A screw self-locking electric cylinder device adopting a planetary gear mechanism

Abstract

The present invention relates to the technical field of vehicle braking control systems or their components, and particularly relates to a screw self-locking electric cylinder using a planetary gear mechanism, which includes a housing, a motor connected to the housing, a cylinder block, a transmission mechanism, and a piston assembly slidably disposed inside the housing. The transmission mechanism includes: a first screw pair, which is disposed inside the housing. The first screw pair includes a first screw connected to the motor and a first nut that meshes with the first screw and can only move axially; a second screw pair, which includes a second screw sleeved on the outer periphery of the first nut, and a second nut that meshes with the second screw and can only move axially; and a planetary gear mechanism, which is arranged for the transmission of the first screw and the second screw. The beneficial effects of the present invention are as follows: It can achieve parking braking, has a simple structure, low cost, and convenient layout; by adopting a planetary gear structure, the transmission ratio is increased, the nut stroke is increased, and a greater braking pressure is generated.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle braking control systems or their components, and particularly relates to a screw self-locking electric cylinder using a planetary gear mechanism. Background Art

[0002] An automotive braking system is closely related to vehicle driving safety. In traditional automobiles, the hydraulic braking system applies braking pressure to the wheel cylinders of each wheel brake by the driver stepping on the brake pedal, thereby achieving braking and decelerating the vehicle. Intelligent vehicle systems such as advanced driver assistance systems (ADAS) and autonomous driving systems (ADS) require the braking system to be able to perform autonomous braking on the vehicle, that is, to apply braking to some or all wheels without stepping on the brake pedal.

[0003] Currently, most braking systems capable of performing autonomous braking use electric assistance and retain braking control devices such as the brake pedal. However, for the development of driverless logistics delivery vehicles, since there is no longer a need for braking control devices, this method is not applicable. Moreover, in addition to service braking, autonomous driving vehicles such as driverless logistics delivery vehicles also require parking braking. Most existing motor vehicles are equipped with two sets of systems, namely a service braking system and a parking braking system. That is, the existing electric cylinder device can only realize service braking and has no parking braking function. To achieve the parking function of the vehicle, other parking mechanisms need to be added on the basis of the existing braking electric cylinder, making its structure and corresponding control relatively complex and the cost relatively high. For service braking and parking braking, a certain reliability in practical applications is also required.

[0004] Therefore, how to design a braking device with a simple structure, reliable use, low cost and capable of meeting the needs of both service and parking braking at the same time is an urgent problem to be solved in the autonomous driving system of motor vehicles. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide an electric cylinder device with a simple structure, reliable use and capable of meeting the needs of both service and parking braking at the same time.

[0006] To achieve the above purpose, the present invention provides a screw self-locking electric cylinder device using a planetary gear mechanism, including a housing, a motor connected to the housing, a cylinder block, a transmission mechanism, and a piston assembly slidably disposed inside the cylinder block. The transmission mechanism includes:

[0007] A first screw pair, which is disposed inside the housing; the first screw pair includes a first screw connected to the motor and a first nut that meshes with the first screw and is only movable axially.

[0008] A second screw pair, which includes a second screw sleeved on the outer periphery of the first nut, and a second nut meshed with the second screw and arranged to be only axially translatable; a rotation limiting element is inserted on the first nut and the second nut; and the lead of the first screw pair is smaller than that of the second screw pair, and the axial translation speed of the first nut is greater than the axial translation speed of the second nut;

[0009] A planetary gear mechanism, which includes a sun gear connected to the first screw and a planet carrier connected to the second screw.

[0010] Further, the rotation limiting element is a rotation limiting element; a through hole is provided on the second nut, a groove is provided on the first nut, and the rotation limiting element sequentially passes through the housing and the through hole along the radial direction of the housing until it is in sliding fit with the groove on the first nut. The rotation limiting element restricts the rotation of the first nut and the second nut and converts the rotation into translation.

[0011] Further, the sun gear is sleeved on the outer periphery of the first screw, the planetary gear mechanism further includes a planetary gear meshed with the sun gear, and the planet carrier is sleeved on the central axis of the planetary gear; the planetary gear mechanism further includes an internal gear ring sleeved on the outer periphery of the planetary gear and meshed with it; the planet carrier is sleeved on the outer periphery of the first screw through a bearing. The number of the planetary gears is at least one. The bearing includes a sleeve provided on its outer periphery and a left shaft retaining ring and a right shaft retaining ring respectively provided on its two end faces.

[0012] Further, a cylindrical pin is inserted through the axial center position of the planetary gear, and the cylindrical pin sequentially passes through the planetary gear, the planet carrier, and the second screw. The second screw is driven to rotate through the cylindrical pin.

[0013] Further, the piston assembly includes a piston slidably arranged in the cylinder body, and an elastic resetting member is arranged between the end face of the piston away from the motor and the inner side wall of the cylinder body. Further, a protrusion is provided at the center position of the end face of the piston away from the motor, and one end of the elastic resetting member is sleeved on the protrusion. The piston assembly abuts and cooperates with the first screw pair and the second screw pair.

[0014] Further, a compensation hole and a liquid supply hole are radially provided on the upper inner wall of the cylinder body, and a liquid discharge hole is radially provided on the lower inner wall of the cylinder body; a leather cup is provided on the outer periphery of the piston, and the leather cup cooperates with the liquid supply hole; the compensation hole and the liquid supply hole are communicated with an oil pot. A sealing ring is provided at the connection between the housing and the cylinder body. The leather cup is arranged at one end of the piston close to the elastic resetting member, and a sealing leather cup is provided at one end of the outer periphery of the piston away from the leather cup.

[0015] Further, an end face of the piston away from the motor and the cylinder block form a first cavity, and an outer periphery of the piston and the cylinder block form a second cavity. A leather cup provided on the piston makes the housing and the cylinder block relatively sealed. The elastic reset member is disposed in the first cavity.

[0016] In an initial position, a preset gap smaller than a length of the groove exists between the first nut and the piston, the second nut abuts against an end face of the piston, and the cylindrical pin presses against an inner side wall of a left end of the groove and the through hole; the leather cup is axially located between the compensation hole and the liquid supply hole, and the first cavity is communicated with the compensation hole and the liquid discharge hole.

[0017] In a self-locking position, the first nut abuts against the end face of the piston, and the second nut is not in contact with the piston; at this time, the first cavity is only communicated with the liquid discharge hole.

[0018] The first screw rod is a single-start screw rod and has a self-locking function; the second screw rod is a multi-start screw rod and has no self-locking function.

[0019] Further, the motor, the internal gear ring and the housing are sequentially connected by bolts.

[0020] Thus, the torque output by the motor drives the first screw rod through the coupling, thereby driving the first nut, and drives the planetary gear mechanism to rotate, thereby driving the second screw rod and the second nut. The rotation of the two nuts is converted into linear motion by the rotation limiting element; when the vehicle is in a braking state, the second nut pushes the piston to output a braking pressure to achieve braking. In a self-locking state, the lead of the first screw pair is smaller than that of the second screw pair, but due to the speed reduction effect of the planetary gear mechanism, the rotation speed of the first screw rod is higher than that of the second screw rod, so that the linear motion speed of the first nut is faster than that of the second nut. Therefore, the first nut pushes the piston to achieve braking, and when the motor is powered off, due to the self-locking effect of the first screw pair.

[0021] The beneficial effects of the present invention are as follows:

[0022] 1. The present invention can achieve parking braking, which is applicable to the parking braking requirements of unmanned logistics distribution vehicles or ordinary driving vehicles. Its structure is simple, the cost is low, and the layout is convenient;

[0023] 2. The present invention directly drives the piston of the electric cylinder by the motor through the transmission device, and has a short pressure building time and a fast braking response;

[0024] 3. The transmission device of the present invention adopts a planetary gear structure, which increases the transmission ratio, further increases the nut stroke, and generates a greater braking pressure;

[0025] 4. The electric cylinder device of the present invention uses a single - start screw pair to push the piston for braking. When the motor loses power, the screw pair self - locks, and the parking function can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of a screw self - locking type electric cylinder device using a planetary gear mechanism according to the present invention;

[0027] Figure 2 It is a schematic structural diagram of the cylinder body part of the double - chamber electric cylinder in the present invention.

[0028] In the figure: 101 - motor, 102 - coupling, 103 - sun gear, 104 - planet gear, 105 - internal gear ring, 106 - cylindrical pin, 107 - planet carrier, 108 - second screw, 109 - second nut, 110 - rotation limiting element, 112 - right shaft retaining ring, 113 - sleeve, 114 - bearing, 115 - left shaft retaining ring, 116 - first screw, 117 - first nut, 118 - housing, 119 - sealing ring, 120 - piston, 121 - leather cup, 122 - elastic resetting member, 123 - cylinder block, 124 - oil pot, A - second cavity, B - liquid supply hole, C - compensation hole, D - first cavity, E - liquid discharge hole;

[0029] 212 - first piston, 213 - first leather cup, 214 - connecting member, 215 - liquid storage tank, 216 - first elastic member, 217 - electric cylinder cylinder block, 218 - second leather cup, 219 - second piston, 220 - second elastic member, 221 - limit pin, 222 - limit hole, 214a - cross bar, 214b - partition plate, A1 - fifth cavity, B1 - first liquid supply hole, B2 - second liquid supply hole, C1 - first compensation hole, C2 - second compensation hole, D1 - third cavity, D2 - fourth cavity, E1 - first liquid discharge hole, E2 - second liquid discharge hole. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The present invention will be further described below with reference to the drawings and embodiments.

[0031] Embodiment 1

[0032] As Figure 1As shown in the figure, a screw self-locking electric cylinder device using a planetary gear mechanism includes a housing 118 and a motor 101 connected thereto, and a cylinder block 123 fixedly connected to the housing 118. It further includes: a first screw 116 disposed inside the housing 118 and coupled to the motor 101, a first nut 117 rotatably engaged with the first screw 116, a planetary gear mechanism rotatably engaged with the first screw 116, a second screw 108 connected to the planetary gear mechanism, a second nut 109, and a piston assembly disposed inside the housing 118; the first screw 116 and the first nut 117 are sleeved inside the transmission assembly. The motor 101 is fixedly connected to the housing 118 by bolts. The first screw 116 is coupled to the output shaft of the motor 101 through a coupling 102; the first screw 116 is axially sleeved inside the first nut 117.

[0033] The planetary gear mechanism includes a sun gear 103 fixedly connected to the outer periphery of the first screw 116, a planet gear 104 meshed with the sun gear 103, a planet carrier 107 sleeved on the central axis of the planet gear 104, and an internal gear ring 105 sleeved on the outer periphery of the planet gear 104 and meshed with it. In this embodiment, the number of planet gears 104 is 3, and in other embodiments, the number of planet gears 104 can exceed 3. A cylindrical pin 106 is inserted through the central axis position of the planet gear 104, and the planet carrier 107 is sleeved on the outer periphery of the part of the cylindrical pin 106 extending out of the planet gear 104; in this embodiment, the planet carrier 107 is sleeved on the outer periphery of the first screw 116 through a pair of bearings 114, and in other embodiments, the number of bearings 114 can be one or other suitable numbers. The bearing 114 includes a sleeve 113 disposed on its outer periphery, and a left shaft retaining ring 115 and a right shaft retaining ring 112 respectively disposed on its two end faces.

[0034] The second screw 108 is connected to the part of the cylindrical pin 106 extending out of the planet gear 104, and the second nut 109 is sleeved on the outer periphery of the second screw 108 and meshed with it; a rotation limiting element 110 is inserted radially into the second nut 109, and the rotation limiting element 110 passes through the through holes formed on the surfaces of the housing 118 and the second nut 109, and is slidably engaged with the groove formed on the surface of the first nut 117. The second screw 108 is driven by the cylindrical pin 106; the rotation limiting element 110 restricts the rotation of the first nut 117 and the second nut 109, and converts the rotation into linear motion. In this embodiment, the rotation limiting element is a guide pin.

[0035] The piston assembly includes a piston 120 slidably disposed within a cylinder block 123, a leather cup 121 disposed at one end of the outer periphery of the piston 120 near the elastic restoring member 122, and a sealing leather cup disposed at one end of the outer periphery of the piston 120 away from the leather cup 121. An elastic restoring member 122 is disposed between the end face of the piston 120 away from the motor 101 and the inner side wall of the cylinder block 123. Further, a protrusion is provided at the center position of the end face of the piston 120 away from the motor 101, and one end of the elastic restoring member 122 is sleeved on the protrusion. In this embodiment, the elastic restoring member 122 is a spring. In other embodiments, the elastic restoring member may be an elastic member such as a spring plate or other elements having a restoring function. Further, the protruding end of the second nut 109 abuts against the end face of the piston 120 near the motor 101. The reciprocating working state between the second nut 109 and the piston 120 can be achieved through this abutment.

[0036] A compensation hole C and a liquid supply hole B for cooperating with the leather cup 121 are radially formed on the upper inner wall of the cylinder block 123, and a liquid discharge hole E is radially formed on the lower inner wall of the cylinder block 123. A sealing ring 119 is provided at the connection between the housing 118 and the cylinder block 123. After fastening, the sealing ring 119 is pressed at the joint surface to play a sealing role. The compensation hole C and the liquid supply hole B are connected to an oil pot 124.

[0037] The left end face of the piston 120 and the cylinder block 123 form a first cavity D communicating with the corresponding wheel brake through the liquid discharge hole E, and a second cavity A is formed between the outer periphery of the piston 120 and the cylinder block 123. Through the leather cup 121 provided on the piston 120, the housing 118 and the cylinder block 123 are relatively sealed. The elastic restoring member 122 is disposed within the first cavity D.

[0038] The working state of the present invention is divided into a driving braking condition and a self-locking braking condition, and their working principles are as follows:

[0039] Driving braking condition:

[0040] As Figure 1 shown, the controller inside the vehicle receives a braking signal to drive the motor 101 to rotate, drives the planet carrier 107 to rotate through the coupling 102, the sun gear 103, and the planet gears 104, and then drives the second screw 108 to rotate through the cylindrical pin 106. The rotation limiting element 110 limits the rotation of the second nut 109 and converts the rotation of the second screw 109 into the translation of the second nut 109, thereby pushing the piston 120 to move leftward until the leather cup 121 seals the compensation hole C. At this time, the second nut 109 continues to push the piston 120 leftward, squeezing the brake fluid in the first cavity D and outputting the braking pressure from the liquid discharge hole E.

[0041] When braking needs to be released, the drive motor 101 is powered off, and the braking pressure and the return force of the elastic return member 122 push the piston 120 and the large nut 109 to translate rightward together. The second screw pair is a multi-start screw pair and cannot self-lock until the second nut 109 returns to its initial position.

[0042] Self-locking working condition:

[0043] The controller receives the self-locking signal and drives the motor 101 to rotate. The first screw 116 is driven to rotate rapidly through the coupling 102. The rotation limiting element 110 restricts the rotation of the first nut 117, and converts the rotation of the first screw 116 into the translation of the first nut 117. The lead of the first screw pair is smaller than that of the second screw pair, but the rotation speed of the first screw 116 is high. Overall, the translation speed of the first nut 117 is faster than that of the second nut 109. When the second nut 109 pushes the piston 120 to generate the maximum pressure, the first nut 117 overcomes the initial gap △X and is flush with the left end face of the second nut 109. When the motor 101 continues to rotate, the first nut 117 will push the piston 120 to move leftward a small distance, and the left end face of the second nut 109 is separated from the piston 120. At this time, the motor 101 is powered off, and the braking pressure acts on the first nut 117 through the piston 120. Moreover, the first screw is a single-start screw. Due to the self-locking effect of the single-start screw, the position of the piston 120 will be maintained unchanged, and the output pressure of the electric cylinder will be kept to realize parking.

[0044] Embodiment 2

[0045] The electric cylinder in Embodiment 1 can also be set as the double-chamber electric cylinder in this embodiment; the cylinder body 217 part of the double-chamber electric cylinder is as Figure 2 shown, and other parts are the same as those in Embodiment 1.

[0046] As Figure 2 shown, the electric cylinder in this embodiment is a double-chamber electric cylinder. A piston assembly is slidably arranged in the electric cylinder cylinder body 217. The piston assembly includes a first piston 212 and a second piston 219 arranged along its sliding direction and a connecting member 214 for connecting the first piston 212 and the second piston 219. A third cavity D1 is formed between the first piston 212, the inner wall of the electric cylinder cylinder body 217 and the connecting member 214, and a fourth cavity D2 is formed between the second piston 219 and the inner wall of the electric cylinder cylinder body 217.

[0047] Specifically, a first elastic member 216 and a second elastic member 220 are arranged inside the electric cylinder body 217. The first elastic member 216 is arranged between the connecting member 214 and the first piston 212, and the second elastic member 220 is arranged between the electric cylinder body 217 and the second piston 219. The first piston 212 is slidably connected to the connecting member 214. A third cavity A1 is formed between the first piston 212 and the inner wall of the electric cylinder body 217. The connecting member 214 includes a partition 214b for isolating the third cavity D1 and the fourth cavity D2, and crossbars 214a extending outward along both sides of the partition 214b and connected to the first piston 212 and the second piston 219.

[0048] The specification of the partition 214b should be adapted to the specification of the electric cylinder body 217, that is, no hydraulic fluid can pass through. In this embodiment, a leather cup is also added to the partition 214b. The crossbar 214a penetrates the partition 214b and is threadedly connected to the second piston 219 at one end and slidably connected to the first piston 212 at the other end.

[0049] The working principle after adopting the above structure is as follows: Under the action of the motor 101, the first piston 212 will receive a force to the left. Due to the existence of the first elastic member 216 and the second elastic member 220, the pressure on the first elastic member 216 and the second elastic member 220 is always in a balanced state. That is, when the first elastic member 216 and the second elastic member 220 can make the piston assembly move to the left simultaneously under the action of the force, the first elastic member 216 will be compressed again, and the reaction force will also increase. At this time, the second elastic member 220 will also be compressed accordingly.

[0050] In this embodiment, the elastic coefficient of the first elastic member 216 is greater than that of the second elastic member 220. Since the elastic coefficient of the first elastic member 216 is greater than that of the second elastic member 220, in the initial stage, both the first piston 212 and the second piston 119 will move to the left together under the action of the force and compress the second elastic member 220, while the first elastic member 216 will not be further compressed due to the force. During the compression process of the second elastic member 220, its elastic force will gradually increase until it is greater than the force required for the deformation of the first elastic member 216. At this time, the first elastic member 216 will be compressed, and the above work will continue, so that the first elastic member 216 and the second elastic member 220 are always in a balanced state, realizing the establishment of pressure in the third cavity D1 and the fourth cavity D2.

[0051] In this embodiment, a limit pin 221 is provided on the first piston 212, and a limit hole 222 mating with the limit pin 221 is formed in the cross bar 214a. Both the limit pin 221 and the limit hole 222 are arranged in the horizontal direction, that is, along the sliding direction of the piston assembly. The first piston 212 is slidably connected to the cross bar 214a through the limit pin 221 and the limit hole 222. When the force for compressing the first elastic member 216 is less than the force for compressing the second elastic member 220, the limit pin 221 will move leftward along the limit hole 222 under the drive of the first piston 213, while the second piston 219 remains stationary; when the force for compressing the first elastic member 216 is less than the force for compressing the second elastic member 220, the entire piston assembly moves leftward simultaneously. A first leather cup 213 is provided on the first piston 212, and a second leather cup 118 is provided on the second piston 219.

[0052] The electric cylinder block 217 is provided with: a first compensation hole C1 communicating the liquid storage tank 215 with the third cavity D1, a first liquid supply hole B1 communicating the liquid storage tank 215 with the third cavity A1, a first liquid discharge hole E1 communicating the third cavity D1, a second compensation hole C2 communicating the liquid storage tank 215 with the fourth cavity D2, a second liquid supply hole B2 communicating the liquid storage tank 215, and a second liquid discharge hole E2 communicating the fourth cavity D2.

[0053] When the first elastic member 216 is in the preloading state, the first leather cup 213 is located between the first compensation hole C1 and the first liquid supply hole B1. When the second elastic member 220 is in the preloading state, the second leather cup 218 is located between the second compensation hole C2 and the second liquid supply hole B2.

[0054] The leather cup can open and close the corresponding compensation hole by moving along with the piston. Here, the preloading state means an initial state of the elastic member according to its position when no external force acts on the elastic member.

[0055] As Figure 2 shown, the working principle of this embodiment is that under the action of the motor 101, the first piston 212 will receive a leftward force. Since the elastic coefficient of the first elastic member 216 is greater than that of the second elastic member 220, in the initial stage, both the first piston 213 and the second piston 219 will move leftward together under the action of the force and compress the second elastic member 220, while the first elastic member 216 will not be subjected to force; during the compression process of the second elastic member 220, its elastic force will gradually increase until it is greater than the force required for the deformation of the first elastic member 216. At this time, the first elastic member 216 will be compressed, and the above work continues, so that the first elastic member 216 and the second elastic member 220 are always in a balanced state. When the leather cup blocks the compensation hole, high pressure is established in the third cavity D1 and the fourth cavity D2, and the oil is discharged through the first liquid discharge hole E1 and the second liquid discharge hole E2 to brake the vehicle.

[0056] In this embodiment, the first piston 212 abuts and cooperates with the second nut 109 and the first nut 117 in the first embodiment, that is, the first piston 212 can axially move under the push of the second nut and the first nut.

[0057] The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. It is not intended to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A screw self-locking electric cylinder device using a planetary gear mechanism, comprising a housing (118), a motor (101) connected to the housing (118), a cylinder block (123), a transmission mechanism, and a piston assembly slidably disposed inside the housing (118), characterized in that, The transmission mechanism includes: A first screw pair, which is arranged inside the housing (118); the first screw pair includes a first screw (116) connected to the motor (101) and a first nut (117) that meshes with the first screw (116) and is arranged to be only axially translatable; A second screw pair, which includes a second screw (108) sleeved on the outer periphery of the first nut (117), and a second nut (109) that meshes with the second screw (108) and is arranged to be only axially translatable; A planetary gear mechanism, which is arranged for the transmission of the first screw (116) and the second screw (108); The transmission mechanism has an initial position and a self-locking position. In the initial position, the second nut (109) abuts against the piston assembly, and the first nut (117) is separated from the piston assembly; in the self-locking position, the first nut (117) abuts against the piston assembly, and the second nut (109) is separated from the piston assembly.

2. The screw self-locking electric cylinder device with a planetary gear mechanism according to claim 1, characterized in that, The speed of the axial translation of the first nut (117) is greater than the speed of the axial translation of the second nut (109).

3. A screw self-locking electric cylinder device using a planetary gear mechanism according to claim 1, characterized in that, The piston assembly includes a piston (120) slidably arranged in the cylinder block (123). The piston (120) is slidably arranged in the cylinder block (123), and an elastic reset member (122) is arranged between the inner side wall of the cylinder block (123) and the piston (120); the cylinder block (123) is provided with a compensation hole (C), a liquid supply hole (B) and a liquid discharge hole (E); a leather cup (121) is arranged on the outer periphery of the piston (120). When the elastic reset member (122) is in a pre-compressed state, the leather cup is located between the compensation hole (C) and the liquid supply hole (B); an oil pot (124) communicating with the compensation hole (C) and the liquid supply hole (B) is further arranged on the cylinder block (123).

4. The screw self-locking electric cylinder device adopting a planetary gear mechanism according to claim 3, characterized in that, A first cavity (D) is formed between the end face of the piston (120) far from the motor (101) and the cylinder block (123), and the liquid discharge hole (E) communicates with the first cavity (D); a second cavity (A) is formed between the outer periphery of the piston (120) and the cylinder block (123), and the liquid supply hole (B) communicates with the second cavity (A).

5. A screw self-locking electric cylinder device using a planetary gear mechanism according to claim 1, characterized in that, The planetary gear mechanism includes a sun gear (103), a planetary gear (104), an internal gear ring (105) and a planetary carrier (107). The internal gear ring (105) is fixedly connected to the housing (118); the driving member is the sun gear (103) fixedly sleeved on the outer periphery of the first screw (116), and the driven member is the planetary carrier (107) fixedly connected to the second screw (108) and arranged to rotate synchronously.

6. The screw self-locking electric cylinder device adopting a planetary gear mechanism according to claim 5, characterized in that, The planetary carrier (107) is sleeved on the outer periphery of the first screw (116) through a bearing (114).

7. A screw self-locking electric cylinder device using a planetary gear mechanism according to claim 5, characterized in that, A cylindrical pin (106) is inserted through the axial center position of the planetary gear (104), and the planetary gear (104), the planetary carrier (107) and the second screw (108) are fixedly connected together through the cylindrical pin (106).

8. A screw self-locking electric cylinder device using a planetary gear mechanism according to any one of claims 1-7, characterized in that, The screw self-locking electric cylinder device further includes a rotation limiting element (110). A through hole is axially formed in the second nut (109), and a groove is axially formed in the first nut (117). The rotation limiting element (110) is fixed on the housing (118) and radially movably passes through the through hole and then slidably cooperates with the groove on the first nut (117).

9. A screw self-locking electric cylinder device using a planetary gear mechanism according to claim 8, characterized in that, In the initial position, a preset gap exists between the first nut (117) and the piston assembly, and the preset gap is smaller than the length of the groove.

10. A screw self-locking electric cylinder device using a planetary gear mechanism according to claim 8, characterized in that, In the initial position, the rotation limiting element (110) abuts against the inner side wall of the end of the groove and the through hole close to the piston assembly.

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