JP2000326070A - Delay time measuring instrument for ac arc welding machine with automatic voltage reducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the delay time of an automatic voltage reducing device without actually generating an arc. SOLUTION: A delay time measuring instrument is equipped with a pair of input terminals 11a, 11b to be connected to a welding machine 1, a resistor 13 for starting sensitivity measurement, which includes a variable resistor 132 connected between the input terminals 11a, 11b via a switch 12, a voltage detecting part 15 for detecting a voltage appearing between the input terminals 11a, 11b and a control means 18 for controlling by switching the switch 12 according to the output signal of the voltage detecting part 15 and a control means 18 performing a prescribed timing processing, etc. After turning the switch 12 on by connecting the resistor 13 for starting sensitivity measurement to the welding machine 1, when an automatic voltage reducing device is started by the change in the resistance value of the variable resistor 132 and the output voltage of the welding machine 1 is turned from a safety voltage to a no-load voltage, the switch 12 is turned off. A delay time required from the time when the switch 12 is turned off to the time, when the output voltage of the welding machine 1 is turned again from the no-load voltage to the safety voltage by the operation of the automatic electric shock preventing device is timed, and the delay time obtained is displayed on a prescribed display means 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for measuring a delay time of an automatic electric shock prevention device attached to an AC arc welding machine. More specifically, the present invention relates to a technique for measuring a delay time without actually generating an arc. The present invention relates to a delay time measuring device for measuring a delay time of an automatic electric shock prevention device in a proper state.

[0002]

2. Description of the Related Art AC arc welding is one of dangerous operations because it involves a high voltage. So, 19
A partial revision of the Occupational Safety and Health Regulations in 1991 required the use of automatic electric shock prevention devices for AC arc welding machines.

[0003] As schematically illustrated in FIG.
The automatic electric shock prevention device A has a current transformer CT for detecting a current flowing to a secondary output of the AC arc welding machine, and a main transformer TR1 or an auxiliary transformer TR2 is operated by a switch SW according to the detected current value. Select one of

That is, when the current value is zero or very small, it is determined that the welding operation is in a halt state, and the voltage between the welding rod D and the base material M is made safe for the human body by switching to, for example, the auxiliary transformer TR2. Voltage (less than 25V,
In any case, including when the input voltage fluctuates, the voltage is reduced to 30 V or less.

When the welding rod D is brought into contact with a base material (for example, an iron plate) M, the automatic electric shock prevention device A starts. That is, the switch SW is switched to the main transformer TR1, and a voltage of, for example, about 80 V is output instantaneously (see FIG. 5). While the welding rod D is in contact with the base material M (during welding operation), an arc voltage of 30 to 40 V is maintained.

[0006] When the welding rod D is separated from the base material M and no load is applied, the voltage between the welding rod D and the base material M rises to about 80 V (see FIG. 5). This voltage is called no-load voltage. Then, when the predetermined time has elapsed, the switch SW is switched to the auxiliary transformer TR2 side, and the voltage between the welding rod D and the base metal M decreases to a safe voltage (25 V) (see FIG. 5).

As described above, the time between the time when the voltage between the welding rod D and the base metal M becomes the no-load voltage and the time when the voltage drops to the safe voltage is determined by the "automatic shock prevention device A". Delay time ". The delay time is determined to be about 1 second, and at most 1.3 seconds. On the other hand, the resistance value between the welding rod D and the base material M when changing from the safe voltage to the no-load voltage is referred to as “starting sensitivity resistance”.

[0008] Conventionally, the measurement of the delay time has been performed as follows. That is, as shown in FIG. 6, a welding machine (with an automatic electric shock prevention device) 1
Rod D and test base material M are connected to the secondary output terminals 1a and 1b of
Connect. Further, the measuring device 2 is connected to the secondary output terminals 1a,
1b. The measuring device 2 has, for example, a voltage detecting function, a timing function, and a display.

After the welding rod D is brought into contact with the test base material M to generate an arc, the welding rod D is separated from the test base material M.
Thereby, a no-load voltage is generated. When the no-load voltage is detected by the voltage detection function, the timekeeping function starts, and the time until the voltage drops to the safe voltage is measured. When the timing is completed, the measured time is displayed on the display as a delay time.

[0010]

As described above, the delay time of the automatic electric shock prevention device is measured. However, this has the following problems.

That is, in order to actually generate an arc, it is necessary to prepare a welding rod holder and a test base material and perform the same operation as the actual operation. This places a burden on the operator. Further, it is not preferable because the welding rod is wasted.

[0012]

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to actually generate an arc by applying a pseudo load to a welding machine. It is an object of the present invention to provide a delay time measuring device capable of measuring a delay time of an automatic electric shock prevention device without causing the delay time to be measured.

In order to achieve the above object, the present invention operates according to the resistance value between the secondary output terminals of a welding machine, and adjusts the output voltage of the welding machine to a predetermined value required for arc welding during welding work. In the delay time measuring device of an AC arc welding machine having an automatic electric shock prevention device for reducing the voltage to a safe voltage that is considered to be safe for the human body when the welding operation is stopped, the secondary output terminal of the welding machine A starting sensitivity measuring resistor including a variable resistor connected between the input terminals via a switch, and a voltage detecting unit for detecting a voltage appearing between the input terminals. Control means for performing switching control of the switch based on an output signal of the voltage detection unit and performing predetermined time counting processing, and the control means includes a secondary output terminal of the welding machine when the switch is turned on. The starting sensitivity measuring resistor is connected to the automatic electric shock prevention device by the change in the resistance value of the variable resistor, and when the output voltage of the welding machine changes from the safe voltage to the no-load voltage, By turning off the switch, the starting sensitivity measuring resistor is disconnected from the secondary output terminal of the welding machine, and from the time of the disconnection, the output voltage of the welding machine is reduced from the no-load voltage by operating the automatic electric shock prevention device. It is characterized in that the time until the voltage changes to the safe voltage again is measured, and the time is displayed on predetermined display means as a delay time.

In the present invention, it is preferable to further include a current detecting section for detecting a current flowing through the starting sensitivity measuring resistor. According to this, even the starting sensitivity resistance value can be measured. That is, when the output voltage of the welding machine is changed from the safe voltage to the no-load voltage, the starting sensitivity resistance value of the automatic electric shock prevention device is obtained by the voltage from the voltage detecting unit and the current from the current detecting unit. Can be requested.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described with reference to an embodiment shown in the drawings.

As shown in FIG. 1, the delay time measuring apparatus 10 includes a pair of input terminals connected to secondary output terminals 1a and 1b of an AC arc welding machine 1 via a measuring probe or the like. 11a and 11b are provided. Although the AC arc welding machine 1 is provided with an automatic electric shock prevention device, the form may be either external or internal.

A starting sensitivity measuring resistor 13 is connected via a switch 12 between the input terminals 11a and 11b. In this embodiment, the starting sensitivity measuring resistor 13 is constituted by a series circuit of a fixed resistor 131 and a variable resistor 132. Further, a current detection resistor 141 of a current detection unit 14 is connected to the starting sensitivity measurement resistor 13. That is, the current flowing through the starting sensitivity measuring resistor 13 is detected by the current detecting unit 14.

The delay time measuring device 10 includes a voltage detector 15 for detecting a voltage appearing between the input terminals 11a and 11b. As shown in FIG. 2, in this embodiment, the voltage detection unit 15 includes a full-wave rectifier circuit 151 and a filter circuit 152.

The outputs of the current detection unit 14 and the voltage detection unit 15 are sent to the CPU (central processing unit) as control means via an A / D converter 17.
nit) 18.

According to this embodiment, the input terminals 11a, 1
1b is connected to one of the input terminals 11a.
Is connected. The start detecting section 19 is for detecting a start point of the automatic electric shock prevention device, and a specific configuration thereof will be described with reference to FIG.

The start detecting section 19 is provided with a comparator 191
And a switching element 192 controlled by the output of the comparator 191. Comparator 191
The half-wave signal of the welding machine output voltage appearing on the input terminal 11a side is input to one of the + input terminals, and the reference voltage Vref is input to the other-input terminal.

In this example, the switching element 192
Is connected between the power supply Vcc in the device and the ground G.
A PN transistor is used. Comparator 19
1 outputs a drive pulse to the base of the transistor when the welding machine output voltage is higher than the reference voltage Vref. As a result, the transistor is turned on and the CPU
18 is supplied with a start detection signal.

In the delay time measuring device 10, the welding machine 1
In order to measure the delay time of the automatic electric shock prevention device attached to, the secondary terminals 1a and 1b of the welding machine 1 are connected to the input terminals 11a and 11b via a probe or the like. At this time, the switch 12 is turned off, and the variable resistor 132 is set to the maximum resistance value.

Since the resistance value when the human body is wet with water is about 500 Ω, it is preferable that the resistance 13 for starting sensitivity measurement be set to at least 501 Ω at first (the type of the automatic electric shock prevention device). 200-500Ω depending on
Because some start with).

The no-load voltage of the welding machine 1 is, for example, 80
As V, the reference voltage Vref of the start detecting unit 19 is set to a lower value, for example, 60 V. Power is supplied to the primary side of the welding machine 1, and it is confirmed that the output current of the secondary side is maximum.

Then, the switch 12 is turned on. If the output resistance of the welding machine 1 is equal to or greater than 501Ω, the automatic electric shock prevention device does not start.
5V. Therefore, the start detection unit 19 does not output a start detection signal.

The resistance value of the variable resistor 132 is gradually reduced. Then, at a certain point in time (time t1 in the output voltage waveform of FIG. 3)
Then, the automatic electric shock prevention device is started, and the output voltage of the welding machine 1 becomes the no-load voltage (80 V). Therefore, the start detecting unit 1
9 outputs a start detection signal to the CPU 18.

At the same time as receiving the start detection signal, C
The PU 18 turns off the switch 12 and disconnects the starting sensitivity measuring resistor 13 from the welding machine 1. As a result, the welding machine 1 has no load, so that the automatic electric shock prevention device
At 2:00 (see FIG. 3), the output voltage of the welding machine 1 is switched from the no-load voltage to the safe voltage. Along with this, the start detection signal from the start detection unit 19 also disappears.

The CPU 18 measures the time from t1 to t2 from when the start detection signal is received from the start detection unit 19 until the start detection signal disappears, and displays the measured time as a delay time. Is displayed on the container 20.

The time may be measured by the internal clock of the CPU 18 or separately by using a timer circuit or the like. A liquid crystal display panel, a plasma display, or the like is used for the display 20, but a printer may be used in some cases.

According to the delay time measuring device 10, the starting sensitivity resistance of the automatic electric shock prevention device can also be measured. That is, the CPU 18 includes the current detection unit 14
, The current I flowing through the starting sensitivity measuring resistor 13 is supplied as a voltage signal, and the output voltage V of the welding machine 1 is supplied from the voltage detector 15 via the A / D converter 17.

Accordingly, the resistance of the secondary side of the welding machine 1, that is, the resistance value of the starting sensitivity measuring resistor 13 is obtained from the current I and the voltage V at the time t1. This resistance value is the starting sensitivity resistance of the automatic electric shock prevention device, and the starting sensitivity resistance is also displayed on the display 20 according to the selection of the measurer.

Although the present invention has been described with reference to specific embodiments, the present invention is not limited to these embodiments. In the above embodiment, the switch 12 is turned on manually and the switch 12 is turned off by the CPU 18. However, a separate measurement start button may be provided so that both the on and off of the switch 12 are left to the CPU 18. Good.

The variable resistor 132 can also be a motor drive system, and the variable resistor 132 can be controlled by the CPU 18. The resistor for measuring the starting sensitivity may be only the variable resistor 132. Of course, the control means may be a microprocessor.

In the above embodiment, the start detecting section 19 is provided separately from the voltage detecting section 15, and the start detecting section 19 detects the start of the automatic electric shock prevention device.
This is because the comparator type start detection unit 19 has a higher detection response speed than the voltage detection unit 15.

Therefore, if a voltage detector that can respond at a high speed is used as the voltage detector 15, it is not necessary to provide the start detector 19 as in the above embodiment. This start detection unit 1
9 is also a kind of voltage detector. In this sense, in the present invention, either one may be present. When it is not necessary to determine the starting sensitivity resistance, the current detection unit 14 is not required.

[0037]

As described above, according to the present invention,
The delay time of the automatic electric shock prevention device can be measured without actually generating an arc. Further, by further providing a current detection unit flowing through the starting sensitivity measuring resistor, it is possible to measure even the starting sensitivity resistance value of the automatic electric shock prevention device.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of a delay time measuring device according to the present invention.

FIG. 2 is a circuit diagram showing a configuration of a voltage detector and a start detector in the embodiment.

FIG. 3 is a timing chart showing an output voltage waveform of a welding machine when a resistor for starting sensitivity measurement in the above embodiment is used as a load.

FIG. 4 is a schematic diagram schematically showing a configuration of an automatic electric shock prevention device attached to the AC arc welding machine.

FIG. 5 is a timing chart showing an output voltage waveform of a welding machine controlled by the automatic electric shock prevention device.

FIG. 6 is a schematic diagram for explaining a conventional example of delay time measurement.

[Explanation of symbols]

 Reference Signs List 10 delay time measuring device 11a, 11b input terminal 12 switch 13 starting sensitivity measuring resistor 131 fixed resistor 132 variable resistor 14 current detecting unit 15 voltage detecting unit 17 A / D converter 18 CPU 19 start detecting unit 20 display

Claims (2)

[Claims] An operation is performed in accordance with a resistance value between a secondary output terminal of a welding machine, an output voltage of the welding machine is set to a predetermined no-load voltage required for arc welding during a welding operation, and the welding operation is stopped. Sometimes in a delay time measuring device of an AC arc welding machine having an automatic electric shock prevention device for lowering to a safe voltage that is safe for the human body, a pair of input terminals connected to a secondary output terminal of the welding machine. A starting sensitivity measuring resistor including a variable resistor connected between the input terminals via a switch, a voltage detecting unit for detecting a voltage appearing between the input terminals, and an output signal of the voltage detecting unit. Control means for controlling the switching of the switch and performing a predetermined timekeeping process. The control means connects the starting sensitivity measuring resistor to the secondary output terminal of the welding machine when the switch is turned on. The automatic electric shock prevention device is started by the change in the resistance value of the variable resistor, and when the output voltage of the welding machine is changed from the safe voltage to the no-load voltage, the switch is turned off to turn off the welding machine. The starting sensitivity measuring resistor is disconnected from the secondary output terminal, and the time from the disconnection time until the output voltage of the welding machine changes from the no-load voltage to the safe voltage again by the operation of the automatic electric shock prevention device is determined. A delay time measuring device for an AC arc welding machine with an automatic electric shock prevention device, which measures the time and displays the time as a delay time on predetermined display means. 2. The control device according to claim 1, further comprising a current detecting unit configured to detect a current flowing through the starting sensitivity measuring resistor.
When the output voltage of the welding machine is changed from the safe voltage to the no-load voltage, a starting sensitivity resistance value of the automatic electric shock prevention device is obtained from a voltage from the voltage detecting unit and a current from the current detecting unit. The delay time measuring device for an AC arc welding machine with an automatic electric shock prevention device according to claim 1.