JPH03193277A - DC resistance welding equipment - Google Patents

Abstract

PURPOSE:To reduce operating burden and to apply a high current by carrying out switching operation according to base driving signals produced by time- dividing semiconductor devices of plural full bridge circuits. CONSTITUTION:The base driving signals when the semiconductor devices Tra, Trm, Trb, Trn, Trc, Tro, Trd and Trp of the full bridge circuits 14a and 14b connected in parallel carry out switching operation are time-divided and supplied. By this method, in comparison with the case the base driving signals are not time-divided and the semiconductor devices carry out switching operation, the operating burden is reduced and the higher current can be applied.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a DC resistance welding device used in welding robots, etc., and particularly to an inverter in which full-bridge circuits are connected in parallel, or in which multiple full-bridge circuits are connected in series. The present invention relates to a DC resistance welding device in which a large current can be suitably drawn by time-divisionally driving switching semiconductor elements of connected inverters.

[Prior Art] Recently, a DC resistance welding device (inverter spot DC welding machine) capable of drawing a large current of tens of thousands of amperes has been used in welding robots and the like when welding aluminum, etc. It is being

It is known that a DC resistance welding device that draws such a large current has a configuration in which switching semiconductor elements of an inverter are connected in parallel to drive the base.

Furthermore, a configuration is known in which multiple inverter power supplies are installed, each consisting of a converter, an inverter, a welding transformer, and a double-wave rectifier (rectifier), and a large current is obtained by combining the DC outputs of each rectifier in parallel. ing.

Such DC resistance welding equipment is provided with a feedback control means using a well-known PWM control circuit, etc., which detects the energizing current of the welding gun or the inverter and performs comparison control with the energization setting value. ing.

[Problems to be Solved by the Invention] However, in the conventional DC resistance welding apparatus described above, in the above example, it is necessary to make the characteristics (Hfe) and input/output impedance of each switching semiconductor element the same.

In an example to be described later, the secondary coil output of each welding transformer of a plurality of inverter power supplies is formed to a low voltage, and further, direct currents that are rectified outputs are combined in parallel to supply a large current to a member to be welded. Therefore, when used in welding robots, etc., the inverter that derives the high voltage and the welding transformer are separated from each other in order to prevent power loss in the current-carrying path (cable) due to large DC current. A cable connects the two, and a welding transformer and rectifier are mounted on the welding gun.

In this case, cables connecting the inverter and the welding transformer, for example, 5 to 8 cables are required for an inverter power supply that operates in 4 parallels, and it is also necessary to make the characteristics of each welding transformer uniform.

In such a case, it is difficult to easily obtain a desired large current as a result, and there is a drawback that it is difficult to obtain a degree of freedom in arrangement.

The present invention has been made in view of the above points, and an object of the present invention is to provide a DC resistance welding device that has a relatively simple configuration, increases the degree of freedom in its arrangement, and effectively enables the derivation of a large current. Our goal is to provide the following.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the DC resistance welding apparatus of the present invention includes: an inverter section to which full-bridge circuits made of semiconductor elements are connected in parallel; Drive signal generation means for generating a base drive signal for causing a semiconductor element to perform a switching operation; and drive signal time-division sending means for time-divisionally dividing the base drive signal and sending it to the semiconductor element of the full-bridge circuit. It is characterized by

Furthermore, an inverter section in which output terminals of a plurality of full-bridge circuits configured with semiconductor elements are connected in series, and a drive signal sending means for generating a base drive signal for switching the semiconductor elements of the plurality of full-bridge circuits. and drive signal time-division sending means for time-divisionally sending the base drive signal to the semiconductor elements of the full-bridge circuit.

[Operation] In the above configuration, the base drive signal used when the semiconductor elements of the parallel-connected full bridge circuit perform a switching operation is supplied in a time-division manner. This reduces the operational burden on each semiconductor element compared to, for example, a case where the semiconductor element performs switching operations without time-sharing base drive signals, and allows switching operations with larger currents to be performed. This makes it possible to conduct large currents.

[Example 7] Next, an example of the DC resistance welding apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

Fig. 1 is a block diagram showing the first embodiment, Fig. 2 is a timing chart showing processing waveforms on the time axis in the operation of the first embodiment, and Fig. 3 is a block diagram showing the second embodiment. , 4th
The figure is a timing chart showing processing waveforms on the time axis in the operation of the second embodiment.

First, the configuration of the first embodiment will be explained (see FIG. 1).

The example shown in FIG. 1 is schematically composed of a welding power supply section 10, a welding section 20, a drive control section 30, and a system controller 40 that performs welding control.

The welding power supply unit 10 includes a converter 12 that is connected to a three-phase AC source (three-phase 400V) and derives DC (rectified voltage);
It has an inverter 14. As can be easily understood from the figure, the inverter 14 includes full bridge circuits 14a and 14b connected in parallel to convert a rectified voltage into a pulsed high frequency (alternating current). Full bridge circuit 14a114b
are switching semiconductor elements Tra, Trb, Trc, .
Trd and Trm, Trn, Tro.

Trp is provided.

Furthermore, in order to obtain a large current, it includes a welding transformer 16 that converts a low voltage of, for example, 10 V, and a rectifier DaSDb that performs double-wave rectification and derives a DC voltage Vc.

The welding section 20 is connected to a welding gun 21 to which a DC voltage Vc is applied.
and welding electrodes 21a, 21 that constitute this welding gun 21.
and a member to be welded 22 sandwiched between the members b. Note that the pressure control means and the like are omitted.

The drive control section 30 includes connected switching semiconductor elements T.
raSTrm and Trb, Trn and Trc% Tro and Tr
dSTrp passes through the amplifier circuit 32 to output terminals nSm, p,
4 such as flip-flop circuits (F/F) connected to
It has a divider 34. Furthermore, it has a 2-divider 36 having a buffer and an inverter for sending a 2-divided PWM signal S bs S c to the 4-divider 34 .

The system controller 40 is connected to a setting means/centralized control device such as an FMS computer that performs full-closed NC control, receives an interlocking control signal Cm, and further cooperates with a pressurization control means, a conveying means, etc., and an interlocking device. The microprocessor (MPU) 42 includes a CPU, a ROMSRAM, etc., and a PWM circuit 44. Furthermore, a current detector 48 (detection means) such as a toroidal coil for detecting the current flowing through the welding gun 21 is provided.

Next, the operation of the above configuration will be explained (see FIG. 2).

The three-phase 400V supplied from the three-phase AC power supply is converted into DC by the converter 12 and then supplied to the full bridge circuits 14a and 14b of the inverter 14. Further, an interlock control signal Cm is supplied to the MPU 42. And PWM circuit 4
4 to the PWM signal Sa shown in FIG.
PWM signals Sb and Sc shown in e) are derived. These PWM signals Sb and Sc are input to the input terminals a and b of the 4-divider 34.
is input. Here, the PWM signals Sb and Sc are shown in Fig. 2 (
C), (d), (f), (PWM signals Sm, 5n from the output terminals m, n, o, p of the 4-way divider 34 as shown in the marks)
SSo and Sp are derived in a time-divided manner. The time-divided PWM signals Sm and 5nSSoSSp are supplied to the connected switching semiconductor elements TraSTrm, Trb, Trn, TrcSTro, Trd, and Trp via the amplifier circuit 32, and are sequentially driven.

As a result, as shown in FIG. 2, an AC output is derived which is combined with the primary coil of the welding transformer 16, that is, the output end of the inverter 14. FIG. 2(i) shows the combined AC output Va.

Here, the circuit configuration related to the amplifier circuit 32 and the PWM circuit 44 is such that the switching semiconductor elements Tra to Trd and Trm to Trp are ON10 while the switching frequency is fixed.
In addition, the AC output Va is supplied to the welding transformer 16, and the secondary coil is supplied with, for example, a relatively low voltage, large current. Converted to AC 10V. Subsequently, rectifiers Da and Db perform double-wave rectification to derive a DC voltage Vc. This DC voltage Vc is applied to the welding gun 21.

In this way, the time-divided PWM signal Sm% Sn
, 3oSsp.
a, Trm and Trb, Trn and TrcSTro and Trd
STrp is sequentially driven. In this case, for example, the operating load is reduced compared to the case where the semiconductor element performs switching operation without time-sharing the base drive signal, and larger current switching operation becomes possible, and the large current AC output Va is reduced. derived.

Next, a second example will be described.

First, the configuration will be explained.

The example shown in Figure 3 is a three-phase alternating current source (AC400V) 5
It is generally composed of AC power supply units A and B connected to 0, a welding transformer/rectifier unit 60, a welding unit 70, a drive control unit 80, and a system controller 90.

AC power supply units A and B include converters 52a and 52b and inverters 54a and 54b. Inverter 54
a and 54b, switching semiconductor elements Trs, Tr tSTruSTrv and Tr that constitute a full bridge circuit are shown.
w, Trx.

TrV% Trz is provided.

The welding transformer/rectifier 60 is connected to the inverters 54a and 5.
It has a welding transformer 62 whose output ends are connected in parallel to the primary coil, and rectifying elements 56a and 56b which perform double-wave rectification and derive a DC voltage Vc.

The welding section 70 has a welding gun 72 to which a DC voltage Vc is applied, and a welding electrode? A welded member (work) W is provided between 2a and 72b. Note that the pressure driving means and the like are omitted.

The drive control unit 80 includes switching semiconductor elements Trv, Trs and Try, T'rw of the inverters 54a and 54b, respectively.
and Tru, Trt and Trx.

The bases of the Trz are connected to each other and have a shift register 84 connected to the output terminal v% 3'% uz X via a base drive circuit 82. Furthermore, shift register 8
4 has a 2-divider 86 having a buffer and an inverter for sending out 2-divided PWM signals Se and Sd at input terminals e and d.

The system controller 90 is CPU% A/D.

It has a microprocessor (MPU) 92 equipped with RAM, ROM, Ilo, etc. Here, we will explain how to set up the FMS computer, etc. that performs full-closed NC control.
The interlocking control signal Cm from the central control device is supplied, and the interlocking control signal Cn is further sent out to perform so-called welding sequence control. Furthermore, a PWM circuit is supplied with a set value signal Cr for setting the switching frequency of the inverters 54a, 54b and changing the DC voltage Vc applied to the welding gun 72, that is, setting the welding energy to a desired value from the MPU 92. 94, detection circuits 96a and 96b for performing constant current control, and detection signal derivation circuits 98a and 98b.

Here, detection signal deriving circuits 98a and 98b.

Constant current control (closed loop control) is performed based on the detection signal derived from the sensor.

Next, the operation in the above configuration will be explained.

The three-phase 400V supplied from the three-phase AC power supply is converted to DC by converters 52a and 52b, and then converted to DC by converters 52a and 52b.
54b full bridge circuit. Furthermore, MPU
92 is connected to a setting means/central control device and supplied with an interlock control signal Cm, and then a PWM signal Sf shown in FIG. 4(a) is supplied from a PWM circuit 94 to a two-part divider 86. Here, Fig. 4(b) and (
PWM signals Se and Sd shown in e) are derived. These PWM signals 3e and Sd are input to input terminals e and d of the shift register 84. The PWM signals Se and Sd are the fourth
(As shown in Figures (C), (6), (f), the signals are time-divided from the output terminal of the shift register 84 vs Vs ll5X and are derived as PWM signals Sv, Sy, 5uSSx. PWM signal 5VSSySSu
.

Sx is a switching semiconductor element TrvST connected to
r s and TryNTrW and Tru, Trt and Trx, T
is supplied to the base of rz via the base drive circuit 82,
Driven sequentially. Here, as shown in FIG. 4(5), an AC output is derived which is combined with the primary coil of the welding transformer 62, that is, the parallel-connected output end of the inverter 54a154b. FIG. 4(i) shows the combined AC output vb.

The circuit configuration of the base drive circuit 82 and the PWM circuit 94 is such that the switching semiconductor elements Trs to Trv and Trw to Trz are 0N1 while the switching frequency is fixed.
This is a so-called fixed frequency pulse width modulation method (PWM) that changes the ratio of 0FF time.

Here, the AC output vb is supplied to the welding transformer 62, and is converted into a relatively low voltage, large current, AC 10V, for example, to a secondary coil. Subsequently, rectifier satin 56a, 56b
Double-wave rectification is performed at , and a DC voltage Vc is derived. This DC voltage VC is applied to the welding gun 72.

In this way, the time-divided PWM signal Svs
In ys S uSS x, the articulated switching semiconductor elements Trv, Trs (!:Try.

Trw and TruSTrt! :Trx and Trz are driven sequentially. In this case, for example, the operating load is reduced compared to the case where the semiconductor element performs switching operation without time-sharing the base drive signal, and larger current switching operation becomes possible, and the large current AC output vb derived.

Although the two full bridge circuits 14a and 14b are connected in parallel in the first embodiment, the present invention is not limited to this. In the parallel connection of three or more full bridge circuits, the same effect as described above can be obtained, and furthermore, although the AC power supply unit ASB is arranged in the second embodiment, it is possible to configure three or more AC power supply units. The present invention also includes obtaining the same effects as described above.

[Effects of the Invention] As described above, the DC resistance welding apparatus of the present invention has the following effects and advantages. That is, it is characterized in that the semiconductor elements of a plurality of full-bridge circuits perform switching operations using time-divided base drive signals.

This reduces the operational burden on each semiconductor element compared to, for example, a case where the semiconductor element performs switching operation without time-sharing the base drive signal, and allows a larger current switching operation to be performed. , it becomes possible to conduct large currents. In addition, since there is only one inverter and one welding transformer, the number of cables does not increase and there is no need to match the characteristics of the welding transformers. Therefore, the configuration is simplified and the degree of freedom in arrangement is improved.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the DC resistance welding apparatus of the present invention, and FIG. 2 is a timing chart showing processing waveforms on the time axis in the operation of the first embodiment shown in FIG. , FIG. 3 is a configuration diagram showing a second embodiment of the DC resistance welding device of the present invention, and FIG. 4 shows processing waveforms on the time axis in the operation of the second embodiment shown in FIG. 2. This is a timing chart. 10... Welding power supply section 12... Converter 14... Inverter 14a, 14b... Full bridge circuit 16... Welding transformer 20... Welding section 21... Welding gun 21a, 21b... Welding electrode 22... Workpiece to be welded 30... Drive control unit 34... 4-divider 36... 2-divider 40... System controller 42... Microprocessor 48... Current detector 52a , 52b... Converters 54a, 54 b... Inverters 56a, 56b... Rectifying element 60... Welding transformer/rectifying section 62... Welding transformer 70... Welding section 72... Welding gun 80 ...Drive control section 84...Shift register 86...2 divider 90...System controller 92...Microprocessor (MPU) 94...P
WM circuits A, B... AC power supply section DaSDb... Rectifier S a-3f, Sm-3p... PWM signal mSn
, o, p... Output terminals Tra, Trb, Trs ~ Trz... Switching semiconductor elements Va, Vb... AC output Vc... DC voltage

Claims (2)

[Claims] (1) an inverter section in which full-bridge circuits made up of semiconductor elements are connected in parallel; drive signal generation means for generating a base drive signal for switching the semiconductor elements of the full-bridge circuit; and the base drive signal. A direct current resistance welding device comprising: time-divisional drive signal transmission means for time-divisionally transmitting a drive signal to the semiconductor elements of the full-bridge circuit. (2) an inverter section in which the output ends of a plurality of full-bridge circuits made up of semiconductor elements are connected in series; and a drive signal sending out that generates a base drive signal for switching the semiconductor elements of the plurality of full-bridge circuits. A direct current resistance welding device comprising: means for time-divisionally transmitting the base drive signal and transmitting the base drive signal to the semiconductor elements of the full-bridge circuit.