Abstract:
A brake assembly includes first and second brakes, a gearset including first and second members, a hub held against rotation, the first brake selectively producing a connection between the hub and the first member, the second brake selectively producing a connection between the hub and the second member, and a support secured to a transmission case and the hub, the support formed with brake-apply circuits, each circuit corresponding to one of the brakes.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to an automatic transmission brake hub that reduces hydraulic drag due to open-brake rotation and eliminates transmission case splines. 
     2. Description of the Prior Art 
     In a hydraulically-actuated automatic transmission for a motor vehicle, transmission brakes produce high drag losses, which adversely affect fuel economy. 
     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. 
     Forming spine 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 
     A brake assembly includes first and second brakes, a gearset including first and second members, a hub held against rotation, the first brake selectively producing a connection between the hub and the first member, the second brake selectively producing a connection between the hub and the second member, and a support secured to a transmission case and the hub, the support formed with brake-apply circuits, each circuit corresponding to one of the brakes. 
     This brake hub eliminates machining of spline teeth in the transmission case and reduces hydraulic drag due to open-clutch rotation. 
     Cutouts in the hub allow for the brake piston to pass through the cutouts and are also large enough for the assembler to see the brake splines while installing the clutch pack. 
     The brake hub is tabbed to the pump support instead of the case to prevent rotation, thereby allowing for the rotating brake cylinder to be outside of the clutch pack and providing a large clearance for exhausting oil from the clutch pack. Oil can be quickly exhausted from the open clutch pack, reducing drag loss. 
     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 
       The invention will be more readily understood by reference to the following description, taken with the accompanying drawings, in which: 
         FIG. 1  is a schematic diagram showing a side view of the kinematic assembly for an automatic transmission for a motor vehicle; 
         FIG. 2  is a cross section of the kinematic assembly of  FIG. 1 ; and 
         FIG. 3  is a cross section of the kinematic assembly of  FIG. 1  showing a brake hub. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     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 . 
     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 . 
     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 . 
     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 . 
     A first brake  64  selectively holds ring gear  24  against rotation. 
     A second brake  66  selectively holds sun gears  22 ,  34  against rotation on the transmission case  124 . 
     A first clutch  68  selectively couples ring gear  36  to a clutch housing  70  rotation also on the transmission case  124 . 
     A second clutch  72  selectively couples carrier  48  to clutch housing  70 . 
     A third clutch  74  selectively couples ring gear  46  and sun gear  54  to input  12 . 
     A fourth clutch  76  selectively couples shell  58  to clutch housing  70 . 
       FIG. 2  shows that carrier  38  is secured to drum shell  58 . 
     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 . 
     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  88  completes the connection. Clutch housing  70  is supported by axially spaced bushings  90 ,  92  on the radial outer surface of intermediate shaft  16 . 
     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 . 
     External teeth on the spacer plates  98  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 . 
     Located between bushings  90 ,  92  and formed in the hub  100  of clutch housing  70  are four feed circuits. A single balance oil feed supplies automatic transmission fluid (ATF) 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 . 
     Each of the servo cylinders  69 ,  73 ,  77  of clutches  68 ,  72 ,  76  is supplied with actuating pressure through individual circuits formed in the clutch housing  70 . 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 . 
       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  131  formed with external and internal axial splines, to which the spacer plates  133 ,  135  of the brakes  64 ,  66  brake and clutch are secured, respectively. 
     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 . 
     The planet pinions  30  of gearset  20  are supported for rotation on a pinion shaft  142 , which is supported on carrier  26 . 
     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 radial arm  130  allow an assembler of the brake hub assembly to see though the arm while aligning friction plates  136  with disc  138 . 
     Pump 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 second cylinder  154 . 
     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 . 
     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.