the planetary carrier by a powder metallurgy process. However, in another aspect of the invention at least one groove in the planetary carrier is machined into the carrier.  
         [0008]     In another aspect of the invention, the apertures in the main shaft and sun gear shaft are designed to be small enough to maintain a predetermined pressure level in the planetary carrier cavity while being large enough to permit the passage of the lubricating material.  
         [0009]     Finally, the invention includes a method of lubricating the planetary carrier. The steps of the method include: directing a lubricating material from a supply in the transmission to the main shaft; further directing the lubricating material from the main shaft to the sun gear shaft which has radially extending apertures through which the lubricating material can flow; directing the lubricating material through the apertures of the sun gear shaft to a planetary carrier having a grooved spider section and a grooved flange section; receiving the lubricating material from the interior of the sun gear shaft in the grooves of the spider section of the planetary carrier; directing the lubricating material along the grooves in the spider section of the planetary carrier to a first thrust washer having an axial slot; receiving the lubricating material; carrying the lubricating material through the axial slot in the first thrust washer into the pinion bearing; directing the lubricating material across the pinion bearings to a second thrust washer located at the flange side of the planetary carrier which has an axial slot for receiving the lubricating material from the pinion bearing; directing the lubricating material received from the pinion bearings through the axial slot in the second thrust washer to a groove in the flange section; and carrying the lubricating material away from the planetary carrier through the groove in the flange section of the planetary carrier and onto other transmission components.  
         [0010]     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a block diagram for directing lubricating material through an automatic transmission to sufficiently cool the pinion bearings of the planetary carrier;  
         [0012]      FIG. 2 a  fragmentary cross-sectional view of the planetary carrier taken along one side of the centerline of the front portion of the electro-mechanical transmission to schematically show oil flow to and through the planetary carrier;  
         [0013]      FIG. 3  is a front view of a thrust washer;  
         [0014]      FIG. 4   a  is a front or face view of the grooved flange section of the planetary carrier showing five grooved areas for receiving a thrust washer like in  FIG. 3 ;  
         [0015]      FIG. 4   b  is a cross-sectional side view of the planetary carrier partially in elevation; and  
         [0016]      FIG. 4   c  is a front or face view of the grooved spider section of the planetary carrier showing five grooved areas for receiving a thrust washer like in  FIG. 3 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]     Referring to the drawings,  FIG. 1  schematically illustrates a method for directing lubricating material through an automatic planetary transmission to sufficiently cool the pinion gears of the planetary carrier. First, the lubricating material (oil or other reasonably appropriate transmission fluids) is supplied to the transmission at step  110  through an inlet on the exterior of the transmission housing where the lubricating material is then directed from the supply to the inner diameter of the main shaft at step  112 . Next, the lubricating material is directed from the main shaft to the interior of the sun gear shaft at step  114  where the oil travels along the sun gear and its neighboring components. From the sun gear the oil is directed to the spider section of the planetary carrier at step  116 . The planetary carrier, being configured with machined and formed grooves, receives the lubricating material and directs the lubricating material into the grooves of the spider section at step  118 . Next, the oil is directed into the axial slots ( 56  shown in  FIGS. 1, 2  and  3 ) of the first thrust washer ( 50 ) at step  120 . From the first thrust washer the lubricating material is directed axially and radially to the pinion bearings and the spindle of the pinion gear to specifically cool that area of the planetary carrier at step  122 . The oil is then directed to a second thrust washer ( 62 ) at step  124 , which directs the oil axially through axial slots  56  in the thrust washer to the flange section ( 28  shown in  FIGS. 1,2 ,  4   a  and  4   b ) of the planetary carrier at step  126 . The oil is then directed radially outward, at step  127 , through grooves ( 65  shown in  FIG. 4   a ) in the flange section  28 . Finally, the oil is dispersed to components adjacent to the planetary carrier ( 16 ) at step  128  and directed back to the sump (or supply) to repeat the process at  112 .  
         [0018]     The lubricating material  10  is directed through the transmission by pressurizing the inner cavity of the transmission. In the preferred embodiment, a pump (not shown) sends the lubricating material  10 , as shown in  FIG. 2 , from a source at 30 p.s.i. to the inner diameter of the main shaft  12 . To maintain the desired pressure level, the transmission components are designed to nest substantially close with respect to each another. This significantly seals the connection between the components and prevents the lubricating material  10  from flowing in unintended areas. For example, in  FIG. 2 , the sun gear  14 —adjacent to the planetary carrier  16 —rests on a bushing  18  and steel sleeve  20  that substantially prevent the lubricating material  10  from flowing away from the planetary carrier  16 . Therefore, the bushing  18  and steel sleeve  20  help to maintain the desired pressure level in the vicinity of the planetary carrier  16  so that the lubricating material  10  can successfully reach the pinion bearings  22  of the pinion gears  24 .  
         [0019]     The planetary carrier  16  consists of at least one pinion gear  24  (three of the five are shown in  FIG. 4   b ) and a two-piece housing defined by a spider section  26  and a flange section  28  which are sintered brazed together. The face of the spider section  26  of the planetary carrier  16  is shown in FIG.  4   c . The spider section  26  contains cylindrical openings  29  to receive posts  30  which add stiffness and strength to the planetary carrier  16  to react the pinion bearing  22  loading.  FIG. 4   a  shows the face of the flange section  28 , which is the more frontward portion of the planetary carrier  16 . The flange section  28  contains splines  32 , which connect the planetary carrier  16  to the main shaft  34 , as shown in  FIG. 2 , and transmit power to the rear of the transmission (not shown).  
         [0020]     As shown in  FIG. 2 , the planetary carrier  16  is designed so that the pinion gears  24  are in a drivable relationship with a sun gear  14  and ring gear  36 . Together, the three gear types ( 14 ,  24  and  36 ) encircle the main shaft  34  of the transmission and through engagement with clutches (not shown) determine the output speed of the transmission. One technical advantage of this invention is in the redesign of the spider section  26  and flange section  28  of the planetary carrier  16 . The spider section  26  of the planetary carrier  16  has five grooved areas, each having a first and second groove formed therein ( 38  and  40  respectively). The grooves  38 ,  40  have several functions including, directing the lubricating material  10  from the inner diameter of the planetary carrier  42  to the pinion bearings  22  at the inner diameter of the pinion gears  44 .  
         [0021]     Each first groove  38 , as shown in  FIG. 4   c , is concave, facing the inner diameter of the planetary carrier  42  so as to receive lubricating material  10  from the sun gear  14  and sun gear shaft  15 . The first groove  38  is also segmentally annular, extending about the inner diameter of the planetary carrier  42  in each first groove. The first groove  38  is intersected by a second groove  40 , which extends radially to intersect the first groove  38  and radially along the grooved spider section  26  of the planetary carrier  16  to transfer the lubricating material  10  into a first pocket  46 . In the preferred embodiment, the second groove  40  is formed in the spider section  26  of the planetary carrier  16  by an alteration to the die (not shown) of the planetary carrier  16 . Formed by a powder metallurgy process, the planetary carrier  16  is constructed with a die having a protrusion defining the second formed groove  40 . Powder metallurgy was chosen because the process is ideal for parts with irregular curves or for small recesses that are difficult to machine. Moreover, the process reduces the amount of material waste since the intricacies of the part can be included in the die instead of being sculpted from a blank through a series of machining processes.  
         [0022]     Still, powder metallurgy has its limitations. The intricacies of the die must be such that the part is removable from the die. For this reason, in the preferred embodiment, the first groove  38  was machined into the spider section  26  of the planetary carrier  16 . The first groove  38  was designed to intersect the second groove  40  (as shown in  FIG. 4   c ) and transfer the lubricating material  10  radially into the first pocket  46  where a first thrust washer  50  will aid in directing the lubricating material  10  into the pinion bearings  22 . The intersection between the first groove  38  and second groove  40  forms a shoulder at  52 , which acts as a dam to substantially prevent oil from escaping the pinion area of the spider section  26  of the planetary carrier  16 . The second groove  40  leads to and defines the first pocket  46  that extends radially to the inner diameter the pinion gear  44  where an axial slot  56  in the first thrust washer  50  receives the lubricating material  10 .  
         [0023]     Adjacent to the first pocket  46  is the first thrust washer  50 , which is better shown in  FIG. 3 . The first thrust washer  50  has radially extending slots  54  (or conned depressions) spanning across the face of the first thrust washer  50 . The radially extending slots  54  in the first thrust washer  50  serve to direct the lubricating material  10  toward the first pocket  46 , as shown in  FIG. 2 . In the preferred embodiment, the thrust washer  50  also has axial slots  56  (or notches), shown in  FIGS. 2 and 3 , which, along with groove  40 , carry the lubricating material  10  to the spindle  58  and bearings  22  of the pinion gear  24  where the spindle  58  is supported or press fit into the carrier bore  59 . Moreover, the first thrust washer  50  also has a flanged edge  60 . The flanged edge  60  extends axially into the radially extending flange slots  61  of the spider section  26  and functions to keep each washer from rotating with respect to the spider section  26  of the planetary carrier  16  by nesting in the spider section  26  at  61  (as shown in  FIGS. 2 and 4   c ).  
         [0024]     From the first thrust washer  50 , the lubricating material  10  is directed to the pinion bearings  22 . The pinion bearings  22 , as shown in  FIG. 2 , are aligned axially along the spindle  58 . The pinion bearings  22  act to provide support for the pinion gear  24 . Since the pinion gears  24  are in a drivable relationship with the ring gear  36  as well as the sun gear  14 , the pinion bearings  22  see a substantial amount of loading during operation of the transmission. Therefore, this area requires lubrication for cooling to enhance the lifecycle of the pinion bearings  22 .  
         [0025]     Also shown in  FIG. 2 , a second thrust washer  62  is attached to the pinion gear  24 . Each second thrust washer  62  has radially and axially extending slots similar to  54  and  56  shown in  FIG. 3 . The slots of the second thrust washer  62  are operative to direct the lubricating material  10  axially away from the spindle  58  of the pinion gear  24  through axial slot  56  and towards a third groove  64  formed in the flanged section  28  of the planetary carrier  16 . The second thrust washer  62  also has a flanged edge  60  which nests in the flange section  28  at  65  (as shown in  FIG. 4   a ). From each third groove  64 , the lubricating material  10  exits the planetary carrier  16  and is directed to other transmission components (not shown) for cooling and is eventually returned to the transmission sump for reuse.  
         [0026]     The configuration of transmission components adjacent to the planetary carrier  16  also assists in directing the lubricating material  10  to the spider section  26  of the planetary carrier  16  and into the pinion bearings  22 . The sun gear shaft  15  for example, which encircles the main shaft  34 , has at least one radially extending aperture  68  to direct the lubricating material  10  from the inner diameter of the main shaft  12  to the sun gear  14  and eventually the spider section  26  of the planetary carrier  16 . The sun gear shaft  15  is attached to the sun gear  14  by a section of splines  70  between the sun gear  14  and sun gear shaft  15 . The sun gear  14  is adjacent to a thrust bearing  72 , which further restricts the passage of the lubricating material  10  away from the planetary carrier  16  and its pinion gears  24 . Moreover, the main shaft  34  is fitted with apertures like  74  that extend radially and direct the lubricating material  10  from the inner diameter of the main shaft  12  to the outer diameter of the main shaft  76 . The apertures— 68  and  74 —are designed to be large enough to permit the passage of the lubricating material  10  but small enough to maintain the pressure in the cavity of the planetary carrier  16 . Lastly, the ring gear  36  also has a radially extending aperture  78  to permit the lubricating material  10  to exit the planetary carrier  16 .  
         [0027]     While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.