Laser welding method and laser welding apparatus

Abstract

To suppress the occurrence of a defective product by individually detecting a case where a welding defect is likely to occur in advance.SOLUTION: When a case body 21 is held between a reference long side clamp CLF and a movable long side clamp CLM, reference long side clamp position detection parts P5, P4 and movable long side clamp position detection parts P1, P2 are recognized by an imaging part, and the side face of the case body 21 is detected by the imaging part based on the recognized position detection parts. The case width of the case body 21 is measured based on the detected position of the side surface of the case body 21. An allowable threshold based on the case width of a standard product is stored in advance, and a step of case width determination for comparing the measured case width of the case body with the allowable threshold is executed.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a laser welding method and a laser welding apparatus, and more particularly to a laser welding method and a laser welding apparatus that suppress welding defects at joints. [Background technology]

[0002] For example, in the case of a plate-shaped lithium-ion secondary battery cell for use in a vehicle, a battery case is used that includes a cylindrical case body with a bottom and a rectangular opening, and a lid that is disposed to close the opening of the case body. In the manufacture of such lithium-ion secondary battery cells, it is extremely important to reliably seal the battery case by welding. Therefore, laser welding is used, in which a laser beam is irradiated onto the joint between the opening and the lid to weld the case body and the lid.

[0003] For example, the laser welding device described in Patent Document 1 includes a clamp (facing part) disposed opposite the side surface of the case body (case body) and a laser irradiation unit that irradiates the parts to be welded with laser light. An image of an area including a first gap between the clamp and the case body and a second gap between the case body and the lid, where the first gap is located, is recognized and the position of the outer edge of the case body is determined by identifying the first gap. Based on the determined position of the outer edge of the case body, an image recognition unit that identifies the position and size of the second gap identifies the position and size of the second gap. The clamp has a groove that faces the side surface of the case body as a position detection unit. This groove penetrates from one end of the case body on the open end side to the other end on the bottom side. The imaging unit captures an image of the welding area to include the groove.

[0004] In the laser welding device disclosed in Patent Document 1, the groove portion is easily illuminated, so in the captured image, the luminance [cd / m 2] difference becomes larger. As a result, the image recognition unit can accurately grasp the groove and easily identify the first gap adjacent to the groove. By identifying this first gap, the position of the outer edge of the case body located at its end can be easily determined. Furthermore, the image recognition unit can easily recognize, in the image, a line portion located at a position offset by a desired distance toward the lid body from the determined position of the outer edge of the case body, as the second gap. The size and position of the second gap can be accurately identified. As a result, the laser irradiation condition determination unit can appropriately determine laser irradiation conditions, including the laser irradiation position, based on the identified size and position of the second gap. As a result, the lid and the case body can be accurately welded. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-84536 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in actual laser welding sites, the width of the case body may vary due to curvature, and the thickness of the side surface of the case body may vary from lot to lot. Furthermore, a gap may occur between the case body and the clamping state. Therefore, even if the position of the first gap adjacent to the groove can be accurately identified, the second gap may not necessarily be located at a desired distance from the groove toward the lid.

[0007] Furthermore, depending on the imaging conditions (hereinafter referred to as exposure conditions), such as exposure time, the image recognition unit may not easily recognize a line portion located at a desired distance toward the lid from the position of the outer edge of the case body determined in the image as the second gap. Even if the image recognition unit recognizes a line portion located at a desired distance as the second gap, it may mistakenly recognize a scratch or chip as the second gap. Therefore, the size and position of the second gap may not be accurately determined based solely on the position of the groove.

[0008] In such cases, welding may occur at a position other than the proper welding position. Nevertheless, such an abnormality may be discovered only after subsequent processing. As a result, the completed lithium-ion secondary battery may be discarded as a defective product. This has traditionally led to problems such as defective products after welding or unnecessary manufacturing processes.

[0009] The problem to be solved by the laser welding apparatus and laser welding method of the present invention is to prevent the occurrence of defective products by individually detecting in advance cases where welding defects are likely to occur. [Means for solving the problem]

[0010] In order to solve the above problems, the laser welding method of the present invention is a laser welding method using a laser welding device for welding a battery case including a cylindrical case body with a bottom having a rectangular bottom, four side surfaces, and a rectangular opening that opens at the top, and a lid body arranged to close the opening of the case body, by irradiating a laser beam to a joint between the opening and the lid body, the laser welding device including clamps C each having a position detection unit P and contacting each side surface of the case body, a laser irradiation unit that irradiates a laser beam to the joint portion of the case body fixed to the clamps C, an imaging unit that images the joint portion, and a control unit that controls the clamps C, the laser irradiation unit, and the imaging unit, and the clamps C are connected to a reference long side clamp C that contacts one long side of the rectangle. LFand a movable long side clamp C in contact with the other long side of the rectangle. LM and the position detection unit P detects the reference long side clamp C LF a pair of reference long side clamp position detecting units P5 and P4 that are provided at positions symmetrical with respect to the center of the longitudinal direction of the movable long side clamp C, and whose positions are recognized by the imaging unit; LM and a pair of movable long side clamp position detectors P1 and P2, which are provided at positions opposite to the pair of reference long side clamp position detectors P5 and P4 in the width direction and whose positions are recognized by the imaging unit, and the control unit LF and the movable long side clamp C LM By clamping the case body with these, the imaging unit recognizes the reference long side clamp position detection units P5 and P4 and the movable long side clamp position detection units P1 and P4, respectively, and based on the recognized position detection units P, the imaging unit detects the side surfaces of the case body, and based on the detected positions of the side surfaces of the case body, the case width D in the width direction perpendicular to the longitudinal direction of the rectangle of the case body is calculated. 20 Measure the case width M of the standard product M in advance. 20 The tolerance threshold D based on th is stored, and the case width D of the case body measured 20 The tolerance threshold D th The method is characterized in that a case width determination step is performed by comparing the case width with the case width determination step.

[0011] In the case width determination step, the control unit determines the case width D 20 is the tolerance threshold D th If the difference is not within the above range, the exposure conditions of the imaging unit can be changed and the case width determination step can be performed again.

[0012] The control unit is configured to calculate the luminance Lu [cd / m 2 ] and the measured luminance Lu [cd / m 2 ] is the set brightness threshold Lu th [cd / m 2], and a step of determining the luminance of the joint portion is provided, in which the luminance Lu [cd / m 2 ] is the brightness threshold Lu th [cd / m 2 If the value is outside the range of

[0045] , the exposure conditions of the imaging unit can be changed and the case width determination step can be performed again.

[0013] When welding a plurality of the battery cases together in succession, the control unit 20 is continuously measured, and the tolerance threshold D th The case width of the standard product M is M 20 The continuous control value judgment threshold D is close to S and the measurement value measured continuously the set number of times is set to the allowable threshold D th The continuous control value judgment threshold D S If the size is outside the range of the allowable threshold D, check the size of the case body 21 and, if necessary, th A step of determining a continuous control value that changes the value can be performed.

[0014] When welding a plurality of the battery cases together in succession, the control unit 20 is continuously measured, and the tolerance threshold D th The case width of the standard product M is M 20 The moving average value judgment threshold D is close to A The average value of the measured values ​​measured continuously for the set number of times is set to the allowable threshold D th The moving average value judgment threshold D A If the dimensions of the case body are outside the range of th A step of moving average determination that changes the value of the moving average may be performed.

[0015] The clamp C is a reference short side clamp C that contacts one short side of the rectangle. SF and a movable short side clamp C in contact with the other short side of the rectangle. SM The reference short side clamp C SFThe reference short side clamp position detection unit P3, the position of which is recognized by the imaging unit, and the movable short side clamp C SM and a movable short side clamp position detection unit P6, the position of which is recognized by the imaging unit, and the control unit detects the reference short side clamp C SF and the movable short side clamp C SM By clamping the case body with the clamping members, the imaging unit recognizes the reference short side clamp position detection unit P3 and the movable short side clamp position detection unit P6, and the case length D in the longitudinal direction of the rectangular shape of the case body is L and the case length D of the standard product M stored in advance is measured. L The tolerance threshold D based on th and the measured case length D of the case body. L A step of determining the case body length can be performed by comparing the

[0016] The control unit is configured to control the case width M of the standard product M. 20 and the case width D of the case body 20 Difference ΔD 20 Calculate the difference ΔD 20 The threshold ΔD 20th and the camera center distance M from the camera center Ax of the imaging unit to the side end face of the case of the standard product M. CA and the camera center distance D from the camera center Ax to the side surface of the case body. CA and a case position deviation determination step can be executed in which the difference between the side of the standard product M and the side of the case body is calculated based on the difference.

[0017] The control unit is configured to LF and the movable long side clamp C LMand P2, the imaging unit can recognize the pair of reference long side clamp position detectors P5 and P4 and the pair of movable long side clamp position detectors P1 and P2 facing each other in the width direction, and can execute a tilt detection step of detecting the tilt of the case body in the longitudinal direction from at least one of the difference in widthwise position between the pair of reference long side clamp position detectors P5 and P4 and the difference in widthwise position between the pair of movable long side clamp position detectors P1 and P2. In this case, the control unit can execute a tilt error cause recording step of comparing the difference in widthwise position between the pair of reference long side clamp position detectors P5 and P4 with the difference in widthwise position between the pair of movable long side clamp position detectors P1 and P2, and identifying and recording the one with the larger difference in widthwise position as the cause of the tilt error.

[0018] The control unit detects the width M of the position detection unit of the standard product M. P and case width M 20 Difference ΔM 20 and the width of the position detection section D P and the case width D of the case body 20 The control unit can execute a step of determining the degree of contact between the clamp C and the case body by comparing the difference between the width M of the position detection unit of the standard product M and the contact threshold value ΔP. P and case width M 20 Difference ΔM 20 and the width of the position detection section D P and the case width D of the case body 20 Difference ΔD 20 If the difference is greater than the contact threshold value ΔP, it is determined that the contact between the clamp and the side of the case body is poor, and a step of recording the cause of poor contact is executed in which the difference in widthwise position between the pair of reference long side clamp position detection units P5 and P4 and the difference in widthwise position between the pair of movable long side clamp position detection units P1 and P2 are compared, and the one with the larger widthwise difference is identified and recorded as the cause of the poor contact.

[0019] In order to solve the above problems, the laser welding device of the present invention is a laser welding device for a battery case including a cylindrical case body with a bottom having a rectangular bottom, four side surfaces, and a rectangular opening that opens at the top, and a lid body arranged to close the opening of the case body, which irradiates a joint portion WP between the opening and the lid body with laser light LB to weld the case body and the lid body, and the laser welding device includes four clamps C each having a position detection unit P and contacting each of the four side surfaces of the case body, a laser irradiation device that irradiates the joint portion WP of the case body fixed to the clamps C with laser light LB, an imaging unit that images the joint portion WP, and a control unit that controls the clamps C, the laser irradiation device, and the imaging unit, and the clamps C are connected to a reference long side clamp C that contacts one long side of the rectangle. LF and a movable long side clamp C in contact with the other long side of the rectangle. LM and a reference short side clamp C that contacts one short side of the rectangle. SF and a movable short side clamp C in contact with the other short side of the rectangle. SM The position detection unit P detects the reference long side clamp C LF a pair of reference long side clamp position detecting units P5 and P4 that are provided at positions symmetrical with respect to the center of the longitudinal direction of the movable long side clamp C, and whose positions are recognized by the imaging unit; LM and a pair of movable long side clamp position detectors P1 and P2, which are provided at positions opposite to the pair of reference long side clamp position detectors P5 and P4 in the width direction and whose positions are recognized by the imaging unit, and the control unit LF and the movable long side clamp C LM By clamping the case body with these, the imaging unit recognizes the reference long side clamp position detection units P5 and P4 and the movable long side clamp position detection units P1 and P4, respectively, and based on the recognized position detection units P, the imaging unit detects the case side surfaces that are the side surfaces of the case body, and measures the case width D1 in the width direction perpendicular to the longitudinal direction of the rectangle of the case body based on the detected position of the side surface of the case body, and also measures the case width M of the standard product M in advance. 20 The tolerance threshold D based on this stored, and the case width D of the measured case body 20 is compared with the allowable threshold D th characterized by executing a step of case width determination.

Effect of the Invention

[0020] According to the laser welding method and the laser welding apparatus of the present invention, there is an effect that the occurrence of defective products can be suppressed by individually detecting in advance a case where welding defects are likely to occur.

Brief Description of the Drawings

[0021] [Figure 1] It is a perspective view of a lithium-ion secondary battery. [Figure 2] It is a plan view of a lithium-ion secondary battery. [Figure 3] It is a block diagram showing the configuration of the laser welding apparatus 1. [Figure 4] It is a schematic view showing a state in which a lithium-ion secondary battery in FIG. 3 is irradiated with a laser beam LB. [Figure 5] It is a plan view of a state in which a lithium-ion secondary battery shown in FIG. 4 is irradiated with a laser beam LB. [Figure 6] It is a plan view in which a battery case is fixed by four clamps C which are fixing jigs. [Figure 7] It is a diagram showing welding position detection (gap profile). [Figure 8] It is a diagram showing each data used in this embodiment. [Figure 9] It is a flowchart showing the steps of the laser welding method of this embodiment. [Figure 10] It is a flowchart showing the procedure of welding position adjustment (S2) in FIG. 9. [Figure 11] It is a flowchart showing the procedure of the laser welding method in more detail. [Figure 12] It shows the relationship between the case width M20 of a standard product and the case width D20 of the case body 21, and (a) shows the case where M20 < D20, and (b) shows the case where M²0 > D20. [Figure 13] FIG. 12(a) is a diagram showing a measurement example of continuous control values when M20 < D20. [Figure 14] FIG. 12(b) is a diagram showing a measurement example of continuous control values when M20 > D20. [Figure 15] FIG. 12(a) is a diagram showing a measurement example of moving average values when M20 < D20. [Figure 16] FIG. 12(b) is a diagram showing a measurement example of moving average values when M20 > D20. [Figure 17] FIG. shows the joint portion WP at the time of joint portion luminance determination. [Figure 18] FIG. is a schematic diagram showing the step (S26) of case position deviation determination. [Figure 19] FIG. is a diagram for explaining the step (S28) of clamp adhesion determination.

MODE FOR CARRYING OUT THE INVENTION

[0022] Hereinafter, the configuration of the present embodiment will be described in detail with reference to FIGS. 1 to 19 using an embodiment of a laser welding method using the laser welding apparatus 1. (Outline of the Present Embodiment) As described in the background art, in the actual laser welding site, the width of the case body 21 shown in FIGS. 6 and 8 may vary due to curvature or the like, or the case body thickness S of the side surface 21a of the case body 21 21 may vary for each production lot. Further, depending on the state of the clamp C, a gap may occur between the case body 21. For this reason, the case body 21 and the second gap portion G IN are not necessarily located at a position desired distance away from the outer edge position of the case body 21 toward the lid body side.

[0023] Further, depending on the exposure conditions, the image recognition unit 50 (FIG. 3) positions a line portion that is located at a position desired distance away from the side surface 21a of the case body 21 determined in the image toward the lid body 22 side as the second gap portion G INIn addition, it may be difficult to easily recognize the line portion located at a desired distance from the second gap portion G. IN If the second gap G is recognized as a defect, scratches or chips may be mistakenly recognized. IN In such cases, welding may be performed at a position other than the proper joint WP, and the lithium ion secondary battery 2 completed through subsequent processes may be discarded as a defective product.

[0024] Therefore, in the laser welding method using the laser welding apparatus 1 of this embodiment, the control unit 70 analyzes the data obtained by the image recognition unit 50, thereby extracting the above-mentioned problems in advance and eliminating defective products from the production process, thereby improving the production yield and production efficiency.

[0025] One of the methods is to use the case width D obtained by the image recognition unit 50. 20 The data of the case width M of the standard product M that should be 20 By comparing with the case width D 20 The reliability of the data is evaluated. In addition, the continuous case width D 20 The data obtained may be such that the data continuously deviates from the set threshold value. In such a case, by knowing the tendency of the production lot of the case body 21, the threshold value can be reset to match the production lot. This makes it possible to perform laser welding efficiently and appropriately. On the other hand, when the case width D of the battery cases 20 to be continuously welded is 20 By acquiring data and evaluating it as a moving arithmetic average of, for example, four data, the variation of each product is averaged out to determine the case width D 20 It is possible to properly judge trends.

[0026] Furthermore, whether the imaging by these imaging units 40 was performed under appropriate conditions, and the luminance Lu [cd / m 2 In this test, the luminance Lu [cd / m 2] is not appropriate, the luminance Lu [cd / m 2 ] to obtain the desired luminance Lu [cd / m 2 ] to retry.

[0027] Furthermore, there are cases where the clamp C, which is a jig for fixing the case body 21, is tilted when fixing the case body 21, or where a gap is formed. In order to detect such cases, the position of the opposing clamp C can be compared with the data when it is properly clamped to the standard product M, and the case width D 20 Evaluate the reliability of the data.

[0028] As described above, welding using the laser welding device 1 of this embodiment performs measurements while verifying the measured data from various angles, making it possible to identify measurement errors due to various causes. This allows problems such as those described above to be extracted and defective products to be eliminated from the production process. This allows for improvements in production yield and production efficiency.

[0029] (Configuration of this embodiment) <Lithium-ion secondary battery 2 of this embodiment> First, an example of the configuration of the lithium ion secondary battery 2 that is the premise of this embodiment will be briefly described.

[0030] FIG. 1 is a perspective view of a lithium-ion secondary battery 2. FIG. 2 is a plan view of the lithium-ion secondary battery 2. As shown in FIG. 1, the lithium-ion secondary battery 2 is configured as a cell battery that constitutes an assembled battery (not shown). The battery case 20 includes a cylindrical case body 21 with a bottom, which has a rectangular bottom 21b, four side surfaces 21a, and a rectangular opening 21c that opens at the top. The battery case 20 also includes a lid body 22 that is arranged to close the opening 21c of the case body 21. A laser welding device 1 irradiates a laser beam LB onto a joint WP between the opening 21c and the lid body 22, welding the case body 21 and the lid body 22 so as to hermetically seal them together.

[0031] An electrode assembly 28 is housed inside the battery case 20. The battery case 20 is filled with a non-aqueous electrolyte 27. The case body 21 and the lid 22 are made of a metal such as an aluminum alloy. The lithium ion secondary battery 2 is formed into a sealed battery container by attaching the lid 22 to the case body 21. The lithium ion secondary battery 2 is also provided with a negative electrode external terminal 24 and a positive electrode external terminal 26 on the lid 22, which are used for charging and discharging power. The negative electrode external terminal 24 and the negative electrode connecting portion 23 are connected via the lid 22. The positive electrode external terminal 26 and the positive electrode connecting portion 25 are connected via the lid 22.

[0032] The laminate of the electrode body 28 of the lithium ion secondary battery 2 is constructed by winding a positive electrode plate on the innermost side, a separator on the outer side thereof, a negative electrode plate on the outer side thereof, and a separator on the outermost periphery.

[0033] <Laser welding device 1> 3 is a block diagram showing the configuration of the laser welding apparatus 1. The laser welding apparatus 1 includes a head unit 30 as a laser irradiation device, four clamps C (see FIG. 6), an imaging unit 40, an image recognition unit 50, a laser irradiation condition determination unit 60, and a control unit 70. The control unit 70 is configured as a computer and controls the laser welding apparatus 1 using a stored program. Specifically, the case body 21 is fixed with the clamps C while being photographed by the imaging unit 40, and the joining portion WP is determined from the image by the image recognition unit 50. The laser irradiation conditions are then determined by the laser irradiation condition determination unit 60, and the head unit 30 irradiates the joining portion WP of the battery case 20 with laser light LB to perform welding.

[0034] The head unit 30 irradiates the joint part WP with laser light LB emitted from the laser oscillation source 101 and transmitted through the optical fiber 102. The head unit 30 includes an optical system 110, an XY galvanometer scanner unit 120, a Z lens driving unit 130, an XYZ galvanometer scanner driver 140, and a protective glass 150.

[0035] The optical system 110 includes a collimating lens 111 , a dichroic mirror 112 , a reflecting mirror 113 , a diffractive optical element 114 , a Z lens 115 , a reflecting mirror 116 , and a condenser lens 117 .

[0036] Laser light LB incident from laser oscillation source 101 is collimated by collimating lens 111. Of the collimated laser light LB, laser light LB having a desired wavelength is reflected by dichroic mirror 112 toward reflecting mirror 113.

[0037] Laser light LB incident on reflection mirror 113 is reflected toward diffractive optical element 114. Diffractive optical element 114 splits the incident laser light LB into multiple light beams. The laser light LB split into multiple light beams passes through Z lens 115.

[0038] Z lens 115 is a lens for scanning the focal point of laser light LB emitted from head unit 30 in the Z axis direction. Z lens 115 is moved by Z lens drive unit 130, thereby scanning the focal point in the Z axis direction. The operation of Z lens drive unit 130 is controlled by XYZ galvano scanner driver 140.

[0039] The laser light LB that has passed through the Z lens 115 is reflected by a reflecting mirror 116 toward a condenser lens 117. The laser light LB that has entered the condenser lens 117 is condensed and enters the XY galvano scanner unit 120.

[0040] The XY galvanometer scanner unit 120 includes an X-direction galvanometer mirror and a Y-direction galvanometer mirror. The X-direction galvanometer mirror is a mirror for scanning the focal point of the laser light LB emitted from the head unit 30 in the X-axis direction. The Y-direction galvanometer mirror is a mirror for scanning the focal point of the laser light LB emitted from the head unit 30 in the Y-axis direction.

[0041] The X-direction galvanometer mirror and the Y-direction galvanometer mirror are rotated by respective drive units to scan the focal point in any direction within the XY plane. The operation of the drive units is controlled by an XYZ galvanometer scanner driver 140.

[0042] The laser light LB adjusted by the XY galvano scanner unit 120 passes through the protective glass 150 and is irradiated onto the joint portion WP. Note that a laser pointer 160, an air knife 170, and an air nozzle 180 are disposed below the head unit 30. The laser pointer 160 irradiates the position irradiated with the laser light LB with light having the same wavelength as the laser light LB. The air knife 170 sprays air to prevent plumes and spatter scattered by welding from adhering to the protective glass 150. The air nozzle 180 supplies shielding gas to the welding position.

[0043] <Clamp C> Fig. 4 is a schematic diagram showing a state in which laser light LB is irradiated onto the lithium ion secondary battery 2 of Fig. 3. Fig. 5 is a plan view showing a state in which laser light LB is irradiated onto the lithium ion secondary battery 2 shown in Fig. 4.

[0044] As shown in FIGS. 4 and 5, the clamps C are disposed so as to face and come into close contact with the vertical side surfaces 21a of the case body 21 of the lithium ion secondary battery 2. 6 is a plan view of the battery case 20 fixed by four clamps C, which are fixing jigs. The clamps C in this embodiment are standard long side clamps C that contact one long side of the rectangle. LF and the movable long side clamp C that contacts the other long side. LM Also, a reference short side clamp C that contacts one of the short sides of the rectangle SF and the movable short side clamp C that contacts the other short side. SM It is equipped with:

[0045] Standard long side clamp C LF and standard short side clamp C SFThe movable long side clamp C is fixed in position relative to a work table (not shown) on which the battery case 20 is placed for welding. LM and movable short side clamp C SM can be biased with a predetermined pressure so as to come into close contact with the upper part of the side surface 21a of the case main body 21, and can be released by the control unit 70. When there is no particular distinction between these, they are referred to as clamps C.

[0046] Furthermore, these clamps C are equipped with position detection units P. These position detection units P detect the reference long side clamps C LF The movable long side clamp C has a pair of reference long side clamp position detecting units P5 and P4 that are provided at positions symmetrical with respect to the center in the longitudinal direction of the clamp C and whose positions are recognized by the imaging unit 40. LM The pair of reference long side clamp position detectors P5 and P4 are provided at positions opposite to each other in the width direction, and the positions of the pair of movable long side clamp position detectors P1 and P2 are recognized by the imaging unit 40. SF The reference short side clamp position detector P3, whose position is recognized by the imaging unit 40, and the movable short side clamp C SM and a movable short-side clamp position detection unit P6, the positions of which are recognized by the imaging unit 40. When there is no particular need to distinguish between these, they will be referred to as the position detection unit P.

[0047] As shown in FIG. 5, the position detection portion P has a notched shape with a rectangular cross section in a plan view. The position detection portion P is a vertically formed groove. Therefore, when an image is captured by the imaging unit 40, the luminance Lu [cd / m 2 First, when the light is irradiated from above as in this embodiment, the position detection unit P detects the darkest luminance Lu [cd / m 2 By configuring the position detection unit P in this way, the outline of the unit can be clearly recognized when the image is captured by the image capture unit 40. Therefore, the reference plane P RWhen the image is captured by the imaging unit 40, the position can be accurately identified, and therefore the image recognition unit 50 can accurately identify the position of the clamp C itself.

[0048] As shown in FIG. 4, a second gap G is a gap between the inside of the opening at the top end of the case body 21 and the end of the lid body 22. IN The gap is normally maintained at about 10 μm. IN However, if the gap becomes large, the laser light LB may penetrate into the inside of the case body 21. However, it is difficult to detect such an abnormality visually from the outside, and subsequent post-processing is carried out. If a defect is discovered for the first time in an inspection process after the completion of the post-processing, the entire production lot, which may have the same problem, may be discarded. For this reason, the second gap G IN Management of this is extremely important.

[0049] (Laser welding method) In this embodiment, the laser welding method described below is carried out by the laser welding apparatus 1 described above.

[0050] First, measurement data that is the premise of the laser welding method of this embodiment will be described. The battery case 20 shown in Fig. 2 is fixed by four clamps C as shown in Fig. 6. In Fig. 6, the reference long side clamp C LF The battery case 20 is placed on the standard short side clamp C so that the side surface 21a of the lower long side is in close contact with the standard short side clamp C. SF The battery case 20 is placed so that the side surface 21a of the right short side of the battery case 20 is in close contact with the movable long side clamp C. LM 6, the movable short side clamp C is pressed with a constant pressure so as to be in close contact with the side surface 21a of the upper long side. SM 6 with a constant pressure so that it adheres tightly to the side surface 21a of the left short side. In this way, the case body 21 is fixed by the clamp C from above, below, left and right directions.

[0051] In this state, the laser welding device 1 determines six image capturing areas IA including the position detection area P and the joint area WP under predetermined exposure conditions using the image capturing unit 40. The imaging unit 40 recognizes the position detection parts P1 to P6 in the six imaging ranges IA, respectively, in the image recognition unit 50.

[0052] In the welding position detection (gap profile) generated based on the position detection parts P1 to P6, the joint part WP is, in principle, located on the inside, and the thickness of the case body D 21 As described in the background art, the laser welding method of the present embodiment is characterized in that, whereas the offset amount has conventionally been a fixed value, the offset amount is corrected by analyzing data and eliminating defective products in advance.

[0053] <Explanation of each data> 8 shows the data used in this embodiment. First, the width between both side surfaces 21a of the battery case 20 is defined as the case width D 20 The case width D 20 is synonymous with the width of the case body 21. The width of the lid body 22 is the lid body width D 22 The thickness of the side surface 21a of the case body 21 is defined as the case body thickness D 21 The second gap G is defined as the joint portion WP between the case body 21 and the cover body 22. IN This second gap G IN is the joint part WP. Ideally, it is about 10 μm. Then, the case width D 20 is D 20 =D 21 +G IN +D 22 +G IN +D 21 The relationship is as follows.

[0054] The center of the imaging range IA of the camera of the imaging unit 40 is defined as the camera center Ax. The distance between the pair of camera centers Ax is the camera center distance D CAThis camera center Ax is associated with the control of the XY galvano scanner unit 120 of the head unit 30. In other words, if the joint part WP is outside the imaging range IA of the camera of the imaging section 40, it may cause problems with welding.

[0055] Position detection section width D P is the reference surface P at the bottom of the groove of the movable long side clamp position detection part P1 on the positive electrode side and the reference long side clamp position detection part P5 on the opposing positive electrode side. R This is the distance between the reference plane P R The position of the position detection area width D is the boundary between high and low brightness, so it is highly reliable and hardly affected by noise or external light. P is highly reliable.

[0056] In addition, this position detection section width D P The clamp width D is obtained by subtracting the depth of the groove of the position detection part P from the above. CL The groove depth is also highly accurate, so the clamp width D CL This clamp width D CL is the actual contact surface C of the opposing clamp C R If the clamp C is completely attached to the case body 21, the clamp width D CL and case width D 20 matches.

[0057] However, the side surface 21a of the case body 21 and the contact surface C of the clamp C R There is a first gap G between OUT When this occurs, the clamp width D CL and case width D 20 This can occur, for example, when a foreign object gets in, when the center of the case body 21 is curved outward, when the clamping force is insufficient, or when the clamp C is tilted.

[0058] This first gap G OUT This causes the contact surface C RThe second gap G between the case body 21 and the lid body 22 is located at a position offset by a predetermined value from the IN The position may be shifted. In addition, the case body thickness D 21 The thickness D of the case body may vary within the design value due to wear or replacement of the mold. Also, a broken portion occurs at the opening 21c of the case body during molding of the case, and depending on the shape of the broken portion, the broken portion may not be accurately read. 21 The detected value of the case body thickness D caused by such a mold varies. 21 The error occurs in each production lot.

[0059] <Components of laser welding method> 9 is a flowchart showing the steps of the laser welding method of this embodiment. In the laser welding method of this embodiment, first, center position determination / welding position detection (S1) is performed. Here, the positional relationship between the laser welding device 1 and the battery case 20 fixed by the clamp C is determined in relation to the camera center Ax of the imaging range IA of the imaging unit 40.

[0060] Fig. 7 is a diagram showing welding position detection (gap profile). A gap profile is generated based on the positions of the six position detection units P1 to P6 obtained in this way. The gap profile recognizes the positions of the position detection units P1 to P6 and creates a trajectory that continuously connects them (welding position detection). The welding is performed by welding a portion offset a certain width inward from this trajectory as a joint portion WP.

[0061] Next, a welding position adjustment (S2) is performed to analyze the detailed positional relationship of the battery case 20 thus fixed by the clamp C in the laser welding device 1. The detailed procedure will be described later.

[0062] After the welding position adjustment (S2) is completed, temporary welding (S3) is performed to fix the relative positions of the case body 21 and the lid body 22. In this state, main welding (S4) is performed to completely seal the case body 21 and the lid body 22.

[0063] <Welding position adjustment (S2)> FIG. 10 is a flowchart showing the procedure of the welding position adjustment (S2). In the welding position adjustment (S2), the control unit 70 performs steps of: A: case width determination (S21), B: continuous management value determination (S22), C: moving average value determination (S23), D: joint portion luminance determination (S25), E: case position deviation determination (S26), F: inclination detection (S27), G: recording of inclination error cause (S30), H: clamp adhesion determination (S28), and I: recording of adhesion failure cause (S33). Note that these procedures are listed by elements and do not limit the order, and can be implemented by appropriately swapping them.

[0064] Each of the following steps will be specifically described. <A: Step of case width determination (S21)> As shown in FIG. 6, the clamp C includes a reference long-side clamp C LF and a movable long-side clamp C LM and a reference short-side clamp C SF and a movable short-side clamp C SM and is provided with.

[0065] The position detection unit P includes a movable long-side clamp position detection unit P1·P2, a reference short-side clamp position detection unit P3, a reference long-side clamp position detection unit P5·P4, and a movable short-side clamp position detection unit P6, respectively.

[0066] The control unit 70 sandwiches the case body 21 by the reference long-side clamp C LF and the movable long-side clamp C LM and thereby the imaging unit 40 recognizes the reference long-side clamp position detection units P5·P4 and the movable long-side clamp position detection units P1·P2, respectively. Based on these recognized position detection units P, the imaging unit 40 detects the side surface 21a of the case body 21. Based on the detected position of the side surface 21a of the case body 21, the case width D1 of the case body 21 is measured.

[0067] Here, the case width M of the standard product M is previously stored in the control unit 7020 The allowable threshold D based on th is stored, and the measured case width D 20 is compared with the allowable threshold D th . Also, in this embodiment, the case width D 20 is measured together with the case length D L . The case body 21 is clamped in the longitudinal direction by the reference short-side clamp C SF and the movable short-side clamp C SM . The imaging unit 40 recognizes the reference short-side clamp position detection unit P3 and the movable short-side clamp position detection unit P6 respectively, and measures the case length D L (see FIG. 6) of the case body 21.

[0068] The step of measuring the case body length, which compares the allowable threshold D L based on the case length M of the standard product M stored in advance Lth with the measured case length D of the case body 21 L is executed. In addition, in the case width measurement step (S21), when the control unit 70 determines that the case width D 20 is not within the range of the allowable threshold D th , the exposure condition of the imaging unit 40 is changed, and the case width determination step is re-executed.

[0069] By this step, the production efficiency can be improved by eliminating the waste of removing the case body 21 with an abnormal case width D <00OO172>from the production line and performing subsequent post-processes. In addition, it is possible to prevent the lithium-ion secondary battery 2 with a welding problem in airtightness from being shipped as a product.

[0070] <B: Step of determining continuous management value (S22)> In this embodiment, when the control unit 70 continuously welds a plurality of battery cases 20, the control unit 70 continuously measures the case width D 20 of the case body 21. A continuous management value determination threshold D th that is closer to the case width M of the standard product M than the allowable threshold D 20 is used. SSet it. At the same time, when the measured values measured continuously for the set number of times (4 times in this embodiment) are within the allowable threshold D th but outside the continuous management value determination threshold D S range, check the dimensions of the case body 21 and, if necessary, change the allowable threshold D th . The number of times to be set may be 2 or more, or 5 or more. Due to variations within the same production lot.

[0071] In this step B: continuous management value determination (S22), by detecting the abnormality of the continuous case width D th within the allowable threshold D 20 , it is possible to detect the dimensional deviation for each production lot. This is because the error in the case width D 20 generally caused by mold replacement, mold wear or deformation, etc. occurs continuously. If the dimensional deviation for each production lot is known, by setting thresholds adjusted to these without treating them as abnormalities, it is possible to manufacture products of these production lots without waste and while maintaining accuracy with settings adapted to that production lot.

[0072] <C: Moving average value determination step (S23)> When the control unit 70 continuously welds a plurality of battery cases 20, it continuously measures the case width D 20 of the case body 21, and sets a moving average value determination threshold D th closer to the case width M 20 of the standard product M than the allowable threshold D A . At the same time, when the average value of the measured values measured continuously for the set number of times (4 times in this embodiment) is within the allowable threshold D th but outside the moving average value determination threshold D A range, check the dimensions of the case body 21 and, if necessary, change the allowable threshold D th . This measurement can also use the data collected in step B: continuous management value determination (S22).

[0073] <D: Joint part luminance determination step (S25)> The control unit 70 measures the luminance Lu [cd / m 2 of the joint portion WP imaged by the imaging unit 40 as a step of determining the luminance of the joint portion. Along with this, the measured luminance Lu [cd / m 2 is compared with the set luminance threshold value Lu th [cd / m 2 .

[0074] Note that when the luminance Lu [cd / m 2 is not within the range of the luminance threshold value Lu th [cd / m 2 , the possibility of misrecognition increases, so the exposure conditions of the imaging unit 40 are changed and the case width determination step (S21) is re-executed.

[0075] <E: Step (S26) for determining case position deviation> The control unit 70 calculates the difference ΔD 20 between the case width M 20 of the standard product M and the case width D 20 of the case body 21, and compares the difference ΔD 20 with the threshold value ΔD 20th . The camera center distance M CA from the camera center Ax of the imaging unit 40 to the side surface 21a of the case body 21 of the standard product M is compared with the camera center distance D CA from the camera center Ax to the side surface 21a of the case body 21. The deviation in the width direction between the side surface 21a of the standard product M and the side surface 21a of the case body 21 is calculated from the difference.

[0076] <F: Step (S27) for detecting inclination> The control unit 70 clamps the case body 21 by the reference long-side clamp C LF and the movable long-side clamp C LM to recognize the pair of reference long-side clamp position detection units P5·P4 and the pair of movable long-side clamp position detection units P1·P2 that face each other in the width direction by the imaging unit 40. The inclination in the longitudinal direction of the case body 21 is detected from at least one of the difference in the width direction positions between the pair of reference long-side clamp position detection units P5·P4 and the difference in the width direction positions between the pair of movable long-side clamp position detection units P1·P2.

[0077] <G: Step (S30) of Recording Inclination Error Cause> The control unit 70 compares the difference in the widthwise positions between the pair of reference long-side clamp position detectors P5 and P4 with the difference in the widthwise positions between the pair of movable long-side clamp position detectors P1 and P2. Then, it identifies and records the one with the larger difference in the lateral position as the cause of the inclination error.

[0078] <H: Step (S28) of Determining Clamp Adhesion Degree> The control unit 70 determines the adhesion degree between the clamp C and the case body 21 by comparing the difference ΔM between the width of the position detector M of the standard product M and the case width M, and the difference ΔD between the width of the position detector D and the case width D of the case body 21. P and the case width M 20 and the difference ΔM 20 and the width of the position detector D P and the case width D of the case body 21 20 and the difference ΔD 20 and the difference between them.

[0079] <I: Step (S33) of Recording Adhesion Failure Cause> The control unit 70 determines that the adhesion between the clamp C and the side surface 21a is poor when the difference between the difference ΔM between the width of the position detector M of the standard product M and the case width M, and the difference ΔD between the width of the position detector D and the case width D of the case body 21 is greater than the adhesion threshold Th. In this case, it compares the difference in the widthwise positions between the pair of reference long-side clamp position detectors P5 and P4 with the difference in the widthwise positions between the pair of movable long-side clamp position detectors P1 and P2. It identifies and records the one with the larger lateral difference as the cause of the adhesion failure. P and the case width M 20 and the difference ΔM 20 and the width of the position detector D P and the case width D of the case body 21 20 and the difference ΔD 20 and the difference is greater than the adhesion threshold Th 20 In this case, it compares the difference in the widthwise positions between the pair of reference long-side clamp position detectors P5 and P4 with the difference in the widthwise positions between the pair of movable long-side clamp position detectors P1 and P2. It identifies and records the one with the larger lateral difference as the cause of the adhesion failure.

[0080] <Procedure of the Laser Welding Method of the Present Embodiment> FIG. 11 is a flowchart showing the procedure of the laser welding method in more detail. Hereinafter, an example of the laser welding method of the present embodiment will be described in detail with reference to this flowchart.

[0081] <A: Is it within the case width determination threshold? (S21)> First, measure the case width D 20 The measurement is performed by imaging with the default imaging conditions by the imaging unit 40, and image analysis is performed by the image recognition unit 50 from the image obtained there. Here, first, each position detection unit P where the change in luminance Lu from the surroundings is large is detected, and the positions of each clamp C are specified. Here, the contact surface C R of the clamp C is estimated to be at the position of the side surface 21a of the case body 21. Then, the distances between the opposing movable long-side clamp position detection unit P1 and the reference long-side clamp position detection unit P5, the movable long-side clamp position detection unit P2 and the reference long-side clamp position detection unit P4, and the reference short-side clamp position detection unit P3 and the movable short-side clamp position detection unit P6 are calculated. The case width D 20 and the case length D L obtained here are compared with the case width M 20 and the case length M[[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Figure 12 shows the case width M of the standard product M. 20 and the case width D of the case body 21 20 (a) shows the relationship between M 20 <D 20 In the case of (b), M 20 >D 20 This shows the case.

[0085] Here, the lid width D of the lid 22 22 Since the case body 21 is generally a simple plate-shaped member, its dimensional accuracy is high and there is little error. On the other hand, the side surface 21a in the longitudinal direction of the case body 21 is 20 The case body thickness D 21 Also, the case body thickness D 21 Since the error is caused by the mold, it shows a certain tendency between the same production lot using the same mold.

[0086] FIG. 13 shows the M 20 <D 20 FIG. 14 shows an example of measurement of continuous control values ​​in the case of M shown in FIG. 20 >D 20 An example of measurement of continuous control values ​​in this case is shown below. In this determination step, when a plurality of battery cases 20 are welded together in succession, the case width D of the case body 21 is 20 Measure the case width D continuously. 20 is the tolerance threshold D th However, the tolerance threshold D th Case width M than standard product M 20 The continuous control value judgment threshold D is close to S Then, if the measurement value measured consecutively for the set number of times (for example, four times in this embodiment) is less than the allowable threshold value D th Within the range of the continuous control value judgment threshold D S If the value is outside the range of D, check the dimensions of the case body 21 and, if necessary, set the allowable threshold D th Change the

[0087] As shown in Figure 13, M 20 <D20 In the measurement example in the case of, the case width D which is a measurement value 20 is determined to be within the case width determination threshold (S21), so the allowable threshold D th (upper limit) and the allowable threshold D th (lower limit). Then, it is determined whether the measurement values are out of the range of the continuous management value determination threshold D S (upper limit) and the continuous management value determination threshold D S (lower limit) for four consecutive times. In the example shown in FIG. 13, the measured values marked with circles deviate above the continuous management value determination threshold D S (upper limit) for four consecutive times, so it is determined that it is outside the continuous management value determination threshold D S (S22: NO).

[0088] Also, as shown in FIG. 14, in the measurement example in the case of M 20 [[ID=2l]]>D 20 in the case of, the case width D which is a measurement value 20 is such that the measured values marked with circles deviate below the continuous management value determination threshold D S (lower limit) for four consecutive times, so it is determined that it is outside the continuous management value determination threshold D S (S22: NO).

[0089] Thus, when it is outside the continuous management value determination threshold (S22: NO), the dimensions are checked and the threshold is changed as necessary (S24). Specifically, for example, in the case of FIG. 13, the allowable threshold D th (upper limit) is corrected to shift upward. In the case of FIG. 13, for example, at the part where the production lot is switched, the average thickness of the case width D 20 is increasing, but in that production lot, such a case body thickness D21 is stable. Therefore, if the joining part WP is corrected to the thickness and welded, it is not judged as defective unnecessarily and good products can be produced stably. Also, in the case of FIG. 1l4, the allowable threshold D th (lower limit) is corrected to shift downward.

[0090] <C: Is it within the moving average value determination threshold? (S23)> FIG. 15 shows M shown in FIG. 12(a) 20 <D20 shows a measurement example of the moving average value in the case of. FIG. 16 shows the M shown in FIG. 12(b) 20 >D 20 shows a measurement example of the moving average value in the case of.

[0091] When the control unit 70 continuously welds a plurality of battery cases 20, a moving average value determination threshold D th closer to the case width M of the standard product M than 20 is set. Then, the case width D of the case body 21 A is continuously measured, and together with this, the average value of the measured values measured continuously for the set number of times (4 times in this embodiment) is calculated. 20 If the average value of the measured values measured continuously 4 times is within the range of the moving average value determination threshold D

[0092] A A If it is within the range (S23: YES), even if there is some variation in the individual measured values, as a whole, it is considered to be within an appropriate range and is judged as a good product.

[0093] On the other hand, if this moving average value is within the range of the allowable threshold D th but outside the range of the moving average value determination threshold D A A A (upper limit), such an example applies. Also, as shown in FIG. 16, an example where the moving arithmetic average value of the four most recent measured values is below the moving average value determination threshold D A (lower limit) applies. In these cases, the dimensions of the case body 21 are checked, and if necessary, the allowable threshold D th is changed (S36).

[0094] Here, even if an individual measured value exceeds the moving average value determination threshold D A (upper limit) and is below the moving average value determination threshold D A (lower limit), it is judged as normal (S23: YES). <D: Step of determining the luminance of the joint part (S25)> FIG. 17 shows the joint WP when the luminance of the joint is determined. Basically, the image capturing unit 40 captures an image of the joint WP with a default predetermined light amount, aperture, and exposure time. However, variations in the color, gloss, and shape of the clamp C, the upper end surface of the case body 21, and the surface of the lid 22, or the entry of external light, can cause erroneous recognition by the image recognition unit 50. The position detection unit P detects the luminance Lu [cd / m 2 ], the boundary line, the contact surface C R Detect.

[0095] If the luminance of the joint part WP is inappropriate, for example, the luminance Lu [cd / m 2 ] is small, the luminance Lu [cd / m 2 ] becomes smaller, and the contact surface C R On the other hand, if halation occurs at the position detection part P due to external light or stray light, the luminance Lu [cd / m 2 ] becomes smaller, and the contact surface C R It becomes difficult to detect such luminance Lu [cd / m 2 The difference in luminance Lu [cd / m] also varies greatly depending on the condition of the upper end of the case body 21. For example, if the upper end of the case body 21 is a smooth surface, the luminance Lu [cd / m] will vary depending on the angle of the light beam, etc. 2 ] becomes extremely low, or conversely, the luminance Lu [cd / m 2 On the other hand, the fracture radius may become extremely high. UP In the case of "areas where the skin is rough," the light rays are diffusely reflected and averaged, resulting in a constant luminance Lu [cd / m 2 ] range.

[0096] On the other hand, the upper surface of the lid 22 is often smooth due to the surface of the mold being transferred onto it. For this reason, the image recognition unit 50 detects the contact surface C RIf the broken portion R is erroneously detected, the image recognition unit 50 will attempt to recognize the joining portion WP, which is offset inward by a certain width from this position, by the difference in brightness. UP and scratches C ra If there is a joint WP, it may be misrecognized.

[0097] In this way, even if the determination in S21, S22, and S23 is YES, the luminance Lu [cd / m 2 ] can be adjusted correctly to avoid such misrecognition.

[0098] The control unit 70 determines the luminance of the joint WP captured by the imaging unit 40 by calculating the luminance Lu [cd / m 2 ] is measured. At the same time, the measured luminance Lu [cd / m 2 ] is set as the brightness threshold Lu th [cd / m 2 ] and compare it with

[0099] In addition, luminance Lu [cd / m 2 ] is the brightness threshold Lu th [cd / m 2 If the case width is not within the range of

[0055] , the exposure conditions of the imaging unit 40 are changed and the case width determination step is performed again. That is, even if the acquired data is judged as YES in S21, S22, and S23, the correct luminance Lu [cd / m 2 If the image had not been recognized using [], it may have been misrecognized.

[0100] Luminance of the joint WP [cd / m 2 If it is determined that the exposure conditions are not appropriate (S23: NO), it is determined whether the exposure conditions can be changed and the detection can be retried (S36). If it is determined that the exposure conditions can be changed and the detection can be retried, the process returns to S21, where the exposure conditions are changed and the detection is retried (S21).

[0101] On the other hand, if it is determined that detection retry is impossible even if the exposure conditions are changed (such as the error being too large or retry having already been performed) (S36: NO), the process ends (ends), and the product is removed from the line.

[0102] When the luminance Lu [cd / m 2 of the bonding part WP is determined to be appropriate (S23: YES), the data is considered reliable and the process proceeds to the next step. <E: Step for determining case misalignment (S26)> FIG. 18 is a schematic diagram showing the step for determining case misalignment (S26). In the figure, the inclination is exaggerated.

[0103] Already in S22, the case width D 20 is within the allowable threshold D th . Therefore, it is determined whether the position of the side surface 21a of the case body 21 imaged in the imaging range IA by the imaging unit 40 is at the original position. For this reason, the positional relationship between the camera center Ax of the imaging range IA and the position of the side surface 21a of the case body 21 is grasped.

[0104] The control unit 70 calculates the difference ΔD 20 between the case width M 20 of the standard product M and the case width D 20 of the case body 21, and compares the difference ΔD 20 with the threshold value ΔD 20th . Specifically, it compares the camera center distance M CA from the camera center Ax of the imaging unit 40 to the side end face of the case of the standard product M with the camera center distance D CA from the camera center Ax to the side surface 21a of the case body 21. The deviation in the width direction between the side surface 21a of the standard product M and the side surface 21a of the case body 21 is calculated from the difference (S26).

[0105] Here, the range irradiated with laser is interlocked with the imaging range IA. For this reason, laser welding becomes difficult if the battery case 20 is outside the imaging range IA. Therefore, the camera center Ax is used as a reference for an absolute position as a judgment criterion, and the camera center distance D CAis calculated and compared. Then, this camera center distance D CA is compared with the camera center distance M CA to determine the displacement.

[0106] If the displacement is small and within the range of the threshold value ΔD 20th the battery case 20 is determined to be a normal non-defective product (S26: YES), and the process ends. On the other hand, if the displacement is large and outside the range of the threshold value ΔD 20th the position of the battery case 20 is determined to be an abnormal defective product (S26: NO).

[0107] <F: Step of detecting inclination (S27)> E: In the step of determining the case position displacement (S26), if it is determined that the range of the threshold value ΔD 20th is exceeded (S26: NO), the step of F: detecting inclination (S27) is performed.

[0108] The control unit 70 sandwiches the case body 21 by the reference long-side clamp C LF and the movable long-side clamp C LM to recognize the pair of reference long-side clamp position detection parts P5·P4 and the pair of movable long-side clamp position detection parts P1·P2 facing in the width direction by the imaging part 40, respectively. The inclination in the longitudinal direction of the case body 21 is detected from at least one of the difference in the width direction positions between the pair of reference long-side clamp position detection parts P5·P4 and the difference in the width direction positions between the pair of movable long-side clamp position detection parts P1·P2. If the inclination detection deviates from the threshold value in the step of detecting inclination (S27) (S27: NO), the process proceeds to the step of recording the cause of the inclination error (S30). Note that when it is determined as NO in S29, it does not immediately proceed to the next step S33, and retries may be performed.

[0109] <G: Step of recording the cause of the inclination error (S30)> The control unit 70 compares the difference in the widthwise positions between the pair of reference long-side clamp position detectors P5 and P4 with the difference in the widthwise positions between the pair of movable long-side clamp position detectors P1 and P2. Then, it identifies and records the one with the larger difference in the lateral position as the cause of the inclination error.

[0110] Here, when the error is large on the side of the reference long-side clamp position detectors P5 and P4, the control unit 70 stores in the control unit 70 that the cause of the poor adhesion is on the side of the reference long-side clamp position detectors P5 and P4 and ends the process (S31). Also, when the error is large on the side of the movable long-side clamp position detectors P1 and P2, the control unit 70 stores in the control unit 70 that the cause of the poor adhesion is on the side of the movable long-side clamp position detectors P1 and P2 and ends the process (S32). The recording here is utilized as traceability information which is a record at the time of manufacture.

[0111] <H: Steps of Clamp Adhesion Degree Judgment (S28)> FIG. 19 is a diagram for explaining the steps of H: clamp adhesion degree judgment (S28). The control unit 70 determines the adhesion degree between the clamp C and the case body 21 by comparing the difference between the position detector width M of the standard product M P and the case width M 20 ΔM 20 with the difference between the position detector width D P and the case width D of the case body 21 20 ΔD 20 of the case body 21.

[0112] In an ideal state, the clamp C is adhered to the case body 21 of the standard product M, and there is no first gap G OUT . Also, when the case width D 20 is equal to the case width M 20 of the standard product M, the position detector width M P of the standard product M is equal to the position detector width D P . However, even when the case width D 20 is equal to the case width M 20 of the standard product M, the position detector width M P of the standard product M and the position detector width D Pand may not be equal.

[0113] This may be caused by an inappropriate pressing force of the clamp C. Since the case body 21 is formed in a box shape, the center may bulge. By pressing the clamp C, it may be possible to correct the side surface 21a of the case body 21 so that it is flat. However, if the clamp C does not have a sufficient pressing force, this correction will not be possible, and the first gap G will be detected at the position detection part P at the end. OUT Furthermore, if the curve is wavy, it cannot be corrected by the clamp C. Also, foreign matter may get in between the clamp C and the case body 21. Alternatively, the clamp C may be tilted.

[0114] The control unit 70 detects the width M of the position detection unit of the standard product M. P and case width M 20 Difference ΔM 20 and the width of the position detection section D P and the case width D of the case body 21 20 Difference ΔD 20 The difference between these is the contact threshold Th 20 In this case, the clamp C and the side surface 21a are in good contact with each other, and the first gap G OUT It is determined that no abnormality has occurred (S29: YES). In this case, the product is determined to be normal, and the process proceeds to the next step (END).

[0115] The control unit 70 detects the width M of the position detection unit of the standard product M. P and case width M 20 Difference ΔM 20 and the width of the position detection section D P and the case width D of the case body 21 20 Difference ΔD 20 The difference between these is the contact threshold Th 20 In this case, it is determined that the contact between the clamp C and the side surface 21a is poor (S29: NO). Note that if the determination is NO in S29, a retry may be performed without immediately proceeding to the next step S33.

[0116] <I; Step (S33) of Recording Reasons for Poor Adhesion> When it is determined that the adhesion between the clamp C and the side surface 21a is poor (S29: NO), the larger difference ΔD 20 is specified and recorded as the cause of the poor adhesion.

[0117] Compare the difference in the widthwise positions between the pair of reference long-side clamp position detectors P5 and P4 and the difference in the widthwise positions between the pair of movable long-side clamp position detectors P1 and P2. When the difference in the widthwise positions between the pair of reference long-side clamp position detectors P5 and P4 is large, the cause of the poor adhesion is specified as the reference long-side clamp position detectors P5 and P4, and the control unit 70 stores it and ends the process (S34). Also, when the difference in the widthwise positions between the pair of movable long-side clamp position detectors P1 and P2 is large, the cause of the poor adhesion is specified as the movable long-side clamp position detectors P1 and P2, and the control unit 70 stores it and ends the process (S34). The recording here is utilized as traceability information, which is a record during manufacturing.

[0118] (Effects of this Embodiment) According to the laser welding apparatus 1 and the laser welding method of this embodiment, the following effects are achieved.

[0119] (1) According to the laser welding apparatus 1 and the laser welding method of this embodiment, there is an effect that the occurrence of defective products can be suppressed by individually detecting in advance cases where welding defects are likely to occur.

[0120] (2) The case body 21 is clamped by the reference long-side clamp C LF opposing the movable long-side clamp C LM . The image recognition unit 50 calculates the case width D 20 from the position of the clamp C by the opposing position detectors P. Then, an abnormality of the case body 21 is detected by comparing it with the case width M 20 of the standard product M. For this reason, there is an effect that an abnormal case body 21 can be excluded from the production line in advance.

[0121] (3) When welding a plurality of battery cases 20 together, the case width D of the case body 21 20 is measured continuously. th Case width M than standard product M 20 The continuous control value judgment threshold D is close to S If the measurement value measured consecutively for a set number of times (for example, four times) is less than the tolerance threshold D th Within the range of the continuous control value judgment threshold D S In this case, check the dimensions of the case body 21 and adjust the allowable threshold D as necessary. th A step of determining the continuous control value that changes the value is executed.

[0122] Therefore, for example, if the thickness of the side surface 21a is formed too thick due to the mold, by correcting the threshold value taking into account the tendency of these dimensional errors, it is possible to prevent unnecessary defective product determinations. Also, by correcting the joint portion WP in response to these, it is possible to manufacture high-quality lithium-ion secondary batteries 2.

[0123] (4) Also, the tolerance threshold D th Case width M than standard product M 20 The moving average value judgment threshold D is close to A Set the case width D, which is the measurement value measured consecutively a set number of times (for example, four times). 20 The moving arithmetic mean value of th The moving average value is within the range of the threshold D A In this case, check the dimensions of the case body 21 and adjust the allowable threshold D as necessary. th A moving average value determination step is performed to change the moving average value.

[0124] Therefore, for example, if the clamp C does not come into close contact with the case body 21 due to a foreign object, the case width D 20Even if the measured value is large, it is averaged with the other measured values. This makes it possible to suppress the influence of the variations even when there is variation in the individual measured values, and correctly determine the dimensional trends of the entire production lot. By incorporating the trends of these dimensional errors and correcting the threshold value, it is possible to prevent unnecessary product defects. In addition, by correcting the joint portion WP in response to these errors, it is possible to manufacture high-quality lithium-ion secondary batteries 2.

[0125] (5) In the case width determination step (S21), the case width D 20 is the tolerance threshold D th In such a case, the exposure conditions of the imaging unit 40 are changed and the case width determination step (S21) is performed again.

[0126] Therefore, for example, case width D 20 is the tolerance threshold D th If it is determined that the case width D is not within the range, the exposure conditions of the imaging unit 40 are inappropriate, and this is the cause 20 is the tolerance threshold D th Therefore, it may be judged that the case width D 20 is the tolerance threshold D th If the result is outside the above range, the exposure conditions of the image capturing unit 40 are checked, and if the exposure conditions are inappropriate, the exposure conditions are changed and a retry is performed. This has the effect of preventing erroneous recognition due to the exposure conditions.

[0127] (6) In the step (S26) of determining the case position deviation, the case width M of the standard product M is 20 and the case width D of the case body 21 20 Difference ΔD 20 Calculate the difference ΔD 20 The threshold ΔD 20th The camera center distance M from the camera center Ax of the imaging unit 40 to the side surface 21a of the case body 21 of the standard product M is compared with CA and the camera center distance D from the camera center Ax to the side surface 21a of the case body 21. CAThe difference between these values ​​makes it possible to calculate the deviation in the width direction between the side surface 21a of the standard product M and the side surface 21a of the case body 21.

[0128] (7) Case width M of standard product M 20 and the case width D of the case body 21 20 Difference ΔD 20 Calculate the difference ΔD 20 The threshold ΔD 20th The camera center distance M from the camera center Ax of the imaging unit 40 to the side end surface of the case body 21 of the standard product M is compared with CA and the camera center distance D from the camera center Ax to the side surface 21a of the case body 21. CA The difference is used to calculate the deviation in the width direction between the side surface 21a of the standard product M and the side surface 21a of the case body 21. 20 is within the allowable range, it is possible to determine whether or not the position is deviated from the specified position.

[0129] (8) In this case, if the case body 21 is significantly misaligned with the imaging range IA, it becomes difficult to irradiate the laser beam in conjunction with the imaging range IA. In particular, if the tilt with respect to the imaging range IA is large, it is not possible to simultaneously guide the movable long side clamp position detector P1 and the movable long side clamp position detector P2 to the appropriate positions.

[0130] Therefore, the tilt detection step (S27) is executed. LF and movable long side clamp C LM The case body 21 is clamped by these clamps. The imaging unit 40 then recognizes the pair of reference long side clamp position detectors P5 and P4 and the pair of movable long side clamp position detectors P1 and P2 that face each other in the width direction. The difference in widthwise position between the pair of reference long side clamp position detectors P5 and P4 and the difference in widthwise position between the pair of movable long side clamp position detectors P1 and P2 are detected. This difference has the effect of enabling the tilt of the case body 21 in the longitudinal direction to be detected.

[0131] (9) In the step of recording the cause of the tilt error (S30), the difference in the widthwise positions of the pair of reference long side clamp position detectors P5 and P4 is compared with the difference in the widthwise positions of the pair of movable long side clamp position detectors P1 and P2. From this comparison, the one with the larger difference in the widthwise positions is identified and recorded as the cause of the tilt error.

[0132] This has the effect of enabling the causes of tilt errors during the manufacturing process to be collected as so-called traceability data, and improving the manufacturing process. (10) In the step (S28) of determining the degree of clamp contact, the width M of the position detection part of the standard product M is P and case width M 20 Difference ΔM 20 and the width of the position detection section D P and the case width D of the case body 21 20 The difference between the contact threshold ΔP and

[0133] This makes it possible to determine the degree of contact between the clamp C and the case body 21. By accurately determining the degree of contact, it is possible to effectively detect erroneous recognition. (11) In the step (S33) of recording the cause of poor adhesion, the width M of the position detection part of the standard product M P and case width M 20 Difference ΔM 20 and the width of the position detection section D P and the case width D of the case body 21 20 Difference ΔD 20 It is determined whether the difference between the reference long side clamp position detectors P5 and P4 and the movable long side clamp position detectors P1 and P2 is greater than the contact threshold value ΔP. If the difference is large, it is determined that there is poor contact between the clamp C and the side surface 21a of the case body 21. The difference in widthwise position between the pair of reference long side clamp position detectors P5 and P4 is then compared with the difference in widthwise position between the pair of movable long side clamp position detectors P1 and P2. The larger difference in widthwise position is then identified and recorded as the cause of the poor contact.

[0134] This has the effect of enabling the causes of poor adhesion during the manufacturing process to be collected as so-called traceability data, and improving the manufacturing process. (12) The above effects work together to prevent the occurrence of poorly welded lithium ion secondary batteries 2.

[0135] (Variation) The above embodiment is an example of the implementation of the present invention, and can be implemented with the following modifications.

[0136] The groove-shaped position detection part P does not reflect external illumination, so the luminance Lu [cd / m 2 ] is extremely low, but on the other hand, the internal lighting in the grooves makes it appear high in luminance Lu [cd / m 2 ] may be displayed.

[0137] Furthermore, the arrangement of the position detection units P is not limited to the example shown, and the number and positions of the position detection units P can be freely changed. For example, multiple position detection units P can be arranged on the short side.

[0138] The configuration of the position detection unit P is not limited to the groove-shaped configuration shown as an example, and is not limited to, for example, coloring or surface processing, as long as the image recognition unit 50 can recognize the image from the video captured by the imaging unit 40.

[0139] The shape, number, position, etc. of the clamp C are not limited to those illustrated, and the clamp C may be configured to be divided into two. In this embodiment, a lithium-ion secondary battery 2, which is a plate-shaped cell battery for vehicle use, is used as an example of a nonaqueous electrolyte secondary battery. However, the present invention is not limited to this, and can be implemented for other applications, such as stationary applications. Furthermore, the present invention is not limited to the lithium-ion secondary battery 2 shown as an example, and can be applied to any battery in which a metal battery case 20 is airtightly sealed with a lid 22 by laser welding to a case body 21. Furthermore, the present invention is not limited to a plate-shaped battery case 20, and can be applied to, for example, a battery case in which the opening 21c is square, or a battery case formed of opposing flat surfaces and a curved surface connecting them, such as a racing track.

[0140] The drawings are for use in explaining the present embodiment, and are not intended to be limiting, as some figures may be omitted or dimensional balance may be exaggerated for clarity.

[0141] The flowcharts shown in Figures 9, 10, and 11 are examples of the present invention, and steps can be added, deleted, their order changed, or replaced with different procedures without departing from the scope of the claims.

[0142] Various numerical values ​​and ranges are examples and can be optimized and implemented by those skilled in the art. Furthermore, data processing and utilization methods can be optimized according to the purpose by those skilled in the art, and the methods are not limited to these.

[0143] This embodiment is one embodiment of the present invention, and it goes without saying that those skilled in the art can add, delete, or modify the configuration without being limited to the embodiment, as long as it does not deviate from the scope of the claims. [Explanation of symbols]

[0144] C...Clamp C LF …Standard long side clamp C LM ... Movable long side clamp C SF …Standard short side clamp C SM ... Movable short side clamp P...Position detection section P R …Reference surface P1 (upper left)...(negative side) movable long side clamp position detector P2 (top right)...(positive pole side) movable long side clamp position detector P3 (right side)...(positive side) Reference short side clamp position detection part P4 (bottom right)...(positive side) reference long side clamp position detector P5 (bottom left)...(negative side) Reference long side clamp position detector P6 (left side)...(negative side) Movable short side clamp position detection part WP…joint part G OUT …First gap part G IN …Second gap part D…width D th …tolerance threshold D 20 …(measured) case width (=D 22 +D 21 ×2+D GIN ×2) D CL …Clamp width D PR … Position detection section width D CA ...Camera center distance D S …Continuous control value judgment threshold D A …Moving average value judgment threshold D 22 …Lid width D 21 …Case body thickness DG OUT …First gap width DG IN …Second gap width D L …Case length M…Standard product M 20 …(standard product) case width M 21 …(Standard product) case thickness M 22 …(Standard product) lid width M CL …Clamp width (standard product) M PR …(Standard product) Position detection section width M CA …Camera center distance (standard product) M L …(Standard product) case length ΔP…adhesion threshold ΔD 20 …difference ΔD 20th … Deviation threshold ΔM 20 …Width of the position detection part of standard product M P and case width M20 The difference with Lu [cd / m 2 ]…brightness Lu th [cd / m 2 ]…Luminance threshold 1...Laser welding device, 2...Lithium-ion secondary battery 20...Battery case 21...Case body 21a...side 21b…bottom 21c...Opening 22...lid body 23...Negative electrode connection part 24...Negative external terminal 25...Positive electrode connection 26...Positive external terminal 27…Nonaqueous electrolyte 28...Electrode body 30...Head unit (laser irradiation device) LB...laser light 40...imaging unit IA...Imaging range Ax...Camera center 50...Image recognition unit 60...Laser irradiation condition determination unit 70...Control unit

Claims

1. A laser welding method for a battery case including a cylindrical case body with a bottom having a rectangular bottom, four side surfaces, and a rectangular opening that opens at a top, and a lid body arranged to close the opening of the case body, using a laser welding device to irradiate a joint between the opening and the lid body with laser light, The laser welding apparatus includes: Clamps C each having a position detection unit P and contacting a side surface of the case body; a laser irradiation device that irradiates laser light onto the joint portion of the case body fixed to the clamp C; an imaging unit that images the joint portion; a control unit that controls the clamp C, the laser irradiation device, and the imaging unit, The clamp C is a reference long side clamp C that contacts one long side of the rectangle. ＬＦ and, A movable long side clamp C contacting the other long side of the rectangle ＬＭ and, Equipped with The position detection unit P is The reference long side clamp C ＬＦ a pair of reference long side clamp position detecting units P5 and P4 that are provided at positions symmetrical with respect to the center of the longitudinal direction of the clamping member P1; and The movable long side clamp C ＬＭ a pair of movable long side clamp position detectors P1 and P2 that are provided at positions opposite to the pair of reference long side clamp position detectors P5 and P4 in the width direction and whose positions are recognized by the imaging unit, The control unit The reference long side clamp C ＬＦ and the movable long side clamp C ＬＭ By clamping the case body with the above-mentioned clamping members, the imaging unit recognizes the reference long side clamp position detection units P5 and P4 and the movable long side clamp position detection units P1 and P2, respectively. Based on the recognized position detection unit P, the side surface of the case body is detected by the imaging unit, Based on the detected position of the side surface of the case body, the case width D in the width direction perpendicular to the longitudinal direction of the rectangular case body is calculated. ２０ and measure The case width M of the standard product M ２０ The tolerance threshold D based on ｔｈ is stored, and the case width D of the measured case body is ２０ The tolerance threshold D ｔｈ Execute the case width determination step to compare with A laser welding method characterized by:

2. The control unit In the case width determination step, the case width D ２０ is the tolerance threshold D ｔｈ 2. The laser welding method according to claim 1, wherein if the case width is not within the above range, the exposure conditions of the imaging unit are changed and the case width determination step is performed again.

3. The control unit The luminance Lu [cd / m ２ ] and the measured luminance Lu [cd / m ２ ] is the set brightness threshold Lu ｔｈ [cd / m ２ ] and a step of determining the luminance of the joint portion by comparing the luminance of the joint portion with the luminance of the The luminance Lu [cd / m ２ ] is the brightness threshold value Lu ｔｈ [cd / m ２ 2. The laser welding method according to claim 1, wherein, if the difference is outside the range, the exposure conditions of the imaging unit are changed and the case width determination step is performed again.

4. The control unit When a plurality of the battery cases are welded together, the case width D of the case body is ２０ is continuously measured, and the tolerance threshold D ｔｈ The case width M of the standard product M is ２０ The continuous control value judgment threshold D is close to Ｓ is set, and the measurement value measured continuously the set number of times is set to the allowable threshold D ｔｈ The continuous control value determination threshold D Ｓ If the size is outside the range of the allowable threshold D, the size of the case body 21 is checked and, if necessary, ｔｈ 2. The laser welding method according to claim 1, further comprising the step of determining a continuous control value that changes the control value.

5. The control unit When a plurality of the battery cases are welded together, the case width D of the case body is ２０ is continuously measured, and the tolerance threshold D ｔｈ The case width M of the standard product M is ２０ The moving average value judgment threshold D is close to Ａ The average value of the measured values ​​measured continuously for the set number of times is set to the allowable threshold value D ｔｈ The moving average value determination threshold D Ａ If the size is outside the range of the allowable threshold D, check the dimensions of the case body and, if necessary, ｔｈ 2. The laser welding method according to claim 1, further comprising the step of determining a moving average value by changing the moving average value.

6. The clamp C is A reference short side clamp C that contacts one short side of the rectangle ＳＦ and, Movable short side clamp C in contact with the other short side of the rectangle ＳＭ and The reference short side clamp C ＳＦ The reference short side clamp position detection unit P3, the position of which is recognized by the imaging unit, and the movable short side clamp C ＳＭ and a movable short side clamp position detection unit P6, the position of which is recognized by the imaging unit, The control unit The reference short side clamp C ＳＦ and the movable short side clamp C ＳＭ By clamping the case body with the clamping members, the imaging unit recognizes the reference short side clamp position detection unit P3 and the movable short side clamp position detection unit P6, and the case length D in the longitudinal direction of the rectangular shape of the case body is measured. Ｌ and measure The case length D of the standard product M stored in advance Ｌ The tolerance threshold D based on ｔｈ and the measured case length D of the case body. Ｌ Execute the step to determine the case body length by comparing 2. The laser welding method according to claim 1.

7. The control unit Case width M of the standard product M ２０ and the case width D of the case body ２０ The difference ΔD ２０ Calculate the difference ΔD ２０ is the threshold value ΔD ２０ｔｈ In comparison with The distance M from the camera center Ax of the imaging unit to the side end surface of the case of the standard product M ＣＡ and a camera center distance D from the camera center Ax to the side surface of the case body. ＣＡ 2. The laser welding method according to claim 1, further comprising the step of: comparing the measured values ​​of the standard product M and the case body M with each other; and calculating the widthwise deviation between the side surface of the standard product M and the side surface of the case body M from the difference between the measured values ​​of the standard product M and the case body M.

8. The control unit The reference long side clamp C ＬＦ and the movable long side clamp C ＬＭ By clamping the case body with the above-mentioned clamping members, the pair of reference long side clamp position detecting units P5 and P4 and the pair of movable long side clamp position detecting units P1 and P2 facing each other in the width direction are recognized by the imaging unit, The laser welding method described in claim 1, characterized in that a tilt detection step is performed to detect the tilt of the case body in the longitudinal direction from at least one of the difference in widthwise position between the pair of reference long side clamp position detection units P5 and P4 and the difference in widthwise position between the pair of movable long side clamp position detection units P1 and P2.

9. The control unit The laser welding method according to claim 8, further comprising the step of: comparing the difference in widthwise position between the pair of reference long side clamp position detection units P5 and P4 with the difference in widthwise position between the pair of movable long side clamp position detection units P1 and P2; and identifying and recording the one with the larger difference in widthwise position as the cause of the tilt error.

10. The control unit Width M of the position detection part of standard product M Ｐ and case width M ２０ The difference ΔM ２０ and the position detection section width D Ｐ and the case width D of the case body ２０ 2. The laser welding method according to claim 1, further comprising the step of: determining the degree of contact between the clamp C and the case body by comparing the difference between the contact threshold ΔP and the clamp C.

11. The control unit Width M of the position detection part of standard product M Ｐ and case width M ２０ The difference ΔM ２０ and the position detection section width D Ｐ and the case width D of the case body ２０ The difference ΔD ２０ If the difference is greater than the contact threshold value ΔP, it is determined that the contact between the clamp and the side surface of the case body is poor, The laser welding method described in claim 10, characterized in that a step of recording the cause of poor adhesion is carried out, in which the difference in widthwise position between the pair of reference long side clamp position detection units P5 and P4 is compared with the difference in widthwise position between the pair of movable long side clamp position detection units P1 and P2, and the one with the larger widthwise difference is identified and recorded as the cause of poor adhesion.

12. A laser welding device for a battery case including a cylindrical case body with a bottom having a rectangular bottom, four side surfaces, and a rectangular opening that opens at a top, and a lid body arranged to close the opening of the case body, the laser welding device irradiating a joint portion WP between the opening and the lid body with laser light LB to weld the case body and the lid body, four clamps C each having a position detection unit P and contacting four side surfaces of the case body, respectively; a laser irradiation device that irradiates the joint portion WP of the case body fixed to the clamp C with a laser beam LB; an imaging unit that images the joint part WP; a control unit that controls the clamp C, the laser irradiation device, and the imaging unit, The clamp C is a reference long side clamp C that contacts one long side of the rectangle. ＬＦ and, A movable long side clamp C contacting the other long side of the rectangle ＬＭ and, A reference short side clamp C that contacts one short side of the rectangle ＳＦ and, Movable short side clamp C in contact with the other short side of the rectangle ＳＭ and The position detection unit P is The reference long side clamp C ＬＦ a pair of reference long side clamp position detecting units P5 and P4 that are provided at positions symmetrical with respect to the center of the longitudinal direction of the clamping member P1; and The movable long side clamp C ＬＭ a pair of movable long side clamp position detectors P1 and P2 that are provided at positions opposite to the pair of reference long side clamp position detectors P5 and P4 in the width direction and whose positions are recognized by the imaging unit, The control unit The reference long side clamp C ＬＦ and the movable long side clamp C ＬＭ By clamping the case body with the above-mentioned clamping members, the imaging unit recognizes the reference long side clamp position detection units P5 and P4 and the movable long side clamp position detection units P1 and P2, respectively. Based on the recognized position detection unit P, the imaging unit detects the case side surface, which is the side surface of the case main body, Based on the detected position of the side surface of the case body, the case width D in the width direction perpendicular to the longitudinal direction of the rectangular case body is calculated. １ and measure The case width M of the standard product M ２０ The tolerance threshold D based on ｔｈ is stored, and the case width D of the measured case body is ２０ The tolerance threshold D ｔｈ Execute the case width determination step to compare with A laser welding device characterized by:

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