Linear driving mechanism

Abstract

Provided in the present invention is a linear driving mechanism, comprising a housing, a front cover, a rear cover, a stator and a rotor. The rotor comprises a hollow rotor magnet and a differential lead screw sleeved in the rotor magnet. The differential lead screw comprises a lead screw nut, a first bracket and a second bracket corresponding thereto, a plurality of first lead screws annularly distributed between the first bracket and the second bracket, and a central lead screw arranged in the center of the lead screw nut and extending through the front cover, wherein two ends of each first lead screw are connected to the first bracket and the second bracket, respectively, the plurality of first lead screws are rotationally connected to the lead screw nut, and the plurality of first lead screws are in threaded connection with the central lead screw. The stator drives the rotor magnet to rotate so as to drive the lead screw nut to rotate, such that the first lead screws rotate to drive the central lead screw to achieve linear telescopic motion. Compared with the prior art, the linear driving mechanism of the present invention has a good linear driving effect, good real-time controllability, high multi-stage transmission efficiency and high reliability, and saves on the mounting space.

Description

Linear driving mechanism TECHNICAL FIELD

[0001] The present application relates to the technical field of linear driving, in particular to a linear driving mechanism. BACKGROUND

[0002] With the rapid development of artificial intelligence and robot industry, the fingers of humanoid robots are an important part to achieve actions and complete tasks. Due to the requirements of space and energy saving, linear actuators are required to be more stringent, and linear actuators are developing towards high integration, smaller size, higher carrying capacity and faster response. The linear driving mechanism is a kind of linear actuator, which adopts a screw rod as a driving part, and a nut as a linear output, that is, the nut does not rotate but runs in and out along the axial direction, and the screw rod rotates in operation. TECHNICAL PROBLEM

[0003] In the related art, the finger driving mechanism adopts a brush motor and a multi-stage planetary reducer structure. The motor force transmission has obvious hysteresis phenomenon after multi-stage reduction, and the real-time control performance is poor. After multi-stage transmission, the efficiency decreases rapidly with the increase of the number of stages. The brush motor itself also has the problems of poor reliability of the brush, unbalanced three-phase resistance caused by contact problems, unbalanced torque, etc. At the same time, in order to ensure the safety of the system, the motor stator outer diameter and the outer part of the nut must be constrained in a whole shell, which increases the overall size of the linear driving mechanism.

[0004] Therefore, it is necessary to provide a new linear driving mechanism to solve the above technical problems. TECHNICAL SOLUTION

[0005] The purpose of the present application is to provide a linear driving mechanism with good linear driving effect, excellent real-time control performance, high multi-stage transmission efficiency, high reliability and saved installation space.

[0006] In order to achieve the above purpose, the present application provides a linear driving mechanism, comprising a shell with two open ends, a front cover and a rear cover fixed respectively at opposite ends of the shell, a stator arranged in the shell, and a rotor arranged in the stator and in rotational connection with the stator; the rotor comprises a hollow rotor magnet and a differential screw rod sleeved in the rotor magnet.

[0007] The differential screw rod comprises a screw rod nut fixedly inserted into the rotor magnet, a first support and a corresponding second support arranged at the inner circumferal side of the screw rod nut near one end of the front cover, a plurality of first screw rods annularly arranged between the first support and the second support, and a central screw rod arranged at the center of the screw rod nut and extending through the center of the front cover, both ends of the first screw rod being connected with the first support and the second support respectively, the first screw rod being rotatably connected with the screw rod nut, and the first screw rod being screw-connected with the central screw rod; the stator drives the rotor magnet to rotate to drive the screw rod nut to rotate, so that the first screw rod drives the central screw rod to realize linear extension and contraction.

[0008] Preferably, the screw rod nut comprises a hollow nut body fixedly inserted into the rotor magnet and a first thread structure formed at the inner circumferal side of one end of the nut body near the front cover; the first screw rod is in contact with and rotatably connected with the first thread structure.

[0009] The central screw rod comprises a central screw rod body arranged in the nut body and provided with a second thread structure at the outer circumferal side, and an extended end formed by one end of the central screw rod body near the front cover, the first screw rod being screw-connected with the second thread structure, and the extended end penetrating the front cover near one end of the front cover.

[0010] Preferably, the screw rod nut further comprises an annular avoiding groove recessed from one side of the first thread structure near the central screw rod to the side away from the central screw rod.

[0011] The first screw rod comprises a first screw rod body rotatably connected with the first support and the second support, a third thread structure protruded at the outer circumferal side of the first screw rod body, and two fourth thread structures protruded at both ends of the first screw rod body respectively, the two fourth thread structures being arranged at both ends of the third thread structure respectively, and the fourth thread structure being screw-connected with the first thread structure; one side of the third thread structure is located in the avoiding groove, and the other side of the third thread structure is screw-connected with the second thread structure.

[0012] Preferably, the cross section of the extended end is non-circular, and the extended end is in sliding connection with the front cover along the axial direction of the central screw rod body.

[0013] Preferably, the linear driving mechanism further comprises a rectangular block, a control board and a linear position sensor, the block is sleeved and fixed to the extension end, the control board is fixed to the cabinet and the front cover respectively, the linear position sensor is electrically connected with the control board, and the linear position sensor is used to collect linear movement data of the block and transmit the data to the control board.

[0014] Preferably, the linear position sensor comprises a linear sensor magnet embedded in the block near the control board and at least one Hall sensor fixed to the control board near the center screw rod, and any Hall sensor is located within the magnetic field range of the linear sensor magnet when the Hall sensor directly faces the linear sensor magnet.

[0015] Preferably, the linear position sensor comprises a spring fixed to the block near the control board and a long strip-shaped conductor resistor fixed to the control board near the center screw rod, the spring slides on the surface of the conductor resistor with the block, and the linear extension length of the extension end is collected by sensing the resistance values of different positions of the conductor resistor.

[0016] Preferably, the stator comprises a stator core fixed to the cabinet near the differential screw rod and a coil winding fixed in the stator core, the coil winding is spaced from the rotor, and the coil winding drives the rotor to rotate after being energized.

[0017] Preferably, the stator core is an annular magnetic steel sleeve or a circular ring-shaped core formed by bonding multiple silicon steel sheets.

[0018] Preferably, the screw nut is a magnetic hollow shaft structure, and the permanent magnet installed on the magnetic hollow shaft structure is a radial 4-pole or 6-pole magnetic ring structure.

[0019] Preferably, the linear driving mechanism further comprises an angle position sensor, the angle position sensor is sleeved and fixed to the screw nut, and the angle position sensor is used to collect rotation angle position data of the rotor.

[0020] Preferably, the linear driving mechanism further comprises an angle position sensor, the angle position sensor is fixed to the control board and forms an electrical connection, and the angle position sensor is used to collect rotation angle position data of the rotor.

[0021] Preferably, the linear driving mechanism further comprises an angle position sensor, the angle position sensor is fixed to one end of the screw nut near the rear cover, and the angle position sensor is used to collect rotation angle position data of the rotor.

[0022] Preferably, the angular position sensor comprises a collecting part fixed to the rear cover and a rotating part fixed to the screw nut near the rear cover, and the collecting part and the rotating part are arranged opposite and spaced apart.

[0023] Preferably, the linear driving mechanism further comprises a first bearing and a second bearing, the first bearing and the second bearing are respectively sleeved and fixed to two ends of the screw nut, and the outer periphery of the first bearing and the outer periphery of the second bearing are respectively fixed to the cabinet.

[0024] Preferably, a flat structure is formed by recessing the protruding end, and a flat hole is formed through the front cover at the corresponding position of the protruding end. Beneficial effects

[0025] Compared with the prior art, in the linear driving mechanism of the present application, the differential screw rod is sleeved in the rotor magnet, the differential screw rod comprises a screw nut inserted and fixed in the rotor, a first support and a corresponding second support arranged at the inner periphery side of one end of the screw nut near the front cover, a plurality of first screw rods annularly distributed between the first support and the second support, and a central screw rod arranged at the center of the screw nut and extending through the front cover, the two ends of the first screw rod are respectively fixedly connected with the first support and the second support, a plurality of the first screw rods are respectively rotationally connected with the screw nut, and a plurality of the first screw rods are screw-connected with the central screw rod; the stator drives the rotor magnet to rotate to drive the screw nut to rotate, so that the first screw rod rotates to drive the central screw rod to realize linear extension and contraction; the motor and the motion mechanism are directly driven, which is easy to control, has high system reliability, low overall height, small length, and friendly installation size. Further, cost is saved, and installation space is saved. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort, wherein:

[0027] Fig. 1 is a perspective structural schematic view of the linear driving mechanism provided by the embodiment one of the present application;

[0028] Fig. 2 is a perspective structural exploded view of the linear driving mechanism provided by the embodiment one of the present application;

[0029] Fig. 3 is a cross-sectional view of A-A line in Fig. 1;

[0030] Fig. 4 is a perspective structural schematic view of the linear driving mechanism provided by the embodiment two of the present application;

[0031] Fig. 5 is a B-B line section view of Fig. 4;

[0032] Fig. 6 is a perspective structural schematic view of the linear driving mechanism provided by the third embodiment of the present application;

[0033] Fig. 7 is a perspective structural exploded view of the linear driving mechanism provided by the third embodiment of the present application;

[0034] Fig. 8 is a C-C line section view of Fig. 6;

[0035] Fig. 9 is a structural schematic view of the differential screw provided by the present application.

[0036] In the figure, 100, linear driving mechanism, 1, machine shell, 2, front cover, 21, flat position hole, 3, rear cover, 4, stator, 41, stator core, 42, coil winding, 5, rotor magnet, 6, differential screw, 61, screw nut, 611, nut body, 612, first thread structure, 613, avoiding slot, 62, center screw, 621, center screw body, 622, second thread structure, 623, extending end, 624, flat position structure, 63, first support, 64, second support, 65, first screw, 651, first screw body, 652, third thread structure, 653, fourth thread structure, 7, stop block, 71, stop block body, 72, slot, 8, control board, 9, linear position sensor, 91, linear sensor magnet, 92, Hall sensor, 93, elastic sheet, 94, conductor resistance, 10, angle position sensor, 101, rotating part, 102, acquisition part, 11, first bearing, 12, second bearing, 13, magnet seat, 20, rotor. Embodiment of the present application

[0037] The technical solutions in the embodiments of the present application will be described clearly and completely below with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0038] Embodiment one

[0039] In combination with FIG. 1 to FIG. 9, the linear driving mechanism 100 provided by the embodiment of the present application comprises a shell 1 with two open ends, a front cover 2 and a rear cover 3 fixed to the opposite ends of the shell 1 respectively, a stator 4 arranged in the shell 1, and a rotor 20 arranged in the stator 4 and rotationally connected with the stator 4. The rotor 20 comprises a hollow rotor magnet 5 and a differential lead screw 6 sleeved in the rotor magnet 5. Optionally, the front cover 2 is made of non-metallic material, such as peek (polyether ether ketone), pom (polyoxymethylene resin), polytetrafluoroethylene, etc.

[0040] The differential lead screw 6 comprises a lead screw nut 61 fixed in the rotor magnet 5, a first support 63 and a corresponding second support 64 arranged at the inner circumferential side of one end of the lead screw nut 61 close to the front cover 2, a plurality of first lead screws 65 annularly distributed between the first support 63 and the second support 64, and a central lead screw 62 arranged at the center of the lead screw nut 61 and extending through the center of the front cover 2. The two ends of the first lead screw 65 are fixedly connected with the first support 63 and the second support 64 respectively, the plurality of first lead screws 65 are rotationally connected with the lead screw nut 61, and the plurality of first lead screws 65 are screw-connected with the central lead screw 62. The stator 4 drives the rotor magnet 5 to rotate to drive the lead screw nut 61 to rotate, so that the first lead screw 65 rotates to drive the central lead screw 62 to realize linear extension and contraction. The rotor 20 is driven to rotate by the mutual driving of the stator 4 and the rotor 20, the lead screw nut 61 is driven to rotate by the rotation of the rotor magnet 5, the plurality of first lead screws 65 are driven to rotate by the rotation of the lead screw nut 61, and the central lead screw 62 is driven to rotate by the rotation of the first lead screw 65 to realize linear extension and contraction. The differential lead screw 6 is directly driven by the rotor magnet 5, which is high in efficiency and simple in structure. The stator 4 drives the rotor 20 to rotate to drive the lead screw nut 61 to rotate, so that the first lead screw 65 rotates to drive the central lead screw 62 to realize linear extension and contraction. The motor is directly driven with the motion mechanism, which is easy to control and has high system reliability, low overall height, small length, and friendly installation size. At the same time, the differential lead screw 6 has small lead and high precision. The cost is further saved, and the installation space is saved.

[0041] In the embodiment, the lead screw nut 61 comprises a hollow nut body 611 fixed in the rotor magnet 5 and a first thread structure 612 formed at the inner circumferential side of one end of the nut body 611 close to the front cover 2. The plurality of first lead screws 65 are in contact with and rotationally connected with the first thread structure 612.

[0042] The center screw rod 62 comprises a center screw rod body 621 provided in the nut body 611 and provided with a second threaded structure 622 on the outer periphery, and an extended end 623 formed by the center screw rod body 621 extending from one end close to the front cover 2, and a plurality of first screw rods 65 are screwed with the second threaded structure 622, and the extended end 623 penetrates the front cover 2 from one end close to the front cover 2.

[0043] By taking the nut body 611 of the screw nut 61 as a hollow shaft of the rotor 20, the hollow shaft is made of magnetic conductive metal material and is provided with a first threaded structure 612 on the inner wall, the driving center screw rod 62 is driven to extend forward and backward, as a linear motion part of the finger driving mechanism, a plurality of first screw rods 65 are arranged in the space between the center screw rod 62 and the screw nut 61, the first screw rods 65 are driven to rotate by the rotation of the screw nut 61, so that the center screw rod 62 is driven to extend linearly by the first screw rods 65, and the linear driving performance of the motor is realized.

[0044] In the embodiment, the screw nut 61 further comprises a ring-shaped avoidance groove 613 formed by the first threaded structure 612 recessing from one side close to the center screw rod 62 to the other side away from the center screw rod 62.

[0045] The first screw rod 65 comprises a first screw rod body 651 rotatably connected with the first support 63 and the second support 64, a third threaded structure 652 protruding from the outer periphery of the first screw rod body 651, and two fourth threaded structures 653 protruding from both ends of the first screw rod body 651, respectively, the two fourth threaded structures 653 are arranged at both ends of the third threaded structure 652, and the two fourth threaded structures 653 are screwed with the first threaded structure 612; one side of the third threaded structure 652 is located in the avoidance groove 613, and the other side of the third threaded structure 652 is screwed with the second threaded structure 622. By arranging the third threaded structure 652 in the avoidance groove 613, the first threaded structure 612 is connected with the fourth threaded structure 653, since the third threaded structure 652 is screwed with the second threaded structure 622 and the fourth threaded structure 653 is screwed with the first threaded structure 612, the diameter of the fourth threaded structure 653 is smaller than that of the third threaded structure 652, so that the screw nut 61 drives the large diameter when rotating, the rotating speed of the center screw rod 62 is the same, the linear speed is different, the extension and retraction movement of the center screw rod 62 is facilitated, the motor has small jitter when the speed is adjusted, and the motion control precision is high.

[0046] In the embodiment, the cross section of the extended end 623 is non-circular, and the extended end 623 forms a sliding connection with the front cover 2 along the axial movement of the center screw rod body 621.

[0047] Preferably, the front cover 2 is sleeved with a sliding bearing near one side of the center screw body 621, and the sliding bearing is in sliding connection with the extension end 623. In this way, the sliding effect is improved.

[0048] In the embodiment, the linear driving mechanism 100 further comprises a rectangular stopper 7, a control board 8 and a linear position sensor 9. The stopper 7 is sleeved and fixed to the extension end 623. The control board 8 is fixed to the shell 1 and the front cover 2 respectively. The linear position sensor 9 is electrically connected to the control board 8. The linear position sensor 9 is used to collect the linear movement data of the stopper 7 and transmit the data to the control board 8. Optionally, the control board 8 is a flexible circuit control board 8 (PCB).

[0049] In the embodiment, the linear position sensor 9 comprises a linear sensor magnet 91 embedded in the stopper 7 near one side of the control board 8 and at least one Hall sensor 92 fixed to the control board 8 near one side of the center screw 62. When any of the Hall sensors 92 directly faces the linear sensor magnet 91, the Hall sensor 92 is located within the magnetic field range of the linear sensor magnet 91.

[0050] In the embodiment, the linear position sensor 9 comprises a spring piece 93 fixed to the stopper 7 near one side of the control board 8 and a long strip-shaped conductor resistor 94 fixed to the control board 8 near one side of the center screw 62. The spring piece 93 slides on the surface of the conductor resistor 94 along with the stopper 7. By sensing the resistance values of different positions of the conductor resistor 94, the linear extension length of the extension end 623 is collected.

[0051] In the embodiment, the stator 4 comprises a stator core 41 fixed to the shell 1 near one side of the differential screw 6 and a coil winding 42 fixed in the stator core 41. The coil winding 42 is spaced from the rotor 20. The coil winding 42 drives the rotor 20 to rotate after being electrified. The stator 4 is a toothless slot structure, and the motor has no tooth slot torque. When the motor is speed-regulated, the motor has small jitter. At the same time, the motor driving force is stable, the thrust is stable in the required driving length range, the fluctuation is small, and the driving control is simple.

[0052] In the embodiment, the coil winding 42 is a ring-shaped hollow coil structure. The coil winding 42 is conveniently fixed to the inner circumferential side of the stator core 41, and the assembly is convenient.

[0053] The stator core 41 is a ring-shaped magnetic steel sleeve or a circular ring-shaped core formed by bonding multiple silicon steel sheets. A circular surface is provided on the outer circle of the screw nut 61, and a permanent magnet sleeve is bonded to the outer surface of the hollow shaft of the motor rotor 20. The stator 4 structure of the motor is provided with an air gap outside the permanent magnet, and the stator core 41 is a ring-shaped structure, which is sleeved in the housing 1. The air gap between the outer circle of the permanent magnet is provided with a winding coil on the inner surface of the stator core 41. The winding coil is energized to drive the rotor 20 and the screw nut 61 to rotate.

[0054] Specifically, the stator core 41 is a ring-shaped magnetic steel sleeve; the stator core 41 is formed by stacking silicon steel sheets and bonding into a circular ring shape; and the stator core 41 is formed by stacking silicon steel sheets and riveting into a circular ring shape.

[0055] In this embodiment, the rotor 20 is a magnetic hollow shaft structure, and the permanent magnet installed on the magnetic hollow shaft structure is a radial 4-pole or 6-pole magnetic ring structure. The rotor 20 is a permanent magnet magnetic ring structure, which is simple in structure, has no brush friction, and has fast dynamic response.

[0056] Optionally, the permanent magnet magnetic ring material is neodymium iron boron, and the performance grade is not less than N45H. The magnetic guiding effect is good.

[0057] In this embodiment, the linear drive mechanism 100 further includes an angle position sensor 10, which is sleeved and fixed to the screw nut 6. The angle position sensor 10 is used to collect the rotational angle position data of the screw nut 6.

[0058] Example Two

[0059] In combination with FIGS. 1-9, the basic structure of Example Two is the same as that of Example One, and the same technical effects are achieved. The difference between them is that in this embodiment, the linear drive mechanism 100 further includes an angle position sensor 10, which is fixed to the control board 8 and forms an electrical connection. The angle position sensor 10 is used to collect the rotational angle position data of the rotor 20.

[0060] Example Three

[0061] With reference to FIGS. 1-9, the third embodiment is basically the same as the first embodiment and has the same technical effects, and the difference is that the linear driving mechanism 100 further comprises an angle position sensor 10 fixed to one end of the screw nut 61 close to the rear cover 3, and the angle position sensor 10 is used to collect the rotational angle position data of the rotor 20. Specifically, the angle position sensor 10 comprises a collection part 102 fixed to the rear cover 3 and a rotating part 101 fixed to one end of the screw nut 61 close to the rear cover 3, and the collection part 102 is arranged opposite to the rotating part 101. The angle position sensor 10 is used to provide angle position information for motor control.

[0062] In this embodiment, the Hall sensor chip of the angle position sensor 10 has two Hall sensor chips, which are respectively located at one end of the control panel 8 away from the linear driving mechanism 100 and in the radial direction of the rotor 20, and the angle position of the rotor 20 of the motor is identified by sensing the angle phase signal of the magnetic field of the rotor 20.

[0063] In this embodiment, the linear driving mechanism 100 further comprises a magnet seat 13 fixed to one end of the screw nut 61 close to the rear cover 3, and the rotating part 101 is fixed in the magnet seat 13.

[0064] In this embodiment, the linear driving mechanism 100 further comprises a first bearing 11 and a second bearing 12, and the first bearing 11 and the second bearing 12 are respectively sleeved and fixed to both ends of the screw nut 61, and the outer periphery of the first bearing 11 and the outer periphery of the second bearing 12 are respectively fixed in the machine shell 1.

[0065] Optionally, the first bearing 11 and the second bearing 12 are both rolling bearings.

[0066] In this embodiment, a flat structure 624 is formed by recessing the protruding end 623, and a flat hole 21 is formed through the front cover 2 at the position corresponding to the protruding end 623. The stop block 7 is sleeved on the flat structure 624, and the flat structure 624 is arranged in the flat hole 21.

[0067] In this embodiment, the machine shell 1 has an open structure at both ends, and the machine shell 1, the front cover 2 and the rear cover 3 are connected into one body by bolts.

[0068] In this embodiment, the machine shell 1 comprises a front section machine shell and a rear section machine shell, and the rear section machine shell is integrated into the rear cover 3, and the front cover 2, the front section machine shell and the rear cover 3 integrated with the rear section machine shell are connected into one body by bolts.

[0069] Embodiment four

[0070] In combination with the drawings 1-9, the embodiment four and the embodiment one have the same basic structure and the same technical effect, and the difference is that: in the embodiment, the linear position sensor 9 includes a linear sensor magnet 91 embedded on the side of the stop block 7 close to the control plate 8 and at least one Hall sensor 92 fixed on the side of the control plate 8 close to the center screw 62, and the Hall sensor 92 is located in the magnetic field range of the linear sensor magnet 91.

[0071] In the embodiment, the stop block 7 includes a stop block body 71 sleeved on the protruding end 623 and a slot 72 recessed from the side of the stop block body 71 close to the control plate 8 to the side away from it, and the linear sensor magnet 91 is fixed in the slot 72.

[0072] Optionally, the linear sensor magnet 91 can be directly pasted on the protruding end 623 and located in the original position of the stop block 7 to save cost.

[0073] In the embodiment, the linear driving mechanism 100 is applied to the electrically driven linear actuator of the robot dexterous finger or joint, so that the integration degree is high and the process is simplified.

[0074] Compared with the prior art, in the linear driving mechanism of the application, the differential screw is sleeved in the rotor magnet, the differential screw includes a screw nut fixed in the rotor, a first support and a corresponding second support which are arranged at the inner circumferential side of the screw nut close to the front cover, a plurality of first screws which are annularly distributed between the first support and the second support, and a center screw which is arranged at the center of the screw nut and extends through the center of the front cover, both ends of the first screw are fixedly connected with the first support and the second support respectively, a plurality of first screws are rotationally connected with the screw nut respectively, and a plurality of first screws are screw-connected with the center screw; the stator drives the rotor magnet to rotate to drive the screw nut to rotate, so that the first screw rotates to drive the center screw to realize linear extension and contraction; the motor and the motion mechanism are directly driven, which is easy to control, has high system reliability, low overall height, small length, and friendly installation size. Further cost saving and installation space saving.

[0075] The above only describes the embodiments of the application, and it should be pointed out that those skilled in the art can make improvements without departing from the inventive concept, and these improvements are within the protection scope of the application.

Claims

1. A linear drive mechanism comprising a housing with two open ends, a front cover and a rear cover fixed to the opposite ends of the housing respectively, a stator arranged in the housing, and a rotor arranged in the stator and rotatably connected with the stator; characterized in that, The rotor comprises a rotor magnet in a hollow shape and a differential screw rod sleeved in the rotor magnet; The differential screw rod comprises a screw nut fixedly inserted in the rotor magnet, a first support and a corresponding second support which are arranged at the inner circumferential side of the screw nut near the front cover, a plurality of first screw rods which are annularly distributed between the first support and the second support, and a central screw rod arranged at the center of the screw nut and extending through the center of the front cover, both ends of the first screw rod being connected with the first support and the second support respectively, a plurality of the first screw rods being rotationally connected with the screw nut respectively, and a plurality of the first screw rods being screwed with the central screw rod; the stator drives the rotor magnet to rotate to drive the screw nut to rotate, so that the first screw rod rotates to drive the central screw rod to realize linear extension and contraction.

2. The linear drive mechanism according to claim 1, characterized by The screw nut comprises a hollow nut body fixed in the rotor magnet and a first thread structure formed at the inner circumferential side of the screw nut near the front cover; a plurality of the first screw rods are in contact with and rotationally connected with the first thread structure; The central screw rod comprises a central screw rod body arranged in the screw nut body and provided with a second thread structure at the outer circumferential side, and an extended end formed by the central screw rod body near the front cover, a plurality of the first screw rods being screwed with the second thread structure, and the extended end near the front cover penetrating the front cover.

3. The linear drive mechanism according to claim 2, characterized by The screw nut further comprises an annular avoiding groove recessed from the first thread structure from the side near the central screw rod to the side away from the central screw rod; The first screw rod comprises a first screw rod body rotationally connected with the first support and the second support respectively, a third thread structure protruded at the outer circumferential side of the first screw rod body, and two fourth thread structures respectively protruded at both ends of the first screw rod body, the two fourth thread structures being arranged at both ends of the third thread structure respectively, and the two fourth thread structures being screwed with the first thread structure; one side of the third thread structure is located in the avoiding groove, and the other side of the third thread structure is screwed with the second thread structure.

4. The linear drive mechanism of claim 2, wherein The cross section of the extended end is non-circular, and the extended end forms a sliding connection with the front cover for axial movement along the central screw rod body.

5. The linear drive mechanism according to claim 4, characterized by The linear driving mechanism further comprises a rectangular stopper, a control board and a linear position sensor, the stopper being sleeved and fixed to the extended end, the control board being fixed to the shell and the front cover respectively, and the linear position sensor being electrically connected with the control board, the linear position sensor being used to collect linear movement data of the stopper and transmit the data to the control board.

6. The linear drive mechanism according to claim 5, characterized by The linear position sensor comprises a linear sensor magnet embedded in the side of the stopper near the control board and at least one Hall sensor fixed to the side of the control board near the central screw rod, any Hall sensor being located in the magnetic field range of the linear sensor magnet when the Hall sensor directly faces the linear sensor magnet.

7. The linear drive mechanism of claim 5, wherein The linear position sensor comprises a spring sheet fixed to the side of the control plate close to the center screw rod and a long strip-shaped conductor resistor fixed to the side of the control plate close to the center screw rod, the spring sheet slides on the surface of the conductor resistor with the stopper, the linear extension length of the extension end is collected by sensing the resistance value of different positions of the conductor resistor.

8. The linear drive mechanism of claim 1, wherein, The stator comprises a stator core fixed to the side of the shell close to the differential screw rod and a coil winding fixed in the stator core, the coil winding is spaced from the rotor, and the coil winding drives the rotor to rotate after being electrified.

9. The linear drive mechanism of claim 8, wherein, The stator core is an annular magnetic steel sleeve or a circular ring-shaped core formed by bonding multiple silicon steel sheets.

10. The linear drive mechanism of claim 1, wherein, The screw rod nut is a magnetic hollow shaft structure, and the permanent magnet installed on the magnetic hollow shaft structure is a radial 4-pole or 6-pole magnetic ring structure.

11. The linear drive mechanism of claim 5, wherein, The linear drive mechanism further comprises an angle position sensor, the angle position sensor is fixed to the screw rod nut, and the angle position sensor is used to collect the rotation angle position data of the rotor.

12. The linear drive mechanism of claim 5, wherein, The linear drive mechanism further comprises an angle position sensor, the angle position sensor is fixed to the control plate and forms an electrical connection, and the angle position sensor is used to collect the rotation angle position data of the rotor.

13. The linear drive mechanism of claim 5, wherein, The linear drive mechanism further comprises an angle position sensor, the angle position sensor is fixed to the end of the screw rod nut close to the rear cover, and the angle position sensor is used to collect the rotation angle position data of the rotor.

14. The linear drive mechanism of claim 13, wherein, The angle position sensor comprises a collection part fixed to the rear cover and a rotating part fixed to the end of the screw rod nut close to the rear cover, and the collection part and the rotating part are oppositely spaced.

15. The linear drive mechanism of claim 1, wherein, The linear drive mechanism further comprises a first bearing and a second bearing, the first bearing and the second bearing are respectively fixed to the two ends of the screw rod nut, and the outer periphery of the first bearing and the outer periphery of the second bearing are respectively fixed in the shell.

16. The linear drive mechanism of claim 4, wherein The extension end is recessed to form a flat position structure; the front cover is perforated to form a flat hole at the corresponding position of the extension end.

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