Linear actuator

Abstract

The utility model discloses a linear actuator which comprises a motor, a tubular telescopic component and a force transmission chain. The force transmission chain is arranged to transmit power of the motor to the tubular telescopic component so as to drive the tubular telescopic component to do linear motion. The first force transmission chain comprises a planet wheel speed reducing mechanism in transmission connection with the output end of the motor, a second force transmission chain in transmission connection with the first force transmission chain, and a third force transmission chain in transmission connection with the second force transmission chain; the third force transmission chain comprises a lead screw and a transmission nut which is in threaded fit with the lead screw, and the transmission nut is connected with the tubular telescopic component; the force transmission direction of the first force transmission chain intersects with the force transmission direction of the second force transmission chain, and the force transmission direction of the second force transmission chain intersects with the force transmission direction of the third force transmission chain. According to the linear actuator, the situation that the output shaft of the motor is perpendicular to the lead screw is avoided, the overall size of the linear actuator is reduced, and transportation and installation are convenient.

Description

Technical Field

[0001] The utility model relates to the field of linear actuators, and in particular to a linear actuator. Background Art

[0002] Electrically driven actuation systems are widely used in equipment such as electric lifting tables, electric beds, and electric sofas / chairs. These devices rely on the motor to output torque to achieve linear displacement or move the load in other ways. Usually, the motor cannot directly output torque to the execution component (lead screw nut assembly) because insufficient thrust will be obtained in this way. A speed reduction mechanism needs to be used between them to implement the conversion and transmission of power. For example, worm and worm gear transmission, but the upper limit of the reduction ratio it provides is low and the range is narrow, resulting in a small rated load of the actuation system and limited applications. The common linear actuator using worm and worm gear as the speed reduction mechanism is disclosed in CN118293189A.

[0003] There is also a prior art that uses a planetary gear speed reduction mechanism. As recorded in CN109083998A: Through the transmission of the planetary gear assembly, the rotation speed of the worm can be reduced, and the torque of the lead screw can be increased, so that the lead screw has greater thrust. However, the planetary gear speed reduction mechanism and the worm are arranged in the same straight line direction, which undoubtedly increases the length of the actuator.

[0004] In the above-mentioned solutions, because worm and worm gear transmission is used, the motor is vertically arranged relative to the lead screw. The vertically placed motor needs to occupy a large side space of the linear actuator, which is not conducive to the transportation and installation of the product. Summary of the Utility Model

[0005] In order to overcome the deficiencies in the prior art, the utility model provides a linear actuator with the advantage of a small overall volume.

[0006] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0007] A linear actuator, comprising:

[0008] A motor;

[0009] A tubular telescopic member;

[0010] A force transmission chain, which is arranged to transmit the power of the motor to the tubular telescopic member to drive the tubular telescopic member to perform linear motion;

[0011] The force transmission chain includes:

[0012] A first force transmission chain, including a planetary gear speed reduction mechanism that is in transmission connection with the output end of the motor;

[0013] The second force transmission chain drivingly connected to the first force transmission chain includes a speed change transmission mechanism having gears and / or worm gears and worm wheels;

[0014] The third force transmission chain drivingly connected to the second force transmission chain includes a lead screw and a transmission nut threadedly engaged with the lead screw, and the transmission nut is connected to the tubular telescopic member;

[0015] The force transmission direction of the first force transmission chain intersects with the force transmission direction of the second force transmission chain, and the force transmission direction of the second force transmission chain intersects with the force transmission direction of the third force transmission chain;

[0016] A clutch that rotationally locks the internal gear ring of the planetary gear reduction mechanism;

[0017] A release member that drives the clutch to release the internal gear ring to activate the release function of the linear actuator.

[0018] By adopting the above technical solution, during normal operation, the torque generated by the motor is transmitted to the lead screw through the first force transmission chain and the second force transmission chain. The first force transmission chain includes a planetary gear reduction mechanism, and the second force transmission chain transmitting to the lead screw includes a speed change transmission mechanism. In this way, through multiple speed reductions and torque increases by the planetary gear reduction mechanism and the speed change transmission mechanism, the speed reduction effect and torque increase effect are good; when releasing, the load drives the lead screw to rotate in the reverse direction and is transmitted to the first force transmission chain through the second force transmission chain. At this time, the release member drives the clutch to release the internal gear ring, so that the internal gear ring rotates to complete the unloading. The second force transmission chain plays a role in increasing speed and reducing torque, making the load torque transmitted to the first force transmission chain smaller, thereby starting to reduce the impact force on the reduction mechanism; the output end of the motor is drivingly connected to the planetary gear reduction mechanism of the first force transmission chain, so that the axial direction of the output end of the motor is parallel to the force transmission direction of the first force transmission chain. At the same time, the force transmission direction of the first force transmission chain intersects with the force transmission direction of the second force transmission chain, and the force transmission direction of the second force transmission chain intersects with the force transmission direction of the third force transmission chain. The force transmission direction of the first force transmission chain parallel to the axial direction of the output end of the motor and the force transmission direction of the third force transmission chain where the lead screw is located will not be perpendicular to each other, avoiding the situation where the output shaft of the motor is perpendicular to the lead screw, reducing the overall volume of the linear actuator, and facilitating transportation and installation.

[0019] Optionally, the force transmission direction of the first force transmission chain is from the input end to the output end direction of the planetary gear reduction mechanism;

[0020] The force transmission direction of the second force transmission chain is from the input end to the output end direction of the speed change transmission mechanism;

[0021] The force transmission direction of the third force transmission chain is the displacement direction of the transmission nut on the lead screw;

[0022] The force transmission direction of the first force transmission chain and the force transmission direction of the third force transmission chain are arranged in parallel.

[0023] By adopting the above technical solution, when the force transmission direction of the first force transmission chain and the force transmission direction of the third force transmission chain are set to be parallel, compared with the previous method of setting the motor perpendicular to the lead screw, the first force transmission chain and the third force transmission chain are close to each other in a parallel posture. Generally speaking, the motor can directly output torque to the first force transmission chain, which makes the output shaft axial direction of the motor parallel to the force transmission direction of the first force transmission chain, and then makes the motor parallel to the lead screw, and the overall volume of the linear actuator is reduced, which is convenient for transportation and installation in a small space.

[0024] Optionally, the first force transmission chain and the third force transmission chain are located on the same side of the second force transmission chain.

[0025] By adopting the above technical solution, when the first force transmission chain and the third force transmission chain are located on the same side of the second force transmission chain, the overall length of the linear actuator depends on the relatively larger length of the first force transmission chain and the third force transmission chain, rather than the sum of the lengths of the first force transmission chain and the third force transmission chain, thereby greatly reducing the overall length of the linear actuator.

[0026] Optionally, the linear actuator further comprises a centrifugal brake for balancing the load torque applied to the first force transmission chain after the linear actuator releases its function.

[0027] By adopting the above technical solution, when released, the centrifugal brake balances the load torque applied to the first force transmission chain and plays a braking role, thereby reducing the reversal speed of the screw rod, thereby reducing the retraction speed of the tubular telescopic part, avoiding the impact of the tubular telescopic part due to excessive retraction speed.

[0028] Optionally, the planetary gear reduction mechanism further includes:

[0029] A sun gear drivingly connected to the output end of the motor;

[0030] A planetary gear meshed between the sun gear and the inner gear ring;

[0031] A retaining frame drivingly connected to the third power transmission chain, used for carrying the planetary gear;

[0032] When the inner gear ring is locked by the clutch, the power of the motor does not trigger the centrifugal brake, and is output to the third power transmission chain through the retaining frame to reduce speed and increase torque;

[0033] When the inner gear ring is released by the clutch, the load torque is output to the centrifugal brake through the inner gear ring to increase the speed and reduce the torque, and the centrifugal brake is triggered to brake by the load torque.

[0034] By adopting the above technical solution, during normal operation, the internal gear ring is locked against rotation by the clutch, and the power of the motor does not trigger the centrifugal brake, avoiding affecting normal operation; when released, the internal gear ring is released. At this time, due to the braking torque of the motor itself, the sun gear cannot rotate, and the load torque is transmitted to the internal gear ring through the cage and the planet gears to drive its rotation. The rotating internal gear ring activates the centrifugal brake, and the centrifugal brake plays a braking role.

[0035] Optionally, the centrifugal brake includes:

[0036] A rotating member driven to rotate by the internal gear ring;

[0037] A brake housing providing a braking friction surface;

[0038] A brake block disposed between the rotating member and the brake housing, which generates a centrifugal motion by means of the rotational motion of the rotating member and contacts the braking friction surface.

[0039] By adopting the above technical solution, the internal gear ring drives the rotating member to rotate, and the rotating member drives the brake block to generate a centrifugal motion so as to contact the braking friction surface of the brake housing to generate a frictional force, thereby generating a braking force in a certain direction and realizing the function of decelerating and braking; in addition, the greater the load torque, the greater the rotational speed of the rotating member, and thus the greater the frictional braking force generated, while the smaller the load torque, the smaller the rotational speed of the rotating member, and thus the smaller the frictional braking force generated. In this way, an approximate release speed can be achieved under different loads.

[0040] Optionally, the rotating member is configured as a part of the internal gear ring or attached to the internal gear ring.

[0041] By adopting the above technical solution, when the rotating member is integrated with the internal gear ring, the number of components is reduced, which is beneficial to assembly; when the rotating member is attached to the internal gear ring, it is convenient for subsequent disassembly and replacement of the rotating member.

[0042] Optionally, one of the brake block and the rotating member is provided with a radial guiding groove, and the other is provided with a radial guiding block, and the radial guiding block is inserted into the radial guiding groove to guide the centrifugal motion of the brake block;

[0043] Alternatively, the outer peripheral surface of the rotating member has a guiding groove adapted to the brake block, and the brake block is fitted into the guiding groove, and the brake block rotates synchronously with the rotating member in the circumferential direction and can move radially relative to the rotating member;

[0044] Alternatively, one end of the brake block is pivotally connected to the rotating member, and the other end forms a free end that can move radially relative to the rotating member.

[0045] By adopting the above technical solution, the brake block will rotate together with the rotating component, and centrifugal force will be generated during the rotation. At least part of the brake block will press against the brake friction surface due to the centrifugal force to generate friction.

[0046] Optionally, the linear actuator further comprises a torsion spring brake for balancing the load torque applied to the third force transmission chain after the linear actuator activates a release function.

[0047] By adopting the above technical solution, before the load torque is transmitted to the centrifugal brake, reverse braking is first performed through the torsion spring brake, so that the load torque transmitted to the centrifugal brake will be relatively smaller, thereby reducing the wear of the centrifugal brake and increasing the service life of the centrifugal brake; in addition, the centrifugal brake and the torsion spring brake play a role in balancing the load torque together, so that the entire actuator can withstand a larger load torque, and there is no need to set the braking performance of the centrifugal brake and the torsion spring brake in a scenario where the two work separately; when one of the centrifugal brake and the torsion spring brake fails, the entire actuator still has the function of balancing the load torque.

[0048] Optionally, the torsion spring brake comprises a first torsion spring seat, a second torsion spring seat, a braking torsion spring and a friction element, wherein the first torsion spring seat is non-rotatably connected to the lead screw;

[0049] When the screw rotates in the first direction, the braking torsion spring holds the first torsion spring seat and the second torsion spring seat tightly to form a braking state, and the friction damping force provided by the friction element to the second torsion spring seat balances the load torque applied to the third force transmission chain;

[0050] When the lead screw rotates in a second direction opposite to the first direction, the brake torsion spring is forced to release the first torsion spring seat.

[0051] By adopting the above technical solution, during braking, the screw rod rotates in the opposite direction to drive the first torsion spring seat to move and rotate. During this process, the torsion force of the braking torsion spring gradually increases, thereby driving the second torsion spring seat and the friction element to rotate together, thereby generating friction to achieve braking effect.

[0052] Optionally, the clutch includes a fixed sleeve, a movable sleeve and a biasing element, the connection between the fixed sleeve and the movable sleeve allows the two to move axially relative to each other and be fixed circumferentially relative to each other, the movable sleeve engages with the inner gear ring to implement anti-rotation locking, the release component drives the movable sleeve to disengage from the inner gear ring, and the movable sleeve maintains a tendency to engage with the inner gear ring due to the biasing force of the biasing element.

[0053] By adopting the above technical solution, the rotation stop and unlocking of the internal gear ring are achieved by engaging or disengaging the movable sleeve that axially moves relative to the fixed sleeve, and the structure is simple. Meanwhile, the presence of the biasing element makes it difficult for the movable sleeve to disengage from the internal gear ring, ensuring normal operation.

[0054] Optionally, the engagement between the movable sleeve and the internal gear ring is set to be one of ratchet fit, spline fit, and axial hole and pin fit.

[0055] By adopting the above technical solution, one of ratchet fit, spline fit, and axial hole and pin fit can restrict the rotation stop of the movable sleeve and the internal gear ring in at least one direction, with more configurations and more flexible combinations.

[0056] Optionally, the linear actuator further includes a housing that houses the first force transmission chain and the second force transmission chain, and the fixed sleeve is directly or indirectly fixed to the housing.

[0057] By adopting the above technical solution, the first force transmission chain and the second force transmission chain are arranged in the housing, and the first force transmission chain and the second force transmission chain are well protected. Meanwhile, it is convenient for the installation and support of the first force transmission chain and the second force transmission chain. The fixed sleeve is directly or indirectly fixed to the housing, and the fixing of the fixed sleeve is more convenient and stable, thus facilitating the improvement of the accuracy of the axial movement of the movable sleeve.

[0058] Optionally, the linear actuator further includes a partition plate fixedly connected to the housing. The first force transmission chain is housed between the partition plate and the first side of the housing, the second force transmission chain is housed between the partition plate and the second side of the housing opposite to the first side, and the fixed sleeve is fixed to the partition plate.

[0059] By adopting the above technical solution, the partition plate serves as an intermediate support, making the installation positions of the first force transmission chain and the second force transmission chain more stable.

[0060] Optionally, the release component includes an operating rod and a lever. The lever is axially translated or rotated under the traction of the operating rod to drive the clutch to release the internal gear ring.

[0061] By adopting the above technical solution, the lever drives the clutch to axially move, with a simple structure and convenient operation.

[0062] Optionally, a circumferential annular stop is provided on the clutch along its circumference. The lever has an arc-shaped dial block, and the dial block axially pushes against the annular stop to drive the clutch.

[0063] By adopting the above technical solution, the annular stop cooperates with the arc-shaped dial block of the lever, with simple processing and convenient connection.

[0064] Optionally, the release component includes at least two groups of operating rods and shifting rods circumferentially distributed along the clutch, and all the operating rods are connected by connecting rods and can be synchronously pulled.

[0065] By adopting the above technical solution, all the operating rods and shifting rods circumferentially distributed along the clutch can be synchronously moved through the connecting rods, which is convenient for operation. In addition, the cooperation between multiple shifting rods and the clutch makes the relative position between the two more stable, so that the moving direction of the driven clutch is more accurate.

[0066] Optionally, the speed change transmission mechanism includes:

[0067] An input component configured as one of a gear, a worm gear, and a worm, for drivingly connecting with the planet carrier in the planetary gear reduction mechanism;

[0068] An output component configured as one of a gear, a worm gear, and a worm, for fixedly connecting with the lead screw;

[0069] A speed change unit, meshing with the input component and the output component respectively to form at least two speed change stages.

[0070] By adopting the above technical solution, the speed change unit with at least two speed change stages has a better deceleration effect, thus further increasing the torque of the lead screw and enabling the lead screw to have a greater thrust. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 is a schematic structural diagram of the present invention.

[0072] Figure 2 is a schematic cross-sectional structural diagram of the present invention.

[0073] Figure 3 is a schematic structural diagram of the present invention with the outer housing omitted.

[0074] Figure 4 is a schematic cross-sectional structural diagram of the motor side of the present invention.

[0075] Figure 5 is a schematic cross-sectional structural diagram of the planetary gear set of the present invention.

[0076] Figure 6 is an exploded schematic diagram of the present invention.

[0077] Figure 7 is an exploded schematic diagram of the planetary gear set of the present invention.

[0078] Figure 8 is a schematic structural diagram of the clutch and the internal gear ring of the present invention.

[0079] Figure 9 It is a schematic structural diagram of the torsion spring brake of the present utility model.

[0080] Figure 10 It is a schematic diagram of the force transmission chain direction of other embodiments of the present utility model.

[0081] Figure 11 It is a schematic structural diagram of the cross-section of other embodiments of the present utility model.

[0082] Description of the reference numerals:

[0083] 10. Outer tube; 11. Upper shell; 12. Lower shell; 13. Housing; 14. Motor cover; 15. Partition; 16. Top bearing;

[0084] 20. Tubular telescopic member;

[0085] 30. Telescopic drive mechanism; 31. Lead screw; 32. Transmission nut;

[0086] 40. Variable speed transmission mechanism; 41. Three-stage straight teeth; 42. Central transmission shaft; 43. Second-stage second straight teeth; 44. Second-stage first straight teeth; 45. First-stage straight teeth;

[0087] 50. Motor;

[0088] 60. Planetary gear reduction mechanism; 61. Cage; 611. Main cage; 612. Planetary gear shaft; 613. Bottom plate; 614. Snap ring; 62. Planetary gear; 63. Sun gear; 64. Internal gear ring; 640. Locking spline groove; 641. Radial guide block; 65. Brake block; 650. Radial guide groove; 66. Brake housing; 661. Installation insert;

[0089] 70. Clutch; 71. Movable sleeve; 711. Sliding spline; 712. Annular stop; 713. Locking spline; 72. Fixed sleeve; 73. Compression spring;

[0090] 80. Torsion spring brake; 81. First torsion spring seat; 82. Brake torsion spring; 83. Second torsion spring seat; 84. Friction element;

[0091] 90. Release component; 91. Connecting rod; 911. Outer screw; 92. Operating rod; 93. Poking rod;

[0092] 100. First force transmission chain;

[0093] 200. Second force transmission chain;

[0094] 300. Third force transmission chain;

[0095] a. First force transmission direction; b. Second force transmission direction; c. Third force transmission direction. Detailed implementation manners

[0096] The following will further elaborate on the present utility model in conjunction with the attached Figures 1-11 drawings.

[0097] Embodiment 1: Disclosed is a linear actuator. Referring to Figures 1-3 , it includes an outer tube 10, a housing 13, a motor 50, a tubular telescopic member 20, and a force transmission chain; the force transmission chain includes a first force transmission chain 100, a second force transmission chain 200, and a third force transmission chain 300; the motor 50 is fixed to the housing 13 by bolts; the first force transmission chain 100 and the second force transmission chain 200 are arranged inside the housing 13; the third force transmission chain 300 is arranged on the housing 13; the outer tube 10 is fixed to the housing 13; the tubular telescopic member 20 is telescopically arranged inside the outer tube 10; the power of the motor 50 sequentially passes through the first force transmission chain 100, the second force transmission chain 200, and the third force transmission chain 300 to drive the tubular telescopic member 20 to perform linear motion. When the tubular telescopic member 20 extends, the force transmission direction of the first force transmission chain 100 is the first force transmission direction a, the force transmission direction of the second force transmission chain 200 is the second force transmission direction b, and the force transmission direction of the third force transmission chain 300 is the third force transmission direction c.

[0098] Referring to Figures 1-4 , the housing 13 includes an upper housing 11, a lower housing 12, and a partition 15; the upper housing 11 and the lower housing 12 are assembled by screws to form a transmission box with a hollow interior; the outer tube 10 is fixed to the end face of the upper housing 11 away from the lower housing 12 by screws; the partition 15 is fixed inside the upper housing 11 by screws; the first force transmission chain 100 is located between the partition 15 close to the motor 50 and the upper housing 11; the second force transmission chain 200 is located between the partition 15 away from the motor 50 and the lower housing 12; the first force transmission chain 100 and the third force transmission chain 300 are located on the same side of the partition 15 and their force transmission directions are arranged in parallel. The overall length of the linear actuator depends on the relatively larger length among the first force transmission chain 100 and the third force transmission chain 300, rather than the sum of the lengths of the first force transmission chain 100 and the third force transmission chain 300. Therefore, the overall length of the linear actuator is greatly reduced; in addition, compared with the conventional method of setting the motor perpendicular to the lead screw, the first force transmission chain 100 and the third force transmission chain 300 approach each other in a parallel posture. Generally speaking, the motor can directly output torque to the first force transmission chain 100, which makes the axial direction of the output shaft of the motor parallel to the first force transmission direction a, and further makes the motor parallel to the lead screw, reducing the overall volume of the linear actuator and facilitating transportation and installation in small spaces.

[0099] Referring to Figure 1 and Figure 3 , in order to protect the motor 50, referring to Figure 1 and Figure 2 , a motor cover 14 is sleeved outside the motor 50; the motor cover 14 is fixed to the upper housing 11 by screws.

[0100] Reference Figures 2-7 The first force transmission chain 100 includes a planetary gear reduction mechanism 60. The planetary gear reduction mechanism 60 includes a sun gear 63, a cage 61, four planet gears 62 rotatably connected to the cage 61, and an internal gear ring 64. The sun gear 63 is coaxially disposed within the internal gear ring 64. The four planet gears 62 are located between the sun gear 63 and the internal gear ring 64. The planet gears 62 are respectively meshed with the sun gear 63 and the internal gear ring 64. The end of the output shaft of the motor 50 has a double-flat position. A slot matching with the output shaft of the motor 50 is formed on the end face of the rotating shaft of the sun gear 63 close to the motor 50. The input end of the first force transmission direction a is the sun gear 63, and the output end is the cage 61.

[0101] Reference Figures 2-7 The cage 61 includes a main cage 611 and a cross-shaped bottom plate 613. Four connecting through holes are formed on both the main cage 611 and the cross-shaped bottom plate 613. The planet gear 62 is integrally formed with a planet gear shaft 612. The two ends of the planet gear shaft 612 respectively pass through the corresponding connecting through holes on the side. Ring-shaped grooves are respectively formed at the two ends of the planet gear shaft 612. A snap ring 614 is clamped in the groove. A vertically penetrating central through hole is formed at the center of the bottom plate 613. The sun gear 63 passes through the central through hole. During installation, the four planet gear shafts 612 pass through the four central through holes of the main cage 611 in sequence, then the bottom plate 613 is sleeved on the other ends of the four planet gear shafts 612, and finally the snap ring 614 is clamped in the grooves of the four planet gear shafts 612. Circular contact rings are respectively formed at the two ends of the planet gear 62 and are coaxially disposed. The contact rings are in contact with the bottom plate 613 or the main cage 611. Since the area of the contact ring is smaller than the end area of the planet gear 62, such a design can reduce the friction force.

[0102] Reference Figure 2 、 Figure 3 and Figure 5 The third force transmission chain 300 includes a telescopic driving mechanism 30. The telescopic driving mechanism 30 includes a lead screw 31 and a transmission nut 32 threadedly engaged with the lead screw. The lead screw 31 is connected to the partition plate 15 through a bearing. The axial direction of the lead screw 31 is parallel to the axial direction of the cage 61. The tubular telescopic member 20 is fixed to the transmission nut 32 by screws. When the tubular telescopic member 20 extends, the third force transmission direction c is the displacement direction of the transmission nut 32 on the lead screw 31, so that the third force transmission direction c is parallel to the first force transmission direction a.

[0103] Reference Figure 2 、 Figure 3 and Figure 5The second force transmission chain 200 includes a speed transmission mechanism 40; the speed transmission mechanism 40 includes a primary spur gear 45, a secondary spur gear and a tertiary spur gear 41; the tertiary spur gear 41 is coaxially connected to the screw rod 31 and the connection method between the two can refer to the connection method between the rotating shaft of the sun gear 63 and the output shaft of the motor 50, that is, the connection method through a non-circular hole and a non-cylindrical shaft; the partition 15 is rotatably connected to a central transmission shaft 42 through a bearing; the secondary spur gear is coaxially fixed on the central transmission shaft 42; the secondary spur gear includes a secondary second spur gear 43 and a secondary first spur gear 44 connected as one body; the primary spur gear 45 is integrally formed The type has a primary spur gear shaft; the primary spur gear 45 meshes with the secondary first spur gear 44; the secondary second spur gear 43 meshes with the tertiary spur gear 41; the diameter of the primary spur gear 45 is smaller than the diameter of the secondary first spur gear 44; the diameter of the secondary second spur gear 43 is smaller than the diameter of the tertiary spur gear 41; the end of the screw rod 31 away from the outer tube 10 is double flat, and the center of the tertiary spur gear 41 is formed with a hole that matches one end of the double flat of the screw rod 31; the end of the rotating shaft of the retaining frame 61 holding the main frame 611 is double flat; the end face of the primary spur gear shaft of the primary spur gear 45 is formed with a slot that matches the rotating shaft of the star main frame 611. The input end of the second force transmission direction b is the primary spur gear 45, and the output end is the tertiary spur gear 41.

[0104] The above-mentioned speed change transmission mechanism 40 is a two-stage speed change. Of course, according to actual needs, the speed change transmission mechanism 40 can also be provided with a multi-stage speed change such as a three-stage speed change.

[0105] In addition, the second force transmission chain 200 may also change speed through a worm gear instead of a gear meshing speed change. Of course, the gear and the worm gear may be combined to achieve the speed change purpose. At the same time, other common speed change structures may also be used.

[0106] To sum up, during normal operation, the speed transmission mechanism 40 can select one of the gear, worm wheel and worm as the input component, which is connected to the retaining frame 61; and can select one of the gear, worm wheel and worm as the output component, which is connected to the screw 31.

[0107] In order to improve the installation stability of the planetary gear reduction mechanism 60 and the speed change transmission mechanism 40, refer to Figure 3 An inner abutment column 141 is formed on the inner side wall of the lower shell 14; a top bearing 16 is installed on the inner abutment column 141; and a coaxially arranged mounting groove that cooperates with the top bearing 16 is formed at the center of the end of the first-stage spur gear 45.

[0108] In order to realize the release function, that is, the load drives the tubular telescopic part 20 to contract, a clutch 70 and a release part 90 are also arranged between the upper shell 11 and the partition 15; the clutch 70 is used to implement anti-rotation locking of the inner ring gear 64; the release part 90 is used to drive the clutch 70 to release the inner ring gear 64 and activate the release function of the linear actuator.

[0109] Reference Figures 4-6 and Figure 8 As shown in FIGS. 1 and 2, the clutch 70 includes a fixed sleeve 72, a movable sleeve 71 and a compression spring 73; the movable sleeve 71 includes an annular central clutch ring; one end of the central clutch ring is formed with a coaxial annular sliding ring; five circumferentially uniformly distributed sliding splines 711 are formed on the outer cylindrical surface of the sliding ring; the fixed sleeve 72 is connected to the partition 15 by screws; a clutch through hole for the first-stage spur gear shaft of the first-stage spur gear 45 to pass through is formed at the bottom of the sliding cavity of the fixed sleeve 72; a sliding cavity for the sliding ring to axially slide is formed at one end of the fixed sleeve 72; one end of the compression spring 73 abuts against the bottom of the sliding cavity and the other end abuts against the movable sleeve 71; five sliding spline grooves for the sliding splines 711 to axially move are formed on the inner cylindrical surface of the sliding cavity; the inner diameter of the internal gear ring 64 is larger than that of the central clutch ring; four circumferentially uniformly distributed locking splines 713 are formed on the outer cylindrical surface of the central clutch ring; four locking spline grooves 640 for the locking splines 713 to axially insert are formed at one end of the internal gear ring 64 close to the movable sleeve 71; the function of the compression spring 73 is to bias the movable sleeve 71 towards the internal gear ring 64 so that the locking splines 713 are inserted into the locking spline grooves 640. In addition, the outer diameter of the central clutch ring is larger than the inner diameter of the sliding cavity, so that there is a spacing limit for the moving direction of the movable sleeve 71 away from the internal gear ring 64. When the movable sleeve 71 reaches the limit position on the moving side away from the internal gear ring 64, the locking splines 713 disengage from the locking spline grooves 640.

[0110] The anti-rotation of the internal gear ring 64 is achieved by the spline fit method described above. That is, during normal operation, the internal gear ring 64 cannot rotate, so the power of the motor 50 can be transmitted to the first-stage spur gear 45 through the sun gear 63, the planetary gear 62 and the cage 61 in sequence. Therefore, the engagement method between the internal gear ring 64 and the movable sleeve 71 can also be one of ratchet fit and axial hole and pin fit. In the case of ratchet fit, one of the internal gear ring 64 and the movable sleeve 71 is fixed with a ratchet and the other is rotatably connected with ratchet teeth. During normal operation, the cooperation between the ratchet and the ratchet teeth makes the internal gear ring 64 unable to rotate forward. When released, the internal gear ring 64 can rotate backward; in the case of axial hole and pin fit, one of the internal gear ring 64 and the movable sleeve 71 is formed with a hole that is non-coaxial but axially parallel to both of them, and the other is formed with a pin that cooperates with it.

[0111] Reference Figure 6 and Figure 8, the release member 90 includes a pair of toggle levers 93, a pair of operating levers 92, and a connecting rod 91; the operating levers 92 correspond to the toggle levers 93 one by one; the toggle lever 93 includes an arc-shaped toggle block and a vertical plate portion formed on the outer cylindrical surface of the toggle block; screw rods are formed at both ends of the operating lever 92 respectively; one screw rod of the operating lever 92 is screwed on the vertical plate portion of the toggle lever 93, and the other screw rod vertically passes through the end of the connecting rod 91 and is screwed with a nut; a pair of annular stoppers 712 are formed in the middle of the movable sleeve 71; the toggle blocks of the pair of toggle levers 93 are radially inserted between the pair of annular stoppers 712; the pair of operating levers 92 pass through the lower housing 12 and the connecting rod 91 is located outside the transmission case. In order to reduce friction, the movable sleeve 71 is made of self-lubricating plastic material, ultimately reducing noise.

[0112] In order to facilitate pulling the release member 90, an external screw rod 911 is vertically fixed in the middle of the end face of the connecting rod 91 away from the transmission case; the external screw rod 911 can be used to connect an external handle or a pedal to facilitate driving the release operating member; preferably, the external screw rod 911 is located exactly in the middle of the pair of operating levers 92.

[0113] Of course, the toggle lever 93 may not be translated. The center of the vertical plate portion of the toggle lever 93 is rotatably connected to the transmission case, and then the end of the vertical plate portion of the toggle lever 93 away from the toggle block extends out of the transmission case and is connected to the operating lever 92. In this way, the operating lever 92 drives the toggle lever 93 to rotate, and the toggle block of the toggle lever 93 abuts against and pushes the corresponding annular stopper 712 to drive the movable sleeve 71 to move axially along the fixed sleeve 72; due to the presence of the compression spring 73, there may be only one annular stopper 712 and it is located on the side of the toggle block of the toggle lever 93 away from the internal gear ring 64.

[0114] In addition to the above situation where the release member 90 includes a pair of toggle levers 93 and a pair of operating levers 92, in other embodiments, the number of toggle levers 93 and operating levers 92 of the release member 90 can be more than two, so that during the movement of the movable sleeve 71, there will be no situation of movement deviation due to eccentric force on the movable sleeve 71 when driven by a single fork. In this way, there is no need for high fitting accuracy between the movable sleeve 71 and the fixed sleeve 72 to achieve precise guidance, thereby reducing the processing cost.

[0115] Working principle of Embodiment 1: During normal operation, one end of the central clutch ring of the movable sleeve 71 is inserted into one end of the internal gear ring 64. At this time, the locking spline 713 is located in the locking spline groove 640 of the internal gear ring 64. Since the movable sleeve 71 is axially slidably arranged in the fixed sleeve 72 and the fixed sleeve 72 is fixedly connected to the partition plate 15, the internal gear ring 64 is locked and cannot rotate at this time. The motor 50 drives the sun gear 63 to rotate, and the sun gear 63 drives the four planet gears 62 to rotate on their own axes. Due to the action of the fixed internal gear ring 64, the four planet gears 62 drive the cage 61 to rotate on its own axis, thereby driving the first-stage straight gear 45 to rotate. Then, through the second-stage first straight gear 44, the second-stage second straight gear 43, and the third-stage straight gear 41, the lead screw 31 of the third transmission chain 300 is driven to rotate. The transmission nut 32 of the third transmission chain 300 moves axially along the outer tube 11, thereby driving the tubular telescopic member 20 to extend.

[0116] When the motor 50 loses power, the motor 50 itself has a braking torque, so the sun gear 63 cannot rotate. In this way, the fixed sun gear 63 and the internal gear ring 64 restrict the rotation of the planet gears 62, so that the cage 61 cannot rotate, and thus the electric lifting linear actuator cannot contract. At this time, the connecting rod 91 is pulled, and through a pair of operating rods 92 and the axial movement of the movable sleeve 71, the movable sleeve 71 is moved away from the internal gear ring 64, so that the locking spline 713 is disengaged from the locking spline groove 640. In this way, the internal gear ring 64 is unlocked and can rotate freely. Due to the self-weight of the load, the tubular telescopic member 20 is driven to retract, that is, the transmission nut 32 returns to its original position, which drives the lead screw 31 to rotate in the reverse direction. Then, through the third-stage straight gear 41, the second-stage second straight gear 43, the second-stage first straight gear 44, and the first-stage straight gear 45 in sequence, the cage 61 is driven to rotate, thereby realizing the release. At the same time, the internal gear ring 64 is driven by the planet gears 62 to rotate.

[0117] Embodiment 2: The difference between Embodiment 2 and Embodiment 1 lies in: Refer to Figure 5 and Figure 6, further comprising a centrifugal brake; the centrifugal brake is connected to the internal gear ring 64 and only when the internal gear ring 64 rotates, the centrifugal brake will generate a braking force to balance the load torque applied to the first force transmission chain 100; combined with the first embodiment, when the tubular telescopic member 20 extends, the internal gear ring 64 is restricted and at this time the internal gear ring 64 cannot rotate, so that the centrifugal brake will not be triggered. The power of the motor 50 sequentially passes through the sun gear 63, four planet gears 62, the cage 61, the second force transmission chain 200 and the third force transmission chain 300, and the third force transmission chain 300 outputs with deceleration and torque increase. During this process, the centrifugal brake does not work; when the motor 50 loses power and the internal gear ring 64 is released, the load torque sequentially passes through the third force transmission chain 300, the second force transmission chain 200, the cage 61, the planet gears 62 and the four planet gears 62 to drive the internal gear ring 64 to rotate. The rotating internal gear ring 64 triggers the centrifugal brake, and the centrifugal brake generates a centrifugal braking force to balance the load torque.

[0118] Reference Figure 5 , the centrifugal brake includes a rotating member and a brake housing 66; the rotating member is integrally formed on the outer peripheral surface of the internal gear ring 64 and the two are coaxially arranged; the internal gear ring 64 is located inside the brake housing 66 and the two are coaxially arranged; there is a gap between the rotating member and the brake housing 66 and six fan-shaped brake blocks 65 are arranged in this gap.

[0119] Reference Figure 5 , wherein six radially guiding blocks 641 evenly distributed in the circumferential direction are formed on the outer peripheral surface of the rotating member; the radially guiding blocks 641 correspond to the brake blocks 65 one by one; a radially guiding groove 650 matching the radially guiding block 641 is formed in the middle of the inner surface of the brake block 65 close to the internal gear ring 64; the radially guiding groove 650 is radially sleeved on the corresponding radially guiding block 641; the brake block 65 can move radially in the gap between the rotating member and the brake housing 66. Of course, the radially guiding blocks 641 can also be arranged on the inner side surface of the brake block 65, and the radially guiding grooves 650 are arranged on the outer peripheral surface of the rotating member; in other embodiments, six guiding grooves can also be formed on the outer cylindrical surface of the rotating member, and the brake block 65 moves radially in the guiding grooves. The above structures all drive the brake block 65 to rotate together with the rotating internal gear ring 64, so that the brake block 65 generates a centrifugal force and moves radially outward to friction with the brake housing 66 to generate a braking force.

[0120] In addition, the brake block 65 does not have to be in the above-mentioned radially guiding manner. One end of the brake block 65 is hinged to the outer peripheral surface of the rotating member, and the other end is in a free state. When the brake block 65 is subjected to a centrifugal force, the free end of the brake block 65 can abut against the inner peripheral surface of the brake housing 66 to generate a reverse braking force.

[0121] To facilitate the connection between the brake housing 66 and the upper housing 11, a pair of mounting inserts 661 evenly distributed in a circle are formed on the outer cylindrical surface of the brake housing 66; a pair of mounting slots that cooperate with the mounting inserts 661 are formed on the inner surface of the upper housing 11; one end of the mounting slot facing the lower housing 12 is open.

[0122] In addition, to facilitate the subsequent maintenance of the rotating component, the rotating component can also be an independent part and is connected to the internal gear ring 64 in a detachable manner such as by screws.

[0123] The working principle of the second embodiment: When releasing, the rotating internal gear ring 64 drives the rotating component and the brake block 65 to rotate. Since the brake block 65 is arranged to move radially, the brake block 65 moves outward due to centrifugal force and generates frictional force with the brake housing 66, thereby playing a role of reverse braking. In this way, the contraction speed will not be too fast and no impact will be formed. In addition, with different loads, the moving speed of the transmission nut 32 is different, and the rotation speed of the lead screw 31 is also different. Thus, the rotation speed of the internal gear ring 64 after transmission is also different, that is, the rotation of the brake block 65 is also different, and finally different frictional forces are generated; the greater the load, the greater the frictional force and the greater the reverse braking force; the smaller the load, the smaller the frictional force and the smaller the reverse braking force; so it is possible to achieve similar release speeds under different loads.

[0124] Embodiment Three: The difference between Embodiment Three and Embodiment One lies in: Refer to Figure 9 , the linear actuator further includes a torsion spring brake 80, and the torsion spring brake 80 includes a first torsion spring seat 81, a second torsion spring seat 83, a brake torsion spring 82, and a friction element 84; the first torsion spring seat 81 is connected to one end of the lead screw 31 away from the transmission nut 32, and the lead screw 31 rotates synchronously with the first torsion spring seat 81 at the same speed. The connection method between the two can refer to the connection method between the rotating shaft of the sun gear 63 and the output shaft of the motor 50, that is, by connecting through a non-circular hole and a non-cylindrical shaft. In this way, the first torsion spring seat 81 is non-rotatably connected to the lead screw 31, and a nut is screwed on the end of the lead screw 31 to separate the first torsion spring seat 81 from the lead screw 31; both ends of the brake torsion spring 82 are respectively clamped with the first torsion spring seat 81 and the second torsion spring seat 83; when the first torsion spring seat 81 and the second torsion spring seat 83 rotate relative to each other, the brake torsion spring 82 can be released or tightened; the friction element 84 is fixed to one end of the second torsion spring seat 83 away from the brake torsion spring 82 and abuts against the inner surface of the lower housing 12. During operation, the first torsion spring seat rotates with the lead screw 31 to release the brake torsion spring; when releasing, the first torsion spring seat rotates with the lead screw 31 to tighten the brake torsion spring, and finally drives the second torsion spring seat and the friction element to rotate together, and the friction element generates frictional braking force with the inner surface of the lower housing 12.

[0125] In this way, when released, before the load torque is transmitted to the centrifugal brake, reverse braking is first performed through the torsion spring brake, so that the load torque transmitted to the centrifugal brake will be relatively smaller, thereby reducing the wear of the centrifugal brake and increasing the service life of the centrifugal brake; in addition, the centrifugal brake and the torsion spring brake play a role in balancing the load torque together, so that the entire actuator can withstand a larger load torque, and there is no need to set the braking performance of the centrifugal brake and the torsion spring brake in a scenario where the two work separately; when one of the centrifugal brake and the torsion spring brake fails, the entire actuator still has the function of balancing the load torque.

[0126] Example 3: Reference Figure 2 , the first force transmission direction a, the second force transmission direction b and the third force transmission direction c of the first embodiment are all on the XY plane, the first force transmission direction a intersects with the second force transmission direction b, and the second force transmission direction b intersects with the third force transmission direction c; reference Figure 10 In embodiment three, the second force transmission direction b and the third force transmission direction c can be set on the XY plane, and the first force transmission direction a can be set on the XZ plane. In this way, the first force transmission direction a and the installation direction of the motor connected to the first force transmission chain 100 can be changed to adapt to different usage spaces, which is more adaptable.

[0127] Embodiment 4: The difference between Embodiment 4 and Embodiment 2 is: Figure 11 The fixed sleeve 72 is fixed in the upper shell 11 , the planetary gear reduction mechanism 60 and the clutch 70 are located in the fixed sleeve 72 ; the clutch 70 is located between the planetary gear reduction mechanism 60 and the motor 50 ; the output shaft of the motor 50 coaxially passes through the movable sleeve 71 .

[0128] The above are all preferred embodiments of the present utility model, and are not intended to limit the protection scope of the present utility model. Therefore, any equivalent changes made based on the structure, shape, and principle of the present utility model should be included in the protection scope of the present utility model.

Claims

1. A linear actuator, comprising: A motor; A tubular telescopic member; A force transmission chain configured to transmit the power of the motor to the tubular telescopic member to drive the tubular telescopic member to perform a linear motion; Characterized in that: the force transmission chain comprises: A first force transmission chain including a planetary gear reduction mechanism drivingly connected to the output end of the motor; A second force transmission chain drivingly connected to the first force transmission chain, including a speed change transmission mechanism having gears and / or worm gears; A third force transmission chain drivingly connected to the second force transmission chain, including a lead screw and a transmission nut threadedly engaged with the lead screw, the transmission nut connecting the tubular telescopic member; The force transmission direction of the first force transmission chain intersects with the force transmission direction of the second force transmission chain, and the force transmission direction of the second force transmission chain intersects with the force transmission direction of the third force transmission chain; A clutch for rotationally locking the internal gear ring of the planetary gear reduction mechanism; A release member for driving the clutch to release the internal gear ring to activate the release function of the linear actuator.

2. The linear actuator according to claim 1, characterized in that: The force transmission direction of the first force transmission chain is from the input end to the output end of the planetary gear reduction mechanism; The force transmission direction of the second force transmission chain is from the input end to the output end of the speed change transmission mechanism; The force transmission direction of the third force transmission chain is the displacement direction of the transmission nut on the lead screw; The force transmission directions of the first force transmission chain and the third force transmission chain are arranged in parallel.

3. A linear actuator according to claim 2, characterized in that: The first force transmission chain and the third force transmission chain are located on the same side of the second force transmission chain.

4. A linear actuator according to claim 1, characterized in that: The linear actuator further includes a centrifugal brake for balancing the load torque applied to the first force transmission chain after the release function of the linear actuator.

5. A linear actuator according to claim 4, characterized in that: The planetary gear reduction mechanism further includes: A sun gear drivingly connected to the output end of the motor; Planetary gears meshing between the sun gear and the internal gear ring; A cage drivingly connected to the third force transmission chain for carrying the planetary gears; When the internal gear ring is rotationally locked by the clutch, the power of the motor does not trigger the centrifugal brake and outputs decelerated and torque-increased power to the third force transmission chain through the cage; When the internal gear ring is released by the clutch, the load torque outputs speed-increased and torque-decreased power to the centrifugal brake through the internal gear ring, and the centrifugal brake is triggered to brake by the load torque.

6. A linear actuator according to claim 4, characterized in that: The centrifugal brake includes: A rotating member driven to rotate by the internal gear ring; A brake housing providing a braking friction surface; A brake block provided between the rotating member and the brake housing, which generates a centrifugal motion by the rotational motion of the rotating member and contacts the braking friction surface.

7. A linear actuator according to claim 6, characterized in that: The rotating member is configured as a part of the internal gear ring or attached to the internal gear ring.

8. The linear actuator according to claim 6, characterized in that: One of the brake block and the rotating member is provided with a radial guiding groove, and the other is provided with a radial guiding block, and the radial guiding block is inserted into the radial guiding groove to guide the centrifugal motion of the brake block; Alternatively, the outer peripheral surface of the rotating component has a guide groove adapted to the brake block, the brake block is embedded in the guide groove, and the brake block and the rotating component keep synchronous rotation in the circumferential direction and can move relative to each other in the radial direction; Alternatively, one end of the brake block is pivotally connected to the rotating component, and the other end constitutes a free end capable of radially moving relative to the rotating component.

9. A linear actuator according to claim 4, characterized in that: The linear actuator further comprises a torsion spring brake for balancing the load torque applied to the third force transmission chain after the linear actuator activates a release function.

10. A linear actuator according to claim 9, characterized in that: The torsion spring brake comprises a first torsion spring seat, a second torsion spring seat, a braking torsion spring and a friction element, wherein the first torsion spring seat is non-rotatably connected to the lead screw; When the screw rotates in the first direction, the braking torsion spring holds the first torsion spring seat and the second torsion spring seat tightly to form a braking state, and the friction damping force provided by the friction element to the second torsion spring seat balances the load torque applied to the third force transmission chain; When the lead screw rotates in a second direction opposite to the first direction, the brake torsion spring is forced to release the first torsion spring seat.

11. A linear actuator according to claim 1, characterized in that: The clutch includes a fixed sleeve, a movable sleeve and a biasing element. The connection between the fixed sleeve and the movable sleeve allows the two to move axially relative to each other and to be fixed circumferentially relative to each other. The movable sleeve is engaged with the inner gear ring to implement anti-rotation locking. The release component drives the movable sleeve to disengage from the inner gear ring. The movable sleeve is biased by the biasing force of the biasing element and maintains a tendency to engage with the inner gear ring.

12. A linear actuator according to claim 11, characterized in that: The engagement between the movable sleeve and the inner gear ring is configured as one of a ratchet fit, a spline fit and an axial hole pin fit.

13. A linear actuator according to claim 11, characterized in that: The linear actuator further comprises a housing for accommodating the first force transmission chain and the second force transmission chain, and the fixing sleeve is directly or indirectly fixed to the housing.

14. A linear actuator according to claim 13, characterized in that: The linear actuator also includes a partition fixedly connected to the shell, the first force transmission chain is accommodated between the partition and the first side of the shell, the second force transmission chain is accommodated between the partition and the second side of the shell opposite to the first side, and the fixed sleeve is fixed to the partition.

15. A linear actuator according to claim 1, characterized in that: The release component includes an operating rod and a shifting rod. The shifting rod is pulled by the operating rod to generate axial translation or rotation, so as to drive the clutch to release the inner gear ring.

16. A linear actuator according to claim 15, characterized in that: An annular stop is arranged on the clutch along its circumference, and the shifting rod has an arc-shaped shifting block, and the shifting block axially pushes against the annular stop to drive the clutch.

17. A linear actuator according to claim 16, characterized in that: The release component comprises at least two groups of operating rods and shifting rods distributed along the circumference of the clutch, and all the operating rods are connected by connecting rods so as to be pulled synchronously.

18. A linear actuator according to claim 1, characterized in that: The speed change transmission mechanism comprises: An input component configured as one of a gear, a worm wheel, and a worm, and configured to be drivingly connected to a planetary gear holder in the planetary gear reduction mechanism; An output component configured as one of a gear, a worm wheel, and a worm, and used for fixed connection with the lead screw; The speed change unit engages the input member and the output member to form at least two speed change stages.

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