Release mechanism of electric brake device and use method thereof

Abstract

A release mechanism for an electric brake device and a method for using the same. The release mechanism proposed in the present invention is composed of a nut, a ball nut, a lower shell, and a pad in a pressure plate assembly in an electric brake actuator, and cooperates with the electric brake actuator and the pressure plate to work: specifically, there are four evenly distributed fan-shaped protrusions on the closed end face of the nut in the electric brake actuator, and the grooves between the fan-shaped protrusions form a movable groove for the pad on the surface of the pressure plate. Expansion tubes are symmetrically installed on the outer circumference of the open end port of the ball nut in the lower shell of the electric brake actuator, and guide balls are embedded in each expansion tube. There are four evenly distributed waist-shaped grooves on the non-friction surface of the pressure plate in the pressure plate assembly, and a pad is fixed in each waist-shaped groove. The present invention enables the brake force to be released in time when the ball screw in the electric brake actuator is stuck, avoiding the possibility of aircraft tire blowout or brake wheel overheating caused by the ball screw being stuck.

Description

Technical Field

[0001] The invention relates to the technical field of aircraft electric brakes, in particular to a release mechanism in an electric brake device and a use method thereof. Background Art

[0002] Electric brakes are a new technology that is beginning to be used in aircraft brakes. Electric brake devices are generally composed of electric brake actuators, actuator supports, brake housings and brake discs. The electric brake actuator is installed on the actuator support, and the brake disc is installed on the brake housing. When braking, the piston of the electric brake actuator extends under the command of the controller, presses the brake disc, and generates braking thrust. When releasing the brake, the piston retreats under the command of the controller, so that a certain gap is maintained between the piston and the brake disc. Electric brake actuators are generally composed of components such as housings, motors, ball screws and force sensors.

[0003] The role of the ball screw in the electric brake actuator is to convert the motor torque amplified by the reduction gear into the linear force required to clamp the brake disc. The ball screw is generally composed of a ball nut and a ball screw, a steel ball and a return device. Under certain conditions of use, such as when the steel ball is broken or the return device is damaged, the ball screw may produce a failure mode called jamming. When a jamming failure occurs, the ball screw loses the torque / linear force conversion function, and relative motion cannot be generated between the ball nut and the ball screw, and the piston of the actuator cannot extend or retract according to the brake command.

[0004] The ball screw jamming problem in the electric brake actuator will cause unacceptable aircraft brake failure. During high-speed landing braking, the brake force cannot be released quickly when jamming occurs, which may cause the aircraft tire to blow; during taxi braking, jamming will cause the brake wheel to overheat due to long-term non-commanded braking.

[0005] During use, the electric brake actuator has a ball screw stuck, which is a fault with a low probability of occurrence. In the prior art, this type of fault can only be handled passively. After the aircraft returns to the parking position, the faulty electric brake actuator is removed and replaced with a new one. Due to the delay in handling, this treatment method cannot avoid tire blowout or wheel overheating caused by ball screw sticking, which poses a safety hazard. Summary of the invention

[0006] In order to overcome the delay in processing timing in the prior art, the inability to avoid tire blowout or wheel overheating due to ball screw jamming, and the existence of potential safety hazards, the present invention proposes a release mechanism for an electric brake device and a method for using the same.

[0007] The release mechanism of the electric brake device proposed in the present invention is composed of a nut, a ball nut, a lower shell in the electric brake actuator, and a pad in the pressure plate assembly, and the electric brake actuator and the pressure plate cooperate to work; specifically, an axially protruding annular boss is added to the end face of the closed end of the nut in the electric brake actuator, and four evenly distributed fan-shaped protrusions are processed on the end face of the boss; the grooves between each of the fan-shaped protrusions form a moving groove for the pad on the surface of the pressure plate. Expansion tubes are symmetrically installed on the outer circumference of the open end of the ball nut installed in the lower shell of the electric brake actuator, and guide balls are embedded in each expansion tube. Two guide ball grooves with arc-shaped cross sections are symmetrically provided on the inner hole wall of the lower shell, and the position of the guide ball groove corresponds to the position of the guide ball.

[0008] In order to cooperate with the ball nut, there are four evenly distributed waist-shaped grooves on the non-friction surface of the pressure plate. A pad is fixed in each waist-shaped groove. Four fan-shaped protrusions are evenly distributed around the geometric center of each pad. The upper surface of each protrusion is 3 to 6 mm higher than the surface of the pressure plate. The height of each protrusion is the same as the height of the fan-shaped protrusion on the ball nut. There are riveted mounting surfaces on the surfaces of both ends of each pad.

[0009] The height of the fan-shaped protrusion must be greater than the axial elastic deformation of the brake device caused by the load when the electric brake actuator pushes the brake disc to squeeze toward the rear end of the brake housing.

[0010] The included angle between the two oblique sides of the fan-shaped protrusion is 40°; the included angle between the two oblique sides of the pad moving groove is 50°.

[0011] The ball nut is installed in the lower housing of the electric brake actuator. A pair of arc grooves are symmetrically distributed on the inner surface of the lower housing; the radius of the arc grooves is adapted to the radius of the guide ball.

[0012] One end of the expansion tube is an expansion section for installing a guide ball, and the outer diameter of the expansion section is the same as the inner diameter of the blind hole on the nut, and the inner diameter is the same as the diameter of the guide ball; the other end face of the expansion tube contacts the bottom surface of the blind hole.

[0013] The guide ball is made of bearing steel with a hardness of HRC55 or above. The expansion tube is made of GH600 high temperature alloy seamless tube with a hardness not greater than HRC30.

[0014] A pair of blind holes for installing the expansion tube are symmetrically distributed on the outer circumference of the open end of the ball nut.

[0015] The cushion blocks are waist-shaped blocks, and each cushion block is riveted to the compression plate by rivets. The middle position of each cushion block has four evenly distributed fan-shaped protrusions of the same height, and the circumferential angle of each fan-shaped protrusion is 40 degrees.

[0016] The method for releasing the working force by using the release mechanism of the electric brake device proposed by the present invention comprises the following specific processes:

[0017] Step 1: Set the maximum operating current of the motor in the electric brake actuator.

[0018] Before the brake device is started, the controller limits the maximum working current of the motor in each electric brake actuator in the brake device. The working current of the motor has a linear corresponding relationship with the driving torque of the motor. The greater the current, the greater the driving torque.

[0019] The maximum working current of the motor is set to not exceed 3A, corresponding to the maximum driving torque of the motor not exceeding 3N·m. Step 2: Monitor the working status of the electric brake actuator:

[0020] By testing the working status of the electric brake actuator, it is determined whether the ball screw in the electric brake actuator is stuck. If an electric brake actuator is stuck, go to step 3;

[0021] The criteria for determining whether a ball screw in an electric brake actuator is stuck are:

[0022] Ⅰ The command sent by the controller to the electric brake actuator corresponds to releasing the brake;

[0023] Ⅱ The motor current is large enough but does not exceed the limit value. If the motor current is greater than 1A but less than 3A, the corresponding motor drive torque is greater than 1N·m;

[0024] ⅢThe motor speed remains zero for 10ms.

[0025] Step 3, release of brake force:

[0026] When the ball screw in the electric brake actuator is stuck, a command is issued to start the release mechanism and complete the release of the brake force, specifically:

[0027] When it is determined that the ball screw in the electric brake actuator is stuck, the controller sends a command to start the release mechanism, and the motor in the faulty electric brake actuator rotates in the direction of releasing the brake with a large current; the current of the motor is greater than 4A, and the driving torque of the motor is greater than 4N·m. At this time, because the driving torque of the motor is large enough, the squeezing force of the guide ball on the expansion tube causes the expansion tube to expand and deform, and the guide ball moves toward the small end of the expansion tube to get rid of the restriction of the arc groove; the ball nut rotates relative to the arc groove.

[0028] When the command to start the release mechanism is issued, the initial rotation angle of the motor is recorded as 0° when the start command is issued; when the motor rotates through an angle of 42°, the power to the motor is cut off and the motor has no current output, so that the four raised sector blocks on the nut are aligned and embedded in the grooves between the raised sector blocks on the pad, and the operating force applied to the brake disc by the faulty electric brake actuator is released.

[0029] The present invention enables the braking force to be released in time when the ball screw in the electric brake actuator is stuck, thereby avoiding aircraft tire blowout or brake wheel overheating that may be caused by the ball screw being stuck.

[0030] The present invention monitors the working state of the electric brake actuator during the braking process. If the monitoring and analysis determine that the ball screw of the electric brake actuator is stuck during the braking process, the release mechanism of the electric brake device is activated to timely release the braking thrust of the electric brake actuator where the ball screw is stuck. Because this processing method can timely handle the faulty electric brake actuator during the aircraft braking process, rather than waiting for the aircraft to return to the parking position to handle the fault, it can avoid aircraft tire blowout or brake wheel overheating caused by ball screw sticking, thereby ensuring flight safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural diagram of the electric brake device;

[0032] Figure 2 is a structural diagram of the hold-down plate assembly;

[0033] Figure 3 It is a structural diagram of the electric brake actuator;

[0034] Figure 4 is the structural diagram of the ball nut; among them, Figure 4 a is the main view, Figure 4 b is Figure 4 AA section view in a;

[0035] Figure 5 is a schematic diagram of the arc groove on the lower shell;

[0036] Figure 6 is the force analysis diagram of the guide ball and the expansion tube; Figure 6 a is a schematic diagram of the force on the ball nut after the ball nut is matched with the lower housing; Figure 6 b is the force diagram of the guide ball; Figure 6 c is a schematic diagram of the force on the expansion tube; Figure 6 d is a schematic diagram of the decomposition of the force exerted by the guide ball on the expansion tube;

[0037] Figure 7 is a schematic diagram of the structure of the release mechanism;

[0038] Figure 8 is a schematic diagram of the release mechanism working to the release position;

[0039] Fig. 9 It is a three-dimensional structural schematic diagram of the release mechanism.

[0040] In the figure: 1. Electric brake actuator; 2. Actuating support; 3. Pressure plate assembly; 4. Moving plate assembly; 5. Static plate; 6. Pressure plate assembly; 7. Brake housing; 8. Pressure plate; 9. Pad; 10. Rivet; 11. Upper housing; 12. Lower housing; 13. Motor; 14. Ball screw; 15. Ball nut; 16. Force sensor; 17. Nut; 18. Guide ball; 19. Expansion tube; 20. Guide ball groove. DETAILED DESCRIPTION

[0041] This embodiment is a release mechanism in an electric brake device.

[0042] The release mechanism is obtained by improving the electric brake actuator in the prior art. The improvement lies in that an axially protruding annular boss is added to the outer edge of the end face of the closed end of the nut 17 in the electric brake actuator, and four evenly distributed fan-shaped protrusions are processed on the end face of the boss; the boss is located outside the lower end face of the lower shell 12 in the electric brake actuator. The grooves between the fan-shaped protrusions form a moving groove for the pad located on the surface of the clamping plate. The height of the fan-shaped protrusion must be greater than the axial elastic deformation of the brake device caused by the load when the electric brake actuator 1 pushes the brake disc to squeeze toward the rear end of the brake housing; in this embodiment, the height of the fan-shaped protrusion is 3 to 6 mm. The angle between the two hypotenuses of the fan-shaped protrusion is 40°; the angle between the two hypotenuses of the pad moving groove is 50°. A pair of blind holes are symmetrically distributed on the outer circumference of the open end of the ball nut, and an expansion tube 19 is installed in each blind hole, and a guide ball 18 is embedded in each expansion tube; the guide ball is a steel ball with a hardness of HRC55 or above.

[0043] The ball nut is installed in the lower housing of the electric brake actuator 1. A pair of arc grooves 20 are symmetrically distributed on the inner surface of the lower housing; the radius of the arc grooves is adapted to the radius of the guide ball.

[0044] In order to cooperate with the ball nut, the pressure plate in the brake device is improved. Specifically, four evenly distributed waist-shaped grooves are processed on the non-friction surface of the pressure plate. A pad is fixed in each waist-shaped groove. Four fan-shaped protrusions are evenly distributed around the geometric center of each pad. The upper surface of each protrusion is 3 to 6 mm higher than the surface of the pressure plate. The height of each protrusion is the same as the height of the fan-shaped protrusion on the ball nut. There are riveted mounting surfaces on the surfaces at both ends of each pad.

[0045] The electric brake actuator 1 is of prior art, and includes an upper shell 11, a lower shell 12, a motor 13, a ball screw and a force sensor 16. The ball screw includes a ball screw 14, a ball nut 15, a ball and a return device. When the electric brake actuator 1 is working, the motor drives the ball screw 14 to rotate, and the ball nut 15 performs linear motion. During the braking process, the ball nut acts as a piston and is directly pressed on the pad 9 on the clamping plate. Two radial blind holes are evenly distributed on the outer circumferential surface of the open end of the nut 17, and expansion tubes 19 are respectively installed in the blind holes, and guide balls 18 are installed at the top of the expansion tubes. Two guide ball grooves 20 with arc-shaped cross sections are symmetrically arranged on the inner hole wall of the lower shell 12, and the position of the guide ball groove corresponds to the position of the guide ball on the expansion tube.

[0046] The expansion tube 19 is a metal tube, one end of which is an expansion section for installing the guide ball 18, and the outer diameter of the expansion section is the same as the inner diameter of the blind hole on the nut, and the inner diameter is the same as the diameter of the guide ball; the other end face of the expansion tube 19 contacts the bottom surface of the blind hole. The guide ball 18 is made of bearing steel such as GCr15 material, and the hardness is above HRC55. The expansion tube is made of a metal material with relatively low hardness and a yield strength that changes very little in the temperature range of -55℃ to 150℃. In this embodiment, the expansion tube uses a GH600 high-temperature alloy seamless tube with a hardness not greater than HRC30. Due to the large difference in hardness between the guide ball 18 and the expansion tube 19, when the extrusion force of the guide ball 18 on the expansion tube 19 exceeds the expansion force of the expansion tube, the unexpanded portion of the inner diameter of the expansion tube 19 will continue to expand, and the guide ball 18 will slide from the large end to the small end in the inner cavity of the expansion tube 19. The bottom end of the nut 17 has four evenly spaced sector-shaped protrusions, and the circumferential angle and protrusion height of each sector-shaped protrusion are the same as those of each sector-shaped protrusion on the cushion block 9. After the nut 17 is extended, it contacts the cushion block 9, and the four sector-shaped protrusions on the bottom end of the nut 17 are of the same size as the four sector-shaped protrusions on the cushion block 9 and are positioned opposite to each other.

[0047] The spacer block 9, the arc groove 20 and the ball nut 15 together constitute a release mechanism of the electric brake device.

[0048] like Figure 2The clamping plate assembly 3 is composed of a clamping plate 8, a pad 9 and a rivet 10. The number of pads 9 is the same as the number of electric brake actuators on the electric brake device. The pad 9 is a waist-shaped block made of metal materials with low thermal conductivity such as titanium alloy or stainless steel. Each pad 9 is riveted to the clamping plate 8 by rivets 10. There are four evenly distributed fan-shaped protrusions of the same height in the middle position of each pad 9, and the circumferential angle of each fan-shaped protrusion is 40°. The protrusion height of the fan-shaped protrusion is greater than the maximum axial deformation generated during the use of the brake device. When braking, there is a keyway on the inner diameter of the clamping plate 8 that cooperates with the brake housing. The clamping plate 8 and the pad 9 can only slide axially on the brake housing. Each electric brake actuator 1 on the brake device corresponds to a pad 9. When braking, the piston of the electric brake actuator extends and directly presses on the pad 9.

[0049] When the ball screw is not stuck, the ball nut 15 is driven by the ball screw 14 and guided by the guide ball 18 to slide in the arc groove 20 of the lower housing 12. When the ball screw is stuck, the ball screw 14 and the ball nut 15 are completely locked, and the ball nut 15 can only rotate but not move linearly. After being stuck, the force analysis of the guide ball 18 and the expansion tube 19 is as follows: Figure 6 Among them, M 驱动 M is the driving torque of the ball screw 14 on the ball nut 15. 摩擦 is the friction torque of the ball nut 15, M 摩擦 The size of F can be measured through experiments. 下壳体 is the supporting force of the arc groove 20 on the guide ball 18. From the force relationship in the figure, according to the moment balance equation, it can be known that M 驱动 、M 摩擦 and F 下壳体 Between: M 驱动 -M 摩擦 =F 下壳体 × L. F 扩胀管 is the support force of the expansion tube 19 on the guide ball 18. When the guide ball is stationary, F 下壳体 and F 扩胀管 Equal in size. 球 F is the squeezing force of the guide ball 18 on the expansion tube 19. 扩胀管 and F 球 It is a pair of action and reaction forces, which are equal in magnitude. 球 It can be decomposed into two mutually perpendicular components F 球1 and F 球2 From the relationship between the above forces, it can be deduced that: F 球2 =F 下壳体 × sinθ. Therefore, M 驱动 The larger the F 下壳体 The larger the pressure, the greater the compressive force F of the guide ball 18 on the expansion tube 19. 球2 The larger the M驱动 When F exceeds a certain value, 球2 The increase will cause the unexpanded portion of the inner diameter of the expansion tube 19 to continue to expand, and the guide ball 18 slides from the large end to the small end in the inner cavity of the expansion tube 19.

[0050] The release mechanism works as follows Figure 7 and Figure 8 . In normal use, a portion of the guide ball 18 is exposed at the flared end of the expansion tube 19, and the exposed portion cooperates with the arc groove 20 to guide the ball nut 15 to perform linear motion. If the guide ball 18 is to be released from the guidance of the arc groove 20, the guide ball 18 must be moved toward the small end of the expansion tube 19, that is, the small end of the inner diameter of the expansion tube 19 must be expanded to overcome the expansion force of the expansion tube 19 and cause the expansion tube 19 to expand and deform. The minimum axial extrusion force required when the expansion tube 19 begins to expand and deform is defined as the expansion force F1. The size of F1 is determined by the yield strength and wall thickness of the expansion tube 19. After the structural dimensions of the expansion tube 19 are determined, the size of F1 is determined. When the extrusion force F1 of the guide ball 18 on the expansion tube 19 球2 When the expansion force is less than F1, the expansion tube 19 will not expand and deform. 球2 The expansion tube will expand and deform only when the expansion force F1 is greater than the expansion force F1. The expansion force F1 of the expansion tube 19 is designed as follows: the guide ball 18 overcomes the expansion force F1 of the expansion tube 19 and moves toward the small end of the expansion tube, so that the minimum driving torque for the ball nut 15 to rotate relative to the arc groove 20 is M1. In the normal operation of the electric brake actuator, by controlling the output torque of the motor 13, the ball screw 14 drives the ball nut 15 with a torque M1. 驱动 No more than M1. Therefore, in normal use, no matter whether the nut 17 is in contact with the spacer 9 or not, the guide ball 18 will not overcome the expansion force F1 of the expansion tube 19 and move toward the small end of the expansion tube. In this way, the position of the guide ball 18 in the expansion tube 19 always remains stable, and the ball nut 15 is guided by the guide ball 18 and can only slide on the arc groove 20. Under this condition, after the ball nut 15 is extended, the four fan-shaped protrusions at its bottom end are directly opposite to the four fan-shaped protrusions on the spacer 9. When the ball screw is stuck, the brake system will recognize this fault state. At this time, the system will instruct the motor to reverse with a torque much greater than that in normal use, so that the driving torque M 驱动 Subtract the friction torque M 摩擦 The torque value after the release is large enough to start the release mechanism. Since the driving torque acting on the ball nut 15 is large enough, the extrusion force F exerted by the guide ball 18 on the expansion tube 19 球2 Greater than the expansion force F1. 球2Under the action of the expansion tube 19, the unexpanded part of the inner diameter will continue to expand, and the guide ball 18 will slide from the large end to the small end in the inner cavity of the expansion tube 19, so that the guide ball will be free from the restriction of the arc groove 20, and the ball nut 15 will continue to rotate relative to the lower shell 12. After the ball nut 15 rotates 41° relative to the initial position, it stops. At this time, the four sector-shaped protrusions on the nut 17 are opposite to the grooves between the four sector-shaped protrusions on the cushion block 9. And the axial clearance between the nut 17 and the cushion block 9 increases, and the increased clearance is equal to the height of the four sector-shaped protrusions on the nut 17. Since the protrusion height of the sector-shaped block is greater than the maximum value of the axial deformation generated during the use of the brake device, an axial spacing will be maintained between the nut 17 and the cushion block 9 at this position. In this way, after the ball screw is stuck, the linear force applied to the brake disc by the faulty electric brake actuator is actively unloaded.

[0051] This embodiment also proposes a method for releasing the actuating force by using the release mechanism, and the specific process is as follows:

[0052] Step 1: Set the maximum operating current of the motor in the electric brake actuator.

[0053] Before the brake device is started, the controller limits the maximum working current of the motor in each electric brake actuator in the brake device. The working current of the motor has a linear corresponding relationship with the driving torque of the motor. The greater the current, the greater the driving torque.

[0054] The maximum working current of the motor is set to be no more than 3A, corresponding to a maximum driving torque of the motor of no more than 3N·m. When the driving torque of the motor is no more than 3N·m, the squeezing force generated by the guide ball 18 will not cause the expansion tube to expand and deform, thereby preventing the release mechanism from being triggered when the ball screw is not stuck.

[0055] Step 2, monitor the working state of the electric brake actuator to determine whether a ball screw in the electric brake actuator is stuck.

[0056] After the brake device is activated, the controller command status, motor current, motor speed, and motor angle corresponding to each electric brake actuator are continuously monitored in real time. The controller command status is monitored to determine whether the current controller command corresponds to the release of the brake. The motor current is monitored to determine whether the motor has an open or short circuit fault and whether the motor drive torque is large enough. The motor speed is monitored to determine whether the motor has a speed response under a sufficiently large drive torque.

[0057] During the test, if an electric brake actuator meets the following three conditions at a certain moment, it is considered that the ball screw is stuck:

[0058] 1. The command sent by the controller to the electric brake actuator corresponds to releasing the brake;

[0059] 2. The motor current is large enough but does not exceed the limit value. If the motor current is greater than 1A but less than 3A, the corresponding motor drive torque is greater than 1N·m;

[0060] 3. The motor speed remains zero for 10ms.

[0061] The stuck fault is manifested as the controller instructing the electric brake actuator to release the brake, the motor does not have an open / short circuit fault and the driving torque of the motor is large enough, but the motor cannot rotate.

[0062] The electric brake actuator is prior art.

[0063] The transmission components of the electric brake actuator include transmission gears, bearings and ball screws. During the use of the electric brake actuator, the transmission gears, bearings and ball screws will wear. Excessive wear of the transmission gears, bearings and ball screws will result in unstable transmission of the electric brake actuator, but will not cause mechanical jamming. During use, the jamming of the ball screw itself is the only reason for the mechanical jamming of the electric brake actuator. The working state of the electric brake actuator at a certain moment that satisfies the above three conditions at the same time can be used as a basis for determining whether the ball screw has a jamming fault. If it is determined that the electric brake actuator has not been jammed, the electric brake actuator will continue to brake or release the brake according to the instructions of the controller, and then enter step 3.

[0064] Step 3, when the ball screw in the electric brake actuator is stuck, an instruction to start the release mechanism is issued to complete the release of the brake force.

[0065] According to the determination conditions of the ball screw stuck fault described in step 2, when it is determined that the ball screw in the electric brake actuator is stuck, the controller sends a command to start the release mechanism, and the motor in the faulty electric brake actuator rotates in the direction of releasing the brake with a large current; the current of the motor is greater than 4A, and the driving torque of the motor is greater than 4N·m. At this time, since the driving torque of the motor is large enough, the squeezing force of the guide ball 18 on the expansion tube 19 will cause the expansion tube to expand and deform, and the guide ball moves toward the small end of the expansion tube to get rid of the restriction of the arc groove 20; the ball nut 15 rotates relative to the arc groove 20.

[0066] When issuing the command to start the release mechanism, the initial rotation angle of the motor is recorded as 0° when the start command is issued; when the motor rotates through an angle of 42°, the power is cut off and the motor has no current output, so that the four raised sector blocks on the nut 17 are aligned and embedded in the grooves between the raised sector blocks on the pad 9, and the actuating force applied to the brake disc by the faulty electric brake actuator is released.

Claims

1. A release mechanism for an electric brake device, characterized in that: It is composed of the ball nut in the electric brake actuator, the lower shell and the pad in the clamping plate assembly, and the electric brake actuator and the clamping plate assembly work together; the clamping plate assembly is composed of the clamping plate, the pad and the rivet; An axially protruding annular boss is added to the closed end face of the ball nut in the electric brake actuator, and four evenly distributed fan-shaped protrusions are processed on the end face of the boss; the grooves between the fan-shaped protrusions form a moving groove for the pad on the surface of the pressure plate; expansion tubes are symmetrically installed on the outer circumference of the open end port of the ball nut installed in the lower shell of the electric brake actuator, and a guide ball is embedded in each expansion tube; two guide ball grooves with arc-shaped cross sections are symmetrically arranged on the inner hole wall of the lower shell, and the positions of the guide ball grooves correspond to the positions of the guide balls; one end of the expansion tube is an expansion section for installing the guide ball, and the outer diameter of the expansion section is the same as the inner diameter of the blind hole on the ball nut, and the inner diameter is the same as the diameter of the guide ball; the other end face of the expansion tube contacts the bottom surface of the blind hole; In order to cooperate with the ball nut, there are four evenly distributed waist-shaped grooves on the non-friction surface of the clamping plate; Four pads are fixed in each waist-shaped groove; the four pads are four fan-shaped pads evenly distributed around the geometric center; the upper surface of each fan-shaped pad is 3 to 6 mm higher than the surface of the clamping plate; the height of each fan-shaped pad is the same as the height of the fan-shaped protrusion on the ball nut; and there are riveted mounting surfaces on the surfaces of both ends of each fan-shaped pad; The height of the fan-shaped protrusion must be greater than the axial elastic deformation of the brake device caused by the load when the electric brake actuator pushes the brake disc to squeeze toward the rear end of the brake housing; The squeezing pressure of the guide ball on the expansion tube will cause the expansion tube to expand and deform, and the guide ball moves toward the small end of the expansion tube to get rid of the restriction of the guide ball groove; the ball nut rotates relative to the guide ball groove; the four fan-shaped protrusions on the ball nut are aligned and embedded in the groove formed by the fan-shaped pads on the pressure plate assembly, and the actuating force applied to the brake disc by the faulty electric brake actuator is released.

2. The release mechanism of the electric brake device according to claim 1, characterized in that: The included angle between the two oblique sides of the fan-shaped protrusion is 40°; the included angle between the two oblique sides of the moving groove of the cushion block is 50°.

3. The release mechanism of the electric brake device according to claim 1, characterized in that: A pair of guide ball grooves are symmetrically distributed on the inner surface of the lower shell; the radius of the guide ball grooves is adapted to the radius of the guide balls.

4. The release mechanism of the electric brake device according to claim 1, characterized in that: The guide ball is made of bearing steel with a hardness of HRC55 or above; the expansion tube is made of GH600 high-temperature alloy seamless tube with a hardness not greater than HRC30.

5. The release mechanism of the electric brake device according to claim 1, characterized in that: A pair of blind holes for installing the expansion tube are symmetrically distributed on the outer circumference of the open end of the ball nut.

6. The release mechanism of the electric brake device according to claim 1, characterized in that: The cushion blocks are waist-shaped blocks, and each cushion block is riveted to the pressing plate through rivets.

7. A method for releasing actuating force using the release mechanism of the electric brake device according to claim 1, characterized in that: The specific process is: Step 1, set the maximum operating current of the motor in the electric brake actuator: Before starting the brake device, the controller limits the maximum working current of the motor in each electric brake actuator in the brake device; the working current of the motor has a linear corresponding relationship with the driving torque of the motor, and the greater the current, the greater the driving torque; The maximum operating current of the motor is set to not exceed 3A, corresponding to a maximum driving torque of the motor not exceeding 3N·m; Step 2: Monitor the working status of the electric brake actuator: By detecting the working state of the electric brake actuator, it is determined whether the ball screw in the electric brake actuator is stuck; if a certain electric brake actuator is stuck, go to step 3; Step 3, release of brake force: When the ball screw in the electric brake actuator is stuck, a command is issued to start the release mechanism and release the brake force: When it is determined that the ball screw in the electric brake actuator is stuck, the controller sends a command to start the release mechanism, and the motor in the faulty electric brake actuator rotates in the direction of releasing the brake with a large current; the current of the motor is greater than 4A, and the driving torque of the motor is greater than 4N·m; at this time, since the driving torque of the motor is large enough, the squeezing force of the guide ball on the expansion tube causes the expansion tube to expand and deform, and the guide ball moves toward the small end of the expansion tube to get rid of the restriction of the guide ball groove; the ball nut rotates relative to the guide ball groove; When the command to start the release mechanism is issued, the initial rotation angle of the motor is recorded as 0° when the start command is issued; when the motor rotates through an angle of 42°, the power to the motor is cut off and the motor has no current output, so that the four fan-shaped protrusions on the ball nut are aligned and embedded in the groove formed by the fan-shaped pads on the pressure plate assembly, and the actuating force applied to the brake disc by the faulty electric brake actuator is released.

8. A method for releasing actuating force using a release mechanism of an electric brake device according to claim 7, characterized in that: The criteria for determining whether the ball screw in the electric brake actuator is stuck are: Ⅰ The command sent by the controller to the electric brake actuator corresponds to releasing the brake; Ⅱ The motor current is large enough but does not exceed the limit value; the motor current is greater than 1A but less than 3A, which means that the corresponding motor driving torque is greater than 1N·m; ⅢThe motor speed remains zero for 10ms.

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