Multi-pass distributed liquid nitrogen jet cooling system and method for hot forming

Abstract

The present disclosure relates to a multi-channel distributed liquid nitrogen jet cooling system and method for hot forming, relating to the field of forming technology. The system comprises a liquid nitrogen storage and pressure stabilizing module, a plurality of flexible standard cooling modules and a control module. The method divides and extracts targeted cooling feature points based on the workpiece thinning rate, realizes accurate mapping of the thinning area and the flexible standard cooling module, and dynamically triggers jet cooling of the corresponding channel according to the thinning rate change curve; the control module calculates the flash evaporation degree based on real-time pipeline temperature and pressure data, dynamically compensates the electric regulating valve opening, and maintains the actual liquid cooling capacity stable when the system undergoes phase change. The system can automatically merge channels based on the spatial and temporal characteristic differences of each region, and flexibly match different cooling conditions such as dynamic closed loop, periodic interruption or fixed parameter static. Through zoning, grading and multi-condition coordinated control, the problems of uneven cooling of complex components and multi-channel parallel interference are solved, and efficient, accurate and low-cost application of liquid nitrogen jet is realized.

Description

Technical Field

[0001] This disclosure relates to the field of thermoforming technology, specifically to the field of hot stamping cooling technology, and particularly to a multi-channel distributed liquid nitrogen jet cooling system and method for thermoforming. Background Technology

[0002] In hot stamping processes, the thinning rate varies greatly in different areas of complex components. Uneven cooling may occur during the hot forming process of complex components, resulting in poor quality of the formed components. Summary of the Invention

[0003] According to a first aspect of the present disclosure, a multi-channel distributed liquid nitrogen jet cooling system for thermoforming is provided, comprising: a liquid nitrogen storage and pressure stabilization module for storing liquid nitrogen and adjusting the liquid nitrogen output pressure; multiple flexible standard cooling modules, the multiple flexible standard cooling modules being connected in parallel on a main liquid supply pipe and in series with the liquid nitrogen storage and pressure stabilization module, each flexible standard cooling module including a liquid nitrogen output pipe, and a channel regulating valve group and a channel sensing element disposed on the liquid nitrogen output pipe; wherein, the liquid nitrogen output pipe is connected to the cooling channel of the thermoforming mold, different cooling channels and different numbers of jet holes on the cooling channels correspond to different thinning areas of the part to be formed, and each flexible standard cooling module... The module corresponds to one thinning region or a merged region of multiple thinning regions; the control module is connected to multiple flexible standard cooling modules, which are used to adjust the corresponding flexible standard cooling modules according to the cooling conditions selected for each thinning region and / or each merged region, based on the cooling start time and liquid nitrogen output pressure of each thinning region and / or each merged region under different cooling conditions, so as to control the liquid nitrogen jet flow rate during the cooling process; it is also used to determine the liquid nitrogen gas mass fraction based on the data of the passage sensing element, and when a gas-liquid phase change occurs in the liquid nitrogen output pipeline, it adjusts the passage regulating valve group according to the liquid nitrogen gas mass fraction to regulate the liquid nitrogen flow rate of the liquid nitrogen output pipeline.

[0004] In some embodiments of this disclosure, the liquid nitrogen storage and pressure stabilization module includes: a liquid nitrogen storage tank; a pressure regulating valve group connected to the output end of the liquid nitrogen storage tank for regulating the liquid nitrogen output pressure of the liquid nitrogen storage tank; a pressure sensor installed on the gas phase valve of the liquid nitrogen storage tank for monitoring the liquid nitrogen output pressure of the liquid nitrogen storage tank; and a flow regulating valve group including a check valve, a manual valve, a solenoid valve, and a regulating valve; the check valve is used to prevent liquid nitrogen backflow; the manual valve regulates the liquid nitrogen volume flow rate by adjusting the valve opening K; wherein, during the thermoforming cooling process, based on the pressure stabilization characteristics in the main liquid supply pipe and the check valves on each liquid nitrogen output pipe, when the liquid nitrogen volume flow rate of any liquid nitrogen output pipe is dynamically adjusted, the remaining parallel liquid nitrogen output pipes... The liquid nitrogen volumetric flow rate of the pipeline remains stable; the sensing elements in the pipeline include a flow measurement element, a pressure sensor, and a temperature sensor; the control module is connected to the solenoid valve, regulating valve, flow measurement element, pressure sensor, and temperature sensor of each flexible standard cooling module; the control module regulates the corresponding flexible standard cooling module by adjusting the solenoid valve and regulating valve, and determines the liquid nitrogen gas mass fraction by using the data from the pressure sensor and temperature sensor after the pipeline is pre-cooled, so as to control the regulating valve to adjust the opening according to the amount of compensation, which is determined based on the liquid nitrogen gas mass fraction; the control module receives real-time feedback from the flow measurement element and adjusts the flow rate based on the target volumetric flow rate of each liquid nitrogen output pipeline. and / or the target average flow rate of each liquid nitrogen output line The output pulse signal controls the solenoid valve to achieve rapid on / off switching and intermittent cooling, and / or outputs a continuous analog signal to control the opening of the regulating valve to achieve continuous flow regulation; the control module realizes the opening and closing of each component in the flexible standard cooling module according to different working conditions.

[0005] According to a second aspect of the present disclosure, a multi-path distributed liquid nitrogen jet cooling method for thermoforming is proposed, executed by the multi-path distributed liquid nitrogen jet cooling system for thermoforming provided in the first aspect of the present disclosure, comprising: dividing the thermoformed sheet into thinning regions to determine n thinning regions of the thermoformed sheet, where n is a positive integer; at any time or time period during the thermoforming stamping process of the thermoformed sheet, selecting x feature points from the thinning regions, and determining the feature point with the smallest thickness among the x feature points as the targeted cooling feature point; the liquid nitrogen output pipeline in the flexible standard cooling module corresponding to the targeted cooling feature point at the time or time period is used to preferentially perform directional jet cooling on the targeted cooling feature point; and based on the average thinning rate of each thinning region... Curve of variation with total forming time t , g∈[1,n], the average thinning rate will reach the thinning rate threshold. The time is determined as the cooling start time t of the jet stream starting in the region where the targeted cooling feature point is located. gBased on the differences in cooling start time and liquid nitrogen volumetric flow rate requirements between different thinning regions, if the differences in cooling start time and / or volumetric flow rate requirements of at least two thinning regions meet preset conditions, then at least two thinning regions are merged into a merged region. The merged region is uniformly controlled by the same flexible standard cooling module, and the merged region has a unified cooling start time and volumetric flow rate. For each thinning region and / or each merged region, based on the thinning characteristics and process requirements of the thinning region and / or merged region in the thermoforming process, the corresponding cooling condition is selected for the flexible standard cooling module corresponding to the thinning region and / or merged region. The cooling conditions include: dynamic feedforward anti-thinning jet condition, multi-channel periodic pressure holding quenching condition, and fixed parameter batch static cooling condition. Based on the differences in cooling start time and / or volumetric flow rate requirements of each thinning region and / or each... The cooling conditions selected for the merging regions are determined by controlling the activation of the flexible standard cooling modules corresponding to each thinning region and / or each merging region based on the cooling start time of each thinning region and / or each merging region. During the hot forming stamping process, as the position of the targeted cooling feature point shifts, the opening and closing of the flexible standard cooling modules corresponding to each thinning region and / or each merging region are dynamically controlled under different cooling conditions. Specifically, when the position of the targeted cooling feature point exceeds the critical distance of the first jet hole corresponding to the current time or time period, causing a change in the matching relationship between the targeted cooling feature point and the first jet hole, the flexible standard cooling module corresponding to the first jet hole is dynamically controlled to close, and the flexible standard cooling module corresponding to the second jet hole corresponding to the targeted cooling feature point after the change is simultaneously controlled to open.

[0006] In some embodiments of this disclosure, the thermoformed sheet is divided into thinning regions to determine multiple thinning regions, including: dividing the thermoformed sheet into a grid to determine multiple grid cells of the thermoformed sheet, wherein the number of grid cells is X, and the x-th grid cell is denoted as u. x , x∈[1,X]; based on the initial thickness of each grid cell The actual thickness of the thermoformed part obtained after thermoforming of thermoformed sheet metal. Determine the thinning rate of each grid cell in the thermoformed part. :

[0007] (1)

[0008] Based on the thinning rate, the thermoformed sheet is divided into m continuous and independent cooling characteristic regions, denoted as I = {I1, I2, I3…I...} m-1 I m}, the average thinning rate of the i-th cooling feature region is expressed as , i∈[1,m], where the average thinning rate satisfies The cooling characteristic region is the thinning region, labeled I.j1 I j2 I j3 ...I j（n-1） I jn The average thinning rate meets the requirements. The cooling characteristic region is the non-thinning region, labeled I. f1 I f2 I f3 ...I f（m-n-1） I f（m-n） n thinning zones correspond to n liquid nitrogen output pipelines C = {C1, C2, C3...C...} n-1 C n}, The threshold value for thinning rate is m ≥ 2 and is a positive integer.

[0009] In some embodiments of this disclosure, the flexible standard cooling modules corresponding to each thinning region and / or each merging region are controlled to open based on the cooling start time corresponding to each thinning region and / or each merging region, including: determining the total system time lag advance based on the mechanical response time of the regulating valve and the liquid nitrogen pipeline transmission delay time.

[0010] (2)

[0011] in To regulate the mechanical response time of the valve, The liquid nitrogen pipeline transmission delay time; based on the total system time delay advance, the flow control valve group in the multi-path distributed liquid nitrogen jet cooling system is adjusted to advance the time delay; during the hot forming stamping process, in conjunction with valve C v -K characteristic curve, dynamically controls the valve opening degree K of the valve corresponding to the target area, so as to dynamically regulate the opening and closing of the flexible standard cooling module. The target area is any thinning area or any merging area.

[0012] In some embodiments of this disclosure, dynamically controlling the valve opening K of the valve corresponding to the target area includes: acquiring the material parameters of the thermoformed sheet, the jet parameters of each thinning region, and the mapping relationship between them and the heat transfer coefficient h.

[0013] (3)

[0014] The material parameters include at least the material type. Initial thickness Initial temperature of thermoformed sheet The jet parameters include at least the jet distance L and the jet flow rate Q; thermoforming simulation is performed with the goal of minimizing the thinning rate of the thermoformed part, and the heat transfer coefficient variation curve of each thinning region of the thermoformed sheet is obtained; the jet flow rate is determined based on the mapping relationship and the heat transfer coefficient variation curve. The instantaneous change curve; based on the jet flow rate The instantaneous change curve, combined with valve C v -K characteristic curve, determine valve opening degree K.

[0015] In some embodiments of this disclosure, merging at least two thinning regions into a merged region includes: based on any two thinning regions and Cooling start time and volumetric flow rate Calculate the jet initiation time difference between the two thinning regions respectively. Difference with volumetric flow rate ;like Less than the preset time threshold ,and Less than the preset flow threshold Then the two thinned regions and Merge, the cooling start time of the merged region is The volumetric flow rate of the merged region is .

[0016] In some embodiments of this disclosure, the selection of corresponding cooling conditions for the flexible standard cooling modules corresponding to the thinning region and / or merging region includes: when the target region is a critical thinning region where the rate of change of the thinning rate gradient exceeds a preset threshold during the forming process, a dynamic feedforward anti-thinning jet condition is selected for the target region, where the target region is any thinning region or merging region; wherein, the dynamic feedforward anti-thinning jet condition is: during the thermoforming process, only the regulating valve in the flexible standard cooling module is adjusted, and the check valve, manual valve, and solenoid valve in the flexible standard cooling module remain normally open; under the dynamic feedforward anti-thinning jet condition, the opening and closing of the flexible standard cooling modules corresponding to each thinning region and / or each merging region are dynamically controlled, including: before the jet is opened, the pipeline is pre-cooled by opening the valve in advance, and the inlet pressure of the liquid nitrogen output pipeline is collected in real time by the pressure sensor. and export pressure and the temperature collected in real time by the temperature sensor Calculate the initial predicted gas mass fraction without considering heat loss during transmission. :

[0017] (4)

[0018] in, For inlet pressure Specific enthalpy of saturated liquid nitrogen; export pressure Specific enthalpy of saturated liquid nitrogen; The latent heat of vaporization under outlet pressure is used; to compensate for the insufficient cooling capacity provided by liquid nitrogen vaporization, a flash evaporation compensation coefficient is determined. The jet flow rate Q obtained from the mapping relationship is compensated to Q based on the flash compensation coefficient. v :

[0019] (5)

[0020] According to inlet pressure and export pressure Calculate the voltage drop of the actual system ;

[0021] Calculate the critical pressure ratio coefficient of liquid :

[0022] (6)

[0023] in, This is the vapor pressure of liquid nitrogen at the current operating temperature. Given the thermodynamic critical pressure of liquid nitrogen; determine the limiting pressure drop caused by liquid blockage. :

[0024] (7)

[0025] in, The sum of the liquid pressure recovery coefficient of the valve equipped with fittings and the pipe geometry coefficient. For pipe geometry coefficients; calculate the required flow coefficient. :

[0026] (8)

[0027] in, It is a numerical constant. The actual density of liquid nitrogen, It is the density of pure water at 15.5℃ and the pressure drop. It is the actual system voltage drop. and ultimate pressure drop The smaller of the two; combined valve Characteristic curves are used to determine the valve opening K of the control valve; the target volumetric flow rate of each liquid nitrogen output pipeline is calculated. With actual volumetric flow rate Instantaneous flow deviation between Based on the basic valve opening degree K and the instantaneous flow deviation, the opening command of the control valve is adjusted in real time. :

[0028] (9)

[0029] in, These are the proportional, integral, and derivative gain coefficients of the control module; the actual volumetric flow rate after the opening command reaches the effective adjustment limit. Still unable to meet the target volumetric flow rate The demand for [something] leads to an increased pressure on entry points. For any thinning or merging region, once the actual jetting time reaches the target cooling duration, the valve in the corresponding flexible standard cooling module is closed to end the cooling of the thinning or merging region.

[0030] In some embodiments of this disclosure, selecting corresponding cooling conditions for the flexible standard cooling modules corresponding to the thinned regions and / or merged regions includes: when the target region has intermittent cooling requirements to maintain a specific cooling rate under constant pressure, selecting a multi-channel periodic pressure holding quenching condition for the target region, where the target region is any thinned region or merged region; wherein, the multi-channel periodic pressure holding quenching condition involves: adjusting the regulating valve and solenoid valve in the flexible standard cooling module during the pressure holding quenching process, while keeping the check valve and manual valve in the flexible standard cooling module normally open; under the multi-channel periodic pressure holding quenching condition, dynamically controlling the opening and closing of the flexible standard cooling modules corresponding to each thinned region and / or each merged region includes: calculating the compensated volumetric flow rate based on the pre-cooling experiment. Calculate the required flow coefficient Combined with the regulating valve Characteristic curves are used to determine the valve opening K of the regulating valve; during the pressure holding and quenching process, the target average flow rate of the liquid nitrogen output pipeline via the regulating valve is determined based on the required change in cooling capacity. Then, the target pulse ratio required by the solenoid valve is calculated:

[0031] (10)

[0032] During the periodic intermittent cooling process, based on the target average flow rate and actual volumetric flow rate Real-time update of the solenoid valve's real-time pulse ratio :

[0033] (11)

[0034] in, The gain coefficient is adjusted by integral feedback for flow error; a pulse signal at the target frequency is output to control the periodic on / off state of the solenoid valve.

[0035] In some embodiments of this disclosure, selecting corresponding cooling conditions for the flexible standard cooling modules corresponding to the thinning regions and / or merging regions includes: when the forming process enters the mass production stage or the thinning rate of the target region stabilizes, selecting a fixed-parameter batch static cooling condition for the target region, where the target region is any thinning region or merging region; wherein, the fixed-parameter batch static cooling condition involves: adjusting the manual valve and solenoid valve in the flexible standard cooling module, while keeping the check valve and regulating valve in the flexible standard cooling module normally open; under the fixed-parameter batch static cooling condition, dynamically controlling the opening and closing of the flexible standard cooling modules corresponding to each thinning region and / or each merging region includes: calculating the compensated volumetric flow rate based on the pre-cooling experiment during the thermoforming process. Calculate the required flow coefficient Combined with manual valve C v -K characteristic curve, and then determine the valve opening K of the manual valve; and set the jet stamping and pressure holding quenching time of the hot-formed sheet to control the precise opening and closing of the solenoid valve; and monitor the flow rate change during the hot forming process by a flow meter to adjust the valve opening K of the manual valve.

[0036] According to the multi-channel distributed liquid nitrogen jet cooling system for thermoforming proposed in this disclosure, multiple flexible standard cooling modules can be set up. Then, the control module can adjust the corresponding flexible standard cooling modules according to the cooling conditions selected by each thinning region and / or each merging region under different cooling conditions. This can realize the cooling rate requirements of different regions under different cooling conditions, achieve precise control of the cooling of different regions of complex components, improve the uniformity of cooling, and ensure that multiple flexible standard cooling modules are connected in parallel on a main liquid supply pipe and connected in series with a liquid nitrogen storage and pressure stabilization module. This can ensure that when the valve opening of any channel is dynamically adjusted, the liquid nitrogen volume flow rate of the other parallel flexible standard cooling modules remains basically stable, and there is no significant interference between the flexible standard cooling modules. This can avoid the interference problem of multi-channel parallel connection and realize the efficient, precise and low-cost application of liquid nitrogen jet. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the accompanying drawings required for the description of the embodiments are introduced below. The following drawings are only some embodiments of this disclosure and do not impose specific limitations on the protection scope of this disclosure.

[0038] Figure 1 This is a schematic diagram of the overall architecture of a multi-channel distributed liquid nitrogen jet cooling system for thermoforming provided according to an embodiment of this disclosure;

[0039] Figure 2 This is a schematic diagram of the overall architecture of another multi-channel distributed liquid nitrogen jet cooling system for thermoforming provided according to an embodiment of this disclosure;

[0040] Figure 3 This is a structural schematic diagram of a single flexible standard cooling module provided according to an embodiment of the present disclosure;

[0041] Figure 4 This is one of the schematic flowcharts of a multi-channel distributed liquid nitrogen jet cooling method for thermoforming provided according to an embodiment of this disclosure;

[0042] Figure 5 This is a second schematic flowchart of a multi-channel distributed liquid nitrogen jet cooling method for thermoforming provided according to an embodiment of this disclosure;

[0043] Figure 6 This is a third schematic diagram of a multi-channel distributed liquid nitrogen jet cooling method for thermoforming provided according to an embodiment of this disclosure;

[0044] Figure 7 This is a schematic diagram of a distributed liquid nitrogen targeted cooling control strategy based on the average thinning rate of the region and calculation, according to an embodiment of this disclosure.

[0045] Figure 8 This is a schematic diagram of the thinning rate of a thinning region versus forming time according to an embodiment of the present disclosure;

[0046] Figure 9 This is a schematic diagram of a liquid nitrogen jet partitioned cooling multi-condition system provided according to an embodiment of the present disclosure.

[0047] Figure label:

[0048] Control module 100;

[0049] Liquid nitrogen storage and pressure stabilization module 200, liquid nitrogen storage tank 201, pressure regulating valve group 202, pressure sensor 203;

[0050] Flexible standard cooling module 300, liquid nitrogen output pipeline 301, flow regulating valve group 302, check valve 3021, manual valve 3022, solenoid valve 3023, regulating valve 3024, flow sensing element 303, flow measuring element 3031, pressure sensor 3032, temperature sensor 3033;

[0051] Thermoformed sheet material 400. Detailed Implementation

[0052] This disclosure presents a multi-channel distributed liquid nitrogen jet cooling system and method for thermoforming.

[0053] This disclosure is not exhaustive, but merely illustrative of some embodiments, and is not intended to limit the scope of protection of this disclosure. Unless otherwise specified, each step, component, part, device, or apparatus in a particular embodiment can be implemented as an independent embodiment, and these steps, components, parts, devices, and apparatuses can be arbitrarily combined. For example, the solution after removing some steps, components, parts, devices, or apparatuses in a particular embodiment can also be implemented as an independent embodiment, and the order of steps in a particular embodiment can be arbitrarily interchanged. Furthermore, the optional implementation methods in a particular embodiment can be arbitrarily combined; moreover, the embodiments can be arbitrarily combined. For example, some or all steps, components, parts, devices, and apparatuses of different embodiments can be arbitrarily combined, and a particular embodiment can be arbitrarily combined with the optional implementation methods of other embodiments. In all embodiments of this disclosure, unless otherwise specified or logically conflicting, the terminology and / or descriptions between the embodiments are consistent and can be mutually referenced. Technical features in different embodiments can be combined to form new embodiments based on their inherent logical relationships.

[0054] The terminology used in the embodiments of this disclosure is for the purpose of describing particular embodiments only and is not intended to limit the scope of this disclosure.

[0055] In hot stamping processes, complex components may exhibit uneven thickness and microstructure distribution, leading to significant differences in thinning rates across different regions. Uneven cooling may also occur during the hot forming process, such as over-cooling in some areas and under-cooling in others, resulting in poor quality of the formed component. Furthermore, related hot stamping technologies typically employ uniform cooling control across the entire complex component, such as controlling multiple cooling channels to output the same amount of cooling medium. However, this method fails to account for uneven thickness and microstructure distribution within the complex component, potentially resulting in poor-quality components.

[0056] Therefore, in order to solve the above problems, this solution proposes a multi-channel distributed liquid nitrogen jet cooling system for thermoforming, which can effectively solve the problem of uneven cooling of complex components and realize the efficient, precise and low-cost application of liquid nitrogen jet.

[0057] like Figure 1 The diagram shown is a schematic of a multi-channel distributed liquid nitrogen jet cooling system for thermoforming provided in this disclosure.

[0058] In some embodiments, such as Figure 1As shown, the multi-channel distributed liquid nitrogen jet cooling system for thermoforming includes: a liquid nitrogen storage and pressure stabilization module 200 for storing liquid nitrogen and adjusting the liquid nitrogen output pressure; multiple flexible standard cooling modules 300, which are connected in parallel on a main liquid supply pipe and in series with the liquid nitrogen storage and pressure stabilization module. Each flexible standard cooling module includes a liquid nitrogen output pipe 301, a flow regulating valve group 302, and a flow sensing element 303 configured on the liquid nitrogen output pipe. The liquid nitrogen output pipe is connected to the cooling channel of the thermoforming mold. Different cooling channels and different numbers of jet holes on the cooling channels correspond to different thinning areas of the part to be formed. Each flexible standard cooling module... This corresponds to one thinning region or a merged region formed by combining multiple thinning regions. The control module 100 is connected to multiple flexible standard cooling modules. It is used to adjust the corresponding flexible standard cooling modules according to the selected cooling conditions for each thinning region and / or each merged region, based on the cooling start time and liquid nitrogen output pressure of each region under different cooling conditions, to control the liquid nitrogen jet flow rate during the cooling process. It is also used to determine the liquid nitrogen gas mass fraction based on data from the path sensing element. When a gas-liquid phase change occurs in the liquid nitrogen output pipeline, it adjusts the path regulating valve group according to the liquid nitrogen gas mass fraction to regulate the liquid nitrogen flow rate in the liquid nitrogen output pipeline. The part to be formed is a component awaiting hot stamping.

[0059] In some embodiments, liquid nitrogen can be a medium used to cool thermoformed sheets during hot stamping. For example, during component forming, liquid nitrogen can flow from the liquid nitrogen storage and stabilization module to the cooling channels and / or jet holes of the mold to cool the component through the cooling channels and / or jet holes. The liquid nitrogen storage and stabilization module can be used to store liquid nitrogen and adjust the output pressure of liquid nitrogen to avoid excessively high output pressure leading to safety accidents, and to avoid excessively low output pressure preventing liquid nitrogen from flowing normally to the cooling channels, jet holes, etc.

[0060] In some embodiments, a multi-channel distributed liquid nitrogen jet cooling system for thermoforming may include multiple flexible standard cooling modules. These modules can be connected in parallel to a main liquid supply pipe. Liquid nitrogen from the liquid nitrogen storage and pressure stabilization module flows through the main supply pipe and is then branched off to multiple parallel liquid nitrogen output pipes, which then enter the multiple flexible standard cooling modules. The flexible standard cooling modules can then control the flow rate, direction, etc., of the liquid nitrogen output to the cooling channels via control channel regulating valve groups. Channel sensing elements are used to detect parameters such as pressure, temperature, and flow rate within the channel in real time. Optionally, each flexible standard cooling module may correspond to one liquid nitrogen output pipe.

[0061] In some embodiments, the liquid nitrogen output pipe of each flexible standard cooling module can be connected to a cooling channel inside the thermoforming mold. Optionally, since the degree of thinning varies at different locations on the thermoformed sheet, the required cooling rate also varies. Therefore, multiple cooling channels can be designed in the thermoforming mold. Different cooling channels can be used to cool different cooling areas of the thermoformed sheet. Optionally, multiple flexible standard cooling modules can be provided. A different number of jet holes can be arranged on the cooling channel corresponding to each flexible standard cooling module. Liquid nitrogen can flow through the cooling channel corresponding to the flexible standard cooling module and be sprayed out through the jet holes to the surface of the thermoformed sheet. The liquid nitrogen sprayed from the jet holes can be sprayed onto different thinned areas of the thermoformed sheet to cool the different thinned areas of the thermoformed sheet.

[0062] In some embodiments, different cooling channels and different numbers of jet holes correspond to different thinning regions of the thermoformed sheet. Each flexible standard cooling module can correspond to an independent thinning region. Each flexible standard cooling module can be used to cool a thinning region. Alternatively, when the cooling requirements of multiple thinning regions are similar, multiple thinning regions can be merged into a merged region, and a flexible standard cooling module can uniformly control the cooling of the merged region. This can achieve precise cooling of different regions of the thermoformed sheet while minimizing costs.

[0063] In some embodiments, the multi-channel distributed liquid nitrogen jet cooling system for thermoforming further includes a control module. The control module can be connected to multiple flexible standard cooling modules respectively, so as to independently control each flexible standard cooling module. The control module can control the flexible standard cooling module corresponding to each thinning region or merging region under different cooling conditions, so that each flexible standard cooling module cools each thinning region or merging region according to the cooling conditions corresponding to each thinning region or merging region. In addition, the control module can independently adjust the corresponding flexible standard cooling module according to the cooling start time of each thinning region or merging region and the output pressure provided by the liquid nitrogen storage and stabilization module, so as to achieve precise control of the liquid nitrogen jet flow rate of each thinning region or merging region.

[0064] In some embodiments, the control module can also acquire data collected by the access sensing element, such as pressure and temperature data. The control module can then determine the liquid nitrogen gas mass fraction based on the data collected by the access sensing element. When a gas-liquid phase change occurs in the liquid nitrogen output pipeline, the access regulating valve group in the flexible standard cooling module can be adjusted according to the liquid nitrogen gas mass fraction to regulate the liquid nitrogen flow rate in the liquid nitrogen output pipeline. Optionally, the liquid nitrogen gas mass fraction can be used to indicate the liquid nitrogen flow rate from the inlet pressure. Turning into export pressure During the process, the percentage of steam mass generated relative to the total mass of liquid nitrogen, optionally, the inlet pressure The value of the liquid nitrogen output pressure can be the same, and the gas mass fraction can also be the dryness fraction. The gas-liquid phase change can refer to the phenomenon of some liquid nitrogen changing from a liquid to a gaseous state in the pipeline. The degree of phase change can be the ratio of gas to liquid. Optionally, the gas mass fraction is calculated using temperature and pressure data collected from the liquid nitrogen output pipeline.

[0065] Optionally, the control module can dynamically adjust the flow path regulating valve group according to the degree of phase change to compensate for the cooling loss due to liquid nitrogen vaporization. For example, the valve opening can be increased or decreased according to the degree of phase change to adjust the actual liquid nitrogen flow rate of the liquid nitrogen output pipeline, thereby compensating for the cooling loss due to liquid nitrogen vaporization, ensuring that the liquid nitrogen flow rate reaching the cooling channel and / or jet orifice is stable, and that the liquid nitrogen flow rate reaching the cooling channel and / or jet orifice matches the cooling requirements of the corresponding thinning area.

[0066] In some embodiments, such as Figure 2 As shown, the liquid nitrogen storage and pressure stabilization module includes: a liquid nitrogen storage tank 201; a pressure regulating valve group connected to the output end of the liquid nitrogen storage tank for regulating the liquid nitrogen output pressure of the liquid nitrogen storage tank; a pressure sensor 203 installed on the gas phase valve (not shown) of the liquid nitrogen storage tank for monitoring the liquid nitrogen output pressure of the liquid nitrogen storage tank; and a flow regulating valve group including a check valve 3021, a manual valve 3022, a solenoid valve 3023, and a regulating valve 3024; the check valve is used to prevent liquid nitrogen backflow; the manual valve regulates the liquid nitrogen volume flow rate by adjusting the valve opening K; wherein, during the thermoforming cooling process, based on the pressure stabilization characteristics in the main liquid supply pipe and the check valves on each liquid nitrogen output pipe, when the liquid nitrogen volume flow rate of any liquid nitrogen output pipe is dynamically adjusted, the remaining parallel liquid nitrogen output pipes... The liquid nitrogen volumetric flow rate in the outlet pipeline remains stable; the sensing elements include a flow measurement element 3031, a pressure sensor 3032, and a temperature sensor 3033; the control module is connected to the solenoid valve, regulating valve, flow measurement element, pressure sensor, and temperature sensor of each flexible standard cooling module; the control module regulates the corresponding flexible standard cooling module by adjusting the solenoid valve and regulating valve, and determines the liquid nitrogen gas mass fraction by using data collected by the pressure sensor and temperature sensor after pipeline pre-cooling, so as to control the regulating valve to adjust the opening according to the compensation amount, which is determined based on the liquid nitrogen gas mass fraction; the control module receives real-time feedback from the flow measurement element and, based on the target volumetric flow rate of each liquid nitrogen outlet pipeline, adjusts the flow rate accordingly. and / or the target average flow rate of each liquid nitrogen output line The output pulse signal controls the solenoid valve to achieve rapid on / off switching and intermittent cooling, and / or outputs a continuous analog signal to control the opening of the regulating valve to achieve continuous flow regulation; the control module realizes the opening and closing of each component in the flexible standard cooling module according to different working conditions.

[0067] In some embodiments, the liquid nitrogen storage tank can be used to store liquid nitrogen and output liquid nitrogen, a pressure regulating valve group is connected to the output end of the liquid nitrogen storage tank to regulate the pressure of the liquid nitrogen output from the liquid nitrogen storage tank; and a pressure sensor is deployed on the liquid nitrogen storage tank to monitor the liquid nitrogen output pressure of the liquid nitrogen storage tank.

[0068] In some embodiments, such as Figure 2 As shown, U1 to U j For multiple flexible standard cooling modules, 400 is a thermoformed sheet, and the thermoformed part is obtained by thermoforming the thermoformed sheet, I1 to I n For n thinning regions on a thermoformed sheet, C1 to C n There are n liquid nitrogen output pipelines corresponding to n thinning regions.

[0069] In some embodiments, the flow control valve group in each flexible standard cooling module may include four types of valves, among which a check valve can prevent liquid nitrogen backflow. During the thermoforming cooling process, based on the pressure stabilizing characteristics in the main liquid supply pipe and the function of the check valves placed in each flow pipe, when the valve opening of any flow is dynamically adjusted, the liquid nitrogen volume flow rate of the remaining parallel flexible standard cooling modules will be affected. The system remains largely stable, with no significant interference between the various flexible standard cooling modules. Optionally, the operator can adjust the opening degree K of the manual valve to change the volumetric flow rate of liquid nitrogen. Optionally, the control module can output a reminder message when the manual valve needs to be adjusted, prompting the operator to adjust the manual valve. Figure 2 As shown, the control module can be connected to solenoid valves and regulating valves to facilitate the control of the solenoid valves and regulating valves.

[0070] In some embodiments, the passage sensing element in each flexible standard cooling module may include a flow measurement element for real-time detection of the volumetric flow rate of liquid nitrogen in the passage; a pressure sensor for monitoring the pressure of the liquid nitrogen in the passage; and a temperature sensor for acquiring the temperature of the liquid nitrogen in the passage. Figure 2 As shown, the flow measurement element, pressure sensor, and temperature sensor can be connected to the control module. The control module can acquire the data collected by the flow measurement element, pressure sensor, and temperature sensor, and then control the flexible standard cooling module based on the data collected by the flow measurement element, pressure sensor, and temperature sensor.

[0071] For example, the control module can acquire data collected by the pressure sensor and the temperature sensor after the pipeline is pre-cooled, and determine the mass fraction of liquid nitrogen gas based on the data after the pipeline is pre-cooled. Then, it can determine the compensation amount based on the mass fraction of liquid nitrogen gas. The compensation amount is the liquid nitrogen volume flow rate compensation amount. Finally, the opening of the regulating valve can be adjusted according to the size of the compensation amount.

[0072] For example, the control module can receive real-time feedback from the flow measurement element to obtain the flow rate in the pipeline, and can also determine the target volumetric flow rate of each liquid nitrogen output pipeline. and / or the target average flow rate of each liquid nitrogen output line Then, based on the real-time feedback of the flow rate value and target volume flow rate from the flow measurement element, and / or target average flow The control module controls the solenoid valve. Optionally, the control module can output pulse signals to control the solenoid valve to achieve rapid on / off switching and intermittent cooling. For example, in multi-channel periodic pressure holding and quenching conditions, the pressure change is small and the cooling demand is also small. In this case, the control module can control the solenoid valve to achieve rapid on / off switching and intermittent cooling to achieve dynamically adjusted intermittent cooling. Optionally, the control module can output continuous analog signals to control the opening of the regulating valve to achieve continuous flow regulation.

[0073] In some embodiments, the control module can control the opening and closing of each component in the flexible standard cooling module according to the needs of different cooling conditions. For example, in one condition, the solenoid valve may be kept open and only the regulating valve may be adjusted; in another condition, the regulating valve may be kept fixed and the solenoid valve may be periodically opened and closed. Cooling conditions such as dynamic feedforward anti-thinning jet conditions, periodic pressure holding quenching conditions, and fixed-parameter batch static cooling conditions allow the control module to consider the needs of different cooling conditions and precisely control the components in the flexible standard cooling module, thereby meeting the requirements of different cooling conditions and improving cooling performance.

[0074] In some embodiments, such as Figure 3As shown, taking a flexible standard cooling module as an example, the liquid nitrogen output from the liquid nitrogen storage tank can flow to the check valve of the flexible standard cooling module after passing through the main liquid supply pipe. After passing through the check valve, the liquid nitrogen will not flow back to the main liquid supply pipe, or to the liquid nitrogen output pipeline of other flexible standard cooling modules. After passing through the check valve, the liquid nitrogen flows through a manual valve, a solenoid valve (e.g., a cryogenic solenoid valve), and a regulating valve (e.g., an electric regulating valve). The control module controls the rapid opening and closing of the solenoid valve via pulse control to perform intermittent cooling. The control module outputs a continuous analog signal to control the opening of the regulating valve. The flow rate is continuously regulated by a flow meter (K). A flow measurement element, a pressure sensor, and a temperature sensor are also installed on the liquid nitrogen output pipeline. The flow measurement element sends a flow signal to the control module to report real-time flow data. The pressure sensor sends a pressure signal to the control module to report the pressure data collected in the liquid nitrogen output pipeline. The temperature sensor sends a temperature signal to the control module to report the temperature data collected in the liquid nitrogen. Finally, the liquid nitrogen is output through the liquid nitrogen output pipeline to the cooling channel and / or jet orifice to cool the thermoformed sheet.

[0075] In summary, the multi-channel distributed liquid nitrogen jet cooling system for thermoforming provided in this embodiment can, based on the pressure stabilization characteristics in the main liquid supply pipe and the check valves on each liquid nitrogen output pipe, dynamically adjust the valve opening and liquid nitrogen volume flow rate of any liquid nitrogen output pipe while maintaining a stable liquid nitrogen volume flow rate in the remaining parallel liquid nitrogen output pipes, thus avoiding interference problems in multi-channel parallel connections. Furthermore, the control module determines the gas mass fraction of liquid nitrogen based on the pre-cooled data of the pipes. When a gas-liquid phase change is detected in the liquid nitrogen output pipe, the control module controls the regulating valve according to the degree of phase change corresponding to the liquid nitrogen gas mass fraction, compensating for the liquid cooling loss in the pipes and maintaining the stability of the actual injected liquid nitrogen cooling capacity. Further, the control module can control each flexible standard cooling module, and each flexible standard cooling module corresponds to a single thinning area or multiple combined areas with similar cooling requirements. This allows for precise cooling control of each thinning area or multiple combined areas with similar cooling requirements, enabling efficient, precise, and low-cost application of liquid nitrogen jets.

[0076] Figure 4 This is one of the schematic flowcharts of a multi-channel distributed liquid nitrogen jet cooling method for thermoforming provided according to an embodiment of this disclosure. The method can be executed by the multi-channel distributed liquid nitrogen jet cooling system for thermoforming provided in this disclosure, or by a control module within the multi-channel distributed liquid nitrogen jet cooling system for thermoforming. The method includes the following:

[0077] Step 401: Divide the thermoformed sheet into thinning regions and determine n thinning regions of the thermoformed sheet.

[0078] In some embodiments, the thermoformed sheet can be a component before forming treatment; alternatively, the thermoformed sheet can be a component that has undergone high-temperature heating treatment; alternatively, the thermoformed sheet can be compression molded to obtain a thermoformed part.

[0079] In some embodiments, before compressing the thermoformed sheet, the thermoformed sheet can be divided into thinning regions to determine n thinning regions of the thermoformed sheet, where n is a positive integer.

[0080] In some embodiments, the thermoformed sheet can be divided according to the size of a preset thinning region, according to the thinning rate of different regions of the thermoformed sheet, according to the thickness of different regions of the thermoformed sheet, according to the structure of different regions, or according to the microstructure distribution of different regions of the thermoformed sheet, etc.

[0081] Optionally, the thermoformed sheet is divided into thinning regions to determine multiple thinning regions, including: dividing the thermoformed sheet into meshes to determine multiple mesh cells, where the number of mesh cells is X, and the x-th mesh cell is denoted as u. x , x∈[1,X]; based on the initial thickness of each grid cell The actual thickness of the thermoformed part obtained after thermoforming of thermoformed sheet metal. Determine the thinning rate of each grid cell in the thermoformed part. :

[0082] (1)

[0083] Based on the thinning rate, the thermoformed sheet is divided into m continuous and independent cooling characteristic regions I = {I1, I2, I3...I...} m-1 I m}, the average thinning rate of the i-th cooling feature region is expressed as , i∈[1,m], where the average thinning rate satisfies The cooling characteristic region is the thinning region, labeled I. j1 I j2 I j3 ...I j（n-1） I jn The average thinning rate meets the requirements. The cooling characteristic region is the non-thinning region, labeled I. f1 I f2 I f3...I f（m-n-1） I f（m-n） n thinning zones correspond to n liquid nitrogen output pipelines C = {C1, C2, C3...C...} n-1 C n}, The threshold for the thinning rate is m≥2, where m is a positive integer.

[0084] In some embodiments, when dividing the thermoformed sheet, the thermoformed sheet can first be divided into grids, for example, the thermoformed sheet can be divided into multiple continuous grid units according to a preset grid size. Then, the thinning rate of the sheet in each grid unit can be determined according to the initial thickness of each grid unit and the actual thickness of the thermoformed part. The initial thickness of each grid unit is the thickness of the grid unit on the thermoformed sheet. For example, the thickness at the center point of the grid unit on the thermoformed sheet can be determined as the initial thickness of the grid unit, or the average thickness of the grid unit on the thermoformed sheet can be determined as the initial thickness of the grid unit, etc. This application does not limit this. When calculating the thinning rate of a grid unit, the actual thickness of the thermoformed part can be the thickness of the area corresponding to the grid unit on the thermoformed part.

[0085] In some embodiments, after determining the thinning rate of each grid cell, the thermoformed sheet can be divided into m continuous and independent cooling characteristic regions based on the thinning rate. Optionally, multiple grid cells with a thinning rate difference less than or equal to a preset threshold can be divided into one cooling characteristic region. Then, the thinning rate threshold can be set to... If the average thinning rate of multiple grid cells in a cooling feature region satisfies Then the cooling feature region is a thinning region. If the average thinning rate of multiple grid cells in a cooling feature region satisfies... The cooling characteristic area is the non-thinning area, and the n thinning areas correspond to n liquid nitrogen output pipelines. In other words, liquid nitrogen in different liquid nitrogen output pipelines can be used to cool different thinning areas. Optionally, the thinning area is the area that needs to be cooled, and the non-thinning area can be the area that does not need to be cooled.

[0086] Step 402: At any moment or time during the hot forming stamping process of the hot-formed sheet, x feature points are selected from the thinning area, and the feature point with the smallest thickness among the x feature points is determined as the targeted cooling feature point.

[0087] In some embodiments, after determining n thinning regions, x feature points can be selected from the thinning regions, where the x feature points can be points where the thinning rate is greater than or equal to a thinning rate threshold.

[0088] In some embodiments, the feature point with the smallest thickness among x feature points can be determined as the targeted cooling feature point. The liquid nitrogen output pipeline in the flexible standard cooling module corresponding to the targeted cooling feature point at a given time or time period is used to preferentially perform directional jet cooling on the targeted cooling feature point. In other words, the flexible standard cooling module corresponding to the targeted cooling feature point can cool a thinned area on the thermoformed sheet. The flexible standard cooling module can preferentially perform precise jet cooling on the targeted cooling feature point in the thinned area. Optionally, each thinned area may include a targeted cooling feature point, and the area where the targeted cooling feature point is located can be preferentially cooled.

[0089] Step 403: Based on the curve of the average thinning rate of each thinning region changing with the total forming time, the time when the average thinning rate reaches the thinning rate threshold is determined as the cooling start time for the region where the targeted cooling feature point is located to start jet cooling.

[0090] In some embodiments, the average thinning rate of each thinning region can be used as a reference. Curve of variation with total forming time t , g∈[1,n], the average thinning rate will reach the thinning rate threshold. The time is determined as the cooling start time t of the jet stream starting in the region where the targeted cooling feature point is located. g The cooling start time is the time from the start of hot forming to the activation of jet cooling.

[0091] In some embodiments, since the shape, microstructure distribution, thickness, etc. of the thermoformed sheet change during the hot stamping process, the thinning rate of the same thinning region will also change accordingly. Therefore, the thinning rate of a thinning region will change throughout the hot stamping process, so the curve of the average thinning rate of each thinning region changing with the total forming time can be determined.

[0092] In some embodiments, the cooling initiation time of the jet flow in the region where each targeted cooling feature point is located can be determined; alternatively, the average thinning rate of each thinning region can be determined. Curve of variation with total forming time t The variation curve of each thinning region The curves for each thinning region can be different. This may be related to the material parameters, initial thickness, initial temperature, shape, etc. of the thinned region. Optionally, it can be determined which thinned region each targeted cooling feature point is located in, and then the change curve of the corresponding thinned region can be used. The cooling start time for the region where each targeted cooling feature point is located is determined. Optionally, the time when the average thinning rate reaches the thinning rate threshold can be determined as the cooling start time for the jet to begin in the region where the targeted cooling feature point is located.

[0093] For example, such as Figure 8 The diagram shown is a schematic representation of the thinning rate of a thinning region versus molding time according to an embodiment of this disclosure. Specifically, Figure 8 Different thinning regions I1...I are shown. n The thinning rate is at the set maximum thinning rate. Within, the thinning rate threshold for initiating jetting is reached. The required time varies, corresponding to the cooling start time t1...t of the initial jet in each thinning region. n For example, the cooling start time of the thinning region corresponding to I1 is t1, I n The corresponding cooling start time of the thinned region is t. n .

[0094] Step 404: Based on the differences in cooling start time and liquid nitrogen volume flow rate requirements between different thinning regions, if the differences in cooling start time and / or volume flow rate requirements of at least two thinning regions meet preset conditions, then at least two thinning regions are merged into a merged region.

[0095] In some embodiments, after determining the cooling start time of the jet in the region where each targeted cooling feature point is located, the cooling start time of each thinning region can be determined. Since a thinning region includes a targeted cooling feature point, the cooling start time of the region where the targeted cooling feature point is located can be determined as the cooling start time of the thinning region where the targeted cooling feature point is located.

[0096] In some embodiments, it can be determined whether there are thinning regions that can be merged based on the cooling start time and liquid nitrogen volume flow rate requirement of multiple thinning regions. Optionally, when the cooling requirements of multiple thinning regions are similar, multiple thinning regions can be merged. The similar cooling requirements are, for example, similar cooling time, similar liquid nitrogen volume flow rate requirement, etc.

[0097] For example, if the differences in cooling start time and / or volumetric flow rate requirements between at least two thinning regions meet preset conditions, then the at least two thinning regions are merged into a merged region. This merged region is uniformly controlled by the same flexible standard cooling module and has a unified cooling start time and volumetric flow rate. In other words, after merging multiple thinning regions, the cooling start time and volumetric flow rate of the merged region can be determined, and a single flexible standard cooling module can be used to uniformly control the cooling of multiple thinning regions within the merged region.

[0098] In the above embodiments, a flexible standard cooling module can uniformly control a merged region, thereby reducing costs while meeting different thinning cooling requirements. For example, if the cooling time of two thinning regions differs by 0.5 seconds, these two thinning regions can be merged into one. A flexible standard cooling module can control the output of liquid nitrogen to these two thinning regions to cool them. This reduces the number of flexible standard cooling modules that need to be set up, avoids frequent activation of flexible standard cooling modules, and avoids problems such as high control logic complexity and high control difficulty caused by too many flexible standard cooling modules running at the same time.

[0099] Step 405: For each thinning region and / or each merging region, select the corresponding cooling condition for the flexible standard cooling module corresponding to the thinning region and / or merging region based on the thinning characteristics and process requirements of the thinning region and / or merging region during the thermoforming process.

[0100] In some embodiments, selecting a corresponding cooling condition for the flexible standard cooling module corresponding to the thinning region and / or merging region includes: when the target region is a critical thinning region where the rate of change of the thinning rate gradient exceeds a preset threshold during the forming process, selecting a dynamic feedforward anti-thinning jet condition for the target region, where the target region is any thinning region or merging region; wherein, the dynamic feedforward anti-thinning jet condition is: during the thermoforming process, only the regulating valve in the flexible standard cooling module is adjusted, and the check valve, manual valve, and solenoid valve in the flexible standard cooling module remain normally open; under the dynamic feedforward anti-thinning jet condition, dynamically controlling the opening and closing of the flexible standard cooling module corresponding to each thinning region and / or each merging region includes: before the jet is opened, pre-cooling the pipeline by opening the valve in advance, and collecting the inlet pressure of the liquid nitrogen output pipeline in real time according to the pressure sensor. and export pressure and the temperature collected in real time by the temperature sensor Calculate the initial predicted gas mass fraction without considering heat loss during transmission. :

[0101] (4)

[0102] in, For inlet pressure Specific enthalpy of saturated liquid nitrogen; export pressure Specific enthalpy of saturated liquid nitrogen; The latent heat of vaporization under outlet pressure is used; to compensate for the insufficient cooling capacity provided by liquid nitrogen vaporization, a flash evaporation compensation coefficient is determined. The jet flow rate Q obtained from the mapping relationship is compensated to Q based on the flash compensation coefficient. v To ensure the required volumetric flow rate Able to pass through valves:

[0103] (5)

[0104] According to inlet pressure and export pressure Calculate the voltage drop of the actual system ;

[0105] Calculate the critical pressure ratio coefficient of liquid :

[0106] (6)

[0107] in, This is the vapor pressure of liquid nitrogen at the current operating temperature. Given the thermodynamic critical pressure of liquid nitrogen; determine the limiting pressure drop caused by liquid blockage. :

[0108] (7)

[0109] in, The sum of the liquid pressure recovery coefficient of the valve equipped with fittings and the pipe geometry coefficient. For pipe geometry coefficients; calculate the required flow coefficient. :

[0110] (8)

[0111] in, It is a numerical constant. The actual density of liquid nitrogen, It is the density of pure water at 15.5℃ and the pressure drop. It is the actual system voltage drop. and ultimate pressure drop The smaller of the two; combined valve Characteristic curves are used to determine the valve opening K of the control valve; the target volumetric flow rate of each liquid nitrogen output pipeline is calculated. With actual volumetric flow rate Instantaneous flow deviation between Based on the basic valve opening degree K and the instantaneous flow deviation, the opening command of the control valve is adjusted in real time. :

[0112] (9)

[0113] in, These are the proportional, integral, and derivative gain coefficients of the control module; the actual volumetric flow rate after the opening command reaches the effective adjustment limit. Still unable to meet the target volumetric flow rate The demand for [something] leads to an increased pressure on entry points. For any thinning or merging region, once the actual jetting time reaches the target cooling duration, the valve in the corresponding flexible standard cooling module is closed to end the cooling of the thinning or merging region.

[0114] In the above embodiment, the jet flow rate Q is compensated to Q. v The process is the process of performing flash compensation calculation.

[0115] In the above embodiments, when the target area is where the thinning rate gradient changes rapidly during the forming process, the target area can be identified as a critical area. The working condition corresponding to the target area is the dynamic feedforward anti-thinning jet working condition. Under the dynamic feedforward anti-thinning jet working condition, only the regulating valve in the flexible standard cooling module is adjusted during the thermoforming process. At this time, the check valve, manual valve, and solenoid valve in the flexible standard cooling module remain open. Furthermore, during the thermoforming process, the check valve, manual valve, and solenoid valve in the flexible standard cooling module corresponding to the target area remain open. By adjusting the regulating valve in the flexible standard cooling module, the liquid nitrogen flow rate in the target area is precisely controlled, thereby achieving precise cooling control of the target area.

[0116] In some embodiments, when the operating condition corresponding to the target area is a dynamic feedforward anti-thinning jet condition, the regulating valve can be opened in advance before the jet starts to pre-cool the pipeline with liquid nitrogen. This can avoid the problem of severe liquid nitrogen vaporization caused by a large temperature difference between the liquid nitrogen and the pipeline during the jet process. Furthermore, the inlet pressure of the liquid nitrogen output pipeline can be collected in real time by a pressure sensor. and export pressure and the temperature collected in real time by the temperature sensor Calculate the initial predicted gas mass fraction without considering heat loss during transmission. This means that we can assume that there is no heat exchange between the pipeline and the environment, and use this data to calculate an initial predicted gas mass fraction. This initial predicted gas mass fraction reflects the severity of flashing of liquid nitrogen due to pressure changes. The larger the Y value, the more severe the flashing and the higher the proportion of liquid nitrogen vaporization.

[0117] In some embodiments, due to flash evaporation of liquid nitrogen during transport, the actual liquid nitrogen volumetric flow rate sprayed onto the thinning area may be less than the jet flow rate Q required by the thinning area, resulting in insufficient cooling of the thinning area. Therefore, the actual output liquid nitrogen volumetric flow rate can be controlled to be greater than the jet flow rate Q required by the thinning area to compensate for the flow loss caused by liquid nitrogen flash evaporation. Optionally, the flow loss caused by liquid nitrogen flash evaporation can be compensated according to a flash evaporation compensation coefficient, or the compensated liquid nitrogen volumetric flow rate can be determined according to the flash evaporation compensation coefficient. The flash evaporation compensation coefficient can be determined based on the initially predicted gas mass fraction. After determining the flash evaporation compensation coefficient, the compensated liquid nitrogen volumetric flow rate Q can be determined according to the flash evaporation compensation coefficient. v .

[0118] In some embodiments, after determining the compensated liquid nitrogen volumetric flow rate Q v Next, the valve opening command can be determined so that the control valve can be opened according to the valve opening command, or the valve opening can be dynamically adjusted according to the valve opening command, so that the actual output liquid nitrogen flow rate matches the compensated liquid nitrogen volumetric flow rate Q. v Similarly, it achieves compensation for the liquid nitrogen flow rate loss due to liquid nitrogen flash evaporation.

[0119] In some embodiments, the valve opening is adjusted via a valve opening command to ensure the required volumetric flow rate Q. v The valve can optionally be adjusted according to the inlet pressure. and export pressure Calculate the voltage drop of the actual system ; Calculate the critical pressure ratio coefficient of the liquid Determine the limiting pressure drop caused by fluid blockage. Calculate the required flow coefficient C v Then it can be combined with valve C v -K characteristic curve, and then determine the valve opening K of the control valve.

[0120] Among them, valve C v The -K characteristic curve represents the C of the control valve. v -K characteristic curve, optionally, C v -K characteristic curves can be nonlinear mapping curves. When the flexible standard cooling module corresponds to a thinning region, a single-path nonlinear mapping curve can be selected; when the flexible standard cooling module corresponds to a merged region, a multi-path nonlinear mapping curve can be selected to match the flow requirements under different control modes.

[0121] Alternatively, different valves can have different C values. v -K characteristic curve, for example, C vThe -K characteristic curve is a mapping curve between the required flow coefficient and the control valve opening. That is, after determining the required flow coefficient using the above method, it can be determined based on C. v The -K characteristic curve determines the basic valve opening K of the control valve, which is determined by the required flow coefficient.

[0122] In some embodiments, the actual volumetric flow rate of each liquid nitrogen output line can be obtained after the jetting begins. For example, the actual volumetric flow rate can be obtained from the flow measurement element, and then the target volumetric flow rate of each liquid nitrogen output pipeline can be calculated. With actual volumetric flow rate Instantaneous flow deviation between Because there is an instantaneous flow rate deviation between the target volumetric flow rate and the actual volumetric flow rate in the liquid nitrogen output pipeline, the opening command of the regulating valve can be adjusted in real time based on the basic valve opening degree K and the instantaneous flow rate deviation. This allows for adjustment of the valve opening to compensate for the actual volumetric flow rate or to prevent excessive actual volumetric flow rate.

[0123] In some embodiments, the actual volumetric flow rate after the opening command reaches the effective adjustment limit. Still unable to meet the target volumetric flow rate Q v If the required flow rate is not met, simply adjusting the opening of the regulating valve may not be enough to increase the flow rate. In this case, the inlet pressure can be actively increased. Increasing the actual pressure drop at the outlet and inlet of the liquid nitrogen output pipeline to increase the liquid nitrogen flow rate can ensure steady-state compensation during the jetting process.

[0124] In some embodiments, for any thinning or merging region, once the actual jetting time reaches the target cooling duration, it can be determined that the cooling process for that region has been completed. At this point, the valve in the corresponding flexible standard cooling module can be closed, and liquid nitrogen injection can stop, thereby ending the cooling of the thinning or merging region. Optionally, the target cooling duration can be equal to the thermoforming duration, the target cooling duration can be the end time of the jetting process, the target cooling duration can be from the start of thermoforming to the end of the stamping stage, the target cooling duration can be from the start of thermoforming to before the start of pressure holding, etc.

[0125] In some embodiments, selecting a corresponding cooling condition for the flexible standard cooling module corresponding to the thinned region and / or merged region includes: when the target region has intermittent cooling requirements to maintain a specific cooling rate under constant pressure, selecting a multi-channel periodic pressure holding quenching condition for the target region, where the target region is any thinned region or merged region; wherein, the multi-channel periodic pressure holding quenching condition involves: adjusting the regulating valve and solenoid valve in the flexible standard cooling module during the pressure holding quenching process, while keeping the check valve and manual valve in the flexible standard cooling module normally open; under the multi-channel periodic pressure holding quenching condition, dynamically controlling the opening and closing of the flexible standard cooling module corresponding to each thinned region and / or each merged region includes: calculating the compensated volumetric flow rate based on the pre-cooling experiment. Calculate the required flow coefficient Combined with the regulating valve Characteristic curves are used to determine the valve opening K of the regulating valve; during the pressure holding and quenching process, the target average flow rate of the liquid nitrogen output pipeline of the regulated regulating valve is determined based on the required change in cooling capacity. Then, the target pulse ratio required by the solenoid valve is calculated:

[0126] (10)

[0127] During the periodic intermittent cooling process, based on the target average flow rate and actual volumetric flow rate Real-time update of the solenoid valve's real-time pulse ratio :

[0128] (11)

[0129] in, The gain coefficient is adjusted by integral feedback for flow error; a pulse signal at the target frequency is output to control the periodic on / off state of the solenoid valve.

[0130] In some embodiments, when the pressure in the target area remains constant and there is an intermittent cooling requirement, the hot-formed sheet is typically in the pressure holding and quenching stage. At this time, a multi-channel periodic pressure holding and quenching condition can be selected for the target area. Under the multi-channel periodic pressure holding and quenching condition, the regulating valve and solenoid valve in the flexible standard cooling module can be adjusted. Optionally, the magnitude of the single flow rate can be adjusted by controlling the regulating valve, and the intermittent cooling requirement of the target area can be met by adjusting the solenoid valve to quickly switch on and off. Intermittent cooling can be achieved without frequently changing the opening of the regulating valve, thus meeting the requirement of maintaining a specific cooling rate.

[0131] In some embodiments, under multi-channel periodic pressure holding quenching conditions, the compensated volumetric flow rate can be calculated based on pre-cooling experiments. Calculate the required flow coefficient Combined with the regulating valve The characteristic curve is used to determine the valve opening K of the control valve. This process is the same as the process of determining the valve opening K under the dynamic feedforward anti-thinning jet condition, and will not be repeated here. Optionally, the valve opening K is adjusted under the dynamic feedforward anti-thinning jet condition. After the dynamic feedforward anti-thinning jet condition ends, the multi-channel periodic pressure holding and quenching condition can be entered. Under the multi-channel periodic pressure holding and quenching condition, the valve opening of the control valve at the end of the dynamic feedforward anti-thinning jet condition can be kept unchanged, and only the solenoid valve is adjusted.

[0132] In some embodiments, during the pressure holding quenching process, the cooling demand of the target region may vary over time, thus requiring a target average flow rate for the target region. This also changes accordingly; this solution can be based on the target average flow rate. The target pulse ratio required for the solenoid valve is determined. The target pulse ratio can be the ratio of the time the solenoid valve is open to the length of the cycle in each cycle. However, since there is usually a deviation between the actual volumetric flow rate and the target volumetric flow rate in actual intermittent cooling processes, the target pulse ratio can be corrected to obtain the actual pulse ratio. Then, the solenoid valve can be adjusted according to the actual pulse ratio. For example, if the actual pulse ratio is 0.3, the solenoid valve can be controlled to be open for 30% of the time and closed for 70% of the time in each cycle. Optionally, the control module can output a pulse signal of the corresponding frequency according to the actual pulse ratio to control the duty cycle of the cryogenic solenoid valve's periodic on and off, thereby realizing the periodic on and off of the cryogenic solenoid valve.

[0133] In some embodiments, selecting a corresponding cooling condition for the flexible standard cooling module corresponding to the thinning region and / or merging region includes: when the forming process enters the mass production stage or the thinning rate of the target region stabilizes, selecting a fixed-parameter batch static cooling condition for the target region, where the target region is any thinning region or merging region; wherein, the fixed-parameter batch static cooling condition involves: adjusting the manual valve and solenoid valve in the flexible standard cooling module, and keeping the check valve and regulating valve in the flexible standard cooling module normally open; under the fixed-parameter batch static cooling condition, dynamically controlling the opening and closing of the flexible standard cooling module corresponding to each thinning region and / or each merging region includes: calculating the compensated volumetric flow rate based on the pre-cooling experiment during the thermoforming process. Calculate the required flow coefficient Combined with manual valve The characteristic curve is used to determine the valve opening degree K of the manual valve; the time of jet stamping and pressure holding quenching of the hot-formed sheet is set by the time signal to control the precise opening and closing of the solenoid valve; and the flow rate change during the hot forming process is monitored by the flow meter to adjust the valve opening degree K of the manual valve.

[0134] In some embodiments, when the forming process enters the mass production stage or the thinning rate of the target area stabilizes, frequent adjustments to cooling parameters are not required. To reduce system costs and simplify control logic, a fixed-parameter batch static cooling condition can be selected for the flexible standard cooling module corresponding to the target area. Here, "static" can mean that cooling parameters, such as flow rate and on-time, remain essentially unchanged during the mass production stage.

[0135] In some embodiments, after entering a fixed-parameter batch static cooling condition, the manual valve and the solenoid valve can be adjusted. The manual valve is a manual valve with graduation markings. Real-time closed-loop operation can be achieved without the need for a flow meter. Instead, the liquid nitrogen mass loss within a set time can be directly measured using a liquid nitrogen weighing system, and the actual flow rate can be calculated by combining the density. For example, the compensated volumetric flow rate can be calculated based on a pre-cooling experiment. Calculate the required flow coefficient Combined with manual valve The characteristic curve is used to determine the valve opening K of the manual valve. This allows the valve opening to be determined throughout the entire batch production process through a single pre-cooling process, which can reduce costs. This process is the same as the process for determining the valve opening K under dynamic feedforward anti-thinning jet conditions, so it will not be repeated here. After determining the valve opening K, information can be output, such as an instruction, to instruct the operator to adjust the manual valve opening to valve opening K.

[0136] In some embodiments, the start and end of cooling can be controlled by controlling the on / off state of the solenoid valve. For example, a time signal can be set according to the jet stamping and pressure holding quenching time of the hot-formed sheet, and then the jet stamping and pressure holding quenching time of the hot-formed sheet can be set by the time signal to control the precise opening and closing of the solenoid valve.

[0137] Step 406: Based on the cooling conditions selected for each thinning region and / or each merging region, control the activation of the flexible standard cooling modules corresponding to each thinning region and / or each merging region according to the cooling start time corresponding to each thinning region and / or each merging region.

[0138] In some embodiments, after determining the cooling start time and cooling conditions corresponding to each thinning region and / or each merging region, the flexible standard cooling modules corresponding to each thinning region and / or each merging region can be turned on according to the corresponding cooling start time and cooling conditions. This can realize differentiated flow and valve regulation by combining pipeline sensor data and valve characteristics. Optionally, the valves in the flexible standard cooling modules can be controlled to precisely control the output liquid nitrogen flow rate, so as to precisely cool different areas of the thermoformed sheet.

[0139] In some embodiments, during the hot forming stamping process, as the position of the targeted cooling feature point shifts, the opening and closing of the flexible standard cooling modules corresponding to each thinning region and / or each merging region are dynamically controlled under different cooling conditions. That is, when the position of the targeted cooling feature point shifts, the flexible standard cooling modules corresponding to each thinning region and / or each merging region may also change. Therefore, the flexible standard cooling modules can be dynamically opened and closed to adapt to the changes in the position of the targeted cooling feature point.

[0140] In some embodiments, when the position of the targeted cooling feature point exceeds the critical distance of the first jet hole corresponding to the current time or the current time period, causing a change in the matching relationship between the targeted cooling feature point and the first jet hole, the flexible standard cooling module corresponding to the first jet hole is dynamically controlled to close, and the flexible standard cooling module corresponding to the second jet hole corresponding to the targeted cooling feature point is simultaneously controlled to open.

[0141] In some embodiments, during the hot forming stamping process, as thinning occurs, the position of the targeted cooling feature point may also shift, and the area where the targeted cooling feature point is located may also change. When the position of the targeted cooling feature point exceeds the critical distance of the jet hole of the current flexible standard cooling module, causing the optimal matching jet hole to change, the valve corresponding to the original jet hole can be dynamically closed according to the updated shortest distance matching result, and the valve corresponding to the new matching jet hole can be opened simultaneously. Through the dynamic opening and closing of the multi-channel cryogenic solenoid valve, precise jet cooling of the targeted cooling feature point can be achieved.

[0142] In some embodiments, the overall operation control process within a single hot forming cycle includes the following steps: before the start of hot forming stamping, the jet path is divided and flexible standard cooling modules are merged based on the thinning characteristics of the hot forming sheet; after stamping begins, the control module tracks the physical displacement of the thinning area, dynamically updates and switches the optimal matching flexible standard cooling module, or matches the jet orifice; as stamping progresses, when the system determines that the current forming time has reached the target jet start time after deducting the total time lag advance of the pipeline and valves, the control module wakes up the flexible standard cooling module corresponding to the target area; the control module adjusts the current process according to the current working conditions. During the process, the corresponding operating logic is directly called for the flexible standard cooling module: the dynamic feedforward anti-thinning jet operating condition is called when thinning is suppressed in the early stage of forming; the multi-channel pulse pressure holding and quenching operating condition is called when the phase change of the microstructure is controlled in the pressure holding stage; the fixed parameter batch static cooling operating condition is called in the batch stable production stage; during the multi-path concurrent cooling, each branch relies on the pipeline pressure stabilization and backflow prevention characteristics to maintain dynamic anti-interference and flow self-balance; when each flexible standard cooling module reaches its independently set target cooling duration, the control module cuts off the control signal of the corresponding liquid nitrogen output pipeline in sequence, the system resets and enters the standby state of the next thermoforming cycle.

[0143] The jet path can include all the pipes in the multi-channel distributed liquid nitrogen jet cooling system for thermoforming, and the jet path can include all the pipes for conveying liquid nitrogen in the multi-channel distributed liquid nitrogen jet cooling system for thermoforming. The jet path can include multiple flexible standard cooling modules.

[0144] In summary, the embodiments disclosed herein divide and extract targeted cooling feature points based on the workpiece thinning rate, achieving precise mapping between the thinning region and the flexible standard cooling module. Jet cooling of the corresponding path is dynamically triggered based on the thinning rate change curve. The control module calculates flash dryness based on real-time pipeline temperature and pressure data and dynamically compensates for the opening of the electric regulating valve to maintain stable actual liquid cooling capacity during phase change. The system can automatically merge channels based on the spatiotemporal differences in each region and flexibly match differentiated cooling conditions such as dynamic closed-loop, periodic intermittent, or static with fixed parameters. Through zoning, grading, and multi-condition coordinated control, the problems of uneven cooling of complex components and interference from multiple parallel paths are solved, achieving efficient, precise, and low-cost application of liquid nitrogen jets.

[0145] Figure 5 This is a second schematic flowchart of a multi-channel distributed liquid nitrogen jet cooling method for thermoforming provided in this disclosure. The method can be executed by the multi-channel distributed liquid nitrogen jet cooling system for thermoforming provided in this disclosure, and includes the following:

[0146] Step 501: Determine the total system time lag advance based on the mechanical response time of the regulating valve and the transmission delay time of the liquid nitrogen pipeline.

[0147] In some embodiments, when the flexible standard cooling module corresponding to each thinning region and / or each merging region is turned on according to the cooling start time corresponding to each thinning region and / or each merging region, the mechanical response time of the regulating valve and the transmission delay time of the liquid nitrogen pipeline can be taken into account.

[0148] In some embodiments, the total system time lag advance is the time delay s from the opening of the control valve to the actual spraying of liquid nitrogen onto the thermoformed sheet. Optionally, the total system time lag advance is expressed as follows:

[0149] (2)

[0150] in To regulate the mechanical response time of the valve, The liquid nitrogen pipeline transmission delay time can be the time delay from when the control module sends a control signal / control command to the control valve until the control valve opens. The liquid nitrogen pipeline transmission delay time can be the time delay from when the control valve opens until the liquid nitrogen reaches the jet orifice through the valve of the flexible standard cooling module during transmission in the pipeline, or the time delay from when the jet begins to flow.

[0151] Step 502: Based on the total time delay advance of the system, adjust the time delay advance of the channel regulating valve group in the multi-channel distributed liquid nitrogen jet cooling system.

[0152] In some embodiments, there is a time delay in opening the valve during jetting, and there is also a time delay in the transmission of liquid nitrogen from the pipeline to the jet orifice. If the valve is controlled to start jetting only when the thinning rate of the thinning region reaches the threshold, the time delay will cause the liquid nitrogen to be sprayed into the thinning region after the thinning rate of the thinning region has reached the threshold. This may result in insufficient cooling of the thinning region, excessive thinning rate, excessively thin thinning region, poor quality of thermoformed parts, etc. Therefore, the valves in the passage regulating valve group can be opened in advance according to the total system time delay advance.

[0153] Optionally, the timing delay of the flow control valve group in the multi-path distributed liquid nitrogen jet cooling system can be controlled by opening the valves in the flow control valve group in advance. For example, if the moment when the thinning rate of the thinning area reaches the threshold is determined as the first time, the cooling start time can be determined by subtracting the total timing delay of the system from the first time. This can eliminate the mechanical response time of the control valve and the transmission delay time of the liquid nitrogen pipeline, meet the cooling requirements of the thinning area, and ensure the quality of the thermoformed parts.

[0154] In some embodiments, after determining the total system time delay advance of a valve, the valve can be time-delayed and adjusted according to the total system time delay advance each time the valve is opened; or after determining the total system time delay advance of a valve, any valve can be time-delayed and adjusted according to the total system time delay advance.

[0155] Step 503, during the hot forming stamping process, combined with valve C v -K characteristic curve, dynamically control the valve opening degree K of the valve corresponding to the target area, so as to dynamically regulate the opening and closing of the flexible standard cooling module.

[0156] In some embodiments, during the cooling process, the valve opening can be adjusted in real time according to the actual required liquid nitrogen flow rate of the target area, wherein the target area is any thinning area or any merging area.

[0157] In some embodiments, dynamically controlling the opening degree K of the valve corresponding to the target area includes: acquiring the material parameters of the thermoformed sheet, the jet parameters of each thinning region, and the mapping relationship between them and the heat transfer coefficient h.

[0158] (3)

[0159] The material parameters include at least the material type. Initial thickness Initial temperature of thermoformed sheet The jet parameters include at least the jet distance L and the jet flow rate Q; thermoforming simulation is performed with the goal of minimizing the thinning rate of the thermoformed part, and the heat transfer coefficient variation curve of each thinning region of the thermoformed sheet is obtained; the jet flow rate is determined based on the mapping relationship and the heat transfer coefficient variation curve. The instantaneous change curve; based on the jet flow rate The instantaneous change curve, combined with valve C v -K characteristic curve, determine valve opening degree K.

[0160] Optionally, at least one of the material parameters of the thermoformed sheet, the jet parameters of each thinning region, and the heat transfer coefficient h can be obtained through jet cooling experiments using a liquid nitrogen jet cooling system. During the simulation, the goal is to minimize the thinning rate of the thermoformed part and achieve a uniform thickness distribution. Different cooling conditions can be set during the simulation, such as different candidate heat transfer coefficient variation curves. The variation of the thinning rate under different candidate heat transfer coefficient variation curves can be determined, and the candidate heat transfer coefficient variation curve that minimizes the thinning rate can be selected as the heat transfer coefficient variation curve used to determine the actual jet flow rate.

[0161] In some embodiments, the jet flow rate is the required liquid nitrogen flow rate for the target area, and the jet distance can be the distance from the jet orifice to the target area. A relationship between jet flow rate and material type can be established. Initial thickness Initial temperature of thermoformed sheet The mapping relationship between heat transfer coefficient h can then be determined based on material type. Initial thickness Initial temperature of thermoformed sheet The required jet flow rate for the target area is determined by considering the heat transfer coefficient, which can vary with cooling time (i.e., a heat transfer coefficient curve). Therefore, based on the mapping relationship and the heat transfer coefficient curve, the instantaneous change curve of the jet flow rate Q during the cooling process can be determined. The required jet flow rate for the target area at each cooling time point can be obtained from this curve. Then, at each cooling time point, the required jet flow rate for the target area can be determined in conjunction with valve C. v-K characteristic curve, determine the valve opening degree K at each time point, and then dynamically adjust the opening and closing of the flexible standard cooling module according to the valve opening degree K at each time point, and further control the opening and closing and opening degree of the valve in the flexible standard cooling module.

[0162] In summary, the embodiments of this disclosure, by considering the total system time lag advance, can avoid problems such as excessive thinning caused by deviations in the actual liquid nitrogen ejection time by opening the valve before the thinning rate in the thinning region reaches the threshold; and by obtaining the heat transfer coefficient variation curve of each thinning region with the goal of minimizing the thinning rate, and determining the instantaneous variation curve of the jet flow rate required for the target region based on the mapping relationship, combined with valve C v The -K characteristic curve dynamically determines the valve opening K at each cooling time point, which allows the cooling flow rate to match the dynamic needs of the thinning area in real time, realizing the efficient and precise application of liquid nitrogen jet.

[0163] Figure 6 This is a third schematic flowchart of a multi-channel distributed liquid nitrogen jet cooling method for thermoforming provided in this disclosure. The method can be executed by the multi-channel distributed liquid nitrogen jet cooling system for thermoforming provided in this disclosure, and includes the following:

[0164] Step 601: Based on the cooling start time and volumetric flow rate of any two thinning regions, calculate the jet start time difference and volumetric flow rate difference of the two thinning regions respectively.

[0165] In some embodiments, when determining whether multiple thinning regions can be merged into one merged region, it can be based on any two thinning regions. and Cooling start time and volumetric flow rate Calculate the jet initiation time difference between the two thinning regions respectively. Difference with volumetric flow rate The jet initiation time difference is 100%. The volumetric flow rate difference is .

[0166] Step 602: If the difference in jet initiation time between the two thinning regions is less than a preset time threshold and the difference in volumetric flow rate is less than a preset flow rate threshold, then the two thinning regions are merged.

[0167] In some embodiments, if Less than the preset time threshold ,and Less than the preset flow threshold If it can be determined that the cooling requirements of the two thinning regions are relatively similar, then the two thinning regions can be... and They are merged into a single merged region, which is controlled by a flexible standard cooling module.

[0168] In some embodiments, the cooling start time of the merging region can be determined based on the cooling start time of the multiple thinning regions included in the merging region. For example, the cooling start time of the merging region is... This means that the minimum cooling start time of multiple thinning regions can be determined as the start time of the merging region, and the volumetric flow rate of the merging region can be determined based on the volumetric flow rates of the multiple thinning regions included in the merging region. For example, the volumetric flow rate of the merging region is... This means that the maximum volumetric flow rate of multiple thinning regions can be the volumetric flow rate of the merged region, where the volumetric flow rate can be the compensated volumetric flow rate.

[0169] In summary, the above embodiments of this disclosure can merge thinning regions with similar cooling requirements into a single merged region. Then, a flexible standard cooling module can perform overall cooling control on the merged region, which can meet the cooling requirements of different thinning regions while reducing the complexity of the control logic.

[0170] The above method will be explained and illustrated through specific embodiments below.

[0171] like Figure 7 The diagram illustrates a distributed liquid nitrogen targeted cooling control strategy based on the average thinning rate of a region. It mainly comprises five core stages: region division, matching jet paths, calculating the cooling start time for the initial jet flow, path merging, and selecting cooling conditions. First, the thermoformed sheet is divided into regions, and the average thinning rate of each region is calculated. If the average thinning rate is greater than or equal to a thinning rate threshold, the region is identified as a thinning region; otherwise, it is identified as a non-thinning region. For non-thinning regions, no cooling is required, so the corresponding jet paths can be closed. For thinning regions, the targeted cooling characteristic points for each region are determined, and a jet path is matched for each region (cooling region). Then, the cooling start time for each thinning region is calculated. Optionally, the required jet flow rate for each thinning region can also be determined.

[0172] In some embodiments, channels can be merged based on the cooling start time of each thinning region and the jet flow rate required for each thinning region. If the difference between the jet start times of any two thinning regions is less than a preset time threshold and the difference in volumetric flow rate is less than a preset flow rate threshold, the two thinning regions are merged and cooled by the same flexible standard cooling module (flexible path). If the difference between the jet start times is less than the preset time threshold and / or the difference in volumetric flow rate is less than the preset flow rate threshold, independent cooling control can be maintained for each thinning region (i.e., independent channel control is maintained).

[0173] In some embodiments, after determining the target area through the above process, a cooling condition can be selected for each target area, and then the flow rate regulation of the corresponding condition can be performed. When the cooling time corresponding to the target area is reached, the jet path can be closed to stop cooling the target area.

[0174] Figure 9 This is a schematic diagram of a liquid nitrogen jet partitioned cooling multi-condition system provided according to an embodiment of this disclosure. Specifically, Figure 9 This paper demonstrates how a multi-channel distributed liquid nitrogen jet cooling system for thermoforming can meet the diverse needs of three operating conditions through different hardware combinations: dynamic feedforward anti-thinning jet operation, periodic pressure holding and quenching operation, and fixed-parameter batch static cooling operation. The paper shows the usage status of each valve under each condition and explains the system's control logic. This allows for equipment selection based on the corresponding operating condition and real-time valve adjustment to meet different requirements during the thermoforming process.

[0175] Optionally, under the dynamic feedforward anti-thinning jet condition, the flow measurement element of the flexible standard cooling module is a flow meter, the opening adjustment unit is an electric regulating valve, the jet control unit is a control module, the check valve and manual valve are always open, and the low-temperature solenoid valve remains open.

[0176] Optionally, under multi-channel periodic pressure holding and quenching conditions, the flow measurement element of the flexible standard cooling module is a flow meter, the opening adjustment unit is an electric regulating valve, and the jet control unit includes a control module and a cryogenic solenoid valve, a check valve, and a manual valve that are always open.

[0177] Optionally, under fixed-parameter batch static cooling conditions, the flow measurement unit of the flexible standard cooling module is a liquid nitrogen weighing system, the opening adjustment unit is a manual valve with scale markings, the jet control unit is a control module and a cryogenic solenoid valve, and the check valve and electric regulating valve are always open.

[0178] In this disclosure, unless otherwise stated, elements expressed in the singular form, such as "a," "an," "the," "the," "the," "the," "the," "the," "this," etc., can mean "one and only one," or "one or more," "at least one," etc. For example, when using articles such as "a," "an," "the," etc. in translation, the noun following the article can be understood as either a singular or a plural expression.

[0179] In the embodiments of this disclosure, "multiple" refers to "two or more", "at least two", etc. The terms "at least one of A or B", "at least one of A and B", "one or more", "a plurality of", "multiple" etc. can be used interchangeably.

[0180] In some embodiments, the notation "A or B" may include the following technical solutions, depending on the situation: in some embodiments, A (execute A regardless of whether a branch B exists); in some embodiments, B (execute B regardless of whether a branch A exists); in some embodiments, execution is selected from A and B (A and B are selectively executed). The same applies when there are more branches such as A, B, and C.

[0181] The prefixes "first," "second," etc., used in the embodiments of this disclosure are merely for distinguishing different descriptive objects and do not impose restrictions on the position, order, priority, quantity, or content of the descriptive objects. The description of the descriptive objects is found in the claims or the context of the embodiments, and the use of prefixes should not constitute unnecessary restrictions. For example, if the descriptive object is a "field," the ordinal numbers preceding "field" in "first field" and "second field" do not restrict the position or order of the "fields." "First" and "second" do not restrict whether the "fields" they modify are in the same message, nor do they restrict the order of "first field" and "second field." Similarly, if the descriptive object is a "level," the ordinal numbers preceding "level" in "first level" and "second level" do not restrict the priority between "levels." Furthermore, the number of descriptive objects is not limited by ordinal numbers and can be one or more. For example, in "first device," the number of "devices" can be one or more. Furthermore, the objects modified by different prefixes can be the same or different. For example, if the object being described is "device", then "first device" and "second device" can be the same device or different devices, and their types can be the same or different. Similarly, if the object being described is "information", then "first information" and "second information" can be the same information or different information, and their content can be the same or different.

[0182] In some embodiments, terms such as “in response to…”, “in response to determining…”, “in the case of…”, “when…”, “when…”, “if…”, etc. can be used interchangeably. These descriptions all refer to the device making a corresponding action under certain objective circumstances. They do not necessarily limit the time, nor do they require the device to make a judgment action when implementing it, nor do they mean that there must be other limitations.

[0183] In some embodiments, the terms “greater than,” “greater than or equal to,” “not less than,” “more than,” “more than or equal to,” “not less than,” “higher than,” “higher than or equal to,” “not lower than,” and “above” can be used interchangeably, as can the terms “less than,” “less than or equal to,” “not greater than,” “less than,” “less than or equal to,” “not more than,” “lower than,” “lower than or equal to,” “not higher than,” and “below”.

[0184] In some embodiments, devices, etc., may be interpreted as physical or virtual, and their names are not limited to those described in the embodiments. Terms such as “device,” “equipment,” “device,” “node,” “unit,” “section,” “system,” “entity,” and “body” are interchangeable.

[0185] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A multi-channel distributed liquid nitrogen jet cooling system for thermoforming, characterized in that, include: Liquid nitrogen storage and pressure stabilization module, used to store liquid nitrogen and adjust the liquid nitrogen output pressure; Multiple flexible standard cooling modules are connected in parallel on a main liquid supply pipe and in series with the liquid nitrogen storage and stabilization module. Each flexible standard cooling module includes a liquid nitrogen output pipe, a flow regulating valve group and a flow sensing element configured on the liquid nitrogen output pipe. The liquid nitrogen output pipe is connected to the cooling channel of the thermoforming mold. Different cooling channels and different numbers of jet holes on the cooling channels correspond to different thinning areas of the part to be formed. Each flexible standard cooling module corresponds to one thinning area or a combined area of ​​multiple thinning areas. The control module is connected to the plurality of flexible standard cooling modules respectively. It is used to adjust the corresponding flexible standard cooling modules according to the cooling conditions selected for each thinning region and / or each merging region, and according to the cooling start time and liquid nitrogen output pressure of each thinning region and / or each merging region under different cooling conditions, so as to control the liquid nitrogen jet flow rate during the cooling process. It is also used to determine the liquid nitrogen gas mass fraction based on the data of the passage sensing element. When a gas-liquid phase change occurs in the liquid nitrogen output pipeline, it adjusts the passage regulating valve group according to the liquid nitrogen gas mass fraction to adjust the liquid nitrogen flow rate of the liquid nitrogen output pipeline.

2. The system according to claim 1, characterized in that, The liquid nitrogen storage and pressure stabilization module includes: a liquid nitrogen storage tank; a pressure regulating valve group connected to the output end of the liquid nitrogen storage tank for regulating the liquid nitrogen output pressure of the liquid nitrogen storage tank; and a pressure sensor installed on the gas phase valve of the liquid nitrogen storage tank for monitoring the liquid nitrogen output pressure of the liquid nitrogen storage tank. The passage regulating valve group includes a check valve, a manual valve, a solenoid valve, and a regulating valve; the check valve is used to prevent liquid nitrogen backflow; the manual valve regulates the liquid nitrogen volume flow rate by adjusting the valve opening K; wherein, during the thermoforming cooling process, based on the pressure stabilization characteristics in the main liquid supply pipe and the check valves on each liquid nitrogen output pipe, when the liquid nitrogen volume flow rate of any liquid nitrogen output pipe is dynamically adjusted, the liquid nitrogen volume flow rate of the remaining parallel liquid nitrogen output pipes remains stable; The channel sensing element includes a flow measurement element, a pressure sensor, and a temperature sensor; The control module is connected to the solenoid valve, regulating valve, flow measurement element, pressure sensor, and temperature sensor of each flexible standard cooling module. The control module regulates the corresponding flexible standard cooling module by adjusting the solenoid valve and regulating valve, and determines the liquid nitrogen gas mass fraction based on data from the pressure sensor and temperature sensor after pipeline pre-cooling. This control module then adjusts the opening of the regulating valve according to the compensation amount, which is determined based on the liquid nitrogen gas mass fraction. The control module receives real-time feedback from the flow measurement element and adjusts the flow rate based on the target volumetric flow rate of each liquid nitrogen output pipeline. and / or the target average flow rate of each liquid nitrogen output line The control module outputs pulse signals to control the solenoid valve to achieve rapid on / off switching and intermittent cooling, and / or outputs continuous analog signals to control the opening of the regulating valve to achieve continuous flow regulation; the control module realizes the opening and closing of each component in the flexible standard cooling module according to different working conditions.

3. A multi-channel distributed liquid nitrogen jet cooling method for thermoforming, characterized in that, Performed by the multi-channel distributed liquid nitrogen jet cooling system for thermoforming as described in claim 1 or 2, comprising: The thermoformed sheet is divided into thinning regions to determine n thinning regions, where n is a positive integer; At any moment or time period during the hot forming stamping process of the hot-formed sheet, x feature points are selected from the thinning area, and the feature point with the smallest thickness among the x feature points is determined as the targeted cooling feature point. The liquid nitrogen output pipeline in the flexible standard cooling module corresponding to the targeted cooling feature point at the moment or time period is used to preferentially perform directional jet cooling on the targeted cooling feature point. Based on the average thinning rate of each thinning region Curve of variation with total forming time t , g∈[1,n], the average thinning rate reaches the thinning rate threshold. The time is determined as the cooling start time t of the jet stream starting in the region where the targeted cooling feature point is located. g ; Based on the differences in cooling start time and liquid nitrogen volume flow rate requirements between different thinning regions, if the differences in cooling start time and / or volume flow rate requirements of at least two thinning regions meet preset conditions, then the at least two thinning regions are merged into a merged region. The merged region is uniformly controlled by the same flexible standard cooling module, and the merged region has a uniform cooling start time and volume flow rate. For each thinning region and / or each merging region, based on the thinning characteristics and process requirements of the thinning region and / or the merging region during the thermoforming process, the corresponding cooling conditions are selected for the flexible standard cooling modules corresponding to the thinning region and / or the merging region. The cooling conditions include: dynamic feedforward anti-thinning jet condition, multi-channel periodic pressure holding quenching condition, and fixed parameter batch static cooling condition. Based on the selected cooling conditions for each thinning region and / or each merging region, and according to the cooling start time corresponding to each thinning region and / or each merging region, the flexible standard cooling modules corresponding to each thinning region and / or each merging region are controlled to open. During the hot forming stamping process, as the position of the targeted cooling feature point shifts, the opening and closing of the flexible standard cooling modules corresponding to each thinning region and / or each merging region are dynamically controlled under different cooling conditions. Specifically, when the position of the targeted cooling feature point exceeds the critical distance of the first jet hole corresponding to the current time or the current time period, causing a change in the matching relationship between the targeted cooling feature point and the first jet hole, the flexible standard cooling module corresponding to the first jet hole is dynamically controlled to close, and the flexible standard cooling module corresponding to the second jet hole corresponding to the targeted cooling feature point after the change is simultaneously controlled to open.

4. The method according to claim 3, characterized in that, The process of dividing the thermoformed sheet into thinning regions to determine multiple thinning regions includes: The thermoformed sheet is divided into meshes to determine multiple mesh cells, the number of which is X, and the x-th mesh cell is denoted as u. x , x∈[1,X]; Based on the initial thickness of each grid cell The actual thickness of the thermoformed part obtained after the thermoformed sheet is thermoformed. Determine the thinning rate of each grid cell of the thermoformed part. : （1） Based on the thinning rate, the thermoformed sheet is divided into m continuous and independent cooling characteristic regions I = {I1, I2, I3...I...} m-1 I m }, the average thinning rate of the i-th cooling feature region is expressed as , i∈[1,m], where the average thinning rate satisfies The cooling characteristic region is the thinning region, denoted as I. j1 I j2 I j3 ...I j（n-1） I jn The average thinning rate satisfies The cooling characteristic region is the non-thinning region, labeled I. f1 I f2 I f3 ...I f（m-n-1） I f（m-n） The n thinning regions correspond to n liquid nitrogen output pipelines C = {C1, C2, C3...C...} n-1 C n }, The threshold for the thinning rate is m≥2, where m is a positive integer.

5. The method according to claim 3, characterized in that, The step of controlling the activation of the flexible standard cooling modules corresponding to each thinning region and / or each merging region based on the cooling start time of each thinning region and / or each merging region includes: Based on the mechanical response time of the control valve and the transmission delay time of the liquid nitrogen pipeline, determine the total system time lag advance: （2） in The mechanical response time of the regulating valve. The liquid nitrogen pipeline transmission delay time; Based on the total time delay advance of the system, the time delay advance of the channel regulating valve group in the multi-channel distributed liquid nitrogen jet cooling system is adjusted. During the hot forming stamping process, valve C is used in conjunction with v -K characteristic curve, dynamically control the valve opening degree K of the valve corresponding to the target area, so as to dynamically regulate the opening and closing of the flexible standard cooling module. The target area is any thinning area or any merging area.

6. The method according to claim 5, characterized in that, The dynamic control of the valve opening K of the valve corresponding to the target area includes: Obtain the material parameters of the thermoformed sheet, the jet parameters of each thinning region, and the mapping relationship between them and the heat transfer coefficient h: （3） The material parameters mentioned above include at least the material type. Initial thickness Initial temperature of thermoformed sheet The jet parameters include at least the jet distance L and the jet flow rate Q. Thermoforming simulation was performed with the goal of minimizing the thinning rate of the thermoformed part, and the heat transfer coefficient variation curve of each thinning region of the thermoformed sheet was obtained. The jet flow rate is determined based on the mapping relationship and the heat transfer coefficient variation curve. The instantaneous change curve; According to the jet flow rate The instantaneous change curve, combined with the valve C v -K characteristic curve, determine the valve opening degree K.

7. The method according to claim 3, characterized in that, The step of merging the at least two thinned regions into a merged region includes: Based on any two thinning regions and Cooling start time and volumetric flow rate Calculate the jet initiation time difference between the two thinning regions respectively. Difference with volumetric flow rate ; like Less than the preset time threshold ,and Less than the preset flow threshold Then the two thinned regions and The merging process begins when the cooling of the merged region is initiated. The volumetric flow rate of the merged region is .

8. The method according to claim 3, characterized in that, The selection of corresponding cooling conditions for the flexible standard cooling modules corresponding to the thinned region and / or the merged region includes: When the target region is a critical thinning region where the rate of change of the thinning rate gradient exceeds a preset threshold during the forming process, a dynamic feedforward anti-thinning jet condition is selected for the target region, and the target region can be any thinning region or a merged region. The dynamic feedforward anti-thinning jet working condition is as follows: during the thermoforming process, only the regulating valve in the flexible standard cooling module is adjusted, and the check valve, manual valve, and solenoid valve in the flexible standard cooling module remain open. Under the dynamic feedforward anti-thinning jet condition, dynamically controlling the opening and closing of the flexible standard cooling modules corresponding to each thinning region and / or each merging region includes: Before the jet is activated, the pipeline is pre-cooled by opening the valve in advance, and the inlet pressure of the liquid nitrogen output pipeline is collected in real time by the pressure sensor. and export pressure and the temperature collected in real time by the temperature sensor Calculate the initial predicted gas mass fraction without considering heat loss during transmission. : （4） in, For inlet pressure Specific enthalpy of saturated liquid nitrogen; export pressure Specific enthalpy of saturated liquid nitrogen; The latent heat of vaporization under export pressure; To compensate for the insufficient cooling capacity provided by liquid nitrogen vaporization, a flash evaporation compensation coefficient is determined. And based on the flash compensation coefficient, the jet flow rate Q obtained according to the mapping relationship is compensated to Q. v : （5） According to the inlet pressure and the aforementioned outlet pressure Calculate the voltage drop of the actual system ; Calculate the critical pressure ratio coefficient of liquid : （6） in, This is the vapor pressure of liquid nitrogen at the current operating temperature. The thermodynamic critical pressure of liquid nitrogen; Determine the limiting pressure drop caused by fluid blockage. : （7） in, The sum of the liquid pressure recovery coefficient of the valve equipped with fittings and the pipe geometry coefficient. These are the pipe geometry coefficients; Calculate the required flow coefficient : （8） in, It is a numerical constant. The actual density of liquid nitrogen, It is the density of pure water at 15.5℃ and the pressure drop. It is the actual system voltage drop. and ultimate pressure drop The smaller of the two; Combined with C v -K valve characteristic curve, and then determine the valve opening K of the regulating valve; Calculate the target volumetric flow rate for each liquid nitrogen output pipeline. With actual volumetric flow rate Instantaneous flow deviation between ; Based on the basic valve opening degree K and the instantaneous flow deviation, the opening degree command of the regulating valve is adjusted in real time. : （9） in, These are the proportional, integral, and derivative gain coefficients of the control module; the actual volumetric flow rate after the opening command reaches the effective adjustment upper limit. The target volumetric flow rate still cannot be met. If the demand is met, then the inlet pressure will be actively increased. ; For any thinning or merging region, once the actual jetting time reaches the target cooling duration, the valve in the corresponding flexible standard cooling module is closed to end the cooling of the thinning or merging region.

9. The method according to claim 3, characterized in that, The selection of corresponding cooling conditions for the flexible standard cooling modules corresponding to the thinned region and / or the merged region includes: When the target area has an intermittent cooling requirement to maintain a specific cooling rate under constant pressure, a multi-channel periodic pressure holding quenching condition is selected for the target area, where the target area is any thinning area or merged area. The multi-channel periodic pressure holding quenching condition is as follows: during the pressure holding quenching process, the regulating valve and solenoid valve in the flexible standard cooling module are adjusted, and the check valve and manual valve in the flexible standard cooling module are kept open. Under the multi-channel periodic pressure holding quenching condition, dynamically controlling the opening and closing of the flexible standard cooling modules corresponding to each thinning region and / or each merging region includes: The compensated volumetric flow rate was calculated based on the pre-cooling experiment. Calculate the required flow coefficient Combined with the C of the regulating valve v -K characteristic curve, and then determine the valve opening K of the regulating valve; during the pressure holding and quenching process, determine the target average flow rate of the liquid nitrogen output pipeline through the regulating valve according to the required change in cooling capacity. Then, the target pulse ratio required by the solenoid valve is calculated: （10） During the periodic intermittent cooling process, based on the target average flow rate and actual volumetric flow rate The real-time pulse ratio of the solenoid valve is updated in real time. : （11） in, The gain coefficient is adjusted using integral feedback for flow error. A pulse signal at the target frequency is output to control the periodic opening and closing of the solenoid valve.

10. The method according to claim 3, characterized in that, The selection of corresponding cooling conditions for the flexible standard cooling modules corresponding to the thinned region and / or the merged region includes: When the forming process enters the mass production stage or the thinning rate of the target area stabilizes, the fixed parameter batch static cooling condition is selected for the target area, where the target area is any thinning area or a merged area. The fixed parameter batch static cooling condition is as follows: the manual valve and solenoid valve in the flexible standard cooling module are adjusted, and the check valve and regulating valve in the flexible standard cooling module are kept open. Under the fixed-parameter batch static cooling condition, dynamically controlling the opening and closing of the flexible standard cooling modules corresponding to each thinning region and / or each merging region includes: During the thermoforming process, the compensated volumetric flow rate Q is calculated based on the pre-cooling experiment. v Calculate the required flow coefficient C v Combined with manual valve C v -K characteristic curve, thereby determining the valve opening degree K of the manual valve; and using time signals to set the jet stamping and pressure holding quenching time of the hot-formed sheet to control the precise opening and closing of the solenoid valve; and using a flow meter to monitor the flow rate change during the hot forming process to adjust the valve opening degree K of the manual valve.

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