JPH0780058B2 - DC resistance welding equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a DC resistance welding apparatus in which inverter power supplies operate in parallel, and in particular, a DC (rectified) output is added in series to supply a higher voltage and a larger current. The present invention relates to a DC resistance welding device capable of

[Prior Art] Recently, when welding aluminum, which requires a current of tens of thousands of amperes, a plurality of inverter power supplies including a converter, an inverter, a welding transformer, and a double-wave rectifying element (rectifier). , And a DC resistance welding apparatus (inverter spot DC welding machine) for obtaining a large current by synthesizing the DC outputs of the respective rectifiers in parallel is used.

In such a DC resistance welding apparatus, a DC voltage of several tens of volts is derived and applied to a member to be welded that is sandwiched by welding electrodes, whereby energization of tens of thousands of amperes is achieved.

Further, when a DC resistance welding device is used in a welding robot, the switching frequency of the inverter is formed at a higher frequency in order to facilitate portability, and the size and weight of the welding transformer are reduced.

[Problems to be Solved by the Invention] However, when the switching frequency of the inverter is formed at a higher frequency to obtain a DC voltage of several tens of volts,
A rectifier that rectifies the secondary output AC of the welding transformer requires, for example, a Schottky barrier diode capable of high-speed switching operation. In this case, since the reverse breakdown voltage is low, a configuration in which Schottky barrier diodes are connected in series is conceivable, but the forward / reverse voltage differs due to variations in individual characteristics. Therefore, when a Schottky barrier diode having a low reverse breakdown voltage is used, it is difficult to rectify a higher voltage. In such a case, there is a drawback that it is difficult to realize a DC welding resistance device with a reduced device cost (cost).

The present invention has been made in view of the above point, and in a relatively simple configuration, a DC resistance welding capable of supplying a higher voltage and a larger current by adding in series DC outputs when the inverter power supplies operate in parallel. The purpose is to provide a device.

[Means for Solving the Problems] In order to solve the above problems, in the DC resistance welding apparatus of the present invention, the output AC of each of n inverters is one or n primary coil sides of a welding transformer. In a DC resistance welding apparatus that is supplied in series additively or in parallel with each other, double-wave rectification is performed on each secondary coil side of the welding transformer, each double-wave rectified output is connected in series, and the series double-wave rectified output is It is characterized in that it is supplied to the object to be welded.

[Operation] In the above configuration, a DC output is obtained by rectifying the AC output of the secondary coils of the welding transformers of a plurality of power sources with each rectifying element, and by adding the DC outputs in series, a relatively low order. / It becomes possible to adopt a reverse voltage rectifying element.

[Embodiment] Next, an embodiment of the DC resistance welding apparatus according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the entire structure of the first embodiment, FIG. 2 is a block diagram showing the essential parts of a modification of the first embodiment, and FIG. 3 is a block showing the structure of the second embodiment. It is a figure.

In FIG. 1, reference numeral 10 is a three-phase 400V ON / OFF section (including ELB etc.). Further, A, B, C, and D are power supplies that perform parallel operations and are well-known inverter control power supplies used for welding robots and the like.

Converters 12a, 12b, 12c, 12d are provided for the power supplies A to D, respectively.
And inverters 14a, 14b, 14c, 14d and welding transformer 16
It has a, 16b, 16c, 16d and rectifiers 18a, 18b, 18c, 18d. The rectifiers 18a to 18d are respectively provided with rectifying elements Da, Db and Dc, Dd and De, Df and Dg, Dh for performing double-wave rectification.

Further, it has an adder circuit E, and this adder circuit E has output terminals a, b, c, d connected to rectifying elements Da, Db and Dc, Dd and De, Df and Dg, Dh, respectively. As can be easily understood from the drawing, the welding transformers 16a, 16b, 16c and 16d are connected in series with the middle points h, i, j and k of the secondary coils.

The added voltage here, that is, the output end a and the midpoint k is connected to the welding gun 20, and the added DC voltage Ea is applied. Further, a member to be welded (workpiece) 22 is held between the welding electrodes 20a and 20b of the welding gun 20.

Further, base drive circuits 26a, 26b, 26c, 26d for performing base drive of the switching transistors Tra, Trb, Trc, Trd (full bridge circuit) of the inverters 14a to 14d are provided.

Current detectors 27a, 27b, 27c, 27d such as toroidal coils for detecting the current of the switching operation are provided on the connection lines of the converters 12a to 12d and the inverters 14a to 14d, respectively, and are subsequently derived from this. Detection signals Sa, Sb, S
Detecting / amplifying circuits 28a, 28b, 28c, 28d for deriving c and Sd are provided.

The reference numeral 40 is a microprocessor (MPU) equipped with a CPU, RAM, ROM, I / O, etc., for example, from a setting means / centralized control device such as a computer for FMS that performs full-closed NC control. The system controller is supplied with the interlocking control signal Cm and performs so-called welding control.

Further, the system controller 40 sets the switching frequency of the inverters 14a to 14d to change the added DC voltage Ea applied to the welding gun 20, that is, a set value signal Cr for setting the welding energy to a desired value is supplied. The PWM circuit 41 is provided.

The operation of the above configuration will be described below.

The system controller 40 is supplied with the interlocking control signal Cm, and the PWM circuit 41 is supplied with the set value signal Cr. Then P
Timing gate signals based on the set value signals are supplied from the WM circuit 41 in synchronization with the base drive circuits 26a to 26d, respectively. Here, the circuit configuration related to the base drive circuits 26a to 26d and the PWM circuit 41 changes the ON / OFF time ratio of the switching transistors Tra to Trd while fixing the switching frequency, that is, a so-called fixed frequency pulse width modulation method (PWM). Is.

The base drive pulses from the base drive circuits 26a to 26d are switching transistors Tra of the inverters 14a to 14d.
Through to the base of Trd for switching operation. As a result, the direct current supplied from the converters 12a to 12d is converted into pulsed high frequency waves (alternating current). Further, the alternating current is supplied to the welding transformers 16a to 16d and converted into, for example, an alternating current of 10V having a relatively low voltage and a large current. Then, the rectifying elements Da, Db and Dc of the rectifiers 18a to 18d,
Double-wave rectification is performed at Dd and De, Df and Dg, and Dh, and output terminals a, b, c, and d and welding transformers 16a, 16b, and 16 respectively.
Between the midpoints h to k of the secondary coils of c and 16d, positive and negative DC outputs, for example, a DC voltage of 10V are obtained. The respective DC outputs are added, that is, the added DC voltage Ea of about 4 times is obtained.

In this way, by adding the respective DC outputs obtained from the power supplies A to D in series by the adding circuit E, the added DC voltage Ea of about 4 times can be obtained. In this case, the rectifying elements Da, Db
, Dc, Dd and De, Df and Dg, and Dh are derived from a DC voltage of approximately 1/4, and a Schottky barrier diode having a relatively low forward / reverse voltage can be adopted.

Next, a modification of the first embodiment shown in FIG. 2 will be described.

This example shows a welding transformer 52 connected to an inverter 50.
As you can easily see from the figure, one primary coil
52a and two secondary coils 52b and 52c are arranged. Further, it has rectifiers 54 and 56 for rectifying the output AC of the secondary coils 52b and 52c, respectively. Rectifiers Di, Dj and Dk, Dl are connected in parallel to the rectifiers 54, 56, and their output terminals m, n are secondary coils 52b, 52c, as can be easily understood from the figure.
Are connected in series with the middle points r and s.

The basic operation is similar to that of the first embodiment, and detailed description thereof will be omitted.

In this case, the respective DC outputs obtained from the rectifiers 54 and 56 are added in series to obtain an approximately doubled added DC voltage Eb. In this case, the rectifying elements Di, Dj and Dk, Dl are approximately 1/2.
The DC voltage is derived, and a Schottky barrier diode having a relatively low forward / reverse voltage can be employed as described above.

Further, a second embodiment shown in FIG. 3 will be described.

In this example, a higher added DC voltage Ec is obtained.

Power supplies X and Y are isolation transformers 62 and 64 and converter 66, respectively.
It has 68, inverters 72 and 74 connected in series, a welding transformer 76, and rectifiers 82 and 84. Rectifiers Dm, Dn and Do, Dp are arranged in the rectifiers 82, 84, respectively.

In this case, the inverter 7
Reference numerals 2 and 74 have switching transistors Trm, Trn, Tro, Trp and Trs, Trt, Tru, Trv which form a full bridge circuit. The output terminals of the full-bridge circuit are connected in series, where each AC output is the welding transformer 76.
Is supplied to the primary coil 76a. Furthermore, the rectifying elements Dm, D
The output terminals of n, Do, and Dp are connected to each other, and as can be easily understood from the figure, the midpoint t of the secondary coils 76b and 76c,
It is connected in series with u. The system controller 40 is omitted. The more basic operation is the first
This is the same as the embodiment described above, and detailed description thereof will be omitted.

In this case, first, the added AC voltage supplied to the primary coil 76a of the welding transformer 76 is formed, and then the rectifier 82,
Higher added DC voltage Ec is obtained by adding the respective DC outputs obtained from 84 in series. Further, the rectifying elements Dm, Dn and Do, Dp are those in which a DC voltage of approximately 1/2 is derived, and it is possible to adopt a Schottky barrier diode having a relatively low forward / reverse voltage as described above. It is effective in obtaining a DC voltage to which a high voltage is added.

The structure up to each welding transformer shown in the first embodiment, the modified example, and the second embodiment is not particularly limited and may be any structure.

[Effects of the Invention] As described above, according to the present invention, the output alternating currents of the n inverters are supplied to the primary coil side of one or n welding transformers in series additive or in parallel. In the DC resistance welding device, the double-wave rectified outputs on the secondary coil side of the welding transformer are connected in series, and the series double-wave rectified outputs are supplied to the object to be welded.

As a result, the DC outputs when the inverter power supplies operate in parallel are added in series, and it becomes possible to supply a higher voltage and a larger current. In addition, it is possible to employ a rectifying element having a relatively low forward / reverse voltage.

[Brief description of drawings]

FIG. 1 is a block diagram showing the entire construction of a first embodiment of a DC resistance welding apparatus of the present invention, FIG. 2 is a block diagram showing the essential parts of a modification of the first embodiment, and FIG. It is a block diagram which shows the structure of Example 2 of this invention. 12a to 12d …… Converter 14a to 14d …… Inverter 16a to 16d …… Welding transformer 18a to 18d …… Rectifier 20 …… Welding gun 26a to 26d …… Base drive circuit 40 …… System controller A to D …… Power supply E …… Adding circuit Ea …… Adding DC voltage

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Fumio Takano 1-10-1 Shin-Sayama, Sayama City, Saitama Prefecture Honda Engineering Co., Ltd. (72) Hidenori Koga 1-10-1 Shin-Sayama, Sayama City, Saitama Prefecture Within Honda Engineering Co., Ltd. (56) References Special Table Sho 58-500702 (JP, A)

Claims (1)

[Claims] 1. A direct current resistance welding apparatus in which the output alternating current of each of n (n ≧ 2) inverters is supplied in series additive or parallel to the primary coil side of one or n welding transformers. Double-wave rectification is performed on each secondary coil side of the welding transformer, respective double-wave rectification outputs are connected in series, and the series double-wave rectification output is supplied to a workpiece.