A preparation method of a new energy vehicle filter shell

Abstract

The application discloses a preparation method of a new energy automobile filter shell, and aims to solve the problem that interface peeling easily occurs between a metal insert and plastic due to thermal expansion difference. The application obtains the local sliding direction and sliding amount of the plastic relative to the metal insert through thermodynamic simulation; then, grooves arranged in an array are processed on the surface of the metal insert, each groove has a bottom wall and an end wall arranged at the extension end of the bottom wall, the extension direction of the groove is parallel to the local sliding direction of the plastic relative to the metal insert, and the depth of the end wall in the metal insert is positively correlated with the sliding amount of the plastic relative to the metal insert in the processing area; during the cooling and setting stage after injection molding, the volume shrinkage of the plastic is utilized to force the plastic to slide inward along the bottom wall and abut against the vertical end wall. The application converts the adverse shrinkage of injection molding into micro locking kinetic energy, and realizes the combination of high-reliability mechanical interlocking and long-acting sealing.

Description

Technical Field

[0001] This invention relates to the field of new energy vehicle component manufacturing technology, and more specifically, to a method for preparing a filter housing for a new energy vehicle. Background Technology

[0002] In the high-voltage electrical systems of new energy vehicles, filters are core components for suppressing electromagnetic interference and ensuring stable system operation. Because filters operate under high voltage and generate significant heat, their housings typically require injection molding of a composite of metal inserts and insulating plastic to meet multiple requirements, including conductive grounding, structural support, and electrical insulation.

[0003] Traditional filter housings are typically manufactured by roughening or creating uniformly distributed straight grooves on the surface of a metal insert, followed by injection molding to cover it with plastic. However, there is an inherent difference in the coefficient of thermal expansion between the metal insert and the insulating plastic. Under the extremely harsh temperature fluctuations of new energy vehicles, complex and unevenly distributed thermal stresses are generated inside the filter housing. The traditional uniform grooving process does not consider the spatial differences and directions of thermal stress distribution. When components undergo high and low temperature cycles or during the cooling phase after injection molding, the plastic is prone to slippage along the surface of the metal insert in areas of stress concentration. This uncontrollable slippage can overcome the microscopic bonding force between the metal insert and the plastic, leading to micro-cracks or even complete peeling at the coating interface. This can cause external moisture intrusion or internal high-voltage leakage, seriously endangering the electrical safety of the entire vehicle. Summary of the Invention

[0004] In view of the technical problem in the prior art that the metal insert and plastic are prone to interface peeling and sealing failure in the filter housing of new energy vehicles under temperature alternating environment due to the difference in thermal expansion coefficients, the present invention provides a method for preparing the filter housing of new energy vehicles.

[0005] The present invention provides a method for manufacturing a filter housing for new energy vehicles. The filter housing includes a metal insert and a plastic covering the outside of the metal insert. The manufacturing method includes the following steps: S1. Perform thermal stress simulation analysis based on the three-dimensional model of the filter housing to obtain the thermal stress distribution data of the filter housing at a preset operating temperature; S2. Based on the thermal stress distribution data, obtain the sliding direction and sliding amount of the plastic relative to various parts of the surface to be covered by the metal insert under the action of thermal stress generated by the plastic at a preset working temperature; and divide the surface to be covered into multiple processing areas, wherein the sliding direction of the plastic is the same in the same processing area. S3. In each of the processing areas, a plurality of grooves are processed in an array, and the extension direction of each groove is parallel to the sliding direction of the plastic in the processing area. Each of the grooves includes a bottom wall and an end wall located at the extended end of the bottom wall; along the sliding direction of the plastic in the processing area where the groove is located, the bottom wall extends obliquely from the surface to be covered toward the interior of the metal insert, and the end wall is perpendicular to the surface to be covered; and the depth of the end wall inside the metal insert is positively correlated with the amount of sliding of the plastic in the processing area. S4. Fix the metal insert into the cavity of the injection mold, and inject the molten plastic into the cavity so that the plastic fills each of the slots; During the cooling and shaping stage of the plastic, under the action of cooling and shrinkage, the plastic filled in each of the grooves slides along the bottom wall of the groove toward the interior of the metal insert and abuts against the end wall at the extended end of the bottom wall, thereby wedging the plastic tightly into each of the grooves.

[0006] Preferably, after step S4, the following step is also included: S5. After the plastic cools and sets, a laser beam is used to weld the welding end of the metal insert that extends outside the plastic to the external connector, so as to realize the electrical connection between the metal insert and the external connector. The welding process includes multiple welding stages performed sequentially. In any two adjacent welding stages, the output power of the laser beam in the later welding stage is less than the output power of the laser beam in the previous welding stage.

[0007] Preferably, in step S3, the depth H of the end wall inside the metal insert satisfies the following relationship: ; in, The amount of slippage of the plastic within the processing area, where k is a preset depth scaling factor and k > 0. The preset base groove depth and .

[0008] Preferably, in S3, the distribution spacing between two adjacent grooves within the same processing area is negatively correlated with the magnitude of the thermal stress at the location of the two adjacent grooves. The magnitude of the thermal stress is obtained from the thermal stress distribution data.

[0009] Preferably, each groove further includes two opposing sidewalls, which are respectively connected to both sides of the bottom wall and extend to the end wall; the distance between the two sidewalls gradually decreases along the direction of extension from the bottom wall to the end wall.

[0010] Preferably, in step S3, each groove is processed using a laser etching process; the angle of the bottom wall's tilting extension and the depth of the end wall are controlled by adjusting the laser focus and the number of scans in the laser etching process.

[0011] Preferably, after S3 and before S4, the step further includes: S31. Perform plasma cleaning treatment on the surface of the metal insert to be covered and the inner wall of each groove.

[0012] Preferably, the metal insert is a brass insert, and the plastic is a polyphenylene sulfide composite material containing glass fiber.

[0013] One or more technical solutions provided in this invention have at least the following technical effects or advantages: This invention addresses the technical pain point of interface peeling and sealing failure in the housing of new energy vehicle filters under alternating temperature environments. It innovatively maps thermodynamic simulation data to microscopic physical structures. By pre-observing the local slip direction and amount of the plastic relative to the metal insert under thermal stress, this invention constructs multiple arrayed grooves with highly spatially adaptive characteristics on the surface of the metal insert to be covered. The extension direction of these grooves is strictly parallel to the local slip direction of the plastic, and the end-wall depth is positively correlated with the slip amount. This allows areas with concentrated thermal stress and severe slippage to achieve deeper mechanical anchoring resistance, while areas with gentler stress maintain a shallower processing depth to ensure the overall strength of the metal insert.

[0014] Furthermore, this invention transforms the physical phenomenon of plastic cooling and shrinkage, which is highly prone to causing cracking in traditional injection molding, into locking kinetic energy that enhances bonding strength. During the plastic cooling and setting stage, the plastic in the tank slides directionally along the inclined bottom wall into the interior of the metal insert, eventually abutting against the vertical end wall, spontaneously forming a dense microscopic wedge state purely through its own cooling and shrinkage instinct. Through the synergistic effect of the above-mentioned microscopic mechanical anchoring and spontaneous wedge tightening, this invention eliminates the hidden danger of interfacial stress misalignment caused by the difference in thermal expansion coefficients, achieving a highly reliable mechanical interlock and long-term sealing bond between the metal insert and the plastic under high-pressure conditions. Attached Figure Description

[0015] Figure 1 A partial cross-sectional view of the metal insert provided in an embodiment of the present invention; Figure 2This is a partial cross-sectional view of the wedge-tight state during the plastic cooling and shaping stage provided in an embodiment of the present invention. Figure 3 This is a partial top view of two adjacent slots provided in an embodiment of the present invention.

[0016] Explanation of reference numerals in the attached drawings: 10, metal insert; 11, surface to be covered; 20, plastic; 30, groove; 31, bottom wall; 32, end wall; 33, side wall; H, depth of the groove inside the metal insert; D, spacing between two adjacent grooves; F, sliding direction. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the following description is provided in conjunction with the appendix. Figure 1-3 The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention.

[0018] In this embodiment, a method for manufacturing a high-voltage filter housing for a new energy vehicle is used as an example. The filter housing is mainly composed of a metal insert 10 and a plastic 20 covering the outside of the metal insert 10, which are injection molded together. As a preferred embodiment, the metal insert 10 can be made of brass, which has excellent conductivity and heat dissipation properties, such as H62 brass; in order to meet the requirements of high-voltage insulation and mechanical strength, the plastic 20 is made of polyphenylene sulfide composite material containing glass fiber, such as PPS material with a glass fiber mass fraction of 40%. In other embodiments, it can also be replaced by engineering plastics such as modified polyamide.

[0019] Due to the significant difference in the coefficients of thermal expansion between the metal insert 10 and the plastic 20, complex thermal stress will occur at the interface between the two under the typical high and low temperature alternating conditions of -40℃ to 125℃ in new energy vehicles. To fundamentally eliminate the interface peeling and sealing failure caused by this thermal stress, the preparation method of this embodiment specifically includes the following steps: S1. Obtain thermal stress distribution data.

[0020] The 3D model of the filter housing was imported into finite element analysis software, and a preset operating temperature cycle curve was set to simulate the temperature rise process from vehicle startup to high-load operation. Through thermodynamic coupling solution, the thermal stress distribution data of the filter housing at the extreme operating temperature was obtained. This step, through digital means, pre-captured the interfacial mechanical weaknesses of the product, providing a data foundation for the subsequent precise processing of the anti-detachment structure.

[0021] S2. Obtain the sliding direction and sliding amount, and divide the processing area.

[0022] Based on the aforementioned thermal stress distribution data, the local slip direction F and micro-slip amount of the plastic 20 relative to various parts of the surface 11 to be covered by the metal insert 10 under thermal stress are extracted. Subsequently, the surface 11 to be covered is divided into multiple processing areas. The principle of division is that within the same processing area, the slip direction F of the plastic 20 is substantially the same or within a very small angular tolerance range.

[0023] S3. Process multiple slots arranged in an array.

[0024] In each processing area, multiple grooves 30 arranged in an array are processed using laser etching. In this embodiment, picosecond lasers or femtosecond lasers are used for etching to avoid the formation of heat-affected zones or carbonized slag on the surface 11 to be coated.

[0025] Combination Figure 2 and Figure 3 As shown, the extension direction of each groove 30 is parallel to the sliding direction F of the plastic 20 within its processing area. Each groove 30 includes a bottom wall 31 and an end wall 32 located at the extended end of the bottom wall 31. Along the sliding direction F of the plastic 20, the bottom wall 31 extends obliquely from the surface to be covered 11 toward the interior of the metal insert 10, forming a ramp structure, while the end wall 32 is perpendicular to the surface to be covered 11, serving as a load-bearing retaining wall.

[0026] Based on this, the depth H of the end wall 32 within the metal insert 10 is not only a fixed value, but is positively correlated with the amount of slippage of the plastic 20 within the processing area. Specifically, the depth H satisfies the following relationship: ; in, The amount of slippage of the plastic within the processing area, where k is a preset depth scaling factor and k > 0. The preset base groove depth and .

[0027] In the actual preparation process, the depth of the base trench The depth is set to 0.15mm, and the depth scaling factor k is set to 8. For a specific machining area, if the slippage at that location is obtained through simulation... If the depth is 0.05mm (in areas with high thermal stress), then after calculation using the formula and machining by increasing the number of laser scans on the machine tool, the end wall depth H of the groove at that location will be machined to 0.55mm; for another machining area, if the slippage at that location... For a depth of only 0.01 mm (in areas with gentle thermal stress), the corresponding end wall depth H is machined to 0.23 mm. This spatial topology mapping process not only provides deeper mechanical anchoring force in high-stress areas but also avoids excessive cutting in low-stress areas, which would weaken the structural strength of the metal insert body.

[0028] Furthermore, during the processing of each groove 30, adjusting the laser focus and the number of scans in the laser etching process controls not only the depth H of the end wall 32 but also the angle of the bottom wall 31's tilting extension. Specifically, the machine tool controls the lateral movement step of the laser focus through a program and adjusts the number of laser scans at the corresponding positions to achieve a gradual etching and peeling of the metal material from shallow to deep, thereby precisely processing the bottom wall 31 with a specific tilt angle that meets the requirements for guiding local thermal stress slippage.

[0029] Furthermore, combined Figure 3 As shown, each groove 30 also includes two opposing sidewalls 33. The distance between the two sidewalls 33 gradually decreases along the direction extending from the bottom wall 31 to the end wall 32, so that the entire groove 30 presents a converging shape with a gradually decreasing width inside.

[0030] Meanwhile, the spacing D between the slots 30 arranged in the array is negatively correlated with the magnitude of the thermal stress at that location (the thermal stress is obtained from S1 simulation). It should be noted that, as... Figure 3 As indicated by the markings, since the sidewalls 33 of the grooves 30 have a converging structure, the distribution spacing D refers to the distance between the sidewalls of two adjacent grooves 30 near the widest part of the opening, that is, the minimum metal solid spacing between two adjacent grooves 30. By adjusting the position of the laser focus, the spacing D is processed to be smaller (i.e., the grooves 30 are more densely distributed) in areas with greater thermal stress; and by using the minimum solid spacing as a benchmark, the breakage of the metal insert 10 body due to excessively dense groove opening can be prevented to the greatest extent.

[0031] S31. Perform plasma cleaning treatment.

[0032] After laser etching and before injection molding, the surface 11 of the metal insert 10 to be coated and the inner wall of each groove 30 are subjected to plasma cleaning. In some embodiments, conventional ultrasonic cleaning can also be used as an alternative, but in this preferred embodiment, because plasma has a strong penetrating and activating ability, it can penetrate deep into the blind groove to thoroughly remove the dust remaining after etching and improve the surface energy of the interface, laying the foundation for subsequent plastic wetting.

[0033] S4. Injection molding and cooling / setting.

[0034] Combination Figure 1 and Figure 2 As shown, the metal insert 10 is fixed in the cavity of the injection mold, and molten plastic 20 is injected. The molten plastic fully fills each groove 30 under high pressure.

[0035] During the cooling and setting stage of plastic 20, plastic 20 itself undergoes volume shrinkage. Under the action of shrinkage stress, plastic 20 filled in the groove 30 slides directionally along the inclined bottom wall 31 into the metal insert 10, and finally abuts against the vertical end wall 32; at the same time, under the compression of the two side walls 33, plastic 20 is mechanically locked in space. This process relies on the cooling shrinkage to spontaneously form a dense wedge-tight state, achieving a reliable sealing joint.

[0036] S5. Welding is performed using a laser beam.

[0037] After the plastic 20 has completely cooled and set, the assembly stage begins. A laser beam is used to weld the welding end of the metal insert 10 extending outside the plastic 20 to an external connector (such as an external wiring harness terminal or a high-voltage copper busbar) to achieve electrical connection.

[0038] To prevent intense welding heat from being transferred back to the injection interface along the metal insert 10, the welding process in this embodiment strictly includes multiple welding stages performed sequentially, and in any two adjacent welding stages, the laser output power of the later stage is less than that of the previous stage.

[0039] In the actual production line welding process, taking the welding of a 2.0mm thick copper busbar as an example, the welding process is divided into three stages with continuous heat input. The first stage uses 2000W power for 0.5s to quickly establish a molten pool; the second stage reduces the power to 1200W for 0.8s; and the third stage further reduces the power to 600W for 0.3s. This decreasing heat input characteristic not only ensures the bonding strength of the welded ends on the welded surface, but also strictly controls the total heat conducted along the metal insert 10 to the injection molding interface below the heat distortion temperature of the plastic 20, forming a tight process closed loop.

Claims

1. A preparation method of a new energy vehicle filter shell, characterized in that, The filter housing includes a metal insert and a plastic covering the outside of the metal insert. The manufacturing method includes the following steps: S1. Perform thermal stress simulation analysis based on the three-dimensional model of the filter housing to obtain the thermal stress distribution data of the filter housing at a preset operating temperature; S2. Based on the thermal stress distribution data, obtain the sliding direction and sliding amount of the plastic relative to various parts of the surface to be covered by the metal insert under the action of thermal stress generated by the plastic at a preset working temperature; and divide the surface to be covered into multiple processing areas, wherein the sliding direction of the plastic is the same in the same processing area. S3. In each of the processing areas, a plurality of grooves are processed in an array, and the extension direction of each groove is parallel to the sliding direction of the plastic in the processing area. Each of the grooves includes a bottom wall and an end wall located at the extended end of the bottom wall; along the sliding direction of the plastic in the processing area where the groove is located, the bottom wall extends obliquely from the surface to be covered toward the interior of the metal insert, and the end wall is perpendicular to the surface to be covered; and the depth of the end wall inside the metal insert is positively correlated with the amount of sliding of the plastic in the processing area. S4. Fix the metal insert into the cavity of the injection mold, and inject the molten plastic into the cavity so that the plastic fills each of the slots; During the cooling and shaping stage of the plastic, under the action of cooling and shrinkage, the plastic filled in each of the grooves slides along the bottom wall of the groove toward the interior of the metal insert and abuts against the end wall at the extended end of the bottom wall, thereby wedging the plastic tightly into each of the grooves.

2. The production method according to claim 1, characterized by, Following S4, the following steps are also included: S5. After the plastic cools and sets, a laser beam is used to weld the welding end of the metal insert that extends outside the plastic to the external connector, so as to realize the electrical connection between the metal insert and the external connector. The welding process includes multiple welding stages performed sequentially. In any two adjacent welding stages, the output power of the laser beam in the later welding stage is less than the output power of the laser beam in the previous welding stage.

3. The method of claim 1, wherein, In S3, the depth H of the end wall inside the metal insert satisfies the following relationship: ； wherein, is the amount of the slip of the plastic in the processing area, k is a preset depth proportionality coefficient and k > 0, is a preset base groove depth and .

4. The method of claim 1, wherein, In S3, the distribution spacing between two adjacent grooves within the same processing area is negatively correlated with the magnitude of the thermal stress at the location of the two adjacent grooves. The magnitude of the thermal stress is obtained from the thermal stress distribution data.

5. The preparation method according to claim 1, characterized in that, Each of the slots also includes two opposing sidewalls, which are respectively connected to the two sides of the bottom wall and extend to the end wall; the distance between the two sidewalls gradually decreases along the direction of extension from the bottom wall to the end wall.

6. The preparation method according to claim 1, characterized in that, In step S3, each groove is fabricated using a laser etching process; by adjusting the laser focus and the number of scans in the laser etching process, the angle of the bottom wall's tilting extension and the depth of the end wall are controlled.

7. The preparation method according to claim 1, characterized in that, The method further includes the following steps after S3 and before S4: S31. Perform plasma cleaning treatment on the surface of the metal insert to be covered and the inner wall of each groove.

8. The preparation method according to claim 1, characterized in that, The metal insert is a brass insert, and the plastic is a polyphenylene sulfide composite material containing glass fiber.

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