A preheating tunnel furnace for armature spraying

Abstract

This application relates to the field of heating device technology, specifically to a preheating tunnel furnace for armature spraying, comprising a feeding section, a gradient heating section, a heat preservation section, and a discharge section, as well as a conveying system and an intelligent control system running through each section; the gradient heating section is equipped with a composite heating system, including multiple sets of variable frequency electromagnetic induction coil heating modules and tunable mid-wave infrared heating modules arranged symmetrically in the upper and lower parts; the intelligent control system is used to adjust the electromagnetic induction working frequency of 10kHz-100kHz to control the skin depth of 0.1mm-0.5mm, and simultaneously adjust the mid-wave infrared emission wavelength of 2.0μm-4.0μm to control the penetration depth of 0.05mm-0.3mm, forming a controllable surface gradient temperature field in the thickness direction of the thin sheet-like soft magnetic alloy armature, so that the temperature of the coating bonding layer of 0.1mm-0.3mm on the armature surface reaches 220℃-260℃, and the internal substrate temperature below 0.3mm does not exceed 100℃. This invention achieves gradient preheating with high surface temperature and low internal temperature by combining heating and intelligent control of energy injection depth, thus ensuring coating adhesion while avoiding overheating of the substrate.

Description

Technical Field

[0001] This application relates to the field of heating device technology, specifically to a preheating tunnel furnace for armature spraying. Background Technology

[0002] The armature is a key magnetic component in an electric motor, made of thin, laminated soft magnetic alloy sheets. Preheating is required before applying the insulating coating. Traditional tunnel furnaces often use hot air circulation or far-infrared radiation heating, with heat conducted from the surface inwards. Due to the anisotropic thermal conductivity and small heat capacity of the thin, laminated structure, the core temperature is easily overheated, causing insulation damage between sheets and attenuation of the substrate's magnetic properties. Lowering the heating temperature makes it difficult to reach the 220°C or higher required for coating curing, resulting in insufficient adhesion.

[0003] Existing technologies generally aim for "uniform heating," but this is precisely the cause of thermal deformation, magnetic performance degradation, and excessive energy consumption. While fixed-frequency electromagnetic induction heating can utilize the skin effect, the frequency is not adjustable, and the skin depth is fixed, making it impossible to meet the precise heating depth requirements of different armature specifications, and it is also difficult to form a stable and controllable temperature gradient in the thickness direction. Infrared heating has a fixed wavelength and a single penetration depth, making it impossible to coordinate with induction heating. In addition, traditional methods often result in uneven heating of the upper and lower surfaces, affecting coating consistency. Summary of the Invention

[0004] The purpose of this application is to provide a preheating tunnel furnace for armature spraying.

[0005] This application provides a preheating tunnel furnace for armature spraying, comprising a feeding section, a stepped heating section, a heat preservation section and a discharge section connected in sequence, as well as a conveying system and an intelligent control system running through each section;

[0006] The gradient heating section is equipped with a composite heating system, which includes multiple sets of variable frequency electromagnetic induction coil heating modules and tunable mid-wave infrared heating modules arranged symmetrically in the upper and lower parts.

[0007] The intelligent control system is electrically connected to the variable frequency electromagnetic induction coil heating module and the tunable mid-wave infrared heating module, respectively. It is used to adjust the working frequency of the electromagnetic induction to control the skin depth of the induction heating. The working frequency of the electromagnetic induction is adjustable from 10kHz to 100kHz, corresponding to a skin depth of 0.1mm to 0.5mm. At the same time, it adjusts the emission wavelength of the mid-wave infrared to control the penetration depth of the infrared heating. The emission wavelength of the mid-wave infrared is adjustable from 2.0μm to 4.0μm, corresponding to a penetration depth of 0.05mm to 0.3mm, so that a controllable surface gradient temperature field is formed in the thickness direction of the thin sheet soft magnetic alloy armature.

[0008] The controllable surface gradient temperature field satisfies that the coating bonding layer temperature of the armature surface (0.1mm-0.3mm) is 220℃-260℃, and the internal substrate temperature of the armature (below 0.3mm) is ≤100℃.

[0009] Furthermore, the gradient heating section is divided into at least three temperature control zones along the conveying direction. The frequency conversion electromagnetic induction coil and the tunable mid-wave infrared heating module of each temperature control zone can independently adjust the frequency, wavelength and heating power, so that the armature forms a longitudinal gradient temperature rise along the conveying direction, with a heating rate between 5℃ / min and 15℃ / min.

[0010] Furthermore, it also includes an online gradient temperature field detection system, which includes an infrared thermal imager detection unit installed at the outlet of the heat preservation and heat equalization section and a thermocouple array detection unit embedded in the tooling of the conveying system;

[0011] The infrared thermal imager detection unit is used to detect the temperature distribution on the surface of the armature in real time, and the thermocouple array detection unit includes at least three miniature thermocouples corresponding to different depth positions of the armature, which are used to detect the internal temperature of the armature in real time.

[0012] Furthermore, the intelligent control system is equipped with a multi-physics coupled mathematical model of "sensing frequency-infrared wavelength-power-temperature gradient" to dynamically adjust heating parameters according to the following priorities based on the actual temperature data obtained by the online detection system, so as to control the accuracy of the temperature gradient in the armature thickness direction:

[0013] First priority: Adjust the operating frequency of the electromagnetic induction and change the skin depth;

[0014] Second priority: Adjust the emission wavelength of mid-wave infrared to change the penetration depth;

[0015] Third priority: Adjust the heating power of electromagnetic induction and mid-wave infrared.

[0016] Furthermore, the conveying system includes a conveying chain and multiple clamping components. The conveying bar is provided with a mounting platform, and the clamping components are mounted on the mounting platform. The multiple clamping components are spaced apart and are connected to the conveying chain for transmission. Adjacent sets of clamping components are staggered.

[0017] Furthermore, it also includes a self-rotating component, which includes a fixed rack and a transmission gear. The fixed rack is fixedly arranged along the feeding direction, and the transmission gear is rotatably arranged on the mounting platform and is connected to the fixed rack in a transmission manner. The clamping component is arranged on the transmission gear.

[0018] Furthermore, the heat preservation section is a heat preservation and heat equalization section, used to maintain the controllable surface gradient temperature field of the armature stable for 30s-300s; the end of the heat preservation and heat equalization section is connected to a spraying transition section, the length of which is ≤0.5m and is sealed to the spraying chamber.

[0019] Furthermore, the inner sides of the spraying transition section are respectively provided with liftable water-cooled isolation doors. The isolation doors are closed during spraying to prevent spraying dust from entering the heating section.

[0020] Furthermore, it also includes a gas protection system, which includes a nitrogen circulation unit and a triple air curtain device;

[0021] The nitrogen circulation system is set in the gradient heating section and the heat preservation and heat homogenization section to keep the oxygen concentration in the furnace ≤20ppm and the pressure in the furnace between 50Pa and 100Pa.

[0022] The triple air curtain device is respectively installed at the inlet of the feeding section and the outlet of the discharging section, and consists of an air curtain, a nitrogen curtain and an inert gas curtain from the outside to the inside.

[0023] A preheating control method for a preheating tunnel furnace for armature spraying, based on the aforementioned preheating tunnel furnace, includes the following steps:

[0024] S1. A multi-physics field coupling database of "armature material-thickness-coating requirements-induction frequency-infrared wavelength-power-temperature gradient" is established in advance, and the optimal heating control parameters are automatically matched according to the specific parameters of the armature to be processed.

[0025] S2, place the armature to be preheated on the clamping assembly, and continuously feed it into the gradient heating section through the conveyor chain, controlling the armature to rotate at a speed of 30rpm-60rpm;

[0026] S3, start the composite heating system, adjust the electromagnetic induction frequency and infrared wavelength according to the matching parameters, so that the armature forms a controllable surface gradient temperature field with a surface temperature of 220℃-260℃ on the 0.1mm-0.3mm surface and ≤100℃ inside;

[0027] S4, send the heated armature into the heat preservation and heat equalization section to maintain a stable temperature field for 30s-300s;

[0028] S5 uses an infrared thermal imager and a thermocouple array to detect the temperature gradient in real time. When the actual value deviates from the set value, the heating parameters are dynamically adjusted according to the following priorities to control the temperature gradient accuracy in the armature thickness direction:

[0029] First priority: Adjust the operating frequency of the electromagnetic induction and change the skin depth;

[0030] Second priority: Adjust the emission wavelength of mid-wave infrared to change the penetration depth;

[0031] Third priority: Adjust the heating power of electromagnetic induction and mid-wave infrared;

[0032] S6, the heat-insulated armature is directly transported to the spraying station through the spraying transition section, with a transfer time of ≤2s and a surface temperature drop of ≤5℃.

[0033] The beneficial effects of this application are as follows: This invention utilizes a combination of frequency conversion electromagnetic induction and tunable mid-wave infrared composite heating, along with intelligent control, to precisely form a controllable surface gradient temperature field along the thickness direction of a thin-film soft magnetic alloy armature. The induction frequency is adjustable between 10kHz and 100kHz, with a skin depth infinitely variable from 0.1mm to 0.5mm; the infrared wavelength is adjustable between 2.0μm and 4.0μm, with a penetration depth continuously adjustable from 0.05mm to 0.3mm. The synergistic effect of these two energy sources concentrates heat highly on the 0.1mm-0.3mm coating bonding layer, maintaining a stable temperature of 220℃-260℃, perfectly matching the melting and curing requirements of powder coatings. Simultaneously, it ensures that the substrate temperature below 0.3mm does not exceed 100℃, effectively preventing insulation aging and magnetic performance degradation between stacked layers. The symmetrically arranged heating modules, combined with the rotating conveyor, eliminate circumferential temperature differences, significantly improving coating thickness consistency. The intelligent control system dynamically adjusts the frequency, wavelength, and power based on real-time detection, achieving closed-loop control of the gradient temperature field with high precision and fast response. Because energy is precisely applied to the required surface layer, ineffective heating of the core is avoided, resulting in a significant improvement in overall thermal efficiency and outstanding energy-saving performance. This invention breaks through the traditional overall uniform temperature mode, realizing an "external heat, internal cool" gradient field. While ensuring excellent coating adhesion, it also preserves the magnetic properties of the substrate, significantly reducing the scrap rate and improving the armature coating yield and motor reliability. Attached Figure Description

[0034] Figure 1 This is a structural diagram of a preheating tunnel furnace for armature spraying according to this application;

[0035] Figure 2 This is a schematic diagram of the self-rotating component in this application;

[0036] Figure 3 This is a flowchart of a preheating control method according to this application.

[0037] Reference numerals: 1. Feeding section; 2. Gradient heating section; 3. Insulation section; 4. Discharge section; 5. Conveying system; 51. Conveying chain; 52. Clamping assembly; 53. Mounting platform; 6. Spraying transition section; 61. Water-cooled isolation door; 7. Online detection system; 8. Rotation assembly; 81. Fixed rack; 82. Transmission gear; 9. Triple air curtain device. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0039] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0040] In the embodiments provided in this application, it should be understood that the disclosed apparatus and methods can also be implemented in other ways. The apparatus embodiments described above are merely illustrative. For example, the flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of apparatus, methods, and computer program products according to various embodiments of this application. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than those marked in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram and / or flowchart, and combinations of blocks in block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions.

[0041] In addition, the functional modules in the various embodiments of this application can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0042] If the aforementioned functions are implemented as software functional modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0044] In view of this, the first aspect of this application provides a preheating tunnel furnace for armature spraying.

[0045] Example 1

[0046] Reference Figure 1 This embodiment discloses a preheating tunnel furnace for armature spraying. The preheating tunnel furnace is a segmented closed furnace structure. Along the material conveying direction, the feeding section 1, gradient heating section 2, heat preservation and homogenization section, spraying transition section 6, and discharge section 4 are arranged in sequence. Each section is sealed and connected to form a through furnace cavity. It is equipped with a conveying system 5, a composite heating system, a gradient temperature field online detection system 7, an intelligent control system, and a gas protection system. All structural units work together to complete the continuous preheating operation of the armature.

[0047] Each section of the furnace body adopts a multi-layered insulated composite furnace wall structure, which serves to insulate against heat loss and maintain a stable furnace cavity temperature. The gradient heating section 2 is divided into at least three independent temperature control zones along the conveying direction. Each temperature control zone is equipped with an insulated partition, which can achieve independent temperature control of each zone to meet the longitudinal gradient heating requirements of the armature. The insulation layer thickness of the furnace wall in the heat-insulating and homogenizing section is greater than that in the gradient heating section 2. It relies solely on its own insulation performance to maintain a stable internal temperature field without the need for additional active heating devices. The spraying transition section 6 connects the heat-insulating and homogenizing section with the external spraying chamber. Its overall length is limited. The inner side of the transition section is equipped with liftable water-cooled isolation doors 61. The isolation doors have cooling channels inside and are coated with a high-temperature resistant, non-stick coating. They can be closed during spraying operations to prevent dust from flowing back into the furnace cavity.

[0048] Reference Figure 2The conveying system 5 runs through all sections of the furnace body and includes a conveyor chain 51, mounting platforms 53, clamping assemblies 52, and a rotating assembly 8. The conveyor chain 51 is a closed-loop transmission structure, with its operating speed controlled by a frequency converter, allowing for stepless speed adjustment to adapt to different process cycles. Multiple mounting platforms 53 are equidistantly fixed to the surface of the conveyor chain 51 and move synchronously with the chain. The clamping assemblies 52 are mounted above the mounting platforms 53 and are made of high-temperature resistant insulating material. They limit and fix the armature using a multi-point contact method, contacting only the non-coated edge area of ​​the armature to reduce local temperature deviations caused by contact heat exchange. Multiple clamping assemblies 52 are arranged at intervals, and adjacent clamping assemblies 52 are staggered to improve the utilization rate of the furnace cavity space. The self-rotating component 8 consists of a fixed rack 81 and a transmission gear 82. The fixed rack 81 is fixedly arranged along the conveying direction of the furnace body. The transmission gear 82 is rotatably mounted on the mounting platform 53 and meshes with the fixed rack 81. The clamping component 52 is fixedly connected above the transmission gear 82. During the movement of the conveying chain 51, the transmission gear 82 rolls and meshes with the fixed rack 81, driving the clamping component 52 and the armature to rotate at a uniform speed.

[0049] In some embodiments, the rotation component 8 can be replaced by an independent drive structure. Each clamping component 52 is configured with a micro drive component. Each drive component is independently controlled and can adjust the rotation speed of a single armature individually, adapting to the synchronous processing conditions of multiple armature specifications.

[0050] The composite heating system is deployed within each temperature control zone of the gradient heating section 2. It includes multiple sets of variable frequency electromagnetic induction coil heating modules and tunable mid-wave infrared heating modules, both types of heating modules being symmetrically arranged vertically. The variable frequency electromagnetic induction coil heating modules are equipped with variable frequency power supply units, which can adjust the electromagnetic induction operating frequency and control the skin depth of induction heating through frequency changes. The tunable mid-wave infrared heating modules are equipped with tuning power supply units, which can adjust the infrared radiation emission wavelength and control the infrared heating penetration depth through wavelength changes. The heating modules in each temperature control zone can independently adjust their frequency, wavelength, and heating power, achieving zoned differentiated heating control.

[0051] The gradient temperature field online detection system 7 includes an infrared thermal imager detection unit and a thermocouple array detection unit. The infrared thermal imager detection unit is installed at the outlet of the heat preservation and heat dissipation section to collect the surface temperature distribution of the armature in a non-contact manner; the thermocouple array detection unit is embedded inside the clamping assembly 52 and has at least three miniature thermocouples arranged to correspond to different depth positions of the armature to collect multi-layer temperature data inside the armature in a contact manner.

[0052] In some embodiments, auxiliary infrared temperature measuring devices can be added to the outlet of each temperature control zone of the gradient heating section 2 to collect the armature heating temperature in real time and provide feedforward control data for the intelligent control system.

[0053] The intelligent control system is electrically connected to the conveying system (5), composite heating system, online detection system (7), and gas protection system. It incorporates a data storage unit, a multi-physics coupling calculation unit, and an execution control unit. The storage unit stores preset process parameters, multi-physics coupling mathematical models, and a process database. The calculation unit receives temperature measurement data and performs temperature gradient calculations, deviation comparisons, and parameter optimization calculations. The execution control unit issues commands to regulate the conveying speed, rotation speed, heating module operating parameters, and gas system operating status.

[0054] The gas protection system includes a nitrogen circulation unit and a triple gas curtain device 9. The nitrogen circulation unit connects the gradient heating section 2 and the heat preservation and soaking section of the furnace cavity, continuously supplying inert protective gas to the furnace cavity to maintain a slightly positive pressure environment, control the oxygen concentration in the furnace, and simultaneously achieve heat exchange and reuse of the protective gas. The triple gas curtain device 9 is installed at the inlet of the feeding section 1 and the outlet of the discharging section 4, respectively. It consists of three layers of air curtains—an air curtain, a nitrogen curtain, and an inert gas curtain—arranged sequentially from the outside to the inside, preventing outside air from seeping into the furnace cavity and reducing the leakage of internal protective gas.

[0055] Example 2

[0056] Reference Figure 3 This application discloses a preheating control method, including: S1 establishing a multiphysics coupling database corresponding to armature parameters and heating control parameters in advance, and automatically matching the optimal heating control parameters based on the armature parameters to be processed.

[0057] A multiphysics coupled mathematical model is constructed, which is divided into an electromagnetic field module, a heat conduction module, and a structural mechanics module. Each module is coupled and correlated in pairs for computation. The electromagnetic field module characterizes the distribution of the electromagnetic field in induction heating based on Maxwell's equations.

[0058]

[0059] Where E is the electric field intensity vector, H is the magnetic field intensity vector, ω is the angular frequency, μ is the permeability of the material, ε is the dielectric constant of the material, and J is the current density vector. The relationship between current density and electric field intensity is J = σE, where σ is the conductivity of the material.

[0060] Establish the relationship between frequency and heating depth based on the skin depth formula:

[0061]

[0062] Where δ is the skin depth, ρ is the resistivity of the material, ω is the angular frequency, and μ is the permeability of the material. This formula establishes a quantitative relationship between the operating frequency of electromagnetic induction and the skin depth, providing a theoretical basis for frequency adjustment.

[0063] The heat conduction module uses the Fourier heat conduction equation to characterize the heat transfer behavior inside the armature:

[0064]

[0065] Where ρ is the density of the material, c is the specific heat capacity of the material, T is the temperature, t is the time, k is the thermal conductivity of the material, and Q is the internal heat source density. The internal heat source density Q is provided by the Joule heat calculated by the electromagnetic field module, realizing the coupling between the electromagnetic field and the thermal conduction field.

[0066] The penetration depth of tunable mid-wave infrared heating refers to the depth at which the infrared radiation intensity decays to 1 / e of the surface value, and its calculation formula is as follows:

[0067]

[0068] Where d is the penetration depth. Let λ be the absorption coefficient of the material at wavelength λ. The absorption coefficient of the material varies with the infrared wavelength. This formula can be used to establish a quantitative relationship between the infrared emission wavelength and the penetration depth, providing a theoretical basis for wavelength adjustment.

[0069] The structural mechanics module is used to calculate the thermal stress and deformation of the armature under a temperature gradient. Its governing equations are the equilibrium equations and geometric equations. The relationship between thermal strain and temperature change is as follows:

[0070]

[0071] in, For thermal strain tensor, The thermal expansion coefficient tensor of the material. This represents the temperature change. The total strain tensor consists of the elastic strain tensor and the thermal strain tensor, i.e. According to Hooke's law, the relationship between the elastic strain tensor and the stress tensor is: Where D is the elastic stiffness matrix and σ is the stress tensor. From this, the equation for calculating thermal stress can be obtained:

[0072]

[0073] Changes in the temperature field can affect the mechanical properties of materials, such as the coefficient of thermal expansion and the modulus of elasticity, which in turn affects the calculation results of thermal stress and deformation, thus achieving the coupling of the heat conduction field and the structural mechanical field.

[0074] Multiple sets of experimental data were collected for model training and validation:

[0075] Thin-film soft magnetic alloy armatures of different materials, thicknesses, and coating requirements were selected as experimental samples. Preheating experiments were conducted under different combinations of electromagnetic induction frequency, infrared wavelength, and heating power. During the experiments, an infrared thermal imager was used to collect the temperature distribution on the armature surface, miniature thermocouples embedded in the sample were used to collect temperature values ​​at different depths, a displacement sensor was used to measure the deformation of the armature, a magnetic property tester was used to measure the change in magnetic properties of the armature before and after preheating, and a tensile testing machine was used to measure the bonding strength between the coating and the substrate.

[0076] The collected experimental data were preprocessed to remove outliers caused by equipment malfunctions, environmental interference, and other factors. The remaining valid data were then standardized, converting data of different dimensions and orders of magnitude into a unified standard format to facilitate subsequent model training and data processing.

[0077] Training and optimizing multiphysics coupling mathematical models:

[0078] The preprocessed experimental data were divided into a training set and a validation set. The training set was used for model training, while the validation set was used for model validation and optimization. The multiphysics coupled mathematical model was trained using the training set data, and the material property parameters, boundary condition parameters, etc., in the model were adjusted to minimize the error between the model's predictions and the experimental data.

[0079] The trained model is validated using validation set data, and evaluation metrics such as mean squared error and mean absolute error between the model's predicted values ​​and experimental values ​​are calculated. If the model's prediction accuracy meets the requirements, the model is used for subsequent database construction; if the model's prediction accuracy does not meet the requirements, the model's parameters and structure are readjusted, and training and validation are performed again until the model's prediction accuracy reaches the predetermined standard.

[0080] Constructing a multiphysics coupled database:

[0081] The trained multiphysics coupled mathematical model, model prediction results under different parameter combinations, experimental data, and corresponding heating control parameters are stored in the database. The database adopts a relational database structure and establishes a mapping relationship between input parameters such as armature material, thickness, and coating requirements and output parameters such as electromagnetic induction frequency, infrared wavelength, heating power, and heating rate.

[0082] The intelligent control system can quickly obtain the corresponding optimal heating control parameters by querying a database based on the specific parameters of the armature to be processed. Simultaneously, the database supports dynamic updates; new experimental data or optimized model parameters can be added to the database in a timely manner, continuously improving its accuracy and applicability.

[0083] In some embodiments, the multiphysics coupling mathematical model can also incorporate an atmosphere field module to consider the influence of gas flow within the furnace on the temperature field. The governing equations of the atmosphere field module include continuity, momentum, and energy equations. By calculating the gas velocity, pressure, and temperature distribution within the furnace, the layout of the heating system and gas flow parameters are optimized. The atmosphere field module and the heat conduction module are coupled through convective heat transfer boundary conditions, using the convective heat transfer between the gas and the armature surface as the boundary condition for the heat conduction module.

[0084] S2 Place the armature to be preheated on the clamping assembly and continuously feed it into the gradient heating section via a conveyor chain, controlling the armature to rotate at a predetermined speed.

[0085] This step is the feeding and conveying stage of the preheating process. The armature to be preheated is continuously fed into the furnace through the conveying system, and the armature is kept rotating during the preheating process by the rotation component to ensure that the armature is heated evenly.

[0086] Prepare the armature and conveying system for preheating:

[0087] Clean the surface of the armature to be preheated, removing oil, dust, scale, and other impurities to prevent them from affecting the preheating effect and coating quality. Check the operation of the conveyor system to ensure that the conveyor chain, mounting platform, clamping components, and rotation components are working properly without any jamming or loosening.

[0088] Place the armature on the clamping assembly and secure it:

[0089] Place the armature to be preheated with the uncoated side facing the clamping assembly on the support position of the clamping assembly. Adjust the clamping force of the clamping assembly to ensure that the armature is firmly fixed and will not shift, shake, or fall off during transport and rotation. The clamping force should be moderate, ensuring the armature is firmly fixed without deforming it due to excessive force.

[0090] Start the conveyor chain to continuously feed the armature into the gradient heating section:

[0091] The drive unit of the conveyor chain is activated, causing the conveyor chain to move at a uniform speed in the predetermined direction. The conveyor chain drives the mounting platform and clamping assembly sequentially through the feeding section, gradient heating section, heat preservation and homogenization section, spraying transition section, and discharge section. The running speed of the conveyor chain can be steplessly adjusted according to the preheating time requirements of the armature to be processed, so as to meet the preheating needs of armatures of different specifications.

[0092] During the conveying process, the gas protection system in the feeding section operates continuously to prevent outside air from entering the furnace. The triple air curtain device at the inlet of the feeding section forms an air curtain, a nitrogen curtain, and an inert gas curtain from the outside to the inside. Through the barrier effect of the multiple layers of air curtains, the exchange between outside air and the gas inside the furnace is effectively blocked.

[0093] The rotation component is activated, controlling the armature to rotate at a predetermined speed:

[0094] When the conveyor chain drives the mounting platform to move along the feeding direction, the transmission teeth roll along the fixed rack, thereby causing the clamping assembly and armature to rotate around their own axis. By adjusting the tooth pitch of the fixed rack and the number of teeth of the transmission teeth, the transmission ratio can be changed, thus adjusting the rotation speed of the armature. The rotation speed of the armature can be adjusted according to the size, shape, and heating requirements of the armature, ensuring that all surfaces of the armature are heated evenly and avoiding temperature gradient deviations and deformation caused by uneven local heating.

[0095] S3 activates the composite heating system, adjusting the electromagnetic induction frequency and infrared wavelength according to matched parameters to create a predetermined, controllable surface gradient temperature field in the armature.

[0096] This step is the heating stage of the preheating process. The armature is heated by a composite heating system to create a controllable surface gradient temperature field in the thickness direction of the armature, where the surface coating bonding layer has a higher temperature and the internal substrate has a lower temperature.

[0097] Based on the specific parameters of the armature to be processed, the optimal heating control parameters are matched from the multiphysics coupling database:

[0098] The parameters such as the material, thickness, and coating requirements of the armature to be processed are input into the intelligent control system. Based on the input parameters, the intelligent control system queries a pre-established multiphysics coupling database to obtain the corresponding optimal heating control parameters, such as the electromagnetic induction frequency, infrared wavelength, heating power, and heating rate. If no perfectly matching parameter combination is found in the database, the intelligent control system will invoke the multiphysics coupling mathematical model to calculate the optimal heating control parameters in real time based on the input parameters.

[0099] Start the composite heating system with gradient heating section:

[0100] The variable frequency electromagnetic induction coil heating modules and the tunable mid-wave infrared heating module of each temperature control zone in the gradient heating section are activated sequentially. The heating modules, which are arranged symmetrically on the top and bottom, start working simultaneously to heat the upper and lower surfaces of the armature synchronously.

[0101] Adjust the electromagnetic induction frequency and infrared wavelength of each temperature control zone according to the matched parameters:

[0102] The intelligent control system sends control signals to the variable frequency electromagnetic induction coil heating module and the tunable mid-wave infrared heating module in each temperature control zone according to the matched heating control parameters. The variable frequency electromagnetic induction coil heating module adjusts its operating frequency according to the control signal to match the skin depth of induction heating with the thickness of the coating bonding layer of the armature. The tunable mid-wave infrared heating module adjusts its emission wavelength according to the control signal to match the penetration depth of infrared heating with the thickness of the coating bonding layer of the armature.

[0103] Through the combined effect of electromagnetic induction and infrared heating, heat is mainly concentrated within the coating bonding layer on the armature surface, while the temperature of the internal substrate rises slowly, thus forming a controllable surface gradient temperature field with a higher surface temperature and a lower internal temperature. This temperature field can meet the surface temperature requirements for coating bonding while avoiding performance changes in the internal substrate due to excessively high temperatures.

[0104] Adjust the heating power of each temperature control zone to create a longitudinal temperature gradient in the armature along the conveying direction:

[0105] The intelligent control system adjusts the heating power of each temperature control zone sequentially according to the matched heating rate parameters. Along the conveying direction, the set temperature of each temperature control zone gradually increases, causing the armature's temperature to gradually rise from the initial temperature to the predetermined surface temperature as it passes through the gradient heating section. The heating rate is controlled within a predetermined range to avoid thermal shock and thermal stress concentration caused by excessively rapid heating.

[0106] The heating power of each temperature control zone can be adjusted independently. The intelligent control system can adjust the heating power in real time based on the actual temperature feedback of the armature in each temperature control zone, ensuring the accuracy and stability of the longitudinal gradient heating. At the same time, the gas protection system works continuously in the gradient heating section, and the nitrogen circulation unit continuously supplies high-purity nitrogen into the furnace to maintain a slightly positive pressure state inside the furnace, keeping the oxygen concentration inside the furnace within a predetermined range and preventing oxidation of the armature surface during the heating process.

[0107] S4 The heated armature is sent into the heat preservation and homogenization section to maintain the controllable surface gradient temperature field of the armature stable for a predetermined time.

[0108] This step is the heat preservation and homogenization stage of the preheating process. The heat preservation and homogenization stage maintains the stability of the controllable surface gradient temperature field of the armature, so that the temperature and microstructure of the coating bonding layer meet the spraying requirements.

[0109] The armature, having reached the predetermined surface temperature, is then fed into the heat-preserving and homogenizing section.

[0110] When the armature passes through the last temperature-controlled zone of the gradient heating section, its surface temperature reaches the predetermined coating bonding temperature. The conveyor chain continues to drive the armature, sending it into the heat-preserving and homogenizing section.

[0111] Maintain the controllable surface gradient temperature field of the armature stable for a predetermined time:

[0112] The armature rotates at a predetermined speed within the heat-preserving and heat-equalizing section, resulting in a more uniform surface temperature distribution and stable temperature of the coating bonding layer, while keeping the internal substrate temperature within a predetermined range. During the heat preservation process, heat is transferred from the armature to the interior via thermal conduction. However, because the initial temperature of the internal substrate is low and the heat preservation time is controlled within a predetermined range, the temperature of the internal substrate will not exceed a predetermined upper limit, thus maintaining the stability of the controllable surface gradient temperature field.

[0113] The holding time is adjusted according to the armature's material, thickness, and coating requirements. An appropriate holding time can homogenize the temperature of the coating bonding layer, eliminate localized temperature differences on the surface, and allow for appropriate changes in the microstructure of the coating bonding layer, thereby improving the bonding strength between the coating and the substrate.

[0114] Real-time monitoring of furnace temperature changes within the heat preservation and heat soaking section:

[0115] Multiple temperature sensors are installed at different locations within the heat preservation and homogenization zone to monitor temperature changes within the furnace in real time. The temperature sensors transmit the collected temperature data to the intelligent control system, which compares the actual furnace temperature with the set furnace temperature. When the furnace temperature deviates from the predetermined range due to heat loss or other reasons, the intelligent control system adjusts the heating power of the temperature control zone at the end of the gradient heating section to compensate for the furnace's heat loss and maintain temperature stability within the heat preservation and homogenization zone.

[0116] Meanwhile, the gas protection system continues to operate in the heat preservation and heat homogenization section, and the nitrogen circulation unit continuously supplies high-purity nitrogen into the furnace to maintain a slightly positive pressure and low oxygen concentration in the furnace, preventing oxidation of the armature surface during the heat preservation process.

[0117] S5 uses an online detection system to monitor the temperature gradient in real time. When the actual value deviates from the set value, it dynamically adjusts the heating parameters according to a predetermined priority to control the temperature gradient accuracy in the armature thickness direction.

[0118] This step is the online detection and closed-loop control stage of the preheating process. The temperature gradient of the armature is detected in real time by the gradient temperature field online detection system, and the heating parameters are dynamically adjusted according to the detection results to ensure the control accuracy of the temperature gradient.

[0119] The gradient temperature field online detection system is activated to monitor the surface and internal temperatures of the armature in real time.

[0120] The infrared thermal imager detection unit acquires real-time infrared radiation images of the armature surface passing through the heat-preserving and homogenizing section outlet, and converts the image data into temperature data. The thermocouple array detection unit acquires real-time temperature data at different depths inside the armature.

[0121] The detected temperature data is transmitted to the intelligent control system to calculate the actual temperature gradient.

[0122] The infrared thermal imager detection unit and the thermocouple array detection unit transmit the collected temperature data to the intelligent control system in real time. The intelligent control system filters and reduces noise in the received temperature data to remove random errors caused by environmental interference, sensor noise, and other factors, thereby improving the accuracy of the temperature data.

[0123] The intelligent control system calculates the actual temperature gradient along the armature thickness based on the armature thickness and temperature values ​​at different depths. The formula for calculating the temperature gradient is:

[0124]

[0125] Where G is the temperature gradient, The average temperature of the armature surface. Let h be the temperature at a predetermined depth inside the armature, and h be the distance from the surface to that depth. By calculating the temperature gradient at different depths, the temperature gradient distribution along the thickness of the armature can be obtained.

[0126] The actual temperature gradient is compared with the set temperature gradient to determine whether it deviates from the predetermined range.

[0127] The intelligent control system compares the calculated actual temperature gradient with the set temperature gradient matched from a multiphysics coupling database, calculating the deviation between the two. The allowable deviation range of the set temperature gradient is determined based on the coating quality requirements and armature performance requirements. If the deviation between the actual and set temperature gradients is within the allowable range, the current heating parameters are kept unchanged, and the preheating process continues. If the deviation exceeds the allowable range, a parameter adjustment program is initiated to dynamically adjust the heating parameters.

[0128] The heating parameters are dynamically adjusted according to a predetermined priority to restore the actual temperature gradient to the set range.

[0129] The intelligent control system adjusts the heating parameters according to a predetermined priority order to restore the actual temperature gradient to the set range as quickly as possible. The priority order for parameter adjustment is as follows: first priority is adjusting the operating frequency of the electromagnetic induction, second priority is adjusting the emission wavelength of the mid-wave infrared, and third priority is adjusting the heating power of both the electromagnetic induction and mid-wave infrared.

[0130] First, the intelligent control system adjusts the operating frequency of the electromagnetic induction. According to the skin depth calculation formula, changes in the electromagnetic induction frequency directly affect the skin depth of induction heating, thereby altering the heating depth and temperature distribution inside the armature. By fine-tuning the electromagnetic induction frequency, the temperature inside the armature can be quickly adjusted, thus changing the temperature gradient along the thickness direction.

[0131] If adjusting the electromagnetic induction frequency does not restore the actual temperature gradient to the set range, the intelligent control system adjusts the emission wavelength of the mid-wave infrared light. According to the infrared penetration depth calculation formula, changes in the infrared wavelength directly affect the penetration depth of infrared heating, thereby altering the temperature distribution on and near the surface of the armature. By fine-tuning the infrared wavelength, the temperature difference between the armature surface and its interior can be further adjusted, restoring the temperature gradient to the set range.

[0132] If adjusting the electromagnetic induction frequency and infrared wavelength does not restore the actual temperature gradient to the set range, the intelligent control system adjusts the heating power of electromagnetic induction and mid-wave infrared. By changing the heating power, the overall heating intensity can be adjusted, thereby adjusting the surface and internal temperatures of the armature, so that the temperature gradient returns to the set range.

[0133] The adjustment range of the parameters is determined based on the magnitude of the actual deviation; the larger the deviation, the larger the adjustment range. The intelligent control system adopts an incremental adjustment method, waiting a certain period of time after each adjustment to observe the change in the temperature gradient before making the next adjustment, thus avoiding over-adjustment. The weighting formula for parameter adjustment is:

[0134]

[0135] in, The total parameter adjustment is represented by w1, w2, and w3, which are the weighting coefficients for frequency adjustment, wavelength adjustment, and power adjustment, respectively. Δf is the frequency adjustment amount, and Δλ is the wavelength adjustment amount. This represents the power adjustment. The weighting coefficients are determined based on the prediction results of the multiphysics coupling model and experimental data to ensure the efficiency and accuracy of parameter adjustment.

[0136] S6 directly conveys the heat-insulated armature to the spraying station through the spraying transition section, with the transfer time and surface temperature drop controlled within a predetermined range.

[0137] This step is the material discharge and spraying connection stage of the preheating process. The spraying transition section achieves a seamless connection between preheating and spraying, reduces the temperature drop and oxidation of the armature surface, and ensures the quality of spraying.

[0138] The armature, having completed its heat insulation and homogenization process, is then transferred from the heat insulation and homogenization section to the spraying transition section.

[0139] After the armature has completed its heat preservation in the heat preservation and homogenization section, the conveyor chain continues to move the armature, sending it from the heat preservation and homogenization section into the coating transition section. The coating transition section forms a closed channel to prevent outside air from entering and to prevent the surface temperature of the armature from dropping.

[0140] Control the status of the isolation doors within the spraying transition section to prevent spraying dust from entering the heating section:

[0141] When the armature passes through the spraying transition section, the isolation door is open, allowing it to pass smoothly. When the armature enters the spraying station to begin spraying, the isolation door closes under the drive of the actuator, blocking the passage between the spraying transition section and the heating section. The closed isolation door effectively prevents dust generated during spraying from entering the heating section, contaminating the heating module and furnace interior, and affecting the normal operation of the heating system. After spraying is completed, the isolation door reopens, awaiting the next armature to pass.

[0142] The armature is directly conveyed to the spraying station for spraying operations:

[0143] The conveyor chain drives the clamping assembly and armature through the spraying transition section, directly reaching the spraying station. The spraying equipment performs spraying operations on the armature's surface, evenly applying the coating material. During the spraying process, the clamping assembly continues to drive the armature to rotate, ensuring the coating evenly covers the entire sprayed surface of the armature, preventing missed areas or uneven coating thickness.

[0144] Because the length of the spraying transition section is controlled within a predetermined range, the transfer time of the armature from the heat preservation and warming section to the spraying station is sufficiently short, and the temperature drop of the armature surface is controlled within a predetermined range, which can meet the surface temperature requirements for spraying. At the same time, the gas protection system in the spraying transition section continues to work, maintaining a low oxygen concentration environment to prevent oxidation of the armature surface during the transfer process.

[0145] The coated armature is then fed out through the discharge section:

[0146] The coated armature continues to move under the drive of the conveyor chain and is sent out of the furnace through the discharge section. The triple air curtain device at the discharge section outlet has the same function as the triple air curtain device at the feed section inlet, preventing outside air from entering the furnace and preventing nitrogen from leaking into the outside environment.

[0147] After the armature cools naturally to room temperature in the discharge section, it is removed from the clamping assembly, completing the entire preheating and spraying process. The clamping assembly, after removing the armature, returns to the feeding section driven by the conveyor chain, ready for the preheating of the next armature.

[0148] The technical solution provided in this embodiment controls the skin depth of induction heating by adjusting the operating frequency of electromagnetic induction and controls the penetration depth of infrared heating by adjusting the emission wavelength of mid-wave infrared radiation. This enables a temperature distribution along the armature thickness direction where the surface coating bonding layer has a higher temperature and the internal substrate temperature is lower. This temperature distribution reduces thermal deformation of the armature during preheating, maintains the performance stability of the internal substrate, and improves the bonding strength between the coating and the substrate. Furthermore, heating only the surface coating bonding layer of the armature reduces energy consumption during preheating and improves energy efficiency. Real-time monitoring of the armature's temperature gradient using an online detection system and dynamic adjustment of heating parameters according to predetermined priorities improves the control accuracy of the temperature gradient and ensures consistency in the preheating quality of armatures from the same batch. A spraying transition section is set to achieve seamless connection between preheating and spraying, reducing temperature drop and oxidation on the armature surface and further improving coating quality. A gas protection system prevents oxidation of the armature surface during preheating, improving the surface quality of the armature.

[0149] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

[0150] It will be apparent to those skilled in the art that this application is not limited to the details of the exemplary embodiments described above, and that this application can be implemented in other specific forms without departing from the spirit or essential characteristics of this application. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this application is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this application. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A preheating tunnel furnace for armature spraying, characterized in that, It includes a feeding section (1), a ladder heating section, a heat preservation section (3) and a discharge section (4) connected in sequence, as well as a conveying system (5) and an intelligent control system running through each section; The gradient heating section (2) is equipped with a composite heating system, which includes multiple sets of variable frequency electromagnetic induction coil heating modules and tunable mid-wave infrared heating modules arranged symmetrically in the upper and lower parts. The intelligent control system is electrically connected to the variable frequency electromagnetic induction coil heating module and the tunable mid-wave infrared heating module, respectively. It is used to adjust the working frequency of the electromagnetic induction to control the skin depth of the induction heating. The working frequency of the electromagnetic induction is adjustable from 10kHz to 100kHz, corresponding to a skin depth of 0.1mm to 0.5mm. At the same time, it adjusts the emission wavelength of the mid-wave infrared to control the penetration depth of the infrared heating. The emission wavelength of the mid-wave infrared is adjustable from 2.0μm to 4.0μm, corresponding to a penetration depth of 0.05mm to 0.3mm, so that a controllable surface gradient temperature field is formed in the thickness direction of the thin sheet soft magnetic alloy armature. The controllable surface gradient temperature field satisfies that the coating bonding layer temperature of the armature surface (0.1mm-0.3mm) is 220℃-260℃, and the internal substrate temperature of the armature (below 0.3mm) is ≤100℃.

2. The preheating tunnel furnace according to claim 1, characterized in that, The gradient heating section (2) is divided into at least three temperature control zones along the conveying direction. The frequency conversion electromagnetic induction coil and the tunable medium-wave infrared heating module of each temperature control zone can independently adjust the frequency, wavelength and heating power, so that the armature forms a longitudinal gradient temperature rise along the conveying direction, with a heating rate between 5℃ / min and 15℃ / min.

3. The preheating tunnel furnace according to claim 1, characterized in that, It also includes an online gradient temperature field detection system (7), which includes an infrared thermal imager detection unit set at the outlet of the heat preservation and heat equalization section and a thermocouple array detection unit embedded in the tooling of the conveying system (5); The infrared thermal imager detection unit is used to detect the temperature distribution on the surface of the armature in real time, and the thermocouple array detection unit includes at least three miniature thermocouples corresponding to different depth positions of the armature, which are used to detect the internal temperature of the armature in real time.

4. The preheating tunnel furnace according to claim 1, characterized in that, The intelligent control system is equipped with a multi-physics coupling mathematical model of "sensing frequency-infrared wavelength-power-temperature gradient" to dynamically adjust the heating parameters according to the following priorities based on the actual temperature data obtained by the online detection system (7) in order to control the temperature gradient accuracy in the armature thickness direction: First priority: Adjust the operating frequency of the electromagnetic induction and change the skin depth; Second priority: Adjust the emission wavelength of mid-wave infrared to change the penetration depth; Third priority: Adjust the heating power of electromagnetic induction and mid-wave infrared.

5. The preheating tunnel furnace according to claim 1, characterized in that, The conveying system (5) includes a conveying chain (51) and multiple clamping components (52). A mounting platform (53) is provided on the conveying bar. The clamping components are mounted on the mounting platform (53). Multiple clamping components (52) are spaced apart and connected to the conveying chain (51) for transmission. Adjacent sets of clamping components are staggered.

6. The preheating tunnel furnace according to claim 5, characterized in that, It also includes a self-rotating component (8), which includes a fixed rack (81) and a transmission gear (82). The fixed rack (81) is fixedly arranged along the feeding direction, and the transmission gear (82) is rotatably arranged on the mounting platform (53) and is connected to the fixed rack (81) in a transmission manner. The clamping component (52) is arranged on the transmission gear (82).

7. The preheating tunnel furnace according to claim 1, characterized in that, The heat preservation section (3) is a heat preservation and heat equalization section, used to maintain the controllable surface gradient temperature field of the armature stable for 30s-300s; the end of the heat preservation and heat equalization section is connected to the spraying transition section (6), the length of the spraying transition section (6) is ≤0.5m, and it is sealed to the spraying chamber.

8. The preheating tunnel furnace according to claim 7, characterized in that, The inner sides of the spraying transition section (6) are respectively provided with liftable water-cooled isolation doors (61). The isolation doors are closed during spraying to prevent spraying dust from entering the heating section.

9. The preheating tunnel furnace according to claim 1, characterized in that, It also includes a gas protection system, which includes a nitrogen circulation unit and a triple air curtain device (9); The nitrogen circulation system is set in the gradient heating section (2) and the heat preservation and heat equalization section to ensure that the oxygen concentration in the furnace is ≤20ppm and the pressure in the furnace is between 50Pa and 100Pa. The triple air curtain device (9) is respectively installed at the inlet of the feeding section (1) and the outlet of the discharging section (4), and from the outside to the inside are an air curtain, a nitrogen curtain and an inert gas curtain.

10. A preheating control method for a preheating tunnel furnace for armature spraying, based on the preheating tunnel furnace according to any one of claims 1-9, characterized in that, Includes the following steps: S1. A multi-physics field coupling database of "armature material-thickness-coating requirements-induction frequency-infrared wavelength-power-temperature gradient" is established in advance, and the optimal heating control parameters are automatically matched according to the specific parameters of the armature to be processed. S2, place the armature to be preheated on the clamping assembly, and continuously feed it into the gradient heating section through the conveyor chain, controlling the armature to rotate at a speed of 30rpm-60rpm; S3, start the composite heating system, adjust the electromagnetic induction frequency and infrared wavelength according to the matching parameters, so that the armature forms a controllable surface gradient temperature field with a surface temperature of 220℃-260℃ on the 0.1mm-0.3mm surface and ≤100℃ inside; S4, send the heated armature into the heat preservation and heat equalization section to maintain a stable temperature field for 30s-300s; S5 uses an infrared thermal imager and a thermocouple array to detect the temperature gradient in real time. When the actual value deviates from the set value, the heating parameters are dynamically adjusted according to the following priorities to control the temperature gradient accuracy in the armature thickness direction: First priority: Adjust the operating frequency of the electromagnetic induction and change the skin depth; Second priority: Adjust the emission wavelength of mid-wave infrared to change the penetration depth; Third priority: Adjust the heating power of electromagnetic induction and mid-wave infrared; S6, the heat-insulated armature is directly transported to the spraying station through the spraying transition section, with a transfer time of ≤2s and a surface temperature drop of ≤5℃.

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