JPH0763857B2 - Control method for welding robot - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a welding robot having a spot welding gun capable of switching the opening between a pair of gun arms when the gun is opened.

2. Description of the Related Art A spot welding gun having a gun arm opening switching means is disclosed in, for example, Japanese Patent Laid-Open No. 59-1072.
In this kind of spot welding gun, for example, as shown in FIG.
When the P _1, P _2, P ₃ and the welding spot performs under a narrow gun arm opening if the strike position P ₁ is moved gun (electrode chip 6, 7) to P _2, on the other hand, RBI After welding at the position P ₂ , when moving the gun from the hitting position P ₂ to P ₃ , the gun is moved under a wide gun arm opening so as to avoid the overhang B. Therefore, the time required to move the gun can be shortened compared to the case where the gun arm opening is constant.
Further, since the protruding portion B and the like can be avoided simply by switching the opening degree, it is not necessary to make the robot itself having the gun move excessively.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the conventional spot welding gun, the opening position of the gun arm, that is, the operating state of the opening switching means is compared with the predetermined gun arm opening command on the teaching data side. I didn't do it.

In other words, the limit switch detects whether the gun arm opening is set to the wide side or the narrow side.The detection signal is the timing of pressurization and energization corresponding to the working stroke of the gun. However, it does not detect whether or not the gun is operating according to the teaching data, and the gun continues to operate even if it is not operating according to the teaching data. For example, when moving from the hitting point position P ₂ to P _{3 in} FIG. 6, if the gun arm opening may not switch to a wider one, the gun and the overhanging portion B may interfere with each other. The gun and the work W will be damaged.

Means for Solving Problems The present invention has been made in view of the above points, and detects the operating state of the gun arm opening switching means at the end of the gun pressurizing operation at a predetermined hitting position. , Comparing this operating state with the gun arm opening command at the time of gun release after gun pressurization operation at the corresponding hitting position in the teaching data,
When they do not match, the welding robot is stopped.

Embodiment FIG. 2 shows an example of a spot welding gun having a gun arm opening switching means. The spot welding gun 1 is attached to the tip of the robot arm 2 of the welding robot.
Based on the position information (teaching data) that has been taught in advance, the positioning is sequentially moved to a predetermined dot position,
The work W is automatically welded by repeating pressurization, energization and release.

The pair of gun arms 3 and 4 is rotatably supported by a pin 5 at the tip of the robot arm 2 so that each gun arm 3 and 4 can be rotated.
Electrode chips 6 and 7 are attached to the tip of the. An air cylinder 8 is attached to the rear end of the gun arm 3, and its piston rod 9 is connected to the rear end of the gun arm 4 via a link 10. Therefore, by pulling the piston rod 9 from the state shown in FIG. 2 by the action of the air cylinder 8, the gun arms 3 and 4 respectively rotate outward, and the electrode chips 6 and 7 respectively open. On the contrary, when the piston rod 9 is pushed out, the gun arms 3 and 4 perform a pressure operation, and the electrode chips 6 and 7 hold the work W under pressure.

Further, the spot welding gun 1 is provided with a gun arm opening switching mechanism 11 as a gun arm opening switching means for switching the opening between the pair of gun arms 3 and 4 in two stages of wide and narrow when the gun is opened. That is, the stopper pins 12 and 13 are attached to the inner portions of the rear ends of the pair of gun arms 3 and 4, respectively, and the contact of the stopper pins 12 and 13 with the opening set member 14 causes the opening of the pair of gun arms 3 and 4. Is being decided.

3 is a sectional view taken along the line AA of FIG. 2, in which the opening set member 14 is a so-called stepped shaft having a large diameter portion 14a and a small diameter portion 14b, and air cylinders 15 on both sides. , 16 fixed to piston rod 17. Therefore, the air cylinder
When the opening set member 14 is set to the position shown in FIG. 3 by the extension operation of 15, the stopper pins 12, 13 abut the small diameter portion 14b of the opening set member 14, and as shown in FIG. 4 is widened (offset state), on the other hand, when the air cylinder 16 is extended to move the large diameter portion 14a of the opening set member 14 to the position where the stopper pins 12 and 13 are opposed to each other, this large Since the movement of the stopper pins 12 and 13 is restricted by the diameter portion 14a, the opening degrees of the gun arms 3 and 4 are the fifth.
It will be narrowed as shown (set state).

In the following description, the small diameter portion 14 of the opening set member 14
The state where b is moved to a position facing the stopper pins 12 and 13 is called the off-set state of the gun arms 3 and 4 or the gun arm opening degree switching mechanism 11, while the large diameter portion of the opening set member 14 is on the other hand.
The state in which 14a is opposed to the stopper pins 12 and 13 is called the set state. That is, the opening of gun arms 3 and 4 increases in the off-set state, and the gun arms 3 and 4 open in the set state.
The openings of 3 and 4 are set to be small.

In the vicinity of the opening set member 14, there is a limit switch 19 which is operated by the dog 18, and from the output of this limit switch 19, the operating state of the gun arm opening switching mechanism 11 is confirmed.
To be detected.

An embodiment of the method of the present invention using the above spot welding gun will be described with reference to FIGS. 1 and 6.

At the first hitting point position P ₁ in FIG. 6, the gun 1 which has moved from the previous hitting point position in the set state is positioned, and a pressurization energization command is output by so-called normal operation processing. When the pressurizing and energizing command is given, it is judged in the step of FIG. 1 whether or not the teaching data of the current position is the gun set. That is, it is determined whether or not the set state is required on the teaching data as the opening degree of the gun arms 3 and 4 after welding at the hitting point P ₁ . This can be understood by extracting the step teaching data corresponding to the current position of the welding robot. The gun arm opening at the hitting position P ₁ is the opening required to move to the next hitting position P ₂ and is a small opening as is clear from FIG.
Therefore, since it is a command for the gun set in the above-mentioned teaching data of the hitting point position P ₁ , it is the first command as it is.
Go to the next step in the figure.

In step, it is judged whether or not the gun arm opening, that is, the opening set member 14 is actually set. This is detected from the output of the limit switch 19 described above.
Since the gun arm opening required at the hitting position P ₁ is in the set state as described above, the opening set member 14 remains in the set state.

Therefore, the gun arm opening on the teaching data at the hitting position P ₁ and the actual operating state of the gun arm opening switching mechanism 11 match, and the step resets the gun arm opening mismatch flag. .

On the other hand, if the gun arm opening degree on the teaching data does not match the actual operating state of the gun arm opening degree switching mechanism 11, the gun arm opening degree mismatching process is performed in step. That is, while the welding robot is stopped on the spot, an abnormality is displayed.

When welding at the hitting point P ₁ is completed, the gun arms 3 and 4 are in the set state, that is, the gun arm opening is small, and the next hitting point position is reached.
Positioning move to P _2, and repeats the flow of FIG. 1.

When a pressurization / energization command is given in the initial step in the same figure, it is determined in the next step whether the teaching data at the current position is a gun set. The gun arm opening degree on the teaching data of the hitting point position P ₂ is an opening instruction necessary to move to the next hitting point position P ₃ and therefore is an offset command. In response to this off-set command, an off-set command is given to the gun arm opening switching mechanism 11, and in parallel with the pressurizing and energizing operation, the opening set member 14 is operated by the operation of the air cylinder 16.
Is switched to the offset position.

In the step of FIG. 1, it is judged whether or not the gun arm opening on the teaching data is in the gun-offset state, and the state is the gun-offset state as described above, and therefore the next step is executed. In step, it is judged whether or not the opening set member 14 which was previously switched is in the set state, and if it matches the teaching data, the step moves to step and the gun arm opening mismatch flag is reset.

On the other hand, if the two do not match in step, the process proceeds to step and the gun arm opening degree mismatch processing is performed in the same manner as above.

Further, if neither the set command nor the offset command is present in the teaching data at the step, it is obvious that the data is abnormal. Therefore, the processing is shifted to the step and the abnormal processing of the teaching data is performed.

When the welding at the hitting point P ₂ is completed, the gun arms 3 and 4 are opened so as to have the large arm opening shown in FIG. 4 in response to the step reset process of FIG. 1, and the next hitting point P ₃
While moving to step 1, the flow of FIG. 1 is repeated.

EFFECTS OF THE INVENTION According to the present invention, the operating state of the gun arm opening switching means and the gun arm opening commanded on the teaching data are collated, and if the two do not match, the robot itself is stopped. , It is possible to prevent the spot welding gun from interfering with the workpiece while operating the welding robot at high speed.

[Brief description of drawings]

FIG. 1 is a flow chart showing an embodiment of the present invention.
FIG. 3 is an explanatory view of a spot welding gun having a gun arm opening switching mechanism, FIG. 3 is a sectional view corresponding to line AA in FIG.
FIGS. 4 and 5 are operation explanatory views of the spot welding gun of FIG. 2, and FIG. 6 is an explanatory view for explaining the relationship between the spot welding gun and the hitting point position. 1 …… Spot welding gun, 3,4 …… Gun arm, 11 ……
Gun arm opening switching mechanism (gun arm opening switching means),
12,13 …… Stopper pin, 14 …… Opening set member, 15,16
...... Air cylinder, 19 ...... Limit switch, W ...... Workpiece.

Claims (1)

[Claims] Claim: What is claimed is: 1. A playback type welding robot having a spot welding gun at the tip of the robot arm, wherein the spot welding gun abuts against the pair of gun arms when the guns are released, and the position of the gun arms can be adjusted to regulate the opening. If the gun arm opening required for releasing the gun after the pressurizing operation of the gun is different from that before the pressurizing operation of the gun, the open position setting member is used as the center. And a gun arm opening switching means for selectively switching the position of the opening setting member during the gun pressurizing operation at the hitting position in order to switch the gun arm opening in advance in case of releasing the gun after the gun pressurizing operation. The operation state of the gun arm opening switching means is detected at the end of the gun pressurizing operation at a predetermined hitting point, and this operation state and teaching data are detected. Control method of welding robot characterized by comparing with the gun arm opening command at the time of gun release after gun pressurization operation at the corresponding hit point position and stopping the welding robot when both do not match .