Metal layer spraying method of metallized film capacitor

Abstract

The invention relates to the technical field of capacitor manufacturing, and discloses a metal layer spraying method of a metallized film capacitor, comprising the following steps: initializing parameters and environmental conditions of spraying equipment, the spraying equipment comprising at least one spray gun and a cooling device; the upper end and the lower end of the capacitor core are subjected to multi-layer metal layer spraying, the metal layers at least comprise a first layer, a second layer and a third layer, and the metal layers have different functions; a slow release layer is sprayed between the at least two metal layers so as to reduce interface thermal stress concentration; and the sprayed metal layer is subjected to temperature control through staged cooling, so that the interface temperature difference is reduced, and the residual stress is reduced. Through spraying parameter optimization, multi-layer function layered design, slow release layer introduction and staged cooling strategies, the problems that spraying particles are uneven, the thickness design is single, interface thermal stress is concentrated and cooling is uneven are solved, and the conductivity, heat dissipation performance and interface stability of the metallized film capacitor are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of capacitor manufacturing, and specifically to a method for spraying a metal layer on a metallized film capacitor. Background Art

[0002] As an important electronic component, the metallized film capacitor is widely used in power electronic devices and new energy systems. Its core structure is usually composed of a wound polypropylene film, and multiple metal layers are sprayed on the film surface to form conductive electrodes. However, there are still many deficiencies in the existing metal layer spraying process in practical applications, resulting in limited performance of the capacitor and difficulty in meeting the requirements of high-current and high-frequency application scenarios; The commonly used pure zinc or zinc-tin alloy materials for existing metallized film capacitors are difficult to meet the conductivity and heat dissipation requirements of high-current and high-frequency applications due to their high resistivity and poor thermal conductivity; However, the spray coating thickness of existing metallized film capacitors usually adopts a uniform design, without optimizing for the current density and thermal load in different regions of the capacitor core, resulting in insufficient local heat dissipation and easy overheating problems; the multi-layer metal material spraying does not introduce a slow-release layer, and serious thermal stress concentration occurs at the interface due to differences in thermal expansion coefficient and elastic modulus, resulting in obvious interface cracks and delamination phenomena; the spraying and cooling processes lack real-time monitoring and dynamic regulation, and cannot be adjusted according to the deviation of thickness and temperature distribution, reducing the consistency and stability of the spray coating.

[0003] Therefore, the present invention proposes a method for spraying a metal layer on a metallized film capacitor to solve the deficiencies of the existing technology. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the present invention provides a method for spraying a metal layer on a metallized film capacitor, which solves the problems that the spray coating thickness of existing metallized film capacitors usually adopts a uniform design, without optimizing for the current density and thermal load in different regions of the capacitor core, resulting in insufficient local heat dissipation and easy overheating problems; the multi-layer metal material spraying does not introduce a slow-release layer, and serious thermal stress concentration occurs at the interface due to differences in thermal expansion coefficient and elastic modulus, resulting in obvious interface cracks and delamination phenomena.

[0005] To achieve the above objectives, the present invention is realized through the following technical solutions: A method for spraying a metal layer on a metallized film capacitor, comprising the following steps: Initialize the parameters and environmental conditions of the spraying equipment, and the spraying equipment includes at least one spray gun and a cooling device; Spray multiple metal layers on the upper and lower ends of the capacitor core, and the metal layer at least includes a first layer, a second layer, and a third layer, and each metal layer has different functions; Spray a slow-release layer between at least two metal layers to reduce the concentration of interfacial thermal stress; Control the temperature of the sprayed metal layer by staged cooling to reduce the interfacial temperature difference and residual stress; Use a real-time monitoring system to monitor the thickness and temperature distribution of the sprayed coating, and dynamically adjust the working parameters of the spraying equipment and the cooling device.

[0006] Preferably, the first layer of the metal layer is a tin-zinc alloy layer with a thickness of 0.1 mm, which is used to enhance the adhesion to the capacitor core; The third layer of the metal layer is a tin-zinc alloy layer with a thickness of 0.15 mm, which is used to improve the corrosion resistance and mechanical strength of the sprayed coating.

[0007] Preferably, the second layer of the metal layer is a pure aluminum layer, and its thickness is non-uniformly distributed along the spraying direction, forming a gradient with a gradually decreasing thickness. The maximum value of the thickness distribution is 0.25 mm, and the minimum value is 0.15 mm, so as to improve the thermal stress distribution.

[0008] Preferably, the thickness distribution of the second layer of the metal layer, which is a pure aluminum layer, is controlled by the following formula: where h(x) represents the thickness of the pure aluminum layer at position x; h max is the maximum thickness of the central region of the pure aluminum layer; β is the thickness adjustment coefficient; x represents the distance from the starting point of the metal layer to the current position; L represents the total width of the spraying area of the pure aluminum layer; γ is the non-linear adjustment exponent.

[0009] Preferably, the slow-release layer is located between the second pure aluminum layer and the third tin-zinc alloy layer. The material of the slow-release layer is a copper-zinc alloy, its elastic modulus is 100 GPa, the thermal expansion coefficient is 16 to 20 μm / (m·°C), and the thickness of the slow-release layer is 0.05 mm.

[0010] Preferably, the gun parameters of the spraying equipment are as follows: The gun distance for spraying the first layer of tin-zinc alloy layer is 130 ± 10 mm, and the spraying current is 30 to 45 A; The gun distance for spraying the second layer of pure aluminum layer is 230 ± 30 mm, and the spraying current is 50 to 70 A; The gun distance for spraying the third layer of tin-zinc alloy layer is 110 ± 10 mm, and the spraying current is 55 to 70 A.

[0011] Preferably, the staged cooling includes: In the first stage, cool the first layer to 25 °C; In the second stage, cool the second layer to 50 °C, and the cooling rate is dynamically adjusted to keep the temperature difference of the sprayed coating not exceeding 40 °C; In the third stage, the metal layer is cooled to room temperature by natural cooling.

[0012] Preferably, the cooling rate of the staged cooling is controlled by the following formula: R c =-k·T wherein, R c is the cooling rate; T is the temperature of the current spray coating layer; k is the cooling coefficient.

[0013] Preferably, the real-time monitoring system is used to monitor the thickness distribution and temperature distribution of the metal layer during the spraying process. The thickness monitoring accuracy is ±0.005 mm, and the temperature monitoring accuracy is ±2 °C, and the monitoring results are used to dynamically adjust the spraying and cooling parameters.

[0014] Preferably, the metal layer spraying system of the metallized film capacitor includes: Spraying module: including at least three spray guns, which are respectively used to spray the first layer of tin-zinc alloy layer, the second layer of pure aluminum layer and the third layer of tin-zinc alloy layer. The spraying module has a dynamic parameter adjustment function, including spraying voltage, spraying current and spraying distance; Cooling module: having a staged cooling function, realizing precise cooling of different spray coating layers through a combination of forced cooling and natural cooling, and the cooling rate can be dynamically adjusted; Monitoring module: including a thickness sensor and a temperature sensor, which are used to monitor the thickness and temperature distribution of the spray coating layer in real time, and the monitoring accuracies are ±0.005 mm and ±2 °C respectively; Control module: used to receive the real-time data of the monitoring module, and automatically adjust the parameters of the spraying module and the cooling module to optimize the uniformity and interface performance of the spray coating layer; Slow-release layer spraying module: used to form a slow-release layer between the second layer and the third layer. The spraying material of the slow-release layer is copper-zinc alloy, and its thickness is controlled at 0.05 mm. The elastic modulus and thermal expansion coefficient can be dynamically optimized and adjusted by the control module.

[0015] The present invention provides a method for spraying a metal layer of a metallized film capacitor. It has the following beneficial effects: 1. By optimizing the spraying parameters of the spray gun and controlling the temperature and humidity conditions of the spraying environment, the present invention ensures the uniformity and adhesion of the spraying particles. Compared with the prior art technical solutions that do not precisely control the equipment parameters and spraying environment, the problems of metal layer thickness error and insufficient adhesion caused by uneven distribution of spraying particles are solved.

[0016] 2. Through the functional hierarchical design of the tin-zinc alloy layer, pure aluminum layer, and slow-release layer, and combined with the optimization of the thickness gradient of the second pure aluminum layer, the present invention improves the electrical conductivity and heat dissipation capacity of the capacitor. Compared with the prior art solutions where the thickness of the metal layer is single and the spray coating structure is not hierarchically designed, it solves the problems of shortened capacitor life and limited performance caused by high resistivity and poor heat dissipation capacity.

[0017] 3. By introducing a copper-zinc alloy slow-release layer with intermediate elastic modulus and coefficient of thermal expansion between the pure aluminum layer and the tin-zinc alloy layer, the present invention smooths the interfacial thermal stress distribution and improves the interfacial stability of the metal layer. Compared with the prior art solutions where direct contact between different metal layers leads to concentrated interfacial thermal stress and easy cracking of materials, it solves the deficiencies of interfacial failure and poor overall stability of the spray coating.

[0018] 4. Through the multi-stage cooling strategy of forced cooling, step cooling, and natural cooling for the spray coating, combined with dynamic cooling rate regulation, the present invention reduces the interfacial temperature difference and plastic strain accumulation during the spraying process. Compared with the prior art solutions where a single cooling mode is used, resulting in the failure to release interfacial thermal stress and cracking of the spray coating, it solves the problems of large internal temperature difference in the spray coating and ineffective alleviation of interfacial thermal stress. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the flowchart of the method steps of the present invention; Figure 2 is the system architecture diagram of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0021] The present invention provides a method for spraying a metal layer of a metallized film capacitor. By combining the hierarchical design of the spraying process, thickness distribution optimization, slow-release layer setting, and staged cooling technology, precise control of the thickness uniformity of the spray coating, interfacial thermal stress distribution, and adhesion performance of the metal layer is achieved, improving the electrical conductivity, heat dissipation, and long-term use reliability of the metallized film capacitor.

[0022] As Figure 1 shown, a method for spraying a metal layer of a metallized film capacitor may include the following steps: S1. Initialization of the spraying equipment and environmental pre-treatment; S2. Multilayer metal spraying process design; S3. Precision spraying of the interface slow-release layer; S4. Staged dynamic cooling control; S5. Real-time monitoring and parameter optimization and adjustment.

[0023] For step S1, before spraying the metal layer of the metallized film capacitor, it is necessary to initialize the parameters of the spraying equipment and fully prepare the spraying environment to ensure the stability of the subsequent spraying process and the uniformity of the metal layer. Generally, the initial parameters of the spraying equipment need to be adjusted according to the physical properties of the selected metal material and the spraying requirements, such as the spraying speed of metal particles, spraying current, spraying distance, etc. In addition, the control of temperature and humidity in the spraying environment has an important impact on the distribution uniformity and adhesion performance of spraying particles. As an option, in the present invention, it is preferred to perform an air spraying test of the spray gun before spraying to ensure the fineness of metal particle spraying and the stability of equipment performance.

[0024] In this embodiment, to achieve the best effect of the spraying process, the following specific operations are carried out: The air supply pressure of the spray gun is set between 0.52 and 0.6 MPa. The air pressure within this range can ensure the stable spraying speed of metal particles during the spraying process, while avoiding uneven particle distribution caused by too low air flow pressure or particle scattering caused by too high pressure.

[0025] The spraying voltage range is set to 21 to 25 volts. The voltage within this range can provide sufficient energy to evenly distribute metal particles on the surface of the capacitor core, while avoiding particle melting caused by too high voltage or insufficient particle adhesion force caused by too low voltage.

[0026] The spraying current range is adjusted to 30 to 70 A, and the specific value is dynamically adjusted according to the thickness requirement of the sprayed layer. For example, the spraying current of the first layer of tin-zinc alloy layer is preferably 30 to 45 A, the spraying current of the second layer of pure aluminum layer is preferably 50 to 70 A, and the spraying current of the third layer of tin-zinc alloy layer is preferably 55 to 70 A.

[0027] As an option, a multi-spray gun cooperative operation mode can be used. Specifically, each spray gun can independently adjust parameters and work synchronously or sequentially to further improve the spraying coverage efficiency and thickness uniformity.

[0028] Generally, the spraying environment temperature is controlled between 20 and 25 °C. This temperature range can not only maintain the fluidity of metal particles but also avoid changes in particle adhesion caused by too high or too low environmental temperature during the spraying process. In addition, the relative humidity is preferably controlled to be less than 50% to reduce the oxidation effect of moisture on the surface of metal particles.

[0029] In a possible implementation, the temperature and humidity of the spraying environment can be monitored and adjusted in real time by installing an air dehumidification device and an environmental temperature control system. For example, when the humidity exceeds 50%, the system will automatically activate the dehumidification function to reduce the humidity to a predetermined range.

[0030] In actual operation, to ensure the stable spraying performance of the equipment, it is preferably to perform an air spraying operation for 5 to 10 minutes before spraying. Specifically, the clogging of the spray gun or abnormal spraying parameters can be judged by observing the fineness and uniform distribution of the spraying particles. If it is found that the spray gun is clogged or the spraying particles are uneven, the nozzle can be cleaned or the equipment parameters can be readjusted in time according to the equipment feedback signal.

[0031] In some embodiments, the particle size of the spraying particles can be detected in real time by installing a particle detection device. For example, for the first layer of tin-zinc alloy layer, the preferred particle size range is 5 to 20 microns, while the particle size range of the second layer of pure aluminum layer is preferably 10 to 30 microns. The detection device can combine with the equipment feedback mechanism to automatically adjust the particle screening parameters of the feeding device when the particle size deviates from the target range.

[0032] As an extended technology, a metal particle preheating function can be added to the spraying equipment to reduce the possibility of particle condensation or caking. Specifically, the preferred preheating temperature of the particles is 50 to 80 degrees Celsius, so that the particles maintain good fluidity and adhesion during the spraying process.

[0033] During the spraying process, the relationship between the spraying rate v of the metal particles, the gas supply pressure P, and the particle density ρ can be approximately expressed as: Among them, v represents the velocity of the metal particles ejected during the spraying process; P represents the gas supply pressure of the spraying equipment; ρ represents the density of the spraying metal particles.

[0034] Generally, when the gas supply pressure is 0.55 MPa, the particle density is 2700 kg / m³ (corresponding to pure aluminum), and the nozzle diameter is 1 mm, the spraying velocity can reach 32.02 m / s.

[0035] For step S2, after the initialization of the spraying equipment and the environmental pretreatment, it is necessary to perform multi-layer spraying of the metal layer on the upper and lower ends of the capacitor core. Generally, the capacitor core uses a wound polypropylene film as the basic structure, and its surface needs to be covered with at least three metal layers with different functions to respectively achieve functions such as conductivity, heat dissipation, and protection. In the present invention, the multi-layer metal spraying process optimizes the spraying parameters and thickness distribution to ensure the adhesion, conductivity, and overall uniformity of each layer of metal material, while reducing the concentration of thermal stress.

[0036] In this embodiment, a multi-layer spraying of a first layer of tin-zinc alloy layer, a second layer of pure aluminum layer, and a third layer of tin-zinc alloy layer is specifically realized. The spraying process is as follows: In this embodiment, the first layer of metal material is selected as tin-zinc alloy, and its main function is to enhance the adhesion to the capacitor core and serve as a mechanical support for the subsequent metal layer. As an option, the composition of the tin-zinc alloy is preferably 70% tin and 30% zinc.

[0037] During the spraying process, the distance between the spray gun and the capacitor core is preferably 130 ± 10 mm, the spraying voltage is set to 21 to 22 volts, and the spraying current is 30 to 45 amperes to ensure that the metal particles are evenly distributed and cover the surface of the core.

[0038] The thickness of the first layer is preferably 0.1 mm, and the entire surface of the capacitor core is covered by uniform spraying. In some embodiments, the thickness deviation of the first layer is controlled within ±0.005 mm to ensure its surface flatness and provide a good foundation for the adhesion of the subsequent metal layer.

[0039] The second layer of metal material is selected as pure aluminum, and its main functions are to provide excellent electrical conductivity and heat dissipation performance. Generally, the purity of pure aluminum is preferably not less than 99.5% to ensure electrical conductivity and corrosion resistance.

[0040] The second layer adopts an optimized design of thickness distribution to reduce the interfacial thermal stress. Its thickness forms a non-uniform gradient distribution along the surface of the capacitor core, with a maximum thickness of 0.25 mm and a minimum thickness of 0.15 mm. Specifically, the thickness distribution formula is: where h(x) represents the thickness of the pure aluminum layer at position x; h max is the maximum thickness of the central region of the pure aluminum layer; β is the thickness adjustment coefficient; x represents the distance from the starting point of the metal layer to the current position; L represents the total width of the spraying area of the pure aluminum layer; γ is the non-linear adjustment index.

[0041] During the spraying process, the distance between the spray gun and the capacitor core is preferably 230 ± 30 mm, the spraying voltage is 22 to 25 volts, and the spraying current is 50 to 70 amperes. As a possible implementation, the spraying of the second layer adopts a multi-spray gun cooperation mode to reduce the spraying time and improve the uniformity of the thickness distribution.

[0042] The third layer of metal material is again selected as tin-zinc alloy, and its main functions are to provide mechanical protection and corrosion resistance, and to prevent the performance of the metal layer from deteriorating due to environmental factors during the use of the capacitor.

[0043] During the spraying process, the distance between the spray gun and the capacitor core is preferably 110 ± 10 mm, the spraying voltage is set to 23 to 25 V, and the spraying current is 55 to 70 A to ensure the density and adhesion of the third layer.

[0044] The thickness of the third layer is preferably 0.15 mm, and its thickness deviation is also controlled within ±0.005 mm. In some embodiments, an additional spraying protection process can be added, such as using a higher particle injection speed to increase the density of the metal layer surface.

[0045] As an extended method, the surface of the third layer can be micro - processed, such as by introducing a small amount of corrosion - resistant coating to further improve the oxidation resistance of the metal layer.

[0046] For step S3, after spraying the multi - layer metal layer, to further optimize the interface characteristics between the metal layers, reduce the interface thermal stress concentration and the risk of crack generation due to the difference in the thermal expansion coefficients of the materials, a release layer design is introduced in the present invention. Generally, the release layer is arranged between the second pure aluminum layer and the third tin - zinc alloy layer as a transition layer to smooth the interface stress. Specifically, the material of the release layer needs to have both a suitable elastic modulus and a thermal expansion coefficient to minimize the difference in the elastic modulus and thermal expansion coefficient of the upper and lower layer metal materials as much as possible.

[0047] In this embodiment, the spraying process and parameters of the release layer are as follows: The release layer material is selected as copper - zinc alloy, and its main function is to relieve the stress concentration between the pure aluminum layer and the tin - zinc alloy layer through a suitable elastic modulus and thermal expansion coefficient. As an option, the elastic modulus of the copper - zinc alloy is preferably 100 GPa, and the thermal expansion coefficient is preferably 16 to 20 μm / m·°C.

[0048] In some embodiments, the composition ratio of the copper - zinc alloy can be adjusted according to actual needs. For example, when the thermal expansion coefficient needs to be further reduced, the copper content can be appropriately increased; when the corrosion resistance requirement is high, the zinc content can be appropriately increased.

[0049] The thickness of the release layer is preferably 0.05 mm. Generally, this thickness can ensure the release effect while avoiding the influence of an overly thick release layer on the overall structural strength of the capacitor.

[0050] During the spraying process, the distance between the spray gun and the capacitor core is preferably 120 ± 10 mm, the spraying voltage is set to 23 V, and the spraying current is 40 to 50 A. In a possible implementation, the spraying of the release layer can be carried out by multiple thin - layer spraying methods, that is, the thickness of each spraying is about 0.01 mm, and it is completed in 5 times to improve the uniformity and stability of the sprayed layer.

[0051] In the present invention, the addition of the release layer significantly improves the thermal stress distribution between the metal layers. Specifically, since the second pure aluminum layer has a relatively high elastic modulus (about 70 GPa) and a relatively small coefficient of thermal expansion (about 23 μm / m·°C), while the third tin-zinc alloy layer has a relatively low elastic modulus (about 50 GPa) and a relatively large coefficient of thermal expansion (about 30 μm / m·°C), direct contact may lead to interfacial thermal stress concentration.

[0052] After introducing the copper-zinc alloy release layer, its elastic modulus and coefficient of thermal expansion are both between those of the pure aluminum layer and the tin-zinc alloy layer, thus significantly reducing the thermal stress caused by the physical property differences between the upper and lower layers of materials and improving the interfacial stability of the metal layers.

[0053] As an option, a multi-gun cooperative operation mode can be used during the spraying process of the release layer, and the spraying parameters of each gun can be adjusted individually to adapt to the geometric structure of the surface of the capacitor core. For example, in the edge area of the core, the spraying current can be appropriately reduced to avoid excessive thickness of the release layer; while in the central area of the core, the spraying voltage can be appropriately increased to improve the coverage density of the release layer.

[0054] In a possible implementation, a real-time thickness monitoring device can be equipped to collect the thickness data of the release layer in real time through laser scanning technology. When the thickness deviates from the predetermined range (for example, exceeds ±0.002 mm), the monitoring system will automatically send an adjustment signal to the spraying equipment to dynamically correct the spraying parameters.

[0055] In some embodiments, trace additives (such as nickel) can be introduced into the release layer to further improve the mechanical properties and corrosion resistance of the release layer. Specifically, the mass ratio of the additive is preferably not more than 5% to avoid affecting the flexibility and thermal expansion characteristics of the release layer.

[0056] As an extended method, a heat treatment process after spraying can be combined to cure the release layer. Generally, the curing temperature of the release layer is preferably 120 to 150 °C, and the curing time is 30 to 60 minutes to enhance the interfacial bonding strength and stability of the release layer.

[0057] For step S4, after spraying the multi-layer metal layer and the release layer, the sprayed metal layer needs to be cooled in stages to control the temperature gradient inside the sprayed layer and reduce the accumulation of interfacial thermal stress and plastic strain. Generally, the heat generated during the spraying process will cause a large interfacial temperature difference between the metal layer and the capacitor core. If the cooling is not carried out in a timely and effective manner, it may lead to cracking of the sprayed layer, a decrease in adhesion, and even local detachment of the metal layer. In the present invention, the staged cooling ensures that the temperature of each layer of metal drops evenly by precisely controlling the cooling rate and temperature distribution, providing guarantee for the stability and durability of the sprayed layer.

[0058] In this embodiment, the following staged cooling process is specifically carried out: In this embodiment, the first-stage cooling mainly targets the first layer of tin-zinc alloy layer, and the forced air cooling method is adopted to rapidly reduce the temperature of the metal layer to 25 degrees Celsius.

[0059] The cooling rate is calculated according to the cooling rate formula as follows: R c =-k·T Wherein, R c is the cooling rate; T is the current temperature of the spray coating; k is the cooling coefficient.

[0060] In this stage, it is preferably set that the value of k is 0.1 to 0.3, and the specific value is adjusted according to the cooling capacity of the spraying equipment. For example, when the initial temperature of the spray coating is 150 degrees Celsius, the calculated cooling rate is 15 degrees Celsius per second.

[0061] Generally, forced air cooling can be achieved through a compressed air nozzle, and the air flow pressure is preferably 0.2 to 0.4 MPa to ensure rapid cooling while avoiding shrinkage instability of metal particles due to excessive cooling. The second-stage cooling targets the second layer of pure aluminum layer. Since aluminum has high thermal conductivity and low specific heat capacity, a stepped temperature reduction strategy needs to be adopted during the cooling process. Specifically, the temperature is gradually reduced to 50 degrees Celsius in two steps.

[0062] In a possible implementation manner, the forced cooling method can be continued in the initial stage, but when the temperature approaches 80 degrees Celsius, the method of slowing down the cooling rate is adopted. Specifically, the air flow pressure can be reduced or switched to the natural cooling mode to avoid the accumulation of internal thermal stress caused by rapid temperature drop.

[0063] In some embodiments, the cooling equipment in the second stage is equipped with a cooling rate adjustment device, which automatically adjusts the flow rate of the cooling medium according to the temperature change of the spray coating. For example, when it is monitored that the cooling rate exceeds 20 degrees Celsius per second, the device will automatically reduce the air flow speed to control the cooling rate within the target range.

[0064] The third-stage cooling targets the third layer of tin-zinc alloy layer and the slow-release layer, and mainly makes the temperature of the spray coating gradually drop to room temperature through natural cooling.

[0065] The natural cooling process in this stage mainly relies on the heat conduction and convection of ambient air. Generally, the natural cooling time is preferably 10 to 20 minutes, and the specific time is adjusted according to the initial temperature of the spray coating and environmental conditions.

[0066] In a possible implementation, a low-speed fan can be used for auxiliary cooling during the natural cooling process to improve cooling uniformity and avoid local overheating.

[0067] In some embodiments, heat preservation treatment can be introduced after the second-stage cooling to further reduce the thermal stress caused by the temperature difference. Specifically, a constant-temperature module can be added to the cooling device to maintain the sprayed coating at a constant temperature of 50 to 60 degrees Celsius for about 5 to 10 minutes to alleviate the impact of the sudden temperature drop on the interface performance.

[0068] As an extended method, the temperature distribution of the metal layer can be monitored in real time during the cooling process. By installing a non-contact infrared temperature measurement device in the spraying equipment, the surface temperature of each layer of metal is dynamically monitored. When the temperature difference in a certain area is detected to exceed 5 degrees Celsius, the cooling system can automatically adjust the distribution of the cooling medium to quickly balance the temperature.

[0069] The control of the cooling rate is the core of the staged cooling. In this embodiment, the cooling rate in the first stage is relatively fast, aiming to quickly reduce the initial high temperature of the metal layer; while in the second and third stages, the cooling rate is gradually reduced to avoid generating a large thermal gradient inside the metal layer.

[0070] The optimization of the cooling rate is closely related to the thickness, thermal conductivity, and heat capacity of the sprayed coating. For example, for the second pure aluminum layer, due to its high thermal conductivity, the cooling rate can be appropriately increased; while for the third tin-zinc alloy layer, the cooling rate needs to be reduced to ensure stress balance between the slow-release layer and it.

[0071] For step S5, the thickness distribution, temperature change, and interface state of the sprayed coating are dynamically monitored through a real-time monitoring system, and the working parameters of the spraying equipment and the cooling device are adjusted in combination with the monitoring results. Generally, during the spraying and cooling processes, deviations in the thickness of the metal layer or the temperature difference may occur due to equipment errors or environmental fluctuations. Through real-time monitoring and parameter feedback control, the thickness uniformity of the sprayed coating and the stability of the temperature distribution can be effectively improved, and quality problems caused by human or external factors can be avoided.

[0072] In this embodiment, the following operations of real-time monitoring and parameter adjustment are specifically carried out: The real-time monitoring system includes a thickness monitoring module, a temperature monitoring module, and a data processing module. Specifically: The thickness monitoring module uses a laser scanning device to monitor the thickness distribution of the sprayed coating in real time, and the monitoring accuracy is ±0.005 mm. The laser scanner can perform non-contact detection on the surface of the metal layer and obtain the thickness curve of the sprayed coating through high-frequency sampling.

[0073] The temperature monitoring module uses an infrared temperature measuring device to collect the temperature distribution on the surface and interface of the sprayed coating in real time, with a monitoring accuracy of ±2 degrees Celsius. The infrared thermometer can combine with the dynamic thermal field changes during the spraying process to provide accurate temperature data.

[0074] The data processing module receives the above monitoring data and analyzes the thickness and temperature deviation of the sprayed coating through a built-in algorithm. If the deviation exceeds the preset range (for example, the thickness deviation exceeds ±0.01 mm, or the temperature difference exceeds 5 degrees Celsius), the system will automatically send a feedback signal to the spraying equipment or the cooling device to adjust the relevant parameters.

[0075] In this embodiment, the key point of thickness monitoring is to ensure that the thickness of the metal layer is uniform and meets the design requirements. For example, for the second pure aluminum layer, its thickness needs to form a gradient distribution that gradually decreases from the center to the edge along the spraying direction. The laser scanning module can record the thickness distribution in real time through multi-point sampling.

[0076] The processing algorithm for thickness monitoring data can be calculated based on the mean square error, and the formula is as follows: where MSE represents that the sprayed coating thickness distribution is closer to the target value; h i represents the actual thickness of the monitored sprayed coating at this point; h target represents the theoretical thickness set according to the spraying design requirements; N represents the number of sampling points selected during the spraying thickness monitoring process; i represents the position of the current sampling point among the total sampling points.

[0077] Generally, when the mean square error exceeds the set threshold (for example, 0.005 mm), the data processing module will trigger the feedback control mechanism of the spraying equipment to correct the thickness error by adjusting the spraying current or spraying time.

[0078] In this embodiment, the key point of temperature monitoring is to control the temperature distribution uniformity and cooling rate of the sprayed coating. For example, during the second-stage cooling process, the infrared temperature measuring device can monitor the temperature difference of the sprayed coating in real time. If the detected temperature difference in a local area exceeds 5 degrees Celsius, the system will automatically adjust the flow rate or distribution of the cooling medium.

[0079] In a possible implementation, a non-linear temperature control algorithm can be used to optimize the cooling rate. Specifically, the system dynamically adjusts the flow rate of the cooling medium according to the current temperature and the target cooling rate to make the temperature gradually tend to be balanced.

[0080] In the thickness deviation adjustment, if the thickness of a certain area is lower than the target value, the system will automatically increase the spraying current or extend the spraying time to compensate for the thickness shortage in this area; while for the area with too high thickness, it will be corrected by reducing the spraying current or shortening the spraying time.

[0081] In the temperature difference adjustment, the system can dynamically change the pressure or flow rate of the cooling medium according to the infrared temperature measurement data. For example, when the cooling rate in a certain area is too fast, resulting in a sudden temperature drop, the cooling process can be slowed down by reducing the pressure of the cooling air flow (such as from 0.4 MPa to 0.2 MPa).

[0082] In some embodiments, multi-dimensional analysis can be performed by combining thickness monitoring data and temperature monitoring data. For example, when it is detected that the thickness deviation and temperature difference in a certain area are both large, the system can preferentially correct the thickness parameters to ensure that the basic functions of the sprayed coating are not affected.

[0083] As an extended method, an artificial intelligence algorithm can be introduced into the data processing module. By learning historical spraying and cooling data, the strategy of feedback control can be optimized. For example, based on a machine learning model, the possible weak points of the sprayed coating can be predicted, and parameter adjustment can be made in advance to reduce abnormalities in the spraying and cooling processes.

[0084] A metal layer spraying system for a metallized film capacitor described below can be referred to in correspondence with a metal layer spraying method for a metallized film capacitor described above.

[0085] Please refer to the atta Figure 2 , The present invention also provides a metal layer spraying system for a metallized film capacitor. The system combines technologies such as a spraying module, a cooling module, a monitoring module, a control module, and a slow-release layer spraying module. By efficiently integrating the functions of each module, the system can dynamically regulate the spraying process parameters, real-time monitor the thickness distribution and temperature distribution of the metal layer, and automatically optimize the spraying and cooling parameters through a feedback mechanism to ensure the quality consistency of the sprayed coating, reduce the interfacial thermal stress, and achieve an efficient and stable metal layer spraying process for metallized film capacitors, providing technical support for the high performance, miniaturization, and long-term stability of the capacitors.

[0086] The spraying module is used to spray multiple layers of metal materials on the surface of the core of the metallized film capacitor. The module can accurately control the spraying current, voltage, and distance, and supports the coordinated operation of multiple spray guns to ensure the uniformity and efficiency of the spraying process.

[0087] In this embodiment, the spraying module is equipped with at least three spray guns, which are respectively used to spray a tin-zinc alloy layer, a pure aluminum layer, and a slow-release layer. The parameters of each spray gun can be independently adjusted. For example, when the first spray gun is used to spray the tin-zinc alloy, its voltage is set to 23 volts, and the spraying distance is set to 130 ± 10 mm. When the third spray gun is used to spray the slow-release layer, the current is set to 40 to 50 A. The spraying module also incorporates a dynamic parameter adjustment function, which automatically corrects possible errors during the spraying process through data linkage with the monitoring module.

[0088] The spraying module ensures the accuracy and uniformity of the thickness distribution of the sprayed coating, while improving the spraying efficiency and reducing the fluctuations in spraying quality caused by manual intervention, providing a stable basis for subsequent cooling and detection.

[0089] The cooling module cools the sprayed metal layer through staged temperature control. The module supports two modes: forced cooling and natural cooling, and can dynamically adjust the cooling rate and air flow distribution to prevent the accumulation of thermal stress caused by uneven cooling.

[0090] In this implementation, the cooling module combines high-pressure air flow and natural environment cooling methods. In the first stage, high-pressure air flow cooling is used to quickly reduce the temperature of the sprayed coating to 25 degrees Celsius, and then the air flow pressure is gradually reduced to enter the natural cooling mode. The cooling module also has the function of adjusting the flow rate of the cooling medium. When the temperature difference in a certain area exceeds the set value, the module will make real-time adjustments by increasing or decreasing the air flow intensity.

[0091] The cooling module effectively reduces the thermal gradient inside the sprayed coating, avoiding cracking and adhesion problems of the sprayed coating caused by uneven cooling. At the same time, through the dynamic adjustment of the cooling rate, the interface stability and overall quality of the sprayed coating are improved.

[0092] The monitoring module is used to detect the thickness distribution and temperature change of the sprayed coating in real time, and transmit the data to the control module for guiding the parameter adjustment in the spraying and cooling processes.

[0093] In this implementation, the monitoring module is equipped with a laser scanning device and an infrared temperature measuring device. The laser scanning device performs non-contact thickness measurement on the surface of the metal layer, with an accuracy of ±0.005 mm; the infrared temperature measuring device collects the temperature of the surface and interface of the sprayed coating in real time, with an accuracy of ±2 degrees Celsius. The data of the monitoring module is linked with the control module in real time through a high-speed transmission network. When a deviation is detected, the feedback mechanism is immediately triggered.

[0094] The monitoring module improves the accuracy and consistency of the spraying and cooling processes, can quickly detect potential problems and correct them during the spraying process, and ensures the final quality of the metal layer.

[0095] The control module analyzes the thickness and temperature distribution of the sprayed coating by receiving the real-time data of the monitoring module, and dynamically adjusts the working parameters of the spraying module and the cooling module to optimize the spraying process.

[0096] In this implementation, the control module is built-in with a feedback control algorithm and can quickly process the monitoring data. For example, when it is detected that the thickness deviation of the sprayed coating exceeds the allowable range, the control module will send an instruction to the spraying module to adjust the spraying current or spraying time. In addition, the control module also integrates the function of learning historical data, and optimizes the cooling strategy and spraying efficiency by analyzing the previous spraying data.

[0097] Through real-time data processing and feedback adjustment functions, the control module significantly improves the stability and accuracy of the spraying process, reduces human intervention, and enhances the overall production efficiency and product consistency.

[0098] The slow-release layer spraying module is dedicated to forming a slow-release layer between metal layers to reduce interfacial thermal stress and improve interfacial bonding performance.

[0099] In this embodiment, the slow-release layer spraying module combines a spray gun and dynamic control functions to ensure a uniform thickness of the slow-release layer, with a preferred thickness of 0.05 mm. During spraying, the module will collect thickness data in real time and adjust the spraying speed according to the feedback information. In addition, the material of the slow-release layer is copper-zinc alloy, and this module supports the method of multiple thin-layer spraying to further enhance the bonding strength and uniformity of the slow-release layer.

[0100] The slow-release layer spraying module significantly reduces the risk of interfacial thermal stress concentration by optimizing the interfacial characteristics of the metal layer, and improves the adhesion of the sprayed layer and the overall structural stability.

[0101] The system of this embodiment can be used to execute the method embodiment above. The principle and technical effect are similar, and will not be elaborated here.

[0102] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for spraying a metal layer of a metallized film capacitor, characterized in that: The following steps are involved: Initializing parameters and environmental conditions of a spraying device, the spraying device comprising at least one spray gun and a cooling device; Spraying multiple metal layers on the upper and lower ends of the capacitor core, wherein the metal layers include at least a first layer, a second layer and a third layer, and each metal layer has a different function; Spraying a slow-release layer between at least two metal layers to reduce thermal stress concentration at the interface; The temperature of the metal layer after spraying is controlled by staged cooling to reduce the interface temperature difference and residual stress; The real-time monitoring system is used to monitor the thickness and temperature distribution of the spray layer, and dynamically adjust the working parameters of the spraying equipment and cooling device.

2. The method for spraying a metal layer of a metallized film capacitor according to claim 1, characterized in that: The first layer of the metal layer is a tin-zinc alloy layer with a thickness of 0.1 mm, which is used to enhance the adhesion with the capacitor core; The third layer of the metal layer is a tin-zinc alloy layer with a thickness of 0.15 mm, which is used to improve the corrosion resistance and mechanical strength of the sprayed layer.

3. The method for spraying a metal layer of a metallized film capacitor according to claim 1, characterized in that: The second layer of the metal layer is a pure aluminum layer, and its thickness is non-uniformly distributed along the spraying direction, forming a gradient with gradually decreasing thickness. The maximum value of the thickness distribution is 0.25 mm and the minimum value is 0.15 mm, so as to improve the thermal stress distribution.

4. The method for spraying a metal layer of a metallized film capacitor according to claim 3, characterized in that: The thickness distribution of the pure aluminum layer is controlled by the following formula: Where h(x) represents the thickness of the pure aluminum layer at position x; h max is the maximum thickness of the central area of ​​the pure aluminum layer; β is the thickness adjustment coefficient; x represents the distance from the starting point of the metal layer to the current position; L represents the total width of the pure aluminum layer spraying area; γ is the nonlinear adjustment index.

5. The method for spraying a metal layer of a metallized film capacitor according to claim 1, characterized in that: The sustained-release layer is located between the second pure aluminum layer and the third tin-zinc alloy layer. The material of the sustained-release layer is copper-zinc alloy, and its elastic modulus is 100 gigapascals, the thermal expansion coefficient is 16 to 20 microns per meter per degree Celsius, and the thickness of the sustained-release layer is 0.05 mm.

6. The method for spraying a metal layer of a metallized film capacitor according to claim 1, characterized in that: The spray gun parameters of the spray equipment are: The first layer of tin-zinc alloy is sprayed at a spray gun distance of 130 ± 10 mm and a spray current of 30 to 45 amps; The second pure aluminum layer is sprayed at a spray gun distance of 230 ± 30 mm and a spray current of 50 to 70 amps; The third tin-zinc alloy layer is sprayed at a spray gun distance of 110±10 mm and a spray current of 55 to 70 amps.

7. The method for spraying a metal layer of a metallized film capacitor according to claim 1, characterized in that: The staged cooling includes: In the first stage, the first layer is cooled to 25 degrees Celsius; In the second stage, the second layer is cooled to 50 degrees Celsius, and the cooling rate is dynamically adjusted to keep the temperature difference of the spray layer no more than 40 degrees Celsius; The third stage is to cool the metal layer to room temperature by natural cooling.

8. The method for spraying a metal layer of a metallized film capacitor according to claim 1, characterized in that: The cooling rate of the staged cooling is controlled by the following formula: R c =-k·T Among them, R c is the cooling rate; T is the current temperature of the sprayed layer; k is the cooling coefficient.

9. The method for spraying a metal layer of a metallized film capacitor according to claim 1, characterized in that: The real-time monitoring system is used to monitor the thickness distribution and temperature distribution of the metal layer during the spraying process. The thickness monitoring accuracy is ±0.005 mm, and the temperature monitoring accuracy is ±2 degrees Celsius. The monitoring results are used to dynamically adjust the spraying and cooling parameters.

10. A metal layer spraying system for a metallized film capacitor, applied to a metal layer spraying method for a metallized film capacitor according to any one of claims 1 to 9, characterized in that: The metal layer spraying system of the metallized film capacitor comprises: Spraying module: comprising at least three spray guns, respectively used for spraying the first tin-zinc alloy layer, the second pure aluminum layer and the third tin-zinc alloy layer, the spraying module having a dynamic parameter adjustment function, including spraying voltage, spraying current and spraying distance; Cooling module: It has a staged cooling function, which can achieve accurate cooling of different spray layers by combining forced cooling and natural cooling, and the cooling rate can be dynamically adjusted; Monitoring module: including thickness sensor and temperature sensor, used to monitor the thickness and temperature distribution of the spray layer in real time, with monitoring accuracy of ±0.005 mm and ±2 degrees Celsius respectively; Control module: used to receive real-time data from the monitoring module and automatically adjust the parameters of the spraying module and cooling module to optimize the uniformity and interface performance of the spray layer; Sustained-release layer spraying module: used to form a sustained-release layer between the second layer and the third layer. The spraying material of the sustained-release layer is copper-zinc alloy, and its thickness is controlled at 0.05 mm. The elastic modulus and thermal expansion coefficient can be dynamically optimized and adjusted by the control module.

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