JPH0780060B2 - DC resistance welding equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a DC resistance welding apparatus used for welding robots and the like, and particularly to an inverter having transistors connected in parallel or a full bridge drive type. The present invention relates to a DC resistance welding apparatus in which a large current is preferably derived by time-divisionally driving switching semiconductor elements of inverters connected in parallel.

[Prior Art] Recently, a DC resistance welding device (inverter spot DC welding machine) has been used, which is used for welding robots and is capable of deriving a large current of tens of thousands of amperes when welding aluminum and the like. There is.

A DC resistance welding apparatus for deriving such a large current is known to have a configuration in which switching semiconductor elements of an inverter are connected in parallel to drive a base.

Further, the present applicant is provided with a plurality of inverter power supplies including a converter, an inverter, a welding transformer, and a double-wave rectifying element (rectifier), and further combines the DC outputs of the respective rectifiers in parallel to generate a large current. We have applied for a DC resistance welding device with the desired structure (Japanese Patent Application No. 63-290949).

Such a DC resistance welding apparatus is provided with feedback control means using a so-called well-known PWM control circuit or the like, which performs comparison control with the energization set value by detecting the energization current of the welding gun or the input / output of the inverter. ing.

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

In the example described later, the secondary coil output of the welding transformer of each of the plurality of inverter power supplies is formed to a low voltage, and the rectified output DC is combined in parallel to supply a large current to the member to be welded. Therefore, when it is used in a welding robot or the like, the inverter for deriving a high voltage and the welding transformer are separated from each other in order to prevent the conduction loss of the energization path (cable) due to a large DC current. In addition to connecting the cables with a cable, a welding transformer and a rectifier are mounted on the welding gun.

In this case, a cable for connecting the inverter and the welding transformer, for example, 5 to 8 cables are required for an inverter power supply that performs four parallel operations, and the characteristics of each welding transformer must be made uniform.

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

The present invention has been made in view of the above points, and its purpose is to improve the degree of freedom of the arrangement in a relatively simple structure and to further effectively derive a large current from direct current resistance welding. To provide a device.

[Means for Solving the Problems] In the present invention, for example, as shown in FIG. 1, an inverter section (14) for converting a DC input into an AC output (Va) by pulse width modulation control to a welding transformer (16). In the DC resistance welding apparatus which supplies the AC output to the primary coil and supplies the rectified output (Vc) of the secondary coil to the object to be welded (22), the inverter units are connected in parallel except for the drive terminal. A current drawing semiconductor device (Trm, Trn) and a current drawing semiconductor device (Tro, Trn) connected in parallel except for the drive terminal
rp) are connected in series (14b) are arranged in parallel (14b, 14a) between the DC inputs, and each of the drive terminals of the current-feeding semiconductor element is sequentially driven in a time division manner. In response to this, each of the drive terminals of the current drawing semiconductor element is sequentially driven in a time division manner.

Further, according to the present invention, for example, as shown in FIG. 3, the AC output is supplied to the primary coil of the welding transformer (62) from an inverter unit which converts a DC input into an AC output (Vb) by pulse width modulation control. , Rectified output of secondary coil (V
In the DC resistance welding device for supplying c) to the work piece (W), the inverter unit includes four semiconductor elements (Trv, Trs, Tr).
u, Trt) are connected to each other in a full bridge drive type, and a plurality of inverters (54a) are arranged in parallel (54a, 54b) to sequentially drive the semiconductor elements constituting each of the inverters in a time division manner. .

[Operation] According to the present invention, the current-flowing semiconductor elements (Trm, Trn) connected in parallel except the drive terminal and the current-drawing semiconductor elements (Tro, Trp) connected in parallel except the drive terminal
In the inverter section (14) in which a plurality of (14b) in which and are connected in series are arranged in parallel between the DC inputs (14b, 14a),
Each of the drive terminals of the current outflowing semiconductor element is sequentially driven in time division, and correspondingly, each of the drive terminals of the current drawing semiconductor element is sequentially driven in time division.

Further, according to the present invention, four semiconductor devices (Trv, Trs,
Tru, Trt) are connected in a full-bridge drive type, and a plurality of inverters (54a) are arranged in parallel (54a, 54b) to form an inverter unit.

Therefore, according to the present invention, a large current can be taken out without simultaneously driving the semiconductor elements in parallel, and the characteristics of the semiconductor elements do not have to be matched because they are not driven in parallel at the same time. Further, the welding transformer and the inverter can be provided with two wires.

[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 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 drawing 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 described (see FIG. 1).

The example shown in FIG. 1 is a welding power source unit 10, a welding unit 20, a drive control unit 30, and a system controller 40 for performing welding control.
It is roughly composed of.

The welding power source unit 10 has a converter 12 connected to a three-phase AC source (three-phase 400V) to derive a direct current (rectified voltage), and an inverter 14. As can be easily understood from the figure, the inverter 14 is connected in parallel with full bridge circuits 14a and 14b for converting a rectified voltage into a pulsed high frequency (AC). The full bridge circuits 14a and 14b are provided with switching semiconductor elements Tra, Trb, Trc, Trd and Trm, Trn, Tro, Trp.

Furthermore, in order to obtain a large current, for example, a welding transformer 16 that performs low voltage conversion of 10 V and a DC voltage that performs both-wave rectification
It has rectifiers Da and Db for deriving Vc.

The welded portion 20 includes a welding gun 21 to which a DC voltage Vc is applied, and a member 22 to be welded which is sandwiched between welding electrodes 21a and 21b forming the welding gun 21. The pressure control means and the like are omitted.

The drive control unit 30 is a connected switching semiconductor device Tr.
a, Trm and Trb, Trn and Trc, Tro and Trd, and Trp are connected to output terminals n, m, p, and o through an amplifier circuit 32, and a quad divider 34 such as a flip-flop circuit (F / F) is provided. Have Further, the 4-divider 34 has a 2-divider 36 having a buffer and an inverter for sending 2-divided PWM signals Sb and Sc.

The system controller 40 is, for example, a fully closed NC
The interlocking control signal Cm is input by being connected to the setting means / centralized control device such as an FMS computer for controlling, and further sends out the control signal Cn for performing cooperative control between the pressurizing control means, the conveying means and the interlocking device. In addition, I / that performs constant current control etc.
Microprocessor (MP with O, CPU, ROM, RAM, etc.
U) 42 and a PWM circuit 44. Further welding gun 21
And a current detector 46 (detection means) such as a toroidal coil for detecting the energization current.

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

The three-phase 400V supplied from the three-phase AC power source is converted to DC by the converter 12, and then the full bridge circuit 14 of the inverter 14
It is supplied to a and 14b. Further, the interlocking control signal Cm is supplied to the MPU 42. The PWM signal Sa shown in FIG. 2 (a) is supplied from the PWM circuit 44 to the two-divider 36, and the PWM signals Sb, S shown in FIGS.
c is derived. The PWM signals Sb and Sc are input to the input terminals a and b of the quarter divider 34. Here, as shown in FIGS. 2 (c), (d), (f) and (g), the PWM signals Sb and Sc are output from the output terminals m, n, o and p of the quadrant divider 34 to the PWM signal Sm, Sn, S
o and Sp are calculated by time division. Switching semiconductor element in which PWM signals Sm, Sn, So, and Sp that are time-divided are connected
Amplification circuit 32 for Tra, Trm and Trb, Trn and Trc, Tro and Trd, Trp
Are supplied through the motor and driven sequentially. This allows the second
As shown in FIG. 3H, the AC output combined with the primary coil of the welding transformer 16, that is, the output end of the inverter 14 is derived. AC output Va synthesized in Fig. 2 (i)
Indicates.

Here, the circuit configuration related to the amplifier circuit 32 and the PWM circuit 44 is a switching semiconductor device with the switching frequency fixed.
This is a so-called fixed frequency pulse width modulation method (PWM) that changes the ratio of ON / OFF times of Tra to Trd and Trm to Trp.

Further, the AC output Va is supplied to the welding transformer 16 and is supplied to the secondary coil, for example, AC 10V with a relatively low voltage and a large current.
Is converted to. Then, double-wave rectification is performed by the rectifiers Da and Db to derive the DC voltage Vc. This DC voltage Vc is applied to the welding gun 21.

In this way, the time-divided PWM signals Sm, Sn, So, Sp
Switching semiconductor devices Tra, Trm and Trb, T connected by
rn and Trc, Tro, Trd and Trp are driven sequentially. in this case,
For example, compared with the case where the semiconductor element performs a switching operation without time-sharing the base drive signal, the conduction time of the switching semiconductor element is shortened and the operation load is reduced, and a larger current switching operation is possible. A large current AC output Va is derived.

Next, a second embodiment will be described.

First, the configuration will be described.

The example shown in FIG. 3 is an AC power supply unit A, B connected to a three-phase AC source (AC400V) 50, and 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 are converters 52a and 52b and an inverter.
54a and 54b. Inverters 54a and 54b include switching semiconductor devices Trs and T that form a full bridge circuit.
rt, Tru, Trv and Trw, Trx, Try, Trz are arranged.

The welding transformer / rectifier unit 60 has a welding transformer 62 in which output terminals of the inverters 54a and 54b are connected in parallel and is connected to a primary coil, and rectifying elements 56a and 56b for performing double-wave rectification and deriving a DC voltage Vc. is doing.

The weld 70 has a welding gun 72 to which a DC voltage Vc is applied,
Further, a member to be welded (workpiece) W sandwiched between the welding electrodes 72a and 72b is provided. It should be noted that the pressure driving means and the like are omitted.

The drive control unit 80 has the bases of the switching semiconductor elements Trv, Trs and Try, Trw and Tru, Trt and Trx, and Trz of the inverters 54a and 54b connected to each other, and output terminals v, y, and u via the base drive circuit 82. , X connected to the shift register 84. Further, the input terminals e and d of the shift register 84 have a two-way divider 86 having a buffer and an inverter for transmitting the two-way PWM signals Se and Sd.

The system controller 90 has a microprocessor (MPU) 92 including a CPU, A / D, RAM, ROM, I / O and the like.
Here, the interlocking control signal Cm from the setting means / centralized control device such as a computer for FMS that performs full-closed NC control
Is supplied and further sends out the interlocking control signal Cn, so-called,
The welding sequence is controlled. Furthermore MPU92
From the change of the DC voltage Vc applied to the welding gun 72 by setting the switching frequency of the inverters 54a, 54b, that is, the PWM circuit 94 to which the set value signal Cr for setting the welding energy to a desired value is supplied. It has detection circuits 96a and 96b for performing constant current control and detection signal derivation circuits 98a and 98b.

Here, constant current control (closed loop control) is performed based on the detection signals derived from the detection signal derivation circuits 98a and 98b.

Next, the operation of the above configuration will be described.

Three-phase 400V supplied from three-phase AC power supply is converter 52
After being converted to a direct current by a and 52b, it is supplied to the full bridge circuit of the inverters 54a and 54b. Further, the interlocking control signal Cm is supplied to the MPU 92 by being connected to the setting means / centralized control device, and then the PWM signal Sf shown in FIG.
Are supplied to the two-divider 86. Here, the PWM signals Se and Sd shown in FIGS. 4 (b) and 4 (e) whose polarities are respectively inverted are derived. The PWM signals Se and Sd are input to the input terminals e and d of the shift register 84. The PWM signals Se and Sd are time-divided from the output terminals v, y, u and x of the shift register 84 as shown in FIGS. 4 (c), (d), (f) and (g),
It is derived as PWM signals Sv, Sy, Su, Sx. This time-divided PWM signal Sv, Sy, Su, Sx are connected switching semiconductor elements Trv, Trs and Try, Trw and Tru, Trt and Trx, T
It is supplied to the base of rz through a base drive circuit 82 and is driven sequentially. Here, as shown in FIG. 4 (h), the primary coil of the welding transformer 62, that is, the inverter 54.
An AC output combined with the parallel-connected output terminals of a and 54b is derived. FIG. 4 (i) shows the synthesized AC output Vb.

The circuit configuration of the base drive circuit 82 and the PWM circuit 94 changes the ON / OFF time ratio of the switching semiconductor devices Trs to Trv and Trw to Trz while fixing the switching frequency, a so-called fixed frequency pulse width modulation method ( PWM).

Here, the AC output Vb is supplied to the welding transformer 62, and is supplied to the secondary coil, for example, an AC 10V with a relatively low voltage and a large current.
Is converted to. Subsequently, the double-wave rectification is performed by the rectifying elements 56a and 56b, and the DC voltage Vc is derived. This DC voltage Vc is applied to the welding gun 72.

In this way, time-divided PWM signals Sv, Sy, Su, Sx
Switching semiconductor devices Trv, Trs connected in
And Try, Trw and Tru, Trt, Trx, and Trz are driven sequentially. In this case, for example, the conduction time of the switching semiconductor element is shortened and the operation load is reduced, as compared to the case where the semiconductor element performs the switching operation without time-sharing the base drive signal, and the switching operation with a larger current can be performed. It becomes possible, and a large current AC output Vb is derived.

In the first embodiment, the two full bridge circuits 14a and 14b are connected in parallel and the present invention is not limited to this. Three
In the parallel connection of the above full bridge circuits, the same effects as the above can be obtained, and the AC power supply units A and B are arranged in the second embodiment, but three or more AC power supply units are formed. It is also included in the present invention to obtain the same effect as the 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 element forming the inverter section performs a time-division switching operation.

Thereby, the operation time of each semiconductor element, for example, the conduction time of the switching semiconductor element is shortened and the operation load is reduced as compared with the case where the semiconductor element performs the switching operation without time-sharing the base drive signal, A larger current switching operation is performed, and a larger current can be energized. Further, even if the semiconductor elements are not simultaneously driven in parallel, a large current can be taken out, and since they are not simultaneously driven in parallel, it is not necessary to match the characteristics of the semiconductor elements. In addition, since there is only one welding transformer, the number of wiring cables between the inverter and the welding transformer does not increase, the number of wiring cables can be two, and the characteristics of the welding transformer need not be made uniform. Therefore, the structure is simplified and the degree of freedom of arrangement is improved.

[Brief description of drawings]

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

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Makoto Suzuki 1-10-1 Shin-Sayama, Sayama-shi, Saitama Honda Engineering Co., Ltd. (72) Hidenori Koga 1-10-1 Shin-Sayama, Sayama-shi, Saitama Prefecture Hondaae (56) Reference JP-A-62-148091 (JP, A) JP-A-60-137581 (JP, A)

Claims (2)

[Claims] 1. An AC output is supplied from an inverter section (14) for converting a DC input to an AC output (Va) by pulse width modulation control to a primary coil of a welding transformer (16), and a rectified output of a secondary coil ( In the DC resistance welding device for supplying Vc) to the object to be welded (22), the inverter section is connected in parallel except for the driving terminals and the current-flowing semiconductor elements (Trm, Trn) are connected in parallel except for the driving terminals. Connected current drawing semiconductor device (Tro, T
rp) are connected in series (14b) are arranged in parallel (14b, 14a) between the DC inputs, and each of the drive terminals of the current-feeding semiconductor element is sequentially driven in a time division manner. Corresponding to this, the DC resistance welding apparatus is characterized in that each of the drive terminals of the current drawing semiconductor element is sequentially driven in a time division manner. 2. An inverter section for converting a DC input into an AC output (Vb) by pulse width modulation control, and a welding transformer (6).
2) In the DC resistance welding apparatus that supplies the AC output to the primary coil and the rectified output (Vc) of the secondary coil to the work piece (W), the inverter unit includes four semiconductor elements (Trv). , Trs, Tr
u, Trt) are connected to each other in a full bridge drive type, and a plurality of inverters (54a) are arranged in parallel (54a, 54b) to sequentially drive the semiconductor elements constituting each of the inverters in a time division manner. DC resistance welding equipment.