JPS595075B2 - Voltage measurement method and device for resistance welding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for measuring the power supply voltage of a resistance welding machine during energization.

It is well known that welding current is the most important factor in controlling the quality of resistance welding machines.

Therefore, when controlling the welding current, it is generally measured with an instantaneous ammeter, but in many cases it is also desirable to record the voltage of the power supply at the time. .

For example, if there is a shortage of current, and it is not clear whether the cause is an increase in impedance such as cable wear, or the most common cause is a drop in the power supply voltage10, the power supply voltage may drop when measuring the current. I need to know if it was on or not. However, since the energization time for spot welding is short, such as 0.2 seconds, the power drop during energization only drops for this amount of time, so 15 on a commercially available voltmeter indicates an average voltage with a slow response time. Therefore, it is not possible to display the instantaneous voltage fluctuations as described above. The present invention provides a device that can quickly measure such instantaneous voltage drops during welding. Embodiments of the present invention will be described below with reference to block diagrams of the drawings.

1 shows an electric path of a welding power source whose load is a welding machine 2 including a control device.

3 is a voltage change detection circuit that receives the power supply voltage of electric line 1 as an input and detects a sudden drop in voltage; 4 is a welding energization receiving circuit that notifies this measuring instrument of the start of welding energization of electric line 1; In some cases, the signal is given as an energization start signal from the welding machine control device included in the welding machine 2, and in other cases, it is given by detecting the welding current that actually flows.

Reference numeral 5 denotes a selection circuit 30 which selects whether to open the measuring gate 6 (described later) by a signal from the voltage fluctuation detection circuit 3 or by a signal from the welding energization receiving circuit 4 given as an external signal. It is selected depending on the voltage fluctuation situation at the site and the purpose of measurement.

For example, in the case of selection circuit 1, the measurement start signal is from the voltage fluctuation detection circuit 3 that self-detects the start of energization, so it is very convenient that the measurement start signal cannot be received from the outside, and the voltage fluctuation detection circuit 3 Depending on the detection level setting, it is also possible to measure the power supply voltage of other welding machines (not shown in the figure) when they are energized.

By setting the selection circuit 5 to ◎ and switching the switch 15 to the O side, it is possible to measure the power supply voltage only when the target welding machine is energized. However, an apparatus that does not include a selection circuit, ie, has only either the voltage fluctuation detection circuit 3 or the welding energization receiving circuit, may be sufficient for practical purposes.
The measurement gate 6 is for appropriately controlling whether to guide or block the power supply voltage to be measured to the measurement circuit, and is a gate that receives an output signal from the completion pulse generation circuit 14, which will be described later, and ends the measurement. be.

Reference numeral 7 denotes a delay gate, which is used to start measurement at the end of the slope current at the initial stage of energization, but this circuit is not necessarily required depending on the application.

Reference numeral 8 denotes a voltage measurement circuit that performs measurement when one input 8 is allowed to measure while logic 1 is applied, and a power supply voltage detection input to be measured is applied to the other input θ, and the voltage measurement circuit does not include waveforms. converts the power supply voltage into an effective value or an average value, and converts it into an analog →
It is converted into digital data by a digital converter (A/D) 9.

Further, when the voltage measurement circuit 8 starts measuring and the input (E) becomes logic 0, or after a certain period of time has elapsed, it is applied to the completion pulse generation circuit 14 in order to generate a completion pulse, and this pulse output causes the digital converter ( The output of the A/D) 9 enters a latch circuit 10 where it is held and output to a display 11. Reference numeral 16 is a flicker generator, and when the welding machine is not energized, that is, when measuring normal power fluctuations regardless of the output of the voltage fluctuation detection circuit 3 or the welding energization receiving circuit 4, the switch 15 is set to the @ side. The measurement gate 6 is then opened by a flicker signal, and the average value or effective average value of the output period (for example, 1 second) of this flicker generator 16 is displayed, and then the next cycle is displayed. This is a circuit that displays the average value of voltage for one second.

The above is a case of a digital display embodiment, but in the case of an analog display, the output of the voltage measurement circuit 8 is shown by a virtual line instead of the digital converter (A/D) 9, latch circuit 10, and display 11. The same effect can be achieved even if the measurement value is inputted into a sampling hold circuit or the like corresponding to the holding circuit 12, held by the completion pulse generating circuit 14, and this measured value is displayed by a device such as the meter 13.

Next, the operation according to the embodiment of the present invention will be explained.

If you want to detect the energization of the welding machine by yourself, select the selection circuit 5 to the 4 side and use the output of the voltage fluctuation detection circuit 3 connected to the electric line 1 of the welding machine to detect the power supply voltage when the welding machine is energized. It self-detects that it has fallen, and this output is sent to the selection circuit 5,
The signal passes through the measurement gate 6 and enters the delay gate 7. Upon receiving this output, the delay gate 7 causes the voltage measuring circuit 8 to start measuring after a delay time of about 4 cycles in order to cut the slope time for starting the current supply. Since this voltage measurement circuit 8 is given the power supply voltage to the other input, it calculates the effective voltage value of the detected voltage while the measurement permission signal from the delay gate 7 is being input, and transfers the calculation result to one side. The output is given to a digital converter (A/D) 9. When the predetermined measurement time is completed, a measurement completion signal is generated from the other output of the voltage measurement circuit 8, and this is applied to the completion pulse generation circuit 14, which closes the measurement gate 6 with this output. Measurement by the voltage measuring circuit 8 is prohibited until a measurement start command is received. A digital converter (A/D) 9 that receives a measurement result from one output of the voltage measurement circuit 8 digitally converts this input value, and converts the voltage measurement digital value into a latch circuit 10 using this completion pulse. Latch, display 11
Display the voltage value.

When the voltage is displayed in analog form, the output of the voltage measuring circuit 8 is fed to the holding circuit 12 and the meter 13, and when the voltage drop due to energization is small, the energization signal or energizing current from the welding machine is used to receive the welding energization signal. In response to the signal from the circuit 4, the selection circuit 5 can be selected to the ◎ side via the switch 15 and applied to the measurement gate 6 to notify the start of energization. As explained above, according to the device of the present invention, it is possible to easily measure the power supply voltage during energization of a resistance welding machine, which could not be measured conventionally, so it is useful for welding management such as welding quality and maintenance inspection. It can be of great help.

Further, according to the device of the present invention, voltage fluctuations due to the welding current flowing through the welding machine's electrical circuit are detected by itself and this is given to the measurement gate as a measurement start signal, or a detection signal of the actual current flowing or a timer etc. A function that allows you to arbitrarily select whether to open the measurement gate with the energization start signal given by an external device, depending on the measurement purpose and the voltage fluctuation situation at the production site. This makes it possible to realize an extremely reliable and practical monitor.

[Brief explanation of drawings]

The drawing is a circuit diagram showing, in block form, an embodiment of an apparatus for carrying out the voltage measuring method of the present invention. 1... Electric circuit, 2... Welding machine, 3...
... Voltage fluctuation detection circuit, 4 ... Welding energization receiving circuit, 5 ... Selection circuit, 6 ... Measurement gate, 8 ... Voltage measurement circuit , 11...
display.

Claims (1)

[Claims] 1. A voltage fluctuation detection circuit that detects a sudden change in the power supply voltage of a resistance welder, a welding energization reception signal circuit that receives a welding energization signal given from the outside, and either the detection circuit or the welding energization reception circuit. a selection circuit that selects one of the outputs; a measurement gate that is maintained in a state to start measurement by one of the outputs selected based on the selection circuit; voltage of a resistance welding machine, which is equipped with a measurement circuit that measures the power supply voltage, a holding circuit that holds the value measured by this measurement circuit, and a display that displays the held measurement value. measuring device.