JPH0780059B2 - DC resistance welding equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] According to the present invention, when a plurality of inverter power supplies operate in parallel, the demagnetization of each welding transformer is made uniform, and the demagnetization control thereafter is suitably performed. The present invention relates to a DC resistance welding device.

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

Such a DC resistance welding apparatus is provided with a plurality of inverter power sources including a converter, an inverter, a welding transformer, and a double-wave rectifying element (rectifier). Further, each rectifier combines a DC output to obtain a large current, and detects the energizing current and performs comparison control with a preset energizing set value, so-called feedback using a well-known PWM control circuit, etc. Control means are provided.

By the way, in such a DC resistance welding apparatus, there arises a problem of magnetic bias that occurs due to variations in individual characteristics of welding transformers respectively arranged in a plurality of inverter power supplies. 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, there is provided a bias magnetizing control means for detecting a current relating to the switching operation of the inverter and correcting the applied current in response to the bias magnetizing of the welding transformer.

[Problems to be Solved by the Invention] However, in the above-described conventional welding transformer, a gap is provided by disposing a resin material or the like at each joint of a set of U-shaped cores or EI-shaped cores. The magnetic bias 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. Therefore, the bias magnetic control means is arranged in each inverter power supply. Therefore, there is a drawback that the structure becomes complicated and the device scale increases.

The present invention has been made in view of the above points, and an object thereof is to provide a DC resistance welding device having a relatively simple configuration, in which the bias magnetisms of the welding transformers of a plurality of inverter power supplies are the same, and the subsequent bias magnetism control is excellent. To do.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides, for example, a first
As shown in the figure, for each of the n primary coils of the welding transformer T having n primary coils 24a to 24d and one secondary coil 26, n timing gates from the PWM circuit 41 are provided. The outputs of n inverters 14a to 14d, which are on / off controlled by signals, are connected to each other, and the secondary coil side has a rectifying element 28a.
It is characterized in that the rectifying elements are connected in parallel in the DC resistance welding device in which the both-wave rectification is performed by using ~ 28f and the both-wave rectification output is supplied to the workpiece.

The present invention also includes n current detecting means 16a to 16d for detecting the currents flowing to the input sides of the respective inverters 14a to 14d.
When the detected current is supplied, the set value signal Cr that determines the timing of the timing gate signal is sent to the PWM circuit 41.
And a control means 40 for supplying to the input side of the control means, which control means obtains an arithmetic mean value of the detected current and corrects it based on a difference between the arithmetic mean value and a set value signal. It is characterized in that the set value signal is changed so that the timing gate signal is output from the PWM circuit to perform the magnetic bias control.

Further, the present invention, for example, as shown in FIGS. 1 and 4, includes n primary coils 52a to 52d and n secondary coils 56a to 56d.
To each of the n primary coils of the welding transformer TB, which has the output of the n inverters that are on / off controlled by the n timing gate signals from the PWM circuit, are connected to the n secondary coils. Double-wave rectification is performed using rectifying elements (Da, Db), (Dc, Dd), (De, Df), (Dg, Dh), and each double-wave rectified output is connected in parallel. In a DC resistance welding device in which the output Ec is supplied to the work piece, n current detection means for detecting the current flowing to the input side of each inverter, and the detected current are supplied, and the timing gate signal And a control means for supplying a set value signal for determining the timing to the input side of the PWM circuit, and this control means obtains an arithmetic mean value of the detected current, and the arithmetic mean value and the set value signal Compensation based on the difference Same timing gate signal alters the set value signal as output from the PWM circuit and performing magnetic deflection control.

[Operation] According to the present invention, since the rectifying elements of the double-wave rectifying circuit on the secondary coil side of the welding transformer driven in parallel by n inverters are connected in parallel, one rectifying element is allowed. A large current can be supplied to the object to be welded even if the forward current value is small.

Further, according to the present invention, in the DC resistance welding device in which the rectifying elements of the double-wave rectifying circuit on the secondary coil side of the welding transformer driven in parallel by n inverters are connected in parallel, The timing gate signals output from the PWM circuits that drive the inverters are the same timing gate signals for the magnetic bias control based on the difference between the arithmetic mean value of the input current values of the respective inverters and the set value signal.

Furthermore, according to the present invention, in the direct current resistance welding device in which the double-wave rectified outputs of the n secondary coils of the welding transformer driven in parallel by the n inverters are connected in parallel, PW that drives each inverter
The timing gate signal output from the M circuit is the same timing gate signal for the magnetic bias control based on the difference between the arithmetic mean value of the input current values of the respective inverters and the set value signal.

In the present invention which performs the demagnetization control with the above configuration, since a plurality of primary coils are wound around one welding transformer, this welding transformer is demagnetized by the sum of the DC components of the current supplied from the inverter. As a result, the demagnetization of each primary coil becomes the same, the efficiency of the welding transformer is improved, and
For example, the configuration related to the subsequent demagnetization control is simplified.

[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 embodiment, FIG. 2 is a diagram used for explaining the operation of the embodiment, FIG. 3 is a flow chart relating to a welding control program of the embodiment, and FIG. It is a block diagram which shows the principal part of a modification.

First, the configuration will be described.

The example shown in Fig. 1 is an ON / OFF section (ELB
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, 12c, 1 respectively.
2d, inverters 14a, 14b, 14c, 14d, and converter 12
a to 12d and a detection circuit 16a, 16b, 16c, 16d such as a toroidal coil disposed in the connection line between the inverters 14a to 14d,
It has detection signal derivation circuits 18a, 18b, 18c, 18d.
Further, base driving circuits 20a, 20b, 20c, 2 for driving the bases of the switching transistors Tra, Trb, Trc, Trd which form the full bridge circuit of the inverters 14a to 14d.
It has 0d and.

As can be easily understood from the drawing, 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. Core 27 (a set of U-shaped cores or EI-shaped cores).

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

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

The system controller G has a microprocessor (MPU) 40 equipped with a CPU, A / D, RAM, ROM, I / O and the like.
And 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,
Welding control such as sequence is performed. Further MP
A change in the DC voltage Ea applied to the welding gun 30 by setting the switching frequency of the inverters 14a to 14d from U40, that is, a distributor to which the set value signal Cr for setting the welding energy to a desired value is supplied. It has a provided PWM circuit 41.

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. Here the base drive circuit 20
The circuit configuration related to a to 20d and the PWM circuit 41 is such that each switching transistor Tr remains fixed at the switching frequency.
This is a so-called fixed frequency pulse width modulation method (PWM) that changes the ON / OFF time ratio of a to Trd.

Drive pulses from the base drive circuits 20a to 20d are transmitted to the respective 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). The respective alternating currents are the primary coils 24a, 24b, 24 of the welding transformer T.
It is supplied to c and 24d and converted into a secondary coil 26 into, for example, an alternating current of 10V having a relatively low voltage and a large current. In this case, the primary coils 24a to 24d and the secondary coil 26 form a set of cores 27.
It is wound around. Here, the alternating currents derived from the inverters 14a 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 (rush current). In this case, the primary coils 24a to 24d are wound around the set of cores 27, and the sum of the DC components of the AC derived from the inverters 14a to 14d causes the demagnetization. Therefore, the demagnetizations of the individual primary coils 24a to 24d are the same without any difference.

Then, the 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 eccentricity control relating to the eccentricity of the welding transformer T is performed on the derived DC voltage Ea. 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 the demagnetization control are performed based on the welding control of the MPU 40 described later.

The welding control will be described below based on the program stored in the ROM of the MPU 40 (see FIGS. 2 and 3).

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

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. 2 (b)).

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

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

In step 105, the set value signal Cr is determined 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 Tra by gate signal
Through Trd are driven. Therefore, the alternating current (output) projecting currents of the inverters 14a to 14d are blocked without being out of synchronization.

Next, a modification of the embodiment shown in FIG. 3 (see FIG. 4)
Will be explained.

This example shows a larger DC voltage Ec
As can be easily understood from the figure, the welding transformer TB has a primary coil 52a, 52b, 52c, 52d connected to the output terminals of the inverters 14a, 14b, 14c, 14d, respectively, and a secondary coil. 56a, 56b, 56c, 56d are wound around a set of cores 58.

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

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.
The primary coils 24a to 24d (52a to 52d) of (TB) have the same demagnetization, and therefore the same control operation can be performed by using any one of the detection signals Sa to Sd. Further, the primary coils 24a to 24d, 52a of the welding transformers T and TB
Although the description has been given of the example in which the to 52d are formed, 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.

[Advantages of the Invention] As described above, according to the present invention, the rectifying elements of the double-wave rectification circuit on the secondary coil side of the welding transformer driven in parallel by n inverters are connected in parallel. ,
The effect that a large current can be supplied to the work piece is achieved.

Further, according to the present invention, since one welding transformer driven in parallel by n inverters is used, the eccentricity of the welding transformer is made uniform, and the eccentricity control is simple and the effect is obtained. Has the advantage that

[Brief description of drawings]

FIG. 1 is a block diagram showing an entire embodiment of a DC resistance welding apparatus of the present invention, FIG. 2 is a diagram used for explaining the operation of the embodiment shown in FIG. 1, and FIG. The flowchart which concerns on the welding control program of the Example shown by FIG. 4, FIG. 4 is a block diagram which shows the principal part of the modification of the Example shown by FIG. 12a ~ 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) 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) Reference JP-A-55-71173 (JP, A) JP-A-51-84750 (JP, A) Special table-Sho 58-500702 (JP, A)

Claims (3)

[Claims] 1. A welding gate having n (n ≧ 2) primary coils and one secondary coil is provided with n timing gate signals from a PWM circuit for each of the n primary coils. In a direct current resistance welding apparatus in which outputs of n inverters controlled to be turned on and off are respectively connected, the secondary coil side is double-wave rectified by using a rectifying element, and the double-wave rectified outputs are supplied to a workpiece. A DC resistance welding device characterized in that rectifying elements are connected in parallel. 2. An n number of current detection means for detecting a current flowing to the input side of each inverter, and a set value signal for determining the timing of the timing gate signal while the detected current is supplied.
Control means for supplying the input side of the circuit, the control means obtaining an arithmetic mean value of the detected currents and correcting the same based on a difference between the arithmetic mean value and the set value signal. 2. The DC resistance welding apparatus according to claim 1, wherein the set value signal is changed so that the timing gate signal of FIG. 3. A welding gate transformer having n (n ≧ 2) primary coils and n secondary coils, wherein n timing gate signals from a PWM circuit are applied to each of the n primary coils. Outputs of n inverters controlled to be turned on / off are respectively connected, the n secondary coil sides are respectively double-wave rectified using rectifying elements, and the double-wave rectified outputs are connected in parallel. In a DC resistance welding apparatus in which an output is supplied to an object to be welded, n number of current detection means for respectively detecting a current flowing to an input side of each inverter, the detected current is supplied, and the timing gate signal is supplied. The set value signal that determines the timing of the PWM
Control means for supplying the input side of the circuit, the control means obtaining an arithmetic mean value of the detected currents and correcting the same based on a difference between the arithmetic mean value and the set value signal. A DC resistance welding apparatus, characterized in that the set value signal is changed so that the timing gate signal is output from the PWM circuit to perform magnetic bias control.