JP6497629B2 - Spot welding electrode - Google Patents

Description

  The present invention relates to an electrode for spot welding suitable for use in a table spot welder having a cantilevered articulated arm structure.

  The above-mentioned table spot welder has a flat plate electrode called a table electrode for placing an object to be welded, and a cantilever that can hold the welding gun in a lateral orientation parallel to the plate electrode surface. An articulated arm. The welding gun includes a spot welding electrode and a shank holder that holds the spot welding electrode, and the spot welding electrode includes a cap tip and a shank that holds the cap tip. The cap chip is attached to the tip of the shank, and the shank is attached to the tip of the shank holder. A flow path through which cooling water flows is formed in each of the shank and the shank holder.

  By the way, it is difficult for the table spot welder to hit the tip of the electrode for spot welding at a right angle to the work piece because of the cantilevered articulated arm structure. For this reason, as shown in FIG. 16, the tip of the cap chip 500 is formed in a spherical shape so as to absorb the deviation with respect to the right angle. For example, Patent Documents 1 and 2 describe such a cap chip.

JP 2011-173152 A Japanese Unexamined Patent Publication No. 7-075881

However, since the cap tip having a spherical tip has a small contact area with the workpiece, there is a problem that it is difficult to maintain a sufficient welding strength because the generation area of the molten nugget cannot be increased.
In spot welding, a method of shortening the energization time may be used in order to minimize burning and indentation on the surface of the work piece, but a spot welding electrode having a spherical tip is used. If the energization time is shortened in a situation where the generation area of the molten nugget cannot be increased, the growth of the molten nugget is suppressed, so that the welding strength further decreases.

  This invention is made | formed in view of the situation which concerns, and it aims at providing the electrode for spot welding which can take the contact area with respect to the to-be-welded object of a cap chip | tip, and a table spot welder. .

The electrode for spot welding of the present invention is movable in a flat plate-like electrode on which an object to be welded is placed, and in a lateral posture parallel to the plate-like electrode surface, and the tip portion is bent toward the plate-like electrode. A welding gun having a shank holder, and a spot welding electrode for use in a table spot welder, the shank being attached to the tip portion of the shank holder, the tip portion being formed in a substantially spherical shape, and having a substantially hemispherical space for rotatably fitted to the distal end portion of the shank has a groove along the circumferential direction to the opening inside of the symbolic hemispherical space, the central portion of the further tip side together along the axial direction to protrude at a constant cross-sectional area, the inner cap chip having a protrusion tip becomes flat, the groove formed in the opening inside of the approximately hemispherical space of the cap chip And a ring-shaped engaging member having elasticity to be.

According to the above configuration, since the cap tip is rotatably fitted to the tip portion of the shank, the flat surface at the tip of the cap tip is welded when the tip of the cap tip is brought into contact with the work piece. It can be adhered to the surface of the object. Therefore, the contact area between the cap chip and the work piece can be increased, so that a larger welding nugget can be generated than before, and the communication time can be shortened to minimize burning and indentation on the surface of the work piece. Even with this, high welding strength can be obtained.
Further, in particular, by projecting the central portion on the tip end side of the flattened cap chip with a constant cross-sectional area along the axial direction, the contact area of the cap chip with the workpiece can be made constant over a long period of time. In other words, simply flattening a part of the tip of the cap tip will change the direction of contact with the workpiece to be increased due to wear due to use or wear due to cleaning (polishing). By projecting the central part on the side with a constant cross-sectional area along the axial direction, even if wear due to use or wear due to cleaning occurs, the contact area with the work piece can be made constant until there is no protrusion. Moreover, since the cap chip is fitted so as to be rotatable (so-called swingable) with respect to the tip portion of the shank, it is difficult for the corner of the tip of the projection to hit the work piece, This also contributes to the constant contact area. In this way, it is possible to obtain a stable welding quality over a long period of time, compared to simply flattening a part of the tip of the cap chip.

  Further, since the locking member locks the cap chip to the shank, the cap chip can be prevented from dropping from the shank. In addition, since the locking member has elasticity, the cap chip can be easily attached to and detached from the shank, and workability during product assembly and maintenance can be improved.

  The table spot welder of the present invention includes a welding transformer that converts a current generated in a secondary coil into a direct current by supplying high-frequency alternating current to the primary coil, a flat plate-like electrode on which a workpiece is placed, A welding gun that is supplied with a direct current generated in the secondary coil of the welding transformer, and a vertical direction that is perpendicular to the surface of the plate electrode and a horizontal direction that is parallel to the surface of the plate electrode. Table spot welding comprising: a cantilever articulated arm that is movably held in a direction; an inverter circuit that supplies high-frequency alternating current to a primary coil of the welding transformer; and a welding control circuit that controls the operation of the inverter circuit. The welding transformer includes an annular magnetic core composed of a parallel portion and U-shaped curved portions at both ends, and a space between the parallel portion of the annular magnetic core, divided into a plurality of portions. A plurality of positive coils that are wound around the parallel part of the annular magnetic core together with the primary coil and sandwiched one by one in the gaps provided in the primary coil. A secondary coil in which a coil and a plurality of negative coils are alternately arranged and the plurality of positive coils are all connected in parallel or all or a part thereof are connected in series, and the plurality of negative coils are all connected in parallel. Terminals of the positive side coil and the negative side coil are connected so that all or part of them are connected in series, and the plurality of connected positive side coils and the plurality of negative side coils are connected in series to each other. A conductor group that electrically connects each other, and includes a connection board that supports and fixes all the positive side coils and the negative side coil on one surface by the conductor group, and the plurality of positive side coils. One terminal is the connection On the other surface of the plate, it is electrically connected to a first connecting pole plate extending in a direction parallel to the parallel portion of the annular magnetic core, and one terminal of the plurality of negative side coils is connected to the other side of the connection substrate On the surface side, it is electrically connected to a second connecting plate extending in a direction parallel to the parallel part of the annular magnetic core, and the other terminal of the positive coil and the other terminal of the negative coil are both connected On the other surface side of the substrate, electrically connected to a third connecting plate extending in a direction parallel to the parallel portion of the annular magnetic core, a positive conductor is connected to the first connecting plate, and the first A negative-side conductor is connected to the two-connected electrode plate, and the positive-side conductor and the negative-side conductor are arranged on a boundary surface extending in a direction away from the other surface on the other surface side of the connection board. A pair of conductor plates that are overlapped with each other through the insulating layer, and the positive conductor and the plus electrode are A first rectifier element sandwiched between a connected first electrode plate, a positive electrode in contact with the positive conductor, and a negative electrode in contact with the first electrode plate, and the negative conductor and a negative electrode are connected. A second rectifying element sandwiched between the second electrode plate and having a positive electrode in contact with the negative conductor and a negative electrode in contact with the second electrode plate, and supporting the first electrode plate and the second electrode plate. And a third electrode plate that electrically connects both, and the welding gun includes the spot welding electrode, a shank holder for connecting the plus electrode of the welding transformer to the spot welding electrode, The negative electrode of the welding transformer is connected to the plate electrode.

  According to the above configuration, since the electrode for spot welding according to the invention is provided, spot welding can be performed with high welding strength even if the energization time is shortened for the purpose of minimizing burning and indentation on the surface of the workpiece. It can be carried out.

According to the present invention, since the cap tip is rotatably fitted to the tip portion of the shank, when the tip of the cap tip is brought into contact with the work piece, the flat portion of the tip is set to the work piece. Can be in close contact with the surface. Therefore, the contact area between the cap tip and the work piece can be increased, so that it is possible to generate a larger melt nugget than before, and the energization time is shortened in order to minimize burning and indentation on the surface of the work piece. Even with this, high welding strength can be obtained.
Further, since the locking member locks the cap chip to the shank, the cap chip can be prevented from dropping from the shank. In addition, since the locking member has elasticity, the cap chip can be easily attached to and detached from the shank, and workability during product assembly and maintenance can be improved.
In addition, when a protrusion with a flat tip is provided at the center of the tip of the cap chip, even if wear due to use or wear due to cleaning occurs, until the protrusion disappears, the contact area with the workpiece Can be made constant. In addition, since the cap chip is pivotable (so-called swingable), it is difficult for the corner of the tip of the projection to come into contact with the work piece, and this also contributes to a constant contact area. . In this way, it is possible to obtain a stable welding quality over a long period of time, compared to simply flattening a part of the tip of the cap chip.

The side view which shows the external appearance of the table spot welder which concerns on one Embodiment of this invention. The top view which shows the external appearance of the table spot welder which concerns on one Embodiment of this invention. The side view which shows a part of vertical arm of the table spot welder which concerns on one Embodiment of this invention, and the external appearance of a welding gun The figure which shows the external appearance of the front-end | tip part of the shank holder of the welding gun of the table spot welder which concerns on one Embodiment of this invention, and the electrode for spot welding, and the figure which shows the cross section of the vertical direction of the electrode for spot welding The figure which shows the front-end | tip part of the electrode for spot welding of the welding gun of the table spot welder which concerns on one Embodiment of this invention. The figure which shows the modification of the electrode for spot welding of the welding gun of the table spot welder which concerns on one Embodiment of this invention. The figure which shows the other modification of the electrode for spot welding of the welding gun of the table spot welder which concerns on one Embodiment of this invention. The figure which shows schematic structure of the power supply unit of the table spot welder which concerns on one Embodiment of this invention. The figure which shows the connection with the welding transformer of the table spot welder which concerns on one Embodiment of this invention, a welding gun, and a table electrode. The figure for demonstrating operation | movement of the welding transformer of the table spot welder which concerns on one Embodiment of this invention. The figure for demonstrating operation | movement of the welding transformer of the table spot welder which concerns on one Embodiment of this invention. The figure which shows the control pulse for controlling the electric current supplied to the primary side of the welding transformer of the table spot welder which concerns on one Embodiment of this invention, a primary current, and the welding current after a rectification | straightening. The perspective view which shows the external appearance of the welding transformer of the table spot welder which concerns on one Embodiment of this invention. The perspective view which shows the assembly state of the welding transformer of the table spot welder which concerns on one Embodiment of this invention. The wave form diagram which shows the welding current supplied to a welding gun from a welding transformer in the table spot welding machine which concerns on one Embodiment of this invention. A longitudinal sectional view showing a cap tip of a welding gun of a conventional table spot welder

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments for carrying out the invention will be described in detail with reference to the drawings.

  FIG. 1 is a side view showing an appearance of a table spot welder 1 according to an embodiment of the present invention. FIG. 2 is a plan view showing the appearance of the table spot welder 1 according to the present embodiment. FIG. 3 is a side view showing an appearance of the welding gun 6 of the table spot welder 1 according to the present embodiment.

  1 and 2, a table spot welder 1 according to this embodiment includes a cooling unit 2, a power supply unit 3, a support post 4, a support arm (cantilevered articulated arm) 5, and a welding gun 6. And conductive cables 7 </ b> A and 7 </ b> B, a plate-like electrode (hereinafter referred to as a table electrode) 8, a welding condition setting device 9, a welding transformer 10, and a table driving unit 100.

  The cooling unit 2 supplies cooling water for cooling the heat generated from the welding gun 6 during welding. The cooling unit 2 always operates while the power is on, and circulates the cooling water between the welding gun 6. The power supply unit 3 converts the three-phase alternating current power supplied from the power receiving facility 450 (see FIG. 8) into direct current using a rectifier, and further generates and outputs high-frequency alternating current from the converted direct current. Details of the power supply unit 3 will be described later. The conductive cables 7 </ b> A and 7 </ b> B are used for supplying current to the welding gun 6. One end of the conductive cable 7 </ b> A is connected to the plus electrode of the secondary output end of the welding transformer 10 built in the front surface portion of the table driving unit 100, and the other end is connected to the welding gun 6. One end of the conductive cable 7 </ b> B is connected to the negative electrode of the secondary output end of the welding transformer 10, and the other end is connected to the table electrode 8.

  When a bus bar is used to connect both the positive electrode and the negative electrode of the welding transformer 10, the negative electrode of the welding transformer 10 and the table electrode 8 are directly connected by the bus bar, and the positive electrode of the welding transformer 10 and the welding gun 6 are connected. Are connected by a conductive cable 7A through a bus bar. In FIG. 1, the conductive cable 7B is depicted as a bus bar.

  The welding transformer 10 is a resistance transformer for resistance welding previously proposed by the inventors of the present application in JP2012-210654A and JP2013-179205A. Details of the welding transformer 10 will be described later.

  The support post 4 is erected in the vertical direction in the vicinity of the cooling unit 2 and the power supply unit 3, and supports the support arm 5 so as to be rotatable in the horizontal direction. The support arm 5 holds the welding gun 6, and includes a horizontal arm portion 5A extending in the horizontal direction with respect to the support post 4, and a vertical arm extending vertically downward from the tip portion of the horizontal arm portion 5A. It is substantially L-shaped with the part 5B. A rotation shaft 5Aa is provided at each of the base end portion 5a and the intermediate portion 5b of the horizontal arm portion 5A of the support arm 5, and the welding gun 6 can be moved in the horizontal direction by these rotation shafts 5Aa. It has become.

  The table electrode 8 is formed in a substantially square flat plate shape, and a product to be welded (for example, a metal plate such as two steel plates, not shown) is placed thereon. For the table electrode 8, a metal material excellent in conductivity and thermal conductivity such as a copper material is used. The table electrode 8 is moved up and down by the table driving unit 100. The distance between the welding gun 6 and the table electrode 8 can be adjusted by moving the table electrode 8 up and down. An operator moves the table electrode 8 up and down. The welding condition setting unit 9 sets the welding conditions such as the material of the workpiece (not shown), the plate thickness, and the applied pressure. A welding current corresponding to the welding conditions set by the welding condition setting unit 9 is determined. The operator also performs an operation for setting the welding conditions.

  In FIG. 3, the welding gun 6 includes a handle 6A having a built-in lever-type start switch (not shown) on the base end side. The start switch of the handle 6A outputs a welding command. When the handle 6A is gripped, the switch is turned on and the welding command is output. When a welding command is output by operating the start switch of the handle 6 </ b> A, the welding command is taken into the power supply unit 3. The power supply unit 3 starts operation by receiving a welding command and outputs a high-frequency alternating current. The high-frequency alternating current output from the power supply unit 3 is supplied to the primary coil 12 (see, for example, FIG. 9) of the welding transformer 10.

The welding gun 6 is held by the tip portion 5Ba of the vertical arm portion 5B of the support arm 5 so as to be swingable in the vertical direction. In this case, since the welding gun 6 is supported by the vertical arm portion 5B with the substantially central portion serving as a fulcrum Ps, the vertical trajectory of the tip of the welding gun 6 has an arc shape.
Further, the welding gun 6 is urged by a spring coil 5C stretched between the base end portion and the vertical arm portion 5B so that the base end portion side is lifted upward. The welding gun 6 can be easily moved up and down by the spring coil 5C.

Next, the welding gun 6 will be described in detail.
FIG. 4 is a diagram showing the external appearance of the tip portion 300a of the shank holder 300 of the welding gun 6 and the spot welding electrode 400, and a diagram showing a longitudinal section of the spot welding electrode 400. As shown in FIG. 4A shows the appearance of the tip portion 300a of the shank holder 300 and the spot welding electrode 400, and FIG. 4B shows a longitudinal section of the spot welding electrode 400. FIG. The shank holder 300 has a tip portion 300a bent at a substantially right angle with respect to the main body. The spot welding electrode 400 is attached to the tip portion 300a. Inside the shank holder 300, a flow path 301 for allowing cooling water to flow is formed. The flow path 301 of the shank holder 300 is formed in a tapered shape so as to have a maximum diameter at the opening end 300b.

  The spot welding electrode 400 includes a shank 401, a cap chip 402 that is rotatably attached to a tip portion of the shank 401, and a locking member 403 that locks the cap chip 402 to the shank 401. As a material constituting the shank 401 and the cap chip 402, for example, a metal material considering the mechanical strength, conductivity, and thermal conductivity of chrome copper (CrCu) is suitable.

The shank 401 is formed in a rod shape in which a tip portion is formed in a substantially spherical shape and a central portion is bent in a substantially Z shape. Inside the shank 401, a flow path 401a for allowing cooling water to flow is formed. The flow path 401 a formed in the shank 401 is open at the proximal end side of the spot welding electrode 400 and closed at the distal end side of the spot welding electrode 400. Spot welding electrode 400, so as to be attached to the tip portion 300a of the shank holder 300, the proximal portion is tapered.

FIG. 5 is a view showing a tip portion of the spot welding electrode 400. In this case, FIG. 5A shows a cross section of the tip portion of the shank 401, FIG. 5B shows a cross section of the cap chip 402, and FIG. 5C shows the mounting position of the locking member 403. Show. As shown in FIG. 5A, the shank 401 has a tip portion 401b formed in a substantially spherical shape. Further, as shown in FIG. 5B, the cap chip 402 has a substantially hemispherical space 402a that is rotatably fitted to the tip portion 401b of the shank 401, and has a flat surface at the center portion of the tip. 402b, and further includes a groove 402c along the circumferential direction inside the opening of the substantially hemispherical space 402a. The area of the flat surface 402b of the cap chip 402 is determined according to the magnitude of current that the welding transformer 10 can flow in a short time. That is, the larger the current that the welding transformer 10 can flow in a short time, the larger the area of the flat surface 402b of the cap chip 402 can be.

The locking member 403 is made of heat-resistant O-ring rubber, and is inserted into the groove portion 402 c of the cap chip 402. For example, nitrile rubber, silicone rubber, or fluororubber is suitable for the material constituting the locking member 403. The locking member 403 is a Ru used for locking the cap chip 402 to the tip portion 401b of the shank 401. In addition, if the effect | action which latches the cap chip | tip 402 to the front-end | tip part 401b of the shank 401 is obtained, it does not necessarily need to comprise with O ring rubber, for example, it may be square ring rubber or D ring rubber.

  In the spot welding electrode 400, since the cap tip 402 is rotatable with respect to the shank 401, when the cap tip 402 is brought into contact with the workpiece, the flat surface 402b at the tip of the cap tip 402 is attached to the workpiece. Can be in close contact with. In particular, because the welding gun 6 is supported at its substantially central portion, the vertical trajectory of the tip of the welding gun 6 has an arcuate shape. Since it rotates with respect to 401, the flat surface 402b of the front-end | tip of the cap chip | tip 402 can be applied to a to-be-welded object at right angle. As described above, the flat surface 402b is provided at a part of the tip of the cap chip 402, and the cap chip 402 is rotatable with respect to the tip portion 401b of the shank 401. Can be greatly increased. And since the contact area with respect to the to-be-welded object of the cap chip | tip 402 can be taken large, the production | generation area of a fusion | melting nugget can be enlarged and it becomes possible to obtain high welding strength.

The cap chip 402 may have any shape as long as it has a flat surface at a part of its tip. FIG. 6 is a view showing a modification of the spot welding electrode 400. The spot welding electrode 400B shown in FIG. 6A protrudes with a constant cross-sectional area along the axial direction in the central portion on the tip side , and has a protrusion 402Ba having a flat tip. It is equipped with. The shape of the tip surface of the protrusion 402Ba of the cap chip 402B is preferably a round shape, but may be a square shape (for example, a square shape). By using the cap chip 402B having the protrusion 402Ba, even if wear due to use or wear due to cleaning occurs, the contact area with the workpiece can be made constant until the protrusion 402Ba disappears. By providing the projection 402Ba, it is easy for the corner of the tip to come into contact with the object to be welded. However, by making the cap chip 402B pivotable (so-called swingable), the contact is caused. It can be difficult. On the other hand, the cap tip 402C of the spot welding electrode 400C shown in FIG. 6B is obtained by making the projection 402Ca larger than the projection 402Ba of the spot welding electrode 400B described above. In this case as well, the shape of the tip surface of the protrusion 402Ca is preferably a round shape, but may be a square shape (for example, a square shape).

  Further, the above-described spot welding electrode 400 is obtained by bending the central portion of the shank 401 into a substantially Z-shape, but the shank 401 may be linear without partially bending. 7A and 7B are diagrams showing a spot welding electrode 400D provided with a linear shank 401. FIG. 7A is an external view, and FIG. 7B is a longitudinal sectional view.

Next, the power supply unit 3 will be described.
FIG. 8 is a diagram showing a schematic configuration of the power supply unit 3. In the figure, the power supply unit 3 includes a rectifier 80, a smoothing capacitor 81, a welding control circuit 82, and an inverter circuit 83. The rectifier 80 employs a single-phase full-wave rectification type, and rectifies and converts three-phase alternating current from the power receiving facility 450 into direct current. The welding control circuit 82 controls the magnitude of the welding current and the energization time. The welding control circuit 82 is configured using, for example, a microcomputer. In this case, the microcomputer holds a program for welding control and operates according to the program. The welding control circuit 82 detects a welding command from the start switch 6A provided in the welding gun 6, and thereby generates a timing signal corresponding to the material and thickness of the workpiece set by the welding condition setting unit 9. It is generated and output to the inverter circuit 83. The welding control circuit 82 generates a timing signal so that the welding current becomes a maximum value within 15 milliseconds from the start of energization and the welding is completed within an energization time of 50 milliseconds or less.

  The inverter circuit 83 includes an inverter control unit 831, four switches S <b> 1 to S <b> 4 using, for example, an IGBT (Insulated Gate Bipolar Transistor), and a current sensor 832 using, for example, a CT (Current Transformer). The inverter control unit 831 performs on / off control of each of the switches S1 to S4 based on the timing signal generated by the welding control circuit 82 and the primary current detected by the current sensor 832 to generate high-frequency alternating current. The magnitude of the high-frequency alternating current generated by the inverter control unit 831 varies depending on the on / off duty of each of the switches S1 to S4. By changing the on / off duty of each of the switches S1 to S4, the width of W of the switching waveform changes as shown in FIG.

  FIG. 9 is a diagram showing a connection between the welding transformer 10, the welding gun 6 and the table electrode 8. In the figure, the primary coil 12 of the welding transformer 10 is connected to the output terminal of an inverter circuit 83 (see FIG. 8) of the power supply unit 3. By outputting high-frequency alternating current from the inverter circuit 83, a primary current flows through the primary coil 12 of the welding transformer 10. The secondary coil 15 of the welding transformer 10 does not need to consider the polarity itself, but for the sake of convenience, the secondary coil 15 of the welding transformer 10 has a positive coil 14 and a negative coil 16 connected in series. I will call it. The anode (positive electrode) of the first rectifying element 18 is connected to one end of the positive side coil 14, and the anode (positive electrode) of the second rectifying element 20 is connected to one end of the negative side coil 16. The cathode (negative electrode) of the first rectifying element 18 and the cathode (negative electrode) of the second rectifying element 20 are commonly connected to the plus electrode 22. The other end of the positive side coil 14 and the other end of the negative side coil 16 are commonly connected to the negative electrode 24. The welding gun 6 is connected to the plus electrode 22 via the conductive cable 7A. The table electrode 8 is connected to the negative electrode 24 via the conductive cable 7B.

  FIG. 10 is a diagram illustrating a circuit operation when a forward current flows through the first rectifying element 18. FIG. 11 is a diagram illustrating a circuit operation when a forward current flows through the second rectifier element 20. 10 and 11, an equivalent inductance component that causes a problem in circuit operation is added to the circuit shown in FIG. That is, the inductance of the positive side conductor 30 connecting the positive side coil 14 and the first rectifying element 18, the inductance of the negative side conductor 32 connecting the negative side coil 16 and the second rectifying element 20, and the conductive cables 7A and 7B The welding gun 6 and the inductance of the conductor in the table electrode 8 are considered to affect the performance of the table spot welder 1.

  If a large amount of heat generated in each of the welding transformer 10, the conductive cables 7 </ b> A and 7 </ b> B, and the welding gun 6 can be suppressed, energy saving of the table spot welding machine 1 can be achieved, and a large power saving effect can be expected. This can be realized if it can be controlled so that a larger current than in the prior art is supplied to the welding gun 6 for a short time. On the other hand, in order to supply the optimum welding current for the material or structure to be welded, it is necessary to control the welding current supply time with extremely high accuracy. This can be realized by connecting the inverter circuit 83 to the primary side of the welding transformer 10 for supplying the welding current, and controlling the magnitude of the welding current and the supply time by PWM control.

  FIG. 12 is a diagram illustrating a control pulse for controlling a current supplied to the primary side of the welding transformer 10, a primary current, and a welding current after rectification. In the figure, the pulse (switching pulse) having a width W controlled by the inverter circuit 83 is repeated a certain number of times within a certain time H, in this case, a total of 10 times including a positive pulse and a negative pulse. It is supplied to the primary coil 12. Thereby, the primary current as shown in FIG. 12B flows through the primary coil 12 of the welding transformer 10. When the primary current flows through the primary coil 12 of the welding transformer 10, the secondary current generated on the secondary side of the welding transformer 10 is full-wave rectified by the rectifying elements 18 and 20, and is shown in FIG. Such a welding current flows to the welding gun 6.

  The magnitude of the welding current can be adjusted by increasing or decreasing the pulse width W shown in FIG. In addition, the welding time can be adjusted by increasing or decreasing the number of times of pulse supply. That is, when the pulse repetition frequency is increased, the welding time can be finely adjusted. Further, if the power supplied to the primary coil 12 of the welding transformer 10 is increased, a larger welding current can be taken out from the secondary coil 15.

  Here, the conventional table spot welder is designed to supply a welding current of 200 ms to 700 ms, for example, at 10,000 amperes, but when the welding current is doubled to 20,000 amperes, the welding gun The power loss consumed as heat energy in places other than 6 becomes extremely large, which is a problem in practice. Therefore, even if the welding current is doubled, if the welding time is reduced to 1/10, the power consumption can be reduced to 1/5, which is not a problem in practice.

  On the other hand, the control pulse of the inverter circuit for supplying the welding current has conventionally used a repetition frequency of about 1 kHz. However, in order to supply a large current for a short time, a control pulse with higher resolution is required. become. In the inverter circuit 83 of the table spot welder 1 of the present embodiment, pulses with a repetition frequency of about 5 kHz to 50 kHz are output. When a pulse having a repetition frequency as high as several times to several tens of times is supplied to a conventional welding transformer, a predetermined welding current cannot be obtained, but the welding transformer 10 used in the table spot welding machine 1 of the present embodiment is And, it has a structure capable of obtaining a predetermined welding current even with a pulse having a repetition frequency as high as several times to several tens of times the conventional one. Hereinafter, the structure of the welding transformer 10 used with the table spot welder 1 of this embodiment is demonstrated.

  FIG. 13 is a perspective view showing an appearance of the welding transformer 10 of the table spot welder 1 of the present embodiment. FIG. 14 is a perspective view showing an assembled state of the welding transformer 10. 13 and 14, the welding transformer 10 is divided into a plurality of parts, an annular magnetic core 25 constituted by a parallel part 25 a and U-shaped curved parts 25 b at both ends, and a parallel part 25 a of the annular magnetic core 25. The primary coil 12 that is divided and wound with a gap 12a, and the primary coil 12 are wound around the parallel portion 25a of the annular magnetic core 25 so as to be sandwiched one by one in each gap 12a provided in the primary coil 12. The secondary coil 15 in which a plurality of positive side coils 14 and a plurality of negative side coils 16 are alternately arranged, and the plurality of positive side coils 14 are all connected in parallel or all or part of them are connected in series, The negative side coils 16 are all connected in parallel or all or part of them are connected in series, and the positive side coils 16 and the negative side coils 16 are connected in series so that the connected positive side coils 14 and the negative side coils 16 are connected in series. Connection board having a conductor group electrically connecting the terminals of the cable 14 and the negative side coil 16 and supporting and fixing all the positive side coil 14 and the negative side coil 16 on one surface by the conductor group. 62, and one terminal of each of the plurality of positive side coils 14 is electrically connected to the first connecting pole plate 44 extending in the direction parallel to the parallel portion 25a of the annular magnetic core 25 on the other surface of the connection substrate 62. One terminal of the plurality of negative side coils 16 is electrically connected to the second connecting electrode plate 46 extending in the direction parallel to the parallel part 25a of the annular magnetic core 25 on the other surface side of the connection substrate 62, and is connected to the positive side. The other terminal of the coil 14 and the other terminal of the negative coil 16 are both connected to the third connecting pole plate 48 extending in the direction parallel to the parallel portion 25 a of the annular magnetic core 25 on the other surface side of the connection substrate 62. The first conductor plate 44 is electrically connected to the positive conductor 30, The negative electrode conductor 32 is connected to the two-connection electrode plate 46, and the positive electrode conductor 30 and the negative electrode conductor 32 extend on the other surface side of the connection board 62 in a direction perpendicular to the other surface. A pair of conductor plates stacked via an insulating layer 31 disposed between the positive electrode 30 and the first electrode plate 34 to which the positive electrode 22 (see FIG. 9) is connected. A first rectifying element 18 having an anode (positive electrode) in contact with the side conductor 30 and a cathode (negative electrode) in contact with the first electrode plate 34; a second electrode plate 36 to which the negative conductor 32 and the negative electrode 24 are connected; The second rectifying element 20 having the anode (positive electrode) in contact with the negative conductor 32 and the cathode (negative electrode) in contact with the second electrode plate 36, the first electrode plate 34, and the second electrode plate 36 are And a third electrode plate 38 that supports and electrically connects the both.

  Since the welding transformer 10 has such a structure, a predetermined welding current can be obtained even with a pulse having a high frequency (about 5 kHz to 50 kHz) from the inverter circuit 83.

  By the way, a full-wave rectification type secondary circuit using two rectifying elements 18 and 20 as shown in FIG. 9 has a smaller number of rectifying elements than a circuit using a bridge, and can be reduced in size and power loss. Since it is small, it is known that it is suitable for welding equipment. However, in this secondary circuit, when the voltage induced in the secondary coil 15 is reversed due to the polarity reversal of the current flowing through the primary coil 12, the load current supplied through one rectifier element is A commutation that changes the flow occurs on the rectifying element side.

  When the welding current becomes large, the current energy accumulated in the inductance of each part of the circuit becomes very large. The commutation time during which this current energy moves from one rectifying element to the other rectifying element becomes longer as the inductance of each part of the secondary coil 15 shown in FIGS. If the commutation of the secondary circuit is not completed during the time M from the start of the fall of the current of the primary coil 12 shown in FIG. 12 to the end of the rise of the current of the opposite polarity, the rise of the secondary current is delayed. As indicated by the broken line 12, the planned welding current cannot be obtained.

  As described above, the welding transformer 10 shown in FIGS. 13 and 14 is equivalent to the welding transformer described in Japanese Patent Laid-Open No. 2013-179205, and can follow high-speed and precise large-current welding control. FIG. 15 is a waveform diagram showing a welding current supplied from the welding transformer 10 to the welding gun 6. In the figure, the portion where the current increase rate is the maximum from the welding current supply start time t0 to the subsequent time t1 is called the start-up control period T1, and the peak current value C1 from the subsequent time t1 to the time t2 is shown. A period during which a current of a predetermined level is maintained is referred to as a peak level control period T2, and a period from time t2 to the current cutoff time t3 is referred to as a temperature maintenance control period T3. The period T1 is 10 milliseconds or less, the sum (T1 + T2) of the start-up control period T1 and the peak level control period T2 is 15 milliseconds or less, the start-up control period T1, the peak level control period T2, and the temperature maintenance control period T3. The sum (T1 + T2 + T3) time is controlled to be 50 milliseconds or less. Thus, the energization time of the welding current iw is suppressed to 50 milliseconds or less. This is about one fifth of the conventional energization time. In FIG. 15, the symbol C2 indicates the end value of the welding current iw.

  In the welding transformer 10 used in the table spot welder 1 of the present embodiment, the positive conductor 30 and the negative conductor 32 are in close contact via the insulating layer 31, and the positive coil 14 of the secondary coil 15 is negative. Since these coils are arranged so that the primary coil 12 is sandwiched between the side coils 16, the inductance at the time of commutation of the secondary circuit of the welding transformer 10 is reduced, and the commutation in the secondary circuit is reduced. Time is shortened. Therefore, by using the welding transformer 10, higher frequency inverter control is possible.

  Moreover, the welding transformer 10 can make the heat distribution of the whole welding transformer uniform by the arrangement of the primary coil 12 and the secondary coil 15.

  Further, since the welding transformer 10 divides and winds the positive coil 14 and the negative coil 16 of the primary coil 12 and the secondary coil 15, respectively, the primary coil 12 and the secondary coil 15 are coupled to each other. The coupling between the secondary coil 12 and the secondary coil 15 can be strengthened, and magnetic saturation due to a large secondary current can be prevented.

  In addition, since the relationship between the positive coil 14 and the negative coil 16 of the primary coil 12 and the secondary coil 15 is uniform everywhere in the welding transformer 10, the welding transformer 10 can be disposed in close contact with each other. The transformer 10 can be miniaturized.

Thus, according to the spot welding electrode 400 of the table spot welder 1 according to the present embodiment, the cap tip 402 is rotatably fitted to the tip portion 401b of the shank 401. When the tip is brought into contact with the workpiece, the flat surface 402b at the tip of the cap chip 402 can be brought into close contact with the surface of the workpiece. Therefore, since the contact area of the cap tip 402 with the workpiece can be increased, it is possible to generate a larger melt nugget than before, and shorten the energization time for the purpose of minimizing burning and indentation on the surface of the workpiece. High weld strength can be obtained even if it is made easier.
In particular, in the cap chip 402B having the protruding portion 402Ba or the cap chip 402C having the protruding portion 402Ca at the center portion on the tip side, the protrusion 402Ba or 402Ca is applied to the object to be welded for a long time until it disappears due to wear. The contact area can be made constant. Moreover, since the cap chip 402B (402C) is fitted to the tip portion 401b of the shank 401 so as to be rotatable (so-called swingable), the corner portion at the tip of the projection 402Ba or 402Ca is welded. It is difficult for the piece to hit the object and this contributes to the constant contact area. In this way, it is possible to obtain a stable welding quality over a long period of time, compared to simply flattening a part of the tip of the cap chip.

  Further, since the locking member 403 locks the cap chip 402 to the shank 401, the cap chip 402 can be prevented from dropping from the shank 401. In addition, since the cap chip 402 can be easily attached to and detached from the shank 401, workability during product assembly and maintenance can be improved.

  Although the present invention has been described with reference to particular embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

  INDUSTRIAL APPLICABILITY The present invention has an effect that a contact area of a cap tip with an object to be welded can be increased, and is suitable for a table spot welder adopting a cantilevered articulated arm structure.

DESCRIPTION OF SYMBOLS 1 Table spot welding machine 2 Cooling unit 3 Power supply unit 4 Support post 5 Support arm 5A Horizontal arm part 5a Base end part 5b Middle part 5Aa Rotating shaft 5B Vertical arm part 5C Spring coil 6 Welding gun 6A Welding gun handle 7A, 7B Conductivity Cable 8 Table electrode 9 Welding condition setting device 10 Welding transformer 12 Primary coil of welding transformer 14 Positive coil of secondary coil of welding transformer 15 Secondary coil of welding transformer 16 Negative coil of secondary coil of welding transformer 18 DESCRIPTION OF SYMBOLS 1 Rectification element 20 2nd rectification element 22 Positive electrode of welding transformer 24 Negative electrode of welding transformer 30 Positive side conductor 32 Negative side conductor 80 Rectifier 81 Smoothing capacitor 82 Welding control circuit 83 Inverter circuit 100 Table drive part 300 Shank holder
The flow path of the distal end portion 301 the shank holder 300a shank holder 400,400B, 400C, 400D spot welding electrode 401 shank 401a shank of the channel 401 b shank of the tip section 402,402B, substantially hemispherical 402C cap chip 402a Cap chip Space 402b Flat surface of cap chip 402c Groove portion of cap chip 402Ba, 402Ca Cap chip protrusion 403 Locking member 450 Power receiving equipment 831 Inverter control unit 832 Current sensor S1 to S4 switch

Claims (1)

A flat plate electrode on which the work piece is placed;
A welding gun having a shank holder that is movable in a lateral orientation parallel to the plate-like electrode surface and has a tip portion bent toward the plate-like electrode;
An electrode for spot welding used in a table spot welder equipped with
A shank attached to the tip portion of the shank holder, the tip portion having a substantially spherical shape;
Wherein with a tip portion substantially hemispherical space which fits rotatably against, has a groove along the circumferential direction to the opening inside of the symbolic hemispherical space, further a central portion of the tip end of the shank Projecting with a constant cross-sectional area along the axial direction, and a cap chip having a protrusion with a flat tip ,
A ring-shaped locking member having elasticity inserted in the groove formed inside the opening of the substantially hemispherical space of the cap chip;
An electrode for spot welding.