Intelligent precision casting equipment and method for new energy vehicle thermal management multi-way valve body

Abstract

This invention relates to the field of casting technology, specifically to a precision intelligent casting equipment and method for multi-way valve bodies for thermal management in new energy vehicles. The method includes: during the pressure holding process in low-pressure casting, determining the flow channel pressure drop characterization value of the casting based on the casting pressure of the mold cavity corresponding to the ends of each flow channel; determining the pressure holding state of the casting based on the flow channel pressure drop characterization value; for castings in a critical pressure holding state, further determining the pressure holding state of the casting based on the acoustic emission activity value of the casting; classifying the causes of castings in abnormal pressure holding states based on the pressure-temperature response deviation index of the casting; implementing corresponding control strategies based on the causes of castings in abnormal pressure holding states; and depressurizing and opening the mold to obtain the multi-way valve body casting, thereby improving the casting efficiency of multi-way valve bodies for thermal management in new energy vehicles.

Description

Technical Field

[0001] This invention relates to the field of casting technology, specifically to precision intelligent casting equipment and methods for multi-way valve bodies for thermal management in new energy vehicles. Background Technology

[0002] The multi-way valve body for thermal management in new energy vehicles is a core functional component of the heat pump system. Its internal flow channels have numerous branches and complex, varied cross-sections, placing extremely stringent requirements on casting density and airtightness. Any minute internal defect can lead to system leakage and failure. Low-pressure casting, due to its stable filling and sequential solidification of molten metal under pressure, can better meet the forming requirements of such complex thin-walled castings, and has therefore become one of the mainstream production processes.

[0003] In low-pressure casting, the holding pressure stage is a crucial step in determining the final density of the casting. During the holding pressure period, the molten metal, under continuous pressure, feeds the ends of each flow channel to compensate for solidification shrinkage. However, due to significant differences in the shape, wall thickness, and heat dissipation conditions of each flow channel in a multi-way valve body, the solidification sequence and feeding requirements of each channel are not entirely the same. This can easily lead to problems such as premature closure of local feeding channels or asynchronous decay of feeding pressure, resulting in internal defects such as shrinkage porosity and gas bubbles.

[0004] The causes of defects during the pressure holding stage are not singular. Defects with different causes require fundamentally different control strategies. If uniform measures such as extending the pressure holding period or stopping the machine for investigation are applied without differentiation, it will not only fail to effectively improve casting quality, but may also lead to defect exacerbation or a significant reduction in production efficiency due to incorrect control direction. However, current technologies for monitoring the pressure holding process typically rely solely on threshold monitoring of a single process parameter or post-process offline flaw detection, making it difficult to differentiate the causes of abnormal feeding during the casting process online.

[0005] Therefore, how to achieve abnormal identification and accurate differentiation of causes during the pressure holding stage of low-pressure cast multi-way valve bodies, and then implement targeted control, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address this, the present invention provides a precision intelligent casting equipment and method for multi-way valve bodies for thermal management in new energy vehicles, which overcomes the problems in the prior art where internal defects in castings are caused by differences in the synchronization of multi-channel feeding during the pressure holding stage, and where the inability to accurately distinguish the causes of abnormalities affects the targeting of control strategies, thus resulting in poor casting efficiency of multi-way valve bodies for thermal management in new energy vehicles.

[0007] To achieve the above objectives, on the one hand, the present invention provides a precision intelligent casting method for a multi-way valve body for thermal management in new energy vehicles, comprising: During the pressure holding stage of low-pressure casting, the low-pressure casting machine holds the pressure at a preset pressure for a preset holding time. Based on the casting pressure of the mold cavity corresponding to the end of each flow channel of the casting, the flow channel pressure drop characterization value of the casting is determined. The pressure holding state of the casting is determined based on the pressure drop characterization value of the flow channel, wherein the pressure holding state includes normal pressure holding state, critical pressure holding state and abnormal pressure holding state; For castings in a critical holding pressure state, the holding pressure state of the casting is determined a second time based on the acoustic emission activity value of the casting, wherein the acoustic emission activity value is determined based on the acoustic emission signal at the end of each flow channel of the casting; The causes of castings in abnormal holding pressure are classified based on the pressure-temperature response deviation index of the castings. The causes include invasive porosity abnormalities and shrinkage abnormalities. According to the cause of the abnormal pressure holding state of the casting, a corresponding control strategy is executed, wherein the control strategy is to issue an alarm or increase the preset pressure holding time. The casting is depressurized and the mold is opened to obtain a multi-way valve body casting.

[0008] Preferably, the process of determining the holding pressure state of the casting based on the flow channel pressure drop characterization value of the casting includes: The pressure drop characterization value of the flow channel is compared with the first preset pressure drop characterization value and the second preset pressure drop characterization value, respectively; Based on the result that the pressure drop characterization value of the flow channel is less than the first preset pressure drop characterization value of the flow channel, it is determined that the casting is in a normal pressure holding state; Based on the result that the flow channel pressure drop characterization value is greater than or equal to the first preset flow channel pressure drop characterization value and less than the second preset flow channel pressure drop characterization value, it is determined that the casting is in a critical pressure holding state. Based on the result that the flow channel pressure drop characterization value is greater than or equal to the second preset flow channel pressure drop characterization value, it is determined that the casting is in an abnormal pressure holding state. Wherein, the first preset flow channel pressure drop characterization value is less than the second preset flow channel pressure drop characterization value.

[0009] Preferably, the process for obtaining the flow channel pressure drop characterization value includes: The casting pressure of the mold cavity corresponding to the end of each flow channel of the casting is obtained, and the casting pressure-time series of each flow channel is obtained. Based on the casting pressure-time series of each flow channel, the pressure decay rate of each flow channel within the preset pressure holding window is determined. Calculate the average and standard deviation of the pressure decay rate for all the flow channels, and determine the ratio of the standard deviation to the average as the pressure drop characteristic value of the flow channel; The term "runner end" refers to the cavity position at the end of the runner that is furthest from the main gate of the mold.

[0010] Preferably, for castings in a critical holding pressure state, the process of determining the holding pressure state of the casting a second time based on the acoustic emission activity value of the casting includes: If the acoustic emission activity value is less than the preset acoustic emission activity value, the casting is determined to be in a normal pressure holding state. If the acoustic emission activity value is greater than or equal to the preset acoustic emission activity value, the casting is determined to be in an abnormal pressure holding state.

[0011] Preferably, the process of obtaining the acoustic emission activity value includes: Acquire acoustic emission signals from the ends of each flow channel of the casting; The acoustic emission signal is bandpass filtered to retain the acoustic emission signal in a preset frequency band; Calculate the root mean square amplitude of all acoustic emission signals in the preset frequency band within a preset time window, and determine the ratio of the maximum root mean square amplitude to the duration of the preset time window as the acoustic emission activity value.

[0012] Preferably, the process of classifying the causes of castings in abnormal holding pressure states based on the pressure-temperature response deviation index of the castings includes: When the pressure-temperature response deviation index is less than the preset pressure-temperature response deviation index, the causes of invasive porosity abnormalities are classified. When the pressure-temperature response deviation index is greater than or equal to the preset pressure-temperature response deviation index, the cause of shrinkage abnormality is classified.

[0013] Preferably, the process of obtaining the pressure-temperature response deviation index includes: The casting pressure and mold temperature at the end of each flow channel of the casting are obtained, and the casting pressure-time series and mold temperature-time series of each flow channel are obtained respectively. Based on the casting pressure-time series and mold temperature-time series of each flow channel, the pressure decay rate and mold temperature drop rate of each flow channel within the preset holding pressure window are determined. The pressure-temperature response coefficient of each flow channel is determined based on the ratio of the pressure decay rate to the mold temperature drop rate of each flow channel. Based on the pressure-temperature response coefficient of each flow channel, the maximum and minimum values ​​of the pressure-temperature response coefficient of each flow channel are determined, and the ratio of the maximum value to the minimum value is determined as the pressure-temperature response deviation index.

[0014] Preferably, the process of implementing a corresponding control strategy based on the cause of the abnormal pressure holding state of the casting includes: An alarm is issued when the cause of the casting in the abnormal pressure holding state is determined to be an invasive porosity abnormality. When the cause of the casting in the abnormal holding pressure state is determined to be abnormal shrinkage porosity, the preset holding pressure time is increased according to the ratio of the pressure-temperature response deviation index to the preset pressure-temperature response deviation index.

[0015] Preferably, the increase in the preset pressure holding time is positively correlated with the pressure-temperature response deviation comparison value, wherein the pressure-temperature response deviation comparison value is the ratio of the pressure-temperature response deviation index to the preset pressure-temperature response deviation index.

[0016] On the other hand, the present invention provides a precision intelligent casting apparatus suitable for the above-described precision intelligent casting method, comprising: Low-pressure casting machine is used to fill the mold cavity of multi-way valve body with molten metal from bottom to top along the riser pipe under the drive of compressed air, and to hold the filling casting under pressure to solidify and form it. The data acquisition module, which is connected to the low-pressure casting machine, includes a casting pressure acquisition unit set at the mold cavity corresponding to the end of each flow channel of the casting, an acoustic emission signal acquisition unit set on the outer surface of the mold cavity, and a mold temperature acquisition unit adjacent to the casting pressure acquisition unit. The control module is connected to the data acquisition module and the low-pressure casting machine, and includes a function to determine the holding pressure state of the casting based on the flow channel pressure drop characterization value of the casting, a function to determine the holding pressure state of the casting in the critical holding pressure state based on the acoustic emission activity value of the casting, and a function to classify the causes of the casting in the abnormal holding pressure state based on the pressure-temperature response deviation index of the casting. An adjustment module, connected to the control module and the low-pressure casting machine, executes a corresponding control strategy based on the cause of the abnormal pressure holding state of the casting. The control strategy is to issue an alarm or increase the preset pressure holding time.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention establishes a multi-level progressive judgment and closed-loop control mechanism that runs through the low-pressure casting holding stage. It identifies overall feeding anomalies by synchronizing the pressure decay of multiple flow channels, further eliminates process fluctuation interference by cross-verifying acoustic emission activity values, and finally distinguishes between two types of defects with different causes, namely invasive porosity and shrinkage porosity, online through the pressure-temperature response deviation index. It also implements differentiated process control and early warning strategies according to different causes of anomalies. For invasive porosity anomalies, it issues an alarm in a timely manner to investigate potential problems in the process system. For shrinkage porosity anomalies, it dynamically adjusts the holding time according to the severity of the anomaly. This ensures the internal density of the casting and avoids the production efficiency loss caused by overly conservative process parameters, thereby improving the casting efficiency of multi-way valve bodies for thermal management in new energy vehicles.

[0018] 2. This invention collects the casting pressure at the end of each flow channel cavity and calculates the pressure decay rate within a preset pressure holding window. The ratio of the standard deviation to the average value of the pressure decay rate is then used as the flow channel pressure drop characterization value. This achieves a quantitative characterization of the consistency of the multi-flow channel feeding process, effectively eliminating the reference error and range difference of different pressure sensors, and providing an objective and unified evaluation basis for pressure holding state determination. By setting two progressive preset thresholds, the pressure holding state is divided into three levels: normal, critical, and abnormal. This enables accurate identification and grading of feeding anomalies of different degrees, avoiding misjudgments and omissions caused by single threshold determination. This ensures the stability of the normal production process and lays the foundation for subsequent secondary verification of critical states and diagnosis of the causes of abnormal states.

[0019] 3. This invention effectively eliminates environmental noise interference by real-time acquisition of acoustic emission signals from the ends of each flow channel of the casting and performing bandpass filtering, thus achieving accurate extraction of effective acoustic emission signals within a preset frequency band. The acoustic emission activity value is determined by calculating the ratio of the root mean square amplitude to the duration of the signal within a preset time window, enabling quantitative characterization of microscopic deformation and crack initiation activities within the casting. Furthermore, the acoustic emission activity value is introduced for secondary judgment under critical holding pressure, achieving cross-validation of the preliminary screening results and effectively eliminating interference from normal process fluctuations in anomaly identification.

[0020] 4. This invention achieves panoramic monitoring of the dynamic evolution of multiple physical fields during the holding pressure stage by simultaneously collecting casting pressure and mold temperature at the ends of each flow channel, constructing pressure-time series and temperature-time series; by calculating the ratio of the pressure decay rate of each flow channel to the mold temperature drop rate, the pressure-temperature response coefficient reflecting the cooling and feeding balance between flow channels is determined, and then the pressure-temperature response deviation index is determined, achieving precise quantification; based on the comparison of the pressure-temperature response deviation index with a preset threshold, the causes of defects are accurately classified, thereby improving the reliability of the judgment.

[0021] 5. This invention implements differentiated control strategies for invasive porosity and shrinkage abnormalities, and dynamically determines the increase in holding time based on the ratio of the pressure-temperature response deviation index to a preset threshold. This achieves a precise correspondence between defect causes and process control measures, thereby ensuring the density of the multi-way valve body casting for thermal management in new energy vehicles. Attached Figure Description

[0022] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0023] Figure 1 This is a flowchart illustrating the precision intelligent casting method for a multi-way valve body for thermal management in new energy vehicles, as described in an embodiment of the present invention. Figure 2This is a flowchart illustrating how the pressure holding state of a casting is determined based on the flow channel pressure drop characterization value of the casting, according to an embodiment of the present invention. Figure 3 This is a flowchart illustrating how, in an embodiment of the present invention, the pressure holding state of a casting is determined a second time based on the acoustic emission activity value of the casting when the casting is in a critical pressure holding state. Figure 4 This is a schematic diagram of the module connection of a precision intelligent casting equipment for a multi-way valve body for thermal management of new energy vehicles, according to an embodiment of the present invention. Detailed Implementation

[0024] 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.

[0025] Please see Figure 1 , Figure 2 , Figure 3 as well as Figure 4 The following are flowcharts of the precision intelligent casting method for the multi-way valve body of the thermal management system of new energy vehicles according to an embodiment of the present invention; the flowchart of determining the pressure holding state of the casting based on the flow channel pressure drop characterization value of the casting according to an embodiment of the present invention; the flowchart of determining the pressure holding state of the casting a second time based on the acoustic emission activity value of the casting for the casting in the critical pressure holding state according to an embodiment of the present invention; and the module connection diagram of the precision intelligent casting equipment for the multi-way valve body of the thermal management system of new energy vehicles according to an embodiment of the present invention.

[0026] On one hand, the precision intelligent casting method for the multi-way valve body of thermal management in new energy vehicles according to embodiments of the present invention includes: Step S1: After preheating the mold to 250-300℃ (preferably 280℃), install it on a low-pressure casting machine. The mold will be refined (to ensure a hydrogen content ≤0.15ml / 100g). The A356 aluminum alloy molten metal (Al) is held at 720±10℃; the low-pressure casting machine is started, and the molten metal is smoothly filled into the mold cavity along the riser pipe at a pressure increase rate of 0.01-0.02MPa / s (preferably 0.015MPa / s); the filling pressure is controlled at 0.03-0.05MPa (preferably 0.04MPa), and the filling time is adjusted to 10-15s (preferably 12s) to ensure that the molten metal fills the cavity in a laminar flow state; after filling, the pressure holding stage begins. Based on the wall thickness at the hot spot of the casting and / or the filling pressure, a preset pressure holding pressure and a preset pressure holding time are set: the preset pressure holding pressure is set to 1.4-1.6 times the filling pressure, preferably 1.5 times the filling pressure (i.e., when the filling pressure is 0.04MPa, the preset pressure holding pressure is set to 0.06MPa); the preset pressure holding time (T, unit: s) can be calculated using the formula T= The calculation involves K×H, where K is an empirical coefficient ranging from 3 to 8 s / mm, with K=5 s / mm being preferred in this embodiment; H is the wall thickness at the hot spot of the casting. For example, for a casting with a wall thickness H=8mm at the hot spot in this embodiment, the initial preset holding time is calculated to be 40 seconds. During the holding process of the low-pressure casting machine with the preset holding pressure and preset holding time, the flow channel pressure drop characterization value of the casting is determined based on the casting pressure of the mold cavity corresponding to the end of each flow channel of the casting. Step S2: Determine the pressure holding state of the casting based on the pressure drop characterization value of the flow channel, wherein the pressure holding state includes normal pressure holding state, critical pressure holding state and abnormal pressure holding state; Step S3: For castings in critical pressure holding state, the pressure holding state of the casting is determined a second time based on the acoustic emission activity value of the casting, wherein the acoustic emission activity value is determined based on the acoustic emission signal at the end of each flow channel of the casting. Step S4: Based on the pressure-temperature response deviation index of the casting, the causes of the casting in abnormal pressure holding state are classified, including invasive porosity abnormality and shrinkage abnormality. Step S5: Execute the corresponding control strategy according to the cause of the abnormal pressure holding state of the casting, wherein the control strategy is to issue an alarm or increase the preset pressure holding time. Step S6: After the pressure holding process is completed, control the low-pressure casting machine to reduce the pressure to atmospheric pressure at a depressurization rate of 0.01MPa / s, and then open the mold to obtain the casting of the multi-way valve body for thermal management of new energy vehicles.

[0027] Specifically, this embodiment takes a new energy vehicle thermal management multi-way valve body with 6 flow channels as an example for illustration; the valve body material is A356 aluminum alloy, the maximum outline size of the casting is 180mm×150mm×120mm, the wall thickness is 3-8mm, and the main gate is set at the center of the bottom of the valve body.

[0028] Specifically, the process of determining the holding pressure state of the casting based on the flow channel pressure drop characterization value includes: The pressure drop characterization value of the flow channel is compared with the first preset pressure drop characterization value of 0.08 and the second preset pressure drop characterization value of 0.15. Based on the result that the pressure drop characterization value of the flow channel is less than the first preset pressure drop characterization value of the flow channel, it is determined that the casting is in a normal pressure holding state; Based on the result that the flow channel pressure drop characterization value is greater than or equal to the first preset flow channel pressure drop characterization value and less than the second preset flow channel pressure drop characterization value, it is determined that the casting is in a critical pressure holding state. Based on the result that the flow channel pressure drop characterization value is greater than or equal to the second preset flow channel pressure drop characterization value, it is determined that the casting is in an abnormal pressure holding state. Wherein, the first preset flow channel pressure drop characterization value is less than the second preset flow channel pressure drop characterization value.

[0029] Specifically, the flow channel pressure drop characterization value quantifies the dispersion of the pressure decay rate of each flow channel. This value directly reflects the synchronicity of the solidification and feeding processes in each region of the casting (corresponding to different flow channels) during the pressure holding stage. When the flow channel pressure drop characterization value is less than the first preset threshold, it indicates that the dispersion of each flow channel is low, the solidification and shrinkage processes of the casting in each flow channel are basically synchronized, the pressure holding pressure can be evenly transmitted to the end of each flow channel, the feeding channels of all flow channels remain unobstructed, there is no feeding blockage caused by local premature solidification, and there is no pressure transmission abnormality caused by gas interference. At this time, the casting completes solidification and forming in a uniform pressure field, the internal structure is dense, and the defect risk is the lowest. Therefore, it is judged as a normal pressure holding state, and there is no need to trigger subsequent judgment steps. When the flow channel pressure drop characterization value is between the first preset threshold and the second preset threshold, it indicates that the pressure decay rate of each flow channel has a certain degree of dispersion, but the deviation is not enough to be confirmed as a serious abnormality. It may be that local thin-walled areas begin to solidify prematurely, or the feeding channels are slightly blocked. The deviation could also stem from a slight disturbance in pressure transmission caused by the local accumulation of trace gases. However, this deviation could simply be a normal process fluctuation, such as a slight fluctuation in the temperature of molten aluminum, resulting in a temporary phenomenon that does not necessarily indicate the formation of defects. Deeming this state abnormal would lead to frequent false alarms and excessive process intervention. Simply classifying it as normal might miss the optimal intervention window for early, minor defects. Therefore, this ambiguous zone between obvious normality and obvious abnormality is defined as the critical pressure holding state, and a secondary acoustic emission judgment is introduced. When the pressure drop value of the flow channel is greater than or equal to the second preset threshold, it indicates that the dispersion of the pressure decay rate of each flow channel has exceeded the normal fluctuation range. This could be because the feeding channel of the flow channel has been completely blocked by pre-solidified metal, preventing effective pressure transmission at the end of the flow channel; or it could be due to a large amount of gas accumulating locally, causing overall interference to the pressure field. Regardless of the specific cause, defects have likely formed inside the casting at this point, and the cause identification process must be initiated immediately to determine the specific type of defect and take corresponding control measures.

[0030] Specifically, the first preset flow channel pressure drop characterization value ranges from [0.05, 0.10], and the second preset flow channel pressure drop characterization value ranges from [0.12, 0.17]. Preferably, the first preset flow channel pressure drop characterization value is 0.08, and the second preset flow channel pressure drop characterization value is 0.15. Full-process data collection and verification were conducted on a total of 1200 A356 aluminum alloy multi-way valve bodies produced in different batches and using different molds. All castings underwent 100% X-ray flaw detection and were clearly marked with their pass / defect status. The following objective patterns were statistically derived: Among the 850 castings that passed the flaw detection test, the flow channel pressure drop characterization value ranged from 0.02 to 0.11. Among them, 95% of the qualified castings had a flow channel pressure drop characterization value ≤ 0.08, and 99% of the qualified castings had a flow channel pressure drop characterization value ≤ 0.10. Among the 350 castings confirmed to have internal defects (shrinkage porosity, air porosity) through flaw detection, the flow channel pressure drop characterization values ​​ranged from 0.11 to 0.42. 95% of the defective castings had flow channel pressure drop characterization values ​​≥0.15, and 99% of the defective castings had flow channel pressure drop characterization values ​​≥0.12.

[0031] Based on the above statistical results, the upper limit of the first preset flow channel pressure drop characterization value is set to 0.10 (covering 99% of qualified castings), and the lower limit is set to 0.05 (ensuring minimum judgment sensitivity); the lower limit of the second preset flow channel pressure drop characterization value is set to 0.12 (covering 99% of defective castings), and the upper limit is set to 0.17 (avoiding oversensitivity leading to misjudgment), forming a general value range. The preferred values ​​of 0.08 and 0.15 correspond to the statistical quantiles with a 95% confidence level. However, the above values ​​are not limited to these, and those skilled in the art can adjust the above values ​​according to actual needs. It is understood that for multi-way valve bodies of different materials and structural dimensions, those skilled in the art can, according to the method described in this specification, collect samples from normal production batches and batches confirmed to have defects through subsequent testing, and redetermine the corresponding preset thresholds according to the above statistical method. In this process, the statistical samples must ensure that they cover multiple sets of normal process fluctuations and typical defect patterns to ensure the representativeness and reliability of the determined thresholds. When using a thermal management multi-way valve body with the same or similar materials and structure as the embodiments of this invention, the above value range and preferred values ​​can be directly applied.

[0032] Specifically, the process of obtaining the flow channel pressure drop characterization value includes: In this embodiment, the multi-way valve body has 6 independent flow channels, and micro pressure sensors (high temperature melt micro pressure sensors in this embodiment) are pre-embedded in the corresponding mold cavity wall. The probes of the micro pressure sensors are flush with the inner wall of the mold cavity to avoid interfering with the flow of molten metal and the forming of the casting. After the low-pressure casting machine completes the filling and enters the pressure holding stage, the casting pressure signals at the ends of the six flow channels are collected synchronously at a fixed sampling frequency of 100Hz. The collection continues until the end of the pressure holding stage, and the casting pressure-time series of the six flow channels are obtained respectively, denoted as P1(t), P2(t), P3(t), P4(t), P5(t), and P6(t), where t is the pressure holding time. The Savitzky-Golay filtering method was used to smooth and denoise the casting pressure-time series of these 6 channels. The filtering window size was set to 5 data points and the polynomial order was set to 2. The purpose was to remove high-frequency noise caused by electromagnetic interference and equipment vibration in the industrial environment, while preserving the overall trend of pressure decay, and to obtain the denoised casting pressure-time series of the 6 channels. In this embodiment, the preset pressure holding window is set from the 5th to the 25th second of the pressure holding stage (i.e., the preset pressure holding window duration Δt = 20 seconds). This window avoids the pressure fluctuation stage at the beginning of the pressure holding period and the pressure instability stage at the end of the pressure holding period, and can accurately reflect the pressure decay law during the solidification process of the casting. For the denoised casting pressure-time series of each flow channel, the pressure value P at the beginning of the preset pressure holding window (the 5th second) is extracted. i，start The pressure value P at the end time (25s) i，end (i=1, 2, ..., 6), according to formula k i =(P i，start -P i，end The pressure decay rate k1, k2, k3, k4, k5, and k6 of each flow channel within the preset pressure holding window are calculated using Δt. The pressure decay rate directly reflects the difference in the rate of solidification shrinkage of the casting within each flow channel. The ratio of the standard deviation to the average value of the pressure decay rate is denoted as the pressure drop characteristic value of the flow channel.

[0033] Specifically, for castings in a critical holding pressure state, the process of determining the holding pressure state of the casting a second time based on the acoustic emission activity value of the casting includes: If the acoustic emission activity value is less than the preset acoustic emission activity value of 0.010V / s, the casting is determined to be in a normal pressure holding state. If the acoustic emission activity value is greater than or equal to the preset acoustic emission activity value, the casting is determined to be in an abnormal pressure holding state.

[0034] Specifically, when the pressure drop value of the flow channel is between the first and second preset thresholds, the casting pressure parameters alone cannot distinguish between early defect precursors such as slight blockage of the local feeding channel or trace gas interference and normal process fluctuations, which poses a risk of misjudgment. When the acoustic emission activity value is greater than or equal to the preset threshold, it indicates that a non-negligible active defect process is occurring inside the casting, thus upgrading the unconfirmed "critical suspicious" state to an "abnormal confirmed" state. Conversely, if the acoustic emission activity value is less than the preset acoustic emission activity value, it indicates that the slight deviation of the macroscopic pressure is only caused by process fluctuations and no internal defects are formed, thus downgrading the critical state to a normal state, effectively avoiding false alarms, and improving the accuracy and robustness of the pressure holding state determination.

[0035] Specifically, the preset acoustic emission activity value is 0.010 V / s. Production data and corresponding complete acoustic emission signals of 500 mold castings determined to be in the "critical holding pressure state" are continuously collected and recorded. All castings in the critical state undergo 100% X-ray non-destructive testing to clearly define their final internal quality status as either actually qualified or actually defective. For each critical state casting with calibrated quality, the acoustic emission activity value calculated during the preset holding pressure window (5s to 25s) during production is traced back. The acoustic emission activity values ​​of actually qualified castings are mainly distributed between 0.002 V / s and 0.012 V / s, with a 99th percentile value of 0.010 V / s. More than 90% of the castings with actual defects have acoustic emission activity values ​​greater than 0.010 V / s. Therefore, the preset acoustic emission activity value is set to 0.010 V / s. However, the above value is not limited to this; those skilled in the art can adjust the above value according to actual needs.

[0036] Specifically, the process of obtaining the acoustic emission activity value includes: At the position of the outer surface of the mold cavity corresponding to the end of each independent flow channel of the multi-way valve body, a broadband acoustic emission sensor is pre-embedded (in this embodiment, a piezoelectric ceramic sensor is used, with a frequency response range of 20kHz-2MHz and a sensitivity greater than or equal to 95dB. It is in close contact with the mold surface through a high-temperature coupling agent such as a silicone grease-based coupling agent to ensure good acoustic coupling). When the pressure drop characterization value of the flow channel is determined to be in the critical range, the acoustic emission sensors corresponding to the ends of each flow channel are synchronously collected at a sampling frequency of 2MHz. The collection time is from the 5th to the 25th second of the pressure holding phase (completely synchronized with the preset pressure holding window) to obtain the original acoustic emission signals of the ends of the 6 flow channels. The original acoustic emission signal is subjected to FIR bandpass filtering to retain the effective signal in the 50kHz-800kHz frequency band, thus obtaining the filtered acoustic emission signal. A 20-second acoustic emission signal that is perfectly synchronized with the preset pressure holding window (5s to 25s) is extracted. The root mean square (RMS) amplitude of the acoustic emission signal of each channel during this time period is calculated. The maximum RMS amplitude among the 6 channels is taken, and the acoustic emission activity value is calculated according to the following formula: A=TRMSmax / T; where A is the acoustic emission activity value (unit: V / s), RMSmax is the maximum RMS amplitude (unit: V) of the acoustic emission signal of several channels (6 in this embodiment), and T is the preset time window duration (T=20s in this embodiment).

[0037] Specifically, the process of classifying the causes of castings in abnormal holding pressure states based on the pressure-temperature response deviation index of the castings includes: When the pressure-temperature response deviation index is less than the preset pressure-temperature response deviation index of 2.0, the causes of invasive porosity abnormalities are classified. When the pressure-temperature response deviation index is greater than or equal to the preset pressure-temperature response deviation index, the cause of shrinkage abnormality is classified.

[0038] Specifically, the preset pressure-temperature response deviation index was set to 2.0. Statistical analysis was conducted on castings with internal defects confirmed by X-ray inspection out of a cumulative total of 350 molds. Further confirmation through airtightness testing and cross-sectional analysis revealed that 140 molds exhibited invasive porosity abnormalities, and 210 molds exhibited shrinkage malformation abnormalities. Statistical analysis showed that the pressure-temperature response deviation index for castings with invasive porosity abnormalities ranged from 1.0 to 2.2, with a mean of 1.45 and a standard deviation of 0.25; while the index for castings with shrinkage malformation abnormalities ranged from 1.8 to 5.5, with a mean of 3.20 and a standard deviation of 0.68. There was a slight overlap in the pressure-temperature response deviation indices between the two types of defects within the 1.8-2.2 range. To further improve the distinction between the two types of defects, the median value of the pressure-temperature response deviation index of the invasive porosity abnormal sample (approximately 1.93) and the 5th percentile value of the pressure-temperature response deviation index of the shrinkage abnormal sample (approximately 2.08) was taken, and the preset pressure-temperature response deviation index was set to 2.0.

[0039] Specifically, after the casting is initially identified as being in an abnormal holding pressure state by the pressure drop characterization value of the flow channel and the acoustic emission activity value at the critical holding pressure state, the interference of normal process fluctuations has been eliminated, and the presence of active defects inside the casting has been confirmed. However, the causes of the abnormal state still include two possibilities: shrinkage porosity and invasive porosity. The two are completely different in terms of control strategies and must be further distinguished at the causal level. Shrinkage porosity originates from the blockage of local feeding channels, which only affects specific flow channels. This is manifested by the pressure-temperature response coefficient of the flow channel deviating significantly from that of other flow channels, resulting in a significant increase in the ratio of the maximum to minimum values ​​of the response coefficients of each flow channel. Invasive porosity originates from the overall interference of high-pressure gas in the mold cavity, which has a systematic impact on the pressure-temperature response of all flow channels. The response coefficients of each flow channel are basically the same, and the ratio of the maximum to minimum values ​​approaches 1. The ratio of the maximum to minimum values ​​of the pressure-temperature response coefficients of each flow channel is determined as the pressure-temperature response deviation index. By comparing the pressure-temperature response deviation index with a preset threshold, the causes of the two types of defects can be distinguished in real time during the holding pressure stage. Thus, the flow channel pressure drop characterization value, acoustic emission activity value, and pressure-temperature response deviation index constitute a progressive judgment system that progresses from macroscopic pressure synchronicity screening to microscopic acoustic emission cross-verification and then to pressure-temperature synergistic response cause identification. This system advances step by step and converges gradually, ultimately achieving accurate differentiation and differentiated control of defect types.

[0040] In this embodiment, the process of obtaining the pressure-temperature response deviation index includes: Miniature temperature sensors are pre-embedded in the mold cavity wall corresponding to the end of each independent flow channel of the multi-way valve body. In this embodiment, K-type thermocouples are pre-embedded as miniature temperature sensors at the positions adjacent to the ends of each flow channel where miniature pressure sensors have been pre-embedded. The temperature measuring end of the thermocouple is 1-2 mm away from the inner wall of the mold cavity and is arranged adjacent to the miniature pressure sensor (the center distance between the miniature temperature sensor and the miniature pressure sensor is 10 mm), ensuring that both measure the physical state of the same flow channel end position. At the same 100Hz sampling frequency as the aforementioned casting pressure signal acquisition, within the preset pressure holding window, casting pressure signals and mold temperature signals from the ends of six flow channels are simultaneously acquired, resulting in casting pressure-time series P1(t), P2(t), P3(t), P4(t), P5(t), P6(t) for the six flow channels and mold temperature-time series T1(t), T2(t), ..., T6(t). The acquisition of the casting pressure signal and mold temperature signal is kept completely time-synchronized to ensure the accuracy of subsequent pressure-temperature response coefficient calculations.

[0041] The same Savitzky-Golay filtering method as described above was used to smooth and denoise the mold temperature-time series of the six flow channels. The filtering window size was set to 5 data points, and the polynomial order was set to 2, resulting in the denoised mold temperature-time series of the six flow channels. The denoising results of the casting pressure-time series were already completed during the acquisition of the flow channel pressure drop characterization values, and are directly used here. In this embodiment, the preset pressure holding window is set from the 5th to the 25th second of the pressure holding phase (i.e., the preset pressure holding window duration Δt = 20 seconds), which is completely consistent with the window used in the aforementioned calculation of the flow channel pressure drop characterization value. For each flow channel after noise reduction, the pressure value P at the start time of the preset pressure holding window (the 5th second) is extracted. i，start and temperature value T i，start And the pressure value P at the end time (25s). i，end and temperature value T i，end (i=1, 2, ..., 6), calculate the pressure decay rate and mold temperature drop rate for each flow channel according to the following formula: Pressure decay rate ki=(P i，start -P i，end ) / Δt; mold temperature drop rate v i =(T i，start -T i，end ) / Δt; Subsequently, the pressure-temperature response coefficient for each flow channel was calculated: Pressure-temperature response coefficient R i =k i / vi ; A total of 6 pressure-temperature response coefficients R1, R2, ..., R6 were obtained; Among all pressure-temperature response coefficients R1, R2, ..., R6, determine their maximum and minimum values, and determine the ratio of the maximum value to the minimum value as the pressure-temperature response deviation index.

[0042] Specifically, the process of implementing corresponding control strategies based on the causes of the abnormal pressure holding state of the casting includes: An alarm is issued when the cause of the casting in the abnormal pressure holding state is determined to be an invasive porosity abnormality. When the cause of the casting in the abnormal holding pressure state is determined to be abnormal shrinkage porosity, the preset holding pressure time is increased according to the ratio of the pressure-temperature response deviation index to the preset pressure-temperature response deviation index.

[0043] Specifically, invasive porosity and shrinkage porosity have fundamentally different formation mechanisms. Invasive porosity originates from the overall interference of high-pressure gas within the mold cavity. Its formation is weakly correlated with solidification parameters such as holding pressure and holding time. Simply extending the holding time cannot fundamentally eliminate the gas source; on the contrary, the continuous high pressure may cause the gas to further penetrate into the casting, exacerbating the defect. In this case, an alarm should be issued to guide operators to check the gas source, such as the mold venting system, the gas emission from the core, or the gas content in the molten metal, in order to solve the invasive porosity problem at its root. Abnormal shrinkage porosity originates from insufficient feeding due to blockage of local feeding channels. The core problem is that the feeding driving force is interrupted before solidification is complete. In this case, increasing the holding time can delay the closing time of the feeding channels, allowing the holding pressure to continue acting on the solidifying casting, thereby effectively filling the tiny pores between dendrites and improving the internal density of the casting.

[0044] Specifically, the increase in the preset holding time is positively correlated with the pressure-temperature response deviation comparison value. The positive correlation can be linear or nonlinear. The slope of the linear positive correlation is not specifically limited. It can be understood that the larger the pressure-temperature response deviation comparison value, the greater the increase in the preset holding time. The pressure-temperature response deviation comparison value is the ratio of the pressure-temperature response deviation index to the preset pressure-temperature response deviation index.

[0045] On the other hand, the embodiments of the present invention are applicable to precision intelligent casting equipment for the above-described precision intelligent casting method, including: Low-pressure casting machine is used to fill the mold cavity of multi-way valve body with molten metal from bottom to top along the riser pipe under the drive of compressed air, and to hold the filling casting under pressure to solidify and form it. The data acquisition module, which is connected to the low-pressure casting machine, includes a casting pressure acquisition unit set at the mold cavity corresponding to the end of each flow channel of the casting, an acoustic emission signal acquisition unit set on the outer surface of the mold cavity, and a mold temperature acquisition unit adjacent to the casting pressure acquisition unit. The control module is connected to the data acquisition module and the low-pressure casting machine, and includes a function to determine the holding pressure state of the casting based on the flow channel pressure drop characterization value of the casting, a function to determine the holding pressure state of the casting in the critical holding pressure state based on the acoustic emission activity value of the casting, and a function to classify the causes of the casting in the abnormal holding pressure state based on the pressure-temperature response deviation index of the casting. An adjustment module, connected to the control module and the low-pressure casting machine, is used to execute a corresponding control strategy based on the cause of the abnormal pressure holding state of the casting. The control strategy is to issue an alarm or increase the preset pressure holding time.

[0046] Specifically, the specific structure of the control module and the adjustment module is not limited. They themselves and their units can be composed of logic components, including field-programmable components, computers or microprocessors in computers.

[0047] Specifically, the casting pressure acquisition unit is a miniature pressure sensor installed within the mold cavity wall at the end of each flow channel. In this embodiment, it is a high-temperature melt miniature pressure sensor, with its probe flush with the inner wall of the mold cavity to avoid interfering with the flow of molten metal and the forming of the casting, and directly measuring the casting pressure of the casting during the holding pressure stage. The acoustic emission signal acquisition unit is a broadband acoustic emission sensor installed on the outer surface of the mold cavity, corresponding to the position at the end of each flow channel. In this embodiment, the acoustic emission sensor is a piezoelectric ceramic sensor. The mold temperature acquisition unit is a miniature temperature sensor installed within the mold cavity wall, adjacent to the casting pressure acquisition unit. In this embodiment, it is a K-type thermocouple, with its measuring end 1-2 mm from the inner wall of the mold cavity, used to obtain the mold temperature at the corresponding flow channel end position during the holding pressure stage.

[0048] Specifically, the low-pressure casting machine is a conventional low-pressure casting machine suitable for the production of multi-way valve bodies for thermal management in new energy vehicles, and its basic structure and working principle are well known to those skilled in the art. In this embodiment, the low-pressure casting machine mainly includes a holding furnace, a riser pipe, a mold, an air supply system, and a main frame. The holding furnace is used to contain refined A356 aluminum alloy liquid and maintain the temperature of the aluminum liquid at 720±10℃ during the casting process. The lower end of the riser pipe is immersed in the aluminum liquid in the holding furnace, and the upper end is connected to the mold gate, forming a channel for the aluminum liquid to enter the mold cavity from the holding furnace. The mold includes an upper mold and a lower mold, which, after being closed, form a cavity corresponding to the shape and internal flow channels of the multi-way valve body. The air supply system includes a compressed air source, an air inlet pipe, an exhaust valve, and a pressure control valve, used to introduce dry compressed air into the holding furnace, precisely controlling the air pressure inside the furnace to drive the aluminum liquid to rise along the riser pipe and complete the filling and pressure holding process.

[0049] Specifically, during the operation of the low-pressure casting machine, the gas supply system introduces compressed air into the holding furnace, increasing the furnace pressure and driving the molten aluminum to smoothly fill the mold cavity from bottom to top along the riser pipe. After filling, the gas supply system continues to maintain the furnace pressure, holding the casting in the cavity under pressure to solidify and form it. After the pressure holding is completed, the gas supply system releases pressure through the exhaust valve, and then the mold is opened to remove the multi-port valve body casting. Specifically, to realize the precision intelligent casting method of the present invention, the low-pressure casting machine is also equipped with interfaces for the data acquisition module, the control module, and the adjustment module. Sensor mounting positions are pre-reserved within the mold cavity for installing pressure and temperature sensors from the data acquisition module. The pressure control valve of its air supply system receives and executes instructions from the adjustment module, adjusting the holding pressure duration by changing the opening degree of the pressure control valve. The control system of the low-pressure casting machine is connected to the control module via an industrial bus (such as a CAN bus or Ethernet), feeding back real-time operating status parameters such as the current holding pressure, holding stage timing, and the valve opening degree of the pressure control valve of the air supply system.

[0050] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A precision intelligent casting method for a multi-way valve body for thermal management in new energy vehicles, characterized in that, include: During the pressure holding stage of low-pressure casting, the low-pressure casting machine holds the pressure at a preset pressure for a preset holding time. Based on the casting pressure of the mold cavity corresponding to the end of each flow channel of the casting, the flow channel pressure drop characterization value of the casting is determined. The pressure holding state of the casting is determined based on the pressure drop characterization value of the flow channel, wherein the pressure holding state includes normal pressure holding state, critical pressure holding state and abnormal pressure holding state; For castings in a critical holding pressure state, the holding pressure state of the casting is determined a second time based on the acoustic emission activity value of the casting, wherein the acoustic emission activity value is determined based on the acoustic emission signal at the end of each flow channel of the casting; The causes of castings in abnormal holding pressure are classified based on the pressure-temperature response deviation index of the castings. The causes include invasive porosity abnormalities and shrinkage abnormalities. According to the cause of the abnormal pressure holding state of the casting, a corresponding control strategy is executed, wherein the control strategy is to issue an alarm or increase the preset pressure holding time. The casting is depressurized and the mold is opened to obtain a multi-way valve body casting.

2. The precision intelligent casting method for the multi-way valve body of thermal management in new energy vehicles according to claim 1, characterized in that, The process of determining the holding pressure state of the casting based on the flow channel pressure drop characterization value includes: The pressure drop characterization value of the flow channel is compared with the first preset pressure drop characterization value and the second preset pressure drop characterization value, respectively; Based on the result that the pressure drop characterization value of the flow channel is less than the first preset pressure drop characterization value of the flow channel, it is determined that the casting is in a normal pressure holding state; Based on the result that the flow channel pressure drop characterization value is greater than or equal to the first preset flow channel pressure drop characterization value and less than the second preset flow channel pressure drop characterization value, it is determined that the casting is in a critical pressure holding state. Based on the result that the flow channel pressure drop characterization value is greater than or equal to the second preset flow channel pressure drop characterization value, it is determined that the casting is in an abnormal pressure holding state. Wherein, the first preset flow channel pressure drop characterization value is less than the second preset flow channel pressure drop characterization value.

3. The precision intelligent casting method for the multi-way valve body of thermal management in new energy vehicles according to claim 2, characterized in that, The process of obtaining the flow channel pressure drop characterization value includes: The casting pressure of the mold cavity corresponding to the end of each flow channel of the casting is obtained, and the casting pressure-time series of each flow channel is obtained. Based on the casting pressure-time series of each flow channel, the pressure decay rate of each flow channel within the preset pressure holding window is determined. Calculate the average and standard deviation of the pressure decay rate for all the flow channels, and determine the ratio of the standard deviation to the average as the pressure drop characteristic value of the flow channel; The term "runner end" refers to the cavity position at the end of the runner that is furthest from the main gate of the mold.

4. The precision intelligent casting method for the multi-way valve body of thermal management in new energy vehicles according to claim 2, characterized in that, For castings in a critical holding pressure state, the process of secondary determination of the holding pressure state of the casting based on the acoustic emission activity value of the casting includes: If the acoustic emission activity value is less than the preset acoustic emission activity value, the casting is determined to be in a normal pressure holding state. If the acoustic emission activity value is greater than or equal to the preset acoustic emission activity value, the casting is determined to be in an abnormal pressure holding state.

5. The precision intelligent casting method for the multi-way valve body of thermal management in new energy vehicles according to claim 4, characterized in that, The process of obtaining the acoustic emission activity value includes: Acquire acoustic emission signals from the ends of each flow channel of the casting; The acoustic emission signal is bandpass filtered to retain the acoustic emission signal in a preset frequency band; Calculate the root mean square amplitude of all acoustic emission signals in the preset frequency band within a preset time window, and determine the ratio of the maximum root mean square amplitude to the duration of the preset time window as the acoustic emission activity value.

6. The precision intelligent casting method for the multi-way valve body of thermal management in new energy vehicles according to claim 2, characterized in that, The process of classifying the causes of castings in abnormal holding pressure states based on the pressure-temperature response deviation index of the castings includes: When the pressure-temperature response deviation index is less than the preset pressure-temperature response deviation index, the causes of invasive porosity abnormalities are classified. When the pressure-temperature response deviation index is greater than or equal to the preset pressure-temperature response deviation index, the cause of shrinkage abnormality is classified.

7. The precision intelligent casting method for the multi-way valve body of thermal management in new energy vehicles according to claim 6, characterized in that, The process of obtaining the pressure-temperature response deviation index includes: The casting pressure and mold temperature at the end of each flow channel of the casting are obtained, and the casting pressure-time series and mold temperature-time series of each flow channel are obtained respectively. Based on the casting pressure-time series and mold temperature-time series of each flow channel, the pressure decay rate and mold temperature drop rate of each flow channel within the preset holding pressure window are determined. The pressure-temperature response coefficient of each flow channel is determined based on the ratio of the pressure decay rate to the mold temperature drop rate of each flow channel. Based on the pressure-temperature response coefficient of each flow channel, the maximum and minimum values ​​of the pressure-temperature response coefficient of each flow channel are determined, and the ratio of the maximum value to the minimum value is determined as the pressure-temperature response deviation index.

8. The precision intelligent casting method for the multi-way valve body of thermal management in new energy vehicles according to claim 7, characterized in that, The process of implementing corresponding control strategies based on the causes of the abnormal pressure holding state of the casting includes: An alarm is issued when the cause of the casting in the abnormal pressure holding state is determined to be an invasive porosity abnormality. When the cause of the casting in the abnormal holding pressure state is determined to be abnormal shrinkage porosity, the preset holding pressure time is increased according to the ratio of the pressure-temperature response deviation index to the preset pressure-temperature response deviation index.

9. The precision intelligent casting method for the multi-way valve body of thermal management in new energy vehicles according to claim 8, characterized in that, The increase in the preset pressure holding time is positively correlated with the pressure-temperature response deviation comparison value, wherein the pressure-temperature response deviation comparison value is the ratio of the pressure-temperature response deviation index to the preset pressure-temperature response deviation index.

10. A precision intelligent casting device applicable to the precision intelligent casting method according to any one of claims 1-9, characterized in that, include: Low-pressure casting machine is used to fill the mold cavity of multi-way valve body with molten metal from bottom to top along the riser pipe under the drive of compressed air, and to hold the filling casting under pressure to solidify and form it. The data acquisition module, which is connected to the low-pressure casting machine, includes a casting pressure acquisition unit set at the mold cavity corresponding to the end of each flow channel of the casting, an acoustic emission signal acquisition unit set on the outer surface of the mold cavity, and a mold temperature acquisition unit adjacent to the casting pressure acquisition unit. The control module is connected to the data acquisition module and the low-pressure casting machine, and includes a function to determine the holding pressure state of the casting based on the flow channel pressure drop characterization value of the casting, a function to determine the holding pressure state of the casting in the critical holding pressure state based on the acoustic emission activity value of the casting, and a function to classify the causes of the casting in the abnormal holding pressure state based on the pressure-temperature response deviation index of the casting. An adjustment module, connected to the control module and the low-pressure casting machine, executes a corresponding control strategy based on the cause of the abnormal pressure holding state of the casting. The control strategy is to issue an alarm or increase the preset pressure holding time.

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