JPH07115209B2 - Welding current controller for DC resistance welding equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding current control device for a DC resistance welding device, and more particularly to detecting a change in magnetic flux generated in an iron core of a welding transformer arranged in the DC resistance welding device and detecting the change. The present invention relates to a welding current control device for a DC resistance welding device that controls the welding current based on the result.

[0002]

2. Description of the Related Art Conventionally, a DC resistance welding apparatus has been widely used for welding various works. A schematic configuration of this type of DC resistance welding apparatus 1 is shown in FIG.

The operation of supplying a welding current to the work W in the DC resistance welding apparatus 1 will be described.

The alternating current output from the power supply 2 is converted into direct current by the converter circuit 3, and this direct current is output to the inverter circuit 4.

On the other hand, the welding controller 5 generates a control pulse P _T based on the target welding current I _T read from a storage circuit (not shown), and outputs this control pulse P _T to the inverter circuit 4. The inverter circuit 4 converts the direct current output from the converter circuit 3 into a high frequency alternating current by the control pulse P _T.

The high-frequency alternating current is supplied to a primary winding (not shown) of the welding transformer circuit 6 as a primary welding current, and a secondary voltage is induced in the secondary winding of the welding transformer circuit 6 by this primary welding current. . A welding current I _W is applied to the work W held by the welding gun portion 7 by the secondary voltage, and welding is performed.

In this case, a current detector 8 composed of a toroidal coil or the like is arranged between the secondary winding of the welding transformer circuit 6 and the welding gun portion 7, and the welding current I _W supplied to the welding gun portion 7 is supplied. Is detected as feedback data, and this data is output to the welding controller 5. The welding controller 5 compares the welding current I _W detected by the current detector 8 with the target welding current I _T, and if they do not match, controls the operation amount in automatic control engineering so that they match. To do.

[0008]

However, in the above-mentioned conventional method for controlling the welding current, the feedback data is detected by the expensive and large toroidal coil, so that the manufacturing cost of the DC resistance welding apparatus can be reduced. However, there is a problem that the device cannot be downsized.

The present invention has been made to solve such a conventional problem, and it is possible to reduce the manufacturing cost of the DC resistance welding apparatus and to downsize the apparatus. An object is to provide a welding current control device for an apparatus.

[0010]

In order to achieve the above-mentioned object, the present invention relates to an iron core of a welding transformer, which is wound around the iron core and is applied to the iron winding by a primary current applied to the primary winding of the welding transformer. A magnetic flux change detecting means for detecting a change in the generated magnetic flux as a voltage, an integrating means for integrating the voltage detected by the magnetic flux change detecting means to generate an integrated voltage, and the integrated voltage and a preset set value. A calculation means for performing calculation, and a welding transformer 1 based on the output value of the calculation means.
Welding current control means for controlling the primary welding current supplied to the secondary winding.

[0011]

In the welding current control device of the DC resistance welding device according to the present invention, the magnetic flux change detecting means wound around the iron core of the welding transformer is energized to the primary winding of the welding transformer.
The change in the magnetic flux generated in the iron core by the next current is detected as a voltage, and the integrating means integrates the voltage to generate an integrated voltage.

Next, the calculating means calculates the integrated voltage and the preset value, and the welding current control means energizes the primary winding of the welding transformer based on the obtained calculation result. Control the welding current. Therefore, the primary welding current for generating the welding current can be controlled by the change in the magnetic flux generated in the iron core of the welding transformer detected by the magnetic flux change detection means.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a welding current control device for a DC resistance welding device 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 overall structure of a DC resistance welding apparatus 10 for carrying out the present invention.

The DC resistance welding apparatus 10 includes a converter circuit 14 for full-wave rectifying the AC output from the AC power supply 12,
An inverter circuit 16 including a plurality of transistors S1~S4 a switching element for converting a DC to the full-wave rectified high frequency AC, induces the high frequency alternating primary welding current I ₁ by the secondary voltage V ₂ welding Transformer T
And a diode D for rectifying the secondary welding current I ₂ energized by the secondary voltage V ₂ to generate the welding current I _W
1 and D2, and a welding gun section 20 for welding the work W by the welding current I _W supplied from the welding transformer circuit 18.

The welding transformer T is composed of a primary winding N ₁ , a secondary winding N ₂ , and a core C, and a search coil SC is wound around the core C.

Further, the DC resistance welding device 10 is equipped with the above-mentioned server.
Voltage V output from the coil C _CAbsolute value of | V_C｜
From the absolute value circuit 22 that outputs
Absolute value output | V_CAn integrating circuit 24 for integrating |
The voltage V output from the integrating circuit 24_SPreset to
An arithmetic circuit 26 for performing an operation of multiplying the calculated constant K, and
Sample that samples and holds the output voltage of the arithmetic circuit 26
Output from the hold circuit 28 and the sample hold circuit 28.
Applied voltage V_PThe inverter circuit 16 based on
Welding coil that controls the pulse width of the driving pulse for energizing
And a controller 30.

FIG. 2 is a block diagram showing the structure of the welding controller 30.

The welding controller 30 is provided with a control circuit 32. The control circuit 32 includes a central processing unit (hereinafter referred to as a CPU) 34, a preliminary energization control, a main energization delay control, a slow-up control, a main energization control and a pseudo welding stop control. ROM 36 for storing a program for performing the above, and the CPU
A RAM 38 in which a calculation result is temporarily stored and a preset value such as a preset target welding current I _T is stored.
An interface circuit (hereinafter referred to as I / F) to which a keyboard (not shown) as an input means, a CRT (display), etc. are connected, and the output terminal of the sample hold circuit 28, the integrating circuit 24 and the arithmetic circuit 26 are connected. ) 40 and.

Further, the welding controller 30 has a digital / analog (hereinafter referred to as D / A) conversion circuit 42 connected to the output terminal of the control circuit 32, an analog voltage output from the D / A conversion circuit 42 and a triangular wave. Generation circuit 4
And a comparison circuit 46 for comparing the triangular wave output from 4
An AND gate 48 for performing a logical product operation of the output of the comparison circuit 46 and the signal output from the CPU 34, and AN
The pulse control circuit 54 distributes the pulse output from the D gate 48 to the A-phase drive circuit 50 and the B-phase drive circuit 52.

The drive pulses output from the A-phase drive circuit 50 and the B-phase drive circuit 52 energize the bases of the transistors S1 to S4 forming the inverter circuit 16.

In the DC resistance welding apparatus 10 configured as described above, when the welding current I _W is applied to the work W in accordance with the program stored in the ROM 36, the search coil wound around the core C of the welding transformer T. the SC, detects the voltage V _C of the primary voltages V ₁ and similar arising across the primary winding N _1, on the basis of the voltage V _C, is energized to the primary winding N ₁ of the welding transformer T The operation of controlling the primary welding current I ₁ so as to match the target welding current I _T will be described with reference to FIGS. 1 to 4.

The operator calculates the constant K by the operator 26.
When the energization is started (step S1) and the energization is started (step S2), the target welding current I _T read from the RAM 38 to the CPU 34 is converted into an analog value by the D / A conversion circuit 42 to be compared with the comparison circuit 46. Is output to.

The comparison circuit 46 compares the target welding current I _T with
The triangular wave generated by the triangular wave generating circuit 44 is compared, and a pulse of "H" is output only during the time when the target welding current I _T is larger than the triangular wave (step S3).
In this case, the comparison circuit 46 constitutes a pulse width modulation (PWM) circuit that generates a pulse having a width proportional to the analog voltage output from the D / A conversion circuit 42.

The pulse generated by the comparison circuit 46 is input to the pulse control circuit 54 through the AND gate 48, and the pulse control circuit 54 drives the input pulse in the A phase by the control signal output from the CPU 34. It is distributed to the circuit 50 and the B-phase drive circuit 52.

The bases of the transistors S1 and S4 forming the inverter circuit 16 are energized by the A-phase pulse output from the A-phase drive circuit 50 (see FIG. 4).
(A)), B output from the B-phase drive circuit 52
The phase pulse energizes transistors S2 and S3 (step S4) (see FIG. 4 (b)). The A-phase pulse and the B-phase pulse are input to the CPU 34.

At this time, the CPU 34 synchronizes with the positive edge of the first A-phase pulse (see FIG. 4A1) (see FIG. 4).
Then, the clear signal for erasing the contents is output to the integrating circuit 24 (see FIG. 4) (step S5).

On the other hand, transistors S1 and S4 are energized by the first A-phase pulse, and welding transformer circuit 18
When the primary welding current I ₁ is started to be applied to the primary winding N ₁ (see FIG. 4C) (step S6), the magnetic flux Φ induced in the core C by the primary welding current I ₁ is generated. Is detected by the search coil SC, and the search coil SC outputs the voltage V _C corresponding to the change in the magnetic flux (see FIG. 4D). When the number of turns of the search coil SC is n, the voltage V _C output from the search coil SC is V _C = n × (d
Φ / dt).

Next, when the CPU 34 reads the negative edge of the first A-phase pulse (see FIG. 4), it cancels the clear signal of the integrating circuit 24 (see FIG. 4). The integration of the absolute value | V _C | output via the absolute value circuit 22 is started (see FIG. 4) (step S7).

The integrated voltage V _S output from the integrating circuit 24 is multiplied by a constant K (A / V · μS) in the arithmetic circuit 26 (step S8) and corresponds to the peak value of the primary welding current I _1. Voltage V _P is output. This voltage V _P is held by the sample hold circuit 28 (step S
9), read by the CPU 34 of the welding controller 30.

Here, the inventor of the present application outputs from the search coil SC during the period (see FIG. 4) from when the A-phase pulse becomes “L” until the primary welding current I ₁ becomes “0”. It is found that the value obtained by integrating the absolute value of the voltage V _C is proportional to the peak value I _P of the primary welding current I ₁ , and
The proportional constant K in this case was determined by an experiment.

The welding controller 30 is obtained by calculating an effective value of the primary welding current I ₁ from the voltage V _P was substituted for peak I _P of the primary welding current I ₁ read.

Next, the CPU 34 determines whether or not the welding at this welding point is completed (step S1).
0), when it is finished, the control of the primary welding current I ₁ is finished, and when the energization is not finished, the primary welding current I ₁ is set as the target welding current I _T based on the voltage V _P read in step S9. In order to make them coincide with each other, the pulse width of the second A-phase pulse (see FIG. 4A2) to be output next is calculated (step S11), and "output of B-phase pulse" in step S4 is executed.

In this case, the voltage V _P corresponding to the peak value of the primary welding current I ₁ read from the sample hold circuit 28 is the “feedback amount” in the automatic control engineering, and the CPU 34 is the “addition point”. In step 3, the "operation signal", which is the difference between the "feedback amount" and the target welding current I _T read from the RAM 38, is obtained by calculation, and the "operation amount", which is a correction value, is output.

As described above, the pulse width of the A phase pulse output from the A phase drive circuit 50 is controlled based on the voltage V _C output from the search coil SC, and the B phase pulse output from the B phase drive circuit 52. The pulse width of is similarly controlled.

As described above, according to this embodiment,
Absolute value of voltage V _C detected in search coil SC | V _C
| Is calculated by the absolute value circuit 22, and the absolute value | V _C | is integrated by the integrating circuit 24 to obtain the voltage V _S. The voltage V _S
Then, the constant K obtained by the experiment is multiplied by the arithmetic circuit 26 to obtain the voltage V _P. Since this voltage V _P is the voltage V _P was substituted for peak I _P of the energized primary welding current I _1, the voltage V _P as feedback data, corrects the target welding current I _T.

Therefore, by the output of the search coil SC wound around the core C of the welding transformer T, the primary welding current I
It becomes possible to control ₁ easily.

[0038]

With the welding current control device for the DC resistance welding device according to the present invention, the magnetic flux generated in the iron core of the welding transformer detected by the magnetic flux change detecting means can be eliminated without disposing an expensive and large current detector. Since the primary welding current for generating the welding current can be controlled by the change, it is possible to reduce the manufacturing cost of the DC resistance welding device and
It is possible to achieve the downsizing of the DC resistance welding device.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a DC resistance welding apparatus for carrying out the present invention.

FIG. 2 is a block diagram showing a configuration of a welding controller in the apparatus shown in the embodiment of FIG.

FIG. 3 is a flowchart showing an operation of controlling a welding current in the apparatus shown in the embodiment of FIG.

FIG. 4 is a timing chart showing the output timing of the search coil with respect to the control pulse composed of the A-phase pulse and the B-phase pulse for activating the inverter circuit in the device shown in the embodiment of FIG. 1.

FIG. 5 is a block diagram showing a configuration of a DC resistance welding device according to a conventional technique.

[Explanation of symbols]

 10 ... DC resistance welding device 14 ... Converter circuit 16 ... Inverter circuit 18 ... Welding transformer circuit 20 ... Welding gun part 22 ... Absolute value circuit 24 ... Integrating circuit 26 ... Arithmetic circuit 28 ... Sample hold circuit 30 ... Welding controller 32 ... Control circuit 34 ... CPU 36 ... ROM 38 ... RAM 40 ... I / F 42 ... D / A conversion circuit 46 ... Comparison circuit 50 ... A-phase drive circuit 52 ... B-phase drive circuit 54 ... Pulse control circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenji Miyanaga 1-10-1 Shin-Sayama, Sayama-shi, Saitama Honda Engineering Co., Ltd. (56) References JP-A-62-192276 (JP, A) JP-A-SHO 61-189882 (JP, A) JP-A-63-84774 (JP, A)

Claims (1)

[Claims] 1. A magnetic flux change detecting means wound around an iron core of a welding transformer to detect a change in magnetic flux generated in the iron core by a primary current supplied to a primary winding of the welding transformer as a voltage, and the magnetic flux. Integrating means for integrating the voltage detected by the change detecting means to generate an integrated voltage, computing means for computing the integrated voltage and a preset set value, and welding based on the output value of the computing means A welding current control device for a DC resistance welding device, comprising: a welding current control means for controlling a primary welding current supplied to a primary winding of a transformer.