Abstract:
An assembly includes a torque converter concentric with an axis and including a casing, a rotor hub drivably connected for rotation about the axis to an electric machine, a coupler connected to the rotor hub, and a flex plate coupled for elastic displacement between the coupler and a surface of the casing that faces away from the coupler.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a powertrain for hybrid electric vehicles, particularly to a powertrain module that is located between and secured to an engine output and a transmission input. 
     2. Description of the Prior Art 
     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. 
     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. 
     This module is sometimes called a front module (FM), since it is part of the modular hybrid transmission (MHT) and is bolted in front of the transmission. Since this module adds length to the powertrain, the module should be as short as possible. A conventional attachment between the flex plate on the FM and the torque converter does not provide the access that torque converters normally have to flex plates resulting in added length to the powertrain. 
     SUMMARY OF THE INVENTION 
     An assembly includes a torque converter concentric with an axis and including a casing, a rotor hub drivably connected for rotation about the axis to an electric machine, a coupler connected to the rotor hub, and a flex plate coupled for elastic displacement between the coupler and a surface of the casing that faces away from the coupler. 
     The assembly includes a deep drawn flex plate that reaches around the front of the torque converter to the backside of the torque converter where bolts are installed radially without increasing the axial dimension between the front module and a forward surface of the transmission. 
     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: 
         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. 
         FIG. 2  is side cross-sectional view of the powertrain of  FIG. 1  showing a torque converter having a bolted, integrated flex plate; 
         FIG. 3  is side cross-sectional view of the powertrain of  FIG. 1  showing a torque converter having an elastically coupled integrated flex plate; and 
         FIG. 4  is side cross-sectional view of the powertrain of  FIG. 3  showing a flex plate connecting the rotor hub and a rear surface of the torque converter casing. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       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  or by bolts  110  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. 
     Torque converters suitable for use in the powertrain are disclosed in and described with reference to FIGS. 4a, 4b, 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. 
     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 . 
     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 . 
     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. 
     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 . 
     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 . 
     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 . 
     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 . 
     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 . 
     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. 
     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  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 . 
     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. 
     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 . 
     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 crankshaft  146  and module  10 . 
     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 . 
     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 is operating and the clutch is disengaged; and by both the engine and electric machine concurrently. 
     In  FIG. 2 , input shaft  160  is driveably connected to the engine output  12  through flywheel  66 , flexplate  162  and spline  18 . A bolt  164 , installed through the front side of the front module, is inserted through a bore in input shaft  160  and through a web  108  of rotor hub  40 . Bolt  164  is threaded into a tapped bore formed at the front side of a coupler shaft  166 , thereby providing axial force continuity between rotor hub  40  and coupler shaft  166 . Coupler shaft  166  is connected for rotation with rotor hub  40  through a spline connection  167 , which includes mutually engaged axial spline teeth formed on an inner radial surface of rotor hub  40  and axial spline teeth formed on the external radial surface of coupler shaft  166 . 
     A flex plate  168  is secured, preferably by a weld  170 , to the torque converter casing  48  and by a series of rivets  172  to a flange  174  of coupler shaft  166 , thereby securing rotor hub  40  to torque converter casing  48 . Bolt  164  secures torque converter  49  to the front module  10  and carries axial load between the torque converter  49  and module  10 . 
     In  FIG. 3 , input shaft  180  is driveably connected to the engine output  12  through flywheel  66 , flexplate  162  and spline  18 . A flex plate  168  is secured, preferably by a weld  170 , to the torque converter casing  48  and by a series of rivets  172  to a flange  174  of coupler shaft  182 , thereby securing rotor hub  40  to torque converter casing  48 . 
     Coupler shaft  182  is connected for rotation to rotor hub  40  through a spline connection  184 , which includes mutually engaged axial spline teeth formed on an inner radial surface of rotor hub  40  and axial spline teeth formed on the external radial surface of coupler shaft  182 . 
     Rotor hub  40  is formed with an annular recess located at a radial inner surface of a bore in the rotor hub. Similarly, coupler shaft  182  is formed with an annular recess located at a radial outer surface and aligned axially with e recess of rotor hub  40 . A c-clip  186  mutually engages the recess of rotor hub  40  and coupler shaft  182 , thereby securing torque converter  49  to the front module  10  and carrying axial load between the torque converter  49  and module  10 . 
       FIG. 4  shows a deep drawn flex plate  200  that extends radially outward and axially rearward from rivets  172 , by which it is secured to the coupler shaft  182 . The opposite end of flex plate  200  is secured by a series of bolts  202  spaced about axis  39  and engaged with internal screw threads  204  formed in the bore of mounting blocks  206 , which are fastened to the outer surface of the torque converter casing  49 . 
     Preferably flex plate  200  extends around the front of the torque converter  49  to the back of the torque converter where bolts  202  and mounting blocks  206  are located. Preferably bolts  202  are installed radially in the mounting blocks  206  without increasing the axial dimension between rear bulkhead  60  and the forward surface of transmission  54 . 
     Alternatively flex plate  200  may be formed with apertures in its horizontal or radial length portions. The horizontal length portion of flex plate  200  may comprise a series of angularly spaced horizontal legs extending from its radial length portion. 
     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.