JPH05151B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a monitoring device for a resistance welding gun, and more particularly, a monitoring device for a resistance welding gun for detecting an abnormality in the welding process by the resistance welding gun or an abnormality in the welding device itself. Regarding.

Generally, in resistance welding, two metal plates (workpieces) in a superposed state are sandwiched between two electrodes made of copper alloy or the like, and a large current is passed between the electrodes while applying pressure. At this time, Joule heat is generated under the action of a large current flowing through the workpiece, locally melting the contact portion of the workpiece, and in conjunction with the pressurizing force, the workpiece is welded. This is the principle of resistance welding.

Therefore, in order to prevent an abnormal temperature rise in the electrode part of a welding gun, a cooling medium flow path is provided inside the electrode, and cooling water is passed through this to minimize the temperature rise in the electrode. It is configured to keep it at a minimum. However, due to wear and the like at the tip of the electrode, the contact between the electrode and the workpiece may become insufficient, and the electrical resistance of the contact portion may increase beyond a predetermined value. In such a case, the electrode and the workpiece will be welded together due to the Joule heat generated at the contact portion.

Therefore, conventionally, the presence or absence of the above-mentioned electrode welding accident has been detected by checking the opening operation of the welding gun. That is, a limit switch that operates in response to the opening operation of the welding gun is installed on the arm of the welding gun to detect the open state of the welding gun with respect to the workpiece, and if the electrode and the workpiece are welded, the welding gun is turned off after applying the welding current. This state was detected by the limit switch as it could not be opened even if an attempt was made to open it, and as a result, it was revealed that the electrode had been welded.

However, in such a configuration, if a cap-shaped electrode is attached to the welding gun, the electrode welded to the workpiece will come off from the welding gun, and on the other hand, the limit switch will be removed due to the opening movement of the welding gun's arm. The open state of the welding gun is mistakenly detected. In other words, even when the limit switch was detected, there was a possibility that the electrode and the workpiece were still welded together. If this is not detected even though the electrode has been pulled out, a large amount of cooling water will be released from the part where the electrode has been pulled out, causing damage to the welding gun if welding continues.

Therefore, if the electrode is removed, the cooling water will be discharged from the tip of the welding gun as described above, and the cooling water will not flow into the cooling water delivery passage after passing through the electrode. Therefore, a method is also used in which a cooling water flow detection means is provided in the delivery passage to determine whether or not the cooling water is flowing, thereby detecting removal of the electrode. That is, as described above, the opening of the welding gun and the flow of cooling water are detected to confirm whether or not welding has been performed normally.

By the way, in order to perform normal welding, as described above, it is necessary to apply welding current while pressurizing the workpiece at a predetermined pressure with a welding gun while cooling water is flowing. However, in the past, only the opening operation of the welding gun and the removal of the electrode were detected, but if the welding gun was not applying a predetermined pressure to the workpiece, or the welding current was insufficient due to a malfunction in the electric circuit. If electricity was not applied, it was impossible to detect the abnormality.

The present invention has been made in order to overcome the above-mentioned disadvantages.The present invention has been made in order to overcome the above-mentioned disadvantages. A signal, a gun pressure signal, and a welding current signal are obtained, and these signals are introduced into a discrimination circuit, and if the flow of cooling water, pressure by the welding gun, and welding current are carried out normally, a predetermined value is determined. Welding process configured to output a signal,
An object of the present invention is to provide a resistance welding gun monitoring device that detects the presence or absence of an abnormality in the welding device itself.

In order to achieve the above object, the present invention provides a cooling water passage for cooling an electrode, a pressure fluid passage supplied for displacing the electrode to pressurize or release a workpiece, and a welding to the electrode. In a resistance welding gun monitoring device having an electric circuit for supplying a current, a cooling water flow detection means for outputting a cooling water signal corresponding to the cooling water flow state is connected to the cooling water passage, and an electrode is connected to the cooling water passage. A pressure detection means for outputting a gun pressure signal corresponding to the pressurization state of the workpiece is connected to the pressure fluid passage, and a current conduction sensor for outputting a welding current signal corresponding to the energization state of the welding current is connected to the pressure fluid passage. The present invention is characterized in that it includes a determination circuit that is provided in the electric circuit and receives output signals from the cooling water flow detection means, pressure detection means, and energization sensor to determine whether or not the welding state is normal.

Next, preferred embodiments of the resistance welding gun monitoring device according to the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, reference numeral 10 indicates a welding gun. Gun arm 1 constituting the welding gun 10
The vicinity of one end of the gun arms 12, 14 is bent, while brackets 20, 22 are integrally formed at the other end of the gun arms 12, 14. The gun arms 12 and 14 are supported in a hollow manner by a support member 24 fixed to a holding device (not shown), and are configured to open and close via a support shaft 26.
A cylinder 28 is attached to one end of the bracket 20. A piston 30 is installed inside this cylinder 28, and rods 32a, 3 are attached to the piston 30.
2b are secured, while their other ends are connected to the bracket 22.

Further, passages communicating with both chambers in the cylinder 28 partitioned by the piston 30 are bored, respectively, and pipe joints 34 and 36 for connecting passages to be described later are provided to these passages. That is, by alternately supplying fluid to both chambers partitioned by the piston 30, the piston 30 reciprocates, thereby causing the gun arms 12 and 14 to move toward the support shaft 2.
Opening/closing operations are performed via 6.

The gun arm 12 is provided with cooling water passages 42 and 44 that reach its tip.
4 are provided with passages 46 and 48 leading to their distal ends. At that time, a pipe joint 50 for connecting a passage to be described later to one end of each passage 42, 44, 46, 48
A to 50d are arranged in advance.

Tube bodies 54a, 54b as shown in FIG. 2 are connected to the distal ends of the gun arms 12, 14, and cap-shaped electrodes 56a, 56b are attached to the gun arms 12, 14 so as to fit over the tube bodies 54a, 54b. Fits onto the tip of the In this case, a part of the tube 54a is loosely fitted into the electrode 56a as shown, and a cooling water flow path 53a is formed between the outer peripheral surface of the tube 54a and the inner peripheral surface of the electrode 56a. is formed. Similarly, the outer peripheral surface of the tube body 54b and the electrode 5
A flow path 53b is also formed between the inner circumferential surface portion of 6b. In the gun arm 12, a passage 42
The tube body 54a is connected to the end of the tube 54a, and the passage 44 is connected to the flow path 53a. Similarly, in the gun arm 14, a tube body 54b is connected to the end of the passage 46, and the passage 48 is communicated with the flow passage 53b.

Next, the flow path of the cooling water supplied to the welding gun 10 will be explained.

First, connect the passage 58 to the pipe joint 50b,
A flow switch 60 for detecting whether a predetermined amount of cooling water is flowing is provided at one end of the passage 58. That is, the flow switch 60
is a cooling water flow detection means. Therefore, as long as the device is capable of reliably detecting the flow of cooling water, it is possible to configure the cooling water flow detection means by using not only the flow switch 60 but also a pressure switch, for example. The flow switch 60 is configured to obtain an output signal having a high potential if a predetermined amount of cooling water is flowing through the passage 58, and a low potential if not. In this embodiment, the output signal will hereinafter be referred to as a cooling water signal.

Further, a passage 62 is connected to the flow switch 60, and a check valve 64 is connected to one end of the passage 62.
to be placed. Next, the passage 66 is connected to the check valve 64.
The tank 68 is connected to the tank 68 through a passage 70, and one end of this passage 70 enters a tank 72.

Further, a passage 74 extending from the pipe joint 50a to the pipe joint 50d is provided to bring the passage 42 and the passage 48 into communication. A passage 76 is connected to the pipe joint 50c,
A switching valve 78 for opening and closing the flow path is connected to one end of this passage 76. Next, a switch 82 is connected to the switching valve 78 via a passage 80. Further, a passage 84 is connected to the pot 82, and one end of this passage 84 is introduced into a pressure source 86 which is a supply source of cooling water.

The cooling water flow path connected to the welding gun 10 is configured as described above. Next, the fluid path for opening and closing the gun arms 12 and 14 will be explained.

First, a passage 88 is connected to the pipe joint 34, and one end of this passage 88 is connected to a switching valve 90. The passage 88 is provided with a pilot line 92 that branches off from the middle, and this pilot line 92 is connected to a pressure switch 94. In this case, the fluid supplied through the passage 88 moves the piston 30 in the direction of arrow A in FIG. Different. In such a contact state, since the piston 30 is stopped at a predetermined position, the fluid pressure in the passage 88 increases and the workpiece W is pressurized at a predetermined pressure. Passage 88 at this time
The pressure switch 94 is actuated in accordance with the fluid pressure of the gun to obtain a gun pressurizing signal which has a high potential when the workpiece W is pressurized at a predetermined pressure and has a low potential when the workpiece W is not pressurized. Configure.

The switching valve 90 has a passage 8 at the switch position shown in the figure.
A passage 96 is connected to communicate with 8. A passage 100 is connected to the passage 96 via a plug 98, and one end of this passage 100 is connected to a pressure source 102. On the other hand, a passage 104 is connected to the pipe joint 36, and one end of this passage 104 is connected to the switching valve 90. Furthermore, a silencer 108 is connected to the switching valve 90 via a passage 106.

The fluid passage for opening and closing the gun arms 12, 14 is configured as described above, and then the third
In the figure, the electrode 56 is in pressure contact with the workpiece W.
A and 56b schematically show an electric circuit for applying welding current.

In this case, a transformer 112 is connected to the primary power source 110 to obtain a low voltage and large current on the secondary side. An electrode 56a is connected to one output terminal of the transformer 112 via a switch 114 and an energization sensor 116, and an electrode 56a is connected to the other output terminal of the transformer 112.
b is connected. The energization sensor 116 is a means for detecting welding current. And energization sensor 1
16 is configured to generate a high potential output when the current is flowing, and generate a low potential output when the welding current does not flow or the welding current does not reach a predetermined value. In this embodiment, the high potential or low potential output generated in accordance with the welding current is referred to as a welding current signal and will be used in the following explanation.

As described above, the system is configured to obtain a cooling water signal, a gun pressure signal, and a welding current signal and introduce these signals to a discrimination circuit.The discrimination circuit will be explained next.

In Figure 4, the cooling water signal is AND gate 1
18. The gun pressure signal is introduced into the other input terminal of the AND gate 118, as well as the synchronous input terminal of the flip-flop 120 and the input terminal of the monostable multivibrator 122. In addition, flip-flop 1
20 is of a negative edge trigger type. The output side of the AND gate 118 is a flip-flop 124.
is connected to the D input terminal of The welding current signal is also introduced into the synchronous input terminal of the flip-flop 124. The Q output terminal of flip-flop 124 is connected to one input terminal of AND gate 126, and the Q output terminal of flip-flop 120 is connected to the other input terminal of AND gate 126.
The Q output terminal of monostable multivibrator 122 is connected to the clear input terminal of flip-flop 120 and the clear input terminal of flip-flop 124.

In this way, the discrimination circuit is constructed, and the display lamp 128 is connected to the output side of the AND gate 126 included in the discrimination circuit. This indicator lamp 1
28 is a display means for making it possible to identify the binary output of the AND gate 126. In this case, the indicator lamp 128 lights up when the output of the AND gate 126 is at a high potential, and goes out when the output is at a low potential. Note that a display element such as an LED can be used as the display means, and it is also possible to amplify the output of the AND gate 126 and make the light bulb blink.

The resistance welding gun monitoring device according to the present invention is basically constructed as described above.Next, the operation and effects of the device will be explained using the time chart shown in FIG.

At the time t ₁ to _{t 2} shown in FIG. 5, the welding gun 1
The welding process using 0 is normal, and this case will be explained. First, cooling water supplied from the pressure source 86 is supplied to the inside of the electrode 56b through the passage 84, the tank 82, the passage 80, the switching valve 78, the passages 76, 46, and the pipe body 54b. And the electrode 56
The cooling water supplied to the tube 54b passes through the flow path 53b between the outer peripheral surface of the tube 54b and the inner peripheral surface of the electrode 56b, and further flows through the passages 48, 74, 42 and the tube 54a to cool the electrode 56a. Supplied inside. In this way, the cooling water supplied to the electrode 56a flows through the channel 53a, and then passes through the channels 44, 58, the flow switch 60, the channel 62, the check valve 64,
It communicates with a passage 66, a pot 68, and a passage 70, and reaches a tank 72. If the cooling water flows in this way and the amount exceeds the predetermined value, the flow switch 6
The cooling water signal obtained by zero is at a high potential.
Therefore, a high potential signal is introduced into one input terminal of AND gate 118.

Next, fluid supplied from the pressure source 102 is introduced into one chamber in the cylinder 28 by flowing through the passage 100, the cock 98, the passage 96, the switching valve 90, and the passage 88, and the piston 30 is moved in the direction of arrow A. Moving.
As a result, the gun arms 12 and 14 close, the electrodes 56a and 56b press the workpiece W, and the piston 30 stops at a predetermined position. At this time, when the fluid pressure in the passage 88 reaches a predetermined pressure, the pressure switch 9
4 is activated, and the gun pressure signal rises from a low potential to a high potential. Therefore, a high potential signal is introduced into the other input terminal of the AND gate 118, and the rising signal introduced into the input terminal of the monostable multivibrator 122 causes a signal to be input from the Q output terminal of the monostable multivibrator 122. A pulse having a predetermined time width is output. This pulse is applied to the clear input terminals of flip-flops 120 and 124, and
The initial state of the Q output of No. 24 is set to a low potential. Also,
As described above, since the high potential signals of the cooling water signal and the gun pressure signal are input to the AND gate 118, a high potential is generated on the output side of the AND gate 118, and this high potential signal is applied to the flip-flop 1.
24 D input terminals.

In this way, the workpiece W is
is pressurized, and then switch 114 is closed to apply welding current. At this time, the energization sensor 116 detects the energization of the welding current, and the welding current signal becomes a high potential. Therefore, the rising edge signal of the welding current signal is input to the synchronous input terminal of the flip-flop 124 to which the high potential signal is supplied, and the Q output of the flip-flop 124 becomes a high potential, and this high potential signal is applied to one side of the AND gate 126. Supplied to the input terminal.

After the supply of welding current is completed, the flow path direction of the switching valve 90 is switched from the pressure source 102 to the passage 10.
0, the fluid supplied to the switching valve 90 via the cock 98 and the passage 96 is forced into the cylinder 28 from the passage 104, and the piston 30 is moved in the direction of arrow B to open the gun arms 12, 14. At that time, aisle 8
8 communicates with the passage 106 to which the silencer 108 is connected, and the fluid pressure in the passage 88 decreases.
The gun pressure signal obtained by pressure switch 94 rises from high potential to low potential. That is, a falling signal supplied to the synchronous input terminal of flip-flop 120 causes flip-flop 12 to
The Q output of 0 becomes a high potential. Therefore, AND gate 126 includes flip-flops 120 and 12.
A high potential signal is input from 4, and AND gate 126 generates a high potential signal. The indicator lamp 128 is then turned on by the high potential signal supplied from the AND gate 126, thereby indicating that welding has been performed normally.

Next, a case will be described in which the welding current is not normally applied as shown at time _t2 to _t3 in FIG.

In this case, the cooling water is flowing normally, and a high potential signal is supplied to one input terminal of the AND gate 118. Then, by pressurizing the work in the same manner as described above, the gun pressure signal becomes high potential, and this signal is supplied to the other input terminal of AND gate 118, and AND gate 118 outputs a high potential signal. On the other hand, since the gun pressure signal is also introduced into the monostable multivibrator 122,
As the gun pressure signal rises, the monostable multivibrator 122 derives a pulse from the Q output terminal. The pulse causes flip-flop 1
The outputs of 20 and 124 are cleared, thus
The output of the AND gate 126 becomes a low potential and the indicator lamp 128 is turned off.

Next, if you try to apply welding current, but the specified welding current does not apply due to some kind of failure,
The welding current signal obtained via the energization sensor 116 does not rise and has a low potential. Therefore, no rising signal is supplied to the synchronous input terminal of flip-flop 124, and the Q output of flip-flop 124 maintains a low potential. Therefore, since a low potential signal is input to one input terminal of the AND gate 126, the AND gate 126 derives a low potential signal regardless of the output of the flip-flop 120 connected to the other input terminal of the AND gate 126. . Therefore, the indicator lamp 128 does not light up, thereby making it possible to detect that there is an abnormality in the welding process.

Further, the time t ₃ to _{t 4} shown in FIG. 5 shows a case where the cooling water does not flow normally, and this will be explained next.

When the electrodes 56a and 56b are welded to the workpiece W and at least one of them separates from the gun arm 12 or 14, cooling water is discharged from the tip of the corresponding gun arm, and the flow switch is activated so that the cooling water does not flow into the passage 58. The cooling water signal obtained by 60 will be at a low potential. That is, a low potential signal is supplied to one input terminal of the AND gate 118, and the AND gate 118 is supplied with a low potential signal regardless of the gun pressure signal.
The output of is a low potential. Therefore, the output of the flip-flop 124 to which the low potential signal is supplied maintains a low potential, and the output of the AND gate 126 also becomes a low potential. Therefore, the indicator lamp 128 does not light up, indicating that welding has not been performed normally.

Furthermore, during times _t4 to _t5 in FIG. 5, each signal is shown when the cooling water is not flowing and the welding current is not flowing. In this case as well, the Q output of the flip-flop 124 is at a low potential, and therefore the indicator lamp 128 does not light up, as described above.

By the way, welding is normally performed from time _t6 to time _t7 in FIG. 5, and the work W is not pressurized in the welding process after time _t7 . Therefore, this case will be explained next.

When pressurizing the workpiece W, the piston 30 is pressed by the fluid supplied from the pressure source 102 and moves in the direction of arrow A in FIG.
a, 56b come into contact with the workpiece W and pressurize it,
The gun pressure signal changes as shown by phantom line 130 in FIG. However, if the fluid pressure of the pressure source 102 decreases due to some kind of failure, the electrode 5
Since 6a and 56b do not contact the workpiece W, the workpiece W cannot be pressurized. In this case, passage 8
Since the fluid pressure at 8 does not reach the predetermined pressure, the gun pressurization signal obtained by pressure switch 94 remains at a low potential. On the other hand, the indicator lamp 128 that is lit during the welding process from time t ₆ to _{t 7} is normally
It is configured to turn off in accordance with the pulse output from the monostable multivibrator 122,
The pulse is output at the rising edge of the gun pressure signal. However, the gun pressure signal maintains a low potential as described above and does not rise, and since no pulse is output from the monostable multivibrator 122, the indicator lamp 128 does not go out. That is, when the workpiece W is not pressurized, the indicator lamp 1
28 does not go out, and this allows the operator to
It is possible to know abnormalities in the pressurized state.

As explained above, according to the resistance welding gun monitoring device of the present invention, if all of the cooling water flow, pressurization by the welding gun, and welding current flow are normal during the welding process, After the welding process is completed, the indicator lamp lights up, and if there is an abnormality in at least one of the flow of cooling water and the flow of welding current, the indicator lamp will not light up. Furthermore, if no pressure is applied by the welding gun, the indicator lamp, which has been lit due to the previous normal welding process, will not go out. Therefore, by visually checking the indicator lamp that flashes at predetermined time intervals, it is possible to easily detect whether or not there is an abnormality in the welding process. Therefore, when an abnormality is detected, it is possible to take appropriate measures such as immediately stopping welding work and the supply of cooling water to minimize the splashing of cooling water due to electrode separation. .

Furthermore, failures in the equipment that supplies the fluid that opens and closes the welding gun, or failures in the electric circuit that supplies the welding current, can be detected at an early stage.As a result, production efficiency is increased and safety is fully ensured. The effect is that it can be secured.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to this embodiment. For example, a signal tone generator may be used in place of a display lamp as a display means. Of course, various improvements and changes in design are possible without departing from the gist of the present invention.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a monitoring device for a resistance welding gun according to the present invention, FIG. 2 is an enlarged vertical sectional view of the electrode portion of the welding gun shown in FIG. 1, and FIG.
4 is a schematic explanatory diagram of an electric circuit for applying current to the electrode shown in the figure; FIG.
The figure is a time chart for explaining the monitoring device for a resistance welding gun according to the present invention. 10... Welding gun, 12, 14... Gun arm, 2
8...Cylinder, 30...Piston, 54a, 54b
...Pipe body, 56a, 56b...Electrode, 60...Flow switch, 64...Check valve, 78...Switching valve, 86
...Pressure source, 90...Switching valve, 102...Pressure source, 10
8... Silencer, 112... Transformer, 116... Energization sensor, 118... AND gate, 120... Flip-flop, 122... Monostable multivibrator, 124... Flip-flop, 126... AND gate, 128... Display lamp, W... Work.

Claims (1)

[Claims] 1. A cooling water passage for cooling the electrode, a pressure fluid passage supplied to displace the electrode to pressurize or release the workpiece, and a welding current supplied to the electrode. In a resistance welding gun monitoring device having an electric circuit, a cooling water flow detection means that outputs a cooling water signal corresponding to the cooling water flow state is connected to the cooling water passage, and the electrode is pressurized against the workpiece. A pressure detection means that outputs a gun pressure signal corresponding to the state is connected to the pressure fluid passage, and further, an energization sensor that outputs a welding current signal corresponding to the energization state of the welding current is provided in the electric circuit. , a monitoring device for a resistance welding gun, further comprising a determination circuit that receives output signals from the cooling water flow detection means, pressure detection means, and energization sensor to determine whether the welding state is normal or not. . 2. In the device according to claim 1,
A resistance welding gun monitoring device comprising a display means connected to the output side of a discrimination circuit. 3. In the device according to claim 1,
The discrimination circuit includes a monostable multivibrator to which a gun pressure signal is input, and the discrimination circuit is initialized according to the output pulse of the monostable multivibrator.