JPS6130288A - Control device for starting welding of welding robot - Google Patents

Abstract

PURPOSE:To speed up welding operation without deteriorating welding quality by commanding the start of welding by a welding robot when the change rate of the driving current value of each driving motor attains a stationary value. CONSTITUTION:Comparator circuits C1-Cn output a high-level signal to an AND gate 36 at the point of the time when the stationary values, i.e., the differential values by differentiating circuits D1-Dn attain zero after the respective axes of the welding robots are driven under the pressure and after the output levels of the circuits D1-Dn are increased by driving of motors 24-1-24-n. When all the output levels of the comparator circuits C1-Cn attain high levels, the start of welding by the welding robot is commanded via an AND gate 36 and an external interlock terminal to a timer conductor. The welding current is then supplied through a welding transformer to a welding gun and is passed to base metals to be welded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a welding start control device, and particularly to a welding start control device for a welding robot suitable for controlling the welding start timing of a welding robot.

[Background of the invention]

In recent years, systems using welding robot sounds have been adopted in welding systems such as resistance and arc spot welding. In this system, when welding the welding base material, the arm of the robot is moved to the welding position, and at the same time, a bath contact command signal is given to the timer conductor, and the welding is performed via the welding transformer according to the command from the timer conductor. Welding was carried out by supplying welding current between the base metals. However, if welding were started at the same time as the arm of the robot reached the welding position, welding would be performed before a predetermined pressure was applied to the welding member, which could lead to deterioration in welding quality. Therefore, in conventional systems, control is performed to delay the entire welding start time by the initial pressurization time, that is, after the robot arm reaches the welding position, until a predetermined pressure is applied to the welding member. This initial pressurization time To was set to approximately T n '' 0.4 seconds in advance to avoid deterioration of welding quality.For this reason, in conventional systems, the welding cycle time becomes long. However, there are some problems that reduce welding efficiency.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a welding start control device for a welding robot that can improve the efficiency of welding work without degrading welding quality. There is a particular thing.

[Summary of the invention]

To achieve the above object, the present invention provides a group of current sensors that detect the current values of a group of drive motors that drive each axis of a welding robot, and a current change amount sensor that detects the amount of change in the detection signal of each current sensor. The group and the detection output of each current change sensor are monitored, and after each axis of the welding robot is pressurized, when the level of the detection signal of each current change sensor reaches a steady value, the welding robot starts welding. The above purpose is achieved by the welding command device that commands and the equipment including the meeting fc.
It is characterized by

[Embodiments of the invention]

Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 shows the configuration of a preferred embodiment of the present invention. In FIG. 1, the welding robot 10 has an arm 12.1.
4.16, and the support column 18 is fixed to the base 20ff. 22 welding guns are attached to the arm 12, and each arm 12.1 is moved by the operation of the drive motor group 24.
4.16 can be driven within a range of n degrees of freedom, and can move the welding gun 22 to the welding position of the welding base material 26. Control of the movement of the welding gun 22 and the like is performed by control commands from the robot controller 28. Therefore, the robot controller 28 is taught ρ before each arm of the robot IO moves, and the robot controller 28 supplies control commands to the drive motor group 24 based on the teaching.

Further, the welding gun 22 is connected to the robot controller 28 via a welding transformer 30 and a timer conductor 3'2, and welding current is supplied to the welding gun 22 in response to a command from the robot controller 28. That is,
Is the welding start command from the robot controller 28 to the timer conductor 3? When the signal is given to the welding gun 22 via the welding transformer 30 in response to a command from the timer conductor 32,
The structure is such that welding current flows through the welding current.

Here, the present invention is characterized in that a welding start command is given to the timer conductor 32 after a predetermined pressure is applied to the welding base material 26 by driving each axis of the welding robot 10. The robot controller 28 in the embodiment is configured as follows.

That is, as shown in FIG. 2, drive motors 24-1.
The drive circuit for 24-2----/24-'n includes a resistor R1.
-...Rn, operational amplifier AMP l...AMp
A current sensor is provided that detects each drive current value of the drive motors 24-1 to 24-11.

The output signals of each operational amplifier AMP1 to AMP% are supplied to differentiating circuits DI...D% as a group of current change amount sensors that detect the amount of change in the output signal of each operational amplifier. The output signals of the differentiating circuits D1 to l)s are sent to the welding command device 34.
supplied to

The welding command device 34 has comparison circuits C1 to C? It is made up of an AND gate 36. Comparison circuits C1 to Cn are connected to the differential circuit D1 after each axis of the welding robot (10) is pressurized and driven.
As shown in FIG. 3, the output levels of ~Dn of motors 24-1 to 24-? After increasing by driving 1, when the steady value, that is, the differential value by the differentiating circuits D1 to Dn becomes 0, a high level signal '1 is outputted to the AND gate 36. Then, when all the output levels of the comparison circuits CI-Cn become high level, AND
, a command is sent to the timer conductor 32 via the external interlocker terminal 38 for the welding robot 10 to start welding. When a command to start welding is given to the timer conductor 32, welding current is supplied to the welding gun 22 via the welding transformer 30, and the welding current flows through the welding base material 26.

Here, when the amount of change in the output level of the differential circuit Di-Dn reaches a steady value, it means that appropriate pressure has been applied to the P welding base material 26 by driving the arms 12 to 16, and the differential circuit Di-Dn If welding is performed immediately after the output level of circuit DI-Dfi reaches a steady value, welding quality will not deteriorate. Also, each differential circuit Di~D? Since welding is performed immediately after the + output level reaches a steady value, there is no need to set a long welding start time in advance. Therefore, the differential circuit D1~
D? By starting welding immediately when the output level of I reached a steady value, the welding work could be performed quickly without deteriorating the welding quality.

When all welding was carried out using the apparatus according to the above embodiment,
If the time required for the drive motors 24-1 to 24-n to generate the maximum torque is about 0.1 seconds, welding can be performed without any deterioration in welding quality when welding is performed after each axis of the welding robot IO is pressurized. I was able to do it. On the other hand, in the conventional system, the initial pressurization time was To-0-4 seconds, so if the device according to this embodiment is used, the initial pressurization time is To"0".
．． 1 second, and if there is a working sound of 50 points by welding robot) 10, then 9,0.3 per l welding cycle time.
X 50 = 15.0 seconds can be saved.

Note that the above embodiment can be applied even when a welding power source is used in place of the welding transformer 30, and a torch is used in place of the welding gun.

〔Effect of the invention〕

As explained above, according to the present invention, all drive current values of the drive motors that drive each axis of the welding robot are detected, and their output levels are monitored, and after each axis of the welding robot is pressurized, each drive motor is Since the welding robot is commanded to start welding when the amount of change in the drive current value reaches a steady value, it has the excellent effect of speeding up welding work without degrading welding quality. can get.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a one-shot embodiment of the present invention, and FIG.
FIG. 3 is an internal configuration diagram of the robot controller shown in the figure, and FIG. 3 is a diagram showing the relationship between time and current value.

Claims (1)

[Claims] (1) A current sensor group that detects each current value of the drive motor group that drives each axis of the welding robot, a current change sensor group that detects the amount of change in the detection signal of each current sensor, and a current change amount sensor group that detects the amount of change in the detection signal of each current sensor. A welding command device that monitors the detection output and instructs the welding robot to start welding when the level of the detection signal of each current change sensor reaches a steady value after pressurizing each axis of the welding robot. A welding start control device for a welding robot, which is characterized by: