JP2787931B2 - Welding equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding apparatus for spot welding a work by pressing a welding tip from both sides of the work.

[0002]

2. Description of the Related Art Conventionally, a welding apparatus used for spot welding a panel material or the like as a work has a C-shaped or X-shaped gun arm, and a welding tip, that is, a welding electrode is provided at the tip of the gun arm. Is installed. Conventionally, a pair of welding tips are moved toward and away from each other by a pneumatic cylinder, and the pressing force on the workpiece is set by the pneumatic cylinder.

[0003]

When a welding device is mounted on a welding robot to weld a work such as a panel material, it is usual to sequentially weld a plurality of places to one work. In some cases, it may be necessary to change the welding conditions for the workpiece according to the hitting position. In such a case, in a conventional welding device that drives a welding tip by a pneumatic cylinder, when teaching the movement trajectory of a welding robot, welding conditions, such as pneumatic cylinder Was required to be taught. The taught data is stored in a teach table in a memory.

[0004] When welding a work having a different plate thickness or a work having a coated surface with a single welding apparatus, a pressure increasing valve is used to change the pressure of the pneumatic slider. Is done. However, in a welding device provided with a pressure-intensifying valve, it is difficult to increase the pressure in a stepless manner, and only the pressure can be changed in several steps. For this reason, it has been difficult to select an optimum pressing force according to the thickness of the work and the like. And adversely affected the welding quality.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to enable spot welding with an optimum pressing force according to the hitting position of a workpiece.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a first welding tip and a second welding tip which are movable toward and away from each other and form a pair, and at least one of these welding tips. A gun arm provided with a servomotor that moves forward and backward toward the other, a servomotor controller that controls the rotation of the servomotor, and detects a current value flowing through a cable that is connected to each of the welding tips and supplies a current. A welding apparatus comprising: a current detecting unit that performs a pressing operation; and a pressing force instruction unit that outputs a pressing command signal that adjusts a pressing force applied to the workpiece by the two welding tips based on a detection signal from the current detecting unit.

[0007]

In the present invention having the above-described structure, the first welding tip and the second welding tip provided as a pair on the gun arm are movable toward and away from each other by the servomotor. In a cable for supplying a current to each welding tip, a current value flowing through the welding tip is detected by a current detecting means, and welding is performed by a servo motor via a servo motor controller so that the current value becomes a predetermined current value. The pressure applied to the workpiece by the chip is adjusted to a predetermined pressure. Therefore, the pressing force of the welding tip on the work is automatically adjusted, and no unnecessary pressing force acts on the work.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on one embodiment of the present invention shown in the drawings. FIG. 1 is a view showing an example of a welding robot R having a servo gun. A pedestal 10 attached to a base (not shown) is provided with a swivel 11 which can swing in the direction of arrow J1. A robot shaft 12 is attached to 11 so as to be swingable in the direction of arrow J2. The robot axis 12 has the robot axis 1
3 is mounted so as to be swingable in the direction indicated by arrow J3 and rotatable in the direction indicated by arrow J4. At the end of the robot shaft 13, a servo gun, that is, a welding gun 14 is attached so as to be swingable and rotatable in the direction indicated by arrow J5 and rotatable in the direction of arrow J6. Therefore, the illustrated robot R has a function of a total of six axes.

The welding gun 14 has a C-shaped gun arm 15. The gun arm 15 is formed by a fixed welding tip 21 as a first welding tip and a pair of the fixed welding tip 21 and a panel material or the like. And a movable welding tip 22 as a second welding tip for welding the workpiece W. The movable welding tip 22 is fixed to the fixed welding tip 2
Servo motor 23 for moving forward and backward toward 1
It is attached to the gun arm 15. Control of a total of seven axes, including the operation of the servomotor 23, is controlled by the robot controller 24 shown in FIG.

FIG. 2 is a view showing details of the gun arm 15 shown in FIG. 1. A drive rod 25 having a movable welding tip 22 mounted on the tip thereof slides in a bearing 26 mounted on the gun arm 15 in the axial direction. It is movably supported. A pulley 27 provided on a main shaft of a servo motor 23 attached to the gun arm 15 is connected to a nut 28 fitted on a ball screw formed outside the drive rod 25 by a timing belt 29. Therefore,
When the servomotor 23 is driven, the nut portion 28 rotates via the belt 29, and the driving rod 25 slides in the axial direction by the portion of the ball screw meshing with the nut portion 28.

FIG. 3 is a diagram showing a control circuit of the above-described welding apparatus. Secondary cables 31a, 31b of a transformer 30 for supplying a current to the welding tips 21, 22 are connected to the respective welding tips 21, 22. I have. The primary cable 32 of the transformer 30 is connected to a power supply 33, and the welding tips 21 and 22 are connected to the power supply 33 via the transformer 30.
Is supplied. Since the illustrated welding device is attached to the robot shaft 13 of the welding robot R, the current supply timing to the welding tips 21 and 22 is controlled by the robot controller 3 that controls the movement of the welding robot R.
4 is controlled by a start-up start signal. The activation start signal from the robot controller 34 is sent to a weld timer 35 that controls the timing of starting and ending the current supply to the welding tips 21 and 22. The weld timer 35 has a switching element 36 provided on the primary cable 32, a gate controller 37 for sending an operation signal to the switching element 36, and a current detection amplifier 37.

The rotation of the servo motor 23 is controlled by a servo motor controller 39.
And a predetermined voltage set by a control signal from the amplifier 41 is supplied to the servomotor 23. The motor 23 is provided with a pulse generator 42 for detecting the number of rotations of the servo motor 23.
Sends a feedback signal to the motor amplifier 41. The start and stop timings of the servo motor 23 are controlled by signals from the robot controller 34.

The secondary cable 31b is provided with a current detector (CT) 43 for detecting a current flowing through the secondary cable 31b. The current value detected by the current detector 43 is fed back to the current detection amplifier 38. When spot welding is performed on a workpiece W such as a panel,
The movable welding tip 22 is moved forward toward the fixed welding tip 21 by driving the servo motor 23. If the pressing force of the two chips 21 and 22 to the work does not reach the predetermined pressing force, the current value supplied to the two chips 21 and 22 does not become the predetermined current value. The current value is detected by the current detector 43, fed back to the current detection amplifier 38, and a control signal is sent to the motor amplifier 41. Thus, the current detection amplifier 38 is connected to the current detector 43
A pressure command means for outputting to the motor amplifier 41 a pressure command signal for adjusting the pressure applied to the work by the welding tips 21 and 22 based on the detection signal from the motor. By controlling the rotation of the servomotor 23 by a control signal from the shunt detection amplifier 38 as the pressurizing command means, the servomotor 23 is controlled in accordance with the current flowing through the secondary cables 31a and 31b, and a predetermined load is applied. Pressure is applied to the workpiece.

Therefore, when teaching the operation of the welding robot R, if the movement trajectory of the robot axis of the welding robot R is instructed, the pressing positions of the welding tips 21 and 22 need not be taught, and the positions of the respective strike points can be determined. Is automatically set to the desired pressure. Moreover, since the pressing force is controlled so that the current value flowing through the work W becomes a predetermined current value, an unnecessary pressing force is not applied to the work W, and high-quality welding with little deformation of the work W is achieved. Is done.

The welding device shown is a welding robot R
However, even if the welding device is of a type that is not mounted on the welding robot R, the present invention can be applied to a welding device of a type that drives at least one of a pair of welding tips by a servomotor 23. It is possible to apply.

[0016]

As described above, according to the present invention, by detecting the welding current flowing through both welding tips, the pressing force on the welding tips of the servomotors driving the paired welding tips is adjusted. In addition, an optimum pressing force is applied to the work by the welding tip, so that an effect that the work quality is high without deforming the work can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a welding robot equipped with a welding device of the present invention,

FIG. 2 is a front view showing details of the gun arm shown in FIG. 1;

FIG. 3 is a schematic diagram showing a control circuit of the welding device.

[Explanation of symbols]

15 ... Gun arm, 21 ... Fixed (first) welding tip, 2
2 movable (second) welding tip, 23 servo motor, 3
1a, 31b: cable, 38: current detection amplifier (pressing force command means), 39: servo motor controller, 43
... current detector (current detection means), R ... robot, W ... workpiece.

Claims (1)

(57) [Claims] 1. A gun arm comprising a first welding tip and a second welding tip which are movable toward and away from each other and form a pair, and a servomotor for driving at least one of these welding tips toward the other. A servo motor controller that controls the rotation of the servo motor; a current detection unit that detects a current value flowing through a cable that is connected to each of the welding tips and supplies a current; and a detection signal from the current detection unit. A pressure commanding means for outputting a pressure command signal for adjusting a pressure applied to the workpiece by the two welding tips.