JPS5913583A - Disconnection detecting device of solenoid valve driving circuit for pressurizing welding gun in welding robot - Google Patents

Abstract

PURPOSE:To obtain a titled device which can detect disconnection of a solenoid valve driving circuit before flowing a welding current by constituting said device so that an energizing current of a solenoid valve is detected, by providing a current detector on a driving circuit of the solenoid valve for controlling a pressurizing cylinder of a welding gun. CONSTITUTION:In a welding robot provided with a welding gun 2 consisting of electrode tips 2a, 2b for pinching and welding a material 5 to be welded, and a solenoid valve 4 for controlling its pressurizing cylinder 3 on the tip part of an arm 1, a driving circuit of the solenoid valve 4 is constituted through a solenoid valve driving switch 21, a wiring breaker 22 and electric wires 6a, 6b from an AC power source 20. Also, a current transformer 23 which penetrates the electric wire 6b side is provided, a voltage signal proportional to an energizing current of the solenoid valve 4, which is detected by said current transformer is applied to a transistor TR through an amplifier 24, a diode D2, a resistance R2, etc., a relay 25 is operated, and a normally opening contact 25a is closed. When a detecting output of said current transformer 23 becomes ''0'' due to disconnection of the electric wire 6, etc., the contact 25a is opened, an interlock is applied to a welding current igniting circuit 12, and the welding current is cut.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting disconnection of a solenoid valve drive circuit in a welding robot equipped with a solenoid valve for controlling a welding can and its pressurizing cylinder at the tip of the arm.

Generally, a welding robot has an arm 1 as shown in FIG.
5. The welding gun 2 is attached to the tip of the welding gun 2, and the direction of supply of compressed air from the pneumatic pipe to the pressurizing cylinder 3 is changed to control the pressurization of the welding gun 2.5. The welding gun 2 is provided with a solenoid valve 4, and the material 5 to be welded is held between the electrode tips 2a and 2b of the welding gun 2 and pressurized for welding.

In this way, since the solenoid valve 4 for pressurizing the welding gun is attached to the tip of the arm 1 together with the welding gun 2, an excitation current is supplied to this solenoid valve 4 from a power source provided in the robot body (not shown). The electric wire 6 constituting the drive circuit for moving the electric wire 6 is moved following the movement of the wires 1 and 1, and is subjected to various stresses, which may cause the wire to break.

If this happens, the solenoid valve 4 will not operate, and the work will continue without applying pressure to the welding valve 2, resulting in the production of defective products.

Therefore, conventionally, such a disconnection of the welding can pressurizing electric foundation valve drive circuit has been detected using a device as shown in FIG. 2, for example.

That is, AC power supply 10. A current transformer 14 for detecting welding current is provided on the primary side of the welding current supply circuit, which also includes a single switch 11, a welding current ignition circuit 12, and a welding transformer 13, and the detection signal is binarized by an amplifier 15. , AND circuit 16 performs a logical product of the welding current detection signal and the 7Jll river command number, and the furinob flow 'l'i'il circuit 7 is set by the output and reset by the welding completion signal. Due to the Q output of
Solenoid valve, drive circuit normality detection IT"l) 1/-18 is activated.

Figure 3 is a tights chart of each signal generated during welding.

In such a conventional device, if the solenoid valve drive circuit is disconnected and the solenoid valve is constantly operating, the welded part 2 is connected to the welded part 4. When the power switch 11 is turned on by the bath contact command signal, a large welding current flows, or the electromagnetic valve (αX drive circuit wire 6 is disconnected) and no pressure is applied.・Since this takes advantage of the fact that almost no welding current flows, the solenoid valve 5 is indirectly
It is designed to detect whether the drive circuit is normal or not.

However, since the welding current cannot be detected unless the welding current is applied, the solenoid valve drive circuit may be disconnected.
There was the inconvenience of having to start spot welding twice.

This invention was made by focusing on such conventional problems, and it is an object of the present invention to detect a break in a solenoid valve drive circuit and take appropriate measures before applying welding current to the d-contact can. With the goal.

Therefore, the disconnection detection device of the solenoid valve drive circuit for pressurizing the m-welt gun in the m-junction loch according to the present invention includes a current detector in the solenoid valve drive circuit to detect the excitation current of the solenoid valve.
The detection signal is amplified to operate a detection output means such as a relay.

An embodiment of the present invention shown in FIG. 4 will be described below.

A drive circuit for the solenoid valve 4 is configured by connecting the solenoid valve, the drive circuit d1, and the AC power source 20 to a solenoid valve drive switch 21, a circuit breaker (CB') 22, and electric wires 5a and 5b. As a current detector for detecting the excitation current of the solenoid valve 4 in the circuit, a current transformer 23 is provided, for example, by penetrating the electric wire 61 side.

This current transformer 23 detects a lightning pressure signal proportional to the excitation current of the solenoid valve 4, which is detected by an amplifier 24. Adjusted by C, -117,7'jj↑, resistance R
1 is applied to the base of a transistor TR for driving the relay via a resistor R2, and when normal, the relay 25 as a detection output means is operated and its normally open contact 25 is activated.
Try to close a.

Therefore, the electric wire 6a or id of the solenoid valve drive circuit:
5 +), or if the wire breaks due to fatigue due to movement following the movement of the arm, even if the switch 21 is closed by the pressurization command 1 symbol mentioned above, the excitation current of the solenoid valve 4 will not flow or the current will change. Since the sensor 23 also does not generate a detection output and the transistor TR is turned off, the relay 25 also does not operate and its contact 25a does not close.

Therefore, when the contact 25a is about to close, the welding current ignition circuit 12 can be interlocked to prevent the welding current from flowing (see also FIG. 2).

As a current detector, a resistor is inserted in place of the current transformer 23, and the exciting current is detected by the voltage and voltage generated across the resistor.

The detection output means is not limited to relays, it is also possible to use switching transistors, and it is also possible to use a normally closed switching circuit (and the switching circuit will not turn off even after the pressurization command is sent manually). You can also sound a buzzer or turn on a warning light when the time comes.If you use a small relay that operates with an AC signal, you can omit the rectifier/smoothing circuit.

As described above in the embodiments, according to the present invention, the excitation current of the solenoid valve is detected face-to-face, and disconnection of the solenoid valve or drive circuit is detected based on the presence or absence of the excitation current.
It can be detected before welding current is applied to the M contact.

Therefore, even if the electric wire of the solenoid valve drive circuit becomes fatigued and breaks due to the complicated movements of the welding gun of the welding robot and the tip of the arm on which the pressurizing solenoid valve is mounted, the welding gun can be immediately welded. 1.1.- It is possible to take appropriate measures during work to prevent the occurrence of defective products.
) I can do it.

[Brief explanation of the drawing]

Figure 1 shows the Arp welding robot to which this invention is applied.
Figure 2 is a circuit diagram showing an example of a conventional solenoid valve for pressurizing a welding gun and a device bar for detecting disconnection in the drive circuit. Time chart 1 of each signal generated during welding. 41st line is a circuit diagram showing an embodiment of the present invention. 1 - Arm 2... Welding horn/ 3/Linda 4... Solenoid valve for addition II- 6, 6a, 6b... Button 1 wire 20... AC power supply 21... Solenoid valve, drive switch 23... Current transformer (current detection 24 ・Amplifier 25 Re1 No (detection output means)

Claims (1)

[Claims] 1. In a welding robot equipped with a solenoid valve that controls a Kg contacting gun at the tip of the arm and its pressurizing cylinder, a current detector provided in the drive circuit of the solenoid valve and a signal detected by this current detector are amplified. A disconnection detection device for a solenoid valve drive circuit for pressurizing a U-contact gun, comprising an amplifier and a detection output means operated by an output signal of the amplifier.