Abstract:
A transmission includes gearsets each including rotating members, a support held against rotation, brake servos located in the support, brakes each actuated by one of the brake servos for producing a connection between the support and a respective gearset member, a housing, clutch servos located in the housing, and clutches each actuated by one of the clutch servos for producing a drive connection between the housing and a respective gearset member.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates generally to an automatic transmission, in which a clutch module contains clutch servo pistons and a pump support contains brake servo pistons. 
         [0003]    2. Description of the Prior Art 
         [0004]    In the kinematic arrangement of an automatic transmission, certain control elements, such as hydraulically-actuated clutches, have no fixed connection to any other transmission lever component. 
         [0005]    In such cases, a need exists for a technique that simplifies the feed circuit to those clutches, i.e. pressure feeds for each clutch-apply circuit and respective feeds to balance volumes. 
         [0006]    In a hydraulically-actuated automatic transmission for a motor vehicle, transmission brakes produce high drag losses, which adversely affect fuel economy. 
         [0007]    When the brake&#39;s separator plates are splined directly to the transmission case, automatic transmission fluid in the case is difficult to evacuate, which leads to high drag. When the brake&#39;s separator plates are splined directly to the transmission case, installation of the separator plates and friction plates must be completed as a final assembly, instead of as a subassembly, which is preferred. 
         [0008]    Forming spline teeth in the transmission case that engage spline teeth on the brake&#39;s separator plates can be costly to machine and produces excessive, unwanted scrap. 
       SUMMARY OF THE INVENTION 
       [0009]    A transmission includes gearsets each including rotating members, a support held against rotation, brake servos located in the support, brakes each actuated by one of the brake servos for producing a connection between the support and a respective gearset member, a housing, clutch servos located in the housing, and clutches each actuated by one of the clutch servos for producing a drive connection between the housing and a respective gearset member. 
         [0010]    The transmission provides an optimized location for all the brakes, clutches and gearsets. It enables three of the rotating clutches to be housed in the same component, two of the clutches being stacked radially to minimize axial length. The brake pistons are housed in the front support to reduce housing cost and length. 
         [0011]    The input shaft is formed with four axial feed passages, three passages for each of three clutch-apply circuits and one passage for supplying the balance volumes. One of the passages in the input shaft is multiplexed and used also to feed the rearmost clutch from the rear. 
         [0012]    The transmission has a minimum number of splines formed in the transmission case. 
         [0013]    The scope of applicability of the preferred embodiment will become apparent from the following detailed description, claims and drawings. It should be understood, that the description and specific examples, although indicating preferred embodiments of the invention, are given by way of illustration only. Various changes and modifications to the described embodiments and examples will become apparent to those skilled in the art. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0014]    The invention will be more readily understood by reference to the following description, taken with the accompanying drawings, in which: 
           [0015]      FIG. 1  is a schematic diagram of the kinematic assembly of an automatic transmission for a motor vehicle; 
           [0016]      FIG. 2  is a cross sectional side view of an intermediate length portion of the kinematic assembly of  FIG. 1  showing a clutch housing; and 
           [0017]      FIG. 3  is a cross sectional side view of a front length portion of the kinematic assembly of  FIG. 1  showing a brake assembly. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0018]    The assembly  10   FIG. 1  includes an input  12 ; output  14 ; intermediate shaft  16 ; a first planetary gear set  20  having a first sun gear  22 , a first ring gear  24 , a first carrier  26 ; and a set of planet pinions  30  supported on carrier  26  and in continuous meshing engagement with the sun gear  22  and the ring gear  24 . 
         [0019]    A second planetary gear set  32  includes a second sun gear  34  fixedly coupled to sun gear  22 ; a second ring gear  36 ; a second carrier  38  fixedly coupled to the input  12 ; and a set of planet pinions  40  in supported on carrier  38  and in continuous meshing engagement with sun gear  34  and ring gear  36 . 
         [0020]    A third planetary gear set  42  includes a third sun gear  44  fixedly coupled to ring gear  36 ; a third ring gear  46 ; a third carrier  48 ; and a set of planet pinions  50  supported on carrier  48  and in continuous meshing engagement with sun gear  44  and ring gear  46 . 
         [0021]    A fourth planetary gear set  52  includes a fourth sun gear  54  fixedly coupled to ring gear  46 ; a fourth ring gear  56  fixedly coupled by a shell  58  to carrier  26 ; a fourth carrier  60  fixedly coupled to output  14 ; and a set of planet gears  62  supported on carrier  60  and in continuous meshing engagement with sun gear  54  and ring gear  56 . 
         [0022]    A first brake  64  selectively holds ring gear  24  against rotation. 
         [0023]    A second brake  66  selectively holds sun gears  22 ,  34  against rotation on the transmission case  124 . 
         [0024]    A first clutch  68  selectively couples ring gear  36  to a clutch housing  70 . 
         [0025]    A second clutch  72  selectively couples carrier  48  to clutch housing  70 . 
         [0026]    A third clutch  74  selectively couples ring gear  46  and sun gear  54  to input  12 . 
         [0027]    A fourth clutch  76  selectively couples shell  58  to clutch housing  70 . 
         [0028]      FIG. 2  shows that carrier  26  is secured to shell  58 . 
         [0029]    Clutch housing  70  includes an axial arm  82  formed with internal spine teeth, to which external teeth on the spacer plates  84  of clutch  68  are fixed for rotation with clutch housing  70 . The friction plates of clutch  68  are splined to external spline teeth formed on a ring  85 , which is formed with ring gear  36 . 
         [0030]    Intermediate shaft  16 , which extends along axis  86  on the radial outer side of input  12 , is secured to ring  85  where a snap ring completes the connection. Clutch housing  70  is supported by axially spaced bushings  90 ,  92  on the radial outer surface of intermediate shaft  16 . 
         [0031]    Clutch housing  70  includes another axial arm  94  formed with external spine teeth, to which internal teeth on the spacer plates  96  of clutch  76  are fixed for rotation with clutch housing  70 . The friction plates of clutch  76  are splined to internal spline teeth formed on a shell  58 . 
         [0032]    External teeth  98  on the spacer plates of clutch  72  engage internal spline teeth formed on arm  94  of the clutch housing  70 . The friction plates of clutch  72  are splined to external spline teeth formed on carrier  48 . 
         [0033]    Located between bushings  90 ,  92  and formed in the hub  100  of clutch housing  70  are four feed circuits. A single balance dam oil feed supplies automatic transmission fluid (ATF), a hydraulic fluid, to the pressure balance volumes  102 ,  104 ,  106  of clutches  68 ,  72 ,  76 . Balance dams  103 ,  105 ,  107  seal the pressure balance volumes  102 ,  104 ,  106  at the pistons  110 ,  112 ,  114  of the clutches  68 ,  72 ,  76 . 
         [0034]    Each of the servo cylinders of clutches  68 ,  72 ,  76  is supplied with actuating pressure through individual circuits formed in the clutch housing  70  and communicating with fluid passages formed in the input shaft  12 . When no actuating pressure is applied to clutches  68 ,  72 ,  76 , the clutch housing  70  has no fixed connection to any other component of assembly  10 . 
         [0035]      FIG. 3  shows a pump support  120  secured by bolts  122  to the transmission case  124  and supporting the input shaft  12  on a bushing  126 . A hub  128  for brakes  64 ,  66  includes a radial arm  130 , secured to the pump support, and an axial arm formed with external and internal axial splines, to which the spacer plates of brakes  64 ,  66  are secured, respectively. 
         [0036]    The friction discs  132  of brake  66  are connected to external, axial spline teeth formed on a disc  134 , which is secured to the sun gears  22 ,  34  through intermediate shaft  18 . The friction discs  136  of brake  64  are connected to internal, axial spline teeth formed on a disc  138 , which is secured to ring gear  24  and is supported between two thrust bearings  140  located on the carrier  26 . 
         [0037]    The planet pinions  30  of gearset  20  are supported for rotation on a pinion shaft  142 , which is supported on carrier  26 . 
         [0038]    Pump support  120  is formed with a first cylinder  144  containing a piston  146 , which extends though openings  148  into contact with one of the spacer plates of brake  64 . Brake-apply pressure is carried through passages  150 ,  151  to cylinder  144 . The openings  148  in hub arm  130  allow an assembler of the brake hub assembly to see though the arm while aligning friction plates  136  with disc  138 . 
         [0039]    Support  120  is also formed with a second cylinder  154  containing a piston  156 , which contacts one of the spacer plates of brake  66 . Brake-apply pressure is carried through passage  158  to cylinder  154 . 
         [0040]    The radial arm  130  of the brake hub  128  is secured to the transmission case  124  such that the arm contacts an axial stop  152 , which limits axial displacement of the arm and provides an axial reaction force to the force of piston  146  applied to the plates of brake  64  and the force of piston  156  applied to the plates of brake  66 . 
         [0041]    In accordance with the provisions of the patent statutes, the preferred embodiment has been described. However, it should be noted that the alternate embodiments can be practiced otherwise than as specifically illustrated and described.