Sealing structure and forming process of flexible waterproof FFC wire harness

Abstract

The invention relates to a sealing structure of a flexible waterproof FFC wire harness and a forming process, and belongs to the technical field of automobile electronic wire harness manufacturing, the sealing structure comprises an FFC wire, a connector shell, a sealing ring and a blanking cap, the sealing ring is made of a fluororubber and hydrogenated butadiene-acrylonitrile rubber composite modified material, the connector shell is made of a glass fiber reinforced PP or PA66 material, and the blanking cap is made of a glass fiber reinforced PP or PA66 material. Under the cooperation of a vulcanizing agent system and an anti-aging agent system, double-material injection molding is adopted for integral forming, and double sealing is achieved through interference fit of the blanking cap and the sealing ring. The waterproof grade of the FFC wire harness reaches IP67, the weight is reduced, the size is reduced, the production efficiency is improved, and the FFC wire harness can be widely applied to wet area scenes such as automobile door lines, ceilings and seats, has the cost advantage and the environmental protection benefit, and has remarkable industrial application value.

Description

Technical Field

[0001] This invention relates to the field of automotive electronic wiring harness manufacturing technology, specifically a sealing structure for a flexible waterproof FFC wiring harness and the molding process for the sealing structure. Background Technology

[0002] For ease of assembly and reliable electrical connections, traditional wiring harnesses used in automobiles typically use 0.35mm² signal wires. 2 Or 0.5 mm 2 The wires are heavy and bulky, accounting for 70% of the total weight of the wiring harness. At the same time, due to the lack of rigidity in the connection of single wires in traditional wiring harnesses, they can only be installed manually by workers, resulting in low automation. Furthermore, manual assembly inevitably leads to unstable quality, reducing the reliability of the wiring harness and posing risks to driving safety.

[0003] FFC (Flexible Flat Cable) harnesses are widely used in automotive electronics due to their advantages such as high flexibility, small wiring space, and stable transmission performance. Based on the existing structure of FFC harnesses, sometimes a sealing structure is placed inside the harness connector near the connection between the FFC harness and the terminal for sealing considerations. Therefore, the application of this type of FFC harness is limited to the dry areas of the automotive environment. Applications in wet environments, such as near door wiring and the chassis, are not yet seen on the market. In wet environments, high humidity and water splashes can easily cause wastewater to seep into the terminals, leading to rapid metal corrosion, poor contact, and reduced harness lifespan. Therefore, the sealing problem of existing FFC harnesses must be solved. Current sealing measures often use rubber sealing rings or strips, but due to the small size of the harness connectors, improper installation and poor adhesion of sealing rings or strips can lead to them easily falling off in the vibration environment of a vehicle. Therefore, there is currently no reliable sealing structure for FFC harnesses. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a sealing structure and molding process for a flexible waterproof FFC harness, resulting in an FFC harness that can adapt to complex operating conditions in wet automotive environments.

[0005] The technical problem to be solved by the present invention is achieved through the following technical solution: A sealing structure for a flexible waterproof FFC wire harness includes an FFC wire, a connector housing, and a sealing ring disposed within the connector housing to achieve a seal between the connector housing and the FFC wire. The sealing ring is disposed within the opening at the tail of the connector, with its outer surface tightly fitted to the inner surface of the connector housing, and a slot adapted to the FFC wire is formed inside, with the FFC wire forming a sealed connection with the inner wall of the slot.

[0006] In this invention, a plug is provided at the tail opening of the connector. The plug has a through hole in the center for the FFC wire to pass through. A plug seal is provided on the side of the plug facing the connector. The plug seal has a through hole in the center for the FFC wire to pass through, which is aligned with the through hole in the center of the plug. The plug seal is inserted into the tail opening of the sealer and is interference-fitted with the sealing ring at the tail of the connector.

[0007] Furthermore, the side of the plug seal is designed as an arc shape protruding to both sides. After the plug seal is inserted into the tail of the sealer, the central perforation is interference-fitted with the FFC wire.

[0008] Furthermore, the edge of the plug bends toward the connector and engages with the outer side of the seal tail opening to form a snap, thereby enabling a detachable connection between the plug and the connector housing via the snap.

[0009] In this invention, the sealing ring is integrally formed with the connector housing using a two-material injection molding process.

[0010] In this invention, the compression set of the sealing ring (120℃×24 h) is ≤15%, the tensile strength is ≥8.5MPa, the elongation at break is ≥450%, the peel strength with the connector housing is ≥3.5 N / mm, and the Shore hardness of the sealing ring is 30-40HA.

[0011] In this invention, the sealing ring is composed of the following components in the indicated mass percentages: 60-65% fluororubber (KFM 26), 25-30% hydrogenated nitrile butadiene rubber (HNBR), 4-6% maleic anhydride-grafted polypropylene (MAH-g-PP), 2-3% graphene microflakes, 1-2% nano-silica, 0.6-1% vulcanizing agent, and 0.1-0.3% anti-aging agent, wherein the graphene microflakes have a particle size of 5 μm and the nano-silica has a particle size of 20 nm; the connector housing is made of polypropylene (PP) or PA66 material reinforced with 30% glass fiber.

[0012] Furthermore, the vulcanizing agent is one or more of the following: peroxide vulcanizing agent, sulfur-accelerator system vulcanizing agent, oxime vulcanizing agent, and sulfur carrier type vulcanizing agent; and the anti-aging agent is one or more of the following: amine anti-aging agent, phenolic anti-aging agent, and heterocyclic anti-aging agent.

[0013] Furthermore, the vulcanizing agent is preferably a compound system of JYA-56 as the main component, dicumyl peroxide (DCP) and triallyl isocyanurate (TAIC), with a mass ratio of 5:3:2; the anti-aging agent is preferably a compound system of 4010NA, 6PPD, RD amines and SP-P styrene-based phenol, with a mass ratio of 2:1:1:1.

[0014] In this invention, based on the above-mentioned sealing structure, its molding process includes the following steps: (1) Hard plastic molding stage: Inject the connector housing material into the mold. The temperature of the front section of the barrel is 190-200℃, the middle section is 210-220℃, the rear section is 180-190℃, the injection pressure is 80-100 MPa, the holding pressure is 60-70 MPa, the holding time is 15-20 s, the mold temperature is 75-85℃, and the cooling time is 25-50 s to ensure that the connector housing is completely formed and the dimensions are stable. (2) Soft rubber molding stage: A dual-material injection molding machine is used to inject the composite modified material of the sealing ring into the mold and combine it with the connector housing. The temperature of the front section of the barrel is 150-160℃, the middle section is 165-175℃, and the rear section is 140-150℃. The injection pressure is 40-60 MPa, the holding pressure is 30-40 MPa, and the holding time is 10-15 s. The mold temperature is dynamically controlled. The temperature of the injection stage is 35-45℃, the holding pressure stage is 55-65℃, the cooling stage is 45-55℃, and the cooling time is 20-25 s. The integrated sealing ring is formed. (3) Vulcanization treatment: After injection molding, the sealing ring material undergoes two vulcanization processes. The first vulcanization temperature is 160-170℃ and the vulcanization time is 10-15 min. The second vulcanization temperature is 150℃ and the vulcanization time is 2 h to improve the crosslinking density and aging resistance of the material. (4) Assembly stage: Install the plug and embed the sealing ring in sequence on the FFC wire so that the plug seals the sealing ring at the tail of the connector to form an interference fit. The clamping force is controlled at 5-8 N to complete the sealing assembly.

[0015] In this invention, multi-point hot runner feeding is used in step (2), the temperature of the hot runner is consistent with the temperature of the middle section of the barrel, and the feeding speed uniformity error is ≤ ±5%.

[0016] In this invention, step (2) employs an adaptive floating ejection mechanism with an ejection pressure of 15-20 MPa and an ejection speed of 4-6 mm / s. The ejector pins are circumferentially distributed on the outside of the sealing ring.

[0017] In this invention, a flexible waterproof FFC wire harness includes a connector and an FFC wire. The connector includes a connector housing and a terminal. A sealing ring is provided inside the connector housing. The connector housing, the sealing ring, and the FFC wire cooperate to form the sealing structure.

[0018] In this invention, the sealing effect of the FFC wiring harness is achieved through three dimensions: sealing material, sealing structure, and molding process. Regarding sealing materials: The substrate is a composite substrate of fluororubber and hydrogenated nitrile rubber. Fluororubber has excellent high temperature resistance, oil resistance, and chemical corrosion resistance, which is the basis for sealing wet areas in automobiles. However, fluororubber alone lacks flexibility and is prone to cracking when the FFC wire swings. Hydrogenated nitrile rubber makes up for this. Hydrogenated nitrile rubber has both high elasticity and aging resistance. When compounded with fluororubber, it can improve the elongation at break of the material through the synergistic effect of molecular chain segments, which is suitable for the flexible bending characteristics of FFC wires. The addition of graphene microsheets and nano-silica to the composite system can not only improve the thermal conductivity of the sealing surface and avoid the accumulation of heat during FFC transmission, but also fill the micropores of the material and enhance the fit of the sealing surface. In the vulcanization system, sulfur-carrier JYA-56 releases active sulfur species H2S at a vulcanization temperature of 160-170℃, forming stable SC crosslinking bonds with the unsaturated bonds of the rubber molecular chain to achieve basic crosslinking. Peroxide-based DCP decomposes at the same vulcanization temperature to generate free radicals, which on the one hand assist JYA-56 in initiating crosslinking of rubber molecules, and on the other hand capture unstable groups on the rubber molecular chain through free radicals, inhibiting the side effects of molecular chain breakage during vulcanization and improving the integrity of the crosslinking network. The crosslinking aid TAIC combines with free radicals through three active allyl double bonds to construct a three-dimensional crosslinking structure between rubber molecular chains, improve the uniformity of crosslinking density, reduce compression set, and adapt to the sealing stability under long-term vibration environment of automobiles. In the anti-aging system, the amine compound components 4010NA (N-isopropyl-N'-phenyl-p-phenylenediamine) and 6PPD (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) specifically capture ozone molecules to generate stable amine oxides, preventing ozone from attacking the rubber molecular chains and causing cracking. RD (2,2,4-trimethyl-1,2-dihydroquinoline polymer) can inhibit high-temperature thermo-oxidative degradation. The three components work synergistically to provide environmental aging protection over a wide temperature range of -40 to 150°C. The phenolic synergistic component SP-P (styrene-modified phenol) releases hydrogen atoms through hydroxyl groups, terminating the peroxide free radical chain reaction generated by thermal aging. It is colorless and does not migrate, avoiding the possible discoloration problem of amine anti-aging agents. It forms a three-dimensional protective network with amines to ensure stable performance under long-term high-temperature environments.

[0019] Regarding the sealing structure: The sealing ring is integrally molded with the connector housing through a two-material injection molding process. MAH-g-PP forms a chemical bond with the hard plastic substrate of the connector housing to prevent detachment. The sealing ring has a slot inside that is compatible with the FFC wire, and the outside is interference-fitted with the connector housing. Utilizing the 30-40 HA flexibility of the sealing ring, it continuously applies uniform pressure to the surface of the FFC wire after assembly, filling the gaps and creating a waterproof barrier. The edge of the plug is bent to form an elastic cantilever buckle, which forms a mechanical interlock with the slot on the outside of the opening at the rear of the connector housing. During assembly, a 5-8 N axial pressure causes the buckle to elastically deform and slide into the slot. The anti-detachment boss achieves positioning and fixation. The pre-tightening force of the buckle is converted into a continuous clamping force between the sealing ring inside the plug and the sealing ring at the rear of the housing, forming another waterproof barrier. At the same time, the plug's wire exit limit is interference-fitted with the flat structure of the FFC wire, forming a third waterproof barrier.

[0020] In terms of molding process: The first step of the two-material injection molding, hard rubber molding, is achieved through precise control of injection parameters. High-temperature flow and rapid shaping ensure the connector shell is fully formed and stable during storage, with the tail opening tightly fitting the sealing ring. This lays the foundation for the interface bonding and interference seal of the subsequent soft rubber molding. The second step, soft rubber molding, adopts a dynamic control method: during the injection stage, 40°C slows down the curing speed of the sealing ring material and ensures uniform filling of the slot; during the holding pressure stage, 60°C promotes the interface bonding between the soft and hard rubber; and during the cooling stage, 50°C stabilizes the dimensions and avoids deformation, thereby improving the quality of integrated molding. During the process, low-pressure injection combined with multi-point hot runner feeding effectively maintains uniform stress and thickness of the sealing ring, and adaptive floating ejection avoids deformation of the sealing ring during ejection. The third step, vulcanization and assembly, is coordinated. Different parameters are used for the two vulcanization processes to gradually increase the crosslinking density, enhance the material's aging resistance and sealing performance, and pressure control during the assembly stage ensures that the sealing ring is fully pressurized and sealed without damaging the FFC wire.

[0021] Compared with the prior art, the present invention has the following advantages: (1) The sealing ring of this application is integrally formed with the connector housing and combined with the interference fit design of the plug, the waterproof rating reaches IP67, the sealing performance is significantly improved, and it can be adapted to wet areas such as automotive door wires and chassis, breaking through the application limitations of existing FFC wire harnesses. (2) This application constructs chemical bonding force through maleic anhydride grafting modifier, the sealing ring and connector housing have high peel strength, do not fall off or crack after long-term use, have strong structural stability, and meet the 10-year / 150,000-kilometer service life requirements of automobiles. (3) In the FFC harness of this application, the diameter of the FFC conductor is only ≤0.24 mm, and the weight of the harness is reduced to 1 kg / km, compared to 0.35 mm. 2 0.5 mm 2The wires are more than 70% lighter and more than 75% smaller, demonstrating excellent performance in lightweighting and miniaturization, and are suitable for the wiring needs of compact automotive spaces. (4) The process of this application adopts a two-material injection molding process to achieve automated production, which improves efficiency by more than 10 times compared with traditional manual assembly, resulting in high production efficiency, stable production and assembly quality, and effective cost reduction; (5) The sealing ring of this application has a wide temperature range, is resistant to corrosion from engine oil and brake fluid, maintains excellent performance in long-term high-temperature environment thermal aging, has no heavy metal precipitation, excellent environmental adaptability, and complies with RoHS 2.0 standard. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the sealing structure of this application; Figure 2 This is a diagram illustrating the connector used in this application; Figure 3 The image shown is a physical photograph of the FFC wire harness product described in this application. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0024] Example 1 A sealing structure for flexible, waterproof FFC wiring harnesses, applicable to FFC wiring harnesses in wet automotive environments, such as... Figure 1 As shown, it includes an FFC wire, a connector housing, a sealing ring, and a plug. The connector housing and the sealing ring are integrally formed. The connector housing has an opening at the tail. The sealing ring is disposed in the opening at the tail of the connector housing. The outer surface of the sealing ring is tightly fitted with the inner surface of the connector housing. A slot adapted to the FFC wire is opened inside the sealing ring. The FFC wire forms a tight connection with the inner wall of the slot.

[0025] The plug is located at the opening at the tail of the connector. The edge of the plug is bent towards the connector and engages with the outer side of the opening at the tail of the seal to form a snap. The plug and the connector housing are detachably connected via the snap. A plug seal is provided on the side of the plug facing the opening. Both the plug and the plug seal have a through hole in the center for the FFC wire to pass through and are aligned. The plug seal is inserted into the opening at the tail of the seal and is interference-fitted with the sealing ring. The side of the plug seal is designed as an arc protruding to both sides. After the plug seal is inserted into the tail of the seal, the through hole in its center is interference-fitted with the FFC wire.

[0026] Connectors with the above-mentioned sealing structure, such as Figure 2 As shown.

[0027] Example 2 A flexible waterproof FFC harness, such as Figure 1As shown, the device includes a connector and an FFC wire. The connector includes a connector housing, terminals, and a sealing structure as described in Example 1. The FFC wire extends into the connector housing from the tail end and is electrically connected to the terminals. The sealing structure is located at the tail end of the connector housing. The other end of the connector housing is a socket for insertion into automotive conductive components, electrically connected via terminals. The socket has a built-in socket sleeve, and the terminals are fixed inside the socket sleeve. A pre-set circular groove for insertion is located outside the socket sleeve, and a sleeve sealing ring is provided within the circular groove to maintain a waterproof seal at the terminal insertion point of the socket. The overall product is as follows. Figure 3 .

[0028] Example 3 A molding process for a sealing structure of a flexible waterproof FFC wire harness includes the following steps: (a) Preparation of materials and equipment 1. Sealing Ring: Prepare raw materials according to the following mass percentages: 26.62% fluororubber FKM, 28% hydrogenated nitrile butadiene rubber (HNBR), 5% maleic anhydride-grafted polypropylene (MAH-g-PP), 2.5% graphene microsheets, 1.5% nano-silica, 0.8% vulcanizing agent (JYA-56:DCP:TAIC=5:3:2), and 0.2% anti-aging agent (4010NA:6PPD:RD:SP-P=2:1:1:1). Place the fluororubber and HNBR in a mixer and plasticize at 120℃ and 60 r / min for 15 min to achieve initial relaxation of the molecular chains. Then, sequentially add MAH-g-PP, graphene microsheets, and nano-silica, and heat to 140℃ to mix for 20 min to ensure uniform dispersion of the functional fillers. After cooling to 80℃, add the vulcanizing agent and anti-aging agent, and mix at a low speed of 30 r / min for 8 minutes. To prevent premature decomposition of the vulcanizing agent, the film is then extruded through a two-roll mill to a thickness of 3 mm. It is then left to mature at room temperature for 24 hours before use.

[0029] 2. Connector housing: PA66 granules with 30% glass fiber reinforcement are selected and dried in an 80℃ oven for 4 hours to remove moisture, so that the moisture content does not exceed 0.05% to avoid air bubbles during injection molding.

[0030] 3. FFC conductor: Select a flat flexible conductor with a diameter of 0.2 mm and 2 cores. The insulation material is polyimide. Wipe the surface of the conductor with anhydrous ethanol in advance to remove oil and dust, and let it dry before use.

[0031] 4. Plug: PP material plug (including built-in plug seal), individually injection molded, buckle elasticity test meets the standard, pressing deformation ≤1 mm, rebound rate 100%, spare.

[0032] 5. Dual-material injection molding equipment: A 12-cavity Jiangmi dual-material injection molding machine is selected, equipped with a dynamic mold temperature control system, a multi-point hot runner module and an adaptive floating ejection mechanism. The barrel temperature, injection pressure and holding pressure parameters are adjusted to ensure that the equipment accuracy meets the standards.

[0033] 6. Mold: Install the connector housing and sealing ring into an integrated mold. The mold cavity surface is smooth with a roughness Ra≤0.02 μm. Check the fit clearance between the positioning pin and the positioning hole to be 0.03-0.05 mm to ensure the dimensional accuracy of the FFC wire slot. Preheat the mold to 80℃ and keep it at that temperature for 30 min.

[0034] (II) Two-material injection molding 1. Rigid molding (connector housing molding) Feeding and Injection: Add the dried PA66 reinforced material into the main barrel of the injection molding machine. Set the following parameters: barrel front temperature 195℃, middle temperature 215℃, rear temperature 185℃, nozzle temperature 220℃, injection pressure 90 MPa, injection speed 50 mm / s, and injection time 3 s to ensure that the material fully fills the mold cavity. Pressure holding and cooling: The pressure holding pressure is 65 MPa and the holding time is 18 s to maintain stable cavity pressure and avoid shell shrinkage. The temperature is simulated to be 80℃ and the cooling time is 28 s to make the shell curing degree ≥90%. The shell is smoothly ejected at a pressure of 15 MPa and a speed of 5 mm / s through an adaptive ejection mechanism. After removing the connector shell and checking that there are no burrs or cracks, it is transferred to the soft rubber molding station.

[0035] 2. Soft rubber molding (integrated molding of sealing ring) Feeding and parameter settings: Add the cured sealing ring composite rubber material to the auxiliary barrel of the injection molding machine. Set the following parameters: front section of barrel 155℃, middle section 170℃, rear section 145℃, nozzle temperature 165℃, low-pressure injection, injection pressure 50 MPa, injection speed 30 mm / s to avoid high pressure damage to the insulation layer of the subsequently embedded FFC wires. Dynamic mold temperature control: The mold temperature is 40℃ during the injection stage to slow down the curing speed of the rubber material and ensure uniform filling of the slots. During the holding pressure stage, the mold temperature is raised to 60℃ to promote the bonding between the soft and hard rubber interfaces. During the cooling stage, the mold temperature is lowered to 50℃ to stabilize the dimensions. Holding pressure and ejection: The holding pressure is 35 MPa and the holding time is 12 s to strengthen the bonding force between the sealing ring and the part. After a cooling time of 22 s, the integral molded part is ejected through 3 sets of circumferentially evenly distributed floating ejector pins at a pressure of 18 MPa and a speed of 5 mm / s. The pressure is monitored in real time during the ejection process to prevent the sealing ring from warping or deforming.

[0036] (III) Vulcanization strengthening 1. Single vulcanization The integrated molded part after dual-material injection molding is placed in a flat vulcanizing machine. The vulcanization temperature is 165℃, the vulcanization pressure is 10MPa, and the vulcanization time is 12 min. During this process, JYA-56 decomposes and releases active sulfur, DCP generates free radicals, and TAIC bridges to form a three-dimensional structure. The three work together to achieve cross-linking of rubber molecular chains, laying the foundation for the basic performance of the sealing ring.

[0037] 2. Secondary vulcanization After the first vulcanization, the molded parts are transferred to an oven for a second vulcanization treatment at 150℃ for 2 hours to further increase the crosslinking density of the rubber, reduce compression set, and enhance aging resistance and sealing stability.

[0038] (iv) Assemble the seal 1. FFC wire embedding First, the flat, sheet-shaped crimp terminals are pre-installed into the pre-reserved mounting cavity of the formed connector. The pre-treated FFC wire is aligned with the sealing ring slot. Using a semi-active assembly device, the wire is slowly inserted with axial thrust to ensure that it slowly fits against the inner wall of the slot without wrinkles or misalignment. After insertion, the wire extension length is checked to avoid the wire being too long or too short, which would affect the seal. Then, the crimping machine is used to press the wire deeper from the socket, so that the crimping claws at the terminal end completely wrap around the FFC wire end and mechanically engage, thus achieving electrical connection between the terminal and the FFC wire.

[0039] 2. Endcap assembly Align the plug pre-connected to the FFC wire with the opening at the tail of the connector housing, position it along the guide chamfer, apply 5-8 N axial pressure to make the edge of the plug fit onto the outside of the connector housing opening, achieve interlocking, and complete mechanical fixation. At this time, the plug is inserted into the tail opening of the connector housing. Post-assembly inspection: The gap between the plug and the housing should be ≤0.1 mm. The plug should be sealed to the sealing ring at the tail of the connector housing with an interference fit of 0.25 mm to ensure that the sealing surface is under continuous pressure.

[0040] (v) Finished product inspection and testing 1. Appearance and Dimensions Inspect the connector housing, sealing ring, and plug for burrs, cracks, and overflow. Ensure the FFC wire insulation layer is undamaged. Measure the key dimensions of the connector housing with an error ≤ ±0.05 mm and the thickness of the connector body is 1.3 mm.

[0041] 2. Sealing performance test Waterproof rating test: The finished product is placed in an IP67 testing device and immersed in water at a depth of 1 m for 30 minutes. After removal, the inside is checked and there is no water leakage, indicating that the sealing performance meets the standard.

[0042] 3. Mechanical and environmental performance testing Mechanical properties: The tensile strength of the sealing ring is ≥9.2 MPa, the elongation at break is ≥480%, and the peel strength from the shell is ≥3.8 N / mm. Environmental adaptability: After 24 hours of low-temperature impact at -40℃, there is no brittleness; after 1000 hours of heat aging at 150℃, the performance retention rate is ≥88%; after 1000 cycles of FFC wire bending (±30°) test, the buckle does not loosen and the sealing ring does not fall off. Environmental testing: The amount of heavy metals released is ≤0.1 ppm, and the content of volatile organic compounds (VOCs) is ≤0.5%, which complies with RoHS 2.0 standards.

[0043] 4. Batch sampling inspection Sampling is performed at 3‰ of each batch's output. The above tests are repeated, and a pass rate of ≥98.5% indicates that the batch is qualified and transferred to finished product storage.

[0044] Example 4 This embodiment compares the product obtained by the process in Example 3 with the existing technology to verify the technical effect of this solution.

[0045] (a) Sample preparation The test group consisted of 30 FFC wire harness products prepared in Example 3. The control group consisted of existing dry-area FFC wire harnesses, including FFC conductors (0.2 mm cores, 2 cores, polyimide insulation), ordinary connectors (without the sealing structure in Example 1), and a plug-free design, with 30 samples.

[0046] Both groups of samples underwent the same basic electrical performance calibration and appearance inspection, namely, initial on-resistance ≤0.01 Ω, no burrs on the surface, and no damage to the conductors, to ensure that all basic conditions are consistent except for the sealing structure and material system, thus guaranteeing the fairness of the test.

[0047] (ii) Testing and Experimentation 1. Sealing performance test Test standard: GB / T 4208-2017 "Degrees of protection provided by enclosures (IP codes)".

[0048] Test method: Both groups of samples were immersed in 1 m deep clean water at a temperature of 25±2℃ for 30 min, during which time the FFC wire and the terminal connection were kept connected to 12 V DC. After immersion, the samples were removed, the surface was wiped dry with a dry cloth, and the samples were disassembled to observe whether water stains had seeped into the interior. At the same time, the conductivity was tested.

[0049] Judgment criteria: The qualified standard is no internal water seepage and the change in conduction resistance is ≤0.005 Ω. The failure standard is internal water stains, sudden change in conduction resistance exceeding 0.1Ω, or open circuit.

[0050] 2. Environmental adaptability test ① High and low temperature cycling test Test standards: Low temperature GB / T 2423.1-2008, High temperature GB / T 2423.2-2008; Test method: Hold at -40℃ for 8 hours, allow to recover to room temperature for 2 hours, raise the temperature to 125℃ and hold for 8 hours, allow to recover to room temperature for 2 hours, and repeat the above cycle 10 times; Judgment criteria: No cracks after cycling, no detachment of the sealing structure, and the change in conduction resistance ≤ 0.01 Ω.

[0051] ② Damp heat cycle test Test standard: GB / T 2423.4-2008; Test method: Place in an environment of 40℃ and 95% relative humidity for 12 hours, dry at room temperature for 12 hours, and repeat the above cycle 10 times; Judgment criteria: No mold growth or oxidation of the conductor after cycling, and the change in on-resistance is ≤0.01 Ω.

[0052] ③ Ozone aging test Testing standard: GB / T 7762-2014; Test method: ozone concentration 50 pphm, temperature 40℃, stretching 20%, continuous for 72 h; Judgment criteria: no cracking, no embrittlement (Shore hardness change ≤ ±5 HA), and no decrease in sealing performance of the experimental group.

[0053] 3. Mechanical reliability testing ① Vibration test Testing standard: GB / T 2423.10-2019; Test method: Frequency 10-2000 Hz, acceleration 20 g, vibration of each of the XYZ axes for 100 h; Judgment criteria: No parts loosen after vibration, the change in conduction resistance is ≤0.005 Ω, and there is no poor contact.

[0054] ② Bending fatigue test Test method: The FFC wire is bent back and forth at an angle of ±30°, with a bending frequency of 10 times / min, for a total of 1000 times; Judgment criteria: No conductor breakage, no insulation layer damage, no cracks in the sealing ring, and the change in conduction resistance ≤ 0.005Ω after bending.

[0055] ③ Insertion and removal life test (experimental group only, control group without plugs) Test method: Insert and remove the plug, with an insertion and removal force of 5-8 N, for a total of 100 cycles; Judgment criteria: No deformation after insertion and removal, sealing performance still reaches IP67, and conduction resistance is normal.

[0056] 4. Electrical performance stability test ① Long-term power-on stability test Test method: Both groups of samples were continuously subjected to a 12V 1A DC current and an ambient temperature of 85℃ for 1000 h. Judgment criteria: No overheating during the period, i.e., surface temperature ≤100℃, and the change in on-resistance after the period is ≤0.01 Ω, with no short circuit.

[0057] ② Salt spray corrosion test Test standard: GB / T 2423.17-2008; Test method: 5% sodium chloride solution, salt spray deposition rate 1-2 mL / (h·80cm) 2 ), temperature 35℃, for 48 hours; Judgment criteria: No corrosion on the terminals after testing, and the change in conduction resistance ≤ 0.01 Ω.

[0058] 5. Long-term accelerated life testing Test method: The temperature accelerated aging model was adopted, and the vehicle was placed in an environment of 85℃ for 5000 hours, which is approximately equivalent to the service life of a car of 10 years / 150,000 kilometers. Judgment criteria: After aging, there is no obvious damage to the appearance, the sealing performance still reaches IP65 or above, the change in conduction resistance is ≤0.01 Ω, and the tensile strength retention rate is ≥80%.

[0059] (III) Test Results 1. Sealing performance test (Table 1) Table 1 shows the comparison results of sealing performance. Group Test Results pass rate experimental group None of the 30 pieces showed any water leakage, and the change in conductivity was ≤0.003 Ω. 100% control group All 30 pieces showed internal water leakage, 22 pieces had a conductivity ≥0.1 Ω, and 8 pieces had open circuits. 0% 2. Environmental adaptability test (Table 2) Table 2 shows the results of the environmental adaptability comparison. Test Project experimental group performance control group performance High and low temperature cycling No cracks, no detachment of the sealing structure, conduction resistance variation ≤0.008 Ω, 100% pass rate. Fifteen pieces had cracked rubber, eight pieces had loose terminals, and the change in conductivity was ≥0.05 Ω, resulting in a pass rate of 23%. Humid heat circulation No mold growth, no conductor oxidation, 100% pass rate. 20 conductors had blackened surfaces, and 12 had poor conductivity, resulting in a pass rate of 27%. Ozone aging No cracks, Shore hardness variation ≤ ±3 HA, 100% pass rate. 28 pieces showed rubber cracking, with crack width ≥ 0.1 mm, resulting in a pass rate of 7%. 3. Mechanical reliability testing (Table 3) Table 3 shows the comparison results of mechanical reliability. Test Project experimental group performance control group performance Vibration test The plug did not fall off, and the change in conduction resistance was ≤0.004 Ω, achieving a 100% pass rate. 18 pieces had loose terminals, and 10 pieces had FFC detached from the terminals, resulting in a pass rate of 7%. Bending fatigue No conductor breaks, no cracks in the sealing rings, 100% pass rate. 12 conductors were broken, and 8 had damaged insulation, resulting in a pass rate of 33%. Insertion and removal lifespan After 100 insertions and removals, it still maintains an IP67 rating, with no conductivity issues, achieving a 100% pass rate. - (No plug design) 4. Electrical performance stability test (Table 4) Table 4 shows the comparison results of electrical performance stability. Test Project experimental group performance control group performance Long-term power supply No overheating, on-resistance change ≤0.007 Ω, 100% pass rate. Ten pieces had terminal overheating issues, eight had short circuits, and surface temperatures were ≥120℃, resulting in a pass rate of 40%. Salt spray corrosion The terminals were free of rust, achieving a 100% pass rate. 25 terminals had surface finishing defects, and 15 had poor conductivity, resulting in a pass rate of 17%. 5. Long-term accelerated life testing Table 5 shows the comparison results of long-term life accelerated testing. Group Test Results pass rate experimental group The exterior is undamaged, the sealing performance reaches IP66, the change in conduction resistance is ≤0.009 Ω, and the tensile strength retention rate is ≥85%. 100% control group 20 pieces showed rubber embrittlement damage, 18 pieces showed open circuits, and the tensile strength retention rate was ≤60%. 7% (iv) Experimental Conclusions 1. Breakthrough in sealing performance: The test group achieved an IP67 waterproof rating by using a dual-material injection molded integrated sealing ring and an interference fit with a plug cap, which completely solved the problem of water leakage due to lack of sealing in the existing technology of the control group, and successfully expanded the application range of FFC wiring harnesses from dry areas to wet areas in automobiles; 2. Leading environmental adaptability: The test group performed well in complex environments such as high and low temperatures, humidity and heat, and ozone, while the pass rate of the control group was less than half. The synergistic effect of the composite rubber material and the vulcanization / three-dimensional anti-aging system ensures that the product is suitable for extreme automotive operating conditions. 3. Reliable mechanical and electrical performance: In vibration, bending fatigue and other tests, the experimental group was evaluated as having accurate positioning of the snap-fit ​​connection and performed well. The control group was unable to meet the requirements due to its loose structure. In addition, the electrical performance stability of the experimental group was also better than that of the control group. 4. Long-term lifespan meets standards: The test group passed a 5000-hour accelerated aging test, demonstrating high performance retention, while the control group failed to meet the requirements. In summary, this solution's flexible waterproof FFC wiring harness is superior to existing dry-area FFC wiring harnesses in terms of sealing, environmental adaptability, reliability, and lifespan. It fully meets the technical requirements for large-scale application in automotive wet areas, while also offering advantages in lightweight design, automated mass production, and environmental protection, making it highly valuable for industrial applications.

Claims

1. A sealing structure for a flexible waterproof FFC wire harness, characterized in that, It includes an FFC wire, a connector housing, and a sealing ring disposed inside the connector housing to seal between the connector housing and the FFC wire. The sealing ring is disposed inside the opening at the tail of the connector, with its outer surface tightly fitting the inner surface of the connector housing, and a slot inside that is adapted to the FFC wire, so that the FFC wire and the inner wall of the slot form a sealed engagement.

2. The sealing structure according to claim 1, characterized in that, A plug is provided at the tail opening of the connector. The plug has a through hole in the center for the FFC wire to pass through. A plug seal is provided on the side of the plug facing the connector. The plug seal has a through hole in the center for the FFC wire to pass through, which is aligned with the through hole in the center of the plug. The plug seal is inserted into the tail opening of the sealer and is interference-fitted with the sealing ring at the tail of the connector.

3. The sealing structure according to claim 2, characterized in that, The side of the plug seal is designed to be an arc shape that protrudes to both sides. After the plug seal is inserted into the tail of the sealer, the central perforation is interference-fitted with the FFC wire.

4. The sealing structure according to claim 2, characterized in that, The edge of the plug bends toward the connector and engages with the outer side of the seal's tail opening to form a snap fastener. The plug and the connector housing are detachably connected via the snap fastener.

5. The sealing structure according to claim 1, characterized in that: The sealing ring is integrally formed with the connector housing using a two-material injection molding process.

6. The sealing structure according to claim 5, characterized in that: The sealing ring has a compression set (120℃×24 h) ≤15%, tensile strength ≥8.5 MPa, elongation at break ≥450%, peel strength to connector housing ≥3.5 N / mm, and Shore hardness of 30-40 HA.

7. The sealing structure according to claim 6, characterized in that, The sealing ring is composed of the following components in the indicated mass percentages: 60-65% fluororubber, 25-30% hydrogenated nitrile rubber, 4-6% maleic anhydride-grafted polypropylene, 2-3% graphene microflakes, 1-2% nano-silica, 0.6-1% vulcanizing agent, and 0.1-0.3% anti-aging agent, wherein the graphene microflakes have a particle size of 5 μm and the nano-silica has a particle size of 20 nm; the connector housing is made of polypropylene or PA66 material with 30% glass fiber reinforcement, wherein the vulcanizing agent is one or more of the following: peroxide vulcanizing agent, sulfur-accelerator system vulcanizing agent, oxime vulcanizing agent, and sulfur carrier type vulcanizing agent; and the anti-aging agent is one or more of the following: amine anti-aging agent, phenolic anti-aging agent, and heterocyclic anti-aging agent.

8. The sealing structure according to claim 7, characterized in that, The preferred vulcanizing agent is a compound system of JYA-56 as the main component, dicumyl peroxide and triallyl isocyanurate, with a mass ratio of 5:3:2; the preferred anti-aging agent is a compound system of 4010NA, 6PPD, RD amines and SP-P styrene-based phenol, with a mass ratio of 2:1:1:

1.

9. The molding process of the sealing structure according to any one of claims 1-8 includes the following steps: (1) Hard plastic molding stage: Inject the connector housing material into the mold. The temperature of the front section of the barrel is 190-200℃, the middle section is 210-220℃, the rear section is 180-190℃, the injection pressure is 80-100 MPa, the holding pressure is 60-70 MPa, the holding time is 15-20 s, the mold temperature is 75-85℃, and the cooling time is 25-50 s to ensure that the connector housing is completely formed and the dimensions are stable. (2) Soft rubber molding stage: A dual-material injection molding machine is used to inject the composite modified material of the sealing ring into the mold and combine it with the connector housing. The temperature of the front section of the barrel is 150-160℃, the middle section is 165-175℃, and the rear section is 140-150℃. The injection pressure is 40-60 MPa, the holding pressure is 30-40 MPa, and the holding time is 10-15 s. The mold temperature is dynamically controlled. The temperature of the injection stage is 35-45℃, the holding pressure stage is 55-65℃, the cooling stage is 45-55℃, and the cooling time is 20-25 s. The integrated sealing ring is formed. (3) Vulcanization treatment: After injection molding, the sealing ring material undergoes two vulcanization processes. The first vulcanization temperature is 160-170℃ and the vulcanization time is 10-15 min. The second vulcanization temperature is 150℃ and the vulcanization time is 2 h to improve the crosslinking density and aging resistance of the material. (4) Assembly stage: Install the plug and embed the sealing ring in sequence on the FFC wire so that the plug seals the sealing ring at the tail of the connector to form an interference fit. The clamping force is controlled at 5-8 N to complete the sealing assembly.

10. A flexible waterproof FFC wire harness, comprising a connector and FFC wires, the connector comprising a connector housing and terminals, characterized in that, The connector housing is provided with a sealing ring. The connector housing, the sealing ring and the FFC wire cooperate to form a sealing structure as described in any one of claims 1-8 or a sealing structure obtained by the molding process of claim 9.

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