Abstract:
A power train of a hybrid vehicle according to the invention has a simple configuration, high power performance, and reduced weight and fuel consumption, while being easily equipped in the vehicle. In particular, it is possible to reduce a significant amount of fuel consumption especially when a vehicle is traveling at a constant high-velocity.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is based on, and claims priority from, Korean Application Serial Number 10-2008-0054518, filed on Jun. 11, 2008, the disclosure of which is hereby incorporated by reference herein in its entirety. 
       TECHNICAL FIELD 
       [0002]    The present invention relates to a power train of a hybrid vehicle, particularly a power train of a hybrid vehicle that uses an internal combustion engine and a motor generator driven by electricity as a power source providing a driving force to driving wheels. 
       BACKGROUND ART 
       [0003]    Hybrid vehicles using an engine and a motor generator reduce the fuel consumption on the basis of a technology that uses, as a driving force, power from a motor generator having relatively good low-velocity torque characteristics at a low velocity and uses power from an engine having relatively good high-velocity torque characteristics at a high velocity. Further, as the hybrid vehicles do not generate exhaust gas while being driven by only the motor generator, it is environment-friendly. Techniques for reducing fuel consumption with a simpler configuration have been proposed. 
         [0004]    The above information disclosed in this Background ART section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
       SUMMARY 
       [0005]    Embodiments of the present invention provide a power train of a hybrid vehicle having simple configuration, high power performance, and reduced weight and fuel consumption, while being easily equipped in the vehicle. 
         [0006]    A power train of a hybrid vehicle includes a first planetary gear set, a second planetary gear set, a third planetary gear set, a first planetary gear set, a second planetary gear set, and a clutch. The second planetary gear set includes three elements. The third planetary gear set includes three elements. The two of the three elements are directly connected with two elements of the second planetary gear set and connected with a first motor generator and an engine. The first planetary gear set includes three elements. One of the three elements is connected with an output shaft, and another element is connected with a second motor generator. The other element of the three is directly connected with one of the elements of the second planetary gear set and the third planetary gear set other than the elements connected with the first motor generator and the engine and is intermittently connected with the other one of the elements of the second planetary gear set and the third planetary gear set other than the elements connected with the first motor generator and the engine. The brake selectively fixes the element of the first planetary gear set other than the elements connected with the output shaft and the second motor generator. The clutch can intermittently connect the element of the first planetary gear set connected with the brake to any one of the elements of the second planetary gear set and the third planetary gear set other than the elements connected with the first motor generator and the engine. 
         [0007]    Preferably, the first motor generator and the engine are each connected with the two elements of the second planetary gear set and the third planetary gear set, which are directly connected to each other. The output shaft is connected with an element of the first planetary gear set directly connected with an element of the second planetary gear set. The clutch intermittently connects the element of the first planetary gear set with the element of the third planetary gear set. 
         [0008]    Preferably, the first planetary gear set is a single-pinion type planetary gear set including a first sun gear connected with the second motor generator, a first carrier connected with the output shaft, and a first ring gear connected with the brake and the clutch. The second planetary gear set is a single-pinion type planetary gear set including a second sun gear connected with the first motor generator, a second carrier connected with the engine, and a second ring gear connected with the first carrier of the first planetary gear. The third planetary gear set is a double-pinion type planetary gear set including a third sun gear connected with the first motor generator, a third carrier connected with the engine, and a third ring gear connected with the first ring gear of the first planetary gear set through the clutch. 
         [0009]    The planetary gear sets are coaxially arranged in parallel in the order of the first planetary gear set, the second planetary gear set, and the third planetary gear set. The first motor generator is connected with the second planetary gear set through the third planetary gear set. The second motor generator is connected with the first planetary gear set. The engine is connected with the third planetary gear set through the second planetary gear set, passing through between the first planetary gear set and the second planetary gear set. The output shaft is connected with the second planetary gear set through the first planetary gear set. 
         [0010]    The first planetary gear set, in the lever analysis diagram, is arranged on a first straight line in the order of an element connected with the second motor generator, an element connected with the output shaft, and an element connected with the brake. The second planetary gear set, in the lever analysis diagram, is arranged on a second straight line in the order of an element connected with the output shaft, an element connected with the engine, and an element connected with the first motor generator. The third planetary gear set, in the lever analysis diagram, is arranged on the second straight line in the order of an element connected with the engine, an element connected with the first planetary gear set through the clutch, and an element connected with the first motor generator, in which when the clutch is engaged, the first straight line and second straight line make a single straight line. 
         [0011]    The elements of the planetary gear sets are arranged on the second straight line in the order of the element of the second planetary gear set connected with the output shaft, the element of the second planetary gear set and the element of the third planetary gear set connected with the engine, the element of the third planetary gear set connected with the first planetary gear set through the clutch, the element of the second planetary gear set and the element of the third planetary gear set connected with first motor generator. 
         [0012]    The power train of a hybrid vehicle according to the invention has a simple configuration, high power performance, and reduced weight and fuel consumption, while being easily equipped in the vehicle. In particular, since an engine mode that makes it possible to drive the vehicle using only engine to reduce the fuel consumption at constant high-velocity driving, the fuel consumption in long time driving on a highway can be reduced. 
         [0013]    It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles. 
         [0014]    The above and other features of the invention are discussed infra. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    For better understanding of the nature and objects of the present invention, reference should be made to the following detailed description with the accompanying drawings, in which: 
           [0016]      FIG. 1  is a view illustrating an example of the configuration of a power train of a hybrid vehicle according to the invention; 
           [0017]      FIG. 2  shows a power flow diagram and a lever analysis diagram illustrating that the power train of  FIG. 1  achieves an electric vehicle mode; 
           [0018]      FIG. 3  shows a power flow diagram and a lever analysis diagram illustrating that the power train of  FIG. 1  achieves a first hybrid mode; 
           [0019]      FIG. 4  shows a power flow diagram and a lever analysis diagram illustrating that the power train of  FIG. 1  achieves a second hybrid mode; 
           [0020]      FIG. 5  shows a power flow diagram and a lever analysis diagram illustrating that the power train of  FIG. 1  achieves an engine mode; 
           [0021]      FIG. 6  is a lever analysis diagram illustrating the operation of the clutch and the brake in the power train of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    Embodiments of the invention are described hereafter in detail with reference to the accompanying drawings, but theses embodiments are just examples and can be achieved in various modifications by those skilled in the art. Therefore, the present invention is not limited to the embodiments. 
         [0023]    Referring to  FIG. 1 , a power train of a hybrid vehicle includes: a second planetary gear set  5  including three elements; a third planetary gear set  7  including three elements two elements of which are directly connected with two elements of the second planetary gear set  5  and connected with a first motor generator  1  and an engine  3 ; a first planetary gear set  13  including three elements one element of which is connected with an output shaft  11 , another element of which is connected with a second motor generator  15 , and the other element of which is directly connected with one of the elements of the second planetary gear set  5  and the third planetary gear set  7  other than the elements connected with the first motor generator  1  and the engine  3  and is intermittently connected with the other one; a brake  17  that selectively fixes the element of the first planetary gear set  13  other than the elements connected with the output shaft  11  and the second motor generator  15 ; and a clutch  9  that intermittently connects the element of first planetary gear set  13  connected with the brake  17  to any one of the elements of the second planetary gear set  5  and the third planetary gear set  7  other than the elements connected with the first motor generator  1  and the engine  3 . 
         [0024]    That is, the power train includes the three planetary gear sets  5 ,  7 ,  13 , one clutch  9 , and one brake  17  such that it can transmit/receive power to/from the two motor generators  1 ,  15 , and receives power from the engine  3  and outputs shifted power through the output shaft  11 . 
         [0025]    The first motor generator  1  and the engine  3  are each connected with the two elements of second planetary gear set  5  and the third planetary gear set  7 , which are directly connected to each other. The output shaft  11  is connected with an element of the first planetary gear set  13  directly connected with an element of the second planetary gear set  5 . 
         [0026]    That is, the first motor generator  1  is connected with one element of the third planetary gear set  7  and one element of the second planetary gear set  5 . The engine  3  is connected with one element of the second planetary gear set  5  and one element of the third planetary gear set  7 . Further, the output shaft  11  is connected with one element of the first planetary gear set  13  and one element of the second planetary gear set  5 . 
         [0027]    The first planetary gear set  13  is a single-pinion type planetary gear set, in which a first sun gear is connected with the second motor generator  15 , a first carrier is connected with the output shaft  11 , and a first ring gear is connected with the brake  17  and the clutch  9 . 
         [0028]    The second planetary gear set  5  is a single-pinion type planetary gear set, in which a second sun gear is connected with the first motor generator  1 , a second carrier is connected with the engine  3 , and a second ring gear is connected with the first carrier of the first planetary gear set  13 . 
         [0029]    The third planetary gear set  7  is a double-pinion type planetary gear set, in which a third sun gear is connected with the first motor generator  1 , a third carrier is connected with the engine  3 , and a third ring gear is connected with the first ring gear of the first planetary gear set  13  through the clutch  9 . 
         [0030]    In this embodiment, the planetary gear sets are coaxially arranged in the order of the first planetary gear set  13 , the second planetary gear set  5 , and the third planetary gear set  7 . The first motor generator  1  is connected with the second planetary gear set  5  through the third planetary gear set  7 . The second motor generator  15  is connected with the first planetary gear set  13 . The engine  3  is connected with the third planetary gear set  7  through the second planetary gear set  5 , passing through between the first planetary gear set  13  and the second planetary gear set  5 . The output shaft  11  is connected with the second planetary gear set  5  through the first planetary gear set  13 . 
         [0031]    As shown in the lever analysis diagrams of  FIGS. 2 to 6 , the first planetary gear set  13  is arranged on a first straight line  19  in the order of an element connected with the second motor generator  15 , an element connected with the output shaft  11 , and an element connected with the brake  17 . The second planetary gear set  5  is arranged on a second straight line  21  in the order of an element connected with the output shaft  11 , an element connected with the engine  3 , and an element connected with the first motor generator  1 . The third planetary gear set  7  is arranged on the second straight line  21  in the order of an element connected with the engine  3 , an element connected with the first planetary gear set  13  through the clutch  9 , and an element connected with the first motor generator  1 , in which when the clutch  9  is engaged, the first straight line  19  makes a single straight line that is synchronized with the second straight line  21 . 
         [0032]    The elements of the planetary gear sets are arranged on the second straight line  21  in the order of the element of the second planetary gear set  5  connected with the output shaft  11 , the element of the second planetary gear set  5  and the element of the third planetary gear set  7  connected with the engine  3 , the element of the third planetary gear set  7  connected with the first planetary gear set  13  through the clutch  9 , and the element of the second planetary gear set  5  and the element of the third planetary gear set  7  connected with the first motor generator  1 . 
         [0033]    The operation in each mode of the power train of a hybrid vehicle according to an embodiment of the invention is described hereafter with reference to the lever analysis diagrams of  FIGS. 2 to 6 , which shows arrangement of the elements of the planetary gear sets and relative gear ratios of the elements as well. 
         [0034]      FIG. 2  illustrates an electric vehicle mode driving the vehicle using at least one motor generator while not operating an engine. 
         [0035]    In this mode, the brake  17  is engaged such that the first ring gear is fixed, and the clutch  9  is disengaged. 
         [0036]    As torque is generated by the second motor generator  15 , power from the second motor generator  15  is transmitted to the first sun gear of the first planetary gear set  13 . Since the first ring gear is fixed by the brake  17 , the power from the second motor generator  15  is reduced through the first carrier and outputted to the output shaft  11 . 
         [0037]    For illustration purposes, the rotational direction of the output shaft  11  is defined as a normal direction and the opposite direction is defined as an inverse direction hereafter. 
         [0038]    The engine  3  is stopped and connected with the second carrier of the second planetary gear set  5  and the third carrier of the third planetary gear set  7 , such that the first motor generator  1  rotates in the inverse direction without torque. 
         [0039]      FIG. 3  illustrates a first hybrid mode, in which the brake  17  fixes the first ring gear and the clutch  9  is disengaged, such that first ring gear is disengaged from the third ring gear. 
         [0040]    As the first motor generator  1  that has rotated in the inverse direction in the electric vehicle mode is rotated in the normal direction by torque as shown in  FIG. 3 , the engine  3  increases in rotational velocity and can be started and generate torque, and thus power supplied from the second motor generator  15  and power supplied from the engine  3  are simultaneously outputted to the output shaft  11 . 
         [0041]    The first motor generator  1  functions as a generator that provides a reaction force according to the torque of engine  3 , thereby substantially controlling the shift ratio. 
         [0042]    The second motor generator  15  cannot control the shift ratio because the first ring gear is fixed by the brake  17 , such that it only functions as a motor that transmits torque to the output shaft  11  through the first carrier. 
         [0043]      FIG. 4  illustrates a second hybrid mode that is different from the first hybrid mode, which is achieved by a process involving a change from the lever condition shown in  FIG. 3  to that shown in  FIG. 6 . 
         [0044]    More specifically, in order to change from the first hybrid mode to the second hybrid mode, the engine  3  and the first motor generator  1  are controlled in the first hybrid mode to make the velocity of the third ring gear reach 0 as shown in  FIG. 6 , and then the clutch  9  is engaged and the brake  17  is disengaged. 
         [0045]    After all of the first planetary gear set  13 , the second planetary gear set  5 , and the third planetary gear set  7  make a lever on a single straight line by engaging the clutch  9  as described above and the first ring gear can be rotated by disengaging the brake  17 , the first motor generator  1  and the second motor generator  15  are controlled to meet the condition shown in  FIG. 4 , thereby achieving the second hybrid mode. 
         [0046]    Here, the first motor generator  1  functions as a motor, rotating in the normal direction, and the second motor generator  15  functions as a generator, rotating in the inverse direction. 
         [0047]      FIG. 5  shows an engine mode that can be provided by the power train of the invention. 
         [0048]    The engine mode is achieved by controlling the shift ratio in the second hybrid mode such that the velocities of the first ring gear and the third ring gear are 0 as shown in the condition of  FIG. 6 , engaging the brake  17 , and then removing torque of the first motor generator  1  and the second motor generator  15 . 
         [0049]    Here, the engine  3  undertakes all of the torque supplied to the output shaft  11  and an overdrive shift ratio in which the second ring gear connected with the output shaft  11  rotates at a higher velocity than the second carrier connected with the engine  3  is achieved. 
         [0050]    Therefore, since it is possible to achieve high-velocity traveling at the overdrive shift ratio only using the engine  3 , without driving the first motor generator  1  and the second motor generator  15 , it is possible to reduce a significant amount of fuel consumption especially when a vehicle is traveling at a high speed for a long time. 
         [0051]    Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.