Abstract:
A power transmitting apparatus of hybrid vehicles that transmits torque from an engine and first and second motor/generators to an output shaft is provided. The apparatus may include: a first planetary gear set having a first operating member fixedly connected to the second motor/generator, a second operating member selectively connected to the first operating member, and a third operating member; and a second planetary gear set having a fourth operating member fixedly connected to the engine and selectively connected to the second operating member, a fifth operating member fixedly connected to the first motor/generator and selectively connected to the second operating member, and a sixth operating member fixedly connected to the third operating member and the output shaft. With the apparatus, fuel efficiency can be remarkably improved.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2008-0039489 filed on Apr. 28, 2008, the entire contents of which are incorporated herein by reference. 
       BACKGROUND 
       [0002]    (a) Technical Field 
         [0003]    The present invention relates to hybrid vehicles. More particularly, the present invention relates to a power transmitting apparatus of hybrid vehicles. 
         [0004]    (b) Related Art 
         [0005]    A hybrid vehicle means a vehicle driven by at least two different energy sources. Mostly, a hybrid vehicle is called a hybrid electric vehicle which includes an engine using fuel and an electric motor using electricity in order to generate power. 
         [0006]    Since such a hybrid vehicle uses power of the engine as a main energy source and power of the motor as an auxiliary energy source, a conversion ratio of mechanical energy into electrical energy is low and power delivery efficiency is very high. 
         [0007]      FIG. 1  is a schematic diagram showing an exemplary conventional power transmitting apparatus of hybrid vehicles. 
         [0008]    As shown in  FIG. 1 , an exemplary conventional power transmitting apparatus of hybrid vehicles includes an engine  10 , first and second motor/generators  20  and  30 , and a planetary gear set  60 . 
         [0009]    The engine  10  supplies combustion energy of the fuel as power. The first and second motor/generators  20  and  30  are connected to a battery  40  respectively and supply power from the battery  40  or recharge the battery  40  by means of regenerative braking. 
         [0010]    The planetary gear set  60  includes a sun gear  62 , a ring gear  64 , a plurality of pinion gears  68  engaged to the sun gear  62  and the ring gear  64 , and a planet carrier  66  rotatably supporting the plurality of pinion gears  68 . 
         [0011]    The sun gear  62  is fixedly connected to the first motor/generator  20 , the ring gear  64  is fixedly connected respectively to the second motor/generator  30  and the output shaft  50 , and the planet carrier  66  is fixedly connected to the engine  10 . 
         [0012]    Therefore, a vehicle provided with the exemplary conventional power transmitting apparatus can realize a hybrid mode where a vehicle drives with power received from the engine  10  and the first and second motor/generators  20  and  30 . In this case, various shift speeds can be continuously realized by controlling the first and second motor/generators  20  and  30 . 
         [0013]    Since the hybrid vehicle provided with such a conventional power transmitting apparatus, as shown in  FIG. 2 , supplies only one hybrid mode, maximum efficiency can be achieved near a gear ratio of 0.7 and efficiency may become deteriorated as the gear ratio increases higher than 0.7. 
         [0014]      FIG. 3  is a schematic diagram showing another exemplary conventional power transmitting apparatus of hybrid vehicles. 
         [0015]    As shown in  FIG. 3 , another exemplary conventional power transmitting apparatus of hybrid vehicles includes an engine  10 , first and second motor/generators  20  and  30 , and first and second planetary gear sets  70  and  80 . 
         [0016]    The engine  10  supplies combustion energy of the fuel as power. The first and second motor/generators  20  and  30  are connected to a battery  40  respectively and supply power from the battery  40  or recharge the battery  40  by means of regenerative braking. 
         [0017]    The first planetary gear set  70  includes a first sun gear  72 , a first ring gear  74 , a plurality of first pinion gears  78  engaged to the first sun gear  72  and the first ring gear  74 , and a first planet carrier  76  rotatably supporting the plurality of first pinion gears  78 . 
         [0018]    The first sun gear  72  is fixedly connected to the first motor/generator  20 , and the first planet carrier  76  is fixedly connected to the engine  10 . 
         [0019]    The second planetary gear set  80  includes a second sun gear  82 , a second ring gear  84 , a plurality of second pinion gears  88  engaged to the second sun gear  82  and the second ring gear  84 , and a second planet carrier  86  rotatably supporting the plurality of second pinion gears  88 . 
         [0020]    The second sun gear  82  is fixedly connected to the second motor/generator  30 , the second planet carrier  86  is fixedly connected to a transmission case  90 , and the second ring gear  84  is fixedly connected respectively to the first ring gear  74  and an output shaft  50 . 
         [0021]    Therefore, a vehicle provided with this exemplary conventional power transmitting apparatus can realize a hybrid mode where a vehicle drives with power received simultaneously from the engine  10  and the first and second motor/generators  20  and  30 . In this case, various shift speeds can be continuously realized by controlling the first and second motor/generators  20  and  30 . 
         [0022]    In addition, power transmitted from the second motor/generator  30  is transmitted to the output shaft through the second sun gear  82  and the second ring gear  84  according to the exemplary conventional power transmitting apparatus. In this process, the rotational speed of the second motor/generator  30  is reduced according to a teeth ratio of the second sun gear  82  to the second ring gear  84 . 
         [0023]    Therefore, this exemplary conventional power transmitting apparatus can acquire the same performance as the exemplary conventional power transmitting apparatus shown in  FIG. 1  even if using the second motor/generator  30  of smaller capacity. 
         [0024]    However, a hybrid vehicle provided with the power transmitting apparatus shown in  FIG. 3 , as shown in  FIG. 4 , also supplies only one hybrid mode. Therefore, maximum efficiency can be achieved near a gear ratio of 0.7 and efficiency may become deteriorated as the gear ratio increases higher than 0.7. 
         [0025]    The above information disclosed in this Background 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 
       [0026]    The present invention has been made in an effort to provide a power transmitting apparatus of hybrid vehicles having advantages of realizing two hybrid modes, two engine modes, and one electric mode. 
         [0027]    Power transmitting apparatuses of hybrid vehicles according to exemplary embodiments of the present invention may transmit torque from an engine and first and second motor/generators to an output shaft. 
         [0028]    The power transmitting apparatus may include: a first planetary gear set including a first operating member fixedly connected to the second motor/generator, a second operating member selectively connected to the first operating member, and a third operating member; and a second planetary gear set having a fourth operating member fixedly connected to the engine and selectively connected to the second operating member, a fifth operating member fixedly connected to the first motor/generator and selectively connected to the second operating member, and a sixth operating member fixedly connected to the third operating member and the output shaft. 
         [0029]    The first planetary gear set may be a single pinion planetary gear set including a first sun gear, a first planet carrier, and a first ring gear as operating members thereof, wherein the first sun gear is operated as the first operating member, the first planet carrier is operated as the second operating member, and the first ring gear is operated as the third operating member. 
         [0030]    The second planetary gear set may be a single pinion planetary gear set having a second sun gear, a second planet carrier, and a second ring gear as operating members thereof, wherein the second sun gear is operated as the fourth operating member, the second planet carrier is operated as the sixth operating member, and the second ring gear is operated as the fifth operating member. 
         [0031]    The power transmitting apparatus may further include: a first clutch selectively connecting the second operating member to the fifth operating member; a second clutch selectively connecting the first operating member to the second operating member; and a third clutch selectively connecting the second operating member to the fourth operating member. 
         [0032]    The power transmitting apparatus may further include a brake selectively connecting the first operating member to a transmission case. 
         [0033]    In the power transmitting apparatus of hybrid vehicles according to a first exemplary embodiment of the present invention, the second and third clutches may be disposed at the same side with reference to the second motor/generator. 
         [0034]    In the power transmitting apparatus of hybrid vehicles according to a second exemplary embodiment of the present invention, the third clutch may be disposed on an opposite side to the second clutch with reference to the second motor/generator. 
         [0035]    In the power transmitting apparatus of hybrid vehicles according to a third exemplary embodiment of the present invention, the third clutch may be disposed between the first and second planetary gear sets. 
         [0036]    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. 
         [0037]    The above and other features of the invention are discussed infra. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0038]      FIG. 1  is a schematic diagram showing an exemplary conventional power transmitting apparatus of hybrid vehicles. 
           [0039]      FIG. 2  is a graph showing efficiency of a hybrid vehicle provided with the power transmitting apparatus shown in  FIG. 1 . 
           [0040]      FIG. 3  is a schematic diagram showing another exemplary conventional power transmitting apparatus of hybrid vehicles. 
           [0041]      FIG. 4  is a graph showing efficiency of a hybrid vehicle provided with the power transmitting apparatus shown in  FIG. 3 . 
           [0042]      FIG. 5  is a schematic diagram of a power transmitting apparatus of hybrid vehicles according to a first exemplary embodiment of the present invention. 
           [0043]      FIG. 6  is a graph showing rotational speed of each operating member in a case that a hybrid vehicle provided with the power transmitting apparatus shown in  FIG. 5  drives in a first hybrid mode. 
           [0044]      FIG. 7  is a graph showing rotational speed of each operating member in a case that a hybrid vehicle provided with the power transmitting apparatus shown in  FIG. 5  drives in a second hybrid mode. 
           [0045]      FIG. 8  is a graph showing efficiency in a case that a hybrid vehicle provided with the power transmitting apparatus shown in  FIG. 5  drives in the first hybrid mode. 
           [0046]      FIG. 9  is a graph showing efficiency in a case that a hybrid vehicle provided with the power transmitting apparatus shown in  FIG. 5  drives in the second hybrid mode. 
           [0047]      FIG. 10  is a schematic diagram of a power transmitting apparatus of hybrid vehicles according to a second exemplary embodiment of the present invention. 
           [0048]      FIG. 11  is a schematic diagram of a power transmitting apparatus of hybrid vehicles according to a third exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0049]    Exemplary embodiments of the present invention will hereinafter be described in detail with reference to the accompanying drawings. 
         [0050]      FIG. 5  is a schematic diagram of a power transmitting apparatus of hybrid vehicles according to a first exemplary embodiment of the present invention. 
         [0051]    As shown in  FIG. 5 , a power transmitting apparatus of hybrid vehicles according to the first exemplary embodiment of the present invention includes an engine  100 , an output shaft  200 , a transmission case  300 , first and second motor/generators  400  and  500 , first and second planetary gear sets PG 1  and PG 2 , first, second, and third clutches CL 1 , CL 2 , and CL 3 , and a brake BK 1 . 
         [0052]    The engine  100  generates torque by burning fuel. Non-limiting examples of the engine  100  includes a gasoline engine, a diesel engine, a liquefied petroleum gas (LPG) engine, a methanol engine, and a hydrogen engine. 
         [0053]    The output shaft  200  outputs torque from the power transmitting apparatus. 
         [0054]    The first and second motor/generators  400  and  500  are connected to a battery (not shown), and supply torque from the battery or recharge the battery by means of regenerative braking. 
         [0055]    The first planetary gear set PG 1  is a single pinion planetary gear set, and includes a first sun gear SG 1 , a first planet carrier CR 1 , and a first ring gear RG 1  as operating members thereof. In addition, the first planetary gear set PG 1  includes a plurality of first pinion gears (not shown) engaged to the first sun gear SG 1  and the first ring gear RG 1 , and the first planet carrier CR 1  rotatably supports the plurality of first pinion gears. 
         [0056]    The second planetary gear set PG 2  is a single pinion planetary gear set, and includes a second sun gear SG 2 , a second planet carrier CR 2 , and a second ring gear RG 2  as operating members thereof. In addition, the second planetary gear set PG 2  includes a plurality of second pinion gears (not shown) engaged to the second sun gear SG 2  and the second ring gear RG 2 , and the second planet carrier CR 2  rotatably supports the plurality of second pinion gears. 
         [0057]    According to the first exemplary embodiment of the present invention, the engine  100  is fixedly connected to the second sun gear SG 2 , the first motor/generator  400  is fixedly connected to the second ring gear RG 2 , and the second motor/generator  500  is fixedly connected to the first sun gear SG 1 . 
         [0058]    In addition, the second planet carrier CR 2  is fixedly connected respectively to the output shaft  200  and the first ring gear RG 1 . 
         [0059]    The first planet carrier CR 1  is selectively connected to the second ring gear RG 2  by operation of the first clutch CL 1 , the first sun gear SG 1  is selectively connected to the first planet carrier CR 1  by operation of the second clutch CL 2 , and the second sun gear SG 2  is selectively connected to the first planet carrier CR 1  by operation of the third clutch CL 3 . 
         [0060]    In addition, the first sun gear SG 1  is selectively connected to the transmission case  300  by operation of the brake BK 1 . 
         [0061]    In the power transmitting apparatus of hybrid vehicles according to the first exemplary embodiment of the present invention, the second and third clutches CL 2  and CL 3  are disposed on an opposite side to the brake BK 1  and the first clutch CL 1  with reference to the second motor/generator  500 . 
         [0062]    Hereinafter, each drive mode of a hybrid vehicle provided with the power transmitting apparatus according to the first exemplary embodiment of the present invention will be described in detail. 
       Electric Mode 
       [0063]    When the second clutch CL 2  is engaged, the first sun gear SG 1  and the first planet carrier CR 1  are connected to each other and all the operating members of the first planetary gear set PG 1  rotate with the same rotational speed. If the torque of the second motor/generator  500  is input at this state, all the operating members of the first planetary gear set PG 1  rotate with the same speed as the second motor/generator  500 . Accordingly, the torque of the second motor/generator  500  is transmitted to the output shaft  200  through the second planet carrier CR 2  fixedly connected to the first ring gear RG 1 . The gear ratio in the electric mode is 1.0. 
         [0064]    In addition, since the second sun gear SG 2  connected to the engine  100  is stopped, the first motor/generator  400  rotates faster than the second motor/generator  500 . 
         [0000]    Conversion from Electric Mode into First Hybrid Mode 
         [0065]    If the rotational speed of the first motor/generator  400  is reduced in the electric mode, the engine  100  is started. In this case, since torque of the output shaft  200  is partially transmitted to the second planet carrier CR 2  but the entire torque of the output shaft  200  does not change, impact does not occur by the engine starting. 
         [0066]    If the rotational speed of the first motor/generator  400  is reduced to the rotational speed of the engine  100 , the second clutch CL 2  is released, and the first clutch CL 1  is engaged in this state, the drive mode of the hybrid vehicle is converted into the first hybrid mode. 
       First Hybrid Mode 
       [0067]    If the first clutch CL 1  is engaged, the first planet carrier CR 1  and the second ring gear RG 2  are connected with each other and the second planet carrier CR 2  and the first ring gear RG 1  are connected with each other such that the first hybrid mode is realized. 
         [0068]    In this case, various shift speeds can be continuously realized by controlling operations of the first and second motor/generators  400  and  500 . 
         [0069]    The rotational speed of each operating member at each gear ratio in the first hybrid mode is shown in  FIG. 6 . 
       Second Hybrid Mode 
       [0070]    If the third clutch CL 3  is engaged, the first planet carrier CR 1  and the second sun gear SG 2  are connected with each other and the first ring gear RG 1  and the second planet carrier CR 2  are connected with each other such that the second hybrid mode is realized. 
         [0071]    In this case, various shift speeds can be continuously realized by controlling operations of the first and second motor/generators  400  and  500 . 
         [0072]    The rotational speed of each operating member at each gear ratio in the second hybrid mode is shown in  FIG. 7 . 
       Conversion Between First and Second Hybrid Mode 
       [0073]    When the first sun gear SG 1  selectively connected to the first planet carrier CR 1  and the first ring gear RG 1  rotate with the same rotational speed, conversion between the first and second hybrid modes can occur. Accordingly, with the gear ratio of 1.0, the first clutch CL 1  is changed from an engaged state to a released state while the third clutch CL 3  is changed from a released state to an engaged state or the first clutch CL 1  is changed from a released state to an engaged state while the third clutch CL 3  is changed from an engaged state to a released state. 
       First Engine Mode 
       [0074]    If the third clutch CL 3  is engaged, the first planet carrier CR 1  and the second sun gear SG 2  are connected with each other. In addition, if the brake BK 1  is engaged, the first sun gear SG 1  is stopped. Therefore, there is no use transmitting torque to the second motor/generator  500 . 
         [0075]    At this time, if the first motor/generator does not supply torque, the hybrid vehicle drives only with torque of the engine  100 . Since the first planet carrier CR 1  connected to the engine  100  rotates with a slower rotational speed than the first ring gear RG 1  connected to the output shaft  200 , the hybrid vehicle drives in overdrive state. 
         [0076]    In a case where the vehicle drives with a high speed, since regeneration of power by means of regenerative braking is low, the motor must be driven by electricity that is generated by the generator. In this case, electrical energy is converted back into mechanical energy after the mechanical energy is converted into electrical energy, which may cause energy loss. 
         [0077]    Therefore, it is advantageous that a vehicle is driven only by torque of the engine  100  in this state. 
       Second Engine Mode 
       [0078]    If the second clutch CL 2  and the third clutch CL 3  are engaged, all the operating members of the first planetary gear set PG 1  are locked and the gear ratio of 1.0 is realized. At this state, if torque of the first motor/generator MG 1  is not supplied, torque is not transmitted to any of the operating members of the second planetary gear set PG 2 . Therefore, engine torque is transmitted only to the first planet carrier CR 1  among the second sun gear SG 2  and the first planet carrier CR 1  connected with each other. 
         [0079]      FIG. 8  is a graph showing efficiency in a case that a hybrid vehicle provided with the power transmitting apparatus shown in  FIG. 5  drives in the first hybrid mode, and  FIG. 9  is a graph showing efficiency in a case that a hybrid vehicle provided with the power transmitting apparatus shown in  FIG. 5  drives in the second hybrid mode. 
         [0080]    As shown in  FIG. 8 , in a case that the vehicle drives in the first hybrid mode, efficiency of the vehicle is very high near a gear ratio of 1.75 and 4.0. 
         [0081]    In addition, in a case that the vehicle drives in the second hybrid mode, efficiency of the vehicle is very high near a gear ratio of 0.8 and 4.0, as shown in  FIG. 9 . 
         [0082]    Therefore, fuel mileage may be enhanced by converting between the first hybrid mode and the second hybrid mode according to a running state of the vehicle. 
         [0083]    Hereinafter, referring to  FIG. 10  and  FIG. 11 , the second and third exemplary embodiments of the present invention will be described. 
         [0084]      FIG. 10  is a schematic diagram of a power transmitting apparatus of hybrid vehicles according to the second exemplary embodiment of the present invention, and  FIG. 11  is a schematic diagram of a power transmitting apparatus of hybrid vehicles according to the third exemplary embodiment of the present invention. 
         [0085]    The power transmitting apparatus of hybrid vehicles according to the second and third exemplary embodiments of the present invention are similar to the power transmitting apparatus of hybrid vehicles according to the first exemplary embodiment of the present invention except for arrangements of the clutches CL 1 , CL 2 , and CL 3 . 
         [0086]    As shown in  FIG. 10 , in the power transmitting apparatus of hybrid vehicles according to the second exemplary embodiment of the present invention, the third clutch CL 3  is disposed on an opposite side to the brake BK 1  and the first and second clutches CL 1  and CL 2  with reference to the second motor/generator  500 . 
         [0087]    As shown in  FIG. 11 , in the power transmitting apparatus of hybrid vehicles according to the third exemplary embodiment of the present invention, the second clutch CL 2  is disposed on an opposite side to the brake BK 1  and the first and third clutches CL 1  and CL 3  with reference to the second motor/generator  500 . In addition, the third clutch CL 3  is disposed between the first planetary gear set PG 1  and the second planetary gear set PG 2 . 
         [0088]    The power transmitting apparatus of hybrid vehicles according to exemplary embodiments of the present invention provide advantages including the following. It is possible to provide two hybrid modes, two engine modes, and one electric mode by using two planetary gear sets, three clutches, and one brake in a simple manner. No impact occurs when an engine is started in a state of the electric mode or when conversion between the electric mode and the hybrid mode occurs. Since an engine may not be started even if a driver turns on an ignition key, fuel is not consumed and noise may not occur due to exhaust and combustion in a state that a vehicle moves with low speed. Fuel mileage may be enhanced since two hybrid modes are suitably conversed according to the running state of a vehicle. 
         [0089]    While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.