Linear actuator

Abstract

The utility model discloses a linear actuator which comprises a motor and a transmission unit. The lead screw is driven by the power transmitted by the transmission unit to rotate, and the telescopic assembly is driven by the lead screw to do linear telescopic motion; the transmission unit comprises a shell and a planetary speed reducing mechanism contained in the shell, the planetary speed reducing mechanism comprises a sun gear, an inner gear ring fixedly arranged relative to the shell, a planetary retainer in transmission connection with the lead screw and a planetary gear rotationally installed on the planetary retainer, and the planetary gear is meshed between the sun gear and the inner gear ring; the lead screw freely penetrates through the sun gear, and the motor is used for driving the sun gear to rotate. A bearing step is arranged on the inner side of the shell and used for bearing the axial load thrust of the lead screw guided by the inner gear ring so as to prevent the planetary retainer, the planetary gear and the sun gear from bearing the axial load thrust of the lead screw.

Description

[Technical Field]

[0001] This utility model relates to the field of linear actuator technology. [Background Technology]

[0002] Linear actuators are widely used in various fields, including medical equipment, home and office applications, and solar power generation. Existing linear actuators include a motor, a transmission unit, a lead screw, and a telescopic assembly. The motor drives the lead screw to rotate through the transmission unit, and the telescopic assembly is driven by the lead screw to perform linear telescopic motion, thereby causing an object connected to the telescopic assembly to move linearly, achieving the driving purpose. Existing lead screws have a bearing at the tail end to withstand the axial load thrust. However, the bearing increases the length of the lead screw, increasing the difficulty of manufacturing it, and the increased length also makes it difficult to guarantee coaxiality during operation. [Utility Model Content]

[0003] The technical problem to be solved by this utility model is to overcome the shortcomings of the prior art and provide a linear actuator that bears the axial load thrust of the lead screw guided by the internal gear ring through the load-bearing step in the housing. This eliminates the need for the bearing at the tail of the lead screw, thereby shortening the length of the lead screw and improving the ease of machining and coaxiality during operation.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] Linear actuators, including:

[0006] Motors and drive units; and,

[0007] A lead screw and a telescopic assembly, wherein the lead screw is driven to rotate by power transmitted by a transmission unit, and the telescopic assembly is driven by the lead screw to perform linear telescopic motion;

[0008] The transmission unit includes a housing and a planetary reduction mechanism housed within the housing. The planetary reduction mechanism includes a sun gear, an internal gear ring fixed relative to the housing, a planetary cage connected to a lead screw drive, and planetary gears rotatably mounted on the planetary cage. The planetary gears mesh between the sun gear and the internal gear ring. The lead screw freely passes through the sun gear. The motor is used to drive the sun gear to rotate.

[0009] The inner side of the housing is provided with a load-bearing step to withstand the axial load thrust of the lead screw guided by the internal gear ring, so as to avoid the planetary cage, planet gears and sun gear being subjected to the axial load thrust of the lead screw.

[0010] In this invention, by providing a load-bearing step on the inner side of the housing, and having the load-bearing step bear the axial load thrust of the lead screw guided by the internal gear ring, the planetary cage, planet gears, and sun gear can be prevented from being subjected to the axial load thrust of the lead screw. This avoids damage to the sun gear, planet gears, and planetary cage due to the load thrust, or a reduction in transmission efficiency. In addition, the bearing at the tail of the lead screw in the prior art can be eliminated, thereby shortening the length of the lead screw and improving the ease of lead screw processing and coaxiality during operation.

[0011] In the aforementioned linear actuator, the linear actuator further includes a first torsion spring brake connected to the lead screw. The first torsion spring brake is located outside the transmission chain of the transmission unit. When the lead screw is subjected to a first directional actuating torque, the first torsion spring brake releases the first braking torsion spring to release the brake. When the lead screw is subjected to an axial load thrust torque, the first braking torsion spring brakes the first braking torsion spring to apply reverse braking to the lead screw. The first torsion spring brake is located between the telescopic assembly and the transmission unit and guides the axial load thrust of the lead screw to the internal gear ring. With this design, after the load is driven by the motor to a designated position and the motor stops working, the first torsion spring brake can be used to apply reverse braking to the lead screw to ensure the accuracy of the load's position.

[0012] In the above-mentioned linear actuator, the first torsion spring brake includes a first active torsion spring seat, a first driven torsion spring seat, a first braking torsion spring, and a first friction element that is circumferentially fixed relative to the housing. The first active torsion spring seat is connected to the lead screw and the two cannot rotate relative to each other. The first active torsion spring seat is used to bear the axial load thrust of the lead screw. The first braking torsion spring respectively hugs the first active torsion spring seat and the first driven torsion spring seat. The first driven torsion spring seat is subjected to the load thrust guided by the first braking torsion spring and maintains frictional engagement with the first friction element. The first directional actuation torque of the lead screw forces the first braking torsion spring to release the first active torsion spring seat. With this design, when the lead screw rotates in the first direction, it can drive the first active torsion spring seat to rotate synchronously, causing the first brake torsion spring to release the first active torsion spring seat, thereby preventing the torque from being transmitted to the first driven torsion spring seat. That is, the first active torsion spring seat rotates in the first direction, while the first driven torsion spring seat does not rotate, thus releasing the brake. When the lead screw is subjected to the load thrust torque, it will drive the first active torsion spring seat to rotate synchronously in the second direction, causing the first brake torsion spring to clamp the first active torsion spring seat and the first driven torsion spring seat. Since the first driven torsion spring seat is subjected to the load thrust and maintains frictional engagement with the first friction element, the first driven torsion spring seat will be unable to rotate in the second direction due to the friction braking force. That is, the first active torsion spring seat cannot rotate in the second direction, thus applying rotational braking to the lead screw in the second direction.

[0013] In the aforementioned linear actuator, the first torsion spring brake further includes a first thrust bearing axially supported between the first driving torsion spring seat and the first driven torsion spring seat. This design allows for smoother relative rotation between the first driving and driven torsion spring seats when the lead screw rotates under a first-direction actuating torque. Simultaneously, the first thrust bearing can bear the axial force, extending its service life.

[0014] In the aforementioned linear actuator, a first support seat axially supports the first torsion spring brake and the internal gear ring. The first support seat and the internal gear ring are circumferentially fixed. The first friction element is connected to the first support seat, and the two cannot rotate relative to each other. The load-bearing step is used to withstand the axial load thrust of the lead screw guided by the first torsion spring brake, the first support seat, and the internal gear ring. This design allows the first support seat to provide a mounting position for the first friction element, facilitating its installation.

[0015] In the aforementioned linear actuator, the first support seat has a groove adapted to the first friction element and / or the first driven torsion spring seat, serving as a centering and support for the first torsion spring brake. This design not only provides centering and support for the first torsion spring brake but also reduces axial space, thereby shortening the length of the lead screw and facilitating its machining.

[0016] In the aforementioned linear actuator, a second support is fitted onto the lead screw. The second support axially abuts against the internal gear ring to transmit the axial load thrust of the lead screw to the internal gear ring. The transmission unit includes a self-locking device that brakes the lead screw's rotation in a second direction under load torque. The self-locking device is located within the space formed by the internal gear ring, the second support, and the planetary cage. This design allows the lead screw to reverse direction after the load is driven to a designated position by the motor and the motor stops, ensuring the accuracy of the load's position. Furthermore, placing the self-locking device within the space formed by the internal gear ring, the second support, and the planetary cage makes the structure more compact, further reducing axial space and allowing for a shorter lead screw length, facilitating lead screw machining.

[0017] In the aforementioned linear actuator, the self-locking device includes a coupling transmission unit and a friction braking unit.

[0018] The coupled transmission unit includes an input component that is connected to the planetary cage transmission and an output component that is connected to the lead screw transmission. The output component is provided with a self-locking angle for synchronous rotation.

[0019] The friction braking unit includes a brake ring and a retaining ring on which a brake block is mounted. The internal gear ring is wrapped around the outside of the brake ring and the two cannot rotate relative to each other. The retaining ring is wrapped around the outside of the coupling transmission unit. The brake ring is relatively fixed around the outside of the retaining ring. The brake block rotates synchronously with the retaining ring in the circumferential direction. At least one of the brake block and the self-locking angle has a gradient surface that gradually moves away from the screw axis along a first direction.

[0020] When the input component is subjected to an actuating torque in a first direction, it drives the retaining ring and the output component to rotate synchronously.

[0021] When the output component is subjected to a load torque in the second direction, it drives the self-locking angle to rotate relative to the retaining ring in the second direction. The brake block is squeezed by the self-locking angle and moves radially outward to frictionally engage with the brake ring to perform friction braking.

[0022] When the input component is subjected to an actuating torque in the second direction, it causes the retaining ring to rotate in the second direction relative to the self-locking angle, thereby releasing the friction braking state in advance.

[0023] The first direction is opposite to the second direction.

[0024] Actuation torque refers to the torque provided by the motor. When the actuation torque causes the input component to rotate in the first direction, it drives the retaining ring and output component to rotate synchronously, thereby driving the lead screw to rotate and achieve linear displacement of the load. When the actuation torque is stopped, the load applies a reverse torque to the lead screw, causing the output component to rotate in the second direction under the load torque. This causes the self-locking angle to rotate relative to the retaining ring in the second direction. At this time, the brake block is squeezed by the self-locking angle and moves radially outward, thus frictionally engaging with the brake ring to implement friction braking, preventing the output component from continuing to rotate in the second direction, thereby preventing the lead screw from rotating. This prevents large displacement changes in the load and maintains stability. This verifies the accuracy of the load's location. Furthermore, when the input component is actuated by a torque in the second direction, the retaining ring rotates relative to the self-locking angle in the second direction, releasing the friction braking state in advance. That is, there is no frictional resistance between the brake block and the brake ring, thus reducing the motor's power consumption. In addition, by setting a brake block on the retaining ring and using the radial outward movement of the brake block to achieve self-locking performance through friction braking with the brake ring, not only is the axial space occupied small, reducing the length of the lead screw and thus lowering the machining difficulty of the lead screw, but the machining process of the brake ring and brake block is also more convenient. This ensures the controllability of the performance of the brake ring and brake block, thereby achieving better self-locking controllability.

[0025] In the aforementioned linear actuator, the portion of the output component surrounded by the retaining ring has a circumferential surface. The self-locking angle protrudes radially from the circumferential surface and has a first gradient surface facing the brake block. The brake block has a second gradient surface facing the first gradient surface. Both the first and second gradient surfaces gradually move away from the screw axis along a first direction. With this design, when the brake block is compressed by the self-locking angle, the cooperation of the first and second gradient surfaces allows the brake block to be radially pushed outwards as a whole, increasing the contact area between the brake block and the brake ring, thereby increasing the frictional braking force.

[0026] In the aforementioned linear actuator, the input component has multiple circumferentially spaced input keyways, the output component has multiple circumferentially spaced output keyways, and the retaining ring has multiple circumferentially spaced retaining keyways. The input keyways, retaining keyways, and output keyways engage alternately in sequence. This design enables circumferential transmission between the input component, output component, and retaining ring, resulting in higher transmission reliability and a more compact radial dimension after assembly.

[0027] In the above-mentioned linear actuator, when the input component is subjected to an actuating torque in a first direction, a first gap is formed between the input key and the retaining key;

[0028] When the output component is subjected to a load torque in a second direction, the first gap is eliminated and a second gap is formed between the output key and the retaining key;

[0029] When the input component is subjected to an actuating torque in a second direction, the second gap is eliminated and a third gap is formed between the output key and the input key.

[0030] This design allows the retaining ring to remain stationary while the output component is subjected to a load torque in the second direction, during the elimination of the first gap. The output component then drives the self-locking angle to rotate in the second direction, thus achieving rotation of the self-locking angle relative to the retaining ring in the second direction. Simultaneously, when the input component is subjected to an actuating torque in the second direction, the retaining ring drives the brake block to rotate relative to the self-locking angle in the second direction during the elimination of the second gap. This causes the brake block to move radially inward and reset, disabling frictional braking between the brake block and the brake ring. Consequently, the input component does not need to overcome braking force during subsequent rotation in the second direction under the actuating torque, thereby reducing motor power consumption. Finally, when the input component is subjected to an actuating torque in the first direction, the third gap is eliminated, and a first gap is formed between the input key and the retaining key.

[0031] In the above-mentioned linear actuator, the transmission unit further includes a worm gear and a worm shaft. The worm gear is connected to the sun gear and rotates synchronously, and the worm shaft is connected to the output shaft of the motor.

[0032] These features and advantages of the present invention will be disclosed in detail in the following specific embodiments and accompanying drawings. [Attached Image Description]

[0033] The present invention will be further described below with reference to the accompanying drawings:

[0034] Figure 1 This is a schematic diagram of the linear actuator in Embodiment 1 of this utility model;

[0035] Figure 2 This is an exploded view of the linear actuator in Embodiment 1 of this utility model;

[0036] Figure 3 This is an exploded view of the linear actuator section of the present invention in Embodiment 1.

[0037] Figure 4 This is a cross-sectional view of the linear actuator in Embodiment 1 of this utility model;

[0038] Figure 5 for Figure 4 A magnified view of part A in the diagram;

[0039] Figure 6 This is an exploded view of the planetary deceleration mechanism in Embodiment 1 of this utility model;

[0040] Figure 7 This is a schematic diagram of the structure of the first support seat in Embodiment 1 of this utility model;

[0041] Figure 8 This is an exploded view of the linear actuator portion of the structure in Embodiment 2 of this utility model;

[0042] Figure 9 This is a cross-sectional view of the linear actuator in Embodiment 1 of this utility model;

[0043] Figure 10 for Figure 9 A magnified view of part B in the diagram;

[0044] Figure 11 This is a schematic diagram of the input component in Embodiment 2 of this utility model;

[0045] Figure 12 This is a schematic diagram of the output component in Embodiment 2 of this utility model;

[0046] Figure 13 This is a schematic diagram of the structure of the retaining ring and the braking block in Embodiment 2 of this utility model;

[0047] Figure 14 This is an assembly diagram of the linear actuator part of the structure in Embodiment 2 of this utility model;

[0048] Figure 15 for Figure 14 The main view;

[0049] Figure 16 for Figure 14 Sectional view of CC;

[0050] Figure 17 for Figure 14 Sectional view of DD;

[0051] Figure 18 This is a schematic diagram showing the formation of a first gap between the input key teeth and the retaining key teeth in Embodiment 2 of this utility model;

[0052] Figure 19 This is a schematic diagram showing the formation of a second gap between the output key teeth and the retaining key teeth in Embodiment 2 of this utility model;

[0053] Figure 20 for Figure 14 Top view;

[0054] Figure 21 for Figure 20 A magnified view of part of E in the diagram;

[0055] Figure label:

[0056] 100. Motor; 200. Transmission unit; 210. Planetary reduction mechanism; 211. Sun gear; 212. Planet gears; 213. Planetary cage; 2130. Internal spline; 214. Internal gear ring; 2140. Body; 2141. Brake seat; 21411. Support step; 220. Coupling; 221. Driving coupling; 2210. External spline; 222. Driven coupling; 230. Housing; 2301. Half housing; 2302. Load-bearing step; 240. Worm; 250. Worm wheel; 300. Lead screw; 340. Second bearing; 400. Telescopic assembly; 410. Inner tube; 420. Outer tube; 430. Nut; 500. First torsion spring brake; 510. First brake torsion spring; 520. First driving torsion spring seat; 530. First driven torsion spring seat; 5 40. First friction element; 550. First thrust bearing; 600. Friction braking unit; 610. Brake ring; 620. Retaining ring; 621. Retaining key; 622. First limiting angle; 623. Second limiting angle; 624. Guide hole; 630. Braking block; 631. Second gradient surface; 710. First support seat; 711. First groove; 712. Second groove; 720. Second radial bearing; 730. Third thrust bearing; 800. Second support seat; 900. Coupling transmission unit; 910. Input component; 911. Input key; 912. Input keyway; 920. Output component; 921. Self-locking angle; 9210. First gradient surface; 9211. First limiting surface; 9212. Second limiting surface; 922. Output key; 1000. Limiting block;

[0057] 001, First gap; 002, Second gap; 003, Third gap.

Detailed Implementation Methods

[0058] This utility model provides a linear actuator, including:

[0059] Motors and drive units; and,

[0060] A lead screw and a telescopic assembly, wherein the lead screw is driven to rotate by power transmitted by a transmission unit, and the telescopic assembly is driven by the lead screw to perform linear telescopic motion;

[0061] The transmission unit includes a housing and a planetary reduction mechanism housed within the housing. The planetary reduction mechanism includes a sun gear, an internal gear ring fixed relative to the housing, a planetary cage connected to a lead screw drive, and planetary gears rotatably mounted on the planetary cage. The planetary gears mesh between the sun gear and the internal gear ring. The lead screw freely passes through the sun gear. The motor is used to drive the sun gear to rotate.

[0062] The inner side of the housing is provided with a load-bearing step to withstand the axial load thrust of the lead screw guided by the internal gear ring, so as to avoid the planetary cage, planet gears and sun gear being subjected to the axial load thrust of the lead screw.

[0063] In this invention, by providing a load-bearing step on the inner side of the housing, and having the load-bearing step bear the axial load thrust of the lead screw guided by the internal gear ring, the planetary cage, planet gears, and sun gear can be prevented from being subjected to the axial load thrust of the lead screw. This avoids damage to the sun gear, planet gears, and planetary cage due to the load thrust, or a reduction in transmission efficiency. In addition, the bearing at the tail of the lead screw in the prior art can be eliminated, thereby shortening the length of the lead screw and improving the ease of lead screw processing and coaxiality during operation.

[0064] The technical solutions of the embodiments of this utility model will be explained and described below with reference to the accompanying drawings. However, the following embodiments are only preferred embodiments of this utility model and not all of them. Based on the embodiments in the implementation, other embodiments obtained by those skilled in the art without creative effort are all within the protection scope of this utility model. In addition, it should be understood that the terms "upper," "lower," "left," "right," "longitudinal," "lateral," "inner," "outer," "vertical," "horizontal," "top," and "bottom," etc., indicating orientation or positional relationship, are only based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description. They are not intended to indicate or imply that the device / component must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0065] Example 1

[0066] like Figures 1 to 7 As shown, the linear actuator in this embodiment includes a motor 100, a transmission unit 200, a lead screw 300, and a telescopic assembly 400. The transmission unit 200 is connected between the motor 100 and the lead screw 300. The motor 100 drives the lead screw 300 to rotate through the transmission unit 200. The telescopic assembly 400 is driven by the lead screw 300 to perform linear telescopic motion. The telescopic assembly 400 includes an inner tube 410, an outer tube 420, and a nut 430. The nut 430 is fixedly disposed inside the inner tube 410 and threadedly connected to the lead screw 300. The nut 430 is circumferentially related to the inner tube 410. Fixed and axially fixed, the load is connected to the extendable end of the inner tube 410. In this embodiment, the linear actuator is mainly used as a push actuator. When the motor 100 drives the lead screw 300 to rotate in the first direction through the transmission unit 200, the nut 430 drives the inner tube 410 to move outward so that the telescopic component 400 extends, thereby pushing the load to a specified height. When the motor 100 drives the lead screw 300 to rotate in the second direction through the transmission unit 200, the nut 430 drives the inner tube 410 to move inward so that the telescopic component 400 shortens, thereby causing the load to move downward.

[0067] The transmission unit 200 in this embodiment includes a housing 230 and a planetary reduction mechanism 210. The housing 230 is assembled from two half-housings 2301 connected by screws. The planetary reduction mechanism 210 is housed within the housing 230. The planetary reduction mechanism 210 has a sun gear 211 with a through hole, planet gears 212, a planetary cage 213, and an internal gear ring 214. The planetary cage 213 is rotatably mounted within the housing 230. The sun gear 211 is rotatably mounted at the center of the planetary cage 213. Multiple planet gears 212 are rotatably mounted on the planetary cage 213, surrounding the sun gear 211 and meshing with it. The internal gear ring 214 surrounds the multiple planet gears 212 and meshes with them. The lead screw 300 includes a smooth shaft section and a threaded section. The smooth shaft section passes through the sun gear 211 and rotates with it, allowing the lead screw 300 to rotate and move freely relative to the sun gear 211. The threaded section is threadedly connected to the nut 430. The smooth shaft section and the threaded section are integrally machined or separately machined and then assembled. The sun gear 211 is driven to rotate by the motor 100, while the planetary cage 213 is connected to the lead screw 300. The internal gear ring 214 is fixed relative to the housing 230, meaning it cannot rotate or move axially relative to the housing 230. Thus, the power from the motor 100 is input through the sun gear 211, transmitted through the planetary gears 212, and output through the planetary cage 213, which drives the lead screw 300 to rotate. This design allows the high-speed rotation of the motor 100 to be reduced to the required low speed by the planetary reduction mechanism 210, adapting to the working needs of the mechanical equipment.

[0068] Furthermore, the housing 230 in this embodiment is provided with a load-bearing step 2302 on its inner side to bear the axial load thrust F1 of the lead screw 300 guided by the internal gear ring 214, so as to avoid the planetary cage 213, planet gear 212 and sun gear 211 being subjected to the axial load thrust F1 of the lead screw 300. This avoids the sun gear 211, planet gear 212 and planetary cage 213 being subjected to the load thrust F1 and being damaged or having their transmission efficiency reduced. In addition, the bearing at the tail of the lead screw in the prior art can be eliminated to shorten the length of the lead screw 300, thereby improving the ease of machining of the lead screw 300 and the coaxiality during operation.

[0069] Specifically, in this embodiment, the linear actuator also includes a first torsion spring brake 500 connected to the lead screw 300. The first torsion spring brake 500 is located outside the transmission chain of the transmission unit 200, that is, the first torsion spring brake 500 does not participate in the transmission. When the lead screw 300 is subjected to the first directional actuation torque, the first torsion spring brake 500 releases the first brake torsion spring 510 to release the brake. When the lead screw 300 is subjected to the axial load thrust torque, the first brake torsion spring 510 is tightened to apply reverse braking to the lead screw 300. The first torsion spring brake 500 is located between the telescopic component 400 and the transmission unit 200 and guides the axial load thrust F1 of the lead screw 300 to the internal gear ring 214. With this design, after the load is driven to a designated position by the motor 100 and the motor 100 stops working, the first torsion spring brake 500 can be used to reverse the braking of the lead screw 300 to ensure the accuracy of the load's position. For example, when the linear actuator is used as a lifting structure to control objects such as hospital beds or desktop platforms, it can prevent the hospital beds or desktop platforms from falling rapidly when the linear actuator is powered off, thus avoiding damage to patients on the hospital beds or items placed on the desktop platforms and ensuring the safety of using the linear actuator. It should be noted that when the motor 100 drives the lead screw 300 to rotate in the second direction through the transmission unit 200, it needs to overcome the self-locking force of the first torsion spring brake 500.

[0070] like Figures 3 to 5 As shown, the first torsion spring brake 500 in this embodiment includes, in addition to the first brake torsion spring 510, a first active torsion spring seat 520, a first driven torsion spring seat 530, and a first friction element 540. The first active torsion spring seat 520 is connected to the lead screw 300, and the two cannot rotate relative to each other. For example, the first active torsion spring seat 520 is provided with a non-circular hole, and the lead screw 300 is provided with a first non-circular segment that matches the non-circular hole. Alternatively, the first active torsion spring seat 520 and the lead screw 300 are connected by a spline. The first brake torsion spring 510 respectively hugs the first active torsion spring seat 520 and the first driven torsion spring seat 530. The first brake torsion spring 510 is axially limited between the first active torsion spring seat 520 and the first driven torsion spring seat 530. The first friction element 540 is axially and circumferentially... Both are fixed upwards. The first driven torsion spring seat 530 is located between the first driving torsion spring seat 520 and the first friction element 540. The lead screw 300 has a shoulder portion pressed onto the side of the first driving torsion spring seat 520 away from the first driven torsion spring seat 530, or is pressed onto the side of the first driving torsion spring seat 520 away from the first driven torsion spring seat 530 by other components, so that the first driving torsion spring seat 520 can bear the axial load thrust F1 of the lead screw 300. When the lead screw 300 is subjected to the axial load thrust F1, it will be transmitted to the first driven torsion spring seat 530 through the first driving torsion spring seat 520, so that the first driven torsion spring seat 530 will maintain frictional engagement with the first friction element 540 after being subjected to the load thrust F1, so as to implement reverse braking of the lead screw 300.

[0071] In this embodiment, the rotation direction of the lead screw 300 in the first direction is opposite to the rotation direction of the first brake torsion spring 510. For example, if the first brake torsion spring 510 is a left-handed torsion spring with a clockwise rotation, then the rotation direction of the lead screw 300 in the first direction is counterclockwise. When the lead screw 300 receives the actuating torque applied in the first direction by the motor 100, the lead screw 300 drives the first active torsion spring seat 520 to rotate synchronously in the first direction, which can cause the first brake torsion spring 510 to release the first active torsion spring seat 520, thereby avoiding the transmission of torque to the first driven torsion spring seat 530. That is, the first active torsion spring seat 520 rotates in the first direction, while the first driven torsion spring seat 530 does not rotate. At this time, the first driven torsion spring seat 530 and the first active torsion spring seat 520 rotate in the first direction. No frictional braking force is generated between the friction elements 540, thus releasing the brake. When the lead screw 300 is subjected to the load thrust torque, it will drive the first active torsion spring seat 520 to rotate synchronously in the second direction, that is, drive the first active torsion spring seat 520 to rotate clockwise. This will cause the first brake torsion spring 510 to hold the first active torsion spring seat 520 and the first driven torsion spring seat 530 tightly. Since the first driven torsion spring seat 530 is subjected to the load thrust F1 and maintains frictional engagement with the first friction element 540, the first driven torsion spring seat 530 will be unable to rotate in the second direction due to the frictional braking force. That is, the first active torsion spring seat 520 will be unable to rotate in the second direction, thus applying rotational braking to the lead screw 300 in the second direction.

[0072] Preferably, the first torsion spring brake 500 further includes a first thrust bearing 550, which is axially supported between the first active torsion spring seat 520 and the first driven torsion spring seat 530. This design allows for smoother relative rotation between the first active torsion spring seat 520 and the first driven torsion spring seat 530 when the lead screw 300 is subjected to a rotational actuation torque in the first direction. Simultaneously, the first thrust bearing 550 can bear the axial force, extending its service life.

[0073] Furthermore, in this embodiment, the planetary cage 213 drives the lead screw 300 to rotate via a coupling 220. The coupling 220 includes a driving coupling 221 and a driven coupling 222, both of which are ratchet structures. The planetary cage 213 includes an upper support and a lower support, with the planetary gear 212 rotatably mounted between the upper and lower supports. The upper support is provided with an internal spline 2130, and the outer periphery of the driving coupling 221 is provided with an external spline. 2210, so that the upper bracket and the driving coupling 221 are connected by a spline, or the upper bracket is provided with a non-circular hole, and the driving coupling 221 is provided with a non-circular part that matches the non-circular hole, thereby enabling the driving coupling 221 to rotate synchronously with the upper bracket in the circumferential direction. The inner side of the driven coupling 222 is connected to the lead screw 300 by a spline or by a non-circular hole and a non-circular segment, so that the driven coupling 222 and the lead screw 300 can maintain synchronous rotation in the circumferential direction and can move relative to each other in the axial direction.

[0074] Secondly, in this embodiment, a first support seat 710 axially supports the first torsion spring brake 500 and the internal gear ring 214. The first support seat 710 and the internal gear ring 214 are circumferentially fixed. The first friction element 540 is connected to the first support seat 710 and the two cannot rotate relative to each other. The coupling 220 passes through the first support seat 710 and partially extends into the clearance space formed by the first driving torsion spring seat 520 and the first driven torsion spring seat 530 to further reduce the axial space dimension, thereby further shortening the length of the lead screw 300 and facilitating the machining of the lead screw 300. The load-bearing step 2302 is used to bear the load thrust of the lead screw 300 guided by the first torsion spring brake 500, the first support seat 710 and the internal gear ring 214. The first support seat 710 has an axial clearance with the planetary cage 213 and the coupling 220 to prevent the first support seat 710 from transmitting the load thrust to the planetary cage 213. Therefore, by using the coupling 220 to maintain circumferential synchronous rotation with the lead screw 300 and to allow axial relative movement, the lead screw 300 can avoid transmitting the load thrust F1 to the planetary cage 213, planetary gears 212 and sun gear 211 via the coupling 220. This prevents the sun gear 211, planetary gears 212 and planetary cage 213 from being damaged or having their transmission efficiency reduced due to the load thrust. Then, the load thrust is guided to the load-bearing step 2302 on the housing 230 by the first torsion spring brake 500, the first support seat 710 and the internal gear ring 214, so that the housing 230 can bear the load thrust F1.

[0075] To achieve coaxiality between the planetary reduction mechanism 210 and the lead screw 300, in this embodiment, second radial bearings 720 are respectively provided between the two axial ends of the outer periphery of the internal gear ring 214 and the inner surface of the housing 230. The two second radial bearings 720 can axially fix the internal gear ring 214 and center it. In addition, a third thrust bearing 730 is provided between the load-bearing step 2302 and the adjacent second radial bearings 720. The third thrust bearing 730 can withstand axial force. The lower end of the internal gear ring 214 is connected to the load-bearing platform. The step 2302 may be in contact with or have an axial gap between them. The inner circumference of the internal gear ring 214 is provided with a limiting step. The first support seat 710 is clamped and fixed between the limiting step and the first torsion spring brake 500 to provide axial support for the first torsion spring brake 500 and the internal gear ring 214. Thus, the load thrust F1 can be guided through the first torsion spring brake 500, the first support seat 710 and the internal gear ring 214, the second radial bearing 720 and the third thrust bearing 730 to the load-bearing step 2302 on the housing 230.

[0076] Better, such as Figure 7 As shown, the first support seat 710 has a groove, which includes a first groove 711 adapted to the outer periphery of the bottom of the first driven torsion spring seat 530 and a second groove 712 provided on the bottom surface of the first groove 711 and in the shape of a polygon. The shape of the first friction element 540 is adapted to the shape of the second groove 712 so that the first friction element 540 is circumferentially fixed to the first support seat 710, and the bottom of the first driven torsion spring seat 530 is limited in the first groove 711, thereby being used for centering and supporting the first torsion spring brake 500. The bottom surfaces of the first driven torsion spring seat 530 and the second groove 712 cooperate to axially limit the first friction element 540. Furthermore, in this embodiment, the outer periphery of the first support seat 710 is splined with the internal gear ring 214 so that the first support seat 710 and the internal gear ring 214 are circumferentially fixed. Since the internal gear ring 214 is circumferentially fixed relative to the housing 230, the first support seat 710 and the first friction element 540 can be circumferentially fixed. By designing a groove to accommodate the first friction element 540 and at least part of the first driven torsion spring seat 530, the axial space can be reduced, thereby shortening the length of the lead screw 300 and facilitating the machining of the lead screw 300.

[0077] It is understood that in other embodiments of this utility model, the first support seat is only provided with a groove for adapting the first friction element, and the first driven torsion spring seat is supported on the end face of the first support seat.

[0078] Finally, the transmission unit 200 in this embodiment also includes a worm 240 and a worm wheel 250 that mesh with each other. The worm 240 is connected to the motor 100. The worm wheel 250 and the lead screw 300 are fitted on the outside of the sun gear 211 through a spline or interference fit so that the worm wheel 250 and the sun gear 211 can rotate synchronously in the circumference. This allows the worm wheel 250 to indirectly drive the lead screw 300 to rotate. The worm 240 is connected to the output shaft of the motor 100. Thus, the power of the motor 100 is transmitted to the sun gear 211 after being reduced by the worm wheel and worm gear. This further reduces the output speed of the planetary cage 213 and increases the output torque of the transmission unit 200, which means increasing the reduction ratio of the transmission unit 200. This can further meet the requirements of high thrust output.

[0079] It is understood that in other embodiments of this utility model, in the absence of a first torsion spring brake, the lead screw is provided with a shoulder portion that abuts axially against the internal gear ring or abuts axially against the internal gear ring through other components. In this case, the load-bearing step can be used to bear the axial load thrust of the lead screw guided by the internal gear ring.

[0080] It is understood that in other embodiments of this utility model, the planetary cage is directly connected to the lead screw through a spline engagement or a non-circular hole and non-circular segment engagement to achieve transmission.

[0081] Example 2

[0082] like Figures 8 to 21 As shown, compared with Embodiment 1, the difference in this embodiment is that a second support seat 800 is fitted on the lead screw 300, and the transmission unit 200 also includes a self-locking device for braking the lead screw 300 to rotate in the second direction under the action of load torque. The self-locking device participates in the transmission and is located in the space formed by the internal gear ring 214, the second support seat 800, and the planetary cage 213. The lead screw 300 is provided with a shoulder or threaded portion that abuts against the second support seat 800 axially, or abuts against the second support seat 800 axially through other components. The screw 300 is abutted against the internal gear ring 214 to transmit the axial load thrust of the screw 300 to the internal gear ring 214. With this design, after the load is driven by the motor 100 to a designated position and the motor 100 stops working, the screw 300 can be braked to reverse through the self-locking device to ensure the accuracy of the load position. In addition, the self-locking device is located in the space formed by the internal gear ring 214, the second support seat 800 and the planetary cage 213, which makes the structure more compact, further reduces the axial space, and can further shorten the length of the screw 300, which facilitates the machining of the screw 300.

[0083] Specifically, the self-locking device in this embodiment includes a friction braking unit 600 and a coupling transmission unit 900. The coupling transmission unit 900 includes an input component 910 and an output component 920. The input component 910 is connected to the planetary cage 213, while the output component 920 is connected to the lead screw 300. In this embodiment, the output component 920 is equivalent to the active coupling in the first embodiment. When it is connected to the driven coupling 222 provided on the lead screw 300, it remains circumferentially fixed and can move axially relative to it. In this embodiment, the output component 920 is provided with a synchronously rotating self-locking angle 921. The friction braking unit 600 includes a brake ring 610, a retaining ring 620, and a brake block 630. The brake block 630 is mounted on the retaining ring 620, which surrounds the outer side of the coupling transmission unit 900. The internal gear ring 214 surrounds the outer side of the brake ring 610, and the two cannot rotate relative to each other, so that the brake ring 610 is relatively fixed around the outer side of the retaining ring 620. The brake block 630 rotates synchronously with the retaining ring 620 in the circumferential direction. Both the brake block 630 and the self-locking angle 921 have a gradient surface that gradually moves away from the screw axis along the first direction.

[0084] When an actuating torque is applied in the first direction, the input component 910 drives the retaining ring 620 and the output component 920 to rotate synchronously.

[0085] When the output component 920 is subjected to a load torque in the second direction, it causes the self-locking angle 921 to rotate relative to the retaining ring 620 in the second direction. The brake block 630 is squeezed by the self-locking angle 921 and moves radially outward to frictionally engage with the brake ring 610 to perform friction braking.

[0086] When the input component 910 is subjected to an actuating torque in the second direction, it causes the retaining ring 620 to rotate in the second direction relative to the self-locking angle 921, thereby releasing the friction braking state in advance.

[0087] The actuating torque refers to the torque provided by the motor 100. When the actuating torque causes the input component 910 to rotate in the first direction, it drives the retaining ring 620 and the output component 920 to rotate synchronously, thereby driving the lead screw 300 to rotate. The rotation of the lead screw can drive the load to achieve linear displacement. When the actuating torque is stopped from being applied to the input component 910, the load will apply a reverse torque to the lead screw 300. Therefore, the output component 920 will rotate in the second direction under the action of the load torque, and the self-locking angle 921 will rotate relative to the retaining ring 620 in the second direction. At this time, the brake block... The brake block 630 is compressed by the self-locking angle 921 and moves radially outward, thereby frictionally engaging with the brake ring 610 to implement friction braking, preventing the output component 920 from continuing to rotate in the second direction, and thus preventing the lead screw 300 from rotating, thereby ensuring the accuracy of the load position; in addition, when the input component 910 is actuated by the second direction, the retaining ring 620 is driven to rotate in the second direction relative to the self-locking angle 921, thus releasing the friction braking state in advance, that is, there is no frictional resistance between the brake block 630 and the brake ring 610, thereby reducing the power consumption of the motor 100. Therefore, it can be seen that in this embodiment, by setting a brake block 630 on the retaining ring 620 and using the radial outward movement of the brake block 630 to frictionally brake with the brake ring 610, the self-locking performance is achieved. Compared with torsion spring braking, it not only occupies less axial space and can reduce the length of the lead screw to reduce the machining difficulty of the lead screw, but also the machining process of the brake ring 610 and brake block 630 is more convenient. This ensures the controllability of the performance of the brake ring 610 and brake block 630, and thus achieves better self-locking controllability.

[0088] In this embodiment, the internal gear ring 214 includes a body 2140 and a brake seat 2141 arranged and connected along the axial direction of the lead screw. The body 2140 and the brake seat 2141 are connected by a spline engagement or by integral machining so that they cannot rotate relative to each other. The body 2140 meshes with the planetary gear 212, and the brake seat 2141 is sleeved on the outside of the brake ring 610 and the two cannot rotate relative to each other. That is, the brake seat 2141 and the brake ring 610 are connected by a spline engagement or by integral machining.

[0089] like Figures 11 to 13 as well as Figure 17As shown, in this embodiment, the input component 910 is connected to the planetary cage 213 via a spline connection or a non-circular hole and non-circular groove connection, so that the input component 910 and the planetary cage 213 rotate synchronously in the circumferential direction. The input component 910 has a plurality of circumferentially spaced input key teeth 911, which protrude radially outward from the outer periphery of the input component 910. The output component 920 has a plurality of circumferentially spaced output key teeth 922, which protrude axially downward from the lower end face of the output component 920. The retaining ring 620 is formed by the production of multiple circumferentially spaced retaining key teeth 621. The retaining key teeth 621 protrude radially inward from the inner circumferential side of the retaining ring 620. The input key teeth 911, the retaining key teeth 621 and the output key teeth 922 mesh alternately in sequence, that is, the output key teeth 922 are located between the input key teeth 911 and the retaining key teeth 621. With this design, the input component 910, the output component 920 and the retaining ring 620 can be transmitted in the circumferential direction, which has higher transmission reliability and the three components are more compact in the radial direction after assembly.

[0090] like Figure 17 and Figure 18 As shown, in Figure 17 In the state where the input component 910 is subjected to an actuating torque in the first direction, the input component 910 rotates relative to the retaining ring 620 in the first direction to eliminate the third gap 003 until the input key 911 contacts the output key 922, thereby driving the output component 920 and the retaining ring 622 to rotate synchronously, so that the load moves to the specified position and the motor 100 stops working. At this time, a first gap 001 is formed between the input key 911 and the retaining key 621 (e.g., ...). Figure 18 (as shown); in Figure 18 In this state, the lead screw 300 will be subjected to a reverse torque applied by the load. At this time, the output component 920 will be driven by the lead screw 300 to rotate synchronously in the second direction through the output key 922 driving the input key 911. Initially, the retaining ring 620 is in a non-rotating state. Both the output component 920 and the input component 910 rotate relative to the retaining ring 620 to eliminate the first gap 001 and form a second gap 002 between the output key 922 and the retaining key 621 (e.g., Figure 19 As shown, during the process of the output component 920 rotating relative to the retaining ring 620 in the second direction to eliminate the first gap 001, the self-locking angle 921 applies a radially outward compressive force to the brake block 630, causing the brake block 630 to move radially outward and frictionally engage with the brake ring 610 to perform friction braking, thereby preventing the lead screw 300 from continuing to rotate and ensuring the accuracy of the load's position. Figure 19In the state where the motor 100 applies an actuating torque in the second direction to the input component 910, the output component 920 is initially in a non-rotating state. At this time, the input key 911 drives the retaining ring 620 to rotate relative to the output component 920, thereby eliminating the second gap 002 and forming a third gap 003 between the output key 922 and the input key 911 (e.g., Figure 17 As shown, during the process of the retaining ring 620 driving the brake block 630 to rotate relative to the output component 920 in the second direction, the brake block 630 will move radially inward to reset and fail to engage with the brake ring 610, thereby releasing the friction braking state in advance. When the retaining key 621 contacts the output key 922, it can drive the output component 920 to rotate synchronously in the second direction, thereby driving the lead screw 300 to rotate in the second direction. During this process, since there is no frictional resistance between the brake block 630 and the brake ring 610, the power consumption of the motor 100 can be reduced.

[0091] like Figure 10 and Figure 11 As shown, in this embodiment, an input keyway 912 with a bottom surface is formed between adjacent input key teeth 911. The retaining key teeth 621 are located in the input keyway 912 and are axially limited by the bottom surface and the output component 920. With this design, the retaining key teeth 621 are axially limited by the bottom surface and the output component 920, thereby indirectly achieving the axial limitation of the retaining ring 620. There is no need to rely on other structures to axially limit the retaining ring 620, thus simplifying the structure of the self-locking device.

[0092] Preferably, the retaining ring 620 overlaps with the axial projection of the input component 910, and the retaining ring 620 overlaps with the axial projection of the output component 920. The axial direction is parallel to the direction of the lead screw axis. This design can further reduce the axial dimension of the self-locking device, thereby reducing the axial space occupied by the self-locking device and shortening the length of the lead screw.

[0093] like Figures 12 to 13 ,as well as Figures 20 to 21 As shown, in this embodiment, the portion of the output component 920 surrounded by the retaining ring 620 has a circumferential surface. A self-locking angle 921 protrudes radially from the circumferential surface and has a first gradient surface 9210 facing the brake block 630. The brake block 630 has a second gradient surface 631 facing the first gradient surface 9210. Both the first gradient surface 9210 and the second gradient surface 631 gradually move away from the screw axis along a first direction. Figures 20 to 21As shown, when the output component 920 is subjected to a load torque in the second direction, it will drive the self-locking angle 921 to rotate relative to the retaining ring 620 in the second direction. At this time, the first gradient surface 9210 will gradually push the second gradient surface 631 to move radially outward. Through the cooperation of the first gradient surface 9210 and the second gradient surface 631, the brake block 630 can be pushed out radially as a whole to increase the contact area between the brake block 630 and the brake ring 610, thereby increasing the friction braking force.

[0094] Preferably, the self-locking angle 921 and the output component 920 are integrated into one structure. This design eliminates the need for assembly between the self-locking angle 921 and the output component 920, reducing assembly steps, and also improves the connection reliability and rotational synchronization between the self-locking angle 921 and the output component 920.

[0095] In this embodiment, the first gradient surface 9210 extends spirally or straight from the end near the lead screw axis to the end away from the lead screw axis; the second gradient surface 631 extends spirally or straight from the end near the lead screw axis to the end away from the lead screw axis. The first gradient surface 9210 and the second gradient surface 631 are adapted to each other. That is, when the first gradient surface 9210 extends spirally, the second gradient surface 631 also extends spirally; when the first gradient surface 9210 extends straight, the second gradient surface 631 extends straight. This design makes the process of the brake block 630 moving radially outward under the pressure of the self-locking angle 921 more stable.

[0096] In this embodiment, both the first gradient surface 9210 and the second gradient surface 631 extend in a spirally involute manner. The central angle of the first gradient surface 9210 relative to the screw axis is smaller than the central angle of the second gradient surface 631 relative to the screw axis. During the relative rotation of the output component 920 and the retaining ring 620, the first gradient surface 9210 is always located within the circumferential range of the second gradient surface 631. This is because: when the central angle of the first gradient surface 9210 relative to the screw axis is greater than the central angle of the second gradient surface 631 relative to the screw axis, part of the first gradient surface 9210 will abut against the inner side of the retaining ring 620. When the brake block 630 is squeezed by the self-locking angle 921, the first gradient surface 9210 will radially outward squeeze the inner side of the retaining ring 620 during the rotation in the second direction, causing the retaining ring 620 to break. This technical solution avoids the first gradient surface 9210 from contacting the inner side of the retaining ring 620, thereby avoiding the breakage of the retaining ring 620.

[0097] To ensure that the first gradient surface 9210 is always within the circumferential range of the second gradient surface 631, in this embodiment, a first limiting surface 9211 and a second limiting surface 9212 are formed at the two circumferential ends of the self-locking angle 921, respectively. A first limiting angle 622 and a second limiting angle 623 are circumferentially spaced on the inner ring surface of the retaining ring 620. The first limiting angle 622 is located in the radial direction of one end of the braking block 630 and forms circumferential interference with the first limiting surface 9211. The second limiting angle 623 is located in the radial direction of the other end of the braking block 630 and forms circumferential interference with the second limiting surface 9212. This design limits the rotation angle of the self-locking angle 921 through the first limiting angle 622 and the second limiting angle 623, ensuring that the first gradient surface 9210 is always within the circumferential range of the second gradient surface 631 during the relative rotation of the output component 920 and the retaining ring 620.

[0098] To form the aforementioned first limiting angle 622 and second limiting angle 623, the retaining ring 620 in this embodiment is provided with a guide hole 624 adapted to the brake block 630. The guide hole 624 extends from the inner ring surface of the retaining ring 620 to the outer ring surface. The brake block 630 is fitted into the guide hole 624. The brake block 630 and the retaining ring 620 maintain circumferential synchronous rotation and can move radially relative to each other. The first limiting angle 622 is formed between one axial sidewall of the guide hole 624 and the inner ring surface of the retaining ring 620, and the second limiting angle 623 is formed between the other axial sidewall and the inner ring surface of the retaining ring 620. By designing the guide hole 624, the brake block 630 can move radially and the brake block 630 and the retaining ring 620 can rotate circumferentially synchronously. The structure is relatively simple and the assembly is relatively convenient. In addition, the brake block 630 can be independently machined to facilitate the individual replacement of the brake block 630 in the later stage, thereby reducing maintenance costs.

[0099] like Figure 10As shown, in order to achieve axial limiting of the brake block 630, a limiting block 1000 is provided on one side of the brake block 630 in this embodiment. The brake seat 2141 is provided with a support step 21411 that is higher than the top surface of the brake block 630. The limiting block 1000 is supported on the support step 21411 and has a gap with the top surface of the brake block 630. In this way, the axial limiting of the brake block 630 is achieved by the limiting block 1000 cooperating with the bottom wall of the guide hole 624. There is a gap between the limiting block 1000 and the brake block 630, which can avoid The two contact each other, thus facilitating the radial movement of the brake block 630. The second bearing 340 is located on the support step 21411 and supported on the top of the limit block 1000. The second support seat 800 is supported on the second bearing 340. The second bearing 340 is a thrust bearing capable of withstanding axial force. Thus, the axial load thrust of the lead screw can be guided through the second support seat 800 to the load-bearing step 2302 on the housing 230 via the second bearing 340, the internal gear ring 214, the second radial bearing 720 and the third thrust bearing 730.

[0100] It is understood that in other embodiments of this utility model, the brake block and the retaining ring form an integral structure, and the brake block can produce elastic deformation when squeezed by the gradient surface. This design allows the output component to be made of elastic material, and when part of the output component is squeezed by the self-locking angle, it will produce radially outward elastic deformation, thereby enabling friction braking with the brake ring.

[0101] It is understood that in other embodiments of this utility model, the self-locking angle is provided with a first gradient surface, while the braking block is not provided with a second gradient surface; or, the braking block is provided with a second gradient surface, while the self-locking angle is not provided with a first gradient surface.

[0102] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Those skilled in the art should understand that this utility model includes, but is not limited to, the content described in the accompanying drawings and the specific embodiments above. Any modifications that do not depart from the functional and structural principles of this utility model will be included within the scope of the claims.

Claims

1. A linear actuator, including: Motor and transmission unit; as well as, A lead screw and a telescopic assembly, wherein the lead screw is driven to rotate by power transmitted by a transmission unit, and the telescopic assembly is driven by the lead screw to perform linear telescopic motion; The transmission unit is characterized in that it includes a housing and a planetary reduction mechanism housed within the housing. The planetary reduction mechanism includes a sun gear, an internal gear ring fixedly disposed relative to the housing, a planetary cage connected to a lead screw drive, and planetary gears rotatably mounted on the planetary cage. The planetary gears mesh between the sun gear and the internal gear ring. The lead screw freely passes through the sun gear, and the motor is used to drive the sun gear to rotate. The inner side of the housing is provided with a load-bearing step to withstand the axial load thrust of the lead screw guided by the internal gear ring, so as to avoid the planetary cage, planet gears and sun gear being subjected to the axial load thrust of the lead screw.

2. The linear actuator as claimed in claim 1, characterized in that, The linear actuator further includes a first torsion spring brake connected to the lead screw. The first torsion spring brake is located outside the transmission chain where the transmission unit is located. When the lead screw is subjected to a first directional actuation torque, the first torsion spring brake releases the first brake torsion spring to release the brake. When the lead screw is subjected to an axial load thrust torque, the first brake torsion spring tightens to apply reverse braking to the lead screw. The first torsion spring brake is located between the telescopic assembly and the transmission unit and guides the axial load thrust of the lead screw to the internal gear ring.

3. The linear actuator as described in claim 2, characterized in that, The first torsion spring brake includes a first active torsion spring seat, a first driven torsion spring seat, a first braking torsion spring, and a first friction element fixed circumferentially relative to the housing. The first active torsion spring seat is connected to the lead screw and the two cannot rotate relative to each other. The first active torsion spring seat is used to bear the axial load thrust of the lead screw. The first braking torsion spring respectively hugs the first active torsion spring seat and the first driven torsion spring seat. The first driven torsion spring seat is subjected to the load thrust guided by the first braking torsion spring and maintains frictional engagement with the first friction element. The first directional actuating torque of the lead screw forces the first braking torsion spring to release the first active torsion spring seat.

4. The linear actuator as described in claim 3, characterized in that, The first torsion spring brake further includes a first thrust bearing axially supported between the first driving torsion spring seat and the first driven torsion spring seat.

5. The linear actuator as claimed in claim 3, characterized in that, The first torsion spring brake and the internal gear ring are provided with a first support seat that axially supports both of them. The first support seat and the internal gear ring are circumferentially fixed. The first friction element is connected to the first support seat and the two cannot rotate relative to each other. The load-bearing step is used to bear the axial load thrust of the lead screw guided by the first torsion spring brake, the first support seat and the internal gear ring.

6. The linear actuator as claimed in claim 5, characterized in that, The first support has a groove adapted to the first friction element and / or the first driven torsion spring seat for centering and supporting the first torsion spring brake.

7. The linear actuator as claimed in claim 1, characterized in that, The lead screw is fitted with a second support seat, which axially abuts against the internal gear ring to transmit the axial load thrust of the lead screw to the internal gear ring. The transmission unit includes a self-locking device that brakes the lead screw to rotate in a second direction under the action of load torque. The self-locking device is located in the space formed by the internal gear ring, the second support seat and the planetary cage.

8. The linear actuator as claimed in claim 7, characterized in that, The self-locking device includes a coupling transmission unit and a friction braking unit. The coupled transmission unit includes an input component that is connected to the planetary cage transmission and an output component that is connected to the lead screw transmission. The output component is provided with a self-locking angle for synchronous rotation. The friction braking unit includes a brake ring and a retaining ring on which a brake block is mounted. The internal gear ring is wrapped around the outside of the brake ring and the two cannot rotate relative to each other. The retaining ring is wrapped around the outside of the coupling transmission unit. The brake ring is relatively fixed around the outside of the retaining ring. The brake block rotates synchronously with the retaining ring in the circumferential direction. At least one of the brake block and the self-locking angle has a gradient surface that gradually moves away from the screw axis along a first direction. When the input component is subjected to an actuating torque in a first direction, it drives the retaining ring and the output component to rotate synchronously; when the output component is subjected to a load torque in a second direction, it drives the self-locking angle to rotate relative to the retaining ring in the second direction, and the brake block is squeezed by the self-locking angle and moves radially outward to frictionally engage with the brake ring to perform friction braking; When the input component is subjected to an actuating torque in the second direction, it causes the retaining ring to rotate in the second direction relative to the self-locking angle, thereby releasing the friction braking state in advance. The first direction is opposite to the second direction.

9. The linear actuator as claimed in claim 8, characterized in that, The output component has a circumferential surface surrounded by a retaining ring. The self-locking angle protrudes radially from the circumferential surface and has a first gradient surface facing the brake block. The brake block has a second gradient surface facing the first gradient surface. Both the first gradient surface and the second gradient surface gradually move away from the screw axis along a first direction.

10. The linear actuator as claimed in claim 8, characterized in that, The input component has multiple circumferentially spaced input key teeth, the output component has multiple circumferentially spaced output key teeth, and the retaining ring has multiple circumferentially spaced retaining key teeth. The input key teeth, retaining key teeth, and output key teeth engage alternately in sequence.

11. The linear actuator as claimed in claim 10, characterized in that, When the input component is subjected to an actuating torque in a first direction, a first gap is formed between the input key teeth and the retaining key teeth; When the output component is subjected to a load torque in a second direction, the first gap is eliminated and a second gap is formed between the output key and the retaining key; When the input component is subjected to an actuating torque in a second direction, the second gap is eliminated and a third gap is formed between the output key and the input key.

12. The linear actuator as claimed in any one of claims 1 to 11, characterized in that, The transmission unit also includes a worm gear and a worm shaft. The worm gear is connected to the sun gear and rotates synchronously, and the worm shaft is connected to the output shaft of the motor.

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