KR102816454B1 - Eddy current sensor for detecting crack of battery cell and method for detecting crack of battery cell using the same - Google Patents

Abstract

The present invention relates to an eddy current sensor for crack inspection of a battery cell and a method for crack inspection of a battery cell using the same, which can easily detect the presence or absence and location of cracks occurring on an electrode, electrode tab, or weld.

Description

{EDDY CURRENT SENSOR FOR DETECTING CRACK OF BATTERY CELL AND METHOD FOR DETECTING CRACK OF BATTERY CELL USING THE SAME}

The present invention relates to an eddy current sensor for crack inspection of a battery cell and a method for crack inspection of a battery cell using the same.

As the price of energy sources rises due to the depletion of fossil fuels and concerns about environmental pollution increase, the demand for eco-friendly alternative energy sources is becoming an essential factor for future life. In particular, as technological development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing.

In terms of battery shape, there is a high demand for square secondary batteries and pouch-type secondary batteries that can be applied to products such as mobile phones due to their thin thickness, and in terms of materials, there is a high demand for lithium secondary batteries such as lithium-ion batteries and lithium-ion polymer batteries that have high energy density, discharge voltage, and output stability.

Secondary batteries are also classified by the structure of the electrode assembly, which comprises a positive electrode, a negative electrode, and a separator structure interposed between the positive and negative electrodes. Representative examples thereof include a jelly-roll electrode assembly in which long sheet-shaped positive and negative electrodes are rolled up with a separator interposed between them, a stack-type electrode assembly in which a plurality of positive and negative electrodes cut into units of a predetermined size are sequentially laminated with a separator interposed between them, and a stack-folding electrode assembly in which unit cells such as a bi-cell or full cell are rolled up with a predetermined number of positive and negative electrodes laminated with a separator interposed between them.

Additionally, secondary batteries are manufactured by injecting a liquid electrolyte, which is an electrolyte, into a battery container while the electrode assembly is housed therein and sealing the battery container.

During the manufacturing process of the electrode or the assembly process of the electrode assembly as described above, cracks may occur on the electrode, tab, or welded portion due to reasons such as differences in elongation between the maintenance portion and the non-maintenance portion or physical external force due to welding, and such cracks may further cause low-voltage failure.

However, battery cells have problems in that it is difficult to sort out defects through vision inspection when cracks occur inside, and it is also difficult to non-destructively detect cracks inside the sealed battery cell once sealing is complete.

Accordingly, there is a need for technological development for devices and methods that can non-destructively detect defects such as cracks inside battery cells.

Korean Patent No. 10-2023739

In order to solve the problems of the prior art as described above, the present invention provides an eddy current sensor for crack inspection of a battery cell capable of non-destructively detecting cracks in the battery cell, and a method for crack inspection of a battery cell using the same.

The present invention is intended to solve the above problems, and provides an eddy current sensor for inspecting cracks inside a battery cell. In one example, the eddy current sensor according to the present invention includes: a probe; a transmitter having a structure in which a transmitter coil is wound, which is disposed on the probe and induces an eddy current in a battery cell to be evaluated; and a receiver having a structure in which a receiver coil is wound, which is disposed on the probe and is disposed in a region spaced apart from the transmitter coil and detects a signal change due to an eddy current induced in the battery cell by the transmitter coil.

At this time, the ratio (N2/N1) of the number of turns (N1) of the transmitting coil wound on the transmitting unit and the number of turns (N2) of the receiving coil wound on the receiving unit is in the range of 2.0 to 5.0, and the ratio (D1/D2) of the diameter (D1) of the transmitting coil wound on the transmitting unit and the diameter (D2) of the receiving coil wound on the receiving unit is in the range of 1.5 to 5.0.

In a specific example, the number of turns of the transmitting coil wound on the transmitting unit is in the range of 30 to 200, and the number of turns of the receiving coil wound on the receiving unit is in the range of 60 to 400. In addition, the diameter (D1) of the transmitting coil may be in the range of 0.01 to 2.0 mm, and the diameter (D2) of the receiving coil may be in the range of 0.01 to 1.0 mm.

In another example, the ratio (S1/R1) of the cross-sectional area of the transmitter section around which the transmitter coil is wound and the cross-sectional area (R1) of the receiver section around which the receiver coil is wound is in the range of 1.5 to 10.

In one example, the ratio (S2/R2) of the width (S2) of the transmitter section around which the transmitter coil is wound and the width (R2) of the receiver section around which the receiver coil is wound is in the range of 1.5 to 10. In a specific example, the width (S2) of the transmitter section around which the transmitter coil is wound is in the range of 20 to 150 mm, and the width (R2) of the receiver section around which the receiver coil is wound is in the range of 5 to 100 mm.

In another example, the transmitter and receiver are structured with a gap in the range of 2 to 15 mm.

In another example, the transmitter and receiver are coupled to each other, and have a structure in which a part or all of an area from one end of the transmitter and receiver is interlocked and the gap is adjusted. In a specific example, the transmitter has a structure in which a groove is formed along the length of the probe from one end. In addition, the receiver may have a structure in which a part or all of an area is inserted into the groove of the transmitter.

In addition, the present invention provides a method for inspecting cracks in a battery cell using the eddy current sensor described above.

According to the eddy current sensor for crack inspection of a battery cell of the present invention and the method for crack inspection of a battery cell using the same, the presence or absence and location of cracks occurring on an electrode, electrode tab, or welded portion can be easily detected.

In particular, the eddy current sensor has the effect of improving the accuracy of crack inspection of a battery cell to be evaluated by winding a large-diameter transmitting coil around the transmitting section.

Figure 1 is a schematic diagram illustrating the principle of crack detection using eddy current.
Figure 2 is a schematic diagram of an eddy current sensor according to one embodiment of the present invention.
FIG. 3 is a drawing showing an embodiment of a method for inspecting a battery cell for cracks using an eddy current sensor according to one embodiment of the present invention.
FIG. 4 is a graph showing the results of inspecting whether a battery cell has cracks using an eddy current sensor according to one embodiment of the present invention.
Figure 5 is a schematic diagram of a conventional eddy current sensor.
Figure 6 is a graph showing the results of inspecting whether a battery cell has cracks using a conventional eddy current sensor.
Figure 7 is a schematic diagram of an eddy current sensor according to another embodiment of the present invention.
Figure 8 is a schematic diagram of an eddy current sensor according to another embodiment of the present invention.

The present invention can be modified in various ways and can 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 present invention to specific disclosed forms, but should be understood to include all modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention.

In this application, it should be understood that terms such as "include" or "have" are intended to specify the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof. In addition, when a part such as a layer, film, region, or plate is said to be "on" another part, this includes not only the case where it is "directly above" the other part, but also the case where there is another part in between. Conversely, when a part such as a layer, film, region, or plate is said to be "under" another part, this includes not only the case where it is "directly below" the other part, but also the case where there is another part in between. In addition, in this application, being placed "on" may include the case where it is placed below as well as above.

The present invention provides an eddy current sensor for crack inspection of a battery cell and a method for crack inspection of a battery cell using the same.

Typically, secondary batteries are manufactured by injecting a liquid electrolyte, which is an electrolyte, into a battery container while the electrode assembly is housed therein, and sealing the battery container. During the above-described electrode manufacturing process or electrode assembly assembly process, cracks may occur on the electrodes, tabs, and welded portions due to reasons such as differences in elongation between the supporting portion and the non-supporting portion, and physical external force due to welding, and such cracks may further cause low-voltage defects. However, if cracks occur inside a battery cell, it is difficult to select defects through vision inspection, and once sealing is complete, it is difficult to non-destructively detect cracks inside the sealed battery cell. Accordingly, the present invention provides an eddy current sensor for crack inspection of a battery cell that can non-destructively detect cracks in the battery cell, and a method for crack inspection of a battery cell using the same. In particular, the eddy current sensor according to the present invention has the effect of increasing the accuracy of crack inspection of a battery cell to be evaluated by winding a transmitting coil having a larger diameter than a receiving coil around a transmitting portion.

Hereinafter, an eddy current sensor for crack inspection of a battery cell and a method for crack inspection of a battery cell using the same are described in detail.

The present invention utilizes the principle of crack detection using eddy current. Fig. 1 is a schematic diagram illustrating the principle of crack detection using eddy current.

Referring to Fig. 1, when an AC current is passed through a coil, a primary magnetic field is generated around the coil. When the transmitting coil forming the primary magnetic field is brought to a conductor, an induced electromotive force is generated in the conductor due to the electromagnetic induction phenomenon, and this induced electromotive force causes a current to flow that interferes with the primary magnetic field according to Lenz's law, and this current is called an eddy current. A secondary magnetic field that interferes with the primary magnetic field is generated by the eddy current. At this time, the eddy current changes depending on changes in the state, position, defect, material, etc. of the conductor, and this brings about a change in the secondary magnetic field. In addition, a change in the secondary magnetic field brings about a change in the induced electromotive force and impedance on the receiving coil side. By measuring this change and comparing it with a preset induced electromotive force or impedance change value or by substituting the change value into a statistically derived predetermined discriminant function to obtain a discriminant value, it is possible to determine whether there is a defect in a conductor, such as a battery cell.

In the present invention, a crack inside a battery cell means a crack that occurs on an electrode, an electrode tab, or a welded portion. In a specific example, the crack of the electrode means a crack on a current collector that occurs during an electrode process such as drying and rolling after an electrode mixture including an electrode active material, a binder, a conductive material, etc. is applied on a current collector, and then an electrode is manufactured due to a difference in elongation between the current collector and the electrode mixture. In addition, a crack in an electrode tab may be a crack that occurs due to stress accumulated in an electrode bulge or a wrinkle at a boundary caused by a difference in elongation between a support portion and a non-support portion, and due to vibration or external force during welding. Furthermore, a crack in a welded portion may be an unwelded portion that occurs due to insufficient welding during welding, or a crack that occurs during the welding process.

The cracks that occur on the electrodes, electrode tabs, and welds listed above are cracks that cannot be observed from the outside of the battery cell because the inside of the battery cell is covered by the battery case when the electrode assembly is sealed with a battery case such as a laminate sheet during a sealing process. However, by using the eddy current sensor for inspecting cracks inside the battery cell of the present invention, there is an effect of being able to detect the cracks. Meanwhile, by measuring the impedance value of the battery cell with the eddy current sensor according to the present invention, and inputting the impedance value measured by the eddy current sensor into the determination function, the state of the battery metal part can be inspected quickly and accurately.

In one example, an eddy current sensor according to the present invention is configured to include: a probe; a transmitter having a structure in which a transmitter coil is wound, which is disposed on the probe and induces an eddy current in a battery cell to be evaluated; and a receiver having a structure in which a receiver coil is wound, which is disposed on the probe and is disposed in a region spaced from the transmitter, and detects a signal change due to an eddy current induced in the battery cell by the transmitter coil. The transmitter coil and the receiver coil can be disposed in a non-contact state at a predetermined distance from a metal portion of the battery cell to be measured. The transmitter coil and the receiver coil are provided in the shape of a cylinder, a square column, a polygonal column, or the like, and can be wound on the probe so that a magnetic field is formed in the longitudinal direction of the transmitter coil and the receiver coil.

The ratio (N2/N1) of the number of turns (N1) of the transmitting coil wound on the transmitting unit and the number of turns (N2) of the receiving coil wound on the receiving unit may be in the range of 2 to 5. More specifically, the ratio (N2/N1) of the number of turns (N1) of the transmitting coil wound on the transmitting unit and the number of turns (N2) of the receiving coil wound on the receiving unit may be in the range of 3 to 4, in the range of 3.5 to 3.8, or about 3.75. In a specific example, the number of turns (N2) of the transmitting coil wound on the transmitting unit may be in the range of 30 to 200 turns, and the number of turns (N1) of the receiving coil wound on the receiving unit may be in the range of 60 to 400 turns. Specifically, the number of turns (N2) of the transmitting coil wound on the transmitting unit can be in a range of 30 to 180 turns, a range of 40 to 160 turns, a range of 50 to 140 turns, a range of 60 to 120 turns, a range of 70 to 100 turns, or about 80 turns. In addition, the number of turns (N2) of the receiving coil wound on the receiving unit can be in a range of 60 to 400 turns, a range of 120 to 380 turns, a range of 180 to 360 turns, a range of 240 to 340 turns, a range of 280 to 320 turns, or about 300 turns. For example, the number of turns of the transmitting coil wound on the transmitting unit can be 80 turns, and the number of turns of the receiving coil wound on the receiving unit can be 300 turns.

The eddy current sensor according to the present invention has a transmitting coil and a receiving coil wound as described above in each of the transmitting unit and the receiving unit, so that the accuracy of crack inspection of a battery cell to be evaluated can be improved. Specifically, since the receiving coil is wound more than the transmitting coil, an eddy current signal generated in a battery cell can be effectively received. Meanwhile, the impedance of an AC circuit connected to the receiving coil is determined by the primary magnetic field generated in the transmitting coil and the secondary magnetic field caused by the eddy current induced in the evaluation target, and the intensity of the secondary magnetic field caused by the eddy current may be smaller than the intensity of the primary magnetic field generated in the transmitting coil. Therefore, in order to effectively receive an eddy current signal, it is necessary to reduce the intensity of the magnetic field of the transmitting coil. Accordingly, the number of turns of the transmitting coil may be smaller than the number of turns of the receiving coil.

In one example, in the eddy current sensor according to the present invention, the ratio (D1/D2) of the diameter (D1) of the transmitting coil to the diameter (D2) of the receiving coil may be in the range of 1.5 to 5.0. Specifically, the ratio (D1/D2) of the diameter (D1) of the transmitting coil to the diameter (D2) of the receiving coil may be in the range of 1.8 to 4.5, in the range of 2.1 to 4.0, in the range of 2.4 to 3.5, or in the range of 2.6 to 3.0. For example, the ratio (D1/D2) may be about 2.85. That is, the diameter of the transmitting coil may be structured to be larger than the diameter of the receiving coil. This is to generate a stronger and more uniform magnetic field in the battery cell to be evaluated.

In specific examples, the diameter of the transmitting coil can be in a range of 0.01 to 2.0 mm, in a range of 0.03 to 1.3 mm, in a range of 0.07 to 1.0 mm, in a range of 0.1 to 0.8 mm, in a range of 0.15 to 0.5 mm, or in a range of 0.18 to 0.3 mm. For example, the diameter of the transmitting coil can be about 0.2 mm. In addition, the diameter of the receiving coil can be in a range of 0.01 to 1.0 mm, in a range of 0.02 to 0.8 mm, in a range of 0.03 to 0.5 mm, in a range of 0.04 to 0.2 mm, in a range of 0.05 to 0.1 mm, or in a range of 0.06 to 0.08 mm. For example, the diameter of the receiving coil can be about 0.07 mm. Meanwhile, if the diameters of the transmitting coil and the receiving coil are outside the above range, a sufficient magnetic field may not be generated to induce eddy currents in the battery cell being evaluated.

In another example, the eddy current sensor according to the present invention may have a ratio (S1/R1) of a cross-sectional area (S1) of a transmitter around which a transmitter coil is wound and a cross-sectional area (R1) of a receiver around which a receiver coil is wound in a range of 1.5 to 10. Specifically, the ratio (S1/R1) may be in a range of 1.5 to 10, in a range of 2 to 8, in a range of 3 to 6, or in a range of 3.5 to 5, and for example, the ratio of the cross sections (S1/R1) may be about 4.

If the cross-sectional area ratio (S1/R1) of the transmitter and receiver is less than 1.5, the sizes of the cross-sectional areas of the transmitter and receiver are similar to each other, so that the area of the magnetic field generated from the transmitter coil and the area of the magnetic field received from the receiver coil are similar to each other. Accordingly, it may not be easy to distinguish between normal and defective signals. In other words, it may be difficult to detect cracks inside the battery cell. In addition, if the cross-sectional area ratio (S1/R1) of the transmitter and receiver exceeds 10, the cross-sectional area of the receiver is too small compared to the cross-sectional area of the transmitter, so that it may be difficult to detect signal changes due to eddy currents induced in the battery cell to be evaluated.

In addition, in the eddy current sensor according to the present invention, the ratio (S2/R2) of the width (S2) of the transmitter, around which the transmitter coil is wound, and the width (R2) of the receiver, around which the receiver coil is wound, may be in the range of 1.5 to 10. Specifically, the ratio (S2/R2) of the width (S2) of the transmitter and the width (R2) of the receiver may be in the range of 1.6 to 8, 1.7 to 6, 1.8 to 4, or 1.9 to 3, and for example, the ratio of the widths (S2/R2) may be 2. If the ratio (S2/R2) of the widths of the transmitter and the receiver is less than 1.5, the lengths of the widths of the transmitter and the receiver are similar to each other, so that the area of the magnetic field generated from the transmitter coil and the area of the magnetic field received from the receiver coil are similar to each other. Accordingly, it may not be easy to distinguish between normal and defective signals. That is, it may be difficult to detect a crack inside a battery cell. In addition, when the ratio of the width of the transmitter and receiver (S2/R2) exceeds 10, the width of the receiver (R2) is too small compared to the width of the transmitter (S2), making it difficult to detect signal changes caused by eddy currents induced in the battery cell being evaluated.

In another example, in the eddy current sensor according to the present invention, the width (S2) of the transmitter is structured to have a range of 20 to 150 mm. For example, the width (S2) of the transmitter may be structured to correspond to the length (L) of the evaluation area of the battery cell to be evaluated. This is to easily induce eddy current in the evaluation area.

In a specific example, the width (S2) of the transmitter portion around which the transmitter coil is wound can be in a range of 20 to 150 mm, a range of 35 to 130 mm, a range of 50 to 110 mm, a range of 65 to 100 mm, a range of 75 to 95 mm, or 80 mm. In addition, the width (R2) of the receiver portion around which the receiver coil is wound can be in a range of 5 to 100 mm, a range of 10 to 80 mm, a range of 15 to 60 mm, a range of 20 to 50 mm, a range of 30 to 45 mm, or 40 mm. For example, the eddy current sensor according to the present invention can have a structure in which the width (S2) of the transmitter portion is 80 mm and the width (R2) of the receiver portion is 40 mm.

Meanwhile, when evaluating whether or not there is a crack in an electrode having a width of 80 mm, an eddy current sensor having a width (S2) of a transmitter having a width of 80 mm can be used to perform a crack inspection of a battery cell. Furthermore, when the width (S2) of the transmitter is less than 20 mm, the width (S2) of the transmitter may be shorter than the length of the evaluation target, so that a magnetic field cannot be generated in the entire evaluation target area, and when the width (S2) of the transmitter exceeds 100 mm, the width (S2) of the transmitter may be too large compared to the length of the evaluation target, so that the accuracy of the inspection may be low.

In another example, in an eddy current sensor according to the present invention, a transmitter and a receiver are coupled to each other, and have a structure in which a part or the entire area from one end of the transmitter and receiver is interlocked and the gap is adjusted.

In a specific example, the receiver may be installed so as to be able to slide up and down at the bottom of the transmitter. The transmitter may have a structure in which a groove is formed along the length of the probe from one end. In addition, the receiver may have a part or an entire area inserted into the groove formed in the transmitter. At this time, the perimeter of the receiver is formed to correspond to the inner perimeter of the groove formed in the transmitter. However, it is preferable that the groove of the transmitter be formed larger than the perimeter of the receiver. That is, the receiver has a structure in which it is installed so as to be able to slide in the groove of the transmitter. Accordingly, the eddy current sensor according to the present invention can easily adjust the gap between the transmitter and the receiver.

In another example, the gap between the transmitter and the receiver is easily adjusted within the range of 2 to 15 mm. More specifically, the gap between the transmitter and the receiver may be within the range of 2 to 15 mm, 5 to 14 mm, 8 to 12 mm, or an average of 10 mm. If the gap between the transmitter and the receiver is less than 2 mm, the influence of the primary magnetic field generated around the transmitter coil is greater than the influence of the secondary magnetic field generated in the evaluation subject, making it difficult to distinguish the difference in signals generated by cracks in the battery cell, which may lower the accuracy of the inspection. Here, the influence of the primary magnetic field refers to the influence of the transmitter coil on the receiver coil due to the mutual induction phenomenon, and the influence of the secondary magnetic field generated in the evaluation subject refers to the influence of the secondary magnetic field generated in the evaluation subject on the receiver coil when an eddy current is formed in the evaluation subject due to the primary magnetic field generated from the transmitter coil. In addition, if the distance between the transmitter and the receiver exceeds 15 mm, the distance between the transmitter and the evaluation subject becomes too far, so that the magnetic field of the transmitter does not always reach the evaluation subject, making it difficult to receive a signal generated from the evaluation subject. Therefore, the distance between the transmitter and the receiver is preferably within the above-described range.

Meanwhile, the transmitter and receiver may be arranged on the same plane, but in this case, the magnetic field generated from the transmitter coil and the magnetic field received from the receiver coil may interfere with each other, so it is preferable that the transmitter and receiver be spaced apart within the above-described range. The eddy current sensor according to the present invention can increase the accuracy of crack inspection of a battery cell to be evaluated by adjusting the gap between the transmitter and receiver within the above-described range.

In another example, in the eddy current sensor according to the present invention, the transmitter and receiver have a structure in which a winding groove is formed in an area where the transmitter coil and the receiver coil are wound, respectively. Specifically, the winding groove may be a structure formed along the outer surface of the transmitter and receiver in the probe. By the winding groove, the transmitter coil and the receiver coil can be wound more stably on the first and second probes.

In addition, the present invention provides a method for inspecting a battery cell for cracks using the eddy current sensor described above. In one example, the method for inspecting a battery cell for cracks according to the present invention includes the steps of: inducing an eddy current in a battery cell to be evaluated using the eddy current sensor, and then detecting a signal change caused by the induced eddy current; and determining whether the battery cell to be evaluated has a crack based on the distribution of the amplitude and phase difference of the detected signal. In a specific example, the step of detecting the signal change further includes a process of adjusting the gap between the transmitter and receiver of the eddy current sensor according to the present invention. This is to find an optimal signal depending on the area or type of the battery cell to be evaluated.

Furthermore, the step of determining whether the battery cell has a crack can be determined as defective if the measurement signal of the battery cell to be evaluated is outside the range of the reference signal based on the reference signal of the normal battery cell.

Meanwhile, the battery cell to be evaluated may be a pouch type unit cell. In a specific example, the pouch type battery cell has a structure in which an electrode assembly having a positive electrode/separator/negative electrode structure is embedded in a laminate sheet outer material and connected to electrode leads formed on the outside of the outer material. At this time, the electrode leads may be extended to the outside of the sheet and may extend in the same direction or in the opposite direction.

The method for inspecting cracks in a battery cell according to the present invention can easily detect the presence or absence and location of cracks occurring on an electrode, an electrode tab, or a welded portion. In particular, the method for inspecting cracks in a battery cell using eddy current according to the present invention has the effect of increasing the accuracy of crack inspection in a battery cell by using two eddy current sensors arranged in parallel.

Hereinafter, various types of eddy current sensors for crack inspection inside a battery cell according to the present invention will be described in detail.

(First embodiment)

FIG. 2 is a schematic diagram of an eddy current sensor according to one embodiment of the present invention. Referring to FIG. 2, an eddy current sensor (100) according to the present invention comprises: a probe (110); a transmitter (120) having a structure in which a transmitter coil (121) is wound, which is disposed on the probe (110) and induces an eddy current in a battery cell to be evaluated; and a receiver (130) having a structure in which a receiver coil (131) is wound, which is disposed on the probe (110) but is disposed in a region spaced apart from the transmitter (120) and detects a signal change due to an eddy current induced in the battery cell by the transmitter coil (121).

Specifically, when an alternating current is applied to the transmitting coil (121), a primary magnetic field is formed around the transmitting coil (121). In the drawing, the coil has a spring shape, but is not limited thereto. When the coil in which the primary magnetic field is formed is brought to a battery cell, which is an object to be inspected, an induced electromotive force is generated in the battery cell due to the electromagnetic induction phenomenon, causing an eddy current to flow that interferes with the primary magnetic field. In this way, the transmitting coil (121) induces an eddy current in the battery cell to be evaluated.

And, the receiving coil (131) is located below the transmitting coil (121), but is located closer to the battery cell, which is the object to be inspected, than the transmitting coil (121). The receiving coil (131) has a function of detecting an eddy current signal induced by the transmitting coil (121). The receiving coil (131) detects an attenuated eddy current signal, which is formed, reflected, or absorbed by factors such as the state, position, defect, and material of the battery cell, which is the object to be inspected, of the eddy current induced by the transmitting coil (121). Therefore, when there is a crack inside the battery cell, a change in the eddy current signal occurs, and the receiving coil (131) detects the eddy current signal and transmits it to the signal receiving unit and data processing unit of the crack detection system of the battery cell.

Meanwhile, the ratio (N2/N1) of the number of turns (N1) of the transmitting coil (121) wound on the transmitting unit (120) and the number of turns (N2) of the receiving coil (131) wound on the receiving unit (130) has a range of 2 to 5. Specifically, the number of turns (N2) of the transmitting coil (131) wound on the transmitting unit (120) is in a range of 30 to 200 turns, and the number of turns (N1) of the receiving coil (131) wound on the receiving unit (130) is in a range of 60 to 400 turns. For example, the number of turns of the transmitting coil (131) wound on the transmitting unit (120) is 80 turns, and the number of turns of the receiving coil (131) wound on the receiving unit (130) is 300 turns. The eddy current sensor (100) according to the present invention has a transmitting coil (121) and a receiving coil (131) wound around each of the transmitting unit (120) and the receiving unit (130) as described above, so that the accuracy of crack inspection of a battery cell to be evaluated can be increased. Specifically, since the receiving coil (131) is wound more than the transmitting coil (121), there is an effect of effectively receiving an eddy current signal generated within the battery cell.

The ratio (D1/D2) of the diameter (D1) of the transmitting coil (121) wound around the transmitting unit (120) and the diameter (D2) of the receiving coil (131) wound around the receiving unit (130) is in the range of 1.5 to 5.0. Specifically, the diameter (D1) of the transmitting coil (121) is in the range of 0.01 to 2.0 mm, and the diameter (D2) of the receiving coil (131) is in the range of 0.01 to 1.0 mm. For example, the diameter (D1) of the transmitting coil (121) is 0.2 mm, and the diameter (D2) of the receiving coil (131) is 0.07 mm. That is, the eddy current sensor (100) of the present invention has a structure in which the diameter of the transmitting coil (121) is larger than the diameter of the receiving coil (131). This is to generate a stronger and more uniform magnetic field in the battery cell to be evaluated.

Example 1

FIG. 3 is a drawing showing an embodiment of performing a crack inspection of a battery cell using an eddy current sensor according to one embodiment of the present invention. A crack inspection inside a battery cell (1) was performed using the eddy current sensor (100). Specifically, the transmitter (120) of the eddy current sensor (100) used in the crack inspection of the battery cell has a structure in which a 0.2 mm diameter transmitting coil (121) is wound 80 times, and the receiver (130) has a structure in which a 0.07 mm diameter receiving coil (131) is wound 300 times.

In addition, the gap between the transmitter (120) and receiver (130) of the eddy current sensor (100) was about 10 mm. The eddy current sensor (100) was spaced about 1.5 cm apart from the battery cell (1) to be measured, and then AC power was applied to the eddy current sensor to conduct a crack inspection inside the battery cell. And, the results are shown in Fig. 4.

FIG. 4 is a graph showing the results of inspecting whether a battery cell has a crack using an eddy current sensor according to one embodiment of the present invention. In FIG. 4, the x-axis represents a normal battery cell and an abnormal battery cell, and the y-axis represents the resistance value of the eddy current sensor. Meanwhile, an abnormal battery cell means a battery cell in which a crack has formed in an electrode tab area. Referring to FIG. 4, it can be seen that the resistance values of a normal battery cell and a defective battery cell in which a crack has occurred are clearly different. That is, it can be confirmed that the eddy current sensor for inspecting cracks inside a battery cell according to the present invention has increased the accuracy of the inspection when inspecting for cracks inside a battery cell.

Comparative examples 1-6

Figure 5 is a schematic diagram of a conventional eddy current sensor.

Referring to FIG. 5, the eddy current sensor (10) of this type includes a probe (11); a transmitter (12) having a structure in which a transmitter coil (12-1) is wound around the probe (11); and a receiver (13) having a structure in which a receiver coil (13-1) is wound around the probe (11). The specific form of the eddy current sensor is shown in Table 1 below.

Number of turns of the transmitter coil (N1) Number of turns of the receiving coil (N2) Number of turns ratio (N2/N1) Transmitter coil diameter (D1) Receiver coil diameter (D2) Coil diameter ratio (D1/D2) Comparative Example 1 66 60 1.1 0.21 0.7 3 Comparative Example 2 20 120 6 0.21 0.7 3 Comparative Example 3 80 300 3.75 0.11 0.1 1.1 Comparative Example 4 80 300 3.75 0.3 0.05 6 Comparative Example 5 60 60 1 0.07 0.07 1 Comparative Example 6 15 60 4 0.2 0.07 3.75

Meanwhile, the distance between the transmitter (12) and receiver (13) was about 10 mm.

Using the above conventional eddy current sensor (10), a crack inspection inside a battery cell was performed in the same manner as in the first embodiment. And, the results are shown in Fig. 6. Figs. 6a to 6f are graphs for crack inspection inside a battery cell using Comparative Examples 1 to 6, respectively.

In Figure 6, the x-axis represents normal and abnormal battery cells, and the y-axis represents the resistance value of the eddy current sensor.

Referring to FIG. 6, it can be seen that the resistance values of a normal battery cell and a defective battery cell with a crack are almost similar. This is because the size of the magnetic field coming from the transmitting coil is large, so it seems that the receiving coil has difficulty receiving the eddy current signal from the battery cell to be evaluated. Meanwhile, in the case of Comparative Example 6, although the ratio of the number of turns and the coil diameter was similar to those of the embodiment of the present invention, it seems that the number of turns of each coil was smaller than that of the present invention, so the eddy current signal was not effectively received. Accordingly, it is judged that it is not easy for a conventional eddy current sensor to distinguish between normal and defective signals.

(Second embodiment)

FIG. 7 is a schematic diagram of an eddy current sensor according to another embodiment of the present invention. Referring to FIG. 7, an eddy current sensor (200) according to the present invention comprises: a probe (210); a transmitter (220) having a structure in which a transmitter coil (221) is wound, which is disposed on the probe (210) and induces an eddy current in a battery cell to be evaluated; and a receiver (230) having a structure in which a receiver coil (231) is wound, which is disposed on the probe (210) but is disposed in a region spaced apart from the transmitter (220) and detects a signal change due to an eddy current induced in the battery cell by the transmitter coil (221).

Meanwhile, in the eddy current sensor (200) according to the present invention, the cross-sectional area (S1) of the transmitter (220) around which the transmitter coil (221) is wound has a structure larger than the cross-sectional area (R1) of the receiver (230) around which the receiver coil (231) is wound. Here, the cross-sectional area (S1) of the transmitter (220) means the cross-sectional area of the region around which the transmitter coil (221) is wound, and the cross-sectional area of the receiver (230) means the cross-sectional area of the region around which the receiver coil (231) is wound.

In particular, the eddy current sensor (200) according to the present invention has a structure in which the cross-sectional area (S1) of the transmitter (220) around which the transmitter coil (221) is wound is larger than the cross-sectional area (R1) of the receiver (230) around which the receiver coil (231) is wound, so that the area of the magnetic field generated from the transmitter coil (221) and the area of the magnetic field received from the receiver coil (231) are set differently. Specifically, the transmitter coil (221) can generate a primary magnetic field strongly and uniformly, and the receiver coil (231) can receive a magnetic field having a different area from the primary magnetic field generated from the transmitter coil (221). Accordingly, the eddy current sensor (200) of the present invention can increase the accuracy of inspection for cracks inside a battery cell to be evaluated, etc.

The eddy current sensor (200) according to the present invention has a ratio (S1/R1) of the cross-sectional area (S1) of the transmitting section (220) around which the transmitting coil (221) is wound and the cross-sectional area (R1) of the receiving section (230) around which the receiving coil (231) is wound, in the range of 1.5 to 10. For example, the ratio (S1/R1) of the cross-sectional areas (R1) is about 4.

In addition, the eddy current sensor (200) according to the present invention has a ratio (S2/R2) of the width (S2) of the transmitter (220) around which the transmitter coil (221) is wound and the width (R2) of the receiver (230) around which the receiver coil (231) is wound, which is in the range of 1.5 to 10. For example, the ratio (S2/R2) of the widths (R2) is 2. At this time, the width (S2) of the transmitter (220) has a structure having a range of 10 to 100 mm. Specifically, the width (S2) of the transmitter (220) has a structure corresponding to the length (L) of the evaluation area of the battery cell to be evaluated. This is to easily induce eddy current in the evaluation area. More specifically, the eddy current sensor (200) according to the present invention has a structure in which the width (S2) of the transmitter (220) is 80 mm and the width (R2) of the receiver (230) is 40 mm.

Descriptions of each component have been provided above, and detailed descriptions of each component will be omitted.

(Third embodiment)

FIG. 8 is a schematic diagram of an eddy current sensor according to another embodiment of the present invention. Referring to FIG. 8, an eddy current sensor (300) according to the present invention comprises: a probe (310); a transmitter (320) having a structure in which a transmitter coil (321) is wound, which is disposed on the probe (310) and induces an eddy current in a battery cell to be evaluated; and a receiver (330) having a structure in which a receiver coil (331) is wound, which is disposed on the probe (310) but is disposed in a region spaced apart from the transmitter coil (320) and detects a signal change due to an eddy current induced in the battery cell by the transmitter coil (321).

Meanwhile, in the eddy current sensor (300) according to the present invention, the transmitter (320) and the receiver (330) are coupled to each other, and have a structure in which a part or the entire area from one end of the transmitter (320) and the receiver (330) are interlocked to adjust the gap. Specifically, the receiver (330) is installed at the lower end of the transmitter (320) so as to be able to slide up and down. Specifically, the transmitter (320) has a structure in which a groove (311) is formed along the length of the probe (310) from one end. In addition, the receiver (330) has a structure in which a part or the entire area is inserted into the groove (311) formed in the transmitter (320). The perimeter of the receiver (330) is formed to correspond to the inner perimeter of the groove (311) formed in the transmitter (320). However, the groove (311) of the transmitter (320) is formed to be larger than the perimeter of the receiver (330).

That is, the receiver (330) has a structure that is installed so as to be slidable in the groove (311) of the transmitter (320). Accordingly, the eddy current sensor (300) according to the present invention can easily adjust the gap between the transmitter (320) and the receiver (330). Specifically, the gap between the transmitter (320) and the receiver (330) can be easily adjusted within a range of 2 to 15 mm.

Meanwhile, the transmitter (320) and receiver (330) may be arranged on the same plane, but in this case, the magnetic field generated from the transmitter coil (321) and the magnetic field received from the receiver coil (331) may interfere with each other, so it is preferable that the transmitter (320) and receiver (330) be spaced apart within the above-described range.

The eddy current sensor (300) according to the present invention can increase the accuracy of crack inspection of a battery cell to be evaluated by adjusting the gap between the transmitter (320) and the receiver (330) within the above range.

Descriptions of each component have been provided above, and detailed descriptions of each component will be omitted.

Above, the present invention has been described in more detail through drawings and examples. However, the configurations described in the drawings or examples described in this specification are only one embodiment of the present invention and do not represent all of the technical ideas of the present invention. Therefore, it should be understood that there may be various equivalents and modified examples that can replace them at the time of filing this application.

1: Battery cell
10: Eddy current sensor
11: Probe
12: Transmitter
12-1: Transmitter coil
13: Receiver
13-1: Receiver coil
100, 200, 300: Eddy current sensor
110, 210, 310: Probe
120, 220, 320: Transmitter
121, 221, 321: Transmitter coil
130, 230, 330: Receiver
131, 231, 331: Receiver coil
311: Home

Claims (11)

probe;
A transmitter having a structure in which a transmitter coil is wound and placed on a probe to induce an eddy current in a battery cell to be evaluated; and
A receiving unit having a structure in which a receiving coil is wound, which is disposed on the probe but is spaced apart from the transmitting unit and detects a signal change caused by an eddy current induced in the battery cell by the transmitting coil,
The ratio (N2/N1) of the number of turns (N1) of the transmitting coil wound on the transmitting section and the number of turns (N2) of the receiving coil wound on the receiving section is in the range of 2.0 to 5.0,
The ratio (D1/D2) of the diameter (D1) of the transmitting coil wound on the transmitting unit and the diameter (D2) of the receiving coil wound on the receiving unit is in the range of 1.5 to 5.0,
The transmitter and receiver are coupled to each other, and the structure is such that part or all of the area from one end of the transmitter and receiver is interlocked and the gap is adjusted.
The transmitter has a structure in which a groove is formed along the length of the probe from one end.
The above-mentioned receiver is an eddy current sensor for inspecting cracks inside a battery cell having a structure in which part or all of the receiver is inserted into the groove of the transmitter.
In paragraph 1,
An eddy current sensor having a transmitting coil wound on a transmitter having a number of turns in the range of 30 to 200.
In paragraph 1,
An eddy current sensor having a receiving coil wound on a receiving section having a number of turns in the range of 60 to 400.
In paragraph 1,
The diameter (D1) of the transmitting coil is in the range of 0.01 to 2.0 mm.
An eddy current sensor having a receiving coil diameter (D2) in the range of 0.01 to 1.0 mm.
In paragraph 1,
An eddy current sensor, characterized in that the ratio (S1/R1) of the cross-sectional area (S1) of a transmitter around which a transmitter coil is wound and the cross-sectional area (R1) of a receiver around which a receiver coil is wound is in the range of 1.5 to 10.
In paragraph 1,
An eddy current sensor, characterized in that the ratio (S2/R2) of the width (S2) of a transmitter section around which a transmitter coil is wound and the width (R2) of a receiver section around which a receiver coil is wound is in the range of 1.5 to 10.
In paragraph 6,
An eddy current sensor in which the width (S2) of the transmitter section around which the transmitter coil is wound is in the range of 20 to 150 mm, and the width (R2) of the receiver section around which the receiver coil is wound is in the range of 5 to 100 mm.
In paragraph 1,
An eddy current sensor having a structure in which a transmitter and a receiver have a gap in the range of 2 to 15 mm.
A method for inspecting cracks in a battery cell using an eddy current sensor according to claim 1. delete delete