Patent Abstract:
A rotating electrical machine is provided with: a plurality of bus bars that provide an electrical relay between an external power line, which is positioned on the outside of a housing, and a multiphase coil; an insulation cover that is mounted on the plurality of bus bars with a prescribed gap between each, and covers at least part of the bottom surface of each bus bar; and a coolant supply means that supplies a cooling fluid, which cools a stator, inside the housing. A through-hole, which vertically penetrates a bottom surface, is formed on the bottom surface of the insulation cover.

Full Description:
TECHNICAL FIELD 
     The present invention relates to a rotary electric machine (rotating electrical machine) having an insulating cover which can insulate bus bars and be suitably used for a cooling structure. 
     BACKGROUND ART 
     Japanese Laid-Open Patent Publication No. 2006-340585 (hereinafter referred to as “JP 2006-340585 A”) discloses an electric motor 1 which comprises a terminal 40 electrically connecting coil terminal metal fittings 30a, 30b, 30c with external cables 50a, 50b, 50c, respectively (see FIGS. 1 and 2, and paragraph [0023]). The terminal 40 is an integrated component in which three conductor bars 41a, 41b, 41c each made of a copper plate are molded with a resin part 42 (see paragraph [0023]). Each of the conductor bars 41a, 41b, 41c extends vertically with respect to the electric motor 1 (see FIGS. 1 and 2). 
     SUMMARY OF INVENTION 
     As mentioned above, while each of the conductor bars 41a, 41b, 41c of JP 2006-340585 A is arranged extending vertically with respect to the electric motor 1, another arrangement of the conductor bars 41a, 41b, 41c, other than the arrangement in the vertical direction, is not considered in JP 2006-340585 A. Also, an insulation method or cooling structure for another arrangement in which the conductor bars 41a, 41b, 41c are arranged differently is not mentioned at all. 
     The present invention has been made in view of the aforementioned problems. An object of the present invention is to provide a rotary electric machine that is excellent in insulation and cooling performance. 
     According to the present invention, a rotary electric machine includes a stator with coils in a plurality of phases wound thereon, a housing that houses the stator therein, a plurality of bus bars configured to electrically join the coils in the plurality of phases and external electric power lines to each other, the external electric power lines disposed outside of the housing, an insulating cover attached to the bus bars with gaps between the bus bars and the insulating cover, and configured to cover at least portions of lower surfaces of the bus bars, and a coolant supply unit configured to supply a cooling fluid for cooling the stator to inside of the housing. A through hole is defined in a bottom surface of the insulating cover and extends vertically through the bottom surface. 
     According to the present invention, since the insulating cover covers at least portions of lower surfaces of the bus bars, it is possible to improve the insulation between the bus bars and their surrounding components. 
     Further, since the through hole is formed in the bottom surface of the insulating cover, the cooling fluid can be discharged from the through hole when the cooling liquid enters the insulating cover. Accordingly, the cooling fluid is avoided from remaining in the insulating cover, and a short circuit between the bus bars due to the remaining cooling fluid can be prevented. Also, the insulating cover or the cooling liquid itself can be prevented from being deteriorated due to the remaining cooling fluid. 
     The bus bars may extend from an outer circumferential side of the stator along an axial direction thereof, and the insulating cover may be disposed between an outer circumferential surface of the stator and the bus bars. Accordingly, the bus bars can be connected to the terminals of the external electric power lines at positions shifted from the stator in the axial direction. Therefore, the dimension of the rotary electric machine along the radial directions can be reduced, rather than a case in which the bus bars are connected to the terminals of the external electric power lines at positions radially outward of the outer circumferential surface of the stator. Also, since the insulating cover is disposed between the outer circumferential surface of the stator and the bus bars, it is possible to improve the insulation between the outer circumferential surface of the stator and the bus bars. 
     The through hole may be disposed at a position remote from the outer circumferential surface of the stator in the axial direction. Accordingly, it is possible to prevent degradation of the insulation between the outer circumferential surface of the stator and the bus bars due to the formation of the through hole. 
     The insulating cover may include a partition wall positioned between the bus bars, the bottom surface of the insulating cover may be inclined with respect to a horizontal plane, and the through hole may be positioned at a corner where the partition wall and the bottom surface cross each other. In this structure, since the bottom surface of the insulating cover is inclined with respect to the horizontal plane, it is possible to dispose the insulating cover along the outer circumferential surface of the stator. Therefore, it is possible to prevent the dimension of the rotary electric machine along the radial directions from being increased. Further, since the through hole is positioned at a corner where the bottom surface and the partition wall cross each other, the cooling liquid can be discharged effectively. 
     The bus bars may be formed of plate-like members, and each of the bus bars may include a bent portion, which is made up of a portion of the plate-like member that is bent in a direction along thickness of the plate-like member. Accordingly, when there is a change in temperature, the bent portions are flexed to absorb extensions and contractions of the bus bars. Therefore, stresses caused in the bus bars when the temperature changes are reduced, thereby preventing the bus bars from becoming damaged. 
     One of the bus bars may include a stepped portion, which is formed in a height direction, and the through holes of the insulating cover may be formed on upper and lower sides of the stepped portion. 
     The insulating cover may include a lower cover that covers the lower surfaces of the bus bars, and the insulating cover may be coupled to an upper cover that covers upper surfaces of the bus bars. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a fragmentary cross-sectional view of a vehicle, especially a cooling system thereof, in which there is incorporated a motor that serves as a rotary electric machine according to an embodiment of the present invention; 
         FIG. 2  is an enlarged fragmentary cross-sectional view showing flows of an oil coolant in the motor; 
         FIG. 3  is a fragmentary perspective view, partially cut away, of an electric power system of the vehicle; 
         FIG. 4  is a fragmentary cross-sectional view taken along line IV-IV of  FIG. 3 ; 
         FIG. 5  is a perspective view of a side cover that functions as a portion of the cooling system; 
         FIG. 6  is a plan view, which is illustrated in a simplified form, showing the positions of through holes in a motor rotor; 
         FIG. 7  is a perspective view of a joint between a motor stator and a junction conductor; 
         FIG. 8  is a perspective view showing a positional relationship between the motor stator and the junction conductor; 
         FIG. 9  is a perspective view of a fusing member; 
         FIG. 10  is a front elevational view showing a positional relationship between fusing members and a terminal base; 
         FIG. 11  is a view showing a stator that is illustrated in FIG. 3 of Japanese Laid-Open Patent Publication No. 2009-017667; 
         FIG. 12  is a first perspective view of the terminal base with bus bars assembled thereon; 
         FIG. 13  is a second perspective view of the terminal base with the bus bars assembled thereon; 
         FIG. 14  is a view showing a positional relationship between a motor housing and the terminal base with the bus bars assembled thereon; 
         FIG. 15  is an exploded perspective view of the terminal base and the bus bars; 
         FIG. 16  is a perspective view of a second cover (insulating cover) with the bus bars assembled thereon; 
         FIG. 17  is a perspective view of the insulating cover; 
         FIG. 18  is a cross-sectional view, taken along line XVIII-XVIII of  FIG. 16 , of the insulating cover, at a position where oil discharge ports are not present; and 
         FIG. 19  is a fragmentary cross-sectional view, taken along line XIX-XIX of  FIG. 16 , of the insulating cover, at a position where an oil discharge port is present. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A. Embodiment 
     1. Description of Overall Arrangement 
     [1-1. Overall Arrangement] 
       FIG. 1  is a fragmentary cross-sectional view of a vehicle  10 , especially a cooling system (coolant supply unit) thereof, which incorporates a motor  12  as a rotary electric machine according to an embodiment of the present invention.  FIG. 2  is an enlarged fragmentary cross-sectional view showing flows of an oil coolant  42  in the motor  12 . In  FIG. 2 , the thick arrows represent flows of the oil coolant  42 .  FIG. 3  is a fragmentary perspective view, partially cut away, of an electric power system of the vehicle  10 .  FIG. 4  is a fragmentary cross-sectional view taken along line IV-IV of  FIG. 3 . It should be noted that, for facilitating understanding of the present invention,  FIGS. 1 and 2  are cross-sectional views taken along line I-I of  FIG. 6 , to be described later. Further, a side cover  30  (to be described later) in  FIGS. 1 and 2  is shown in cross section (taken along line I-I of  FIG. 5 ) through all of an inlet hole  32  and first through third outlet holes  36 ,  38 ,  40 , to be described later (see  FIG. 5 ). 
     As shown in  FIG. 1 , the vehicle  10  has a speed reducer  14 , which serves as a gear mechanism, in addition to the motor  12 . A portion of the speed reducer  14  is disposed in the motor  12 . 
     The motor  12  serves as a drive source for generating a drive force F for the vehicle  10 . The motor  12  comprises a three-phase AC brushless motor for generating the drive force F for the vehicle  10  based on electric power supplied from a non-illustrated battery through a non-illustrated inverter. The motor  12  also regenerates electric power (regenerative electric power Preg) [W] in a regenerative mode, and outputs the regenerative electric power Preg to the battery in order to charge the battery. The regenerative electric power Preg may be output to a 12-volt system or a non-illustrated accessory device. 
     As shown in  FIGS. 1 through 4 , the motor  12  has a motor rotor  20  (hereinafter also referred to as a “rotor  20 ”), a motor stator  22  (hereinafter also referred to as a “stator  22 ”), a resolver rotor  24 , a resolver stator  26 , a motor housing  28 , and the side cover  30 . The resolver rotor  24  and the resolver stator  26  jointly make up a resolver  31 . 
     [1-2. Cooling System] 
     (1-2-1. Side Cover  30 ) 
       FIG. 5  is a perspective view of the side cover  30 , which functions as a portion of the cooling system. As shown in  FIGS. 1, 2, and 5 , the side cover  30  has a single inlet hole  32 , a flow passage  34 , a single first outlet hole  36 , a single second outlet hole  38 , and a plurality of third outlet holes  40 . The first through third outlet holes  36 ,  38 ,  40  are supplied with an oil coolant  42  from a non-illustrated pump, which may be an electric pump or a mechanical pump. 
     As shown in  FIGS. 1, 2, and 5 , according to the present embodiment, the oil coolant  42  is ejected or discharged from the side cover  30  toward the rotor  20  and the stator  22 . 
     More specifically, the first outlet hole  36  ejects or discharges the oil coolant  42  primarily toward a rotational shaft  50  of the rotor  20 . The second outlet hole  38  ejects or discharges the oil coolant  42  primarily toward a tubular member  52  of the rotor  20 . The third outlet hole  40  ejects or discharges the oil coolant  42  primarily toward the stator  22 . Each of the outlet holes  36 ,  38 ,  40  is in the form of a nozzle for ejecting or discharging the oil coolant  42 . 
     (1-2-2. Motor Rotor  20 ) 
     (1-2-2-1. Rotational Shaft  50 ) 
     As shown in  FIGS. 1 and 2 , the rotational shaft  50  of the rotor  20  has an axial opening  53  for supplying the oil coolant  42  to the inside of the rotational shaft  50 , a single first axial flow passage  54  that extends along axial directions X1, X2 (see  FIG. 1 ), and a plurality of second axial flow passages  56 , which establish fluid communication along radial directions R1, R2 (see  FIG. 6 ) of the motor  12  between the first axial flow passage  54  and the outside of the rotational shaft  50 . 
     The oil coolant  42 , which is supplied from the first outlet hole  36  of the side cover  30 , is guided through the first axial flow passage  54  into the second axial flow passages  56 , and then is discharged through the second axial flow passages  56  from the rotational shaft  50 . The discharged oil coolant  42  is supplied to the inside of the rotor  20  or to a portion of the speed reducer  14 . 
     (1-2-2-2. Tubular Member  52 ) 
     (1-2-2-2-1. General) 
     As shown in  FIG. 2 , etc., the rotor  20  has, in addition to the rotational shaft  50 , a bottomed tubular member  52 , a rotor core  60 , and a rotor yoke  62 . 
     The tubular member  52  includes a bottom wall  70  fixed to the outer circumferential surface of the rotational shaft  50  near the side cover  30 , and a side wall  72  that extends in the axial direction X2 from the outer edge of the bottom wall  70 . The side wall  72  opens remotely from the bottom wall  70 , i.e., the side wall  72  has an opening  74  remote from the bottom wall  70 . The speed reducer  14  has a planet gear  76  disposed in the tubular member  52 . 
     (1-2-2-2-2. Bottom Wall  70 ) 
     As shown in  FIG. 2 , the bottom wall  70  includes a base  80 , a first protrusive wall  82 , and a second protrusive wall  84 . The base  80  extends along the radial direction R1. The base  80  has a plurality of through holes  86  defined in a portion thereof. The through holes  86  extend along the axial directions X1, x2 through the bottom wall  70  (base  80 ). 
       FIG. 6  is a plan view showing the positions of the through holes  86  in the motor rotor  20 , which is illustrated in a simplified form. As shown in  FIG. 6 , according to the present embodiment, there are four through holes  86 , which are spaced at equal intervals. The oil coolant  42 , which is ejected from the side cover  30  toward the bottom wall  70 , is supplied through the through holes  86  to the inside of the tubular member  52 . 
     The first protrusive wall  82  projects toward the side cover  30  (along the direction X1) from a portion positioned radially outward (along the direction R1) of the through holes  86 . The first protrusive wall  82  has an annular shape. For this reason, if the oil coolant  42 , which is ejected or discharged from the side cover  30  toward the bottom wall  70  during rotation of the rotor  20 , does not enter the through holes  86  directly, then the oil coolant  42  remains in an inner circumferential region of the first protrusive wall  82 , i.e., a region surrounded by the base  80  and the first protrusive wall  82 , under centrifugal forces that act on the oil coolant  42 . Stated otherwise, the base  80  and the first protrusive wall  82  jointly provide a reservoir  88  for the oil coolant. Therefore, even if the oil coolant  42  does not enter the through holes  86  directly, the oil coolant  42  remains in the reservoir  88  and thereafter is supplied through the through holes  86  to the inside of the tubular member  52 . 
     The first protrusive wall  82  has a portion that overlaps with the axial opening  53  of the rotational shaft  50 , as viewed along the radial directions R1, R2 of the rotor  20 . Therefore, the oil coolant  42 , which overflows the first axial flow passage  54  through the axial opening  53 , remains in the inner circumferential region of the first protrusive wall  82  under centrifugal forces or by gravity, and thereafter, the oil coolant  42  is supplied through the through holes  86  to the inside of the tubular member  52 . Consequently, the oil coolant  42 , which flows over the first axial flow passage  54  through the axial opening  53 , can be used to cool the rotor core  60  efficiently. 
     In addition, as shown in  FIG. 2 , the first protrusive wall  82  has a greater-diameter portion  90 , which is progressively greater in diameter in a direction from the side cover  30  toward the base  80  of the bottom wall  70 , i.e., in the direction X2. The greater-diameter portion  90  makes it easy for the reservoir  88  to be formed radially inward of the first protrusive wall  82 , i.e., in the direction R2, thereby minimizing the amount of oil coolant  42  that does not enter into the tubular member  52  after being supplied radially inward of the first protrusive wall  82 , i.e., in the direction R2. In  FIG. 2 , the first protrusive wall  82  is shown as being increased in diameter in both radial inward and radial outward directions. However, even if the first protrusive wall  82  is increased in diameter in the radial inward direction only, the first protrusive wall  82  is capable of operating in the aforementioned manner to offer the advantages described above. 
     The resolver rotor  24 , i.e., the rotor of a rotary sensor, is fixed to a radial outer surface of the first protrusive wall  82 , i.e., a surface thereof that faces in the direction R1. Therefore, the first protrusive wall  82  functions both to provide the reservoir  88  for the oil coolant  42 , and to retain the resolver rotor  24 . Consequently, the motor  12  can be simpler in structure than if a member for retaining the resolver rotor  24  were provided separately from the first protrusive wall  82 . 
     As shown in  FIG. 2 , the second protrusive wall  84  projects toward the opening  74  (along the direction X2 in  FIG. 2 ) from a portion positioned radially outward (along the direction R1) of the through holes  86 . The second protrusive wall  84  has an annular shape. A distal end of the second protrusive wall  84  overlaps with a portion of the planet gear  76 , as viewed along a radial outward direction of the rotor  20  (along the direction R1). Therefore, the oil coolant  42 , which is guided by the second protrusive wall  84 , is supplied to a portion of the planet gear  76  when the oil coolant  42  is discharged under centrifugal forces in a radial outward direction (along the direction R1). 
     (1-2-2-2-3. Side Wall  72 ) 
     As shown in  FIGS. 1 and 2 , the rotor core  60  and the rotor yoke  62  are fixed to a radial outer surface (which faces in the direction R1) of the side wall  72  of the tubular member  52 . As described above, the oil coolant  42  is supplied from the side cover  30  to the inside of the tubular member  52  through the rotational shaft  50  or the bottom wall  70  of the tubular member  52 . Thereafter, as the oil coolant  42  moves along the side wall  72  while the rotor  20  rotates, the oil coolant  42  cools the rotor core  60 . 
     The oil coolant  42 , which has reached the side wall  72 , moves along the side wall  72  into the opening  74  from which the oil coolant  42  is discharged. Thereafter, the oil coolant  42 , which is discharged from the opening  74 , is pooled on the bottom (not shown) of the motor housing  28 , whereupon the oil coolant  42  is ejected or discharged again from the side cover  30  toward the rotor  20  or the stator  22  by the pump. Heat from the oil coolant  42  may undergo heat transfer by a cooler or a warmer, not shown, before the oil coolant  42  is ejected or discharged again. 
     (1-2-3. Motor Stator  22 ) 
     The oil coolant  42 , which is supplied from the third outlet holes  40  of the side cover  30 , passes through the stator  22  while cooling various parts of the stator  22 , and drops onto the bottom of the motor housing  28 . 
     As will be described in detail later, even if the oil coolant  42  enters a second cover  182  (insulating cover) upon moving through the stator  22 , the oil coolant  42  is discharged through oil discharge ports  190  (see  FIGS. 16, 17, and 19 ). 
     As shown in  FIG. 2 , etc., the resolver stator  26  is disposed on the motor stator  22  radially outward of the resolver rotor  24  along the direction R1. The resolver stator  26  produces an output signal depending on the rotational angle of the resolver rotor  24 . Therefore, the resolver  31  is capable of detecting the rotational angle of the motor rotor  20 . 
     [1-3. Electric Power System] 
     (1-3-1. General) 
     As described above,  FIG. 3  is a fragmentary perspective view, partially cut away, of the electric power system of the vehicle  10  in which the motor  12 , which serves as a rotary electric machine according to the present embodiment, is incorporated.  FIG. 4  is a fragmentary cross-sectional view taken along line IV-IV of  FIG. 3 . 
     In addition to the rotor  20  and the stator  22 , the electric power system of the motor  12  according to the present embodiment includes a harness  100  (external electric power lines  102 ) and a junction conductor  104 . 
     (1-3-2. Motor Stator  22 ) 
       FIG. 7  is a perspective view of a joint between the motor stator  22  and the junction conductor  104 .  FIG. 8  is a perspective view showing a positional relationship between the motor stator  22  and the junction conductor  104 . 
     The stator  22  includes coils  112  in a plurality of phases (phase U, phase V, phase W) wound on stator cores  110  with insulating members  111  interposed therebetween. As shown in  FIG. 7 , the coils  112  have respective ends bundled into coil ends  114  in the respective phases. As shown in  FIG. 7 , the coil ends  114  project radially outward (along the direction R1). Reference should also be made to FIG. 7 of Japanese Laid-Open Patent Publication No. 2009-017667 (hereinafter referred to as “JP 2009-017667 A”), which provides a description of the manner in which the ends of the coils  112  are bundled in the respective phases. 
     As shown in  FIGS. 3, 4, 7, and 8 , the stator cores  110  are housed in a stator holder  116  (stator housing), which is disposed on a radial outward side (along the direction R1). 
     (1-3-3. Harness  100  (External Electric Power Lines  102 ) 
     The harness  100  includes external electric power lines  102  in the plural phases (phase U, phase V, phase W). The external electric power lines  102  refer to electric power lines, which connect the motor  12  and the non-illustrated inverter outside of the motor housing  28 . As shown in  FIG. 4 , terminals  120  of the external electric power lines  102  are connected to the junction conductor  104 . According to the present invention, joints (external electric power line joints  122 ) between the terminals  120  and the junction conductor  104  are disposed radially inward (along the direction R2) of the outer circumferential surface of the stator  22  (and the outer circumferential surface of the stator holder  116 ). Therefore, the overall dimension of the motor  12  along the directions R1, R2 is small. The external electric power line joints  122  are positioned closer to the speed reducer  14  than the stator  22  along the axial directions X1, X2. 
     (1-3-4. Junction Conductor  104 ) 
     The junction conductor  104  serves to electrically join (connect) the coils  112  and the external electric power lines  102 . The junction conductor  104  comprises fusing members  130  (coil-side conductors) in the respective phases, bus bars  132   a  through  132   c  (external electric power line-side conductors) in the respective phases, and a terminal base  134 . The fusing members  130  and the bus bars  132   a  through  132   c  jointly make up a junction. 
     (1-3-4-1. Fusing Members  130 ) 
       FIG. 9  is a perspective view of a fusing member  130 .  FIG. 10  is a front elevational view showing a positional relationship between the fusing members  130  and the terminal base  134 . As shown in  FIGS. 7 and 9 , etc., each of the fusing members  130  is in the form of a bent plate. 
     More specifically, the fusing member  130  includes a coil connecting panel  140 , a terminal base connecting panel  142 , and an intermediate panel  144  disposed between the coil connecting panel  140  and the terminal base connecting panel  142 . 
     As shown in  FIG. 9 , the coil connecting panel  140  has an opening  146  defined therein for insertion of the coil ends  114 . After the coil ends  114  have been inserted in the opening  146 , the tip end of the coil connecting panel  140  is biased in the direction indicated by the arrow A1 in  FIG. 9  so as to close the opening  146 , and the coil ends  114  and the coil connecting panel  140  are joined by being crimped with heat (see  FIG. 7 , etc.). The joints between the coil ends  114  and the coil connecting panel  140  will hereinafter be referred to as “coil joints  147 ”. 
     As shown in  FIGS. 3, 7, and 10 , the terminal base connecting panels  142  are fastened to the terminal base  134  by bolts  148  and nuts  150  (see also  FIG. 15 ). 
     As seen from  FIGS. 3, 7, and 10 , the coil connecting panel  140 , the terminal base connecting panel  142 , and the intermediate panel  144  according to the present embodiment lie in directions (the directions R1, R2) perpendicular to the outer circumferential surface of the stator  22  (or the stator holder  116 ). 
     More specifically, the coil connecting panel  140  and the terminal base connecting panel  142  are disposed in circumferential directions (the directions C1, C2 in  FIG. 10 ) and radial directions (the directions R1, R2 in  FIG. 10 ). The thicknesswise directions of the coil connecting panel  140  and the terminal base connecting panel  142  are disposed parallel to the axial directions X1, X2 and are not oriented toward the outer circumferential surface of the stator  22 . The intermediate panel  144  is disposed along axial directions (the directions X1, X2 in  FIG. 4 ) and radial directions (the directions R1, R2 in  FIG. 10 ). The thicknesswise direction of the intermediate panel  144  is located in close proximity to the circumferential directions C1, C2 and is not oriented toward the outer circumferential surface of the stator  22 . The intermediate panel  144  is oriented in this manner for the following reasons. 
     If the intermediate panel  144  were disposed along the circumferential directions C1, C2 and the axial directions X1, X2, for example, or stated otherwise, if the thicknesswise direction of the intermediate panel  144  were to lie parallel to the radial directions R1, R2, then the intermediate panel  144  would be disposed more closely to the outer circumferential surface of the stator  22  by the thickness dimension thereof. In such a case, for insulating the intermediate panel  144  from the outer circumferential surface of the stator  22 , it is necessary for the intermediate panel  144  to be spaced away from the outer circumferential surface of the stator  22 , which results in an increase in the radial dimensions of the motor  12 . 
       FIG. 11  shows a stator (hereinafter referred to as a “stator  200 ”), which is illustrated in FIG. 3 of JP 2009-017667 A. The stator  200  shown in  FIG. 11  has a lead frame  202 , the thicknesswise direction of which faces toward the outer circumferential surface of a stator holder  204 . Therefore, in order to be insulated from each other, the lead frame  202  and the stator holder  204  need to be spaced from each other by a relatively large distance Lc. 
     In contrast thereto, according to the present embodiment, from the standpoint of insulating the intermediate panel  144  and the stator  22  from each other, since the intermediate panel  144  is disposed along the axial directions X1, X2 and the radial directions R1, R2, it is possible to make the distance L1 ( FIG. 10 ) between the intermediate panel  144  and the outer circumferential surface of the stator  22  shorter. The same feature holds true for the coil connecting panel  140  and the terminal base connecting panel  142 . 
     As shown in  FIG. 10 , according to the present embodiment, each of the fusing members  130  includes the coil connecting panel  140  and the terminal base connecting panel  142 , which are staggered along the circumferential directions C1, C2. Therefore, when a worker or a manufacturing apparatus assembles the terminal base connecting panel  142  and thereafter assembles the coil connecting panel  140  in the axial direction X2, assembly of each of the terminal base connecting panel  142  and the coil connecting panel  140  is facilitated, because the respective members do not overlap with each other. 
     Furthermore, inasmuch as the intermediate panel  144  of the fusing member  130  is disposed along the axial directions X1, X2 and the radial directions R1, R2, the intermediate panel  144  is less likely to overlap with the terminal base connecting panel  142 , thereby facilitating assembly of the intermediate panel  144 . Also, the dimensions of the fusing member  130  are prevented from increasing along the circumferential directions C1, C2. 
     (1-3-4-2. Bus Bars  132   a  through  132   c ) 
       FIGS. 12 and 13  are first and second perspective views, respectively, of the terminal base  134  with the bus bars  132   a  through  132   c  assembled thereon.  FIG. 14  is a view showing a positional relationship between the terminal base  134  with the bus bars  132   a  through  132   c  assembled thereon, and the motor housing  28 .  FIG. 15  is an exploded perspective view of the terminal base  134  and the bus bars  132   a  through  132   c .  FIG. 16  is a perspective view of a second cover  182  (insulating cover) with the bus bars  132   a  through  132   c  assembled thereon. As shown in  FIG. 15 , etc., each of the bus bars  132   a  through  132   c  comprises a plate-like member (e.g., a copper plate) that is blanked and bent. 
     As shown in  FIG. 15 , etc., each of the bus bars  132   a  through  132   c  has one end (fusing member connector  160 ) fastened to the terminal base connecting panel  142  of the fusing member  130  by a bolt  148  and a nut  150  on the terminal base  134 . The other end of each of the bus bars  132   a  through  132   c  (external electric power line joints  162 ) is fastened to the terminal  120  of the external electric power line  102  by a bolt  164  ( FIG. 4 ) and a nut  166 . As shown in  FIG. 4 , external electric power line joints  162  of the bus bars  132   a  through  132   c , and external electric power line joints  122  of the terminals  120  of the external electric power lines  102  are positioned radially inward (along the direction R2) of the outer circumferential surface of the motor stator  22  (or the stator holder  116 ). 
     As shown in  FIGS. 15 and 16 , etc., each of the bus bars  132   a  through  132   c  includes a fusing member connector  160 , an external electric power line joint  162 , and an intermediate member  168 , although these respective elements differ in shape from each other. 
     More specifically, the intermediate member  168  of the bus bar  132   a  in the first phase (e.g., the phase U) basically extends parallel to the axial directions X1, X2, and further includes a bent portion  170  disposed between the fusing member connector  160  and the external electric power line joint  162 , and a bent portion  172  disposed between the bent portion  170  and the external electric power line joint  162 . 
     The intermediate member  168  of the bus bar  132   b  in the second phase (e.g., the phase V) basically extends parallel to the axial directions X1, X2, and further includes a bent portion  170  disposed between the fusing member connector  160  and the external electric power line joint  162 , a bent portion  172  disposed between the bent portion  170  and the external electric power line joint  122 , and a stepped portion  174  disposed between the bent portion  172  and the external electric power line joint  122 . 
     The intermediate member  168  of the bus bar  132   c  in the third phase (e.g., the phase W) basically extends parallel to the axial directions X1, X2, and further includes a stepped portion  174  disposed between the fusing member connector  160  and the external electric power line joint  162 , and a bent portion  170  disposed between the stepped portion  174  and the external electric power line joint  122 . 
     Since the respective bus bars  132   a  through  132   c  are shaped in the foregoing manner, it is possible to maintain the external electric power line joints  162  in an array parallel to a horizontal plane H, as shown in  FIG. 14 . As a result, it is easy to connect the bus bars  132   a  through  132   c  and the external electric power lines  102  to each other. 
     The bent portions  170  include bent regions, which are formed by blanking. The bent portions  172  are formed by bending portions of the bus bars  132   a ,  132   b  in the thicknesswise direction thereof. The stepped portions  174  are formed by bending portions of the bus bars  132   b ,  132   c  in the thicknesswise direction thereof. 
     When there is a change in temperature, the bent portions  172  or the stepped portions  174  are flexed to absorb extensions and contractions of the bus bars  132   a  through  132   c . Therefore, stresses caused in the bus bars  132   a  through  132   c  when the temperature changes are reduced, thereby preventing the bus bars  132   a  through  132   c  from becoming damaged. 
     (1-3-4-3. Terminal Base  134 ) 
     The terminal base  134  connects the fusing members  130  and the bus bars  132   a  through  132   c  to each other. As shown in  FIG. 15 , etc., the terminal base  134  has a first cover  180  that covers a radial outer side (facing in the direction R1) of the fusing members  130 , and further includes joints (intermediate joints  178 ) between the fusing members  130  and the bus bars  132   a  through  132   c , a second cover  182  that covers portions of the lower surfaces of the bus bars  132   a  through  132   c , and a third cover  184  that covers portions of the upper surfaces of the bus bars  132   a  through  132   c.    
     As shown in  FIGS. 15 and 16 , etc., the second cover  182  has prongs  186  with teeth  187  thereon. The third cover  184  includes recesses  188  defined at positions that are aligned with the prongs  186 . As shown in  FIG. 13 , etc., the second cover  182  and the third cover  184  are coupled to each other when the prongs  186  engage within the recesses  188 . 
     The first cover  180 , the second cover  182 , and the third cover  184  of the terminal base  134  also function as insulating covers for insulating the bus bars  132   a  through  132   c  from surrounding components (the coils  112  of the stator  22 , etc.). Therefore, the second cover  182  will hereinafter also be referred to as an “insulating cover  182 ”. 
     As shown in  FIG. 10 , etc., the intermediate joints  178  are positioned radially outward (along the direction R1) of the outer circumferential surface of the motor stator  22 . 
     Further, as shown in  FIG. 10 , etc., the coil joints  147  (the joints between the coil ends  114  and the fusing members  130 ) and the intermediate joints  178  (the joints between the fusing members  130  and the bus bars  132   a  through  132   c ) are disposed on circumferential planes, portions of which have the same radius. In addition, the coil joints  147  and the intermediate joints  178  are disposed in positions that are mutually staggered circumferentially as viewed from the axial direction X2. 
     Therefore, when a worker or a manufacturing apparatus assembles the intermediate joints  178 , and thereafter assembles the coil joints  147  in the axial direction X2, it is easy to assemble each of the intermediate joints  178  and the coil joints  147 , because the intermediate joints  178  and the coil joints  147  do not overlap with each other. 
       FIG. 17  is a perspective view of the insulating cover  182  (second cover  182 ).  FIG. 18  is a cross-sectional view, taken along line XVIII-XVIII of  FIG. 16 , of the insulating cover  182 , at a position where oil discharge ports  190  are not present.  FIG. 19  is a fragmentary cross-sectional view, taken along line XIX-XIX of  FIG. 16 , of the insulating cover  182 , at a position where an oil discharge port  190  is present. 
     As shown in  FIG. 4 , etc., the insulating cover  182  is disposed between the outer circumferential surface of the motor stator  22  (or the stator holder  116 ) and the bus bars  132   a  through  132   c  at the coil ends  114  (in the axial direction X1). The insulating cover  182  also extends along the axial direction X2. 
     As shown in  FIG. 18 , etc., the insulating cover  182  has a bottom surface  192 , which is inclined to the horizontal plane H (along the directions X1, X2 and the directions Y1, Y2), for thereby guiding the oil coolant  42  downwardly by gravity. 
     As shown in  FIGS. 17 and 19 , etc., the insulating cover  182  has partition walls  194  for securing the bus bars  132   a  through  132   c  and for insulating the bus bars  132   a  through  132   c  from each other. 
     As shown in  FIGS. 18 and 19 , a predetermined gap exists between the lower surfaces of the bus bars  132   a  through  132   c  and the bottom surface  192  of the insulating cover  182 . Such a gap is created as a result of the bus bars  132   a  through  132   c  being fitted in the insulating cover  182 , rather than being insert-molded. The gap may be created intentionally due to the shapes of the bus bars  132   a  through  132   c , or may be created due to tolerances. If the bus bars  132   a  through  132   c  are insert-molded, then if the bus bars  132   a  through  132   c  were to become deformed due to a change in temperature, a resin that is held in intimate contact with the bus bars  132   a  through  132   c  tends to crack. However, since the gap is present between the bus bars  132   a  through  132   c  and the insulating cover  182 , the bus bars  132   a  through  132   c  are allowed to become deformed, thereby preventing damage to the insulating cover  182  due to a change in temperature. 
     The insulating cover  182  includes the oil discharge ports  190 , which are defined in the bottom surface  192  and extend vertically through the bottom surface  192 . The oil discharge ports  190  are positioned at corners where the bottom surface  192  and the partition walls  194  cross each other, and in particular, the oil discharge ports  190  are disposed at corners that are positioned relatively on the lower side when the insulating cover  182  is installed. The oil discharge ports  190  are disposed on both upper and lower sides of a step that is formed on the insulating cover  182 . 
     Furthermore, as shown in  FIG. 8 , etc., the oil discharge ports  190  are spaced adequately from the stator  22  along the axial direction X2, so that the oil discharge ports  190  do not impair the insulation between the stator  22  and the bus bars  132   a  through  132   c.    
     The oil coolant  42 , which is supplied from the side cover  30  to the motor stator  22 , may potentially pass through the inside of the stator  22  into the terminal base  134 . If the oil discharge ports  190  according to the present embodiment are not defined in the insulating cover  182 , then the oil coolant  42  is likely to be retained on the insulating cover  182 , thereby increasing the likelihood of a short circuit between the bus bars  132   a  through  132   c , and leading to deterioration of the insulating cover  182 . 
     According to the present embodiment, since the insulating cover  182  has the oil discharge ports  190  defined therein, the oil discharge ports  190  are effective to prevent the oil coolant  42  from being retained on the insulating cover  182 . 
     2. Advantages of the Present Embodiment 
     According to the present embodiment, as described above, since the insulating cover  182  covers the portions of the lower surfaces of the bus bars  132   a  through  132   c , it is possible to improve the insulation between the bus bars  132   a  through  132   c  and surrounding components (the coils  112  of the stator  22 , etc.). 
     Further, since the oil discharge ports  190  (through holes) are formed in the bottom surface  192  of the insulating cover  182 , the oil coolant  42  can be discharged from the oil discharge ports  190  when the oil coolant  42  enters the insulating cover  182 . Accordingly, the oil coolant  42  is avoided from remaining in the insulating cover  182 , and a short circuit between the bus bars  132   a  through  132   c  due to the remaining oil coolant  42  can be prevented. Also, the insulating cover  182  or the oil coolant  42  itself can be prevented from being deteriorated due to the remaining oil coolant  42 . 
     In the present embodiment, the bus bars  132   a  through  132   c  extend from the outer circumferential side of the stator  22  along the axial direction X2, and the insulating cover  182  is disposed between the outer circumferential surface of the stator  22  and the bus bars  132   a  through  132   c  (see  FIG. 4 ). Accordingly, the bus bars  132   a  through  132   c  can be connected to the terminals  120  of the external electric power lines  102  at positions shifted from the motor stator  22  in the axial direction X2. Therefore, the dimension of the motor  12  along the radial directions R1, R2 can be reduced, rather than a case in which the bus bars  132   a  through  132   c  are connected to the terminals  120  of the external electric power lines  102  at positions radially outward of the outer circumferential surface of the stator  22 . Also, since the insulating cover  182  is disposed between the outer circumferential surface of the stator  22  and the bus bars  132   a  through  132   c , it is possible to improve the insulation between the outer circumferential surface of the stator  22  and the bus bars  132   a  through  132   c.    
     In the present embodiment, the oil discharge ports  190  are disposed at positions remote from the outer circumferential surface of the stator  22  in the axial direction X2 (see  FIG. 8 , etc.). Accordingly, it is possible to prevent degradation of the insulation between the outer circumferential surface of the stator  22  and the bus bars  132   a  through  132   c  due to the formation of the oil discharge ports  190 . 
     In the present embodiment, the insulating cover  182  includes the partition walls  194 , which are positioned between the bus bars  132   a  through  132   c  in plural phases. Also, the bottom surface  192  of the insulating cover  182  is inclined with respect to the horizontal plane H. Further, the oil discharge ports  190  are positioned at corners where the bottom surface  192  and the partition walls  194  cross each other. In this structure, since the bottom surface  192  of the insulating cover  182  is inclined with respect to the horizontal plane H, it is possible to dispose the insulating cover  182  along the outer circumferential surface of the stator  22 . Therefore, it is possible to prevent the dimension of the motor  12  along the radial directions R1, R2 from being increased. Further, since the oil discharge ports  190  are positioned at corners where the bottom surface  192  and the partition walls  194  cross each other, the oil coolant  42  can be discharged effectively. 
     In the present embodiment, the bus bars  132   a  through  132   c  are formed of plate-like members (see  FIG. 15 , etc.), and the bus bars  132   a  through  132   c  include the bent portions  172 , which are made up of portions of the plate-like members that are bent in the thicknesswise direction (the direction along the thickness of the plate). Accordingly, when there is a change in temperature, the bent portions  172  are flexed to absorb extensions and contractions of the bus bars  132   a  through  132   c . Therefore, stresses caused in the bus bars  132   a  through  132   c  when the temperature changes are reduced, thereby preventing the bus bars  132   a  through  132   c  from becoming damaged. 
     B. Modifications 
     The present invention is not limited to the above embodiment, but various other arrangements may be employed based on the disclosed content of the present description. For example, the present invention can employ the following arrangements. 
     1. Objects to which the Present Invention is Applicable 
     In the above embodiment, the motor  12  is mounted on the vehicle  10 . However, the present invention is applicable to other situations in which the motor  12  may be employed. For example, although the motor  12  is used to propel the vehicle  10  in the above embodiment, the motor  12  may be used in other applications in the vehicle  10  (e.g., an electric power steering system, an air conditioner, an air compressor, etc.). Alternatively, the motor  12  may be used on industrial machines, home electric appliances, etc. 
     2. Motor  12   
     In the above embodiment, the motor  12  is a three-phase AC motor. However, the motor  12  may be another type of AC motor or a DC motor, for example, which is cooled by a cooling fluid, or which is of a reduced size. In the above embodiment, the motor  12  comprises a brushless motor. However, the motor  12  may be a brush motor. In the above embodiment, the motor stator  22  is disposed radially outward (along the direction R1) of the motor rotor  20  (see  FIG. 1 , etc.). However, the motor stator  22  may be disposed radially inward of the motor rotor  20 . 
     3. Resolver  31   
     In the above embodiment, the resolver rotor  24  is mounted on the first protrusive wall  82 . However, the resolver rotor  24  may be fixed to another member other than the first protrusive wall  82 , insofar as the oil coolant  42  is capable of being supplied from the bottom wall  70  of the tubular member  52  to the inside of the tubular member  52 , or in view of the structure of the electric power system. 
     4. Cooling System 
     [4-1. Cooling Fluid] 
     In the above embodiment, the oil coolant  42  is used as a cooling fluid. However, rather than the oil coolant  42 , another cooling fluid (e.g., water or the like) may be used from the standpoint of effecting the cooling function. However, in this case, potentially, the other cooling fluid may not be used as a lubricant for lubricating the gear mechanisms such as the planet gear  76 , etc. 
     [4-2. Tubular Member  52 ] 
     In the above embodiment, the planet gear  76 , which is coupled to the rotational shaft  50 , is disposed in the tubular member  52 . However, a different type of gear mechanism may be disposed in the tubular member  52 . Alternatively, other members may be disposed in the tubular member  52  that are cooled by the cooling medium. For example, a frictional engagement unit (clutch mechanism), which is coupled to the rotational shaft  50 , may be disposed in the tubular member  52 . 
     By disposing a frictional engagement unit in the tubular member  52 , it is possible to reduce the dimension of the motor  12  along the axial directions X1, X2. Further, in addition to cooling the rotor core  60 , it also is possible to cool or lubricate the frictional engagement unit (assuming that the cooling fluid doubles as a lubricating oil). Therefore, as opposed to providing the cooling structure for the rotor core  60  and the cooling structure for the frictional engagement unit separately from each other, the structure can be made simpler. 
     5. Electric Power System 
     [5-1. Junction Conductor  104 ] 
     In the above embodiment, the junction conductor  104  is made up of the fusing members  130  and the bus bars  132   a  through  132   c . However, the junction conductor  104  is not limited to such a structure, insofar as the terminals  120  of the external electric power lines  102  are disposed radially inward (along the direction R2) of the outer circumferential surface of the stator  22 , for example. For example, the coil ends  114  and the external electric power lines  102  may be connected by either the fusing members  130  or the bus bars  132   a  through  132   c.    
     Furthermore, the shapes of the fusing members  130  or the bus bars  132   a  through  132   c  may be changed, insofar as the terminals  120  of the external electric power lines  102  are disposed radially inward (along the direction R2) of the outer circumferential surface of the stator  22 , for example. For example, in the above embodiment (see  FIG. 4 ), although the bus bars  132   a  through  132   c  basically lie parallel to the axial directions X1, X2, the bus bars  132   a  through  132   c  may be inclined to the axial directions X1, X2. For example, the bus bars  132   a  through  132   c  may be inclined from an upper left position toward a lower right position in  FIG. 4 . 
     In the above embodiment, the intermediate joints  178 , which connect the terminal base connecting panels  142  of the fusing members  130  and the fusing member connectors  160  of the bus bars  132   a  through  132   c , are disposed radially outward (along the direction R1) of the outer circumferential surface of the motor stator  22 . However, insofar as the terminals  120  of the external electric power lines  102  are disposed radially inward (along the direction R2) of the outer circumferential surface of the stator  22 , for example, the intermediate joints  178  may also be disposed radially inward (along the direction R2) of the outer circumferential surface of the stator  22 . 
     In the above embodiment, the respective portions of the coil joints  147  and the intermediate joints  178  are staggered mutually on circumferential planes that have the same radius as viewed from the axial direction X2 (see  FIG. 10 , etc.). However, insofar as the terminals  120  of the external electric power lines  102  are disposed radially inward (along the direction R2) of the outer circumferential surface of the stator  22 , for example, the respective portions of the coil joints  147  and the intermediate joints  178  need not necessarily be disposed on circumferential planes having the same radius as viewed from the axial direction X2. 
     In the above embodiment, the coil connecting panels  140  of the fusing members  130  extend along the radial directions R1, R2 and the circumferential directions C1, C2, and the intermediate panels  144  are coupled to the coil connecting panels  140  so as to extend along the axial direction X2 and the radial direction R1 radially outward (along the direction R1) of the outer circumferential surface of the stator  22 . However, insofar as the coil ends  114  and the external electric power lines  102  are connected in such a manner that the terminals  120  of the external electric power lines  102  are disposed radially inward (along the direction R2) of the outer circumferential surface of the stator  22 , for example, the intermediate panels  144  may extend along the axial directions X2 and the circumferential directions C1, C2, or stated otherwise, the intermediate panels  144  may be disposed parallel to the outer circumferential surface of the stator  22 , for example. 
     In the above embodiment, the motor  12  is coupled to the end of the speed reducer  14 , and the external electric power line joint  122  is disposed closer to the speed reducer  14  than the stator  22  along the axial directions X1, X2. However, insofar as the coil ends  114  and the external electric power lines  102  are connected in such a manner that the terminals  120  of the external electric power lines  102  are disposed radially inward (along the direction R2) of the outer circumferential surface of the stator  22 , for example, the external electric power line joint  122  may be disposed opposite to the speed reducer  14  across the stator  22  along the axial directions X1, X2. 
     In the above embodiment, the external electric power line joint  122  is disposed radially inward (along the direction R2) of the outer circumferential surface of the stator  22 . However, insofar as the function of the insulating cover  182  can be fulfilled, the external electric power line joint  122  may be disposed radially outward (along the direction R1) of the outer circumferential surface of the stator  22 . 
     [5-2. Insulating Cover  182 ] 
     In the above embodiment, the insulating cover  182  is provided for the bus bars  132   a  through  132   c . However, insofar as the terminals  120  of the external electric power lines  102  are disposed radially inward (along the direction R2) of the outer circumferential surface of the stator  22 , for example, the insulating cover  182  may be dispensed with. If the insulating cover  182  is dispensed with, then the length of the fusing members  130  along the axial direction X2 preferably is increased in order to provide insulation between the stator  22  and the bus bars  132   a  through  132   c.    
     In the above embodiment, the number and layout of the oil discharge ports  190  are as shown in  FIGS. 16 and 17 . However, insofar as the oil coolant  42  is capable of being discharged through the oil discharge ports  190 , it is sufficient to provide at least one oil discharge port  190 , and the layout of the oil discharge ports  190  can be changed appropriately. 
     In the above embodiment, the bus bars  132   a  through  132   c  extend along the axial direction X2 from the outer circumferential side of the stator  22 . However, the bus bars  132   a  through  132   c  may be positioned in a different location, insofar as insulation can be provided between the stator  22  and the bus bars  132   a  through  132   c  and the oil coolant  42  can be discharged through the oil discharge ports  190 . For example, the bus bars  132   a  through  132   c  may extend radially outward (along the direction R1) from the outer circumferential surface of the stator  22 . Further, the insulating cover  182  may be disposed between the bus bars  132   a  through  132   c  and the outer circumferential surface of the stator  22 . 
     In the above embodiment, the insulating cover  182  includes the partition walls  194 , which are positioned in plural phases between the bus bars  132   a  through  132   c . However, the partition walls  194  may be dispensed with, insofar as sufficient insulation can be provided between the stator  22  and the bus bars  132   a  through  132   c , and the oil coolant  42  can still be discharged through the oil discharge ports  190 . 
     In the above embodiment, the bottom surface  192  of the insulating cover  182  is inclined with respect to the horizontal plane H. However, the bottom surface  192  may lie parallel to the horizontal plane H, insofar as sufficient insulation can be provided between the stator  22  and the bus bars  132   a  through  132   c , and the oil coolant  42  can still be discharged through the oil discharge ports  190 . 
     In the above embodiment, the bus bars  132   a  through  132   c  include the bent portions  172 , which are made up of portions of the plate-like members that are bent in the thicknesswise direction. The number or layout of the bent portions  172  may be changed, or the bent portions  172  may be dispensed with, insofar as sufficient insulation can be provided between the stator  22  and the bus bars  132   a  through  132   c , and the oil coolant  42  can still be discharged through the oil discharge ports  190 .

Technology Classification (CPC): 7