Welding apparatus for cylindrical batteries equipped with a welding rod overlap measuring unit

Abstract

The present invention relates to a welding apparatus comprising an upper welding section including an upper welding rod, a first workpiece located below the upper welding rod, a second workpiece located below the first workpiece, and a lower welding section including a lower welding rod located below the second workpiece, wherein the first workpiece and the second workpiece are welded by resistance welding of the upper welding rod and the lower welding rod, and the welding apparatus is equipped with a displacement measuring unit that can measure the displacement of a buffer portion provided at least one of the upper end of the upper welding rod or the lower end of the lower welding rod by additional pressing while the upper welding rod, the first workpiece, the second workpiece, and the lower welding rod are in close contact and facing each other.

Description

Technical Field

[0001] The present invention relates to a welding apparatus for a cylindrical battery provided with a welding rod overlap measurement unit. Specifically, it relates to a welding apparatus for a cylindrical battery provided with a welding rod overlap measurement unit capable of grasping the degree of adhesion of welding rods that contact each other on the upper and lower surfaces of the bottom of a cylindrical can of a cylindrical battery cell when resistance welding the cylindrical can and a negative electrode tab.

Background Art

[0002] A lithium secondary battery includes a positive electrode coated with a positive electrode active material, a negative electrode coated with a negative electrode active material, a separator film located between the positive electrode and the negative electrode to prevent short circuit and allowing the movement of lithium ions (Li-ion) laminated electrode assembly, a battery case housing the electrode assembly, and an electrolytic solution injected inside the battery case to allow the movement of lithium ions.

[0003] Lithium secondary batteries are classified into cylindrical batteries or prismatic batteries that incorporate an electrode assembly in a cylindrical or prismatic metal can depending on the shape of the battery case, and pouch-type batteries that incorporate an electrode assembly in a pouch-shaped case of an aluminum laminate sheet. Cylindrical batteries have the advantages of relatively large capacity and structural safety.

[0004] A cylindrical battery is manufactured by housing a jelly roll electrode assembly in which a separator film sheet is interposed between a positive electrode sheet and a negative electrode sheet and wound, in a cylindrical battery case and sealing it. The jelly roll electrode assembly is housed inside a cylindrical can, and the inner bottom of the cylindrical can and a negative electrode tab located at the lower part of the jelly roll electrode assembly are welded.

[0005] Typically, the negative electrode tab of a cylindrical battery is welded to the bottom of the cylindrical can using resistance welding. Because the negative electrode tab is located at the bottom of the cylindrical battery, resistance welding is often used to avoid the risk of laser irradiation affecting other parts of the jelly roll electrode assembly. The positive electrode tab is often welded to the top cap using laser welding. In the case of pouch-type batteries, laser welding is also used to weld the electrode tab to the electrode lead.

[0006] Figure 1 is an exploded cross-sectional view of a cylindrical battery and a conventional resistance welding apparatus; Figure 2 is a cross-sectional view showing the state in which welding is performed by connecting the cylindrical battery and the conventional resistance welding apparatus; and Figure 3 is a schematic diagram of the upper part of a conventional resistance welding apparatus.

[0007] A conventional resistance welding apparatus will be described with reference to Figures 1 to 3. The cylindrical battery 100 houses a jelly roll electrode assembly 110 inside a cylindrical can 120. A negative electrode tab 130 protrudes from the bottom of the jelly roll electrode assembly 110. For reference, the positive electrode tab is omitted in Figures 1 to 3. The cylindrical battery 100 is fixed to a jig 200 for resistance welding.

[0008] A conventional resistance welding apparatus includes an upper welding section 300 containing an upper welding rod 310 and a lower welding section 400 containing a lower welding rod 410. Prior to performing resistance welding, the cylindrical battery 100 is housed in the jig 200 with the upper welding section 300 and the lower welding section 400 separated vertically. Subsequently, the upper welding section 300 moves downward and the lower welding section 400 moves upward, so that the upper welding rod 310, the negative electrode tab 130, the cylindrical can 120, and the lower welding rod 410 are arranged in that order in the lower region inside the cylindrical can 120.

[0009] For welding, the upper welding rod 310 and the lower welding rod 410 must be in close contact. For resistance welding, the upper welding rod 310 and the lower welding rod 410 must be pressed together. Once the upper welding rod 310, negative electrode tab 130, cylindrical can 120, and lower welding rod 410 are physically in close contact, further movement is impossible. However, for resistance welding, the upper welding rod 310, negative electrode tab 130, cylindrical can 120, and lower welding rod 410 must be in very close contact, and the quality of the weld will vary depending on the degree of this contact.

[0010] The upper welding rod 310 is fixed to the welding rod jig 320 and to the welding rod storage section 330 located at the bottom of the upper welding section 300. A buffer section 340 exists between the welding section body 350, which is located at the top and is used for fixing and moving the entire upper welding section 300, and the welding rod storage section 330.

[0011] Since the upper welding rod 310 and the lower welding rod 410 must be in close contact, the term "overlap" is used to indicate this degree of overlap. However, since the upper welding rod 310 and the lower welding rod 410 cannot physically overlap, the overlap can be indicated as follows.

[0012] The position in which the upper welding rod 310 can move downward and descend without the cylindrical can is measured or set. The welding body 350 and the like are equipped with a control unit that can store the position of the welding rods. The position in which the upper welding rod 310 moves upward again and the lower welding rod 410 rises is measured or set. Here, the set positions of the upper welding rod 310 and the lower welding rod 410 are essentially the positions where the end of the upper welding rod 310 and the end of the lower welding rod 410 overlap. Since the end of the upper welding rod 310 and the end of the lower welding rod 410 cannot physically overlap, the upper welding rod 310 is retracted further back by the buffer section 340 for this reason. The tension on the buffer section 340 changes depending on the degree of retraction, and the greater the degree of retraction, the higher the tension. In other words, by pre-setting the overlap section, the tension applied to the upper welding rod 310 and the lower welding rod 410 can be adjusted, thereby allowing adjustment of the degree of contact between the upper welding rod 310, the negative electrode tab 130, the cylindrical can 120, and the lower welding rod 410.

[0013] Conventional resistance welding apparatuses are equipped with a buffer section 340, but the extent of the buffering is not directly known. Prior to performing welding, an overlap section is set through the aforementioned process, and welding is performed accordingly.

[0014] Since the jelly roll electrode assembly differs for each cylindrical battery, the shape and position of the negative electrode tab 130 differ from one another, the degree to which the jelly roll assembly is inserted into the cylindrical can differs, and the degree to which each cylindrical battery 100 is fixed to the jig 200 may also differ for each cylindrical battery 100. Therefore, if the overlap section is set by a single consistent standard and welding is performed accordingly, it is not possible to grasp the welding quality of each cylindrical battery. Also, since welding is performed several times with a single welding rod, the length of the welding rod changes as welding progresses. Furthermore, since the tension of springs and other components inside the buffer section may change, even if the overlap section is determined by length using conventional technology, the actual pressure applied may not be the same.

[0015] Conventional technologies relied solely on worker observation to identify these problems and lacked concrete means to clearly understand them.

[0016] Patent Document 1 discloses a method and apparatus for joining dissimilar metals, which includes upper and lower electrodes for welding and distance sensors located on the side of the upper electrode. Patent Document 1 directly measures the change in distance to the workpiece while welding is being performed and determines whether the welding can be completed by understanding the degree of this change. In the present invention, resistance welding is used, the welding is performed in a very short time, and the numerical value of the workpiece itself changes to almost nothing due to welding. In the present invention, the change in distance is not measured while welding is being performed, but rather the degree of overlap is determined in advance and welding is simply performed based on this, so the configuration of Patent Document 1, which grasps the change in real time, cannot be applied.

[0017] Patent documents 2 to 4 also do not present a buffer portion corresponding to the main components of the present invention, nor a configuration for confirming their displacement.

[0018] Thus, conventional technology lacks the means to understand or measure the degree of overlap, which is an important factor in resistance welding of cylindrical batteries. [Prior art documents] [Patent Documents]

[0019] [Patent Document 1] Japanese Patent Publication No. 2008-284570

[0020] [Patent Document 2] Japanese Patent Publication No. 2020-019060

[0021] [Patent Document 3] Korean Utility Model Registration No. 20-0259892

[0022] [Patent Document 4] Chinese Patent Publication 115815769

Summary of the Invention

Problems to be Solved by the Invention

[0023] The present invention is for solving the above problems, and an object thereof is to provide means capable of grasping or measuring the degree of overlap, which is an important factor in the resistance welding of cylindrical batteries.

Means for Solving the Problems

[0024] In order to achieve the above object, the present invention provides a welding apparatus including an upper welding part including an upper welding rod, a first joined body located below the upper welding rod, a second joined body located below the first joined body, and a lower welding part including a lower welding rod located below the second joined body. The first joined body and the second joined body are welded by resistance welding of the upper welding rod and the lower welding rod, and a displacement measuring part capable of measuring the displacement of a buffer part provided in at least one of the upper end of the upper welding rod or the lower end of the lower welding rod is provided by additional pressing in a state where the upper welding rod, the first joined body, the second joined body, and the lower welding rod are in close contact with each other and facing each other.

[0025] The upper welding part may include a welding part main body located at the upper part and having a moving part for moving and fixing the entire upper welding part, and a buffer part located between the welding part main body and the upper welding rod and having a length between the welding part main body and the upper welding rod changed by the pressure applied to the upper welding rod.

[0026] The upper welding part may include a welding rod jig for fixing the upper welding rod, a welding rod housing part for housing and fixing the welding rod jig, a welding part main body located at the upper part and having a moving part for moving and fixing the entire upper welding part, and a buffer part located between the welding part main body and the welding rod housing part and having a length between the welding part main body and the welding rod housing part changed by the pressure applied to the upper welding rod.

[0027] The displacement measuring unit may include a measuring dog attached to the welding rod housing and a displacement measuring sensor attached to the welding body for measuring the distance to the measuring dog. The measuring dog and the displacement measuring sensor may be arranged with their positions reversed relative to each other.

[0028] The displacement measuring sensor can measure displacement using a physical chip or a laser. The displacement measuring sensor may be fixed to the weld body by a sensor fixing part. The value measured by the displacement measuring sensor may also be converted to digital and transmitted.

[0029] Furthermore, the present invention provides a resistance welding apparatus for a negative electrode tab of a cylindrical battery, comprising a cylindrical battery housing a jelly roll electrode assembly, a jig for fixing the lower part of the cylindrical battery, and a welding apparatus according to the present invention, wherein the first workpiece is a negative electrode tab and the second workpiece is the lower bottom of a cylindrical can.

[0030] The upper welding rod can penetrate the central part of the jelly roll electrode assembly to perform welding.

[0031] The system may be equipped with a visual device for observing the end of the upper welding rod.

[0032] Furthermore, the present invention provides a method for resistance welding the negative electrode tab of a cylindrical battery using a resistance welding apparatus for cylindrical battery negative electrode tabs, comprising: a first step of fixing a cylindrical battery containing a jelly roll electrode assembly to the jig; a second step of moving the upper welding rod and the lower welding rod, respectively, to bring the upper welding rod, the negative electrode tab, the lower bottom of the cylindrical can, and the lower welding rod into close contact; a third step of further pressing the upper welding rod and adjusting the degree of pressure on the upper welding rod so that a desired displacement value is obtained from the displacement measuring unit while measuring the displacement of the buffer portion caused by this pressing; and a fourth step of performing resistance welding after adjusting the degree of pressure on the upper welding rod in the third step.

[0033] Furthermore, the present invention provides a cylindrical battery in which the negative electrode tab of the cylindrical battery is welded by a resistance welding apparatus.

[0034] Furthermore, the present invention can provide problem-solving means by arbitrarily combining the aforementioned problem-solving means. [Effects of the Invention]

[0035] The present invention provides a welding apparatus comprising an upper weld portion including an upper welding rod, a first workpiece located below the upper welding rod, a second workpiece located below the first workpiece, and a lower weld portion including a lower welding rod located below the second workpiece, wherein the first workpiece and the second workpiece are welded by resistance welding of the upper welding rod and the lower welding rod, and the welding apparatus is equipped with a displacement measuring unit that can measure the displacement of a buffer portion provided at least one of the upper end of the upper welding rod or the lower end of the lower welding rod by additional pressing when the upper welding rod, the first workpiece, the second workpiece, and the lower welding rod are in close contact and facing each other.

[0036] Furthermore, since the present invention can grasp or measure the degree of overlap, which is an important factor in resistance welding of cylindrical batteries, it can provide welding results of consistent quality. [Brief explanation of the drawing]

[0037] [Figure 1] This is an exploded cross-sectional view of a cylindrical battery and a conventional resistance welding apparatus.

[0038] [Figure 2] This is a cross-sectional view showing a cylindrical battery and a conventional resistance welding device coupled together to perform welding.

[0039] [Figure 3] This is a schematic diagram of the upper part of a conventional resistance welding apparatus.

[0040] [Figure 4]This is an exploded cross-sectional view of a cylindrical battery and a resistance welding apparatus according to the present invention.

[0041] [Figure 5] This is a cross-sectional view showing a state in which a cylindrical battery and a resistance welding apparatus according to the present invention are coupled together to perform welding.

[0042] [Figure 6] This is a schematic diagram illustrating the measurement of the upper part of a resistance welding apparatus according to the present invention. [Modes for carrying out the invention]

[0043] Hereinafter, with reference to the attached drawings, embodiments that allow a person with ordinary skill in the art to which the present invention pertains to be easily implemented will be described in detail. In describing the operating principles of embodiments of the present invention in detail, if it is determined that a specific description of a related known function or configuration may unnecessarily obscure the gist of the present invention, such detailed description will be omitted.

[0044] Furthermore, the same reference numerals shall be used throughout the drawings for parts that have similar functions and operations. Throughout the specification, when it is said that one part is connected to another part, this includes not only direct connection but also indirect connection through other elements in between. Also, when it is said that a component is included, unless otherwise stated, it does not mean that other components are excluded, but rather that other components may be included.

[0045] Furthermore, explanations that limit or add specific components are applicable to all inventions, unless otherwise specified, and are not limited to a particular invention.

[0046] Furthermore, unless otherwise specified, the singular form used throughout the description of this invention and the claims also includes the plural form.

[0047] Furthermore, throughout the description and claims of this invention, "or" includes "and" unless otherwise specified. Therefore, "including A or B" means three cases: including A, including B, or including both A and B.

[0048] Furthermore, all numerical ranges include the values ​​at both ends and all intermediate values ​​between them, unless otherwise explicitly stated.

[0049] The present invention will be described in detail with reference to the accompanying drawings, along with specific embodiments.

[0050] Figure 4 is an exploded cross-sectional view of a cylindrical battery and a resistance welding apparatus according to the present invention, Figure 5 is a cross-sectional view showing the state in which the cylindrical battery and the resistance welding apparatus according to the present invention are coupled and welding is performed, and Figure 6 is a schematic diagram showing the displacement measurement of the upper part of the resistance welding apparatus according to the present invention.

[0051] Referring to Figures 4 to 6, the present invention relates to a welding apparatus comprising an upper welding section 300 including an upper welding rod 310, a first workpiece 130 located below the upper welding rod 310, a second workpiece 125 located below the first workpiece 130, and a lower welding rod 410 located below the second workpiece 125, wherein the first workpiece 130 and the second workpiece 125 are welded by resistance welding of the upper welding rod 310 and the lower welding rod 410, and the welding apparatus is equipped with a displacement measuring unit 600 that can measure the displacement of a buffer portion 340 provided on at least one of the upper end of the upper welding rod 310 or the lower end of the lower welding rod 410 by additional pressing when the upper welding rod 310, the first workpiece 130, the second workpiece 125, and the lower welding rod 410 are in close contact and facing each other.

[0052] The upper weld section 300 includes a welding rod jig 320 for fixing the upper welding rod 310, a welding rod housing section 330 for housing and fixing the welding rod jig 320, a welding section body 350 located at the top and equipped with a movable section (not shown) for moving and fixing the entire upper weld section 300, and a buffer section 340 located between the welding section body 350 and the welding rod housing section 330, the length between the welding section body 350 and the welding rod housing section 330 changing due to the pressure applied to the upper welding rod 310.

[0053] The welding rod jig 320 allows for the insertion and fixing of an upper welding rod 310 of a fixed length to a fixed depth. The welding rod jig 320 can be fixed to the welding rod storage section 330 by gripping it with a clamp.

[0054] The displacement measuring unit 600 includes a measuring dog 335 attached to the welding rod housing 330 and a displacement measuring sensor 500 attached to the welding unit body 350 for measuring the distance to the measuring dog 335. The measuring dog 335 and the displacement measuring sensor 500 may be arranged with their positions reversed relative to each other.

[0055] The displacement measuring sensor 500 can measure displacement using a physical chip or a laser. The displacement measuring sensor 500 is fixed to the weld body 350 via a sensor fixing part 550. The value measured by the displacement measuring sensor 500 is converted to digital and transmitted.

[0056] Furthermore, the present invention relates to a resistance welding apparatus for a negative electrode tab of a cylindrical battery, comprising a cylindrical battery 100 housing a jelly roll electrode assembly 110, a jig 200 for fixing the lower part of the cylindrical battery 100, and a welding apparatus according to the present invention, wherein the first workpiece is a negative electrode tab 130 and the second workpiece is the lower bottom 125 of a cylindrical can.

[0057] The upper welding rod 310 penetrates the central part of the jelly roll electrode assembly 110 to perform welding.

[0058] A visual device (not shown) for observing the end of the upper welding rod 310 can be provided. Since the upper welding rod 310 is normally used for resistance welding, its length decreases as welding is performed. However, the present invention replaces the upper welding rod 310 when its end changes from a uniform state to an uneven state, before its length decreases. Therefore, it can be assumed that a single upper welding rod 310 has a constant length while welding is being performed. The welding rod can be replaced by observing the surface of the end of the upper welding rod 310 or by observing the state of the welding. It is preferable to continuously observe the end of the upper welding rod 310 with a visual device such as a camera, and replace it before the end surface becomes rough, as welding cannot be performed properly at that point.

[0059] Furthermore, the present invention relates to a method for resistance welding the negative electrode tab 130 of a cylindrical battery 100 using a resistance welding apparatus for the negative electrode tab of a cylindrical battery, comprising: a first step of fixing the cylindrical battery 100 containing the jelly roll electrode assembly 110 to a jig 200; a second step of moving the upper welding rod 310 and the lower welding rod 410 respectively to bring the upper welding rod 310, the negative electrode tab 130, the lower bottom 125 of the cylindrical can, and the lower welding rod 410 into close contact; a third step of further pressing the upper welding rod 310 and adjusting the degree of pressure on the upper welding rod 310 so that a desired displacement value is obtained from the displacement measuring unit 600 while measuring the displacement of the buffer portion 340 caused by this; and a fourth step of performing resistance welding after adjusting the degree of pressure on the upper welding rod 310 in the third step.

[0060] The changes in the buffer section D1-D2 are identical to the changes in displacement values ​​H1-H2. Therefore, the actual changes in the buffer section can be determined through the displacement values.

[0061] A person with ordinary skill in the field to which this invention belongs will be able to make various applications and modifications within the scope of this invention based on the above description. [Explanation of symbols]

[0062] 100 cylindrical batteries 110 Jelly Roll Electrode Assembly 120 Cylindrical Can 125 Lower bottom of cylindrical can, second joined body 130 Negative electrode tab, first bonded body 200 jigs 300 Upper weld 310 Upper welding rod 320 Welding Rod Jig 330 Welding rod storage section 335 Measurement Dog 340 Buffer 350 Welded body 550 Sensor mounting part 400 Lower weld 410 Lower welding rod 500 Displacement Measurement Sensor 600 Displacement measuring section (335, 500) Length of the buffer section D, D1, D2 H1, H2 displacement values

Claims

1. The upper welded section including the upper welding rod, The first workpiece located below the upper welding rod, A second joined body located below the first joined body, The lower weld portion includes a lower welding rod located at the lower part of the second body to be joined, A welding apparatus including, The first workpiece and the second workpiece are welded together by resistance welding of the upper welding rod and the lower welding rod. A welding apparatus comprising a displacement measuring unit capable of measuring the displacement of a buffer portion provided at least one of the upper end of the upper welding rod or the lower end of the lower welding rod by applying additional pressure while the upper welding rod, the first workpiece, the second workpiece, and the lower welding rod are in close contact and facing each other.

2. The upper welded portion is, A welding body located at the top, equipped with a movable part for moving and fixing the entire upper welding section, The welding apparatus according to claim 1, further comprising a buffer portion located between the welding body and the upper welding rod, wherein the length between the welding body and the upper welding rod changes depending on the pressure applied to the upper welding rod.

3. The upper welded portion is, A welding rod jig for fixing the upper welding rod, A welding rod housing section for housing and fixing the welding rod jig, A welding body located at the top, equipped with a movable part for moving and fixing the entire upper welding section, The welding apparatus according to claim 1, further comprising a buffer portion located between the welding body and the welding rod housing portion, wherein the length between the welding body and the welding rod housing portion changes due to the pressure applied to the upper welding rod.

4. The displacement measuring unit is A measuring dog attached to the welding rod housing, A displacement measuring sensor attached to the welded body and measuring the distance to the measuring dog, The welding apparatus according to claim 3, including the following:

5. The welding apparatus according to claim 4, wherein the displacement measuring sensor measures the displacement using a physical chip or a laser.

6. A cylindrical battery housing a jelly roll electrode assembly, A jig for securing the lower part of the cylindrical battery, A welding apparatus according to any one of claims 1 to 4, A resistance welding apparatus for the negative electrode tab of a cylindrical battery, including, The first object to be bonded is a negative electrode tab, The second object to be joined is the lower bottom of a cylindrical can, and the device is a resistance welding apparatus for the negative electrode tab of a cylindrical battery.

7. The resistance welding apparatus for the negative electrode tab of a cylindrical battery according to claim 6, wherein the upper welding rod penetrates the central part of the jelly roll electrode assembly to perform welding.

8. The resistance welding apparatus for the negative electrode tab of a cylindrical battery according to claim 6, further comprising a visual device for observing the end of the upper welding rod.

9. A method for resistance welding the negative electrode tab of a cylindrical battery using the resistance welding apparatus for the negative electrode tab of a cylindrical battery described in claim 6, The first step is to fix the cylindrical battery containing the jelly roll electrode assembly to the jig, The second step involves moving the upper welding rod and the lower welding rod respectively to bring the upper welding rod, the negative electrode tab, the lower bottom of the cylindrical can, and the lower welding rod into close contact. A third step involves further pressing the upper welding rod and adjusting the degree of pressure on the upper welding rod so that a desired displacement value is obtained from the displacement measuring unit while measuring the resulting displacement of the buffer portion with the displacement measuring unit. In the third stage, the degree of pressure applied to the upper welding rod is adjusted, followed by a fourth stage in which resistance welding is performed. A method for resistance welding the negative electrode tab of a cylindrical battery, including the method described above.

10. A cylindrical battery, wherein the negative electrode tab of the cylindrical battery is welded by a resistance welding apparatus for cylindrical batteries as described in claim 6.

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