JP2004181493A - Welding torch for arc welding robot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a welding torch having a compact shock detection circuit of high detection sensitivity of collision. <P>SOLUTION: A welding torch for an arc welding robot comprises an acceleration sensor which is disposed inside the welding torch and provided on each axis so as to detect shocks received when the welding torch is brought into contact with a structure to be welded as the vibration acceleration in three axial directions orthogonal to each other, and a contact detection means 102 which is connected to the acceleration sensor on each axis and outputs the pulse signal when the detection signal of the acceleration sensor exceeds the threshold for the reference, and further comprises a signal processing circuit 101 comprising a first AND circuit to convert the signal output from the contact detection means of each axis into the contact signal, and a shock detection circuit 14 built therein to stop the robot after the contact detection signal output from the signal processing circuit is transmitted to a robot controller 15. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a welding torch that detects the application of an external force to a welding torch of an industrial arc welding robot and an automatic welding device to prevent damage before it occurs.
[0002]
[Prior art]
In a conventional industrial arc welding robot, a welding torch is provided at an end thereof as an end effector, and when performing a welding operation in accordance with a control operation of a robot arm or a wrist, the welding torch comes into contact with a welding structure and the welding torch is damaged. There are cases.
As means for solving such a problem, a position deviation of the servo system is detected, and when the position deviation becomes equal to or larger than a set value, a collision is detected as a load abnormality, or a driving current of the servo motor is detected. There is a method of detecting a collision when it is determined that a collision or the like has occurred when the current exceeds a set value.
Further, a bending change and a rush change of the welding torch caused by the contact of the welding torch with the welding structure are converted into vertical movement by a mechanical transmission structure, and the vertical movement is further electrically converted, and the robot is used as a shock sensor. (See, for example, Patent Document 1)
Further, a carbon plate composed of a plurality of ring-shaped conductive members on a non-conductive flanged wire guide in a bracket provided on a welding torch where a consumable electrode wire passes through the center of the shaft, and a good conductor sandwiching the carbon plate. A structure in which a conductive material is guided and held by the non-conductive flanged wire guide, and a good conductive material sandwiching the carbon plate is pressed against the non-conductive flange by a spring from above, and a bracket provided on the welding torch. There is a method of providing a shock sensor for detecting a change in electric resistance between the lead wires and a lead made of a conductive material sandwiching the carbon plate and the carbon plate (for example, see Patent Document 2).
[0003]
[Patent Document 1] JP-A-58-171279
[Patent Document 2] JP-A-4-66277
[0004]
[Problems to be solved by the invention]
However, in the method of detecting a collision or the like by detecting an increase in the position deviation or an increase in the drive current, the servomotor is already outputting a large torque at the time of detecting the collision. Damage may not be prevented.
Further, in the case of Patent Document 1, troubles occur frequently due to a complicated transmission structure, and there is a problem in maintenance.
In the case of Patent Document 2, it is possible to follow the increase in speed, but similarly to Patent Document 1, there is a problem in high sensitivity and miniaturization because an accessory mechanism is required between the robot arm and the welding torch. .
Therefore, the present invention has been made in view of such problems, and detects a collision with high sensitivity, and does not require an accessory mechanism between the robot arm and the welding torch. It is intended to provide a torch for use.
[0005]
[Means for Solving the Problems]
To solve the above problems, the present invention is configured as follows.
The invention according to claim 1 is a welding torch attached to an arm tip of an arc welding robot, wherein the welding torch is disposed inside the welding torch and receives an impact when the welding torch comes into contact with a welding structure or the like. An acceleration sensor provided on each axis so as to detect vibration acceleration in three axes directions orthogonal to each other, and a threshold value provided in connection with the acceleration sensor on each axis and based on a detection signal of the acceleration sensor as a reference And a signal processing circuit comprising: a contact detection unit that outputs a pulse signal when the number of signals exceeds the limit; a first AND circuit that converts a signal output from the contact detection unit of each axis into a contact signal; After the contact detection signal output from the processing circuit is sent to the robot controller, a shock detection circuit for stopping the robot is incorporated.
With this configuration, the robot can be stopped instantaneously when the welding torch comes into contact with the welding structure or the like, and damage to the welding torch, the speed reducer of the robot, and the welding structure can be prevented.
In the invention described in claim 2, the shock detection circuit includes a buffer amplifier for impedance-converting an acceleration signal from the acceleration sensor and a band-pass for discriminating a frequency band of vibration acceleration subjected to impedance conversion by the buffer amplifier. A filter, an amplifier for amplifying an output signal of the band-pass filter, and a first signal for comparing an output signal of the vibration acceleration amplified by the amplifier with an upper limit signal and a lower limit signal of the vibration acceleration serving as the threshold value. , A second comparator, and a second AND circuit that converts the signal compared by the two comparators into a signal that outputs the presence or absence of interference when contact is detected when the signal exceeds one of the thresholds. And is composed of
With this configuration, the robot can be instantaneously stopped when the welding torch comes into contact with the welding structure, etc., and the welding torch, the speed reducer of the robot and the welding structure can be prevented from being damaged. However, a malfunction does not occur due to vibration during normal operation of the arc welding robot.
According to a third aspect of the present invention, there is provided a latch circuit for holding a pulse signal from the contact detection means longer than a sampling time of the robot controller between the first AND circuit of the shock detection circuit and the robot controller. Is provided so that all of the contact detection signals can be detected by the robot controller.
With this configuration, the robot can be instantaneously stopped when the welding torch comes into contact with the welding structure, etc., and the welding torch, the speed reducer of the robot and the welding structure can be prevented from being damaged. Even when a contact signal shorter than the sampling interval of the controller of the arc welding robot is output, the robot can be reliably stopped.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a sectional view of a welding torch for an arc welding robot according to the present invention. In the figure, 11 is a welding wire, 12 is an electrode tip, 13 is an insulating outer cylinder, and 14 is a shock detection circuit. FIG. 2 shows details of the shock detection circuit 14. 102 is a contact detecting means. Reference numeral 106 denotes a first AND circuit for converting an output signal into a contact signal when at least one of the output signals obtained from the contact detection means of each axis outputs a LOW level signal. A latch circuit 107 holds the contact signal of the first AND circuit 106 longer than the sampling time of the robot controller 15 so that the robot controller 15 can detect all the final contact detection signals 108. The contact detection signal 108 output from the latch circuit 108 is sent to the robot controller 15, and the robot controller 15 generates a command to stop the robot.
Next, an X-axis contact detection unit of the above-described respective shaft contact detection units will be described with reference to FIG.
In FIG. 3, reference numeral 21 denotes a buffer amplifier for impedance-converting an acceleration signal from the X-axis acceleration sensor. Reference numeral 22 denotes a high-pass filter 23 and a low-pass filter 24 provided for discriminating a frequency band of the acceleration signal whose impedance has been converted by the buffer amplifier 21. And 25 is an amplification amplifier for amplifying the output signal of the band-pass filter 22. 26 is a reference signal source indicating the upper limit of the reference acceleration signal, 27 is a reference signal source indicating the lower limit of the reference acceleration signal, 28 is the acceleration signal Sa amplified by the amplifier 25 and the signal of the reference signal source 26 This is a first comparator that compares Sb1 and outputs a LOW level signal when contact is detected when the signal Sa is greater than the signal Sb1. 29 is a second comparator which compares the acceleration signal Sa amplified by the amplifier 25 with the signal Sb2 of the reference signal source 26, and outputs a LOW level signal upon detecting contact when the signal Sa is smaller than the signal Sb2. It is. Reference numeral 30 denotes a contact signal when at least one of the signals Sc1 and Sc2 obtained by the first comparator 28 and the second comparator 29 outputs a LOW level signal, indicating whether or not there is a contact. This is a second AND circuit that converts the signal into a signal. Here, the X-axis contact detection unit has been described, but the Y-axis and Z-axis contact detection units have the same configuration, and thus description thereof will be omitted.
Although a latch circuit is provided in the present embodiment, it is not necessary to provide a latch circuit when the sampling speed of the robot controller is sufficiently high.
Further, an OR circuit may be provided instead of the AND circuit provided in the signal processing circuit. In this case, the signs of the input terminals of the first and second comparators are reversed.
[0007]
【The invention's effect】
As described above, according to the welding torch of the present invention, the robot can be stopped instantaneously when the welding torch comes into contact with the welding structure or the like, and the welding torch or the speed reducer of the robot or the welding structure can be stopped. There is an effect that damage can be prevented.
[Brief description of the drawings]
FIG. 1 is a side sectional view of a welding torch showing an embodiment of the present invention. FIG. 2 is an explanatory view showing details of a shock detection circuit of the present invention. FIG. 3 is a view showing details of an X-axis contact detecting means of the present invention. Figure [Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Welding wire 12 Electrode tip 13 Insulated outer cylinder 14 Shock detection circuit 15 Robot controller 102 Contact detection means 103 Contact detection means (X axis)
104 Contact detection means (Y-axis)
105 Contact detection means (Z axis)
106 First AND circuit 107 Latch circuit 108 Final contact detection signal 20 Acceleration sensor (X-axis)
21 buffer amplifier 22 band pass filter 23 high pass filter 24 low pass filter 25 amplifying amplifier 26 reference signal source (upper limit)
27 Reference signal source (lower limit)
28 first comparator 29 second comparator 30 second AND circuit

Claims (3)

In a welding torch attached to the tip of an arm of an arc welding robot, vibration accelerations in three axial directions, which are arranged inside the welding torch and receive shocks when the welding torch contacts a welding structure or the like, are orthogonal to each other. An acceleration sensor provided for each axis so as to be detected, and a pulse signal is output when the detection signal of the acceleration sensor exceeds a reference threshold value provided in connection with the acceleration sensor of each axis. And a first AND circuit for converting a signal output from the contact detection means of each axis into a contact signal, and a contact detection signal output from the signal processing circuit. Characterized in that a shock detection circuit for stopping the robot after sending the robot to the robot controller is provided. Torch. The shock detection circuit includes a buffer amplifier that impedance-converts the acceleration signal from the acceleration sensor, a band-pass filter that discriminates a frequency band of the vibration acceleration whose impedance is converted by the buffer amplifier, and an output signal of the band-pass filter. An amplification amplifier for amplifying, first and second comparators for comparing an output signal of the vibration acceleration amplified by the amplification amplifier with an upper limit signal and a lower limit signal of the vibration acceleration serving as the threshold value, And a second AND circuit that converts the signal into a signal that outputs the presence or absence of interference when contact is detected when the signal compared by the comparator exceeds any of the threshold values. The welding torch for an arc welding robot according to claim 1. A latch circuit is provided between the first AND circuit of the shock detection circuit and the robot controller for holding a pulse signal from the contact detection means for longer than the sampling time of the robot controller. 3. The welding torch for an arc welding robot according to claim 1, wherein the welding torch can be detected by a controller.

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