Linear actuator with self-locking function

Abstract

The invention discloses a linear actuator with a self-locking function. The linear actuator comprises a lead screw; 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 invention relates to the technical field of linear actuators, and in particular to a linear actuator with a self-locking function. [Background technology]

[0002] The linear actuator in the prior art includes a lead screw, an actuating unit and a telescopic assembly. The actuating unit can selectively output a forward actuating torque and a reverse actuating torque to drive the lead screw to rotate forward and reversely. The telescopic assembly is driven by the lead screw to perform a linear telescopic motion. The existing linear actuator usually has a self-locking function to prevent the lead screw from rotating when subjected to an external load force after the actuating unit stops running, causing the linear actuator to lose lock. The existing linear actuator basically adopts a torsion spring clamping method, that is, when the lead screw reverses due to an external force, the torsion spring clamping generates friction resistance to the reversal of the lead screw to achieve braking of the lead screw. This will cause the actuating unit to overcome the clamping force of the torsion spring when driving the lead screw to reverse, which will cause serious heat generation, reduced efficiency and high power consumption. [Summary of the invention]

[0003] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a linear actuator with a self-locking function. When the actuator unit drives the lead screw to reverse, the friction between the brake torsion spring and the transmission torsion spring seat can be effectively reduced to reduce heat and energy consumption and improve efficiency.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] Linear actuator with self-locking function, including:

[0006] Screw rod;

[0007] An actuating unit, which can selectively output a forward actuating torque and a reverse actuating torque to drive the screw to rotate forward and reverse;

[0008] The linear actuator further comprises:

[0009] a fixed torsion spring seat, which is non-rotatably mounted in the linear actuator;

[0010] A transmission torsion spring seat, comprising an outer transmission ring which is transmission-connected to a lead screw and rotates synchronously with the lead screw, and an inner transmission ring which is arranged in the outer transmission ring and driven to rotate by an actuating unit, wherein a plurality of transmission keys are arranged circumferentially at intervals on the inner transmission ring, and at least one transmission key is provided with a cam surface; the outer transmission ring is provided with a plurality of key slots, and the plurality of transmission keys can be relatively rotatably engaged in the plurality of key slots, so that the outer transmission ring and the inner transmission ring generate synchronous rotation after relative rotation at a predetermined angle, and a movable unlocking element is provided on the outer transmission ring corresponding to the cam surface;

[0011] The braking torsion spring is set such that its winding direction is opposite to the forward rotation actuation torque direction. The braking torsion spring holds the fixed torsion spring seat and the outer transmission ring respectively, and is used to maintain the holding state of the outer transmission ring when the lead screw generates a reverse rotation tendency caused by the load torque, thereby implementing self-locking. During the rotation of the inner transmission ring relative to the outer transmission ring driven by the reverse rotation actuation torque, the unlocking element is squeezed through the cam surface, and the braking torsion spring is pushed by the unlocking element to generate radial expansion.

[0012] When the linear actuator in the present invention is in use, the actuation unit applies a forward rotation actuation torque to the inner transmission ring to make the inner transmission ring and the outer transmission ring rotate forward. The forward rotation of the outer transmission ring drives the lead screw to rotate forward. At this time, since the winding direction of the braking torsion spring is opposite to the forward rotation actuation torque direction, the forward rotation of the outer transmission ring will not cause the braking torsion spring to wind up. Therefore, the actuation unit does not need to overcome a large frictional force when driving the forward rotation of the lead screw.

[0013] When the lead screw generates a reverse rotation tendency caused by the load torque, the lead screw will drive the outer transmission ring to rotate reversely. Since the reverse rotation direction of the outer transmission ring is the same as the holding direction of the braking torsion spring, the reverse rotation of the outer transmission ring will cause the braking torsion spring to hold the outer transmission ring and the fixed torsion spring seat, thereby implementing braking on the outer transmission ring and further implementing self-locking.

[0014] When the actuation unit applies a reverse rotation actuation torque to the inner transmission ring to drive the lead screw to rotate reversely, the inner transmission ring will rotate a predetermined angle relative to the outer transmission ring before driving the outer transmission ring to rotate synchronously. During the relative rotation of the two, the inner transmission ring squeezes the unlocking element through the cam surface, causing the braking torsion spring to be pushed by the unlocking element to generate radial expansion. Since the contact area between the expanded braking torsion spring and the outer transmission ring decreases, the frictional force between the two is reduced, thereby reducing the heat generated by friction when the subsequent lead screw is driven to rotate reversely by the actuation unit. At the same time, the energy consumption of the actuation unit is also reduced and the efficiency is improved.

[0015] Finally, when the actuation unit applies a forward rotation actuation torque to the inner transmission ring again, the inner transmission ring will rotate a predetermined angle relative to the outer transmission ring before driving the outer transmission ring to rotate synchronously. During the relative rotation of the two, the unlocking element is pressed by the braking torsion spring to reset, thereby driving the braking torsion spring to contract and reset, so as to ensure that when the lead screw generates a reverse rotation tendency caused by the load torque, the braking torsion spring holds the outer transmission ring and the fixed torsion spring seat to implement self-locking.

[0016] In the above-mentioned linear actuator with self-locking function, at least one transmission key is provided with a toothed portion protruding radially outward, and the protruding height of the toothed portion increases unidirectionally in the direction of the forward rotation actuation torque, so that a cam surface gradually moves away from the axis of the inner transmission ring in the direction of the forward rotation actuation torque is formed on the toothed portion, and a tooth groove is provided on the circumferential groove wall of the key groove, and the depth of the tooth groove increases unidirectionally in the direction of the forward rotation actuation torque, and the toothed portion is engaged in the tooth groove and can rotate relatively. With such a design, the unlocking element can be driven radially by the cam surface, and when the actuating unit drives the inner transmission ring to reverse, the portion of the cam surface with a higher protruding height gradually approaches the unlocking element to achieve the purpose of driving the unlocking element to move radially outward and cause the brake torsion spring to expand radially, and when the actuating unit drives the inner transmission ring to rotate forward, the portion of the cam surface with a lower protruding height gradually approaches the unlocking element, so that the unlocking element moves radially inward under the pressure of the brake torsion spring to reset the brake torsion spring. In this scheme, the structure of the cam surface is relatively simple and the processing is relatively convenient.

[0017] In the above-mentioned linear actuator with self-locking function, the relative rotation angle of the transmission key in the key slot is less than or equal to the relative rotation angle of the toothed portion in the tooth slot. Such a design can ensure that the inner transmission ring contacts the outer transmission ring through the transmission key when rotating forward and reverse, thereby driving the outer transmission ring to rotate synchronously, avoiding the toothed portion becoming a transmission part alone and driving the outer transmission ring to rotate and cause damage, thereby extending the service life of the toothed portion.

[0018] In the above-mentioned 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 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 pressed by the brake torsion spring and partially protrudes from the inner port, and the inner transmission ring is driven by the reverse actuation torque to rotate relative to the outer transmission ring, and the unlocking element is pressed by the cam surface, so that the unlocking element partially protrudes from the outer port to push the brake torsion spring to generate radial expansion. With such a design, 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 so that it partially protrudes from the outer port to push the brake torsion spring to generate radial expansion, and after the slope surface and the cam surface are circumferentially misaligned, the unlocking element can be reset by the brake torsion spring pressing the part of the unlocking element protruding from the outer port.

[0019] In the above-mentioned linear actuator with self-locking function, the opening widths of the outer port and the inner port are set to allow only part of the unlocking element to pass therethrough. With such a design, the unlocking element can be restricted from escaping from the guide hole by the inner port and the outer port, thereby improving the installation reliability of the unlocking element.

[0020] In the above-mentioned linear actuator with self-locking function, the surface friction coefficient of the unlocking element is smaller than the surface friction coefficient of the outer transmission ring. With such a design, after the brake torsion spring is pushed by the unlocking element to generate radial expansion, the friction between the brake torsion spring and the unlocking element can be reduced, thereby further reducing the heat generated by friction.

[0021] In the above-mentioned 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 generates rolling friction with the brake torsion spring when pushing the brake torsion spring to expand radially. Such a design can further reduce the friction between the brake torsion spring and the unlocking element, so as to further reduce the heat generated by friction.

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

[0023] In the above-mentioned 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 portion of the brake torsion spring that holds the outer transmission ring. With such a design, when the axial length of the unlocking element is less than the axial length of the portion of the brake torsion spring that holds the outer transmission ring, there will be a problem that part of the brake torsion spring does not expand radially because it is not pushed by the unlocking element, and thus part of the brake torsion spring still holds the outer transmission ring, resulting in more heat generated when the screw is reversed, and the technical solution can further reduce the heat generated by friction.

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

[0025] In the above-mentioned linear actuator with self-locking function, the actuating unit includes a motor, a worm gear assembly and a planetary gear assembly which are sequentially connected in transmission, the planetary cage of the planetary gear assembly is connected in transmission 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 driven. With such a design, 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 above-mentioned linear actuator with self-locking function, the linear actuator also includes a housing, the housing at least contains a fixed torsion spring seat, a transmission torsion spring seat and a planetary gear assembly, the screw rod extends out through one end of the housing, a tail pull component is installed at the other end of the housing, a support seat for axially supporting the tail pull component and the inner gear ring of the planetary gear assembly is provided between the tail pull component and the inner gear ring of the planetary gear assembly, the screw rod has a shoulder that abuts against the outer transmission ring, the outer transmission ring can be relatively rotatably supported on the inner gear ring of the planetary gear assembly, and the screw rod load thrust is guided to the tail pull component through the outer transmission ring, the inner gear ring and the support seat. In the prior art, a bearing is provided at the tail of the screw rod to bear the axial load thrust of the screw rod. Such a design makes the length of the screw rod longer, thereby increasing its processing difficulty and deteriorating its concentricity during operation. However, the technical solution can omit the bearing at the tail by changing the transmission path of the axial load thrust, so as to shorten the length of the screw rod, thereby improving the processing convenience of the screw rod and the coaxiality during operation.

[0027] In the above-mentioned linear actuator with self-locking function, the planetary retainer is connected to the inner transmission ring through a coupling transmission, and the coupling includes a driving coupling, a driven coupling and a reset spring. The driving coupling and the planetary retainer rotate synchronously, and the driven coupling and the inner transmission ring form a connection that is relatively fixed in the circumferential direction and relatively movable in the axial direction. The driving coupling and the driven coupling form a connection that is relatively fixed in the circumferential direction and relatively movable in the axial direction. The outer transmission ring and the screw rod form a connection that is relatively fixed in the circumferential direction and relatively movable in the axial direction. The driven coupling can be relatively rotatably mounted on the tail of the screw rod and is axially limited by a retaining ring. The reset spring acts on the driven coupling to keep it in engagement with the driving coupling. With such a design, when the motor drives the lead screw to retract the inner tube of the linear actuator and clamps an object or a person, the lead screw will drive the driven coupling to move outward to disconnect it from the active coupling, thereby cutting off the transmission of the actuating torque. The lead screw stops rotating and the inner tube stops retracting, thereby achieving an anti-pinch effect. When the clamped object or person is removed, the lead screw is reset under the action of the reset spring to reconnect the driven coupling and the active coupling, thereby allowing the linear actuator to resume normal operation.

[0028] In the above-mentioned linear actuator with self-locking function, the linear actuator further includes a release torsion spring and an operable release unit, the inner gear ring of the planetary gear assembly is held tightly by the release torsion spring and restricted from rotating, and the release unit activates the release function of the linear actuator by driving the release torsion spring to loosen the inner gear ring and driving the brake torsion spring to loosen the outer transmission ring. With such a design, when the release torsion spring holds the inner gear ring tightly and implements a rotation lock on the inner gear ring under normal conditions, the planetary retainer can transmit the actuating torque to the inner transmission ring so that the screw can rotate normally, and when the screw needs to be released quickly, the release unit drives the release torsion spring to loosen to release the rotation lock on the inner gear ring and drives the brake torsion spring to loosen the outer transmission ring to activate the release function of the linear actuator, so that the inner gear ring and the outer transmission ring can both rotate freely, in this case, the planetary gear assembly will not transmit power, so that the screw can be quickly rotated by pushing and pulling the screw to make the telescopic assembly quickly telescope, thereby realizing the quick release function, without the need for motor drive, and is suitable for encountering motor failure or power failure or other situations where power needs to be cut off.

[0029] In the above-mentioned linear actuator with self-locking function, the release unit includes an operating rod, a gear driven to rotate by the operating rod, and a gear ring meshed with the gear, the linear actuator has a fixed sleeve for fixing the torsion spring seat, the gear ring is rotatably mounted outside the fixed sleeve, a torsion spring foot of the release torsion spring and a torsion spring foot of the brake torsion spring are hung on the gear ring, and the rotation of the gear ring synchronously releases the release torsion spring and the brake torsion spring. With such a design, when the release function of the linear actuator needs to be activated, the gear ring can be driven to rotate by driving the operating rod to rotate, and the rotation of the gear ring will synchronously release the release torsion spring and the brake torsion spring, thereby activating the release function of the linear actuator, which is simple and convenient to operate; and the release speed of the screw rod depends on the rotation angle of the gear ring, so the release speed of the screw rod can be controlled by controlling the rotation angle of the gear ring.

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

Brief Description of the Drawings

[0031] The present invention will be further described below in conjunction with the accompanying drawings:

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

[0033] Figure 2 for Figure 1 Sectional view of AA in the middle;

[0034] Figure 3 for Figure 2 A partial enlarged schematic diagram of B in the middle;

[0035] Figure 4Cross-sectional view of the linear actuator in the first embodiment of the present invention;

[0036] Figure 5 is Figure 4 Partial enlarged schematic view of C in;

[0037] Figure 6 Explosion schematic view of part of the structure in the first embodiment of the present invention;

[0038] Figure 7 Structural schematic view of the outer transmission ring in the first embodiment of the present invention;

[0039] Figure 8 is Figure 6 Structural schematic view after assembling each component in;

[0040] Figure 9 Structural schematic view of the linear actuator without the housing in the first embodiment of the present invention;

[0041] Figure 10 Cross-sectional view of the linear actuator when the motor drives the lead screw to reverse in the first embodiment of the present invention;

[0042] Figure 11 is Figure 10 Partial enlarged schematic view of D in;

[0043] Reference numerals:

[0044] 100, lead screw; 110, retaining ring; 120, shaft shoulder; 200, actuator unit; 210, motor; 220, worm and worm gear assembly; 221, worm gear; 222, worm; 230, planetary gear assembly; 231, sun gear; 232, planetary gear; 233, planetary carrier; 234, internal gear ring; 300, telescopic assembly; 310, inner tube; 320, outer tube; 330, nut; 400, fixed torsion spring seat; 500, transmission torsion spring seat; 510, outer transmission ring; 511, keyway; 512, tooth groove; 5120, slope; 513, outer ring 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, tooth-shaped part; 530, unlocking element; 600, braking torsion spring; 700, coupling; 710, driving coupling; 720, driven coupling; 721, first transmission protrusion; 722, second transmission protrusion; 730, return spring; 800, housing; 810, fixed sleeve; 900, tail pulling component; 1000, support seat; 1100, release torsion spring; 1200, release unit; 1210, operating rod; 1220, gear; 1230, toothed ring.

Detailed implementation manners

[0045] The present invention provides a linear actuator with a self-locking function, comprising:

[0046] A lead screw;

[0047] An actuating unit that selectively outputs a forward rotation actuating torque and a reverse rotation actuating torque to drive the lead screw to rotate forward and backward;

[0048] The linear actuator further comprises:

[0049] A fixed torsion spring seat that is non-rotatably installed inside the linear actuator;

[0050] A transmission torsion spring seat, which includes an outer transmission ring that is drivingly connected to the lead screw and rotates synchronously with the lead screw, and an inner transmission ring that is arranged inside the outer transmission ring and is driven to rotate by the actuating unit. A plurality of transmission keys are circumferentially spaced on the inner transmission ring, and at least one transmission key is provided with a cam surface; a plurality of key grooves are provided on the outer transmission ring, and the plurality of transmission keys are rotatably engaged in the plurality of key grooves so that the outer transmission ring and the inner transmission ring generate synchronous rotation after rotating relative to each other by a predetermined angle. An active unlocking element is provided on the outer transmission ring corresponding to the cam surface;

[0051] A braking torsion spring, which is set to have a tightening direction opposite to the forward rotation actuating torque direction. The braking torsion spring respectively holds the fixed torsion spring seat and the outer transmission ring, and is used to maintain the holding state of the outer transmission ring when the lead screw generates a reverse rotation trend caused by the load torque to implement self-locking; during the process that the inner transmission ring is driven by the reverse rotation actuating torque to rotate relative to the outer transmission ring, the cam surface squeezes the unlocking element, and the braking torsion spring is pushed by the unlocking element to generate radial expansion.

[0052] When the linear actuator in the present invention is in use, the actuating unit applies a forward rotation actuating torque to the inner transmission ring to make the inner transmission ring and the outer transmission ring rotate forward. The forward rotation of the outer transmission ring drives the lead screw to rotate forward. At this time, since the tightening direction of the braking torsion spring is opposite to the forward rotation actuating torque direction, the forward rotation of the outer transmission ring will not cause the braking torsion spring to tighten. Therefore, the actuating unit does not need to overcome a large frictional force when driving the lead screw to rotate forward;

[0053] When a reverse rotation trend caused by the load torque occurs on the lead screw, the lead screw will drive the outer transmission ring to rotate backward. Since the reverse rotation direction of the outer transmission ring is the same as the holding direction of the braking torsion spring, the reverse rotation of the outer transmission ring will cause the braking torsion spring to hold the outer transmission ring and the fixed torsion spring seat to implement braking on the outer transmission ring, and further implement self-locking;

[0054] When the actuating unit applies a reverse actuating 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 driving the outer transmission ring to rotate synchronously. During the relative rotation of 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 expand radially. 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 the friction of the subsequent lead screw when the actuating unit drives the reverse rotation, and also reducing the energy consumption of the actuating unit and improving the efficiency.

[0055] Finally, when the actuating unit applies the forward actuating torque to the inner transmission ring again, the inner transmission ring will rotate a predetermined angle relative to the outer transmission ring before driving the outer transmission ring to rotate synchronously. During the relative rotation of the two, the unlocking element is compressed by the brake torsion spring and reset, thereby driving the brake torsion spring to retract and reset, so as to ensure that when the screw rod generates a reversal trend caused by the load torque, the brake torsion spring holds the outer transmission ring and the fixed torsion spring seat to implement self-locking.

[0056] The technical solutions of the embodiments of the present invention are explained and illustrated below in conjunction with the drawings of the embodiments of the present invention, but the following embodiments are only preferred embodiments of the present invention, not all of them. Based on the embodiments in the implementation mode, other embodiments obtained by those skilled in the art without creative work all belong to the protection scope of the present invention. In addition, it should be understood that the following words indicating orientation or position relationship such as "up", "down", "left", "right", "longitudinal", "lateral", "inside", "outside", "vertical", "horizontal", "top", "bottom", etc. are only based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device / element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0057] Embodiment 1

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

[0059] In this embodiment, the fixed torsion spring seat 400 is non-rotatably installed in the linear actuator. The transmission torsion spring seat 500 includes an outer transmission ring 510 that is drivingly connected to the lead screw 100 and rotates synchronously with the lead screw 100, and an inner transmission ring 520 that is disposed inside the outer transmission ring 510 and is driven to rotate by the actuating unit 200. A plurality of transmission keys 521 are circumferentially spaced on the inner transmission ring 520. 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 rotatably engaged in the plurality of key grooves 511, so that the outer transmission ring 510 and the inner transmission ring 520 generate synchronous rotation after relatively rotating a predetermined angle. An active unlocking element 530 is provided on the outer transmission ring 510 corresponding to the cam surface 522;

[0060] The braking torsion spring 600 is set such that the winding direction is opposite to the forward rotation actuating torque direction. The braking torsion spring 600 respectively holds the fixed torsion spring seat 400 and the outer transmission ring 510, and is used to maintain the holding state of the outer transmission ring 510 when the lead screw 100 generates a reverse rotation trend caused by the load torque, thereby implementing self-locking. During the process that the inner transmission ring 520 is driven by the reverse rotation actuating torque to rotate relative to the outer transmission ring 510, the unlocking element 530 is squeezed by the cam surface 522, and the braking torsion spring 600 is pushed by the unlocking element 530 to generate radial expansion.

[0061] When the linear actuator in this embodiment is in use, the actuating unit 200 applies a forward rotation actuating torque to the inner transmission ring 520, so that the inner transmission ring 520 and the outer transmission ring 510 rotate forward. The forward rotation of the outer transmission ring 510 drives the lead screw 100 to rotate forward. At this time, since the winding direction of the braking torsion spring 600 is opposite to the forward rotation actuating torque direction, the forward rotation of the outer transmission ring 510 will not cause the braking torsion spring 600 to wind. Therefore, the actuating unit 200 does not need to overcome a large frictional force when driving the forward rotation of the lead screw 100;

[0062] When the lead screw 100 generates a reverse rotation trend caused by the load torque, the lead screw 100 will drive the outer transmission ring 510 to reverse. Since the reverse rotation direction of the outer transmission ring 510 is the same as the holding direction of the braking torsion spring 600, the reverse rotation of the outer transmission ring 510 will cause the braking torsion spring 600 to hold the outer transmission ring 510 and the fixed torsion spring seat 400, thereby implementing braking on the outer transmission ring 510, and further implementing self-locking;

[0063] When the actuating unit 200 applies a reverse actuating torque to the inner transmission ring 520 to drive the lead screw 100 to reverse, the inner transmission ring 520 will rotate relative to the outer transmission ring 510 by a predetermined angle before driving the outer transmission ring 510 to rotate synchronously. During the relative rotation of the two, the inner transmission ring 520 squeezes the unlocking element 530 through the cam surface 521, so that the brake torsion spring 600 is pushed by the unlocking element 530 to expand radially. Since the contact area between the expanded brake torsion spring 600 and the outer transmission ring 510 is reduced, the friction between the two is reduced, thereby reducing the heat generated by the friction of the lead screw 100 when the actuating unit 200 drives the reverse rotation, and also reducing the energy consumption of the actuating unit 200 and improving the efficiency.

[0064] Finally, when the actuating unit 200 applies a forward actuating torque to the inner transmission ring 520 again, the inner transmission ring 520 will rotate a predetermined angle relative to the outer transmission ring 510 before driving the outer transmission ring 510 to rotate synchronously. During the relative rotation of the two, the unlocking element 530 is compressed by the braking torsion spring 600 and resets, thereby driving the braking torsion spring 600 to retract and reset, so as to ensure that when the lead screw 100 generates a reversal trend caused by the load torque, the braking torsion spring 600 holds the outer transmission ring 510 and the fixed torsion spring seat 400 to implement self-locking.

[0065] Specifically, Figures 2 to 6As shown, the braking torsion spring 600 in this embodiment is left-handed. The transmission keys 521 and the key grooves 511 are arranged in one-to-one correspondence, and the central angle corresponding to the transmission key 521 is smaller than the central angle corresponding to 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 relative to the outer transmission ring 510. At least one of the transmission keys 521 is provided with a radially protruding tooth portion 523. Preferably, each transmission key 521 is provided with at least one radially protruding tooth portion 523. In this embodiment, two of the tooth portions 523 are circumferentially spaced on each transmission key 521. The protruding height of the tooth portion 523 increases unidirectionally in the direction of the forward rotation actuation torque, so that the outer side surface of the tooth portion 523 forms the above-mentioned cam surface 522 that gradually moves away from the axis of the inner transmission ring 520 in the direction of the forward rotation actuation torque. A tooth groove 512 is provided on the circumferential groove wall of the key groove 511. The radial depth of the tooth groove 512 increases unidirectionally in the direction of the forward rotation actuation torque. The central angle corresponding to the tooth groove 512 is larger than the central angle corresponding to the tooth portion 523, so that the tooth portion 523 can be engaged in the tooth groove 512 and can rotate relatively, and the unlocking element 530 can move radially along the outer transmission ring 510. With such a design, the unlocking element 530 can be radially driven through the cam surface 522. When the actuating unit 200 drives the inner transmission ring 520 to rotate reversely, the part with a higher protruding height of the cam surface 522 gradually approaches the unlocking element 530 to drive the unlocking element 530 to move radially outwards, so as to cause the braking torsion spring 600 to expand radially. When the actuating unit 200 drives the inner transmission ring 520 to rotate forward, the part with a lower protruding height of the cam surface 522 gradually approaches the unlocking element 530, so that the unlocking element 530 moves radially inwards under the pressure of the braking torsion spring 600 to reset the braking torsion spring 600. In this solution, the structure of the cam surface 522 is relatively simple and convenient to process.

[0066] In addition, in this embodiment, the maximum protruding height of the tooth portion 523 is smaller than the protruding height of the outer peripheral surface of the transmission key 521 protruding from the outer peripheral surface of the inner transmission ring 520, so as to reduce the outer diameter of the inner transmission ring 520. And the relative rotation angle of the transmission key 521 in the key groove 511 is less than or equal to the relative rotation angle of the tooth portion 523 in the tooth groove 512, that is, the difference a between the central angle corresponding to the key groove 511 and the central angle corresponding to the transmission key 521 is less than or equal to the difference b between the central angle corresponding to the tooth groove 512 and the central angle corresponding to the tooth portion 523. With such a design, it can be ensured that the inner transmission ring 520 drives the outer transmission ring 510 to rotate synchronously by contacting the outer transmission ring 510 through both side surfaces of the transmission key 521 during both forward and reverse rotations, avoiding the tooth portion 523 alone becoming the transmission part and driving the outer transmission ring 510 to rotate, resulting in damage, thereby prolonging the service life of the tooth portion 523.

[0067] Such as Figures 2 to 3 、 Figure 7As shown, in order to realize the radial movement of the unlocking element 530 installed on the outer transmission ring 510, the outer transmission ring 510 of this embodiment includes 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, and the guide hole 514 passes through from the outer ring surface 513 to the slope surface 5120, and forms an outer port 5141 located on the outer ring surface 513 and an inner port 5142 located 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. When the brake torsion spring 600 holds the outer transmission ring 510 tightly, the unlocking element 530 is locked. 10 and the self-locking state of the fixed torsion spring seat 400, the slope surface 5120 and the cam surface 522 are circumferentially misaligned, that is, the shallowest depth of the slope surface 5120 and the shallowest protrusion height of the cam surface 522 are circumferentially misaligned, so that the unlocking element 530 can be pressed by the brake torsion spring 600 to move radially inward and partially protrude from the inner port 5142. During the rotation of the inner transmission ring 520 relative to the outer transmission ring 510 driven by the reverse actuating torque applied by the actuating unit 200, the unlocking element 530 can be radially pressed outward by the cam surface 522, so that the unlocking element 530 moves radially outward and partially protrudes from the outer port 5141, thereby pushing the brake torsion spring 600 to generate radial expansion (such as Figure 11 ). In this design, 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 so that it partially protrudes from the outer port 5141 to push the brake torsion spring 600 to generate radial expansion, and after the ramp surface 5120 and the cam surface 522 are circumferentially misaligned, the brake torsion spring 600 can press the unlocking element 530 protruding from the outer port 5141 to make the unlocking element 530 move radially inward and reset.

[0068] The opening widths of the outer port 5141 and the inner port 5142 are set to allow only part of the unlocking element 530 to pass therethrough. With such a design, the unlocking element 530 can be restricted from escaping from the guide hole 514 through the inner port 5142 and the outer port 5141, thereby improving the installation reliability of the unlocking element 530.

[0069] In this embodiment, the unlocking element 530 rotates synchronously with the outer transmission ring 510 and can rotate relative to the outer transmission ring 510. In order to simplify the structure of the unlocking element 530 and reduce the manufacturing cost, the unlocking element 530 in this embodiment is a cylinder or a sphere. By the unlocking element 530 rotating relative to the outer transmission ring 510, the unlocking element 530 can push the braking torsion spring 600 to expand radially. When the outer transmission ring 510 drives the unlocking element 530 to reverse under the drive of the actuating unit 200, the unlocking element 530 and the braking torsion spring 600 generate rolling friction. Compared with sliding friction, the friction between the braking torsion spring 600 and the unlocking element 530 can be further reduced, so as to further reduce 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 as to allow only a portion of the unlocking element 530 to pass therethrough. In order to facilitate the assembly of the unlocking element 530 into the guide hole 514, in this embodiment, the guide hole 514 is open toward one end of the fixed torsion spring seat 400, and the unlocking element 530 is inserted into the guide hole 514 through the end, and then the unlocking element 530 can be prevented from escaping from the guide hole 514 by limiting the fixed torsion spring seat 400. The outer transmission ring 510 in this embodiment 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 so that the insertion section 515 and the fixed torsion spring seat 400 can be rotatably matched. A non-circular hole 5150 is provided on the insertion section 515, and the screw rod 100 is provided with a non-circular optical axis section that matches the non-circular hole 5150 so that the insertion section 515 and the screw rod 100 form a connection that is relatively fixed in the circumferential direction and relatively movable in the axial direction. The guide hole 514 is provided on the exposed section 516. In order to further reduce the outer diameter of the exposed section 516, the outer diameter of the insertion section 515 in this embodiment is An avoidance groove corresponding to the guide hole 514 is provided on the side to reduce the area of ​​the guide hole 514 opening distributed on the end face of the exposed section 516, thereby achieving the purpose of 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 is abutted against the end face of the exposed section 516 or a small gap exists between the two, which can prevent the unlocking element 530 from escaping from the guide hole 514. The braking torsion spring 600 is partially clamped on the outside of the fixed torsion spring seat 400 and partially clamped 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 fixed circumferentially or can move within a certain circumferential range.

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

[0072] Preferably, the unlocking element 530 in this embodiment is a cylinder, and the unlocking element 530 axially extends 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 braking torsion spring 600 that holds the outer transmission ring 510 tightly, 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 that is held tightly by the braking torsion spring 600. Such a design is because when the axial length of the unlocking element 530 is less than the axial length of the part of the braking torsion spring 600 that holds the outer transmission ring 510 tightly, there will be a problem that part of the braking torsion spring 600 does not generate radial expansion because it is not pushed by the unlocking element 530. As a result, part of the braking torsion spring 600 still holds the outer transmission ring 510 tightly, resulting in more heat generated between the braking torsion spring 600 and the outer transmission ring 510 when the lead screw 100 reverses. And this technical solution can further reduce the heat generated by friction.

[0073] It can be understood that in other embodiments of the present invention, the unlocking element can also be a column with a rectangular cross-section, and the guiding hole is a rectangular hole. With such a design, the braking torsion spring can also be driven by the unlocking element to generate radial expansion, reducing the contact area between the braking torsion spring and the outer transmission ring, so as to reduce the heat generated by friction.

[0074] Preferably, in this embodiment, multiple groups of cam surfaces 522 and unlocking elements 530 are evenly distributed along 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 is at least three groups. With such a design, the braking torsion spring 600 can be pushed by multiple unlocking elements 530 to be completely separated from the outer transmission ring 510, so that the braking torsion spring 600 only contacts the unlocking elements 530, thereby further reducing the frictional force and the heat generated by friction.

[0075] In addition, the actuating unit 200 in this embodiment includes a motor 210, a worm gear assembly 220 and a planetary gear assembly 230 which are sequentially connected in transmission. The worm gear assembly 220 includes a meshing worm wheel 221 and a worm 222. The worm 222 is connected in transmission with the output shaft of the motor 210, and 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 includes a sun gear 231, planetary gears 232, a planetary retainer 233 and an inner gear ring 234. The planetary retainer 233 is connected in transmission with the inner transmission ring 520. The planetary gears 232 are rotatably mounted on the planetary retainer 233. A plurality of planetary gears 232 surround the outer side of the sun gear 231 and are connected to the sun gear 231. The worm gear 221 is sleeved on the outside of the sun gear 231 and is connected to the sun gear 231 by spline or interference fit, so that the worm gear 221 and the sun gear 231 can rotate synchronously, and the inner gear ring 234 surrounds the outside of the plurality of planetary gears 232 and meshes with the planetary gears 232. When the motor 210 drives the inner transmission ring 520 to rotate forward through the worm gear assembly 220 and the planetary gear assembly 230, the inner gear ring 234 is in a locked state in the circumferential direction. At this time, the power of the motor 210 is input through the worm gear assembly 220 and the sun gear 231, and is output by the planetary holder 233 after being transmitted by the planetary gear 232. The planetary holder 233 drives the screw 100 to rotate through the inner transmission ring 520 and the outer transmission ring 510. With such a design, multi-stage reduction can be achieved to reduce the high-speed rotation of the motor 210 to the required low speed to meet the working requirements of the linear actuator.

[0076] like Figure 5 and Figure 6As shown, the planet cage 233 in this embodiment is drivingly connected to the inner drive ring 520 through a coupling 700. The coupling 700 includes a driving coupling 710, a driven coupling 720, and a return spring 730. The driving coupling 710 and the planet cage 233 maintain synchronous rotation through non-circular fitting methods such as splines. The driven coupling 720 and the inner drive ring 520 form a connection that is circumferentially relatively fixed and axially relatively movable through non-circular fitting methods such as splines. The driving coupling 710 and the driven coupling 720 form a connection that is circumferentially relatively fixed and axially relatively movable. For example, the outer peripheral side of the driving coupling 710 is in spline fit with the planet cage 233. The outer peripheral side of the driven coupling 720 is provided with a first driving protrusion 721 and a second driving protrusion 722 distributed along its axial direction. The driving coupling 710 is sleeved outside the driven coupling 720, and the inner peripheral side of the driving coupling 710 forms a spline fit with the first driving protrusion 721. The second driving protrusion 722 forms a spline fit with the inner peripheral side of the inner drive ring 520. The driven coupling 720 is rotatably sleeved on the tail of the lead screw 100. A retaining ring 110 is installed at the tail end of the lead screw 100 through a screw (not shown in the figure). The outer diameter of the retaining ring 110 is greater than the inner diameter of the driven coupling 720 and less than the inner diameter of the driving coupling 710, so that the retaining ring 110 blocks the driven coupling 720 to perform a lower limit in the axial direction. The return spring 730 is press-fitted between the fixed torsion spring seat 400 and the driven coupling 720, so that the driven coupling 720 remains connected to the driving coupling 710 and is in an engaged state. Such a design is because when the motor 210 drives the inner tube 310 to retract through the drive of the lead screw 100 and clamps an object or a human body, since the nut 330 cannot move axially, the lead screw 100 will be forced to move axially outward relative to the nut 330. The outward movement of the lead screw 100 will drive the driven coupling 720 to move axially outward relative to the inner drive ring 520, disconnecting the driven coupling 720 from the driving coupling 710 to cut off the transmission of the actuation torque, stopping the rotation of the lead screw 100, and stopping the retraction of the inner tube 310 to achieve the anti-pinch effect; and 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] In addition, the linear actuator in this embodiment also includes a housing 800, which accommodates at least a fixed torsion spring seat 400, a transmission torsion spring seat 500, a motor 210, a worm gear assembly 220 and a planetary gear assembly 230. The screw 100 extends out through one end of the housing 800, and a tail pull component 900 is installed at the other end of the housing 800. A support seat 1000 is provided between the tail pull component 900 and the inner gear ring 234. The support seat 1000 axially supports the tail pull component 900 and the inner gear ring 234. A thrust bearing is provided between the support seat 1000 and the inner gear ring 234, and a radial bearing is provided between the inner gear ring 234 and the housing 800, so that the inner gear ring 234 can rotate relative to the housing 800. The screw rod 100 has a shoulder 120 axially abutting against the outer transmission ring 510, and a thrust bearing is provided between the exposed section 516 and the inner gear ring 234 so that the outer transmission ring 510 can be relatively rotatably supported on the inner gear ring 234. In addition, a radial bearing is provided between the exposed section 516 and the inner gear ring 234. In this way, after the screw rod 100 is subjected to load thrust, it is guided to the tail pull component 900 through the outer transmission ring 510, the inner gear ring 234, and the support seat 1000. In the prior art, the screw rod needs to pass through the planetary gear assembly and set a bearing at one end close to the tail pull component. The bearing is supported on the tail pull component, and the axial load thrust of the screw rod is borne by the bearing and transmitted to the tail pull component. Such a design makes the screw rod longer, which increases its processing difficulty and deteriorates its concentricity during operation. However, the present technical solution sets the transmission torsion spring seat 500 on the side of the planetary gear assembly 230 away from the tail pull component 900, and changes the transmission path of the axial load thrust so that the tail pull component 900 bears the load thrust. It is unnecessary for the screw rod 100 to pass through the planetary gear assembly 230, thereby shortening the length of the screw rod 100 and eliminating the bearing at the tail, thereby improving the processing convenience of the screw rod 100 and the coaxiality during operation. (Marking the force transmission path)

[0078] In addition, if Figures 5 to 9As shown, the linear actuator in this embodiment also includes a release torsion spring 1100 and an operable release unit 1200. The release torsion spring 1100 normally grips the inner gear ring 234 to restrict its rotation, so as to achieve circumferential locking of the inner gear ring 234. The release unit 1200 activates the release function of the linear actuator by driving the release torsion spring 1100 to release the inner gear ring 234 and driving the braking torsion spring 600 to release the outer transmission ring 510. With such a design, when the release torsion spring 1100 normally holds the inner gear ring 234 and implements a rotation-proof lock on the inner gear ring 234, the planetary retainer 233 can transmit the actuating torque to the inner transmission ring 520 to enable the screw rod 100 to rotate normally. When the screw rod 100 needs to be released quickly, the release unit 1200 drives the release torsion spring 1100 to loosen, which can release the rotation-proof lock on the inner gear ring 234 and drive the brake torsion spring 600 to loosen the outer transmission ring 510 to activate the release function of the linear actuator. In this way, the inner gear ring 234 and the outer transmission ring 510 can both rotate freely. In this case, the planetary gear assembly 230 will not transmit power, so that the screw rod 100 can be pushed and pulled to make the screw rod 100 rotate quickly, so that the telescopic assembly 300 can be quickly telescoped, thereby realizing the quick release function. No motor 210 drive is required, and it is suitable for situations where the motor 210 fails or the power is off, or other situations where the power needs to be cut off.

[0079] The release unit 1200 in this embodiment includes a joystick 1210, a gear 1220, and a toothed ring 1230. The joystick 1210 extends along the axial direction of the lead screw 100 and is located outside the outer tube 320. A fixed sleeve 810 is fixedly installed in the housing 800. The fixed torsion spring seat 400 is fixedly connected to the fixed sleeve 810 by means of screw connection or welding. The toothed ring 1230 is rotatably sleeved outside the fixed sleeve 810. A fixed shaft perpendicular to the lead screw 100 is provided between the fixed sleeve 810 and the housing 800. The gear 1220 is rotatably installed on the fixed shaft. The gear 1220 meshes with the toothed ring 1230. One end of the joystick 1210 is rotatably connected to the gear 1220 through a pin rod, so that after pulling the joystick 1210, the joystick 1210 can drive the gear 1220 to rotate. The winding directions of the release torsion spring 1100 and the braking torsion spring 600 are opposite, that is, the release torsion spring 1100 is right-handed. The lower torsion spring leg of the release torsion spring 1100 is fixed to the housing 800, and the upper torsion spring leg of the release torsion spring 1100 is hooked on the toothed ring 1230. The lower torsion spring leg of the braking torsion spring 600 passes through the fixed sleeve 810 and is hooked on the toothed ring 1230. By driving the gear 1220 to rotate through the joystick 1210, the toothed ring 1230 can drive the upper torsion spring leg of the release torsion spring 1100 and the lower torsion spring leg of the braking torsion spring 600 to rotate in the direction of unwinding the respective torsion springs, that is, synchronously loosen the release torsion spring 1100 and the braking torsion spring 600. That is, the lower torsion spring leg of the braking torsion spring 600 in this solution can move within a certain range in the circumferential direction. With such a design, when it is necessary to activate the release function of the linear actuator, driving the gear 1220 to rotate through the joystick 1210 can drive the toothed ring 1230 to rotate. The rotation of the toothed ring 1230 will synchronously loosen the release torsion spring 1100 and the braking torsion spring 600, thereby activating the release function of the linear actuator, and the operation is simple and convenient; and the release speed of the lead screw 100 depends on the rotation angle of the toothed ring 1230. Therefore, the release speed of the lead screw 100 can be controlled by controlling the rotation angle of the toothed ring 1230; when the joystick 1210 is released, the release torsion spring 1100 and the braking torsion spring 600 drive the toothed ring 1230 to rotate and reset under the action of their own restoring forces.

[0080] It can be understood that in other embodiments of the present invention, when the linear actuator does not have a quick release function, the release unit and the release torsion spring can be omitted. At this time, the lower torsion spring leg of the braking torsion spring is connected to the housing to achieve circumferential fixation.

[0081] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes but is not limited to the content described in the drawings and the above specific implementation manner. Any modification that does not deviate from the functional and structural principles of the present invention will be included in the scope of the claims.

Claims

1. A linear actuator with self-locking function, comprising: Screw rod; An actuating unit, which can selectively output a forward actuating torque and a reverse actuating torque to drive the screw to rotate forward and reverse; Characterized in that the linear actuator also includes: a fixed torsion spring seat, which is non-rotatably mounted in the linear actuator; A transmission torsion spring seat, comprising an outer transmission ring which is transmission-connected to a lead screw and rotates synchronously with the lead screw, and an inner transmission ring which is arranged in the outer transmission ring and driven to rotate by an actuating unit, wherein a plurality of transmission keys are arranged circumferentially at intervals on the inner transmission ring, and at least one transmission key is provided with a cam surface; the outer transmission ring is provided with a plurality of key slots, and the plurality of transmission keys can be relatively rotatably engaged in the plurality of key slots, so that the outer transmission ring and the inner transmission ring generate synchronous rotation after relative rotation at a predetermined angle, and a movable unlocking element is provided on the outer transmission ring corresponding to the cam surface; The brake torsion spring is arranged so that the tightening direction is opposite to the direction of the forward actuating torque. The brake torsion spring respectively clamps and fixes the torsion spring seat and the outer transmission ring, and is used to maintain the clamping state of the outer transmission ring and implement self-locking when the screw rod generates a reverse trend caused by the load torque; the inner transmission ring is driven by the reverse actuating torque to rotate relative to the outer transmission ring, and the unlocking element is squeezed by the cam surface, and the brake torsion spring is pushed by the unlocking element to produce radial expansion.

2. The linear actuator with self-locking function as claimed in claim 1, characterized in that: At least one transmission key is provided with a radially outwardly protruding toothed portion, and the protruding height of the toothed portion increases unidirectionally in the direction of the forward actuating torque, so that a cam surface is formed on the toothed portion which gradually moves away from the axis of the inner transmission ring in the direction of the forward actuating torque. A tooth groove is provided on the circumferential groove wall of the key groove, and the depth of the tooth groove increases unidirectionally in the direction of the forward actuating torque. The toothed portion is engaged in the tooth groove and can rotate relatively.

3. The linear actuator with self-locking function as claimed in claim 2, characterized in that: The relative rotation angle of the transmission key in the keyway 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 as claimed in claim 2, characterized in that: 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, and the guide hole passes through 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, and the unlocking element is compressed by the brake torsion spring and partially protrudes from the inner port. During the rotation of the inner transmission ring relative to the outer transmission ring driven by the reverse actuating torque, the unlocking element is squeezed through the cam surface, so that the unlocking element partially protrudes from the outer port to push the brake torsion spring to produce radial expansion.

5. The linear actuator with self-locking function as claimed in claim 4, characterized in that: The opening widths of the outer port and the inner port are set to allow only a portion of the unlocking element to pass therethrough.

6. The linear actuator with self-locking function as claimed in claim 1, characterized in that: The coefficient of friction of the surface of the unlocking element is smaller than the coefficient of friction of the surface of the outer transmission ring.

7. The linear actuator with self-locking function as claimed in claim 1, characterized in that: The unlocking element rotates synchronously with the outer transmission ring and can generate self-rotation relative to the outer transmission ring. When the unlocking element pushes the brake torsion spring to expand radially, rolling friction is generated between the unlocking element and the brake torsion spring.

8. The linear actuator with self-locking function as claimed in claim 7, characterized in that: The unlocking element is a cylinder or a sphere.

9. The linear actuator with self-locking function as claimed in claim 1, characterized in that: 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 portion of the brake torsion spring that holds the outer transmission ring.

10. The linear actuator with self-locking function as claimed in claim 1, characterized in that: The cam surface and the unlocking element are distributed in multiple groups at intervals along the circumference of the transmission torsion spring seat, so that the braking torsion spring can be pushed by multiple unlocking elements and completely separated from the outer transmission ring.

11. The linear actuator with self-locking function as claimed in claim 1, characterized in that: The actuating unit comprises a motor, a worm gear assembly and a planetary wheel assembly which are sequentially connected in transmission. The planetary retainer of the planetary wheel assembly is connected in transmission with the inner transmission ring. The worm wheel, the planetary wheel assembly, the transmission torsion spring seat and the lead screw of the worm gear assembly are coaxially driven.

12. The linear actuator with self-locking function according to claim 11, characterized in that: The linear actuator also includes a housing, which at least accommodates a fixed torsion spring seat, a transmission torsion spring seat and a planetary gear assembly. The screw rod extends out through one end of the housing, and a tail pull component is installed at the other end of the housing. A support seat is provided between the tail pull component and the inner gear ring of the planetary gear assembly to axially support the two. The screw rod has a shoulder that abuts against an outer transmission ring, and the outer transmission ring is relatively rotatably supported on the inner gear ring of the planetary gear assembly. The screw rod load thrust is guided to the tail pull component through the outer transmission ring, the inner gear ring and the support seat.

13. The linear actuator with self-locking function according to claim 11, characterized in that: The planetary holder and the inner transmission ring are connected through a coupling transmission. The coupling includes a driving coupling, a driven coupling and a reset spring. The driving coupling and the planetary holder rotate synchronously. The driven coupling and the inner transmission ring form a connection that is relatively fixed in the circumferential direction and relatively movable in the axial direction. The driving coupling and the driven coupling form a connection that is relatively fixed in the circumferential direction and relatively movable in the axial direction. The outer transmission ring and the screw rod form a connection that is relatively fixed in the circumferential direction and relatively movable in the axial direction. The driven coupling can be relatively rotatably mounted on the tail of the screw rod and is axially limited by a retaining ring. The reset spring acts on the driven coupling to keep it in engagement with the driving coupling.

14. The linear actuator with self-locking function according to claim 11, characterized in that: The linear actuator also includes a release torsion spring and an operable release unit. The inner gear ring of the planetary gear assembly is clamped by the release torsion spring to restrict rotation. The release unit activates the release function of the linear actuator by driving the release torsion spring to loosen the inner gear ring and driving the braking torsion spring to loosen the outer transmission ring.

15. The linear actuator with self-locking function as claimed in claim 14, characterized in that: The release unit includes an operating rod, a gear driven to rotate by the operating rod, and a gear ring meshing with the gear. The linear actuator has a fixed sleeve for fixing the torsion spring seat. The gear ring is rotatably mounted outside the fixed sleeve. A torsion spring foot of the release torsion spring and a torsion spring foot of the braking torsion spring are hung on the gear ring. The rotation of the gear ring synchronously loosens the release torsion spring and the braking torsion spring.

Images