Abstract:
An inverter is disposed on a cover, lead wires from an electric motor are disposed nearby an output gear in a dead space formed by diameter difference between the output gear and the motor, and the lead wires are routed to the outside of the cover at a position corresponding to the output gear portion. An upper side portion of the electric motor, which is used as a space for routing the lead wires in the conventional unit, can thus be used as a space for disposing the inverter. That is, the inverter can be disposed in the upper side of the vehicle drive unit, which now has available space as compared to the conventional unit. As a result, the vehicle drive unit and the inverter are more compact.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The invention relates to a vehicle drive unit, such as a hybrid vehicle and an electric vehicle, obtaining a vehicle drive force by a drive motor. 
     2. Description of Related Art 
     A conventional vehicle drive unit is shown in back elevation in FIG. 6 with FIG. 7 a side cross sectional diagram of the drive unit of FIG.  6 . 
     In a conventional hybrid vehicle and an electric vehicle, an inverter (not shown), connected to an electric motor and a generator  57 , is separately arranged from a hybrid drive unit  55 , the vehicle drive unit. As shown in FIGS. 6 and 7, the inverter and the hybrid drive unit  55  are connected with a motor lead wires  53  routed, or pulled out, from a rear cover  52  side, which is at an opposite side to an output gear  51  of the electric motor  50 . 
     In this structure, the upper face, side face and the rear cover  52  of the hybrid drive unit  55  are enlarged to obtain a space for routing, or positioning, the motor lead wires  53  connecting to terminals  56 . As a result, the parts, especially the rear cover portion is prone to interfere with a side member of the vehicle. 
     Especially in the case where the inverter could be integrally disposed on an upper portion of a hybrid drive unit  55 , that is the necessary space is available, the inverter can not be so disposed because a terminal  56  for routing a motor lead wire is in the way, i.e., is located at that position. 
     SUMMARY OF THE INVENTION 
     In view of the above problems associated with the related art, an object of the invention is to provide a vehicle drive unit, in which an inverter can be disposed on the upper portion of the vehicle drive unit and a rear cover side of the vehicle drive unit is compactly covered. 
     In order to achieve the foregoing object, according to the invention, a vehicle drive unit that obtains a drive force for driving a vehicle from an electric motor comprises the electric motor, a differential unit, a gear unit transmitting a drive force from the electric motor to the differential unit, a cover covering the electric motor, an inverter disposed on the cover, and a lead wire from the electric motor disposed in neighborhood of an output gear of the electric motor, the output gear a part of the gear unit, and in a space structured by diameter differences between the output gear and the electric motor so as to route to the outside of the cover at a position corresponding to the output gear. The electric motor and the inverter are electrically connected through the lead wire. 
     The lead wire is structured from a first lead wire, terminal and a second lead wire, the terminal is disposed in a portion of the cover near to the output gear by penetrating the cover. The electric motor and the terminal are connected with the first lead wire, and the inverter and the terminal are connected with the second lead wire. 
     A lead wire from the electric motor is connected to a stator of the electric motor. 
     An inverter case, in which the inverter is disposed is integrated with the cover, and a grooving space is formed between the rear portion of the cover and the inverter case. A heat sink for cooling the inverter is formed in a part of the cover between the inverter and the electric motor. A chamber portion is formed on the rear portion of the cover corresponding to the rear portion of the electric motor which substantially outlines, i.e., follows the contour of, the stator of the electric motor. 
     According to the invention, a lead wire from the electric motor is disposed in the vicinity of an output gear of the electric motor and in a space structured by diameter differences between the output gear and the electric motor. The lead wire is routed to the outside of the cover from the space. Therefore, the upper face portion of the electric motor of the vehicle drive unit, which is used as a space for routing or positioning the lead wire in the conventional unit, is used as a space for disposing the inverter. The inverter can then be disposed on the upper face of the vehicle drive unit, which comparatively available space in the vehicle. As a result, the vehicle drive unit is compactly structured with the inverter. 
     Further, the lead wire is not routed from the rear portion of the cover or the rear cover portion. Therefore, the rear cover portion is compactly structured. As a result, interference between the vehicle drive unit and vehicle side members is appreciably prevented when the vehicle drive unit is mounted. 
     The terminal, which is a comparatively large member, is disposed a portion of the cover near to the output gear. Therefore, the space structured by the diameter differences between the output gear and the electric motor is effectively used. 
     A brushless DC motor can be used as an electric motor. In such a case, the structure of the vehicle drive unit is simplified. 
     Because the grooving space is formed, interference with side members of a vehicle is prevented. 
     The heat sink for cooling the inverter is formed at a position corresponding to the rotor portion of the electric motor along with the outline of the rotor. Therefore, the heat sink is formed without wasted space. 
     A chamfer portion is formed on the rear portion of the cover along the outline of the stator of the electric motor, and the outline of the cover is formed along with the electric motor. Therefore, unneeded thickness of the rear portion of the cover is prevented and, then, interference with side members of a vehicle is prevented. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described in conjunction with the following drawings in which like features are designated with like reference characters, and wherein: 
     FIG. 1 is a schematic diagram showing an example of a vehicle drive unit; 
     FIG. 2 is a side cross sectional diagram of a developed portion of FIG. 1; 
     FIG. 3 is an elevation of a vehicle drive unit of FIG. 2; 
     FIG. 4 is a back elevation of a vehicle drive unit of FIG. 2; 
     FIG. 5 is a partial side cross sectional diagram showing the vehicle drive unit of FIG. 2; 
     FIG. 6 is a back elevation showing a conventional vehicle drive unit; and 
     FIG. 7 is a side cross sectional diagram showing the vehicle drive unit of FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The invention will become more apparent from the detailed description of a preferred embodiment with reference to the accompanying drawings. 
     A hybrid drive unit  1 , as a vehicle drive unit, comprises an internal engine  2 , a generator  3  having a first electric rotation member  17 ,  19 , a brake unit  4 , an electric motor  5  having a second electric rotation member  25 ,  26 , a planetary gear  6 , a hydraulic pressure generating unit  7 , and a differential unit  9 . The generator  3 , the brake unit  4 , the motor  5 , the planetary gear  6 , the hydraulic pressure generating unit  7  and the differential unit  9  are disposed in a cover  10 . A first axis A is aligned with an engine output shaft  2   a , a second axis B structured from a counter shaft  11 , a third axis C structured from a motor output shaft  5   a , a fourth axis D structured from drive wheel shafts extending from the differential unit  9  to left and right sides, and a fifth axis E (FIGS. 1 and 3) structured from a drive shaft  8 , a drive member of an oil pump are disposed as shown in FIGS. 2 and 3. That is, the first axis A, the third axis C and the fourth axis D are disposed so as to surround the second axis B structured from the counter shaft. The fifth axis E is disposed below the first axis A and to the side of the fourth axis D. FIG. 2 shows the vehicle drive unit, in which the first through fourth axes A, B, C, D are schematically portrayed whereas FIG. 3 is a cross-section of the vehicle drive unit. 
     On the first axis A, an input shaft  13  is connected, through a flywheel  14  and a damper  12 , to the engine output shaft  2   a . Further, the generator  3 , the brake unit  4  and the planetary gear  6  are disposed along the first axis A. The oil pump  7  is connected to the input shaft  13 . The sun gear S of the planetary gear  6  is connected to a transmission shaft (rotor shaft)  15  transmitting a torque to the generator  3 ; the carrier CR, supporting the pinions P, is connected to the input shaft  13 , the ring gear R is connected to a running rotation shaft  16  structured from a sleeve which is arranged around the input shaft  13 . The generator  3  comprises a rotor  17  fixed to the transmission shaft  15  and a stator  19  fixed to the cover  10 . An excitational generator and the like are usable as the generator  3 , however, a magneto generator, such as a brushless DC motor/generator, in which a permanent magnet is used in the rotor, is preferable. A rotational position sensor  20 , such as a resolver, is disposed on a portion of the transmission shaft  15 , which passes through the rear cover  10   c , and correctly detects a rotational position of the rotor for minutely controlling the rotation. 
     A counter drive gear  21  for engine output is fixed to the running rotation shaft  16 , a large gear  22  and a small gear  23  are integrally fixed on the counter shaft  11 , and the counter drive gear  21  is in mesh with the large gear  22 . The positional relationship of the large gear  22  and the small gear  23  in FIG. 1 is reversed in FIG.  2 . This is for expediency in explanation. 
     The electric motor  5  comprises a rotor  25  integrally fixed to the output shaft  5   a  and a stator  26  fixed to the case  10 . A DC motor, an induction AC motor and the like can be used as the electric motor. However, a brushless DC motor having a permanent magnet in the rotor is preferable. A rotational position sensor  27 , such as a resolver, is disposed on a portion of the output shaft  5   a , which passes through the cover  10  at the opposite side of the motor  5 , and correctly detects a rotational position of the rotor  25  for controlling the motor output. A counter drive gear  29  for motor output is integrally fixed to the motor output shaft  5   a , and the gear  29  is also meshed with the large gear  22  on the counter shaft. 
     The differential unit  9  comprises an input gear  31  fixed to a differential case  30 . The input gear  31  is meshed with the small gear  23  on the counter shaft. A center gear  32 , which is supported by the differential case  30 , is meshed with left and right side gears  33   l ,  33   r , separates and transmits an input torque from the input gear  31  to the left and right side gears  33   l ,  33   r , then, left and right drive wheel shafts connected to left and right front wheels are driven. 
     As shown in FIG. 5, a cylindrical main cover  10   b  is disposed at the center position, a front cover  10   a  is connected to the main cover  10   b  at the right side, in FIG. 5, and a rear cover  10   c  is connected to the main cover  10   b  at the left side of FIG.  5 . Thus, the cover  10  is integrally structured from the main cover  10   b , the front cover  10   a  and the rear cover  10   c . As shown in FIG. 5, the electric motor  5  is disposed in the main cover  10   b.    
     One end of three first lead wires  35  are connected to the stator  26 , including a coil, of the electric motor  5 . The generator  3  is connected to three first lead wires  35  in the same manner (not shown). The first lead wires  35  are routed from a portion of the electric motor  5  close to the counter drive gear  29  and through a peripheral space of the counter drive gear  29 . The portion close to the counter drive gear  29  is a portion which is within the axial, which is left-right direction in FIG. 5, length of the gear unit structured from the counter drive gear  29 , the large gear  22 , the small gear  23  and the input gear  31  of the differential unit  9  and which is at a radial outer side of the output shaft  5   a . Generally, the counter drive gear  29  of the electric motor  5  is structured from a smaller diameter gear than the large gear  22  on the counter shaft  11  which is connected to the differential unit  9 . Therefore, in a portion S, which is adjacent to the periphery of the counter drive gear  29  and to a right side of the electric motor  5  in FIG. 5, a dead space is formed around the counter drive gear  29  by the stator  26  of the electric motor  5  having comparatively large diameter and the counter drive gear  29  having a smaller diameter. Thus, the first lead wires  35  are disposed in the space S, which surrounds the counter drive gear  29  and is dead space. 
     Six penetrating holes  10   f  are formed on the center upper portion of the cover  10 , which correspond to the peripheral space S of the counter drive gear  29 . A terminal  36  is disposed in each of the penetrating holes  10   f . The other ends of the first lead wires  35  from the electric motor  5  are individually connected to three terminals  36  arranged to the left side of FIG. 3, and the other ends of the first lead wires  35  from the generator  3  are connected to the other three terminals  36  arranged to the right side of FIG.  3 . 
     A heat sink  10   d  for cooling is formed in the main cover  10   b , as shown in the upper portion of FIG. 5, adjacent the electric motor  5 . An inverter  37  is disposed on the heat sink  10   d . Second lead wires  39  from the six terminals  36  are connected to terminals  37   a  of the inverter  37 . The cover  40  covers the upper portion of the inverter  37 . To the left side of FIG. 5, a streamlined chamfer portion  10   e  is formed on the upper portion of the rear cover  10   c  corresponding to the electric motor  5 . The streamlined chamfer portion  10   e  is formed extending in the radial direction from the output shaft  5   a  and around an outline of the stator  26 . A space  43  having a cross section of a triangular groove is formed between an inverter case  41 , integrated with the cover  10  and covering the inverter  37 , and a periphery portion  10   g  of the rear cover  10   c.    
     The hybrid drive unit  1  comprises the aforementioned structure, the drive force occurred by the rotation of the electric motor  5  is transmitted through the counter drive gear  29  to the large gear  22  on the counter shaft  11 , and further outputted through the differential unit  9  to the drive wheel shaft D. The output from the engine  2  is transmitted to the input shaft  13 , separated by the planetary gear  6 , disposed on the same axis as the input shaft  13 . Thus, the output from the engine  2  rotationally drives the generator  3  as necessary. Further, the output from the engine  2  is transmitted to the large gear  22  on the counter shaft  11 , and is transmitted through the differential unit  9  to the drive wheel axis D. 
     The first lead wires  35 , connecting the electric motor  5  and the terminals  36  in the cover  10 , and the terminals  36 , connecting the first lead wires  35  through the first lead wires  39  to the inverter  37 , are disposed in the periphery space S of the counter drive gear  29  of the electric motor  5 , that is, in the front dead space of the counter drive gear  29  of the electric motor  5 . Therefore, space for disposing the first lead wires  35  and the terminals  36  is not needed at the rear cover  10   c  side. As a result, the rear cover  10   c  can be formed to conform with the outline of the stator  26  of the electric motor  5 . 
     As with the electric motor  5 , the first lead wires  35  and the terminals  36  for the generator  3  are routed or positioned at the counter drive gear  21  side which is on the right side of the generator  3  in FIG.  2 . 
     Further, the first lead wires  35  are not limited to connecting to the stators  26 ,  29  of the electric motor  5  and the generator  3 , respectively, the first lead wires  35  can be connected to the rotors  25 ,  17  according to the motor structure. 
     Further, the disposition of the first lead wires  35  and the terminals  36  is flexible so long as they are disposed near the counter drive gear  29 , as the output gear, and in the dead space formed by the diameter difference between the output gear and the electric motor. Therefore, an appropriate cable supporting portion, such as grooves, can be formed in the cover  10  for supporting the lead wires. 
     In this embodiment, the invention is described with a vehicle drive unit comprising an electric motor of a hybrid vehicle obtaining a drive force from an electric motor and an internal engine. However, the invention is not limited to a hybrid vehicle, and is applicable to a vehicle drive unit of an electric vehicle obtaining a drive force from only an electric motor. 
     The invention should not be limited to the foregoing embodiments but can be modified in various ways based on its gist, and any such modifications should not be excluded from the scope of the invention.