Abstract:
An electrically variable drive unit having two electric motors is provided. The first electric motor is mounted along the same axis as an engine. The second electric motor is mounted along the same axis as a transmission output.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Ser. No. 61/569,552, filed Dec. 12, 2011. 
    
    
     FIELD 
     The present disclosure relates to an electrically variable drive unit and, more particularly, to an electrically variable drive unit having a first electric motor on a first axis and a second electric motor on a second axis. 
     BACKGROUND 
     Hybrid drive units featuring a combination of electric motors and a conventional internal combustion engine are becoming increasingly popular in modern automobiles. However, typical prior art hybrid drive units are often complex, bulky, and difficult to package within the engine bay of an automobile. Typical prior art hybrid drive units have many moving components and large electrical motors that take up space within the transmission housing. What is needed, therefore, is a hybrid drive unit with better packaging and a lower center of gravity to improve vehicle handling and performance. A hybrid drive unit having a simpler design than prior art hybrid drive units is also desirable. 
     SUMMARY 
     In one form, the present disclosure provides a drive unit including a transmission input shaft, an output shaft, a first electric motor coaxial with the transmission input shaft, and a second electric motor coaxial with the output shaft. The first electric motor and the input shaft are coupled to the second electric motor and the output shaft 
     In another form, the present disclosure provides a hybrid transmission including a transmission input shaft, an output shaft, a first electric motor coaxial with the transmission input shaft, a second electric motor coaxial with the output shaft, and an input planetary gear set. The input planetary gear set includes an input carrier coupled to the transmission input shaft, a plurality of input pinion gears rotatably mounted on the input carrier, an input sun gear meshed with the plurality of input pinion gears and coupled to the first electric motor, and an input ring gear meshed with the plurality of input pinion gears and coupled to an output chain driver gear. The hybrid transmission also includes an electric motor planetary gear set including an electric motor carrier coupled to an output chain driven gear, a plurality of electric motor pinion gears rotatably mounted on the electric motor carrier, an electric motor sun gear meshed with the plurality of electric motor pinion gears and coupled to the second electric motor, and an electric motor ring gear meshed with the plurality of electric motor pinion gears and coupled to a transmission housing. The hybrid transmission further includes an output planetary gear set including an output sun gear coupled to the output chain driven gear and the electric motor carrier, an output carrier coupled to the output shaft, a plurality of output pinion gears rotatably mounted on the output carrier and meshed with the output sun gear, and an output ring gear meshed with the plurality of output pinion gears. The output chain driver gear is coupled to the output chain driven gear. 
     Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description, including disclosed embodiments and drawings, are merely exemplary in nature intended for purposes of illustration only and are not intended to limit the scope of the invention, its application or use. Thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic representation of an exemplary electrically variable drive unit according to the principles of the present disclosure; 
         FIG. 2  is a schematic representation of another exemplary electrically variable drive unit according to the principles of the present disclosure; 
         FIG. 3  is a schematic representation of another exemplary electrically variable drive unit according to the principles of the present disclosure; 
         FIG. 4  is a schematic representation of yet another exemplary electrically variable drive unit according to the principles of the present disclosure; 
         FIG. 5  is a schematic representation of yet another exemplary electrically variable drive unit according to the principles of the present disclosure; 
         FIG. 6  is a schematic representation of yet another exemplary electrically variable drive unit according to the principles of the present disclosure; 
         FIG. 7  is a schematic representation of yet another exemplary electrically variable drive unit according to the principles of the present disclosure; and 
         FIG. 8  is a schematic representation of yet another exemplary electrically variable drive unit according to the principles of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates an example schematic representation of an exemplary electrically variable drive unit according to the principles of the present disclosure. An engine  1  is coupled to a transmission input shaft  2 . The engine  1  may be any type of internal combustion engine or any other power source suitable for a vehicle. The transmission input shaft  2  is coupled to an input carrier  24  of an input planetary gear set  20 . Input pinion gears  22  of the input planetary gear set  20  are rotatably mounted on the input carrier  24 . The input pinion gears  22  are continuously meshed with an input sun gear  21  and an input ring gear  23  of the input planetary gear set  20 . The input sun gear  21  is coupled by a shaft  71  to a first electric motor  11  (“EMA  11 ”). The engine  1  and EMA  11  are coaxial. The input ring gear  23  is coupled to an output chain driver gear  61 . 
     A chain  60  couples the output chain driver gear  61  to an output chain driven gear  62 . The chain  60  may be a belt or any other means of connecting the output chain driver gear  61  to the output chain driven gear  62 . In one embodiment, the output chain driver gear  61  may be meshed with the output chain driven gear  62 . In another embodiment, the output chain driver gear  61  may be coupled to the output chain driven gear  62  by a plurality of gears  80 , as shown in  FIG. 5 . 
     The output chain driven gear  62  is coupled by a shaft  73  to an EMB carrier  34  of an EMB planetary gear set  30 . EMB pinion gears  32  of the EMB planetary gear set  30  are rotatably mounted on the EMB carrier  34 . The EMB pinion gears  32  are continuously meshed with an EMB sun gear  31  of the EMB planetary gear set  30  and an EMB ring gear  33  of the EMB planetary gear set  30 . The EMB ring gear  33  is non-rotatably coupled to the drive unit housing  10 . The EMB sun gear  31  is coupled by a shaft  72  to a second electric motor  12  (“EMB  12 ”). The shaft  73  coupled to the output chain driven gear  62  is also coupled to an output sun gear  41  of an output planetary gear set  40 . In one embodiment, the output planetary gear set  40  is on a first side of the chain  60  and the EMB planetary gear set  30  is on a second side of the chain  60 . Output pinion gears  42  of the output planetary gear set  40  are continuously meshed with the output sun gear  41  and an output ring gear  43  of the output planetary gear set  40 . The output ring gear  43  is non-rotatably coupled to the drive unit housing  10 . The output pinion gears  42  are rotatably mounted on an output carrier  44  of the output planetary gear set  40 . The output carrier  44  is coupled to an output shaft  3 . The output shaft  3  may be coupled to vehicle wheels, a differential, or to any other desired component. The output shaft  3  and EMB  12  are coaxial. 
       FIG. 2  illustrates an example schematic representation of another exemplary electrically variable drive unit according to the principles of the present disclosure. An engine  201  is coupled to a transmission input shaft  202 . The engine  201  may be any type of internal combustion engine or any other power source suitable for a vehicle. The transmission input shaft  202  is coupled to an input carrier  224  of an input planetary gear set  220 . Input pinion gears  222  of the input planetary gear set  220  are rotatably mounted on the input carrier  224 . The input pinion gears  222  are continuously meshed with an input sun gear  221  and an input ring gear  223  of the input planetary gear set  220 . The input sun gear  221  is coupled by a shaft  271  to a first electric motor  211  (“EMA  211 ”). The engine  201  and EMA  211  are coaxial. The input ring gear  223  is coupled to an output chain driver gear  261 . 
     A chain  260  couples the output chain driver gear  261  to an output chain driven gear  262 . The chain  260  may be a belt or any other means of connecting the output chain driver gear  261  to the output chain driven gear  262 . In one embodiment, the output chain driver gear  261  may be meshed with the output chain driven gear  262 . In another embodiment, the output chain driver gear  261  may be coupled to the output chain driven gear  262  by a plurality of gears  280 , as shown in  FIG. 6 . 
     The output chain driven gear  262  is coupled by a shaft  272  to an output sun gear  241  of an output planetary gear set  240 . Output pinion gears  242  of the output planetary gear set  240  are continuously meshed with the output sun gear  241  and an output ring gear  243  of the output planetary gear set  240 . The output ring gear  243  is non-rotatably coupled to the drive unit housing  210 . The output pinion gears  242  are rotatably mounted on an output carrier  244  of the output planetary gear set  240 . The output carrier  244  is non-rotatably coupled to an output driven gear  251 . The output driven gear  251  is continuously meshed with an output driver gear  252  coupled by a shaft  273  to a second electric motor  212  (“EMB  212 ”). The output carrier  244  is also coupled to an output shaft  203 . The output shaft  203  may be coupled to vehicle wheels, a differential, or to any other desired component. The output shaft  203  and EMB  212  are coaxial. 
       FIG. 3  illustrates an example schematic representation of another exemplary electrically variable drive unit according to the principles of the present disclosure. An engine  301  is coupled to a transmission input shaft  302 . The engine  301  may be any type of internal combustion engine or any other power source suitable for a vehicle. The transmission input shaft  302  is coupled to an input carrier  324  of an input planetary gear set  320 . Input pinion gears  322  of the input planetary gear set  320  are rotatably mounted on the input carrier  324 . The input pinion gears  322  are continuously meshed with an input sun gear  321  and an input ring gear  323  of the input planetary gear set  320 . The input sun gear  321  is coupled by a shaft  371  to a first electric motor  311  (“EMA  311 ”). The engine  301  and EMA  311  are coaxial. The input ring gear  323  is coupled to an output chain driver gear  361 . 
     A chain  360  couples the output chain driver gear  361  to an output chain driven gear  362 . The chain  360  may be a belt or any other means of connecting the output chain driver gear  361  to the output chain driven gear  362 . In one embodiment, the output chain driver gear  361  may be meshed with the output chain driven gear  362 . In another embodiment, the output chain driver gear  361  may be coupled to the output chain driven gear  362  by a plurality of gears  380 , as shown in  FIG. 7 . 
     The output chain driven gear  362  is coupled by a shaft  373  to an EMB carrier  334  of an EMB planetary gear set  330 . EMB pinion gears  332  of the EMB planetary gear set  330  are rotatably mounted on the EMB carrier  334 . The EMB pinion gears  332  are continuously meshed with an EMB sun gear  331  and an EMB ring gear  333  of the EMB planetary gear set  330 . The EMB ring gear  333  is non-rotatably coupled to the drive unit housing  310 . The EMB sun gear  331  is coupled by a shaft  372  to a second electric motor  312  (“EMB  312 ”). The shaft  373  coupled to the output chain driven gear  362  is also coupled to an output sun gear  341  of an output planetary gear set  340 . In one embodiment, the output planetary gear set  340  and the EMB planetary gear set  330  are on the same side of the chain  360 . Output pinion gears  342  of the output planetary gear set  340  are continuously meshed with the output sun gear  341  and an output ring gear  343  of the output planetary gear set  340 . The output ring gear  343  is non-rotatably coupled to the drive unit housing  310 . The output pinion gears  342  are rotatably mounted on an output carrier  344  of the output planetary gear set  340 . The output carrier  344  is coupled to an output shaft  303 . The output shaft  303  may be coupled to vehicle wheels, a differential, or to any other desired component. The output shaft  303  and EMB  312  are coaxial. 
     The drive unit of  FIGS. 1-3  may be operated as purely electric drive unit in which EMB  12  provides propulsion (“EV mode”) or as a parallel hybrid in which EMA  11  generates electricity or provides propulsion and EMB  12  and the engine  1  provide propulsion (“Parallel mode”). To operate the drive unit in the EV mode, EMB  12  is powered and rotates. EMA  11  is powered to rotate (“freewheel”) at the RPM necessary to prevent the engine  1  from rotating. The rotation of EMB  12  and freewheeling of EMA  11  causes the output shaft  3  to rotate. 
     To operate the drive unit in the Parallel mode, the engine  1  is powered and rotates, thereby, causing the transmission input shaft  2  to rotate. Some power from the engine  1  passes to EMA  11 , thereby, generating electricity to charge the drive unit&#39;s batteries and to power EMB  12 . The remainder of the power from the engine  1  is transferred to the output chain driver gear  61  and, thereby, the output shaft  3 . EMB  12  is powered and rotates, thereby, causing the output shaft  3  to rotate. In one embodiment, EMA  11  may also be powered to provide propulsive force. 
     In one embodiment, the center of gravity of the drive unit is reduced by configuring EMB  12  on the same axis as the output shaft  3 . This may improve vehicle handling performance and packaging ability of the drive unit. In one embodiment, the layout of EMA  11  and EMB  12  enables packaging of power electronics on top of the drive unit when installed in a vehicle. In one embodiment, the gearing between EMB  12  and the output shaft  3  achieves a gear reduction from EMB  12  to the output shaft. The gear reduction improves the ability of EMB  12  to power to vehicle. In one embodiment the gear reduction between EMB  12  and the output shaft  3  is approximately 9:1. In one embodiment, the gear ratio may be higher or lower. 
       FIG. 4  illustrates an example schematic representation of another exemplary electrically variable drive unit according to the principles of the present disclosure. An engine  401  is coupled to a transmission input shaft  402 . The engine  401  may be any type of internal combustion engine or any other power source suitable for a vehicle. The transmission input shaft  402  is coupled to an input carrier  424  of an input planetary gear set  420 . Input pinion gears  422  of the input planetary gear set  420  are rotatably mounted on the input carrier  424 . The input pinion gears  422  are continuously meshed with an input sun gear  421  and an input ring gear  423  of the input planetary gear set  420 . The input sun gear  421  is coupled by a shaft  471  to a first electric motor  411  (“EMA  411 ”). The engine  401  and EMA  411  are coaxial. The input ring gear  423  is coupled to an output chain driver gear  461 . 
     A chain  460  couples the output chain driver gear  461  to an output chain driven gear  462 . The chain  460  may be a belt or any other means of connecting the output chain driver gear  461  to the output chain driven gear  462 . In one embodiment, the output chain driver gear  461  may be meshed with the output chain driven gear  462 . In another embodiment, the output chain driver gear  461  may be coupled to the output chain driven gear  462  by a plurality of gears  480 , as shown in  FIG. 8 . The output chain driver gear  461  is coupled by a shaft  472  to a first clutch assembly  416 . The first clutch assembly  416  selectively couples the output chain driver gear  461  and, thereby, the chain  460  and output chain driven gear  462  to the drive unit housing  410 . 
     The output chain driven gear  462  is coupled by a shaft  473  to a second clutch assembly  417 . The second clutch assembly  417  selectively couples the shaft  473  and, thereby, output chain driven gear  462  to a shaft  474 . Shaft  474  couples the second clutch assembly  417  to an EMB carrier  434  of an EMB planetary gear set  430 . EMB pinion gears  432  of the EMB planetary gear set  430  are rotatably mounted on the EMB carrier  434 . The EMB pinion gears  432  are continuously meshed with an EMB sun gear  431  and an EMB ring gear  433  of the EMB planetary gear set  430 . The EMB ring gear  433  is non-rotatably coupled to the drive unit housing  410 . The EMB sun gear  431  is coupled by a shaft  475  to a second electric motor  412  (“EMB  412 ”). 
     The shaft  474  coupled to the second clutch assembly  417  is also coupled to an output sun gear  441  of an output planetary gear set  440 . In one embodiment, the output planetary gear set  440  is on a first side of the chain  460  and the EMB planetary gear set  430  is on a second side of the chain  460 . In another embodiment, the output planetary gear set  440  and the EMB planetary gear set  430  are on the same side of the chain  460 . Output pinion gears  442  of the output planetary gear set  440  are continuously meshed with the output sun gear  441  and an output ring gear  443  of the output planetary gear set  40 . The output ring gear  443  is non-rotatably coupled to the drive unit housing  410 . The output pinion gears  442  are rotatably mounted on an output carrier  444  of the output planetary gear set  440 . The output carrier  444  is coupled to an output shaft  403 . The output shaft  403  may be coupled to vehicle wheels, a differential, or to any other desired component. The output shaft  403  and EMB  412  are coaxial. 
     To start the engine  401 , the first clutch assembly  416  is activated, thereby, non-rotatably coupling the output chain driver gear  461  and shaft  472  to the drive unit housing  410 . Thus, EMA  411  will cause the input sun gear  421  to rotate when EMA  411  is powered. Because the input sun gear  423  is non-rotatably fixed in place, the input pinion gears  422  and input carrier  424  will rotate causing the input shaft  402  to rotate, thereby, starting the engine  401 . 
     The drive unit may be operated as purely electric drive unit in which EMB  412  provides propulsion (“EV mode”), as a series hybrid in which EMA  411  generates electricity and EMB  412  provides propulsion (“Series mode”), or as a parallel hybrid in which EMA  411  generates electricity and EMB  412  and the engine  401  provide propulsion (“Parallel mode”). To operate the drive unit in the EV mode, the second clutch assembly  417  is deactivated, thereby, permitting shaft  474  to rotate independently of shaft  473  and the output chain driven gear  462 . EMB  412  is powered and rotates, thereby, causing the output shaft  403  to rotate. All power from EMB  412  passes to the output shaft  403 . The first clutch assembly  416  may be either activated or deactivated. 
     To operate the drive unit in the Series mode, the first clutch assembly  416  is activated, thereby, non-rotatably coupling the output chain driver gear  461  and shaft  472  to the drive unit housing  410 , and the second clutch assembly  417  is deactivated, thereby, permitting shaft  474  to rotate independently of shaft  473  and the output chain driven gear  462 . The engine  401  is powered and rotates, thereby, causing the transmission input shaft  402  to rotate. All power from the engine  401  passes to EMA  411 , thereby, generating electricity to charge the drive unit&#39;s batteries and to power EMB  412 . EMB  412  is powered and rotates, thereby, causing the output shaft  403  to rotate. All power from EMB  412  passes to the output shaft  403 . 
     To operate the drive unit in the Parallel mode, the first clutch assembly  416  is deactivated, thereby, permitting the output chain driver gear  461  and chain  460  to rotate, and the second clutch assembly  417  is activated, thereby, coupling shaft  474  to shaft  473  and the output chain driven gear  462 . The engine  401  is powered and rotates, thereby, causing the transmission input shaft  402  to rotate. Some power from the engine  401  passes to EMA  411 , thereby, generating electricity to charge the drive unit&#39;s batteries and to power EMB  412 . The remainder of the power from the engine  401  is transferred to the output chain driver gear  461  and, thereby, the output shaft  403 . EMB  412  is powered and rotates, thereby, causing the output shaft  403  to rotate. 
     In one embodiment, the drive unit may be used in a range-extended hybrid vehicle. The drive unit may be operated in a purely EV mode until its batteries are depleted and then switch to a series hybrid or parallel hybrid mode utilizing the engine  401 . In one embodiment, the center of gravity of the drive unit is reduced by configuring EMB  412  on the same axis as the output shaft  403 . This may improve vehicle handling performance and packaging ability of the drive unit. In one embodiment, the layout of EMA  411  and EMB  412  enables packaging of power electronics on top of the drive unit when installed in a vehicle. In one embodiment, the gearing between EMB  412  and the output shaft  403  achieves a gear reduction from EMB  412  to the output shaft. The gear reduction improves the ability of EMB  412  to power to vehicle. In one embodiment the gear reduction between EMB  412  and the output shaft  403  is approximately 9:1. In one embodiment, the gear ratio may be higher or lower. 
     Thus, a hybrid drive unit with better packaging and a lower center of gravity to improve vehicle handling and performance is provided. The hybrid drive unit features a simpler design than many prior art hybrid drive units.