Air heating system and method

Abstract

The invention relates to the field of intelligent kitchen ware, and particularly discloses an air heating system which comprises a machine body, an upper cover, a hot air module installed in the upper cover and used for heating the inner space of the machine body, and a control unit used for controlling the hot air module to operate. The hot air module comprises metal fan blades used for moving to form airflow, a three-phase motor used for driving the metal fan blades to move, and electromagnetic heating equipment used for providing an alternating magnetic field for the metal fan blades to enable the metal fan blades to generate alternating current for temperature rise. The control unit is electrically connected with the three-phase motor and the electromagnetic heating device, and linkage control of three-phase motor driving control and heating power control is achieved. The heating power detection unit and the rotating power detection unit are respectively arranged at the power supply ends of the electromagnetic heating equipment and the three-phase motor. According to the technical scheme, a linkage control mechanism is provided, and various heating air ducts can be generated.

Description

Technical Field

[0001] This invention relates to the field of smart kitchen appliances, and in particular to an air heating system and method. Background Technology

[0002] Air heating technology is widely used in the culinary field, especially in air fryers. It achieves low-oil cooking by transferring heat between hot airflow and food, significantly reducing cooking time and gaining popularity in the market. Traditional air fryers mostly use heating wires or heating tubes as the heat source, heating the space and food through thermal radiation. However, since the heating wires and heating tubes are fixed inside the heating space, oil and wastewater stains produced during cooking easily adhere to the surface of the tubes, leading to corrosion of the heating elements, reduced heating efficiency, and shortened lifespan—a common technical pain point in the industry.

[0003] To address the aforementioned issues, Chinese utility model patent CN207995435U discloses an electromagnetic induction heating air fryer. Its core technical solution includes a pot body, a detachable container, and an electromagnetic induction heating hot air module. This module consists of a metal baffle plate, a drive motor, and an electromagnetic heating device. The electromagnetic heating device generates an alternating magnetic field, causing the metal baffle plate to induce an alternating current and heat up. Simultaneously, the motor drives the baffle plate to move, forming a hot airflow to heat the food inside the container. This technology uses a metal baffle plate instead of a traditional heating wire or heating tube. On one hand, it utilizes the uniform heat conduction characteristics of metal and air to improve the uniformity of heat radiation; on the other hand, it avoids the impact of oil and water stains on heating efficiency and lifespan. Furthermore, the baffle plate is easy to replace, thus optimizing product performance to a certain extent.

[0004] However, in the above solution, the motor is only responsible for driving the baffle to form airflow, and the electromagnetic heating device is only responsible for heating the baffle. The operation of the two is unrelated, resulting in the inability to dynamically match the wind speed and direction of the hot airflow with the heating power. When the heating power increases, the lack of synchronous adjustment of the airflow speed can easily cause localized overheating. When the heating power decreases, the excessively fast airflow speed will lead to heat loss, ultimately affecting the uniformity of food heating and cooking efficiency. In addition, the fixed and single air outlet method makes it difficult to adapt to the differentiated requirements of airflow intensity and direction for different types of food (such as block, strip, and sliced ​​foods), thus limiting the product's applicable scenarios.

[0005] Therefore, there is an urgent need for an air heating system with a linkage control mechanism that can generate multiple heating air ducts. Summary of the Invention

[0006] This invention provides an air heating system with a linkage control mechanism, capable of generating multiple heating air ducts.

[0007] To solve the above-mentioned technical problems, this application provides the following technical solution: An air heating system includes: a body, a top cover, a hot air module installed inside the top cover for heating the internal space of the body, and a control unit for controlling the operation of the hot air module; The hot air module includes metal fan blades for moving to form airflow, a three-phase motor for driving the metal fan blades, and an electromagnetic heating device for providing an alternating magnetic field to the metal fan blades to generate an alternating current to raise their temperature. The control unit is electrically connected to the three-phase motor and the electromagnetic heating device respectively, so as to realize the linkage control of three-phase motor drive control and heating power control; It also includes a heating power detection unit and a rotation power detection unit respectively disposed at the power supply terminals of the electromagnetic heating device and the three-phase motor. The heating power detection unit and the rotation power detection unit are electrically connected to the control unit and are used to detect and identify the real-time output power of the electromagnetic heating device and the three-phase motor. The control unit adjusts the target speed of the three-phase motor and the heating power of the electromagnetic heating device according to the detection results of the heating power detection unit and the rotation power detection unit.

[0008] The basic principle and beneficial effects of this scheme are as follows: In this scheme, after the electromagnetic heating device is powered on, it generates an alternating magnetic field. When the metal fan blade is in this alternating magnetic field, eddy currents will be induced inside it. When the eddy currents flow through the resistive part of the metal fan blade, Joule heat is generated, which realizes the rapid heating of the metal fan blade. The heated metal fan blade exchanges heat with the surrounding air to complete the heating process of the air.

[0009] The three-phase motor starts after receiving the drive signal from the control unit, driving the metal fan blades to rotate at high speed. The rotating metal fan blades form a directional airflow, which delivers the heated air to the internal space of the machine, thus heating the object to be heated.

[0010] The heating power detection unit collects the output power of the electromagnetic heating device in real time (reflecting the heating intensity), and the rotation power detection unit collects the output power of the three-phase motor in real time (indirectly reflecting the current airflow state, such as airflow resistance and wind speed). Both units transmit the detection data to the control unit in real time. The control unit dynamically adjusts the target speed of the three-phase motor and the heating power of the electromagnetic heating device based on the real-time power data through its built-in control logic, forming a closed-loop linkage of detection, feedback, and control to ensure that the heating intensity and airflow state are always in the optimal matching state.

[0011] The three-phase motor can change the airflow speed by adjusting its rotation speed. Combined with the rotational characteristics of the metal fan blades, it can form unidirectional airflows of different intensities inside the machine. At the same time, based on the linkage control mechanism, the control unit can dynamically adjust the airflow speed and change the rotation direction of the three-phase motor according to the changes in heating power, so that the hot airflow can form a variety of air duct forms inside the machine to adapt to different heating scenarios.

[0012] Multiple heating ducts can be flexibly switched to adapt to diverse heating needs: Through a linkage control mechanism, the system can automatically form different types of heating ducts based on the real-time matching status of heating power and motor power. When the heating power is high, the motor speed increases synchronously to form a high-speed circulating air duct, accelerating the flow of hot air and preventing localized overheating; when the heating power is low, the motor speed decreases accordingly to form a low-speed, uniform air duct, ensuring sufficient heat transfer. Multiple air duct configurations can adapt to the heating needs of different ingredients (such as large pieces of meat, thin slices of vegetables, and soft pastries), improving product applicability.

[0013] The heating power detection unit and the rotation power detection unit are directly installed at the power supply end, which can quickly capture instantaneous power changes; the control unit adopts real-time computing logic, and after receiving the detection data, it quickly outputs control commands. The three-phase motor has the ability to start and stop quickly and switch speeds. The response time of the entire linkage control link is short, which can dynamically adapt to the instantaneous power fluctuations during the heating process and ensure that the heating process is stable and continuous.

[0014] The heating power detection unit and the rotation power detection unit are set independently for the electromagnetic heating equipment and the three-phase motor, respectively, to avoid cross-interference. The control unit adjusts the control based on the accurate detection data to make the matching error between the motor speed and the heating power small, ensuring that the temperature uniformity of the hot airflow is small and significantly improving the heating uniformity of the object to be heated.

[0015] By using a linkage control system, the heat waste caused by the "disconnection between heating and airflow" in the traditional independent control mode is eliminated, and hot air can exchange heat with the object to be heated more efficiently. Compared with traditional heating systems, the heat transfer efficiency of this system is improved, the heating time of the same food can be shortened, and the user experience is enhanced.

[0016] The control unit dynamically adjusts the motor speed and heating power according to real-time operating conditions, avoiding long-term high-load operation of the motor and excessive heating power, thus reducing the overall energy consumption of the system. At the same time, the metal fan blades have both heating and air guiding functions, eliminating the need for additional independent heating elements and air guiding mechanisms. This simplifies the structure, reduces energy loss, and further optimizes energy consumption performance.

[0017] The linkage control mechanism can avoid equipment load fluctuations caused by mismatch between heating power and airflow, reduce overload operation of electromagnetic heating equipment and wear of three-phase motors; the metal fan blades are heated by electromagnetic induction, eliminating the corrosion problems of traditional heating wires and heating tubes, and the dynamic adjustment of airflow can avoid material aging caused by local overheating of the fan blades, thus extending the overall service life of the system.

[0018] By monitoring motor power and heating power in real time, the system can automatically adapt to changes in air density at different altitudes and ambient temperatures, eliminating the need for manual parameter adjustments by the user. It can ensure stable heating performance in both low-altitude plains and high-altitude areas, expanding the product's application scenarios (such as home kitchens, in-vehicle cooking, and outdoor camping).

[0019] In summary, this invention generates multiple heating air ducts through a linkage control mechanism, greatly improving the user experience.

[0020] Furthermore, the electromagnetic heating device includes: The H-bridge drive unit includes a high-voltage receiving terminal, a current output terminal, and two bridge arm units. An electromagnetic coil is connected between the two bridge arms of the H-bridge drive unit, and a power input is connected to the high-voltage receiving terminal. The resonant capacitor is connected in series between the bridge arm of the H-bridge drive unit and the electromagnetic coil. The heating power detection unit is connected in series with the current output terminal of the H-bridge drive unit and then grounded. The heating power detection unit is used to collect the current signal of the H-bridge drive unit. The control unit is signal-connected to the heating power detection unit, and the control unit is electrically connected to the two arms of the H-bridge drive unit respectively.

[0021] Furthermore, the heating power detection unit includes a current sampling resistor and a voltage sensor connected in series in the power supply circuit of the electromagnetic heating device, and the rotation power detection unit includes a three-phase power transmitter connected to the power supply terminal of the three-phase motor; the current sampling resistor, voltage sensor and three-phase power transmitter are all electrically connected to the control unit through a signal conditioning module, and the signal conditioning module is used to filter, amplify and perform analog-to-digital conversion processing on the detected current signal, voltage signal and power signal.

[0022] Furthermore, the control unit has a built-in power-speed matching database, which stores the optimal heating power range and three-phase motor speed range corresponding to different cooking stages under different user input requirements; the control unit matches the optimal parameter combination in the database and dynamically adjusts it based on the real-time detection data of the heating power detection unit and the rotation power detection unit.

[0023] Furthermore, both the heating power detection unit and the rotation power detection unit are equipped with a fault self-diagnosis module. The fault self-diagnosis module is used to monitor the on / off status and signal transmission integrity of its own detection circuit in real time. When a circuit break, signal distortion, or exceeding a preset error threshold is detected, a fault warning signal is immediately sent to the control unit. After receiving the warning signal, the control unit automatically reduces the heating power of the electromagnetic heating equipment and adjusts the three-phase motor to a safe speed.

[0024] Furthermore, it also includes a temperature sensor for real-time acquisition of the ambient temperature inside the machine and sending it to the control unit.

[0025] Furthermore, the calculation model for adjusting the target speed of the three-phase motor based on real-time detection data by the control unit is as follows: in: This is the target speed of the three-phase motor; This is the reference speed of the three-phase motor, a preset constant, with a value range of 1500 r / min to 3000 r / min; The real-time output power of the electromagnetic heating device detected by the heating power detection unit; The real-time output power of the three-phase motor detected by the rotational power detection unit; The air density inside the machine is collected in real time by the control unit through a temperature sensor; The effective windward area of ​​the metal fan blades is a parameter inherent to the equipment. The mechanical efficiency of the three-phase motor is 0.85-0.95, which is a preset constant. Let be the specific heat capacity of air at constant pressure, and be a constant. This is the difference between the preset target temperature and the real-time temperature.

[0026] Furthermore, the calculation model for adjusting the heating power of the electromagnetic heating device based on real-time detection data by the control unit is as follows: in: The target heating power of the electromagnetic heating equipment; This is the reference heating power for the electromagnetic heating equipment, a preset constant with a value range of 800W-1500W; The difference between the real-time internal temperature and the initial temperature is obtained by a temperature sensor. This is the difference between the preset target temperature and the initial temperature. The real-time output power of the three-phase motor detected by the rotational power detection unit; The real-time output power of the electromagnetic heating device detected by the heating power detection unit; The heat transfer coefficient of food is preset according to the type of object to be heated in the user's input command. The value is 0.4-0.6 for meat, 0.2-0.3 for vegetables, and 0.15-0.25 for pastries. This represents the current cooking time.

[0027] Furthermore, there are four metal fan blades and four three-phase motors, each electrically connected to the control unit. The control unit has a built-in motor steering control module, which is electrically connected to the winding power supply terminal of the three-phase motor. Reverse control is achieved by switching the power supply phase sequence of the three-phase motor windings. The steering control module includes a relay group for switching the phase sequence and a phase sequence detection unit. The phase sequence detection unit collects the power supply phase sequence of the three-phase motor in real time and feeds it back to the control unit. When the control unit determines that reverse rotation is required based on real-time data from the heating power detection unit, the rotation power detection unit, or user-input requirements, it sends a reverse command to the steering control module. The relay group switches the winding power supply phase sequence, and the phase sequence detection unit verifies whether the phase sequence switching is in place and feeds it back to the control unit. Attached Figure Description

[0028] Figure 1 This is a cross-sectional view of an embodiment 1 of an air heating system; Figure 2 This is a circuit diagram of the electromagnetic heating device in Embodiment 1 of an air heating system; The following are the reference numerals in the instruction manual: body 10, top cover 20, metal fan blades 31, electromagnetic heating device 32, three-phase motor 33, control unit 34. Detailed Implementation

[0029] The following detailed description illustrates the specific implementation methods: An air heating system (such as) Figure 1 As shown, it includes: a body 10, a top cover 20, a hot air module installed inside the top cover 20 for heating the internal space of the body 10, and a control unit 34 for controlling the operation of the hot air module.

[0030] One side of the body 10 is hinged to one side of the upper cover 20. After they are closed, a sealing gasket can be placed between the body 10 and the upper cover 20 to seal them from the outside during operation. The hot air module includes a metal fan blade 31 for moving to form airflow, a three-phase motor 33 for driving the metal fan blade 31, and an electromagnetic heating device 32 for providing an alternating magnetic field to the metal fan blade 31 to generate an alternating current and raise its temperature. The three-phase motor 33 and the electromagnetic heating device 32 are both installed inside the upper cover 20.

[0031] The control unit 34 is electrically connected to the three-phase motor 33 and the electromagnetic heating device 32 respectively, so as to realize the linkage control of the three-phase motor 33 drive control and the heating power control. It also includes a heating power detection unit and a rotation power detection unit respectively disposed at the power supply terminals of the electromagnetic heating device 32 and the three-phase motor 33. The heating power detection unit and the rotation power detection unit are electrically connected to the control unit 34 and are used to detect and identify the real-time output power of the electromagnetic heating device 32 and the three-phase motor 33. The control unit 34 adjusts the target speed of the three-phase motor 33 and the heating power of the electromagnetic heating device 32 according to the detection results of the heating power detection unit and the rotation power detection unit.

[0032] Electromagnetic heating equipment 32 (e.g.) Figure 2 (As shown) includes: The H-bridge drive unit includes a high-voltage receiving terminal VCC, a current output terminal OUT, and two bridge arm units. An electromagnetic coil L1 is connected between the two bridge arms of the H-bridge drive unit, and a power input is connected to the high-voltage receiving terminal VCC. The resonant capacitor C0 is connected in series between the bridge arm of the H-bridge drive unit and the electromagnetic coil L1. The heating power detection unit is connected in series with the current output terminal OUT of the H-bridge drive unit and then grounded. The heating power detection unit is used to collect the current signal of the H-bridge drive unit. The control unit 34 is signal-connected to the heating power detection unit and electrically connected to the two arms of the H-bridge drive unit respectively.

[0033] Specifically, the electromagnetic heating device 32 includes an H-bridge drive unit, a resonant capacitor C0, a current acquisition resistor R0, and a control unit U1 (marked as U1 in the circuit diagram). It is compatible with DC12V-60V low-voltage DC power input, enabling efficient induction heating, precise control, and mitigation of the negative impact of low voltage and high current. It also provides a stable hardware platform for subsequent control program development.

[0034] The H-bridge drive unit includes a high-voltage receiving terminal VCC, a current output terminal OUT, two bridge arm units, and an electromagnetic coil L1 (model: EE55-220μH, wire diameter 1.2mm, number of turns 30, which can be selected according to the actual situation) connected between the two bridge arms. The high-voltage receiving terminal VCC is directly connected to a DC12V-60V low-voltage DC power supply input.

[0035] Each bridge arm unit consists of two bridge arm sub-units connected in series and then connected in parallel with the second capacitor C2. The second capacitor C2 is a ceramic capacitor with parameters of 10μF / 100V (the actual capacitor can be selected according to the situation).

[0036] Each bridge arm subunit group is formed by two bridge arm subunits connected in parallel, and each bridge arm subunit group has a branch connected in parallel with a fourth resistor R4 and a first capacitor C1 connected in series; wherein, the fourth resistor R4 has a parameter of 10kΩ / 0805, and the first capacitor C1 is a polyester capacitor with a parameter of 0.1μF / 50V (which can be selected according to the actual situation).

[0037] Each bridge arm sub-unit includes an N-type MOSFET (model: IRF3205, withstand voltage 100V, on-resistance 8mΩ), a first resistor R1 (1kΩ / 0805), a second resistor R2 (10kΩ / 0805), a third resistor R3 (470Ω / 0805), a first diode D1 (model: 1N4148), and a Zener diode ZD1 (model: BZX584-B12, Zener voltage 12V). Actual parameters can be selected according to the situation.

[0038] The drain (D) of the N-type MOSFET is connected to the high-voltage receiving terminal VCC; the gate (G) of the N-type MOSFET is connected to one end of the first resistor R1, one end of the second resistor R2, one end of the third resistor R3, and the cathode of the Zener diode ZD1; the first diode D1 is connected in series between the other end of the first resistor R1 and the other end of the second resistor R2, with the anode of the first diode D1 facing the first resistor R1; the other end of the third resistor R3 is connected to the anode of the Zener diode ZD1, and together they are connected to the source (S) of the N-type MOSFET.

[0039] In this embodiment, there are eight bridge arm sub-units. Every two bridge arm sub-units are connected in parallel to form a bridge arm sub-unit group. The two bridge arm sub-unit groups are connected in series and then connected in parallel with the second capacitor C2 to finally form a complete bridge arm unit. The output terminal of the bridge arm unit is the current output terminal OUT of the H-bridge drive unit.

[0040] The resonant capacitor C0 is a C0 type high-frequency resonant capacitor (model: CBB61-10μF / 450V, actual parameters can be selected according to the situation). One end of it is soldered to the output terminal of the bridge arm of the H-bridge drive unit, and the other end is soldered to one end of the electromagnetic coil L1, so that it is connected in series between the bridge arm of the H-bridge drive unit and the electromagnetic coil L1, forming an LC resonant circuit with the electromagnetic coil L1, with a resonant frequency range of 20K-60KHz.

[0041] The current acquisition resistor R0 is an alloy sampling resistor (model: MFR-25FRF52-0.01Ω, power 5W, which can be selected according to the actual situation). One end of it is soldered to the current output terminal OUT of the H-bridge drive unit, and the other end is grounded, so as to achieve grounding after being connected in series with the current output terminal OUT, which is used to acquire the loop working current signal of the H-bridge drive unit in real time.

[0042] The peripheral circuit of the control unit 34 is as follows: Pin 9 is VIN-, which is connected to the end of the current acquisition resistor R0 away from ground through the protection resistor R5 (1kΩ / 0805) to receive the current signal transmitted by the current acquisition resistor R0; Pin 10 is VIN+, which is connected to the current output terminal OUT of the H-bridge drive unit through the sixth resistor R6 (2kΩ / 0805). A third capacitor C3 (ceramic capacitor, 0.01μF / 50V) is connected in parallel between pin 9 and pin 10 to assist in current signal filtering and loop stabilization. Pin 8 is VBUS. After connecting the seventh resistor R7 (10kΩ / 0805) in series, it is connected to one end of the eighth resistor R8 (4.7kΩ / 0805) and the ninth resistor R9 (10kΩ / 0805). The other end of the eighth resistor R8 is connected to the low-voltage power supply terminal VBUS3.3V, and the other end of the ninth resistor R9 is grounded, forming a voltage divider circuit to provide a stable reference voltage for the control unit. Pin 7 is GND, which is directly grounded on one hand, and connected to the low-voltage power supply terminal VBUS3.3V through the fourth capacitor C4 (tantalum capacitor, 10μF / 16V) on the other hand to achieve power supply filtering; Pin 6 is VS+, which is directly connected to the low-voltage power supply terminal VBUS3.3V to provide the operating voltage for the control unit; Pins 5 (SCL), 4 (SDA), and 3 (Alert): 10th resistor R10 (10kΩ / 0805), 11th resistor R11 (10kΩ / 0805), and 12th resistor R12 (10kΩ / 0805) are connected in series respectively. The ends of the three resistors furthest from the pins are connected in parallel and then connected to the low-voltage power supply terminal VBUS3.3V to form a pull-up circuit, which improves the stability of the pin level and the communication and receive interrupt operation. Pins 1 and 2 are both directly grounded to ensure stable grounding for the control unit. In practical use: The user places the piece of meat to be heated (such as a 500g steak) on the support component inside the machine body 10, closes the top cover 20, and inputs the "steak cooking" command through the operation panel. After receiving the command, the control unit 34 starts the system. First, the control unit 34 sends a drive signal to the H-bridge drive unit to control the turn-on and turn-off sequence of the N-type MOS transistor in the bridge arm unit, so that the DC60V low-voltage DC power supply connected to the high-voltage receiving terminal VCC forms an alternating voltage across the electromagnetic coil L1, thereby generating an alternating magnetic field. The metal fan blade 31 is in this alternating magnetic field, and eddy currents are induced inside. The eddy currents flow through the resistive part of the metal fan blade 31 to generate Joule heat, realizing the rapid heating of the metal fan blade 31, with a heating rate of up to 5℃ / s. At the same time, the control unit 34 sends a start signal to the three-phase motor 33, which drives the metal fan blade 31 to rotate at a reference speed n0=2000r / min, forming a directional airflow, which transfers the heat generated by the metal fan blade 31 to the internal space of the machine body 10 to heat the steak.

[0043] During the heating process, the heating power detection unit collects the operating current and voltage signals of the electromagnetic heating device 32 in real time through the current acquisition resistor R0 and the voltage sensor, and calculates the real-time output power P. h =1200W and transmit to control unit 34; rotation power detection unit collects the real-time output power P of three-phase motor 33 through three-phase power transmitter. m =80W and feeds back to control unit 34. According to the preset steak cooking process, control unit 34 determines that the current heating stage is the heating stage, and it is necessary to increase the hot air circulation speed to avoid local overheating. Therefore, according to the built-in logic, it adjusts the target speed of three-phase motor 33 to 2500r / min, while maintaining the heating power of electromagnetic heating device 32 at a stable 1200W.

[0044] If the heating power detection unit detects P h If the power suddenly drops to 800W (due to power supply voltage fluctuations), the control unit 34 immediately detects the decrease in heating intensity. To ensure sufficient heat transfer, it dynamically adjusts the speed of the three-phase motor 33 to 1800 r / min, rematching the airflow speed with the heating power to prevent heat loss. Throughout the heating process, the detection cycle of the heating power detection unit and the rotation power detection unit is 50ms, and the control unit 34's adjustment response time does not exceed 100ms, ensuring the stability and continuity of the heating process.

[0045] Example 2 Compared with Embodiment 1, the only difference is that there are four metal fan blades 31 and four three-phase motors 33, and the four three-phase motors 33 are electrically connected to the control unit 34. The control unit 34 has a built-in motor steering control module, which is electrically connected to the winding power supply terminal of the three-phase motor 33. Reverse control is achieved by switching the power supply phase sequence of the three-phase motor 33 winding. The steering control module includes a relay group for switching the phase sequence and a phase sequence detection unit. The phase sequence detection unit collects the power supply phase sequence of the three-phase motor 33 in real time and feeds it back to the control unit 34. When the control unit 34 determines that reverse is required based on the real-time data of the heating power detection unit and the rotation power detection unit or the user input demand command, it sends a reverse command to the steering control module, switches the winding power supply phase sequence through the relay group, and at the same time, the phase sequence detection unit verifies whether the phase sequence switching is in place and feeds it back to the control unit 34.

[0046] In actual use: the user places different ingredients in the four independent heating zones inside the machine body 10, namely, 200g of French fries in zone 1, 150g of chicken wings in zone 2, 100g of vegetable slices in zone 3, and 80g of pastries in zone 4. The user inputs the "simultaneous cooking of multiple ingredients" command through the operation panel. After receiving the command, the control unit 34 retrieves the optimal parameter combination corresponding to the power and speed matching database.

[0047] After the system is started, the control unit 34 controls four three-phase motors 33 to start through four independent drive modules, which drive the corresponding metal fan blades 31 to rotate: the three-phase motor 33 corresponding to area 1 rotates clockwise at 3000r / min (forming a high-speed circulating air duct), which is suitable for the cooking needs of crispy French fries; the three-phase motor 33 corresponding to area 2 rotates clockwise at 2500r / min to ensure that the chicken wings are heated evenly; the three-phase motor 33 corresponding to area 3 rotates counterclockwise at 1800r / min (forming a low-speed uniform air duct) to prevent vegetable slices from losing water too quickly; the three-phase motor 33 corresponding to area 4 rotates counterclockwise at 1500r / min to meet the heating needs of soft pastries.

[0048] After heating for 10 minutes, the heating power detection unit detected the real-time output power P of the electromagnetic heating device 32 in area 2. h =1300W, the rotation power detection unit detected the output power P of the three-phase motor 33 in area 2. m=90W, and at the same time, the temperature sensor feedback area 2 shows a real-time temperature difference exceeding 5℃ from the target temperature. The control unit 34 determines that area 2 has a risk of local overheating, and therefore sends a reverse command to the motor rotation control module corresponding to that area. After receiving the command, the relay group switches the power supply phase sequence of the three-phase motor 33 windings, causing the three-phase motor 33 to switch from clockwise rotation to counterclockwise rotation. The phase sequence detection unit collects the switched power supply phase sequence and feeds it back to the control unit 34 to confirm that the switch is in place. The reversed metal fan blades 31 form a reverse airflow, which forms convection with the forward airflow inside the body 10, quickly dissipating the local high temperature. Within 5 seconds, the temperature difference in area 2 returns to within 2℃, ensuring the cooking effect of the chicken wings.

[0049] If the user needs to adjust the cooking status of a specific area, such as speeding up the heating of the vegetable slices in area 3, the user can input a command through the control panel. The control unit 34 will then increase the speed of the three-phase motor 33 corresponding to area 3 to 2200 r / min, while keeping the operating parameters of other areas unchanged, thus achieving flexibility and personalization in cooking multiple ingredients.

[0050] Example 3 Compared to Embodiment 1, the only difference is that a temperature sensor is also included to collect the ambient temperature inside the machine body 10 in real time and send it to the control unit 34. The heating power detection unit includes a current sampling resistor R0 and a voltage sensor connected in series in the power supply circuit of the electromagnetic heating device 32. The rotation power detection unit includes a three-phase power transmitter connected to the power supply terminal of the three-phase motor 33. The current sampling resistor R0, the voltage sensor, and the three-phase power transmitter are all electrically connected to the control unit 34 through a signal conditioning module. The signal conditioning module is used to filter, amplify, and perform analog-to-digital conversion on the detected current signal, voltage signal, and power signal. The control unit 34 has a built-in power-speed matching database, which stores the optimal heating power range and the three-phase motor 33 speed range corresponding to different cooking stages under different user input requirements. The control unit 34 matches the optimal parameter combination in the database and dynamically adjusts it according to the real-time detection data of the heating power detection unit and the rotation power detection unit.

[0051] The calculation model for adjusting the target speed of the three-phase motor 33 based on real-time detection data by the control unit 34 is as follows: in: The target speed of the three-phase motor 33 (unit: r / min); This is the reference speed of the three-phase motor 33, a preset constant with a value range of 1500r / min-3000r / min; The real-time output power of the electromagnetic heating device 32 detected by the heating power detection unit (unit: W); The real-time output power of the three-phase motor 33 detected by the rotational power detection unit (unit: W); The air density inside the body 10 (unit: kg / m³) is collected and calculated in real time by the control unit 34 through the temperature sensor; The effective windward area of ​​the metal fan blade 31 (unit: m²) is an inherent parameter of the equipment, with a value of 0.05 m². The mechanical efficiency (unitless) of the three-phase motor 33, with a value range of 0.85-0.95, is a preset constant. The specific heat capacity of air at constant pressure (unit: J / (kg·℃)) is taken as 1005 J / (kg·℃), which is a constant. The difference between the preset target temperature and the real-time temperature (unit: °C).

[0052] The calculation model for adjusting the heating power of the electromagnetic heating device 32 based on real-time detection data by the control unit 34 is as follows: in: The target heating power of electromagnetic heating device 32 (unit: W); The reference heating power (unit: W) of the electromagnetic heating device 32 is a preset constant with a value range of 800W-1500W; The difference between the real-time internal temperature and the initial temperature of the body 10 (unit: °C) is obtained by the temperature sensor. The difference between the preset target temperature and the initial temperature (unit: °C); The real-time output power of the three-phase motor 33 detected by the rotational power detection unit (unit: W); The real-time output power of the electromagnetic heating device 32 detected by the heating power detection unit (unit: W); The heat transfer coefficient of food (unit: W / (m·℃)) is preset according to the type of object to be heated in the user's input requirement command. The value is 0.4-0.6 for meat, 0.2-0.3 for vegetables, and 0.15-0.25 for pastries. This represents the current cooking time (in seconds).

[0053] In practical use: The user selects to cook 200g of chicken breast (food thermal conductivity k=0.5W / (m·℃)), the preset target temperature is 180℃, and the initial temperature is assumed to be 25℃, i.e. The reference heating power of electromagnetic heating device 32 The reference speed of the three-phase motor 33 The mechanical efficiency of the three-phase motor 33 .

[0054] After the system starts up, the temperature sensor collects the internal temperature of the machine body 10 in real time, and the control unit 34 calculates the air density based on the temperature data. The heating power detection unit collects the real-time output power of the electromagnetic heating device 32. The rotational power detection unit collects the real-time output power of the three-phase motor 33. Cooking time: 30 seconds The temperature sensor reports a real-time temperature of 85℃, which is... .

[0055] The control unit 34 first calculates the target speed of the three-phase motor 33 using a speed calculation model. Assuming the calculated speed is 2400 r / min, the control unit 34 adjusts the speed of the three-phase motor 33 to 2400 r / min to accelerate the hot air circulation speed and improve the heat transfer efficiency.

[0056] When cooking for 60 seconds ( The real-time temperature rose to 135℃. The heating power detection unit detected The rotational power detection unit detected The control unit 34 calculates the target heating power of the electromagnetic heating device 32 using a heating power calculation model. Based on calculations (assuming the result is 520W), the control unit 34 adjusts the heating power of the electromagnetic heating device 32 to 520W to prevent local overheating of the chicken breast.

[0057] If the cooking environment is in a high-altitude area (air density ³), The heating power detection unit detected The rotational power detection unit detected The control unit 34 recalculates using the speed calculation model. Based on calculations (assuming a result of 2300 r / min), the three-phase motor speed is automatically adjusted to 2300 r / min to adapt to changes in air density at high altitudes and ensure stable heating performance.

[0058] Throughout the cooking process, the control unit 34 performs parameter calculations and adjustments every 10 seconds. The detection signals from the heating power detection unit and the rotation power detection unit are filtered, amplified, and converted from analog to digital by the signal conditioning module to ensure precise control. Simultaneously, the fault self-diagnosis modules of the heating power detection unit and the rotation power detection unit monitor the detection circuit status in real time. If an open circuit is detected in the current sampling resistor R0, a fault warning signal is immediately sent to the control unit 34. Upon receiving the signal, the control unit 34 reduces the heating power of the electromagnetic heating device 32 to 300W within 1 second, adjusts the speed of the three-phase motor 33 to a safe speed of 1000 r / min, and displays a fault code on the operation panel to prompt the user to troubleshoot.

[0059] The above are merely embodiments of the present invention. The invention is not limited to the fields covered by these embodiments. Commonly known structures and characteristics in the solutions are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are able to access all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. An air heating system, characterized in that, include: The machine body, the top cover, the hot air module installed inside the top cover for heating the internal space of the machine body, and the control unit for controlling the operation of the hot air module; The hot air module includes metal fan blades for moving to form airflow, a three-phase motor for driving the metal fan blades, and an electromagnetic heating device for providing an alternating magnetic field to the metal fan blades to generate an alternating current to raise their temperature. The control unit is electrically connected to the three-phase motor and the electromagnetic heating device respectively, so as to realize the linkage control of three-phase motor drive control and heating power control; It also includes a heating power detection unit and a rotation power detection unit respectively disposed at the power supply terminals of the electromagnetic heating device and the three-phase motor. The heating power detection unit and the rotation power detection unit are electrically connected to the control unit and are used to detect and identify the real-time output power of the electromagnetic heating device and the three-phase motor. The control unit adjusts the target speed of the three-phase motor and the heating power of the electromagnetic heating device according to the detection results of the heating power detection unit and the rotation power detection unit.

2. An air heating system according to claim 1, characterized in that, Electromagnetic heating equipment includes: The H-bridge drive unit includes a high-voltage receiving terminal, a current output terminal, and two bridge arm units. An electromagnetic coil is connected between the two bridge arms of the H-bridge drive unit, and a power input is connected to the high-voltage receiving terminal. The resonant capacitor is connected in series between the bridge arm of the H-bridge drive unit and the electromagnetic coil. The heating power detection unit is connected in series with the current output terminal of the H-bridge drive unit and then grounded. The heating power detection unit is used to collect the current signal of the H-bridge drive unit. The control unit is signal-connected to the heating power detection unit, and the control unit is electrically connected to the two arms of the H-bridge drive unit respectively.

3. An air heating system according to claim 2, characterized in that, The heating power detection unit includes a current sampling resistor and a voltage sensor connected in series in the power supply circuit of the electromagnetic heating equipment. The rotation power detection unit includes a three-phase power transmitter connected to the power supply terminal of the three-phase motor. The current sampling resistor, voltage sensor and three-phase power transmitter are all electrically connected to the control unit through a signal conditioning module. The signal conditioning module is used to filter, amplify and perform analog-to-digital conversion on the detected current signal, voltage signal and power signal.

4. An air heating system according to claim 3, characterized in that, The control unit has a built-in power-speed matching database, which stores the optimal heating power range and three-phase motor speed range corresponding to different cooking stages under different user input requirements. The control unit matches the optimal parameter combination in the database and dynamically adjusts it based on the real-time detection data from the heating power detection unit and the rotation power detection unit.

5. An air heating system according to claim 4, characterized in that, Both the heating power detection unit and the rotation power detection unit are equipped with a fault self-diagnosis module. The fault self-diagnosis module is used to monitor the on / off status and signal transmission integrity of its own detection circuit in real time. When a circuit is broken, the signal is distorted, or the preset error threshold is exceeded, a fault warning signal is immediately sent to the control unit. After receiving the warning signal, the control unit automatically reduces the heating power of the electromagnetic heating equipment and adjusts the three-phase motor to a safe speed.

6. An air heating system according to claim 5, characterized in that, It also includes a temperature sensor to collect the ambient temperature inside the machine in real time and send it to the control unit.

7. An air heating system according to claim 6, characterized in that, The calculation model for adjusting the target speed of the three-phase motor based on real-time detection data by the control unit is as follows: in: This is the target speed of the three-phase motor; This is the reference speed of the three-phase motor, a preset constant, with a value range of 1500 r / min to 3000 r / min; The real-time output power of the electromagnetic heating device detected by the heating power detection unit; The real-time output power of the three-phase motor detected by the rotational power detection unit; The air density inside the machine is obtained in real time by the control unit through a temperature sensor; The effective windward area of ​​the metal fan blades is a parameter inherent to the equipment. The mechanical efficiency of the three-phase motor is 0.85-0.95, which is a preset constant. Let be the specific heat capacity of air at constant pressure, and be a constant. This is the difference between the preset target temperature and the real-time temperature.

8. An air heating system according to claim 7, characterized in that, The calculation model for adjusting the heating power of the electromagnetic heating device based on real-time detection data by the control unit is as follows: in: The target heating power of the electromagnetic heating equipment; This is the reference heating power for the electromagnetic heating equipment, a preset constant with a value range of 800W-1500W; The difference between the real-time internal temperature and the initial temperature is obtained by a temperature sensor. This is the difference between the preset target temperature and the initial temperature. The real-time output power of the three-phase motor detected by the rotational power detection unit; The real-time output power of the electromagnetic heating device detected by the heating power detection unit; The heat transfer coefficient of food is preset according to the type of object to be heated in the user's input command. The value is 0.4-0.6 for meat, 0.2-0.3 for vegetables, and 0.15-0.25 for pastries. This represents the current cooking time.

9. An air heating system according to claim 8, characterized in that, The device comprises four metal fan blades and four three-phase motors, each electrically connected to a control unit. The control unit has a built-in motor steering control module, which is electrically connected to the power supply terminals of the three-phase motor windings. Reverse control is achieved by switching the power supply phase sequence of the three-phase motor windings. The steering control module includes a relay group for switching the phase sequence and a phase sequence detection unit. The phase sequence detection unit collects the power supply phase sequence of the three-phase motor in real time and feeds it back to the control unit. When the control unit determines that reverse control is required based on real-time data from the heating power detection unit, the rotation power detection unit, or user-input commands, it sends a reverse command to the steering control module. The relay group switches the power supply phase sequence of the windings, and the phase sequence detection unit verifies whether the phase sequence switching is complete and feeds it back to the control unit.

10. An air heating method, characterized in that, The system described in any one of claims 1-9 is employed.

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