JP2004017154A - Current control method of resistance welding machine - Google Patents

Abstract

The present invention relates to a method for controlling a welding current by controlling an inverter frequency of a battery-driven inverter-operated resistance welding machine and a welding machine for automatically controlling an inverter frequency so that the welding current matches a target value of the welding current. It is.
【Constitution】
As shown in FIG. 1, the inverter frequency can be varied by its command value _fr and can be set to a frequency suitable for welding.
When S is connected to the b side, the inverter frequency is automatically adjusted so as to coincide with the command value _{IW, r} of the welding current.
【effect】
Since the inverter frequency can be set arbitrarily or the welding current can be arbitrarily controlled by forming a closed loop, even a person who has no experience in resistance welding can easily perform welding.
[Selection diagram]
FIG.

Description

[0001]
[Industrial applications]
In resistance welding, welding is performed by flowing a large current of several thousand amps through a welding portion for several seconds. Therefore, the welded portion rapidly rises from room temperature to, for example, near the melting temperature of the steel sheet in a few seconds. Therefore, it is necessary to supply a welding current suitable for the welding material. That is, if the current is small, incomplete welding may be completed, and if the current is too large, the welding material may be melted.
This means that the conventional welding machine is of an open loop type in terms of an electric circuit, and the magnitude of the current is set by experience, visual measurement, and intuition.
If the welding current can be set arbitrarily, even a person who has no experience in resistance welding can easily perform welding.
The present invention relates to a current control method for a resistance welding machine, and enables a person without special experience to easily perform resistance welding.
[0002]
[Prior art]
A technique for continuously and arbitrarily controlling the welding current in a battery-operated resistance welding machine has not yet been established except for the present invention.
[0003]
[Problems to be solved by the invention]
In resistance welding, welding conditions are greatly changed due to the fact that a large current of several thousand amperes flows through a weld for several seconds to perform welding. In contrast, in the present invention, first, the welding current is controlled by varying the excitation frequency of the inverter. In other words, the welding transformer itself and the cable connecting the welding transformer and the welding electrode have a leakage inductance. Therefore, the present invention positively uses the property that the reactance component of the leakage inductance depends on the excitation frequency.
Next, the welding current is detected, and the inverter frequency is controlled so that the welding current matches the target value of the welding current. That is, by forming the current control system in a closed loop, higher-precision resistance welding is realized.
[0004]
[Means for Solving the Problems]
In order to control the magnitude of the welding current, the frequency of the inverter is varied, and a voltage-controlled oscillator VCO is used for this. That is, the current control is enabled by taking the inductance existing in the welding transformer itself and the cable connecting the welding transformer and the welding electrode as an AC resistance.
Then, the welding current is detected, and a closed loop is formed so that the welding current matches the target value of the welding current, thereby realizing high-precision resistance welding.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the invention will be described with reference to the drawings.
FIG. 1 is an example of a current control circuit of an inverter operation type resistance welding machine. When the switch S shown in the figure is connected to the a side, the inverter frequency can be changed by the command value _fr , and can be set to a frequency suitable for welding.
Next, when S is connected to the b side, the inverter frequency is automatically adjusted so as to coincide with the command value _{IW, r} of the welding current.
[0006]
【Example】
FIG. 1 shown in the embodiment of the invention is one example.
[0007]
【The invention's effect】
In resistance welding, it is necessary to appropriately control the welding current because a large current of several thousand amps is passed through the weld for several seconds to perform welding. That is, if the current is small, the welding is incomplete, and if the current is too large, the welding material may be melted. On the other hand, since the welding current can be controlled by controlling the inverter frequency, the welding current can be set arbitrarily, and even a person who has no experience in resistance welding can easily perform welding.
[Brief description of the drawings]
FIG. 1 is an example of a circuit that controls a welding current by controlling an inverter frequency. The symbols in the figure are as follows.
S: control selector switch _{I W} of the inverter _{frequency, r:} welding current command _{f r:} inverter frequency command value epsilon _{IW: I W,} the detection value _{I W} of _r and the welding current _{I W,} the deviation G (s) and _det: error amplifier VCO welding current: voltage controlled oscillator _PT 1, PT _2: thyristor _Th 1, a pulse transformer for ignition of the Th ₂

Claims (2)

Method of controlling welding current by controlling inverter frequency of storage battery driven inverter operated resistance welding machine A welding machine for detecting a welding current according to claim 1 and automatically controlling an inverter frequency so that the welding current matches a target value of the welding current.

Images