JPS6018284A - Control device for resistance spot welding machine - Google Patents

Abstract

PURPOSE:To detect the abnormal short circuiting on the secondary side such as secondary cable of a welding transformer and to prevent welding defects and the like by turning on a start switch to conduct current while a welding gun is open and enabling detection of the current value on said secondary side in this stage. CONSTITUTION:Plural kinds of welding conditions are selected with, for example, a control device, by start switches 1-4. If the switch 2 is turned on here, interlocking contact points a2-e2 are closed. As a result, the preset preliminary pressing time, welding time, welding current and holding time are inputted and set from setters 7, 10, 9, 13 to respective circuits 6, 8, 12, 11. A driving circuit 14 for a pressurizing valve is turned on at the same instant, by which a welding gun is closed and welding is accomplished by the on operation of the circuit 6 and others. On the other hand if the switch 5 is turned on in the stage of detecting short circuiting, the circuit 6, etc. are inputted and set and the other contact points e5 are closed, by which a detecting circuit 15 is turned on and the welding gun is held open. The circuit 15 passes the welding current I5 until welding time W5 passes by after the lapse of the preliminary pressing time S5. The presence or absence of the short circuiting on the secondary side is thus detected with a current detector 17.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for controlling the operation and energization of a welding gun in a J3 resistance spot welding machine.

For example, it is well known that welding is frequently used in the assembly of an automobile body, and these welding operations have recently come to be performed automatically using robots and the like.

By the way, resistance spot welding involves sandwiching and pressurizing the stacked objects to be welded between electrodes, and then passing a large current through the areas where the contact resistance has locally decreased. This is the way to do it. Therefore, the secondary cable connecting the welding lance and the welding gun has
During welding, a current of several thousand to several thousand amperes flows, which generates heat, so conventionally water-cooled cables have been used as secondary cables, and recently, especially, the reciprocating cable is housed in one rubber hose. The built-in kickless cable accounts for the majority. Although the reciprocating lines of this type of cable are electrically insulated by a rubber diaphragm, they are frequently bent, a large current flows intermittently, and the rubber hose is filled with cooling water. During use, the reciprocating line of the cable may become N(m) and cause an internal short circuit.In such a case, the welding current flows through the short circuit point and through the reciprocating line and does not flow between the electrodes, so welding should not be performed. become unable to do so.

However, with the above-mentioned kickless cable, the internal situation cannot be seen from the outside, and furthermore, in automatic welding processes using robots, etc., it is not possible to check the quality of welding each time, and there is a risk that welding defects will occur frequently. .

In order to eliminate such inconveniences, it is possible to conduct periodic inspections of the secondary cable frequently, but it is extremely difficult to predict internal short circuits through periodic inspections, which may result in welding defects or There is a risk that a secondary cable that is still usable may be replaced, resulting in an increase in welding costs. Therefore, in the past, the actual situation was to increase the frequency of welding quality inspections, strive to discover welding defects, and discover short circuits such as secondary cables and -pulls through welding defects, which only placed a heavy burden on the workers. However, there were problems such as poor efficiency.

This invention was made in view of the above circumstances, and is a control device for a resistance spot welding machine that is capable of not only controlling normal welding work but also detecting abnormal short circuits on the secondary side of a welding transformer such as a secondary cable. The purpose is to provide the following. And the system of this invention! The II device is operated by any of a plurality of start switches, and includes a pressurizing valve drive circuit that drives a valve to open the welding gun, and a pressurizing valve drive circuit that drives the valve to open the welding gun, and A preload time control circuit that controls the pressurization time, that is, a preload time, a welding time control circuit that controls the welding time during which welding current should flow, and a holding time that controls the holding time that allows the welding gun to continue opening after energization ends. A control circuit, a welding current control circuit that conducts current after the elapse of the preload period until the welding time elapses, and a welding current control circuit that causes the current value on the primary side or the secondary side of the welding valve to exceed a predetermined reference current value. When one of the start switches is turned on, the other circuits except the pressurizing valve drive circuit are turned on, and the The present invention is characterized in that the circuits other than the detection circuit are turned on when any one of the other starting switches is turned on.

The control device of the present invention will be explained in more detail below based on an actual flow example.

10 is a block diagram schematically showing an embodiment of the present invention, and the control device shown here is configured to be able to set a plurality of types of welding conditions, that is, a plurality of current values such as energization time for 1 g. , the welding conditions are selected from a plurality of (Figure C shows five starting switches 1, 2, 3, 4, 5).The starting switches 1 to 5 are manually operated. 1 to 1l = 11 = 11, or the C circuit by input from another controller (not shown) such as a blanking device. When any of the switches 1 to 5 is closed, the preload time Pj control circuit 6 is turned on (1 (made -C).
There is. The preload time control circuit 6 includes start switches 1 to 1.
Multiple g corresponding to 5! Preload time S1, S2, S3,
A setting device 7 that can set S4.35 is connected, and the preload time control circuit 6 is connected to one of the starting switches 1.
~5 is turned on by closing, and the circuit is interlocked with the start switches 1~5 (contact a1 in the figure).
, a2, a3, a4, and a5) are closed, so that a signal is output after one of the preload times S1 to S5 set in the setting device 7 has elapsed.

The output signal of the preload time control circuit 6 is input to a welding time control circuit 8 and a welding current control circuit 9, respectively. The welding time control circuit 8 has a welding time Wl of multiple types A corresponding to the riser suits 1 to 5.
, W2, W3, 'V'l/4, W5 is connected, and these welding times W1 to W5 are connected.
W5 is a circuit that operates quickly when any of the starting switches 1 to 5 is turned on (in the figure, the contact old, b
2.1) 3, b4, and b5) are closed, and accordingly, the corresponding welding times W1 to W5 are input and set from the setting device 10 to the welding time control circuit 8, and the welding time control circuit 8 receives the preload. When a signal is input from the time control circuit 6, the welding time control circuit l1j48 turns on, and turns on operation 1.
After the welding times W1 to W5 input and set in accordance with the start switches 1 to 5 have elapsed, the welding time control circuit 8 outputs a signal to the welding current control circuit 9 and the holding time control circuit 11. It is supposed to be done.

On the other hand, the welding current control circuit 9 controls the current flowing between the electrodes (not shown) in the welding gun, and is turned on by the signal inputted from the preload time control circuit 6 so that >f! i 't35, and the configuration is such that it is activated by No. 18 inputted from the welding time control circuit 8 to stop the energization. II i= i'f't I:'before M
'2 Flj! 'Fl equipment 10 welding r! one tense tP
'1 Welding input/set to circuit 8 [i temple 11]\x,
'1--~~15 I melted soup! The gastric flow; The reason for the welding current is 1.12.
13, T4, ■5 are circuits that turn υ1 in conjunction with the starting switches 1- and 5 (at t+, contacts c1, C2, c, 3,
C4, C5 (not shown) from the t2 regulator 12 to the r1 contact current Pj carp circuit, (□ input, so 1.1 f
, 'i *~. stomach. .

Further (2 retention time control circuits'f5111,) 7 contact flow 1
This is a holding time control circuit for controlling the holding time that further continues the clamping and pressurization of the welding gun (not shown) after the energization is completed. 11 includes a circuit that opens in conjunction with the above-mentioned movement switch 5 (contacts 11, C2, C3, C4, C5).
When the setting device 13 is connected to the setter 13 via the switch (shown with 1) and any of the starting switches 1 to 5 is turned on, the contacts d1 to d5 that are linked thereto are closed, corresponding to the starting switches 1 to 5 that have been turned on. Retention time H1, H2, H3, )-1
4, H5 is input and set to the retention time control circuit 11. The holding time control circuit 11 is turned on in response to the signal input from the welding time control circuit 8, and after the holding times H1 to H5 input and set from the setting device 13 have elapsed, a termination signal is sent. is configured to output.

Furthermore, the control device shown in FIG. 1 includes a pressurizing valve drive circuit 14. The pressurizing valve drive circuit 14 is
It operates a solenoid SQL of a pressurizing valve (not shown) that controls a pressurized fluid such as air that opens and closes the welding gun, and operates the pressurizing valve, and is any one of the start switches 1 to 5. Other activation switches 1 to 1 except for one activation switch, for example, the fifth activation switch 5
4 (contacts e1, C2, C3 in the figure)
, C4) is closed, it turns on and energizes the solenoid SQL, and when a termination signal is input from the holding time control circuit 11, it turns on and stops energizing the solenoid SQL, causing the solenoid SQL to be energized. The pressure valve is configured to return.

Therefore, in FIG. 1, the poly control device closes the welding gun to clamp and pressurize the workpiece when the first to fourth starting switches 1 to 4 are turned on, and in this state, preload time S1 to S4 is applied. After the welding interval W1 to W4 has elapsed, welding and welding currents 11 to 4 are applied, and after the energization is finished, the welding gun is opened when the holding time H1 to H4 has elapsed, and the fifth activation is performed. When switch 5 turns on,
The welding current is configured to be energized without closing the welding gun.

Furthermore, the above control device has a detection circuit 15 that turns on when the welding gun is not closed, that is, a circuit that closes in conjunction with the fifth starting switch 5 among the starting switches 1 to 5 (indicated by contact e5 in the figure). The detection circuit 15 has a detection circuit 15 that is turned on through the circuit.

The detection circuit 15 outputs an alarm signal when the current value on the primary side or secondary side of a welding transformer (not shown) exceeds a predetermined reference current value. Shown in Figure 2. Reference numeral 16 in FIG. 2 is an integrator, which differentiates the applied current input from a current detector 17 such as a toroidal coil, Hall element, or current transformer attached to the primary or secondary side of the welding transformer to form its differential waveform. The current waveform is converted into a current waveform, and the output thereof is provided to the waveform shaper 18. The waveform shaper 18 is the integrator 1
The signal input from 6 is rectified and converted into a DC voltage according to the energizing current value, and the DC voltage is further converted to a DC voltage by a comparator 19.
The configuration is such that the information is input to the On the other hand, a reference generator 20 is connected to the comparator 19, and the reference generator 20 sets a reference voltage corresponding to the reference current value, and the reference voltage and the voltage manually inputted from the waveform shaper 18 are combined. are compared in the comparator 19, and if the voltage input from the waveform shaper 18, that is, the measured current value is larger than the reference current value, a signal is output to the alarm signal generator 21, and the alarm signal generator 21 is designed to output an alarm signal. Note that the reference current value is used as a standard for determining whether or not the actual measured current value indicates an abnormality, and specifically, the welding electrodes are turned on while being insulated from each other When the no-load current value flowing to the primary side of the welding transformer is set to an intermediate value and the welding current value flowing to the primary side during actual welding, or when the configuration is configured to detect the secondary side current. It is preferable to set φ to half the welding current value on the secondary side.

Next, the operation of the control device configured as described above will be explained. Selection of welding conditions and start of welding work are performed by pressing J: on the first to fourth starting switches 1 to 4 among the starting switches 1 to 5.

That is, for example, when the second starting switch 2 is turned on, the contacts a2, b2, C2, d2,
C2 is closed, and as a result, the preload time S2, welding time W2, and welding current I set in advance corresponding to the second starting switch 2 are
2. Each of the holding times H2 is set by setting device 7.10.12.13
are input and set to each of the preload time control circuit 6, welding time control circuit 8, welding current control circuit 9, and holding time control circuit 11.

At the same time, the pressure valve drive circuit 14 is turned on and the solenoid SQL is energized, and as a result, the pressure valve is switched and the welding gun is closed, thereby clamping and pressurizing the workpiece. Similarly, the preload time control circuit 6 is turned on, and after the preload time S2 input from the setting device 7 has elapsed, the preload time control circuit 6 outputs a signal to the welding time system 1 circuit 8 and the welding current control circuit 9. do. In accordance with this, the welding current control circuit 9 is turned on, so that the second starting switch 2 is turned on, and a selected welding current I2 of a predetermined current value is applied to one electrode of the welding gun. flowing between. Further, the welding time control circuit 8 outputs a signal after the welding time W2 selected by the start switch 2 of the rear section 2 which is turned on by a signal from the preload time control circuit 6 has elapsed,
As a result, the welding current control circuit 9 is turned off and the current supply is stopped. In other words, the application of the welding current I2 continues until the welding time W2 has elapsed. After the energization ends, that is, the holding time control circuit 11 is turned on by the output signal of the welding @ quantity control circuit 8, and the holding time control circuit 11 is operated by input/setting by turning on the second starting switch 2. After the hold time H2 has elapsed, a termination signal is output, and as a result, the pressurizing valve drive circuit 14 is turned off and the solenoid SQL is demagnetized, so the welding gun opens and the workpiece is released. Therefore, as shown in FIG. 3, the welding gun pressurizes the workpiece until the preload time S2, welding time W2, and holding time respectively selected by turning on the start switch 2 have elapsed. I will do it. The time chart is shown in the third factor.

On the other hand, when detecting a short circuit, the fifth starting switch 5 among the starting switches 1 to 5 is turned on. Accordingly, each contact a5 interlocks with the fifth starting switch 5,
Since b5, C5, and d5 are closed, the fifth starting switch 5
The preload time S5 and the welding time W5 are set in advance in accordance with
, welding current I5 and holding time H5 are set by the setting device 7.
From 10.12.13, it is input and set to each of the preload time control circuit 6, welding time control circuit 8, welding N flow control circuit 9, and holding time control circuit 11. Further, since the other contact e5 interlocked with the fifth starting switch 5 is closed, the detection circuit 15 is turned on. In that case, since a circuit (contact) that closes in conjunction with the fifth start switch 5 is not installed on the pressure valve drive circuit 14 side, the pressure valve drive circuit 14 will not be turned on, and therefore the welding gun will not turn on. remains open.

Then, after the preload time S5 has elapsed and until the welding time W5 elapses, the welding current control circuit 15 controls the welding current I that has been input in advance.
I'm working hard to pass 5. In that case, unless there is a short circuit on the secondary side of the welding transformer, the circuit is open, so no current flows at all on the secondary side, and a few amperes to tens of amperes flows on the primary side. Only current flows, but if there is a short circuit on the secondary side of the secondary cable or welding gun, welding current I5 of several thousand to several thousand amperes will flow to the secondary side.
flows, and a current of several hundred amperes flows in the primary side. Therefore, the current on the primary or secondary side of the welding transformer is
It is detected by the current detector 17 shown in FIG.
The output signal of the current detector 17 passes through the integrator 16 and waveform shaper 18 in the detection circuit 15, is converted into a voltage corresponding to the energizing current, and is further compared with a reference voltage in a comparator 19. In this case, if FIN occurs on the secondary side of the welding lance, the large current as described above will flow to the primary and secondary sides despite the welding gas]/. Therefore, the actual measured current value is based on the reference generator 2.
0, the preset reference current value is significantly exceeded, and as a result, the comparator 19 outputs a signal. Since the alarm signal generator 21 is turned on by the output signal of the comparator 19, a short circuit on the secondary side of the welding transformer can be easily detected by lighting a lamp or sounding an alarm in response to the alarm signal. be able to. Note that the holding time control circuit 11 outputs a termination signal after the holding time H5 has elapsed after the end of energization, but if there is a short circuit on the secondary side of the welding transformer as described above, an appropriate reset/operation is required. Make sure that the start switches 1-5 do not function until the
It is preferable to

As explained above, according to the control device of the present invention, by turning on any predetermined start switch among the start switches, the welding gun is energized with the welding gun open, and one of the welding transformers at that time is turned on. Since the current value on the next side or secondary side can be detected and compared with the reference current value, if a short circuit occurs on the secondary side of the welding lance or lance, you can directly know the short circuit, and therefore, this According to the device of the invention, it is possible to deal with an abnormal short circuit by replacing the secondary cable before a welding failure due to an abnormal short circuit occurs, so that inconveniences such as welding failures and their rework can be eliminated in advance.

[Brief explanation of drawings]

FIG. 1 is a block diagram schematically showing an embodiment of the present invention, FIG. 2 is a block diagram showing an example of the detection circuit, and FIG.
The figure is a time chart showing the timing of pressurization and energization during welding and when detecting a short circuit. 1.2.3.4.5... Start switch, 6... Preload time control circuit, 7.10, 12.13... Setting device, 8... Welding time control circuit, 9... - Welding current control circuit, 11... Holding time control circuit, 14... Pressure valve drive circuit, 15... Detection circuit. Applicant Toyota Motor Corporation Representative Patent Attorney Yutaka 1) Hisashi Take (and 1 other person)

Claims (1)

[Claims] By making the welding gun electrically connected to the secondary side of the welding transformer jump, the object to be welded is clamped and pressurized by a pair of electrodes provided on the welding gun, and in this state, the welding gun is placed on the primary side of the welding transformer. In a resistance spot welding machine that welds a workpiece by flowing a welding current between the electrodes, the pressurization valve that drives a plurality of start switches and a valve for closing the welding gun. a drive circuit, a preload time control circuit that controls the preload time from welding i to flowing current to the primary side of the lance after one of the starting switches is turned on; 1
A welding time control circuit that controls the welding opening that energizes the next side, a holding time control circuit that controls the holding time that continues the closing operation of the welding gun that has finished energizing, and Equipped with a welding current control circuit that performs intermittent welding until the time elapses, and a detection circuit that outputs a signal when the current value on the primary or secondary side of the welding transformer exceeds a predetermined reference current value. When any of the starting switches is turned on, the circuits other than the pressurizing valve drive circuit are turned on, and any other starter switch is turned on. 1. A resistance point, welding control m1 device, characterized in that the circuits other than the detection circuit among the respective circuits are turned on.