Abstract:
A transmission used in a hybrid vehicle comprising a planetary gear set and a synchronizer. The planetary gear set having a plurality of members and the synchronizer coupling and decoupling one of the members to change a speed ratio in the transmission.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application relates to, and is entitled to the benefit of the earlier filing date and priority of U.S. patent application Ser. No. 11/565,782, filed Dec. 1, 2006, the disclosure of which is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates generally to transmissions, and more particularly to transmissions used in hybrid vehicles. 
     BACKGROUND OF THE INVENTION 
     Hybrid vehicles commonly use at least two different energy conversion processes that can include a mechanical engine and an electric motor. And the associated transmission, or whether a transmission is used at all, sometimes depends on the particular drive configuration of the hybrid vehicle—parallel, serial, or mixed. One example of a transmission that can be used in a mixed hybrid is an electrically variable transmission (EVT). 
     EVT transmissions typically have at least one planetary gear set where the mechanical engine and the electric motor are operatively connected to different members of the planetary gear sets. Further, wet clutches are used to change speed ratios in the transmission, and hydraulic systems are in turn used to control the wet clutches. Hydraulic systems are complex, costly, and require many components including the particularly bulky and difficult to manufacture valve bodies. 
     SUMMARY OF THE INVENTION 
     One implementation of a presently preferred transmission that is used in a hybrid vehicle comprises at least one planetary gear set with a plurality of members, and at least one synchronizer that selectively couples and decouples at least one of the plurality of members to change a speed ratio in the transmission. 
     Another implementation of a presently preferred transmission that is used in a hybrid vehicle comprises an input shaft, an output shaft, a first planetary gear set, a second planetary gear set, a third planetary gear set, a first electric motor, a second electric motor, and at least one synchronizer. The first planetary gear set is operatively connected to the input shaft, the second planetary gear set is operatively connected to the first planetary gear set, and the third planetary gear set is operatively connected to the second planetary gear set. Further, the first electric motor is operatively connected to both the first and second planetary gear sets, and the second electric motor is operatively connected to both the second and third planetary gear sets. Lastly, the synchronizer can be actuated and deactuated to change a speed ratio in the transmission. 
     Another implementation of a presently preferred transmission that is used in a hybrid vehicle comprises an input shaft, an output shaft, a first planetary gear set, a second planetary gear set, a third planetary gear set, a first electric motor, a second electric motor, a first synchronizer, a second synchronizer, and a third synchronizer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objects, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments and best mode, appended claims and accompanying drawings in which: 
         FIG. 1  is a schematic of the general configuration of an embodiment of a transmission used in a hybrid vehicle; 
         FIG. 2  is an enlarged view of a synchronizer shown in the transmission of  FIG. 1 ; 
         FIG. 3  is a graph showing different component speeds on the y-axis versus vehicle speed on the x-axis for the transmission of  FIG. 1 , as the transmission changes speed ratios; and 
         FIG. 4  is a chart showing the status of each synchronizer at the different operating modes of the transmission of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring in more detail to the drawings,  FIG. 1  shows an exemplary configuration of a transmission  10  used in a hybrid vehicle (not shown) that does not require wet clutches to change speed ratios in the transmission. The hybrid vehicle itself can include, among other components, a mechanical engine  12  that sends torque to the transmission  10 , one or more batteries  14  that store electrical power, one or more power inverters  16  that deliver electrical power, and various controllers (not shown) that control components in the transmission. The mechanical engine  12  can be an internal combustion engine, a diesel engine, or the like, that can for example emit torque at about a constant 2,000 revolutions per minute (rpm) throughout transmission operating modes. The battery  14  can be used to store and dispense electrical power to electric motors. The battery can be a high voltage DC battery, or any other device that can likewise store and dispense electrical power. The power inverter  16  delivers that stored electrical power to electric motors and also enables the battery  14  to store power during regenerative braking. And the various controllers can include a motor controller (not shown) for an electric motor. 
     The transmission  10  can be of any type suitable for use in hybrid vehicles that receive torque from the mechanical engine  12  and deliver that torque to wheels (not shown) of the vehicle; in particular, the transmission  10  can be the two-mode type. The transmission  10  has at least one planetary gear set to provide a mechanical advantage, and at least one synchronizer to help provide that mechanical advantage. The transmission  10  can further include at least one electric motor that can give torque to the transmission, several shafts that can carry torque, and a housing  18  to provide structure to the transmission and that can be in the form of a transmission case or supports. The above transmission components, and others, take the transmission through various operating modes to change speed ratios. And many of these components are “operatively connected or joined” to one another, meaning that they emit or drive torque to one another either directly, as when the components physically touch each other, or indirectly, as when the components are connected through one or more other components. 
     As mentioned, a planetary gear set is used in the transmission  10  to give the transmission any one of numerous known mechanical advantages. For instance, the planetary gear set can include several members that—depending on a particular condition, i.e., whether the particular member is driving, driven, or held stationary—can provide a speed increase with a torque decrease, a speed decrease with a torque increase, a direct drive, a reverse drive, and others. Each condition can constitute a different operating mode with its own speed ratios, output torques, and output speeds. 
     Particular to this embodiment, a first planetary gear set  26  can include a sun gear  28 , a plurality of planet gears  30  that are meshed with the sun gear  28  and disposed on a carrier  32 , and a ring gear  34  that is meshed with the planet gears  30 . Likewise, a second planetary gear set  36  can include a sun gear  38 , a plurality of planet gears  40  that are meshed with the sun gear  38  and disposed on a carrier  42 , and a ring gear  44  that is meshed with the planet gears  40 . And a third planetary gear set  46  can include a sun gear  48 , a plurality of planet gears  50  that are meshed with the sun gear  48  and disposed on a carrier  52 , and a ring gear  54  that is meshed with the planet gears  50 . As between these planetary gear sets, the sun gear  28  can be operatively joined to the ring gear  44  through a hub plate gear  86 , and the sun gear  38  can be operatively connected to the sun gear  48  through a second sleeve shaft  62 . 
     The several shafts generally carry torque through the transmission  10  from the mechanical engine  12  to drive the hybrid vehicle. An input shaft  20  receives torque from the mechanical engine  12  and sends that torque to other transmission components. The input shaft can be driven directly by the mechanical engine or indirectly through a torque transfer device (not shown). The torque transfer device can be incorporated between the mechanical engine  12  and the input shaft  20  to provide a selective torque-dampened connection between the mechanical engine and the input shaft. At its other end, the input shaft  20  is operatively connected to a planetary gear set; specifically, the input shaft  20  can be operatively connected or directly connected to the ring gear  34 . 
     An intermediate shaft  22  can also be included. The intermediate shaft  22  can operatively join one planetary gear set to another planetary gear set, and can be selectively operatively connected to one more planetary gear set. Specifically, the intermediate shaft  22  can operatively join the carrier  32  to the carrier  42 . In this way, the intermediate shaft can carry torque between these planetary gear sets. 
     An output shaft  24  can be further included that receives torque from other transmission components and sends it eventually to the drive wheels. To do this, the output shaft  24  is operatively connected to the carrier  52  of the third planetary gear set  46 . 
     Also mentioned, an electric motor can be used in the transmission  10  that can act as a motor or a generator in a particular operating mode. For example, the electric motor can give torque to, or drive, one or more planetary gear sets, provide a braking function, and can substantially synchronize the speeds of different transmission components. The term “substantially synchronize” can mean bringing the relative rotation speed of each different transmission component within a particular range, for example within a +/−50 rpm range, so that the components can eventually engage each other at about the same speed. 
     Still referring to  FIG. 1 , a first electric motor  56 , or generator, can be incorporated between the first planetary gear  26  and the second planetary gear set  36 . The first electric motor  56  can be operatively connected to, and thus can drive, a member on each of the first and second sets by a first sleeve shaft  58 . Specifically, the first electric motor  56  can be operatively connected to the sun gear  28  and the ring gear  44 . 
     Similarly, a second electric motor  60 , or generator, can be incorporated between the second planetary gear set  36  and the third planetary gear set  46 . The second electric motor  60  can be operatively connected to, and thus can drive, a member on each of the second and third planetary gear sets by the second sleeve shaft  62 . Specifically, the second electric motor  60  can be operatively connected to the sun gear  38  and the sun gear  48 . 
     A synchronizer is used in the transmission  10  to smoothly engage two rotating transmission components so that they rotate at the same speed while avoiding a transmission bump, or noticeable impulse load during an operating mode change. The synchronizer can be selectively actuated or deactuated to couple/decouple or ground/unground the particular transmission component when the transmission changes operating modes. In general, synchronizers will be known to those of ordinary skill in the art, and suitable synchronizers can include those used in manual transmissions or in transfer cases. 
     In this embodiment, a first synchronizer  64  is disposed adjacent the third planetary gear set  46 , specifically adjacent the ring gear  54  so that the first synchronizer can ground the ring gear to the transmission housing  18  when actuated, and unground the ring gear from the housing when deactuated. Referring to  FIG. 2 , the first synchronizer  64  is a double cone synchronizer, but it could be a single or triple cone synchronizer depending partly on the thermal load it will endure. The first synchronizer  64  can have, among other components, a sleeve  66 , a hub  68 , and one or more cones or rings  70 ,  72 , and  74 . The sleeve  66  has an external groove  76  for receiving a shift fork  78  which can be carried by a shift rail  80  that both can direct the sleeve&#39;s movement. The shift fork and rail can be controlled by a controller (not shown) to actuate and deactuate the synchronizer. The hub  68  can be splined to a transmission component, or in this case, attached to the transmission housing  18 . And the cones or rings  70 ,  72 , and  74  can provide various contact and friction surfaces during synchronization. The above construction and functionality are similar for a second synchronizer  82  and a third synchronizer  84 . 
     The second synchronizer  82  is disposed adjacent the third planetary gear set  46 , specifically adjacent the carrier  52  so that the second synchronizer can couple the carrier to the intermediate shaft  22  when actuated, and decouple the carrier from the intermediate shaft when deactuated. The second synchronizer  82  is also a double cone synchronizer that can have a sleeve, a hub, and one or more cones or rings. A controller similarly controls a shift fork and a shift rail. 
     The third synchronizer  84  is disposed adjacent the second planetary gear set  36 , specifically adjacent the ring gear  44  so that the third synchronizer can ground the ring gear to the transmission housing  18  when actuated, and unground the ring gear from the housing when deactuated. The third synchronizer  84  can further couple the ring gear  44  to the second sleeve shaft  62  when actuated, and decouple the ring gear from the second sleeve shaft when deactuated. The third synchronizer  84  is also a double cone synchronizer that can have a sleeve, a hub, and one or more cones or rings. A controller similarly controls a shift fork and a shift rail. 
       FIG. 1  is only a schematic of the configuration of the transmission  10 , and as such does not show the physical packaging of the transmission. But in general, the transmission can be packaged so that the input shaft  20 , the intermediate shaft  22 , and the output shaft  24  are generally aligned along an axis constituting the center axis of the transmission. Also, the first, second, and third planetary gear sets  26 ,  36 , and  46  can be all coaxially arranged about the intermediate shaft  22 ; as can the first and second electric motors  56  and  60 . Further, the first and second electric motors can circumscribe, or partly surround the first, second, and third planetary gear sets. And the first and second sleeve shafts  58  and  62  can circumscribe the intermediate shaft  22 . 
     Referring to  FIGS. 3 and 4 , the transmission  10  can be dynamically shifted through several operating modes including a low EVT mode with a 1 st  mode and a 2 nd  mode, a high EVT mode with a 3 rd  mode and a 4 th  mode, and a reverse mode. In general, the operating modes can be controlled by various devices, sources, signals and the like. For example, an ECU (not shown) can be used to monitor various operating conditions—including speed resolvers  88 ,  90  to monitor the respective electric motor speeds, and speed sensors  92 ,  94  to monitor the respective input and output shaft speeds—and respond by controlling certain transmission components, like the synchronizers, to put the transmission in a particular operating mode. In each mode, a synchronizer can be actuated or deactuated to provide different speed ratios, output torques, and output speeds. 
     As mentioned, the transmission  10  can be of the two-mode type. This means that the transmission first goes through a low range, and then a high range. In the low range, the transmission  10  can operate in the low EVT mode with the first synchronizer  64  continually actuated “on” (S 1 ) when the transmission shifts in the 1 st  and 2 nd  modes. And in the high range, the transmission  10  can operate in the high EVT mode with the second synchronizer  82  continuously actuated on (S 2 ) when the transmission shifts in the 3 rd  and 4 th  modes. 
     For example, the transmission  10  can start in the low EVT mode to move the vehicle. Here, the transmission can have two operating options, both where the first synchronizer  64  can be actuated on (S 1 ) to ground the ring gear  54 . In option one, the second electric motor  60  (EM 2 ) can alone drive the third planetary gear set  46  independent of the first electric motor  56  (EMI) and the mechanical engine  12  (ME). Or in option two, the second electric motor  60  can drive the third planetary gear set  46  in one direction to move the vehicle, while the first electric motor  56  can run in an opposite direction and then the mechanical engine  12  can also run. In either option, the electric motors can substantially synchronize the speed of the ring gear  44  with that of the second sleeve shaft  62  so that the third synchronizer  84  can be actuated on (S 4 ) to couple the ring gear  44  to the second sleeve shaft  62 . The transmission  10  is then shifted in the 1 st  mode. 
     Still in the low EVT mode, the electric motors can substantially synchronize the speed of the carrier  52  with that of the intermediate shaft  22  so that the second synchronizer  82  can be actuated on (S 2 ) to couple the carrier  52  to the intermediate shaft  22 . Also, the third synchronizer  84  (S 4 ) can be deactuated to decouple the ring gear  44  from the second sleeve shaft  62 . The transmission  10  is then shifted in the 2 nd  mode. 
     In the high range, the transmission  10  can operate in the high EVT mode. The electric motors can substantially synchronize the speed of the ring gear  44  with that of the second sleeve shaft  62  so that the third synchronizer  84  can be actuated on (S 4 ) to couple the ring gear  44  to the second sleeve shaft  62 . Also, the first synchronizer  64  can be deactuated to unground the ring gear  54 , and, as mentioned, the second synchronizer  82  can be actuated on (S 2 ). The transmission  10  is then shifted in the 3 rd  mode. 
     Still in the high EVT mode, the third synchronizer  84  (S 4 ) can be deactuated to decouple the ring gear  44  from the second sleeve shaft  62 . Also, the electric motors can slow the speed of the ring gear  44  so that the third synchronizer  84  can be actuated on (S 3 ) to ground the ring gear  44 , and the second synchronizer  82  can be actuated on (S 2 ). The transmission  10  is then shifted in the 4 th  mode. 
     To shift in the reverse mode, the first synchronizer  64  can be actuated on (S 1 ) to ground the ring gear  54 , and the second electric motor  60  can rotate in a direction opposite of the direction it rotates when the vehicle moves forward. Further operating modes can include an engine start-stop mode and an electric mode, both where the first synchronizer  64  can be actuated on (S 1 ). 
     Indeed, the graph of  FIG. 3  shows that while the transmission is dynamically shifting through the 1 st , 2 nd , 3 rd , and 4 th  operating modes, the mechanical engine speed (ME) can remain generally constant and the vehicle output speed gradually increases. 
     While certain preferred embodiments have been shown and described, persons of ordinary skill in this art will readily recognize that the preceding description has been set forth in terms of description rather than limitation, and that various modifications and substitutions can be made without departing from the spirit and scope of the invention. The invention is defined by the following claims.