Abstract:
A hybrid transmission providing multiple modes of operation in a compact package. The hybrid transmission utilizes compact electric motors and features simple construction in comparison to conventional hybrid transmissions.

Description:
FIELD 
       [0001]    The present disclosure relates to a hybrid drive unit, more particularly, to a multi-mode hybrid variable drive unit. 
       BACKGROUND 
       [0002]    Many modern automobiles utilize a hybrid transmission system in which an internal combustion engine, electric machine(s), or combination of the two provides propulsion for the vehicle. In a typical hybrid transmission system, torque from the engine and electric machines is supplied to a plurality of gears to drive the wheels of the vehicle. Many typical hybrid transmissions provide only a single mode of operation. This single mode of operation presents overall system compromises. A decision must be made between a transmission that provides optimum torque during low speed operation or optimum efficiency for operation at highway speeds. Many typical hybrid transmissions are unable to provide both optimum low speed torque and highway speed efficiency. Typically, in an attempt to remedy this problem, large and powerful electric machines must be used. However, large and powerful electric machines are more expensive and take up more space within the hybrid transmission. 
         [0003]    Alternatively, some hybrid transmissions provide multiple modes of operation whereby different transmission gear ratios may be achieved. However, typical prior art multi-mode hybrid transmissions include many gears and clutches and are very inefficient. For example, many prior art hybrid transmissions feature multiple planetary gear sets that must rotate at all times. This negatively impacts vehicle fuel economy. Moreover, many prior art hybrid transmissions are complex and large in size. This increases manufacturing costs and makes it difficult to fit the hybrid transmission within the vehicle. Therefore, improvement in the art is desirable. 
       SUMMARY 
       [0004]    In one form, the present disclosure provides a hybrid drive unit including a first planetary gear set coupled to a hybrid input shaft, a second planetary gear set coupled to the first planetary gear set, and a first electric machine coupled to the first planetary gear set. The hybrid drive unit also includes a second electric machine coupled to the first planetary gear set, a first clutch mechanism configured to selectively lock the second planetary gear set; and a second clutch mechanism configured to selectively couple a ring gear of the second planetary gear set to a hybrid drive unit housing. 
         [0005]    In another form, the present disclosure provides a hybrid drive unit including a hybrid input shaft and a first planetary gear set coupled to the hybrid input shaft. The first planetary gear set includes a first planetary gear set sun gear, a first planetary gear set carrier, and a first planetary gear set ring gear. The hybrid drive unit also includes a second planetary gear set coupled to the first planetary gear set. The second planetary gear set includes a second planetary gear set sun gear, a second planetary gear set carrier, and a second planetary gear set ring gear. The hybrid drive unit further includes a first electric machine coupled to the first planetary gear set sun gear, a second electric machine coupled to the first planetary gear set ring gear, a first clutch mechanism configured to selectively lock the second planetary gear set, and a second clutch mechanism configured to selectively couple the second planetary gear set ring gear to a hybrid drive unit housing. The first planetary gear set carrier is coupled to the hybrid input shaft and the second planetary gear set sun gear is coupled to the first planetary gear set ring gear. 
         [0006]    Thus, a hybrid transmission is provided that offers multiple modes of operation in a compact package. The hybrid transmission utilizes smaller and more compact electric machines. The hybrid transmission also features simpler construction than prior art designs. 
         [0007]    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 
         [0008]      FIG. 1  is a schematic representation of an exemplary hybrid drive unit constructed in accordance with the disclosed principles; and 
           [0009]      FIG. 2  is a schematic representation of another exemplary hybrid drive unit constructed in accordance with the disclosed principles. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]      FIG. 1  is an example schematic representation of a hybrid drive unit  10  according to an embodiment disclosed herein. An engine  1  is coupled to a torsional vibration damper  2 . The engine  1  may be any type of power source including an internal combustion engine, turbine engine, electric machine, or any other desired power source. The torsional vibration damper  2  is coupled to a hybrid drive unit  10  by a hybrid input shaft  6 . The hybrid input shaft  6  couples the torsional vibration damper  2  to a carrier  24  of a first planetary gear set  20 . A plurality of planet gears  22  are rotationally mounted on the carrier  24  and are continuously meshed with a sun gear  21  and a ring gear  23 . The sun gear  21  is coupled by a shaft  41  to a first electric machine  11  (“EMA”). The ring gear  23  is coupled by a shaft  7  to a second electric machine  12  (“EMB”). The first electric machine  11  and second electric machine  12  may be electric motors, electric generators, or any other type of desired power source. 
         [0011]    Shaft  41  is also coupled to a second clutch mechanism  52  that selectively couples shaft  41  to a carrier  34  of a second planetary gear set  30 . A plurality of planet gears  32  are rotationally mounted on the carrier  34  and are continuously meshed with a sun gear  31  and a ring gear  33 . The ring gear  33  is also coupled to a third clutch mechanism  53 . The third clutch mechanism  53  selectively couples the ring gear  33  to a hybrid assembly housing  16 . The sun gear  31  is coupled to shaft  7 . The carrier  34  is also coupled to a first driver gear  35  that is continuously meshed with a first driven gear  36 . The first driven gear  36  is coupled by a shaft  8  to a second driver gear  37 . The second driver gear  37  is continuously meshed with a second driven gear  38  that is coupled to an output shaft  9 . Shaft  7  is also coupled to a first clutch mechanism  51  that selectively couples shaft  7  to the second driven gear  38 . 
         [0012]    The hybrid drive unit  10  of  FIG. 1  may be operated in three different modes referred to herein as Mode 1, Mode 2, and Mode 3. To operate the hybrid drive unit  10  in Mode 1, the third clutch mechanism  53  is activated, thereby, coupling the ring gear  33  to hybrid assembly housing  16 . The first clutch mechanism  51  and second clutch mechanism  52  are deactivated. Thus, shaft  7  is free to rotate at a different RPM than second driven gear  38  and shaft  41  is free to rotate at a different RPM than carrier  34 . Torque to the output shaft  9  may be provided by the engine  1  in combination with the second electric machine  12 . The first electric machine  11  may be used to generate electricity during vehicle braking or as otherwise desired. In one embodiment, the hybrid drive unit  10  achieves a hybrid drive unit gear ratio of approximately 4.5:1 when operated in Mode 1. 
         [0013]    To transition the hybrid drive unit  10  from operation in Mode 1 to operation in Mode 2, the first electric machine  11  is powered to cause the RPM of shaft  41  to approximately match the RPM of carrier  34 . In one embodiment, the engine  1 , second electric machine  12 , first electric machine  11 , or any combination of the three may be utilized to cause the RPM of shaft  41  to approximately match the RPM of carrier  34 . Once the RPM of shaft  41  approximately matches the RPM of carrier  34 , the second clutch mechanism  52  is activated followed by deactivation of the third clutch mechanism  53 . In one embodiment, the shifting process includes activation of the second clutch mechanism  52  and deactivation of the third clutch mechanism  53  and takes approximately 500 milliseconds. In one embodiment, the shift takes more than 500 milliseconds. In another embodiment, the shift takes less than 500 milliseconds. A shift from Mode 2 to Mode 1 would be performed in a manner similar to the shift from Mode 1 to Mode 2 except that one, or any combination of the engine  1 , second electric machine  12 , first electric machine  11 , would be utilized to cause the RPM of ring gear  33  to be approximately the same as the RPM of hybrid assembly housing  16 . Then, the first clutch mechanism  51  would be activated, followed by deactivation of the second clutch mechanism  52 . 
         [0014]    To operate the hybrid drive unit  10  in Mode 2, the second clutch mechanism  52  is activated, thereby, coupling shaft  41  to carrier  34 . The first clutch mechanism  51  and third clutch mechanism  53  are deactivated. Thus, shaft  7  is free to rotate at a different RPM than second driven gear  38  and ring gear  33  is free to rotate at a different RPM than hybrid assembly housing  16 . Torque to the output shaft  9  may be provided by the engine  1  in combination with the first electric machine  11 . The second electric machine  12  may be used to generate electricity during vehicle braking or as otherwise desired. When the hybrid drive unit  10  is operated in Mode 2, the second planetary gear set  30  is locked and, thereby, unloaded. Locking and unloading the second planetary gear set  30  reduces friction losses within the hybrid drive unit  10 . In one embodiment, the hybrid drive unit  10  achieves a hybrid drive unit gear ratio of between approximately 4.5:1 and 1:1 when operated in Mode 2. 
         [0015]    To transition the hybrid drive unit  10  from operation in Mode 2 to operation in Mode 3, the engine  1  and second electric machine  12  are powered to cause the RPM of shaft  7  to approximately match the RPM of second driven gear  38 . Simultaneously, the first electric machine  11  is operated at an approximately constant RPM. Once the RPM of shaft  7  approximately matches the RPM of second driven gear  38 , the first clutch mechanism  51  is activated. In one embodiment, the shifting process includes activation of the first clutch mechanism  51  and takes approximately 500 milliseconds. In one embodiment, the shift takes more than 500 milliseconds. In another embodiment, the shift takes less than 500 milliseconds. A shift from Mode 3 to Mode 2 would be performed by simply deactivating the first clutch mechanism  51 . 
         [0016]    To operate the hybrid drive unit  10  in Mode 3, the first clutch mechanism  51  and second clutch mechanism  52  are activated. Thus, shaft  7  is coupled to second driven gear  38  and shaft  41  is coupled to carrier  34 . The third clutch mechanism  53  is deactivated, thereby allowing ring gear  33  to rotate at a different RPM than hybrid assembly housing  16 . Torque to the output shaft  9  may be provided by the engine  1  in combination with the second electric machine  12 . The first electric machine  11  may be used to generate electricity during vehicle braking or as otherwise desired. In one embodiment, the hybrid drive unit  10  achieves a hybrid drive unit gear ratio of approximately 1:1 when operated in Mode 3. 
         [0017]      FIG. 2  illustrates an example of another hybrid drive unit  210  according to another embodiment disclosed herein. An engine  201  is coupled to a torsional vibration damper  202 . The engine  201  may be any type of power source including an internal combustion engine, turbine engine, electric machine, or any other desired power source. The torsional vibration damper  202  is coupled to a hybrid drive unit  210  by a hybrid input shaft  206 . The hybrid input shaft  206  couples the torsional vibration damper  202  to a carrier  224  of a first planetary gear set  220 . A plurality of planet gears  222  are rotationally mounted on the carrier  224  and are continuously meshed with a sun gear  221  and a ring gear  223 . The sun gear  221  is coupled by a shaft  207  to a first electric machine  211  (“EMA”). The ring gear  223  is coupled to a second electric machine  212  (“EMB”). The first electric machine  211  and second electric machine  212  may be an electric motor, electric generator, or any other type of desired power source. 
         [0018]    Shaft  207  is also coupled to a second clutch mechanism  252  that selectively couples shaft  207  to a first driver gear  239 . The first driver gear  239  is coupled by a chain drive  260  to a first driven gear  240 . The chain drive  260  may be a chain, belt, or any other suitable linkage. The first driven gear  240  is coupled by a shaft  242  to a ring gear  233  of a second planetary gear set  230 . The ring gear is continuously meshed with a plurality of planet gears  232  rotationally mounted on a carrier  234 . The plurality of planet gears  232  are continuously meshed with a sun gear  231 . The sun gear  231  is coupled by a shaft  208  to a second driven gear  236 . A first clutch mechanism  251  selectively couples shaft  242  to a hybrid assembly housing  216 . A third clutch mechanism  253  selectively couples shaft  242  to shaft  208  and, thereby, sun gear  231 . 
         [0019]    The second driven gear  236  is continuously meshed with a second driver gear  235  coupled by a shaft  241  to the first electric machine  212  and ring gear  223 . The carrier  234  is coupled by a shaft  244  to an output driver gear  237  that is continuously meshed with an output driven gear  238 . In one embodiment, the output driven gear  238  may directly or otherwise connected to a vehicle&#39;s wheels (not shown). 
         [0020]    The hybrid drive unit  210  of  FIG. 2  may be operated in two different modes: Mode 1 and Mode 2. To operate the hybrid drive unit  210  in Mode 1, the first clutch mechanism  251  is activated, thereby, coupling shaft  242  to hybrid assembly housing  216 . The second clutch mechanism  252  and third clutch mechanism  253  are deactivated. Thus, shaft  207  is free to rotate at a different RPM than first driver gear  239  and shaft  242  is free to rotate at a different RPM than sun gear  231 . Because the first clutch mechanism  251  is activated, the second planetary gear set  230  is effectively locked and, thereby, unloaded. Locking and unloading the second planetary gear set  230  reduces friction losses within the hybrid drive unit  210 . Torque to the output driven gear  238  may be provided by the engine  201  in combination with the second electric machine  212 . The first electric machine  211  may be used to generate electricity during vehicle braking or as otherwise desired. 
         [0021]    To transition the hybrid drive unit  210  from operation in Mode 1 to operation in Mode 2, the second clutch mechanism  252  is activated. Once the second clutch mechanism  252  is fully activated, the first clutch mechanism  251  is deactivated. During this transition period, the first electric machine  211  is used to provide torque and the second electric machine  212  is used to generate electricity. The engine  201 , first electric machine  211 , second electric machine  212 , or any combination of the three, are used to cause the RPM of shaft  242  to be approximately the same as the RPM of sun gear  231 . Once the RPM of shaft  242  is approximately the same as the RPM of sun gear  231 , the third clutch mechanism  252  is activated followed by deactivation of the second clutch mechanism  252 . In one embodiment, the shifting process includes activation of the second clutch mechanism  252 , deactivation of the first clutch mechanism  251 , activation of the third clutch mechanism  253 , deactivation of the second clutch mechanism  252  and takes approximately 500 milliseconds. In one embodiment, the shift takes more than 500 milliseconds. In another embodiment, the shift takes less than 500 milliseconds. 
         [0022]    A shift from Mode 2 to Mode 1 would be performed in a similar manner except that one, or any combination of the engine  201 , second electric machine  212 , first electric machine  211 , would be utilized to cause the RPM of shaft  207  to be approximately the same as the RPM of first driver gear  239 . Then, the second clutch mechanism  252  would be activated followed by deactivation of the third clutch mechanism  253 . Next, the first clutch mechanism  251  would be activated, followed by deactivation of the second clutch mechanism  252 . 
         [0023]    To operate the hybrid drive unit  210  in Mode 2, the third clutch mechanism  253  is activated, coupling shaft  242  to sun gear  231 . The first clutch mechanism  251  and second clutch mechanism  252  are deactivated. Thus, shaft  242  is free to rotate at a different RPM than hybrid assembly housing  216  and shaft  207  is free to rotate at a different RPM than first driver gear  239 . Torque to the output driven gear  238  may be provided by the engine  201  in combination with the second electric machine  212 . The first electric machine  211  may be used to generate electricity during vehicle braking or as otherwise desired. 
         [0024]    In one embodiment, the first clutch mechanism  51 , second clutch mechanism  52 , and third clutch mechanism  53  may be any desired type of coupling device including a wet clutch, dry clutch, dog clutch, or multi-plate clutch. In one embodiment, the clutch mechanisms  51 ,  52 ,  53  may couple together two components when they are rotating within a predetermined RPM of each other. For instance, the clutch mechanisms  51 ,  52 ,  53  may couple together two components once they are rotating within approximately 50 RPM of each other. In another embodiment, the clutch mechanisms  51 ,  52 ,  53  may couple together two components once they are rotating within greater than or less than 50 RPM of each other. As an example, a wet clutch, dry clutch, or multi-plate clutch may be used to couple together two components rotating within approximately 50 RPM of each other. In another embodiment, the clutch mechanisms  51 ,  52 ,  53  may couple together two components only once they are rotating at approximately the same RPM. As an example, a dog clutch may be used to couple together two components rotating at approximately the same RPM. 
         [0025]    Thus, a hybrid transmission providing multiple modes of operation in a compact package is disclosed herein. Moreover, the hybrid transmission includes smaller and more compact electric machines. The hybrid transmission also features simpler construction than prior art designs, because it utilizes fewer parts.