Forming process of automobile heat exchanger harvester water chamber

Abstract

This invention discloses a molding process for a Haval-type water chamber in an automotive heat exchanger. This invention relates to the field of thermal management technology for power batteries in new energy vehicles. The process involves composite injection molding: a hot runner system combined with a multi-point sequential valve gating system is used to injection mold the water chamber half-shell. By independently programming and controlling the opening time sequence and holding pressure curve of each valve needle, the polymer melt is guided to flow unidirectionally from the edge area of ​​the water chamber sealing surface to the inner cavity guide structure area. The weld line position is controlled in a non-sealing surface and a non-stress concentration area. The advantages of this invention are: by using 3D-printed conformal cooling water channels, the cooling difference of the mold surface is controlled within 15%. Combined with three-zone dynamic independent mold temperature control, the absolute error of the flatness of the complex sealing surface of the large Haval-type water chamber (up to 500mm) is drastically reduced from 0.3-0.5mm in traditional processes to ≤0.1mm.

Description

Technical Field

[0001] This invention relates to the field of thermal management technology for power batteries in new energy vehicles, specifically a molding process for a Haval-style water chamber in an automotive heat exchanger. Background Technology

[0002] In the liquid cooling system of electric vehicle power batteries, the coolant is driven by an electric water pump to flow through the liquid cooling plate to absorb the heat of the battery cells during charging and discharging. Then, it exchanges heat with the air conditioning refrigerant through an external circulation loop to achieve active cooling, forming a sealed closed-loop circulation to ensure that the battery is in the optimal operating temperature range of 25~40℃. The heat exchanger water chamber undertakes the core function of precise distribution and efficient collection of coolant. Its molding process directly determines the system's sealing reliability, flow field uniformity and long service life. At present, the industry widely adopts the Haval-type water chamber structure, which is to inject the shell into upper and lower half shells and then weld them together to form a sealed cavity.

[0003] However, the existing Haver-type water chamber molding process has the following technical defects: First, traditional injection molding processes have not been thermodynamically optimized for the complex geometry of the water chamber. The wall thickness changes significantly between the thin-walled area and the thick-walled boss area of ​​the shell. Uneven cooling and shrinkage leads to severe residual stress and warping deformation of the sealing surface. Furthermore, the weld line is easily located in a high stress concentration area, which is very easy to generate penetrating microcracks under long-term hot and cold alternating impact, resulting in leakage. Second, the flash fragments generated during conventional vibration friction welding may block the microchannels inside the liquid cooling plate, causing local cells to lose cooling protection and triggering the risk of thermal runaway. At the same time, the sealing surface contains complex three-dimensional trajectories such as arc corners, resulting in uneven distribution of welding quality and easy occurrence of incomplete welds, weak welds, or areas of thermal degradation and embrittlement. Third, there is a prominent contradiction between lightweighting and structural durability. Thinning the wall thickness can easily cause short shot and insufficient glue. Solid injection molding in thick-walled areas prolongs the production cycle and causes shrinkage problems. Welding process has high energy consumption, and the failure rate of post-weld airtightness test is 3% to 5%, which seriously restricts large-scale and efficient production. Summary of the Invention

[0004] In response to numerous technical defects in the aforementioned comparative documents and existing technologies, such as injection molding sealing surface warping, welding flash contamination of flow channels, uneven weld strength, large temperature differences in multiple flow channels, and localized shrinkage due to thick walls, this invention aims to provide a molding process for a Haval-style water chamber in an automotive heat exchanger. This invention is specifically applied to the manufacturing of water chambers for heat exchangers in power battery pack liquid cooling systems. By innovatively and deeply integrating multi-point sequential valve control, conformal cooling, supercritical micro-foaming injection molding, and infrared preheating-assisted cleaning vibration friction welding, this invention fundamentally solves the problems of injection molding warping and welding contamination, achieving high-precision, high-strength, and high-cleanliness integrated molding of the water chamber, and significantly reducing weight while ensuring structural durability.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: A molding process for a Haval-type water chamber in an automotive heat exchanger, the overall flow of which includes: raw material pretreatment, composite injection molding, online dimensional and geometric tolerance inspection, precision machining of the sealing surface, infrared preheating-assisted cleaning welding assembly, online airtightness testing, and finished product inspection and packaging, the specific process steps are as follows: Step 1: Raw material pretreatment (1) Material selection: Considering the harsh working conditions of the power battery liquid cooling system being in long-term contact with 50% ethylene glycol aqueous solution, PA66-GF33 (33% glass fiber reinforced nylon 66) or high-performance PPA-GF35 (35% glass fiber reinforced polyphthalamide) are selected as the base material of the water chamber shell. Compared with traditional materials, PPA-GF35 has a higher heat distortion temperature (HDT>280℃@1.82MPa), better hydrolytic stability and extremely low saturated moisture absorption rate.

[0006] (2) Deep drying and compounding treatment: In view of the strong water absorption characteristics of the material, the raw material resin particles are placed in a dehumidifying dryer for deep drying. For PA66, the drying temperature is set to 80-100℃ and the time is 4-6 hours. For PPA, the drying temperature is set at 120-140℃ for 4-6 hours. Through deep drying, the residual moisture content of the material is strictly controlled to below 0.05%, eliminating defects such as silver streaks on the surface, internal bubbles, and hydrolytic degradation of the matrix caused by high-temperature vaporization of moisture during injection molding. Subsequently, according to the customized marking requirements of the battery pack, the dried raw materials are blended with special color masterbatch, composite antioxidants, and special flow modifiers to ensure the weather resistance and mechanical stability of the material throughout its entire life cycle.

[0007] Step 2: Composite Injection Molding This step is a core innovative process that determines the quality of the water chamber substrate. It completely solves the problem of thick-walled shrinkage by introducing local micro-foaming technology.

[0008] (1) Multi-dimensional collaborative design of molds: Multi-point sequential valve gating control: A hot runner system combined with a multi-point sequential valve gating system (6-10 independent valve pin points are evenly distributed throughout the cavity) is adopted. The injection molding machine controller performs millisecond-level independent programming control on the opening time sequence and holding pressure curve of each valve pin. This forces the polymer melt to flow unidirectionally from the edge area of ​​the water chamber sealing surface to the complex flow guiding structure area of ​​the inner cavity. This precisely drives and controls the unavoidable weld line position in a safe area that is not sealed and not in a stress concentration area (such as the low stress area in the middle of the water chamber cavity or the non-load-bearing root of the reinforcing rib).

[0009] 3D Printed Conformal Cooling Water Channel: Abandoning the straight dead-angle cooling water channels produced by traditional mechanical drilling, the three-dimensional conformal cooling water channel inside the mold cavity and core insert is integrally formed by selective laser melting (SLM) 3D printing technology. The trajectory of this water channel closely fits the complex and ever-changing geometric contour of the cavity surface of the water chamber, and the normal distance between the edge of the water channel and the cavity surface is precisely and uniformly controlled at 8-12mm.

[0010] Three-dimensional zoned dynamic temperature control system: The temperature control loop of the entire mold is divided into three independent zones: a high-temperature zone corresponding to the water chamber sealing surface (set mold temperature 100-120℃), a medium-temperature zone corresponding to the thin-walled flow channel and transition structure (set mold temperature 80-100℃), and a low-temperature zone corresponding to the thick-walled mounting boss (set mold temperature 60-80℃). The temperature is controlled separately by an independent PID-controlled mold temperature controller, so that each geometric area with different thicknesses maintains the same volume shrinkage rate during the cooling stage, completely eliminating the internal stress caused by asynchronous cooling.

[0011] (2) Localized supercritical microfoaming combined with injection molding: This invention innovatively combines MuCell supercritical microfoaming technology with multi-point sequential valve positioning. For thick-walled mounting bosses (wall thickness > 4mm) used for bolt fixing in water chambers, supercritical nitrogen (N2) fluid is introduced into the independent valve needle path corresponding to the thick-walled area at the moment of transition from the injection filling stage to the holding pressure stage. The supercritical nitrogen gas and the high-temperature melt instantly form a single-phase melt. When the internal pressure of the melt inside the thick-walled cavity drops sharply due to temperature decrease and slight volume shrinkage, the dissolved nitrogen gas instantly breaks the thermodynamic equilibrium, causing homogeneous nucleation and expansion to form a large number of dense micron-scale closed-cell structures (micro-cellular structures). This microfoaming expansion force from the inside out perfectly offsets the macroscopic volume shrinkage caused by polymer cooling and crystallization in the thick-walled area. This not only completely eliminates surface shrinkage (shrinkage cavity) defects, but also further reduces the local weight of the thick-walled area by 5%-10%, significantly improving dimensional stability.

[0012] (3) Execution of precision injection molding process parameters: A high-precision all-electric servo injection molding machine with a clamping force in the range of 200-350 tons was selected. The screw melt temperature was set as follows: PA66-GF33 barrel temperature was controlled at 280-295℃, and PPA-GF35 barrel temperature was controlled at 310-330℃. The injection action adopted multi-stage segmented speed curve control: a low-speed injection of 30-50mm / s was used in the initial stage of filling to avoid cold material jetting marks at the gate. The main filling stage is switched to high-speed injection of 80-120 mm / s to overcome the huge flow resistance at the thin-walled flow guide baffle and ensure filling integrity; During the pressure holding phase, switch to low-speed, high-pressure mode, set the pressure holding pressure to 70-80% of the maximum injection pressure, and maintain the pressure holding time for 8-15 seconds. The plasticizing back pressure is precisely controlled between 5-10 MPa to ensure uniform mixing and degassing of glass fiber, matrix resin, and micro-foamed gas.

[0013] In addition, for the inlet and outlet pipes of the water chamber, an insert-integrated injection molding technology is adopted. The metal quick-connect inserts that have undergone plasma surface activation treatment are pre-placed in the mold cavity for encapsulation molding, thereby obtaining a pipe interface with automotive-grade leak-proof characteristics in one step, eliminating the need for subsequent gluing or secondary welding processes and significantly improving pull-out strength.

[0014] Step 3: Online Dimensioning and Geometric Tolerance Inspection After injection molding and demolding, a machine vision online inspection system equipped with a high-resolution CCD and laser profilometer is used to perform a 100% panoramic scan inspection on each water chamber half shell that comes off the line. The core quality control indicators include: the absolute value of the flatness of the sealing surface must not be greater than 0.10mm. The dimensional tolerance of the sealing surface contour width is controlled within ±0.05mm; The positional tolerance of the metal connector assembly is controlled within ±0.15mm; The overall macroscopic warpage of the casing must not exceed 0.3mm. At the same time, AI image algorithms automatically identify appearance defects such as flash, shrinkage, and silver streaks and classify them according to their severity. Any defective products that exceed the tolerance are automatically rejected and intercepted by the robotic arm.

[0015] Step 4: Fine machining of sealing surfaces and prefabrication of anti-fouling structures To meet the requirements of subsequent high-cleanliness welding, the qualified water chamber half-shell sealing surface is subjected to high-precision CNC milling. The cutting process removes the trace flash generated by injection molding venting and the surface floating fibers formed by exposed glass fibers. The surface roughness is strictly controlled to Ra≤3.2μm, and the overall width dimension of the sealing surface is kept highly consistent. More importantly, during the milling process, a continuous micro-shallow groove (defined as flash receiving groove) is machined parallel to the inner edge of the sealing surface. The depth of the groove is precisely controlled to be 0.2-0.3mm and the width is controlled to be 1.0-1.5mm. This groove is specifically used to accurately accommodate and guide the extruded viscous molten flash in the subsequent welding stage, as the first physical barrier to prevent welding slag from falling into the water chamber cavity.

[0016] Step 5: Improved infrared preheating-assisted cleaning welding assembly (core innovative process) Abandoning the traditional direct friction welding which easily generates extremely high residual stress and a large amount of flash, this invention adopts infrared preheating assisted cleaning vibration friction welding (IR-CVF) process, or laser transmission welding process for extremely thin-walled structures.

[0017] When using infrared preheating-assisted cleaning vibration friction welding, the process is as follows: (1) Non-contact infrared preheating stage: The upper and lower shells to be assembled are precisely positioned and vacuum-adsorbed and fixed in two sets of high-rigidity contour welding fixtures. A specially made high-frequency short-wave infrared radiation array generator is introduced. Its radiation profile is completely matched with the two-dimensional projection of the water chamber sealing surface. The infrared generator is inserted between the two shells to perform high-intensity non-contact directional radiation heating on the upper and lower sealing surface areas. This causes the material of the sealing surface surface (within 0.2-0.5mm depth) to quickly pass the glass transition temperature and soften and heat up to 150-180℃. This preheating process directly transforms the sealing surface surface into a highly plastic state, which greatly reduces the instantaneous shear force required in the initial stage of subsequent mechanical friction pressure building. It reduces the amount of friction flash generated by 40%-60% from the source, and at the same time, annealing eliminates the internal stress remaining in the sealing surface area after injection molding.

[0018] (2) Micro-negative pressure suction and low amplitude friction welding stage: The infrared heater is quickly withdrawn, and the upper and lower fixtures are quickly closed and contacted. At this time, the vacuum suction system preset inside the welding fixture is started. Through the liquid inlet and outlet reserved in the upper and lower half shells, the semi-closed inner cavity of the water chamber formed by splicing is continuously evacuated, so that the inner cavity is maintained in a micro-negative pressure state of -0.01MPa to -0.03MPa in real time. Then, the vibration spindle is immediately started and the parameters are applied as follows: reciprocating vibration frequency 240Hz. Due to sufficient infrared preheating, the amplitude can be significantly reduced from 1.0-1.8mm in the traditional process to 0.5-0.8mm. The vertical welding pressure is set to 2-4 MPa, and the effective high-frequency friction time is only 3-5 seconds (the traditional process requires 6-10 seconds). During the vibration welding process, the small amount of molten flash that is squeezed out is 100% qualitatively adsorbed and filled into the flash receiving groove prefabricated in step four under the aerodynamic guidance of the micro negative pressure in the inner cavity. The very few fine dust-level fragments that fail to fall into the tank are immediately sucked out of the body by the vacuum negative pressure airflow, achieving absolute "zero welding slag" contamination in the inner cavity. Through closed-loop monitoring by high-precision displacement sensors, when the relative welding sinking of the upper and lower shells reaches the threshold of 0.5-1.0mm, the vibration stops instantly, and the solidification and bonding are completed after maintaining pressure cooling for 0.5 seconds.

[0019] (3) Alternative welding scheme (laser transmission welding): For precision microchannel water chambers with wall thickness ≤2.0mm or extremely narrow internal space and strict medical-grade cleanliness requirements, step five is replaced with laser transmission welding process without mechanical vibration and flash. The upper shell is made of special nylon material with high light transmittance (transmittance >85%), and the lower shell is made of black high light-absorbing nylon material doped with trace amounts of carbon black (or nano-carbon-based light-absorbing coating is precisely sprayed onto the sealing surface of the lower shell). Under the pressure of the transparent pneumatic clamp (clamping force 0.5-1.5MPa), a high-energy laser beam with a wavelength of 808nm to 980nm is emitted by a semiconductor laser generator. After the laser beam penetrates the upper shell, it is instantly absorbed by the light-absorbing layer of the lower shell at the bonding interface and converted into heat energy, which is locally melted and diffused for welding. The laser power is set to 50-150W, and the speed of the laser head scanning along the sealing surface is controlled at 10-30mm / s. This process is absolutely silent and there is no macroscopic material displacement or deformation.

[0020] Step Six: Online High-Precision Airtightness Testing After assembly, welding, and cooling, the finished water chamber is immediately subjected to non-destructive airtightness testing without being taken offline, using either high-precision helium vacuum leak detection or micro-pressure differential attenuation leak detection.

[0021] Using a tooling fixture to automatically seal the inlet and outlet of the liquid, clean and dry test gas (such as a nitrogen mixture mixed with 5% helium) with an absolute pressure of 0.3-0.5MPa (which is 1.5 to 2.5 times the actual maximum working pressure of the vehicle's liquid cooling system) is injected into the water chamber. After the gas source is cut off, a pressure holding and stabilization period of 30-60 seconds is entered.

[0022] At this stage, this manual uses the following formula for differential pressure attenuation leakage rate for theoretical determination and data acquisition: ; in: The differential pressure attenuation leakage rate characterizes the overall airtightness of the water chamber sealing cavity, and the unit is Pascal per second (Pa / s). The initial absolute pressure at the start of the airtightness test, expressed in Pascals (Pa). The final absolute pressure at the end of the airtightness test is expressed in Pascals (Pa). The effective pressure holding measurement time for airtightness testing is expressed in seconds (s).

[0023] This process strictly stipulates that the product's acceptance criteria are as follows: if the differential pressure method is used, the total differential pressure decrease within 30 seconds of pressure holding must be ≤50Pa (i.e., ≤1.67 Pa / s); If a highly sensitive helium gas chromatography-mass spectrometry method is used, the absolute leakage rate must be ≤1×10⁻⁶. -3 mbar·L / s, all test data are automatically entered into the Manufacturing Execution System (MES) and uniquely bound to the laser-engraved QR code on the shell surface to achieve full life-cycle quality and safety traceability.

[0024] Step 7: Final inspection and packaging of finished products Products that pass 100% airtightness testing enter the sampling destructive testing and final inspection stage. Visual and video-assisted inspections are conducted to confirm that the extrusion volume around the weld is uniform, there are no signs of coking, and there are no assembly scratches on the shell surface. A high-precision coordinate measuring machine is used to perform Cpk analysis and sampling inspection on key assembly interface dimensions such as mounting hole spacing and pipe coaxiality. In the destructive testing, it is ensured that the products can withstand water pressure ≥1.0MPa to burst on a hydraulic destructive testing machine (with a safety redundancy of more than 5 times the working pressure). It can withstand 1000 cycles of rapid alternating high and low temperatures from -40℃ to 120℃ in a thermal shock test chamber without any microscopic peeling or leakage. Finally, the inlet and outlet are tightly sealed with antistatic and high-cleanliness dust caps, and the water chamber is placed in a thickened PE dust bag and vacuumed or heat-sealed for warehousing.

[0025] In this invention, when implementing the above process, the following formula system is used to quantitatively control and evaluate the injection molding thermodynamics and welding kinetics behavior: Formula 1 (Volume Shrinkage Rate Assessment Model): (Formula 1); in: The volume shrinkage rate represents the percentage reduction in size of the molded part after cooling and solidification. This process minimizes regional differences by controlling the mold temperature in different zones. The dimension of the internal cavity of the injection mold in a specific direction under normal temperature conditions, in millimeters (mm). The actual dimensions of the product at room temperature after injection molding and 48 hours of stress release, in millimeters (mm).

[0026] Formula 2 (Calculation Model for Microfoaming Expansion Rate): (Formula 2); in: The microfoaming expansion rate represents the degree of volume compensation caused by the expansion of internal pores in thick-walled materials under the action of supercritical nitrogen. The standard density of solid PA66 or PPA polymer matrix without foaming treatment, combined with glass fiber, is expressed in grams per cubic centimeter (g / cm³). 3 ); The apparent density of this specific thick-walled protrusion region after treatment with a localized supercritical microfoaming process is expressed in grams per cubic centimeter (g / cm³). 3 By adjusting the pressure holding curve and the intake pressure, this process typically... Precisely controlled between 5% and 10%.

[0027] Formula 3 (Welding Friction Heat Energy Input Model): (Formula 3); in: The total effective frictional heat energy input to the sealing surfaces of the upper and lower shells during the welding process determines the thickness and mixing degree of the polymer molten layer, and is measured in joules (J). The transient dynamic friction coefficient of the sealing surface material of the two halves of the shell after infrared preheating treatment at 150-180℃ is a dimensionless quantity. The instantaneous constant welding pressure applied by the welding equipment through the fixture in a direction perpendicular to the normal direction of the sealing surface, is measured in Newtons (N). The effective displacement amplitude of the vibration friction spindle driving the upper shell relative to the lower shell in the horizontal direction is expressed in millimeters (mm). The reciprocating vibration operating frequency of the vibration friction equipment is expressed in Hertz (Hz). The duration for which the equipment maintains a high-pressure state to effectively generate heat through friction after reaching the set amplitude, measured in seconds (s).

[0028] Formula 4 (Model for Uniform Cooling of Mold Surface): ; in: The surface cooling rate of the mold is extremely poor, and it is used to measure the absolute uniformity of the three-dimensional temperature field distribution after the intervention of the 3D conformal cooling water channel. It is a dimensionless quantity. The maximum local cooling rate is the maximum temperature drop rate captured by an infrared thermal imager at the moment of demolding of the mold cavity among various characteristic temperature measurement points, in degrees Celsius per second (°C / s). The minimum local cooling rate at each characteristic temperature measurement point during the instant of mold cavity demolding is expressed in degrees Celsius per second (°C / s). The arithmetic mean cooling rate, measured in degrees Celsius per second (°C / s), is captured by all 36 pre-set characteristic temperature measurement points on the mold cavity surface. Through conformal cooling design, this process strictly ensures... ≤0.15.

[0029] Compared with the prior art, the beneficial effects of the present invention by adopting the above technical solution are as follows: (1) A qualitative leap in sealing reliability: By using 3D printed conformal cooling water channels, the cooling difference of the mold surface is controlled within 15%. Combined with three-zone dynamic independent mold temperature control, the absolute error of the flatness of the complex sealing surface of the large Haver-type water chamber with a length of 500mm is reduced from 0.3-0.5mm in the traditional process to ≤0.1mm. With infrared preheating and low amplitude friction welding process, the weld depth is uniform and the internal stress is extremely low. The finished product can meet the requirements of continuous 10 years / 300,000 kilometers of leak-free safe operation under the high intensity pulse alternating pressure of 0.3MPa system. (2) Ensures the absolute cleanliness of the core channels of the power battery system: large pieces of debris generated by traditional vibration welding are softened and reduced by infrared, and the remaining trace amounts of viscous flash are completely collected by the innovative prefabricated physical flash receiving groove. The suspended dust in the space is completely discharged under the micro negative pressure strong suction system. This combination of measures fundamentally eliminates the fatal hidden danger of clogging the micro channels of the battery liquid cooling plate, so that the flow resistance fluctuation rate of the entire thermal management system does not exceed ±2% throughout the entire life cycle; (3) Uniform internal flow field distribution and integrated structure: A thin-walled flow guide baffle with a height of 60%-80% of the total cavity and a vortex diffusion cone structure that suppresses cavitation caused by high-speed impact are integrally formed in the water chamber cavity, reducing the complicated multi-part assembly to one injection molding. The water chamber is not only a pressure-bearing shell, but also a high-precision fluid distributor, which greatly reduces the volume flow deviation of the coolant in each row of microchannels of the heat exchanger from ±20% in the existing technology to ≤±5%, directly helping to keep the extreme temperature difference between hundreds and thousands of cells in the same power battery pack within a strict range of ≤3℃. (4) Achieved deep lightweight and green low-carbon manufacturing: By applying high specific strength PPA material and innovatively introducing local supercritical micro-foaming (MuCell) process in the thick-walled boss mounting area, the contradiction between weight reduction and pressure resistance and shrinkage prevention is effectively resolved, and the weight of a single part is reduced by 15%-25%. Moreover, by reducing the single-part injection molding cooling time and eliminating the long hot plate melting waiting time, the overall single-part cycle time of the production line is shortened from the traditional 120 seconds to 60 seconds. The infrared preheating greatly reduces the peak starting current and continuous work burden required by the friction spindle motor, resulting in a reduction of manufacturing energy consumption of a single product by more than 30%, which perfectly meets the strategic needs of the global automotive industry to transform towards extreme low-carbon manufacturing. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the overall architecture of the power battery pack liquid cooling system in an embodiment of the present invention; Figure 2 This is a schematic diagram of a typical explosion structure of a Haver-type water chamber in an embodiment of the present invention; Figure 3 This is a simulation diagram of the layout of the multi-point sequential valve gate system and the melt flow path in an embodiment of the present invention; Figure 4 This is a schematic cross-sectional view comparing the three-dimensional conformal cooling water channel and the traditional straight-hole cooling water channel in an embodiment of the present invention; Figure 5 This is a partially enlarged schematic diagram of the cross-sectional geometry of the sealing surface and the flash receiving groove in an embodiment of the present invention; Figure 6 This is a schematic diagram of the timing process of infrared preheating assisted cleaning vibration friction welding in an embodiment of the present invention; Figure 7 This is a schematic diagram of CFD simulation verification of the flow field trace distribution and velocity uniformity of the coolant in the water chamber of this invention embodiment; Figure 8 This is a topology diagram of the complete process flow chain and quality control parameters for the water chamber of an automotive heat exchanger in an embodiment of the present invention. Detailed Implementation

[0031] To enable those skilled in the art to more deeply and clearly understand the inventive logic, technical details, and practical industrial application value of this invention, the following detailed explanation of the molding process of a Haval-type water chamber for an automotive heat exchanger, proposed in this invention, is provided in conjunction with three specific and different parameterized embodiments. It should be stated in advance that the embodiments listed below are merely typical representatives of the best implementation path of this invention and do not constitute an absolute limitation on the scope of protection of this invention. Without departing from the core process concept of this invention (such as the synergistic application of conformal cooling control, local micro-foaming injection molding to prevent shrinkage, and infrared-assisted micro-negative pressure cleaning welding), conventional parameter adjustments or equivalent substitutions made according to the specific dimensions and pressure levels of battery packs from different car manufacturers all fall within the protection scope of this invention.

[0032] During the execution of all embodiments, the evaluation formulas for the five physical quantities defined above (including volume shrinkage rate) are used. Microfoaming expansion rate Welding friction heat energy Differential pressure attenuation leakage rate And extremely poor cooling Rigorous quantitative verification and closed-loop control are implemented for all process parameters, due to the aforementioned physical quantity identifiers (such as...). , , The specific meanings of (etc.) have been uniquely and clearly defined in the "Summary of the Invention" section. Their physical meanings will not be redefined here. Instead, their calculation values ​​and control logic under specific implementation conditions will be explained.

[0033] Please see the appendix Figure 1 - Appendix Figure 8 This invention relates to a molding process for a Haval-type water chamber in an automotive heat exchanger.

[0034] Example 1: Manufacturing of PA66-GF33 standard water chamber for liquid cooling system of a mainstream passenger vehicle power battery This embodiment aims to produce a typical passenger vehicle liquid cooling plate water chamber with dimensions of approximately 450mm × 80mm, a system working pressure requirement of 0.25MPa, and a working temperature limit of -30℃ to 105℃.

[0035] First, proceed to the raw material pretreatment in step one: Select PA66-GF33 high rigidity composite resin. To prevent silver streaks, place it in a vacuum dehumidification dryer and bake it continuously at a constant temperature of 90℃ for 5 hours. After verification by a moisture tester, its residual moisture content drops below the safe level of 0.03%. Simultaneously, add 2% by mass of dark black masterbatch for uniform premixing.

[0036] Step Two: Composite Injection Molding Process. This fixture is equipped with a complex 1-out-1 (one mold, one cavity) precision mold with conformal cooling. In the hot runner design, eight sequential control valves, independently driven by pneumatic cylinders, are arranged along the long, narrow water chamber cavity. The temperatures of each section of the injection molding machine's feed tube are set sequentially from back to front to 280℃, 285℃, and 290℃, with the nozzle temperature at 295℃. The mold is activated with three-zone dynamic temperature control: the joint sealing surface area is connected to a 110℃ high-temperature oil temperature controller; the middle transition zone of the runner is connected to a 90℃ water temperature controller; and the installation positioning boss area with a thickness of 5.5mm at the end is connected to a 70℃ chiller. At this point, based on the cooling difference monitoring results, the following calculations are made: = 0.08, which is far below the control limit of 0.15, indicating that the cooling field is highly uniform. At the start of injection, the main valve needle opens and the melt enters the mold at a low speed of 40mm / s. After 1 second, it is cut into a high-speed injection of 100mm / s to fill the cavity; When the volume is filled to 95% and pressure holding begins, the control program instantly opens the micro-bubble valve at the mounting boss, injecting supercritical nitrogen gas at a pressure of 12 MPa into the local area. This pressure is maintained for 10 seconds, with the holding pressure set at 85 MPa. The demolded and cooled samples from this batch are then removed, and the reference cavity width is obtained through coordinate measuring machine (CMM) measurement. = 80.00mm, while the actual measured diameter of the part is... =79.85mm, substitute into Formula 1 to calculate the volume shrinkage rate. = 0.187%, which is within the extremely low ideal range. No minute shrinkage depressions were found on the surface of the boss by either the naked eye or instruments. Simultaneously, the density of the unfoamed portion of the boss was measured. =1.40 g / cm 3 After foaming, the local density decreased to = 1.32 g / cm 3 The expansion rate of micro-foaming was calculated using Formula 2. ≈5.71%.

[0037] After injection molding, the batch underwent a full visual online inspection in step three. The system showed that the flatness index of this batch was 0.08mm, indicating that all batches were qualified.

[0038] Then proceed to step four: transfer it to a CNC four-axis machining center, mill a closed-loop shallow groove (flash accommodating groove) 0.25mm deep and 1.2mm wide along the inner side of the sealing surface 0.5mm, and control the Ra of the sealing surface surface to 1.8μm.

[0039] The core assembly, step five, involves fixing the upper and lower shells into a special fixture for a high-frequency vibration friction welding machine. An infrared heating plate slides into the gap between them, radiating with extremely high power density for 3 seconds. The temperature within approximately 0.3mm of the sealing surface reaches 165℃ (at this temperature, the material softens and becomes highly viscous, significantly reducing the coefficient of friction; in this embodiment, the transient dynamic friction coefficient was measured). =0.35), the mold is closed immediately after the heating plate is removed, at which point the interior is evacuated to a vacuum of -0.02MPa, and then a welding constant pressure of 3MPa (converted to vertical constant force) is applied. =4500N), turn-on frequency = 240Hz, amplitude =0.6mm high-frequency micro-amplitude vibration, actual effective welding time = The set downward displacement of 0.8mm is reached in 3.5s. Substituting into Formula 3, the frictional heat energy input to the sealing surface during this welding is calculated. = 0.35×4500×0.6×240×3.5 = 793,800J. Under the combined effect of preheating and this heat energy, the high-strength macromolecular chains fully penetrate and entangle with each other, while a very small amount of extruded plastic material precisely rolls into the flash receiving groove of the previous processing.

[0040] Finally, perform the airtightness test in step six: fill the tank with an absolute pressure of 0.4 MPa (i.e., The detection gas (Pa = 400000) underwent... = After holding the pressure for 30 seconds, read the final pressure. = 399965Pa, substituting into formula four, we get = (400000 - 399965) / 30 = 1.16Pa / s, which is far lower than the standard requirement of 1.67 Pa / s (i.e., total pressure drop ≤ 50Pa / 30s). Ultimately, the product passed the water pressure burst test, with a burst value as high as 1.3MPa.

[0041] Example 2: High-performance PPA-GF35 integrated molding for fatigue-resistant liquid cooling system of commercial heavy-duty truck power battery packs For heavy-duty truck heat exchangers that need to withstand the impact of strong heavy-load vibrations over millions of kilometers and the surge in system pipeline pressure (up to 0.35MPa working pressure), this embodiment adopts the extremely high-performance PPA-GF35 solution and combines it with laser transmission welding to pursue the medical-grade cleanliness of "absolute zero residue" in the inner cavity.

[0042] In step one, PPA-GF35 particles with excellent temperature resistance and dimensional stability are placed in a 130℃ dehumidifying drying oven and baked for 6 hours to reduce the moisture content to 0.02%. In order to cooperate with the laser transmission welding in step five, the upper shell material, which is the light-transmitting body, is left uncolored (light amber) without the addition of color powder, while the lower shell material is granulated by incorporating high light absorption nano-sized carbon black masterbatch at a mass ratio of 2.5%.

[0043] In the second injection molding stage, to address the challenge of the extremely narrow flow window of PPA, the barrel temperature surged to 320°C at the front and 330°C at the nozzle. The mold was equipped with a denser 10-point sequential valve needle, and 6061 aluminum alloy automotive-grade quick-connect fittings with anodized and plasma-activated surfaces were directly embedded in the mold cavity corresponding to the inlet to achieve integrated molding of the insert. The oil temperature in the high-temperature zone of the sealing surface reached 130°C, and the temperature in the thick-walled low-temperature water channel zone reached 80°C, resulting in extremely poor mold surface cooling. = 0.05, while simultaneously intensifying the micro-foaming effect at thick-walled areas, increasing the nitrogen injection pressure to 15 MPa, and measuring... = 1.55 g / cm 3 , = 1.42g / cm 3 The micro-foaming expansion rate was calculated according to Formula 2. = 8.38%, which not only offsets the reduction in the thickness of the heavy-duty truck's water chamber mounting base (7.5mm), but also achieves an astonishing 11% single-unit local weight reduction. Due to extremely strong temperature control, its measured reference dimensions = 650.00mm, while the dimensions of parts manufactured at room temperature = 648.96mm, substituting into Formula 1 yields the total longitudinal shrinkage rate. =0.16%.

[0044] Skipping the mechanical milling finishing process that easily generates debris, the upper and lower shells are directly sent to the cleanroom for step five, laser transmission welding. The transparent upper shell and the pure black lower shell are precisely fitted and pressed together. A 980nm wavelength fiber semiconductor laser with a maximum emission power of 120W is used, with a laser spot diameter focused at 1.5mm. The laser beam continuously and seamlessly scans the irregular joint sealing surface of the water tank at a scanning speed of 20mm / s. The laser beam passes through the upper shell without damage and instantly generates huge heat at the black light-absorbing interface of the lower shell, melting the two-phase interface. There is no mechanical relative movement or friction throughout the entire process.

[0045] In step six, the airtightness test of the finished product is tightened. = 500000Pa helium mixture, pressure maintained =60s, pressure at the end of the test = 499985Pa, calculated according to Formula 4 = 0.25Pa / s, exhibiting crush-level advantages in airtightness. Subsequent tensile strength tests of the finished product showed that the directly injection-molded aluminum joint did not loosen or leak when subjected to longitudinal external forces up to 1800N.

[0046] Example 3: Comparative Demonstration of High-Temperature Weather-Resistant Water Chambers with Focus on Uniform Fluid Distribution and Process Performance This embodiment focuses on solving the hydrodynamic problem of flow rate attenuation at the end of an ultra-long heat exchanger core (with up to 60 rows of microchannels) and conducts process verification and comparison.

[0047] The product material uses PA66-GF33, and the molding process mainly follows Example 1. However, the cavity design in step two strengthens the one-piece molding functional component: multiple micro-guide baffles with logarithmically varying heights are injection molded into the upper shell, and a parabolic vortex diffusion cone with an angle of 15 degrees is integrally injection molded directly behind the liquid inlet pipe axis. This geometric feature is very prone to causing glue jamming on the back of the flow channel, but... With the support of precise three-dimensional conformal water channel forced cooling (= 0.10) and segmented high-speed demolding mechanism, it successfully and completely demolded with zero surface scratches. After micro-foaming, its... It remained stable at approximately 6.5%.

[0048] The welding end uses an upgraded IR-CVF, with the following control parameters: = 0.38, = 3800N, = 0.5mm, = 260Hz, 3.0s, calculate the frictional heat energy according to Formula 3. = 563160J. Compared to traditional non-preheated vibration welding (which often requires over 1,000,000 J of violent dry friction mechanical heat energy to melt the surface), this heat input just maintains the diffusion of polymer chains without degradation, and the extremely small amount of flash generated is safely locked in the flash receiving tank by vacuum negative pressure.

[0049] Comparative airtightness test: Take a comparison sample of the same model that was not produced using this molding process (i.e., traditional injection molding plus dry friction welding process without micro-foaming pressure holding, infrared preheating, and micro-negative pressure suction groove), and conduct a pressure difference attenuation test (inflation). =400,000 Pa, duration = 30s), traditional comparison sample The Pa is only 399780 Pa, calculated using Formula 4 for the comparative sample. = 7.33Pa / s, a serious leakage exceeding the standard; The measured average final pressure of the same batch of products in this embodiment = 399982Pa, that is =0.60Pa / s, the density is increased by more than ten times. The water chamber of this embodiment was cut open and the flow field was measured. The liquid distribution flow deviation between the leftmost and rightmost microchannels was stable within an amazing range of ±3.8%, which fully meets or even exceeds the abnormal technical specifications of new energy vehicle companies regarding temperature difference ≤3℃. This fully demonstrates the excellent engineering value of the process chain of this invention.

Claims

1. A molding process for a Haval-style water chamber in an automotive heat exchanger, characterized in that, Includes the following steps: Raw material pretreatment: The glass fiber reinforced polymer resin is subjected to deep drying treatment to control the residual moisture content to below 0.05%; Composite injection molding: The water chamber half shell is injection molded using a hot runner system combined with a multi-point sequential valve gate system. The opening time sequence and holding pressure curve of each valve needle are independently programmed and controlled to guide the polymer melt to flow unidirectionally from the edge area of ​​the water chamber sealing surface to the inner cavity guide structure area, and the weld line position is controlled in the non-sealing surface and non-stress concentration area. Three-dimensional conformal cooling water channels are set inside the mold cavity and core insert; The mold temperature control circuit is divided into three zones: a high-temperature zone corresponding to the sealing surface, a medium-temperature zone corresponding to the thin-walled flow channel and transition structure, and a low-temperature zone corresponding to the thick-walled mounting boss. The three zones are dynamically controlled independently. The water chamber half-shell has a thin-walled flow channel and transition structure inside, and its outer edge is provided with a thick-walled mounting boss area with a wall thickness greater than 4mm; for the thick-walled mounting boss area, when the injection filling stage ends and the pressure holding stage begins, supercritical nitrogen is introduced through the independent valve needle circuit of the corresponding area to form a micron-level closed-cell bubble structure inside the thick-walled area. Precision machining of sealing surface: The sealing surface of the injection-molded water chamber half shell is precision machined to remove burrs and surface floating fibers, and a continuous burr receiving groove is machined on the inner edge of the sealing surface. Infrared preheating assisted cleaning welding assembly: The upper and lower shells are positioned and fixed in the welding fixture respectively. The upper and lower sealing surface areas are heated by non-contact directional radiation through an infrared radiation array generator, so that the surface material of the sealing surface is heated to 150 to 180°C and passes the glass transition temperature to a highly plastic state. After the infrared radiation array generator is removed, the upper and lower fixtures are closed, and the vacuum suction system is activated to continuously evacuate the water chamber formed by the assembly to maintain a slight negative pressure state in the inner cavity. Then, low-amplitude vibration friction welding is performed. During the welding process, the molten flash that is squeezed out is filled into the flash receiving groove under the aerodynamic guidance of the slight negative pressure in the inner cavity. Air tightness test: Perform non-destructive air tightness test on the finished water chamber after welding.

2. The molding process according to claim 1, characterized in that, The multi-point sequential valve gating system has 6 to 10 independent valve pin points evenly distributed in the water chamber cavity. Each valve pin is independently driven by a pneumatic cylinder, and the opening time sequence of each valve pin is independently programmed and controlled at the millisecond level by the injection molding machine controller.

3. The molding process according to claim 1, characterized in that, The three-dimensional conformal cooling water channel is integrally formed inside the mold cavity and core insert using selective laser melting 3D printing technology. The trajectory of the three-dimensional conformal cooling water channel conforms to the geometric contour of the water chamber cavity surface, and the normal distance between the edge of the water channel and the cavity surface is controlled between 8 and 12 mm.

4. The molding process according to claim 1, characterized in that, In the independent zone dynamic temperature control, the mold temperature of the high temperature zone is set to 100 to 120°C, the mold temperature of the medium temperature zone is set to 80 to 100°C, and the mold temperature of the low temperature zone is set to 60 to 80°C. The three zones are controlled by independent PID-controlled mold temperature controllers, so that the corresponding high temperature zone, medium temperature zone and low temperature zone have the same volume shrinkage trend during the cooling and cooling stage, and the cooling rate difference is controlled within 15%.

5. The molding process according to claim 1, characterized in that, The supercritical nitrogen gas forms a single-phase solution with the high-temperature melt. When the internal pressure of the melt decreases due to the temperature drop inside the thick-walled cavity, the dissolved nitrogen gas undergoes homogeneous nucleation and expands to form the micron-scale closed-cell bubble structure. By adjusting the holding pressure curve and the inlet pressure, the micro-foaming expansion rate is controlled between 5% and 10%. The micro-foaming expansion rate is the ratio of the difference between the standard density of the unfoamed solid polymer matrix and the apparent density of the foamed thick-walled region to the standard density.

6. The molding process according to claim 1, characterized in that, The sealing surface is finely machined using CNC milling, and the surface roughness of the sealing surface is controlled to Ra≤3.2μm; The flash accommodating groove is located on the inner edge of the sealing surface and is continuously distributed parallel to the edge of the sealing surface. The depth of the flash accommodating groove is 0.2 to 0.3 mm and the width is 1.0 to 1.5 mm.

7. The molding process according to claim 1, characterized in that, The infrared radiation array generator is a high-frequency short-wave infrared radiation array generator, whose radiation profile matches the two-dimensional projection of the water chamber sealing surface. The infrared radiation array generator is inserted between the upper and lower shells, heating the material within a depth of 0.2 to 0.5 mm on the surface of the sealing surface to 150 to 180°C, causing the surface material of the sealing surface to cross the glass transition temperature and transform into a highly plastic state, while eliminating the internal stress remaining in the sealing surface area after injection molding.

8. The molding process according to claim 1, characterized in that, The micro-negative pressure state is that the inner cavity is maintained at a gauge pressure of -0.01MPa to -0.03MPa. The vacuum suction system continuously evacuates the water chamber cavity through the liquid inlet and outlet ports reserved in the upper and lower half shells. The parameters for the low-amplitude vibration friction welding are: reciprocating vibration frequency 240Hz, amplitude 0.5 to 0.8mm, vertical welding pressure 2 to 4MPa, and effective friction time 3 to 5 seconds. By using a displacement sensor in a closed-loop monitoring system, when the relative welding subsidence of the upper and lower shell halves reaches 0.5 to 1.0 mm, the vibration stops and pressure cooling is maintained to complete the solidification and bonding.

9. The molding process according to claim 1, characterized in that, In the composite injection molding process, for the inlet and outlet pipes of the water chamber, an insert-integrated injection molding technology is adopted. The metal quick-connect insert, which has undergone plasma surface activation treatment, is pre-placed in the mold cavity for overmolding, thereby obtaining the pipe interface in one step.

10. The molding process according to claim 1, characterized in that, In the airtightness test, test gas with an absolute pressure of 0.3 to 0.5 MPa is filled into the water chamber cavity; After the gas supply is cut off, a pressure holding and stabilization period of 30 to 60 seconds is entered. The qualified standard is that the total pressure difference decrease within 30 seconds of pressure holding is not greater than 50 Pa.

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