Patent Publication Number: US-2022212534-A1

Title: P2 hybrid transmission

Description:
The present disclosure relates to motor vehicle powertrains. More specifically, aspects of this disclosure relate to a hybrid powertrain having a P2 hybrid transmission. 
     Many available motor vehicles, such as the modern-day automobile, include a powertrain that operates to propel the vehicle and power the onboard vehicle electronics. The powertrain, which is inclusive of and sometimes improperly referred to as a drivetrain, is generally comprised of an engine that delivers driving power to the vehicle&#39;s final drive system (e.g., rear differential, axle, and wheels) through a multi-speed power transmission. Automobiles have traditionally been powered by a reciprocating-piston type internal combustion engine (ICE) because of its ready availability and relatively inexpensive cost, light weight, and overall efficiency. Such engines include 2- or 4-stroke compression-ignited diesel engines and 4-stroke spark-ignited gasoline engines. 
     Hybrid vehicles, on the other hand, utilize alternative power sources to propel the vehicle, minimizing reliance on the engine for power and thereby increasing overall fuel economy. A hybrid electric vehicle (HEV), for example, incorporates both electric energy and chemical energy, and converts the same into mechanical power to propel the vehicle and power the vehicle systems. The HEV generally employs one or more electric machines, such as electric motor-generator units (MGUs), that operate individually or in concert with an internal combustion engine to propel the vehicle. Since hybrid vehicles can derive their power from sources other than the engine, engines in hybrid vehicles can be turned off while the vehicle is propelled by the alternative power source(s). 
     One example of a hybrid powertrain is a P2 hybrid powertrain. In a P2 hybrid arrangement, a MGU and an engine provide power input to a transmission in parallel. Either one of the MGU or the engine separately, or in combination may provide power to the input side of the transmission. In a P2 arrangement the MGU is often positioned adjacent to the transmission, or off-axis, wherein power from the MGU is transferred to the input side of the transmission through a belt or chain connection. In other arrangements, the MGU is placed coaxially to the input of the transmission, up-stream of the transmission. In either of these instances, the addition of the MGU creates packaging concerns requiring increase in the lateral and axial space needed for the powertrain within the vehicle. Other arrangements include an MGU housed within the transmission to reduce packaging and power transfer concerns, however, the overall size of the transmission must be increased to accommodate the addition of the MGU, thereby creating packaging concerns for placement of the transmission within the automobile. 
     Thus, while current P2 hybrid powertrains achieve their intended purpose, there is a need for a new and improved P2 hybrid powertrain that requires minimal additional space within the transmission and minimizes packaging concerns. 
     SUMMARY 
     According to several aspects of the present disclosure, a hybrid powertrain for an automobile includes a transmission adapted to provide power to wheels of the automobile, an engine adapted to provide power to an input shaft of the transmission, and an electric motor-generator unit adapted to provide power to the input shaft of the transmission, wherein the electric motor-generator is positioned within the transmission, coaxial with the transmission input shaft, the electric motor-generator being supported by and enclosed within a pump support of the transmission. 
     According to another aspect, the hybrid powertrain includes a torque converter positioned between and interconnecting the engine to the input shaft of the transmission, the torque converter having a one-way clutch adapted to drivingly connect the torque converter to the input shaft of the transmission when power is being provided to the torque converter from the engine and to allow the input shaft of the transmission to rotate freely relative to the torque converter when power is being provided to the input shaft of the transmission from the electric motor-generator unit. 
     According to another aspect, the pump support defines a motor housing, the electric motor-generator including a stator that is positioned coaxially with the input shaft of the transmission and secured to inner walls of the motor housing and a rotor that is rotatably positioned coaxially with the input shaft of the transmission within the motor housing in operational engagement with the stator and rotatably attached to the input shaft of the transmission. 
     According to another aspect, the transmission includes a two-piece stator shaft having a first piece and a second piece, wherein a gap between the first piece of the stator shaft and the second piece of the stator shaft is adapted to allow rotational attachment of the rotor of the electric motor-generator unit to the input shaft of the transmission. 
     According to another aspect, the electric motor-generator unit is an axial flux electric motor-generator unit, wherein the stator and rotor are axially aligned. 
     According to another aspect, the electric motor-generator unit is a radial flux electric motor-generator unit, wherein the stator is radially outward and encircles the rotor. 
     According to another aspect, the hybrid powertrain further includes a planetary gearset positioned between and interconnecting the rotor and the input shaft of the transmission. 
     According to another aspect, the planetary gearset includes a ring gear, a sun gear, a carrier and a plurality of pinion gears supported on the carrier and in geared engagement with the sun gear and the ring gear, the carrier rotatably attached to the input shaft of the transmission. 
     According to another aspect, the hybrid powertrain further includes a connection hub positioned between and interconnecting the rotor and the input shaft of the transmission. 
     According to another aspect, the connection hub includes oil passages defining a fluid connection between the motor housing and a lube channel within the input shaft of the transmission. 
     According to several aspects of the present disclosure, a hybrid transmission includes an input shaft adapted to receive power from an engine of the automobile, and an electric motor-generator unit adapted to provide power to the input shaft of the transmission, wherein the electric motor-generator is positioned within the transmission, coaxial with the transmission input shaft, the electric motor-generator being supported by and enclosed within a pump support of the transmission. 
     According to another aspect, the hybrid transmission further includes a torque converter adapted to interconnect an engine to the input shaft of the transmission, the torque converter having a one-way clutch adapted to drivingly connect the torque converter to the input shaft of the transmission when power is being provided to the torque converter and to allow the input shaft of the transmission to rotate freely relative to the torque converter when power is being provided to the input shaft of the transmission from the electric motor-generator unit. 
     According to another aspect, the pump support defines a motor housing, the electric motor-generator including a stator that is positioned coaxially with the input shaft of the transmission and secured to inner walls of the motor housing and a rotor that is rotatably positioned coaxially with the input shaft of the transmission within the motor housing in operational engagement with the stator and rotatably attached to the input shaft of the transmission. 
     According to another aspect, the hybrid transmission further includes a two-piece stator shaft having a first piece and a second piece, a gap between the first piece of the stator shaft and the second piece of the stator shaft adapted to allow rotational attachment of the rotor of the electric motor-generator unit to the input shaft of the transmission. 
     According to another aspect, the electric motor-generator unit is an axial flux electric motor-generator unit, wherein the stator and rotor are axially aligned. 
     According to another aspect, the electric motor-generator unit is a radial flux electric motor-generator unit, wherein the stator is radially outward and encircles the rotor. 
     According to another aspect, the hybrid transmission further includes a planetary gearset positioned between and interconnecting the rotor and the input shaft of the transmission. 
     According to another aspect, the planetary gearset includes a ring gear, a sun gear, a carrier and a plurality of pinion gears supported on the carrier and in geared engagement with the sun gear and the ring gear, the carrier rotatably attached to the input shaft of the transmission. 
     According to another aspect, the hybrid transmission further includes a connection hub positioned between and interconnecting the rotor and the input shaft of the transmission, the connection hub including oil passages defining a fluid connection between the motor housing and a lube channel within the input shaft of the transmission. 
     According to several aspects of the present disclosure, a hybrid transmission for an automobile includes an input shaft, a two-piece stator shaft having a first piece and a second piece, a torque converter adapted to interconnect an engine to the input shaft of the transmission, a pump support defining a motor housing, and an electric motor-generator unit adapted to provide power to the input shaft of the transmission, wherein the electric motor-generator is positioned within the motor housing and includes a stator that is positioned coaxially with the input shaft of the transmission and secured to inner walls of the motor housing and a rotor that is rotatably positioned coaxially with the input shaft of the transmission within the motor housing in operational engagement with the stator and rotatably attached to the input shaft of the transmission by one of a planetary gearset and a connection hub, the electric motor-generator unit being one of an axial flux electric motor-generator unit, wherein the stator and rotor are axially aligned, and a radial flux electric motor-generator unit, wherein the stator is radially outward and encircles the rotor, wherein, the torque converter includes a one-way clutch adapted to drivingly connect the torque converter to the input shaft of the transmission when power is being provided to the torque converter and to allow the input shaft of the transmission to rotate freely relative to the torque converter when power is being provided to the input shaft of the transmission from the electric motor-generator unit, and the rotor of the electric motor-generator unit is rotationally attached to the input shaft of the transmission through a gap between the first piece of the stator shaft and the second piece of the stator shaft. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  is a schematic view of an automobile incorporating a hybrid powertrain and hybrid transmission according to an exemplary embodiment; 
         FIG. 2  is a partial cross-sectional view of a hybrid transmission according to an exemplary embodiment; and 
         FIG. 3  is a partial cross-sectional view of a hybrid transmission according to another exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
     Referring now to the drawings, wherein like reference numbers refer to like features throughout the several views, there is shown in  FIG. 1  a schematic illustration of a representative automobile  10  with a P2 hybrid-electric powertrain  12  in accordance with the present disclosure. The illustrated automobile  10  is merely an exemplary application with which the novel aspects of this disclosure may be practiced. The implementation of the present concepts into a P2 hybrid electric architecture should also be appreciated as an exemplary application of the novel concepts disclosed herein. As such, it will be understood that the aspects and features of the present disclosure may be integrated into other vehicle powertrain configurations and utilized for any logically relevant type of motor vehicle. Lastly, the hybrid powertrain  12  shown in  FIG. 1  hereof has been greatly simplified, it being understood that further information regarding the standard construction and operation of a hybrid vehicle is known. 
     The exemplary hybrid powertrain shown in  FIG. 1  includes an engine  14  that is drivingly connected to a multi-speed transmission  16 . The transmission  16  is drivingly connected to a drive shaft  18 , rear differential  20  and rear axle  22  to provide power to the rear wheels  24  of the automobile  10 . The engine  14  transfers power, preferably by way of torque through an engine crankshaft, to an input shaft  26  of the transmission  16 . The transmission  16 , in turn, is adapted to manipulate and distribute power from the engine  14  to the drive shaft  18 , rear differential  20 , rear axle  22  and, finally to the rear wheels  24  of the automobile  10 . The engine  14  may be any now known or hereinafter developed engine, such as a 2-stroke or 4-stroke diesel or a 4-stroke gasoline engine, which is readily adapted to provide its available power output typically at a number of revolutions per minute (RPM). Although not explicitly portrayed in  FIG. 1 , it should be appreciated that the automobile may comprise any known configuration, such as, but not limited to front wheel drive (FWD), rear wheel drive (RWD), four-wheel drive (4WD), all-wheel drive (AWD). 
     The hybrid powertrain  12  includes an electric motor-generator unit  28  that is adapted to provide power to the input shaft  26  of the transmission  16 . The electric motor-generator unit  28  is positioned within the transmission  16 , coaxial with the transmission input shaft  26 , and is supported by and enclosed within a pump support  30  of the transmission  16 . 
     The electric motor-generator unit  28  may be of any conventional type, such as, but not limited to DC series motor, brushless DC motor, permanent magnet synchronous motor, three-phase induction AC motor and multi-phase (greater than three) induction AC motors, and switched reluctance motors. The electric motor-generator unit  28  serves a dual purpose. The electric motor-generator unit  28  provides torque to drive the input shaft  26 , and when the automobile  10  is braking, the electric motor-generator unit  28  can become a generator and charge the batteries. The electric motor-generator unit  28  may be used in conjunction with the engine  14  so the automobile  10  is powered by both simultaneously, or the electric motor-generator unit  28  may solely provide power to the automobile  10 , allowing the engine  14  to idle or shut off. The automobile  10  includes a battery pack  32  to provide power to the electric motor-generator unit  28  and a charging port  34  to allow the battery pack  32  to be charged from an external power source. 
     Referring to  FIG. 2 , the hybrid transmission  16  includes a main housing  36  that encases the pump support  30 . The input shaft  26  of the transmission  16  transfers power to one or more selectively engageable torque transmitting mechanisms  38  (e.g., clutch, brake, etc.) and planetary gearsets to rotate a transmission output shaft (not shown). The main housing  36  covers the innermost components of the transmission  16 , such as the pump support  30 , planetary gear arrangements, input shaft  26 , and torque transmitting devices  38  (all of which are mentioned for explanatory purposes and not all are shown). 
     The transmission  16  of the hybrid powertrain  12  further includes a torque converter  40  positioned between and interconnecting the engine  14  to the input shaft  26  of the transmission  16 . The torque converter  40  includes a one-way clutch  42  adapted to drivingly connect the torque converter  40  to the input shaft  26  of the transmission  16  when power is being provided to the torque converter  40  from the engine  14  and to allow the input shaft  26  of the transmission  16  to rotate freely relative to the torque converter  40  when power is being provided to the input shaft  26  of the transmission  16  from the electric motor-generator unit  28 . 
     The torque converter  40  is a fluid coupling for operatively connecting the engine  14  with the input shaft  26  of the transmission  16 . The torque converter  40  includes an impeller  44 , a turbine  46 , and a stator  48 . To protect these components, the torque converter  40  is constructed with an annular housing  50  that defines a working hydraulic fluid chamber  52 . The annular housing  50  is drivingly connected to the engine  14  such that rotational power is transferable back-and-forth therebetween. 
     The impeller  44 , also referred to in the art as “pump,” is situated in serial power-flow fluid communication with the turbine  46 . Interposed between the impeller  44  and turbine  46  is a stator  48  that selectively alters fluid flow returning from the turbine  46  to the impeller  44  such that returning fluid aids, rather than impedes, rotation of the impeller  44 . The transfer of engine torque to the turbine  46  via the annular housing  50  and impeller  44  is through the operation of hydraulic fluid, such as transmission oil, in the fluid chamber  52 . More specifically, rotation of the impeller  44  causes the hydraulic fluid to be directed toroidally outward toward the turbine  46 . When this occurs with sufficient force to overcome the inertial resistance to rotation, the turbine  46 , coaxially oriented with the impeller  44  begins to rotate with the impeller  44 . The fluid flow exiting the turbine  46  is directed back into the impeller  44  by way of the stator  48 . The stator  48 , located between the flow exit section of the turbine  46  and the flow entrance section of the impeller  44 , redirects the fluid flow from the turbine  46  to the impeller  44  in the same direction as impeller rotation, thereby reducing pump torque and causing torque multiplication. 
     The one-way clutch  42  is positioned and interconnects the turbine  46  of the torque converter  40  to the input shaft  26  of the transmission  16 . The one-way clutch  42  functions to automatically operatively connect (or “lock”) the turbine  46  to the input shaft  26  when positive torque is being transferred from the turbine  46  to the input shaft  26 . During a positive torque operating mode, when power is being transferred to the input shaft  26  from the engine  14 , the one-way clutch  42  contemporaneously locks such that the turbine  46  is mechanically coupled to the input shaft  26 . Conversely, the one-way clutch  42  functions to automatically operatively disconnect (or “overrun”) the turbine  46  from the input shaft  26  when the torque reverses direction. 
     The pump support  30  defines a motor housing  54 . The electric motor-generator unit  28  is positioned within the motor housing  54 . By modifying current pump support designs to include a motor housing  54  therein, the amount of additional space needed to implement the electric motor-generator unit  28  is minimized. The electric motor-generator unit  28  includes a stator  56  that is positioned coaxially with the input shaft  26  of the transmission  16  and secured to inner walls  58  of the motor housing  54 . A rotor  60  is rotatably positioned coaxially with the input shaft  26  of the transmission  16  within the motor housing  54  in operational engagement with the stator  56  and rotatably attached to the input shaft  26  of the transmission  16 . 
     In an exemplary embodiment, the transmission  16  includes a two-piece stator shaft  62  having a first piece  62 A and a second piece  62 B. A gap  64  between the first piece  62 A of the stator shaft  62  and the second piece  62 B of the stator shaft  62  allows rotational attachment of the rotor  60  of the electric motor-generator unit  28  to the input shaft  26  of the transmission  16 . As shown in  FIG. 2 , in an exemplary embodiment, the electric motor-generator unit  28  is an axial flux electric motor-generator unit, wherein the stator  56  and rotor  60  are axially aligned. Referring to  FIG. 3 , in another exemplary embodiment, the electric motor-generator unit  28  is a radial flux electric motor-generator unit, wherein the stator  56  is radially outward and encircles the rotor  60 . 
     Referring again to  FIG. 3 , in an exemplary embodiment, the transmission  16  includes a planetary gearset  66  positioned between and interconnecting the rotor  60  of the electric motor-generator unit  28  and the input shaft  26  of the transmission  16 . The planetary gearset  66  provides a gear reduction between the electric motor-generator unit  28  and the input shaft  26  of the transmission  16  to increase torque. 
     As shown, the planetary gearset  66  includes a ring gear  68 , a sun gear  70 , a carrier  72  and a plurality of pinion gears  74  supported on the carrier  72  and in gear mesh engagement with the sun gear  70  and the ring gear  68 . This arrangement affords several advantages over other possible arrangements, including compactness, the possibility for the sun gear  70 , ring gear  68 , and carrier  72  to use a common central shaft, high ‘torque density’ due to the load being shared by multiple pinion gears  74 , and tangential forces between the gears  68 ,  70 ,  74  being cancelled out at the center of the gears  68 ,  70 ,  74  due to equal and opposite forces distributed among the meshes between the pinion gears  74  and the ring and sun gears  68 ,  70 . 
     The ring gear  68  is attached to or integrally formed within a radially inward surface of the rotor  60 . The sun gear  70  is attached to or integrally formed within a portion of the pump support  30 . The carrier  72  is rotatably attached to the input shaft  26  of the transmission  16 . The carrier is rotatably attached to the input shaft  26  by a splined or geared engagement. As the rotor  60  spins, the carrier  72  rotates at a slower rate due to the gear reduction of the planetary gearset  66 , and rotates the input shaft  26  of the transmission  16 . With the sun gear  70  held stationary, the side of the pinion gears  74  in meshed engagement with the sun gear  70  can&#39;t move either, and the pinion gears  74  will roll along the outside of the sun gear  70 . In an exemplary embodiment, the tangential speed at the mesh with the ring gear  68  (rotor  60 ) will be equal for both the ring gear  68  and the pinion gears  74 , and the center of the pinion gears  74  and the carrier  72  will be moving at half of that, being halfway between a point moving at full speed, and one not moving at all, thus providing a 2:1 reduction. It should be understood that the planetary gearset  66  may provide any suitable desired gear reduction ratio. 
     Referring again to  FIG. 2 , in an exemplary embodiment, the transmission  16  includes a connection hub  76  positioned between and interconnecting the rotor  60  and the input shaft  26  of the transmission  16 . Rotation of the rotor  60  of the electric motor-generator unit  28  is directly transferred to the input shaft  26  of the transmission  16 . The connection hub  76  rotatably interconnects the rotor  60  and the input shaft  26  of the transmission  16  with a splined or geared engagement between the rotor  60  and the connection hub  76  and between the connection hub  76  and the input shaft  26 . 
     In another exemplary embodiment, the connection hub  76  includes oil passages  78  defining a fluid connection between the motor housing  54  and a lube channel  80  within the input shaft  26  of the transmission  16 . A radial orifice  82  extends between the motor housing  54  and the lube channel  80  to allow transmission fluid to flow from the motor housing  54  through the orifice  82  and into the lube channel  80 , where the transmission fluid can flow axially through the input shaft to a sump (not shown) within the transmission. Seals positioned between the rotor  60  and the non-rotating pump support  30  direct transmission fluid through the oil passages  78  back to an oil sump within the transmission  16 . 
     A hybrid powertrain and hybrid transmission of the present disclosure offers several advantages. The placement of the electric motor-generator unit  28  within the motor housing  54  of the pump support  30  allows the addition of the electric motor-generator unit  28  without changing apply and release pressures of an existing transmission without the electric motor-generator unit  28 . This allows easy re-design of an existing multi-speed automatic transmission to incorporate an electric motor-generator unit  28  while minimizing any increase in size of the transmission. 
     The description of the present disclosure is merely exemplary in nature and variations that do not depart from the gist of the present disclosure are intended to be within the scope of the present disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure.