Abstract:
The present invention relates to a drive device for a vehicle with an electric motor, for which at least a drive motor is utilized as a drive source, and the drive motor and a drive wheel are connected by means of a constant velocity universal joint. The drive device is provided with a drive motor. A drive shaft is connected to the drive motor via an inboard joint. The inboard joint is housed at the inner periphery section of the drive motor. An outer cup, a constituent of the inboard joint, is provided with a guide race on the inner periphery section in order for a roller member to slide. The outer periphery section of the outer cup is rotatably supported by the inner periphery section of the drive motor.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a drive device for use on a vehicle with an electric motor, which includes at least a drive motor as a drive source that is coupled to a drive wheel by constant velocity universal joints. 
       BACKGROUND ART 
       [0002]    Some vehicles such as automobiles or the like include a drive motor as a drive source. Actually, there are known in the art hybrid automobiles having an engine and a drive motor and vehicles with an electric motor, such as electric automobiles (or fuel-cell electric automobiles) having only a drive motor as a drive source. 
         [0003]    Such vehicles with an electric motor are generally propelled when their drive wheels (tires) are rotated under rotational forces that are transmitted from the drive motor through constant velocity universal joints to the drive wheels. 
         [0004]    One known technology of the kind described above is a drive mechanism for electric automobiles as disclosed in Japanese Laid-Open Patent Publication No. 04-325803, for example. As shown in  FIG. 11 , the drive mechanism includes a motor case  1  and a stator  3  with coils  2  wound thereon, the stator  3  being pressure-fitted in the motor case  1 . The motor case  1  houses therein a cup-shaped rotor  4  of an air-core motor which rotates under magnetic forces from permanent magnets  5 . A motor-side constant velocity universal joint  6  is fixed to an inner surface of the bottom of the cup-shaped rotor  4  and coupled to an end of a drive shaft  7  whose other end is connected to a tire  9  through a tire-side constant velocity universal joint  8 . 
         [0005]    The drive shaft  7  has a portion extending into the air core of the cup-shaped rotor  4 . The length of the drive shaft  7  can be made more than twice the length of the drive shaft in conventional drive mechanisms. 
       SUMMARY OF INVENTION 
       [0006]    According to the above drive mechanism, the cup-shaped rotor  4  that is disposed in the motor case  1  makes it possible to provide an air-core motor. However, since the air core is included in the motor, the motor in its entity is considerably large in radial directions. 
         [0007]    It is a general object of the present invention to provide a drive device for a vehicle with an electric motor, which does not need an air core therein. 
         [0008]    A major object of the present invention is to provide a drive device for a vehicle with an electric motor, which is reduced in size and weight. 
         [0009]    Another object of the present invention is to provide a drive device for a vehicle with an electric motor, which can maintain the stroke of a drive shaft. 
         [0010]    Still another object of the present invention is to provide a drive device for a vehicle with an electric motor, which is capable of well increasing an output torque. 
         [0011]    The present invention is concerned with a drive device for use on a vehicle with an electric motor, which includes at least a drive motor as a drive source that is coupled to a drive wheel by an inboard constant velocity universal joint, a drive shaft, and an outboard constant velocity universal joint. 
         [0012]    According to an embodiment of the present invention, the inboard constant velocity universal joint is housed in an inner circumferential region of the drive motor, and includes an outer cup having, on an inner circumferential surface thereof, a sliding surface held in sliding contact with a joint member and having an outer circumferential surface rotatably supported on an inner circumferential surface of the drive motor. 
         [0013]    The outer cup of the inboard constant velocity universal joint is rotatably supported on the inner circumferential surface of the drive motor. Therefore, the rotational force of the drive motor is directly transmitted to the outer cup. Therefore, the drive force is reliably and easily transmitted to the inboard constant velocity universal joint, and the drive device does not need the conventional air core and hence is reduced in size and weight. 
         [0014]    Furthermore, the joint member of the inboard constant velocity universal joint is housed within the inner circumferential region of the drive motor, thus allowing the drive shaft to well maintain a stroke. 
         [0015]    In the drive device, preferably, a speed reducer mechanism is housed in the inner circumferential region of the drive motor, the speed reducer mechanism reducing speed of rotation of the drive motor and transmitting the rotation to the inboard constant velocity universal joint. 
         [0016]    According to another embodiment of the present invention, the inboard constant velocity universal joint includes an outer cup housing a joint member therein, and a shaft projecting axially outwardly from a bottom of the outer cup. The drive device further comprises a speed reducer mechanism coupled to the shaft and housed in an inner circumferential region of the drive motor. 
         [0017]    With the above arrangement, the rotational force of the drive motor is directly transmitted to the outer cup by the speed reducer mechanism. Therefore, the drive force is reliably and easily transmitted to the inboard constant velocity universal joint. 
         [0018]    Therefore, the drive device does not need the conventional air core and hence is reduced in size and weight. It is possible for the drive device to well increase the output torque with a speed reduction ratio set by the speed reducer mechanism. 
         [0019]    In the drive device, the speed reducer mechanism should preferably comprise a sun gear mounted on a rotor of the drive motor, a planet gear supported on a carrier which is fixed to the shaft, an internal gear fixed to a stator of the drive motor. Preferably, the sun gear, the planet gear, and the internal gear are housed in an inner circumferential region of the rotor. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0020]      FIG. 1  is a view of a vehicle incorporating a drive device for a vehicle with an electric motor according to a first embodiment of the present invention; 
           [0021]      FIG. 2  is a schematic cross-sectional view of the drive device; 
           [0022]      FIG. 3  is a schematic cross-sectional view of a drive device for a vehicle with an electric motor according to a first modification of the first embodiment; 
           [0023]      FIG. 4  is a cross-sectional view taken along line IV-IV of  FIG. 3 , showing a speed reducer mechanism of the drive device; 
           [0024]      FIG. 5  is a schematic cross-sectional view of a drive device for a vehicle with an electric motor according to a second modification of the first embodiment; 
           [0025]      FIG. 6  is a cross-sectional view taken along line VI-VI of  FIG. 5 , showing a speed reducer mechanism of the drive device; 
           [0026]      FIG. 7  is a view of a vehicle incorporating a drive device for a vehicle with an electric motor according to a second embodiment of the present invention; 
           [0027]      FIG. 8  is a schematic cross-sectional view of the drive device; 
           [0028]      FIG. 9  is a cross-sectional view taken along line IX-IX of  FIG. 8 , showing a speed reducer mechanism of the drive device; 
           [0029]      FIG. 10  is a view showing the manner in which the speed reducer mechanism operates; and 
           [0030]      FIG. 11  is a view of a drive mechanism disclosed in Japanese Laid-Open Patent Publication No. 04-325803. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0031]    Drive devices for a vehicle with an electric motor according to preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. 
         [0032]    As shown in  FIG. 1 , a drive device  10  for a vehicle with an electric motor according to a first embodiment of the present invention is mounted on a vehicle  11  having a drive wheel DW that is coupled to the drive device  10  through a drive shaft  12 . 
         [0033]    The drive wheel DW is resiliently supported on a vehicle body by a suspension SP. The suspension SP includes a link mechanism L coupling the drive wheel DW to the vehicle body and a shock absorber SA that absorbs vibrations applied to the drive wheel DW. 
         [0034]    An inboard joint (inboard constant velocity universal joint)  16  that is coupled to a drive motor  14  is connected to one end of the drive shaft  12 . The inboard joint  16  comprises a tripod constant velocity universal joint, for example. The other end of the drive shaft  12  is connected to an outboard joint (outboard constant velocity universal joint)  17  that is coupled to the drive wheel DW. 
         [0035]    As shown in  FIG. 2 , the one end of the drive shaft  12  has a splined shaft  18 , and the inboard joint  16  has a joint member, e.g., a spider  20 , fitted over the splined shaft  18 . The spider  20  has a plurality of, e.g., three, trunnions  22  integral with the outer circumferential surface thereof, the trunnions  22  being angularly spaced at predetermined angular intervals (equal angular intervals). 
         [0036]    Ring-shaped rollers  26  are rotatably supported on the outer circumferential surfaces of the respective trunnions  22  by respective rolling members (needles, rollers, or the like)  24 . 
         [0037]    The inboard joint  16  has a bottomed hollow cylindrical outer cup  28  having a shaft  30  integral with one end (bottom end) thereof and an open opposite end. 
         [0038]    The outer cup  28  has an inner circumferential region  32  with a plurality of, e.g., three, guide grooves  34  defined therein in which the rollers  26  are rollingly movable. The guide grooves  34  are angularly spaced at equal angular intervals and extend axially of the outer cup  28 . 
         [0039]    A boot  36  has opposite ends fastened respectively to the tip of the open end of the outer cup  28  and the drive shaft  12  by respective bands  38 . 
         [0040]    The drive motor  14  includes a motor case  40  made up of a first case member  40   a  and a second case member  40   b . The second case member  40   b  houses therein a plurality of coils  44  disposed in an annular pattern, making up a stator  42 . The coils  44  are connected to a drive circuit  46 , and the stator  42  includes a Hall device  48  for detecting a magnetic field. 
         [0041]    The drive motor  14  comprises a brushless motor. The Hall device  48  detects a magnetic field for the drive circuit  46  to determine timings to control and switch between S and N poles. 
         [0042]    A rotor  50  is disposed in the stator  42 . The rotor  50  includes the outer cup  28  and a plurality of permanent magnets  52  directly fixed to the outer circumferential surface of the outer cup  28 . The outer cup  28  is rotatably supported in the first case member  40   a  and the second case member  40   b  by a plurality of angular bearings  54 . The permanent magnets  52  are disposed in an annular pattern on the outer circumferential surface of the outer cup  28 , with their S and N poles alternating with each other. 
         [0043]    Operation of the drive device  10  thus constructed will be described below. 
         [0044]    The drive motor  14 , which comprises a brushless DC motor, has its S and N poles controlled and switched over by the drive circuit  46 . The outer cup  28  is rotated under repulsive and attractive forces generated between the coils  44  and the permanent magnets  52  with the S and N poles alternating with each other on the outer circumferential surface of the outer cup  28 . 
         [0045]    The rotational force is transmitted from the outer cup  28  to the drive shaft  12  through the spider  20  with the rollers  26  held in sliding contact with the inner circumferential region  32  of the outer cup  28 . The rotational force is then transmitted to the drive wheel DW that is coupled to the outboard joint  17  connected to the drive shaft  12  (see  FIG. 1 ), thereby propelling the vehicle. 
         [0046]    According to the first embodiment, the outer cup  28  of the inboard joint  16  is rotatably supported in an inner circumferential region of the motor case  40  of the drive motor  14  by the angular bearings  54 . 
         [0047]    The outer cup  28  with the permanent magnets  52  disposed on the outer circumferential surface thereof serves as the rotor  50 . The rotational force of the drive motor  14  is directly transmitted to the outer cup  28 . Therefore, the drive force (rotational force) is reliably and easily transmitted to the inboard joint  16 , and the drive device  10  does not need the conventional air core and hence is reduced in size and weight. 
         [0048]    The spider  20  as the joint member of the inboard joint  16  is housed within an inner circumferential region of the drive motor  14 , thus allowing the drive shaft  12  to well maintain a stroke. 
         [0049]      FIG. 3  is a schematic cross-sectional view of a drive device  60  for a vehicle with an electric motor according to a first modification of the first embodiment. 
         [0050]    Those parts of the drive device  60  which are identical to those of the drive device  10  according to the first embodiment are denoted by identical reference characters, and will not be described in detail below. Similarly, those parts of a second modification of the first embodiment, to be described later, which are identical to those of the drive device  10  according to the first embodiment, will not be described in detail below. 
         [0051]    The drive device  60  includes a drive motor  62  having a stator  42  and a rotor  64 . The rotor  64  has a shaft  66  rotatably supported centrally in a motor case  40  by angular bearings  54 , and a ring  68  of a relatively large diameter is integrally joined to an inner end of the shaft  66 . A plurality of permanent magnets  52  are disposed in an annular pattern on the outer circumferential surface of the ring  68 , with their S and N poles alternating with each other. 
         [0052]    A speed reducer mechanism  72  is disposed between an outer cup  70  of an inboard joint  16  and the rotor  64 . As shown in  FIGS. 3 and 4 , the speed reducer mechanism  72  has a sun gear  74  fixed to the rotational central axis of the rotor  64 , a plurality of, e.g., three, planet gears  76  rotatably supported on an end face  70   a  of the outer cup  70 , and an internal gear  78  having teeth on its inner circumferential region and extending in a direction perpendicular to the end face  70   a  of the outer cup  70 . The planet gears  76  are held in mesh with the sun gear  74  and the internal gear  78 . 
         [0053]    According to the first modification, the rotor  64  rotates under a switching action of the drive circuit  46 . The sun gear  74  fixed coaxially to the rotor  64  rotates in the direction indicated by the arrow a 1  in  FIG. 4 , for example. 
         [0054]    The planet gears  76  are held in mesh with the sun gear  74 . When the sun gear  74  rotates in the direction indicated by the arrow a 1 , a rotational force in the direction indicated by the arrow b 1  is applied to each of the planet gears  76 . The planet gears  76  are also held in mesh with the internal gear  78 . 
         [0055]    The planet gears  76  are rotatably supported on the end face  70   a  of the outer cup  70 , and the internal gear  78  is directly disposed in the outer cup  70 . Therefore, the outer cup  70  rotates in the direction indicated by the arrow c in  FIG. 4 . The speed reducer mechanism  72  reduces the speed based on the gear ratios between the sun gear  74 , the planet gears  76 , and the internal gear  78 . 
         [0056]    According to the first modification, as described above, the speed reducer mechanism  72  is effectively to increase the ability to transmit the rotational force from the drive motor  62  to the inboard joint  16  and also to be able to set a torque and a rotational speed to desired levels. 
         [0057]      FIG. 5  is a cross-sectional view of a drive device  90  for a vehicle with an electric motor according to a second modification of the first embodiment. 
         [0058]    The drive device  90  includes a drive motor  92  having a stator  42  and a rotor  94 . The rotor  94  has a shaft  96  rotatably supported axially centrally in a motor case  40 . A ring  68  and an enlarged boss  98  are integrally joined to an inner end of the shaft  96 . 
         [0059]    The drive device  90  includes a speed reducer mechanism  100 . As shown in  FIGS. 5 and 6 , the speed reducer mechanism  100  has a sun gear  102  on an outer circumferential surface of the enlarged boss  98  of the rotor  94 , a plurality of, e.g., three, planet gears  106  supported on an outer cup  104  of the inboard joint  16 , and an internal gear  108  disposed on the motor case  40 . 
         [0060]    The planet gears  106  are rotatably mounted on a carrier  110  fixed to the tip end of the outer cup  104 , and are angularly spaced at equal angular intervals. The internal gear  108  is disposed on the tip end of an inner circumferential of a hollow cylindrical member  112  that extends from an inner circumferential end of a second case member  40   b  into a first case member  40   a.    
         [0061]    According to the second modification, for example, the rotor  94  rotates in the direction indicated by the arrow a 2  in  FIG. 6  under a switching action of the drive circuit  46 . The sun gear  102  on the enlarged boss  98  of the rotor  94  now rotates in the direction indicated by the arrow a 2 , and the planet gears  106  that are held in mesh with the sun gear  102  rotate in the direction indicated by the arrow b 2 . 
         [0062]    The planet gears  106  are held in mesh with the internal gear  108  on the hollow cylindrical member  112  of the motor case  40 . Therefore, when the planet gears  106  rotate in the direction indicated by the arrow b 2 , the outer cup  104  is caused by the carrier  110  to rotate in the direction indicated by the arrow d, which is opposite to the direction indicated by the arrow c. 
         [0063]    According to the second embodiment, therefore, the rotation of the drive motor  92  is reduced in speed and reliably transmitted to the inboard joint  16 , thereby offering the same advantages as those of the first embodiment 
         [0064]    A second embodiment of the present invention will be described below. Those parts of the second embodiment which are identical to those of the drive device shown in  FIGS. 1 through 6  are denoted by identical reference characters, and will not be described in detail below. 
         [0065]    As shown in  FIG. 7 , a drive device  210  for a vehicle with an electric motor according to the second embodiment is mounted on a vehicle  11  having a drive wheel DW that is coupled to the drive device  210  through a drive shaft  12 . 
         [0066]    The drive wheel DW is resiliently supported on a vehicle body by a suspension SP. The suspension SP includes a link mechanism L coupling the drive wheel DW to the vehicle body and a shock absorber SA that absorbs vibrations applied to the drive wheel DW. 
         [0067]    An inboard joint (inboard constant velocity universal joint)  216  that is coupled to a drive motor  214  is connected to one end of the drive shaft  12 . The inboard joint  216  comprises a tripod constant velocity universal joint, for example. The other end of the drive shaft  12  is connected to an outboard joint (outboard constant velocity universal joint)  17  that is coupled to the drive wheel DW. 
         [0068]    As shown in  FIG. 8 , the one end of the drive shaft  12  has a splined shaft  18 , and the inboard joint  216  has a joint member, e.g., a spider  20 , fitted over the splined shaft  18 . The spider  20  has a plurality of, e.g., three, trunnions  22  integral with the outer circumferential surface thereof, the trunnions  22  being angularly spaced at predetermined angular intervals (equal angular intervals). The inboard joint  216  may comprise any of various conventional constant velocity universal joints. 
         [0069]    Ring-shaped rollers  26  are rotatably supported on the outer circumferential surfaces of the respective trunnions  22  by respective rolling members (needles, rollers, or the like)  24 . 
         [0070]    The inboard joint  216  has a bottomed hollow cylindrical outer cup  228  having a shaft  230  integrally projecting axially outwardly from a bottom (one end) thereof and an open opposite end. 
         [0071]    The outer cup  228  has an inner circumferential region  232  with a plurality of, e.g., three, guide grooves  34  defined therein in which the rollers  26  are rollingly movable. The guide grooves  34  are angularly spaced at equal angular intervals and extend axially of the outer cup  228 . 
         [0072]    A boot  36  has opposite ends fastened respectively to the tip of the open end of the outer cup  228  and the drive shaft  12  by respective bands  38 . 
         [0073]    The drive device  210  includes a speed reducer mechanism  240  coupled to the shaft  230  of the outer cup  228  and housed in an inner circumferential region of the drive motor  214 . The drive motor  214  has a motor case  242  having a bottomed hollow cylindrical shape. The motor case  242  includes a disk-shaped bottom  242   a  on one end thereof. 
         [0074]    As shown in  FIGS. 8 and 9 , the motor case  242  houses therein a plurality of coils  246  disposed in an annular pattern, making up a stator  244 . The coils  246  are connected to a drive circuit, not shown. The drive motor  214  comprises a brushless DC motor, for example. 
         [0075]    A rotor  248  is disposed in an inner circumferential region of the stator  244 . As shown in  FIG. 8 , the rotor  248  has a shaft  252  rotatably supported centrally in the bottom  242   a  of the motor case  242  by a bearing  250 . The shaft  252  has an integral ring  256  of a relatively large diameter joined thereto through a disk  254 . An enlarged boss  258  is disposed inwardly of the shaft  252  and integrally coupled coaxially therewith. 
         [0076]    The ring  256  accommodates therein a plurality of permanent magnets  260  disposed in an annular pattern with their S and N poles alternating with each other. The rotor  248  may comprise a laminated assembly of magnetic steel sheets, rather than the permanent magnets  260 . 
         [0077]    The speed reducer mechanism  240  has a sun gear  262  on an outer circumferential surface of the enlarged boss  258  of the rotor  248 , a plurality of, e.g., three, planet gears  264  supported on the outer cup  228  of the inboard joint  216 , and an internal gear  266  disposed on the motor case  242 . In the speed reducer mechanism  240 , the sun gear  262 , the planet gears  264 , and the internal gear  266  are housed in an inner circumferential region of the rotor  248 . 
         [0078]    The planet gears  264  are rotatably mounted on a carrier  268  fixed to the tip end of the shaft  230  of the outer cup  228 , and are angularly spaced at equal angular intervals (see  FIGS. 8 and 9 ). As shown in  FIG. 8 , a disk  270  has a radially outer end integrally or separately joined to an open end of the motor case  242  and a radially inner end that is integrally joined to a tubular member  272 . The internal gear  266  is disposed on an inner circumferential surface of the tubular member  272 . 
         [0079]    The shaft  230  of the outer cup  228  is rotatably supported in the motor case  242  by bearings  274  disposed between the shaft  230  and the tubular member  272 . The enlarged boss  258  of the rotor  248  is relatively rotatably held in engagement with the tip end of the shaft  230 . 
         [0080]    Operation of the drive device  210  thus constructed will be described below. 
         [0081]    When an electric current flows through the coils  246  of the stator  244 , they generate electromagnetic forces in the drive motor  214 . The rotor  248  including the ring  256  is rotated under repulsive and attractive forces generated between the coils  246  and the permanent magnets  260  with the S and N poles alternating with each other on the ring  256 . 
         [0082]    As shown in  FIG. 10 , when the rotor  248  rotates in the direction indicated by the arrow a 3 , for example, the sun gear  262  on the enlarged boss  258  of the rotor  248  rotates in unison with the rotor  248  in the direction indicated by the arrow a 3 . 
         [0083]    The planet gears  264  are held in mesh with the sun gear  262 . When the sun gear  262  rotates in the direction indicated by the arrow a 3 , a rotational force in the direction indicated by the arrow b 3  is applied to each of the planet gears  264 . The planet gears  264  are also held in mesh with the internal gear  266 . The internal gear  266  is disposed on the inner circumferential surface of the tubular member  272  fixed to or integral with the motor case  242 . 
         [0084]    When the planet gears  264  rotate in the direction indicated by the arrow b 3 , therefore, the outer cup  228  is caused by the carrier  268  to rotate in the direction indicated by the arrow a 3 . The speed reducer mechanism  240  reduces the speed based on the gear ratios between the sun gear  262 , the planet gears  264 , and the internal gear  266 . 
         [0085]    The rotational force is transmitted from the outer cup  228  to the drive shaft  12  through the spider  20  with the rollers  26  held in sliding contact with the inner circumferential region  232  of the outer cup  228 . The rotational force is then transmitted to the drive wheel DW that is coupled to the outboard joint  17  connected to the drive shaft  12  (see  FIG. 7 ), thereby propelling the vehicle. 
         [0086]    According to the second embodiment, as shown in  FIG. 8 , the speed reducer mechanism  240  is coupled to the shaft  230  that projects axially outwardly from the bottom of the outer cup  228  of the inboard joint  216 , and housed in an inner circumferential region of the drive motor  214 . Consequently, the rotational force from the drive motor  214  is directly transmitted through the speed reducer mechanism  240  to the outer cup  228 , so that the drive force can reliably and easily be transmitted to the inboard joint  216 . 
         [0087]    Therefore, the drive device  210  does not need the conventional air core and hence is reduced in size and weight. It is possible for the drive device  210  to well increase the output torque with a speed reduction ratio set by the speed reducer mechanism  240 .