A current overload protection method for electric jack circuit board

Abstract

The application discloses a current overload protection method for an electric jack circuit board, and the protection method comprises the following steps: S1, magnetic induction detection; S2, dynamic parameter calculation; S3, multi-stage overload response; and S4, self-recovery control. The four steps of magnetic induction detection, dynamic parameter calculation, multi-stage overload response and self-recovery control are cooperatively operated, the gap magnetic field detection technology of a radial magnetic pin and a Hall device is adopted, and the adjustable mounting seat is combined to realize 0.5-1.2 mm gap precision adjustment. The current overload protection is realized through a three-stage triggering mechanism: the first-stage response adopts a weak magnetic field of an inner layer winding of an electromagnetic coil to drive a bimetallic strip slow-break contact, the second-stage response realizes 0.1 second rapid power-off through a strong magnetic field of an outer layer winding, and the third-stage response is triggered by temperature to automatically cut off the bimetallic strip. The disturbance is eliminated by cooperating with a permalloy magnetic shielding cover, the deformation precision is improved by the arc-shaped compensation groove of the bimetallic strip, and the heat dissipation is enhanced by combining the 2oz copper thick copper-clad plate with the aluminum fin array, so that the response speed of the current overload protection of the circuit board is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of circuit board, in particular to a current overload protection method for electric jack circuit board. BACKGROUND

[0002] As the core power unit of mechanical jacking equipment, the electric jack is mainly composed of a DC motor, a planetary gear box, a trapezoidal screw rod and a bearing nut. Its working principle is that the motor drives the gear shaft to rotate, which drives the screw rod to move linearly to realize the lifting of heavy objects. Compared with the traditional hydraulic jack, the electric type product has the advantages of convenient operation and controllable lifting speed, and is widely used in the fields of automobile maintenance and engineering machinery positioning.

[0003] At present, Chinese patent application No. CN201120277830.0 discloses a current overload recoverable electromagnetic speed regulating motor control device, which comprises a shell and a circuit board arranged in the shell. A control panel is arranged on the surface of the shell, and a current overload recoverable device is arranged on the circuit board.

[0004] However, the existing electric jack circuit board control system has the following technical bottlenecks: the traditional scheme relies on a mechanical circuit breaker. When the motor is blocked or short-circuited, the bimetallic strip needs to absorb enough heat to deform and trip. The response time is slow, which causes the circuit board components to continuously bear overcurrent during overcurrent, resulting in problems such as PCB copper foil melting or MOSFET breakdown. SUMMARY

[0005] The present application aims to provide a current overload protection method for electric jack circuit board to solve the problems raised in the background art.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme: a current overload protection method for electric jack circuit board, comprising the following steps:

[0007] S1, magnetic induction detection: a radial magnetic pin rotating with the shaft is installed at the end of the motor gear shaft of the electric jack. A periodic magnetic field change is generated through the 0.5-1.2mm gap formed by the radial magnetic pin and the Hall device on the circuit board, and the number of motor rotation is collected in real time;

[0008] S2, dynamic parameter calculation: the control module on the circuit board receives the Hall signal and temperature sensor data, and combines the preset electric jack screw pitch parameters to calculate the current position of the nut and the current load strength;

[0009] S3, multi-stage overload response: an electronic circuit breaker is integrated on the circuit board, and the electronic circuit breaker is linked with the current sensor, continuously collecting the working current of the circuit board, when the current exceeds the threshold value, the electromagnetic coil on the circuit board drives the bimetallic strip to deform and cut off the main circuit of the circuit board according to the preset logic;

[0010] S4, self-recovery control: after the bimetallic strip cools down, the contact of the bimetallic strip is reset by the reset spring, and the system returns to the standby state;

[0011] The gear shaft end is provided with an adjustable mounting seat, and radial magnetic pins are located on both sides of the adjustable mounting seat, the distance from the gear shaft end to the Hall device is adjusted by changing the screwing depth of the adjustable mounting seat; the Hall device is wrapped with a permalloy magnetic shield cover with an opening angle of 120-150 degrees to shield the non-axial magnetic field interference; the electromagnetic coil adopts a double-layer winding structure.

[0012] Preferably, in the S3 step, the electromagnetic coil on the circuit board drives the bimetallic strip to deform and cut off the main circuit of the circuit board according to the preset logic, which has a three-stage triggering mechanism and is executed in the following manner:

[0013] (1) First response: when the current exceeds 120% of the rated value for 3-5 seconds, the inner winding of the electromagnetic coil is energized to generate a weak magnetic field, causing the bimetallic strip to bend slowly and disconnect the contact;

[0014] (2) Second response: when the current instantaneously exceeds 200% of the rated value, the outer winding of the electromagnetic coil and the bimetallic strip jointly act to complete the contact separation within 0.1 seconds;

[0015] (3) Third response: when the temperature sensor detects that the temperature of the circuit board exceeds the limit, the bimetallic strip deforms to cut off the circuit.

[0016] Preferably, the temperature sensor detects the temperature of the circuit board, and the upper limit of the temperature is set to 60 degrees.

[0017] Preferably, the bimetallic strip surface is provided with an arc-shaped compensation groove with a curvature radius of 8-12 mm to compensate for the deformation deviation caused by thermal stress, and the contact separation response time is ≤0.5 seconds.

[0018] Preferably, in the S2 step, the travel control of the nut is realized in the following manner:

[0019] The touch display screen connected to one side of the circuit board receives the user input lifting distance, and the microprocessor on the circuit board converts it into the theoretical number of rotation turns according to the screw pitch; the Hall device detects the actual number of rotation turns in real time, and the motor speed is dynamically adjusted through the PWM drive circuit.

[0020] Preferably, the inner winding of the electromagnetic coil is wound with 0.5mm enameled wire for 30-35 turns, and is covered with a high-temperature-resistant insulating layer, and the outer winding of the electromagnetic coil is wound with 0.3mm enameled wire for 45-50 turns, and the turns are filled with heat-conducting silica gel.

[0021] Preferably, the temperature sensor detects that the circuit board environment temperature increases by 1 degree, the control module reduces the current threshold by 0.5A, and the real-time temperature of the temperature sensor is fed back to the PWM drive circuit, and the output frequency is adjusted by 5%-10% gradient.

[0022] Preferably, the substrate layer of the circuit board adopts a 2oz copper thick copper-clad plate, and an aluminum fin array with a spacing of 1.2-1.8mm is arranged on the surface of the circuit board, and a flow guide groove with an inclination angle of 15-25 degrees is arranged between adjacent fins.

[0023] Preferably, the reset spring is a conical spiral spring with a wire diameter of 0.8-1.2mm and a free height of 12-15mm.

[0024] Preferably, the circuit board is installed in a waterproof shell, the waterproof shell is mounted on the top of the electric jack shell by bolts, and a rubber sealing ring is arranged between the waterproof shell and the electric jack shell.

[0025] Preferably, the bimetallic strip is made of a nickel-iron alloy sheet with a thickness of 0.15-0.25mm.

[0026] Compared with the prior art, the beneficial effects of the present application are:

[0027] The present application realizes a three-stage response trigger mechanism for current overload protection through the design of double-layer winding of the electromagnetic coil. The first-stage response adopts the weak magnetic field of the inner winding of the electromagnetic coil to drive the bimetallic strip to slowly break the contact, the second-stage response realizes 0.1 second fast power-off through the strong magnetic field of the outer winding, and the third-stage response is triggered by the temperature to automatically cut off by the bimetallic strip, which improves the response speed compared with the traditional mechanical circuit breaker.

[0028] The present application adopts the gap magnetic field detection technology of the radial magnetic pin and the Hall device, and realizes the precise adjustment of the gap of 0.5-1.2mm by combining with the adjustable mounting seat.

[0029] The present application reduces the current threshold by 0.5A when the temperature increases by 1 degree, and combines with the PWM frequency gradient adjustment to avoid the heat accumulation effect, and the Hall device is wrapped with a permalloy magnetic shielding cover with an opening angle of 120-150 degrees to shield the non-axial magnetic field interference. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The flow chart of the current overload protection method of the present application;

[0031] Figure 2 This is a schematic diagram of the connection between the gear shaft and the radial magnetic pin of the present invention;

[0032] Figure 3 This is a bottom view of the circuit board of the present invention after it has been installed inside a waterproof housing;

[0033] Figure 4 This is a system structure connection diagram of the present invention.

[0034] In the diagram: Gear shaft-1, Radial magnetic pin-2, Circuit board-3, Hall effect device-4, Control module-5, Electronic circuit breaker-6, Current sensor-7, Electromagnetic coil-8, Bimetallic strip-9, Return spring-10, Touch screen-11, Microprocessor-12, PWM drive circuit-13, Temperature sensor-14, Waterproof housing-a. Detailed Implementation

[0035] To further explain the technical solution of the present invention, a detailed description is provided below through specific embodiments.

[0036] Please see Figures 1-4 This invention provides a current overload protection method for a circuit board of an electric jack, comprising the following steps:

[0037] S1. Magnetic induction detection: A radial magnetic pin 2 that rotates with the shaft is installed at the end of the motor gear shaft 1 of the electric jack. The 0.5-1.2mm gap between the radial magnetic pin 2 and the Hall device 4 on the circuit board 3 generates a periodic magnetic field change, and the number of motor rotations is collected in real time.

[0038] S2. Dynamic parameter calculation: The control module 5 on the circuit board 3 receives the Hall signal from the Hall device 4 and the data from the temperature sensor 14, and calculates the current position of the nut and the current load intensity by combining the preset electric jack screw pitch parameters.

[0039] S3, Multi-level overload response: An electronic circuit breaker 6 is integrated on the circuit board 3, and the electronic circuit breaker 6 is linked with the current sensor 7 to continuously collect the operating current of the circuit board 3. When the current exceeds the threshold, the electromagnetic coil 8 on the circuit board 3 drives the bimetallic strip 9 to deform and cut off the main circuit of the circuit board 3 according to the preset logic.

[0040] S4. Self-recovery control: After the bimetallic strip 9 cools down, the contacts of the bimetallic strip 9 are reset by the reset spring 10, and the system returns to standby state.

[0041] The gear shaft 1 has an adjustable mounting base at its end, and radial magnetic pins 2 are located on both sides of the adjustable mounting base. The distance between the adjustable mounting base and the Hall device 4 is adjusted by changing the screw depth of the adjustable mounting base at the end of the gear shaft 1. The Hall device 4 is surrounded by a permalloy magnetic shield with an opening angle of 120-150 degrees to shield non-axial magnetic field interference. The electromagnetic coil 8 adopts a double-layer winding structure, and the reset spring 10 is a conical helical spring with a wire diameter of 0.8-1.2mm and a free height of 12-15mm. The bimetallic strip 9 is made of nickel-iron alloy with a thickness of 0.15-0.25mm, and the surface of the bimetallic strip 9 is provided with an arc-shaped compensation groove with a curvature radius of 8-12mm to compensate for deformation deviation caused by thermal stress. Its contact separation response time is ≤0.5 seconds.

[0042] In step S3, the electromagnetic coil 8 on circuit board 3 drives the bimetallic strip 9 to deform and cut off the main circuit of circuit board 3 according to the preset logic. This has a three-level triggering mechanism and is executed in the following manner:

[0043] (1) Level 1 response: When the current on the circuit board 3 exceeds 120% of the rated value for 3-5 seconds, the inner winding of the electromagnetic coil 8 is energized to generate a weak magnetic field, causing the bimetallic strip 9 to slowly bend and disconnect the contact.

[0044] (2) Secondary response: When the current on the circuit board 3 instantaneously exceeds 200% of the rated value, the outer winding of the electromagnetic coil 8 and the bimetallic strip 9 work together to complete the contact separation within 0.1 seconds;

[0045] (3) Three-level response: When the temperature sensor 14 detects that the temperature of the circuit board 3 exceeds the upper limit of 60 degrees, the bimetallic strip 9 autonomously deforms and cuts off the circuit.

[0046] In step S2, the stroke control of the nut is achieved in the following way:

[0047] The lifting distance input by the user is received by the touch screen 11 connected to one side of the circuit board 3, and the microprocessor 12 on the circuit board 3 converts it into the theoretical number of rotations according to the lead screw pitch; the Hall device 4 detects the actual number of rotations in real time, and dynamically adjusts the motor speed of the electric jack through the PWM drive circuit 13.

[0048] The inner winding of the electromagnetic coil 8 is made of 0.5mm enameled wire with 30-35 turns and covered with a high-temperature resistant insulation layer. The outer winding of the electromagnetic coil 8 is made of 0.3mm enameled wire with 45-50 turns and filled with thermally conductive silicone between the turns.

[0049] Specifically, for every 1 degree increase in ambient temperature of circuit board 3 detected by temperature sensor 14, control module 5 reduces current threshold by 0.5A, and the real-time temperature of temperature sensor 14 is fed back to PWM drive circuit 13 to adjust output frequency in a 5%-10% gradient.

[0050] The circuit board 3 has a 2oz thick copper-clad laminate as its substrate layer, and an array of aluminum fins with a spacing of 1.2-1.8mm is set on the surface of the circuit board 3. A guide groove with an inclination angle of 15-25 degrees is opened between adjacent fins. The circuit board 3 is installed in a waterproof housing a. The waterproof housing a is installed on the top of the electric jack housing by bolts, and a rubber sealing ring is set between the waterproof housing a and the electric jack housing.

[0051] The principle of the circuit board's overload protection method is as follows:

[0052] First, by adjusting the depth of the adjustable mounting base above the gear shaft 1 of the electric jack to change the distance (0.5-1.2mm) between the radial magnetic pin 2 and the Hall device 4, 4-6 standard pulse signals are generated per revolution. When the gear shaft 1 drives the radial magnetic pin 2 to rotate, a periodic magnetic field change is formed at the Hall device 4. The permalloy shielding cover confines the magnetic field to the 120-150° detection area, eliminating radial magnetic field interference.

[0053] Second, after receiving the Hall pulse signal from the Hall device 4, the control module 5 calculates the nut stroke based on the screw pitch parameter of the electric jack: Stroke L = Pulse number N × Screw pitch P, and the current load intensity I is calculated according to the formula:

[0054]

[0055] Where T is the motor torque, ω is the angular velocity, and K t K is the torque constant. e It is the back electromotive force constant;

[0056] Third, when the current on circuit board 3 exceeds 120% of the rated value for more than 3 seconds, the inner winding of electromagnetic coil 8 is energized to generate a magnetic field of 50-70mT, and bimetallic strip 9 bends and disconnects the contact within 20-30 seconds; when the current on circuit board 3 instantaneously exceeds 200% of the rated value, the outer winding of electromagnetic coil 8 generates a magnetic field of 120-150mT, which works together with bimetallic strip 9 to complete contact separation within 0.1 seconds; when temperature sensor 14 detects that the temperature of circuit board 3 exceeds 60 degrees, bimetallic strip 9 deforms autonomously to cut off the circuit.

[0057] Fourth, when the bimetallic strip 9 cools to a temperature below 40 degrees Celsius, the conical helical spring generates a restoring force, pushing the contacts of the bimetallic strip 9 to reset.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for overload protection of current in a circuit board for an electric jack, characterized in that: Includes the following steps: S1. Magnetic induction detection: A radial magnetic pin that rotates with the shaft is installed at the end of the motor gear shaft of the electric jack. The 0.5-1.2mm gap between the radial magnetic pin and the Hall device on the circuit board generates a periodic magnetic field change, and the number of motor rotations is collected in real time. S2. Dynamic parameter calculation: The control module on the circuit board receives Hall signals and temperature sensor data, and calculates the current position of the nut and the current load intensity by combining the preset electric jack screw pitch parameters. S3, Multi-level overload response: An electronic circuit breaker is integrated on the circuit board, and the electronic circuit breaker is linked with the current sensor to continuously collect the circuit board's operating current. When the current exceeds the threshold, the electromagnetic coil on the circuit board drives the bimetallic strip to deform and cut off the main circuit of the circuit board according to the preset logic. S4. Self-recovery control: After the bimetallic strip cools down, the contacts of the bimetallic strip are reset by the reset spring, and the system returns to standby state. An adjustable mounting base is provided at the end of the gear shaft, and radial magnetic pins are located on both sides of the adjustable mounting base. The distance between the adjustable mounting base and the Hall device is adjusted by changing the screw depth of the adjustable mounting base at the end of the gear shaft. The Hall device is surrounded by a permalloy magnetic shield with an opening angle of 120-150 degrees to shield non-axial magnetic field interference. The electromagnetic coil adopts a double-layer winding structure.

2. The current overload protection method for a circuit board of an electric jack according to claim 1, characterized in that: In step S3, the electromagnetic coil on the circuit board drives the bimetallic strip to deform and cut off the main circuit of the circuit board according to the preset logic. This has a three-level triggering mechanism and is executed in the following manner: (1) First-level response: When the current exceeds 120% of the rated value for 3-5 seconds, the inner winding of the electromagnetic coil is energized to generate a weak magnetic field, causing the bimetallic strip to slowly bend and disconnect the contact. (2) Secondary response: When the current instantaneously exceeds 200% of the rated value, the outer winding of the electromagnetic coil and the bimetallic strip work together to complete the contact separation within 0.1 seconds; (3) Three-level response: When the temperature sensor detects that the circuit board temperature exceeds the limit, the bimetallic strip deforms autonomously to cut off the circuit.

3. The current overload protection method for a circuit board of an electric jack according to claim 2, characterized in that: The temperature sensor detects the temperature of the circuit board, and the upper limit of the temperature is preset to 60 degrees.

4. The current overload protection method for a circuit board of an electric jack according to claim 1, characterized in that: The surface of the bimetallic strip is provided with an arc-shaped compensation groove with a curvature radius of 8-12mm to compensate for deformation deviation caused by thermal stress, and its contact separation response time is ≤0.5 seconds.

5. The current overload protection method for a circuit board of an electric jack according to claim 1, characterized in that: In step S2, the stroke control of the nut is achieved in the following way: The lifting distance is received by the user through a touch screen connected to one side of the circuit board, and the microprocessor on the circuit board converts it into the theoretical number of rotations based on the lead screw pitch. The Hall effect device detects the actual number of rotations in real time and dynamically adjusts the motor speed through the PWM drive circuit.

6. The current overload protection method for a circuit board of an electric jack according to claim 2, characterized in that: The inner winding of the electromagnetic coil is made of 0.5mm enameled wire with 30-35 turns and covered with a high-temperature resistant insulation layer. The outer winding of the electromagnetic coil is made of 0.3mm enameled wire with 45-50 turns and thermally conductive silicone is filled between the turns.

7. The current overload protection method for a circuit board of an electric jack according to claim 2, characterized in that: The temperature sensor detects that for every 1 degree Celsius increase in the ambient temperature of the circuit board, the control module reduces the current threshold by 0.5A, and the real-time temperature of the temperature sensor is fed back to the PWM drive circuit to adjust the output frequency in a 5%-10% gradient.

8. The current overload protection method for a circuit board of an electric jack according to claim 1, characterized in that: The circuit board has a 2oz thick copper-clad laminate as its substrate layer, and an array of aluminum fins with a spacing of 1.2-1.8mm is provided on the surface of the circuit board. A guide groove with an inclination angle of 15-25 degrees is opened between adjacent fins.

9. The current overload protection method for a circuit board of an electric jack according to claim 1, characterized in that: The return spring is a conical helical spring with a wire diameter of 0.8-1.2 mm and a free height of 12-15 mm.

10. The current overload protection method for a circuit board of an electric jack according to claim 1, characterized in that: The circuit board is installed in a waterproof housing, which is bolted to the top of the electric jack housing, and a rubber sealing ring is provided between the waterproof housing and the electric jack housing.

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