Material heating system and control method

Abstract

The present application relates to the technical field of material heating, and in particular to a material heating system and a control method, which specifically comprises: a furnace body for accommodating a workpiece, the inner wall of the furnace body being provided as a diffuse reflection surface; a thermal convection heater for heating the workpiece through a thermal convection mode; a thermal radiation heater for emitting thermal radiation with a peak value covering multiple different wave bands to heat the workpiece; a contact heater in direct contact with the workpiece for heating the workpiece through a thermal conduction mode; at least one photoelectric sensor for measuring the thermal radiation spectrum emitted or reflected by the workpiece; and a controller for calculating the absorption peak wave band of the workpiece and the thermal radiation absorption rate according to the thermal radiation spectrum measured by the photoelectric sensor, controlling the working peak wave band of the thermal radiation heater according to the absorption peak wave band, calculating the power ratio according to the thermal radiation absorption rate, and determining the power of each heater according to the power ratio and the design temperature rise curve of the workpiece.

Description

Technical Field

[0001] This invention relates to the field of material heating technology, specifically to a material heating system and control method. Background Technology

[0002] As competition in the new energy vehicle industry intensifies, battery technology is rapidly iterating and upgrading, and the materials used in battery casings are becoming increasingly diverse, ranging from metals with coatings to composite materials. Battery manufacturers are constantly trying to use more complex and advanced materials to manufacture high-performance batteries. In the production process of battery casings, heat shaping is an essential step. Some materials (such as aluminum alloys) need to be preheated to prepare for the subsequent shaping process, while other materials (polymer materials, composite materials, etc.) need to be heated to solidify their shape.

[0003] In particular, when heating some mirrored metal shells, due to the low emissivity and high reflectivity of mirrored metals, most of the energy is reflected by the mirror and cannot be absorbed by the material being heated when heating by thermal radiation alone, resulting in extremely slow heating speed and extremely low energy utilization. For some materials with high internal stress, more uniform heating is required to release the internal stress evenly and improve the heating effect; in actual operation, the heating method is often relatively simple.

[0004] Furthermore, existing heating devices often rely on fixed, preset temperature control strategies to heat the battery casing, using temperature sensors installed inside the furnace to control the ambient temperature. However, different materials possess different thermal properties (thermal conductivity, coefficient of thermal expansion), making fixed temperature control strategies poorly adaptable to the heating requirements of various materials. This can easily lead to uneven heating of some materials, localized overheating, or failure to reach the required process temperature. This not only affects the subsequent shaping accuracy and structural strength of the battery casing but also causes unnecessary energy waste, increasing overall production costs. Summary of the Invention

[0005] To address the technical problem of poor adaptability of existing heating technologies to materials with different thermodynamic properties, this application provides a material heating system and control method, wherein the material heating system includes: A furnace body for holding workpieces, wherein the inner wall of the furnace body is configured as a diffuse reflective surface; A thermal convection heater is used to heat a workpiece by means of thermal convection. Thermal radiation heaters are used to emit thermal radiation with peak values ​​covering multiple different wavelengths to heat workpieces; A contact heater, which comes into direct contact with the workpiece, is used to heat the workpiece through heat conduction. At least one photoelectric sensor is used to measure the thermal radiation spectrum emitted or reflected by the workpiece; The controller is used to calculate the absorption peak band and thermal radiation absorptivity of the workpiece based on the thermal radiation spectrum measured by the photoelectric sensor, and to control the operating peak band of the thermal radiation heater based on the absorption peak band. The controller is also used to activate the contact heater when the thermal radiation absorptivity is lower than a preset reflection threshold, and to calculate the power ratio of the thermal radiation heater, the thermal convection heater and the contact heater according to the thermal radiation absorptivity, and to determine the thermal radiation heating power of the thermal radiation heater, the thermal convection heating power of the thermal convection heater and the contact heating power of the contact heater according to the power ratio and the design temperature rise curve of the workpiece.

[0006] The control method provided in this application is used to control the above-mentioned heating system, and specifically includes the following steps: Before heating begins, broadband thermal radiation is emitted. After the radiation stabilization time, the measured reflection spectrum of the workpiece is measured. The absorption peak band of the workpiece is calculated based on the empty furnace reflection spectrum, and the thermal radiation absorptivity of the workpiece in the absorption peak band is calculated. Calculate the power ratio of the thermal radiation heater, the thermal convection heater, and the contact heater based on the thermal radiation absorptivity. The thermal radiation heating power, thermal convection heating power, and contact heating power are determined based on the power ratio and the design temperature rise curve of the workpiece.

[0007] The technical effects and advantages of the invention: By measuring the reflectance spectrum of the workpiece to calculate its actual absorptivity in real time, the system can automatically identify the heat absorption characteristics of different materials and dynamically adjust the power ratio of heat convection and heat radiation. This allows the system to adaptively output matching heating energy according to the characteristics of different materials (such as light alloys or composite materials), avoiding the blindness of traditional fixed-program heating, shortening the process cycle and reducing energy consumption. Attached Figure Description

[0008] Figure 1 This is a top view of the heating system provided by the present invention.

[0009] Figure 2 This is a front view of the heating system provided by the present invention.

[0010] Figure 3 This is a perspective view of the rotating support structure in Embodiment 2 of the present invention.

[0011] Figure 4 This is a front view of the rotating support structure in Embodiment 2 of the present invention.

[0012] Figure 5 This is a flowchart of the control method for the heating system of the present invention.

[0013] The attached figures are labeled as follows: 1. Furnace body; 2. Convection heater; 21. Heating unit; 22. Blower; 23. Wind speed sensor; 24. Temperature sensor; 25. Protective gas source; 3. Radiation heater; 4. Photoelectric sensor; 5. Controller; 6. Rotary support mechanism; 61. Drive motor; 62. Support assembly; 621. Driven gear; 622. Support platform; 63. Central drive gear; 64. Transmission assembly; 65. Driven rack. Detailed Implementation

[0014] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] Against the backdrop of the rapid development of the new energy vehicle industry, the battery casing, as a key structural component protecting the core battery cell, directly affects the safety performance, energy density, and overall service life of the battery pack through its material selection and molding process. Currently, to meet multiple stringent requirements such as lightweighting, high strength, and flame retardancy, the manufacturing materials for battery casings have gradually evolved from traditional single steel or ordinary aluminum alloys to high-strength aluminum alloys (such as 6-series and 7-series aluminum alloys), carbon fiber reinforced thermoplastic composites (CFRTP), glass fiber reinforced polymers (GFRP), and laminate structures combining multiple materials. These advanced materials all require a rigorous heating and shaping stage before molding or during curing. However, different material systems have drastically different thermophysical properties. For example, aluminum alloys have extremely high thermal conductivity and high surface reflectivity (especially metallic materials with mirror-like surfaces); while carbon fiber composites exhibit anisotropic thermal conductivity and extremely high absorption rates for specific wavelengths of thermal radiation. In existing technologies, most heating devices adopt a fixed preset temperature control strategy, relying solely on single-point or multi-point thermocouples inside the furnace to provide feedback on the ambient temperature. This single-factor control method is difficult to cope with the frequent material changes in production enterprises. When a fixed heating power-temperature mapping relationship is used to control the power of the heating furnace, different materials have different thermodynamic properties and different temperature rise rates during actual heating. This can lead to a large deviation between the actual temperature and the theoretical temperature of the battery casing, resulting in the final product quality failing to meet standards.

[0016] To solve the above technical problems, refer to Figure 1 and Figure 2 The present invention provides a material heating system, comprising: Furnace body 1, used to hold workpieces, the inner wall of furnace body 1 is set as a diffuse reflective surface; The heat convection heater 2 is used to heat the workpiece by heat convection. Thermal radiation heater 3 is used to emit thermal radiation with peak values ​​covering multiple different wavelengths to heat the workpiece; At least one photoelectric sensor 4 is used to measure the thermal radiation spectrum emitted or reflected by the workpiece; The controller 5 is used to calculate the absorption peak band and thermal radiation absorptivity of the workpiece based on the thermal radiation spectrum measured by the photoelectric sensor 4, and to control the working peak band of the thermal radiation heater 3 based on the absorption peak band. It also calculates the power ratio of the thermal radiation heater 3 to the thermal convection heater 2 based on the thermal radiation absorptivity, and determines the thermal radiation heating power of the thermal radiation heater 3 and the thermal convection heating power of the thermal convection heater 2 based on the power ratio and the design temperature rise curve of the workpiece.

[0017] Specifically, in one embodiment, the diffuse reflection surface inside the furnace body 1 can be achieved by performing high-intensity sandblasting on the stainless steel substrate of the inner wall of the furnace body 1, followed by depositing an extremely thin high-temperature anti-oxidation diffuse reflection coating (such as a composite ceramic micro-powder coating of alumina and titanium oxide) using physical vapor deposition (PVD) technology. In this structure, when thermal radiation irradiates the furnace wall, it will scatter uniformly in all directions according to Lambert's cosine law, thereby forming a uniform thermal radiation field inside the furnace body 1, similar to an optical integrating sphere, significantly improving the uniformity of heating. In another embodiment, the inner wall of the furnace body 1 can be assembled from prefabricated high-alumina refractory fiber felt, and the surface of the fiber felt can be sprayed with a silicon carbide radiation coating with micron-level roughness. This not only achieves the same excellent diffuse reflection effect but also significantly reduces heat loss from the furnace body 1 by utilizing the low thermal conductivity of the refractory fibers, thus improving energy utilization.

[0018] The use of a diffuse reflective surface on the inner wall of furnace body 1 can avoid the problem of excessive heat focusing in local areas due to the specular reflection of traditional heat radiation on the inner wall of the furnace (i.e., eliminating the hot spot effect), thereby reducing the uneven heating of the workpiece.

[0019] The radiant heat heater 3 is a common heat source in heating furnaces. It uses electromagnetic waves to directly transfer energy to the workpiece, resulting in extremely fast heating. It can serve as the core heat source of the heating system. The convection heat heater 2 is mainly used for heat exchange with the workpiece surface through forced gas flow. Its heating process is relatively gentle, and although its penetration is weak, it produces excellent surface uniformity. It is particularly suitable for overall preheating or heat preservation of temperature-sensitive workpieces with complex surface shapes, and can serve as an auxiliary heat source for the heating system. The system provided by this invention uses a dual heating mechanism of convection and radiation. It can dynamically adjust the power ratio of the two heating methods according to the heat radiation absorption characteristics of different workpieces. While ensuring heating efficiency and shortening the overall heating cycle, it can also take into account the surface temperature uniformity of the workpiece, avoiding the impact of excessively high local temperatures on workpiece performance. At the same time, it accurately matches the preset temperature rise requirements of the workpiece, ensuring the stability of the heating process and the quality of the final product.

[0020] Specifically, the photoelectric sensor 4 can be a phenomenological fiber optic spectrometer or an infrared pyrometer array. The fiber optic spectrometer extends into the furnace chamber via a high-temperature resistant sapphire optical lens and a fiber optic probe, with the probe facing the workpiece surface. The fiber optic spectrometer internally contains a diffraction grating and a high-speed linear CCD / CMOS array or InGaAs detector array, capable of instantaneously (millisecond-level) acquiring high-resolution continuous spectral curves in the wavelength range from 0.3 micrometers (ultraviolet) to 2.5 micrometers (near-mid-infrared). This implementation offers extremely high precision, accurately capturing the minute characteristic absorption peaks of materials at specific wavelengths, making it ideal for heating control of composite battery casings with complex compositions and diverse surface coatings.

[0021] The multi-channel narrowband filter-type infrared pyrometer array consists of multiple independent infrared detector elements, each equipped with a narrowband interference filter with a different center wavelength (e.g., corresponding to 2.1 μm, 3.9 μm, 5.0 μm, 7.9 μm, etc.). Although this implementation cannot obtain a continuous spectrum, it offers faster response speed in key characteristic bands, stronger resistance to high furnace temperature background interference, lower cost, and extremely high reliability. It is particularly suitable for use in hot stamping preheating production lines for metal battery casings in environments with extremely high temperatures and large dust levels.

[0022] Preferably, in order to obtain an accurate thermal radiation spectrum inside the furnace body 1, multiple photoelectric sensors 4 can be arranged at multiple different locations inside the furnace body 1 to synchronously collect thermal radiation signals from the battery casing at different locations. All collected spectral data are integrated through a signal fusion algorithm to offset the positional error caused by single-point acquisition, thereby further improving the accuracy of temperature measurement and spectral feature recognition.

[0023] Specifically, in some embodiments, the thermal radiation heater 3 can use a single heat source to achieve a wide range of thermal radiation. According to Wien's displacement law in physics, the higher the absolute temperature of the heating source, the shorter the peak wavelength of its radiant energy. Therefore, burning the lamp to extremely high brightness (over two thousand degrees Celsius) emits short waves; keeping it in a dark red or non-visible light state (several hundred degrees Celsius) emits mainly medium or long waves. Although this method can achieve continuous adjustment of the peak wavelength of thermal radiation and has a wider adaptability to material differences, the peak wavelength of thermal radiation is controlled by the power of the heater, and the power of thermal radiation cannot be changed in a fixed wavelength range, making the adjustment inflexible.

[0024] In some embodiments, the thermal radiation heater 3 provided in this application is composed of three independent heating modules with different wavelengths: a short-wave heater (emitting thermal radiation with wavelengths between 0.5 and 3 micrometers); a medium-wave heater (emitting thermal radiation with wavelengths between 3 and 8 micrometers); and a long-wave heater (emitting thermal radiation with wavelengths between 8 and 14 micrometers). The short-wave heater can use a double-ended quartz tungsten filament infrared lamp filled with halogen gas, with a color temperature exceeding 2500K. It has extremely high radiation energy and strong penetrating power, capable of quickly penetrating the surface layer of certain translucent composite materials to reach the interior. The medium-wave heater uses an infrared quartz heating tube with carbon fiber braided tape as the heating element. It heats up rapidly, and its spectral radiation highly coincides with the absorption intrinsic frequency of most plastic materials. The long-wave heater uses a ceramic heating brick (with embedded resistance wire) coated with a far-infrared high-radiation coating. Its surface temperature is relatively low (typically between 400°C and 800°C), but the generated long-wave radiation has an excellent gentle heating effect on the paint layer of metal surfaces or specific polymer resins, and is less likely to cause surface charring.

[0025] In some embodiments, the thermal radiation heater 3 can also be integrated into a silicon carbide / molybdenum disilicide composite heating element. This element is divided into three independent power supply zones, with the current density of each zone controlled by an independent high-frequency transformer and a thyristor voltage regulator. Utilizing the temperature differences between the zones (high-temperature zone generates short waves, medium-temperature zone generates medium waves, and low-temperature zone generates long waves), independent adjustment across the entire spectrum can be achieved within a single physical module. When the controller 5 detects an extremely high absorption peak at a 5-micron wavelength for a specific carbon fiber battery casing, the system not only increases the total power of the thermal radiation but also precisely and significantly increases the output power of the medium-wave heater while suppressing the output of short and long waves.

[0026] Specifically, the thermal radiation heater 3 can be in the form of a multi-heat source array, for example... Figure 2The 4×4 heating module array shown is composed of three independent heat sources integrated into each heating module. This multi-heat source array can not only adjust the heat radiation intensity of different wavelengths, but also ensure the uniformity of heat radiation intensity in each area within the furnace body 1.

[0027] Specifically, in some embodiments, the heat convection heater 2 in the heating system provided in this application includes: a heating unit 21, a blower 22, a wind speed sensor 23, and a temperature sensor 24. The heating unit 21 is used to heat the airflow and can be a finned electric heating tube array or a PTC ceramic heater. The blower 22 is used to force the gas inside the furnace body 1 to circulate and can be a high-temperature resistant high-pressure centrifugal fan. The wind speed sensor 23 (e.g., a high-temperature resistant Pitot tube anemometer or a hot-wire anemometer) and the temperature sensor 24 are used to achieve precise closed-loop control of the fluid dynamics. When it is necessary to change the operating state of the heat convection heater 2, the controller 5 can not only adjust the current of the heating unit 21 to control the air temperature, but also dynamically adjust the speed of the blower 22 through a PID algorithm to change the wind speed and adjust the convective heat transfer coefficient.

[0028] Furthermore, considering that the battery casing involves a large amount of active metals (such as magnesium-aluminum alloys) and easily oxidized carbon materials during the heating and forming process, the thermal convection heater 2 also incorporates a protective gas source 25 system for filling the furnace body 1 with protective gas (such as high-purity nitrogen or argon).

[0029] As a preferred real-time method, reference Figure 1 The heating system provided in this application includes one thermal convection heater 2 and two thermal radiation heaters 3. The thermal convection heater 2 includes two blowers 22 respectively arranged on the left and right side walls of the furnace body 1, as well as a wind speed sensor 23 and a temperature sensor 24 installed in the air duct. The two thermal radiation heaters 3 are respectively arranged on the front and rear side walls of the furnace body 1 to heat the workpiece from the side.

[0030] Specifically, the controller 5 can accurately identify which wavelength of thermal radiation the workpiece absorbs most strongly at the current temperature by analyzing the spectral data captured by the photoelectric sensor 4 (i.e., the absorption peak wavelength is measured), and then directly control the thermal radiation heater 3 to work on the peak band that matches the absorption peak wavelength, and dynamically calculate the power distribution ratio (power ratio) between the thermal radiation heater 3 and the thermal convection heater 2 according to the peak absorptivity of the workpiece.

[0031] To enable a workpiece to heat up faster while maintaining a constant total heating power, the key lies in dynamically adjusting the power ratio of thermal radiation and thermal convection heating based on its peak absorptivity. The core principle is: the higher the peak absorptivity of the workpiece for thermal radiation, the greater the proportion of power allocated to thermal radiation heating should be.

[0032] The power ratio (R) is defined as the ratio of the power (P_rad) of the radiant heater 3 to the power (P_conv) of the convection heater 2. Its value can be set to a non-zero real number from 1 to 9, and can be calculated using the following formula: R=k*α_peak in: α_peak is the peak absorptivity (i.e., thermal radiation absorptivity, typically ranging from 0 to 1) of the workpiece in a specific wavelength band (usually near the absorption peak wavelength), as measured by the controller 5 through the broadband heating light source and the photoelectric sensor 4.

[0033] k is the system adjustment coefficient (k > 0), which is a constant that needs to be calibrated experimentally to map the absorption rate to a reasonable power distribution range.

[0034] After obtaining the power ratio R, and combining it with the total heating power P_total set by the system, the specific power of the two parts can be calculated separately: P_rad = P_total * [R / (R+1)] P_conv=P_total*[1 / (R+1)] If the system detects that the currently placed component is a composite battery casing with a heat-absorbing coating, which has an extremely high peak absorption rate for thermal radiation, the controller 5 will significantly increase the power ratio of the radiant heater 3, utilizing the high efficiency of radiant heating to quickly raise the workpiece temperature. Conversely, if the placed component is a smooth, polished aluminum alloy part, the system detects that it exhibits high reflection and low absorption characteristics for most thermal radiation. In this case, simply increasing the radiation power would only lead to overheating of the furnace wall and energy waste. The controller 5 will then quickly adjust its strategy, increasing the power ratio of the convection heater 2, relying on forced convection of the high-temperature airflow to complete the heating. After determining the power ratio, the controller 5, combined with the workpiece's preset process requirements (i.e., the designed temperature rise curve), accurately calculates and outputs the absolute target power of the radiant heater 3 and the convection heater 2.

[0035] This application effectively solves the problem that existing technologies cannot detect differences in workpiece materials through a real-time "sensing-computing-response" closed-loop mechanism, and achieves the optimal configuration of energy delivery. It ensures that battery casings of different materials can be heated strictly according to the ideal temperature rise rate, preventing thermal damage, and significantly shortens the overall heating cycle time, reducing the ineffective energy consumption of the equipment.

[0036] Specifically, due to the diffuse reflection of the inner surface of the furnace body 1, when measuring the thermal radiation spectrum emitted or reflected by the workpiece, the thermal radiation received by the photoelectric sensor 4 includes not only the thermal radiation spectrum reflected or emitted by the workpiece, but also the thermal radiation emitted by the thermal radiation heater 3, which will affect the calculation result of the workpiece's thermal radiation absorptivity. To address this, the thermal radiation absorptivity of the present invention is obtained through the following steps: S1. Before the workpiece enters the furnace body 1, the thermal radiation heater 3 emits broadband thermal radiation into the furnace body 1 and sets a radiation stabilization time. During this period, the heating elements (such as tungsten wires or silicon carbide rods) inside the broadband heating light source rapidly heat up from room temperature and reach thermal equilibrium, resulting in a stable spectral distribution. This avoids transient spectral shifts caused by instability of the light source, typically set to 2 to 5 seconds based on the thermal inertia of the light source. Once the spectrum stabilizes, the photoelectric sensor 4 collects the furnace reflection spectrum (i.e., empty furnace reflection spectrum) from all directions in the empty furnace state. Since there is no workpiece in the furnace at this time, this spectrum fully represents the background reflection characteristics of the current furnace body 1 system itself and stores it in the memory of the controller 5 as a dynamic baseline.

[0037] S2. After the workpiece to be heated is fed into the furnace body 1 and positioned, before the formal heating begins, the thermal radiation heater 3 emits the same broadband thermal radiation again. After the radiation stabilization time, the photoelectric sensor 4 measures and acquires the measured reflectance spectrum including the workpiece. The controller 5 calculates the absorption peak band of the workpiece based on the empty furnace reflectance spectrum and calculates the thermal radiation absorptivity of the workpiece in the absorption peak band.

[0038] Specifically, the controller 5 performs differential comparison between the measured reflection spectrum containing the thermal radiation emitted by the workpiece and the pre-acquired empty furnace reflection spectrum. By comparing the energy attenuation of the two at various wavelengths, the radiation energy absorption band caused purely by the workpiece itself can be accurately separated, thereby accurately calculating the absorption peak band of the workpiece, and further integrating to calculate the absolute thermal radiation absorptivity of the workpiece in the absorption peak band.

[0039] After obtaining the power ratio of the three heaters, it is necessary to determine their respective heating power based on the design temperature rise curve of the workpiece. Specifically, this includes the following steps: S3. Measure the real-time temperature of the workpiece, calculate the real-time temperature gradient, and derive the functional relationship between the real-time temperature gradient and the total real-time heating power based on the real-time temperature gradient and the total real-time heating power obtained at all sampling times. Establish the temperature gradient-power function with the total heating power as the dependent variable and the temperature gradient as the independent variable. For example, after T time intervals, T-1 real-time temperature gradient values ​​and corresponding T-1 total power values ​​are obtained. A function curve (temperature gradient - power function) is fitted to represent the temperature gradient and total power. The workpiece is heated by both convection and radiation. According to Newton's law of cooling, the convective heat transfer density is linearly related to the temperature difference between the workpiece and the convection flow. The temperature gradient power function contains at least one first-order term representing convection. For radiation, although according to the Stefan-Boltzmann law, the net radiative heat transfer is linearly related to the fourth power of the object's absolute temperature (the absolute temperature of the radiative heater), considering that the net radiative heat transfer absorbed by the workpiece is linearly related to its temperature gradient (linearly related to the workpiece's mass and specific heat capacity), and that the absolute temperature of the radiative heater can be approximated as linearly related to its own power under most operating conditions, the radiative power and the workpiece's temperature gradient can be simplified to a linear relationship. For heat conduction heating, according to Fourier's law of heat conduction, the heat conduction rate is linearly related to the temperature gradient. In summary, the temperature gradient power function can be obtained by fitting the coefficients of a polynomial containing three linear terms using recursive least squares or a multilayer perceptron neural network.

[0040] Specifically, the workpiece temperature can be measured using either a contact temperature sensor 24 or an infrared thermometer. Of course, the photoelectric sensor 4 used in this application also has temperature measurement capabilities, utilizing Planck's law of blackbody radiation and a two-color or multi-color colorimetric temperature measurement algorithm (which compensates for errors caused by changes in emissivity by calculating the ratio of radiant energy at two or more adjacent wavelengths) to accurately determine the real-time absolute temperature of the workpiece surface. This part is prior art and will not be elaborated further here.

[0041] S4. Calculate the real-time temperature gradient deviation between the real-time temperature gradient and the target temperature gradient. When the real-time temperature gradient deviation value is greater than the safety threshold, calculate the required total heating power based on the real-time temperature gradient and the temperature gradient-power function. Calculate the thermal radiation heating power and thermal convection heating power based on the total heating power and the power ratio.

[0042] To avoid frequent oscillations caused by minor noise, a safety threshold is set for the system. Only when the real-time temperature gradient deviation exceeds this threshold, indicating a significant deviation of the workpiece's temperature rise rate from the process requirements (e.g., excessively rapid heating may cause blistering on the polymer surface, while excessively slow heating affects the cycle time), will the controller 5 not only perform simple proportional adjustments but also substitute the current real-time temperature gradient into the newly established high-dimensional "temperature gradient-power function." By solving the inverse function or using gradient descent, it accurately calculates the total heating power "truly needed" for the temperature rise rate to return to the target value at the next moment. The controller 5 multiplies this macroscopic total heating power by the power ratio previously calculated based on the absorptivity, precisely extracts and issues specific thermal radiation heating power and thermal convection heating power commands to the underlying actuators, achieving adaptive feedforward temperature control. Example 2

[0043] In practical applications, due to the varying sizes and models of battery casings produced, it is often necessary to heat multiple battery casings simultaneously to improve production efficiency. If the heater arrangement provided in Embodiment 1 is used to heat multiple battery casings at the same time, it will inevitably lead to mutual obstruction of heat radiation and heat convection, resulting in uneven heating of battery casings in different locations.

[0044] In this embodiment, a rotating support mechanism 6 is provided inside the furnace body 1 to support and drive the workpiece to rotate, thereby changing the heated surface of the workpiece during the heating process and achieving uniform heating of the workpiece.

[0045] Specifically, the rotating support mechanism 6 includes a drive motor 61 (such as a servo geared motor with a water-cooled flange installed outside the furnace body 1) and at least one support component 62. The support component 62 can drive the workpiece to rotate around a first direction under the drive of the drive motor 61. The first direction is the vertical direction, so that different positions of the workpiece face the thermal radiation heater 3 during the heating process.

[0046] Specifically, in some embodiments, for lighter composite material upper cover shells, the rotating support mechanism 6 can be set on the top of the furnace body 1, using a stepper motor to drive the suspended high-temperature alloy hook, suspending the shell like a pendulum and rotating it at a uniform speed. This implementation method is often seen in the painting fixtures of automotive parts.

[0047] In some embodiments, the rotating support mechanism 6 may also be disposed at the bottom of the furnace body 1, and a gear transmission mechanism is used to drive the support assembly 62 and the drive motor 61. Specifically, refer to Figure 3 and Figure 4 The rotating support mechanism 6 also includes a central drive gear 63, a transmission assembly 64, and a driven rack 65. The support assembly 62 includes a driven gear 621 and a support platform 622.

[0048] The drive motor 61 is fixedly connected to the furnace body 1. The central drive gear 63 is connected to the drive motor 61 via a transmission assembly 64 (including a transmission shaft and a pair of helical gears). Simultaneously, the central drive gear 63 is rotatably connected to the furnace body 1 (mounted at the bottom of the furnace body 1 via a heat-insulating sealed bearing). The driven rack 65 is slidably connected to the bottom of the furnace body 1. The driven rack 65 has two tooth surfaces: one meshes with the central drive gear 63, and the other meshes with the driven gear 621 of the support assembly 62. The driven gear 621 is rotatably connected to the bottom of the furnace body 1. The support platform 622 is fixedly connected to the driven gear 621. The workpiece is placed on the support platform 622. If necessary, a special fixture can be installed on the support platform 622 to fix the workpiece (the special fixture is not shown in the diagram and needs to be customized according to the shape and size of the workpiece). When the drive motor 61 drives the central drive gear 63 to rotate via the transmission assembly 64, the central drive gear 63 can drive the support platform 622 to rotate via the driven rack 65, thereby causing the workpiece to rotate.

[0049] Specifically, the range of rotation angles that the support platform 622 can rotate can be changed by altering the transmission ratio of the central drive gear 63, the driven rack 65, and the driven gear 621. Under reasonable design, the support platform 622 can rotate 180°, allowing all vertical surfaces of the workpiece to face the thermal radiation heater 3, thus achieving uniform heating of the workpiece.

[0050] The specific implementation of the rotating support mechanism 6 is not limited to Figure 3 and Figure 4 The structure shown can also be rotated by setting a separate drive motor 61 for each support platform 622, but this method is more expensive in practical applications.

[0051] Furthermore, mirror-finished metal materials (such as polished aluminum alloys) have extremely high reflectivity and extremely low absorptivity to thermal radiation. Relying solely on thermal radiation heating would result in a large amount of energy being reflected, leading to low efficiency and potentially overheating of the furnace walls. While convection heating can be effective, its heat transfer rate is relatively slow. Considering the extremely high thermal conductivity of metals, this application also includes a contact heater. Through direct physical contact, it utilizes the excellent thermal conductivity of the metal workpiece itself for rapid heat conduction heating, thereby improving heating efficiency.

[0052] Specifically, the controller compares the calculated thermal radiation absorptivity with a preset reflection threshold (generally set to 0.2~0.3). When the thermal radiation absorptivity is lower than the reflection threshold, it is identified as a mirror surface or a highly reflective metal, and the system switches to a heating mode primarily based on contact heating and thermal convection. The power ratio calculation process then becomes as follows: P_rad=P_total*α_peak P_cont=(P_total-P_rad)*[R / (R+1)] P_conv=(P_total-P_rad)*[1 / (R+1)] Where P_cont is the power of the contact heater (contact heating power).

[0053] Specifically, the construction form of the temperature gradient power function in the above control process also needs to be adjusted accordingly. For heating methods involving heat conduction, according to Fourier's law of heat conduction, the heat conduction rate is linearly related to the temperature gradient. Therefore, the temperature gradient power function can be based on a polynomial containing three linear terms, and then the coefficients can be fitted using recursive least squares or a multilayer perceptron neural network.

[0054] This embodiment directly utilizes thermal radiation absorptivity to reduce the working power of thermal radiation, using thermal radiation heating as an auxiliary heating method, while the remaining heating power is distributed between the contact heater and the thermal convection heater. Through a triple heating mechanism of heat conduction, thermal convection, and thermal radiation, the power ratio of the three heating methods can be dynamically allocated according to the thermal radiation absorption characteristics of different workpieces, further improving the heating efficiency of the workpiece.

[0055] Specifically, in this embodiment, the contact heater can be integrated into the aforementioned support platform 622. For example, the support platform 622 can be made of a high thermal conductivity material (such as beryllium copper alloy or aluminum nitride ceramic) and can directly contact the workpiece. The internal heating element (such as a PTC resistance heating rod or a high-frequency electromagnetic induction heating coil) is embedded inside the support platform 622 or on the side facing away from the workpiece, using the high thermal conductivity material to evenly transfer heat to the workpiece. Furthermore, a flexible thermally conductive pad (such as a high-temperature resistant graphene thermally conductive film or a liquid metal thermally conductive silicone grease composite pad) can be provided on the side of the support platform 622 that contacts the workpiece to fill the tiny gap between the rigid support platform 622 and the workpiece, thereby improving the thermal conductivity.

[0056] In some embodiments, the contact heater can also be disposed in a special fixture to support workpieces with special shapes that are inconvenient to place directly on the support table 622. Accordingly, the support table 622 can be provided with mounting interfaces (such as threaded holes) corresponding to these special fixtures to fix the workpiece on the support table 622. Example 3

[0057] This embodiment provides a control method for controlling a heating system to heat workpieces of different materials. This method is implemented by executing code logic through a microprocessor or industrial control computer pre-installed within the controller. (See reference) Figure 5 Specifically, it includes the following steps: S10. Before heating begins, emit broadband thermal radiation. After the radiation stabilization time, measure the actual reflection spectrum of the workpiece. Calculate the absorption peak band of the workpiece based on the empty furnace reflection spectrum, and calculate the thermal radiation absorptivity of the workpiece in the absorption peak band.

[0058] S20. Calculate the power ratio of the thermal radiation heater, the thermal convection heater, and the contact heater based on the thermal radiation absorptivity.

[0059] S30. Determine the thermal radiation heating power, thermal convection heating power, and contact heating power based on the power ratio and the design temperature rise curve of the workpiece.

[0060] Specifically, the steps for obtaining the reflectance spectrum of an empty furnace are as follows: S11. Before the workpiece enters the furnace, emit broadband thermal radiation into the furnace (for example, the three independent heating modules in Example 1 are fully turned on, emitting thermal radiation from 0.5 to 14 micrometers). After the radiation stabilization time, obtain the furnace reflection spectrum in the empty furnace state, which is the empty furnace reflection spectrum.

[0061] The radiation stabilization time refers to the time required for the spectrum of thermal radiation generated by the broadband heating light source to reach a stable state.

[0062] The reflectance spectrum of an empty furnace generally only needs to be calibrated once before use, and does not need to be calibrated repeatedly before each processing.

[0063] Specifically, the process of obtaining the thermal radiation heating power and the thermal convection heating power includes: S31. During the workpiece heating process, the real-time temperature of the workpiece is obtained and the real-time temperature gradient is calculated.

[0064] S32. Based on the real-time temperature gradient and real-time total heating power obtained at all sampling times, derive the functional relationship between the real-time temperature gradient and the total heating power, and establish the temperature gradient-power function with the total heating power as the dependent variable and the temperature gradient as the independent variable.

[0065] S33. Calculate the real-time temperature gradient deviation between the real-time temperature gradient and the target temperature gradient. When the real-time temperature gradient deviation value is greater than the safety threshold, calculate the required total heating power based on the real-time temperature gradient and the temperature gradient-power function.

[0066] S34. Calculate the thermal radiation heating power, thermal convection heating power, and contact heating power based on the total heating power and power ratio.

[0067] The beneficial effect of the above control method is that by establishing a corresponding function between the temperature gradient and the total heating power, the total heating power can be flexibly adjusted according to the temperature gradient deviation. Combined with the preset power ratio to allocate the heating power of thermal radiation, thermal convection and thermal conduction, it can not only ensure that the heating rate of the workpiece meets the processing requirements, but also maintain the uniformity of the thermal field in the furnace through the combination of the three heating methods, avoid the problem of local overheating or insufficient heating of the workpiece, and improve the quality stability of material heat treatment.

[0068] The method provided in this embodiment can be implemented based on the system provided in Embodiment 2, or it can be implemented based on other heating systems that can implement this method.

[0069] It should be noted that the above-mentioned material heating system and its control method are not only applicable to heating battery casings, but can also be used in other scenarios, such as production processes that require heating, such as mobile phone casings and car bodies.

[0070] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A material heating system, characterized in that, include: A furnace body for holding workpieces, wherein the inner wall of the furnace body is configured as a diffuse reflective surface; A thermal convection heater is used to heat a workpiece by means of thermal convection. Thermal radiation heaters are used to emit thermal radiation with peak values ​​covering multiple different wavelengths to heat workpieces; A contact heater, which comes into direct contact with the workpiece, is used to heat the workpiece through heat conduction. At least one photoelectric sensor is used to measure the thermal radiation spectrum emitted or reflected by the workpiece; The controller is used to calculate the absorption peak band and thermal radiation absorptivity of the workpiece based on the thermal radiation spectrum measured by the photoelectric sensor, and to control the operating peak band of the thermal radiation heater based on the absorption peak band. The controller is also used to activate the contact heater when the thermal radiation absorptivity is lower than a preset reflection threshold, and to calculate the power ratio of the thermal radiation heater, the thermal convection heater and the contact heater according to the thermal radiation absorptivity, and to determine the thermal radiation heating power of the thermal radiation heater, the thermal convection heating power of the thermal convection heater and the contact heating power of the contact heater according to the power ratio and the design temperature rise curve of the workpiece.

2. The system according to claim 1, characterized in that, The thermal radiation absorptivity is obtained through the following steps: Broad-spectrum thermal radiation is emitted into the furnace before the workpiece enters the furnace. After the radiation stabilization time, the furnace reflection spectrum under empty furnace conditions is obtained, which is the empty furnace reflection spectrum. Before heating begins, broadband thermal radiation is emitted. After the radiation stabilization time, the measured reflection spectrum of the workpiece is measured. The absorption peak band of the workpiece is calculated based on the empty furnace reflection spectrum, and the thermal radiation absorptivity of the workpiece in the absorption peak band is calculated. The radiation stabilization time refers to the time required for the spectrum of thermal radiation generated by the thermal radiation heater to reach a stable state.

3. The system according to claim 1, characterized in that, The controller is also used to calculate the real-time temperature of the workpiece based on the thermal radiation spectrum; The steps for the controller to acquire thermal radiation heating power, thermal convection heating power, and contact heating power include: The real-time temperature gradient is calculated based on the real-time temperature of the workpiece, and the functional relationship between the real-time temperature gradient and the total real-time heating power is derived based on the real-time temperature gradient and the total real-time heating power obtained at all sampling times. The temperature gradient-power function is established with the total heating power as the dependent variable and the temperature gradient as the independent variable. Calculate the real-time temperature gradient deviation between the real-time temperature gradient and the target temperature gradient. When the real-time temperature gradient deviation value is greater than the safety threshold, calculate the required total heating power based on the real-time temperature gradient and the temperature gradient-power function. Calculate the thermal radiation heating power, thermal convection heating power, and contact heating power based on the total heating power and the power ratio.

4. The system according to claim 1, characterized in that, The thermal radiation heater includes: Shortwave heaters are used to emit thermal radiation with wavelengths between 0.5 and 3 micrometers. Medium-wave heaters are used to emit thermal radiation with wavelengths between 3 and 8 micrometers. Long-wave heaters are used to emit thermal radiation with wavelengths between 8 and 14 micrometers.

5. The system according to claim 1, characterized in that, The thermal convection heater also includes a protective gas source for filling the furnace body with protective gas.

6. The system according to claim 1, characterized in that, The system also includes a rotating support mechanism for supporting the workpiece; The rotating support mechanism includes a drive motor and at least one support component. The support component can drive the workpiece to rotate around a first direction, which is the vertical direction, under the drive of the drive motor.

7. The system according to claim 6, characterized in that, The contact heater assembly is fixedly connected to the support assembly.

8. A method for controlling a material heating system, used to control the material heating system according to any one of claims 1-7, characterized in that, Includes the following steps: Before heating begins, broadband thermal radiation is emitted. After the radiation stabilization time, the measured reflection spectrum of the workpiece is measured. The absorption peak band of the workpiece is calculated based on the empty furnace reflection spectrum, and the thermal radiation absorptivity of the workpiece in the absorption peak band is calculated. Calculate the power ratio of the thermal radiation heater, the thermal convection heater, and the contact heater based on the thermal radiation absorptivity. The thermal radiation heating power, thermal convection heating power, and contact heating power are determined based on the power ratio and the design temperature rise curve of the workpiece.

9. The method according to claim 8, characterized in that, The empty furnace reflectance spectrum was obtained through the following steps: Broad-spectrum thermal radiation is emitted into the furnace before the workpiece enters the furnace. After the radiation stabilization time, the furnace reflection spectrum under empty furnace conditions is obtained, which is the empty furnace reflection spectrum. The radiation stabilization time refers to the time required for the spectrum of thermal radiation generated by the thermal radiation heater to reach a stable state.

10. The method according to claim 8, characterized in that, The process of obtaining the thermal radiation heating power, thermal convection heating power, and contact heating power includes: The real-time temperature of the workpiece is acquired during the heating process, and the real-time temperature gradient is calculated. Based on the real-time temperature gradient and real-time total heating power obtained at all sampling times, the functional relationship between the real-time temperature gradient and the total heating power is derived. With the total heating power as the dependent variable and the temperature gradient as the independent variable, the temperature gradient-power function is established. Calculate the real-time temperature gradient deviation between the real-time temperature gradient and the target temperature gradient. When the real-time temperature gradient deviation value is greater than the safety threshold, calculate the required total heating power based on the real-time temperature gradient and the temperature gradient-power function. Calculate the thermal radiation heating power, thermal convection heating power, and contact heating power based on the total heating power and power ratio.

Images