JPS5964180A - Detector for disconnection of cable for spot welding - Google Patents

Abstract

PURPOSE:To provide a detection circuit for disconnection which detects abnormality for each core wire by providing detection coils, and filter, peak holding and comparison circuits in accordance with the number of core wires and providing a changeover switch to the comparators. CONSTITUTION:Detection circuits 8 consisting of magnetic sensors of the number corresponding to the number of core wires of a cable for welding of a spot welding device are provided to detect the change in welding current. The output of each coil 8 is fed through an amplifier circuit 12 to a filter circuit 13, by which a smooth DC voltage is obtd. and is stored in a peak holding circuit 14. The voltage is compared with a reference voltage in a comparator 15, and when said voltage is higher than a reference voltage, an output voltage is generated at an output terminal 16. The result of the discrimination is displayed on an indicating lamp 22. The output side of each set of the comparator 15 is changed over by a changeover switch 23 and the reference value is set at an optional value. The disconnection of the core wire is quickly and surely detected by such circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a cable breakage detection device for spot welding, which can be used until just before the core wire of the cable is completely broken.

A spot welding device connects a transformer and a spot gun with a welding cable (hereinafter referred to as a cable), and sends welding current to the spot gun. Since this cable carries a low voltage and a large current, it is best to minimize the actance during energization. Therefore, as shown in FIG.
2.3 is used, which is called a kickless cable. Cores 1 and 2 are for the positive side circuit, and core wire 5 is for the negative side circuit.

These core wires 2.5 are connected in parallel and used.

If a break occurs in the core wire 2.3, the current to the spot gun will be reduced or cut off, resulting in defective spot welding or inability to weld.

Therefore, it is desirable to monitor the deterioration state of the core wire t>'L periodically or from beginning to end to prevent unexpected situations due to cable breakage. However, in the past, there was no disconnection detection device for the kickless cable mentioned above, so the cable was replaced periodically taking into consideration the average lifespan of the cable. .

This resulted in considerable waste.

This invention has been made in view of this point, and is designed to make it possible to detect the state of deterioration of 1) ili+2.3 during contact work. And the heart line 2.3 of the double book
This allows the state of the current flowing through both to be grasped at the same time.

Next, a practical example of this invention will be explained with reference to the drawings.

First, what is shown in FIG. 2 is a detection coil storage box 4. As shown in FIG.

This detection coil storage box 4 has two parts 5 and 6 which are pivoted by hinges 7 so that they can be opened and closed. There is always Q) f. The detection coil 8σ corresponds to the number of centers to be measured, 11; and as shown in FIG.
When four detection coil storage boxes are installed on the external device of this cable, each detection coil 8 is connected to IE? as shown in FIG. sister!
2. There is C who comes to confront 3. Furthermore, II! y
, 1s<l Ii This sign is 11°C.The one shown is the following.

:1-5 figure tj,, 4. Toda coil 8, cape lumino [pure detection device [! ? 1 with 11. ”, indicates the SA staff. Cable μ) “Pre-1 Tori 1^11 &”
, six sets (six channels) of the following circuits are installed corresponding to the coil 8 of 61 yen. Since these tj are exactly the same circuit, one set of them is
I will explain.

ib of the welding current flowing into the detection coil 8t core wire 2.3
, changes in flow jii'j are detected by induced lifting and force. The detection coil 8 is connected to a filter circuit 13 via an amplification circuit 12.

The filter circuit 15 has an induced voltage 11. Pulse from the power! It is the 7th extension of the JE industry with smooth DC tW and JE industry. The output 11111 of the filter circuit 13 is connected to the peak hold circuit 14. The peak hold circuit 14 detects all output voltages of the filter circuit 13 and stores I'iL. Peak hold circuit 1
The output side of 4 is connected to a comparison circuit 15. The comparison circuit 15 compares the output voltage of the peak hold circuit 14 with a preset reference voltage, and generates an output voltage at the output width 16 when the output voltage of the peak hold circuit 14 is higher than the reference voltage. It is something.

17 is a channel changeover switch. The changeover switch 17 has a movable contact 18 and six fixed contacts 19 that the movable contact 18 selectively contacts. The fixed contacts 19 are connected to the outputs 1 of the peak hold circuits 14 of each set. Changeover switch 17
The movable contact 18 is connected to the positive side measurement terminal 20. 21VJ is a negative side measurement terminal and is grounded. In comparison circuit 15! l'lJ constant result display lamp 22 is also connected, and 1. is connected to measurement terminal 2D. When the B force 'tortoise pressure is generated, it lights up and the 6 cores Ho, -> which core wire 2.
It is designed to notify you if there is something wrong with 3.

A reference voltage and voltage are applied to the comparison circuit 15. This reference voltage is obtained by a divided voltage of a resistor connected in series and an r+J variable resistor HOG. Therefore, any value can be set by operating the variable resistor. Since this voltage setting is performed for each set of comparison circuits 15, it is desirable to be able to measure the voltage according to necessity. Therefore, each set of reference voltages is connected to the fixed contact 24 of the changeover switch 23 for measuring the reference voltage, and the movable contact 2
5 can be switched as appropriate. Movable contact 25
The positive side measurement terminal 26 is connected to. 27 is a negative side measurement terminal and is grounded. A reset switch 28 is of a normally closed type and is commonly connected to each set of peak hold circuits 14.

Next, make this device! vI'i will explain. First, the detection coil storage box 4 is fixed to the outer cable device as shown in FIG. At this time, as shown in FIG. 4, each detection coil 8 is made to correspond to the core wire 2 or the core wire 3. In the cable, three core wires 2 for the positive circuit and three core wires 3 for the negative circuit are arranged every other wire, but these are arranged in three rows in parallel. ] to be used. When current flows through the core wires 2 and 3 to re-feed the spot gun 10, the detection coil 8 detects an induced force waveform as shown in FIG. This induced electromotive force is amplified rlJ by the amplifier circuit 12 and converted into a DC component having a waveform as shown in FIG. 7 by the filter circuit 13.

Either core of cable +5ffl (21ycr yo 3)
If there is a K disconnection, the disconnected core 91 (2 or Iti 5
) and the other core wires (219i, I 3 ) of the same polarity Mif, the DC value changes. FIG. 8 shows this state. In this diagram, horizontal lll1lI is 61
14 core wires are shown, and the vertical 'l'll+ represents the output i; pressure.

If there is no abnormality in the core wire 2.3, the output KL g, e will be the 8th
As shown in (a) of the figure, it is an average value. This is detected by sequentially switching the changeover switch 17.

If the first core wire (2 or 3) breaks,
As shown in Φ) in FIG. 8, the output direct pressure of the remaining core wires of the river rises and exceeds the reference withstand pressure value, causing the -C peak value to become unbalanced. As a result, the comparison circuit 15 causes the output aphrodisiac 16 to generate an output signal, and the judgment result display lamp 2
Turn the lights down to 2'. As a result, which mind-making (2 or 3
) can tell if there are different layers. The extent of the abnormality can be accurately determined by connecting a voltmeter to the measurement terminals 20 and 21 and measuring the voltage. One time rllllll is over
Then, the reset switch 28 is closed for a moment, and the output of the peak hold circuit 14 is returned to zero.

In this embodiment, a detection coil 8 is used as a magnetic sensor to detect a magnetic signal due to a break in a core wire.
The same objective can also be achieved by using a semiconductor magnetic sensing element such as a Hall element or a magnetoresistive element.

Since this invention has the structure DK L as described above, it is possible to quickly and reliably detect the first breakage of the core wire (2 or 5), and to quickly and reliably detect the first break in the core (2 or 5) ) Appropriate treatment such as repair can be carried out before a K disconnection occurs.

Therefore, unlike conventional tijl VC, the core wire is disconnected.
There is no need to replace it regularly, and it can be used until the wire breaks.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a cable to which the present invention is applied; Fig. 2 is a perspective view of a detection coil storage box according to the invention; Fig. 3 is a perspective view showing the detection coil storage box attached to the cable; 4 is an enlarged sectional view taken along IV-fl/m in FIG. 6, 51st is a circuit diagram of an embodiment of the present invention, FIG. Figure 8 is a waveform diagram of the output direct pressure that is smoothed by a filter circuit and converted into a DC component. 2.3... Core wire 8... Detection coil 1o.
... Spot gun 11 ... Cable disconnection detection device 13 ... Filter circuit 14 ... Peak hold circuit 15 ... Comparison 1i-11 path 17 ... Changeover switch patent applicant Toyota Tunnel Co., Ltd. No. 5 Figure 6 Figure 7 Cause Figure 8

Claims (1)

[Claims] 1) a magnetic sensor that converts a magnetic signal generated by a change in current value into an electrical signal; a filter circuit that removes pulsation from the electrical signal output from the magnetic sensor to obtain a smooth DC component; and the filter. A current to be measured is passed through a peak hold circuit that detects and stores the output voltage of the circuit, and a comparison circuit that extracts the output voltage of the peak hold circuit and determines whether the voltage value is large or small with respect to a predetermined reference voltage value. 1. A cable breakage detection device for spot welding, characterized in that a number of switches are provided corresponding to the number of core wires of the cable, and are provided with changeover switches for switching the output side I of each comparison circuit corresponding to the number of core wires of the cable.