Patent Publication Number: US-2021178891-A1

Title: Power transmission structure for hybrid vehicle comprising two motor generators and three clutches

Description:
TECHNICAL FIELD 
     The present invention relates to a power transmission structure of a hybrid vehicle and, more particularly, a power transmission system for a hybrid vehicle, the power transmission system including an engine and two motors, which are power sources of the vehicle, and three clutches and being able to achieve optimal performance and fuel efficiency in accordance with the driving status of the vehicle by selectively transmitting power from the power sources to a transmission. 
     BACKGROUND ART 
     Recently, the automotive industrial field is considerably interested in development of a hybrid vehicle that is more eco-friendly and can improve fuel efficiency. A hybrid vehicle uses two or more power sources and is generally driven by an internal combustion engine and a motor/generator (hereafter, referred to as a motor) that are power sources. 
     The power transmission systems of hybrid vehicle using an engine and a motor can be largely classified into a type that uses a single motor and a type that uses two motors. As common vehicles using a single motor, there are SONATA hybrid and IONIQ hybrid by Hyundai, hybrids by Nissan, hybrids by Audi, etc., and as common vehicle using two motors, there are Accord hybrid by Honda, Prius by Toyota, Bolt by Chevrolet etc. 
     As compared with the case that uses one motor, when two motors are used to drive a vehicle, not only there is a need for separate circuits and PCUs for respectively controlling the two motors, but the manufacturing cost is increased and the vehicle body becomes heavy. However, it is possible to drive the vehicle with one motor and generate electricity with the other motor, which is called a real time series mode, which is advantageous in terms of function. 
     However, in all the hybrid vehicles of the related art, once batteries are fully discharged, motors that cannot be operated become a passive load on an engine, so the power from the engine is considerably reduced than it is known. To this end, hybrid vehicles use a method of charging batteries in advance by generating electricity at all times, but in reality the batteries cannot be recharged and are fully discharged, depending on the driving status of vehicles, unless a large-capacity battery is mounted. If the batteries are forcibly charged, a vicious cycle in which the fuel efficiency and performance are reduced is repeated, so there is a need for corrective measures. 
     DISCLOSURE 
     Technical Problem 
     The present invention has been made in an effort to solve the problems and an object of the present invention is to provide a power transmission structure for a hybrid vehicle, the power transmission structure being able to keep the advantage when electricity remains in a battery and can minimize the disadvantage when a battery is fully discharged. 
     Technical Solution 
     A power transmission structure for a hybrid vehicle having two motor generators and three clutches according to an aspect of the present invention includes an engine ( 10 ), a second motor ( 20 ), and an output shaft ( 40 ) transmitting power from the engine ( 10 ) and the second motor ( 20 ) to a transmission ( 30 ), in which the second motor ( 20 ) is disposed in parallel with the engine ( 10 ), a first motor ( 50 ) directly connected to the output shaft ( 40 ) of the transmission ( 30 ) is disposed between the second motor ( 20 ) and the transmission ( 30 ), the output shaft ( 40 ) is connected to the transmission ( 30 ) through a center of the second motor ( 20 ), a first clutch ( 111 ) and a second clutch ( 112 ) constituting a double clutch are disposed on the output shaft ( 40 ) between the engine ( 10 ) and the second motor ( 20 ), and a third clutch ( 113 ) connecting or disconnecting power transmitted through the output shaft ( 40 ) is disposed between the second motor ( 20 ) and the first motor ( 50 ). 
     A power transmission structure for a hybrid vehicle having two motor generators and three clutches according to another aspect of the present invention includes an engine ( 10 ), a second motor ( 20 ), and an output shaft ( 40 ) transmitting power from the engine ( 10 ) and the second motor ( 20 ) to a transmission ( 30 ), in which the second motor ( 20 ) is disposed in parallel with the engine ( 10 ), a first motor ( 50 ) directly connected to the output shaft ( 40 ) of the transmission ( 30 ) is disposed between the second motor ( 20 ) and the transmission ( 30 ), the output shaft ( 40 ) is connected to the transmission ( 30 ) through a center of the second motor ( 20 ), a second clutch ( 112 ) and a first clutch ( 111 ) constituting a double clutch are disposed on the output shaft ( 40 ) between the second motor ( 20 ) and the first motor ( 50 ), and a third clutch ( 113 ) connecting or disconnecting power transmitted through the output shaft ( 40 ) is disposed between the engine ( 10 ) and the second motor ( 20 ). 
     A power transmission structure for a hybrid vehicle having two motor generators and three clutches according to another aspect of the present invention includes an engine ( 10 ), a second motor ( 20 ), and an output shaft ( 40 ) transmitting power from the engine ( 10 ) and the second motor ( 20 ) to a transmission ( 30 ), in which the second motor ( 20 ) is disposed in parallel with the engine ( 10 ), a first motor ( 50 ) directly connected to the output shaft ( 40 ) of the transmission ( 30 ) is disposed between the second motor ( 20 ) and the transmission ( 30 ), the output shaft ( 40 ) is connected to the transmission ( 30 ) through a center of the second motor ( 20 ), a second clutch ( 112 ) and a first clutch ( 111 ) constituting a dual clutch are disposed on the output shaft ( 40 ) between the second motor ( 20 ) and the transmission ( 30 ), and a third clutch ( 113 ) connecting or disconnecting power transmitted through the output shaft ( 40 ) is disposed between the dual clutch and the first motor ( 50 ). 
     A power transmission structure for a hybrid vehicle having two motor generators and three clutches according to another aspect of the present invention includes an engine ( 10 ), a second motor ( 20 ), and an output shaft ( 40 ) transmitting power from the engine ( 10 ) and the second motor ( 20 ) to a transmission ( 30 ), in which the second motor ( 20 ) is disposed in parallel with the engine ( 10 ), a first motor ( 50 ) directly connected to the output shaft of the transmission ( 30 ) is disposed between the second motor ( 20 ) and the transmission ( 30 ), the output shaft ( 40 ) is connected to the transmission ( 30 ) through a center of the second motor ( 20 ), a first clutch ( 111 ) and a second clutch ( 112 ) constituting any one of a dual clutch and a double clutch are disposed between the engine ( 10 ) and the second motor ( 20 ), and a third clutch ( 113 ) connecting or disconnecting power generated by the second motor ( 20 ) and transmitted through the output shaft ( 40 ) is disposed on the output shaft ( 40 ) between the second motor ( 20 ) and the first motor ( 50 ). 
     A power transmission structure for a hybrid vehicle having two motor generators and three clutches according to another aspect of the present invention includes an engine ( 10 ), a second motor ( 20 ), and an output shaft ( 40 ) transmitting power from the engine ( 10 ) and the second motor ( 20 ) to a transmission ( 30 ), in which the second motor ( 20 ) is disposed in parallel with the engine ( 10 ), a first motor ( 50 ) directly connected to the output shaft ( 40 ) of the transmission ( 30 ) is disposed between the second motor ( 20 ) and the transmission ( 30 ), the output shaft ( 40 ) is connected to the transmission ( 30 ) through a center of the second motor ( 20 ), a first clutch ( 111 ) and a second clutch ( 112 ) constituting a dual clutch are disposed on the output shaft ( 40 ) between the engine ( 10 ) and the second motor, and a third clutch ( 113 ) is disposed on the output shaft between the engine ( 10 ) and the dual clutch. 
     A power transmission structure for a hybrid vehicle having two motor generators and three clutches according to another aspect of the present invention includes an engine ( 10 ), a second motor ( 20 ), and an output shaft ( 40 ) transmitting power from the engine ( 10 ) and the second motor ( 20 ) to a transmission ( 30 ), in which the second motor ( 20 ) is disposed in parallel with the engine ( 10 ), a first motor ( 50 ) directly connected to the output shaft ( 40 ) of the transmission ( 30 ) is disposed between the second motor ( 20 ) and the transmission ( 30 ), the output shaft ( 40 ) is connected to the transmission ( 30 ) through a center of the second motor ( 20 ), a third clutch ( 113 ) is disposed between the engine ( 10 ) and the second motor ( 20 ), and a second clutch ( 112 ) and a first clutch ( 111 ) constituting one of a dual clutch and a double clutch is disposed on the output shaft ( 40 ) between the second motor ( 20 ) and the first motor ( 50 ). 
     A power transmission structure for a hybrid vehicle having two motor generators and three clutches according to another aspect of the present invention includes an engine ( 10 ), a second motor ( 20 ), and an output shaft ( 40 ) transmitting power from the engine ( 10 ) and the second motor ( 20 ) to a transmission ( 30 ), in which the second motor ( 20 ) is disposed in parallel with the engine ( 10 ), a first motor ( 50 ) directly connected to the output shaft ( 40 ) of the transmission ( 30 ) is disposed between the second motor ( 20 ) and the transmission ( 30 ), the output shaft ( 40 ) is connected to the transmission ( 30 ) through a center of the second motor ( 20 ), and a first clutch ( 211 ), a second clutch ( 212 ), and a third clutch ( 213 ) constituting a triple clutch are disposed on the output shaft between the engine ( 10 ) and the second motor ( 20 ). 
     A power transmission structure for a hybrid vehicle having two motor generators and three clutches according to another aspect of the present invention includes an engine ( 10 ), a second motor ( 20 ), and an output shaft ( 40 ) transmitting power from the engine ( 10 ) and the second motor ( 20 ) to a transmission ( 30 ), in which the second motor ( 20 ) is disposed in parallel with the engine ( 10 ), a first motor ( 50 ) directly connected to the output shaft ( 40 ) of the transmission ( 30 ) is disposed between the second motor ( 20 ) and the transmission ( 30 ), the output shaft ( 40 ) is connected to the transmission ( 30 ) through a center of the second motor ( 20 ), and a third clutch ( 213 ), a second clutch ( 212 ), and a first clutch ( 211 ) constituting a triple clutch are disposed on the output shaft between the second motor ( 20 ) and the first motor ( 50 ). 
     Advantageous Effects 
     According to the present invention, as compared with hybrid vehicles of the related art, it is possible to minimize driven load by driving motors that may reduce the output of an engine when a vehicle is driven only by an engine, and it is also possible to selectively use a motor having larger capacity from two motors or both of the two motors when additional output is needed when additional output is required such as high-speed driving or accelerating in a motor mode. 
     Furthermore, according to the present invention, it is possible to drive a vehicle only with a first motor at a low speed in a motor mode and to drive a vehicle using any one or both of a first motor and a second motor at a high speed, whereby it is possible to improve the fuel efficiency (km/kw) of an electric vehicle in a motor mode. 
     Furthermore, it is possible to add power from one or both of a first motor and a second motor in a parallel mode and it is also possible to apply a real time series mode in which the second motor of the first motor and the second motor generates electricity by an engine and a vehicle is driven only by the first motor. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view schematically showing a configuration of a power transmission structure for a hybrid vehicle according to the present invention; 
         FIG. 2  is a view schematically showing another configuration of a power transmission structure for a hybrid vehicle according to the present invention; 
         FIG. 3  is a view schematically showing another configuration of a power transmission structure for a hybrid vehicle according to the present invention; 
         FIG. 4  is a view schematically showing another configuration of a power transmission structure for a hybrid vehicle according to the present invention; 
         FIG. 5  is a view schematically showing another configuration of a power transmission structure for a hybrid vehicle according to the present invention; 
         FIG. 6  is a view schematically showing another configuration of a power transmission structure for a hybrid vehicle according to the present invention; 
         FIG. 7  is a view schematically showing another configuration of a power transmission structure for a hybrid vehicle according to the present invention; and 
         FIG. 8  is a view schematically showing another configuration of a power transmission structure for a hybrid vehicle according to the present invention. 
     
    
    
     DESCRIPTION OF THE REFERENCE NUMERALS IN THE DRAWINGS 
       
     
       
         
           
               
               
               
             
               
                   
                   
               
             
            
               
                   
                 10: Engine 
                 20: Second motor 
               
               
                   
                 30: Transmission 
                 40: Output shaft 
               
               
                   
                 50: First motor 
                 111, 211: First clutch 
               
               
                   
                 112, 212: Second clutch 
                 113, 213: Third clutch 
               
               
                   
                   
               
            
           
         
       
     
     BEST MODE 
     Exemplary embodiments of the present invention are described hereafter in detail with reference to the accompanying drawings. In the following description of exemplary embodiments of the present invention, configurations that are not directly in associated with the technical features of the present invention or that are apparent to those skilled in the art will not be described in detail. 
       FIGS. 1 to 8  are views schematically showing configurations of a power transmission structure for a hybrid vehicle according to the present invention. As shown in the figures, the power transmission structure is technically characterized by including an engine  10 , a second motor  20 , a first motor  50 , a transmission  30 , an output shaft  40 , and first and second clutch  111  and  112  and a third clutch  113  or a triple clutch. These components are described in detail. 
     The engine  10 , which is an internal combustion engine that is generally used in the art, may be a piston engine. Through not shown in the figures, the present invention does not exclude a case providing a low-voltage starter of 12V at a side of the engine  10 . The 12V starter does not need a separate high-voltage electrical connection unit or a separate control unit, unlike a high-voltage starter generator. 
     The second motor  20 , which is a high-voltage motor generator that is generally used in the art, is a device that generates power by consuming electricity or generates electricity by receiving power. The second motor  20  is disposed at a predetermined distance from and in parallel with the engine  10  and has a hollow rotary shaft. 
     That is, an output shaft  40  connected to the engine  10  is disposed through the second motor  20 . This is for preventing some of power generated by the engine and transmitted to the output shaft  40  from losing due to the second motor  20 . When a clutch is operated, the power from the second motor is connected or disconnected. According to this configuration, a motor having large capacity relative to the engine displacement can be mounted in the present invention. 
     The second motor  20  is connected to a battery (not shown) and generates power by consuming the electricity accumulated in the battery. The motor may be any one of various motors that can be used to drive a vehicle and may be configured to operate as a power generator in an engine electricity generation mode or a regenerative mode. 
     The first motor  50 , which is a device complementing the operation of the second motor  20 , may be a high-voltage motor generator that is generally used in the art. In the present invention, the first motor  50  is directly connected to the transmission  30 , so the first motor  50  can function as a load when the engine  10  is operated. 
     In consideration of this, the capacity of the first motor  50  is appropriately determined relative to the capacity of the engine to be mounted such that a driven load when a vehicle is driven only by an engine and the first motor  50  is not operated and forcibly rotated without generating electricity can be minimized and independent electric vehicle mode driving or series mode driving is possible only by the first motor  50  in high constant-speed driving. The capacity of the first motor  50  may be smaller than the capacity of the second motor  20 . 
     The capacity of the second motor  20  may be set such that maximally efficient engine electricity generation is possible relative to the capacity of the engine to be mounted (maximum electricity generation efficiency=maximum amount of electricity generation/amount of fuel consumption at predetermined number of revolutions) and the capacity of the second motor  20  may be set to be larger than the capacity of the first motor  50  and to be able to achieve maximum engine electricity generation efficiency. 
     In hybrid vehicles (Prius and Bolt) that are mainly driven in a series mode using two motors in the related art, the capacity of the first motor connected to a transmission is close to a double of the capacity of the second motor connected to an engine, because, in most cases, the vehicles are driven only by the first motor and the second motor is generally used to generate electricity by operating the engine. This is because driving that uses only the engine (two motors stopped) is applied only to high constant-speed driving. In this case, it is advantageous in terms of the series mode, but is disadvantageous in terms of the engine mode. Accordingly, according to these hybrid vehicles, the fuel efficiency is higher in cities and lower in high-speed driving. 
     That is, the performance of the hybrid vehicles using two motors in the related art is low in performance in high constant-speed driving and high accelerating, in comparison to vehicles using only an engine in the related art, so they are suitable for driving in cities or driving a long distance at medium speeds. Furthermore, a motor is usually used to drive the vehicles, so when a vehicle is driven only by an engine, it is required to charge the battery at all times by generating electricity, depending on the status of the output from the engine, in order to reduce the defect when the battery is fully discharged. Accordingly, these vehicle are advantageous in terms of fuel efficiency, but have a limit in terms of performance, so the vehicles is difficult to be used as sports cars or luxury cars. 
     However, according to the present invention, when the capacity of the first motor is set within a range in which motor mode driving is possibly only by the first motor  50  in high constant-speed driving with a high gear, which can maximally achieve the advantage of parallel hybrid, engaged, a driven load by the first motor when a vehicle is driven only by an engine and the output from the first motor and the second motor can be increased, so the motor power performance is sufficient to drive the vehicle. Furthermore, the fuel efficiency (Km/Kw) in an electric vehicle mode can be improved. 
     The transmission  30  appropriately controls and transmits power, which is generated by the engine  10  and (or) the second motor  20  and the driving motor  50  to transmitted through the output shaft  40 , to wheels (not shown). The transmission  30  may be any one of a CVT, a toroidal CVT, an AT, and a DCT and the configuration connecting the transmission and the output can be slightly changed, depending on the types of transmissions to be mounted. This means that since the CVT does not have a neutral position, the single clutch at the transmission in the drawings is necessary, while, since the AT and DCT has a neutral position, the single clutch at the transmission can be removed. 
     The first and second clutches  111  and  112  and the third clutch  113  or the triple clutch according to the present invention can be arranged, as shown in  FIGS. 1 to 8 , and the power transmission processes by the clutches are described in detail. 
     First, as shown in  FIG. 1 , the first and second clutches  111  and  112  may be disposed on the output shaft  40  between the engine  10  and the second motor  20  and the third clutch  113  may be disposed on the output shaft  40  between the second motor  20  and the first motor  50 . The first and second clutches  111  and  112  constitute a double clutch and are disposed at a first side, which faces the engine  10 , of the second motor  20 . 
     In this case, when the output end of the engine  10  is connected to the output shaft  40  by operating the first clutch  111  with the third clutch  113  engaged, the power from the engine  10  (or power from the engine and an auxiliary motor) is transmitted to the transmission  30 . Furthermore, when the output end of the second motor  20  (the rotary shaft of the motor, which is the same in the following description) is connected to the output shaft  40  by operating the second clutch  112 , the power from the second motor  20  (or the motor from the second motor and the first motor) is transmitted to the transmission  30  or is used for regenerative electricity generation. 
     Furthermore, the output end of the engine  10  and the output end of the second motor  20  are connected to the output shaft  40  by operating both of the first and second clutches  111  and  112 , the power from the engine  10  and the second motor  20  (or the power from the engine, the second motor, and the first motor) is transmitted to the transmission  30 . Alternatively, when the output end of the engine  10  is connected to the output end of the second motor  20  by operating the first and second clutches  111  and  112  with the third clutch  113  disengaged, the power from the engine  10  is fully transmitted to the second motor  20 , so the engine electricity generation efficiency becomes maximum. Furthermore, the engine  10  can be started by operating the second motor  20 . 
     Next, as shown in  FIG. 2 , the second and first clutches  112  and  111  may be disposed on the output shaft  40  between the second motor  20  and the first motor  50  and the third clutch  113  may be disposed on the output shaft  40  between the engine  10  and the second motor  20 . The second clutch  112  and the first clutch  111  constitute a double clutch and are disposed at the other side, which faces the first motor  50 , of the second motor  20 . In  FIG. 2 , power transmission by the first, second, and third clutches  111 ,  112 , and  113  is almost the same as that in  FIG. 1 . 
     Next, as shown in  FIG. 3 , the second, first, and third clutches  112 ,  111 , and  113  may be all disposed on the output shaft  40  between the second motor  20  and the first motor  50 . In detail, the second and third clutches  112  and  111  may be disposed at the side, which faces the first motor  50 , of the second motor  20  and the third clutch  113  may be disposed between the second and first clutches  112  and  111  and the first motor  50 . The second and first clutches  112  and  111  constitute a double clutch. 
     In the cases shown in  FIGS. 1 and 2 , both sides of each of the first and second clutches  111  and  112  are used to connect/disconnect a contact point, but in the case shown in  FIG. 3 , one side of each of the second and first clutches  112  and  111  is used to connect/disconnect a contact point. Technology related to this is well known in the art, so the detailed description is not provided. In  FIG. 3 , power transmission by the second, first, and third clutches  112 ,  111 , and  113  is almost the same as that in  FIG. 1 . 
     Next, as shown in  FIG. 4 , the first and second clutches  111  and  112  may be disposed on the output shaft  40  between the engine  10  and the second motor  20  and the third clutch  113  may be disposed on the output shaft  40  between the second motor  20  and the first motor  50 . This configuration is similar to the configuration shown in  FIG. 1 , but is different in that the power that is connected/disconnected by the third clutch  113  is the power that is generated by the second motor  20  and transmitted to the output shaft  40 . The first and second clutches  111  and  112  may constitute any one of a double clutch and a dual clutch. 
     When the output end of the engine  10  is connected to the output shaft  40  by operating the first clutch  111  with the third clutch  113  disengaged, the power from the engine  10  is transmitted to the transmission  30 . Furthermore, when the first and second clutches  111  and  112  are engaged, the power from the engine  10  is transmitted to the transmission  30  through the second motor  20 . In this process, the third clutch  113  has been disengaged. Furthermore, when the output end of the engine  10  is connected to the input end of the second motor  20  (the left side of the second motor  20  in the figure) by engaging only the second clutch  112  with the third clutch  113  disengaged, power can be generated by operating the second motor  20  using the engine  10  or the engine  10  can be started by the second motor  20 . 
     Alternatively, when the output end of the second motor  20  (the right side of the second motor  20  in the figure) is connected to the output shaft  40  by operating the third clutch  113  without the first and second clutches  111  and  112  operated, the power from the second motor  20  is transmitted to the transmission  30  and the vehicle can be driven or regenerative electricity generation in deceleration is possible. Furthermore, the output end of the engine  10  and the output end of the second motor  20  are connected to the output shaft  40  by operating the first and third clutches  111  and  113 , the power from the engine  10  and the second motor  20  is transmitted to the transmission  30 . In this process, the second clutch  112  is disengaged. 
     Next, as shown in  FIG. 5 , the third, first, and second clutches  113 ,  111 , and  112  may be disposed between the engine  10  and the second motor  20 . The configuration shown in  FIG. 5  is similar to the configuration shown in  FIG. 3 , but is different in that the first and second clutches  111  and  112  are disposed between the third clutch  113  and the second motor  20 . The first and second clutches  111  and  112  are disposed at a first side, which faces the third clutch  113 , of the second motor  20  and may constitute a dual clutch. 
     In this case, when the output end of the engine  10  is connected to the output shaft  40  by operating the first clutch  111  with the third clutch  113  engaged, the power from the engine  10  is transmitted to the transmission  30 . Furthermore, when the output end of the engine  10  and the output end of the second motor  20  are connected to the output shaft  40  by operating both of the first clutch  111  and the second clutch  112 , the power from the engine  10  and the second motor  20  is transmitted to the transmission  30 . 
     Alternatively, when the output end of the engine  10  and the output end of the second motor  20  are connected to each other and the first clutch  111  is disengaged with the third clutch  113  engaged, the power from the engine  10  is fully transmitted to the second motor  20 , so power can be generated or the engine  10  can be started by operating the second motor  20 . If the output end of the second motor  20  is connected to the output shaft  40  by operating the first and second clutches  111  and  112  with the third clutch  130  disengaged, the power from the second motor  20  is transmitted to the transmission  30  or is used for regenerative electricity generation. 
     Next, as shown in  FIG. 6 , the third clutch  113  may be disposed on the output shaft  40  between the engine  10  and the second motor  20  and the second and first clutches  112  and  111  may be disposed on the output shaft  40  between the second motor  20  and the first motor  50 . The second and first clutches  112  and  111  may constitute any one of a double clutch and a dual clutch. There is a different between  FIGS. 6 and 4  in that the positions of the first and second clutches  111  and  112  and the third clutch  113  are different. 
     In  FIG. 6 , the third clutch  113  connects/disconnects a contact point between the input end of the second motor  20  (the left side of the motor  20  in  FIG. 6 ) and the output shaft of the engine  10 . That is, when the third clutch  113  is operated with the output end of the engine  10  and the output end of the second motor  20  disconnected from the output shaft (the first and second clutches  111  and  112  disengaged), the power from the engine  10  is transmitted to the second motor  20  through the input end of the second motor  20  and is used for electricity generation or is used to operate the second motor  20  and the engine  10  can be started. The operation mechanism of the second and first clutches  112  and  111  as a dual clutch except for the above description is almost the same as that described above with reference to  FIG. 4 . 
     Next, as shown in  FIG. 7 , a first clutch  211 , a second clutch  212 , and a third clutch  213  may be disposed, as a triple clutch, between the engine  10  and the second motor  20 , in which the triple clutch may be disposed at a first side, which faces the engine  10 , of the second motor  20 . Unlike  FIGS. 1 to 6 , the configuration shown in  FIG. 7  is characterized by controlling power transmission using a single clutch structure. 
     When the output of the engine  10  is connected to the output shaft  40  by operating the first clutch  211 , the power from the engine  10  is transmitted to the transmission  30  through the output shaft  40 . Alternatively, when the output end of the second motor  20  is connected to the output shaft  40  by operating the second clutch  212  with the third clutch  211  disengaged, the power from the second motor  20  is transmitted to the transmission  30  or is used for regenerative electricity generation. 
     Furthermore, when any one of the second clutch  211  and the third clutch  213  is engaged with the first clutch  211 , the power from the engine  10  and the second motor  20  is transmitted to the transmission  30 . If the output end of the engine  10  is connected to the output end of the second motor  20  by operating only the third clutch  113  with the first and second clutches  211  and  212  disengaged, the power from the engine  10  is fully transmitted to the second motor  20  and is used to generate electricity. Furthermore, the engine  10  can be started by operating the second motor  20 . 
     Furthermore, the third, second, and first clutches  213 ,  222 , and  211  constituting a triple clutch may be disposed between the second motor  20  and the first motor  50 , as shown in  FIG. 8 , in which the triple clutch may be disposed at a second side, which faces the first motor  50 , of the second motor  20 . In this case, when the output end of the engine  10  is connected to the output shaft  40  by operating the first clutch  211 , the power from the engine  10  is transmitted to the transmission  30  through the output shaft  40 . Furthermore, when the output end of the second motor  20  connected to the output shaft  40  by operating the second clutch  212  with the first clutch  211  disengaged, the power from the engine  20  is transmitted to the transmission  30  or is used for regenerative electricity generation. 
     Furthermore, when any one of the second clutch  211  and the third clutch  213  is engaged with the first clutch  211 , the power from the engine  10  and the second motor  20  is transmitted to the transmission  30 . Furthermore, when the output end of the engine  10  is connected to the output end of the second motor  20  by operating only the third clutch  213  with the first and second clutches  211  and  212  disengaged, the power from the engine  10  is fully transmitted to the second motor  20  and is used to generate electricity or is used to start the engine  10  by operating the second motor  20 . 
     The clutches that are applied to the present invention may be fundamentally wet clutches, but other various clutches that are generally used in the art can also be applied. That is, the clutch disposed at a side of an engine may be a dry clutch, and the clutch disposed at a side of a motor and the clutch disposed at a side of a transmission may be a magnetic clutch. 
     In particular, the clutch disposed at a side of a motor generator should be disengaged when a vehicle is driven only by an engine and should be connected in regenerative electricity generation or electricity generation by an engine, in which the numbers of revolutions should be synchronized to reduce contact shock. An electronic magnetic clutch is advantageous in this synchronization. However, even if a wet clutch is used, synchronization can be easily achieved by controlling the number of revolutions of a motor before contact, so a wet clutch can be applied. 
     Meanwhile, though not clearly shown in the drawings, the present invention does not exclude a case in which a planetary gear is disposed around the output end or the input end of a motor, as shown in  FIGS. 5 a  to 5 d    in Korean Patent No. 1580773 by the applicant(s). When a planetary gear is provided, a motor can maximally generate electricity using input power, so the fuel efficiency of an engine can be improved and the efficiency of the regenerative power generation can also be improved. 
     Connection of an engine, a second motor, and a first motor for each driving mode when there are provided a second motor and a first motor, and first, second, and third clutches or a triple clutch, as in the present invention, is described hereafter. 
     Motor Mode 
     A vehicle is driven by operating the second motor  20  and (or) the first motor  50  without operating the engine  10 . That is, three driving states of independently operating any one of the second motor  20  and the first motor  50  and both of the second motor  20  and the first motor  50  are possible. In this mode, the engine  10  is not connected to the output shaft  40  by disengaging the clutch close to the engine  10  ( 111  in  FIGS. 1, 3, 4, and 6, 113  in  FIG. 5, and 211  in  FIGS. 7 and 8 ). 
     Furthermore, when it is required to increase a speed or more output for acceleration is needed while a vehicle is driven only by the first motor, the second motor  20  is operated and synchronized in the number of revolutions with the first motor  50  and then a motor and an auxiliary motor are connected to be simultaneously operated. When a predetermined speed is reached and then the vehicle is driven at a constant speed, a high gear is engaged and the second motor  20  is stopped, so the vehicle can be driven only by the first motor  50 . Furthermore, when electricity remains in a battery, the second motor  20  and the first motor  50  can be independently or simultaneously operated in high constant-speed driving, if necessary. 
     Series Mode 
     The engine  10  and the first motor  50  are operated, a vehicle is driven by the first motor  50 , and the engine  10  is connected to the second motor  20  to generate electricity. In detail, the components  111  and  112  are operated for connection and the component  113  is disengaged in  FIG. 1 , the components  113  and  112  are operated for connection and the component  111  is disengaged in  FIG. 2 , and the components  111  and  112  are operated for connection and the component  113  is disengaged in  FIG. 3 . 
     Furthermore, the component  112  is operated for connection and the components  111  and  113  are disengaged in  FIG. 4 , the components  113  and  112  are operated for connection and the component  111  is disengaged in  FIG. 5 , the component  113  is operated for connection and the components  111  and  112  are disengaged in  FIG. 6 , and the component  213  is operated for connection and the components  211  and  212  are disengaged in  FIGS. 7 and 8 . 
     This function according to the present invention is a real time series mode, there is no configuration corresponding to this function in Korean Patent No. 1490917, and an electric vehicle mode operating a driving motor using electricity stored in a battery is provided, instead of this function of the present invention, in Korean Patent No. 1490917. 
     Parallel Mode 
     The engine  10  and the second motor  20  and (or) the first motor  50  are independently operated. The engine  10  and the second motor  20  is simultaneously operated, or the engine  10  and the first motor  50  are simultaneously operated, or the engine  10 , the second motor  20 , and the first motor  50  are simultaneously operated, thereby driving a vehicle. 
     When the engine  10  and the second motor  20  are simultaneously operated, the components  111 ,  112 , and  113  are connected in  FIGS. 1 to 3, and 5 , and the component  111  is connected and any one of the components  112  and  113  is selectively connected in  FIGS. 4 and 6 . The component  211  is connected and any one of the components  212  and  213  is selectively connected in  FIGS. 7 and 8 . In this case, the first motor  50  is operated, but forcibly rotated. 
     When the engine  10  and the first motor  50  are simultaneously operated, the second motor  20  is not clutched. Furthermore, when the engine  10  and the first motor  50  are simultaneously operated and the second motor  20  is not operated, the second motor  20  is not clutched. 
     When the engine  10 , the second motor  20 , and the first motor  50  are simultaneously operated, the clutching state is the same, but there is a difference in that the first motor  50  is operated, as compared with the case in which the engine  10  and the second motor  20  are simultaneously operated. 
     Engine Mode 
     Only the engine  10  is independently operated, and the second motor  20  and the first motor  50  are not operated. The components  111  and  113  are connected in  FIGS. 1 to 3, and 5 , the component  111  is connected in  FIGS. 4 and 6 , and the component  211  is connected in  FIGS. 7 and 8 . The second motor  20  is not clutched and is not associated with the power transmission process, so there is no driven load, and the first motor  50  is only forcibly rotated without operating. 
     Regenerative Mode 
     When a vehicle is decelerated while driving in the motor mode, the first motor  50 , or the second motor  20  and the first motor  50  can perform regenerative electricity generation, and when a vehicle is decelerated while driving in the engine mode, the first motor  50  can perform regenerative electricity generation and the second motor  20  can be connected to the engine  10 , whereby electricity is generated by the engine. When the engine  10  is not operated, the first motor  50 , or the second motor  20  and the first motor  50  can perform regenerative electricity generation. 
     Inertia Driving &amp; Engine Electricity Generation Mode 
     A vehicle is coasted by inertia, in which the engine  10  and the second motor  20  are connected and electricity is generated by the engine. The clutch close to the engine has been disengaged. Regenerative electricity generation is not performed during coasting, so the first motor  50  is forcibly rotated without operating and performing regenerative electricity generation. 
     Stop &amp; Engine Electricity Generation Mode 
     A vehicle is temporarily stopped, in which the engine  10  and the second motor  20  are connected and generate electricity. 
     Driving &amp; Engine Electricity Generation Mode 
     A vehicle is driven by the engine, and any one or both of the first motor  50  and the second motor  20  can generate electricity, depending on the output state of the engine  10 . That is, the output of the engine is insufficient for uphill driving, so a vehicle can be driven without the engine generating electricity or any one or both of the first motor and the second motor can help drive the vehicle. Furthermore, the output of the engine is sufficient in constant-speed driving or downhill driving, so electricity can be generated by any one of the types described above, depending on the output state of the engine. 
     The most ideal operation configuration according to the driving state of a vehicle is described by combining the driving modes of the present invention. 
     First, when a vehicle that has been stopped is started, the first motor  50  is used to start the vehicle if there is electricity remaining in the battery or, the vehicle is driven only by the engine  10  or electricity is generated by connecting the engine  10  and the second motor  20  to each other and the vehicle is driven in the real time series mode by the first motor  50  if there is no electricity remaining in the battery. 
     When the speed of the vehicle exceeds a predetermined value, the vehicle is driven in the motor mode by operating both of the second motor  20  and the first motor  50  if there is electricity remaining in the battery, and the vehicle is driven by the engine  10  if there is no electricity remaining in the battery. In this case, there is no driven load by the second motor  20 . When the vehicle needs to be accelerated, any one of the parallel modes can be applied, in which if there is no electricity remaining in the battery, the vehicle may be driven only by the engine. 
     When the vehicle is driven at a high constant speed, the vehicle is driven by the first motor  50  if there is electricity remaining in the battery and, the vehicle is driven only by the engine or may be driven by the first motor  50  with the second motor  20  generating electricity in the series mode if there is no electricity remaining in the battery. When there is no electricity remaining in the battery, constant-speed driving in the motor mode at a higher speed is possible to use both the second motor  20  and the first motor  50  rather than using only the first motor  50 . 
     Unlike the hybrid vehicles of the related art, according to the present invention, even if the battery is fully discharged and the first motor cannot be operated, there is no driven load by the second motor  20  in the engine mode and there is also little driven load by the first motor  50  because the capacity of the first motor  50  is small. Accordingly, reduction of engine output by forcible rotation of the first motor  50  can be minimized. 
     A large difference between the present invention and the hybrid vehicle having one motor in the related art is that the real time series mode can be applied in the present invention. Accordingly, a vehicle can be driven in the electric vehicle mode and the real time series mode regardless of whether electricity remains in a battery even at a high constant speed about 130 km/h at 2,000 rpm. Furthermore, according to the present invention, since a minimum-capacity first motor is used, the driven load by the driving motor can be minimized when a vehicle is driven only by an engine. Furthermore, the first motor is always forcibly rotated, so it is possible to immediately perform regenerative electricity generation without shock. 
     Meanwhile, another function of the present invention that is not provided by the hybrid vehicles of the related art is that since a clutch is disposed between the first motor and the second motor, it is possible to selectively operate only the first motor, only the second motor, or both the first and second motors in the electric vehicle mode, so the driving motors can be selectively operated, depending on the driving state, and the electric vehicle fuel efficiency (km/kw) can be improved. This can be considered as being similar to COD (cylinder on demand) for improving fuel efficiency in a piston engine. 
     The actual difference between the present invention and Prius and Bolt having two motors is that the driven load by the first motor is smaller when a vehicle is driven only by the engine. That is, both of first and second motors act as loads, so the driven load is large in Prius and Bolt, but there is no driven load by the second motor and the driven load by the first motor is also minimized in the present invention. 
     Furthermore, according to the present invention, it is possible to apply the electricity vehicle mode and the real time series mode with a low RPM even in high constant-speed driving. However, Prius or Bolt is driven only by an engine at high constant speed and motors should be rotated with high RPM when the electric vehicle mode is applied, so the electric vehicle fuel efficiency (km/kw) is lower than the present invention. Accordingly, Prius or Bolt is lower in high-speed fuel efficiency than fuel efficiency in cities, but the present invention provides high fuel efficiency in cities and high-speed efficiency. 
     Although the present invention was described with reference to exemplary embodiments, the embodiments are only examples and it would be apparent to those skilled in the art that the present invention is not limited thereto and may be modified in various ways, and specific technological characteristics may be added on the basis of the spirit of the present invention.