JPH0644531Y2 - Welding detection device in spot welder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an apparatus for detecting welding between a spot welding machine and a workpiece in a plurality of spot welding machines used in industrial robots or automatic machines. is there.

[Prior Art] Welding conditions such as voltage in the spot welding process of automobiles are set somewhat higher in consideration of wear of the welding electrode in the spot welding machine and poor work alignment, but immediately after electrode polishing In some cases, the flow of current is locally concentrated for some reason, the welding electrode melts at the contact portion with the work, and a state (welding) of fusion with the work, which is the object to be welded, may occur.

If the robot or automatic machine is operated with the welding electrode and the work piece welded without detecting this welding, water leakage may occur due to the welding electrode coming off from the spot welding gun, or the motor of the robot, etc. may be overloaded. However, there is a problem that the work is deformed or the bracket of the welding gun is deformed.

In order to prevent these problems, as a conventional technique, for example, there is a welding detection device as disclosed in Japanese Utility Model Laid-Open No. 62-61379. That is, in a spot welding machine that performs spot welding on a work by holding the work under pressure by a spot welding gun and energizing it, a voltage signal is applied to the spot welding gun side for a required delay time from the end of the pressure holding. A signal applying means, a signal detecting means for detecting a voltage signal generated on the work side, a pulse detecting means for detecting a pulse signal due to a difference between the both voltage signals, and a pulse signal after being detected by the pulse detecting means. A signal holding means for continuously generating an output signal until the delay time elapses; and a welding detection device in a spot welding machine.

Further, in the spot welding gun, means for supplying the primary circuit or the secondary circuit during the electrode opening time, means for detecting the voltage between the positive and negative electrodes of the current or energization control element, and the current or the voltage are detected. A welding detection device for spot welding electrode tips, which has a means for issuing an alarm or a stop signal in the event of an occurrence, is also known as disclosed in, for example, JP-A-57-56178.

[Problems to be Solved by the Invention] Generally, in an IC circuit, it is desirable that the IC circuit and the outside are electrically completely separated from each other because noise does not enter the IC circuit. That is.

In the former case of the prior art as described above, the signal detecting means for detecting the voltage signal generated on the work side is used, and in order to guide this voltage signal to the analog / theoretical circuit (IC circuit) which is the signal processing means, the signal is detected. It is impossible to electrically insulate the detection means, the signal processing means and the external wiring (jig). Therefore, there is a possibility that the control as a whole becomes inaccurate because the intrusion of noise cannot be prevented.

Further, in the latter of the conventional techniques as described above, since an electric current is simply passed through a normal welding circuit, an alarm or stop signal is normally issued when both electrodes are welded to a work. If one side of the electrode is welded (there are many cases like this), no current flows and no alarm for one side welding or a stop signal is issued, which results in a malfunction and is difficult to put into practical use.

Further, in many cases, a plurality of spot welding machines used in industrial robots or automatic machines are used at the same time, and in such a welding detection device, a signal applying means for applying a voltage signal to the spot welding gun side is used. Since it is effective in terms of cost, it is conceivable to use the former technique and make the power source common as shown in FIG. In this case, for example, assuming that the welding detection device 22 of the spot welding gun 21 and the welding detection device 24 of the spot welding gun 23 perform welding detection of the respective spot welding guns 21 and 23 using a common signal-giving power supply 25, First, each spot welding gun 2
Spot welding of each work is performed by pressing and holding each work 26, 27 with 1, 23 and energizing them. Then, for a required delay time from the end of the pressurizing and holding, the signal applying power supply 25 is applied to each transistor
A voltage signal is applied via 8, 29. The pulse detection device 30, 31 for detecting a pulse signal due to the difference between the voltage signal and the voltage signal generated on the side of the workpieces 26, 27 respectively.
To each spot welding gun 2 by the pulse signal.
Welding detection of 1,23 is performed.

However, it is generally said that the works 26 and 7 are electrically connected to each other with a considerably low resistance. Therefore, even if the welding phenomenon occurs between the workpiece 26 and the spot welding gun 21 and the welding phenomenon does not occur between the spot welding gun 23 and the workpiece 27,
An erroneous determination that a current flows from the work piece 26 to the work 27 and that the welding is detected by the welding detection device 22 and also that the welding is detected by the welding detection device 24 on the non-welding spot welding gun 23 side. There is an excessive risk that

The present invention has been made in view of such problems of the conventional technique, and the purpose thereof is to accurately distinguish between pseudo welding and true welding due to contact between a spot welding gun and a workpiece. Of course, it is possible to completely electrically insulate the IC circuit and external wiring,
A welding detection device for a spot welding machine that eliminates malfunctions due to external noise, and that can perform accurate detection without noise and malfunctions by using multiple common malfunctioning devices and using a common power supply, at low cost. It is the one we are trying to provide.

[Means for Solving the Problems] In order to achieve the above object, the welding detection device according to the present invention is a spot welding that performs spot welding of a work by pressurizing and holding each work in a plurality of spot welding guns and energizing them. In the machine, signal applying means for simultaneously applying voltage signals to the respective spot welding guns simultaneously from the same power source for a required delay time from the end of pressurization and holding of the respective spot welding guns, and the current flowing to the work side are independent of each other. And a means for detecting the current flowing to the work side by independently comparing it with a set value, and after a pulse signal is detected by each of the detecting means, a predetermined time or external Welding in a spot welding machine provided with a signal holding means for continuously generating an output signal until a return signal from It is a detection device.

[Operation] According to the above configuration, the spot welding machine performs spot welding of a work by holding the work under pressure to each of a plurality of spot welding guns and energizing the work. Voltage signals are simultaneously applied from the same power source to each spot welding gun side for various delay times, and the welding of the electrodes in each welding gun is detected by the current sensors that detect the current flowing to each workpiece side. The current detected by the current sensor is independently compared with the set value, and it is possible to accurately detect whether or not the spot welding gun and the workpiece are continuously in contact with each other by the pulse signals detected thereby. . Then, in one welding gun, a current flows through the work due to welding, and even if a current flows between the works of other welding guns, this current does not affect the current sensors of other welding guns at all. Welding of the electrodes in the individual spot welding guns can be accurately identified.

[Embodiment] FIG. 1 is an embodiment of a circuit diagram of a main part of a welding detection device in a spot welding machine according to the present invention, and FIG. 2 is a timing chart of the detection mechanism.

The welding detection device in this circuit diagram is arranged on the spot welding gun side after the holding end signal shown in FIG. 2 (d) is generated.
As shown in Figure (e), the voltage signal of waveform A that continues until after the judgment timing is given, while the current (f) or (g) or (h) flowing to the work side is detected by the current sensor, and the value is detected for welding. Whether or not the level is higher than or equal to each other is checked at each welding determination timing, and whether or not a current continuously flows in the work is detected and stored to determine the presence or absence of welding. Here, the waveform (f) shows that at the time when the applied pressure is 0, even if the voltage signal of the waveform A which continues until after the determination timing is given to the spot welding gun side as shown in FIG. It becomes zero, and the current is 1 during the judgment.
If it is detected that the flow has occurred once or multiple times,
In such a case, it is determined that the welding is a pseudo welding due to the contact between the spot welding gun and the work, and the welding signal is not emitted. The waveform (g) shows the case where the current flowing to the work side becomes zero at the time when the applied pressure is 0, and it is detected that no current flows even during the determination. In such a case, of course, the spot welding gun is used. Between the workpiece and the work, it is determined that there is no welding and no welding signal is emitted. The waveform (h) is continuous to the work side even during the determination after the pressing force is 0 when the voltage signal of the waveform A which continues until after the determination timing is given to the spot welding gun side as shown in FIG. 2 (e). Then, it is detected that a current flows, and in such a case, it is determined that welding is present between the spot welding gun and the work, and a welding signal is issued.

As shown in FIG. 1, a voltage signal is applied to the spot welding gun 1 from a DC power supply 3 via a transistor 2, while the base of the transistor 2 is
A start signal is applied through the fort coupler 4 which is operated by a welding detection start signal for applying a signal for applying a voltage signal to the spot welding gun side for a required delay time from the end of the pressure holding. A current sensor 5 is arranged between the transistor 2 and the spot welding gun 1, and the work 6 is connected to the power source 3. Therefore, when the voltage signal of the waveform A which continues until after the determination timing as shown in FIG. 2 (e) is given to the spot welding gun side after the generation of the holding end signal, an electrical signal is generated between the spot welding gun 1 and the work 6. If there is contact, the current sensor 5 detects the flow.

This detected current is used as a comparison circuit 7 (for example, operational amplifier).
At, the detected current is compared with a certain level or not, and the result is input to the microcomputer 8. The microcomputer 8 starts its operation in response to the welding detection start signal and operates for a required delay time from the end point of pressurizing and holding, and stores the input signal from the comparison circuit 7, As a result, when the waveform of FIG. 2 (h) is determined, a welding signal is issued to the welding signal generator 9 to suspend the operation of the industrial robot or the automatic machine to repair the spot welding gun and the work. Let it be done. In addition, the second waveform
When it is determined to be (f) or (g) in the figure, a completion signal is issued to the welding detection completion output device 10 to continue the operation of the industrial robot or the automatic machine.

Reference numeral 11 is a function selection switch, and each function in the microcomputer is appropriately selected and changed by appropriately selecting the switch.

The above is the basic technique of the welding detection device in the spot welding machine, and the present invention applies this technique to the welding detection device in a plurality of spot welding machines. FIG. 3 shows an embodiment of the invention when two spot welding machines are used at the same time. In this case, a voltage signal is applied to each spot welding gun side in the welding detection device because it is effective in terms of cost. The power supply for signal application is common. Since each welding detection device is substantially the same as that described in FIG. 1 except for the power supply unit, one welding detection device is given the same reference numeral as that shown as a main part in FIG. However, the other welding detection device is attached with a dash and its description is omitted.

In the figure, the welding detection device 12 for the spot welding gun 1 and the welding detection device 12 'for the spot welding gun 1'use their common signal-applying power source 3 respectively.
Welding detection is performed. Therefore, first, spot welding of each work is performed by pressing and holding each work 6, 6'by each spot welding gun 1, 1'and energizing them. Then, a voltage signal is applied to each spot welding gun 1, 1'side from the signal applying power source 3 through each transistor 2, 2'for a required delay time from the end of the pressurizing and holding. Therefore, after the holding end signal is generated, the second
When the voltage signal of the waveform A which continues until after the determination timing is given as shown in FIG. 8E, the current sensor 5 detects the flow if there is electrical contact between the spot welding gun 1 and the work 6. . Since the work 6 and the work 6'are generally electrically connected to each other with a considerably low resistance as described above, a current flows from the work 6'to the power source 3. However, if there is no electrical contact between the spot welding gun 1'and the workpiece 6 ', the current sensor 5'will not detect the current flow.

Therefore, as described with reference to FIGS. 1 and 2, in the welding detection device 12 to which the spot welding gun 1 belongs, a welding signal is issued to the welding signal generator 9 to suspend the operation of the industrial robot or the automatic machine. The spot welding gun 1 and the work 6 are repaired, and the welding detection device 12 'to which the spot welding gun 1'belongs issues a completion signal to the welding detection completion output device 10' to operate an industrial robot or an automatic machine. To continue.

As described above, when the works 6 and 6'are electrically connected, the welding detection devices 12, 12 'can accurately instruct the welding without any malfunction.

[Advantage of the Invention] The welding detection device in the spot welding machine according to the present invention uses a current flowing from the welding cancer side to the work side as the welding detection means, detects this with a current sensor, and detects the pulse signal resulting from this current. Since the welding of the electrodes is determined, it is of course possible to accurately distinguish the pseudo welding and the true welding due to the contact between the spot welding gun and the work, and the IC circuit and the external wiring. Since it is possible to electrically insulate completely, an accurate welding detection device that eliminates malfunctions due to external noise can be obtained.Moreover, workpieces are spot-welded by pressing and holding each workpiece with multiple spot welding guns and energizing them. In a spot welding machine that performs the operation, a common power source can be used to perform accurate detection without noise and malfunction while being inexpensive. It is those that can.

[Brief description of drawings]

FIG. 1 is a circuit diagram for explaining an essential part of a welding detection device in a spot welding machine according to the present invention, FIG. 2 is a timing chart diagram of the detection mechanism, and FIG. 3 is a circuit diagram of the welding detection device according to the present invention. FIG. 4 shows a circuit diagram of a welding detection device predicted from a conventional example. 1,1 ′ …… Spot welding gun, 2,2 ′ …… Transistor, 3 …… Signal power supply, 4,4 ′ …… Fort coupler, 5,5 ′ …… Current sensor, 6,6 ′ …… Workpiece , 7,7 '... Comparison circuit, 8,8' ... Microcomputer, 9,9 '... Welding signal generator, 10,10' ... Welding detection completion output device.

Claims (1)

[Scope of utility model registration request] 1. A spot welding machine for spot welding a work by holding the work under pressure to a plurality of spot welding guns and energizing the work, and a delay time required from the end of the pressure holding of each spot welding gun. Between the spot welding gun side, a signal applying means for simultaneously applying a voltage signal from the same power source, a means for detecting the current flowing through the work side by an independent current sensor respectively, and a current flowing through the work side with a set value. And a signal holding means for continuously generating an output signal after a pulse signal is detected by each of the detecting means and for a predetermined time or until a return signal from the outside is given. A welding detection device in a spot welding machine.