JP2006231379A - Multi-spot welding equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-spot welding equipment capable of ensuring a consistent welding condition by preventing leakage of the welding current at a weld point, enhancing the welding efficiency, and improving the welding quality. <P>SOLUTION: A plurality of upper electrodes 6-1, 6-2, ..., 6-n and a plurality of lower electrodes 7-1, 7-2, ..., 7-n are connected to a three-phase AC power supply (a welding power source) 1 in parallel. Control means (a welding control circuit 3 and an IGBT control circuit 4) are provided, in which switching elements IGBT-1, IGBT-2, ..., IGBT-n are connected to connection lines a1, a2, ..., an of the upper electrodes 6-1, 6-2, ..., 6-n and connection lines b1, b2, ..., bn of the lower electrodes 7-1, 7-2, ..., 7-n in series, respectively, and a pair of IGBT-1, IGBT-2, ..., IGBT-n facing each other are simultaneously and orderly turned ON/OFF to change the supply of the welding current to each weld point of metal plate W1, W2, and the welding current runs orderly to the plurality of weld points of the metal plates W1, W2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a multi-spot welding apparatus that performs multi-point welding of workpieces.

  Spot welding (spot welding) is known as a typical resistance welding. In this spot welding, a welding current is passed between both electrodes while the workpiece is sandwiched and pressed between the upper electrode and the lower electrode. This is a welding method in which the workpiece is spot-welded.

  By the way, a multi-spot welding apparatus for performing multi-point welding has been put into practical use. However, since the conventional apparatus employs a method in which a plurality of upper electrodes at each welding point are energized at the same time, the current flowing through each welding point. As a result, there is a problem that not only the welding points can be welded uniformly, but also a large current needs to flow at a time, so that a large-capacity welding transformer is required and the apparatus becomes large.

  Therefore, for example, Patent Document 1 proposes a multi-spot welding apparatus that employs a method in which a plurality of welding points are not welded at a time but are welded one by one in order. In the multi-spot welding apparatus described in Patent Document 1, switching elements provided for each upper electrode are sequentially turned on at predetermined time intervals by the control means, and the ON-state switching elements are connected during this ON period. Further, a method is employed in which the welded portion of the work piece corresponding to the upper electrode is welded for each electrode.

JP 2000-351081 A

  However, in the multi-spot welding apparatus described in Patent Document 1, since the lower electrode is common to each welding point and these are not individually connected to the welding power source, the welding current is applied to the adjacent welding point in the lower electrode. Leaks, welding conditions are not stable, and welding efficiency is poor.

  The present invention has been made in view of the above problems, and its objective is to prevent welding current leakage at the welding point to ensure stable welding conditions, to improve welding efficiency and to improve welding quality. An object of the present invention is to provide a multi-spot welding apparatus capable of performing the above.

  In order to achieve the above-mentioned object, the invention according to claim 1 is characterized in that a welding current is passed between both electrodes from a welding power source while sandwiching and pressing an object to be welded with a plurality of upper electrodes and the same number of lower electrodes. As a multi-spot welding apparatus for multi-point welding of the workpiece, a plurality of the upper electrode and the lower electrode are connected in parallel to the welding power source, and a switching element is connected to each connection line of the upper electrode and the lower electrode. Welding current to each welding point of the workpiece to be welded by simultaneously turning on and off the pair of switching elements provided in each connecting line of the pair of upper electrode and lower electrode facing each other in series The control means which switches supply of this is provided, A welding current is sent in order to several welding points of a to-be-welded object, It is characterized by the above-mentioned.

  According to a second aspect of the present invention, in the first aspect of the present invention, the control means simultaneously turns on / off each pair of the switching elements according to a preset order.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the control means is a predetermined preset from the welding power source to each welding point while the pair of switching elements are ON. The welding current of the magnitude | size of this is made to flow only for the predetermined time set beforehand.

  According to the present invention, a switching element is provided not only in each connection line between a plurality of upper electrodes and a welding power source but also in each connection line between a plurality of lower electrodes and a welding power source, and a pair of upper electrodes facing each other, A plurality of welding points of the work piece are switched by simultaneously turning on and off a pair of switching elements provided in each connection line of the lower electrode to switch the supply of the welding current to each welding point of the work piece. As a result, the welding current is flowed in order to prevent leakage of the welding current to other welding points, ensuring stable welding conditions at each welding point and improving welding efficiency. The welding is homogenized and the welding quality is improved.

  In addition, since the welding current is not flowed to all the welding points at once, but it is made to flow to each welding point in order, a large current can be flowed to each welding point, and high welding efficiency can be ensured, Speeding up can be realized and welding time can be shortened.

  Furthermore, since the intermittent control method is adopted as the energization control method, the value of the welding current supplied to each welding point, the energizing time, and the order of the welding points to be energized can be arbitrarily set. Optimum current control suitable for each is possible, and high welding quality can be ensured.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing a basic configuration of a multi-spot welding apparatus according to the present invention. The illustrated multi-spot welding apparatus includes a general-purpose welding machine 2 connected to a three-phase AC power source 1 and a welding control circuit (sequencer). 3, IGBT control circuit 4, welding start switch (welding start SW) 5, and n (n is an integer of 2 or more) upper electrodes (welding guns) 6-1, 6-2,. And the same number (n) of lower electrodes 7-1, 7-2,..., 7-n arranged opposite to each other below the upper electrodes 6. For convenience, a plurality of upper electrodes 6-1, 6-2,..., 6-n and lower electrodes 7-1, 7-2,. “2”, “3”,..., “N” are attached.

  The welding general-purpose machine 2 includes a welding power source unit 21, a welding transformer 22 and a rectifier circuit 23. Although not shown, the welding power source unit 21 receives three-phase AC from the three-phase AC power source 1. A converter for converting to direct current, a capacitor for smoothing direct current, and an inverter for converting the smoothed direct current to high frequency alternating current are provided. The primary side coil L1 of the welding transformer 22 is connected to the output end of the welding power source 21, and the rectifier circuit 23 is connected to the secondary side coil L2 of the welding transformer 22. Here, the rectifier circuit 23 performs full-wave rectification on the high-frequency current induced in the secondary coil L2 of the welding transformer 22, and includes two diodes D1 and D2.

  The n upper electrodes 6-1, 6-2,..., 6-n and the lower electrodes 7-1, 7-2,. -1,6-2,..., 6-n are connected in parallel to the (+) terminal of the rectifier circuit 23 via connection lines a1, a2,. 2,..., 7-n are connected in parallel to the (−) terminal of the rectifier circuit 23 via connection lines b1, b2,. Then, connection lines a1, a2,..., An of the upper electrodes 6-1, 6-2,..., 6-n and lines b1, b2 connecting the lower electrodes 7-1, 7-2,. ,..., Bn are respectively connected in series with IGBTs (Insulated Gate Bipolar Transistors) as switching elements for turning on / off electrical conduction. It should be noted that a pair of IGBTs connected to each of the connection lines a1, a2,..., An and b1, b2,..., Bn are IGBT-1, IGBT-2,. indicate.

  .., An and the n IGBT-1, IGBT-2,..., IGBT-n respectively connected to the connection lines b1, b2,. Are connected to each. Here, the IGBT control circuit 4 selects an IGBT to be driven (ON / OFF) based on the IGBT selection signal transmitted from the welding control circuit 3, and uses the IGBT open / close signal transmitted from the welding control circuit 3 as well. In this embodiment, the selected IGBT is turned on / off. In the present embodiment, a pair of upper electrodes 6-1, 6-2,. .., 7-n, and a pair of IGBT-1, IGBT-2,..., IGBT-n connected to the respective connection lines a1 and b1, a2 and b2,. The control means is configured to switch the supply of the welding current to each welding point of the two metal plates (workpieces) W1 and W2 which are ON / OFF.

  On the other hand, the welding control circuit 3 receives a welding start signal transmitted from the welding start switch 5 and transmits a welding start signal to the general-purpose welding machine 2, and a welding current having a preset magnitude is set in advance. When the welding end signal transmitted from the general-purpose welding machine 2 is received, the IGBT control circuit 4 is output with an IGBT open / close signal and turned on. A pair of IGBTs are turned OFF, an IGBT selection signal is transmitted to the IGBT control circuit 4 to select the next pair of IGBTs, and the pair of IGBTs are turned ON simultaneously. Thereafter, the welding control circuit 3 repeats the same action n times.

  Next, multi-point welding of an object to be welded by the multi-spot welding apparatus having the above configuration will be described with reference to FIG. FIG. 2 is a timing chart showing energization control to the welding point of the workpiece.

  As shown in FIG. 1, when two metal plates (workpieces) W1 and W2 are welded as multi-point welding (in this embodiment, n-point welding), these two metal plates W1 and W2 are welded. W2 are stacked one above the other and sandwiched between n upper electrodes 6-1, 6-2,..., 6-n and lower electrodes 7-1, 7-2,. The two metal plates W1, W2 are pressurized by the upper electrodes 6-1, 6-2,..., 6-n and the lower electrodes 7-1, 7-2,.

  In the above state, when the welding start switch 5 is turned on and a welding start signal is output to the welding control circuit 3, the welding control circuit 3 transmits an IGBT selection signal to the IGBT control circuit 4, for example, a welding point. A pair of IGBTs corresponding to the first point (in this embodiment, a pair of IGBTs 1 connected to the connection lines a1 and b1 of the upper electrode 6-1 and the lower electrode 6-2 with the number "1") At the same time, an IGBT open / close signal is transmitted to the IGBT control circuit 4, and the selected pair of IGBT-1 is simultaneously turned ON as shown in FIG. Then, the upper electrode 6-1 and the lower electrode 7-1 at the first welding point are in a conductive state via the metal plates W1 and W2. At this time, the other pairs of IGBT-2, IGBT-3,..., IGBT-n are all in the OFF state, and the connection lines a2 and b2, a3 and b3,. Is in a state.

  In addition, the welding control circuit 3 outputs a welding start signal (first welding start signal) as a command for flowing a welding current to the first welding point with respect to the general-purpose welding machine 2. Then, as shown in FIG. 2, predetermined energization is performed between the upper electrode 6-1 and the lower electrode 7-1 of the number “1” in which the high-frequency current rectified in the rectifier circuit 23 of the general-purpose welding machine 2 is in a conductive state. The first welding point is spot-welded on the two metal plates W1 and W2 by the flow of time t1. Note that the order of the welding points to be spot-welded (that is, the order of IGBTs to be turned ON / OFF), the magnitude of the welding current passed through each welding point, and the energization time are arbitrarily set in advance. These are the welding control circuit 3. Is stored in a memory (not shown) incorporated in the memory.

  By the way, in the present embodiment, spot welding is sequentially performed on the metal plates W1 and W2 from the left end in FIG. 1 (that is, in the order of numbers “1”, “2”, “3”,..., “N”). When the welding current is passed from the general-purpose welding machine 2 to the first welding point for a predetermined energization time t1 as described above, the welding end signal (first A welding end signal) is transmitted to the welding control circuit 3. Then, the welding control circuit 3 outputs an IGBT selection signal to the IGBT control circuit 4 and selects a pair of IGBT-2 corresponding to the next second welding point, as shown in FIG. After turning off IGBT-1 corresponding to the previous first point welding point, the next selected second point IGBT-2 is turned on. Then, the conduction between the upper electrode 6-1 and the lower electrode 7-1 at the first welding point is interrupted, and the upper electrode 6-2 and the lower electrode 7-2 at the second welding point are conducted. It becomes a state.

  In addition, the welding control circuit 3 outputs a welding start signal (second welding start signal) as a command for flowing a welding current to the second welding point with respect to the general-purpose welding machine 2. Then, as shown in FIG. 2, the high-frequency current rectified in the general-purpose welding machine 2 flows between the upper electrode 6-2 and the lower electrode 7-2 of the number “2” in the conductive state for a predetermined energization time t2, As a result, the second welding point of the two metal plates W1, W2 is spot-welded.

  Thereafter, similarly, ON / OFF of each pair of IGBT-3,..., IGBT-n after the third point is sequentially switched, and the third point,..., Nth point of the metal plates W1, W2 A welding current having a preset magnitude is supplied for a preset energization time t3,..., Tn, respectively, and is applied to a total of n welding points from the first point to the nth point of the two metal plates W1, W2. Spot welding is successively performed in this order.

  As described above, in the present embodiment, each connection line a1 between the plurality of upper electrodes 6-1, 6-2, ..., 6-n and the welding power source (general-purpose welding machine 2 in the present embodiment). , A2,... An as well as connection lines b1, b2,..., Bn between the plurality of lower electrodes 7-1-7-2,. , IGBT-2,..., IGBT-n, respectively, and a pair of IGBT-1, IGBT-2,. Since the welding current is sequentially supplied to the n welding points of the metal plates W1 and W2 by switching the supply of the welding current to each of the n welding points in total, the welding current is supplied to the other welding points. Leakage is reliably prevented, and stable welding conditions at each welding point Welding efficiency is increased is coercive, improvement in the welding quality can be achieved by welding the homogenization at each weld point.

  In addition, since the welding current is not flowed to all the welding points at once, but it is made to flow to each welding point in order, a large current can be flowed to each welding point, and high welding efficiency can be ensured, Speeding up can be realized and welding time can be shortened.

  Furthermore, since the intermittent control method is adopted as the energization control method, the value of the welding current supplied to each welding point, the energizing time, and the order of the welding points to be energized can be arbitrarily set. Optimum current control suitable for each is possible, and high welding quality can be ensured.

  In this embodiment, the order of the welding points to be energized is the order of numbers “1”, “2”,..., “N” from the left end in FIG. It can be set arbitrarily.

  The present invention is useful for a multi-spot welding apparatus that welds a plurality of welding points one by one in order.

It is a block diagram which shows the basic composition of the multi-spot welding apparatus which concerns on this invention. It is a timing chart which shows the electricity supply control in the multi spot welding apparatus which concerns on this invention.

Explanation of symbols

1 Three-phase AC power supply (welding power supply)
2 General-purpose welding machine 3 Welding control circuit (control means)
4 IGBT control circuit (control means)
5 Welding start switch 6-1, ..., 6-n Upper electrode 7-1, ..., 7-n Lower electrode 21 Welding power source 22 Welding transformer 23 Rectifier circuit a1, ..., an Upper electrode connection line b1, ..., bn Lower electrode connection line D1, D2 Diode IGBT-1, ..., IGBT-n Switching element L1 Welding transformer primary coil L2 Welding transformer secondary coil t1, ..., tn Energizing time W1, W2 Metal plate (covered Welded)

Claims (3)

A multi-spot welding apparatus for performing multi-point welding of a workpiece by passing a welding current between both electrodes from a welding power source while sandwiching and pressing the workpiece with a plurality of upper electrodes and the same number of lower electrodes. ,
A plurality of the upper electrode and the lower electrode are connected in parallel to the welding power source, and a switching element is connected in series to each connection line of the upper electrode and the lower electrode, and a pair of upper electrodes facing each other, A control means is provided for switching the supply of welding current to each welding point of the work piece by simultaneously turning on and off the pair of switching elements provided in each connection line of the lower electrode in order, A multi-spot welding apparatus, wherein a welding current is passed through the welding points in order.   The multi-spot welding apparatus according to claim 1, wherein the control means simultaneously turns on / off each pair of the switching elements according to a preset order.   The control means causes a welding current of a predetermined magnitude to flow from the welding power source to each welding point for a preset predetermined time while the pair of switching elements are ON. The multi-spot welding apparatus according to claim 1 or 2.

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