KR102633209B1 - Inspection Method and Device for Aluminum Pouch Thickness of Lithium Ion Battery - Google Patents

Abstract

After molding the aluminum pouch, which is the exterior material of a pouch-type lithium-ion battery, the thickness of the transparent or translucent film on the top or bottom of the pouch aluminum foil is measured using optical coherence tomography (OCT) in areas vulnerable to pinholes, cracks, and insulation defects. ), which relates to a method and device for inspecting the thickness of an aluminum pouch that allows simple and accurate inspection of all aluminum pouches by attaching and loading the molded aluminum pouch to a loading robot and photographing the aluminum pouch to determine reference coordinates and extract contours. An image is acquired, a scan path of the OCT probe is created based on the acquired reference coordinate determination and contour extraction image, and the movement of the loading robot is controlled using the determined reference coordinate to place the aluminum pouch in the scan area of the OCT probe. , and scan the scan area of the aluminum pouch moved to the inspection area to obtain an OCT inspection image. Based on this, the thickness of the curved part of the aluminum pouch is measured using a thickness measurement algorithm to determine whether the aluminum pouch is good or bad.

Description

{Inspection Method and Device for Aluminum Pouch Thickness of Lithium Ion Battery}

The present invention relates to a method and device for checking the thickness of an aluminum pouch. In particular, the aluminum pouch, which is the exterior material of a pouch-type lithium-ion battery, is transparent at the top or bottom of the pouch aluminum foil in areas vulnerable to pinholes, cracks, and insulation defects after molding. Alternatively, it relates to a method and device for inspecting the thickness of an aluminum pouch that allows the thickness of a translucent film to be inspected simply and accurately using optical coherence tomography (OCT).

In general, unlike primary batteries, which cannot be recharged, secondary batteries that can be charged and discharged are being actively researched for application in cutting-edge fields such as digital cameras, smartphones, laptops, hybrid cars, and electric vehicles.

Secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, nickel-hydrogen batteries, and lithium secondary batteries.

Among these, lithium secondary batteries have an operating voltage of 3.2V or higher and are used as a power source for portable electronic devices, or by connecting multiple batteries in series and used in high-output hybrid vehicles, etc., compared to nickel-cadmium batteries or nickel-metal hydride batteries. The operating voltage is three times higher and the energy density per unit weight is excellent, so its use is increasing.

Here, lithium secondary batteries refer to lithium-based secondary batteries such as lithium-ion batteries, lithium-ion batteries, lithium polymer batteries, and lithium polymer batteries. In the present invention, lithium-ion batteries are explained as an example.

Lithium-ion batteries can be manufactured in various shapes, and representative shapes include cylindrical type and prismatic type, which are mainly used in lithium-ion batteries. Lithium polymer batteries, which have recently been in the spotlight, are manufactured in a flexible pouch type, so their shape is relatively free.

A pouch-type lithium-ion battery has a structure in which an aluminum pouch made of a multi-layer film is filled with electrolyte by embedding a battery cell formed of a positive electrode coated with a positive electrode active material, a negative electrode coated with a negative electrode active material, and a separator sandwiched between them.

Aluminum pouches usually have a structure in which three to four different films are laminated with an adhesive depending on the purpose of application, with the outermost layer being nylon such as PET (polyester) and PA (polyamide), and the innermost layer being non-stretched poly. It is made of propylene (CPP, casted polypropylene) film, and aluminum foil is located in the middle layer. Nylon serves as a protective layer and insulating layer that prevents external shock, and aluminum foil serves as a barrier layer that blocks moisture and gas. CPP film serves as a heat-sealing layer to ensure that the pouch is well sealed during the sealing process, which is a subsequent process in battery manufacturing. Each film and its characteristics are combined to be used as an exterior material that can maintain the stability and reliability of the battery.

In order to embed battery cells in an aluminum pouch, it is necessary to form a compartment to accommodate them, and this process is called forming or deep drawing process. Through the molding process, a punch is pressed into the aluminum pouch film to form a receiving portion. At this time, the aluminum pouch film is stretched and deformed in the direction of the press of the punch. In general, the molding area and depth of the pouching are determined by the capacity of the battery, and recently, as the capacity of the unit battery applied to electric vehicles increases, the molding area and depth have also increased.

As the molding depth increases, the edge curved area, where the thickness can decrease the most during molding, is less than the allowable value due to abnormalities in the molding conditions such as abnormal pouch material or die and punch. If the thickness is less than the allowable value, pinholes or cracks may occur, and battery damage such as insulation failure may occur. It is very important to measure the thickness after molding because it affects performance, but since the pouch is thin and the inspection surface is highly curved, it is impossible to apply non-destructive testing methods such as ultrasonic testing. In most cases, thickness is checked using a cutting method through sampling, making inspection easy. A method is desperately needed.

There is an ultrasonic test method that can measure the total thickness of an aluminum pouch through non-destructive testing, but the thickness detection resolution is about 30㎛ or more, so considering the thickness of the pouch, the detection resolution is not sufficient, and the curved surface of the pouch required for inspection is not sufficient. Swelling makes ultrasound examination difficult.

Meanwhile, proposed technologies related to inspection related to aluminum pouches are disclosed in <Patent Document 1> to <Patent Document 3>.

<Patent Document 1> and <Patent Document 2> are methods of measuring resistance or passing current by contacting a probe with the aluminum foil portion and electrode portion of the pouch, respectively, to test the insulation of the pouch, and inspecting insulation breakdown. After assembling the pouch, if a defect occurs in the pouch, the battery cell including the pouch must be treated as defective and a probe must be installed.

<Patent Document 3> is a method of injecting gas into a battery pack to determine defects including liquid leakage, gas leakage, and damage to the pack housing. This also inspects the pouch after assembling the battery cells, and if a pouch defect occurs, the pouch is inspected. Battery cells containing must be treated as defective.

In this way, <Patent Document 1> to <Patent Document 3> do not detect pinholes, cracks, and insulation defects due to thickness reduction after the molding of the pouch is completed, but rather detect pouch defects after battery cell assembly. It is necessary to develop a method to detect whether all pouches are defective.

Republic of Korea registered patent 10-21487496 (registered on January 22, 2015) (Insulation test method and device for pouch-type secondary batteries) Republic of Korea registered patent 10-2094539 (registered on March 23, 2020) (Battery non-destructive testing device) Republic of Korea registered patent 10-2179683 (registered on November 11, 2020) (Method for easily determining defects in battery packs)

Therefore, the present invention was proposed to solve the shortcomings arising from the method of detecting defects related to the aluminum pouch, which is the exterior material of the general pouch-type lithium-ion battery as described above, and various problems arising from the prior art. The thickness of the transparent or translucent film on the top or bottom of the pouch aluminum foil is simply measured using optical coherence tomography (OCT) in areas where the aluminum pouch, which is the exterior material of the product, is vulnerable to pinholes, cracks, and insulation defects after molding. The purpose is to provide a method and device for inspecting the thickness of aluminum pouches that can accurately inspect all of them while performing a thorough inspection.

Another object of the present invention is that the inspection position of the curved edge of the pouch after molding is not constant when the pouch is attached for inspection, and it is also difficult to measure the area with the smallest thickness in the curved portion, so non-destructive testing is performed using optical coherence tomography. The aim is to provide a method and device for inspecting the thickness of an aluminum pouch that can be easily inspected.

In order to achieve the above-mentioned object, the “aluminum pouch thickness inspection device” according to the present invention,

A loading robot that attaches the molded aluminum pouch and loads it into the inspection area;

A vision imaging device that acquires images for determining reference coordinates and extracting outlines by photographing the aluminum pouch mounted by the loading robot;

An OCT probe that acquires an OCT examination image by scanning the scan area of the aluminum pouch moved to the examination area;

The scan path of the OCT probe is generated based on the reference coordinate determination and outline extraction image acquired through the vision imaging device, and the movement of the loading robot is controlled using the determined reference coordinate to place the aluminum pouch on the OCT probe. It moves to the scan area, and includes a pouch discrimination device that determines the quality of the aluminum pouch by measuring the thickness of the curved surface of the aluminum pouch using a thickness measurement algorithm based on the OCT inspection image acquired through the OCT probe. .

In the above, the loading robot is,

A body with a built-in robot arm driving means;

a robot arm rotatably installed on the body and rotated by the driving means;

It is characterized by including a suction plate mounted on the end of the robot arm to attach and transfer the aluminum pouch loaded on the loading table.

In the above, the pouch discrimination device is,

The reference coordinates of the corner curved portion of the aluminum pouch are determined based on the reference coordinate determination and the image for contour extraction, and the scan path of the OCT probe is generated based on the determined reference coordinates and corner outline positions.

In the above, the OCT probe is,

An OCT examination image is generated by scanning the curved portion of each corner of the aluminum pouch along the scan path, and the OCT examination image includes a horizontal cross-sectional image and a vertical cross-sectional image of each corner.

In the above, the pouch discrimination device is,

Based on the reference coordinate determination and outline extraction image acquired through the vision imaging device, the reference coordinates of the corner curved portion of the aluminum pouch are determined, and the scan path of the OCT probe is generated based on the determined reference coordinates and corner outline position. A vision reading unit that does;

a robot control unit that controls the movement path of the robot arm of the loading robot using the reference coordinates determined by the vision reading unit; and

It is characterized by comprising an OCT determination unit that processes the OCT inspection image scanned from the OCT probe with a thickness measurement algorithm to measure the thickness of the curved portion of the aluminum pouch to determine whether the aluminum pouch is good or bad.

In the above, the OCT determination unit,

Using the thickness measurement algorithm, the curvature of the horizontal cross-sectional image among the obtained OCT inspection images is calculated. If the calculated curvature is not the maximum compared to the reference curvature, the scan position is corrected. If the calculated curvature is maximum, the horizontal cross-sectional image is calculated. The inflection point position is determined using the determined inflection point position, and the thickness of the horizontal and vertical cross-sectional images is calculated for each position of the scan path. The calculated thickness data for each position is collected to calculate the thickness measurement value, and the calculated thickness measurement value and It is characterized by comparing the acceptable standard values to determine whether the aluminum pouch is good or defective based on the size or absence.

In the above, the OCT determination unit,

If any of the thickness measurements of each corner of the aluminum pouch is less than the tolerance standard, the molded aluminum pouch is judged to be defective. If the thickness measurements of each corner of the aluminum pouch are all greater than the tolerance standard, the molded aluminum pouch is judged as defective. It is characterized by judging it as a good product.

In order to achieve the above-described object, the “thickness inspection method of an aluminum pouch” according to the present invention is,

(a) attaching the molded aluminum pouch to a loading robot and loading it into a random area;

(b) acquiring images for determining reference coordinates and extracting outlines by photographing the aluminum pouch mounted by the loading robot in a vision imaging device;

(c) Generate a scan path of the OCT probe based on the obtained reference coordinate determination and contour extraction image, and control the movement of the loading robot using the determined reference coordinate to place the aluminum pouch in the scan area of the OCT probe. moving to;

(d) acquiring an OCT examination image by scanning the scan area of the aluminum pouch moved from the OCT probe to the examination area; and

(e) measuring the thickness of the curved portion of the aluminum pouch using a thickness measurement algorithm based on the OCT inspection image to determine whether the aluminum pouch is good or bad.

In step (c) above,

The reference coordinates of the corner curved portion of the aluminum pouch are determined based on the reference coordinate determination and the image for contour extraction, and the scan path of the OCT probe is generated based on the determined reference coordinates and corner outline positions.

In step (d) above,

An OCT examination image is generated by scanning the curved portion of each corner of the aluminum pouch along the scan path, and the OCT examination image includes a horizontal cross-sectional image and a vertical cross-sectional image of each corner.

In step (e) above,

(e1) calculating the curvature of a horizontal cross-sectional image among the obtained OCT examination images using the thickness measurement algorithm, and correcting the scan position if the calculated curvature is not maximum;

(e2) determining the location of the inflection point using the horizontal cross-sectional image if the calculated curvature is maximum;

(e3) calculating the thickness of the horizontal and vertical cross-sectional images for each position of the scan path based on the determined inflection point position;

(e4) calculating a thickness measurement value by collecting the calculated thickness data for each location;

(e5) Comparing the calculated thickness measurement with an acceptance standard to determine whether the aluminum pouch is good or bad based on whether it is large or small.

In step (e5) above,

If any of the thickness measurements of each corner of the aluminum pouch is less than the tolerance standard, the molded aluminum pouch is judged to be defective. If the thickness measurements of each corner of the aluminum pouch are all greater than the tolerance standard, the molded aluminum pouch is judged as defective. It is characterized by judging it as a good product.

According to the present invention, pin holes and cracks in areas where the thickness is significantly reduced after molding of the aluminum pouch, as well as changes in thickness, can be inspected before final assembly of the battery cells, thereby eliminating the possibility of problems that may occur due to insufficient pouch rigidity due to poor pouch thickness. It has the effect of helping to improve the problem of battery quality deterioration due to leakage or poor insulation.

In addition, through strategic analysis of accumulated thickness changes, it is possible to monitor in real time the presence or absence of abnormalities in the punch and die related to the pouch molding process, which has the effect of maintaining optimal molding conditions.

1 is a schematic diagram showing a representative aluminum pouch that is the subject of the battery aluminum pouch inspection device of the present invention;
Figure 2 is a schematic cross-sectional structure of an aluminum pouch;
Figure 3 is a schematic diagram of an inspection device capable of measuring the minimum thickness of the four corner curved portions of a pouch according to an embodiment of the present invention;
Figure 4 is a schematic diagram showing the setting of OCT scan reference points as a preliminary step for measuring OCT cross-section according to the present invention;
Figure 5 is a schematic diagram showing the measurement concept of a curved portion for acquiring an OCT cross-sectional image according to an embodiment of the invention;
6A and 6B are schematic diagrams showing an example of acquiring the thickness from the OCT horizontal cross-sectional image and vertical cross-sectional image of the upper transparent film layer of the curved portion of the pouch according to the embodiment of the present invention;
Figure 7 is a flowchart showing a method for inspecting the thickness of an aluminum pouch according to a preferred embodiment of the present invention.

Hereinafter, a method and device for inspecting the thickness of an aluminum pouch according to a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

The terms or words used in the present invention described below should not be construed as limited to their usual or dictionary meanings, and the inventor may appropriately define the concept of the term in order to explain his/her invention in the best way. It must be interpreted with meaning and concept consistent with the technical idea of the present invention based on the principle that it can be done.

Therefore, the embodiments described in this specification and the configurations shown in the drawings are only preferred embodiments of the present invention and do not represent the entire technical idea of the present invention, and therefore various equivalents and It should be understood that variations may exist.

Figure 3 is a schematic configuration diagram of an aluminum pouch thickness inspection device according to a preferred embodiment of the present invention, which includes a loading robot 200 for attaching a molded aluminum pouch 100 and loading it into an inspection area, and the loading robot 200 A vision imaging device 300 acquires an image for determining reference coordinates and extracting outlines by photographing an aluminum pouch 100 attached by a vision imaging device 300, and obtains an OCT inspection image by scanning the scan area of the aluminum pouch 100 moved to the inspection area. A scan path of the OCT probe 400 is generated based on the OCT probe 400 that acquires and the image for determining reference coordinates and extracting contours acquired through the vision imaging device 300, and using the determined reference coordinates The movement of the loading robot 200 is controlled to move the aluminum pouch 100 to the scan area of the OCT probe 400, and a thickness measurement algorithm is used based on the OCT inspection image acquired through the OCT probe 400. It includes a pouch determination device 500 that determines the quality of the aluminum pouch by measuring the thickness of the curved surface of the aluminum pouch.

The loading robot 200 includes a body with a built-in robot arm driving means, a robot arm 210 rotatably installed on the body and rotated by the driving means, and mounted on an end of the robot arm 210. It includes a suction plate 220 that attaches and transfers the aluminum pouch 100 loaded on the loading table.

The pouch determination device 500 determines the reference coordinates of the corner curved portion of the aluminum pouch 100 based on the reference coordinate determination and outline extraction image acquired through the vision imaging device 300, and determines the reference coordinates of the corner curved portion of the aluminum pouch 100 and the determined reference coordinates. A vision reading unit 501 that generates a scan path of the OCT probe 400 based on the edge outline position, and a robot arm 210 of the loading robot 200 using the reference coordinates determined by the vision reading unit 501. ), and a robot control unit 502 that controls the movement path of the aluminum pouch 100 by processing the OCT inspection image scanned from the OCT probe 400 with a thickness measurement algorithm to measure the thickness of the curved portion of the aluminum pouch 100. It includes an OCT determination unit 503 that determines good quality.

The “aluminum pouch thickness inspection device” according to the present invention configured as described above will be described in detail as follows.

As shown in Figure 1, a representative form of the aluminum pouch of the pouch-type lithium-ion battery applied to the present invention is a laminated type (stacked type) in which the anode and cathode cut into arbitrary size units and a separator interposed between them are sequentially laminated. The electrode assembly 110 is sealed with an aluminum pouch 100 by attaching a positive lead tab (or electrode tab) and a negative lead tab, respectively, to form a battery cell.

The total thickness of a typical aluminum pouch applied to an electric vehicle is about 150 to 160㎛, and the structure and thickness of each part of a representative aluminum pouch are shown in Figure 2.

For example, the aluminum pouch 100 usually has a structure in which 3 to 4 different films are laminated with an adhesive depending on the purpose of application, and the outermost layer is made of PET (polyester) 101, PA (polyamide), etc. The nylon film (103), the innermost layer is made of non-stretched polypropylene (hereinafter, CPP) (105), and the aluminum foil (104) is located in the middle layer. Nylon serves as a protective layer and insulating layer that prevents external shock, and aluminum foil serves as a barrier layer that blocks moisture and gas. CPP film serves as a heat-sealing layer to ensure that the pouch is well sealed during the sealing process, which is a subsequent process in battery manufacturing. Each layer is firmly attached with an adhesive 102 with a thickness of 3 to 5㎛, and for stable adhesion between the aluminum foil and the polymer film, there is a surface treatment layer with a thickness of approximately 1㎛ on the top and bottom of the aluminum foil.

Thickness can be measured by OCT with a thickness resolution of 1 to 2㎛ for transparent or semi-transparent materials, but since it is not possible to measure the aluminum foil part where light does not pass through OCT, the thickness of the top or bottom of the aluminum, which is a transparent film layer, must be measured. Measure the change and estimate the overall thickness change to determine the quality of the aluminum pouch.

Figure 3 is a diagram showing the configuration of a device for inspecting an aluminum pouch after molding with OCT. The molded aluminum pouch 100 has an inspection portion with a curved edge of an arbitrary shape, and light passes through it to obtain a resolution in ㎛ units. Since it is not easy to transport it to the correct inspection location for inspection, a small robot, the loading robot 200, is used to attach the aluminum pouch 100 to the suction plate 220 mounted on the robot arm 210 to prevent aluminum pouch adversity. Loading. Here, the suction plate 220 can attach the aluminum pouch 100 using a vacuum.

It is difficult to place each aluminum pouch subject to inspection in the same position after molding, and the position of the curved edge portion is also not constant. In addition, because the focal length of the OCT probe 400 is short and the field of view is narrow, it is very difficult to predetermine an appropriate examination area and scan path using only the OCT image. To solve this problem, the aluminum pouch 100 is attached to the loading robot 200 and then scanned using OCT using the image of the aluminum pouch 100 captured using the vision imaging device 300, which is a video camera. The approximate positions of the start and end points for the area are determined, and the aluminum pouch 100 is moved to the location where the OCT probe 400 is located using the loading robot 200.

The aluminum pouch (100) to be inspected is attached to the suction plate (220) attached to the robot arm (210), placed on the same horizontal plane, and the aluminum pouch (100) is photographed using the vision imaging device (300), which is a vision camera. do.

Next, as shown in FIG. 4, in the captured aluminum pouch image (referred to as the image for reference coordinate determination and contour extraction), the vision reading unit 501 uses a contour detection algorithm used in a typical image recognition technique to The outline 310 is detected. Next, based on the detected outline, the approximate position of the curved surface start of each corner is calculated as each scan reference point (x1, y1)(x2, y2)(x3, y3)(x4, y4) (320), and the calculated Generate a rough OCT scan path by referring to the reference coordinates and corner outline positions.

Next, the robot control unit 502 controls the robot arm 210 through control of the driving means of the loading robot 200, and calculates the OCT based on the reference coordinates 320 (x1, y1) of the aluminum pouch 100. The aluminum pouch 100 is moved to the scan position of the probe 400, and as shown in FIG. 5, the OCT probe 400 is operated to scan the aluminum pouch 100 along the rectangular curved surface, that is, the scan path 330. Scan to obtain an OCT image and measure the thickness.

There is an ultrasonic test method that can measure the overall thickness of an aluminum pouch through non-destructive testing. However, the thickness detection resolution is approximately 30㎛ or more, so considering the thickness of the pouch, the detection resolution is not sufficient, and the aluminum pouch required for inspection is not covered. Curved surfaces make ultrasonic inspection difficult.

An inspection method using optical coherence tomography (OCT), which is applied for ophthalmology, has recently been attracting attention as a non-destructive inspection method for industrial purposes, such as being applied to measure the thickness of a transparent coating layer.

Optical coherence tomography is a method that measures changes in light intensity caused by light scattering from the microstructure of an object to display two-dimensional or high-resolution images. The principle is that the incident light is divided into two using a beam splitter. When the reference beam, which is divided into parts and reflected from the mirror by the sample beam and irradiated to the inspection object at 90 degrees through the beam splitter, reaches the photodetector, partial interference occurs between the two beams, resulting in interference. Images that appear differently are realized using numerical analysis methods such as Fourier transform.

Figure 6a is an example of a horizontal cross-sectional image of a corner of an aluminum pouch acquired by the OCT probe 400, and Figure 6b is an example of a vertical cross-sectional image of a corner of an aluminum pouch acquired by the OCT probe 400, showing the curved portion of the aluminum pouch. This is a conceptual diagram of the thickness measurement method.

In the aluminum pouch 100, the part where the thickness change of the curved part is greatest is the part where the curvature of the curved part is the greatest, and the location of the inflection point (point b in the horizontal cross-sectional image of FIG. 6a) appearing in the horizontal cross-sectional image as shown in FIG. 6a is shown in FIG. 6b. Reset the scan center line by adjusting the robot arm 210 to be at the center of the vertical cross-sectional image (point b in the vertical cross-sectional image in FIG. 6B). The vision reading unit 501 allows the robot arm 210 to measure the thickness from the OCT vertical section image at the point of greatest curvature based on the OCT horizontal section image while updating the scan path with reference to the rough scan path 330. ), by a predetermined scan pitch (e.g., 0.5 mm) along the updated scan path in the pouch determination device 500 equipped with an algorithm that performs the calculations and controls required for the OCT determination unit 503 and the robot control unit 402. Move it and measure the thickness continuously. The updated scan path is judged good or bad based on the lowest thickness value from the measured thickness, and if normal, controls the loading robot 200 and moves to the OCT probe 400 by referring to the reference point (x2, y2) of the next corner curved surface. Perform the above process for all edges.

Ideally, the change in thickness of a molded aluminum pouch should be measured by measuring the change in overall thickness. However, since the film attached to the aluminum foil is maintained without peeling, it is difficult to estimate the change in overall thickness by measuring the change in thickness of the upper film. does not exist. If there is a gap due to peeling of the adhesive part after molding, according to the principle of OCT, this is also brightly displayed due to the difference in refractive index between the film and the air layer and can be easily distinguished in the OCT image. Pinholes can also be easily distinguished in the OCT image.

Figure 7 is a flow chart showing the "pouch thickness inspection method" according to the present invention, (a) attaching the molded aluminum pouch 100 to the loading robot 200 and loading it to an arbitrary area (S101 - S102), ( b) acquiring an image for determining reference coordinates and extracting outlines by photographing the aluminum pouch 100 mounted by the loading robot 200 in the vision imaging device 300 (S103), (c) pouch discrimination device ( In 500), a scan path of the OCT probe 400 is generated based on the obtained reference coordinate determination and outline extraction image, and the movement of the loading robot 200 is controlled using the determined reference coordinate to remove the aluminum pouch ( 100) moving to the scan area of the OCT probe 400 (S104), (d) scanning the scan area of the aluminum pouch moved from the OCT probe 400 to the examination area to obtain an OCT examination image. Step (S105), and (e) measuring the thickness of the curved portion of the aluminum pouch using a thickness measurement algorithm based on the OCT inspection image to determine whether the aluminum pouch is good or bad (S106 - S117).

Step (e) is (e1) calculating the curvature of the horizontal cross-sectional image among the obtained OCT examination images using the thickness measurement algorithm, and correcting the scan position if the calculated curvature is not maximum (S106 - S108). , (e2) If the calculated curvature is maximum, determining the inflection point position using the horizontal cross-sectional image (S109), (e3) the thickness of the horizontal and vertical cross-sectional images based on the determined inflection point position is determined as the location of the scan path. Calculating step by step (S110 - 112), (e4) Step of calculating thickness measurement by collecting the calculated thickness data for each location (S113), (e5) Comparing the calculated thickness measurement with the acceptance standard value to determine whether the thickness is large or small. It includes steps (S114 to S117) of determining whether the aluminum pouch is good or defective.

The “pouch thickness inspection method” according to the present invention configured as described above will be described in detail as follows.

First, when the aluminum pouch 100 that has completed the aluminum pouch forming process is transferred to the loading table, the aluminum pouch 100 is loaded onto the robot arm 210 equipped with the suction plate 220 (S101 - S102).

Next, the aluminum pouch 100 is maintained in a horizontal state, the aluminum pouch is photographed with the vision imaging device 300, which is a vision camera, and the vision reading unit 501 recognizes the square outline 310 using the outline recognition algorithm. The reference coordinates 320 of four locations (each corner) for OCT scanning are set, and a rough scan path 340 is set with reference to the outline and reference coordinates (S103).

Next, the robot arm 220 is controlled so that the reference coordinate is centered on the focal distance and viewing angle of the OCT probe 400, referring to the first reference coordinate (x1, y1) 320 of the aluminum pouch 100. Then, the OCT image is obtained by controlling the robot arm 201 with the OCT probe 400 at a scan interval (e.g., 0.5 mm) along the scan path from the reference coordinate (S104 - S105). Here, OCT images acquire vertical and horizontal images.

Next, the curvature of the horizontal cross-sectional image is calculated using the thickness determination algorithm, and if the calculated curvature is not the maximum, the scan position is corrected (S106 - S108). In other words, when the horizontal cross-sectional image begins to have curvature in a flat state, it has approached the corner curved part, so the center line of curvature is at the center of the OCT image at the point where the curvature is maximum while maintaining the Z-axis position that coincides with the plane of the aluminum pouch. Control the robot arm 210 so that it comes.

Afterwards, the thickness of the inflection point (b in FIG. 6A) on the horizontal curvature center line is measured at the point where the curvature is maximum, and at the same time, the thickness of the corresponding position is measured in the vertical cross-sectional image (S109 - S110).

Since the thickness measured from the horizontal cross-sectional image and the thickness measured from the vertical cross-sectional image are measured at similar positions, they must match within the measurement error range, and in this case, they are stored as the thickness of the corresponding position on the curved surface.

Next, repeat the above process by moving the aluminum pouch along the scan path by the already set scan interval. The scan path is updated with reference to the coordinates of the center of curvature, which are calculated each time by the maximum curvature determination process of the thickness determination algorithm (S111 - S112).

The end point of the scan path is determined by considering the molding depth of the aluminum pouch, and when the measurement position reaches the scan end point, the OCT scan is terminated, and the thickness of each interval measured on the scan path is added to calculate the edge thickness measurement (113 ).

Next, the calculated thickness measurement value is compared with a preset acceptance standard to determine whether the aluminum pouch is good or bad, and if the thickness measurement value is less than the acceptance standard, the robot arm 210 is controlled to transfer the aluminum pouch to the defective loading table (S114 - S115).

If the thickness measured during the OCT scan is less than the acceptable standard, further scanning can be stopped immediately and transferred to the defective loading zone. However, it is desirable to secure data up to the scan end point to analyze problems in the molding process.

When the scanning of the first curved corner portion is completed, the aluminum pouch is transferred to the reference coordinates of the second curved surface using the robot arm and the above process is repeated to complete the thickness measurement of the four corner curved portions.

If the thickness measurements of each corner of the aluminum pouch are greater than the acceptable standard, the molded aluminum pouch is determined to be a good product (S116 - S117).

According to the present invention described above, pin holes and cracks in areas where the thickness is significantly reduced after molding of the aluminum pouch, as well as changes in thickness, can be inspected before final assembly of the battery cells, resulting in a lack of pouch rigidity due to poor pouch thickness. It can improve battery quality problems caused by leakage or poor insulation.

In addition, through strategic analysis of accumulated thickness changes, it is possible to monitor in real time the presence or absence of abnormalities in the punch and die related to the pouch molding process, helping to maintain optimal molding conditions.

Although the invention made by the present inventor has been described in detail according to the above embodiments, the present invention is not limited to the above embodiments, and various changes can be made without departing from the gist of the invention, as is known in the art. It is self-evident to those who have it.

100: Aluminum pouch
110: battery cell
101: PET layer
102: Adhesive
103: Nylon layer
104: Aluminum foil
105: CCP layer
200: loading robot
210: Robot arm
220: Suction plate
300: Vision imaging device
310: Contour
320: Reference coordinates
330: OCT scan path
340: horizontal section
400: OCT probe
500: Pouch discrimination device
501: Vision readout unit
502: Robot control unit
503: OCT determination unit

Claims (10)

A device for inspecting the thickness of the aluminum pouch of a pouch-type lithium-ion battery,
A loading robot that attaches the molded aluminum pouch and loads it into the inspection area;
A vision imaging device that acquires images for determining reference coordinates and extracting outlines by photographing the aluminum pouch mounted by the loading robot;
An OCT probe that acquires an OCT examination image by scanning the scan area of the aluminum pouch moved to the examination area; and
The scan path of the OCT probe is generated based on the reference coordinate determination and outline extraction image acquired through the vision imaging device, and the movement of the loading robot is controlled using the determined reference coordinate to place the aluminum pouch on the OCT probe. It moves to the scan area and includes a pouch discrimination device that determines the quality of the aluminum pouch by measuring the thickness of the curved surface of the aluminum pouch using a thickness measurement algorithm based on the OCT inspection image acquired through the OCT probe,
The pouch discrimination device is,
Using the thickness measurement algorithm, the curvature of the horizontal cross-sectional image among the acquired OCT inspection images is calculated. If the calculated curvature is not maximum, the scan position is corrected. If the calculated curvature is maximum, the inflection point is calculated using the horizontal cross-sectional image. Determine the location, calculate the thickness of the horizontal and vertical cross-sectional images for each location of the scan path based on the determined inflection point location, collect the calculated thickness data for each location to calculate the thickness measurement, and set the calculated thickness measurement and acceptance standard. A thickness inspection device for aluminum pouches, characterized in that it compares and determines whether the aluminum pouch is good or defective based on the presence or absence of the size.
In claim 1, the loading robot,
A body with a built-in robot arm driving means;
a robot arm rotatably installed on the body and rotated by the driving means; and
An aluminum pouch thickness inspection device comprising a suction plate mounted on an end of the robot arm to attach and transport aluminum pouches loaded on a loading table.
In claim 1, the pouch discrimination device,
An aluminum pouch characterized in that the reference coordinates of the corner curved portion of the aluminum pouch are determined based on the reference coordinate determination and the image for contour extraction, and the scan path of the OCT probe is generated based on the determined reference coordinates and corner outline positions. Thickness inspection device.
In claim 1, the pouch discrimination device,
Based on the reference coordinate determination and outline extraction image acquired through the vision imaging device, the reference coordinates of the corner curved portion of the aluminum pouch are determined, and the scan path of the OCT probe is generated based on the determined reference coordinates and corner outline position. A vision reading unit that does;
a robot control unit that controls the movement path of the robot arm of the loading robot using the reference coordinates determined by the vision reading unit; and
An aluminum pouch thickness inspection device comprising an OCT determination unit that processes the OCT inspection image scanned from the OCT probe using a thickness measurement algorithm to measure the thickness of the curved portion of the aluminum pouch to determine whether the aluminum pouch is good or bad.
delete In claim 4, the OCT determination unit,
If any of the thickness measurements of each corner of the aluminum pouch is less than the tolerance standard, the molded aluminum pouch is judged to be defective. If the thickness measurements of each corner of the aluminum pouch are all greater than the tolerance standard, the molded aluminum pouch is judged as defective. Thickness inspection device for aluminum pouches, characterized in that they are judged as good products.
A method of inspecting the thickness of an aluminum pouch of a pouch-type lithium-ion battery using the aluminum pouch thickness inspection device described in any one of claims 1 to 4 and claim 6, comprising:
(a) attaching the molded aluminum pouch to a loading robot and loading it into a random area;
(b) acquiring images for determining reference coordinates and extracting outlines by photographing the aluminum pouch mounted by the loading robot in a vision imaging device;
(c) Generate a scan path of the OCT probe based on the obtained reference coordinate determination and contour extraction image, and control the movement of the loading robot using the determined reference coordinate to place the aluminum pouch in the scan area of the OCT probe. moving to;
(d) acquiring an OCT examination image by scanning the scan area of the aluminum pouch moved from the OCT probe to the examination area; and
(e) measuring the thickness of the curved portion of the aluminum pouch using a thickness measurement algorithm based on the OCT inspection image to determine whether the aluminum pouch is good or bad,
In step (e),
(e1) calculating the curvature of a horizontal cross-sectional image among the obtained OCT examination images using the thickness measurement algorithm, and correcting the scan position if the calculated curvature is not maximum; (e2) determining the location of the inflection point using the horizontal cross-sectional image if the calculated curvature is maximum; (e3) calculating the thickness of the horizontal and vertical cross-sectional images for each position of the scan path based on the determined inflection point position; (e4) calculating a thickness measurement value by collecting the calculated thickness data for each location; and (e5) comparing the calculated thickness measurement with an acceptance standard to determine whether the aluminum pouch is good or defective based on whether it is large or small.
In claim 7, step (c) is,
An aluminum pouch characterized in that the reference coordinates of the corner curved portion of the aluminum pouch are determined based on the reference coordinate determination and the image for contour extraction, and the scan path of the OCT probe is generated based on the determined reference coordinates and corner outline positions. Thickness inspection method.
delete In claim 7, step (e5) is,
If any of the thickness measurements of each corner of the aluminum pouch is less than the tolerance standard, the molded aluminum pouch is judged to be defective. If the thickness measurements of each corner of the aluminum pouch are all greater than the tolerance standard, the molded aluminum pouch is judged as defective. A method of inspecting the thickness of an aluminum pouch, characterized in that it is judged as a good product.