Patent Publication Number: US-2023155453-A1

Title: Electric system

Description:
TECHNICAL FIELD 
     The present invention relates to an electric system of a vehicle driving device. 
     BACKGROUND ART 
     In recent years, use of a motor as a vehicle driving device has been expanded. A motor as a vehicle driving device is driven by an inverter, and drives a vehicle through a gear arranged at an output shaft end of the motor. The gear has a function of reducing a rotational speed of the motor and transmitting motor torque to the axle. In such an electric system, there is demand for using lubricating oil of the gear for coil cooling of the motor to improve cooling capability of a coil, downsizing the motor, and obtaining high torque. 
     As a background art of the present technical field, there is PTL 1 (JP 2012-105457 A). PTL 1 discloses a motor including a rotor configured to be rotatable around a rotation axis, a stator provided around the rotor, a cooling pipe that is arranged in an oil reservoir in which oil is stored and circulates cooling water for cooling the oil in the oil reservoir, and a speed reducer having an external gear that converts a rotation speed of the rotor and stirs the oil in the oil reservoir (see claim  1 ). 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: JP 2012-105457 A 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     In such an electric system, heat generation of a wiring (for example, a bus bar) connecting the motor and an inverter is large, and it is required to cool the bus bar. When lubricating oil is used for cooling the bus bar, temperature of the lubricating oil increases, and thus the lubricating oil needs to be further cooled. On the other hand, installation of an oil cooler generally used for cooling lubricating oil increases cost. 
     For this reason, there is demand for improving cooling capability for the bus bar with a simple system. 
     Solution to Problem 
     A representative example of an invention disclosed in the present application is as described below. That is, the representative example is an electric system including a motor unit including a stator and a rotor, the motor unit being cooled by a refrigerant, an inverter unit that supplies electric power to a winding of the stator, a wiring portion that transmits electric power output from the inverter unit to the motor unit, and a pipe that supplies or discharges a refrigerant to or from the motor unit. The pipe is provided at a position at which the wiring portion can exchange heat with an oily medium cooled by the pipe. 
     Advantageous Effects of Invention 
     According to the present invention, a bus bar can be cooled by lubricating oil of a gear, and cooling capability of the motor can be improved. 
     An object, a configuration, and an advantageous effect other than those described above will be clarified in description of embodiments described below. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a lateral cross-sectional view of an electric system according to a first embodiment of the present invention. 
         FIG.  2    is a cross-sectional perspective view of a motor and an inverter portion according to the first embodiment of the present invention. 
         FIG.  3    is a cross-sectional perspective view of the motor and the inverter portion according to the first embodiment of the present invention. 
         FIG.  4    is a front view of the electric system according to the first embodiment of the present invention as viewed from an axial direction. 
         FIG.  5    is a cross-sectional perspective view of the motor and the inverter portion according to a second embodiment of the present invention. 
         FIG.  6    is a cross-sectional perspective view of the motor and the inverter portion according to a third embodiment of the present invention. 
         FIG.  7    is a cross-sectional perspective view of the motor and the inverter portion according to a fourth embodiment of the present invention. 
         FIG.  8    is a cross-sectional perspective view of a liquid reservoir of the fourth embodiment of the present invention as viewed from below. 
         FIG.  9    is a cross-sectional perspective view of the motor and the inverter portion according to a fifth embodiment of the present invention. 
         FIG.  10    is a cross-sectional perspective view of the motor and the inverter portion according to a sixth embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     &lt;First embodiment&gt;  FIG.  1    is a lateral cross-sectional view of an electric system of a first embodiment.  FIGS.  2  and  3    are cross-sectional perspective views of a motor and an inverter portion of the electric system of the first embodiment, and  FIG.  3    illustrates a state in which a rotor and a gear are removed from  FIG.  2   .  FIG.  4    is a front view of the electric system of the first embodiment as viewed from an axial direction. 
     The electric system of the present embodiment includes a motor  1 , an inverter  2  arranged at a position adjacent to the motor  1 , and a gear assembly  3  arranged in an output direction of the motor  1 . In the motor  1 , a rotor  11  is arranged on the inner peripheral side of a stator  10 , and a winding  12  is wound around a stator core. A type of the motor  1  may be a permanent magnet motor having a permanent magnet, a synchronous motor having a field winding, an induction motor having a squirrel cage conductor, a reluctance motor formed only of a rotor core, or the like, and a component for generating a magnetic field from a rotor and its shape are not limited. The winding  12  is configured by distributed winding or concentrated winding, the winding  12  may be composed of either a corner wire or a round wire, and a winding method and a type of the winding are not limited. In the motor  1 , power (for example, three-phase AC) is supplied to the motor  1  via a terminal of a bus bar  19 . 
     The stator  10  is fixed to the inner peripheral side of a frame  16  by shrink fitting, bolt fastening, or the like. The frame  16  is formed by low-pressure casting, die casting, or the like, and is not limited in shape or size, including a bracket that supports a bearing. A cooling water flow path  16 A is formed in the frame  16 , and the cooling water flow path  16 A is connected to an upper pipe  18 A and a lower pipe  18 B. That is, cooling water flows in from, the upper pipe  18 A, cools the motor  1  while passing through the cooling water flow path  16 A, and is discharged from the lower pipe  18 B. Further, the cooling water flow path  16 A preferably also communicates with a case of the inverter  2  to cool the inverter  2  with cooling water. The inverter  2  may be cooled via the frame  16  of the motor  1 . A refrigerant flowing through the upper pipe  18 A, the cooling water flow path  16 A, and the lower pipe  18 B may be water or another type of liquid such as oil. 
     A switching element of the inverter  2  may be an IGBT, SIC, or the like, and a type and a shape of the inverter  2  are not limited. A motor input terminal drawn from the winding  12  is connected to an inverter output terminal via the bus bar  19 , and when current and voltage are applied from the inverter  2 , current flows through the winding  12  and a rotating magnetic field is generated, and the rotor  11  is rotated to generate torque. The rotor  11  is connected to a gear assembly  3  through a shaft  17 , and a gear output shaft  23  inside the gear assembly  3  is connected to an axle so that a vehicle is driven. As illustrated in  FIG.  2   , the shaft  17  may be a hollow shaft or a solid shaft, and a shape and a dimension of the shaft  17  are not limited. 
     In the gear assembly  3 , a plurality of gears  22 A to  22 D are arranged inside a gear box  21 , and a gear ratio of the gears  22 A to  22 D is configured such that rotation of the motor  1  is decelerated by the gears  22 A to  22 D and output from the gear output shaft  23 . In the example illustrated in  FIG.  1   , a gear is composed of a parallel shaft spur gear, but the gear may be a single planetary gear or a combination of a planetary gear and a spur gear, and a configuration as to whether a parallel shaft or a single shaft is used and a gear ratio are not limited. Further, although not illustrated in the diagram, a differential gear is usually arranged between the gear assembly  3  and an axle. 
     As shown in gray in  FIG.  1   , an oily medium is retained in a lower portion in the gear assembly  3 , the gear  225  is immersed in the oily medium, and a space between the gear  225  and the gear  22 A is lubricated as the gear  22 B rotates. Further, the oily medium is scraped upward with rotation of the gears  22 B and  22 A and is applied to the upper pipe  18 A. The oily medium and cooling water exchange heat in an upper portion of the motor, and the oily medium is cooled by the cooling water in the upper pipe  18 A. 
     Further, as illustrated in  FIGS.  2  to  4   , the bus bar  19  is provided immediately below the upper pipe  18 A, and the oily medium scraped upward by the gears  225  and  22 A drops from the upper pipe  18 A to the bus bar  19  as indicated by a dotted line in  FIGS.  3  and  4   , so that the bus bar  19  is cooled with the oily medium. Furthermore, the lower pipe  18 B is provided immediately below the bus bar  19 , and the oily medium drops from the bus bar  19  to the upper pipe  18 A so that the oily medium is cooled with the cooling water in the lower pipe  18 B. 
     Further, the oily medium may be introduced into the frame  16 , and the lower pipe  18 B may be immersed in the oily medium retained in a lower portion of the frame  16  to cool the cooling water flowing through the lower pipe  18 B. 
     In the present embodiment, the oily medium scraped upward by the gears  22 B and  22 A can be cooled by the cooling water flowing through the upper pipe  18 A, and the bus bar  19  can be cooled by the oily medium that drops from the upper pipe  18 A. For this reason, cooling capability of the motor  1  and the inverter  2  can be improved without addition of a water pipe, and a cooling water pipe for cooling the motor  1  and the inverter  2  can be simplified. 
     &lt;Second embodiment&gt; Next, the electric system according to a second embodiment will be described. The electric system of the second embodiment is provided with a fin  30  protruding from the cooling water pipes  18 A and  18 B. Note that, in the second embodiment, description of a configuration having the same function as that of the above-described embodiment will be omitted, and different configurations will be mainly described. 
       FIG.  5    is a cross-sectional perspective view of the motor and the inverter portion of the electric system of the second embodiment. 
     The fin  30 , which is a protruding portion protruding from an outer surface of the upper pipe  18 A with which an oily medium is in contact, is provided. The protruding portion may be the fin  30  having a plate shape illustrated in the diagram, or may have a pin shape protruding from an outer surface of the upper pipe  18 A. As illustrated by a dotted line, the fin  30  is provided immediately above the bus bar  19  so that the oily medium drops from the fin  30  onto the bus bar  19 . Further, as illustrated in the diagram, the protruding portion may have a fin shape that is flat in an extending direction of the upper pipe  18 A, but may have a spiral shape on an outer surface of the upper pipe  18 A, and may have various shapes. Note that the fin  30  preferably extends at least vertically below the upper pipe  18 A. 
     As illustrated in the diagram, the fin  30  may be provided on both of the upper pipes  18 A and  18 B, or may be provided on either of them. Desirably, the fin  30  is preferably provided on at least the upper pipe  18 A. 
     In the present embodiment, a surface area of the cooling water pipes  18 A and  18 B can be increased, and cooling capability for an oily medium by cooling water can be improved. 
     &lt;Third embodiment&gt; Next, the electric system according to a third embodiment will be described. In the electric system of the third embodiment, the cooling water pipes  18 A and  18 B are bent at positions in contact with an oily medium. Note that, in the third embodiment, description of a configuration having the same function as that of the above-described embodiment will be omitted, and different configurations will be mainly described. 
       FIG.  6    is a cross-sectional perspective view of the motor and the inverter portion of the electric system of the third embodiment. 
     In the third embodiment, the upper pipe  18 A is bent downward at a position in contact with an oily medium to form a U-shape. A lowermost portion of the upper pipe  18 A may be provided immediately above the bus bar  19  so that an oily medium drops onto the bus bar  19  from the upper pipe  18 A. A bent portion of the upper pipe  18 A may extend in a vertical direction or may extend obliquely downward. 
     Further, the lower pipe  18 B is bent upward at a position in contact with an oily medium to form a U-shape. The lower pipe  18 B is preferably provided immediately below the bus bar  19  so that an oily medium that drops from above the bus bar  19  is in contact with a bent portion of the lower pipe  18 B. 
     As illustrated in the diagram, the bent portion may be provided on both of the upper pipes  18 A and  18 B, or may be provided on either of them. Desirably, the fin  30  is preferably provided on at least the upper pipe  18 A. 
     In the present embodiment, an area where an oily medium is in contact with the cooling water pipes  18 A and  18 B is increased, and the cooling capability for an oily medium by cooling water can be improved. 
     &lt;Fourth embodiment&gt; Next, the electric system according to a fourth embodiment will be described. In the electric system of the fourth embodiment, a liquid reservoir  31  is provided below the upper pipe  18 A. Note that, in the fourth embodiment, description of a configuration having the same function as that of the above-described embodiment will be omitted, and different configurations will be mainly described. 
       FIG.  7    is a cross-sectional perspective view of the motor and the inverter portion of the electric system of the fourth embodiment, and  FIG.  8    is a cross-sectional perspective view of the liquid reservoir of the fourth embodiment as viewed from below. 
     In the fourth embodiment, the liquid reservoir  31  is provided below the upper pipe  18 A. The liquid reservoir  31  has, for example, a bottom surface and a side wall having a predetermined height, and stores a predetermined amount of an oily medium scraped upward by the gears  22 B and  22 A until a liquid level of the stored oily medium overflows beyond the height of the side wall. A discharge portion serving as an outlet of an overflowing oily medium is preferably provided immediately above the bus bar  19  so that the oily medium overflowing from the liquid reservoir  31  drops onto the bus bar  19 . In the oily medium stored in the liquid reservoir  31 , at least a part of the upper pipe  18 A is immersed and the oily medium is cooled by cooling water flowing through the upper pipe  18 A. 
     Further, a discharge portion may be provided on the bottom surface of the liquid reservoir  31 . For example, a discharge hole  31 A may be provided immediately above the bus bar  19  on the bottom surface of the liquid reservoir  31  so that an oily medium drops onto the bus bar  19  from the liquid reservoir  31  (indicated by a dotted line in  FIG.  8   ). An inclination may be provided on the inner side of the bottom surface of the liquid reservoir  31  so that a position of the discharge hole  31 A is lowered. 
     In the present embodiment, since an oily medium is cooled by the liquid reservoir  31 , the cooling capability of the oily medium can be improved, and the bus bar  19  can be efficiently cooled. Further, the oily medium can accurately drop on the bus bar  19  by the discharge portion (for example, an outlet of the oily medium and the discharge hole  31 A), and temperature of the bus bar  19  can be lowered. 
     &lt;Fifth embodiment&gt; Next, the electric system according to a fifth embodiment will be described. In the electric system of the fifth embodiment, the liquid reservoir  31  is provided below the upper pipe  18 A. Note that, in the fifth embodiment, description of a configuration having the same function as that of the above-described embodiment will be omitted, and different configurations will be mainly described. 
       FIG.  9    is a cross-sectional perspective view of the motor and the inverter portion of the electric system of the fifth embodiment. 
     In the fifth embodiment, in the upper pipe  18 A, an inlet portion  18 D of cooling water is arranged at a position higher than an outlet portion  18 E in a vertical direction. That is, the upper pipe  18 A has an inclined portion whose height in the vertical direction gradually decreases as a distance from the inlet portion  18 D increases. Then, the upper pipe  18 A is arranged at a position where a bent portion  18 F where the outlet part  185  of the upper pipe  18 A and the inclined portion are connected is immediately above the bus bar  19 . An oily medium in contact with the upper pipe  18 A flows down a lower surface of the inclined portion of the upper pipe  18 A from the inlet portion  18 D and drops onto the bus bar  19  from a position of the bent portion  18 F as illustrated by a dotted line. 
     In the present embodiment, a position where an oily medium accurately drops onto the bus bar  19  is determined by the bent portion  18 F so that cooling efficiency of the bus bar  19  can be improved. 
     &lt;Sixth embodiment&gt; Next, the electric system according to a sixth embodiment will be described. The electric system of the sixth embodiment is provided with axial oil passages  32  and  33  for allowing an oily medium to flow to the non-gear side. Note that, in the sixth embodiment, description of a configuration having the same function as that of the above-described embodiment will be omitted, and different configurations will be mainly described. 
       FIG.  10    is a cross-sectional perspective view of the motor and the inverter portion of the electric system of the sixth embodiment. 
     In the motor  1 , an oily medium flows to a coil end in which the winding  12  protrudes from an end surface of a stator core or the coil end is immersed in the oily medium, so that cooling capability is obtained, and the coil end also exists on the side far from the gear assembly  3 . In the electric system of the present embodiment, by providing the oil passage  32  communicating from the gear assembly  3  to the side far from the gear assembly  3  of the motor  1 , an oily medium scraped upward by the gears  22 A and  22 B in the gear box  21  can flow to the coil end on the side far from the gear assembly  3  of the motor  1 , and the cooling capability of the winding  12  can be improved. Further, the oily medium can also be used for cooling a bearing on the side far from the gear assembly  3 . 
     Furthermore, by providing the oil passage  33  leading from the side far from the gear assembly  3  of the motor  1  to the gear assembly  3 , an oily medium can be returned to the gear assembly  3  from the side far from the gear assembly  3  of the motor  1 , and the oily medium can circulate through the entire electric system. 
     Note that, in  FIG.  10   , the oil passages  32  and  33  are provided between the motor  1  and the inverter  2 . However, the oil passages  32  and  33  may be provided on the top side (upper side) in the vertical direction of the motor  1 , on the side opposite to the inverter  2  of the motor  1 , or the like, and are not limited to the positions illustrated in  FIG.  10   . Note that, although  FIG.  10    illustrates a cross-sectional view of positions of the oil passages  32  and  33  so that the oil passages  32  and  33  can be seen, a pipeline is actually formed. Further, shapes of the oil passages  32  and  33  are not limited to the shapes illustrated in  FIG.  10   , and may be cylindrical or the like as long as a pipeline is formed. 
     Note that the present invention is not limited to the above-described embodiment, and includes various variations and equivalent configurations within the scope of the appended claims. For example, the above embodiments are described in detail for easy understanding of the present invention, and the present invention is not necessarily limited to one that includes all the described configurations. Further, a part of a configuration of one embodiment may be replaced with a configuration of another embodiment. Further, a configuration of a certain embodiment may be added to a configuration of another embodiment. Further, for part of a configuration of each embodiment, another configuration may be added, deleted, or replaced with. 
     REFERENCE SIGNS LIST 
     
         
           1  motor 
           2  inverter 
           3  gear assembly 
           10  stator 
           11  rotor 
           12  winding 
           16  frame 
           16 A cooling water flow path 
           17  shaft 
           18 A upper pipe 
           18 B lower pipe 
           18 D inlet portion 
           18 E outlet portion 
           18 F bent portion 
           19  bus bar 
           21  gear box 
           22 A,  22 B,  22 C,  22 D gear 
           23  gear output shaft 
           30  fin 
           31  liquid reservoir 
           31 A discharge hole 
           32 ,  33  axial oil passage