An inductance, inductance glue filling stress release filling process

Abstract

The application relates to the technical field of inductance and discloses an inductance and a potting process for releasing stress of inductance glue injection, the inductance comprising a shell with an opening and a bottom portion arranged opposite to the opening; an inductance body arranged in the shell; at least one flexible sleeve with one end sealed, the flexible sleeve being inserted into a gap between the inductance body and the shell, and the sealed end of the flexible sleeve being arranged towards the bottom portion of the shell; a potting glue layer filled in the gap between the shell and the inductance body, and the open end of the flexible sleeve extending to the outside of the potting glue layer, the inside of the flexible sleeve being hollow to serve as a stress releasing space when the potting glue is heated and expanded. The application provides a controllable retreat channel for the heated expansion of the potting glue by using the hollow reserved space, so that the internal stress generated by the heated expansion of the potting glue is transferred from the magnetic core and guided into the hollow space of the flexible sleeve for orderly releasing without increasing the packaging volume and without changing the original structure of the inductance body.

Description

Technical Field

[0001] This invention relates to the field of inductor technology, and more specifically to an inductor and an inductor potting stress relief process. Background Technology

[0002] Currently, the inductor and transformer industry is facing the dual pressures of miniaturization and high performance. On the one hand, intensified market competition is driving continuous reduction in product size and design margins, resulting in increasingly compact aluminum shell packaging space. On the other hand, to meet the heat dissipation requirements of high-end applications, the industry generally uses potting compound to assist in heat conduction. However, under high-temperature conditions, such as long-term operation or high-temperature baking, the potting compound will undergo significant thermal expansion. The narrow aluminum shell space forms a rigid constraint on the expanding compound, thereby generating large internal stress.

[0003] Meanwhile, the difference in thermal expansion coefficients between the potting compound and the core material further exacerbates stress concentration. When the inductor is arranged vertically or horizontally, the expansion stress concentrates upwards onto the core cover or center column, which can easily lead to quality defects such as core cracking and breakage, causing a significant decrease in inductance and seriously affecting product reliability and service life. Summary of the Invention

[0004] This invention provides an inductor and an inductor potting stress relief process to solve the problem that the thermal expansion stress of the potting adhesive cannot be released in existing aluminum-cased inductors, leading to core cracking and inductance attenuation.

[0005] In a first aspect, the present invention provides an inductor, comprising: The housing has an opening and a bottom disposed opposite the opening; The inductor body is housed within the casing; At least one flexible sleeve sealed at one end, the flexible sleeve is inserted in the gap between the inductor body and the housing, and the sealed end of the flexible sleeve is positioned facing the bottom of the housing; A potting compound layer fills the gap between the housing and the inductor body, and the open end of the flexible sleeve extends to the outside of the potting compound layer. The interior of the flexible sleeve is hollow to serve as a stress release space when the potting compound layer expands thermally.

[0006] In one optional embodiment, the axial length of the flexible sleeve is a, the vertical distance between the bottom inner wall of the housing and the outer end face of the potting compound is b, the total internal depth of the housing is c, where b≤a≤c, and / or, the inner diameter of the flexible sleeve is d, the minimum horizontal distance between the outer wall of the inductor body and the inner wall of the housing is e, the rated temperature rise of the inductor body is f, where d is positively correlated with e and f, and / or, the number of flexible sleeves is n, the overall volume of the inductor body is v, the rated temperature rise of the inductor body is f, where n is positively correlated with v and f.

[0007] In one optional embodiment, the sealing end of the flexible sleeve has a sealing region with a flat structure, the thickness of the sealing region is h1, h1 is 1.7mm to 1.9mm, and the axial length of the sealing region along the flexible sleeve is L, L is 7mm to 9mm.

[0008] In one alternative embodiment, a plurality of flexible sleeves are evenly spaced along the annular gap between the inner peripheral wall of the housing and the inductor body.

[0009] In one optional embodiment, the wall thickness of the flexible sleeve is h2, which is 3.95 mm to 4.05 mm, and / or the axial length of the flexible sleeve is 63.5 mm to 66.5 mm, and / or the inner diameter of the flexible sleeve is 7 mm to 7.5 mm.

[0010] In one optional embodiment, the flexible sleeve is made of a flexible polymer material or composite material with a temperature resistance greater than 150°C, including any one of silicone rubber, fluororubber, polytetrafluoroethylene, or polytetrafluoroethylene-coated fiberglass cloth.

[0011] Secondly, the present invention also provides a potting process for stress relief in inductor potting, using the above-mentioned inductor, the potting process including: The inductor body is housed inside the casing; The sealing end of the flexible sleeve, which is sealed at one end, is oriented toward the inner wall of the bottom of the housing so that the flexible sleeve is placed in the gap between the inner wall of the housing and the inductor body. Inject potting compound into the housing so that the filling liquid level of the potting compound is lower than the height of the open end of the flexible sleeve.

[0012] In one alternative implementation, the end face of the open end of the flexible sleeve is configured to be flush with or lower than the port surface of the housing.

[0013] In one optional embodiment, before the step of placing the inductor body inside the housing, the method further includes: immersing the sealing end of the flexible sleeve in water to a depth of 25mm to 35mm, letting it stand for 4 to 6 minutes, and then checking whether there is water leakage inside the flexible sleeve to confirm that the sealing end is qualified.

[0014] After injecting potting compound into the housing so that the filling liquid level of the potting compound is lower than the height of the open end of the flexible sleeve, the process further includes: placing the potted inductor in a curing oven and curing it at a constant temperature of 80℃ to 120℃ for 2 to 4 hours.

[0015] In one optional embodiment, in the step of injecting potting compound into the housing such that the filling liquid level of the potting compound is lower than the height of the open end of the flexible sleeve, the injection rate of the potting compound is 0.5L / min to 2L / min, the potting compound fills naturally under the action of gravity, and the potting compound completely covers the inductor body.

[0016] This invention solves the technical problem in existing aluminum-cased inductors where the thermal expansion stress of the potting compound cannot be released, leading to core cracking and inductance at one end. The sealed end of the flexible sleeve faces the bottom of the casing, while the open end extends to the outside of the potting compound layer. The flexible sleeve is hollow to provide a stress release space, allowing for a controllable retreat channel for the thermal expansion of the potting compound. This allows the internal stress generated by the thermal expansion of the potting compound to be transferred from the magnetic core and guided to the hollow space of the flexible sleeve for orderly release, without increasing the package volume or altering the original structure of the inductor. This avoids stress concentration on the core cover or central pillar, prevents core cracking and breakage, and maintains the original insulation, heat dissipation, and structural stability of the inductor. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a top view of an inductor according to an embodiment of the present invention; Figure 2 This is a front view of an inductor according to an embodiment of the present invention; Figure 3 This is a front view of a flexible sleeve for an inductor according to an embodiment of the present invention; Figure 4 for Figure 3 Cross-sectional view at point A in the middle; Figure 5 for Figure 3 Cross-sectional view at point B; Figure 6 This is a schematic diagram of a potting process for stress relief of an inductor in an embodiment of the present invention.

[0019] Explanation of reference numerals in the attached figures: 10. Housing; 20. Inductor body; 30. Encapsulating layer; 40. Flexible sleeve. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] The following is combined Figures 1 to 6 The following describes embodiments of the present invention.

[0022] According to an embodiment of the present invention, in one aspect, an inductor is provided. For example... Figure 1 , Figure 2 As shown, the inductor includes a housing 10, an inductor body 20, a potting compound layer 30, and at least one flexible sleeve 40 sealed at one end.

[0023] The housing 10 is made of high thermal conductivity aluminum alloy and has a rectangular box-like structure with a bottom inner wall and four side walls, and an open top. The bottom inner wall of the housing 10 supports the inductor body 20, and an annular gap is formed between the side walls of the housing 10 and the inductor body 20 for filling the potting compound layer 30. The open top of the housing 10 is the injection port for the potting compound. After potting, the liquid level of the potting compound layer 30 is located at a preset position below the open top.

[0024] The internal dimensions of the housing 10 are determined based on the volume of the inductor body 20, heat dissipation requirements, and installation space. In this embodiment, an annular gap of 1mm to 5mm is reserved between the internal cavity of the housing 10 and the inductor body 20 to accommodate the flexible sleeve 40 and ensure that the potting compound layer 30 can completely wrap the inductor body 20.

[0025] The inductor body 20 is disposed inside the housing 10; the inductor body 20 includes a magnetic core and a coil assembly wound on the magnetic core, and the magnetic core and the coil assembly are fixedly connected.

[0026] The magnetic core is made of soft magnetic materials such as ferrite, amorphous nanocrystals, or metal magnetic powder cores, and is in the shape of E, U, or ring. The magnetic core includes a bottom core, a middle post, and a top cover plate (or side posts). The middle post is located between the bottom core and the top cover plate, and the coil assembly is wound on the middle post.

[0027] The coil assembly is made of enameled copper wire or Litz wire, and the number of turns and wire diameter are determined according to the inductance and rated current requirements of the inductor. The coil assembly is fixedly connected to the magnetic core by insulating glue or a mounting bracket to form an integrated inductor body 20.

[0028] The inductor body 20 is placed inside the housing 10. Its bottom is fixed to the bottom inner wall of the housing 10 by means of a thermally conductive pad or adhesive to ensure that the inductor body 20 does not shift during potting and subsequent use.

[0029] The potting compound layer 30 fills the gap between the housing 10 and the inductor body 20. The potting compound layer 30 is formed by mixing and degassing any one of two-component addition-type or condensation-type silicone potting compound, epoxy resin potting compound, or polyurethane potting compound, and then injecting it into the housing 10 for curing.

[0030] The potting compound layer 30 fills the bottom gap between the bottom inner wall of the housing 10 and the bottom of the inductor body 20, the side gap between the side wall of the housing 10 and the side of the inductor body 20, and the top gap between the top of the inductor body 20 and the surface of the potting compound. The height of the potting compound layer 30 is not lower than the top surface of the inductor body 20 to ensure that the inductor body 20 is completely encapsulated by the potting compound.

[0031] In this embodiment, a height difference of 1 mm to 5 mm is maintained between the liquid level of the potting compound layer 30 and the open end of the housing 10 to prevent the potting compound from overflowing.

[0032] The potting compound layer 30 completely encapsulates the inductor body 20. On the one hand, it can conduct the heat generated by the inductor body 20 during operation to the housing 10 through the potting compound, achieving efficient heat dissipation. On the other hand, it can fix the inductor body 20, resist vibration and mechanical shock, and improve product reliability. At the same time, the potting compound layer 30, as an insulating medium, can enhance the electrical insulation performance between the inductor body 20 and the housing 10.

[0033] At least one flexible sleeve 40 is sealed at one end, with the sealed end of the flexible sleeve 40 facing the bottom of the housing 10, and the open end of the flexible sleeve 40 extending to the outside of the potting compound layer 30. The interior of the flexible sleeve 40 is hollow to serve as a stress relief space when the potting compound layer 30 expands thermally.

[0034] The flexible sleeve 40 is a flexible tubular structure that is closed at one end and open at the other. The sealed end of the flexible sleeve 40 is arranged facing the bottom inner wall of the housing 10, and the open end extends upward and extends beyond the preset filling liquid surface of the potting compound layer 30. The interior of the flexible sleeve 40 forms a hollow reserved space, which is not filled with potting compound, so as to serve as a stress release space for the potting compound when it expands in volume due to heat.

[0035] The hollow space inside the flexible sleeve 40 provides a controllable release channel for the thermal expansion of the potting compound. When the inductor operates under high temperature conditions, the potting compound expands in volume due to heat. Because the flexible sleeve 40 is hollow, the expanding compound is squeezed towards the hollow space, allowing the expansion stress to be released in an orderly manner along the hollow space. This avoids stress concentration on the core cover or the central column, thus eliminating quality defects such as core cracking and breakage at the source.

[0036] In this embodiment, the open end of the flexible sleeve 40 is connected to the external atmospheric environment, so that the hollow reserved space can maintain the air pressure balance with the outside atmosphere.

[0037] The flexible sleeve 40 is disposed in the gap between the inner wall of the housing 10 and the inductor body 20. The flexible sleeve 40 maintains a clearance fit with both the inductor body 20 and the inner wall of the housing 10. That is, the flexible sleeve 40 does not directly contact the inductor body 20 or the inner wall of the housing 10, so as to avoid affecting the assembly accuracy of the inductor body 20 and the uniformity of the potting compound filling.

[0038] The sealing end of the flexible sleeve 40 is sealed by hot pressing, high-frequency welding or adhesive sealing. The sealing strength of the sealing end must be sufficient to withstand the impact pressure when the potting compound is injected and the thermal expansion and extrusion during the curing process of the potting compound without leakage.

[0039] By providing at least one one-end sealed flexible sleeve 40 inside the housing 10, with the sealed end of the flexible sleeve 40 facing the bottom of the housing 10 and the open end extending to the outside of the potting compound layer 30, and keeping the interior of the flexible sleeve 40 hollow to serve as a stress release space, this hollow reserved space provides a controllable clearance channel for the thermal expansion of the potting compound. This allows the internal stress generated by the thermal expansion of the potting compound to be transferred from the magnetic core and guided to the hollow space of the flexible sleeve 40 for orderly release without increasing the package volume or altering the original structure of the inductor body 20. This avoids stress concentration on the magnetic core cover or central column, prevents magnetic core cracking and breakage, and maintains the original insulation, heat dissipation, and structural fixation performance of the inductor. Thus, the technical problem of the inability to release the thermal expansion stress of the potting compound in existing aluminum-cased inductors, leading to magnetic core cracking and inductance attenuation, is solved.

[0040] In one embodiment, the flexible sleeve 40 is made of a flexible polymer material or composite material with a temperature resistance greater than 150°C, and the flexible polymer material or composite material includes any one of silicone rubber, fluororubber, polytetrafluoroethylene, or polytetrafluoroethylene-coated fiberglass cloth.

[0041] Specifically, silicone rubber, such as methyl vinyl silicone rubber, has excellent high and low temperature resistance, with a working temperature range of -60℃ to +250℃, good elasticity and resilience, and can still recover its original shape after repeated extrusion. At the same time, it has good chemical compatibility with most potting compound systems, such as silicone potting compounds, and does not swell or deteriorate in performance after long-term contact.

[0042] Fluororubber has superior oil and chemical resistance, making it suitable for highly corrosive environments where potting compounds contain acidic or alkaline components. Its maximum temperature resistance can reach 200℃~250℃, but the material cost is relatively high.

[0043] Polytetrafluoroethylene (PTFE) has an extremely low coefficient of friction (0.04 to 0.10) and excellent chemical stability. It hardly reacts with any potting compound components and has a wide operating temperature range (-200℃ to +260℃). However, its flexibility is slightly inferior to that of silicone rubber.

[0044] Polytetrafluoroethylene-coated fiberglass cloth is a composite material formed by coating a PTFE coating on the surface of fiberglass woven cloth. The fiberglass woven layer provides the pipe with tensile strength and tear resistance, with a tensile strength of over 200 MPa. The PTFE coating provides good sealing and chemical inertness. This composite material has both high strength and high flexibility, making it suitable for applications with thin walls that need to withstand large compressive stress.

[0045] The aforementioned materials exhibit excellent chemical inertness to acidic or alkaline components in potting compounds, as well as high-temperature aging products, and do not swell, corrode, or degrade in performance with prolonged contact. The design, with a temperature resistance exceeding 150℃, ensures that the mechanical and sealing properties of the flexible sleeve 40 do not significantly degrade due to temperature during high-temperature baking and curing of inductor products and long-term high-temperature operation.

[0046] By selecting flexible polymer or composite materials that are resistant to temperatures above 150℃ and corrosion from potting compounds, the flexible bushing 40 maintains stable flexibility and structural integrity throughout the entire lifecycle of the inductor product. The high elasticity of silicone rubber and fluororubber ensures that the bushing continues to provide buffering and pressure relief during repeated thermal cycling; the chemical inertness of PTFE and glass fiber composite materials ensures that the bushing wall does not swell, thicken, or become brittle after long-term contact with potting compounds, preventing the collapse or failure of the hollow reserved space due to high-temperature aging, hardening, embrittlement, or corrosion damage of the material, thus ensuring the long-term effectiveness and reliability of the stress relief function.

[0047] like Figure 3 As shown, in one embodiment, the axial length of the flexible sleeve 40 is a, the vertical distance between the bottom inner wall of the housing 10 and the potting compound layer 30 is b, and the total internal depth of the housing 10 is c, where b≤a≤c.

[0048] When a ≥ b, the open end of the flexible sleeve 40 can reliably extend above the liquid surface of the potting compound layer 30, ensuring that the hollow reserved space remains connected to the external atmosphere. If a < b, the open end of the flexible sleeve 40 will be completely submerged by the potting compound, and the air in the hollow reserved space will be sealed inside the sleeve, forming a closed air cavity. In this case, when the potting compound thermally expands, it compresses the air in the closed air cavity. After the air is compressed, the pressure increases sharply. According to the ideal gas law PV=nRT, the pressure doubles when the volume is compressed by 50%. As the pressure increases, the air cavity's ability to yield to the expansion of the external colloid decreases sharply. Eventually, the high-pressure air in the air cavity can no longer be compressed, and the expansion stress of the potting compound will be transferred to the magnetic core, leading to stress release failure.

[0049] When a ≤ c, the sealing end of the flexible sleeve 40 will not extend beyond the opening end of the housing 10, ensuring that the entire flexible sleeve 40 is located inside the housing 10, and the open end is not higher than the surface of the opening end of the housing 10. If a > c, the sealing end of the flexible sleeve 40 will extend beyond the opening end of the housing 10 and be exposed to the air. The exposed part will interfere with other components during subsequent assembly (such as aluminum shell cover installation, PCB board mounting), and the exposed sleeve end may be squeezed, bent, or even damaged during handling or assembly, causing the sealing end to rupture and lose its sealing performance.

[0050] Specifically, for a typical application scenario where the total internal depth c of the housing 10 is 70mm and the liquid level of the potting compound 30 is 55mm from the bottom of the housing 10 (i.e., b=55mm), the axial length a of the flexible sleeve 40 can be selected as 60mm to 68mm (i.e., satisfying 55mm≤a≤70mm). Within this range, when a=60mm, the open end extends 5mm beyond the liquid surface, which is sufficient to ensure the unobstructed flow of the gas pressure balance channel; when a=68mm, the open end is basically close to the opening end of the housing 10, maximizing the use of the internal height of the housing 10 to provide the longest stress release space.

[0051] By limiting the axial length 'a' of the flexible sleeve 40 to between 'b' and 'c', the open end extends above the surface of the potting compound, ensuring that the hollow reserved space remains connected to the outside atmosphere. This ensures that as the potting compound rises from room temperature (25°C) to the maximum operating temperature (150°C), air in the hollow reserved space can freely escape without creating reverse pressure that hinders the flow of the compound. It also ensures that the entire flexible sleeve 40 does not extend beyond the open end of the housing 10, allowing the sleeve to be fully contained within the housing 10 without altering the overall dimensions and mechanical interfaces of the inductor product. This ensures compatibility between the product and downstream systems, such as photovoltaic inverters and on-board chargers. Furthermore, it ensures that the potting compound layer 30 covers the top of the inductor body 20 for complete encapsulation and sufficient heat dissipation. Since 'a ≥ b' means that the open end extends beyond the top of the inductor body, this length condition also ensures that the inductor body 20 is completely encapsulated by the potting compound.

[0052] like Figure 3 , Figure 5 As shown, in one embodiment, the sealing end of the flexible sleeve 40 has a sealing region with a flat structure. The thickness of the sealing region is h1, where h1 is 1.7mm to 1.9mm, and the axial length of the sealing region along the flexible sleeve 40 is L, where L is 7mm to 9mm.

[0053] The sealing area is formed through a hot-pressing fusion process. During the hot-pressing process, the inner and outer layers of the flexible sleeve 40 melt and fuse together under the combined action of heating and pressurization, forming a uniform, interface-free, flat sealing structure. The temperature is typically heated to 200℃–350℃, depending on the material type, and the pressure is usually 0.2MPa–0.5MPa. The inner surface of the flat structure is tightly fitted, without any microchannels or interfacial gaps that allow liquid penetration.

[0054] The thickness of the flat structure is controlled between 1.7mm and 1.9mm, a range of optimal parameters determined through extensive process verification. If the thickness is less than 1.7mm, it means that the amount of material in the hot-pressed fusion area is insufficient, and there may be local weak points at the fusion interface. When subjected to the impact of potting compound injection (the injection pressure is usually 0.1MPa to 0.3MPa), micro-leakage may occur at the weak points. If the thickness is greater than 1.9mm, the material in the hot-pressed area is excessively accumulated, and the rigidity of the sealing end is significantly increased. This causes a rigid tip effect at the sealing end of the entire flexible sleeve 40, that is, stress concentration occurs at the junction of the flexible section and the rigid sealing section of the sleeve. During repeated thermal cycling, fatigue fracture may occur at this junction.

[0055] In some alternative embodiments, h1 is 1.7 mm to 1.8 mm.

[0056] In some alternative embodiments, h1 is 1.8 mm to 1.9 mm.

[0057] In some alternative embodiments, h1 is 1.7mm, 1.8mm, 1.9mm, 1.81mm, 1.82mm, etc.

[0058] The axial length of the sealing area is controlled between 7mm and 9mm. This length provides sufficient area for thermoforming to ensure sealing strength, while avoiding an excessively long sealing area that would shorten the effective hollow length of the flexible sleeve 40. Taking an axial length a=65mm as an example, when the sealing area length is 8mm, the effective hollow length is 57mm (accounting for 87.7% of the total sleeve length); if the sealing area length increases to 15mm, the effective hollow length is only 50mm (accounting for only 76.9%), and the effective volume of the stress relief space is reduced by approximately 14%.

[0059] In some alternative embodiments, L is 7mm to 8mm.

[0060] In some alternative embodiments, L is 8mm to 9mm.

[0061] In some alternative embodiments, L is 7mm, 8mm, 9mm, 8.1mm, 8.2mm, 8.3mm, etc.

[0062] By defining the flat structure, thickness, and axial length of the sealing area, the airtightness of the flexible sleeve 40 is ensured from both structural and process perspectives. It can withstand the impact pressure and thermal expansion during potting compound injection without leakage, preventing potting compound from seeping into the hollow reserved space and causing stress relief failure. The flat structure design of the sealing area allows the flexible sleeve 40 to occupy less radial space in the narrow gap between the housing 10 and the inductor body 20. The thickness of the flat sealing end is only 1.7mm to 1.9mm, much smaller than the outer diameter of the sleeve body, effectively avoiding interference between the sealing end and the inductor body 20 or the inner wall of the housing 10. While ensuring sealing strength, the effective hollow length of the flexible sleeve 40 is maximized, ensuring sufficient volume for stress relief. Through the optimization of hot pressing process parameters, the material structure of the sealing area is uniformly densified, ensuring consistent sealing performance at the sealing end and avoiding the quality risk of poor sealing in individual products during mass production.

[0063] like Figure 4 As shown, in one embodiment, the inner diameter of the flexible sleeve 40 is d, the minimum horizontal distance between the outer wall of the inductor body 20 and the inner wall of the housing 10 is e, and the rated temperature rise of the inductor body 20 is f, wherein d is positively correlated with e and f.

[0064] In other words, the larger the minimum horizontal distance e between the outer wall of the inductor body 20 and the inner wall of the housing 10, the wider the annular gap between the housing 10 and the inductor body 20, the more radial space is available for arranging the flexible sleeve 40, and the inner diameter d can be increased accordingly to make fuller use of the gap space to provide a larger stress relief volume; conversely, the smaller e is, the more compact the packaging space is, and the inner diameter d must be reduced accordingly to avoid interference between the outer wall of the flexible sleeve 40 and the inductor body 20 or the inner wall of the housing 10.

[0065] The larger the rated temperature rise value f of the inductor body 20, the greater the heat generated by the magnetic core and coil assembly when the inductor operates under rated conditions, the higher the surface temperature of the inductor body 20, and the higher the temperature rise of the potting compound layer 30. According to the solid thermal expansion formula ΔV=α·V0·ΔT (where α is the volumetric thermal expansion coefficient of the potting compound, and α for typical silicone potting compounds is approximately 6×10⁻⁶),... -4 / ℃~9×10 -4 / ℃, V0 is the initial volume of the potting compound, ΔT is the temperature change), the larger the temperature rise ΔT, the larger the volume expansion increment ΔV of the potting compound. Therefore, a larger inner diameter d is needed to provide a larger stress relief volume to accommodate more expansion displacement of the colloid.

[0066] Specifically, for applications with e=12mm and f=85℃, d can be selected as 7mm~8mm; for applications with e=6mm and f=45℃, d can be selected as 2.5mm~3.5mm. In actual design, the positive correlation between d and e, f can be quantitatively determined through the empirical formula d = k1·e + k2·f + d0 (where k1 and k2 are proportionality coefficients, and d0 is the minimum inner diameter constant) or by looking up a table.

[0067] By making the inner diameter d of the flexible sleeve 40 positively correlated with the distance e from the outer wall of the inductor body 20 to the inner wall of the housing 10 and the rated temperature rise value f, a precise match is achieved between the inner diameter of the sleeve and the actual packaging space and heat generation characteristics of the inductor. Specifically, for high-power (e.g., 150kW class) and high-heat-generating inductor products, the rated temperature rise value f is relatively large, reaching 80℃~100℃. The inner diameter d is automatically configured to a larger value, providing sufficient stress relief volume to accommodate the large volume expansion increment of the potting compound caused by the large temperature rise (for potting compound volume V0=1L, ΔT=80℃, α=8×10). -4In scenarios with a temperature of / ℃, the volume expansion increment ΔV≈64mL, requiring multiple large-diameter sleeves to provide the corresponding volume; for low-power (e.g., 60kW level), low-heat inductor products or scenarios with extremely compact packaging space (e≤5mm), the inner diameter d is automatically configured to a smaller value to ensure that the flexible sleeve 40 can be reliably placed into the narrow gap without extrusion deformation or spatial interference; ③ This positive correlation design means that the technical solution of the present invention does not require independent sleeve size simulation and verification for each inductor product. The optimal inner diameter can be quickly determined based on the two parameters e and f, which has good design versatility and engineering convenience, and can flexibly adapt to various inductor products from kW level to MW level, with different power levels and different packaging sizes.

[0068] In one embodiment, the number of flexible sleeves 40 is n, the overall volume of the inductor body 20 is v, and the rated temperature rise of the inductor body 20 is f, wherein n is positively correlated with v and f.

[0069] In other words, the larger the overall volume v of the inductor body 20, the larger the product size and the more potting compound is required. The amount of potting compound is approximately proportional to the volume v of the inductor body 20, because the size of the housing 10 needs to increase synchronously with the volume v of the inductor body 20 to maintain clearance. Under the same temperature rise conditions, the larger the total volume of the potting compound, the larger the total volume increment ΔVtotal of thermal expansion, requiring more flexible sleeves 40 to provide sufficient total stress relief volume (total volume is the sum of the cross-sectional area of ​​the inner diameter of each sleeve × its effective length).

[0070] The higher the rated temperature rise value f of the inductor body 20, the greater the thermal expansion increment per unit volume of potting compound, and the more flexible sleeves 40 are needed to distribute and release the expansion stress. By reasonably increasing the number of flexible sleeves 40, the amount of thermal expansion displacement borne by each sleeve can be reduced, that is, the amount of compound squeezed into each sleeve can be reduced, avoiding excessively large inner diameters of individual sleeves. Excessively large inner diameters mean that the outer diameter of the sleeves also increases accordingly (when the wall thickness remains constant), which may encroach on the flow channels and heat conduction paths of the potting compound within the limited annular gap, affecting the uniformity of the potting compound's coating on the inductor body 20 and the heat dissipation efficiency.

[0071] Specifically, for the GT 150kW BOOST inductor (V≈2.5×10), 6 (mm³, f≈85℃), 4 to 6 flexible bushings can be installed; for SMT 60kW BOOST inductors (v≈1.2×10), 6 (mm³, f≈55℃), 2 to 3 flexible sleeves 40 can be installed. In engineering design, the determination of n can also consider redundancy design, that is, adding 1 sleeve as failure redundancy based on the theoretically calculated number of sleeves, further improving the reliability margin of the system.

[0072] By making the number n of flexible sleeves 40 positively correlated with the overall volume v and rated temperature rise f of the inductor body 20, and based on the matching relationship between the total stress relief capacity and the total thermal expansion of the potting compound, for large-volume, high-power inductor products, increasing the number of sleeves provides sufficient total stress relief volume, effectively avoiding the problem of insufficient expansion stress release and some residual stress still acting on the magnetic core due to insufficient capacity of a single sleeve. By sharing the expansion displacement with multiple sleeves, the inner diameter of each sleeve can be kept within a reasonable range, avoiding excessive occupation of the potting compound flow channel and heat conduction path by a single ultra-large inner diameter sleeve, ensuring that the potting compound can continuously wrap the inductor body 20 and form a complete heat conduction path inside the housing 10. The uniform distribution of each sleeve along the circumference also allows the expansion stress to be released uniformly in all directions of the circumference, avoiding additional bending deformation caused by the magnetic core being subjected to asymmetrical extrusion force due to the concentration of sleeves in a certain direction. For small-volume, low-power products, a smaller number of sleeves can meet the pressure relief requirements, which helps to simplify the assembly process, reduce material costs and assembly time, and improve production efficiency.

[0073] In one embodiment, a plurality of flexible sleeves 40 are arranged at uniform intervals along the annular gap between the inner peripheral wall of the housing 10 and the inductor body 20.

[0074] Uniformly spaced arrangement means that each flexible sleeve 40 is distributed at equal angles or equal arc lengths in the circumferential direction. For example, when two flexible sleeves 40 are installed, the adjacent sleeves are 180° apart in the circumferential direction (symmetrical arrangement); when three are installed, they are 120° apart; and when four are installed, they are 90° apart.

[0075] The uniform spacing ensures that each sleeve is symmetrically distributed within the annular gap between the housing 10 and the inductor body 20, resulting in symmetrical and balanced stress relief channels for the magnetic core in the circumferential direction. During assembly, this uniform spacing can be achieved using a positioning fixture. The positioning fixture has positioning claws corresponding to the number of sleeves, distributed at equal angles along the circumference. The operator inserts each flexible sleeve 40 into its corresponding positioning claw, ensuring the uniform distribution accuracy of each sleeve in the circumferential direction.

[0076] In contrast to uniformly spaced arrangements, there is a concentrated arrangement (i.e., all sleeves are concentrated in the same circumferential area). With a concentrated arrangement, stress relief channels are dense and pressure-relieving capabilities are strong within this concentrated area, while there are no stress relief channels on the opposite side. When the potting compound thermally expands, the expansion stress will concentrate on one side of the magnetic core in the area without sleeves, causing the magnetic core to experience asymmetrical unidirectional thrust and bend. This bending deformation can also cause cracks in the core's central pillar or cover plate, especially for E-type magnetic cores with a larger aspect ratio, where the bending moment generated by the unidirectional thrust is greater, increasing the risk of cracking.

[0077] By arranging multiple flexible sleeves 40 evenly spaced along the annular gap, the internal stress generated during the thermal expansion of the potting compound is uniformly released in all directions of the circumference. This avoids the problem of lateral load on the magnetic core caused by insufficient stress release in a certain direction due to uneven sleeve arrangement. Specifically, the symmetrical pressure relief mechanism brought about by the uniform spacing ensures that the resultant compressive force on the magnetic core in the circumference is zero or close to zero. The magnetic core is only subjected to uniform hydrostatic pressure rather than directional shear stress or bending stress. This is especially important for ferrite cores, whose shear strength is much lower than their compressive strength, further ensuring the structural integrity and long-term reliability of the magnetic core.

[0078] like Figure 3 , Figure 4 As shown, in one embodiment, the wall thickness of the flexible sleeve 40 is h2, which is 3.95mm to 4.05mm, and / or the axial length of the flexible sleeve 40 is 63.5mm to 66.5mm, and / or the inner diameter of the flexible sleeve 40 is 7mm to 7.5mm.

[0079] The above three dimensional parameters constitute the core geometric dimension combination of the flexible sleeve 40, which is suitable for inductor product packaging scenarios with medium power levels (such as 60kW to 150kW).

[0080] The wall thickness of 3.95mm to 4.05mm ensures that the flexible sleeve 40 has sufficient structural strength to maintain the shape of the hollow reserved space. From the perspective of solid mechanics, the circumferential bending stiffness of the sleeve corresponding to a wall thickness of 3.95mm is sufficient to resist the lateral pressure during the injection of potting compound (injection pressure of approximately 0.1MPa to 0.2MPa) without significant deformation (radial deformation ≤0.3mm). This ensures the morphological stability of the hollow cavity during the potting process and prevents the sleeve from being flattened, resulting in a reduction in the hollow volume or complete closure and failure. At the same time, the wall thickness of approximately 4mm also provides flexibility, allowing the sleeve to undergo slight elastic deformation under the expansion and compression of the potting compound (radial compressibility of approximately 0.2mm to 0.5mm), absorbing and buffering some of the impact stress through elastic deformation.

[0081] In some alternative embodiments, h2 is 3.95 mm to 4.00 mm.

[0082] In some alternative embodiments, h2 is 4.00 mm to 4.05 mm.

[0083] In some alternative embodiments, h2 is 3.95mm, 3.96mm, 4mm, 4.05mm, etc.

[0084] The axial length of 63.5mm to 66.5mm is suitable for the internal depth of a typical medium-power inductor aluminum case (usually 70mm to 75mm), while considering that the potting compound level is usually set at a height of 60mm to 65mm from the bottom of the case. In this scenario, when a=64mm, the open end extends approximately 4mm to 1mm beyond the liquid surface, ensuring unobstructed air pressure balance channels and that the end face does not exceed the opening end of the case (70mm to 75mm), providing sufficient axial length margin.

[0085] In some alternative embodiments, a is 63.5 mm to 65 mm.

[0086] In some alternative embodiments, a is 65mm to 66.5mm.

[0087] In some alternative embodiments, a is 63.5mm, 64mm, 64.5mm, 65mm, 65.5mm, 66mm, 66.5mm, etc.

[0088] The inner diameter of 7mm to 7.5mm provides ample stress relief volume. Calculated using a single sleeve with an inner diameter of 7mm and an effective hollow length of 56mm (total length 64mm minus the 8mm sealing section), the stress relief volume of a single sleeve is approximately π×(7 / 2)²×56≈2155mm³ (approximately 2.15mL). With four sleeves, the total stress relief volume is approximately 8.6mL, sufficient to accommodate the volume expansion of the potting compound in a 150kW inductor at 85℃ (total potting compound volume approximately 1.2L, expansion increment at ΔT=85℃ approximately 1.2×10⁻⁶). 6 ×8×10 -4 ×85≈81.6mm³). The volume of a single sleeve is much larger than the actual amount of colloid extruded into a single sleeve (81.6 / 4≈20.4mm³, which is only 0.95% of the volume of a single sleeve of 2.15mL), with an extremely high safety margin (safety factor>100), ensuring that the potting compound will not produce stress residue due to insufficient stress release space under any extreme working conditions.

[0089] In some alternative embodiments, d is 7mm, 7.1mm, 7.2mm, 7.3mm, 7.4mm, 7.5mm, etc.

[0090] In one embodiment, the flexible sleeve 40 is disposed between the inductor body 20 and the inner wall of the housing 10, and is clearance-fitted with both the inductor body 20 and the inner wall of the housing 10. The potting compound layer 30 forms a continuous heat conduction path inside the housing 10, and the potting compound layer 30 is used to conduct the heat generated by the inductor body 20 during operation to the housing 10.

[0091] Clearance fit refers to the presence of minute gaps of 0.2mm to 0.5mm between the outer wall of the flexible sleeve 40 and the outer wall of the inductor body 20, and between the outer wall of the flexible sleeve 40 and the inner wall of the housing 10. These minute gaps are filled with potting compound during the potting process, so that the flexible sleeve 40 is completely surrounded by the potting compound, but does not form rigid contact with the inductor body 20 and the housing 10.

[0092] Meanwhile, the potting compound layer 30 forms a continuous heat conduction path inside the housing 10, which is used to conduct the heat generated by the inductor body 20 during operation to the housing 10. Specifically, the heat conduction path is as follows: inductor body 20 (magnetic core and coil assembly) → potting compound in contact with the surface of the inductor body 20 → potting compound passing through the annular gap between the housing 10 and the inductor body 20 (including the small gap around the outer wall of the flexible sleeve 40) → potting compound in contact with the inner wall of the housing 10 → housing 10 (aluminum shell) → external environment (heat is dissipated through natural convection or air cooling).

[0093] The thermal conductivity of the potting compound is typically 0.6 W / (m·K) to 2.0 W / (m·K), while the thermal conductivity of the aluminum shell is as high as 237 W / (m·K). Therefore, the bottleneck in the heat conduction path lies in the heat conduction of the potting compound layer, not the aluminum shell. The gap fit design ensures that the flexible sleeve 40 is completely surrounded by the potting compound, forming a continuous layer around the outer wall of the sleeve. If the flexible sleeve 40 is in direct contact with the inductor body 20 or the inner wall of the shell 10, the potting compound layer thickness at the contact point is zero, and an effective heat conduction path cannot be formed. Heat can only be conducted around the contact point, resulting in increased local thermal resistance and decreased heat transfer efficiency.

[0094] According to an embodiment of the present invention, in another aspect, a potting process for stress relief of inductor potting is also provided, employing the aforementioned inductor, such as... Figure 6 As shown, the potting process includes: S11. The inductor body 20 is placed inside the housing 10.

[0095] First, an aluminum housing 10 with an open top is provided. The inner cavity of the housing 10 is cleaned to remove oil, dust, and metal debris from the inner wall, ensuring good adhesion between the subsequent potting compound and the inner wall of the housing 10. Cleaning can be done by blowing with compressed air and wiping with an organic solvent (such as anhydrous ethanol or acetone), and then letting it air dry.

[0096] Secondly, a pre-wound and assembled inductor body 20 is provided. The inductor body 20 includes a magnetic core and a coil assembly wound on the magnetic core. The magnetic core and coil assembly are fixedly connected by insulating adhesive or a mounting bracket to ensure that the magnetic core and coil assembly do not shift relative to each other during subsequent potting and long-term operation. Before being placed into the housing 10, the inductor body 20 undergoes electrical performance testing, including inductance, quality factor Q, DC resistance DCR, and insulation withstand voltage, to ensure that the inductor body 20 placed into the housing 10 is a qualified product.

[0097] Then, the inductor body 20 is placed inside the housing 10 according to a preset arrangement. Depending on the application scenario and installation space requirements of the inductor product, the inductor body 20 can be placed vertically or horizontally. Vertical placement means that the central column of the magnetic core is perpendicular to the bottom inner wall of the housing 10, while horizontal placement means that the central column of the magnetic core is parallel to the bottom inner wall of the housing 10. After the inductor body 20 is placed, its bottom is bonded and fixed to the bottom inner wall of the housing 10 with thermally conductive adhesive, or a positioning boss or positioning groove is preset on the bottom inner wall of the housing 10 to limit the horizontal displacement of the inductor body 20. After the inductor body 20 is fixed, an annular gap is formed between the outer wall of the inductor body 20 and the inner wall of the housing 10. This annular gap is used to subsequently accommodate the flexible sleeve 40 and the filling potting compound layer 30.

[0098] After the inductor body 20 is inserted and fixed, check again whether the position of the inductor body 20 inside the housing 10 is accurate, ensuring that the inductor body 20 is centered and the distance between it and each side wall of the housing 10 is uniform. If the inductor body 20 is biased to one side, it will cause the gap on one side to be too small and the gap on the other side to be too large, affecting the placement of the flexible sleeve 40 and the uniformity of the filling of the potting adhesive layer 30. After confirming that the position is correct, proceed to step S12.

[0099] By cleaning the inner cavity of the housing 10, the interface between the potting compound and the inner wall of the aluminum housing is kept clean and free of contamination, improving the adhesive strength and thermal conductivity of the potting compound. By fixing the inductor body 20 to the housing 10, displacement or floating of the inductor body 20 due to the flow and impact of the potting compound during subsequent potting processes is prevented, ensuring the positioning accuracy of the inductor body 20 within the housing 10 and the uniformity of the potting compound layer 30 thickness. Electrical performance testing of the inductor body 20 before insertion prevents defective products from flowing into subsequent potting processes, thus avoiding waste of materials and time.

[0100] S12. Position the sealed end of the flexible sleeve 40, which is sealed at one end, toward the inner wall of the bottom of the housing 10, so that the flexible sleeve 40 is placed in the gap between the inner wall of the housing 10 and the inductor body 20.

[0101] Depending on the type of inductor product, a flexible sleeve 40 of appropriate specifications is selected. The inner diameter of the flexible sleeve 40 is determined based on the minimum horizontal distance between the outer wall of the inductor body 20 and the inner wall of the housing 10, as well as the rated temperature rise of the inductor body 20. The axial length is determined based on the internal depth of the housing 10 and the height of the pre-set potting compound filling liquid. The flexible sleeve 40 is made of a glass fiber and silicone composite sleeve, or any one of silicone rubber, fluororubber, or polytetrafluoroethylene.

[0102] At least one flexible sleeve 40, having passed the sealing test, is placed sequentially in the annular gap between the inner wall of the housing 10 and the inductor body 20, according to a predetermined arrangement and position. The placement method is as follows: with the sealed end facing the bottom inner wall of the housing 10 and the open end facing upwards, the flexible sleeve 40 is slowly inserted from top to bottom along the annular gap. During insertion, the flexible sleeve 40 must be kept vertical to avoid bending or twisting. Care must be taken to prevent the sealed end from scraping against the bottom inner wall of the housing 10 or the surface of the inductor body 20 to prevent damage to the sealed end or the insulation layer on the surface of the inductor body 20.

[0103] After the flexible sleeve 40 is placed in position, its axial position is adjusted so that the open end face extends above the pre-set potting compound filling liquid surface. Specifically, it is necessary to ensure that the axial length of the flexible sleeve 40 is not less than the vertical distance between the bottom inner wall of the housing 10 and the pre-set potting compound filling liquid surface, so that the open end face is higher than the potting compound liquid surface by a certain height (approximately 1mm to 5mm), ensuring that the hollow reserved space remains connected to the outside atmosphere. At the same time, a certain gap (approximately 0.5mm to 2mm) is left between the sealing end of the flexible sleeve 40 and the bottom inner wall of the housing 10 to prevent the sealing end from directly contacting the bottom inner wall, which could lead to pressure deformation or damage to the sealing area.

[0104] When adjusting the axial position of the flexible sleeve 40, it is also necessary to ensure that the open end faces of each flexible sleeve 40 are approximately flush in the height direction. Especially when multiple flexible sleeves 40 are installed, if the heights of the sleeves are not uniform, the open ends of some sleeves may be submerged in potting compound, resulting in a loss of air pressure balance function. In specific operations, the same height reference can be used for positioning, such as using a straightedge or height gauge to assist in measurement, ensuring that the open end faces of each sleeve are on the same horizontal plane, and the height deviation is controlled within ±1mm.

[0105] After the flexible sleeve 40 is placed in position, it needs to be temporarily fixed to prevent displacement, tilting, or floating due to the impact of the potting compound flow during subsequent potting. Temporary fixing can be achieved using the following methods: At the open end of the flexible sleeve 40, use high-temperature resistant tape (such as polyimide tape) to temporarily bond and fix the open end of the flexible sleeve 40 to the edge of the open end of the housing 10; or use a dedicated annular positioning fixture, which covers the open end of the housing 10. The fixture has positioning holes corresponding to the number and arrangement of the flexible sleeves 40, and the open end of each flexible sleeve 40 passes through the corresponding positioning hole, constraining the circumferential and axial positions of the sleeve. After temporary fixing, confirm again that the open end of each flexible sleeve 40 extends above the preset potting compound filling liquid level, and that the end face is not higher than the surface of the open end of the housing 10. After confirmation, proceed to step S13.

[0106] S13. Inject potting compound into the housing 10 so that the filling liquid level of the potting compound is lower than the height of the open end of the flexible sleeve 40.

[0107] First, select the appropriate potting compound type based on the performance requirements of the inductor product. For high-power, high-heat-generating inductors, a two-component addition-curing silicone potting compound is preferred, as it features high thermal conductivity, good flexibility, and a wide temperature range. The potting compound should be prepared strictly according to the specified mixing ratio. Thoroughly mix the compound in a mixing container for at least 5 minutes until the mixture is uniform in color and free of obvious color differences or streaks.

[0108] After the potting compound is thoroughly mixed, it undergoes a vacuum degassing process to remove air bubbles introduced during mixing. The degassing process is carried out in a vacuum drying oven. The mixed potting compound is placed inside the oven, and vacuum is applied for 5 to 10 minutes at a vacuum level ≤ -0.095 MPa, until no more air bubbles emerge from the surface of the potting compound. After vacuum degassing is complete, the potting compound is removed and allowed to stand until it reaches room temperature for later use.

[0109] Slowly inject the prepared potting compound into the filling port of the housing 10. The injection method can be a manual glue gun or an automatic metering glue injection machine. When injecting the compound, align the injection nozzle with the annular gap between the inner wall of the housing 10 and the inductor body 20, rather than directly with the top of the inductor body 20, so that the potting compound rises slowly from the bottom of the housing 10 to facilitate the expulsion of air.

[0110] During the potting process, the following three key points must be continuously observed: First, observe the filling condition of the bottom and side walls of the housing 10 to ensure that the potting compound is evenly filled to all corners of the housing 10 without leaving gaps. This can be aided by observing through the side viewing window of the housing 10. Second, observe the open ends of each flexible sleeve 40 to ensure that the potting compound level never submerges the open ends, i.e., a certain distance is maintained between the potting compound and the open end face of the flexible sleeve 40. If the potting compound level is found to be close to the open end of the flexible sleeve 40, the potting should be stopped immediately, and the potting should be slowly resumed after the level stabilizes. Third, observe the rising height of the potting compound level. When the potting compound level rises to the preset level mark inside the housing 10, the potting should be stopped immediately.

[0111] Controlling the injection speed is crucial for ensuring potting quality. The injection speed should be moderate and uniform to avoid the potting compound impacting the open end of the flexible sleeve 40 and flowing into the hollow reserved space due to excessive speed; at the same time, it should also avoid excessively slow speed, which would lead to low production efficiency. During the injection process, the potting compound flows naturally under gravity, gradually filling the shell 10 from the bottom upwards, while air is expelled from the top by the potting compound.

[0112] After the potting compound is stopped, it continues to flow and self-level under gravity, causing the surface to become smooth. Wait 1 to 3 minutes to observe whether the surface stabilizes at the preset position. If the surface level drops slightly, add a small amount of potting compound up to the preset level mark. The preset potting compound level should at least cover the top surface of the inductor body 20 (including the top cover of the magnetic core and the top of the coil assembly) to ensure that the inductor body 20 is completely encapsulated. Simultaneously, the preset potting compound level should be a certain distance below the open end surface of the housing 10 to allow space for subsequent cover installation or hermetic encapsulation.

[0113] After the potting compound is applied, the encapsulated inductor is placed in a curing oven for curing. Curing conditions vary depending on the type of potting compound: for two-component addition-curing silicone potting compounds, the curing temperature is 80℃~120℃, and the curing time is 2 hours~4 hours. During curing, a uniform temperature field should be maintained inside the curing oven, with temperature deviation controlled within ±5℃ to ensure consistent curing of all inductor products. After curing, the product is removed from the curing oven and allowed to cool naturally to room temperature. After curing, the encapsulated inductor undergoes visual inspection and electrical performance testing. Visual inspection mainly confirms that the surface of the potting compound layer 30 is smooth, free of cracks, bubbles, and dents, and that the open end of the flexible sleeve 40 is exposed above the potting compound surface with no potting compound seeping into the interior. Electrical performance testing mainly confirms that the inductance L and insulation withstand voltage meet the product specifications. Once the visual and electrical performance tests are passed, the potting process for the inductor is complete.

[0114] By sequentially performing the assembly steps of placing the inductor body into the housing, the sleeve fixing step of placing the flexible sleeve with the sealed end facing down in the gap between the housing and the inductor body and the open end extending out of the preset potting compound level, and the injection step of injecting potting compound into the housing to the preset liquid level, the entire process of inductor potting is completed in a three-step coordinated manner. This forms a packaging structure inside the housing in which the potting compound completely covers the inductor body, and the hollow reserved space in the flexible sleeve remains unobstructed. This realizes the use of the hollow reserved space as a channel for releasing the thermal expansion stress of the potting compound, while the potting compound layer provides a complete heat conduction path and insulation protection.

[0115] In one embodiment, before the step of placing the inductor body 20 inside the housing 10, the method further includes: immersing the sealing end of the flexible sleeve 40 in water to a depth of 25mm to 35mm, letting it stand for 4 to 6 minutes, and then checking whether there is water leakage inside the flexible sleeve 40 to confirm that the sealing end is qualified.

[0116] Specifically, this sealing test step is performed before step S11; that is, before operating on the inductor body 20 and the housing 10, the sealing of each flexible sleeve 40 to be used is first tested. The specific method of the test operation is as follows: Prepare a transparent testing container (such as a glass beaker or plastic measuring cup), and fill it with sufficient room temperature water to a depth of at least 50 mm. Take a flexible sleeve 40 to be tested, with its sealed end facing down and its open end facing up. Holding the open end, slowly immerse the sealed end into the water. The immersion depth should be strictly controlled to be 25 mm to 35 mm (preferably 30 mm), ensuring that the sealed end is completely submerged below the water surface, while the open end remains above the water surface and connected to the atmosphere.

[0117] After the flexible sleeve 40 is immersed in water, it should be kept still, and timing should begin. The settling time is 4 to 6 minutes (preferably 5 minutes). During the settling process, the water surface must be kept stable without violent fluctuations, and the flexible sleeve 40 should be prevented from shaking or shifting in the water. If the flexible sleeve 40 shakes during the settling process, it may cause a momentary change in water pressure, causing water to be forced into the tube from the tiny gap at the sealing end, resulting in false leakage and affecting the accuracy of the test results.

[0118] After the settling time is up, remove the flexible sleeve 40 from the water and wipe the water off its outer surface with a clean, dry cloth or absorbent paper. Then carefully observe the inner wall of the flexible sleeve 40 for any water stains, droplets, or water accumulation. During inspection, a flashlight or strong light can be used to shine into the tube from the open end to observe whether the reflected light on the inner wall is uniform and continuous. If there is water on the inner wall, uneven reflection spots will appear. Alternatively, a clean, dry cotton swab can be inserted into the flexible sleeve 40 to wipe it; after removing it, observe whether the cotton swab becomes wet.

[0119] If, after the above inspection, the inner wall of the flexible sleeve 40 is dry, free of water stains, water droplets, and water accumulation, then the sealing end is deemed to be in good condition, and the flexible sleeve 40 can be used normally in subsequent steps. If water leakage is found inside the flexible sleeve 40, then the sealing end is deemed to be in poor condition, and the sleeve has a sealing defect. Before being placed inside the housing 10, the flexible sleeve 40 that has passed the sealing test must be properly stored to prevent the sealing end from being bumped, squeezed, or punctured by sharp objects. Place the qualified flexible sleeve 40 in a clean, dry special tray or storage box with the sealing end facing upwards to avoid pressure on the sealing end.

[0120] Before placing the inductor body 20 inside the housing 10, the sealing end of the flexible sleeve is immersed in water with a strictly controlled immersion depth of 25mm to 35mm. After standing for 4 to 6 minutes, the sleeve is checked for water leakage to confirm that the sealing end is qualified. The sealing end of each sleeve is fully inspected using the principle of water pressure difference. This allows unqualified sleeves with defects such as micropores and delamination of the fusion interface to be screened out before potting. This achieves simple operation without special equipment and avoids potting compound from seeping into the hollow reserved space from the sealing end, which would cause the stress release function to be lost.

[0121] In one embodiment, the end face of the open end of the flexible sleeve 40 is configured to be flush with or lower than the port surface of the housing 10.

[0122] Specifically, when adjusting the axial position of the flexible sleeve 40 in step S12, the end face of the open end of the flexible sleeve 40 must not be higher than the surface of the open end of the housing 10. The position of the open end face can be set in two ways: Flush configuration: The open end face of the flexible sleeve 40 is located on the same horizontal plane as the open end surface of the housing 10. In this case, the axial length 'a' of the flexible sleeve 40 is exactly equal to the total internal depth 'c' of the housing 10 (i.e., a=c), the sealing end of the flexible sleeve 40 just touches or approaches the bottom inner wall of the housing 10, and the open end face is flush with the open end of the housing 10. This configuration makes full use of the entire internal space of the housing 10, providing a maximized axial length of stress relief space.

[0123] Lower setting: The open end face of the flexible sleeve 40 is lower than the open end surface of the housing 10, with a height difference of 1mm to 5mm. In this case, the axial length 'a' of the flexible sleeve 40 is less than the total internal depth 'c' of the housing 10 (i.e., 'a' = 'c-1mm' to 'c-5mm'), and the open end face of the flexible sleeve 40 is recessed inside the housing 10. This setting provides operating space for subsequent processes.

[0124] When the open end face is lower than the open end surface of the housing 10, it is also necessary to ensure that the end face is still higher than the preset potting compound filling liquid level. That is, the distance between the preset potting compound filling liquid level and the open end surface of the housing 10 should be greater than the distance between the open end face and the open end surface, so as to ensure that the potting compound liquid level is always lower than the open end face.

[0125] By setting the open end face of the flexible sleeve to be flush with or lower than the surface of the housing port, the open end face of the flexible sleeve does not exceed the top contour of the product. This ensures that the inductor product has a flat top plane after potting, and avoids mechanical interference caused by the open end of the sleeve protruding from the product surface during subsequent installation of the cover plate or mounting of the PCB board. At the same time, the edge of the housing port forms physical protection for the open end to prevent damage from external impacts.

[0126] In one embodiment, during the sleeve fixing step, the open end of the flexible sleeve 40 is exposed to air after the potting compound is filled, in order to maintain the pressure balance between the hollow reserved space of the flexible sleeve 40 and the external atmosphere.

[0127] Specifically, this embodiment defines the final state after potting: the open end of the flexible sleeve 40 is not covered or closed by the potting compound layer 30, but is always exposed to the air. This state is achieved through the coordination of steps S12 and S13: in step S12, the open end of the flexible sleeve 40 is pre-set to extend beyond the preset potting compound filling liquid surface; in step S13, the injection liquid level of the potting compound is strictly controlled to be no higher than the open end face, thereby ensuring that the open end is exposed to the air after potting.

[0128] During and after the potting compound cures, the open end of the flexible sleeve 40 is in direct contact with the outside air, while the hollow reserved space remains connected to the atmosphere through the open end. When the potting compound expands due to heat, the air inside the hollow reserved space is discharged outward through the open end, preventing the internal air pressure from rising and hindering the entry of the compound; when the potting compound cools and contracts, external air is drawn into the hollow reserved space through the open end, replenishing the internal gas volume and preventing the formation of negative pressure inside.

[0129] After curing, if the product needs to work in a humid or dusty environment, a waterproof and breathable membrane, such as expanded polytetrafluoroethylene film, can be covered at the open end of the housing 10. This membrane has the characteristics of being breathable but not water-permeable. The membrane covers the open end of the flexible sleeve 40, allowing air to pass through but preventing moisture and dust from entering the hollow reserved space, while not affecting the air pressure balance function.

[0130] By fixing the sleeve, the open end of the flexible sleeve is exposed to the air after the potting compound is filled. This maintains the pressure balance between the hollow reserved space and the external atmospheric pressure, making the hollow reserved space an open air pressure balance system rather than a closed air cavity. This achieves the purpose of allowing air to be freely discharged when the potting compound expands thermally and allowing external air to be freely drawn in when it cools and contracts. It avoids the reverse pressure generated by the compression of air in the closed air cavity from hindering the entry of the colloid, and at the same time prevents the sleeve from collapsing or closing due to negative pressure during cooling and contraction.

[0131] In one embodiment, in the step of injecting potting compound into the housing 10 to a preset potting compound filling level, the injection rate of the potting compound is 0.5L / min to 2L / min, the potting compound fills naturally under the action of gravity, and the potting compound completely covers the inductor body 20.

[0132] Regarding the potting speed: The potting speed range of 0.5L / min to 2L / min is the optimal parameter range determined through extensive process testing. At a speed of 0.5L / min, the potting compound fills the interior of the housing 10 at a slower rate, suitable for inductor products with complex structures and narrow gaps. This ensures the potting compound fully penetrates all the fine gaps, but production efficiency is relatively low. At a speed of 2L / min, the potting compound fills at a faster rate, suitable for inductor products with relatively simple structures and larger gaps. Production efficiency is high, but the monitoring requirements for operators are higher. In actual operation, the potting speed can be steplessly adjusted within the range of 0.5L / min to 2L / min according to the specific structure of the inductor product: for precision inductors with complex winding structures and irregular core shapes, low-speed potting (0.5L / min to 1.0L / min) is preferred; for conventional inductors with regular structures and wide gaps, a higher speed (1.0L / min to 2.0L / min) can be selected.

[0133] The dispensing speed is controlled by adjusting the output pressure or flow valve of the dispensing equipment. When using an automatic metering dispensing machine, the flow parameters can be set directly on the equipment control panel; when using a manual dispensing gun, the dispensing volume is adjusted by controlling the trigger stroke and pressing speed. During dispensing, the speed should be kept uniform, avoiding sudden changes in speed. When the potting compound level approaches the open end of the flexible sleeve 40, the dispensing speed should be reduced to below 0.5 L / min to accurately control the final liquid level position.

[0134] Regarding the potting method, the potting compound fills naturally under gravity. That is, after the potting compound is injected into the housing 10, it gradually rises from the bottom of the housing 10 under its own weight until it reaches the preset liquid level. During this process, the injection nozzle is always kept near the bottom of the housing 10 or below the potting compound level to prevent air from being drawn in when the potting compound falls from a height.

[0135] Regarding the filling effect, the potting compound completely encapsulates the inductor body 20, meaning that the potting compound layer 30 covers every outer surface of the inductor body 20, including the bottom, top, and side surfaces of the magnetic core, as well as all accessible surfaces of the coil assembly, including the top, bottom, inner, and outer coils. Complete encapsulation means there are no unfilled air gaps between the potting compound and the inductor body 20. After potting, complete encapsulation can be verified in the following ways: First, observe the transparent viewing window on the side wall of the housing 10 to confirm that the potting compound level is higher than the top of the inductor body 20; second, use X-ray non-destructive testing equipment to confirm that there are no voids inside or on the surface of the inductor body 20; third, use a weighing method to weigh the inductor product before and after potting to calculate whether the actual filling volume of the potting compound matches the theoretically calculated volume.

[0136] In one embodiment, after the step of injecting potting compound into the housing 10 to the preset potting compound filling liquid level, the method further includes: placing the potted inductor in a curing oven and curing it at a constant temperature of 80°C to 120°C for 2 to 4 hours.

[0137] Specifically, in this embodiment, after the potting process in step S13 is completed, a curing step is added. After the potting process is completed, the potting compound inside the inductor product is still in a liquid or semi-solid state and has not yet formed a stable three-dimensional cross-linked network structure. It needs to be cured by heating to fully cross-link and achieve the final performance.

[0138] The curing process is carried out in an electrically heated curing oven. The curing oven should have a precise temperature control system. The inductor products with the adhesive applied are placed on the trays of the curing oven, with a certain distance between each product to ensure that the hot air can circulate freely between the products and avoid uneven local temperature caused by dense placement of products.

[0139] The choice of curing temperature depends on the type of potting compound and product performance requirements: Curing at 80℃ for 4 hours is suitable for scenarios with high requirements for internal stress control and where the magnetic core is temperature-sensitive (e.g., large-size magnetic cores may experience thermal stress at high temperatures). Low-temperature, long-time curing helps reduce curing shrinkage stress and thermal stress, lowering the risk of magnetic core cracking. Curing at 100℃ for 3 hours is a commonly recommended general curing condition, balancing curing efficiency and product quality. Curing at 120℃ for 2 hours is suitable for scenarios with high production efficiency requirements and sufficient product temperature resistance. High-temperature, short-time curing can accelerate production cycle time and increase equipment turnover.

[0140] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. An inductor, characterized in that, include: The housing (10) has an opening and a bottom disposed opposite to the opening; An inductor body (20) is disposed within the housing (10); At least one flexible sleeve (40) sealed at one end, the flexible sleeve (40) being inserted into the gap between the inductor body (20) and the housing (10), and the sealed end of the flexible sleeve (40) being disposed facing the bottom of the housing (10); A potting compound layer (30) fills the gap between the housing (10) and the inductor body (20), and the open end of the flexible sleeve (40) extends to the outside of the potting compound layer (30). The interior of the flexible sleeve (40) is hollow to serve as a stress relief space when the potting compound layer (30) expands thermally.

2. The inductor according to claim 1, characterized in that, The axial length of the flexible sleeve (40) is a, the vertical distance between the bottom inner wall of the housing (10) and the outer end face of the potting compound layer (30) is b, and the total internal depth of the housing (10) is c, where b≤a≤c, and / or, The inner diameter of the flexible sleeve (40) is d, the minimum horizontal distance between the outer wall of the inductor body (20) and the inner wall of the housing (10) is e, and the rated temperature rise of the inductor body (20) is f, wherein d is positively correlated with e and f, and / or, The number of flexible sleeves (40) is n, the overall volume of the inductor body (20) is v, and the rated temperature rise value of the inductor body (20) is f, where n is positively correlated with v and f.

3. The inductor according to claim 1 or 2, characterized in that, The sealing end of the flexible sleeve (40) has a sealing area, which has a flat structure and a thickness of h1, where h1 is 1.7mm to 1.9mm. The axial length of the sealing area along the flexible sleeve (40) is L, where L is 7mm to 9mm.

4. The inductor according to claim 2, characterized in that, Multiple flexible sleeves (40) are evenly spaced along the annular gap between the inner peripheral wall of the housing (10) and the inductor body (20).

5. The inductor according to claim 1, characterized in that, The wall thickness of the flexible sleeve (40) is h2, which is 3.95mm to 4.05mm, and / or the axial length of the flexible sleeve (40) is 63.5mm to 66.5mm, and / or the inner diameter of the flexible sleeve (40) is 7mm to 7.5mm.

6. The inductor according to claim 1, characterized in that, The flexible sleeve (40) is made of a flexible polymer material or composite material with a temperature resistance greater than 150°C. The flexible polymer material or composite material includes any one of silicone rubber, fluororubber, polytetrafluoroethylene or polytetrafluoroethylene coated glass fiber cloth.

7. A potting process for stress relief in inductors, characterized in that, Using the inductor described in any one of claims 1-6, the potting process includes: The inductor body (20) is disposed inside the housing (10); The sealing end of the flexible sleeve (40) with one end sealed is directed toward the bottom inner wall of the housing (10) so that the flexible sleeve (40) is placed in the gap between the inner wall of the housing (10) and the inductor body (20). Inject potting compound into the housing (10) such that the filling liquid level of the potting compound is lower than the height of the open end of the flexible sleeve (40).

8. The potting process for stress relief of inductors according to claim 7, characterized in that, The open end face of the flexible sleeve (40) is configured to be flush with or lower than the port surface of the housing (10).

9. The potting process for stress relief of inductors according to claim 7, characterized in that, Before the step of placing the inductor body (20) inside the housing (10), the method further includes: immersing the sealing end of the flexible sleeve (40) in water to a depth of 25mm to 35mm, allowing it to stand for 4 to 6 minutes, and then checking whether there is water leakage inside the flexible sleeve (40) to confirm that the sealing end is qualified, and / or, After the step of injecting potting compound into the housing (10) so that the filling liquid level of the potting compound is lower than the height of the open end of the flexible sleeve (40), the method further includes: placing the potted inductor in a curing oven and curing it at a constant temperature of 80°C to 120°C for 2 to 4 hours.

10. The potting process for stress relief of inductors according to claim 7, characterized in that, In the step of injecting potting compound into the housing (10) so that the filling liquid level of the potting compound is lower than the height of the open end of the flexible sleeve (40), the injection speed of the potting compound is 0.5L / min to 2L / min, the potting compound fills naturally under the action of gravity, and the potting compound completely covers the inductor body (20).

Images