JPH09285870A - Electrode pressing device of resistance welding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the response characteristics of a pressing force during forming a nugget. SOLUTION: This device is an electrode pressing device of a resistance welding machine, in an actuator using an electric motor as a driving source, a direct driving shaft 7 having an electrode 8 is connected directly to a power shaft 4 of the motor, in this mechanism, the rotary torque of the motor is converted directly to the linear driving of the electrode part. Therefore, because the regulation of pressing force is executed with a motion of the friction coefficient being zero or a small friction coefficient, the response speed is improved largely.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses an electric motor as a drive source of an electrode pressurizing drive device of a resistance welding machine. More specifically, the rotating torque of the motor can be directly measured without using a ball screw. The present invention relates to an electrode pressurizing device for a resistance welding machine that converts an electrode driving shaft into a linear motion and obtains appropriate pressure response characteristics while a nugget is being formed on a workpiece.

[0002]

2. Description of the Related Art FIG. 7 shows a conventional resistance welding machine. Generally, a pneumatic cylinder or a hydraulic cylinder is widely used as a drive source of an electrode pressurizing device. Here, the pressurizing force is adjusted by controlling the torque of a servo motor. An example of the welding machine to perform is shown. The pressurizing device is related to the electric pressurization of various welding machines such as a stationary spot welding machine, a tabletop spot welding machine, and a spot welding gun.

Reference numeral 70 in the figure denotes a servo motor for adjusting the pressure by moving the electrode and controlling the torque, which is supported on the upper portion of the main body 79 of the spot welding machine. Reference numeral 71 is a ball screw that converts rotational movement into linear movement to the ball screw 72, and 73 is an arm holder that is connected to the ball screw and is guided by a linear motion bearing 74 of the main body. 75 and 76 are secondary arms having high rigidity and little bending. The welding transformer is connected via a conductive member. Reference numerals 77 and 78 denote electrodes for sandwiching the object to be welded to apply a pressing force to the welded portion and to conduct electricity, and are supported by the tip of the secondary arm.

In this type of conventional resistance welding machine, generally, pneumatic cylinders and hydraulic cylinders are set to pressurization, and electric motors press the generated torque by setting armature current to drive the secondary arm and electrodes. After the electrode touches the work piece, the pressure of the same actuator is adjusted to obtain a predetermined pressure.

In this case, the secondary arm is generally made of an electric conductor such as a copper alloy or aluminum. Although there are restrictions such as weight and thickness, the electric resistance is as low as possible.
It has been said that the higher the strength, the better.

[0006]

In the method of presetting the force generated by the pressurizing actuator itself, in the cylinder, there are individual variations in the pressure setting due to the influence of friction and the like, and the pressure is not always correct. Also, in an electric motor, its torque is
That is, since the pressure is set, the electric motor becomes special and the cost is high. In particular, in the case of electric pressurization, the frictional force of the ball screw becomes a disturbance and accurate pressurization cannot be transmitted. On the contrary, the displacement of the electrode in the pressing direction due to the expansion and contraction of the workpiece cannot be measured accurately from the motor shaft.

When the pressure is directly controlled by the actuator in this way, the compression effect of the air pressure, the delay of the servo response, etc., and the influence of friction and prying in the pressurizing mechanism may cause the initial energization. Even if the applied force at the tip of the electrode tip changes due to disturbance such as the work being softened and deformed and sinking, or the electrode being forced out by the thermal expansion of the weld in the middle of energization It was not possible to obtain a sufficient pressure response speed.

Further, in a pressurizing device using a pneumatic cylinder or the like, a spring may be inserted in the pressurizing mechanism for the purpose of improving the response of the pressing force. However, they have not been able to perform arbitrary pressing force control in combination with arbitrary positioning control, and the pressing force control itself was also performed by an actuator such as a pneumatic cylinder. Accordingly, the spring merely improves the electrode follow-up against the disturbance by a fixed spring constant, and cannot always perform a desired arbitrary pressure control.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and takes the following specific technical means.

According to a first aspect of the present invention, there is provided an electrode pressurizing device of a resistance welding machine for driving an electrode part to generate a pressing force required for welding, and an actuator using an electric motor as a pressurizing drive source thereof. , An output shaft of the electric motor,
A power transmission mechanism, which is a combination of a lever and / or a link or a pinion, and a gear, is interposed between the electrode portion or a direct acting shaft that supports the secondary arm thereof, and the rotation torque of the motor is changed by the power transmission mechanism. The direct drive of the electrode portion is directly converted. This is effective for performing precise pressure adjustment of C type spot welding guns as well as various spot welding machines.

According to a second aspect of the present invention, there is provided an electrode pressurizing device of a resistance welding machine for driving an electrode part to generate a pressing force necessary for welding, and an actuator using an electric motor as a pressurizing drive source thereof. , On the output shaft of the electric motor,
The secondary arm having the electrode portion is connected to directly convert the rotational torque of the motor into linear drive of the electrode portion. This is effective for rotating the main shafts of two gun arms (secondary arms) such as the X type spot welding gun to perform highly accurate pressure adjustment on the electrodes.

According to a third aspect of the present invention, there is provided an electrode pressurizing device of a resistance welding machine for driving an electrode part to generate a pressing force required for welding, and an actuator using a linear motor as a pressurizing drive source thereof. , A movable part of the linear motor is connected to a linear motion part having the electrode, and a mechanism having a friction coefficient of zero or close to it is interposed between the linear motion part and its guide part, The driving force is directly converted into linear driving of the electrode portion. As a result, by making the direct acting part non-contact or making the coefficient of friction close to zero,
The response speed of the pressing force can be dramatically increased.

According to the first to third aspects of the invention, the structure of the direct-acting secondary arm having a smaller mass than that of the conventional system in which the pressing force is finely controlled for the entire pressurizing mechanism having a large mass. And the motion with a smaller friction coefficient is performed, the response speed is significantly improved. In other words, the ball screw that has been used in the past has a low efficiency in converting a linear movement into a rotation, and therefore it is possible to accurately transmit a change in force and a subtle movement when the welding nugget expands or contracts to the motor shaft. Although not possible, in the present invention, focusing on the fluctuation due to the disturbance of the pressing force such as the friction of the ball screw and stopping the use of the ball screw and the screw nut to bring the friction coefficient close to zero as much as possible, it is possible to perform the positioning control which is easier to control. Highly accurate pressure control is possible because the pressure is adjusted.

Further, by this, the displacement amount in the pressing direction due to the expansion and contraction of the welded portion is fed back sensitively to the linear shaft driven by the motor, and the displacement of the pressurizing mechanism by the servomotor is improved.
The dynamic response of 00HZ can be sufficiently dealt with, the pressurizing operation during the generation of the nugget described above can be precisely followed, and the effect of improving the welding quality can be obtained.

As described above, according to the configuration of the present invention, a power transmission mechanism such as a ball screw and a screw nut is used as compared with the conventional electric spot welding machine in which the positioning mechanism is controlled by the ball screw and the screw nut in the pressurizing mechanism by the electric motor. Instead, the required pressing force can be directly and accurately applied by the pendulum type power transmission mechanism (claims 1 and 2) in which the motor shaft torque is installed between the servo mechanism and the secondary arm. Thus, the response speed can be dramatically improved.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the device of the present invention will be described below with reference to the drawings. In Fig. 1, the servomotor does not use a power transmission mechanism such as a ball screw, a screw nut, or a speed reducer, but a linear motion arm is directly controlled through a power transmission mechanism consisting of a lever or a link to adjust the pressure. 2 is an embodiment of a welding machine according to the present invention. The welding machine will be described on behalf of a desk-top type micro spot welder, but the pressurizing device of various resistance welding machines including a commonly known stationary spot welding machine and spot welding gun is also applicable.

1 to 3, an electric motor 3 is mounted on an upper member 2 of a welding machine body 1, a lever 5 is attached to an output shaft 4 of the electric motor, and a spherical joint 6 is provided at the tip of the lever 5. Electrode section 8 by the linear motion shaft 7 connected by
And / or drive a secondary arm (not shown). The linear shaft 7 is guided by a bearing 9 which is precisely ground. For this bearing, for example, a ball spline having a small friction coefficient is preferable.

A fixed-side electrode portion 10 corresponding to the movable-side electrode portion 8 is fixed to the lower member of the main body, and the movable-side electrode 8 is attached to the object to be welded set on the fixed-side electrode portion 10.
Contact and pressurize.

A specified pressurization energization is performed between the electrodes by a command issued from a control device (not shown) via a secondary conductor 11 and a secondary conductor 12 connected to a welding transformer (not shown), and a constant pressure is applied. It can be opened after the time limit.

Next, FIG. 4 shows another embodiment of the present invention.
A lever 5 is attached to the output shaft 4 of the electric motor 3, and the linear motion shaft 7 is driven at the tip of the lever 5 via a link 13 to apply pressure by the electrode 8. In this case, the pressurizing force is transmitted from the link 13 to the direct drive shaft 7 by the hinge portion 14 of the output shaft of the electric motor. Use a link to prevent rotation of the linear drive shaft.

FIG. 5 shows another embodiment of the present invention. A pinion 15 is provided on the output shaft 4 of the electric motor, and the pinion and the rack 16 provided with the direct drive shaft 7 are meshed with each other.

In FIG. 6, a pinion for an output shaft of an electric motor is provided, a lever 5 is attached to a gear 17 meshed with the pinion 15, and a linear shaft 7 is driven at a tip of the lever 5 through a link 13 to drive an electrode. 8 is applied. In this case as well, the link 13 is used to prevent rotation of the linear motion shaft.

FIG. 8 shows an embodiment in which an air bearing is used as a linear guide for making a friction coefficient close to zero by using a linear motor as an electrode driving source. FIG. 9 is a view on arrow AA. Reference numeral 80 denotes a linear motor which also serves as a welding machine main body 81 and a motor casing, and 82 denotes an air bearing supported by the casing of the linear motor 80, but a ball bush guide may be used instead of this bearing. 83 is a magnet supported in the casing, 8
4 is a movable part inserted between the magnets, and 85 is a linear motion part supported by the movable part 84. Clean air is introduced between the linear motion part 85 and the guide part 87 to move the linear motion part 85. It can be floated from the guide part 87 and moved without contact. 88,89
Is a linear encoder and its linear encoder head for measuring the amount of movement of the linear motion portion on the moving side and the fixed side.

FIG. 10 shows an embodiment in which the present invention is applied to a pressurizing device for an X type spot welding gun. In this case, one secondary arm 19 is directly connected to the output shaft 4 of the electric motor 3 via the span ring 18 without using a ball screw, and the other secondary arm 20 is a gun bracket 21 to which the electric motor 3 is fixed. It is fixed to.

According to this structure, fluctuations of the applied pressure such as friction of the ball screw due to the disturbance can be eliminated, the friction coefficient can be made as close to zero as possible, the mass of the movable portion can be reduced, and the rigidity of the transmission path of the applied pressure can be reduced. Can be raised to reduce deflection. The required pressing force can be applied to the motor shaft torque directly and accurately from the servo mechanism, and the minute displacement in the pressing direction when the welding nugget expands or contracts must be sensitively fed back to the motor output shaft. The robot can intelligently control the response speed, which is important for spot welding.

In the operation of the spot welding machine shown in the embodiment of FIG. 1, first, when a start switch, which is omitted in the drawing, is turned on, the timer of the resistance welding control device starts counting the time limit and the electric motor 3 is activated. The output shaft 4 rotates the lever 5 about a hinge to a predetermined angle, linearly drives the linear shaft 7, and the upper electrode portion 8 is placed on the surface of the workpiece to be set in the lower electrode portion 10 in advance. Contact and start pressurization.

In this case, the movement of the linear motion shaft 7 is operated at a high speed, and in order to soften the impact of the electrode portion 8 on the object to be welded, it is controlled so as to drop at a low speed just before contacting the object to be welded, The number of revolutions of the output shaft 4 is counted by an encoder provided behind the output shaft of the electric motor. When the number of revolutions reaches a preset value, the motor rotation is decelerated, and when the torque sharply increases, the electric motor Switches from speed control to torque control, and the welding current flows according to the energization command from the welding controller after the time when the pressure required for welding is applied between the upper and lower electrodes, and the controller releases the command after a certain time. Is generated, the electric motor is rotated in reverse by the command, and the electrode portion 8 returns to the open position. In this way, one cycle of welding is completed, and the next welding is prepared.

In this way, compared with the conventional system in which the entire pressurizing mechanism having a large mass is pneumatically or hydraulically pressure-adjusted or the servo mechanism is used for delicate pressurizing control, a ball screw, a screw nut, a speed reducer, etc. Except for the servo mechanism, the response speed is greatly improved because the force is adjusted directly by the servo mechanism, and high-precision force control is possible with easy positioning control.

[0029]

As described above, according to the present invention, a lever and / or a link or a pinion and a gear are combined between an electric motor and a direct acting shaft of an electrode as a pressurizing mechanism of a resistance welding machine. Intervening a power transmission mechanism
Since the rotational torque of the motor is directly converted into the linear drive to the electrode portion by this power transmission mechanism,
A linear motor is used as a pressure drive source, and the linear motion guide section uses a mechanism with zero friction force or a mechanism in which the friction force is brought close to zero to drive the electrode section. To provide a structure of a linear motion arm with a smaller mass compared to the conventional method that performs subtle pressure control with pneumatic or hydraulic pressure adjustment or a servo mechanism, and to adjust the pressure with motion with a smaller friction coefficient The response speed is greatly improved. That is, since the pressure control is performed by the positioning control, which is easier to control, with respect to the fluctuation due to the disturbance of the pressure such as the air pressure and the friction of the ball screw, the pressure control can be performed with high accuracy.

On the other hand, as a result, the displacement amount in the pressing direction due to the expansion and contraction of the welded portion is properly fed back to the linear drive shaft driven by the motor, and the dynamic response of 100HZ of the pressurization mechanism driven by the servo motor is sufficiently provided. Can respond,
The pressurizing operation described above can be followed accurately, and the effect of improving welding quality can be obtained. That is, compared with the conventional method in which the pressure is adjusted by air pressure or hydraulic pressure or the servo mechanism is used to adjust the pressing force by the physical elastic coefficient of the tip end side of the secondary arm, a pendulum type power transmission mechanism using an electric motor is used to directly drive the shaft. The direct pressure control can be performed by driving, and the response speed can be greatly improved.

[Brief description of drawings]

FIG. 1 is an overall front view for explaining the principle of a pressure device according to an embodiment of the present invention, in which a power transmission mechanism including a lever and a spherical joint is interposed between an electric motor and a direct acting shaft. Here is an example:

FIG. 2 is a plan view of the device of the present invention.

FIG. 3 is a side view of the device of the present invention.

FIG. 4 is an entire front view for explaining the principle of a pressurizing device according to another embodiment of the present invention, in which a power transmission mechanism including a link is interposed between an electric motor and a direct acting shaft. Indicates.

FIG. 5 is an overall front view for explaining the principle of a pressurizing device according to another embodiment of the present invention, in which a power transmission mechanism including a rack / pinion is interposed between an electric motor and a direct acting shaft. Here is an example.

FIG. 6 is an overall front view for explaining the principle of a pressurizing device according to another embodiment of the present invention, in which power consisting of a rack / pinion, a lever, and a link is provided between an electric motor and a direct acting shaft. An example in which a transmission mechanism is interposed is shown.

FIG. 7 is a schematic diagram showing a case where a pressurizing mechanism of a conventional electric resistance spot welding machine adjusts a pressing force by torque control of a servo motor.

FIG. 8 is an overall front view for explaining the principle of a pressure device according to another embodiment of the present invention, which is an example of the case where a linear motor is used as a drive source.

9 is a view on arrow AA of FIG.

FIG. 10 is an overall front view for explaining the principle of the pressurizing device according to another embodiment of the present invention, in which the motor output shaft is directly connected to the secondary arm of the pressurizing device of the X type spot welding gun. This is an example of connecting and transmitting the electrode driving force.

11 is a plan view of FIG.

[Explanation of symbols]

1 ... Welder body 20 ...
Secondary arm 2 ... Upper member 80 ...
Linear motor 3 ... Electric motor 84 ...
Movable part 4 ... Output shaft 86 ...
Direct acting part 5 ... Lever 87 ...
Guide part 6 ・ ・ ・ ・ Spherical joint 7 ・ ・ ・ ・ ・ ・ Linear shaft 8 ・ ・ ・ ・ Electrode part 9 ・ ・ ・ ・ Bearing 10 ・ ・ ・ ・ Electrode part 11 ・ ・ ・ ・ ・ ・ Secondary conductor 12 ・ ・ ・Secondary conductor 13 ・ ・ ・ ・ Link 14 ・ ・ ・ ・ ・ ・ Hinge part 15 ・ ・ ・ ・ Pinion 16 ・ ・ ・ ・ Rack 17 ・ ・ ・ ・ Gear 19 ・ ・ ・ ・ ・ ・ Secondary arm

Claims (3)

[Claims] 1. An electrode pressurizing device of a resistance welding machine for driving an electrode part to generate a pressurizing force required for welding, wherein an actuator using an electric motor as a pressurizing drive source thereof comprises: A power transmission mechanism, which is a combination of a lever and / or a link or a pinion and a gear, is interposed between the output shaft and the direct acting shaft that supports the electrode portion or the secondary arm thereof, and the motor is driven by the power transmission mechanism. Electrode pressurizing device for resistance welding machine that directly converts the rotating torque of the above into linear drive of the electrode part. 2. An electrode pressurizing device of a resistance welding machine for driving an electrode part to generate a pressurizing force required for welding, wherein an actuator using an electric motor as a pressurizing drive source thereof comprises: An electrode pressurizing device for a resistance welding machine in which a secondary arm having the electrode is connected to an output shaft and the rotational torque of the motor is directly converted into linear drive of the electrode portion. 3. An electrode pressurizing device of a resistance welding machine for driving an electrode part to generate a pressurizing force necessary for welding, wherein an actuator using a linear motor as a pressurizing drive source of the linear motor is used. The movable part is connected to the linear motion part having the electrode, and the driving force of the motor is directly applied to the direct motion part by interposing a mechanism between the linear motion part and the guide part with a friction coefficient of zero or close to it. Electrode pressurizing device of resistance welding machine that converts into linear drive of the part.