Novel seat slide rail transmission structure

Abstract

The utility model relates to a novel seat slide rail transmission structure, the utility model discloses two parallelly arranged slide rails, each slide rail is arranged with slide rail screw rod, and the slide rail screw rod is installed with screw rod nut, at least one motor gear box, and the motor gear box includes drive motor and first transmission gear group, when two slide rails are all configured with motor gear box, the drive motor of two motor gear boxes respectively synchronous action, or, the first transmission gear group of two motor gear boxes respectively is connected with synchronous bar between, when only one slide rail is configured with motor gear box, the second transmission gear group is configured on the other slide rail, and the output of the first transmission gear group of motor gear box is connected with the input of the second transmission gear group with synchronous bar, and the output of the second transmission gear group is meshed with the screw rod nut of the other slide rail and is connected, the utility model gives both transmission efficiency, installation flexibility and safety performance.

Description

Technical Field

[0001] This utility model relates to the field of automotive seat transmission structure technology, and in particular to a novel seat slide rail transmission structure. Background Technology

[0002] Car seat slide rails are key components for enabling seat fore-and-aft adjustment, and their transmission structure directly affects the smoothness, safety, and overall ride comfort of the vehicle. Currently, common transmission methods for long automotive slide rails mainly include rack and pinion transmission structures and motor-driven flexible shaft and lead screw transmission structures.

[0003] In traditional rack and pinion transmission structures, the drive gear meshes with the rack on the slide rail to adjust the seat position, and a locking mechanism is usually added for self-locking. This structure has the following problems: First, the locking position must be precisely in the predetermined fixed position. Even a slight deviation can lead to failure to lock in time, posing a safety hazard. Second, when the electronic control system malfunctions, the self-locking function may fail, posing a risk of not being able to maintain the lock in extreme situations such as collisions. Third, the impact energy from a collision is transmitted to the seat and occupant via the rack and pinion, resulting in insufficient impact absorption and poor riding comfort. Fourth, the locking mechanism has a complex structure and high cost, which is not conducive to lightweight design and cost control.

[0004] The motor-driven flexible shaft lead screw transmission structure uses a motor to rotate a flexible shaft, which in turn drives a gearbox and a lead screw to move the seat. It also utilizes the helical transmission characteristics of the lead screw to achieve a reverse self-locking function. While this structure simplifies the mechanical locking mechanism, it still has the following drawbacks: the flexible shaft transmission has high frictional resistance and low efficiency, resulting in slow transmission speed. To achieve the same slide rail movement speed, the nut rotation speed needs to be increased, leading to greater noise. Furthermore, to overcome transmission losses, a higher-powered motor is required, increasing energy consumption and system cost. Summary of the Invention

[0005] Therefore, this utility model provides a novel seat slide rail transmission structure that can achieve real-time self-locking function, taking into account transmission efficiency, installation flexibility and safety performance, and solving the problems of poor self-locking reliability, low transmission efficiency and high cost in existing slide rail transmission structures.

[0006] To solve the above-mentioned technical problems, this utility model provides a novel seat slide rail transmission structure, comprising: Two parallel slide rails, each of which has a slide rail lead screw arranged along its length, and a lead screw nut is installed on the slide rail lead screw; At least one motor gearbox, the motor gearbox including a drive motor and a first transmission gear set, the output end of the drive motor being meshed with the input end of the first transmission gear set, and the output end of the first transmission gear set being meshed with the lead screw nut; When both slide rails are equipped with motor gearboxes, the drive motors of the two motor gearboxes operate synchronously; or, a synchronizing rod is connected between the first transmission gear sets of the two motor gearboxes. When only one of the slide rails is equipped with the motor gearbox, the other slide rail is equipped with an HDM gearbox. The HDM gearbox includes a second transmission gear set. A synchronizing rod is connected between the output end of the first transmission gear set of the motor gearbox and the input end of the second transmission gear set. The output end of the second transmission gear set is engaged with the lead screw nut of the other slide rail.

[0007] In one embodiment of this utility model, both the first transmission gear set and the second transmission gear set include a first transmission gear, a second transmission gear, and a third transmission gear. The first transmission gear meshes with the second transmission gear and their axes are arranged parallel to each other. The second transmission gear is connected to the third transmission gear and is arranged coaxially. The third transmission gear meshes with the external teeth of the lead screw nut and their axes are arranged perpendicular to each other.

[0008] In one embodiment of this utility model, the first transmission gear, the second transmission gear, and the third transmission gear are all helical gears, and the outer peripheral end of the lead screw nut is provided with helical teeth.

[0009] In one embodiment of this utility model, when both slide rails are equipped with the motor gearbox and no synchronizing rod is provided, the output end of the drive motor is connected to a drive gear, and the drive gear meshes with the first transmission gear.

[0010] In one embodiment of this utility model, the two ends of the synchronizing rod are respectively provided with external spline structures.

[0011] In one embodiment of this utility model, when both slide rails are equipped with the motor gearbox and the synchronizing rod is provided, the output end of the drive motor is connected to the drive gear, a transition gear is provided between the drive gear and the first transmission gear, the transition gear is meshed with the drive gear, the transition gear is coaxially arranged with the first transmission gear and both are provided with internal spline structures, and the external spline structure of the synchronizing rod is respectively connected to the internal spline structures of the transition gear and the first transmission gear.

[0012] In one embodiment of this utility model, when only one of the slide rails is equipped with the motor gearbox, the output end of the drive motor is connected to a drive gear, a transition gear is provided between the drive gear and the first transmission gear of the first transmission gear group, the transition gear meshes with the drive gear, both the transition gear and the first transmission gear are provided with internal spline structures, the transition gear is coaxially arranged with the first transmission gear of the first transmission gear group, the external spline structure at one end of the synchronizing rod is respectively connected to the internal spline structure of the transition gear and the first transmission gear of the first transmission gear group, and the external spline structure at the other end of the synchronizing rod is connected to the internal spline structure of the first transmission gear of the second transmission gear group.

[0013] In one embodiment of the present invention, the motor gearbox further includes a first gearbox body, a first gearbox cover, and a motor mounting housing. The first transmission gear set and the lead screw nut are installed between the first gearbox body and the first gearbox cover, and the drive motor is installed inside the motor mounting housing.

[0014] In one embodiment of the present invention, the HDM gearbox further includes a second gearbox body and a second gearbox cover, and the second transmission gear set and the lead screw nut are installed between the second gearbox body and the second gearbox cover.

[0015] The above-mentioned technical solution of this utility model has the following advantages compared with the prior art: This utility model discloses a novel seat slide rail transmission structure. The motor gearbox adopts a modular design, which can be flexibly configured as a single motor or dual motor structure according to the seat layout space and performance requirements. Each motor gearbox module can be independently installed on either side of the slide rail, or arranged in pairs at both ends of the slide rail to achieve different output power and transmission speed.

[0016] The synchronizing rod establishes a mechanical coupling between the two slide rails, ensuring synchronized operation of both rails. It can be selectively installed as needed to enhance assembly flexibility. This structure not only supports multi-model platform development but also facilitates customized matching between different models.

[0017] The motor gearbox module of this utility model is equipped with a high-speed motor and a multi-stage reduction gear set. The motor output is reduced in speed and increased in torque by the gearbox, which drives the lead screw nut of the slide rail lead screw to realize the back and forth movement of the seat along the slide rail.

[0018] Depending on the configuration, the transmission modes include the following three: Single-motor with synchronizer structure: Power is output from the gearbox of one motor and transmitted to the slide rail on the other side via the synchronizer, achieving synchronous drive on both sides. This structure can significantly reduce system cost and weight while ensuring high synchronization accuracy, making it suitable for economy vehicles or scenarios with lower power requirements.

[0019] Dual-motor with synchronizer structure: Motor gearboxes are installed on both sides, and output coupling is achieved through synchronizers. This configuration can improve the system's output power and transmission speed, making it suitable for mid-to-high-end seating systems with high requirements for adjustment response and load capacity, while maintaining high synchronization and low noise operation.

[0020] Dual-motor, synchronizerless structure: The gearboxes of the two motors independently drive their respective slide rails, and the control system achieves electronic synchronization through closed-loop control of motor speed and position. This structure significantly improves the assembly efficiency and modularity of the slide rails, facilitating transportation, monorail loading, and rapid adaptation to multiple platforms.

[0021] Through the three configuration methods described above, this utility model achieves a flexible combination of structural layout, performance output, and cost control for the seat slide rail transmission system, enabling personalized configuration according to vehicle model, space, and performance requirements. Meanwhile, the modular design ensures the system's maintainability and reliability, and the real-time self-locking structure maintains seat stability in the event of electronic control failure or collision, improving overall vehicle safety and passenger comfort. Attached Figure Description

[0022] To make the content of this utility model easier to understand, the present utility model will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0023] Figure 1 This is a schematic diagram of the seat slide rail transmission structure of Embodiment 1 of this utility model.

[0024] Figure 2 This is a schematic diagram of the seat slide rail transmission structure of Embodiment 1 of this utility model.

[0025] Figure 3 This is a schematic diagram of the composition structure of the motor gearbox in Embodiment 1 of this utility model.

[0026] Figure 4 This is a schematic diagram of the external structure of the motor gearbox of Embodiment 1 of this utility model.

[0027] Figure 5 This is a schematic diagram of the connection structure between the motor gearbox and the synchronizing rod in Embodiment 1 of this utility model.

[0028] Figure 6 This is an exploded structural diagram of the second transmission gear set in Embodiment 1 of this utility model.

[0029] Figure 7 This is a schematic diagram of the seat slide rail transmission structure of Embodiment 2 of this utility model.

[0030] Figure 8 This is a schematic diagram of the seat slide rail transmission structure of Embodiment 2 of this utility model.

[0031] Explanation of reference numerals in the instruction manual: 1. Slide rail; 11. Slide rail lead screw; 12. Lead screw nut; 2. Motor gearbox; 20. HDM gearbox; 21. Drive motor; 211. Drive gear; 22a. First transmission gear set; 22b. Second transmission gear set; 221. First transmission gear; 222. Second transmission gear; 223. Third transmission gear; 224. Internal spline structure; 23. First gearbox body; 24. First gearbox cover; 25. Motor mounting housing; 26. Second gearbox body; 27. Second gearbox cover; 28. Transition gear; 3. Synchronizing rod; 31. External spline structure. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments are not intended to limit the present invention.

[0033] In this utility model, when directions (up, down, left, right, front, and back) are described, it is only for the convenience of describing the technical solution of this utility model, and does not indicate or imply that the technical features referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this utility model.

[0034] In this utility model, "several" means one or more, "multiple" means two or more, "greater than," "less than," "exceeding," etc. are understood to exclude the stated number; "above," "below," "within," etc. are understood to include the stated number. In the description of this utility model, if "first" or "second" is used, it is only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the order of the indicated technical features.

[0035] In this utility model, unless otherwise explicitly defined, terms such as "set," "install," and "connect" should be interpreted broadly. For example, they can refer to a direct connection or an indirect connection through an intermediate medium; a fixed connection, a detachable connection, or an integrally formed connection; a mechanical connection, an electrical connection, or a connection capable of mutual communication; or the internal connection of two components or the interaction between two components. Those skilled in the art can reasonably determine the specific meaning of the above terms in this utility model based on the specific content of the technical solution.

[0036] Example 1: Single motor with synchronizing rod structure Reference Figures 1 to 3 As shown, this embodiment provides a novel seat slide rail transmission structure, including: Two parallel slide rails 1, each slide rail 1 having a slide rail screw 11 arranged along its length, and a screw nut 12 installed on the slide rail screw 11; The motor gearbox 2 and the second transmission gear set 22b are provided. One of the slide rails 1 is equipped with the motor gearbox 2, and the other slide rail 1 is equipped with an HDM gearbox 20. The HDM gearbox 20 includes the second transmission gear set 22b. The motor gearbox 2 includes a drive motor 21 and a first transmission gear set 22a. The output end of the drive motor 21 is meshed with the input end of the first transmission gear set 22a. The output end of the first transmission gear set 22a is meshed with the lead screw nut 12 of one of the slide rails 1. A synchronizing rod 3 is connected between the output end of the first transmission gear set 22a and the input end of the second transmission gear set 22b of the motor gearbox 2. The output end of the second transmission gear set 22b is meshed with the lead screw nut 12 of the other slide rail 1.

[0037] Reference Figure 3 As shown, both the first transmission gear set 22a and the second transmission gear set 22b include a first transmission gear 221, a second transmission gear 222, and a third transmission gear 223. The first transmission gear 221 meshes with the second transmission gear 222 and their axes are arranged parallel to each other. The second transmission gear 222 is connected to the third transmission gear 223 and is arranged coaxially. The third transmission gear 223 meshes with the external teeth of the lead screw nut 12 and their axes are arranged perpendicular to each other.

[0038] Specifically, the first transmission gear 221, the second transmission gear 222 and the third transmission gear 223 are all helical gears, and the outer peripheral end of the lead screw nut 12 is provided with helical teeth.

[0039] Reference Figure 3 , Figure 5 , Figure 6As shown, the two ends of the synchronizing rod 3 are respectively provided with external spline structures 31. The output end of the drive motor 21 is connected to a drive gear 211. A transition gear 28 is provided between the drive gear 211 and the first transmission gear 221 of the first transmission gear set 22a. The transition gear 28 is meshed with the drive gear 211. Both the transition gear 28 and the first transmission gear 221 are provided with internal spline structures 224. The transition gear 28 is coaxially arranged with the first transmission gear 221 of the first transmission gear set 22a. The external spline structure 31 at one end of the synchronizing rod 3 is connected to the internal spline structure 224 of the transition gear 28 and the first transmission gear 221 of the first transmission gear set 22a, respectively. The external spline structure 31 at the other end of the synchronizing rod 3 is connected to the internal spline structure 224 of the first transmission gear 221 of the second transmission gear set 22b.

[0040] It should be noted that the tooth diameter of the drive gear 211 is smaller than that of the transition gear 28, so as to achieve a speed reduction effect.

[0041] Specifically, refer to Figure 4 As shown, the motor gearbox 2 also includes a first gearbox body 23, a first gearbox cover 24, and a motor mounting housing 25. The first transmission gear set 22a and the lead screw nut 12 are installed between the first gearbox body 23 and the first gearbox cover 24, and the drive motor 21 is installed inside the motor mounting housing 25.

[0042] Specifically, refer to Figure 6 As shown, the HDM gearbox 20 also includes a second gearbox body 26 and a second gearbox cover 27, with the second transmission gear set 22b and the lead screw nut 12 installed between the second gearbox body 26 and the second gearbox cover 27.

[0043] By using this single-motor-synchronous-rod 3 structure, power is output from the gearbox of one motor and transmitted to the slide rail 1 on the other side via the synchronous rod 3, achieving synchronous drive on both sides. This structure can significantly reduce system cost and weight while ensuring high synchronization accuracy, making it suitable for economy vehicles or scenarios with lower power requirements.

[0044] Example 2: Dual-motor structure with synchronizer rod Reference Figure 7 , Figure 8 As shown, this embodiment provides a novel seat slide rail transmission structure, including: Two parallel slide rails 1, each slide rail 1 having a slide rail screw 11 arranged along its length, and a screw nut 12 installed on the slide rail screw 11; Two motor gearboxes 2 are respectively set corresponding to the two slide rails 1. Each motor gearbox 2 includes a drive motor 21 and a first transmission gear set 22a. The output end of the drive motor 21 is meshed with the input end of the first transmission gear set 22a, and the output end of the first transmission gear set 22a is meshed with the lead screw nut 12. A synchronizing rod 3 is connected between the first transmission gear sets 22a of each of the two motor gearboxes 2.

[0045] Specifically, the first transmission gear set 22a includes a first transmission gear 221, a second transmission gear 222 and a third transmission gear 223. The first transmission gear 221 meshes with the second transmission gear 222 and their axes are arranged parallel. The second transmission gear 222 is connected to the third transmission gear 223 and is arranged coaxially. The third transmission gear 223 meshes with the external teeth of the lead screw nut 12 and their axes are arranged perpendicularly.

[0046] Specifically, the first transmission gear 221, the second transmission gear 222 and the third transmission gear 223 are all helical gears, and the outer peripheral end of the lead screw nut 12 is provided with helical teeth.

[0047] Specifically, the two ends of the synchronizing rod 3 are respectively provided with external spline structures 31. The output end of the drive motor 21 is connected to a drive gear 211. A transition gear 28 is provided between the drive gear 211 and the first transmission gear 221 of the first transmission gear set 22a. The transition gear 28 is meshed with the drive gear 211. Both the transition gear 28 and the first transmission gear 221 are provided with internal spline structures 224. The transition gear 28 is coaxially arranged with the first transmission gear 221 of the first transmission gear set 22a. The external spline structures 31 at both ends of the synchronizing rod 3 are respectively connected to the internal spline structures 224 of the transition gear 28 and the first transmission gear 221 of the first transmission gear set 22a.

[0048] Specifically, the motor gearbox 2 further includes a first gearbox body 23, a first gearbox cover 24, and a motor mounting housing 25. The first transmission gear set 22a and the lead screw nut 12 are installed between the first gearbox body 23 and the first gearbox cover 24, and the drive motor 21 is installed inside the motor mounting housing 25.

[0049] With this dual-motor setup and synchronizer rod 3, motor gearboxes are mounted on both guide rails, and output coupling is achieved through the synchronizer rod 3. This configuration enhances the system's output power and transmission speed, making it suitable for mid-to-high-end seating systems with high requirements for adjustment response and load capacity, while maintaining high synchronization and low noise operation.

[0050] Example 3: Dual-motor structure without synchronizer This embodiment provides a novel seat slide rail transmission structure. Based on embodiment 2, the synchronizing rod 3 is omitted, and its structure includes: Two parallel slide rails 1, each slide rail 1 having a slide rail screw 11 arranged along its length, and a screw nut 12 installed on the slide rail screw 11; Two motor gearboxes 2 are respectively set for the two slide rails 1. Each motor gearbox 2 includes a drive motor 21 and a first transmission gear set 22a. The output end of the drive motor 21 is meshed with the input end of the first transmission gear set 22a, and the output end of the first transmission gear set 22a is meshed with the lead screw nut 12. The drive motors 21 of each of the two motor gearboxes 2 operate synchronously.

[0051] Specifically, the first transmission gear set 22a includes a first transmission gear 221, a second transmission gear 222 and a third transmission gear 223. The first transmission gear 221 meshes with the second transmission gear 222 and their axes are arranged parallel. The second transmission gear 222 is connected to the third transmission gear 223 and is arranged coaxially. The third transmission gear 223 meshes with the external teeth of the lead screw nut 12 and their axes are arranged perpendicularly.

[0052] Specifically, the first transmission gear 221, the second transmission gear 222 and the third transmission gear 223 are all helical gears, and the outer peripheral end of the lead screw nut 12 is provided with helical teeth.

[0053] Specifically, the motor gearbox 2 further includes a first gearbox body 23, a first gearbox cover 24, and a motor mounting housing 25. The first transmission gear set 22a and the lead screw nut 12 are installed between the first gearbox body 23 and the first gearbox cover 24, and the drive motor 21 is installed inside the motor mounting housing 25.

[0054] With this dual-motor, synchronizerless structure, the gearboxes of the two motors independently drive their respective slide rails 1, and the control system achieves electronic synchronization through closed-loop control of the speed and position of the corresponding drive motors 21. This structure can significantly improve the assembly efficiency and modularity of the slide rails 1, facilitating transportation, monorail loading, and rapid adaptation to multiple platforms.

[0055] In summary, through three configuration methods, this utility model achieves flexible combinations in terms of structural layout, performance output, and cost control of the seat slide rail 1 transmission system, enabling personalized configuration according to vehicle model, space, and performance requirements. Meanwhile, the modular design ensures the system's maintainability and reliability, and the real-time self-locking structure maintains seat stability in the event of electronic control failure or collision, improving overall vehicle safety and passenger comfort.

[0056] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solution of this utility model and not to limit it. Although this utility model has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solution of this utility model without departing from the spirit and scope of the technical solution of this utility model, and all such modifications and substitutions should be covered within the scope of the claims of this utility model.

Claims

1. A novel seat slide transmission structure, characterized by, include: Two parallel slide rails (1) are arranged, and each slide rail (1) has a slide rail screw (11) arranged along its length direction. A screw nut (12) is installed on the slide rail screw (11). At least one motor gearbox (2), the motor gearbox (2) includes a drive motor (21) and a first transmission gear set (22a), the output end of the drive motor (21) is meshed with the input end of the first transmission gear set (22a), and the output end of the first transmission gear set (22a) is meshed with the lead screw nut (12); When both slide rails (1) are equipped with motor gearboxes (2), the drive motors (21) of the two motor gearboxes (2) operate synchronously; or, a synchronizing rod (3) is connected between the first transmission gear sets (22a) of the two motor gearboxes (2). When only one of the slide rails (1) is equipped with the motor gearbox (2), the other slide rail (1) is equipped with an HDM gearbox (20), the HDM gearbox (20) includes a second transmission gear set (22b), a synchronizing rod (3) is connected between the output end of the first transmission gear set (22a) of the motor gearbox (2) and the input end of the second transmission gear set (22b), and the output end of the second transmission gear set (22b) is engaged with the lead screw nut (12) of the other slide rail (1).

2. The novel seat slide transmission structure according to claim 1, characterized in that, Both the first transmission gear set (22a) and the second transmission gear set (22b) include a first transmission gear (221), a second transmission gear (222), and a third transmission gear (223). The first transmission gear (221) meshes with the second transmission gear (222) and their axes are arranged parallel to each other. The second transmission gear (222) is connected to the third transmission gear (223) and arranged coaxially. The third transmission gear (223) meshes with the external teeth of the lead screw nut (12) and their axes are arranged perpendicular to each other.

3. The novel seat slide transmission structure according to claim 2, characterized in that, The first transmission gear (221), the second transmission gear (222) and the third transmission gear (223) are all helical gears, and the outer peripheral end of the lead screw nut (12) is provided with helical teeth.

4. The novel seat slide transmission structure according to claim 2, characterized in that, When both slide rails (1) are equipped with motor gearboxes (2) and no synchronizing rod (3) is provided, the output end of the drive motor (21) is connected to a drive gear (211), and the drive gear (211) meshes with the first transmission gear (221).

5. The novel seat slide transmission structure according to claim 2, characterized in that, The two ends of the synchronizing rod (3) are respectively provided with external spline structures (31).

6. The novel seat slide rail transmission structure according to claim 3, characterized in that, When both slide rails (1) are equipped with motor gearboxes (2) and synchronizing rods (3), the output end of the drive motor (21) is connected to a drive gear (211). A transition gear (28) is provided between the drive gear (211) and the first transmission gear (221). The transition gear (28) meshes with the drive gear (211). The transition gear (28) is coaxially arranged with the first transmission gear (221) and both are provided with internal spline structures (224). The external spline structure (31) of the synchronizing rod (3) is connected to the internal spline structures (224) of the transition gear (28) and the first transmission gear (221) respectively.

7. The novel seat slide rail transmission structure according to claim 3, characterized in that, When only one of the slide rails (1) is equipped with the motor gearbox (2), the output end of the drive motor (21) is connected to a drive gear (211). A transition gear (28) is provided between the drive gear (211) and the first transmission gear (221) of the first transmission gear set (22a). The transition gear (28) meshes with the drive gear (211). Both the transition gear (28) and the first transmission gear (221) are provided with an internal spline structure (224). The gear (28) is coaxially arranged with the first transmission gear (221) of the first transmission gear set (22a). The external spline structure (31) at one end of the synchronizing rod (3) is connected to the internal spline structure (224) of the transition gear (28) and the first transmission gear (221) of the first transmission gear set (22a), respectively. The external spline structure (31) at the other end of the synchronizing rod (3) is connected to the internal spline structure (224) of the first transmission gear (221) of the second transmission gear set (22b).

8. The novel seat slide rail transmission structure according to claim 1, characterized in that, The motor gearbox (2) further includes a first gearbox body (23), a first gearbox cover (24), and a motor mounting housing (25). The first transmission gear set (22a) and the lead screw nut (12) are installed between the first gearbox body (23) and the first gearbox cover (24), and the drive motor (21) is installed inside the motor mounting housing (25).

9. The novel seat slide rail transmission structure according to claim 1, characterized in that, The HDM gearbox (20) also includes a second gearbox body (26) and a second gearbox cover (27), with the second transmission gear set (22b) and the lead screw nut (12) installed between the second gearbox body (26) and the second gearbox cover (27).

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