JP2000117455A - Resistance welding machine and its assembly method - Google Patents

Abstract

(57) [Summary] [Purpose] Based on the electrode drive mechanism of a resistance welding machine using a linear guide, the purpose is to make it possible to easily rearrange parts standardized for each function according to the variation of the welding machine. And An arm 2 having one electrode tip 3, a drive unit 4 including a linear guide for driving the other electrode tip 5 corresponding to the electrode tip, a gun bracket 13 for supporting the welding machine by a robot, and / or Or a welding unit 7 including a welding transformer T for supplying a secondary current to the welding machine, and a common base 6 for each unit.
Alternatively, each rail is made detachable with reference to the rail body 8 included in the linear guide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the field of electric resistance welding machines, and more particularly to the classes of spot welding guns (including C type and X type), stationary spot welding machines, projection welding machines and resistance seam welding machines. More specifically, a linear guide is used for a press-type guide mechanism that opens and closes the movable electrode tip, and various unit parts that are unified for each function of the welding machine are combined into one common base or linear unit. The present invention relates to a resistance welding machine configured to be assembled based on a rail main body of a guide and an assembling method thereof.

[0002]

2. Description of the Related Art Regarding a conventional spot welding gun, a spot welding gun using a linear guide system for a drive mechanism of a movable electrode tip is known. For example, this is the invention described in the specification and drawings of Japanese Patent Application Laid-Open No. 10-34346.

[0003] A conventional welding gun of this type is a pressurizing device comprising a ball screw, a sliding nut, a linear guide and a servomotor provided in a gun body with a second gun arm corresponding to a first gun arm fixed to the gun body. It is driven along the gun body by the drive mechanism, sandwiches the laminated plate (work) between the two electrode tips, applies the necessary pressure for welding, and applies a welding current to heat and join the local part. .

According to this type of conventional apparatus, the number of parts that interfere with each other is reduced as compared with conventional conventional welding guns, so that there are fewer restrictions on the movement path and welding position, and the size and shape of the workpiece can be reduced. Accordingly, the gun arm can be freely changed every time the stroke is different.

[0005]

However, since this type of conventional spot welding gun has a pressure drive mechanism integrally provided inside the gun body, a welding transformer and an equalizing device are integrated with the welding gun. However, it is necessary to design a new structure so that these units can be mounted, and it is difficult to assemble or change the unit components for each function of the welding machine. Was.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems. According to a first aspect of the present invention, there is provided a method for forming a component in which a resistance welding machine is unitized for each function based on one common base. In a method of configuring the welding machine by assembling, an arm having one electrode tip, a driving unit for driving the other electrode tip corresponding to the electrode tip, a gun bracket for supporting the welding machine on a robot, and And / or a welding unit including a welding transformer for supplying a secondary current to the welding machine can be attached and detached on the basis of one common base for each unit.

According to the method of claim 1, a gun arm, a welding transformer and a drive unit are provided on the basis of one common base rather than having a pressure drive mechanism integrally provided inside the gun body as compared with the conventional spot welding gun. Since the units and the like can be attached and detached, a new structural design is not required, and it is easy to assemble or reassemble unit parts standardized for each function according to the intended use.

Next, in addition to the above-mentioned units, an equalizing unit for performing an electrode tip positioning operation or an electrode moving amount correction operation of the welding machine can be attached and detached based on the common base. It is a condition.

According to the device of the second aspect, the equalizing unit can be easily attached and detached according to the variation of the welding machine in the same manner as the unit components.

A third aspect of the present invention provides an arm having one electrode tip, a drive unit for driving the other electrode tip corresponding to the electrode tip, a gun bracket for supporting the welding machine by a robot, and / or Alternatively, an electric pressurized resistance provided that a welding unit including a welding transformer for supplying a secondary current to the welding machine is configured to be attached to and detached from one common base for each unit. In the welding machine, the drive unit has a nut block incorporated in a ball screw provided in the unit body, the other electrode tip is supported on the nut side, and the ball screw is rotated by an electric motor, so that the nut is rotated. The block is linearly moved, and the ball bearing housed in the nut block is provided on the raceway surface provided in the direction in which the block moves. Configured to guide the block by rolling the ring.

According to the third aspect of the invention, the following items can be satisfied. Easy to assemble. Since the rigidity is high and the weight can be reduced, followability during welding is improved. Easy assembly and maintenance. When the guide center and the electrode pressing center are at the offset positions, the electrode rotation preventing mechanism required when the center is at the offset position is not required. Since the drive unit can use commercially available standard parts that can be mass-produced, the cost can be significantly reduced.

According to the third aspect of the present invention, since both sides of the common base are used as mounting reference planes, the equalizing unit, the gun arm,
It is easy to attach and remove the welding transformer and replace it for each standard unit, and it is possible to manufacture a lightweight and compact.

Further, the invention of claim 4 is characterized in that the equalizing unit includes an air circuit for canceling the weight load of the welding machine.

Next, a fifth aspect of the present invention is characterized in that the air circuit of the equalizing unit includes a balancing cylinder for performing various operations for obtaining a weight balance of the welding machine.

According to the fourth and fifth aspects of the present invention, the equalizing operation and the balancing operation are not performed by the program on the robot side, but are fixed by using an independent equalizing mechanism and one pneumatic circuit for balancing. Even without adding the number of robot control axes or software for soft touching or approaching the side electrode chip to the work, only a single axis servo spot gun is added to the existing robot axes, so the structure is simple. Equipment costs can be reduced.

According to a sixth aspect of the present invention, the common base member is made of an aluminum-based material.

According to the sixth aspect of the present invention, the weight reduction on the robot list can be reduced by promoting the weight reduction of the common base.

According to a seventh aspect of the present invention, a ball screw is arranged along a rail body, a nut block is incorporated in the ball screw, and a gun arm having one electrode tip is supported on the nut block side. When the ball screw is rotated by an electric motor, the nut block moves linearly, and a ball bearing housed in the nut block rolls on a raceway surface provided in the direction of the linear movement to guide the nut block. A linear guide electrode drive unit, whereby a torque for pressing force is generated on the electrode tip, wherein the point holder having the other electrode tip corresponding to the electrode tip or the other gun arm including the holder is provided; A gun bracket and / or welding to support the drive unit on the robot Nsu and is, provided that removably mounted the rail body to a reference.

[0019] This makes it possible to attach the gun arm, gun bracket, equalizing unit, welding transformer, and the like to each unit based on the rail body as compared with the conventional system in which the drive mechanism is integrally provided inside the gun body. This eliminates the need for a new design of the mounted robot gun, and in this case, the above-mentioned common base can be omitted, so that the size and weight can be reduced.

The invention according to claim 8 is based on the condition that the gun arm is directly connected to the output terminal of the welding transformer, thereby reducing the number of parts and the number of assembling steps by omitting at least one secondary bar. And promote lighter weight.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a side view showing a first embodiment in which the method of the present invention is applied to a C-type servo spot welding gun. FIG. 2 is a view taken in the direction of the arrow Z in FIG. FIG. 3 is a view taken in the direction of the arrow A in FIG. FIG. 4 is a plan view showing an example of the drive unit. FIG. 5 is a view taken in the direction of the arrow Y in FIG.

In the drawing, reference numeral 1 denotes a resistance welding machine, which is a so-called servo spot gun for a robot using a servo motor M as an electrode actuator. Reference numeral 2 denotes a C-shaped gun arm to which one electrode tip 3 is fixed at the tip. Reference numeral 4 denotes a drive unit for driving the other electrode chip 5 corresponding to the electrode chip 3. Reference numeral 6 denotes a common base on which various unit parts are assembled, and is made of an aluminum-based material in consideration of weight reduction.

Reference numeral 7 denotes a welding unit. This unit has a welding transformer T for supplying a secondary current to the welding machine.
And bus bars B1 and B constituting a secondary circuit connected to the output terminals E1 and E2 of the transformer.
2 and a shunt F connected to the bus bar B3 and the movable point holder H.

The drive unit 4 may be a commercially available one. For example, as shown in FIGS. 4 and 5, the rail main body 8 has a concave cross-sectional shape, and both sides of the rail main body have a concave cross-sectional shape. The linear guide rails 9 are arranged in parallel to the guide rails, and a track surface U having a guide groove is formed inside the guide rails. The rail body 8 of this unit has a bolt b on the common base 6
1, a mounting surface d is formed.

A nut block N is incorporated in a ball screw 10 provided along a raceway surface U in a groove having a concave cross section of the rail main body 8. The nut block N is formed with a mounting surface c of the gun arm 2.

The ball body 10 includes the rail main body 8.
Output shaft 1 of electric motor M fixed to housing 11
2 are directly connected. In order to avoid the interference condition between the work and the electric motor as shown in FIG. 4, the electric motor M is folded back on the side surface of the rail body 8 and is connected via an arbitrary power transmission mechanism 16 such as a gear, a belt or a chain. It may be connected to the ball screw 10.

When the ball screw 10 is rotated by the power of the motor M, the nut block N moves directly,
The other electrode tip 5 supported on the nut side is
It approaches or separates from the electrode tip 3 on the one fixed arm side, and welding pressure or electrode opening is performed by this operation.

In this case, the drive unit 4 has a drive unit for pressurizing the gun configured as one drive unit. The specific configuration thereof is, for example, as shown in the sectional view of FIG. By rolling a plurality of ball bearings br housed inside N sequentially,
The nut block N is guided along the raceway surface provided in the direction of the linear motion.

On the common base 6, a gun arm 2 is fixed to one of the two surfaces by a plurality of bolts b2 via an insulating plate, and a gun bracket 13 having a robot mounting surface is provided on the same surface. And is fixed by a plurality of bolts b3. A welding transformer T is fixed to the gun bracket 13 with a plurality of bolts b4.

The drive unit 4 is fixed to one surface of the common base 6 on the opposite side by a plurality of bolts b1. A point holder H is fixed to the nut block N of the drive unit 4 with a plurality of bolts b5, and one end of the electrode tip 5 is supported at the tip.

A cover (1 in FIG. 3) is mounted on the rail main body of the drive unit in a direction in which the nut block N moves directly.
7) is provided to protect the raceway surface and the ball screw from the adhesion of foreign substances (spatter, water, oil, dust, etc. generated during welding).

The cover 17 is arranged along the longitudinal direction of the rail body so as to cover the rail, and
Both ends of the cover 17 are fixed to the housing on both sides of the cover 17.

A cover guide groove 21 is formed in the nut block N so that the cover 17 does not interfere when the nut block moves along the rail.
That is, the nut block N can move without any trouble as the cover plate 17 passes through the cover guide groove 21. This cover may be bellows.

(Second Embodiment) FIG. 6 shows a second embodiment in which the method of the present invention is applied to the above-mentioned conventional spot welding gun for an X type robot.

In this case, a movable gun arm 15 corresponding to the fixed gun arm 14 fixed to the gun body is provided with an electrode drive comprising a ball screw 10, a nut block N, a linear guide rail 9 and a servo motor M provided on the rail body. This unit is driven by a unit. This point is common to the conventional welding gun. However, the difference according to the present invention is that by using the common base 6, a welding transformer, an equalizing unit, etc. can be welded by function in addition to the gun arm and the driving unit. The point is that attachment and detachment are facilitated according to conditions or work interference conditions.

According to the assembling method in this case, the common base 6 has a substantially U-shaped cross section, and a fixed-side gun arm 14 is provided on one side of the lower surface of the common base 6 via an insulating plate. The rail body 8 of the drive unit 4 is fixed to the same surface by a plurality of bolts b1. The movable gun arm 15 is fixed to the nut block N of the drive unit 4 by bolts (not shown).

The gun bracket 13 is fixed by a plurality of bolts b3 via an insulating plate with reference to both side plates of the common base, and the welding transformer T is firmly fixed to the gun bracket 13 by a plurality of bolts b4.

In the drive unit 4 fixed to the common base 6, the nut block N is incorporated in the linear guide rail (9 in FIGS. 4 and 5) and the ball screw 10 as shown in the above embodiment. I have.

The nut block N is constituted by a linear motion unit having a rolling element such as a sliding element or a ball bearing br incorporated in a groove formed in the linear guide.

In this guide unit, when the ball screw 10 is rotated by the electric motor M, a plurality of ball bearings br roll on the raceway surface U or the groove of the linear guide rail 9 in order, so that the nut block N moves. The movable gun arm 15 is opened and closed by the movement of the nut block N.

(Third Embodiment) Next, FIG. 7 shows a third embodiment in which the equalizing unit 18 is attached to the welding machine of the present invention.
The following shows an example. FIG. 8 is a view taken in the direction of the arrow X in FIG. 7, and the two-dot chain line shows the arrangement of the electric motor M folded back to the side surface of the rail body as shown in FIG.

In this case, the equalizing unit 18 is provided with two parallel guide rods 1 at predetermined positions on the common base 6.
Both ends of the guide rod 9a and the guide rod 19b are fixed by a rod support plate 13b and a rod support plate 13c fixed to a transformer fixing plate 13a of the gun bracket 13.

The guide rods 19a and 19b pass through bearings incorporated in the housings 22a and 22b which are integrally or mechanically detachably mounted on the common base 6 by bolting or the like. It is slidably supported.

The equalizing unit 18 has a balancing cylinder 20 in which a cylinder body is fixed to a gun bracket 13, and a piston rod 21 of this cylinder is connected to a housing, so that a weight balance effect of the gun body to the cylinder is obtained. The entire pneumatic gun is floated to absorb the reaction force when the movable electrode tip presses the work by the pneumatic circuit to obtain the work, and the structure prevents the work from being deformed and distorted.

In the drawings of the present invention, the configuration example of the pneumatic circuit has been omitted.
The operation side pneumatic circuit and the return side pneumatic circuit are provided with solenoid valves capable of various operations such as increasing and decreasing the internal pressure and / or switching direction, and air is supplied in the direction to cancel most of the weight load of the welding gun. It is supplied.

For example, fluid pressure adjustment to the cylinder is performed by switching the solenoid valve ON and OFF by an external signal in a direction in which a weight balance is obtained according to a change in the gun posture by an electropneumatic proportional valve or the like. It is done automatically.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described with reference to the following drawings. FIG. 9 is a plan view of the device of the present invention. FIG. 10 is a side view of the entire apparatus. FIG.
Is a view on arrow Q. FIG. FIG. 12 is a view as seen from the arrow R in FIG.
The reference numerals in the drawings denote the same functional parts as the constituent parts shown in the above-described embodiments (FIGS. 1 to 8), and the details thereof are omitted.

In the welding gun shown in the above-mentioned drawings, an electric motor M is used as a drive source of the electrode tip 5. One electrode tip 3 is fixed to the tip of a C-shaped gun arm 2.
In the drive unit 4 for driving the other electrode tip 5 corresponding to the electrode tip 3, the gun arm 2 and the gun bracket 13 are directly attached to the rail body 8 by a plurality of bolts b2 and bolts b3 via an insulating plate. Can be In this case, the gun arm 2 is
It may be attached directly to the side in an insulated form.

A nut block N is incorporated in a ball screw 10 provided on the rail body along the raceway surface. The other electrode tip 5 is provided on the nut block.
(For example, 15 in FIG. 6) or the point holder H is directly attached by a plurality of bolts b5.

A bus bar B3 is integrally formed on the point holder H so as to protrude from the point holder body, and is connected to an output terminal E1 of a welding transformer T for supplying a secondary current to the welding machine. A shunt F having flexibility corresponding to the linear movement of the nut block is connected between B1 and the bull bar 3.

The ball screw 10 is connected via a coupling 22 to an output shaft of an electric motor M fixed to a housing 11 on one side of the rail body 8. As the electric motor M, a servomotor, a motor with a speed reducer, and the like are generally used.

In this embodiment, the case where the output shaft of the servo motor is directly connected to the ball screw 10 has been described. However, if the electric motor M is elongated backward as described above, as shown in FIG. It is folded back and connected to the side.

A plurality of ball bearings br are housed inside the nut block N, and the plurality of ball bearings br are rolled along the track surface of the rail body 8 in order.
The nut block N is guided in the direction of the linear motion.

In the present embodiment, instead of the cover 17 of the above-described embodiment, a box-type which can be opened and closed to surround the entire sliding portion such as a track surface and a ball screw above the opening of the rail body 8. A cover casing 23 is provided. Although not shown in the drawing, the casing 23 is provided with an opening or an escape groove for avoiding interference with movable parts such as the bus bar B3, the electrode tip 5 and the point holder H which protrude outside the cover. The drive unit can be protected from foreign matter generated during welding, for example, spatter, water, oil, dust, and the like, by containing the sliding portion in the cover casing 23.

In the welding gun of this embodiment, the nut block N is moved directly by rotating the ball screw 10 by the power of the electric motor M as described above, and the other of the nut blocks N supported on the nut side. The electrode tip 5 approaches or separates from the electrode tip 3 on one fixed arm side,
With this operation, welding pressure or release is performed.

The operation of the present invention will be described below with reference to FIG. Control elements such as movement and positioning of the welding gun between welding spots, gun opening amount and acceleration / deceleration are taught in advance by a robot controller, and spot welding is performed by its reproduction operation.

When the welding gun moves to the welding point by the robot operation and the point is inserted between the electrode tips,
When the electric motor M is operated by the command of the robot controller and the ball screw 10 is rotated, the nut block N moves linearly along the linear guide, and a work is placed between the movable-side electrode tip and the fixed-side electrode tip. The required pressure is applied for pinch welding, a welding current is passed between the electrodes, and the welding point is heated and joined.

The welding operation is continuously performed for each welding point one after another by the robot program control. During this time, the robot operation and the electrode opening / closing operation of the welding gun are performed by synchronous control of the axis on the robot side and one axis on the gun side. It is performed efficiently with short welding tact time.

When the specifications such as the maximum pressing force, the size of the rolling roller and the maximum opening stroke are different due to changes in the work material, plate thickness or work shape, size, welding position, etc. In response to this, units of different shapes, such as the shape and size of gun arms and / or point holders, drive units (including selection of electric motor capacities), and welding units, etc., are re-arranged from multiple units to the desired units. As a result, a welding gun can be assembled according to welding conditions and work interference conditions.

[0060]

As described above, according to the method of the first aspect of the present invention, as compared with the conventional resistance spot welding gun, a pressure driving mechanism is not provided integrally inside the gun body. , Standardized unit parts such as gun arm, drive unit, welding transformer, equalizing device, gun bracket, etc. can be attached and detached based on one common base. Recombination becomes easy.

According to the device of the first aspect of the present invention, it is possible to assemble various standard units with existing components such as a drive unit on the basis of a common base.

According to the second aspect, since the equalizing unit can also be mounted on the basis of the common base, it can be freely mounted and dismounted as required, similarly to the gun arm, welding transformer, etc., and can be manufactured to be lightweight and compact. be able to.

Next, according to the drive unit of the third aspect, all of the following items can be satisfied. Easy to assemble. Since the rigidity is high and the weight can be reduced, followability during welding is improved. Assembly adjustment and maintenance work become easy. When the guide center and the electrode pressing center are at the offset positions, the electrode rotation preventing mechanism required when the center is at the offset position is not required. Cost reduction can be achieved because commercial standard products that can be mass-produced can be used.

Next, according to the fourth and fifth aspects of the present invention, the equalizing operation and the balancing operation are not performed by the program on the robot side, but by using an independent equalizing mechanism and a single pneumatic circuit for balancing. Air pressure is always applied to the balancing cylinder in a direction that balances the weight load of the entire welding machine, and the existing number of robot control axes and software for soft touching or approaching the fixed electrode tip to the workpiece is not required. By simply adding a one-axis servo spot gun to the number of robot axes, the structure is simple and the equipment cost can be reduced.

[0065] Thus, compared to the conventional method in which the replacement time of the electrode tip and the wear amount of the electrode tip are directly controlled and the feed amount of the electrode tip is corrected in accordance with the wear of the electrode tip, the robot can be controlled according to the wear amount. It is possible to cope with the existing number of robot axes only by adding an independent one-axis servo spot gun without using a means for driving the arm to allow the electrode tip to contact the work.

Therefore, the equalizing operation is not driven on the robot side, but simply uses the pneumatic circuit of the conventional equalizing cylinder in the existing six-axis robot, so that the structure is simple and the equipment cost can be reduced. Can be.

According to the sixth aspect of the invention, by using the aluminum-based common base, the weight can be reduced, the weight load on the robot wrist can be further reduced, and the life of the wrist can be extended.

According to the seventh aspect of the invention, the conventional C
Type and X type electric spot welding gun,
Instead of incorporating the drive unit integrally in the gun body, the gun arm, welding transformer, gun bracket, equalizing unit, etc. can be replaced for each function-based unit based on the rail body of the linear guide unit.

This eliminates the need for a new structural design for a robot gun equipped with a welding transformer.
The common base can be omitted, and the structure can be simplified and the weight can be further reduced.

According to the eighth aspect of the present invention, by eliminating the secondary bar between the gun arm and the output terminal of the welding transformer in this type of welding gun, the number of parts and the number of assembling steps and the weight can be reduced. I do.

[Brief description of the drawings]

FIG. 1 is a side view showing the outer shape of a welding gun according to a first embodiment when the method of the present invention is applied to a C-type resistance spot welding gun.

FIG. 2 is a view as seen in the direction of the arrow Z in FIG. 1;

FIG. 3 is a view taken in the direction of the arrow A in FIG. 1;

FIG. 4 is a plan view showing an example of a linear guide actuator including a drive unit according to the present invention.

FIG. 5 is an enlarged view taken in the direction of arrow Y in FIG. 4;

FIG. 6 is a side view showing a second embodiment when the method of the present invention is applied to another X-type spot welding gun.

FIG. 7 is a side view showing a third embodiment when an equalizing unit is provided in the apparatus of the present invention.

8 is a view as viewed in the direction of the arrow X in FIG. 7;

FIG. 9 is a plan view showing a fourth embodiment of the device of the present invention.

FIG. 10 is a side view of the entire apparatus of the present invention.

FIG. 11 is a view as viewed in the direction of the arrow Q in FIG. 10;

FIG. 12 is a view as seen from the arrow R in FIG. 10;

[Explanation of symbols]

1 ... resistance welding machine (servo spot welding gun for robot) 2 ... gun arm 3 ... electrode tip 4 ... drive unit 5 ... electrode tip 6 ... common base 7 Welding unit 8 Rail body 9 Linear guide rail 10 Ball screw 11 Housing 12 Output shaft 13 Gun bracket 14 ···························································································· Point holder M: Electric motor N: Nut block br: Ball bearing

Claims (8)

[Claims] An arm having one electrode tip of a resistance welding machine, a drive unit for driving the other electrode tip corresponding to the electrode tip, a gun bracket for supporting the welding machine on a robot, and / or the welding. A method for assembling a resistance welding machine on the condition that a welding unit including a welding transformer for supplying a secondary current to the machine can be attached and detached on the basis of one common base for each unit. 2. An equalizing unit for performing an electrode tip positioning operation or an electrode moving amount correcting operation of the welding machine in addition to the units, provided that the equalizing unit can be attached and detached with respect to the common base. How to assemble the resistance welding machine. 3. An arm having one electrode tip, a drive unit for driving the other electrode tip corresponding to the electrode tip, a gun bracket for supporting the welding machine on a robot and / or a secondary for the welding machine. In a resistance welding machine provided that a welding unit including a welding transformer for passing a current is configured to be attached to and detached from a common base for each unit, the drive unit is the unit. A nut block is incorporated in a ball screw provided in the main body, and the other electrode tip is supported on the nut side. By rotating the ball screw by an electric motor, the nut block is linearly moved. The ball bearing housed in the nut block is rolled on the raceway surface provided in the An electric pressurized resistance welding machine characterized by being configured to guide. 4. The electric pressurized resistance welding machine according to claim 3, wherein said equalizing unit includes an air circuit for canceling a weight load of said welding machine. 5. The air circuit according to claim 4, wherein the air circuit includes a balancing cylinder for performing various operations such as increasing and decreasing air pressure and / or switching direction to obtain a weight balance of the welding machine. Electric pressurized resistance welding machine. 6. The electric pressurized resistance welding machine according to claim 3, wherein the common base member is made of an aluminum-based material. 7. A ball screw is disposed along a rail body, a nut block is incorporated in the ball screw, a gun arm having one electrode tip is supported on the nut block side, and the ball screw is rotated by an electric motor. As a result, the nut block linearly moves, and the ball bearing housed in the nut block rolls on the raceway surface provided in the direction of the linear movement to guide the nut block, whereby the electrode tip In a linear guide type electrode drive unit in which a torque for applying pressure is generated, a point holder having the other electrode tip corresponding to the electrode tip or another gun arm including the holder, and the drive unit supported by a robot A gun bracket and / or welding transformer for An electric pressurized spot welder that must be detachably mounted on the body. 8. The electric pressurized spot welding machine according to claim 7, wherein the gun arm is directly connected to an output terminal of the welding transformer.