JP2002120074A - Resistance spot welding machine and electrode drive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a weight of a portable type electrically operated spot gun and to improve operability. SOLUTION: The apparatus is provided with a press rod to support one of electrode tips, an actuator to drive the press rod and a gun arm which is supported to an actuator side and has the other of the electrode tips corresponding to the tip, the actuator includes a ball screw rotation-driven by an electric motor and a ball nut assembled into the ball screw, the ball screw and the press rod are arranged in parallel in a casing, further, the press rod and the ball nut are integrally connected, by this arrangement, a rotation motion by the electric motor is converted to a linear motion of the press rod, the torque for welding force is generated between the electrode tips.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technical field of a resistance welding machine, and more particularly, to a portable servo spot welding machine using a servomotor drive as a pressure drive source for an electrode tip, and an electrode driving apparatus therefor.

[0002]

2. Description of the Related Art Portable spot welding guns are used for welding large parts such as railway cars and automobile bodies by hand. Generally, a large portable spot air gun in which a welding gun and a welding transformer are integrated is used. Because this large gun is heavy, the welding gun and welding transformer are separated and only the gun body is hung with hanging hardware to balance the gun weight so that the direction of the portable spot gun can be changed as desired. However, this type of gun has a heavy low reactance cable from a welding transformer (so-called kickless cable)
Because the cable is connected, the cable is manually routed together with the gun, and the operability is poor, and the work efficiency cannot be satisfied.

[0003] C-type air guns and X-type air guns are known as portable spot welders, but a portable servo spot using a servomotor drive is known.
C and X guns are disclosed in, for example, Japanese Patent Application Laid-Open No. 7-29025.
No. 1, JP-A-2000-94143, JP-A-2000-12
There is known a spot welding gun and a pressure unit disclosed in the 6867 published patent publication.

In this type of servo spot welding gun and pressurizing unit, a motor rotor is disposed on a shaft of an electric motor, and a ball nut fixed to the rotor is combined with a screw of a motor shaft. One electrode tip is attached to the tip of the motor shaft which is inserted and meshes with the ball nut, and the other electrode tip facing the electrode tip is fixed to the other end of the gun arm fixed to the motor side. And a structure in which the pressure operation of the electrode tip can be performed by the reciprocating operation of the ball screw.
290251, JP-A-2000-94143).

In another pressurizing unit, a screw portion is formed on a motor shaft extending forward of the motor, and a screw portion formed on the inner diameter of the pressurizing shaft is concentric with the screw portion of the motor shaft. The motor shaft is rotationally driven to linearly drive the pressurizing shaft, thereby supplying a pressing force necessary for welding between the movable electrode tip and the fixed electrode tip on the gun arm side (Japanese Patent Application Laid-Open No. 2000-2000). 126867).

According to this type of conventional apparatus, it is understood that the overall length of the electric spot C gun and the spot X gun is reduced, the weight is reduced, and the operability is improved.

[0007]

However, in both the conventional servo spot gun and the pressurizing unit of this type, the motor shaft corresponding to the pressurizing shaft is disposed through the axis of the electric motor. Since the rear side of the motor is sealed from the outside air, power can be supplied only from the pressure shaft side (that is, the point holder) extending forward of the electric motor.

Therefore, since the shunt is attached to the point holder attached to the tip of the pressure shaft, the space around the electrode, that is, the height of the electrode arm, is restricted, and the problem of work interference when inserting the gun is inevitable.

In the method of driving the nut-sleeve type pressurizing shaft by rotating the motor shaft, the pressurizing shaft overlaps concentrically with the screw portion of the motor shaft, so that the diameter of the pressurizing shaft increases and the electric motor has a larger diameter. A new frame case design is required.

According to the prior art, the mechanism for preventing the rotation of the pressure shaft may be provided inside the pressure shaft and the frame case, or the guide rail of the linear motion bearing may be used to prevent the rotation. In addition, standard parts for conventional air guns cannot be used.

[0011]

Accordingly, the present invention provides a resistance spot welding machine and an electrode which can be easily shifted to a servo motor drive without changing the standard type of the conventional pneumatic portable spot welding gun as much as possible, thereby making it possible to manufacture at low cost. A drive is provided.

[0012]

SUMMARY OF THE INVENTION The present invention has been developed to achieve the above-mentioned object. The gist of the present invention is that a pressing rod for supporting one electrode tip and a driving rod for driving the pressing rod are provided. And a gun arm supported on the actuator side and having the other electrode tip at the tip corresponding to the electrode tip. The actuator has a ball screw driven by an electric motor and a ball screw. A ball nut incorporated therein, wherein the ball screw and the pressure rod are arranged in parallel in the casing, and the pressure rod and the ball nut are integrally connected, whereby the rotation by the electric motor is performed. The driving device converts the movement into the linear movement of the pressure rod and generates a torque for pressing force between the electrode tips.

According to another aspect of the present invention, one electrode tip is supported at the tip of a pressure rod penetrating the head side of the casing, and the pressure rod is driven by an actuator supported on the cap side of the casing. A gun arm having the other electrode tip corresponding to the electrode tip is supported on the actuator side, the actuator having a ball screw driven to rotate by an electric motor and a ball nut incorporated in the ball screw; Moreover, the ball screw and the pressure rod are arranged in parallel in the casing, the pressure rod and the ball nut are integrally connected, and the rotational motion of the electric motor is converted into a linear motion of the pressure rod. A resistance spot welding machine that generates torque for pressing force between electrode tips
The ball screw serves as a pressing drive shaft of the pressing rod and a detent of the pressing rod.

Further, the pressure rod penetrates a bearing on the cap side of the casing, and a feeder can be connected to a rear portion of the rod.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram when the driving method of the present invention is applied to a portable spod welding gun.

This embodiment is representative of a portable spot welding gun 1 of the C type. The pressure rod is a bearing 3 on the head side and the cap side of the casing 2.
4 and advance and retreat. One electrode tip 6 is supported at the tip of the pressure rod 5. An arm support bracket 7 is integrally or detachably supported on the casing side.

The casing covers a cylindrical body (cylinder type) or a main body opening having a concave cross section with a cover to allow sliding parts such as ball bearings, ball screws, and ball nuts to enter from outside such as spatter and dust. It has a structure that is sealed from the outside air to protect it from foreign matter.

One end of the C-shaped gun arm 8 is detachably mounted on the bracket by bolts 9 with an insulating plate interposed therebetween. At the tip of the gun arm 8, the other electrode tip 10 corresponding to the electrode tip 6 is supported via a tip holder.

The bracket 7 may be formed integrally with the casing 2 or may be formed integrally with the gun arm 8. The bracket 7 may be omitted.
The casing 2 and the gun arm 8 may have an integrated structure or a detachable assembly structure.

The actuator 11 includes the pressure rod 5
A drive unit including a servomotor M for driving the drive unit, wherein the drive unit includes:
The ball screw 12 is directly connected to the output shaft Q of the servo motor M via a coupling S. A ball nut 13 is engaged with the ball screw 12 and incorporated therein.

A pulley is attached to the output shaft Q of the servo motor M and the ball screw 12, and a gear is provided between the pulleys.
It can also be connected via a power transmission mechanism (not shown) such as a timing belt or a chain.

In this case, the servomotor M shown in FIG. 1 is not directly connected to the ball screw but is folded and disposed on the side wall 15 on the cap side.

The ball screw 12 and the pressure rod 5 are disposed in parallel in the casing 2 and have a side wall 14 on the head side.
And the bearings 3 and 4 and the bearings 16 and 17 provided on the side wall 15 on the cap side. The pressure rod 5 and the ball nut 13 are integrally connected by a connecting member 18. The pressure rod passes through the bearings 3 and 4 and outputs the ball screw 1 with the output of the servomotor M.
By rotating 2, the ball nut 13 linearly moves integrally.

The ball screw 12 of the actuator 11
It is also possible to adopt a configuration in which the mounting angle can be changed in the circumferential direction around the axial center line of the pressure rod 5.

The gun body is hung by a hanging bracket (not shown) so that the entire gun can be moved smoothly while maintaining the weight balance of the gun body.

At the rear of the gun arm 8, a connection terminal 19 for connecting a secondary cable is mounted. One cable terminal of the secondary cable is connected to the gun arm side via the connection terminal. The other cable terminal is connected to the conductive member 20 having flexibility or the flat knitting conductor connected to the rear part of the pressure rod 5 via an insulating plate on the gun arm side via an insulating plate.

If a secondary cable is connected to the connection portion of the secondary cable via, for example, a swivel-type universal joint (not shown), the degree of freedom of the movement of the gun body can be further increased. Become.

In this embodiment, a low-reactance cable generally known as a water-cooled secondary cable is used as the secondary cable. The cooling water passes through the cooling water flow path flowing in the cable, branches off from the connection terminal 19, one passes through the inside of the gun arm 8, and the other passes through the inside of the pressurizing rod from the rear of the pressurizing rod 5 to each electrode tip 6. , 10 are formed so as to return and circulate at the tips of the cooling water passages 22.

That is, the cooling water circulates through the pressurizing rod 5 and the gun arm 8 in the actuator and the reciprocating water passage formed in each of the electrode tips 6 and 10.

The portable device of the present invention having such a configuration
The operation of the servo spot welding gun will be described. The gun body is operated by a human in a free state and moved to the hitting position of the work to adjust the hitting angles of the electrode tips 6 and 10. Once the position of the welding gun has been determined, lock and secure the welding gun.

When the gun start switch 21 is pressed after the welding gun is locked, the servomotor M is operated, the ball screw 12 is rotated, and the ball nut 13 is moved forward. When a torque is applied to the tip for the pressing force and the work inserted into the electrode tip 10 is sandwiched and a sufficient pressing force is applied, an energization start signal is issued and energization is performed.

The welding current flows from the welding transformer through the water-cooled secondary cable to the terminal, the flexible conductive wire 20 (flat knitted conductive wire), the pressure rod 5 and the electrode tip 6, and to the electrode tip 10 on the gun arm side through the work.

The current passes through the gun arm 8 and returns from the terminal to the welding transformer via the secondary cable. In this cycle, the hitting positions of the workpiece are the electrode tip 6 and the electrode tip 10.
The temperature rises due to the resistance heating of the current, melting the metal to form a nugget and join.

When the welding at the predetermined position is completed and the welding gun is moved to the next welding position, the actuator 11 is operated so as to be in a free state before welding as described above. Can be moved lightly at hand.

In this embodiment, the portable spot welding gun of the C type has been described. However, the basic concept of the present invention is not limited to these models. The range of application can be easily expanded to C-type and X-type robot guns.

[0036]

As described above, according to the present invention, when welding a large-sized work such as a railway car or a car body by hand, a conventional electric portable spot gun is compared with a conventional electric portable spot gun. Power can be supplied from the pressure rod extending to the rear (cap side) of the casing, so the space around the electrodes, that is, the dimensions of the electrode arm, is smaller than that of a conventional servo motor drive that mounts a shunt on the head side of the cylinder casing. Is no longer restricted, thereby eliminating the problem of interference between the welding gun and the workpiece or jig, dramatically improving operability, and ensuring workability and safety.

According to the spot welding gun of the present invention,
Compared to the conventional one described above, which is concentric with the screw part of the motor shaft, the diameter of the pressurizing shaft becomes large. The transition from the formula to the servo motor drive becomes easy, and the conventional standard products can be used for the gun arm, bearing, etc., and it is simple and requires less assembly accuracy and fewer parts.

In the present invention, the ball screw included in the drive unit also serves as the drive shaft of the pressure rod and the rotation preventing mechanism.
Since there is no need to provide a rotation stopping mechanism between the pressurizing shaft of the motor penetrating type and the frame case or use an expensive linear motion guide rail as in the related art, the manufacturing cost is also reduced.

Further, the present invention makes it possible to circulate the cooling water flowing in the water-cooled secondary cable not only in the gun arm and the electrode tip but also in the inside of the pressurizing rod 5 so as to enhance the cooling effect and to increase the electrode temperature due to the high temperature. The deformation of the tip can be suppressed.

The present invention also provides a sufficient cooling effect on the power supply shaft in comparison with the conventional motor-driven servo spot welding gun which drives the pressurizing shaft by rotating the motor shaft as described above. In particular, the piping route of a water-cooled hose, etc. is compared with the conventional one, and it can be connected from the rear of the pressure rod that extends to the cap side opposite to the head side (that is, the point holder side) of the casing. Maintenance is easy.

Further, according to the present invention, it is possible to support the actuator on the arm side of the robot or on another hanging bracket device, and to extend the range of use of the motor drive unit to X guns and other resistance welding machines. Can be.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an overall concept including a cross section of a portable electric pressurized resistance spot welding machine according to an embodiment of the present invention.

[Description of Signs] 1 Portable servo spot welding gun 2 Casing 3 Bearing 4 Bearing 5 Pressure rod 6 Electrode tip 7 Arm support bracket 8 Gun arm 9 Bolt 10 Electrode tip 11 Actuator 12 Ball screw 13 Ball nut 14 Head side wall 15 Cap side wall 16 Bearing 17 Bearing 18 Connector 19 Connection terminal 20 Flexible conductive member 21 Start switch 22 Cooling water passage

Claims (3)

[Claims] 1. A pressure rod for supporting one electrode tip, an actuator for driving the pressure rod, and another electrode tip supported on the actuator side and corresponding to the electrode tip at a tip. A gun arm, wherein the actuator includes a ball screw rotatably driven by an electric motor and a ball nut incorporated in the ball screw, wherein the ball screw and the pressure rod are disposed in parallel in a casing; A resistance spot that integrally connects the pressure rod and the ball nut, thereby converting a rotary motion of the electric motor into a linear motion of the pressure rod and generating a torque for pressing between the electrode tips. Electrode drive of welding machine. 2. An electrode tip is supported at a tip of a pressure rod penetrating through a head side of a casing. The pressure rod is driven by an actuator supported on a cap side of the casing, and the electrode tip is driven. A gun arm having the other electrode tip corresponding to the ball screw is supported on the actuator side, and the actuator has a ball screw rotated by an electric motor and a ball nut incorporated in the ball screw. And the pressure rod are disposed in parallel in the casing, and the pressure rod and the ball nut are integrally connected,
A resistance spot welder for converting a rotary motion of the electric motor into a linear motion of the pressure rod to generate a torque for pressing force between electrode tips, wherein the ball screw is used to press the pressure rod. A resistance spot welding machine, which also serves as a detent for a drive shaft and the pressure rod. 3. The resistance spot welding machine according to claim 2, wherein the pressure rod penetrates a bearing on the cap side of the casing, and a power feeding unit is connected to a rear portion of the rod.