Linear actuator with self-locking function

Abstract

The utility model discloses a linear actuator with a self-locking function. The linear actuator comprises a screw rod; an actuating unit; the fixed torsion spring seat is mounted in the linear actuator in a non-rotating manner; the transmission torsion spring seat comprises an outer transmission ring and an inner transmission ring driven by the actuating unit to rotate, a transmission key is arranged on the inner transmission ring, and the transmission key is provided with a cam surface; the outer transmission ring is provided with a plurality of key grooves, the transmission keys can be meshed in the key grooves in a relatively rotating mode, so that the outer transmission ring and the inner transmission ring synchronously rotate after relatively rotating by a preset angle, and the outer transmission ring is provided with a movable unlocking element corresponding to the cam face. The screwing direction of the braking torsion spring is opposite to the forward rotation actuating torque direction, and the braking torsion spring tightly holds and fixes the torsion spring seat and the outer transmission ring and is used for implementing self-locking when the lead screw generates the reverse rotation trend caused by the load torque; when the inner transmission ring is driven by reverse actuating torque to rotate relative to the outer transmission ring, the unlocking element is extruded through the cam surface, and the brake torsion spring is pushed by the unlocking element to generate radial expansion.

Description

TECHNICAL FIELD

[0001] The utility model relates to linear actuator technical field especially linear actuator with self locking function. BACKGROUND

[0002] The linear actuator in prior art includes screw rod, actuating unit and telescopic assembly, the actuating unit selectively outputs positive rotation actuating torque and reverse rotation actuating torque to drive the screw rod to rotate reversely, and the telescopic assembly is driven by the screw rod to make linear telescopic motion. The linear actuator usually has self locking function to avoid the screw rod from rotating when the actuating unit stops running under the action of external load, which leads to the phenomenon of lock loss of the linear actuator. The linear actuator in prior art basically adopts the mode of clamping by torsional spring, that is, when the screw rod reverses under the action of external force, the frictional resistance is generated to the reverse rotation of the screw rod by the clamping of the torsional spring to realize the braking of the screw rod. This leads to the problems of serious heating, reduced efficiency and high power consumption when the actuating unit drives the screw rod to reverse. SUMMARY

[0003] The utility model provides a linear actuator with self locking function to overcome the defects of prior art, which can effectively reduce the frictional force between the braking torsional spring and the transmission torsional spring seat when the actuating unit drives the screw rod to reverse, thereby reducing the heating and energy consumption and improving the efficiency.

[0004] To solve the above technical problems, the utility model adopts the following technical scheme:

[0005] The linear actuator with self locking function comprises:

[0006] a screw rod;

[0007] an actuating unit selectively outputting positive rotation actuating torque and reverse rotation actuating torque to drive the screw rod to rotate reversely;

[0008] The linear actuator further comprises:

[0009] a fixed torsional spring seat fixedly installed in the linear actuator;

[0010] a transmission torsional spring seat comprising an outer transmission ring transmissionally connected to the screw rod and synchronously rotating with the screw rod and an inner transmission ring driven to rotate by the actuating unit and arranged in the outer transmission ring, a plurality of transmission keys being arranged on the inner transmission ring in a circumferential direction, at least one transmission key being provided with a cam surface, the outer transmission ring being provided with a plurality of key grooves, the plurality of transmission keys being relatively rotatably engaged in the plurality of key grooves to make the outer transmission ring and the inner transmission ring synchronously rotate after relatively rotating by a predetermined angle, and a movable unlocking element being arranged on the outer transmission ring corresponding to the cam surface;

[0011] The brake torsion spring is arranged in a tightening direction opposite to the positive rotation actuating torque direction, and grips the fixed torsion spring seat and the outer transmission ring respectively, and is used to keep the gripping state of the outer transmission ring and implement self-locking when the screw rod generates a reverse rotation tendency caused by the load torque; the inner transmission ring is driven to rotate relative to the outer transmission ring by the cam surface extruding the unlocking element, and the brake torsion spring is pushed by the unlocking element to generate radial expansion.

[0012] In the linear actuator, the actuating unit applies positive rotation actuating torque to the inner transmission ring to make the inner transmission ring and the outer transmission ring rotate positively, and the positive rotation of the outer transmission ring drives the screw rod to rotate positively, and at this time, the positive rotation of the outer transmission ring does not promote the brake torsion spring to tighten because the tightening direction of the brake torsion spring is opposite to the positive rotation actuating torque direction, so the actuating unit does not need to overcome a large friction force when driving the screw rod to rotate positively.

[0013] When the screw rod generates a reverse rotation tendency caused by the load torque, the screw rod drives the outer transmission ring to rotate reversely, and because the reverse rotation direction of the outer transmission ring is the same as the gripping direction of the brake torsion spring, the reverse rotation of the outer transmission ring promotes the brake torsion spring to grip the outer transmission ring and the fixed torsion spring seat to implement braking of the outer transmission ring, and further implement self-locking.

[0014] When the actuating unit applies reverse rotation actuating torque to the inner transmission ring to drive the screw rod to rotate reversely, the inner transmission ring can drive the outer transmission ring to rotate synchronously after rotating relative to the outer transmission ring by a predetermined angle, and in the process of relative rotation, the inner transmission ring extrudes the unlocking element through the cam surface, so that the brake torsion spring is pushed by the unlocking element to generate radial expansion, and because the contact area between the expanded brake torsion spring and the outer transmission ring is reduced, the friction force between them is reduced, and further, the heat generated by friction when the screw rod is driven to rotate reversely by the actuating unit is reduced, and the energy consumption of the actuating unit is also reduced and the efficiency is improved.

[0015] Finally, when the actuating unit applies positive rotation actuating torque to the inner transmission ring again, the inner transmission ring can drive the outer transmission ring to rotate synchronously after rotating relative to the outer transmission ring by a predetermined angle, and in the process of relative rotation, the unlocking element is reset by the brake torsion spring to drive the brake torsion spring to retract and reset, so as to ensure that the brake torsion spring grips the outer transmission ring and the fixed torsion spring seat to implement self-locking when the screw rod generates a reverse rotation tendency caused by the load torque.

[0016] In the linear actuator with self-locking function, the at least one transmission key is provided with a radially outward protruding tooth-shaped part, the protruding height of the tooth-shaped part is unidirectionally increased in the positive rotation actuating torque direction, a cam surface is formed on the tooth-shaped part and gradually away from the axis of the inner transmission ring in the positive rotation actuating torque direction, the circumferential groove wall of the key groove is provided with a tooth groove, the depth of the tooth groove is unidirectionally increased in the positive rotation actuating torque direction, and the tooth-shaped part is engaged in the tooth groove and can rotate relatively. In this way, the radial driving of the unlocking element can be realized through the cam surface. When the inner transmission ring is driven to reverse by the actuating unit, the part of the cam surface with higher protruding height gradually approaches the unlocking element to drive the unlocking element to move radially outward and make the brake torsional spring radially expand. When the inner transmission ring is driven to rotate positively by the actuating unit, the part of the cam surface with lower protruding height gradually approaches the unlocking element to make the unlocking element move radially inward under the compression of the brake torsional spring and reset. The structure of the cam surface is relatively simple and convenient to process.

[0017] In the linear actuator with self-locking function, the relative rotation angle of the transmission key in the key groove is less than or equal to the relative rotation angle of the tooth-shaped part in the tooth groove. In this way, it can be ensured that the inner transmission ring is in contact with the outer transmission ring through the transmission key to drive the outer transmission ring to rotate synchronously when the inner transmission ring rotates positively or reversely, and the tooth-shaped part is prevented from being damaged by driving the outer transmission ring to rotate alone, thereby prolonging the service life of the tooth-shaped part.

[0018] In the linear actuator with self-locking function, the outer transmission ring includes an outer ring surface and a guide hole for accommodating the unlocking element, the tooth groove has a slope surface facing the cam surface, the guide hole penetrates from the outer ring surface to the slope surface to form an outer port on the outer ring surface and an inner port on the slope surface, in the self-locking state, the slope surface and the cam surface are circumferentially misaligned, the unlocking element is partially protruded from the inner port under the compression of the brake torsional spring, and the inner transmission ring is driven to rotate relative to the outer transmission ring through the cam surface to extrude the unlocking element and make the unlocking element partially protrude from the outer port to push the brake torsional spring to radially expand. In this way, by ensuring that the unlocking element partially protrudes from the inner port, the inner transmission ring can drive the unlocking element to move radially outward to make it partially protrude from the outer port to push the brake torsional spring to radially expand, and after the slope surface and the cam surface are circumferentially misaligned, the unlocking element can move radially inward to reset by the brake torsional spring pressing the part of the unlocking element protruding from the outer port.

[0019] In the linear actuator with self-locking function, the opening width of the outer port and the inner port is set to only allow part of the unlocking element to pass through. In this way, the unlocking element can be limited to exit the guide hole through the inner port and the outer port, and the installation reliability of the unlocking element is improved.

[0020] In the linear actuator with self-locking function, the surface friction coefficient of the unlocking element is less than the surface friction coefficient of the outer transmission ring. In this way, after the brake torsion spring is pushed to expand radially by the unlocking element, the friction between the brake torsion spring and the unlocking element can be reduced, and the heat generated by friction can be further reduced.

[0021] In the linear actuator with self-locking function, the unlocking element rotates synchronously with the outer transmission ring and can rotate relative to the outer transmission ring, and the unlocking element pushes the brake torsion spring to expand radially and generates rolling friction with the brake torsion spring. In this way, the friction between the brake torsion spring and the unlocking element can be further reduced, and the heat generated by friction can be further reduced.

[0022] In the linear actuator with self-locking function, the unlocking element is a cylinder or a sphere. In this way, the structure is simple and the cost is low.

[0023] In the linear actuator with self-locking function, the unlocking element extends axially on the outer transmission ring, and the axial length of the unlocking element is greater than or equal to the axial length of the part of the brake torsion spring that clamps the outer transmission ring. In this way, when the axial length of the unlocking element is less than the axial length of the part of the brake torsion spring that clamps the outer transmission ring, some of the brake torsion springs will not expand radially because they are not pushed by the unlocking element, and some of the brake torsion springs will still clamp the outer transmission ring, resulting in more heat generated by the reverse rotation of the lead screw. The present technical solution can further reduce the heat generated by friction.

[0024] In the linear actuator with self-locking function, the cam surface and the unlocking element are distributed in multiple groups along the circumference of the transmission torsion spring seat, so that the brake torsion spring can be pushed by multiple unlocking elements to completely separate from the outer transmission ring. In this way, the brake torsion spring can be completely separated from the outer periphery of the outer transmission ring, and the brake torsion spring only contacts the unlocking element, thereby further reducing the friction and the heat generated by friction.

[0025] In the linear actuator with self-locking function, the actuating unit includes a motor, a worm gear assembly and a planetary gear assembly connected in sequence, the planetary carrier of the planetary gear assembly is in transmission connection with the inner transmission ring, and the worm gear of the worm gear assembly, the planetary gear assembly, the transmission torsion spring seat and the lead screw are coaxially transmitted. In this way, multi-stage reduction can be achieved to reduce the high-speed rotation of the motor to the required low speed to meet the working requirements of the linear actuator.

[0026] In the linear actuator with self-locking function, the linear actuator further comprises a housing which houses at least the fixed torsion spring seat, the transmission torsion spring seat and the planetary gear assembly, the lead screw extends through one end of the housing, the other end of the housing is provided with a tail pulling component, the tail pulling component and the inner ring of the planetary gear assembly are axially supported by a support seat, the lead screw has an axial shoulder which abuts against the outer transmission ring, the outer transmission ring is rotatably supported on the inner ring of the planetary gear assembly, and the axial load thrust of the lead screw is guided to the tail pulling component through the outer transmission ring, the inner ring and the support seat. In the prior art, a bearing is arranged at the tail of the lead screw to bear the axial load thrust of the lead screw. Such a design makes the length of the lead screw longer, thereby increasing the difficulty of processing and the concentricity during operation. The present technical solution changes the transmission path of the axial load thrust, thereby omitting the bearing at the tail of the lead screw to shorten the length of the lead screw, thereby improving the processing convenience of the lead screw and the concentricity during operation.

[0027] In the linear actuator with self-locking function, the planetary cage and the inner transmission ring are connected by a shaft coupling, the shaft coupling comprises a driving shaft coupling, a driven shaft coupling and a return spring, the driving shaft coupling rotates synchronously with the planetary cage, the driven shaft coupling is connected to the inner transmission ring in a circumferential fixed and axial movable manner, the driving shaft coupling and the driven shaft coupling are connected in a circumferential fixed and axial movable manner, the outer transmission ring is connected to the lead screw in a circumferential fixed and axial movable manner, the driven shaft coupling is rotatably sleeved on the tail of the lead screw and is axially limited by a retaining ring, and the return spring acts on the driven shaft coupling to keep the driven shaft coupling engaged with the driving shaft coupling. In this way, when the motor drives the lead screw to retract the inner tube of the linear actuator and clamp an object or a human body, the lead screw drives the driven shaft coupling to move outward and disconnects the driving shaft coupling, thereby cutting off the transmission of the actuating torque, the lead screw stops rotating, the inner tube stops retracting, and the anti-clamping effect is achieved. When the clamped object or human body is removed, the lead screw is reset under the action of the return spring to reconnect the driven shaft coupling and the driving shaft coupling, so that the linear actuator resumes normal operation.

[0028] In the linear actuator with self-locking function, the linear actuator further comprises a release torsion spring and an operable release unit, the inner ring gear of the planetary gear assembly is clamped by the release torsion spring to limit rotation, and the release unit activates the release function of the linear actuator by driving the release torsion spring to loosen the inner ring gear and driving the brake torsion spring to loosen the outer transmission ring. In this way, when the release torsion spring clamps the inner ring gear to implement the rotation locking of the inner ring gear in the normal state, the actuating torque can be transmitted to the inner transmission ring by the planetary carrier, so that the screw rod can rotate normally. When the screw rod needs to be quickly released, the rotation locking of the inner ring gear by the release torsion spring can be released by driving the release torsion spring by the release unit, and the brake torsion spring is driven to loosen the outer transmission ring to activate the release function of the linear actuator. In this way, the inner ring gear and the outer transmission ring can rotate freely. In this case, the planetary gear assembly does not transmit power, so that the screw rod can be quickly rotated by pushing and pulling the screw rod to make the telescopic assembly quickly extend and retract, thereby realizing the quick release function without the need of motor driving, and being suitable for the case of motor failure or power failure or other cases of cutting off power.

[0029] In the linear actuator with self-locking function, the release unit comprises a control rod, a gear driven to rotate by the control rod and a tooth ring engaged with the gear, the linear actuator has a fixing sleeve for fixing the torsion spring seat, the tooth ring is rotatably sleeved outside the fixing sleeve, one torsion spring leg of the release torsion spring and one torsion spring leg of the brake torsion spring are hung on the tooth ring, and the rotation of the tooth ring synchronously loosens the release torsion spring and the brake torsion spring. In this way, when the release function of the linear actuator needs to be activated, the rotation of the tooth ring can be realized by driving the gear to rotate by the control rod, and the release torsion spring and the brake torsion spring are synchronously loosened by the rotation of the tooth ring, so as to activate the release function of the linear actuator. The operation is simple and convenient, and the release speed of the screw rod depends on the rotation angle of the tooth ring, so that the release speed of the screw rod can be controlled by controlling the rotation angle of the tooth ring.

[0030] These features and advantages of the present application will be described in detail in the following specific embodiments and drawings.

DRAWINGS

[0031] The present application will be further described below with reference to the drawings:

[0032] Figure 1 It is a front view of the linear actuator in the first embodiment of the present application.

[0033] Figure 2 It is Figure 1 A-A sectional view in the middle.

[0034] Figure 3 It is Figure 2 A local enlarged schematic view of B.

[0035] Figure 4A sectional view of the linear actuator in the embodiment one of the utility model;

[0036] Figure 5 For Figure 4 A partial enlarged schematic view of C;

[0037] Figure 6 An exploded schematic view of part structure in the embodiment one of the utility model;

[0038] Figure 7 A structure schematic view of the outer transmission ring in the embodiment one of the utility model;

[0039] Figure 8 For Figure 6 A structure schematic view of each component after assembly in the embodiment one of the utility model;

[0040] Figure 9 A structure schematic view of the linear actuator after removing the shell in the embodiment one of the utility model;

[0041] Figure 10 A sectional view when the motor drives the screw rod reversely in the embodiment one of the utility model;

[0042] Figure 11 For Figure 10 A partial enlarged schematic view of D.

[0043] Reference signs:

[0044] 100, screw rod; 110, baffle ring; 120, shaft shoulder; 200, actuating unit; 210, motor; 220, worm and gear assembly; 221, worm wheel; 222, worm; 230, planetary gear assembly; 231, sun gear; 232, planetary gear; 233, planetary carrier; 234, inner ring gear; 300, telescopic assembly; 310, inner tube; 320, outer tube; 330, nut; 400, fixed torsional spring seat; 500, transmission torsional spring seat; 510, outer transmission ring; 511, key groove; 512, tooth groove; 5120, slope surface; 513, outer annular surface; 514, guide hole; 5141, outer port; 5142, inner port; 515, insertion section; 5150, non-circular hole; 516, exposed section; 520, inner transmission ring; 521, transmission key; 522, cam surface; 523, toothed part; 530, unlocking element; 600, brake torsional spring; 700, shaft coupling; 710, driving shaft coupling; 720, driven shaft coupling; 721, first transmission protrusion; 722, second transmission protrusion; 730, return spring; 800, shell; 810, fixed sleeve; 900, tail pulling component; 1000, support seat; 1100, release torsional spring; 1200, release unit; 1210, operating lever; 1220, gear; 1230, tooth ring.

DETAILED DESCRIPTION

[0045] The utility model provides a linear actuator with self locking function, include:

[0046] Lead screw;

[0047] Actuating unit, can select the output positive rotation actuating torque and reverse rotation actuating torque to drive lead screw positive and negative rotation;

[0048] The linear actuator further includes:

[0049] Fixed torsional spring seat, it is not rotatablely installed in linear actuator;

[0050] Transmission torsional spring seat, it includes the outer transmission ring of transmission connection to lead screw and synchronous rotation with lead screw and the inner transmission ring of being arranged in the outer transmission ring and being driven to rotate by actuating unit, a plurality of transmission keys are arranged on the inner transmission ring and are spaced apart in the circumference, at least one transmission key is equipped with cam surface;The outer transmission ring is equipped with a plurality of key grooves, a plurality of transmission keys are relatively rotatablely engaged in a plurality of key grooves, so that the outer transmission ring and the inner transmission ring generate synchronous rotation after relative rotation of predetermined angle, the outer transmission ring is equipped with movable unlocking element corresponding to the cam surface;

[0051] Brake torsional spring, it is set to the direction of screwing and the direction of positive rotation actuating torque is opposite, brake torsional spring is embraced tightly fixed torsional spring seat and outer transmission ring respectively, is used to keep the embrace state of outer transmission ring when lead screw generates the reverse tendency caused by load torque and implements self locking;The inner transmission ring is extruded unlocking element by cam surface in the process of being driven to rotate relative to the outer transmission ring by reverse rotation actuating torque, and the brake torsional spring is pushed by unlocking element and generates radial expansion.

[0052] The linear actuator in the utility model uses, and actuating unit applies positive rotation actuating torque to the inner transmission ring, so that the inner transmission ring and the outer transmission ring positive rotation, and the positive rotation of outer transmission ring drives lead screw positive rotation, at this time, because the direction of screwing of brake torsional spring and the direction of positive rotation actuating torque are opposite, therefore the positive rotation of outer transmission ring will not promote brake torsional spring screwing, thus actuating unit does not need to overcome great friction when driving lead screw positive rotation;

[0053] When lead screw generates the reverse tendency caused by load torque, lead screw will drive outer transmission ring reverse rotation, because the reverse rotation direction of outer transmission ring and the embrace direction of brake torsional spring are same, therefore will promote brake torsional spring embrace outer transmission ring and fixed torsional spring seat by the reverse rotation of outer transmission ring and implement the brake of outer transmission ring, and then implement self locking;

[0054] When the actuation unit applies a reverse actuation torque to the inner transmission ring to drive the lead screw to reverse, the inner transmission ring will rotate relative to the outer transmission ring by a predetermined angle before it can drive the outer transmission ring to rotate synchronously. During the relative rotation between the two, the inner transmission ring squeezes the unlocking element through the cam surface, causing the brake torsion spring to be pushed by the unlocking element to generate radial expansion. Since the contact area between the expanded brake torsion spring and the outer transmission ring is reduced, the friction between the two is reduced, thereby reducing the heat generated by friction when the lead screw is driven to reverse by the actuation unit. At the same time, the energy consumption of the actuation unit is reduced and the efficiency is improved.

[0055] Finally, when the actuation unit applies forward actuation torque to the inner drive ring again, the inner drive ring will rotate relative to the outer drive ring by a predetermined angle before driving the outer drive ring to rotate synchronously. During the relative rotation between the two, the unlocking element is reset by the pressure of the brake torsion spring, thereby driving the brake torsion spring to retract and reset, so as to ensure that when the screw generates a reverse tendency caused by the load torque, the brake torsion spring will hold the outer drive ring and the fixed torsion spring seat to implement self-locking.

[0056] 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.

[0057] Example 1

[0058] like Figures 1 to 11 As shown, the linear actuator with self-locking function in this embodiment includes a lead screw 100, an actuation unit 200, a telescopic assembly 300, a fixed torsion spring seat 400, a transmission torsion spring seat 500, and a braking torsion spring 600. The actuation unit 200 can selectively output forward and reverse actuation torques to drive the lead screw 100 to rotate forward and backward. The telescopic assembly 300 includes an inner tube 310, an outer tube 320, and a nut 330. The nut 330 is fixed inside the inner tube 310 and threadedly connected to the lead screw 100. The nut 330 is circumferentially and axially fixed relative to the inner tube 310. The actuation unit 200 drives the lead screw 100 to rotate forward and backward, which can cause the nut 330 to drive the inner tube 310 to move axially relative to the outer tube 320, thereby extending and retracting the telescopic assembly 300.

[0059] The fixed torsion spring seat 400 in the embodiment is non-rotatably installed in the linear actuator, the transmission torsion spring seat 500 comprises an outer transmission ring 510 which is transmissionally connected to the lead screw 100 and synchronously rotates with the lead screw 100, and an inner transmission ring 520 which is arranged in the outer transmission ring 510 and is driven to rotate by the actuating unit 200, a plurality of transmission keys 521 are arranged on the inner transmission ring 520 in a circumferential direction, at least one transmission key 521 is provided with a cam surface 522, the outer transmission ring 510 is provided with a plurality of key grooves 511, the plurality of transmission keys 521 are relatively rotatably engaged in the plurality of key grooves 511, so that the outer transmission ring 510 and the inner transmission ring 520 synchronously rotate after a relative rotation of a predetermined angle, and the outer transmission ring 510 is provided with a movable unlocking element 530 corresponding to the cam surface 522;

[0060] The brake torsion spring 600 is arranged in a tightening direction opposite to the positive rotation actuating torque direction, and the brake torsion spring 600 tightly holds the fixed torsion spring seat 400 and the outer transmission ring 510, respectively, so as to implement self-locking when the lead screw 100 generates a reverse rotation tendency caused by a load torque, and the brake torsion spring 600 is pushed by the unlocking element 530 to generate radial expansion.

[0061] When the linear actuator in the embodiment is used, the actuating unit 200 applies a positive rotation actuating torque to the inner transmission ring 520, so as to make the inner transmission ring 520 and the outer transmission ring 510 rotate in a positive direction, and the positive rotation of the outer transmission ring 510 drives the lead screw 100 to rotate in a positive direction, at this time, since the tightening direction of the brake torsion spring 600 is opposite to the positive rotation actuating torque direction, the positive rotation of the outer transmission ring 510 does not promote the tightening of the brake torsion spring 600, and therefore the actuating unit 200 does not need to overcome a large frictional force when driving the lead screw 100 to rotate in a positive direction.

[0062] When the lead screw 100 generates a reverse rotation tendency caused by a load torque, the lead screw 100 drives the outer transmission ring 510 to rotate in a reverse direction, and since the reverse rotation direction of the outer transmission ring 510 is the same as the holding direction of the brake torsion spring 600, the reverse rotation of the outer transmission ring 510 promotes the brake torsion spring 600 to hold the outer transmission ring 510 and the fixed torsion spring seat 400, so as to implement braking of the outer transmission ring 510, and further implement self-locking.

[0063] When the actuating unit 200 applies a reverse rotation actuating torque to the inner transmission ring 520 to drive the screw rod 100 to reverse rotation, the inner transmission ring 520 can drive the outer transmission ring 510 to rotate synchronously after rotating a predetermined angle relative to the outer transmission ring 510. In the process of relative rotation, the inner transmission ring 520 extrudes the unlocking element 530 through the cam surface 521, so that the brake torsional spring 600 is pushed by the unlocking element 530 to expand radially. Since the contact area between the expanded brake torsional spring 600 and the outer transmission ring 510 is reduced, the friction therebetween is reduced, thereby reducing the heat generated by friction when the screw rod 100 is subsequently driven to reverse rotation by the actuating unit 200, and also reducing the energy consumption of the actuating unit 200 and improving the efficiency.

[0064] Finally, when the actuating unit 200 applies a positive rotation actuating torque to the inner transmission ring 520 again, the inner transmission ring 520 can drive the outer transmission ring 510 to rotate synchronously after rotating a predetermined angle relative to the outer transmission ring 510. In the process of relative rotation, the unlocking element 530 is reset under the pressure of the brake torsional spring 600, thereby driving the brake torsional spring 600 to retract and reset, so as to ensure that when the screw rod 100 has a reverse rotation trend caused by a load torque, the brake torsional spring 600 tightly holds the outer transmission ring 510 and the fixed torsional spring seat 400 to implement self-locking.

[0065] Specifically, as shown in FIG. 6, the inner transmission ring 520 is provided with a plurality of cam surfaces 521, and the unlocking element 530 is provided with a plurality of cam grooves 531 corresponding to the cam surfaces 521. Figures 2 to 6As shown, the brake torsion spring 600 in the embodiment is left-handed, and the transmission key 521 is arranged one-to-one with the key groove 511, and the central angle of the transmission key 521 is smaller than the central angle of the key groove 511, so that the inner transmission ring 520 can drive the outer transmission ring 510 to rotate synchronously after rotating a predetermined angle. At least one toothed portion 523 is arranged on the transmission key 521, and preferably, at least one toothed portion 523 is arranged on each transmission key 521. In the embodiment, two toothed portions 523 are arranged on each transmission key 521 at intervals in the circumferential direction, and the protruding height of the toothed portion 523 increases in the positive rotation direction of the actuating torque, so that the outer side surface of the toothed portion 523 forms the cam surface 522 which gradually moves away from the axis of the inner transmission ring 520 in the positive rotation direction of the actuating torque. The tooth groove 512 is arranged on the circumferential groove wall of the key groove 511, and the radial depth of the tooth groove 512 increases in the positive rotation direction of the actuating torque. The central angle of the tooth groove 512 is larger than the central angle of the toothed portion 523, so that the toothed portion 523 is engaged in the tooth groove 512 and can rotate relatively, and the unlocking element 530 can move in the radial direction of the outer transmission ring 510. In this way, the radial driving of the unlocking element 530 can be realized through the cam surface 522. When the actuating unit 200 drives the inner transmission ring 520 to rotate reversely, the part of the cam surface 522 with a higher protruding height gradually approaches the unlocking element 530, so as to drive the unlocking element 530 to move outward in the radial direction and make the brake torsion spring 600 expand radially. When the actuating unit 200 drives the inner transmission ring 520 to rotate positively, the part of the cam surface 522 with a lower protruding height gradually approaches the unlocking element 530, so as to make the unlocking element 530 move inward in the radial direction under the compression of the brake torsion spring 600 and reset the brake torsion spring 600. The structure of the cam surface 522 in the scheme is relatively simple and convenient to process.

[0066] In addition, in the embodiment, the maximum protruding height of the toothed portion 523 is smaller than the protruding height of the outer circumferential surface of the transmission key 521 from the outer circumferential surface of the inner transmission ring 520, so as to reduce the outer diameter of the inner transmission ring 520. The relative rotation angle of the transmission key 521 in the key groove 511 is smaller than or equal to the relative rotation angle of the toothed portion 523 in the tooth groove 512, that is, the difference a between the central angle of the key groove 511 and the central angle of the transmission key 521 is smaller than or equal to the difference b between the central angle of the tooth groove 512 and the central angle of the toothed portion 523. In this way, it can be ensured that the inner transmission ring 520 drives the outer transmission ring 510 to rotate synchronously through the contact between the two sides of the transmission key 521 and the outer transmission ring 510 when the inner transmission ring 520 rotates reversely or positively, and the toothed portion 523 is prevented from being damaged by driving the outer transmission ring 510 to rotate alone, thereby prolonging the service life of the toothed portion 523.

[0067] As Figures 2 to 3 , Figure 7As shown, in order to achieve the radial movement of the unlocking element 530 mounted on the outer transmission ring 510, the outer transmission ring 510 of the present embodiment comprises an outer ring surface 513 and a guide hole 514 for accommodating the unlocking element 530, the tooth groove 512 has a slope surface 5120 facing the cam surface 522, the guide hole 514 penetrates from the outer ring surface 513 to the slope surface 5120, and forms an outer port 5141 on the outer ring surface 513 and an inner port 5142 on the slope surface 5120, the unlocking element 530 moves radially along the guide hole 514 and can partially protrude from the outer port 5141 or partially protrude from the inner port 5142, in the self-locking state of the brake torsion spring 600 clamping the outer transmission ring 510 and the fixed torsion spring seat 400, the slope surface 5120 and the cam surface 522 are circumferentially misaligned, i.e. the shallowest part of the depth of the slope surface 5120 is circumferentially misaligned with the shallowest part of the protrusion height of the cam surface 522, so that the unlocking element 530 can be radially moved inward and partially protrude from the inner port 5142 under the pressure of the brake torsion spring 600, and during the rotation of the inner transmission ring 520 driven by the reverse rotation actuating torque applied by the actuating unit 200 relative to the outer transmission ring 510, the unlocking element 530 can be radially extruded outward by the cam surface 522, so that the unlocking element 530 is radially moved outward and partially protrudes from the outer port 5141 to push the brake torsion spring 600 to expand radially (as shown in FIG. 6B). Figure 11 ) Thus, by ensuring that the unlocking element 530 partially protrudes from the inner port 5142, the inner transmission ring 520 can drive the unlocking element 530 to move radially outward and partially protrude from the outer port 5141 to push the brake torsion spring 600 to expand radially, and after the circumferential misalignment of the slope surface 5120 and the cam surface 522, the part of the unlocking element 530 protruding from the outer port 5141 can be radially moved inward under the pressure of the brake torsion spring 600 to reset.

[0068] wherein the opening width of the outer port 5141 and the inner port 5142 is set to only allow part of the unlocking element 530 to pass through. Thus, the unlocking element 530 can be limited from escaping from the guide hole 514 through the inner port 5142 and the outer port 5141, and the installation reliability of the unlocking element 530 is improved.

[0069] In this embodiment, the unlocking element 530 rotates synchronously with the outer drive ring 510 and can rotate relative to the outer drive ring 510. To simplify the structure of the unlocking element 530 and reduce manufacturing costs, the unlocking element 530 in this embodiment is a cylinder or a sphere. By rotating relative to the outer drive ring 510, the unlocking element 530 pushes the brake torsion spring 600 to expand radially. When the outer drive ring 510, driven by the actuation unit 200, causes the unlocking element 530 to reverse, rolling friction occurs between the unlocking element 530 and the brake torsion spring 600. Compared to sliding friction, this further reduces the frictional force between the brake torsion spring 600 and the unlocking element 530, thereby further reducing the heat generated by friction.

[0070] like Figure 5 and Figure 7 As shown, when the unlocking element 530 is a cylinder or a sphere, the opening widths of the outer port 5141 and the inner port 5142 are smaller than the outer diameter of the unlocking element 530, so that only a portion of the unlocking element 530 can pass through. To facilitate the assembly of the unlocking element 530 into the guide hole 514, in this embodiment, the guide hole 514 is open at one end facing the fixed torsion spring seat 400. The unlocking element 530 is inserted into the guide hole 514 through this end, and then the fixed torsion spring seat 400 limits its movement to prevent the unlocking element 530 from coming out of the guide hole 514. In this embodiment, the outer transmission ring 510 includes an insertion section 515 inserted into the fixed torsion spring seat 400 and an exposed section 516 located outside the fixed torsion spring seat 400. A radial bearing is provided between the insertion section 515 and the fixed torsion spring seat 400 to allow the insertion section 515 to rotate with the fixed torsion spring seat 400. The insertion section 515 is provided with a non-circular hole 5150, and the lead screw 100 is provided with a non-circular shaft section that mates with the non-circular hole 5150, so that the insertion section 515 and the lead screw 100 form a connection that is circumferentially fixed and axially movable. The guide hole 514 is provided on the exposed section 516. In order to further reduce the outer diameter of the exposed section 516, in this embodiment, the outer periphery of the insertion section 515 is... A clearance groove corresponding to the guide hole 514 is provided on the side to reduce the area of ​​the guide hole 514 opening on the end face of the exposed section 516, thereby reducing the outer diameter of the exposed section 516. After the unlocking element 530 is installed in the guide hole 514, the end face of the fixed torsion spring seat 400 abuts against the end face of the exposed section 516 or there is a small gap between them, which can prevent the unlocking element 530 from coming out of the guide hole 514. The braking torsion spring 600 is partially held tightly on the outside of the fixed torsion spring seat 400 and partially held tightly on the outside of the exposed section 516. The upper torsion spring foot of the braking torsion spring 600 is connected to the fixed torsion spring seat 400, and the lower torsion spring foot is circumferentially fixed or can move within a certain range of circumferential direction.

[0071] In order to further reduce the friction between the brake torsion spring 600 and the unlocking element 530, the surface friction coefficient of the unlocking element 530 in the embodiment is less than the surface friction coefficient of the outer transmission ring 510, so as to further reduce the heat generated by friction.

[0072] Preferably, the unlocking element 530 in the embodiment is a cylindrical body, and the unlocking element 530 extends axially on the outer transmission ring. The axial length of the unlocking element 530 is greater than or equal to the axial length of the part of the brake torsion spring 600 that clamps the outer transmission ring 510, that is, the axial length of the unlocking element 530 is greater than or equal to the axial length of the part of the exposed section 516 clamped by the brake torsion spring 600. The reason for this design is that when the axial length of the unlocking element 530 is less than the axial length of the part of the brake torsion spring 600 clamping the outer transmission ring 510, part of the brake torsion spring 600 will not be radially expanded due to not being pushed by the unlocking element 530, thereby part of the brake torsion spring 600 is still clamped on the outer transmission ring 510, resulting in more heat generated between the brake torsion spring 600 and the outer transmission ring 510 when the lead screw 100 is reversed. The technical solution can further reduce the heat generated by friction.

[0073] It can be understood that in other embodiments of the utility model, the unlocking element can also be a cylindrical body with a rectangular cross section, and the guide hole can be a rectangular hole. In this way, the unlocking element can also drive the brake torsion spring to expand radially to reduce the contact area between the brake torsion spring and the outer transmission ring, thereby reducing the heat generated by friction.

[0074] Preferably, the cam surface 522 and the unlocking element 530 in the embodiment are uniformly distributed in multiple groups in the circumferential direction of the transmission torsion spring seat 500. One cam surface 522 and one unlocking element 530 form a group, and the number of groups is at least three. In this way, the brake torsion spring 600 can be pushed by multiple unlocking elements 530 to completely separate from the outer transmission ring 510, so that the brake torsion spring 600 only contacts the unlocking element 530, thereby further reducing the friction and the heat generated by friction.

[0075] Furthermore, the actuating unit 200 in the embodiment comprises a motor 210, a worm and gear assembly 220 and a planetary gear assembly 230 connected in sequence, the worm and gear assembly 220 comprises a worm wheel 221 and a worm 222 engaged, the worm 222 is in driving connection with the output shaft of the motor 210, while the worm wheel 221, the planetary gear assembly 230, the transmission torsion spring seat 500 and the lead screw 100 are coaxially driven, the planetary gear assembly 230 comprises a sun gear 231, a planet gear 232, a planet carrier 233 and an inner ring gear 234, the planet carrier 233 is in driving connection with the inner transmission ring 520, the planet gear 232 is rotatably installed on the planet carrier 233, a plurality of planet gears 232 are arranged outside the sun gear 231 and engaged with the sun gear 231, the worm wheel 221 is sleeved outside the sun gear 231 and is in driving connection with the sun gear 231 through spline or interference fit, so that the worm wheel 221 and the sun gear 231 can rotate synchronously, while the inner ring gear 234 is arranged outside the plurality of planet gears 232 and engaged with the planet gears 232, when the motor 210 drives the inner transmission ring 520 to rotate in the positive direction through the worm and gear assembly 220 and the planetary gear assembly 230, the inner ring gear 234 is in a locked state in the circumferential direction, at this time, the power of the motor 210 is input through the worm and gear assembly 220 and the sun gear 231, then is transmitted through the planet gear 232 and is output by the planet carrier 233, the planet carrier 233 drives the lead screw 100 to rotate through the inner transmission ring 520 and the outer transmission ring 510. Such design can realize multi-stage speed reduction, so as to reduce the high-speed rotation of the motor 210 to the required low speed, so as to adapt to the working requirements of the linear actuator.

[0076] As Figure 5 and Figure 6As shown, the planetary holder 233 in the embodiment is drivingly connected with the inner transmission ring 520 through a coupling 700, which includes a driving coupling 710, a driven coupling 720 and a return spring 730. The driving coupling 710 is kept synchronous rotation with the planetary holder 233 through non-circular fitting such as spline. The driven coupling 720 is connected with the inner transmission ring 520 in a way that they are fixed in circumference and movable in axial direction. The driving coupling 710 and the driven coupling 720 are connected in a way that they are fixed in circumference and movable in axial direction. For example, the outer circumference of the driving coupling 710 is connected with the planetary holder 233 through spline. The outer circumference of the driven coupling 720 is provided with a first transmission protrusion 721 and a second transmission protrusion 722 distributed along the axial direction of the driven coupling 720. The driving coupling 710 is sleeved on the outer side of the driven coupling 720. The inner circumference of the driving coupling 710 is spline-fitted with the first transmission protrusion 721. The second transmission protrusion 722 is spline-fitted with the inner circumference of the inner transmission ring 520. The driven coupling 720 is rotatably sleeved on the tail of the lead screw 100. The tail of the lead screw 100 is provided with a stop ring 110 through a screw (not shown in the figure). The outer diameter of the stop ring 110 is larger than the inner diameter of the driven coupling 720 and smaller than the inner diameter of the driving coupling 710, so that the stop ring 110 stops the driven coupling 720 to limit the axial movement. The return spring 730 is press-fitted between the fixed torsional spring seat 400 and the driven coupling 720, so that the driven coupling 720 is kept connected with the driving coupling 710 in the engaged state. This design is because, when the motor 210 drives the lead screw 100 to retract the inner tube 310 to clamp an object or a human body, the nut 330 cannot move axially, so that the lead screw 100 is forced to move axially outward relative to the nut 330. The outward movement of the lead screw 100 drives the driven coupling 720 to move axially outward relative to the inner transmission ring 520, so that the driven coupling 720 is disconnected from the driving coupling 710 to cut off the transmission of the actuating torque. The lead screw 100 stops rotating, and the inner tube 310 stops retracting, achieving the anti-clamping effect. When the clamped object or human body is removed, the lead screw 100 is reset under the action of the return spring 730 to reconnect the driven coupling 720 and the driving coupling 710, so that the linear actuator resumes normal operation.

[0077] Further, the linear actuator in the embodiment also comprises a housing 800, which houses the fixed torsion spring seat 400, the transmission torsion spring seat 500, the motor 210, the worm and gear assembly 220 and the planetary gear assembly 230, the lead screw 100 extends out of one end of the housing 800, and a tail pulling component 900 is installed at the other end of the housing 800, and the tail pulling component 900 and the inner ring 234 have a support seat 1000 therebetween, the support seat 1000 axially supports the tail pulling component 900 and the inner ring 234, a thrust bearing is arranged between the support seat 1000 and the inner ring 234, and a radial bearing is arranged between the inner ring 234 and the housing 800, so that the inner ring 234 can rotate relative to the housing 800. The lead screw 100 has an axial shoulder 120 abutting against the outer transmission ring 510, and a thrust bearing is arranged between the exposed section 516 and the inner ring 234, so that the outer transmission ring 510 is supported on the inner ring 234 in a relative rotation manner, and in addition, a radial bearing is arranged between the exposed section 516 and the inner ring 234, so that when the lead screw 100 is subjected to a load thrust, it is guided to the tail pulling component 900 through the outer transmission ring 510, the inner ring 234 and the support seat 1000. In the prior art, the lead screw needs to pass through the planetary gear assembly and set a bearing at the end close to the tail pulling component, the bearing is supported on the tail pulling component, and the axial load thrust of the lead screw is borne by the bearing and transmitted to the tail pulling component, such a design makes the length of the lead screw longer, thereby increasing the processing difficulty and the working concentricity, while the technical solution can shorten the length of the lead screw 100 and save the bearing at the tail end, by arranging the transmission torsion spring seat 500 on the side of the planetary gear assembly 230 away from the tail pulling component 900, and changing the transmission path of the axial load thrust to make the tail pulling component 900 bear the load thrust, thereby improving the processing convenience of the lead screw 100 and the working concentricity.

[0078] In addition, as Figures 5 to 9As shown, the linear actuator in the embodiment further comprises a release torsion spring 1100 which normally holds the inner ring 234 to restrict its rotation to achieve circumferential locking of the inner ring 234, and a release unit 1200 which activates the release function of the linear actuator by driving the release torsion spring 1100 to release the inner ring 234 and driving the brake torsion spring 600 to release the outer transmission ring 510. In this way, when the release torsion spring 1100 normally holds the inner ring 234 to implement rotation locking of the inner ring 234, the actuating torque can be transmitted to the inner transmission ring 520 by the planetary holder 233 to enable normal rotation of the lead screw 100, and when it is necessary to quickly release the lead screw 100, the release function of the linear actuator is activated by driving the release torsion spring 1100 to release the rotation locking of the inner ring 234 by the release unit 1200 and driving the brake torsion spring 600 to release the outer transmission ring 510, so that the inner ring 234 and the outer transmission ring 510 can rotate freely. In this case, the planetary wheel assembly 230 does not transmit power, so that the lead screw 100 can be quickly rotated by pushing and pulling the lead screw 100 to make the telescopic assembly 300 quickly extend and retract, thereby achieving the quick release function without the need for the motor 210 to drive, which is suitable for situations where the motor 210 fails or is powered off or other situations where power needs to be cut off.

[0079] The release unit 1200 in the embodiment comprises a handle 1210, a gear 1220 and a tooth ring 1230, wherein the handle 1210 extends along the axial direction of the screw rod 100 and is located outside the outer tube 320, a fixed sleeve 810 is fixedly installed in the shell 800, the fixed torsional spring seat 400 is fixedly connected with the fixed sleeve 810 through screw connection or welding, the tooth ring 1230 is rotatably sleeved outside the fixed sleeve 810, a fixed shaft perpendicular to the screw rod 100 is arranged between the fixed sleeve 810 and the shell 800, the gear 1220 is rotatably installed on the fixed shaft, the gear 1220 is engaged with the tooth ring 1230, one end of the handle 1210 is rotatably connected with the gear 1220 through a pin, so that the handle 1210 drives the gear 1220 to rotate after the handle 1210 is pulled, wherein the rotation directions of the release torsional spring 1100 and the brake torsional spring 600 are opposite, that is, the release torsional spring 1100 is right-handed, the lower torsional spring foot of the release torsional spring 1100 is fixed to the shell 800, the upper torsional spring foot of the release torsional spring 1100 is hung on the tooth ring 1230, the lower torsional spring foot of the brake torsional spring 600 passes through the fixed sleeve 810 and is hung on the tooth ring 1230, the upper torsional spring foot of the release torsional spring 1100 and the lower torsional spring foot of the brake torsional spring 600 are driven to rotate in the direction of untwisting of the respective torsional springs by rotating the gear 1220 driven by the handle 1210, that is, the release torsional spring 1100 and the brake torsional spring 600 are simultaneously untwisted, that is, the lower torsional spring foot of the brake torsional spring 600 in the scheme is movable within a certain range in the circumferential direction. In this way, when the release function of the linear actuator needs to be activated, the gear 1220 is driven to rotate by the handle 1210, so that the tooth ring 1230 is driven to rotate, the tooth ring 1230 is simultaneously untwisted with the release torsional spring 1100 and the brake torsional spring 600, so as to activate the release function of the linear actuator, which is simple and convenient to operate; and the release speed of the screw rod 100 depends on the rotation angle of the tooth ring 1230, so that the release speed of the screw rod 100 can be controlled by controlling the rotation angle of the tooth ring 1230; after the handle 1210 is untwisted, the release torsional spring 1100 and the brake torsional spring 600 drive the tooth ring 1230 to rotate and reset under the action of the self-restoring force.

[0080] It can be understood that in other embodiments of the utility model, when the linear actuator does not have the quick release function, the release unit and the release torsional spring can be omitted, at this time the lower torsional spring foot of the brake torsional spring is connected with the shell to realize circumferential fixation.

[0081] The above is only a specific implementation of the utility model, but the protection scope of the utility model is not limited to this, and those skilled in the art should understand that the utility model includes but is not limited to the contents described in the drawings and the above specific implementation. Any modification not deviating from the functional and structural principles of the utility model shall be included in the scope of claims.

Claims

1. A linear actuator with self-locking function, comprising: a screw rod; an actuating unit, which selectively outputs a forward rotation actuating torque and a reverse rotation actuating torque to drive the screw rod to rotate forward and reverse; characterized in that the linear actuator further comprises: a fixed torsion spring seat, which is non-rotatably installed in the linear actuator; a transmission torsion spring seat, which comprises an outer transmission ring that is transmissionally connected to the screw rod and synchronously rotates with the screw rod, and an inner transmission ring that is driven to rotate by the actuating unit, a plurality of transmission keys are circumferentially arranged on the inner transmission ring, at least one of the transmission keys is provided with a cam surface, the outer transmission ring is provided with a plurality of key grooves, the plurality of transmission keys are relatively rotatably engaged in the plurality of key grooves, so that the outer transmission ring and the inner transmission ring synchronously rotate after relatively rotating by a predetermined angle, and a movable unlocking element is arranged on the outer transmission ring corresponding to the cam surface; a brake torsion spring, which is arranged in a tightening direction opposite to the direction of the forward rotation actuating torque, and clamps the fixed torsion spring seat and the outer transmission ring respectively, so as to keep the clamping state of the outer transmission ring and implement self-locking when the screw rod generates a reverse rotation trend caused by a load torque, the inner transmission ring is extruded by the cam surface during the relative rotation of the inner transmission ring with respect to the outer transmission ring driven by the reverse rotation actuating torque, and the brake torsion spring is pushed by the unlocking element to generate radial expansion.

2. The linear actuator with self-locking function according to claim 1, wherein, The at least one transmission key is provided with a radially outward protruding toothed portion, the protruding height of the toothed portion is unidirectionally increased in the direction of the forward rotation actuating torque, so that the cam surface is formed on the toothed portion and gradually away from the axis of the inner transmission ring in the direction of the forward rotation actuating torque, the circumferential groove wall of the key groove is provided with a tooth groove, the depth of the tooth groove is unidirectionally increased in the direction of the forward rotation actuating torque, and the toothed portion is relatively rotatably engaged in the tooth groove.

3. The linear actuator with self-locking function according to claim 2, wherein, The relative rotation angle of the transmission key in the key groove is less than or equal to the relative rotation angle of the toothed portion in the tooth groove.

4. The linear actuator with self-locking function according to claim 2, wherein, The outer transmission ring comprises an outer ring surface and a guide hole for accommodating the unlocking element, the tooth groove has a slope surface facing the cam surface, the guide hole penetrates from the outer ring surface to the slope surface to form an outer port located on the outer ring surface and an inner port located on the slope surface, in the self-locking state, the slope surface and the cam surface are circumferentially misaligned, the unlocking element is partially protruded from the inner port under the compression of the brake torsion spring, and the inner transmission ring is extruded by the cam surface during the relative rotation of the inner transmission ring with respect to the outer transmission ring driven by the reverse rotation actuating torque, so that the unlocking element is partially protruded from the outer port to push the brake torsion spring to generate radial expansion.

5. The linear actuator with self-locking function according to claim 4, wherein, The opening width of the outer port and the inner port is arranged to only allow part of the unlocking element to pass therethrough.

6. The linear actuator with self-locking function according to claim 1, wherein, The surface friction coefficient of the unlocking element is less than the surface friction coefficient of the outer transmission ring.

7. The linear actuator with self-locking function according to claim 1, wherein, The unlocking element synchronously rotates with the outer transmission ring and can produce autorotation relative to the outer transmission ring, and the unlocking element generates rolling friction with the brake torsion spring when pushing the brake torsion spring to radially expand.

8. The linear actuator with self-locking function according to claim 7, wherein, The unlocking element is a cylinder or a sphere.

9. The linear actuator with self-locking function according to claim 1, wherein, The unlocking element axially extends on the outer transmission ring, and the axial length of the unlocking element is greater than or equal to the axial length of the part of the brake torsion spring clamping the outer transmission ring.

10. The linear actuator with self-locking function according to claim 1, wherein, The cam surfaces and the unlocking elements are distributed in multiple groups along the transmission torsion spring seat in a circumferential direction, so that the brake torsion spring can be pushed by multiple unlocking elements to completely separate from the outer transmission ring.

11. The linear actuator with self-locking function according to claim 1, wherein, The actuating unit comprises a motor, a worm gear assembly and a planetary gear assembly connected in sequence, the planetary carrier of the planetary gear assembly is in transmission connection with the inner transmission ring, the worm gear of the worm gear assembly, the planetary gear assembly, the transmission torsion spring seat and the lead screw are coaxially transmitted.

12. The linear actuator with self-locking function according to claim 11, wherein, The linear actuator further comprises a housing which houses at least the fixed torsion spring seat, the transmission torsion spring seat and the planetary gear assembly, the lead screw extends out of one end of the housing, the other end of the housing is provided with a tail pulling component, the tail pulling component and the inner ring gear of the planetary gear assembly have a support seat which axially supports both, the lead screw has an axial shoulder which abuts against the outer transmission ring, the outer transmission ring is rotatably supported on the inner ring gear of the planetary gear assembly, and the load thrust of the lead screw is guided to the tail pulling component through the outer transmission ring, the inner ring gear and the support seat.

13. The linear actuator with self-locking function according to claim 11, wherein the first and second elastic members are springs. The planetary carrier and the inner transmission ring are in transmission connection through a shaft coupling, the shaft coupling comprises a driving shaft coupling, a driven shaft coupling and a return spring, the driving shaft coupling rotates synchronously with the planetary carrier, the driven shaft coupling and the inner transmission ring are in circumferential relative fixation and axial relative movement connection, the driving shaft coupling and the driven shaft coupling are in circumferential relative fixation and axial relative movement connection, the outer transmission ring and the lead screw are in circumferential relative fixation and axial relative movement connection, the driven shaft coupling is rotatably sleeved on the tail of the lead screw and is axially limited by a retaining ring, and the return spring acts on the driven shaft coupling to keep it in engagement with the driving shaft coupling.

14. The linear actuator with self-locking function according to claim 11, wherein, The linear actuator further comprises a release torsion spring and an operable release unit, the inner ring gear of the planetary gear assembly is tightly gripped by the release torsion spring to limit rotation, and the release unit activates the release function of the linear actuator by driving the release torsion spring to loosen the inner ring gear and driving the brake torsion spring to loosen the outer transmission ring.

15. The linear actuator with self-locking function according to claim 14, wherein, The release unit comprises a control lever, a gear driven to rotate by the control lever and a gear ring engaged with the gear, the linear actuator has a fixing sleeve for fixing the torsion spring seat, the gear ring is rotatably sleeved outside the fixing sleeve, one torsion spring leg of the release torsion spring and one torsion spring leg of the brake torsion spring are hung on the gear ring, and rotation of the gear ring synchronously loosens the release torsion spring and the brake torsion spring.

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