CN117213749A - Helium detection method for thin-wall battery and weld detection parameter optimizing system thereof - Google Patents
Helium detection method for thin-wall battery and weld detection parameter optimizing system thereof Download PDFInfo
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- 238000001514 detection method Methods 0.000 title claims abstract description 117
- 239000001307 helium Substances 0.000 title claims abstract description 105
- 229910052734 helium Inorganic materials 0.000 title claims abstract description 105
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 title claims abstract description 105
- 238000003466 welding Methods 0.000 claims abstract description 79
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 43
- 238000007689 inspection Methods 0.000 claims abstract description 4
- 238000000034 method Methods 0.000 claims description 55
- 238000012360 testing method Methods 0.000 claims description 54
- 230000008569 process Effects 0.000 claims description 30
- 238000004519 manufacturing process Methods 0.000 claims description 14
- 238000004140 cleaning Methods 0.000 claims description 10
- 238000004088 simulation Methods 0.000 claims description 8
- 239000007789 gas Substances 0.000 claims description 7
- 238000002360 preparation method Methods 0.000 claims description 7
- 238000011056 performance test Methods 0.000 claims description 4
- 238000009864 tensile test Methods 0.000 claims description 3
- 238000005457 optimization Methods 0.000 claims description 2
- 239000007788 liquid Substances 0.000 abstract description 2
- 230000035515 penetration Effects 0.000 description 15
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 12
- 238000002347 injection Methods 0.000 description 10
- 239000007924 injection Substances 0.000 description 10
- 230000008859 change Effects 0.000 description 9
- 238000013461 design Methods 0.000 description 6
- 229910052757 nitrogen Inorganic materials 0.000 description 6
- 230000007547 defect Effects 0.000 description 5
- 239000000243 solution Substances 0.000 description 5
- 230000002159 abnormal effect Effects 0.000 description 4
- 238000002844 melting Methods 0.000 description 4
- 230000008018 melting Effects 0.000 description 4
- 238000004364 calculation method Methods 0.000 description 3
- 230000009466 transformation Effects 0.000 description 3
- 230000002950 deficient Effects 0.000 description 2
- 239000000428 dust Substances 0.000 description 2
- 238000012544 monitoring process Methods 0.000 description 2
- 238000005086 pumping Methods 0.000 description 2
- 238000007789 sealing Methods 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- 230000032683 aging Effects 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 239000000356 contaminant Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 238000005088 metallography Methods 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000012216 screening Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000009966 trimming Methods 0.000 description 1
- 238000012795 verification Methods 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The application relates to a helium detection method of a thin-wall battery and a weld detection parameter optimizing system thereof, belonging to the technical field of thin-wall battery detection. After the large leakage detection is finished, injecting helium into the battery to a preferred pressure value, wherein the preferred pressure value is a simulated critical pressure value of the failure of a welding line of the battery; maintaining the optimal pressure value of the preset time, reducing the pressure in the battery to the preset pressure value, and entering the small leakage detection. A weld inspection parameter optimizing system, comprising: welding a plurality of batteries based on preset welding parameters; applying water pressure to each battery, determining whether air leakage is formed at the welding seam of each battery, removing the battery with leakage, wherein each battery corresponds to one water pressure; and performing performance detection on the battery which is not leaked, determining the water pressure of the battery with qualified performance detection, and determining the maximum water pressure as a preferred pressure value. The helium detection accuracy of the welding line in the boundary state is improved, and potential safety hazards caused by liquid leakage due to the fact that the welding line expands and cracks after the battery is aged and expanded are avoided.
Description
Technical Field
The application relates to the technical field of thin-wall battery detection, in particular to a thin-wall battery helium detection method and a welding line detection parameter optimizing system thereof.
Background
In recent years, as the energy density of batteries has been increased, particularly thin-walled batteries, the thickness of battery cases has been reduced from 1.0mm to 0.8mm, and even thinner, such as 0.35mm or 0.3mm. Thin-walled batteries, while improving energy density, also provide more compact designs and superior thermal management. However, this trend also poses manufacturing challenges. The preparation of thin-walled batteries involves multiple processes, wherein the key element is to ensure the tightness and safety of the battery. The battery seal welding link is particularly important, and a common battery seal tightness detection method is helium detection. However, current helium detection methods, while meeting the needs to some extent, still have limitations in some respects.
The existing helium detection method generally adopts a mode of micro-positive pressure helium injection and negative pressure air leakage rate test. The basic principle of these methods is to inject helium into the cell and evaluate the sealability of the cell by monitoring the concentration change of the leaked helium. However, in the preparation of thin-wall batteries, particularly in the high-frequency welding forming and scraper trimming welding modes, the characteristics of the welding seams are complex, tiny defects possibly exist, and when the pressure reaches a certain degree, the welding seams at the defects are easily broken by expansion, so that cracks appear at the welding seams. For these micro defects, the existing method cannot generally simulate the condition that the welding line is broken when the pressure reaches a certain degree, so that defective products with the micro defects exist, and the defective batteries possibly flow into the market. In addition, cracks may lead to leakage of liquid, causing some safety problems.
Disclosure of Invention
In order to overcome the defects in the prior art, the embodiment of the application aims to provide a helium detection method for a thin-wall battery, so as to improve the helium detection accuracy of a welding line in a boundary state.
In a first aspect, an embodiment of the present application provides a helium testing method for a thin-walled battery, where a welding seam of the battery is tested by an outer cover cavity of a helium testing machine, that is, a helium filling expansion joint, including: firstly, carrying out large leakage detection, namely first-stage leakage detection, and injecting helium into the battery to a preferred pressure value, wherein the preferred pressure value is a simulated critical pressure value of battery weld failure; and (3) maintaining the optimal pressure value for a preset time, reducing the pressure in the battery to the preset pressure value, and finally entering a small leakage detection, namely a second-stage leakage detection.
The failure pressure of the welding line is different from other parts of the battery, so that helium is injected into the battery to detect the welding line under certain pressure. Expanding the welding seam by injecting helium into the battery to make the welding seam invalid, wherein the main purpose is to find a critical pressure value corresponding to the boundary state of the bearing capacity of the welding seam; based on the critical pressure value, a more accurate acceptable pressure range of the weld can be obtained. Therefore, the welding seam detection is realized, the problem of the welding seam in the boundary state can be screened out in time, the comprehensiveness of detection is improved, unqualified battery products can be screened out in time, and the potential safety hazard is reduced.
In some embodiments of the application, simulation of the pressure values is preferred for selecting the weld detection optimum pressure value. Specifically, firstly, manufacturing a sample, and welding a plurality of batteries based on preset welding parameters; thus forming a plurality of control groups, and searching the optimal pressure value by using a control variable mode. Then, carrying out a water pressure test, applying water pressure to each battery, determining whether air leakage is formed at the welding seam of the battery, removing the battery with the air leakage, wherein each battery corresponds to one water pressure; the test method is equivalent to using the water pressure to simulate helium test, and using the water pressure test with the clamp to gradually increase the water pressure test pressure for test. And finally, performing parameter optimization, performing performance detection on the battery without air leakage, determining the water pressure of the battery with qualified performance detection, and selecting the maximum water pressure as the optimal pressure value. And selecting a pressure value corresponding to the failure critical pressure value of the welding line of the battery under a certain parameter from a group of batteries.
The welding parameters in the application are laser welding parameters, and the main components of the application include: heat affected zone ratio, annular beam power, central beam power, welding speed, defocus, weld seam track, nitrogen flow, nitrogen dryness and dedusting wind speed.
In some embodiments of the present application, after the performance of the non-leaking battery is detected, the method further includes: if any one of the process capability indexes of the battery performance detection is not qualified, returning to the sample preparation, and replacing the preset welding parameters again to prepare the battery. The performance test includes metallographic phase test, tensile test and battery vibration test.
The application relates to performance test, which is mainly used for calculating CPK (process capability index), wherein CPK reflects the reliability degree or consistency of product quality in the production process and aims at evaluating process capability and process stability. In particular, CPK refers to whether manufacturing errors of a product can remain within an acceptable range where process parameters can vary. Wherein the calculation formula of CPK is:
CPK＝(USL-Xbar)/3σ
USL is the upper specification limit, xbar is the sample mean, σ is the sample standard deviation.
Under the specification limitation in the detection based on metallographic detection, tensile detection and battery vibration detection, the corresponding CPK value is obtained based on the above formula by using the detected data. And the CPK for the battery is 1.67. Therefore, CPK values of metallographic detection, tensile detection, battery vibration detection and welding parameters all need to meet the requirements of more than 1.67.
In some embodiments of the present application, after the reducing the pressure in the battery to a preset pressure value, the method further includes: performing second-stage leakage detection based on the preset pressure value, detecting the leakage rate of the battery, and performing the next step when the leakage rate meets the first preset requirement; otherwise, cleaning the housing cavity and carrying out the helium detection flow again. Because the leakage rate of the weld joint detection is low, the weld joint detection is directly used for detecting the weld joint, but the pressure value after the weld joint detection operation is higher than the pressure of the second-stage leakage detection, the second-stage leakage detection is carried out based on the preset pressure value after adjustment is needed. Therefore, helium filling expansion joint operation of the welding joint is achieved, small leakage detection is performed at the same time, the detection comprehensiveness is improved, and the detection quality is improved.
In some embodiments of the present application, the step of re-performing helium test specifically includes: and when the same battery is in the helium detection and cleaning housing cavity, after the preset times of circulation, exiting the test flow. The small leakage detection (namely second-stage leakage detection) has less leakage quantity, if the leakage exists at the connection part of the leakage detection interface and the valve block, or the sealing ring between the electromagnetic valve and the valve block, or the sealing ring between each part has leakage; these can lead to misinterpretations of the battery as small leaks, so when small leaks are detected, the housing cavity needs to be disassembled and cleaned, and then helium inspection is performed again. Once the process is repeated for three times, whether the gas leakage occurs to the outer cover body or the battery can be obtained, so that the accuracy of helium detection is ensured.
In some embodiments of the present application, the step of cleaning the housing cavity specifically includes:
the helium detector is controlled to open the cavity of the outer cover, and the mechanical arm is controlled to remove the battery; cleaning the housing cavity by using preset compressed gas; i.e. the helium remaining in the housing cavity is blown away by means of a high-pressure air gun. Vacuumizing the cleaned outer cover cavity; detecting the leakage rate of the outer cover cavity, and if the leakage rate meets a second preset requirement, breaking vacuum of the outer cover cavity and the battery, and re-entering the helium detection flow; and otherwise, cleaning the outer cover cavity again.
In the application, after the same battery is cleaned again and the housing cavity exceeds the preset times, the test flow is exited. This also means that after the enclosure chamber has been cleaned a number of times, it is confirmed that leakage has occurred and that it is not a problem with the battery, thereby further improving the accuracy of helium detection.
In some embodiments of the present application, after completing the second stage leak detection, the method further comprises: vacuumizing the battery; and breaking vacuum in the battery and the housing cavity. The vacuum pumping aims at removing helium in the battery and the outer cover cavity, and in the helium detection process, in order to measure pressure changes of the battery and the outer cover cavity, the pressure difference between the battery and the outer cover cavity is kept in a manner of being in vacuum, so that the air leakage condition is judged. After the helium test is finished, the helium test needs to be restored to normal pressure, so that the damage to the battery caused by different internal and external pressures is avoided.
In a second aspect, embodiments of the present application provide a weld detection parameter optimizing system that aims to find a simulated critical pressure value for a battery weld failure during helium filling expansion joints. Specifically, in the sample manufacturing module, according to the input preset welding parameters, controlling an automatic welding machine to weld a plurality of batteries; after welding, entering a water pressure testing module, applying water pressure to each battery, determining whether air leakage is formed at the welding seam of the battery by using pressure detection equipment, and removing the leaked battery, wherein each battery corresponds to one water pressure; and then, using a parameter optimizing module to perform performance detection on the battery which is not leaked, determining the water pressure of the battery which is qualified in the performance detection, and determining the maximum water pressure as the optimized pressure value. After the optimal pressure value and the welding parameters are screened out in a hydraulic simulation mode, the helium detection accuracy of the welding line in the boundary state can be improved, and potential safety hazards caused by leakage due to expansion of the cracking seam after aging and expansion of the battery are avoided.
In some embodiments of the present application, after the performance of the non-leaking battery is detected, the system further includes: the circulation module is used for returning to the sample preparation and replacing preset welding parameters and manufacturing a battery if any one of the process capability indexes of the battery performance detection is unqualified; the performance test includes metallographic phase test, tensile test and battery vibration test.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a helium test method for a thin-walled battery according to an embodiment of the present application;
FIG. 2 is a flow chart of a simulation method of a preferred pressure value in an embodiment of the application.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments of the present application. The components of the embodiments of the present application generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the application, as presented in the figures, is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures. Furthermore, the terms "first," "second," and the like, are used merely to distinguish between descriptions and should not be construed as indicating or implying relative importance.
It should be understood that the embodiments of the present application and the specific features in the embodiments are detailed descriptions of the technical solutions of the present application, and not limited to the technical solutions of the present application, and the embodiments of the present application and the technical features in the embodiments may be combined with each other without conflict.
The helium detection method and the weld detection parameter optimizing system for the thin-wall battery are specifically described below.
The embodiment of the application provides a thin-wall battery helium detection method shown in fig. 1, which is used for detecting a battery welding line and comprises the following steps of:
step S101: ensuring that no impurities or contaminants are present inside the cavity and that all components are installed. The mechanical arm is controlled to grasp the battery to be detected and send the battery to the helium detector, and then the jacking mechanism is controlled to lift the cavity until the cavity and the cover are completely combined to form an outer cover cavity. Simultaneously, the helium injecting cylinder compresses the helium injecting nozzle. In this process, it is ensured that the pressure inside the cavity has reached a preset level to ensure tightness.
Step S102: and vacuumizing the cavity of the outer cover, and detecting the pressure of the gas leakage after the battery is leaked, so that the leakage is detected.
Step S103: detecting the large leakage, detecting the pressure change of the battery by using an air pressure detecting instrument, setting a threshold value to detect whether the pressure is lower than the threshold value, if so, judging that the leakage holes exist at the periphery of the battery shell, judging that the battery is large leakage, and exiting the testing process; otherwise, the next flow is entered.
Step S104: the battery and housing cavity are evacuated to create a pressure differential, allowing helium to leak from the gas leak or orifice and to be detected based on the pressure.
Step S105: judging the environment before helium injection, keeping the pressure for a period of time, if the leak rate of the cavity of the outer cover is lower than a threshold value, entering the next process, otherwise, exiting the test process after equipment is abnormal;
step S106: and at the moment, helium filling expansion joints are carried out on the battery, namely helium filling is carried out to test whether the welding joints can expand in the boundary state. The optimal pressure values corresponding to the boundary states are mainly obtained by adopting a plurality of groups of batteries in a water pressure simulation mode, namely, the purpose of water pressure test is to expand the welding line to fail, so that the optimal pressure values corresponding to the failed boundary states are found.
In detail, a preferable pressure value acquisition method is as follows:
s201: screening parameters participating in the test, wherein the laser welding parameters mainly comprise: heat affected zone ratio, annular beam power, central beam power, welding speed, defocus, weld seam trajectory, nitrogen flow, nitrogen dryness, and dust removal wind speed.
S202: different water pressure tests were performed, one for each cell.
S203: each set of laser welding parameters corresponds to a plurality of batteries, respectively marked with a symbol.
S204: each group of batteries is firstly subjected to a clamp water pressure test, and the batteries with air leakage are removed. And after the hydraulic pressure test is passed, continuing metallographic phase, stretching and battery vibration tests, and calculating a process capability index according to test results.
S205: if each group of batteries passes all the test items and the welding parameter CPK is more than 1.67, the group of batteries is taken into the database to be checked;
s206: the optimal parameters are selected from the database according to the following principles: the bearing water pressure is high; welding parameters CPK is more than 1.67; CPK such as metallographic penetration, melting width and the like is more than 1.67; the tensile strength and the yield strength CPK are more than 1.67. Since the present embodiment uses a battery, and the CPK of the battery is standardized to 1.67, other tests should also be standardized to 1.67.
Step S107: helium is drawn from the cell until the pressure required for small leak detection is available.
Step S108: performing helium detection (small leakage detection) on the battery, namely detecting the helium leakage rate of the cavity of the outer cover, maintaining the pressure for a period of time, and if the helium leakage rate is within a preset range, performing the helium detection to be qualified, and entering a step S109 if the gas tightness of the battery is good; otherwise, if the helium test is not qualified, which means that there is less leakage of the battery, the process is continuously circulated for 3 times, and the process steps S111 to S116 are performed. The principle of the small leakage detection is the same as that of the large leakage detection, and the difference is that the threshold value of the large leakage detection is larger than that of the small leakage detection.
Step S109: after the battery is inspected, the battery is vacuumized and returns helium, and the vacuum of the outer cover cavity is broken at the same time, so that the battery and the outer cover cavity are in normal pressure, and the damage of pressure to equipment is avoided.
Step S110: and controlling the cavity of the helium detector to descend, injecting a helium cylinder to back, and grabbing the detected battery to a qualified recovery area by the mechanical arm, so that the test flow is finished.
The following steps S111 to S116 aim at further detection of a battery failing in small leaks, thereby confirming which of the housing wall and the battery is problematic.
Step S111: the battery is vacuumized and returns helium, and the vacuum of the battery and the cavity of the outer cover is broken at the same time.
Step S112: the cavity of the helium detector descends, the helium injection cylinder retreats, and the manipulator grabs the battery.
Step S113: and the helium detector cavity is lifted to form an outer cover cavity, and compressed air is blown to the outer cover cavity for cleaning helium.
Step S114: after the helium in the outer cover cavity is removed, helium leakage rate detection is carried out on the outer cover cavity, if the helium is qualified, step S115 is carried out; otherwise, continuously circulating for 5 times, and after the step S113 to the step S114 are circulated, the equipment is judged to be abnormal and the test flow is exited;
step S115: and after the helium is qualified, breaking vacuum in the cavity of the outer cover.
Step S116: the helium test is performed again on the battery, and the process proceeds to step S101 to step S108.
In general, the failure pressure of the weld is different from other parts of the battery, so that helium is injected into the battery to detect the weld under a certain pressure. Expanding the welding seam by injecting helium into the battery to make the welding seam invalid, wherein the welding seam mainly finds out a critical pressure value corresponding to the boundary state of the bearing capacity of the welding seam; namely, a plurality of experimental groups are utilized to simulate different water pressures through water injection so as to find the maximum pressure value meeting the CPK index requirement as a critical pressure value (namely, a preferable pressure value). And finally, obtaining a more accurate qualified pressure range of the welding seam based on the critical pressure value. Therefore, the welding seam detection is realized, the problem of the welding seam in the boundary state can be screened out in time, the comprehensiveness of detection is improved, unqualified battery products can be screened out in time, and the potential safety hazard is reduced.
In a second aspect, an embodiment of the present application provides a weld detection parameter optimizing system based on the same inventive concept, which aims to find a simulated critical pressure value of a battery weld failure. In the sample manufacturing module, according to parameter data input by manpower, the automatic welding machine is controlled to weld the corresponding battery. The mechanical arm is used for clamping the battery to enter a preset position of the water pressure testing device, and the water injection pipe is connected into the battery injection hole by the other mechanical arm to inject water pressure into the battery. And monitoring the water pressure change inside and outside the battery by adopting a pressure detector so as to judge whether the battery leaks or not, and rejecting the battery judged to leak. And carrying out welding parameters, metallographic detection, tensile detection and battery vibration detection on the battery which is not leaked, respectively carrying out process capability index calculation based on detection results, removing the battery with the process capability index smaller than 1.67 from any detection item, and taking the qualified battery into a database to be checked. The database is screened for the most affordable value of the preferred pressure.
The features and capabilities of the present application are described in further detail below in connection with the examples.
Example 1
Fig. 1 is a flow chart of a helium inspection method of a thin-walled battery according to an embodiment of the present application, please refer to fig. 1.
The embodiment provides a helium detection method for a thin-wall battery, which comprises the following steps:
large leak detection stage (i.e. first stage leak detection):
step S101: the mechanical arm grabs the battery to be detected and sends the battery to the helium detector, the cavity of the helium detector lifts the closing cover to form an outer cover cavity, and the outer cover cavity and the helium cylinder are simultaneously injected to compress the helium injection nozzle.
Step S102: the housing cavity was evacuated for 20 seconds.
Step S103: detecting the pressure change of the battery by using a detecting instrument for 2 to 5 seconds, if the pressure change of the battery is lower than-15 kPa, indicating that the periphery of the battery shell is provided with a leakage hole, judging that the battery is greatly leaked, exiting the testing process, otherwise, entering the next process if the pressure change of the battery is-15 kPa to 0.
Weld detection stage (i.e. helium filling expansion stage):
step S104: and vacuumizing the battery to-85 kPa, vacuumizing the housing cavity to 20kPa, and closing the housing cavity and the battery to vacuumize.
Step S105: judging the environment before helium injection for 2 seconds, wherein the leakage rate of the housing cavity reaches 6.0 x 10 -7 And (3) Pa.m3/s, entering the next flow, otherwise, exiting the test flow when the equipment is abnormal.
Step S106: and helium filling expansion joints are carried out on the battery, the helium filling pressure is the optimizing parameter after the water pressure simulation, the embodiment is 0.6MPa, and the pressure stabilizing time is 5-20 seconds.
Step S107: helium is pumped from the battery, and when the helium pressure is reduced from 0.6MPa to between-30 kPa and 10kPa, helium pumping is stopped.
Step S108: helium testing is carried out on the battery, namely the helium leakage rate of the cavity of the outer cover is detected, the time is 5 seconds, and when the helium leakage rate is 1.1-10 -11 ～9.9*10 -7 Pa.m3/s, checking the helium OK, and entering a step nine flow if the gas tightness of the battery is good; otherwise, the helium is checked for NG, which indicates that the battery has small leakage, and the battery is continuously circulated for 3 times, and the steps are performedStep S111 to step S116.
Step S109: after the helium is detected, the battery is vacuumized and returned to helium, the pressure of the battery is up to-85 kPa, the battery and the cavity of the outer cover are vacuumized at the same time, the pressure of the battery is raised to 30kPa, and the pressure of the cavity of the outer cover is 102kPa.
Step S110: and the helium detector cavity descends, the helium injection cylinder retreats, the mechanical arm grabs the detected battery, and the testing process is finished.
Small leakage unqualified cycle rechecking stage:
step S111: vacuumizing the battery to-85 kPa, breaking vacuum of the battery and the housing cavity at the same time, and raising the pressure of the battery to 30kPa and the housing cavity to 102kPa;
step S112: the cavity of the helium detector descends, the helium injection cylinder retreats, and the manipulator grabs the battery;
step S113: lifting the helium detector cavity to form an outer cover cavity, blowing compressed air into the outer cover cavity to remove helium for 5S;
step S114: vacuumizing to 10kPa for 30S after helium in the outer cover cavity is removed; helium leak rate detection of the housing cavity, for example, up to 6.0X10 -7 Pa.m3/S, if the clear helium is qualified, continuously circulating for 5 times, otherwise, continuously circulating for the steps from S113 to S114, if the clear helium is not used, indicating that the equipment is abnormal, and exiting the test flow;
step S115: after the clear helium is qualified, the vacuum of the outer cover cavity is broken, and the pressure of the outer cover cavity is 102kPa
Step S116: the helium test is performed again on the battery, and the process proceeds to step S101 to step S108.
Example 2
Fig. 2 is a flowchart of a simulation method of a preferred pressure value according to an embodiment of the application, please refer to fig. 2.
The simulation method of the preferred pressure value provided in the embodiment includes:
step S201: the heat affected zone ratio, the annular beam power, the central beam power, the welding speed, the defocus amount, the weld seam track, the nitrogen flow, the nitrogen dryness and the dust removal wind speed are selected as laser welding parameters.
Step S202: the hydraulic pressure test is carried out on the battery, because the design pressure of the explosion-proof valve of the battery is 0.9MPa-1.3MPa, and the pressure can be at least resisted by 0.9/1.15=0.8 MPa according to the design allowance of 1.15 times, the upper limit of the hydraulic pressure design is 0.8MPa, and because the welding process difficulty based on the side seam of the aluminum shell is started, only 0.3MPa can be ensured not to leak, but the product design requirement is not met, the upward test is carried out from 0.3MPa every 0.1MPa until the upper limit of the hydraulic pressure design is 0.8MPa. So that the water pressures are respectively set to 0.3MPa,0.4MPa,0.5MPa,0.6MPa,0.7MPa and 0.8MPa. If higher precision is required, smaller intervals are set.
Step S203: each group of laser welding parameters corresponds to a plurality of batteries, and the marks are A, B … N groups respectively;
step S204: and carrying out a water pressure test on each group of batteries, and judging that the battery which does not leak is qualified. And after the water pressure test is passed, continuing to detect welding parameters, metallography, stretching and battery vibration. The purpose of these tests is to make a calculation of the process capability index. Taking a metallographic examination as an example,
a plurality of samples are randomly extracted from a certain group of cells for metallographic detection. And collecting data of penetration and width. Each sample has a plurality of penetration as penetration data; the melting depth is calculated as the average value and standard deviation of the melting width, and the process capability index CPK formula is as follows:
CPK＝(USL-Xbar)/3σ
where USL is the upper specification limit, xbar is the sample mean, and σ is the sample standard deviation.
Thus, a metallographic CPK result corresponding to the sample is obtained, and the process capacity index of the battery in the embodiment is required to be 1.67, so that whether the battery pack is qualified or not can be judged according to comparison between the CPK result and 1.67, and unqualified batteries are removed. And the critical value of metallographic detection can be converted based on the test result, the penetration is more than or equal to 0.04mm, and the melting width is more than or equal to 0.7mm.
Step S205: if each detection item of each group of batteries meets batteries (including welding parameters Cpk) which are more than 1.67, storing the batteries into a database to be checked;
step S206: the optimal parameters and preferred pressure values are selected from the database according to the following principles: the bearing water pressure is the largest; the welding parameter Cpk is greater than 1.67; cpk of metallographic penetration, width and the like is more than 1.67; the tensile strength and yield strength are greater than 1.67.
Based on the method, the verification result of the full welding process parameters for reducing the heat affected zone is as follows:
e1 group before mass production and model change, 65.9 percent of heat affected zone, 0.6mm of track deviation, 200mm/s of welding speed, 900W of inner ring power, 1350W of outer ring power, 1mm of defocusing amount, qualified metallographic result (effective penetration is more than or equal to 0.4mm, effective width is more than or equal to 0.7 mm), qualified voltage withstand result (1.2 Mpa voltage withstand), qualified battery vibration detection Z direction, and qualified conclusion.
F1 group before mass production and transformation, 100% of heat affected zone, 0.6mm of track deviation, 120mm/s of welding speed, 650W of inner ring power, 1400W of outer ring power, 2mm of defocused positive pole, 1mm of negative pole, qualified metallographic result (effective penetration is more than or equal to 0.4mm, effective width is more than or equal to 0.7 mm), qualified withstand voltage result (withstand voltage of 1.2 Mpa), unqualified Z direction of battery vibration detection, unqualified conclusion, and battery leakage.
After mass production and model change, A1 groups, 100% of heat affected zone, 0.6mm of track deviation, 120mm/s of welding speed, 650W of inner ring power, 1400W of outer ring power, 1.5mm of defocus, qualified metallographic result (effective penetration is more than or equal to 0.4mm, effective fusion width is more than or equal to 0.7 mm), qualified voltage withstand result (1.2 Mpa voltage withstand), qualified battery vibration detection Z direction, and qualified conclusion.
After mass production and model change, A2 groups are subjected to 100 percent of heat affected zone, the track deviation is 0.45mm, the welding speed is 120mm/s, the inner ring power is 650W, the outer ring power is 1400W, the defocusing amount is-1.5 mm, the metallographic result is qualified (the effective penetration is more than or equal to 0.4mm, the effective penetration is more than or equal to 0.7 mm), the withstand voltage result is qualified (the withstand voltage of 1.2 Mpa), the battery vibration detection Z direction is qualified, and the conclusion is qualified.
After mass production and transformation, the D1 group has 67% of heat affected zone, the track offset is 0.6mm, the welding speed is 200mm/s, the inner ring power is 900W, the outer ring power is 1400W, the defocusing amount is-1.5 mm, the metallographic result is qualified (effective penetration is more than or equal to 0.4mm, effective penetration is more than or equal to 0.7 mm), the withstand voltage result is qualified (withstand voltage of 1.2 Mpa), and the conclusion is qualified.
After mass production and transformation, the D2 group has 67 percent of heat affected zone, the track offset is 0.5mm, the welding speed is 200mm/s, the inner ring power is 900W, the outer ring power is 1400W, the defocusing amount is-1.5 mm, the metallographic result is qualified (the effective penetration is more than or equal to 0.4mm, the effective penetration is more than or equal to 0.7 mm), the withstand voltage result is qualified (the withstand voltage of 1.2 Mpa), and the conclusion is qualified.
The embodiments described above are some, but not all embodiments of the application. The detailed description of the embodiments of the application is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
Claims (10)
1. The helium detection method for the thin-wall battery comprises a helium detector and is characterized in that a first-stage leakage detection and a second-stage leakage detection are sequentially carried out on the battery through an outer cover cavity of the helium detector; the first-stage leakage detection and the second-stage leakage detection also comprise:
weld detection, comprising:
after the first-stage leak detection is completed, helium is injected into the battery to a preferred pressure value, wherein the preferred pressure value is a simulated critical pressure value of battery weld failure;
and maintaining the optimal pressure value for a preset time, reducing the pressure in the battery to a preset pressure value, and entering the second-stage leakage detection.
2. The method according to claim 1, wherein the simulation method of the preferred pressure value comprises:
sample preparation, namely welding a plurality of batteries based on preset welding parameters;
the method comprises the steps of water pressure testing, namely applying water pressure to each battery, determining whether air leakage is formed at a welding seam of each battery, removing the battery with the air leakage, and enabling each battery to correspond to one water pressure;
and (3) performing performance detection on the battery without air leakage, determining the water pressure of the battery with qualified performance detection, and selecting the maximum water pressure as the optimal pressure value.
3. The method of claim 2, wherein after performance testing of the non-leaky battery, the method further comprises:
and if any one of the process capability indexes of the battery performance detection is not qualified, returning to the sample preparation, and replacing the preset welding parameters again to prepare the battery.
4. The method of claim 2, wherein the performance test comprises a metallographic test, a tensile test, and a battery vibration test.
5. The method of claim 1, wherein after said reducing the pressure within the cell to a preset pressure value, the method further comprises:
performing second-stage leakage detection based on the preset pressure value, detecting the leakage rate of the battery, and performing the next step when the leakage rate meets the first preset requirement; otherwise, cleaning the outer cover cavity, and carrying out the first-stage leakage detection again.
6. The method of claim 5, wherein the step of cleaning the housing cavity comprises:
the helium detector is controlled to open the cavity of the outer cover, and the mechanical arm is controlled to remove the battery;
cleaning the housing cavity by using compressed gas;
vacuumizing the cleaned outer cover cavity;
detecting the leakage rate of the outer cover cavity, and if the second preset requirement is met, breaking vacuum of the outer cover cavity and the battery, and re-entering the first-stage leakage detection; and otherwise, cleaning the outer cover cavity again.
7. The method of claim 6, wherein after rescuing the housing cavity, the method further comprises:
and after the same battery is cleaned again and the housing cavity exceeds the preset times, exiting the testing process.
8. The method of claim 1, wherein after completing the second stage leak detection, the method further comprises:
vacuumizing the battery;
and breaking vacuum in the battery and the housing cavity.
9. A weld inspection parameter optimizing system, the system comprising:
the sample manufacturing module is used for welding a plurality of batteries based on preset welding parameters;
the water pressure testing module is used for applying water pressure to each battery, determining whether air leakage is formed at the welding seam of the battery, eliminating the battery with leakage, and each battery corresponds to one water pressure;
and the parameter optimization module is used for detecting the performance of the battery which is not leaked, determining the water pressure of the battery which is qualified in performance detection, and selecting the maximum water pressure as an optimal pressure value.
10. The system of claim 9, wherein after performance testing of the non-leaky battery, the system further comprises:
the circulation module is used for returning to the sample preparation and replacing preset welding parameters and preparing a battery if any one of the process capability indexes of the battery performance detection is not qualified;
the performance detection comprises metallographic detection, tensile detection and battery vibration detection.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117824942A (en) * | 2024-03-05 | 2024-04-05 | 宁德时代新能源科技股份有限公司 | Helium detection system and method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117824942A (en) * | 2024-03-05 | 2024-04-05 | 宁德时代新能源科技股份有限公司 | Helium detection system and method |
| CN117824942B (en) * | 2024-03-05 | 2024-07-12 | 宁德时代新能源科技股份有限公司 | Helium detection system and method |
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