Air tightness detection method for molecular sieve nitrogen generation module

Abstract

The invention belongs to the field of fluid sealing performance testing of structural components, and particularly provides an air tightness detection method for a molecular sieve nitrogen generation module. The method comprises the following steps: S1, filling gas with set pressure P into a box body, maintaining the pressure for T1 time, testing for T2 time, and obtaining the leakage rate A0 of the box body; s2, different connectors on the box body are connected through gas pipes, so that a gas inlet of the molecular sieve, a nitrogen outlet and a nitrogen filling path leading to the battery pack form a closed loop, valves on the loop are opened, one of the remaining connectors is externally connected with a high-pressure gas source, and the other connectors are plugged; and S3, the box body is filled with gas with the set pressure P, the pressure is kept for T1 time, the test time is T2 time, the leakage rate A1 of the box body is obtained, and the difference value delta A between A0 and A1 is the leakage rate of the pipeline. The leakage rate of the pipeline is reflected through the difference value of the box leakage rates measured twice, the influence caused by oxygen adsorption of the molecular sieve can be avoided, and the method is suitable for air tightness detection of the molecular sieve nitrogen generation module.

Description

Technical Field

[0001] The invention belongs to the field of fluid tightness testing of structural components, and in particular relates to a method for testing the air tightness of a molecular sieve nitrogen production module. Background Art

[0002] As the penetration rate of new energy vehicles continues to increase, the safety of power batteries, as the core power source of new energy vehicles, has become a focus of industry attention. Once a power battery experiences thermal runaway, it may cause a fire, resulting in personal injury and property damage.

[0003] The utility model patent with authorization announcement number CN217908665U discloses a nitrogen protection system for a battery pack, which includes an air compressor, a filter, a nitrogen storage tank, a main controller, a nitrogen separation module, an electromagnetic pressure detection module, a pressure / flow regulation module, an oxygen / pressure control module, connecting pipelines and three gas circuit switches, among which the nitrogen separation module, the electromagnetic pressure detection module (i.e., the pressure detection solenoid valve), the pressure / flow regulation module, the oxygen / pressure control module (i.e., the gas detection module) and the connecting pipelines connecting the modules are encapsulated in a box. The high-pressure air generated by the air compressor can enter the nitrogen separation module, which can separate the nitrogen and oxygen in the air. The nitrogen generated by the separation can be stored in the nitrogen storage tank. The outlet of the nitrogen storage tank is connected to the electromagnetic pressure detection module. The electromagnetic pressure detection module, the pressure / flow regulation module, and the oxygen / pressure control module are connected in series in sequence. The nitrogen in the nitrogen storage tank can enter the battery pack through the electromagnetic pressure detection module, the pressure / flow regulation module, and the oxygen / pressure control module. The oxygen / pressure control module is used to detect whether the oxygen content of the gas in the current gas path meets the requirements. If it does not meet the requirements, the gas can be discharged from the exhaust pipe connected to the oxygen / pressure control module. Since different modules need to be connected to the filter, nitrogen storage tank, battery pack, etc. outside the box respectively, or it is necessary to discharge unqualified gas with high oxygen content, corresponding interfaces are also provided on the box as needed. This patent achieves the effect of suppressing combustion by introducing high-purity nitrogen into the battery pack to replace the oxygen in the battery pack to block the combustion conditions.

[0004] Regarding the nitrogen separation module, the aforementioned patent discloses the use of a nitrogen separation membrane or a PSA pressure swing adsorption (PSA) air separation nitrogen generator. The PSA system separates nitrogen and oxygen based on the different adsorption capacities of molecular sieves for oxygen and nitrogen. This technology is relatively mature and less expensive than nitrogen separation membranes.

[0005] Based on the goal of reducing costs, the applicant of this application provides a nitrogen protection system using molecular sieve as a nitrogen generator, such as Figure 1As shown, the overall principle of the nitrogen protection system is consistent with the above-mentioned patent, wherein the nitrogen making device has an air inlet and an exhaust port, and a molecular sieve is provided inside. The air inlet is connected to a three-way joint, and the other two parts of the three-way joint are used to connect the gas source and the exhaust pipeline. The exhaust port is used to connect the gas tank to pass the nitrogen generated by the nitrogen making device into the gas tank. After the molecular sieve is saturated with adsorption, the air supply to the nitrogen making device is stopped, and the pressure relief solenoid valve on the exhaust pipeline is opened, and the oxygen adsorbed by the molecular sieve can be discharged from the exhaust pipeline. Similarly, the nitrogen making device is located inside the box, and the box is provided with matching interfaces, such as a gas tank inlet interface for connecting to the inlet end of the gas tank, a gas tank outlet interface for connecting to the outlet end of the gas tank, and a battery pack interface for connecting to the battery pack. In addition, a breathable valve is also provided on the box.

[0006] It's easy to understand that to ensure the proper functioning of the battery protection system, the housing and the modules and pipelines encapsulated within it must be well sealed. After module encapsulation is complete, it's necessary to perform an airtightness test on the housing and pipelines. Traditional methods for testing pipeline airtightness include the positive pressure method, which involves injecting compressed air into the pipeline at a certain pressure. After the pressure in the pipeline rises to the target value and is maintained for a certain period of time, the pressure change during the holding phase is measured to determine the leakage rate. The measured leakage rate is then compared with the preset acceptable value to determine if the airtightness is acceptable.

[0007] However, since molecular sieves can absorb oxygen in the air, when testing air tightness using traditional methods, the oxygen in the compressed air will be absorbed by the molecular sieve. In reality, it will take a long time to raise the pressure in the pipeline to the target value, making it difficult to determine whether the pipeline is airtight.

[0008] It should be noted that the above content is for the convenience of understanding, searching and examining this application and does not necessarily belong to the prior art. Summary of the Invention

[0009] The object of the present invention is to provide a method for detecting the air tightness of a molecular sieve nitrogen production module, so as to solve the technical problem in the prior art that the air tightness of a molecular sieve-based nitrogen production module is difficult to detect.

[0010] To achieve the above objectives, the technical solution of the molecular sieve nitrogen production module air tightness detection method provided by the present invention is: A method for testing the air tightness of a molecular sieve nitrogen production module comprises the following steps: S1: filling a box with gas at a set pressure P, maintaining the pressure for a time of T1, testing for a time of T2, and obtaining a leakage amount A0 of the box; S2: connecting different interfaces on the box with an air pipe so that the air inlet of the molecular sieve, the nitrogen outlet, and the nitrogen filling path leading to the battery pack form a closed loop, opening each valve on the loop, connecting one of the remaining interfaces to an external high-pressure gas source, and blocking the other interfaces; S3: again filling the box with gas at a set pressure P, maintaining the pressure for a time of T1, testing for a time of T2, and obtaining a leakage amount A1 of the box; the difference ΔA (A0-A1) is the leakage amount of the pipeline, and the result is compared with a preset qualified value.

[0011] As a further improvement, in S2, an air pipe is used to short-circuit the oxygen-rich exhaust interface and the battery pack interface, and the gas tank inlet interface and the gas tank outlet interface are short-circuited. A plug is used to seal the unqualified exhaust interface, and a high-pressure gas source is connected to the main air inlet interface.

[0012] As a further improvement, in S1, after A0 is measured, A0 is first compared with a preset qualified value, and subsequent steps are performed only after the airtightness of the box is determined to be qualified.

[0013] As a further improvement, the qualified range of A0 is -200Pa~200Pa.

[0014] As a further improvement, the qualified range of ΔA is -100Pa~100Pa.

[0015] As a further improvement, the air valve of the box body is removed, and an airtightness detection device is connected from the installation position of the air valve to fill the box body with gas.

[0016] The present invention is a pioneering invention and has the following beneficial effects: the present invention utilizes the difference between the leakage amounts of the box measured twice to indirectly reflect the air tightness of the pipeline. Specifically, the closed loop formed in S2 can directly connect the air inlet of the molecular sieve and the nitrogen outlet. At this time, after the high-pressure gas is introduced, the high-pressure gas source fills the interior of the pipeline. However, due to the pressure balance at both ends of the molecular sieve inlet and the nitrogen outlet, the high-pressure gas will not enter the molecular sieve, and the influence of the molecular sieve on the measurement results can be avoided. At this time, the leakage value of the box is measured again, and the difference is obtained to determine the air tightness of the pipeline. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of the principle of the molecular sieve nitrogen production module in the nitrogen protection system mentioned in the background technology; Figure 2 This is a schematic diagram of the pipeline connection positions of an embodiment of the method for detecting air tightness of a molecular sieve nitrogen production module of the present invention. DETAILED DESCRIPTION

[0018] To test the airtightness of a molecular sieve nitrogen production module, the basic technical concept of the present invention is to first measure the leakage of the nitrogen production module casing, then connect the pipeline inside the casing to form a closed loop, with the two ends of the loop connected to the air inlet and nitrogen outlet of the molecular sieve nitrogen production device, respectively. High-pressure gas is introduced into the closed loop, and then the leakage of the casing is measured again. The difference between the two results is used to reflect the leakage of the pipeline.

[0019] Based on the above concept, the present invention is further described in detail below in combination with some embodiments.

[0020] In order to facilitate understanding of this embodiment, first combine Figure 1 This article introduces the structure and working principle of the molecular sieve nitrogen generator module. The main function of the molecular sieve nitrogen generator module is to separate nitrogen and oxygen from the air and deliver the generated nitrogen to the battery pack after testing. Specifically, the molecular sieve nitrogen generator module includes a housing, which houses a molecular sieve nitrogen generator. Naturally, the molecular sieve nitrogen generator has an air inlet, a nitrogen outlet, and an oxygen-enriched gas outlet. When in use, the molecular sieve nitrogen generator module can be connected to the vehicle's air source (such as an air compressor). Naturally, the housing should be equipped with a main air inlet interface for connecting to the air source. A tee is connected to the air inlet of the molecular sieve nitrogen generator, and the other two interfaces of the tee are connected to the air intake line and the oxygen-enriched exhaust line, respectively. The oxygen-enriched exhaust line is equipped with a pressure relief solenoid valve, and the air intake line is equipped with a boost solenoid valve. The gas sent from the air source is increased to a certain pressure by the boost solenoid valve and then enters the molecular sieve nitrogen generator. The molecular sieve inside the molecular sieve nitrogen generator absorbs oxygen, and nitrogen is discharged from the nitrogen outlet. Once the molecular sieve is saturated with oxygen, the boost solenoid valve can be closed and the pressure relief solenoid valve opened. Once the pressure drops, the oxygen adsorbed by the molecular sieve can be discharged from the air inlet and out of the box through the oxygen-enriched exhaust line. In other words, the air inlet is the outlet for the oxygen-enriched gas. Alternatively, one port of the T-joint is the air inlet, and the other is the outlet for the oxygen-enriched gas. Naturally, the box is equipped with an oxygen-enriched exhaust port.

[0021] The nitrogen outlet of the molecular sieve nitrogen production device is connected to the inlet of the gas tank through a pipeline, and the nitrogen can enter the gas tank for storage. Naturally, a gas tank inlet interface for connecting to the inlet of the gas tank is provided on the box. A nitrogen filling circuit is also provided in the box, and the nitrogen in the gas tank can enter the nitrogen filling circuit. Naturally, a gas tank outlet interface for connecting to the outlet of the gas tank is also provided on the box. A pressure detection solenoid valve and a gas detection module are provided on the nitrogen filling circuit. The gas detection module is used to detect whether the oxygen content of the gas in the current gas circuit is qualified. Qualified nitrogen enters the battery pack, and unqualified nitrogen can be discharged through the exhaust pipeline. Naturally, a battery pack interface for connecting to the battery pack and an unqualified exhaust interface for discharging unqualified gas are provided on the box.

[0022] In this embodiment, the air tightness test of the molecular sieve nitrogen production module mainly includes the following steps: S1: Fill the box with gas at a set pressure P, maintain the pressure for a certain time T1, and perform a test for a certain time T2 to obtain the leakage amount A0 of the box.

[0023] S2: For reference Figure 2 Use an air pipe to short-circuit the oxygen-enriched exhaust port and the battery pack port, short-circuit the gas tank inlet and outlet ports, seal the unqualified exhaust port with a plug, connect a high-pressure air source to the main air inlet port, and open all valves (solenoid valves). The high-pressure air source here can be an air compressor or a high-pressure air source in the workshop, without specific restrictions.

[0024] S3: Fill the chamber with gas at the set pressure P again, maintain the pressure for a certain time T1, and test for a certain time T2 to obtain the chamber leakage volume A1. The difference ΔA between A0 and A1 is the pipeline leakage volume, and this result is compared with the preset qualified value.

[0025] In S2, the molecular sieve's air inlet, nitrogen outlet, and nitrogen filling line are connected to form a closed loop, and the pressure at both ends of the molecular sieve's air inlet and nitrogen outlet is consistent, so the high-pressure gas source does not enter the molecular sieve. If the pipeline is airtight, the structure of the leakage volume of the box measured twice should be relatively consistent. Therefore, taking the difference can reflect the leakage of the pipeline, thereby realizing the airtightness test of the molecular sieve nitrogen production module. Specifically, in actual operation, the reference normal qualified range, that is, the normal range of ΔA, is -100Pa~100Pa.

[0026] It is understandable that in some other embodiments, in S2, the other interfaces can be short-circuited with an air pipe, so that the molecular sieve air inlet, nitrogen outlet and nitrogen filling gas path can be connected to form a closed loop. For example, the oxygen-rich exhaust interface and the unqualified exhaust interface can be short-circuited, the gas tank inlet interface and the gas tank outlet interface can be short-circuited, and the battery pack interface can be blocked. For another example, the oxygen-rich exhaust interface and the gas tank outlet interface can be short-circuited, the gas tank inlet interface and the battery pack interface can be short-circuited, and the unqualified exhaust interface can be blocked. After forming a closed loop, of the remaining interfaces, only one interface needs to be left to connect to the high-pressure gas source, and the remaining interfaces are blocked. For example, in some other embodiments, the main air inlet interface can also be blocked, and the unqualified exhaust interface can be connected to the gas source.

[0027] In S1 and S3, existing, mature airtightness testing equipment can be used to complete the test. Once the airtightness testing equipment is set up, it can automatically perform inflation, pressure maintenance, testing, and result determination, making it convenient and efficient. For example, in one embodiment, the inflation pressure P can be set to 20kPa, the inflation time to 80s, the pressure maintenance time T1 to 30s, and the test time T2 to 60s.

[0028] Preferably, in S1, after A0 is first measured, A0 can be compared with a preset qualified value to prove that the airtightness of the box is qualified before proceeding with subsequent operations. Specifically, in actual operation, the reference normal qualified range, i.e., the normal range of A0, is -200Pa~200Pa.

[0029] In addition, when conducting a test, the air valve on the box can be removed and connected to the air tightness testing equipment through the air valve to inflate the box and complete the test. In this case, there is no need to open an additional testing interface on the box. After the test is completed, the air valve can be reinstalled.

[0030] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments without inventive effort, or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for detecting the air tightness of a molecular sieve nitrogen production module, characterized in that: The following steps are involved: S1: Fill the box with gas of set pressure P, maintain the pressure for T1 time, test for T2 time, and obtain the leakage amount A0 of the box; S2: Use air pipes to connect different interfaces on the box, so that the air inlet of the molecular sieve, the nitrogen outlet and the nitrogen filling path leading to the battery pack form a closed loop, open the valves on the loop, and among the remaining interfaces, one interface is connected to an external high-pressure gas source, and the other interfaces are blocked; S3: Fill the box with gas of set pressure P again, maintain the pressure for T1 time, test for T2 time, and obtain the leakage amount A1 of the box. The difference ΔA of A0-A1 is the leakage amount of the pipeline, and this result is compared with the preset qualified value.

2. The method for detecting air tightness of a molecular sieve nitrogen production module according to claim 1, wherein: In S2, an air pipe is used to short-circuit the oxygen-rich exhaust interface and the battery pack interface, and the gas tank inlet interface and the gas tank outlet interface are short-circuited. A plug is used to seal the unqualified exhaust interface, and a high-pressure gas source is connected to the main air inlet interface.

3. The method for detecting air tightness of a molecular sieve nitrogen production module according to claim 1 or 2, wherein In S1, after A0 is measured, A0 is first compared with the preset qualified value, and the subsequent steps are performed only after the air tightness of the box is determined to be qualified.

4. The method for detecting air tightness of a molecular sieve nitrogen production module according to claim 3, wherein: The qualified range of A0 is -200Pa~200Pa.

5. The method for detecting air tightness of a molecular sieve nitrogen production module according to claim 1 or 2, wherein: The qualified range of ΔA is -100Pa~100Pa.

6. The method for detecting air tightness of a molecular sieve nitrogen production module according to claim 1 or 2, wherein: Remove the air valve of the box and connect the air tightness detection equipment from the installation position of the air valve to fill the box with gas.

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