Automatic welding condition inspection device

Abstract

To provide an apparatus for automatically inspecting the welding state which can automatically evaluate the welding state of a battery in a non-destructive manner.SOLUTION: The present invention relates to a welding state quality inspection, more concretely, relates to an apparatus for inspecting lead welding of a secondary battery. An apparatus for automatically inspecting the welding state of a battery module in which a plurality of leads for electrical connection are welded according to some embodiments of the present invention is configured to determine the welding state of welding parts on the basis of an internal penetration inspection using application of eddy current to the welding parts of the leads.SELECTED DRAWING: Figure 7a

Description

Technical Field

[0001] The present invention relates to quality inspection of welding states, and more particularly to an apparatus for inspecting lead welding of secondary batteries.

Background Art

[0002] Secondary batteries are energy storage devices and are used in various fields. For example, secondary batteries are configured to provide energy required for driving electric vehicles, which have been attracting attention in recent years. The secondary batteries included in electric vehicles are manufactured in the form of battery packs in which modules are composed of a plurality of battery cells and a plurality of battery modules are assembled and finally mounted on the vehicle in order to implement high voltage and high capacity required for driving the vehicle. A battery module is composed of a plurality of battery cells assembled together. Here, for energization, the battery cells are welded to each other. Specifically, the leads of each cell are bent and joined, and the joined leads are laser-welded by a laser source. In the assembly process, since welding quality has a very important influence on the performance of the battery, much effort must be put into welding quality control.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention was made to solve the above-mentioned problems, and the object of the present invention is to provide an automatic welding condition inspection device that can automatically evaluate the welding condition of a battery in a non-destructive manner. Another object of the present invention is to provide an automatic welding condition inspection device that can obtain accurate and uniform results. The object of the present invention is not limited to the object mentioned above, and other objections not mentioned will be clearly understood by a person with ordinary skill in the art to which the present invention belongs (hereinafter referred to as "persons skilled in the art") from the following description. [Means for solving the problem]

[0005] The features of the present invention that achieve the aforementioned objectives and perform the characteristic functions of the present invention described later are as follows.

[0006] The present invention provides an automatic inspection device for the welding condition of a battery module, wherein the battery module is assembled with a plurality of battery cells, and the leads connected to each battery cell are welded to a busbar so as to be electrically conductive to each other, and the automatic inspection device for the welding condition of the battery module is configured to inspect the weld between the leads of each battery cell and the busbar, and includes a sensor assembly configured to apply an eddy current to the weld and measure the signal of change in the eddy current due to the depth of the weld, the sensor assembly including a plurality of sensing parts configured to be movable as a whole, and each sensing part configured to simultaneously contact the weld of each battery cell, and a controller configured to receive the signal of change in the eddy current obtained by the sensor assembly and to determine the quality of the weld based on the signal of change in the eddy current. [Effects of the Invention]

[0007] According to the present invention, an automatic welding condition inspection device can be provided that can automatically evaluate the welding condition of a battery in a non-destructive manner. According to the present invention, an automatic welding condition inspection device can be provided that can obtain accurate and uniform results. The effects of the present invention are not limited to those described above, and other effects not mentioned above should be clearly recognizable to an ordinary engineer from the following description. [Brief explanation of the drawing]

[0008] [Figure 1a] This is a perspective view of a cell-laden structure. [Figure 1b] This diagram shows the leads of each cell in a cell stack. [Figure 1c] This is a diagram showing a battery module assembled from stacked cells. [Figure 1d] This is a conceptual diagram showing the welding of the cell leads to the busbars that make up a battery module. [Figure 2] This is a flowchart showing the operation flow of the automated welding condition inspection device according to the present invention. [Figure 3] This is a block diagram showing the configuration of an automatic welding condition inspection device according to the present invention. [Figure 4] This figure shows the sensor for the automatic welding condition inspection device according to the present invention. [Figure 5] This is a side view of the automatic welding condition inspection device according to the present invention. [Figure 6a] This figure shows the battery module, which is the object of inspection for the automatic welding condition inspection device according to the present invention, mounted on a plate. [Figure 6b] This diagram compares the diameter of the side sensor for aluminum leads with the diameter of the side sensor for copper leads. [Figure 6c] This diagram compares the diameter of the side sensor for aluminum leads with the diameter of the side sensor for copper leads. [Figure 7a] This is a plan view of the automatic welding condition inspection device according to the present invention. [Figure 7b] This is a partial plan view of the automatic welding condition inspection device according to the present invention. [Figure 8] It is an enlarged view of the part shown by the circle in FIG. 6. [Figure 9] It is a plan view of the sensor of the welding state automatic inspection apparatus according to the present invention. [Figure 10] It is a diagram showing a state in which a battery module, which is an inspection target of the welding state automatic inspection apparatus according to the present invention, is mounted on a plate. [Figure 11a] It is a diagram showing the noise removal process of the welding state automatic inspection apparatus according to the present invention. [Figure 11b] It is a diagram showing the noise removal process of the welding state automatic inspection apparatus according to the present invention. [Figure 11c] It is a diagram showing the noise removal process of the welding state automatic inspection apparatus according to the present invention. [Figure 12] It is a diagram showing the comparison result of the signals processed by the noise removal algorithm.

Embodiments for Carrying Out the Invention

[0009] The description of the specific structures and functions presented in the embodiments of the present invention is for illustrative purposes to explain the embodiments according to the concept of the present invention, and the embodiments according to the concept of the present invention can be implemented in various forms. Also, it should not be construed that the present invention is limited by the embodiments described in this specification, and it must be understood that it includes all modifications, equivalents, and alternatives included in the spirit and technical scope of the present invention. On the other hand, in the present invention, terms such as first and / or second are used to describe various components, and the components are not limited by the terms. The terms are used for the purpose of distinguishing one component from another. For example, within the scope not departing from the scope of rights according to the concept of the present invention, the first component can be named the second component, and similarly, the second component can be named the first component.

[0010] When a component is referred to as being "coupled" or "connected" to another component, it should be understood that it can be directly coupled or connected to the other component, but there can also be other components in between. On the other hand, when a component is referred to as being "directly coupled" or "in direct contact" with another component, it should be understood that there are no other components in between. Other expressions for describing the relationship between components, such as "between" and "immediately between" or "adjacent to" and "directly adjacent to", should be interpreted in the same way.

[0011] The same reference numerals throughout the specification indicate the same components. The terms used in this specification are for the purpose of describing embodiments and are not intended to limit the present invention. In this specification, the singular form includes the plural form unless otherwise specified in the context. The use of "comprises" and / or "comprising" in the specification does not exclude the presence or addition of one or more other components, steps, operations, and / or elements.

[0012] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

[0013] As shown in FIG. 1a, for the assembly of the battery module M, a certain number of cells C are stacked to form a cell stack A. Then, as shown in FIG. 1b, for each cell C, a lead L is connected and bent for electrical connection. The bent lead L is welded to the bus bar B, thereby energizing the entire battery module M.

[0014] In a battery, numerous parts are welded to each cell C of the battery module M. For example, if a single battery module M contains 12 cells C, the 12 cells are welded to the busbar and leads at 24 locations (12 on the front and 12 on the rear of each cell). This welding includes side welding (part W2) performed after bending the leads of the outermost cells to the side. Also, as shown in Figure 1c, a cover 2 is assembled for assembly into the battery module M. Here, clamp welding is also required, as indicated by W1. Laser welding is generally used for this welding. Figure 1d schematically shows that the welded part W is formed when the leads L of cell C are bent and welded to the busbar B.

[0015] Since welding quality plays a crucial role in battery performance, quality inspection is essential. Currently, welding quality is evaluated by a 100% flip inspection performed by workers. The flip inspection is performed by using a tool such as a sharp-tipped drive to flip over a portion of the lead end after welding. However, this process is susceptible to errors due to the worker's perception and requires a considerable amount of labor. In other words, depending on the inspection method performed by workers, it is difficult to achieve accurate yet uniform evaluation. Therefore, the objective of the present invention is to provide an automated welding condition inspection device that can automatically evaluate the welding condition of batteries in a non-destructive manner and guarantee accuracy and uniformity.

[0016] For this purpose, the automated welding condition inspection device 1 according to the present invention includes inspection using a vision camera and deep penetration inspection. As shown in Figure 2, the device 1 is configured to inspect the welding condition of the lead L immediately after welding the lead L (S1) (S3). If it is determined that the welding condition of the lead L meets the standard quality, clamping welding (S5) is then performed, and the clamping welding condition can be inspected immediately afterward (S7). According to the present invention, welding and welding quality inspection are carried out continuously and automatically.

[0017] As shown in Figure 3, the automatic welding condition inspection device 1 includes a sensor assembly 10, a camera 30, lighting 50, a driver 70, a display unit 90, and a controller 100. The controller 100 is configured to control and supervise the operation of each component of the device 1. The sensor assembly 10 is configured to perform a deep penetration inspection. The deep penetration inspection is configured to proceed to a separate process after welding to measure the molten state after welding. In particular, the deep penetration inspection is performed by applying eddy currents. Specifically, the sensor assembly 10 is configured to apply eddy currents to the weld W and measure the change in eddy currents with respect to the depth of the weld W.

[0018] As shown in Figure 4, the sensor assembly 10 includes a magnetic field generating coil 11 and a sensing coil 13. When a voltage of a specific frequency is applied to the magnetic field generating coil 11, a primary magnetic field is formed. The formed primary magnetic field induces rotational motion in the free electrons of the object under inspection, i.e., the welded lead L. This rotational motion is called an eddy current. This eddy current generates a secondary magnetic field. The secondary magnetic field induces an electromotive force in the sensing coil 13, which is then processed and quantified. In the sensor assembly 10, the undescribed drawing reference numeral 15 is an oscillator, and 17 indicates a voltmeter.

[0019] Eddy currents attenuate with increasing depth within the object being inspected, and the degree of attenuation depends on the applied frequency and the material properties such as permeability and conductivity. Since frequency is a constant, the material properties are what change depending on the welding condition. Permeability and conductivity change with the depth and size of the welded molten material, so the controller 100 determines whether it is a weak weld by obtaining the amount of variation in permeability and conductivity based on the sensing results of the sensor assembly 10. Ultimately, these amounts of variation can be obtained as phase delay. In the case of a normal weld, the permeability and conductivity are smaller than in a weak weld, and the phase delay is smaller than in a weak weld.

[0020] The standard penetration depth of a weld is inversely proportional to frequency, permeability, and conductivity. Furthermore, the phase delay at any depth in the weld is inversely proportional to the standard penetration depth. In the case of normal welding, the standard penetration depth is greater than in the case of weak welding, so the permeability and conductivity in normal welding are smaller than in weak welding, and therefore the phase delay in normal welding is smaller than in weak welding. Based on this principle, the sensing result of the sensor assembly 10 forms the basis for determining the welding state. The sensor assembly 10 includes a number of sensor assemblies corresponding to the number of cells C provided in the battery module M. The sensor assembly 10 is configured to have multiple sensing parts so that each sensing part 10', 10'' of the sensor assembly 10 can simultaneously inspect the lead welding state of multiple cells C.

[0021] As shown in Figure 5, the sensor assembly 10, which includes multiple sensing parts, is configured to move vertically (z-axis) and vertically (x-axis) to contact the welded lead. For this purpose, the driver 70 may include a z-axis driver 70b and an x-axis driver 70c. The driver 70 includes a linear driver, such as an electric cylinder. The sensor assembly 10 performs inspections at multiple points per lead welded to cell C. For example, in Figure 6a, the sensor assembly 10 moves vertically (z-axis) and senses the weld condition of at least five points on the welded lead.

[0022] Referring to Figures 6b and 6c, in the lead welding of the battery module M, the leads include an anode aluminum lead and a cathode copper lead (e.g., side sensors 10b and 10c). In deep penetration inspection, a correlation with welding output was confirmed in the case of aluminum electrodes. It was confirmed that a difference in the width of the aluminum weld bead occurs due to the difference in the melting point of the materials. To compensate for this, the diameter of the side sensor 10b for the aluminum electrode lead and the diameter of the side sensor 10c for the copper electrode lead are configured to be different from each other. That is, according to the present invention, the diameter of the side sensor 10b for the aluminum electrode lead is configured to be larger than the diameter of the side sensor 10c for the copper electrode. In an embodiment of the present invention, at an applicable frequency of 80 kHz, the side sensor 10b for the aluminum electrode lead has a sensor diameter of 1.48 mm, and the side sensor 10c for the copper electrode lead has a sensor diameter of 1.19 mm, and it was confirmed that this improves the resolution of the side sensor 10c for the copper electrode.

[0023] Referring to Figures 7a and 7b, the camera 30 provided in the apparatus 1 is configured to perform vision inspection. Based on the image captured by the camera 30, the length of the weld, the width of the bead, the number and size of pores, etc., can be evaluated. The camera 30 may include at least three cameras 30a, 30b, and 30c. The side cameras 30a and 30c are configured to capture the side weld condition of the battery module M, and the front camera 30b can capture the weld condition of the front or rear of the battery module M. Inspection of the side weld is performed by the additionally provided side sensors 10b and 10c as described above. The camera 30 is also configured to determine the center of the weld bead during deep penetration inspection. As shown in Figure 8, the camera 30 can sense the center coordinates of the weld bead or weld W after visually confirming them numerically. The camera 30 numerically interprets and displays two points on either side and one point in the middle of the width of the weld bead W.

[0024] Referring to Figure 9, the pitch P of the sensor assembly 10 (for example, between sensing portion 10' and sensing portion 10") is determined using the pitch determined during welding (the center pitch between adjacent weld beads). Therefore, since the irradiation position of the laser beam is determined during laser welding, the pitch P is determined based on this. That is, the sensor assembly 10 has its pitch P pre-set to measure the center portion of the weld bead determined in this way. However, the pitch between the sensor assemblies 10 is designed to be manually adjustable so that it can be adjusted arbitrarily. For example, by comparing it with the center coordinates of the weld W determined based on the image captured by the camera 30, it is confirmed that each sensing portion of the sensor assembly 10 is correctly positioned at the center coordinates.

[0025] In some implementations, the sensor assembly 10 may be a pogo pin type sensor. Since sensing is performed by contact with the weld bead, it is preferable to use a pogo pin type sensor, but it is not limited to this, and other types of sensors may be used.

[0026] Referring again to Figure 5, the illumination 50 is driven when the camera 30 takes an image. The illumination 50 is configured to be movable in the vertical direction (z-axis), and is configured to provide illumination to the battery module M, which is the workpiece, while the camera 30 takes an image. The illumination 50 is mounted on the z-axis drive unit 70a and controlled to be movable up and down.

[0027] As mentioned above, the drive unit 70 includes an x-axis drive unit 70c and z-axis drive units 70a and 70b. The drive unit 70 also includes additional drive units not shown in the drawings. For example, the plate 120 for mounting the battery module M is configured to be movable on the transport rail 140. Since the plate 120 with the battery module M mounted on it can be continuously supplied to perform inspection by the device 1, continuous and automatic inspection is possible. The plate 120 is also configured to be rotatable. After inspecting the lead weld on the front of the battery module M, the plate 120 rotates to inspect the lead weld on the rear of the battery module M. Also, as shown in Figure 10, the plate 120 rotates when inspecting the side weld W2 and clamp weld W1. The plate 120 is driven by the drive unit 70. Any known device such as a motor or electric cylinder can be used as the drive unit 70, and is not limited to the type shown.

[0028] The apparatus 1 further includes a display unit 90. The display unit 90 is an interface space with the operator and provides the operator with the results of vision inspection and deep penetration inspection. If the welding condition is poor, it generates an alarm and displays the corresponding cell. The controller 100 is configured to control each component of the apparatus 1 and output inspection results via the display unit 90. In some embodiments, the controller 100 controls the sensing and movement of the sensor assembly 10. In some embodiments, the controller 100 instructs the camera 30 to take images and controls the illumination and movement of the lighting 50. In some embodiments, the controller 100 moves or rotates the associated components by driving the driver 70.

[0029] Furthermore, the controller 100 provides more accurate results by removing noise from the test signal or the acquired phase delay signal. As shown in Figure 11a, the peaks in the test signal are noise components. The controller 100 uses the zero-crossing point of the graph to perform data cropping, cutting the interval so that the periodic signal repeats normally. Then, as shown in Figure 11b, the controller 100 performs a Fast Fourier Transform (FFT) on the cropped data to detect the maximum frequency component. It is configured to extract the detected frequency by controlling all other frequencies to zero, excluding the detected frequency. Then, as shown in Figure 11c, the controller 100 restores the frequency components using an Inverse Fast Fourier Transform (iFFT) and compares them with the original signal. Figure 12 shows the comparison results of measurement data to which this noise reduction algorithm by the controller 100 was applied and measurement data to which it was not applied.

[0030] The apparatus 1 is driven as follows: The battery module M, which is the object to be inspected, is placed on plate 120. Plate 120 is placed on a transfer rail 140 and moved to apparatus 1. Multiple plates 120 are placed on the transfer rail 140 at regular intervals and are sequentially transferred to apparatus 1 for inspection. Then, the lead welding state on the front of the battery module M is imaged by camera 30. Based on the image captured by camera 30, the center portion of the weld bead to be inspected is determined.

[0031] The controller 100 is configured to inspect the welding condition of multiple points in the central portion of a determined weld bead by moving the sensor assembly 10 using the driver 70 of the sensor assembly 10 and activating the sensor assembly 10. The readings from the sensor assembly 10 are transmitted to the controller 100 to perform the analysis. The controller 100 then rotates the plate 120 by 180 degrees. This allows the lead weld condition on the rear surface of the battery module M to be inspected. Similar to the front inspection, the camera 30 captures an image of the lead weld condition on the rear surface of the battery module M, and based on the captured image, the center portion of the weld bead to be inspected is determined.

[0032] The controller 100 inspects multiple points in the center of the weld bead determined by the sensor assembly 10, and transmits the results to the controller 100. In addition, the welding condition of the left and right sides of the battery module M is determined via sensors 10b and 10c. The controller 100 outputs the inspection results to the display unit 90 and informs the operator of the cell C with a defective welding condition.

[0033] Thus, the automatic welding condition inspection device according to the present invention automatically inspects not only the appearance of the weld bead but also the welding (molten) state. According to the present invention, an automatic welding condition inspection device is provided that can reduce labor and related costs. According to the present invention, an automatic welding condition inspection device is provided that can provide accurate and reliable results.

[0034] The present invention described above is not limited to the embodiments and accompanying drawings, and it will be apparent to those with ordinary skill in the art to which the present invention pertains that various substitutions, modifications, and changes are possible without departing from the technical spirit of the present invention. [Explanation of Symbols]

[0035] A Cell Stack B Bus Bar C cell M module L Lead P pitch W Weld joint, weld bead W1 Clamp Welding W2 side welding 1 device 2 Covers 10 Sensor Assembly 10b Side sensor for aluminum electrode leads 10c copper electrode side sensor 10', 10” sensing section 11 Magnetic field generating coil 13 Sensing Coil 15 Oscillator 17 voltmeter 30 Cameras 30a Side camera 30b Front Camera 30c side camera 50 Lighting 50a, 50b, 50c lighting 70 Drive unit 70a (Lighting) Z-axis drive 70b (Sensor assembly) z-axis driver 70c (x-axis driver of sensor assembly) 90 Display section 100 controllers 120 Plate 140 Transfer Rails

Claims

1. An automated inspection device for the welding condition of battery modules, The battery module is assembled with multiple battery cells, and the leads connected to each battery cell are welded to a busbar to conduct electricity to each other. The automatic welding condition inspection device for the battery module is configured to inspect the welds between the leads of each battery cell and the busbar. A sensor assembly configured to measure the signal of change in eddy current due to the depth of the weld by applying an eddy current to the weld, the sensor assembly comprising a plurality of sensing parts configured to be movable together, each sensing part configured to simultaneously contact the weld of each battery cell, The controller includes a sensor assembly that receives the eddy current change signal obtained by the sensor assembly and is configured to determine the quality of the weld based on the eddy current change signal, An automatic inspection device for the welding condition of a battery module, characterized in that the sensing unit is configured to measure at multiple points on the weld while simultaneously moving along the longitudinal direction of the weld of each battery cell.

2. The lead consists of a copper lead provided on one side of the battery cell and an aluminum lead provided on the other side of the battery cell. The sensor assembly includes a side sensor comprising a copper electrode side sensor that inspects the weld on one side of the battery cell and an aluminum electrode lead side sensor that inspects the weld on the other side of the battery cell. The automatic welding condition inspection device for a battery module according to claim 1, characterized in that the side sensors are configured to measure the welding condition of the copper lead and the aluminum lead on the side of the battery cell, respectively.

3. The automatic welding condition inspection device for a battery module according to claim 2, characterized in that the side sensor for the copper lead is configured to have a smaller sensor diameter than the sensor diameter of the side sensor for the aluminum lead.

4. The automatic welding condition inspection device for a battery module according to claim 1, comprising a camera configured to image the welded portion, and performing a visual inspection of the welded portion based on the image captured by the camera.

5. The automatic welding condition inspection device for a battery module according to claim 4, characterized in that the controller is configured to determine the central portion of the weld that the sensor assembly senses based on the image captured by the camera.

6. The automatic welding condition inspection device for a battery module according to claim 5, characterized in that the sensor assembly is configured to measure the weld while moving along the determined central portion.

7. The automatic welding condition inspection device for a battery module according to claim 1, characterized in that the eddy current change signal is processed as a phase delay signal, and the controller is configured to determine the quality of the weld based on the phase delay signal.

8. The automatic welding condition inspection device for a battery module according to claim 7, characterized in that the controller is configured to obtain a corrected phase delay signal by removing noise from the phase delay signal, and to determine the quality of the weld based on the corrected phase delay signal.

9. The controller is, A zero intersection of the phase delay signal is selected, and the phase delay signal is cropped with respect to the selected zero intersection. A Fourier transform is applied to the cropped phase delay signal to extract only the predefined frequency components, and components other than the extracted frequency components are removed. The automatic welding condition inspection device for a battery module according to claim 8, characterized in that it is configured to obtain a corrected phase delay signal by applying an inverse Fourier transform to restore the components that have been erased, and then comparing them with the phase delay signal.

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