Abstract:
A method for forming a rotor hub that includes a sheet metal cylinder including spline teeth including angularly spaced crests and valleys, a tube surrounding the cylinder, secured to the crests and supporting a rotor thereon, a hub secured to the cylinder and supported for rotation, a torque converter, and a flex plate secured to the hub and the torque converter.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a divisional application of pending U.S. application Ser. No. 14/154,223, filed Jan. 14, 2014, which is a continuation-in-part application of U.S. application Ser. No. 13/362,018, filed Jan. 31, 2012. 
     
    
     BACKGROUND OF INVENTION 
       [0002]    This invention relates to a powertrain of hybrid electric vehicles, particularly to a powertrain module that can be installed between and secured to an engine output and a transmission input. 
         [0003]    Hybrid electric vehicles (HEVs) have both an internal combustion engine and an electric machine, which are alternately, or in combination, used to propel the vehicle. A variety of different powertrains are used in hybrid vehicles such as a parallel configuration, in which the engine is connected to the motor by a disconnect clutch with the motor driving a torque converter input of an automatic power transmission. The transmission has an output which is connected to a differential coupled to the two driven wheels of the vehicle. 
         [0004]    A need exists in the industry for a hybrid electric powertrain that includes a modular subassembly for use with a variety of engines and transmissions, such that the module can be installed between and secured to an output of one of a number of engines and to an input of one of a number of transmissions. The assembled powertrain may then be employed in a variety of vehicles. The module should include a hydraulically actuated disconnect clutch, the electric machine and suitable power paths between the engine and electric machine to the transmission input. Preferably, the module provides for hydraulic communication from the transmission&#39;s hydraulic system to the clutch, a balance dam and the electric machine. The module must provide an oil sump containing hydraulic fluid delivered to the module, and a path for continually returning that fluid to the transmission&#39;s oil sump so that the transmission pump is continually supplied reliably with fluid. 
         [0005]    Most disconnect clutches are dry, but wet clutches are generally more controllable and allow oil cooling of the clutch and motor. Nesting the disconnect clutch inside the motor rotor allows improves packaging but generally requires an expensive rotor hub since it must hold the rotor, clutch piston and clutch plates. 
         [0006]    The module should require low manufacturing and assembly costs, no vehicle body modification, and must provide reliable performance. 
       SUMMARY OF INVENTION 
       [0007]    A rotor hub includes a sheet metal cylinder including spline teeth including angularly spaced crests and valleys, a tube surrounding the cylinder, secured to the crests and supporting a rotor thereon, a hub secured to the cylinder and supported for rotation, a torque converter, and a flex plate secured to the hub and the torque converter. 
         [0008]    A method for forming a rotor hub includes forming a sheet metal cylinder having spline teeth defining angularly spaced crests and valleys, securing a tube surrounding the cylinder to the crests, securing a rotor on the tube, forming a hub secured to the cylinder, and supporting the hub for rotation about an axis. 
         [0009]    The rotor hub is comprises three simple, low-cost components a cylinder, a cylindrical tube, and a hub. Torque is transmitted between the hub and the torque converter through the flex plate. 
         [0010]    Centrifugal force causes automatic transmission fluid (ATF) to flow radially continually outward through the cylinder, tube and rotor, thereby carrying heat from clutch plates, cylinder and tube away from the module. ATF that exits the assembly falls due to gravity to a sump at the bottom of the module, passes through a cooler and returns to the transmission sump, from which it is drawn by suction into the transmission pump for recirculation through the hydraulic system. 
         [0011]    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. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0012]    The invention will be more readily understood by reference to the following description, taken with the accompanying drawings, in which: 
           [0013]      FIGS. 1A and 1B  comprise a side cross-sectional view of a powertrain module showing a front connection to an engine output and a rear connection to a transmission torque converter input; 
           [0014]      FIG. 2  is a side cross-sectional view of a portion of the powertrain module showing a component functioning as a clutch reaction plate and a forward support of the electric machine&#39;s rotor; and 
           [0015]      FIG. 3  is a side cross-sectional view of a rotor hub formed from stamped components; 
           [0016]      FIG. 4  is a cross section taken at plane  4 - 4  of  FIG. 3 ; 
           [0017]      FIG. 5  is a cross section taken at plane  5 - 5  of  FIG. 3 ; and 
           [0018]      FIG. 6  is a side view of the rotor and end plates. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]      FIGS. 1A and 1B  illustrate a module  10  of a powertrain for a hybrid electric vehicle that includes an engine having a rotary output  12 ; a torsional damper  14 , secured to the engine output  12 ; an input shaft  16 , secured by a spline  18  to an output  20  of damper  14 ; a disconnect clutch  22 , supported on a clutch hub  24  that is secured by a spline  26  to input shaft  16 ; an electric machine  28 , which includes a stator  30  bolted to a front bulkhead  32  and a rotor  34  supported by a first leg  36  and a second leg  38  for rotation about an axis  39 ; a rotor hub  40 , secured preferably by a weld to leg  38 ; and a flexplate  42 , secured at one end by a spline connection  44  to rotor hub  40  and secured at the opposite end by bolts  46  to a torque converter casing  48 , which encloses a hydrokinetic torque converter  49 . The electric machine  28  may be an electric motor or an electric motor-generator. 
         [0020]    Torque converters suitable for use in the powertrain are disclosed in and described with reference to FIGS. 4 a,  4 b,  5, 12 and 15 of U.S. patent application Ser. No. 13/325,101, filed Dec. 14, 2011, the entire disclosure of which is herein incorporated by reference. 
         [0021]    The torque converter  49  includes a bladed impeller wheel located within and secured to casing  48 ; a bladed turbine, driven hydrokinetically by the impeller and secured by a spline  50  to the input shaft  52  of an automatic transmission  54 ; and a bladed stator wheel, located between the turbine and stator and secured to a stator shaft  56 , which is held against rotation on a transmission housing  58 . 
         [0022]    A rear bulkhead  60 , secured by bolts  62  to the transmission housing  58 , is fitted at its radial inner surface with a hydraulic seal  64 , which contacts the radial outer surface of rotor hub  40 . 
         [0023]    A flywheel  66 , secured by bolts  68  to the engine&#39;s rotary output  12 , carries an engine starting gear  70 , which is secured by a disc  72 , welded to the starting gear and flywheel. 
         [0024]    A bearing  74  supports the first leg  36  for rotation on the front bulkhead  32 . A bearing  76  supports the second leg  38  for rotation on the rotor hub  40 . A tube  78 , aligned with axis  39  and supporting the rotor  34  for rotation about the axis, is secured to the first leg  36  and second leg  38 . Lips  80 ,  82  at the front and rear ends, respectively, of tube  78  may be rolled radially outward to secure the rotor  34  to tube  78  and to prevent axial displacement of the rotor  34  relative to the tube. The inner surface of tube  78  is formed with an axial spline  81 , which is engaged by the legs  36 ,  38  and alternate plates  83  of the disconnect clutch  22 . The friction plates  84  of clutch  22  are secured by an axial spline formed on the radial outer surface of clutch hub  24 . 
         [0025]    A hydraulic servo for actuating clutch  22  includes a piston  86 , balance dam  88 , return spring  90  and hydraulic lines for transmitting actuating pressure to the pressure control volume  92  at the right hand side of piston  86  and to the pressure balance volume  94  at the left hand side of the piston. Piston  86  moves leftward in a cylinder formed by the rear leg  38  when actuating pressure and hydraulic fluid is supplied to volume  92 , by the use of seals  151  and  152 , thereby causing clutch  22  to engage and driveably connect rotor  34  and the engine output  12  through damper  14 , input shaft  16 , clutch hub  24  and clutch  22 . 
         [0026]    Because the piston  86 , balance dam  88  and return spring  90  are supported on the rotor hub  40 , rotational inertia of the piston  86 , balance dam  88  and return spring  90  is located on the output side, i.e., the rotor side of clutch  22 . 
         [0027]    Rotor  34  is continually driveably connected to the transmission input shaft  52  through the torque path that includes rear leg  38 , rotor hub  40 , flexplate  42 , torque converter casing  48 , the hydrodynamic drive connection between the torque converter impeller and turbine, which is connected by spline  50  to transmission input shaft  52 . 
         [0028]    A resolver  100 , a highly accurate type of rotary electrical transformer used for measuring degrees of rotation, is secured by bolts  102  to the front bulkhead  32 , is supported on the front bulkhead  32  and first leg, and is located axially between the front bulkhead  32  and rear bulkhead  60 . 
         [0029]    The teeth of spline  44 , which produces a rotary drive connection between flexplate  42  and rotor hub  40 , are fitted together such that no lash is produced when torque is transmitted between the flexplate and rotor hub. Flexplate  42  is formed with a thick walled portion  104  having a threaded hole  106  that terminate at a web  108 . The external spline teeth on flexplate  42  are forced axially into engagement with the internal spline teeth on rotor hub  40  by bolts  110 , which engage threaded holes in the right-hand end of rotor hub  40 . The engaged spline teeth at the spline connection  44  are disengaged upon removing bolts  110  and threading a larger bolt into hole  106  such that the bolt contacts web, thereby forcing flexplate axial rightward. 
         [0030]    Rotor hub  40  is formed with multiple axially-directed hydraulic passages  120  and laterally-directed passages  122 ,  124 ,  126 ,  128 ,  129 , which carry hydraulic fluid and pressure to module  10  from the hydraulic system of the transmission  54 . Passages  120 ,  122 ,  124 ,  126 ,  128 ,  129  carry hydraulic fluid and pressure which includes to the control volume  92  of the servo of clutch  22  located at the right hand side of piston  86 , to the pressure balance volume  94  between balance dam  88  and the piston, to a variable force solenoid (VFS)  130 , and to the surfaces of rotor  34  and stator  30 , which surfaces are cooled by the fluid. The rear bulkhead  60  is formed with passage  128 , which communicates hydraulically with VFS  130 . 
         [0031]    The rear bulkhead  60  supports a sump  132 , which contains fluid supplied to module  10  from the hydraulic system of the transmission  54 . Transmission  54  includes a sump  136 , which contains hydraulic fluid that is supplied by a transmission pump  134  to the transmission hydraulic system, from which fluid and control pressure is supplied to module  10 , torque converter  49 , transmission clutches and brakes, bearings, shafts, gears, etc. 
         [0032]    A bearing  140 , fitted in the front bulkhead  32 , and a bearing  142 , fitted in the rotor hub  40 , support input shaft  16  in rotation about axis  39 . The front bulkhead  32  also supports the stator  30  in its proper axial and radial positions relative to the rotor  34 . Bearing  76 , fitted between rear bulkhead  60  and rotor hub  40 , and bearing  142  support rotor hub  40  in rotation about axis  39 . The front and rear bulkheads  32 ,  60  together support rotor  34  in rotation about axis  39  due to bearing  74 , fitted in bulkhead  32 , and bearing  76 , fitted in bulkhead  60 . 
         [0033]    Seal  64 , fitted in the rear bulkhead  60 , and seal  141 , fitted in the front bulkhead  32 , prevent passage of fluid from module  10  located between the bulkheads  32 ,  60 . Another dynamic seal  144  prevents passage of contaminants between the engine compartment  146  and module  10 . 
         [0034]    The components of module  10  are installed and assembled in the module. The assembled module can then be installed between and connected to the engine output  12  and the torque converter casing  48 . 
         [0035]    In operation, when the engine output  12  is driven by an engine, torque is transmitted from the engine through rotor hub  40  and flexplate  42  to the torque converter casing  48 , provided that clutch  22  is engaged. The rotor  34  electric machine  28  is continually driveably connected through tube  78 , leg  38 , rotor hub  40  and flexplate  42  to the torque converter casing  48 . Therefore, the torque converter casing  48  can be driven by the engine alone, provided the electric machine  28  is off and clutch  22  is engaged; by the electric machine alone, provided the engine is off or the engine in operating and the clutch is disengaged; and by both the engine and electric machine concurrently. 
         [0036]    Referring to  FIG. 2 , the rotor  34  of electric machine  28  is supported on tube  78 , which is supported by a shell  160 , connected by a weld  162  to tube  78  and by welding to rotor hub  40 , and by a leg  164 , secured through an axial, inner spline  166  to shell  160 . A single snap ring  168 , secured to the shell  160  and contacting leg  164 , limits axial displacement of the friction plates  84 , which are secured by spline  166  to shell  160 . Spacer plates  83  are secured by an external axial spline  170  on clutch hub  24 . 
         [0037]    A thrust bearing  172  contacts clutch hub  24  and a flange  174  on a shaft  176  that is parallel to axis  19 . A bearing supports clutch hub On shaft  176 . The engine output  12  is connected through flywheel  66 , damper  20 , input shaft  16  and spline  26  to clutch hub  24 . 
         [0038]    A bearing  182 , fitted between front bulkhead  32  and leg  164 , supports the rotor  34  for rotation about axis  19  and provides a reaction to axial force transmitted between leg  164  and bulkhead  32 . 
         [0039]    In operation, piston  86  moves leftward against the force of return spring  90  when pressurized hydraulic fluid is supplied through passage  184  to the cylinder  186  that contains piston  86 . Disconnect clutch  22  is engaged when friction plates  83  and spacer plates  84  are forced by piston  86  into mutual frictional contact, thereby producing a drive connection between rotor hub  40  and the engine output  12 . Rotor  34  is continually driveably connected to rotor hub  40  through shell  160 . 
         [0040]    The leftward axial force applied by piston  86  is transmitted through plates  83 ,  84  through  164 , snap ring  168 , and shell  160 . 
         [0041]      FIGS. 3-6  illustrate a rotor hub formed from stamped components comprising a clutch cylinder  200 , a tube  202  and a hub  204 . Cylinder  200  includes a bore  204 , which contains clutch piston  86 , preferably, formed by a stamping process, and axial splines  166 , which engage clutch separator plates  84 , the cylinder  200  and splines  166  being formed by any of several methods including hammer forging. 
         [0042]    Rotor  34  of electric machine  28  is supported on tube  202 , which has rolled ends  208  for retaining the rotor on the tube. Tube  202  can be of seamless tubing or of tubing having a continuous welded seam. Cylinder  200  is preferably secured to tube  202  by a press fit. 
         [0043]    Hub  40  is preferably secured to cylinder  200  by welding. Hub  40  transmits torque from the electric machine  28  and from the engine through the clutch  22  to the torque converter  49  by flex plate  42 . 
         [0044]      FIG. 4  shows that the axial spline  166  of cylinder  200 , comprises a series of mutually, angularly-spaced valleys at the bore  206  and crests  210 . Each crest  210  is secured to the radial inner surface  212  of tube  202 . 
         [0045]    Angularly-spaced, axially-directed first channels  214  are defined by surface  212  and the splines  166  of cylinder  200 . The surfaces of cylinder  200  that forms the valleys is formed with a radial hole  216 , which communicates with the channel  214  that is located radially outboard of the respective valley. Cylinder  202  is formed with a series of axially-spaced drain holes  218 , each communicating with one of the channels  214 . 
         [0046]      FIG. 5  shows that rotor  34  is formed with a series of axially-directed second channels  220 , each communicating through a drain hole  218  with one of the channels  214  of the cylinder  200 . Some of the channels  214  receive an axially-directed protrusion  222  that extends radially into the channel, thereby connecting tube  202 , cylinder  200 , and rotor  34  such that they rotate as a unit about axis  39  keeping rotor  34  from spinning on the outer surface  404  of the tube  202 . 
         [0047]      FIG. 6  shows that each axial second channel  220  terminates at one of the end plates  224 ,  226 , located at opposite axial ends of rotor  34 . Each end plate  224 ,  226  is formed with a series of radially-directed passages  228 ,  230 , each passage aligned with one of the axial second channels  220 . 
         [0048]    In operation, centrifugal force causes automatic transmission fluid (ATF) in module  10  to flow radially outward through holes  216 , channels  214  holes  218 , channels  220  and passages  228 ,  230 , thereby carrying heat from clutch plates  83 ,  84 , cylinder  200 , tube  202  and rotor  34  away from the module  10 . As the fluid exits channels  228  and  230 , the oil sprays radially outward due to centrifugal force, contacting the endwindings of stator  30 , thereby cooling the stator. ATF that exits the assembly falls due to gravity to a sump at the bottom of module  10 , passes through a cooler and returns to the transmission sump, from which it is drawn by suction into the transmission pump for recirculation through the hydraulic system. 
         [0049]    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.