JP2001179462A - Electric pressurized resistance welding machine - Google Patents

Abstract

(57) [Summary] [Purpose] To double the opening / closing speed between electrode tips to be spot-welded to shorten welding tact time. The present invention comprises a guide unit G for pressing and driving opposing electrode tips with a single ball screw 2. The ball screw includes a right-hand screw 2a and a left-hand screw 2b, and nuts corresponding to the right-hand and left-hand screws, respectively. The blocks N1 and N2 are incorporated, and the ball screw is driven by an electric motor, whereby the pressing or releasing operation of the opposing electrode tips 5, 6 arranged in each nut block is performed simultaneously by both electrodes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the technical field of metal working machines, and includes stationary spot welders, seam welders,
It includes projection welding machines, spot welding guns for robots, portable spot welding guns, and the like.

In particular, as one example, an electric pressurizing type useful for pressurizing welding by simultaneously driving opposing electrode tips with one motor to generate torque for obtaining a stable pressing force required for welding. It relates to a welding gun (including C type and X type).

[0003]

2. Description of the Related Art Conventionally, an electric pressurizing gun using a linear guide as an electrode pressurizing drive mechanism has been known. An electric pressurized gun of this type incorporates a ball screw into a rolling bearing that slides by circulating a ball bearing on the rail of the linear guide, and drives the ball screw with an electric motor.
As a result, the rolling bearing moves directly on the guide rail to generate a torque between the electrode tips to obtain a pressing force required for welding, thereby performing pressure welding.

As an example, as shown in FIG. 4, a first gun arm 41 having an electrode tip E1 at the tip thereof as shown in FIG.
Is fixed to the linear guide body 40 corresponding to the gun body, and the electrode tip E2 corresponding to the first gun arm.
Is driven by a pressure drive mechanism including a ball screw 43, a screw nut 44, a guide rail 45, and a servomotor M provided on the gun body 40, and a laminated plate (work) is sandwiched between the electrode chips. Pinch it. A spot welding gun has been disclosed in which after applying a sufficient pressing force to spot welding at the pinching position, a welding current is applied to heat and melt to form a nugget and join it (see Japanese Patent Application Laid-Open No. H11-197842 and JP-A-11-197842). Kaihei 10-3434
No. 6).

[0005]

Conventionally, in this type of spot welding gun for robots, one electrode tip is mounted on a fixed-side gun arm 42, whereas only the other electrode tip is movable. It is supported by a gun arm 41 or a pressure drive shaft mounted on a linear guide unit, and presses the movable electrode tip by driving a ball screw mechanism included in the guide unit with an electric motor M.

However, in order to shorten the welding tact, it is necessary to speed up the opening and closing operation of the electrode tip. For this purpose, driving the electrode tip from both sides enables high-speed driving in half the time required in the past. However, to drive two electrodes simultaneously, an extra drive unit including a servomotor must be provided. This increases the structure and weight of the welding gun as a whole and places a large load on the arm of the robot, and if rigidity and speed are required to be increased, the capacity of the power source also increases, and the equipment becomes slimmer and lower in cost. There were still issues to be solved to realize it.

[0007]

Therefore, the present invention has been developed to solve the above-mentioned problem, and employs technical means as shown in FIG. That is, claim 1
According to the invention, a portion corresponding to the welding machine body 1 is constituted by a drive mechanism, and the drive mechanism is unitized to form one guide unit G, and a nut block N included in the guide unit is arranged along a raceway surface. Placed to move,
One ball screw 2 is incorporated in the nut block, and the ball screw is driven by an electric motor M so that the block moves on the raceway surface. In the driving device for generating the torque for obtaining the torque, the one ball screw 2 includes a right-hand thread 2a and a left-hand thread 2b in a thread groove winding direction.
The ball screw includes a nut block N1 for a right-hand thread,
A nut block N2 for a left-handed screw is incorporated, and a gun arm 3, 4 or a member similar thereto is attached to each of the blocks N1, N2, and each of the electrode tips 5, 5 supported by the gun arm. 6 is driven by the electric motor M substantially simultaneously in the pressing or releasing direction from opposite sides.

According to a second aspect of the present invention, the guide unit main body is detachably supported by a gun bracket, and the block is a rolling bearing that linearly moves by rolling a ball bearing along a rail of the guide unit. There is a condition.

According to a third aspect of the present invention, the winding direction of the right-hand thread and the left-hand thread of the ball screw is equal in pitch, and the gap between the electrode tips when pressed and released is driven at a constant speed. It is a condition.

Further, according to a fourth aspect of the present invention, the winding direction of the right-hand thread and the left-hand thread of the ball screw has a variable pitch, and the gap between the electrode tips when pressed and released is driven at a variable speed or a variable stroke. On the condition that

[0011]

According to the first and third aspects of the present invention, the two electrode tips can be driven from one side of the workpiece by one driving source by using the left and right screws for one ball screw in the electrode pressure driving device. It is possible to generate a torque to obtain a stable pressing force by driving at almost the same speed at the same speed, and at the same time, the same pressure is applied. Amount, gun arm deflection,
This eliminates the need for an equalizing mechanism for compensating the work-up of the workpiece overlap, load pressure, etc., and the equalizing operation on the robot side, so that the equalizing auxiliary equipment can be cut and the shortening of the welding tact time can be doubled. it can.

According to the second aspect of the present invention, the arm is mounted on the gun bracket only by attaching the arm common to the left and right to the ready-made linear guide unit, so that the structural design becomes compact and the assembling accuracy is reduced. Is improved.

According to the fourth aspect of the present invention, by changing the pitch of the right and left threads of the driving ball screw, the movement of the gun arms on both sides when the electrode is released from the pressure, for example, the movement of one electrode and the other electrode. The change of the moving speed and / or the change of the large and small strokes can be controlled simultaneously by one motor.

In this case, one of the electrodes can be moved at a high speed, and the other electrode can be driven at a low speed. In addition to the high and low speed strokes between the electrodes, the above-mentioned equalizing control on the robot side is synchronized with the electrode positioning and positioning. Welding speed can be doubled.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a front view showing a specific structure of an electric pressure welding gun showing a most preferred example for carrying out the present invention. FIG. 2 is a view taken in the direction of the arrow A in FIG.

In this embodiment, a right-hand screw and a left-hand screw are provided on one driving ball screw, and two electrode tips are simultaneously operated by the output of one electric motor. The purpose is to reduce the welding tact time by half.

In the drawing, a drive mechanism uses a unitized linear guide G, the unit itself is a gun body, and a ball screw 2 is a nut that moves along a ball raceway surface (including a groove) of the guide unit. Built in blocks.

The ball screw 2 has one right-hand screw 2a and one left-hand screw 2b. The ball screw 2 incorporates a nut block N1 for a right-hand thread and a nut block N2 for a left-hand thread. Opposing gun arms 3 and 4 are attached to the blocks N1 and N2 by bolts B1, and opposing electrode tips 5 and 6 are attached to tips of the gun arms 3 and 4, respectively.

According to this embodiment, one electric motor M
By rotating one ball screw 2, the work can be simultaneously clamped from the left and right between the electrode tips 5 and 6, and pressure welding can be performed, thereby shortening the welding tact time.

The welding gun 1 of the present invention is mounted on an industrial robot. A gun bracket 7 for supporting the welding gun is supported by a wrist shaft at the tip of a robot arm. As shown in FIG. 3, the base 8 of the guide unit G is detachably attached to the gun bracket 7 with bolts.

The base 8 has a rail body 1 having a concave cross section.
0 is detachably attached by bolts. A ball bearing 12 is provided in the concave groove of the rail body 10.
The ball raceway surface 9 (including the groove) on which the circulates and rolls is formed in a line shape while maintaining a precise parallelism.

A bearing plate 11 is fixed to both ends of the base of the guide unit G, a ball screw 2 is supported on the bearing plate 11, and is disposed in a concave groove of the rail body 10. The ball screw 2 incorporates a linear motion rolling bearing N (nut block).

The bearing N moves along the ball raceway surface 9 on the rail by rotating the ball screw 2. On the bearing N, R / L-side common gun arms 3 and 4 having electrode tips are detachably attached by bolts B1.

The drive unit D includes a servo motor M for rotating and driving the ball screw 2 and a gear 13 fixed to one end of the ball screw 2 by the output of the servo motor M.
And a gear 14 fixed to the rotating shaft 16 of the servomotor M
The gears 13 and 14 are connected to each other via a power transmission mechanism 15 such as a timing belt, a gear, and a chain. The ball screw is driven to rotate by the torque of the motor. Further, as shown in the drawing, this drive mechanism can be directly driven by directly connecting a servo motor to the speed reducer without using the power transmission mechanism 15 or the like.

The motor M is not limited to an AC motor, a DC motor or the like, but includes other various motors. In this case, the drive unit D is arranged so as to be turned back below the base 17, thereby avoiding interference with the outside and enabling a compact structure design.

As shown in FIG. 1, the welding transformer T is arranged between the two plates of the gun bracket 7 and is fixed by bolts B2.

Each of the output terminals Ta and Tb of the welding transformer T has a secondary conductor (a bus bar, a movable copper plate, etc.) for forming a current path between the right and left gun arms 3 and 4 between the positive electrode and the negative electrode.
18 and 19 are connected.

The hitting position is previously taught, the robot reproduces the recorded welding operation, and moves the welding gun to the work set on the work jig. In this case, the electrode tips 5 and 6 stop at the opened position, the workpiece W is inserted between the electrode tips 5 and 6 by the operation of the robot, and the welding point is positioned between the left and right electrode tips 5 and 6. Is done.

After the welding gun 1 is positioned on the work, the servo motor M of the drive unit D operates according to a command from the robot controller, and the ball screw 2 is rotated by the motor torque. The rolling bearing moves, the electrode tip simultaneously presses the work hitting position, and a servo motor M is placed between the electrode tips.
Then, a torque for the pressing force required for welding is generated, and a predetermined amount of welding current is supplied to perform spot welding.

Thus, when welding is completed, the servo motor M rotates in the reverse direction, the bearing moves in the left-right direction, and the welding position is opened.

A method for controlling the positioning and the moving speed of the electrode tip when the electrode tip is moved by pressing or opening is, for example, a method in which the motor M is provided with a position sensor such as an encoder together with a speed sensor such as a tachometer. The number of rotations of the output shaft of the motor or the ball screw or the ball nut is converted into the number of pulses by an encoder, and the number of pulses is counted.
When the counted number of pulses reaches a set value corresponding to the moving distance of the electrode tip, the motor rotation is controlled at a timing to perform positioning.

The moving speed is obtained by feeding back a signal from the tachogenerator, calculating the difference between the speed and the position of the electrode, and accelerating and / or decelerating the electrode to a predetermined speed to move the electrode to the workpiece welding position. .

The pressing force between the electrode tips is detected from the armature current of the motor at the time of pressurization and is fed back to control the pressing force.

As another embodiment, when the moving speed of both electrode tips is simultaneously changed by one motor, or the stroke amount of both electrode tips is changed to a large stroke and a small stroke, or one motor is used. In order to set the moving order of the pressure electrode tip by contacting one electrode in advance with the workpiece, it is possible to change the pitch in the winding direction of the screw groove of the right-hand screw and the left-hand screw of the ball screw. Become.

Accordingly, the electrode moving speed, the opening stroke amount, and the electrode moving order that comes into contact with the workpiece in advance in accordance with the thickness, shape or rigidity of the workpiece, the workpiece interference problem, etc., are simultaneously controlled by one electric motor, and are stabilized. Pressing torque can be generated between the electrodes.

[0036]

As described above, according to the first and third aspects of the present invention, the right and left screws are driven by one electric motor by using one left and right screw for the electrode pressure driving device. Thus, the opposing electrode tips can be driven in the pressing direction or the opening direction at substantially the same speed at the same speed.

In this way, not only is it possible to obtain a stable pressing force as if picking up the electrode from both sides of the work, but also, compared to the conventional electric press drive mechanism, the amount of electrode wear, the amount of deflection of the gun arm, the work overlapping portion This eliminates the need for an equalizing mechanism or a robotic equalizing operation to correct the load pressure, etc., thereby reducing the need for ancillary equipment, doubling the speed of opening and closing operations between electrode tips, and shortening the welding tact time. Can be dramatically reduced.

Further, according to the present invention, the assembly structure of the welding gun is made up of standard unit parts. In particular, the left and right gun arms can be shared, the design cost can be reduced, and the assembly accuracy can be reduced. Weight reduction becomes possible.

Next, according to the second aspect of the present invention, since the ready-made linear guide unit is supported by the gun bracket, the structural design becomes compact and the assembling accuracy is improved.

According to the fourth aspect of the invention, by changing the pitch in the winding direction of the thread groove of the right-hand thread and the left-hand thread, the movement of the gun arms on both sides when the electrode is pressed and released, that is, the moving speed is high and low and / or large and small. The stroke amount can be controlled by one motor at the same time.

Accordingly, the order of movement of the electrode tips which comes into contact with the workpiece in advance can be set, so that a stable pressurizing torque can be set according to the thickness of the workpiece, the material or the rigidity of the workpiece, and other welding conditions. It can be generated between the electrodes and the welding quality can be improved.

Also, the electrode opening stroke can be selected directly and freely, and correction and positioning control of the electrode displacement due to the wear of the electrode tip and the deflection of the gun arm become precise and easy, so that the welding condition width is reduced. Expanding. Furthermore, by synchronizing the equalizing operation by the robot side in addition to the high-speed and low-speed strokes between the electrodes, the electrode positioning and the welding speed can be doubled.

[Brief description of the drawings]

FIG. 1 is a front view of an electric pressurized spot welding gun showing a most preferred embodiment for carrying out the present invention.

FIG. 2 is a view as viewed from an arrow A in FIG. 1;

FIG. 3 is a sectional view showing an embodiment of a linear guide unit.

FIG. 4 is a front view showing an embodiment of the conventional device.

FIG. 5 is a front view for explaining the operation of the device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric pressurization resistance welding machine (welding gun) 2 Ball screw 3 Gun arm 4 Gun arm 5 Electrode tip 6 Electrode tip 7 Gun bracket 8 Base 9 Ball raceway surface 10 Rail main body 11 Bearing plate 12 Ball bearing 13 Gear 14 Gear 15 Power transmission mechanism (Timing belt) 16 Rotary axis 17 Base G Guide unit D Drive unit M Servo motor N Nut block T Welding transformer

Claims (4)

[Claims] A driving mechanism for driving an electrode tip constitutes a main body of the welding machine, and the driving mechanism is unitized to constitute one guide unit, and a nut block included in the guide unit is provided. A ball screw is incorporated in the nut block, and the ball screw is driven by an electric motor, so that the block moves on the track surface to move the electrode tip. In a pressure driving device that generates torque for obtaining a pressing force required for welding between the one ball screw, the winding direction of the thread groove is composed of a right-handed screw and a left-handed screw. A nut block N1 for a right-hand thread and a nut block N2 for a left-hand thread are incorporated respectively, and each of the blocks has a gun arm facing it or Members have attached to,
An electric pressurized resistance welding machine provided that each electrode tip supported by the gun arm is driven by the electric motor from opposite sides in a pressing or opening direction substantially simultaneously. 2. The guide unit according to claim 1, wherein the unit body is detachably supported by a gun bracket, and the block is a rolling bearing that linearly moves by rolling a ball bearing along a rail of the guide unit. The electric pressurized resistance welding machine according to claim 1. 3. The condition that the winding directions of the right-hand thread and the left-hand thread of the ball screw are equal in pitch, and that the gap between the electrode tips when pressed and opened is driven at a constant speed. 1
Or 2) an electric pressurized resistance welding machine. 4. The condition that the winding direction of the thread groove of the right-hand thread and the left-hand thread of the ball screw is a variable pitch, and that the gap between the electrode tips when pressed and released is driven at a variable speed or a variable stroke. The electric pressurized resistance welding machine according to any one of claims 1 to 3.