JPH0947881A - Controller for c type welding gun - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controller for C shaped welding gun capable of surely executing rotation-locking of moving arm without excessively pressurizing a work at any gun position and precisely operating. SOLUTION: Two servo motors 1, 21 are arranged to a housing 2 of welding gun, C shaped arm 27 is fixed to the housing, and ball screw mechanisms 7, 8, by which the rotation of an output shaft 3 of one of servo motor 1 is transformed to the reciprocal movement of moving arm 9, are arranged in the housing. Mechanisms 23, 24, by which the rotation of an output shaft 22 of other servo motor 21 is transformed to the reciprocating movement of C shaped arm, are arranged between a wrist 25 of robot and the housing, a rolling guide mechanism 12 consisting of ball and guide groove is arranged between the moving arm, in which a nut 8 of ball screw mechanism is held, and the housing. By simultaneously driving both servo motors and based on an abutting signal of the electrode 26 at the side of C shaped arm on a work 29, other servo motor is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a C-type welding gun in which a welding gun connected to a wrist of a robot is driven by a servo motor.

[0002]

2. Description of the Related Art Conventionally, a C-type welding gun in which a welding gun connected to a wrist of a robot is driven by a servomotor is known (see, for example, Japanese Utility Model Laid-Open No. 5-18774). In this known C-type welding gun, a ball screw of a movable arm moving mechanism is connected to a shaft of a servo motor, and the ball screw is rotated by the servo motor to move the movable arm. -The arm moving mechanism is reciprocated, which causes the movable arm side electrode provided in the movable arm moving mechanism to reciprocate, and the servo motor causes the belt to move the other ball screw. Synchronous rotation is performed, whereby the equalizing mechanism is reciprocated, and the C-shaped arm side electrode disposed in the C-shaped arm integrally connected to the equalizing mechanism is reciprocated. ing.
The moving amount of the movable arm side electrode is measured by the moving amount detecting device, and when the movable arm side electrode moves by a predetermined amount, the movement of the servo motor is stopped by the instruction of the controller. I am trying.

[0003]

However, in the case of the conventional example described above, since the weight of the gun in the equalizing portion is supported by the spring, the gun weight applied to the spring changes depending on the posture of the gun. Depending on the posture, the spring does not operate effectively and the equalizing function is not sufficiently fulfilled. Especially, when the posture of the gun is changed by 180 degrees and the gun is directed upward, the equalizing function is not fulfilled at all. In addition, since one servo motor stops when the electrode on the movable arm side moves by a predetermined amount, the distance between the electrode on the movable arm side and the work, the C-shaped arm side Due to the difference in the distance between the electrode and the work, the thickness of the plate, or the difference in deformation due to wear of the movable arm side electrode and the C-shaped arm side electrode over time, etc. Since both electrodes cannot reach the work at the same time, there is a possibility that the work may be deformed due to the electrode that reaches the work being pressed quickly to the work.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to apply unreasonable pressure to a work regardless of the posture of a gun. In other words, it is an object of the present invention to provide a control device for a C-type welding gun, in which the movable arm is securely prevented from rotating, and operates accurately.

[0005]

In order to achieve the above object, a control device for a C-type welding gun according to the present invention is provided with two servomotors in a housing of the welding gun and at the same time, in the housing. A ball screw mechanism for fixing the C-shaped arm and converting the rotation of the output shaft of one servomotor into the reciprocating motion of the movable arm is provided inside the housing, and the other screw is installed.
A mechanism that converts the rotation of the output shaft of the motor into the reciprocating motion of the C-shaped arm is provided between the wrist of the robot and the housing, and a movable arm that holds the nut of the ball screw mechanism.
A rolling guide mechanism consisting of a ball and a guide groove is provided between the housing and the housing to drive both servo motors at the same time and to apply the C-shaped arm side electrode to the work. It is characterized in that the other servo motor is stopped by a contact signal.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. In the figure, reference numeral 1 is a servomotor held by a housing 2, and the servomotor is a servomotor.
A pulley 4 is attached to the output shaft 3 of the motor 1, and a belt 6 is stretched between the pulley 4 and the pulley 5 attached to the screw shaft 7. Reference numeral 8 is a ball nut that meshes with the screw shaft 7.

The ball nut 8 is built in the rear end portion 10 of the movable arm 9 in a non-rotatable state and has a flange portion 11 formed therein.
It is fixed to the movable arm 9 by. A ball box 1 for a rolling guide mechanism is provided above the rear end portion 10.
As shown in FIG. 2, two pieces 2 are attached symmetrically so that a large number of balls 13 in the ball box can move endlessly in the box as the movable arm 9 moves back and forth. Has become. Further, the ball box 1 is provided on the inner wall of the cylinder 14 in which the rear end portion 10 is movably accommodated.
A rail 16 having a guide groove 15 formed opposite to No. 2 is attached in the axial direction of the cylinder 14. An electrode 18 is attached to the front end of the movable arm 9 through a point holder 17 at the tip.

Brackets 19 and 20 are provided outside the cylinder 14 formed in the housing 2,
A servo motor 21 is attached to and held by the bracket 19. A screw shaft 23 is connected to the output shaft 22 of the servo motor 21, and the screw shaft 23 is rotatably suspended between the brackets 19 and 20.

The nut 2 meshing with the screw shaft 23
4 is fixed to the wrist side 25 of the robot, and a C-shaped arm 27 having an electrode 26 at its tip is also fixed to the outside of the cylinder 14 formed in the housing 2.

Further, 28 is a controller added to the control panel or the robot controller, which is the above-mentioned both servo controllers.
The servomotors 1 and 21 are controlled respectively, and both the servomotors 1 and 21 are simultaneously started, the servomotor 21 is stopped,
Further, it controls stop of the servo motor 1 after the pressurizing operation.

In the control device for the C-type welding gun as described above, the welding gun is moved to the welding position by the wrist side 25 of the robot, and the electrode 26 on the arm 29 in the C-shape with respect to the work 29. It is placed in the taught position. At this position, it is advisable to teach the C-shaped arm-side electrode 26 so that both electrodes 18 and 26 are equidistant from the work 29, but at least the electrode 18 is the electrode. Do not set it so that it is closer to work 29 than 26. In this state, the controller 28 controls both sides.
Start the motors 1 and 21 at the same time.

By driving these, one servo
The rotation of the output shaft 3 of the motor 1 is transmitted from the pulley 4 to the pulley 5 via the belt 6, and the rotation of the pulley 5 causes the screw shaft 7 to rotate and the nut 8 causes the movable arm 9 to move. Move forward, electrode 1
8 approaches and advances toward work 29. At the same time, the rotation of the output shaft 22 of the other servo motor 21 causes the screw shaft 2 to rotate.
3 rotates. The rotation of the screw shaft 23 is performed by the nut 24 fixed to the wrist side 25 of the robot.
Since it operates so as to move backward (upward in the figure),
The C-shaped arm 27 fixed to the housing 2 moves rearward together with the housing 2, and the electrode 26 on the C-shaped arm side approaches the work 29.

Since the C-shaped arm-side electrode 26 is set at a predetermined position as described above, the C-shaped arm 26 is set by the approach of the electrodes 18 and 26 to the work 29. -
The electrode 26 on the arm side is brought into contact with the work 29 simultaneously with the electrode 18 on the movable arm side or before the electrode 18 on the movable arm side. Since this contact can be known by a pulse signal or the like interlocked with the rotation of the other servo motor 21, the drive of the other servo motor 21 is stopped by the controller 28 by the corresponding contact signal. It As described above, the electrode 26 on the side of the C-shaped arm 27 that abuts the work 29 is fixed to the housing 2 of the welding gun connected to the wrist side 25 of the robot. Work 2
Since the movement of the electrode 26 is stopped at the same time as it comes into contact with 9, the electrode 26 does not apply unreasonable stress to the work 29 regardless of the posture of the gun.

If the electrode 18 on the movable arm 9 side is simultaneously in contact with the work 29 at the time when the other servo motor 21 is stopped, the one servo The pressurizing action on the work 29 is immediately performed by the robot 1,
If the electrode 18 on the movable arm 9 side is not yet in contact with the work 29, go to the work 29 on the electrode 18 on the movable arm 9 side by the one servo motor 1. After the approach is continued, the work 29 pressurizes the work 29 by the other servo motor 1.

Then, when the pressing operation of the work 29 by the one servo motor 1 is completed, the work is welded to the work 29. Also, when this welding is completed,
Drive both servo motors 1 and 21 by the controller 28,
Both electrodes 18, 26 are opened.

By the way, the movable arm 9 has a screw shaft 7
Since the rotation of the movable arm 9 is reciprocated by the ball screw mechanism, the movable arm 9 tends to rotate during the reciprocating movement, and thus requires a detent. In particular, when the work 29 is pressed by the movable arm 9, its resistance is large, so that a large rotational force acts on the movable arm 9. The rotational force from the screw shaft 7 acting on the movable arm 9 tends to rotate the ball 13 in the radial direction of the cylinder. Therefore, the ball 13 is the rail 16
It is pressed by the guide groove 15 and absorbs the rotational force to perform an effective detent function.

[0017]

According to the present invention, two servomotors are arranged in the housing of the welding gun, and a C-shaped arm is fixed to the housings so that one of the servomotors can be mounted. A mechanism for converting the rotation of the output shaft into the reciprocating motion of the movable arm is provided in the housing, and the rotation of the output shaft of the other servomotor is converted into the reciprocating motion of the C-shaped arm. A mechanism is provided between the wrist of the robot and the housing, and both the servo
The other servomotor is stopped by the contact signal of the electrode on the side of the C-shaped arm on the work at the same time, so that the work thickness, This is a control device for a C-type welding gun that does not require special consideration for electrode wear and the like, and operates accurately regardless of the posture of the gun and without excessive pressing of the work.

Further, by providing a rolling guide mechanism consisting of a ball and a guide groove between the movable arm for holding the nut of the ball screw mechanism and the housing, a device having an excellent anti-rotation function is provided. Becomes

Since the other servo motor is driven only by the movement of the welding gun with respect to the wrist of the robot, it has a smaller output than that of the one servo motor. Good.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional side view of a control device for a C-type welding gun according to the present invention.

[Explanation of symbols]

 1,21 Servo motor 2 Housing 3,22 Output shaft 7,8 Ball screw mechanism 9 Movable arm 12 Ball box 13 Ball 14 Cylinder 15 Guide groove 16 Rail 23,24 Reciprocating motion Mechanism to convert to 25 robot wrist 27 C-shaped arm 28 controller

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[Procedure amendment]

[Submission date] December 7, 1995

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Change

[Correction contents]

[Brief description of drawings]

FIG. 1 is a partial cross-sectional side view of a control device for a C-type welding gun according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

[Explanation of symbols] 1,21 Servo motor 2 Housing 3,22 Output shaft 7,8 Ball screw mechanism 9 Movable arm 12 Ball box 13 Ball 14 Cylinder 15 Guide groove 16 Rails 23, 24 Mechanism for converting to reciprocating motion 25 Robot Wrist 27 C-shaped arm 28 Controller

Claims (1)

[Claims] 1. A C-type welding gun in which a welding gun connected to a wrist of a robot is driven by a servomotor, in which two servomotors are provided in a housing of the welding gun and the housing is provided in the housing. A ball screw mechanism for fixing the C-shaped arm and converting the rotation of the output shaft of one servomotor into the reciprocating motion of the movable arm is provided inside the housing, and the other screw is installed. A movable arm for providing a mechanism for converting the rotation of the output shaft of the motor into the reciprocating motion of the C-shaped arm between the wrist of the robot and the housing and holding the nut of the ball screw mechanism. A rolling guide mechanism consisting of a ball and a guide groove is provided between the housing and the housing to drive both of the servomotors at the same time and contact the electrode of the C-shaped arm with the work. A feature is that the other servo motor is stopped by a signal. Control device for C-type welding gun.