Patent Publication Number: US-2004043861-A1

Title: Method and an apparatus for transferring torque and a hybrid vehicle incorporating the method and apparatus

Description:
FIELD OF THE INVENTION  
       [0001] The present invention generally relates to a method and an apparatus for transferring torque and to a hybrid vehicle incorporating the method and apparatus and more particularly, to an assembly for use within a hybrid vehicle which provides several gear ratios and which dynamically modifies the provided gear ratio in response to a sensed operational mode of the hybrid vehicle, effective to allow the hybrid vehicle to be efficiently operated and to be quickly and efficiently launched.  
       BACKGROUND OF THE INVENTION  
       [0002] A hybrid electric vehicle typically includes an internal combustion engine and an electric motor which cooperatively or independently generate torque which is communicated to the wheels of the vehicle, effective to allow the hybrid vehicle to be selectively driven and maneuvered.  
       [0003] At launch (e.g., during a desired acceleration of the vehicle), it is desirable to communicate a relatively large amount of torque emanating from the electric motor and/or from the internal combustion engine to the wheels (e.g., though a torque multiplier assembly) in order to allow the launch to quickly occur. However, once the launch has occurred, it is desirable to reduce the amount of torque which is communicated to the wheels in order to conserve fuel and/or to increase the amount of vehicular speed.  
       [0004] Conventionally, in a hybrid vehicle, the gear assembly, which couples the internal combustion engine and/or the electric motor (e.g., each of the torque generators or sources) to the wheels, provides a fixed gear ratio which allows a fixed amount of the generated torque to be communicated to the wheels and hence does not allow the amount of transferred torque to be desirably varied in the manner set forth above.  
       [0005] While some attempts have been made to provide different gear ratios in a hybrid electric vehicle, these attempts require the use of multiple types of gears (e.g., a planetary gear and several spur gears), thereby increasing the overall complexity and cost of the vehicle. Further, these arrangements also fail to provide a “neutral” gear arrangement which desirably reduces the likelihood of engine or component damage as the vehicle is towed, and these arrangements do not easily allow the electrical power source to be regenerated.  
       [0006] There is therefore a need for an assembly which dynamically adjusts the amount of torque which is transferred or communicated to the wheels of a hybrid type vehicle by selectively providing one of several gear ratios, effective to allow vehicular launch to quickly and efficiently occur and to allow an electric motor and internal combustion engine to efficiently operate, and which provides these operational benefits in a manner which overcomes some or all previously delineated drawbacks of prior assemblies/techniques.  
       SUMMARY OF THE INVENTION  
       [0007] It is a first non-limiting advantage of the present invention to provide a method and an apparatus for transferring torque in a manner which overcomes some or all of the previously delineated drawbacks of prior methods and apparatuses.  
       [0008] It is a second non-limiting advantage of the present invention to provide a hybrid vehicle which utilizes the method and apparatus of the preferred embodiment of the invention.  
       [0009] According to a first non-limiting aspect of the present invention, an assembly which regulates the amount of torque which is communicated to at least one wheel of a hybrid vehicle is provided.  
       [0010] According to a second non-limiting aspect of the present invention, a hybrid vehicle is provided and includes at least two torque production sources; at least one wheel; and a transmission assembly which is adapted to selectively receive a first amount of torque from at least one of the at least two sources and to communicate a second and third amounts of torque to the at least one wheel; and a controller which is coupled to the transmission assembly and which causes the second amount of torque to be communicated to the at least one wheel during launch and the third amount of torque to be communicated to the at least one wheel after launch, wherein the third amount of torque is less than the second amount of torque.  
       [0011] According to a third aspect of the present invention, a method for transmitting torque emanating from at least one of two torque production sources to at least one wheel is provided. The method comprises the steps of providing an assembly having a selectable gear ratio; transmitting the torque to the assembly; and communicating at least a portion of the torque from the assembly to the at least one wheel.  
       [0012] These and other features, aspects, and advantages of the present invention will become apparent from a reading of the following detailed description of the preferred embodiment of the invention and by reference to the following drawings. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0013]FIG. 1 is block diagram of a torque transfer assembly which is made in accordance with the teachings of the preferred embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION  
     [0014] Referring now to FIG. 1, there is shown a hybrid vehicle  10  having a torque transfer assembly  11  which is made in accordance with the teachings of the preferred embodiment of the invention.  
     [0015] Particularly, assembly  11  comprises a transmission assembly and/or may be used as part of an overall transmission assembly and issued within a hybrid vehicle having an internal combustion engine  12 , an electric motor  14 , a generator  16 , a differential or gear assembly  18 , at least one wheel  20 , a source of electrical power  22  (which may comprise a vehicular battery), and an accelerator pedal or member  23 . It should be appreciated that the invention is applicable to and may be used within a wide variety of hybrid vehicles and is not limited to use within a hybrid electric vehicle.  
     [0016] As shown, assembly  11  includes a first clutch assembly  24 , a second clutch assembly  26 , actuators  27 ,  29 , a controller  28  which is operable under stored program control, and a source of control fluid  31 . Controller  28  is physically coupled to the source of electrical power  22 , by bus  30 , and to the actuators  27 ,  29  by respective busses  32  and  34 . Actuators  27 ,  29  are respectively and communicatively coupled to the control fluid source  31 , by conduit  33 , and are respectively and communicatively coupled to clutch assemblies  24 ,  26 . Assembly  10  further includes a position sensor  36  which senses the position of the accelerator pedal or member  23  and which is communicatively coupled to the controller  28  by bus  38 . Moreover, controller  28  may be controllably coupled to the internal combustion engine  12 , to the generator  16 , and to the electric motor  14  by the use of bus  40 .  
     [0017] In operation, the controller  28  selectively causes one or both of the internal combustion engine  12  and the electric motor  14  to be operated. More particularly, the electric motor  14  is operated upon receipt of electrical power from the generator  16 . Internal combustion engine  12  is “activated” by causing a mixture of air and fuel to selectively enter the various cylinders (not shown) of the internal combustion engine  12  and to be respectively combusted in these cylinders. In one alternate embodiment, controller  28  is not connected to generator  16 , internal combustion engine  12 , and electric motor  14 .  
     [0018] Rather, the previously delineated control is accomplished by another controller within the hybrid vehicle (not shown).  
     [0019] As shown, clutch assembly  24  is physically and operatively coupled to the clutch assembly  26  and these operatively coupled clutch assemblies  24 ,  26  include a ring gear or portion  44 , a sun gear or portion  46 , and a carrier gear or portion  48 . The internal combustion engine  12  is physically and operatively coupled to the generator  16  and to the clutch  24 , and the generator  16 , is coupled to the electric motor  14 . Further, the electic motor  14  and the internal combustion engine  12  are each coupled to the carrier  48 .  
     [0020] In this non-limiting embodiment, only the electric motor  14  is used during launch. That is, launch is sensed by sensor  36  due to a change in the position of accelerator member  23 . A signal is then generated and communicated to the controller  28 , by the sensor  36 , effective to cause the controller  28  to activate actuator  29  thereby causing actuator  29  to provide some of the fluid from source  31  to assembly  11 , effective to disengage clutch  24  (e.g., plates  50  and  52  engage) and to engage clutch  26  (e.g., plates  54 ,  56  engage), thereby providing a relatively high gear ratio, allowing the torque energy to be communicated to the gear assembly  18  through the sun gear  46 . In one non-limiting embodiment the “higher” gear ratio in about 6.0. After launch, the controller  28  activates actuator  27  and deactivates actuator  29  (e.g., actuator  27  provides fluid from source  31  to assembly  11  and actuator  29  is prevented from supplying such fluid), thereby causing the clutch  24  to be engaged (e.g., plates  50  and  58  engage) and the clutch  26  to be disengaged (e.g., plates  56  and  60  engage), thereby providing a relatively low gear ratio which is dependent upon the ratio of the sun gear  46  to the carrier gear  48 . In one non-limiting embodiment the “low” gear or ratio is about 1.8. The torque emanating from the internal combustion engine  12  and/or from the electric motor  14  is communicated to the gear assembly  18  through the sun gear or portion  46 . In the foregoing manner, the gear ratio provided by the assembly  11  is dynamically adjustable depending upon the operational mode of the vehicle. Further, sensor  36  may be replaced with a speed sensor which senses the speed of the vehicular engine (e.g., acceleration is sensed by use of the speed of the engine  12 ).  
     [0021] Further, in another non-limiting embodiment, when both actuators  27 ,  29  are deactivated (e.g., neither supply fluid to the assembly  11 ), plate  50  (e.g., by the use of a spring assembly), resides between plates  52 ,  58  and plate  56  resides between plates  54 ,  60 , thereby desirably providing a neutral gear arrangement. In yet another non-limiting embodiment, the control fluid source  31  may be coupled to a pump (not shown) which may be selectively activated even when the internal combustion engine  12  is not operational. The pump may therefore selectively cause the contained fluid to be selectively communicated to the assembly  11  even when the engine  12  is not operational.  
     [0022] Further, in yet another non-limiting embodiment, plate  52  may be biased against plate  50 , thereby allowing electric power to be communicated to the power source  22  from the generator  16 . Hence, assembly  11  dynamically “regulates” the torque which is provided to the wheels  20  by dynamically allocating the amount of torque which is provided to the at least one wheel  20  depending upon the operational mode of the vehicle and by allowing a neutral gear arrangement to be selected without the use of a complicated spur gear arrangement.  
     [0023] It is to be understood that the invention is not limited to the exact construction which has been previously delineated above, but that various changes and modifications may be made without departing from the spirit and the scope of the inventions as are more fully delineated in the following claims.