Abstract:
An assembly for a hydraulically actuated automatic transmission comprising a balance dam, a carrier partially enclosing the balance dam, and a pinion shaft secured to the carrier having a fluid passage interconnecting the balance dam and an outer surface of the pinion shaft. Fluid exiting the passage is used to lubricate a bearing supported on the pinion shaft.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates generally to the field of planetary gear sets for automatic transmissions. More particularly it pertains to supplying pressurized hydraulic lubricant to bearings that support pinions on a pinion carrier assembly.  
         [0002]     In automatic transmissions disclosed in the prior art, a planet carrier assembly of a front gear set is mated to a balance dam piston assembly of a forward clutch by an external spline formed on the carrier. Fluid overflow from the balance dam enters the forward clutch assembly without entering or flowing through the gear set. A needle bearing, located on the pinion shaft, is lubricated from a plastic lube deflector, which catches fluid flung radially by centrifugal force from a nearby axial thrust bearing assembly.  
         [0003]     It is preferred that both the balance dam and a pinion shaft lube feed source be integrated into one part, such that hydraulic fluid flows through the pinion shaft needle bearing before entering the clutch pack. This action reduces the number of components and allows a simplified assembly process. In addition, overall transmission lash can be reduced by eliminating the spline between the balance dam and carrier, thereby eliminating a potential leak path between the pinion shaft and lube deflector.  
       SUMMARY OF THE INVENTION  
       [0004]     The integrated carrier-balance dam assembly of the present invention is applicable to any transmission design having a planet carrier adjacent to a hydraulically actuated clutch assembly. It requires no piston in the balance dam. By combining the balance dam and carrier, it simplifies the assembly procedure and eliminates lash produced by a spline connection between previously mated components.  
         [0005]     The external diameter of the carrier contains a seal that defines the outer balance point for the dam. The planet pinion carrier contains cross drilled pinion shafts, which are open to the fluid between a forward clutch piston and the carrier. The balance exit point for the oil dam fluid is defined by the radial location of the drilled pinion shaft holes. By orientating the radial drilled pinion shaft hole, the balance exit point is variable, thereby allowing flexibility in clutch balance.  
         [0006]     To eliminate any restriction through the pinion needle bearings during clutch stroke, additional fluid exit holes are added at a lower radial dimension.  1 o The assembly provides a direct lube feed source for the pinion shaft and ensures that the shafts are always completely full of oil.  
         [0007]     It requires no separate oil dam assembly to retrieve oil radial spun from a nearby axial thrust bearing. Because the feed path of the pinion shafts is within the sealed balance cavity, the potential leak path between the pinion shaft and lube deflector of the previous design is eliminated.  
         [0008]     Because the integrated planet carrier and balance dam assembly of this invention simplifies the assembly operation, it reduces the overall cost of the assembly. Substantially all of the hydraulic fluid exiting the balance dam flows through the needle bearings on the carrier before exiting the carrier. The rate of pressurized fluid flow to the pinion needle bearings increases as a function of rotational speed of the pinions, due a centrifugal pressure head.  
         [0009]     An assembly for a hydraulically-actuated automatic transmission includes a balance dam, a planet carrier, and pinion shafts, each secured to the carrier and formed with a fluid passage that interconnects the balance dam and an outer surface of the pinion shaft. Fluid exiting the balance dam passes through ports in the carrier, into the passages, to the outer surface of the pinion shafts where it lubricates a bearing supported on each pinion shaft. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0010]     The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment when considered in the light of the accompanying drawings in which:  
         [0011]      FIG. 1  is a cross-section taken through a plane of a portion of automatic transmission for a motor vehicle showing the integrated carrier-balance dam according to this invention;  
         [0012]      FIG. 2  is a cross-section similar to that of  FIG. 1 , but taken at a diametric plane, showing the carrier and its components in greater detail;  
         [0013]      FIG. 3  is a perspective view of the servo hub;  
         [0014]      FIG. 4  is a perspective view of a carrier plate;  
         [0015]      FIG. 5  is a perspective view of a Belleville spring; and  
         [0016]      FIG. 6  is cross-section through a diametric plane of a pinion shaft. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0017]     Referring first to  FIG. 1 , a planetary gear set  10  for an automatic transmission, of the type used in a motor vehicle, includes a sun gear  12  formed on the stator  14  of a hydraulic pump, a ring gear  16  secured to an input shaft  18 , a carrier  20 , and a set of planet pinions  22 , each pinion supported on the carrier for rotation about the axis of a pinion shaft  24 . The opposite axial ends of each pinion shaft  24  are secured to the carrier  20 . A needle bearing  26 , located on the outer surface of each pinion shaft  24 , supports a planet pinion  22 .  
         [0018]     A hub  30 , supported on the stator  14  for rotation, includes four legs  32 , angularly space about a longitudinal axis  34  of the assembly. The hub  30  is driveably connected to a plate  34  of the carrier  20  at a spline  36 , and the axial position of the hub is secured to plate  34  by a snap ring  38 . Carrier  20  includes a second plate  40 , which is spaced axially from plate  34  by four legs  42  that extend axially and are angularly spaced about axis  34 .  
         [0019]     A hydraulically actuated clutch  44 , such as the forward clutch of an automatic transmission, alternately produces a drive connection between the carrier  20  and an intermediate shaft  46  when clutch  44  is engaged and releases the drive connection when the clutch is disengaged. A clutch cylinder  50  is secured at a welded connection  52  to the hub  30 , which is secured to the carrier  20 . Intermediate shaft  46  is secured to a hub  54  of clutch  44  at a welded connection  56 . Clutch  44  includes multiple spacer plates  58 , splined to the inner surface of the clutch cylinder  50 , and multiple friction discs  60 , splined to the outer surface  62  of the clutch hub  54 . A blocker ring  64 , secured to the cylinder  50 , limits the range of motion of the friction discs  60  and spacer plates  58  in the axial direction when clutch  44  is engaged.  
         [0020]     Clutch  44  is actuated by a hydraulic servo that includes a piston  66 , which is located for axial displacement within cylinder  50 . Servo hub  30  is formed with a fluid passage  70 , through which hydraulic fluid is supplied to a volume  68  of cylinder  50  in order to displace piston  66  rightward into engagement. Servo hub  30  is also formed with a fluid passage  75  through which hydraulic fluid is supplied to a balance dam  74  located on the opposite side of the clutch piston  66  from the cylinder volume  68 .  
         [0021]     Piston  66  is formed with a surface  72 , which partially encloses the balance dam  74 , and the carrier plate  34  is formed with a surface  76 , which partially encloses the balance dam. A Belleville spring  78 , located within the balance dam  74 , includes an outer ring that bears against the piston  66  and radial fingers  80  that are secured against displacement at their radially inner end. The Belleville spring  78  resists axial displacement of piston  66  rightward from the position shown in  FIG. 1 , and it restores the piston to the position shown in  FIG. 1  when hydraulic pressure in cylinder volume  68  is vented.  
         [0022]     An O-ring  82 , fitted within a recess at the radial outer surface of carrier plate  34 , provides an elastic, dynamic seal at piston surface  72  against the passage of hydraulic fluid as the pistons moves relative to the carrier  20 . Another O-ring  84 , fitted in a recess on the outer surface of piston  66 , seals cylinder volume  68  against the passage of hydraulic fluid between the piston and cylinder  50 . Similarly, O-ring  86 , fitted in a recess formed in the radial inner surface of piston  66 , seals against the passage of hydraulic fluid between piston  66  and the servo hub  30 .  
         [0023]     Each pinion shaft  24  of the carrier  20  is formed with an axial passage portion  90  and a radial passage portion  92 , which extends radially outward from the axial passage portion. Each pinion shaft  24  is secured to the carrier plates  34 ,  40 , preferably by deforming the ends of each pinion shaft radially outward into engagement with the carrier plates. Carrier plate  34  is formed with multiple exit ports  94 , each port aligned with a pinion shaft  24  such that the balance dam  74  is continually open to the passages  90 ,  92  of the pinion shaft  24 . Each radial passage  92  has an exit port at the outer surface  96  of the pinion shaft  24 , which port allows hydraulic fluid from the balance dam to flow continually through the pinion shaft  24  to the needle bearings  26 . The angular position of the radial passages  92  can be adjusted about the axis of the respective pinion shaft  24  in order to adjust the balance forces on the piston  66 .  
         [0024]     In operation, when clutch cylinder volume  68  is pressurized, piston  66  moves rightward in cylinder  50  against the spring  78 , thereby forcing the pack of spacer plates  58  and friction discs  60  into mutual frictional contact. This action engages the clutch  44  and produces a drive connection between carrier  20  and intermediate shaft  46 . With clutch  44  engaged and sun gear  12  held against rotation on stator  14 , the gear set  10 , whose input is shaft  18  and whose out put is carrier  20 , underdrives shaft  46  in a forward direction relative to the speed and direction of input shaft  18 . Hydraulic transmission fluid, which is continually supplied to balance dam  74 , flows continually to the bearings  26  on the pinion shafts  24 .  
         [0025]     When clutch volume  68  is vented, piston  66  moves leftward in cylinder  50  aided by the force of return spring  78 , thereby releasing the frictional contact among the spacer plates  58  and friction discs  60 . This action disengages the clutch  44  and releases the drive connection between carrier  20  and intermediate shaft  46 . Hydraulic transmission fluid flows continually to the bearings  26  on the pinion shafts  24  when clutch  44  is disengaged.  
         [0026]     In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.