JPH082509B2 - 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 in particular, when a plurality of inverter power supplies operate in parallel, the demagnetization of each welding transformer is performed. The present invention relates to a direct current resistance welding apparatus in which the same is controlled to perform demagnetization control and a large current is preferably derived.

[Prior Art] A DC resistance welding device (inverter spot DC welding machine) capable of deriving a large current of tens of thousands of amps when used for welding robots and the like to weld aluminum and the like.
Is used.

Such DC resistance welding equipment includes converters, inverters, welding transformers, and double-wave rectifiers (rectifiers).
A plurality of inverter power supplies including the above are disposed. Furthermore, a feedback control means using a so-called well-known PWM control circuit, etc. is provided, which combines the DC outputs of the respective rectifiers to obtain a large current, and detects the energization current to perform comparison control with the energization set value. Has been.

By the way, in such a DC resistance welding apparatus, there is a problem of demagnetization due to generation of inrush current in the welding transformers respectively arranged in the plurality of inverter power sources. In this case, a gap in which a resin material or the like is arranged is provided at the joints of the cores of the welding transformer, for example, a set of U-shaped cores or EI-shaped cores, to reduce the demagnetization. Further, each of the inverter power supplies is provided with a bias magnetizing control means to perform bias magnetizing control for correcting the value of the energizing current corresponding to the bias magnetizing.

[Problems to be Solved by the Invention] However, in the above-described conventional welding transformer, a gap is formed by inserting a resin material or the like into each joint of a set of U-shaped cores or EI-shaped cores. The magnetism is reduced. In this case, a gap is created in the closed magnetic circuit of the set of U-shaped cores or EI-shaped cores, and the efficiency of the welding transformer is reduced. Further, the magnetic bias is different in each welding transformer, and the magnetic bias means is provided in each feedback power source, which complicates the configuration. In this case, as a result, there is an inconvenience that it is difficult to derive a large current.

The present invention has been made in view of the above point, and in a relatively simple configuration, the biasing magnetisms of the welding transformers of a plurality of inverter power supplies are made the same, and the biasing control is effectively performed so that a large current can be derived. An object is to provide a DC resistance welding device.

[Means for Solving the Problems] In order to solve the above problems, the DC resistance welding apparatus of the present invention, as shown in the claim correspondence diagram of FIG. 1, includes at least a plurality of welding transformers (A). A plurality of primary coils connected to the respective output terminals of the inverter and a secondary coil connected to the rectifier are wound around one or a set of cores and used.

The detection means (B) detects the current generated by the switching operation of the inverter and derives the detection signal (Sa).

In the control means (C), the respective inverters are drive-controlled by the timing gate control signal (Sb) having the same width based on the difference between the arithmetic mean value of the detection signal (Sa) and the energization instruction signal. .

[Operation] In the above configuration, the welding transformer has one or a set of cores around which the primary coil and the secondary coil are wound, and this welding transformer is biased by the sum of the DC components of the current supplied from the inverter. Magnetize, and thereby, the demagnetization of each primary coil becomes the same. The detection signal of the switching operation current of the inverter in the same bias magnetic field is derived, and the control of the inverter performs the bias magnetic control related to the feedback with the preset energization set value.

As a result, the efficiency of the welding transformer is improved, and as a result, it becomes possible to derive a large current.

[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. 2 is a block diagram showing the whole of the embodiment, FIG. 3 is a diagram for explaining the operation of the embodiment, and FIG. 4 is a flowchart relating to a welding control program of the embodiment.

 First, the configuration will be described.

The example shown in Fig. 2 is the ON / OFF part (EL
AC power supply units A, B, C, D connected to 10)
, A welding transformer T, a rectifying section E, a welding section F, and a system controller G.

The AC power supply units A to D are converters 12a, 12b, 12 respectively.
c, 12d, inverters 14a, 14b, 14c, 14d, detection circuits 16a, 16b, 16c, 16d such as toroidal coils arranged in the connecting lines of the converters 12a to 12d and the inverters 14a to 14d.
And detection signal derivation circuits 18a, 18b, 18c, 18d. Furthermore, the switching transistors Tra, Trb, Trc, Trd that form the full bridge circuit of the inverters 14a to 14d.
Base drive circuits 20a, 20b, 20 for performing base drive of
It is equipped with c and 20d.

As can be easily understood from the figure, the welding transformer T includes a set of a primary coil 24a, 24b, 24c, 24d connected to the output terminals of the inverters 14a, 14b, 14c, 14d, and a secondary coil 26, respectively. It is wound around a core 27 (a set of U-shaped cores or EI-shaped cores, etc.).

The rectifier E has rectifiers 28a, 28b, 28c, 28d, 28e, 28f for performing double-wave rectification and deriving a DC voltage Ea.

The welded portion F has a welding gun 30 to which a DC voltage Ea is applied, and further has a member to be welded (work) W sandwiched between the welding electrodes 30a and 30b. Further provided is a conduction current detector 32 such as a current transformer utilizing the Hall effect, which is connected to the intermediate end of the welding gun 30 and the secondary coil 26. It should be noted that the pressure driving means and the like are omitted.

System controller G is CPU, A / D, RAM, ROM, I / O
And a microprocessor (MPU) 40 including the above. Then, a so-called welding control or the like is performed in which the interlocking control signal Cm is supplied from the setting means / centralized control device such as a computer for FMS that performs full-closed NC control, and further the interlocking control signal Cn is sent out. Furthermore, the change of the DC voltage Ea applied to the welding gun 30 by setting the switching frequency of the inverters 14a to 14d from the MPU 40, that is, the set value signal Cr for setting the welding energy to a desired value.
Is provided with a PWM circuit 41 having a distributor.

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

The interlocking control signal Cm is supplied to the MPU 40, and the set value signal Cr is sent to the PWM circuit 41. Then, the timing gate signals based on the set value signal Cr are supplied from the PWM circuit 41 to the base drive circuits 20a to 20d, respectively. Where base drive circuit
The circuit configurations of 20a to 20d and the PWM circuit 41 are the respective switching transistors with the switching frequency fixed.
This is a so-called fixed frequency pulse width modulation method (PWM) that changes the ON / OFF time ratio of Tra to Trd.

The drive pulses from the base drive circuits 20a to 20d are the respective switching transistors Tr of the inverters 14a to 14d.
The switching operation is performed by being supplied to the bases of a to Trd. As a result, the direct current supplied from the converters 12a to 12d is converted into pulsed high frequency waves (alternating current). The respective alternating currents are the primary coils 24a, 24b, 24 of the welding transformer T.
It is supplied to c and 24d, and is led to the secondary coil 26 after being converted into, for example, an alternating current of 10 V having a relatively low voltage and a large current. In this case, the primary coils 24a to 24d and the secondary coil 26 are wound around a set of cores 27. Here, the inverter 14
The alternating currents derived from a to 14d are supplied to the primary coils 24a to 24d to excite the core 27. At the same time, a DC component causes a biased magnetism (inrush current). In this case, the primary coils 24a to 24d are wound around a set of cores 27, and the inverter 14a
Thus, the sum of the DC components of the AC derived from 14 to 14d causes the magnetic bias. Therefore, the individual primary coils 24a
The deviations at 24 to 24d are the same without any difference.

Further, double-wave rectification is performed by the rectifiers 28a to 28f to derive the DC voltage Ea, which is subsequently applied to the welding gun 30.

In this way, the derived DC voltage Ea is subjected to the magnetic bias control related to the magnetic bias of the welding transformer T. This magnetic bias control is performed by the energization instruction signal in the interlocking control signal Cm and the detection signal S derived from each of the detection signal derivation circuits 18a to 18d.
Compare the average of the values of a, Sb, Sc, and Sd (arithmetic mean),
The so-called closed loop control is performed in which the timing gate signal with the difference corrected is supplied to each of the switching transistors Tra to Trd, whereby the protruding current of the inverters 14a to 14d due to the synchronization deviation is blocked. Also,
The constant current control is performed based on the energization detection signal Sf.

The operations such as magnetic bias control will be described later in the MPU40.
Welding control.

The welding control based on the program stored in the ROM of the MPU 40 will be described below (see FIGS. 3 and 4).

After the operation related to the whole is started, the interlocking control signal Cm from the setting means / centralized control device is taken in and the welding target member W is conveyed,
Clamping and initial pressure are applied and the program starts.

In step 101, the energization instruction signal (setting value signal Cr) in the interlocking control signal Cm is supplied to the PWM circuit 41 as shown in FIG.

In step 102, the detection signals Sa to Sd are fetched (see FIG. 3 (b)).

In step 103, an arithmetic operation for obtaining the arithmetic mean of the detection signals Sa to Sd is performed.

In step 104, a difference (t) between the average (arithmetic mean) of the energization instruction signal and the detection signals Sa to Sd shown in FIG. 3C is calculated and determined.

In step 105, the set value signal Cr is obtained based on the difference (t).

In step 106, the set value signal Cr is supplied from the MPU 40 to the PWM circuit 41 in order to supply the timing gate signal corrected based on the difference (t) to each of the switching transistors Tra to Trd.

In this way, one process of the continuously executed magnetic bias control program is completed.

In this case, the eccentricity control is performed by the average (arithmetic mean) of the detection signals Sa to Sd based on the eccentricity of the sum of the DC components of the welding transformer T, and the same timing shown in FIG. Switching transistor Tr by gate signal
a to Trd are driven. Therefore, the alternating current (output) projecting currents of the inverters 14a to 14d are blocked without the synchronization being deviated.

 Next, a modification of the embodiment shown in FIG. 5 will be described.

This example shows a DC voltage with a larger current
Ec is obtained, the welding transformer TB, as can be easily understood from the figure, primary coils 52a, 52b, 52c, 52d connected to the output terminals of the inverters 14a, 14b, 14c, 14d, respectively,
Secondary coils 56a, 56b, 56c, 56d are wound around a set of cores 58.

The rectifying unit EB is a rectifying element Da, Db and D for performing both-wave rectification.
The ends of c, Dd and De, Df and Dg, and Dh are connected. The output terminals a, b, c, d here are connected in parallel with the respective midpoints s, t, u, v of the secondary coils 56a, 56b, 56c, 56d, as can be easily understood from the figure. ing.

In such a configuration, the DC voltages at the output terminals a, b, c, d are arranged in parallel, and a DC voltage Ec equal to the DC voltage Ea in the above embodiment is obtained. In this case, the demagnetization control similar to the above is performed, so that the large current is effectively derived.

In the above embodiment, the magnetic bias control is performed using the arithmetic mean value of the detection signals Sa to Sd.
(TB) The primary coils 24a to 24d (52a to 52d) have the same bias magnetization, and therefore, the same bias control can be performed using any one of the detection signals Sa to Sd. Further, the primary coils 24a to 24d, 52 of the welding transformers T and TB
The example in which a to 52d are formed has been described, but the present invention is not limited to this. It is also included in the present invention that two, three, or five or more secondary coils are wound around one or a set of cores to obtain the same effect as the above.

[Effects of the Invention] As described above, in the DC resistance welding apparatus of the present invention,
It has the following effects and advantages. That is, in the welding transformer, a primary coil and a secondary coil are wound around one or a set of cores, and this welding transformer is demagnetized by the sum of the DC components of the current supplied from the inverter and The magnetic bias of the coils is the same. It is characterized in that the control signal of the inverter is controlled by the detection signal of the switching operation current of the inverter based on the same bias magnetism to perform the bias magnetization control related to the feedback with the preset energization set value.

As a result, in a relatively simple configuration, the welding transformers of a plurality of inverter power supplies are made to have the same bias magnetization, and the bias control can be effectively performed, so that a large current can be derived.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to the claims relating to the DC resistance welding apparatus of the present invention, FIG. 2 is a configuration diagram showing an entire embodiment of the DC resistance welding apparatus of the present invention, and FIG. 3 is shown in FIG. FIG. 4 is a flow chart relating to the welding control program of the embodiment shown in FIG. 2, and FIG. 5 is a modification of the embodiment shown in FIG. It is a block diagram which shows the principal part. 12a to 12d …… Converter 14a… 14d …… Inverter 20a ～ 20d …… Base drive circuit 24a ～ 24d …… Primary coil 26 …… Secondary coil 27 …… Core 28a ～ 28f …… Rectifier 30 …… Welding gun A ～ D: AC power supply F: Weld G: System controller T: Welding transformer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hitoshi Saito 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 Hondaae Engineering Co., Ltd. (56) References Special Table Sho 58-500702 (JP, A)

Claims (2)

[Claims] 1. Welding in which a plurality of primary coils to which respective output ends of a plurality of inverters are respectively connected correspondingly and a secondary coil connected to a rectifier are wound around one or a set of cores. A transformer; detection means for deriving a detection signal by respectively detecting currents generated by the switching operations of the plurality of inverters; and each inverter based on the difference between the arithmetic mean value of the detection signal and the energization instruction signal. And a control means for driving and controlling each of them with a timing gate control signal having the same width. 2. The DC resistance welding apparatus according to claim 1, wherein the control means includes a PWM circuit and a feedback P
DC resistance welding equipment characterized by WM control.