JP7257089B2 - Welding electrode polishing method and polishing apparatus - Google Patents

Description

The present invention relates to a polishing method and polishing apparatus for welding electrodes used in indirect spot welding.

In the automobile assembly process, a vehicle body is assembled by joining a plurality of parts made of metal plates by spot welding. As spot welding, direct spot welding is often used in which a plurality of metal plates are sandwiched between a pair of welding electrodes and energized. However, depending on the shape of the part, a plurality of metal plates cannot be sandwiched between a pair of welding electrodes, and there are restrictions on the parts to which direct spot welding can be applied. As another example of spot welding, there is series spot welding in which a pair of welding electrodes are pressed against a plurality of metal plates from one side and energized to weld two locations simultaneously. However, since series spot welding also requires two adjacent welding points, there are restrictions on places where welding can be performed.

Indirect spot welding is an example of spot welding that is not subject to the above restrictions. In indirect spot welding, the parts to be joined of a plurality of metal plates are pressed from one side by a welding electrode, and a ground electrode is brought into contact with a part different from the parts to be joined. Weld. In such indirect spot welding, there are few structural restrictions on the applied portion, and the degree of freedom in design can be expanded.

During spot welding, the welding electrode is energized and placed under high temperature and high pressure. Repeated welding causes the tip of the welding electrode to wear out and flatten, and metal pieces, etc. adhere to the tip. and alloyed. In particular, when the surface of the metal plate is galvanized, the galvanized electrode (copper) is alloyed with the welding electrode (copper) and repeatedly deposited and peeled off, resulting in deformation of the welding electrode. Continuing to use the welding electrode in such a state will cause poor welding, so it is necessary to regularly shape the tip portion by cutting, polishing, or the like. As a technology related to shaping, for example, Patent Literature 1 discloses an electrode polishing apparatus that rotates a cutter holder provided with a blade (cutter) and cuts by pressing the tip of a welding electrode against the blade.

JP 2018-89638 A

As described above, when the tip portion of the welding electrode is polished and regenerated by the electrode polishing apparatus, it is necessary to inspect whether or not the tip portion has a desired shape suitable for welding. Particularly in indirect spot welding, the shape of the tip of the welding electrode has a great influence on the welding quality, so it is desired to inspect the state of the tip after polishing with high accuracy.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a welding electrode polishing method and a polishing apparatus that can inspect the state of a welding electrode for indirect spot welding after polishing. .

The present invention is intended to solve the above problems, and in a method for polishing a welding electrode used for indirect spot welding, the welding electrode includes a body portion, a tip portion that contacts a member to be welded, and the an intermediate portion located between the main body portion and the tip portion, wherein the electrode material contained in the intermediate portion is moved from the intermediate portion to the tip portion by a rotating polishing tool; and an inspection step of detecting the state of the tip by a sensor.

Further, the present invention provides a welding electrode polishing apparatus for use in indirect spot welding, wherein the welding electrode includes a main body, a tip that contacts a member to be welded, and a gap between the main body and the tip. a polishing tool for moving the electrode material contained in the intermediate portion from the intermediate portion to the tip portion; and a sensor for detecting the state of the tip portion. Characterized by

According to the above configuration, in the polishing step, the worn tip portion can be regenerated by moving the metal material contained in the intermediate portion from the intermediate portion to the tip portion with the polishing tool. In the present invention, it is possible to inspect the quality of the tip by detecting the state of the regenerated tip with a sensor.

ADVANTAGE OF THE INVENTION According to this invention, the state of the welding electrode for indirect spot welding can be inspected after grinding|polishing.

1 is a cross-sectional view showing an embodiment of indirect spot welding; FIG. FIG. 4 is a side view of a welding electrode; 1 is a cross-sectional view of a polishing apparatus according to a first embodiment; FIG. It is a top view of a polishing tool. It is a block diagram of a control device. FIG. 4 is an enlarged cross-sectional view of a main part showing a polishing process; FIG. 4 is an enlarged cross-sectional view of a main part showing an inspection process; It is a cross-sectional view of a polishing apparatus according to a second embodiment.

EMBODIMENT OF THE INVENTION Hereinafter, it demonstrates, referring drawings for the form for implementing this invention. 1 to 7 show a first embodiment for carrying out the invention.

FIG. 1 illustrates a mode of welding frame parts W of a vehicle body by indirect spot welding performed in the assembly process of an automobile body. This frame component W is a frame-like component extending in a direction perpendicular to the plane of FIG. The frame component W includes a first metal plate 1 having a substantially flat plate shape, a second metal plate 2 having a hat-shaped cross section, and a cross section disposed between the first metal plate 1 and the second metal plate 2. and a hat-shaped third metal plate 3 .

The first metal plate 1 and the flange portion 2a of the second metal plate 2 are joined via a pre-welded point Q1 welded in advance by direct spot welding. The bottom portion 2b of the second metal plate 2 and the flange portion 3a of the third metal plate 3 are joined via a pre-welded point Q2 welded in advance by direct spot welding.

In this embodiment, the top plate portion 3b of the third metal plate 3 and the first metal plate 1 are exemplified as objects to be welded (members to be welded) by the indirect spot welding method. In the indirect spot welding, the portion to be joined P between the first metal plate 1 and the top plate portion 3b of the third metal plate 3 is pressed from one side in the thickness direction (upper side in the figure) by the welding electrode 4, and In a state in which the earth electrode 5 is brought into contact with a portion of the skeleton component W different from the portion to be joined P, the portion to be joined P is welded by energizing between the two electrodes 4 and 5 . Each of the electrodes 4 and 5 is made of a highly conductive material such as a Cu-based metal. In the illustrated example, the ground electrode 5 is brought into contact with the bottom portion 2b of the second metal plate 2 from below.

In this indirect spot welding, an indirect spot welding device having the welding electrode 4 and the ground electrode 5 is connected to the indirect spot welding device, and the welding force of the welding electrode 4 and the current value between the two electrodes 4 and 5 are connected to the indirect spot welding device. It is carried out in a facility equipped with a control device that controls the The indirect spot welding apparatus includes pressurizing means that presses the first metal plate 1 and the third metal plate 3 by driving the welding electrode 4 in the axial direction. An air cylinder or an electric cylinder can be used as the pressurizing means, and an air cylinder is used in this embodiment.

As shown in FIG. 2, the welding electrode 4 includes a body portion 6, a tip portion 7 that contacts the first metal plate 1, and an intermediate portion 8 positioned between the body portion 6 and the tip portion 7. .

The body portion 6 is configured in a cylindrical shape. The tip portion 7 functions as a pressing portion that presses the portion P to be joined. The end surface of the tip portion 7 is a circular flat surface. The width W1 (diameter) of the end face of the tip portion 7 is set to 1 mm, for example, but is not limited to this dimension. A projection height (length) H1 of the tip portion 7 from the intermediate portion 8 is set to, for example, 1.8 mm, but is not limited to this dimension. The intermediate portion 8 is configured by a curved surface (convex curved surface) that tapers from the main body portion 6 toward the distal end portion 7 .

3 to 5 show a polishing apparatus 9 used in the polishing method according to the invention. The polishing apparatus 9 mainly includes a polishing tool 10 , an inspection section 11 , and a control device 12 that controls the polishing tool 10 and the inspection section 11 .

The polishing tool 10 is rotationally driven by a driving device 13 such as a motor. The polishing tool 10 is formed of a tapered tubular body (cylindrical body) whose both ends are open and whose inner diameter and outer diameter gradually decrease from one end to the other end.

As shown in FIGS. 3 and 4, the polishing tool 10 includes a first opening 14 formed at one end, a second opening 15 formed at the other end, and an electrode material contained in the intermediate portion 8. to the tip portion 7 via the second opening 15, and a discharge port 17 for discharging the polishing powder.

The first opening 14 functions as an insertion opening for inserting the welding electrode 4 inside the polishing tool 10 . The first opening 14 has a circular edge and its opening area is larger than the opening area of the second opening 15 . The diameter of the first opening 14 is larger than the outer diameter of the main body 6 related to the welding electrode 4 .

The second opening 15 functions as a guide opening for exposing the tip 7 of the welding electrode 4 inserted from the first opening 14 . The second opening 15 has a circular edge, the diameter of which is smaller than the diameter of the second opening 15 and larger than the width W1 of the tip portion 7 of the welding electrode 4 .

As shown in FIGS. 3 and 4, the guide portion 16 protrudes radially inward from the inner peripheral surface 10a of the polishing tool 10. As shown in FIGS. More specifically, the guide portion 16 is a ridge formed along the axial center (cylindrical center) direction of the polishing tool 10 from the first opening 14 to the second opening 15 . A top portion 16a of the guide portion 16 has an arc-shaped curved surface. In this embodiment, the polishing tool 10 having four guide portions 16 is exemplified, but the number of the guide portions 16 is not limited to this, and can be appropriately set according to the shape and size of the welding electrode 4 .

As shown in FIG. 3, the inner peripheral surface 10a of the polishing tool 10 is configured as a tapered surface or curved surface (concave curved surface) whose inner diameter gradually decreases from the first opening 14 toward the second opening 15. be done. Further, the guide portion 16 has a constant protrusion height (length) H2 from the first opening portion 14 to the second opening portion 15 (see FIG. 4). A first distance (radius) D1 between the top portion 16a of the guide portion 16 and the central axis O of the polishing tool 10 at a first position P1 near the first opening 14, and a second distance (radius) D1 near the second opening 15 When comparing the second distance (radius) D2 between the top portion 16a of the guide portion 16 and the central axis O at the position P2, D1>D2. That is, the guide portion 16 is formed in a curved shape in which the distance from the central axis O in the radial direction gradually decreases from the first opening portion 14 toward the second opening portion.

With the configuration of the guide portion 16 described above, when the polishing tool 10 is rotating at a constant speed (the direction of rotation is indicated by symbol R in FIG. 4), the first peripheral speed V1 of the guide portion 16 at the first position P1 is and the second peripheral velocity V2 of the guide portion 16 at the second position P2, V1<V2. That is, the guide portion 16 is configured such that the circumferential velocity increases from the first opening portion 14 toward the second opening portion 15 . Therefore, the circumferential velocity of the guide portion 16 at the position of the first opening portion 14 is the smallest, and the circumferential velocity of the guide portion 16 at the position of the second opening portion 15 is the largest.

The discharge port 17 is provided around the second opening 15 and is composed of a plurality of holes penetrating from the inner peripheral surface 10a of the polishing tool 10 to the outer peripheral surface 10b. Due to the action of the guide portion 16, the electrode material of the intermediate portion 8 flows to the tip portion 7 without being scraped off, but a small amount of the electrode material is separated from the intermediate portion 8 as polishing powder. The discharge port 17 allows the minute amount of polishing powder to pass therethrough and discharge it to the outside of the polishing tool 10 .

The inspection unit 11 includes a sensor 18 that can contact the tip portion 7 of the welding electrode 4 . The sensor 18 is made of a conductor (for example, a Cu-based metal) and has a rod shape. The sensor 18 is configured to be linearly reciprocatable by a driving device 19 such as a linear servomotor.

The driving device 19 advances the sensor 18 from a reference position (standby position) at a predetermined distance from the polishing tool 10 to bring it into contact with the tip portion 7 of the welding electrode 4 attached to the polishing tool 10, and the sensor 18 is moved from that position. to the reference position again. When the sensor 18 contacts the tip portion 7 of the welding electrode 4 , the driving device 19 can detect the contact and stop the sensor 18 . The driving device 19 can measure the moving distance when the sensor 18 comes into contact with the tip portion 7 of the welding electrode 4 from the reference position.

The control device 12 includes a computer (eg, PC, control panel, etc.) that implements various hardware such as CPU, ROM, RAM, HDD, monitor, input interface (keyboard, mouse, etc.).

As shown in FIG. 5, the control device 12 includes an arithmetic processing unit 20 configured by a CPU, etc., a storage unit 21 configured by a ROM, RAM, HDD, etc., and a polishing control unit 22 for controlling the polishing tool 10. , and an inspection control unit 23 that controls the inspection unit 11 . These elements 20-23 are interconnected by buses.

The arithmetic processing section 20 executes various calculations necessary for controlling the polishing tool 10 and the inspection section 11 based on data and programs stored in the storage section 21, data acquired by the inspection section 11, and the like. The arithmetic processing unit 20 includes a determination unit 24 that determines whether the state of the tip portion 7 of the welding electrode 4 polished by the polishing device 9 is good or bad. The determination unit 24 determines whether the state of the distal end portion 7 is good or bad based on the reference values stored in the storage unit 21 .

The storage unit 21 stores data and programs required for controlling the polishing tool 10 and the inspection unit 11, data acquired by the inspection unit 11, and the like. The polishing control section 22 is connected to the driving device 13 of the polishing tool 10 and transmits control signals from the arithmetic processing section 20 to the driving device 13 . The inspection control unit 23 is connected to the sensor 18 and the driving device 19 of the inspection unit 11, and transmits control signals from the arithmetic processing unit 20 to the inspection unit 11 or receives data acquired by the inspection unit 11. . The inspection control section 23 includes a current measurement section 25 capable of measuring the current flowing through the sensor 18 . The current measuring section 25 is electrically connected to the sensor 18 . Current measurement unit 25 measures the current when sensor 18 contacts welding electrode 4 and is energized.

A method of polishing the welding electrode 4 with the polishing apparatus 9 having the above configuration will be described below. As welding is repeated, the end face of the tip portion 7 of the welding electrode 4 is alloyed and worn, and is flattened as indicated by the chain double-dashed line in FIG. 2 . This method includes a step (polishing step) of regenerating the worn tip portion 7 of the welding electrode 4 with a polishing tool 10 and a step (inspection step) of inspecting the state of the welding electrode 4 by an inspection unit 11 after the polishing step. .

In the polishing process, the worn welding electrode 4 is attached to the polishing tool 10 . Welding electrode 4 is inserted into first opening 14 of abrasive tool 10 . The welding electrode 4 inserted through the first opening 14 is attached to the polishing tool 10 with the tip portion 7 protruding (exposed) from the second opening 15 . When the welding electrode 4 is attached to the polishing tool 10, the inner peripheral surface 10a of the polishing tool 10 does not contact the intermediate portion 8 of the welding electrode 4, and only the guide portion 16 of the polishing tool 10 is in contact with the surface of the intermediate portion 8. will come into contact with (pressure contact). After that, the polishing device 9 rotates the polishing tool 10 to start polishing the welding electrode 4 . During the polishing process, the sensor 18 of the inspection unit 11 is on standby at a reference position away from the polishing tool 10 so as not to contact the welding electrode 4 .

As shown in FIG. 6 , in the polishing process, the guiding portion 16 slides while contacting (pressing) the intermediate portion 8 due to the rotation of the polishing tool 10 , so that the electrode material contained in the surface of the intermediate portion 8 is removed. can move (plastic flow) from the side of the first opening 14 where the peripheral velocity is low to the side of the second opening 15 where the peripheral velocity is high (in FIG. 6, the direction of flow of the electrode material is indicated by an arrow).

The electrode material that has flowed to the first opening 14 due to the action of the guide portion 16 flows out from the second opening 15 and is drawn toward the tip portion 7 side. The polishing tool 10 moves the electrode material flowing out of the second opening 15 to the tip 7 . The distal end portion 7 is raised by the moved electrode material, and is shaped (regenerated) from the flat state indicated by the solid line in FIG. 6 to the state indicated by the two-dot chain line. During the polishing process, the guiding portion 16 slides on the surface of the intermediate portion 8 of the welding electrode 4, thereby generating minute polishing dust. Polishing powder is discharged through the discharge port 17 .

After a predetermined time has passed, the control device 12 sends a control signal to the driving device 13 of the polishing device 9 to stop the polishing tool 10 . After that, the inspection process is performed by the control device 12 .

As shown in FIG. 7 , in the inspection process, the sensor 18 waiting at the reference position advances toward the polishing tool 10 and contacts the tip portion 7 of the welding electrode 4 . When the sensor 18 contacts the distal end portion 7, the driving device 19 stops the sensor 18 and measures the movement distance of the sensor 18 concerned. The driving device 19 transmits data related to the measured moving distance to the inspection control section 23 of the control device 12 .

The arithmetic processing unit 20 of the control device 12 calculates the protrusion height (length) of the tip portion 7 of the welding electrode 4 based on the measurement data related to the movement distance received by the inspection control unit 23 . The arithmetic processing unit 20 determines whether the state of the distal end portion 7 is good or bad based on the calculated protrusion height value. The determination unit 24 of the arithmetic processing unit 20 compares the reference value of the protrusion height H1 stored in the storage unit 21 with the calculated protrusion height. In that case, it is determined to be defective.

In the present embodiment, the distance from the edge of the second opening 15 of the polishing tool 10 to the end face of the tip portion 7 may be regarded as the protrusion height of the tip portion 7 and compared with the reference value. good. In addition, the control device 12 determines the state (protrusion height) of the tip portion 7 by comparing the measurement data related to the movement distance of the sensor 18 with a predetermined reference value without calculating the protrusion height of the tip portion 7. Acceptance/rejection judgment can be performed.

In the inspection process, a voltage for welding or a voltage for inspection is applied to the welding electrode 4 by the indirect spot welding device while the sensor 18 is in contact with the tip portion 7 of the welding electrode 4 . At this time, the inspection control unit 23 of the control device 12 measures the current flowing through the sensor 18 using the current measurement unit 25 . The arithmetic processing unit 20 determines whether the state of the tip portion 7 of the welding electrode 4 is good or bad based on the measured current value. The determination unit 24 of the arithmetic processing unit 20 compares the measured data of the current value with the reference value stored in the storage unit 21, and if the value is equal to or greater than the reference value, it is judged to be good, and if it is less than the reference value, it is judged to be defective. judge.

As a result of the above determination, when the determination unit 24 determines that the sensor is defective, the control device 12 transmits a control signal to the driving device 19 of the inspection unit 11 to move the sensor 18 backward to the standby position. After that, the control device 12 sends a control signal to the driving device 13 of the polishing tool 10 to rotate the polishing tool 10 and perform the polishing process again. If the judgment result is good, the welding electrode 4 is removed from the polishing tool 10 .

In the present embodiment, the quality of the tip portion 7 is determined based on the protrusion height of the tip portion 7 of the welding electrode 4 and the current value measured via the sensor 18. Acceptance or rejection may be determined based on only one of them.

According to the polishing method and the polishing apparatus according to the present embodiment described above, in the polishing process, the electrode material contained in the surface of the intermediate portion 8 is moved (flowed) to the tip portion 7 by the polishing tool 10, thereby 7 can be played. Further, in the inspection process, the quality of the ground state of the welding electrode 4 can be inspected by detecting the state (protrusion height, current) of the ground tip portion 7 by the sensor 18 of the inspection section 11 . .

FIG. 8 shows a second embodiment of the invention. In the polishing apparatus 9 according to the first embodiment described above, the inspection unit 11 is composed of the contact-type sensor 18 , but the inspection unit 11 according to this embodiment is composed of the non-contact-type sensor 18 . The sensor 18 is configured by, for example, a laser distance sensor capable of emitting laser light L, but is not limited to this configuration. The sensor 18 is positioned away from the abrasive tool 10 so as not to contact the welding electrode 4 attached to the abrasive tool 10 .

In this embodiment, only the distance between the sensor 18 and the end surface of the tip portion 7 of the welding electrode 4 is measured in the inspection process. Data relating to the measured distance is converted into the protrusion height of the tip portion 7 by the control device 12 and compared with a reference value. Without being limited to this, the quality of the polished state of the tip portion 7 can be determined by comparison with a reference value without converting the data related to the measured distance.

In this embodiment, air is blown by a blower or the like from the inspection unit 11 side toward the polishing tool 10 so that the polishing powder discharged from the discharge port 17 does not adhere to the sensor 18, and the inside of the polishing tool 10 is exposed. pressure is desirable. This effectively prevents polishing powder from adhering to the inspection section 11 .

Components other than the inspection unit 11 in this embodiment are the same as those in the first embodiment. Components in this embodiment that are common to the first embodiment are denoted by common reference numerals.

In addition, the present invention is not limited to the configuration of the above-described embodiment, nor is it limited to the above-described effects. Various modifications can be made to the present invention without departing from the gist of the present invention.

In the above embodiment, an example in which the polishing tool 10 is formed with the discharge port 17 is shown, but the present invention is not limited to this configuration. For example, without forming the exhaust port 17 in the polishing tool 10, a blower such as a blower is arranged below the polishing tool 10, and air is blown into the polishing tool 10 from the blower through the second opening 15, thereby polishing. Polishing powder in tool 10 may be discharged from first opening 14 .

1 First metal plate (member to be welded)
4 Welding Electrode 6 Body of Welding Electrode 7 Tip of Welding Electrode 8 Intermediate Part of Welding Electrode 9 Polishing Device 10 Polishing Tool 18 Sensor

Claims (2)

In a method for polishing a welding electrode used for indirect spot welding,
The welding electrode includes a main body, a tip that contacts a member to be welded, and an intermediate part positioned between the main body and the tip,
A polishing step of moving the electrode material contained in the intermediate portion of the welding electrode from the intermediate portion to the tip portion of the welding electrode by a rotating polishing tool, and an inspection step of detecting the state of the tip portion with a sensor. and
The polishing tool has a first opening formed at one end, a second opening formed at the other end, and an electrode material contained in the intermediate portion of the welding electrode. a guide portion that moves to the tip portion of the welding electrode through
The second opening of the polishing tool is a guide opening for exposing the tip of the welding electrode inserted from the first opening of the polishing tool,
The welding electrode polishing method, wherein in the inspection step, the sensor inspects the tip of the welding electrode exposed from the second opening of the polishing tool. In a polishing device for welding electrodes used for indirect spot welding,
The welding electrode includes a main body, a tip that contacts a member to be welded, and an intermediate part positioned between the main body and the tip,
a polishing tool that moves the electrode material contained in the intermediate portion of the welding electrode from the intermediate portion to the tip portion of the welding electrode ; and a sensor that detects the state of the tip portion;
The polishing tool has a first opening formed at one end, a second opening formed at the other end, and an electrode material contained in the intermediate portion of the welding electrode. a guide portion that moves to the tip portion of the welding electrode through
The second opening of the polishing tool is a guide opening for exposing the tip of the welding electrode inserted from the first opening of the polishing tool,
The welding electrode polishing apparatus, wherein the sensor inspects the tip portion of the welding electrode exposed from the second opening of the polishing tool .

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