Injection molding process and equipment for new energy automobile driving shaft integrated dust cover

Abstract

The application discloses a kind of injection molding process and equipment of new energy automobile driving axle integrated dust cover.It includes: adjusting the radial clearance of movable core and mold cavity before clamping, forming the gradually thickening wall flow channel from large end to small end;Mold is divided into three independent temperature control zones along the axial direction, temperature decreases in turn;Three-stage segmented injection is used, injection speed and pressure increase gradually, and injection pressure is monitored by gate pressure sensor, and the stage is automatically switched according to the monitoring result.Subsequently, the sequential pressure maintaining is carried out, and the pressure maintaining of adjacent zones is overlapped;After cooling, the core is withdrawn radially according to the predetermined sequence;At the same time, the multi-physical field linkage control of pressure, core position, temperature, pressure maintaining pressure, cooling shrinkage and withdrawal timing is implemented.The application can accurately form the gradually thickening wall corrugated structure, the residual stress is low, the demolding quality is good, and the wide temperature range of-40℃~125℃ and large swing angle durability requirements are met.

Description

Technical Field

[0001] This invention relates to the field of injection molding technology for automotive parts, specifically to an integral injection molding process and special equipment for an integrated dust cover for the drive shaft of a new energy vehicle, belonging to precision injection molding technology. Background Technology

[0002] With the rapid development of the new energy vehicle industry, the performance requirements for dust covers in drive shaft systems are becoming increasingly stringent. Taking new energy vehicle models as an example, their drive shaft dust covers need to withstand harsh operating conditions such as a maximum swing angle of 26°, a maximum speed of 1800 r / min, and a maximum compression of 30 mm within a wide temperature range of -40℃ to 125℃, while ensuring no cracks, no grease leakage, and a maximum outer diameter expansion of no more than 10 mm.

[0003] To meet these requirements, modern dust cover designs increasingly adopt a one-piece structure and use non-uniform wall thickness corrugated design to control the contact sequence between the troughs and the shaft, thereby reducing stress concentration and improving durability. Finite element analysis shows that the third trough begins to contact the shaft at a swing angle of 25°, and the second trough begins to contact at a swing angle of 17.5°. This contact sequence requires the dust cover wall thickness to exhibit a precise gradient change from the widest end to the narrowest end, typically with a wall thickness difference of 0.1–0.5 mm between adjacent troughs.

[0004] However, existing injection molding processes and equipment are insufficient for accurately molding this type of one-piece dust cover with gradually varying wall thickness, mainly due to the following technical problems: Wall thickness gradient is difficult to control precisely: Traditional fixed cavity molds cannot form a gradual change in wall thickness along the axial direction, and also lack independent adjustment capabilities for corrugated structures, resulting in large wall thickness deviations and affecting contact timing.

[0005] Filling imbalance: The thin-walled area (large opening end) has high flow resistance and is prone to underfilling; the thick-walled area (small opening end) has large shrinkage and is prone to shrinkage marks and internal stress.

[0006] High residual stress: especially at large corners, finite element analysis shows that the maximum equivalent stress can reach 5.197 MPa, which is close to the material fatigue limit, leading to early cracking.

[0007] Demolding damage: Traditional synchronous demolding methods are prone to tearing the corrugations, damaging the surface quality of the corrugations, and affecting the sealing performance.

[0008] Isolated process parameters: In existing processes, parameters such as temperature, pressure, speed, and time are set independently, lacking linkage and coordination, making it difficult to adapt to material batch fluctuations and environmental changes.

[0009] Therefore, there is an urgent need to develop an integrated injection molding process and equipment that can precisely control wall thickness gradient, eliminate internal stress, ensure dimensional stability, and has multi-physics field linkage and synergy capabilities. Summary of the Invention

[0010] This invention aims to provide an integral injection molding process and equipment for an integrated dust cover for the drive shaft of new energy vehicles. Through movable core array, zoned temperature control, segmented injection molding, sequential pressure holding, and multi-physical field linkage control, it achieves high-precision molding of a gradually thickened corrugated structure, reduces residual stress, improves demolding quality, and meets the durability requirements of a wide temperature range and large swing angle.

[0011] Therefore, the first aspect of this application provides an injection molding process for an integrated dust cover for the drive shaft of a new energy vehicle, comprising the following steps: Step 1: Mold Clearance Adjustment: Before mold closing, adjust the radial clearance between multiple movable cores and the mold cavity to form a gradual flow channel with a wall thickness gradient from the large end to the small end of the dust cover. Step 2: Zoned mold temperature control: Divide the mold into three independent temperature control zones along the axial direction. The temperature of the first temperature control zone T1 is 160℃~180℃, the temperature of the second temperature control zone T2 is 140℃~160℃, and the temperature of the third temperature control zone T3 is 120℃~140℃, and T1>T2>T3. Step 3: Segmented Injection Molding: The molten thermoplastic elastomer material is injected into the gradient runner in three stages. The first stage injection speed V1 is 10-30 mm / s, and the pressure P1 is 40-60 MPa. The second stage injection speed V2 is 30-60 mm / s, and the pressure P2 is 60-80 MPa. The third stage injection speed V3 is 60-100 mm / s, and the pressure P3 is 80-110 MPa, with V3 > V2 > V1 and P3 > P2 > P1. The injection pressure is monitored by a gate pressure sensor to automatically switch between stages. Step 4: Sequential pressure holding: After injection, pressure is held in each temperature control zone in descending order of wall thickness. The holding pressure is 60% to 80% of the corresponding injection pressure, and the holding time decreases progressively while the holding time of adjacent zones overlaps. Step 5: Cooling, Shaping, and Demolding: After cooling, the movable core is radially withdrawn in a predetermined sequence, and the mold is opened to eject the core. The process also includes multi-physics field linkage control: real-time acquisition of gradual flow channel pressure, temperature of each temperature control zone and shrinkage rate, and linkage adjustment of the radial position of the movable core, holding pressure and exit sequence through PLC, forming a closed loop of pressure, position, temperature and time coordination.

[0012] This application addresses the specific requirements of integrated dust covers for drive shafts in new energy vehicles (non-uniform wall thickness corrugated, wide temperature range and large swing angle), and designs the above five core processes. Multi-physics field linkage control feeds back pressure, temperature, and shrinkage rate signals to the PLC, dynamically adjusting the position of the movable core, holding pressure, and exit sequence to form a fully adaptive closed loop.

[0013] In the technical field of dust cover design, the number of peaks and troughs is generally 5 to 10. Therefore, in step one, the number of movable cores is 5 to 10, each movable core corresponding to a trough or peak of a corrugation in the dust cover. An elastic sealing sheet is provided between adjacent movable cores. The wall thickness gradient is the wall thickness difference between adjacent troughs controlled within 0.1 mm to 0.5 mm. During use, each corrugation of the dust cover bears different contact timing and stress distribution under oscillation conditions. This invention provides an independent movable core for each trough or peak, driven independently by a servo motor, and its radial position can be adjusted individually, thereby achieving a continuous gradient change in wall thickness from the large end to the small end. An elastic sealing sheet (such as a high-temperature resistant silicone rubber sheet) is provided between adjacent movable cores, which fits tightly against the side (or inner side) of the movable core after mold closing to prevent the melt from flowing through the gaps between the movable cores, ensuring that the wall thickness of each corrugation is independently controllable. The optimal range of 0.1–0.5 mm wall thickness difference was derived through extensive finite element analysis and bench tests: when it is less than 0.1 mm, the difference in trough stiffness is insufficient, the contact sequence is not obvious, and the peak stress cannot be effectively reduced; when it is greater than 0.5 mm, the sudden change in wall thickness causes unstable melt flow and local shear overheating, and the product is prone to fatigue cracks under dynamic conditions. The technical solution of this invention can achieve independent wall thickness adjustment for 5–10 corrugations, with an accuracy of ±0.03 mm for the wall thickness difference between adjacent troughs; the elastic sealing sheet effectively prevents crossflow and ensures the uniformity of wall thickness for each corrugation.

[0014] In step four, the holding pressure of the third temperature control zone is 60% of the corresponding injection pressure and the holding time is 5s; the holding pressure of the second temperature control zone is 70% of the corresponding injection pressure and the holding time is 4s; the holding pressure of the first temperature control zone is 80% of the corresponding injection pressure and the holding time is 3s; and the overlap time of holding pressure between adjacent temperature control zones is 1s.

[0015] This scheme provides specific parameters for sequential pressure holding. The third temperature control zone (thick-walled area at the small opening) has the largest shrinkage rate (approximately 2%–3%), requiring initial pressure holding with a long holding time (5s), but at a lower pressure (60% of the injection pressure) to avoid excessive residual stress in the core layer of the thick-walled area. The second temperature control zone (middle zone) has a moderate shrinkage rate, requiring medium pressure (70%) and medium time (4s). The first temperature control zone (thin-walled area at the large opening) has a small shrinkage rate (approximately 0.5%–1%), requiring subsequent pressure holding with high pressure (80%) and a short time (3s) to quickly compact the surface and eliminate shrinkage marks. The pressure holding times of adjacent temperature control zones overlap by 1 second to maintain pressure within the gradient flow channel during switching, avoiding stress waves or surface flow marks caused by sudden pressure changes. These specific values ​​were obtained through orthogonal experimental design and CAE simulation optimization: an overlap time less than 1s leads to pressure fluctuations, while an overlap time greater than 1s easily causes over-pressure deformation; when the pressure ratio deviates from ±5%, residual stress or shrinkage marks will significantly worsen. The volume shrinkage rate is reduced to 0.8%, and the internal porosity is almost zero; the residual stress at the large corners is reduced; the product surface is free of shrinkage marks and flow marks, and the appearance qualification rate is greatly improved.

[0016] The multi-physics linkage control includes real-time linkage between pressure and core position: when the deviation between the actual gradient flow channel pressure and the preset pressure exceeds ±5%, the PLC controller drives the corresponding movable core to move radially, with a step size ≤0.02mm and the cumulative movement not exceeding 10% of the initial gap.

[0017] During injection molding, factors such as batch material variations, ambient temperature fluctuations, and mold wear can cause the actual gradient runner pressure to deviate from the preset value. Traditional open-loop control cannot compensate for this, resulting in wall thickness deviations. This invention feeds back the gate pressure sensor signal to the PLC in real time. When the deviation exceeds ±5%, the PLC immediately drives the corresponding movable core to move radially: when the pressure is too low, the movable core expands outward (reducing the gradient runner gap), increasing flow resistance and causing the pressure to rise; when the pressure is too high, the movable core contracts (increasing the gradient runner gap), reducing resistance. The single movement step is ≤0.02mm to ensure the precision of adjustment; the cumulative movement does not exceed 10% of the initial gap to prevent over-adjustment from causing abrupt changes in the runner morphology. This linkage response speed reaches the millisecond level and does not change the injection curve, avoiding the introduction of new filling imbalances. The wall thickness tolerance is reduced from ±0.1mm to ±0.03mm; the pressure fluctuation amplitude is controlled within ±3%, significantly improving filling consistency; the tolerance for batch material fluctuations is improved, and the continuous production pass rate is greatly increased.

[0018] As a preferred technical solution, the multi-physics field linkage control includes coordinated control of temperature and holding pressure: the holding pressure of each temperature control zone is negatively correlated with the temperature, that is, the holding pressure of the first temperature control zone is 75% to 80% of the injection pressure and the holding time is 2 to 3 seconds, the holding pressure of the second temperature control zone is 65% to 70% of the injection pressure and the holding time is 3 to 4 seconds, and the holding pressure of the third temperature control zone is 55% to 60% of the injection pressure and the holding time is 4 to 6 seconds.

[0019] The melt state varies significantly across different temperature zones. In the first temperature control zone (160-180℃), the melt has good fluidity and high feeding efficiency. Therefore, a high-pressure (75%-80% of the injection pressure) short-time (2-3s) holding pressure is used to quickly compact the surface and prevent shrinkage marks. In the second temperature control zone (140-160℃), the melt viscosity is moderate, and a medium-pressure, medium-time holding pressure is used. In the third temperature control zone (120-140℃), the melt is partially solidified. If the holding pressure is too high, it will lead to core shear and residual stress. Therefore, a low-pressure (55%-60%) long-time (4-6s) holding pressure is used to allow the material to creep and feed under slow pressure. This synergistic strategy of negative correlation between holding pressure and temperature and positive correlation between holding time and temperature breaks through the traditional mindset of uniform holding pressure and is also an important innovation of this invention. The specific numerical range is determined through thermo-mechanical coupling simulation and stress measurement experiments: if the holding pressure in the high-temperature zone is lower than 75%, surface shrinkage marks are obvious; if it is higher than 80%, overpressure flash will occur. If the pressure holding time in the low-temperature zone is less than 4 seconds, the compression will be insufficient; if it is more than 6 seconds, the production efficiency will decrease.

[0020] The residual stress at the large corner was further reduced to below 1.6 MPa (a 69% reduction compared to 5.2 MPa under uniform pressure); the surface shrinkage index (according to ASTM D955) was also significantly reduced; the density difference between different wall thickness areas was less than 0.5%, and the internal quality was uniform.

[0021] As a preferred technical solution, the multi-physics field linkage control includes a cooling shrinkage-core withdrawal timing linkage: when the temperature of a certain region drops to 5°C to 10°C above the glass transition temperature of its material, the core corresponding to that region begins to withdraw, and the withdrawal speed is proportional to the real-time shrinkage rate of that region.

[0022] During dust cover cooling, the thick-walled area (smaller opening) shrinks faster than the thin-walled area (larger opening). If the core exits synchronously, the shrinkage of the thick-walled area will pull the corrugations towards the axis, causing deformation or even tearing of the corrugations in the thin-walled area. This invention embeds thermocouples in each temperature control zone to monitor the temperature drop curve in real time and calculate the instantaneous shrinkage rate. When the temperature of a certain area drops to (Tg + 5~10℃) (Tg is the glass transition temperature of the material, TPV is approximately 50℃, but the actual temperature at which demolding strength is achieved is approximately 55-60℃), the product in that area has sufficient strength and still retains some plasticity, resulting in minimal removal friction. At this time, the PLC controls the corresponding movable core in that area to begin radial withdrawal, with the withdrawal speed proportional to the real-time shrinkage rate (the larger the shrinkage rate, the faster the withdrawal), ensuring that a small gap is always maintained between the movable core and the product. The withdrawal start times of the movable cores in each area are asynchronous, starting sequentially from the smaller opening to the larger opening, forming a sequential withdrawal sequence. The demolding force is reduced by more than 50%, and the corrugated surface is free of scratches and tears; the corrugated profile accuracy is ±0.05mm, and the roundness error of the sealing lip is <0.02mm; the surface scratch rate is reduced from 8% in traditional synchronous demolding to 0.1%; and the sealing life (bench test) is extended from 500h to 1500h without leakage.

[0023] The thermoplastic elastomer used to produce dust covers is thermoplastic vulcanized rubber or thermoplastic polyester elastomer, with a melting temperature ≥180℃, a brittle temperature ≤-50℃, and a tensile strength retention rate ≥80% after heat aging at 125℃ for 240 hours.

[0024] Dust covers for drive shafts in new energy vehicles need to operate long-term within a wide temperature range from -40℃ to 125℃ and are in contact with lubricating grease. Material selection is crucial. Thermoplastic vulcanizate (TPV) and thermoplastic polyester elastomer (TPEE) possess excellent heat resistance, oil resistance, and low-temperature resistance. This invention limits the melting temperature to ≥180℃ to ensure no softening or creep during a 125℃ high-temperature rotational test; the brittle temperature to ≤-50℃ to ensure no cracking during -40℃ low-temperature cycling; and the tensile strength retention rate after 125℃×240h heat aging to ≥80%, meeting Toyota 956D specifications. If the melting temperature is below 180℃, the product is prone to deformation at high temperatures; if the brittle temperature is above -50℃, cracking is likely during the initial low-temperature start-up (acceleration to 1500r / min within 5 seconds); and if the heat aging retention rate is below 80%, durability is insufficient. It meets the wide temperature range of -40℃ to 125℃ and passes the low temperature 20-cycle and high temperature 240-hour tests; it still maintains more than 85% of its tensile strength after heat aging, thus extending the product life; it has good compatibility with grease and does not swell or precipitate.

[0025] A second aspect of this application provides an injection molding apparatus for carrying out the above-described process, comprising: The mold body includes a fixed template, a movable template, a fixed cavity, and multiple movable cores arranged along the axial direction; The core drive mechanism includes a servo motor and a transmission assembly, with each movable core independently connected to a servo motor; A zoned temperature control system, comprising at least three independently controlled heating elements, temperature sensors, and cooling channels; Injection molding control system, including PLC controller, gate pressure sensor and screw position sensor; The sequential demolding mechanism, controlled by a PLC controller, allows each movable core to exit radially in sequence from the small opening end to the large opening end.

[0026] This equipment is specifically designed to achieve the above-mentioned processes. The movable cores in the mold body are arranged axially, each corresponding to a corrugated trough or crest. Driven by an independent servo motor via a ball screw or star-shaped variable-diameter mechanism, their radial position is adjustable, thus precisely forming a wall thickness gradient. The zoned temperature control system includes at least three sets of independent heating rods and thermocouples, and each temperature control zone also has an independent cooling water channel, which can quickly establish and maintain a temperature gradient decreasing along the axial direction. The PLC controller in the injection molding control system receives signals from the gate pressure sensor and screw position sensor, controlling the injection speed and pressure switching according to the preset segmented injection molding curve. After cooling and solidification, the sequential demolding mechanism, controlled by the PLC, sequentially ejects each movable core radially from the small opening end (thick-walled area) to the large opening end (thin-walled area), avoiding tearing. All components of this equipment work together to achieve high-precision, high-efficiency integral injection molding of the gradient wall thickness dust cover. The movable core has a repeatability accuracy of ±0.005mm and precise wall thickness gradient control; the zoned temperature control response time is <2s and the temperature fluctuation is ±1℃; sequential demolding reduces demolding force and significantly improves product integrity; the entire molding cycle is ≤90s, making it suitable for mass production.

[0027] As a preferred technical solution, the outer surface of the movable core is provided with a micron-level surface texture that is non-uniformly distributed along the axial direction, wherein the texture density corresponding to the thinner wall region is higher than that in the thicker wall region; the surface texture is a diamond-shaped texture or annular microgroove with a depth of 5 to 20 μm.

[0028] The functions of high-density texture are: ① During injection molding, the melt flowing through the high-density textured area generates stronger shear force, increasing the local temperature by 5-10℃, effectively reducing melt viscosity and improving the filling capacity of thin-walled areas; ② After molding, the inner surface of the dust cover replicates a micro-uneven structure, forming an oil reservoir, maintaining a lubricating film during the reciprocating motion of the drive shaft, reducing friction and wear. The texture depth of 5-20μm is optimized: a depth less than 5μm results in insufficient oil storage; a depth greater than 20μm easily traps dirt and affects sealing. The filling integrity of thin-walled areas is improved; the friction coefficient of the inner surface of the dust cover is reduced; and the wear life is improved (no wear leakage after 2000 hours of bench testing).

[0029] The movable core is connected to a piezoelectric ceramic vibrator on its side, which applies axial high-frequency micro-amplitude vibration to the core during the injection molding filling stage. The vibration frequency is 20-50kHz and the amplitude is 1-10μm.

[0030] A piezoelectric ceramic vibrator is installed on the inner side of a movable core, applying axial high-frequency micro-amplitude vibration during the injection filling stage. The vibration frequency of 20–50 kHz falls within the ultrasonic range, allowing the melt to be in an ultrasonically softened state: high-frequency vibration induces polymer chain untangling, reducing apparent viscosity by 20%–30%, thus significantly improving flowability in thin-walled areas. Simultaneously, vibration promotes molecular chain orientation along the flow direction, improving the tensile strength and surface finish of the product. Within the amplitude range of 1–10 μm, viscosity is effectively reduced without causing melt splashing or core wear. This vibration-assisted injection molding technology is particularly suitable for dust covers with extremely thin walls (≤0.5 mm), breaking through the wall thickness limits of traditional injection molding.

[0031] To achieve cooling and temperature control, the cooling channels in this application are conformal cooling channels, and their orientation is consistent with the corrugated contour of the dust cover; each temperature control zone's cooling channel is equipped with an independent solenoid valve, and the PLC controller adjusts the cooling water flow rate in real time according to the zone's temperature.

[0032] Traditional mold cooling channels are straight holes with varying distances from the product surface, resulting in uneven cooling. This invention employs conformal cooling technology, utilizing 3D printing or precision casting processes to ensure the cooling channel orientation perfectly matches the corrugated contour of the dust cover, guaranteeing uniform and rapid cooling to each corrugated area. Each temperature-controlled zone's cooling channel is equipped with an independent solenoid valve and flow sensor. The PLC controller dynamically controls the cooling water flow by adjusting the solenoid valve opening based on the difference between the real-time temperature and the target temperature of that zone using a PID algorithm, strictly maintaining the temperature of each zone within the set range (fluctuation ±1℃). This conformal + zoned independent flow control cooling system significantly shortens cooling time and reduces warpage. Cooling time is reduced from the traditional 60-80 seconds to 30-45 seconds; product warpage is reduced by 60%, corrugated contour accuracy is ±0.05mm; temperature fluctuation in each zone is ±1℃, improving process stability.

[0033] In step five, the cooling medium is water at 10℃~20℃, the cooling time is 30~60s, and the movable core is removed after the dust cover temperature drops below 60℃.

[0034] Cooling medium temperature: 10-20℃. Too low a temperature (<10℃) will cause rapid cooling of the product, resulting in cold spots and internal stress on the surface; too high a temperature (>20℃) will result in low cooling efficiency and prolonged molding cycle. Cooling time: 30-60s, adjusted according to wall thickness: 30s for thin-walled dust covers, 60s for thick-walled dust covers. The movable core should be removed after the dust cover temperature drops below 60℃. This is because TPE material has sufficient demolding strength below 60℃ (approximately 70% of room temperature strength) and still retains some plasticity, minimizing friction and preventing tearing. If the temperature is above 60℃, the product will be too soft and easily deformed; if below 40℃, the material will become brittle and prone to cracking during removal. The cooling cycle should be minimized, with a total molding cycle ≤90s; demolding temperature controlled below 60℃ prevents tearing and deformation; and product internal stress is low, preventing subsequent warping.

[0035] In summary, the present invention has the following outstanding substantive features and significant progress compared with the prior art: 1. Multi-physics field linkage and coordination: For the first time, the three linkage controls of pressure-core position, temperature-holding pressure, and cooling shrinkage-core exit are integrated into the same injection molding process to form a fully adaptive closed loop.

[0036] 2. Gradual wall thickness high-precision forming: Through independent movable core array and pressure-position linkage, the wall thickness tolerance is ±0.03mm, and the wall thickness difference between adjacent valleys is 0.1~0.5mm, which is precisely controllable and meets the stringent requirements of valley contact sequence design.

[0037] 3. Significant reduction in residual stress: Temperature-pressure holding synergistic control reduced the residual stress at the large-diameter corner from 5.2 MPa to below 1.6 MPa, a reduction of 69%, far exceeding the 20-30% expected reduction by conventional optimization methods.

[0038] 4. Significantly improved demolding quality: The cooling shrinkage-exit sequence reduces demolding force by 50%, reduces surface scratch rate from 8% to 0.1%, and extends sealing life by 2 times.

[0039] 5. Process robustness and adaptability: Multi-physics field linkage increases the product qualification rate from 82% to 97.5%, and supports vibration-assisted injection molding, with the minimum wall thickness reduced to 0.3mm.

[0040] 6. Meets stringent bench specifications: Molded products pass all Toyota 956D tests (-40℃~125℃, swing angle 26°, 1500r / min, expansion ≤6mm), reaching the international advanced level.

[0041] Therefore, the process and equipment of the present invention have significant inventiveness and industrial applicability. Attached Figure Description

[0042] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0043] Figure 1 This is a flowchart illustrating the overall injection molding process of the present invention. Figure 2 This is a schematic diagram of the main structure of the mold for the integral injection molding equipment of the present invention; Figure 3 This is a schematic diagram of the axial arrangement of the zoned temperature control system of the present invention, with three temperature control zones and temperature curves marked. Figure 4 This is a schematic diagram of the segmented injection molding pressure-time curve and stage switching of the present invention; Figure 5 The pressure-time curves for sequential pressure holding in this invention show the overlapping areas; Figure 6 This is a block diagram of the multi-physics linkage control logic of the present invention (PLC input-output relationship); Figure 7 This is a schematic diagram of the non-uniform texture distribution on the surface of the movable core of the present invention (the texture is dense in the thin-walled area and sparse in the thick-walled area). Figure 8 This is a schematic diagram of the product structure after injection molding according to the present invention; Figure 9 This is the first finite element analysis report (stretched 24mm) of the dust cover design stage of the present invention. Figure 10 This is the second finite element analysis report (stretching 10mm, swing angle 26°) of the dust cover design stage of the present invention. Figure 11 This is the third finite element analysis report (compression 8.06mm, swing angle 26°) for the dust cover design stage of this invention. Figure 12 This is the fourth finite element analysis report for the dust cover design stage of the present invention (compression 21.5mm, swing angle 19°).

[0044] The markings in the attached diagram are as follows: 1. Fixed template; 2. Moving template; 3. Fixed cavity; 4. Movable core; 5. Servo motor; 6. Elastic sealing sheet. Detailed Implementation

[0045] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0046] Reference Figure 1 The first aspect of this application provides an injection molding process for an integrated dust cover for a drive shaft of a new energy vehicle, comprising: Step 1, Mold Clearance Adjustment: Before mold closing, adjust the radial clearance between multiple movable cores and the mold cavity to form a gradient flow channel with a wall thickness gradient from the large end to the small end of the dust cover. The gradient flow channel and the fixed cavity form an integral dust cover injection cavity. Step 2, Zoned Mold Temperature Control: Divide the mold into three independent temperature control zones along the axial direction. The temperature of the first temperature control zone T1 is 160℃~180℃, the temperature of the second temperature control zone T2 is 140℃~160℃, and the temperature of the third temperature control zone T3 is 120℃~140℃, with T1>T2>T3. Step 3, Segmented Injection Molding: Molten thermoplastic elastomer material is injected into the gradient runner and fixed cavity in three stages. The injection speed V1 in the first stage is 10-30 mm / s, and the pressure P1 is 40-60 MPa. The injection speed V2 in the second stage is 30-60 mm / s, and the pressure P2 is 60-80 MPa. The injection speed V3 in the third stage is 60-100 mm / s, and the pressure P3 is 80-110 MPa, with V3 > V2 > V1 and P3 > P2 > P1. The injection pressure is monitored by a gate pressure sensor, and the stages are automatically switched according to the monitoring results. Step 4, Sequential Pressure Holding: After injection, pressure is held in each temperature control zone sequentially from thickest to thinnest wall thickness. The holding pressure is 60% to 80% of the corresponding injection pressure, and the holding time decreases progressively while the holding time of adjacent temperature control zones overlaps. Step 5, Cooling, Shaping, and Demolding: After cooling, the movable core is radially ejected in a predetermined sequence, and the mold is opened to eject the core. This process also includes multi-physics field linkage control: real-time acquisition of gradual flow channel pressure, temperature of each temperature control zone and shrinkage rate, and linkage adjustment of the radial position of the movable core, holding pressure and exit sequence through PLC, forming a closed loop of pressure, position, temperature and time coordination.

[0047] In this application, by constructing a gradually decreasing flow channel from the large end to the small end and matching it with a decreasing temperature gradient, the high-temperature zone is used to reduce the melt viscosity at the thin-walled end to prevent underfilling, and the low-temperature zone is used to accelerate the shaping of the thick-walled end to reduce shrinkage marks. Combined with segmented increasing injection speed and pressure, the melt flow resistance and nonlinear filling process are dynamically matched, thereby solving the problems of traditional fixed cavity molding being unable to form precise wall thickness gradients and filling imbalances. It achieves precise control of the wall thickness difference between adjacent troughs from 0.1 mm to 0.5 mm, and reduces the residual stress at the large-mouth corner from 5.2 MPa in the prior art to below 1.6 MPa.

[0048] More specifically, this application discloses an injection molding process for an integrated dust cover for a drive shaft of a new energy vehicle. In step one, the number of movable core units is 5 to 10, each movable core unit corresponding to a corrugation trough or peak of the dust cover. An elastic sealing sheet is provided between adjacent movable core units. The wall thickness gradient is such that the wall thickness difference between adjacent troughs is controlled within 0.1 mm to 0.5 mm. By setting 5 to 10 independently driven movable cores corresponding to each corrugation, and using elastic sealing sheets to block melt flow at the gaps between the movable cores, the wall thickness of each corrugation can be adjusted independently without interference. Combined with the wall thickness difference limit of 0.1 mm to 0.5 mm, the accuracy of the contact sequence between the trough and the drive shaft is ensured. This solves the problem of large wall thickness dispersion and insufficient accuracy caused by local flow under multi-corrugated structures. The wall thickness difference accuracy between adjacent troughs can reach ±0.03 mm, and the contact sequence deviation of the troughs is less than 0.5°, meeting the stress distribution requirements under a large swing angle of 26°.

[0049] In step four, the holding pressure of the third temperature control zone is 60% of the corresponding injection pressure and the holding time is 5s; the holding pressure of the second temperature control zone is 70% of the corresponding injection pressure and the holding time is 4s; the holding pressure of the first temperature control zone is 80% of the corresponding injection pressure and the holding time is 3s; and the overlap time of holding pressure in adjacent temperature control zones is 1s. In step five, the cooling medium is water at 10℃~20℃, and the cooling time is 30~60s. After the dust cover temperature drops below 60℃, the core is removed.

[0050] By using low-pressure, long-term holding pressure in thick-walled areas to compensate for large shrinkage, and high-pressure, short-term holding pressure in thin-walled areas to compact the surface, and utilizing a 1-second overlap time to maintain pressure continuity, combined with cooling water at 10℃~20℃ and a demolding temperature window below 60℃, the core layer in thick-walled areas does not generate excessive shear stress, and the surface of thin-walled areas is free of shrinkage marks. This solves the problems of residual stress caused by coarse holding pressure response and product deformation caused by improper demolding timing. Its beneficial effects are that the volume shrinkage rate is stabilized within 0.8%, there are no shrinkage marks or flow marks on the surface, and the demolding force is significantly reduced.

[0051] Furthermore, the process in this application also includes multi-physics linkage control, specifically including real-time linkage between gradual flow channel pressure and movable core position: when the deviation between the actual pressure and the preset pressure exceeds ±5%, the PLC controller drives the corresponding movable core to move radially, with a step size ≤0.02mm and a cumulative movement not exceeding 10% of the initial gap. By monitoring the pressure in real time and finely adjusting the radial position of the movable core to change the flow channel gap when the deviation exceeds the threshold, the flow resistance changes caused by material batch differences or mold wear are dynamically compensated using a fine step size of ≤0.02mm and a 10% cumulative movement limit, thereby solving the problem of wall thickness fluctuation caused by production disturbances that cannot be adapted to under open-loop control.

[0052] Of course, the multi-physics field linkage control in this application also includes the coordinated control of temperature and holding pressure in each temperature control zone: the holding pressure in each temperature control zone is negatively correlated with temperature. By establishing a negative correlation control strategy of high pressure for short periods in high-temperature zones and low pressure for long periods in low-temperature zones, the melt in the high-temperature zone is rapidly compacted when it has good fluidity, and the melt in the low-temperature zone is slowly compensated for by creep when it is partially solidified. This solves the contradiction between high stress in thick-walled zones and shrinkage marks in thin-walled zones caused by the inability of traditional uniform holding pressure strategy to adapt to the differences in melt state in different temperature zones. Its beneficial effects are that the residual stress at the large-mouth corner is further reduced, the surface shrinkage index is significantly reduced, and the density difference in different wall thickness areas is less than 0.5%.

[0053] To achieve sequential cooling and demolding, the multiphysics-based linkage control in this application also includes sequential linkage between cooling shrinkage and movable core withdrawal: when the temperature of a certain area drops to 5℃~10℃ above its material's glass transition temperature, the movable core corresponding to that area begins to withdraw, and the withdrawal speed is proportional to the real-time shrinkage rate of that area. By initiating withdrawal at the critical temperature point (Tg+5℃~10℃) where the product has sufficient demolding strength but still retains a certain degree of plasticity, and matching the withdrawal speed to the real-time shrinkage rate, a small gap is always maintained between the movable core and the product. This solves the problems of thick-walled area shrinkage pulling thin-walled area deformation and corrugation scratches caused by synchronous demolding, resulting in a significant reduction in the corrugated surface scratch rate, a significant reduction in the roundness error of the sealing lip, and an extended sealing life of up to 1500h without leakage.

[0054] The thermoplastic elastomers used in this application are thermoplastic vulcanized rubber or thermoplastic polyester elastomers with a melting temperature ≥180℃, a brittle temperature ≤-50℃, and a tensile strength retention rate ≥80% after heat aging at 125℃ for 240 hours. By selecting thermoplastic vulcanized rubber or thermoplastic polyester elastomers that meet specific melting temperature, brittle temperature, and heat aging retention rate indicators, it is ensured that the material does not soften or creep at a high temperature of 125℃, does not crack at a low temperature of -40℃, and maintains its mechanical properties after long-term heat aging. This solves the problem of conventional materials being prone to failure under wide temperature range and large swing angle conditions. Its beneficial effect is that the product fully meets the durability requirements of a wide temperature range of -40℃ to 125℃ and a swing angle of 26°, and the tensile strength retention rate after heat aging is above 85%.

[0055] The second aspect of this application provides an injection molding apparatus for carrying out the above-described process, including a mold body, the mold body including a fixed template, a movable template, a fixed cavity, and a plurality of movable cores arranged along the axial direction; The core drive mechanism includes a servo motor and a transmission assembly, with each movable core independently connected to a servo motor; A zoned temperature control system, comprising at least three independently controlled heating elements, temperature sensors, and cooling channels; Injection molding control system, including PLC controller, gate pressure sensor and screw position sensor; The sequential demolding mechanism, controlled by a PLC controller, allows each movable core to exit radially in sequence from the small opening end to the large opening end.

[0056] In this application, submicron-level radial positioning is achieved through a movable core array driven by an independent servo. Combined with a zoned temperature control system and a PLC control system based on sensor feedback, the mold can accurately perform complex actions such as gradient flow channel construction, segmented injection molding, and sequential pressure holding. This solves the problem that existing general-purpose equipment lacks dedicated control capabilities for gradient wall thickness structures, resulting in a significant improvement in core repeatability positioning accuracy, a zoned temperature control response time of less than 2 seconds, and a significant increase in product integrity.

[0057] The movable core features a non-uniformly distributed micron-level surface texture on its outer surface, with a higher texture density in thinner regions than in thicker regions. The surface texture consists of diamond-shaped patterns or circumferential microgrooves with a depth of 5–20 μm. By incorporating a high-density texture in the thin-walled region to enhance shear heat generation and reduce melt viscosity, and by forming an oil-storing microstructure after molding, the 5–20 μm depth balances oil storage and sealing performance. This solves the problems of difficult filling in thin-walled regions and high internal surface friction coefficient, significantly improving the filling integrity of thin-walled regions, greatly reducing the internal surface friction coefficient, and increasing wear life by 30%.

[0058] In addition, a piezoelectric ceramic vibrator is connected to the rear end of the movable core, applying axial high-frequency micro-amplitude vibration to the movable core during the injection filling stage. The vibration frequency is 20-50kHz, and the amplitude is 1-10μm. The cooling channel is a conformal cooling channel, and its direction is consistent with the corrugated profile of the dust cover. Each temperature control zone's cooling channel is equipped with an independent solenoid valve, and the PLC controller adjusts the cooling water flow in real time according to the temperature of that zone. By applying 20-50kHz ultrasonic vibration to induce polymer chain untangling to reduce apparent viscosity, combined with conformal cooling channels with the same direction as the corrugations and independent flow regulation, the ultra-thin wall area can be smoothly filled and the cooling rate of each area is uniform. This breaks through the thin-wall molding limit of traditional equipment and eliminates warping caused by uneven cooling, reducing the minimum moldable wall thickness to 0.3mm, reducing product warping deformation, and shortening the molding cycle.

[0059] Unless otherwise specified, all materials, reagents and instruments used in the embodiments of this invention can be obtained through commercial channels.

[0060] Main materials: Thermoplastic vulcanized rubber (TPV), grade Santoprene 121-75M200, melting temperature 185℃, brittle temperature -55℃; thermoplastic polyester elastomer (TPEE), grade Hytrel 5556, melting temperature 210℃, brittle temperature -65℃.

[0061] Main equipment: All-electric precision injection molding machine (equipped with Siemens S7-1500 PLC controller), customized multi-core injection mold (including 5-10 independent servo-driven core units), piezoelectric gate pressure sensor (range 0-200MPa), magnetostrictive screw position sensor, piezoelectric ceramic vibrator (model PSt150 / 10 / 20).

[0062] Test methods: Wall thickness was measured using a coordinate measuring machine (accuracy ±0.002mm); residual stress was measured using the drilling method (ASTM E837); surface roughness was measured using a profilometer; bench tests were conducted according to Toyota 956D specifications (including temperature cycling from -40℃ to 125℃, 26° swing angle durability, and rotational expansion tests).

[0063] To provide a more complete understanding of this application, a more specific implementation method is as follows: Example 1: This embodiment provides an injection molding process for an integrated dust cover for a new energy vehicle drive shaft, aiming to verify the high-precision molding effect of a corrugated structure with gradually varying wall thickness under multi-physics field linkage control.

[0064] like Figure 2 As shown, Figure 2The schematic diagram of the overall structure of the mold body of the injection molding equipment of the present invention is shown, including a fixed template 1, a movable template 2, a fixed cavity 3, and five movable cores 4 arranged along the axial direction.

[0065] During mold closing, the movable template 2 moves towards the fixed template 1 to form a closed mold. Before mold closing, the mold gap is adjusted first. The servo motor 5 drives each movable core 4 to move radially. The gaps between the movable core 4 corresponding to the 1st to 5th wave valleys and the inner surface of the mold cavity are set to 0.8, 0.9, 1.0, 1.1, and 1.2 mm, respectively. High-temperature resistant silicone rubber elastic sealing sheets 6 are installed between adjacent movable cores 4 to prevent crossflow. The servo motor can drive each movable core 4 to move radially in the following way: the servo motor 5 rotates, driving the star-shaped variable diameter mechanism to extend and retract, thereby realizing the radial adjustment of the movable core 4.

[0066] Next, zoned mold temperature control is implemented, such as... Figure 3 As shown, the mold body after mold closing is divided into three temperature control zones. The temperature of the first temperature control zone (large opening end) is set to 170℃, the second temperature control zone (middle) to 150℃, and the third temperature control zone (small opening end) to 130℃. Then, segmented injection molding is performed, as follows: Figure 4 As shown, Figure 4 This is a curve showing the pressure change over time during segmented injection molding, using three progressively increasing parameters: Stage 1: Injection speed 20 mm / s, pressure 50 MPa; Stage 2: Injection speed 45 mm / s, pressure 70 MPa; Stage 3: Injection speed 80 mm / s, pressure 100 MPa. The injection pressure is monitored by a gate pressure sensor, and the stage is automatically switched based on the monitoring results. This is followed by sequential pressure holding, such as... Figure 5 As shown, Figure 5 This diagram illustrates the pressure changes over time and overlapping areas during the sequential pressure holding process. Pressure is held sequentially from the smaller opening to the larger opening. The third temperature-controlled zone holds pressure at 60 MPa for 5 seconds, the second at 70 MPa for 4 seconds, and the first at 80 MPa for 3 seconds, with adjacent zones overlapping by 1 second. Finally, cooling and demolding are performed. 15°C cooling water is introduced for 45 seconds. Once the temperature drops below 60°C, the movable core is radially withdrawn sequentially from the smaller opening to the larger opening. The entire process utilizes multi-physics linkage control; the logic diagram is shown below. Figure 6 As shown, the PLC collects pressure, temperature and shrinkage rate signals in real time and dynamically adjusts the core position, holding pressure and exit sequence.

[0067] Testing revealed that the actual wall thicknesses of the five troughs were 0.81, 0.90, 1.00, 1.11, and 1.20 mm, with a maximum deviation of +0.01 / -0.00 mm. The residual stress at the large-angle corner was 1.58 MPa; the surface roughness Ra was 0.45 μm; and no tearing was observed in the corrugations after demolding. Bench tests showed that the product exhibited no cracks or leaks within a temperature range of -40℃ to 125℃ and under a 26° swing angle condition, with a maximum outer diameter expansion of 5.8 mm.

[0068] This embodiment demonstrates that, through the synergy of five core processes and multi-physics field linkage, a dust cover with a wall thickness gradient of 0.1 mm can be precisely molded, significantly reducing residual stress and ensuring excellent demolding quality.

[0069] Example 2: This embodiment aims to verify the effect of vibration-assisted injection molding on filling thin-walled areas and improving product performance.

[0070] With other preparation conditions the same as in Example 1, the piezoelectric ceramic vibrator installed at the rear end of the movable core was activated to apply axial high-frequency micro-amplitude vibration to the movable core during the injection filling stage. The vibration frequency was set to 35 kHz and the amplitude to 5 μm. The vibration continued from the start of injection until the start of holding pressure.

[0071] Test data show that the filling integrity of the thin-walled area (0.8mm) is significantly improved; the molding cycle is shortened from 90s to 82s; the residual stress at the large-mouth corner is reduced to 1.42MPa; the coefficient of friction of the inner surface of the product is reduced from 0.32 to 0.27; and the tensile strength along the corrugation direction is increased from 14.2MPa to 15.9MPa.

[0072] The results show that introducing ultrasonic vibration at 35 kHz and 5 μm can effectively reduce the apparent viscosity of the melt, improve the thin-wall filling capacity and enhance the mechanical properties, demonstrating the significant effect of vibration-assisted technology within this parameter range.

[0073] Example 3: This embodiment aims to verify the adaptability of the process to different wall thickness gradients (parameter upper limit edge values).

[0074] Keeping the other reaction conditions of Example 1 unchanged, only the parameter of the difference in wall thickness between adjacent troughs is adjusted from 0.1 mm to 0.25 mm (i.e., the core gap is set to 1.0, 1.25, 1.5, 1.75, 2.0 mm), the material is changed to TPEE, the temperature of the first temperature control zone is adjusted to 185°C, the injection pressure of the third stage is adjusted to 115 MPa, and the holding time of the third temperature control zone is adjusted to 6 s.

[0075] The maximum deviation of the wall thickness of the product was +0.02 / -0.03 mm, and the difference between adjacent values ​​was controlled between 0.23 and 0.27 mm; the residual stress at the large corner was 2.1 MPa; the product showed no leakage or cracks in the harsh bench test at a 30° swing angle and 2000 r / min, and the expansion was 7.2 mm.

[0076] The results show that even under non-preferred conditions with a large wall thickness gradient (0.25 mm), the technical solution of the present invention can still achieve precise molding and meet high performance requirements, proving the wide applicability of the process parameter range.

[0077] Example 4: This embodiment aims to verify the effect of surface texture density distribution on filling and demolding performance.

[0078] Referring to the method of Example 1, the difference lies in that the outer surface of the movable core is provided with a non-uniformly distributed micron-level surface texture, such as... Figure 7 As shown, Figure 7 This is a schematic diagram showing the non-uniform texture distribution on the surface of a movable core. The texture density corresponding to the thin-walled region at the large end is set to 200 textures / mm², and the texture density corresponding to the thick-walled region at the small end is set to 50 textures / mm². The texture is a diamond pattern with a depth of 10μm. A separate scale model is also provided, using a smooth, untextured core, with all other conditions identical.

[0079] The specific test results are shown in Table 1.

[0080] Table 1. Performance Comparison Results with and without Surface Texture As shown in Table 1, the core with non-uniform texture significantly improves the filling integrity of the thin-walled area, reduces the coefficient of friction and demolding force, and improves the wear life.

[0081] The results show that the non-uniformly distributed surface texture along the axial direction can improve filling by enhancing shear heat generation and reduce friction through the micro-oil storage structure, verifying the necessity and effectiveness of this technical feature.

[0082] Example 5: This embodiment aims to verify the effectiveness of the boundary between the vibration frequency and amplitude parameter ranges.

[0083] Based on the process of Example 2, parallel experiments were conducted at different vibration frequencies (20kHz, 50kHz) and amplitudes (1μm, 10μm), with the remaining conditions the same as in Example 2.

[0084] The specific test results are shown in Table 2.

[0085] Table 2 Performance test results under different vibration parameters As shown in Table 2, the thin-walled region can be completely filled in the frequency range of 20-50kHz and the amplitude range of 1-10μm. Among them, 35kHz / 5μm is the optimal combination for overall energy efficiency, but the boundary values ​​are also feasible.

[0086] The results show that the vibration frequency range of 20-50kHz and the amplitude range of 1-10μm defined by the present invention have good technical effect coverage and can break through the thin-wall limit of traditional injection molding.

[0087] Example 6: This embodiment provides several comparative examples to verify the inventiveness of the key technical features of the present invention and the criticality of the parameter range.

[0088] Comparative Example 1: Using a traditional fixed cavity mold (equal wall thickness 1.2mm), uniform mold temperature of 150℃, single-stage constant speed injection, uniform pressure holding, and synchronous demolding.

[0089] Comparative Example 2: The same equipment and basic process steps as in Example 1 were used, but all multiphysics linkage control functions were turned off.

[0090] Comparative Example 3: An attempt was made to increase the difference in wall thickness between adjacent troughs to 0.7 mm, with other conditions the same as in Example 1.

[0091] The specific test results are shown in Table 3.

[0092] Table 3. Performance comparison results between the examples and the comparative examples. like Figure 4 and Figure 5 The trend comparison analysis shows that Comparative Example 1 suffers from severe stress concentration due to the lack of a gradual flow channel and sequential control; Comparative Example 2 has the hardware foundation, but due to the lack of a linkage closed loop, its accuracy and stress control are significantly worse than those of Example 1; Comparative Example 3 suffers from unstable flow and stress concentration due to excessive wall thickness gradient, which verifies the criticality of the 0.1mm to 0.5mm range.

[0093] The results show that the present invention achieves significant technical effects through multi-physics field linkage and specific parameter range coordination, and each technical feature is indispensable.

[0094] Example 7: In this application embodiment, the test samples include dust cover products prepared according to each of the embodiments in Examples 1 to 5.

[0095] Experimental results show that the integrated dust cover for the drive shaft of new energy vehicles prepared by this invention exhibits good fatigue resistance, aging resistance, and sealing performance in a wide temperature range model of -40℃ to 125℃. In particular, it shows no cracks or grease leakage under conditions of a large swing angle of 26° and a high speed of 1800 r / min, and the outer diameter expansion is strictly controlled within 10 mm. Furthermore, the dust cover prepared by this application meets the initial design requirements. Figure 9-12 The design requirements are shown.

[0096] Figure 9 The figure shows that when the dust cover is stretched by 24mm, the stress is greatest at the fifth trough, and the maximum equivalent stress is 1.261Mpa.

[0097] Figure 10 As shown, when the dust cover is stretched by 10mm and the swing angle is 26°, the stress is greatest at the fifth trough on the tension side, and the maximum equivalent stress is 4.846 MPa. When the swing angle is 25°, the third trough on the compression side begins to contact the shaft.

[0098] Figure 11 As shown, when the dust cover is compressed by 8.06 mm and the swing angle is 26°, the stress is the greatest at the corner of the large opening on the pressure side, and the maximum equivalent stress is 5.197 MPa. When the swing angle is 17.5°, the second trough on the pressure side begins to contact the shaft.

[0099] Figure 12 As shown, when the dust cover is compressed by 21.5 mm and the swing angle is 19°, the stress is greatest at the corner of the large opening on the pressure side, and the maximum equivalent stress is 4.308 MPa. When the swing angle is 15°, the second trough on the pressure side begins to contact the shaft.

[0100] Those skilled in the art should understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any equivalent substitution or simple modification of specific parameters within the spirit and principles of the present invention, as well as the application of the present invention to the injection molding of other similar corrugated tubular products (such as shock-absorbing sleeves, corrugated pipes, medical catheters, etc.), should fall within the scope of protection of the present invention.

Claims

1. The injection molding process for an integrated dust cover for the drive shaft of a new energy vehicle, characterized in that, Includes the following steps: Step 1: Mold Clearance Adjustment: Before mold closing, adjust the radial clearance between multiple movable cores and the mold cavity to form a gradual flow channel with a wall thickness gradient from the large end to the small end of the dust cover. Step 2: Zoned mold temperature control: Divide the mold into three independent temperature control zones along the axial direction. The temperature of the first temperature control zone T1 is 160℃~180℃, the temperature of the second temperature control zone T2 is 140℃~160℃, and the temperature of the third temperature control zone T3 is 120℃~140℃, and T1>T2>T3. Step 3: Segmented Injection Molding: Molten thermoplastic elastomer material is injected into the gradient runner in three stages. The first stage injection speed V1 is 10-30 mm / s, and the pressure P1 is 40-60 MPa. The second stage injection speed V2 is 30-60 mm / s, and the pressure P2 is 60-80 MPa. The third stage injection speed V3 is 60-100 mm / s, and the pressure P3 is 80-110 MPa, with V3 > V2 > V1 and P3 > P2 > P1. The injection pressure is monitored by a gate pressure sensor to automatically switch between stages. Step 4: Sequential pressure holding: After injection, pressure is held in each temperature control zone in descending order of wall thickness. The holding pressure is 60% to 80% of the corresponding injection pressure, and the holding time decreases progressively while the holding time of adjacent temperature control zones overlaps. Step 5: Cooling, Shaping, and Demolding: After cooling, the movable core is radially withdrawn in a predetermined sequence, and the mold is opened to eject the core. The process also includes multi-physics field linkage control: real-time acquisition of gradual flow channel pressure, temperature of each temperature control zone and shrinkage rate, and linkage adjustment of the radial position of the movable core, holding pressure and exit sequence through PLC, forming a closed loop of pressure, position, temperature and time coordination.

2. The injection molding process according to claim 1, characterized in that, In step one, the number of movable cores is 5 to 10, each movable core corresponds to a corrugated trough or crest of the dust cover, and an elastic sealing sheet is provided between adjacent movable cores; the wall thickness gradient is the difference in wall thickness between adjacent troughs, controlled within 0.1 mm to 0.5 mm.

3. The injection molding process according to claim 1, characterized in that, In step four, the holding pressure of the third temperature control zone is 60% of the corresponding injection pressure and the holding time is 5s; the holding pressure of the second temperature control zone is 70% of the corresponding injection pressure and the holding time is 4s; the holding pressure of the first temperature control zone is 80% of the corresponding injection pressure and the holding time is 3s; and the overlap time of holding pressure in adjacent temperature control zones is 1s. In step five, the cooling medium is water at 10°C to 20°C, and the cooling time is 30 to 60 seconds. After the temperature of the dust cover drops below 60°C, the movable core is removed.

4. The injection molding process according to claim 1, characterized in that, The multi-physics linkage control includes real-time linkage between the gradual flow channel pressure and the movable core position: when the deviation between the actual gradual flow channel pressure and the preset pressure exceeds ±5%, the PLC controller drives the corresponding movable core to move radially, with a step size ≤0.02mm and the cumulative movement not exceeding 10% of the initial gap.

5. The injection molding process according to claim 1, characterized in that, The multi-physics field linkage control includes the coordinated control of temperature and holding pressure in each temperature control zone: the holding pressure in each temperature control zone is negatively correlated with the temperature.

6. The injection molding process according to claim 1, characterized in that, The multi-physics field linkage control includes the timing linkage of cooling contraction and movable core withdrawal: when the temperature of a certain temperature control zone drops to 5°C to 10°C above the glass transition temperature of its material, the movable core corresponding to the temperature control zone begins to withdraw, and the withdrawal speed is proportional to the real-time contraction rate of the temperature control zone.

7. The injection molding process according to claim 1, characterized in that, The thermoplastic elastomer is a thermoplastic vulcanized rubber or a thermoplastic polyester elastomer with a melting temperature ≥180℃, a brittle temperature ≤-50℃, and a tensile strength retention rate ≥80% after heat aging at 125℃ for 240h.

8. An injection molding apparatus for carrying out the process according to any one of claims 1 to 7, characterized in that, include: The mold body includes a fixed template, a movable template, a fixed cavity, and multiple movable cores arranged along the axial direction; The core drive mechanism includes a servo motor and a transmission assembly, with each movable core independently connected to a servo motor and a transmission assembly; A zoned temperature control system, comprising at least three independently controlled heating elements, temperature sensors, and cooling channels; Injection molding control system, including PLC controller, gate pressure sensor and screw position sensor; The sequential demolding mechanism, controlled by a PLC controller, allows each movable core to exit radially in sequence from the small opening end to the large opening end.

9. The device according to claim 8, characterized in that, The outer surface of the movable core is provided with a micron-level surface texture that is non-uniformly distributed along the axial direction, wherein the texture density corresponding to the thinner wall region is higher than that in the thicker wall region; the surface texture is a diamond-shaped texture or annular microgroove with a depth of 5 to 20 μm.

10. The device according to claim 8, characterized in that, The movable core is connected to a piezoelectric ceramic vibrator, which applies axial high-frequency micro-amplitude vibration to the movable core during the injection molding filling stage. The vibration frequency is 20-50kHz and the amplitude is 1-10μm. The cooling channel is a conformal cooling channel, and its direction is consistent with the corrugated outline of the dust cover; each temperature control zone's cooling channel is equipped with an independent solenoid valve, and the PLC controller adjusts the cooling water flow in real time according to the temperature of that zone.

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