An automobile battery box weld seam air tightness detection device

Abstract

The application discloses a kind of automobile battery box weld seam air tightness detection device, is in the cylindrical shell setting light detection unit, including elastic mechanism as air leakage detection device, laser light source as the light source of detection unit exit laser beam;First plane mirror and elastic mechanism follow-up form reflecting surface, and laser beam forms reflected light through reflecting surface;Reflected light is projected on the detection surface of photoelectric detector by twice reflection of plane mirror, and obtains detection light position signal;By pressurizing, the air leakage hole of weld seam to be measured section in the battery box to be measured generates airflow, to be measured section weld seam is judged by the air leakage of the battery box to be measured whether or not by the corresponding detection light position signal in photoelectric detector and the pressurization value of battery box to be measured;Each weld seam to be measured section is detected gradually, and the air tightness detection of automobile battery box is realized.

Description

Technical Field

[0001] This invention belongs to the field of defect detection technology, and more specifically, it is a device and method for detecting the airtightness of weld seams in automotive battery boxes, used to detect tiny air leaks in battery box weld seams. Background Technology

[0002] In new energy vehicles, the power battery receives and stores high-voltage direct current (VDC) power from onboard chargers, generators, regenerative braking devices, or external charging devices, providing VDC power to the electric vehicle. The battery box acts as a barrier protecting the power battery, and its sealing performance directly affects the safety of the battery and even the entire vehicle. However, during the welding process of the battery box cover, micropores can easily form due to incomplete welding. If gas or liquid enters the battery box through these micropores, it will affect the normal operation of the battery, thus threatening the safety of the entire vehicle. Current technologies primarily employ immersion tests, direct pressure tests, differential pressure tests, and helium mass spectrometry to detect micropores in battery box welds. Among the various testing methods, the immersion test involves submerging the battery box under test in water and inflating it, observing the presence of air bubbles on the surface to determine if the battery box is leaking. This method has low sensitivity; even with a small leak rate, it's difficult to observe surface bubbles during immersion, making it impossible to accurately detect tiny air leaks in the weld seams. The direct pressure test involves increasing the internal pressure of the power supply box to a certain level, maintaining it for a period of time, and then observing whether the pressure drops to determine if there are air leaks. This method is time-consuming, resulting in low efficiency, and it cannot pinpoint the location of air leaks. The differential pressure test involves simultaneously filling the battery box with gas... The test piece and the standard piece are kept in contact for a period of time, and the pressure difference between the two is compared to determine whether there is a leak in the test piece. This detection method requires a high-precision differential pressure sensor, and the sensors on both sides must have the same performance and be symmetrically set. It places high demands on the detection instrument, is difficult to detect, and is difficult to apply in practice. Helium mass spectrometry detection involves filling the test piece with high-purity helium gas and using a helium mass spectrometer to measure the helium concentration in the detection area to determine whether the test piece is leaking. Although this method has high detection accuracy, the system setup is complex, the helium gas used as the detection medium cannot be recycled, and the detection cost is high. Summary of the Invention

[0003] To overcome the shortcomings of the prior art, this invention provides a low-cost, high-accuracy automotive battery box weld airtightness testing device that can detect the location of weld leaks, thus ensuring the airtightness testing of automotive battery box welds.

[0004] To achieve its objectives, the present invention employs the following technical solution:

[0005] The invention relates to an airtightness testing device for automotive battery box welds, characterized by: a photodetector unit housed within a cylindrical shell, comprising an elastic mechanism as a leak detection device and a laser source as the light source for the detection unit, emitting a laser beam; a first planar reflector and the elastic mechanism moving together to form a reflective surface, through which the laser beam is reflected; the reflected light is reflected twice by the planar reflector group to form detection light, which is then projected onto the detection surface of a photodetector to obtain a detection light position signal; by applying pressure, airflow is generated in the leak holes of the weld section to be tested in the battery box, causing the elastic mechanism to deform due to the airflow, and a corresponding detection light position signal is obtained in the photodetector; based on the detection light position signal and the pressure value of the battery box, it is determined whether the weld section to be tested leaks; each weld section to be tested is tested segment by segment to achieve airtightness testing of the automotive battery box.

[0006] The features of the automotive battery box weld airtightness testing device of the present invention are as follows: the elastic mechanism is set at the open bottom port of the cylindrical shell; the laser light source is set on the inner wall of the cylindrical shell; the first plane reflector is fixedly set on the top surface of the elastic mechanism; the plane reflector group is a signal amplification unit composed of a second plane reflector and a third plane reflector; the photodetector is set on the inner wall of the cylindrical shell; the battery box to be tested is placed below the testing device, and the battery box to be tested is moved so that the long strip weld on it is positioned directly below the elastic mechanism as the weld test segment.

[0007] The invention also features an automotive battery box weld airtightness testing device, which includes: a testing platform below the testing device, a linear guide rail on the testing platform, and a slider that slides in cooperation with the linear guide rail; a groove on the top surface of the slider, in which the battery box to be tested is embedded; the elongated weld seam in the battery box to be tested is parallel to the linear guide rail; during the testing process, the slider drives the battery box to be tested to move along the linear guide rail, so that the elongated weld seam on the battery box to be tested is positioned segment by segment directly below the elastic mechanism as the weld seam to be tested.

[0008] The feature of the automotive battery box weld air tightness detection device of the present invention is that: a grating is set on the linear guide rail, and the grating is used to locate the section of the weld to be tested, so as to realize the location detection of leakage holes.

[0009] The feature of the automotive battery box weld air tightness detection device of the present invention is that: the elastic mechanism is made of beryllium bronze and has a central disk and an outer ring fixing ring. The outer ring fixing ring is fixedly installed on the cylindrical shell. The central disk and the outer ring fixing ring are connected by a spring to form a support for the central disk. The central disk is used to detect the airflow generated by the leakage hole.

[0010] Compared with existing technologies, the beneficial effects of this invention are reflected in:

[0011] 1. Compared with differential pressure detection and helium mass spectrometry, the detection device of the present invention has a simpler structure, lower cost, and meets the detection requirements in terms of accuracy.

[0012] 2. The detection device of the present invention has higher accuracy than the immersion test and direct pressure test, and can detect air leakage holes with a diameter of 75μm in the weld of the battery box.

[0013] 3. The method of the present invention has high detection efficiency and can detect the specific location of the air leakage hole in the weld. Attached Figure Description

[0014] Figure 1 This is a schematic diagram illustrating the detection principle of the present invention;

[0015] Figure 2 This is a schematic diagram of the detection device of the present invention;

[0016] Figure 3 This is a schematic diagram of the elastic mechanism in this invention;

[0017] Figure 4 This is a schematic diagram of the assembly of the planar reflector in this invention;

[0018] Figure 5 This is a schematic diagram of the assembly of the fine-tuning seat and the side plate in this invention;

[0019] Figure 6 This is a schematic diagram of the battery box model tested in the experimental example;

[0020] Figure 7 This is a schematic diagram of the actual power supply box under test in this invention;

[0021] Figure 8 This is a schematic diagram of the photosensitive surface of the four-quadrant photodetector used in the experimental example.

[0022] Figure 9 This is a graph showing the variation of the normalized value X with a 1μm step size in the experimental example.

[0023] Figure 10 This is a graph showing the variation of the normalized value Y with a 1μm step size in the experimental example.

[0024] Figure 11 This is a diagram showing the experimental results of detecting 75μm air leaks in the first group of experimental examples;

[0025] Figure 12 This is a diagram showing the experimental results of detecting 75μm air leaks in the second group of experimental examples;

[0026] Figure 13 This is a diagram showing the experimental results of detecting 75μm air leaks in the third group of experimental examples;

[0027] Figure 14 This is a diagram showing the results of the fourth group of experiments in the test case, which detected 75μm air leaks.

[0028] Figure 15 This is a diagram showing the results of the fifth group of experiments detecting 75μm air leaks.

[0029] Figure 16 This is a diagram showing the experimental results of detecting 75μm air leaks in the sixth group of experimental examples;

[0030] The diagram is labeled as follows: 1. Elastic mechanism, 1a. Central disk, 1b. Outer ring fixing ring, 1c. Spring, 2. First plane mirror, 3. Laser source, 4. Second plane mirror, 5. Third plane mirror, 5a. Mirror pressure plate, 5b. Mirror fine-tuning seat, 5c. Fine-tuning seat fixing seat, 6. Photodetector, 7. Battery box under test, 7a. Weld, 7b. Air inlet, 8. Slider, 9. Linear guide rail, 10. Grating, 11. Base plate, 12. Left side wall, 13. Right side wall, 14. Rear wall, 15. Battery box model, 15a. Model air inlet, 15b. Air hole defect, 16. Light spot. Detailed Implementation

[0031] See Figure 1 , Figure 2 , Figure 3 and Figure 7 In this embodiment, the automotive battery box weld airtightness detection device is equipped with a photodetector unit inside a cylindrical shell. This unit includes an elastic mechanism 1 as a leak detection device and a laser source 3 as the detection unit light source, emitting a laser beam. A first planar reflector 2 and the elastic mechanism move to form a reflective surface, and the laser beam is reflected by the reflective surface. The reflected light is reflected twice by the planar reflector group to form detection light, which is then projected onto the detection surface of the photodetector 6 to obtain a detection light position signal. Pressure is applied to generate airflow in the leak hole of the weld section to be tested in the battery box. The airflow forces the elastic mechanism to deform, and a corresponding detection light position signal is obtained in the photodetector 6. Based on the detection light position signal and the pressure value of the battery box, it is determined whether the weld section to be tested leaks. Each weld section is tested segment by segment to achieve the airtightness detection of the automotive battery box.

[0032] In specific implementation, the corresponding technical measures include: the elastic mechanism 1 is set at the open bottom port of the cylindrical shell using the base plate 11; the laser source 3 is set on the left side wall 12 of the cylindrical shell; the first plane mirror 2 is fixedly set on the top surface of the elastic mechanism 1; the plane mirror group is a signal amplification unit composed of the second plane mirror 4 and the third plane mirror 5.

[0033] The photodetector 6 is mounted on the rear wall 14 of the cylindrical shell; the battery box to be tested is placed below the detection device, and the battery box to be tested is moved so that the long strip weld 7a on it is positioned directly below the elastic mechanism 1 as the weld test section.

[0034] In practice, the corresponding technical measures also include:

[0035] A testing platform is set below the testing device, and a linear guide rail 9 is set on the testing platform, with a slider 8 slidingly engaging with the linear guide rail 9. A groove is set on the top surface of the slider 8, and the battery box 7 to be tested is embedded in the groove. The long strip weld 7a in the battery box 7 to be tested is parallel to the linear guide rail 9. During the testing process, the battery box 7 to be tested is pressurized through the air inlet 7b, and the slider 8 drives the battery box 7 to move along the linear guide rail 9, so that the long strip weld 7a on the battery box to be tested is placed segment by segment directly below the elastic mechanism 1 as the weld test segment for testing.

[0036] In this embodiment, a grating 10 is set on the linear guide rail 9, and the grating 10 is used to locate the section of the weld to be tested, so as to realize the location detection of the leakage hole.

[0037] The elastic mechanism 1 is made of beryllium bronze and has a central disk 1a and an outer ring fixing ring 1b. The outer ring fixing ring 1b is fixedly installed on the cylindrical shell. The central disk 1a and the outer ring fixing ring 1b are connected by a spring 1c to form a support for the central disk. The central disk is used to detect the airflow generated by the leakage hole.

[0038] See Figure 4 and Figure 5 The second plane mirror 5 is fixed to the mirror fine-tuning seat 5b via the mirror pressure plate 5a. The mirror fine-tuning seat 5b is mounted on the left side wall 12 via the fine-tuning seat fixing seat 5c. The first plane mirror 4 is also fixed to the right side wall 13 in the same way. The orientation of the plane mirror is adjusted by the mirror fine-tuning seat so that, before the airtightness test, the detection light is irradiated at the center of the detection surface of the photodetector 6.

[0039] This embodiment describes the detection process for the battery box model. (See [link to documentation]). Figure 6 , Figure 8 , Figure 9 and Figure 10 The battery box model to be tested is 15. Figure 6 As shown, there is a model air inlet 15a and a pore defect 15b with a diameter of 75μm on the top cover of the battery box model 15. By pumping air into the model air inlet 15a to increase its internal pressure, an airtightness test experiment is carried out on the pore defect 15b.

[0040] The optical detection unit used in this experimental example is a four-quadrant photodetector. The principle of the four-quadrant photodetector for detecting the displacement change of the elastic mechanism is as follows: Figure 8As shown, the changes in the X and Y coordinates of the two-dimensional plane containing the four-quadrant photodetector correspond to changes in the position of the light spot 16 emitted from the laser 3. These changes in the light spot position cause corresponding changes in the current signals output from the four quadrants of the four-quadrant photodetector. A current-to-voltage conversion circuit then converts the current signals output from quadrants A, B, C, and D into voltage signals V. A V B V C V D The position of the light spot on the four-quadrant photodetector can be converted into normalized values ​​of two mutually perpendicular directions in a two-dimensional plane, namely the values ​​of X and Y.

[0041]

[0042] S=k1X=k2Y (3)

[0043] In equations (1), (2), and (3), X and Y are the normalized values ​​of the light spot in two mutually perpendicular directions within the same plane, S is the deformation of the center of the elastic mechanism 1 in the vertical direction, k1 is the proportionality coefficient of S to the normalized value X, and k2 is the proportionality coefficient of S to the normalized value Y. Since the elastic mechanism 1 is an asymmetrical structure, when a vertically upward force is applied to the center of the elastic mechanism, it will simultaneously undergo elevation and deflection deformation, causing changes in both the X and Y values ​​when the light spot illuminates the four-quadrant photoelectric detector. Therefore, given a known deformation S, the proportionality coefficients k1 and k2 can be calibrated to obtain their values.

[0044] Testing process:

[0045] Step 1: Calibrate the normalized X and Y axis values ​​of the four-quadrant photodetector using a PI nano-stage to determine the relationship between the normalized values ​​and the deformation of the elastic mechanism. The specific operation is as follows: 1. Fix the airtightness detection device, fix the probe on the PI nano-stage and ensure the probe is aligned with the center of the elastic mechanism to induce displacement at the center of the elastic mechanism; 2. After bringing the probe close to the elastic mechanism, control the step size of the PI nano-stage to 1 μm so that the probe just contacts the elastic mechanism; 3. Control the step size of the PI nano-stage to 1 μm to push the elastic mechanism forward and backward by several steps, while recording the changes in the normalized X and Y values ​​of the four-quadrant photodetector, thus obtaining the relationship between the normalized values ​​and the displacement changes produced by the elastic mechanism, i.e., the proportionality coefficients k1 and k2.

[0046] Figure 9 The relationship between the normalized X value and the change in step size of 1μm is given. Figure 10To normalize the relationship between the Y-value and the 1μm step size, for every 1μm forward movement of the PI nano-stage on the elastic mechanism, the X-value changes by approximately 0.0014, and the Y-value changes by approximately 0.01, i.e., k1 = 714μm and k2 = 100μm. Calibration experiments show that the Y-axis has higher sensitivity and a very clear step size, capable of distinguishing at least a 1μm step size. Therefore, in subsequent experiments, the change in the Y-value is used to determine the deformation of the elastic mechanism for detection purposes.

[0047] Step 2: Place the battery box model 15 below the elastic mechanism 1 and adjust the position of the battery box model so that the pore defect 15b is located directly below the elastic mechanism 1.

[0048] Step 3: Adjust the height of the airtightness testing device so that the elastic mechanism 1 is located 1 mm directly above the pore defect 15b.

[0049] Step 4: Use an air pump to pump air into the battery box model 15 through the air inlet 15a, record the pressure change, and record the normalized coordinate values ​​of the four-quadrant photodetector. Perform six sets of repeated experiments to prove good repeatability.

[0050] Step 5: Using equation (3), the recorded Y-axis normalized value is converted into the deformation generated by the center position of the elastic mechanism 1, and plotted as an image along with the air pressure value.

[0051] Six sets of repeated experiments were conducted to detect 75μm porosity defects 7b. Figure 11 This is a diagram showing the experimental results of detecting 75μm air leaks in the first group of experiments. Figure 12 This is a diagram showing the experimental results of detecting 75μm air leaks in the second group of experiments. Figure 13 This is a diagram showing the experimental results of detecting 75μm air leaks in the third group of experiments. Figure 14 This is a diagram showing the results of the fourth group of 75μm air leakage hole detection experiments. Figure 15 This is a diagram showing the results of the fifth group of 75μm air leakage hole detection experiments. Figure 16 The image shows the experimental results of the sixth group of tests for detecting 75μm air leaks. When the internal pressure of the battery box model approached four atmospheres, the displacement change at the center of the elastic mechanism was approximately 30–45μm. When the pressure decreased to one atmosphere, the elastic mechanism quickly returned to its initial state. The experimental phenomena of the six repeated experiments were basically the same, and the deformation of the elastic mechanism all exceeded 30μm. The detection device used in this experiment had a resolution of at least 1μm, meeting the measurement requirements. The experimental results show that the detection device of this invention can detect air leaks with a diameter of 75μm.

[0052] The above description is merely an example and illustration of the apparatus and method proposed in this invention. Any modifications or additions made by those skilled in the art to the specific embodiments described, or any substitutions made in a similar manner, as long as they do not deviate from the concept of this invention or exceed the scope defined in these claims, shall fall within the protection scope of this invention.

Claims

1. A device for detecting the airtightness of weld seams in automotive battery boxes, characterized in that: A light detection unit is set inside the cylindrical shell, including an elastic mechanism (1) as a leak detection device and a laser source (3) as the light source of the detection unit to emit a laser beam; the first plane mirror (2) and the elastic mechanism move to form a reflective surface, and the laser beam is reflected by the reflective surface to form reflected light; the reflected light is reflected twice by the plane mirror group to form detection light and is projected onto the detection surface of the photodetector (6) to obtain the detection light position signal; by applying pressure, the leak hole of the weld section to be tested in the battery box under test is generated by airflow, and the elastic mechanism is deformed by the airflow, and the corresponding detection light position signal is obtained in the photodetector (6); the detection light position signal and the pressure value of the battery box under test are used to determine whether the weld section under test is leaking; the detection of each weld section under test is carried out segment by segment to realize the air tightness detection of the car battery box; the elastic mechanism (1) is set at the open bottom port of the cylindrical shell; the laser source (3) is set on the inner side wall of the cylindrical shell; the first plane mirror (2) is fixedly set on The top surface of the elastic mechanism (1); the plane mirror group is a signal amplification unit composed of a second plane mirror (4) and a third plane mirror (5); the photodetector (6) is set on the inner wall of the cylindrical shell; the battery box to be tested is placed below the detection device, and the battery box to be tested is moved so that the long strip weld seam on it is placed directly below the elastic mechanism (1) as the weld seam to be tested segment; a detection platform is set below the detection device, and a linear guide rail (9) is set on the detection platform, and a slider (8) slides with the linear guide rail (9); a groove is set on the top surface of the slider (8), and the battery box to be tested (7) is embedded in the groove. The long strip weld seam in the battery box to be tested (7) is parallel to the linear guide rail (9). During the detection process, the slider (8) is used to drive the battery box to be tested (7) to move along the linear guide rail (9) so that the long strip weld seam on the battery box to be tested is placed directly below the elastic mechanism (1) as the weld seam to be tested segment for detection.

2. The automotive battery box weld airtightness testing device according to claim 1, characterized in that: in A grating (10) is set on the linear guide rail (9). The grating (10) is used to locate the weld section to be tested, so as to realize the location detection of the leakage hole.

3. The automotive battery box weld airtightness testing device according to claim 1, characterized in that: The elastic mechanism (1) is made of beryllium bronze and has a central disk and an outer ring fixing ring. The outer ring fixing ring is fixedly installed on the cylindrical shell. The central disk and the outer ring fixing ring are connected by a spring to form a support for the central disk. The central disk is used to detect the airflow generated by the leakage hole.

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