JPH04333379A - Electrode mobile speed control method for resistance welding machine by motor driving - Google Patents

Abstract

PURPOSE:To prevent the occurrence of wear and deformation of an electrode by controlling the mobile speed of the electrode by the number of pulses and a pulse interval from a pulse oscillator linking with rotation of a motor. CONSTITUTION:When the motor 1 is driven to rotate an axis 3 of rotation, the electrode 4 in an open state advances toward a work 11 and the approximate number of pulses till this electrode 4 attains the vicinity of a pressurizing force point is inputted to a controller 10 in advance. Accordingly, a pulse is sent to the controller 10 from the pulse oscillator 9 with driving of the motor 1 and the electrode 4 advances at high speed till the number of pulses attains the predetermined number of pulses. When the predetermined number of pulses is sent to the controller 10, braking is applied to the motor 1 by the controller 10 and the electrode 4 is slowed down up to the low speed. When the rotating speed of the motor, namely, the mobile speed of the electrode 4 attains the specified low speed by this braking, the position is known by the number of pulses and the pulse interval from the time of braking. In addition, when the electrode 4 attains the low speed, the pressurizing force of a set current value of the motor 1 is obtained by subjecting the motor 1 to constant current control.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the moving speed of an electrode in a resistance welding machine driven by an electric motor.

0002

[Prior Art] Conventionally, the electrode of a resistance welding machine driven by a DC or AC electric motor is moved at a constant speed from its open position to a pressurizing point, and pressurized from the pressurizing point at a low speed. Ta.

0003

By the way, in order to perform the welding work quickly, it is better to quickly move the electrode from its open position to the pressurizing point. However, it is very difficult to control this, and usually this is done using multiple sensors, but if this is done incorrectly, the electrode movement speed is too high.
There is a problem in that the impact during pressurization causes severe electrode wear and deformation.

The present invention has been made in view of the above-mentioned problems of the conventional technology, and its purpose is to brake the electric motor near the pressurizing point to reduce the moving speed of the electrode. The object of the present invention is to provide a method for controlling the electrode movement speed of a resistance welding machine driven by an electric motor, which prevents wear and deformation of the electrode by dropping the electrode.

Another object of the present invention is to provide a method for controlling the electrode moving speed of a resistance welding machine driven by an electric motor, in which the pressurizing force can be easily controlled by controlling the electric motor at a constant current in the vicinity of the pressurizing point.

[0006]

[Means for Solving the Problems] In order to achieve the above object, a method for controlling the electrode movement speed of a resistance welding machine driven by an electric motor according to the present invention includes disposing a pulse transmitter that is linked to the rotation of the electric motor in a control circuit. , detect the position and electrode movement speed of the electrode from the number of pulses and pulse interval from the transmitter, increase the electrode movement speed from the open position of the electrode to the vicinity of the pressurizing point, and then decelerate it to the vicinity of the pressurizing point. This device is characterized in that the electrode movement speed is reduced.

[0007] Also, the present invention is characterized in that the electric motor is controlled at a constant current in the vicinity of the pressurizing point at a reduced electrode moving speed.

[0008]

[Operation] Since the control method is configured as above,
The number of pulses corresponding to the movement of the electrode from the open position of the electrode to the vicinity of the pressurizing point is input into the controller in advance, the movement speed of the electrode is increased during this time, and when the planned number of pulses is measured, the controller is inputted in advance. applies brakes to the electric motor. The position where the rotational speed of the motor, that is, the moving speed of the electrode, becomes a predetermined low speed due to this braking is detected based on the number of pulses and the interval between pulses, and the position where the speed becomes low is located in the vicinity of the pressurizing point. Correct the number of pulses. Furthermore, by controlling the motor at a constant current at the position where the moving speed of the electrode becomes slow, the motor current is maintained at the set current value, so by adjusting the set current value, the pressurizing force can be controlled. can.

[0009]

Embodiment An embodiment of the present invention will be described with reference to FIGS. 1 and 2. In the figure, 1 is an electric motor installed at the rear end of a cylinder 2, and a rotating shaft 3 of the electric motor is threaded. Further, a rod 6 having an electrode 4 attached to its tip and a nut 5 fixed to its rear end that is screwed into the screw of the rotating shaft 3 is disposed in the cylinder 2 so as to be non-rotatable but movable back and forth. Reference numeral 7 designates a fixed arm having an electrode 8 attached to one end and fixed to the cylinder 2 at the other end.

The electric motor 1 is provided with a pulse transmitter 9 that is linked to the rotation of the electric motor.
The controller 10 is actuated by a signal from the motor 1 to control the electric motor 1.

[0011]The above resistance welding machine has a workpiece 11.
The electric motor 1 is driven with the electrode 8 in contact with the rotating shaft 3.
When the rod 6 is rotated, the rod 6 is moved forward by the nut 5, and the electrode 4 comes into contact with the workpiece 11, pressurizes the workpiece 11 and then performs the welding operation.

By the way, the number of pulses transmitted in conjunction with the rotation of the electric motor 1 is proportional to the amount of movement of the electrode 4. Further, the pulse transmission interval is inversely proportional to the moving speed of the electrode 4, and the pulse transmission interval at the pressurized position is extremely large, and this limit value can be easily determined by learning.

When the electrode 4 in the open state drives the electric motor 1 and rotates the rotary shaft 3, it advances toward the workpiece 11. However, the electrode 4 moves forward toward the workpiece 11 approximately until it reaches point A near the pressurizing point. The number of pulses is input into the controller 10 in advance. Therefore, as the electric motor 1 is driven, pulses are sent from the pulse generator 9 to the controller 10, and the electrode 4 moves forward at high speed V1 (close to the maximum speed of the electric motor 1) until the number reaches the predetermined number of pulses.

When the predetermined number of pulses is sent to the controller 10, the controller 10 applies a brake to the motor 1 to reduce the electrode 4 to a low speed V2 (about 1/3 of the high speed). The position B at which the rotational speed of the motor, that is, the moving speed of the electrode reaches a predetermined low speed V2 due to this braking, can be determined from the number of pulses and the interval between pulses from the time of braking.

[0015] If the position of the electrode 4 at low speed V2 is point B, which is closest to the pressurizing position, there is no need to modify the planned pulse number, but if the position of the electrode 4 is at point B, which is the closest to the pressurizing position, it is not necessary to modify the planned pulse number. If it is before, it means that the scheduled number of pulses is insufficient, so correction is made to increase the scheduled number of pulses. Furthermore, if the electrode 4 reaches the pressurizing position at the speed V3 before reaching the low speed V2, the planned number of pulses is too large, so the planned number of pulses is corrected to decrease.

In addition to the above control, the electrode 4 is controlled at low speed V
2, the motor current is maintained at the set current value by constant current control of the motor 1, and a pressing force matching the set current value is obtained.

[0017]

Effects of the Invention The present invention controls the moving speed of the electrode by the number of pulses and the pulse interval from the pulse transmitter that is linked to the rotation of the electric motor. By slowing down the movement of the electrode in the immediate vicinity, it is possible to soften the impact from the electrode during pressurization, thereby preventing wear and deformation of the electrode, and improving welding efficiency.

[0018] Furthermore, since the motor is controlled at a constant current near the pressurizing point where the electrode movement speed is reduced, the motor current is maintained at the set current value, and by adjusting the set current value, the work It is easy to control the pressurizing force to suit.

Furthermore, by applying a pulse oscillator linked to the rotation of the electric motor to the control circuit, no other special sensor is required, so the system is further simplified.
Accidents such as breakdowns will also be reduced.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a resistance welding machine driven by an electric motor to which an electrode movement speed control method according to the present invention is applied.

FIG. 2 is an explanatory diagram of an electrode movement speed control method according to the present invention.

[Explanation of symbols]

1 Electric motor 4 Electrode 9 Pulse transmitter 10 Controller

Claims (2)

[Claims] Claim 1: In a resistance welding machine driven by an electric motor, a pulse transmitter that is linked to the rotation of the electric motor is disposed in a control circuit, and the electrode position and electrode movement speed can be determined from the number of pulses and pulse intervals from the transmitter. is detected, and the electrode movement speed from the open position of the electrode to the vicinity of the pressurizing point is increased.
A method for controlling an electrode moving speed of a resistance welding machine driven by an electric motor, characterized in that the electrode moving speed is reduced in the vicinity of a pressurizing point by decelerating thereafter. 2. The method of controlling the electrode movement speed of a resistance welding machine driven by a motor according to claim 1, wherein the electric motor is controlled at a constant current in the vicinity of a pressurizing point where the electrode movement speed is reduced.