Electrode polishing apparatus and cutting tools

Abstract

To provide an electrode polishing device and a cutting tool which can improve abradability of a tip of an electrode for spot weld.SOLUTION: An electrode polishing device 1 includes a cutting tool 10 which is rotationally driven by a drive motor 62 to polish surface of an electrode 72 for spot weld. The cutting tool includes: a disk-like holder 20a which has a hole 24 for receiving electrode at the center part and has an approximately circular shaped peripheral surface polishing blade 26 arranged in an inner wall part of the hole for receiving electrode to polish a peripheral part surface of the electrode; and a tip part grinder 50 which is laminatedly arranged on the holder to have a tip part polishing blade 55 on a surface facing the holder to polish a tip part surface of the electrode exposed from the hole for receiving electrode. The holder rotates around a rotation center of the electrode received in the hole for receiving electrode, and the tip part grinder rotates around a rotation axis Q decentered from the rotation center of the holder.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electrode polishing apparatus for polishing a spot welding electrode and a cutting tool used in the electrode polishing apparatus. [Background Art]

[0002] As a method of welding metal panels, resistance welding is known, in which a current is passed while pressing a base material formed by overlapping a plurality of panels, and the panels are welded to each other by resistance heat generated between the panels. In spot welding, which is one type of resistance welding, a pair of electrodes sandwiches and presses the overlapping panels, bringing the panels into contact with each other to ensure electrical conductivity at the welded portion.

[0003] In spot welding, the condition of the tip end of the electrode that abuts the base material is important for maintaining welding quality. However, when the tip end of the electrode becomes worn due to multi-spot welding, or plating or the like on the surface of the base material adheres to the surface of the electrode during welding to form an alloyed metal layer on the electrode surface, this leads to a decrease in welding quality.

[0004] In order to maintain welding quality, an electrode polishing apparatus is used to polish the electrode surface to maintain the surface condition of the electrode. For example, Patent Document 1 describes an electrode polishing apparatus provided with a cutting tool that contacts and polishes the surface of an electrode.

[0005] Figure 5 is a side view illustrating the cutting tool 90 of a conventional electrode polishing apparatus. In the cutting tool 90, the polishing blade 92 that contacts the electrodes 72 and 74 of the spot welding apparatus is formed in an arc shape so as to contact the electrode surface from the tip to the base end of the electrodes 72 and 74. In this electrode polishing apparatus, with the pair of electrodes 72 and 74 pressed against the polishing blade 92, the cutting tool 90 is rotated by a drive motor around a central axis that coincides with the center of the electrodes 72 and 74. Figure 6 is a diagram illustrating the amount of movement of the polishing blade 92 of the cutting tool 90 relative to the electrode 72 in a conventional electrode polishing apparatus. As indicated by the arrows in Figure 6, the amount of movement of the polishing blade 92 relative to the electrode 72 increases radially outward from the center of the electrode 72. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-54567 [Overview of the project] [Problems that the invention aims to solve]

[0007] In recent years, the materials used for welding have become diverse, and in spot welding equipment that welds to various base materials, a hard alloy layer can form on the tip surface of the electrode, where the metal materials of the various base materials are alloyed. As mentioned above, the condition of the electrode tip that contacts the base material is important in spot welding, but with conventional electrode polishing equipment, the amount of movement of the polishing blade relative to the electrode tip is small, making it difficult to sufficiently remove the alloy layer attached to the electrode tip.

[0008] The present invention has been made in view of the above problems, and aims to provide an electrode polishing apparatus and a cutting tool that can improve the polishability of the tip of a spot welding electrode. [Means for solving the problem]

[0009] To achieve the above objective, an embodiment of the present invention provides an electrode polishing apparatus equipped with a cutting tool that is rotationally driven by a drive motor to polish the surface of an electrode for spot welding, wherein the cutting tool comprises a holder formed in the shape of a disc, having an electrode receiving hole in the center, and having a substantially arc-shaped circumferential polishing blade on the inner wall of the electrode receiving hole for polishing the circumferential surface of the electrode, and a tip polishing plate stacked on the holder and having a tip polishing blade on the surface facing the holder for polishing the tip surface of the electrode exposed from the electrode receiving hole, wherein the holder rotates with the center of the electrode received in the electrode receiving hole as its center of rotation, and the tip polishing plate rotates around a rotation axis eccentric to the center of rotation of the holder.

[0010] Furthermore, in order to achieve the above objective, one embodiment of the present invention is a cutting tool that is rotationally driven by a drive motor to press and polish an electrode for spot welding, comprising: a holder formed in the shape of a disc and having an electrode receiving hole in the center, and having a substantially arc-shaped circumferential surface polishing blade on the inner wall of the electrode receiving hole for polishing the circumferential surface of the electrode; and a tip polishing plate stacked on the holder and having a tip polishing blade on the surface facing the holder for polishing the tip surface of the electrode exposed from the electrode receiving hole, wherein the holder rotates with the center of the electrode received in the electrode receiving hole as the center of rotation, and the tip polishing plate rotates around a rotation axis eccentric to the center of rotation of the holder. [Effects of the Invention]

[0011] The electrode polishing apparatus and grinding tool according to the present invention can improve the polishability of the tip portion of spot welding electrodes. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic partial cross-sectional view showing the main part of an electrode polishing apparatus, which is one embodiment of the present invention. [Figure 2] This is a schematic diagram of a spot welding machine. [Figure 3]This is an exploded perspective view of a cutting tool, which is one embodiment of the present invention. [Figure 4A] This is an explanatory diagram showing the operation of a cutting tool. [Figure 4B] This is an explanatory diagram showing the operation of a cutting tool. [Figure 4C] This is an explanatory diagram showing the operation of a cutting tool. [Figure 4D] This is an explanatory diagram showing the operation of a cutting tool. [Figure 5] This is a side view illustrating the cutting tool of a conventional electrode polishing apparatus. [Figure 6] This diagram illustrates the amount of movement of the cutting tool relative to the electrode in a conventional electrode polishing apparatus. [Modes for carrying out the invention]

[0013] Figure 1 is a schematic partial cross-sectional view showing the main parts of an electrode polishing apparatus 1, which is one embodiment of the present invention. The electrode polishing apparatus 1 is a device for polishing the surfaces of electrodes 72 and 74 for spot welding. The electrode polishing apparatus 1 comprises a cutting tool 10, a drive gear 60 that meshes with gear teeth provided around the cutting tool 10, and a drive motor 62 that rotationally drives the drive gear 60. The cutting tool 10 is given rotational force by the drive motor 62 via the drive gear 60.

[0014] Figure 2 is a schematic diagram of a spot welding apparatus 70 equipped with a pair of electrodes 72 and 74 that are polished by an electrode polishing apparatus 1. The spot welding apparatus 70 is used, for example, in the manufacturing process of vehicles such as automobiles (such as joining panels that make up the vehicle body). The spot welding apparatus 70 clamps a base material 80 consisting of a plurality of metal panels 81 and 82 that are at least partially overlapped between the pair of electrodes 72 and 74, and welds the panels 81 and 82 together by applying pressure and current between the electrodes 72 and 74.

[0015] The spot welding device 70 includes a first electrode 72, a second electrode 74 coaxially arranged opposite to the first electrode 72, and a control device 76. The second electrode 74 is fixed to the device body of the spot welding device 70, and the first electrode 72 is configured to be able to approach and separate from the second electrode 74. In the present embodiment, tip portions 72a and 74a of the respective electrodes 72 and 74 are formed in a planar shape.

[0016] The control device 76 is configured to include, for example, an information processing unit such as a CPU, a storage unit such as a RAM and a ROM, an input / output interface, and the like. The control device 76 controls the movement of the first electrode 72, the pressing force applied to these base materials 80, the current value of the welding current supplied to the respective electrodes 72 and 74, and the like based on a program stored in the storage unit. FIG. 2 shows a state where, in a base material 80 composed of a first panel 81 and a second panel 82, a laminated portion of the first and second panels 81 and 82 is sandwiched, pressed and welded by the first and second electrodes 72 and 74. As welding proceeds, a nugget 84 is formed between the first and second panels 81 and 82.

[0017] The surfaces of the respective electrodes 72 and 74 of the spot welding device 70 are damaged or worn due to repeated welding such as multi-spot welding. Further, when the base material 80 is welded, the molten base material may adhere to the surfaces of the electrodes 72 and 74 to form an alloyed layer thereon. If the surface condition of the electrodes 72 and 74 changes due to wear of the electrodes 72 and 74 or formation of the alloyed layer as described above, intended current conduction performance cannot be obtained and welding quality deteriorates, so polishing of the surfaces of the electrodes 72 and 74 is required.

[0018] FIG. 3 is an exploded perspective view of a cutting tool attached to an electrode grinding apparatus 1. In the present embodiment, the cutting tool 10 is configured to be capable of grinding a first electrode 72 and a second electrode 74 simultaneously. The cutting tool 10 comprises a pair of peripheral surface grinding blade holders (holders) 20A, 20B each having a peripheral surface grinding blade 26, plates 30A, 30B attached to the respective peripheral surface grinding blade holders 20A, 20B, an annular holder 40, and a tip grinding disc 50 having a tip grinding blade 55. In the cutting tool 10, the peripheral surface grinding blade holders 20A and 20B are formed in the same shape, and the plates 30A and 30B are formed in the same shape, so one of the peripheral surface grinding blade holders 20A and one of the plates 30A will be described in detail below.

[0019] The peripheral surface grinding blade holder 20A is formed in a disc shape, and has an electrode receiving hole 24 for receiving an electrode 72 at the center thereof. The electrode receiving hole 24 penetrates through the peripheral surface grinding blade holder 20A, and a peripheral surface grinding blade 26 for grinding the peripheral surface of the spot welding electrode 72 is attached to the inner wall of the electrode receiving hole 24. Specifically, the electrode receiving hole 24 has, in a part in the circumferential direction, a recessed portion 25 recessed radially outward, and the peripheral surface grinding blade 26 is detachably attached to this recessed portion 25. The peripheral surface grinding blade 26 grinds a peripheral surface 72b of the spot welding electrode 72, and has a substantially arcuate blade along the peripheral surface 72b.

[0020] Gear teeth (third gear teeth) 22 are formed over the entire circumference on the outer peripheral surface of the peripheral surface grinding blade holder 20A. Further, in the peripheral surface grinding blade holder 20A, a circular recess 28 for fitting and installing the plate 30A is formed on a surface facing the tip grinding disc 50, that is, a surface located on the tip side of the electrode 72.

[0021] The plate 30A is formed in the shape of a disc that fits into a recess 28 of the holder 20A for the circumferential polishing blade, and has a circular through hole 32 at an eccentric position from the center of the disc. The through hole 32 is a hole into which the protrusion 54 of the tip polishing disc 50, which will be described later, is fitted. The plate 30A rotates together with the holder 20A for the circumferential polishing blade.

[0022] The annular holder 40 is formed in the shape of an annular plate and has an outer diameter equal to that of the holder 20A for the circumferential polishing blade, while having an inner diameter larger than the outer diameter of the disc-shaped polishing disc 50 for the tip. Gear teeth (second gear teeth) 44 that mesh with gear teeth (first gear teeth) 52 formed on the outer surface of the polishing disc 50 for the tip are formed on the inner circumferential surface of the annular holder 40. In addition, the same number of gear teeth (third gear teeth) 42 as the gear teeth 22 of the holder 20A for the circumferential polishing blade are formed on the outer circumferential surface of the annular holder 40.

[0023] The tip polishing disc 50 is positioned inside the annular holder 40 and stacked on the circumferential polishing blade holder 20A, with the tip polishing blade 55 provided on the surface facing the circumferential polishing blade holder 20A. In the cutting tool 10 of this embodiment, a pair of circumferential polishing blade holders 20A and 20B are stacked on both sides of the tip polishing disc 50 so as to sandwich it.

[0024] As previously described, the tip polishing disc 50 is formed in a disc shape, and gear teeth 52 are formed on its outer circumferential surface. The tip polishing disc 50 in this embodiment has columnar protrusions 54 on both sides. The protrusions 54 have a diameter smaller than the inner diameter of the recesses 28 of the circumferential polishing blade holders 20A and 20B, and a flat tip polishing blade 55 is provided on the end surface of these protrusions 54. The tip polishing blade 55 is a blade that polishes the tip surfaces of the electrodes 72 and 74 that are exposed from the electrode receiving holes 24 of each circumferential polishing blade holder 20A and 20B when the electrodes 72 and 74 are polished by the cutting tool 10. The surface area of ​​the tip polishing blade 55 is larger than the surface area of ​​the tip 72a of the electrode 72. In this embodiment, a cylindrical protrusion 54 is provided so as to be coaxial with the tip polishing disc 50, but the shape of the protrusion 54 is not limited to a cylinder and may be a polygonal prism. The polishing plate 50 for the tip rotates integrally with the plates 30A and 30B as the plates rotate, because the protrusions 54 provided on both sides are fitted into the through holes 32 of the plates 30A and 30B.

[0025] A pair of holders 20A and 20B for the circumferential polishing blades and an annular holder 40 positioned between them are fixed together by fasteners such as screws that penetrate them in the thickness direction, with their gear teeth 22 and 42 aligned. The cutting tool 10 is mounted on the main body of the electrode polishing apparatus 1 (not shown) so as to be rotatable around the central axis P of the disc-gear-shaped cutting tool 10. Furthermore, as shown in Figure 1, in the electrode polishing apparatus 1, the cutting tool 10 is mounted so that the gear teeth 22 and 42 of the circumferential polishing blade holders 20A and 20B and the annular holder 40 mesh with the gear teeth formed on the outer circumferential surface of the drive gear 60.

[0026] Next, the operation of the electrode polishing apparatus 1 equipped with the cutting tool 10 will be described. First, as shown in Figure 1, the pair of electrodes 72 and 74 are inserted into the electrode receiving holes 24 of the pair of circumferential polishing blade holders 20A and 20B, so that they are held in place by the electrode receiving holes 24, and the pair of electrodes 72 and 74 are brought close together and pressed against the cutting tool 10. As a result, the tip polishing blade 55 of the cutting tool 10 comes into contact with the tip portions 72a and 74a of the electrodes 72 and 74 that are exposed from the electrode receiving holes 24. Also, the pair of circumferential polishing blades 26 of the cutting tool 10 come into contact with the circumferential portions 72b and 74b of each electrode 72 and 74.

[0027] In this state, when the drive motor 62 is driven, the drive gear 60 rotates, and consequently, the holders 20A, 20B for the circumferential polishing blades and the annular holder 40 that mesh with the drive gear 60 rotate together around the central axis P. The central axis P coincides with the central axis of the electrodes 72 and 74. In addition, as the holders 20A and 20B for the circumferential polishing blades rotate, the plates 30A and 30B, which are integrated with the holders 20A and 20B, also rotate around the central axis P. Furthermore, as the plates 30A and 30B rotate, the tip polishing plate 50, in which the protrusions 54 are fitted into the through holes 32 of the plates 30A and 30B, also rotates. At this time, the tip polishing plate 50 rotates around a rotation axis Q that is eccentric to the central axis P.

[0028] Figures 4A, 4B, 4C, and 4D illustrate the rotation state of the cutting tool 10 by the drive motor 62. The annular holder 40, the tip polishing plate 50 rotating inside it, and the tip 72a of the electrode 72 that contacts the tip polishing blade 55 are shown by solid lines, and the plate 30A is shown by a dashed line. The cutting tool 10 rotates in the order of Figures 4A, 4B, 4C, and 4D. The outer shapes of the circumferential polishing blade holders 20A and 20B are the same as the outer shape of the annular holder 40 in Figures 4A to 4D. In Figure 4A, distance d indicates the eccentricity distance between the central axis P of the circumferential polishing blade holders 20A and 20B and the rotation axis Q, which is the center of the tip polishing plate 50.

[0029] As shown in Figures 4A to 4D, when the circumferential polishing blade holders 20A, 20B and the annular holder 40 rotate counterclockwise, the rotational force of the circumferential polishing blade holders 20A, 20B is transmitted to the tip polishing disc 50 via plates 30A, 30B, causing the tip polishing disc 50 to rotate counterclockwise. At this time, the tip polishing disc 50 rotates inside the annular holder 40 while meshing with the gear teeth 44 formed on the inner circumferential surface of the annular holder 40, and also rotates with its center as the axis of rotation Q. In other words, the tip polishing disc 50 rotates on its own axis Q while revolving around the central axis P, exhibiting the motion of a planetary gear.

[0030] In Figure 4B, the position of the electrode tip 72a on the tip polishing blade 55 in Figure 4A is shown by a dashed line. Similarly, in Figures 4C and 4D, the positions of the electrode tip 72a on the tip polishing blade 55 in Figures 4B and 4C are shown by dashed lines. As shown in the illustrated example, in the grinding tool 10 of this embodiment, the position of the electrode tip 72a that contacts the tip polishing blade 55 changes, thereby increasing the amount by which the tip polishing blade 55 moves relative to the tip 72a.

[0031] Each electrode 72, 74 of the spot welding apparatus 70 undergoes surface wear and the formation of an alloy layer due to the adhesion of molten material from the base material 80 to the surface during multi-spot welding and welding to various types of base materials 80. In order to maintain welding quality, the condition of the tips 72a, 74a of the electrodes 72, 74 that come into contact with the base material 80 is particularly important, and therefore the electrode polishing apparatus 1 is required to have polishability for the tips 72a, 74a.

[0032] As described above, in the electrode polishing apparatus 1 of this embodiment, the tip portions 72a, 74a and the circumferential portions 72b, 74b of electrodes 72, 74 are polished with separate blades, namely the tip polishing blade 55 and the circumferential portion polishing blade 26, respectively, and the tip polishing blade 55 is rotated on a rotation axis Q that is eccentric from the center of electrodes 72, 74. This increases the amount of movement of the tip polishing blade 55 that contacts the tip portions 72a, 74a of electrodes 72, 74, thereby improving the polishing performance of the tip portions 72a, 74a.

[0033] Furthermore, in the cutting tool 10 of this embodiment, tip polishing blades 55 are provided on both sides of the tip polishing plate 50, and a pair of circumferential polishing blade holders 20A and 20B, each having a circumferential polishing blade 26, are stacked on both sides of the tip polishing plate 50, allowing a pair of electrodes 72 and 74 to be polished simultaneously. In addition, the cutting tool 10 employs a planetary gear structure in which the tip polishing plate 50 is placed inside the annular holder 40 and the gears 44 and 52 mesh together. By transmitting driving force to the tip polishing plate 50 via plates 30A and 30B, a single drive motor 62 can simultaneously rotate the tip polishing plate 50 and the pair of circumferential polishing blade holders 20A and 20B, which have different rotation axes.

[0034] It should be noted that the present invention is not limited to the embodiments or modifications described above, and various modifications are possible without departing from the spirit of the invention.

[0035] For example, a structure may be used in which each holder 20A, 20B for polishing the circumferential surface and the polishing disc 50 for the tip are rotated individually using multiple drive sources.

[0036] Furthermore, for example, the cutting tool 10 may be configured to include a tip polishing plate 50 having at least one tip polishing blade 55, and at least one circumferential polishing blade holder 20A, 20B stacked thereon, so that at least one electrode 72, 74 can be polished.

[0037] Furthermore, for example, if the shape of the tip portions 72a and 74a of electrodes 72 and 74 is not flat but curved or has a gentle R shape, it is also possible to change the surface shape of the tip polishing blade 55 that contacts them to match the electrode tip portions 72a and 74a. [Explanation of symbols]

[0038] 1 Electrode polishing device 10 Cutting tools Holder for 20A and 20B surface polishing blades 22 gear teeth 24 electrode receiving holes 25 Recessed area 26 Surface polishing blade 28 recesses 30A, 30B Plate 32 Through holes 40 Annular holder 42 gear teeth 44 gear teeth 50 Polishing machine for the tip 52 gear teeth 55. Tip polishing blade 60 Drive gears 62 Drive motor 70 Spot welding machine 72 First electrode 74 Second electrode 72a,74b Tip 72b,74b Peripheral part 76 Control device 80 Base material

Claims

1. In an electrode polishing apparatus equipped with a cutting tool that is rotationally driven by a drive motor to polish the surface of an electrode for spot welding, The cutting tool is A holder formed in a disc shape, having an electrode receiving hole in the center, and equipped with a substantially arc-shaped circumferential surface polishing blade on the inner wall of the electrode receiving hole for polishing the circumferential surface of the electrode, A polishing plate for the tip is stacked on the holder and has a tip polishing blade on its surface facing the holder for polishing the tip surface of the electrode exposed from the electrode receiving hole, Equipped with, The holder rotates with the center of the electrode received in the electrode receiving hole as its center of rotation. The electrode polishing apparatus is characterized in that the polishing disc for the tip rotates around a rotation axis that is eccentric to the rotation center of the holder.

2. The cutting tool comprises a pair of holders, The aforementioned polishing disc for the tip is equipped with the tip polishing blades on both sides, The electrode polishing apparatus according to claim 1, characterized in that the pair of holders are stacked and arranged on both sides of the tip polishing plate.

3. The holder has a circular recess on the surface facing the polishing disc for the tip, The polishing disc for the tip has a first gear tooth on its outer circumferential surface, and a columnar protrusion on the surface facing the holder, having a diameter smaller than the inner diameter of the recess. The tip polishing blade is provided on the end surface of the protrusion, The cutting tool is A plate formed in the shape of a disc that fits into the recess of the holder, and having a through hole at an eccentric position from the center into which the protrusion of the tip polishing plate is fitted, An annular holder formed in the shape of an annular plate having an inner diameter larger than the outer diameter of the polishing plate for the tip, having a second gear tooth on its inner circumferential surface that meshes with the first gear tooth, and rotating integrally with the holder, The electrode polishing apparatus according to claim 1 or 2, characterized by comprising the following features.

4. The drive gear is rotated by the aforementioned drive motor, The electrode polishing apparatus according to claim 3, characterized in that the holder and / or the annular holder have third gear teeth on their outer circumferential surface that mesh with the drive gear.

5. In a cutting tool that is rotationally driven by a drive motor and polishes by pressing an electrode for spot welding against it, A holder formed in a disc shape, having an electrode receiving hole in the center, and equipped with a substantially arc-shaped circumferential surface polishing blade on the inner wall of the electrode receiving hole for polishing the circumferential surface of the electrode, A polishing plate for the tip is stacked on the holder and has a tip polishing blade on its surface facing the holder for polishing the tip surface of the electrode exposed from the electrode receiving hole, Equipped with, The holder rotates with the center of the electrode received in the electrode receiving hole as its center of rotation. The cutting tool is characterized in that the polishing disc for the tip rotates around a rotation axis that is eccentric to the rotation center of the holder.

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