Welding inspection system and methods of welding inspection using eddy current

Abstract

The present invention relates to a welding condition inspection system that improves the ability to distinguish between weak welding and normal welding, comprising: an inspection unit including a first sensor that irradiates a primary magnetic field to a weld portion of a battery cell and a second sensor that detects an eddy current signal induced by the first sensor; and a data processing unit that collects the eddy current signal detected by the inspection unit and evaluates the welding condition of the weld portion of the battery cell, wherein the first sensor receives a sinusoidal wave and the data processing unit determines the welding condition of the weld portion based on the amplitude of the eddy current signal.

Description

Technology Field

[0001] The present invention relates to a system and method for inspecting the welding condition of a welded part of a battery cell, and more specifically, to an inspection system and inspection method capable of determining whether the welded part is a normal weld, an unwelded weld, or a weak weld by using eddy currents. Background Technology

[0003] As the price of energy sources rises due to the depletion of fossil fuels and concerns about environmental pollution intensify, the demand for eco-friendly alternative energy sources is becoming an indispensable factor for future life; in particular, with the technological development and increasing demand for mobile devices, the demand for secondary batteries as an energy source is rapidly rising.

[0004] In terms of battery shape, there is high demand for prismatic and pouch-type rechargeable batteries, which are thin and suitable for applications such as mobile phones; in terms of materials, there is high demand for lithium-ion batteries and lithium-ion polymer batteries, which offer high energy density, discharge voltage, and output stability.

[0005] Secondary batteries are classified according to the structure of the electrode assembly, which consists of a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes. Representative examples include a jelly-roll (wound type) electrode assembly in which long sheet-type positive and negative electrodes are wound with a separator interposed; a stack type (stacked type) electrode assembly in which a plurality of positive and negative electrodes cut into units of a predetermined size are sequentially stacked with a separator interposed; and a stack-folding type electrode assembly in which unit cells such as bi-cells or full cells are wound with a predetermined unit of positive and negative electrodes stacked with a separator interposed.

[0006] Such a battery may be provided with a structure in which an electrode assembly is embedded in a battery case. The battery may include electrode terminals formed by welding electrode tabs protruding from an electrode current collector to electrode leads.

[0007] At this time, if processes such as welding are not performed properly in the tab-lead connection area of ​​the battery, the current may flow abnormally, or the electrical connection may become unstable due to shock or vibration applied to the battery, and in severe cases, the electrode tab and electrode lead may become separated.

[0008] Therefore, when inspecting the welding condition of the weld in the tab-lead connection area of ​​a battery, a method is required to distinguish unwelded and weak welds from normal welds.

[0009] Korean Registered Patent No. 2023739 discloses a technology for detecting cracks using eddy currents. The aforementioned document is intended for non-destructive crack detection and can detect unwelded conditions, but has limitations in detecting weak welds. Prior art literature

[0011] Korean Registered Patent No. 2023739 The problem to be solved

[0012] The present invention aims to solve the above-mentioned problems by providing a welding condition inspection system and an inspection method that improve the detection capability of weak welding. means of solving the problem

[0014] A welding condition inspection system according to the present invention comprises: an inspection unit including a first sensor that irradiates a primary magnetic field to a welded portion of a battery cell and a second sensor that detects an eddy current signal induced by the first sensor; and a data processing unit that collects the eddy current signal detected by the inspection unit and evaluates the welding condition of the welded portion of the battery cell, wherein a sinusoidal wave is input to the first sensor and the data processing unit determines the welding condition of the welded portion based on the amplitude of the eddy current signal.

[0015] In one embodiment of the present invention, the sinusoidal wave may be a sine wave.

[0016] In one embodiment of the present invention, the frequency of the sinusoidal wave is 100 to 1000 Hz.

[0017] In one embodiment of the present invention, the first sensor and the second sensor are respectively positioned opposite each other on the upper and lower portions of the welded part of the battery cell.

[0018] In one embodiment of the present invention, the first sensor and the second sensor are spaced apart from the weld of the battery cell at a predetermined distance and are configured to move along a set driving path and perform an eddy current inspection in a non-contact state with the weld.

[0019] In one embodiment of the present invention, the first sensor includes a transmitting coil that irradiates a primary magnetic field to a weld, and the second sensor includes a receiving coil that receives a secondary magnetic field radiated by an eddy current generated in the weld by the primary magnetic field and generates an electromotive force.

[0020] In one embodiment of the present invention, the data processing unit determines whether the weld is normal, weak, or unwelded through the shape, symmetry, and area of ​​a graph plotting the amplitude of an eddy current signal.

[0021] In one embodiment of the present invention, weak welding or incomplete welding is determined by comparing with normal welding data.

[0022] The welding condition inspection method of the present invention is a method for inspecting the welding condition of a battery cell weld using a first sensor that irradiates a primary magnetic field to the weld of a battery cell and a second sensor that detects an eddy current signal induced by the first sensor, wherein a sinusoidal wave having a frequency of a predetermined range is input to the first sensor, and the normal welding / weak welding / unwelding of the weld is determined through the shape, symmetry, and area of ​​a graph plotting the amplitude of the eddy current signal.

[0023] In one embodiment of the present invention, the first sensor and the second sensor perform an eddy current inspection along a set driving path in a non-contact state at a position spaced apart from the battery cell weld.

[0024] In one embodiment of the present invention, the frequency of the sinusoidal wave is 100 to 1000 Hz. Effects of the invention

[0026] The welding condition inspection system and welding condition inspection method of the present invention can distinguish between weak welding and normal welding, thereby having the effect of improving the detection capability of weak welding. Brief explanation of the drawing

[0028] FIG. 1 is a schematic diagram of an inspection system according to one embodiment of the present invention. Figure 2 is a diagram showing the eddy current sensor of the present invention performing an inspection. FIGS. 3 to 6 are amplitude graphs of eddy current signals according to an embodiment. Figures 7 to 10 are amplitude graphs of eddy current signals according to comparative examples. Specific details for implementing the invention

[0029] The present invention is capable of various modifications and may take various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the invention to the specific disclosed forms, and it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0030] In this application, terms such as "comprising" or "having" are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof. Furthermore, when a part such as a layer, film, region, or plate is described as being "on" another part, this includes not only cases where it is "immediately above" the other part, but also cases where there is another part in between. Conversely, when a part such as a layer, film, region, or plate is described as being "under" another part, this includes not only cases where it is "immediately below" the other part, but also cases where there is another part in between. Additionally, in this application, being placed "on" may include cases where it is placed on the lower part as well as on the upper part.

[0032] Hereinafter, a welding condition inspection system according to the present invention will be described in detail.

[0033] FIG. 1 is a schematic diagram of a welding condition inspection system for a battery cell according to an embodiment of the present invention. Referring to FIG. 1, the inspection system (100) of the present invention includes: an inspection unit (100) comprising a first sensor (111) that irradiates a primary magnetic field to a welding portion (A) of a battery cell and a second sensor (112) that detects an eddy current signal induced by the first sensor; and a data processing unit (120) that collects the eddy current signal detected by the inspection unit (100) and evaluates the welding condition of the welding portion of the battery cell.

[0034] The inspection system of the present invention uses an eddy current sensor to non-destructively inspect a weld included in a battery cell, a sinusoidal wave is input to the eddy current sensor, and the welding condition is determined based on the amplitude of the eddy current signal collected by the eddy current sensor.

[0035] Conventional systems or methods for inspecting the welding condition of a weld using eddy currents evaluated the welding condition based on the phase difference of eddy current signals received by an eddy current sensor. However, while such methods can detect welding defects caused by incomplete welding, they have the disadvantage of being difficult to distinguish welding defects caused by incomplete welding from normal welding.

[0036] The present invention is characterized by inputting a sinusoidal wave having a frequency of a specific range to a first sensor, so that the first sensor applies a sinusoidal wave of a specific frequency to the weld portion of a battery cell, and a second sensor detects an eddy current signal induced by the first sensor, and a data processing unit analyzes the waveform data of the eddy current signal detected by the second sensor to determine whether the weld condition of the weld portion is normal weld, weak weld, or unwelded.

[0037] The inspection system of the present invention, which determines the welding quality of a weld based on the amplitude of an eddy current signal, has the effect of accurately distinguishing between normal welding and weak welding compared to a method that evaluates the welding condition based on the phase difference of an eddy current signal.

[0038] In one specific example, the sinusoidal wave input to the first sensor may be a sine wave, and the frequency of the sinusoidal wave is 100 to 1000 Hz. In the present invention, if the numerical range is less than 100 Hz, the inspection speed may be too slow, and conversely, if it exceeds 1000 Hz, the detection capability of weak welding may be reduced, which is undesirable.

[0039] In the inspection system of the present invention, the battery cell weld part to be inspected may be the electrode current collector, electrode tab, and electrode lead itself included in the battery cell, or a connection area where the electrode current collector, electrode tab, and electrode lead are connected to each other. Specifically, as shown in FIG. 1, it may be a tab-lead connection area (A) where an electrode tab (11) protruding from the electrode current collector and an electrode lead (12) connected to an electrical terminal of an external device are connected to each other by welding or the like.

[0040] FIG. 2 is a diagram showing the eddy current sensor of the present invention performing an inspection. Referring to FIG. 2, the first sensor (111) and the second sensor (112) are positioned facing each other at the upper and lower portions of the weld (A) of the battery cell (10). At this time, the first sensor (111) and the second sensor (112) are spaced apart from the weld (A) of the battery cell by a predetermined distance. Specifically, the first sensor (111) is positioned at a predetermined distance in the upward direction from the weld (A), and the second sensor (112) is positioned at a predetermined distance in the downward direction from the weld (A). Furthermore, the first sensor (111) and the second sensor (112) are configured to move along a predetermined travel path (dotted line) within the area of ​​the weld while maintaining a non-contact state with the weld. In this way, the first sensor and the second sensor move along the above-mentioned travel path, induce eddy currents, detect the induced eddy current signals, and perform an eddy current inspection.

[0041] The inspection system of the present invention determines the welding condition based on the amplitude of an eddy current signal, and the determination based on amplitude is possible only if the weld to be inspected is located between the first sensor and the second sensor. That is, it is difficult to implement the present invention with eddy current sensors in which both the first sensor and the second sensor are located on the upper surface of the weld, or both the first sensor and the second sensor are located on the lower surface of the weld.

[0042] In one specific example, the first sensor (111) includes a transmitting coil (not shown) that irradiates a primary magnetic field onto the weld (A), and the second sensor (112) includes a receiving coil (not shown) that receives a secondary magnetic field radiated by an eddy current generated on the weld (A) by the primary magnetic field and generates an electromotive force.

[0043] The above-mentioned transmitting coil and receiving coil may each be provided in a cylindrical, square columnar, or polygonal columnar shape, and may be in a form in which wires are wound so as to generate a magnetic field in the longitudinal direction of the transmitting coil and receiving coil.

[0044] The above data processing unit (120) determines whether the weld is normal / weak / unwelded through the shape, symmetry, and area of ​​a graph plotting the amplitude of the eddy current signal.

[0045] The data processing unit (120) can store eddy current signals detected by the first sensor and the second sensor as they move along a predetermined driving path, and can plot the amplitude of the eddy current signals according to the length of the driving path.

[0046] Referring to FIG. 2, the first sensor (111) and the second sensor (112) move along the dotted line on the weld (A) to perform an inspection by eddy current, and the inspection unit (110) can detect the eddy current signal in real time from the point where the inspection starts (B) to the point where the inspection ends (E) and transmit it to the data processing unit. Accordingly, the data processing unit can plot the amplitude of the eddy current signal according to the length of the weld.

[0047] Typically, a graph plotting the amplitude of an eddy current signal forms a "U" shape and is symmetrical when the weld (A) is a normal weld. On the other hand, when there is an un-welded portion in part of the weld (A), the amplitude of the eddy current signal changes in the un-welded portion compared to the normal weld, so the shape of the graph does not form a symmetry.

[0048] On the other hand, when the weld is a weak weld, the graph shape may have a symmetrical "U" shape similar to a normal weld, but since the amplitude value increases overall, the internal area of ​​the "U" shape decreases.

[0049] As such, the present invention can distinguish between non-welding and weak welding from normal welding through the shape, symmetry, and area of ​​a graph plotting the amplitude of an eddy current signal, and has the effect of improving the detection capability of weak welding.

[0050] The battery cell subject to inspection by the inspection system of the present invention may have a structure in which an electrode assembly having a structure in which a positive electrode, a separator, and a negative electrode are alternately stacked is housed inside a battery case. The positive and negative electrodes each have a structure in which an active material layer is formed after an electrode slurry containing an electrode active material is applied to a current collector, followed by a drying and rolling process. Once the electrode assembly is housed in the battery case, an electrolyte is injected into the interior and sealed to manufacture the battery cell.

[0051] Here, the current collector may be a positive current collector or a negative current collector, and the electrode active material may be a positive active material or a negative active material. In addition, the electrode slurry may further include a conductive material and a binder in addition to the electrode active material.

[0052] In the present invention, the positive current collector is generally made with a thickness of 3 to 500 μm. Such a positive current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. The current collector may also form fine irregularities on its surface to increase the adhesion of the positive active material, and various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics are possible.

[0053] In the case of sheets for negative electrode current collectors, they are generally made with a thickness of 3 to 500 μm. Such negative electrode current collectors are not particularly limited as long as they are conductive without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloys may be used. In addition, similar to positive electrode current collectors, fine irregularities may be formed on the surface to strengthen the bonding strength of the negative electrode active material, and they may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

[0054] In the present invention, the positive electrode active material is a material capable of causing an electrochemical reaction, and is a lithium transition metal oxide comprising two or more transition metals, for example, a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2) substituted with one or more transition metals; lithium manganese oxide substituted with one or more transition metals; and the chemical formula LiNi 1-y M yLithium nickel-based oxide represented by O2 (wherein M = Co, Mn, Al, Cu, Fe, Mg, B, Cr, Zn, or Ga and contains one or more of the above elements, 0.01≤y≤0.7); Li 1+z Ni 1 / 3 Co 1 / 3 Mn 1 / 3 O2, Li 1+z Ni 0.4 Mn 0.4 Co 0.2 Li, like O2, etc. 1+z Ni b Mn c Co 1-(b+c+d) M d O (2-e) A e A lithium nickel cobalt manganese composite oxide represented by (where -0.5≤z≤0.5, 0.1≤b≤0.8, 0.1≤c≤0.8, 0≤d≤0.2, 0≤e≤0.2, b+c+d<1, M = Al, Mg, Cr, Ti, Si or Y, and A = F, P or Cl); chemical formula Li 1+x M 1-y M' y PO 4-z X z Examples include olivine-based lithium metal phosphates expressed as (where M = transition metal, preferably Fe, Mn, Co, or Ni, M' = Al, Mg, or Ti, X = F, S, or N, and -0.5≤x≤+0.5, 0≤y≤0.5, 0≤z≤0.1), but are not limited to these.

[0055] The cathode active material is carbon, for example, non-graphitizable carbon, graphite-based carbon, etc.; Li x Fe2O3(0≤x≤1), Li x WO2(0≤x≤1), Sn x Me 1-x Me y O z(Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group 1, 2, and 3 elements of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8) 등의 금속 복합 산화물; 리튬 금속; 리튬 합금; 규소계 합금; 주석계 합금; SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5등의 금속 산화물; 폴리아세틸렌 등의 도전성 고분자; Li-Co-Ni 계 재료 등을 사용할 수 있다.

[0056] The above conductive material is typically added in an amount of 1 to 30 weight percent based on the total weight of the mixture containing the positive electrode active material. Such conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fibers such as carbon fibers or metal fibers; metal powders such as carbon fluoride, aluminum, or nickel powder; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive materials such as polyphenylene derivatives may be used.

[0057] The above binder is a component that assists in the bonding of the active material and the conductive material, and in the bonding to the current collector, and is typically added in an amount of 1 to 30 weight percent based on the total weight of the mixture containing the positive active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber, and various copolymers.

[0058] Meanwhile, the above-mentioned separator is interposed between the anode and the cathode, and an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally 0.01 to 10 μm, and the thickness is generally 5 to 300 μm. For example, olefin-based polymers such as chemically resistant and hydrophobic polypropylene; sheets or nonwoven fabrics made of glass fibers or polyethylene are used as such separators.

[0059] Meanwhile, in the electrode assembly, an electrode tab is formed on one side of the electrode, and the electrode tab may be a positive tab or a negative tab. A positive lead and a negative lead are connected to the positive tab and the negative tab, respectively. The positive lead and the negative lead are drawn out to the outside of the battery case and serve as terminals that are electrically connected to the outside. At this time, the positive lead and the negative lead may be joined to the positive tab and the negative tab, respectively, by welding. Known welding methods may be used, for example, ultrasonic welding or laser welding may be used.

[0060] At this time, the battery case is not particularly limited as long as it is used as an exterior material for packaging the battery, and cylindrical, prismatic, or pouch-type cases may be used; specifically, a pouch-type battery case may be used. A pouch-type battery case is typically made of an aluminum laminate sheet and may consist of an internal sealant layer for sealing, a metal layer to prevent the penetration of substances, and an external resin layer forming the outermost part of the case. The battery cell is manufactured by heat-sealing the upper case and the lower case after the electrode assembly is housed inside the pouch-type battery case and the electrode leads are drawn out, so a heat-sealed portion may be formed at the end of the battery case. Specific details regarding the battery case below are known to those skilled in the art, so a detailed explanation is omitted.

[0062] In addition, the present invention provides a method for inspecting the welding condition.

[0063] A welding condition inspection method according to the present invention is a method for inspecting the welding condition of a battery cell weld using a first sensor that irradiates a primary magnetic field to the weld of a battery cell and a second sensor that detects an eddy current signal induced by the first sensor, wherein a sinusoidal wave having a frequency of a predetermined range is input to the first sensor, and the normal welding / weak welding / unwelding of the weld is determined through the shape, symmetry, and area of ​​a graph plotting the amplitude of the eddy current signal.

[0064] Conventionally, a method for inspecting the welding condition of a weld using eddy currents evaluated the welding condition based on the phase difference of the eddy current signal received by an eddy current sensor. However, this method has the disadvantage that it is difficult to distinguish welding defects caused by weak welding from normal welding.

[0065] The present invention is characterized by inputting a sinusoidal wave having a frequency of a specific range to a first sensor, so that the first sensor applies a sinusoidal wave of a specific frequency to the weld of a battery cell, the second sensor detects an eddy current signal induced by the first sensor, and analyzes the waveform data of the eddy current signal detected by the second sensor to determine whether the weld condition of the weld is normal weld, weak weld, or unwelded.

[0066] Compared to a method that evaluates the welding condition based on the phase difference of an eddy current signal, the inspection method of the present invention has the effect of accurately distinguishing between normal welding and weak welding.

[0067] In one specific example, the frequency of the sinusoidal wave is 100 to 1000 Hz. If the numerical range is less than 100 Hz, the inspection speed may be too slow, and conversely, if it exceeds 1000 Hz, the detection capability of weak welds may be reduced, which is undesirable.

[0068] In one specific example, the first sensor and the second sensor perform an eddy current test along a set driving path in a non-contact state at a location spaced apart from the battery cell weld.

[0069] The inspection method of the present invention determines the welding condition based on the amplitude of an eddy current signal, and the welding part to be inspected must be located between the first sensor and the second sensor for the determination based on amplitude to be possible. That is, it is difficult to implement the present invention with eddy current sensors in which both the first sensor and the second sensor are located on the upper surface of the welding part, or both the first sensor and the second sensor are located on the lower surface of the welding part.

[0071] Example 1

[0072] For the welded portion of a battery cell in which the electrode tab and electrode lead are properly welded, an eddy current test was performed by a first sensor and a second sensor as shown in FIG. 1. At this time, the frequency of the sine wave input to the first sensor is 500 Hz.

[0073] Based on the eddy current signal detected by the second sensor, the welding length was plotted on the X-axis and the amplitude value on the Y-axis, and the result is shown in Figure 3.

[0075] Example 2

[0076] For the welded portion of the battery cell including the unwelded portion of the electrode tab and electrode lead, an eddy current inspection was performed by a first sensor and a second sensor as shown in FIG. 1. At this time, the frequency of the sine wave input to the first sensor is 500 Hz.

[0077] Based on the eddy current signal detected by the second sensor, the welding length was plotted on the X-axis and the amplitude value on the Y-axis, and the result is shown in Figure 4.

[0079] Example 3

[0080] For the welded portion of the battery cell in which the electrode tab and the electrode lead are loosely welded, an eddy current test was performed by a first sensor and a second sensor as shown in FIG. 1. At this time, the frequency of the sine wave input to the first sensor is 500 Hz.

[0081] Based on the eddy current signal detected by the second sensor, the welding length was plotted on the X-axis and the amplitude value on the Y-axis, and the result is shown in Fig. 5.

[0083] Comparative Example 1

[0084] In the above Example 1, a plotting graph was obtained in the same manner as in Example 1, except that the frequency of Saipan input to the first sensor was changed to 20 kHz. The result is shown in FIG. 7.

[0086] Comparative Example 2

[0087] In the above Example 2, a plotting graph was obtained in the same manner as in Example 2, except that the frequency of Saipan input to the first sensor was changed to 20 kHz. The result is shown in FIG. 8.

[0089] Comparative Example 3

[0090] In the above Example 3, a plotting graph was obtained in the same manner as in Example 3, except that the frequency of Saipan input to the first sensor was changed to 20 kHz. The result is shown in FIG. 9.

[0092] The graphs of FIGS. 3 to 5 obtained from Examples 1 to 3 above were combined and shown in FIG. 6, and the graphs of FIGS. 7 to 9 obtained from Comparative Examples 1 to 3 above were combined and shown in FIG. 10.

[0093] Referring to Figures 3 to 5, the amplitude graphs of normal welding and weak welding show a "U"-shaped symmetrical graph form, while the amplitude graph of unwelded welding does not show symmetry in certain parts as shown in Figure 4.

[0094] Referring to FIG. 6, the graph of weak welding shows an overall increase in amplitude compared to the graph of normal welding, and is smaller than the "U" shape of the normal welding graph. Therefore, according to the inspection system and inspection method of the present invention, it is possible to distinguish not only unwelded but also weak welding from normal welding.

[0095] Referring to FIGS. 7 to 9, the amplitude graph of the unwelded weld shown in FIG. 8 is not symmetrical in certain areas. Referring to FIG. 10, the normal weld graph and the weak weld graph completely overlap, so the normal weld and the weak weld cannot be distinguished.

[0096] As such, the inspection system and inspection method of the present invention have the effect of improving the detection capability to detect a weak welding state.

[0098] Although preferred embodiments of the present invention have been described above with reference to the drawings, those skilled in the art or those with ordinary knowledge in the relevant technical field will understand that various modifications and changes can be made to the present invention without departing from the spirit and technical scope of the invention as described in the claims.

[0099] Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be determined by the claims. Explanation of the symbols

[0101] 10: Battery cell 11: Electrode tab 12: Electrode Lead 100: Welding condition inspection system 110: Inspection Department 111: 1st sensor 112: Second sensor 120: Data processing unit A: Welded part

Claims

Claim 1 A battery cell welding condition inspection system comprising: an inspection unit including a first sensor that irradiates a primary magnetic field to a welded portion of a battery cell and a second sensor that detects an eddy current signal induced by the first sensor; and a data processing unit that collects the eddy current signal detected by the inspection unit and evaluates the welding condition of the welded portion of the battery cell, wherein the first sensor receives a sinusoidal wave, and the data processing unit determines whether the welded portion is normal welding, weak welding, or unwelded through the shape, symmetry, and area of ​​a graph plotting the amplitude of the eddy current signal. Claim 2 In claim 1, the above sinusoidal wave is a sine wave, a welding condition inspection system for a battery cell. Claim 3 A battery cell welding condition inspection system according to claim 1, wherein the frequency of the sinusoidal wave is 100 to 1000 Hz. Claim 4 In claim 1, the first sensor and the second sensor are a battery cell welding condition inspection system positioned oppositely to the upper and lower portions of the battery cell welding portion. Claim 5 A battery cell welding condition inspection system according to claim 4, wherein the first sensor and the second sensor are spaced apart from the weld of the battery cell at a predetermined distance and are configured to move along a set travel path and perform an eddy current inspection without contacting the weld. Claim 6 A welding condition inspection system for a battery cell according to claim 1, wherein the first sensor comprises a transmitting coil that irradiates a primary magnetic field to a welded part, and the second sensor comprises a receiving coil that receives a secondary magnetic field radiated by an eddy current generated in the welded part by the primary magnetic field and generates an electromotive force. Claim 7 delete Claim 8 A welding condition inspection system for a battery cell according to claim 1, which determines weak welding or incomplete welding by comparing with normal welding data. Claim 9 A method for inspecting the welding condition of a battery cell weld using a first sensor that irradiates a primary magnetic field to the weld of a battery cell and a second sensor that detects an eddy current signal induced by the first sensor, wherein a sinusoidal wave having a frequency of a predetermined range is input to the first sensor, and the normal welding / weak welding / incomplete welding of the weld is determined through the shape, symmetry, and area of ​​a graph plotting the amplitude of the eddy current signal. Claim 10 A method for inspecting the welding condition of a battery cell according to claim 9, wherein the first sensor and the second sensor perform an eddy current inspection along a set driving path in a non-contact state at a position spaced apart from the battery cell weld. Claim 11 A method for inspecting the welding condition of a battery cell according to claim 9, wherein the frequency of the sinusoidal wave is 100 to 1000 Hz.

Images