Electromechanical brake

Abstract

The application discloses an electromechanical brake, which comprises a brake shell, a rotation-stopping platform and a transmission assembly, the transmission assembly is sealedly installed on the brake shell, the rotation-stopping platform is sealedly installed on the brake shell, and the transmission assembly is sealedly connected with the rotation-stopping platform; a hydraulic cavity is formed between the brake shell, the rotation-stopping platform and the transmission assembly, a spring is arranged in the hydraulic cavity, the spring extends along the axial direction of the transmission assembly, and the spring is located between the brake shell and the rotation-stopping platform; when the hydraulic cavity is vacuumized and filled with liquid, the rotation-stopping platform moves towards the brake shell along the axial direction, the spring applies a reverse force to the rotation-stopping platform, and a gap always exists between the rotation-stopping platform and the brake shell. The technical scheme of the application guarantees that a gap always exists between the rotation-stopping top surface of the rotation-stopping platform and the shell bottom surface of the brake shell when the hydraulic cavity is compressed by arranging the spring in the hydraulic cavity, so that the hydraulic sensor can always measure the pressure change in the hydraulic cavity.

Description

Technical Field

[0001] This invention relates to the field of new energy vehicle technology, and in particular to an electromechanical brake. Background Technology

[0002] Currently, there are two types of sensors used in EMB (Electromechanical Brake) equipment. The first type is a mechanical pressure sensor. Most mechanical sensors used in brakes currently have cables protruding, and the compact space inside the caliper leaves little room for cable routing, making installation difficult. The second type is a hydraulic pressure sensor. Hydraulic sensor technology is now very mature and can be directly selected. In terms of installation, hydraulic sensors are integrated into one unit, with a hydraulic sensing head on one end and a connector on the other, eliminating the need for wiring and making installation relatively simple. However, they still face the problem of large size. Although the hydraulic sensor is installed on the outside of the caliper, the area outside the caliper includes the steering knuckle, wheel rim, and motor, limiting the space available for the hydraulic sensor. It is not suitable for all projects. Summary of the Invention

[0003] One of the objectives of this invention is to overcome the shortcomings of the prior art. In the prior art, when assembling EMB equipment, evacuating the hydraulic chamber and adding liquid causes the anti-rotation platform to contact the bottom surface of the brake housing, making it difficult for the hydraulic sensor to detect pressure changes in the hydraulic chamber. Therefore, this invention provides an electromechanical brake.

[0004] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0005] In a first aspect, the present invention provides an electromechanical brake, comprising a brake housing, an anti-rotation platform, and a transmission assembly, wherein the transmission assembly is sealed and mounted on the brake housing, the anti-rotation platform is sealed and mounted on the brake housing, and the transmission assembly is sealed and connected to the anti-rotation platform.

[0006] A hydraulic chamber is sealed between the brake housing, the anti-rotation platform, and the transmission assembly. A spring is disposed in the hydraulic chamber, extending along the axial direction of the transmission assembly, and the spring is located between the brake housing and the anti-rotation platform.

[0007] When the hydraulic chamber is evacuated and filled with liquid, the anti-rotation platform moves toward the brake housing in the axial direction, and the spring applies a reverse force to the anti-rotation platform, so that there is always a gap between the anti-rotation platform and the brake housing.

[0008] In a preferred embodiment of this application, along the axial direction of the transmission assembly, the anti-rotation platform has an anti-rotation top surface, and the brake housing has a housing bottom surface;

[0009] The transmission assembly has a transmission surface in the circumferential direction surrounding the axial direction;

[0010] The hydraulic cavity is formed by sealing between the transmission surface, the anti-rotation top surface, and the bottom surface of the housing. The two ends of the spring are respectively connected to the anti-rotation top surface and / or the bottom surface of the housing, or the two ends of the spring are not connected to either the anti-rotation top surface or the bottom surface of the housing.

[0011] When the hydraulic chamber is evacuated and liquid is added, the two ends of the spring are compressed by the anti-rotation top surface and the bottom surface of the housing, generating the reverse force.

[0012] In a preferred embodiment of this application, an anti-rotation boss is provided on the top surface of the anti-rotation platform, and an anti-rotation groove is provided on the bottom surface of the housing. The number and position of the anti-rotation boss and the anti-rotation groove are correspondingly arranged in the axial direction. The anti-rotation boss and the anti-rotation groove cooperate with each other to prevent the anti-rotation platform from rotating along the circumferential direction with the transmission component.

[0013] In a preferred embodiment of this application, the transmission assembly and the brake housing, the anti-rotation platform and the brake housing, and the transmission assembly and the anti-rotation platform are respectively sealed and connected by sealing rings.

[0014] In a preferred embodiment of this application, in the radial direction perpendicular to the axial direction of the transmission assembly, the anti-rotation platform has an inner wall and an outer wall, and a sealing groove is formed on both the inner wall and the outer wall, and the sealing ring is embedded in the sealing groove.

[0015] In a preferred embodiment of this application, a hydraulic sensor is provided on the brake housing, and the hydraulic sensor is in communication with the hydraulic chamber.

[0016] In a preferred embodiment of this application, in the radial direction perpendicular to the axial direction of the transmission assembly, the diameter of the sealing surface of the hydraulic chamber is smaller than the diameter of the main cylinder bore surface of the brake housing.

[0017] In a preferred embodiment of this application, it further includes a motor, a gearbox, a bracket, a piston, and a pair of friction plates. The motor is mounted inside the gearbox, the brake housing is fixedly connected to the gearbox, the bracket is fixedly connected to the brake housing, and the pair of friction plates are mounted inside the bracket.

[0018] In the axial direction, the transmission assembly has a first end and a second end, the gearbox is connected to the first end of the transmission assembly, the piston is sleeved on the second end of the transmission assembly, and a pair of friction plates are located at the second end of the transmission assembly. The pair of friction plates has an inner plate and an outer plate, the inner plate is disposed close to the piston, and the outer plate is disposed away from the piston.

[0019] When the piston is driven by the transmission assembly to move along the axial direction, the piston pushes the inner plate toward the outer plate.

[0020] In a preferred embodiment of this application, the transmission assembly is a ball screw, including a nut, a screw rod, and a load-bearing platform;

[0021] The lead screw has a first rod portion, a second rod portion, and a connecting portion. The first rod portion is connected to the first end, the second rod portion is connected to the second end, and the connecting portion connects the first rod portion and the second rod portion. In the radial direction perpendicular to the axial direction of the transmission assembly, the outer diameter of the first rod portion is smaller than the outer diameter of the second rod portion, and the outer diameter of the connecting portion gradually increases from the first rod portion to the second rod portion in the axial direction.

[0022] The anti-rotation platform is sleeved around the first part of the lead screw, the bearing platform is sleeved around the connecting part of the lead screw, and the nut is sleeved around the second part of the lead screw.

[0023] The electromechanical brake disclosed in this invention ensures that there is always a gap between the anti-rotation top surface of the anti-rotation platform and the bottom surface of the brake housing when the hydraulic chamber is compressed by setting a spring inside the hydraulic chamber, so that the hydraulic sensor can always detect the pressure change in the hydraulic chamber. Attached Figure Description

[0024] The present invention is described with reference to the following figures:

[0025] Figure 1 This is a perspective view of the electromechanical brake in an embodiment of the present invention;

[0026] Figure 2 This is a cross-sectional view (AA) of the electromechanical brake in an embodiment of the present invention;

[0027] Figure 3 yes Figure 2 Enlarged view of region B in the middle;

[0028] Figure 4 yes Figure 3 A magnified view of a portion of the image;

[0029] Figure 5This is a schematic diagram of the anti-rotation platform in the electromechanical brake of an embodiment of the present invention;

[0030] Figure 6 This is a schematic diagram of the bottom surface of the brake housing in an embodiment of the present invention.

[0031] Figure label:

[0032] 10-Motor;

[0033] 20-Gearbox;

[0034] 30-Brake housing; 31-Bottom surface of housing; 32-Caliper; 33-Pawl; 34-Master cylinder bore surface; 35-Anti-rotation groove;

[0035] 40-Staff;

[0036] 50 - Friction plate; 51 - Inner plate; 52 - Outer plate;

[0037] 60 - Transmission assembly; 61 - First end; 62 - Second end; 63 - Transmission surface; 64 - Nut; 65 - Lead screw; 651 - First rod section; 652 - Second rod section; 653 - Connecting part; 66 - Bearing platform;

[0038] 70 - Anti-rotation platform; 71 - Anti-rotation top surface; 72 - Inner wall; 73 - Outer wall; 74 - Sealing groove; 75 - Anti-rotation boss;

[0039] 80-Piston;

[0040] 90 - Hydraulic chamber; 91 - Sealing surface;

[0041] 100-Spring;

[0042] 110 - Hydraulic sensor;

[0043] 120-gap;

[0044] 130 - Sealing Ring One;

[0045] 140 - Sealing Ring Two;

[0046] 150 - Sealing Ring Three;

[0047] D1 - Axial direction; D2 - Circumferential direction; D3 - Radial direction. Detailed Implementation

[0048] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0049] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0050] This invention discloses an electromechanical brake driven by a motor. The braking performance of the electromechanical brake in this embodiment is detected by measuring the pressure change in the hydraulic chamber using a hydraulic sensor.

[0051] See Figures 1 to 6 The electromechanical brake of this embodiment includes a motor 10, a gearbox 20, a brake housing 30, a bracket 40, a pair of friction plates 50, a transmission assembly 60, an anti-rotation platform 70, a piston 80, a hydraulic chamber 90, a spring 100, and a hydraulic sensor 110. The motor 10 is mounted inside the gearbox 20. The brake housing 30 is fixedly connected to the gearbox 20, and the bracket 40 is fixedly connected to the brake housing 30. The pair of friction plates 50 are mounted inside the bracket 40. The transmission assembly 60 is sealed and mounted on the brake housing 30, and the anti-rotation platform 70 is sealed and mounted on the transmission assembly 60. The transmission assembly 60 and the anti-rotation platform 70 are sealed and connected. A hydraulic chamber 90 is sealed between the brake housing 30, the anti-rotation platform 70, and the transmission assembly 60. A spring 100 is disposed in the hydraulic chamber 90, extending along the axial direction D1 of the transmission assembly 60. The spring 100 is located between the brake housing 30 and the anti-rotation platform 70. When the hydraulic chamber 90 is evacuated and filled with liquid, the anti-rotation platform 70 moves toward the brake housing 30 in the axial direction D1, and the spring 100 applies a reverse force to the anti-rotation platform 70, so that there is always a gap 120 between the anti-rotation platform 70 and the brake housing 30.

[0052] like Figures 1 to 3 As shown, along the axial direction D1 of the transmission assembly 60, the transmission assembly 60 has a first end 61 and a second end 62. A gearbox 20 is connected to the first end 61 of the transmission assembly 60. A piston 80 is sleeved on the second end 62 of the transmission assembly 60. A pair of friction plates 50 are located at the second end 62 of the transmission assembly 60. Each pair of friction plates 50 has an inner plate 51 and an outer plate 52. The inner plate 51 is positioned close to the piston 80, and the outer plate 52 is positioned away from the piston 80. When the piston 80 is driven by the transmission assembly 60 to move along the axial direction D1, the piston 80 pushes the inner plate 51 towards the outer plate 52. The brake housing 30 has a caliper 32 and a pawl 33. The caliper 32 is connected to the first end 61 of the transmission assembly 60, and the pawl 33 is positioned close to the outer plate 52 of the friction plate 50. When clamped, the pawl 33 contacts the outer plate 52 of the friction plate 50 and drives the outer plate 52 towards the inner plate 51.

[0053] The transmission assembly 60 is a ball screw, including a nut 64, a screw 65, and a bearing platform 66. The screw 65 has a first rod portion 651, a second rod portion 652, and a connecting portion 653. The first rod portion 651 connects to a first end 61, the second rod portion 652 connects to a second end 62, and the connecting portion 653 connects the first rod portion 651 and the second rod portion 652. In the radial direction D3 perpendicular to the axial direction D1 of the transmission assembly 60, the outer diameter of the first rod portion 651 is smaller than the outer diameter of the second rod portion 652, and the outer diameter of the connecting portion 653 gradually increases from the first rod portion 651 to the second rod portion 652 in the axial direction D1. An anti-rotation platform 70 is sleeved around the first rod portion 651 of the screw 65, the bearing platform 66 is sleeved around the connecting portion 653 of the screw 65, and the nut 64 is sleeved around the second rod portion 652 of the screw 65. The piston 80 is sleeved around the second rod portion 652 of the lead screw 65, and the nut 64 is sleeved inside the piston 80.

[0054] Along the axial direction D1 of the transmission assembly 60, the anti-rotation platform 70 has an anti-rotation top surface 71, and the brake housing 30 has a housing bottom surface 31; along the circumferential direction D2 of the transmission assembly 60 surrounding the axial direction D1, the transmission assembly 60 has a transmission surface 63. A hydraulic cavity 90 is sealed between the transmission surface 63, the anti-rotation top surface 71, and the housing bottom surface 31. This hydraulic cavity 90 is a compressible sealed cavity structure. There are four ways to set the spring 100 in the hydraulic chamber 90. One way is that neither end of the spring 100 is connected to the anti-rotation top surface 71 or the bottom surface 31 of the housing. When the hydraulic chamber 90 is compressed due to vacuuming and liquid injection, the anti-rotation top surface 71 of the anti-rotation platform 70 moves closer to the bottom surface 31 of the brake housing 30. During the movement, the anti-rotation top surface 71 contacts one end of the spring 100 and pushes the spring 100 to move together until the other end of the spring 100 contacts the bottom surface 31 of the housing. Then, as the anti-rotation platform 70 continues to move, the two ends of the spring 100 are respectively connected to the anti-rotation top surface. 71 and the bottom surface 31 of the housing are compressed, and the spring 100 generates a reverse force due to compression. This reverse force is applied to the anti-rotation top surface 71. At this time, the other end of the spring 100 near the anti-rotation top surface 71 can press against the anti-rotation top surface 71, so that the anti-rotation platform 70 is in the lowest position, and thus the anti-rotation top surface 71 will not contact the bottom surface 31 of the housing. Secondly, one end of the spring 100 is fixed to the bottom surface 31 of the brake housing 30, and the other end is not connected to the anti-rotation component 70. When the hydraulic chamber 90 is compressed due to vacuuming and liquid injection, the anti-rotation top surface 71 of the anti-rotation platform 70 presses against the bottom surface 31 of the brake housing 30. When the bottom surface 31 of the body moves closer, the other end of the spring 100 near the anti-rotation top surface 71 can press against the anti-rotation top surface 71, so that the anti-rotation platform 70 is in the lowest position, and thus the anti-rotation top surface 71 will not contact the bottom surface 31 of the housing; thirdly, one end of the spring 100 is fixed on the anti-rotation top surface 71 of the anti-rotation platform 70, and the other end is not connected to the brake housing 30. When the hydraulic chamber 90 is compressed due to vacuuming and liquid filling, the anti-rotation top surface 71 of the anti-rotation platform 70 moves closer to the bottom surface 31 of the brake housing 30. At this time, the other end of the spring 100 near the bottom surface 31 of the housing can press against the bottom surface 31 of the housing. The bottom surface 31 of the housing keeps the anti-rotation platform 70 in its lowest position, so that the anti-rotation top surface 71 will not contact the bottom surface 31 of the housing; fourthly, the two ends of the spring 100 are respectively connected to the anti-rotation top surface 71 and the bottom surface 31 of the housing. When the hydraulic chamber 90 is compressed due to vacuuming and liquid injection, the anti-rotation top surface 71 of the anti-rotation platform 70 moves closer to the bottom surface 31 of the brake housing 30. At this time, the spring 100 is compressed and generates a reverse force toward the anti-rotation top surface 71, which holds the anti-rotation top surface 71 and keeps the anti-rotation platform 70 in its lowest position, so that the anti-rotation top surface 71 will not contact the bottom surface 31 of the housing.When the transmission assembly 60 moves axially towards the gearbox 20 along direction D1, the anti-rotation platform 70 moves accordingly and applies a force to the spring 100 through the anti-rotation top surface 71, causing the spring 100 to be in a compressed state. Due to the presence of the spring 100, a gap 120 is always maintained between the anti-rotation top surface 71 and the bottom surface 31 of the housing. The gap 120 between the bottom surface 31 of the housing and the anti-rotation top surface 71 is maintained by the spring 100. By setting a spring of a length whose force is greater than the vacuuming force, the gap 120 between the bottom surface 31 of the housing and the anti-rotation top surface 71 can always be maintained when vacuuming and adding liquid, and the hydraulic chamber 90 can be compressed. When the caliper 32 of the brake housing 30 clamps, the nut 64 of the transmission assembly 60 moves outward, and the bearing platform 66 of the transmission assembly 60 applies a force in the opposite direction. The hydraulic chamber 90 is subjected to positive pressure. The hydraulic sensor 110 is directly connected to the hydraulic chamber 90 and can directly measure the change in hydraulic pressure. The hydraulic chamber 90 and the brake housing 30 are arranged coaxially around the center. To ensure the sealing of the hydraulic chamber 90, the transmission assembly 60 and the brake housing 30, the anti-rotation platform 70 and the brake housing 30, and the transmission assembly 60 and the anti-rotation platform 70 are respectively sealed and connected by sealing ring 130, sealing ring 240, and sealing ring 350.

[0055] like Figure 4 As shown, in the radial direction D3 of the transmission assembly 60, the diameter of the sealing surface 91 of the hydraulic chamber 90 is smaller than the diameter of the main cylinder bore 34 of the brake housing 30. This has the advantage that the O-ring will not twist during assembly when installing the second sealing ring 140. If the diameter of the sealing surface 91 were less than or equal to the diameter of the main cylinder bore 34, the straight section traversed by the second sealing ring 140 during installation would be too long, easily leading to localized twisting and loss of sealing effectiveness.

[0056] like Figure 5 As shown, the anti-rotation platform 70 in the radial direction D3 has an inner wall 72 and an outer wall 73, both of which have sealing grooves 74, into which a sealing ring is embedded. The advantage of providing an outer sealing groove 74 on the anti-rotation platform 70 is that the installation of the sealing ring is easier. If the sealing groove 74 were located on the brake housing 30, its depth would easily be too deep, making installation difficult.

[0057] like Figure 6As shown, the anti-rotation platform 70 has an anti-rotation boss 75 on its top surface 71, and the brake housing 30 has an anti-rotation groove 35 on its bottom surface 31. The number and position of the anti-rotation boss 75 and the anti-rotation groove 35 are correspondingly arranged in the axial direction D1. The anti-rotation boss 75 and the anti-rotation groove 35 cooperate with each other to prevent the anti-rotation platform 70 from rotating along the circumferential direction D2 with the transmission assembly 60. The anti-rotation boss 75 and the anti-rotation groove 35 cooperate to prevent rotation between the brake housing 30 and the transmission assembly 60. The benefit of preventing rotation is to improve the life of the sealing ring 150. The outer circumference of the sealing ring 150 is much larger than that of the sealing ring 130 and the sealing ring 140. For the same rotation, the linear velocity of the sealing ring 150 is higher than that of the sealing ring 130 and the sealing ring 140, and its wear will also be higher. If the brake housing 30 and the transmission assembly 60 can easily rotate relative to each other, the sealing requirement of the caliper 32-cycle life of the brake housing 30 cannot be met. Therefore, anti-rotation is required.

[0058] The working principle of the electromechanical brake in this embodiment is as follows: the motor 10 outputs torque, which is reduced and increased by the gearbox 20 and then transmitted to the transmission component 60. The function of the transmission component 60 is to convert the torque into axial force. When working, the nut 64 of the transmission component 60 contacts the piston 80 and pushes the piston 80 out. The piston 80 then pushes the inner plate 51 of the friction pad 50 towards the brake disc (not shown in the figure). At the same time, the caliper 32 of the brake housing 30 and the piston 80 move in opposite directions. The pawl 33 of the brake housing 30 pulls the outer plate 52 of the friction pad 50 towards the brake disc, thereby achieving the purpose of clamping the brake disc.

[0059] The electromechanical brake disclosed in this invention ensures that there is always a gap between the anti-rotation top surface of the anti-rotation platform and the bottom surface of the brake housing when the hydraulic chamber is compressed by setting a spring inside the hydraulic chamber, so that the hydraulic sensor can always detect the pressure change in the hydraulic chamber.

[0060] It should be understood that the above description of specific embodiments of the present invention is only for illustrating the technical approach and features of the present invention, and is intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. However, the present invention is not limited to the specific embodiments described above. All changes or modifications made within the scope of the claims of the present invention should be covered within the protection scope of the present invention.

Claims

1. An electromechanical brake, characterized in that, It includes a brake housing, an anti-rotation platform, and a transmission assembly. The transmission assembly is sealed and mounted on the brake housing, the anti-rotation platform is sealed and mounted on the anti-rotation platform, and the transmission assembly is sealed and connected to the anti-rotation platform. A hydraulic chamber is sealed between the brake housing, the anti-rotation platform, and the transmission assembly. A spring is disposed in the hydraulic chamber, extending along the axial direction of the transmission assembly, and the spring is located between the brake housing and the anti-rotation platform. When the hydraulic chamber is evacuated and filled with liquid, the anti-rotation platform moves toward the brake housing in the axial direction, and the spring applies a reverse force to the anti-rotation platform, so that there is always a gap between the anti-rotation platform and the brake housing.

2. The electromechanical brake according to claim 1, characterized in that, Along the axial direction of the transmission assembly, the anti-rotation platform has an anti-rotation top surface, and the brake housing has a housing bottom surface; The transmission assembly has a transmission surface in the circumferential direction surrounding the axial direction; The hydraulic cavity is formed by sealing between the transmission surface, the anti-rotation top surface, and the bottom surface of the housing; the two ends of the spring are respectively connected to the anti-rotation top surface and / or the bottom surface of the housing, or the two ends of the spring are not connected to either the anti-rotation top surface or the bottom surface of the housing. When the hydraulic chamber is evacuated and liquid is added, the two ends of the spring are compressed by the anti-rotation top surface and the bottom surface of the housing, generating the reverse force.

3. The electromechanical brake according to claim 2, characterized in that, The anti-rotation top surface is provided with an anti-rotation boss, and the bottom surface of the housing is provided with an anti-rotation groove. The number and position of the anti-rotation boss and the anti-rotation groove are correspondingly arranged in the axial direction. The anti-rotation boss and the anti-rotation groove cooperate with each other to prevent the anti-rotation platform from rotating along the circumferential direction with the transmission component.

4. The electromechanical brake according to claim 1, characterized in that, The transmission assembly and the brake housing, the anti-rotation platform and the brake housing, and the transmission assembly and the anti-rotation platform are respectively sealed and connected by sealing rings.

5. The electromechanical brake according to claim 4, characterized in that, In the radial direction perpendicular to the axial direction of the transmission assembly, the anti-rotation platform has an inner wall and an outer wall, and a sealing groove is formed on both the inner wall and the outer wall, and the sealing ring is embedded in the sealing groove.

6. The electromechanical brake according to claim 1, characterized in that, A hydraulic sensor is installed on the brake housing, and the hydraulic sensor is in communication with the hydraulic chamber.

7. The electromechanical brake according to claim 1, characterized in that, In the radial direction perpendicular to the axial direction of the transmission assembly, the diameter of the sealing surface of the hydraulic chamber is smaller than the diameter of the main cylinder bore of the brake housing.

8. The electromechanical brake according to claim 1, characterized in that, It also includes a motor, a gearbox, a bracket, a piston, and a pair of friction plates. The motor is installed inside the gearbox, the brake housing is fixedly connected to the gearbox, the bracket is fixedly connected to the brake housing, and the pair of friction plates are installed inside the bracket. In the axial direction, the transmission assembly has a first end and a second end, the gearbox is connected to the first end of the transmission assembly, the piston is sleeved on the second end of the transmission assembly, and a pair of friction plates are located at the second end of the transmission assembly. The pair of friction plates has an inner plate and an outer plate, the inner plate is disposed close to the piston, and the outer plate is disposed away from the piston. When the piston is driven by the transmission assembly to move along the axial direction, the piston pushes the inner plate toward the outer plate.

9. The electromechanical brake according to claim 8, characterized in that, The transmission component is a ball screw, including a nut, a screw, and a load-bearing platform; The lead screw has a first rod portion, a second rod portion, and a connecting portion. The first rod portion is connected to the first end, the second rod portion is connected to the second end, and the connecting portion connects the first rod portion and the second rod portion. In the radial direction perpendicular to the axial direction of the transmission assembly, the outer diameter of the first rod portion is smaller than the outer diameter of the second rod portion, and the outer diameter of the connecting portion gradually increases from the first rod portion to the second rod portion in the axial direction. The anti-rotation platform is sleeved around the first part of the lead screw, the bearing platform is sleeved around the connecting part of the lead screw, and the nut is sleeved around the second part of the lead screw.

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