Automobile brake oil pot air tightness detection system

Abstract

This invention discloses an airtightness testing system for automotive brake fluid reservoirs, specifically relating to the field of airtightness testing. It addresses the technical problem of unstable leak detection caused by the superposition of float disturbance and test pipeline drift. After the fixture clamps the brake fluid reservoir and seals non-test ports, the product isolation valve is first closed to perform positive and negative pressure self-tests on the test pipeline, obtaining the positive and negative reference slopes of the pipeline, which are then written into the fixture reference table. Next, the product isolation valve is opened to form a test chamber, limiting the air supply and collecting the stop-air pressure sequence after stabilization, generating a state marker based on adjacent differences. When the state marker indicates float disturbance, an alternating short-pulse valve opening and closing sequence is executed, and the reference pressure signal is resampled and locked. Subsequently, during the positive and negative pressure holding stages, the holding pressure sequence is collected and the slope is fitted. The pipeline reference slope in the fixture reference table is subtracted to obtain the positive and negative correction slopes, respectively. A leak conclusion is output and recorded through bidirectional mutual verification.

Description

Technical Field

[0001] This invention relates to the field of airtightness testing, and more specifically, to an airtightness testing system for automotive brake fluid reservoirs. Background Technology

[0002] In automotive hydraulic braking systems, brake fluid reservoirs are used to store and replenish brake fluid. After the reservoir body is welded, it usually needs to undergo airtightness testing on the production line to prevent leakage due to poor sealing, which could affect braking safety. Existing testing devices generally place the assembled brake fluid reservoir on a positioning fixture, fix the reservoir body with a clamping mechanism, and then seal non-test holes with adjustable plugs. Gas is then introduced into the reservoir, and pressure and other signals are collected to determine airtightness. Simultaneously, these devices emphasize the ability to confirm the proper installation of the float inside the reservoir online, thus completing assembly status inspection and airtightness testing at the same workstation. This approach can be found in "A Brake Fluid Reservoir Airtightness Testing Device" (Application No.: CN201310006744XA).

[0003] However, when performing airtightness testing in this "float-equipped state," the testing system often assumes that the internal state of the reservoir is relatively static, and that pressure changes mainly come from leaks. In reality, the float is a freely moving component. The airflow and pressure changes during inflation or deflation can cause the float to swing or shift briefly, resulting in instantaneous changes in the effective internal space and fluctuations in the pressure signal. As a result, "changes caused by float movement" are mixed into the test curve. The system may mistake this disturbance for a leak based solely on pressure decay or stability, or it may relax its judgment to avoid disturbances, thus masking the real, minute leaks. Ultimately, this leads to difficulties in distinguishing between real leaks and float disturbances, poor judgment stability, and insufficient consistency in retests. This problem also occurs in the online testing scenario described in "A Brake Fluid Reservoir Airtightness Testing Device" (application number: CN201310006744XA).

[0004] To address the aforementioned problems, a technical solution is provided. Summary of the Invention

[0005] To overcome the aforementioned deficiencies of the prior art, embodiments of the present invention provide an automotive brake fluid reservoir airtightness testing system. After the clamp presses the brake fluid reservoir and seals the non-test ports, the product isolation valve is first closed to perform positive and negative pressure self-tests on the test pipeline, obtaining the positive and negative reference slopes of the pipeline, which are then written into the clamp reference table. Next, the product isolation valve is opened to form a test chamber, limiting the air supply and collecting the stop-air pressure sequence after stabilization, generating a state marker based on adjacent differences. When the state marker is in the float disturbance state, an alternating short-pulse valve opening and closing sequence is executed, and the reference pressure signal is resampled and locked. Subsequently, during the positive and negative pressure holding stages, the holding pressure sequence is collected and the slope is fitted. The pipeline reference slope in the clamp reference table is subtracted to obtain the positive correction slope and the negative correction slope, respectively. The leakage conclusion is output and recorded through bidirectional mutual verification, thereby solving the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] Pipeline reference module: The clamp presses the brake fluid reservoir and seals the non-test port, closes the product isolation valve, isolates the test pipeline, performs positive pressure gas stop sampling and negative pressure gas stop sampling respectively, and obtains the positive reference slope and the reverse reference slope of the pipeline by linear fitting, and writes them into the clamp reference table;

[0008] Test chamber construction module: Open the product isolation valve, connect the test pipeline and brake fluid reservoir to form a test chamber, limit the air supply until it stabilizes, close the air supply valve, collect the air stop pressure sequence according to a fixed sampling rhythm and write it into the test buffer;

[0009] Disturbance state determination module: Calculates adjacent differences to form a difference sequence for the gas outage pressure sequence. When the difference sequence has both positive and negative differences, it generates a state flag for the float disturbance state. When the difference sequence maintains a unidirectional change, it generates a state flag for the determineable state.

[0010] Pulse voltage regulator module: When the status is marked as float disturbance state, the air supply valve is closed, and the exhaust valve and air supply valve are alternately driven to form a short pulse airflow. The gas stop pressure sequence is re-acquired and the differential sequence is recalculated. When the differential sequence maintains unidirectional change, the starting pressure is locked as the reference pressure signal.

[0011] Two-way mutual verification module: The reference pressure signal enters the isolation and pressure holding section, and the positive detection slope is obtained by fitting the pressure holding pressure sequence with a straight line. The positive correction slope is obtained by subtracting the positive reference slope of the pipeline. The negative pressure holding sequence is fitted in the isolation negative pressure section to obtain the reverse correction slope. The leakage conclusion is mutually verified and recorded.

[0012] Furthermore, the road reference module is used for:

[0013] The product isolation valve is closed to form a pipeline cavity in the test pipeline. Positive pressure self-test and negative pressure self-test are performed respectively. In the gas-stop state, the gas-stop pressure sequence and sampling time sequence are collected. The positive reference slope and the reverse reference slope of the pipeline are calculated by linear fitting. The validity is judged based on the consistency of the sign of the average absolute deviation, the first and last pressure difference and the adjacent pressure difference. The positive reference slope, the reverse reference slope of the pipeline and the time mark are written into the fixture reference table.

[0014] Furthermore, the cavity construction module is used for testing:

[0015] Open the product isolation valve to connect the test pipeline with the brake fluid reservoir to form a test chamber. Clear the test buffer and start the timer. The timer records the sampling time sequence and pressure sequence of the inflation section according to a fixed sampling rhythm. The air supply side flow restriction channel remains open and drives the air supply valve to open, so that the pressure in the test chamber rises steadily.

[0016] Furthermore, the cavity construction module is also used for:

[0017] Stability determination is based on the adjacent pressure difference sequence. The resolution of the pressure sensor is used to record small adjacent pressure differences as zero. The stability determination window length is fixed and the adjacent pressure differences are required to meet the conditions of non-negativity, no increase in absolute value, and continuous zeroing at the end. The gas supply valve is triggered to close and the start time of gas stoppage is recorded. The gas stoppage sampling time sequence and gas stoppage pressure sequence are collected according to a fixed number of sampling points and written into the detection buffer.

[0018] Furthermore, the disturbance determination module is used for:

[0019] The gas outage pressure sequence and gas outage sampling time sequence are read from the detection cache. The gas outage sampling time sequence is checked to ensure that it is increasing. Adjacent difference values ​​are calculated according to the sampling order. Based on the resolution of the pressure sensor, adjacent difference values ​​are zeroed to obtain the purification difference value, and the purification difference value is written into the detection cache.

[0020] Furthermore, the disturbance determination module is also used for:

[0021] Based on the purification difference value, establish a positive difference set and a negative difference set. Extract the positive difference continuous segment and the negative difference continuous segment according to the index adjacency and calculate the length of the continuous segment. Use the fixed minimum continuous length to determine whether the positive difference continuous segment and the negative difference continuous segment simultaneously satisfy the condition. Generate a state mark as float disturbance state. Otherwise, generate a state mark as determineable state. Write the state mark to the detection cache.

[0022] Furthermore, the pulse voltage regulator module is used for:

[0023] The status flag is read from the detection buffer and the valve state is frozen. When the status flag is in the float disturbance state, the alternating short pulse valve opening and closing sequence is executed. The alternating short pulse valve opening and closing sequence consists of alternating exhaust short pulses and supply short pulses and cycles until the number of alternating short pulse groups ends. During the execution of the alternating short pulses, the product isolation valve remains open.

[0024] Furthermore, the pulse voltage regulator module is also used for:

[0025] After the alternating short pulse ends, the gas stop pressure sequence is collected and stabilized. Once the stabilization is confirmed, a status mark verification value is generated according to the rules of the disturbance state judgment module. When the status mark verification value is a definite state, the reference pressure signal is locked. The reference pressure signal is the first sampling pressure after the stabilization is confirmed and written into the detection buffer. At the same time, the reference pressure signal locking time is written.

[0026] Furthermore, the two-way mutual authentication module is used for:

[0027] Read the forward and reverse reference slopes of the pipeline in the fixture reference table, read the reference pressure signal and the reference pressure signal lock time in the detection buffer, keep the product isolation valve open and the air supply valve and exhaust valve closed, perform smooth confirmation of adjacent pressure difference purification, and collect the forward holding pressure sequence and the forward holding sampling time sequence after smooth confirmation.

[0028] Furthermore, the two-way verification module is also used for:

[0029] The least squares slope is calculated for the positive pressure holding sequence and the representativeness is verified by the mean absolute deviation and the pressure difference between the beginning and end. The positive detection slope is subtracted from the positive reference slope of the pipeline to obtain the positive correction slope. After establishing negative pressure and completing the smooth confirmation, the negative pressure holding pressure sequence is collected and the reverse correction slope is calculated. Based on the downward trend of the positive correction slope and the upward trend of the reverse correction slope, the leakage conclusion is output and written to the detection cache.

[0030] The technical effects and advantages of the automotive brake fluid reservoir airtightness testing system of this invention are as follows:

[0031] 1. The fixture reference table records the forward and reverse reference slopes of the pipeline. First, the forward and reverse drift characteristics of the pipeline itself are solidified. Then, the slope subtraction method is used to eliminate the obscuring of the test chamber trend by the pipeline drift. The forward and reverse correction slopes focus more on the sealing changes of the brake fluid reservoir body. With the bidirectional mutual verification judgment of the forward and negative pressure holding pressure sequences, the unidirectional deviation caused by the clamping micro deformation and the gradual change of environment is less likely to be misjudged as leakage. The test results are more stable and the verification path is clearer.

[0032] 2. A gas supply with limited flow is used to form a gas outage pressure sequence. Adjacent differentials are used to generate state markers to transform alternating directional fluctuations into definite events. Alternating short-pulse valve opening and closing sequences are used to stabilize the float disturbance state. The state markers are verified using a resampled gas outage pressure sequence. Then, a reference pressure signal is locked. The reference pressure signal is taken from the gas outage smooth section where the state can be determined. This ensures that the slope fitting window avoids interference from valve residual vibration and float oscillation. The state markers, reference pressure signal, and bidirectional slope correction form a coherent signal management chain. Even when the float structure is present, the detection rhythm and judgment consistency can still be maintained, reducing the risk of false detection and missed detection. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of the automotive brake fluid reservoir airtightness testing system of the present invention. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1: Figure 1 The present invention provides a system for testing the air tightness of automotive brake fluid reservoirs, comprising:

[0036] Pipeline reference module: The clamp presses the brake fluid reservoir and seals the non-test port, closes the product isolation valve, isolates the test pipeline, performs positive pressure gas stop sampling and negative pressure gas stop sampling respectively, and obtains the positive reference slope and the reverse reference slope of the pipeline by linear fitting, and writes them into the clamp reference table;

[0037] Test chamber construction module: Open the product isolation valve, connect the test pipeline and brake fluid reservoir to form a test chamber, limit the air supply until it stabilizes, close the air supply valve, collect the air stop pressure sequence according to a fixed sampling rhythm and write it into the test buffer;

[0038] Disturbance state determination module: Calculates adjacent differences to form a difference sequence for the gas outage pressure sequence. When the difference sequence has both positive and negative differences, it generates a state flag for the float disturbance state. When the difference sequence maintains a unidirectional change, it generates a state flag for the determineable state.

[0039] Pulse voltage regulator module: When the status is marked as float disturbance state, the air supply valve is closed, and the exhaust valve and air supply valve are alternately driven to form a short pulse airflow. The gas stop pressure sequence is re-acquired and the differential sequence is recalculated. When the differential sequence maintains unidirectional change, the starting pressure is locked as the reference pressure signal.

[0040] Two-way mutual verification module: The reference pressure signal enters the isolation and pressure holding section, and the positive detection slope is obtained by fitting the pressure holding pressure sequence with a straight line. The positive correction slope is obtained by subtracting the positive reference slope of the pipeline. The negative pressure holding sequence is fitted in the isolation negative pressure section to obtain the reverse correction slope. The leakage conclusion is mutually verified and recorded.

[0041] Even after the brake fluid reservoir is clamped and the non-test ports are sealed, the test pipeline may still experience micro-leakage from the valve assembly and pressure drift caused by slow changes in ambient temperature. When a float is present inside the brake fluid reservoir, the pressure sequence after the air stop is more prone to fluctuations. If this pressure drift is superimposed on the air stop pressure sequence, the float disturbance and leakage trend can become confused. However, test pipeline drift is a characteristic of the testing device itself, while the brake fluid reservoir is a characteristic of the object being tested. Both need to be clearly separated within the same testing cycle. Therefore, the pipeline reference module first independently measures the forward and reverse drift characteristics of the test pipeline with the product isolation valve closed, and records the results in the clamp reference table.

[0042] S101 pipeline cavity isolation and sampling timing establishment.

[0043] The product isolation valve closes, disconnecting the detection line from the brake fluid reservoir. The detection line, valve assembly, and pressure sensor form a pipeline cavity. The air supply and exhaust valves remain closed, and the pressure sensor enters continuous reading mode to confirm that the pressure change in the pipeline cavity is gradual. The controller clears the buffer storing the air stop pressure sequence, starts the timer, and sets a fixed sampling rhythm. The fixed sampling rhythm means that the timer triggers the pressure sensor at equal intervals, recording the sampling time and pressure with each trigger. The sampling time is represented by the timer reading, and the sampling pressure is represented by the pressure sensor output.

[0044] S102 positive pressure self-test gas outage pressure sequence acquisition.

[0045] The gas supply-side flow restriction channel opens, the gas supply valve opens, and the pressure in the pipeline cavity rises steadily to the self-test pressure range. Once the pressure enters the self-test pressure range, the gas supply valve immediately closes, and the pipeline cavity enters a gas-stopped state. The controller continuously reads the pressure sensor output at a fixed sampling rhythm, writing each line into the gas-stopped pressure sequence, and simultaneously writing the corresponding sampling time sequence. The gas-stopped pressure sequence starts from the first sampling record and stops writing at the end of the gas-stopped observation window. The gas-stopped observation window covers the time length during which the pressure drift trend can be identified. The end condition of the gas-stopped observation window is triggered by a timer reaching the preset gas-stopped observation duration.

[0046] S103 Pipeline Forward Reference Slope Calculation and Consistency Judgment.

[0047] After the gas outage pressure sequence is formed, the controller calculates the average sampling time of the sampling time sequence and the average sampling pressure of the gas outage pressure sequence. For each sampling point, the controller performs two deviation calculations: the sampling time deviation equals the sampling time minus the average sampling time, and the sampling pressure deviation equals the sampling pressure minus the average sampling pressure. The controller multiplies the sampling time deviation and sampling pressure deviation of each sampling point and sums the products. The controller also squares the sampling time deviation of each sampling point and sums the squares. The positive reference slope of the pipeline is equal to the sum of the products divided by the sum of squares. The physical meaning of the positive reference slope of the pipeline is the rate of pressure change per unit time during the gas outage phase.

[0048] To confirm that the forward reference slope of the pipeline can represent the true drift of the pipeline cavity, the controller further calculates the predicted pressure sequence of the linear fit. The predicted pressure sequence is calculated as follows: using the average sampling pressure as the reference point, multiplying the forward reference slope of the pipeline by the sampling time deviation as a correction factor, and adding the reference point and the correction factor to obtain the predicted pressure at each sampling point. The controller calculates the absolute deviation for each sampling point; the absolute deviation is equal to the absolute value of the difference between the sampling pressure and the predicted pressure. The controller accumulates all absolute deviations and divides them by the number of sampling points to obtain the average absolute deviation. The controller calculates the absolute value of the first-to-last pressure difference; the first-to-last pressure difference is equal to the absolute value of the sampling pressure at the end of the gas outage pressure sequence minus the absolute value of the sampling pressure at the beginning of the gas outage pressure sequence. Simultaneously, the controller calculates the adjacent pressure difference sequence; the adjacent pressure difference is equal to the difference between two adjacent sampling pressures. The controller checks the sign consistency of adjacent pressure differences; sign consistency means that adjacent pressure differences are all positive, all negative, or all zero.

[0049] The controller confirms the validity of the pipeline's positive reference slope and proceeds to step S104 when both of the following conditions are met: The first condition is that the pressure difference between the beginning and end points is not less than the average absolute deviation; the second condition is that the signs of adjacent pressure differences are consistent. These two conditions distinguish between linear drift and random fluctuations, preventing the incorrect recording of valve group transient disturbances into the fixture reference table. If neither condition is met, the controller abandons the current gas shut-off pressure sequence and returns to step S102 to reacquire the positive pressure self-test gas shut-off pressure sequence.

[0050] S104 negative pressure self-test gas outage pressure sequence acquisition and pipeline reverse reference slope calculation.

[0051] The exhaust-side vacuum channel opens, the exhaust valve opens, and the pressure in the pipeline cavity steadily decreases to the self-test negative pressure range. Once the pressure enters the self-test negative pressure range, the exhaust valve immediately closes, and the pipeline cavity enters a shut-off state. The controller continuously reads the pressure sensor output at a fixed sampling rhythm, forming a negative pressure self-test shut-off pressure sequence and a sampling time sequence.

[0052] The method for calculating the pipeline reverse reference slope is the same as in step S103. The controller first calculates the average sampling time and average sampling pressure, then calculates the sampling time deviation and sampling pressure deviation, and then calculates the sum of products and the sum of squares. The pipeline reverse reference slope is equal to the sum of products divided by the sum of squares. The controller also calculates the predicted pressure sequence, absolute deviation, average absolute deviation, and first-to-last pressure difference, and checks the consistency of the signs of adjacent pressure differences. If the first-to-last pressure difference is not less than the average absolute deviation and the signs of adjacent pressure differences are consistent, the controller confirms the pipeline reverse reference slope is valid and proceeds to step S105. If not, the controller abandons the current negative pressure shutdown pressure sequence, and repeats the negative pressure self-check sampling and calculation until a pipeline reverse reference slope that meets the consistency criteria is obtained.

[0053] S105 Fixture Reference Table Writing and Static Status Confirmation.

[0054] After obtaining the forward and reverse reference slopes of the pipeline within the same detection cycle, the controller reads the current timer reading as a time marker. The controller writes the forward and reverse reference slopes along with the time marker into the fixture reference table. The fixture reference table only stores the forward and reverse drift characteristics of the detection pipeline itself. After writing, the product isolation valve, air supply valve, and exhaust valve remain closed. The pressure sensor continues to read until the pressure change returns to a smooth state, and the pipeline cavity remains stationary, providing a stable starting point for connecting the brake fluid reservoir.

[0055] In one embodiment, the brake fluid reservoir enters the airtightness testing station, and the fixture completes clamping and sealing of non-test ports. The product isolation valve closes, forming a pipeline cavity. The air supply side flow restriction channel opens, the air supply valve opens, and the air supply valve closes after the pipeline cavity pressure enters the self-test pressure range. The controller collects the stop-air pressure sequence and sampling time sequence according to a fixed sampling rhythm. The controller calculates the average sampling time and average sampling pressure, calculates the sampling time deviation and sampling pressure deviation for each sampling point, obtains the sum of products and the sum of squares, and calculates the positive reference slope of the pipeline. The controller generates a predicted pressure sequence, obtains the average absolute deviation, obtains the first and last pressure difference, and checks the consistency of the signs of adjacent pressure differences. After passing the consistency judgment, the positive reference slope of the pipeline is retained. The exhaust side vacuum channel opens, the exhaust valve opens, and the exhaust valve closes after the pipeline cavity pressure enters the self-test negative pressure range. The controller repeats the same sampling and calculation process to obtain the reverse reference slope of the pipeline and passes the consistency judgment. The controller reads the timer reading as a time identifier and writes the positive and reverse reference slopes of the pipeline and the time identifier into the fixture reference table.

[0056] Before the brake fluid reservoir airtightness test enters the float disturbance identification stage, the drift of the test pipeline itself needs to be quantified. The pipeline reference module isolates the test pipeline into a separate pipeline cavity by closing the product isolation valve. The positive and negative pressure stop-air pressure sequences are used to measure the positive and negative reference slopes of the pipeline, respectively, and the representativeness of the slopes is ensured by the residuals and consistency with the first and last differences. After the slope and time marker are written into the fixture reference table, the test pipeline returns to a static state, the pressure signal has a unified reference, and the action connecting the brake fluid reservoir has a clear starting point.

[0057] After the fixture reference table is written, it saves the forward and reverse reference slopes of the pipeline, and the test pipeline is in the pipeline cavity state with the product isolation valve closed. When the brake fluid reservoir needs to undergo airtightness testing, the test pipeline must be connected to the brake fluid reservoir to form a test cavity, and the pressure sensor output must transition from the inflation stage to the de-inflation sampling stage. However, excessive inflation will amplify float disturbances, while insufficient inflation will result in a lack of trend information in the de-inflation pressure sequence. Therefore, the test cavity construction module focuses on controlled inflation and stability determination to ensure that the de-inflation pressure sequence has both fluctuation and trend information.

[0058] S201 test chamber connection and sampling rhythm start.

[0059] The product isolation valve opens, connecting the detection line to the brake fluid reservoir and forming the test chamber. The air supply valve and exhaust valve remain closed, the pressure sensor enters continuous reading mode, and the detection buffer is cleared. The timer starts, recording a fixed sampling rhythm. Each time the timer is triggered, it simultaneously records the sampling time and pressure reading. The sampling time is written to the inflation section sampling time sequence, and the pressure reading is written to the inflation section pressure sequence. The pressure reading is used synchronously to determine the inflation section status. After the test chamber is connected, the pressure reading remains stable, and the valve state is consistent with the sampling sequence.

[0060] S202 flow-limited inflation and inflation section pressure sequence record.

[0061] The gas supply-side flow restriction channel remains open, and the gas supply valve opens, causing the test chamber pressure to rise. The timer triggers the pressure sensor to read at a fixed sampling rhythm, and the sampling time sequence and pressure sequence of the inflation phase are continuously written to the detection buffer. The inflation phase sampling time sequence continues to increase, and the inflation phase pressure sequence maintains an upward trend. The gas supply-side flow restriction channel limits the rate of pressure increase, preventing abrupt changes in the pressure sensor readings. The float's movement is less affected by the pressure differential, and the inflation phase pressure sequence exhibits continuity.

[0062] S203 stability determination and gas supply valve closing time determination.

[0063] The gas supply valve must close when the pressure change convergence phase occurs. Stability is determined using adjacent pressure differences. Adjacent pressure differences are obtained by subtracting the previous sampled pressure from the subsequent sampled pressure, forming a sequence of adjacent pressure differences in the sampling order. The pressure sensor resolution is used to eliminate quantization jitter; if the absolute value of a single adjacent pressure difference is less than the pressure sensor resolution, the adjacent pressure difference is recorded as zero. The stability determination window length is a fixed number of times, composed of the most recent fixed number of adjacent pressure differences. The stability determination conditions include three criteria: first, all adjacent pressure differences within the stability determination window are zero or positive; second, the absolute values ​​of adjacent pressure differences within the stability determination window do not increase sequentially over time; and third, adjacent pressure differences at the end of the stability determination window continuously return to zero. When all three conditions are met simultaneously, the gas supply valve closes. The current timer reading is recorded as the start time of the gas outage, and this start time is written to the detection buffer. After the gas supply valve closes, the pressure enters the outage phase, and the pressure change rate enters a low-fluctuation range.

[0064] S204 Gas Outage Pressure Sequence Formation and Integrity Verification.

[0065] After the gas supply valve is closed, the exhaust valve remains closed, and the test chamber remains in a gas-stopped state. The timer continues to trigger the pressure sensor to read at a fixed sampling rhythm, and the gas-stop sampling time sequence and gas-stop pressure sequence are written into the detection buffer. The gas-stop observation window uses a fixed number of sampling points, which is fixed in the controller parameter area. Data acquisition stops when the gas-stop pressure sequence reaches the fixed number of sampling points. The integrity check includes two items: the gas-stop sampling time sequence remains strictly incremental, and the number of sampling points in the gas-stop pressure sequence equals the fixed number of sampling points. When the integrity check passes, the gas-stop sampling time sequence and gas-stop pressure sequence remain in the detection buffer, and the gas-stop pressure sequence maintains its original order and original readings, without reordering or resampling. When the integrity check fails, the gas supply valve remains closed, the exhaust valve remains closed, and gas-stop sampling is re-executed until the integrity check passes.

[0066] In one embodiment, the brake fluid reservoir enters the airtightness testing station, the fixture completes clamping and sealing of non-test ports, and the fixture reference table has been written with the forward and reverse reference slopes of the pipeline. After the product isolation valve opens, the test chamber is formed, the air supply side flow restriction channel opens, the air supply valve opens, and the timer records the sampling time sequence and pressure sequence of the inflation segment according to a fixed sampling rhythm. After the adjacent pressure difference sequence meets the stability judgment window condition after being processed by the pressure sensor resolution, the air supply valve closes, and the start time of air stoppage is written into the detection buffer. Air stoppage sampling continues until the fixed number of sampling points is met, the air stoppage sampling time sequence strictly increases, and the air stoppage pressure sequence is written into the detection buffer.

[0067] The product isolation valve opening, flow-limiting inflation, stability determination, and gas stop sampling constitute the execution chain of the test cavity construction module. The pressure sensor resolution processing eliminates the interference of quantization jitter on stability determination. The fixed-number stability determination window locks the gas supply valve closing time at the convergence segment. The fixed number of sampling points in the gas stop observation window ensures that the time span of the gas stop pressure sequence is consistent. After the gas stop pressure sequence enters the detection buffer, it has a stable sampling structure and repeatable pressure pattern.

[0068] The gas outage pressure sequence has been written into the detection cache of the test cavity construction module. The gas outage pressure sequence is collected at a fixed sampling rhythm, and the sequence increases continuously at the time of gas outage sampling. After the gas outage pressure sequence enters the gas outage stage, the pressure change may come from either the leakage trend or the alternating fluctuations caused by the buoy's oscillation. However, the leakage trend and the buoy disturbance overlap in the shape of the pressure curve. Directly entering the slope fitting may easily mistake the buoy disturbance for the leakage trend. Therefore, the disturbance state determination module converts the gas outage pressure sequence into a purified differential value, and then generates a state label through continuous segment rules to ensure that the state label represents the true fluctuation pattern rather than an occasional jump.

[0069] S301 Gas Outage Pressure Sequence Reading and Data Integrity Verification.

[0070] The system caches and stores the out-of-gas pressure sequence and the out-of-gas sampling time sequence. The pressure sequence reflects pressure changes, while the sampling time sequence ensures correct adjacency relationships. Before reading the pressure sequence, the increasing order of the sampling time sequence is checked. Reversal in the sampling time sequence will distort adjacent difference values. The sampling time sequence compares adjacent sampling times one by one; the later sampling time must be greater than the earlier sampling time. Only after the increasing order is confirmed can the pressure sequence be read. After the increasing order check is completed, the pressure sequence is entered into the difference operation in its original order. The difference sequence corresponds one-to-one with the pressure sequence, and the difference sequence index is consistent with the pressure sequence index, ensuring no misalignment occurs during difference discrimination.

[0071] S302 Adjacent Difference Calculation and Purification Difference Generation.

[0072] The morphological information of the gas outage pressure sequence is reflected in the direction of change between adjacent sampling points. Adjacent difference values ​​can separate slow unidirectional changes from alternating directional fluctuations. Adjacent difference values ​​are calculated item by item according to the sampling order of the gas outage pressure sequence. The adjacent difference value is obtained by subtracting the previous sampling pressure from the subsequent sampling pressure. The calculation starts from the second sampling point of the gas outage pressure sequence and ends at the last sampling point. Pressure sensor readings exhibit quantization steps, which produce small, alternating positive and negative adjacent difference values ​​in the stable segment. Float disturbance identification is easily interfered with by these quantization steps; therefore, pressure sensor resolution is introduced for purification. The purification rule is executed by comparing the absolute value of the adjacent difference value with the pressure sensor resolution. When the absolute value of the adjacent difference value is less than the pressure sensor resolution, the adjacent difference value is rewritten to zero, and a purified difference value of zero indicates that the pressure change falls within the quantization step range. When the absolute value of the adjacent difference value is not less than the pressure sensor resolution, the purified difference value remains the original adjacent difference value. The purification differential value replaces the original adjacent differential value record in the detection cache. The detection cache only retains the purification differential value version. The sign of the purification differential value comes from the actual pressure change, and occasional quantization jitter is weakened.

[0073] S303 establishes and extracts continuous segments from the positive and negative difference sets.

[0074] State markers require verifiable directional information. Positive and negative difference sets can convert directional information into explicit events. The cleansing difference values ​​are evaluated item by item for sign. Indices with cleansing difference values ​​greater than zero are added to the positive difference set, those with cleansing difference values ​​less than zero are added to the negative difference set, and those with cleansing difference values ​​equal to zero are neither added to either set. Single-point transitions may still leave isolated indices in the positive and negative difference sets, which can easily trigger false positives. Therefore, continuous segment extraction is performed on both sets. Continuous segment extraction is based on index adjacency. Indices within a positive difference set that exhibit a continuous increasing relationship are merged into a single positive difference continuous segment, and vice versa. Each positive difference continuous segment records its length, which equals the number of indices it contains. Similarly, each negative difference continuous segment records its length, which equals the number of indices it contains. When positive and negative difference continuous segments appear simultaneously and each has a continuous segment whose length reaches the minimum continuous length, the alternating directional fluctuations are continuous, the float disturbance characteristics are stable, and single-point jumps will not meet the continuous segment length requirements.

[0075] S304 Status Flag Generation and Detection Cache Writing.

[0076] The status flag needs to generate a unique value, which is used to trigger stabilization actions. The minimum continuous length is a fixed value, permanently stored in the controller parameter area and does not change with individual components. The judgment logic is executed based on the length of the continuous segment. If a positive differential continuous segment exists with a length not less than the minimum continuous length, or a negative differential continuous segment exists with a length not less than the minimum continuous length, the status flag is written to the float disturbance state. If neither the positive nor negative differential continuous segment satisfies the condition, the status flag is written to the determineable state. The detection cache contains the gas outage pressure sequence, gas outage sampling time sequence, purification differential value, size of the positive differential set, size of the negative differential set, list of positive differential continuous segment lengths, list of negative differential continuous segment lengths, and status flags. The detection cache records maintain a consistent representation of a single gas outage event, with a clear correlation between the status flag and the gas outage pressure sequence, and the judgment criteria for the float disturbance state can be verified.

[0077] In one embodiment, after the brake fluid reservoir completes its flow-limited inflation and enters the air-stop phase, the air-stop pressure sequence and the air-stop sampling time sequence are stored in the detection buffer. After the purification differential value is calculated, a continuous positive variation segment and a continuous negative variation segment appear in the purification differential value. The length of the positive differential continuous segment meets the minimum continuous length, and the length of the negative differential continuous segment meets the minimum continuous length. The state flag is written to the float disturbance state, and the lists of positive and negative differential continuous segment lengths are recorded. The air-stop pressure sequence of the other brake fluid reservoir shows a slow, unidirectional change. The purification differential value only forms a continuous positive differential segment, and there is no continuous negative differential segment. The state flag is written to the determineable state.

[0078] The state marker generation starts from the gas outage pressure sequence, proceeds through adjacent difference value calculation and resolution purification, and then completes the determination by extracting continuous segments from the positive and negative difference sets. Occasional reading jumps are difficult to form continuous segments that meet the minimum continuous length, making the distinction between float disturbance state and determineable state more stable. Alternating short pulse stabilization actions obtain clear triggering conditions, and the fluctuation pattern of the gas outage pressure sequence is consistently expressed.

[0079] After the brake fluid reservoir completes the air stop sampling and generates a status marker, the status marker categorizes the air stop pressure sequence into a float disturbance state or a determineable state. When a float disturbance state occurs, the air stop pressure sequence exhibits alternating directional fluctuations. These alternating directional fluctuations, combined with trend judgment, can expand the error range. However, brake fluid reservoir airtightness testing requires converging the float swing amplitude without altering the test chamber connectivity. Therefore, the pulse pressure stabilization module uses the status marker as a trigger condition, alternating short pulses to induce small reciprocating changes in the test chamber pressure, and then resamples the air stop pressure sequence to verify the status marker before locking the reference pressure signal.

[0080] S401 status flag reading and valve state freeze.

[0081] The float disturbance state requires a stabilization action to be triggered under stable valve conditions to prevent additional fluctuations introduced by the valve switching itself. The controller reads the status flag, the gas stop pressure sequence, and the gas stop sampling time sequence from the detection buffer. When the status flag value is in the float disturbance state, it enters the alternating short pulse process; when the status flag value is in the determineable state, it skips the alternating short pulse process and enters the reference pressure signal locking process. During the reading action, the gas supply valve remains closed, the gas exhaust valve remains closed, the product isolation valve remains open, the pressure sensor continues to read, the detection buffer writes a judgment record and the judgment time, and the judgment result forms a consistent record with the valve state.

[0082] S402 executes an alternating short pulse valve opening and closing sequence.

[0083] When the float is impacted by airflow within the test chamber, it oscillates. Unidirectional impacts tend to push the float in one direction and cause it to rebound, while alternating, small impacts more easily compress the float's oscillation amplitude to near its limit. The controller generates an alternating short-pulse valve opening and closing sequence, which consists of several pulse groups. Each pulse group includes an exhaust short pulse and an air supply short pulse. During the exhaust short pulse phase, the air supply valve remains closed, the exhaust valve opens and maintains a preset pulse width, and closes after the preset pulse width is reached. During the air supply short pulse phase, the exhaust valve remains closed, the air supply valve opens and maintains a preset pulse width, and closes after the preset pulse width is reached. The above exhaust and air supply short pulses are executed cyclically according to their group numbers until the number of alternating short pulse groups is reached. The number of alternating short pulse groups, the exhaust short pulse width, and the air supply short pulse width are fixed in the controller parameter area. After the alternating short-pulse valve opening and closing sequence is completed, the air supply valve closes, the exhaust valve closes, the product isolation valve remains open, the test chamber enters a gas-stopped state, the pressure change in the test chamber enters the sampleable range, and the float's oscillation amplitude tends to converge.

[0084] S403 resampling gas outage pressure sequence and status marker verification.

[0085] The valve closure lingering vibration occurs at the moment the alternating short pulses end. Directly inputting data from this lingering vibration segment into the judgment process would amplify the risk of misjudgment. Therefore, during the resampling phase, the pressure change needs to be allowed to stabilize before the status marker is verified. After the alternating short pulses end, the controller initiates the resampling stop-gas pressure sequence acquisition. The timer triggers the pressure sensor to read the data at a fixed sampling rhythm. The resampling stop-gas pressure sequence and the resampling stop-gas sampling time sequence are written to the detection buffer. At the beginning of the resampling phase, stability confirmation is performed according to the length of the stability determination window. Stability confirmation uses the adjacent pressure difference as the criterion. The adjacent pressure difference is obtained by subtracting the previous sampling pressure from the subsequent sampling pressure. The pressure sensor resolution is used to purify the adjacent pressure difference; the purification rule is that if the absolute value of the adjacent pressure difference is less than the pressure sensor resolution, it is recorded as zero. Stability confirmation is established when the adjacent pressure differences within the stability determination window are non-negative, their absolute values ​​do not increase sequentially over time, and the adjacent pressure differences at the end of the window continuously return to zero. After stability is confirmed, the controller calculates the purification differential value for the resampled gas stop pressure sequence according to the same rules as the disturbance judgment module, establishes positive and negative differential sets, extracts continuous segments of positive and negative differentials, and generates a state marker verification value using the minimum continuous length judgment rule. The state marker verification value is written to the detection buffer. The verification logic maps the alternating short pulse effect to the signal morphology, and a clear conclusion is obtained as to whether the alternating directional fluctuations have disappeared.

[0086] S404 reference pressure signal locking and associated recording.

[0087] The reference pressure signal represents the starting pressure of the test chamber in a determineable state. Since the starting pressure falls within the residual vibration range, its representativeness is weakened. Therefore, the locking action needs to be bound to the stability confirmation result and the status flag verification value. The controller executes the locking action when stability confirmation is achieved and the status flag verification value is in a determineable state. The reference pressure signal is taken from the first sampling pressure after stability confirmation in the resampled gas stop pressure sequence. The reference pressure signal locking time is taken from the corresponding sampling time. The reference pressure signal and the reference pressure signal locking time are written to the detection buffer. The detection buffer also writes associated fields, which include the status flag, status flag verification value, number of alternating short pulse groups, exhaust short pulse width, supply short pulse width, and stability determination window length. The source path of the reference pressure signal can be traced, and the reference pressure signal is locked during the gas stop smooth phase, resulting in more stable consistency in repeated detections.

[0088] In one embodiment, after the brake fluid reservoir completes the air stop sampling, a status flag is generated in the detection buffer, and the status flag value is the float disturbance state. The air supply valve remains closed, the exhaust valve remains closed, and the product isolation valve remains open. The controller executes an alternating short pulse valve opening and closing sequence. The exhaust valve opens and closes according to the width of the exhaust short pulse, and the air supply valve opens and closes according to the width of the air supply short pulse, repeating this cycle until the number of alternating short pulse sets is completed. After the alternating short pulses end, the controller collects the resampled air stop pressure sequence and performs stability confirmation. After stability confirmation is established, the status flag is checked according to the rules of the disturbance state judgment module, and the status flag check value is the determineable state. The controller locks the first sampling pressure after stability confirmation as the reference pressure signal and writes the reference pressure signal and the reference pressure signal lock time into the detection buffer.

[0089] Alternating short pulses compress float disturbances from the signal level into a determinable form. Resampling the gas-stop pressure sequence transforms the action effect into verifiable purification differential values ​​and continuous segment results. The state marker verification value becomes the confirmation basis for the stable action. The reference pressure signal and the reference pressure signal lock time are taken from the determinable state starting point and written into the detection buffer. The test chamber obtains a consistent determination starting point in the gas-stop state. Bidirectional slope correction and mutual verification result in more stable input conditions.

[0090] The brake fluid reservoir is stabilized and locked to a reference pressure signal via alternating short pulses. The reference pressure signal and its locking time are stored in a detection buffer. A fixture reference table stores the positive and negative reference slopes of the pipeline. Air tightness assessment requires eliminating the influence of pipeline drift during pressure changes in the test chamber and cross-referencing positive and negative pressure trends to arrive at a clear conclusion. However, valve switching and vacuum establishment introduce short-term pressure residual vibrations. When these vibrations are mixed into the fitting window, the slope no longer represents the leakage trend. Therefore, a two-way verification module determines the fitting window based on a smooth confirmation process before performing two-way slope correction and verification.

[0091] S501 reference information reading and valve state fixation.

[0092] The fixture reference table records the forward and reverse drift characteristics of the detection pipeline itself, and the detection buffer records the reference pressure signal and the reference pressure signal lock-in time. Only when both types of information are available simultaneously can the trend of the test chamber be interpreted as the product-side trend. The controller reads the reference pressure signal and the reference pressure signal lock-in time from the detection buffer, and reads the forward reference slope and the reverse reference slope of the pipeline from the fixture reference table. The product isolation valve remains open, the air supply valve remains closed, the exhaust valve remains closed, and the pressure sensor continues to read continuously. The continuous readings are written to the detection buffer to form a transitional reading sequence. The transitional reading sequence retains the true pressure starting point after the valve group state stabilizes. Subsequent sampling windows enter the same valve state environment, and the pressure curve is not affected by the transient interference of valve switching.

[0093] S502 positive smooth confirmation and positive pressure holding sequence acquisition.

[0094] Forward detection requires sampling during the stable phase after the gas supply valve is closed; residual vibration points entering the sequence will skew the fitting results. Smoothness confirmation uses adjacent pressure differences for judgment. The controller reads the pressure sensor output at a fixed sampling rhythm, and the difference between two consecutive sampling pressures is used to obtain the adjacent pressure difference. The pressure sensor resolution is used to purify adjacent pressure differences; the purification rule is that when the absolute value of an adjacent pressure difference is less than the pressure sensor resolution, it is recorded as zero. The smoothness confirmation window uses a fixed number of sampling points. Within the window, the adjacent pressure differences satisfy the following condition after purification: the amplitude does not increase successively, and consecutive adjacent pressure differences with purified values ​​of zero appear at the end of the window. After smoothness confirmation is established, the controller begins writing the forward pressure holding sampling time sequence and the forward pressure holding sequence. The sampling time is generated by a timer at a fixed sampling rhythm and increases continuously. The forward pressure holding sequence retains its original readings and original order and enters the detection buffer. The forward pressure holding sequence starts sampling from the beginning of the smooth phase; the pressure curve shape is closer to the superposition of linear drift and actual leakage, and the fitting slope is more representative.

[0095] S503 forward detection slope calculation and forward correction slope calculation.

[0096] The forward detection slope is used to characterize the trend of the forward holding pressure sequence over time. Least squares slope calculation can smooth short-term fluctuations into the overall trend. The controller first calculates the average sampling time of the forward holding pressure sampling time sequence, and then calculates the average sampling pressure of the forward holding pressure sequence. For each sampling point, the controller calculates the sampling time deviation, which equals the sampling time minus the average sampling time. The controller also calculates the sampling pressure deviation for each sampling point, which equals the sampling pressure minus the average sampling pressure. The controller multiplies the sampling time deviation and sampling pressure deviation for each sampling point and then sums the products. Finally, the controller squares the sampling time deviation for each sampling point and sums the squares. The forward detection slope is equal to the sum of the products divided by the sum of the squares.

[0097] The representativeness of the fit needs to be verifiable. The controller uses the average sampled pressure as a reference point and the forward detection slope multiplied by the sampling time deviation as a correction factor to generate the fitted predicted pressure point by point. The controller calculates the absolute deviation between the sampled pressure and the fitted predicted pressure point by point, and the sum of the absolute deviations is divided by the number of sampling points to obtain the average absolute deviation. The controller calculates the absolute value of the pressure difference between the first and last pressures in the forward holding pressure sequence. When the average absolute deviation is not greater than the absolute value of the pressure difference between the first and last pressures, the forward detection slope is written to the detection buffer.

[0098] The positive reference slope of the pipeline reflects the drift of the detection pipeline itself. The controller calculates the positive correction slope using a difference rule, which is the positive detection slope minus the positive reference slope of the pipeline. The positive correction slope is written into the detection buffer and assigned the same record number as the positive holding pressure sequence. After the positive correction slope is completed, the pipeline drift component of the positive trend is removed, and the positive trend is more focused on the brake fluid reservoir sealing status.

[0099] S504 negative pressure establishment, smoothing confirmation, negative pressure holding pressure sequence acquisition and reverse correction slope calculation.

[0100] Negative pressure detection is used to observe the pressure recovery trend under negative pressure conditions. Residual vibrations at the end of vacuuming and the transient state of valve closure can contaminate the start of the sequence. Therefore, negative pressure establishment and negative pressure holding sampling need to be processed in segments. The controller drives the exhaust-side vacuum channel, opening the exhaust valve to allow the test chamber pressure to enter the decreasing phase. After the pressure sensor reading enters the preset negative pressure detection range, the exhaust valve closes, the air supply valve remains closed, and the product isolation valve remains open. After the exhaust valve closes, the controller performs a smooth confirmation according to the adjacent pressure difference purification rule consistent with the forward direction. Once the smooth confirmation is successful, it begins writing the negative pressure holding sampling time sequence and the negative pressure holding pressure sequence. The sampling rhythm is consistent with the forward direction, and the sampling time continues to increase.

[0101] The reverse detection slope is calculated using the same least squares procedure as the forward slope. This procedure includes calculating the average sampling time and average sampling pressure, the sampling time deviation and sampling pressure deviation, and the sum of products and the sum of squares. The reverse detection slope is equal to the sum of products divided by the sum of squares. Before writing the reverse detection slope to the detection cache, the fitted predicted pressure generation and mean absolute deviation calculation are also performed, and the representativeness is confirmed by comparing it with the absolute value of the pressure difference between the beginning and end.

[0102] The controller calculates the reverse correction slope using a difference rule, which is the reverse detection slope minus the pipeline reverse reference slope. The reverse correction slope is written into the detection buffer and assigned the same record number as the negative pressure holding pressure sequence. The negative pressure holding pressure sequence is sampled from the beginning of the flat section, making the reverse correction slope a more stable representation of the negative pressure recovery trend.

[0103] S505 Two-way mutual verification judgment and record solidification.

[0104] Unidirectional slopes are easily affected by slight deformation during clamping and gradual temperature changes. Bidirectional verification binds the leakage mechanism to the simultaneous occurrence of positive pressure decline and negative pressure rise, resulting in clearer judgment boundaries. The controller reads the positive and negative correction slopes from the detection buffer. When the positive correction slope shows a pressure decline trend and the negative correction slope shows a pressure rise trend, the controller outputs a leakage conclusion. Other combinations output a non-leakage conclusion. The controller writes the leakage conclusion, positive detection slope, positive correction slope, negative detection slope, and negative correction slope into the detection buffer, along with the positive and negative pressure holding sampling time ranges, and records them in association with the reference pressure signal locking time. The bidirectional verification relationship establishes a correspondence with the original holding pressure sequence, providing a clear verification path and stronger judgment consistency.

[0105] In one embodiment, the brake fluid reservoir completes alternating short pulses and locks the reference pressure signal. The detection buffer stores the reference pressure signal and the time it locks. The fixture reference table stores the forward and reverse reference slopes of the pipeline. The product isolation valve remains open, the air supply valve is closed, and the exhaust valve is closed. The controller performs a forward smoothing confirmation and acquires a forward holding pressure sequence. The controller calculates the forward detection slope using a least-squares process and subtracts the pipeline's forward reference slope to obtain a forward corrected slope. The exhaust valve opens to establish negative pressure and then closes. The controller performs a negative smoothing confirmation and acquires a negative pressure holding pressure sequence. The controller calculates the reverse detection slope using the same process and subtracts the pipeline's reverse reference slope to obtain a reverse corrected slope. When the forward corrected slope reflects a pressure decline trend and the reverse corrected slope reflects a pressure rise trend, the controller writes a leakage conclusion and saves the bidirectional slope record.

[0106] The two-way mutual verification module introduces smooth confirmation in both positive and negative detection paths, the fitting window avoids valve residual vibration points, the least squares slope calculation and fitting representativeness verification jointly constrain the slope validity, the fixture reference table subtraction realizes pipeline drift stripping, the positive correction slope and the negative correction slope use directional mutual verification to output leakage conclusions, the detection cache saves the correspondence between trend quantity and original sequence, and the airtightness judgment is more stable and easier to verify.

[0107] Specifically, the above are merely preferred embodiments of this application and are not intended to limit this application.

[0108] In the description of this specification, references to terms such as "an embodiment," "example," and "specific example" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0109] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to any specific implementation. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A system for detecting the airtightness of an automotive brake fluid reservoir, characterized in that, include: Pipeline reference module: The clamp presses the brake fluid reservoir and seals the non-test port, closes the product isolation valve, isolates the test pipeline, performs positive pressure gas stop sampling and negative pressure gas stop sampling respectively, and obtains the positive reference slope and the reverse reference slope of the pipeline by linear fitting, and writes them into the clamp reference table; Test chamber construction module: Open the product isolation valve, connect the test pipeline and brake fluid reservoir to form a test chamber, limit the air supply until it stabilizes, close the air supply valve, collect the air stop pressure sequence according to a fixed sampling rhythm and write it into the test buffer; Disturbance state determination module: Calculates adjacent differences to form a difference sequence for the gas outage pressure sequence. When the difference sequence has both positive and negative differences, it generates a state flag for the float disturbance state. When the difference sequence maintains a unidirectional change, it generates a state flag for the determineable state. Pulse voltage regulator module: When the status is marked as float disturbance state, the air supply valve is closed, and the exhaust valve and air supply valve are alternately driven to form a short pulse airflow. The gas stop pressure sequence is re-acquired and the differential sequence is recalculated. When the differential sequence maintains unidirectional change, the starting pressure is locked as the reference pressure signal. Two-way mutual verification module: The reference pressure signal enters the isolation and pressure holding section, and the pressure holding pressure sequence is fitted with a straight line to obtain the positive detection slope. The positive correction slope is obtained by subtracting the positive reference slope of the pipeline. The negative pressure holding sequence is fitted in the isolation negative pressure section to obtain the reverse correction slope. Based on the downward trend of the positive correction slope and the upward trend of the reverse correction slope, the leakage conclusion is output and written to the detection cache.

2. The automotive brake fluid reservoir airtightness testing system according to claim 1, characterized in that, The pipeline reference module is used for: The product isolation valve is closed to form a pipeline cavity in the test pipeline. Positive pressure self-test and negative pressure self-test are performed respectively. In the gas-stop state, the gas-stop pressure sequence and sampling time sequence are collected. The positive reference slope and the reverse reference slope of the pipeline are calculated by linear fitting. The validity is judged based on the consistency of the sign of the average absolute deviation, the first and last pressure difference and the adjacent pressure difference. The positive reference slope, the reverse reference slope of the pipeline and the time mark are written into the fixture reference table.

3. The automotive brake fluid reservoir airtightness testing system according to claim 2, characterized in that, The cavity building test module is used for: Open the product isolation valve to connect the test pipeline with the brake fluid reservoir to form a test chamber. Clear the test buffer and start the timer. The timer records the sampling time sequence and pressure sequence of the inflation section according to a fixed sampling rhythm. The air supply side flow restriction channel remains open and drives the air supply valve to open, so that the pressure in the test chamber rises steadily.

4. The automotive brake fluid reservoir airtightness testing system according to claim 3, characterized in that, The cavity building module is also used for: Stability determination is based on the adjacent pressure difference sequence. The resolution of the pressure sensor is used to record small adjacent pressure differences as zero. The stability determination window length is fixed and the adjacent pressure differences are required to meet the conditions of non-negativity, no increase in absolute value, and continuous zeroing at the end. The gas supply valve is triggered to close and the start time of gas stoppage is recorded. The gas stoppage sampling time sequence and gas stoppage pressure sequence are collected according to a fixed number of sampling points and written into the detection buffer.

5. The automotive brake fluid reservoir airtightness testing system according to claim 4, characterized in that, The disturbance determination module is used for: The gas outage pressure sequence and gas outage sampling time sequence are read from the detection cache. The gas outage sampling time sequence is checked to ensure that it is increasing. Adjacent difference values ​​are calculated according to the sampling order. Based on the resolution of the pressure sensor, adjacent difference values ​​are zeroed to obtain the purification difference value, and the purification difference value is written into the detection cache.

6. The automotive brake fluid reservoir airtightness testing system according to claim 5, characterized in that, The disturbance determination module is also used for: Based on the purification difference value, establish a positive difference set and a negative difference set. Extract the positive difference continuous segment and the negative difference continuous segment according to the index adjacency and calculate the length of the continuous segment. Use the fixed minimum continuous length to determine whether the positive difference continuous segment and the negative difference continuous segment simultaneously satisfy the condition. Generate a state mark as float disturbance state. Otherwise, generate a state mark as determineable state. Write the state mark to the detection cache.

7. The automotive brake fluid reservoir airtightness testing system according to claim 6, characterized in that, The pulse voltage regulator module is used for: The status flag is read from the detection buffer and the valve state is frozen. When the status flag is in the float disturbance state, the alternating short pulse valve opening and closing sequence is executed. The alternating short pulse valve opening and closing sequence consists of alternating exhaust short pulses and supply short pulses and cycles until the number of alternating short pulse groups ends. During the execution of the alternating short pulses, the product isolation valve remains open.

8. The automotive brake fluid reservoir airtightness testing system according to claim 7, characterized in that, The pulse voltage regulator module is also used for: After the alternating short pulse ends, the gas stop pressure sequence is collected and stabilized. Once the stabilization is confirmed, a status mark verification value is generated according to the rules of the disturbance state judgment module. When the status mark verification value is a definite state, the reference pressure signal is locked. The reference pressure signal is the first sampling pressure after the stabilization is confirmed and written into the detection buffer. At the same time, the reference pressure signal locking time is written.

9. The automotive brake fluid reservoir airtightness testing system according to claim 8, characterized in that, The two-way mutual authentication module is used for: Read the forward and reverse reference slopes of the pipeline in the fixture reference table, read the reference pressure signal and the reference pressure signal lock time in the detection buffer, keep the product isolation valve open and the air supply valve and exhaust valve closed, perform smooth confirmation of adjacent pressure difference purification, and collect the forward holding pressure sequence and the forward holding sampling time sequence after smooth confirmation.

10. The automotive brake fluid reservoir airtightness testing system according to claim 9, characterized in that, The two-way mutual authentication module is also used for: The least squares slope is calculated for the positive pressure holding sequence and the representativeness is verified by the mean absolute deviation and the pressure difference between the beginning and end. The positive detection slope is subtracted from the positive reference slope of the pipeline to obtain the positive correction slope. After establishing negative pressure and completing the smooth confirmation, the negative pressure holding pressure sequence is collected and the reverse correction slope is calculated. Based on the downward trend of the positive correction slope and the upward trend of the reverse correction slope, the leakage conclusion is output and written to the detection cache.

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