CN110864059B

CN110864059B - Screw rod self-locking type electric cylinder device

Info

Publication number: CN110864059B
Application number: CN201911072172.9A
Authority: CN
Inventors: 邓伟文; 丁能根; 张凯
Original assignee: Nanjing Jingweida Automobile Technology Co ltd
Current assignee: Nanjing Jingweida Automobile Technology Co ltd
Priority date: 2019-11-05
Filing date: 2019-11-05
Publication date: 2024-06-11
Anticipated expiration: 2039-11-05
Also published as: CN110864059A

Abstract

The invention discloses a screw self-locking electric cylinder device, and belongs to the technical field of vehicle brake control systems or parts thereof. The device comprises a motor, a transmission mechanism, a piston and a shell, wherein the transmission mechanism comprises a coupler, a first screw pair, a second screw pair and a nut spring. The motor drives the first screw rod to rotate, the first screw rod is connected with the second screw rod, the first nut is attached to the piston, and the second nut is connected with the piston through a bolt. The braking method provided by the invention comprises a conventional service braking mode and a parking braking mode. The invention has the advantages that: the manual braking device is omitted, the structure is simple, the cost is low, and the arrangement is convenient. The parking function is realized by utilizing the self-locking effect of the single-head screw pair, and the device has the advantages of quick braking response, simple structure, high reliability and the like.

Description

Screw rod self-locking type electric cylinder device

Technical Field

The invention belongs to the technical field of vehicle brake control systems or parts thereof, and particularly relates to a screw self-locking electric cylinder device.

Background

The automobile braking system is closely related to automobile driving safety. The conventional hydraulic brake system of an automobile is configured such that a driver applies a brake pressure to wheel cylinders of respective wheel brakes by depressing a brake pedal, thereby achieving braking and decelerating the vehicle. Intelligent automotive systems such as Advanced Driving Assistance Systems (ADAS) and Automated Driving Systems (ADS) require that the brake system be capable of applying autonomous braking to the vehicle, i.e., applying braking to some or all of the wheels without depressing the brake pedal.

At present, an electric power assisting device is mostly adopted in a brake system capable of implementing autonomous braking, and a brake operating device such as a brake pedal and the like is reserved. For the development of unmanned logistics distribution vehicles, this approach is not applicable because the brake operating device is no longer required. Besides the service braking, the parking braking is also needed for automatic driving vehicles such as unmanned logistics distribution vehicles and the like. The existing motor vehicles are mostly provided with two sets of systems, namely a service braking system and a parking braking system, namely the existing electric cylinder device can only realize service braking without a parking braking function, and other parking mechanisms are needed to be added on the basis of the existing braking electric cylinder for realizing the parking function of the vehicle, so that the structure and corresponding control of the vehicle are complex, and the cost is high. While for service and parking brakes, a certain reliability of the actual application is required.

Therefore, how to design a braking device with a simple structure, reliable use and low cost, which meets the requirements of both the service and the parking braking is a problem to be solved in the automatic driving system of the motor vehicle.

Disclosure of Invention

The invention aims to solve the technical problem of providing the screw self-locking electric cylinder device with simple structure and higher reliability aiming at the defects in the prior art.

In order to achieve the above purpose, the invention adopts the following technical scheme: the device comprises a shell, a motor, a piston arranged in the shell in a sliding manner, and a transmission mechanism connected with the motor to drive the piston, and is characterized in that the transmission mechanism comprises:

A first screw pair including a first screw coupled to an output shaft of the motor, a first nut screw-coupled to the first screw to push the piston, the first nut being slidably disposed only in the housing in an axial direction;

The second screw rod pair comprises a second screw rod and a second nut, and the second screw rod and the first screw rod are connected and synchronously rotate and can be arranged in a sliding manner along the same axial direction. The second nut is fixedly connected with the piston, and a threaded hole is formed in the side wall of one side, far away from the piston, of the second nut. A cavity communicated with the threaded hole is formed in the second nut, the second screw rod movably penetrates into the cavity through the threaded hole, and one end of the second screw rod, which is positioned in the cavity, is provided with an end thread matched with the threaded hole;

and the elastic reset piece is arranged between the inner side wall of the shell and the piston.

Further, the transmission mechanism is provided with an initial position and a self-locking position, when in the initial position, one end of the first nut, which is far away from the motor, is propped against the piston, and the end threads of the second screw rod are separated from the threaded hole; when the self-locking position is adopted, one end, far away from the motor, of the first nut is separated from the piston, and the end threads of the second screw rod are matched and connected with the threaded holes.

Further, a first cavity and a second cavity are formed between the piston and the housing. The shell is provided with: the liquid storage tank is communicated with the compensation hole of the first cavity, the liquid supply hole of the liquid storage tank and the second cavity and the liquid discharge hole of the first cavity. The piston is provided with a first leather cup, and when the elastic reset piece is in a pre-pressing state, the first leather cup is positioned between the compensation hole and the liquid supply hole. The leather cup can realize the opening and closing of the compensation hole along with the movement of the piston.

Further, a second leather cup is further arranged on the piston, and the second cavity is located between the first leather cup and the second leather cup.

Further, a connecting hole is formed in one side, far away from the motor, of the first screw rod, the second screw rod is provided with a matching portion penetrating into the connecting hole, and a preset axial gap is formed between the matching portion and the connecting hole. The outer diameter of the matching part of the second screw penetrating into the connecting hole is larger than the outer diameter of the second screw.

Further, the second screw is connected with the first screw through a spline, and the spline connection enables better guidance.

Further, the end part of the second nut, which is movably far away from the piston, is arranged in the first nut, a chute extending along the axial direction is formed in the side wall of the first nut, and a guiding part extending along the radial direction and penetrating through the chute is arranged on the periphery of the second nut. The inner wall of the shell is provided with a limiting groove, the guide part is arranged in the limiting groove in a sliding mode, and the radial extending end of the small nut extends into the limiting groove of the shell to limit rotation of the large nut.

Further, a first elastic piece is arranged between the first nut and the inner wall of the shell, and a second elastic piece is arranged between the second nut and the first nut.

Further, the housing includes a master cylinder housing, a transmission housing, and a motor housing coupled in sequence. The piston is disposed within the master cylinder housing. The motor is fixed on the outer side of the motor shell, a bearing mounting part is formed on the inner wall of the motor shell, and the first screw rod is supported on the bearing mounting part through a bearing. The inner wall of the first nut is provided with an inner shoulder, and the first elastic piece is arranged in the first nut, and two ends of the first elastic piece are propped against the inner shoulder and the second nut. The outer wall of the first nut is provided with an outer shoulder, and two ends of the second elastic piece are propped against between the outer shoulder and the bearing mounting part. The chute is positioned at the inner side of the transmission shell, and the mounting part of the bearing is positioned on the motor shell.

Further, the first elastic member and the second elastic member are both springs. Under the action of the spring, the nut and the screw pitch screw part can be guaranteed to be tightly attached together all the time.

The invention also provides a braking method of the screw self-locking type electric cylinder device, which comprises the following braking modes.

Service braking mode: when the controller receives a braking signal, the driving motor rotates around the omega 1 direction, and the coupler drives the first screw rod to rotate. Under the action of the first nut spring, the first nut is always tightly attached to the large-pitch screw rod part, so that the first nut is immediately screwed into the first screw rod. The radial extending end of the second nut stretches into the limiting groove of the shell to limit the rotation of the first nut, and the rotation of the first screw is converted into the leftward translation of the first nut. The first nut pushes the piston to the leather cup to seal the compensation hole. The first nut continues to push the piston to start to squeeze the brake fluid in the first cavity, so that the brake fluid can output the brake pressure from the fluid discharge hole E.

When the braking needs to be released, the driving motor is powered off, and the piston starts to push the first nut rightwards under the action of braking pressure and the elastic reset piece. The first screw pair is a multi-head screw pair which cannot be self-locked until the first nut returns to the initial position.

Parking brake mode: when the controller receives the self-locking signal, the motor is driven to rotate rapidly, and the coupler drives the first screw rod to rotate rapidly. The radially extending end of the second nut limits the rotation of the first nut, and converts the rotation of the first screw into the translation of the first nut. The first nut pushes the piston to move leftwards, and the parking pressure is output. The second screw is in spline connection with the first screw, and the motor drives the first screw to enable the second screw to rotate together. The piston is connected with the second nut through a bolt to drive the second nut to translate leftwards. At first, a small section clearance s is reserved between the right end face of the second screw and the right end face of the inner hole of the first screw, and the axial movement of the second screw cannot be limited. And when the first nut is about to be screwed out of the left small section of travel s of the first screw, under the action of the spring force of the second nut spring, the second nut and the threaded part of the second screw start to be screwed, the second screw can convert rotation into left translation, and locking of a threaded mechanism caused by inconsistent leads of the small-lead first nut and the large-lead second nut can be eliminated.

When the first screw is screwed out of the first screw, the rotation of the motor cannot be converted into the translation of the first screw, the electric cylinder reaches the maximum braking pressure, and the left end thread of the second screw is screwed into the inner thread of the second screw. The right end face of the second screw rod is attached to the right end face of the inner hole of the first screw rod, the reserved small section gap s becomes 0, and the second screw rod cannot move leftwards and axially any more. The motor continues to rotate, the rotation of the second screw rod is converted into the translation of the second nut, and the piston is pushed to continue to translate leftwards by a small stroke delta x. The piston is out of contact with the first nut. The motor is powered off, and the hydraulic reaction force of the electric cylinder and the elastic reset piece act on the second screw rod pair together through the piston. By means of the self-locking effect of the second screw pair, the position of the piston is maintained unchanged, the output pressure of the electric cylinder is maintained unchanged, and the parking function is realized.

When the self-locking is released, the motor rotates reversely around the omega 2 direction. Under the combined action of the first nut spring and the second nut spring, the first nut is immediately screwed with the first screw rod, and the rotation of the first screw rod is converted into the rightward rapid movement return of the first nut. The self-locking action makes the second nut keep the position unchanged temporarily, and the second screw rod converts the rotation of the motor into leftward movement until the screw thread is released from screwing with the second nut. And the hydraulic reaction force of the electric cylinder acts together with the restoring force of the elastic restoring piece to push the second nut to move rightwards until the second nut returns to the initial position, so that parking is finished.

Due to the application of the technical scheme, the invention has the following advantages: simple structure, low cost, definite installation position, convenient installation, short pressure building time and quick braking response. The screw pair is adopted to drive the piston to brake, and when the motor is powered off, the parking function is realized by utilizing the self-locking effect of the single-head screw pair.

Drawings

FIG. 1 is a schematic view of the structure of an initial state of a screw self-locking electric cylinder device;

FIG. 2 is a schematic diagram of a screw self-locking electric cylinder device in a self-locking state;

fig. 3 is a schematic structural view of a cylinder body portion of the dual-chamber electric cylinder in the present invention.

In the accompanying drawings: 101-motor, 102-coupling, 103-motor housing, 104-shaft retainer ring, 105-bearing, 106-first nut spring, 107-first screw, 108-first nut, 109-second nut spring, 110-limit nut, 111-transmission housing, 112-second nut, 113-second screw, 114-cup, 115-piston, 116-screw, 117-elastic return member, 118-master cylinder housing, 119-reservoir, A-second chamber, B-supply port, C-compensation port, D-first chamber, E-drain port,

212-A first piston, 213-a third cup, 214-a connecting piece, 215-a first liquid storage tank, 216-a first elastic piece; 217-an electric cylinder body, 218-a fourth leather cup, 219-a second piston, 220-a second elastic piece and 221-a limiting pin; 222-limiting holes, 214 a-cross bars, 214B-partition plates, A1-third cavities, B1-first liquid supply holes, B2-second liquid supply holes, C1-first compensation holes, C2-second compensation holes, D1-fourth cavities and D2-fifth cavities; e1-a first liquid discharge hole and E2-a second liquid discharge hole.

Detailed Description

In the description of the present invention, it should be understood that terms indicating orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are merely for convenience in describing the present invention and simplifying the description, rather than indicating or implying that the elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the present invention.

Embodiments of the present invention are further described below with reference to the accompanying drawings.

Example 1

Referring to fig. 1 and 2, the screw self-locking electric cylinder device of the present invention includes a housing, a motor 101, a piston 115 slidably disposed in the housing, and a transmission mechanism coupled to the motor 101 to drive the piston 115, wherein the transmission mechanism includes:

A first screw pair including a first screw 107 coupled to an output shaft of the motor 101, a first nut 108 threadedly coupled to the first screw to push a piston 115, the first nut 108 being slidably disposed only in an axial direction within the housing. In this embodiment, the first screw 107 is a multi-head screw.

The second screw pair comprises a second screw 113 and a second nut 112, the second screw 113 and the first screw 107 are connected and synchronously rotate and can be arranged in a sliding manner along the same axial direction, the second nut 112 is fixedly connected with the piston 115, the piston 115 is fixedly provided with a screw 116, a side wall of the second nut 112, which is far away from the piston 115, is provided with a threaded hole, a cavity communicated with the threaded hole is formed in the second nut 112, the second screw 113 movably penetrates into the cavity through the threaded hole, and one end of the second screw 113, which is positioned in the cavity, is provided with an end thread matched with the threaded hole. In this embodiment, the second screw is a single-head screw.

And an elastic restoring member 117 provided between the inner sidewall of the housing and the piston 115. In this embodiment, the elastic restoring member is a spring.

The transmission mechanism has an initial position in which one end of the first nut 108 remote from the motor 101 abuts against the piston 115, and a self-locking position in which the end thread of the second screw 113 is separated from the threaded hole. In the self-locking position, the end of the first nut 108 away from the motor 101 is separated from the piston 115, and the end thread of the second screw 113 is in matched connection with the threaded hole. The first screw 107 has a connection hole formed at a side far from the motor 101, and the second screw 113 has a fitting portion penetrating into the connection hole, with a preset axial gap between the fitting portion and the connection hole. The second screw 113 is connected with the first screw 107 through a spline, and a limit nut 110 is connected between the second screw 113 and the first screw 107. The end portion of the second nut 112, which is far away from the piston 115, is movably arranged in the first nut 108, a chute extending along the axial direction is formed in the side wall of the first nut 108, a guiding portion extending along the radial direction and penetrating through the chute is arranged on the periphery of the second nut 112, a limiting groove is formed in the inner wall of the shell, and the guiding portion is slidably arranged in the limiting groove. A first elastic piece is arranged between the first nut 108 and the inner wall of the shell; a second elastic member is provided between the second nut 112 and the first nut 108. The first elastic member is a first spring nut 106 and the second elastic member is a second spring nut 109.

A first cavity D and a second cavity a are formed between the piston 115 and the housing. The shell is provided with: the liquid storage tank 119 is communicated with the compensation hole C of the first cavity D, the liquid supply hole B of the liquid storage tank 119 is communicated with the second cavity A, and the liquid discharge hole E is communicated with the first cavity D. The piston 115 is provided with a first cup, and the first cup is located between the compensating hole C and the liquid supply hole B when the elastic restoring member 117 is in a pre-pressed state.

The housing includes a master cylinder housing 118, a transmission housing 111, and a motor housing 103, which are coupled in sequence. The piston 115 is disposed within the master cylinder housing 118. The motor 101 is fixed to the outside of the motor housing 103, a bearing mounting portion is formed on the inner wall of the motor housing 103, the first screw 107 is supported by the bearing mounting portion via a bearing 105, and a shaft retainer ring 104 is provided at one end of the bearing 105 close to the motor. The first nut 108 has an inner shoulder on its inner wall, and the first elastic member is disposed in the first nut 108 with both ends abutting between the inner shoulder and the second nut 112. The outer wall of the first nut 108 has an outer shoulder, and both ends of the second elastic member are abutted between the outer shoulder and the bearing mounting portion.

Service braking mode working principle: when the controller receives the braking signal, the motor 101 is driven to rotate around the omega 1 direction, and the coupler 102 drives the first screw 107 to rotate. Under the action of the first nut spring 106, the first nut 108 is always tightly attached to the large-pitch screw portion, so that the first nut 108 is immediately screwed into the first screw 107. The radially extending end of the second nut 112 extends into the housing limiting groove to limit the rotation of the first nut 108, and the rotation of the first screw 107 is converted into the leftward translation of the first nut 108. The first nut 108 pushes the piston to the cup 114 to seal the compensating bore C. The first nut 108 continues to push the piston 115, starting to squeeze the brake fluid of the first chamber D, allowing it to output the brake pressure from the drain hole E.

When the braking needs to be released, the driving motor 101 is powered off, and the piston 115 starts to push the first nut 108 rightward under the braking pressure and the action of the elastic restoring member 117. The first screw pair is a multi-headed screw pair that cannot be self-locked until the first nut 108 returns to the initial position.

Parking brake mode theory of operation: as shown in fig. 1, when the controller receives the self-locking signal to drive the motor 101 to rotate rapidly, the coupler 102 drives the first screw 107 to rotate rapidly. The radially extending end of the second nut 112 limits the rotation of the first nut 108, converting the rotation of the first screw 107 into a translation of the first nut 108. The first nut 108 pushes the piston 115 to move leftward, outputting the parking pressure. The second screw 113 is in spline connection with the first screw 107, and the motor 101 drives the first screw 107 to rotate the second screw 113 together. The piston 115 is coupled with the second nut 112 by a bolt, and drives the second nut 112 to translate leftwards. Initially, a small gap s is reserved between the right end face of the second screw 113 and the right end face of the inner hole of the first screw 107, and the second screw 113 cannot be limited to axially move. When the first nut 108 is about to be screwed out of the first screw 107 for a small stroke s, the second nut 112 starts to be screwed with the threaded portion of the second screw 113 under the action of the spring force of the second nut spring 112, and the second screw 113 can convert rotation to left translation, so that locking of the threaded mechanism caused by inconsistent leads of the small-lead first nut 108 and the large-lead second nut 112 can be eliminated.

As shown in fig. 2, when the first screw rod 107 is screwed out of the first nut 108, the rotation of the motor 101 cannot be converted into the translation of the first nut 108, the electric cylinder reaches the maximum braking pressure, and the left end thread of the second screw rod 113 is screwed into the inner thread of the second nut 112. The right end face of the second screw 113 is attached to the right end face of the inner hole of the first screw 107, the reserved small section gap s becomes 0, and the second screw 113 cannot move axially leftwards any more. The motor 101 continues to rotate, the rotation of the second screw 113 is converted into the translation of the second nut 112, and the piston 115 is pushed to continue to translate leftwards by a small stroke deltax. The piston 115 is out of contact with the first nut 108. The motor 101 is de-energized and the hydraulic reaction force of the electric cylinder acts on the second screw pair through the piston 115 together with the elastic return 117. By means of the self-locking effect of the second screw pair, the position of the piston is maintained unchanged, the output pressure of the electric cylinder is maintained unchanged, and the parking function is realized.

When the self-locking is released, the motor 101 rotates reversely around the ω2 direction. Under the coaction of the first nut spring 106 and the second nut spring 109, the first nut 108 is immediately screwed with the first screw 107, and the rotation of the first screw 107 is converted into the rightward rapid movement of the first nut 108 to return. The self-locking action temporarily keeps the second nut 112 in place, and the second screw 113 converts the motor rotation into a leftward movement until the screw-thread engagement with the second nut 112 is released. The hydraulic reaction force of the electric cylinder acts together with the restoring force of the elastic restoring member 117 to push the second nut 112 to move rightward until the second nut 112 returns to the initial position, ending the parking.

Example two

The electric cylinder in the first embodiment may also be provided as the two-chamber electric cylinder in the present embodiment; the cylinder block 217 portion of the dual chamber electric cylinder is shown in fig. 3, and the other portions are identical to the embodiment.

The piston assembly includes a first piston 212 and a second piston 219 disposed along a sliding direction thereof, and a connecting member 214 for connecting the first piston 212 and the second piston 219, a fourth cavity D1 is formed between the first piston 212, an inner wall of the electric cylinder block 217, and the connecting member 214, and a fifth cavity D2 is formed between the second piston 219 and the inner wall of the electric cylinder block 217.

A first elastic member 216 and a second elastic member 220 are arranged in the electric cylinder body 217, the first elastic member 216 is arranged between the connecting member 214 and the first piston 212, the second elastic member 220 is arranged between the electric cylinder body 217 and the second piston 219, and the first piston 212 is in sliding connection with the connecting member 214; in this embodiment, both elastic members are springs.

The third cavity A1 is formed between the connecting member 214, the second piston 219 and the inner wall of the electric cylinder block 217, and the connecting member 214 includes a partition 214b for isolating the fourth cavity D1 from the fifth cavity D2 and a cross bar 214a extending outwardly along both sides of the partition 214b and connected to the first piston 212 and the second piston 219. The first piston 212 is provided with a third cup 213 and the second piston 219 is provided with a fourth cup 218.

The specification of the partition 214b should be adapted to the specification of the electric cylinder block 217, i.e. no oil can pass, and in this embodiment, a cup is added to the partition 214 b. The cross bar 214a extends through the partition 214b and has one end threadedly coupled to the second piston 219 and the other end slidably coupled to the first piston 212.

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

when the first elastic member 216 is in the pre-pressing state, the third cup 213 is located between the first compensating hole C1 and the first liquid supply hole B1, and when the second elastic member 220 is in the pre-pressing state, the fourth cup 218 is located between the second compensating hole C2 and the second liquid supply hole B2.

The working principle after the structure is adopted is as follows: under the action of the motor 101, the first piston 212 receives a leftward force, and the pressures of the first elastic member 216 and the second elastic member 220 are always balanced. When the piston assembly moves leftwards under the action of the force of the first elastic member 216 and the second elastic member 220, the first elastic member 216 compresses again, the reaction force increases, and the second elastic member 220 compresses.

In the present embodiment, the elastic coefficient of the first elastic member 216 is larger than that of the second elastic member 220. The elastic coefficient of the first elastic member 216 is larger than that of the second elastic member 220, and in the initial stage, the first piston 212 and the second piston 219 move leftwards together under the action of force to compress the second elastic member 220, so that the first elastic member 216 is not further compressed under the action of force; in the compression process of the second elastic member 220, the elastic force of the second elastic member is gradually increased until the elastic force is larger than the force required by deformation of the first elastic member 216, the first elastic member 216 compresses, the operation is continued, the first elastic member 216 and the second elastic member 220 are always in a balanced state, and after the corresponding compensation holes are blocked by the third leather cup 213 and the fourth leather cup 218, high pressure is built in the fourth cavity D1 and the fifth cavity D2, and oil is discharged through the first liquid discharge hole E1 and the second liquid discharge hole E2 to brake the automobile.

In this embodiment, the first piston 212 is provided with a limiting pin 221, the cross rod 214a is provided with a limiting hole 222 matched with the limiting pin 221, and the limiting pin 221 and the limiting hole 222 are both arranged along the horizontal direction and along the sliding direction of the piston assembly. The first piston 212 is slidably coupled to the cross bar 214a by a stop pin 221 and a stop hole 222. When the force compressing the first elastic member 216 is smaller than the force compressing the second elastic member 220, the limiting pin 221 will move leftwards along the limiting hole 222 under the driving of the first piston 212, and the second piston 219 will not move; when the force compressing the first elastic member 216 is smaller than the force compressing the second elastic member 220, the entire piston assembly moves leftward at the same time.

In the present embodiment, the first piston 212 is fixedly connected to the second nut 112 in the first embodiment, that is, the first piston 212 can move axially under the drive of the second nut.

The above embodiments are provided to illustrate the technical concept and features of the present invention and are intended to enable those skilled in the art to understand the content of the present invention and implement the same, and are not intended to limit the scope of the present invention. All equivalent changes or modifications made in accordance with the spirit of the present invention should be construed to be included in the scope of the present invention.

Claims

1. A screw self-locking electric cylinder device, comprising a housing, a motor (101), a piston (115) slidingly arranged in the housing, and a transmission mechanism coupled with the motor (101) to drive the piston (115), characterized in that the transmission mechanism comprises:

a first screw pair including a first screw (107) coupled to an output shaft of the motor (101), a first nut (108) threadedly connected to the first screw to push the piston (115), the first nut (108) being slidably disposed only in an axial direction within the housing;

the second screw pair comprises a second screw (113) and a second nut (112), the second screw (113) is connected with the first screw (107) to rotate synchronously and can slide relatively along the same axial direction, the second nut (112) is fixedly connected with the piston (115), a threaded hole is formed in the side wall of the second nut (112) far away from the piston (115), a cavity communicated with the threaded hole is formed in the second nut (112), the second screw (113) movably penetrates into the cavity through the threaded hole, and one end of the second screw (113) positioned in the cavity is provided with an end thread matched with the threaded hole;

an elastic return member (117) provided between an inner side wall of the housing and the piston (115); the transmission mechanism is provided with an initial position and a self-locking position, when in the initial position, one end of the first nut (108) away from the motor (101) is propped against the piston (115), and the end thread of the second screw (113) is separated from the threaded hole; in the self-locking position, one end of the first nut (108) away from the motor (101) is separated from the piston (115), and the end thread of the second screw (113) is matched and connected with the threaded hole;

A connecting hole is formed in one side, far away from the motor (101), of the first screw (107), the second screw (113) is provided with a matching part penetrating into the connecting hole, and a preset axial gap is formed between the matching part and the connecting hole;

The end part of the second nut (112) which is movably far away from the piston (115) is arranged in the first nut (108), a chute which extends along the axial direction is formed in the side wall of the first nut (108), a guide part which extends along the radial direction and passes through the chute is arranged on the periphery of the second nut (112), a limit groove is formed in the inner wall of the shell, and the guide part is arranged in the limit groove in a sliding manner;

A first elastic piece is arranged between the first nut (108) and the inner wall of the shell; a second elastic piece is arranged between the second nut (112) and the first nut (108);

The housing comprises a master cylinder housing (118), a transmission housing (111) and a motor housing (103) which are sequentially connected; the piston (115) is disposed within the master cylinder housing (118); the motor (101) is fixed on the outer side of the motor shell (103), a bearing mounting part is formed on the inner wall of the motor shell (103), and the first screw (107) is supported on the bearing mounting part through a bearing (105); an inner wall of the first nut (108) is provided with an inner shoulder, and the first elastic piece is arranged in the first nut (108) and two ends of the first elastic piece are propped between the inner shoulder and the second nut (112); the outer wall of the first nut (108) is provided with an outer shoulder, and two ends of the second elastic piece are propped against between the outer shoulder and the bearing mounting part.

2. The screw self-locking electric cylinder device of claim 1, wherein: a first cavity (D) and a second cavity (A) are formed between the piston (115) and the shell, and the shell is provided with: a compensation hole (C) for communicating the liquid storage tank (119) with the first cavity (D), a liquid supply hole (B) for communicating the liquid storage tank (119) with the second cavity (A) and a liquid discharge hole (E) for communicating the first cavity (D);

the piston (115) is provided with a first leather cup, and when the elastic reset piece (117) is in a pre-pressing state, the first leather cup is positioned between the compensation hole (C) and the liquid supply hole (B).

3. The screw self-locking electric cylinder device of claim 2, wherein: the piston (115) is also provided with a second leather cup, and the second cavity (A) is positioned between the first leather cup and the second leather cup.

4. The screw self-locking electric cylinder device of claim 1, wherein: the second screw (113) is connected with the first screw (107) through a spline.

5. The screw self-locking electric cylinder device of claim 1, wherein: the first elastic piece and the second elastic piece are springs.