Abstract:
The present invention provides a power train for a hybrid vehicle that can achieve a fixed gear ratio mode where a vehicle is driven at a fixed gear ratio, such as shift stages of common transmission, only by the driving force of an engine without driving a motor generator, as well as an electric vehicle mode and a hybrid mode that are basic driving modes of a hybrid vehicle, such that it is possible to drive the vehicle with high efficiency in accordance with traveling conditions of the vehicle and improve fuel efficiency. Further, according to the power train for a hybrid vehicle, the number of teeth of a sun gear and a pinion of a planetary gear set, which is a component, can be changed in various ways, such that it is possible to more freely select the capacity of a clutch or a motor generator. Therefore, it is possible to design a compact transmission.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to Korean Patent Application Number 10-2009-0035353 filed Apr. 23, 2009, the entire contents of which application is incorporated herein for all purposes by this reference. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present disclosure relates to a power train for a hybrid vehicle, in more detail a technology for transmitting power from power sources to the driving wheels in a hybrid vehicle equipped with two or more different power sources, including an internal combustion engine. 
         [0004]    2. Related Art 
         [0005]    Hybrid vehicles using an engine and a motor generator improve fuel efficiency of the vehicles by achieving functions of idle stop and regenerative braking, on the basis of a technology of driving the vehicles at low velocity by using power from the motor generator having relatively excellent low-velocity torque characteristics and driving the vehicles at high velocity by using power from the engine having relatively excellent high-velocity characteristics. 
         [0006]    Further, hybrid vehicles do not produce exhaust gas from the engine when being driven only by a motor generator, which is recognized as an environmental-friendly vehicle technology having advantages of improving fuel efficiency and reducing exhaust gas. 
         [0007]    The power train for hybrid vehicles is required to provide sufficient driving force and high fuel efficiency. 
         [0008]    The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art. 
       BRIEF SUMMARY OF THE DISCLOSURE 
       [0009]    Various aspects of the present invention are directed to provide a power train for a hybrid vehicle that can achieve a fixed gear ratio mode where a vehicle is driven at a fixed gear ratio, such as shift stages of common transmission, only by the driving force of an engine without driving a motor generator, as well as an electric vehicle mode and a hybrid mode that are basic driving modes of a hybrid vehicle, thereby driving the vehicle with high efficiency in accordance with traveling conditions of the vehicle and improving fuel efficiency. 
         [0010]    In one aspect, the present invention provides a power train for a hybrid vehicle comprising: a first planetary gear set that includes at least four rotary elements; a second planetary gear set that includes at least three rotary elements one of which is connected with at least one of the rotary elements of the first planetary gear set; a first clutch that is configured to connect/disconnect a rotary element of the first planetary gear set with/from a rotary element of the second planetary gear set; and a first brake that is provided to restrain rotation of a rotary element of the second planetary gear set, wherein at least two or more independent power sources and an output element are connected to the rotary elements of the first planetary gear set and the second planetary gear set. 
         [0011]    Preferably, the rotary element, the rotation of which is restrained by the first brake, of the second planetary gear set may be disconnectably connected to the rotary element of the first planetary gear set through the first clutch. In this case, the power source may include an engine and a first motor generator that are connected to the first planetary gear set, and a second motor generator that is connected to the second planetary gear set, and the output element may be connected to the second planetary gear set. Suitably, the engine, the first planetary gear set, the second planetary gear set, the first motor generator, and the second motor generator may be arranged such that rotary shafts overlap each other to form a single shaft. Suitably, the first planetary gear set may be a long pinion type planetary gear set including a first sun gear and a third sun gear that are independently engaged with one long pinion, and the second planetary gear set may be a single pinion planetary gear set including three rotary elements. 
         [0012]    Preferably, a first ring gear of the first planetary gear set may be connected to a second carrier of the second planetary gear set, the third sun gear of the first planetary gear set may be connected to a second ring gear of the second planetary gear set through the first clutch, the engine may be connected to a first carrier of the first planetary gear set, the first motor generator may be connected to the first sun gear of the first planetary gear set, the second motor generator may be connected to a second sun gear of the second planetary gear set, the output element may be connected to a second carrier of the second planetary gear set, the first clutch may be configured to connect/disconnect the third sun gear of the first planetary gear set with/from the second ring gear of the second planetary gear set, and the first brake may be configured to restrain rotation of the second ring gear of the second planetary gear set. In this case, the long pinion of the first planetary gear set may have the same number of gear teeth at portions where the first sun gear and the third sun gear are engaged. Alternatively, the long pinion of the first planetary gear set may have the different numbers of teeth at portions where the first sun gear and the third sun gear are engaged. 
         [0013]    Preferably, the first planetary gear set and the second planetary gear set may be disposed adjacent to each other, the first motor generator is disposed adjacent to the first planetary gear set and the second motor generator may be disposed adjacent to the second planetary gear set, such that with the first planetary gear set and the second planetary gear set are disposed between the first motor generator and the second motor generator, the output element may be connected to the outside through a space between the second motor generator and the second planetary gear set, and the first clutch may be provided to connect/disconnect the third sun gear of the first planetary gear set with/from the second ring gear of the second planetary gear set through a space between the first motor generator and the first planetary gear set. In this case, suitably, the power train may further comprise: a second brake that restrains rotation of the second sun gear of the second planetary gear set; and a second clutch that is provided between the first carrier of the first planetary gear set and the second ring gear of the second planetary gear set to restrain rotation therebetween. 
         [0014]    Preferably, the first planetary gear set and the second planetary gear set may be disposed adjacent to each other, the first motor generator may be disposed to be connected to the second planetary gear set, the second motor generator may be disposed to be connected to the second planetary gear set such that the second motor generator is disposed between the second planetary gear set and the first motor generator, the output element may be connected to the outside through a space between the second motor generator and the second planetary gear set, and the first clutch may be configured to connect/disconnect the third sun gear of the first planetary gear set with/from the second ring gear of the second planetary gear set through a space around the first planetary gear set. In this case, the power train may, suitably, further comprise: a second brake that restrains rotation of the second sun gear of the second planetary gear set; and a second clutch that is provided between the first carrier of the first planetary gear set and the second ring gear of the second planetary gear set to restrain rotation therebetween. 
         [0015]    In another aspect, the present invention provides a power train for a hybrid vehicle, comprising: a first planetary gear set that includes at least four rotary elements; a second planetary gear set that includes two rotary elements that are disconnectably connected with two rotary elements of the first planetary gear set and a rotary element that is always connected to one of the other rotary elements of the first planetary gear set; a first brake that is configured to restrain rotation of a rotary elements of the second planetary gear set; and a second brake that is configured to restrain rotation of another rotary element of the second planetary gear set, wherein at least two or more independent power sources and an output element are connected to the rotary elements of the first planetary gear set and the second planetary gear set. 
         [0016]    In this case, preferably, the power source may include an engine and a first motor generator that are connected to the first planetary gear set, and a second motor generator that is connected to the second planetary gear set, and the output element may be connected to the second planetary gear set. Suitably, the first planetary gear set may be a long pinion type planetary gear set including a first sun gear and a third sun gear that are independently engaged with one long pinion, and the second planetary gear set may be a single pinion planetary gear set including three rotary elements. Preferably, a second ring gear of the second planetary gear set may be disconnectably connected with the third sun gear of the first planetary gear set by a first clutch and disconnectably connected with a first carrier of the first planetary gear set by a second clutch. In this case, a second carrier of the second planetary gear set may be always connected with a first ring gear of the first planetary gear set and connected to the output element, and the second ring gear of the second planetary gear set may be connected such that rotation is restrained by the first brake. Further, suitably, the engine may be connected to the first carrier of the first planetary gear set, the first motor generator may be connected to the first sun gear of the first planetary gear set, the second motor generator may be connected to the second sun gear of the second planetary gear set, and the second brake may be configured to restrain rotation of the second sun gear of the second planetary gear set. In this case, the long pinion of the first planetary gear set may have the same number or different numbers of gear teeth at portions where the first sun gear and the third sun gear are engaged. 
         [0017]    According to the present invention, a power train for a hybrid vehicle can achieve a fixed gear ratio mode where a vehicle is driven at a fixed gear ratio, such as shift stages of common transmission, only by the driving force of an engine without driving a motor generator, as well as an electric vehicle mode and a hybrid mode that are basic driving modes of a hybrid vehicle, such that it is possible to drive the vehicle with high efficiency in accordance with traveling conditions of the vehicle and improve fuel efficiency. 
         [0018]    Further, the present invention can provide a power train for a hybrid vehicle that makes it possible to set the number of teeth of a sun gear and a pinion of a planetary gear set, which is a component, in various ways, such that it is possible to more freely select the capacity of a clutch or a motor generator and design a compact transmission. 
         [0019]    The above and other features and advantages will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description of the Invention, which together serve to explain certain principles of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a diagram illustrating the structure of a power train for a hybrid vehicle according to an embodiment of the present invention. 
           [0021]      FIG. 2  is a lever analysis diagram of the power train of  FIG. 1 . 
           [0022]      FIG. 3  is a diagram illustrating a modified example of the power train of  FIG. 1 . 
           [0023]      FIG. 4  is a diagram illustrating another modified example of the power train of  FIG. 1 . 
           [0024]      FIG. 5  is a diagram illustrating the structure of a power train for a hybrid vehicle according to another embodiment of the present invention. 
           [0025]      FIG. 6  is a driving mode table of the power train of  FIG. 5 . 
           [0026]      FIG. 7  is a lever analysis diagram of the power train of  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0027]    Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims. 
         [0028]    Referring to  FIGS. 1 and 2 , a power train for a hybrid vehicle according to an embodiment of the present invention includes: a first planetary gear set PG 1  that includes at least four rotary elements; a second planetary gear set PG 2  that includes at least three rotary elements one of which is connected with at least one of the rotary elements of the first planetary gear set PG 1 ; a first clutch CL 1  that is provided to connect/disconnect one rotary element of the first planetary gear set PG 1  with/from one rotary element of the second planetary gear set PG 2 ; and a first brake BK 1  that is provided to restrain rotation of one rotary element of the second planetary gear set PG 2 . At least two or more independent power sources and an output element OUT are connected to the rotary elements of the first planetary gear set PG 1  and the second planetary gear set PG 2 . 
         [0029]    Preferably, the rotary element, the rotation of which is restrained by the first brake BK 1 , of the second planetary gear set PG 2  is disconnectably connected to the rotary element of the first planetary gear set PG 1  through the first clutch CL 1 . 
         [0030]    The power source includes an engine E/G and a first motor generator MG 1  that are connected to the first planetary gear set PG 1 , and a second motor generator MG 2  that is connected to the second planetary gear set PG 2 , and the output element OUT is connected to the second planetary gear set PG 2 . 
         [0031]    The engine E/G, the first planetary gear set PG 1 , the second planetary gear set PG 2 , the first motor generator MG 1 , and the second motor generator MG 2  are arranged such that their rotary shafts overlap each other to form a single shaft. 
         [0032]    Suitably, the first planetary gear set PG 1  is a long pinion type planetary gear set including a first sun gear S 1  and a third sun gear S 3  that are independently engaged with one long pinion and the second planetary gear set PG 2  is a single pinion planetary gear set including three rotary elements. 
         [0033]    That is, suitably, a first ring gear R 1  of the first planetary gear set PG 1  is connected to a second carrier C 2  of the second planetary gear set PG 2 , the third sun gear S 3  of the first planetary gear set PG 1  is connected to a second ring gear R 2  of the second planetary gear set PG 2  through the first clutch CL 1 , the engine E/G is connected to a first carrier C 1  of the first planetary gear set PG 1 , the first motor generator MG 1  is connected to the first sun gear S 1  of first planetary gear set PG 1 , the second motor generator MG 2  is connected to a second sun gear S 2  of the second planetary gear set PG 2 , the output element OUT is connected to the second carrier C 2  of the second planetary gear set PG 2 , the first clutch CL 1  is disposed to connect/disconnect the third sun gear S 3  of the first planetary gear set PG 1  with/from the second ring gear R 2  of the second planetary gear set PG 2  and the first brake BK 1  is disposed to restrain rotation of the second ring gear R 2  of the second planetary gear set PG 2 . 
         [0034]    In a power train according to an embodiment of the present invention, as shown in  FIG. 1 , the first planetary gear set PG 1  and the second planetary gear set PG 2  are disposed adjacent to each other, the first motor generator MG 1  is disposed adjacent to the first planetary gear set PG 1 , and the second motor generator MG 2  is disposed adjacent to the second planetary gear set PG 2  such that the first planetary gear set PG 1  and the second planetary gear set PG 2  disposed between the first motor generator MG 1  and the second motor generator MG 2 . The output element OUT is connected to the outside through a space between the first motor generator MG 1  and the second motor generator MG 2 , the first clutch CL 1  is connected to connect/disconnect the third sun gear S 3  of the first planetary gear set PG 1  with/from the second ring gear R 2  of the second planetary gear set PG 2  through a space between the first motor generator MG 1  and the first planetary gear set PG 1 . 
         [0035]    As shown in  FIG. 3 , in a modified example of the power train of  FIG. 1 , the first planetary gear set PG 1  and the second planetary gear set PG 2  are disposed adjacent to each other, the first motor generator MG 1  is disposed to be connected to the second planetary gear set PG 2 , the second motor generator MG 2  is disposed to be connected to the second planetary gear set PG 2  such that the second motor generator MG 2  is disposed between the second planetary gear set PG 2  and the first motor generator MG 1 . The output element OUT is connected to the outside through a space between the second motor generator MG 2  and the second planetary gear set PG 2 , the first clutch CL 1  is disposed to connect/disconnect the third sun gear S 3  of the first planetary gear set PG 1  with/from the second ring gear R 2  of the second planetary gear set PG 2  through a space around the first planetary gear set PG 1 . 
         [0036]    In the embodiments of  FIG. 1  and  FIG. 3  described above, preferably, the long pinion of the first planetary gear set PG 1  has the same number of gear teeth at the portions where the first sun gear S 1  and the third sun gear S 3  are engaged, and it is designated by P in the embodiments of  FIG. 1  and  FIG. 3  and an embodiment of  FIG. 5  which is described below. On the other hand, in an embodiment shown in  FIG. 4 , preferably, the long pinion of the first planetary gear set PG 1  has different numbers of teeth at the portions where the first sun gear S 1  and the third sun gear S 3  are engaged. 
         [0037]    As shown in  FIG. 4 , in another modified example of the power train of  FIG. 1 , in the long pinion of the first planetary gear set PG 1 , the portions with different numbers of teeth are integrally formed with steps of a first pinion portion P 1  and a third pinion portion P 3  and it is possible to independently set the relationship of the number of gear teeth between the first pinion portion P 1  and the first sun gear S 1  and the relationship of the number of gear teeth between the third pinion portion P 3  and the third sun gear S 3 , when the first sun gear S 1  and the third sun gear S 3  are engaged. Therefore, it is possible to design the capacity of the first motor generator MG 1  connected to the first sun gear S 1  while adjusting the relationship of the number of gear teeth between the first pinion portion P 1  and the first sun gear S 1  and to design the capacity of the first clutch CL 1  connected to the third sun gear S 3  while adjusting the relationship of the number of gear teeth between the third pinion portion P 3  and the third sun gear S 3 , which allows for free design such that a compact transmission can be designed. 
         [0038]    A power train according to another embodiment of the present invention, as shown in  FIG. 5 , further includes a second brake BK 2  that restrains rotation of the second sun gear S 2  of the second planetary gear set PG 2  and a second clutch CL 2  provided between the first carrier C 1  of the first planetary gear set PG 1  and the second ring gear R 2  of the second planetary gear set PG 2  to restrain rotation between them. Description of the other components is omitted since they are the same as those of the power train of  FIG. 1 . 
         [0039]    As shown in the driving mode table of  FIG. 6 , the power train according to this embodiment can be operated in various driving modes: an electric vehicle (EV) mode, a hybrid (HEV) mode, and a fixed gear mode. 
         [0040]    The EV mode allows for an EV 1  mode that is achieved by engaging only the first brake BK 1  and an EV 2  mode that is achieved by engaging the second clutch CL 2  and the first brake BK 1 . 
         [0041]    The HEV mode allows for an HEV  1  mode that is achieved by engaging the first brake BK 1  and an HEV 2  mode that is achieved by engaging the first clutch CL 1 . 
         [0042]    The fixed gear ratio mode can be operated in first to third stages at respective predetermined shift ratios while only the engine E/G is operated, as shown in the table. 
         [0043]    It is possible to improve fuel efficiency while effectively driving the hybrid vehicle by appropriately combining various driving modes in accordance with traveling conditions of a vehicle. 
         [0044]    The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.