JPS5938875B2 - Pressure/release detection device for resistance welding electrodes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting pressurization/release of an electrode in a resistance welding machine. The initial pressurization time (squeeze time) is determined by detecting the change in the primary impedance of the welding transformer as viewed from the power source using a measurement circuit, and is determined by the initial pressurization time (squeeze time) regardless of the electrode stroke.
is kept constant, and the electrode or workpiece movement start signal in the automatic machine is ensured, so that welding of the electrode can be detected.

Generally used control devices start counting the initial pressurization time at the same time as the welding start signal as shown in FIG. 1, and therefore are affected by the time of the electrode stroke.

That is, in the conventional case, the initial pressurization time starts from the time when the start signal is input, and it is necessary to change the setting widely depending on the electrode stroke, and if it is set too long for the sake of welding quality, wasted time will occur. On the other hand, in an automatic machine, a delay time is taken based on a hold time completion signal, and the electrode release is estimated and given, which is less reliable. Furthermore, the method of confirming the return position of the electrode using LS or the like has disadvantages in that the area around the electrode has a complicated special structure, which hinders the operation of the electrode. Therefore, the present invention provides an extremely useful control method for purely electrically detecting the open/closed state of the electrode circuit when pressurizing/releasing the electrode during welding on the primary side of the welding transformer, that is, within the control device of the welding machine. The device was developed.

Embodiments of the control device according to the present invention will be described below based on the drawings.

In Fig. 2, 1 is an AC power supply, 2 is an electronic switch for power switching corresponding to a thyristor or conductor, 3 is a voltage detector that constitutes a measurement circuit, 4 is a welding transformer, 5 is a resistance welder 6 is a high impedance welding machine In the circuit, 1, 1 is a welding electrode, and 8 is a workpiece to be welded.

In this device, a welding transformer 4 and its power switching electronic switch 2 are connected in series to an AC power source 1, and a high impedance circuit 6 is connected in parallel to the electronic switch. And a welding control device installed on the primary side of the welding transformer (
A voltage detector 3 constituting a measurement circuit for detecting changes in impedance on the primary side is inserted on the output terminal side of the sensor (not shown).

In the above configuration, first, when the thyristor and the conductor are not in a conductive state, an impedance Z1 due to a surge of the thyristor, an absorber, etc., and an impedance Z2 due to a welding transformer etc. are inserted in series in the AC power circuit.

Then, when the electrodes 7 and 7' in the secondary circuit of the welding transformer sandwich the workpiece 8 and short-circuit by pressure contact, the impedance Z2 decreases and the voltage sharing with Z changes. By monitoring the terminal voltage of this impedance Z2 using the voltage detector 3 and detecting its fluctuation, the voltage applied to the electrode Ff.
/You can know the release status. That is, the present invention
Since the initial pressurization time starts from the time when both electrodes start contact with the object to be welded between them, it is independent of the electrode stroke time and can be kept at a constant value.

Furthermore, it is more reliable to open the electrodes using a signal that confirms an open circuit between the electrodes than to use a holding time completion signal instead. In the embodiment shown in the drawings, the change in the primary impedance of the welding transformer due to the opening and closing of the electrodes can be measured and detected by the force (measuring the primary current) at the output terminal of the welding control device. Similarly, an extremely reliable device can be obtained.

As explained above, according to the present invention, the control device for spot welding, projection welding, seam welding, and other resistance welding machines can be used, especially for two-stroke electrode pressurizing devices and welding robots. When rapid and repeated operations are required, even if the electrode stroke movement time changes after the electrode pressurization start signal is sent,
Since a constant net initial pressurization time can always be ensured, the initial pressurization time can be accurately maintained regardless of the length of the electrode stroke or changes over time, and without having to modify mechanical devices such as stroke adjustments as in the past. high welding quality.

Further, since the working time can be shortened to the necessary minimum, workability can be significantly improved. On the other hand, this can be instantly confirmed when the electrode is separated from the workpiece.
In the case of an automatic machine, a signal for starting the movement of the electrode to the next step and the workpiece to be welded can be reliably retrieved within the control device of the welding machine, and many other effects never seen before can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship among the conventional electrode stroke, electrode pressing force, control timing, etc., and FIG. 2 is an electric circuit principle diagram showing an embodiment according to the present invention. 1...AC power supply, 2...Electronic power switch, 3...Measurement circuit, 4...
Welding transformer, 5...Resistance welding machine, Z1...
...High impedance circuit.

Claims (1)

[Claims] 1. In a resistance welding machine in which a welding transformer and its power on/off electronic switch are connected in series to an AC power source, a high impedance circuit is connected in parallel with the electronic switch to supply a small amount of power to the welding transformer during the open period of the electronic switch. A device that detects the pressurized/open state of the electrode by supplying the voltage and measuring the primary terminal voltage or primary current of the welding transformer with a detector as the electrode circuit on the secondary side of the welding transformer opens and closes.