JP2940848B2 - Electrode tip detachment detection device for welding gun - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the detection of a detachment of a welding electrode tip of a welding gun for spot welding two members in a vehicle body assembly line of an automobile or the like, and reports the detachment. The present invention relates to an electrode tip detachment detecting device for a welding gun for stopping a welding operation of a welding gun.

[0002]

2. Description of the Related Art Conventionally, in performing spot welding, when an electrode tip is welded to a member to be welded and the electrode tip is detached from a mounting portion of a welding gun, poor contact between the electrode and a member to be welded or an electrode tip is formed. Welding failure due to lack of
There was a problem with the quality of the product.

In particular, in a vehicle body welding process or the like formed as a line, when an electrode tip of a welding gun used is welded to a member to be welded, the electrode tip moves to the next step with the electrode tip remaining on the welding member. An obstacle such as interference with a welding member to be welded in the next step occurs, causing problems such as damage to the member and damage to the welding machine.

In order to solve this problem, Japanese Utility Model Application Laid-Open No. 62-158 discloses a means for detecting detachment of an electrode tip.
An electrode tip detachment detecting device of a spot welding machine described in Japanese Patent Publication No. 74, and an electrode tip detachment detecting device of a welding gun described in Japanese Utility Model Laid-Open Publication No. 62-105771 are known.

[0005] In the former, when an electrode falls off, an energization failure is generated by interposing an insulating gap between the members to be welded at the opposing portion of the gun arm and the electrode holder, and this is detected by an energization failure detection device. Is what you do.

The latter is a switching means for switching in response to the detachment movement of the electrode tip formed over the gun body and the electrode tip, and detects the detachment of the electrode tip.

[0007]

In such a device for detecting the detachment of an electrode tip of a welding gun, the electrode tip does not come off completely, and the electrode tip remains in an incompletely attached state in which it comes off to the attachment portion. In such a case, it becomes difficult to reliably detect the occurrence of the energization failure and to switch the switching means.

For this reason, the reliability of the operation as a detecting device is insufficient, and the reliability of the electrode tip detachment detecting device in a welding gun as a line is lacking. May come.

In addition, there is a risk that the quality assurance of the product, especially the reliability, may be serious, and the structure of the apparatus is complicated, and the equipment cost is high.

The present invention solves the above-mentioned problems in the conventional welding gun electrode tip detachment detection device, and reliably and promptly detects detachment of the welding gun electrode tip.
The purpose is to ensure the reliability and reliability of product quality in the next process with welding guns at low cost.

[0011]

According to the present invention, there is provided an electrode tip detachment detecting device for a welding gun for achieving the above-mentioned object, wherein an electrode tip provided at a tip end of a gun body of the welding gun is detachable. Mounting portions that can be fitted to the mounting portion, an air passage communicating with the mounting portion, and a communication pipe that connects the two air passages; and compressed air that fills the air passage with a constant pressure and compressed air whose supply flow rate is restricted. Filling means and the compressed air filling
Means for supplying said compressed air to said means and said gun body
The electrode tips of the mounting portions provided in
Supply the compressed air to the air cylinder to be touched and pressed
A compressed air tank; reduced pressure detecting means for detecting reduced pressure of compressed air in the air passage when the electrode tip is detached; and control means for receiving a reduced pressure detection signal from the reduced pressure detecting means. And

[0012]

According to the electrode tip detachment detecting device of the welding gun of the present invention, since the mounting portion of each electrode tip is communicated with the air passage, when the electrode tip is detached, the pressure drop is of course caused.
Even at the time of decompression due to a small amount of air leaking in the state of being separated, the supply flow rate of the compressed air is limited, so that the supply of the compressed air is delayed and the decompression is promoted.

For this reason, the pressure reduction detecting means can be operated as the pressure reduction directly in a time close to the time of the rapid pressure reduction, and the detachment of the electrode tip can be detected promptly and reliably.

[0014]

Next, an embodiment of the present invention will be described below with reference to the drawings. The welding gun in this embodiment is shown in FIG.
As shown in FIG. 2, two arms 3 each provided with a mounting portion 2 to which the electrode tip 1 can be mounted at the tip are pivotally mounted on a support shaft 4 near the center so as to be rotatable up and down.

An air cylinder 5 is attached to the base end of the arm 3 to press the base end to contact and press the electrode tip 1 mounted on the mounting portion 2 at each end. 2 and 3, the two welded members 6 located between the electrode tips 1 shown in FIGS. 2 and 3 are sandwiched, and a current flows between the electrode tips 1 to generate heat due to the electric resistance of the welded members 6. And spot welding of the member 6 to be welded.

Each of the arms 3 has an air passage 8 for compressed air which communicates with the mounting portion 2 of the electrode chip 1 from the connection ports 7a and 7b provided respectively. A manual opening / closing valve 10 for supplying and shutting off the compressed air from the compressed air tank 9 is connected to the connection port 7a of the one arm 3, and the pressure of the compressed air is kept constant (for example, a set pressure of 2 kg / cm ² ). The compressed air tank 9 is connected via a pressure adjusting valve 11, a flow control valve 12 for limiting the flow rate of the compressed air to a constant value, and an electromagnetic valve 13 which shuts off when the electrode tip 1 is detached.

The pressure of the compressed air is maintained at a constant pressure (for example, a set pressure of 1 kg / cm) at the connection port 7b of the other arm 3.
² ) A pressure switch 14 that is turned on when the pressure becomes below is connected, and a control circuit 16 is connected to the pressure switch 14. The control circuit 16 controls the pressure switch 14
When ON or OFF is detected, it is output to the electromagnetic valve 13, a release indicator lamp described later, or the like.

Further, a communication pipe 15 for communicating between the air passages 8 is provided between the arms 3 in order to communicate compressed air between the arms 3. Therefore, in this embodiment, the opening and closing valve 10 is opened before the use of the welding gun, and the compressed air in the compressed air tank 9 is supplied to the pressure adjusting valve 11.
To a constant pressure, and restrict the flow rate to a constant flow rate with a flow control valve 12 and introduce it into the air passage 8.
5. Keep the pressure switch 14 and the pressure constant.

When this operation is started according to the flowchart shown in FIG. 5, in step S1, the air supply pressure is set to a predetermined supply pressure in the air passage 8 by manually opening the on-off valve 10.

After the preparation work for spot welding is performed, the welding work is started as step S2. During the progress of the welding work, the supply pressure to the pressure switch 14 is increased to a predetermined value or more in step S3. It is continued to confirm that there is a certain value. If NO is maintained at a certain value or more, the process returns to step S2.
This is continued until it becomes FF.

That is, as shown in FIG. 4, when a part of the electrode tip 1 is welded to the member 6 during spot welding of the member 6 to be welded, the entire electrode tip 1 or a part of the electrode tip 1 is mounted. 2 and the compressed air escapes from the air passage 8.

In this case, not only when the electrode tip 1 is completely removed from the mounting section 2 but also when the electrode tip 1 is not completely removed, compressed air leaks. The air pressure in the air passage 8 is reduced.

As described above, when the pressure switch 14 is turned off in step S3 due to a decrease in air pressure as described above, the control circuit 16 which has detected this OFF in step S4.
Indicates that the release indicator light is on in step S5, the welding control power supply is off in step S6, and the electromagnetic valve 13 in step S8.
Is output, and the welding operation for the member 6 to be welded is stopped, and the state of the operation is displayed by turning on an indicator lamp.

Thus, when the detachment of the electrode tip 1 is known, the recovery is performed in step S8, and upon completion of the recovery, the control circuit 16 outputs the signal to the electromagnetic valve 13 in step S9 to make it conductive so that the air passage 8 is closed. The operation of increasing the pressure and returning to step S8 is repeated until the pressure switch 14 is turned on.

When the restoring operation is completed, the pressure in the air passage 8 increases as described above, and when the pressure switch 14 is turned on, the process returns to step S2 to repeat the above operation.

FIG. 6 shows a change in the compressed air pressure in the air passage 8 due to the detachment of the electrode tip 1 and the restoration thereof. In this figure, the compressed air pressure set by the pressure adjusting valve 11 is 2 kg / cm ² , This is the case where the reduced pressure at which the switch 14 is turned off is 1 kg / cm ² .

In this embodiment, as described above, not only the complete detachment of the electrode tip 1 but also the detachment to the extent that the compressed air leaks is detected and notified to the operator, or spot welding is performed. The process can be automatically stopped to prevent a decrease in product quality and reliability due to poor welding and to prevent problems in the line.

[0028]

As described above, the present invention reliably and quickly detects not only the complete detachment of the electrode tip of the welding gun but also the relatively incomplete detachment of compressed air. can do.

Therefore, not only problems such as deterioration of the quality of the product due to poor welding and lack of reliability can be prevented, but also if a line is provided with a welding gun, the following steps can be performed. The welding gun can be prevented from being damaged or damaged, and can be carried out at low equipment cost.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment including a circuit of the present invention.

FIG. 2 is a side view showing a welding state of the welding gun embodying the present invention.

FIG. 3 is a sectional view of the same.

FIG. 4 is a side view of the electrode tip in a detached state according to the first embodiment.

FIG. 5 is a flowchart of FIG.

FIG. 6 is a diagram showing a change in pressure of an air passage of compressed air when the electrode tip of the embodiment is detached.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrode chip 2 Mounting part 8 Air passage 11 Pressure adjustment valve 12 Flow control valve 14 Pressure switch 15 Communication pipe 16 Control circuit

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-57-62878 (JP, A) JP-A 58-143076 (JP, U) JP-A 62-15874 (JP, U) JP-A 62-874 105771 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) B23K 11/00-11/36 330

Claims (1)

(57) [Claims] 1. A mounting portion provided at a tip end portion of a gun body of a welding gun and capable of detachably mounting an electrode tip, an air passage communicating with the mounting portion, and a communication pipe communicating both air passages. at a constant pressure in the air passage, the compressed air filling means for filling the compressed air supply flow rate is limited, the compression
Supplying the compressed air to the air filling means;
The electrode tips of the mounting portions provided on the gun body are
The compressed air is applied to air cylinders that contact and press each other.
A compressed air tank to be supplied; a reduced pressure detecting unit configured to detect a reduced pressure of the compressed air in the air passage when the electrode chip is detached; and a control unit configured to receive a reduced pressure detection signal from the reduced pressure detecting unit. An electrode tip detachment detection device for a welding gun.