热处理箱式电阻炉自动控制系统

Abstract

本实用新型具体的为热处理箱式电阻炉自动控制系统，包括控制部、执行部和传感部；控制部包括热处理箱式电阻炉的人机界面、可编程控制器PLC、开关电源；PLC包括输入端、输出端；PLC接收所有来自热处理箱式电阻炉人机界面的指令和PLC输入端信号，经过逻辑判断后向PLC输出端发出控制命令；执行部通过通讯线缆接在PLC的输出端，负责根据控制部的控制命令，通过一系列中间继电器驱动热处理箱式电阻炉中的执行元件；传感部通过通讯线缆接在PLC的输入端，负责将热处理箱式电阻炉中的一系列传感器信号反馈给PLC。本实用新型能够自动化实现航空零件热处理作业，能严格保持炉膛温度始终满足热处理要求。

Claims

1. An automatic control system for a heat treatment box-type resistance furnace, characterized by: It includes a control unit, an execution unit, and a sensing unit; The control unit includes a human-machine interface (HMI) for the heat treatment box-type resistance furnace, a programmable logic controller (PLC), and a switching power supply (SMPS). The PLC includes input terminals and output terminals. The switching power supply converts 220V AC power to 24V DC power to supply power to the HMI and the output terminals of the PLC. The HMI is connected to the PLC via a communication cable and displays the status parameters of the automatic control system and provides an interface for manual input of commands. The control unit receives all commands from the HMI and input signals from the PLC, and after logical judgment, sends control commands to the output terminals of the PLC. The actuator is connected to the output terminal of the control unit's PLC via a communication cable. It is responsible for driving the actuators in the heat treatment box-type resistance furnace through a series of intermediate relays according to the control commands from the control unit. The actuator includes a first intermediate relay KA1, a second intermediate relay KA2, a third intermediate relay KA3, a fourth intermediate relay KA4, a fifth intermediate relay KA5, a sixth intermediate relay KA6, a seventh intermediate relay KA7, an eighth intermediate relay KA8, a ninth intermediate relay KA9, a red indicator light, a yellow indicator light, a green indicator light, and a buzzer. The actuators in the heat treatment box-type resistance furnace include a furnace door lifting motor, a fan motor, a first heater R1, a second heater R2, and a third heater R3. The sensing unit is connected to the input terminal of the control unit PLC via a communication cable, and is responsible for feeding back a series of sensor signals from the heat treatment box-type resistance furnace to the control unit PLC. The sensing unit includes a furnace door upper limit sensor, a furnace door high position sensor, a furnace door lower position sensor, a furnace door motor thermal relay feedback terminal, a furnace door motor brake signal device, a fan on signal device, a fan off signal device, a fan thermal relay feedback terminal, a first temperature controller, a second temperature controller, a third temperature controller, a timer, a first limit switch, a second limit switch, and a grating.

2. The automatic control system for heat treatment box resistance furnace according to claim 1, characterized in that: The control unit also includes a cabinet and installed inside the cabinet are a first circuit breaker QF1, a second circuit breaker QF2, a current transformer, a first contactor KM1, a second contactor KM2, a third contactor KM3, a first solid-state relay SSR1, a second solid-state relay SSR2, a third solid-state relay SSR3, a first thermal relay FR1, a second thermal relay FR2, a first fuse FU1, a second fuse FU2, and a third fuse FU3; The human-machine interface of the heat treatment box-type resistance furnace is located on the cabinet panel. The first temperature controller, the second temperature controller, and the third temperature controller are located on the cabinet panel, while the PLC and the switching power supply are located inside the cabinet. The first circuit breaker QF1 is a 4-pole switch, and the second circuit breaker QF2 is a 1-pole switch. After the cabinet is connected to 380V AC power via the first circuit breaker QF1, it is divided into five main control circuits. The first main control circuit, after protection by the first circuit breaker QF1, the first contactor KM1, the second contactor KM2, and the first thermal relay FR1, supplies power to the furnace door lifting motor. The second main control circuit, after protection by the first circuit breaker QF1, the third contactor KM3, and the second thermal relay FR2, supplies power to the fan motor. The third main control circuit, after protection by the first circuit breaker QF1, the current transformer, the first solid-state relay SSR1, and the first fuse FU1, supplies power to the first heater R1. The fourth main control circuit, after protection by the first circuit breaker QF1, the current transformer, the second solid-state relay SSR2, and the second fuse FU2, supplies power to the second heater R2. The fifth main control circuit, after protection by the first circuit breaker QF1, the current transformer, the third solid-state relay SSR3, and the third fuse FU3, supplies power to the third heater R3. The second relay KM2 is connected in sequence with the first intermediate relay KA1 and the first contactor KM1 to form the first secondary control circuit; the first relay KM1 is connected in sequence with the second intermediate relay KA2 and the second contactor KM2 to form the second secondary control circuit; the third intermediate relay KA3 is connected with the third contactor KM3 to form the third secondary control circuit; the fourth intermediate relay KA4 is connected with the first solid-state relay SSR1 to form the fourth secondary control circuit; the fifth intermediate relay KA5 is connected with the second solid-state relay SSR2 to form the fifth secondary control circuit; the sixth intermediate relay KA6 is connected with the third solid-state relay SSR3 to form the sixth secondary control circuit; the seventh intermediate relay KA7 is connected to the temperature controller power supply to form the seventh secondary control circuit; the eighth intermediate relay KA8 is connected to the timer power supply to form the eighth secondary control circuit; and the ninth intermediate relay KA9 is connected to the furnace door brake power supply to form the ninth secondary control circuit. The second circuit breaker is connected to one of the live wires of the power supply connected to the first circuit breaker. The second circuit breaker supplies power to the secondary control circuit, PLC, and switching power supply in sequence. The switching power supply has a built-in rectifier circuit to convert 220V AC to 24V DC. The output port of the switching power supply is connected to the human-machine interface and PLC output of the heat treatment box-type resistance furnace, and supplies power to the components of the execution part of the human-machine interface and PLC output of the heat treatment box-type resistance furnace. Below the human-machine interface on the cabinet panel is an operation panel, which includes an automatic / manual switch button, a start button, a stop button, a reset button, an emergency stop button, a furnace door raise button, and a furnace door lower button. These buttons are connected to the input terminals of the PLC in the control unit via communication cables. The automatic / manual switch button is used to switch control modes; the start button is used to initiate automatic operation; the stop button is used to stop the operation; the reset button is used to unlock the program and return the system to its initial state after an anomaly is resolved; and the emergency stop button is used for emergency stop. The furnace door raise button sends a command to the PLC to raise the furnace door, and the furnace door lower button sends a command to the PLC to lower the furnace door.

3. The automatic control system for heat treatment box resistance furnace according to claim 2, characterized in that: The control unit also includes a remote controller, which is connected to the input terminal of the control unit PLC. The remote controller is equipped with the same automatic / manual switching button, start button, stop button, reset button, emergency stop button, furnace door raise button, and furnace door lower button as the operation panel, and can remotely control the same functions as the control panel buttons.

4. The automatic control system for heat treatment box resistance furnace according to claim 2, characterized in that: The first and second secondary control circuits are used to control the on / off state of the power supply path of the furnace door lifting motor; the third secondary control circuit is used to control the on / off state of the power supply path of the fan motor; the fourth secondary control circuit is used to control the on / off state of the power supply path of the first heater R1; the fifth secondary control circuit is used to control the on / off state of the power supply path of the second heater R2; the sixth secondary control circuit is used to control the on / off state of the power supply path of the third heater R3; the seventh secondary control circuit is used to control the power supply of the temperature controller; the eighth secondary control circuit is used to control the power supply of the timer; and the ninth secondary control circuit is used to control the power supply of the furnace door brake.

5. The automatic control system for heat treatment box resistance furnace according to claim 2, characterized in that: The specific control of the association between the actuator and the sensor and the heat treatment box-type resistance furnace is as follows: The heat treatment box-type resistance furnace includes a furnace chamber, a first heater R1, a second heater R2, a third heater R3, a first thermocouple, a second thermocouple, a third thermocouple, a furnace door, a circulating fan, a robotic arm, and a basket. The first heater R1, the second heater R2, and the third heater R3 are evenly distributed around the furnace to heat the furnace to a set temperature. The first heater R1 is powered by the third main control circuit and its on / off state is controlled by the PLC through the fourth intermediate relay KA4 of the actuator. The second heater R2 is powered by the fourth main control circuit and its on / off state is controlled by the PLC through the fifth intermediate relay KA5 of the actuator. The third heater R3 is powered by the fifth main control circuit and its on / off state is controlled by the PLC through the sixth intermediate relay KA6 of the actuator. The first, second, and third thermocouples are positioned at three different locations within the furnace to measure the temperature at different points within the furnace. The first thermocouple is connected to a first temperature controller to control the furnace temperature. The second thermocouple is connected to a second temperature controller to measure the temperature. The third thermocouple is connected to a third temperature controller and is also used to measure the temperature. The human-machine interface of the heat treatment box-type resistance furnace displays the furnace temperatures measured by the three thermocouples in real time. The furnace temperatures measured by the second and third thermocouples are used as a reference for the first thermocouple. If the temperature difference between the first thermocouple and the second or third thermocouple exceeds a set range, an alarm sounds, a red indicator light illuminates, and the human-machine interface indicates an abnormal furnace temperature. The circulating fan is driven by a fan motor to circulate air within the furnace, ensuring uniform temperature. The fan motor is powered by a third main control circuit and controlled by the PLC via the third intermediate relay KA3 of the actuator. The feedback terminal of the second thermal relay FR2 is connected to the input terminal of the PLC to detect whether the fan motor is overloaded and to provide an overload protection signal to the PLC. If the fan motor is overloaded, the equipment stops, a red indicator light flashes, a buzzer sounds an alarm, and the human-machine interface displays a message indicating that the fan motor is overloaded. The first temperature controller, based on the furnace temperature measured by the first thermocouple, outputs a heating signal to the PLC if the furnace temperature is lower than the set value. The PLC then activates the coils of the fourth intermediate relay KA4, the fifth intermediate relay KA5, and the sixth intermediate relay KA6, which in turn activates SSR1, SSR2, and SSR3. SSR1, SSR2, and SSR3 conduct the heating circuit, causing the first heater R1, the second heater R2, and the third heater R3 to heat the furnace. When the temperature reaches the set value, the first temperature controller disconnects the heating request signal to the PLC, and the PLC disconnects the coils of the fourth intermediate relay KA4, the fifth intermediate relay KA5, and the sixth intermediate relay KA6, stopping the heating and ensuring that the furnace temperature is maintained at the set value. Furthermore, when the furnace temperature reaches the set value, the PLC activates the coil of the eighth intermediate relay KA8, which in turn activates the timer, and the timer begins counting. When the first temperature controller outputs a heating signal to the PLC, the PLC immediately connects the coil of the third intermediate relay KA3, which in turn connects the coil of the third contactor KM3. The contactor is energized, the fan motor starts to circulate hot air, and keeps running to ensure that the temperature of the working area inside the furnace is uniform. The furnace door is driven by a furnace door lifting motor, used to open and close the heat treatment box-type resistance furnace. The furnace door lifting motor is powered by a first main control circuit and a second main control circuit, and its on / off state is controlled by the PLC through the first intermediate relay KA1 and the second intermediate relay KA2 of the actuator. When the first main control circuit is on, the furnace door lifting motor rotates forward and the furnace door rises; when the second main control circuit is on, the furnace door lifting motor rotates in reverse and the furnace door falls. The feedback terminal of the first thermal relay FR2 is connected to the input terminal of the control unit PLC to detect whether the furnace door lifting motor is overloaded and to provide the PLC with an overload protection signal for the furnace door lifting motor. If the furnace door lifting motor is overloaded, the equipment stops, the red indicator light flashes, the buzzer sounds an alarm, and the human-machine interface of the heat treatment box-type resistance furnace indicates that the furnace door lifting motor is overloaded. The furnace door upper limit sensor, furnace door high position sensor, and furnace door lower position sensor are located at the furnace door entrance to detect the furnace door position in real time. The grating is installed at the furnace door to detect whether there is a person or foreign object at the furnace door, which serves as a condition for starting or emergency stopping. When the grating detects a person or foreign object at the furnace door, the PLC sends a furnace door brake motor signal, and the PLC connects the coil of the ninth intermediate relay KA9, which in turn connects the furnace door brake power supply, and the furnace door stops in an emergency. The robotic arm, in conjunction with a basket, is used to transport metal parts placed in the basket to the central heating area inside the furnace. The first and second limit switches are located on the platform in front of the furnace door and are used to monitor the entry and exit records of products. When the basket enters the furnace and presses the first limit switch, the entry of the product into the furnace is recorded and displayed in real time on the human-machine interface of the heat treatment box-type resistance furnace. When the basket exits the furnace and presses the second limit switch, the exit of the product from the furnace is recorded and displayed in real time on the human-machine interface of the heat treatment box-type resistance furnace.

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