Elevator car emergency braking system and control method thereof

Abstract

The elevator car emergency braking system comprises safety tongs, tong blocks on the two sides of the safety tongs are used for clamping a guide rail so as to brake an elevator car, jacking devices are arranged at the bottoms of the tong blocks on the two sides, each jacking device comprises a jacking oil cylinder and a piston rod arranged in the oil cylinder, and the jacking oil cylinders are fixed to a safety tongs base; piston rods are connected with the bottoms of the clamp blocks; the system further comprises a controller, and the controller is used for receiving an overspeed signal of the speed limiter. The jacking oil cylinder is controlled to output pressure according to the overspeed signal, so that the piston rod generates jacking force to jack the bottom of the clamp block; according to the safety tongs, the jacking device is additionally arranged on the basis of traditional safety tongs, when mechanical triggering brake of the traditional safety tongs fails, the jacking device can make the safety tongs move upwards so as to clamp a guide rail, and accidents are avoided.

Description

Technical Field

[0001] The present application relates to the field of elevator safety technology, and in particular to an elevator car emergency braking system and a control method thereof. Background Art

[0002] Speed limiter-safety clamp and upward overspeed safety device play a pivotal role in ensuring the safe operation of elevators. However, in recent years, there have been cases of elevators falling and hitting the top, causing casualties and property losses. Therefore, it is urgent to add a set of safety protection devices on the basis of the original safety devices to avoid the risk of overspeeding or accidental movement of the elevator car when the speed limiter, safety clamp, upward overspeed protection device, brake, etc. fail, so as to effectively stop the elevator and ensure the safety of passengers' lives and property.

[0003] The prior art can realize the function of stopping the elevator when overspeeding, but there are still defects. For example, the patent document with publication number CN106966253A, entitled "An Elevator Emergency Braking System", proposes the use of bidirectional safety clamps, speed limiters, rope clamps and other components. The speed limiter triggers the rope clamp so that the speed limiter rope drives the safety clamp to operate and perform emergency braking on the elevator. However, bidirectional speed limiters are rarely installed on domestic elevators at present, and are not applicable to the realization of the emergency braking function of elevators in use. In addition, the cost of bidirectional safety clamps is higher than that of unidirectional safety clamps. This solution has certain shortcomings.

[0004] Another example is the patent document with publication number CN114057056A, entitled Elevator Overspeed Protection Device, which proposes to remove the traditional speed limiter-safety clamp linkage mechanism and adopt a speed detection mechanism and an electromagnetic safety clamp mode. When the elevator is overspeeding, the electromagnetic safety clamp is mechanically triggered, and the clamp acts on the elevator guide rail, causing the elevator to brake urgently. However, due to the characteristics of the electromagnetic safety clamp, when the power is suddenly lost, the clamp immediately acts on the elevator guide rail, generating a very large impact force on the guide rail, which is easy to damage the guide rail. At the same time, if the mechanical triggering of the electromagnetic safety clamp fails, it will cause harm to the passengers in the car, and a major accident will occur.

[0005] Therefore, there is an urgent need for a new low-cost elevator car emergency braking system with multiple trigger braking mechanisms and a control method thereof to improve the safety performance of the elevator. Summary of the invention

[0006] To solve the above problems, the present application provides an elevator car emergency braking system and a control method thereof. By adding a jacking device at the bottom of the clamp block, when the traditional speed limiting safety clamp linkage mechanism fails, the present application can use the jacking device to move the safety clamp upward to clamp the guide rail, thereby forming a multi-level coordination mechanism to ensure reliable braking of the elevator and improve the safety of passengers.

[0007] The technical solution adopted in this application is: The present application provides an elevator car emergency braking system, including a safety gear, the clamping blocks on both sides of which are used to clamp the guide rail to brake the elevator car. Lifting devices are provided at the bottoms of the clamping blocks on both sides. The lifting device includes a lifting oil cylinder and a piston rod built in the oil cylinder. The lifting oil cylinder is fixed to the safety gear base, and the piston rod is connected to the bottom of the clamping block; The system further includes a controller, which is used to receive the overspeed signal of the speed limiter; control the pressure output of the lifting oil cylinder according to the overspeed signal to generate a lifting force on the piston rod and lift the bottom of the clamping block.

[0008] Further, it includes a speed limiter, which includes an acceleration sensor for detecting the real-time speed of the car running. When the acceleration sensor detects that the elevator speed exceeds the first threshold, the controller outputs to the lifting oil cylinder to generate a lifting force on the piston rod and lift the bottom of the clamping block, control the output of the lifting oil cylinder to generate a lifting force on the piston rod and lift the bottom of the clamping block.

[0009] When the speed limiter detects that the car speed exceeds its mechanical action speed, it will cooperate with the safety gear for mechanical braking. When the mechanical braking fails, the present application starts the lifting device when the car speed exceeds the first threshold to form a double protection barrier, reduce the risk of completely relying on a single braking system, and reduce the risks of high-speed overshoot and falling.

[0010] Further, a single lifting device further includes an oil pump motor, a high-pressure oil pump, a throttle valve, a solenoid valve and a hydraulic oil tank connected in sequence. The lifting oil cylinder is installed between the high-pressure oil pump and the throttle valve, and the structures of the two lifting devices on both sides are the same; The controller is connected to a driving chip, and the driving chip is connected to the oil pump motor. The controller is used to output a driving signal to the driving chip, and the driving chip outputs current and starts the oil pump motor. The oil pump motor inputs hydraulic oil into the lifting oil cylinder, and the piston rod lifts the safety gear clamping block upward; the solenoid valve is also connected to the controller. When the elevator resumes operation, it is necessary to release the lifting device. The controller outputs a release signal, the solenoid valve is activated, and the pressure chamber of the lifting oil cylinder slowly discharges hydraulic oil to the hydraulic oil tank through the throttle valve.

[0011] Further, the ratio of the inner hole diameter d to the outer diameter D of the piston rod satisfies 0.3 ≤ d / D ≤ 0.6.

[0012] Further, when the acceleration sensor detects that the elevator speed exceeds the second threshold, the lifting force maintained by the lifting oil cylinder driving the piston rod is always 90%-95% of the minimum pressure for the clamping block to start moving. To avoid misoperation and ensure quick response, once the car speed exceeds the second threshold, the piston can complete the preparation work before lifting and increase the lifting force to the critical value for the clamping block to move. Once the mechanical braking of the speed limiter fails and the car speed further increases, that is, when it reaches the first threshold, the piston can quickly lift.

[0013] Further, the first threshold is 105% of the mechanical action speed of the speed limiter, and the second threshold is 95% of the mechanical action speed of the speed limiter.

[0014] The present application also provides a control method for an elevator car emergency braking system, including the following steps: Step S1: When the acceleration sensor detects that the elevator speed exceeds the second threshold, the controller pre-charges the jacking device so that the jacking force maintained by the jacking oil cylinder driving the piston rod is lower than the minimum pressure at which the clamping block starts to move; Step S2: When the acceleration sensor detects that the car speed further increases, that is, reaches the first threshold, control the piston rod to jack up the safety clamp clamping block upward; Step S3: After the elevator fault is eliminated, the controller sends a release signal to the solenoid valve, the solenoid valve opens, and the pressurized chamber of the jacking oil cylinder slowly releases pressure to the oil tank through the throttle valve.

[0015] Further, to avoid overloading and failure of the guide rail and out-of-control tilting of the car, and to extend the service life of the safety clamp, the jacking forces of the bilateral jacking devices are monitored and adjusted; it also includes a plurality of fiber optic strain sensors, which are arranged inside the piston rods of the bilateral jacking devices and are connected to the controller for measuring the stress of the piston rods. The structures and materials of the two piston rods are the same; After the piston rod jacks up the safety clamp clamping block upward, the fiber optic strain sensor outputs the collected stress value σ to the controller in real time. The controller calculates the actual jacking force through the formula F = σ * A, where A is the cross-sectional area of the piston rod. The controller calculates the bilateral jacking forces in real time and calculates the jacking force deviation ΔF = ∣ - ∣. When the jacking force deviation ΔF exceeds the preset value, start the asymmetric pressure compensation to increase the pressure ΔP of the low-pressure side oil cylinder, so that the error converges to the set threshold. The calculation formula of ΔP is ΔP = ΔF \, where is the effective action area of the oil cylinder.

[0016] Advantages of the present application: The present application adds a jacking device on the basis of the traditional safety clamp. When the mechanical trigger braking of the traditional safety clamp fails, the jacking device can make the safety clamp move upward to clamp the guide rail, avoiding the occurrence of accidents. Description of the Drawings

[0017] Figure 1 It is a diagram of the action of the existing traditional safety clamp on the guide rail.

[0018] In the figure, 1 is the upper plate, 2 is the clamp body, 3 is the clamping block, 4 is the lower plate, and 5 is the guide plate.

[0019] Figure 2 It is a schematic structural diagram of the jacking device of the present application.

[0020] Figure 3 Schematic diagram of the electrical structure of the present application.

[0021] Figure 4 Schematic diagram of the specific structure of the jacking oil cylinder and piston rod of the present application; In the figure, 6 is the jacking oil cylinder, 61 is the cylinder block, 62 is the end cover, 63 is the sealing ring, 64 is the oil inlet, 65 is the oil outlet, and 7 is the piston rod.

[0022] Figure 5 Flowchart of the control method for an emergency braking system of an elevator car of the present application. Detailed implementation manners

[0023] To make the objectives, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be clearly and completely described below in conjunction with the accompanying drawings and a preferred implementation manner.

[0024] The safety tongs of the prior art, for example, an explosion-proof safety tong for intelligent elevators with the publication text CN211733509U, refer to Figure 1 , including an upper plate 1 and a lower plate 4, a tong body 2 fixed between the upper plate 1 and the lower plate 4, tong blocks 3 and a guide plate 5. When the elevator is operating normally, the safety tongs move up and down along the guide rail and maintain a working distance of 3 mm. The tong blocks 3 on both sides maintain a certain distance from the two sides of the working surface of the guide rail, in a non-contact state. In the case of an emergency braking of the elevator, the tong blocks 3 of the safety tongs move upward to firmly clamp the guide rail. When the elevator descends at an excessive speed, the pull rod of the speed limiter restrains the tong blocks 3 to keep them stationary in the running direction of the elevator, and the other components of the safety tongs move downward relatively.

[0025] In the present application, a jacking device is added to the safety tongs of the above prior art, and corresponding electrical design and related software design are carried out. The speed limiter of the prior art detects the speed of the elevator car. Once it is overspeed, it will be mechanically triggered, and the speed limiter will act. There is a centrifugal force sensing system and a mechanical trigger linkage device inside the speed limiter. The centrifugal force sensing system is used to calculate the speed of the car. When the speed of the car exceeds the set threshold, generally the mechanical action speed value of the speed limiter, the mechanical trigger linkage device is passively triggered to lift by locking the steel wire rope. The steel wire rope is connected to the speed limiter and the safety tongs. The action of the speed limiter will drive the movement of the steel wire rope, and then pull the lifting component of the safety tongs. After the lifting mechanism of the safety tongs is pulled, the tong blocks of the safety tongs will firmly clamp the elevator guide rail. In the present application, after the mechanical trigger fails, the safety tongs can still clamp the elevator guide rail through the jacking device.

[0026] The jacking device of the present application is arranged at the bottom of the tong blocks on both sides. The jacking device includes a jacking oil cylinder 6 and a piston rod 77 disposed inside the oil cylinder. The jacking oil cylinder 6 is fixed to the safety tong base, and the piston rod 7 is connected to the bottom of the tong block; Specifically, the piston rod 7 is made of titanium alloy or high-strength alloy steel, with an outer diameter of 50 - 200 mm and an inner diameter of 20 - 80 mm.

[0027] The base of the safety tongs in this application is the support and fixation structure of the tong body, that is, the lower plate of the above-mentioned published text CN211733509U. The base of the safety tongs can be separated from the safety tongs individually or integrally formed. The jacking oil cylinder 6 and the piston rod 7 in this application are installed on the side or below the base of the safety tongs through flanges, maintaining a safety distance of ≥10 mm from the mechanical lifting mechanism of the speed limiter to avoid movement interference.

[0028] In some other embodiments, a traditional speed limiter is used to trigger the safety tongs to brake when detecting that the car speed exceeds a preset threshold; the specific model of the speed limiter used in this application is XS18B, its rated speed is 2.5 m / s, the mechanical action speed is 3.13 m / s, and the electrical action speeds for both upward and downward travel are 2.96 m / s. The upward electrical action speed, downward electrical action speed, and mechanical action speed of the speed limiter can all be determined through the speed limiter nameplate, and each parameter is marked on the nameplate. This application also includes an acceleration sensor and a controller connected to each other. The acceleration sensor is used to detect the real-time speed of the car running, avoiding relying solely on the mechanical speed signal of the speed limiter and improving the overall safety of the system. When the speed limiter detects that the car speed exceeds the mechanical action speed value, it triggers mechanical braking to make the safety tongs clamp the guide rail. When the mechanical braking of the speed limiter fails and the car is still in an out-of-control state, such as accelerating downward or upward, the acceleration sensor in this application, in combination with the existing preset program, detects that the car speed exceeds the first threshold, and the controller controls the output of the jacking oil cylinder 6 to generate a jacking force on the bottom of the piston rod 7. When setting the first threshold, the first threshold should be greater than the mechanical action speed value of the speed limiter.

[0029] Preferably, the setting of the mechanical action speed of the speed limiter needs to meet the requirements stipulated by the technical specifications. a) It should be at least equal to 115% of the rated speed, but should be less than the following values: 1) For instantaneous safety tongs other than non-detachable roller type, it is 0.8 m / s; 2) For non-detachable roller type instantaneous safety tongs, it is 1.00 m / s; 3) For progressive safety tongs with a rated speed less than or equal to 1.00 m / s, it is 1.50 m / s; 4) For progressive safety tongs with a rated speed greater than 1.00 m / s, it is 1.25v + 0.25 / v, with the unit of meters per second.

[0030] And for elevators with a rated speed greater than 1.00 m / s, it is recommended to select a value as close as possible to the operating speed specified in 4). For low-speed elevators, it is recommended to select a value as close as possible to the lower limit of the operating speed specified in a).

[0031] This application activates the jacking device when the mechanical brake of the speed limiter fails, forming a double protection barrier on the basis of the mechanical brake of the speed limiter, reducing the risk of complete dependence on a single braking system and reducing the risks of high-speed overshoot and falling.

[0032] Reference Figure 2 , a single jacking device also includes an oil pump motor, a high-pressure oil pump, a check valve, a throttle valve, a solenoid valve, and a hydraulic oil tank connected in sequence. The jacking cylinder 6 is installed between the check valve and the throttle valve. The check valve prevents reverse flow. In addition, a safety valve is connected between the high-pressure oil pump and the check valve. The safety valve performs overpressure protection to avoid danger caused by too high cylinder pressure. The structures of the jacking devices on both sides are the same. Specifically, the oil pump motor, the high-pressure oil pump, the throttle valve, the solenoid valve, and the hydraulic oil tank are installed at the bottom of the hoistway or on the side wall of the pit. The oil pump motor, the high-pressure oil pump, the throttle valve, the solenoid valve, and the hydraulic oil tank are connected by oil pipes. The oil pipes are fixed on the hoistway wall. The controller is installed in the control box on the car top.

[0033] Reference Figure 3 , the controller of this application uses the Arduino Nano microcontroller U2, with the specific model being Arduino Nano 33 BLE Rev2. The drive chip uses the L298N drive chip. The two solenoid valves are also connected to the single-chip microcomputer L9110. The Arduino Nano microcontroller U2 is built-in with a 3-axis accelerometer and a 3-axis gyroscope. By using the existing preset program in the user manual, it can collect the instantaneous speed of the elevator without the need to additionally set an acceleration sensor. The microcontroller U2 is also connected to a display module and a voice prompt module. Specifically, the display module uses OLED1 to output overspeed information. The display module can be placed inside the elevator to remind passengers to take braking measures when necessary. The voice prompt module uses a 3W 4Ω speaker to remind passengers that the elevator is overspeed and to take emergency measures when necessary. The system of this application also includes an emergency button. The emergency button is set in the area where the car can be touched by people. The emergency button is connected to the D0 interrupt port of the single-chip microcomputer. When triggered, it performs the same functions as above. The emergency button is manually controlled. Traditionally, it is all about passive safety for passengers. Through this application, active safety for passengers can be achieved.

[0034] The controller of the present application is connected to the drive chip, and the drive chip is connected to the oil pump motor. When the controller detects that the car speed exceeds the mechanical action speed of the speed limiter, the controller sends a drive signal to the drive chip. The drive signal includes a PWM (pulse width modulation) signal generated by the controller, which is used to control the rotation speed of the oil pump motor. By adjusting the duty cycle (PWM) or the voltage amplitude, the rotation speed of the oil pump motor is controlled, and thus the output flow rate (Q) and pressure (P) of the high-pressure oil pump are adjusted. Specifically, according to the formula P = / , where P is the output pressure of the hydraulic oil (MPa), is the jacking force (N), is the effective area of the piston of the jacking cylinder , There is a linear relationship between the motor speed and the output flow rate of the oil pump, and there is a linear relationship between the drive signal and the motor speed. The method for adjusting the output pressure of the hydraulic oil in the present application by the drive signal is: changing the motor speed through the drive signal, directly affecting the output flow rate of the oil pump, and then adjusting the output pressure of the hydraulic oil.

[0035] In this embodiment, the piston diameter is 50 mm, the piston area is π times the square of the piston radius, which is 0.00196 square meters. The safety clamp blocks applicable to the elevator in the present application are progressive safety clamp blocks. The length of the surface in contact with the piston is 150 mm, and the width is 80 mm. The safety clamp blocks are located on the jacking path of the piston. The initial gap between the piston and the safety clamp blocks is 3 ± 0.5 mm. The design of the gap needs to ensure that the piston can quickly jack up the clamp blocks and avoid mis-triggering caused by vibration or thermal expansion.

[0036] The comparison table of the output pressure of the hydraulic oil and the jacking force in this embodiment is shown in the following table: Output pressure P (MPa) of hydraulic oil Lifting force (N) Duty ratio of drive signal (%) Rotational speed of oil pump motor (rpm) 5 9800 30% 540 10 19600 60% 1080 15 29400 90% 1620 20 39200 100% 1800 Specifically, when the output pressure P of the hydraulic oil is 5 MPa, the jacking force = 5 × 0.00196 = 9800 N, and so on........

[0037] Workflow of this application: When the elevator speed exceeds the set value of the system, the controller outputs drive signals to the L298N drive chip through pins D1 and D2. The L298N drive chip outputs current through pins OUT1 and OUT2, and starts the oil pump units U1 and U2 to work. The oil pump motor inputs hydraulic oil into the jacking cylinder 6, and the piston rod 7 jacks up the safety clamp block upward until the elevator stops running; alternatively, this application can be manually controlled. By pressing the emergency button, the piston rod 7 can be jacked up to move the safety clamp block upward; when the elevator of this application resumes operation, the jacking device needs to be released, which can be manually operated. Then, the controller outputs release signals through pins D9 and D10. After receiving the control signal, L9110 starts the solenoid valve through OA1 and OB1. The pressurized chamber of the jacking cylinder 6 slowly discharges hydraulic oil to the hydraulic oil tank through the throttle valve.

[0038] Reference Figure 4 , the piston rod 7 of this application is built into the jacking cylinder 6. The jacking cylinder 6 includes a cylinder block 61, an end cover 62, a sealing ring 63, an oil inlet 64, and an oil outlet 65. The inside of the cylinder block accommodates the piston rod 7 and hydraulic oil. There are multiple sealing rings 63 between the end cover 62 and the piston rod 7, and between the cylinder block 61 and the piston rod 7 to ensure the airtightness of the piston rod 7. The oil inlet 64 and the oil outlet 65 are arranged on both sides of the bottom of the cylinder block. The hydraulic oil enters from the oil inlet 64 and exits from the oil outlet 65; those skilled in the art can add a friction device between the piston end face and the bottom of the clamp block to increase the friction.

[0039] In some other embodiments, the ratio of the inner hole diameter d to the outer diameter D of the piston rod 7 satisfies 0.3 ≤ d / D ≤ 0.6.

[0040] d / D ratio Flexural rigidity (GN·m²) Mass (kg / m) Critical buckling load (kN) Strain monitoring sensitivity (με / pm) 0.2 1.05 12.3 185 1.2 0.4 0.92 9.8 162 1.5 0.6 0.75 7.2 130 2.1 According to the above table, when 0.3 ≤ d / D ≤ 0.6, the piston rod 7 is within an acceptable range of the decrease in bending stiffness, can achieve mass reduction, and the strain sensitivity is improved.

[0041] In some other embodiments, when the acceleration sensor detects that the elevator car speed exceeds the second threshold, the jacking force maintained by the jacking cylinder 6 driving the piston rod 7 is always 90% - 95% of the minimum pressure at which the clamp block starts to move. To avoid misoperation and ensure quick response, once the car speed further increases on the basis of the mechanical action speed of the speed limiter, that is, when it reaches the first threshold, then the controller can quickly make the piston rod 7 push the clamp block to clamp the guide rail. In this embodiment, the first threshold is set to 105% of the mechanical action speed of the speed limiter, that is, 3.2865 m / s, and the second threshold is specifically set to 95% of the mechanical action speed of the speed limiter, that is, 2.9735 m / s.

[0042] Reference Figure 5The present application also provides a control method for an elevator car emergency braking system, which specifically includes the following steps: Step S1: When the acceleration sensor detects that the elevator speed exceeds the second threshold, the controller pre-charges the lifting device, starts the oil pump motor, and pumps the hydraulic oil from the oil tank into the lifting cylinder 6, so that the lifting force maintained by the lifting cylinder 6 driving the piston rod 7 is lower than 90% of the minimum pressure for the clamp block to start moving; Step S2: When the acceleration sensor detects that the car speed further increases on the basis of the mechanical action speed of the speed limiter, that is, when it reaches the first threshold, the controller controls the piston rod 7 to lift the safety clamp block 3 to move upward; Step S3: After the elevator fault is eliminated, the controller sends a release signal to the solenoid valve, the solenoid valve opens, and the pressure chamber of the lifting cylinder 6 slowly releases pressure to the oil tank through the shut-off valve.

[0043] In actual application, the setting values of the mechanical action speed of the speed limiter when going up and when going down may be different. Therefore, the first threshold value can be set to 105% of the mechanical action speed of the speed limiter, and the setting of the second threshold value is different when the elevator goes up and down. When going up, the second threshold value is the electrical action speed of the speed limiter when going down, and when going down, the second threshold value is the electrical action speed of the speed limiter when going down. For the XS18B speed limiter in this embodiment, the electrical action speeds of both going up and going down are 2.96m / s.

[0044] Specifically, in step S1, the controller can be set to synchronously receive the mechanical speed signal of the speed limiter and the electronic speed signal of the acceleration sensor, and perform real-time comparison. If the error is higher than the preset value, an alarm signal is output to avoid relying on a single mechanical speed signal. When an error occurs, relevant staff can be promptly reminded to conduct investigation and repair.

[0045] In some other embodiments, in order to avoid guide rail overload failure and uncontrolled tilting of the car and to extend the life of the safety clamp, the lifting force of the double-sided lifting device is monitored and adjusted; it also includes a plurality of optical fiber strain sensors, which are arranged in the piston rods 7 of the lifting devices on both sides and connected to the controller to measure the stress of the piston rods 7, and the two piston rods 7 have the same structure and material; After the piston rod 7 lifts the safety clamp block upward, the optical fiber strain sensor outputs the collected stress value σ to the controller in real time. The controller calculates the actual lifting force through the formula F=σ*A, where A is the cross-sectional area of the piston rod 7. The controller calculates the lifting force on both sides in real time and calculates the lifting force deviation ΔF=| - |, when the jacking force deviation ΔF exceeds the preset value, start the asymmetric pressure compensation to increase the pressure ΔP of the cylinder on the low-pressure side, so that the error converges to the set threshold. Among them, the calculation formula of ΔP is ΔP = ΔF , is the effective acting area of the cylinder.

[0046] In practical applications, the above ΔF and ΔP can be gradually adjusted according to the actual situation and the formula can be optimized to make the result accurate.

[0047] The above are only the preferred embodiments of the present application. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present application, several improvements and refinements can be made, and these improvements and refinements are also within the protection scope of the present application.

Claims

1. An elevator car emergency braking system, including a safety clamp, the clamping blocks (3) on both sides of which are used to clamp the guide rail to brake the elevator car, characterized in that, Lifting devices are provided at the bottoms of both clamping blocks (3). The lifting device includes a lifting oil cylinder (6) and a piston rod (7) disposed inside the oil cylinder. The lifting oil cylinder (6) is fixed to the safety clamp base, and the piston rod (7) is connected to the bottom of the clamping block (3). The system further includes a controller configured to receive an overspeed signal from the speed limiter; control the pressure output of the lifting oil cylinder (6) according to the overspeed signal to generate a lifting force on the piston rod (7) to lift the bottom of the clamping block (3).

2. The emergency braking system for an elevator car according to claim 1, wherein It includes an acceleration sensor for detecting the real-time speed of the car. When the acceleration sensor detects that the elevator speed exceeds the first threshold, the controller outputs to the lifting oil cylinder (6) to generate a lifting force on the piston rod (7) to lift the bottom of the clamping block (3), and controls the output of the lifting oil cylinder (6) to generate a lifting force on the piston rod (7) to lift the bottom of the clamping block (3).

3. An emergency braking system for an elevator car according to claim 2, wherein, A single lifting device further includes an oil pump motor, a high-pressure oil pump, a throttle valve, a solenoid valve, and a hydraulic oil tank connected in sequence. The lifting oil cylinder (6) is installed between the high-pressure oil pump and the throttle valve. The structures of the two lifting devices are the same; The controller is connected to a driving chip, and the driving chip is connected to the oil pump motor. The controller is configured to output a driving signal to the driving chip, and the driving chip outputs current to start the oil pump motor. The oil pump motor inputs hydraulic oil into the lifting oil cylinder, and the piston rod lifts the safety clamp block (3) upward; the solenoid valve is also connected to the controller. When the elevator resumes operation, the lifting device needs to be released. The controller outputs a release signal, the solenoid valve is activated, and the pressure chamber of the lifting oil cylinder (6) slowly discharges hydraulic oil to the hydraulic oil tank through the throttle valve.

4. An emergency braking system for an elevator car according to claim 1, characterized in that, The ratio of the inner hole diameter d to the outer diameter D of the piston rod (7) satisfies 0.3 ≤ d / D ≤ 0.

6.

5. The emergency braking system for an elevator car according to claim 2, characterized in that, When the acceleration sensor detects that the elevator speed exceeds the second threshold, the lifting force maintained by the lifting oil cylinder (6) driving the piston rod (7) is 90% - 95% of the minimum pressure at which the clamping block (3) starts to move.

6. The emergency braking system for an elevator car according to claim 5, characterized in that, The first threshold is 105% of the mechanical action speed of the speed limiter, and the second threshold is 95% of the mechanical action speed of the speed limiter.

7. A control method for an emergency braking system of an elevator car according to claim 1, characterized in that, It includes the following steps: Step S1: When the acceleration sensor detects that the elevator speed exceeds the second threshold, the controller pre-charges the lifting device so that the lifting force maintained by the lifting oil cylinder (3) driving the piston rod is lower than the minimum pressure at which the clamping block (3) starts to move; Step S2: When the acceleration sensor detects that the car speed further increases, i.e., reaches the first threshold, control the piston rod (7) to lift the safety clamp block (3) upward; Step S3: After the elevator fault is eliminated, the controller sends a release signal to the solenoid valve, the solenoid valve opens, and the pressure chamber of the lifting oil cylinder (6) slowly releases pressure to the oil tank through the throttle valve.

8. A control method for an emergency braking system of an elevator car according to claim 7, characterized in that, It further includes a plurality of fiber optic strain sensors. The plurality of fiber optic strain sensors are disposed inside the piston rods (7) of the two lifting devices and are connected to the controller for measuring the stress of the piston rods (7). The structures and materials of the two piston rods (7) are the same; After the piston rod (7) jacks up the safety clamp block (3) and moves upward, the fiber optic strain sensor outputs the collected stress value σ to the controller in real time. The controller calculates the actual jacking force through the formula F = σ * A, where A is the cross-sectional area of the piston rod. The controller calculates the bilateral jacking force in real time and calculates the jacking force deviation ΔF = ∣ - ∣. When the jacking force deviation ΔF exceeds the preset value, asymmetric pressure compensation is started to increase the pressure ΔP of the low-pressure side cylinder. The calculation formula of ΔP is ΔP = ΔF\ ; where is the effective action area of the cylinder, so that the error converges to the set threshold value.

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