Air tightness testing system and method for plastic welding kettle
By using a high-precision flow meter and the principle of air pressure gradient force, combined with zero-leakage samples and standard leak holes, the problems of high cost, inaccurate results, and inconvenient compensation of air tightness testing equipment have been solved, achieving low-cost and efficient air tightness testing.
Patent Information
- Application Number
- CN202511234152.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-01
- Publication Date
- 2025-12-05
AI Technical Summary
Existing airtightness testing equipment is costly, the test results are not intuitive and accurate, and the leakage value compensation of the measurement system is inconvenient, resulting in a decrease in the yield rate.
A high-precision flow meter is used to replace the dedicated air tightness tester. Combining the principle of air pressure gradient force, the leakage rate is directly read through the flow meter. The system is verified and compensated using zero-leakage samples and standard leak holes.
It achieves low-cost, accurate, and short-time airtightness testing, improves testing efficiency and accuracy, reduces equipment costs by more than 50%, reduces misjudgments, and improves yield.
Smart Images
Figure CN121068136A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of automotive manufacturing, and specifically relates to a system and method for testing the airtightness of a plastic welded kettle. Background Technology
[0002] Integrated water tanks are an important component of the integrated thermal management module in new energy vehicles. Their structure is relatively complex, typically consisting of two or more welded plastic tank bodies. After welding, an airtightness test is required to ensure the tank is leak-free. Since the wet bubbling method is unsuitable for industrial mass production, a dry pressure testing method is usually used for inspection. Commonly used dry pressure testing methods in the industry are the direct pressure method and the differential pressure method. The principle is to connect the integrated water tank to an airtightness tester, which fills the tank with air, maintains the pressure, and then measures the pressure change inside the tank to evaluate the airtightness of the integrated water tank.
[0003] Common airtightness testing methods have the following problems:
[0004] 1. High cost of testing equipment. The price of industrial air tightness testers (direct pressure method and differential pressure method) is generally over 20,000 yuan, while the price of imported brand air tightness testers can even exceed 50,000 yuan.
[0005] 2. The test results are neither intuitive nor accurate. Dedicated airtightness testers (direct pressure method and differential pressure method) can only detect gas pressure changes (ΔP: unit Pa); these must be converted to a gas leakage rate (Q: unit ml / min) using a formula. The conversion formula is: Q = ΔP / Po × Vw × 60 / t. (Po: standard atmospheric pressure; Vw: volume of the tested product; t: testing time). As can be seen from the formula, the volume of the tested product (Vw) is strongly correlated with the leakage rate (Q). When the volume of the tested product is different, the same pressure difference ΔP corresponds to different leakage rates, which is neither intuitive nor accurate.
[0006] 3. Inconvenient compensation for leakage values in the measurement system. Any dry pressure testing method requires sealing the open ports of the product under test before inflation and pressure testing. Some leakage is inevitable between these sealing components and the product. When using a dedicated airtightness tester, the source of leakage cannot be distinguished, and the leakage value of the testing system itself will be superimposed on the product leakage value. This can lead to qualified airtight parts being mistakenly judged as unqualified parts, reducing the yield rate. To improve testing accuracy, compensation is necessary; however, due to the conversion relationship between leakage rate and pressure difference, the compensation amount cannot be accurately calculated, making compensation inconvenient. Summary of the Invention
[0007] This invention provides an airtightness testing system and method for plastic welded kettles, using a high-precision flow meter instead of a dedicated airtightness tester to detect the product's airtightness. It features low cost, accurate measurement, and short measurement time.
[0008] The technical solution of the present invention is: an airtightness testing system for a plastic welded kettle, comprising an air inlet valve, a pressure regulating valve, a flow meter, a replenishing air valve, an exhaust valve, a barometer, and a sealing mechanism;
[0009] One end of the air inlet valve is connected to the air source, and the other end of the air inlet valve is connected to one end of the pressure regulating valve. The other end of the pressure regulating valve is divided into two paths: one path is connected to one end of the air replenishment valve, and the other path is connected to one end of the flow meter. The other end of the air replenishment valve is used to connect to the air replenishment port of the product under test. The other end of the flow meter is used to connect to the air inlet of the product under test.
[0010] The air inlet of the product under test is also connected to one end of the exhaust valve, and the other end of the exhaust valve is connected to the outside atmosphere.
[0011] The barometer is connected to the pressure measuring port of the product being tested;
[0012] The sealing mechanism is used to seal the sealing port of the product being tested.
[0013] Furthermore, the air inlet and the pressure measuring port are located at the head and tail ends of the product being tested, respectively.
[0014] Furthermore, the tested product is detachable and replaceable, including the plastic welded kettle to be tested and a zero-leakage plastic welded kettle sample.
[0015] Furthermore, including a PLC controller, the air intake valve, the air replenishment valve, and the exhaust valve are all shut-off valves controlled by the PLC controller.
[0016] Furthermore, the sealing mechanism is detachable and replaceable, including a sealing head and a standard leak hole.
[0017] This invention also provides a method for testing the airtightness of a plastic welded kettle according to the aforementioned airtightness testing system. A flow meter is placed between the product under test and the test pressure pipeline. During the test preparation stage, i.e., the inflation stage, the pressure in both cavities of the flow meter is increased to be completely uniform. After the test begins, if there is no leak on one side of the product under test, the air pressure on both sides of the flow meter is the same, no gas passes through the flow meter, and the flow meter reading tends to zero. If there is a leak in the product under test, the gas inside the product on one side continuously leaks out, causing its pressure to decrease. A pressure difference appears on both sides of the flow meter, and the gas in the test pressure pipeline will enter the inner cavity of the product on one side of the product under test through the flow meter. At this time, the flow meter can read a stable gas flow rate, which is the leakage rate of the product under test.
[0018] Furthermore, the testing process is divided into an inflation phase, a measurement phase, and an deflation phase;
[0019] Inflation stage: All components of the airtightness testing system are connected to the plastic welding kettle. The exhaust valve is closed, and the air inlet valve and air replenishment valve are opened. The air replenishment circuit begins to inflate the plastic welding kettle. When the barometer monitors that the pressure inside the plastic welding kettle reaches the test requirements, the test stage begins.
[0020] Testing phase: Close the air supply valve, monitor the flow count value, and display the value as the test result after the flow count value stabilizes, then proceed to the exhaust phase;
[0021] Exhaust phase: Close the intake valve and open the exhaust valve. The test gas in the kettle is quickly discharged from the exhaust valve. The test ends when the pressure measured by the barometer drops to the specified level.
[0022] Furthermore, leakage compensation of the testing system: a zero-leakage plastic welded kettle sample is connected to the testing system for airtightness testing; the measured flow count value is the leakage rate Qb of the system itself, which can be used to compensate for the actual measured value of the product.
[0023] Further, the test system is verified as follows: First, the product under test is tested according to the normal procedure, and its leakage value Q1 is recorded; then, the standard leak hole is connected to the plug for testing, and its leakage value Q2 is recorded; calculate the difference ΔQ between Q2 and Q1. If ΔQ is equal to or close to the specification of the standard leak hole, the test system is normal; if the difference deviates too much from the standard leak hole, the test system has an error, and the cause of the deviation needs to be found.
[0024] The beneficial effects of this invention are:
[0025] 1. The method implemented by this testing system does not use a dedicated airtightness tester. The total cost of setting up the testing system is about 10,000 yuan, which can reduce costs by more than 50%.
[0026] 2. The method implemented by this testing system utilizes the principle of air pressure gradient force. The leakage rate of the integrated kettle is directly read by a high-precision gas flow meter. By comparing the pressure drop / leakage rate conversion with that of a dedicated airtightness tester, the influence of the internal cavity volume on the measurement results is avoided, making the test more accurate.
[0027] 3. The method implemented by this testing system can shorten the testing time; the dedicated air tightness tester requires setting fixed inflation, pressure holding and testing times, and the test cycle is about 90 seconds; this testing method can eliminate the pressure holding time, and the inflation and testing times are not fixed. By reading the values of the pressure gauge and flow meter in real time, once the values meet the test specifications, it can be judged as qualified and the test can be stopped, thus improving the testing efficiency.
[0028] 4. The method implemented in this testing system connects the gas replenishment circuit and the test circuit in parallel at the left end of the same pressure regulating valve. This ensures that the pressure inside the product is completely consistent with the pressure in the test circuit during both the gas filling and testing phases. This effectively prevents gas flow caused by non-leakage factors due to inconsistencies between the product's internal pressure and the test circuit pressure at the start of the test, reducing test interference and improving test accuracy.
[0029] 5. The method implemented by this testing system involves placing the barometer at a location far from the inflation port, which allows for more accurate monitoring and feedback of the internal air pressure of the product during the inflation stage; once the pressure reaches the test requirements, the testing stage can begin, which can shorten the inflation time and improve testing efficiency.
[0030] 6. The method implemented by this testing system can conveniently measure the system leakage value using zero-leakage samples, and perform numerical compensation directly without conversion, thus improving the accuracy of the test;
[0031] 7. The method implemented in this testing system allows for convenient verification of the testing system using standard leaks, thus improving testing stability. Attached Figure Description
[0032] Figure 1 A schematic diagram for testing the airtightness of a plastic welded kettle;
[0033] Figure 2 This is a schematic diagram of leakage compensation for the test system.
[0034] In the diagram: 1 is the air inlet valve, 2 is the pressure regulating valve, 3 is the flow meter, 4 is the air supply valve, 5 is the exhaust valve, 6 is the barometer, 7 is the sealing mechanism, 8 is the air supply port, 9 is the air inlet, and 10 is the pressure measuring port. Detailed Implementation
[0035] The present invention will now be further described with reference to the accompanying drawings.
[0036] Figure 1 This is a schematic diagram of the airtightness test for a plastic welded kettle. Based on the principle of pressure gradient force, gas always flows from high pressure to low pressure. In this test method, a flow meter is placed between the product under test and the test pressure pipeline. During the test preparation phase (inflation phase), the pressure in both chambers of the flow meter is increased to be completely uniform. After the test begins, if there is no leak in the left side of the product under test, the air pressure on both sides of the flow meter is the same, no gas passes through the flow meter, and the flow meter reading tends to zero. If there is a leak in the product under test, the gas inside the left side of the product continuously leaks out, causing its pressure to decrease. A pressure difference appears on both sides of the flow meter, and the gas on the right side (high pressure zone) will pass through the flow meter into the inner cavity of the left side (low pressure zone). At this time, the flow meter can read a stable gas flow rate, which is the leakage rate of the product under test.
[0037] The testing system mainly includes: an intake valve 1, a pressure regulating valve 2, a flow meter 3, a make-up air valve 4, an exhaust valve 5, a barometer 6, and several connecting air pipe joints and sealing mechanisms 7.
[0038] One end of the air inlet valve 1 is connected to an air source, and the other end is connected to one end of the pressure regulating valve 2. The other end of the pressure regulating valve 2 is divided into two paths: one path connects to one end of the air replenishment valve 4, and the other path connects to one end of the flow meter 3. The other end of the air replenishment valve 4 is used to connect to the air replenishment port 8 of the product under test. The other end of the flow meter 3 is used to connect to the air inlet 9 of the product under test. The air inlet 9 of the product under test is also connected to one end of the exhaust valve 5, and the other end of the exhaust valve 5 is connected to the outside atmosphere. The barometer 6 is connected to the pressure measuring port 10 of the product under test. The sealing mechanism 7 is used to seal the sealing port of the product under test.
[0039] The air inlet valve is a PLC-controlled shut-off valve. Its function is to control the connection and disconnection of the external air source and the test pipeline. When the air inlet valve is open, the external air source is connected to the test pipeline, allowing testing to proceed. When the air inlet valve is closed, the external air source is disconnected from the test pipeline, allowing high-pressure gas inside the product to be discharged.
[0040] The pressure regulating valve is an electronic pressure reducing valve, which adjusts the higher air pressure (600~800Kpa) of the factory air source to a lower air pressure (250Kpa) that meets the test requirements.
[0041] The air replenishment valve is a PLC-controlled shut-off valve. Its function is to quickly increase the pressure inside the kettle to the test pressure, shortening the test time. During the inflation phase, the air replenishment valve opens, allowing gas to quickly enter the kettle. During the test phase, the air replenishment valve closes, and gas can only enter the kettle through the flow meter.
[0042] The flow meter is a high-precision gas flow meter. Its function is to read the gas flow rate (in ml / min) passing through it during the testing phase. This flow rate value is the leakage rate (Q, in ml / min).
[0043] The barometer is a digital barometer, and its function is to monitor the air pressure inside the product during the inflation stage. Once the test pressure is reached, the testing stage can begin, thus avoiding wasting too much time on inflation and shortening the overall testing time.
[0044] The exhaust valve is a PLC-controlled shut-off valve; its function is to quickly vent the gas inside the product and end the test; during the inflation and testing phases, the exhaust valve is closed; during the venting phase, the exhaust valve is opened, and the product quickly vents gas.
[0045] The sealing head (which can be fitted with a standard leak hole) is used to seal open parts such as the water pipe opening on the kettle to facilitate inflation and airtightness testing.
[0046] Zero-leakage sample: The purpose of the zero-leakage sample is to assist in measuring the leakage between the sealing mechanism and the product under test. When the zero-leakage sample is connected to the testing system and tested according to the procedure, the measured leakage rate is the leakage rate between the sealing mechanism and the product under test (i.e., the leakage rate of the testing system itself), which can be used to compensate for the actual measured value of the product; the compensation formula is: Q = Qa - Qb (Q: actual leakage rate of the product; Qa: actual leakage rate of the product; Qb: leakage rate of the zero-leakage sample)
[0047] Standard orifice: The purpose of a standard orifice is to verify the effectiveness and accuracy of the testing system. A standard orifice is a standard component calibrated by a national certification body, and its gas throughput capacity at a specific pressure is a fixed value. For example, at a pressure of 250 kPa, the air flow rate is 4 ml / min.
[0048] The testing process is divided into three stages: inflation, measurement, and deflation.
[0049] Inflation stage: All air intake and sealing mechanisms are connected to the plastic welded kettle → the exhaust valve is closed → the air intake valve and the air replenishment valve are opened, and the air replenishment circuit begins to inflate the integrated kettle → when the barometer monitors that the internal pressure reaches the test requirements, the next stage begins.
[0050] Testing phase: Close the air supply valve → Monitor the flow count value → Once the flow count value stabilizes, display the value as the test result → Proceed to the next phase;
[0051] Exhaust phase: Close the intake valve → Open the exhaust valve. The test gas in the kettle is quickly discharged from the exhaust valve. When the pressure measured by the barometer drops to the specified level, the test ends.
[0052] Leakage compensation for the test system ( Figure 2 ): Connect the zero-leakage sample to the test system for airtightness testing; the measured flow count value is the leakage rate Qb of the system itself, which can be used to compensate for the actual measured value of the product;
[0053] Verification of the testing system: First, test the product under test according to the normal procedure and record its leakage value Q1; then connect the standard leak hole to the plug and test it, and record its leakage value Q2; calculate the difference ΔQ between Q2 and Q1. If ΔQ is equal to or close to the specification of the standard leak hole, the testing system is normal; if the difference deviates too much from the standard leak hole, the testing system has an error and the cause of the deviation needs to be found.
[0054] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A system for testing the airtightness of a plastic welded kettle, characterized in that: It comprises an air inlet valve (1), a pressure regulating valve (2), a flow meter (3), a gas supplement valve (4), an air outlet valve (5), an air pressure gauge (6) and a sealing mechanism (7). One end of the air inlet valve (1) is connected to an air source, and the other end of the air inlet valve (1) is connected to one end of the pressure regulating valve (2), and the other end of the pressure regulating valve (2) is divided into two paths: one path is connected to one end of the gas supplement valve (4), and the other path is connected to one end of the flow meter (3); the other end of the gas supplement valve (4) is used to connect a gas supplement port (8) of the product to be tested; the other end of the flow meter (3) is used to connect an air inlet port (9) of the product to be tested. The air inlet port (9) of the product to be tested is also connected to one end of the air outlet valve (5), and the other end of the air outlet valve (5) is connected to the external atmosphere. The air pressure gauge (6) is connected to a pressure measuring port (10) of the product to be tested. The sealing mechanism (7) is used to seal a sealing port of the product to be tested.
2. The system for testing the air tightness of a plastic welded kettle according to claim 1, wherein: The gas supplement port (8) and the pressure measuring port (10) are respectively located at the head end and the tail end of the product to be tested.
3. The system for testing the air tightness of a plastic welded kettle according to claim 1, wherein: The product to be tested can be replaced, including a plastic welded kettle to be tested and a zero-leakage plastic welded kettle sample.
4. The system for testing the air tightness of a plastic welded water bottle according to claim 1, wherein: It comprises a PLC controller, and the air inlet valve (1), the gas supplement valve (4) and the air outlet valve (5) are all stop valves controlled by the PLC controller.
5. The system for testing the air tightness of a plastic welded water bottle according to claim 1, wherein: The sealing mechanism (7) can be replaced, including a sealing head and a standard leak hole.
6. The plastic welded kettle airtightness test method of any one of claims 1-5, wherein: The flow meter is arranged between the product to be tested and the test pressure pipeline; and in the test preparation stage, i.e. the inflation stage, the pressures of the two cavities on both sides of the flow meter are inflated to be completely consistent; after the test starts, if there is no leakage point on the side of the product to be tested, the air pressures on both sides of the flow meter are the same, no gas passes through the flow meter, and the reading of the flow meter tends to be zero; if there is a leakage point in the product to be tested, the gas inside the product to be tested continuously leaks out, causing the pressure to decrease, a pressure difference appears between the two sides of the flow meter, and the test pressure pipeline gas enters the inner cavity of the product to be tested through the flow meter, at this time, the flow meter can read a stable gas flow, and the value is the leakage rate of the product to be tested.
7. The method of claim 6, wherein: The test process is divided into an inflation stage, a measurement stage and an air exhaust stage. In the inflation stage, the air tightness test system is connected to the plastic welded kettle, the air outlet valve is closed, the air inlet valve and the gas supplement valve are opened, the gas supplement circuit starts to inflate the plastic welded kettle, and when the air pressure gauge monitors that the pressure in the inner cavity of the plastic welded kettle reaches the test requirement, the test stage is entered. In the test stage, the gas supplement valve is closed, the flow meter value is monitored, and when the flow meter value is stable, the value is displayed as the test result, and the air exhaust stage is entered. In the air exhaust stage, the air inlet valve is closed, the air outlet valve is opened, and the test gas in the kettle is quickly exhausted from the air outlet valve, and when the air pressure gauge measures that the pressure decreases to a specified value, the test is ended.
8. The method of claim 7, wherein, Leakage compensation of the test system: the zero-leakage plastic welded kettle sample is connected to the test system for air tightness test; the measured flow meter value is the leakage rate Qb of the system itself, which can be used to compensate the actual measured value of the product.
9. The method of claim 7, wherein, Calibration of test system: first, test the product to be tested according to the normal process, record its leakage value Q1; then connect the standard leak to the plug for testing, record its leakage value Q2; calculate the difference AQ of Q2-Q1, if AQ is equal to or close to the specification of the standard leak, the test system is normal; if the difference is too large from the standard leak, the test system has errors, and the deviation reason needs to be found.