Welding device for button-type secondary battery

Abstract

A welding device for a button-type secondary battery, by which an electrode tab protruding from an electrode assembly is welded to a can in which the electrode assembly is installed. The welding device is characterized by including: a base which faces an upper side of an inner surface of the can and supports a bottom surface of the can when the electrode tab contacts the inner surface of the can; a jig which is disposed on the base and fixes the electrode tab on the base, and has a through-hole through which a laser is emitted to weld the electrode tab to the can; a laser irradiation device which emits a laser to the through-hole when the jig fixes the electrode tab to the can; and four probes which are installed to the base or the jig. Two of the probes are connected to a power source and allow a current to flow to a welding area of the can and the electrode tab when in contact with the welding area, and the remaining two probes are connected to a voltmeter and measure a voltage at the welding area when in contact with the welding area.

Description

TECHNICAL FIELD

[0001] This application claims priority to Korean Patent Application No. 10-2020-0149609, filed on November 10, 2020, the entire contents of which are incorporated herein by reference.

[0002] The present application relates to a welding device for a coin type secondary battery, and more particularly, to a welding device capable of welding an electrode tab of an electrode assembly to an electrode tab by using a laser, in which whether a welding defect occurs is rapidly checked after welding by measuring a resistance value at a welding point. BACKGROUND

[0003] A coin type battery or a coin type battery generally used as a coin type battery has a thin coin shape and is widely used in various devices such as a remote controller, a watch, a toy, a computer part, etc.

[0004] Such a coin type battery is mainly manufactured as a non-rechargeable primary battery, but as a small-sized device is developed, it is also widely manufactured as a rechargeable and dischargeable secondary battery.

[0005] In addition, like a coin type secondary battery or a cylindrical or pouch type secondary battery, the coin type secondary battery also has a structure in which an electrode assembly and an electrolyte are embedded in a case to repeatedly perform charging and discharging.

[0006] Specifically, the coin type secondary battery has different properties in that the structure is simpler and the height of the can is low, but the similar point in the structure is that a jelly-roll type electrode assembly is installed in the inside of the can.

[0007] The coin type secondary battery is manufactured in a form in which the electrode assembly is embedded in a can formed by connecting an upper can to a lower can.

[0008] The electrode assembly is manufactured by winding a separator, a negative electrode, a separator, and a positive electrode in a stacked state around a core. Accordingly, the electrode assembly has a structure in which a center hole is formed in the center after the core is removed and is manufactured so that electrode tabs (a negative electrode tab and a positive electrode tab) protrude upward and downward, respectively. In general, when the electrode tabs are located in the lower can, the electrode tab disposed on the upper side is the positive electrode tab, and the electrode tab disposed on the lower side is the negative electrode tab. That is, when the electrode assembly is embedded, the upper can and the lower can are coupled and sealed so that the upper can and the lower can are electrically insulated from each other. Here, the upper can is connected to the positive electrode tab to form a positive electrode, and the lower can is connected to the negative electrode tab to form a negative electrode.

[0009] As Figure 1aAs shown, it shows a state in which the electrode tab is welded to the upper can in the process of assembling the button-type secondary battery according to the related art, in a state in which the electrode assembly 3 is installed in the lower can 2 such that the negative electrode tab 3b among the electrode tabs 3a, 3b according to the related art is disposed inside the central hole, laser is irradiated to weld the negative electrode tab 3b on the bottom surface inside the lower can 2, and the positive electrode tab 3a is pulled out to the outside and then welded to the inner surface of the can 1 which is the upper can. After the welding is performed in a state in which the can 1 is disposed on the base 6 such that the inner surface thereof faces the upper side, the can 1 is press-fitted into the upper portion of the lower can 2 and then coupled.

[0010] When the welding is performed in a state in which the positive electrode tab 3a is disposed on the inner surface of the can 1, in a state in which the jig 7 having a tubular shape presses and fixes the positive electrode tab, if laser is irradiated from the laser irradiation device 5 through the hole of the jig 7, the positive electrode tab 3a is melted and welded to the can 1.

[0011] The magnitude of the resistance value between the electrode tab 3a and the can 1 varies according to the length of the bead generated at the welding portion during the welding.

[0012] That is, referring to Figure 1b which exemplifies the bead shape during weak welding and the bead shape during normal welding, and shows a graph showing the difference in internal resistance during weak welding and normal welding, when the normal welding is performed for a sufficient length to form a bead having a long length, the contact area between the electrode tab 3a and the can 1 increases, and thus, the DC resistance as the internal resistance between the electrode tab 3a and the can 1 relatively decreases. However, when a sufficient bead is not formed and weak welding is performed, the contact area between the electrode tab 3a and the can 1 decreases, and thus, the magnitude of the DC resistance relatively increases. SUMMARY

[0013] TECHNICAL PROBLEM

[0014] Therefore, the main object of the present application is to provide a welding device for a button-type secondary battery which is capable of determining whether a welding defect occurs immediately after the welding is performed using the phenomenon that the magnitude of the internal resistance varies according to the welding quality as described above.

[0015] TECHNICAL SOLUTION

[0016] A welding device for a button-type secondary battery according to the present application to achieve the above object, which welds an electrode tab protruding from an electrode assembly to a can in which the electrode assembly is installed, the welding device including: a base configured to support a bottom surface of the can when an inner surface of the can faces an upper side and the electrode tab is in contact with the inner surface of the can; a jig provided on the base to fix the electrode tab on the base and having an open hole through which a laser is passed to weld the electrode tab to the can; a laser irradiation device configured to irradiate a laser to the open hole when the jig fixes the electrode tab to the can; and four probes installed on the base or the jig, wherein two of the probes are connected to a power source so that a current flows to a welded portion of the electrode tab when the probes are in contact with the welded portion, and the remaining two of the probes are connected to a voltmeter to measure a voltage at the welded portion when in contact with the welded portion.

[0017] Two of the four probes can be installed on the jig, and two of the four probes can be installed on the base.

[0018] A gap between the two probes through which a current flows can be greater than a gap between the two probes connected to the voltmeter.

[0019] Alternatively, the two probes through which a current flows can be installed on the jig, and the two probes connected to the voltmeter can be installed on the base, or the two probes through which a current flows can be installed on the base, and the two probes connected to the voltmeter can be installed on the jig.

[0020] The probes can be disposed at a predetermined distance apart from a point at which the laser is irradiated.

[0021] The jig can be capable of ascending and descending to approach the base when descending and to be away from the base when ascending.

[0022] Each of the probes can be a pogo pin disposed to be pressed against an elastic force of a spring inside the probe.

[0023] The welding device can further include a controller to calculate a resistance of each of the welded portions by calculating a current supplied from the power source and a voltage measured by the voltmeter, and to compare the calculated resistance with input data to determine whether a welding defect occurs.

[0024] When the probes are installed on the base or the jig, the probes can be installed to be electrically insulated from the base and the jig.

[0025] Technical Effects

[0026] The welding device for a coin-type secondary battery of the present application having the above technical features can determine whether a welding defect occurs immediately after performing welding by measuring the resistance between the electrode tab and the can.

[0027] The probe can be disposed at a predetermined distance apart from the point of laser irradiation, thereby preventing thermal damage caused by the laser from occurring.

[0028] The clamp can be configured to rise and fall to approach the base when falling and to be away from the base when rising, thereby measuring the resistance of secondary batteries having various sizes.

[0029] The probe can be provided as a spring needle that is pressed against the internal elastic force of the spring, such that the probe is in contact with the surface of the electrode tab and the can at an appropriate pressure without leaving a scratch on the surface.

[0030] A controller can be further provided that determines whether a welding defect occurs by comparing the calculated resistance with data input in advance, to more quickly determine whether a welding defect occurs.

[0031] The probe can be mounted to be electrically insulated from the base or the clamp, thereby preventing the measured value from being changed due to external factors. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1a FIG. 1 is a diagram illustrating a state in which an electrode tab is welded to an upper can in a process of assembling a coin-type secondary battery according to the related art.

[0033] Figure 1b FIG. 3 is a diagram illustrating a bead shape during weak welding and a bead shape during normal welding, and is a graph showing a difference in internal resistance during weak welding and normal welding.

[0034] Figure 2 FIG. 4 is a simplified diagram illustrating a welding device for a coin-type secondary battery according to the present application.

[0035] Figure 3 FIG. 5 is a diagram illustrating a state in which a can and an electrode tab are placed on the welding device shown in FIG. 4 and before the clamp is lowered. Figure 2

[0036] FIG. 7 is a diagram illustrating a state in which the clamp is lowered and laser is irradiated in the state of FIG. 6. Figure 4 Figure 2

[0037] Figure 5

[0038] Figure 6 ​​​is a graph illustrating a change in DC resistance and separation strength according to weld length. DETAILED DESCRIPTION

[0039] Hereinafter, preferred embodiments of the present application will be described in detail with reference to the accompanying drawings so as to be easily practiced by those of ordinary skill in the art to which the present application pertains. However, the present application can be embodied in different forms and should not be construed as limited to the embodiments set forth herein.

[0040] In order to clearly describe the present application, portions unrelated to the description are omitted, and the same reference numerals are assigned to the same or similar components throughout the specification.

[0041] In addition, the terms or words used in the present specification and claims should not be interpreted as being limited to the ordinary meanings or the meanings based on the dictionary meanings, but should be interpreted as having meanings and concepts conforming to the technical spirit of the present application based on the principle that the inventor can properly define the concept of the terms to best describe and conceptualize his or her application.

[0042] The present application relates to a welding device for a button-type secondary battery, which is capable of calculating an internal resistance by applying electric power between an electrode tab (positive electrode tab) and a can (upper can), and comparing an internal resistance value after performing welding with a phenomenon that a magnitude of the internal resistance varies according to a welding quality, to determine whether the welding quality is defective.

[0043] Hereinafter, embodiments according to the present application will be described with reference to the accompanying drawings.

[0044] Embodiment 1

[0045] Figure 2 is a simplified diagram illustrating a welding device for a button-type secondary battery according to the present application, Figure 3 is a diagram illustrating a state in which a can and an electrode tab are placed on Figure 2 the welding device shown in the drawing, and before a clamp is lowered, and Figure 4 is a diagram illustrating a state in which the clamp is lowered and laser light is irradiated in Figure 2 the state.

[0046] The welding device for a button-type secondary battery provided in the present embodiment is configured to weld an electrode tab 3a protruding from an electrode assembly to a can 1 in which the electrode assembly 3 is installed, and includes a base 10, a clamp 20, a laser irradiation device 30, and four probes 40 (41 and 42). In the present application, it is assumed that the electrode tab 3a is a positive electrode tab, and the can 1 is an upper can. However, the electrode tab can be a negative electrode tab, and the can can be a lower can according to a welding position.

[0047] The base 10 is configured as a flat plate with a predetermined thickness to support the bottom surface of the can 1 when the electrode connector 3a contacts the inner surface of the can 1, and also has a structure with a plurality of vertically punched holes for inserting probes 42 (42a and 42b).

[0048] A clamp 20 is mounted on a base 10 to press an electrode connector 3a mounted on the base 10 under load, and an opening 21 is formed to allow a laser for welding the electrode connector 3a to the tank 1 to pass through it. While the size and shape of the clamp 20 are not limited, the lower end resting on the electrode connector 3a has sufficient dimensions to rest on the electrode connector 3a and sufficient thickness to prevent thermal damage during laser irradiation. Furthermore, it has a structure with multiple holes punched out for inserting probes 41 (41a and 41b).

[0049] When the clamp 20 fixes the electrode connector 3a to the tank 1, the laser irradiation device 30 irradiates the electrode connector 3a through the opening 21, causing the electrode connector 3a to melt and be welded to the surface of the tank 1.

[0050] The laser irradiation device 30 irradiates the laser under controlled output and irradiation path conditions, thereby forming a weld bead with a predetermined width and length.

[0051] In addition, two probes 41a and 42a are mounted on the base 10, and two probes 41b and 42b are mounted on the fixture 20. That is, a total of four probes 40 (41 and 42) are mounted on the base 10 and the fixture 20 respectively.

[0052] Two probes 41 (41a and 41b) of probe 40 are connected to power supply 50 to contact the welded portion of can 1 and electrode connector 3a, thereby allowing current to flow to the welded portion, and the remaining two probes 42 (42a and 42b) of probe 40 are connected to voltmeter 60 to measure the voltage at the welded portion when in contact with the welded portion.

[0053] Since the input current and voltage are known, the resistance at the solder joint can be calculated according to Ohm's law.

[0054] In other words, such as Figure 6 As shown, it illustrates the changes in DC resistance and separation strength with weld length. It can be seen that the longer the weld length (that is, the weld length), the lower the DC resistance value, and the greater the separation strength between electrode joint 3a and tank 1.

[0055] Therefore, if the output of the laser irradiated from the laser irradiation device 30 and the resistance value relative to the moving distance are higher than the reference value, the weld can be identified as defective, and if the resistance value is within the predetermined reference value range, the weld can be identified as normal.

[0056] Accordingly, the welding device for a coin-type secondary battery according to the present embodiment can include a controller 70 that calculates the resistance of the welding portion by calculating the current supplied from the power supply 50 and the voltage measured by the voltmeter 60, and compares the calculated resistance with input data to determine whether a welding defect has occurred.

[0057] When the resistance value is high and thus it is confirmed that a welding defect has occurred, the controller 70 can be linked to or communicate with the laser irradiation device 30 so that the laser is additionally irradiated to and / or near the welding point.

[0058] As described above, two of the four probes 40 in the present embodiment are mounted on the jig 20, and two are mounted on the base 10, so that the resistance is measured at four points. Here, the gap d1 between the two probes 41a, 41b through which the current flows is set to be wider than the gap d2 between the two probes 42a, 42b connected to the voltmeter 60. Here, it is preferable that the distances between the probes 41a, 41b, 42a, 42b are constant in the vertical direction (i.e., it is preferable that the gaps between the probes 41a and 42a among the probes, the gap between the probes 42a and 42b, and the gap between the probes 42b and 41b are all constant).

[0059] Accordingly, when the current flows between the probes 41a and 41b mounted on the upper jig 20, the voltage can be measured by the probes 42a and 42b mounted on the lower base 10. Here, the resistance at the point (welding point) at which the probes 40 are in contact can be calculated.

[0060] Figures 2 to 4 , the two probes 41a and 41b through which the current flows are mounted on the jig 20, and the two probes 42a and 42b connected to the voltmeter 60 are mounted on the base 10. Alternatively, the two probes 41a and 41b through which the current flows are mounted on the base 10, and the two probes 42a and 42b connected to the voltmeter 60 can be mounted on the jig 20.

[0061] In addition, the probes 42a and 42b mounted on the base 10 are disposed at a predetermined distance from the point of laser irradiation to prevent heat damage caused by welding from occurring. That is, the laser welding point is preferably determined to be between the probes 42a and 42b mounted on the base 10.

[0062] Further, the jig 20 can be configured to rise and fall to approach the base 10 when falling and to move away from the base 10 when rising. In addition, when the probes 40 are mounted on the base 10 or the jig 20, it is preferable that the probes 40 are mounted to be electrically insulated from the base 10 or the jig 20 (e.g., the probes are mounted in a state of being coupled to an insulating pad on the outer surface in contact with the jig or the base or in a state of being coated with an insulating layer).

[0063] Embodiment 2

[0064] In the present invention, a probe as a pogo pin is provided as Embodiment 2.

[0065] Typically, a probe commonly called a pogo pin is a probe provided with a spring installed therein and contactable using an elastic force applied therein. In general, the probe is mainly used when inspecting an electronic circuit or a semiconductor chip.

[0066] Referring to Figure 5 which illustrates an exploded view of a probe having a pogo pin structure, each of the probes 40 (41 and 42) provided in the present embodiment includes a hollow tubular body 45, a spring 44 inserted into the body 45, a first probe 43 having a portion inserted into one side of the body 45 and having an end portion fixed to one end of the spring 44, and a second probe 46 configured to support the other end of the spring 44 and having a portion inserted into the other side of the body 45.

[0067] Here, the first probe 43 and the second probe 46 are prevented from being separated from the body 45 and are coupled to press the spring 40 such that the spring is pressed by a predetermined distance (inserted into the body).

[0068] In addition, any one of the first probe 43 and the second probe 46 is electrically connected to a power source 50 or a voltmeter 60 for applying a current, and the other is provided to be in contact with the electrode terminal 3a or the can 1.

[0069] Therefore, when the jig 20 is disposed on the electrode terminal 3a and the can 1 in a state in which the electrode terminal 3a and the can 1 are seated on the base 10, in the probes 41 and 42 having the above-described pogo pin structure, since the probes 43 and 46 are retracted by the pressing of the spring 44, it is possible to secure stable contact of the electrode terminal 3a and the can 1 while maintaining electrical connection.

[0070] The spring 44 is made of a metal having electrical conductivity so that the first probe 43 and the second probe 46 are electrically connected, and an insulating layer can be applied to an outer surface of the body 45 to be insulated from the base 10 and the jig 20.

[0071] The welding device for a coin-type secondary battery of the present invention having the technical characteristics as described above can determine whether a welding defect occurs immediately after performing welding by measuring the electrical resistance between the electrode terminal 3a and the can 1.

[0072] The probe 40 can be disposed to be spaced apart from a point of laser irradiation by a predetermined distance, thereby preventing occurrence of thermal damage caused by laser.

[0073] The clamp 20 can be configured to rise and fall to approach the base 10 when falling and to be away from the base 10 when rising, thereby measuring the resistance of the secondary battery having various sizes.

[0074] The probe 40 can be provided as a spring needle that overcomes the internal elastic force of the spring and is pressed, such that the probe is in contact with the electrode terminal 3a and the surface of the can 1 under appropriate pressure without leaving a scratch on the surface.

[0075] A controller 70 can be further provided, which determines whether a welding defect occurs by comparing the calculated resistance with data input in advance, to more quickly determine whether a welding defect occurs.

[0076] The probe 40 can be installed to be electrically insulated from the base 10 or the clamp 20, thereby preventing a measured value from being changed due to external factors.

[0077] Although embodiments of the present application have been described with reference to specific embodiments thereof, it is evident that many changes and modifications can be made thereto without departing from the spirit and scope of the application as defined by the appended claims.

[0078] [Description of reference numerals]

[0079] 10: base

[0080] 20: clamp

[0081] 30: laser irradiation device

[0082] 40: probe

[0083] 50: power supply

[0084] 60: voltmeter

[0085] 70: controller

Claims

1. A welding apparatus for a button-type secondary battery that welds an electrode tab protruding from an electrode assembly to a can in which the electrode assembly is installed, the welding apparatus comprising: a base configured to support a bottom surface of the can when an inner surface of the can faces an upper side and the electrode tab is in contact with the inner surface of the can; a jig provided on the base to fix the electrode tab to the can and having an open hole through which a laser is passed to weld the electrode tab to the can; a laser irradiation device configured to irradiate a laser to the open hole when the jig fixes the electrode tab to the can; and four probes mounted on the base or the jig, wherein two of the four probes are connected to a power source so that a current flows to a welded portion of the electrode tab when the two probes are in contact with the welded portion, and the remaining two of the four probes are connected to a voltmeter to measure a voltage at the welded portion when the remaining two probes are in contact with the welded portion, wherein the two of the four probes are mounted on the jig, and the remaining two of the four probes are mounted on the base, and wherein a gap between the two probes through which the current flows is greater than a gap between the two probes connected to the voltmeter connection.

2. The welding device of claim 1, wherein, The two probes through which the current flows are mounted on the jig, and the two probes connected to the voltmeter are mounted on the base.

3. The welding device of claim 1, wherein, The two probes through which the current flows are mounted on the base, and the two probes connected to the voltmeter are mounted on the jig.

4. The welding device of claim 1, wherein, Each probe is provided as a spring needle pressed against an elastic force of a spring inside thereof.

5. The welding device of claim 1, wherein, Each probe comprises:

6. The welding device of any one of claims 1 to 5, wherein, a main body that is a hollow tube; 7. The welding device of claim 6, wherein, the spring inserted into the main body; a first probe having a portion inserted into one side of the main body and having an end portion fixed to one end of the spring; and a second probe configured to support the other end of the spring and having a portion inserted into the other side of the main body. 8.The welding apparatus of claim 6, further comprising a controller that calculates a resistance of each of the welded portions by calculating a current supplied from the power source and a voltage measured by the voltmeter, and compares the calculated resistance with input data to determine whether a welding defect occurs. When the probes are mounted on the base or the jig, the probes are mounted to be electrically insulated from the base or the jig. ​ 9. The welding device of claim 6, wherein, ​

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