Patent Publication Number: US-2022224197-A1

Title: Motor, powertrain and electric vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Chinese Patent Application No. 202110350795.9, filed on Mar. 31, 2021, which is hereby incorporated by reference in its entirety. 
     TECHNICAL FIELD 
     This application relates to the field of electric vehicle technologies, and in particular, to a motor, a powertrain, and an electric vehicle. 
     BACKGROUND 
     During operation of a drive motor of an electric vehicle, a shaft voltage is formed on a motor shaft. If the shaft voltage exceeds a breakdown threshold of lubricating grease in a shaft bearing, partial discharge occurs between a rolling element and a rolling path of the shaft bearing, leading to formation of an electric melting pit on the rolling path and occurrence of electric corrosion of the bearing. The electrical erosion of the bearing aggravates a damage to the shaft bearing, leading to specific order noise and high-frequency noise of the shaft bearing, which affects ride comfort of the entire vehicle, and even a failure of the shaft bearing and interruption of power. 
     SUMMARY 
     This application provides a motor, a powertrain, and an electric vehicle, to prevent a bearing from electric corrosion and ensure reliability of the shaft bearing. 
     According to a first aspect, this application provides a motor, including a housing, a shaft bearing, a motor shaft, a first sealing member, a conductive post, a conductive bearing, a second sealing member, and a conductive connecting member. The shaft bearing is fixed to the housing. The motor shaft is rotatably installed on the housing through the shaft bearing. A part of the motor shaft is located inside the housing, and the motor shaft has a cavity. The first sealing member, the conductive bearing, the second sealing member, the conductive post, and the conductive connecting member are all located inside the housing. The first sealing member is located inside the cavity, and an outer circumferential surface of the first sealing member is fixedly connected to a cavity wall of the cavity. At least a part of the conductive post is located inside the cavity, and the conductive post is located on a side of the first sealing member. The second sealing member is located inside the cavity, and the second sealing member is sleeved on an outer circumference surface of the conductive post. An inner side of the second sealing member is in slidable contact with the outer circumferential surface of the conductive post, and an outer circumferential surface of the second sealing member is fixedly connected to the cavity wall of the cavity. The second sealing member, the first sealing member, and the cavity wall of the cavity enclose a sealed space. The conductive bearing is located inside the sealed space, an outer ring of the conductive bearing is fixedly connected to the cavity wall of the cavity, and an inner ring of the conductive bearing is fixedly connected to the outer circumferential surface of the conductive post. The conductive connecting member is connected to one end, facing away from the first sealing member, of the conductive post and is electrically connected to the housing. 
     The motor in this application may be an oil-cooled motor, that is, cooling oil is used for cooling and heat dissipation. The cooling oil can flow in the housing and in the cavity to achieve cooling and heat dissipation. The housing may have an internal space, and the housing may be grounded (for example, earthed). The shaft bearing is configured to implement rotation of the motor shaft relative to the housing. An interference fit may be formed between the outer circumferential surface of the first sealing member and the cavity wall of the cavity, so that the first sealing member rotates with rotation of the motor shaft. An interference fit may be formed between the outer circumferential surface of the second sealing member and the cavity wall of the cavity, so that the second sealing member rotates with rotation of the motor shaft. When the second sealing member rotates, the inner side of the second sealing member is slidable on the outer circumferential surface of the conductive post. The inner and outer rings of the conductive bearing can respectively form interference fits with the outer circumferential surface of the conductive post and the cavity wall of the cavity, and the conductive bearing is used to electrically connect the motor shaft and the conductive post. The conductive post may be stationary relative to the housing. The conductive connecting member is configured to electrically connect the conductive post and the housing. 
     In this way, when a shaft voltage is generated during rotation of the motor shaft, a shaft current can be conducted along the following path: motor shaft-&gt;conductive bearing-&gt;conductive post-&gt;conductive connecting member-&gt;housing-&gt;ground. Therefore, in the solutions of this application, the shaft voltage on the motor shaft can be released to the ground, preventing the shaft bearing from electric corrosion. Furthermore, the conductive bearing can be sealed by using the first sealing member and the second sealing member, to ensure that the conductive bearing operates in an oil-free environment and that the conductive bearing can be conductive reliably. 
     In an implementation, the first sealing member includes a base plate and a rim, the rim surrounds an outer circumference surface of the base plate, and an outer circumferential surface of the rim is fixedly connected to the cavity wall of the cavity. The rim and the base plate enclose an opening, the opening faces the conductive post, and both the base plate and the rim are spaced from the conductive post. Such a first sealing member may be an oil plug, and has a simple structure and high sealing performance. The base plate and the rim are spaced from the conductive post, so that during rotation, the first sealing member does not rub against the conductive post. 
     In an implementation, the second sealing member includes a fitting portion and a sealing lip. The sealing lip is connected to the fitting portion, the fitting portion faces the cavity wall of the cavity, and the sealing lip faces the outer circumferential surface of the conductive post. The fitting portion is annular, and a surface, facing away from the sealing lip, of the fitting portion is the outer circumferential surface of the second sealing member. The sealing lip includes two intersecting surfaces, and a side at which the two surfaces intersect is an inner side of the second sealing member. Such a second sealing member may be a skeleton oil seal, and has a mature structure and high sealing performance, and is easy for mass production. 
     In an implementation, the motor includes a bracket located inside the housing, and the bracket is fixedly connected to the housing. The bracket is connected to one end, facing away from the first sealing member, of the conductive post. The conductive connecting member connects the conductive post and the bracket, to electrically connect to the housing through the bracket. The bracket can be used to suspend and support the conductive post, thereby ensuring that the conductive post can be installed reliably in the cavity. 
     In an implementation, the bracket includes an outer circumferential portion, a connecting portion, and an inner circumferential portion, and the connecting portion connects the outer circumferential portion and the inner circumferential portion. The outer circumferential portion is fixedly connected to the housing. The inner periphery portion has a fitting hole, and one end, facing away from the first sealing member, of the conductive post passes through the fitting hole. In such a structure, the bracket has a reliable structure, can occupy small space, can be used to support another component, and has good reusability. 
     In an implementation, the outer circumferential portion is in an arc-shaped plate shape, at least two connecting portions are provided, and the at least two connecting portions are distributed in a radiative divergence shape. In such a structure, the bracket has a reliable structure, can occupy small space, can be used to support another component, and has good reusability. 
     In an implementation, an outer circumferential surface of one end, facing away from the first sealing member, of the conductive post includes two planes, and the two planes are disposed opposite to each other. The fitting hole is adapted to the outer circumferential surface of the end, facing away from the first sealing member, of the conductive post. In such a structure, the bracket can limit the conductive post, so that the conductive post does not have significant movement in a circumferential direction of the cavity. 
     In an implementation, the conductive connecting member includes a first contact portion, a middle portion, and a second contact portion. The middle portion connects the first contact portion and the second contact portion, the first contact portion is connected to the middle portion in a bent manner, and the middle portion is connected to the second contact portion in a bent manner. The first contact portion is connected to an end part of the end, facing away from the first sealing member, of the conductive post, and the second contact portion is connected to the bracket. Such a conductive connecting member has a reliable structure and reliable conduction, and assembly precision can be easily ensured. 
     In an implementation, the end, facing the first sealing member, of the conductive post is a hollow cylindrical structure. The inner ring of the conductive bearing is in interference fit with the outer circumferential surface of the hollow cylindrical structure. The end of the conductive post is a hollow cylindrical structure, which can reduce structural strength of the end, to achieve easy interference fit between the end and the conductive bearing. 
     In an implementation, the end, facing away from the first sealing member, of the conductive post has a connection hole. The motor includes a connecting member, and the connecting member fits the connection hole and fixes the conductive connecting member to the conductive post. The end of the conductive post has a connection hole, and such a design can easily and reliably achieve assembly of the conductive connecting member and the conductive post. 
     According to a second aspect, this application provides a powertrain, including a motor controller and a motor. The motor controller is electrically connected to the motor to control operation of the motor. Because the shaft bearing can be prevented from electric corrosion, reliability of the shaft bearing is relatively high, and reliability of the entire powertrain is ensured. 
     According to a third aspect, this application provides an electric vehicle, including a vehicle frame and a powertrain, and the powertrain is installed on the vehicle frame. According to the solutions of this application, reliability of the shaft bearing can be ensured, thereby ensuring reliability of the entire vehicle. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       To describe the technical solutions in embodiments of this application or in the background, the following briefly describes the accompanying drawings for describing embodiments of this application or the background. 
         FIG. 1  is a schematic diagram of a structure of an electric vehicle according to an embodiment of this application; 
         FIG. 2  is a schematic block diagram of a structure of a powertrain of an electric vehicle according to an embodiment of this application; 
         FIG. 3  is a schematic diagram of a three-dimensional structure of a motor of a powertrain according to an embodiment of this application; 
         FIG. 4  is a schematic side view of a structure of the motor in  FIG. 3 ; 
         FIG. 5  is a schematic sectional view of a structure of the motor in  FIG. 4 ; 
         FIG. 6  is a schematic diagram of a partially enlarged structure of a position A in  FIG. 5 ; 
         FIG. 7  is a schematic diagram of a three-dimensional assembly structure of a motor shaft and components cooperating with the motor shaft in  FIG. 6 ; 
         FIG. 8  is a schematic diagram of a three-dimensional assembly structure of some components in  FIG. 7 ; 
         FIG. 9  is a schematic exploded view of the assembly structure of  FIG. 8 ; 
         FIG. 10  is a schematic diagram of a three-dimensional structure of a conductive post in  FIG. 9 ; 
         FIG. 11  is a schematic sectional view of a structure of the conductive post in  FIG. 10 ; 
         FIG. 12  is a schematic sectional view showing the assembly structure of  FIG. 8 ; 
         FIG. 13  is a schematic diagram of a partially enlarged structure of a position B in  FIG. 12 ; 
         FIG. 14  is a schematic diagram of a three-dimensional structure of a bracket in  FIG. 9 ; and 
         FIG. 15  is a schematic diagram of a three-dimensional structure of a conductive connecting member in  FIG. 9 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An embodiment of this application provides an electric vehicle, including but not limited to an electric car, an electric bus, an electric motorcycle, and the like. For example,  FIG. 1  shows an electric SUV (Sport Utility Vehicle, sport utility vehicle)  10 . The electric vehicle  10  may include a vehicle frame and a powertrain installed on the vehicle frame. The vehicle frame, serving as a structural framework of the electric vehicle  10 , is configured to support, fix, and connect assemblies, and bear load from the inside of a vehicle system and from an external environment. The powertrain is a system including a series of components and configured to generate power and transmit the power to a road surface. As shown in  FIG. 2 , a powertrain  11  may include a motor controller  12  and a motor  13 . The motor controller  12  is electrically connected to the motor  13  and is configured to control operation of the motor  13 . 
     As shown in  FIG. 3 ,  FIG. 4 , and  FIG. 5  ( FIG. 5  is a schematic sectional view of a structure of the motor  13  shown in  FIG. 4 , with a cross section parallel to the paper surface), the motor  13  of this embodiment may include a housing  131 , a motor shaft  132 , and a shaft bearing  141 . The housing  131  may enclose an accommodating space. Both the motor shaft  132  and the shaft bearing  141  are installed on the housing  131 . A part of the motor shaft  132  may be located inside the accommodation space, and a part of the motor shaft  132  may extend to the outside of the housing  131 . The exposed part of the motor shaft  132  may serve as an output end, and an end opposite to the output end may be referred to as a positioning end. The positioning end may be located inside the receiving space. There may be two shaft bearings  141 , which are installed, for example, on both sides of the housing  131 . The motor shaft  132  rotates with respect to the housing  131  through the shaft bearing  141 . 
     In this embodiment, specific structures of the housing  131 , the motor shaft  132 , and the shaft bearing  141 , and positions of the motor shaft  132  and the shaft bearing  141  on the housing  131  may all be designed according to actual requirements, and are not limited in this embodiment. 
     As shown in  FIG. 5 , the motor shaft  132  has a cavity  132   a , and the cavity  132   a  may extend in an axial direction of the motor shaft  132  and through the motor shaft  132 . A cavity wall of the cavity  132   a  may be, for example, a cylindrical surface. Depending on product requirements, the cavity  132   a  may include segments, each of which may not have a same inner diameter. The motor  13  in this embodiment may be an oil-cooled motor, that is, cooling oil is used for cooling and heat dissipation. The cooling oil may flow in the housing  131  and in the cavity  132   a  to achieve cooling and heat dissipation. 
       FIG. 6  is a schematic diagram of a partially enlarged structure of a position A in  FIG. 5 . With reference to  FIG. 5  and  FIG. 6 , the motor  13  may further include a first sealing member  133 , a conductive post  136 , a conductive bearing  134 , a second sealing member  135 , a bracket  139 , and a conductive connecting member  138  that are installed in the housing  131 . The first sealing member  133 , the conductive bearing  134 , and the second sealing member  135  are located entirely inside the cavity  132   a  of the motor shaft  132 . A part of the conductive post  136  may be located inside the cavity  132   a , and another part may extend to the outside of the cavity  132   a . The bracket  139  is located substantially entirely outside the interior cavity  132   a , and the conductive connecting member  138  may be located entirely outside the interior cavity  132   a . The first sealing member  133 , the conductive post  136 , the conductive bearing  134 , the second sealing member  135 , the bracket  139 , and the conductive connecting member  138  may all be close to the positioning end of the motor shaft  132 . 
       FIG. 7  may show an assembly structure of the motor shaft  132  and components located inside the housing  131 , and components located inside the cavity  132   a  of the motor shaft  132  are not shown. As shown in  FIG. 7 , the bracket  139  may be located at the positioning end of the motor shaft  132 , and the bracket  139  may be connected to the conductive post  136  through a first connecting member  137  (for example, a connecting member such as a screw or a bolt). With reference to  FIG. 7  and  FIG. 6 , the bracket  139  may be further connected to the housing  131  (described below) through a second connecting member  140  (for example, a connecting member such as a screw or a bolt). 
     Installation positions of the first sealing member  133 , the conductive post  136 , the conductive bearing  134 , the second sealing member  135 , the bracket  139 , and the conductive connecting member  138  are briefly described with examples. Installation positions of the components may be adjusted according to product requirements, and are not limited thereto. The following describes the components one by one. 
     As shown in  FIG. 8  and  FIG. 9 , the first sealing member  133  may be approximately in a shape of a cylindrical groove, and may include a base plate  1332  and a rim  1331 . The rim  1331  surrounds an outer circumference surface of the base plate  1332 , that is, the rim  1331  surrounds an outer circumference surface of the base plate  1332 . The rim  1331  may be approximately annular, the rim  1331  has an outer circumferential surface  133   a  (peripheral circumferential surface), and the outer circumferential surface  133   a  may be approximately an annular surface. The rim  1331  and the base plate  1332  enclose an opening  133   b . The first sealing member  133  may be, for example, an oil plug. 
     With reference to  FIG. 9  and  FIG. 6 , the outer circumferential surface  133   a  of the rim  1331  may be fixedly connected to the cavity wall of the cavity  132   a  of the motor shaft  132 . For example, an interference fit may be formed between the outer circumferential surface  133   a  and the cavity wall, so that the outer circumferential surface closely adheres to the cavity wall and connection between them is formed. In this way, the cooling oil in the cavity  132   a  will be blocked by the first sealing member  133 . In addition, when the motor shaft  132  rotates, the first sealing member  133  rotates with rotation of the motor shaft  132 . 
     As shown in  FIG. 10  and  FIG. 11 , the conductive post  136  may be approximately a stepped cylinder as a whole. The conductive post  136  may include a first portion  1361 , a second portion  1362 , and a third portion  1363  that are sequentially connected. Outer diameters of the first portion  1361  and the third portion  1363  may be relatively small, and an outer diameter of the second portion  1362  may be relatively large. The first portion  1361  may have a cavity  136   a , the cavity  136   a  may extend in an axial direction of the first portion  1361 , and the cavity  136   a  may pass through an end part of the first portion  1361 . The cavity  136   a  may be, for example, a round hole. There may be a connection hole  136   b  inside the third portion  1363 , and the connection hole  136   b  may be, for example, a threaded hole. The connection hole  136   b  may pass through an end part of the third portion  1363  and may extend to the second portion  1362 . The connection hole  136   b  and the cavity  136   a  may not be connected, that is, the connection hole  136   b  and the cavity  136   a  may be separated by a material. An outer circumferential surface of the third portion  1363  may include a plane  136   c  and a plane  136   d , which may be disposed opposite to each other, and the plane  136   c  and the plane  136   d  may be substantially parallel. The plane  136   c  and the plane  136   d  may be spaced apart by arcs. The structure of the conductive post  136  described above is merely an example. Actually, the structure of the conductive post  136  may be flexibly designed according to product requirements, and is not limited to the foregoing description. 
     As shown in  FIG. 6 , for example, a large part of the conductive post  136  may be located inside the cavity  132   a  of the motor shaft  132 , and a small part of the conductive post  136  may be exposed to the outside of the cavity  132   a . With reference to  FIG. 6  and  FIG. 11 , for example, all of the first portion  1361  and the second portion  1362  of the conductive post  136  and a large part of the third portion  1363  may be located inside the cavity  132   a , and an end part of the third portion  1363  may be exposed to the outside of the cavity  132   a . Alternatively, the conductive post  136  may be all located inside the cavity  132   a . The conductive post  136  is located on a side, facing away from the output end of the motor shaft  132 , of the first sealing member  133 . For example, from the perspective of  FIG. 6 , the conductive post  136  is located on the right side of the first sealing member  133 . 
       FIG. 12  may show an assembly structure of components in the vicinity of the conductive post  136 .  FIG. 13  is a schematic diagram of a partially enlarged structure of a position B in  FIG. 12 . With reference to  FIG. 11  and  FIG. 12 , the first portion  1361  of the conductive post  136  may face the opening  133   b  of the first sealing member  133 , and the third portion  1363  of the conductive post  136  may face away from the opening  133   b . The first portion  1361  keeps spaced apart from both the rim  1331  and the base plate  1332  of the first sealing member  133 . The conductive post  136  needs to keep stationary in the cavity  132   a  of the motor shaft  132 , and the first portion  1361  keeps spaced apart from both the rim  1331  and the base plate  1332  to facilitate implementation of this design objective. The first portion  1361  fits the conductive bearing  134 , the second portion  1362  fits the second sealing member  135 , and the third portion  1363  fits the bracket  139 , the conductive connecting member  138 , and the first connecting member  137  (which is further described below). 
     As shown in  FIG. 9  and  FIG. 13 , the second sealing member  135  may be approximately annular as a whole. The second sealing member  135  may be, for example, a skeleton oil seal, and may include a fitting portion  1351 , a dust-proof lip  1352 , and a sealing lip  1353 . The dust-proof lip  1352  and the sealing lip  1353  are connected on a side of the fitting portion  1351 . The fitting portion  1351  may serve as an outer ring structure of the second sealing member  135 , and the dust-proof lip  1352  and the sealing lip  1353  may serve as an inner ring structure of the second sealing member  135 . A notch may be formed between the dust-proof lip  1352  and the sealing lip  1353 . The dust-proof lip  1352  is configured to block dust particles, and the sealing lip  1353  is configured to block cooling oil. The sealing lip  1353  includes intersecting surfaces  135   a  and  135   b , an included angle of which may be, for example, an acute angle. The foregoing skeleton oil seal structure is merely an example, and this embodiment is not limited thereto. For example, a skeleton oil seal without a dust-proof lip may alternatively be used. Alternatively, another component having a sealing function may be used according to product requirements, and is not limited to a skeleton oil seal. 
     As shown in  FIG. 13 , the second sealing member  135  may be sleeved on an outer circumferential surface  136   f  of the second portion  1362  of the conductive post  136 . A side at which the surface  135   a  and the surface  135   b  intersect (this side may form a very narrow contact surface) may be in contact with the outer circumferential surface  136   f  of the second portion  1362  at specific pressure. There may be a lubricating fluid between this side and the outer circumferential surface  136   f  of the second portion  1362 . The fitting portion  1351  faces away from the outer circumferential surface  136   f . The dust-proof lip  1352  may face the first sealing member  133 , and the sealing lip  1353  may face away from the first sealing member  133 . 
     With reference to  FIG. 13  and  FIG. 6 , the fitting portion  1351  has an outer circumferential surface  135   c  facing away from the sealing lip  1353 , and the outer circumferential surface  135   c  is fixedly connected to the cavity wall of the cavity  132   a  of the motor shaft  132 , for example, to form an interference fit. In this way, the second sealing member  135  as a whole can rotate with rotation of the motor shaft  132 , and the sealing lip  1353  slides on the outer circumferential surface  136   f  of the second portion  1362 . When the sealing lip  1353  slides on the outer circumferential surface  136   f , the sealing lip  1353  and the outer circumferential surface  136   f  of the second portion  1362  can be sealed under action of the lubricating fluid, so that cooling oil inside the housing  131  is blocked by the second sealing member  135 . Therefore, the second sealing member  135 , the first sealing member  133 , and the cavity wall of the cavity  132   a  may enclose a sealed space, and cooling oil from the side of the second sealing member  135  and the side of the first sealing member  133  cannot enter the sealed space. This sealed space is used for installation of the conductive bearing  134  (described below). 
     As shown in  FIG. 13 , the conductive bearing  134  may include an outer ring  1341 , an inner ring  1342 , and a rolling element  1343 , and the rolling element  1343  is installed between the outer ring  1341  and the inner ring  1342 , to implement relative rotation between the outer ring  1341  and the inner ring  1342 . Conductive grease is further sealed between the outer ring  1341  and the inner ring  1342 , so that the conductive bearing  134  has a conductive property. 
     As shown in  FIG. 13 , the conductive bearing  134  may be located between the first sealing member  133  and the second sealing member  135 . The inner ring  1342  of the conductive bearing  134  may be sleeved on an outer circumferential surface  136   e  of the first portion  1361  of the conductive post  136 , and the inner ring  1342  may be fixedly connected to the outer circumferential surface  136   e , for example, to form an interference fit. A distance between the conductive bearing  134  and the first sealing member  133  may be relatively small, and a distance between the conductive bearing  134  and the second sealing member  135  may be relatively large, which is merely an example. Actually, both the foregoing two distances may be determined according to actual requirements, and this is not limited in this embodiment. 
     With reference to  FIG. 13  and  FIG. 6 , the outer ring  1341  of the conductive bearing  134  is fixedly connected to the cavity wall of the cavity  132   a  of the motor shaft  132 , for example, to form an interference fit, so that the outer ring  1341  can rotate with rotation of the motor shaft  132 . 
     Therefore, the conductive bearing  134  is installed in the sealed space described above. In such a design, the cooling oil from both the side of the first sealing member  133  and the side of the second sealing member  135  is blocked from entering the conductive bearing  134 . This ensures that the conductive bearing  134  operates in an oil-free environment and prevents a failure of the conductive bearing  134  caused by scouring of the conductive bearing  134  by the cooling oil, thereby improving reliability of the conductive bearing  134 . 
     In this embodiment, a shaft voltage on the motor shaft  132  can be transmitted to the housing  131  by using the conductive bearing  134 , which is further described below. 
     As shown in  FIG. 9  and  FIG. 14 , the bracket  139  may include an outer circumferential portion  1391 , a connecting portion  1392 , and an inner circumferential portion  1393 . The connecting portion  1392  connects the outer circumferential portion  1391  and the inner circumferential portion  1393 . The outer circumferential portion  1391  may be approximately an arcuate annular plate structure, and a central angle of the outer circumferential portion  1391  may be, for example, greater than 180 degrees. The connecting portion  1392  may be approximately a bent plate-like structure, and may be formed by bending and connecting several segments (for example, three segments). There may be, for example, at least two (for example, three) connecting portions  1392 , and these connecting portions  1392  may be distributed in a radially divergent form, that is, each connecting portion  1392  may extend in a radial direction of the outer circumferential portion  1391 , and radius positions of different connecting portions  1392  may be different. Included angles of adjacent connecting portions  1392  may be approximately equal or not equal to each other. The inner circumferential portion  1393  may be approximately a flat plate shape, and may be provided with a fitting hole  139   a . A shape of the fitting hole  139   a  may be adapted to a shape of the outer circumferential surface of the third portion  1363  of the conductive post  136 . For example, an inner surface of the fitting hole  139   a  may include two planes and two arcs. The planes are spaced apart by and connected to the arcs. In such a structure, the bracket  139  has a reliable structure, can occupy small space, can be used to support another component, and has good reusability. 
     The structure of the bracket  139  described above is merely an example. Another variant structure may be further provided according to product requirements, and this is not limited in this embodiment. 
     With reference to  FIG. 11 ,  FIG. 12 , and  FIG. 14 , the bracket  139  may fit the third portion  1363  of the conductive post  136 . Specifically, the third portion  1363  may pass through the fitting hole  139   a  in the inner circumferential portion  1393  of the bracket  139 , and the plane  136   c  on the third portion  1363  fits one plane on the inner surface of the fitting hole  139   a . For example, the plane  136   c  may maintain a relatively small specified gap between the plane  136   c  and the plane. The plane  136   d  on the third portion  1363  fits another plane on the inner surface of the fitting hole  139   a . For example, the plane  136   c  may maintain a relatively small specified gap between the plane  136   d  and the another plane. A curved surface on the third portion  1363  fits a curved surface on the inner surface of the fitting hole  139   a , for example, to maintain a relatively small specified gap. In such a fitting design of fitting between the bracket  139  and the third portion  1363  of the conductive post  136 , the bracket  139  can clasp the third portion  1363 , so that the third portion  1363  does not produce significant relative movement in a circumferential direction of the cavity  132   a.    
     With reference to  FIG. 14  and  FIG. 6 , the outer circumferential portion  1391  of the bracket  139  may be fixedly connected to the housing  131 . With reference to  FIG. 9 , the outer circumferential portion  1391  may be fixed to the housing  131 , for example, by using several (for example, three) second connecting members  140 . In this way, the bracket  139  can suspend, support, and limit the conductive post  136 , thereby ensuring reliable positioning of the conductive post  136  in the cavity  132   a  of the motor shaft  132 . In other embodiments, a corresponding structural design may be employed to ensure reliable positioning of the conductive post  136  in the cavity  132   a  of the motor shaft  132 , without using the bracket  139 . 
     As shown in  FIG. 15 , the conductive connecting member  138  may be approximately a bent plate-like (or sheet-like) structure, and may include a first contact portion  1381 , a middle portion  1382 , and a second contact portion  1383 , which may be sequentially connected in a bent manner, and a bend angle may be approximately 90 degrees. The first contact portion  1381  is provided with a through-hole  138   a . Such a conductive connecting member  138  has a reliable structure and reliable conduction, and assembly precision can be easily ensured. The structure of the conductive connecting member  138  described above is merely an example. Another variant may be provided according to product requirements, and this is not limited in this embodiment. For example, the conductive connecting member  138  may also be replaced with a cable (such as a stranded copper wire). 
     With reference to  FIG. 15 ,  FIG. 12 , and  FIG. 11 , the first contact portion  1381  of the conductive connecting member  138  may be in contact with the end part of the third portion  1363  of the conductive post  136 . The through-hole  138   a  in the first contact portion  1381  may be aligned with the connection hole  136   b  in the third portion  1363 . The first connecting member  137  passes through the through-hole  138   a  and is connected to the connection hole  136   b , to fix the first contact portion  1381  to the end part of the third portion  1363 . 
     With reference to  FIG. 15  and  FIG. 8 , the second contact portion  1383  of the conductive connecting member  138  may be fixedly connected to the inner circumferential portion  1393  of the bracket  139 . For example, the second contact portion  1383  and the inner circumferential portion  1393  may be connected through a connecting member such as a rivet or a screw, or through welding, bonding, or the like. 
     The conductive connecting member  138  may be made of a conductive material. The conductive connecting member  138  is capable of electrically connecting the conductive post  136  and the bracket  139 . Because the bracket  139  is connected to the housing  131 , the conductive post  136  and the housing  131  can be electrically connected by the conductive connecting member  138  and the bracket  139 . In other embodiments, when the bracket  139  is not disposed, the conductive connecting member  138  may also be electrically connected to the housing  131 , to electrically connect the conductive post  136  and the housing  131  as well. 
     Refer to  FIG. 5  and  FIG. 6 , when a shaft voltage is generated on the motor shaft  132 , a shaft current may be conducted along the following path: motor shaft  132 -&gt;conductive bearing  134 -&gt;conductive post  136 -&gt;conductive connecting member  138 -&gt;bracket  139 -&gt;housing  131 . The housing  131  is grounded (for example, earthed), so that the shaft current can be transmitted to the ground. Therefore, the shaft voltage on the motor shaft  132  is released to the ground, preventing the shaft bearing  141  from electrical corrosion. 
     According to the solutions of the embodiments, the foregoing shaft current conduction path is designed, to prevent the shaft bearing  141  from bearing electrical erosion, and ensure reliability of the shaft bearing  141 . In addition, the conductive bearing  134  can be sealed by using the first sealing member  133  and the second sealing member  135 , to ensure that the conductive bearing  134  operates in an oil-free environment and that the conductive bearing  134  can be conductive reliably. 
     The foregoing descriptions are merely specific implementations of this application, but are not intended to limit the protection scope of this application. Any variation or replacement readily figured out by a person skilled in the art within the technical scope disclosed in this application shall fall within the protection scope of this application. Therefore, the protection scope of this application shall be subject to the protection scope of the claims.