Powertrain and powertrain assembly method

Abstract

The application provides a power assembly and a power assembly assembling method. The power assembly comprises a main shell provided with a first mounting hole; a rear cover provided with a second mounting hole and an assembling hole, the assembling hole is used for cooperating with an assembling tool to mount the rear cover on one side of the main shell, and the rear cover and the main shell form an accommodating cavity; and a motor shaft installed in the accommodating cavity, two ends of the motor shaft in the length direction are movably inserted into the first mounting hole and the second mounting hole respectively. Through the arrangement, the motor shaft can be quickly assembled between the main shell and the rear cover by cooperating the assembling hole with the assembling tool, the step of cooperating the assembling tool with the cover plate is omitted, the assembling process is reduced, the assembling efficiency of the power assembly is improved, meanwhile, the number of parts of the power assembly is reduced by omitting the cover plate, the axial length size and the weight of the power assembly are effectively reduced, and the structure of the power assembly is more compact.

Description

Technical Field

[0001] This application relates to the field of powertrain technology, and in particular to a powertrain and a powertrain assembly method. Background Technology

[0002] The hybrid transmission is an important powertrain component in hybrid electric vehicles. It can couple the power of the engine and the drive motor in a certain way to achieve the purpose of changing speed and torque, and to regulate and transmit the power output of the engine.

[0003] A common hybrid transmission structure includes: a main housing, a motor shaft, a motor housing rear cover, and a cover plate. The motor shaft is assembled between the main housing and the motor housing rear cover. The cover plate is located on the side of the motor housing rear cover away from the main housing. The cover plate is equipped with oil passages and sealing structures, which can simplify the structure of the motor housing rear cover.

[0004] However, this structure increases the axial dimension and weight of the hybrid transmission, increasing the space occupied by the hybrid transmission in the vehicle, which is not conducive to reducing the size and weight of the vehicle. Furthermore, the assembly tooling needs to cooperate with the cover plate to press the motor shaft into the main housing, which increases the assembly steps and affects the assembly efficiency of the hybrid transmission. Summary of the Invention

[0005] In view of this, this application provides a powertrain and a powertrain assembly method to improve the assembly efficiency of the powertrain.

[0006] Specifically, the following technical solutions are included: In a first aspect, embodiments of this application provide a powertrain, including: The main housing has a first mounting hole; The rear cover is provided with a second mounting hole and an assembly hole. The assembly hole is used to cooperate with an assembly tool to install the rear cover on one side of the main housing. The rear cover and the main housing together form a receiving cavity. The motor shaft is installed in the receiving cavity, and the two ends of the motor shaft along its length are respectively movably inserted into the first mounting hole and the second mounting hole.

[0007] In one optional embodiment, the powertrain further includes a first bearing and a second bearing, the first bearing and the second bearing being respectively sleeved at both ends of the motor shaft along its length, the first bearing being installed in the first mounting hole and the second bearing being installed in the second mounting hole.

[0008] In one optional embodiment, the powertrain further includes a bearing retainer ring, the main housing has a retainer ring groove communicating with the first mounting hole, the bearing retainer ring is installed in the retainer ring groove and sleeved on one end of the motor shaft, and the bearing retainer ring is adjacent to the first bearing.

[0009] In one optional embodiment, there are multiple mounting holes, which are spaced apart on the rear cover.

[0010] In one optional embodiment, the assembly hole communicates with the second mounting hole, so that the assembly fixture passes through the assembly hole and abuts against the end face of the motor shaft.

[0011] In one alternative embodiment, the powertrain further includes a plug for sealing the mounting hole.

[0012] In one alternative embodiment, the sealing element is threadedly connected to the mounting hole.

[0013] In one optional embodiment, the motor shaft includes a sidewall and an inner cavity formed by the sidewall. A branch oil passage is provided on the sidewall, and the extending direction of the branch oil passage is set at an angle to the axial direction of the motor shaft. The branch oil passage passes through the sidewall and communicates with the inner cavity. The rear cover is provided with an oil passage, which is connected to the inner cavity.

[0014] Secondly, embodiments of this application provide a powertrain assembly method, applied to the powertrain described in any embodiment of the first aspect, the powertrain assembly method comprising: The first end of the motor shaft is fitted into the second mounting hole of the rear cover; The assembly tool is inserted into the assembly hole, and the second end of the motor shaft is installed into the first mounting hole of the main housing through the assembly tool. Separate the assembly fixture from the rear cover; Connect the main housing to the rear cover.

[0015] In one optional embodiment, the powertrain further includes a first bearing and a second bearing; Before assembling the first end of the motor shaft into the second mounting hole of the rear cover, the powertrain assembly method further includes: Install the first bearing into the first mounting hole; The second bearing is installed in the second mounting hole.

[0016] In one optional embodiment, the powertrain further includes a bearing retaining ring, and the main housing has a retaining ring groove communicating with the first mounting hole; After installing the first bearing into the first mounting hole, the powertrain assembly method further includes: The bearing retainer is installed in the retainer groove so that the bearing retainer is adjacent to the first bearing.

[0017] In one optional embodiment, the assembly hole communicates with the second mounting hole, and the powertrain further includes a sealing element; After separating the assembly fixture from the rear cover, the powertrain assembly method further includes: The sealing element is inserted into the assembly hole.

[0018] The beneficial effects of the technical solution provided in this application include at least the following: by providing assembly holes on the rear cover, the motor shaft can be quickly assembled between the main housing and the rear cover by using the assembly holes and assembly tooling, eliminating the step of assembling the assembly tooling with the cover plate, reducing assembly processes, and improving the assembly efficiency of the powertrain; at the same time, by eliminating the cover plate, the number of powertrain parts is reduced, effectively reducing the axial length and weight of the powertrain, making the structure of the powertrain more compact. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 An assembly diagram of the powertrain provided in an embodiment of this application; Figure 2 One of the cross-sectional views of the powertrain provided in the embodiments of this application; Figure 3 A second cross-sectional view of the powertrain provided in an embodiment of this application; Figure 4 A schematic flowchart of a powertrain assembly method provided in one embodiment of this application; Figure 5 This is a schematic flowchart of the powertrain assembly method provided in Embodiment 2 of this application; Figure 6 This is a schematic flowchart of the powertrain assembly method provided in Embodiment 3 of this application.

[0021] The reference numerals in the figure are respectively: 1-Main housing; 11-Receiving cavity; 12-First mounting hole; 2-Rear cover; 21-Oil passage; 22-Oil inlet; 3-Motor shaft; 31-Inner cavity; 41-First bearing; 42-Second bearing; 5-Bearing retainer; 6-Stator; 7-Rotor; 8-Sealing component; 100 - Assembly tooling; 101 - Top pin.

[0022] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] In the embodiments of this application, directional terms such as "upper," "lower," and "side" are generally used in the following ways: Figure 1 The relative positions shown are based on the given information, and these directional terms are used only to more clearly describe the relationships between structures, not to describe absolute positions. Positions may change when the product is placed in different orientations; for example, "up" and "down" may be interchanged.

[0025] Unless otherwise defined, all technical terms used in the embodiments of this application have the same meaning as commonly understood by those skilled in the art. Some technical terms appearing in the embodiments of this application are described below.

[0026] To make the technical solutions and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0027] like Figures 1 to 3 As shown in the figure, this application provides a powertrain including a main housing 1, a rear cover 2, and a motor shaft 3.

[0028] The main housing 1 is provided with a first mounting hole 12. The rear cover 2 is provided with a second mounting hole and an assembly hole. The assembly hole is used to cooperate with the assembly tool 100, so as to install the rear cover 2 on one side of the main housing 1. The rear cover 2 and the main housing 1 form a receiving cavity 11.

[0029] The motor shaft 3 is installed in the receiving cavity 11, and its two ends along the length direction are respectively movably inserted into the first mounting hole 12 and the second mounting hole. The rear cover 2 and the main housing 1 are joined together along the length direction of the motor shaft 3 to form the receiving cavity 11, thus confining the motor shaft 3 within the receiving cavity 11.

[0030] For example, the powertrain is a hybrid transmission, and when the powertrain is assembled, the first mounting hole 12 and the second mounting hole are coaxially spaced along the length direction of the motor shaft 3. The shapes of the first mounting hole 12 and the second mounting hole can be circular, rectangular, or other polygonal shapes.

[0031] The powertrain also includes a stator 6 and a rotor 7 installed in the housing 11. The rotor 7 is sleeved on the outside of the motor shaft 3, and the stator 6 is encircled on the outer periphery of the rotor 7. With the cooperation of the stator 6 and the rotor 7, the motor shaft 3 can rotate around its own central axis.

[0032] The mounting holes extend along the thickness direction of the rear cover 2, such as... Figure 1 As shown, the assembly fixture 100 is provided with a top pin 101, which can be inserted into the assembly hole, so that the assembly fixture 100 moves the rear cover 2 and presses the rear cover 2 onto the end face of the main housing 1, thereby completing the assembly of the powertrain.

[0033] Existing hybrid transmissions typically include a main housing, a motor shaft, a rear cover for the motor housing, and a cover plate. The cover plate is installed on the side of the rear cover facing away from the main housing and includes oil passages and sealing structures. During assembly, the assembly fixture 100 needs to mate with the cover plate to abut against the motor shaft, moving the motor shaft to install it onto the main housing. The cover plate increases the axial dimensions and weight of the hybrid transmission, adds assembly steps, and affects the assembly efficiency of the hybrid transmission.

[0034] The powertrain provided in this application embodiment, by providing assembly holes on the rear cover 2, can quickly assemble the motor shaft 3 between the main housing 1 and the rear cover 2 by using the assembly holes to cooperate with the assembly fixture 100, eliminating the step of mates between the assembly fixture 100 and the cover plate, reducing assembly processes, and improving the assembly efficiency of the powertrain; at the same time, by eliminating the cover plate, the number of parts in the powertrain is reduced, effectively reducing the axial length and weight of the powertrain, making the structure of the powertrain more compact.

[0035] In a further embodiment, such as Figure 2 As shown, the powertrain also includes a first bearing 41 and a second bearing 42. The first bearing 41 and the second bearing 42 are respectively sleeved at both ends of the motor shaft 3 along its length. The first bearing 41 is installed in the first mounting hole 12, and the second bearing 42 is installed in the second mounting hole.

[0036] For example, the first bearing 41 and the second bearing 42 are rolling bearings such as deep groove ball bearings, cylindrical roller bearings, and needle roller bearings, used to bear radial loads, support the motor shaft 3 and reduce rotational friction, and ensure that the motor shaft 3 rotates normally.

[0037] For example, the first bearing 41 and the main housing 1, and the second bearing 42 and the rear cover 2 are both fitted with clearance to store lubricating oil and compensate for errors.

[0038] For example, the first bearing 41 and the motor shaft 3, and the second bearing 42 and the motor shaft 3 are both interference fits, which result in a high degree of tightness and make it less likely to fall off.

[0039] Optionally, the shape and size of the first mounting hole 12 are adapted to the shape and size of the first bearing 41, and the shape and size of the second mounting hole are adapted to the shape and size of the second bearing 42. For example, the outer contours of the first mounting hole 12 and the second mounting hole are circular, the same as the outer contours of the first bearing 41 and the second bearing 42, and the radial dimension of the first mounting hole 12 is equal to or slightly larger than the radial dimension of the first bearing 41, and the radial dimension of the second mounting hole is equal to or slightly larger than the radial dimension of the second bearing 42.

[0040] For example, in this embodiment, the powertrain assembly process includes: assembling the first bearing 41 into the first mounting hole 12; pressing the second bearing 42 onto the motor shaft 3, and assembling the motor shaft 3 and the second bearing 42 together into the second mounting hole; inserting the top pin 101 of the assembly fixture 100 into the assembly hole, moving the rear cover 2, the motor shaft 3 and the second bearing 42 as a whole, and assembling the motor shaft 3 into the first mounting hole 12; and connecting the rear cover 2 and the main housing 1 by means of bonding, interference fit, fastener connection, etc.

[0041] In a further embodiment, the powertrain also includes a bearing retainer 5. The main housing 1 has a retainer groove that communicates with the first mounting hole 12. The bearing retainer 5 is installed in the retainer groove and sleeved on one end of the motor shaft 3. The bearing retainer 5 is adjacent to the first bearing 41.

[0042] For example, the bearing retainer 5 is made of materials such as spring steel or stainless steel.

[0043] For example, the retaining ring groove is located on the side of the first mounting hole 12 near the rear cover 2, so as... Figure 2 As shown, the bearing retainer 5 is positioned on the side of the first bearing 41 closer to the second bearing 42, and the bearing retainer 5 abuts against the first bearing 41.

[0044] By setting the bearing retainer 5, the correct positioning of the first bearing 41 during operation can be ensured, the stability of the first bearing 41 can be improved, and the axial movement of the first bearing 41 can be prevented from causing excessive vibration or wear, thus avoiding affecting the service life of the first bearing 41.

[0045] For example, in this embodiment, the powertrain assembly process includes: assembling the first bearing 41 into the first mounting hole 12; assembling the bearing retainer 5 into the retainer groove; pressing the second bearing 42 onto the motor shaft 3, and assembling the motor shaft 3 and the second bearing 42 together into the second mounting hole; inserting the top pin 101 of the assembly fixture 100 into the assembly hole, moving the rear cover 2, the motor shaft 3 and the second bearing 42 as a whole, and assembling the motor shaft 3 into the first mounting hole 12; and connecting the rear cover 2 and the main housing 1 by means of plug-in connection, fastener connection or other methods.

[0046] In one specific embodiment, there are multiple assembly holes, which are spaced apart on the back cover 2 to improve the connection stability between the assembly fixture 100 and the back cover 2.

[0047] For example, there are three mounting holes, which are spaced apart around the second mounting hole. The shape of the mounting holes can be circular, rectangular, triangular, or other polygonal. Optionally, the shape and size of the mounting holes are adapted to the shape and size of the top pin 101 of the assembly tooling 100.

[0048] The mounting hole can be a blind hole or a through hole. For example, the mounting hole communicates with the second mounting hole so that the assembly tool 100 passes through the mounting hole and abuts against the end face of the motor shaft 3.

[0049] In this embodiment, the top pin 101 of the assembly fixture 100 can pass through the assembly hole and abut against the end face of the motor shaft 3, thereby directly pressing the motor shaft 3 into the first mounting hole 12. This is beneficial to improving the tightness, stability and reliability of the connection between the motor shaft 3 and the main housing 1, reducing the assembly difficulty and improving the assembly efficiency.

[0050] In a further embodiment, the powertrain also includes a plug 8 for sealing the mounting hole.

[0051] Specifically, the sealing component 8 is used to seal the assembly hole after the motor shaft 3 is assembled, thereby improving the sealing performance of the powertrain and preventing the lubricating oil in the receiving cavity 11 from leaking from the assembly hole.

[0052] For example, the shape and size of the sealing element 8 are adapted to the shape and size of the mounting hole, so that... Figure 2 The sealing element 8 shown can be tightly inserted into the mounting hole and securely connected to the rear cover 2.

[0053] The sealing component 8 can be connected to the assembly hole by means of bonding, welding, interference fit, etc.

[0054] In an optional embodiment, the plug 8 is threadedly connected to the mounting hole.

[0055] Specifically, the sealing component 8 includes a connected nut part and a screw body part. The outer wall of the screw body part is provided with an external thread, and the assembly hole is provided with an internal thread that matches the external thread. With the cooperation of the external thread and the internal thread, the screw body part can be screwed into the assembly hole until the nut part abuts against the side surface of the rear cover 2 away from the receiving cavity 11, thus completing the sealing of the assembly hole by the sealing component 8.

[0056] It is understandable that when there are multiple assembly holes, there are also multiple sealing elements 8, with each assembly hole being equipped with a sealing element 8.

[0057] Based on any of the above embodiments, the motor shaft 3 includes a sidewall and an inner cavity 31 formed by the sidewall. A branch oil passage is provided on the sidewall, and the extending direction of the branch oil passage is set at an angle to the axial direction of the motor shaft 3. The branch oil passage penetrates the sidewall and communicates with the inner cavity 31. Figure 3 As shown, the rear cover 2 is provided with an oil passage 21, which is connected to the inner cavity 31.

[0058] The inner cavity 31 extends axially along the motor shaft 3, and there are one or more branch oil passages, with the oil outlet of at least one branch oil passage leading to the receiving cavity 11. The branch oil passages may extend radially along the motor shaft 3 or in a direction inclined to the axial direction of the motor shaft 3.

[0059] For example, the rear cover 2 is provided with an oil inlet hole 22, through which lubricating oil can enter the oil passage 21 and flow to the inner cavity 31. During the rotation and throwing process of the motor shaft 3, the lubricating oil in the inner cavity 31 flows out through the branch oil passage under the action of centrifugal force and sprays onto the surface of components such as bearings, stator 6, and rotor 7 to cool and lubricate them.

[0060] This application also provides a powertrain assembly method, applicable to the powertrain provided in any of the above embodiments. For example... Figure 4 As shown, the powertrain assembly method includes: S1: Assemble the first end of the motor shaft 3 into the second mounting hole of the rear cover 2; S2: Insert the assembly fixture 100 into the assembly hole, and install the second end of the motor shaft 3 into the first mounting hole 12 of the main housing 1 through the assembly fixture 100. S3: Separate assembly fixture 100 from back cover 2; S4: Connect the main housing 1 to the rear cover 2.

[0061] For example, the assembly fixture 100 is provided with a top pin 101. In step S2, the top pin 101 is inserted into the assembly hole, which moves the rear cover 2 and presses it onto the end face of the main housing 1. In step S3, the top pin 101 is disengaged from the assembly hole, which separates the assembly fixture 100 from the rear cover 2.

[0062] It is understandable that the first end and the second end of the motor shaft 3 are the two ends along the length of the motor shaft 3.

[0063] For example, in step S4, the main housing 1 and the rear cover 2 can be connected by means of bonding, interference fit, fastener connection, etc.

[0064] In existing technologies, hybrid transmissions typically include a main housing, a motor shaft, a motor housing rear cover, and a cover plate. The cover plate is installed on the side of the motor housing rear cover opposite to the main housing, and it contains oil passages and sealing structures. During assembly, the assembly fixture 100 needs to mate with the cover plate to abut against the motor shaft, moving the motor shaft to install it onto the main housing. The cover plate increases the axial dimensions and weight of the hybrid transmission, adds assembly steps, and affects the assembly efficiency of the hybrid transmission.

[0065] The powertrain assembly method provided in this application embodiment can quickly assemble the motor shaft 3 between the main housing 1 and the rear cover 2 by using the assembly holes and the assembly tool 100 to cooperate. This eliminates the step of the assembly tool 100 cooperating with the cover plate, reduces the assembly process, and helps to improve the assembly efficiency of the powertrain. At the same time, by eliminating the cover plate, the number of powertrain parts is reduced, effectively reducing the axial length and weight of the powertrain, making the structure of the powertrain more compact.

[0066] In a further embodiment, the powertrain also includes a first bearing 41 and a second bearing 42. The first bearing 41 and the second bearing 42 are respectively sleeved at both ends of the motor shaft 3 along its length, for bearing radial loads, supporting the motor shaft 3 and reducing rotational friction, and ensuring normal rotation of the motor shaft 3.

[0067] like Figure 5 As shown, before assembling the first end of the motor shaft 3 into the second mounting hole of the rear cover 2 in step S1, the powertrain assembly method further includes: S101: Install the first bearing 41 into the first mounting hole 12; S102: Install the second bearing 42 into the second mounting hole.

[0068] For example, the first bearing 41 and the main housing 1, and the second bearing 42 and the rear cover 2 are both fitted with clearance to store lubricating oil and compensate for errors.

[0069] For example, the first bearing 41 and the motor shaft 3, and the second bearing 42 and the motor shaft 3 are both interference fits, which result in a high degree of tightness and make it less likely to fall off.

[0070] It is understandable that the implementation order of steps S101 and S102 can be either step S101 before step S102 or step S102 before step S101.

[0071] In a further embodiment, the powertrain also includes a bearing retaining ring 5, and the main housing 1 has a retaining ring groove communicating with the first mounting hole 12. After installing the first bearing 41 into the first mounting hole 12 in step S101, the powertrain assembly method further includes: S1011: Install the bearing retainer 5 in the retainer groove so that the bearing retainer 5 is adjacent to the first bearing 41.

[0072] The bearing retainer 5 is used to ensure the correct positioning of the first bearing 41 during operation, improve the stability of the first bearing 41, prevent the first bearing 41 from axially moving and causing excessive vibration or wear, and avoid affecting the service life of the first bearing 41.

[0073] In an optional embodiment, the mounting hole communicates with the second mounting hole, and the powertrain further includes a sealing element 8. After separating the assembly fixture 100 from the rear cover 2 in step S3, the powertrain assembly method further includes: S301: Insert the sealing component 8 into the assembly hole.

[0074] In step S301, after the motor shaft 3 is assembled, the assembly hole is sealed by the sealing member 8, which can improve the sealing performance of the powertrain and prevent the lubricating oil in the receiving cavity 11 from leaking from the assembly hole.

[0075] In an optional embodiment, the plug 8 is threadedly connected to the mounting hole.

[0076] Specifically, the sealing component 8 includes a connected nut part and a screw body part. The outer wall of the screw body part is provided with an external thread, and the assembly hole is provided with an internal thread that matches the external thread. With the cooperation of the external thread and the internal thread, the screw body part can be screwed into the assembly hole until the nut part abuts against the side surface of the rear cover 2 away from the receiving cavity 11, thus completing the sealing of the assembly hole by the sealing component 8.

[0077] like Figure 6 As shown, in a specific embodiment, the powertrain assembly method includes: S101: Install the first bearing 41 into the first mounting hole 12; S102: Install the second bearing 42 into the second mounting hole; S1: Assemble the first end of the motor shaft 3 into the second mounting hole of the rear cover 2; S2: Insert the assembly fixture 100 into the assembly hole, and install the second end of the motor shaft 3 into the first mounting hole 12 of the main housing 1 through the assembly fixture 100. S3: Separate assembly fixture 100 from back cover 2; S301: Insert the sealing component 8 into the assembly hole; S4: Connect the main housing 1 to the rear cover 2.

[0078] In this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "multiple" refers to two or more unless otherwise expressly defined.

[0079] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0080] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only.

[0081] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A powertrain, characterized in that, include: The main housing (1) is provided with a first mounting hole (12); The rear cover (2) is provided with a second mounting hole and an assembly hole. The assembly hole is used to cooperate with the assembly tool (100) to install the rear cover (2) on one side of the main housing (1). The rear cover (2) and the main housing (1) form a receiving cavity (11). The motor shaft (3) is installed in the receiving cavity (11). The two ends of the motor shaft (3) in the length direction are respectively movably inserted into the first mounting hole (12) and the second mounting hole. The assembly hole is connected to the second mounting hole so that the assembly tool (100) passes through the assembly hole and abuts against the end face of the motor shaft (3).

2. The powertrain according to claim 1, characterized in that, The powertrain also includes a first bearing (41) and a second bearing (42), which are respectively sleeved on both ends of the motor shaft (3) along its length. The first bearing (41) is installed in the first mounting hole (12), and the second bearing (42) is installed in the second mounting hole.

3. The powertrain according to claim 2, characterized in that, The powertrain also includes a bearing retainer (5). The main housing (1) has a retainer groove that communicates with the first mounting hole (12). The bearing retainer (5) is installed in the retainer groove and sleeved on one end of the motor shaft (3). The bearing retainer (5) is adjacent to the first bearing (41).

4. The powertrain according to claim 1, characterized in that, The assembly holes are multiple and are spaced apart on the rear cover (2).

5. The powertrain according to claim 1, characterized in that, The powertrain also includes a plug (8) for sealing the assembly hole.

6. The powertrain according to claim 5, characterized in that, The sealing element (8) is threadedly connected to the assembly hole.

7. The powertrain according to any one of claims 1 to 6, characterized in that, The motor shaft (3) includes a side wall and an inner cavity (31) formed by the side wall. A branch oil passage is provided on the side wall. The extension direction of the branch oil passage is set at an angle to the axial direction of the motor shaft (3). The branch oil passage passes through the side wall and is connected to the inner cavity (31). The rear cover (2) is provided with an oil passage (21), which is connected to the inner cavity (31).

8. A powertrain assembly method, applied to the powertrain according to any one of claims 1 to 7, characterized in that, The powertrain assembly method includes: The first end of the motor shaft (3) is fitted into the second mounting hole of the rear cover (2); The assembly tool (100) is inserted into the assembly hole, and the second end of the motor shaft (3) is installed into the first mounting hole (12) of the main housing (1) through the assembly tool (100); Separate the assembly fixture (100) from the rear cover (2); Connect the main housing (1) to the rear cover (2).

9. The powertrain assembly method according to claim 8, characterized in that, The powertrain also includes a first bearing (41) and a second bearing (42). Before the first end of the motor shaft (3) is fitted into the second mounting hole of the rear cover (2), the powertrain assembly method further includes: The first bearing (41) is installed in the first mounting hole (12); The second bearing (42) is installed in the second mounting hole.

10. The powertrain assembly method according to claim 9, characterized in that, The powertrain also includes a bearing retainer (5), and the main housing (1) has a retainer groove that communicates with the first mounting hole (12); After the first bearing (41) is installed in the first mounting hole (12), the powertrain assembly method further includes: The bearing retainer (5) is installed in the retainer groove so that the bearing retainer (5) is adjacent to the first bearing (41).

11. The powertrain assembly method according to claim 8, characterized in that, The assembly hole is connected to the second mounting hole, and the powertrain also includes a sealing element (8). After separating the assembly fixture (100) from the rear cover (2), the powertrain assembly method further includes: The sealing element (8) is inserted into the assembly hole.

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