Patent Publication Number: US-2019168601-A1

Title: Transaxle device

Description:
TECHNICAL FIELD 
     The present invention relates to a transaxle device used in a hybrid vehicle including an engine and two rotating electric machines. 
     BACKGROUND ART 
     Conventionally, among hybrid vehicles including an engine and a rotating electric machine (a motor, a generator, and a motor generator), vehicles traveling while switching traveling modes are in practical use. A traveling mode includes an EV mode in which the vehicle travels only by a motor using charged power of a battery, a series mode in which the vehicle travels only by a motor while driving a generator to generate electric power by an engine, and a parallel mode in which the vehicle travels by using an engine and a motor together. The switching of the traveling mode is performed by controlling a mechanism such as a sleeve or a clutch interposed on a power transmission path inside a transaxle device. This mechanism is disposed on, for example, a shaft inside the power transmission path between the engine and the generator or a shaft inside the power transmission path between the engine and a drive wheel (see Patent Literatures 1 and 2). 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     Patent Document 1: Japanese Laid-open Patent Publication No. 11-170877 
     Patent Document 2: Japanese Laid-open Patent Publication No. 2013-180680 
     SUMMARY OF INVENTION 
     Problem to be Solved by Invention 
     Incidentally, when it is possible to switch gears in response to a driver&#39;s request output or vehicle speed without switching the traveling mode, a traveling pattern increases and hence improvement of drivability or fuel economy is expected. In order to realize this, a plurality of switchable gears may be provided inside the transaxle device. However, since a differential gear (hereinafter, referred to as a “differential”) is provided inside the transaxle device, the transaxle device easily increases in size when a plurality of gear stages and a mechanism for switching the gear stages are built therein. 
     Further, since a drive shaft is connected from the outside of the casing of the transaxle device to the output shaft having the differential interposed therein, a space for connecting the drive shaft is provided on the extension line of the output shaft outside the casing. Thus, when a plurality of gears or a mechanism for switching the gears are provided inside the casing, it is desirable to provide a structure capable of suppressing an increase in size of the transaxle device after securing the space. 
     The object of the invention is to provide a transaxle device capable of increasing a traveling pattern and securing a drive shaft connection space while suppressing an increase in size of the transaxle device. Furthermore, this object is not limited and another object of the invention is to exhibit operations and effects which are derived by each configuration illustrated in the embodiment for carrying out the invention to be described later and which is not obtainable by the conventional technique. 
     Solution to Problem 
     (1) A transaxle device disclosed herein is a transaxle device for a hybrid vehicle including an engine, a first rotating electric machine, and a second rotating electric machine and operable to individually transmit power of the engine and power of the first rotating electric machine to an output shaft on a drive wheel side and also to transmit the power of the engine to the second rotating electric machine, the transaxle device including: a differential gear which is interposed in the output shaft; and a switching mechanism which is interposed on a power transmission path from the engine to the output shaft and switches a high gear stage and a low gear stage, and wherein the high gear stage is disposed on the opposite side to the differential gear with respect to the low gear stage inside a casing of the transaxle device. Further, the first rotating electric machine means an electric power generator (a motor generator) or an electric motor which includes a rotating armature or field and has at least an electric motor function. Furthermore, the second rotating electric machine means an electric power generator (a motor generator) or an electric power generator which includes a rotating armature or field and has at least an electric power generator function. 
     (2) The switching mechanism may include a high side clutch which connects or disconnects the high gear stage in the power transmission path and a low side clutch which connects or disconnects the low gear stage in the power transmission path. 
     (3) The switching mechanism may be obtained by a combination of the high side clutch and the low side clutch as an integrated object. 
     (4) Alternatively, in the switching mechanism, the high side clutch and the low side clutch may be interposed on different shafts so as to be located at a position overlapping each other in a direction orthogonal to an axial direction. 
     (5) The transaxle device may further include: an input shaft which is coaxially connected to a rotating shaft of the engine, wherein in the switching mechanism, at least one of the high side clutch and the low side clutch may be interposed on the input shaft so as to be located at a position overlapping the differential gear in a direction orthogonal to an axial direction. 
     (6) The transaxle device may further include: a counter shaft which is disposed on a power transmission path between the output shaft and an input shaft coaxially connected to a rotating shaft of the engine; and a casing which includes a cylindrical portion protruding from an attachment surface of the first rotating electric machine and the second rotating electric machine outward in an axial direction around the counter shaft so as not to interfere with the first rotating electric machine and the second rotating electric machine, wherein in the switching mechanism, at least one of the high side clutch and the low side clutch may be disposed inside the cylindrical portion. 
     (7) The transaxle device may further include: an input shaft which is coaxially connected to a rotating shaft of the engine; and a second rotating electric machine shaft which is coaxially connected to a rotating shaft of the second rotating electric machine, wherein the switching mechanism may include a component which rotates together with the input shaft, and wherein a gear which normally engages with a fixed gear fixed to the second rotating electric machine shaft may be fixed to the component. 
     Advantageous Effects of Invention 
     It is possible to increase the traveling pattern by the switching mechanism for switching the high gear stage and the low gear stage. Further, it is possible to secure a space for connecting the drive shaft while suppressing an increase in size of the transaxle device based on the positional relationship between the high gear stage and the low gear stage. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a top view illustrating an internal configuration of a vehicle including a transaxle device according to an embodiment. 
         FIG. 2  is a schematic side view of a power train including the transaxle device of  FIG. 1 . 
         FIG. 3  is a cross-sectional view in which the transaxle device of  FIG. 1  is cut in an axial direction along a power transmission path. 
         FIG. 4  is a skeleton diagram illustrating a power train including the transaxle device of  FIG. 3 . 
         FIG. 5  is a skeleton diagram illustrating a power train according to a first modified example. 
         FIG. 6  is a skeleton diagram illustrating a power train according to a second modified example. 
         FIG. 7  is a skeleton diagram illustrating a power train according to a third modified example. 
         FIG. 8  is a skeleton diagram illustrating a power train according to a fourth modified example. 
         FIG. 9  is a skeleton diagram illustrating a power train according to a fifth modified example. 
         FIG. 10  is a skeleton diagram illustrating a power train according to a sixth modified example. 
         FIG. 11  is a skeleton diagram illustrating a power train according to a seventh modified example. 
         FIG. 12  is a skeleton diagram illustrating a power train according to an eighth modified example. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A transaxle device of an embodiment will be described with reference to the drawings. Each of the following embodiments is merely an example and there is no intention to exclude the application of various modifications and techniques not mentioned in the following embodiments. The configurations of the embodiments can be modified into various forms without departing from the gist thereof. Further, the configurations can be appropriately selected or combined as appropriate. 
     1. OVERALL CONFIGURATION 
     A transaxle  1  (a transaxle device) of the embodiment is applied to a vehicle  10  illustrated in  FIG. 1 . The vehicle  10  is a hybrid vehicle which includes an engine  2 , a traveling motor  3  (an electric motor, a first rotating electric machine), and an electric power generator  4  (an electric power generator, a second rotating electric machine). The generator  4  is connected to the engine  2  and is operable independently from the operation state of the motor  3 . Further, the vehicle  10  is provided with three traveling modes including an EV mode, a series mode, and a parallel mode. These traveling modes are alternatively selected in response to a vehicle state, a travel state, or a driver&#39;s request output by an electronic control device (not illustrated) and hence the engine  2 , the motor  3 , and the generator  4  can be separately used in response to the type. It is to be noted that, the motor  3  may have a power generation function (a function of a generator) and the generator  4  may have an electric motor function (a function of a motor). 
     The EV mode is a traveling mode in which the vehicle  10  is driven only by the motor  3  using charged power of a driving battery (not illustrated) while the engine  2  and the generator  4  are stopped. The EV mode is selected in a case in which the traveling load and the traveling speed are low or the battery charge level is high. The series mode is a traveling mode in which the vehicle  10  is driven by the motor  3  using power while driving the generator  4  to generate electric power by the engine  2 . The series mode is selected in a case in which the traveling load and the traveling speed are intermediate or the battery charge level is low. The parallel mode is a traveling mode in which the vehicle  10  is mainly driven by the engine  2  and the driving of the vehicle  10  is assisted by the motor  3  as appropriate and is selected in a case in which the traveling load and the traveling speed are high. 
     The engine  2  and the motor  3  are connected in parallel to a drive wheel  8  through the transaxle  1  and the power of each of the engine  2  and the motor  3  is individually transmitted thereto. Further, the generator  4  and the drive wheel  8  are connected in parallel to the engine  2  through the transaxle  1  and the power of the engine  2  is also transmitted to the generator  4  in addition to the drive wheel  8 . 
     The transaxle  1  is a power transmission device which is obtained by integrating a final drive (a final speed reducer) including a differential gear  18  (a differential device, hereinafter referred to as the “differential  18 ”) and a transmission (a speed reducer) and includes a plurality of mechanisms which are in charge of transmission of power between a drive source and a driven device. The transaxle  1  of the embodiment is configured to be switchable between a high/low state (a high speed stage and a low speed stage). When the vehicle travels in the parallel mode, a high gear stage and a low gear stage are switched in response to the travel state or the request output by the electronic control device. 
     The engine  2  is an internal combustion engine (a gasoline engine or a diesel engine) which burns gasoline or light oil. The engine  2  is a so-called transverse engine in which a direction of a crankshaft  2   a  (a rotating shaft) is disposed laterally to be aligned with a vehicle width direction of the vehicle  10  and is fixed to the right side surface of the transaxle  1 . The crankshaft  2   a  is disposed in parallel to a drive shaft  9  of the drive wheel  8 . The operation state of the engine  2  is controlled by the electronic control device. 
     Both the motor  3  and the generator  4  are an electric power generator (a motor generator) which has a function of an electric motor and a function of an electric power generator. The motor  3  mainly functions as an electric motor to drive the vehicle  10  and functions as an electric power generator at the time of regeneration. The generator  4  functions as an electric motor (a starter) at the time of starting the engine  2  and generates electric power by the power of the engine at the time of operating the engine  2 . An inverter (not illustrated) which converts a DC current and an AC current is provided in the periphery (or the inside) of each of the motor  3  and the generator  4 . The rotation speed of each of the motor  3  and the generator  4  is controlled by controlling the inverter. The operation state of each of the motor  3 , the generator  4 , and each inverter is controlled by the electronic control device. 
     The motor  3  of the embodiment is foiled such that an outer shape is formed in a cylindrical shape using a rotating shaft  3   a  as a center axis and is fixed to the left side surface (attachment surface) of the transaxle  1  in a posture in which a bottom surface thereof faces the transaxle  1 . The generator  4  of the embodiment is formed such that an outer shape is formed in a cylindrical shape using a rotating shaft  4   a  as a center axis and is fixed to the left side surface of the transaxle  1  in a posture in which a bottom surface thereof faces the transaxle  1  similarly to the motor  3 . 
       FIG. 2  is a side view when the engine  2 , the motor  3 , the generator  4 , and a power train  7  including the transaxle  1  are viewed from the left side. The engine  2  is omitted in the side view. As illustrated in  FIG. 2 , a pump  5  is fixed to the left side surface of the transaxle  1  in addition to the motor  3  and the generator  4 . The pump  5  is a hydraulic pressure generation device which pressure-feeds oil functioning as working oil or lubricating oil to a hydraulic circuit (not illustrated) using power of the drive wheel  8 . 
     2. TRANSAXLE 
       FIG. 3  is a cross-sectional view in which the transaxle  1  of the embodiment is cut in the axial direction along the power transmission path and  FIG. 4  is a skeleton diagram of the power train  7  including the transaxle  1 . In the skeleton diagram after  FIG. 4 , the pump  5  and the transaxle  1  are illustrated in an integrated state (a state in which the pump  5  is built in the casing  1 C). 
     As illustrated in  FIGS. 2 to 4 , the transaxle  1  is provided with six shafts  11  to  16  which are arranged in parallel. Hereinafter, a rotating shaft which is coaxially connected to the crankshaft  2   a  will be referred to as an input shaft  11 . Similarly, rotating shafts which are coaxially connected to the drive shaft  9 , the rotating shaft  3   a  of the motor  3 , and the rotating shaft  4   a  of the generator  4  will be respectively referred to as an output shaft  12 , a motor shaft  13  (a first rotating electric machine shaft), and a generator shaft  14  (a second rotating electric machine shaft). Further, a rotating shaft which is disposed on the power transmission path between the input shaft  11  and the output shaft  12  will be referred to as a first counter shaft  15  and a rotating shaft which is disposed on the power transmission path between the motor shaft  13  and the output shaft  12  will be referred to as a second counter shaft  16 . 
     As illustrated in  FIG. 3 , both end portions of all of six shafts  11  to  16  are journaled to the casing  1 C through bearings lie to  16   e . Further, an opening is formed in the side surface of the casing  1 C located on each of the input shaft  11 , the output shaft  12 , the motor shaft  13 , and the generator shaft  14  and the shafts are connected to the crankshaft  2   a  and the like through the opening. Furthermore, a torque limiter  6  having a function of protecting the power transmission mechanism by interrupting excessive torque is interposed on the crankshaft  2   a . As illustrated in  FIG. 4 , the rotating shaft of the pump  5  is connected to the first counter shaft  15 . 
     Three power transmission paths are formed inside the transaxle  1 . Specifically, a power transmission path (hereinafter, referred to as a “first path  51 ”) extending from the input shaft  11  to the output shaft  12 , a power transmission path (hereinafter, referred to as a “second path  52 ”) extending from the motor shaft  13  to the output shaft  12 , and a power transmission path (hereinafter, referred to as a “third path  53 ”) extending from the input shaft  11  to the generator shaft  14  are formed as indicated by a two-dotted chain line in  FIG. 2 . 
     The first path  51  (the first mechanism) is a path which involves in the transmission of power from the engine  2  to the drive wheel  8  and is in charge of the transmission of power during the operation of the engine  2 . A switching mechanism  20  to be described later is interposed in the course of the first path  51  to switch a power transmission enabled/disabled state and a high/low state. The second path  52  (the second mechanism) is a path which involves in the transmission of power from the motor  3  to the drive wheel  8  and is in charge of the transmission of power of the motor  3 . The third path  53  (the third mechanism) is a path which involves in the transmission of power from the engine  2  to the generator  4  and is in charge of the transmission of power at the time of starting the engine and generating electric power by the engine  2 . 
     Next, a configuration of the transaxle  1  will be described in detail with reference to  FIGS. 3 and 4 . In the following description, the “fixed gear” means a gear which is integrated with the shaft and is not rotatable relative to the shaft. Further, the “idle gear” means a gear which is pivotally supported to the shaft so as to be relatively rotatable. 
     The input shaft  11  is provided with two fixed gears  11 H and  11 L. Two fixed gears  11 H and  11 L have different number of teeth and respectively normally engage with two idle gears  15 H and  15 L provided in the first counter shaft  15  to have different number of teeth. 
     In the embodiment, one fixed gear  11 L having a small number of teeth is disposed at the right side (the side of the differential  18 ) and the other fixed gear  11 H having a large number of teeth is disposed at the left side (the opposite side to the differential  18  with respect to one fixed gear  11 L). One fixed gear  11 L having a small number of teeth engages with one idle gear  15 L having a large number of teeth to form the low gear stage. In contrast, the other fixed gear  11 H having a large number of teeth engages with the other idle gear  15 H having a small number of teeth to form the high gear stage. It is to be noted that, the fixed gear  11 L normally engages with the fixed gear  14   a  provided in the generator shaft  14  and transmits power between the engine  2  and the generator  4 . 
     In the first counter shaft  15 , the idle gear  15 L having a large diameter is disposed at a position close to the differential  18  and the idle gear  15 H having a small diameter is disposed at a position away from the differential  18 . Since the first counter shaft  15  is near (adjacent to) the output shaft  12  having the differential  18  interposed therein, for example, a portion along the first counter shaft  15  in the casing  1 C can be decreased in diameter in an outward direction (a direction moving away from the differential  18 ) in accordance with the arrangement of the gears. Alternatively, when a casing side surface provided with the opening of the output shaft  12  is provided between the idle gear  15 L having a large diameter and the idle gear  15 H having a small diameter, a portion along the first counter shaft  15  in the casing  1 C can be decreased in size on the whole. With such a configuration, a space for connecting the drive shaft  9  is secured on the extension line of the output shaft  12  outside the casing  1 C. 
     The casing  1 C of the embodiment includes a cylindrical portion  1 D which is provided on the left side surface attached with the motor  3  and the generator  4  so as to protrude outward (leftward) in the axial direction around the first counter shaft  15 . The cylindrical portion  1 D is a part of the cylindrical casing  1 C and is formed to have an arrangement and a shape so as not to interfere with the motor  3  and the generator  4 . The cylindrical portion  1 D is disposed inside an area between the rotating shaft  3   a  (the motor shaft  13 ) of the motor  3  and the rotating shaft  4   a  (the generator shaft  14 ) of the generator  4  when the power train  7  is viewed from the left side (in a side view). Here, “the area” above mentioned means an area which is orthogonal to a line connecting two shafts  3   a  and  4   a  and interposed between two lines passing through the shafts  3   a  and  4   a  in a side view. Further, the pump  5  is attached to the outer end face (the left end face) of the cylindrical portion  1 D. 
     Two idle gears  15 H and  15 L of the embodiment are disposed on the same shaft (the first counter shaft  15 ) and form a double pipe structure. Specifically, a right portion of the low side idle gear  15 L is provided with a tooth surface portion which engages with the fixed gear  11 L and an engagement component  21 L of the switching mechanism  20  is fixed to a front end of the cylindrical portion  1 D protruding from the left side of the tooth surface portion (that is, a left portion of the idle gear  15 L). Further, in the high side idle gear  15 H, the engagement component  21 H of the switching mechanism  20  is fixed to the left side of the tooth surface portion engaging with the fixed gear  11 H. Furthermore, the idle gear  15 H is pivotally supported by the outer periphery of the cylindrical portion  1 D of the low side idle gear  15 L so as to be relatively rotatable. 
     The switching mechanism  20  is used to control the power connection/disconnection state of the engine  2  and to switch the high gear stage and the low gear stage and is disposed inside the cylindrical portion  1 D while being interposed in the first counter shaft  15 . The switching mechanism  20  of the embodiment is obtained by a combination of a high side multiple disc type clutch (a high side clutch) which connects or disconnects the high gear stage in the first path  51  and a low side multiple disc type clutch (a low side clutch) which connects or disconnects the low gear stage in the first path  51  as an integrated object. The working hydraulic pressure of each clutch is supplied from each of two oil passage inlets  5   a  and  5   a ′ provided in the first counter shaft  15 . 
     The switching mechanism  20  of the embodiment includes two engagement components  21 H and  22 H constituting the high side clutch and two engagement components  21 L and  22 L constituting the low side clutch. The drive-side engagement components  21 H and  21 L are respectively fixed to two idle gears  15 H and  15 L and receive power from the engine  2 . Meanwhile, the driven-side engagement components  22 H and  22 L are respectively fixed to the first counter shaft  15  and output power to the drive wheel  8 . Each of the high side engagement components  21 H and  22 H and the low side engagement components  21 L and  22 L is driven in a separating direction (a disengagement direction) and an approaching direction (an engagement direction) in response to the hydraulic pressure of the oil flowing from the oil passage inlets  5   a ′ and  5   a . It is to be noted that, a pressure adjuster which adjusts the hydraulic pressure of the oil pressure-fed from the pump  5  to an appropriate pressure may be provided in a hydraulic pressure circuit. The pressure adjuster includes, for example, a plurality of solenoid valves (an on/off solenoid valve, a linear solenoid valve, and the like). 
     When all of the engagement components  21 H,  22 H,  21 L, and  22 L of the switching mechanism  20  are disengaged, all of two idle gears  15 H and  15 L enter an idle rotation state. In this case, even when the engine  2  is operated, the power of the engine  2  (the rotation of the input shaft  11 ) is not transmitted to the output shaft  12 . That is, in this case, the transmission of the power of the engine  2  to the drive wheel  8  is interrupted. Meanwhile, when one of the high and low side clutches of the switching mechanism  20  is engaged and the other thereof is disengaged, the high gear stage or the low gear stage is selected and the power of the engine  2  is transmitted to the output shaft  12 . 
     That is, when the high side clutch engagement components  21 H and  22 H are engaged and the low side clutch engagement components  21 L and  22 L are disengaged, the high gear stage is selected. In this case, the power of the engine  2  is transmitted to the drive wheel  8  through the fixed gear  11 H and the idle gear  15 H. In contrast, when the low side clutch engagement components  21 L and  22 L are engaged and the high side clutch engagement components  21 H and  22 H are disengaged, the low gear stage is selected. In this case, the power of the engine  2  is transmitted to the drive wheel  8  through the fixed gear  11 L and the idle gear  15 L. 
     In the first counter shaft  15 , the fixed gear  15   a  is provided near the right side of the low side idle gear  15 L. The fixed gear  15   a  normally engages with the ring gear  18   a  of the differential  18  provided in the output shaft  12 . 
     Further, the second counter shaft  16  is provided with two fixed gears  16   a  and  16   b  and a parking gear  19 . The fixed gear  16   a  which is disposed near the right side surface of the casing  1 C normally engages with a fixed gear  13   a  provided in the motor shaft  13 . Meanwhile, the fixed gear  16   b  which is disposed near the left side surface of the casing  1 C normally engages with the ring gear  18   a  of the differential  18 . That is, the power of the motor  3  is transmitted to the output shaft  12  through the fixed gears  13   a ,  16   a , and  16   b  and the differential  18 . 
     The parking gear  19  is a component constituting the parking lock device and is fixed to the second counter shaft  16 . When a P range is selected by a driver, the parking gear  19  engages with a parking sprag (not illustrated) to prohibit the rotation of the second counter shaft  16  (that is, the output shaft  12 ). 
     As illustrated in  FIG. 3 , the differential  18  transmits the power transmitted to the ring gear  18   a  to the output shaft  12  through a differential casing  18   b , a pinion shaft  18   c , a differential pinion  18   d , and a side gear  18   e.    
     3. OPERATION AND EFFECT 
     (1) The above-described transaxle  1  is provided with the switching mechanism  20  and the high gear stage and the low gear stage are switched in response to the travel state or the request output when the vehicle travels in the parallel mode. That is, since the power of the engine  2  can be transmitted (output) while being switched into two levels in the parallel mode, it is possible to increase the traveling pattern and to obtain the effect of improving the drivability and the fuel economy and improving the vehicle merchantability. 
     Further, in the above-described transaxle  1 , the high gear stage (the fixed gear  11 H, the idle gear  15 H) is disposed on the opposite side to the differential  18  with respect to the low gear stage (the fixed gear  11 L, the idle gear  15 L) inside the casing  1 C. That is, since a gear (the idle gear  15 L) having a large diameter is disposed at a position close to the differential  18  and a gear (the idle gear  15 H) having a small diameter is disposed at a position away from the differential  18  on the shaft (the first counter shaft  15 ) near the output shaft  12 , a portion along the first counter shaft  15  in the casing  1 C can be decreased in diameter or size on the whole, for example, in an outward direction (a direction moving away from the differential  18 ). That is, according to the above-described transaxle  1 , it is possible to secure a space for connecting the drive shaft  9  on the extension line of the output shaft  12  outside the casing  1 C while suppressing an increase in size of the transaxle  1 . 
     Further, in the above-described vehicle  10 , since the respective outputs of the power of the engine  2  and the power of the motor  3  are provided the torque omission generated at the time of switching the high/low state can be covered with the power of the motor  3 . Accordingly, a shift shock can be suppressed. 
     (2) In the above-described transaxle  1 , since the high/low state is switched by the switching mechanism  20  including the high side clutch and the low side clutch, a configuration can be simplified. 
     (3) Further, in the above-described transaxle  1 , since the switching mechanism  20  is obtained by a combination of the high side clutch and the low side clutch as an integrated object, the transaxle  1  can be compact. 
     (4) In the above-described transaxle  1 , the switching mechanism  20  is disposed inside the cylindrical portion  1 D of the casing  1 C. Since the cylindrical portion  1 D is a portion protruding from the left side surface attached with the motor  3  and the generator  4  and is provided so as not to interfere with the motor  3  and the generator  4 , it is possible to assemble the switching mechanism  20  to the transaxle  1  without increasing the size of the power train  7  by providing the switching mechanism  20  inside the cylindrical portion  1 D. 
     4. MODIFIED EXAMPLES 
     The above-described transaxle  1  is an example and a configuration thereof is not limited to the above-described configuration. Hereinafter, modified examples of the transaxle  1  will be described with reference to  FIGS. 5 to 12 .  FIGS. 5 to 12  are skeleton diagrams illustrating the power train  7  including the transaxle  1  according to first to eighth modified examples. In the components of the above-described embodiment or the modified examples, the same reference numerals as those of the above-described embodiment or the modified examples or the similar reference numerals (reference numerals having the same numbers and different alphabets) will be given to the components and a repetitive description thereof will be omitted. 
     4-1. First Modified Example 
     As illustrated in  FIG. 5 , the transaxle  1  according to the first modified example has the same configuration as that of the above-described embodiment except that the arrangement of idle gears  11 H′ and  11 L′ and a switching mechanism  20 ′ is different. In the modified example, all of the high side idle gear  11 H′ and the low side idle gear  11 L′ are provided in the input shaft  11  to form a double pipe structure and the switching mechanism  20 ′ is interposed on the same shaft (the input shaft  11 ). 
     The high side idle gear  11 H′ is disposed on the opposite side (the left side) of the differential  18  with respect to the low side idle gear  11 L′ and normally engages with a high side fixed gear  15 H′ provided in the first counter shaft  15 . The low side idle gear  11 L′ is disposed near the fixed gear  11   a  provided in the input shaft  11  and normally engages with a low side fixed gear  15 L′ provided in the first counter shaft  15 . It is to be noted that, the fixed gear  11   a  is disposed near the right side surface of the casing  1 C and normally engages with the fixed gear  14   a  of the generator shaft  14 . That is, the input shaft  11  and the generator shaft  14  are connected to each other through two fixed gears  11   a  and  14   a  so that power can be transmitted between the engine  2  and the generator  4 . 
     The switching mechanism  20 ′ of the modified example is obtained by a combination of the high side clutch and the low side clutch as an integrated object. In the switching mechanism  20 ′, all of drive-side engagement components  21 H′ and  21 L′ are fixed to the input shaft  11  and driven-side engagement components  22 H′ and  22 L′ are respectively fixed to the idle gears  11 H′ and  11 L′. Each of the high side clutch engagement components  21 H′ and  22 H′ and the low side clutch engagement components  21 L′ and  22 L′ receives oil pressure-fed from the pump  5  through oil passage inlets  5   b  and  5   b ′ provided in the input shaft  11  and is driven in a separating direction (a disengagement direction) and an approaching direction (an engagement direction) in response to the hydraulic pressure (or the adjusted hydraulic pressure). 
     When all of the engagement components  21 H′,  22 H′,  21 L′, and  22 L′ of the switching mechanism  20 ′ are disengaged, all of two idle gears  11 H′ and  11 L′ enter an idle rotation state, so that the transmission of the power of the engine  2  to the drive wheel  8  is interrupted. Meanwhile, when any one of the high side clutch and the low side clutch is engaged and the other thereof is disengaged, the high gear stage or the low gear stage is selected, so that the power of the engine  2  is transmitted to the output shaft  12 . Also in such a configuration, the same effect as that of the above-described embodiment can be obtained. 
     In the transaxle  1  according to the modified example, a connection/disconnection mechanism which enables or disables the transmission of the power from the motor  3  is provided on the second counter shaft  16  in the course of the second path  52 . The connection/disconnection mechanism includes an idle gear  16   c  and a motor side clutch  17 . The idle gear  16   c  is fixed to a first engagement component  17   a  of the motor side clutch  17  and normally engages with the fixed gear  13   a  provided in the motor shaft  13  so as to rotate while following the rotation of the motor shaft  13 . The motor side clutch  17  is a multiple disc type clutch which controls the power connection/disconnection state of the motor  3  and includes a first engagement component  17   a  and a second engagement component  17   b  fixed to the second counter shaft  16 . The motor side clutch  17  is disposed near the right side surface of the casing  1 C. 
     The first engagement component  17   a  is one to which power is input from the motor  3  and the second engagement component  17   b  is one which outputs power to the drive wheel  8 . These engagement components  17   a  and  17   b  receive oil pressure-fed from the pump  5  through the oil passage inlet  5   c  and are driven in a separating direction (a disengagement direction) and an approaching direction (an engagement direction) in response to the hydraulic pressure (or the adjusted hydraulic pressure). When the motor side clutch  17  is engaged, the power of the motor  3  is transmitted to the drive wheel  8  through the fixed gear  13   a  and the idle gear  16   c  and the rotation of the drive wheel  8  is transmitted to the motor  3 . That is, in a state in which the motor side clutch  17  is engaged, power running and regenerative power generation by the motor  3  becomes possible. 
     In contrast, when the motor side clutch  17  is disengaged while the vehicle  10  travels by the engine  2  (while the motor  3  is stopped), the idle gear  16   c  idly rotates, so that the rotation of the drive wheel  8  is not transmitted to the motor  3 . Accordingly, since the motor  3  is not rotated, a resistance becomes small. It is to be noted that, an electric coupling may be provided instead of the pump  5  and the multiple disc type motor side clutch  17  to serve as a connection/disconnection mechanism which controls the power connection/disconnection state by an electronic control device. When such a connection/disconnection mechanism is provided, it is possible to prevent the motor  3  from rotating together and to reduce running resistance. 
     It is to be noted that, the connection/disconnection mechanism is not an indispensable configuration and may be omitted. Further, in the modified example, the parking gear  19  is provided in the second counter shaft  16 , but the arrangement of the parking gear  19  is not limited thereto. 
     4-2. Second Modified Example 
     As illustrated in  FIG. 6 , the transaxle  1  according to the second modified example is different from that of the first modified example ( FIG. 5 ) in that a positional relationship of the switching mechanism  20 ′ and the idle gears  11 H′ and  11 L′ is different and a gear for transmitting power to the generator  4  is different. That is, also in the modified example, the switching mechanism  20 ′ and the idle gears  11 H′ and  11 L′ are provided in the input shaft  11 , but have a different positional relationship. Further, the gear  11   b  is provided instead of the fixed gear  11   a  of the first modified example. 
     In the modified example, the switching mechanism  20 ′ is disposed near the right side surface inside the casing  1 C and two idle gears  11 H′ and  11 L′ are disposed at the left side of the switching mechanism  20 ′. Specifically, the switching mechanism  20 ′ is disposed at a position overlapping the ring gear  18   a  of the differential  18  in a direction (hereinafter, referred to as a “width direction”) orthogonal to the axial direction. As illustrated in  FIG. 3 , the fixed gear  15   a  of the first counter shaft  15  engages with the ring gear  18   a  of the differential  18 . For this reason, when a gear (for example, the fixed gear  11 L) engaging with other gears (for example, the idle gear  15 L) of the first counter shaft  15  is provided in the input shaft  11 , the gear can be disposed only at a position offset from the ring gear  18   a  in the width direction. That is, a space in the periphery of the input shaft  11  overlapping the differential  18  (in particular, the ring gear  18   a ) in the width direction easily becomes a dead space. 
     In contrast, as illustrated in  FIG. 6 , the switching mechanism  20 ′ of the modified example is disposed in the dead space. Further, the low side idle gear  11 L′ is disposed near the left side of the switching mechanism  20 ′ and the high side idle gear  11 H′ is disposed near the left side of the idle gear  11 L′ (on the opposite side to the differential  18  with respect to the low gear stage). All of the idle gears  11 H′ and  11 L′ include tooth surface portions respectively foiled at the left portions thereof to engage with the fixed gears  15 H′ and  15 L′ and respectively include the driven-side engagement component  22 H′ and  22 L′ of the switching mechanism  20 ′ formed at the right portions thereof. 
     The drive-side engagement components  21 H′ and  21 L′ of the switching mechanism  20 ′ are fixed to the input shaft  11 . In the modified example, the gear  11   b  which normally engages with the fixed gear  14   a  of the generator shaft  14  is fixed to the outer peripheral surface of the clutch pack corresponding to the engagement component  21 L′ rotating together with the input shaft  11 . That is, the input shaft  11  and the generator shaft  14  are connected through the gear  11   b  and the fixed gear  14   a  so that power can be transmitted between the engine  2  and the generator  4 . 
     Thus, also in the transaxle  1  according to the modified example, the same effect as that of the above-described embodiment can be obtained. Further, a space in which the switching mechanism  20 ′ of the modified example is disposed becomes a dead space in the conventional structure. For this reason, in the transaxle  1  of the modified example, a dead space can be efficiently used and space efficiency inside the casing  1 C can be improved. Furthermore, since the gear  11   b  transmitting power to the generator  14  is fixed to the clutch pack (the engagement component  21 L′), the axial dimension of the input shaft  11  can be shortened and the transaxle  1  can be made compact. 
     The switching mechanism  20 ′ may be disposed at a position overlapping a component (for example, the differential casing  18   b  or the differential pinion  18   d ) other than the ring gear  18   a  of the differential  18  in the width direction. Further, the fixed gear  11   a  of the above-described first modified example may be provided in the input shaft  11  instead of fixing the gear  11   b  to the outer periphery of the engagement component  21 L′ (the clutch pack) of the switching mechanism  20 ′. 
     4-3. Third Modified Example 
     As illustrated in  FIG. 7 , the transaxle  1  according to the third modified example is different from that of the first modified example ( FIG. 5 ) in that the switching mechanism includes a high side clutch  30 H and a low side clutch  30 L respectively interposed in different shafts. The high side clutch  30 H is disposed near the left side surface of the first counter shaft  15  and the low side clutch  30 L is disposed at a position close to the right side surface of the input shaft  11  and overlapping the ring gear  18   a  of the differential  18  in the width direction. 
     In the input shaft  11 , an idle gear  11 La is provided near the left side of the low side clutch  30 L. Further, the high side fixed gear  11 H and the fixed gear  11   a  are provided at the left side of the idle gear  11 La. In the first counter shaft  15 , an idle gear  15 Ha is provided near the right side of the high side clutch  30 H. Furthermore, the low side fixed gear  15 L′ and the fixed gear  15   a  are provided at the right side of the idle gear  15 Ha. The high side clutch  30 H includes a drive-side engagement component  31 H fixed to the left side of the idle gear  15 Ha and a driven-side engagement component  32 H fixed to the first counter shaft  15 . The low side clutch  30 L includes a drive-side engagement component  31 L fixed to the input shaft  11  and a driven-side engagement component  32 L fixed to the right side of the idle gear  11 La. 
     The engagement components  31 H and  32 H of the high side clutch  30 H and the engagement components  31 L and  32 L of the low side clutch  30 L respectively receive oil pressure-fed from the pump  5  through the oil passage inlets  5   a  and  5   b  and are driven in a separating direction (a disengagement direction) and an approaching direction (an engagement direction) in response to the hydraulic pressure (or the adjusted hydraulic pressure). When the high side clutch  30 H is engaged and the low side clutch  30 L is disengaged, the high gear stage is selected. In this case, the power of the engine  2  is transmitted to the drive wheel  8  through the fixed gear  11 H and the idle gear  15 Ha. In contrast, when the low side clutch  30 L is engaged and the high side clutch  30 H is disengaged, the low gear stage is selected. In this case, the power of the engine  2  is transmitted to the drive wheel  8  through the idle gear  11 La and the fixed gear  15 L′. 
     Thus, also in the transaxle  1  according to the modified example, it is possible to obtain the effect (1) of the above-described embodiment. Further, similarly to the above-described second modified example, it is possible to efficiently use a dead space and to improve space efficiency inside the casing  1 C. 
     In the modified example, the low side clutch  30 L may be disposed at a position overlapping a component (for example, the differential casing  18   b  or the differential pinion  18   d ) other than the ring gear  18   a  of the differential  18  in the width direction. 
     4-4. Fourth Modified Example 
     As illustrated in  FIG. 8 , the transaxle  1  according to the fourth modified example is different from that of the third modified example ( FIG. 7 ) in that the arrangement of two clutches  30 H′ and  30 L′ of the switching mechanism and the arrangement of the idle gears  11 Ha and  15 La are different. That is, in the modified example, the input shaft  11  is provided with the fixed gears  11   a  and  11 L and the high side clutch  30 H′ and the idle gear  11 Ha. Further, the first counter shaft  15  is provided with the fixed gears  15   a  and  15 H′ and the low side clutch  30 L′ and the idle gear  15 La. 
     The high side clutch  30 H′ includes a drive-side engagement component  31 H′ fixed to the input shaft  11  and a driven-side engagement component  32 H′ fixed to the right side of the high side idle gear  11 Ha. The low side clutch  30 L′ includes a drive-side engagement component  31 L′ fixed to the left side of the low side idle gear  15 La and a driven-side engagement component  32 L′ fixed to the first counter shaft  15 . These engagement components  31 H′,  32 H′,  31 L′, and  32 L′ are engaged or disengaged in response to the hydraulic pressure similarly to the above-described third modified example. 
     In the modified example, the idle gear  11 Ha and the fixed gear  15 H′ forming the high gear stage are disposed near the left side surface of the casing  1 C and the fixed gear  11   a  normally engaging with the fixed gear  14   a  of the generator shaft  14  is disposed near the right side surface thereof. Further, the high side clutch  30 H′ is interposed at the right side of the idle gear  11 Ha and the fixed gear  11 L and the idle gear  15 La forming the low gear stage are disposed between the clutch  30 H′ and the fixed gear  11   a . Meanwhile, the low side clutch  30 L′ is interposed at the left side of the idle gear  15 La and is interposed at a position overlapping the high side clutch  30 H′ in the width direction. 
     Thus, also in the transaxle  1  according to the modified example, since the high gear stage is disposed on the opposite side to the differential  18  with respect to the low gear stage, it is possible to obtain the effect (1) of the above-described embodiment. Further, in the modified example, the high side idle gear  11 Ha and the low side idle gear  15 La are disposed on different shafts and two clutches  30 H′ and  30 L′ coaxial to the idle gears  11 Ha and  15 La are interposed at an overlapping position in the width direction. For this reason, the axial dimension (the entire length) of the transaxle  1  can be shortened and the transaxle  1  can be made compact. 
     4-5. Fifth Modified Example 
     As illustrated in  FIG. 9 , the transaxle  1  according to the fifth modified example is different from those of the third modified example ( FIG. 7 ) and the fourth modified example ( FIG. 8 ) in that all of the idle gears  11 Ha and =a and two clutches  30 H′ and  30 L of the switching mechanism are provided in the input shaft  11 . That is, in the modified example, the low gear stage (the idle gear  11 La, the fixed gear  15 L′) is disposed at the left side of the fixed gear  11   a  provided near the right side surface of the casing  1 C on the input shaft  11  and the low side clutch  30 L is interposed at the left side of the idle gear  11 La. Further, the high gear stage (the idle gear  11 Ha, the fixed gear  15 H′) is disposed at the left side of the low gear stage and the high side clutch  30 H′ is interposed at the left side of the idle gear  11 Ha. 
     In the modified example, the driven-side engagement components  32 H′ and  32 L of the high and low side clutches  30 H′ and  30 L are respectively fixed to the left side of the idle gears  11 Ha and  11 La. These engagement components  32 H′ and  32 L may be fixed to the right side of the idle gears  11 Ha and =a similarly to the third and fourth modified examples. Also in such a configuration, it is possible to obtain the effect (1) of the above-described embodiment. 
     4-6. Sixth Modified Example 
     As illustrated in  FIG. 10 , the transaxle  1  according to the sixth modified example is different from that of the fifth modified example ( FIG. 9 ) in that all of the idle gears  15 Ha and  15 La and two clutches  30 H and  30 L′ of the switching mechanism are provided in the first counter shaft  15 . That is, in the modified example, the low gear stage (the fixed gear  11 L, the idle gear  15 La) is disposed at the left side of the fixed gear  11   a  provided near the right side surface of the casing  1 C on the input shaft  11  and the high gear stage (the fixed gear  11 H, the idle gear  15 Ha) is disposed at the left side of the low gear stage. The clutches  30 H and  30 L′ are respectively interposed at the left side of the idle gears  15 Ha and  15 La. Also in such a configuration, it is possible to obtain the effect (1) of the above-described embodiment. 
     4-7. Seventh Modified Example 
     As illustrated in  FIG. 11 , the transaxle  1  according to the seventh modified example is different from the fifth modified example ( FIG. 9 ) in that the positions of clutches  40 H and  40 L with respect to idle gears  11 Hb and  11 Lb are different. In the modified example, the inner diameters of the idle gears  11 Hb and  11 Lb are formed to be large as compared with the above-described embodiment or the first to sixth modified examples and the clutches  40 H and  40 L are respectively disposed at the inside in the radial direction (hereinafter, referred to as the “inside”) of the idle gears  11 Hb and  11 Lb. 
     The switching mechanism of the modified example is also used to control the power connection/disconnection state of the engine  2  and to switch the high gear stage and the low gear stage and includes the high side clutch  40 H and the low side clutch  40 L all formed as the multiple disc type clutch. The high side clutch  40 H includes a drive-side engagement component  41 H fixed to the input shaft  11  and a driven-side engagement component  42 H fixed to the inside of the idle gear  11 Hb forming the high gear stage. Further, the low side clutch  40 L includes a drive-side engagement component  41 L fixed to the input shaft  11  and a driven-side engagement component  42 L fixed to the inside of the idle gear  11 Lb forming the low gear stage. These engagement components  41 H,  42 H,  41 L, and  42 L are engaged or disengaged in response to the hydraulic pressure similarly to the above-described modified example. 
     Thus, also in the transaxle  1  according to the modified example, it is possible to obtain the effect (1) of the above-described embodiment. Further, according to the configuration of the modified example, since the clutches  40 H and  40 L are provided inside the idle gears  11 Hb and  11 Lb, the axial dimension can be shortened and the transaxle  1  can be made compact. 
     4-8. Eighth Modified Example 
     As illustrated in  FIG. 12 , the transaxle  1  according to the eighth modified example is different from that of the seventh modified example ( FIG. 11 ) in that the arrangement of idle gears  15 Hb and  15 Lb and clutches  40 H′ and  40 L′ is different. In the modified example, all of the idle gears  15 Hb and  15 Lb are provided in the first counter shaft  15  and the clutches  40 H′ and  40 L′ are respectively disposed inside the idle gears  15 Hb and  15 Lb. 
     The high side clutch  40 H′ includes a drive-side engagement component  41 H′ fixed to the inside of the idle gear  15 Hb forming the high gear stage and a driven-side engagement component  42 H′ fixed to the first counter shaft  15 . Further, the low side clutch  40 L′ includes a drive-side engagement component  41 L′ fixed to the inside of the idle gear  15 Lb forming the low gear stage and a driven-side engagement component  42 L′ fixed to the first counter shaft  15 . These engagement components  41 H′,  42 H′,  41 L′, and  42 L′ are engaged or disengaged in response to the hydraulic pressure similarly to the above-described other modified examples. Also in such a configuration, the same effect as that of the above-described seventh modified example can be obtained. 
     5. OTHERS 
     While the embodiment and the modified examples of the invention have been described, the invention is not limited to the above-described embodiment and the like and can be modified into various forms without departing from the gist of the invention. 
     For example, the transaxle  1  of the above-described modified examples is provided with the connection/disconnection mechanism, but as in the above-described embodiment, it is possible that the connection/disconnection mechanism is not provided. Further, the position of the parking gear  19  is not particularly limited and can be appropriately set. 
     All of the above-described switching mechanisms include the high side clutch and the low side clutch, but the high gear stage and the low gear stage may be switched by using a sleeve or a planetary gear instead of the clutch. 
     Further, the relative positions of the engine  2 , the motor  3 , the generator  4 , and the pump  5  with respect to the transaxle  1  are not limited to the above-described examples. In response to the relative positions, the arrangement of six shafts  11  to  16  inside the transaxle  1  may be set. Furthermore, the arrangement of the gears provided in the shafts inside the transaxle  1  is also exemplary and is not limited to the above-described example. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1  TRANSAXLE (TRANSAXLE DEVICE) 
               1 C CASING 
               1 D CYLINDRICAL PORTION 
               2  ENGINE 
               2   a  CRANKSHAFT (ROTATING SHAFT) 
               3  MOTOR (ELECTRIC MOTOR, FIRST ROTATING ELECTRIC MACHINE) 
               4  GENERATOR (ELECTRIC POWER GENERATOR, SECOND ROTATING ELECTRIC MACHINE) 
               4   a  ROTATING SHAFT 
               8  DRIVE WHEEL 
               10  VEHICLE 
               11  INPUT SHAFT 
               11   b  GEAR 
               12  OUTPUT SHAFT 
               14  GENERATOR SHAFT (SECOND ROTATING ELECTRIC MACHINE SHAFT) 
               15  FIRST COUNTER SHAFT (COUNTER SHAFT) 
               18  DIFFERENTIAL (DIFFERENTIAL GEAR) 
               20 ,  20 ′ SWITCHING MECHANISM 
               30 H,  30 H′,  40 H,  40 H′ HIGH SIDE CLUTCH (SWITCHING MECHANISM) 
               30 L,  30 L′,  40 L,  40 L′ LOW SIDE CLUTCH (SWITCHING MECHANISM) 
               51  FIRST PATH (POWER TRANSMISSION PATH)