A method for controlling the start and stop of a vacuum insulation carrier pump set timing

Abstract

The application relates to the field of vacuum heat preservation transport vehicles, and discloses a vacuum heat preservation transport vehicle pump group time sequence start-stop control method, which comprises the following steps: acquiring a pump group operation instruction; outputting a mechanical pump starting instruction based on the pump group operation instruction; acquiring a transport chamber cavity pressure and calculating an initial exhaust rate of the transport chamber cavity pressure; outputting a vacuum valve opening instruction when the transport chamber cavity pressure is less than a valve opening pressure threshold value and the initial exhaust rate is greater than or equal to an exhaust rate threshold value; continuously acquiring the transport chamber cavity pressure, and outputting a Roots pump starting instruction when the transport chamber cavity pressure drops to be less than a Roots pump starting pressure threshold value. According to the technical scheme, the Roots pump is started only after the cavity exhaust has been sufficiently attenuated and the pressure drops to a safe range.

Description

Technical Field

[0001] This application relates to the field of vacuum insulated transport vehicles, and in particular to a method for controlling the timing start and stop of a pump unit in a vacuum insulated transport vehicle. Background Technology

[0002] Vacuum insulated transport vehicles are mainly used to transfer high-temperature workpieces between various processing chambers such as carburizing chambers, gas quenching chambers, and oil quenching chambers. During the transfer process, it is necessary to ensure that the workpiece is in a high vacuum and insulated state to prevent the workpiece surface from being oxidized or from generating heat loss.

[0003] In the control execution logic of related technologies, the vacuuming timing generally adopts a combination of fixed delay and static threshold. For example, after the mechanical pump starts, it is forced to wait for a fixed period of time before opening the vacuum valve. Then, when the vacuum gauge detects that the vacuum level in the cavity has reached a certain set value, the contactor is triggered to close to start the Roots pump.

[0004] Because high-temperature workpieces and their supporting trays undergo continuous venting under low-pressure conditions, releasing a large amount of gas, the gas flow field in the handling chamber is highly fluctuating. When the venting volume is large, forcibly opening the vacuum valve simply to meet the fixed delay time will cause the Roots pump to operate under extremely high gas loads. This causes the rotor to experience severe gas impact resistance, and in severe cases, it may even cause the main motor operating current of the Roots pump to momentarily exceed the load, triggering the circuit breaker to trip. Summary of the Invention

[0005] This application provides a method for controlling the timing of pump unit start-stop in a vacuum insulated transport vehicle, which at least partially solves the above-mentioned technical problems.

[0006] To achieve the above objectives, this application provides a timing start-stop control method for a vacuum-insulated transport vehicle pump unit, comprising:

[0007] Obtain pump set operation instructions;

[0008] Based on the pump set operation command, a mechanical pump start command is output;

[0009] Obtain the pressure in the transport chamber and calculate the initial exhaust rate of the pressure in the transport chamber;

[0010] When the pressure in the transport chamber is less than the valve opening pressure threshold and the initial exhaust rate is greater than or equal to the exhaust rate threshold, a vacuum valve opening command is output.

[0011] The pressure in the transport chamber is continuously acquired, and when the pressure in the transport chamber drops below the Roots pump start-up pressure threshold, a Roots pump start-up command is output.

[0012] In this embodiment, the above technical solution overcomes the defect in the related technology that the fixed delay still forces the vacuum valve to open when the high-temperature workpiece is violently venting, resulting in excessive gas load on the Roots pump; the Roots pump only starts after the gas venting in the cavity has sufficiently decayed and the pressure has dropped to a safe range.

[0013] Other features and advantages of this application will be described in detail in the following detailed description section. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a flowchart illustrating the steps of a timing start-stop control method for a vacuum insulated transport vehicle pump unit provided in an exemplary embodiment of this application.

[0016] Figure 2 This is a schematic diagram of an empty insulated transport vehicle. Detailed Implementation

[0017] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the protection scope of this application.

[0018] This application provides a timing start-stop control method for a vacuum-insulated transport vehicle pump unit. Please refer to [link / reference]. Figure 1 The present application provides a method for controlling the timing start-stop of a vacuum-insulated transport vehicle pump unit, which includes the following steps:

[0019] Step 101: Obtain the pump set operation command.

[0020] Step 102: Based on the pump set operation command, output the mechanical pump start command.

[0021] Step 103: Obtain the pressure of the transport chamber and calculate the initial exhaust rate of the pressure of the transport chamber.

[0022] Step 104: When the pressure in the transport chamber is less than the valve opening pressure threshold and the initial exhaust rate is greater than or equal to the exhaust rate threshold, output a vacuum valve opening command.

[0023] Step 105: Continuously acquire the pressure of the transport chamber cavity, and when the pressure of the transport chamber cavity drops to less than the Roots pump start-up pressure threshold, output a Roots pump start-up command.

[0024] This method is executed by a controller unit; in one feasible scheme, the controller unit is implemented using a programmable logic controller; in another feasible scheme, it is implemented using an embedded microcontroller in conjunction with a dedicated analog front-end chip; and in yet another feasible scheme, it is implemented using a microcontroller; the controller unit and each actuator communicate with each other through digital output ports or fieldbus communication.

[0025] Obtaining pump set operation commands; pump set operation commands refer to control commands issued by the host computer or operator to initiate the vacuum pumping process. These commands typically include the pump set number, target vacuum level, and operation sequence. In some implementations, the host computer or operation panel sends the pump set start command to the controller unit; in one implementation, a hard-wired button signal triggers the controller input port; in another implementation, operation commands are input via a touchscreen interface and transmitted to the controller via a communication bus; in yet another implementation, pump set operation is triggered by scheduling commands from a remote monitoring system.

[0026] The initial exhaust rate is calculated in one way: by dividing the pressure difference between two consecutive sampling periods by the sampling period; in another way: by taking a weighted average of multiple pressure difference data after sliding window mean filtering; and in yet another way: by calculating it based on the relative rate of change of the pressure in the cavity per unit time. In specific calculations, the exponentially weighted moving average method can be optionally used to smooth the exhaust rate to suppress the measurement noise of the pressure sensor.

[0027] In one implementation, when the cavity pressure is lower than the valve opening pressure threshold and the initial exhaust rate reaches or exceeds the exhaust rate threshold simultaneously, it is determined that the venting in the cavity has become gradual, and a vacuum valve opening command is output at this time. In another implementation, the judgment of the exhaust rate change trend is added. When the slope of the exhaust rate changes from negative to positive or approaches zero, it indicates that the main venting stage has passed, and the vacuum valve is opened at this time. In yet another implementation, the rolling average of the exhaust rate is calculated by multi-cycle continuous sampling. The vacuum valve opening command is triggered only when the rolling average meets the threshold condition for three consecutive cycles, so as to improve the reliability of the judgment.

[0028] The timing of Roots pump startup can be determined in several ways. In one implementation, a Roots pump startup command is immediately output when the chamber pressure continues to drop and falls below the Roots pump startup pressure threshold for the first time. In another implementation, the startup command is only triggered when the chamber pressure remains below the startup threshold for two consecutive sampling periods, thus eliminating false triggering caused by pressure fluctuations. In yet another implementation, an exhaust rate condition is added on top of the pressure condition, requiring the Roots pump to start only when the chamber pressure is below the threshold and the exhaust rate is below the safety threshold, further reducing the startup load.

[0029] The above technical solution, which obtains the cavity pressure in real time and calculates the initial exhaust rate, makes the opening timing of the vacuum valve no longer dependent on a fixed delay but on the actual venting state. This overcomes the defect of related technologies where a fixed delay forces the vacuum valve to open when the workpiece is venting violently at high temperatures, resulting in excessive gas load on the Roots pump. The Roots pump only starts after the venting in the cavity has sufficiently decayed and the pressure has dropped to a safe range, avoiding overload tripping of the Roots pump main motor, preventing backflow of mechanical pump oil, and improving the operational stability of the vacuum insulation transport vehicle.

[0030] In some embodiments, calculating the initial exhaust rate of the transport chamber pressure includes:

[0031] Extract consecutive first and second pressure sample values ​​according to the sampling period;

[0032] Calculate the difference between the first pressure sample value and the second pressure sample value;

[0033] The initial exhaust rate is obtained by dividing the difference by the sampling period.

[0034] Specifically, regarding the sampling period, in one implementation, it is set to 100 milliseconds, which balances response speed and noise immunity requirements; in another implementation, an adaptive sampling period is adopted, which adjusts the sampling frequency according to the severity of changes in cavity pressure, shortening the sampling period during periods of rapid pressure change and extending the sampling period during periods of gradual pressure change to balance response speed and computational resource consumption.

[0035] In one implementation, the first pressure sample value corresponds to the cavity pressure reading at the current time t, and the second pressure sample value corresponds to the cavity pressure reading at the previous time t-1. In another implementation, the pressure values ​​of three consecutive sampling periods are averaged and then subtracted pairwise to reduce the influence of random noise from the pressure sensor. In yet another implementation, a sampling strategy with outlier rejection is adopted. When the difference between a sample value and the previous sample value exceeds an outlier threshold, the sample value is determined to be a sensor glitch and rejected to avoid distorting the calculation results of the exhaust rate by outlier sample values.

[0036] When the difference is positive, it indicates that the pressure is decreasing, and its absolute value is taken as the exhaust rate. In another implementation, the scalar value of the exhaust rate is obtained by dividing the pressure drop by the sampling time. In yet another implementation, the original pressure sampling value is low-pass filtered before the differential operation to remove power frequency interference and high-frequency noise components caused by sensor temperature drift.

[0037] In some embodiments, after the output mechanical pump start command, the method further includes:

[0038] When the pressure in the transport chamber is less than the valve opening pressure threshold and the initial exhaust rate is less than the exhaust rate threshold, the pump oil protection step is triggered.

[0039] In the oil pump protection step, the exhaust rate difference between the exhaust rate threshold and the initial exhaust rate is calculated, and a corresponding duty cycle parameter is generated based on the exhaust rate difference.

[0040] Based on the duty cycle parameter, a pulse control signal is generated as a pulse command for the gas ballast valve and output.

[0041] Start the gas ballast protection timer and cancel the gas ballast valve pulse command when the gas ballast protection timer reaches the gas ballast purification time.

[0042] Specifically, in one implementation, when the chamber pressure is lower than the valve opening pressure threshold but the initial venting rate is lower than the venting rate threshold, it indicates that the current venting speed is still relatively fast. If the vacuum valve is opened at this time, the Roots pump will be subjected to excessive atmospheric load, thus triggering the pump oil protection step. In another implementation, based on the above conditions, the judgment of the chamber pressure decreasing trend is added. When the venting rate is not up to standard but shows an upward trend, the triggering of the pump oil protection step is delayed. In yet another implementation, if the venting rate is consistently lower than the threshold for three consecutive sampling cycles and the slope of the chamber pressure decrease tends to flatten, it is determined that the venting is about to end, and the pump oil protection step can be exited in advance.

[0043] In one implementation, a linear proportional mapping is used, where a larger difference in exhaust rates corresponds to a smaller duty cycle parameter, meaning a higher opening ratio of the gas ballast valve, allowing more dry gas to enter the mechanical pump compression chamber to suppress the condensation of condensable gases in the oil. In another implementation, a segmented lookup table mapping is used, where the corresponding duty cycle parameter is retrieved based on the interval where the difference lies. In yet another implementation, a mapping rule based on fuzzy logic is used, dividing the exhaust rate difference into several fuzzy subsets and corresponding to different duty cycle outputs to achieve a smoother gas ballast control effect.

[0044] In one implementation, the frequency and duty cycle of the pulse signal are adjusted according to the difference in exhaust rates. The larger the difference, the higher the pulse frequency and the larger the duty cycle. In another implementation, during the pulse command output of the gas ballast valve, the operating current value of the mechanical pump is monitored. When the operating current fluctuates significantly, the duty cycle parameter is increased to enhance the gas ballast effect.

[0045] In one implementation, the gas ballast purification time is calculated based on the ratio of the chamber volume to the mechanical pump speed; the larger the volume or the smaller the pump speed, the longer the purification time. In another implementation, the exhaust rate is continuously sampled during the timing period, and the pump oil protection step is immediately exited when the exhaust rate first reaches or exceeds the exhaust rate threshold, without waiting for the timing to end.

[0046] By using the mapping relationship between the exhaust rate difference and the duty cycle parameter to control the opening degree of the gas ballast valve, the amount of dry gas introduced is matched with the actual exhaust intensity, avoiding the loss of pumping efficiency caused by excessive gas ballast, effectively inhibiting the condensation of condensable gases in the oil, and achieving the effect of protecting the quality of the mechanical pump oil and extending the service life of the mechanical pump.

[0047] In some embodiments, prior to the output vacuum valve opening command, the method further includes:

[0048] Obtain real-time water temperature sampling values ​​or real-time furnace temperature sampling values ​​of the insulation jacket located at the outlet of the cooling water pipeline of the transport vehicle;

[0049] Extract the real-time water temperature sampling value or the real-time furnace temperature sampling value within a continuous time period and calculate the temperature change rate;

[0050] The threshold compensation amount is calculated based on the temperature compensation equation and the temperature change rate.

[0051] The exhaust rate threshold is updated by adding the threshold compensation amount to the exhaust rate reference value.

[0052] Specifically, in one implementation, the cooling water temperature is obtained by a temperature sensor located at the cooling water outlet of the mechanical pump to reflect the current heat dissipation status of the mechanical pump; in another implementation, the temperature difference value is obtained by a temperature difference sensor at the cooling water inlet and outlet to indirectly characterize the pump body temperature; in yet another implementation, multiple temperature sensors are connected in series in the cooling water pipeline and the weighted average value is taken as the water temperature sampling value to reduce the impact of single-point sensor failure.

[0053] In one implementation, the real-time temperature inside the insulation interlayer is obtained by using thermocouple temperature sensors arranged inside the insulation interlayer; in another implementation, the temperature of the outer wall of the cavity is measured non-contactly by an infrared temperature sensor and converted into a furnace temperature sampling value; in yet another implementation, the temperature values ​​at multiple locations inside the insulation interlayer are collected simultaneously and the arithmetic mean is taken as the furnace temperature sampling value to reflect the overall temperature status of the insulation area.

[0054] The temperature change rate is obtained by using the same differential calculation method as the initial exhaust rate, i.e., dividing the temperature difference between two consecutive sampling periods by the sampling period. In another implementation, the temperature change rate is calculated using the exponentially weighted moving average method to suppress instantaneous fluctuations in temperature sampling. In yet another implementation, when the temperature change rate exceeds the temperature mutation threshold, a temperature anomaly alarm is triggered and the vacuum valve opening process is paused until the temperature change rate returns to the normal range.

[0055] For the temperature compensation equation, in one implementation, a linear compensation equation is used: the threshold compensation amount is equal to the temperature change rate multiplied by the compensation coefficient; in another implementation, a nonlinear compensation equation is used, and the compensation amount has a piecewise linear or exponential relationship with the temperature change rate; in yet another implementation, a multivariate compensation equation based on experimental data fitting is used, and the threshold compensation amount is calculated by considering two input variables: the temperature change rate and the current cavity pressure.

[0056] The new, compensated threshold is added to the original baseline value and used as the exhaust rate threshold for the current control cycle. In another implementation, a smooth update strategy is adopted, where the new exhaust rate threshold is equal to the weighted average of the old threshold and the compensation amount, in order to avoid control instability caused by threshold abrupt changes. In yet another implementation, upper and lower limit constraints are set, and the amplitude is automatically limited when the updated threshold exceeds the range.

[0057] By adopting the above scheme, the exhaust rate threshold can be adjusted according to the thermal conditions, overcoming the defect in related technologies that the static threshold cannot be adaptively adjusted when the exhaust of high-temperature workpieces is violent.

[0058] In some embodiments, after the output Roots pump start command, the method further includes:

[0059] Receive pump unit shutdown command;

[0060] Based on the pump set shutdown command, the Roots pump start command is revoked, and the first timer is started;

[0061] When the first timer reaches the valve closing time, the vacuum valve opening command is canceled and the gas ballast valve normally open command is output simultaneously to introduce dry gas into the compression chamber of the mechanical pump.

[0062] Start the second timer, and when the second timer reaches the pumping time after the mechanical pump is exhausted, simultaneously cancel the mechanical pump start command and the gas ballast valve normally open command.

[0063] Specifically, when the pump set shutdown command arrives, the drive signal of the Roots pump is immediately cut off to stop its operation, and the first timer is started. In another implementation, before canceling the Roots pump start command, speed ramp control is performed to gradually reduce the rotor speed of the Roots pump to reduce the shutdown impact before the drive signal is cut off. In yet another implementation, the chamber pressure value at the time of shutdown is recorded so that it can be used as historical reference data for the next startup.

[0064] In one implementation, the valve closing time is set between 5 and 15 seconds, specifically determined by the pipeline volume and the vacuum valve response time. In another implementation, an adjustable valve closing time is used, adjusted according to the running time of the Roots pump before shutdown; the longer the running time, the longer the waiting time before valve closing, ensuring that the gas in the chamber has sufficient time to be discharged by the mechanical pump. In yet another implementation, the rate of pressure recovery in the chamber is detected while the vacuum valve is closed; if the pressure recovery is too rapid, the waiting time before valve closing is automatically extended.

[0065] The normally open command for the gas ballast valve keeps it fully open, allowing the mechanical pump's compression chamber to be flushed with the maximum flow of dry gas. In another implementation, the gas ballast valve is kept at a moderate opening, providing only the minimum flow of dry gas required to maintain positive pressure, thus reducing the consumption of dry gas. In yet another implementation, the opening of the gas ballast valve is adjusted in stages based on the cumulative running time of the mechanical pump before shutdown; the longer the running time, the greater the flow of dry gas.

[0066] When the second timer reaches the pumping time after the mechanical pump stops, the mechanical pump enable signal and the gas ballast valve drive signal are cut off, causing the mechanical pump to stop completely. In another implementation, the normally open command of the gas ballast valve is canceled before the mechanical pump stops, and the mechanical pump start command is canceled after a short delay to ensure that the mechanical pump stops smoothly without additional gas load. In yet another implementation, the mechanical pump stops using soft stop control, which gradually reduces the mechanical pump speed to zero by decreasing the duty cycle of the drive signal to reduce the instantaneous impact of stopping.

[0067] By adopting the above scheme, the coordinated control of introducing dry gas into the mechanical pump during shutdown ensures that residual gas in the cavity can be fully discharged before the mechanical pump stops, preventing the problem of condensable gas condensing and flowing back into the pump cavity at the moment of shutdown, and overcoming the defect of oil backflow in the pump cavity caused by improper shutdown sequence in related technologies.

[0068] In some embodiments, the output vacuum valve opening command includes:

[0069] Output the drive signal with the first duty cycle to the vacuum valve actuator;

[0070] Extract the pressure sampling values ​​of the transport chamber cavity for N consecutive cycles according to the time interval, and calculate the standard deviation of the pressure sampling values ​​of the transport chamber cavity for the N cycles.

[0071] The standard deviation is defined as the fluctuation range of the pressure in the transport chamber.

[0072] When the fluctuation amplitude is less than the pressure fluctuation threshold, a drive signal with a second duty cycle is output to the vacuum valve actuator, wherein the second duty cycle is greater than the first duty cycle;

[0073] When the pressure in the transport chamber continues to decrease, a valve full-open drive signal is sent to the vacuum valve actuator.

[0074] Specifically, for the drive signal outputting the first duty cycle, in one implementation, the first duty cycle is set between 30% and 40%, causing the vacuum valve to open slowly with a small initial opening, in order to avoid impact noise and valve disc damage caused by excessive pressure difference across the valve; in another implementation, the first duty cycle is calculated based on the difference between the cavity pressure and atmospheric pressure, and the larger the pressure difference, the smaller the first duty cycle, in order to achieve a smoother valve start-up; in yet another implementation, the first duty cycle is set to zero, and the opening of the vacuum valve is gradually increased through multiple short pulses to achieve a smooth initial opening effect.

[0075] Extract pressure sampling values ​​for N consecutive cycles and calculate the standard deviation. In another implementation, N is determined by the ratio of cavity volume to mechanical pump pumping speed. The larger the volume, the larger the value of N to obtain a more reliable fluctuation assessment.

[0076] The second duty cycle is set as the first duty cycle multiplied by the amplification factor. In another implementation, the second duty cycle is calculated based on the proximity of the fluctuation amplitude to the pressure fluctuation threshold. The closer the fluctuation amplitude is to the threshold but has not yet reached it, the larger the second duty cycle is to accelerate the valve opening increase. In yet another implementation, the second duty cycle is determined by a lookup table. The corresponding second duty cycle value is retrieved based on the interval into which the fluctuation amplitude falls.

[0077] The pressure is determined to be continuously decreasing by the pressure value of three consecutive sampling cycles being lower than the value of the previous cycle; in another implementation, the pressure is determined to be continuously decreasing when the rate of decrease of the cavity pressure is greater than the rate of decrease threshold; in yet another implementation, the output of the valve fully open signal must simultaneously satisfy the condition that the cavity pressure has been continuously decreasing and has been stable for a period of time, in order to avoid the valve from being mistakenly fully opened due to a brief pressure rebound.

[0078] By adopting the above solution, the defects of the related technologies, such as sudden changes in system pressure and gas impact noise caused by directly opening the valve to the fullest extent, are overcome.

[0079] In some embodiments, the output Roots pump start command includes:

[0080] The pressure and frequency mapping table is found based on the current pressure in the transport chamber.

[0081] Extract the first target operating frequency corresponding to the pressure in the transport chamber;

[0082] The output includes a drive signal containing the first target operating frequency as the start command for the Roots pump;

[0083] When the pressure in the transport chamber continues to drop to the ultimate vacuum threshold, the Roots pump start command is updated to a second target operating frequency, wherein the second target operating frequency is greater than the first target operating frequency.

[0084] Specifically, the pressure-frequency mapping table can be implemented in several ways. In one implementation, the table is obtained through experimental calibration, with the horizontal axis representing the recommended inlet pressure of the Roots pump and the vertical axis representing the optimal operating frequency corresponding to that pressure value. In another implementation, the mapping table uses a multi-segment linear interpolation method, with the intermediate frequency calculated using linear interpolation between adjacent calibration pressure points. In yet another implementation, the mapping table is generated by a simulation model and updated periodically based on actual operating data to compensate for performance changes caused by Roots pump wear.

[0085] In one implementation, the controller obtains the first target operating frequency from a table based on the current chamber pressure, and then outputs an AC drive signal of the corresponding frequency through the frequency converter to make the Roots pump motor operate at that frequency. In another implementation, a frequency ramp start is performed before outputting the drive signal to gradually increase the speed of the Roots pump from zero to the first target operating frequency to reduce the start-up impact. In yet another implementation, the starting frequency of the Roots pump is set according to the last operating frequency recorded before shutdown to reduce the number of frequency adjustments during frequent start-stop cycles.

[0086] When the chamber pressure drops below the ultimate vacuum threshold, it indicates that the demand for pumping speed increases. The controller raises the target operating frequency of the Roots pump from the first target frequency to the second target frequency to accelerate the pumping speed. In another implementation, the frequency increase process adopts a step-by-step approach, gradually increasing from the first target frequency to the second target frequency, with a time interval maintained between each increase to ensure the stability of the rotor system. In yet another implementation, the second target operating frequency is calculated based on the difference between the chamber pressure and the target vacuum level; the larger the difference, the higher the second target frequency.

[0087] By adopting the above solution, the defect of Roots pumps operating at a fixed frequency in related technologies that cannot adapt to changes in chamber pressure is overcome.

[0088] In some embodiments, prior to the output mechanical pump start command, the method further includes:

[0089] Obtain hydraulic feedback signals from the cooling water circuit and limit feedback signals from the furnace door of the transport chamber;

[0090] When the hydraulic feedback signal indicates that the water pressure is greater than or equal to the safe water pressure, and the limit feedback signal indicates that the furnace door is in the locked position, the pump set operation command is responded to and executed.

[0091] After the output mechanical pump start command or the output Roots pump start command, the motor operating current value is continuously acquired;

[0092] When the motor operating current exceeds the overload current threshold, an abnormal alarm signal is generated, and the Roots pump start command, the vacuum valve opening command, and the mechanical pump start command are simultaneously revoked.

[0093] Specifically, in one implementation, the hydraulic feedback signal is provided by a water pressure sensor in the cooling water circuit. When the water pressure reaches or exceeds the safe water pressure, it indicates that the cooling system is normal. In another implementation, two water pressure sensors are connected in series in the cooling water circuit. When either sensor detects insufficient water pressure, it is determined that the cooling is abnormal. In yet another implementation, in addition to the water pressure signal, the cooling water flow signal is also collected as a basis for judgment. The mechanical pump is only allowed to start when both the water pressure and flow rate meet the conditions.

[0094] In one implementation, a mechanical limit switch is installed on the furnace door of the transfer chamber. After the furnace door is fully closed and locked, the limit switch outputs a closing signal. In another implementation, the furnace door limit signal is linked with the safety interlock system. The mechanical interlock of the vacuum system can only be released to allow the vacuum valve to open when the furnace door is locked. In yet another implementation, the furnace door limit signal is combined with the furnace door position signal from the infrared detector to determine the position, in order to prevent safety hazards caused by the failure of a single sensor.

[0095] The motor operating current value is continuously acquired. In one implementation, the operating current of the mechanical pump motor is collected by a current transformer and sent to the controller for real-time monitoring after analog-to-digital conversion. In another implementation, the operating current of the Roots pump motor is collected to achieve simultaneous overload monitoring of the two pump sets.

[0096] For the generation of abnormal alarm signals and emergency shutdown control, in one implementation, when the motor operating current exceeds the overload current threshold, the buzzer and indicator light are immediately triggered to alarm, and all pump group commands are simultaneously revoked according to the shutdown sequence. In another implementation, a graded protection strategy is adopted according to the extent of the overload current exceeding the limit. In the case of slight overload, the speed of the Roots pump is reduced and an alarm is triggered first. In the case of severe overload, a full emergency shutdown is executed. In yet another implementation, the alarm signal is simultaneously reported to the host computer monitoring system via the communication bus so that operators can obtain abnormal information in a timely manner.

[0097] In some embodiments, after calculating the initial exhaust rate of the transport chamber pressure, the method further includes:

[0098] Start the third timer;

[0099] When the initial exhaust rate is greater than or equal to the exhaust rate threshold and the count value of the third timer reaches the timeout threshold, a vacuum valve closing command is output.

[0100] The pressure rise rate of the transport chamber cavity pressure is collected during the pressure holding test cycle;

[0101] When the pressure rise rate is greater than the leakage threshold, a sealing abnormality shutdown signal is generated;

[0102] When the pressure rise rate is less than or equal to the leakage threshold, the vacuum valve opening command is re-output.

[0103] Specifically, when the initial venting rate meets the standard but the chamber pressure drops too slowly, it indicates that venting is nearing its end but the mechanical pump speed is insufficient. At this point, the third timer is activated, and the vacuum valve is forcibly closed to stop ineffective venting when the timer reaches the timeout threshold. In another implementation, the timeout threshold is calculated based on the ratio of the chamber volume to the mechanical pump speed; the larger the volume or the smaller the pump speed, the longer the timeout threshold. In yet another implementation, if the chamber pressure has reached the Roots pump start-up pressure threshold before the timeout threshold is reached, the Roots pump is immediately triggered to start, and the timeout timer is canceled.

[0104] In one implementation, the pressure holding detection cycle is set to 30 to 60 seconds. During this cycle, the continuous sampling value of the cavity pressure is recorded and the pressure rise per unit time is calculated as the pressure rise rate. In another implementation, after the vacuum valve is closed, a stabilization period is waited to eliminate the transient impact of valve closure before the pressure holding detection is started.

[0105] When the pressure rise rate exceeds the leakage threshold, it indicates that there is a gas leak in the cavity. At this time, a sealing abnormality shutdown signal is generated and an emergency shutdown procedure is executed. In another implementation, when the pressure rise rate exceeds the standard, an alarm is triggered first and the operator is prompted to confirm. After confirmation, the shutdown is executed to avoid false triggering.

[0106] When the pressure rise rate is within the normal range, it indicates that the seal is good. At this time, the vacuum valve is reopened to continue pumping. In another implementation, the vacuum valve is reopened and output with a smaller initial duty cycle.

[0107] In some embodiments, after calculating the initial exhaust rate of the transport chamber pressure, the method further includes:

[0108] Extract the absolute value of the initial exhaust rate;

[0109] Based on the absolute value lookup of the mapping relationship between exhaust rate and sealing pressure, the target sealing compensation pressure is obtained.

[0110] Output a command containing the target sealing compensation pressure to the docking chamber sealing ring inflation solenoid valve.

[0111] Specifically, the absolute value of the initial exhaust rate is extracted. In one implementation, the positive value of the initial exhaust rate calculation result is taken to eliminate the influence of sign in the pressure differential calculation. In another implementation, the exhaust rate is low-pass filtered while taking the absolute value to obtain a more stable compensation benchmark value. In yet another implementation, the moving average of the absolute value of the exhaust rate is extracted as the compensation benchmark to avoid the influence of instantaneous fluctuations on the sealing compensation result.

[0112] The mapping relationship between exhaust rate and sealing pressure is stored in the form of a two-dimensional lookup table. The absolute value of the exhaust rate is used as the horizontal axis to look up the corresponding target sealing compensation pressure value. In another implementation, a linear proportional mapping is used. The larger the absolute value of the exhaust rate, the higher the target sealing compensation pressure, which can maintain a more sufficient positive sealing pressure in the docking chamber when the gas discharge is violent. In yet another implementation, the mapping relationship uses a piecewise linear function. Linear interpolation is used between adjacent calibrated exhaust rate points to obtain a smoother compensation pressure output.

[0113] The controller converts the target sealing compensation pressure value into a corresponding solenoid valve drive voltage or current signal, which, after digital-to-analog conversion, drives the solenoid valve for inflating the sealing ring in the docking chamber. In another implementation, the target sealing compensation pressure is limited before outputting the command to ensure that the compensation pressure does not exceed the pressure resistance limit of the sealing ring and docking chamber structure. In yet another implementation, the solenoid valve drive signal adopts a closed-loop control method, with the compensation pressure value fed back in real time by a pressure sensor inside the sealing chamber. The controller continuously adjusts the opening of the solenoid valve based on the deviation between the feedback value and the target value to achieve sealing pressure control.

[0114] By adopting the above technical solution, the positive pressure compensation of the sealing ring of the docking chamber can be adjusted in real time according to the venting intensity in the cavity. When the venting is violent, the compensation pressure is automatically increased to maintain the sealing effectiveness, and when the venting is slow, the compensation pressure is appropriately reduced to reduce the consumption of dry gas. This overcomes the problem of seal failure when the venting is violent or resource waste when the venting is slow caused by the fixed sealing compensation pressure in related technologies.

[0115] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0116] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0117] The embodiments, implementation methods, and related technical features of this application can be combined and substituted for each other without conflict.

[0118] The above are merely preferred embodiments of this application and are not intended to limit this application in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. A method for controlling the sequential start-stop of a pump unit in a vacuum-insulated transport vehicle, characterized in that, include: Obtain pump set operation instructions; Based on the pump set operation command, a mechanical pump start command is output; Obtain the pressure in the transport chamber and calculate the initial exhaust rate of the pressure in the transport chamber; When the pressure in the transport chamber is less than the valve opening pressure threshold and the initial exhaust rate is greater than or equal to the exhaust rate threshold, a vacuum valve opening command is output. The pressure in the transport chamber is continuously acquired, and when the pressure in the transport chamber drops below the Roots pump start-up pressure threshold, a Roots pump start-up command is output. After the output mechanical pump start command, the method further includes: When the pressure in the transport chamber is less than the valve opening pressure threshold and the initial exhaust rate is less than the exhaust rate threshold, the pump oil protection step is triggered. In the oil pump protection step, the exhaust rate difference between the exhaust rate threshold and the initial exhaust rate is calculated, and a corresponding duty cycle parameter is generated based on the exhaust rate difference. Based on the duty cycle parameter, a pulse control signal is generated as a pulse command for the gas ballast valve and output. Start the gas ballast protection timer and cancel the gas ballast valve pulse command when the gas ballast protection timer reaches the gas ballast purification time.

2. The method according to claim 1, characterized in that, The initial exhaust rate for calculating the pressure in the transport chamber includes: Extract consecutive first and second pressure sample values ​​according to the sampling period; Calculate the difference between the first pressure sample value and the second pressure sample value; The initial exhaust rate is obtained by dividing the difference by the sampling period.

3. The method according to claim 2, characterized in that, Before the output vacuum valve opening command, the method further includes: Obtain real-time water temperature sampling values ​​or real-time furnace temperature sampling values ​​of the insulation jacket located at the outlet of the cooling water pipeline of the transport vehicle; Extract the real-time water temperature sampling value or the real-time furnace temperature sampling value within a continuous time period and calculate the temperature change rate; The threshold compensation amount is calculated based on the temperature compensation equation and the temperature change rate. The exhaust rate threshold is updated by adding the threshold compensation amount to the exhaust rate reference value.

4. The method according to claim 3, characterized in that, Following the output Roots pump start command, the method further includes: Receive pump unit shutdown command; Based on the pump set shutdown command, the Roots pump start command is revoked, and the first timer is started; When the first timer reaches the valve closing time, the vacuum valve opening command is canceled and the gas ballast valve normally open command is output simultaneously to introduce dry gas into the compression chamber of the mechanical pump. Start the second timer, and when the second timer reaches the pumping time after the mechanical pump is exhausted, simultaneously cancel the mechanical pump start command and the gas ballast valve normally open command.

5. The method according to claim 4, characterized in that, Output vacuum valve opening command, including: Output the drive signal with the first duty cycle to the vacuum valve actuator; Extract the pressure sampling values ​​of the transport chamber cavity for N consecutive cycles according to the time interval, and calculate the standard deviation of the pressure sampling values ​​of the transport chamber cavity for the N cycles. The standard deviation is defined as the fluctuation range of the pressure in the transport chamber. When the fluctuation amplitude is less than the pressure fluctuation threshold, a drive signal with a second duty cycle is output to the vacuum valve actuator, wherein the second duty cycle is greater than the first duty cycle; When the pressure in the transport chamber continues to decrease, a valve full-open drive signal is sent to the vacuum valve actuator.

6. The method according to claim 5, characterized in that, Output Roots pump start command, including: The pressure and frequency mapping table is found based on the current pressure in the transport chamber. Extract the first target operating frequency corresponding to the pressure in the transport chamber; The output includes a drive signal containing the first target operating frequency as the start command for the Roots pump; When the pressure in the transport chamber continues to drop to the ultimate vacuum threshold, the Roots pump start command is updated to a second target operating frequency, wherein the second target operating frequency is greater than the first target operating frequency.

7. The method according to claim 6, characterized in that, Prior to the output of the mechanical pump start command, the method further includes: Obtain hydraulic feedback signals from the cooling water circuit and limit feedback signals from the furnace door of the transport chamber; When the hydraulic feedback signal indicates that the water pressure is greater than or equal to the safe water pressure, and the limit feedback signal indicates that the furnace door is in the locked position, the pump set operation command is responded to and executed. After the output mechanical pump start command or the output Roots pump start command, the motor operating current value is continuously acquired; When the motor operating current exceeds the overload current threshold, an abnormal alarm signal is generated, and the Roots pump start command, the vacuum valve opening command, and the mechanical pump start command are simultaneously revoked.

8. The method according to claim 7, characterized in that, After calculating the initial exhaust rate of the transport chamber pressure, the method further includes: Start the third timer; When the initial exhaust rate is greater than or equal to the exhaust rate threshold and the count value of the third timer reaches the timeout threshold, a vacuum valve closing command is output. The pressure rise rate of the transport chamber cavity pressure is collected during the pressure holding test cycle; When the pressure rise rate is greater than the leakage threshold, a sealing abnormality shutdown signal is generated; When the pressure rise rate is less than or equal to the leakage threshold, the vacuum valve opening command is re-output.

9. The method according to claim 8, characterized in that, After calculating the initial exhaust rate of the transport chamber pressure, the method further includes: Extract the absolute value of the initial exhaust rate; Based on the absolute value lookup of the mapping relationship between exhaust rate and sealing pressure, the target sealing compensation pressure is obtained. Output a command containing the target sealing compensation pressure to the docking chamber sealing ring inflation solenoid valve.

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