Current overload protection method for electric jack circuit board

Abstract

The invention discloses a current overload protection method for an electric jack circuit board. The protection method comprises the steps of S1, magnetic induction detection; s2, dynamic parameter calculation; s3, performing multi-stage overload response; s4, performing self-recovery control; through four-step cooperative work of magnetic induction detection, dynamic parameter calculation, multi-stage overload response and self-recovery control, a gap magnetic field detection technology of a radial magnetic pin and a Hall device is adopted, and precise adjustment of a gap of 0.5-1.2 mm is realized in combination with an adjustable mounting seat; current overload protection is realized through a three-stage trigger mechanism: in a first-stage response, a low-intensity magnetic field of an inner-layer winding of an electromagnetic coil is adopted to drive a bimetallic strip to slowly break a contact, in a second-stage response, 0.1-second quick power-off is realized through a high-intensity magnetic field of an outer-layer winding, and in a third-stage response, the bimetallic strip is triggered by temperature to be automatically cut off Interference is eliminated in cooperation with a permalloy magnetic shielding cover, deformation precision is improved through a bimetallic strip arc-shaped compensation groove, heat dissipation is enhanced through combination of a 2oz copper-thick copper-clad plate and an aluminum fin array, and the response speed of current overload protection of the circuit board is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit boards, and specifically to a method for protecting against current overload of a circuit board for an electric jack. Background Art

[0002] As the core power unit of a mechanical jacking device, an electric jack mainly consists of a DC motor, a planetary gearbox, a trapezoidal lead screw, and a load-bearing nut. Its working principle is that the motor drives the gear shaft to rotate, driving the lead screw to perform a linear motion to achieve the lifting and lowering of heavy objects. Compared with traditional hydraulic jacks, electric products have the advantages of convenient operation and controllable lifting speed, and are widely used in fields such as automobile maintenance and engineering machinery positioning.

[0003] Currently, Chinese Patent Application No.: CN201120277830.0 discloses a current-overload recoverable electromagnetic speed control motor control device, including a housing and a circuit board installed inside the housing. A control panel is provided on the surface of the housing, and a current-overload recoverable device is provided on the circuit board.

[0004] However, the circuit board control system of the existing electric jack has long faced the following technical bottlenecks: The traditional solution relies on a mechanical circuit breaker. When the motor is blocked or short-circuited, the bimetal needs to absorb enough heat to deform and trip, and the response time is slow, resulting in the circuit board components continuously bearing over-limit current during overcurrent, leading to problems such as PCB copper foil fusing or MOSFET breakdown. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for protecting against current overload of a circuit board for an electric jack to solve the problems raised in the above background art.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions: A method for protecting against current overload of a circuit board for an electric jack includes the following steps:

[0007] S1. Magnetic induction detection: Install a radial magnetic pin that rotates with the shaft at the end of the motor gear shaft of the electric jack. Generate a periodic magnetic field change through the 0.5 - 1.2 mm gap formed by the radial magnetic pin and the Hall device on the circuit board, and collect the number of motor rotations in real time;

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

[0009] S3. Multi - level overload response: An electronic circuit breaker is integrally installed on the circuit board, and the electronic circuit breaker is linked with the current sensor to continuously collect the working current of the circuit board. When the current exceeds the threshold value, the electromagnetic coil on the circuit board drives the bimetal sheet to deform according to the preset logic to cut off the main circuit of the circuit board;

[0010] S4. Self - recovery control: After the bimetal sheet cools down, the contact of the bimetal sheet is reset by the return spring, and the system resumes the standby state;

[0011] An adjustable mounting seat is arranged at the end of the gear shaft, and the radial magnetic pins are located on both sides of the adjustable mounting seat. The distance from the Hall device is adjusted by changing the screwing depth of the adjustable mounting seat at the end of the gear shaft; The Hall device is surrounded by a permalloy magnetic shielding cover with an opening angle of 120 - 150 degrees to shield 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 bimetal sheet to deform according to the preset logic to cut off the main circuit of the circuit board, which has a three - level trigger mechanism and is executed as follows:

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

[0014] (2) Second - level response: When the current instantaneously exceeds 200% of the rated value, the outer - layer winding of the electromagnetic coil and the bimetal sheet act together to complete the contact separation within 0.1 second;

[0015] (3) Third - level response: When the temperature sensor detects that the temperature of the circuit board exceeds the limit, the bimetal sheet deforms autonomously to cut off the circuit.

[0016] Preferably, the temperature sensor detects the temperature of the circuit board, and the preset upper - limit value of the temperature is 60 degrees.

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

[0018] Preferably, in the S2 step, the stroke control of the nut is achieved in the following way:

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

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

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

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

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

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

[0025] Preferably, the bimetal sheet uses a nickel-iron alloy sheet with a thickness of 0.15 - 0.25 mm.

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

[0027] The present invention realizes a three-level response trigger mechanism through the double-layer winding design of the electromagnetic coil to achieve current overload protection. The first-level response uses the weak magnetic field of the inner winding of the electromagnetic coil to drive the bimetal sheet to slowly break the contact. The second-level response realizes a rapid power-off in 0.1 second through the strong magnetic field of the outer winding. The third-level response is triggered by temperature and the bimetal sheet independently cuts off, which improves the response speed compared with the traditional mechanical circuit breaker;

[0028] The present invention adopts the gap magnetic field detection technology of the radial magnetic pin and the Hall device, and combines the adjustable mounting seat to achieve precise adjustment of the gap of 0.5 - 1.2 mm;

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

[0030] Figure 1 It is a flowchart of the current overload protection method of the present invention;

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

[0032] Figure 3 Bottom view after the circuit board of the present invention is installed inside the waterproof housing;

[0033] Figure 4 System structure connection block diagram of the present invention.

[0034] In the figure: gear shaft - 1, radial magnetic pin - 2, circuit board - 3, Hall device - 4, control module - 5, electronic circuit breaker - 6, current sensor - 7, electromagnetic coil - 8, bimetallic strip - 9, return spring - 10, touch display screen - 11, microprocessor - 12, PWM drive circuit - 13, temperature sensor - 14, waterproof housing - a. Specific embodiments

[0035] In order to further explain the technical solution of the present invention, the following will be elaborated in detail through specific embodiments.

[0036] Please refer to Figures 1 - 4 , the present invention provides a method for protecting against current overload of a circuit board for an electric jack, including the following steps:

[0037] S1. Magnetic induction detection: Install a radial magnetic pin 2 that rotates with the shaft at the end of the motor gear shaft 1 of the electric jack, and generate a periodic magnetic field change through the 0.5 - 1.2 mm gap formed by the radial magnetic pin 2 and the Hall device 4 on the circuit board 3, and collect the number of motor rotations in real time;

[0038] S2. Dynamic parameter calculation: The control module 5 on the circuit board 3 receives the Hall signal of the Hall device 4 and the data of the temperature sensor 14, and combines the preset lead pitch parameter of the electric jack screw rod to calculate the current position of the nut and the current load intensity;

[0039] S3. Multi - level overload response: Integrate and set an electronic circuit breaker 6 on the circuit board 3, and the electronic circuit breaker 6 is linked with the current sensor 7 to continuously collect the working 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 according to the preset logic to cut off the main circuit of the circuit board 3;

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

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

[0042] Among them, in step S3, 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 a preset logic, which has a three-level trigger mechanism and is executed in the following manner:

[0043] (1) First-level response: When the current on the circuit board 3 continuously 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 contacts;

[0044] (2) Second-level 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 act together to complete the contact separation within 0.1 second;

[0045] (3) Third-level response: When the temperature sensor 14 detects that the temperature of the circuit board 3 exceeds the upper limit of the preset value of 60 degrees, the bimetallic strip 9 deforms independently to cut off the circuit.

[0046] Among them, in step S2, the stroke control of the nut is achieved in the following manner:

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

[0048] Among them, the inner winding of the electromagnetic coil 8 is wound with 0.5 mm enameled wire for 30 - 35 turns, and is covered with a high-temperature resistant insulating layer. And the outer winding of the electromagnetic coil 8 is wound with 0.3 mm enameled wire for 45 - 50 turns, and heat-conducting silica gel is filled between the turns.

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

[0050] Among them, the substrate layer of the circuit board 3 uses a 2oz copper-clad laminate, and an aluminum fin array with a spacing of 1.2 - 1.8 mm is arranged on the surface of the circuit board 3. A diversion 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 through bolts, and a rubber sealing ring is arranged between the waterproof housing a and the electric jack housing.

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

[0052] First, above the gear shaft 1 of the electric jack, the distance between the radial magnetic pin 2 and the Hall device 4 is changed by screwing in depth through an adjustable mounting seat (0.5 - 1.2 mm), ensuring that 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 in a 120 - 150° detection area to eliminate radial magnetic field interference;

[0053] Second, after the control module 5 receives the Hall pulse signal from the Hall device 4, it calculates the nut stroke in combination with the lead pitch parameter of the electric jack: Stroke L = number of pulses N × lead pitch P. The current load intensity I is calculated according to the formula:

[0054]

[0055] Among them, T is the motor torque, ω is the angular velocity, K t is the torque constant, K e is the back electromotive force constant;

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

[0057] Fourth, when the bimetallic strip 9 cools to a temperature less than 40 degrees, the conical spiral spring generates a restoring force to push the contact of the bimetallic strip 9 to reset.

[0058] The above are only the preferred examples of the present invention and are not used 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 recorded in the foregoing embodiments or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for current overload protection of a circuit board for an electric jack, characterized in that: It 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. A periodic magnetic field change is generated through the 0.5 - 1.2 mm gap formed by the radial magnetic pin and the Hall device on the circuit board, and the number of motor rotation turns is collected in real time; S2. Dynamic parameter calculation: The control module on the circuit board receives the Hall signal and the temperature sensor data, and combines with the preset lead pitch parameter of the electric jack screw rod to calculate the current position of the nut and the current load intensity; S3. Multi - level overload response: An electronic circuit breaker is integrally arranged on the circuit board, and the electronic circuit breaker is linked with the current sensor to continuously collect the working current of the circuit board. When the current exceeds the threshold, the electromagnetic coil on the circuit board drives the bimetal sheet to deform according to the preset logic to cut off the main circuit of the circuit board; S4. Self - recovery control: After the bimetal sheet cools down, the contact of the bimetal sheet is reset by the reset spring, and the system returns to the standby state; An adjustable mounting seat is arranged at the end of the gear shaft, and the radial magnetic pins are located on both sides of the adjustable mounting seat. The distance from the Hall device is adjusted by changing the screwing depth of the adjustable mounting seat at the end of the gear shaft; The periphery of the Hall device is wrapped with a permalloy magnetic shielding cover 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 method for current overload protection of a circuit board for an electric jack according to claim 1, characterized in that: In the step S3, the electromagnetic coil on the circuit board drives the bimetal sheet to deform according to the preset logic to cut off the main circuit of the circuit board, which has a three - level trigger mechanism and is executed in the following way: (1) First - level response: When the current exceeds 120% of the rated value for 3 - 5 seconds, the inner - layer winding of the electromagnetic coil is energized to generate a weak magnetic field, causing the bimetal sheet to slowly bend and disconnect the contact; (2) Second - level response: When the current instantaneously exceeds 200% of the rated value, the outer - layer winding of the electromagnetic coil and the bimetal sheet act together to complete the contact separation within 0.1 second; (3) Third - level response: When the temperature sensor detects that the temperature of the circuit board exceeds the limit, the bimetal sheet deforms independently to cut off the circuit.

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

4. The current overload protection method for the circuit board of an electric jack according to claim 1, wherein: The surface of the bimetal sheet 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 its contact separation response time ≤ 0.5 second.

5. The method for current overload protection of a circuit board for an electric jack according to claim 1, characterized in that: In the step S2, the stroke control of the nut is realized in the following way: The lifting distance input by the user is received through the touch - control display screen connected to one side of the circuit board, and is converted into the theoretical number of rotation turns by the micro - processor on the circuit board according to the lead pitch of the screw rod; The Hall device detects the actual number of rotation turns in real time, and dynamically adjusts the motor speed through the PWM drive circuit.

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

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

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

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

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