JPH03189079A - Dc resistance welding equipment - Google Patents

Abstract

PURPOSE:To reduce the number of connecting cords and to lead out a high current by providing an AC power source part to lead out added AC output produced by supplying DC to plural inverters and adding in series output AC and a transformer part to supply the added AC output to a primary coil. CONSTITUTION:A set signal Cr is supplied from a MPU 42 to a PWM circuit 44. A timing gate signal is supplied to a base driving circuit 18a, etc. A base driving pulse is supplied in synchronization with a base of a switching transistor Tra, etc., of an inverter 16a, etc., from the base driving circuit 18a, etc., and switching operation is carried out. DC of a converter 14a, etc., is added in series at an output end of the inverter 16a, etc., and added AC Va are obtained from the inverter 16a and 16b and supplied to the primary coil Ca, etc., in series of a welding transformer 22a, etc. The AC voltage having the same value led out from a secondary coil of the welding transformer 22a, etc., is subjected to full-wave rectification by a rectifier 24a, etc., and the composite DC voltage Vc is impressed on a welding gun 32. By this method, the high current is led out effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a DC resistance welding device used in welding robots, etc., and in particular, high voltage AC obtained by connecting a plurality of inverter power supplies in series is The number of connection cords is reduced by supplying the welding transformer that is installed as
The present invention relates to a DC resistance welding device that has improved flexibility in its arrangement and is capable of drawing a large current.

[Prior Art] Recently, when welding aluminum or the like using a welding robot or the like, a DC resistance welding device (inverter spot DC welding machine) capable of drawing a large current of up to 100 amperes has been used.

Such a DC resistance welding device is equipped with a plurality of inverter power supplies including a converter, an inverter, a welding transformer, a double-wave rectifying element (rectifier), and the like. Furthermore, a feedback control means using a well-known PWM control circuit, etc., is provided, which combines the DC outputs of the respective rectifiers to obtain a large current, and also detects the energizing current and performs comparison control with the energization setting value. It is being

[Problems to be Solved by the Invention] The plurality of inverter power supplies provided in the conventional DC resistance welding apparatus described above each form the secondary coil output of the welding transformer to a low voltage, and further combine the DC outputs in parallel to A large current is supplied to the parts to be welded. Therefore, when used in welding robots, etc., in order to prevent current loss due to large DC current, a welding transformer and a rectifier that derive a relatively high voltage AC output are placed near the welding gun, and an inverter and a rectifier are installed near the welding gun. are connected by a cable.

In this configuration, a plurality of inverter power supplies operating in parallel require cables to connect the inverters and welding transformers, for example, five to eight cables are required in an inverter power supply operating in four parallels. In this case, it is difficult to obtain a degree of freedom in movement or configuration of the welding robot. Furthermore, in order to prevent biased magnetism in each welding transformer, a gap is formed by inserting a resin sheet or the like at the joint of the core.
This has the drawback that the efficiency of voltage conversion decreases, making it difficult to obtain a large current.

The present invention has been made in view of the above points, and an object of the present invention is to provide a relatively simple configuration in which each inverter and a welding transformer disposed separately when a plurality of inverter power supplies operate in parallel. The number of connection cords between the
It is an object of the present invention to provide a DC resistance welding device which has an improved degree of freedom in its arrangement and can effectively draw a large current.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the DC resistance welding device of the present invention has the following features: Direct current is supplied to each of the plurality of inverters, and the output AC associated with each switching operation is added in series. an AC power supply unit that derives the added AC output to two terminals; a two-wire connection line that is connected to the two ends and derives the added AC output; and a two-wire connection line that is connected to the two ends to output the added AC output. A transformer section in which is supplied to the primary coil;

Furthermore, the present invention includes a plurality of isolation transformers connected to an AC power source to obtain an AC output, a converter and an inverter to which the AC output is supplied, and the DC output of the converter is supplied to the inverter, and each an AC power supply unit that derives an added AC output obtained by adding AC outputs associated with a switching operation in series to two terminals; a two-wire connection line that is connected to the two ends and derives the added AC output; and a connection line of the two wires. A transformer unit is connected to which the added AC output is supplied to the primary coil; obtained and supplied to a spaced apart welding transformer.

This reduces the number of connection cords and makes it possible to effectively draw a large current.

[Example] Next, an example 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 embodiment, Fig. 2 is a block diagram showing a welding transformer and a rectifier of a first modification of the embodiment, and Fig. 3 is a welding transformer of a second modification of the embodiment. , is a configuration diagram showing a rectifier.

First, the configuration will be explained.

The example shown in Figure 1 is a three-phase AC 400v 0N10F
Power supply unit ASB connected to F unit (including ELB etc.) 10
, C, D, the welding section 30, and the system controller 40
It is roughly composed of.

The power supply sections A to A are each provided with an isolation transformer 12a.

12b, 12c, 12cl and converter 14a114
b, 14c, 14d and inverters 16a116b, 1
6c, 16d, and base drive circuits 18a, 18b, 18c, 1 for driving the bases of switching transistors Tra, Trb, Trc, and Trd constituting the full bridge circuit of each of the inverters 16a to 16d.
8d.

Furthermore, welding transformers 22a, 22b, 22C122d
and rectifier 24a% 24b, 24C.

24d. As can be easily understood from the figure, the output ends of the inverters 16a to 16d are connected in series, and the summed AC Va is obtained from the inverters 16a and 16d. Further, as can be easily understood from the figure, the welding transformers 22a to 22d have secondary coils Ca and C, respectively.
b.

CcSCd are connected in series to supply the addition AC Va.

Rectifiers 24a, 24b, and 24c each include a rectifying element DaSDb that further performs double-wave rectification and derives a DC voltage Vc.
, 24d.

The welding section 30 includes a welding gun 32 to which a DC voltage Vc is applied, and further includes a welded member (work) W held between welding electrodes 32a and 32b.

Furthermore, the system controller 40 is a CPU.

It has a microprocessor (MPU) 42 equipped with A/D, RAM, ROM, Ilo, etc.

Here, an interlock control signal Cm is supplied from a setting means/central control device of a computer or the like for FMS that performs full-closed NC control, and an interlock control signal Cn is sent out to perform so-called welding control. Furthermore, MPU4
2, a distributor is supplied with a set value signal Cr for setting the switching frequency of the inverters 16a to 16d to change the DC voltage Vc applied to the welding gun 32, that is, to set the welding energy to a desired value. Prepared PW
It has an M circuit 44. Furthermore, it is arranged between the output end of the inverter 16d and the primary coil of the welding transformer 22d,
It is equipped with a current detector 46 such as a toroidal coil that derives a detection signal Sa for performing constant current control, biased magnetic control, etc.

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

The interlock control signal Cm is supplied to the MPU 42, and the set value signal Cr is supplied to the PWM circuit 44.

Subsequently, timing gate signals based on the set value signal Cr are sent from the PWM circuit 44 to the base drive circuits 18a to 1, respectively.
8d. Here, the base drive circuits 18a to 1
The circuit configuration of 8d and the PWM circuit 44 is a so-called fixed frequency pulse width modulation method (PWM) in which the ratio of the ON10 FF times of the switching transistors Tra to Trd is changed while the switching frequency is fixed.

The base drive circuits 18a to 18d supply base drive Hals to the bases of the switching transistors Tra to Trd of the inverters 16a to 16d in synchronization, thereby performing a switching operation.

Thereby, the direct currents supplied from converters 14a to 14d are added in series at the output ends of inverters 16a to 16d, and added alternating current Va is obtained from inverters 16a and 16d. Subsequently, the addition AC Va is applied to the welding transformer 22a.
It is supplied to primary coils Ca to Cd connected in series. Then, the AC voltage of the same value derived from the secondary coils of each of the welding transformers 22a to 22d is applied to the rectifier 2.
Both-wave rectification is performed by each rectifying element DaSDb of 4a to 24d. Here, the synthesized DC voltage Vc is obtained,
The voltage is applied to the welding gun 32.

In this way, when the addition alternating current Va added in series at the output ends of the inverters 16a to 16d is applied to the series-connected primary coils Ca to Cd of the welding transformers 22a to 22d, the connection path is two wires. become. Further, the AC voltages of the same value derived from the secondary coils of the welding transformers 22a to 22d are subjected to double-wave rectification by the rectifying elements DaSDb of the rectifiers 24a to 24d, and combined, resulting in a large current DC voltage. A voltage Vc is obtained.

Next, a first modification will be explained (see FIG. 2).

This example uses one welding transformer 52. The welding transformer 52 includes a primary coil 52a and a secondary coil 52b.
52c, 52d, and 52e are provided. - Addition alternating current Va derived from inverters 16a and 16d is applied to the secondary coil 52a, and further secondary coils 52b and 52c
The same AC voltage from 152d and 52e is applied to the rectifier 24a.
It is supplied to each rectifying element DaSDb of 24d to 24d.

Here, double-wave rectification is performed to obtain a combined DC voltage Vc, which is then applied to the welding gun 32. Note that the other configurations and operations are the same as those of the previous embodiment, and detailed explanation thereof will be omitted. In this case, only one welding transformer 52 is required, which simplifies the configuration when mounted on a welding robot or the like, and further reduces the size and weight.

Next, a second modification shown in FIG. 3 will be explained. This example uses one welding transformer 62 and the primary coil 6
2a and a secondary coil 62b are provided. - The additional AC Va is supplied to the secondary coil 62H, and the AC derived from the secondary coil 62b is further supplied to the rectifier 64a,
Double-wave rectification is performed at 64b. In this case, the rectifier 54a
, 64b are constructed by connecting rectifying elements DeSDf, Dg, and Dh in parallel, respectively, so that a large current DC voltage Vc
It becomes possible to derive Note that the other configurations and operations are the same as those of the previous embodiment, and detailed explanation thereof will be omitted. In this case, only one welding transformer 62 is required, and furthermore, one primary coil 62a and one secondary coil 62b are provided, and the alternating current here is connected in parallel with rectifying elements De and D.
By performing double-wave rectification using f, Dg, and Dh, the welding transformer 62 is miniaturized. In this case, for example, the configuration when mounted on a welding robot or the like is simplified, and the device can be made smaller and lighter.

In the above embodiment, the power supply units A, B, C, and D are provided, but the present invention is not limited thereto.

The present invention also includes providing the same effects as described above by providing 2.3 or 5 or more power supply units and adding the respective inverter outputs in series.

[Effects of the Invention] As described above, the DC resistance welding apparatus of the present invention has the following effects and advantages.

That is, the inverter is characterized in that a plurality of inverters are connected in series to obtain a high-voltage alternating current output, and that it is connected to a welding transformer that is spaced apart using two wires.

As a result, in a relatively simple configuration, when multiple inverter power supplies operate in parallel, the number of connection cords between each inverter and the separately placed welding transformer can be reduced, allowing freedom of arrangement. This has the effect of improving efficiency and effectively making it possible to derive a large current.

Ca-Cd...-Next coil

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the entire structure of an embodiment of the DC resistance welding apparatus of the present invention, and FIG. 2 is a block diagram showing a welding transformer and a rectifier of a first modification of the embodiment shown in FIG. , FIG. 3 is a configuration diagram showing a welding transformer and a rectifier according to a second modification of the embodiment shown in FIG. 1. 12a to 12d...Isolation transformers 14a to 14d...Converters 16a to 16b...Inverters 22a to 22d...Welding transformers 24a to 24d...Rectifier 30...Welding section 32...Welding gun 40 ...System controller A-D...Power supply section FIG, 3 Lln 4D

Claims (3)

[Claims] (1) an AC power supply section that supplies direct current to each of the plurality of inverters, and outputs to two terminals an added AC output obtained by adding in series the output ACs associated with each switching operation; A DC resistance welding device comprising: a two-wire connection line for deriving an output; and a transformer section to which the two-wire connection line is connected and the added AC output is supplied to a primary coil. (2) It has a plurality of isolation transformers connected to an AC power source to obtain an AC output, a converter and an inverter to which the AC output is supplied, and the DC output of the converter is supplied to the inverter and is used for each switching operation. an AC power supply unit that derives an added AC output obtained by adding the accompanying AC outputs in series to two terminals; a two-wire connection line that is connected to the two ends and that derives the added AC output; and the two-wire connection line are connected to each other. A direct current resistance welding device comprising: a transformer section through which the added alternating current output is supplied to a primary coil. (3) The DC resistance welding apparatus according to claim 1, wherein the transformer section has a plurality of transformer primary coils connected in series and is connected to two ends of the AC power supply section. (4) The apparatus according to claim 1, wherein the transformer section has a transformer in which one primary coil and a plurality of secondary coils are wound around one or a set of cores. Device.